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Sample Position (sample + position)
Selected AbstractsSample movement optimization for uniform heating in microwave heating ovensINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 2 2007J. L. Pedreño-Molina Abstract A technique for improving the uniformity of heating patterns of dielectric samples in a multimode cavity is presented based on a strategic movement of the sample inside the microwave applicator. Different optimization algorithms are compared to determine the best microwave irradiation period for each sample position. A new optimization procedure that minimizes electric field variance is also presented and assessed. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007. [source] Application of white-beam X-ray microdiffraction for the study of mineralogical phase identification in ancient Egyptian pigmentsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007P. A. Lynch High-brightness synchrotron X-rays together with precision achromatic focusing optics on beamline 7.3.3 at the Advanced Light Source have been applied for Laue microdiffraction analysis of mineralogical phases in Egyptian pigments. Although this task is usually performed using monochromatic X-ray diffraction, the Laue technique was both faster and more reliable for the present sample. In this approach, white-beam diffraction patterns are collected as the sample is raster scanned across the incident beam (0.8,µm × 0.8,µm). The complex Laue diffraction patterns arising from illumination of multiple grains are indexed using the white-beam crystallographic software package XMAS, enabling a mineralogical map as a function of sample position. This methodology has been applied to determine the mineralogy of colour pigments taken from the ancient Egyptian coffin of Tjeseb, a priestess of the Apis bull dating from the Third Intermediate to Late period, 25th Dynasty to early 26th Dynasty (747 to 600 BC). For all pigments, a ground layer of calcite and quartz was identified. For the blue pigment, cuprorivaite (CuCaSi4O10) was found to be the primary colouring agent with a grain size ranging from ,10 to 50,µm. In the green and yellow samples, malachite [Cu2(OH)2CO3] and goethite [FeO(OH)] were identified, respectively. Grain sizes from these pigments were significantly smaller. It was possible to index some malachite grains up to ,20,µm in size, while the majority of goethite grains displayed a nanocrystalline particle size. The inability to obtain a complete mineralogical map for goethite highlights the fact that the incident probe size is considerably larger than the grain size. This limit will continue to improve as the present trend is toward focusing optics approaching the diffraction limit (,1000× smaller beam area). [source] MarqX: a new program for whole-powder-pattern fittingJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2000Y. H. Dong MarqX is a computer program for the modelling of powder diffraction data. It can be used for an unconstrained profile fitting (pattern decomposition, PD) or constrained modelling of the whole powder pattern (Pawley method, PM), for single- as well as multiple-phase samples. The program output includes: lattice parameters or peak positions (for PM and PD, respectively), width and shape of the diffraction peak (in terms of half width at half-maximum and mixing parameter of a pseudo-Voigt function), corrected for the instrumental broadening component, intensity, peak area and profile asymmetry. In addition, errors on the goniometer zero and shift in sample position with respect to the goniometric axis can also be modelled, together with distance and relative intensity of the spectral components of the X-ray beam (e.g.K,1 and K,2). Specific output files are provided for line-profile analysis, including the Williamson,Hall plot and Warren,Averbach method. [source] Coherence and wavefront characterization of Si-111 monochromators using double-grating interferometryJOURNAL OF SYNCHROTRON RADIATION, Issue 3 2010Ana Diaz A study of the coherence and wavefront properties of a pseudo-channel-cut monochromator in comparison with a double-crystal monochromator is presented. Using a double-grating interferometer designed for the hard X-ray regime, the complex coherence factor was measured and the wavefront distortions at the sample position were analyzed. A transverse coherence length was found in the vertical direction that was a factor of two larger for the channel-cut monochromator owing to its higher mechanical stability. The wavefront distortions after different optical elements in the beam, such as monochromators and mirrors, were also quantified. This work is particularly relevant for coherent diffraction imaging experiments with synchrotron sources. [source] Temperature gradient analyzers for compact high-resolution X-ray spectrometersJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2010D. Ishikawa Compact high-resolution X-ray spectrometers with a one-dimensional temperature gradient at the analyzer crystal are considered. This gradient, combined with the use of a position-sensitive detector, makes it possible to relax the usual Rowland-circle condition, allowing increased space at the sample position for a given energy resolution or arm radius. Thus, for example, it is estimated that ,meV resolution is possible with a 3,m analyzer arm and 200,mm clearance between the sample and detector. Simple analytic formulae are provided, supported by excellent agreement with ray-tracing simulations. One variation of this method also allows the detector position sensitivity to be used to determine momentum transfer, effectively improving momentum resolution without reducing (slitting down) the analyzer size. Application to medium-resolution (,10,100,meV) inelastic X-ray scattering spectrometers with large angular acceptance is discussed, where this method also allows increased space at the sample. In some cases the application of a temperature gradient can improve the energy resolution even with a single-element detector. [source] Recent developments in microdiffraction on protein crystalsJOURNAL OF SYNCHROTRON RADIATION, Issue 1 2004Christian Riekel Protein crystallography microdiffraction and micro small-angle X-ray scattering at a third-generation synchrotron radiation source undulator beamline both require a compromise on beam size and beam divergence. Micro small-angle X-ray scattering requires in addition an as-close-as-possible angular approach to the direct beam, which is mainly limited by the beam divergence at the sample position. Both techniques have been developed at the ESRF microfocus beamline in a complimentary way. The development of a dedicated