Checkers - The Fundamentals of the Game

 
Checkers is a game for two persons played on a board marked in 64 small squares of alternate colors (light and dark) in eight rows of eight squares each. Each contestant is provided with 12 disks, called men or checkers; the object is to move these pieces diagonally across the board in such a way as to capture all the opponent's men or block their progress. Because of the simplicity of its fundamentals, checkers is a popular children's game. At the expert's level, checkers ranks in profundity with the complicated game of chess.


The players, designated as black and white, place the board between them so that each has a double corner of dark squares at his or her right. The players arrange their men on the first three rows of dark squares as shown in the accompanying illustration. The notation used in describing the game is based on numbering the squares as in the illustration. A move is denoted by the number of the square from which a piece starts, followed by the number of the square moved to, joined by a hyphen. In the notation, black and white moves alternate, and no distinction is made for color or captures.
Black makes the first move, and white counters. (There are 47 playable combinations of these first two moves.) Players alternate thereafter, moving on the dark squares only. The move is diagonally forward one square, if that square is vacant. For example, black might start by playing 11-15, or 9-13; and white might reply 22-18, or 24-20. A man may not move to an occupied square, but it may jump over and capture an adverse man on an adjacent square, if the square beyond is vacant.

For example, if black opens 11-15 and white counters 22-18, then black must jump 15-22 and remove white's man on 18. White in turn must jump either 26-17 or 25-18, and remove black's man on 22. If a jumping piece lands on a square from which another jump is possible it must continue to jump until it runs out of captures. A player must make a capturing move, if one is possible, but may choose if there is more than one. At the outset all checkers are single men.

The dark squares farthest from a player form the king row. A single man reaching one of these squares is crowned king by the opponent. The promotion is made by placing a second checker of the same color on top of the single one. A king may move both forward or backward one move at a time and jump one or more pieces in either or both directions. If a single man reaches the king row by capture, the turn to play ends with the crowning.

The winner is the first player to leave the adversary without a move, either by capturing or blocking all of his men. A game is drawn when both contestants agree that neither has a prospect of winning.

How to Play Go? Is It That Hard? Not Really...

 
Go is a board game for two players, originated in China about 2300 B.C. and was taken up in Japan about 735 A.D. The game is now also popular outside Asia. The rules, however, have never been codified. Go is played on the 361 intersections (points) of a grid having 19 vertical and 19 horizontal lines. One player starts with 181 circular black pieces, or men; his opponent has 180 white men. When the players are of unequal ability, a handicap of 2 to 9 points is given the weaker.


Each player in turn places one man on any unoccupied intersection, from which it never moves. Any point or space surrounded by men of one color belongs to that player. When players agree that ownership of all points on the board has been established, each one's score is the total of his enclosed points less the number of his men lost by capture.

Two men are "connected" if they are adjacent on the same vertical or horizontal line. (The white men are connected and the blacks are not in group I in the grid shown here.) Men "live" as long as they are connected to at least one vacant intersection; they "die" if they are completely enclosed. (White men are dead in II, III, IV, and V.) If a player disputes ownership, he must invade the adversary's space and establish a live group in the area. Captured players are removed from the board at once; doomed forces are removed at the end of play. Vacant points connected to both colors belong to neither side.

In group VI, the whites are doomed; black wins men and space by playing H 14 and killing the white forces. Whites in VII are forever safe because black loses a man by playing G 7 or H 6, and neither play kills the white men. An eye is a point surrounded by 4 men of the same color. A force with two separate eyes is safe. In VIII, black saves his men and space with N 7; if it is white's move he can win the group starting with N 7. Because of the many possible series of moves, Go is a most complicated board game.

All About Marbles - History and Games

 
Marbles are brightly colored and polished balls of glass or agate used in a wide variety of games for children. In many countries, marbles are made of wood, baked clay, plastics, obsidian, or onyx. In the Middle East, marbles games are even played with the knucklebones of sheep. Thousands of marbles games are known. Some have rigidly prescribed rules, such as Ringer, the official game of the National Marbles Tournament played each year at Wildwood-by-the-Sea in New Jersey. Others, with rules improvised on the spot, have spawned such familiar games as bagatelle, bowling, golf, billiards, Chinese checkers, and the pinball machine.


History

Marbles and its games are ancient. Marbles games are known to have been played in the civilizations of the Nile Valley and the Tigris and Euphrates valleys and then spread to Africa, Greece, Sicily, and Rome. Small balls of clay, flint, or stone have been dug up in the tombs of the pharaohs and in caves in Europe. Pre-Christian terra cottas and other statuary often depict children playing at knucklebones or astragals, which are thought to be forerunners of marbles games. Marbles also have been discovered in the digs of the Mound Builder Indians of Mississippi, and the Aztecs played a form of marbles.

