Experimental fetal tracheal ligation reverses the structural and physiological effects of pulmonary hypoplasia in congenital diaphragmatic hernia

Infants with congenital diaphragmatic hernia (DH) and profound pulmonary hypoplasia are currently unsalvageable. The authors previously demonstrated that tracheal ligation (TL) accelerates fetal lung growth and reverses the pulmonary hypoplasia of fetal nephrectomy. The purpose of this study was to determine if the pulmonary hypoplasia of experimental DH could be similarly reversed and, if so, whether the resulting lungs would show better function than those of their DH counterparts. Eighteen fetal lambs were divided into three experimental groups of six animals each. In group 1, DH was created at 90 days' gestation. In group 2, DH was created at 90 days' gestation and TL performed during the same operation. Group 3 consisted of sham-operated controls. These animals were delivered near full-term, and their lungs analyzed by standard morphometric techniques. Ten additional fetal lambs were divided into two experimental groups of five animals each. In group 4, DH was created at 90 days' gestation. In group 5, DH was created at 90 days' gestation and TL performed 20 days later, at 110 days' gestation. These animals were pressure-ventilated via tracheostomy over a 2-hour period in which PaO2, PaCO2, and compliance were measured. Intratracheal pressure (ITP) was measured at the time of delivery in all groups. Upon retrieval, DH animals had abdominal viscera in the chest and small lungs; in contrast, DH/TL animals had the herniated viscera reduced from the chest by enlarged lungs. DH/TL lungs showed markedly increased growth, with significant increases in lung volume:body weight ratio (LV:BW; P = .0001), alveolar surface area (ALV.SA; P = .0001), and alveolar number (ALV#) (P = .0001) when compared with those of the DH or control group. This growth was associated with a normal maturation pattern based on histological appearance, normal airspace fraction, and normal alveolar numerical density. ITP in the DH/TL group was increased when compared with that of DH and control animals (P = .0001). Total lung DNA and protein were both elevated in the DH/TL animals (P = .0001). However, the DNA:protein ratio remained normal, suggesting lung growth had occurred through cell proliferation, not by hypertrophy. When ventilated over a range of settings, DH/TL lungs were more compliant (P = .0001) and achieved higher PaO2s (P < .003) and lower PaCO2s (P = .0001) than their DH counterparts. From these data, the authors conclude: (1) Experimental fetal DH produces hypoplastic lungs that are not capable of adequate gas exchange with conventional ventilation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Nanocell logic gates for molecular computing

Molecular electronics seeks to build electrical devices to implement computation - logic and memory - using individual or small collections of molecules. These devices have the potential to reduce device size and fabrication costs, by several orders of magnitude, relative to conventional CMOS. However, the construction of a practical molecular computer will require the molecular switches and their related interconnect technologies to behave as large-scale diverse logic, with input/output wires scaled to molecular dimensions. It is unclear whether it is necessary or even. possible to control the precise regular placement and interconnection of these diminutive molecular systems. This paper describes genetic algorithm-based simulations of molecular device structures in a nanocell where placement and connectivity of the internal molecular switches are not specifically directed and the internal topology is generally disordered. With some simplifying assumptions, these results show that it is possible to use easily fabricated nanocells as logic devices by setting the internal molecular switch states after the topological molecular assembly is complete. Simulated logic devices include an inverter, a NAND gate, an XOR gate and a 1-bit adder. Issues of defect and fault tolerance are addressed.     

Dynamic thermographic imaging for estimation of regional perfusion in the tuberculin reaction in healthy adults

A sensitive method for measurement of the volume of blood flow through the skin, based on the kinetics of reheating after localised cooling, is described in this paper. This method has been used to study the tuberculin reaction as a model of cutaneous delayed-type hypersensitivity (DHS) in man. Over the positive reaction there is accelerated reheating similar in kinetics and extent to that seen after maximal hyperaemia induced by intradermal injection of histamine or prostaglandin E2. The earlier phase of reheating (10-100 s) is more dependent on blood flow, whereas the later phase (100-300 s) is apparently more dependent on non-perfusion heat exchange mechanisms, including conduction. The reheat kinetic method is largely dependent on blood flow in the deep dermal vessels (diameter > 50 microns), whereas the alternative approach of measurement of the velocity of flow of erythrocytes in the microcirculation by laser Doppler (LD) flowmetry gives results biased towards the most superficial dermal circulation. Previous studies with LD flowmetry have shown that the blood velocity is greatest at the centre of weak and strong reactions, while in the most intense reactions it is raised at the centre but maximal at the periphery (central relative slowing, CRS) raising the possibility of central ischaemia. The reheat kinetics approach has now indicated that the deep dermal circulation is not impaired in CRS reactions. It is concluded that there must be partial obstruction of the parts of the microcirculation communicating between the deep and superficial dermal plexuses, presumably from the accumulation of exudate oedema in the most intense tuberculin reactions.     

