4,677 research outputs found

    Control system for a variable period undulator prototype

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    The magnetic structure of the proposed variable period undulator consists of cylindrical magnets. Each magnet can be rotated by a small stepper motor, in order to adjust the magnetic field and form an arbitrarily shaped magnetic field profile on-axis. Meanwhile, a short prototype exists, equipped with a scalable control system to drive a large amount of stepper motors. This paper describes details of the control system implementation, results of the tests on different rotary encoder concepts for a magnet positioning feedback, and first magnetic measurements of the variable period undulator prototype

    Enzymatically Polymerized Organic Conductors on Model Lipid Membranes

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    Seamless integration between biological systems and electrical components is essential for enabling a twinned biochemical-electrical recording and therapy approach to understand and combat neurological disorders. Employing bioelectronic systems made up of conjugated polymers, which have an innate ability to transport both electronic and ionic charges, provides the possibility of such integration. In particular, translating enzymatically polymerized conductive wires, recently demonstrated in plants and simple organism systems, into mammalian models, is of particular interest for the development of next-generation devices that can monitor and modulate neural signals. As a first step toward achieving this goal, enzyme-mediated polymerization of two thiophene-based monomers is demonstrated on a synthetic lipid bilayer supported on a Au surface. Microgravimetric studies of conducting films polymerized in situ provide insights into their interactions with a lipid bilayer model that mimics the cell membrane. Moreover, the resulting electrical and viscoelastic properties of these self-organizing conducting polymers suggest their potential as materials to form the basis for novel approaches to in vivo neural therapeutics

    Модель формирования акустических характеристик твердых сред с упорядоченной трещиноватостью

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    Introduction. The development of new structural materials and improvement of existing technologies for the production of new products on their basis lead to the emergence of new types of medium discontinuities. Therefore, the development of new models of discontinuities that take the previously ignored parameters into account seems to be relevant for the purposes of nondestructive testing and structural measurements. This concerns, e.g., the roughness of adjacent surfaces of microcrack ordered sets.Aim. Theoretical substantiation for the processes of elastic waves propagation through an elastic medium containing an ordered lattice of microcracks with boundary conditions in the linear slip approximation, modified by taking into account the parameters of micro-convexities of microcrack rough boundaries. Database formation for experimental studies aimed at determining the physical and mechanical characteristics of structural materials.Materials and methods. The acoustic characteristics of materials were determined based on the derivation and solutions of dispersion equations describing the formation and propagation of effective longitudinal, transverse, and Rayleigh surface elastic waves in elastic media with ordered cracking. Their values were also used to determine the effective speed of Rayleigh surface waves.Results. The conducted simulation of elastic wave formation processes showed that an increase in the concentration of microcracks leads to a decrease in the phase velocities of effective longitudinal, transverse, and surface waves, as well as to an increase in the attenuation coefficients at given ultrasound frequencies and material parameters.Conclusion. The radius of the microsphere that replaces the surface micro-convexity and the roughness parameter Rz have a significant impact on the formation of physical and mechanical characteristics of materials, which are determined by the results of ultrasonic measurements. The developed model can be recommended as a basis for interpreting the results of ultrasonic measurements.Введение. Появление новых конструкционных материалов и совершенствование имеющихся технологий изготовления из них новых видов изделий приводят к появлению новых видов нарушений сплошности. В связи с этим актуальной для целей неразрушающего контроля и структурометрии является задача разработки новых моделей нарушений сплошности, учитывающих ранее не принимавшиеся во внимание параметры.Цель работы. Теоретическое описание процессов распространения упругих волн через среду, содержащую упорядоченную решетку микротрещин с граничными условиями в приближении "линейного скольжения", модернизированными с учетом параметров микровыступов шероховатых границ микротрещин. Формирование базы данных для экспериментальных исследований при определении физико-механических характеристик конструкционных материалов.Материалы и методы. Акустические характеристики материалов определялись на основе вывода и решений дисперсионных уравнений, описывающих образование и распространение в упругих средах с упорядоченной трещиноватостью эффективных продольных и поперечных, а также поверхностных волн.Результаты. Результаты моделирования процессов формирования упругих волн показали, что увеличение концентрации микротрещин приводит к уменьшению значений фазовых скоростей эффективных продольных, поперечных и поверхностных волн и повышению коэффициентов затухания при заданных значениях частоты ультразвука и параметров материала.Заключение. Учтенные параметры модели: среднее значение радиуса микросферы, замещающей микровыступ поверхности, и параметр шероховатости Rz существенно влияют на формирование физико-механических характеристик материалов, определяемых по результатам ультразвуковых измерений. Разработанная модель может рекомендоваться в качестве научной базы для интерпретации результатов ультразвуковых измерений

