SILAR controlled CdSe nanoparticles sensitized ZnO nanorods photoanode for solar cell application: Electrolyte effect.

Controlled growth of different sizes of cadmium selenide (CdSe) nanoparticles over well aligned ZnO nanorods have been performed using successive ionic layer adsorption and reaction (SILAR) technique at room temperature (27 °C) in order to form nano heterostructure solar cells. Deposition of compact layer of zinc oxide (ZnO) by SILAR technique on fluorine doped tin oxide (FTO) coated glass substrate followed by growth of vertically aligned ZnO nanorods array using chemical bath deposition (CBD) at low temperature (<100 °C). Different characterization techniques viz. X-ray diffractometer, UV-Vis spectrophotometer, field emission scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy have been used to know the structural, optical, morphological and compositional properties of synthesized nano heterostructure. The photovoltaic performance of the cells with variation in SILAR cycles for CdSe and with use of different electrolytes have been recorded as J-V characteristics and the maximum conversion efficiency of 0.63% have been attained with ferro/ferri cyanide electrolyte for 12 cycles CdSe coating over 1-D ZnO nanorods.

Periodic Grating-like Patterns Induced by Self-Assembly of Gelator Fibres in Nematic Gels.

Periodic orientation patterns occurring in nematic gels, revealed by optical and scanning electron microscopy, are found to be formed by spontaneous self-assembly of fibrous aggregates of a low-molecular-weight organogelator in an aligned thermotropic liquid crystal (LC). Self-organization into periodic structures is also reflected in a calorimetric study, which shows the occurrence of three thermoreversible states, namely, isotropic liquid, nematic and nematic gel. The segregation and self-assembly of the fibrous aggregates leading to pattern formation are attributed to the highly polar LC and to hydrogen bonding between gelator molecules, as shown by X-ray diffraction and vibrational spectroscopy. This study aims to investigate in detail the effect of the chemical nature and alignment of an anisotropic solvent on the morphology of the gelator fibres and the resulting gelation process. The periodic organization of LC-rich and fibre-rich regions can also provide a way to obtain templates for positioning nanoparticle arrays in an LC matrix, which can lead to novel devices.

Cellular structures arising from viscoelastic phase separation in binary mixtures of thermotropic liquid crystals.

Viscoelastic effects are known to influence pattern formation during phase separation in dynamically asymmetric mixtures. Evidence is shown for such an effect in some binary mixtures composed of liquid crystals made of rod-like (R) and bent-core (BC) molecules. The difference in dynamics at phase separation manifests itself in the form of cellular structures (CSs). This is mainly driven by dissimilarities in flow and rotational viscosities of the two types of molecules which differ in size and shape. The heterogeneous structure has been characterized by optical and confocal microscopy along with X-ray diffraction studies and found to be composed of coexisting liquid crystalline phases. The striking resemblance to CSs of biological systems further enriched by topological defects is unique to this system. The morphology and stability of the CSs are dictated by the smectic ordering influenced by the relative concentration and mutual orientation of the R and BC molecules. This type of phase separation process can also be utilized to form functional ordered assemblies of nanoparticles embedded in a liquid crystal matrix.

Psychological autopsy and necropsy of an unusual case of suicide by intravenous toluene.

Toluene (methylbenzene; volatile hydrocarbon) is an industrial solvent that causes major injury to the lungs; the organ being the first capillary bed encountered. We report an unusual case of suicide by a 24-year-old male, paramedical professional, with fatal outcome within 16 h of intentional, intravenous self-administration of toluene, with clinical presentation of acute respiratory distress syndrome. Psychological autopsy revealed severe depressive disorder and solvent (inhalant) abuse, with marital disharmony as the precipitating stressor for suicide. Necropsy revealed diffuse congestion of internal organs like lungs and liver, epicardial petechial hemorrhages, and gastric hemorrhages. Treatment of toluene poisoning includes supportive care as no specific antidote is available. Early and aggressive management may be conducive to a favorable outcome with minimal residual pulmonary sequelae. Relevant literature of toluene poisoning was identified via PubMed, PubChem, ToxNet, Hazardous Substances Data Bank (HSDB), Embase, and PsycINFO. To our knowledge, this is the first case of suicide by intravenous administration of toluene in the literature.

