排序方式: 共有39条查询结果,搜索用时 15 毫秒
1.
R. A. Wind P. D. Majors K. R. Minard E. J. Ackerman D. S. Daly G. R. Holtom B. D. Thrall T. J. Weber 《Applied magnetic resonance》2002,22(2):145-158
Confocal fluorescence optical microscopy and magnetic resonance microscopy are each used to study live cells in a minimally invasive way. Both techniques provide complementary information. Therefore, by examining cells simultaneously with both methodologies, more detailed information is obtained than is possible with each microscope individually. In this paper two configurations of a combined confocal and magnetic resonance microscope are described. The first configuration is capable of studying large single cells or three-dimensional cell agglomerates, whereas the second configuration is designed for the investigation of monolayers of mammalian cells. In both cases the sample compartment is part of a temperature regulated perfusion system. Images obtained with the combined system are shown forXenopus laevis oocytes, model JB6 tumor spheroids, and a single layer of Chinese hamster ovary cells. Finally, potential applications of the combined microscope are discussed. 相似文献
2.
ALEPH Collaboration D. Buskulic I. De Bonis D. Decamp P. Ghez C. Goy J. P. Lees A. Lucotte M. N. Minard P. Odier et al. 《Zeitschrift fur Physik C Particles and Fields》1996,71(1):31-44
The lifetimes of theB
0 andB
+ mesons have been measured with theAleph detector at LEP, using approximately 3 million hadronic Z decays collected in the period 1991–1994. In the first of three
methods, semileptonic decays ofB
0 andB
+ mesons were partially reconstructed by identifying events containing a lepton with an associatedD*− or meson. The second method used fully reconstructedB
0 andB
+ mesons. The third method, used to measure theB
0 lifetime, employed a partial reconstruction technique to identifyB
0→D*−
π
+
X decays. 相似文献
3.
Jacob RE Laicher G Minard KR 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2007,188(2):357-366
In (3)He magnetic resonance images of pulmonary air spaces, the confining architecture of the parenchymal tissue results in a non-Gaussian distribution of signal phase that non-exponentially attenuates image intensity as diffusion weighting is increased. Here, two approaches previously used for the analysis of non-Gaussian effects in the lung are compared and related using diffusion-weighted (3)He MR images of mechanically ventilated rats. One approach is model-based and was presented by Yablonskiy et al., while the other approach utilizes the second order decay contribution that is predicted from the cumulant expansion theorem. Total lung coverage is achieved using a hybrid 3D pulse sequence that combines conventional phase encoding with sparse radial sampling for efficient gas usage. This enables the acquisition of nine 3D images using a total of only approximately 1 L of hyperpolarized (3)He gas. Diffusion weighting ranges from 0 s/cm(2) to 40 s/cm(2). Results show that the non-Gaussian effects of (3)He gas diffusion in healthy rat lungs are directly attributed to the anisotropic geometry of lung microstructure as predicted by the Yablonskiy model, and that quantitative analysis over the entire lung can be reliably repeated in time-course studies of the same animal. 相似文献
4.
ALEPH Collaboration D. Buskulic I. De Bonis D. Decamp P. Ghez C. Goy J. P. Lees A. Lucotte M. N. Minard P. Odier et al. 《Zeitschrift fur Physik C Particles and Fields》1996,71(3):357-378
The electroweak mixing angle is determined with high precision from measurements of the mean difference between forward and
backward hemisphere charges in hadronic decays of the Z. A data sample of 2.5 million hadronic Z decays recorded over the
period 1990 to 1994 in the ALEPH detector at LEP is used. The mean charge separation between event hemispheres containing
the original quark and antiquark is measured for
and
events in subsamples selected by their long lifetimes or using fastD*’s. The corresponding average charge separation for light quarks is measured in an inclusive sample from the anticorrelation
between charges of opposite hemispheres and agrees with predictions of hadronisation models with a precision of 2%. It is
shown that differences between light quark charge separations and the measured average can be determined using hadronisation
models, with systematic uncertainties constrained by measurements of inclusive production of kaons, protons andΛ’s. The separations are used to measure the electroweak mixing angle precisely as sin2
ϑ
w
eff
=0.2322±0.0008(exp.stat.) ±0.0007(exp.syst.)±0.0008(sep.). The first two errors are due to purely experimental sources whereas
the third stems from uncertainties in the quark charge separations.
Supported by Dirección General de Investigación Científica y Técnica, Spain 相似文献
5.
Minard KR Timchalk C Corley RA 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2005,173(1):90-96
In a gas-filled material like the lung parenchyma, the transverse relaxation time (T2) for 3He is shortened by the deposition of magnetic microspheres and rapid molecular diffusion through induced field distortions. Here, this unique relaxation process is described theoretically and predicted T2-shortening is validated using pressurized 3He gas in a foam model of alveolar airways. Results demonstrate that: (1) significant T2-shortening is induced by microsphere deposition, (2) shortened 3He T2s are accurately predicted, and (3) measured relaxation times are exploitable for quantifying local deposition patterns. Based on these findings the feasibility of imaging inhaled particulates in vivo with hyperpolarized 3He is examined and performance projections are formulated. 相似文献
6.
