What You Should Know about Stem Cells Essay - 1171 Words

What You Should Know about Stem Cells A topic of extended scientific and ethical debate in our society as of late has been the question of Stem Cell research. Going down this path could yield unprecedented medical leaps in treatment and prevention that medicine will be able to offer. Before I address the debate of whether or not Stem Cell research should be done, I want to first explain to my readers what stem cells are, how they come to be and what we can use them for. We must first start with the different types of cells, I will explain them as I take you through part of the fetal development process. The first type of cell is the totipotent cell. This cell is created when a sperm fertilizes an egg. This kind of cell can†¦show more content†¦Once we are able to create these stem cell lines a variety of possibilities will be open to us. The first is the ability to speed up our future drug testing. This benefit should please animal rights activists. If we create a line of human stem cells for new drugs to b e tested on than we can assess the negative and positive effects on the stem cell tissue before the drug is ever used on an animal or a human. Not only that but testing new drugs on stem cells increase the amount of information we can learn because we can target specific and more varied tissues that previously we had access to. Now I will get into more direct benefits of stem cell research. Pluripotent stem cells can be directed to develop into almost any kind of tissue, and this creates the possibility for a renewable source of replacement tissues and cells. What does that mean? We would be able to better treat and cure a large number of diseases and injuries including but not limited to: Parkinson?s, Alzheimer?s, spinal cord injury, stroke, burns, heart disease, diabetes, osteoarthritis and rheumatoid arthritis. I have included an example taken from the National Institute of Health?s Primer on Stem Cells: Transplant of healthy heart muscle cells could provide new hope for patients with chronic heart disease whose hearts can no longer pump adequately. The hope is to developShow MoreRelatedThe Debate Of Stem Cell Research1519 Words   |  7 Pagesbring the topic of stem cell research to the table to inform you on a topic you most likely know nothing about. According to the bible the strong need to bear with the failings of the weak. Why should we please ourselves if we don’t care for stem cell research? Among one of the, if not the most, controversial topics of our time comes one medical science that can save lives if legalized nationwide. We are talking about stem cells of course, and why the allowance of these basic cells in common medicalRead MoreThe Ethics Of Stem Cell Research1557 Words   |  7 Pagesthese outstanding medical advances a self-renewing stem cell that regenerates and gives rise to all cells and tissues of the body was discovered. The controversy of such find ing of abilities of stem cell is that they can only be extracted from the human embryo. In order to extort stem cells from the embryo it needs to be aborted. The extraction needs to be done just days after conception or between the fifth and the ninth week. Though stem cell research has astonishing potential to save many livesRead MoreEssay about Stem Cell Research808 Words   |  4 PagesStem Cell Research Works Cited Not Included Stem cell research is an ongoing controversial issue. What exactly is stem cell research? How would this type of research affect peoples lives? What are stem cells? Where do they come from and what are their uses in the human body? What diseases and medical conditions could be helped if not eventually cured completely? Scientists are very optimistic regarding stem cell research. Whether or not that research will be allowedRead MoreStem Cell Type Is Best?1264 Words   |  6 PagesTopic: Stem research, which stem cell type is best? Umbilical cord stem cells or embryonic stem cells. General Purpose: To inform Specific Purpose: To inform the audience of the advantages and disadvantage of using embryonic and umbilical cord stem cells in research. Central Ideal: While medical researchers believe that the use of embryonic stem cells is their best option in research, others believe it to be unethical and immoral, and that umbilical stem cells are a good alternative to embryonicRead MoreStem Cell Research Essay940 Words   |  4 Pageswe were a small bundle of cells that would one day become who we are today. Those cells were essential to our body and the development of the fetuses that were us. Put yourself in the place of an embryo. You are a small blastocyst or a bunch of cell, only about 0.1 millimeters big. Even though you are slight and may seem insignificant, you hold all the opportunities of life. You have a soul and are alive, because