College of Sciences E-newsletter

April 2008

In this issue:

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NASA Spitzer Space Telescope

Kentaro Nagamine, assistant professor, department of physics and astronomy, has received a one-year grant ($50,000) in support of his my proposal to the Theory Program of the NASA Spitzer Space Telescope. The proposal, entitled "Infrared Properties of High-z Galaxies", will use cosmological hydrodynamic simulations to predict the infrared properties of high-redshift galaxies observed by Spitzer Telescope.

Abstract: We propose to compute the SEDs of high-redshift galaxies in cosmological hydrodynamicsimulations using the spectrophotometric code GRASIL (Silva et al.  1998) with the wavelength coverage from 100 angstroms to 1 meter. The proposed method will improve the earlier work in the treatment of infrared (IR) emission from dust in high-z star-forming galaxies, by performing the calculation in a more ab initio fashion. Based on the computed SEDs and magnitudes in IRAC/MIPS bands, we will generate the light-cone output of galaxies by stitching numerous simulation output, and examine the number counts, redshift distribution, luminosity functions (LFs) and color-color diagrams by comparing with the Spitzer results directly. In particular, we will assess the validity of the recent claim by Lacey et al. that a top-heavy IMF is necessary to explain the strong evolution of mid-IR LF at 0<z<2 observed by  the Spitzer. The clustering of IR galaxies at 0<z<2 will also be computed and compared with the SWIRE results. Finally we will study the IR properties of massive galaxies at z~6 that were identified by the Spitzer IRAC observations. Our work will provide testable theoretical framework to interpret rich observational datasets provided by Spitzer, and improve physical understanding of galaxy formation and evolution.

http://www.spitzer.caltech.edu/

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Goldwater Scholarship Awarded to UNLV Undergraduate

Karen Levy

Karen Levy, an undergraduate biology and biochemistry major in the College of Sciences and a member of the Honor's College is one of four Nevada residents to receive a Goldwater Scholarship for 2008-2009, and the sole student attending a Nevada institution of higher education. Levy is the second UNLV student to receive this prestigious award, offered annually to approximately 300 students for their outstanding academic and research performance. The 2005 recipient, Archana Nelliott (Biology, 2005) is pursuing her M.D./Ph.D. at Johns Hopkins University.

Levy’s research with associate professor of life sciences Helen Wing focuses on gene expression in a pathogen called Shigella. Shigella and the pathogenic strains of E. coli that we often hear about in the news are close relatives, and Levy’s efforts provide important information about these E. coli strains. Her research focuses on how Shigella modifies its gene expression when it enters the human body and which environmental signals trigger changes in its virulence gene expression. Karen studies the effect of acidic conditions, presence of bile salts, and anaerobic conditions (typically encountered in the lower intestine). These studies will allow scientists to identify conditions that lead to up-regulation of certain virulence genes of during Shigella infection.

Levy observed, "I believe the heart of science is in collaborative learning and communication of knowledge, and I have a great passion for research. Conducting research is important for anyone considering a career in the sciences. Research exposes you to the following truism: advances in scientific knowledge do not come from a textbook, but rather from the exploration of the unknown. Receiving the Goldwater Scholarship enables me to pursue my passion and furthers the potential that my work can have on the world. I am confident my academic plans, commitment to research, and receipt of this award will facilitate my becoming a leader in science. I am truly honored to have received this opportunity; it is a monumental step in my journey toward an M.D./Ph.D."

The Barry M. Goldwater Scholarship and Excellence in Education Program, authorized by the United States Congress in 1986 to honor Senator Barry M. Goldwater establishes in his name a program to foster and encourage excellence in science and mathematics. Goldwater Scholarships seek to alleviate a critical current and future shortage of highly qualified scientists, mathematicians, and engineers and to provide a continuing source of highly qualified individuals to those fields of academic study and research. The awards are made to students who have outstanding potential and intend to pursue careers in mathematics, the natural sciences, or engineering. Each scholarship covers eligible expenses for undergraduate tuition, fees, books, and room and board, up to a maximum of $7,500 annually.