Some biblical scholars suggest that David smote Goliath with a marble. Ovid mentions a marbles-like game played with polished nuts. The Roman legions brought marbles to Britain and to northern Europe and the Germanic tribes. English historians of games mention marbles as being played by the Emperor Augustus and trace their existence to Elizabethan times. Good Friday in England once was celebrated as "Marbles Day," although such frivolity was forbidden at Oxford and at the Great Hall at Westminster.

From Britain the movement of marble games coincided with the spread of empire. English marbles crossed the Atlantic to America, and the marbles played in the United States are derivations of English games such as Taws, Cherry Put, Boss-Out, and Lag. George Washington was a marbles player, as were Thomas Jefferson and John Quincy Adams, and Abraham Lincoln was adept at a game called Old Bowler.

Games
The most famous marbles game is Ringer. Thirteen target marbles are placed in the form of a cross in the middle of a ring 10 feet (3 meters) in diamether. Two shooters compete by "knuckling down" at the edge of the ring and attempting to knock target marbles out of the circle. The first to get seven out wins. If a player knocks one out, he gets another shot, and so on.

In the national tournament held each year, there are both girl and boy champions. Each winner receives a genuine agate shooter, a rare item made only in Germany.

Other games are less structured but just as competitive. Some versions of Ringer use squares or oblongs as well as circles, or holes dug in the ground, and the stakes are always your competitors' marbles. Some games are played like miniature golf. In gambling games, players try to roll marbles into tiny openings cut into the side of a box, with the "house" collecting all misses and paying good odds for all hits. These varieties, traditionally called "keepsies," remain popular in many parts of America.

Commercial Uses of Cryptology

 
Outside of national security, the most important use of cryptology today is in electronic commerce (or e-commerce). New cryptosystems, called public-key ciphers, permit the secure transmission of credit-card numbers from a buyer to a seller without their having had to exchange keys in advance.


In addition the growth of computer and satellite communications, which has escalated the potential for hacking and interception, has made it ever more necessary for businesses to protect their data. Because new cryptosystems are cheap and easy to use, multinational corporations are increasingly encrypting their satellite messages, e-mail, and data banks.

An automated teller machine (ATM) encrypts the account numbers and requests that it transmits to the bank's mainframe, which similarly encrypts the balances and withdrawal authorizations that it sends back to the ATM. Subscription television jumbles its signals so only those who have paid for a decoder can receive clear pictures.

Perhaps out of fear of negative publicity if exposed, companies have rarely intercepted a competitor's messages. Encrypted bank messages are not known to have been solved, probably because there are easier ways to get the money. At least one government has read at least one oil company's encrypted messages, however, and used the information in bargaining over an exploration contract.

Cryptology in Modern Diplomatic and Military Signals Intelligence

 
The most important single encrypted message that was intercepted and solved was the Zimmermann telegram, named for the German foreign minister who sent it. During World War I Arthur Zimmermann, fearing American belligerency because German U-boats (submarines) had been ordered to sink U.S. ships, cabled Mexico with a proposition. If Mexico would wage war upon the United States, Mexico would get back its "lost territory" of Texas, New Mexico, and Arizona. On Jan. 17, 1917, Great Britain intercepted and, several days later, solved the coded German message. Britain passed it on to Pres. Woodrow Wilson, who made it public. The nation's outrage at Germany's presumptuousness in promising to give away a part of America crystallized in a declaration of war a month later, helping to defeat Germany and turning the United States into a major power.


Also of great significance during World War I was the Russian failure to distribute "cryptosystems" to some army units in 1914. The messages that the Germans intercepted were thus uncoded. The Germans used them to encircle and destroy a Russian army at the Battle of Tannenberg (August 25–30). Although the Russians later enciphered their messages, the Germans easily solved them, greatly contributing to Germany's defeat of czarist Russia. Thus German signals intelligence helped deliver Russia to the Bolsheviks.

During World War II massive cryptanalysis of German military and naval cryptograms helped the Allies win that conflict. Solutions of German naval messages that were enciphered using the cipher machine Enigma revealed orders to and reports from U-boats at sea. This intelligence enabled convoys traveling from America to Britain to detour around the "wolf packs" (groups of submarines that made coordinated attacks on shipping). Later it permitted Allied warships to pinpoint the submarines in the vastness of the ocean and sink them.

