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Search Results: 1 - 10 of 252888 matches for " Charles L. Zhao "
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Transcriptional and Metabolic Insights into the Differential Physiological Responses of Arabidopsis to Optimal and Supraoptimal Atmospheric CO2
Fatma Kaplan, Wei Zhao, Jeffrey T. Richards, Raymond M. Wheeler, Charles L. Guy, Lanfang H. Levine
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043583
Abstract: Background In tightly closed human habitats such as space stations, locations near volcano vents and closed culture vessels, atmospheric CO2 concentration may be 10 to 20 times greater than Earth’s current ambient levels. It is known that super-elevated (SE) CO2 (>1,200 μmol mol?1) induces physiological responses different from that of moderately elevated CO2 (up to 1,200 μmol mol?1), but little is known about the molecular responses of plants to supra-optimal [CO2]. Methodology/Principal Findings To understand the underlying molecular causes for differential physiological responses, metabolite and transcript profiles were analyzed in aerial tissue of Arabidopsis plants, which were grown under ambient atmospheric CO2 (400 μmol mol?1), elevated CO2 (1,200 μmol mol?1) and SE CO2 (4,000 μmol mol?1), at two developmental stages early and late vegetative stage. Transcript and metabolite profiling revealed very different responses to elevated versus SE [CO2]. The transcript profiles of SE CO2 treated plants were closer to that of the control. Development stage had a clear effect on plant molecular response to elevated and SE [CO2]. Photosynthetic acclimation in terms of down-regulation of photosynthetic gene expression was observed in response to elevated [CO2], but not that of SE [CO2] providing the first molecular evidence that there appears to be a fundamental disparity in the way plants respond to elevated and SE [CO2]. Although starch accumulation was induced by both elevated and SE [CO2], the increase was less at the late vegetative stage and accompanied by higher soluble sugar content suggesting an increased starch breakdown to meet sink strength resulting from the rapid growth demand. Furthermore, many of the elevated and SE CO2-responsive genes found in the present study are also regulated by plant hormone and stress. Conclusions/Significance This study provides new insights into plant acclimation to elevated and SE [CO2] during development and how this relates to stress, sugar and hormone signaling.
The Interaction of CRM1 and the Nuclear Pore Protein Tpr
Charles L. Zhao, Seyed Hanif Mahboobi, Ruhollah Moussavi-Baygi, Mohammad R. K. Mofrad
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0093709
Abstract: While much has been devoted to the study of transport mechanisms through the nuclear pore complex (NPC), the specifics of interactions and binding between export transport receptors and the NPC periphery have remained elusive. Recent work has demonstrated a binding interaction between the exportin CRM1 and the unstructured carboxylic tail of Tpr, on the nuclear basket. Strong evidence suggests that this interaction is vital to the functions of CRM1. Using molecular dynamics simulations and a newly refined method for determining binding regions, we have identified nine candidate binding sites on CRM1 for C-Tpr. These include two adjacent to RanGTP – from which one is blocked in the absence of RanGTP – and three next to the binding region of the cargo Snurportin. We report two additional interaction sites between C-Tpr and Snurportin, suggesting a possible role for Tpr import into the nucleus. Using bioinformatics tools we have conducted conservation analysis and functional residue prediction investigations to identify which parts of the obtained binding sites are inherently more important and should be highlighted. Also, a novel measure based on the ratio of available solvent accessible surface (RASAS) is proposed for monitoring the ligand/receptor binding process.
Bond order solid of two-dimensional dipolar fermions
S. G. Bhongale,L. Mathey,Shan-Wen Tsai,Charles W. Clark,Erhai Zhao
Physics , 2011, DOI: 10.1103/PhysRevLett.108.145301
Abstract: Recent experimental realization of dipolar Fermi gases near or below quantum degeneracy provides opportunity to engineer Hubbard-like models with long range interactions. Motivated by these experiments, we chart out the theoretical phase diagram of interacting dipolar fermions on the square lattice at zero temperature and half filling. We show that in addition to p-wave superfluid and charge density wave order, two new and exotic types of bond order emerge generically in dipolar fermion systems. These phases feature homogeneous density but periodic modulations of the kinetic hopping energy between nearest or next-nearest neighbors. Similar, but manifestly different, phases of two-dimensional correlated electrons have previously only been hypothesized and termed "density waves of nonzero angular momentum". Our results suggest that these phases can be constructed flexibly with dipolar fermions, using currently available experimental techniques.
