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91.
Tsuge M Berski S Stachowski R Räsänen M Latajka Z Khriachtchev L 《The journal of physical chemistry. A》2012,116(18):4510-4517
We investigate the conditions when noble-gas hydrides can be found in real environments and report on the preparation and identification of the HXeBr···CO(2) complex in a xenon matrix and HXeBr in a carbon dioxide matrix. The H-Xe stretching mode of the HXeBr···CO(2) complex in a xenon matrix is observed at 1557 cm(-1), showing a spectral shift of +53 cm(-1) from the HXeBr monomer. The calculations at the CCSD(T)/aug-cc-pVTZ-PP(Xe,Br) level of theory give two stable structures for the HXeBr···CO(2) complex with frequency shifts of +55 and +103 cm(-1), respectively. On the basis of the calculations, the experimentally observed band is assigned to the more stable structure with a "parallel" geometry. The HXeBr molecule was prepared in a carbon dioxide matrix and has the H-Xe stretching frequency of 1646 cm(-1), meaning a strong matrix shift and stabilization of the H-Xe bond. The deuterated species DXeBr in a carbon dioxide matrix absorbs at 1200 cm(-1). This is the first case where a noble-gas hydride is prepared in a molecular solid. The thermal stabilities of HXeBr and HXeBr···CO(2) complex in a xenon matrix and HXeBr in a carbon dioxide matrix were examined. We have found a high thermal stability of HXeBr in carbon dioxide ice (at least up to 100 K), i.e., under conditions that may occur in nature. 相似文献
92.
93.
E.M. Dutkiewicz J. Suchanicz V. Bovtun K. Konieczny P. Czaja K. Kluczewska 《Phase Transitions》2016,89(7-8):823-828
ABSTRACTThermal expansion, Raman and dielectric properties of the lead-free (1?x)Na0.5Bi0.5TiO3-xSrTiO3 (x = 0, 0.08 and 0.1) ceramic solid solutions, fabricated by the conventional solid-state reaction method, were investigated. The Sr-doping results in an increase of the dielectric permittivity, broadening of the permittivity maximum, enhancement of the relaxation near depolarization temperature, broadening of the Raman bands and shift of all anomalies toward lower temperatures. The observed effects are attributed to an increase of the degree of cationic disorder and enhancement of the relaxor-like features. Anomalies in the thermal expansion strain were observed at the temperatures corresponding to the dielectric anomalies but not related to any phase transitions. These anomalies are supposed to follow changes of the averaged unit cell volume in the temperature interval of tetragonal and rhombohedral phase coexistence. 相似文献
94.
W. Czaja 《Zeitschrift für Physik B Condensed Matter》1971,12(3):226-236
An approximate calculation of the ground state energy of direct and indirect free excitons for group IV and group III–V semiconductors is presented. The basic assumption in this treatment is that the anisotropy of the effective masses can be neglected, however, the degeneracy of the valence band cannot. The resulting exciton ground state energy has the usual form but with a reduced mass \(\overline \mu \) given by ( \(\overline \mu \) )?1=(m e)?1+(m lh)?1+(m hh)?1. The agreement with experiments is considerably improved as compared to the conventional ground state energy comprising the reduced mass defined as (μ)?1=(m e)?1+(m hh)?1. Anisotropy corrections are shown to be of minor importance in many cases. However, for the heavier III–V-compounds the neglect of linear terms inE(k) for the valence band results in more serious errors, which invalidate the present theoretical approach. 相似文献
95.
Weber S Schroeder C Kacprzak S Mathes T Kowalczyk RM Essen LO Hegemann P Schleicher E Bittl R 《Photochemistry and photobiology》2011,87(3):574-583
Blue-light sensitive photoreceptory BLUF domains are flavoproteins, which regulate various, mostly stress-related processes in bacteria and eukaryotes. The photoreactivity of the flavin adenine dinucleotide (FAD) cofactor in three BLUF domains from Rhodobacter sphaeroides, Synechocystis sp. PCC 6803 and Escherichia coli have been studied at low temperature using time-resolved electron paramagnetic resonance. Photoinduced flavin triplet states and radical-pair species have been detected on a microsecond time scale. Differences in the electronic structures of the FAD cofactors as reflected by altered zero-field splitting parameters of the triplet states could be correlated with changes in the amino-acid composition of the various BLUF domains' cofactor binding pockets. For the generation of the light-induced, spin-correlated radical-pair species in the BLUF domain from Synechocystis sp. PCC 6803, a tyrosine residue near the flavin's isoalloxazine moiety plays a critical role. 相似文献
96.