    Development of an APPLE-III undulator for FLASH-2

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    The use of circularly polarized soft X-rays at the FLASH-FEL at DESY will be a very versatile tool for investigation of dynamic properties in nanomagnetism. For that purpose, the development of a variable polarization undulator was started to provide an afterburner downstream of the FLASH2 SASE undulators. It will serve to produce circularly polarized light with a wavelength of 1.33 nm to 1.77 nm (890 eV - 700 eV) to investigate the L-edges of Fe, Co, and Ni. This wavelength range together with the future maximum beam energy of 1.35 GeV at FLASH leaves only a small and ambitious parameter window for the undulator if a noteworthy tunability range shall be provided.We report on design and development of an APPLE-III undulator with 17.5 mm period length operating at a minimum magnetic gap of 8 mm which will make use of a magnetic force compensation scheme. A short prototype has been built to verify and iterate both the mechanical and magnetic concept. Details on the keeper design, results of the magnetic measurements and the tuning concept will be presented

    The CCP4 suite: integrative software for macromolecular crystallography

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    The Collaborative Computational Project No. 4 (CCP4) is a UK-led international collective with a mission to develop, test, distribute and promote software for macromolecular crystallography. The CCP4 suite is a multiplatform collection of programs brought together by familiar execution routines, a set of common libraries and graphical interfaces. The CCP4 suite has experienced several considerable changes since its last reference article, involving new infrastructure, original programs and graphical interfaces. This article, which is intended as a general literature citation for the use of the CCP4 software suite in structure determination, will guide the reader through such transformations, offering a general overview of the new features and outlining future developments. As such, it aims to highlight the individual programs that comprise the suite and to provide the latest references to them for perusal by crystallographers around the world

    Development of cryogenic undulators and measurement equipment for PETRA IV

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    DESY is planning to upgrade its current storage ring PETRA III into the ultra-lowemittance photon source PETRA IV. The current H6BA cell design for the PETRA IV latticewill allow for insertion devices of up to 4 m length in the standard straight sections. In order toallow some beamlines to not only benefit from the performance improvements by the machinebut also from the undulators, we started looking into using advanced undulator schemes aswell. We decided to start the design of cryogenically cooled permanent magnet undulators(CPMUs) based on (Nd,Pr)FeB magnets for PETRA IV, since this technique has already beenproven successfully by various other facilities. We will present the planned design for themagnet keepers, the pole tuning mechanism as well as a testbed for keepers under cryogenicconditions. We will also show a preliminary design for the in-situ Hall-probe bench currentlydeveloped for the upcoming PETRA IV CPMUs

    Effect of Product Removal in Hydrogen Peroxide Electrosynthesis on Mesoporous Chromium(III) Oxide

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    On-site electrosynthesis of hydrogen peroxide (H2O2) is a promising alternative technology to the conversional centralized anthraquinone oxidation process. Here, we report a platinum group metal (PGM)-free H2O2 electrogenerator with mesoporous Cr2O3 and NiCo2O4 used as electrocatalysts for oxygen reduction and evolution reactions (ORR and OER), respectively. The catalysts were synthesized via a hydrothermal synthesis route and had pore sizes of 3 and 7 nm and specific surface areas of 112 and 62 m2 g–1, respectively. Mesoporous Cr2O3 was evaluated in a half cell with 0.1 M KOH for electrocatalytic oxygen reduction, which shows 2.2 transferred electrons per oxygen and an in situ H2O2 yield of 70%. This enables the electrosynthesis of hydrogen peroxide in alkaline medium using Cr2O3 as a 2e-ORR-H2O2 electrocatalyst, with oxygen evolution as an auxiliary reaction on NiCo2O4. The effect of electrolyte flow on the H2O2 electrogenerator was investigated. It is observed that one-way feeding of the catholyte suppresses deterioration of the electrocatalyst and allows a faradic conversion up to ∼90% with a production rate of ∼0.36 [g (h·gcat)−1], operating within the cell voltage of 1.2 V. This work demonstrates both a viable method for electrosynthesis of H2O2 production using PGM-free electrocatalysts and the possibility to obtain a high faradic efficiency by mitigating the effect from catalyst degradation

    The CCP4 suite : integrative software for macromolecular crystallography

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    The Collaborative Computational Project No. 4 (CCP4) is a UK-led international collective with a mission to develop, test, distribute and promote software for macromolecular crystallography. The CCP4 suite is a multiplatform collection of programs brought together by familiar execution routines, a set of common libraries and graphical interfaces. The CCP4 suite has experienced several considerable changes since its last reference article, involving new infrastructure, original programs and graphical interfaces. This article, which is intended as a general literature citation for the use of the CCP4 software suite in structure determination, will guide the reader through such transformations, offering a general overview of the new features and outlining future developments. As such, it aims to highlight the individual programs that comprise the suite and to provide the latest references to them for perusal by crystallographers around the world
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