Boulder, CO, United States
Boulder, CO, United States

The University of Colorado Boulder is a public research university located in Boulder, Colorado, United States. It is the flagship university of the University of Colorado system and was founded five months before Colorado was admitted to the union in 1876. According to The Public Ivies: America's Flagship Public Universities , it is considered one of the thirty "Public Ivy League" schools.In 2010, the university consisted of nine colleges and schools and offered over 150 academic programs and enrolled 29,952 students. Eleven Nobel Laureates, nine MacArthur Fellows, and 18 astronauts have been affiliated with CU-Boulder as students, researchers, or faculty members in its history. The university received nearly US$454 million in sponsored research in 2010 to fund programs like the Laboratory for Atmospheric and Space Physics, and JILA.Colorado Buffaloes competes in nine intercollegiate sports in the NCAA Division I Pacific-12 Conference. The Buffaloes have won 26 NCAA championships: 19 in skiing, six total in men's and women's cross country, and one in football. Approximately 1,500 students participate in 34 intercollegiate club sports annually as well. Wikipedia.

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Nosil P.,University of Colorado at Boulder | Nosil P.,Institute for Advanced Study | Schluter D.,University of British Columbia
Trends in Ecology and Evolution | Year: 2011

The long-standing goal of finding genes causing reproductive isolation is being achieved. To better link the genetics with the process of speciation, we propose that 'speciation gene' be defined as any gene contributing to the evolution of reproductive isolation. Characterizing a speciation gene involves establishing that the gene affects a component of reproductive isolation; demonstrating that divergence at the locus occurred before completion of speciation; and quantifying the effect size of the gene (i.e. the increase in total reproductive isolation caused by its divergence). Review of a sample of candidate speciation genes found that few meet these criteria. Improved characterization of speciation genes will clarify how numerous they are, their properties and how they affect genome-wide patterns of divergence. © 2011 Elsevier Ltd.

Bowman C.N.,University of Colorado at Boulder | Kloxin C.J.,50 Academy Street
Angewandte Chemie - International Edition | Year: 2012

Smart and responsive: Reversible transesterification reactions were recently used within a polymer network to create a covalently crosslinked material that is capable of being processed as well as mended and recycled. This work is highlighted in the context of the covalent adaptable network approach and illustrates the bond cleavage and reformation mechanism that enable the adaptability of these materials (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Lapenta G.,Catholic University of Leuven | Markidis S.,KTH Royal Institute of Technology | Goldman M.V.,University of Colorado at Boulder | Newman D.L.,University of Colorado at Boulder
Nature Physics | Year: 2015

The primary target of the Magnetospheric MultiScale (MMS) mission is the electron-scale diffusion layer around reconnection sites. Here we study where these regions are found in full three-dimensional simulations. In two dimensions the sites of electron diffusion, defined as the regions where magnetic topology changes and electrons move with respect to the magnetic field lines, are located near the reconnection site. But in three dimensions we find that the reconnection exhaust far from the primary reconnection site also becomes host to secondary reconnection sites. Four diagnostics are used to demonstrate the point: the direct observation of topology impossible without secondary reconnection, the direct measurement of topological field line breakage, the measurement of electron jets emerging from secondary reconnection regions, and the violation of the frozen-in condition. We conclude that secondary reconnection occurs in a large part of the exhaust, providing many more chances for MMS to find itself in the right region to hit its target. © 2015 Macmillan Publishers Limited.

Feder J.L.,University of Notre Dame | Egan S.P.,University of Notre Dame | Nosil P.,University of Colorado at Boulder | Nosil P.,University of Sheffield
Trends in Genetics | Year: 2012

The emerging field of speciation genomics is advancing our understanding of the evolution of reproductive isolation from the individual gene to a whole-genome perspective. In this new view it is important to understand the conditions under which 'divergence hitchhiking' associated with the physical linkage of gene regions, versus 'genome hitchhiking' associated with reductions in genome-wide rates of gene flow caused by selection, can enhance speciation-with-gene-flow. We describe here a theory predicting four phases of speciation, defined by changes in the relative effectiveness of divergence and genome hitchhiking, and review empirical data in light of the theory. We outline future directions, emphasizing the need to couple next-generation sequencing with selection, transplant, functional genomics, and mapping studies. This will permit a natural history of speciation genomics that will help to elucidate the factors responsible for population divergence and the roles that genome structure and different forms of hitchhiking play in facilitating the genesis of new biodiversity. © 2012 Elsevier Ltd.

