scholarly journals Terahertz Driven Ultrafast Energy Dissipation in Aqueous Ionic Solutions

2021 ◽  
Author(s):  
Vasileios Balos ◽  
Naveen Kaliannan ◽  
Hossam Elgabarty ◽  
Martin Wolf ◽  
Thomas Kühne ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Low Frequency ◽  
Structural Deformation ◽  
Translational Energy ◽  
External Energy ◽  
Time Resolved ◽  
Dynamics Simulations ◽  
The Impact ◽  
Aqueous Ionic Solutions ◽  
Denaturation Of Proteins

Abstract Solvation of ions changes the physical, chemical and thermodynamic properties of water. The microscopic origin of this process is believed to be the ion-induced perturbation in the structure and dynamics of the hydrogen (H)-bonding network of water. Here, we provide microscopic insight on the local structural deformation of the H-bonding network of water by ions, via investigating the dissipation of external energy in salt solutions by a novel time-resolved terahertz (THz)-Raman spectroscopy. We resonantly drive the low-frequency rotational dynamics of water molecules by intense THz pulses and probe the Raman response of their intermolecular translational motions. We find that the intermolecular rotational-to-translational energy transfer is enhanced by highly-charged cations and it is drastically reduced by highly-charged anions, scaling with the ion surface charge density and concentration. Our molecular dynamics simulations further reveal that the water-water H-bond strength between the first and the second solvation shells of cations (anions) increases (decreases), signifying the opposite effects of cations and anions on the local structure of water. The impact of ion polarity on the ultrafast energy dissipation in water, resembles the effect of ions on stabilization and denaturation of proteins.

scholarly journals Molecular Dynamics Simulations on Influence of Defect on Thermal Conductivity of Silicon Nanowires

2021 ◽  
Vol 9 ◽  
Author(s):  
Hao Li ◽  
Qiancheng Rui ◽  
Xiwen Wang ◽  
Wei Yu
Keyword(s):  
Thermal Conductivity ◽  
Molecular Dynamics ◽  
Silicon Nanowires ◽  
Surface Defects ◽  
Low Frequency ◽  
Simulation Method ◽  
Dynamics Simulation ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact

A non-equilibrium molecular dynamics simulation method is conducted to study the thermal conductivity (TC) of silicon nanowires (SiNWs) with different types of defects. The impacts of defect position, porosity, temperature, and length on the TC of SiNWs are analyzed. The numerical results indicate that SiNWs with surface defects have higher TC than SiNWs with inner defects, the TC of SiNWs gradually decreases with the increase of porosity and temperature, and the impact of temperature on the TC of SiNWs with defects is weaker than the impact on the TC of SiNWs with no defects. The TC of SiNWs increases as their length increases. SiNWs with no defects have the highest corresponding frequency of low-frequency peaks of phonon density of states; however, when SiNWs have inner defects, the lowest frequency is observed. Under the same porosity, the average phonon participation of SiNWs with surface defects is higher than that of SiNWs with inner defects.

scholarly journals Ice-nucleating bacteria control the order and dynamics of interfacial water

2016 ◽  
Vol 2 (4) ◽  
pp. e1501630 ◽  
Author(s):  
Ravindra Pandey ◽  
Kota Usui ◽  
Ruth A. Livingstone ◽  
Sean A. Fischer ◽  
Jim Pfaendtner ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Active Sites ◽  
Frost Damage ◽  
Nucleation Site ◽  
Ice Nucleation ◽  
Time Resolved ◽  
Sum Frequency ◽  
Effective Removal ◽  
Dynamics Simulations ◽  
The Impact

Ice-nucleating organisms play important roles in the environment. With their ability to induce ice formation at temperatures just below the ice melting point, bacteria such as Pseudomonas syringae attack plants through frost damage using specialized ice-nucleating proteins. Besides the impact on agriculture and microbial ecology, airborne P. syringae can affect atmospheric glaciation processes, with consequences for cloud evolution, precipitation, and climate. Biogenic ice nucleation is also relevant for artificial snow production and for biomimetic materials for controlled interfacial freezing. We use interface-specific sum frequency generation (SFG) spectroscopy to show that hydrogen bonding at the water-bacteria contact imposes structural ordering on the adjacent water network. Experimental SFG data and molecular dynamics simulations demonstrate that ice-active sites within P. syringae feature unique hydrophilic-hydrophobic patterns to enhance ice nucleation. The freezing transition is further facilitated by the highly effective removal of latent heat from the nucleation site, as apparent from time-resolved SFG spectroscopy.

