text:
Program synthesis

In computer science, program synthesis is the task to construct a program that provably [sic] satisfies a given high-level formal specification. In contrast to program verification, the program is to be constructed rather than given; however, both fields make use of formal proof techniques, and both comprise approaches of different degrees of automation. In contrast to automatic programming techniques, specifications in program synthesis are usually non-algorithmic statements in an appropriate logical calculus.

The primary application of program synthesis is to relieve the programmer of the burden of writing correct, efficient code that satisfies a specification. However, program synthesis also has applications to superoptimization and inference of loop invariants.

Origin
During the Summer Institute of Symbolic Logic at Cornell University in 1957, Alonzo Church defined the problem to synthesize a circuit from mathematical requirements. Even though the work only refers to circuits and not programs, the work is considered to be one of the earliest descriptions of program synthesis and some researchers refer to program synthesis as "Church's Problem". In the 1960s, a similar idea for an "automatic programmer" was explored by researchers in artificial intelligence.

Since then, various research communities considered the problem of program synthesis. Notable works include the 1969 automata-theoretic approach by Büchi and Landweber, and the works by Manna and Waldinger (c. 1980). The development of modern high-level programming languages can also be understood as a form of program synthesis.

21st century developments
The early 21st century has seen a surge of practical interest in the idea of program synthesis in the formal verification community and related fields. Armando Solar-Lezama showed that it is possible to encode program synthesis problems in Boolean logic and use algorithms for the Boolean satisfiability problem to automatically find programs.

Syntax-guided synthesis
In 2013, a unified framework for program synthesis problems called Syntax-guided Synthesis (stylized SyGuS) was proposed by researchers at UPenn, UC Berkeley, and MIT. The input to a SyGuS algorithm consists of a logical specification along with a context-free grammar of expressions that constrains the syntax of valid solutions. For example, to synthesize a function f that returns the maximum of two integers, the logical specification might look like this:

$(f(x,y) = x ∨ f(x,y) = y) ∧ f(x,y) ≥ x ∧ f(x,y) ≥ y$

and the grammar might be:

where "ite" stands for "if-then-else". The expression

ite(x <= y, y, x)

would be a valid solution, because it conforms to the grammar and the specification.

From 2014 through 2019, the yearly Syntax-Guided Synthesis Competition (or SyGuS-Comp) compared the different algorithms for program synthesis in a competitive event. The competition used a standardized input format, SyGuS-IF, based on SMT-Lib 2. For example, the following SyGuS-IF encodes the problem of synthesizing the maximum of two integers (as presented above):

(set-logic LIA) (synth-fun f ((x Int) (y Int)) Int  ((i Int) (c Int) (b Bool))   ((i Int (c x y (+ i i) (ite b i i))) (c Int (0 1)) (b Bool ((<= i i))))) (declare-var x Int) (declare-var y Int) (constraint (>= (f x y) x)) (constraint (>= (f x y) y)) (constraint (or (= (f x y) x) (= (f x y) y))) (check-synth)

A compliant solver might return the following output:

((define-fun f ((x Int) (y Int)) Int (ite (<= x y) y x)))

Counter-example guided inductive synthesis
Counter-example guided inductive synthesis (CEGIS) is an effective approach to building sound program synthesizers. CEGIS involves the interplay of two components: a generator which generates candidate programs, and a verifier which checks whether the candidates satisfy the specification.

Given a set of inputs I, a set of possible programs P, and a specification S, the goal of program synthesis is to find a program p in P such that for all inputs i in I, S(p, i) holds. CEGIS is parameterized over a generator and a verifier:

 * The generator takes a set of inputs T, and outputs a candidate program c that is correct on all the inputs in T, that is, a candidate such that for all inputs t in T, S(c, t) holds.
 * The verifier takes a candidate program c and returns true if the program satisifies S on all inputs, and otherwise returns a counterexample, that is, an input e in I such that S(c, e) fails.

CEGIS runs the generator and verifier run in a loop, accumulating counter-examples:

algorithm cegis is input: Program generator generate, verifier verify, specification spec, output: Program that satisifies spec, or failure inputs := empty set loop candidate := generate(spec, inputs) if verify(spec, candidate) then return candidate else verify yields a counterexample e add e to inputs end if

Implementations of CEGIS typically use SMT solvers as verifiers.

CEGIS was inspired by counterexample-guided abstraction refinement (CEGAR).

The framework of Manna and Waldinger
The framework of Manna and Waldinger, published in 1980, starts from a user-given first-order specification formula. For that formula, a proof is constructed, thereby also synthesizing a functional program from unifying substitutions.

The framework is presented in a table layout, the columns containing: Initially, background knowledge, pre-conditions, and post-conditions are entered into the table. After that, appropriate proof rules are applied manually. The framework has been designed to enhance human readability of intermediate formulas: contrary to classical resolution, it does not require clausal normal form, but allows one to reason with formulas of arbitrary structure and containing any junctors ("non-clausal resolution"). The proof is complete when $$\it true$$ has been derived in the Goals column, or, equivalently, $$\it false$$ in the Assertions column. Programs obtained by this approach are guaranteed to satisfy the specification formula started from; in this sense they are correct by construction. Only a minimalist, yet Turing-complete, purely functional programming language, consisting of conditional, recursion, and arithmetic and other operators is supported. Case studies performed within this framework synthesized algorithms to compute e.g. division, remainder, square root, term unification, answers to relational database queries and several sorting algorithms.
 * A line number ("Nr") for reference purposes
 * Formulas that already have been established, including axioms and preconditions, ("Assertions")
 * Formulas still to be proven, including postconditions, ("Goals"),
 * Terms denoting a valid output value ("Program")
 * A justification for the current line ("Origin")

Proof rules
Proof rules include:
 * Non-clausal resolution (see table).
 * For example, line 55 is obtained by resolving Assertion formulas $$E$$ from 51 and $$F$$ from 52 which both share some common subformula $$p$$. The resolvent is formed as the disjunction of $$E$$, with $$p$$ replaced by $$\it true$$, and $$F$$, with $$p$$ replaced by $$\it false$$. This resolvent logically follows from the conjunction of $$E$$ and $$F$$. More generally, $$E$$ and $$F$$ need to have only two unifiable subformulas $$p_1$$ and $$p_2$$, respectively; their resolvent is then formed from $$E \theta$$ and $$F \theta$$ as before, where $$\theta$$ is the most general unifier of $$p_1$$ and $$p_2$$. This rule generalizes resolution of clauses.
 * Program terms of parent formulas are combined as shown in line 58 to form the output of the resolvent. In the general case, $$\theta$$ is applied to the latter also. Since the subformula $$p$$ appears in the output, care must be taken to resolve only on subformulas corresponding to computable properties.

 * Logical transformations.
 * For example, $$E \land (F \lor G)$$ can be transformed to $$(E \land F) \lor (E \land G)$$) in Assertions as well as in Goals, since both are equivalent.

 * Splitting of conjunctive assertions and of disjunctive goals.
 * An example is shown in lines 11 to 13 of the toy example below.

 * Structural induction.
 * This rule allows for synthesis of recursive functions. For a given pre- and postcondition "Given $$x$$ such that $$\textit{pre}(x)$$, find $$f(x) = y$$ such that $$\textit{post}(x,y)$$", and an appropriate user-given well-ordering $$\prec$$ of the domain of $$x$$, it is always sound to add an Assertion "$$x' \prec x \land \textit{pre}(x') \implies \textit{post}(x',f(x'))$$". Resolving with this assertion can introduce a recursive call to $$f$$ in the Program term.
 * An example is given in Manna, Waldinger (1980), p.108-111, where an algorithm to compute quotient and remainder of two given integers is synthesized, using the well-order $$(n',d') \prec (n,d)$$ defined by $$0 \leq n' < n$$ (p.110).

Murray has shown these rules to be complete for first-order logic. In 1986, Manna and Waldinger added generalized E-resolution and paramodulation rules to handle also equality; later, these rules turned out to be incomplete (but nevertheless sound).

Example
As a toy example, a functional program to compute the maximum $$M$$ of two numbers $$x$$ and $$y$$ can be derived as follows.

Starting from the requirement description "The maximum is larger than or equal to any given number, and is one of the given numbers", the first-order formula $$\forall X \forall Y \exists M: X \leq M \land Y \leq M \land (X=M \lor Y=M)$$ is obtained as its formal translation. This formula is to be proved. By reverse Skolemization, the specification in line 10 is obtained, an upper- and lower-case letter denoting a variable and a Skolem constant, respectively.

After applying a transformation rule for the distributive law in line 11, the proof goal is a disjunction, and hence can be split into two cases, viz. lines 12 and 13.

Turning to the first case, resolving line 12 with the axiom in line 1 leads to instantiation of the program variable $$M$$ in line 14. Intuitively, the last conjunct of line 12 prescribes the value that $$M$$ must take in this case. Formally, the non-clausal resolution rule shown in line 57 above is applied to lines 12 and 1, with yielding $$\lnot ($$$p$$x=x$$A=A$$x=M$$F[$$$)$$, which simplifies to $$x \leq x \land y \leq x$$.
 * $p$ being the common instance $]$ of $true ∧$ and $x=x$, obtained by syntactically unifying the latter formulas,
 * $F[⋅]$$p$$G[$ being $p$$]$, obtained from instantiated line 1 (appropriately padded to make the context $x ≤ x ∧ y ≤ x ∧$ around $x = x$ visible), and
 * $true ∧$$false$$) ∧ ($ being $x ≤ x ∧ y ≤ x ∧$$true$, obtained from instantiated line 12,

In a similar way, line 14 yields line 15 and then line 16 by resolution. Also, the second case, $$x \leq M \land y \leq M \land y = M$$ in line 13, is handled similarly, yielding eventually line 18.

In a last step, both cases (i.e. lines 16 and 18) are joined, using the resolution rule from line 58; to make that rule applicable, the preparatory step 15→16 was needed. Intuitively, line 18 could be read as "in case $$x \leq y$$, the output $$y$$ is valid (with respect to the original specification), while line 15 says "in case $$y \leq x$$, the output $$x$$ is valid; the step 15→16 established that both cases 16 and 18 are complementary. Since both line 16 and 18 comes with a program term, a conditional expression results in the program column. Since the goal formula $$\textit{true}$$ has been derived, the proof is done, and the program column of the "$$\textit{true}$$" line contains the program.

title: Program synthesis


text:
U.S. Route 71

U.S. Route 71 or U.S. Highway 71 (US 71) is a major north–south United States highway that extends for over 1500 miles (2500 km) in the central United States. This original 1926 route has remained largely unchanged by encroaching Interstate highways. Currently, the highway's northern terminus is in International Falls, Minnesota at the Canada–US border, at the southern end of the Fort Frances-International Falls International Bridge to Fort Frances, Ontario. U.S. Route 53 also ends here. On the other side of the bridge, Trans-Canada Highway (Ontario Highway 11) is an east–west route while Ontario Highway 71 is a north–south route. US 71's southern terminus is between Port Barre and Krotz Springs, Louisiana at an intersection with U.S. Route 190. For the entirety south of Kansas City, Missouri, US 71 runs parallel and concurrent with the existing and future Interstate 49. North of Kansas City, US 71 runs halfway between Interstate 29 and Interstate 35, which they split in the city at an interchange with Interstate 70.