you will become a human. The possibilities are endless; you could be a surfer, an artistRead MoreResearch On Stem Cell Research Essay1708 Words   |  7 Pages Stem Cell Research James A Merritt PIMA Medical institute Embryonic stem cell research is a controversial topic. In the religious aspect its man trying to play the authority of GOD on whether people should live, die or suffer from ailments and injuries. On a scientific and medical aspect it is compassionate people lookingRead MoreThe Government Has Not Funded Stem Cell Research1566 Words   |  7 Pagesgovernment has not funded stem cell research since 2001 for various reasons, some understandable, others I have to disagree on. I believe stem cell research should be funded by the government because it will advance our knowledge on how to treat and cure certain diseases. Many people, researchers and scientist included, strongly agree that we cannot continue our knowledge and technological advancement without the support of our own government. Stem cells are special cells that have the ability toRead MorePros And Cons Of Stem Cell Research1003 Words   |  5 PagesFoundations Ethics Stem Cell Research Stem Cell Research Explorable.com 1.6M reads 32 Comments Printer-friendly versionSend by emailPDF version Pros And Cons in Research The debate of the pros and cons of stem cell research clearly illustrate the difficult ethics evaluations researchers sometimes must do. All scientists must consider whether the positive effects from their research are likely to be significantly higher than the negative effects. What are Stem Cells? Stem Cells are crucial to developRead MoreStem Cell Research Essay1706 Words   |  7 Pagestheir educational short film A Stem Cell Story, there are certain stages of development while in the uterus where most of our cells stop dividing and stabilize into a specific kind of cell. They do not mutate throughout our life. These cells are referred to as specialized cells. Once they are damaged or die they cannot regenerate themselves. There is one kind of cell that never specializes during development. They are called stem cells and they are the only known cells that can renew themselves. WhenRead MoreThere Was A Seventeen-Year-Old Boy Named Joe Beene That1674 Words   |  7 PagesThere was a seventeen-year-old boy named Joe Beene that severely injured himself during a football practice in November. Because of Joe’s injury, Joe’s family had a very difficult moral dilemma that involved the right to conduct stem-cell research to help with medical conditions. The injury that Joe sustained was a broken neck that left Joe paralyzed from the Chest down hindering Joe from any activities including taking care of himself. I couldn’t even start to understand the pain and suffering that

Ban Fire Crackers Free Essays

Diwali is celebrated with great vigour all across the nation. Bursting firecrackers is a tradition on Diwali. Diwali is also known as Deepavali in India. We will write a custom essay sample on Ban Fire Crackers or any similar topic only for you Order Now Firecrackers! Just the term creates joy and excitement in one’s mind. The heart flutters with thrill and enthusiasm developed by the sight those colorful showers and sparkles from the fireworks in the sky. But is it all about fun? Have you ever wondered how many harmful effects and disadvantages do these fireworks create for the environment?. It is yours, theirs and everyone’s duty to take care of the environment, fellow humans and other living beings. You may wonder why and how. You may be having a great time celebrating and enjoying, bursting those boisterous fireworks. But it need not be the same for the others around you! What about your neighbors? Your neighbor could be sick, or many may have an important appointment the next day. He/she could also be having a test or an exam the next morning and they may need some rest. Burning firecrackers late at night at odd hours disturbs everyone living in that community and disturb their sleep and make them less concentrated in their next day. Firecrackers produce very high level of sound and the vibrations can travel over a long distance. These are sometimes over 140 decibels! A human ear can bear a maximum of 85 decibels. Sounds above this limit create disability in hearing and causes permanent damage to the ears. Firecrackers when burnt release a large amount of very tiny toxic particles that can easily enter our lungs and damage the respiratory system. The smoke from firecrackers contain sulfur compounds, heavy metals and other toxic chemicals and harmful fumes of gases such as sulfur dioxide, ozone etc,. People with asthma, multiple chemical sensitivity and other breathing problems suffer largely due to the toxic emissions from these fireworks. Crackers are unnoticeably affecting all of us. We should understand