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Stéphanie Barthe, Giorgio Binelli, Bruno Hérault, Caroline Scotti-Saintagne, Daniel Sabatier, Ivan Scotti
How Quaternary climatic and geological disturbances influenced the composition of Neotropical forests is hotly debated. Rain fall and temperature changes during and/or immediately after the Last Glacial Maximum (LGM) are thought to have strongly affected the geographical distribution and local abundance of tree species. The paucity of the fossil records in Neotropical forests prevents a direct reconstruction of such processes. To describe community-level historical trends in forest composition, we turned therefore to inferential methods based on the reconstruction of past demographic changes...
December 7, 2016: Molecular Ecology
Raphael Ritson-Williams, Cliff Ross, Valerie J Paul
As climate change continues to alter seawater temperature and chemistry on a global scale, coral reefs show multiple signs of degradation. One natural process that could facilitate the recovery of reef ecosystems is coral recruitment, which can be influenced by the benthic organisms in a local habitat. We experimentally tested both a global stressor (increased seawater temperature) and a local stressor (exposure to microcolin A, a natural product from a common marine benthic cyanobacterium) to determine how these stressors impacted coral larval sublethal stress, survival and settlement...
2016: PloS One
Ramakanth Neeli-Venkata, Sofia Startceva, Teppo Annila, Andre S Ribeiro
We studied whether nucleoid exclusion contributes to the segregation and retention of Tsr chemoreceptor clusters at the cell poles. Using live time-lapse, single-cell microscopy measurements, we show that the single-cell spatial distributions of Tsr clusters have heterogeneities and asymmetries that are consistent with nucleoid exclusion and cannot be explained by the diffusion-and-capture mechanism supported by Tol-Pal complexes at the poles. Also, in cells subjected to ampicillin, which enhances relative nucleoid lengths, Tsr clusters locate relatively closer to the cell extremities, whereas in anucleated cells (deletion mutants for mukB), the Tsr clusters are closer to midcell...
December 6, 2016: Biophysical Journal
Jiaqi Lin, Alfredo Alexander-Katz
Biological membranes are normally under a resting transmembrane potential (TMP), which originates from the ionic imbalance between extracellular fluids and cytosols, and serves as electric power storage for cells. In cell electroporation, the ionic imbalance builds up a high TMP, resulting in the poration of cell membranes. However, the relationship between ionic imbalance and TMP is not clearly understood, and little is known about the effect of ionic imbalance on the structure and dynamics of biological membranes...
December 6, 2016: Biophysical Journal
Martin J Fossat, Thuy P Dao, Kelly Jenkins, Mariano Dellarole, Yinshan Yang, Scott A McCallum, Angel E Garcia, Doug Barrick, Christian Roumestand, Catherine A Royer
A complete description of the pathways and mechanisms of protein folding requires a detailed structural and energetic characterization of the conformational ensemble along the entire folding reaction coordinate. Simulations can provide this level of insight for small proteins. In contrast, with the exception of hydrogen exchange, which does not monitor folding directly, experimental studies of protein folding have not yielded such structural and energetic detail. NMR can provide residue specific atomic level structural information, but its implementation in protein folding studies using chemical or temperature perturbation is problematic...
December 6, 2016: Biophysical Journal
Minkoo Ahn, Christine L Hagan, Ana Bernardo-Gancedo, Erwin De Genst, Francisco N Newby, John Christodoulou, Anne Dhulesia, Mireille Dumoulin, Carol V Robinson, Christopher M Dobson, Janet R Kumita
The conversion of human lysozyme into amyloid fibrils is associated with a rare but fatal hereditary form of nonneuropathic systemic amyloidosis. The accumulation of large amounts of aggregated protein is thought to be initiated by the formation of transient intermediate species of disease-related lysozyme variants, essentially due to the loss of global cooperativity under physiologically relevant conditions. Interestingly, all five naturally occurring, amyloidogenic, single-point mutations are located in the β-domain of lysozyme, the region that is predominantly unfolded during the formation of the transient intermediate species...
December 6, 2016: Biophysical Journal
Lian Xu, Ji-Quan Sun, Li-Juan Wang, Xiao-Zhen Liu, Yin-Yao Ji, Zhong-Qiu Shao, Xiao-Lei Wu
A Gram-staining-negative, motile, non-spore-forming bacterium designated strain Y4G10-17T was isolated from the saline-alkali farmland top soil, Inner Mongolia, northern China. Strain Y4G10-17T could grow at 4-45°C (with 30°C as the optimal temperature), pH 6.0-12.0 (optimal at pH 9.0), and in the presence of 1.0-12.0 % (w/v) NaCl (optimal at 4.0-6.0 %). Phylogenetic analysis based on the eight different copies of the 16S rRNA gene sequences revealed that strain Y4G10-17T shared the highest sequence similarities with Aliidiomarina maris CF12-14T, 97...
