Підвищення енергоефективності комплекту розрядна лампа-ЕПРА

The network geometries of rigidly cross-linked fibrin and collagen type I networks are imaged using confocal microscopy and characterized statistically. This statistical representation allows for the regeneration of large, three-dimensional biopolymer networks using an inverse method. Finite element analyses with beam networks are then used to investigate the large deformation, nonlinear elastic response of these artificial networks in isotropic stretching and simple shear. For simple shear, we investigate the differential bulk modulus, which displays three regimes: a linear elastic regime dominated by filament bending, a regime of strain-stiffening associated with a transition from filament bending to stretching, and a regime of weaker strain-stiffening at large deformations, governed by filament stretching convolved with the geometrical nonlinearity of the simple shear strain tensor. The differential bulk modulus exhibits a corresponding strain-stiffening, but reaches a distinct plateau at about 5% strain under isotropic stretch conditions. The small-strain moduli, the bulk modulus in particular, show a significant size-dependence up to a network size of about 100 mesh sizes. The large-strain differential shear modulus and bulk modulus show very little size-dependence.Funding Agencies|BiMaC Innovation||Alf de Ruvo Memorial Foundation of SCA AB||WoodWisdom-net research program||Harvard MRSEC|DMR-0820484|NSF|DMR-1006546|</p

Physical limits to biomechanical sensing in disordered fibre networks

Cells actively probe and respond to the stiffness of their surroundings. Since mechanosensory cells in connective tissue are surrounded by a disordered network of biopolymers, their in vivo mechanical environment can be extremely heterogeneous. Here we investigate how this heterogeneity impacts mechanosensing by modelling the cell as an idealized local stiffness sensor inside a disordered fibre network. For all types of networks we study, including experimentally-imaged collagen and fibrin architectures, we find that measurements applied at different points yield a strikingly broad range of local stiffnesses, spanning roughly two decades. We verify via simulations and scaling arguments that this broad range of local stiffnesses is a generic property of disordered fibre networks. Finally, we show that to obtain optimal, reliable estimates of global tissue stiffness, a cell must adjust its size, shape, and position to integrate multiple stiffness measurements over extended regions of space

Sharp weighted estimates for classical operators

We give a new proof of the sharp one weight $L^p$ inequality for any operator $T$ that can be approximated by Haar shift operators such as the Hilbert transform, any Riesz transform, the Beurling-Ahlfors operator. Our proof avoids the Bellman function technique and two weight norm inequalities. We use instead a recent result due to A. Lerner to estimate the oscillation of dyadic operators. Our method is flexible enough to prove the corresponding sharp one-weight norm inequalities for some operators of harmonic analysis: the maximal singular integrals associated to $T$, Dyadic square functions and paraproducts, and the vector-valued maximal operator of C. Fefferman-Stein. Also we can derive a very sharp two-weight bump type condition for $T$.Comment: We improve different parts of the first version, in particular we show the sharpness of our theorem for the vector-valued maximal functio

Cubierta colgante para el palacio de deportes de Värnamo

The new sports palace at Värnamo, Sweden, has been provided with a roofing structure using the «Jawerth» system of prestressed cables. This method is ideal for the construction of roofs covering very large spans. Although the structural element is a cable considerable stiffness and stability is achieved, even under large temperature variations. The method involves a series of pairs of cables, each acting as a single structural and stable load carrying element In each pair, the top cable is curved so that it is concave towards the top, whilst the lower cable is concave downwords These two mam cables are connected by a third cable, which forms a number of triangles with the other two On stretching the cables, the whole becomes a loadbearing structure of adequate stiffness. The two main cables adopt a polygonal outline, and their loads can be calculated. This constructive method, applied to the roof of the Värnamo sports palace, has proved very satisfactory. In this particular case the fixing of the cables has required 0.285 working hours per square metre of roof structure and the stretching has been accomplished with a hand operated capstan. A number of extensometers and electrical recording units has made it possible to know at all stages of the operation the loading of the cables, and the position of the cable with respect to its final theoretical position.El nuevo palacio de deportes de Värnamo (Suecia), de reciente construcción, ha sido cubierto utilizando el sistema «Jawerth» de cables pretensados. Este sistema constituye una solución ideal para las cubiertas de estos grandes edificios de luz considerable, ya que, aun tratándose de cables, se logra, no sólo una elevada resistencia, sino gran rigidez y estabilidad incluso en el caso de variaciones notables de temperatura. Consiste, en esencia, en una serie de pares de cables, cada uno de los cuales constituye un elemento resistente y rígido. Uno de estos pares está formado por un cable superior, que presenta su concavidad hacia arriba, y otro inferior, cuya concavidad es de sentido opuesto. Entre estos dos cables principales se coloca un tercero formando triángulos entre aquellos dos. Al tensar, este conjunto se deforma de tal suerte que constituye un elemento resistente, con rigidez suficiente para cumplir la función a él reservada; los dos cables principales adoptan una forma poligonal con las tensiones previamente calculadas. Este sistema constructivo, aplicado en la cubierta del palacio de deportes de Värnamo, ha dado excelentes resultados. El montaje de los cables, en este caso particular, ha exigido 0,285 horas de trabajo por metro cuadrado de superficie cubierta y se ha realizado con la ayuda de un cabrestante maniobrado manualmente y de una serie de elongámetros y contadores eléctricos que han permitido, en cada momento, conocer los esfuerzos de tesado y comprobar la posición de cada cable respecto a la que se había calculado