what it’s doing how it’ll threaten our very existence in future. Governments should take it very seriously should: †¢ban the production of crackers †¢enforce laws on its production, sales, use, advertisement †¢popularize the idea of not using crackers among public There’re a lot of causes of global warming pollution. All the other sources are important for our living despite their ill effects. But cracker is absolutely nothing more than garbage. Be smart, be civilized, use your knowledge, don’t worry about what others think, don’t care about society, DON’T USE CRACKER. Let each one of us take a pledge this Diwali to say NO to firecrackers and invest in a safer and greener future. Diwali is the festival of lights and we must enlighten our lives with the sparkle of joy and goodwill, forget past grievances and look ahead towards a brighter and happier future. How to cite Ban Fire Crackers, Papers

Electrical Properties of Materials free essay sample

ELECTRICAL PROPERTIES OF MATERIALS SUBMITTED TO: PROF. MARY GRACE O. CATONG SUBMITTED BY: ALAN, ARLAN H. RAMIREZ, RONEL JAY S. RUSIANA, RODOLFO O. BSEE-3B OHM’S LAW One of the most important electrical characteristics of a solid material is the ease with which it transmits an electric current. Ohm’s law relates the current I—or time rate of charge passage—to the applied voltage V as follows: V=IR. ELECTRICAL CONDUCTIVITY Sometimes, electrical conductivity is used to specify the electrical character of a material. It is simply the reciprocal of the resistivity, or ELECTRONIC AND IONIC CONDUCTION An electric current results from the motion of electrically charged particles in response to forces that act on them from an externally applied electric field. Positively charged particles are accelerated in the field direction, negatively charged particles in the direction opposite. ENERGY BAND STRUCTURES IN SOLIDS In all conductors, semiconductors, and many insulating materials, only electronic conduction exists, and the magnitude of the electrical conductivity is strongly dependent on the number of electrons available to participate in the conduction process. For each individual atom there exist discrete energy levels that may be occupied by electrons, arranged into shells and subshells. Shells are designated by integers (1, 2, 3, etc. ), and subshells by letters (s, p, d, and f ). The electrical properties of a solid material are a consequence of its electron band structure—that is, the arrangement of the outermost electron bands and the way in which they are filled with electrons. Four different types of band structures are possible at 0 K. In the first (Figure18. 4a), one outermost band is only partially filled with electrons. The energy corresponding to the highest filled state at 0 K is called the Fermi energy Ef. CONDUCTION IN TERMS OF BAND AND ATOMIC BONDING MODELS Only electrons with energies greater than the Fermi energy may be acted on and accelerated in the presence of an electric field. These are the electrons that participate in the conduction process, which are termed free electrons. In addition, the distinction between conductors and non-conductors (insulators and semiconductors) lies in the numbers of these free electron and hole charge carriers. Metals For an electron to become free, it must be excited or promoted into one of the empty and available energy states above Ef. For metals having either of the band structures shown in Figures 18. 4a and 18. 4b, there are vacant energy states adjacent to the highest filled state at Thus, very little energy is required to promote electrons into the low-lying empty states, as shown in Figure 18. 5. Generally, the energy provided by an electric field is sufficient to excite large numbers of electrons into these conducting states. Insulators and Semiconductors For insulators and semiconductors, empty states adjacent to the top of the filled valence band are not available. To become free, therefore, electrons must be promoted across the energy band gap and into empty states at the bottom of the conduction band. The number of electrons excited thermally (by heat energy) into the conduction band depends on the energy band gap width as well as temperature. The larger the band gap, the lower is the electrical conductivity at a given temperature. Increasing the temperature of either a semiconductor or an insulator results in an increase in the thermal energy that is available for electron excitation. ELECTRON MOBILITY When an electric field is applied, a force is brought to bear on the free electrons; as a consequence, they all experience acceleration in a direction opposite to that of the field, by virtue of their negative charge. These frictional forces result from the scattering of electrons by imperfections in the crystal lattice, including impurity atoms, vacancies, interstitial atoms, dislocations, and even the thermal vibrations of the atoms themselves. ELECTRICAL RESISTIVITY OF METALS Metals have high conductivities because of the large numbers of free electrons that have been excited into empty states above the Fermi energy. Since crystalline defects serve as scattering centers for conduction electrons in metals, increasing their number raises the resistivity (or lowers the conductivity). The concentration of these imperfections depends on temperature, composition, and the degree of cold work of a metal specimen. known as Matthiessen’s Rule Influence of Temperature For the pure metal and all the copper–nickel alloys shown in Figure 18. 