Institution
California Institute of Technology
Education•Pasadena, California, United States•
About: California Institute of Technology is a education organization based out in Pasadena, California, United States. It is known for research contribution in the topics: Galaxy & Population. The organization has 57649 authors who have published 146691 publications receiving 8620287 citations. The organization is also known as: Caltech & Cal Tech.
Topics: Galaxy, Population, Star formation, Redshift, Mars Exploration Program
Papers published on a yearly basis
Papers
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TL;DR: In this paper, the authors considered a new type of quantum nondemolition measurement called back-action-evading measurement, where the real part of the harmonic oscillator's complex amplitude is measured by a single transducer.
Abstract: The monitoring of a quantum-mechanical harmonic oscillator on which a classical force acts is important in a variety of high-precision experiments, such as the attempt to detect gravitational radiation. This paper reviews the standard techniques for monitoring the oscillator, and introduces a new technique which, in principle, can determine the details of the force with arbitrary accuracy, despite the quantum properties of the oscillator. The standard method for monitoring the oscillator is the "amplitude-and-phase" method (position or momentum transducer with output fed through a narrow-band amplifier). The accuracy obtainable by this method is limited by the uncertainty principle ("standard quantum limit"). To do better requires a measurement of the type which Braginsky has called "quantum nondemolition." A well known quantum nondemolition technique is "quantum counting," which can detect an arbitrarily weak classical force, but which cannot provide good accuracy in determining its precise time dependence. This paper considers extensively a new type of quantum nondemolition measurement—a "back-action-evading" measurement of the real part X_1 (or the imaginary part X_2) of the oscillator's complex amplitude. In principle X_1 can be measured "arbitrarily quickly and arbitrarily accurately," and a sequence of such measurements can lead to an arbitrarily accurate monitoring of the classical force. The authors describe explicit Gedanken experiments which demonstrate that X_1 can be measured arbitrarily quickly and arbitrarily accurately. In these experiments the measuring apparatus must be coupled to both the position (position transducer) and the momentum (momentum transducer) of the oscillator, and both couplings must be modulated sinusoidally. For a given measurement time the strength of the coupling determines the accuracy of the measurement; for arbitrarily strong coupling the measurement can be arbitrarily accurate. The "momentum transducer" is constructed by combining a "velocity transducer" with a "negative capacitor" or "negative spring." The modulated couplings are provided by an external, classical generator, which can be realized as a harmonic oscillator excited in an arbitrarily energetic, coherent state. One can avoid the use of two transducers by making "stroboscopic measurements" of X_1, in which one measures position (or momentum) at half-cycle intervals. Alternatively, one can make "continuous single-transducer" measurements of X_1 by modulating appropriately the output of a single transducer (position or momentum), and then filtering the output to pick out the information about X_1 and reject information about X_2. Continuous single-transducer measurements are useful in the case of weak coupling. In this case long measurement times are required to achieve good accuracy, and continuous single-transducer measurements are almost as good as perfectly coupled two-transducer measurements. Finally, the authors develop a theory of quantum nondemolition measurement for arbitrary systems. This paper (Paper I) concentrates on issues of principle; a sequel (Paper II) will consider issues of practice.
969 citations
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TL;DR: This is a story of the exploration of the olefin-metathesis reaction, a reaction that has been the major emphasis of my independent research and contributed to oleFin metathesis becoming the indispensable synthetic tool that it is today.
Abstract: This is a story of our exploration of the olefin-metathesis reaction, a reaction that has been the major emphasis of my independent research. As with all stories of scientific discovery, there are three components: the discoveries, the resulting applications, and, perhaps the most important of all, the people involved. Starting from observations made from seemingly unrelated work, our investigations into the fundamental chemistry of this transformation have been an exciting journey, with major advances often resulting from complete surprises, mistakes, and simple intuition. Ultimately, these efforts have contributed to olefin metathesis becoming the indispensable synthetic tool that it is today.
969 citations
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TL;DR: Data show that ATR is essential for early embryonic development and must function in processes other than regulation of p53, implying that apoptosis is caused by a loss of genomic integrity.
Abstract: Although a small decrease in survival and increase in tumor incidence was observed in ATR+/− mice, ATR−/− embryos die early in development, subsequent to the blastocyst stage and prior to 7.5 days p.c. In culture, ATR−/− blastocysts cells continue to cycle into mitosis for 2 days but subsequently fail to expand and die of caspase-dependent apoptosis. Importantly, caspase-independent chromosome breaks are observed in ATR−/− cells prior to widespread apoptosis, implying that apoptosis is caused by a loss of genomic integrity. These data show that ATR is essential for early embryonic development and must function in processes other than regulation of p53.
968 citations
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TL;DR: C-met receptor is present beneath the basal lamina on presumptive satellite cells in intact muscle and that c-met mRNA and protein are expressed by all myofiber-associated satellite cells from the time of explant through the course of activation, proliferation, and differentiation.
968 citations
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18 May 1997TL;DR: Analyses of electronic-coupling strengths suggest that the efficiency of long-range ET depends on the protein secondary structure: beta sheets appear to mediate coupling more efficiently than alpha-helical structures, and hydrogen bonds play a critical role in both.
Abstract: Electron-transfer (ET) reactions are key steps in a diverse array of biological transformations ranging from photosynthesis to aerobic respiration. A powerful theoretical formalism has been developed that describes ET rates in terms of two parameters: the nuclear reorganization [lambda] energy (1) and the electronic-coupling strength (HAB). Studies of ET reactions in ruthenium-modified proteins have probed [lambda] and HAB in several metalloproteins (cytochrome c, myoglobin, azurin). This work has shown that protein reorganization energies are sensitive to the medium surrounding the redox sites and that an aqueous environment, in particular, leads to large reorganization energies. Analyses of electronic-coupling strengths suggest that the efficiency of long-range ET depends on the protein secondary structure: [beta]sheets appear to mediate coupling more efficiently than [alpha]-helical structures, and hydrogen bonds play a critical role in both.
967 citations
Authors
Showing all 58155 results
Name | H-index | Papers | Citations |
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Eric S. Lander | 301 | 826 | 525976 |
Donald P. Schneider | 242 | 1622 | 263641 |
George M. Whitesides | 240 | 1739 | 269833 |
Yi Chen | 217 | 4342 | 293080 |
David Baltimore | 203 | 876 | 162955 |
Edward Witten | 202 | 602 | 204199 |
George Efstathiou | 187 | 637 | 156228 |
Michael A. Strauss | 185 | 1688 | 208506 |
Jing Wang | 184 | 4046 | 202769 |
Ruedi Aebersold | 182 | 879 | 141881 |
Douglas Scott | 178 | 1111 | 185229 |
Hyun-Chul Kim | 176 | 4076 | 183227 |
Phillip A. Sharp | 172 | 614 | 117126 |
Timothy M. Heckman | 170 | 754 | 141237 |
Zhenan Bao | 169 | 865 | 106571 |