Effects of Elevated H\u3csup\u3e+\u3c/sup\u3e And P\u3csub\u3ei\u3c/sub\u3e on The Contractile Mechanics of Skeletal Muscle Fibres From Young and Old Men: Implications for Muscle Fatigue in Humans

The present study aimed to identify the mechanisms responsible for the loss in muscle power and increased fatigability with ageing by integrating measures of whole‐muscle function with single fibre contractile mechanics. After adjusting for the 22% smaller muscle mass in old (73–89 years, n = 6) compared to young men (20–29 years, n = 6), isometric torque and power output of the knee extensors were, respectively, 38% and 53% lower with age. Fatigability was ∼2.7‐fold greater with age and strongly associated with reductions in the electrically‐evoked contractile properties. To test whether cross‐bridge mechanisms could explain age‐related decrements in knee extensor function, we exposed myofibres (n = 254) from the vastus lateralis to conditions mimicking quiescent muscle and fatiguing levels of acidosis (H+) (pH 6.2) and inorganic phosphate (Pi) (30 mm). The fatigue‐mimicking condition caused marked reductions in force, shortening velocity and power and inhibited the low‐ to high‐force state of the cross‐bridge cycle, confirming findings from non‐human studies that these ions act synergistically to impair cross‐bridge function. Other than severe age‐related atrophy of fast fibres (−55%), contractile function and the depressive effects of the fatigue‐mimicking condition did not differ in fibres from young and old men. The selective loss of fast myosin heavy chain II muscle was strongly associated with the age‐related decrease in isometric torque (r = 0.785) and power (r = 0.861). These data suggest that the age‐related loss in muscle strength and power are primarily determined by the atrophy of fast fibres, but the age‐related increased fatigability cannot be explained by an increased sensitivity of the cross‐bridge to H+ and Pi

In-vitro resistance of cloned human glioma cells to natural killer activity of allogeneic peripheral lymphocytes.

Cells from an established culture of a human astrocytoma were incubated with normal allogeneic peripheral lymphocytes (PBL) in order to study the natural killer (NK) sensitivity of the in vitro propagated cell line. A proportion of cells in culture formed halos, into which lymphocytes did not penetrate. These cells were successfully cloned and showed a decreased susceptibility to NK cytolysis compared with the parent line. Both cell lines could be transplanted into athymic nude mice. The cloned NK-resistant cells underwent a frequent spontaneous regression in nu/nu mice, despite the fact that when used as targets for nu/nu NK cells in vitro they were only moderately susceptible. Phase-contrast microscopy of the mass-cultured cells co-cultivated with lymphocytes suggested that their morphology and ability to form inpenetrable translucent halos might influence their susceptibility to NK lysis. Experiments performed on this assumption revealed that quiescent and halo forming tumour cells were not the primary targets for NK lysis. Cells in mass culture, although tumorigenic, were thus heterogeneous in respect of susceptibility to NK attack. These findings might be relevant to the mechanism of immune escape and tumour heterogeneity in respect of spontaneous cell-mediated lysis

Method of filling databases of electronic components based on the uniform tables of document parameters

Рассматриваются вопросы разработки методики автоматизированного наполнения баз данных электрорадиоизделий, основанной на объединении таблиц параметров нормативного документа. Показаны её основные этапы и особенности. Предложено оформлять связи между параметрами и правило формирования наименования элементов в текстовом файле-шаблоне. Приводится предварительная оценка времени оформления файлов-шаблонов различных нормативных документов. Показано применениеметодики для автоматического наполнения технологических справочников.The problems of the development of the methodology for the automated filling of databases of electronic products based on the integration of the parameters tables of the normative document are considered. Its main stages and features are shown. It is proposed to formalize the relationship between the parameters and the rule for the formation of the names of elements in a text file-template. A preliminary estimate of the time for creating template files for various normative documents is given. The application of the technique for automatic filling oftechnological databases is shown

The Gaussian beam mode analysis of off-axis aberrations in long wavelength optical systems

