Oxygen isotope effect in high-temperature oxide superconductors     

Loye HC  Leary KJ  Keller SW  Ham WK  Faltens TA  Michaels JN  Stacy AM 《Science (New York, N.Y.)》1987,238(4833):1558-1560

The effect of oxygen isotope substitution on the superconducting transition temperature, T(c), has been measured for BaBi(0.25)Pb(0.75)O(3) (T(c), approximately 11 K) and Lal(1.85) Ca(0.15)CuO(4) (T(c) approximately 20 K), and is compared to the shifts observed for La(1.85)Sr(0.15)CuO(4) (T(c) approximately 37 K) and YBa(2)Cu(3)O(7) (T(c) approximately 92 K). For all four materials, the transition temperature is shifted to lower temperature upon substitution of oxygen-18 for oxygen-16. The observed shifts demonstrate that phonons are involved in the electron-pairing mechanism in these oxide superconductors.  相似文献   

HST2 mediates SIR2-independent life-span extension by calorie restriction     

Lamming DW  Latorre-Esteves M  Medvedik O  Wong SN  Tsang FA  Wang C  Lin SJ  Sinclair DA 《Science (New York, N.Y.)》2005,309(5742):1861-1864

Calorie restriction (CR) extends the life span of numerous species, from yeast to rodents. Yeast Sir2 is a nicotinamide adenine dinucleotide (NAD+-dependent histone deacetylase that has been proposed to mediate the effects of CR. However, this hypothesis has been challenged by the observation that CR can extend yeast life span in the absence of Sir2. Here, we show that Sir2-independent life-span extension is mediated by Hst2, a Sir2 homolog that promotes the stability of repetitive ribosomal DNA, the same mechanism by which Sir2 extends life span. These findings demonstrate that the maintenance of DNA stability is critical for yeast life-span extension by CR and suggest that, in higher organisms, multiple members of the Sir2 family may regulate life span in response to diet.  相似文献   

Microbiology. Antibiotic resistance, not shaken or stirred     

Frisch RL  Rosenberg SM 《Science (New York, N.Y.)》2011,333(6050):1713-1714

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FTIR-ATR analysis of brewed coffee: effect of roasting conditions     

Lyman DJ  Benck R  Dell S  Merle S  Murray-Wijelath J 《Journal of agricultural and food chemistry》2003,51(11):3268-3272

FTIR-ATR was used to study the effect of roasting conditions on the flavor of brewed coffee using Guatemala Antigua coffee beans. The 1800-1680 cm(-1) carbonyl region for vinyl esters/lactones, esters, aldehydes, ketones, and acids was found to provide a flavor-print of the brewed coffee. A study of light, medium, and dark roasts indicated that when the rate of heating to the onset of the first and second cracks was kept constant, the types of carbonyl compounds formed were similar, varying only in their concentration. This difference in concentration is apparently due to the additional heating of the coffee bean beyond the second crack. When the heating rate to the onset of the first and second crack was varied, both the types and concentration of the carbonyl compounds formed during roasting were affected. Thus, heating rates of green coffee beans to the onset of the first and second cracks are important determinants of the basic taste and aroma of brewed coffee.  相似文献   

Screening of Metrosideros polymorpha (‘ōhi‘a) varieties for resistance to Ceratocystis lukuohia     

Blaine Luiz  Elizabeth A. Stacy  Lisa M. Keith 《Forest Pathology》2021,51(1):e12656

Stands of the landscape‐dominant tree, Metrosideros polymorpha (‘ōhi‘a) on the Island of Hawai‘i, HI., USA, are dying from a phenomenon known as rapid ‘ōhi‘a death (ROD). Approximately 180,000 acres of forest have already been impacted by the disease, the majority of which is attributed to C. lukuohia, the more aggressive of the two Ceratocystis species responsible for ROD. Three isolates of C. lukuohia were compared for differences in aggressiveness. Mean disease severity and mean number of days to death did not differ among the three isolates of C. lukuohia. A single isolate was selected for use in a resistance screening of 128 plants across four varieties of M. polymorpha occurring on Hawai‘i Island: incana, glaberrima, polymorpha and newellii. Disease severity was lower in early‐successional var. incana (38.84%) and riparian var. newellii (36.11%) compared to late‐successional var. glaberrima (61.27%) and high‐elevation var. polymorpha (70.27%). Var. incana and var. newellii also had the lowest mortality (63% and 77%, respectively) while var. glaberrima (86%) and var. polymorpha (100%) had the highest mortality. Eighty‐five per cent of the plants that died did so within 49 days post‐inoculation and mean number of days to death was significantly higher for var. glaberrima (46) compared to var. polymorpha (31). The results of this preliminary study suggest that some form of resistance might be present in natural populations of at least one variety of M. polymorpha on Hawai‘i Island and should be investigated more intensively.  相似文献   

Wasted fishery resources: discarded by-catch in the USA   总被引：1，自引：0，他引：1  

Jennie M Harrington  Ransom A Myers  & Andrew A Rosenberg 《Fish and Fisheries》2005,6(4):350-361

