Cascading effects of the loss of apex predatory sharks from a coastal ocean     

Myers RA  Baum JK  Shepherd TD  Powers SP  Peterson CH 《Science (New York, N.Y.)》2007,315(5820):1846-1850

Impacts of chronic overfishing are evident in population depletions worldwide, yet indirect ecosystem effects induced by predator removal from oceanic food webs remain unpredictable. As abundances of all 11 great sharks that consume other elasmobranchs (rays, skates, and small sharks) fell over the past 35 years, 12 of 14 of these prey species increased in coastal northwest Atlantic ecosystems. Effects of this community restructuring have cascaded downward from the cownose ray, whose enhanced predation on its bay scallop prey was sufficient to terminate a century-long scallop fishery. Analogous top-down effects may be a predictable consequence of eliminating entire functional groups of predators.  相似文献   

Population dynamics of exploited fish stocks at low population levels     

Myers RA  Barrowman NJ  Hutchings JA  Rosenberg AA 《Science (New York, N.Y.)》1995,269(5227):1106-1108

Models of population dynamics in which per capita reproductive success declines at low population levels (variously known as depensation, the Allee effect, and inverse density-dependence) predict that populations can have multiple equilibria and may suddenly shift from one equilibrium to another. If such depensatory dynamics exist, reduced mortality may be insufficient to allow recovery of a population after abundance has been severely reduced by harvesting. Estimates of spawner abundance and number of surviving progeny for 128 fish stocks indicated only 3 stocks with significant depensation. Estimates of the statistical power of the tests strengthen the conclusion that depensatory dynamics are not apparent for fish populations at the levels studied.  相似文献   

Polarization observations with the Cosmic Background Imager     

Readhead AC  Myers ST  Pearson TJ  Sievers JL  Mason BS  Contaldi CR  Bond JR  Bustos R  Altamirano P  Achermann C  Bronfman L  Carlstrom JE  Cartwright JK  Casassus S  Dickinson C  Holzapfel WL  Kovac JM  Leitch EM  May J  Padin S  Pogosyan D  Pospieszalski M  Pryke C  Reeves R  Shepherd MC  Torres S 《Science (New York, N.Y.)》2004,306(5697):836-844

Polarization observations of the cosmic microwave background with the Cosmic Background Imager from September 2002 to May 2004 provide a significant detection of the E-mode polarization and reveal an angular power spectrum of polarized emission showing peaks and valleys that are shifted in phase by half a cycle relative to those of the total intensity spectrum. This key agreement between the phase of the observed polarization spectrum and that predicted on the basis of the total intensity spectrum provides support for the standard model of cosmology, in which dark matter and dark energy are the dominant constituents, the geometry is close to flat, and primordial density fluctuations are predominantly adiabatic with a matter power spectrum commensurate with inflationary cosmological models.  相似文献   

Dense-gas chromatography of nonvolatile substances of high molecular weight     

L McLaren  M N Myers  J C Giddings 《Science (New York, N.Y.)》1968,159(811):197-199

Working at pressures of up to 2000 atmospheres, more than ten times higher than in previous gas chromatography, we used the solvent power of dense gases to enable migration of chromatographic substances of molecular weights as high as 400,000. Carotenoids, corticol steroids, sterols, nucleosides, amino acids, carbohydrates, and several polymers have been caused to migrate, separated, and detected in NH(3) and CO(2) carrier gases at temperatures of 140 degrees and 40 degrees C, just above the respective critical points. Previously such compounds either defied separation by gas chromatography or had to be chromatographed as their more volatile derivatives.  相似文献   

DISCUSSION OF A NATIONAL OBSERVATORY     

Newcomb S  Hall A  Young CA  Mendenhall TC  Woodward RS  Doolittle CL  Pickering WH  Searle A  Very FW  Todd DP  Myers GW  Fuertes EA  Elkin WL  Keeler JE 《Science (New York, N.Y.)》1899,9(222):467-476

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Temperature in the monkey: transmitter factors released from the brain during thermoregulation   总被引：2，自引：0，他引：2  

R D Myers  L G Sharpe 《Science (New York, N.Y.)》1968,161(841):572-573

When perfusate is collected from the anterior hypothalamus of a cooled donor monkey and is transfused to a corresponding hypothalamic site in a normal monkey, fever occurs in this recipient. Conversely, perfusate from a heated donor monkey lowers the recipient monkey's temperature when the same hypothalamic transfusion procedure is followed. These experiments provide direct evidence of a neurochemical "coding" within the specific anatomical region of the brain historically implicated in the control of body temperature.  相似文献   

Losartan, an AT1 antagonist, prevents aortic aneurysm in a mouse model of Marfan syndrome     