"Karen works incredibly hard. This passion and her love of science allows her excel in her chosen scientific fields of biochemistry and life sciences," Wing noted. "Karen has worked in Dr. Duane Moser's environmental microbiology laboratory at DRI, Dr. Howard Shuman's bacterial pathogenesis lab at Columbia University, and my bacterial infectious disease laboratory at UNLV. In each research position she has excelled and collected meaningful data sets. These research experiences are so important for young scientists. They allow students to experience the joys and frustrations of science first hand, and these experiences help shape the scientists of the future. Karen will present her research at a regional meeting of the American Society of Microbiology and an International Meeting on Prokaryotic Biology to be held in Estes Park, Colorado. Karen's enthusiasm, ability, and hard work will help her to achieve her goal of entering a M.D./Ph.D. program. I am very proud to mentor such a talented student," Wing added.

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Institute of Physics and Mathematics of the Universe (IPMU)

Kentaro Nagamine, assistant professor, department of physics and astronomy, will serve as a visiting professor at Institute of Physics and Mathematics of the Universe (IPMU), University of Tokyo, Japan from June – August 2008.

http://www.ipmu.jp/

The institute is similar to that of the Institute of Advanced Study (IAS) at Princeton University. The Institute for the Physics and Mathematics of the Universe (IPMU) was launched on Oct 1, 2007. This new research institute will integrate the traditionally separate disciplines, mathematics, statistics, theoretical and experimental physics, and astronomy, with a new organizational structure to address deep mysteries of the universe, and push ahead basic research of the university."


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Spring 2008 College of Sciences Newsletter

The Spring 2008 edition of the College of Sciences Newsletter - including a number of features on the activities and accomplishments of our students, faculty, staff, donors, and friends - is available in print and can also be viewed electronically at:

http://sciences.unlv.edu/pdf/newsletters/newsletterspring2008.pdf

This issue includes a variety of stories and news items, including information about: a $ 1 million dollar gift from the estate of Jack and Fay Ross (to support geoscience graduate students); the inaugural award of the UNLV-Emerson Medal for Science Advocacy; recognition from the National Science Foundation (NSF) on our growth in faculty publications; an endowed scholarship established in honor of Father Walter Nowak; a profile of alumnus Nicole Schmitt; the honor roll of recent donors; news about faculty grants and awards, and other features.

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Lecture: "Stem Cells & Regenerative Medicine: Past, Present & Future"

Dr. Denis Rodgerson presented a lecture, entitled, "Stem Cells & Regenerative Medicine: Past, Present & Future." The talk addressed the evolving nature of stem cell research and applications as well as NeoStem, Inc.'s proprietary Very Small Embryonic Like Stem Cells (VSELs) technology and its potential role in the marketplace.

An audience of approximately 110 people enjoyed the lecture and discussion. In addition to many students and faculty members from UNLV, the audience included representatives from the Clark County School District, the Stem Cell Net Foundation of Las Vegas, the Nevada Cancer Institute, the Nevada Development Authority, and the general public.

Dr. Rodgerson has published more than 150 articles in medical and scientific literature and is the holder of several patents. He is an inventor of the proprietary process that serves as the basis for NeoStem's platform stem cell collection business and was the founder of NeoStem's predecessor company. He has been a consultant to many institutions and corporations, including NASA, National Bureau of Standards, Hewlett Packard, and Beckman Instruments. Prior to founding NeoStem, Dr. Rodgerson founded StemCyte, Inc., an umbilical cord blood banking company, where he served as Chief Operating Officer and Senior Vice President until 2002. He is also Professor Emeritus of Pathology and Laboratory Medicine at the UCLA School of Medicine.

Neostem, Inc., which is pioneering the pre-disease collection, processing and long-term storage of adult stem cells for future medical need, today announced that Denis Rodgerson, Ph.D., NeoStem's Director of Stem Cell Science will lecture at The University of Nevada Las Vegas campus this evening. In October 2007, NeoStem announced the expansion of its network of adult stem cell collection centers into Las Vegas, the first in the region.

