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排序方式: 共有229条查询结果,搜索用时 15 毫秒
201.
Chul Am Kim Hyoung Jin Choi Jun Hee Sung Hyung Min Lee Myung S. Jhon 《Macromolecular Symposia》2005,222(1):169-174
Polymer-induced turbulent drag reduction by adding a minute amount of high-molecular weight polyisobutylene (PIB) into two different organic solvents of n-heptane and xylene was examined using a rotating disk system. The dependence of drag reduction (DR) efficiency on various factors such as polymer molecular weight, polymer concentration (C), and solvent quality was examined. Based on the linear relationship between C and C/DR for different molecular weights of PIB, a universal curve was able to characterize a particular polymer/solvent family, independent of the molecular weight of polymer. 相似文献
202.
Rosa SM Antunes-Madeira MC Jurado AS Madeira VV 《Applied biochemistry and biotechnology》2000,87(3):165-175
The thermophilic eubacterium Bacillus stearothermophilus was used as a model to study the effects of amiodarone (2-butyl-3-[3′,5′diido-4′α-diethyl-aminoethoxybenzoyl]-benzofuran)
in lipid organization and in bacterial growth. Effects on the structural order of lipids were assessed by fluorescence polarization
of 1,6-diphenyl-1,3,5-hexatriene (DPH), probing the bilayer core, and of the propionic acid derivative 3-[p-(6-phenyl)-1,3,5-hexatrienyl] phenylpropionic acid (DPH-PA), probing the outer regions of the bilayer. Amiodarone fluidizes
bacterial polar lipid bilayers for temperatures below the phase transition midpoint, and orders the fluid phase of the bacterial
polar lipids, as evaluated by DPH and DPH-PA. The ordering and disordering effects, which are concentration dependent, are
more extensive when detected by DPH relative to DPH-PA. Growth studies performed in parallel revealed that amiodarone inhibits
bacterial growth as a function of concentration. Amiodarone concentrations in the range from 1 to 2.5 μM increased the lag time, decreased the specific growth rate, and decreased the final cell density. Furthermore, 3 μM amiodarone completely inhibited growth. These in vivo effects of amiodarone can be related to its ability to perturb the
phospholipid bilayer structure, whose integrity is essential for cell function, viability, and growth. 相似文献
203.
Aurélien Soules Cuauhtémoc Pozos Vázquez Bruno Améduri Christine Joly‐Duhamel Mohamed Essahli Bernard Boutevin 《Journal of polymer science. Part A, Polymer chemistry》2008,46(10):3214-3228
The syntheses of original fluorinated maleimide and telechelic bismaleimide bearing C6F13 and C6F12 groups, respectively, and their use as reactive additives in photopolymerizable formulations of telechelic poly(propylene glycol) bismaleimide (PPGBMI) are presented. Fluorinated maleimide was synthetized in five steps in 63% overall yield from C6F13C2H4I precursor, whereas the fluorinated bismaleimide was prepared in six steps in 14% overall yield from IC6F12I. These latter led to fluorinated azido and diazido intermediates that were reduced into the fluorinated amine and diamines in two steps. The condensation of amine and diamine onto maleic anhydride offered an amic acid and a diamic acid, which were subsequently cyclized into fluorinated maleimide and bismaleimide. Formulations of telechelic PPGBMI containing a low concentration of these fluorinated maleimide and bismaleimide were UV cured and the surface properties of the resulting films were investigated. A deep modification of the surface properties was noted when the monomaleimide was used. In all the cases, a selective enrichment of the fluorinated monomer at the film surface was observed. The dependence of the surface properties on the fluorinated maleimide and bismaleimide concentrations were also studied, and showed an asymptotic behavior of the contact angle with only 1.5 wt % of fluorinated maleimide additive, whatever the conditions. This monomaleimide led to better hydrophobic and oleophobic properties of the resulting material than that containing the telechelic one. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 3214–3228, 2008 相似文献
204.
O'Shea PD Chen CY Chen W Dagneau P Frey LF Grabowski EJ Marcantonio KM Reamer RA Tan L Tillyer RD Roy A Wang X Zhao D 《The Journal of organic chemistry》2005,70(8):3021-3030
A practical, chromatography-free catalytic asymmetric synthesis of a potent and selective PDE4 inhibitor (L-869,298, 1) is described. Catalytic asymmetric hydrogenation of thiazole ketone 5a afforded the corresponding alcohol 3b in excellent enantioselectivity (up to 99.4% ee). Activation of alcohol 3b via formation of the corresponding p-toluenesulfonate followed by an unprecedented displacement with the lithium enolate of ethyl 3-pyridylacetate N-oxide 4a generated the required chiral trisubstituted methane. The displacement reaction proceeded with inversion of configuration and without loss of optical purity. Conversion of esters 2b to 1 was accomplished via a one-pot deprotection, saponification, and decarboxylation sequence in excellent overall yield. 相似文献
205.