Louisiana
The southern terminus of US 71 is located in Louisiana, beginning between Port Barre and Krotz Springs, at an intersection with U.S. 190. The highway follows a northwesterly course through Louisiana, passing through the communities of Alexandria, Montgomery, Coushatta, and Shreveport. From its southern terminus to Shreveport, US 71 has largely been superseded by Interstate 49 - which is eventually planned to roughly follow the US 71 alignment as far north as Kansas City, Missouri. After Shreveport, US 71 follows a northerly course, crossing into Arkansas just north of Ida, Louisiana.

Arkansas and Texas
US 71 travels approximately 300 mi in Arkansas, entering the state approximately 1 mi north of Ida, Louisiana.

The route enters Arkansas near the Red River, and runs north through the communities of Doddridge and Fouke. Most motorists can now bypass US 71 from Doddridge to Texarkana via Interstate 49. After approximately 30 mi of paralleling I-49, the route turns west, passes the historic Averitt House and enters Texarkana.

Inside the loop, Highway 71 becomes East Street, passing the Texarkana Country Club and Hobo Jungle Park before becoming Hickory Street in downtown Texarkana. The street is four-lane undivided, passing the Bottoms House and J. K. Wadley House before meeting US 67/US 82. US 71 forms a short, two-block concurrency with US 67/US 82 before turning north along Hazel Street. This minor city street runs northwest to intersect State Line Avenue; at this point, the northbound lanes are in Arkansas, while the southbound lanes are in Texas. While on State Line Avenue, US 71 intersects Loop 14 before U.S. Route 59 joins US 71 at Interstate 30.

From Arkansas Highway 296 north of Texarkana to the Red River, US 71 runs concurrent with US 59 as an expressway. Except for the northbound lanes (which return to the Arkansas side just before the Red River), this section of 3.39 mi is entirely in Texas.

The highways re-enter Arkansas (specifically Little River County) completely at the Red River. US 59/US 71 serve as an eastern terminus for Highway 380 upon entering Ogden. Although US 59/US 71 bypass the community as a four-lane highway, the route formerly served Ogden as Grand Street, which as of 2011 retains original 1926 US 71 paving for some of its length. Further north the routes pass under Highway 32, which skirts the southern part of Ashdown. Serving Little River's county seat as Constitution Avenue, the routes become a five-lane road with center turn lane which passes within two blocks of the Little River County Courthouse. The routes intersect Highway 32B and Highway 108 before exiting town due north to Wilton. Following the Kansas City Southern Railroad tracks, US 59/US 71 enters Wilton, where it passes the S. S. P. Mills and Son Building, Highway 234, and the Texarkana and Fort Smith Railway Depot. Just north of town a former alignment comes into view briefly before the Mills Cemetery and the Sevier County line.

Once across the Little River, US 59/US 71 passes another former alignment, crosses through Pond Creek National Wildlife Refuge, and runs east of Ben Lomond before entering Lockesburg. A junction in Lockesburg joins US 59/US 71 with US 371, with Highway 24 running west from the junction. 5 mi north of Lockesburg US 70 joins US 59/US 71/US 371, and the concurrent routes turn west to De Queen. Upon entering De Queen, US 59/US 71 turns north, US 70 continues west, US 70 Business/Highway 41 (US 70B/AR 41) runs south, and US 371 terminates at the junction. US 59/US 71 continue through Gillham and Grannis to serve as the western terminus of US 278 in Wickes. Junctions with Highway 246 and Highway 4 precede the route entering Mena, the county seat of Polk County. In Mena, US 59/US 71 has a brief overlap with Highway 8, during which the routes pass two NRHP listings, the Kansas City-Southern Depot and the Mena Commercial Historic District. US 59/US 71/AR 8 also has an overlap with Highway 88, although the western end of the overlap serves as the eastern terminus of the Talimena Scenic Drive National Scenic Byway designation. After Highway 8 and Highway 88 have left the route US 59/US 71 run north to a junction with US 270 in Acorn. At a fork in the road, US 59 splits onto US 270 west, and US 270 east begins a concurrency with US 71 northbound into Ouachita National Forest. US 71/US 270 continue into Scott County to Y City, where the concurrency ends and US 270 turns east. US 71 runs north through the forest to Waldron, a town the mainline route bypasses to the west while US 71B runs through downtown Waldron. While skirting Waldron, US 71 has a junction with Highway 272 near Waldron Municipal Airport as well as junctions with Highway 248, Highway 80, and Highway 28. This section of US 71 from north of Mena through Fayetteville (following the original sections bypassing the new Interstate 540 has been designated a scenic byway and the Boston Mountains Scenic Loop.

North of Waldron, US 71 passes through Mansfield and Greenwood before intersecting with Interstate 540 on the south end of Fort Smith. US 71 overlaps I-540 for approximately 12 mi until it reaches Interstate 40, then follows I-40 6 mi to Alma.

US 71 passes through Mountainburg, Winslow, West Fork and Greenland on its way to Fayetteville. At Fayetteville, US 71 continues north to the missouri state line just north of Bentonville, as well as U.S. Route 62.

North of Bentonville US 71 continues another 12 mi passing through Bella Vista to the Missouri state line.

Missouri
In Missouri, US 71 is signed as part of the new section of Interstate 49 from Pineville to the southeast side of the Kansas City metro area. The I-49 designation went into effect in December 2012.

On August 15, 2007, the final section of US 71 south of Kansas City to be converted to a 4-lane divided expressway was opened in McDonald County, between the cities of Lanagan and Jane. In Kansas City, I-49/US 71 is one of the components of the Grandview Triangle interchange. There is a 2 mi section near Swope Park that has three at-grade intersections. Ample right of way exists on the corridor to upgrade to a freeway, though there are no plans to do so in the near future. From downtown Kansas City, US 71 overlaps with Interstate 29 to north of Saint Joseph. From there, US 71 continues as an expressway to Maryville before angling towards Iowa just north of Clearmont. In 2002, US 71 was four laned from Interstate 29, northwest of St. Joseph to Maryville. From there, until it enters Iowa at Braddyville, it continues to be the only remaining rural two lane section of this highway north of Kansas City.

US 71 overlaps Interstate 70 on the east side of downtown Kansas City's freeway loop. US 71 then overlaps Interstate 35 and Interstate 29 for a segment which crosses the Missouri River via the Christopher S. Bond Bridge in Kansas City. It then continues concurrent with Interstate 29 after separating from Interstate 35 north of the Missouri River to just north of St. Joseph, Missouri where it diverges.

An alternative in the design of Interstate 29 called for it to follow US 71 on a more populated route through Maryville, Missouri and Clarinda, Iowa. However the interstate was to be routed along the more direct route to Omaha, Nebraska/Council Bluffs, Iowa and more sparsely populated Missouri River bottoms.

During the Great Flood of 1993, when the Missouri River flooded, I-29 traffic was detoured along US 71 through Maryville and Clarinda.

The four-lane segment between Savannah to Maryville was completed in 2002. It is a two-lane highway north of Maryville to the Iowa state line. The long delay in bringing a four-lane highway to Maryville even as most of the highway from Savannah south to the Arkansas line has been a four lanes for some time was a source of considerable irritation for Maryville and Northwest Missouri State University.

Outlaws Bonnie and Clyde engaged in a shootout with law enforcement officers in 1933 beside the highway at the Red Crown Tourist Court just southeast of Platte County, Missouri. The tourist court (which burned down) was just east of the main exit for I-29 Northbound at the old junction with US 71 Bypass now Missouri Route 291.

Iowa
US 71 passes through a rural section of western Iowa. It enters the state at Braddyville and junctions Interstate 80 near Brayton, northeast of Atlantic. North of I-80, US 71 passes through Carroll, where it intersects U.S. Route 30, and intersects and overlaps U.S. Route 20 at Sac City and U.S. Route 18 through Spencer. The highway crosses the Iowa Great Lakes where West Okoboji and East Okoboji Lake meet before exiting the state.

US 71 formerly entered Storm Lake concurrently with Iowa Highway 7 but was moved to a new alignment east of Storm Lake in 1996 to lessen travel time between Carroll and Spencer, the two largest communities on US 71 in Iowa. A business route of US 71 follows the highway's former alignment through Storm Lake.

A business route for US 71 also passes through Clarinda on a former alignment of US 71.

Minnesota
As is the case in Iowa, US 71 in Minnesota is largely a rural highway. It crosses Interstate 90 at Jackson, passes through Windom, and intersects U.S. Route 14 at Sanborn. It passes through Redwood Falls and Willmar before its junction with Interstate 94/U.S. Highway 52 at Sauk Centre. Around Willmar, US 71 is built to freeway standards. From there, US 71 passes through Long Prairie, Wadena, and Park Rapids before touching Itasca State Park, the source of the Mississippi River. It then crosses the Mississippi and is a major route for northern Minnesota as it goes around Bemidji (the "first city on the Mississippi") and angles northeast to its terminus at the Canada–US border in International Falls. The route between Bemidji and International Falls parallels the Blue Ox Trail, formerly the Northern Pacific Railway. On the Ontario side, Highway 71 links the bridge to Ontario Highway 71 in Fort Frances, which continues north and terminates at Ontario Highway 17 just east of Kenora.

The Minnesota section of US 71 is defined as Routes 4 and 141 in Minnesota Statutes §§ 161.114(2) and 161.115(72).,

History
The original southern terminus of US 71 was in Baton Rouge, Louisiana at the Baton Rouge-Port Allen Mississippi River ferry. This was also the original western terminus of US 190 which continued east from the ferry landing through Baton Rouge, shortly intersecting US 61. US 71 was routed along the Jefferson Highway (pre-1955 State Route 1) from Baton Rouge north to Clarence (near Natchitoches). From Clarence to Shreveport, a more direct route was chosen than that followed by the Jefferson Highway, and US 71 continued north into Arkansas rather than west into Texas.

The current route of US 71 in Louisiana follows or closely parallels the 1926 alignment north of Lebeau. Between Port Allen and Lebeau, US 71 originally followed present-day LA 76 to Rosedale, LA 77 to Ravenswood, and LA 10 to Lebeau, crossing the Atchafalaya River by ferry at Melville. In 1935, US 190 was extended west onto a newly built section of State Route 7 (the Evangeline Highway) with a bridge across the Atchafalaya River at Krotz Springs. The following year, US 71 was moved onto this route, branching northward to Lebeau from its current southern terminus west of Krotz Springs and bypassing the ferry crossing at Melville. In 1940, US 71 and 190 were moved onto the new Mississippi River Bridge at Baton Rouge, bypassing the ferry crossing there. US 71 was cut back to its current southern terminus west of Krotz Springs in 1951.

