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81.
G. Date T. R. Govindarajan P. Sankaran R. Shankar 《Communications in Mathematical Physics》1990,132(2):293-313
We compute the homotopy groups
0 and
1 of the classical configuration space of anO(3) invariant field theory on
×, where
is a compact two dimensional manifold for arbitrary genusg and- denotes the time coordinate. We also present the finite dimensional, unitary, irreducible, inequivalent representations of the appropriate fundamental groups and comment on some of their implications. 相似文献
82.
Hydroxyapatite Ca10(PO4)6(OH)2 has attracted widespread interest from both orthopedic and dental fields due to its excellent biocompatibility and tissue bioactivity properties. Since nanophase materials can mimic the dimensions of constituent components of natural tissues, the implants developed from nanophase material could serve as a successful alternative. However, the defects of hydroxyapatite ceramics, mainly brittleness and low fracture toughness, have been overcome by the use of nanophase hydroxyapatite coatings on the implant surfaces that integrate the good mechanical properties of metals and the bioactivity of hydroxyapatite. In the present investigation, Sol?Cgel hydroxyapatite was prepared from two different phosphorus precursors such as triethyl phosphate and phosphorus pentoxide respectively with calcium nitrate tetrahydrate as a calcium precursor. The effects of pH and liquid P31 Nuclear Magnetic Resonance spectroscopy for the solution aged at different periods were investigated and the synthesized hydroxyapatite powder was characterized by Transmission electron microscopy, X-ray Powder Diffraction, Fourier transform infrared spectroscopy and thermal analysis respectively. In order to fully understand the bioactivity of the synthesized materials, they were coated on 316L Stainless Steel implant surface by spin coating method at the spin speed of 2,000 Revolutions per minute. The effect of nanoparticles on the surface of 316L Stainless Steel implant was studied by adhesive strength measurements. The corrosion resistance property of the hydroxyapatite coatings was evaluated by electrochemical impedance analysis. From the results, it was observed that the hydroxyapatite coatings obtained from different precursors have very high resistance to corrosion with higher adhesive strength. 相似文献
83.
Sumair Imtiaz Nilotpal Kapuria Ibrahim Saana Amiinu Abinaya Sankaran Shalini Singh Hugh Geaney Tadhg Kennedy Kevin M. Ryan 《Advanced functional materials》2023,33(2):2209566
Antimony (Sb) is a promising anode material for potassium-ion batteries (PIBs) due to its high capacity and moderate working potential. Achieving stable electrochemical performance for Sb is hindered by the enormous volume variation that occurs during cycling, causing a significant loss of the active material and disconnection from conventional current collectors (CCs). Herein, the direct growth of a highly dense copper silicide (Cu15Si4) nanowire (NW) array from a Cu mesh substrate to form a 3D CC is reported that facilitates the direct deposition of Sb in a core-shell arrangement (Sb@Cu15Si4 NWs). The 3D Cu15Si4 NW array provides a strong anchoring effect for Sb, while the spaces between the NWs act as a buffer zone for Sb expansion/contraction during K–cycling. The binder-free Sb@Cu15Si4 anode displays a stable capacity of 250.2 mAh g−1 at 200 mA g−1 for over 1250 cycles with a capacity drop of ≈0.028% per cycle. Ex situ electron microscopy revealed that the stable performance is due to the complete restructuring of the Sb shell into a porous interconnected network of mechanically robust ligaments. Notably, the 3D Cu15Si4 NW CC is expected to be widely applicable for the development of alloying-type anodes for next-generation energy storage devices. 相似文献
84.
Let Gn,k denote the oriented grassmann manifold of orientedk-planes in ℝn. It is shown that for any continuous mapf: Gn,k → Gn,k, dim Gn,k = dim Gm,l = l(m −l), the Brouwer’s degree is zero, providedl > 1,n ≠ m. Similar results for continuous mapsg: ℂGm,l → ℂGn,k,h: ℍGm,l → ℍGn,k, 1 ≤ l < k ≤ n/2, k(n — k) = l(m — l) are also obtained. 相似文献
85.
The orientation of hexafluorobenzene (C6F6) on the Cu(1 1 1) surface has been determined for different coverages with the help of near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adsorption geometry and the bonding mode of C6F6 differ significantly in comparison to its hydrocarbon analog C6H6. C6F6 is found to adsorb on Cu(1 1 1) with the ring plane parallel to the surface for coverages below 10 ML. Next to the distinct multilayer, bilayer and monolayer phases we also present evidence of sub-monolayer (i.e., 1/2 ML) coverage with different electronic structure. These findings are explained in a phenomenological model based on fluorine’s property as a σ-acceptor and a π-donor and the resulting bond polarization within the molecule, which is stabilized by image-potential screening within the substrate. 相似文献
86.
