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Articles 811 - 840 of 3640

Full-Text Articles in Physical Sciences and Mathematics

Assessing Near Surface Hydrologic Processes And Plant Response Over A 1600 M Mountain Valley Gradient In The Great Basin, Nv, U.S.A., Dale Devitt, Brian Bird, Brad Lyles, Lynn Fenstermaker, Richard Jasoni, Scotty Strachan, Jay Arnone Iii, Franco Biondi, Scott Mensing, Laurel Saito Apr 2018

Assessing Near Surface Hydrologic Processes And Plant Response Over A 1600 M Mountain Valley Gradient In The Great Basin, Nv, U.S.A., Dale Devitt, Brian Bird, Brad Lyles, Lynn Fenstermaker, Richard Jasoni, Scotty Strachan, Jay Arnone Iii, Franco Biondi, Scott Mensing, Laurel Saito

Life Sciences Faculty Research

This study investigated near surface hydrologic processes and plant response over a 1600 m mountain-valley gradient located in the Great Basin of North America (Nevada, U.S.A.) as part of a long-term climate assessment study. The goal was to assess shifts in precipitation, soil water status and associated drainage with elevation and how this influenced evapotranspiration and plant cover/health estimated by a satellite-derived Normalized Difference Vegetation Index (NDVI), all to better understand how water is partitioned in a mountain valley system. Data were acquired during a three-year period from meteorological stations located in five plant communities ranging in elevation from 1756 …

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Craters Of The Moon National Monument Basalts As Unshocked Compositional And Weathering Analogs For Martian Rocks And Meteorites, Christopher T. Adcock, Arya Udry, Elisabeth M. Hausrath, Oliver Tschauner Apr 2018

Craters Of The Moon National Monument Basalts As Unshocked Compositional And Weathering Analogs For Martian Rocks And Meteorites, Christopher T. Adcock, Arya Udry, Elisabeth M. Hausrath, Oliver Tschauner

Geoscience Faculty Research

The availability of terrestrial sites that are martian analogs allows researchers to investigate Mars using knowledge gained on Earth. Among the terrestrial analog sites for Mars is Craters of the Moon National Monument (COTM) in Idaho, U.S.A. Craters of the Moon National Monument is home to over 60 basalt lava flows, many of which have been dated from 2050 to 18 340 years before present (y.b.p.). Following previous authors, we examined the chemistry and petrogenesis of COTM basalts compared to basaltic martian rocks, martian meteorites, and meteorite clasts, and then examined the results of chemical weathering of the basaltic flows. …

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Predicting The Ground-State Structure Of Sodium Boride, Xin-Ling He, Xiao Dong, Quansheng Wu, Zhisheng Zhao, Qiang Zhu, Artem R. Oganov, Yongjun Tian, Dongli Yu, Xiang-Feng Zhou, Hui-Tian Wang Mar 2018

Predicting The Ground-State Structure Of Sodium Boride, Xin-Ling He, Xiao Dong, Quansheng Wu, Zhisheng Zhao, Qiang Zhu, Artem R. Oganov, Yongjun Tian, Dongli Yu, Xiang-Feng Zhou, Hui-Tian Wang

Physics & Astronomy Faculty Research

Binary borides has been a subject of extensive research. However, the exact compositions and crystal structures of sodium borides remained controversial. Here, using the ab initio variable-composition evolutionary algorithm, a new stable Na2B30 with I212121 symmetry (I212121-Na2B30) is found, which is -7.38meV/atom lower in energy than the Imma-Na2B30 structure reported by experimentalists. Interestingly, the Imma-Na2B30 structure is predicted to be a topological nodal line semimetal, which may result in superior electronic transport. In contrast, I212121-Na2B30 is an ultrahard semiconductor with an unprecedented open-framework structure, whose interstitial helical boron sublattice enhances its hardness and energetic stability.

