美国电力的资金需求

电气工业是一个国家的资金密集型产业之一。在20世纪90年代,发电、输电以及配电资产占美国商业资产的9％左右。1999年,一般的股份制电气工业基础建设支出为228亿美元,到2000年,最新数据显示,该项支出增加为253亿美元。由于商业发电的增长和电力批发市场竞争的日益激烈,零散的电力生产者的基础建设支出也增长显著,电力批发交易收入增长迅速。2000年,股份电气公司发电、输电、环保及其他的总花费接近450亿美元。     

Seasonal effects on Ca(2+) transport of sarcoplasmic reticulum and on meat quality of pigs with different malignant hyperthermia status

The intracellular Ca(2+) concentration is mainly regulated by the sarcoplasmic reticulum (SR). A disturbed regulation leads to an increased metabolism and ultimately to inferior meat quality. In this study, pigs with normal and mutated calcium release channels (referred to as MHR and MHS, respectively) were used. One batch of pigs was slaughtered in winter months and another in summer months. The intention was to elucidate the impact of season on the Ca(2+) transport of SR and on meat quality in dependence of the MH-status. The results show an impact of MH-status and of season on the meat quality with inferior values in summer months, and in MHS pigs. Immediately after slaughter the rate of Ca(2+) sequestration of the SR with biochemically closed and with opened calcium release channels (CRC) was not different between experimental groups. However, with basic CRC (not biochemically manipulated) the Ca(2+) uptake rate of MHR muscle of summer pigs was significantly reduced and at the level of that of MHS pigs. The results indicate an impact of summer season on the ability of SR to regulate Ca(2+) concentration properly even in pigs with a normal CRC. This disturbed Ca(2+) regulation is correlated with diminished meat quality.     

Modelling of the disulphide-swapped isomer of human insulin-like growth factor-1: implications for receptor binding

Insulin-like growth factor-1 (IGF-1) is a serum protein whichunexpectedly folds to yield two stable tertiary structures withdifferent disulphide connectivities; native IGF-1 [18–61,6–48,47–52]and IGF-1 swap [18–61,6–47, 48–52]. Here we demonstratein detail the biological properties of recombinant human nativeIGF-1 and IGF-1 swap secreted from Saccharomyces cerevisiae.IGF-1 swap had a ~30 fold loss in affinity for the IGF-1 receptoroverexpressed on BHK cells compared with native IGF-1.The parallelincrease in dose required to induce negative cooperativity togetherwith the parallel loss in mitogenicity in NIH 3T3 cells impliesthat disruption of the IGF-1 receptor binding interaction ratherthan restriction of a post-binding conformational change isresponsible for the reduction in biological activity of IGF-1swap. Interestingly, the affinity of IGF-1 swap for the insulinreceptor was ~200 fold lower than that of native IGF-1 indicatingthat the binding surface complementary to the insulin receptor(or the ability to attain it) is disturbed to a greater extentthan that to the IGF-1 receptor. A 1.0 ns high-temperature moleculardynamics study of the local energy landscape of IGF-1 swap resultedin uncoiling of the first A-region -helix and a rearrangementin the relative orientation of the A- and B-regions. The modelof IGF-1 swap is structurally homologous to the NMR structureof insulin swap and CD spectra consistent with the model arepresented. However, in the model of IGF-1 swap the C-regionhas filled the space where the first A-region -helix has uncoiledand this may be hindering interaction of Val44 with the secondinsulin receptor binding pocket.     

Effective Sample Size in Diffuse Reflectance Near-IR Spectrometry

Two independent methods for determination of the effectively sampled mass per unit area are presented and compared. The first method combines directional-hemispherical transmittance and reflectance measurements. A three-flux approximation of the equation of radiative transfer is used, to separately determine the specific absorption and scattering coefficients of the powder material, which subsequently are used to determine the effective sample size. The second method uses a number of diffuse reflectance measurements on layers of controlled powder thickness in an empirical approach. The two methods are shown to agree well and thus confirm each other. From the determination of the effective sample size at each measured wavelength in the visible-NIR region for two different model powder materials, large differences was found, both between the two analyzed powders and between different wavelengths. As an example, the effective sample size ranges between 15 and 70 mg/cm(2) for microcrystalline cellulose and between 70 and 300 mg/cm(2) for film-coated pellets. However, the contribution to the spectral information obtained from a certain layer decreases rapidly with increasing distance from the powder surface. With both methods, the extent of contribution from various depths of a powder sample to the visible-NIR diffuse reflection signal is characterized. This information is valuable for validation of analytical applications of diffuse reflectance visible-NIR spectrometry.     

