SOLAR DRYING SIMULATION OF PRUNES ARRANGED IN THIN LAYERS

Solar drying of prunes arranged in thin layers in a multi-shelf type drier is simulated. The weather conditions are those found during harvest in humid pampa region (hot-temperate and humid climate). A mathematical model based on Luikov's theory of drying and including an equation that describes the material shrinkage is employed. The airstream humidification is taken into account in order to analyse the influences of shelves spacing and drier length in the final product characteristics. It is found that the relative moisture content heterogeneity is a useful design criterion. The influence of weather conditions in the drying time and the drying capacity are evaluated.     

Calculations of efficiencies achievable using gallium arsenide and silicon cells mounted together in cavities illuminated by single-stage concentration

Detailed calculations have been performed to predict the efficiencies achievable using gallium arsenide and silicon cells mounted in cavities with concentrated light entering. Prototype devices with power output of the order of 2 W are proposed and analysed. The concept of the elliptical cavity with restriction of the angle of the escaping rays is exploited in order to avoid having to use a secondary concentrator. The light first falls on the gallium arsenide cell, with a concentration of 720 suns, before being reflected onto a silicon cell. Arrangements using both one and two silicon cells are studied. Depending on the type of cells used, and whether a dichroic filter is included, the possible efficiencies (relative to the light entering the cavity) are in the range 30.4–36%. The effect of the cavity is to increase thepower output by about 5% when compared to a similar bandsplitting arrangement not using a cavity. It is concluded that the cavity effect should be of interest for practical photovoltaic converters.     

An Analytical Study of the Delay in Bluetooth Networks Using the Personal Area Network Profile

Bluetooth is the most employed technology to develop wireless personal area networks. This letter studies the performance of Bluetooth transmissions that make use of the PAN (personal area network) profile. In particular, the study offers an analytical model that defines the optimal bound for the end-to-end data delay. The proposed 'delay budget' takes into account the overhead and segmentation provoked by the protocols involved in the transmission of user data. The model is empirically validated by comparing its results with those obtained through the measurements of actual Bluetooth connections.     

Lymphocele after renal transplantation: therapeutic controversies in the age of laparoscopy

We present 11 lymphoceles in 180 consecutive kidney transplants (6%). We study the potential etiologic factors, symptoms, diagnostic evaluation and treatment, stressing the role of laparoscopy in management of bulky and loculated symptomatic lymphoceles. This technique allows to reduce morbidity, increasing efficacy and shortening hospitalization.     

Myotrophic effects of muscle extracts obtained at different intervals after denervation

BACKGROUND: The assessment of return of function within dysfunctional myocardium after acute myocardial infarction (MI) using contractile reserve has been primarily qualitative. Magnetic resonance (MR) myocardial tagging is a novel noninvasive method that measures intramyocardial function. We hypothesized that MR tagging could be used to quantify the intramyocardial response to low-dose dobutamine and relate this response to return of function in patients after first MI. METHODS AND RESULTS: Twenty patients with a first reperfused MI (age, 53+/-12 years; 16 male; 11 inferior MIs) were studied. Patients underwent breath-hold MR-tagged short-axis imaging on day 4+/-2 after MI at baseline and during dobutamine infusion at 5 and 10 microg x kg(-1) x min(-1). At 8+/-1 weeks after MI, patients returned for a follow-up MR tagging study without dobutamine. Quantification of percent intramyocardial circumferential segment shortening (%S) was performed. Low-dose dobutamine MRI was well tolerated. Overall, mean %S was 15+/-11% at baseline (n=227 segments), increased to 16+/-10% at 5 microg x kg(-1) x min(-1) dobutamine (P=NS), 21+/-10% at peak (P<0.0001 versus baseline and 5 microg x kg(-1) x min(-1), and 18+/-10% at 8 weeks (P<0.004 versus baseline and peak). The increase in %S with peak dobutamine was greater in dysfunctional myocardium (103 segments, +9+/-10%) than in normal tissue (124 segments, +4+/-12%, P<0.0001). In dysfunctional regions, %S also increased from 6+/-7% at baseline to 14+/-10% at 8 weeks after MI (P<0.0001). In dysfunctional regions that responded normally to peak dobutamine (> or =5% increase in %S), the increase in %S from baseline to 8 weeks after MI (+9+/-9%) was greater than in those regions that did not respond normally (+5+/-9%, P<0.04). Midmyocardial and subepicardial response to dobutamine were predictive of functional recovery, but the subendocardial response was not. CONCLUSIONS: The response of intramyocardial function to low-dose dobutamine after reperfused MI can be quantified with MR tagging. Dysfunctional tissue after MI demonstrates a larger contractile response to dobutamine than normal myocardium. A normal increase in shortening elicited by dobutamine within dysfunctional midwall and subepicardium predicts greater functional recovery at 8 weeks after MI, but the response within the subendocardium is not predictive.     

Measurements of statistical burst-noise characteristics

In a previous letter, a dislocation model of planar-silicon-transistor burst noise was proposed. The burst statistical parameters have been measured and their dependence on bias is in good agreement with the model.