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How Much Water Can We Save By Achieving Renewable Portfolio Standards In The Southwest United States?, Yuzhen Feng, Sachiko Sueki, Dale Devitt, Kumud Acharya Mar 2018

How Much Water Can We Save By Achieving Renewable Portfolio Standards In The Southwest United States?, Yuzhen Feng, Sachiko Sueki, Dale Devitt, Kumud Acharya

Life Sciences Faculty Research

Electricity in the Southwestern United States is primarily generated with water intensive steam turbines. If energy demand continues to rise this will lead to a further rise in water demand. A comprehensive understanding of water consumption and withdrawal for utility scale generation of electricity is necessary before any improvements in the water efficiency of such systems in arid environments can be made. This study estimated and compared the water usage associated with thermoelectric generation (i.e., natural gas, coal), and solar energy, in the five driest Colorado River Basin states: Utah, New Mexico, Nevada, Arizona, and California. This study also examined …

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Humans Thrived In South Africa Through The Toba Eruption About 74,000 Years Ago, Eugene I. Smith, Zenobia Jacobs, Racheal Johnsen, Minghua Ren, Erich C. Fisher, Simen Oestmo, Jayne Wilkins, Jacob A. Harris, Panagiotis Karkanas, Shelby Fitch, Amber Ciravolo, Deborah Keenan, Naomi Cleghorn, Christine S. Lane, Thalassa Matthews, Curtis W. Marean Mar 2018

Humans Thrived In South Africa Through The Toba Eruption About 74,000 Years Ago, Eugene I. Smith, Zenobia Jacobs, Racheal Johnsen, Minghua Ren, Erich C. Fisher, Simen Oestmo, Jayne Wilkins, Jacob A. Harris, Panagiotis Karkanas, Shelby Fitch, Amber Ciravolo, Deborah Keenan, Naomi Cleghorn, Christine S. Lane, Thalassa Matthews, Curtis W. Marean

Geoscience Faculty Research

Approximately 74 thousand years ago (ka), the Toba caldera erupted in Sumatra. Since the magnitude of this eruption was first established, its effects on climate, environment and humans have been debated1. Here we describe the discovery of microscopic glass shards characteristic of the Youngest Toba Tuff—ashfall from the Toba eruption—in two archaeological sites on the south coast of South Africa, a region in which there is evidence for early human behavioural complexity. An independently derived dating model supports a date of approximately 74 ka for the sediments containing the Youngest Toba Tuff glass shards. By defining the input of shards …

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Revisiting Polymorphism Of Molecular Crystals From The Melt, Alexander Shtukenberg, Qiang Zhu, Bart Kahr Mar 2018

Revisiting Polymorphism Of Molecular Crystals From The Melt, Alexander Shtukenberg, Qiang Zhu, Bart Kahr

Physics & Astronomy Faculty Research

No abstract provided.

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On The Progenitors Of Type Ia Supernovae, Mario Livio, Paolo Mazzali Feb 2018

On The Progenitors Of Type Ia Supernovae, Mario Livio, Paolo Mazzali

Physics & Astronomy Faculty Research

We review all the models proposed for the progenitor systems of Type Ia supernovae and discuss the strengths and weaknesses of each scenario when confronted with observations. We show that all scenarios encounter at least a few serious difficulties, if taken to represent a comprehensive model for the progenitors of all Type Ia supernovae (SNe Ia). Consequently, we tentatively conclude that there is probably more than one channel leading SNe Ia. While the single-degenerate scenario (in which a single white dwarf accretes mass from a normal stellar companion) has been studied in some detail, the other scenarios will need a …

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Frb 121102: A Repeatedly Combed Neutron Star By A Nearby Low-Luminosity Accreting Supermassive Black Hole, Bing Zhang Feb 2018

Frb 121102: A Repeatedly Combed Neutron Star By A Nearby Low-Luminosity Accreting Supermassive Black Hole, Bing Zhang

Physics & Astronomy Faculty Research

The origin of fast radio bursts (FRBs) remains mysterious. Recently, the only repeating FRB source, FRB 121102, was reported to possess an extremely large and variable rotation measure (RM). The inferred magnetic field strength in the burst environment is comparable to that in the vicinity of the supermassive black hole Sagittarius A* of our Galaxy. Here, we show that all of the observational properties of FRB 121102 (including the high RM and its evolution, the high linear polarization degree, an invariant polarization angle across each burst and other properties previously known) can be interpreted within the "cosmic comb" model, which …