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Collaborative Research: COMPRES Grand Challenges for Experimental Study of Plastic Deformation ($5,257)

Assistant professor Pamela Burnley is the principal investigator on an NSF funded grant to establish a new inter-institutional program coordinated with COMPRES (Consortium for Materials Property Research in the Earth Sciences) by utilizing the infrastructure for the operation of national facilities and educational programs, and expand the capabilities of these facilities for the broader scientific community.

Abstract: Quantitative rheological measurements on Earth materials have been conducted only under relatively low-pressure conditions corresponding to the depth of ~60 km or less. The main thrust of this project is to extend this limit, through technical developments, at least to ~800 km covering not only the upper mantle but also the transition zone and the lower mantle. We propose to establish a new inter-institutional program coordinated with COMPRES (Consortium for Materials Property Research in the Earth Sciences) by utilizing the infrastructure for operation of national facilities and educational program, and we will expand the capabilities of these facilities for the broader scientific community. Through inter-institutional collaboration, we will develop two new types of apparatus (a modified cubic apparatus (D-DIA) and a rotational Drickamer apparatus (RDA)) in addition to further improvements to the well-established deformation techniques using a multianvil apparatus (MA). Both D-DIA and RDA (as well as MA) can readily be fitted to synchrotron radiation facilities to allow quantitative measurements of stress and strain at high-pressure and temperature conditions. D-DIA is suited for quantitative rheology measurements including shear localization and resultant instabilities while RDA has a unique capability of large strain deformation experiments at high-pressures, an important feature for study of lattice preferred orientation. These apparatus will be used to obtain the first quantitative data set on rheological properties and deformation-induced microstructures of Earth and planetary materials under high-pressure, high-temperature conditions (to ~15-25 GPa, ~2000 K). The results of such measurements will contribute to better understand (i) the radial and lateral variation of rheological properties for whole mantle, (ii) the interaction of rheological behavior with chemical reactions including phase transformations, and (iii) the nature of deformation-induced microstructures such as lattice preferred orientation (which causes seismic anisotropy). The unique facility thus developed will be accessible to a large mineral and rock physics community and will significantly enhance the contribution of mineral and rock physics research to a wide range of solid Earth sciences.

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Graduate and Professional Student Association Research Forum

On March 29, 2008 the UNLV Graduate & Professional Student Association and Graduate College jointly hosted the Graduate & Professional Student Research Forum in the Student Union. This event showcases excellence in research conducted at the graduate/professional level.

Graduate and professional students participate in the annual forum by sharing their research with peers and faculty from across campus, and experience the wide breadth of scholarship generated by the graduate and professional programs at UNLV.

Students present their research either as a poster or as an oral presentation, the work is judged by volunteer UNLV faculty. Awards are given at the close of the event to recognize outstanding presentations. 1st place receives $150 and 2nd place is $100. There is no monetary amount given to honorable mentions.

Science & Engineering: Poster Session 

1st Place Winner: Rebecca J. Carson, School of Life Sciences
Comparative Phylogeography of Boreal Forest Songbirds

Honorable Mention
Steven J. Maglio, Department of Geoscience
An Experimental Study in the MG2S014-FE1-XS-H20 System: Implications for Ganymede’s Interior

Daniel Curtis, School of Life Sciences
Feeding during Low Salinity in the Dungeness Crab, Cancer Magister, is Hormonally Regulated

Science & Engineering: Platform Session: Room 205

1st Place Winner Robyn A. Howley, Department of Geoscience
Carbon-Isotope Variations Across the Middle Cambrian House Range Embayment, Western Utah and Eastern Nevada: Implications for Regional and Global Correlations

2nd Place Winner Derek D. Houston, School of Life Sciences
Post-Glacial Colonization of the Pacific Northwest by a Western North American Minnow

Honorable Mention
Xavier Glaudas, School of Life Sciences
Do Warning Displays Predict Striking Behavior in a Viperid Snake, the Cottonmouth (Agkistrodon Piscivorus)

Science & Engineering: Platform Session: Room 207

1st Place Winner: Christine N. Serway, School of Life Sciences
Transport through the Nuclear Pore Complex is Involved in Learning and Mushroom Body Development in Drosophila; Mushroom Body Miniature B is Pedulin, the Drosphila Importin Alpha 2

