nucleation. When nucleation in the liquid phase is catalyzed by foreign surfaces other than the material to be crystallized (such as by dust particles or wall surfaces), it is described as primary heterogeneous nucleation. In solutions in which crystals already exist, secondary nucleation is thought to be by far the most significant source of nuclei. The supersaturation at which secondary nucleation rises is much lower than that which gives rise to primary nucleation.( Garside and Davey ,1980; Garside, 1985; Nyvlt et al., 1985); Fig. (I.4) shown A simple scheme for nucleation . Fig.I.4. Simple Scheme for Nucleation. A. Homogeneous Nucleation As stated previously, the supersaturated solution is not in equilibrium. So, in a supersaturated …show more content…
This process is called crystal growth. On the other hand, once the nucleation step has been overcome, nuclei grow into macroscopic crystals. This stage of the crystallization process is known as crystal growth (Rodriguez et al. 1999, Hess and Kok 1996). The kinetics of crystal growth can be described by the following differential equation (Gill et al. 1984): - (dS/dt) = (dP/dt) = kASn (I.16) Where S = supersaturation, t = time, P = precipitation, k = reaction rate constant, A = surface area for crystallization, n = order of the reaction. For Calcium Oxalate, n = 2. Therefore after integration, the above equation becomes: - (1/S) = kAt - (1/S0) (I.17) where So = initial supersaturation. Therefore by keeping the surface area constant in metastable supersaturated solutions, the rate constant (k) can be derived. This can be utilized in the Langmuir adsorption isotherm to compare inhibitory activities of added substances . In whole urine, calcium oxalate crystallization can be directly measured by adding specific quantities of oxalate seed crystals and measuring changes of 14C in the supernatant fraction (Gill et al.
A kidney stone or crystal forms when the urine is supersaturated in regard to a stone forming material, meaning the urine contains a higher concentration of stone material than it can dissolve. There are several factors that can contribute to supersaturation, such as urine volume, pH, and the amount of solute excretion (Worcester and Coe 2009). There are numerous types of stones that can form depending on what material in the urine is in excess. The most common types of stones are calcium kidney stones with calcium oxalate (CaOx) causing 80% of all calcium stones and calcium phosphate (CaP) causing 15% of calcium stones (Sakhaee et al. 2012). Calcium oxalate stones are usually found in patients as white deposits on their papillae, or Randall’s plaques. The stone begins as a deposit of calciu...
The Atomic Age represents the most epic era and composed of diverse controversial issues in the human history. In the late 1945, President Harry Truman informed to drop two atomic bombs on the Japanese cities of Hiroshima and Nagasaki. These two bombs quickly yielded the surrender of Japan and the end the World War 2. However, the impact of it led us to debate whether this decision was actually right or so. First off, it would be hard to imagine how Japan would have been surrendered without the atomic bomb. Therefore to save many American lives, President Truman believed that it was his duty to end the war as soon as possible. But the bombs took away innocent lives and killed civilians indiscriminately. “Atomic Age America” written by Martin
Stones form in the urinary tract when urine contains more stone forming substances than fluid in the urine that would otherwise dilute these substances. With no set ca...
Nuclear energy must be a consideration for the future with the rapidly depleting supply of fossil fuels. This type of energy can be created through nuclear fission and nuclear fusion. Nuclear fission is the splitting of a heavy atom into two or more parts, releasing huge amounts of energy. The release of energy can be controlled and captured for generating electricity. Nuclear fusion involves bombarding hydrogen atoms together to form helium. In the long run, nuclear fusion has greater potential than fission.
Since the dawn of civilization, all living (and some non-living) things have needed energy. When humans discovered fire, the first form of harnessed energy, it made it easier to stay warm, prepare food, make weapons, etc. Since then, humankind has been inventing new ways to harness energy and use it to our advantage. Now-a-days, people in most nations depend extremely heavily on fossil fuels – to work, travel, regulate temperature of homes, produce food, clothing, and furniture, as well as other power industries. Not only are these fossil fuels dominating our society and creating economic vulnerability, but they also produce waste that causes a number of social and environmental concerns. The waste from these fuels leads to acid rain, smog, and climate change. It also releases sulfur dioxide as well as other air pollutants that are very harmful to the human respiratory system (Morris, 1999, p. ix). There are other alternative sustainable energy sources including solar, hydroelectric, wind, and biomass. However, the main source aside from fossil fuel is nuclear energy from controlled nuclear reactions (where nuclei of radioisotopes become stable or nonradioactive by undergoing changes) in a nuclear power plant. Nuclear power produces enormous amounts of energy to serve a community. Unfortunately, nuclear energy has its own set of problems – a big one being its waste. The spent fuel from nuclear plants is radioactive. This means that it emits radiation, or penetrating rays and particles emitted by a radioactive source. Ionizing radiation is known to cause cancer, and therefore makes anyone who lives near spent nuclear waste facilities vulnerable to this incurable disease. The disposal of nuclear waste is a global issue...
