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981.
The charged particle orbits in electromagnetic fields on Kerr background as viewed from a locally non-rotating frame do not
exhibit non-gyrating bound orbits, which was an essential feature in the earlier study of Prasanna and Vishveshwara, thus
showing the non gyration to be due to the effect of dragging of inertial frames produced by the rotating black hole. 相似文献
982.
Amit K. Chakraborty Tiia Plyhm Michel Barbezat Adly Necola Giovanni P. Terrasi 《Journal of nanoparticle research》2011,13(12):6493-6506
A systematic investigation of the dispersion of carbon nanotubes (CNTs), 1–6 nm in diameter and a few microns in length, in
a bisphenol F-based epoxy resin has been presented. Several dispersing techniques including high-speed dissolver, ultrasonic
bath/horn, 3-roll mill, etc. have been employed. Optical microscopy has been extensively used to systematically characterise
the state of CNT dispersion in the epoxy resin during the entire processing cycle from mixing CNT with resin to adding and
curing with hardener. Complimentary viscosity measurements were also performed at various stages of nanocomposite processing.
A method to produce a good CNT dispersion in resin was established, but the state of CNT dispersion was found to be extremely
sensitive to its physical and chemical environments. The cured nanocomposites were further tested for their thermo-mechanical
properties by dynamic mechanical thermal analysis (DMTA), and for flexural and compressive mechanical properties. The measured
properties of various nanocomposite plates were then discussed in view of the corresponding CNT dispersion. 相似文献
983.
In this paper we are concerned with the construction of a general principle that will allow us to produce regular spectral triples with finite and simple dimension spectrum. We introduce the notion of weak heat kernel asymptotic expansion (WHKAE) property of a spectral triple and show that the weak heat kernel asymptotic expansion allows one to conclude that the spectral triple is regular with finite simple dimension spectrum. The usual heat kernel expansion implies this property. The notion of quantum double suspension of a C?-algebra was introduced by Hong and Szymanski. Here we introduce the quantum double suspension of a spectral triple and show that the WHKAE is stable under quantum double suspension. Therefore quantum double suspending compact Riemannian spin manifolds iteratively we get many examples of regular spectral triples with finite simple dimension spectrum. This covers all the odd-dimensional quantum spheres. Our methods also apply to the case of noncommutative torus. 相似文献
984.
Using the basic governing equations for isotropic and homogeneous generalized thermo elastic media under initial stress, the reflection and refraction of thermo elastic plane waves at the interface of two dissimilar thermo elastic solid half-spaces has been investigated. The amplitude ratios of various reflected and refracted waves are obtained for an ideal boundary for the incidence of SV-wave. The numerical computations are carried out for a particular model. The effect of initial stress on the amplitude ratios are shown graphically after numerical calculation. 相似文献
985.
Iranzo O Chakraborty S Hemmingsen L Pecoraro VL 《Journal of the American Chemical Society》2011,133(2):239-251
Herein we report how de novo designed peptides can be used to investigate whether the position of a metal site along a linear sequence that folds into a three-stranded α-helical coiled coil defines the physical properties of Cd(II) ions in either CdS(3) or CdS(3)O (O-being an exogenous water molecule) coordination environments. Peptides are presented that bind Cd(II) into two identical coordination sites that are located at different topological positions at the interior of these constructs. The peptide GRANDL16PenL19IL23PenL26I binds two Cd(II) as trigonal planar 3-coordinate CdS(3) structures whereas GRANDL12AL16CL26AL30C sequesters two Cd(II) as pseudotetrahedral 4-coordinate CdS(3)O structures. We demonstrate how for the first peptide, having a more rigid structure, the location of the identical binding sites along the linear sequence does not affect the physical properties of the two bound Cd(II). However, the sites are not completely independent as Cd(II) bound to one of the sites ((113)Cd NMR chemical shift of 681 ppm) is perturbed by the metalation state (apo or [Cd(pep)(Hpep)(2)](+) or [Cd(pep)(3)](-)) of the second center ((113)Cd NMR chemical shift of 686 ppm). GRANDL12AL16CL26AL30C shows a completely different behavior. The physical properties of the two bound Cd(II) ions indeed depend on the position of the metal center, having pK(a2) values for the equilibrium [Cd(pep)(Hpep)(2)](+) → [Cd(pep)(3)](-) + 2H(+) (corresponding to deprotonation and coordination of cysteine thiols) that range from 9.9 to 13.9. In addition, the L26AL30C site shows dynamic behavior, which is not observed for the L12AL16C site. These results indicate that for these systems one cannot simply assign a "4-coordinate structure" and assume certain physical properties for that site since important factors such as packing of the adjacent Leu, size of the intended cavity (endo vs exo) and location of the metal site play crucial roles in determining the final properties of the bound Cd(II). 相似文献
986.
