Coexistence of Midgap Antiferromagnetic and Mott States in Undoped, Hole- and Electron-Doped Ambipolar Cuprates.

We report the first observation of the coexistence of a distinct midgap state and a Mott state in undoped and their evolution in electron and hole-doped ambipolar Y_{0.38}La_{0.62}(Ba_{0.82}La_{0.18})_{2}Cu_{3}O_{y} films using spectroscopic ellipsometry and x-ray absorption spectroscopies at the O K and Cu L_{3,2} edges. Supported by theoretical calculations, the midgap state is shown to originate from antiferromagnetic correlation. Surprisingly, while the magnetic state collapses and its correlation strength weakens with dopings, the Mott state in contrast moves toward a higher energy and its correlation strength increases. Our result provides important clues to the mechanism of electronic correlation strengths and superconductivity in cuprates.

Bioactivity studies on TiO2-bearing Na2O-CaO-SiO2-B2O3 glasses.

Soda lime silica borate glasses mixed with different concentrations of TiO2 are synthesized by the melt-quenching technique. As a part of study on bioactivity of these glasses, the samples were immersed in simulated body fluid (SBF) solution for prolonged times (~21 days) during which weight loss along with pH measurements is carried out at specific intervals of time. The XRD and SEM analyses of post-immersed samples confirm the formation of crystalline hydroxyapatite layer (HA) on the surface of the samples. To assess the role of TiO2 on the formation of HA layer and degradability of the samples the spectroscopic studies viz. optical absorption and IR spectral studies on post- and pre-immersed samples have been carried out. The analysis of the results of degradability together with spectroscopic studies as a function of TiO2 concentration indicated that about 6.0 mol% of TiO2 is the optimal concentration for achieving better bioactivity of these glasses. The presence of the maximal concentration octahedral titanium ions in this glass that facilitates the formation of HA layer is found to be the reason for such a higher bioactivity.

Dysregulated MicroRNA Expression and Chronic Lung Allograft Rejection in Recipients With Antibodies to Donor HLA.

The pathogenesis of chronic rejection, Bronchiolitis Obliterans Syndrome (BOS) following lung transplantation (LT) is poorly understood. We hypothesized that development of antibodies to HLA (DSA) is associated with dysregulation of microRNA (miRNA) that predisposes BOS. Towards this, miRNA profiling of mononuclear cells from 10 stable LT (DSA(-) BOS(-) ), 10 LT with DSA(+) BOS(-) (DSA group) and 10 LT with DSA(+) BOS(+) (BOS group) were performed. Prediction by mirPath indicated that differential miRNAs in DSA(+) BOS(-) compared to stable are significantly up-regulated (relative fold >2, p < 0.05) for TGF-ß and B cell receptor signal pathways. A total of seventy-four miRNAs were up-regulated and six miRNAs were down regulated in LT with DSA(+) BOS(+) when compared to stable (relative fold >2, p < 0.05). There was also significant enrichment of cell cycle and gap junction pathways. An inverse correlation between expression of two key miRNAs and their target genes were observed: miR-369-5p and miR-548d were down regulated in DSA(+) LT while their gene targets in TGF-ß signal pathways were up-regulated. In addition, miR-628-5p and miR-134 were down regulated and their target genes (B cell development) were up-regulated. Therefore, we conclude that alloimmunity induced changes in miRNAs affecting the TGF-ß and B cell receptor signal pathways play important roles in BOS development.

Theoretical prediction of a time-reversal broken chiral superconducting phase driven by electronic correlations in a single TiSe2 layer.

Bulk TiSe2 is an intrinsically layered transition metal dichalcogenide hosting both superconducting and charge-density-wave ordering. Motivated by the recent progress in preparing two-dimensional transition metal dichalcogenides, we study these frustrated orderings in a single trilayer of TiSe2. Using a renormalization group approach, we find that electronic correlations can give rise to charge-density-wave order and two kinds of superconductivity. One possible superconducting state corresponds to unconventional s(+-) pairing. The other is particularly exciting as it is chiral, breaking time-reversal symmetry. Its stability depends on the precise strength and screening of the electron-electron interactions in two-dimensional TiSe2.

Equations-of-motion method for triplet excitation operators in graphene.

The particle-hole continuum in the Dirac sea of graphene has a unique window underneath, which in principle leaves room for bound state formation in the triplet particle-hole channel (Baskaran and Jafari 2002 Phys. Rev. Lett. 89 016402). In this work, we construct appropriate triplet particle-hole operators and, using a repulsive Hubbard-type effective interaction, we employ equations of motion to derive approximate eigenvalue equations for such triplet operators. While the secular equation for the spin density fluctuations gives rise to an equation which is second order in the strength of the short range interaction, the explicit construction of the triplet operators obtained here shows that, in terms of these operators, the second-order equation can be factorized to two first-order equations, one of which gives rise to a solution below the particle-hole continuum of Dirac electrons in undoped graphene.

Electronic phase separation at the LaAlO3/SrTiO3 interface.

There are many electronic and magnetic properties exhibited by complex oxides. Electronic phase separation (EPS) is one of those, the presence of which can be linked to exotic behaviours, such as colossal magnetoresistance, metal-insulator transition and high-temperature superconductivity. A variety of new and unusual electronic phases at the interfaces between complex oxides, in particular between two non-magnetic insulators LaAlO(3) and SrTiO(3), have stimulated the oxide community. However, no EPS has been observed in this system despite a theoretical prediction. Here, we report an EPS state at the LaAlO(3)/SrTiO(3) interface, where the interface charges are separated into regions of a quasi-two-dimensional electron gas, a ferromagnetic phase, which persists above room temperature, and a (superconductor like) diamagnetic/paramagnetic phase below 60 K. The EPS is due to the selective occupancy (in the form of 2D-nanoscopic metallic droplets) of interface sub-bands of the nearly degenerate Ti orbital in the SrTiO(3). The observation of this EPS demonstrates the electronic and magnetic phenomena that can emerge at the interface between complex oxides mediated by the Ti orbital.

Exact results for spin dynamics and fractionalization in the Kitaev Model.

We present certain exact analytical results for dynamical spin correlation functions in the Kitaev Model. It is the first result of its kind in nontrivial quantum spin models. The result is also novel: in spite of the presence of gapless propagating Majorana fermion excitations, dynamical two spin correlation functions are identically zero beyond nearest neighbor separation. This shows existence of a gapless but short range spin liquid. An unusual, all energy scale fractionalization of a spin-flip quanta, into two infinitely massive pi fluxes and a dynamical Majorana fermion, is shown to occur. As the Kitaev Model exemplifies topological quantum computation, our result presents new insights into qubit dynamics and generation of topological excitations.

Novel electric field effects on Landau levels in graphene.

A new effect in graphene in the presence of crossed uniform electric and magnetic fields is predicted. Landau levels are shown to be modified in an unexpected fashion by the electric field, leading to a collapse of the spectrum, when the value of electric to magnetic field ratio exceeds a certain critical value. Our theoretical results, strikingly different from the standard 2D electron gas, are explained using a "Lorentz boost," and as an "instability of a relativistic quantum field vacuum." It is a remarkable case of emergent relativistic type phenomena in nonrelativistic graphene. We also discuss few possible experimental consequence.

Electronic model for CoO2 layer based systems: chiral resonating valence bond metal and superconductivity.

Takada et al. have reported superconductivity in layered Na(x)CoO(2)yH(2)O (T(c) approximately equal to 5 K). We model a reference neutral CoO2 layer as an orbitally nondegenerate spin-1/2 antiferromagnetic Mott insulator on a triangular lattice and Na(x)CoO(2)yH(2)O as electron doped Mott insulators described by a t-J model. It is suggested that at optimal doping chiral spin fluctuations enhanced by the dopant dynamics lead to a gapful d-wave superconducting state. A chiral resonating valence bond (RVB) metal, a parity and time (PT) reversal violating state with condensed RVB gauge fields, with a possible weak ferromagnetism, and low temperature p-wave superconductivity are also suggested at higher dopings.

Mott insulator to high Tc superconductor via pressure: resonating valence bond theory and prediction of new systems.

Mott insulator superconductor transition, via pressure and no external doping, is studied in orbitally nondegenerate spin-1 / 2 systems. It is presented as another resonating valence bond route to high T(c) superconductivity. We propose a "strong coupling" hypothesis that views long range Coulomb force driven first order Mott transition as a self-doping process that also preserves superexchange on the metal side. We present a two-species t-J model where conserved N0 doubly occupied (e(-)) sites and N0 empty sites (e(+)) hop in the background of N-2N(0) singly occupied (neutral) sites in a lattice of N sites. An equivalence to the regular t-J model is made. Some old and new systems are predicted to be candidates for pressure-induced high T(c) superconductivity.

Seroprevalence of human immunodeficiency virus (HIV) infection among tuberculosis patients in Tamil Nadu.

