Optical negative refraction in bulk metamaterials of nanowires     

Yao J  Liu Z  Liu Y  Wang Y  Sun C  Bartal G  Stacy AM  Zhang X 《Science (New York, N.Y.)》2008,321(5891):930

Negative refraction in metamaterials has generated great excitement in the scientific community. Although negative refraction has been realized in microwave and infrared by using metamaterials and by using two-dimensional waveguide structures, creation of a bulk metamaterial showing negative refraction at visible frequency has not been successful, mainly because of the significant resonance losses and fabrication difficulties. We report bulk metamaterials made of nanowires that show such negative refraction for all incident angles in the visible region. Moreover, the negative refraction occurs far from any resonance, resulting in a low-loss and a broad-band propagation at visible frequencies. These remarkable properties can substantially affect applications such as imaging, three-dimensional light manipulation, and optical communication.  相似文献   

Achieving sustainable use of renewable resources     

Rosenberg AA  Fogarty MJ  Sissenwine MP  Beddington JR  Shepherd JG 《Science (New York, N.Y.)》1993,262(5135):828-829

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Mutational inactivation of STAG2 causes aneuploidy in human cancer     

Solomon DA  Kim T  Diaz-Martinez LA  Fair J  Elkahloun AG  Harris BT  Toretsky JA  Rosenberg SA  Shukla N  Ladanyi M  Samuels Y  James CD  Yu H  Kim JS  Waldman T 《Science (New York, N.Y.)》2011,333(6045):1039-1043

Most cancer cells are characterized by aneuploidy, an abnormal number of chromosomes. We have identified a clue to the mechanistic origins of aneuploidy through integrative genomic analyses of human tumors. A diverse range of tumor types were found to harbor deletions or inactivating mutations of STAG2, a gene encoding a subunit of the cohesin complex, which regulates the separation of sister chromatids during cell division. Because STAG2 is on the X chromosome, its inactivation requires only a single mutational event. Studying a near-diploid human cell line with a stable karyotype, we found that targeted inactivation of STAG2 led to chromatid cohesion defects and aneuploidy, whereas in two aneuploid human glioblastoma cell lines, targeted correction of the endogenous mutant alleles of STAG2 led to enhanced chromosomal stability. Thus, genetic disruption of cohesin is a cause of aneuploidy in human cancer.  相似文献   

Genetic structure of human populations   总被引：1，自引：0，他引：1  

Rosenberg NA  Pritchard JK  Weber JL  Cann HM  Kidd KK  Zhivotovsky LA  Feldman MW 《Science (New York, N.Y.)》2002,298(5602):2381-2385

We studied human population structure using genotypes at 377 autosomal microsatellite loci in 1056 individuals from 52 populations. Within-population differences among individuals account for 93 to 95% of genetic variation; differences among major groups constitute only 3 to 5%. Nevertheless, without using prior information about the origins of individuals, we identified six main genetic clusters, five of which correspond to major geographic regions, and subclusters that often correspond to individual populations. General agreement of genetic and predefined populations suggests that self-reported ancestry can facilitate assessments of epidemiological risks but does not obviate the need to use genetic information in genetic association studies.  相似文献   

Circumsporozoite protein heterogeneity in the human malaria parasite Plasmodium vivax   总被引：8，自引：0，他引：8  

R Rosenberg  R A Wirtz  D E Lanar  J Sattabongkot  T Hall  A P Waters  C Prasittisuk 《Science (New York, N.Y.)》1989,245(4921):973-976

Phenotypic heterogeneity in the repetitive portion of a human malaria circumsporozoite (CS) protein, a major target of candidate vaccines, has been found. Over 14% of clinical cases of uncomplicated Plasmodium vivax malaria at two sites in western Thailand produced sporozoites immunologically distinct from previously characterized examples of the species. Monoclonal antibodies to the CS protein of other P. vivax isolates and to other species of human and simian malarias did not bind to these nonreactive sporozoites, nor did antibodies from monkeys immunized with a candidate vaccine made from the repeat portion of a New World CS protein. The section of the CS protein gene between the conserved regions I and II of a nonreactive isolate contained a nonapeptide repeat, Ala-Asn-Gly-Ala-Gly-Asn-Gln-Pro-Gly, identical at only three amino acid positions with published nonapeptide sequences. This heterogeneity implies that a P. vivax vaccine based on the CS protein repeat of one isolate will not be universally protective.  相似文献   

A comparison of North American avian conservation priority ranking systems     

David W Mehlman  Kenneth V Rosenberg  Bruce Robertson 《Biological conservation》2004,120(3):383-390

