Probing a ferromagnetic critical regime using nonlinear susceptibility

The second order para-ferromagnetic phase transition in a series of amorphous alloys (Fe{_5}Co{_{50}}Ni{_{17-x}}Cr{_x}B{_{16}}Si{_{12}}) is investigated using nonlinear susceptibility. A simple molecular field treatment for the critical region shows that the third order suceptibility (chi{_3}) diverges on both sides of the transition temperature, and changes sign at T{_C}. This critical behaviour is observed experimentally in this series of amorphous ferromagnets, and the related assymptotic critical exponents are calculated. It is shown that using the proper scaling equations, all the exponents necessary for a complete characterization of the phase transition can be determined using linear and nonlinear susceptiblity measurements alone. Using meticulous nonlinear susceptibility measurements, it is shown that at times chi{_3} can be more sensitive than the linear susceptibility (chi{_1}) in unravelling the magnetism of ferromagnetic spin systems. A new technique for accurately determining T{_C} is discussed, which makes use of the functional form of chi{_3} in the critical region.Comment: 11 Figures, Submitted to Physical Review

Some Contour Integrals Involving Generalised Hypergeometric Function

Contour integral involving Fox's H-function and modified Bessel function of the first kind has been calculated. Some important properties and particular cases of H-function, which is a generalization of G-function, have been derived and discussed

Domain wall dynamics in a single CrO2_2 grain

Recently we have reported on the magnetization dynamics of a single CrO$_2$ grain studied by micro Hall magnetometry (P. Das \textit{et al.}, Appl. Phys. Lett. \textbf{97} 042507, 2010). For the external magnetic field applied along the grain's easy magnetization direction, the magnetization reversal takes place through a series of Barkhausen jumps. Supported by micromagnetic simulations, the ground state of the grain was found to correspond to a flux closure configuration with a single cross-tie domain wall. Here, we report an analysis of the Barkhausen jumps, which were observed in the hysteresis loops for the external field applied along both the easy and hard magnetization directions. We find that the magnetization reversal takes place through only a few configuration paths in the free-energy landscape, pointing to a high purity of the sample. The distinctly different statistics of the Barkhausen jumps for the two field directions is discussed.Comment: JEMS Conference, to appear in J. Phys. Conf. Se

Marine Middle Eocene Otoliths from India and Java

Otoliths collected from the Harudi Formation (Lutetian) of Kachchh, Western India and from the Nanggulan Formation (Early Bartonian) of Nanggulan, Java, revealed the presence of respectively 15 and 24 teleost taxa. Seven new species are introduced: "genus Brotulinarum" siremboides, Apogon townsendoides, "genus Apogonidarum" altissimus, Lactarius nonfungus, "genus Menidarum" occultus, "genus Percoideorum" pseudatherina and "genus Percoideorum" sciaenoides. Both associations reveal very shallow neritic environments. They are compared with a previously described neritic Middle Eocene otolith association from central Western Pakistan, and a combined list of all (43) taxa represented in the three associations is provided. Considering the restricted sampling, the number (8) of taxa occuring at more than one locality is remarkable, and one can probably conclude that we sampled several of the most common and widespread teleosts inhabiting the neritic environments of the Indo-West-Pacific region during the Middle Eocene. Biogeographic evaluation of the available data leads to the conclusion that in the Eocene, the Indo-West-Pacific region was already inhabited by many fish taxa not represented elsewhere, and that probably it contained the most diverse fish community of the world, as it does today

Commensurability and arithmetic equivalence for orthogonal hypergeometric monodromy groups

Invariants are computed of quadratic forms associated to orthogonal hypergeometric groups of degree five. Some commensurabilities are then determined between these groups, and it is established that some thin groups cannot be conjugate to each other

K+ Ions Crosslinked Kappa-Carrageenan/Methylene Blue Composite Film. Part-1: Synthesis, Characterization and Application as Controlled Release Device for Photodynamic Therapy Application

K+ ions crosslinked (KC/MB) Methylene blue photosensitizer loaded composite film is prepared for photodynamic therapy (PDT) application as Photosensitizer released by composite film can conveniently be controlled by using different quantities of K+ ions and this application is based on dynamic interaction between light with suitable wavelength, photosensitizer and molecular oxygen, promoting the death of the target tissue or bacterial cells. In this work, the Methylene Blue (MB) loaded Carrageenan polymeric film was prepared by the method of direct addition of MB into pre-polymerization solution of Carrageenan (KC). This composite film and plain KC film were characterized by FTIR, XRD and SEM analysis. The characteristic peaks of MB photosensitizer were obtained in FTIR spectrum of composite film. The composite film KC/MB shows prominence of amorphous nature may be due to MB is present in very small quantity. The SEM analysis reveals that the composite film (KC/MB) having much more smooth surface texture throughout the film. Finally, the result of effect of variation in degree of crosslinking on amount of MB release is, as the amount of K+ ions used to crosslink the film increases, MB release decreases.        &nbsp

