Modeling long-term fluctuations in fish stocks     

Steele JH  Henderson EW 《Science (New York, N.Y.)》1984,224(4652):985-987

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Early optical polarization of a gamma-ray burst afterglow     

Mundell CG  Steele IA  Smith RJ  Kobayashi S  Melandri A  Guidorzi C  Gomboc A  Mottram CJ  Clarke D  Monfardini A  Carter D  Bersier D 《Science (New York, N.Y.)》2007,315(5820):1822-1824

We report the optical polarization of a gamma-ray burst (GRB) afterglow, obtained 203 seconds after the initial burst of gamma-rays from GRB 060418, using a ring polarimeter on the robotic Liverpool Telescope. Our robust (2sigma) upper limit on the percentage of polarization, less than 8%, coincides with the fireball deceleration time at the onset of the afterglow. The combination of the rate of decay of the optical brightness and the low polarization at this critical time constrains standard models of GRB ejecta, ruling out the presence of a large-scale ordered magnetic field in the emitting region.  相似文献   

Graphite whiskers in CV3 meteorites     

Fries M  Steele A 《Science (New York, N.Y.)》2008,320(5872):91-93

Graphite whiskers (GWs), an allotrope of carbon that has been proposed to occur in space, have been discovered in three CV-type carbonaceous chondrites via Raman imaging and electron microscopy. The GWs are associated with high-temperature calcium-aluminum inclusion (CAI) rims and interiors, with the rim of a dark inclusion, and within an inclusion inside an unusual chondrule that bears mineralogy and texture indicative of high-temperature processing. Current understanding of CAI formation places their condensation, and that of associated GWs, relatively close to the Sun and early in the condensation sequence of protoplanetary disk materials. If this is the case, then it is a possibility that GWs are expelled from any young solar system early in its history, thus populating interstellar space with diffuse GWs. Graphite whiskers have been postulated to play a role in the near-infrared (near-IR) dimming of type Ia supernovae, as well as in the thermalization of both the cosmic IR and microwave background and in galactic center dimming between 3 and 9 micrometers. Our observations, along with the further possibility that GWs could be manufactured during supernovae, suggest that GWs may have substantial effects in observational astronomy.  相似文献   

Expression of messenger ribonucleic acid encoding for steroidogenic acute regulatory protein and enzymes, and luteinizing hormone receptor during the spring transitional season in equine follicles     

Watson ED  Bae SE  Steele M  Thomassen R  Pedersen HG  Bramley T  Hogg CO  Armstrong DG 《Domestic animal endocrinology》2004,26(3):215-230

The period of spring transition, from the anovulatory to the ovulatory season, is characterized in many mares by cyclical growth and regression of large dominant follicles. These follicles produce only low concentrations of estradiol and it is thought that acquisition of steroidogenic competence by large follicles during spring transition is prerequisite in stimulating LH prior to first ovulation. In situ hybridization was used to localize and quantify expression of factors that play a key role in follicular steroidogenesis: StAR, P450scc (CYP11A1), P450c17 (CYP17), P450arom (CYP19), and LH receptor (LHr). One ovary was obtained from mares on the day after detection of an actively growing 30 mm transitional anovulatory follicle (defined as the transitional follicle), and the remaining ovary was removed at the third estrus of the breeding season on the day after the preovulatory follicle reached 30 mm in diameter (defined as the preovulatory follicle). Messenger RNAs encoding StAR, CYP11A1, and CYP17 were detected only in theca cells and CYP19 mRNA was confined to the granulosa layer. There was significantly lower expression of mRNAs for the steroidogenic enzymes, StAR (P<0.001) and LHr (P<0.05) in transitional follicles than in preovulatory follicles. In conclusion, large equine follicles during spring transition have low levels of mRNA encoding steroidogenic enzymes, StAR and LHr which will contribute to the steroidogenic incompetence of dominant follicles during spring transition and their subsequent regression.  相似文献   

