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21.
J. Valenta V. Bradnováa V. Kohlováa F. Jukl S. I. Kulikova N. M. Nevzorova 《辐射效应与固体损伤》2013,168(4):333-336
Abstract Solid-state nuclear track detectors, made of Cd doped AgCl crystals, are commonly prepared by rolling into the form of thin foils. Subsequent long-term relaxation is however needed to obtain good quality tracks. The present communication shows for the first time that this detector “ageing” is reflected in lowtemperature (77 K) luminescence spectra. Maximum of the emission band shows a slow (lasting for ~ 100 hours) blue shift, the magnitude of which (as much as 25 nm) depends on the compression ratio caused by the rolling. The shift is believed to be due to the rearrangement of Cd++ ions around freshly introduced dislocations. This finding opens the possibility of monitoring non-destructively the process of detector ageing and to determine the minimum time required for saturation. 相似文献
22.
F. L. Vook 《辐射效应与固体损伤》2013,168(3-4):155-160
This paper was given as the opening address at the 1970 Albany International Conference on Radiation Effects in Semiconductors, and it attempts to establish a general overview of the field by concentrating on recent research developments and important unanswered questions. The continuing importance of impurity-defect interactions, of microscopic defect identification, and of the necessity for more theoretical calculations are emphasized. The rapid development of the field of ion implantation and its close relationship with radiation effects studies are pointed out. It is predicted that research in compound semiconductors will increase rapidly with close beneficial interaction with ion implantation studies. 相似文献
23.
P. C. Deka H. Sarma Subir Sarkar T. D. Goswami B. K. Sarma 《Indian Journal of Physics》2009,83(7):1025-1030
With the growing understanding of the role of radon and its daughter products as major sources of radiation exposure, the
importance of large number of estimation of radon concentration in various parts of the country is realized. Inhalation of
radon, thoron and their decay products is the major source of the total radioactive dose received by the human population
from natural radiation. The indoor radon and thoron progeny levels in Nalbari area of Assam are studied by using the LR-115
(type II) Solid State Nuclear Track Detector in Plastic Twin Chamber dosimeter. Radon and thoron progeny levels in different
types of dwellings for one full calendar year are presented in this paper. For Assam Type (A.T.) houses, indoor radon progeny
concentrations vary from 0.17 to 0.64 mWL with an annual geometric mean of 0.27 mWL and that for Reinforced Cement Concrete
(R.C.C.) houses vary from 0.22 mWL to 0.60 mWL with the annual geometric mean of 0.37 mWL. The thoron progeny levels in A.T.
houses also vary from 0.01 to of 0.05 mWL with an annual geometric mean of 0.02 mWL and that for R.C.C. houses vary from 0.02
to 0.08 mWL with the annual geometric mean of 0.04 mWL.
相似文献
24.
Chitosan is a natural based polymer obtained by alkaline deacetylation of chitin, exhibiting excellent properties such as non‐toxicity, biocompatibility and biodegradability. N‐Methylenephenyl phosphonic chitosan (NMPPC) is synthesized from chitosan by reacting with phenyl phosphonic acid using formaldehyde. The NMPPC was characterized by FTIR, 31P‐NMR, X‐ray diffraction, scanning electron microscopy, thermogravimeteric analysis and solubility studies. A significant decrease of molecular weight was observed in the NMPPC. The TGA studies suggested that NMPPC has less thermal stability than chitosan. The X‐ray diffraction analysis showed that NMPPC was amorphous in nature. The solubility property of the polymer was improved after the incorporation of a phenyl phosphonic group. 相似文献
25.
In this paper the affine connection approach will be used to calculate the elastic constants of nematic liquid crystals. Following this approach, which was originally conceived to compute the nematic viscosity coefficients, an expression for the elastic constants, without adjustable free parameters, will be formulated in terms of a temperature dependent metric, whose non‐isotropic part is proportional to the tensorial order parameter of the nematic phase. The dependence of the elastic constants on the scalar order parameter, in the geometry of the nematic molecules, and in the anisotropic part of the molecular interaction, will be determined. 相似文献
26.
《Journal of carbohydrate chemistry》2013,32(7-8):593-601
The crystal structure of methyl α‐d‐mannofuranoside was determined by X‐ray crystallography. The C‐1–C‐2, C‐2–C‐3, C‐3–C‐4, C‐4–O and O‐4–C‐1 distances within the furanoside ring are 1.513(2), 1.523(2), 1.516(2), 1.445(2) and 1.422(2) Å, respectively. The hydrogen bonding consists of O–H–O interactions which include the anomeric oxygen but exclude the ring oxygen atom. The two hydroxyls OH‐6 and OH‐2 are H‐bond acceptors and donors with H···O distances of 1.92–1.93 Å, whereas the OH‐3 and OH‐5 are only H‐bond donor [H···O distance of 2.04(2) Å]. Additionally, OH‐6 participates in a weak hydrogen bond to the anomeric oxygen [H···O distance of 2.19(3) Å]. The crystalline methyl α‐d‐mannofuranoside adopts an 3 E ring conformation. The analysis of 13C CPMAS NMR chemical shifts for solid methyl α‐d‐mannofuranoside confirm such H‐bonding pattern. 相似文献
27.
