Left ventricular geometric patterns in end‐stage kidney disease: Determinants and course over time

Introduction : While concentric left ventricular hypertrophy (cLVH) predominates in non–dialysis‐dependent chronic kidney disease (CKD), eccentric left ventricular hypertrophy (eLVH) is most prevalent in dialysis‐dependent CKD stage 5 (CKD5D). In these patients, the risk of sudden death is 5× higher than in individuals with cLVH. Currently, it is unknown which factors determine left ventricular (LV) geometry and how it changes over time in CKD5D. Methods : Data from participants of the CONvective TRAnsport Study who underwent serial transthoracic echocardiography were used. Based on left ventricular mass (LVM) and relative wall thickness (RWT), 4 types of left ventricular geometry were distinguished: normal, concentric remodeling, eLVH, and cLVH. Determinants of eLVH were assessed with logistic regression. Left ventricular geometry of patients who died and survived were compared. Long‐term changes in RWT and LVM were evaluated with a linear mixed model. Findings : Three hundred twenty‐two patients (63.1 ± 13.3 years) were included. At baseline, LVH was present in 71% (cLVH: 27%; eLVH: 44%). Prior cardiovascular disease (CVD) was positively associated with eLVH and ß‐blocker use inversely. None of the putative volume parameters showed any relationship with eLVH. Although eLVH was most prevalent in non‐survivors, the distribution of left ventricular geometry did not vary over time. Discussion : The finding that previous CVD was positively associated with eLVH may result from the permanent high cardiac output and the strong tendency for aortic valve calcification in this group of long‐term hemodialysis patients, who suffer generally also from chronic anemia and various other metabolic derangements. No association was found between eLVH and parameters of fluid balance. The distribution of left ventricular geometry did not alter over time. The assumption that LV geometry worsens over time in susceptible individuals, who then suffer from a high risk of dying, may explain these findings.     

Two New Methods for Solving the Path‐Based Stochastic User Equilibrium Problem

In this article, we present two new methods for the path‐based logit stochastic user equilibrium problem, and investigate their convergence properties. First, a two‐level partial linearization method is proposed. Second, a dual method is developed. Both of these two methods use second‐order approximation of the objective function. Our novel methods are compared to Damberg's partial linearization method (Damberg, 1996), which is known to be one of the best performing methods. Numerical results on the different networks show that, if properly scaled, our new methods compare favorably to Damberg's method.     

A mathematical steady-state design model for fully-integrated boost and buck DC–DC converters

This brief discusses a mathematical steady-state model for fully-integrated boost and buck DC–DC converters, which takes all the significant resistive and dynamic power losses into account. The model provides a reduced calculation time by a factor 30 compared to SPICE. A 2%, or less, deviation in comparison with SPICE is achieved. The validation of the model through the measurements of both a fully-integrated boost and buck converter is demonstrated, resulting in an accuracy for the efficiency of 3 and 4% respectively.     

Accuracy improvement of the output impedance model for capacitive down-converters

Contemporary models fail to include the influence of the output buffer capacitor size on the performance of capacitive DC–DC converters. This letter examines the relevance of this dependency and shows how to adapt existing models in order to include it. The improved model is verified mathematically for down-converters, by means of Spice simulations and based on measurements of silicon integrated prototypes. Measurements demonstrate an accuracy improvement of up to 30 % compared with the conventional model.     

Increasing short‐term output in assembly work

Maximization of flexibility is one of the major challenges in assembly line design. This article addresses the question of how to temporarily (in times of peak demand) increase the output of a line, which is already optimized to attain the “normal” output rate. Instead of a costly reconfiguration of the line creating extra workstations for more operators, we applied an approach of keeping the line intact, adding two extra operators, and applying a scheme wherein the operators took their breaks alternately. For two different alternating break schemes, we compared the productivity rates, the physical load on operators, and the operators' experiences to those of the traditional situation. The new approach resulted in an increase in line output of 12–16%, depending on which alternating break scheme was applied. On the operator level, we observed no differences in productivity among conditions, despite the differences in total pause time per operator. Simultaneously, physical loads on the neck and shoulders, expressed by level of discomfort, were found to be significantly lower in one of the new alternating break schemes. A majority of the operators rated this alternating break scheme as “pleasant” (90%), but wanted the scheme to be applied only during the periods of peak demand because of social aspects (80%). In conclusion, an increase in volume flexibility can be achieved by adding two extra workers and applying an alternating work/rest scheme without a costly reconfiguration of the line. © 2010 Wiley Periodicals, Inc.     

Estimation of measles vaccine efficacy and critical vaccination coverage in a highly vaccinated population

Measles is a highly infectious disease that has been targeted for elimination from four WHO regions. Whether and under which conditions this goal is feasible is, however, uncertain since outbreaks have been documented in populations with high vaccination coverage (more than 90%). Here, we use the example of a large outbreak in a German public school to show how estimates of key epidemiological parameters such as the basic reproduction number (R₀), vaccine efficacy (VE_S) and critical vaccination coverage (p_c) can be obtained from partially observed outbreaks in highly vaccinated populations. Our analyses rely on Bayesian methods of inference based on the final size distribution of outbreak size, and use data which are easily collected. For the German public school the analyses indicate that the basic reproduction number of measles is higher than previously thought (, 95% credible interval: 23.6–40.4), that the vaccine is highly effective in preventing infection (, 95% credible interval: 0.993–0.999), and that a vaccination coverage in excess of 95 per cent may be necessary to achieve herd immunity (, 95% credible interval: 0.961–0.978). We discuss the implications for measles elimination from highly vaccinated populations.     

The tapered matrix amplifier: a low-power high-gain broadband amplifier

A new distributed amplifier topology that offers greatly reduced power consumption is presented. The tapered matrix amplifier (TMA) originates from the combination of transmission line tapering and matrix cascading of distributed amplifiers. The design of a TMA is however complicated by contrasting requirements of the tapered lines, the lumped line approximation and the parasitics of the circuit components. Therefore, a pragmatic design approach leveraging circuit optimization is proposed to handle these complexities. As a proof of concept, a prototype broadband amplifier was implemented in a 90 nm bulk CMOS process. It features an average gain of 15.8 dB over the pass-band, stretching from DC to 22 GHz, while consuming only 12.9 mW of DC power. The average noise figure in the pass-band is 5.4 dB, and the average IIP3 is ?7.3 dBm. The die area occupied by the amplifier is only 0.31 mm². In addition, it is shown that the prototype design can be easily adapted for high linearity while keeping the increase in power consumption to a minimum.