2nd Place Winner: Adam Leland, School of Life Sciences
Geographic Patterns of Parthenogenesis in Whiptail Lizards (Genus Aspidoscelis)

Honorable Mention
Margaret Shin, School of Life Sciences
The Role of Arabidopsis WRKY40 in Plant Response to Salt Stress

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William Lowell Putnam Mathematical Competition

The William Lowell Putnam Mathematical Competition, often abbreviated to the Putnam Competition, is an annual mathematics competition for undergraduate college students of the United States and Canada, awarding scholarships and cash prizes ranging from $250 to $2,500 for the top students and $5,000 to $25,000 for the top schools. The competition was founded in 1927 by Elizabeth Lowell Putnam in memory of her husband William Lowell Putnam, who, while alive, was an advocate of intercollegiate intellectual competition. The exam has been offered annually since 1938 and is administered by the Mathematical Association of America.

The 2007 competition included 3,753 contestants from 516 institutions in the United States and Canada. The top five ranking teams (a team consists of three undergraduate students representing their institution) were: Harvard, Princeton, MIT, Stanford, and Duke. The six Putnam fellows (the six highest ranking individuals) hailed from: Caltech (2), MIT (2), Harvard (1), and Princeton (1).

Five students from UNLV took part in the competition and each competitor received a positive score. It should be noted that approximately one-half of all the contestants in this self-selected group of students failed to receive 1 point. The UNLV's team include of Francisco Diaz, David Hannasch, and Nathan Rowe, finished in 83rd place.

UNLV’s highest scoring contestant was Nathan Rowe who, with 36 points out of the maximum of 120 points, took 141st place in the individual ranking. Nathan's performance was particularly impressive. The top five ranking universities were responsible for 117 out of the top 200 contestants and Rose is the highest ranked UNLV student to date.

This is a significant achievement in light of the massive competition and we congratulate all our students.

 

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NASA Summer Internship Award

Lora Griffin, an undergraduate student in the geoscience department, has received a summer internship with the National Aeronautics and Space Administration (NASA), and will work at the National Air and Space Museum of the Smithsonian Institution in Washington D.C. Griffin will help scientists better understand some "bizarre"  geological features on the surface of Mars. Selected students work under the mentorship of a NASA-sponsored Planetary Geology and Geophysics Program Principal Investigator for 8 weeks during the summer months (May through August). 

Griffin will be working with Dr. James R. Zimbelman, Chairman of the Center for Earth and Planetary Studies at the National Air and Space Museum in Washington, D.C. He is internationally known for his work on "topical geologic mapping of Mars and Venus; remote sensing of the terrestrial planets at visual, infrared, and radar wavelengths; lava flow emplacement on the terrestrial planets; sand transport and deposition on Earth and Mars; topographic signatures of paleolake shoreline features on Earth and Mars; and field studies in volcanic and desert terrains.  "Griffin will help him with geologic mapping of some curious yardang features within the Medusae Fossae Formation (MFF) on Mars.  She will measure the yardang orientations and conducting image analyses on the western portions of the MFF.

Planetary geology is the study of the origin and evolution of surfaces and interiors of the solid bodies in the Solar System, including planets, satellites, comets and asteroids. Planetary Geology and Geophysics is a program at NASA established to facilitate the study of the solid bodies in the Solar System.

The Planetary Geology and Geophysics Undergraduate Research Program (PGGURP) was developed to provide undergraduates the opportunity to participate in, and learn from, research in planetary geosciences.

The goals of this program are:

PGGURP provides undergraduates with an excellent opportunity to participate in and consider planetary science research. Participation affords a realistic view of research and a chance for undergraduates to appraise their interest in a particular area of planetary geoscience. Research activities range from participation in theoretical, photogeologic, experimental, laboratory, and/or field studies of processes that occur on other planets or satellites.

 

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Outstanding Thesis

The 2008 recipient for the Outstanding Thesis Award in the College of Sciences is Francisco Javier Virgili. His thesis, entitled, "Monte Carlo Analysis of the Luminosity Function of Gamma Ray Bursts," applies the Monte Carlo simulation technique to constrain gamma-ray burst (GRB) luminosity function (number of GRBs as a function their luminosities) using a set of observational criteria. In particular, he focused on the possibility that low-luminosity GRBs might form a distinct new component. This is a theoretical investigation with the application of observational data.