Energy Analysis for Energy Dissipation Shed-Tunnel’s Rockfall Impact Signal

2011 ◽  
Vol 261-263 ◽  
pp. 1054-1057 ◽  
Author(s):  
Lin Feng Wang ◽  
Hong Mei Tang ◽  
Hong Kai Chen
Keyword(s):  
Energy Dissipation ◽  
Impact Energy ◽  
High Frequency ◽  
Energy Analysis ◽  
Low Frequency ◽  
Prevention Measures ◽  
Impact Frequency ◽  
Wavelet Theory ◽  
Frequency Increase ◽  
The Impact

Shed-tunnel is one of common prevention measures along the highway. First, denoised the rockfall impact signal when the rock impact the ordinary shed-tunnel and the energy dissipation shed-tunnel by the wavelet theory. The calculation result indicated that the wavelet theory’s denoise effect is very good. Then, pick-up each frequency band’s the rockfall impact signal, and analysed the energy for each frequency band’s impact signal. The result indicated that the energy dissipation shed-tunnel’s impact energy concentrate in the low frequency part. There are only 0.4% impact energy in the high frequency part. Besides, the energy dissipation shed-tunnel’s impact energy in the low frequency part is higher than the the ordinary shed-tunnel, and the energy dissipation shed-tunnel’s impact energy depressed velocity when the impact frequency increase is fast than the ordinary shed-tunnel. So the energy dissipation shed-tunnel’s design must consider the low frequency impact,and could ignore the high frequency impact.

scholarly journals Protonation of Glutamate 208 Induces the Release of Agmatine in an Outward-facing Conformation of an Arginine/Agmatine Antiporter

2011 ◽  
Vol 286 (22) ◽  
pp. 19693-19701 ◽  
Author(s):  
Elia Zomot ◽  
Ivet Bahar
Keyword(s):  
Binding Pocket ◽  
Substrate Binding Pocket ◽  
Time Resolved ◽  
Extracellular Region ◽  
Acidic Conditions ◽  
Using Data ◽  
Dynamics Simulations ◽  
The Impact ◽  
First Time

Virulent enteric pathogens have developed several systems that maintain intracellular pH to survive extreme acidic conditions. One such mechanism is the exchange of arginine (Arg+) from the extracellular region with its intracellular decarboxylated form, agmatine (Agm2+). The net result of this process is the export of a virtual proton from the cytoplasm per antiport cycle. Crystal structures of the arginine/agmatine antiporter from Escherichia coli, AdiC, have been recently resolved in both the apo and Arg+-bound outward-facing conformations, which permit us to assess for the first time the time-resolved mechanisms of interactions that enable the specific antiporter functionality of AdiC. Using data from ∼1 μs of molecular dynamics simulations, we show that the protonation of Glu-208 selectively causes the dissociation and release of Agm2+, but not Arg+, to the cell exterior. The impact of Glu-208 protonation is transmitted to the substrate binding pocket via the reorientation of Ile-205 carbonyl group at the irregular portion of transmembrane (TM) helix 6. This effect, which takes place only in the subunits where Agm2+ is released, invites attention to the functional role of the unwound portion of TM helices (TM6 Trp-202–Glu-208 in AdiC) in facilitating substrate translocation, reminiscent of the behavior observed in structurally similar Na+-coupled transporters.

