A programmable data acquisition and control system for magneticresonance imaging: application to mutually coupled surface coil arraysand temperature monitoring

A programmable data acquisition and control system was developed for use in conjunction with magnetic resonance imaging (MRI). The controller consists of two functional blocks: a host system and a remote system. The remote system resides inside the shielded room housing the magnet. The host, an IBM compatible personal computer, is located at the technician's console. Communication between these devices is implemented over a fiber optic RS-232 data link. This configuration allows experiments to be performed remotely by using a series of keyboard typed commands, by programming the host to send a series of commands, or by directly programming the remote system. As an example of its capabilities, the controller was used to tune and match arrays of receiver coils for localized imaging and to record the rectal temperature of a sedated rat during image acquisition.     

Lowland rice response to potassium fertilization and its effect on N and P uptake

Not much is known about the response of lowland rice to K fertilization under Brazilian conditions. A field experiment was conducted during four consecutive years to determine the response of three lowland rice (Oryza sativa L.) cultivars to K fertilization on a Low Humic Gley soil. In the first two years, K was broadcast at rates of 0, 42, 84, 126, and 168 kg K ha^–1. In the last two years K rates were reduced to 0, 25, 50, 75, and 100 kg K ha^–1 and applied in a band. Potassium significantly (P < 0.01) increased grain yields but the response varied from cultivar to cultivar and year to year. Yield responses to K fertilization were superimposed on a general trend of increasing grain yields across the four growing seasons. Mean grain yields increased 14.3% with broadcast application of K in the first two years and 10.4% with banded application of K in the last two years when compared to the control treatments. Extractable soil K increased with K application rate and decreased with soil depth. Potassium was rapidly removed from the soil and yearly broadcast or banded application of K can be expected to result in a significant increase in grain yield of lowland rice in these soils.     

Modeling the intact form of the {alpha}1-proteinase inhibitor

The structure of the intact form of the serpin ₁-proteinaseinhibitor has been modeled based on the assumption that thecentral strand s4A of the six-stranded ß-sheet A ofthe cleaved inhibitor is not incorporated into the sheet ofintact ₁-proteinase inhibitor. This strand was removed fromits position in the center of the sheet by suitable rotationsabout the backbone dihedrals of Lys343 using molecular graphics.The resulting structure was then annealed using molecular dynamics(MD) while applying progressive distance restraints to the reactivepeptide bond (Met358-Ser359) for 50 ps. During this time, thedisrupted ß-sheet reformed to create a five-strandedß-sheet with strands 3 and 5 in a parallel arrangement.This change and accompanying structural rearrangements are largelyconfirmed by the X-ray structure of plakalbumin, whose structurereflects the overall structure of intact serpins. The successfulmodeling experiment demonstrates the utility of MD for makinggross structural predictions based on related structures. Thebinding loop of the intact form is modeled to allow dockingwith serine proteinases, in particular thrombin, which mosthighly constrains the possible conformations of the bindingloop.     

PCB原型能在设计过程中增值

您如何使用原型?是否仅做系统设计中那些棘手部件的原型?您反复制造原型PCB,使之与设计保持一致吗?EDN应如何报道PCB设计?     

Doping efficiency and energy-level scheme in C60F48-doped zinc–tetraphenylporphyrin films

High resolution synchrotron-based core level spectroscopy was used to examine the energy level alignment at the interface of zinc–tetraphenylporphyrin films doped by the surface acceptor C₆₀F₄₈. Two distinct fluorofullerene charge states were identified, corresponding to ionized and neutral molecules, and their relative concentration as a function of coverage was used to evaluate the probability of occupation of the acceptor lowest unoccupied molecular orbital (LUMO). From an initial acceptor energy of ?0.25 eV, the C₆₀F₄₈ LUMO shifts upwards with coverage due to a doping-induced interfacial dipole potential, and stabilization of the LUMO at an energy 0.45 eV above the Fermi energy was obtained. While the energy difference upon saturation is consistent with the results obtained for other donor–acceptor systems that have been interpreted as Fermi level pinning, the present work shows that the energy offset is a direct consequence of the interplay between Fermi–Dirac statistics in combination with the interfacial dipole potential.     