Fishery by‐catch, especially discarded by‐catch, is a serious problem in the world's oceans. Not only are the stocks of discarded species affected, but entire trophic webs and habitats may be disrupted at the ecosystem level. This paper reviews discarding in the marine fisheries of the USA; however, the type, diversity and regulatory mechanisms of the fisheries are similar to developed fisheries and management programmes throughout the world. We have compiled current estimates of discarded by‐catch for each major marine fishery in the USA using estimates from existing literature, both published and unpublished. We did not re‐estimate discards or discard rates from raw data, nor did we include data on protected species (turtles, mammals and birds) and so this study covers discarded by‐catch of finfish and fishable invertebrates. For some fisheries, additional calculations were required to transform number data into weight data, and typically length and weight composition data were used. Specific data for each fishery are referenced in Harrington et al. (Wasted Resources: Bycatch and discards in US Fisheries, Oceana, Washington, DC, 2005). Overall, our compiled estimates are that 1.06 million tonnes of fish were discarded and 3.7 million tonnes of fish were landed in USA marine fisheries in 2002. This amounts to a nationwide discard to landings ratio of 0.28, amongst the highest in the world. Regionally, the southeast had the largest discard to landings ratio (0.59), followed closely by the highly migratory species fisheries (0.52) and the northeast fisheries (0.49). The Alaskan and west coast fisheries had the lowest ratios (0.12 and 0.15 respectively). Shrimp fisheries in the southeast were the major contributors to the high discard rate in that region, with discard ratios of 4.56 (Gulf of Mexico) and 2.95 (South Atlantic). By‐catch and discarding is a major component of the impact of fisheries on marine ecosystems. There have been substantial efforts to reduce by‐catch in some fisheries, but broadly based programmes covering all fisheries are needed within the USA and around the world. In response to international agreements to improve fishery management, by‐catch and discard reduction must become a regular part of fishery management planning.  相似文献   

Food as the Dominant Pathway of Methylmercury Uptake by Fish   总被引：1，自引：0，他引：1  

Hall  B. D.  Bodaly  R. A.  Fudge  R. J. P.  Rudd  J. W. M.  Rosenberg  D. M. 《Water, air, and soil pollution》1997,100(1-2):13-24

A field experiment was conducted to determine the degree to which fish accumulated methylmercury (MeHg) via their food or via passive uptake from water through the gills. Finescale dace (Phoxinus neogaeus) were held in 2000 L enclosed pens floating in an undisturbed, oligotrophic lake in northwestern Ontario. Fish were exposed to water containing either low (0.10–0.40 ng L^-1), intermediate (0.45–1.30 ng L^-1), or high (0.80–2.1 ng L^-1) concentrations of MeHg. Zooplankton with either low (0.16–0.18 µg g^-1 d.w.) or high (0.28–0.76 µg g^-1 d.w.) concentrations of MeHg were added daily to each pen. Fish fed zooplankton with high concentrations of MeHg had significantly higher concentrations of mercury in muscle after 32 days than fish fed zooplankton with low concentrations of MeHg (ANCOVA, P<0.0001). Fish feeding on zooplankton with low concentrations of MeHg had the same amount of Hg in their tissues as fish at the start of the experiment. Uptake from water was at most 15%. This is the first experiment to confirm that food is the dominant pathway of MeHg bioaccumulation in fish at natural levels of MeHg.  相似文献   

Molecular, histologic, and trace mineral characterization of metacarpophalangeal and metatarsophalangeal joint hyperextension in juvenile llamas     

Semevolos SA  Reed SK 《American journal of veterinary research》2011,72(4):550-555

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Temporal and spatial distribution of blastomycosis cases among humans and dogs in Illinois (2001-2007)     

Herrmann JA  Kostiuk SL  Dworkin MS  Johnson YJ 《Journal of the American Veterinary Medical Association》2011,239(3):335-343

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Occurrence of incisional complications and associated risk factors using a right ventral paramedian celiotomy incision in 159 horses     

Anderson SL  Vacek JR  Macharg MA  Holtkamp DJ 《Veterinary surgery : VS》2011,40(1):82-89

Objective: To evaluate the occurrence of, and variables associated with, incisional complications after right ventral paramedian celiotomy in horses. Study Design: Case series. Animals: Horses (n=159). Methods: Occurrence of incisional complications after right ventral paramedian celiotomy was determined in 159 horses (161 celiotomies) that survived at least 30 days after surgery at a private equine hospital (2003–2007). Follow‐up information for 121 horses was obtained ≥90 days after surgery. Univariate analysis and multivariate logistic regression was performed to evaluate variables associated with incisional complications after celiotomy. Results: Of 161 celiotomies, ≥1 incisional complications occurred in 27 (16.8%) during hospitalization and/or after discharge, including: drainage (15.5%), skin dehiscence (3.7%), noticeable cutaneous scarring (1.9%), and herniation (0.6%). Variables significantly associated with incisional complications after multivariate analysis included: Quarter horse‐type breed (odds ratio [OR]: 3.9, 95% confidence interval [95% CI]: 1.3–11.7); use of an abdominal bandage (OR: 9.5, 95% CI: 2.9–30.8); and >4 postoperative febrile (>38.3°C) days (OR: 12.9, 95% CI: 2.8–58.2). Conclusions: Overall occurrence of incisional complications after right paramedian ventral celiotomy compared favorably to those reported for ventral median celiotomies. Several variables were associated with, but not necessarily predictive for, the occurrence of incision complications.  相似文献