排序方式： 共有18条查询结果，搜索用时 359 毫秒
1.
Kamada N Kim YG Sham HP Vallance BA Puente JL Martens EC Núñez G 《Science (New York, N.Y.)》2012,336(6086):1325-1329
The virulence mechanisms that allow pathogens to colonize the intestine remain unclear. Here, we show that germ-free animals are unable to eradicate Citrobacter rodentium, a model for human infections with attaching and effacing bacteria. Early in infection, virulence genes were expressed and required for pathogen growth in conventionally raised mice but not germ-free mice. Virulence gene expression was down-regulated during the late phase of infection, which led to relocation of the pathogen to the intestinal lumen where it was outcompeted by commensals. The ability of commensals to outcompete C. rodentium was determined, at least in part, by the capacity of the pathogen and commensals to grow on structurally similar carbohydrates. Thus, pathogen colonization is controlled by bacterial virulence and through competition with metabolically related commensals. 相似文献
2.
Murali Haran K. Sham Bhat Julio Molineros Erick De Wolf 《Journal of Agricultural, Biological & Environmental Statistics》2010,15(2):158-175
Fusarium Head Blight (FHB), or “scab,” is a very destructive disease that affects wheat crops. Recent research has resulted
in accurate weather-driven models that estimate the probability of an FHB epidemic based on experiments. However, these predictions
ignore two crucial aspects of FHB epidemics: (1) An epidemic is very unlikely to occur unless the plants are flowering, and
(2) FHB spreads by its spores, resulting in spatial and temporal dependence in risk. We develop a new approach that combines
existing weather-based probabilities with information on flowering dates from survey data, while simultaneously accounting
for spatial and temporal dependence. Our model combines two space-time processes, one associated with pure weather-based FHB
risks and the other associated with flowering date probabilities. To allow for scalability, we model spatiotemporal dependence
via a process convolutions approach. Our sample-based approach produces a realistic assessment of areas that are persistently
at high risk (where the probability of an epidemic is elevated for extended time periods), along with associated estimates
of uncertainty. We conclude with the application of our approach to a case study from North Dakota. 相似文献
3.
Ha WY Reid DG Kam WL Lau YY Sham WC Tam SY Sin DW Mok CS 《Journal of agricultural and food chemistry》2011,59(10):5195-5203
Abalones ( Haliotis species) are a popular delicacy and commonly preserved in dried form either whole or in slices or small pieces for consumption in Asian countries. Driven by the huge profit from trading abalones, dishonest traders may substitute other molluscan species for processed abalone, of which the morphological characteristics are frequently lost in the processed form. For protection of consumer rights and law enforcement against fraud, there is a need for an effective methodology to differentiate between fake and genuine abalone. This paper describes a method (validated according to the international forensic guidelines provided by SWGDAM) for the identification of fake abalone species using forensically informative nucleotide sequence (FINS) analysis. A study of the local market revealed that many claimed "abalone slice" samples on sale are not genuine. The fake abalone samples were found to be either volutids of the genus Cymbium (93%) or the muricid Concholepas concholepas (7%). This is the first report of Cymbium species being used for the preparation and sale as "abalone" in dried sliced form in Hong Kong. 相似文献
4.
Chen G Bonadeo NH Steel DG Gammon D Katzer DS Park D Sham LJ 《Science (New York, N.Y.)》2000,289(5486):1906-1909
Optically induced entanglement is identified by the spectrum of the phase-sensitive homodyne-detected coherent nonlinear optical response in a single gallium arsenide quantum dot. The electron-hole entanglement involves two magneto-excitonic states differing in transition energy and polarization. The strong coupling needed for entanglement is provided through the Coulomb interaction involving the electrons and holes. The result presents a first step toward the optical realization of quantum logic operations using two or more quantum dots. 相似文献
5.
