Book reviews     

George H. Axinn  Shelley Feldman  Pat Barnes-McConnell  Michele Lipner  Jere L. Gilles  J. Kathy Parker  William M. Alexander  Judith Krieger  J. P. Brien  James P. Stansbury  Kathleen Staudt  Marcy Rosenbaum  Norman Uphoff  Alan Long  Jere L. Gilles  Constance M. McCorkle  David Brokensha  Kimberley Lucas  Carrie R. Johnston  Robert Lawless 《Agriculture and Human Values》1988,5(1-2):124-168

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EPOXI at comet Hartley 2     

A'Hearn MF  Belton MJ  Delamere WA  Feaga LM  Hampton D  Kissel J  Klaasen KP  McFadden LA  Meech KJ  Melosh HJ  Schultz PH  Sunshine JM  Thomas PC  Veverka J  Wellnitz DD  Yeomans DK  Besse S  Bodewits D  Bowling TJ  Carcich BT  Collins SM  Farnham TL  Groussin O  Hermalyn B  Kelley MS  Kelley MS  Li JY  Lindler DJ  Lisse CM  McLaughlin SA  Merlin F  Protopapa S  Richardson JE  Williams JL 《Science (New York, N.Y.)》2011,332(6036):1396-1400

Understanding how comets work--what drives their activity--is crucial to the use of comets in studying the early solar system. EPOXI (Extrasolar Planet Observation and Deep Impact Extended Investigation) flew past comet 103P/Hartley 2, one with an unusually small but very active nucleus, taking both images and spectra. Unlike large, relatively inactive nuclei, this nucleus is outgassing primarily because of CO(2), which drags chunks of ice out of the nucleus. It also shows substantial differences in the relative abundance of volatiles from various parts of the nucleus.  相似文献   

Assessing coincidence between priority conservation areas for vertebrate groups in a Mediterranean hotspot     

Alba Estrada  Raimundo Real  Juan Mario Vargas 《Biological conservation》2011,(3):1120-1129

The effectiveness of selecting umbrella species or groups of species to protect other groups is a key and unresolved issue in conservation planning. We detected areas important to the four groups of terrestrial vertebrates inhabiting Andalusia (southern Spain) according to four conservation-value criteria, i.e., richness, rarity, vulnerability, and endemicity. We calculated coincidences between criteria and taxa by the degree of correlation and fuzzy overlap between the different criteria for the same group (intra-group coincidence) and between the different groups of species for the same criteria (inter-group coincidence). For the groups to be appropriate umbrella species, inter-group coincidence should be high. The results showed that intra-group coincidence was high, but inter-group coincidence was low. Thus, zones of importance to each group of species tended to be located in different places compared to the other groups, and therefore none of them should be used as an indicator or umbrella group to protect the others. This result has implications for conservation policy, as the Andalusian authorities should not assume that protecting a site important to one group of species will also be relevant to conserve the other groups. Nevertheless, we identified the areas of relatively high conjoint importance for all the groups, and the best umbrella group in this region, which proved to be reptiles.  相似文献   

The ecology of mixed severity fire regimes in Washington, Oregon, and Northern California     

David A. Perry  Paul F. HessburgCarl N. Skinner  Thomas A. SpiesScott L. Stephens  Alan Henry TaylorJerry F. Franklin  Brenda McCombGreg Riegel 《Forest Ecology and Management》2011,262(5):703-717

Forests characterized by mixed-severity fires occupy a broad moisture gradient between lower elevation forests typified by low-severity fires and higher elevation forests in which high-severity, stand replacing fires are the norm. Mixed-severity forest types are poorly documented and little understood but likely occupy significant areas in the western United States. By definition, mixed-severity types have high beta diversity at meso-scales, encompassing patches of both high and low severity and gradients in between. Studies of mixed-severity types reveal complex landscapes in which patch sizes follow a power law distribution with many small and few large patches. Forest types characterized by mixed severity can be classified according to the modal proportion of high to low severity patches, which increases from relatively dry to relatively mesic site conditions. Mixed-severity regimes are produced by interactions between top-down forcing by climate and bottom-up shaping by topography and the flammability of vegetation, although specific effects may vary widely across the region, especially the relation between aspect and fire severity. History is important in shaping fire behavior in mixed-severity landscapes, as patterns laid down by previous fires can play a significant role in shaping future fires. Like low-severity forests in the western United States, many dry mixed-severity types experienced significant increases in stand density during the 20th century, threatening forest health and biodiversity, however not all understory development in mixed-severity forests increases the threat of severe wild fires. In general, current landscapes have been homogenized, reducing beta diversity and increasing the probability of large fires and insect outbreaks. Further loss of old, fire tolerant trees is of particular concern, but understory diversity has been reduced as well. High stand densities on relatively dry sites increase water use and therefore susceptibility to drought and insect outbreaks, exacerbating a trend of increasing regional drying. The need to restore beta diversity while protecting habitat for closed-forest specialists such as the northern spotted owl call for landscape-level approaches to ecological restoration.  相似文献   