GRBs are short blasts of gamma-rays from a given location in the sky whose origin is still mysterious. These bursts are observed in equal numbers from every direction in the sky, suggesting they originate outside the Milky Way galaxy. Astronomers think GRBs are caused by massive collapsing stars, or mergers between very heavy objects such as black holes and neutron stars.

In nominating Virgili, his advisor, assistant professor of physics and astronomy Bing Zhang, noted "In early 2006, some observations by NASA’s Swift satellite raised the possibility that low-luminosity GRBs are probably more common. Our group wrote a paper to suggest the two-component luminosity function for long GRBs. This paper (Liang, Zhang, Virgili & Dai, 2007, The Astrophysical Journal, 662, 1111- 1118) was published in June 20, 2007, and has been widely cited by the GRB community. According to the NASA ADS archives, the paper already had 32 citations as of Feb. 22, 2008. Francisco contributed to this publication as the third author. His role was to independently check the results of the leading authors through his Monte Carlo simulations. Later Francisco further developed his code and used a full set of observational criteria (including the 1-dimensional and 2-dimensional distributions of GRB redshifts and luminosities, as well as the peak flux distribution of the detected GRBs by both Swift and an earlier mission BATSE) to test a list of models that have been discussed in the literature (including the two-component model luminosity function model proposed by our group). He drew the conclusion that all the previous one-component models have the difficulty to reproduce at least one observational constraints. He then drew the firm conclusion that the two-component luminosity function model is demanded by the data. This work has been submitted to Monthly Notices of Royal Astronomical Society for publication, and Francisco is the first author of the paper."

No student submitted his or her dissertation for the 2008 Outstanding Dissertation Award, thus no recipient was selected.

 

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Graduate Research - Pacific Northwest National Laboratory; Radiochemical Science and Engineering Group

On May 19, 2008, Troy Robinson, Ph.D. candidate in the Radiation Chemistry program  will begin a research project with Pacific Northwest National Laboratory; Radiochemical Science and Engineering Group, located in Richland, Washington. Robinson’s research will focus on the "simulation of diversion scenarios related to process monitoring systems," and is funded by an Office of Civilian Radioactive Waste Management Graduate Fellowship, and UNLV’s Transmutation Research Program.

Abstract: In future proposed expansion of nuclear power, the International Atomic Energy Agency and the United States are concerned about safeguarding nuclear materials from diversion by terrorists or rogue nations. One of the easiest stages in the nuclear fuel cycle to divert nuclear materials is during nuclear fuel reprocessing, where weapons materials can be separated from the nuclear fuel and used for bombs. Our project is aimed at developing instrumentation that will measure nuclear materials in process streams and provide a real-time accounting of materials present. This type of instrumentation can then enable international oversight agencies to keep operators of nuclear reprocessing plants accountable for their materials and deter terrorist from attempting to steal materials. In the event of materials diversion, this instrumentation can alert oversight agencies and allow for swift recovery of the missing materials. Our project is focusing on using spectroscopy of liquid streams (both aqueous and organic) to determine the quantities and chemical forms of the special nuclear materials present. Once the spectroscopy of the process streams are known, the project will then focus on possible ways to trick the instrumentation that will allow for materials diversion.

 

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Radiation Chemistry

Recent activities in the UNLV Radiochemistry program include

The radiochemistry program graduate students organized a program open house for potential new graduate students, 29 February 2008.

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Pi Day

Pi, Greek letter (π), is the symbol for the ratio of the circumference of a circle to its diameter. Pi = 3.1415926535... Pi Day is celebrated by math enthusiasts around the world on March 14th. Pi Day and Pi Approximation Day are two holidays held to celebrate the mathematical constant π (pi). Pi Day is observed on March 14 (3/14 in American date format), due to π being equal to roughly 3.14. Sometimes it is celebrated on March 14 at 1:59 p.m. (commonly known as Pi Minute). If π is truncated to seven decimal places, it becomes 3.1415926, making March 14 at 1:59:26 p.m., Pi Second (or sometimes March 14, 1592 at 6:53:58 a.m.). Pi Approximation Day may be observed on any of several dates, most often July 22 (22/7 (European date format) is a popular approximation of π). March 14 also happens to be Albert Einstein's birthday. The Massachusetts Institute of Technology often mails out its acceptance letters to be delivered to prospective students on Pi Day.[3]

On March 14th assistant professor of mathematics Daniel Kern was interviewed on Channel 3 for a story on “Pi Day,” and he discussed the significance of this mathematical formula.