Mccain C.M.,University of Colorado at Boulder | Colwell R.K.,University of Connecticut
Ecology Letters | Year: 2011

Mountains are centres of global biodiversity, endemism and threatened species. Elevational gradients present opportunities for species currently living near their upper thermal limits to track cooler temperatures upslope in warming climates, but only if changes in precipitation are sufficiently in step with temperature. We model local population extirpation risk for a range of temperature and precipitation scenarios over the next 100years for 16848 vertebrate species populations distributed along 156 elevational gradients. Average population extirpation risks due to warming alone were <5%, but increased 10-fold, on average, when changes in precipitation were also considered. Under the driest scenarios (minimum predicted precipitation), local extirpation risks increased sharply (50-60%) and were especially worrisome for hydrophilic amphibians and montane Latin America (c. 80%). Realistic assessment of risks urgently requires improved monitoring of precipitation, better regional precipitation models and more research on the effects of changes in precipitation on montane distributions. © 2011 Blackwell Publishing Ltd/CNRS.

Smith M.B.,University of Colorado at Boulder | Michl J.,University of Colorado at Boulder | Michl J.,Czech Institute of Organic Chemistry And Biochemistry
Chemical Reviews | Year: 2010

Singlet fission is a process in which an organic chromophore in an excited singlet state shares its excitation energy with a neighboring ground-state chromophore and both are converted into triplet excited states. Singlet fission is spin-allowed in the sense that the two resulting triplet excitations produced from an excited singlet are born coupled into a pure singlet state. Like many other internal conversion processes, it can be very fast, particularly in molecular crystals. The wave function of the initially formed pure singlet state 1(TT) is a coherent superposition of the wave functions of these nine sublevels, and their ultimate population will reflect the amplitude of the singlet 1(TT) wave function in each one. As long as the states resulting from singlet fission are of mixed multiplicity, the overall process can also be viewed as a special case of intersystem crossing. Singlet fission does not occur in single small-molecule chromophores, at least not at the usual excitation energies, and is constrained to multichromophoric systems.

Mckinney J.C.,Kavli Institute for Particle Astrophysics and Cosmology | Uzdensky D.A.,University of Colorado at Boulder
Monthly Notices of the Royal Astronomical Society | Year: 2012

Prompt gamma-ray burst (GRB) emission requires some mechanism to dissipate an ultrarelativistic jet. Internal shocks or some form of electromagnetic dissipation are candidate mechanisms. Any mechanism needs to answer basic questions, such as what is the origin of variability, what radius does dissipation occur at, and how does efficient prompt emission occur. These mechanisms also need to be consistent with how ultrarelativistic jets form and stay baryon pure despite turbulence and electromagnetic reconnection near the compact object and despite stellar entrainment within the collapsar model. We use the latest magnetohydrodynamical models of ultrarelativistic jets to explore some of these questions in the context of electromagnetic dissipation due to the slow collisional and fast collisionless reconnection mechanisms, as often associated with Sweet-Parker and Petschek reconnection, respectively. For a highly magnetized ultrarelativistic jet and typical collapsar parameters, we find that significant electromagnetic dissipation may be avoided until it proceeds catastrophically near the jet photosphere at large radii (r~ 1013-1014cm), by which the jet obtains a high Lorentz factor (γ~ 100-1000), has a luminosity ofLj~ 1050-1051ergs-1, has observer variability time-scales of the order of 1s (ranging from 0.001 to 10s), achieves γθj~ 10-20 (for opening half-angle θj) and so is able to produce jet-breaks, and has comparable energy available for both prompt and afterglow emission. A range of model parameters are investigated and simplified scaling laws are derived. This reconnection switch mechanism allows for highly efficient conversion of electromagnetic energy into prompt emission and associates the observed prompt GRB pulse temporal structure with dissipation time-scales of some number of reconnecting current sheets embedded in the jet. We hope this work helps to motivate the development of self-consistent radiative compressible relativistic reconnection models. © 2011 The Authors Monthly Notices of the Royal Astronomical Society © 2011 RAS.

Kenny D.A.,University of Connecticut | Judd C.M.,University of Colorado at Boulder
Psychological Science | Year: 2014

Two rather surprising anomalies relating to statistical power occur in testing mediation. First, in a model with no direct effect for which the total effect and indirect effect are identical, the power for the test of the total effect can be dramatically smaller than the power for the test of the indirect effect. Second, when there is a direct effect of a causal variable on the outcome controlling for the mediator, the power of the test of the indirect effect is often considerably greater than the power of the test of the direct effect, even when the two are of the same magnitude. We try to explain the reasons for these anomalies and how they affect practice. © The Author(s) 2013.

