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Articles 9721 - 9750 of 12196

Full-Text Articles in Physical Sciences and Mathematics

The Galaxy Stellar Mass Function At 3.5 ≤ Z ≤ 7.5 In The Candels/Uds, Goods-South, And Hudf Fields, A. Grazian, A. Fontana, P. Santini, J. S. Dunlop, H. C. Ferguson, M. Castellano, R. Amorin, M. L. N. Ashby, G. Barro, P. Behroozi, K. Boutsia, K. I. Caputi, R. R. Chary, A. Dekel, M. E. Dickenson, S. M. Faber, G. G. Fazio, S. L. Finkelstein, A. Galametz, E. Giallongo, M. Giavalisco, N. A. Grogin, Y. Guo, Dale D. Kocevski, A. M. Koekemoer, D. C. Koo, K.-S. Lee, Y. Lu, E. Merlin, B. Mobasher, M. Nonino, C. Paovich, D. Paris, L. Pentericci, N. Reddy, A. Renzini, B. Salmon, M. Salvato, V. Sommariva, M. Song, E. Vanzella Mar 2015

The Galaxy Stellar Mass Function At 3.5 ≤ Z ≤ 7.5 In The Candels/Uds, Goods-South, And Hudf Fields, A. Grazian, A. Fontana, P. Santini, J. S. Dunlop, H. C. Ferguson, M. Castellano, R. Amorin, M. L. N. Ashby, G. Barro, P. Behroozi, K. Boutsia, K. I. Caputi, R. R. Chary, A. Dekel, M. E. Dickenson, S. M. Faber, G. G. Fazio, S. L. Finkelstein, A. Galametz, E. Giallongo, M. Giavalisco, N. A. Grogin, Y. Guo, Dale D. Kocevski, A. M. Koekemoer, D. C. Koo, K.-S. Lee, Y. Lu, E. Merlin, B. Mobasher, M. Nonino, C. Paovich, D. Paris, L. Pentericci, N. Reddy, A. Renzini, B. Salmon, M. Salvato, V. Sommariva, M. Song, E. Vanzella

Physics and Astronomy Faculty Publications

Context. The form and evolution of the galaxy stellar mass function (GSMF) at high redshifts provide crucial information on star formation history and mass assembly in the young Universe, close or even prior to the epoch of reionization.

Aims. We used the unique combination of deep optical/near-infrared/mid-infrared imaging provided by HST, Spitzer, and the VLT in the CANDELS-UDS, GOODS-South, and HUDF fields to determine the GSMF over the redshift range 3.5 ≤ z ≤ 7.5.

Methods. We used the HST WFC3/IR near-infrared imaging from CANDELS and HUDF09, reaching H ≃ 27 − 28.5 over a total area of 369 …


Transitions To Valence-Bond Solid Order In A Honeycomb Lattice Antiferromagnet, Sumiran Pujari, Fabien Alet, Kedar Damle Mar 2015

Transitions To Valence-Bond Solid Order In A Honeycomb Lattice Antiferromagnet, Sumiran Pujari, Fabien Alet, Kedar Damle

Physics and Astronomy Faculty Publications

We use quantum Monte Carlo methods to study the ground-state phase diagram of a S=1/2 honeycomb lattice magnet in which a nearest-neighbor antiferromagnetic exchange J (favoring Néel order) competes with two different multispin interaction terms: a six-spin interaction Q3 that favors columnar valence-bond solid (VBS) order, and a four-spin interaction Q2 that favors staggered VBS order. For Q3Q2J, we establish that the competition between the two different VBS orders stabilizes Néel order in a large swath of the phase diagram even when J is the smallest energy scale in the …


Ward Identities For Transport In 2+1 Dimensions, Carlos Hoyos, Bom Soo Kim, Yaron Oz Mar 2015

Ward Identities For Transport In 2+1 Dimensions, Carlos Hoyos, Bom Soo Kim, Yaron Oz

Physics and Astronomy Faculty Publications

We use the Ward identities corresponding to general linear transformations, and derive relations between transport coefficients of (2 + 1)-dimensional systems. Our analysis includes relativistic and Galilean invariant systems, as well as systems without boost invariance such as Lifshitz theories. We consider translation invariant, as well as broken translation invariant cases, and include an external magnetic field. Our results agree with effective theory relations of incompressible Hall fluid, and with holographic calculations in a magnetically charged black hole background.


