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Contrast dynamics

Jejoong Yoo, Aleksei Aksimentiev
In contrast to ordinary polymers, the vast majority of biological macromolecules adopt highly ordered three-dimensional structures that define their functions. The key to folding of a biopolymer into a unique 3D structure or to an assembly of several biopolymers into a functional unit is a delicate balance between the attractive and repulsive forces that also makes such self-assembly reversible under physiological conditions. The all-atom molecular dynamics (MD) method has emerged as a powerful tool for studies of individual biomolecules and their functional assemblies, encompassing systems of ever increasing complexity...
March 16, 2018: Physical Chemistry Chemical Physics: PCCP
Feng Feng, Fulin Qiang, Aijun Shen, Donghui Shi, Aiyan Fu, Haiming Li, Mingzhu Zhang, Ganlin Xia, Peng Cao
Objective: To prospectively compare the discriminative capacity of dynamic contrast enhanced-magnetic resonance imaging (DCE-MRI) with that of18 F-fluorodeoxyglucose (18 F-FDG) positron emission tomography/computed tomography (PET/CT) in the differentiation of malignant and benign solitary pulmonary nodules (SPNs). Methods: Forty-nine patients with SPNs were included in this prospective study. Thirty-two of the patients had malignant SPNs, while the other 17 had benign SPNs...
February 2018: Chinese Journal of Cancer Research, Chung-kuo Yen Cheng Yen Chiu
Richard Potts, Anna K Behrensmeyer, J Tyler Faith, Christian A Tryon, Alison S Brooks, John E Yellen, Alan L Deino, Rahab Kinyanjui, Jennifer B Clark, Catherine Haradon, Naomi E Levin, Hanneke J M Meijer, Elizabeth G Veatch, R Bernhart Owen, Robin W Renaut
Development of the African Middle Stone Age (MSA) before 300 thousand years ago (ka) raises the question of how environmental change influenced the evolution of behaviors characteristic of early Homo sapiens We use temporally well-constrained sedimentological and paleoenvironmental data to investigate environmental dynamics before and after the appearance of the early MSA in the Olorgesailie Basin, Kenya. In contrast to the Acheulean archeological record in the same basin, MSA sites are associated with a dramatically different faunal community, more pronounced erosion-deposition cycles, tectonic activity, and enhanced wet-dry variability...
March 15, 2018: Science
Shotaro Kanao, Masako Kataoka, Mami Iima, Debra Masako Ikeda, Masakazu Toi, Kaori Togashi
OBJECTIVES: Benign and malignant inflammatory breast lesions demonstrate similar findings on both T2 weighted imaging (T2WI) and dynamic contrast enhanced (DCE) images. We hypothesized that benign inflammatory lesions might be differentiated form malignancies using a combination of apparent diffusion coefficient (ADC) values derived from diffusion weighted images (DWI) and T2WI. MATERIALS AND METHODS: We retrospectively reviewed 162 patients undergoing breast MRI (T2WI, DWI and DCE images) between 2008 and 2015 who had breast lesions with high T2WI signal intensity (High T2 SI) including 14 benign inflammatory lesions, 69 benign non-inflammatory lesions, 16 malignant inflammatory lesions and 63 malignant non-inflammatory lesions...
March 12, 2018: Magnetic Resonance Imaging
Margarita Braunagel, Florian Ortner, Ulf Schönermarck, Antje Habicht, Andreas Schindler, Manfred Stangl, Frederik F Strobl, Maximilian Reiser, Dirk A Clevert, Christoph Trumm, Andreas Helck
RATIONALE AND OBJECTIVE: The objective of this study was to assess an optimized renal multiphase computed tomography angiography (MP-CTA) protocol regarding reduction of contrast volume. MATERIALS AND METHODS: Thirty patients underwent MP-CTA (12 phases, every 3.5 seconds, 80 kV/120 mAs) using 30 mL of contrast medium. The quality of MP-CTA was assessed quantitatively measuring vessel attenuation, image noise, and contrast-to-noise ratio. MP-CTA was evaluated qualitatively regarding depiction of vessels, cortex differentiation, and motion artifacts (grades 1-4, 1 = best)...
March 12, 2018: Academic Radiology
Simon P Overeem, Esmé J Donselaar, Jorrit T Boersen, Erik Groot Jebbink, Cornelis H Slump, Jean-Paul P M de Vries, Michel M P J Reijnen
PURPOSE: To assess the dynamic behavior of chimney grafts during the cardiac cycle. METHODS: Three chimney endovascular aneurysm repair (EVAR) stent-graft configurations (Endurant and Advanta V12, Endurant and Viabahn, and Endurant and BeGraft) were placed in silicone aneurysm models and subjected to physiologic flow. Electrocardiography (ECG)-gated contrast-enhanced computed tomography was used to visualize geometric changes during the cardiac cycle. Endograft and chimney graft surface, gutter volume, chimney graft angulation over the center lumen line, and the D-ratio (the ratio between the lengths of the major and minor axes) were independently assessed by 2 observers at 10 time points in the cardiac cycle...