Smith M.B.,University of Colorado at Boulder | Michl J.,University of Colorado at Boulder | Michl J.,Czech Institute of Organic Chemistry And Biochemistry
Annual Review of Physical Chemistry | Year: 2013

A survey is provided of recent progress in the understanding of singlet fission, a spin-allowed process in which a singlet excited molecule shares its energy with a ground-state neighbor to produce two triplet excited molecules. It has been observed to occur in single-crystal, polycrystalline, and amorphous solids, on timescales from 80 fs to 25 ps, producing triplet yields as high as 200%. Photovoltaic devices using the effect have shown external quantum efficiencies in excess of 100%. Almost all the efficient materials are alternant hydrocarbons of the acene series or their simple derivatives, and it is argued that a wider structural variety would be desirable. The current state of the development of molecular structure design rules, based on first-principles theoretical considerations, is described along with initial examples of implementation. © 2013 by Annual Reviews. All rights reserved.

Agency: National Science Foundation | Branch: | Program: STTR | Phase: Phase I | Award Amount: 225.00K | Year: 2016

This STTR Phase I project addresses the problem of embedded energy in the manufacture of magnesium metal for use in vehicle light-weighting. Improving fuel economy by incorporation of light metals, especially magnesium, does not save on total lifecycle energy consumed if the magnesium was produced using conventional methods. The most energy efficient production method known is a process technology that was commercially viable during the 2nd World War but not at any other time in history. The project innovation is based on reinvestigation and reinvention of this dated process, discovering and addressing the reasons for technical and economic failure. Domestic magnesium production using the proposed state-of-the-art energy-efficient practices will lead to opportunity and growth for downstream manufacturing methods that support a wide range of military, industrial, and consumer products such as car parts, electronic devices, titanium production, and canned beverages. The economic and environmental benefits of the innovation in the long term will be ever more prescient given the unprecedented rise in use of magnesium metal over the past 100 years and expected continuance of this rate of adoption. Production of magnesium using carbothermic chemistry can be realized at temperatures below 1250 degree C using a combination of three operational parameters: 1) reduced pressure atmosphere, 2) addition of a catalytic material, and 3) extensive size reduction of the reactant materials. In conjunction with a continuous condensation and collection system, magnesium produced from this process entails at least a 50% reduction in energy consumption and greenhouse gas emissions compared to the predominant Pidgeon process. The project will employ a variety of high temperature experimental systems and methods to investigate performance of pelletized reactant materials and obtain recovered metal yields above 85%. An optimized composition will be statistically determined and used in a low-temperature prototype reactor system for continuous production of crude magnesium. The goal of the project is to produce a casted magnesium product and prove the reduction of energy intensity and economic feasibility with a techno-economic analysis.

Horneck G.,German Aerospace Center | Klaus D.M.,University of Colorado at Boulder | Mancinelli R.L.,Search for Extraterrestrial Intelligence Institute
Microbiology and Molecular Biology Reviews | Year: 2010

The responses of microorganisms (viruses, bacterial cells, bacterial and fungal spores, and lichens) to selected factors of space (microgravity, galactic cosmic radiation, solar UV radiation, and space vacuum) were determined in space and laboratory simulation experiments. In general, microorganisms tend to thrive in the space flight environment in terms of enhanced growth parameters and a demonstrated ability to proliferate in the presence of normally inhibitory levels of antibiotics. The mechanisms responsible for the observed biological responses, however, are not yet fully understood. A hypothesized interaction of microgravity with radiation-induced DNA repair processes was experimentally refuted. The survival of microorganisms in outer space was investigated to tackle questions on the upper boundary of the biosphere and on the likelihood of interplanetary transport of microorganisms. It was found that extraterrestrial solar UV radiation was the most deleterious factor of space. Among all organisms tested, only lichens (Rhizocarpon geographicum and Xanthoria elegans) maintained full viability after 2 weeks in outer space, whereas all other test systems were inactivated by orders of magnitude. Using optical filters and spores of Bacillus subtilis as a biological UV dosimeter, it was found that the current ozone layer reduces the biological effectiveness of solar UV by 3 orders of magnitude. If shielded against solar UV, spores of B. subtilis were capable of surviving in space for up to 6 years, especially if embedded in clay or meteorite powder (artificial meteorites). The data support the likelihood of interplanetary transfer of microorganisms within meteorites, the so-called lithopanspermia hypothesis. Copyright © 2010, American Society for Microbiology. All Rights Reserved.

