188 research outputs found
Generalised Einstein Relation for Hot Brownian Motion
The Brownian motion of a hot nanoparticle is described by an effective Markov
theory based on fluctuating hydrodynamics. Its predictions are scrutinized over
a wide temperature range using large-scale molecular dynamics simulations of a
hot nanoparticle in a Lennard-Jones fluid. The particle positions and momenta
are found to be Boltzmann distributed according to distinct effective
temperatures and . For we
derive a formally exact theoretical prediction and establish a generalised
Einstein relation that links it to directly measurable quantities
Puckering Free Energy of Pyranoses: an NMR and Metadynamics--Umbrella Sampling Investigation
We present the results of a combined metadynamics--umbrella sampling
investigation of the puckered conformers of pyranoses described using the
gromos 45a4 force field. The free energy landscape of Cremer--Pople puckering
coordinates has been calculated for the whole series of alpha and beta
aldohexoses, showing that the current force field parameters fail in
reproducing proper puckering free energy differences between chair conformers.
We suggest a modification to the gromos 45a4 parameter set which improves
considerably the agreement of simulation results with theoretical and
experimental estimates of puckering free energies. We also report on the
experimental measurement of altrose conformers populations by means of NMR
spectroscopy, which show good agreement with the predictions of current
theoretical models
A two-species continuum model for aeolian sand transport
Starting from the physics on the grain scale, we develop a simple continuum
description of aeolian sand transport. Beyond popular mean-field models, but
without sacrificing their computational efficiency, it accounts for both
dominant grain populations, hopping (or "saltating") and creeping (or
"reptating") grains. The predicted stationary sand transport rate is in
excellent agreement with wind tunnel experiments simulating wind conditions
ranging from the onset of saltation to storms. Our closed set of equations thus
provides an analytically tractable, numerically precise, and computationally
efficient starting point for applications addressing a wealth of phenomena from
dune formation to dust emission.Comment: 23 pages, 9 figure
A sex-specific switch between visual and olfactory inputs underlies adaptive sex differences in behavior
While males and females largely share the same genome and nervous system, they
differ profoundly in reproductive investments and require distinct behavioral,
morphological and physiological adaptations. How can the nervous system, while
bound by both developmental and biophysical constraints, produce these sexdifferences in behavior? Here we uncover a novel dimorphism in Drosophila
melanogaster that allows deployment of completely different behavioral repertoires in
males and females with minimum changes to circuit architecture. Sexual differentiation
of only a small number of higher-order neurons in the brain leads to a change in
connectivity related to the primary reproductive needs of both sexes - courtship pursuit
in males and communal oviposition in females. This study explains how an apparently
similar brain generates distinct behavioral repertoires in the two sexes and presents a
fundamental principle of neural circuit organization that may be extended to other
species
How nanoporous silicon-polypyrrole hybrids flex their muscles in aqueous electrolytes: In operando high-resolution x-ray diffraction and electron tomography-based micromechanical computer simulations
Macroscopic strain experiments revealed that Si crystals traversed by
parallel, channel-like nanopores functionalized with the muscle polymer
polypyrrole exhibit large and reversible electrochemo-mechanical actuation in
aqueous electrolytes. On the microscopical level this system still bears open
questions, as to how the electrochemical expansion and contraction of PPy acts
on to np-Si pore walls and how the collective motorics of the pore array
emerges from the single-nanopore behavior. An analysis of in operando X-ray
diffraction experiments with micromechanical finite element simulations, based
on a 3D reconstruction of the nanoporous medium by TEM tomography, shows that
the in-plane mechanical response is dominantly isotropic despite the
anisotropic elasticity of the single crystalline host matrix. However, the
structural anisotropy originating from the parallel alignment of the nanopores
lead to significant differences between the in- and out-of-plane
electromechanical response. This response is not describable by a simple 2D
arrangement of parallel cylindrical channels. Rather, the simulations highlight
that the dendritic shape of the Si pore walls, including pore connections
between the main channels, cause complex, inhomogeneous stress-strain fields in
the crystalline host. Time-dependent X-ray scattering on the dynamics of the
actuator properties hint towards the importance of diffusion limitations,
plastic deformation and creep in the nanoconfined polymer upon (counter-)ion
adsorption and desorption, the very pore-scale processes causing the
macroscopic electroactuation. From a more general perspective, our study