Vitamin C increase in aerated potato slices     

D. Hadziyev  L. Steele 《Plant foods for human nutrition (Dordrecht, Netherlands)》1976,26(4):365-388

Increasing the vitamin C content in potato slices by aeration prior to the pre-cooking water blanching step in the production of dehydrated potato granules was investigated as a possible means of offsetting the high losses experienced in the process.Slices of 6 mm thickness of Netted Gem variety that were aerated overnight at 22°C in a dark and moist atmosphere increased their apparent vitamin C content by 38.5%, while longer aeration for up to 52 h brought about a linear increase of close to 4% per hour. Beyond 52 h the rate of vitamin gain was slower, and was accompanied by objectionable browning. The gains were dependent on the length of time the tubers were stored before use, the presence of oxygen, and the thickness of the slices.Overnight aeration at 4°C resulted in a gain that was one fifth that found for the corresponding time at 22°C, while a longer period decreased this factor to one ninth. Slices aerated under water did not show a change in vitamin content.The vitamin C increase in aerated slices is due to actualde novo biosynthesis of L-ascorbic acid and not to reductones, amino acid — sugar interaction products, or to the presence of dehydroascorbic acid. This was proven by titration with 2,6-dichlorophenolindophenol, and by the 2,4-dinitrophenylhydrazine method in which a thin layer chromatographic purification of the vitamin C osazone was carried out. Additional confirmation came from polarographic recordings of the ascorbic acid anodic wave, and of the cathodic wave of the vitamin C — o-phenylenediamine condensation products, with or without chloroform extraction.Electron spin resonance spectra of the juices from the slices also confirmed the findings. Pure 1 or 100 mM aqueous L-ascorbic acid, when oxygenated at pH 5.6, the pH of the potato, or at pH 8.2, gave a hyperfine structure with a splitting constant for the doublet of 1.8 Gauss. However, potato juice did not give a spectrum that could be resolved to that degree. The spectra characteristic of radicals from triose reductone or reductic acid were absent. Potato peel and scalp had a high apparent vitamin C content, and gave strong radical signals that had lifetimes of 48 h or longer, but their behavior and position did not coincide with the signal for pure vitamin C.The finding that true vitamin C is in fact synthesized by aeration of slices may not only be beneficial in the household, but also may have potential practical application in the processing of potatoes in which destruction of vitamin C can occur to an unacceptable extent.

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Zusammenfassung Um die, bei der Herstellung von dehydriertem Kartoffelpulver auftretenden hohen Verluste an Vitamin C auszugleichen wurden die Kartoffelschnitze vor dem Blanchieren belüftet und die Bildung von Vitamin C untersucht.Der scheinbare Vitamin C-Gehalt von 6 mm dicken Schnitzen der Sorte Netted Gem, welche bei 22°C und feuchter Atmosphäre über Nacht belüftet wurden nahm um 38, 5% zu, während bei längerer Belüftungszeit bis zu 52 Std die Vitamin C-Bildung um 4% stündlich zunahm. Oberhalb 52 Std war die Bildungsrate des Vitamins geringer und ging mit dem Auftreten einer unerwünschten Bräunung einher. Die Vitamin Zunahmen waren abhängig von der Lagerungsdauer der Kartoffeln, dem Vorhandensein von Sauerstoff und von der Dicke der Schnitze.Eine über Nacht-Belüftung bei 4°C bewirkte eine Zunahme, welche ein Fünftel derjeniger bei 22°C ausmachte, während bei längerer Zeitdauer dieser Faktor ein Neuntel betrug. Keine Änderung in ihrem Vitamin-Gehalt wurde bei Schnitzen beobachtet, die unter Wasser belüftet wurden.Die Vitamin C-Zunahme in belüfteten Schnitzen ist auf einede novo-Synthese von L-Ascorbinsäure zurückzuführen und nicht auf Reduktone, Aminosäure-Zucker Reaktionsprodukte oder auf das Vorhandensein von Dehydroascorbinsäure. Dies wurde belegt durch Titration mit 2,6-Dichlorphenolindophenol und mithilfe der 2,4-Dinitrophenylhydrazin Methode bei welcher das Vitamin C-Osazon durch Dünnschichtchromatographie gereinigt wurde. Eine zusätzliche Bestätigung lieferten polarographische Aufzeichnungen der anodischen Ascorbinsäure und der kathodischen Vitamin C — o-Phenylendiamin -Kondensationsprodukte, mit und ohne Chloroform — Extraktion.ESR-Spektren vom Saft der Schnitze bestätigten ebenfalls die obigen Ergebnisse. Reine 1-oder 100-mM wässerige L-Ascorbinsäure oxydiert bei pH 5,6 beim pH der Kartoffel oder bei pH 8.2 ergab eine hyperfeine Struktur mit einer Abspalt Konstante für das Doublet von 1,8 G. Kartoffelsaft hingegen, ergab kein Spektrum, das bis zu diesem Grad aufgelöst werden konnte. Die Spektrums — Charakteristik des Trioseredukton oder Reduktinsäure Radikale war nicht vorhanden. Die Kartoffelschalen ergaben einen hohen scheinbaren Vitamin C-Gehalt und starke Radikalsignale, welche eine Lebensdauer von 48 Std und länger aufwiesen. Aber ihr Verhalten und ihre Position stimmten ebenfalls nicht mit dem Signal für reines Vitamin C überein.Der Befund, dass wahres Vitamin C durch Belüftung von Kartoffelschnitzen synthetisiert wird, kann nicht nur für den Haushalt nützlich sein, sondern kann auch eine praktische Bedeutung in der Kartoffelverarbeitung erlangen, in welcher Vitamin C-Verluste in einem unannehmbaren Ausmass auftreten können.

