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Gorcea M.,Materials Science Group | Gorcea M.,University of London | Hadgraft J.,University of London | Moore D.J.,Materials Science Group | Lane M.E.,University of London
International Journal of Pharmaceutics | Year: 2012

The current work describes thermotropic and kinetic Fourier transform infrared (FTIR) spectroscopy studies of lipid dynamics and domain formation in normal and ceramide (CER) deficient lipid samples designed as simple models of the stratum corneum (SC). For the first time, this work focuses on the time dependence of lipid reorganization and domain formation in CER deficient models. By utilizing deuterated fatty acid (FA) and simultaneously monitoring the methylene vibrational modes of both CER and FA chains these experiments follow the time evolution of lipid organization in these SC lipid models following an external stress. Kinetic and thermotropic experiments demonstrate differences in both CER and FA chain fluidity and ordered domain formation with decreased levels of CER. In the CER deficient model, the formation of CER orthorhombic domains is retarded compared to the normal model. Furthermore, there is little evidence of hexongally packed (or mixed) FA domains in the CER deficient model compared to the models of normal SC. These data demonstrate that barrier lipid organization, in terms of ceramide domain formation, is altered in the ceramide deficient model. This work highlights the successful development of an experimental methodology to study time dependent changes in lipid biophysics in simple SC model membranes and suggests this approach will prove useful for understanding some of the biophysical changes that underlie impaired physiological barrier function in diseased skin. © 2011 Elsevier B.V. All rights reserved.

Balamurali S.,Manonmaniam Sundaranar University | Balamurali S.,Sree Sevugan Annamalai College | Chandramohan R.,Sree Sevugan Annamalai College | Suriyamurthy N.,Radiological Safety Division Center | And 4 more authors.
Journal of Materials Science: Materials in Electronics | Year: 2013

Polycrystalline Mn doped ZnO (MZO) semiconductor thin films were deposited onto glass substrates employing different number of dipping at room temperature using Successive Ionic Layers by Adsorption Reaction (SILAR) technique. The thin film deposition conditions were optimized by altering the various deposition parameters based on their structure. The structural study was carried out using X-ray diffractometer (XRD). The XRD analysis indicated that there is no change in the structure of ZnO thin films due to Mn doping. The films exhibited hexagonal wurtzite structure. The structural studies on Mn doped samples revealed that the predominant orientation is (002) lattice plane and the position of this orientation shifted toward lower angle during doping. The intensity of photoluminescence (PL) emission of ZnO is found to be augmented for Mn doped samples. The room temperature Raman spectra measurements revealed the presence of additional modes. The Vibrating Sample Magnetometer (VSM) studies show that MZO thin film has ferromagnetic properties. © 2012 Springer Science+Business Media New York.

Bensaid H.,Solid State Materials Laboratory | Bih L.,Materials Science Group | Manoun B.,Materials Science Group | Azrour M.,Materials Science Group | And 2 more authors.
Journal of Molecular Structure | Year: 2011

Crystal structures of Ba2.15-xNa0.7+ xNb5-xWxO15 (BaNaNbW) materials were investigated by X-ray diffraction and refined using the Rietveld method. It is shown that all the samples crystallize in the tungsten tetragonal bronze (TTB) like structure and form a solid solution in the range (0 ≤ x ≤ 1). To study the temperature induced phase transition in these compounds, Raman spectra were collected in situ at room pressure and elevated temperatures, up to 330°. The Raman results show strong evidence that the materials under study go through a phase transition around Te = 270 °C. The value of the transition temperature depends on the chemical composition and increases with increasing tungsten content in the materials at a linear rate. The observation of this phase transition by Raman technique is in agreement with dielectric spectroscopy anomaly. © 2010 Elsevier B.V. All rights reserved.

