7,487 research outputs found

    α\alpha- and β\beta- Relaxation Dynamics of a fragile plastic crystal

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    We present a thorough dielectric investigation of the relaxation dynamics of plastic crystalline Freon112, which exhibits freezing of the orientational degrees of freedom into a glassy crystal below 90 K. Among other plastic crystals, Freon112 stands out by being relatively fragile within Angell's classification scheme and by showing an unusually strong β\beta-relaxation. Comparing the results to those on Freon112a, having only a single molecular conformation, points to the importance of the presence of two molecular conformations in Freon112 for the explanation of its unusual properties.Comment: 17 pages, 6 figure

    Multiple Charge State Beam Acceleration at Atlas

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    A test of the acceleration of multiple charge-state uranium beams was performed at the ATLAS accelerator. A 238U+26 beam was accelerated in the ATLAS PII linac to 286 MeV (~1.2 MeV/u) and stripped in a carbon foil located 0.5 m from the entrance of the ATLAS Booster section. A 58Ni9+ 'guide' beam from the tandem injector was used to tune the Booster for 238U+38. All charge states from the stripping were injected into the booster and accelerated. Up to 94% of the beam was accelerated through the Booster linac, with losses mostly in the lower charge states. The measured beam properties of each charge state and a comparison to numerical simulations are reported in this paper.Comment: LINAC2000, MOD0

    Value dimensions and relationship postures in dyadic 'key relationship programmes'

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    Business-to-business marketing is often concerned with the way in which companies manage strategically important relationships with their counterparts: their Key Relationship Programmes (KRPs). These relationships can be managed through the implementation of specific managerial and organisational structures, commonly implemented via Key Account Programmes (on the supplier side) or Key Supplier Programmes (on the customer side). Underlying this managerial process is an implicit assumption that these important relationships bring some form of additional value to one or both parties involved. However, a dyadic view of how this value is created and shared between the parties remains an under-researched area. In this conceptual paper, we use the multi-faceted value construct introduced in Pardo et al. (2006) and posit that the buyer's or seller's value strategies can be best understood as being internally, exchange, or relationship based. This in turn allows us to analyse the value gained as being the outcome of one of nine generic key relationship postures within any dyadic KRP. We focus on an analysis of so-called "managed" relationship postures and identify a number of dyadic activities and competencies that we hypothesise are important in managing such KRPs, and which can form the basis for further empirical research

    Upgrade of the ATLAS 10 GHz ECRIS

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    A major renovation of the ATLAS 10 GHz ECRIS, which began operations in 1987, is in the planning and acquisition phase. The old two-stage source will be converted to a single stage design including a high gradient magnetic field, electron donor disk, large radial ports, and flexible modular design. Eight solenoid coils taken from the existing ECR will produce the axial mirror. The individual coils will be encased in an iron yoke that optimizes the magnetic field. Computer modeling of the field profile yields a minimum field along the axis of 3.0 kG with mirror ratios of 4.4 and 2.9. An open hexapole configuration consisting of Nd-Fe-B bars enclosed in an austenitic stainless steel housing will be placed in an aluminium plasma chamber that will be water cooled along the poles of the hexapole. The hexapole field at the chamber wall, 4 cm in radius, is expected to be 9.3 kG along the magnet poles and 5.7 kG along the center of the pole gaps, which are 2.4 cm wide. A 3D model produced from individual 2D field profiles was used to check the end effects of the hexapole. Based on the models this new field configuration is capable of supporting a second ECR resonance zone at 14 GHz, which may be implemented at a later date

    Comparative Genomics Analysis of a New Exiguobacterium Strain from Salar de Huasco Reveals a Repertoire of Stress-Related Genes and Arsenic Resistance