An issue of major concern in the design of long wavelength systems is optical aberration or distortion, which can be particularly severe in off-axis systems. Aberrations occur in both lenses and mirrors and in this paper we present a novel method capable of modelling off-axis mirror configurations. Aberrations degrade fundamental receiver coupling coefficients such as aperture efficiency while increasing spillover power losses. For single pixel instruments this will lead to much longer integration times and the possibility of stray light. For imaging arrays the aberrations cause a departure from perfect point imaging by increasing coupling to array detectors located at angles further off the bore sight of the telescope. This paper verifies a matrix-based scheme using Gaussian beam mode analysis (GBMA) for predicting aberrations from off-axis mirrors. The applied technique was originally described in (S. Withington, A. Murphy, G. Isaak, Representation of mirrors in beam waveguides as inclined phase transforming surfaces, Infrared Phys. Tech. 36(3) (1995) 723–734. [1]) and in this paper we exploit the theory and validate the approach with a series of examples using off-axis conic sections. We present the predictions for both a fundamental Gaussian and a scalar horn field illuminating various off-axis mirror configurations including different angles of incidence. A commercially available physical optics (PO) software package, GRASP8™, is used to validate the accuracy of these scalar GBMA predictions

Shear-Induced Stress Relaxation in a Two-Dimensional Wet Foam

We report on experimental measurements of the flow behavior of a wet, two-dimensional foam under conditions of slow, steady shear. The initial response of the foam is elastic. Above the yield strain, the foam begins to flow. The flow consists of irregular intervals of elastic stretch followed by sudden reductions of the stress, i.e. stress drops. We report on the distribution of the stress drops as a function of the applied shear rate. We also comment on our results in the context of various two-dimensional models of foams

Jamming transition in emulsions and granular materials

We investigate the jamming transition in packings of emulsions and granular materials via molecular dynamics simulations. The emulsion model is composed of frictionless droplets interacting via nonlinear normal forces obtained using experimental data acquired by confocal microscopy of compressed emulsions systems. Granular materials are modeled by Hertz-Mindlin deformable spherical grains with Coulomb friction. In both cases, we find power-law scaling for the vanishing of pressure and excess number of contacts as the system approaches the jamming transition from high volume fractions. We find that the construction history parametrized by the compression rate during the preparation protocol has a strong effect on the micromechanical properties of granular materials but not on emulsions. This leads the granular system to jam at different volume fractions depending on the histories. Isostaticity is found in the packings close to the jamming transition in emulsions and in granular materials at slow compression rates and infinite friction. Heterogeneity of interparticle forces increases as the packings approach the jamming transition which is demonstrated by the exponential tail in force distributions and the small values of the participation number measuring spatial localization of the forces. However, no signatures of the jamming transition are observed in structural properties, like the radial distribution functions and the distributions of contacts.Comment: Submitted to PR

Glasslike Arrest in Spinodal Decomposition as a Route to Colloidal Gelation

Colloid-polymer mixtures can undergo spinodal decomposition into colloid-rich and colloid-poor regions. Gelation results when interconnected colloid-rich regions solidify. We show that this occurs when these regions undergo a glass transition, leading to dynamic arrest of the spinodal decomposition. The characteristic length scale of the gel decreases with increasing quench depth, and the nonergodicity parameter exhibits a pronounced dependence on scattering vector. Mode coupling theory gives a good description of the dynamics, provided we use the full static structure as input.Comment: 14 pages, 4 figures; replaced with published versio

Optical Characterisation of a Camera module Developed for Ultra-low NEP TES Detector Arrays at FIR Wavelengths

Here we report on the optical design and on the spectral-spatial characterisation of a small 16 pixel camera. The prototype uses TES detectors with NEPs ~10-16 W/Hz0.5 which have been fabricated with near identical optical coupling structures to mimic their much lower NEP counterparts (~10-19 W/Hz0.5). This modification, which is achieved through changing only the pixel thermal conductance, G, has allowed us to perform spectral/spatial cryogenic testing using a 100mK ADR to view room temperature thermal sources. The measurements show a flat spectral response across the waveband and minimal side lobe structure in the antenna patterns down to 30dB