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Summer Textbook List

The College of Science is pleased to provide a selected list of courses and textbooks for the Summer 2008 Semester: http://sciences.unlv.edu/pdf/booksummer2008.pdf.

Information for all courses and book lists is not available at this time. Students enrolled in the College of Sciences courses may find the required and/or recommended textbooks and readings available from the Campus Bookstore, area bookstores, and online booksellers.

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Bee Season, Las Vegas Now, Channel 8 News

Bee swarming season is beginning in Clark County. And safety officials are warning residents not to provoke the insects. A local expert spoke with Eye on Health and has some tips in case you find yourself surrounded by a swarm of bees.

Unlike some insects, bees are not afraid of people. Africanized bees, also known as killer bees, are now commonly found in Las Vegas. Tim Szymanski, with Las Vegas Fire and Rescue, says people learn the hard way that bees will attack in large numbers -- if they feel threatened.

"One gentleman, he had a can of Raid and a flyswatter. And when he started spraying inside his fence, he thought he would kill them one by one. When they came out, they literally came out by the hundreds and covered up his head," said Szymanski.

In that case, the man suffered 40 stings. In another situation off Maryland Parkway, a woman was attacked and stung over 500 times. Las Vegas allergist, Joel Katz says for someone who's allergic, any bee sting can trigger a reaction. But he says with multiple stings from aggressive Africanized bees, the toxic reaction can be fatal.

UNLV life-sciences professor, Michelle Elekonich spends a great deal of time studying bees. She says their pollination of agriculture is essential.

"I think the last estimate was that honey bees add over $14 billion to the productivity to U.S. agriculture," said Dr. Elekonich.

Bee swarms are more common this time of year because they're out looking for a new place to build a home. They may become especially aggressive if you're wearing dark clothing or have dark hair. And their keen sense of smell can lock in on sweet beverages. They can also smell fear. Keep that in mind if you encounter a swarm.

"Don't panic. That's the best advice I can give you. Stay calm. Leave them alone. If you see a swarm, and it comes to your yard, wait 24 hours before you do anything because they'll probably go away," said Dr. Elekonich.

If they decide to stay, call a professional. Don't try to get rid of the bees yourself. You may find out the hard way whether or not you're allergic.

"You know you want to leave them alone because they do keep the plants alive. But if they are creating a public safety hazard or a nuisance, then they have to be removed," said Szymanski.

We have more safety tips in case you encounter a swarm. One of them is -- run as fast you can. Bees are slow fliers and probably won't be able to catch up. For other safety tips and information about bees,

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In Memoriam

On February 28, 2008, Michael Arthur Golberg, Ph.D., 66, of Las Vegas, passed away. He was born July 15, 1941, in Montreal, Canada, and resided in Nevada for 44 years. Olberg was a retired professor of mathematics and Professor Emeritus at UNLV. He is survived by his wife, Joyce Golberg; son, Jonathan (Monique) I. Golberg, M.D. of Boynton Beach, Fla.; his daughter, Stefany (Morgan Meis) Golberg of New York City; his brother, Howard (Joan) Golberg of Montreal, Canada; and his grandchildren, Meira, Leah and Sophia Golberg, all of Boynton Beach, Fla. Donations can be made in Michael's name, to the Mathematical Sciences Fund, c/o UNLV Foundation, Box 451006, 4505 S. Maryland Parkway, Las Vegas, NV 89154-1006.