Molecular structures of citrus flavonoids determine their effects on lipid metabolism in HepG2 cells by primarily suppressing apoB secretion     

Lin Y  Vermeer MA  Bos W  van Buren L  Schuurbiers E  Miret-Catalan S  Trautwein EA 《Journal of agricultural and food chemistry》2011,59(9):4496-4503

This study investigated the underlying mechanisms of action for blood lipid lowering effects of citrus flavonoids and their methoxylated analogues (n = 19; dose range: 0-100 μM) in HepG2 cells. Cholesterol (CH) and triglyceride (TG) syntheses were assessed by measuring the incorporation of (14)C-acetate and (14)C-glycerol, respectively, whereas apoB secretion was determined by ELISA. Results show that two polymethoxylated citrus flavonoids (PMFs), tangeretin and nobiletin, potently inhibited apoB secretion (IC(50) = 13 and 29 μM, respectively) and modestly inhibited CH synthesis (IC(50) = 49 and 68 μM) and TG synthesis (IC(50) = 14 and 73 μM), without effecting LDL-receptor activity. Other PMFs (e.g., sinensetin) and non-PMFs (e.g., hesperetin and naringenin) had only weak effects on CH and TG syntheses and apoB secretion (IC(50) > 100 μM). The structure-activity analysis indicated that a fully methoxylated A-ring of the flavonoid structure was associated with a potent inhibitory activity on hepatic apoB secretion. In conclusion, this study using HepG2 cells indicates that citrus flavonoids with a fully methoxylated A-ring may lower blood CH and TG concentrations primarily by suppressing hepatic apoB secretion as a main underlying mode of action.  相似文献   

Protein carbonylation and water-holding capacity of pork subjected to frozen storage: effect of muscle type, premincing, and packaging     

Estévez M  Ventanas S  Heinonen M  Puolanne E 《Journal of agricultural and food chemistry》2011,59(10):5435-5443

The present work aimed to study the relationship between protein carbonylation and the loss of water-holding capacity (WHC) occurring during frozen storage of porcine muscles. Pork samples corresponding to two different muscle types, glycolytic M. longissimus dorsi (LD) and oxidative M. psoas major (PM), and subjected to two different premincing, minced (MINCED) and intact pork pieces (INTACT), and packaging, vacuum packaged (VACUUM) and packed in oxygen-permeable bags (OXYGEN), procedures were frozen (-18 °C/12 weeks) and analyzed at sampling times upon thawing (weeks 1, 4, 8, and 12) for the relative amount of specific protein carbonyls, α-aminoadipic and γ-glutamic semialdehydes (AAS and GGS, respectively), and their ability to hold water using two different techniques. The formation of protein carbonyls occurred concomitantly with the loss of WHC, and both phenomena were found to be more intense in LD muscles and in MINCED and OXYGEN pork samples. The loss in WHC was from ca. 10 to 30% in 12 weeks, depending on the method of determination. Plausible mechanisms by which protein carbonylation may decrease the WHC of pork samples are thoroughly discussed in the present paper. Besides the likely impact of protein carbonylation in the water-myofibrillar protein relationships, the implication of AAS and GGS in further reactions including plausible cross-linking would explain the decrease of these semialdehydes by the end of frozen storage and would reinforce their liability in the loss of WHC of porcine muscles. The exact nature of these reactions, however, should be investigated in further studies.  相似文献   

Factors associated with childhood obesity in Spain. The OBICE study: a case-control study based on sentinel networks     

Zurriaga O  Pérez-Panadés J  Quiles Izquierdo J  Gil Costa M  Anes Y  Quiñones C  Margolles M  Lopez-Maside A  Vega-Alonso AT  Miralles Espí MT;Recent OBICE Research Group 《Public health nutrition》2011,14(6):1105-1113

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Atmospheric science. Whither geoengineering?     

Robock A 《Science (New York, N.Y.)》2008,320(5880):1166-1167

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Behavioral science comes of age     

Leshner AI 《Science (New York, N.Y.)》2007,316(5827):953

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A seven-transmembrane RGS protein that modulates plant cell proliferation     

Chen JG  Willard FS  Huang J  Liang J  Chasse SA  Jones AM  Siderovski DP 《Science (New York, N.Y.)》2003,301(5640):1728-1731

G protein-coupled receptors (GPCRs) at the cell surface activate heterotrimeric G proteins by inducing the G protein alpha (Galpha) subunit to exchange guanosine diphosphate for guanosine triphosphate. Regulators of G protein signaling (RGS) proteins accelerate the deactivation of Galpha subunits to reduce GPCR signaling. Here we identified an RGS protein (AtRGS1) in Arabidopsis that has a predicted structure similar to a GPCR as well as an RGS box with GTPase accelerating activity. Expression of AtRGS1 complemented the pheromone supersensitivity phenotype of a yeast RGS mutant, sst2Delta. Loss of AtRGS1 increased the activity of the Arabidopsis Galpha subunit, resulting in increased cell elongation in hypocotyls in darkness and increased cell production in roots grown in light. These findings suggest that AtRGS1 is a critical modulator of plant cell proliferation.  相似文献