High cubicity of D2O ice inside spherical nanopores of MIL-101(Cr) framework: a neutron diffraction study.

Although cubic ice (ice Ic) is considered to be an important phase of water that impacts ice cloud formation in the Earth's upper atmosphere, its properties have not been studied to the same extent as those of hexagonal ice (ice Ih). This is because pristine ice Ic is not formed in simple laboratory conditions. Ice Ic formed in ambient conditions has a stacking disordered array of both hexagonal and cubic-structured hydrogen-bonded water molecules. It is therefore an active area of research to find ways of developing stacking disorder-free pure ice Ic. We demonstrate the evolution of almost pure ice Ic structure within the spherical nanopores of a hydrostable Cr-based metal-organic framework MIL-101(Cr) with an average pore size of 1 nm by low-temperature neutron diffraction study on D2O. It is observed that at temperatures below 230 K a fraction of liquid D2O transforms into ice and more than 94% of ice crystals evolved inside the pore are cubic in shape. This is a significantly high fraction of ice Ic formed under simple conditions inside the spherical pores of a Cr-based MOF. It is also observed that upon increasing the temperature, ice Ic remains stable until its melting point, without being transformed into ice Ih. This observation is in contrast to our previous observation of ice structure in the 2D cylindrical nanopores of MCM-41, where H2O ice after creeping out from the cylindrical channel was seen to be dominated by hexagonal shape. In the present study, the D2O molecules were confined into well-defined spherical nanopores, which hindered the growth of crystals above a certain size, thus minimizing the stacking disordered array. Nanoconfinement of water inside uniform spherical pores is therefore a promising method for the evolution of a significantly large fraction of cubic ice by minimizing the stacking disorder. This finding may open up the possibility of forming ice Ic with 100% cubicity under simple laboratory conditions, which will help in exploring the microphysics of ice cloud formation in the upper atmosphere.

Exploring Magnetic XY Behavior in a Quasi-2D Anisotropic Triangular Lattice of Cu(II) by Functionalized Graphene.

Study on magnetism in two-dimensional (2D) spin-lattices is advancing rapidly. In this work, phase-pure botallackite (Bo) (Cu2(OH)3Br), a quasi-2D S = 1/2 anisotropic triangular spin-lattice is stabilized over 2D reduced graphene oxide (rGO) nanosheets via simple oxidation-reduction reaction chemistry. In comparison to polycrystalline Bo, such an anchoring resulted in the oriented growth of Bo crystallites in the Bo-rGO system. The Bo-rGO nanocomposite was found to be magnetically active with a Néel transition at ∼8.9 K, crossing over to possible XY anisotropy at ∼5 K-as revealed by complementary dc and ac susceptibility measurements-an unprecedented observation in the field assigned to an interfacial effect. This work demonstrates the potential usage of nonmagnetic 2D functionalized graphene to significantly modulate the magnetic properties of 2D spin-lattices.

Effect of crystallite size on the phase transition behavior of heterosite FePO4.

For advanced lithium-ion battery technology, olivine-based cathodes are considered to be the most dominant and technologically recognized materials. The extraction of lithium ions from olivine LiFePO4 results in the two-phase mixture with heterosite FePO4 exhibiting a deintercalation potential of 3.45 V vs. Li+/Li over a wide range of lithium content. Here, we report the synthesis and characterization of chemically deintercalated heterosite FePO4 with varying crystallite sizes using different analytical techniques. The decrease in the crystallite size of heterosite FePO4 leads to an increase in the lattice parameters including the unit cell volume. The characteristic behavior in the structural properties of heterosite FePO4 shows a strong dependency on the crystallite size which is correlated with the change in the chemical bonding. The volume expansion of the nano-sized heterosite FePO4 with respect to the bulk counterpart is suggested to be a direct consequence of reduced hybridization between the Fe3d and O2p states. Furthermore, the combined X-ray diffraction and Mössbauer spectroscopic studies reveal the appearance of a new phase namely trigonal FePO4 at the lower crystallite sizes due to the enhanced surface energy kinetics. We also find that the observed trigonal FePO4 phase is more magnetically active than the paramagnetic olivine FePO4. For the unique structural advantage of the heterosite phase as an electrode material, the change in bonding characteristics is very useful and can have strong implications on the electronic properties of heterosite FePO4 at the nanoscale level.