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Debate: "Creation and Evolution"

On April 1, 2008, from 7:30 p.m. – 9:30 p.m., "Creation and Evolution,"  a debate between Dean Ronald Yasbin, College of Sciences and Dr. Charles Jackson, Points of Origin Ministries, took place in the Student Union Theater. The speakers focused on the issue of molecular biology and evidence for the existence of evolution. Each speaker offered a brief overview of his position and the presenters had the opportunity to analyze the observations of their colleague. The debate concluded with the opportunity for the audience to ask questions. 

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Dr. James Hansen, NASA Goddard Institute for Laboratory for Atmospheres, Goddard Space Flight Center

Dr. Hansen has studied the effects of greenhouse gases (GHGs) on Earth’s climate throughout most of his illustrious career. Through his development and application of global models to explore the potential climate effects of unchecked increases in GHG concentrations, Dr. Hansen has become one of the most prominent and recognizable scientific spokespersons on the topic of climate change. Dr. Hansen will present highlights of his climate change research which is open to the public at the Rogers Building Conference Room on the DRI Campus,755 East Flamingo Road, Thursday, April 17, 3:00 p.m.

For more information, please call Greg Bortolin at (702) 862-5409,

or e-mail greg.bortolin@dri.edu

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Department of Mathematical Sciences Colloquia

On Friday, March 7, 2008 Dr. William Layton, Department of Mathematics, University of Pittsburgh delivered a presentation entitled, "Mathematical Architecture of Approximate Deconvolution Models of Turbulence," in CBC-C224.

 

Abstract: Direct numerical simulation of many turbulent flows is not feasible for the foreseeable future within time and resource constraints of many applications. There are thus many approaches to finding reduced models of turbulent flows whose solutions have a smaller number of persistent scales (and thus can be solved more quickly and economically). However, the associated closure problem cannot be solved exactly. Thus, it is possible (and in fact not uncommon) that a given turbulence model's solution has little physical fidelity, quantitative agreement and qualitative agreement with the flow averages sought. This talk presented some recent models of the large structures of turbulent flows that have a fairly complete mathematical theory, that are provably high accurate on the large scales, truncate scales, conserve appropriate integral invariants and are unconditionally stable. An outline of their mathematical structure, which is the reason for their effectiveness, was given.

This talk presented the mathematical structure of the ADM, beginning with basic results of a Leray-type theory that unique, smooth strong solutions exist and converge, modulo a subsequence, to a weak solution of the NSE as the averaging radius d ® 0. Layton examined the consequences of the model energy and helicity balance and apply turbulence phenomenology to the model's predictions of turbulent statistics. He showed that the model predicts a helicity and energy cascade correctly up to the cutoff frequency:

over 0 < k < 1/d,

Finally, he outlined some applications of deconvolution ideas to some regularizations of the NSE such as the recently popular NS-alpha model and the new and promising NS-omega model.

On Friday March 21, 2008, in CBC-C323 from 11:00a.m. - 12:00 p.m. Professor Weizhu Bao, Department of Mathematics, National University of Singapore, delivered a talk entitled "Mathematical Analysis and Numerical Simulation of Bose-Einstein Condensation."

Abstract: I review the mathematical results of the dynamcis of Bose-Einstein condensate (BEC) and present some efficient and stable numerical methods to compute ground states and dynamics of BEC. As preparatory steps, we take the 3D Gross-Pitaevskii equation (GPE) with an angular momentum rotation, scale it to obtain a four-parameter model and show how to reduce it to 2D GPE in certain limiting regimes. Then we study numerically and asymptotically the ground states, excited states and quantized vortex states as well as their energy and chemical potential diagram in rotating BEC. Some very interesting numerical results are observed. Finally, we study numerically stability and interaction of quantized vortices in rotating BEC. Some interesting interaction patterns will be reported.

 On Friday, March 21, 2008, in CBC-C323 (11:00 a.m. - 12:00 p.m.), professor Weizhu Bao, Department of Mathematics, National University of Singapore offered a presentation entitled " Mathematical Analysis and Numerical Simulation of Bose-Einstein Condensation."

