Globally convergent edge-preserving regularized reconstruction: anapplication to limited-angle tomography

We introduce a generalization of a deterministic relaxation algorithm for edge-preserving regularization in linear inverse problems. This algorithm transforms the original (possibly nonconvex) optimization problem into a sequence of quadratic optimization problems, and has been shown to converge under certain conditions when the original cost functional being minimized is strictly convex. We prove that our more general algorithm is globally convergent (i.e., converges to a local minimum from any initialization) under less restrictive conditions, even when the original cost functional is nonconvex. We apply this algorithm to tomographic reconstruction from limited-angle data by formulating the problem as one of regularized least-squares optimization. The results demonstrate that the constraint of piecewise smoothness, applied through the use of edge-preserving regularization, can provide excellent limited-angle tomographic reconstructions. Two edge-preserving regularizers-one convex, the other nonconvex-are used in numerous simulations to demonstrate the effectiveness of the algorithm under various limited-angle scenarios, and to explore how factors, such as the choice of error norm, angular sampling rate and amount of noise, affect the reconstruction quality and algorithm performance. These simulation results show that for this application, the nonconvex regularizer produces consistently superior results.     

Reduction of Radiation-Induced Hair Loss by Topical Application of Radioprotectors

ABSTRACT

Our transdermal permeation studies of radioprotectors in permeation-enhancing vehicles led us to hypothesize that radiation-induced hair loss could be reduced by topical application of radioprotectors. In the present study we used a hair regrowth assay in “plucked” mice to measure the radioprotective effectiveness of WR-1065, cysteine and TEMPOL when they were dissolved in a variety of vehicles, i.e., saline, dimethyl formamide (DMF), propylene glycol (PG), dimethyl sulfoxide (DMSO), ethanol. Protector effectiveness varied with radiation dose and vehicles. At 600 R, WR-1065 or cysteine, in any vehicle, reduced radiation-induced baldness scores; at 800 R, only WR-1065 in DMF and cysteine in saline, produced some protection. TEMPOL in ethanol produced protection at both the 600 and 800 R. Results suggest that suitably chosen topical application of protector/vehicle combinations can reduce radiation-induced hair loss.     

构成信号发生器的DDS和变换器

许多设备需要使用能产生高性能、高分辩率信号的低频信号发生器.本实例提供一种能产生0～1MHz频率的电路.你利用这种电路就可产生正弦波、三角波和方波,并能达到优于0.1Hz的频率分辨率和优于0.1°的相位分辨率,从而就可以给精确的相干频率编程.这一特点对于数字调制设备和频率调谐设备来说都是很有用的.该电路使用AD μ C381和AD9834来产生所需的频率(图1).利用PC或基于Unix的工作站来给微控制器AD μ C381编程,然后再通过微控制器,利用一个三线串行接口来对AD9834编程.接口的字长为16位.     

多路同步采样ADC实现高性能多通道电网监测

本文介绍了同步采样ADC在电网监测中的应用,并对构建电力线测量系统时所要考虑的问题进行了讨论.     

Relationship of provider characteristics to outcomes, process, and costs of care for community-acquired pneumonia

OBJECTIVES: The authors describe the relation of provider characteristics to processes, costs, and outcomes of medical care for elderly patients hospitalized for community-acquired pneumonia. METHODS: Using Medicare claims data, Medicare beneficiaries discharged from Pennsylvania hospitals during 1990 with community-acquired pneumonia were identified. Claims data were used to ascertain mortality, readmissions, use of procedures and physician consultations, and the costs of care. The relationship of these measures to provider characteristics was analyzed using regression techniques to adjust for patient characteristics, including comorbidity and microbial etiology. RESULTS: Among 22,294 pneumonia episodes studied, 30-day mortality was 17.0%. After adjusting for patient characteristics, 30-day mortality and readmission rates were unrelated to hospital teaching status or urban location or to physician specialty. Use of procedures and physician consultations was more common and costs were 11% higher among patients discharged from teaching hospitals compared with nonteaching hospitals. Similarly, costs were 15% higher at urban hospitals compared with rural hospitals. General internists and medical subspecialists used more procedures and had higher costs than family practitioners. CONCLUSIONS: Processes and costs of care for community-acquired pneumonia varied by provider characteristics, but neither mortality nor readmission rates did. These differences cannot be explained by clinical variables in the database. Further studies should determine whether less costly patterns of care for pneumonia, and perhaps other conditions, could replace more costly ones without compromising patient outcomes.     

