Simulation of a transcritical CO2 heat pump cycle for simultaneous cooling and heating applications

A steady state simulation model has been developed to evaluate the system performance of a transcritical carbon dioxide heat pump for simultaneous heating and cooling. The simulated results are found to be in reasonable agreement with experimental results reported in the literature. Such a system is suitable, for example, in dairy plants where simultaneous cooling at 4 °C and heating at 73 °C are required. The optimal COP was found to be a function of the compressor speed, the coolant inlet temperature to the evaporator and inlet temperature of the fluid to be heated in the gas cooler and compressor discharge pressure. An optimizing study for the best allocation of the fixed total heat exchanger inventory between the evaporator and the gas cooler based on the heat exchanger area has been carried out. Effect of heat transfer in the heat exchangers on system performance has been presented as well. Finally, a novel nomogram has been developed and it is expected to offer useful guidelines for system design and its optimisation.     

肠病毒71型空斑检测方法的建立

目的建立肠病毒71型(EV71)空斑检测方法,为EV71生物学特性及疫苗的研究提供手段。方法将不同稀释度的5株EV71分别接种至单层RD细胞和Vero细胞,加入甲基纤维素覆盖,计数空斑,并计算病毒滴度。通过3次连续检测,验证空斑法的精密性,并对空斑法与微量细胞病变法检测病毒滴度的结果进行比较。结果采用RD细胞和Vero细胞,通过空斑法对EV71病毒滴度进行检测,96h后均能规律地出现边缘整齐、清晰的空斑,RD细胞和Vero细胞检测的空斑直径分别为1～2mm和0.5～1mm。连续3次重复试验结果显示,试验间变异系数的平均值Vero细胞为2.52%,RD细胞为4.49%。空斑法与微量细胞病变法比较,其检测结果具有良好的线性相关性,相关系数为r=0.972,P=0.006。结论已建立了精密性好、出斑规律的EV71病毒空斑检测方法。     

The Carotid Artery Plaque Size and Echogenicity are Related to Different Cardiovascular Risk Factors in the Elderly

Carotid plaques can be characterised by ultrasound by size and echogenicity. Both size and echogenicity are predictors of cardiovascular events. The aim of this study was to examine whether traditional risk factors and markers of inflammation and oxidation were associated with plaque size and echogenicity. Computerised analysis of carotid plaque size and echogenicity (grey scale median, GSM) were performed by ultrasound in a population-based health survey in 1,016 subjects aged 70 years (PIVUS study). Information on cardiovascular risk factors was collected, together with markers of inflammation and oxidation. Increased Framingham risk score, systolic blood pressure, higher BMI and decreased HDL, lower glutathione levels were related to echolucent plaques. Previous or present smoking was common with significantly more pack-years related to the echorich plaques. Plaque size was associated with increased Framingham risk score, systolic blood pressure, blood glucose levels, smoking, ApoB/A1 ratio, OxLDL, TNF alpha, HOMA insulin resistance, leucocyte count, decreased BCD-LDL and low levels of l-selectin. Low HDL, increased BMI and decreased glutathione levels were associated with the echolucency of carotid plaques, implying metabolic factors to play a role for plaque composition. Markers of inflammation were related to plaque size alone, implying inflammation to be predominantly associated with the amount of atherosclerosis. These results suggest that plaque size and echogenicity are influenced by different risk factors.     

Automatic segmentation and plaque characterization in atherosclerotic carotid artery MR images

In vivo MRI provides a means to non-invasively image and assess the morphological features of atherosclerotic carotid arteries. To assess quantitatively the degree of vulnerability and the type of plaque, the contours of the lumen, outer boundary of the vessel wall and plaque components, need to be traced. Currently this is done manually, which is time-consuming and sensitive to inter- and intra-observer variability. The goal of this work was to develop an automated contour detection technique for tracing the lumen, outer boundary and plaque contours in carotid MR short-axis black-blood images. Seventeen patients with carotid atherosclerosis were imaged using high-resolution in vivo MRI, generating a total of 50 PD- and T1-weighted MR images. These images were automatically segmented using the algorithm presented in this work, which combines model-based segmentation and fuzzy clustering to detect the vessel wall, lumen and lipid core boundaries. The results demonstrate excellent correspondence between automatic and manual area measurements for lumen (r=0.92) and outer (r=0.91), and acceptable correspondence for fibrous cap thickness (r=0.71). Though further optimization is required, our algorithm is a powerful tool for automatic detection of lumen and outer boundaries, and characterization of plaque in atherosclerotic vessels.     

