Physics

The results of 0.5-3.0 keV X-ray observations of the central region of the Perseus cluster carried out with the Imaging Proportional Counter and High Resolution Imager aboard the Einstein Observatory are reported. In addition to the very extended thermal cluster emission and a sharply peaked component at NGC 1275 previously known, the high resolution image reveals a point source coincident with the optical nucleus of NGC 1275. The 0.5-3.0 keV luminosity of the compact source is approximately 10 to the 44th ergs/sec. The Imaging Proportional Counter data show the cluster emission to be a factor of 1.2 more elongated east-west than north-south. The centroid of the cluster emissions is found to be offset 1.7 arcmin east of NGC 1275, in the direction away from the prominent line of galaxies that stretch between NGC 1275 and IC 310. The cluster center determined from galaxy counts lies 6.4 arcmin southwest of the X-ray centroid.

ABSTRACT For a sample of galactic clusters that includes richness class three, four, and five clusters, the significance of the luminosity-richness relation is estimated using nonparametric methods which are valid for any luminosity function. The Kolmogorov-Smirnov test is used to determine the significance at which the X-ray luminosities of clusters in one richness class are statistically equal to those in another. The a priori expectation that the high richness clusters are more luminous on average than lower richness objects is confirmed, but it is found that the luminosity function for clusters of richness class three or higher turns over for luminosities less than about 3 x 10 to the 44th ergs/s, while that for lower richness classes extends to at least an order of magnitude lower luminosity.

En los ultimos anos, la importancia y el desarrollo de los ISFET, transistores de efecto de campo sensibles a iones para determinar la concentracion de iones especificos en soluciones acuosas, ha experimentado un considerable incremento. A ello han contribuido su pequeno tamano, robustez, bajo coste, el rapido tiempo de respuesta, la baja impedancia de salida y sus posibilidades de integracion monolitica con los circuitos electronicos. Aqui se presentan los ISFET utilizados en este estudio y los resultados obtenidos de la medida de pH, iones calcio, potasio y nitratos en suelos de cultivo.

ABSTRACT The paper reports the first extensive detection of X-ray emission from clusters of galaxies at cosmological distances. The properties of these objects are similar to those observed in objects at low redshifts. The 0.5-4.5 keV luminosities are in the range of less than 1 x 10 to the 43rd to 2 x 10 to the 45th ergs/s; the core radii are on the order of 0.5 Mpc; and Bautz-Morgan type I clusters are more luminous than types II or III. The observations are consistent with models assuming an evolving cluster potential and moderately efficient galaxy formation, but do not require them when observational selection is considered. X-ray observations of the 3C 295 cluster indicate that there is sufficient intergalactic medium to cause stripping of the cluster spirals, but the colors of these galaxies imply that they have not been stripped. A possible explanation of this discrepancy is discussed.

En este trabajo se obtiene un modelo estadistico del laser amplificador semiconductor y se desarrolla la metodologia y el software necesarios para poder obtener resultados analiticos. En definitiva, se consigue conocer la estadistica de la luz amplificada por este dispositivo de estado solido. El numero de momentos estadisticos que puede obtenerse depende, unicamente, de la capacidad del ordenador. Pueden entonces evaluarse, mediante la funcion densidad de probabilidad, el valor medio y la potencia de la informacion y del ruido cuantico a la salida del laser amplificador para poder analizar, finalmente, las prestaciones introducidas por el mismo en un enlace optico.

