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排序方式: 共有516条查询结果,搜索用时 15 毫秒
51.
Conny Unger Olga Kofanova Kate Sokolowska Daniel Lehmann Fay Betsou 《Electrophoresis》2015,36(17):2072-2081
The analytical and clinical validity of analyses of RNA samples destined for clinical diagnosis and therapeutic management is directly impacted by RNA quality. RNA is affected by heat, enzymatic degradation, and Ultraviolet (UV) light. RNA from three eukaryotic cell lines was degraded by heat, RNase, or UV light. RNA integrity values obtained with the benchmark Agilent Bioanalyzer 2100 system were compared with those from the more recent QIAxcel Advanced system. The application of this novel method has allowed us to unravel differences between RNA biophysical and biochemical degradation modes. Agilent RNA integrity number (RIN) and QIAxcel RIS were comparable in heat‐degraded and RNase III‐degraded RNA. Agilent RIN and QIAxcel RIS were comparable at a RIN decision level of 7 in UV‐degraded RNA but not overall. The QIAxcel RIS method was more precise than Agilent RIN for RIN<8, while the inverse was true for RIN≥8. Greater degradation of mRNA and rRNA in UV‐damaged samples hampered the Agilent RIN calculation algorithm. Overall, RIS was more robust than RIN for assessing RNA integrity. The ΔΔCt‐values for heat‐ and UV‐degraded RNA samples showed slightly higher correlation with RIS than with RIN. RNA integrity can be used to categorize RNA samples for suitability for downstream gene expression analyses, independently of the RNA degradation mechanism. The new method QIAxcel is more robust and therefore allows more accurate categorization of compromised RNA samples. 相似文献
52.
A number of plane stress numerical analyses of the mode I elastoplastic fracture mechanics problem have been performed in the past using the Huber–Mises yield criterion. This study employs instead the Tresca yield condition using an incremental theory of plasticity for a stationary crack. A commercial finite element program is used to solve the opening mode of fracture problem (mode I) for a square plate containing a central crack under generalized plane stress loading conditions. A biaxial uniform tensile traction is applied to the edges of a thin plate composed of a linear elastic non-work hardening material under small strain assumptions. The finite element results are compared with the analytical predictions of the Dugdale plastic strip model for a crack in an infinite plate subject to a biaxial uniform load at infinity. 相似文献
53.
Dietrich PM Horlacher T Girard-Lauriault PL Gross T Lippitz A Min H Wirth T Castelli R Seeberger PH Unger WE 《Langmuir : the ACS journal of surfaces and colloids》2011,27(8):4808-4815
Carbohydrate films on gold based on dimannoside thiols (DMT) were prepared, and a complementary surface chemical analysis was performed in detail by X-ray photoelectron spectroscopy (XPS), time-of-flight secondary ion mass spectrometry (ToF-SIMS), near-edge X-ray absorption fine structure (NEXAFS), FT-IR, and contact angle measurements in order to verify formation of ω-carbohydrate-functionalized alkylthiol films. XPS (C 1s, O 1s, and S 2p) reveals information on carbohydrate specific alkoxy (C-O) and acetal moieties (O-C-O) as well as thiolate species attached to gold. Angle-resolved synchrotron XPS was used for chemical speciation at ultimate surface sensitivity. Angle-resolved XPS analysis suggests the presence of an excess top layer composed of unbound sulfur components combined with alkyl moieties. Further support for DMT attachment on Au is given by ToF-SIMS and FT-IR analysis. Carbon and oxygen K-edge NEXAFS spectra were interpreted by applying the building block model supported by comparison to data of 1-undecanethiol, poly(vinyl alcohol), and polyoxymethylene. No linear dichroism effect was observed in the angle-resolved C K-edge NEXAFS. 相似文献
54.
