Structure and Mobility of Nanoconfined Polyamide-6,6 Oligomers: Application of a Molecular Dynamics Technique with Constant Temperature, Surface Area, and Parallel Pressure

2009 ◽  
Vol 113 (16) ◽  
pp. 5568-5581 ◽  
Author(s):  
Hossein Eslami ◽  
Florian Müller-Plathe
Keyword(s):  
Molecular Dynamics ◽  
Surface Area ◽  
Constant Temperature ◽  
Temperature Surface

scholarly journals Molecular dynamics simulation of soot formation during diesel combustion with oxygenated fuel addition

2020 ◽  
Vol 22 (36) ◽  
pp. 20829-20836
Author(s):  
Cheng Chen ◽  
Xi Jiang
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Constant Temperature ◽  
Soot Formation ◽  
Dynamics Simulation ◽  
Diesel Combustion ◽  
Oxygenated Additives ◽  
Oxygenated Fuel

The morphology of nascent soot and the effect of oxygenated additives on sooting mitigation at a constant temperature of 3000 K.

scholarly journals Heterogeneous freezing of water droplets containing kaolinite particles

2011 ◽  
Vol 11 (9) ◽  
pp. 4191-4207 ◽  
Author(s):  
B. J. Murray ◽  
S. L. Broadley ◽  
T. W. Wilson ◽  
J. D. Atkinson ◽  
R. H. Wills
Keyword(s):  
Cooling Rate ◽  
Surface Area ◽  
Clay Mineral ◽  
Constant Temperature ◽  
Hydrophobic Surface ◽  
Supercooled Liquid ◽  
Stochastic Approach ◽  
Solid Particles ◽  
Rate Coefficients ◽  
Water Droplets

Abstract. Clouds composed of both ice particles and supercooled liquid water droplets exist at temperatures above ~236 K. These mixed phase clouds, which strongly impact climate, are very sensitive to the presence of solid particles that can catalyse freezing. In this paper we describe experiments to determine the conditions at which the clay mineral kaolinite nucleates ice when immersed within water droplets. These are the first immersion mode experiments in which the ice nucleating ability of kaolinite has been determined as a function of clay surface area, cooling rate and also at constant temperatures. Water droplets containing a known amount of clay mineral were supported on a hydrophobic surface and cooled at rates of between 0.8 and 10 K min−1 or held at constant sub-zero temperatures. The time and temperature at which individual 10–50 μm diameter droplets froze were determined by optical microscopy. For a cooling rate of 10 K min−1, the median nucleation temperature of 10–40 μm diameter droplets increased from close to the homogeneous nucleation limit (236 K) to 240.8 ± 0.6 K as the concentration of kaolinite in the droplets was increased from 0.005 wt% to 1 wt%. This data shows that the probability of freezing scales with surface area of the kaolinite inclusions. We also show that at a constant temperature the number of liquid droplets decreases exponentially as they freeze over time. The constant cooling rate experiments are consistent with the stochastic, singular and modified singular descriptions of heterogeneous nucleation; however, freezing during cooling and at constant temperature can be reconciled best with the stochastic approach. We report temperature dependent nucleation rate coefficients (nucleation events per unit time per unit area) for kaolinite and present a general parameterisation for immersion nucleation which may be suitable for cloud modelling once nucleation by other important ice nucleating species is quantified in the future.

scholarly journals Preparation and characterization of activated carbons from albizia saman pod

2017 ◽  
Vol 36 (3) ◽  
pp. 44-53
Author(s):  
G. D. Akpen ◽  
M. I. Aho ◽  
N. Baba
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
Activated Carbons ◽  
High Surface ◽  
High Surface Area ◽  
Volatile Matter ◽  
Sieve Analysis ◽  
Albizia Saman ◽  
Temperature Surface