In the land campaigns in North Africa and Europe, the breaking of German Air Force and Army messages enciphered in Enigma, among other systems, prepared the Allies to win many battles. In Normandy on Aug. 6, 1944, for example, a decoded message revealed that the Germans would soon launch a heavy attack from around Mortain with fighter plane protection. Owing in part to this warning, the U.S. 30th Infantry Division repelled the onslaught.

Likewise, American "codebreakers" significantly shortened World War II in the Pacific Ocean. The reading of coded Japanese naval messages told the Americans as much about some Japanese plans as the captains of Japanese naval vessels knew and enabled them to ambush the Japanese fleet at Midway Island in the central Pacific on June 4, 1942. The battle there turned the tide of the war in the Pacific. Other solutions facilitated American submarines' sinking of Japanese cargo ships, bringing the island empire to the verge of collapse.

While the solution of the chief Japanese diplomatic cipher machine, called PURPLE by the Americans, did not avert the surprise of Pearl Harbor -because no messages even hinting at the attack ever went to the diplomats- it contributed enormously to wartime intelligence through the reading of reports sent home by Japanese diplomats in Berlin. These revealed Adolf Hitler's thoughts and plans. The Soviet Union, too, broke this machine. Its solutions disclosed time and again that Japan was not planning to attack the USSR from the rear, thus easing Joseph Stalin's decision making.

The value of cryptanalysis during World War II was summarized in 1944 by U.S. Army chief of staff Gen. George C. Marshall: "The conduct of General Eisenhower's campaign [in Europe] and of all operations in the Pacific are closely related in conception and timing to the information we secretly obtain through these intercepted codes. They contribute greatly to the victory."

During the Korean and Vietnamese conflicts, U.S. signals intelligence was responsible for reducing American casualties. And at least once during Operation "Desert Storm" in 1991, intercepted Iraqi communications were sent to U.S. tanks in time to warn of Iraqi artillery that was about to target them, enabling them not only to take evasive action but also to counterattack. More generally, signals intelligence played a considerable part in the victory of the United States and its allies.

Communications intelligence also helps in peacetime. During the naval disarmament conference held in Washington in 1921 and 1922, American solution of Japanese diplomatic cablegrams helped U.S. diplomats to compel Japan to accept the equivalent of a battleship and a half less than it wanted. During the tense American-Japanese negotiations in the spring of 1995 over automobile imports, American interception of telephone conversations between the executives of Toyota and Nissan and Japan's trade minister told the United States trade representative and his staff how far the Japanese could be pressed and helped bring about an accord. By warning of possible hostile actions, cryptanalysts continue to give policymakers time to plan actions and thus figure importantly in stabilizing the international system.

Fan Technology - How Fans Work

 
Fan, in mechanical engineering, is a device for circulating air or other gases in a large space, such as a room, or in a duct system. Fans are employed not only to move air into a space but also to remove, or exhaust, air from a space. They find extensive application in moving the enormous amounts of air required for the ventilation and air-conditioning systems of large buildings and for the ventilation systems of mines. In most ventilated buildings the air inside is changed by fans from one to three times an hour.

 There are two principal types of fans, axial and centrifugal. In axial fans, the air flow is essentially parallel to the axis of rotation of the blades. The ordinary portable household fan is an axial fan of the propeller design. Although fans of the propeller type are capable of moving large quantities of air in open spaces, they are unable to build up enough pressure on the air to be used in duct systems.

Vane axial and tube axial fans resemble propeller fans, but have blades built in different forms, which permit high-speed rotation and consequently can develop sufficient pressure to move gases through duct systems against the flow resistances that must be overcome. These fans are mounted in cylindrical casings. Vane axial fans differ from tube axial fans mainly in that they are provided with guide vanes on either the inlet or outlet or both. The guide vanes convert the rotational motion of the gases, which serves no useful purpose, into pressure, which helps move the gases through the system.

The other principal type of fan, the centrifugal fan, is used where still higher fan pressures are required. Gases enter on one or both sides of the fan in the direction of the axis of rotation. They then turn through 90° and pass through the impeller, leaving in a direction essentially perpendicular to the axis of rotation. The impeller consists of closely spaced, narrow, essentially radial blades. These blades impart a high velocity to the gases, and because of their rotary motion, centrifugal force also acts to send the gases into the volute or scroll housing. In the housing, the high velocity of the gases is reduced, resulting in a pressure buildup.

Centrifugal fans can deliver gases at pressures up to 0.5 pounds per square inch (0.04 kg/sq cm). The delivery pressures of most fans are lower, being equivalent to the pressure of from 1 to 5 inches (2.5 to 12.5 cm) of water. Fan tip speeds can exceed 10,000 feet (3,000 meters) per minute, but in practice they seldom exceed 5,000 feet (1,500 meters) per minute, because of the noise at higher speeds. Generally, the pressure produced by centrifugal fans with blade tips curved forward in the direction of rotation is greater than that of a similar fan with straight blades or blades curved in the opposite direction.