The Dust Geometric Distribution In Seyfert 1 And Seyfert 2 Galaxies, Isolated And In Interaction, S. Mendoza-Castrejón, D. Dultzin, Y. Krongold, J. J. González, Moshe Elitzur Mar 2015

The Dust Geometric Distribution In Seyfert 1 And Seyfert 2 Galaxies, Isolated And In Interaction, S. Mendoza-Castrejón, D. Dultzin, Y. Krongold, J. J. González, Moshe Elitzur

Physics and Astronomy Faculty Publications

We analyse the mid-infrared (MIR) spectra of 39 Seyfert galaxies observed with the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. Our sample consists of 19 Seyfert type 1 (Sy1) galaxies, three intermediate Seyfert galaxies and 17 type 2 Seyfert (Sy2) galaxies in the nearby Universe. This sample was extracted from a larger sample, the circumgalactic environment of which was studied in a previous work by Dultzin-Hacyan et al., who found that Sy2 objects are in interaction more frequently than normal galaxies, while Sy1s are not. In this article, we study the silicate dust distribution that dominates the …


Herbicide Recommendations For Weed Control In Kentucky Bluegrass And Tall Fescue Lawns For Professional Applicators, Gregg Munshaw, Jonathan D. Green, Michael Barrett Mar 2015

Herbicide Recommendations For Weed Control In Kentucky Bluegrass And Tall Fescue Lawns For Professional Applicators, Gregg Munshaw, Jonathan D. Green, Michael Barrett

Agriculture and Natural Resources Publications

The best method to control weeds is to grow a dense and healthy lawn. This objective should be primary for turf professionals.


Fundamental Principles Of Plant Pathology For Agricultural Producers [2015], Paul C. Vincelli Mar 2015

Fundamental Principles Of Plant Pathology For Agricultural Producers [2015], Paul C. Vincelli

Agriculture and Natural Resources Publications

All crop plants produced in Kentucky have the potential to become diseased under certain conditions. Diseases of crops can affect yield and/or quality of the harvested commodity, which can impact profitability and increase the risks of farming.


Memories, Kentucky Alfalfa Conference Feb 2015

Memories, Kentucky Alfalfa Conference

Kentucky Alfalfa and Stored Forage Conference

No abstract provided.


Photo Highlights Of The 35th Kentucky Alfalfa Conference, Darold J. Akridge Feb 2015

Photo Highlights Of The 35th Kentucky Alfalfa Conference, Darold J. Akridge

Kentucky Alfalfa and Stored Forage Conference

No abstract provided.


Farmer Panel--What Hay Quality Means To Me, Clayton Geralds, Ben Cox, John Mccoy, Dennis Wright, Minos Cox Feb 2015

Farmer Panel--What Hay Quality Means To Me, Clayton Geralds, Ben Cox, John Mccoy, Dennis Wright, Minos Cox

Kentucky Alfalfa and Stored Forage Conference

No abstract provided.


Hay Quality: What Is It?, Garry D. Lacefield, Don Ball Feb 2015

Hay Quality: What Is It?, Garry D. Lacefield, Don Ball

Kentucky Alfalfa and Stored Forage Conference

Profitable livestock production almost always requires a forage program that will supply large quantities of adequate quality, homegrown feed. A major percentage of the feed units for beef (83%) and dairy cattle (61%) come from forages. In addition, forages supply an estimated 91%, 72%, 15% and 99% of the nutrients consumed by sheep and goats, horses, swine, and wildlife, respectively.


