Permutation-Symmetric Multicritical Points in Random Antiferromagnetic Spin Chains

The low-energy properties of a system at a critical point may have additional symmetries not present in the microscopic Hamiltonian. This letter presents the theory of a class of multicritical points that provide an interesting example of this in the phase diagrams of random antiferromagnetic spin chains. One case provides an analytic theory of the quantum critical point in the random spin-3/2 chain, studied in recent work by Refael, Kehrein and Fisher (cond-mat/0111295).Comment: Revtex, 4 pages (2 column format), 2 eps figure

Long term Ultra-Violet Variability of Seyfert galaxies

Flux variability is one of the defining characteristics of Seyfert galaxies, a class of active galactic nuclei (AGN). Though these variations are observed over a wide range of wavelengths, results on their flux variability characteristics in the ultra-violet (UV) band are very limited. We present here the long term UV flux variability characteristics of a sample of fourteen Seyfert galaxies using data from the International Ultraviolet Explorer acquired between 1978 and 1995. We found that all the sources showed flux variations with no statistically significant difference in the amplitude of UV flux variation between shorter and longer wavelengths. Also, the flux variations between different near-UV (NUV, 1850 - 3300 A) and far-UV (FUV, 1150 - 2000 A) passbands in the rest frames of the objects are correlated with no time lag. The data show indications of (i) a mild negative correlation of UV variability with bolometric luminosity and (ii) weak positive correlation between UV variability and black hole mass. At FUV, about 50% of the sources show a strong correlation between spectral indices and flux variations with a hardening when brightening behaviour, while for the remaining sources the correlation is moderate. In NUV, the sources do show a harder when brighter trend, however, the correlation is either weak or moderate.Comment: Accepted by Journal of Astrophysics and Astronom

DEVELOPMENT AND VALIDATION OF STABILITY-INDICATING HPTLC METHOD FOR DETERMINATION OF DOLASETRON MESYLATE

Objective: To develop and validate stability indicating HPTLC method for determination of Dolasetron mesylate.Methods: The chromatographic separation was performed on aluminium plates precoated with silica gel 60 F254 using Methanol: Choloroform: Ethyl acetate (7:2:1 v/v/v) as mobile phase followed by densitometric scanning at 280 nm.Results: The chromatographic condition gave a compact spot for Dolasetron mesylate at Rf value of 0.65±0.03. Stress testing was performed in accordance with international conference on harmonization (ICH) Q1A R2 guidelines. Method was validated as per ICH Q2 R1 guidelines. The calibration curve was found to be linear in the concentration range of 100-800 ng/band for Dolasetron mesylate. The limit of detection and quantification was found to2.24 ng/band and 6.79 ng/band, respectively.Conclusion: A new sensitive, simple, and stability indicating high performance thin layer chromatographic (HPTLC) method has been developed and validated for determination of Dolastron mesylate. The proposed method can be used for routine determination of Dolasetron mesylate stability.Â

AN IN VITRO STUDY OF ANTIOXIDANT CAPACITY AND RADICAL SCAVENGING EFFECT OF SPINACIA OLERACEA LEAF EXTRACT

Objective: The study was carried out to evaluate the preliminary phytochemical screening and antioxidant activity of ethanolic extract of Spinacia oleracea (SO).Methods: The leaves of SO were shade dried, and the extract was prepared using solvent ethanol by Soxhlet extraction method. The preliminary phytochemical screening was carried out on the leaf extract of the plant. The total phenolic content and total flavonoids were estimated using Folin- Ciocalteu's and aluminum chloride reagents, respectively. Antioxidant activities were studied using 1,1-diphenyl-2-picrylhydrazyl, nitric oxide, hydrogen radical, lipid peroxidation, and phosphomolybdenum radical scavenging assays.Results: The preliminary phytochemical analysis revealed the presence of bioactive constituents such as phenols, alkaloids, flavonoids, saponins, and glycosides. As SO is a rich source of different bioactive component, it contains a considerable amount of flavonoids and phenols. The different antioxidant assays proved that spinach is one of the best antioxidants with its ability to scavenge different radicals that generate oxidative stress.Conclusion: The observed activity may be associated with bioactive components such as phenols and flavonoids present in the leaf extracts and could have greater importance as nootropic plant in oxidative stress-related degenerative diseases such as Alzheimer and dementia

Comment on "Spin Transport properties of the quantum one-dimensional non-linear sigma model"

In a recent preprint (cond-mat/9905415), Fujimoto has used the Bethe ansatz to compute the finite temperature, zero frequency Drude weight of spin transport in the quantum O(3) non-linear sigma model in a magnetic field $H \neq 0$. We show here that, contrary to his claims, the results are in accord with earlier semiclassical results (Sachdev and Damle, cond-mat/9610115). We also comment on his 1/N expansion, and show that it does not properly describe the long-time correlations.Comment: 4 page