Effects of breed and sire on carcass characteristics and fatty acid profiles of crossbred wagyu and angus steers

In a two-year experiment, 54 steers sired by seven Wagyu bulls [American Wagyu Association (AWA) sire numbers 331, 384, 388, 411, 429, 433 and 488] and 15 steers sired by two Angus bulls, all out of Angus-Hereford cows, were used to evaluate the effects of sire and breed on carcass characteristics and fatty acid composition. Steers were given ad-libitum access to a high-concentrate diet (15 % alfalfa cubes and 85 % barley supplement) for at least 170 days. Breed and individual sire effects were analysed. Wagyu-sired steers had higher marbling, maturity and quality scores, more estimated kidney, pelvic and heart fat, larger longissimus dorsi muscle areas, lower fat thicknesses and yield grades than Angus-sired steers (p < 0.05). Steers sired by 388, 411 and 433 had lower fat thicknesses than steers sired by Angus, 429 and 488 (p < 0.05). Steers sired by 384 and 388 had higher marbling scores per cm subcutaneous fat than steers sired by Angus, 429 and 488, and lower fat thickness per 100 kg of carcass weight than Angus-sired steers (p < 0.05). For both subcutaneous fat and longissimus dorsi muscle, Wagyu-sired steers had higher (p < 0.05) percentages of 14:0, 14:1, 16:0, 16:1, and lower percentages of 18:0 than Angus-sired steers. The genetic differences in carcass characteristics among Wagyu sires may enable us to select for improved marbling with less fat in the Wagyu breed. Some statistically significant (p < 0.05) but small differences existed in fatty acid profiles between breeds and among sires.     

Constraints on the design of single-channel, high-capacity (>10Gb/s) soliton systems

We have examined the design constraints of single-channel soliton systems operating at high data rates (>10 Gb/s). While Gordon-Haus timing jitter is the most important effect for 10 Gb/s transoceanic systems, it is fiber perturbations arising from discrete in-line amplification that severely limit the transmission distance and amplifier spacing at higher data rates. Dispersion-decreasing fiber or distributed optical amplification, both of which locally balance dispersion and fiber nonlinearities, could eliminate this constraint and extend the regime of stable soliton transmission     

Investigation into the temperature dependence of chromaticdispersion in optical fiber

The change in the chromatic dispersion of optical fiber with temperature is an important design parameter for 40-Gb/s systems. We derive an equation for the change in dispersion with a temperature that is more general than what has previously been published. We present experimental results for the change in fiber dispersion with temperature for six commercially available fiber types of interest for 40-Gb/s communication systems. In addition, we demonstrate that the empirical model developed by Ghosh et al in 1994 for the temperature-dependent index of refraction of SiO₂ can be used to accurately model the temperature dependence of the chromatic dispersion of a wide variety of optical fibers     

Mitigating the risk of high power damage to the BT network

Optical powers used in optical telecommunications networks have increased over time with the advent of technologies such as erbium-doped fibre amplifiers, dense WDM, and fibre Raman amplifiers. Erbium fibre and Raman amplifiers with output powers up to 1 W and 2 W respectively are now available for deployment giving optical power densities of ≈ 14 000 MW/m² per Watt launched into a single mode fibre. This compares with 74 MW/m² for the surface of the sun. It is thus essential to ensure that the risk of optical damage to the fibre is understood and steps are taken to mitigate it where necessary. Research carried out by BT over the last few years has shown that fibres carrying relatively modest optical powers, as low as 200 mW for the most sensitive fibres, can be catastrophically damaged at tight fibre bends. Damage is caused by some of the optical power lost at the bend being absorbed by the fibre coating that may over time lead to a sudden increase in temperature to over 700 °C causing either the silica to kink mimicking a fibre break, or the coating to burn off at the bend leading to fibre failure on subsequent handling. This paper describes factors that increase the risk of short-term catastrophic damage at fibre bends, presents experimental results to show the variation in sensitivity between different fibres, and discusses new important theoretical results modelling the temperature rise in the fibre.     

Adhesion studies for probiotics: need for validation and refinement

Adhesion of probiotic bacteria to intestinal epithelial cells is regarded as a prerequisite to exert beneficial health effects. Human intestinal epithelial lines, like Caco-2 or HT-29 cells, have been extensively used to select for adhesive strains in vitro. Adhesion to intestinal mucus has been used to a lesser extent. However, to date, there has been no standardization of the conditions used in in vitro adhesion assays. As a consequence, results obtained in different laboratories using identical strains, but different assay conditions, show great variability. This lack of standardization complicates the interpretation of data and discrepancies emerge on what is meant by effective adhesion. A critical validation of in vitro adhesion is essential for the food industry, using adhesion assays as predicitve screening tools to assess new probiotic strains. In this review we summarize a comparative study on adhesion of the well characterized probiotic bacteria L. johnsonii La1 and L. rhamnosus GG with respect to the influence of bacterial growth conditions, growth phase, buffer, pH, and mucus on adhesion properties. The results are employed in the current scientific discussion to allow a critical evaluation on the reliability of the in vitro assays.