Computer-aided analysis and design of circular waveguide tapers

Two computer programs have been developed for the rigorous performance analysis of circular waveguide tapers. They are based on the direct integration of the coupled wave equations and on a mode-matching procedure applied to a step-ladder equivalent of the taper, respectively. Close agreement has been obtained between the predictions of these two approaches. The computer programs are utilized to examine the usefulness of existing taper design procedures. It has been found that a Dolph-Chebychev design is actually capable of predicting the level of the first unwanted mode, provided that the operational frequency is far above its cutoff. The spurious mode excitation can still be improved by taking into account the reconversion of power from the unwanted into the wanted modes. It has been verified by the computer analysis that the above design procedures are applicable even for frequencies near cutoff of the dominant spurious mode; however, that is at the expense of a certain degradation of the input reflection of the incident mode. A further improvement of the performance is possible only by direct computer optimization of the taper     

Integrated MRI assessment of regional function and perfusion in canine myocardial infarction

A single integrated examination using regional measurements of perfusion from contrast-enhanced MRI and three-dimensional (3D) strain from tissue-tagged MRI was developed to differentiate infarcted myocardium from adjacent tissue with functional abnormalities. Ten dogs were studied at baseline and 10 days after a 2-hour occlusion of the left anterior descending coronary artery (LAD). Strain was determined using a 3D finite element model. Two-dimensional measurements of hypoenhancing regions were highly correlated with myocardial viability (r = 0.96). Signal intensity versus time curves obtained from contrast-enhanced MRI were used for quantitative perfusion analysis. The remote and adjacent noninfarcted tissue of the dogs with LAD occlusion, as well as the infarcted tissue, exhibited abnormal deformation patterns as compared to normal dogs (positive predictive value (PPV) of strain determination of infarction = 66%). Integration of contrast-enhanced MRI results with 3D strain analysis enabled the delineation of the myocardial infarction (PPV = 100%) from functionally compromised myocardium. This integrated cardiac examination shows promise for noninvasive serial assessment of potentially jeopardized noninfarcted myocardium to study the process of infarct remodeling and expansion.     

Neurologic consultation practice in a general hospital of a rural area

The purpose of this ongoing study is to evaluate the safety and efficacy of new minimally invasive pervaginam cystourethropexy and sling procedures for the treatment of female genuine stress urinary incontinence. A total of 75 women (mean age, 52.8 years) underwent either a cystourethropexy or a sling procedure. A miniature bone anchor and a staple-like bone anchor driver were used for the fixation of periurethral tissue or a xenogenic sling to the pubic bone. With a mean follow-up of eight months, 61 patients (82%) were completely cured of stress incontinence, 10 (14%) reported a more than 50% decrease in pad usage, and 4 patients showed failure early following surgery. The exclusively pervaginam cystourethropexy and sling procedures are minimally invasive, safe, and effective. Further experience and longer follow-up are necessary to establish their role in the treatment of women with stress urinary incontinence.     

Antimony removal from dilute solutions using a restrained bed electrochemical reactor

The electrochemical removal of Antimony from 1m sulphuric acid in a restrained bed reactor was studied in terms of current, flow velocity, bed depth, bead size and pressure drop. Current efficiencies are quoted as a function of current density and information is given so that they may be calculated in terms of the above variables. Experimentally-obtained limiting current densities are compared with calculated values, using empirical formulae from the literature.     

Anisotropy of ductile fracture in hot-rolled steel plates-an application of the upset test

Upset testing of cylindrical specimens generates circumferential tensile stresses at the barreled surfaces. These stresses can be utilized in the same manner as the tensile stresses in the tension test to evaluate the ductility of materials. Using the upset test method, the anisotropy of ductile fracture in AISI 1045 hot-rolled steel plates was determined. Ductility parallel to the plane of inclusions is found to be ≈ 50 pet higher than that perpendicular to the inclusions. It is shown that the local surface strains at fracture in upset testing correlate well with the true zero-gage-length fracture strain in tension testing, provided the tensile stresses in the respective tests are in the same direction relative to the inclusion orientation. Thus, compression tests parallel to the inclusion direction, which generate tensile stresses perpendicular to the inclusions, can be utilized to measure ductility transverse to the fiber of wrought materials. This is particularly useful in determining the short transverse or through-thickness ductility in hot-rolled or forged materials having thin sections.