Fans vary in capacity from less than 100 cubic feet (2.8 cubic meters) of air, or other gases, per minute to capacities in excess of 50,000 cubic feet (1,400 cubic meters) per minute. For very high capacities it is advisable to use two or more fans side by side. The capacity of a fan varies directly as its rotational speed. The pressure produced is proportional to the square of the fan speed, and the horsepower required is proportional to the cube of the fan speed.

In choosing a fan for a particular application, it is necessary to consider pressure and capacity requirements, noise, and available space as well as initial and operating costs.

Important Facts about Red Algae

 
Rhodophyta species, which owe their typically reddish color to a phycobilin pigment, possess no flagellated motile cells. Nearly all red algae are marine, although a few genera (for example, Batrachospermum) inhabit swiftly running freshwater. Some simple types are unicellular, but most have a basically filamentous organization, which often is elaborated into compound body structures that frequently show branching of great regularity. In the higher forms there are obvious pit connections between adjacent cells of the same filament.


Sexual reproduction is highly developed and normally exceedingly complex in red algae. It is based on the fertilization of egg cells by small, nonmotile, male gametes (spermatia). In many cases it involves the transfer of fertilized nuclei into specialized auxiliary cells and filaments (gonimoblasts) prior to their inclusion in spores. Alternation of cytologically different generations (usually isomorphic or identical in structure) is found in the more highly evolved genera. The reserve foodstuff is a polysaccharide known as Floridean starch.

The single class Rhodophyceae is divided into two subclasses, Bangiophycidae and Florideophycidae. Members of the former are more primitive and lack the complicated postfertilization processes found in those of the latter. They are also less highly organized morphologically. A well-known representative is laver (Porphyra).

Florideophycidae's orders—which include Ceramiales, Compsopogonales, Corallinales, Cryptonemiales, Gigartinales, Nemaliales, and Rhodymeniales—have been established based on features of the life cycle and postfertilization development of their species. The typical life cycle of one of the higher Florideophycean red algae, such as Polysiphonia, may be briefly summarized as follows.

The first generation, the gametophytes, produces spermatia and egg cells, commonly on different individuals. From the fertilized egg a small organism called the carposporophyte develops parasitically on the female gametophyte. It is diploid (having a double number of chromosomes in its nuclei) and consists of only a few rows of cells or filaments. The carposporophyte gives rise to a cluster of spores, usually inside a protective sheath (cystocarp). These spores are released and germinate to give rise to the second (ordinarily isomorphic) generation of organisms, which, unlike the gametophytes, has diploid nuclei. The number of chromosomes is reduced by half in the developing tetraspores (spores that develop in structures called tetrasporangia, which form on the second-generation algae). On being liberated, the tetraspores germinate to produce a new generation of gametophytes. Thus the life cycle is completed.

Certain genera of the order Corallinales deposit lime in the thallus, making the body rigid and stony. The body can be either solid (as in Lithothamnium) or in articulated segments (as in Corallina).

Some of the better-known representatives of the subclass Florideophycidae are Chondrus (Irish moss), Rhodymenia (dulse), and Ceramium (lobster claws). All are common on northern shores.

Some Important Things You Should Know about Green Algae

 
Chlorophyta is a large and important division, and its members show great diversity in structure and reproduction. Species range from microscopic unicellular forms to structurally complex organisms of moderate size. Practically every possible type of cellular organization is found in the group, including unicellular, colonial, filamentous, leafy, and tubular (siphonaceous). Motility by flagella (usually two, rarely four or more) is widespread, especially in the case of the reproductive cells (zoospores and zoogametes).


Owing to the presence of unmasked chlorophylls a and b, the species are grassy green, their pigmentation also being characteristic in green plants (mosses, ferns, and flowering plants). Starch is produced through assimilation. Some forms are symbiotic with fungi to form lichens, and symbiosis with marine invertebrate animals is also known. Sexual reproduction shows a wide range of variation, from fusion of similar motile gametes (isogamy) to that of dissimilar gametes (anisogamy or oogamy) or the fusion of the entire protoplasm content of different cells, as in the filamentous freshwater genus Spirogyra. Chlorophyceae (to which Spirogyra belongs) is the largest class within Chlorophyta, and its species vary the most in form.