Evolution of confined ice nano structures at different levels of pore filling: a synchrotron based X-ray diffraction study.

We have thoroughly investigated the crystal structure of ice evolved from super cooled water confined in MCM-41 cylindrical nano pores through a synchrotron-based X-ray diffraction (XRD) technique for two different levels of pore filling. A rigorous analysis of XRD data shows that the nucleation dynamics and the structure of nucleated ice highly depend on the level of pore filling. In the nearly fully hydrated pores, ice crystallites start nucleating inside the pores below 240 K and creep out of the pores to form bulk crystals having crystalline structure of a mixed phase of hexagonal and cubic forms. In the partially hydrated pores, on the other hand, ice crystals cannot creep out of the pore crossing the energy barrier. The crystalline ice particles remaining inside the cylindrical pore show a short range "cubic rich" structure. The "pure cubic" phase has not been identified at either of the pore fillings in these 2.5 nm average size pores. A large fraction of water inside the pores remains in the super cooled liquid phase even at 180 K. This observation is relevant for understanding the ice nucleation through the pore condensation and freezing mechanism, which is a major pathway for the formation of cirrus clouds in the upper atmosphere.

Metamagnetism in Nanosheets of CoII-MOF with TN at 26 K and a Giant Hysteretic Effect at 5 K.

Herein, we have synthesized at room-temperature two-dimensional nanosheets of a MOF comprised of cobalt(II) ion with benzenedicarboxylic acid  ligand, which exhibited unusual magnetic properties. Direct-current magnetic susceptibility revealed an antiferromagnetic (AFM) transition at 26 K (Néel temperature,  TN) followed by a canting of the spin moments along with the concomitant appearance of a sigmoidal-shaped magnetization versus field ( M- H) curve at 15 K. Such a canted AFM ordering led to nonzero remnant magnetization with a remarkably high coercive field of ∼10 kOe at 5 K. Metamagnetism was further substantiated by the alternating-current magnetic susceptibility measurements.

Enabling the Electrochemical Activity in Sodium Iron Metaphosphate [NaFe(PO3)3] Sodium Battery Insertion Material: Structural and Electrochemical Insights.

Sodium-ion batteries are widely pursued as an economic alternative to lithium-ion battery technology, where Fe- and Mn-based compounds are particularly attractive owing to their elemental abundance. Pursuing phosphate-based polyanionic chemistry, recently solid-state prepared NaFe(PO3)3 metaphosphate was unveiled as a novel potential sodium insertion material, although it was found to be electrochemically inactive. In the current work, employing energy-savvy solution combustion synthesis, NaFe2+(PO3)3 was produced from low-cost Fe3+ precursors. Owing to the formation of nanoscale carbon-coated product, electrochemical activity was enabled in NaFe(PO3)3 for the first time. In congruence with the first principles density functional theory (DFT) calculations, an Fe3+/Fe2+ redox activity centered at 2.8 V (vs Na/Na+) was observed. Further, the solid-solution metaphosphate family Na(Fe1-xMnx)(PO3)3 (x = 0-1) was prepared for the first time. Their structure and distribution of transition metals (TM = Fe/Mn) was analyzed with synchrotron diffraction, X-ray photoelectron spectroscopy, and Mössbauer spectroscopy. Synergizing experimental and computational tools, NaFe(PO3)3 metaphosphate is presented as an electrochemically active sodium insertion host material.

Fabrication of porous ß-Co(OH)2 architecture at room temperature: a high performance supercapacitor.

A facile, cost-effective, surfactant-free chemical route has been demonstrated for the fabrication of porous ß-Co(OH)2 hierarchical nanostructure in gram level simply by adopting cobalt acetate as a precursor salt and ethanolamine as a hydrolyzing agent at room temperature. A couple of different morphologies of ß-Co(OH)2 have been distinctly identified by varying the mole ratio of the precursor and hydrolyzing agent. The cyclic voltammetry measurements on ß-Co(OH)2 displayed significantly high capacitance. The specific capacitance obtained from charge-discharge measurements made at a discharge current of 1 A/g is 416 F/g for the Co(OH)2 sample obtained at room temperature. The charge-discharge stability measurements indicate retention of specific capacitance about 93% after 500 continuous charge-discharge cycles at a current density of 1 A g(-1). The capacitive behavior of the other synthesized morphology was also accounted. The nanoflower-shaped porous ß-Co(OH)2 with a characteristic three-dimensional architecture accompanied highest pore volume which made it promising electrode material for supercapacitor application. The porous nanostructures accompanied by high surface area facilitates the contact and transport of electrolyte, providing longer electron pathways and therefore giving rise to highest capacitance in nanoflower morphology. From a broad view, this study reveals a low-temperature synthetic route of ß-Co(OH)2 of various morphologies, qualifying it as supercapacitor electrode material.