Zervos M.,Materials Science Group | Papageorgiou P.,University of Cyprus | Othonos A.,University of Cyprus
Journal of Crystal Growth | Year: 2010

Indium sulphide nanowires (NWs) have been grown on Si via the reaction of In and InCl3 with H2S using chemical vapor deposition at temperatures as low as 250 °C. We find that the growth of InxSy NWs via the direct reaction of In with H2S is hindered by the formation of InxSy around the source of In which limits its vapor pressure. Thus a low yield of InxSy NWs with diameters of ≈100 nm, lengths up to ≈5 μm and hexagonal crystals measuring ≈500 nm across, were obtained between 500 and 600 °C, but their growth was not uniform or reproducible. These exhibited weak, but nevertheless clear peaks, in the X-ray diffraction (XRD) spectrum corresponding to tetragonal β-In2S3 and orthorhombic InS. No NWs were obtained for TG≤500 °C while for TG>600 °C we obtained a polycrystalline layer with oriented grains of triangular shape. In contrast, a high yield of InS NWs with diameters ≤200 nm and lengths up to ≈2 μm were obtained at temperatures as low as 250 °C via the reaction of In and InCl3 with H2S. The sublimation of InCl3 enhances the vapor pressure of In and the growth of InS NWs, which organize themselves in urchin like structures at 300 °C, exhibiting very intense peaks in the XRD spectrum, corresponding mainly to orthorhombic InS. Optical transmission measurements through the InS NWs gave a band-gap of 2.4 eV. © 2009 Elsevier B.V. All rights reserved.

Othonos A.,University of Cyprus | Zervos M.,Materials Science Group
Nanoscale Research Letters | Year: 2011

Ultrafast hole carrier relaxation dynamics in CuO nanowires have been investigated using transient absorption spectroscopy. Following femtosecond pulse excitation in a non-collinear pump-probe configuration, a combination of non-degenerate transmission and reflection measurements reveal initial ultrafast state filling dynamics independent of the probing photon energy. This behavior is attributed to the occupation of states by photo-generated carriers in the intrinsic hole region of the p-type CuO nanowires located near the top of the valence band. Intensity measurements indicate an upper fluence threshold of 40 μJ/cm 2 where carrier relaxation is mainly governed by the hole dynamics. The fast relaxation of the photo-generated carriers was determined to follow a double exponential decay with time constants of 0.4 ps and 2.1 ps. Furthermore, time-correlated single photon counting measurements provide evidence of three exponential relaxation channels on the nanosecond timescale. © 2011 Othonos and Zervos; licensee Springer.

Bhowmik R.N.,Pondicherry University | Satya A.T.,Materials Science Group | Bharathi A.,Materials Science Group
Journal of Alloys and Compounds | Year: 2013

Ferromagnetic property of Co1.5Fe1.5O4 ferrite has been studied in a wide range of measurement temperature and magnetic field. Grain size effect on the ferromagnetic parameters has been examined by annealing the chemical routed sample at different temperatures up to 1150 °C. The evolution from hard to soft ferromagnetism of the material has been correlated with undergoing changes of crystal structure, grain morphology, crystalline anisotropy, and transformation of the ferromagnetic grains from single domain to multi-domain structure during annealing process. The present ferrite samples also showed some interesting low temperature features, e.g., blocking of ferromagnetic grains that started above 300 K and its control by varying magnetic field intensity, competition of the crystalline anisotropy between uniaxial and cubic character, large magnetic squareness and variable coercivity as the function of annealing temperature of the samples. The material seems to be technologically interesting for its high squareness value. © 2013 Elsevier B.V. All rights reserved.

Ozkan S.,Materials Science Group | Gillece T.W.,Materials Science Group | Senak L.,Materials Science Group | Moore D.J.,Materials Science Group
International Journal of Cosmetic Science | Year: 2012

