The first law of thermodynamics Essay Example for Free

The first law of thermodynamics Essay The first law of thermodynamics states that energy can neither be created nor destroyed; it can only be converted from one form to another. This can be illustrated using the example of steam power. Thermal energy is stored in steam. This steam can be used to drive an steam engine which converts this thermal energy in the steam into kinetic energy of the unit (say steam driven train). In thermal power plants, fossil fuel is burnt to produce steam and the thermal energy in the steam then drives the turbine to produced electricity. Thus thermal energy of the steam gets converted into electrical energy. From these two illustrations it becomes obvious that energy can neither be created nor destroyed it can only be converted from one form to another. Three types of non-renewable power plants and the fuel consumed by these power plants are listed below. Fuels cells use the electrons produced in a chemical reactions to produce electricity. One example is Hydrogen – Oxygen Fuel cell. In this case Hydrogen is oxidized at anode into hydrogen ions plus electrons and oxygen is reduced at cathode into oxide ions at cathode. Anode and cathode is separated by solid electrolytes and connected by a metallic wire. The electrons move from anode to the cathode through the metallic wire and thus electricity is produced. This is very clean source of electrical energy. Criteria for acceptability of energy alternatives are listed below. Technological feasibility – It should be technologically feasible to convert the energy into usable forms like electricity etc. Abundance – The energy source should be available in abundance. Reliability – The energy source should be reliable. This is particularly relevant for wind energy and solar energy in the regions of unpredictable sky conditions and wind conditions. Capital Expenditure – Generally capital expenditure requirements are high and act as major barrier for exploiting renewable energy sources.

The Ethernet Essay -- essays research papers

Bob Metcalfe of the Xerox Corporation developed the first experimental Ethernet system in late 1972. The goal of the Ethernet was to interconnect the Xerox Alto Aloha Network. The experimental Ethernet was used to link Altos workstations, servers, and laser printers. Data transmission of the Ethernet was 2.94 Mbps. In 1973, Metcalfe changed the name to "Ethernet," to make it clear that the system could support any computer, and not just Altos, and to point out that his new network mechanisms had evolved well beyond the Aloha system. He chose to base the name on the word "ether" as a way of describing an essential feature of the system. The physical medium (cable) carries bits to all stations, much the same way that the old "luminiferous ether" was once thought to propagate electromagnetic waves through space. The Ethernet is a LAN (Local Area Network) technology that uses a shared bus topology, and Carrier Sense Multiple Access/Collision Detection access. It consists of a single, long cable, named the bus, to which computers, or sometimes referred to as workstations, are attached. Ethernet signals are transmitted serially, one bit at a time, over the bus and are received by every attached station. Data in the Ethernet is transmitted in the form of a frame, or packet. The frame consists of a set of bits organized into several fields. These fields include address fields, a variable size data field that carries from 46 to 1,500 bytes of data, and an error checking field that checks the integrity of the bits in the frame to make sure that the frame has arrived intact. The first two fields in the frame carry 48-bit addresses, called the destination and source addresses. The Destination Address contains the physical address of the station to which the frame is being sent. Any signal sent across the shared network reaches all attached workstations. However, communication doesn’t usually involve all workstations. To allow direct communication between stations the addressing scheme is used. Each workstation is assigned a unique numeric value, called a physical address or media access control address (MAC address). Although sharing allows all workstations to receive a copy of a frame, the hardware of each workstation checks the address of each incoming frame to determine whether it should accept the frame. The Source Address contains... ... its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub ports) alone. In a mesh topology each computer is connected to every other computer by separate cabling. This allows for superior redundancy and reliability, as well as ease of troubleshooting. This type of topology is expensive and difficult to install because of the amount of cabling required. The original Ethernet operated at 10 Mbps, a later version Fast Ethernet operates at 100 Mbps and the newest version Gigabit Ethernet operates at 1 Gbps. The Ethernet is the most popular physical layer LAN technology in use today. It is popular because it strikes a good balance between speed, cost and ease of installation. These benefits combined with wide acceptance in the computer marketplace and the ability to support virtually all-popular network protocols, make the Ethernet an ideal networking technology for most computer users today.