Factors influencing unemployment duration with a special emphasis on migration: An investigation using SIPP data and event history methods

The length of time that individuals are unemployed has considerable political and policy significance. Important questions about the factors influencing the duration of unemployment remain to be answered. The purpose of this paper is to carry out an empirical investigation of the factors that cause unemployment to be of a longer or shorter duration. Such factors are identified within a micro-economic framework drawn from human capital and job search theories. Event history methods and panel data are used to model unemployment duration. The data come from the Survey of Income and Program Participation (SIPP) which contains weekly information on labor force status over about a two and a half year period, as well as data on a number of individual and locational attributes. Evidence from the empirical investigation suggests that migration, temporary layoff and income during unemployment combine with individual characteristics to influence the duration of unemployment spells.An earlier version of this paper was presented at the 38th North American Meetings of the RSAI, New Orleans, LA, November 1991.     

Information processing deficits associated with developmental coordination disorder: a meta-analysis of research findings

A meta-analysis was conducted to identify information processing factors that characterise children with Developmental Coordination Disorder (DCD). A total of 50 studies yielded 374 effect sizes based on 983 DCD and 987 control children. A mild generalised performance deficit was indicated, since motor-impaired children were inferior on almost all measures of information processing. There were, however, several areas where their deficiencies were more pronounced. The greatest deficiency was in visual-spatial processing. This was evident regardless of whether or not the tasks involved a motor component. Most other deficiencies were in the small-to-moderate range and included kinaesthetic and cross-modal processing. The findings support the notion that perceptual problems, particularly in the visual modality, are associated with difficulties in motor coordination.     

Use of a subcutaneous glucose sensor to detect decreases in glucose concentration prior to observation in blood

The development of a hypoglycemic alarm system using a subcutaneous glucose sensor implies that a decrease in blood glucose is rapidly followed by a decrease in the signal generated by the sensor. In a first set of experiments the linearity and the kinetics of the response of sensors implanted in the subcutaneous tissue of normal rats were investigated during a progressive increase in plasma glucose concentration: the sensitivities determined between 5 and 10 mM and between 10 and 15 mM were not significantly different, and a 5-10 min delay in the sensor's response was observed. In a second set of experiments, performed in diabetic rats, the kinetics of the decrease in subcutaneous glucose concentration following insulin administration was monitored during a decrease in plasma glucose level, from 15 to 3 mmol/L. During the 20 first min following insulin administration, the sensor monitored glucose concentration in subcutaneous tissue with no lag time. Subsequently, the decrease in the estimation of subcutaneous glucose concentration preceded that of plasma glucose. This phenomenon was not observed when the same sensors were investigated in vitro during a similar decrease in glucose concentration and may be due to a mechanism occurring in vivo, such as the effect of insulin on glucose transfer from the interstitial space to the cells surrounding the sensor. It reinforces the interest of the use of implantable glucose sensors as a part of a hypoglycemic alarm.     

Evaluating Ozone as a Remedial Treatment for Removing RDX from Unsaturated Soils

Years of wastewater discharge at the Department of Energy’s Pantex Plant have contaminated the vadose zone and underlying perched aquifer with hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Because the vadose zone is acting as a continual source of groundwater contamination, removing RDX from the unsaturated zone is paramount to prevent further contamination. We determined the efficacy of ozone to degrade and mineralize RDX. Solution experiments showed that ozone (27?mg?L?1; 150?mL?min?1) was effective in mineralizing 80% of the RDX (30?mg?RDX?L?1) provided that some Pantex soil was present to buffer the solution pH. Soil columns treated with ozone produced 50% RDX mineralization within 1 day and >80% within 7 day. Experiments designed to evaluate aerobic biodegradation following partial ozonation of a RDX solution showed that ozone-generated RDX products were much more biodegradable than untreated controls in aerobic microcosms (35 versus <0.3% cumulative mineralization). These results support the use of ozone as a remedial treatment for the contaminated vadose zone at the Pantex facility.     

混合信号SoC设计的现状与未来

从消费电子市场最容易得到的经验是集成为王。移动型战胜便携型,掌上型战胜移动型,而衬衫口袋型又超过掌上型。即使像游戏机这类桌面设备,时髦的外形和低制造成本目标也要靠更高集成度才能实现。这一趋势并不限于低成本的消费电子产品。军用、汽     

液晶电视屏幕的电路保护选择

平板液晶技术的迅猛发展让大屏幕、宽视角、高质量的视频图像得以实现。但是,随着液晶电视的屏幕变大、亮度更高,工作时所需的电压和电流也逐渐增加。而且,由于液晶电视屏幕中配置了多种供用户使用的接口,所以特别容易由于过电流和过电压的原因而出现损坏。     

Water activity of multicomponent mixture of solutes and non-solutes

An equation has been derived to calculate the water activity (A_w) of multicomponent mixtures of solutes and non‐solutes. The equation is based on a previous Caurie adsorption equation and it depends on the number of component ingredients and the initial moisture contents of the ingredients in the mixture. Solute and non‐solute/water interaction effects in solution were identified as playing important roles in determining accurate equilibrium A_ws of the aqueous mixtures. The new equation allows for interaction effects in mixed solution/suspensions and has been tested on model foods (the data was taken from the literature) containing up to five solutes and non‐solute components. The equation displays a high degree of accuracy. Unlike the Ross equation, which applies only approximately to mixtures of dilute solutions, the new equation applies to mixtures at all solution concentrations and to wet solids.