Activated carbon was prepared from the pods of Albizia saman for the purpose of converting the waste to wealth. The pods were thoroughly washed with water to remove any dirt, air- dried and cut into sizes of 2-4 cm. The prepared pods were then carbonised in a muffle furnace at temperatures of 4000C, 5000C, 6000C ,7000C and 8000C for 30 minutes. The same procedure was repeated for 60, 90, 120 and 150 minutes respectively. Activation was done using impregnationratios of 1:12, 1:6, 1:4, 1:3, and 1:2 respectively of ZnCl2 to carbonised Albizia saman pods by weight. The activated carbon was then dried in an oven at 1050C before crushing for sieve analysis. The following properties of the produced Albizia saman pod activated carbon (ASPAC) were determined: bulk density, carbon yield, surface area and ash, volatile matter and moisture contents. The highest surface area of 1479.29 m2/g was obtained at the optimum impregnation ratio, carbonization time and temperature of 1:6, 60 minutes and 5000C respectively. It was recommended that activated carbon should be prepared from Albizia saman pod with high potential for adsorption of pollutants given the high surface area obtained.Keywords: Albizia saman pod, activated carbon, carbonization, temperature, surface area

Constant-temperature molecular dynamics with momentum conservation

1993 ◽  
Vol 47 (5) ◽  
pp. 3145-3151 ◽  
Author(s):  
K. Cho ◽  
J. D. Joannopoulos ◽  
Leonard Kleinman
Keyword(s):  
Molecular Dynamics ◽  
Constant Temperature ◽  
Momentum Conservation

Accurate and efficient integration for molecular dynamics simulations at constant temperature and pressure

2013 ◽  
Vol 139 (16) ◽  
pp. 164106 ◽  
Author(s):  
Ross A. Lippert ◽  
Cristian Predescu ◽  
Douglas J. Ierardi ◽  
Kenneth M. Mackenzie ◽  
Michael P. Eastwood ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Constant Temperature ◽  
Efficient Integration ◽  
Temperature And Pressure ◽  
Dynamics Simulations

Constant-Temperature Molecular-Dynamics Simulation of the 2D Melting Transition of Rb and K

1992 ◽  
Vol 291 ◽  
Author(s):  
J. D. Fan ◽  
Zhi-Xiong Cai
Keyword(s):  
Molecular Dynamics ◽  
Constant Temperature ◽  
Md Simulations ◽  
Dynamics Simulation ◽  
Melting Transition ◽  
Histogram Method ◽  
Graphite Intercalation ◽  
2D System ◽  
Incommensurate Structures ◽  
First Time

ABSTRACTThe energy histogram method, introduced by Ferrenberg and Swendsen [Phys. Rev. Lett., 61, 2635, (1988) and 63, 1195, (1989)], was applied for the first time to the constant temperature molecular dynamics (MD) simulation of a two-dimensional (2D) system with incommensurate structures. We performed MD simulations for the stage-2 graphite intercalation compounds (GIC's) with Rb or K being the intercalants (Rb-GIC's and K- GIC's). The temperature dependence of the specific heat, Cv, is calculated for various sizes up to 864 atoms. The melting temperature was found to be 158 K for Rb-GIC's and 119 K for K-GIC's, respectively, which are in agreement with the experimental observations.

scholarly journals Molecular dynamics simulations suggest stabilizing mutations in a de novo designed α/β protein

2019 ◽  
Vol 32 (7) ◽  
pp. 317-329
Author(s):  
Matthew Gill ◽  
Michelle E McCully
Keyword(s):  
Molecular Dynamics ◽  
Secondary Structure ◽  
Surface Area ◽  
De Novo ◽  
Md Simulations ◽  
Solvent Accessible Surface Area ◽  
Hydrophobic Core ◽  
Design Strategies ◽  
Major Interest ◽  
Core Packing

Abstract Designing functional proteins that can withstand extreme heat is beneficial for industrial and protein therapeutic applications. Thus, elucidating the atomic-level determinants of thermostability is a major interest for rational protein design. To that end, we compared the structure and dynamics of a set of previously designed, thermostable proteins based on the activation domain of human procarboxypeptidase A2 (AYEwt). The mutations in these designed proteins were intended to increase hydrophobic core packing and inter-secondary-structure interactions. To evaluate whether these design strategies were successfully deployed, we performed all-atom, explicit-solvent molecular dynamics (MD) simulations of AYEwt and three designed variants at both 25 and 100°C. Our MD simulations agreed with the relative experimental stabilities of the designs based on their secondary structure content, Cα root-mean-square deviation/fluctuation, and buried-residue solvent accessible surface area. Using a contact analysis, we found that the designs stabilize inter-secondary structure interactions and buried hydrophobic surface area, as intended. Based on our analysis, we designed three additional variants to test the role of helix stabilization, core packing, and a Phe → Met mutation on thermostability. We performed the additional MD simulations and analysis on these variants, and these data supported our predictions.

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