Professor Questions Essay Example for Free

Professor Questions Essay 1. Discuss how astronomers compare the stars. There may be several terms astronomists use to compare stars, including luminosity, flux, energy flux, apparent magnitude and absolute magnitude. Luminosity is the total amount of energy given from a body every second, measured in Watts Energy flux is the flow of energy out from a particular surface area and is measured in Watts per meter square. Observed flux – As the radius of the circle placed around the radiating object increases, the flow of energy per meter square would decrease.    The observed flux would be higher if the radius of the circle is less (inverse square law) Apparent Magnitude is the amount of light that is received from a particular star.   It is determined using the luminosity of the star and the distance from us.   The apparent magnitude would be low for a brighter object. Absolute magnitude is the amount of light that is received from a particular object when the object is placed at a distance of 10 par secs (AB’s Astronomy Lab, University of Columbia, 2002). 2. From nebulae, stars are formed. Discuss the factors that affect the gestation time for the birth of protostars. The nebulae from which clouds form are nothing but clouds of dust and gas.   They slowly begin to contract to begin the process of star formation.   The mass is known as the ‘protostars’ and it would continue to condense and slowly heat up.   Once it reaches a critical mass phase, the nuclear fusion reaction takes place hydrogen atoms fuse together to form helium, two protons and tremendous amounts of energy.   Once this phase begins, the star is born. Factors that affect gestation time for the birth of protostars †¢ Gravity of the passing star (external energy to help star formation) †¢ Shockwave from a nearby supernova (external energy to help star formation) †¢ Heating by contraction (Giant molecular clouds need to contract to heat up and begin the thermonuclear processes) †¢ Magnetic fields available (helps in contraction) †¢ Rotation or angular momentum of the protostars †¢ Size of the star (smaller stars live longer than larger stars as they take longer to burn their fuel) (Sea Sky, 2008, UNT, 2008) 3. Discuss how a stars life affected by its `fuel`? Once the protostar gets heated up, nuclear fusion reaction begins (thermonuclear processes), and the star now enters its stable phase.   The star would be combating gravitational collapse by fusing atoms together and forming energy.   The star’s life span depends on how much of matter it actually contains.   The process of nuclear fusion in the stars would involve conversion of hydrogen to helium, helium to carbon, until iron is formed.   Once iron is formed, the energy required to fuse iron is much higher and hence the reaction stops.   Larger stars tend to use up larger amounts of fuel compared to smaller stars, and hence would live much shorter. Several large stars in the universe live for about a few hundreds of thousands of years.   As smaller stars would be spending their fuel much more slowly, they would live for billions of years.   Once a star’s fuel gets exhausted, it would transform into a red supergiant (expanding in size), and would be present for sometime.   The star would then collapse, as the force of the nuclear reactions is not effective to combat the force of gravity.   Some of the stars blow away, to form planetary nebulae.   The core of the star would contain some amount of fuel which would burn as white dwarf.   Once they completely burn away, they would remain as a dark ball known as a ‘black dwarf’.   Some massive stars may trigger a violent explosion, known as ‘supernova’ (Airty Nothing, 2008 Sea Sky, 2008). 4. Discuss basic ideas of the main sequence chart (Hertzsprung-Russell (HR) Diagram). The HR diagram is basically a graph in which the luminosity of the stars (absolute magnitude) is charted against the surface temperature (color).   This chart was discovered separately by Ejnar Hertzsprung and Henry Norris Russell in the 1910’s.   This was following several scientists query whether the temperature of the object could be determined from the color of radiation it emitted.