December 7, 2016: International Journal of Systematic and Evolutionary Microbiology
Elizabeth M Corteselli, Michael D Aitken, David R Singleton
The bacterial strain TR3.2T was isolated from aerobic bioreactor-treated soil from a polycyclic aromatic hydrocarbon (PAH)-contaminated site in Salisbury, North Carolina, USA. Strain TR3.2T was identified as a member of "Pyrene Group 2" or "PG2", a previously uncultivated cluster of organisms associated with the degradation of high-molecular-weight PAHs by stable-isotope probing. Based on its 16S rRNA gene sequence the strain was classified as a member of the class Gammaproteobacteria but possessed only 90...
December 7, 2016: International Journal of Systematic and Evolutionary Microbiology
Aude Sivéry, Emmanuel Courtade, Quentin Thommen
Environmental stress, such as oxidative or heat stress, induces the activation of the heat shock response (HSR) and leads to an increase in the heat shock proteins (HSPs) level. These HSPs act as molecular chaperones to maintain cellular proteostasis. Controlled by highly intricate regulatory mechanisms, having stress-induced activation and feedback regulations with multiple partners, the HSR is still incompletely understood. In this context, we propose a minimal molecular model for the gene regulatory network of the HSR that reproduces quantitatively different heat shock experiments both on heat shock factor 1 (HSF1) and HSPs activities...
December 7, 2016: Physical Biology
Hongzhen Bai, Hongjian Zhang
The primary objective of this study is to understand the profiles, sources and cytotoxic effects of atmospheric polycyclic aromatic hydrocarbons (PAHs), which are closely related to urban air contamination and public health, in urban roadside environments. On-road sampling campaigns were conducted from 2014 to 2015 at three urban road sites in Hangzhou, China. Sixteen gaseous and particulate matter (PM) 2.5-bound PAHs were identified and quantified using gas chromatography-mass spectrometry (GC-MS). The total PAH concentrations at the three sites ranged from 750 to1142 ng/m(3) and 1050 to 1483 ng/m(3) in summer and winter, respectively...
December 7, 2016: Journal of Environmental Science and Health. Part A, Toxic/hazardous Substances & Environmental Engineering
Bartomeu Monserrat, David Vanderbilt
We study the effects of temperature on the band structure of the Bi_{2}Se_{3} family of topological insulators using first-principles methods. Increasing temperature drives these materials towards the normal state, with similar contributions from thermal expansion and from electron-phonon coupling. The band gap changes with temperature reach 0.3 eV at 600 K, of similar size to the changes caused by electron correlation. Our results suggest that temperature-induced topological phase transitions should be observable near critical points of other external parameters...
November 25, 2016: Physical Review Letters
Viktor Ivády, Paul V Klimov, Kevin C Miao, Abram L Falk, David J Christle, Krisztián Szász, Igor A Abrikosov, David D Awschalom, Adam Gali
Dynamic nuclear polarization (DNP) is an attractive method for initializing nuclear spins that are strongly coupled to optically active electron spins because it functions at room temperature and does not require strong magnetic fields. In this Letter, we theoretically demonstrate that DNP, with near-unity polarization efficiency, can be generally realized in weakly coupled electron spin-nuclear spin systems. Furthermore, we theoretically and experimentally show that the nuclear spin polarization can be reversed by magnetic field variations as small as 0...
November 25, 2016: Physical Review Letters
J M Little, E Y Choueiri
Electron cooling in a magnetically expanding plasma, which is a fundamental process for plasma flow and detachment in magnetic nozzles, is experimentally investigated using a radio frequency plasma source and magnetic nozzle (MN). Probe measurements of the plasma density, potential, and electron temperature along the center line of the MN indicate that the expansion follows a polytropic law with exponent γ_{e}=1.15±0.03. This value contradicts isothermal electron expansion, γ_{e}=1, which is commonly assumed in MN models...
November 25, 2016: Physical Review Letters
Wenliang Zhang, J T Park, Xingye Lu, Yuan Wei, Xiaoyan Ma, Lijie Hao, Pengcheng Dai, Zi Yang Meng, Yi-Feng Yang, Huiqian Luo, Shiliang Li
The origin of nematic order remains one of the major debates in iron-based superconductors. In theories based on spin nematicity, one major prediction is that the spin-spin correlation length at (0,π) should decrease with decreasing temperature below the structural transition temperature T_{s}. Here, we report inelastic neutron scattering studies on the low-energy spin fluctuations in BaFe_{1.935}Ni_{0.065}As_{2} under uniaxial pressure. Both intensity and spin-spin correlation start to show anisotropic behavior at high temperature, while the reduction of the spin-spin correlation length at (0,π) happens just below T_{s}, suggesting the strong effect of nematic order on low-energy spin fluctuations...
