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911.
C. G. Barham S. S. Alghamdi A. Bhagwat M. Booth I. S. Grant M. Lindroos J. Rikovska B. D. D. Singleton N. J. Stone P. M. Walker 《Hyperfine Interactions》1992,75(1-4):431-438
Assignments for the principal Nilsson configuration in light β+-decaying bromine isotopes were proposed in a contribution to the OLNO-1 conference. These assignments were made on the basis
of magnetic moments derived from the temperature dependence of anisotropies in daughter Se isotopes observed in the DOLIS-COLD
facility at Daresbury. Anisotropy measurements have since been extended to a lower base temperature in74m
Br and72g
Br decay, leading to more stringent limits on the ground state moment of72Br. The proposed π[312]3/2 configuration for75Br has also now been confirmed by a measurement of the sign of its magnetic moment. This was done by observing the β-asymmetry
in75Br decay using high purity Si detectors mounted within the dilution refrigerator. 相似文献
912.
913.
M. Lakrimi S. Khym D. M. Symons R. J. Nicholas F. M. Peeters N. J. Mason P. J. Walker 《Physica E: Low-dimensional Systems and Nanostructures》1998,2(1-4)
We have studied the temperature dependence of the magnetoresistance of semimetallic InAs/GaSb structures with magnetic field applied parallel to the layers. We present the first unambiguous evidence for the presence of a mini-gap at the crossing point between the electron and hole dispersion relations. The resistivity is found to change from semiconductor-like behaviour with a strong temperature dependence at low parallel magnetic fields to that of a semimetal with a weak temperature dependence at high field. Furthermore, the magnetoresistance, for intrinsic samples, is found to decrease with field by as much as 70% at low temperatures. As the parallel magnetic field is increased the centres of the electron and hole dispersions are shifted apart in k-space and at sufficiently high field the mini-gap is destroyed and the bands overlap fully. Finally, a theoretical model allows us to estimate that the mini-gap is of order 7 meV. 相似文献
914.
The phosphenic chloride adduct Im—PO2Cl ( 4 , Im = 2, 3‐dihydro‐1, 3‐diisopropyl‐4, 5‐dimethylimidazol‐2‐ylidene) was prepared by partial hydrolysis of [Im—POCl2]Cl ( 5 ) and characterized by X‐ray structure analysis. 相似文献
915.
916.
917.
Walker SH Lilley LM Enamorado MF Comins DL Muddiman DC 《Journal of the American Society for Mass Spectrometry》2011,22(8):1309-1317
A library of neutral, hydrophobic reagents was synthesized for use as derivatizing agents in order to increase the ion abundance
of N-linked glycans in electrospray ionization mass spectrometry (ESI MS). The glycans are derivatized via hydrazone formation
and are shown to increase the ion abundance of a glycan standard more than 4-fold. Additionally, the data show that the systematic
addition of hydrophobic surface area to the reagent increases the glycan ion abundance, a property that can be further exploited
in the analysis of glycans. The results of this study will direct the future synthesis of hydrophobic reagents for glycan
analysis using the correlation between hydrophobicity and theoretical non-polar surface area calculation to facilitate the
development of an optimum tag for glycan derivatization. The compatibility and advantages of this method are demonstrated
by cleaving and derivatizing N-linked glycans from human plasma proteins. The ESI-MS signal for the tagged glycans are shown to be significantly more abundant,
and the detection of negatively charged sialylated glycans is enhanced. 相似文献
918.
Blake SL Walker SH Muddiman DC Hinks D Beck KR 《Journal of the American Society for Mass Spectrometry》2011,22(12):2269-2275
Color Index Disperse Yellow 42 (DY42), a high-volume disperse dye for polyester, was used to compare the capabilities of the
LTQ-Orbitrap XL and the LTQ-FT-ICR with respect to mass measurement accuracy (MMA), spectral accuracy, and sulfur counting.
The results of this research will be used in the construction of a dye database for forensic purposes; the additional spectral
information will increase the confidence in the identification of unknown dyes found in fibers at crime scenes. Initial LTQ-Orbitrap
XL data showed MMAs greater than 3 ppm and poor spectral accuracy. Modification of several Orbitrap installation parameters
(e.g., deflector voltage) resulted in a significant improvement of the data. The LTQ-FT-ICR and LTQ-Orbitrap XL (after installation
parameters were modified) exhibited MMA ≤ 3 ppm, good spectral accuracy (χ2 values for the isotopic distribution ≤ 2), and were correctly able to ascertain the number of sulfur atoms in the compound
at all resolving powers investigated for AGC targets of 5.00 × 105 and 1.00 × 106. 相似文献
919.
Replicating cells undergo DNA synthesis in the highly regulated, S-phase of the cell cycle. Analogues of the pyrimidine deoxynucleoside thymidine may be inserted into replicating DNA, effectively tagging dividing cells allowing their characterisation. Tritiated thymidine, targeted using autoradiography was technically demanding and superseded by 5-bromo-2-deoxyuridine (BrdU) and related halogenated analogues, detected using antibodies. Their detection required the denaturation of DNA, often constraining the outcome of investigations. Despite these limitations BrdU alone has been used to target newly synthesised DNA in over 20,000 reviewed biomedical studies. A recent breakthrough in "tagging DNA synthesis" is the thymidine analogue 5-ethynyl-2'-deoxyuridine (EdU). The alkyne group in EdU is readily detected using a fluorescent azide probe and copper catalysis using 'Huisgen's reaction' (1,3-dipolar cycloaddition or 'click chemistry'). This rapid, two-step biolabelling approach allows the tagging and imaging of DNA within cells whilst preserving the structural and molecular integrity of the cells. The bio-orthogonal detection of EdU allows its application in more experimental assays than previously possible with other "unnatural bases". These include physiological, anatomical and molecular biological experimentation in multiple fields including, stem cell research, cancer biology, and parasitology. The full potential of EdU and related molecules in biomedical research remains to be explored. 相似文献
920.
Wang TS Lupoli TJ Sumida Y Tsukamoto H Wu Y Rebets Y Kahne DE Walker S 《Journal of the American Chemical Society》2011,133(22):8528-8530
Peptidoglycan glycosyltransferases are highly conserved bacterial enzymes that catalyze glycan strand polymerization to build the cell wall. Because the cell wall is essential for bacterial cell survival, these glycosyltransferases are potential antibiotic targets, but a detailed understanding of their mechanisms is lacking. Here we show that a synthetic peptidoglycan fragment that mimics the elongating polymer chain activates peptidoglycan glycosyltransferases by bypassing the rate-limiting initiation step. 相似文献