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Introduction Cancer is a wide-ranging group of diseases caused by uncontrolled cell growth that more than 200 different types have been identified. In this disease, the cells divide and grow intensity, forming malignant tumors, and invading nearby parts of the body(1). Cancer has been in the whole of human history. The oldest written record dates back to about 1600 years BC in Egypt described breast cancer(2). The cause of cancer is complex and partly unknown. Although only 5-10% of cancers are due to inherited gene defects, tobacco, poor diet, certain infections, treated with radiation, lack of physical activity, obesity and pollution can directly damage genes and ultimately lead to carcinogenic mutations (3). Rendering to recent statistics, cancer is responsible for 23% of all deaths in USA and is the second most common cause of death after heart disease (4). It is expected that by 2020 the world population reaches 7.5 billion that 15 million new cases diagnosed and 12 million patients will lose their lives (5). Based on figures provided in 2013 by the American Cancer Society, the most common cancer in women is breast cancer (29%) and in men is prostate cancer (28%) (6). Surgery as a primary method in treatment of solid cancers involved in pain relief and patients survival. In surgery the tumor was completely removed along with the lymph nodes in the area. This method is the only way to eliminate some cases of cancer (7). Other intrusive processes that commonly used are radiation and chemotherapy with the aim of killing the cancerous cells. Because they grow and divide faster than healthy cells so they are sensitive to chemotherapeutic and radiation agents(8). Regarding that the efficiency of a method directly depends on its ab... ...sed to form silica xerogels loaded with drugs, so a changing production conditions(as the ratio of reagents, temperature and concentration of catalyst may alter the properties of xerogels(14). In comparison, mesoporous silica nanoparticles (MSN) form into homogenous structure with higher surface area that is favorable for adsorption of therapeutic drugs(41). MSN particles possess the ability to load large and small molecules, adsorption of DNA and gene transfering(14). A variety of drugs including antibiotics(42), anticancer drugs(41) and heart disease drugs(43) are loaded into mesoporous silica nanoparticles by chemichal or physical adsorption mechanism(41). Through the work of various research groups, it has been shown that silica particles are biocompatible and have a great potential for a variety of diagnostic and therapeutic applications, but recent studied

Features of bluetooth technology Essay

The logo for Bluetooth is based on Runes surrounding the legend of Harald Bluetooth. Bluetooth the technology is based on communications central to man’s own personal space. Fundamentally Bluetooth operates within the Industrial, Scientific and Medical (ISM) band at 2. 4 GHz. It is a short-range wireless communication standard defined as cable replacement for a Personal Area Network (PAN) (see â€Å"Bluetooth†. Grolier Encyclopedia of Knowledge, pp. 87-94). Figure 1 is the Bluetooth Logo. A cable replacement standard has been defined because cables limit mobility of the consumer; they are cumbersome to carry around, are easily lost or broken. Often connectors are prone to difficult to diagnose failures; or are proprietary. To counteract these limitations Bluetooth is designed to be light and portable. It can be embedded to take the riggers of physical knocks and shocks. It includes standards and protocols to make it mobile, robust, reliable and not limited to one manufacturer (see â€Å"Bluetooth†. Grolier Encyclopedia of Knowledge, pp. 87-94). The operating band also fits the goals of Bluetooth, imposing requirements as a cable replacement. The cost needs to be comparable with cable. Reductions can be achieved by operating in the licence free 2. 4 GHz ISM band, keeping backward compatibility wherever possible lowers the cost of ownership by avoiding upgrades and having a relaxed radio specification enables single chip integrated circuit solutions. It also needs to be as reliable and resilient as cable and cope with errors and degradation caused by interference. For mobile devices it must be compact, lightweight, low power and easy to use (see â€Å"Bluetooth†. Grolier Encyclopedia of Knowledge, pp. 87-94). A. 1 Frequency Hopping We have addressed the reasons for the Bluetooth without delving into the ‘nuts and bolts’ of the technology to discover how it operates. For the majority of countries the ISM band used by Bluetooth is available from 2. 40-2. 4835 GHz, although some countries impose restrictions. In this band Bluetooth uses Frequency Hopping Spread Spectrum (FHSS) techniques in order to improve its immunity from interference (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables†, Prentice Hall). In unrestricted countries the radios hop in pseudo random sequences around all available channels, this equates to 79 RF channels with a channel spacing of 1 MHz. Starting at a base frequency of 2402 MHz then the frequency of the channels, f, can be expressed as: f =2402 + n MHz where, n, is the channel number with an integer value in the range of 0 to 78. In restricted countries a limited frequency hopping schemes with just 23 channels is used and is catered for in the Bluetooth specification. Both hopping schemes have a 1 MHz channel spacing making it possible to design a simple radio interface whereby the baseband only has to specify a channel number and the radio multiplies this up to the appropriate frequency offset (see J.Bray and C. F. Sturman, Bluetooth: Connect Without Cables†, Prentice Hall). In this FHSS scheme there are 1600 hops per second, which is a hop every 625  µs. Part of this hop timing is taken up by the guard time of 220  µs allowing the synthesizer time to settle. The frequency hopping implements time division multiplexing as shown in Figure 2. The basis of the scheme has the Master device transmitting in the first 625 us slot, k, and here the Slave receives. In the next slot k = 1 the Slave is permitted to transmit and the master listens (see J.Bray and C. F. Sturman, Bluetooth: Connect Without Cables†, Prentice Hall). Figure 2: Frequency Hopping, master and slave interact on corresponding slots The radio must be able to retune and stabilise on a new frequency within tight time constraints. This is pushed further when establishing a connection; the hop rate can be shortened to every 312. 5 us. As the radios are constantly hopping to different radio channels, this ensures that packets affected by interference on one channel can be retransmitted on a different frequency channel. To further enhance resilience both ARQ (Automatic Repeat reQuest) and FEC (Forward Error Correction) form part of the specification (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables†, Prentice Hall). One drawback with the normal hop sequence is the time taken for production testing. Bluetooth ensures adequate frequency coverage with a test sequence allowing the radios to be tested at a faster rate (see J. Bray and C. F. Sturman, Bluetooth: Connect Without Cables†, Prentice Hall).