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Résumé L'étude de l'accroissement du contenu en vitamine C de pommes de terre en tranches par aération avant l'étape de cuisson-blanchiement dans la production de granules de pommes de terre déhydratés comme un moyen possible de diminuer les pertes élevées en vitamin C du procédé fait l'objet de ce rapport.Des tranches de pommes de terre (variété Netted Gem) d'une épaisseur de 6 mm aerées pendant la nuit à 22°C dans l'obscurité et en atmosphère humide ont vu leur contenu en vitamine C s'accroitre de 38.5% et une aération subséquente jusqu'à 52 h entraine un acroissement linéaire de presque 4% par heure. Au delà de 52 h l'acroissement est plus lent et est accompagné d'un brunissement non acceptable. L'augmentation totale dépend de la durée de stockage du tubercule avant expérience, de la présence d'oxygène et de l'épaisseur des trances.Le même traitement, mais a 4°C, a donné des résultats 5 fois plus faibles qu'à 22°C, et une exposition prolongée contribue à une diminution supplémentaire allant jusqu'a 1/9. Les tranches aerées dans l'eau ne montrent aucun changement.L'acroissement de la vitamine C dans les tranches aerées est du à une biosynthese effectivede novo d'acide l-ascorbique et non aux réductones provenant des interactions acide amine — sucre, ou à la présence d'acide déhydroascorbique. Ceci est prouvé par titration au 2,6-dichlorophénolindophénol, et par la méthode au 2,4-dinitrophénylhydrazine dans laquelle on a réalisé la purification de l'osazone de la vitamine C par chromatographie en couche mince. Une preuve supplémentaire a été obtenue à partir des enregistrements polarographiques de l'onde anodique de l'acide ascorbique, et de l'onde cathodique des produits de condensation vitamin C — o-phénylène-diamine avec ou sans extraction au chloroform.Les spectres de résonnance paramagnetique électronique du jus des tranches confirment les résultats précédents. Des solutions aqueuses d'acide l-ascorbique de concentration 1 ou 100 mM oxygénées à pH 5.6, pH normal de la pomme de terre, ou à pH 8.2 ont donné une structure hyperfine avec une constante de couplage pour le doublet de 1.8 Gauss. Cependant, le jus de pomme de terre de fournit pas un spectre susceptible d'une telle résolution. Les spectres caractéristiques des radicaux de triose réductone et acide réductique sont absents. Les épluchures de pomme de terre ont un contenu apparent élevé en vitamin C et ont donné des signaux pour les radicaux très important avec une durée de 48 h ou plus, mais leur comportement et position ne correspondent pas avec le signal de la vitamin C pure.La découverte de la synthèse de véritable vitamine C par aération des tranches ne peut qu'être bénéfique au niveau du consommateur, mais offre aussi la possibilité d'une utilisation pratique dans le traitement industriel de la pomme de terre au cours duquel la destruction de vitamine C peut se produire en proportions inacceptables.