Flagellate unicellular forms of the Chlorophyceae are placed in the order Volvocales, the representatives of which may be either single motile cells (such as Chlamydomonas) or colonies of cells joined together. Volvox is the best-known representative of the latter type, its colonies taking the shape of a hollow, slowly revolving sphere just visible to the naked eye. Nonflagellate unicellular or colonial algae compose the order Chlorococcales, of which Trebouxia, the algal symbiont most commonly associated with lichens, is an example.

Filamentous and membranous organization exists in the orders Ulotrichales and Ulvales, respectively. Ulothrix consists of simple unbranched filaments, each cell with a single chromatophore applied to the inner cell wall. Ulva (sea lettuce) forms leafy, platelike thalli two cell layers thick. Coenocytic structure, consisting of a multinucleate mass of protoplasm, is found in the orders Cladophorales, Siphonocladales, Dasycladales, Bryopsidales, and Caulerpales.

The desmids (order Zygnematales) are microscopic unicellular forms with minutely perforated walls. The cells are constricted in the middle and show bilateral to almost radial symmetry. They inhabit freshwater.

Golden Algae, Yellow-Green Algae, and Diatoms

 
Members of Chrysophyta, Xanthophyta, and Bacillariophyta range in size from microscopic, unicellular organisms to relatively small but visible, filamentous types. Although species in each division vary widely from those of the other divisions in form and structure, the groups are united by certain fundamental characteristics. (In fact, some sources do not recognize three separate divisions but instead classify yellow-green algae and diatoms under Chrysophyta.)


Common traits include the presence (in addition to chlorophyll of the a-type) of specific carotenoid accessory pigments (carotenes and xanthophylls), which may or may not mask the green color of chlorophyll a, and the elaboration of oil or a peculiar carbohydrate, chrysose (leucosin), as a product of assimilation (in which nutrients are either transformed or incorporated into protoplasm). The pigments are localized in special structures called chromatophores. Impregnation of the cell wall with silica is widespread in the group, and movement by means of flagella (whiplike processes) is common in many of the unicellular forms and in the sexual reproductive cells. The divisions are distinguished by the following characteristics:

Chrysophyta - chromatophores are golden yellow to brown; unicellular to filamentous
Xanthophyta - chromatophores are green or greenish; unicellular to filamentous
Bacillariophyta - chromatophores are brown; unicellular with an outer sheath, or frustule, of silica.

Chrysophyta species typically move by means of two flagella of unequal length. Many formerly were regarded as protozoa. However, some types are nonmotile, and others show creeping amoeboid movement by means of protoplasmic extrusions. Most of the forms are freshwater.

Certain forms of Xanthophyta use two unequal flagella for motility; others use creeping amoeboid movements. Some (such as those of the genus Vaucheria) form a tubular, unpartitioned, thallus (body), producing multinucleate and multiflagellate zoospores. Xanthophyta contains mainly freshwater and terrestrial species.

Bacillariophyta is peculiar in the form of the silica sheath, or frustule, that it possesses. This consists of two distinct, overlapping halves and is ornamented with symmetrically arranged pores that have a complex ultramicroscopic structure. The symmetry may be radial (around a central axis), as in the order Centrales, or bilateral (right and left sides as mirror images), as in the order Pennales. Free-floating diatoms are an important type of marine and freshwater plankton. Some species form colonies by aggregation of the individual cells.

Introduction to Algal Classification

 
Algae are typically assigned to the kingdom Protista, which also includes protozoa and funguslike organisms (although not the fungi themselves). While that convention will be followed in this article, some experts instead classify algae as plants—kingdom Plantae.


Within Protista, algae are separated into the following taxonomic divisions: golden algae (Chrysophyta), yellow-green algae (Xanthophyta), diatoms (Bacillariophyta), brown algae (Phaeophyta), dinoflagellate algae (Pyrrophycophyta), cryptomonad algae (Cryptophyta), euglenoid algae (Euglenophyta), stoneworts (Charophyta), green algae (Chlorophyta), and red algae (Rhodophyta).

As some of these names indicate, pigmentation plays an important role in algal classification, and its correlation with distinctive structural and reproductive features shows that it is a fundamental trait. In most cases the pigmentation referred to is an accessory one that occurs in addition to the green photosynthetic pigment, chlorophyll, which the accessory pigment frequently masks; thus the externally visible color in some of the groups is not green. In at least two of the divisions (brown algae and red algae), there is strong evidence that the accessory pigment is functional in photosynthetic metabolism, absorbing light energy and transferring it to the chlorophyll.

All algae contain the form of chlorophyll known as chlorophyll a. However, other varieties of the compound may be present as well, depending on the species.

The following article does not discuss blue-green algae. Despite their name, members of this group, which make up the phylum Cyanophycota, are not true algae but are instead a form of bacteria.