Bladder acellular matrix has promising applications in urological and other reconstructive surgery as it represents a naturally compliant, non-immunogenic and highly tissue-integrative material. As the bladder fills and distends, the loosely-coiled bundles of collagen fibres in the wall become extended and orientate parallel to the lumen, resulting in a physical thinning of the muscular wall. This accommodating property can be exploited to achieve complete decellularisation of the full-thickness bladder wall by immersing the distended bladder through a series of hypotonic buffers, detergents and nucleases, but the process is empirical, idiosyncratic and does not lend itself to manufacturing scale up. In this study we have taken a mechanical engineering approach to determine the relationship between porcine bladder size and capacity, to define the biaxial deformation state of the tissue during decellularisation and to apply these principles to the design and testing of a scalable novel laser-printed flat-bed apparatus in order to achieve reproducible and full-thickness bladder tissue decellularisation. We demonstrate how the procedure can be applied reproducibly to fresh, frozen or twice-frozen bladders to render 8×8  cm2 patches of DNA-free acellular matrix suitable for surgical applications.

The avian sarcoma and leukosis virus (ASLV) envelope glycoprotein (Env) is activated to trigger fusion by a two-step mechanism involving receptor-priming and low pH fusion activation. In order to identify regions of ASLV Env that can regulate this process, a genetic selection method was used to identify subgroup B (ASLV-B) virus-infected cells resistant to low pH-triggered fusion when incubated with cells expressing the cognate TVB receptor. The subgroup B viral Env (envB) genes were then isolated from these cells and characterized by DNA sequencing. This led to identification of two frequent EnvB alterations which allowed TVB receptor-binding but altered the pH-threshold of membrane fusion activation: a 13 amino acid deletion in the host range 1 (hr1) region of the surface (SU) EnvB subunit, and the A32V amino acid change within the fusion peptide of the transmembrane (TM) EnvB subunit. These data indicate that these two regions of EnvB can influence the pH threshold of fusion acti...

ABSTRACT It is shown that the linear current flow regime in two-dimensional, two-component textures is unstable for some critical values of the ratio of the linear conductivities of the components. The critical current and critical field are studied as functions of the parameters of the system. The possibility of observing the predicted effect experimentally is discussed.

Penggunaan robot di dalam kehidupan manusia semakin meningkat dari waktu ke waktu. Robot sering digunakan untuk menangani berbagai tugas yang tidak dapat ditangani oleh manusia, seperti di bidang nuklir dan kimia berbahaya. Sekarang ini, robot memegang peranan penting dalam proses produksi di dunia industri. Suara manusia memiliki karakter yang berbeda-beda pada setiap individu. Pengenalan suara adalah kemampuan mesin atau program untuk menerima dan memahami perintah lisan dengan cara membandingkan perintah suara dengan suara yang telah disimpan di dalam basis data, agar perintah suara tersebut dapat dikenali. Penelitian ini bertujuan untuk mengimplementasikan Voice Recognition berbasis Arduino Uno menggunakan modul voice recognition V3 pada lengan robot yang terdiri dari 4 servo SG90. Pada pengujian yang dilakukan oleh user dengan berbagai jarak pengujian yang bervariasi dari 5 cm sampai dengan 30cm, sistem berhasil mengenali suara dengan tingkat keberhasilan rata-rata sebesar 87% ...

ABSTRACT We study the effect of a weak nonlinearity in media on the linear regime of current flow in two-dimensional periodic structures with two equal component concentrations. We find that the asymptotic behavior of the electric field and current as functions of the distance between the angles in heterogeneous media is determined by the parameter h=σ 2/σ 1 (here σ 1 and σ 2 are the linear conductivities of the cells) and the external magnetic field B. This dependence leads to divergence of the higher-order moments of field and current at certain critical values h c and B c and to divergence of the response functions related to the higher-order moments. For square cells the effective nonlinear conductivity diverges at h⩽h c, with $$h_c = (\sqrt 2 - 1)^2 $$ . For structures of general shape we find the dependence of h c on the angles and the external magnetic field. We show that for a given structure the linear regime of current flow in the system can be reversibly transformed into a nonlinear one by varying the magnetic field strength. The critical field B c is approximately determined from the condition ω c τ∼1, where ω c and τ −1 are, respectively, the cyclotron frequency and the collision rate. Finally, we discuss the feasibility of detecting these effects experimentally.