3,763 research outputs found
Custom Flow in Molecular Dynamics
Driving an inertial many-body system out of equilibrium generates complex
dynamics due to memory effects and the intricate relationships between the
external driving force, internal forces, and transport effects. Understanding
the underlying physics is challenging and often requires carrying out
case-by-case analysis. To systematically study the interplay between all types
of forces that contribute to the dynamics, a method to generate prescribed flow
patterns could be of great help. We develop a custom flow method to numerically
construct the external force field required to obtain the desired time
evolution of an inertial many-body system, as prescribed by its one-body
current and density profiles. We validate the custom flow method in a Newtonian
system of purely repulsive particles by creating a slow motion dynamics of an
out-of-equilibrium process and by prescribing the full time evolution between
two distinct equilibrium states. The method can also be used with thermostat
algorithms to control the temperature
Reduced-variance orientational distribution functions from torque sampling
We introduce a method to sample the orientational distribution function in
computer simulations. The method is based on the exact torque balance equation
for classical many-body systems of interacting anisotropic particles in
equilibrium. Instead of the traditional counting of events, we reconstruct the
orientational distribution function via an orientational integral of the torque
acting on the particles. We test the torque sampling method in two- and
three-dimensions, using both Langevin dynamics and overdamped Brownian
dynamics, and with two interparticle interaction potentials. In all cases the
torque sampling method produces profiles of the orientational distribution
function with better accuracy than those obtained with the traditional counting
method. The accuracy of the torque sampling method is independent of the bin
size, and hence it is possible to resolve the orientational distribution
function with arbitrarily small angular resolutions
Applying Demand Response Programs for Electric Vehicle Fleets
In this study, we demonstrate the contribution of IS-supported demand response (DR) programs to the development of a sustainable transport sector. Based on the energy informatics framework, we develop an IS artifact that can be used to apply DR programs for electric vehicle (EV) fleets. Furthermore, we quantify one DR program in economic terms by analyzing data gathered in an electric mobility project with a car-sharing provider that uses EVs. The findings indicate that fleet operators can expect significant cost savings when applying DR programs; energy procurement costs can be reduced significantly by adjusting the time of energy use. Applying DR programs therefore has the potential to make EV fleets economically sensible because the already existing operational cost advantage can be further increased. Consequently, DR for EVs can foster sustainable development, as higher profitability could promote the market penetration of eco-friendly vehicles
Stannites â a new promising class of durable electrocatalysts for efficient water oxidation
The oxygen evolution reaction (OER) through water oxidation is a key process for multiple energy storage technologies required for a sustainable energy economy such as the formation of the fuel hydrogen from water and electricity, or metalâair batteries. Herein, we investigate the suitability of Cu2FeSnS4 for the OER and demonstrate its superiority over iron sulfide, iron (oxy)hydroxides and benchmark nobleâmetal catalysts in alkaline media. Electrodeposited Cu2FeSnS4 yields the current densities of 10 and 1000â
mA/cm2 at overpotentials of merely 228 and 330â
mV, respectively. Stateâofâtheâart analytical methods are applied before and after electrocatalysis to uncover the fate of the Cu2FeSnS4 precatalyst under OER conditions and to deduce structureâactivity relationships. Cu2FeSnS4 is the first compound reported for OER among the broad class of stannite structure type materials containing multiple members with highly active earthâabundant transitionâmetals for OER.DFG, 390540038, EXC 2008: Cluster of Excellence UniSysCatTU Berlin, Open-Access-Mittel - 201
CopperâFree Sonogashira Coupling for HighâSurfaceâArea Conjugated Microporous Poly(aryleneethynylene) Networks
A modified oneâpot Sonogashira crossâcoupling reaction based on a copperâfree methodology has been applied for the synthesis of conjugated microporous poly(aryleneethynylene) networks (CMPs) from readily available iodoarylenes and 1,3,5âtriethynylbenzene. The polymerization reactions were carried out by using equimolar amounts of halogen and terminal alkyne moieties with extremely small loadings of palladium catalyst as low as 0.65â
molâ%. For the first time, CMPs with rigorously controlled structures were obtained without any indications of side reactions, as proven by FTIR and solidâstate NMR spectroscopy, while showing BrunauerâEmmettâTeller (BET) surface areas higher than any poly(aryleneethynylene) network reported before, reaching up to 2552â
m2âgâ1.EC/FP7/278593/EU/Organic Zeolites/ORGZEODFG, 53182490, EXC 314: Unifying Concepts in Catalysi
3D-nanoprinted on-chip antiresonant waveguide with hollow core and microgaps for integrated optofluidic spectroscopy
Here, we unlock the properties of the recently introduced on-chip hollow-core microgap waveguide in the context of optofluidics which allows for intense light-water interaction over long lengths with fast response times. The nanoprinted waveguide operates by the antiresonance effect in the visible and near-infrared domain and includes a hollow core with defined gaps every 176 ”m. The spectroscopic capabilities are demonstrated by various absorption-related experiments, showing that the Beer-Lambert law can be applied without any modification. In addition to revealing key performance parameters, time-resolved experiments showed a decisive improvement in diffusion times resulting from the lateral access provided by the microgaps. Overall, the microgap waveguide represents a pathway for on-chip spectroscopy in aqueous environments
A pilot study of hair and cytokine balance alteration in healthy young women under major exam stress
Mouse models show that experimental stress mimicking prolonged life-stress
exposure enhances neurogenic inflammation, induces adaptive immunity cytokine-
imbalance characterized by a shift to Type 1 T-helper cell cytokines and
increases apoptosis of epithelial cells. This affects hair growth in otherwise
healthy animals. In this study, we investigate whether a prolonged
naturalistic life-stress exposure affects cytokine balance and hair parameters
in healthy humans. 33 (18 exam, 15 comparison) female medical students with
comparable sociobiological status were analyzed during a stressful final
examination period, at three points in time (T) 12 weeks apart. T1 was before
start of the learning period, T2 between the three-day written exam and an
oral examination, and T3 after a 12 week rest and recovery from the stress of
the examination period. Assessments included: self-reported distress and
coping strategies (Perceived Stress Questionnaire [PSQ], Trier Inventory for
the Assessment of Chronic Stress [TICS]), COPE), cytokines in supernatants of
stimulated peripheral blood mononucleocytes (PBMCs), and trichogram (hair
cycle and pigmentation analysis). Comparison between students participating in
the final medical exam at T2 and non-exam students, revealed significantly
higher stress perception in exam students. Time-wise comparison revealed that
stress level, TH1/TH2 cytokine balance and hair parameters changed
significantly from T1 to T2 in the exam group, but not the control. However,
no group differences were found for cytokine balance or hair parameters at T2.
The study concludes that in humans, naturalistic stress, as perceived during
participation in a major medical exam, has the potential to shift the immune
response to TH1 and transiently hamper hair growth, but these changes stay
within a physiological range. Findings are instructive for patients suffering
from hair loss in times of high stress. Replication in larger and more diverse
sample populations is required, to assess suitability of trichogram analysis
as biological outcome for stress studies
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