Li X Wu Y Steel D Gammon D Stievater TH Katzer DS Park D Piermarocchi C Sham LJ 《Science (New York, N.Y.)》2003,301(5634):809-811
We report coherent optical control of a biexciton (two electron-hole pairs), confined in a single quantum dot, that shows coherent oscillations similar to the excited-state Rabi flopping in an isolated atom. The pulse control of the biexciton dynamics, combined with previously demonstrated control of the single-exciton Rabi rotation, serves as the physical basis for a two-bit conditional quantum logic gate. The truth table of the gate shows the features of an all-optical quantum gate with interacting yet distinguishable excitons as qubits. Evaluation of the fidelity yields a value of 0.7 for the gate operation. Such experimental capability is essential to a scheme for scalable quantum computation by means of the optical control of spin qubits in dots. 相似文献
6.
Anarjan N Tan CP Ling TC Lye KL Malmiri HJ Nehdi IA Cheah YK Mirhosseini H Baharin BS 《Journal of agricultural and food chemistry》2011,59(16):8733-8741
A simplex centroid mixture design was used to study the interactions between two chosen solvents, dichloromethane (DCM) and acetone (ACT), as organic-phase components in the formation and physicochemical characterization and cellular uptake of astaxanthin nanodispersions produced using precipitation and condensation processes. Full cubic or quadratic regression models with acceptable determination coefficients were obtained for all of the studied responses. Multiple-response optimization predicted that the organic phase with 38% (w/w) DCM and 62% (w/w) ACT yielded astaxanthin nanodispersions with the minimum particle size (106 nm), polydispersity index (0.191), and total astaxanthin loss (12.7%, w/w) and the maximum cellular uptake (2981 fmol/cell). Astaxanthin cellular uptake from the produced nanodispersions also showed a good correlation with their particle size distributions and astaxanthin trans/cis isomerization ratios. The absence of significant (p > 0.05) differences between the experimental and predicted values of the response variables confirmed the adequacy of the fitted models. 相似文献
7.
Toncaun Ren Shunsuke Koshio Shin-Ichi Teshima Manabu Ishikawa Md. Sham Alam Arthur Panganiban Jr. Yin Yin Moe Tomokazu Kojima Hiroyuki Tokumitsu 《Journal of the World Aquaculture Society》2005,36(4):437-443
A feeding experiment was conducted to determine the optimum dietary level of ascorbic acid (AsA) for Japanese eel juveniles using L-ascorbic acid Ca based on growth, AsA content in tissues, hematology, and bactericidal activity of serum with Escherichia coli . Test diets with six levels of AsA (3, 10, 27,126, 645, and 3,135-mg/kg diet) as Ca ascorbate were fed to juvenile Japanese eels (11.0 ± 0.2 g) once a day for 8 wk. High survival rates (> 80%) were observed among all dietary treatment groups. The specific growth rates of the fish fed diets containing 3 and 10-mg AsA/kg were significantly (P < 0.05) lower than those of other groups. Liver and brain AsA contents of the fish fed diets containing 3, 10, and 27-mg AsA/kg were significantly (P < 0.05) lower than those of the fish fed diets containing 645 and 3,135-mg AsA/kg. Hemoglobin content tended to be higher in the fish fed diets containing 645 and 3,135-mg AsA/kg than those of the fish fed other diets. Hematocrit value and total serum protein content of the fish fed diets containing 645 and 3135 mg AsA/kg were significantly (P < 0.05) higher than those of the other groups. The fish fed diets containing more than 27-mg AsAlkg showed a higher bactericidal activity of serum than the fish fed the diets containing 3-mg and 10-mg AsA/kg. The optimum dietary level of AsA for the Japanese eel juveniles growth was estimated to be more than 27-mg AsA/kg. Furthermore, the inclusion of 645-mg AsA/kg or more also increased the hematocrit, hemoglobin, total serum protein value, and liver and brain vitamin C concentrations. 相似文献
8.