Synopsis Gels made with three different polymers widely used as rheology modifiers in cosmetic formulations (cross-linked poly(acrylic acid), cross-linked poly(maleic acid-alt-methyl vinyl ether) copolymer and cross-linked poly(acrylic acid-co-vinyl pyrrolidone) copolymer) were characterized by rheological and sensory evaluation methods to determine the relationship between sensorial perception and corresponding rheological parameters. Both conventional rheological characterization methods and a more recent method, Fourier Transform Rheology with Large Amplitude Oscillatory Flow data (LAOS), were utilized to characterize the material with and without wall slip. Sensorial analyses were implemented in vivo to evaluate the perceived ease of initial and rub-out spreadability, cushion, pick-up and slipperiness attributes of the gels. Results were statistically analysed by both variance (ANOVA) and principle component analysis (PCA). Sensorial panel testing characteristics discriminated the three materials, and PCA analyses revealed that sensory attributes could be well predicted by rheological methods. Rheological experiments, without wall slip, revealed that gel strength in the linear viscoelastic region (LVR) and yield stress of these materials are similar, but exhibit significantly different wall slip and thixotropy behaviour in the low shear rate region under wall slip conditions. Above the critical shear rate, which corresponds to the yield stress, all tested materials did not slip and behaved as conventional, shear thinning polymeric fluids. In particular, the rheological parameters and sensorial perception of the 1% cross-linked vinyl pyrrolidone/acrylic acid copolymer were significantly affected by wall slip and/or thixotropy-related shear banding phenomena. © 2012 ISP Investments Inc. ICS © 2012 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Gorcea M.,University of London | Gorcea M.,Materials Science Group | Hadgraft J.,University of London | Lane M.E.,University of London | Moore D.J.,Center for Skin Science and Applied Dermatology
International Journal of Cosmetic Science | Year: 2013

Recently, we developed a biophysical approach to characterize in vivo facial cheek skin as a function of stratum corneum (SC) depth, barrier function and during a 24-h recovery period. The current study extends this work and characterizes the human facial cheek after barrier challenge and, for the first time, facial SC barrier recovery over a 4-week period. Changes in the corneocyte size over the 4-week recovery period, and correlations with changes in Trans-Epidermal Water Loss (TEWL) were monitored. This approach allows complete characterization of SC barrier function after a full biological regeneration of the SC barrier following tape stripping. The structural and compositional changes in facial cheek were investigated using Attenuated Total Reflectance-Fourier Transform Infra Red (ATR-FTIR) spectroscopy, tape stripping, TEWL measurements and image analysis combined with optical microscopy to characterize the SC depth profile during the tape stripping stress and over 4-week recovery period. TEWL increased significantly from baseline after sequential tape stripping. Corneocyte size decreased with successive tape stripping. An inverse direct correlation was determined between TEWL and corneocyte surface area. After 4 weeks, the corneocyte size and TEWL for the facial cheek recovered 100% from the tape stripping procedure. The in vivo ATR-FTIR data demonstrated that lipid and sebum components on the surface of the facial cheek SC recovered within 24 h post tape stripping, whereas protein (Amide II) and water components recovered after 1 week. © 2012 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

Bhowmik R.N.,Pondicherry University | Bharathi A.,Materials Science Group
AIP Conference Proceedings | Year: 2013

We have developed ferromagnetic Co1.5Fe1.5O 4 ferrite by chemical route. Size of the magnetic grains is below 10 nm and assumed to be in single domain range. At room temperature (RT), the samples have shown soft ferromagnetic properties. Below RT, ferromagnetic parameters have increased and high magnetic squareness (∼ 0.8-0.9) is seen at 4 K. Ferromagnetic parameters has been tuned by varying pH value during chemical reaction of the metal salts solution. © 2013 American Institute of Physics.

Sornadurai D.,Materials Science Group | Ravindran T.R.,Materials Science Group | Paul V.T.,Metallurgy and Materials Group | Sastry V.S.,Indira Gandhi Center for Atomic Research
AIP Conference Proceedings | Year: 2012

Synthesis parameters are optimized in order to grow single crystals of multiferroic BiFeO3. 2 to 3 mm size pyramid (tetrahedron) shaped single crystals were successfully obtained by solvothermal method. Scanning electron microscopy with EDAX confirmed the phase formation. Raman scattering spectra of bulk BiFeO3 single crystals have been measured which match well with reported spectra. © 2012 American Institute of Physics.

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