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111.
Bailey AS Hughes RW Hubberstey P Ritter C Smith RI Gregory DH 《Inorganic chemistry》2011,50(19):9545-9553
New ternary and quaternary nitride halides, Ba(2)N(X,X') (X = F, Cl, Br; X' = Br, I), have been synthesized from the high temperature reactions of barium subnitride with the respective barium halides under an inert atmosphere. The former include the first fully characterized barium nitride halides for X other than F, and the latter are the first examples of barium nitride mixed halides. The variation in structure with composition has been investigated by powder X-ray and powder neutron diffraction techniques. The heavier ternary and quaternary nitride halides (X, X' = Cl, Br, I) crystallize in the hexagonal space group R3m, with the anti-α-NaFeO(2) structure. Ba(2)NF forms with both an anti-α-NaFeO(2) structure, in which N(3-) and F(-) are ordered and an anion-disordered simple rock salt structure. The hexagonal polymorph of Ba(2)NF is the only example to date of a nitride fluoride adopting this layered structure. Both the ternary and the quaternary compounds display very weak, temperature independent paramagnetism. 相似文献
112.
Buell AK Esbjörner EK Riss PJ White DA Aigbirhio FI Toth G Welland ME Dobson CM Knowles TP 《Physical chemistry chemical physics : PCCP》2011,13(45):20044-20052
Much effort has focussed in recent years on probing the interactions of small molecules with amyloid fibrils and other protein aggregates. Understanding and control of such interactions are important for the development of diagnostic and therapeutic strategies in situations where protein aggregation is associated with disease. In this perspective article we give an overview over the toolbox of biophysical methods for the study of such amyloid-small molecule interactions. We discuss in detail two recently developed techniques within this framework: linear dichroism, a promising extension of the more traditional spectroscopic techniques, and biosensing methods, where surface-bound amyloid fibrils are exposed to solutions of small molecules. Both techniques rely on the measurement of physical properties that are very directly linked to the binding of small molecules to amyloid aggregates and therefore provide an attractive route to probe these important interactions. 相似文献
113.
We present a theory of the dielectric permittivity in which the intermolecular dipole-dipole correlations are treated explicitly. The results for the static permittivity agree with those which have previously been obtained by continuum calculations. The frequency dependence of the permittivity is related to two relaxation times which contain the effects of only short range intermolecular correlations. Approximate relationships are derived between these times and independently measurable properties. 相似文献
114.
Stephen H. Cody Philip N. Dubbin Andrew D. Beischer Noel D. Duncan John S. Hill Andrew H. Kaye David A. Williams 《Micron (Oxford, England : 1993)》1993,24(6):573-580
A fluorescent pH indicator in conjunction with confocal microscopy, was used to map intracellular pH in a variety of cells and tissues with high spatial resolution. The new pH-sensitive fluorescent probe SNARF-1 was excited with the 488 nm band of the argon ion laser of a Bio-Rad MRC-500 confocal microscope. Ratio images were created with pixel-by-pixel division, with the intensity of these images representing a function of pH, that is independent of dye concentration, photobleaching or path length. Cell cultures of rat aortic smooth muscle were loaded with 20 μм SNARF-1/AM for 20 min at 37°C. Intracellular pH levels were calibrated in situ by treatment of each cell with nigericin (20 μм) in solutions of known pH. The cytosolic pH of the majority of cells was uniform, however, pH gradients were evident between the cytosol and nuclear regions, indicating the ability of this technique to map intracellular and intraorganelle pH. Rat C6 glioblastoma spheroids were cultured then loaded with SNARF-1/AM at 10°C for 90 min. The pH values were calibrated in vitro, using SNARF-1 acid in buffered solutions of known pH. Ratio images of the bisected spheroids showed a marked gradient in pH from the outer cells compared with central necrotic cells. The degree of involvement of acidification in muscle fatigue was investigated by simultaneously determining force generation and intracellular pH in individual fibres of an intact rat muscle. The investigation was performed during a stimulation protocol which induced significant fatigue in the force response of the muscle. The fatigue protocol induced little change in cytosolic pH in the fibres. We show that the use of SNARF-1, in conjunction with confocal microscopy is a powerful technique for accurately mapping pH within single cells, multicellular tissues and intact organs, as well as for accurately recording dynamic changes in pH. 相似文献
115.
The synthesis of a benzotriazole azo dye phosphoramidite and the subsequent use in solid phase synthesis of oligonucleotides is reported. The azo dye is shown as a surface enhanced resonance Raman label for oligonucleotides that is capable of immobilisation of the oligonucleotide on metal surfaces such as silver nanoparticles. 相似文献
116.