R. Mateva KR. Zhilkova G. Zamfirova R. Díaz‐Calleja A. Garcia‐Bernabé 《Journal of Polymer Science.Polymer Physics》2010,48(23):2518-2529
The molecular dynamics of new poly (ω‐dodecalactam‐co‐ε‐caprolactam‐co‐propylene oxide) copolymers (DL/CL/PAC) has been investigated by using dynamic mechanical thermal analysis (DMTA) and dielectric relaxation spectroscopy (DRS) measurements. The copolymers were synthesized via anionic polymerization of relevant lactams activated with carbamoyl derivatives of telechelic hydroxyl terminated polypropylene oxide with isophorone diisocyanate (PAC). The calorimetric, X‐ray diffraction, and DMTA measurements were performed to recognize the influence of the composition ratio and the type of PAC on the physical, thermal, and mechanical properties of the synthesized copolymers. The DRS was used to study the frequency dependence of the dielectric permittivity of some isotherms from ?110 to 145 °C. Copolymerization of ε‐caprolactam with about 10 wt % ω‐dodecalactam results in a copolymer that has lower water absorption, a melting point close to that of polyamide 6 and has a high enough degree of crystallinity in respect to high storage modulus. Five dielectric relaxations have been observed in the dielectric spectra, three at lower temperature and two at higher temperature. The copolymers have two glass transition temperatures for polyamide segments and polyether blocks, indicating microphase separation in the copolymers. Other studies directed toward molecular dynamics of polyamide DL/CL/PAC copolymers have not been reported. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010 相似文献
7.
The copper(I) catalyzed reaction of an enamide with an iminoiodane, in the presence of an alcohol, triggers the direct alkoxyamination of the double bond. This transformation represents a straightforward access to α-amino aminals in a completely regio- and diastereoselective manner. Use of a chiral Box ligand allows this reaction to be carried out in an enantioselective fashion. 相似文献
8.
Gábor Blaskó Natesan Murugesan Alan J. Freyer Robert D. Minard Maurice Shamma 《Tetrahedron letters》1981,22(33):3143-3146
Fumaritridine and fumaritrine are not spirobenzylisoquinolines. Rather, they are indenobenzazepines so that fumaritridine is represented by expression and fumaritrine by . Treatment of dihydroparfumine () and dihydroparfumidine () uith trifluoroacetic anhydride folloued by quenching with methanol gives and , respectively. 相似文献
9.
Hélène Guinadeau Alan J. Freyer Robert D. Minard Maurice Shamma Kemal Hüsnü Can Başer 《Tetrahedron letters》1982,23(25):2523-2526
L. var. Boiss. (Ranunculaceae) has yielded (+)-istanbulamine () which is the first aporphine-benzylisoquinoline formed from one (+)-reticuline-type unit linked to a (+)-N-methylcoclaurine moiety. Other new dimers also present are (+)-bursanine () and (+)-iznikine (). 相似文献
10.
Warachai Praditwongwan Phimonphan Chuankhayan Somphot Saoin Tanchanok Wisitponchai Vannajan Sanghiran Lee Sawitree Nangola Saw See Hong Philippe Minard Pierre Boulanger Chun-Jung Chen Chatchai Tayapiwatana 《Journal of computer-aided molecular design》2014,28(8):869-884
Ankyrins are cellular repeat proteins, which can be genetically modified to randomize amino-acid residues located at defined positions in each repeat unit, and thus create a potential binding surface adaptable to macromolecular ligands. From a phage-display library of artificial ankyrins, we have isolated AnkGAG1D4, a trimodular ankyrin which binds to the HIV-1 capsid protein N-terminal domain (NTDCA) and has an antiviral effect at the late steps of the virus life cycle. In this study, the determinants of the AnkGAG1D4-NTDCA interaction were analyzed using peptide scanning in competition ELISA, capsid mutagenesis, ankyrin crystallography and molecular modeling. We determined the AnkGAG1D4 structure at 2.2 Å resolution, and used the crystal structure in molecular docking with a homology model of HIV-1 capsid. Our results indicated that NTDCA alpha-helices H1 and H7 could mediate the formation of the capsid-AnkGAG1D4 binary complex, but the interaction involving H7 was predicted to be more stable than with H1. Arginine-18 (R18) in H1, and R132 and R143 in H7 were found to be the key players of the AnkGAG1D4-NTDCA interaction. This was confirmed by R-to-A mutagenesis of NTDCA, and by sequence analysis of trimodular ankyrins negative for capsid binding. In AnkGAG1D4, major interactors common to H1 and H7 were found to be S45, Y56, R89, K122 and K123. Collectively, our ankyrin-capsid binding analysis implied a significant degree of flexibility within the NTDCA domain of the HIV-1 capsid protein, and provided some clues for the design of new antivirals targeting the capsid protein and viral assembly. 相似文献