Alfalfa And The Environment, Don Ball Feb 2015

Alfalfa And The Environment, Don Ball

Kentucky Alfalfa and Stored Forage Conference

We live in a society in which many people don’t understand or appreciate agriculture as much as they really should. After all, only about 2% of the population of the United States is involved in agriculture, so most people don’t know much about it. Furthermore, most don’t spend much time thinking about it. Forage crops, including alfalfa, are especially under-appreciated because forage is not consumed directly by humans (alfalfa sprouts being a minor exception).


Red Meat, Our Health And Alfalfa--Separating Scientific Fact From Opinions, Policy, Politics, And Bureaucracy, Peter Ballerstedt Feb 2015

Red Meat, Our Health And Alfalfa--Separating Scientific Fact From Opinions, Policy, Politics, And Bureaucracy, Peter Ballerstedt

Kentucky Alfalfa and Stored Forage Conference

The general public is becoming increasingly aware of the failure of the official nutritional policy of United States and other countries. Books like Good Calories, Bad Calories: Fats, Carbs, and the Controversial Science of Diet and Health (Taubes, 2008), Why We Get Fat and What To Do About It (Taubes, 2011) and The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet (Teicholz, 2014) have exposed the disconnect between nutrition science and nutrition policy, and have told the story of how we’ve come to this point in history.


Grazing Alfalfa: Real Cost Of "Fear" Of Bloat, S. Ray Smith, Kenneth H. Burdine, Jeff Lehmkuhler Feb 2015

Grazing Alfalfa: Real Cost Of "Fear" Of Bloat, S. Ray Smith, Kenneth H. Burdine, Jeff Lehmkuhler

Kentucky Alfalfa and Stored Forage Conference

In the Southeast, including legumes like alfalfa and clover in pastures provides many advantages. It reduces the impact of fescue toxicosis, provides free nitrogen, and improves pasture quality leading to increased animal performance. Individual animal performance is greater on grass/legume pastures compared to performance on similar monoculture grass stands. Daily gains for steers grazing clover-fescue swards is improved compared to straight tall fescue pastures (Figure 1). Improved performance is partially due to greater forage intakes. This practice is sound management even though legume bloat is a risk to livestock. If one considers the number of cattle grazing pastures containing legumes …


What's Required To Break The "Beef Per Acre" Kentucky Record, Kenneth R. Johnson Feb 2015

What's Required To Break The "Beef Per Acre" Kentucky Record, Kenneth R. Johnson

Kentucky Alfalfa and Stored Forage Conference

As I approach the task that Garry assigned me, I ask the question, “Do I really want to attempt to produce 1400 or more pounds of beef per acre?” An easy answer is “yes,” but more likely “no.” Most farmers I know, full or part time have all they can do now and to reach record levels of anything requires much more time and management. I am going to attempt to discuss the steps I think that will be required to reach record breaking production. Higher gains are certainly possible. We know alfalfa can produce 8 to 10 tons of …


Alfalfa Is Our Family Farming Operation, Myron Ellis Feb 2015

Alfalfa Is Our Family Farming Operation, Myron Ellis

Kentucky Alfalfa and Stored Forage Conference

Ellis Family Farm is a 5th generation family farm located in Harrodsburg, KY. Currently we farm 1250 acres total of which 870 acres is owned and the remainder is leased. We buy and resale between 1500-1800 head of feeder cattle per year and have 100 head of brood cows. The cattle operation feed is completely supplied by the first cutting of our 580 acres of alfalfa and alfalfa grass mix hay. From the second cutting on, we produce small square bales of alfalfa for the horse market in four states. Our normal production of square bales ranges between 75,000 and …


Kentucky Alfalfa Conference Reflections After 35 Years, Garry D. Lacefield Feb 2015

Kentucky Alfalfa Conference Reflections After 35 Years, Garry D. Lacefield

Kentucky Alfalfa and Stored Forage Conference

This event today marks the 35th consecutive year we have come together for a full day’s conference featuring "Alfalfa - Queen of the Forages" as the theme and focal point. Only one other state (California) in the U.S. has such an annual event.