Unconventional Spin Density Waves in Dipolar Fermi Gases
S. G. Bhongale,L. Mathey,Shan-Wen Tsai,Charles W. Clark,Erhai Zhao
Physics , 2012, DOI: 10.1103/PhysRevA.87.043604
Abstract: The conventional spin density wave (SDW) phase (Overhauser, 1962), as found in antiferromagnetic metal for example (Fawcett 1988), can be described as a condensate of particle-hole pairs with zero angular momentum, $\ell=0$, analogous to a condensate of particle-particle pairs in conventional superconductors. While many unconventional superconductors with Cooper pairs of finite $\ell$ have been discovered, their counterparts, density waves with non-zero angular momenta, have only been hypothesized in two-dimensional electron systems (Nayak, 2000). Using an unbiased functional renormalization group analysis, we here show that spin-triplet particle-hole condensates with $\ell=1$ emerge generically in dipolar Fermi gases of atoms (Lu, Burdick, and Lev, 2012) or molecules (Ospelkaus et al., 2008; Wu et al.) on optical lattice. The order parameter of these exotic SDWs is a vector quantity in spin space, and, moreover, is defined on lattice bonds rather than on lattice sites. We determine the rich quantum phase diagram of dipolar fermions at half-filling as a function of the dipolar orientation, and discuss how these SDWs arise amidst competition with superfluid and charge density wave phases.
Scintillation Properties and Electronic Structure of Intrinsic and Extrinsic Mixed Elpasolites Cs2NaREBr3I3 (RE = La, Y)
Hua Wei,Mao-Hua Du,Luis Stand,Zhao Zhao,Honglin Shi,Mariya Zhuravleva,Charles L. Melcher
Physics , 2015,
Abstract: Scintillators attract wide research interest for their distinct scientific and technological applications. Elpasolite halides are among the most promising scintillators due to their high structural symmetry and good scintillation performance. Better understanding of their underlying scintillation mechanism in elpasolite halides opens up new possibilities in scintillator development. In this work, we employs a variety of experimental techniques to study the two mixed-anion elpasolites Cs2NaREBr3I3 (RE = La, Y). The emission of intrinsic Cs2NaREBr3I3 with a light yield ranging from 20,000 to 40,000 ph/MeV is dominant by self-trapped excitons emission. Partial substitution of RE with Ce introduces a competing emission, the Ce3+ 5d to 4f radiative transition. Such substitution could significantly improve the energy resolution and light yield, i.e., an exceptional light yield of 58,000 ph/MeV was achieved in Cs2NaLaBr3I3. Ab initio calculations were performed to investigate the electronic structures as well as the binding energies of polarons in Cs2NaREBr6. The highly tunable scintillation properties of mixed-anion elpasolites underscore the role of their complex scintillation mechanism. Our study provides guidance for the design of new elpasolites scintillators with exceptional energy resolution and light yield desirable for applications.
Semi-classical properties of geometric quantization with metaplectic correction
L. Charles
Mathematics , 2006, DOI: 10.1007/s00220-006-0155-5
Abstract: The geometric quantization of a symplectic manifold endowed with a prequantum bundle and a metaplectic structure is defined by means of an integrable complex structure. We prove that its semi-classical limit does not depend on the choice of the complex structure. We show this in two ways. First, by introducing unitary identifications between the quantum spaces associated to the various complex polarizations and second, by defining an asymptotically flat connection in the bundle of quantum spaces over the space of complex structures. Furthermore Berezin-Toeplitz operators are intertwined by these identifications and have principal and subprincipal symbols defined independently of the complex structure. The relation with Schrodinger equation and the group of prequantum bundle automorphisms is considered as well.
Symbolic calculus for Toeplitz operators with half-forms
L. Charles
Mathematics , 2006,
Abstract: This paper is devoted to the use of half-form bundles in the symbolic calculus of Berezin-Toeplitz operators on Kahler manifolds. We state the Bohr-Sommerfeld conditions and relate them to the functional calculus of Toeplitz operators, a trace formula and the characteristic classes in deformation quantization. We also develop the symbolic calculus of Lagrangian sections, with the crucial estimate of the subprincipal terms.