Chiral symmetry breaking dictated by electric-field-driven shape transitions of nucleating conglomerate domains in a bent-core liquid crystal.

Generating and controlling chiral symmetry breaking and enantiomeric excess is not only interesting from a fundamental perspective but can also lead to novel functional materials. In this work, we show how the dark conglomerate (DC) liquid crystalline phase characterized by macroscopic chiral domains offers such a possibility if formed under an electric field. In addition the chiral domains are electro-optically switchable. The chiral segregation in the DC phase can be tuned by using dc or ac fields at different frequencies. Consequently, the enantioselectivity, dielectric parameters and switching polarization in the DC phase become tunable. Another interesting aspect is that the nucleating conglomerate domains formed under ac fields exhibit frequency dependent shape transitions which have a striking resemblance to domain shape changes observed in two-dimensional monolayers. This can therefore be used as a model experimental system to get a physical insight into the effects of chiral and electrostatic interactions, under external fields, on domain growth and interface structures. The domain shape transitions can also be used to investigate the role of growth morphology in coarsening and scaling hypotheses. From a technological point of view this opens up the possibility of obtaining chiral thin films with preferential sense of chirality which can be useful in chiroptical and nonlinear optical applications.

Electric-field-induced switchable dark conglomerate phases in a bent-core liquid crystal exhibiting reverse columnar phases.

Electric-field-induced transitions into switchable dark conglomerate (DC) phases from two types of reverse columnar mesophases have been observed in the bent-core (BC) compound 2,7-naphthylene bis[4-(3-methyl-4-n-tetradecyloxybenzoyloxy)] benzoate. Optical and x-ray studies show that the higher temperature columnar phase corresponds to the orthogonal B(1rev) phase, whereas the lower temperature columnar phase is a variant of the B(1revtilt) phase. As the layer fragments in this phase are modulated in order to relieve the steric hindrance caused by an anticlinic tilting in adjacent blocks, it has been named B(1revtiltM). The shape of the chiral domains are different in the DC phases viz. DC-B(1rev) and DC-B(1revtiltM) obtained by applying the electric field in the B(1rev) and B(1revtiltM) phases, respectively. While the chiral domains in the DC-B(1rev) phase appear similar to those observed in other DC phases, the shape of the domains in the DC-B(1revtiltM) phase appear to have some similarity to the domains in the banana leaf texture in the B(1revtiltM) phase implying that the detailed structure in this DC phase may be different. Optical observations, electro-optics, and dielectric studies show that the DC-B(1rev) and DC-B(1revtiltM) phases are both switchable and possess a local SmC(S)P(F) type of structure. As the temperature is decreased the switching behavior changes from ferroelectric to antiferroelectric. The temperature at which this changeover starts occurring coincides with the temperature at which the layer modulation occurs to overcome anticlinic tilt and the B(1rev) to B(1revtiltM) phase transition takes place without the application of the electric field. The change in switching behavior is attributed to a transformation into flat layers with the SmC(A)P(A) type of structure as also evidenced by the nucleation of bright regions alongside the chiral domains.

Solubility Enhancement of Raloxifene Using Inclusion Complexes and Cogrinding Method.

The objective of the present work was to enhance the solubility and dissolution of practically water-insoluble drug raloxifene HCl (RLX), for the same two approaches that were used. In the first approach, drug was kneaded with hydroxypropyl-ß-cyclodextrin (HPßCD), and in the second one drug was cogrinded with modified guar gum (MGG). The drug-cyclodextrin complex and drug-MGG cogrind mixtures were characterized by differential scanning calorimetry, X-ray diffraction studies, scanning electron microscopy, and Fourier transform infrared spectroscopy. The solubility and dissolution study reveals that solubility and dissolution rate of RLX remarkably increased in both methods. It was concluded that the prepared inclusion complex showed a remarkable increase in solubility and dissolution of poorly water-soluble drug raloxifene. In the cogrinding mixture, a natural modified gum is used as a surfactant and enhances the solubility and dissolution of RLX without requiring addition of organic solvent or high temperature for its preparation; thus, process is less cumbersome and cost effective. But when both methods were compared; HPßCD complexation method showed significant enhancement of drug solubility.

Linezolid-induced near-fatal serotonin syndrome during escitalopram therapy: case report and review of literature.