BACKGROUND & OBJECTIVES: The dual epidemic of HIV and tuberculosis is a cause for concern in those countries where these two infections are prevalent in epidemic proportions. We undertook a survey at two sites in North Arcot district of Tamil Nadu in 1992-1993, to know the seroprevalence of HIV infection among tuberculosis patients. The objective of this study was to re-examine the prevalence of HIV infection among tuberculosis patients in a repeat survey. METHODS: The study was undertaken in four centres: District Tuberculosis Centre (DTC), Vellore, Tuberculosis Sanatorium, Pennathur (Vellore), District TB Centre (DTC), Kancheepuram and the Government Thiruvotteswarar Tuberculosis Hospital (GTTH), Chennai in the northern part of Tamil Nadu during 1997-1998. A total of 2361 newly diagnosed TB patients were registered in this study. HIV serology after pre-test counseling was done along with sputum examination for acid-fast bacillus by smear and culture for mycobacteria for all patients. RESULTS: The overall HIV seroprevalence among TB patients was 4.7 per cent. The highest HIV seropositivity rate was found among patients aged 30-39 yr (10.6%). HIV seroprevalence showed a wide variation among the different centres ranging from 0.6. per cent in DTC, Kancheepuram to 9.4 per cent in Pennathur Sanatorium, Vellore. Sputum smear positivity was 88 per cent among the HIV-negative and 83 per cent among HIV-positive tuberculosis patients. INTERPRETATION & CONCLUSION: HIV infection is on the rise among TB patients in Tamil Nadu. Acid-fast smear microscopy is adequate for the diagnosis of pulmonary tuberculosis, and drug resistance among HIV positive patients is not a major problem at this point of time; hence antituberculosis regimens recommended by the Revised National Tuberculosis Control Program (RNTCP) can be used to treat HIV positive patients with tuberculosis.

Gapless spin-1 neutral collective mode branch for graphite.

Using the standard tight binding model of 2D graphite with short range electron repulsion, we predict a gapless spin-1, neutral collective mode branch below the particle-hole continuum with energy vanishing linearly with momenta at the Gamma and K points in the Brillouin zone. This spin-1 mode has a wide energy dispersion, 0 to approximately 2 eV, and is not Landau damped. The "Dirac cone spectrum" of electrons at the chemical potential of graphite generates our collective mode, so we call this "spin-1 zero sound" of the "Dirac sea." Epithermal neutron scattering experiments and spin polarized electron energy loss spectroscopy can be used to confirm and study our collective mode.

Risk of development of tuberculosis in HIV-infected patients.

OBJECTIVE: To estimate the rate of development of active tuberculosis (TB) in a cohort of human immunodeficiency virus (HIV) positive patients, and to identify the characteristics of these patients. DESIGN: A total of 175 HIV-positive individuals were recruited from clinics for sexually transmitted diseases and followed up for 31 +/- 6.8 months. Clinical examination, chest X-ray, sputum smear for acid-fast bacilli and culture for mycobacteria and HIV serology were performed at the time of registration and repeated periodically. RESULTS: Seventeen patients had TB at intake and another 24 developed TB during follow-up, giving a breakdown rate of 6.9/100 person-years (p-y) (95% confidence interval [CI] 4.1-9.6). The attack rates were similar in tuberculin positive (7.1/100 p-y, 95%CI 3.4-10.8) and negative (6.7/100 p-y, 95%CI 2.6-10.8) patients. There was a trend towards higher mortality in patients who developed TB (10.5/100 p-y, 95%CI 4.8-15.2) compared to those who did not (6.1/100 p-y, 95%CI 3.2-8.8). CONCLUSIONS: The results of this study provide information regarding the high risk of development of active tuberculosis and its associated mortality in HIV-infected persons. The risk of developing TB appears to be equally high in tuberculin positive and negative individuals, suggesting that new infections could play a major role in this susceptible population.

Predictive testing for familial adenomatous polyposis in a rural South Indian community.

During the course of genome studies in a rural community in the South Indian state of Karnataka, DNA-based investigations and counselling for familial adenomatous polyposis (FAP) were requested via the community physician. The proposita died in 1940 and FAP had been clinically diagnosed in 2 of her 5 children, both deceased. DNA samples from 2 affected individuals in the third generation were screened for mutations in the APC gene, and a frame-shift mutation was identified in exon 15 with a common deletion at codon 1061. Predictive testing for the mutation was then organized on a voluntary basis. There were 11 positive tests, including confirmatory positives on 2 persons diagnosed by colonoscopy, and to date surgery has been successfully undertaken on 3 previously undiagnosed adults. The ongoing success of the study indicates that, with appropriate access to the facilities offered by collaborating centres, predictive testing is feasible for diseases such as FAP and could be of significant benefit to communities in economically less developed countries.