Habashi JP  Judge DP  Holm TM  Cohn RD  Loeys BL  Cooper TK  Myers L  Klein EC  Liu G  Calvi C  Podowski M  Neptune ER  Halushka MK  Bedja D  Gabrielson K  Rifkin DB  Carta L  Ramirez F  Huso DL  Dietz HC 《Science (New York, N.Y.)》2006,312(5770):117-121

Aortic aneurysm and dissection are manifestations of Marfan syndrome (MFS), a disorder caused by mutations in the gene that encodes fibrillin-1. Selected manifestations of MFS reflect excessive signaling by the transforming growth factor-beta (TGF-beta) family of cytokines. We show that aortic aneurysm in a mouse model of MFS is associated with increased TGF-beta signaling and can be prevented by TGF-beta antagonists such as TGF-beta-neutralizing antibody or the angiotensin II type 1 receptor (AT1) blocker, losartan. AT1 antagonism also partially reversed noncardiovascular manifestations of MFS, including impaired alveolar septation. These data suggest that losartan, a drug already in clinical use for hypertension, merits investigation as a therapeutic strategy for patients with MFS and has the potential to prevent the major life-threatening manifestation of this disorder.  相似文献   

Differences in benthic cover inside and outside marine protected areas on the Great Barrier Reef: influence of protection or disturbance history?     

Monique R. Myers  Richard F. Ambrose 《水产资源保护:海洋与淡水生态系统》2009,19(7):736-747

• 1. Marine protected areas (MPAs) are being used increasingly to manage and protect marine resources. Most studies of MPAs have focused on fish. In this study, the influence of MPA protection on coral reef benthic organisms on the Great Barrier Reef (GBR) was investigated. In addition, the interaction between protection and natural disturbance history was examined.
• 2. Differences in benthic cover inside and outside MPAs were assessed at 15 pairs of Protected and General Use reefs on the GBR using annual monitoring data from the Australian Institute of Marine Science's Long‐Term Monitoring Programme (LTMP). At each reef, benthic cover was determined using a benthic video survey at three sites, with each site consisting of five 50 m transect lines separated by at least 250 m running parallel to the reef crest at 6–9 m depth.
• 3. Benthic cover was related to both protection status and disturbance history, but natural perturbations exerted a stronger influence on benthic cover than did protection status. The influence of natural perturbation was most noticeable for hard coral.
• 4. Most reefs where no natural disturbance events had occurred (‘undisturbed reefs’) had higher hard coral cover and lower soft coral cover than General Use reefs. While the high levels of hard coral on Protected reefs may be a result of protection status, it might also have resulted from selection bias that occurred during the initial zoning of the Great Barrier Reef Marine Park (i.e. managers may have given protection status to reefs with high coral cover).
• 5. These results are likely influenced by the relatively low intensity of human use, both on the Great Barrier Reef in general and at the particular monitoring sites studied. Over time, as local populations and tourism increase, the effect of protection may become more evident at LTMP sites. Copyright © 2009 John Wiley & Sons, Ltd.

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Pilot-Plant Wet-Milling Process for Producing Corn Gluten Meal     

S. Wu  D. J. Myers  L. A. Johnson  S. R. Fox  S. K. Singh 《Cereal Chemistry》1997,74(3):264-267

A pilot-plant wet-milling process was specially used to produce corn gluten meal (CGM) with a relatively high protein content (49.8% from Pioneer 3394 and 53.7% from Wilson D110). The protein content of the CGM obtained from a starch table in our pilot-plant procedure was similar to the results obtained by using the hydrocyclone method. Wilson D110 has a higher protein content in its corn kernels, producing higher yield and protein content gluten than the Pioneer 3394, which has lower protein content in the corn. The effects of drying method and temperature on the color of CGM were also discussed.  相似文献   

Factors Affecting Yield and Composition of Zein Extracted from Commercial Corn Gluten Meal     

Shaowen Wu  Deland J. Myers  Lawrence A. Johnson 《Cereal Chemistry》1997,74(3):258-263

Twelve corn gluten meal samples obtained from six wet-milling plants were processed into zein. Zein was extracted using 88% aqueous isopropyl alcohol at pH 12.5, followed by chilling. Protein recovery ranged from 21.3 to 32.0%, and protein purity ranged from 82.1 to 87.6%. Protein recovery increased as the protein purity increased (r = 0.76) (P < 0.01). One of the major factors influencing extraction yield was protein composition; especially α-zein content, which ranged from 53.4 to 64% of the total protein in the corn gluten meal samples. The intensity of red color of the corn gluten meal was negatively correlated with protein recovery and zein purity (r = -0.66 and -0.72, respectively) (P < 0.02).  相似文献