DEVELOPMENT AND VALIDATION OF STABILITY-INDICATING HPTLC METHOD FOR THE ESTIMATION OF PERINDOPRIL AND INDAPAMIDE

Objective: To develop a validated stability indicating HPTLC method for determination Perindopril and Indapamide. Methods: The method was based on the separation of two drugs on plates precoated with silica gel 60 F254 using Dichloromethane: Methanol: Glacial acetic acid in the ratio of 9.5:0.5:0.1 v/v/v as mobile phase followed by scanning in absorbance mode at 215 nm. Results: The optimized chromatographic conditions gave compact spot for Perindopril and Indapamide at Rf value of 0.30 ± 0.02 and 0.60 ± 0.02 respectively. The calibration curve was found to be linear in range of 1000-5000 ng/band and 200-1000 ng/band for perindopril and indapamide respectively. The limit of detection and quantification were found to 164 ng/band and 491 ng/band for Perindopril and 41.41 ng/band and 125.49ng/band for Indapamide. The method has been successfully applied to tablets and was validated according to ICH Harmonized Tripartite guidelines. Conclusion: A new sensitive, simple, rapid and precise high performance thin layer chromatographic (HPTLC) method has been developed and validated for simultaneous determination of Perindopril and Indapamide in pharmaceutical dosage form. The proposed method can be applicable for simultaneous determination of Perindopril and Indapamide in bulk and formulation

Griffiths Effects in Random Heisenberg Antiferromagnetic S=1 Chains

I consider the effects of enforced dimerization on random Heisenberg antiferromagnetic S=1 chains. I argue for the existence of novel Griffiths phases characterized by {\em two independent dynamical exponents} that vary continuously in these phases; one of the exponents controls the density of spin-1/2 degrees of freedom in the low-energy effective Hamiltonian, while the other controls the corresponding density of spin-1 degrees of freedom. Moreover, in one of these Griffiths phases, the system has very different low temperature behavior in two different parts of the phase which are separated from each other by a sharply defined crossover line; on one side of this crossover line, the system `looks' like a S=1 chain at low energies, while on the other side, it is best thought of as a $S=1/2$ chain. A strong-disorder RG analysis makes it possible to analytically obtain detailed information about the low temperature behavior of physical observables such as the susceptibility and the specific heat, as well as identify an experimentally accessible signature of this novel crossover.Comment: 16 pages, two-column PRB format; 5 figure

DEVELOPMENT AND VALIDATION OF STABILITY INDICATING HPTLC METHOD FOR DETERMINATION OF APIXABAN AS BULK DRUG

Objective: To develop and validate simple, sensitive stability indicating HPTLC (High performance thin layer chromatography) method for apixaban. Methods: The chromatographic separation was performed on aluminium plates precoated with silica gel 60 F254 using toluene: ethyl acetate: methanol (3:6:1 v/v/v) as mobile phase followed by densitometric scanning at 279 nm. Results: The chromatographic condition shows sharp peak of apixaban at Rf value of 0.38±0.03. Stress testing was carried out according to international conference on harmonization (ICH)Q1A (R2) guidelines and the method was validated as per ICH Q2(R1) guidelines. The calibration curve was found to be linear in the concentration range of 100-500 ng/band for apixaban. The limit of detection and quantification was found to be 11.66ng/bandand35.33ng/band, respectively. Conclusion: A new simple, sensitive, stability indicating high performance thin layer chromatographic (HPTLC) method has been developed and validated for the determination of apixaban

Effect of γ-​irradiation on the dielectric and conductivity properties of nano-​Wollastonite

Nanocryst. porous CaSiO3 ceramic powders have been synthesized by a novel low-​temp. initiated self-​propagating, gas-​producing soln. combustion method. Single phase β-​CaSiO3 (Wollastonite) is formed by calcination at 900°C for 3h. The crystn. and phase formation temps. in this method are found to be lower compared to the powder obtained via solid state reaction method. The powder is characterized by powder XRD (X-​Ray Diffraction)​, and crystallite sizes are evaluated using Scherrerf's formula as well as from TEM (Transmission Electron Microscopy)​. The Wollastonite powder is exposed to 60Co γ-​radiation to accumulated doses of 1, 3, and 5 KGy and low-​frequency (102-​106 Hz) dielec. measurements are carried out before and after irradn. The dielec. cond. is estd. from the dielec. const. and loss tangent. Exposure to γ-​radiation results in substantial modification in the properties of the ceramic powder due to changes in the porosity of the material. The correlation between dielec. and cond. properties is discussed in relation to porosity effect

Initial Stages of Bose-Einstein Condensation

We present the quantum theory for the nucleation of Bose-Einstein condensation in a dilute atomic Bose gas. This quantum theory comfirms the results of the semiclassical treatment, but has the important advantage that both the kinetic and coherent stages of the nucleation process can now be described in a unified way by a single Fokker-Planck equation.Comment: Four pages of ReVTeX and no figure