569 research outputs found
A Continuum Poisson-Boltzmann Model for Membrane Channel Proteins
Membrane proteins constitute a large portion of the human proteome and
perform a variety of important functions as membrane receptors, transport
proteins, enzymes, signaling proteins, and more. The computational studies of
membrane proteins are usually much more complicated than those of globular
proteins. Here we propose a new continuum model for Poisson-Boltzmann
calculations of membrane channel proteins. Major improvements over the existing
continuum slab model are as follows: 1) The location and thickness of the slab
model are fine-tuned based on explicit-solvent MD simulations. 2) The highly
different accessibility in the membrane and water regions are addressed with a
two-step, two-probe grid labeling procedure, and 3) The water pores/channels
are automatically identified. The new continuum membrane model is optimized (by
adjusting the membrane probe, as well as the slab thickness and center) to best
reproduce the distributions of buried water molecules in the membrane region as
sampled in explicit water simulations. Our optimization also shows that the
widely adopted water probe of 1.4 {\AA} for globular proteins is a very
reasonable default value for membrane protein simulations. It gives an overall
minimum number of inconsistencies between the continuum and explicit
representations of water distributions in membrane channel proteins, at least
in the water accessible pore/channel regions that we focus on. Finally, we
validate the new membrane model by carrying out binding affinity calculations
for a potassium channel, and we observe a good agreement with experiment
results.Comment: 40 pages, 6 figures, 5 table
The Method of Moving spheres on Hyperbolic Space and Symmetry of Solutions to a Class of PDEs
The classification of solutions of semilinear partial differential equations,
as well as the classification of critical points of the corresponding
functionals, have wide applications in the study of partial differential
equations and differential geometry. The classical moving plane method and the
moving sphere method on provide an effective approach to
capturing the symmetry of solutions. As far as we know, the moving sphere
method has yet to be developed on the hyperbolic space . In the
present paper, we focus on the following equation \begin{equation*}
P_k u = f(u) \end{equation*} on hyperbolic spaces , where
denotes the GJMS operators on and satisfies certain growth conditions. We develop a moving sphere
approach for integral equations on , to obtain the symmetry
property as well as a characterization result towards positive solutions. Our
methods also rely on Helgason-Fourier analysis and Hardy-Littlewood-Sobolev
inequalities on hyperbolic spaces together with a Kelvin transform we introduce
on in this paper.Comment: Some references are added and typos fixe
Establishment of the prediction equations of 1RM skeletal muscle strength in 60- to 75-year-old Chinese men and women
The purpose of this study was to establish the one-repetition maximum (1RM) prediction equations of biceps curl, bench press, and squat from the submaximal skeletal muscle strength of 4-10RM or 11-15RM in older adults. The first group of 109 participants aged 60-75 years was recruited to measure their 1RM, 4-10RM, and 11-15RM of the three exercises. The 1RM prediction equations were developed by multiple regression analyses. A second group of participants with the similar physical characteristics to the first group was used to evaluate the equations. The actual measured 1RM of the second group correlated significantly to the predicted 1RM obtained from the equations (r values were from 0.633 to 0.985), and standard error of estimate ranged from 1.08 to 5.88. Therefore, the equations can be utilized to predict 1RM from submaximal skeletal muscle strength accurately for older adults
Stochastic Downsampling for Cost-Adjustable Inference and Improved Regularization in Convolutional Networks
It is desirable to train convolutional networks (CNNs) to run more
efficiently during inference. In many cases however, the computational budget
that the system has for inference cannot be known beforehand during training,
or the inference budget is dependent on the changing real-time resource
availability. Thus, it is inadequate to train just inference-efficient CNNs,
whose inference costs are not adjustable and cannot adapt to varied inference
budgets. We propose a novel approach for cost-adjustable inference in CNNs -
Stochastic Downsampling Point (SDPoint). During training, SDPoint applies
feature map downsampling to a random point in the layer hierarchy, with a
random downsampling ratio. The different stochastic downsampling configurations
known as SDPoint instances (of the same model) have computational costs
different from each other, while being trained to minimize the same prediction
loss. Sharing network parameters across different instances provides
significant regularization boost. During inference, one may handpick a SDPoint
instance that best fits the inference budget. The effectiveness of SDPoint, as
both a cost-adjustable inference approach and a regularizer, is validated
through extensive experiments on image classification
Soccer training: an effective exercise mode to prevent and treat childhood obesity?