November 25, 2016: Physical Review Letters
K A Flippo, F W Doss, J L Kline, E C Merritt, D Capelli, T Cardenas, B DeVolder, F Fierro, C M Huntington, L Kot, E N Loomis, S A MacLaren, T J Murphy, S R Nagel, T S Perry, R B Randolph, G Rivera, D W Schmidt
Using a large volume high-energy-density fluid shear experiment (8.5  cm^{3}) at the National Ignition Facility, we have demonstrated for the first time the ability to significantly alter the evolution of a supersonic sheared mixing layer by controlling the initial conditions of that layer. By altering the initial surface roughness of the tracer foil, we demonstrate the ability to transition the shear mixing layer from a highly ordered system of coherent structures to a randomly ordered system with a faster growing mix layer, indicative of strong mixing in the layer at a temperature of several tens of electron volts and at near solid density...
November 25, 2016: Physical Review Letters
H-H Kung, S Ran, N Kanchanavatee, V Krapivin, A Lee, J A Mydosh, K Haule, M B Maple, G Blumberg
We study URu_{2-x}Fe_{x}Si_{2}, in which two types of staggered phases compete at low temperature as the iron concentration x is varied: the nonmagnetic "hidden order" (HO) phase below the critical concentration x_{c}, and unconventional antiferromagnetic (AFM) phase above x_{c}. By using polarization resolved Raman spectroscopy, we detect a collective mode of pseudovectorlike A_{2g} symmetry whose energy continuously evolves with increasing x; it monotonically decreases in the HO phase until it vanishes at x=x_{c}, and then reappears with increasing energy in the AFM phase...
November 25, 2016: Physical Review Letters
Se Kwon Kim, Héctor Ochoa, Ricardo Zarzuela, Yaroslav Tserkovnyak
We study a spin Hamiltonian for spin-orbit-coupled ferromagnets on the honeycomb lattice. At sufficiently low temperatures supporting the ordered phase, the effective Hamiltonian for magnons, the quanta of spin-wave excitations, is shown to be equivalent to the Haldane model for electrons, which indicates the nontrivial topology of the band and the existence of the associated edge state. At high temperatures comparable to the ferromagnetic-exchange strength, we take the Schwinger-boson representation of spins, in which the mean-field spinon band forms a bosonic counterpart of the Kane-Mele model...
November 25, 2016: Physical Review Letters
Tommaso Comparin, Werner Krauth
We consider a realistic bosonic N-particle model with unitary interactions relevant for Efimov physics. Using quantum Monte Carlo methods, we find that the critical temperature for Bose-Einstein condensation is decreased with respect to the ideal Bose gas. We also determine the full momentum distribution of the gas, including its universal asymptotic behavior, and compare this crucial observable to recent experimental data. Similar to the experiments with different atomic species, differentiated solely by a three-body length scale, our model only depends on a single parameter...
November 25, 2016: Physical Review Letters
Jolanta Wolska, Michał Czop, Karolina Jakubczyk, Katarzyna Janda
Background: Stinging nettle (Urtica dioica L.) can be found in temperate climate zones of Europe, Africa and America Nettle may be a source of nutritional ingredients, mineral salts, vitamins and antioxidants. Objective: The aim of the study was to determine the effect of temperature and brewing time Urtica dioica L. infusions from different parts of this plant on vitamin C (ascorbic acid) content. Material and methods: Infusions of nettle leaf, stem and root were prepared at room temperature, 50°C, 60°C, 70°C and 80°C for 10 minutes...
2016: Roczniki Państwowego Zakładu Higieny
Yi Wang, Hao-Yi Wang, Man Yu, Li-Min Fu, Yujun Qin, Jian-Ping Zhang, Xi-Cheng Ai
Perovskite films with different particle sizes and PbI₂ contents are prepared by controlled single- or sequential-method. By means of temperature dependent fluorescence spectroscopy, the energetic distribution of intrinsic intra-gap trap states in perovskite is quantitatively determined, and the radiative charge recombinations through band edge and via trap states are respectively studied. Furthermore, a series of thermodynamics parameters, such as the demarcation energy between radiative and non-radiative recombination regions, detrapping activation energy and characteristic temperature, are extracted out, based on which, the possible radiative and non-radiative recombination mechanisms are proposed...
December 7, 2016: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
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