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51.
The knowledge of the valence electron distribution is essential for understanding the properties of materials. However this information is difficult to obtain from HREM images because it is easily obscured by the large scattering contribution of core electrons and by the strong dynamical scattering process. In order to develop a sensitive method to extract the information of valence electrons, we have used an information transmission approach to describe the electron interaction with the object. The scattered electron wave is decomposed in a set of basic functions, which are the eigen functions of the Hamiltonian of the projected electrostatic object potential. Each basic function behaves as a communication channel that transfers the information of the object with its own transmission characteristic. By properly combining the components of the different channels, it is possible to design a scheme to extract the information of valence electron distribution from a series of exit waves. The method is described theoretically and demonstrated by means of computer simulations.  相似文献   
52.
Cyclical production planning is popular in real-life because of its organisational benefits. We study the application and performance of cyclical production planning in a complex stochastic production-inventory system with job shop routings. We propose a decision-support system that allows computing cost efficient cyclical production plans. Insights on the applicability and performance of cyclical production planning are obtained from an extensive simulation study in which the cyclical approach is compared with a state-of-the-art non-cyclical approach.  相似文献   
53.
In this paper, we study a production system that operates under a lead-time performance constraint which guarantees the completion of an order before a pre-determined lead-time with a certain probability. The demand arrival times and the service requirements for the orders are random. To reduce the capacity-related operational costs, the production system under study has the option to use flexible capacity. We focus on periodic capacity policies and model the production system as a queuing system that can change its capacity periodically and choose to operate in one of the two levels: a permanent capacity level and a permanent plus contingent capacity level. Contingent capacity is supplied if needed at the start of a period, and is available during that period, at a cost rate that is decreasing in period length in different functional forms. Next, we propose a search algorithm that finds the capacity levels and the switching point that minimizes the capacity-related costs for a given period length. The behaviour of the capacity-related costs changes drastically under different period lengths and cost structures. In our computational study, we observe that the periodic capacity flexibility can reduce the capacity-related operational costs significantly (up to 35%). However, in order to achieve these savings, the period length must be chosen carefully depending on ambition level and capacity-related costs. We also observe that the percentage savings are higher for more ambitious lead-time performance constraints. Moreover, we observe that the use of contingent capacity makes the total system costs more insensitive to the lead-time performance requirements.  相似文献   
54.
There is an increased demand for more dwelling space in Western countries. In the Netherlands, this is expressed as an overwhelming preference for a single-family dwelling with a garden. In contrast to these consumer preferences, governments pursue a compact-city agenda, which implies high-density and mixed-use cities. This gap between consumer preference and government policy has led many policy makers, planners and developers to design dwelling concepts for urban areas in which the private domestic garden is substituted by public green space. In this paper we investigate whether this substitution makes sense or not by comparing the meanings people attach to both concepts. Our results clearly show that unique combinations of functions and meanings are attached to the domestic garden and public green space. Key aspects of public green space are its contribution to the livability of the dwelling environment and to the experience of nature. A key feature of the domestic garden is that it is considered as an outdoor extension of the dwelling that affords casual leisure. So, public and private green spaces are not just simple substitutes for each other.  相似文献   
55.
Response surface methodology using two food grade solvents, acetone and ethanol, was used to optimise antioxidant extraction from industrially generated apple pomace. Efficiency of extraction was optimised by measuring antioxidant activity, phenol content and three individual polyphenol groups. Conditions for optimal antioxidant activity as measured by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay were 56% ethanol, 80 °C and 31 min. Using these conditions an antioxidant value of 444 mg Trolox/100 g DW was obtained. For acetone extraction the optimal conditions were 65% acetone, 25 °C and 60 min, resulting in an antioxidant value of 436 mg Trolox/100 g DW. Both ethanol and acetone would be suitable to replace methanol for a food grade and more environmental friendly solid–liquid extraction of antioxidants.  相似文献   
56.