Exercise training has been recognized as an effective treatment for childhood obesity. Clinical experience has shown that great efforts are needed to train children around 10 years old when using traditional aerobic exercise modes, such as walking and running. To seek more attractive training methods for children, in this paper, we review the current literature to evaluate the effectiveness of soccer training on childhood obesity prevention and treatment. Future research direction and sport injury prevention are also discussed
Quasi-compactons in inverted nonlinear photonic crystals
We study large-amplitude one-dimensional solitary waves in photonic crystals
featuring competition between linear and nonlinear lattices, with minima of the
linear potential coinciding with maxima of the nonlinear pseudopotential, and
vice versa (inverted nonlinear photonic crystals, INPhCs), in the case of the
saturable self-focusing nonlinearity. Such crystals were recently fabricated
using a mixture of SU-8 and Rhodamine-B optical materials. By means of
numerical methods and analytical approximations, we find that large-amplitude
solitons are broad sharply localized stable pulses (quasi-compactons, QCs).
With the increase of the totalpower, P, the QC's centroid performs multiple
switchings between minima and maxima of the linear potential. Unlike cubic
INPhCs, the large-amplitude solitons are mobile in the medium with the
saturable nonlinearity. The threshold value of the kick necessary to set the
soliton in motion is found as a function of P. Collisions between moving QCs
are considered too.Comment: 11 pages, 8 figures, Physical Review A, in pres
Predominance of Th2 polarization by Vitamin D through a STAT6-dependent mechanism
<p>Abstract</p> <p>Background</p> <p>Vitamin D has several reported immunomodulatory properties including the reduced generation of pro-inflammatory CD4+ T helper 1 (Th1) cells and the increase in levels of the anti-inflammatory Th2 subset. Less clear has been the impact of vitamin D on the pro-inflammatory Th17 subset, and whether and how vitamin D may preferentially drive the polarization of one of the T helper subsets.</p> <p>Methods</p> <p>Using human peripheral blood-derived mononuclear cells and mouse splenocytes and lymph node cells in culture, we examined whether and how vitamin D preferentially skews T cells towards the Th1, Th2 or Th17 subsets. Mice afflicted with the multiple sclerosis-like condition, experimental autoimmune encephalomyelitis (EAE), were examined in vivo for the relevance of the tissue culture-derived results.</p> <p>Results</p> <p>We report that the biologically active form of vitamin D, 1,25-dihydroxyvitamin D3 {1,25(OH)2D3}, consistently generates human and murine Th2 cells in culture, frequently leaving unchanged the levels of Th1/Th17 cytokines. As a result, the ratio of Th2 to Th1 and Th17 is increased by 1,25(OH)2D3. The upregulation of Th2 to Th1 or Th17 subsets by 1,25(OH)2D3 is enabled by an increase of the GATA-3 transcription factor, which itself is promoted upstream by an elevation of the STAT6 transcription factor. In mice, the alleviation of EAE severity by 1,25(OH)2D3 is accompanied by elevation of levels of GATA-3 and STAT6. Significantly, the efficacy of 1,25(OH)2D3 in ameliorating EAE is completely lost in mice genetically deficient for STAT6, which was accompanied by the inability of 1,25(OH)2D3 to raise GATA-3 in STAT6 null lymphocytes.</p> <p>Conclusions</p> <p>These results of vitamin D promoting a Th2 shift through upstream GATA-3 and STAT6 transcription factors shed mechanistic understanding on the utility of vitamin D in MS.</p
Aerobic exercise training at maximal fat oxidation intensity improves body composition, glycemic control, and physical capacity in older people with type 2 diabetes
Background: Aerobic training has been used as one of the common treatments for type 2 diabetes; however, further research on the individualized exercise program with the optimal intensity is still necessary. The purpose of this study was to investigate the effects of supervised exercise training at the maximal fat oxidation (FATmax) intensity on body composition, glycemic control, lipid profile, and physical capacity in older people with type 2 diabetes. Methods: Twenty-four women and 25 men with type 2 diabetes, aged 60–69 years. The exercise groups trained at the individualized FATmax intensity for 1 h/day for 3 days/week over 16 weeks. No dietary intervention was introduced during the experimental period. Whole body fat, abdominal fat, oral glucose tolerance test, lipid profile, and physical capacity were measured before and after the interventions. Results: FATmax intensity was at 41.3 ± 3.2% VO2max for women and 46.1 ± 10.3% VO2max for men. Exercise groups obtained significant improvements in body composition, with a special decrease in abdominal obesity; decreased resting blood glucose concentration and HbA1c; and increased VO2max, walking ability, and lower body strength, compared to the non-exercising controls. Daily energy intake and medication remained unchanged for all participants during the experimental period. Conclusion: Beside the improvements in the laboratory variables, the individualized FATmax training can also benefit daily physical capacity of older people with type 2 diabetes
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