Linezolid is a synthetic antimicrobial agent of the oxazolidinone class with weak, nonspecific inhibitor of monoamine oxidase enzymes. Concomitant therapy with an adrenergic or serotonergic agent or consuming tyramine (>100 mg/day) may induce serotonin syndrome (SS). We present a case report of near-fatal adverse interaction between linezolid and escitalopram inducing SS in a 65-year-old woman with sepsis, under empirical antibiotic treatment. This report also summarizes the current relevant literature as identified via PubMed, EMBASE, and PsycINFO, supplemented with a manual search of cross references.

Morphometry of buccal mucosal cells in fluorosis--a new paradigm.

STUDY BACKGROUND: Fluorosis is one of the manifestations of chronic poisoning from long-term exposure to high levels of fluoride. An estimated 62 million people in 17 states in India are affected with dental and skeletal fluorosis. OBJECTIVE: To evaluate the cytological morphology of exfoliated oral mucosal cells among various stages of fluorosis patients compared with controls. DESIGN AND METHODS: Exfoliative cytology PAP-stained smears of 21 cases of fluorosis and 21 controls subjected to morphometric analysis using image Proplus software. For the assessment parameters like maximum and minimum diameter of the nucleus, cell and perimeter of the cell and nucleus were considered. RESULTS: An increase in maximum and minimum diameter of nucleus, perimeter of nucleus and cell in cases when compared to controls. CONCLUSIONS: Fluorosis induces oxidative stress, DNA damage and apoptosis which can be the reasons for the increase in the nuclear size and decrease in the cell size. Community dental and medical programmes should be stringently implemented in fluorosis-endemic areas, to create awareness regarding the toxic effects of fluoride to the body, especially within the oro-facial region.

Nanoparticle induced director distortion and disorder in liquid crystal-nanoparticle dispersions.

Colloidal dispersions of nanoparticles in liquid crystals have been investigated experimentally using a model system consisting of the thermotropic liquid crystalline compound 4-n-octyloxy-4'-cyanobiphenyl (8OCB) doped with BaTiO(3) nanoparticles. We show that the physical properties of these dispersions can vary considerably depending on the method of preparation of the dispersions. We also find that aging the sample can improve dispersal of the nanoparticles in the host liquid crystal. Decreases in the isotropic to nematic transition temperature, parallel component of the dielectric constant and orientational order parameter are observed for the dispersions compared to the behaviour of pure 8OCB. These decreases have been explained in terms of orientational disorder and defects induced by the nanoparticles.

Polar switching in the smectic- A(d)P(A) phase composed of asymmetric bent-core molecules.

We have studied mesogenic properties in the smectic- A(d)P(A) phase of an asymmetric bent-core liquid crystal by means of polarizing optical microscopy, second-harmonic generation (SHG), electro-optical (EO), and dielectric measurements. In homeotropically aligned cells, EO switching is clearly observed from a schlieren texture with both four- and two-brush defects to a uniform bright domain under the application of very low in-plane electric field below 1 V/microm. The phase is SHG active under an electric field, i.e., SHG gradually increases without a threshold and saturates with the increasing field. In homogeneous cells, by applying triangular wave field at saturated voltage, the splitting of the polarization switching current peak is observed, indicating that the mesophase is antiferroelectric. The dielectric studies indicate a Debye-type relaxation of the transverse dipoles associated with the rotation of the molecules about their long axis. The dc bias-dependent dielectric relaxation time and the dielectric strength suggest that a field-induced antiferroelectric-ferroelectric phase transition occurs continuously beyond 1.2 V/microm and is reversible. The field-dependent texture observation is consistent with the dielectric measurements. Two possible models are proposed to interpret the continuous phase transition.

Orientational order in liquid crystals exhibited by some binary mixtures of rod-like and bent-core molecules.

We report measurements of the temperature variations of the optical birefringence in the nematic (N) and partial bilayer SmA (SmA(d)) phases in 4-n-octyloxy 4(')-cyanobiphenyl made of rod-like (R) molecules and five mixtures of this compound with 1,3-phenylene bis[4-(3-methylbenzoyloxy)] 4(')-n-dodecylbiphenyl 4(')-carboxylate, made of bent-core (BC) molecules. The birefringence decreases with the concentration x of the BC molecules but the macroscopic order parameter initially decreases upto 11 mol% of BC molecules and subsequently increases with x. This is attributed to the possible formation of polar clusters of BC molecules. Orientation of BC molecules changes between the N and SmA(d) phases and the birefringence data in the two phases imply that the kink angle of the BC molecules is approximately 90 degrees rather than approximately 110 degrees as obtained from calculations which minimize the energy of the molecule. IR spectroscopic measurements on the mixture with 11 mol% of BC molecules have been used to estimate the molecular order parameter S of the R molecules, and to provide additional support for a relatively small kink angle of BC molecules.

Splay and bend elastic constants in the nematic phase of some disulfide bridged dimeric compounds.

We report measurements of the temperature dependences of the splay (K11) and bend (K33) elastic constants of several homologues and a binary mixture of disulfide bridged symmetric dimers made of alkoxy cyanobiphenyl monomeric units. All of them have an even number m of carbon and sulfur atoms in the linking chain and expected to have linear conformations. Both K(11) and K(33) alternate depending on the parity of x which is the number of carbon atoms in the alkyl chain of a monomer. We will refer to this as 'odd-even' effect. This effect, occurs near the nematic-isotropic transition temperature. T(NI), but monotonically decrease with m at lower temperatures. We argue that these results imply large rotational fluctuations of the two halves of the dimers about the S-S bond giving rise to average bent conformations near T(NI). At lower temperatures those conformations which can adapt better to the given curvature deformation in the medium are favored.

Tunable optical metamaterial based on liquid crystal-gold nanosphere composite.

Effect of the surrounding anisotropic liquid crystal medium on the surface plasmon resonance (SPR) exhibited by concentrated suspensions of gold nanospheres has been investigated experimentally and compared with the Mie scattering theory. The observed polarization-sensitive SPR and the red-shift in the SPR wavelength with increasing concentration of the gold nanospheres in the liquid crystal matrix have been explained using calculations based on the Maxwell Garnet effective medium theory. Agglomeration of the gold nanospheres that could also lead to such a red-shift has been ruled out using Atomic force microscopy study of thin nanoparticle-doped smectic films obtained on solid substrates. Our study demonstrates feasibility of obtaining tunable optical bulk metamaterials based on smectic liquid crystal - nanoparticle composites.

Anomalous temperature dependence of elastic constants in the nematic phase of binary mixtures made of rodlike and bent-core molecules.

We report on two anomalous trends in the temperature dependences of the splay (K11) and bend (K33) elastic constants in the nematic (N) phase of mixtures of compounds with rodlike (R) and bent-core (BC) molecules: As the sample is cooled from the isotropic to N transition point, (i) K33 increases, attains a maximum value and then decreases, and (ii) close to the N to smectic A (SmA) transition point, K11 decreases sharply. At higher temperatures the bow axes of BC molecules are aligned along the director n, strongly favoring a bend distortion of n as the orientational order parameter is increased. Close to the N-SmA transition point the smecticlike short-range order builds up, and the arrow axes of BC molecules are aligned along n, facilitating a splay distortion of n. A simple model calculation brings out the anomalous trend in K33.

Angiomatoid variant of fibrous histiocytoma: a case report and review of literature.

Fibrous histiocytomas by themselves are not very common in the head and neck region. Apart from considering the above fact, this report describes a unique and relatively rare variant of the neoplasm - the angiomatoid fibrous histiocytoma (AFH) which has a characteristic appearance and predilection for young individuals that occurred in the left lower border of the mandible in a 13-year-old girl. Angiomatoid fibrous histiocytoma is a distinct fibrohistiocytic tumour of children and young adults that combines features of both fibrohistiocytic and vascular neoplasm. It is considered to be a tumour of intermediate malignancy because of its less aggressive course in contrast to the conventional malignant fibrous histiocytoma. The authors would like to stress upon the fact that clinicians should not overlook swellings that may not appear distinct visually and therefore consider it to be a part of normal anatomy, dismiss it as an anomaly with no significance, or treat it injudiciously, for ultimately it may prove to be a tumour that would require appropriate treatment and follow-up.

Enzymatic studies of cisplatin induced oxidative stress in hepatic tissue of rats.