Palacio de los deportes, Estocolmo

Recently a building has been erected in Stockholm, devoted to sport, and especially to house a skating rink. Its horizontal layout is slightly hexagonal, and it is built round an excavated hollow, the bottom of which contains the arena, and the surrounding slopes support the lower public stands. The higher enclosure consists of a concrete portal frame structure. The roof, following the Jawerth system, which is patented in many countries of the world, is a suspended structure, and from the engineering point of view is the most important feature of the building. The roof is supported by a series of cable «trusses», each consisting of two cables spanning a length of 83 ms. One of the cables is concave, and the lower one is convex; both being linked together by means of diagonal cross brazing cables, the whole thus consisting of a triangulated cable trellice. This structural system is very rigid and rapidly damps any oscillation which may be induced by wind pressure. Architecturally the project is pleasing, harmonious and modern, and the approaches to the building are convenient. The suspension cables, which extend outdoors down to the anchorage points, are so disposed that the outside walls are aesthetically very satisfying.<br><br>Recientemente se ha construido un edificio en Estocolmo, Suecia, destinado a la práctica de los deportes y, particularmente, para albergar una pista de patinaje. Es de planta ligeramente hexagonal y se levanta sobre una excavación cuyo fondo constituye la cancha, y sus taludes laterales se han aprovechado para construir el graderío inferior. La parte superior del mismo está constituida por una estructura de hormigón, porticada. La cubierta del edificio —según los principios del sistema. Jawerth, patentado en muchos países— es del tipo suspendido, y constituye la parte de mayor interés estructural. La suspensión se llevó a cabo mediante una serie de «cerchas», compuestas de dos cables que salvan 83 m de luz. Uno de estos cables forma una curva cóncava, mientras que el otro, inferior, presenta una curvatura convexa respecto de la anterior, a la que se solidariza por medio de otro cable que las arriostra, constituyendo una especie de «celosía» o red triangular de cables. El sistema constructivo presenta la particularidad de ser muy rígido y de amortiguar rápidamente cualquier oscilación que el viento pudiera motivar. Arquitectónicamente, la obra presenta un aspecto agradable, armonioso y de línea moderna y tiene fáciles accesos. Los cables de suspensión que se prolongan al exterior hasta las anclajes, van dispuestos de tal forma, que las fachadas conservan un bello sentido estético

Wavelet Denoising of Functional MRI Data

Functional MRI is an imaging technique that provides high resolution information about brain blood flow and oxygenation. This information is used to deduce which regions of the brain are activated by various stimuli. Analysis of functional MRI data is complicated by the low signal-to-noise ratios typically encountered. Two different wavelet-based noise removal algorithms are investigated for potential utility in functional MRI analysis. 1.1 Functional MRI and Brain Mapping In recent years, there has been a tremendous increase in the number of studies that identify the regions of the brain responsible for performing different mental functions. A functional brain mapping study consists of three distinct parts. First, one selects a method of stimulating the brain. A brain stimulus can be as simple as having the subject touch two fingers together, thereby activating the motor cortex. A tremendous variety of methods exist to evoke a desired functional response, and the stimulus chosen is g..