microgoniometer in the frame of an EMBL/ESRF collaboration has revealed the potential of microdiffraction for protein crystallography and is a step in the quest for user friendly instrumentation. [source] The crystallography beamline I711 at MAX,IIJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2000Y. Cerenius A new X-ray crystallographic beamline is operational at the MAX,II synchrotron in Lund. The beamline has been in regular use since August 1998 and is used both for macro- and small molecule diffraction as well as powder diffraction experiments. The radiation source is a 1.8,T multipole wiggler. The beam is focused vertically by a bendable mirror and horizontally by an asymmetrically cut Si(111) monochromator. The wavelength range is 0.8,1.55,Å with a measured flux at 1,Å of more than 1011,photons,s,1 in 0.3,mm × 0.3,mm at the sample position. The station is currently equipped with a Mar345 imaging plate, a Bruker Smart 1000 area CCD detector and a Huber imaging-plate Guinier camera. An ADSC 210 area CCD detector is planned to be installed during 2000. [source] Steady-state and transient thermal lens behavior in the dual beam Z-scan arrangementLASER PHYSICS LETTERS, Issue 6 2006D. Lorenc Abstract Output beam spatial properties of a dual wavelength CW DPSS laser have been studied using the thermal lens (photothermal) effect. In employing the Z-scan technique both the steady-state and time-dependent thermal lens signal as a function of sample position could be examined simultaneously. The influence of sample thickness and laser output power upon obtained spatial properties of incident beam is studied. It is shown, that both the steady state and the transient photothermal signal provide comparable results. (© 2006 by Astro, Ltd. Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Comparison of mass spectra of peptides in different matrices using matrix-assisted laser desorption/ionization and a multi-turn time-of-flight mass spectrometer, MULTUM-IMGRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 10 2008Hisanao Hazama The mass spectra of peptides obtained with different matrices were compared using a matrix-assisted laser desorption/ionization (MALDI) ion source and a multi-turn time-of-flight (TOF) mass spectrometer, MULTUM-IMG, which has been developed at Osaka University. Two types of solid matrices, , -cyano-4-hydroxycinnamic acid (CHCA) and 2,5-dihydroxybenzoic acid (DHB), and a liquid matrix made from a mixture of 3-aminoquinoline and CHCA were used. When measuring the peak signal intensity of human angiotensin II [M+H]+ from a fixed sample position, the liquid matrix produced a stable signal over 1000 laser shots, while the signal obtained with CHCA and DHB decayed after about 300 and 100 shots, respectively. Significant differences in the mass resolving power were not observed between the spectra obtained with the three matrices. Signal peak areas were measured as a function of the cycle number in a multi-turn ion trajectory, i.e., the total flight time over a millisecond time scale. For both [M+H]+ of human angiotensin II and bovine insulin, the decay of the signal peak area was the most significant with CHCA, while that measured with DHB was the smallest. The results of the mean initial ion velocity measurements suggested that the extent of metastable decomposition of the analyte ions increased in order of DHB, the liquid matrix, and CHCA, which is consistent with the difference in the decay of the signal peak area as the total flight time increased. Copyright © 2008 John Wiley & Sons, Ltd. [source] Chemical shift imaging (CSI) by precise object displacement,,MAGNETIC RESONANCE IN CHEMISTRY, Issue 3 2006Sebastien Leclerc Abstract A mechanical device (NMR lift) has been built to displace vertically an object (typically an NMR sample tube) inside the NMR probe with an accuracy of 1 µm. A series of single pulse experiments are performed for incremented vertical positions of the sample. With a sufficiently spatially selective radio-frequency (r.f.) field, one obtains chemical shift information along the displacement direction (one-dimensional chemical shift imaging (CSI)). Knowing the vertical r.f. field profile (the amplitude of the r.f. field along the vertical direction), one can reconstruct the spectrum associated with all the slices corresponding to consecutive sample positions and improve the spatial resolution, which is simply related to the accuracy of the displacement device. Beside tests performed on phantoms, the method has been applied to solvent penetration in polymers and to benzene diffusion in a heterogeneous zeolite medium. Copyright © 2006 John Wiley & Sons, Ltd. [source] A combined ion source for fast switching between electrospray and matrix-assisted laser desorption/ionization in Fourier transform ion cyclotron resonance mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 17 2002Gökhan Baykut A new ion source has been developed for Fourier transform ion cyclotron resonance mass spectrometry (FTICRMS) that enables quick changes between matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) modes. When operating as an ESI source, the sample solution is sprayed through an angled nebulizer. The generated ions pass through a glass capillary followed by a skimmer and three sequential hexapole ion guides. Ions can be accumulated in the third hexapole (storage hexapole) before they are injected into the ICR trap. The second hexapole is mounted on a movable platform which also carries the MALDI sample plate. During the switch from ESI to MALDI, this platform moves the second hexapole out of the hexapole series and locates a MALDI sample plate with 384 sample positions into the area directly in front of the storage hexapole. The storage hexapole is in a medium pressure chamber (MPC) which has windows both for the incoming laser beam and for the observation optics, as well as a gas tube for pulsing collision gas into the chamber. During the MALDI operation the focused laser beam enters the MPC, passes between the hexapole rods and irradiates a MALDI sample on the target plate. The sample molecules are desorbed/ionized into the storage hexapole and simultaneously cooled by collisions with the pulsed gas. Ions desorbed from multiple laser shots can be accumulated in this hexapole before they are transferred to the ICR trap. With the combined ion source a computer-controlled switch between MALDI and ESI modes is possible in less than a minute, depending on the position of the MALDI target on the 384-spot plate. Immediate acquisition of mass spectra is possible after mode switching without the need for tuning or re-calibration. Copyright © 2002 John Wiley & Sons, Ltd. [source] | ||||||||||