2,510 research outputs found

    The Washington University MultiMedia eXplorer

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    The Washington University MultiMedia eXplorer (MMX) is a complete, host-independent multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiographic images over the Washington University broadband ATM network. If the host is equipped with an ATM interface card, normal network traffic is supported via T and Y connections. The MMX consists of an ATMizer and three multimedia subsystems. The ATMizer implements the host interface, the interface to the ATM network, and the interface to the three multimdeia channels. This paper describes the architecture of the MMX, the software used with the system, and the applications which have been developed to demonstrate the capability of broadband ATM networks for multimedia applications

    Production Quality Video Over Broadband Networks: A Description of the System and Two Interactive Applications

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    The Washington University MultiMedia eXplorer (MMX) is a complete, host-independent multimedia system capable of transmitting and receiving JPEG-compressed video, CD-quality audio, and high-resolution radiographic images over the Washington University broadband ATM network. If the host is equipped with an ATM interface card, normal network traffic can be supported via an ATM extension port on the MMX. The major components of the MMX are an ATMizer and three multimedia channels. The ATMizer implements the host interface, the interface to the ATM network, and hte interface to the three multimdeia channels. This paper describes the architecture of the MMX, the software used with the system, and two applications which have been developed to demonstrate the capability of broadband ATM networks for multimedia applications

    Classical limit in terms of symbolic dynamics for the quantum baker's map

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    We derive a simple closed form for the matrix elements of the quantum baker's map that shows that the map is an approximate shift in a symbolic representation based on discrete phase space. We use this result to give a formal proof that the quantum baker's map approaches a classical Bernoulli shift in the limit of a small effective Plank's constant.Comment: 12 pages, LaTex, typos correcte

    Thin-Film Metamaterials called Sculptured Thin Films

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    Morphology and performance are conjointed attributes of metamaterials, of which sculptured thin films (STFs) are examples. STFs are assemblies of nanowires that can be fabricated from many different materials, typically via physical vapor deposition onto rotating substrates. The curvilinear--nanowire morphology of STFs is determined by the substrate motions during fabrication. The optical properties, especially, can be tailored by varying the morphology of STFs. In many cases prototype devices have been fabricated for various optical, thermal, chemical, and biological applications.Comment: to be published in Proc. ICTP School on Metamaterials (Augsut 2009, Sibiu, Romania

    Catalase vs Peroxidase Activity of a Manganese(II) Compound: Identification of a Mn(III)-(ÎĽ-O)2-Mn(IV) Reaction Intermediate by Electrospray Ionization Mass Spectrometry and Electron Paramagnetic Resonance Spectroscopy

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    Herein, we report reactivity studies of the mononuclear water-soluble complex [Mn(II)(HPClNOL)(η1-NO3)(η2-NO3)] 1, where HPClNOL ) 1-(bis-pyridin-2-ylmethyl-amino)-3-chloropropan-2-ol, toward peroxides (H2O2 and tertbutylhydroperoxide). Both the catalase (in aqueous solution) and peroxidase (in CH3CN) activities of 1 were evaluated using a range of techniques including electronic absorption spectroscopy, volumetry (kinetic studies), pH monitoring during H2O2 disproportionation, electron paramagnetic resonance (EPR), electrospray ionization mass spectrometry in the positive ion mode [ESI(+)-MS], and gas chromatography (GC). Electrochemical studies showed that 1 can be oxidized to Mn(III) and Mn(IV). The catalase-like activity of 1 was evaluated with and without pH control. The results show that the pH decreases when the reaction is performed in unbuffered media. Furthermore, the activity of 1 is greater in buffered than in unbuffered media, demonstrating that pH influences the activity of 1 toward H2O2. For the reaction of 1 with H2O2, EPR and ESI(+)-MS have led to the identification of the intermediate [Mn(III)Mn(IV)(μ- O)2(PClNOL)2]+. The peroxidase activity of 1 was also evaluated by monitoring cyclohexane oxidation, using H2O2 or tert-butylhydroperoxide as the terminal oxidants. Low yields (<7%) were obtained for H2O2, probably because it competes with 1 for the catalase-like activity. In contrast, using tert-butylhydroperoxide, up to 29% of cyclohexane conversion was obtained. A mechanistic model for the catalase activity of 1 that incorporates the observed lag phase in O2 production, the pH variation, and the formation of a Mn(III)-(μ-O)2-Mn(IV) intermediate is proposed

    Dynamic clamp with StdpC software

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    Dynamic clamp is a powerful method that allows the introduction of artificial electrical components into target cells to simulate ionic conductances and synaptic inputs. This method is based on a fast cycle of measuring the membrane potential of a cell, calculating the current of a desired simulated component using an appropriate model and injecting this current into the cell. Here we present a dynamic clamp protocol using free, fully integrated, open-source software (StdpC, for spike timing-dependent plasticity clamp). Use of this protocol does not require specialist hardware, costly commercial software, experience in real-time operating systems or a strong programming background. The software enables the configuration and operation of a wide range of complex and fully automated dynamic clamp experiments through an intuitive and powerful interface with a minimal initial lead time of a few hours. After initial configuration, experimental results can be generated within minutes of establishing cell recording

    Matrix Norms, BPS Bounds and Marginal Stability in N=8 Supergravity

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    We study the conditions of marginal stability for two-center extremal black holes in N-extended supergravity in four dimensions, with particular emphasis on the N=8 case. This is achieved by exploiting triangle inequalities satisfied by matrix norms. Using different norms and relative bounds among them, we establish the existence of marginal stability and split attractor flows both for BPS and some non-BPS solutions. Our results are in agreement with previous analysis based on explicit construction of multi-center solutions.Comment: 1+15 pages; v2: some new formulas added and misprints corrected; v3: typos fixed, various refinements, Sec. 2.4 rewritten; to appear on JHE

    Optimum Unambiguous Discrimination of Linearly Independent Pure States

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    Given nn linearly independent pure states and their prior probabilities, we study the problem of optimum unambiguous discrimination of these states. We derive the properties of the optimum solution and the equations that must be satisfied by the optimum measurement strategy which achieves the maximum average success probability, and also give the detailed steps to obtain the optimum solution and the optimum measurement strategy. The general method and results we obtain are also illustrated both numerically and geometrically. We derive a simple analytical formula of the maximum average success probability of unambiguous discrimination for a given set of pure states, and it can be used to simplify the calculation of the optimum solution in some situations. We also obtain the analytical solution of a generalized equal-probability measurement problem using the equations we introduce. Finally, as another application of our result, we study the optimum unambiguous discrimination problem of three linearly independent pure states in details and obtain analytical solutions for some special cases.Comment: 20 pages, 4 figures and 1 tabl
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