Featherstone N.A.,University of Colorado at Boulder | Miesch M.S.,High Altitude Observatory
Astrophysical Journal | Year: 2015

We present a series of 3D nonlinear simulations of solar-like convection, carried out using the Anelastic Spherical Harmonic code, that are designed to isolate those processes that drive and shape meridional circulations (MCs) within stellar convection zones. These simulations have been constructed so as to span the transition between solar-like differential rotation (DR; fast equator/slow poles) and "anti-solar" DR (slow equator/fast poles). Solar-like states of DR, which arise when convection is rotationally constrained, are characterized by a very different convective Reynolds stress (RS) than anti-solar regimes, wherein convection only weakly senses the Coriolis force. We find that the angular momentum transport by convective RS plays a central role in establishing the meridional flow profiles in these simulations. We find that the transition from single-celled to multi-celled MC profiles in strong and weak regimes of rotational constraint is linked to a change in the convective RS, which is a clear demonstration of gyroscopic pumping. Latitudinal thermal variations differ between these different regimes, with those in the solar-like regime conspiring to suppress a single cell of MC, whereas the cool poles and warm equator established in the anti-solar states tend to promote single-celled circulations. Although the convective angular momentum transport becomes radially inward at mid-latitudes in anti-solar regimes, it is the MC that is primarily responsible for establishing a rapidly rotating pole. We conclude with a discussion of how these results relate to the Sun, and suggest that the Sun may lie near the transition between rapidly rotating and slowly rotating regimes. © 2015. The American Astronomical Society. All rights reserved.

Ablowitz M.J.,University of Colorado at Boulder | Musslimani Z.H.,Florida State University
Physical Review Letters | Year: 2013

A new integrable nonlocal nonlinear Schrödinger equation is introduced. It possesses a Lax pair and an infinite number of conservation laws and is PT symmetric. The inverse scattering transform and scattering data with suitable symmetries are discussed. A method to find pure soliton solutions is given. An explicit breathing one soliton solution is found. Key properties are discussed and contrasted with the classical nonlinear Schrödinger equation. © 2013 American Physical Society.

Bauer S.,Swiss Ornithological Institute | Bauer S.,Netherlands Institute of Ecology | Hoye B.J.,University of Colorado at Boulder | Hoye B.J.,Deakin University
Science | Year: 2014

Animal migrations span the globe, involving immense numbers of individuals from a wide range of taxa. Migrants transport nutrients, energy, and other organisms as they forage and are preyed upon throughout their journeys. These highly predictable, pulsed movements across large spatial scales render migration a potentially powerful yet underappreciated dimension of biodiversity that is intimately embedded within resident communities. We review examples from across the animal kingdom to distill fundamental processes by which migratory animals influence communities and ecosystems, demonstrating that they can uniquely alter energy flow, food-web topology and stability, trophic cascades, and the structure of metacommunities. Given the potential for migration to alter ecological networks worldwide, we suggest an integrative framework through which community dynamics and ecosystem functioning may explicitly consider animal migrations.

Radzihovsky L.,University of Colorado at Boulder | Sheehy D.E.,Louisiana State University
Reports on Progress in Physics | Year: 2010

We present an overview of recent developments in species-imbalanced ('polarized') Feshbach-resonant Fermi gases. We summarize the current status of thermodynamics of these systems in terms of a phase diagram as a function of the Feshbach resonance detuning, polarization and temperature. We review instabilities of the s-wave superfluidity across the Bose-Einstein condensation-to-Bardeen-Cooper-Schrieffer crossover to phase separation, Fulde-Ferrell-Larkin-Ovchinnikov states, polarized molecular superfluidity and the normal state, driven by the species imbalance. We discuss different models and approximations of this system and compare their predictions with current experiments. © 2010 IOP Publishing Ltd.

Koban L.,University of Colorado at Boulder | Koban L.,University of Geneva | Pourtois G.,Ghent University
Neuroscience and Biobehavioral Reviews | Year: 2014

Action monitoring allows the swift detection of conflicts, errors, and the rapid evaluation of outcomes. These processes are crucial for learning, adaptive behavior, and for the regulation of cognitive control. Our review discusses neuroimaging and electrophysiological studies that have explored the contribution of emotional and social factors during action monitoring. Meta-analytic brain activation maps demonstrate reliable overlap of error monitoring, emotional, and social processes in the dorsal mediofrontal cortex (dMFC), lateral prefrontal areas, and anterior insula (AI). Cumulating evidence suggests that action monitoring is modulated by trait anxiety and negative affect, and that activity of the dMFC and the amygdala during action monitoring might contribute to the 'affective tagging' of actions along a valence dimension. The role of AI in action monitoring may be the integration of outcome information with self-agency and social context factors, thereby generating more complex situation-specific and conscious emotional feeling states. Our review suggests that action-monitoring processes operate at multiple levels in the human brain, and are shaped by dynamic interactions with affective and social processes. © 2014 Elsevier Ltd.

