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A prominent theme in the modern multidisciplinary nonprofit studies is that commercial activities of nonprofit organizations impair the ability of these organizations to deliver their missions. The present research note argues that this criticism of nonprofit commercialization is based on what von Bertalanffy designated as the ??mechanistic?? view of the nonprofit sector. The research note utilizes von Bertalanffy??s general systems theory to argue that nonprofit organizations are open systems maintaining themselves in an environment in which the supply of critical resources is insecure. Accordingly, commercial activities must be seen as the self-regulatory mechanism that enables, rather than hinders, nonprofit organizations to deliver their missions in hostile environments, as they often are today. 相似文献
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Ledwell JR Montgomery ET Polzin KL St. Laurent LC Schmitt RW Toole JM 《Nature》2000,403(6766):179-182
The overturning circulation of the ocean plays an important role in modulating the Earth's climate. But whereas the mechanisms for the vertical transport of water into the deep ocean--deep water formation at high latitudes--and horizontal transport in ocean currents have been largely identified, it is not clear how the compensating vertical transport of water from the depths to the surface is accomplished. Turbulent mixing across surfaces of constant density is the only viable mechanism for reducing the density of the water and enabling it to rise. However, measurements of the internal wave field, the main source of energy for mixing, and of turbulent dissipation rates, have typically implied diffusivities across surfaces of equal density of only approximately 0.1 cm2 s(-1), too small to account for the return flow. Here we report measurements of tracer dispersion and turbulent energy dissipation in the Brazil basin that reveal diffusivities of 2-4 cm2 s(-1) at a depth of 500 m above abyssal hills on the flank of the Mid-Atlantic Ridge, and approximately 10 cm2 s(-1) nearer the bottom. This amount of mixing, probably driven by breaking internal waves that are generated by tidal currents flowing over the rough bathymetry, may be large enough to close the buoyancy budget for the Brazil basin and suggests a mechanism for closing the global overturning circulation. 相似文献
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Robert A. Fenton Hanne B. Moeller Marina Zelenina Marteinn T. Snaebjornsson Torgeir Holen Nanna MacAulay 《Cellular and molecular life sciences : CMLS》2010,67(5):829-840
Aquaporin 4 (AQP4) is expressed in the perivascular glial endfeet and is an important pathway for water during formation and
resolution of brain edema. In this study, we examined the functional properties and relative unit water permeability of three
functional isoforms of AQP4 expressed in the brain (M1, M23, Mz). The M23 isoform gave rise to square arrays when expressed
in Xenopus
laevis oocytes. The relative unit water permeability differed significantly between the isoforms in the order of M1 > Mz > M23.
None of the three isoforms were permeable to small osmolytes nor were they affected by changes in external K+ concentration. Upon protein kinase C (PKC) activation, oocytes expressing the three isoforms demonstrated rapid reduction
of water permeability, which correlated with AQP4 internalization. The M23 isoform was more sensitive to PKC regulation than
the longer isoforms and was internalized significantly faster. Our results suggest a specific role for square array formation. 相似文献
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Mortality of sea lions along the central California coast linked to a toxic diatom bloom 总被引:35,自引:0,他引:35
Scholin CA Gulland F Doucette GJ Benson S Busman M Chavez FP Cordaro J DeLong R De Vogelaere A Harvey J Haulena M Lefebvre K Lipscomb T Loscutoff S Lowenstine LJ Marin R Miller PE McLellan WA Moeller PD Powell CL Rowles T Silvagni P Silver M Spraker T Trainer V Van Dolah FM 《Nature》2000,403(6765):80-84
Over 400 California sea lions (Zalophus californianus) died and many others displayed signs of neurological dysfunction along the central California coast during May and June 1998. A bloom of Pseudo-nitzschia australis (diatom) was observed in the Monterey Bay region during the same period. This bloom was associated with production of domoic acid (DA), a neurotoxin that was also detected in planktivorous fish, including the northern anchovy (Engraulis mordax), and in sea lion body fluids. These and other concurrent observations demonstrate the trophic transfer of DA resulting in marine mammal mortality. In contrast to fish, blue mussels (Mytilus edulus) collected during the DA outbreak contained no DA or only trace amounts. Such findings reveal that monitoring of mussel toxicity alone does not necessarily provide adequate warning of DA entering the food web at levels sufficient to harm marine wildlife and perhaps humans. 相似文献
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Åsa Fex Svenningsen Svenja Löring Anna Lahn Sørensen Ha Uyen Buu Huynh Simone Hjæresen Nellie Martin Jesper Bonnet Moeller Maria Louise Elkjær Uffe Holmskov Zsolt Illes Malin Andersson Solveig Beck Nielsen Eirikur Benedikz 《Cellular and molecular life sciences : CMLS》2017,74(24):4561-4572
Macrophage migration inhibitory factor (MIF), a small conserved protein, is abundant in the immune- and central nervous system (CNS). MIF has several receptors and binding partners that can modulate its action on a cellular level. It is upregulated in neurodegenerative diseases and cancer although its function is far from clear. Here, we report the finding of a new binding partner to MIF, the serine protease HTRA1. This enzyme cleaves several growth factors, extracellular matrix molecules and is implicated in some of the same diseases as MIF. We show that the function of the binding between MIF and HTRA1 is to inhibit the proteolytic activity of HTRA1, modulating the availability of molecules that can change cell growth and differentiation. MIF is therefore the first endogenous inhibitor ever found for HTRA1. It was found that both molecules were present in astrocytes and that the functional binding has the ability to modulate astrocytic activities important in development and disease of the CNS. 相似文献
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A computer-aided arrangement is described which allows kinetic and regulative studies with enzymes, organelles and cells in an open system. This is demonstrated with some simple examples. 相似文献
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Dumitrescu AM Liao XH Abdullah MS Lado-Abeal J Majed FA Moeller LC Boran G Schomburg L Weiss RE Refetoff S 《Nature genetics》2005,37(11):1247-1252
Incorporation of selenocysteine (Sec), through recoding of the UGA stop codon, creates a unique class of proteins. Mice lacking tRNA(Sec) die in utero, but the in vivo role of other components involved in selenoprotein synthesis is unknown, and Sec incorporation defects have not been described in humans. Deiodinases (DIOs) are selenoproteins involved in thyroid hormone metabolism. We identified three of seven siblings with clinical evidence of abnormal thyroid hormone metabolism. Their fibroblasts showed decreased DIO2 enzymatic activity not linked to the DIO2 locus. Systematic linkage analysis of genes involved in DIO2 synthesis and degradation led to the identification of an inherited Sec incorporation defect, caused by a homozygous missense mutation in SECISBP2 (also called SBP2). An unrelated child with a similar phenotype was compound heterozygous with respect to mutations in SECISBP2. Because SBP2 is epistatic to selenoprotein synthesis, these defects had a generalized effect on selenoproteins. Incomplete loss of SBP2 function probably causes the mild phenotype. 相似文献
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B. Paletta R. Moeller H. Trutnovsky W. Mlekusch 《Cellular and molecular life sciences : CMLS》1979,35(8):1049-1051
Summary A computer-aided arrangement is described which allows kinetic and regulative studies with enzymes, organelles and cells in an open system. This is demonstrated with some simple examples. 相似文献
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