Toeplitz operators and Hamiltonian torus action
L. Charles
Mathematics , 2004,
Abstract: This paper is devoted to semi-classical aspects of symplectic reduction. Consider a compact prequantizable Kahler manifold M with a Hamiltonian torus action. Guillemin and Sternberg introduced an isomorphism between the invariant part of the quantum space associated to M and the quantum space associated to the symplectic quotient of M, provided this quotient is non-singular. We prove that this isomorphism is a Fourier integral operator and that the Toeplitz operators of M descend to Toeplitz operators of the reduced phase space. We also extend these results to the case where the symplectic quotient is an orbifold and estimate the spectral density of a reduced Toeplitz operator, a result related to the Riemann-Roch-Kawazaki theorem.
Genus-Wide Comparative Genomics of Malassezia Delineates Its Phylogeny, Physiology, and Niche Adaptation on Human Skin
Guangxi Wu?,He Zhao,Chenhao Li?,Menaka Priyadarsani Rajapakse?,Wing Cheong Wong?,Jun Xu?,Charles W. Saunders?,Nancy L. Reeder?,Raymond A. Reilman?,Annika Scheynius
PLOS Genetics , 2015, DOI: 10.1371/journal.pgen.1005614
Abstract: Malassezia is a unique lipophilic genus in class Malasseziomycetes in Ustilaginomycotina, (Basidiomycota, fungi) that otherwise consists almost exclusively of plant pathogens. Malassezia are typically isolated from warm-blooded animals, are dominant members of the human skin mycobiome and are associated with common skin disorders. To characterize the genetic basis of the unique phenotypes of Malassezia spp., we sequenced the genomes of all 14 accepted species and used comparative genomics against a broad panel of fungal genomes to comprehensively identify distinct features that define the Malassezia gene repertoire: gene gain and loss; selection signatures; and lineage-specific gene family expansions. Our analysis revealed key gene gain events (64) with a single gene conserved across all Malassezia but absent in all other sequenced Basidiomycota. These likely horizontally transferred genes provide intriguing gain-of-function events and prime candidates to explain the emergence of Malassezia. A larger set of genes (741) were lost, with enrichment for glycosyl hydrolases and carbohydrate metabolism, concordant with adaptation to skin’s carbohydrate-deficient environment. Gene family analysis revealed extensive turnover and underlined the importance of secretory lipases, phospholipases, aspartyl proteases, and other peptidases. Combining genomic analysis with a re-evaluation of culture characteristics, we establish the likely lipid-dependence of all Malassezia. Our phylogenetic analysis sheds new light on the relationship between Malassezia and other members of Ustilaginomycotina, as well as phylogenetic lineages within the genus. Overall, our study provides a unique genomic resource for understanding Malassezia niche-specificity and potential virulence, as well as their abundance and distribution in the environment and on human skin.
Aged rat heart: Modulation of age-related respiratory defects decreases ischemic-reflow injury  [PDF]
Edward J. Lesnefsky, Charles L. Hoppel
Health (Health) , 2013, DOI: 10.4236/health.2013.51001

Myocardial injury increases in the elderly heart during ischemia and reperfusion. Mitochondria, the key targets and sources of injury during ischemia and reperfusion, sustain ischemic damage to the electron transport chain that is superimposed upon age-related defects. In the adult heart, interventions to activate endogenous cytoprotective signaling systems meet in mitochondria to decrease cardiac injury. Unfortunately, these systems are largely ineffective in the aged heart. Thus, new treatment concepts are needed to reduce injury in the aged heart. Our group chose a strategy to directly treat the effector of cardiac injury in the aged heart, the mitochondria. We further utilized a novel approach to ask if the reversal of aging defects in cardiac mitochondria before ischemia could decrease ischemia-reperfusion injury in the heart. Three hours following treatment with the small molecule, nutriceutical acetylcarnitine (AcCN), oxidative phosphorylation as well as age-induced defects in electron transport chain complexes III and IV was corrected in the heart. When such hearts were then exposed to ischemia and reperfusion, cardiac injury was markedly reduced. Contraction during reperfusion improved and recovery became similar to that in adult hearts. Cardiac cell death was substantially reduced. Thus, age-related defects in electron transport are a key mechanism of the increased myocardial injury in the elderly heart during ischemia and reperfusion. Modulation of aging-induced defects in mitochondrial metabolism reduces cardiac injury from ischemia and reperfusion, and is a novel strategy to protect myocardium in the elderly patient at risk for an acute myocardial infarction.

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