The impact of thermostat on interfacial thermal conductance prediction from non-equilibrium molecular dynamics simulations

2021 ◽  
Author(s):  
Song Hu ◽  
C. Y. Zhao ◽  
Xiaokun Gu
Keyword(s):  
Molecular Dynamics ◽  
Heat Flux ◽  
Thermal Conductance ◽  
Low Frequency ◽  
Temperature Calculation ◽  
Interfacial Thermal Conductance ◽  
Non Equilibrium Molecular Dynamics ◽  
Dynamics Simulations ◽  
The Impact ◽  
Non Equilibrium

Abstract The knowledge of interfacial thermal conductance (ITC) is key to understand thermal transport in nanostructures. The non-equilibrium molecular dynamics (NEMD) simulation is a useful tool to calculate the ITC. In this study, we investigate the impact of thermostat on the prediction of the ITC. The Langevin thermostat is found to result in larger ITC than the Nose-Hoover thermostat. In addition, the results from NEMD simulations with the Nose-Hoover thermostat exhibit strong size effect of thermal reservoirs. Detailed spectral heat flux decomposition and modal temperature calculation reveal that the acoustic phonons in hot and cold thermal reservoirs are of smaller temperature difference than optical phonons when using the Nose-Hoover thermostat, but in the Langevin thermostat phonons are of identical temperatures. Such a non-equilibrium state of phonons in the case of the Nose-Hoover thermostat reduces the heat flux of low-to-middle-frequency phonons. We also discuss how enlarging the reservoirs or adding an epitaxial rough wall to the reservoirs affect the predicted ITC, and find these attempts could help to thermalize the phonons, but still underestimate the heat flux from low-frequency phonons.

Structural dynamics of P-type ATPase ion pumps

2019 ◽  
Vol 47 (5) ◽  
pp. 1247-1257 ◽  
Author(s):  
Mateusz Dyla ◽  
Sara Basse Hansen ◽  
Poul Nissen ◽  
Magnus Kjaergaard
Keyword(s):  
Structural Dynamics ◽  
Single Molecule ◽  
New Technologies ◽  
Atp Hydrolysis ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Time Resolved ◽  
Dynamics Simulations ◽  
Types Of Information ◽  
P Type

Abstract P-type ATPases transport ions across biological membranes against concentration gradients and are essential for all cells. They use the energy from ATP hydrolysis to propel large intramolecular movements, which drive vectorial transport of ions. Tight coordination of the motions of the pump is required to couple the two spatially distant processes of ion binding and ATP hydrolysis. Here, we review our current understanding of the structural dynamics of P-type ATPases, focusing primarily on Ca2+ pumps. We integrate different types of information that report on structural dynamics, primarily time-resolved fluorescence experiments including single-molecule Förster resonance energy transfer and molecular dynamics simulations, and interpret them in the framework provided by the numerous crystal structures of sarco/endoplasmic reticulum Ca2+-ATPase. We discuss the challenges in characterizing the dynamics of membrane pumps, and the likely impact of new technologies on the field.

USING FIELD DATA FOR THE EVALUATION OF THE IMPACT OF ULTRA-LOW FREQUENCY MOTIONS ON THE FATIGUE OF MOORING LINES

2019 ◽  
Author(s):  
Guilherme Borzacchiello ◽  
Carl Albrecht ◽  
Fabricio N Correa ◽  
Breno Jacob ◽  
Guilherme da Silva Leal
Keyword(s):  
Field Data ◽  
Low Frequency ◽  
Mooring Lines ◽  
The Impact

scholarly journals A diffusion anisotropy descriptor links morphology effects of H-ZSM-5 zeolites to their catalytic cracking performance

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Xiaoliang Liu ◽  
Jing Shi ◽  
Guang Yang ◽  
Jian Zhou ◽  
Chuanming Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Catalytic Cracking ◽  
Catalytic Performance ◽  
Zeolite Catalysts ◽  
Time Resolved ◽  
Cracking Performance ◽  
Morphology Effect ◽  
Ft Ir ◽  
The Difference ◽  
Dynamics Simulations

AbstractZeolite morphology is crucial in determining their catalytic activity, selectivity and stability, but quantitative descriptors of such a morphology effect are challenging to define. Here we introduce a descriptor that accounts for the morphology effect in the catalytic performances of H-ZSM-5 zeolite for C4 olefin catalytic cracking. A series of H-ZSM-5 zeolites with similar sheet-like morphology but different c-axis lengths were synthesized. We found that the catalytic activity and stability is improved in samples with longer c-axis. Combining time-resolved in-situ FT-IR spectroscopy with molecular dynamics simulations, we show that the difference in catalytic performance can be attributed to the anisotropy of the intracrystalline diffusive propensity of the olefins in different channels. Our descriptor offers mechanistic insight for the design of highly effective zeolite catalysts for olefin cracking.

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