Gilles Le Moullac Claude Soyez Manaarii Sham‐Koua Peva Levy Jacques Moriceau Vincent Vonau Mayalen Maihota Jean Claude Cochard 《Aquaculture Research》2013,44(3):404-411
This study aimed to model the food intake of P. margaritifera to examine the relationship between food level and reproductive activity. The effect of microalgae concentration on ingestion rate and assimilation efficiency was studied over a broad concentration range, using a mixture of Isochrysis galbana and Chaetoceros gracilis. Reproductive effort was assessed using three microalgae concentrations of 0.5, 7 and 18 cell μL?1. Reproductive status was assessed by gonad development index (GDI) – the ratio of the gonad surface to the visceral mass surface – and histological analysis of the gonad based on the presence (continuous or discontinuous) or the absence of gonial cells (GC). Ingestion is a saturating function of seston concentration for bivalves modelled with an adapted Michaelis‐Menten function. The maximum ingestion rate of P. margaritifera adults was 193.50 × 106 cell h?1 g?1 dw and the half saturation coefficient was 15 cell μL?1. The concentration of 18 cell μL?1, supplied for 45 days, induced a significantly higher GDI than the other treatments. GC decreased significantly and even stopped when pearl oysters were under‐fed, suggesting that the mitotic process of the germinal stem cells was altered. Differentiation of germinal stem cells therefore appears to be controlled by food availability. 相似文献
9.
Alison Kan Michael C Dove Wayne A O'Connor Sham V Nair David A Raftos 《Aquaculture Research》2011,42(7):987-995
QX disease causes mass mortalities among Sydney rock oysters (Saccostrea glomerata). To overcome commercial production losses, Industry & Investment NSW has been developing mass selected QX disease‐resistant breeding lines since 1997. This breeding programme has significantly reduced QX‐associated mortality in the Lime Kiln Bar (LKB) breeding line relative to non‐selected, wild‐type (WT) oysters. The current study assessed mortality in families produced by single‐pair mating between LKB and WT oysters. When these families were grown in a QX disease‐prone area, the progeny of LKB × LKB crosses had significantly lower mortality compared with LKB × WT or WT × WT families. Mortality in the different crosses was associated with infection by sporulating Marteilia sydneyi, the parasite responsible for QX disease. Overall, the study identified a strong association between parentage and mortality resulting from QX disease. 相似文献
10.
Is pearl colour produced from Pinctada margaritifera predictable through shell phenotypes and rearing environments selections? 
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下载免费PDF全文 Chin‐Long Ky Lore Le Pabic Manaarii Sham Koua Nicolas Molinari Seiji Nakasai Dominique Devaux 《Aquaculture Research》2017,48(3):1041-1057
The black‐lipped pearl oyster, Pinctada margaritifera, is the most important farmed mollusc species in French Polynesia. Donor oyster selection among wild P. margaritifera individuals, chosen according to their inner shell colour, makes it possible to obtain the broadest range of cultured pearl colours of any species. This study demonstrates the relative influence of using black [B] or red [R] outer shell phenotypes, combined with green [G] or yellow [Y] inner shell phenotypes, on pearl darkness level, colour categories and lustre. A large scale grafting experiment was designed and carried out over five grow‐out locations, covering three archipelagos: Tuamotus, Society and Gambier. Results revealed that the [B + G] phenotypes may be used as donors to produce dark green pearl, which suit the demands of the Asian market; whereas, phenotypes incorporating [R] and/or [Y] phenotypes may be used to obtain multicolour pearls of medium/light darkness, which suit the demands of the European market. From an environmental point of view, the 1) [B] phenotype showed no significant variation for light and other pearl colour production, and 2) [Y] phenotype produced both the same rate of pearl darkness level and green colour pearls whatever the grow‐out location. A classification tree model was built to predict, according to shell phenotype and culture location, the colour and darkness level of harvested pearls. Lustre was shown to be more influenced by the environment than by phenotype. These results should be taken into account in pearl farm production management and in selective breeding programmes. 相似文献