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21.
Moreau DJ Brooks LA Doolan CJ 《The Journal of the Acoustical Society of America》2011,130(4):EL154-EL160
This paper discusses the effects of frequency selection on source localization and geoacoustic inversion methods that use frequency coherent objective functions. Matched-field processors based on frequency-coherent objective functions often have rapidly fluctuating range ambiguity surfaces. Insufficient sampling in frequency domain results in range aliasing terms that affect geoacoustic inversion. Range aliasing and its effects on source localization and environmental parameter inversion are demonstrated on data collected during the MAPEX2000 experiment. Guidance for frequency selection to avoid range aliasing is provided. 相似文献
22.
K. R. Doolan 《Journal of Polymer Science.Polymer Physics》2002,40(6):572-584
Nuclear magnetic resonance (NMR) spin–lattice relaxation times (T1) in various polyethylene and polypropylene resins were measured at 20 MHz and at temperatures of 130–490 K. At each temperature and for all resins, only a single value of T1 was found, which was consistent with the occurrence of rapid spin diffusion throughout the protons attached to the polymer chains. The data were analyzed for the estimation of activation energies corresponding to molecular motion causing spin–lattice relaxation. Two well‐defined minima were found for loge(T1) plotted as a function of temperature for all of the polypropylene resins. Single very broad minima were found for all of the polyethylene samples. In contrast, the free induction decay signals from all of the resins following single radio‐frequency pulses were observed to contain a rapidly decaying component followed by a much more slowly decaying signal. These components were used to estimate the amount of rigid component present in the solid resins at room temperature. Samples of one high‐density polyethylene and one low‐density polyethylene were irradiated with γ radiation up to a 500‐kGy dose to examine the effects of crosslinking on the NMR relaxation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 572–584, 2002; DOI 10.1002/polb.10116 相似文献
23.
The thermal decomposition of propanoic acid dilute in argon has beenstudied in a single-pulse shock tube over the temperature range of 1100-1500 K and over the pressure range of 14-18 atm. The decomposition kinetics have been satisfactorily computer modelled by means of afree radical mechanism involving H and OH chains. Recent single-pulse shock tube product analyses of acetic acid decomposition have been computer modelled using a free radical mechanism for decarboxylation coupled to a unimolecular dehydration reaction. A comparison between the thermal decomposition kinetics of the C1? C3 alkanoic acids is made. The present studies do notprovide evidence for the participation of transition states involving a pentavalent carbon atom in the pyrolyses of the lower alkanoic acids. 相似文献
24.
Shashwati Sen DK Aswal Ajay Singh TV Chandrasekhar Rao KP Muthe JC Vyas LC Gupta SK Gupta VC Sahni 《Pramana》2002,58(5-6):867-870
The MgB2 superconductor, synthesized using solid-state and liquid-phase sintering methods, have been characterized for various properties.
The upper critical field, irreversibility line and critical current density have been determined using magnetization data.
The current-voltage characteristics recorded under an applied magnetic field revealed the existence of vortex glass transition.
The surface analysis using X-ray photoelectron spectroscopy shows that MgB2 is sensitive to atmospheric degradation. 相似文献
25.
Synthesis and Characterisation of Self‐Assembled and Self‐Adjuvanting Asymmetric Multi‐Epitope Lipopeptides of Ovalbumin 下载免费PDF全文
Dr. Sharareh Eskandari Dr. Rachel J. Stephenson Abdullah Ahmad Fuaad Dr. Simon H. Apte Prof. Denise L. Doolan Prof. Istvan Toth 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1251-1261
Designing a lipopeptide (LP) vaccine with a specific asymmetric arrangement of epitopes may result in an improved display of antigens, increasing host‐cell recognition and immunogenicity. This study aimed to synthesise and characterise the physicochemical properties of a library of asymmetric LP‐based vaccine candidates that contained multiple CD4+ and CD8+ T‐cell epitopes from the model protein antigen, ovalbumin. These fully synthetic vaccine candidates were prepared by microwave‐assisted solid phase peptide synthesis. The C12 or C16 lipoamino acids were coupled to the N or C terminus of the OVA CD4 peptide epitope. The OVA CD4 LPs and OVA CD8 peptide constructs were then conjugated using azide–alkyne Huisgen cycloaddition to give multivalent synthetic vaccines. Physiochemical characterisation of these vaccines showed a tendency to self‐assemble in aqueous media. Changes in lipid length and position induced self‐assembly with significant changes to their morphology and secondary structure as shown by transmission electron microscopy and circular dichroism. 相似文献
26.
Results of tests performed in a free-piston shock tunnel on a model scramjet engine are presented. Two conditions which differed
in Mach number were tested. Flow at the lower Mach number condition was achieved using a variable-angle diffuser. Shadowgraph
images and floor static pressure measurements were obtained, the latter used as the basis of a finite-difference calculation
of flow properties in the scramjet.
Received 9 May 1998 / Accepted 30 September 1998 相似文献
27.
Techniques are described for the pyrohydrolysis of a range of sample materials in a silica tube furnace. Samples are mixed with a catalyst and combusted ar 1200°C in a stream of oxygen and steam, and the liberated fluorine is absorbed in solutions appropriate to either ion-selective electrode or ion-chromatographic measurement. Catalyst composition, furnace temperature, and gas flow rates are particular variables discussed with respect to recovery of fluorine ar concentrations up to about 5% (w/w). Recovery and precision are favourable compared with those obtained by the alternative peroxide fusion and oxygen bomb combustion methods for coal analyses. Relative standard deviation is less than 0.05 for most samples. Results agree with certified values of available reference materials including ores and rocks, while new data are provided for several non-certified reference materials. 相似文献
28.
A very simple and rapid procedure is described in which the addition of a large amount of Zn(II) to a water sample before extraction by 2-mercaptobenzothiazole into n-butyl acetate brings about almost total extraction of Cd and allows determination of concentrations down to at least 0.02 ng/ml. High precision is achieved, and the interference of cyanide is also overcome. 相似文献
29.
This paper describes an approach to quantitative analysis using diffuse reflectance spectra of solid materials in conjunction with the infrared data processing technique CIRCOM, to calculate equations correlating the FTIR spectra with the constituents or properties for a calibration set of well-characterised samples. Unknown samples, similar to those in the calibration set, can then be analysed from their infrared spectra. An example from the minerals industry will be given. 相似文献