Pierre-Luc Girard-Lauriault Juan-Carlos Ruiz Thomas Gross Michael R. Wertheimer Wolfgang E. S. Unger 《Plasma Chemistry and Plasma Processing》2011,31(4):535-550
Nitrogen (N)-rich organic thin films were deposited using both low-pressure plasma- and vacuum-ultraviolet-based techniques, from mixtures of ammonia (NH3) and ethylene (C2H4). These films were investigated using angle-resolved and excitation energy resolved X-ray photoelectron spectroscopy (ARXPS and ERXPS, respectively) in order to determine their sub-surface chemical profiles. These two techniques enable one to tune the ??XPS 95%?? information depth, z 95%, by varying either the angle or the excitation energy. Using a combination of both techniques, z 95% can be varied continuously from 0.7 to 11 nm. The surface-near chemistry is investigated using both high-resolution C 1s spectra and elemental concentrations derived from elemental peak intensities. Results show that while laboratory XPS, and even ARXPS, suggest homogenous surface chemistries, the novel combination of ARXPS and ERXPS points to the existence of a compositional profile in the extreme outer surface layer. Our conclusions are supported by simulations using SESSA software. 相似文献
55.
Unger EL Morandeira A Persson M Zietz B Ripaud E Leriche P Roncali J Hagfeldt A Boschloo G 《Physical chemistry chemical physics : PCCP》2011,13(45):20172-20177
The hole transporting medium in solid-state dye-sensitized solar cells can be utilized to harvest sunlight. Herein we demonstrate that a triphenylamine-based dye, used as hole-transporting medium, contributes to the photocurrent in a squaraine-sensitized solid-state dye-sensitized solar cell. Steady-state photoluminescence measurements have been used to distinguish between electron transfer and energy transfer processes leading to energy conversion upon light absorption in the hole-transporting dye. 相似文献
56.
Weakly hyperbolic involutions are introduced and a proof is given of the following local–global principle: a central simple
algebra with involution of any kind is weakly hyperbolic if and only if its signature is zero for all orderings of the ground
field. Also, the order of a weakly hyperbolic algebra with involution is a power of two, this being a direct consequence of
a result of Scharlau. As a corollary an analogue of Pfister's local–global principle is obtained for the Witt group of hermitian
forms over an algebra with involution.
Received: 29 October 2001; in final form: 9 August 2002 /
Published online: 16 May 2003
Mathematics Subject Classification (2000): 16K20, 11E39 相似文献
57.
MnBi films were prepared by annealing Bi-Mn composite films. The grain size of the MnBi films was strongly influenced by the
temperatureT
s
of the film substrate during evaporation of Bi and Mn. For 55-nm-thick films, the numberN of MnBi grains per mm2 decreased from 4×106 per mm2 forT
s
=+90°C to 1 per mm2 forT
s
=−40°C. The diameters of the largest grains observed were about 5 mm. For interpretation of this result, the formation process
of MnBi films was observed magneto-optically and electronmicroscopically. It was found thatN was determined by the structure of Bi in the Bi-Mn composite films and that this strongly depended onT
s
. 相似文献
58.
59.
Among the most commonly occurring mixed-integer problems in operations research are linear programs with fixed charge objective functions. In this paper special structures of the equivalent form of such problems obtained from optimal solutions to their continuous relaxations are characterized and exploited in a series of penalty procedures for branch-and-bound type algorithms. The selection, construction, and solution of such penalty problems are discussed, and computational experience with the procedures is presented. 相似文献
60.
Dr. A. Hubert Dipl. Phys. W. Unger Prof. Dr. J. Kranz 《Zeitschrift für Physik A Hadrons and Nuclei》1969,224(1-3):148-155
The single crystal magnetostriction constants of hexagonal cobalt are measured between ?200 °C and 400 °C in magnetic fields up to 26 kOe. The shear constant λE=2 λD?λA/2?λC/2 which is of interest in connection with domain structures, as well as the volume constant λV=λA+ λB+ λC show a relatively strong temperature dependance, which cannot be explained by present theories. 相似文献