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Institution

University of California, Santa Barbara

EducationSanta 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 & Galaxy. 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, Galaxy, Laser, Quantum well, Quantum dot


Papers
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Proceedings ArticleDOI
18 Apr 2006
TL;DR: This study focuses on user behavior, content access patterns, and their implications on the design of multimedia streaming systems, and introduces a modified Poisson distribution that more accurately models the observations.
Abstract: Video-on-demand over IP (VOD) is one of the best-known examples of "next-generation" Internet applications cited as a goal by networking and multimedia researchers. Without empirical data, researchers have generally relied on simulated models to drive their design and developmental efforts. In this paper, we present one of the first measurement studies of a large VOD system, using data covering 219 days and more than 150,000 users in a VOD system deployed by China Telecom. Our study focuses on user behavior, content access patterns, and their implications on the design of multimedia streaming systems. Our results also show that when used to model the user-arrival rate, the traditional Poisson model is conservative and overestimates the probability of large arrival groups. We introduce a modified Poisson distribution that more accurately models our observations. We also observe a surprising result, that video session lengths has a weak inverse correlation with the video's popularity. Finally, we gain better understanding of the sources of video popularity through analysis of a number of internal and external factors.

728 citations

Journal ArticleDOI
15 Jul 2011-Science
TL;DR: A series of mesoporous molecular sieves are synthesized that possess crystalline microporous walls with zeolitelike frameworks, extending the application of zeolites to the mesoporus range of 2 to 50 nanometers.
Abstract: Crystalline mesoporous molecular sieves have long been sought as solid acid catalysts for organic reactions involving large molecules. We synthesized a series of mesoporous molecular sieves that possess crystalline microporous walls with zeolitelike frameworks, extending the application of zeolites to the mesoporous range of 2 to 50 nanometers. Hexagonally ordered or disordered mesopores are generated by surfactant aggregates, whereas multiple cationic moieties in the surfactant head groups direct the crystallization of microporous aluminosilicate frameworks. The wall thicknesses, framework topologies, and mesopore sizes can be controlled with different surfactants. The molecular sieves are highly active as catalysts for various acid-catalyzed reactions of bulky molecular substrates, compared with conventional zeolites and ordered mesoporous amorphous materials.

728 citations

Journal ArticleDOI
01 Feb 2013-Science
TL;DR: It is shown that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.
Abstract: Extension of nuclear magnetic resonance (NMR) to nanoscale samples has been a longstanding challenge because of the insensitivity of conventional detection methods. We demonstrated the use of an individual, near-surface nitrogen-vacancy (NV) center in diamond as a sensor to detect proton NMR in an organic sample located external to the diamond. Using a combination of electron spin echoes and proton spin manipulation, we showed that the NV center senses the nanotesla field fluctuations from the protons, enabling both time-domain and spectroscopic NMR measurements on the nanometer scale.

727 citations

Journal ArticleDOI
TL;DR: The dynamics of abundance in this coral community can be largely understood through the variation in types and scales of disturbances that occurred, and the processes that took place where disturbances were rare.
Abstract: Observations over a 30-yr period revealed a considerable degree of natural variation in the abundance of corals on Heron Island, Great Barrier Reef, Queensland, Australia. Cover ranged from 80%, with a similar large range in colony density, at several temporal and spatial scales. Much of this variation was due to the type, intensity, and spatial scale of disturbances that occurred. Coral assemblages usually recovered from acute disturbances, both on Heron Island and on other Indo-Pacific reefs. In contrast, corals did not recover from chronic disturbances of either natural or human origins, or from gradual declines. Recovery was slower after acute disturbances that altered the physical environment than after disturbances that simply killed or damaged corals. The space and time scales of declines and recoveries in abundance were much smaller on the wave-exposed side of the reef than on the side protected from storms. Recruitment rates were reduced by preemption of space by corals or macroalgae, and by storms that altered the substratum. Thus, the dynamics of abundance in this coral community can be largely understood through the variation in types and scales of disturbances that occurred, and the processes that took place where disturbances were rare.

726 citations

Journal ArticleDOI
TL;DR: In this article, the topological Chern-Simons theories in the continuum limit are described by a non-Abelian gauge structure over the moduli space which parametrizes a family of model Hamiltonians supporting topologically ordered ground states, and the dynamics of low lying global excitations are shown to be independent of random spatial dependent perturbations.
Abstract: We study a new kind of ordering — topological order — in rigid states (the states with no local gapless excitations). We concentrate on characterization of the different topological orders. As an example we discuss in detail chiral spin states of 2 + 1 dimensional spin systems. Chiral spin states are described by the topological Chern-Simons theories in the continuum limit. We show that the topological orders can be characterized by a non-Abelian gauge structure over the moduli space which parametrizes a family of the model Hamiltonians supporting topologically ordered ground states. In 2 + 1 dimensions, the non-Abelian gauge structure determines possible fractional statistics of the quasi-particle excitations over the topologically ordered ground states. The dynamics of the low lying global excitations is shown to be independent of random spatial dependent perturbations. The ground state degeneracy and the non-Abelian gauge structures discussed in this paper are very robust, even against those perturbati...

726 citations


Authors

Showing all 30652 results

NameH-indexPapersCitations
George M. Whitesides2401739269833
Yi Chen2174342293080
Simon D. M. White189795231645
George Efstathiou187637156228
Peidong Yang183562144351
David R. Williams1782034138789
Alan J. Heeger171913147492
Richard H. Friend1691182140032
Jiawei Han1681233143427
Gang Chen1673372149819
Alexander S. Szalay166936145745
Omar M. Yaghi165459163918
Carlos S. Frenk165799140345
Yang Yang1642704144071
Carlos Bustamante161770106053
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20241
2023150
2022528
20213,351
20203,653
20193,516