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51.
52.
Some cosmological consequences of the superfluid vacuum state developed previously by the authors are discussed, particularly with regard to the initial stages of the universe. The transition temperature of the hadronic superfluid (superfluid during the hadron era) is estimated to be 10
13
K, which is the same as the Hagedorn temperature, giving a physical basis of the thermodynamic bootstrap model. 相似文献
53.
A. Sivaram H. Jagannath D.Ramachandra Rao Putcha Venkateswarlu 《Journal of Physics and Chemistry of Solids》1979,40(12):1007-1018
The steady state and transient fluorescence spectra of CaF2: Dy3+ have been studied using Ar+ and N2 lasers in the temperature range 77–673 K and in the wavelength region 4500–9000 Å. The spectra show the presence of two types of centers (type A and type B) with decay times of 1.3 and 3.5 ms. The observed spectrum is mostly due to type A centers. Three new groups of fluorescence 4F9/2−6H11/2, 4F9/2−(6H9/2, 6F11/2) and 4F9/2−(6H7/2, 6F9/2) have been observed for type A centers, and a tentative assignment of the positions of the Stark levels of 6H11/2, (6H9/2, 6F11/2) and (6H7/2, 6F9/2) has been made. The change in the intensity of the transitions with temperature and excitation wavelength are discussed. 相似文献
54.
Graphical abstract
相似文献55.
Nayaki SK Swaminathan M 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2006,64(3):631-636
Solvatochromic and prototropic behaviour of 4-aminodiphenylamine (4ADA) and 4,4'-diaminodiphenylamine (DADA) have been investigated in the solvents of different polarity and at various acid-base concentrations in the ground and excited states using absorption and fluorescence spectra. Solvatochromic shifts have been analysed and observed shifts are explained by the hydrogen bonding interactions. The prototropic study reveals that (i) absorption maximum of monocation of DADA is red shifted to its neutral form, and (ii) the fluorescence of 4ADA is red shifted on protonation. The abnormal fluorescence of 4ADA+ is found to be due to large solvent relaxation in polar medium. 相似文献
56.
[reaction: see text] 1,3-Diketones were synthesized directly from ketones and acid chlorides and were then converted in situ into pyrazoles by the addition of hydrazine. This method is extremely fast, general, and chemoselective, allowing for the synthesis of previously inaccessible pyrazoles and synthetically demanding pyrazole-containing fused rings. 相似文献
57.
Prakash Kasirajan Senthil Kumar Puvaneswaran Pandiaraj Sekar Karuthapandian Swaminathan 《Research on Chemical Intermediates》2019,45(3):1147-1167
Research on Chemical Intermediates - In the present study, we report novel graphitic carbon nitride (g-C3N4) nanosheets at different calcination temperatures viz 500 °C,... 相似文献
58.
V. Swaminathan V. P. Panov Yu. P. Panarin S. P. Sreenilayam A. Panov 《Liquid crystals》2018,45(4):513-521
An addition of chiral dopant to two achiral smectic liquid crystals from a homologous series, by varying weight percentages with known low values of layer shrinkage, leads to chiral smectic-C* phase with a finite value of the spontaneous polarisation. The electro-optical response arising from changes in the induced apparent tilt angle brought about by a weak electric field in the SmA* phase gives rise to power law dependency on the reduced temperature. The critical exponent γ of the power law depends on the dopant concentration but its value is found to be greater than the typical value of 1.32. This implies that the short-range correlation extends from two dimensions to three dimensions in these materials in the SmA phase. The layer thickness of smectic layers in the guest–host system remains unaltered up to the 15 wt % addition of the chiral dopant to two achiral smectics. The system thus retains the low layer shrinkage of the achiral smectic as evidenced by measurements of the layer thickness from X-ray scattering and thickness measurements from optical interferometry. Results on the optical birefringence and the apparent tilt angle lead us to the conclusion of having successfully obtained chiral smectic materials for devices with de Vries characteristics by chiral doping. 相似文献
59.
The cubic transition metal phosphonates [(t)BuPO3M(2-apy)]4 (M= Zn (1), Co (2)), whose core resembles the D4R SBU of zeolites, have been synthesized from a reaction between the corresponding metal acetate, tert-butylphosphonic acid and 2-aminopyridine (2-apy) at room temperature. X-Ray structure determination reveals that the molecules of 1 and 2, which crystallize in the tetragonal I4(1)/a space group with crystallographically imposed 4 symmetry, form a 3-D supramolecular assembly aided by N-H...O hydrogen bonding. When the same reaction was carried out by using a bridging bidentate Lewis base such as 4,4'-bipyridine, insoluble precipitate is obtained for both zinc and cobalt. In the case of other metal salts such as copper, manganese and nickel, however, one-dimensional polymeric compounds such as [M((t)BuPO3H)2(4,4'-bipy)(H2O)2]n (M= Cu (3), Mn (4)), [(Ni(4,4'-bipy)(H2O)4)((t)BuPO3H)2(H2O)]n (5) have been isolated. The solid-state structures of 3-5 have been determined by single crystal X-ray diffraction studies. Compounds 3 and 4 are isostructural and crystallize in the triclinic P1 space group with two phosphonate ligands coordinated to the metal centers in a [1.100] fashion, whereas in the case of compound 5, the polymeric backbone is formed by Ni-4,4'-bipy units and the phosphonate anions show no bonding interaction to the metal. The 1-D polymeric chains of 3-5 organize in the solid-state as 3-D supramolecular assemblies with the aid of extensive hydrogen bonding interaction between coordinated water molecules and P-OH or P=O groups of the phosphonate ligands. 相似文献
60.
A series of Ru(II) and Ru(III) complexes of the types [RuX(CO)(EPh3)2L] (X = H, E = P; X = Cl, E = P or As) and [RuX2(EPh3)2L] (X = Cl, E = P or As; X = Br, E = As, L = monoanion of dehydroacetic acid) have been synthesized in order to explore their biological activities, such as DNA-binding and antibacterial activity. The complexes were characterized by analytical and spectroscopic techniques. The crystal and molecular structure of [RuCl2(AsPh3)2(L)] has been determined by single crystal XRD. The cyclic voltammograms of the complexes in acetonitrile displayed either quasi-reversible or irreversible redox couples based on the metal centre. The ligand, dehydroacetic acid (DHA) and its metal complexes were tested against five pathogenic bacteria. Absorption titration and cyclic voltammetric studies revealed that the complexes interact with Herring Sperm ds DNA through different binding modes to different extents. 相似文献