Observation of Anisotropic Thermal Expansion and the Jahn-Teller Effect in Double Perovskites Sr2-xLaxCoNbO6 Using Neutron Diffraction.

We use temperature dependent neutron powder diffraction (NPD) to investigate the structural changes and magnetic interactions in double perovskite Sr2-xLaxCoNbO6 (x = 0.4 and 0.6). A structural phase transition from tetragonal (I4/m) to monoclinic (P21/n) is observed between x = 0.4 and 0.6 samples. Interestingly, the temperature evolution of the unit cell parameters follows the Grüneisen approximation, and the analysis suggests an isotropic thermal expansion in the case of the x = 0.4 sample, whereas the x = 0.6 sample shows the anisotropy where the thermal expansion along the c-axis significantly deviates from the Grüneisen function. We observe the z-out Jahn-Teller distortion in the CoO6 and consequently z-in distortion in the adjacent NbO6 octahedra. With an increase in the La substitution, a decrease in the degree of octahedral distortion is evident from the significant reduction in the local distortion parameter Δ around the B-site atoms.

Direct observation of the spin texture in SmB6 as evidence of the topological Kondo insulator.

Topological Kondo insulators have been proposed as a new class of topological insulators in which non-trivial surface states reside in the bulk Kondo band gap at low temperature due to strong spin-orbit coupling. In contrast to other three-dimensional topological insulators, a topological Kondo insulator is truly bulk insulating. Furthermore, strong electron correlations are present in the system, which may interact with the novel topological phase. By applying spin- and angle-resolved photoemission spectroscopy, here we show that the surface states of SmB6 are spin polarized. The spin is locked to the crystal momentum, fulfilling time reversal and crystal symmetries. Our results provide strong evidence that SmB6 can host topological surface states in a bulk insulating gap stemming from the Kondo effect, which can serve as an ideal platform for investigating of the interplay between novel topological quantum states with emergent effects and competing orders induced by strongly correlated electrons.

Unusual temperature dependence of band dispersion in Ba(Fe(1-x)Ru(x))2As2 and its consequences for antiferromagnetic ordering.

We have performed detailed studies of the temperature evolution of the electronic structure in Ba(Fe(1-x)Ru(x))(2)As(2) using angle resolved photoemission spectroscopy. Surprisingly, we find that the binding energy of both hole and electron bands changes significantly with temperature in both pure and Ru substituted samples. The hole and electron pockets are well nested at low temperature in unsubstituted (BaFe(2)As(2)) samples, which likely drives the spin density wave and resulting antiferromagnetic order. Upon warming, this nesting is degraded as the hole pocket shrinks and the electron pocket expands. Our results demonstrate that the temperature dependent nesting may play an important role in driving the antiferromagnetic-paramagnetic phase transition.

Ba(1-x)K(x)Mn2As2: an antiferromagnetic local-moment metal.

The compound BaMn2As2 with the tetragonal ThCr2Si2 structure is a local-moment antiferromagnetic insulator with a Néel temperature T(N)=625 K and a large ordered moment µ=3.9µ(B)/Mn. We demonstrate that this compound can be driven metallic by partial substitution of Ba by K while retaining the same crystal and antiferromagnetic structures together with nearly the same high T(N) and large µ. Ba(1-x)K(x)Mn2As2 is thus the first metallic ThCr2Si2-type MAs-based system containing local 3d transition metal M magnetic moments, with consequences for the ongoing debate about the local-moment versus itinerant pictures of the FeAs-based superconductors and parent compounds. The Ba(1-x)K(x)Mn2As2 class of compounds also forms a bridge between the layered iron pnictides and cuprates and may be useful to test theories of high T(c) superconductivity.

What controls the phase diagram and superconductivity in Ru-substituted BaFe2As2?

We use high resolution angle-resolved photoemission to study the electronic structure of the iron based high-temperature superconductors Ba(Fe(1-x)Ru(x))(2)As(2) as a function of Ru concentration. We find that substitution of Ru for Fe is isoelectronic, i.e., it does not change the value of the chemical potential. More interestingly, there are no measured, significant changes in the shape of the Fermi surface or in the Fermi velocity over a wide range of substitution levels (0

An ultrahigh vacuum compatible sample holder for studying complex metal surfaces.

We present a design of a compact and versatile sample holder meant for studying complex (ternary) metallic crystals that require sputtering and annealing to high temperatures under ultrahigh vacuum (10(-10) mbar range) for obtaining the clean, ordered and stoichiometric surface. A resistive heater is fixed to the sample holder and not to the sample plate, and thus can be thoroughly degassed initially to high temperatures without heating the sample. The heater, which is mounted vertically on the sample holder frame, slides into the sample plate of rectangular cross-section during sample transfer. For efficient cooling that is required for adlayer deposition, Cu braids can be pressed on the sample plate from both sides through a screw mechanism. The sample holder has 5 degrees of freedom including a tilt rotation. The sample holder has been used to study different metal surfaces such as ferromagnetic shape memory alloys, alkali metal and Mn adlayers on Al-Pd-Mn quasicrystal, aluminum metal, and Al-Mn alloys. Here, our recent results on temperature dependent low energy electron diffraction study of Ni(2)MnGa(100) are presented.

Plasmon excitations by photoelectron emission from rare gas nanobubbles in aluminum.

Aluminum bulk, surface, and multiple plasmons have been observed in the core-level spectra of rare gas (Ne, Ar, and Xe) nanobubbles in Al, whose intensities are even higher than those of Al metal. Both intrinsic and extrinsic bulk plasmons are detected, but they exhibit diametrically opposite intensity variation due to change in the size and implantation depth of the bubbles. Furthermore, the existence of bubble surface plasmon is demonstrated.

Manganese adlayers on i-Al-Pd-Mn quasicrystal: growth and electronic structure.

Pseudomorphic growth of thin elemental metal films is often observed on a variety of crystalline solids. On quasicrystalline surfaces with their complex structure and the absence of translational periodicity, the situation is different since elemental metals do not exhibit quasicrystalline order, and hence the specific interaction between overlayer and substrate is decisive. Here we study the growth of manganese films on an icosahedral i-Al-Pd-Mn alloy with a view to establishing the growth mode and electronic structure. Although we observe an exponential intensity variation of the adlayer and substrate related x-ray photoemission spectroscopy (XPS) peaks, low energy electron diffraction (LEED) shows that Mn adlayers do not exhibit quasicrystallinity. The detailed structure of the Mn 2p core level line reveals considerable electronic structure differences between the quasicrystalline and elemental metal environment. Evidence of a substantial local magnetic moment on the Mn atoms in the overlayer (about 2.8  µ(B)) is obtained from the Mn 3s exchange splitting.

EVALUATION OF PUVASOL AND PUVASOL WITH TOPICAL BETAMETHASONE DIPROPIONATE PLUS SALICYLIC ACID LOTION IN THE TREATMENT OF SCALP PSORIASIS.

The efficacy and safety of betamethsone dipropionate 0.05% with salicylic acid 2% scalp lotion was evaluated in 60 patients with moderate to severe scalp psoriasis. Out of 120 patients with scalp psoriasis 60 patients received PUVASOL alone and 60 patients received PUVASOL alongwith lotion 0.05% betamethasone dipropionate with 2% salicylic acid scalp application for 3 weeks. The erythema, induration, scales and pruritus steadily improved in patients throughout the 3 weeks treatment course with betamethasone dipropionate with salicylic acid scalp application. At the end of therapy 84.3% of those patients receiving PUVASOL and betamethasone dipropionate-salicylic acid combination had 75% improvement of their scalp psoriasis versus 34.9% of those patients using PUVASOL alone. Complete clearing of the scalp was seen in 35% patients receiving therapy with topical betamethasone-salicylic acid and 11.6% with PUVASOL alone. Local side effects were primarily burning and stinging in 5 (83%) cases treated with topical betamethasone salicylic acid scalp application and 1 (1.6%) receiving PUVASOL alone. Combined therapy with PUVASOL and topical betamethasone dispropionate 0.05% with salicyclic acid 2% application appears to be safe and an effective treatment for scalp psoriasis.

