Preoperative pulmonary evaluation of the thoracic surgical patient

A test designed to separate those undergoing thoracic surgery without complications and those with complications must be both highly specific and sensitive. Clearly, the difference between patients at opposite ends of the population curves is easy to identify. Spirometry can be helpful for screening, although it is not a very discriminating test. If patients fall in the overlap region between the populations, however, it is impossible to discern the risks with any certainty using low-yield tests. A test with higher sensitivity, specificity, and predictive values is necessary to ascertain such marginal differences. With this kind of analysis at hand, preoperative testing can be divided into three predictive value groups. Calculating the predictive value of each preoperative test can provide a comparative measure of usefulness of discriminative power (Table 1). In this way, spirometry, blood gas analysis, and stair climbing tolerance are shown to be poor predictors of outcome. An intermediate predictive value can be achieved using diffusion capacity, exercise-induced decreases in O2 saturation, and exercise PVR. High predictive value can be accomplished with combination indexes (PPP, possibly PRQ), measurement of VO2 at 40 watts of exercise, or VO2max. Logic dictates a step-wise preoperative evaluation using prediction value analysis (Fig.4). A flow decision chart for the preoperative evaluation of patients for pulmonary resection begins with exercise oximetry, spirometry, and blood gas analysis as general screening tests to separate those patients at minimal or no risks for complications from those patients that require further evaluation. Functional indexes (PPP, PRQ) or exercise testing can aid further in the selection of those patients in whom a nonsurgical option should be considered. Flow decision chart for the preoperative evaluation of patients for pulmonary resection should continue to evolve as new information about outcome studies is gathered. Examination of outcome data will provide us with reduction of the size of the nonoperable population, so that we can deny only those patients who truly pose a prohibitive risk.     

Fast method to compute the scalar product of gradient and given vector

The paper deals with a special problem in Automatic Differentiation. Letf be a rational function ofn variables, let #(f) denote the number of operations to evaluatef(x), letg denote the gradient off. Many algorithms for minimizingf(x) require the scalar productg(u) ^tv. In the standard method for computingg(u) ^tv the amount of work grows withn·#(f). In this note a new method for computingg(u) ^tv is presented. The new method is considerably faster, its amount of work only grows with #(f).     

The content of asbestos bodies in the bronchoalveolar fluid as a parameter of an increased pulmonary asbestos load

Pulmonary asbestos burdens are usually determined by quantitative pulmonary dust analysis. The aim of this study was to investigate the value of bronchoalveolar lavage (BAL) for this purpose. First, the upper limit of normal for asbestos bodies (AB) in BAL fluid was established using a reference group of 371 patients with no evidence of increased exposure to asbestos. 99% of these patients had less than 0.5 AB/ml. In order to see whether BAL fluid AB concentration reflected pulmonary tissue content, BAL fluid and lung tissue from a further 64 patients with diverse histories of asbestos exposure were investigated. There was a positive association between AB concentration in BAL fluid and lung tissue only for the overall group of 64 patients (r = 0.86; P < 0.001). Twelve of 13 patients with more than 1 AB/ml and ten patients with more than 5 AB/ml had more than 1000 AB/cm3 lung tissue, a value that is usually exceeded in asbestosis. When the upper concentration limit was set at 0.5 AB/ml for BAL fluid and 50 AB/cm3 for lung tissue, only two out of 64 patients had a false positive value (specificity 95%), but eleven patients had false negative results (sensitivity 58%). These investigations establish that concentrations of > or = 0.5 AB/ml are a reliable indicator of increased asbestos exposure and concentrations > 1 AB/ml are associated with a higher probability of having more than 1000 AB/cm3 lung tissue. However, exclusion of increased asbestos exposure is not possible on the basis of negative BAL findings, since the sensitivity of the method is too low.     