Alexander Czaja Samer Awad Olga E. Eremina Augusta Fernando Cristina Zavaleta 《Journal of Raman spectroscopy : JRS》2024,55(5):566-580
Surface-enhanced Raman scattering nanoparticles (SERS NPs) offer powerful optical contrast features for imaging assays. Their gold core enhances the inelastic scattering cross section, allowing highly sensitive and rapid detection, and their characteristic sets of narrow spectral bands give them unsurpassed multiplexing capabilities. Multiplexed hyperspectral images are commonly unmixed using a compensation matrix of reference spectra to produce quantitative image channels illustrating the distribution of each material. It is these unmixed channels that are fit for interpretation from assays utilizing SERS NP contrast agents. Some factors that may impact SERS NP quantitative and dynamic range capabilities may include endogenous background heterogeneity, the ability of unmixing algorithms to account for signal variances, and linear system conditioning imposed by contrast agent signals. We report on hyperspectral Raman imaging of mixtures of SERS NPs from an expanded library of contrast agents. We study increasing plexity and varying degrees of system conditioning as inputs to a diverse set of classical, non-negatively constrained, and regularized regression algorithms to investigate which signal features and unmixing methods deliver the most promising quantitation performance with the least error. Raman imaging of SERS NP mixtures is performed on controlled substrates and representative biological specimens, and experimental results are compared against ground truth data. We evaluate spectral fitting fidelity, quantitation, and specificity correlations with system conditioning. Spectral unmixing with a regularized hybrid of least squares regression with principal component analysis (HLP) algorithm approximated spectra with 3.5× better fitting fidelity and 3× better quantitation robustness with tissue background compared with simpler unmixing routines. 相似文献
97.
Atilio Reyes Romero Katarzyna Kubica Radoslaw Kitel Ismael Rodríguez Katarzyna Magiera-Mularz Alexander Dmling Tad A. Holak Ewa Surmiak 《Molecules (Basel, Switzerland)》2022,27(23)
By binding to the spliceosomal protein Snu66, the human ubiquitin-like protein Hub1 is a modulator of the spliceosome performance and facilitates alternative splicing. Small molecules that bind to Hub1 would be of interest to study the protein-protein interaction of Hub1/Snu66, which is linked to several human pathologies, such as hypercholesterolemia, premature aging, neurodegenerative diseases, and cancer. To identify small molecule ligands for Hub1, we used the interface analysis, peptide modeling of the Hub1/Snu66 interaction and the fragment-based NMR screening. Fragment-based NMR screening has not proven sufficient to unambiguously search for fragments that bind to the Hub1 protein. This was because the Snu66 binding pocket of Hub1 is occupied by pH-sensitive residues, making it difficult to distinguish between pH-induced NMR shifts and actual binding events. The NMR analyses were therefore verified experimentally by microscale thermophoresis and by NMR pH titration experiments. Our study found two small peptides that showed binding to Hub1. These peptides are the first small-molecule ligands reported to interact with the Hub1 protein. 相似文献
98.
Radoslaw Bonikowski Jozef Kula Anna Bujacz Anna Wajs Wieslaw Majzner 《Tetrahedron: Asymmetry》2009,20(22):2583-2588
3-Isopropyl-7a-methyl-1,2,3,6,7,7a-hexahydro-inden-5-one is a building block used in the reconstruction of the cyathane skeleton. In this article, a new and efficient method of the synthesis for (3R,7aR)-3-isopropyl-7a-methyl-1,2,3,6,7,7a-hexahydro-inden-5-one has been described. 相似文献
99.
Michal Chudy Ilona Grabowska Patrycja Ciosek Alicja Filipowicz-Szymanska Dorota Stadnik Iwona Wyzkiewicz Elzbieta Jedrych Marcin Juchniewicz Maciej Skolimowski Karina Ziolkowska Radoslaw Kwapiszewski 《Analytical and bioanalytical chemistry》2009,395(3):647-668
This article presents an overview of various miniaturized devices and technologies developed by our group. Innovative, fast and cheap procedures for the fabrication of laboratory microsystems based on commercially available materials are reported and compared with well-established microfabrication techniques. The modules fabricated and tested in our laboratory can be used independently or they can be set up in different configurations to form functional measurement systems. We also report further applications of the presented modules e.g. disposable poly(dimethylsiloxane) (PDMS) microcuvettes, fibre optic detectors, potentiometric sensors platforms, microreactors and capillary electrophoresis (CE) microchips as well as integrated microsystems e.g. double detection microanalytical systems, devices for studying enzymatic reactions and a microsystem for cell culture and lysis. 相似文献
100.
Wojciech Czaja Gitta Kutyniok Darrin Speegle 《Journal of Fourier Analysis and Applications》2008,14(4):514-537
Pseudoframes for subspaces have been recently introduced by Li and Ogawa as a tool to analyze lower dimensional data with
arbitrary flexibility of both the analyzing and the dual sequence.
In this paper we study Gabor pseudoframes for affine subspaces by focusing on geometrical properties of their associated sets
of parameters. We first introduce a new notion of Beurling dimension for discrete subsets of ℝ
d
by employing a certain generalized Beurling density. We present several properties of Beurling dimension including a comparison
with other notions of dimension showing, for instance, that our notion includes the mass dimension as a special case. Then
we prove that Gabor pseudoframes for affine subspaces satisfy a certain Homogeneous Approximation Property, which implies
invariance under time–frequency shifts of an approximation by elements from the pseudoframe.
The main result of this paper is a classification of Gabor pseudoframes for affine subspaces by means of the Beurling dimension
of their sets of parameters. This provides us, in particular, with a Nyquist dimension which separates sets of parameters
of pseudoframes from those of non-pseudoframes and which links a fixed value to sets of parameters of pseudo-Riesz sequences.
These results are even new for the special case of Gabor frames for an affine subspace.
相似文献