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Notes: Water currents in an hydraulic model have been determined by means of a photogrammetric method of detecting the movement of tethered buoys. Single vertical photographs, taken by a non-metric camera, have been analysed to produce the required differential measurements. The use of a non-metric camera is justified by an analysis of the errors involved and a consideration of the requisite type of measurements.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméUne méthode photogrammétrique a été mise au point pour déterminer par mesures différentielles sur un modèle hydraulique les mouvements de bouées en vue d'étudier les courants; seules des photos verticales isolées sont prises, avec une camera non métrique, ici largement suffisante pour l'exactitude requise.〈section xml:id="abs1-3"〉〈title type="main"〉ZusammenfassungBestimmung der Wasserströmungen in einem hydraulischen Modell durch photogrammetrische Ermittlung der Bewegung von verankerten Bojen. Einzeine Steilbilder, die mit einer Amateurkamera aufgenommen wurden, dienten zur Ableitung der geforderten Differenzen-Messungen. Die Verwendung einer Amateurkamera wird durch eine Analyse der auftretenden Fehler und eine Betrachtung der geforderten Messungswerte gerechtfertigt.

Notes: Objective To assess the frequency of abnormal values for hormone measurements commonly used in the biochemical diagnosis of polycystic ovary syndrome (PCOS).Design Hormone measurements in 63 unselecled women with clinical and ultrasound diagnosis of PCOS attending gynaecological and general endocrine clinics in a District General Hospital were compared with those from a group of 20 normal ovula-tory controls in the early follicular phase of their cycles.Measurements Serum levels of luteinizing hormone (LH), follicle stimulating hormone (FSH), LH/FSH ratio, total testosterone, derived free testosterone, sex hormone binding globulin, androstenedione, and dehydroepiandrosterone (DHEA) were measured by radioimmunoassays. LH and FSH measured by two different assays.Results The mean serum LH and LH/FSH ratio were significantly (P〈0.01) higher in the women with PCOS compared with the normal group, but these two measurements were in the abnormal range for only 35% and 41–44%, respectively. Absolute gonadotrophin values were significantly different using the two assay methods, which employed the same reference preparation as standard. Mean serum total testosterone concentration was significantly higher in the PCOS group and was the most frequently (70%) abnormal biochemical marker for PCOS. Sex hormone binding globulin (SHBG) did not differ significantly between the two groups but showed a negative correlation with body mass index in women with PCOS. The combination of SHBG and testosterone to derive a free testosterone value did not further aid the biochemical diagnosis of PCOS. Androstenedione was significantly higher in the PCOS group than in the control group, with a frequency of 53%. There was no significant difference in DHEA-S between the two groups.Conclusion When typical ovarian ultrasound appearances plus the clinical features of oligomenorrhoea and/or hirsuitism were used to define PCOS total testosterone was the best single hormonal marker of the condition. Testosterone, androstenedione or LH, either alone or in combination, were raised in 86% of women with PCOS and these should be the definitive hormonal tests. Using LH/FSH ratio as a biochemical criterion for diagnosis of PCOS should be abandoned because of its low sensitivity. To be of value the normal range for all hormones should be precisely defined in a group of regularly ovulating women in the early follicular phase of the cycle for the assay used in each laboratory.

Notes: Shoulders have been observed in the measured semilogarithmic current-voltage (I–V) characteristics of high-efficiency passivated emitter and rear locally diffused silicon (Si) solar cells. An improved understanding is given of the mechanism proposed to cause these nonideal I–V curves. It is shown that this mechanism is due to the electrostatic behavior of free carriers at the Si/SiO2 interface of oxidized Si devices in which the Si adjacent to the oxide is depleted (or in some cases, inverted) at equilibrium, and results in saturation of the surface recombination rate. Two-dimensional numerical computer simulations are used to investigate this mechanism and its effect on cell performance. In addition, the simulations provide a means of estimating the extent to which lateral conduction in the rear surface channel also contributes to the observed recombination saturation in these cells. It is shown that ohmic limitation of lateral conduction occurs, however, the lateral current flows are negligible in comparison to the recombination currents due to the former mechanism. © 1995 American Institute of Physics.

Notes: The principle of superposition forms the theoretical basis on which the comparison of illuminated and dark current-voltage (I-V) characteristics of solar cells depends. Two cases predicted from computer simulations where the superposition principle does not apply in silicon p-n junction solar cells are reported. These predictions are confirmed experimentally with measurements taken on existing high-efficiency devices, and cannot be accurately described by previous explanations for departures from this principle. The first case, which is the more important in terms of operation under 1 sun illumination, occurs in cells where recombination via defect levels (Shockley–Read–Hall recombination) with unequal electron and hole capture rates dominates the I-V characteristics. The second case is evident at small forward voltages in almost all silicon solar cells. It is shown that the former is due to a saturation in the recombination rate, while the latter is the result of a bias-dependent modification of the carrier concentrations across the p-n junction depletion region which is different under illumination from that in the dark. © 1994 American Institute of Physics.

Notes: Objective To examine how maternal diet in pregnancy and parental body size and birthweight influence an infant's thinness at birth measured by a low ponderal index.Design An observational study of newborn infants and their parents.Setting Southampton, England.Population Five hundred and thirty-eight infants born at term.Main outcome measure Ponderal index at birth.Results Women who had a high intake of carbohydrate in early pregnancy and a low intake of dairy protein in late pregnancy tended to have infants that were thin at birth (P= 0.01 and P= 0.03, respectively, in a simultaneous analysis). Women who themselves had a low birthweight also tended to have thin infants, ponderal index falling from 28.3 kg/m3 to 26.2 kg/m3 as the women's birthweights decreased from more than 4.0 kg to 2.5 kg or less (P 〈 0.0001). Tall fathers had thin infants, but ponderal index was not related to the women's heights or the fathers’ birthweights.Conclusion These associations may reflect constraints on placental development imposed by a woman's nutrition in pregnancy and during her own intrauterine life. Effects of the father's height may be mediated through genetic influences on skeletal growth.