demonstrates that the combination of TEM tomography-based micromechanical
modeling with high-resolution X-ray scattering experiments provides a powerful
approach for in operando analysis of nanoporous composites from the
single-nanopore up to the porous-medium scale.Comment: Supplementary see ancillary file. 20 pages, 11 figure
Early diagnosis of coeliac disease in the Preventive Youth Health Care Centres in the Netherlands: study protocol of a case finding study (GLUTENSCREEN)
Introduction Coeliac disease (CD) occurs in 1% of the population, develops early in life and is severely underdiagnosed. Undiagnosed and untreated disease is associated with short-term and long-term complications. The current healthcare approach is unable to solve the underdiagnosis of CD and timely diagnosis and treatment is only achieved by active case finding. Aim: to perform a case finding project to detect CD children who visit the Youth Health Care Centres (YHCCs) in a well-described region in the Netherlands to evaluate whether it is feasible, cost-effective and well accepted by the population.Methods/analysis Prospective intervention cohort study. Parents of all children aged 12 months and 4 years attending the YHCCs for a regular visit are asked whether their child has one or more CD-related symptoms from a standardised list. If so, they will be invited to participate in the case finding study. After informed consent, a point of care test (POCT) to assess CD-specific antibodies against tissue transglutaminase (TG2A) is performed onsite the YHCCs. If the POCT is positive, CD is highly suspected and the child will be referred to hospital for definitive diagnosis according to the Guideline Coeliac Disease of the European Society for Pediatric Gastroenterology, Hepatology and Nutrition guideline.Main outcomes1. Incidence rate of new CD diagnoses in the study region in comparison to the one in the same age diagnosed by standard of care in the rest of the Netherlands.2. Feasibility and cost-effectiveness of active CD case finding at the YHCCs. All costs of active case finding, diagnostics and treatment of CD and the potential short-term and long-term consequences of the disease will be calculated for the setting with and without case finding.1. Ethical acceptability: by questionnaires on parental and healthcare professionals' satisfaction.A statistical analysis plan was prepared and is published on the GLUTENSCREEN website () and added as annex 1).Ethics and disseminationThe Medical Ethics Committee Leiden approved this study. If we prove that case finding at the YHCC is feasible, cost-effective and well accepted by the population, implementation is recommended.Analysis and support of clinical decision makin
Metabolic investigations prevent liver transplantation in two young children with citrullinemia type I
Acute liver failure may be caused by a variety of disorders including inborn errors of metabolism. In those cases, rapid metabolic investigations and adequate treatment may avoid the need for liver transplantation. We report two patients who presented with acute liver failure and were referred to our center for liver transplantation work-up. Urgent metabolic investigations revealed citrullinemia type I. Treatment for citrullinemia type I avoided the need for liver transplantation. Acute liver failure as a presentation of citrullinemia type I has not previously been reported in young children. Although acute liver failure has occasionally been described in other urea cycle disorders, these disorders may be underestimated as a cause. Timely diagnosis and treatment of these disorders may avoid liver transplantation and improve clinical outcome. Therefore, urea cycle disorders should be included in the differential diagnosis in young children presenting with acute liver failure
The Generation R Study: design and cohort update 2017
The Generation R Study is a population-based prospective cohort study from fetal life until adulthood. The study is designed to identify early environmental and genetic causes and causal pathways leading to normal and abnormal growth, development and health from fetal life, childhood and young adulthood. This multidisciplinary study focuses on several health outcomes including behaviour and cognition, body composition, eye development, growth, hearing, heart and vascular development, infectious disease and immunity, oral health and facial growth, respiratory health, allergy and skin disorders of children and their parents. Main exposures of interest include environmental, endocrine, genomic (genetic, epigenetic, microbiome), lifestyle related, nutritional and socio-demographic determinants. In total, 9778 mothers with a delivery date from April 2002 until January 2006 were enrolled in the study. Response at baseline was 61%, and general follow-up rates until the age of 10 years were around 80%. Data collection in children and their parents includes questionnaires, interviews, detailed physical and ultrasound examinations, behavioural observations, lung function, Magnetic Resonance Imaging and biological sampling. Genome and epigenome wide association screens are available. Eventually, results from the Generation R Study contribute to the deve
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