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.

Insight into the negative magnetization and anomalous exchange-bias in DyFe5Al7 through neutron depolarization and neutron diffraction studies.

We have provided the mesoscopic and microscopic understandings of polarity reversal of the magnetization or negative magnetization (NM) below TCOMP = 93 K in an exotic magnetic material containing three magnetic sublattices, viz., DyFe5Al7 crystallizing in ThMn12 structure, using neutron depolarization and neutron diffraction techniques. A full recovery of the neutron beam polarization at the TCOMP in a neutron depolarization experiment reveals a total compensation of magnetization inside the magnetic domains in the sample. The temperature-dependent neutron diffraction study under zero magnetic field has provided temperature dependencies of antiparallelly coupled Dy (MDy(2a)) and Fe (MFe(8f) and MFe(8j)) sublattice magnetic moments along [100] direction.Thedominance of |MDy(2a)| over total Fe moment, MFetotal = 4*|MFe(8f)| + |MFe(8j)|, below TCOMP leads to the NM in the compound. The magnetization versusmagnetic field curves below the TCOMP indicate the presence of field-induced spin reorientation in the compound. The magnetic field required for spin reorientation (HSR) is maximum at the lowest temperature and it decreases to zero as the temperature is increased to TCOMP. Interestingly, the compound shows a finite exchange-bias (HEB) below the TCOMP only, as evident from the field-cooled hysteresis loops, while at T > TCOMP,HEB is almost zero. The cooling-field (HCOOL) dependent study of HEB shows a slope change at HCOOL ~ HSR indicating a correlation of exchange-bias with spin-reorientation in the compound. This study, apart from revealing microscopic understanding of magnetic behavior of an exotic three magnetic sublattice system, provides a correlation among exchange-bias, magnetic compensation, and spin-reorientation phenomena.

Emergent many-body composite excitations of interacting spin-1/2 trimers.

Understanding exotic forms of magnetism in quantum spin systems is an emergent topic of modern condensed matter physics. Quantum dynamics can be described by particle-like carriers of information, known-as quasiparticles that appear from the collective behaviour of the underlying system. Spinon excitations, governing the excitations of quantum spin-systems, have been accurately calculated and precisely verified experimentally for the antiferromagnetic chain model. However, identification and characterization of novel quasiparticles emerging from the topological excitations of the spin system having periodic exchange interactions are yet to be obtained. Here, we report the identification of emergent composite excitations of the novel quasiparticles doublons and quartons in spin-1/2 trimer-chain antiferromagnet Na2Cu3Ge4O12 (having periodic intrachain exchange interactions J1-J1-J2) and its topologically protected quantum 1/3 magnetization-plateau state. The characteristic energies, dispersion relations, and dynamical structure factor of neutron scattering as well as macroscopic quantum 1/3 magnetization-plateau state are in good agreement with the state-of-the-art dynamical density matrix renormalization group calculations.

Double glassy states and large spontaneous and conventional exchange bias in La1.5Ca0.5CoFeO6ferrimagnetic double perovskite.

The structural and magnetic properties of hole doped double perovskite La1.5Ca0.5CoFeO6have been investigated by measuring x-ray photoemission spectroscopy, neutron powder diffraction and magnetization. A ferrimagnetic transition is observed atTC∼ 167 K. The presence of anti-site disorder (ASD) in La1.5Ca0.5CoFeO6has also been demonstrated. Double re-entrant cluster glass transitions (T1∼ 11 K andTS∼ 35 K) were observed which has been attributed to the ASD effect. The presence of both large spontaneous exchange biasHSEB∼ 2.106 kOe and giant conventional exchange biasHCEB∼ 1.56 T at 5 K has also been observed which can be attributed to the coexistence of long range magnetic ordering and glassy state. The experimental observations were explained with the results obtained by the density functional theory calculation. The presence of double glassy states, large exchange-bias effect and different magnetic phases make this system a potential candidate for spintronic applications.

