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1.
Heavy ion irradiation in the electronic stopping power region induces macroscopic dimensional change in metallic glasses and introduces magnetic anisotropy in some magnetic materials. The present work is on the irradiation study of ferromagnetic metallic glasses, where both dimensional change and modification of magnetic anisotropy are expected. Magnetic anisotropy was measured using Mössbauer spectroscopy of virgin and irradiated Fe40Ni40B20 and Fe40Ni38Mo4B18 metallic glass ribbons. 90 MeV 127I beam was used for the irradiations. Irradiation doses were 5×1013 and 7.5×1013 ions/cm2. The relative intensity ratios D 23 of the second and third lines of the Mössbauer spectra were measured to determine the magnetic anisotropy. The virgin samples of both the materials display in-plane magnetic anisotropy, i.e., the spins are oriented parallel to the ribbon plane. Irradiation is found to cause reduction in magnetic anisotropy. Near-complete randomization of magnetic moments is observed at high irradiation doses. Correlation is found between the residual stresses introduced by ion irradiation and the change in magnetic anisotropy.  相似文献   
2.
Blood platelets are important components of haemostasis. After their activation they cause healing of wounds by forming plugs and initiate repair processes. One important event in regulating this activation is the phosphorylation/dephosphorylation of multiple proteins on various tyrosine, serine and threonine residues. To understand the exact molecular mechanisms in platelet activation it is essential to identify proteins involved in the signalling pathways and to localise and characterise their phosphorylation sites. After treatment with 32P and separation by 2D-PAGE using different pI ranges, phosphorylated platelet proteins were detected by autoradiography. Phosphotyrosine-containing proteins were assigned by immunoblotting with an anti-phosphotyrosine antibody. Another approach for the identification of phosphorylated proteins was immunoprecipitation of tyrosine-phosphorylated proteins using an anti-phosphotyrosine antibody. Protein spots/bands of interest were excised from the gel, digested with trypsin and analysed by MALDI-TOF-MS and nano-LC-ESI-MS/MS, respectively. Several phosphorylated proteins could be identified and the localisation of some in vivo phosphorylation sites was possible.Abbreviations DTT 1,4-dithiothreitol - HCCA -cyano-4-hydroxycinnamic acid - PMSF phenylmethylsulfonylfluoride - PSD post source decay - TFA trifluoroacetic acid - TOF time-of-flight  相似文献   
3.
DC Jana  SS Pradhan 《Pramana》2001,56(1):107-115
In subnormal glow discharge under d.c. excitation at different pressure in a varying transverse magnetic field (0 to 30 G) some measurements have been carried out for various initial average tube currents. The voltage across the discharge increases and average tube current and residual current decreases in the magnetic field. With the help of Beckman’s expression [4] for the axial field and the electron density distribution in a transverse magnetic field the observed variation of current and voltage can be satisfactorily explained. The variation of axial electric field with transverse magnetic field can be represented to a fair degree of accuracy by the derived equation. The behaviour of residual current with magnetic field has been observed in these oscillations.  相似文献   
4.
Current methods for asymmetric α-arylation require blocking groups to prevent reaction at the α'-carbon, basic conditions that promote racemization, or multistep synthesis. This work records the first catalytic enantioselective examples of the diazoalkane-carbonyl homologation reaction. Medium ring 2-aryl ketones are prepared in one step in up to 98:2 er and 99% yield from the unsubstituted lower homologue by Sc-catalyzed aryldiazomethyl insertion with simple bis- and tris(oxazoline) ligands.  相似文献   
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Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS) has been used to determine the mass of a double-stranded 500 base-pair (bp) polymerase chain reaction (PCR) product with an average theoretical mass of the blunt-ended (i.e. unadenylated) species of 308 859.35 Da. The PCR product was generated from the linearized bacteriophage Lambda genome which is a double-stranded template. Utilization of ethanol precipitation in tandem with a rapid microdialysis step to purify and desalt the PCR product was crucial to obtain a precise mass measurement. The PCR product (0.8 pmol/μL) was electrosprayed from a solution containing 75% acetonitrile, 25 mM piperidine, and 25 mM imidazole and was infused at a rate of 200 nL/min. The average molecular mass and the corresponding precision were determined using the charge-states ranging from 172 to 235 net negative charges. The experimental mass and corresponding precision (reported as the 95% confidence interval of the mean) was 309 406 +/- 27 Da (87 ppm). The mass accuracy was compromised due to the fact that the PCR generates multiple products when using Taq polymerase due to the non-template directed 3'-adenylation. This results in a mixture of three PCR products with nearly identical mass (i.e. blunt-ended, mono-adenylated and di-adenylated) with unknown relative abundances that were not resolved in the spectrum. Thus, the experimental mass will be a weighted average of the three species which, under our experimental conditions, reflects a nearly equal concentration of the mono- and di-adenylated species. This report demonstrates that precise mass measurements of PCR products up to 309 kDa (500 bp) can be routinely obtained by ESI-FTICR requiring low femtomole amounts. Copyright 1999 John Wiley & Sons, Ltd.  相似文献   
7.
Molecular cilia, the uncrystallized portions of chains already partly attached to polymer crystals, exert a profound influence on the course of polymeric crystallization with ultimate responsibility for the divergence of adjacent lamellae which leads to spherulitic growth. Their effective size and pressure have been measured, in α-polypropylene, from electron microscopic measurements of the separation and maximum curvature of lamellae in row structures. That cilia exist and extend the effective region occupied by a lamella beyond the geometrical confines of its fold surfaces is important for crystallization theory and may well have implications for the connection of lamellae into networks and for gelation.  相似文献   
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The use of ion chromatography with continuous UV detection for radiochemical separation of Cr with simultaneous yield determination is presented. The RNAA method consists of sample destruction in HNO3+HClO4, extraction of Cr(VI) with tribenzylamine in CHCl3, backextraction in NaOH and chromatography of chromate. From radiotracer experiments, the ratio of signals for51Cr and Cr spike was found to be constant for a chromium mass range of 15 to 100 g. Application of the RNAA method to Cr determination in biological reference materials showed a reasonable agreement with the reference values. A relative standard deviation of 3% on the 100 g/kg level for homogeneous material was achieved.IAEA-fellow, on leave from the Philippine Nuclear Research Institute Philippine  相似文献   
10.
Highlights? Molecular basis for the biosynthesis of a fatal food toxin revealed ? Functional genetics by λ Red recombination in the pathogen Burkholderia gladioli ? Stereochemistry of modular bongkrekic acid PKS decoded ? β-Branching and six-electron methyl oxidation lead to tricarboxylic fatty acid  相似文献   
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