Osprey (Pandion haliaetus) eggs were collected from 1991 to 1997 at nests (n = 121) upstream and downstream of bleached kraft pulp mills and at reference sites in the Fraser and Columbia River drainage systems of British Columbia, Washington, and Oregon. Blood samples were collected from nestling ospreys during the 1992 breeding season on the Thompson River. Samples were analyzed for polychlorinated dibenzo-p-dioxins (PCDDs) and -dibenzofurans (PCDFs). Mean concentrations of 2,3,7,8-TCDD were significantly higher in eggs collected in 1991 at downstream compared to upstream nests near pulp mills at Kamloops and Castlegar, British Columbia. There were no significant temporal trends in 2,3,7,8-TCDD, -TCDF or other measured compounds at a sample of nests monitored between 1991 and 1994 downstream of the Castlegar pulp mill, despite changes in bleaching technology (CIO2 substitution). However, by 1997 concentrations of 2, 3,7,8-TCDD and -TCDF were significantly lower than previous years in nests sampled downstream at both Castlegar and Kamloops. An unusual pattern of higher chlorinated PCDDs and PCDFs was found in many of the osprey eggs collected in this study, and considerable individual variation in the pattern existed among eggs from the same site. For example, eggs from four different nests at one study area (Quesnel) on the Fraser River had concentrations of 1,2,3,4,6,7,8-HpCDD ranging from <1 to 1,100 ng/kg and OCDD from <1 to 7,000 ng/kg wet weight. Higher mean concentrations of HpCDD and OCDD were found in eggs from the Thompson River, a tributary of the Fraser, compared to the Columbia River, and concentrations were generally higher at nests upstream of pulp mills. In plasma samples, 1,2,3,4,6,7,8-HpCDD and OCDD were the main compounds detected, with no significant differences measured between samples upstream versus downstream or earlier versus later in the breeding season. Use of chlorophenolic wood preservatives by lumber processors was considered the main source of higher chlorinated PCDD/Fs throughout the systems, based on patterns of trace PCDFs in eggs and significant correlations between egg concentrations of pentachlorophenol and both HpCDD (r = 0.891, p < 0.01) and OCDD (r = 0.870, p < 0.01).  相似文献   
57.
OBJECTIVE: To estimate the performance of currently available tests in detecting ovarian cancer in asymptomatic women. METHODS: Systematic review of prospective screening studies. RESULTS: Twenty-five studies were identified: sixteen studied women at average risk and nine studied women at higher risk. Most studies evaluated only one screening method, were small, detecting few cancers, and gave few follow up details. Sensitivity estimates are therefore imprecise. In a typical larger study, reported sensitivity of ultrasound screening at one year was around 100% (95% CI 54%-100%), while the sensitivity of CA125 measurement followed by ultrasound (multimodal screening) was about 80% (95% CI 49%-95%). False positive rates ranged between 1.2% and 2.5% for grey scale ultrasound, between 0.3% and 0.7% for ultrasound with colour Doppler and between 0.1% and 0.6% for multimodal screening. This implies that, in annual screening of a population with an incidence of 40 per 100,000, and if no cancers were missed, between 2.5 and 60 women would undergo surgery for every primary ovarian cancer detected. CONCLUSIONS: Ultrasound and multimodal screening can detect ovarian cancer in asymptomatic women, but there is currently no evidence on whether screening improves outcome for women in any risk group. On-going randomised controlled trials should establish the magnitude of any benefit of screening. The low prevalence of ovarian cancer in the population, and its rate of progression, may limit the potential cost-effectiveness of screening.  相似文献   
58.
Negative cognitive structure (particularly for interpersonal content) has been shown in some research to persist past a current episode of depression and potentially to be a stable marker of vulnerability for depression (D. J. A. Dozois, 2007; D. J. A. Dozois & K. S. Dobson, 2001a). Given that cognitive therapy (CT) is highly effective for treating the acute phase of a depressive episode and that this treatment also reduces the risk of relapse and recurrence, it is possible that CT may alter these stable cognitive structures. In the current study, patients were randomly assigned to CT+ pharmacotherapy (n = 21) or to pharmacotherapy alone (n = 21). Both groups evidenced significant and similar reductions in level of depression (as measured with the Beck Depression Inventory–II and the Hamilton Rating Scale for Depression), as well as automatic thoughts and dysfunctional attitudes. However, group differences were found on cognitive organization in favor of individuals who received the combination of CT+ pharmacotherapy. The implications of these results for understanding mechanisms of change in therapy and the prophylactic nature of CT are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
59.