Kirschner C.M.,University of Colorado at Boulder | Brennan A.B.,University of Florida
Annual Review of Materials Research | Year: 2012

Biofouling is a complex, dynamic problem that globally impacts both the economy and environment. Interdisciplinary research in marine biology, polymer science, and engineering has led to the implementation of bio-inspired strategies for the development of the next generation of antifouling marine coatings. Natural fouling defense mechanisms have been mimicked through chemical, physical, andor stimuli-responsive strategies. This review outlines the detrimental effects associated with biofouling, describes the theoretical basis for antifouling coating design, and highlights prominent advances in bio-inspired antifouling technologies. © Copyright ©2012 by Annual Reviews. All rights reserved.

Agency: GTR | Branch: NERC | Program: | Phase: Research Grant | Award Amount: 250.09K | Year: 2015

The hydroxyl radical (OH) is the dominant oxidizing agent in the troposphere, as such its concentration controls the abundances and lifetimes of most atmospheric pollutants, including the important greenhouse gas methane (CH4). Ozone (O3) is also an important oxidant and is itself a greenhouse gas. The concentrations of OH and O3 are interdependent, both being determined by a complex series of reactions involving CH4, carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs) and nitrogen oxides (NOX = NO + NO2). As emissions of these compounds have changed substantially since pre-industrial times, the tropospheric budgets of OH and O3 will also have changed. However, there are large uncertainties associated with current understanding of these past changes and consequently very large uncertainties in projected future changes and associated climate impacts. Most of this uncertainty in past trends comes from lack of observations to constrain studies. Whilst there are a few direct observational data sets which indicate how O3 concentrations changed through the 20th century, there are none for OH. Direct observational data sets of CH4, NMVOCs, CO and NOX, extend, at best, from the 1980s. These time series can be extended backward in time through the analysis of air trapped in firn (unconsolidated snow). Whilst such historic time series have been available for CH4 for some time, only recently have they become available for CO and for some NMVOCs, in particular alkanes. Furthermore, we have also recently determined, from firn analysis, historic time series of alkyl nitrates. Alkyl nitrates are products of the chemistry involving NOX and as such can be used as a diagnostic of the changes in NOX. These new (and in the case of the alkyl nitrates, unique), historic time series provide an exciting opportunity to investigate the changing OH and O3 budgets of the northern hemisphere troposphere since 1950 with observational constraints never available before. Very interestingly, the simple analyses carried out on these time series to date suggest that substantial changes in the atmospheric chemistry have occurred. To exploit the full value of these time series a detailed study is required with a comprehensive chemistry-climate model. Here we propose the first such study. The outcomes of this study will be: 1) a better understanding of the impact of changing anthropogenic emissions on the OH and O3 budgets of the northern hemisphere troposphere; 2) an improved modelling capability with which to project future changes and better inform climate policy. This proposal brings together experts in firn air data interpretation with experts in chemistry-climate modelling. Both groups also have considerable expertise in organic (including alkyl) nitrate chemistry. This proposal specifically builds on past NERC funded work on the trends of alkanes and alkyl nitrates in firm air using simply relationships and models.

Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase I | Award Amount: 79.98K | Year: 2013

As strontium and other alkaline-earth metals become increasingly attractive for ultracold-atom applications, there is a growing need to develop compact, robust systems for cooling, trapping, and studying these elements. In this proposal, ColdQuanta will team with Dr. Jun Ye at JILA and the University of Colorado at Boulder to develop a portable, turn-key system that can produce, utilize, and optically trap ultracold strontium atoms. The resulting system will serve as the foundation for a strontium-based optical clock or gravimeter that is field-deployable for DoD missions.

Agency: Department of Defense | Branch: Navy | Program: STTR | Phase: Phase II | Award Amount: 496.03K | Year: 2015

Our goal in this Phase II effort is to construct and test a compact, robust testbed for generating laser-cooled strontium atoms on a mobile platform. The focus of the Phase I effort was designing and fabricating an ovenized strontium source that also serves as a 2D+ MOT cell. In Phase II, we will integrate the strontium source into an all-glass-and-silicon vacuum system maintained by a miniature ion pump. This effort will reduce SWaP and significantly reduce the amount of metal, including ferrous materials, in the system. The vacuum cell will be integrated into a turnkey with modular components that allow for easy interchangeability of functions such as timekeeping, sensing, and navigation.

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