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Now showing items 1 - 16 of 138660

  • Simulation, Microfabrication, and Control of a Microheater Array

    Zheng, C.   Balasubramanian, G. P. S.   Tan, Y.   Maniatty, A. M.   Hull, R.   Wen, J. T.  

    This paper describes the simulation, fabrication, and feedback control of a microheater array designed for the implementation of real-time control during thermal evolution of microstructure. The ten-channel heating array was designed through finite element simulation and microfabricated to be compatible with in situ imaging in a scanning electronmicroscope. Control algorithms are implemented that demonstrate cooperative control of the temperature (using calibrated Ti heater line resistances as a proxy) across the set of channels in the array. The goal of this system is to be able to generate controlled thermal, and thus microstructural, and property distribution during processing of polycrystalline materials.
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  • Mechanisms of Focused Ion Beam Implantation Damage and Recovery in Si

    Balasubramanian, G. P. S.   Hull, R.  

    The ion current density in focused ion beam (FIB) systems, 0.1-10 A cm(-2), is at least three orders of magnitude greater than that in commercial broad ion beam implanters. This large difference in ion current density is expected to strongly affect the damage recovery dynamics. In this work, we study the ion implantation damage and recovery of Si(100) substrates implanted with 1 x 10(12)-5 x 10(15) Si cm(-2) fluences of 60-keV Si2+ at normal incidence in a mass-selecting FIB. Additionally, damage and recovery in different broad ion beam implants of 60-keV Si+ were studied for a comparison. For recovering implantation damage, specimens were annealed for different times at 730-900A degrees C in an ultra-high purity nitrogen ambient, and for characterizing damage and recovery, Raman spectroscopy at wavelengths 405 nm and 514 nm was carried out. Raman measurements comprised of measurements of crystalline Si (c-Si) peak height of the peak at 520 cm(-1), and the peak shift relative to that of un-implanted reference Si. Our measurements of structural damage-calculated from the attenuation in the c-Si peak heights for the implants relative to that of unimplanted Si(100)-indicates that the FIB implantations lead to a greater as-implanted damage but also typically lead to a better recovery than that for the commercial broad-area implants. The underlying mechanisms for these observations are discussed.
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  • Mechanisms of Focused Ion Beam Implantation Damage and Recovery in Si

    Balasubramanian, G. P. S.   Hull, R.  

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  • Damage recovery of FIB modified Si for directed-assembly of semiconductor nanostructures

    Balasubramanian, G. P. S.   Hull, R.  

    Focused ion beam (FIB) techniques have previously been shown to have applications in templating semiconductor nanostructure growth on Si. To assess crystalline quality in this method, or in other FIB-based nano-fabrication methods in Si, we assess in this work FIB-implantation damage in Si and subsequent recovery by annealing. Specifically, we study Si substrates implanted to 1 x 10(12)-5 x 10(15) ions cm(-2) fluences of 30 kV Si2+, Ge2+ and Ga+ incident normally at room temperature, covering a structural damage regime from almost no damage to amorphization. Raman spectroscopy with incident photons of wavelength 405 and 514 nm were used for probing structural damage in different depths in as-implanted and thermally annealed substrates. Annealing was performed for varying times at 730-900 degrees C in ultra-high purity nitrogen ambient. Structural damage quantification was performed through measurements of peak height and position of the crystalline Si peak at 520 cm(-1). Our analysis shows that a structural damage parameter, D, (defined by subtracting from unity, the ratio of the height of the Si Raman peak in implanted/annealed samples to that for the Si peak in an unimplanted standard, such that D =3D 0.00 and D =3D 1.00 correspond to pristine single crystal and amorphous Si respectively) is 0.05 or less in all the Si and Ge implants after annealing to 900 degrees C, 1800 s. However, D for the Ga implants is close to zero for Ga fluences up to 3 x 10(13) cm(-2) but increases steadily to 0.19 for 5 x 10(15) Ga cm(-2) under these annealing conditions. The underlying damage recovery mechanisms are discussed.
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  • Damage recovery of FIB modified Si for directed-assembly of semiconductor nanostructures

    Balasubramanian, G. P. S.   Hull, R.  

    Focused ion beam (FIB) techniques have previously been shown to have applications in templating semiconductor nanostructure growth on Si. To assess crystalline quality in this method, or in other FIB-based nano-fabrication methods in Si, we assess in this work FIB-implantation damage in Si and subsequent recovery by annealing. Specifically, we study Si substrates implanted to 1 × 1012–5 × 1015 ions cm−2 fluences of 30 kV Si2+, Ge2+ and Ga+ incident normally at room temperature, covering a structural damage regime from almost no damage to amorphization. Raman spectroscopy with incident photons of wavelength 405 and 514 nm were used for probing structural damage in different depths in as-implanted and thermally annealed substrates. Annealing was performed for varying times at 730–900 °C in ultra-high purity nitrogen ambient. Structural damage quantification was performed through measurements of peak height and position of the crystalline Si peak at 520 cm−1. Our analysis shows that a structural damage parameter, D, (defined by subtracting from unity, the ratio of the height of the Si Raman peak in implanted/annealed samples to that for the Si peak in an unimplanted standard, such that D = 0.00 and D = 1.00 correspond to pristine single crystal and amorphous Si respectively) is 0.05 or less in all the Si and Ge implants after annealing to 900 °C, 1800 s. However, D for the Ga implants is close to zero for Ga fluences up to 3 × 1013 cm−2 but increases steadily to 0.19 for 5 × 1015 Ga cm−2 under these annealing conditions. The underlying damage recovery mechanisms are discussed.
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  • P?G Tait\"s statistical models

