641 research outputs found

    An Invisible Quantum Tripwire

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    We present here a quantum tripwire, which is a quantum optical interrogation technique capable of detecting an intrusion with very low probability of the tripwire being revealed to the intruder. Our scheme combines interaction-free measurement with the quantum Zeno effect in order to interrogate the presence of the intruder without interaction. The tripwire exploits a curious nonlinear behaviour of the quantum Zeno effect we discovered, which occurs in a lossy system. We also employ a statistical hypothesis testing protocol, allowing us to calculate a confidence level of interaction-free measurement after a given number of trials. As a result, our quantum intruder alert system is robust against photon loss and dephasing under realistic atmospheric conditions and its design minimizes the probabilities of false positives and false negatives as well as the probability of becoming visible to the intruder.Comment: Improved based on reviewers comments; 5 figure

    Protein Crystal Growth Apparatus for Microgravity

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    Apparatus for growing protein crystals under microgravity environment includes a plurality of protein growth assemblies stacked one above the other within a canister. Each of the protein growth assemblies includes a tray having a number of spaced apart growth chambers recessed below an upper surface. the growth chambers each having an upstanding pedestal and an annular reservoir about the pedestal for receiving a wick and precipitating agents. A well is recessed below the top of each pedestal to define a protein crystal growth receptacle. A flexible membrane is positioned on the upper surface of each tray and a sealing plate is positioned above each membrane, each sealing plate having a number of bumpers corresponding in number and alignment to the pedestals for forcing the membrane selectively against the upper end of the respective pedestal to seal the reservoir and the receptacle when the sealing plate is forced down

    Quantum interferometric optical lithography:towards arbitrary two-dimensional patterns

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    As demonstrated by Boto et al. [Phys. Rev. Lett. 85, 2733 (2000)], quantum lithography offers an increase in resolution below the diffraction limit. Here, we generalize this procedure in order to create patterns in one and two dimensions. This renders quantum lithography a potentially useful tool in nanotechnology.Comment: 9 pages, 5 figures Revte

    Archeological Survey Of The Proposed Loop 288 From IH 35E North Of Denton To IH35E At Vintage Boulevard South Of Denton, Denton County, Texas

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    This report documents the results of an archeological survey conducted on behalf of the Texas Department of Transportation, Dallas District, for proposed construction of a new segment of Loop 288 that would extend from IH 35E north of Denton to IH 35E at Vintage Boulevard south of Denton (CSJs 2250-02-013 and 2250-02-014). The road project involves construction of new location roadway for a distance of approximately eight miles. Archeological work was performed to comply with Section 106 of the National Historic Preservation Act and the Antiquities Code of Texas, under Texas Antiquities Permit 5660. AmaTerra Environmental, Inc. (AmaTerra) personnel conducted an intensive archeological survey of the project area from June 11 to June 17, 2010, to identify possible cultural resources within the Area of Potential Effect (APE). The project area was subject to 100 percent pedestrian survey wherever access to public and private properties was available. Survey included visual inspection of the landscape, 152 shovel test excavations, and excavation of eight backhoe trenches. No archeological sites were identified within the APE, and no artifacts were collected as this was a non-collection survey. Jon J. Dowling served as Project Archeologist and Rachel Feit acted as Principal Investigator. Approximately 224 person-hours were invested in the field investigation. No archeological resources were identified that meet eligibility requirements for designation as a State Archeological Landmark according to 13 Texas Administrative Code 26, or for listing in the National Register of Historic Places under 36 CFR 60.4. Additional work in connection with the proposed undertaking is not recommended. AmaTerra recommends that the proposed project should proceed to completion

    Contingent Fee Litigation in New York City

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    Since 1957, New York courts have required contingent fee lawyers to file closing statements that disclose settlement amounts, lawyers\u27 fees, an accounting of expenses, and other information. This Article provides a preliminary analysis of these data for the period 2004- 2013. Among this Article\u27s findings are that settlement rates in New York state courts are very high (84%) relative to previous studies; that very few cases are resolved by dispositive motions; that litigated cases and settled cases have almost exactly the same average recovery; that median litigation expenses, other than attorney\u27s fees, are 3% of gross recovery; that claims are disproportionately from poor neighborhoods; and that attorneys\u27 fees are almost always one-third of net recovery, which is the maximum allowed by law