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    Indexación: Web of Science; Scopus.The Atacama Desert hosts diverse ecosystems including salt flats and shallow Andean lakes. Several heavy metals are found in the Atacama Desert, and microorganisms growing in this environment show varying levels of resistance/tolerance to copper, tellurium, and arsenic, among others. Herein, we report the genome sequence and comparative genomic analysis of a new Exiguobacterium strain, sp. SH31, isolated from an altiplanic shallow athalassohaline lake. Exiguobacterium sp. SH31 belongs to the phylogenetic Group II and its closest relative is Exiguobacterium sp. S17, isolated from the Argentinian Altiplano (95% average nucleotide identity). Strain SH31 encodes a wide repertoire of proteins required for cadmium, copper, mercury, tellurium, chromium, and arsenic resistance. Of the 34 Exiguobacterium genomes that were inspected, only isolates SH31 and S17 encode the arsenic efflux pump Acr3. Strain SH31 was able to grow in up to 10 mM arsenite and 100 mM arsenate, indicating that it is arsenic resistant. Further, expression of the ars operon and acr3 was strongly induced in response to both toxics, suggesting that the arsenic efflux pump Acr3 mediates arsenic resistance in Exiguobacterium sp. SH31.http://journal.frontiersin.org/article/10.3389/fmicb.2017.00456/ful

    Dielectric spectroscopy in benzophenone: The beta relaxation and its relation to the mode-coupling Cole-Cole peak

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    We report a thorough characterization of the glassy dynamics of benzophenone by broadband dielectric spectroscopy. We detect a well pronounced beta relaxation peak developing into an excess wing with increasing temperature. A previous analysis of results from Optical-Kerr-effect measurements on this material within the mode coupling theory revealed a high-frequency Cole-Cole peak. We address the question if this phenomenon also may explain the Johari-Goldstein beta relaxation, a so far unexplained spectral feature inherent to glass-forming matter, mainly observed in dielectric spectra. Our results demonstrate that according to the present status of theory, both spectral features seem not to be directly related.Comment: 4 pages, 3 figures; second version as published; small changes of text according to referee suggestions; title changed according to editor's demand

    Development and operation of a pixel segmented liquid-filled linear array for radiotherapy quality assurance

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    A liquid isooctane (C8_{8}H18_{18}) filled ionization linear array for radiotherapy quality assurance has been designed, built and tested. The detector consists of 128 pixels, each of them with an area of 1.7 mm ×\times 1.7 mm and a gap of 0.5 mm. The small pixel size makes the detector ideal for high gradient beam profiles like those present in Intensity Modulated Radiation Therapy (IMRT) and radiosurgery. As read-out electronics we use the X-Ray Data Acquisition System (XDAS) with the Xchip developed by the CCLRC. Studies concerning the collection efficiency dependence on the polarization voltage and on the dose rate have been made in order to optimize the device operation. In the first tests we have studied dose rate and energy dependences, and signal reproducibility. Dose rate dependence was found lower than 2.5 % up to 5 Gy min1^{-1}, and energy dependence lower than 2.1 % up to 20 cm depth in solid water. Output factors and penumbras for several rectangular fields have been measured with the linear array and were compared with the results obtained with a 0.125 cm3^{3} air ionization chamber and radiographic film, respectively. Finally, we have acquired profiles for an IMRT field and for a virtual wedge. These profiles have also been compared with radiographic film measurements. All the comparisons show a good correspondence. Signal reproducibility was within a 2% during the test period (around three months). The device has proved its capability to verify on-line therapy beams with good spatial resolution and signal to noise ratio.Comment: 16 pages, 12 figures Submitted to Phys. Med. Bio

    Fiber Optic Tactical Local Network (FOTLAN)

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    A 100 Mbit/s FDDI (fiber distributed data interface) network interface unit is described that supports real-time data, voice and video. Its high-speed interrupt-driven hardware architecture efficiently manages stream and packet data transfer to the FDDI network. Other enhancements include modular single-mode laser-diode fiber optic links to maximize node spacing, optic bypass switches for increased fault tolerance, and a hardware performance monitor to gather real-time network diagnostics
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