March 1, 2018: Journal of Endovascular Therapy
Heidi Lourens, Brian Watermeyer, Leslie Swartz
PURPOSE: Scholars agree that effective rehabilitation relies on a bedrock of reciprocity, relational trust, and authenticity. It is therefore essential for practitioners to develop insight into the complex dynamics within helping relationships. This study aims to provide an in-depth understanding of visually impaired students' experience of informal helping relationships. METHODS: Ten visually impaired students at a South African university participated in one of two semi-structured focus group interviews (six and four in each group, respectively) wherein we explored their experience of informal helping relationships...
March 16, 2018: Disability and Rehabilitation
A R Hopkinson, M I J Probert
We present the results of a theoretical study of H/D diffusion on a Ni(111) surface at a range of temperatures, from 250 K to 75 K. The diffusion is studied using both classical molecular dynamics and the partially adiabatic centroid molecular dynamics method. The calculations are performed with the hydrogen (or deuterium) moving in 3D across a static nickel surface using a novel Fourier interpolated potential energy surface which has been parameterized to density functional theory calculations. The results of the classical simulations are that the calculated diffusion coefficients are far too small and with too large a variation with temperature compared with experiment...
March 14, 2018: Journal of Chemical Physics
Jianguo Li, Roger Beuerman, Chandra Verma
Molecular aggregation plays a significant role in modulating the solubility, permeability, and bioactivity of drugs. The propensity to aggregate depends on hydrophobicity and on molecular shape. Molecular dynamics simulations coupled with enhanced sampling methods are used to explore the early stages of oligomerization of two drug molecules which have a strong aggregation propensity, but with contrasting molecule shapes: the antibiotic ciprofloxacin and the anticancer drug Nutlin-3A. The planar shape of ciprofloxacin induces the formation of stable oligomers at all cluster sizes...
March 14, 2018: Journal of Chemical Physics
Carlos P Herrero, Rafael Ramírez
Thermal properties of graphene monolayers are studied by path-integral molecular dynamics simulations, which take into account the quantization of vibrational modes in the crystalline membrane and allow one to consider anharmonic effects in these properties. This system was studied at temperatures in the range from 12 to 2000 K and zero external stress, by describing the interatomic interactions through the LCBOPII effective potential. We analyze the internal energy and specific heat and compare the results derived from the simulations with those yielded by a harmonic approximation for the vibrational modes...
March 14, 2018: Journal of Chemical Physics
Daniel Stopper, Alice L Thorneywork, Roel P A Dullens, Roland Roth
Using dynamical density functional theory (DDFT), we theoretically study Brownian self-diffusion and structural relaxation of hard disks and compare to experimental results on quasi two-dimensional colloidal hard spheres. To this end, we calculate the self-van Hove correlation function and distinct van Hove correlation function by extending a recently proposed DDFT-approach for three-dimensional systems to two dimensions. We find that the theoretical results for both self-part and distinct part of the van Hove function are in very good quantitative agreement with the experiments up to relatively high fluid packing fractions of roughly 0...
March 14, 2018: Journal of Chemical Physics
Ian Hewson, Kalia S I Bistolas, Jason B Button, Elliot W Jackson
Decades of research have demonstrated the crucial importance of viruses in freshwater ecosystems. However, few studies have focused on the seasonal dynamics and potential hosts of RNA viruses. We surveyed microbial-sized (i.e. 5-0.2 μm) mixed community plankton transcriptomes for RNA viral genomes and investigated their distribution between microbial and macrobial plankton over a seasonal cycle across three temperate lakes by quantitative reverse transcriptase PCR (qRT-PCR). A total of 30 contigs bearing similarity to RNA viral genomes were recovered from a global assembly of 30 plankton RNA libraries...
2018: PloS One
Matthew P Kroonblawd, Fabio Pietrucci, Antonino Marco Saitta, Nir Goldman
We demonstrate the capability of creating robust density functional tight binding (DFTB) models for chemical reactivity in prebiotic mixtures through force matching to short time scale quantum free energy estimates. Molecular dynamics using density functional theory (DFT) is a highly accurate approach to generate free energy surfaces for chemical reactions, but the extreme computational cost often limits the time scales and range of thermodynamic states that can feasibly be studied. In contrast, DFTB is a semi-empirical quantum method that affords up to a thousandfold reduction in cost and can recover DFT-level accuracy...
