University of California

About: University of California is a education organization based out in Oakland, California, United States. It is known for research contribution in the topics: Population & Layer (electronics). The organization has 55175 authors who have published 52933 publications receiving 1491169 citations. The organization is also known as: UC & University of California System.

Global regime shift dynamics of catastrophic sea urchin overgrazing

Abstract: A pronounced, widespread and persistent regime shift among marine ecosystems is observable on temperate rocky reefs as a result of sea urchin overgrazing. Here, we empirically define regime-shift dynamics for this grazing system which transitions between productive macroalgal beds and impoverished urchin barrens. Catastrophic in nature, urchin overgrazing in a well-studied Australian system demonstrates a discontinuous regime shift, which is of particular management concern as recovery of desirable macroalgal beds requires reducing grazers to well below the initial threshold of overgrazing. Generality of this regime-shift dynamic is explored across 13 rocky reef systems (spanning 11 different regions from both hemispheres) by compiling available survey data (totalling 10 901 quadrats surveyed in situ ) plus experimental regime-shift responses (observed during a total of 57 in situ manipulations). The emergent and globally coherent pattern shows urchin grazing to cause a discontinuous ‘catastrophic’ regime shift, with hysteresis effect of approximately one order of magnitude in urchin biomass between critical thresholds of overgrazing and recovery. Different life-history traits appear to create asymmetry in the pace of overgrazing versus recovery. Once shifted, strong feedback mechanisms provide resilience for each alternative state thus defining the catastrophic nature of this regime shift. Importantly, human-derived stressors can act to erode resilience of desirable macroalgal beds while strengthening resilience of urchin barrens, thus exacerbating the risk, spatial extent and irreversibility of an unwanted regime shift for marine ecosystems.

Spin-bag mechanism of high-temperature superconductivity.

Abstract: In oxide superconductors the local suppression of antiferromagnetic correlations in the vicinity of a hole lowers the energy of the system. This quasi two-dimensional bag of weakened spin order follows the hole in its motion. In addition, holes prefer to share a bag, leading to a strong pairing attraction and a high T c superconductivity. There are many experimental consequences of this mechanism for both the superconducting and normal phases.

Efflux and compartmentalization of zinc by members of the SLC30 family of solute carriers.

Abstract: All of the members of this family are thought to facilitate zinc efflux from the cytoplasm either into various intracellular compartments (endosomes, secretory granules, synaptic vesicles, Golgi apparatus, or trans-Golgi network) or across the plasma membrane. Thus, these transporters are thought to help maintain zinc homeostasis and facilitate transport of zinc into specialized intracellular compartments. Counterparts of the SLC30 family are found in all organisms. Most of the members of this class are predicted to have 6 transmembrane domains with both N- and C-termini on the cytoplasmic side of the membrane. Expression of rodent Znt1, Znt2 or Znt4 cDNAs in mammalian cells can confer resistance to zinc toxicity. Loss of function of the mouse Znt1 is embryonic lethal, loss of mouse Znt3 prevents accumulation of zinc in synaptic vesicles, nonfunctional mouse Znt4 (lethal milk) results in zinc-deficient milk, and Znt5-null mice display bone abnormalities and heart failure. No mutations in human counterparts of any of the members of the SLC30 family have been described.

H I shells and supershells

Abstract: The entire sky has now been surveyed in the 21-cm line with an angular resolution of about 05 degree In the north, above declination-20° or so, the “galactic plane” |b|<10° has been completely sampled Weaver and Williams (1973; 1974) Above declination -30° or so, the sky outside the galactic plane has been almost completely sampled (Heiles and Habing, 1974; Heiles, 1975)

Effects of Non-Farm Employment on Rural Income Inequality in Developing Countries: an Investment Perspective

Abstract: This paper makes several points based on a review of household survey evidence from Africa, Asia and Latin America. (i) In contrast to conventional wisdom, the evidence is very mixed as to the effect of non-farm employment on rural income inequality. The non-farm employment and microenterprise programmes now in vogue will not necessarily resolve rural income inequality problems and attendant social tensions nor automatically benefit the poor. (ii) Policymakers should be worried by substantial evidence of poor people's inability to overcome important entry barriers to many non-farm activities. (iii) The main determinants of unequal access to non-farm activities are the distribution of capacity to make investments in non-farm assets and the relative scarcity of low capital entry barrier activities. Therefore, it is crucial for public investments and policy to favour an increase in the access of the poor to assets that allow them to overcome non-farm employment entry barriers, (iv) It would be an error to assume that one can address asset-poverty and inequality in the non-farm sector without addressing farm-side problems and vice versa.