Foreword And Recipients Of Kentucky Alfalfa Awards [2015], Garry D. Lacefield, Christi L. Forsythe Feb 2015

Foreword And Recipients Of Kentucky Alfalfa Awards [2015], Garry D. Lacefield, Christi L. Forsythe

Kentucky Alfalfa and Stored Forage Conference

This is the front matter of the proceedings.


Temperature Dependence Of Anisotropic Magnetoresistance In Antiferromagnetic Sr2Iro4, C. Wang, H. Seinige, Gang Cao, J.-S. Zhou, J. B. Goodenough, M. Tsoi Feb 2015

Temperature Dependence Of Anisotropic Magnetoresistance In Antiferromagnetic Sr2Iro4, C. Wang, H. Seinige, Gang Cao, J.-S. Zhou, J. B. Goodenough, M. Tsoi

Center for Advanced Materials Faculty Publications

Temperature-dependent magnetotransport properties of the antiferromagnetic semiconductor Sr2IrO4 are investigated with point-contact devices. The point-contact technique allows to probe very small volumes and, therefore, to look for electronic transport on a microscopic scale. Point-contact measurements with single crystals of Sr2IrO4 were intended to see whether the additional local resistance associated with a small contact area between a sharpened Cu tip and the antiferromagnet shows magnetoresistance (MR) such as that seen in bulk crystals. Point-contact measurements at liquid nitrogen temperature revealed large MRs (up to 28%) for modest magnetic fields (250 mT) applied within an …


Galaxy Zoo: Are Bars Responsible For The Feeding Of Active Galactic Nuclei At 0.2 < Z < 1.0?, Edmond Cheung, Jonathan R. Trump, E. Athanassoula, Steven P. Bamford, Eric F. Bell, A. Bosma, Carolin N. Cardamone, Kevin R. V. Casteels, S. M. Faber, Jerome J. Fang, Lucy F. Fortson, Dale D. Kocevski, David C. Koo, Seppo Laine, Chris Lintott, Karen L. Masters, Thomas Melvin, Robert C. Nichol, Kevin Schawinski, Brooke Simmons, Rebecca Smethurst, Kyle W. Willett Feb 2015

Galaxy Zoo: Are Bars Responsible For The Feeding Of Active Galactic Nuclei At 0.2 < Z < 1.0?, Edmond Cheung, Jonathan R. Trump, E. Athanassoula, Steven P. Bamford, Eric F. Bell, A. Bosma, Carolin N. Cardamone, Kevin R. V. Casteels, S. M. Faber, Jerome J. Fang, Lucy F. Fortson, Dale D. Kocevski, David C. Koo, Seppo Laine, Chris Lintott, Karen L. Masters, Thomas Melvin, Robert C. Nichol, Kevin Schawinski, Brooke Simmons, Rebecca Smethurst, Kyle W. Willett

Physics and Astronomy Faculty Publications

We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 1042 erg s−1 < LX < 1044 erg s−1, with inactive control galaxies matched in stellar mass, rest-frame colour, size, Sérsic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that …


Deconstructing The Galaxy Stellar Mass Function With Ukidss And Candels: The Impact Of Colour, Structure And Environment, Alice Mortlock, Christopher J. Conselice, William G. Hartley, Ken Duncan, Caterina Lani, Jamie R. Owensworth, Omar Almaini, Arjen Van Der Wel, Kuang-Han Huang, Matthew L.N. Ashby, S. P. Willner, Adriano Fontana, Avishai Dekel, Anton M. Koekemoer, Harry C. Ferguson, Sandra M. Faber, Norman A. Grogin, Dale D. Kocevski Feb 2015