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Diet of the blue petrel at sub-Antarctic Marion Island     

W.K. Steele  N.T. Klages 《African Zoology》2013,48(3):253-256

Food samples were collected from 49 blue petrels Halobaena caerulea at Marion Island in the sub-Antarctic region. These were analysed and the results compared with previously published data collected at other islands. Crustaceans formed the major prey by mass (59,5%) and frequency (100%), with Euphausia vallentini being of particular importance (56,6% by mass of Crustacea). Other prey included fish, cephalopods and two species of insects, a moth (Noctuidae) and an assassin bug Nabis.  相似文献   

Prepubic urethrostomy and vaginoplasty in a female cat     

Przywara J  Byron J  Bennett RA  Ham K  Greenfield CL  Steele K 《Journal of the American Animal Hospital Association》2010,46(6):439-443

A 1-year-old, intact female, domestic shorthaired cat was presented for dysuria resulting from perineal scarring subsequent to injuries incurred during a cat fight. A prepubic urethrostomy was performed to manage the dysuria. Eleven months later, the cat was re-presented with a 3-day history of pyrexia and inappetence. A pinpoint opening extending 0.5 cm ventral to the anus on midline, exuding a clear discharge, was noted in the perineal region. A contrast fistulogram was performed, and a vaginoperineal fistula was diagnosed. The fistulous tract was a result of vulvar stricture from the trauma of the cat fight. A vaginoplasty was performed to create an opening for vaginal secretions. This is the first published report of a prepubic urethrostomy performed in a female cat.  相似文献   

Development and verification of a diagnostic assay based on EF‐1 α for the identification of Armillaria species in Northern Europe     

V. Mulholland  G. A. MacAskill  B. E. Laue  H. Steele  D. Kenyon  S. Green 《Forest Pathology》2012,42(3):229-238

The overall aim of this study was to develop a new, reliable and rapid diagnostic assay for differentiating six European Armillaria species based on variation in their elongation factor‐1 alpha (EF‐1 α) gene sequences and to verify a set of species‐specific primers on 61 Armillaria isolates from Europe. Partial sequences of the EF‐1 α gene obtained in Armillaria borealis, Armillaria cepistipes, Armillaria gallica, Armillaria mellea, Armillaria ostoyae and Armillaria tabescens revealed sufficient interspecific variation to distinguish among species using nested primers. These primers gave unambiguous bands when tested on representative isolates of five of these species. However, the EF‐1 α sequences of European A. borealis isolates clustered into two distinct clades, termed here AbX and AbY. Specific primers were subsequently designed and tested successfully on both AbX‐type and AbY‐type A. borealis isolates. The taxonomy of A. borealis needs to be elucidated to determine whether a new, as yet unnamed Armillaria taxon exists in Europe. Three A. borealis isolates were also found to have heterozygous sites in their EF‐1 α sequences, which suggests that the gene could exist in more than one copy or that these isolates contain hybrid sequences. A pyrosequencing method was also developed, targeting a small region of EF‐1 α intron 4, which was able to differentiate European Armillaria isolates to the species level and additionally could distinguish AbX‐type and AbY‐type A. borealis isolates.  相似文献   

Outcome of retinal reattachment surgery in dogs: a retrospective study of 145 cases     

Steele KA  Sisler S  Gerding PA 《Veterinary ophthalmology》2012,15(Z2):35-40

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Interrelationships between sex and exogenous growth hormone administration on performance, body composition and protein and fat accretion of growing pigs   总被引：2，自引：0，他引：2  

R G Campbell  N C Steele  T J Caperna  J P McMurtry  M B Solomon  A D Mitchell 《Journal of animal science》1989,67(1):177-186

Forty-five pigs with an average initial live weight of 60 kg were used to investigate the effects of daily exogenous porcine pituitary growth hormone administration at two dose levels (pGH; 0, excipient buffer injected, and 100 micrograms.kg-1.d-1) for a 31-d period on the performance and body composition of boars, gilts and barrows allowed to consume feed ad libitum. Excipient boars consumed less feed, exhibited faster and more efficient growth (P less than .01) and produced less fat and more protein and water (P less than .01) in the empty body compared with excipient barrows, which in turn contained more fat and less water (P less than .05) in the empty body than did excipient gilts. These differences were largely eliminated by pGH administration, which induced differential effects in growth performance and body composition in boars, gilts and barrows. Growth hormone administration improved growth rate by 13, 22 and 16% and feed conversion efficiency by 19, 34 and 32% in boars, gilts and barrows, respectively. The reduction of body fat content (g/kg) elicited by pGH was 22, 36 and 33% for boars, gilts and barrows, respectively, with a corresponding increase (P less than .01) of body protein and water content. The magnitude of the pGH responses was greatest for gilts and barrows compared with boars, negating intrinsic sex-effect differences in growth performance and body composition of pigs. Pigs used in this study and treated with pGH exhibited a rate of protein deposition (approximately 225 g/d) far greater than previously reported, and as such redefine the genetic capacity for lean tissue growth by the pig.  相似文献