Institution
University of California, Santa Barbara
Education•Santa Barbara, California, United States•
About: University of California, Santa Barbara is a education organization based out in Santa Barbara, California, United States. It is known for research contribution in the topics: Population & Laser. The organization has 30281 authors who have published 80852 publications receiving 4626827 citations. The organization is also known as: UC Santa Barbara & UCSB.
Topics: Population, Laser, Galaxy, Context (language use), Quantum well
Papers published on a yearly basis
Papers
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TL;DR: The ground-state degeneracy provides a new quantum number in addition to the Hall conductance, characterizing different phases of the FQH systems, and the Ginzburg-Landau theory is a dual theory of the U(1) Chern-Simons topological theory.
Abstract: The fractional quantum Hall (FQH) states are shown to have q\ifmmode \tilde{}\else \~{}\fi{} $^{\mathit{g}}\mathrm{fold}$ ground-state degeneracy on a Riemann surface of genus g, where q\ifmmode \tilde{}\else \~{}\fi{} is the ground-state degeneracy in a torus topology. The ground-state degeneracies are directly related to the statistics of the quasiparticles given by \ensuremath{\theta}=p\ifmmode \tilde{}\else \~{}\fi{}\ensuremath{\pi}/q\ifmmode \tilde{}\else \~{}\fi{}. The ground-state degeneracy is shown to be invariant against weak but otherwise arbitrary perturbations. Therefore the ground-state degeneracy provides a new quantum number, in addition to the Hall conductance, characterizing different phases of the FQH systems. The phases with different ground-state degeneracies are considered to have different topological orders. For a finite system of size L, the ground-state degeneracy is lifted. The energy splitting is shown to be at most of order ${\mathit{e}}^{\mathrm{\ensuremath{-}}\mathit{L}/\ensuremath{\xi}}$. We also show that the Ginzburg-Landau theory of the FQH states (in the low-energy limit) is a dual theory of the U(1) Chern-Simons topological theory.
681 citations
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TL;DR: Several lines of evidence suggest that the accelerated loss and compensatory over-production of red blood cells seen in hemolytic and megaloblastic anemias is the most likely proximate cause of porotic hyperostosis.
Abstract: Porosities in the outer table of the cranial vault (porotic hyperostosis) and orbital roof (cribra orbitalia) are among the most frequent pathological lesions seen in ancient human skeletal collections. Since the 1950s, chronic iron-deficiency anemia has been widely accepted as the probable cause of both conditions. Based on this proposed etiology, bioarchaeologists use the prevalence of these conditions to infer living conditions conducive to dietary iron deficiency, iron malabsorption, and iron loss from both diarrheal disease and intestinal parasites in earlier human populations. This iron-deficiency-anemia hypothesis is inconsistent with recent hematological research that shows iron deficiency per se cannot sustain the massive red blood cell production that causes the marrow expansion responsible for these lesions. Several lines of evidence suggest that the accelerated loss and compensatory over-production of red blood cells seen in hemolytic and megaloblastic anemias is the most likely proximate cause of porotic hyperostosis. Although cranial vault and orbital roof porosities are sometimes conflated under the term porotic hyperostosis, paleopathological and clinical evidence suggests they often have different etiologies. Reconsidering the etiology of these skeletal conditions has important implications for current interpretations of malnutrition and infectious disease in earlier human populations.
679 citations
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TL;DR: Three control methods—iterative learning control, repetitive control (RC), and run-to-run control (R2R)—are studied and compared and some promising fields for learning-type control are revealed.
679 citations
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TL;DR: This work uses field-parameterized population models to develop a null expectation for community dynamics without the stabilizing effects of niche differences, and shows that niche differences collectively stabilize the dynamics of experimental communities of serpentine annual plants.
Abstract: If organisms are involved in a perpetual struggle for existence, how is it that communities are so diverse? The traditional answer is the ecological 'niche' — even at very small scales, environmental differences are enough to allow different species to coexist. Recently, the 'neutral theory' of biodiversity has suggested that this explanation is too complicated, and species are distributed more by chance effects. Jonathan Levine and Janneke HilleRisLambers test these ideas with an intriguing mix of experiment and theory, showing that diversity declines when niches are removed: in this round, at least, traditional explanations have the edge. If organisms are involved in a perpetual struggle for existence, how is it that communities are so diverse? The traditional answer is the ecological niche but this has recently been challenged by the neutral theory of biodiversity, which explains coexistence with the equivalence of competitors. Here, theory and experimentation are integrated in order to explore this problem; the results show that diversity declines when niches are removed. Ecological communities characteristically contain a wide diversity of species with important functional, economic and aesthetic value. Ecologists have long questioned how this diversity is maintained1,2,3. Classic theory shows that stable coexistence requires competitors to differ in their niches4,5,6; this has motivated numerous investigations of ecological differences presumed to maintain diversity3,6,7,8. That niche differences are key to coexistence, however, has recently been challenged by the neutral theory of biodiversity, which explains coexistence with the equivalence of competitors9. The ensuing controversy has motivated calls for a better understanding of the collective importance of niche differences for the diversity observed in ecological communities10,11. Here we integrate theory and experimentation to show that niche differences collectively stabilize the dynamics of experimental communities of serpentine annual plants. We used field-parameterized population models to develop a null expectation for community dynamics without the stabilizing effects of niche differences. The population growth rates predicted by this null model varied by several orders of magnitude between species, which is sufficient for rapid competitive exclusion. Moreover, after two generations of community change in the field, Shannon diversity was over 50 per cent greater in communities stabilized by niche differences relative to those exhibiting dynamics predicted by the null model. Finally, in an experiment manipulating species’ relative abundances, population growth rates increased when species became rare—the demographic signature of niche differences. Our work thus provides strong evidence that species differences have a critical role in stabilizing species diversity.
679 citations
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19 Oct 2008
TL;DR: In this paper, the authors demonstrate THz metamaterials exhibiting either amplitude control via carrier injection or depletion in the active semiconductor substrate or frequency control via photoexcitation of carriers into active semiconducting materials incorporated into the sub-wavelength metammaterial structure.
Abstract: We demonstrate THz metamaterials exhibiting either amplitude control, via carrier injection or depletion in the active semiconductor substrate or frequency control, via photoexcitation of carriers into active semiconducting materials incorporated into the sub-wavelength metamaterial structure.
679 citations
Authors
Showing all 30652 results
Name | H-index | Papers | Citations |
---|---|---|---|
George M. Whitesides | 240 | 1739 | 269833 |
Yi Chen | 217 | 4342 | 293080 |
Simon D. M. White | 189 | 795 | 231645 |
George Efstathiou | 187 | 637 | 156228 |
Peidong Yang | 183 | 562 | 144351 |
David R. Williams | 178 | 2034 | 138789 |
Alan J. Heeger | 171 | 913 | 147492 |
Richard H. Friend | 169 | 1182 | 140032 |
Jiawei Han | 168 | 1233 | 143427 |
Gang Chen | 167 | 3372 | 149819 |
Alexander S. Szalay | 166 | 936 | 145745 |
Omar M. Yaghi | 165 | 459 | 163918 |
Carlos S. Frenk | 165 | 799 | 140345 |
Yang Yang | 164 | 2704 | 144071 |
Carlos Bustamante | 161 | 770 | 106053 |