Edith Head Hollywoods First Woman Fashion Designer Essay

The 1930s ushered in the Golden Age of Hollywood when new technological advances brought lighting, photography, and sound to a new level of excellence. Along with these technical advances, wardrobe departments of major motion picture studios were busy as costume designers, with the assistance of skilled seamstresses, milliners, and tailors, produced stunning garments for glamorous movie stars. During the 1930s and 1940s the field of costume design was dominated by men. But, that didn’t stop Edith Head, who would become one of Hollywood’s most prolific designers, working on more than 500 films, a record for a career such as hers. One thing that separated Edith from her colleagues was that she was making clothes to suit a character; for†¦show more content†¦At this point, Edith enrolled in night classes at first at the Otis Art Institute and later at the Chouinard. Her specialties were landscapes. Edith retreated into her own world while her husband Charles Head traveled and worked. They spent little time together and their lives grew separately. It was her Catholic faith that not only kept her married but also helped her through this trying period. When Howard Greer, chief designer at what would be Paramount, placed an ad in the paper looking for a sketch artists, Edith answered. Because she had no experience in costume design she asked her fellow students at Chouinard to provide some designs which she signed, and headed off to Paramount. Greer was impressed and hired her at fifty dollars a week. She later said of the borrowed portfolio: I was studying seascape and all I could draw was oceans. I need ed a portfolio, so I borrowed sketches  ­ I didn’t steal them. I asked everybody in the class for a few costume design sketches. And I had 3 the most fantastic assortment you’ve ever seen in your life. When you get a class of forty to give you sketches, you get a nice selection. It never occurred to me that it was quite dishonest. And all the students thought it was fun, too, just like a dare to see if I could get the job. I didn’t say the work was mine. I said â€Å"This is the sort of thing we do in our school.† (Head, 19) The pay was good but the work was far from glamorous. Greer was locked in hisShow MoreRelatedThe Fashion Designers : Edith Head1657 Words   |  7 PagesThroughout Hollywood’s history, there have been several great fashion designers. One of these designers is Edith Head. She had a very long and illustrious career that lasted from 1927 to 1981, and she inspired numerous fashion trends based on her costume designs. As the head designer for both Universal and Paramount, she also worked on several popular films including Roman Holiday, Sabrina, and The Sting. Edith Head was very secretive about her childhood and would often lie about it when questionedRead MoreStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesAyana Jones Senior Managing Editor: Judy Leale Production Project Manager: Becca Groves Senior Operations Supervisor: Arnold Vila Operations Specialist: Cathleen Petersen Senior Art Director: Janet Slowik Art Director: Kenny Beck Text and Cover Designer: Wanda Espana OB Poll Graphics: Electra Graphics Cover Art: honey comb and a bee working / Shutterstock / LilKar Sr. Media Project Manager, Editorial: Denise Vaughn Media Project Manager, Production: Lisa Rinaldi Full-Service Project Management: