Nature of the spiral state, electric polarisation and magnetic transitions in Sr-doped YBaCuFeO5_5: A first-principles study

Contradictory results on the ferroelectric response of type II multiferroic YBaCuFeO$_{5}$, in its incommensurate phase, has of late, opened up a lively debate. There are ambiguous reports on the nature of the spiral magnetic state. Using first-principles DFT calculations for the parent compound within LSDA+U+SO approximation, the multiferroic response and the nature of spiral state is revealed. The helical spiral is found to be more stable below the transition temperature as spins prefer to lie in ab plane. The Dzyaloshinskii-Moriya (DM) interaction and the spin current mechanism were earlier invoked to account for the electric polarisation in this system. However, the DM interaction is found to be absent, spin current mechanism is not valid in the helical spiral state and there is no electric polarisation thereof. These results are in good agreement with the recent single-crystal data. We also investigate the magnetic transitions in YBa$_{1-x}$Sr$_x$CuFeO$_5$ for the entire range $0\le x\le 1$ of doping. The exchange interactions are estimated as a function of doping and a quantum Monte Carlo (QMC) calculation on an effective spin Hamiltonian shows that the paramagnetic to commensurate phase transition temperature increases with doping till $x=0.5$ and decreases beyond. Our observations are consistent with experimental findings.Comment: 8 pages, 7 figure

Defects in hides and skins that fect assessment

The defects in raw hides and skins procured from different parts of the country vary considerably in view of the variations in climate and other environmental conditions. Proper identification of the most common defects, therefore assumes much significance in evolving standardized procedures for assessing quality of raw hides and skins. Reference may be due to IS: 7656-1975 Code of practice for curing and preservation of cattle hides and goal and sheep skins by et salting method which gives improved methods of curing and preservation as also precautions to avoid defects in hides and skins

Purification and properties of utral protense isolated from goat skin

A neutral proteinase isolated from goat skin was purified and its physico-chemical properties were studied. The six different treatments when given successively to the original enzyme extract resulted in a I22-fold purification retaining59% of the original activity. The purified enzyme was found to be homogeneous and capable of hydrolysing casein, egg albumin and haemoglobin although to different degrees. Of the skin proteins studied, albumin, globulin and mucoid were readily hydrolysed hy the proteinase, whereas collagen and elastin remained unaffected. The enzyme activity was optimum between pH 7.5 and 8.0 in case of almost all protein substrates. The enzyme was found to be quite stable at a pH range of 6.5 to 8.5. The enzyme was fairly thermolabile and was found to lose its activity when healed at a temperature above 60° C and exposed to ultraviolet rays. The enzyme was inactivated by thiol group, metal chelating agents and heavy metal ions

Temperaturna ovisnost masa fizičkih pseudoskalarnih mezona (η , η` i ι) uz konzistentnu matricu mase i unitarnu matricu

Taking three orthonormal basis states and constructing the Lagrangian, we have obtained the unitary transformation matrix and mass squared matrix of η, η\u27 and ι. The temperature dependence of these pseudoscalar meson masses has been studied while getting the value of the mass of one of the basis states η1 by taking into account the gluon condensate value which yields the pure gluonium mass estimate. Variation of their masses with the temperature has also been studied. The calculations for the radiative decays of these pseudoscalar mesons have also been carried out and the results are encouraging.Polazeći od tri ortonormirana osnovna stanja i konstruiranog lagranzijana, izveli smo unitarnu pretvorbenu matricu i matricu kvadratnih masa mezona η _ η\u27 i ι. Proučavali smo temperaturnu ovisnost masa tih pseudoskalarnih mezona. Dobili smo vrijednost mase jednog od osnovnih stanja η1 uzimajući u obzir iznos gluonskog kondenzata koji daje cistu ocjenu mase gluonijuma. Promjene njihove mase s temperaturom smo također proučili. Izračunali smo i radijativni raspad tih pseudoskalarnih mezona i rezultati su ohrabrujući

Survey of incidence of various surface defects in goat and sheep skin in Madras

23,429 goat skins and 37,026 sheep skins were examined to find out the incidence of various surface defects in them. 33.44 percent of goat skins and 14.6 per cent of sheep skins were found to be affected in quality. Major defects common to both goat and sheep skins were abscess, fire-mark and psoroptosis. In addition to the above common defects demodecosis and sheep pox appreciably deteriorated the quality of goat and sheep skins respectively. Seasonal variation in the incidence of the major defects were also studied