In northwest Arkansas, the 1926 alignment of US 71 followed Highway 102 from Bentonville to Centerton, then north on Highway 102 Business to Highway 72 southeast of Hiwasse. From there, it followed Arkansas 72 to Gravette, where it turned north on Highway 59 to the Missouri state line. In the 1930s, US 71 was rerouted along Arkansas 72 between Bentonville and Gravette, then north on Arkansas 59. This alignment lasted until the early 1960s when it was realigned along Highway 100 between Bentonville and the Missouri state line. In Missouri, the new US 71 replaced Route 88, which had been defined in 1922, while the old US 71 became Route 59.

Highway 71 has a brief concurrency with Highway 237 before crossing over The Loop Interstate 49 instead of (future Interstate 130) in the southeast part of town.

Future
A large section of US 71 through Missouri, Arkansas and Louisiana is being upgraded to Interstate standards as an extension of Interstate 49 from Shreveport, Louisiana to Kansas City, Missouri. It will also connect to New Orleans with "Future I-49" signage being posted, but with no construction, as of 2017, being started.

Major intersections

 * Louisiana
 * west of Krotz Springs
 * southeast of Lecompte. The highways travel concurrently to Alexandria.
 * in Alexandria
 * in Alexandria. The highways travel concurrently to Pineville.
 * in Alexandria
 * in Tioga. The highways travel concurrently to southeast of Creola.
 * in Clarence. The highways travel concurrently to Coushatta.
 * in Coushatta. The highways travel concurrently to the Coushatta–Edgefield line.
 * in Bossier City. The highways travel concurrently to Shreveport.
 * in Shreveport
 * in Shreveport
 * southeast of Hosston

 * Arkansas
 * south-southeast of Doddridge
 * south of Fouke
 * in Texarkana
 * in Texarkana. The highways travel concurrently to the Texas state line at the Texarkana-Texarkana city line.
 * on the Texas state line on the Texarkana–Texarkana, Texas city line. US 59/US 71 travels concurrently to Acorn.

 * Texas
 * north of Texarkana
 * north of Texarkana

 * Arkansas
 * in Lockesburg. The highways travel concurrently to De Queen.
 * north-northwest of Lockesburg. The highways travel concurrently to De Queen.
 * east of De Queen
 * in Wickes
 * in Acorn. US 71/US 270 travels concurrently to Y City.
 * west-southwest of Y City
 * in Mansfield
 * north of Huntington
 * southeast of Fort Smith
 * in Fort Smith. The highways travel concurrently to Van Buren.
 * in Van Buren
 * in Van Buren. The highways travel concurrently to Alma.
 * in Alma
 * in Fayetteville. The highways travel concurrently to Bentonville.
 * in Fayetteville. The highways travel concurrently to Bentonville.
 * in Springdale

 * Missouri
 * south of Pineville. The highways travel concurrently to Kansas City.
 * in Neosho
 * south-southwest of Duenweg. The highways travel concurrently to Fidelity.
 * in Lamar
 * in Nevada
 * in Kansas City. I-470/US 50/US 71 travels concurrently, but on different lanes, through Kansas City.
 * in Kansas City
 * in Kansas City. I-70/US 40/US 71 travels concurrently through Kansas City.
 * in Kansas City. I-29/US 71 travels concurrently to east of Amazonia. I-35/US 71 travels concurrently through Kansas City.
 * on the Gladstone–Kansas City city line
 * on the Gladstone–Kansas City city line
 * in Kansas City
 * in Kansas City. The highways travel concurrently to Platte City.
 * south-southeast of St. Joseph
 * in St. Joseph
 * in St. Joseph
 * in St. Joseph
 * north-northeast of Country Club. The highways travel concurrently to northwest of Savannah.
 * in Maryville. The highways travel concurrently to east-southeast of Burlington Junction.

 * Iowa
 * north of Villisca
 * in Atlantic. The highways travel concurrently to north-northeast of Lorah.
 * north-northeast of Lorah
 * in Carroll
 * northeast of Sac City and north of Early. The highways travel concurrently between these intersections.
 * in Spencer. The highways travel concurrently through Spencer.

 * Minnesota
 * in Jackson
 * north of Sanborn
 * in Olivia. The highways travel concurrently through Olivia.
 * in Willmar
 * in Sauk Centre
 * in Wadena
 * in Bemidji. The highways travel concurrently through Bemidji.
 * in International Falls. The highways travel concurrently to the Canada–United States border at Fort Frances, Ontario.
 * Central Avenue/Church Street at the Canada–United States border at Fort Frances, Ontario

Related U.S. Routes

 * U.S. Route 171
 * U.S. Route 271
 * U.S. Route 371

Auxiliary and suffixed routes
Auxiliary routes of U.S. Route 71

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: U.S. Route 71


text:
List of jungle and drum and bass artists

This is a list of jungle and drum and bass artists/DJs. This includes notable artists who have either been very important to the genre or have had a considerable amount of exposure (such as those who have been on a major label). This list does not include little-known local artists. Artists are listed by the first letter of their pseudonym (not including the words "a", "an", or "the"), and individuals are listed by last name.

0–9

 * 4hero

A

 * AK1200
 * Adam F
 * Alix Perez
 * Amon Tobin
 * Andy C
 * Aphex Twin
 * Aphrodite
 * Aquasky
 * Audio

B

 * B-Complex
 * Bachelors of Science
 * Bad Company
 * Billain
 * Black Sun Empire
 * Blame (music producer)
 * Blu Mar Ten
 * Blanke
 * Blue Stahli
 * Michiel van den Bos
 * Boymerang
 * Breakbeat Era
 * Justin Broadrick
 * Brookes Brothers
 * Danny Byrd

C

 * Calibre
 * Calyx
 * Camo & Krooked
 * Davide Carbone
 * Cause 4 Concern
 * Celldweller
 * Chase & Status
 * Commix
 * Concord Dawn
 * Corrupt Souls
 * Counterstrike
 * Crissy Criss
 * Culture Shock
 * Current Value

D

 * D.Kay
 * DBridge
 * DC Breaks
 * Dimension
 * DJ Craze
 * DJ Dara
 * DJ Dextrous
 * DJ Die
 * DJ Food
 * DJ Fresh
 * DJ Hazard
 * DJ Hidden
 * DJ Hype
 * DJ Kentaro
 * DJ Marky
 * DJ Patife
 * DJ Rap
 * DJ Ron
 * DJ SS
 * DJ Starscream
 * DJ Zinc
 * Danny Breaks
 * Decoder
 * DeeJay Delta
 * Deekline
 * Delta Heavy
 * Demon Boyz
 * Dieselboy
 * Dillinja
 * Dirtyphonics
 * Doc Scott
 * Dom & Roland
 * Doubleclick
 * Drumagick
 * Drumsound & Bassline Smith
 * Dwarf Electro

E

 * E-Z Rollers
 * Eresse
 * Etherwood
 * Evol Intent
 * Tim Exile
 * Eye-D

F

 * Fabio
 * The Flashbulb
 * Fox Stevenson
 * Freaky Flow
 * Friction
 * Fred V & Grafix

G

 * Goldie
 * Grooverider
 * A Guy Called Gerald
 * Gremlinz

H

 * High Contrast
 * Hybrid

I

 * Ill.Skillz
 * Ilk
 * Imanu

J

 * Jade
 * J Majik
 * John B
 * Jonny L
 * Jordana
 * Jumpin Jack Frost

K

 * Keeno
 * Ray Keith
 * Kēvens
 * Kemistry
 * Kemistry & Storm
 * Kenny Ken
 * Kill the Noise
 * Killbot
 * Klute
 * Konflict
 * Kosheen
 * Kove
 * Koven
 * Krust
 * Kuuro

L

 * LTJ Bukem
 * Lamb
 * Left Spine Down
 * Lenzman
 * Limewax
 * Liondub
 * LiveSummit
 * Loadstar
 * Logistics
 * London Elektricity (also released as Peter Nice Trio)
 * Luude

M

 * Maduk
 * Makoto
 * Marcus Intalex
 * Matrix
 * MC Skibadee
 * Metrik
 * Michele Sainte
 * Mickey Flair
 * Missrepresent
 * Muzz

N

 * Nanotek
 * Nerve
 * Netsky
 * Nia Archives
 * Noisia
 * Nucleus
 * Nu:Logic
 * Nu:Tone

O

 * Omni Trio
 * Optical

P

 * PH10
 * The Panacea
 * Panda
 * Paradox
 * Pendulum
 * Peshay
 * Phace
 * Photek
 * Plastikman
 * Plug
 * Podočnjaci
 * Polar
 * Pythius (producer)
 * The Prodigy
 * The Prototypes

Q

 * Q Project
 * The Qemists
 * Quoit

R

 * Rabbit Junk
 * Ragga Twins
 * Ram Trilogy
 * Rawtekk
 * Rebel MC
 * Red Snapper
 * Alex Reece
 * Renegade Soundwave
 * Replicator
 * Roni Size & Reprazent
 * Rregula
 * Rudimental
 * Ed Rush

S

 * Michele Sainte
 * Salmonella Dub
 * Seba
 * Shapeshifter
 * Shimon
 * The Shizit
 * ShockOne
 * Shy FX
 * Si Begg
 * Sigma
 * Slipmatt
 * Ed Solo
 * Source Direct
 * Spectrum
 * Spor
 * Spring Heel Jack
 * Squarepusher
 * Stamina MC
 * Stanton Warriors
 * State of Mind
 * Step 13
 * Fox Stevenson
 * Stevie Hyper D
 * Sub Focus
 * Submerged
 * System 7

T

 * T Power
 * TC
 * The Glitch Mob
 * Tiki Taane
 * Tabla Beat Science
 * Nobukazu Takemura
 * Teebee
 * Soichi Terada
 * Total Science
 * Typecell

U

 * U-ziq

V

 * Vector Burn
 * Venetian Snares
 * Luke Vibert

W

 * Wagon Christ
 * Danny Wheeler
 * Wickaman
 * Wilkinson
 * Witchman

X

 * XRS
 * Xample

Z

 * Zardonic


text:
Slave Trade Act 1807

The Slave Trade Act 1807, officially An Act for the Abolition of the Slave Trade, was an Act of the Parliament of the United Kingdom prohibiting the slave trade in the British Empire. Although it did not automatically emancipate those enslaved at the time, it encouraged British action to press other nation states to abolish their own slave trades. It took effect on 1 May 1807, after 18 years of trying to pass an abolition bill.