Cluster spin-glass-like dynamics in Mn-rich La2Ni0.5Mn1.5O6ferromagnetic insulator.

We report on the physical properties of Mn-rich, nonstoichiometric La2Ni0.5Mn1.5O6ferromagnetic insulator, prepared by sol-gel method. The single-phase orthorhombicPbnmstructure for the compound was confirmed by x-ray diffraction measurements. Dc magnetization measurements revealed a high saturation magnetization of ∼5.95 µB/f.u. at 5 K, and a ferromagnetic to paramagnetic transition at ∼162 K. Ac magnetic susceptibility measurements confirmed a broad frequency-dependent anomaly at lower temperatures indicating the presence of spin-glass type magnetic interactions. The ac susceptibility data have been discussed within the framework of the critical slowing down model and Vogel-Fulcher law, and confirmed the cluster spin-glass dynamics with a relaxation time of the order of 10-5 s. The valence of Ni and Mn ions was verified from the x-ray absorption near edge structure spectroscopy. The origin of cluster spin-glass state was discussed in terms of several possible magnetic exchange interaction pathways among Ni and Mn ions.

Hierarchical superparamagnetic magnetite nanowafers from a resin-bound [Fe(bpy)3]2+ matrix.

The brilliant red [Fe(bpy)(3)](2+) complex upon immobilization on a strongly acidic cation exchanger or in situ formation of the same cationic complex onto a resin matrix and subsequent modified hydrothermolysis (MHT) at approximately 110 degrees C produces unusually stable hierarchical magnetite (Fe(3)O(4)) nanowafers. The slow hydrothermolysis, oxidation, and subsequent dehydration of the complex on the solid-liquid interface produce stable hierarchical nanostructures. The isolation of neat Fe(3)O(4) (uncapped) particles from the resin matrix as hierarchical nanowafers was achieved by magnetically stirring a CH(3)CN suspension of nanocomposites. The solid resin support not only aids nanowafer formation on its surface but also provides unique stability to the magnetite particles, where nanowafer oxidation is largely retarded. The utility of the as-prepared porous nanocomposite and characterization of the nanoparticles are promising for nanotechnological and soft ferromagnetic applications.

Disseminated cutaneous leishmaniasis in HIV positive patient--a case report.

Disseminated cutaneous leishmaniasis and HIV dual-infection is seldom reported. Leishmaniasis and HIV co-infection may intensify the immune defect and is the chief reason for atypical presentation and widespread progression of cutaneous leishmaniasis and its defiance to conventional therapy. Here we report a 38-year-old HIV-positive lady who presented with a 6-month history of a progressive papule and nodular eruptions of leishmaniasis on face, trunk and extremities that was recalcitrant to treatment.

Idiopathic scrotal calcinosis; a rare scrotal tumour: a case report and review of literature.

Idiopathic scrotal calcinosis is a rare benign disease characterized by multiple, asymptomatic and painless nodules on the scrotum. We herein report this rare disease in a Nigerian adult male and briefly review the relevant literature.

Nanocrystalline HoCrO4: facile synthesis and magnetic properties.

Nanocrystalline HoCrO4 powder was synthesized by a combustion technique using glycine and citric acid as the fuels in different oxidant-to-fuel ratios. Fuel-deficient glycine-nitrate combustion reaction resulted in zircon type HoCrO4 free from HoCrO3 phase. The crystallite size for the phase pure product after calcination at 575 degrees C in oxygen atmosphere was found to be 34 nm by X-ray line broadening. The TEM observations showed highly porous structure. Magnetic measurements reveal the ferromagnetic nature of HoCrO4 nano particles with Tc = 18 K. The compound shows high remanence of 30.4 emu x g(-1) and low coercivity of -0.0343 T.

Type 2 segmental Darier's disease in a twelve-year-old Nigerian male--a case report.

Darier's disease is an autosomal dominant disorder characterized clinically by presence of keratotic papules in a seborrheic distribution, nail involvement and mucosal lesions. There are several clinical variants of Darier's disease, but few cases of segmental Darier's disease have been described in the literature. We describe a 12-year-old boy with type 2 mosaic phenotype. This unique clinical variant of Darier's disease has been described very rarely.