Very good and strong are two important words to describe Wisconsin’s background for recycling. To support this; the DNR website said that Wisconsin keeps 2 million tons of trash out of landfills and incinerators every year. This is a fantastic accomplishment, but I think we can do better. This can be done in many ways. Such as recycling newspapers instead of throwing the newspaper away like many people do. In the United States 44 million newspapers out of 62 million are thrown away every year. Another way we could would be to compost more. In Wisconsin we produce almost 500,000 tons of composting material, but yet some people don’t recycle any of it. According to the DNR website, 73% of people in Wisconsin
Paper recycling is the process of mixing used paper with water and chemicals to break it down. This mixture is then chopped up and heated to breaks it down further into strands of cellulose called pulp or slurry. It then strained through screens which remove any glue or plastic that may still be in the mixture. Finally it is cleaned, de-inked, bleached, mixed with water and then it can be made into new recycled paper.
Radioactive isotope dating techniques use present day processes as well as rates of processes to interpret past conditions and infer patterns of distribution and climate change and geology to past events. Techniques used to measure and reconstruct palaeoenvironmental records/frameworks depend on the material (proxy) that is preserved and the events that occurred when it became fossilized. There are radioactive properties in different materials, contained within them there are natural time signals, more often than not they are in the form of isotopic decay, (Roberts, 1998, p. 11-16). Most natural elements are actually an assortment of numerous isotopes. Radioactive isotopes are considered unstable because whilst the number of protons stay the same, there will be a variance in the number of neutrons. The difference of the masses between the two makes an unstable atomic nuclei. When isotopes are not radioactive they are termed stable, as they do not decay like radioactive isotopes. Radioactive isotopes can only become a stable by emitting radiation resulting in the elements having the same number of protons and neutrons, (Rink, n.d). One isotope will always be abundant for each element, for example, carbon’s prevailing isotope is carbon 12, however there are different ones that are less plentiful, such as carbon 13 and carbon 14, (Roberts, 1998, p. 11-16). Each decay event will emit one daughter isotope at a fixed rate. Although it will not be a straight line, the decay will occur quickly at first then it gradually slows over time. Since decay is measurable due to fixed rate at which it decays, the geological clock is set at zero when the isotopic decay commences, to tell how old a proxy is, one measures how much radioactivity re...
nuclei was then inactivated and substituted with dead nuclei from the extinct frog. Some eggs started to grow and divide to early embryo stage (a tiny ball of m...
The aim of eliminating nitrogen, whatever the exact form of the nitrogen compounds in wastewater, was the production of nitrogen gas, an inert, water-insoluble gas which is readily separable from liquid media. The need to produce nitrogen gas in nitrogen removal treatment processes is mainly due to the high solubility of nitrogen compounds such as NO3 ~, NH4 + and NO2 ~ present in the removal of nitrogen, nitrogen. It seems that this old paradigm is being challenged. Because nitrogen gas, as in sewage treatment operations, has no economic value, some researchers seek to remove nitrogen compounds in dissolved form. The most promising method for removing dissolved forms of nitrogen compounds is the application of zeolite columns employing adsorption
Nuclear fusion occurs when two atomic nuclei collide with enough energy to bind together to form one nucleus. Nuclear fusion occurs in the core of our sun, and is the source of its tremendous heat. In the sun hydrogen nuclei, single protons, fuse together and form a new nucleus. In the conversion, a small amount of mass is converted into energy. It is this energy that heats the sun.
Radioactivity is the energy or particles that are released from the nucleus of an atom due to spontaneous changes. Some atoms are unstable, and emitting radiation will achieve a stable state. The main forms of radiation emissions from a decaying and unstable nucleus can be in the form of alpha, beta or gamma radiation. When a positively-charged particle is emitted from the nucleus of an atom, this is called alpha decay. This alpha particle would consist of two protons and two neutrons, similar to a helium-4 nucleus. Whereas when a particle, either as an electron with either negative or positive charge, is emitted from the nucleus, this would be known as beta decay. And finally, when a nucleus is at a high energy state, photons known as gamma particles would be released to lower the energy state. Worldwide, people have found the use of radioactivity for society, from scientific applications to medical uses and to industrial uses. However, there are many positive and negative effects of using radioactivity.
The people of America throw away more trash than any other society in the world! America consumes 80 percent of our planet's resources, even though we make up only 20 percent of the world's population (Cooper 267). The average person throws away 4.3 pounds of trash each day. That's about 30 pounds per week and 120 pounds per month! (“Reduce and Reuse” 1). Americans throw away too much - that's the bottom line (Cooper 265). There is a garbage crisis in America and “the only part of the anti-waste message that has taken hold to any noticeable degree is the call to recycle” (Cooper 267). Our country's issues on trash and recycling go hand in hand. America produces too much trash, and the environment is suffering. There is some effort being put into countering these issues through recycling and trash management, but is it enough? (Cooper 267).
America uses a lot of energy to supply electricity to millions of homes and businesses and needs an energy source that will supply an abundant amount of power but is also efficient. Nuclear energy is a reliable and efficient energy source that America can use. Fossil fuels and other resources used in the United States are running out or are very expensive. Nuclear power will provide a cost effective and long term power supply. America should use nuclear energy because of its many benefits which are environmental benefits, economic benefits, safety, power production, and reliability..
A nuclear reaction in which multiple nuclei of atoms collide at high speed, under high pressure and at a high temperature to form a new nucleus, releasing photons (light and energy) as this happens.