Ganesh?C.?Sankaran Krishna?M.?SivalingamEmail author 《Photonic Network Communications》2017,33(2):87-101
This paper presents a survey of data center network architectures that use both optical and packet switching components. Various proposed architectures and their corresponding network operation details are discussed. Electronic processing-based packet switch architectures and hybrid optical–electronic-based switch architectures are presented. These hybrid optical switch architectures use optical switching elements in addition to traditional electronic processing entities. The choice of components used for realizing functionality including the network interfaces, buffers, lookup elements and the switching fabrics have been analyzed. These component choices are summarized for different architectures. A qualitative comparison of the various architectures is also presented. 相似文献
87.
Vanadia supported on praseodymia (2, 6 and 10 wt.% V2O5) were prepared by wet impregnation and characterized by energy dispersive X-ray analysis (EDAX), X-ray diffraction (XRD),
TGA/DTA and BET surface area measurements. Decomposition of cyclohexanol was conducted over these catalysts in the vapor phase.
Acidity of the catalysts was measured by temperature programmed desorption using ammonia as a probe molecule. The structural
and acidic properties were correlated to the total conversion and cyclohexene selectivity. 相似文献
88.
The adsorption of tyrosine, tryptophan and some related compounds on tryptophan and tryptophanyltryptophan gels is similar to but much stronger than that observed with the parent gel Sephadex G-25. The adsorption has been attributed mainly to charge transfer or redistribution of electrons and protons leading to pi-bonding and hydrogen bonding, in addition to hydrophobic adsorption. The participation of organized water surrounding the gel matrix, the ligands and the solute molecules has been considered. The application of this principle of adsorption has been exemplified by chromatographic experiments with a cellulase preparation of tryptophan-Sepharose 4B. 相似文献
89.
Nedonchelle E Pitiot O Vijayalakshmi MA 《Applied biochemistry and biotechnology》2000,83(1-3):287-295
Catalytic autoimmune antibodies from the sera of lupus patients were purified using histidyl-aminohexyl-Sepharose gel and
compared with the antibodies purified with protein A and protein G affinity chromatography. The IgG preparations from the
histidine affinity column had a much higher catalytic activity in hydrolyzing the peptide substrate Pro-Phe-Arg-methyl-coumarinamide
compared to the antibodies obtained by the conventional protein A/G method. This preservation of catalytic activity is attributed
to the gentle buffer conditions used in the histidine ligand method that allowed the integrity of three-dimensional structure
of purified catalytic antibodies. Thus, histidine affinity offer a superior method for isolating autoimmune catalytic antibodies. 相似文献
90.
Suresh CH Vijayalakshmi PS Iwamatsu S Murata S Koga N 《The Journal of organic chemistry》2003,68(9):3522-3531
The cyclohexadiene derivative of C(60) rearranges photochemically to bis(fulleroid) (two [6,5] open structure) and bis(methano)fullerene (two [6,6] closed structure). During this process, a [6,5] open/[6,6] closed intermediate is observed. The isolated intermediate undergoes photochemical rearrangement to bis(fulleroid) and bis(methano)fullerene. On the other side, it undergoes retrorearrangement to the starting material in the dark. The structure and energetics of these C(60) derivatives have been studied at the AM1, PM3, RHF, and B3LYP levels of theory. It is found that bis(fulleroid) bearing four tert-butoxycarbonyl substituents is 5.8 kcal/mol (B3LYP) more stable than the corresponding bis(methano)fullerene. The isolated intermediate having the [6,5] open/[6,6] closed structure is 6.7 kcal/mol more favorable than the previously proposed two [6,5] closed intermediate, and the formation of this compound is well explained by the di-pi-methane rearrangement. (13)C NMR calculation at the B3LYP level reproduced the experimental chemical shifts with very good accuracy for each molecular system. Theoretical studies mainly at the unrestricted B3LYP level on singlet and triplet state potential energy surfaces on fullerene derivatives support the di-pi-methane rearrangement mechanism. The previously proposed symmetrical [4+4]/[2+2+2] and the novel proposed unsymmetrical di-pi-methane pathways may coexist during the reaction. 相似文献