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Two-Dimensional Ferroelectric Topological Insulators In Functionalized Atomically Thin Bismuth Layers, Liangzhi Kou, Huixia Fu, Yandong Ma, Binghai Yan, Ting Liao, Aijun Du, Changfeng F. Chen Feb 2018

Two-Dimensional Ferroelectric Topological Insulators In Functionalized Atomically Thin Bismuth Layers, Liangzhi Kou, Huixia Fu, Yandong Ma, Binghai Yan, Ting Liao, Aijun Du, Changfeng F. Chen

Physics & Astronomy Faculty Research

We introduce a class of two-dimensional (2D) materials that possess coexisting ferroelectric and topologically insulating orders. Such ferroelectric topological insulators (FETIs) occur in noncentrosymmetric atomic layer structures with strong spin-orbit coupling (SOC). We showcase a prototype 2D FETI in an atomically thin bismuth layer functionalized by CH2OH, which exhibits a large ferroelectric polarization that is switchable by a ligand molecule rotation mechanism and a strong SOC that drives a band inversion leading to the topologically insulating state. An external electric field that switches the ferroelectric polarization also tunes the spin texture in the underlying atomic lattice. Moreover, the functionalized bismuth …

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Integrating System Dynamics And Remote Sensing To Estimate Future Water Usage And Average Surface Runoff In Lagos, Nigeria, Gilles A. Kandissounon, Ajay Karla, Sajjad Ahmad Feb 2018

Integrating System Dynamics And Remote Sensing To Estimate Future Water Usage And Average Surface Runoff In Lagos, Nigeria, Gilles A. Kandissounon, Ajay Karla, Sajjad Ahmad

Civil and Environmental Engineering and Construction Faculty Research

The goal of this study was twofold; first analyze the patterns of water consumption in Lagos, Nigeria and use them in a System Dynamics (SD) model to make projections about future demand. The second part used remote sensing to quantify the contribution of extensive land use/cover change to urban flooding. Land use/cover dynamics over the past decade was analyzed using satellite imagery provided by Landsat Thematic Mapping (TM). Unsupervised classification was performed with false color composite using the Iterative Self-Organizing Data Analysis (ISODATA) technique in a Geographic Information Systems (GIS). The study area was divided into four different land use …

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Grb 130427a Afterglow: A Test For Grb Models, Massimiliano De Pasquale, M. J. Page, D. A. Kann, S. R. Oates, S. Schulze, Bing Zhang, Z. Cano, B. Gendre, D. Malesani, A. Rossi, N. Gehrels, E. Troja, L. Piro, M. Boër, G. Stratta Feb 2018

Grb 130427a Afterglow: A Test For Grb Models, Massimiliano De Pasquale, M. J. Page, D. A. Kann, S. R. Oates, S. Schulze, Bing Zhang, Z. Cano, B. Gendre, D. Malesani, A. Rossi, N. Gehrels, E. Troja, L. Piro, M. Boër, G. Stratta

Physics & Astronomy Faculty Research

Gamma-ray Burst 130427A had the largest fluence for almost 30 years. With an isotropic energy output of 8.5×1053 erg and redshift of 0.34, it combined a very high energy release with a relative proximity to Earth in an unprecedented fashion. Sensitive X-ray facilities such as {\it XMM-Newton} and {\it Chandra} detected the afterglow of this event for a record-breaking baseline of 90 Ms. We show the X-ray light curve of GRB 130427A of this event over such an interval. The light curve shows an unbroken power law decay with a slope of α=1.31 over more than three decades in time. …

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Postaragonite Phases Of Caco3 At Lower Mantle Pressures, Dean Smith, Keith V. Lawler, Miguel Martinez-Canales, Austin W. Daykin, G. Alexander Smith, Christian Childs, Jesse S. Smith, Chris J. Pickard, Ashkan Salamat Jan 2018

Postaragonite Phases Of Caco3 At Lower Mantle Pressures, Dean Smith, Keith V. Lawler, Miguel Martinez-Canales, Austin W. Daykin, G. Alexander Smith, Christian Childs, Jesse S. Smith, Chris J. Pickard, Ashkan Salamat