Urinary proteomic analysis of chronic allograft nephropathy

The pathogenesis of progressive renal allograft injury, which is termed chronic allograft nephropathy (CAN), remains obscure and is currently defined by histology. Prospective protocol-biopsy trials have demonstrated that clinical and standard laboratory tests are insufficiently sensitive indicators of the development and progression of CAN. The study aim was to determine if CAN could be characterized by urinary proteomic data and identify the proteins associated with disease. The urinary proteome of 75 renal transplant recipients and 20 healthy volunteers was analyzed using surface enhanced laser desorption and ionization MS. Patients could be classified into subgroups with normal histology and Banff CAN grades 2-3 with a sensitivity of 86% and a specificity of 92% by applying the classification algorithm Adaboost to urinary proteomic data. Several urinary proteins associated with advanced CAN were identified including α1-microglobulin, β2-microglobulin, prealbumin, and endorepellin, the antiangiogenic C-terminal fragment of perlecan. Increased urinary endorepellin was confirmed by ELISA and increased tissue expression of the endorepellin/perlecan ratio by immunofluoresence analysis of renal biopsies. In conclusion, analysis of urinary proteomic data has further characterized the more severe CAN grades and identified urinary endorepellin, as a potential biomarker of advanced CAN.     

In‐situ Observations of Nanoscale Effects in Germanium Nanowire Growth with Ternary Eutectic Alloys

Vapour‐liquid‐solid (VLS) techniques are popular routes for the scalable synthesis of semiconductor nanowires. In this article, in‐situ electron microscopy is used to correlate the equilibrium content of ternary (Au_0.75Ag_0.25–Ge and Au_0.65Ag_0.35–Ge) metastable alloys with the kinetics, thermodynamics and diameter of Ge nanowires grown via a VLS mechanism. The shape and geometry of the heterogeneous interfaces between the liquid eutectic and solid Ge nanowires varies as a function of nanowire diameter and eutectic alloy composition. The behaviour of the faceted heterogeneous liquid–solid interface correlates with the growth kinetics of the nanowires, where the main growth facet at the solid nanowire–liquid catalyst drop contact line lengthens for faster nanowire growth kinetics. Pronounced diameter dependent growth kinetics, as inferred from liquid–solid interfacial behaviour, is apparent for the synthesised nanowires. Direct in‐situ microscopy observations facilitates the comparison between the nanowire growth behaviour from ternary (Au–Ag–Ge) and binary (Au–Ge) eutectic systems.     

Coronary Artery Ectasia: Review of the Non-Atherosclerotic Molecular and Pathophysiologic Concepts

Coronary artery ectasia (CAE) is frequently encountered in clinical practice, conjointly with atherosclerotic CAD (CAD). Given the overlapping cardiovascular risk factors for patients with concomitant CAE and atherosclerotic CAD, a common underlying pathophysiology is often postulated. However, coronary artery ectasia may arise independently, as isolated (pure) CAE, thereby raising suspicions of an alternative mechanism. Herein, we review the existing evidence for the pathophysiology of CAE in order to help direct management strategies towards enhanced detection and treatment.     

Differentiation of apple juice samples on the basis of heat treatment and variety using chemometric analysis of MIR and NIR data

The potential of mid-infrared (MIR) and near-infrared (NIR) spectroscopy for their ability to differentiate between apple juice samples on the basis of apple variety and applied heat-treatment was evaluated. The heat-treatment involved exposure of juice samples (15 ml) for 30 s in a 900 W microwave oven and the apple varieties used to produce the juice samples were Bramley, Elstar, Golden Delicious and Jonagold. The chemometric procedures applied to the MIR and NIR data were partial least squares regression (PLS1 for differentiation on the basis of heat-treatment, PLS2 for varietal differentiation) and linear discriminant analysis (LDA) applied to principal component (PC) scores. PLS1 and PLS2 gave the highest level of correct classification of the apple juice samples according to heat-treatment (77.2% for both MIR and NIR data) and variety (78.3–100% for MIR data; 82.4–100% for NIR data), respectively.