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Subtle energies

L Chasmer, C Hopkinson
This study demonstrates linkages between the 1997/98 El Niño/Southern Oscillation index and a threshold shift to increased permafrost loss within a southern Taiga Plains watershed, Northwest Territories, Canada. Three-dimensional contraction of permafrost plateaus and changes in vegetation structural characteristics are determined from multi-temporal airborne Light Detection And Ranging (LiDAR) surveys in 2008, 2011 and 2015. Morphological changes in permafrost cover are compared with optical image analogues from 1970, 1977, 2000, and 2008 and time-series hydro-climate data...
October 22, 2016: Global Change Biology
Elisabeth Therese Ulrikkeholm, Martin Hangaard Hansen, Jan Rossmeisl, Ib Chorkendorff
Gd modified Pt(111) single crystals have been prepared in an ultra high vacuum (UHV). By vacuum deposition of ∼200 Å Gd on a sample heated to 800 °C, a Pt5Gd alloy terminated by a single atomic layer of Pt was formed. Subsequently the surfaces were characterized using low energy electron diffraction (LEED), showing that a highly ordered crystal structure had appeared. To study the molecular dynamics on this surface a detailed study of the CO adsorption on the surface was conducted using temperature programmed desorption (TPD) of CO...
October 19, 2016: Physical Chemistry Chemical Physics: PCCP
Grzegorz Szklarz, Karolina Adrjanowicz, Mateusz Dulski, Justyna Knapik, Marian Paluch
In this work, we have carefully investigated the molecular dynamics in the supercooled liquid and glassy states of the pharmaceutical agent fenofibrate. To do that dielectric relaxation studies at ambient and the elevated pressure were performed. Data collected at atmospheric pressure were found to be in a good agreement with that already reported in the literature. High-pressure studies enable us to distinguish the secondary relaxation processes of the different molecular origin. This includes (i) pressure insensitive $\gamma$-relaxation of the activation energy $E_a$=28 kJ/mol and (ii) $\beta$-relaxation that senses the density increase and originates most probably from the intermolecular movements ($E_a$=77 kJ/mol at 480 MPa)...
October 17, 2016: Journal of Physical Chemistry. B
Tony Rosen, Elizabeth M Bloemen, Jasmin Harpe, Allen M Sanchez, Kevin W Mennitt, Thomas J McCarthy, Refky Nicola, Kieran Murphy, Veronica M LoFaso, Neal Flomenbaum, Mark S Lachs
OBJECTIVE: Elder abuse is underrecognized, and identification of subtle cases requires a high index of suspicion among all health care providers. Because many geriatric injury victims undergo radiographic imaging, diagnostic radiologists may be well positioned to identify injury patterns suggestive of abuse. Little is known about radiologists' experience with elder abuse. Our goal was to describe knowledge, attitudes, training, and practice experience in elder abuse detection among diagnostic radiologists...
October 12, 2016: AJR. American Journal of Roentgenology
Xiaoni Qu, Lianjie Zhai, Bozhou Wang, Qing Wei, Gang Xie, Sanping Chen, Shengli Gao
The persistent challenge in the field of energetic materials is how to synthesize energetic compounds with high density, high heat of detonation and outstanding detonation performance by gathering the maximum number of energetic groups in the smallest volume. The self-assembly of energetic groups with metal ions is crucially influenced by the solvent conditions. Here, the reaction of Cu(NO3)2·3H2O with 3-nitro-1H-1,2,4-triazole (Hntz) in aqueous ammonia under hydrothermal conditions via a self-assembly strategy yielded the Cu(i) energetic compound [Cu(ntz)]n (1)...
October 10, 2016: Dalton Transactions: An International Journal of Inorganic Chemistry
Anja Poblotzki, Jonas Altnöder, Martin A Suhm
Methanol is shown to engage two nearly equivalent solvation sites in 2,5-dimethylfuran, the electron-rich π cloud and the electron-deficient oxygen site. The latter only wins by a slight margin, thanks to the methyl group undergoing secondary interactions with the ring. These secondary attractions reduce the hydrogen bond-induced OH frequency shift of the OH-O contact, whereas the π cloud allows for a combined action of both binding mechanisms in the OH-π arrangement. In total, the hydrophobic character of 2,5-dimethylfuran is well reflected in the weak pair interactions, as judged by the small solvation shifts...