March 15, 2018: Journal of Chemical Theory and Computation
Philipp T Dumitrescu, Romain Vasseur, Andrew C Potter
We simulate the dynamics of a disordered interacting spin chain subject to a quasiperiodic time-dependent drive, corresponding to a stroboscopic Fibonacci sequence of two distinct Hamiltonians. Exploiting the recursive drive structure, we can efficiently simulate exponentially long times. After an initial transient, the system exhibits a long-lived glassy regime characterized by a logarithmically slow growth of entanglement and decay of correlations analogous to the dynamics at the many-body delocalization transition...
February 16, 2018: Physical Review Letters
Youmin Hou, Miao Yu, Yuhe Shang, Peng Zhou, Ruyuan Song, Xiaonan Xu, Xuemei Chen, Zuankai Wang, Shuhuai Yao
Preventing or minimizing ice formation in supercooled water is of prominent importance in many infrastructures, transportation, and cooling systems. The overall phase change heat transfer on icephobic surfaces, in general, is intentionally sacrificed to suppress the nucleation of water and ice. However, in a condensation frosting process, inhibiting freezing without compromising the water condensation has been an unsolved challenge. Here we show that this conflict between anti-icing and efficient condensation cooling can be resolved by utilizing biphilic topography with patterned high-contrast wettability...
February 16, 2018: Physical Review Letters
S K Abdrakhmanov, S B Tyulegenov, F I Korennoy, A A Sultanov, I I Sytnik, K K Beisembaev, A A Bainiyazov, A E Munsey, A M Perez, K VanderWaal
Foot-and-mouth disease (FMD) poses a significant obstacle to international trade and economic development, and for that reason, FMD prevention, control and eradication are major goals guiding animal health policy in most countries. The purpose of this study was to conduct a retrospective spatiotemporal analysis of FMD outbreaks among livestock in the Republic of Kazakhstan (RK) from 1955 to 2013. During that time, several FMD control strategies were implemented in RK, which culminated with the World Organization for Animal Health (OIE) recognition of RK as a country that is FMD-free with partial vaccination (2015)...
March 15, 2018: Transboundary and Emerging Diseases
Motohisa Osaka
There are some reports that sympathetic nerve activity (SNA) shows a characteristic pattern a few hours before the onset of lethal ventricular arrhythmias. If so, it could be possible to predict sudden cardiac death a few hours in advance of its occurrence. Recently, we reported that a previously unidentified V-trough of SNA is a potential precursor of lethal cardiac events by examining 24-hour ambulatory electrocardiograms in which such an event was recorded by chance. In contrast, the chaotic nature of heart rate variability has been noted recently from the viewpoint of nonlinear dynamics...
2018: Journal of Nippon Medical School, Nippon Ika Daigaku Zasshi
Cecilia Siliansky de Andreazzi, Paulo R Guimarães, Carlos J Melián
Studies have shown the potential for rapid adaptation in coevolving populations and that the structure of species interaction networks can modulate the vulnerability of ecological systems to perturbations. Although the feedback loop between population dynamics and coevolution of traits is crucial for understanding long-term stability in ecological assemblages, modelling eco-evolutionary dynamics in species-rich assemblages is still a challenge. We explore how eco-evolutionary feedbacks influence trait evolution and species abundances in 23 empirical antagonistic networks...
March 14, 2018: Proceedings. Biological Sciences
Benjamin J Zimmerman, Austin T Mudd, Joanne E Fil, Ryan N Dilger, Bradley P Sutton
Accurate quantitative non-invasive assessments of arterial cerebral blood volume (aCBV) can greatly benefit the study of cerebral vascular health in both humans and in animal models. In recent years, progress has been made in the techniques available to quantify CBV with magnetic resonance imaging (MRI). Here, we compared a non-invasive technique, measuring inflowing vascular space occupancy with dynamic subtraction (iVASO-ds) with a contrast-based vascular space occupancy measurement in piglets. In addition, we measured how the iVASO-ds derived aCBV changed with piglet development from 4 weeks to 8 weeks...
March 11, 2018: Magnetic Resonance Imaging
Krzysztof Kucharz, Martin Lauritzen
Cortical spreading depolarization waves, the cause underlying migraine aura, are also the markers and mechanism of pathology in the acutely injured human brain. Propagation of spreading depolarization wave uniquely depends on the interaction between presynaptic and postsynaptic glutamate N-methyl-d-aspartate receptors (NMDARs). In the normally perfused brain, even a single wave causes a massive depolarization of neurons and glia, which results in transient loss of neuronal function and depression of the ongoing electrocorticographic activity...
March 12, 2018: Brain: a Journal of Neurology
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