Transition metal substituted Fe2P: potential candidate for MRAM application.

We propose transition metal substituted Fe2P as a new promising material for spin-transfer torque magnetic random-access memory (STT-MRAM) application. Using first-principles calculations based on density functional theory and Monte Carlo simulations, we demonstrate that this material can be used as a ferromagnetic electrode in the magnetic tunnel junction (MTJ) of STT-MRAM due to its moderate perpendicular magnetic anisotropy, high ferromagnetic transition temperature, and large tunnel magnetoresistance. This work is expected to provide a basis for the development of a new class of Fe2P-based electrode materials for STT-MRAM devices.

Role of zero-point effects in stabilizing the ground state structure of bulk Fe2P.

Structural stability of Fe2P is investigated in detail using first-principles calculations based on density functional theory. While the orthorhombic C23 phase is found to be energetically more stable, the experiments suggest it to be hexagonal C22 phase. In the present study, we show that in order to obtain the correct ground state structure of Fe2P from the first-principles based methods it is utmost necessary to consider the zero-point effects such as zero-point vibrations and spin fluctuations. This study demonstrates an exceptional case where a bulk material is stabilized by quantum effects, which are usually important in low-dimensional materials. Our results also indicate the possibility of magnetic field induced structural quantum phase transition in Fe2P, which should form the basis for further theoretical and experimental efforts.

A first-principles study of pressure-induced phase transformation in a rare-earth formate framework.

Among the panoply of exciting properties that metal-organic frameworks (MOFs) exhibit, fully reversible pressure-induced phase transformations (PIPTs) are particularly interesting as they intrinsically relate to the flexibility of MOFs. Recently, a number of MOFs have been reported to exhibit this feature, which is attributed to bond rearrangement with applied pressure. However, the experimental assessment of whether a given MOF exhibits PIPT or not requires sophisticated instruments as well as detailed structural investigations. Can we capture such low pressure transformations through simulations is the question we seek to answer in this paper. For this, we have performed first-principles calculations based on the density functional theory, on a MOF, [tmenH2][Y(HCOO)4]2 (tmenH2(2+) = N,N,N',N'-tetramethylethylenediammonium). The estimated lattice constants for both the parent and product phases of the PIPT agree well with the earlier experimental results available for the same MOF with erbium. Importantly, the results confirm the observed PIPT, and thus provide theoretical corroborative evidence for the experimental findings. Our calculations offer insights into the energetics involved and reveal that the less dense phase is energetically more stable than the denser phase. From detailed analyses of the two phases, we correlate the changes in bonding and electronic structure across the PIPT with elastic and electronic conduction behavior that can be verified experimentally, to develop a deeper understanding of the PIPT in MOFs.

Review of Results of QuantiFERON TB Gold Test in Presumed Ocular Tuberculosis in a South Indian Patient Population.

AIM: To review the results of QuantiFERON TB gold (QFT-G) in our patient population of presumed ocular tuberculosis and the effect of antitubercular therapy (ATT) on the QFT-G result. MATERIALS AND METHODS: Retrospective review of 82 cases of presumed ocular tuberculosis with a successful response to ATT and 6 months follow-up post-ATT. Appropriate statistical analysis was done for associations between QFT-G and independent variables. Pre-ATT QFT-G values were also compared to the post-ATT value. RESULTS: There were no statistically significant differences in the results of QFT-G with age (0.635), gender (0.096), history of oral steroids (0.171), or type of uveitis (0.664). There was a statistically significant association between a positive QFT-G and serpiginous-like choroiditis (0.048). The majority of our patients had positive QFT even after completion of ATT but with a significant drop in the mean values post ATT (0.010). CONCLUSIONS: Our study shows significant association of positive QFT with serpiginous-like choroiditis and persistent positivity even after completion of ATT in majority of cases in our population. There was, however, a drop in the mean values of QFT-G post-ATT.

Orbital and adnexal tuberculosis: a case series from a South Indian population.

BACKGROUND: Orbital tuberculosis (OTb) is rare and may be regarded as a manifestation of extrapulmonary tuberculosis. We report an interesting case series of six patients with varied presentations of orbital and adnexal tuberculosis in a South Indian patient population. RESULTS: A retrospective, interventional case series of six patients diagnosed with orbital and adnexal tuberculosis on the basis of clinical, radiological and histopathological evaluations between 2010 and 2013 was performed. Among the six patients with histopathologically proven OTb, five were women. The varied presentations included tubercular dacryoadenitis (two cases), classical periostitis (two cases), OTb with bone involvement (one case) and ocular adnexal tuberculosis (one case). Systemic involvement was seen in one case. All cases were treated with a regimen of antitubercular therapy (ATT). CONCLUSIONS: OTb, though rare, should form a part of the differential diagnosis of orbital lesions in a high tuberculosis (TB) endemic country like ours. Biopsy still remains the mainstay of diagnosis.

Unilateral snow banking in tuberculosis-related intermediate uveitis.

Snow banking is usually a term coined to describe the accumulation of vitreous exudates over the pars plana and the peripheral retina in pars planitis. Snow banking is very rare in tubercular intermediate uveitis. A 32-year-old male was diagnosed to have intermediate uveitis due to tubercular etiology in the right eye. Laboratory investigations include an increased erythrocyte sedimentation rate, positive Mantoux test, and computed tomography thorax showing mediastinal lymphadenopathy. Transbronchial needle aspiration of the lymph nodes showed chronic granulomatous inflammation with caseation. There were no recurrences following antitubercular therapy (ATT). This case report highlights the unique finding of snow banking in tubercular uveitis and course following treatment with ATT.