Many of the supporters thought the Act would lead to the end of slavery. Slavery on English soil was unsupported in English law and that position was confirmed in Somerset's case in 1772, but it remained legal in most of the British Empire until the Slavery Abolition Act in 1833.

Background
As British historian Martin Meredith writes, "In the decade between 1791 and 1800, British ships made about 1,340 voyages across the Atlantic, landing nearly 400,000 slaves. Between 1801 and 1807, they took a further 266,000.  The slave trade remained one of Britain's most profitable businesses."

The Committee for the Abolition of the Slave Trade was formed in 1787 by a group of Evangelical English Protestants allied with the Quakers, to unite in their shared opposition to slavery and the slave trade. The Quakers had long viewed slavery as immoral, and a blight upon humanity. By 1807 the abolitionist groups in Britain had a very sizeable faction of like-minded members in the British Parliament. At their height they controlled 35–40 seats. Known as the "Saints", the alliance was led by the best known of the anti-slave trade campaigners, William Wilberforce, who had taken on the cause of abolition in 1787 after having read the evidence that Thomas Clarkson had amassed against the trade. These dedicated Parliamentarians had access to the legal draughtsmanship of James Stephen, Wilberforce's brother-in-law. They often saw their personal battle against slavery as a divinely ordained crusade. On Sunday, 28 October 1787, Wilberforce wrote in his diary: "God Almighty has set before me two great objects, the suppression of the slave trade and the reformation of manners."

On 2 April 1792, William Wilberforce sponsored a motion in the House of Commons "that the trade carried on by British citizens, for the purpose of obtaining slaves on the coast of Africa, ought to be abolished." He had introduced a similar motion in 1791, which was soundly defeated by MPs, with a vote of 163 opposed, 88 in favour. Henry Dundas was not present for that vote, but when it was again before MPs in 1792, Dundas tabled a petition from Edinburgh residents who supported abolition. He then went on to affirm his agreement in principle with Wilberforce's motion: "My opinion has been always against the Slave Trade." He argued, however, that a vote for immediate abolition would be ineffective, as it would not prevent merchants from other countries from stepping in to continue the trade abandoned by the British. He stated: "this trade must be ultimately abolished, but by moderate measures". He proposed an amendment that would add the word "gradual" to the Wilberforce motion. The amendment was adopted, 192 in favour, 125 opposed. The motion as amended then passed 230 in favour, 85 opposed. Dundas insisted that any abolition of the slave trade would have to be dependent on the support of West Indian colonial legislatures, and the implementation of laws concerning the amelioration of the conditions of slaves. Abolitionists argued that West Indian assemblies would never support such measures, and that making the abolition of the slave trade dependent on colonial reforms would cause indefinite delay.

Three weeks after the vote, Dundas tabled resolutions setting out a plan to implement gradual abolition by the end of 1799. At that time he told the House that proceeding too quickly would cause West Indian merchants and landowners to continue the trade "in a different mode and other channels." He argued that "if the committee would give the time proposed, they might abolish the trade; but, on the contrary, if this opinion was not followed, their children yet unborn would not see the end of the traffic." MPs voted in favour of ending the trade in slaves by the end of 1796, after defeating proposals to end the trade in slaves in 1795 or 1794. The House then amended the supporting resolutions tabled by Dundas, to reflect the new target date of 1796. The motion and resolutions did not receive consent in the House of Lords, however, consideration being formally deferred to a subsequent session on 5 June 1792, where they were never revived.

Thus the 1792 Slave Trade Bill passed the House of Commons; but mangled and mutilated by the modifications and amendments of Pitt, Earl of Mornington, Edward James Eliot and MacDonald, it lay for years, in the House of Lords.

Abolitionists’ numbers were magnified by the precarious position of the government under Lord Grenville, whose short term as prime minister was known as the Ministry of All the Talents. Grenville himself led the fight to pass the bill in the House of Lords, while in the Commons the bill was led by the Foreign Secretary, Lord Howick (Charles Grey, later Earl Grey). Other events also played a part; the Acts of Union 1800 brought 100 Irish MPs into Parliament, most of whom supported abolition. The Bill was first introduced to Parliament in January 1807. It went to the House of Commons on 10 February 1807. On 23 February 1807, twenty years after he first began his crusade, Wilberforce and his team were rewarded with victory. After a debate lasting ten hours, the House agreed to the second reading of the bill to abolish the Atlantic slave trade by an overwhelming 283 votes for to 16. The Bill received Royal Assent by King George III on 25 March 1807. The Act took effect on 1 May 1807. However, Kitty's Amelia had received clearance to sail on 27 April, before the deadline. Thus, when she sailed on 27 July, she did so legally. This was the last legal slave voyage for a British vessel.

All that took place against the background of the ongoing War of the Fourth Coalition. In the last months of 1806, Napoleon had won a major victory, crushing the military power of Prussia, entering into its capital Berlin and there issuing the Berlin Decree, bringing into effect the Continental System whose declared purpose was to weaken the British economy by closing French-controlled territory to its trade. Originally, the French Revolution had abolished slavery, but Napoleon – though claiming the mantle of continuing the revolutionary heritage – had in 1802 taken the reactionary step of reintroducing slavery in the French colonies. Thus, in abolishing the slave trade Britain – which could do little to directly oppose the string of French military victories on the continent – could at least gain the moral high ground against its French foe.

Other nations
By its Act Against Slavery of 1793, the Parliament of Upper Canada in British North America (modern-day Canada) abolished the slave trade, freed slaves immigrating by choice or force, as well as children born to enslaved women subsequently upon their 25th birthday, but did not emancipate existing resident slaves. In 1805 a British Order-in-Council had restricted the importation of slaves into colonies that had been captured from France and the Netherlands. Following adoption of the 1807 Act, Britain used its diplomatic influence to pressure other nations to end their own involvement in the slave trade. With the Anglo-Portuguese Treaty of 1810, Portugal agreed to restrict its trade into its colonies; in the Anglo-Swedish Treaty of 1813, Sweden outlawed its slave trade; and in the Treaty of Paris of 1814 whereby France agreed with Britain that the slave trade was "repugnant to the principles of natural justice" and agreed to abolish its involvement the slave trade in five years. In the 1814 Anglo-Dutch treaty the Netherlands outlawed its slave trade, and the 1817 Anglo-Spanish treaty called for Spain to suppress its trade by 1820.

The United States adopted its Act Prohibiting Importation of Slaves on 2 March 1807, the same month and year as the British action. It provided for the abolition of its Atlantic slave trade but did not alter its internal trade in slaves, while the American abolition of the international slave trade led to the creation of a coastwise slave trade in the United States. Article 1, Section 9, Clause 1 of the United States Constitution forbade the closing of the slave trade for twenty years, until 1808. The long-planned law was passed a year earlier, and with the economic incentives of the slave trade coming to an end, there was both a spike in the number of slaves being traded and a unification of political factions against the trade.

Enforcement
The Act created fines for ship captains who continued with the trade. These fines could be up to £100 per enslaved person found on a ship. Captains would sometimes dump captives overboard when they saw Navy ships coming in order to avoid these fines. The Royal Navy, which then controlled the world's seas, established the West Africa Squadron in 1808 to patrol the coast of West Africa, and between 1808 and 1860 they seized approximately 1,600 slave ships and freed 150,000 Africans who were aboard. The Royal Navy declared that ships transporting slaves would be treated the same as pirates. Action was also taken against African kingdoms which refused to sign treaties to outlaw the trade, such as "the usurping King of Lagos", who was deposed in 1851. Anti-slavery treaties were signed with over 50 African rulers.

In the 1860s, David Livingstone's reports of atrocities within the Arab slave trade in East Africa stirred up the interest of the British public, reviving the flagging abolitionist movement. The Royal Navy throughout the 1870s attempted to suppress "this abominable Eastern trade", at Zanzibar in particular. In 1890 Britain handed control of the strategically important island of Heligoland in the North Sea to Germany in return for control of Zanzibar, in part to help enforce the ban on slave trading.

title: Slave Trade Act 1807


text:
U.S. Route 171

U.S. Highway 171 (US 171) is a part of the United States Numbered Highway System and the only route within that system currently located entirely within the state of Louisiana. It spans 177.44 mi in a north–south direction from the junction of US 90 and Louisiana Highway 14 (LA 14) in Lake Charles to the junction of US 79/US 80 and LA 3094 in Shreveport.

As its designation indicates, US 171 is numbered as a spur of US 71, the principal north–south U.S. Highway through Shreveport, though they technically do not intersect. US 171 traverses six of the seven parishes along the Texas state line, the only exception being Cameron Parish located on the Gulf of Mexico south of Lake Charles. The route connects all six parish seats as it travels through the thick pine forests of western Louisiana on a wide four-lane right-of-way. The northern half of the route serves as the only major north–south corridor between Interstate 49 (I-49) to the east and the Toledo Bend Reservoir along the state line to the west. Between the metropolitan areas at each terminus, US 171 passes through the smaller cities of DeRidder, Leesville, and Mansfield, as well as the towns of Rosepine, Many, Zwolle, and Stonewall. Along the way, the highway has interchanges with many of the state's major east–west routes, including Interstate 10 (I-10), US 190, LA 28, US 84, and I-20.

US 171 was created as one of the original routes of the numbered U.S. Highway system in November 1926. Its only major alignment change occurred in 1937, when the highway was shifted from what is now LA 175 between Many and Mansfield. Improvements over the years have included the paving of the entire route during the early 1930s, the elimination of many at-grade railroad crossings during the remainder of the decade, and the widening of the highway to four lanes through its urban areas during the 1960s and 1970s. Four-laning of the entire route was accomplished between 1990 and 2010 via the state's massive TIMED program with the goal of improving safety and promoting economic development along the corridor.

The route carries several honorary designations, primarily that of the Purple Heart Highway in tribute to all recipients of the Purple Heart military decoration. The route has long been associated with the U.S. Armed Forces due to its proximity to at least four military bases active during the World Wars, the lone survivor of which is Fort Johnson near Leesville.

Lake Charles to Leesville
From the south, US 171 begins at a junction with US 90 (Fruge Street) and LA 14 (South Martin Luther King Highway), in Lake Charles, the largest city in Calcasieu Parish and southwestern Louisiana. Traveling about 2.0 mi east of the downtown area, US 171 continues the route of LA 14 northward along North Martin Luther King Highway, initially as a divided four-lane highway. After immediately crossing over the BNSF and Union Pacific (UP) railroad lines, N. Martin Luther King passes through a partial cloverleaf interchange with I-10 at exit 33, connecting with Beaumont, Texas to the west and Lafayette to the east. The highway gains a center turning lane and an additional northbound travel lane throughout the commercial corridor north of the interstate. Upon exiting Lake Charles, US 171 traverses a strip of wetlands with twin-span bridges over two navigable waterways, English Bayou and the Calcasieu River. After crossing the latter, the roadway remains elevated until reaching the unincorporated suburb of Moss Bluff. A junction here with LA 378 (Sam Houston Jones Parkway) leads west to Sam Houston Jones State Park and the nearby city of Westlake. US 171 maintains a combination of single and double center lanes through Moss Bluff, dropping the N. Martin Luther King Hwy signage as it passes just north of central Moses Bluff. As the surroundings become less developed, the right-of-way widens to accommodate a broad, grassy median.