Dr. Meiling Guo Prof. Dr. Zhaochi Feng Dr. Jan P. Hofmann Prof. Dr. Bert M. Weckhuysen Dr. Fengtao Fan Prof. Dr. Can Li 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14200-14204
Microporous vanadosilicates with octahedral VO6 and tetrahedral SiO4 units, better known as AM‐6, have been hydrothermally synthesized with different morphologies by controlling the Na/K molar ratio of the initial gel mixtures. The morphology of the AM‐6 materials changed from bulky cube to nanofiber aggregates as the Na/K molar ratio decreased from 1.9 to 0.2. Raman spectroscopy revealed that the VO3? intermediate species plays an important role in the formation of the nanofiber morphology. The orientation of ‐V‐O‐V‐ chains in nanofiber aggregates was examined by confocal polarized micro‐Raman spectroscopy. It was found that these aggregates are assemblies of short ‐V‐O‐V‐ chains perpendicular to the axis of nanofibers. The obtained AM‐6 nanofibers greatly increase the exposed proportion of V? O terminals, and thus improve the catalytic performance. 相似文献
28.
Dr. Jörg Wagler Dr. Erica Brendler Prof. Dr. Thomas Heine Dr. Lyuben Zhechkov 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(42):14296-14303
The reaction of 1‐methyl‐3‐trimethylsilylimidazoline‐2‐thione with hexachlorodisilane proceeds toward substitution of four of the disilane Cl atoms during the formation of disilicon complexes with two neighboring hexacoordinate Si atoms. The N,S‐bidentate methimazolide moieties adopt a buttressing role, thus forming paddlewheel‐shaped complexes of the type ClSi(μ‐mt)4SiCl (mt=methimazolyl). Most interestingly, three isomers (i.e., with (ClN4)Si? Si(S4Cl), (ClN3S)Si? Si(S3NCl), and (ClN2S2)Si? Si(S2N2Cl) skeletons as so‐called (4,0), (3,1), and cis‐(2,2) paddlewheels) were detected in solution by using 29Si NMR spectroscopic analysis. Two of these isomers could be isolated as crystalline solids, thus allowing their molecular structures to be analyzed by using X‐ray diffraction studies. In accord with time‐dependent NMR spectroscopy, computational analyses proved the cis‐(2,2) isomer with a (ClN2S2)Si? Si(S2N2Cl) skeleton to be the most stable. The compounds presented herein are the first examples of crystallographically evidenced disilicon complexes with two Si? Si‐bonded octahedrally coordinated Si atoms and representatives of the still scarcely explored class of Si coordination compounds with sulfur donor atoms. 相似文献
29.
A novel imaging tool for hepatic portal system using phase contrast technique with hydrogen peroxide‐generated O2 gas 下载免费PDF全文
Rongbiao Tang Fuhua Yan Wei‐Min Chai Wei Huang Yanan Fu Guo‐Yuan Yang Ke‐Min Chen 《Journal of synchrotron radiation》2015,22(5):1263-1267
The objective of this study was to investigate the potential of hydrogen peroxide‐generated oxygen gas‐based phase contrast imaging (PCI) for visualizing mouse hepatic portal veins. The O2 gas was made from the reaction between H2O2 and catalase. The gas production was imaged by PCI in real time. The H2O2 was injected into the enteric cavity of the lower sigmoid colon to produce O2 in the submucosal venous plexus. The generated O2 gas could be finally drained into hepatic portal veins. Absorption contrast imaging (ACI) and PCI of O2‐filled portal veins were performed and compared. PCI offers high resolution and real‐time visualization of the O2 gas production. Compared with O2‐based ACI, O2‐based PCI significantly enhanced the revealing of the portal vein in vivo. It is concluded that O2‐based PCI is a novel and promising imaging modality for future studies of portal venous disorders in mice models. 相似文献
30.
Cover Picture: Insertion of a Single‐Molecule Magnet inside a Ferromagnetic Lattice Based on a 3D Bimetallic Oxalate Network: Towards Molecular Analogues of Permanent Magnets (Chem. Eur. J. 6/2014) 下载免费PDF全文