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51.
J. Y. Cavaille J. Perez C. Jourdan G. P. Johari 《Journal of Polymer Science.Polymer Physics》1987,25(9):1847-1858
The dynamic mechanical behavior of 10 and 20% poly(vinyl methyl ether)-polystyrene blends has been studied in the frequency range 10?5 Hz to 5 Hz and temperature range 100–450 K. Isochronal plots of modulus G′ and loss factor, tan ?, show the presence of one relaxation process at temperatures below the transition zone. A second relaxation process at intermediate temperatures but below Tg may be inferred from the breadth of the G″ frequency curves in the transition zone of both blends. This process, at 280 < T < 300 K, is independent of PVME concentration and seems to be associated with the local modes of motions of PS chains. The rheological behavior of the blends shows them to be compatible up to 20% PVME. Their G′ and G″ data cannot be shifted along a frequency axis to produce a satisfactory master curve. The departure from thermorheological simplicity is much more clearly observed in the tan ? than in the modulus-frequency plots. This departure is due to the change in the segmental correlation effects, or length, with temperature near Tg. A molecular model of the growth of microshear domains with hierarchically constrained molecular motions, given elsewhere, quantitatively agrees with the dynamic mechanical behavior. 相似文献
52.
The radiative lifetimes of NaH, A1Σ+, excited states have been measured by pulsed dye laser excitation. The hydride is obtained by h.f. discharge in hydrogen and metal vapor, at a total pressure less than 10?1 Torr. The measured lifetimes are: (24.0 ± 3.0) ns for v′ = 3, J′ = 8; (28.3 ± 3.0) ns for v′ = 4, J′ = 11; (27.1 ± 3.0) ns for v′ = 5, J′ = 16. 相似文献
53.
Warren G Wesselmann F Zhu H McKee P Savvinov N Zeier M Aghalaryan A Ahmidouch A Arenhövel H Asaturyan R Ben-Dayan I Bloch F Boeglin W Boillat B Breuer H Brower J Carasco C Carl M Carlini R Cha J Chant N Christy E Cole L Coman L Coman M Crabb D Danagoulian S Day D Duek K Dunne J Elaasar M Ent R Farrell J Fatemi R Fawcett D Fenker H Forest T Garrow K Gasparian A Goussev I Gueye P Harvey M Hauger M Herrera R Hu B Jaegle I Jones M Jourdan J Keith C Kelly J Keppel C Khandaker M Klein A Klimenko A 《Physical review letters》2004,92(4):042301
The electric form factor of the neutron was determined from measurements of the d-->(e-->,e'n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (15ND3) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G(n)(E)=0.0526+/-0.0033(stat)+/-0.0026(sys) and 0.0454+/-0.0054+/-0.0037 at Q(2)=0.5 and 1.0 (GeV/c)(2), respectively. 相似文献
54.
Rohe D Armstrong CS Asaturyan R Baker OK Bueltmann S Carasco C Day D Ent R Fenker HC Garrow K Gasparian A Gueye P Hauger M Honegger A Jourdan J Keppel CE Kubon G Lindgren R Lung A Mack DJ Mitchell JH Mkrtchyan H Mocelj D Normand K Petitjean T Rondon O Segbefia E Sick I Stepanyan S Tang L Tiefenbacher F Vulcan WF Warren G Wood SA Yuan L Zeier M Zhu H Zihlmann B;E- Collaboration 《Physical review letters》2004,93(18):182501
We have carried out an (e,e'p) experiment at high momentum transfer and in parallel kinematics to measure the strength of the nuclear spectral function S(k,E) at high nucleon momenta k and large removal energies E. This strength is related to the presence of short-range and tensor correlations, and was known hitherto only indirectly and with considerable uncertainty from the lack of strength in the independent-particle region. This experiment locates by direct measurement the correlated strength predicted by theory. 相似文献
55.
A DNA aptamer as a new target-specific chiral selector for HPLC 总被引:1,自引:0,他引:1
Michaud M Jourdan E Villet A Ravel A Grosset C Peyrin E 《Journal of the American Chemical Society》2003,125(28):8672-8679
In this paper, a DNA aptamer, known to bind stereospecifically the D-enantiomer of an oligopeptide, i.e., arginine-vasopressin, was immobilized on a chromatographic support. The influence of various parameters (such as column temperature, eluent pH, and salt concentration) on the L- and D-peptide retention was investigated in order to provide information about the binding mechanism and then to define the utilization conditions of the aptamer column. The results suggest that dehydration at the binding interface, charge-charge interactions, and adaptive conformational transitions contribute to the specific D-peptide-aptamer complex formation. A very significant enantioselectivity was obtained in the optimal binding conditions, the D-peptide being strongly retained by the column while the L-peptide eluted in the void volume. A rapid baseline separation of peptide enantiomers was also achieved by modulating the elution conditions. Furthermore, it was established that the aptamer column was stable during an extended period of time. This work indicates that DNA aptamers, specifically selected against an enantiomer, could soon become very attractive as new target-specific chiral selectors for HPLC. 相似文献
56.
A model beta-hairpin peptide has been used to investigate the context-dependent contribution of cross-strand Lys-Glu interactions to hairpin stability. We have mutated two Ser-Lys interstrand pairs to Glu-Lys salt bridges, one close to the type I' Asn-Gly turn sequence (Ser6 --> Glu), and one close to the N- and C-termini (Ser15 --> Glu). Each individual interaction contributes approximately 1.2-1.3 kJ mol(-1) to stability; however, introducing the two salt bridges simultaneously produces a much larger overall contribution (-3.6 kJ mol(-1)) consistent with an important role for preorganization and cooperativity in determining the energetics of weak interactions. We compare and contrast CD and NMR data on the highly folded hairpin with the two Glu-Lys pairs to shed light on the nature of the folded state in water. We show that large cosolvent-induced changes in the CD spectrum, in contrast with the modest effects observed on Halpha chemical shifts, support a hydrophobically collapsed entropy-driven conformation in water whose stability is modulated by long-range Coulombic interactions from the Glu-Lys interactions. Cosolvent stabilizes the structure enthalpically, as is evident from CD melting profiles. 相似文献
57.