Chemistry and Biochemistry Faculty Research

The stability, structure, and properties of carbonate minerals at lower mantle conditions have significant impact on our understanding of the global carbon cycle and the composition of the interior of the Earth. In recent years there has been significant interest in the behavior of carbonates at lower mantle conditions, specifically in their carbon hybridization, which has relevance for the storage of carbon within the deep mantle. Using high-pressure synchrotron x-ray diffraction in a diamond anvil cell coupled with direct laser heating of CaCO3 using a CO2 laser, we identify a crystalline phase of the material above 40 GPa—corresponding to a …

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Visualization For Spatial Comprehension, Gabriel Judkins Jan 2018

Visualization For Spatial Comprehension, Gabriel Judkins

UNLV Best Teaching Practices Expo

Mapping and understanding spatial data are fundamental necessities for geographers, yet challenging for many students (Rapp et al. 2007)

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Lecture Capture / Flipping / Clickers, Darrell Lutey Jan 2018

Lecture Capture / Flipping / Clickers, Darrell Lutey

UNLV Best Teaching Practices Expo

Student Success – UNLV needs to improve retention

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Add Interactive Elements To Videos Using H5p, Benjamin Root Jan 2018

Add Interactive Elements To Videos Using H5p, Benjamin Root

UNLV Best Teaching Practices Expo

To increase student engagement, video materials can include interactive components.

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Elastic Geothermobarometry: Corrections For The Geometry Of The Host-Inclusion System, M. L. Mazzucchelli, Pamela Burnley, R. J. Angel, S. Morganti, M. C. Domeneghetti, F. Nestola, M. Alvaro Jan 2018

Elastic Geothermobarometry: Corrections For The Geometry Of The Host-Inclusion System, M. L. Mazzucchelli, Pamela Burnley, R. J. Angel, S. Morganti, M. C. Domeneghetti, F. Nestola, M. Alvaro

Geoscience Faculty Research

Elastic geothermobarometry on inclusions is a method to determine pressure-temperature conditions of mineral growth independent of chemical equilibrium. Because of the difference in their elastic properties, an inclusion completely entrapped inside a host mineral will develop a residual stress upon exhumation, from which one can back-calculate the entrapment pressure. Current elastic geobarometric models assume that both host and inclusion are elastically isotropic and have an ideal geometry (the inclusion is spherical and isolated at the center of an infinite host). These conditions do not commonly occur in natural rocks, and the consequences for inclusion pressures can only be quantified with …

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Energy Saving In Data Centers, Wolfgang W. Bein Jan 2018

Energy Saving In Data Centers, Wolfgang W. Bein

Computer Science Faculty Research

Globally CO2 emissions attributable to Information Technology are on par with those resulting from aviation. Recent growth in cloud service demand has elevated energy efficiency of data centers to a critical area within green computing. Cloud computing represents a backbone of IT services and recently there has been an increase in high-definition multimedia delivery, which has placed new burdens on energy resources. Hardware innovations together with energy-efficient techniques and algorithms are key to controlling power usage in an ever-expanding IT landscape. This special issue contains a number of contributions that show that data center energy efficiency should be addressed from …

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Linear Algebra Applications In 3d Computer Graphics, Albert A. Antero, Chris Choung, Chris Goff Jan 2018

Linear Algebra Applications In 3d Computer Graphics, Albert A. Antero, Chris Choung, Chris Goff

Math 365 Class Projects

Linear Transformations, Homogenous Coordinates, World Matrix, Project Matrices, Normalized Device Coordinates, View Matrix

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Climate Change And Eutrophication: A Short Review, Mohammad Nazari-Sharabian, Sajjad Ahmad, Moses Karakouzian Jan 2018

Climate Change And Eutrophication: A Short Review, Mohammad Nazari-Sharabian, Sajjad Ahmad, Moses Karakouzian

Civil and Environmental Engineering and Construction Faculty Research

Water resources are vital not only for human beings but essentially all ecosystems. Human health is at risk if clean drinking water becomes contaminated. Water is also essential for agriculture, manufacturing, energy production and other diverse uses. Therefore, a changing climate and its potential effects put more pressure on water resources. Climate change may cause increased water demand as a result of rising temperatures and evaporation while decreasing water availability. On the other hand, extreme events as a result of climate change can increase surface runoff and flooding, deteriorating water quality as well. One effect is water eutrophication, which occurs …