A numerical investigation on the geometry dependence of the crack growth resistance in CT specimens

The influence of the specimen thickness B and the ligament length b on the J _R -curves is numerically investigated for CT specimens. The thickness effect is taken into account with 2-D analyses by dividing a plain sided specimen into a plane stress part and a plane strain part. The fracture process is controlled by experimentally determined critical values of the crack tip opening displacement for crack growth initiation (CTOD_i) and the crack tip opening angle for stable crack growth (CTOA_C). It is shown that for the global behaviour of a plain sided specimen, the B/b ratio is essential. The difference between the geometry dependence of the initiation value of the J-integral and the geometry dependence of the slope of the J _R -curves is also shown.     

Identification of potent P2Y-purinoceptor agonists that are derivatives of adenosine 5'-monophosphate

1. A series of chain-extended 2-thioether derivatives of adenosine monophosphate were synthesized and tested as agonists for activation of the phospholipase C-linked P2Y-purinoceptor of turkey erythrocyte membranes, the adenylyl cyclase-linked P2Y-purinoceptor of C6 rat glioma cells, and the cloned human P2U-receptor stably expressed in 1321N1 human astrocytoma cells. 2. Although adenosine monophosphate itself was not an agonist in the two P2Y-purinoceptor test systems, eleven different 2-thioether-substituted adenosine monophosphate analogues were full agonists. The most potent of these agonists, 2-hexylthio AMP, exhibited an EC50 value of 0.2 nM for activation of the C6 cell receptor. This potency was 16,000 fold greater than that of ATP and was only 10 fold less than the potency of 2-hexylthio ATP in the same system. 2-hexylthio adenosine was inactive. 3. Monophosphate analogues that were the most potent activators of the C6 cell P2Y-purinoceptor were also the most potent activators of the turkey erythrocyte P2Y-purinoceptor. However, agonists were in general more potent at the C6 cell receptor, and potency differences varied between 10 fold and 300 fold between the two receptors. 4. Although 2-thioether derivatives of adenosine monophosphate were potent P2Y-purinoceptor agonists no effect of these analogues on the human P2U-purinoceptor were observed. 5. These results support the view that a single monophosphate is sufficient and necessary for full agonist activity at P2Y-purinoceptors, and provide insight for strategies for development of novel P2Y-purinoceptor agonists of high potency and selectivity.     

Coded differential space-time modulation for flat fading channels

In this paper, powerful coding techniques for differential space-time modulation (DSTM) over Rayleigh flat fading channels and noncoherent detection without channel state information at the receiver are investigated. In particular, multilevel coding, bit-interleaved coded modulation, and so-called hybrid coded modulation (HCM) are devised and compared. For improved noncoherent reception multiple-symbol differential detection (MSDD) is adapted to DSTM. In order to reduce the computational effort required for MSDD, a low-complexity version of MSDD is applied. Evaluating the ergodic channel capacity for the different schemes as appropriate performance measure, HCM with simplified MSDD is shown to offer a favorable tradeoff between complexity and achievable power efficiency. Simulation results employing turbo codes in properly designed HCM schemes confirm the predictions from information theory.     

High quality LTCC resonator for voltage-controlled oscillator

Design and technology of microwave conductor lines embedded in low-temperature cofired ceramic (LTCC) multilayer substrates are summarized with a focus on achieving the highest possible quality (Q) factor for a given line inductance. The work was initiated to test the integrability of base station voltage-controlled oscillators (VCOs) in ceramic multilayer substrates. This approach leads to a miniaturization of current versions by a factor of 2 to 4. However, base station specifications for phase noise and hence resonator Q are extremely demanding. Therefore, both the design and the processing technology were optimized. By choosing a twin-line design with two parallel lines vertically separated by a single LTCC layer, Q factors of 90 and 180 have been achieved for integrated 5.5 nH inductors at frequencies of 640 MHz and 1650 MHz, respectively. Application of this result to VCO modules in standard LTCC technology already yields low phase noise levels, e.g., -136 dBc/Hz at 100 kHz offset, which is suitable for base station applications. However, further noise reduction is expected from a dedicated high Q fabrication process that uses conventional via punching and filling steps to replace the ceramic material between the two lines by conductive silver paste. This raises the Q to 120 and 200, respectively, at the two frequencies and adds extra degrees of freedom to LTCC design for low-loss wireless solutions.