Interface driven magnetoelectric effects in granular CrO2

Antiferromagnetic and magnetoelectric Cr2O3-surfaces strongly affect the electronic properties in half metallic CrO2. We show the presence of a Cr2O3 surface layer on CrO3 grains by high-resolution transmission electron microscopy. The effect of these surface layers is demonstrated by measurements of the temperature variation of the magnetoelectric susceptibility. A major observation is a sign change at about 100 K followed by a monotonic rise as a function of temperature. These electric field induced moments in CrO3 are correlated with the magnetoelectric susceptibility of pure Cr2O3. This study indicates that it is important to take into account the magnetoelectric character of thin surface layers of Cr2O3 in granular CrO2 for better understanding the transport mechanism in this system. The observation of a finite magnetoelectric susceptibility near room temperature may find utility in device applications.Comment: Figure 1 with strongly reduced resolutio

Deccan volcanism, the KT mass extinction and dinosaurs

Recent advances in Deccan volcanic studies indicate three volcanic phases with the phase-1 at 67.5 Ma followed by a 2 m.y. period of quiescence. Phase-2 marks the main Deccan volcanic eruptions in Chron 29r near the end of the Maastrichtian and accounts for ~80% of the entire 3500 m thick Deccan lava pile. At least four of the world's longest lava flows spanning 1000 km across India and out into the Gulf of Bengal mark phase-2. The final phase-3 was smaller, coincided with the early Danian Chron 29n and also witnessed several of the longest lava flows. The KT boundary and mass extinction was first discovered based on planktic foraminifera from shallow marine intertrappean sediments exposed in Rajahmundry quarries between the longest lava flows of the main volcanic phase-2 and smaller phase-3. At this locality early Danian (zone P1a) planktic foraminiferal assemblages directly overlie the top of phase-2 eruptions and indicate that the masse extinction coincided with the end of this volcanic phase. Planktic foraminiferal assemblages also mark the KT boundary in intertrappean sediments at Jhilmili, Chhindwara, where freshwater to estuarine conditions prevailed during the early Danian and indicate the presence of a marine seaway across India at KT time. Dinosaur bones, nesting sites with complete eggs and abundant eggshells are known from central India surrounding the hypothesized seaway through the Narmada-Tapti rift zone. A Maastrichtian age is generally assigned to these dinosaur remains. Age control may now be improved based on marine microfossils from sequences deposited in the seaway and correlating these strata to nearby terrestrial sequences with dinosaur remains

Standardized method to extract phenolic compounds from Lagerstroemia speciosa L. (Jarul) for enhanced antioxidant activity

Phenolic compounds contribute to the antioxidant property of plants and the efficient extraction of plant phenolics could enhance its antioxidant potential. Lagerstroemia speciosa (L.) Pers. has been investigated for its pharmacological activities, but comparing its antioxidant activities of phenolics derived from its various parts has a key role in developing natural antioxidants. This study was conducted to standardize the extraction of phenolics from leaves, pods and branches of L. speciosa plant, followed by determination of antioxidant activities of their solvent fractions. Phenolic compounds were extracted from the leaves, pods and branches under different parameters such as temperature, pH, type of solvent and volume of the solvent. The extracted phenolic compounds were subjected to solvent fractions and antioxidant assays were performed. Among the various extraction methods tested, the best method was 50% ethanol +1% HCl, refluxing temperature, 100 ml of solvent and 1 hour extraction time. The best solvent fractions were determined as NaHCO3 + ethyl acetate for pods and ethyl acetate alone for leaves and branches with extracted phenolics content of 150.2 mg/g, 136.2 mg/g and 82.9 mg/g, respectively. The chloroform fraction was best among the fractions with maximum ascorbic acid equivalent (ASE) in all the parts of L. speciosa tested. Ferrous ion chelating capacity indicated that butanol fraction had the highest chelation and the same was recorded in ferric ion chelating assay with an EC50 value of 28.2. Hydroxyl radical scavenging activity of the fractions indicated that NaHCO3 + EtOAc fraction of pods had potential activity. Thus, the phenolic compounds from L. speciosa are excellent sources for future investigation on potent natural antioxidant compounds