8, the resistivity rises linearly with temperature above about -200? C. Thus, This dependence of the thermal resistivity component on temperature is due to the increase with temperature in thermal vibrations and other lattice irregularities (e. g. , vacancies), which serve as electron-scattering centers. Influence of Impurities For additions of a single impurity that forms a solid solution, the impurity resistivity is related to the impurity concentration in terms of the atom fraction (at%/100) as follows: For a two-phase alloy consisting of and phases, a rule-of-mixtures expression may be utilized to approximate the resistivity as follows: Influence of Plastic Deformation Plastic deformation also raises the electrical resistivity as a result of increased numbers of electron-scattering dislocations. The effect of deformation on resistivity is also represented in Figure 18. 8. Furthermore, its influence is much weaker than that of increasing temperature or the presence of impurities. COMMERCIAL ALLOYS Electrical and other properties of copper render it the most widely used metallic conductor. Oxygen-free high-conductivity (OFHC) copper, having extremely low oxygen and other impurity contents, is produced for many electrical applications. Aluminum, having a conductivity only about one-half that of copper, is also frequently used as an electrical conductor. Silver has a higher conductivity than either copper or aluminum; however, its use is restricted on the basis of cost. SEMICONDUCTIVITY Two Types of Semiconductor * Intrinsic Semiconductor -are those the electrical behaviour is based on the electronic structure inherent to the pure material. Extrinsic Semiconductor -when the electrical characteristics are dictated by impurity atoms. Formula for Electrical Conduction for Intrinsic Conductivity * For intrinsic conductors, every electron promoted across the band gap leaves behind a hole in the valence band; thus, * Two Types of Change Carrier *free electrons *holes * Two Types of Extrinsic Semiconductor *n-type Extrinsic semiconductor *p-type Extrinsic semiconductor -The imp urity of the n-type is called donor. -The impurity of the p-type is called an acceptor. Doping- means adding impurities in various techniques. * The Fermi level of n-type semiconductor, is shifted upward in the band gap. * For p-type semiconductor, the Fermi level is positioned within the band gap and near to the acceptor level. * Factor that Affect Carrier mobility -the magnitude of electrons and hole mobilities are influenced by the presence of these of those some crystalline defects that are responsible for the scattering of electrons in metals. INFLUENCE OF TEMPERATURE * SEMICONDUCTOR DEVICES -Diode(rectifier diode) -Transistor Rectifier Diode- is an electronic device that allows the current to flow in one direction only. * Forward Bias -when a battery is used, the positive terminal may be connected to p-side and the negative terminal to the n-side. * Reverse Bias -opposite to forward bias that when minus to p and plus to n. TRANSISTORS Which extremely important semiconducting devices are in today’s microelectronic circuitry. Capable of two primary types of junction. * They can perform the same operation as their vacuum tube precursor, the triode;that is they can amplify an electrical signal. They serve as a switching device in computers for the processing and storage of information. TWO (2) MAJOR TYPES * JUNCTION (or BIMODAL) TRANSISTOR * MOSFET (METAL-OXIDE-SEMICONDUCTOR FIELD-EFFECT TRANSISTOR) JUNCTION TRANSISTOR The junction transistor is composed of two p-n junctions arranged back to back in either the n-p-n or the p-n-p configuration. A very thin n-type base region is sandwiched in between p-t ype emitter collector regions. (fig. 18. 22) The circuit that includes the emitter-base junction (junction 1) is forward biased. Whereas a reverse bias voltage is applied across the base-collector junction (junction 2). MOSFET One variety of MOSFET consists of two small islands of p-type semiconductor that are created within a substrate of n-type silicon. (Fig. 18. 