Unusual periodicity of sex pheromone production in the large black chaferHolotrichia parallela

(R)-(–)-Linalool was identified as a minor component sex pheromone of the scarab beetleHolotrichia parallela (Coleoptera: Scarabaeidae). Field evaluations revealed that, although not attractive per se, (R)-(–)-linalool enhances the attractiveness of the major sex pheromone,L-isoleucine methyl ester (LIME). Analyses of the pheromone titers in the glands of field-collected females demonstrated the occurrence of peak levels of 48-hr (circabidian) periodicity. The levels of LIME in the glands of 45-day-old virgin females increased over three times from the scototo the photophase of a calling day, but the amounts of (R)-(–)-linalool did not significantly change. Virgin females had in average two times more LIME and 3.6 times more (R)-(–)-linalool than the average amount found in the field-captured beetles throughout the season.     

Modeling of frosting behavior on a cold plate

This paper proposes a mathematical model to predict the frost properties and heat and mass transfer within the frost layer formed on a cold plate. Laminar flow equations for moist air and empirical correlations for local frost properties are employed to predict the frost layer growth. Correlations for local frost density and effective thermal conductivity of the frost layer, derived from various experimental data, are expressed as a function of the various frosting parameters: the Reynolds number, frost surface temperature, absolute humidity and temperature of the moist air, cooling plate temperature, and frost density. The numerical results are compared with experimental data to validate the proposed model, and those agree well with the experimental data within a maximum error of 10%. Heat and mass transfer coefficients obtained from the numerical analyses are also presented. The results show that the model for the frost growth using the correlation of the heat transfer coefficient without considering the air flow has a limitation in its application.     

Two-dimensional turbulent film condensation of vapours flowing inside a vertical tube and between parallel plates: a numerical approach

Film condensation of vapour flowing inside a vertical tube and between parallel plates is treated. A methodology is presented to determine numerically the heat transfer coefficients, the film thickness and the pressure drop. The analysis is based on the resolution of the full coupled boundary layer equations of the liquid and vapour phases and does not neglect inertia and convection terms in the governing equations. Turbulence in the vapour and condensate film is taken into account using mixing length turbulence models. An explicit method and an implicit finite difference procedures are described. The calculated results for the condensation of steam in a 24 mm diameter tube are compared with those obtained from Chen's correlation. The heat flow rate for the condensation of R123 flowing between parallel plates obtained from numerical solution are compared with experimental values. The mean heat transfer coefficients for the condensation of vapour mixture R123/R134a are also presented.     

Major Sex Pheromone Components of the Australian Gum Leaf Skeletonizer Uraba lugens: (10E,12Z)-Hexadecadien-1-yl Acetate and (10E,12Z)-Hexadecadien-1-ol

Two sex pheromone components of the gum leaf skeletonizer, Uraba lugens (Lepidoptera: Nolidae), recently established in New Zealand, were identified. Gas chromatography (GC) electroantennographic detection analyses of female pheromone gland extracts gave three compounds that consistently elicited antennal responses. Chemical analyses, using GC and GC-mass spectrometry, in conjunction with 4-methyl-1,2,4-triazoline-3,5-dione and dimethyldisulfide derivatizations, identified these compounds as (10E,12Z)-hexadecadien-1-yl acetate (E10,Z12-16:Ac), (10E,12Z)-hexadecadien-1-ol (E10,Z12-16:OH), and (Z)-11-hexadecen-1-yl acetate (Z11-16:Ac). A trapping trial in Queensland, Australia, in 2002, indicated that a blend of the two major components E10,Z12-16:Ac and E10,Z12-16:OH could attract gum leaf skeletonizer males. In the same trial, E10,Z12-16:Ac alone trapped large numbers of an unidentified nolid, Nola spp. Further trials in Auckland, New Zealand established that these two components were sufficient and necessary for trap catch of males; adding minor gland components, (10E,12E)-hexadecadien-1-yl acetate (E10,E12-16:Ac), Z11-16:Ac, or octadecan-1-ol (18:OH), to the two-component lure did not result in increased trap catches. Behavioral observations and gland analyses of the Auckland population revealed that female moths begin calling soon after emergence, with peak calling and pheromone production occurring 7 hr into the scotophase. Analysis of gland extract at two-hourly intervals during the first activity period showed that the ratio of E10,Z12-16:Ac to E10,Z12-16:OH (mean of 86: 14, respectively) and pheromone titer were fairly constant. No qualitative or quantitative differences in pheromone components were detected between gland extracts from Tasmanian univoltine and Auckland bivoltine populations of U. lugens.     

四苯硼钠-季胺盐法测定KCl中K^＋含量的研究

文章介绍了用四苯硼钠-季胺盐法测定氯化钾中钾离子含量的方法,测定的试样数据与GB6549-1996《氯化钾》中规定的四苯硼钾重量法的数据采用方差分析,得出两方法间无显著性差异,采用该方法测定结果准确,测定速度快,适用于青海格尔木察尔汗盐湖氯化钾生产企业化工分析的需要。