North of Moss Bluff, a rural area known as Gillis introduces a mixture of open farmland, thick forest, and scattered residential development that characterizes the next 34 mi to the city of DeRidder. During this stretch, US 171 enters Beauregard Parish and engages in a folded diamond interchange with US 190 and LA 12 that allows a grade separation with the Union Pacific Railroad line. Located in Ragley, the landscaped eastern side of the interchange doubles as a recreational area known as Purple Heart Memorial Park, echoing the official designation of US 171 as the Purple Heart Highway. US 171 proceeds due north from Ragley co-signed with US 190 through the community of Longville, located at the eastern terminus of LA 110, and enters the outskirts of DeRidder. Approaching the city limits, US 171 and US 190 pass the western termini of three rural state highways. The first, LA 394 leads to a recreational area on Bundick Lake. The others, LA 26 and LA 112, connect to Oberlin and Oakdale in neighboring Allen Parish.

Curving west into the parish seat, US 171 serves as DeRidder's main east–west commercial thoroughfare. Initially traveling along 1st Street with a center turning lane, the route divides into a one-way pair as westbound traffic transitions onto Mahlon Street. The highway then crosses the Kansas City Southern Railway (KCS) line into the downtown area, where it passes several historic buildings over the next few blocks. These include the Beauregard Parish Courthouse and an infamous Gothic structure known as the Hanging jail. US 171 ends its concurrency with US 190 by turning north onto Pine Street, an undivided four-lane thoroughfare. From this intersection, LA 27 heads south on Pine Street toward DeQuincy while US 190 continues west on the one-way pair of 1st and Shirley Streets toward Merryville. US 171 remains a commercial corridor until it crosses the Vernon Parish line, reverting to its rural configuration as it closely parallels the KCS rail line. DeRidder is separated by the small town of Rosepine by a short distance, during which an intersection with LA 3226 allows southbound traffic to bypass the city en route to US 190 west. At a point known as Pickering, located 7.7 mi north of Rosepine, US 171 intersects LA 10, the first of several connections to the United States Army installation at Fort Johnson. Passing to the west of the base, the highway continues through New Llano and into the larger adjacent city of Leesville.

Leesville to Mansfield
In Leesville, US 171 becomes a busy commercial corridor again, initially traveling along 5th Street's narrow four-lane right-of-way. Another one-way pair is then utilized as the parallel 6th Street begins to carry southbound traffic. In the center of town, three state highway junctions are encountered in the space of a few blocks: LA 467 (University Parkway) to Northwestern State University's Fort Johnson campus; LA 468 (Lula Street) to the historic business district; and westbound LA 8 (Nolan Trace Parkway) toward Jasper, Texas. US 171 proceeds north concurrent with LA 8 and descends below grade to cross under the KCS railroad line. Curving to the northwest, the highway's travel lanes converge as it approaches a roundabout. Here, at the northern end of town, LA 8 departs to the east and travels concurrently with LA 28 toward Alexandria, the principal city of central Louisiana. During its remaining 15.4 mi in Vernon Parish, US 171 crosses the northeastern tip of Vernon Lake and passes through the rural towns of Anacoco and Hornbeck. Junctions there with LA 111 and LA 392, respectively, lead to points along the vast Toledo Bend Reservoir located on the Texas state line.

US 171 enters Sabine Parish winding gently through the rural hilly woodlands while passing the entrance to Hodges Gardens State Park, the largest horticultural park in the United States. The route proceeds through the village of Florien, where a Boise Cascade lumber plant is located, and into Fisher, its smaller neighbor. US 171 then curves northwest and enters the town of Many, the parish seat. Cutting a serpentine path through the street grid outside the downtown area, the highway crosses LA 6 (San Antonio Avenue), which follows a section of the historic Old San Antonio Road (or El Camino Real) between San Antonio, Texas and Natchitoches, Louisiana. Regaining its wide rural right-of-way, US 171 intersects the southern terminus of LA 175, leading to Belmont and Pleasant Hill. US 171 makes a bee-line to the northwest over the 8.8 mi between Many and Zwolle. Served by the highway's only business route, Zwolle is bypassed by mainline US 171, which travels around its east and north sides, intersecting LA 120 in the process. Signage also directs motorists onto US 171 Bus. to access North Toledo Bend State Park. US 171 comes closest to reaching the Toledo Bend Reservoir at Zwolle and the neighboring village of Noble.

After crossing over the KCS Railway at Noble, US 171 curves back to the north and intersects LA 174 in the village of Converse. Closely following the rail line once again, US 171 crosses into DeSoto Parish just south of Benson, a point located at an intersection with LA 512. 5.0 mi later, the highway makes an S-curve across the KCS line on a high twin-span overpass before proceeding due north into South Mansfield, a small village connected to the city of Mansfield, the parish seat. In Mansfield proper, US 171 follows Jenkins Street and intersects US 84 at Washington Avenue, connecting with Logansport to the west. US 84 overlaps US 171 for a short distance until reaching Polk Street, while the bypassed original mainline route follows the continuation of Washington Avenue signed as US 84 Bus. At Polk Street, signage points motorists onto eastbound US 84 toward the Mansfield State Historic Site, a Civil War battlefield, as well as the former Mansfield Female College, the first institution of higher learning for women west of the Mississippi River. US 84 also leads eastward to an interchange with I-49.

Shreveport metropolitan area
As it enters the Shreveport metropolitan area, US 171 begins to approach and eventually parallel the route of I-49, the state's major north–south highway. After curving northwest out of Mansfield, US 171 passes the DeSoto Parish Airport and heads through Grand Cane, located at a junction with LA 3015. 5.0 mi later, the highway bends due north again and then crosses LA 5 at a junction in Gloster known as Kickapoo. Just before crossing into Caddo Parish, US 171 passes through the town of Stonewall and intersects LA 3276, a connector to I-49. Across the parish line, US 171 crosses underneath the Union Pacific Railroad tracks in the unincorporated community of Keithville. Residential development gradually increases as the highway parallels the UPRR line toward the Shreveport city limits.

US 171 enters Shreveport on Mansfield Road and retains its wide median as it becomes a heavily traveled commercial corridor once again. The highway has junctions with LA 525 (Colquitt Road), as well as LA 526, a major thoroughfare along the south side of town called the Bert Kouns Industrial Loop Expressway. Larger shopping developments line the roadway as US 171 approaches an interchange with LA 3132 (Terry Bradshaw Passway), a freeway loop commonly known as the Inner Loop Expressway. LA 3132 complements the I-220 northern bypass of Shreveport and connects to major interchanges with I-20 to the northwest and I-49 to the east. Some movements between US 171 and LA 3132 are accomplished through a connected interchange with Jewella Avenue, a divided thoroughfare that branches off of Mansfield Road.

Proceeding northward, US 171 crosses over the UPRR line for the final time and intersects LA 511 (West 70th Street). The highway immediately branches off of Mansfield Road itself, transferring onto Hearne Avenue. Its median now replaced by a center turning lane, US 171 travels through a primarily residential neighborhood until passing through a diamond interchange with I-20 at exit 16A. This interchange is located at the edge of the State Fair Grounds, an area which also houses the Louisiana State Exhibit Museum and three sports facilities—Independence Stadium, the Hirsch Memorial Coliseum, and a baseball stadium. US 171 reaches its northern terminus a short distance beyond I-20 at a junction with the concurrent US 79/US 80 (Greenwood Road). Hearne Avenue continues straight ahead as LA 3094 toward a junction with northbound US 71/LA 1 just outside Downtown Shreveport.

Route classification and data
US 171 carries at least four lanes of traffic for its entire length. It alternates between a rural and urban principal arterial over the course of its route, as determined by the Louisiana Department of Transportation and Development (La DOTD). Daily traffic volume in 2013 peaked at 37,700 vehicles in Shreveport and 29,800 in Lake Charles. The lowest figure reported was 2,200 vehicles north of Hornbeck in southern Sabine Parish. The posted speed limit ranges from 65 mph throughout most divided rural stretches to as low as 35 mph within some corporate limits.

Since 2003, virtually the entire route of US 171 has been officially designated as the Purple Heart Highway in recognition of all Purple Heart recipients. The only exceptions are the portion from its southern starting point in Lake Charles to central Moses Bluff, named in 1982 for Martin Luther King Jr., and another in Rosepine named for its former mayor Johnnie B. Hall in 1997. Decades earlier, two markers were installed on US 171 identifying it as a Blue Star Memorial Highway as "a tribute to the Armed Forces that have defended the United States of America." The first was dedicated on March 17, 1957 at the roadside park in Ragley. The second was dedicated on November 11, 1964 at the intersection with Washington Street in DeRidder.

Additionally, a 16.7 mi stretch of US 171, extending from LA 26 south of DeRidder to LA 10 south of Leesville, serves as part of the Myths and Legends Byway in the state-designated system of tourist routes known as the Louisiana Scenic Byways.

Original route and early improvements
US 171 was designated in November 1926 as one of the original routes of the numbered U.S. Highway system. The majority of the route, extending from Lake Charles to Many, has remained largely unchanged to the present day. North of Many, however, US 171 was initially routed along the current LA 175 to Mansfield, where it rejoined the modern alignment into Shreveport. The entire route was also initially co-signed with Louisiana's corresponding state highway designations as created in 1921. These consisted of State Route 42 from Lake Charles to Many, State Route 51 from Many to Belmont, and State Route 1 from Belmont to Shreveport. This practice was discontinued when the state highway system was renumbered in 1955.

Upon its designation in 1926, US 171 was generally a gravel road outside the city of Shreveport. By the summer of 1932, however, the entire highway was paved with two lanes of concrete aside from the Many–Mansfield section. Instead, the modern alignment via Zwolle, which was also the northern portion of Route 42 prior to 1955, was being straightened and paved to serve as US 171. The revised route also received two grade separations with the Kansas City Southern Railway line that were constructed in 1934. These consisted of an overpass at Noble and an underpass at Trenton, about 4 mi south of Mansfield. Completed at the end of 1937, this would be the only major alignment change in the highway's history and the only instance in which the paved alignment significantly differed from the established gravel road. Minor deviations, mostly near the highway's southern end, included a diagonal cutoff that bypassed a section line road zigzag running northwest from Gillis and the straightening of the route through Longville.