Krukenberg's tumour.

BACKGROUND: Krukenburg's tumour, a metastatic cancer to the ovary can pose difficulties in early diagnosis. The paucity of reports from our environment coupled with the difficulties we encountered makes it imperative that we report this case. METHODS: We present a 32-year-old lady who presented with mucoid and bloody diarrhoea associated with menstrual irregularity, weight loss and lower abdominal pains 2 years after surgical treatment for gastric cancer. Literature on Krukenburg's tumour was also reviewed. RESULTS: While serum level of CEA was found to be elevated and colonoscopy showed an ulcerated mass obliterating the lumen of the sigmoid colon, abdominal CT scan revealed bilateral adnexal masses. The histology of the colonic lesion showed signet ring carcinoma while the enlarged ovaries turned out to have evidence of metastatic adenocarcinoma. CONCLUSION: Early diagnosis of KT can be difficult. Periodic surveillance is, therefore, essential especially in those who have had a gastrointestinal malignancy.

Revealing magnetic ordering and spin-phonon coupling in Y1-x Tb x MnO3 (0.1 ⩽ x ⩽ 0.3) compounds.

The structural and magnetic properties of the Y1-x Tb x MnO3 (0.1 ⩽ x ⩽ 0.3) compounds were investigated. Neutron diffraction patterns for all three samples, recorded at room temperature (RT), were fitted to the nuclear structure confirming the paramagnetic nature of the compounds. At 2.8 K, for the x = 0.1 sample magnetic moments of the Tb3+ ionic as well as Mn3+ ionic were ordered. At 5 K for the x = 0.2 sample only the Mn3+ ionic magnetic moments were ordered. There were six sites for Mn atoms. Three on the z = 0 plane and three on the z = 0.5 plane (where z corresponds to +c axis).The Mn3+ionic moments were confined to the a-b plane with a net magnitude of 2.78(3) µ B, and 2.90(3) µ B for the x = 0.1 and the x = 0.2 samples. The Tb3+ionic moments had a magnitude of 1.36(4) µ B at 2.8 K and were aligned antiferromagnetically along the crystallographic c-axis for the x = 0.1 sample. The low moment in comparison with Mn3+ free ions has been attributed to crystalline electric fields similar to that found in the parent compound YMnO3 and also in another rare earth manganite viz HoMnO3. The x = 0.3 sample was found to be a canonical spin glass. To investigate the role of the above spin ordering in Y1-x Tb x MnO3 in governing the phonon dynamics, temperature dependent Raman measurements were carried out. We observed the deviation of the phonon frequency near 685 cm-1 and its line-width from the expected anharmonic behaviour around magnetic ordering temperature for Tb substituted compounds with x = 0.1 and 0.2. This was attributed to the spin-phonon coupling in these systems. The anomalous behaviour of this phonon mode in the canonical spin glass compound with x = 0.3, indicated that the coupling sustained even in the presence of only local magnetic ordering.

Structural study of La(0.75)Sr(0.25)CrO(3) at high temperatures.

A high-temperature neutron diffraction study has been carried out on La(0.75)Sr(0.25)CrO(3) compound in the temperature range 300-1400 K. On doping the parent compound LaCrO(3) with Sr at the La site, the orthorhombic (Pbnm) to rhombohedral ([Formula: see text]) structural transition shifts to lower temperatures. From quantitative Rietveld analysis it is found unequivocally that there is a two-phase coexistence (orthorhombic and rhombohedral phases with ∼89 and 11 weight%, respectively) in the temperature range 300-470 K and a three-phase coexistence (with a new cubic phase with space group Pm3m) in the temperature range 480-1400 K. The weight percentages of the orthorhombic, rhombohedral and cubic phases were found to be ∼49%, 37% and 14%, respectively, in the temperature range 480-1300 K, while over 1350-1400 K, the average weight percentages of orthorhombic, rhombohedral and cubic phases were found to be ∼41%, 41% and 18%, respectively. The coefficients of volume thermal expansion and linear thermal expansion have been determined for all three phases. The importance of the present study has been discussed for practical applications of the studied compound in solid oxide fuel cells.