    Quantum Clock Synchronization Based on Shared Prior Entanglement

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    We demonstrate that two spatially separated parties (Alice and Bob) can utilize shared prior quantum entanglement, and classical communications, to establish a synchronized pair of atomic clocks. In contrast to classical synchronization schemes, the accuracy of our protocol is independent of Alice or Bob's knowledge of their relative locations or of the properties of the intervening medium.Comment: 4 page

    Structural diversity in the AdoMet radical enzyme superfamily

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    AdoMet radical enzymes are involved in processes such as cofactor biosynthesis, anaerobic metabolism, and natural product biosynthesis. These enzymes utilize the reductive cleavage of S-adenosylmethionine (AdoMet) to afford l-methionine and a transient 5′-deoxyadenosyl radical, which subsequently generates a substrate radical species. By harnessing radical reactivity, the AdoMet radical enzyme superfamily is responsible for an incredible diversity of chemical transformations. Structural analysis reveals that family members adopt a full or partial Triose-phosphate Isomerase Mutase (TIM) barrel protein fold, containing core motifs responsible for binding a catalytic [4Fe–4S] cluster and AdoMet. Here we evaluate over twenty structures of AdoMet radical enzymes and classify them into two categories: ‘traditional’ and ‘ThiC-like’ (named for the structure of 4-amino-5-hydroxymethyl-2-methylpyrimidine phosphate synthase (ThiC)). In light of new structural data, we reexamine the ‘traditional’ structural motifs responsible for binding the [4Fe–4S] cluster and AdoMet, and compare and contrast these motifs with the ThiC case. We also review how structural data combine with biochemical, spectroscopic, and computational data to help us understand key features of this enzyme superfamily, such as the energetics, the triggering, and the molecular mechanisms of AdoMet reductive cleavage. This article is part of a Special Issue entitled: Radical SAM Enzymes and Radical Enzymology.Wellcome Trust (London, England) (091162/Z/10/Z)National Science Foundation (U.S.) (NSF Grant MCB-0543833)Howard Hughes Medical Institute (Investigator

    Hubble Space Telescope Planetary Camera Images of NGC 1316

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    We present HST Planetary Camera V and I~band images of the central region of the peculiar giant elliptical galaxy NGC 1316. The inner profile is well fit by a nonisothermal core model with a core radius of 0.41" +/- 0.02" (34 pc). At an assumed distance of 16.9 Mpc, the deprojected luminosity density reaches \sim 2.0 \times 10^3 L_{\sun} pc−3^{-3}. Outside the inner two or three arcseconds, a constant mass-to-light ratio of ∼2.2±0.2\sim 2.2 \pm 0.2 is found to fit the observed line width measurements. The line width measurements of the center indicate the existence of either a central dark object of mass 2 \times 10^9 M_{\sun}, an increase in the stellar mass-to-light ratio by at least a factor of two for the inner few arcseconds, or perhaps increasing radial orbit anisotropy towards the center. The mass-to-light ratio run in the center of NGC 1316 resembles that of many other giant ellipticals, some of which are known from other evidence to harbor central massive dark objects (MDO's). We also examine twenty globular clusters associated with NGC 1316 and report their brightnesses, colors, and limits on tidal radii. The brightest cluster has a luminosity of 9.9 \times 10^6 L_{\sun} (MV=−12.7M_V = -12.7), and the faintest detectable cluster has a luminosity of 2.4 \times 10^5 L_{\sun} (MV=−8.6M_V = -8.6). The globular clusters are just barely resolved, but their core radii are too small to be measured. The tidal radii in this region appear to be ≤\le 35 pc. Although this galaxy seems to have undergone a substantial merger in the recent past, young globular clusters are not detected.Comment: 21 pages, latex, postscript figures available at ftp://delphi.umd.edu/pub/outgoing/eshaya/fornax
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