Certificateless signature: a new security model and an improved generic construction 总被引:2,自引:0,他引:2
Bessie C. Hu Duncan S. Wong Zhenfeng Zhang Xiaotie Deng 《Designs, Codes and Cryptography》2007,42(2):109-126
Certificateless cryptography involves a Key Generation Center (KGC) which issues a partial key to a user and the user also
independently generates an additional public/secret key pair in such a way that the KGC who knows only the partial key but
not the additional secret key is not able to do any cryptographic operation on behalf of the user; and a third party who replaces
the public/secret key pair but does not know the partial key cannot do any cryptographic operation as the user either. We
call this attack launched by the third party as the key replacement attack. In ACISP 2004, Yum and Lee proposed a generic
construction of digital signature schemes under the framework of certificateless cryptography. In this paper, we show that
their generic construction is insecure against key replacement attack. In particular, we give some concrete examples to show
that the security requirements of some building blocks they specified are insufficient to support some of their security claims.
We then propose a modification of their scheme and show its security in a new and simplified security model. We show that
our simplified definition and adversarial model not only capture all the distinct features of certificateless signature but
are also more versatile when compared with all the comparable ones. We believe that the model itself is of independent interest.A
conventional certificateless signature scheme only achieves Girault’s Level 2 security. For achieving Level 3 security, that
a conventional signature scheme in Public Key Infrastructure does, we propose an extension to our definition of certificateless
signature scheme and introduce an additional security model for this extension. We show that our generic construction satisfies
Level 3 security after some appropriate and simple modification.
A preliminary version of the extended abstract of partial results appeared in ACISP 2006 [9]. 相似文献
117.
A.M. Rao P.C. Eklund U.D. Venkateswaran J. Tucker M.A. Duncan G.M. Bendele P.W. Stephens J.-L. Hodeau L. Marques M. Núñez-Regueiro I.O. Bashkin E.G. Ponyatovsky A.P. Morovsky 《Applied Physics A: Materials Science & Processing》1997,64(3):231-2239
60 polymers. Pure and mixed phase polymeric samples were synthesized by simultaneously subjecting microcrystalline C60 powder or pellets to various pressures () and temperatures (). The optical spectra of the orthorhombic, tetragonal, and rhombohedral C60 polymer phases are observed to be quite distinct and rich. These spectra exhibit numerous lines and an overall downshift
in frequency relative to C60 is observed, consistent with a loss of double bonds from the fullerene cage. The LDMS spectra of a sample synthesized at
under hydrostatic conditions and , exhibited a succession of clear peaks at mass numbers corresponding to , similar to the LDMS data on the C60 photopolymer. This is taken as further evidence for interfullerene bonds in these high-pressure polymers. The XRD pattern
of this sample indicates the presence of a strong texture in the sample.
Received: 14 November 1996/Accepted: 8 January 1997 相似文献
118.
119.
Duncan Boldy 《European Journal of Operational Research》1977,1(6):347-351
Recent articles in the Operational Research Quarterly in the United Kingdom have discussed the suitability of optimality as the sole, or even the most appropriate, criterion relevant to decision making. This is perhaps particularly so in the case of strategic planning, in which decisions more likely have to be made in situations of uncertainty. Alternative criteria such as satisficing, robustness and stability have been proposed and the paper reflects on their relevance. This paper draws attention to the fact that strategic planning problems often involve multiple, often noncommensurable, objectives and stresses the importance of engaging decision-makers in an interactive dialogue in such situations. In the concluding observations, examples of two different approaches are given, both within the context of mathematical programming. 相似文献
120.
High-performance liquid chromatography with electrochemical detection (HPLC-ED) and combined gas chromatography--mass spectrometry in the single-ion monitoring mode (GC--MS-SIM) have been used for the determination of salsolinol, dopamine, 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylethanol and norepinephrine in a selection of food and beverage samples. The unique specificity of the SIM mode allows a simple one-step extraction to be used even for complex sample matrices. We have been able to demonstrate the quantitative and qualitative advantages offered by GC--MS over HPLC--ED by direct comparison of the chromatographic data obtained. We demonstrate that the specificity of SIM and the benefits offered by the incorporation of deuterated internal standards make GC--MS-SIM the method of choice for valid identification and precise quantitation of salsolinol, dopamine and dopamine metabolites in a complex sample matrix. 相似文献