During the mid- to late 1930s, six additional grade separations were constructed elsewhere along US 171, eliminating nearly every railroad crossing along the route. The first was an overpass of the now abandoned Gulf, Colorado and Santa Fe Railway just east of DeRidder in 1934. The others were constructed beginning in 1935 as part of a federally funded grade separation program. That year, $3.2 million was allocated for this purpose by a Works Progress Administration program and was earmarked by the Louisiana Highway Commission for 28 separate projects. Those projects along US 171 consisted of overpasses of the Southern Pacific Lines at Lake Charles, the Gulf Coast Lines at Ragley, and the Texas and Pacific Railway at both Grand Cane and Shreveport, as well as an underpass of the Kansas City Southern at Leesville. The overpasses were all completed in 1937,  with the Leesville underpass following in 1939. All have since been replaced or supplemented with newer four-lane crossings, except the DeRidder and Grand Cane structures, which have been eliminated due to abandonment of the railroad lines.

Urban improvements and initial widening projects
The next burst of activity in improving US 171 occurred in Caddo Parish, where the entirety of Mansfield Road from the DeSoto Parish line to LA 511 in Shreveport was reconstructed and straightened beginning in 1951. Several sections of the original roadway still exist as local roads, now re-named as Old Mansfield Road, that weave in and out of the current alignment. Additionally, the portion from Southland Park Drive to Jewella Avenue now serves as a frontage road to the modern route. The project was completed in 1954 at a cost of $1,921,000. The new alignment also included an underpass of the Texas and New Orleans Railroad line at Keithville, replacing the grade crossing there. In 1959, the final alignment change in Shreveport had US 171 transition from Mansfield Road onto Hearne Avenue to reach its northern terminus, giving the highway its first section of four-lane pavement. Around 1965, two additional lanes were built on Mansfield Road extending south to LA 526. This was roughly concurrent with the opening of the I-20 interchange on Hearne Avenue, connecting US 171 with the new expressway through Downtown Shreveport and improving access to the US 80 corridor east of the city. The highway was then widened southward through the Keithville area in 1967, making US 171 four lanes throughout both the city of Shreveport and Caddo Parish.

The opposite end of US 171 received its first section of four-lane pavement in the early 1960s when the roadway was widened in Lake Charles between the southern terminus at US 90 (Broad Street) and Fruge Street. However, these few blocks of US 171 soon became part of LA 14. The opening of I-10 through Downtown Lake Charles in April 1963 resulted in the re-routing of US 90 onto Fruge Street, and the southern terminus of US 171 was shifted accordingly. The I-10 interchange on US 171 was partially opened to traffic at this time. Its full opening would occur in February 1964 when the interstate was completed eastward to US 165 at Iowa. In the mid-1960s, four-lane sections of US 171 were also opened to facilitate traffic through two smaller cities. In Mansfield, Washington Avenue was widened and extended southwest, improving the routes of both US 84 and US 171 through town and eliminating two right-angle turns. In DeRidder, a one-way pair was used after Mahlon Street was improved and extended eastward, taking northbound US 171 (and westbound US 190) traffic off of parallel 1st Street.

Two further improvements during the 1960s involved new bridges along the route. The first was a replacement of the Anacoco Creek bridge in 1967 with a higher span. This was necessitated by an impoundment of the creek four years earlier that created the recreational Vernon Lake. A more substantial project completed in 1969 overhauled the two most significant water crossings on US 171, the English Bayou and Calcasieu River bridges between Lake Charles and Moss Bluff. The original narrow two-lane spans dating from the 1920s were replaced with four-lane spans on a new four-lane alignment further west. (Though the bridges were demolished in 1973, the land portions of the route still exist as Old US 171, partially as local roads leading to public boat launches and partially on private property.) In 1972, the remaining gap in the four-lane alignment in Lake Charles between Fruge Street and the new bridge approach was widened. Central to this project was the twinning of the railroad overpass south of I-10.

Completing the four-lane highway
Since the 1970s, construction projects on US 171 have mainly focused on completing the highway to four-lane capacity throughout its entire length. This was cited by commercial and political interests as crucial for the economic development of the corridor and a necessary step in preventing the loss of economic opportunities to the US 59 corridor in East Texas. Leesville was the last urban area through which the highway was widened, despite the Army personnel at Fort Johnson having pushed the Louisiana Department of Highways for this improvement over several decades. Four-lane segments through the Leesville area were completed approximately as follows: through New Llano and north toward LA 467 in 1975, south from New Llano toward Pickering in 1978,  further south to DeRidder in 1981,  and finally northward through the city of Leesville in 1982. This last segment involved the creation of a one-way pair using an improved 6th Street to carry southbound traffic and the construction of a parallel railroad underpass. US 171 was further widened northward from Leesville to Anacoco in 1986. Meanwhile in Shreveport, the highway was widened southward from the Caddo–DeSoto parish line through Stonewall in 1981, joining with the four lanes extending from there to LA 5 in Gloster constructed in the late 1970s. The final highway interchange on US 171 was opened between 1981 and 1983 when the Inner Loop Expressway (LA 3132) was completed through the area.

The above projects left two long segments of two-lane pavement remaining on US 171, extending from Moss Bluff to DeRidder and from Anacoco to Gloster. The widening of these mostly rural stretches was eventually accomplished as a major component of the Transportation Infrastructure Model for Economic Development program. Approved by the Louisiana Legislature in 1989 and declared as the "single largest transportation program in state history," the TIMED program was initially funded from a 4¢ per gallon gasoline tax which allowed an estimated completion date around 2031. After falling far behind schedule by the late 1990s, the legislature approved the first of several bond measures to fast-track the program. The widening of US 171 was divided into 23 projects totaling approximately 121 mi and carried out between 1990 and 2010. As before, the four-lane alignment mostly followed the established two-lane with minor deviations to straighten various curves in the roadbed. This is most evident between Mansfield and Grand Cane, where the entire route was reconstructed and straightened.

However, more significant changes were carried out in a few locations. A new route through Many bypassed the downtown area, discontinuing the concurrency with LA 6. The neighboring town of Zwolle was bypassed altogether with a new alignment constructed around its northeast side. In this case, the old route through town was retained as US 171 Bus., which was designated in 2008. The route through Mansfield was also streamlined via the widening and extension of Jenkins Street, which benefitted the concurrent US 84 as well. Here, the original four-lane section of Washington Avenue was retained as US 84 Bus. These improvements eliminated all but one right-angle turn along the entirety of US 171, located in the center of DeRidder. Finally, the two-lane railroad underpass at Trenton was replaced by a twin-span overpass located about 1.5 mi to the south. The old crossing remains in service as a local road called Old US 171 or Trenton Road. After a total expenditure of $650 million, US 171 was completed as a four-lane highway when a 6.6 mi section between Florien and Many was opened to traffic in July 2010.

The latest improvement to US 171 involved the installation of a roundabout at the northern end of Leesville. It was the first roundabout to be constructed in the seven parishes forming the state highway department's District No. 8. Located at the junction with eastbound LA 8/LA 28, the junction was previously a signalized T-intersection that was the site of numerous accidents and frequent traffic pileups. Construction began in October 2010, and the project was completed with a ribbon-cutting by Governor Bobby Jindal on August 5, 2011 after an expenditure of $2.1 million.

Business route
U.S. Highway 171 Business (US 171 Bus.) runs 3.11 mi in a general north–south direction through Zwolle, a town in Sabine Parish. It follows the original two-lane route of US 171 before the completion of a four-lane bypass in 2008.

From the southeast, US 171 Bus. begins at a junction with mainline US 171 just east of the Zwolle corporate limits. The route heads west into town on North Main Street alongside the Kansas City Southern Railway (KCS) line. In the center of town, signage directs motorists south on Obrie Street (LA 475) toward North Toledo Bend State Park. US 171 Bus. turns north onto the same thoroughfare and proceeds out of the downtown area. At an intersection with Willow Street and Old Pleasant Hill Road, the route begins an S-curve that terminates at a second junction with mainline US 171 at the north end of town.

US 171 Bus. is classified as a rural principal arterial by the Louisiana Department of Transportation and Development (La DOTD). The average daily traffic volume in 2013 ranged from 4,200 to 6,000 vehicles. The posted speed limit ranges from 35 mph through the center of town to 45 mph near the junctions with mainline US 171 at either end of the route.

Major intersections

title: U.S. Route 171


text:
Metropolitan State Hospital (California)

Metropolitan State Hospital is an American public hospital specializing in psychiatric care for those with mental health concerns, located at 11400 Norwalk Blvd in the city of Norwalk in Los Angeles County, California. As of August 2016 it had 780 patients.

Services
The hospital is operated by the California Department of State Hospitals. Currently it admits four different types of categories for patient intake. The four categories being; incompetent to stand trial (PC 1370), offender with a mental health disorder (PCS 2962/2972), not guilty by reason of insanity (PC 1026), and conservatorship Lanterman-Petris-Short (LPS) Act. The hospital is unique among state facilities serving the mental health patients in that it admits a large proportion of acutely ill psychiatric patients resulting in a rapid turnover rate and a shorter length of stay.

From the 1980s to 1990's, the facility had an Intensive Treatment and Research Unit, which was a male inpatient facility for chronically ill persons with mental disabilities, and was co-sponsored by Metropolitan State Hospital and the University of California, Irvine School of Medicine. The program was a major component of research conducted by the two institutions with the treatment focus directed toward the chronically refractory and treatment-resistant patient.

Specific patient programming utilizes individual and group therapy, occupational and rehabilitation therapies and the management of social and financial problems by developing linkages back to the community. Basic treatment services include psychiatry, psychology, social services, rehabilitation therapies, medical, nursing, pharmacy, dietary, etc.

History
In June 1913, based on a study by a group of Los Angeles County Psychiatrists who had projected a need for a Los Angeles area hospital, Governor Hiram Johnson signed Senate Bill No. 739 on June 7, 1913 appropriating authority and funds to create a second state hospital in Southern California for the reception and treatment of California's increasing population of persons with psychiatric disabilities. Three potential sites for the new facility were considered: Beverly Hills, Signal Hill, and Norwalk. The decision to place the hospital in Norwalk was prompted primarily because of its location, with easy access to good roads and railroad service. At its largest, the hospital had a total of 392.30 acres.

The hospital was self-sufficient in its early days. A dairy, garden, pigs, and cows produced income and food products that could be used by the staff and patients. The farm also kept food costs at a minimum, at a time when milk prices alone had increased from 17 cents per gallon in 1916 to 32 cents in 1918 due to the ongoing war.

As the area around the hospital became developed after World War II and the city of Norwalk grew around it, many changes have taken place. The biggest change in patient care has come from the development of psychotropic medications, increased therapies and new community standards. The hospital has since consolidated its grounds and facilities of tudor styled dormitories into its present 162 acre.