Deconstructing The Galaxy Stellar Mass Function With Ukidss And Candels: The Impact Of Colour, Structure And Environment, Alice Mortlock, Christopher J. Conselice, William G. Hartley, Ken Duncan, Caterina Lani, Jamie R. Owensworth, Omar Almaini, Arjen Van Der Wel, Kuang-Han Huang, Matthew L.N. Ashby, S. P. Willner, Adriano Fontana, Avishai Dekel, Anton M. Koekemoer, Harry C. Ferguson, Sandra M. Faber, Norman A. Grogin, Dale D. Kocevski

Physics and Astronomy Faculty Publications

We combine photometry from the Ultra Deep Survey (UDS), Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) UDS and CANDELS the Great Observatories Origins Deep Survey-South (GOODS-S) surveys to construct the galaxy stellar mass function probing both the low- and high-mass end accurately in the redshift range 0.3 < z < 3. The advantages of using a homogeneous concatenation of these data sets include meaningful measures of environment in the UDS, due to its large area (0.88 deg2), and the high-resolution deep imaging in CANDELS (H160 > 26.0), affording us robust measures of structural parameters. We construct stellar mass functions for the entire sample as parametrized by the Schechter function, and find that there is a decline in the values of ϕ and of α with …


The Manga Integral Field Unit Fiber Feed System For Thesloan 2.5 M Telescope, N. Drory, N. Macdonald, M. A. Bershady, K. Bundy, J. Gunn, D. R. Law, M. Smith, R. Stoll, C. A. Tremonti, D. A. Wake, Renbin Yan, A. M. Weijmans, N. Byler, B. Cherinka, F. Cope, A. Eigenbrot, P. Harding, D. Holder, J. Huehnerhoff, K. Jaehnig, T. C. Jansen, M. Klaene, A. M. Paat, J. Percival, C. Sayres Feb 2015

The Manga Integral Field Unit Fiber Feed System For Thesloan 2.5 M Telescope, N. Drory, N. Macdonald, M. A. Bershady, K. Bundy, J. Gunn, D. R. Law, M. Smith, R. Stoll, C. A. Tremonti, D. A. Wake, Renbin Yan, A. M. Weijmans, N. Byler, B. Cherinka, F. Cope, A. Eigenbrot, P. Harding, D. Holder, J. Huehnerhoff, K. Jaehnig, T. C. Jansen, M. Klaene, A. M. Paat, J. Percival, C. Sayres

Physics and Astronomy Faculty Publications

We describe the design, manufacture, and performance of bare-fiber integral field units (IFUs) for the SDSS-IV survey Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) on the the Sloan 2.5 m telescope at Apache Point Observatory. MaNGA is a luminosity-selected integral-field spectroscopic survey of 104 local galaxies covering 360–1030 nm at R ~ 2200. The IFUs have hexagonal dense packing of fibers with packing regularity of 3 μm (rms), and throughput of 96 ± 0.5% from 350 nm to 1 μm in the lab. Their sizes range from 19 to 127 fibers (3–7 hexagonal layers) using Polymicro …


Universality In Fast Quantum Quenches, Sumit R. Das, Damián A. Galante, Robert C. Myers Feb 2015

Universality In Fast Quantum Quenches, Sumit R. Das, Damián A. Galante, Robert C. Myers

Physics and Astronomy Faculty Publications

We expand on the investigation of the universal scaling properties in the early time behaviour of fast but smooth quantum quenches in a general d-dimensional conformal field theory deformed by a relevant operator of dimension Δ with a time-dependent coupling. The quench consists of changing the coupling from an initial constant value λ 1 by an amount of the order of δλ to some other final value λ 2, over a time scale δt. In the fast quench limit where δt is smaller than all other length scales in the problem, δt ≪ λ 1 1/(Δ …


Marshall-Positive Su(N) Quantum Spin Systems And Classical Loop Models: A Practical Strategy To Design Sign-Problem-Free Spin Hamiltonians, Ribku K. Kaul Feb 2015

Marshall-Positive Su(N) Quantum Spin Systems And Classical Loop Models: A Practical Strategy To Design Sign-Problem-Free Spin Hamiltonians, Ribku K. Kaul