BORDERLINE TUBERCULOID LEPROSY: CLINICOPATHOLOGICAL EVALUATION OF MULTIDRUG THERAPY.

Efficacy of multi-drug therapy as per WHO recommendation in 125 fresh cases of borderline tuberculoid (BT) leprosy was evaluated. There were 116 (92.8%) male and 9 (7.2%) female patients. Age of the patients ranged from 18-50 years but the majority (80.8%) were young adults in the age group 21-35 years. The commonest site of lesion was the upper extremity in 65 (52%) cases. Skin smear for acid fast Mycobacterium leprae was positive in 11 (8.8%) patients. All patients were given multidrug therapy consisting of rifampicin 600 mg once a month and dapsone 100 mg daily for 6 months. At the end of 6 months, 42 (33.6%) patients had shown marked improvement, 14 (11.2%) had increase in activity, 51 (45.6%) had shown regression and 12 (9.6%) cases became clinically inactive. Histologically complete clearance of the infiltration was not observed in any patient. Compact granulomas persisted in 30 (24%) cases. In 1 (0.8%) patient M. leprae were found in the skin smear at the end of 6 months. This study indicates that treatment with MDT for 6 months is inadequate to treat all types of BT leprosy cases.

A clinicopathological study of multidrug therapy in borderline tuberculoid leprosy.

A study was undertaken to evaluate the efficacy of multidrug therapy as per WHO recommendation in 50 fresh cases (46 males and 4 females) suffering from borderline tuberculoid leprosy. All were given multidrug therapy consisting of rifampicin 600 mg once a month and dapsone 100 mg daily for 6 months. At the end of 6 months all were evaluated clinically and histopathological examinations of the lesions were studied. The lesions were still active in 60% of patients clinically; 32% cases receiving multidrug therapy had shown marked improvement. Histologically lymphocytic infiltration in skin still persisted in all the slides examined and nerve infiltration was still present in 68% of cases at the end of 6 months after receiving multidrug therapy. The study shows that treatment with multidrug regimen for 6 months may not be sufficient to treat borderline tuberculoid leprosy cases.

A clinico-pathological study of macular lesions in leprosy.

One hundred twenty histologically confirmed cases of leprosy having macular lesions were evaluated clinically and histopathologically according to Ridley-Jopling classification. Of these 120 cases, the majority (91 or 75.8%) were young adults. The main clinical findings were: a single macule in 42 patients (35%), multiple macules 2-5 in numbers in 35 patients (29.1%), 6-10 macules in 17 patients (14.1%) and more than 10 macules in 26 patients (21.6%). Impairment of sensation over the macular lesions was present in 62 cases (51.6%), total loss of sensation was noticed in 31 patients (25.8%) and sensation was intact in 27 patients (22.5%). Acid-fast bacilli were detected in 11 cases (9.1%) by slit-skin smear examination. Clinical examination of the 120 cases revealed features of TT in 16 (13.3%), BT in 41 (34.1%), BB in 11 (9.1%), BL in 13 (10.8%), LL in 7 (5.8%) and indeterminate leprosy (IL) in 32 patients (26.6%). On the contrary, histologically there were 22 cases of TT (18.3%), 38 cases of BT (31.6%), 8 (6.5%) BB, 10 BL (8.3%), 7 LL (5.8%) and 35 cases of IL (29.1%). Histopathological features were consistent with the clinical picture in 84 patients (70%).

OSTEOMA CUTIS (A Case Report).

A case of osteoma cutis in a woman of 48 years is reported. The primary cutaneous ossification has a unique congenital and noninvasive nature. The histological features of the lesion are illustrated.