In 1975, the hospital was the subject of a black-and-white documentary from film makers Richard Cohen and Kevin Rafferty titled Hurry Tomorrow, which alleged coercive drugging of patients with the sedatives Chlorpromazine and Prolixin. In December, 1976 The CBS Evening News with Walter Cronkite ran a story about patient deaths at Metropolitan and Camarillo State Hospitals, and the story featured scenes from Hurry Tomorrow.

Accreditation
Metropolitan State Hospital is accredited by the Joint Commission (formerly the Joint Commission for the Accreditation of Healthcare Organizations) and certified by the Healthcare Finance Administration. Accreditation is a voluntary process. Medical and psychiatric facilities across the country must request to be surveyed with results evaluated against nationally recognized standards of care.


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Metropolitan State Hospital (Massachusetts)

The Metropolitan State Hospital was an American public hospital for the mentally ill, on grounds that extended across parts of Waltham, Lexington, and Belmont, Massachusetts. Founded in 1927, it was at one time the largest and most modern facility of its type in Massachusetts. It was closed in January 1992 as a result of the state's cost-cutting policy of closing its mental hospitals and moving patients into private and community-based settings. The main complex of buildings has subsequently been redeveloped into apartments. The hospital campus was listed on the National Register of Historic Places 1994. The property also housed the Gaebler Children's Center for mentally ill youth.

History
The Metropolitan State Hospital's founding originated in legislation passed by the state in 1900, mandating that the state take over care for the mentally ill, which had in some cases only been handled at the local level. Site selection for a facility in the Greater Boston area, where the demand for additional space was the greatest, took until 1926. Ground was broken on the hospital buildings in 1926, and the facility was formally dedicated in 1928, and opened on October 29, 1930. Construction continued until 1935, with some stages under Works Progress Administration supervision. The complex cost $1.8 million and was considered the most modern mental health facility in the country.

The hospital's design was reflective of the third stage of development of facilities for the mentally ill, after the Kirkbride Plan and the cottage/colony system. It also reflected the advent of roads rather than railroads as major transport arteries, as it was not located near any railroad lines. Its buildings were designed in the Colonial Revival style by Gordon Robb, with landscaping, based on principles laid down by the Olmsted Brothers, by R. Hayward Loring. At its peak, the facility had a patient population of nearly 2,000. The grounds included the Met-Fern cemetery, a burial site it shared with the Fernald School.

In 1978, Metropolitan State patient Anne Marie Davee was murdered by another patient, Melvin W. Wilson.

The facility was closed in 1992 during a deinstitutionalization movement when most state mental hospitals in Massachusetts shut down and patients were placed in smaller group settings. The property was unused until redevelopment began in 2007.

Redevelopment and open space
In 2007, some of the complex's residential wards located in the Lexington portion of the property were adaptively repurposed for conventional residential use as part of larger apartment complex development known as Avalon at Lexington Hills. The Administration Building, pictured above, stands in Waltham. A number of the former hospital buildings were incorporated into the new development including the former Kline Hall which now houses marketing offices, Lexington's cable access station, an auditorium and a fitness area. A large concrete relief from the medical-surgical building has been installed outside the building as a memorial to the state hospital. The extensive wooded grounds are open to the public and protected in perpetuity from further development. The trails include part of the Western Greenway open space, connecting to the Rock Meadow conservation area in Belmont to the east and, according to plans, in 2009, to the Middlesex County Hospital area to the west.


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Wikipedia talk:Selected anniversaries/April 9

 * 193 - Septimus Severus is proclaimed Roman Emperor by the army in Illyricum (in the Balkans).
 * 1336 - Tamerlane is born in Transoxiana.
 * 1241 - Battle of Liegnitz: Mongol forces defeats the Polish and German armies.
 * 1865 - American Civil War: Robert E. Lee surrenders the Army of Northern Virginia (26,765 troops) to Ulysses S. Grant at Appomattox Courthouse, Virginia, effectively ending the war.
 * 1867 - Alaska purchase: By a single vote, the United States Senate ratifies a treaty with Russia for the purchase of Alaska.
 * 1916 - World War I: Battle of Verdun - German forces launch their third offensive of the battle.
 * 1940 - World War II: Germany invades Denmark and Norway.
 * 1942 - World War II: Bataan Death March begins for the United States forces who surrender on Corregidor.
 * 1947 - The Glazier-Higgins-Woodward tornadoes kill 181 and injure 970 in Texas, Oklahoma, and Kansas.
 * 1959 - Mercury program: NASA announces the selection of the United States' first seven astronauts which the news media quickly dub the "Mercury 7".
 * 1967 - The first Boeing 737 (a 100 series) takes its maiden flight.
 * 1991 - Georgia declares its independence from the Soviet Union.
 * 1992 - Manuel Noriega is convicted of eight crimes.
 * 1999 - Ismail Omar Guelleh is elected president of Djibouti.
 * 1999 - Nigerian President Ibrahim Baré Maïnassara is assassinated.
 * 2002 - The Queen Mother of the United Kingdom, Elizabeth Bowes-Lyon has her funeral at Westminster Abbey.
 * 2003 - The Ba'ath regime headed by Saddam Hussein in Iraq is deposed.
 * 2006 - Education and Sharing day

why is he important? Maybe I'm too optimistic, but most of the other people on here are either famous because of a good deed he or she is solely responsible for. (This guy is part of one) I wouldn't object to having that Columbine happened on the page for April 20th. (It's already there.) There are events that are not in the most positive light here too, which isn't a big deal either. Also if a person doesn't have an article (or a very brief one), doesn't that say something? That's why I removed this one too: He can be put back once he has his own article. Sometimes people are important only for a year or too, and then are pretty much forgotten. This article should celebrate people that will be remembered for a long time (like 50 years). I'm not the only one who thinks he's not important: http://www.bellaonline.com/articles/art19344.asp
 * 1981 - Eric Harris, one of the Columbine High School massacre gunmen (d. 1999)
 * 1987 - Jessie McCartney, member of boy band Dreamstreet and actor WB11's Summerland

2012 notes
— howcheng  {chat} 10:30, 8 April 2012 (UTC)
 * Deleted: Septimius Severus (appears on February 4); Chicago Seven (appears on February 18)
 * Omitted: Battle of Appomattox Court House; Battle of Vimy Ridge (ineligible—TFA for 2012); Deir Yassin massacre; Ibrahim Baré Maïnassara; Firdos Square statue destruction
 * Included: Henry V of England (3rd appearance, last in 2005; previously was on March 20); Édouard-Léon Scott de Martinville (first appearance); Marian Anderson (first appearance); Bataan Death March (4th appearance, last in 2007; rescued from Ineligible); Boeing 737 (2nd appearance, last in 2009; rescued from Ineligible)

2013 notes
— howcheng  {chat} 05:39, 8 April 2013 (UTC)
 * Moved to Ineligible: Battle of Appomattox Court House (Civil War-related picture as POTD for 2013)
 * Rescued from Ineligible (unused): Wedding of Charles, Prince of Wales, and Camilla Parker Bowles
 * Omitted: Édouard-Léon Scott de Martinville; Marian Anderson; Bataan Death March; Boeing 737
 * Included: Bataan Day in the Philippines (rescued from Ineligible); Battle of Vimy Ridge (6th appearance, last in 2011); Vidkun Quisling (2nd appearance, last in 2005); Mercury Seven (first appearance); Firdos Square statue destruction (2nd appearance, last in 2011; 10th anniversary)
 * Repeats: Henry V of England (2nd consecutive appearance, 4 total; 600th anniversary)

2014 notes
— howcheng  {chat} 06:24, 8 April 2014 (UTC)
 * Moved to Ineligible: Boeing 737 (maintenance)
 * Rescued from Ineligible (unused): Battle of Appomattox Court House; 1947 Glazier–Higgins–Woodward tornadoes
 * New articles (unused): Journey of Reconciliation
 * Omitted: Henry V of England (ineligible—maintenance); Battle of Vimy Ridge; Mercury Seven; Firdos Square statue destruction
 * Included: Aníbal Milhais/Battle of the Lys (1918) (both: first appearance); Marian Anderson (2nd appearance, last in 2012; 75th anniversary); Ibrahim Baré Maïnassara (5th appearance, last in 2012); Wedding of Charles, Prince of Wales, and Camilla Parker Bowles (3rd appearance, last in 2010)
 * Repeats: Édouard-Léon Scott de Martinville (3rd consecutive appearance, 3 total)

2015 notes
— howcheng  {chat} 07:29, 7 April 2015 (UTC)
 * Omitted: Édouard-Léon Scott de Martinville; Ibrahim Baré Maïnassara
 * Included: Vidkun Quisling (3rd appearance, last in 2013; 75th anniversary); Boeing 737 (3rd appearance, last in 2012; rescued from Ineligible)
 * Repeats: Aníbal Milhais/Battle of the Lys (1918) (both: 2nd appearance, 2 total); Marian Anderson (2nd consecutive appearance, 3 total); Wedding of Charles, Prince of Wales, and Camilla Parker Bowles (2nd consecutive appearance, 4 total; 10th anniversary)
 * Note: Battle of Appomattox Court House has its 150th anniversary, but Ulysses S. Grant is TFA for 2015

2016 notes
— howcheng  {chat} 16:11, 7 April 2016 (UTC)
 * New articles (unused): German cruiser Admiral Scheer
 * Omitted: Marian Anderson; Vidkun Quisling; Boeing 737; Wedding of Charles, Prince of Wales, and Camilla Parker Bowles
 * Included: Édouard-Léon Scott de Martinville (4th appearance, last in 2014); Battle of Appomattox Court House (6th appearance, last in 2011); Deir Yassin massacre (2nd appearance, last in 2011); Firdos Square statue destruction (3rd appearance, last in 2013)
 * Repeats: Aníbal Milhais/Battle of the Lys (1918) (both: 3rd appearance, 3 total)

2017 notes
— howcheng  {chat} 01:52, 10 April 2017 (UTC)
 * New articles (unused): Civil Rights Act of 1866
 * Moved to Ineligible: Marian Anderson (maintenance); 1947 Glazier–Higgins–Woodward tornadoes (maintenance); Mercury Seven (maintenance)
 * Omitted: Vimy Ridge Day (ineligible—maintenance); Bataan Day (ineligible—maintenance); Battle of Appomattox Court House; Aníbal Milhais/Battle of the Lys (1918); Deir Yassin massacre; Firdos Square statue destruction
 * Included: Battle of Vimy Ridge (7th appearance, last in 2013; 100th anniversary); Journey of Reconciliation (first appearance; 70th anniversary); Boeing 737 (4th appearance, last in 2015; 50th anniversary); Wedding of Charles, Prince of Wales, and Camilla Parker Bowles (5th appearance, last in 2015); Francis Bacon (first appearance); Jørn Utzon (first appearance); Mary Jackson (engineer) (first appearance)
 * Repeats: Édouard-Léon Scott de Martinville (2nd consecutive appearance, 5 total)