Physics and Astronomy Faculty Publications

We consider bipartite SU(N) spin Hamiltonians with a fundamental representation on one sublattice and a conjugate to fundamental on the other sublattice. By mapping these antiferromagnets to certain classical loop models in one higher dimension, we provide a practical strategy to write down a large family of SU(N) symmetric spin Hamiltonians that satisfy Marshall's sign condition. This family includes all previously known sign-free SU(N) spin models in this representation and in addition provides a large set of new models that are Marshall positive and can hence be studied efficiently with quantum Monte Carlo methods. …


Planning A Zero-Waste Event, Ashley Osborne Feb 2015

Planning A Zero-Waste Event, Ashley Osborne

Agriculture and Natural Resources Publications

Today the average American creates a little over 4 pounds of waste per day. Of that, roughly 1 ½ pounds is recycled or composted, meaning that more than 2½ pounds of waste per person per day is discarded to landfills or combusted (with energy recovery).


Repressive Mutations Restore Function-Loss Caused By The Disruption Of Trimerization In Escherichia Coli Multidrug Transporter Acrb, Zhaoshuai Wang, Meng Zhong, Wei Lu, Qian Chai, Yinan Wei Jan 2015

Repressive Mutations Restore Function-Loss Caused By The Disruption Of Trimerization In Escherichia Coli Multidrug Transporter Acrb, Zhaoshuai Wang, Meng Zhong, Wei Lu, Qian Chai, Yinan Wei

Chemistry Faculty Publications

AcrAB-TolC and their homologs are major multidrug efflux systems in Gram-negative bacteria. The inner membrane component AcrB functions as a trimer. Replacement of Pro223 by Gly in AcrB decreases the trimer stability and drastically reduces the drug efflux activity. The goal of this study is to identify suppressor mutations that restore function to mutant AcrBP223G and explore the mechanism of function recovery. Two methods were used to introduce random mutations into the plasmid of AcrBP223G. Mutants with elevated drug efflux activity were identified, purified, and characterized to examine their expression level, trimer stability, interaction with AcrA, and …


Λλ Correlation Function In Au+Au Collisions At √SNn=200  Gev, J. Kevin Adkins, Renee Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer Jan 2015

Λλ Correlation Function In Au+Au Collisions At √SNn=200  Gev, J. Kevin Adkins, Renee Fatemi, Suvarna Ramachandran, L. Adamczyk, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, I. Alekseev, J. Alford, C. D. Anson, A. Aparin, D. Arkhipkin, E. C. Aschenauer

Physics and Astronomy Faculty Publications

We present ΛΛ correlation measurements in heavy-ion collisions for Au+Au collisions at √SNN=200  GeV using the STAR experiment at the Relativistic Heavy-Ion Collider. The Lednický-Lyuboshitz analytical model has been used to fit the data to obtain a source size, a scattering length and an effective range. Implications of the measurement of the ΛΛ correlation function and interaction parameters for dihyperon searches are discussed.


An Embedded Active Nucleus In The Oh Megamaser Galaxy Iras16399−0937, Dinalva A. Sales, A. Robinson, D. J. Axon, J. Gallimore, P. Kharb, R. L. Curran, C. O'Dea, S. Baum, Moshe Elitzur, R. Mittal Jan 2015

An Embedded Active Nucleus In The Oh Megamaser Galaxy Iras16399−0937, Dinalva A. Sales, A. Robinson, D. J. Axon, J. Gallimore, P. Kharb, R. L. Curran, C. O'Dea, S. Baum, Moshe Elitzur, R. Mittal

Physics and Astronomy Faculty Publications

We present a multiwavelength study of the OH megamaser galaxy IRAS16399–0937, based on new Hubble Space Telescope (HST)/Advanced Camera for Surveys F814W and Hα+[N II] images and archive data from HST, Two Micron All Sky Survey, Spitzer, Herschel and the Very Large Array. This system has a double nucleus, whose northern (IRAS16399N) and southern (IRAS16399S) components have a projected separation of ~6'' (3.4 kpc) and have previously been identified based on optical spectra as a low ionization nuclear emission line region (LINER) and starburst nucleus, respectively. The nuclei are embedded in a tidally distorted common envelope, …