Vitamin A concentrations in livers of fattening animals and liver-containing products may reach much higher values than was assumed up to now. This effect may be caused by animal feed, which is usually supplemented with vitamins. To support this supposition, 57 liver samples of different species of animals, 97 liver sausages and 106 samples of liver-containing infant food were analysed. For isolation of retinol from the sample matrix the sample was saponified for 16 h under a nitrogen atmosphere at room temperature. Retinol was extracted from the saponification solution by using disposable cartridges. For Chromatographic determination a normalphase HPLC system using a narrow-bore analytical column and a photodiode array detector was used. It was possible to separate all-trans-retinol from other isomers. The identity of the peaks could be confirmed by recording the UV spectra. —The results of the retinol contents found in the analysed samples ranged from 11.6 to 160.7 mg/100 g in liver, from 1.4 to 31.1 mg/100 g in liver sausages and from 0.5 to 3.8 mg/100 g in infant food containing between 5 and 11% liver. By consuming liver-containing meals frequently a multiple amount of the recommended dietary intake ranging from 0.375 mg for infants to 0.8 mg for adults may be taken up. Also the recommended daily intakes of the Deutsche Gesellschaft für Ernährung can be exceeded. —The carry-over effect of daily vitamin A consumption of pigs and their liver vitamin A was investigated by parallel determination of the retinol content in the liver after slaughtering and the vitamin A content in the pig-feed during the fattening period. A clear correlation between their daily vitamin A intake and the resulting retinol content in the livers was found.
Vitamin-A-Bestimmung in Leber und leberhaltigen Lebensmitteln unter Anwendung von Narrow-Bore-Normalphasen-HPLC
Zusammenfassung Die Vitamin-A-Gehalte in Lebern von Schlachttieren können höhere Werte annehmen als man bisher vermutete, u. a.,weil in der Tiermast verwendete Futtermittel mit Vitaminen supplementiert werden. Um den aktuellen Status aufzuzeigen, wurden 57 Leberproben unterschiedlicher Tierarten, 97 Leberwürste und 106 Gläschen vorgefertigter Kleinkindernahrung mit Lebergehalten zwischen 5 und 11% untersucht. Die Proben wurden kalt unter Stickstoffatmosphäre verseift und das Unverseifbare mit Hilfe von Kieselgurkartuschen extrahiert. Zur chromatographischen Bestimmung wurde ein Normalphasen-HPLC-System mit einer Narrow-Bore-Säule verwendet. Detektiert wurde mit einem Photodiodenarray-Detektor. Das all-trans-Retinol konnte von anderen Isomeren getrennt werden. Die gefundenen Retinolkonzentrationen bewegten sich in Bereichen zwischen 11,6 und 160,7 mg/100 g in Leber, zwischen 1,4 und 31,1 mg/100 g in Leberwurst und zwischen 0,5 und 3,8 mg/100 g in Kindernahrung. Bei häufigem Konsum von leberhaltigen Mahlzeiten kann ein Vielfaches des RDI (Recommended dietary intake), der zwischen 0,375 mg für Kleinkinder und 0,8 mg für Heranwachsende liegt, bzw. der von der DGE empfohlenen täglichen Zufuhr, die sich zwischen 0,5 und 1,1 mg bewegt, an Vitamin A zugeführt werden. —Der Zusammenhang zwischen dem täglich aufgenommenen Vitamin A von Mastschweinen und dem Retinol-Gehalt in ihren Lebern wurde untersucht. Hierzu wurde sowohl der Vitamin-A-Gehalt der Schweinelebern nach Schlachtung der Tiere als auch der Gehalt in den Futtermitteln, mit denen sie während der Mastperiode gefüttert wurden, untersucht. Eine deutliche Korrelation wurde festgestellt.
  相似文献   
60.
This study investigated the effect of a touch‐typing course on the spelling and narrative‐writing skills on the computer of elementary school students. Data of 207 students in Grades 4, 5, and 6 were analysed using a pretest–posttest design. Students in the experimental group (n = 154) followed a touch‐typing course, and those in the control group (n = 53) did not. The experimental group showed more progress in typing, spelling, and narrative‐writing skills on the computer than the control group. It can be concluded that the touch‐typing course had a positive effect, not only on typing skills but also on spelling and narrative‐writing skills on the computer.  相似文献   
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