Non-Hodgins Lymphoma with Case Study Example

Non-Hodgkin’s Lymphoma is a cancer of the lymphocytes the white blood cells. The lymphocytes and lymph system are essential in our body’s immune protection. It is an abnormal growth rate of these cells. Since lymph is found throughout the body it is easily spread from one area to another. In 2008 there were over 66,000 new cases and just over 19,000 deaths from it (cancer. gov). It is categorized as slow growing or fast growing, as well as if it starts in the T-cells or the B-cells. Lymphomas from B cells are most common in the United States. The lymphoma can develop in any of the lymph tissues, and discovery of which kind of lymphoma determines the treatment options (cancer. org). Causes Although there are no definite causes to Non Hodgkin’s lymphoma there have cases where it has been linked to persons with another ailment. Autoimmune diseases like RA and SLE have been linked to NHL. Exposures to chemicals such as benzene and treatments in chemotherapy have been seen in trends to cause NHL. People who are immunocompromised like HIV patients and those that are on immunosuppressant from transplants are also at risk for Lymphomas. Also, people having excessive exposure to large amounts of radiation, like cancer treatments have an increased risk of developing this lymphoma. NHL is mostly seen in the older community so age is also a risk factor. Also chronic diseases may increase the chances of getting a lymphoma due to the increased risk of mutations from constantly producing new lymph cells. Some patients can be born with a disease that can lead to NHL due to a defect in their DNA. It is not likely that they can pass on the NHL to their offspring if they don’t have the underlying disease. Most often it develops independently. Discovery Lumps in the skin and lymph nodes can be discovered by the patient, their partner or doctor. Where the lump is located can also give extra symptoms. For instance, if it is found near the skin there would be a swelling in the surrounding tissue. If it’s in the abdomen it can cause severe pain and possible digestive problems. If the lymphoma is on the skin t can cause an itchy patch. If it is in the chest cavity it can cause trouble breathing. Case Study: Non-Hodgkin’s Lymphoma Shannon Z is an active 58 yr old female. In her early twenties she had undergone chemotherapy and radiation for her treatment of breast cancer. When she noticed the lump in her neck she immediately went to see her doctor. The doctor ordered some blood tests and a biopsy of the lump. Her doctor wasn’t very concerned because fighting an infection can also cause enlarged nodes in the neck. She ordered the tests anyway because of the patient’s medical history. Along with the lump, she experienced drenching night sweats which are another symptom of NHL but she thought it was a side effect of menopause. Other signs to look for would be persistent fevers and a sudden loss of weight, usually 10 % body weight or more. An incisional biopsy is a surgical technique used to obtain a sample of the node for observation. This was used because the enlarged node was close to the skin surface. There are other biopsies available. Fine needle biopsies can also be used but often don’t provide enough sample to determine if its lymphoma or not but does not require surgery. Lumbar punctures look for lymphoma in the CNS. Bone marrow aspiration looks for the cancer inside the bone and bone marrow by removing pieces of the bone and/or marrow. Laboratory tests All samples must be diagnosed be a trained pathologist with experience in lymphomas. The most important test would be those differentiating if the patient has a cancer, then T cell lymphoma from the B cell lymphoma. If a concrete diagnosis can’t be made from looking at the cells then other methods must be used. Methods like Immunocytochemistry involve using fluorescent tags on the surface of the cells can differentiate the different lymphomas from each other and non cancerous diseases. Flow cytometry uses antibody tagging and laser beams to cause the cells to emit light if they have the antigen. This is important because different NHL’s have specific antigens. Discovery of the type of NHL helps determine the treatment route. Blood tests cannot determine a lymphoma but they do show significance of the rate of growth of the lymphoma. CT scans and MRIs provide the doctors with images of the size of the actual lymph nodes and how many growths there are through the body. Prognosis There are two staging systems for NHL. The most common is the Ann Arbor system. It uses 1-4 to stage the severity of the disease. Stage 1 has lymphoma in one area in the lymph system and one outside the system (organ). A lymphoma is considered stage 2 if it is found exclusively in 2 areas above or 2 areas below the diaphragm and organs in close proximity to lymph. Stage 3 occurs when it is found on both sides of the diaphragm and other organs near lymph. Stage 4 is when lymphoma reaches the bone marrow, CSF, or an organ not next to a lymph source. This system is used in conjunction with the International Prognosis Index. The IPI uses the age of the patient, stage of the cancer, patient everyday performance status, location of the tumors, and levels of LDH (increases as the lymphoma spreads) Good Prognostic FactorsPoor Prognostic Factors Age 60 or belowAge above 60 Stage I or IIStage III or IV No lymphoma outside of lymph nodes, or lymphoma in only 1 area outside of lymph nodesLymphoma present in more than 1 organ of the body outside of lymph nodes PS: Able to function normallyPS: Needs a lot of help with daily activities Serum LDH is normalSerum LDH is elevated (Chart provided from www. cancer. org) Treatment Chemotherapy is often used in conjunction with radiation for low levels, or with medications like Rituxan or Zavalin. Rituxan is an antibody that targets the cancerous cells. Zavalin is an antibody with a radioactive component. The antibody attaches itself and the radioactive isotope destroys the cell. These drugs are used for the more persistent lymphomas because chemo and radiation have been proven very effective against the lymphoma. Stem cell transplantation is also another option. Once diagnosed, patients are requested to have frequent physicals and blood tests to track the growth of the cancer. Resources http://www. oncologychannel. com/nonhodgkins/diagnosis. shtml http://www. cancer. org http://www. cancer. com http://www. mayoclinic. org