Abstract: In this talk, I review the mathematical results of the dynamcis of Bose-Einstein condensate (BEC) and present some efficient and stable numerical methods to compute ground states and dynamics of BEC. As preparatory steps, we take the 3D Gross-Pitaevskii equation (GPE) with an angular momentum rotation, scale it to obtain a four-parameter model and show how to reduce it to 2D GPE in certain limiting regimes. Then we study numerically and asymptotically the ground states, excited states and quantized vortex states as well as their energy and chemical potential diagram in rotating BEC. Some very interesting numerical results are observed. Finally, we study numerically stability and interaction of quantized vortices in rotating BEC. Some interesting interaction patterns will be reported.

On Friday, March 28, 2008 the Department of Mathematical Sciences hosted a Statistics Seminar in the CBC-C Building, room 224. The speaker, Prof. Yuedong Wang received PhD. degree from the University of Wisconsin, Madison. Currently, he is a Professor in the Department of Statistics and Applied Probability at the University of California, Santa Barbara.  His major research interests include theories and methodologies in biostatistical modeling, bootstrap, calibration, error-in-variable, longitudinal data, spatial-temporal data, smoothing spline, generalized linear model, and model selection.

Title of the Talk:  "Nonlinear Nonparametric Regression Models"

Abstract:   Almost all of the current nonparametric regression methods such as smoothing splines, generalized additive models and varying coefficients models assume a linear relationship when nonparametric functions are regarded as parameters. In this talk we present a general class of nonlinear nonparametric models that allow nonparametric functions to act nonlinearly. They  arise in many fields as either theoretical or empirical models. We propose new estimation methods based on an extension of the Gauss-Newton method to infinite dimensional spaces and the backfitting procedure. We extend the generalized cross validation and the generalized maximum likelihood methods to estimate smoothing parameters. Connections between nonlinear nonparametric models and nonlinear mixed effects models are established. Approximate Bayesian confidence intervals are derived for inference. We will also present a user friendly R function for fitting these models. The methods will be illustrated using two real data examples.

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Physics and Astronomy Colloquium

On Friday, March 7, 2008 Professor Jerry Ostriker, Princeton University, delivered a lecture entitled, "Black Hole Accretion and Radiative Feedback."

Abstract: Black holes resident in the centers of galaxies will be fed by accretion of ambient gas whenever gas reaches those central regions. This can be due to mergers, but even without mergers the evolution of the stellar populations of normal galaxies provides very large amounts of gas, as stars pass through the planetary nebula stage, with the total mass release being greater than 1011 Msolar for normal massive ellipticals. Much of that gas will cool and fall to the centers of the systems, where it will induce starbursts and accretion events onto the central black holes. I follow these events with a high resolution hydrodynamic code, allowing for radiative transfer, supernovae and other relevant physical processes. In addition, I examine the spectral output of accreting black holes and find that the high energy output from these objects will strongly inhibit inflow, causing episodic accretion and a low "duty cycle". The simulations help us to understand many phenomena including the black hole stellar mass relation, the paucity of gas in ellipticals, the incidence of the "K+A" phenomena and the observed fact that most of the black holes found in galactic centers are in the "off" state.

On Friday, March 28, 2008 Professor Mitchell C. Begelman from JILA, University of Colorado, Boulder, offered a talk entitled, ""The First Supermassive Black Holes?" in BPB 217.

Abstract: The existence of  a supermassive black hole in nearly every galactic nucleus is no longer in doubt, but the question of how these black holes  formed is wide open.  I will argue that they could have formed directly via the infall and collapse of gas, without the intermediate stage of star formation, if the infall rate was high enough.  Black hole formation by very rapid infall could have occurred in pregalactic haloes as early as redshifts ~10-20, or at lower redshifts in the nuclei of protogalaxies. Global gravitational instabilities get rid of excess angular momentum, and the infalling gas forms a self-gravitating, optically thick structure - a "quasistar".  As matter piles on, the core of the quasistar heats up until it undergoes runaway neutrino cooling and collapses to form a 10 solar mass black hole.   The black hole then grows by accreting from the quasistar at an extremely super-Eddington rate, possibly reaching thousands of solar masses in less than a million years.  Concurrently, the quasistar expands to form a radiation pressure-dominated, convective envelope reminiscent of a red giant.  I will discuss the structure and evolution of quasistars and their detectability with the James Webb Space Telescope.

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