987.
Joshi P Chakraborty S Dey S Shanker V Ansari ZA Singh SP Chakrabarti P 《Journal of colloid and interface science》2011,355(2):402-409
We have conjugated chloroquine, an anti-malarial, antiviral and anti-tumor drug, with thiol-functionalized gold nanoparticles and studied their binding interaction with bovine serum albumin (BSA) protein. Gold nanoparticles have been synthesized using sodium borohydride as reducing agent and 11-mercaptoundecanoic acid as thiol functionalizing ligand in aqueous medium. The formation of gold nanoparticles was confirmed from the characteristic surface plasmon absorption band at 522 nm and transmission electron microscopy revealed the average particle size to be ~7 nm. Chloroquine was conjugated to thiolated gold nanoparticles by using EDC/NHS chemistry and the binding was analyzed using optical density measurement and Fourier transform infrared spectroscopy. The chloroquine-conjugated gold nanoparticles (GNP-Chl) were found to interact efficiently with BSA. Thermodynamic parameters suggest that the binding is driven by both enthalpy and entropy, accompanied with only a minor alteration in protein's structure. Competitive drug binding assay revealed that the GNP-Chl bind at warfarin binding site I in subdomain IIA of BSA and was further supported by Trp212 fluorescence quenching measurements. Unraveling the nature of interactions of GNP-Chl with BSA would pave the way for the design of nanotherapeutic agents with improved functionality, enriching the field of nanomedicine. 相似文献
988.
Suchandra Chakraborty Gautam Chattopadhyay Chandan Saha 《Journal of heterocyclic chemistry》2011,48(2):331-338
One‐pot oxidations of substituted 1‐keto‐1,2,3,4‐tetrahydrocarbazoles ( 1 ) to carbazole‐1,4‐quinones ( 2 ) are efficiently carried out by CAN‐SiO2‐mediated reaction. This generalized protocol was successfully extended to the synthesis of two naturally occurring carbazoloquinones: murrayaquinone A ( 2b ) and koeniginequinone A ( 2g ). A plausible mechanism for this novel reaction involves formation of a 9‐hydroxy‐2,3,4,9‐tetrahydro‐1H‐carbazole‐1‐one followed by rearrangement to 1‐hydroxycarbazole derivatives, which are further oxidized by cerium (IV) to carbazoloquinones. J. Heterocyclic Chem., (2011). 相似文献
989.
Tycon MA Chakraborty A Fecko CJ 《Journal of photochemistry and photobiology. B, Biology》2011,102(2):161-168
The formation of spatially localized regions of DNA damage by multiphoton absorption of light is an attractive tool for investigating DNA repair. Although this method has been applied in cells, little information is available about the formation of lesions by multiphoton absorption in the absence of exogenous or endogenous sensitizing agents. Therefore, we have investigated DNA damage induced in vitro by direct two-photon absorption of frequency-doubled femtosecond pulses from a Ti:sapphire laser. We first developed a quantitative polymerase chain reaction assay to measure DNA damage, and determined that the quantum yield of lesions formed by one-photon absorption of 254 nm light is 7.86×10(-4). We then measured the yield of lesions resulting from exposure to the visible femtosecond laser pulses, which exhibited a quadratic intensity dependence. The two-photon absorption cross section of DNA has a value (per nucleotide) of 2.6 GM at 425 nm, 2.4 GM at 450 nm, and 1.9 GM at 475 nm. A comparison of these in vitro results to several in vivo studies of multiphoton photodamage indicates that the onset of DNA damage occurs at lower intensities in vivo; we suggest possible explanations for this discrepancy. 相似文献
990.
The problem of water wave scattering by a thin vertical elastic plate submerged in infinitely deep water is investigated here assuming linear theory. The boundary condition on the elastic plate is derived from the Bernoulli–Euler equation of motion satisfied by the plate. This is converted into the condition that the normal velocity of the plate is prescribed in terms of an integral involving the difference in velocity potentials (unknown) across the plate multiplied by an appropriate Green’s function. The reflection and transmission coefficients are obtained in terms of integrals involving combinations of the unknown velocity potential on the two sides of the plate and its normal derivative on the plate, which satisfy three simultaneous integral equations, solved numerically. These coefficients are computed numerically for various values of different parameters and are depicted graphically against the wave number for different situations. The energy identity relating these coefficients is also derived analytically by employing Green’s integral theorem. Results for a rigid plate are recovered when the parameters characterizing the elastic plate are chosen negligibly small. 相似文献