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1.
H Neudeck M Joncic C Schuster S Bisson R Hildebrandt T Oney B Stiemer H Hopp R Graf 《Canadian Metallurgical Quarterly》1997,37(6):449-458
Nitric oxide (NO) acts as a modulator of neuronal transmission in mature neuronal systems, including the retina. Recently, NO has also been suggested to have a trophic function during development. We examined immunocytochemically the distribution of NO-producing cells in developing and transplanted rabbit retinas. An antibody detecting the neuronal isoform of its biosynthetic enzyme, nitric oxide synthase (NOS), was used on normal developing retinas [starting at embryonic day (E) 15] and on rabbit retinal transplants after various survival times (1-139 days after surgery). Weakly stained cell bodies were first observed in the proximal margin of the neuroblastic layer at E 29. Stained processes projecting towards a developing inner plexiform layer were also visible at this time point. Immunoreactive cells were located at later stages in the innermost part of the inner nuclear layer and in the ganglion cell layer, and are likely to correspond mainly to amacrine cells. NOS-labelled cells were also found in retinal transplants. The first NOS-labelled cells appeared, as in normal developing retinas, in ages corresponding to E 29 and were still detected in transplants corresponding to postnatal day 123. NOS-labelled cells were seen in areas between rosettes, where amacrine cells are located. NOS-labelled processes were at times seen to project for long distances, forming very distinct plexuses. NOS-containing amacrine cells thus appear both in the transplants and in developing retinas in the embryonic stages, long before synaptic function involving these cells can be expected, suggesting a role for NO not only in neuromodulation but also in retinal development. 相似文献
2.
TP Hopp 《Canadian Metallurgical Quarterly》1995,4(9):1851-1859
Evidence is presented that the cytoplasmic domain of the type I interleukin-1 receptor (IL-1R) may be a GTPase. This domain conserves segments of hydrophobic amino acids that suggest a structural relatedness to the ras protooncogene protein and other members of the GTPase superfamily, despite a lack of significant detectable sequence homology. When the hydrophobic segments of the IL-1R were aligned with similar segments of the GTPases, it became apparent that the IL-1Rs possess a number of conserved amino acids that represent plausible functional residues for base-specific binding of GTP, magnesium chelation, and phosphate ester hydrolysis. Furthermore, a segment of five contiguous residues were found that is identical between ras and the IL-1R, and which is positioned to form part of the guanine base binding pocket. If this model is correct, then the IL-1Rs possess a highly conserved effector protein binding region, but one that is entirely unrelated to the effector regions of other superfamily members. Therefore, if the IL-1R is indeed a GTPase, then its activation function may be directed to as-yet unrecognized effector target proteins, as part of a unique cellular signal transduction pathway. 相似文献
3.
Tested the ability of 4 adult male Sprague-Dawley rats to use odors in discrimination among littermates living as a group. Ss were trained in a Y-maze to discriminate the presence of a littermate from its absence. Results from transfer of training in 3 subsequent testing periods indicated that the animals were capable of distinguishing among individuals when relatedness and familiarity were held constant, that this ability was not due to training, and that performance was based solely on odor cues. Results suggest that laboratory rats exhibit odor sensitivities conmensurate with very complex social processes. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
4.
Peter Werkhoff Wilfried Bretschneider Matthias Güntert Rudolf Hopp Horst Surburg 《Zeitschrift für Lebensmitteluntersuchung und -Forschung A》1991,192(2):111-115
Summary The direct capillary gas Chromatographic separation oftrans--ionone andtrans--damascone enantiomers is reported using heptakis(2,3,6-tri-O-methyl)--cyclodextrin in polysiloxane as a suitable chiral stationary phase. The method described has been applied to determine the naturally occurring enantiomeric composition oftrans--ionone in the absolutes of the flowers ofBoronia megastigma Nees andOsmanthus fragrance Lour., Costus root oil (Saussurea lappa Clarke) as well as in odor concentrates of violet flowers (Viola odorata L.), fresh raspberries, carrots and vanilla pods. Furthermore, the optical purity oftrans--ionone in the solvent extracts of distilled alcoholic raspberry beverage, raspberry fruit juice concentrate and black tea was investigated.Trans--ionone was either isolated by headspace stripping in vacuo or by organic solvent extraction and subsequently enriched by multidimensional preparative Chromatographic techniques.Trans--damascone was isolated from Virginia tobacco extract and from black tea aroma and was enriched for direct chirospecific analysis by medium pressure liquid chromatography followed by multidimensional preparative capillary gas chromatography. The importance of chirality as an essential criterion for the discrimination of natural and nature-identical aromas is discussed briefly.
Chirale Analysen von Aroma-und etherischen Öl-Inhaltsstoffen Teil B. Direkte Trennung der Enantiomeren von trans--Ionon und trans--Damascon mittels Inklusionsgaschromatographie
Zusammenfassung Mit Heptakis(2,3,6-tri-O-methyl)--cyclodextrin in Polysiloxan als chiraler stationärer GC-Phase können die Enantiomeren vontrans--Ionon undtrans--Damascon direkt stereodifferenziert werden. Mit der beschriebenen Methode wird die Enantiomerenzusammensetzung vontrans--Ionon in den Absolues vonBoronia megastigma Nées undOsmanthus fragrance Lour., in Costuswurzelöl (Saussurea lappa Clarke), in den Headspace-Konzentraten von Veilchenblüten, frischen Himbeeren, Karotten und Vanilleschoten sowie in den Lösungsmittelextrakten von Himbeergeist, Himbeerfruchtsaftkonzentrat und schwarzem Tee bestimmt.Trans--Ionon wurde aus den genannten Naturprodukten mit Hilfe von multidimensionalen präparativen chromatographischen Trenntechniken angereichert und isoliert.Trans--Damascon wurde durch die Kombination MPLC/präparative Capillargaschromatographie aus Virginia Tabakextrakt und aus dem Aromastoffspektrum von schwarzem Tee erhalten und in s eine Enantiomeren aufgetrennt. Die Bedeutung der Chiralität als Beurteilungskriterium zur Unterscheidung natürlicher und naturidentischer Aromastoffe wird kurz diskutiert.相似文献
5.