October 5, 2016: Physical Chemistry Chemical Physics: PCCP
Simon J Schreiner, Thomas Kirchner, Michael Wyss, Jiri M G Van Bergen, Frances C Quevenco, Stefanie C Steininger, Erica Y Griffith, Irene Meier, Lars Michels, Anton F Gietl, Sandra E Leh, Adam M Brickman, Christoph Hock, Roger M Nitsch, Klaas P Pruessmann, Anke Henning, Paul G Unschuld
Low episodic memory performance characterizes elderly subjects at increased risk for Alzheimer's disease (AD) and may reflect neuronal dysfunction within the posterior cingulate cortex and precuneus (PCP) region. To investigate a potential association between cerebral neurometabolism and low episodic memory in the absence of cognitive impairment, tissue-specific magnetic resonance spectroscopic imaging at ultrahigh field strength of 7 Tesla was used to investigate the PCP region in a healthy elderly study population (n = 30, age 70 ± 5...
August 31, 2016: Neurobiology of Aging
Karthika Suresh, Shivprasad Patil, Pattuparambil Ramanpillai Rajamohanan, Guruswamy Kumaraswamy
Subtle variations in the preparation of ice-templated nanoparticle assemblies yield monoliths that are chemically identical, but that exhibit qualitatively different mechanical behavior. We ice template aqueous dispersions to prepare macroporous monoliths comprising largely of silica nanoparticles held together by a crosslinked polymer mesh. When the polymer is crosslinked in the presence of ice crystals, we obtain an elastic sponge that is capable of recovery after imposition of large compressive strains (up to 80%)...
October 7, 2016: Langmuir: the ACS Journal of Surfaces and Colloids
James J P Stewart
A new method for predicting the energy contributions to substrate binding and to specificity has been developed. Conventional global optimization methods do not permit the subtle effects responsible for these properties to be modeled with sufficient precision to allow confidence to be placed in the results, but by making simple alterations to the model, the precisions of the various energies involved can be improved from about ±2 kcal mol(-1) to ±0.1 kcal mol(-1). This technique was applied to the oxidized nucleotide pyrophosphohydrolase enzyme MTH1...
November 2016: Journal of Molecular Modeling
Mireia Díaz-Lobo, Alda Lisa Concia, Livia Gómez, Pere Clapés, Ignacio Fita, Joan J Guinovart, Joan C Ferrer
Glycogen synthase (GS) and glycogen phosphorylase (GP) are the key enzymes that control, respectively, the synthesis and degradation of glycogen, a multi-branched glucose polymer that serves as a form of energy storage in bacteria, fungi and animals. An abnormal glycogen metabolism is associated with several human diseases. Thus, GS and GP constitute adequate pharmacological targets to modulate cellular glycogen levels by means of their selective inhibition. The compound 1,4-dideoxy-1,4-imino-d-arabinitol (DAB) is a known potent inhibitor of GP...
September 26, 2016: Organic & Biomolecular Chemistry
Anthony Cirri, Alexey Silakov, Lasse Jensen, Benjamin J Lear
Thiolate-protected gold nanoparticles have a rich history as model systems for understanding the physical and chemical properties of metallic nanoscale materials that, in turn, form the basis for applications in areas such as molecular electronics, photocatalytic systems, and plasmonic solar cells. It is well known that the electronic properties of gold nanoparticles can be tuned by modifying the geometry, size and dielectric surrounding of the particle. However, much less is known of how modifications to the surface chemistry modulates the electronic properties of gold nanoparticles...
September 14, 2016: Physical Chemistry Chemical Physics: PCCP
Keith Izod, Peter Evans, Paul G Waddell, Michael R Probert
A rare P-E π interaction between the lone pair of a planar P center and the vacant p orbital at the Ge or Sn center provides efficient stabilization for P-substituted tetrylenes (R2P)2E (E = Ge, Sn) and enables isolation of the first example of a compound with a crystallographically authenticated P═Sn bond. Subtle changes in the electronic properties of the bulky aryl substituents in these compounds change the preference for planar versus pyramidal P centers in the solid state; however, variable-temperature NMR spectroscopy indicates that in solution these species are subject to a dynamic equilibrium, which interconverts the planar and pyramidal P centers...
October 17, 2016: Inorganic Chemistry
Rory P Wilson, Mark D Holton, James S Walker, Emily L C Shepard, D Mike Scantlebury, Vianney L Wilson, Gwendoline I Wilson, Brenda Tysse, Mike Gravenor, Javier Ciancio, Melitta A McNarry, Kelly A Mackintosh, Lama Qasem, Frank Rosell, Patricia M Graf, Flavio Quintana, Agustina Gomez-Laich, Juan-Emilio Sala, Christina C Mulvenna, Nicola J Marks, Mark W Jones
BACKGROUND: We are increasingly using recording devices with multiple sensors operating at high frequencies to produce large volumes of data which are problematic to interpret. A particularly challenging example comes from studies on animals and humans where researchers use animal-attached accelerometers on moving subjects to attempt to quantify behaviour, energy expenditure and condition. RESULTS: The approach taken effectively concatinated three complex lines of acceleration into one visualization that highlighted patterns that were otherwise not obvious...