The need to prioritize species based on their perceived endangerment has led to the development of systems for categorizing and assessing their degree of vulnerability. Systems with divergent biological and geographical scopes can result in conflicting lists of high-priority species, potentially confusing conservationists and hampering the efficient allocation of resources. To assess conservation priorities for North American birds, we compare three priority-setting systems; those of the International Union for the Conservation of Nature (IUCN), NatureServe, and Partners in Flight (PIF). We found highest correspondence among the three systems in the highest and lowest categories of the respective systems with lower levels of correspondence in intermediate categories. We suggest that this is because the systems, while using different formulations of criteria, are based on the major factors known to be correlated with extinction risk. The few examples of species listed as a high conservation priority by one group but not one or both of the others appear to be the result of differences in availability or interpretation of data. Better communication and collaboration among those responsible for compiling the priority lists for each system is needed.A primary difference among the systems was the total number of species identified as conservation priorities. IUCN identified the fewest species (47) and PIF the most (157). This difference is the result of differences in geographic and taxonomic scope of each system. However, when considered as the percent of the total number of taxa evaluated by each system, all systems identified approximately 20% of species as of conservation concern. To reconcile disparate lists, we urge that conservationists use a hierarchical approach that first considers species that meet thresholds for endangerment under global systems, followed by species considered most vulnerable relative to all continental biota.  相似文献   

Water use efficiency in a soybean field: influence of plant water stress     

Dennis D Baldocchi  Shashi B Verma  Norman J Rosenberg 《Agricultural and Forest Meteorology》1985,34(1):53-65

Measurements were made in 1980 over a fully-developed soybean (Glycine max (L.) Merrill) canopy at Mead, Nebraska to determine how crop water status influences photosynthesis, evapotranspiration and water use efficiency. Water use efficiency was calculated in terms of the CO₂—water flux ratio (CWFR). Micrometeorological techniques were used to measure the exchange rates of CO₂ and water vapor above the crop canopy. Crop water status was evaluated by reference to volumetric soil moisture (θ_v), stomatal resistance (r_s), and leaf water potential (ψ) measurements.Stomatal resistance (r_s) was independent of ψ when the latter was greater than ?1.1 MPa. r_s increased sharply as ψ dropped below this threshold. Canopy CO₂ exchange (F_c) decreased logarithmically with increasing r_s under strong irradiance. Although F_c was found to be strongly correlated with r_s, the influence of low values of ψ and of high air temperature cannot be discounted since these factors affect the enzymatic reactions associated with photosynthesis. Stomatal closure also reduced evapotranspiration and influenced the partitioning of net radiation.Under strong irradiance the CO₂ water flux ratio (CWFR) decreased with increasing stomatal resistance. This observation is at variance with predictions of certain early ‘resistance’ models, but substantiates predictions of some recent models in which leaf energy balance considerations are incorporated.  相似文献   

Prognostic Factors in Dogs with Lymphoma and Associated Hypercalcemia     

Mona P. Rosenberg DVM    Robert E. Matus DVM  MS  Amiya K. Patnaik BVSc  MVSc 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1991,5(5):268-271

Lymphoma and hypercalcemia were diagnosed in 37 dogs. Twenty-six of the dogs received chemotherapy. The association between some prognostic factors including clinical stage of disease, illness status, presence of bone marrow involvement, and presence of an anterior mediastinal mass and remission duration and survival time was evaluated. Statistical analysis of the prognostic factors showed that the presence of an anterior mediastinal mass had an adverse effect on remission duration (P less than 0.03). Calcium concentration was not significantly related to any of the prognostic factors evaluated. Dogs that received chemotherapy were more likely to be self-supporting than the dogs that were not treated (P less than 0.005). However, initial illness status was not significantly related to remission duration or survival time in the 26 dogs that were treated. Six dogs (25% of dogs treated) survived longer than 14 months. Five of these dogs were female. Overall mean and median remission times were 10.4 and 6 months, respectively.  相似文献   

MAN AND TRANSPORTATION: Symposium, 27-30 December 1967 AAAS Annual Meeting, New York City     

Rosenberg P 《Science (New York, N.Y.)》1967,158(3804):1083-1085

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Acetylcholine receptor: similarity in axons and junctions   总被引：3，自引：0，他引：3  

P Rosenberg  H G Mautner 《Science (New York, N.Y.)》1967,155(769):1569-1571

Sulfur and selenium iso logs of benzoylcholine and its tertiary analog differ greatly in their abilities to block the electrical activity of squid axons. Presumably, differences in the biological activities of these compounds can be correlated with differences in their electron distribution. The relative effects on axons parallel those on junc tions of the electroplax, suggesting the presence of similar receptors.  相似文献