    Lewis   Elizabeth F  

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  • A G(enomic)P(ositioning)S(ystem) for Plant RNAPII Transcription

    Leng, Xueyuan   Thomas, Quentin   Rasmussen, Simon Horskjaer  

    Post-translational modifications (PTMs) of histone residues shape the landscape of gene expression by modulating the dynamic process of RNA polymerase II (RNAPII) transcription. The contribution of particular histone modifications to the definition of distinct RNAPII transcription stages remains poorly characterized in plants. Chromatin immunoprecipitation combined with next-generation sequencing (ChIP-seq) resolves the genomic distribution of histone modifications. Here, we review histone PTM ChIP-seq data in Arabidopsis thaliana and find support for a Genomic Positioning System (GPS) that guides RNAPII transcription. We review the roles of histone PTM 'readers', 'writers', and 'erasers', with a focus on the regulation of gene expression and biological functions in plants. The distinct functions of RNAPII transcription during the plant transcription cycle may rely, in part, on the characteristic histone PTM profiles that distinguish transcription stages.
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  • Quasi $$s^*g$$s∗g-Open and Quasi $$s^*g$$s∗g-Closed Functions

    Kannan, K.; Ganesan, S.  

    The research of functions by algebraic methods shows a very significant part in modern mathematics. The characterization of topological spaces by semigroups of quasi open, continuous, open, and closed mappings was taken by many researchers in recent days. In the present paper quasi s*g-open, quasi s*g-closed functions, some of its characterizations and the property of s*g-normal spaces are studied.
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  • Quasi $$s^*g$$s?g-Open and Quasi $$s^*g$$s?g-Closed Functions

    Kannan, K.   Ganesan, S.  

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  • P&G\"s profits fall because of charge in Venezuela

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  • P G Tait\"s schoolboy introduction to complex numbers

    Lewis   Elizabeth F.  

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  • Structural transition between $L^{p}(G)$ and $L^{p}(G/H)$

    Tavallaei, Narguess   Ramezanpour, Mohammad   Olfatian Gillan, Behrooz  

    Let H be a compact subgroup of a locally compact group G. We consider the homogeneous space G/H equipped with a strongly quasi-invariant Radon measure mu. For 1 <= p <= +infinity, we introduce a norm decreasing linear map from L-p(G) onto L-p(G/H, mu) and show that L-p(G/H, mu) may be identified with a quotient space of L-p(G). Also, we prove that L-p(G/H, mu) is isometrically isomorphic to a closed subspace of L-p(G). These help us study the structure of the classical Banach spaces constructed on a homogeneous space via those created on topological groups.
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  • The QUAX-g(p)g(s) experiment to search for monopole-dipole Axion interaction

    Crescini, N.   Braggio, C.   Carugno, G.   Falferi, P.   Ortolan, A.   Ruoso, G.  

    The QCD axion is an hypothetical particle introduced to solve the strong CP problem of standard model of particle physics and is of interest as a possible component of cold dark matter. In the axion scenario, J.E. Moody and F. Wilczek showed that a new macroscopic long-range force, mediated by axion exchange, acts on electron spins, and that such force can be described in terms of an effective magnetic field. The QUAX-g(p)g(s) experiment, carried out at INFN Laboratori Nazionali di Legnaro, is designed to search for the effects on magnetized samples of the effective field produced by unpolarized mass sources. As this field is macroscopic, it can be detected by measuring the change of magnetization of a paramagnetic Gadolinium silicate (GSO) crystal cooled at liquid helium temperature. The axion effective field induced magnetization can be detected with a SQUID magnetometer. By varying the position of the of source masses, the induced GSO magnetization is modulated at acoustic frequencies. Although the full QUAX-gpgs sensitivity has not been yet exploited, we are able to measure a magnetization of 10(-17) T at few tens of Hz. With this sensitivity we expect to further improve the upper limit of the coupling of the predicted long-range force in the 10(-3) to 1 m interval.
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  • G. P. S. management system

    A management system using Global Positioning System receivers for tracking remote units from a central office and quickly and conveniently determining if those remote units have varied from a set of predetermined parameters of operation. The system also includes provisions that allows information to be sent from the remote units to the central office and vice versa. The system also has safety features that promote the rapid dispatch of law enforcement personnel when requests for emergency assistance have been made from the remote units.
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  • Reply from T. L. Dutka, J. P. Mollica, G. S. Posterino and G. D. Lamb

    T. L. Dutka   J. P. Mollica   G. S. Posterino and G. D. Lamb  

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  • Reply from T. L. Dutka, J. P. Mollica, G. S. Posterino and G. D. Lamb

    Dutka, T. L.   Mollica, J. P.   Posterino, G. S.   Lamb, G. D.  

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