Cross-resistance to Bacillus sphaericus strains in Culex quinquefasciatus resistant to B. sphaericus 1593M.

Bacillus sphaericus 1593M resistant larvae of Culex quinquefasciatus were reared in the laboratory since 1995. Resistance in the larvae was monitored by subjecting selection pressure using B. sphaericus 1593M at every generation. Bioassays were conducted with different strains of B. sphaericus (Bs 2297, Bs 2362 and Bs IAB 59) and confirmed cross-resistance in the present study. The level ranged between 27.3 to 18.2 fold in comparison with susceptible larvae. But Bacillus thuringiensis var israelensis strains (Bti PG14 and Bti 426) did not show any cross-resistance in the larvae and it emphasized a need to study the mode of action of B. sphaericus toxin that induces cross-resistance in the larval strain.

Impact of saturated and trans fatty acid enriched oil blends on atherosclerosis in rabbits fed cholesterol-free diets.

Thirty six-male New Zealand White rabbits subdivided into four dietary groups (9 animals per group) were fed high fat (36% en), cholesterol-free diets for nine months. The dietary oil blends were formulated to contain high levels of the target fatty acids namely trans-rich (partially hydrogenated soybean oil; TRANS), cis monounsaturated-rich (rapeseed, sunflower seed oil and palm olein; MONO), palmitic-rich (palm olein; POL) and lauric-myristic rich (coconut, palm kernel and corn oils; LM). Ad libitum feeding of the rabbits resulted in normal growth throughout the nine months and no differences in the final body weights of the animals were evident at autopsy. Plasma total cholesterol was significantly elevated only by the LM enriched diet compared with all other treatments; values were comparable between the other three treatment groups. Changes in the total cholesterol were not reflected in the VLDL and LDL lipoproteins. However, HDL-cholesterol was significantly lowered by the TRANS diet compared with all other dietary groups. HDL-cholesterol was also significantly increased by the LM diet in comparison to the POL-diet. Both adipose and liver triglyceride fatty acid compositions tended to reflect the type of fatty acids fed the animals. Trans fatty acids were evident only in animals fed the trans diet and it was apparent that the trans fatty acids competed with linoleic acid for incorporation into these tissues. Increased concentrations of lauric and myristic fatty acids in the LM-fed animals were also evident. In the POL and high MONO fed rabbits, palmitic and oleic fatty acids (respectively) were concentrated in the adipose and liver. The diets, however, failed to induce severe atherosclerosis in this study. This can be explained, in part, by the lack of dietary cholesterol and the use of plant (rather than animal) proteins in our dietary formulations. The effect of these important atherosclerosis modulators in association with these fatty acids requires further evaluation.

Hematological impairments in recurrent Plasmodium vivax infected patients.

The hematological parameters were assayed in Plasmodium vivax patients with only one infection, two infections, three infections and more than three malarial infections during a period of six months. A steady fall in the levels of hemoglobin as well as packed cell volume (PVC) level was observed with increasing number of infections. The malarial patients showed a progressive decrease in RBC level with increasing number of attacks. The decrease in the hematological indices was statistically significant at all levels of parasitemia. There was a marked increase in the osmotic fragility of the malarial erythrocytes when compared to that of controls. During repeated malarial attacks, significant decrease in MCH (p < 0.05) and MCH (p < 0.01) and increase in the MCV level (p < 0.05) and Heinz body formation (p < 0.001) were observed. Parasite density significantly influenced the fragility of the erythrocytes, Heinz body formation, MCV, MCH and MCHC levels. Thus, the erythrocytes of the patients repeatedly infected with Plasmodium vivax parasite are subjected to structural and functional impairment, ultimately culminating in anemia.

Relationship between glutathione and DL alpha-lipoic acid against cadmium-induced hepatotoxicity.

Cadmium, a divalent metal toxicant, preferentially localizes in hepatocytes and causes liver injury. DL alpha-lipoic acid is a dithiol which is effective in rendering protection against cadmium-associated liver damage, by virtue of its two sulfhydryl moieties. Lipoate was administered to cadmium-exposed rats which were either prior administered with buthionine sulfoximine to deplete liver glutathione or not. During lipoate treatment, significant protection was rendered against cadmium toxicity even under glutathione-depleted experimental condition. This highlights the antioxidant property of lipoic acid and its efficacy in mitigating cadmium-associated liver assault even in the absence of glutathione synthesis.