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Dynamically Adjusting The Mining Capacity In Cryptocurrency With Binary Blockchain, Yoohwan Kim, Ju-Yeon Jo Jan 2018

Dynamically Adjusting The Mining Capacity In Cryptocurrency With Binary Blockchain, Yoohwan Kim, Ju-Yeon Jo

Computer Science Faculty Research

Many cryptocurrencies rely on Blockchain for its operation. Blockchain serves as a public ledger where all the completed transactions can be looked up. To place transactions in the Blockchain, a mining operation must be performed. However, due to a limited mining capacity, the transaction confirmation time is increasing. To mitigate this problem many ideas have been proposed, but they all come with own challenges. We propose a novel parallel mining method that can adjust the mining capacity dynamically depending on the congestion level. It does not require an increase in the block size or a reduction of the block confirmation …

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Nevada Desert Dust With Heavy Metals Suppresses Igm Antibody Production, Deborah E. Keil, Brenda J. Buck, Dirk Goossens, Brett Mclaurin, Lacey Murphy, Mallory Leetham-Spencer, Yuanxin Teng, James E. Pollard, Russell Gerads, Jamie C. Dewitt Jan 2018

Nevada Desert Dust With Heavy Metals Suppresses Igm Antibody Production, Deborah E. Keil, Brenda J. Buck, Dirk Goossens, Brett Mclaurin, Lacey Murphy, Mallory Leetham-Spencer, Yuanxin Teng, James E. Pollard, Russell Gerads, Jamie C. Dewitt

Geoscience Faculty Research

Systemic health effects from exposure to a complex natural dust containing heavy metals from the Nellis Dunes Recreation Area (NDRA) near Las Vegas, NV, were evaluated. Several toxicological parameters were examined following lung exposure to emissive dust from three geologic sediment types heavily used for recreational off-road activities: yellow sand very rich in arsenic (termed CBN 5); a shallow cover of loose dune sand overlying a gravelly subsoil bordering dune fields (termed CBN 6); and brown claystone and siltstone (termed CBN 7). Adult female B6C3F1 mice were exposed by oropharyngeal administration to these three types of geogenic dusts at 0.01–100 …

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Safe Drinking Water In The U.S.: A Prediction Of When The Entire U.S. Population Will Have Access To Safe Drinking Water, Blossom Hamika, Haley Merrill, Zoyla Orellana Jan 2018

Safe Drinking Water In The U.S.: A Prediction Of When The Entire U.S. Population Will Have Access To Safe Drinking Water, Blossom Hamika, Haley Merrill, Zoyla Orellana

Math 365 Class Projects

This research is to show when all of the U.S. will have access to safe drinking water.

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Encryption And Decryption Using Matricies, Amit Etiel, James Parsons, Shawn Jenkins-Edwards Jan 2018

Encryption And Decryption Using Matricies, Amit Etiel, James Parsons, Shawn Jenkins-Edwards

Math 365 Class Projects

Mathematician Lester Hill developed the Hill Cipher, the first mathematical encryption method ever developed, in 1929. This method was created in order to strengthen the level of security of previous methods and made it possible to encrypt more than three symbols at a time.

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Rock Paper Scissors And Evolutionary Game Theory, Christian Cordova, Rudolf Jovero, Evan Thomas Jan 2018

Rock Paper Scissors And Evolutionary Game Theory, Christian Cordova, Rudolf Jovero, Evan Thomas

Math 365 Class Projects

In Rock Paper Scissors (RPS), three different "species" compete, but no single species has a dominating strategy. In evolutionary game theory, replicator equations model population densities over time. When a mutation is introduced, they are called "replicator-mutator" equations. Using the replicator-mutator equation in [1] we have shown how population density of three species change.

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Modeling Programming Language Trends Using Markov Processes, Cody Clymer, Adrian Alberto, Mike Merrill Jan 2018

Modeling Programming Language Trends Using Markov Processes, Cody Clymer, Adrian Alberto, Mike Merrill

Math 365 Class Projects

Which Languages Are Worth Investing In? One of the many issues in the computer science industry is knowing which technologies to invest in. Programming languages are a prime example of these technologies, so investors and innovators need to know which programming languages will grow in use over time so that new businesses can grow alongside them.

