Lecture 2

Machine Guns

1. In 1881, Hiram Maxim, an American inventor, visited the Paris Electrical Exhibition. While at the exhibition he met a man who told him: "If you wanted to make a lot of money, invent something that will enable these Europeans to cut each other's throats with greater facility." 
   
2. The 1914 machine gun weighed between 30 kg-60 kg. It was usually positioned on a flat tripod and would require a gun crew of four to six operators.  In theory, they could fire 400-600 small-caliber rounds per minute, a figure that was more than doubled by the war's end, with rounds fed via a fabric belt or a metal strip. The shooting distance ranged from 2000 to 4000 yards. The disadvantage was rapid overheating during use which required initially constant water cooling until air cooling was maximized.  This challenge was pursued through further technological advances, which yielded the first portable, fully automatic machine gun.
   
3. Machine Guns stopped infantry attacks and maintained trench war conditions.  Nearly 40% of World War I casualties were caused by machine gun fire.

Chemical Warfare

1. Lance Sergeant Elmer Cotton, described the effects of chlorine gas in 1915:  "It produces a flooding of the lungs - it is an equivalent death to drowning only on dry land. The effects are these - a splitting headache and terrific thirst (to drink water is instant death), a knife edge of pain in the lungs and the coughing up of a greenish froth off the stomach and the lungs, ending finally in insensibility and death. The color of the skin from white turns a greenish black and yellow, the color protrudes and the eyes assume a glassy stare. It is a fiendish death to die."

Gas War

1. 1st use of gas in 1915 at the second battle of Ypres: 5000 dead 15,000 wounded, 2000 permanently blind.
   
2. The French were the first to use chemical weapons during the First World War, using tear gas. The first full-scale deployment of chemical warfare agents was during the Second Battle of Ypres, April 22, 1915, when the Germans attacked Entente troops with chlorine gas. Deaths were light, though causalities relatively heavy. A total 50,965 tons of pulmonary, lachrymatory, and vesicant agents were deployed by both sides of the conflict, including chlorine, phosgene and mustard gas.

Fritz Haber 1868-1934

1. Fritz Haber has rightfully been called the "greatest authority in the world on the relations between scientific research and industry."
   
   1. In 1881 as a young undergraduate Haber presumably synthesized first 3,4-methylenedioxy-methamphetamine (MDMA, called now "Ecstasy").
   2. Haber's institute worked on numerous wartime concerns. Among the contributions Haber made to Germany's war effort was in the development of chemical warfare. With strong purpose and great energy he became involved in the production of protective chemical devices for troops and directed the first gas attacks against enemy troops. Haber is often referred to as the father of modern chemical warfare as he organized and directed the first large scale release of chlorine gas at Ypres, France on April 22, 1915.
      
2. Phosgene was first used as a weapon by the French, under the direction of French chemist Victor Grignard in 1915. Later, the Germans, under the direction of German chemist Fritz Haber added small quantities of it to chlorine to increase the latter's toxicity. Soon after, use of pure phosgene was begun. Phosgene was responsible for most of the about 100,000 gas-caused deaths during the war.
3. Competition among chemists fueled greater advances in chemical creation than had been seen in ages.
4. 1. Germany's Fritz Haber of KWI Berlin develops Chlorine gas:Nobel Prize 1918.
   2. France's Victor Grignard of University of Nancy develops Mustard & Phosgene gas: Nobel Prize 1912.

Chemical Weapons

1. Mustard gas is a strong skin poison. The exposure develops within hours into deep, itching or burning blisters wherever the mustard contacted the skin; the eyes (if exposed) become sore and the eyelids swollen, possibly leading to blindness. At very high concentrations, if inhaled, it causes bleeding and blistering within the respiratory system. Blister agent exposure over more than 50% body surface area is usually fatal. Mustard gas is also chemically reactive with the DNA of exposed cells. This leads to either immediate cellular death or, as recent research has found, cancer. Mustard gas is not very soluble in water but is very soluble in fat, contributing to its rapid absorption into the skin.
2. The Ethical Conflict
3. 1. "A scientist belongs to his country in times of war and to all mankind in times of peace."  - Fritz Haber
   2. Clara Immerwahr-Haber was the first woman to obtain a PhD in Chemistry (Breslau, 1900). She believed that science should be used for constructive purposes, not
      for weapons of mass destruction. Fritz Haber tried to keep Clara in the dark about his work on poison gas. During the night after the Gas attack in Ypres with ~ 5000 dead and ~ 2000 blinded she committed suicide.

A war that changed the world

1. Perhaps most importantly, radiating material is discovered
   
2. 1. Radioactive material such as Uranium - first discovered by Henri Becquerel – was studied extensively by Marie and Pierre Curie. They discovered other natural radioactive elements such as Radium and Polonium.  Their work wins them the Nobel Prize in 1903 and 1911.
      

Physics behind Radioactivity

1. Radioactive Decay Laws
2. 1. Activity of radioactive substance A(t) is at any time t is proportional to number of radioactive particles N(t) :
      
   2. λ≡decay constant; a natural constant for each radioactive element
      
   3. 
      
      

1. Nuclear Isotopes
   
   
   1. A=Mass number (don’t confuse with activity A(t)!)
      Z = Proton Number (Element Symbol)
      N = Neutron Number = A - Z
   2. 1st example:  22Na has a half-life of 2.6 years. What is the decay constant?
   3. 
      
2. Application of Decay Laws
3. 1. A Na-22 exhibits radioactivity of 1 Ci.  How many Na-22 isotopes are contained in the source? (1 Ci = 3.7·1010 decays/s)
      
   2. How many grams of Na-22 are in the source?
      
   3. How many particles are in the source after 1 year, 2 years, 20 years?
   4. Decay in particle number and corresponding activity.
      
   5.