Critical Thinking Exercises for Students

Critical thinking is a skill that students develop gradually as they progress in school. While the skill becomes more important in higher grades, some students find it difficult to understand the concept of critical thinking. The reason critical thinking can be difficult to grasp is because it requires students to set aside assumptions and beliefs to learn to think without bias or judgment. Critical thinking involves suspending your beliefs to explore and question topics from a blank page point of view. It also involves the ability to distinguish fact from opinion when exploring a topic. These exercises are designed to help develop critical thinking skills. Critical Thinking Exercise 1: Tour Guide for an Alien This exercise provides an opportunity to think outside your normal way of thinking. Pretend that you have been assigned the task of conducting a tour for aliens who are visiting the earth and observing human life. Youre riding along in a blimp, viewing the landscape below, and you float over a professional baseball stadium. One of the aliens looks down and is very confused by what he sees. You explain that there is a game going on and he asks several important questions. What is a game?  Why are there no female players?Why do people get so excited about watching other people play games?What is a team?Why cant the people in the seats go down on the field and join in? If you try to answer these questions fully, it will quickly become apparent that we carry around certain assumptions and values. We support a certain team, for instance, because it makes us feel like were a part of a community. This sense of community is a value that matters to some people more than others. Furthermore, when trying to explain team sports to an alien, you have to explain the value we place on winning and losing. When you think like an alien tour guide, you are forced to take a deeper look at the things we do and things we value. Sometimes they dont sound logical from the outside looking in. Critical Thinking Exercise 2: Fact or Opinion Do you think you know the difference between fact and opinion? Its not always easy to discern. When you visit websites, do you believe everything you read? The abundance of available information makes it more important than ever for students to develop critical thinking skills. Additionally, its an important reminder that you must use trustworthy sources in your school work. If you dont learn the difference between fact and opinion, you may end up reading and watching things that continue to reinforce beliefs and assumptions you already own. For this exercise, read each statement and try to determine whether it sounds like a fact or an opinion. This can be completed alone or with a study partner. My mom is the best mom on earth.My dad is taller than your dad.My telephone number is difficult to memorize.The deepest part of the ocean is 35,813 feet deep.Dogs make better pets than turtles.Smoking is bad for your health.Eighty-five percent of all cases of lung cancer in the U.S. are caused by smoking.If you flatten and stretch out a Slinky toy it will be 87 feet long.Slinky toys are fun.One out of every one hundred American citizens is color blind.Two out of ten American citizens are boring. You will probably find some of the statements easy to judge but other statements difficult. If you can effectively debate the truthfulness of a statement with your partner, then its most likely an opinion.