2018 notes
— howcheng  {chat} 07:00, 9 April 2018 (UTC)
 * Moved to Ineligible: Aníbal Milhais (maintenance); Muhammad Baqir al-Sadr (maintenance)
 * Omitted: Battle of Vimy Ridge; Journey of Reconciliation; Boeing 737; Wedding of Charles, Prince of Wales, and Camilla Parker Bowles; Francis Bacon; Jørn Utzon; Mary Jackson (engineer)
 * Included: Civil Rights Act of 1866 (first appearance); Vidkun Quisling (4th appearance, last in 2015); Deir Yassin massacre (3rd appearance, last in 2016; 70th anniversary); Firdos Square statue destruction (4th appearance, last in 2016); Samuel Fritz (first appearance); Isambard Kingdom Brunel (first appearance); Vilhelm Bjerknes (first appearance)
 * Repeats: Édouard-Léon Scott de Martinville (3rd consecutive appearance, 8 total)

2019 notes
— howcheng  {chat} 16:14, 9 April 2019 (UTC)
 * Moved to Ineligible: Battle of Appomattox Court House (maintenance)
 * Rescued from Ineligible (unused): 1947 Glazier–Higgins–Woodward tornadoes
 * Omitted: Édouard-Léon Scott de Martinville; Vidkun Quisling; Deir Yassin massacre; Firdos Square statue destruction (ineligible—maintenance); Samuel Fritz; Isambard Kingdom Brunel; Vilhelm Bjerknes
 * Included: Battle of Vimy Ridge (8th appearance, last in 2017); Bataan Death March (5th appearance, last in 2012); Mercury Seven (2nd appearance, last in 2012; rescued from Ineligible; 60th anniversary); Ibrahim Baré Maïnassara (6th appearance, last in 2014; rescued from Ineligible); François Rabelais (first appearance); Charles Proteus Steinmetz (first appearance); Natascha Engel (first appearance)
 * Repeats: Civil Rights Act of 1866 (2nd consecutive appearance, 2 total)

Muhammad Baqir al-Sadr
Hey, do you think the blurb for Muhammad Baqir al-Sadr would be suitable for inclusion this year? -- M h hossein   talk 07:31, 21 March 2020 (UTC)
 * I don't think the "Scholarship" section is good enough. Sorry. — howcheng  {chat} 16:31, 21 March 2020 (UTC)
 * Thanks for the insight. I should have noticed that myself. I will work on the section and make it ready to become qualified. -- M h hossein   talk 06:43, 22 March 2020 (UTC)
 * I have added some more reliable sources for the sake of the verfiability. Can you evaluate the improvements please? The article had never been on the main page. -- M h hossein   talk 07:02, 24 March 2020 (UTC)
 * Look like it's good to go. Nice work! — howcheng  {chat} 16:15, 24 March 2020 (UTC)

2020 notes
— howcheng  {chat} 16:38, 10 April 2020 (UTC)
 * New articles (unused): Jenna Jameson; Nick Adenhart
 * Omitted: Civil Rights Act of 1866; Battle of Vimy Ridge; Bataan Death March; Mercury Seven; Ibrahim Baré Maïnassara; François Rabelais (ineligible—maintenance); Charles Proteus Steinmetz; Natascha Engel
 * Included: Édouard-Léon Scott de Martinville (7th appearance, last in 2018); Vidkun Quisling (5th appearance, last in 2018; 80th anniversary); German cruiser Admiral Scheer (first appearance; 75th anniversary); Muhammad Baqir al-Sadr (first appearance; 40th anniversary; rescued from Ineligible); Wedding of Prince Charles and Camilla Parker Bowles (6th appearance, last in 2017); Pope Benedict VIII (first appearance); Henrik Rysensteen (first appearance); Jackie Evancho (first appearance; 20th birthday)

2021 notes
— howcheng  {chat} 18:05, 10 April 2021 (UTC)
 * Deleted: François Rabelais (birth/death dates uncertain)
 * Moved to Ineligible: Francis Bacon (maintenance)
 * Omitted: Édouard-Léon Scott de Martinville; Vidkun Quisling; German cruiser Admiral Scheer; Muhammad Baqir al-Sadr; Wedding of Prince Charles and Camilla Parker Bowles; Pope Benedict VIII; Henrik Rysensteen; Jackie Evancho
 * Included: Civil Rights Act of 1866 (3rd appearance, last in 2019); Battle of Vimy Ridge (9th appearance, last in 2019); Deir Yassin massacre (4th appearance, last in 2018); Boeing 737 (5th appearance, last in 2017); Morteza Avini (first appearance); Jean Quintin (first appearance); Mary Jackson (engineer) (2nd appearance, last in 2017; 100th birthday); Vilhelm Bjerknes (2nd appearance, last in 2018; 70th anniversary)

2022 notes
— howcheng  {chat} 07:12, 10 April 2022 (UTC)
 * Rescued from Ineligible (unused): Marian Anderson
 * Omitted: Civil Rights Act of 1866; Deir Yassin massacre; Boeing 737; Morteza Avini; Jean Quintin; Mary Jackson (engineer); Vilhelm Bjerknes
 * Included: Day of Valor (rescued from Ineligible); Édouard-Léon Scott de Martinville (8th appearance, last in 2020); Bataan Death March (6th appearance, last in 2019; 80th anniversary); Muhammad Baqir al-Sadr (2nd appearance, last in 2020); Ibrahim Baré Maïnassara (7th appearance, last in 2019); Al-Muqtafi (first appearance); Charles Proteus Steinmetz (2nd appearance, last in 2019); Nikki Grahame (first appearance)
 * Repeats: Battle of Vimy Ridge (2nd consecutive appearance, 10 total)


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Effective nuclear charge

In atomic physics, the effective nuclear charge is the actual amount of positive (nuclear) charge experienced by an electron in a multi-electron atom. The term "effective" is used because the shielding effect of negatively charged electrons prevent higher energy electrons from experiencing the full nuclear charge of the nucleus due to the repelling effect of inner layer. The effective nuclear charge experienced by an electron is also called the core charge. It is possible to determine the strength of the nuclear charge by the oxidation number of the atom. Most of the physical and chemical properties of the elements can be explained on the basis of electronic configuration. Consider the behavior of ionization energies in the periodic table. It is known that the magnitude of ionization potential depends upon the following factors:

 * 1) Size of atom;
 * 2) The nuclear charge;
 * 3) The screening effect of the inner shells, and
 * 4) The extent to which the outermost electron penetrates into the charge cloud set up by the inner lying electron.

In the periodic table, effective nuclear charge decreases down a group and increases left to right across a period.

Description
The effective atomic number Zeff, (sometimes referred to as the effective nuclear charge) of an atom is the number of protons that an electron in the element effectively 'sees' due to screening by inner-shell electrons. It is a measure of the electrostatic interaction between the negatively charged electrons and positively charged protons in the atom. One can view the electrons in an atom as being 'stacked' by energy outside the nucleus; the lowest energy electrons (such as the 1s and 2s electrons) occupy the space closest to the nucleus, and electrons of higher energy are located further from the nucleus.

The binding energy of an electron, or the energy needed to remove the electron from the atom, is a function of the electrostatic interaction between the negatively charged electrons and the positively charged nucleus. For instance, in iron (atomic number 26), the nucleus contains 26 protons. The electrons that are closest to the nucleus will 'see' nearly all of them. However, electrons further away are screened from the nucleus by other electrons in between, and feel less electrostatic interaction as a result. The 1s electron of iron (the closest one to the nucleus) sees an effective atomic number (number of protons) of 25. The reason why it is not 26 is that some of the electrons in the atom end up repelling the others, giving a net lower electrostatic interaction with the nucleus. One way of envisioning this effect is to imagine the 1s electron sitting on one side of the 26 protons in the nucleus, with another electron sitting on the other side; each electron will feel less than the attractive force of 26 protons because the other electron contributes a repelling force. The 4s electrons in iron, which are furthest from the nucleus, feel an effective atomic number of only 5.43 because of the 25 electrons in between it and the nucleus screening the charge.

Effective atomic numbers are useful not only in understanding why electrons further from the nucleus are so much more weakly bound than those closer to the nucleus, but also because they can tell us when to use simplified methods of calculating other properties and interactions. For instance, lithium, atomic number 3, has two electrons in the 1s shell and one in the 2s shell. Because the two 1s electrons screen the protons to give an effective atomic number for the 2s electron close to 1, we can treat this 2s valence electron with a hydrogenic model.

Mathematically, the effective atomic number Zeff can be calculated using methods known as "self-consistent field" calculations, but in simplified situations is just taken as the atomic number minus the number of electrons between the nucleus and the electron being considered.

Calculations
In an atom with one electron, that electron experiences the full charge of the positive nucleus. In this case, the effective nuclear charge can be calculated by Coulomb's law.

However, in an atom with many electrons, the outer electrons are simultaneously attracted to the positive nucleus and repelled by the negatively charged electrons. The effective nuclear charge on such an electron is given by the following equation: $$Z_\mathrm{eff} = Z - S $$ where
 * Z is the number of protons in the nucleus (atomic number), and
 * S is the shielding constant.

S can be found by the systematic application of various rule sets.

Slater's rules
The simplest method for determining the shielding constant for a given electron is the use of "Slater's rules", devised by John C. Slater, and published in 1930. These algebraic rules are significantly simpler than finding shielding constants using ab initio calculation.

Hartree–Fock method
A more theoretically justified method is to calculate the shielding constant using the Hartree-Fock method. Douglas Hartree defined the effective Z of a Hartree–Fock orbital to be: $$Z_\mathrm{eff} = \frac{\langle r\rangle_{\rm H}}{\langle r\rangle_Z} $$ where
 * $$\langle r\rangle_{\rm H}$$ is the mean radius of the orbital for hydrogen, and
 * $$\langle r\rangle_Z$$ is the mean radius of the orbital for a proton configuration with nuclear charge Z.

Values
Updated effective nuclear charge values were provided by Clementi et al. in 1963 and 1967. In their work, screening constants were optimized to produce effective nuclear charge values that agree with SCF calculations. Though useful as a predictive model, the resulting screening constants contain little chemical insight as a qualitative model of atomic structure.

Comparison with nuclear charge
Nuclear charge is the electric charge of a nucleus of an atom, equal to the number of protons in the nucleus times the elementary charge. In contrast, the effective nuclear charge is the attractive positive charge of nuclear protons acting on valence electrons, which is always less than the total number of protons present in a nucleus due to the shielding effect.

Resources

 * Brown, Theodore; intekhab khan, H.E.; & Bursten, Bruce (2002). Chemistry: The Central Science (8th revised edition). Upper Saddle River, New Jersey 07458: Prentice-Hall. ISBN 0-13-061142-5.

title: Effective nuclear charge