Toby Hopp 《Behaviour & Information Technology》2016,35(5):380-393
This study investigated the role of social capital affinity (the sense of community and likeness felt for people online) and the experience of flow (concentrated engagement in/enjoyment of an activity) as antecedents to a variety of positive outcomes associated with the use of e-commerce sites. Also, based on socio-emotional selectivity theory, the current study assessed the influence of age on social capital affinity and flow. As a subset of data from a telephone sample of Internet users in the USA, 282 e-commerce users responded to questions about site satisfaction, perceived focused and incidental knowledge-gains, and affirmation, in addition to flow and social capital affinity. As predicted by socio-emotional selectivity theory, there was a negative relationship between age and social capital affinity and flow. Flow, for its part, mediated the effects of age and social capital affinity on perceived focused and incidental knowledge-gain, satisfaction and affirmation among participants reporting e-commerce use. Finally, the current results indicated that satisfaction and perceived incidental learning predicted participant affirmation for their chosen e-commerce site. 相似文献
6.
This paper outlines approaches for assessing and classifying manufacturing and service operations in terms of their suitability for use of cross-trained (flexible) workers. We refer to our overall framework as agile workforce evaluation. The primary contributions of this paper are: (i) a strategic assessment framework that structures the key mechanisms by which cross-training can support organizational strategy; (ii) a tactical framework that identifies key factors to guide the selection of an architecture and worker coordination policy for implementing workforce agility; (iii) a classification of workforce agility architectures; (iv) a survey of a broad range of archetypical classes of worker coordination policies; (v) a survey of the literature with an operational perspective on workforce agility; and (vi) identification of opportunities for research and development of architectures for specific production environments. 相似文献
7.
Population data and apparent prevalence data from the Salmonella surveillance and control program in pigs (NSSCP) from 1998 and 1999 were used in a simulation model to evaluate the efficacy of the program. The model consists of three parts: modelling of individual prevalence at the abattoir (abattoir part), modelling of the number of sampled herds of different sizes when carcasses are randomly sampled at the abattoir (sampling strategy part) and finally, modelling of the within herd prevalence (within herd part). A total of 136,550 sows and 2,866,550 finishing pigs slaughtered, 4446 herds and 11 herds positive for Salmonella in 1994/1995-2000 were included in the abattoir part, sampling strategy part and the within herd part of the model, respectively. The abattoir part showed an average estimated prevalence of Salmonella in sows and finishing pigs of (median) 0.4% (5-95 percentiles = 0.03-2%) and 0.1% (0.04-0.2%) respectively. The estimated number of infected sow carcasses that entered the market was 502 (37-2157) while the estimated number of finishing pig carcasses was 2919 (1218-5771). The probability of being sampled for the 10% smallest herds was (mean) 1.9% (1.6-2.2), to 25% (24.7-26.5%) for the 10% largest herds. The within herd prevalence was estimated to be from 1% to 4% for Norwegian pig herds. The conclusions drawn from this evaluation are that the NSSCP does not have any significant consumer protection effect, and that the documentation could be done more effectively using the herd rather than the individual animal as the unit of sampling. Sampling should focus on the larger herds supplying most of the meat on the market and on herds that produce breeding sows and piglets and thus can contribute to the spread of Salmonella among herds. 相似文献
8.
We consider the problem of optimal worksharing between two adjacent workers each of whom processes a fixed task in addition to their shared task(s). We use a Markov Decision Process (MDP) model to compute optimal policies and provide a benchmark for evaluating threshold policy heuristics. Our approach differs from previous studies of dynamic line balancing in that we focus on system architecture factors that affect the performance improvement opportunity possible through worksharing relative to a traditional static worker allocations, as well as practical heuristics for worksharing. We find that three such factors are significant whether we use an optimal or a heuristic control policy: ability to preempt the shared task, granularity of the shared task and overall variability of the task times. Understanding the role of these factors in a given production environment provides a means for determining where and how worksharing can have significant logistical benefits. 相似文献
9.
V. Hopp 《化学,工程师,技术》2012,84(9):1603-1604
10.
Hopp Wallace J. Spearman Mark L. Chayet Sergio Donohue Karen L. Gel Esma S. 《IIE Transactions》2002,34(2):119-130
We develop an Optimized Queueing Network (OQNet) capacity planning tool for supporting the design of new and reconfigured semiconductor fabrication facilities that makes use of queueing network approximations and an optimization routine. The basic problem addressed by this tool is to minimize the facility cost required to meet specified volume and cycle time targets. Features common to semiconductor environments, such as batch processes, re-entrant flows, multiple product classes, and machine setups, are incorporated into the model. Comparisons with simulation show that the queueing and other approximations are reasonably accurate. Tests of the optimization routine demonstrate that it can find good solutions quickly. 相似文献