Cisplatin is an active cytotoxic agent that has proved to be successful in the treatment of various types of solid tumors. The drug-induced nephrotoxicity has been very well documented in clinical oncology. However, hepatotoxicity has been rarely characterized and paid attention to, and is the least studied. We have used rat as the model to evaluate the effect of cisplatin on liver antioxidant enzymes and to determine whether these modulations in enzymatic activities are involved in hepatotoxicity. Reports obtained from our study indicate that cisplatin increases lipid peroxidation in the treated tissue of rat. The drug is also involved in altering the thiol status of the tissue with concomitant alterations in the enzymatic antioxidants. Glutathione and glutathione reductase levels were significantly decreased after cisplatin therapy, whereas glutathione peroxidase, gamma-glutamyl transpeptidase and catalase showed a significant increase. No statistically significant change was observed in glutathione-S-transferase activity. After cisplatin treatment, cytochrome P 450 showed a significant increase, whereas cytochrome b5 was decreased. Thus, an alteration in enzymatic antioxidant status with increase in lipid peroxidation indicates that the enzymes play an important role in combating free radical induced oxidative stress on the tissue.

Two-dimensionally periodic phases in mixtures of compounds made of rodlike and bent-core molecules.

We report two distinct types of two-dimensionally periodic phases in different concentration regions of a binary system composed of the bent-core (BC) compound 1,3-phenylene bis[4-(3-methylbenzoyloxy)] 4(') - n-dodecylbiphenyl 4(') -carboxylate (BC12) and the rodlike (R) compound 4-n-octyloxy 4(') -cyanobiphenyl (8OCB). BC12 exhibits only the lamellar B2 phase. 8OCB which has a highly polar cyano end group exhibits the smectic-A(d) phase with a lamellar structure of partial bilayers made of antiparallel pairs of the polar molecules. The molecular arrangements in the two-dimensionally periodic phases have been deduced based on optical microscopy, polarized infrared and x-ray diffraction studies. The arrangement in the two-dimensionally periodic phase in lower concentration ranges of BC12 (24 to 35 mol% ) is dictated by the partial bilayer structure formed by the rods. The BC molecules arrange themselves with their arrow axes parallel to the long axes of the R molecules and the structure conforms to the c2mm space group symmetry. In higher concentration ranges of BC12 (35 to 60 mol% ) the structure is dominated by the BC molecules, to form the familiar B1 phase with the p2mg space group symmetry. The R molecules lie at the interfaces of these domains stabilizing the structure.

Selective imaging of 3D director fields and study of defects in biaxial smectic A liquid crystals.

We report on the selective imaging of different director fields in a biaxial smectic A (SmAb) liquid crystal using Fluorescence Confocal Polarizing Microscopy (FCPM) and Polarizing Microscopy (PM). The patterns of two directors, namely the director n(a) perpendicular to the lamellae and the director n(b) in their planes are visualized by doping the liquid crystal with two fluorescent dyes with different orientation of the transition dipoles with respect to the lamellar matrix. The properties of defects such as disclinations and focal conic domains (FCDs) are consistent with the non-polar D2h-symmetry of the SmA(b) mesophase in the studied mixture of bent-core and rod-like molecules: (1) majority of defects in the director n(b) are half-integer "+/-1/2" disclinations; (2) the integer-strength "+/-1" defects tend to split into the "+/-1/2" disclinations. We compare the vertical cross-sections of the "+/-1" disclinations in the field in SmA(b) and uniaxial nematic samples. In SmA(b), the "+/-1" disclinations do not escape into the third dimension, while in the nematic samples with Schlieren textures they do despite the surface anchoring at the plates; the experimentally determined director field around the escaped disclination capped by a pair of surface point defects--boojums matches the one predicted recently [C. Chiccoli et al., Phys. Rev. E 66, 030701 (2002)]. The FCD structure in SmA(b) is similar to that in SmA and SmC in terms of the normal to the layers but differs significantly in terms of the director n(b) field parallel to the smectic layers. The FCDs in SmA(b) can be associated with topologically non-trivial configurations of n(b) in the surrounding matrix that are equivalent to the disclination lines.

Phase transitions in liquid crystals under negative pressures.

We report the first measurements of orientational order parameters and phase transition temperatures in nematic and smectic A liquid crystals under negative pressures generated by an isochoric cooling of small droplets embedded in a glass former. Comparison of isobaric and isochoric measurements allows us to estimate the coefficients coupling the order parameter and density of an extended Landau--de Gennes model of the nematic phase.