Approximation Algorithm for Line Segment Coverage for Wireless Sensor Network

The coverage problem in wireless sensor networks deals with the problem of covering a region or parts of it with sensors. In this paper, we address the problem of covering a set of line segments in sensor networks. A line segment ` is said to be covered if it intersects the sensing regions of at least one sensor distributed in that region. We show that the problem of finding the minimum number of sensors needed to cover each member in a given set of line segments in a rectangular area is NP-hard. Next, we propose a constant factor approximation algorithm for the problem of covering a set of axis-parallel line segments. We also show that a PTAS exists for this problem.Comment: 16 pages, 5 figures

Relapses of Plasmodium vivax infection usually result from activation of heterologous hypnozoites.

BACKGROUND: Relapses originating from hypnozoites are characteristic of Plasmodium vivax infections. Thus, reappearance of parasitemia after treatment can result from relapse, recrudescence, or reinfection. It has been assumed that parasites causing relapse would be a subset of the parasites that caused the primary infection. METHODS: Paired samples were collected before initiation of antimalarial treatment and at recurrence of parasitemia from 149 patients with vivax malaria in Thailand (n=36), where reinfection could be excluded, and during field studies in Myanmar (n=75) and India (n=38). RESULTS: Combined genetic data from 2 genotyping approaches showed that novel P. vivax populations were present in the majority of patients with recurrent infection (107 [72%] of 149 patients overall [78% of patients in Thailand, 75% of patients in Myanmar {Burma}, and 63% of patients in India]). In 61% of the Thai and Burmese patients and in 55% of the Indian patients, the recurrent infections contained none of the parasite genotypes that caused the acute infection. CONCLUSIONS: The P. vivax populations emerging from hypnozoites commonly differ from the populations that caused the acute episode. Activation of heterologous hypnozoite populations is the most common cause of first relapse in patients with vivax malaria

Ultraviolet Extinction Properties in the Milky Way

We have assembled a homogeneous database of 417 ultraviolet (UV) extinction curves for reddened sightlines having International Ultraviolet Explorer (IUE) spectra. We have combined these with optical and 2MASS photometry allowing estimates of the ratio of total-to-selective extinction, R(V), for the entire sample. Fitzpatrick-Massa (FM) parameters have also been found for the entire sample. This is the largest study of parameterized UV extinction curves yet published and it covers a wide range of environments, from dense molecular clouds to the diffuse interstellar medium (ISM), with extinctions A(V) ranging from 0.50 to 4.80. It is the first to extend far beyond the solar neighborhood and into the Galaxy at large, with 30 sightlines having distances > 5 kpc. Previously, the longest sightlines with FM parameters and R(V) extended ~ 1 kpc. We find that (1.) the CCM extinction law applies for 93% of the sightlines, implying that dust processing in the Galaxy is efficient and systematic; (2.) the central wavelength of the 2175 A bump is constant; (3.) the 2175 A bump width is dependent on environment. Only four sightlines show systematic deviations from CCM, HD 29647, 62542, 204827, and 210121. These sightlines all sample dense, molecule-rich clouds. The new extinction curves and values of R(V) allow us to revise the CCM law.Comment: 32 pages, 12 figure

Symmetries and novel universal properties of turbulent hydrodynamics in a symmetric binary fluid mixture

We elucidate the universal properties of the nonequilibrium steady states (NESS) in a driven symmetric binary fluid mixture, an example of active advection, in its miscible phase. We use the symmetries of the equations of motion to establish the appropriate form of the structure functions which characterise the statistical properties of the NESS of a driven symmetric binary fluid mixture. We elucidate the universal properties described by the scaling exponents and the amplitude ratios. Our results suggest that these exponents and amplitude ratios vary continuously with the degree of crosscorrelations between the velocity and the gradient of the concentration fields. Furthermore, we demonstrate, in agreement with Celani et al, Phys. Rev. Lett., 89, 234502 (2002, that the conventional structure functions as used in passive scalar turbulence studies exhibit only simple scaling in the problem of symmetric binary fluid mixture even in the weak concentration limit. We also discuss possible experimental verifications of our results.Comment: To appear in JSTAT (letters) (2005