2016: Movement Ecology
Austin T Raper, Zucai Suo
DNA polymerases catalyze DNA synthesis through a stepwise kinetic mechanism that begins with binding to DNA, followed by selection, binding, and incorporation of a nucleotide into an elongating primer. It is hypothesized that subtle active site adjustments in a polymerase to align reactive moieties limit the rate of correct nucleotide incorporation. DNA damage can impede this process for many DNA polymerases, causing replication fork stalling, genetic mutations, and potentially cell death. However, specialized Y-family DNA polymerases are structurally evolved to efficiently bypass DNA damage in vivo, albeit at the expense of replication fidelity...
October 10, 2016: Biochemistry
Seki Park, Hyun Kim, Min Su Kim, Gang Hee Han, Jeongyong Kim
Stacked bilayer molybdenum disulfide (MoS<sub>2</sub>) exhibits interesting physical properties depending on the stacking orientation and interlayer coupling strength. Although optical properties, such as photoluminescence, Raman, and absorption properties, are largely dependent on the interlayer coupling of stacked bilayer MoS<sub>2</sub>, the origin of variations in these properties is not clearly understood. We performed comprehensive confocal Raman and absorption mapping measurements to determine the dependence of these spectra on the stacking orientation of bilayer MoS<sub>2</sub>...
September 19, 2016: Optics Express
Mariana Rossi, Piero Gasparotto, Michele Ceriotti
Molecular crystals often exist in multiple competing polymorphs, showing significantly different physicochemical properties. Computational crystal structure prediction is key to interpret and guide the search for the most stable or useful form, a real challenge due to the combinatorial search space, and the complex interplay of subtle effects that work together to determine the relative stability of different structures. Here we take a comprehensive approach based on different flavors of thermodynamic integration in order to estimate all contributions to the free energies of these systems with density-functional theory, including the oft-neglected anharmonic contributions and nuclear quantum effects...
September 9, 2016: Physical Review Letters
Kellyn M Patros, Jennifer E Mann, Caroline Chick Jarrold
The anion photoelectron imaging spectra of O2(-)·VOC and O4(-)·VOC (VOC = hexane, isoprene, benzene, and benzene-d6) complexes measured using 3.49 eV photon energy, along with the results of ab initio and density functional theory results are reported and analyzed. Photodetachment of these anionic complexes accesses neutrals that model collision complexes, offering a probe of the effects of symmetry-breaking collision events on the electronic structure of normally transparent neutral molecules. The energies of O2(-)·VOC spectral features compared to the bare O2(-) indicate that photodetachment of the anion accesses a modestly repulsive region of the O2-VOC potential energy surface, with subtle VOC dependence on the relative energies of the O2 (X (3)Σg(-))·VOC ground state and O2 (a (1)Δg)·VOC excited state...
October 13, 2016: Journal of Physical Chemistry. A
Pooria Namdari, Hadis Daraee, Ali Eatemadi
The application of silicon nanowire (SiNW) biosensor as a subtle, label-free, and electrical tool has been extensively demonstrated by several researchers over the past few decades. Human ability to delicately fabricate and control its chemical configuration, morphology, and arrangement either separately or in combination with other materials as lead to the development of a nanomaterial with specific and efficient electronic and catalytic properties useful in the fields of biological sciences and renewable energy...
December 2016: Nanoscale Research Letters
G Mamatsashvili, G Khujadze, G Chagelishvili, S Dong, J Jiménez, H Foysi
To understand the mechanism of the self-sustenance of subcritical turbulence in spectrally stable (constant) shear flows, we performed direct numerical simulations of homogeneous shear turbulence for different aspect ratios of the flow domain with subsequent analysis of the dynamical processes in spectral or Fourier space. There are no exponentially growing modes in such flows and the turbulence is energetically supported only by the linear growth of Fourier harmonics of perturbations due to the shear flow non-normality...
August 2016: Physical Review. E
Stefan H A M Leenders, René Becker, Tatu Kumpulainen, Bas de Bruin, Tomohisa Sawada, Taito Kato, Makoto Fujita, Joost N H Reek
There is broad interest in molecular encapsulation as such systems can be utilized to stabilize guests, facilitate reactions inside a cavity, or give rise to energy-transfer processes in a confined space. Detailed understanding of encapsulation events is required to facilitate functional molecular encapsulation. In this contribution, it is demonstrated that Ir and Rh-Cp-type metal complexes can be encapsulated inside a self-assembled M6 L4 metallocage only in the presence of an aromatic compound as a second guest...
October 17, 2016: Chemistry: a European Journal
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