4,239,131 research outputs found

    D\u27Ou Etes-Vous Revisited

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    D\u27Ou Etes-Vous deals with a phenomenon which has always been of interest to me. Not only in French, but in Russian as well, the naming of people from their places of origin is very complicated

    Method for reducing snap in magnetic amplifiers

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    Method of reducing snap in magnetic amplifiers uses a degenerative feedback circuit consisting of a resistor and a separate winding on a magnetic core. The feedback circuit extends amplifier range by allowing it to be used at lower values of output current

    Design and fabrication of densely integrated silicon quantum dots using a VLSI compatible hydrogen silsesquioxane electron beam lithography process

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    Hydrogen silsesquioxane (HSQ) is a high resolution negative-tone electron beam resist allowing for direct transfer of nanostructures into silicon-on-insulator. Using this resist for electron beam lithography, we fabricate high density lithographically defined Silicon double quantum dot (QD) transistors. We show that our approach is compatible with very large scale integration, allowing for parallel fabrication of up to 144 scalable devices. HSQ process optimisation allowed for realisation of reproducible QD dimensions of 50 nm and tunnel junction down to 25 nm. We observed that 80% of the fabricated devices had dimensional variations of less than 5 nm. These are the smallest high density double QD transistors achieved to date. Single electron simulations combined with preliminary electrical characterisations justify the reliability of our device and process

    Experimental library screening demonstrates the successful application of computational protein design to large structural ensembles

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    The stability, activity, and solubility of a protein sequence are determined by a delicate balance of molecular interactions in a variety of conformational states. Even so, most computational protein design methods model sequences in the context of a single native conformation. Simulations that model the native state as an ensemble have been mostly neglected due to the lack of sufficiently powerful optimization algorithms for multistate design. Here, we have applied our multistate design algorithm to study the potential utility of various forms of input structural data for design. To facilitate a more thorough analysis, we developed new methods for the design and high-throughput stability determination of combinatorial mutation libraries based on protein design calculations. The application of these methods to the core design of a small model system produced many variants with improved thermodynamic stability and showed that multistate design methods can be readily applied to large structural ensembles. We found that exhaustive screening of our designed libraries helped to clarify several sources of simulation error that would have otherwise been difficult to ascertain. Interestingly, the lack of correlation between our simulated and experimentally measured stability values shows clearly that a design procedure need not reproduce experimental data exactly to achieve success. This surprising result suggests potentially fruitful directions for the improvement of computational protein design technology

    Fourier transforming a trapped Bose-Einstein condensate by waiting a quarter of the trap period: simulation and applications

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    We investigate the property of isotropic harmonic traps to Fourier transform a weakly interacting Bose–Einstein condensate (BEC) every quarter of a trap period. We solve the Gross–Pitaevskii equation numerically to investigate the time evolution of interacting BECs in the context of the Fourier transform, and we suggest potential applications

    Bootstrapping word alignment via word packing

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    We introduce a simple method to pack words for statistical word alignment. Our goal is to simplify the task of automatic word alignment by packing several consecutive words together when we believe they correspond to a single word in the opposite language. This is done using the word aligner itself, i.e. by bootstrapping on its output. We evaluate the performance of our approach on a Chinese-to-English machine translation task, and report a 12.2% relative increase in BLEU score over a state-of-the art phrase-based SMT system

    Three Little Sacks

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    In former times people depended much more than nowadays on a well-stocked memory, or at least one differently stocked with little reference to printed materials. Few could read, fewer still had many books, and pens and paper were expensive. So it was, for instance, that names of rulers were associated with tags and epithets which immediately summoned up qualities or events which located them in the history of their countries. In the United States we have a few ekenames like The Father of His Country, Honest Abe and The Great Communicator, but of these only the first and second seem to have settled in, although neither is much used. The Great Communicator is more of a movable epithet than anything else, has been applied to others before, and undoubtedly will be applied to others later

    Probing Coherent Vibrations of Organic Phosphonate Radical Cations with Femtosecond Time-Resolved Mass Spectrometry

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    Organic phosphates and phosphonates are present in a number of cellular components that can be damaged by exposure to ionizing radiation. This work reports femtosecond time-resolved mass spectrometry (FTRMS) studies of three organic phosphonate radical cations that model the DNA sugar-phosphate backbone: dimethyl methylphosphonate (DMMP), diethyl methylphosphonate (DEMP), and diisopropyl methylphosphonate (DIMP). Upon ionization, each molecular radical cation exhibits unique oscillatory dynamics in its ion yields resulting from coherent vibrational excitation. DMMP has particularly well-resolved 45 fs (732 ± 28 cm−1) oscillations with a weak feature at 610–650 cm−1, while DIMP exhibits bimodal oscillations with a period of ∼55 fs and two frequency features at 554 ± 28 and 670–720 cm−1. In contrast, the oscillations in DEMP decay too rapidly for effective resolution. The low- and high-frequency oscillations in DMMP and DIMP are assigned to coherent excitation of the symmetric O–P–O bend and P–C stretch, respectively. The observation of the same ionization-induced coherently excited vibrations in related molecules suggests a possible common excitation pathway in ionized organophosphorus compounds of biological relevance, while the distinct oscillatory dynamics in each molecule points to the potential use of FTRMS to distinguish among fragment ions produced by related molecules

    Word-to-Word Models of Translational Equivalence

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    Parallel texts (bitexts) have properties that distinguish them from other kinds of parallel data. First, most words translate to only one other word. Second, bitext correspondence is noisy. This article presents methods for biasing statistical translation models to reflect these properties. Analysis of the expected behavior of these biases in the presence of sparse data predicts that they will result in more accurate models. The prediction is confirmed by evaluation with respect to a gold standard -- translation models that are biased in this fashion are significantly more accurate than a baseline knowledge-poor model. This article also shows how a statistical translation model can take advantage of various kinds of pre-existing knowledge that might be available about particular language pairs. Even the simplest kinds of language-specific knowledge, such as the distinction between content words and function words, is shown to reliably boost translation model performance on some tasks. Statistical models that are informed by pre-existing knowledge about the model domain combine the best of both the rationalist and empiricist traditions
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