24) The operation of a MOSFET is very similar to that described for the junction transistor but the primary difference is that the gate current is exceedingly small in comparison to the base current of a junction transistor. MOSFETs are, therefore, used where the signal sources to be amplified current. SEMICONDUCTORS IN COMPUTER In addition to their ability to amplify an imposed electrical signal, transistor and diodes may also act as switching devices, a feature utilized for arithmetic and logical operations and also for information storage in computers. Transistors and diodes within digital circuit operate as switches that also have two states -on and off, or conducting and non-conducting. MICROELECTRONIC CIRCUITRY During the past few years, the advent of microelectronic circuitry, where millions of electronic components and circuits are incorporated into a very small space, has revolutionized the field of electronic. This revolution was precipitated, in part, by aerospace technology, which necessitated computers and electronics devices that were small and had low power requirements. Also, the use of integrated circuits has become infused into many other facets of our lives- calculators, communications, watches, industrial production and control, and all phases of the electronics industry. ELECTRICAL CONDUCTION IN IONIC CERAMICS AND IN POLYMERS Most polymers and ionic ceramics are insulating materials at room temperature and, therefore, have electron energy band structures. Gives the room-temperature electrical conductivities of several of these materials. Of course many materials are utilized on the basis of their ability to insulate, and thus a high electrical resistivity is desirable. With rising temperature, insulating materials experience an increase in electrical conductivity, which may ultimately be greater than that for semiconductors. CONDUCTION IN IONIC MATERIALS Both cations and anions in ionic materials possess an electric charge and, as a consequence, are capable of migration or diffusion when an electric field is present. Thus an electric current will result from the net movement of these charged ions, which will be present in addition to current due to any electron motion. Of course, anion and cation migration will be opposite direction. The total conductivity of an ionic material ? total is thus equal to the sum of both electronic and ionic contribution, as follows: ELECTRICAL PROPERTIES OF POLYMERS Most polymeric materials are poor conductors of electricity because of the unavailability of large numbers of free electrons to participate in the conduction process. The mechanism of electrical conduction in these materials is not well understood, but it is felt that conduction in polymers of high purity is electronic. CONDUCTING POLYMERS Within the past several years, polymeric materials have been synthesized that have electrical conductivities on par with metallic conductors; they are appropriately termed conducting polymers. Conductivities as high as 1. 5107 (? -m)-1 have been achieved in these materials; on a volume basis, this value corresponds to one-fourth of the conductivity of copper or twice its conductivity on the basis of weight. These conducting polymers have the potential to be used in a host of applications in as much as they have low densities, are highly flexible and are easy to produce. OTHER ELECTRICAL CHARACTHERISTICS OF MATERIALS Two (2) other relatively important and novel electrical characteristics that are found in some materials deserve brief mention-namely: * Ferroelectricity * Piezoelectricity FERROELECTRICITY The group of dielectric materials called ferroelectrics exhibit spontaneous polarization- that is polarization in the absence of an electric field. They are the dielectric analogue of ferromagnetic materials, which may display permanent magnetic behaviour. There must exist in ferroelectric materials permanent electric dipoles, the origin of which is explained for barium titanate, one of the most common ferroelectric. PIEZOELECTRICITY An unusual property exhibit for a few ceramic materials is piezoelectricity, or, literally, pressure electricity: polarization is induced and an electric field is established across a specimen by the application of external forces reversing the sign of an external force ( i. e. from tension to compression) reverses the direction of the field. Piezoelectric materials are utilized in transducers, which are devices that convert electrical energy into mechanical strains, or vice versa. Some other familiar applications that employ piezoelectric include phonograph cartridges, microphones, speakers, audible alarms and ultrasonic imaging. In a phonograph cartridge, as the stylus traverses the grooves on a r ecord, a pressure variation is imposed on a piezoelectric material located in the cartridge, which is then transformed into an electric signal is amplied before going to the speaker.