Implications Of Coronal Line Emission In Ngc 4696*, Marios Chatzikos, R.J.R. Williams, Gary J. Ferland, R. E. A. Canning, A. C. Fabian, J. S. Sanders, P. A. M. Van Hoof, R. M. Johnstone, Matt L. Lykins, R. L. Porter Jan 2015

Implications Of Coronal Line Emission In Ngc 4696*, Marios Chatzikos, R.J.R. Williams, Gary J. Ferland, R. E. A. Canning, A. C. Fabian, J. S. Sanders, P. A. M. Van Hoof, R. M. Johnstone, Matt L. Lykins, R. L. Porter

Physics and Astronomy Faculty Publications

We announce a new facility in the spectral code cloudy that enables tracking the evolution of a cooling parcel of gas with time. For gas cooling from temperatures relevant to galaxy clusters, earlier calculations estimated the [Fe xiv] λ5303/[Fe x] λ6375 luminosity ratio, a critical diagnostic of a cooling plasma, to slightly less than unity. By contrast, our calculations predict a ratio of ∼3. We revisit recent optical coronal line observations along the X-ray cool arc around NGC 4696 by Canning et al., which detected [Fe x] λ6375, but not [Fe xiv] λ5303. We show that these observations are not …


Design Of Organic Ternary Blends And Small-Molecule Bulk Heterojunctions: Photophysical Considerations, Kallarakkal Ramakrishnan Rajesh, Keshab Paudel, Brian Johnson, Rawad Hallani, John E. Anthony, Oksana Ostroverkhova Jan 2015

Design Of Organic Ternary Blends And Small-Molecule Bulk Heterojunctions: Photophysical Considerations, Kallarakkal Ramakrishnan Rajesh, Keshab Paudel, Brian Johnson, Rawad Hallani, John E. Anthony, Oksana Ostroverkhova

Chemistry Faculty Publications

We explored relationships between photophysical processes and solar cell characteristics in solution-processable bulk heterojunctions (BHJs), in particular: (1) polymer donor:fullerene acceptor:small-molecule (SM) nonfullerene acceptor, (2) polymer donor:SM donor:SM nonfullerene acceptor, and (3) SM donor:SM nonfullerene or fullerene acceptor. Addition of a nonfullerene SM acceptor to “efficient” polymer:fullerene BHJs led to a reduction in power conversion efficiency (PCE), mostly due to decreased charge photogeneration efficiency and increased disorder. By contrast, addition of an SM donor to “inefficient” polymer:SM nonfullerene acceptor BHJs led to a factor of two to three improvement in the PCE, due to improved charge photogeneration efficiency and transport. …


Confinement-Deconfinement Transition As An Indication Of Spin-Liquid-Type Behavior In Na2Iro3, Zhanybek Alpichshev, Fahad Mahmood, Gang Cao, Nuh Gedik Jan 2015

Confinement-Deconfinement Transition As An Indication Of Spin-Liquid-Type Behavior In Na2Iro3, Zhanybek Alpichshev, Fahad Mahmood, Gang Cao, Nuh Gedik

Physics and Astronomy Faculty Publications

We use ultrafast optical spectroscopy to observe binding of charged single-particle excitations (SE) in the magnetically frustrated Mott insulator Na2IrO3. Above the antiferromagnetic ordering temperature (TN) the system response is due to both Hubbard excitons (HE) and their constituent unpaired SE. The SE response becomes strongly suppressed immediately below TN. We argue that this increase in binding energy is due to a unique interplay between the frustrated Kitaev and the weak Heisenberg-type ordering term in the Hamiltonian, mediating an effective interaction between the spin-singlet SE. This interaction grows with distance causing …