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Black Hole Hyperaccretion Inflow-Outflow Model. I. Long And Ultra-Long Gamma-Ray Bursts, Tong Liu, Cui-Ying Song, Bing Zhang, Wei-Min Gu, Alexander Heger Dec 2017

Black Hole Hyperaccretion Inflow-Outflow Model. I. Long And Ultra-Long Gamma-Ray Bursts, Tong Liu, Cui-Ying Song, Bing Zhang, Wei-Min Gu, Alexander Heger

Physics & Astronomy Faculty Research

Long-duration gamma-ray bursts (LGRBs) and ultra-LGRBs (ULGRBs) originate from collapsars, in the center of which a newborn rotating stellar-mass black hole (BH) surrounded by a massive accretion disk may form. In the scenario of the BH hyperaccretion inflow-outflow model and Blandford-Znajek (BZ) mechanism to trigger gamma-ray bursts (GRBs), the real accretion rate to power a BZ jet is far lower than the mass supply rate from the progenitor star. The characteristics of the progenitor stars can be constrained by GRB luminosity observations, and the results exceed usual expectations. LGRBs lasting from several seconds to tens of seconds in the rest …

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College Of Engineering Senior Design Competition Fall 2017, University Of Nevada, Las Vegas Dec 2017

College Of Engineering Senior Design Competition Fall 2017, University Of Nevada, Las Vegas

Fred and Harriet Cox Senior Design Competition Projects

Part of every UNLV engineering student’s academic experience, the senior design project stimulates engineering innovation and entrepreneurship. Each student in their senior year chooses, plans, designs, and prototypes a product in this required element of the curriculum. A capstone to the student’s educational career, the senior design project encourages the student to use everything learned in the engineering program to create a practical, real world solution to an engineering challenge. The senior design competition helps focus the senior students in increasing the quality and potential for commercial application for their design projects. Judges from local industry evaluate the projects on …

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Competitive Power Down Methods In Green Computing, James Andro-Vasko Dec 2017

Competitive Power Down Methods In Green Computing, James Andro-Vasko

UNLV Theses, Dissertations, Professional Papers, and Capstones

For the power-down problem one considers a device which has states OFF, ON, and a number of intermediate states. The state of the device can be switched at any time. In the OFF state the device consumes zero energy and in the ON state it works at its full power consumption. The intermediate states consume only some fraction of energy proportional to the usage time but switching back to the ON state has has different constant setup cost depending on the current state. Requests for service (i.e. for when the device has to be in the ON state) are not …

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Probing Broad Line Regions Of Active Galactic Nuclei, Champika Sandamali Weerasooriya Dec 2017

Probing Broad Line Regions Of Active Galactic Nuclei, Champika Sandamali Weerasooriya

UNLV Theses, Dissertations, Professional Papers, and Capstones

The broad line regions (BLR) of Type I Active galactic nuclei (AGN) are too small to be spatially resolved even with the most powerful telescopes available. Observations suggest that BLR gas is moving under the influence of the gravitational potential of the central supermassive black-hole (SMBH) and responds to the variations in the ionizing continuum flux of the accretion disk, giving rise to broad emission line variations with a time delay. Reverberation mapping campaigns seek to use this time variability to resolve the BLRs in the time domain instead of spatial domain, providing a way to infer geometry and kinematics …

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Exterior Giant Planet Effects On Terrestrial Architecture, Anna Corinne Childs Dec 2017

Exterior Giant Planet Effects On Terrestrial Architecture, Anna Corinne Childs

UNLV Theses, Dissertations, Professional Papers, and Capstones

Terrestrial planet formation is a chaotic and violent process which is not fully understood. Prior to Kepler, Solar System observations were the basis for planet formation models. How- ever, Kepler observations have shown that exoplanet systems are very different from our solar system, thus requiring a more complete planet formation model. With advancements in com- putational ability, N-body integrators, and collision models, we can explore planet formation by experimenting with simulations in different parameter space. Our Solar System has shown us that exterior giant planets can play a vital role in the shaping of the final terrestrial planet system. Our …

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