Jean-Pierre?AntoineEmail author Amétépé Lionel?Hohouéto 《Journal of Fourier Analysis and Applications》2003,9(2):141-173
Continuous frames of coherent states of the Poincaré group in 1+3
dimensions
have been obtained previously.
We address in this article the problem of discretizing
(sampling) such continuous frames. The discrete frames constructed here are
sets of coherent states built from compactly supported functions and
the Wigner representation of the group for mass m > 0 and spin
. We examine three specific examples in detail and show that
tight frames may be obtained, under particular conditions, in the case of
the Lorentz section. 相似文献
206.
Urrea-Quintero Jorge-Humberto Fuhg Jan N. Marino Michele Fau Amélie 《Nonlinear dynamics》2021,105(1):277-299
Nonlinear Dynamics - Closed forms of stabilizing sets are generally only available for linearized systems. An innovative numerical strategy to estimate stabilizing sets of PI or PID controllers... 相似文献
207.
Mathematical Programming - The maximum-entropy sampling problem is a fundamental and challenging combinatorial-optimization problem, with application in spatial statistics. It asks to find a... 相似文献
208.
Rochet-Capellan A Schwartz JL 《The Journal of the Acoustical Society of America》2007,121(6):3740-3754
This paper investigates the coordination between the jaw, the tongue tip, and the lower lip during repetition with rate increase of labial-to-coronal (L(a)C(o)) consonant-vowel-consonant-vowel disyllables (e.g., /pata/) and coronal-to-labial (C(o)L(a)) ones (e.g., /tapa/) by French speakers. For the two types of disyllables: (1) the speeding process induces a shift from two jaw cycles per disyllable to a single cycle; (2) this shift modifies the coordination between the jaw and the constrictors, and (3) comes with a progression toward either a L(a)C(o) attractor [e.g., (/pata/ or /tapa/) --> /patá/ --> /ptá/] or a C(o)L(a) one (e.g., /pata/ or /tapa/ --> /tapá/ --> /tpá/). Yet, (4) the L(a)C(o) attractor is clearly favored regardless of the initial sequencing. These results are interpreted as evidence that a L(a)C(o) CVCV disyllable could be a more stable coordinative pattern for the lip-tongue-jaw motor system than a C(o)L(a) one. They are discussed in relation with the so-called LC effect that is the preference for L(a)C(o) associations rather than C(o)L(a) ones in CV.CV disyllables in both world languages and infants' first words. 相似文献
209.
Fortuna A Bicker J Alves G Falcão A Soares-da-Silva P 《Journal of separation science》2011,34(12):1391-1401
For the first time, a selective and sensitive chiral HPLC-UV method was developed and fully validated for the simultaneous quantification of eslicarbazepine acetate (ESL), carbamazepine (CBZ), S-licarbazepine (S-Lic), R-licarbazepine (R-Lic), oxcarbazepine (OXC) and carbamazepine-10,11-epoxide (CBZ-E), in mouse plasma and brain homogenate supernatant. After the addition of chloramphenicol as the internal standard, samples were processed using an SPE procedure. The chiral chromatographic analysis was carried out on a LiChroCART 250-4 ChiraDex column, employing a mobile phase of water and methanol (88:12, v/v) pumped at 0.9 mL/min and the UV detector set at 235 nm. The assay was linear (r(2) ≥0.995) for ESL, CBZ, OXC, S-Lic, R-Lic and CBZ-E in the range of, respectively, 0.2-4, 0.4-30, 0.1-60, 0.2-60, 0.2-60 and 0.2-30 μg/mL, in plasma, and of 0.06-1.5 μg/mL for ESL, 0.12-15 μg/mL for CBZ and CBZ-E and 0.06-15 μg/mL for OXC and both licarbazepine (Lic) enantiomers in brain homogenate supernatant. The overall precision was within 8.71% and accuracy ranged from -7.55 to 8.97%. The recoveries of all the compounds were over 92.1%. Afterwards, the application of the method was demonstrated using real plasma and brain samples obtained from mice administered simultaneously with ESL and CBZ. 相似文献
210.
Fabien Pointurier Amélie Hubert Gaëlle Roger 《Journal of Radioanalytical and Nuclear Chemistry》2013,296(2):593-598
In this study we describe a method for uranium dating (i.e. determination of the date of the last chemical purification undergone by the material) by measurement of the 230Th/234U ratio, applicable to sub-microgram quantities. The chosen protocol (AG1x8 resin in hydrochloric acid medium) has been tested on separation microcolumns (100 μl). This ‘microchemistry’ technique considerably limits the risks of contamination by reagents or the environment. Thorium extraction efficiencies were greater than 90 % and reproducible. The quantities of 230Th introduced by the chemical purification procedure were negligible. Using an ultra-sensitive inductively coupled plasma mass spectrometry measurement technique, detection limits of the order of femtograms (10?15 g) of 230Th were obtained. The complete procedure, chemical separation and isotope measurement, was successfully tested and validated on a few micrograms of uranium. 相似文献