An attempt to extract velocity and molar fraction from a single hot-wire trace within a turbulent mixing zone induced by a
shock accelerated gaseous interface has been proposed. Experiments have been conducted for negative and positive density jumps
across the interface. The hot-wire signals clearly show interfaces between mixed and unmixed regions and the locations of
incident and reflected shocks. With some hypotheses on the temperature, velocity and molar fraction profiles within the turbulent
mixing zone have been obtained solving an inverse problem. Results show that if the molar fraction profiles follow physically
coherent evolutions, those of the local velocity are strongly correlated with the choice of its variation range. So, we reasonably
think that the results obtained from single wire have to remain limited to interface and shock locations. And it is only by
coupling the present technique with the laser Doppler velocimetry, which we will be able to possibly obtain reliable estimates
of the variations of quantities in the turbulent mixing zone.
相似文献
58.
Wesselmann FR Slifer K Tajima S Aghalaryan A Ahmidouch A Asaturyan R Bloch F Boeglin W Bosted P Carasco C Carlini R Cha J Chen JP Christy ME Cole L Coman L Crabb D Danagoulian S Day D Dunne J Elaasar M Ent R Fenker H Frlez E Gan L Gaskell D Gomez J Hu B Jones MK Jourdan J Keith C Keppel CE Khandaker M Klein A Kramer L Liang Y Lichtenstadt J Lindgren R Mack D McKee P McNulty D Meekins D Mkrtchyan H Nasseripour R Niculescu I Normand K Norum B Pocanic D Prok Y Raue B Reinhold J Roche J Rohe D 《Physical review letters》2007,98(13):132003
We have examined the spin structure of the proton in the region of the nucleon resonances (1.085 GeV相似文献
59.
Fomin N Arrington J Day DB Gaskell D Daniel A Seely J Asaturyan R Benmokhtar F Boeglin W Boillat B Bosted P Bruell A Bukhari MH Christy ME Chudakov E Clasie B Connell SH Dalton MM Dutta D Ent R El Fassi L Fenker H Filippone BW Garrow K Hill C Holt RJ Horn T Jones MK Jourdan J Kalantarians N Keppel CE Kiselev D Kotulla M Lindgren R Lung AF Malace S Markowitz P McKee P Meekins DG Miyoshi T Mkrtchyan H Navasardyan T Niculescu G Okayasu Y Opper AK Perdrisat C Potterveld DH Punjabi V Qian X 《Physical review letters》2010,105(21):212502
We present new data on electron scattering from a range of nuclei taken in Hall C at Jefferson Lab. For heavy nuclei, we observe a rapid falloff in the cross section for x>1, which is sensitive to short-range contributions to the nuclear wave function, and in deep inelastic scattering corresponds to probing extremely high momentum quarks. This result agrees with higher energy muon scattering measurements, but is in sharp contrast to neutrino scattering measurements which suggested a dramatic enhancement in the distribution of the "superfast" quarks probed at x>1. The falloff at x>1 is noticeably stronger in 2H and 3He, but nearly identical for all heavier nuclei. 相似文献
60.
Jérôme Vidot Olivier Jourdan Frédéric Szczap Vladimir V. Rozanov 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(4):586-601
A theoretical sensitivity study of the influence of cirrus cloud properties on tropospheric NO2 columns retrieved from the spaceborne Ozone Monitoring Instrument (OMI) measurements is performed. It is conducted within the framework of the synergetic use of A-Train sensors to derive more representative trace gas products. We aim to study the potential effects of cirrus clouds on tropospheric NO2 retrievals using a retrieval algorithm that, unlike the OMI Standard and DOMINO algorithms, does not correct for the effects of clouds. The sensitivity study is based on the radiative transfer code SCIATRAN that performs both simulations of top of atmosphere (TOA) reflectances as measured by an OMI-like band and tropospheric NO2 column retrievals based on the differential optical absorption spectroscopy (DOAS) method. The results of the sensitivity study show that if a correction for cirrus clouds is not included in our simple retrieval that does not account for clouds in the first place, the tropospheric column can be underestimated by 55%. This underestimation depends strongly on cirrus parameters as, in order of importance, cloud fraction, cloud optical depth, asymmetry factor of cirrus cloud phase function and cloud top height. The perspective of the synergy between OMI and cloud information obtained from cloud-derived products of the A-Train is evaluated in two parts by applying a simple cloud correction scheme based on the independent pixel approximation (IPA). Firstly, we evaluated the tropospheric NO2 column retrievals error caused by uncertainties in cirrus cloud properties. Secondly we studied the influence of subpixel cloud optical depth variability on NO2 retrievals. From our simulations, it is demonstrated that the error will be reduced significantly if the cloud fraction is lower or equal to 0.5. In this case, the cloud fraction and the cloud optical depth must be known within accuracy less than 0.05% and 50%, respectively. The cloud top height and the asymmetry factor must be known within uncertainty of at least 1 km and less than 0.05, respectively. The latter result shows that the uncertainty of the asymmetry factor is a major source of error in the cloud correction for tropospheric NO2 retrieval in the presence of cirrus. 相似文献