643 research outputs found

    Comparison of Physical and Chemical Properties of Five Different Alloplastic Bone Graft Materials

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    AIMS AND OBJECTIVES: The present study aims at analysing physicochemical characteristics of 5 different types of alloplastic graft materials used in periodontal regeneration. MATERIALS AND METHODS: The materials used were:- Monophasic Hydroxyapatite – Biograft HA, Tricalcium Phosphate – Biograft TCP, Biphasic Hydroxyapatite – Biograft HT, Bioactive Glass – Perioglas and a combination of Hydroxyapatite and Bioactive Glass – Biograft HABG Active. MATERIAL CHARACTERIZATION: The physicochemical properties of the biomaterials were tested using the following methods: 1. Scanning Electron Microscopy [SEM] - assess the sample`s surface topography & size 2. Thermogravimetry - reflect divergent physical properties and chemical compositions among the specimens resulting from their diverse thermal histories. 3. Fourier Transform Infrared Spectroscopy [FTIR] - to provide information concerning the chemical composition and the major functional groups. 4. X ray diffractometry [XRD] - used to identify phase and composition features and qualitatively evaluate the crystallinity of the materials 5. Dissolution rates - used to evaluate the solubility rate of calcium and silica RESULTS: From the particle size related data it is seen that PG and HA show smaller particles (100 – 300 μm) while TCP, HT and HABG show larger particles (200 – 500 μm). In the present study Biograft HA, Biograft TCP and Biograft HABG showed rough and irregular surface, while Perioglas and Biograft HT showed a smooth surface. The surface of perioglas is said to be smooth with less roughness, Biograft HT shows smooth and sintered surface particles with nano pores visible. All the other materials show rough surface with the presence of micro and nano sized pores ranging from 0.5 – 1 μm. Thermogravimetric analysis is used to determine the content of water, organic material (like collagen) and mineral (CaP). For all of the alloplasts in our study only a minimal weight loss upto 2 % was seen which can be attributed to the presence of moisture or due to oxidation of the samples. As all the test materials were synthetic or alloplastic, there was the absence of lattice water or organic content. All the tested materials were stable upto 10000 C, which renders all test materials to be thermally stable and phase pure and without any impurities. Infra red analysis shows the presence of main functional groups such as phosphates and carbonates. The calcium phosphate class of materials (HA, TCP and HT) and HABG showed almost similar stretching and vibration patterns for both functional groups. Phosphate peak was broad in Perioglas which may be due to the amorphous nature of material. In the Infrared spectra data from the 5 tested materials, hydroxyl peaks had highest intensity in HA, with midway values in HT and almost nil in TCP. HABG does not show a peak corresponding to OH group and PG shows a broadened peak. X ray diffraction patterns of the 5 alloplastic materials indicate their chemical composition (presence of crystalline phases) and lattice parameter information. The XRD peaks of the samples were well defined. Among the 5 alloplastic materials HA, HABG, TCP and HT showed typical crystalline structure whereas PG showed broad peaks indicating the amorphous nature of the material. An increasing order of crystallinity was obtained from XRD data as PG, HABG, TCP, HT and HA. In the dissolution tests done for calcium, all the materials showed positive results. Bioactive glass class of grafts (PG and HABG) had more dissolution when compared to hydroxyapatite class (HA,TCP and HT). The second dissolution test was done for silica, the bioactive glass group of material (PG and HABG) which are silica based were tested. Both PG and HABG showed increased dissolution of silica upto 24 hours, with PG showing constant values and HABG showing decreasing rates after 24 hours. SUMMARY: The main objective of present work was the physicochemical characterization of 5 commercial sample of alloplasts used for bone grafting. The alloplastic biomaterials belonged to 3 main classes calcium phosphate group (HA, TCP and HT), bioactive glass group (PG) and a combination graft (HABG). However even for those with similar chemical characteristics, significant differences were noted with regard to particle size, porosity, surface roughness, presence of functional groups, crystallinity and dissolution properties. Among the materials tested calcium phosphate based ceramics and bioactive glass – ceramic combination showed porous surface architecture parameters conducive to cellular and vascular proliferation. Thermogravimetric analysis revealed that all the materials were phase pure with no impurities. Infra red spectrometry showed presence of functional groups essential for bone integration in all test materials with Perioglas and Biograft HABG showing presence of silica which has a beneficial effect in bone formation. X ray diffractometric analysis revealed that with the exception of Perioglas which was amorphous all the other materials were crystalline in nature. Increased dissolution of calcium and silica were seen in bioactive glass group when compared with calcium phosphate and mixed calcium phosphate grafts

    Probing long-range correlations in the Berezinskii-Kosterlitz-Thouless fluctuation regime of ultra-thin NbN superconducting films using transport noise measurements

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    We probe the presence of long-range correlations in phase fluctuations by analyzing the higher-order spectrum of resistance fluctuations in ultra-thin NbN superconducting films. The non-Gaussian component of resistance fluctuations is found to be sensitive to film thickness close to the transition, which allows us to distinguish between mean field and Berezinskii-Kosterlitz-Thouless (BKT) type superconducting transitions. The extent of non-Gaussianity was found to be bounded by the BKT and mean field transition temperatures and depend strongly on the roughness and structural inhomogeneity of the superconducting films. Our experiment outlines a novel fluctuation-based kinetic probe in detecting the nature of superconductivity in disordered low-dimensional materials.Comment: submitted to PR

    Fast Moving Consumer Goods Industry in Rural Market of India: A Case of Mutual Reinvigoration

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    The present study has been undertaken to make an assessment of the growing eminence of FMCG industry in the era of enriching rural market in India. The Indian Fast Moving Consumer Goods (FMCG) industry began to take shape during the past five decades. The FMCG sector is a keystone of the Indian economy as it touches every aspect of human life. The FMCG sector, which offers tremendous growth prospects, are food and beverage sector, health care and personal care. Presently, rural India accounts for 34% of total FMCG consumption, but it accounts for more than 40% consumption in major FMCG categories like as personal care, hot beverages, and fabric care. Moreover, 80% of FMCG categories are growing faster in rural India as against urban India (Nielson, 2011). There is a huge growth potential for all the FMCG companies as the per capita consumption of almost all products in the country is amongst the lowest in the world. In recent years, rural markets have acquired significance in countries like China and India, as the overall growth of the economy has resulted in substantial increase in the purchasing power of the rural communities. On account of the green revolution in India, the rural areas are consuming a large quantity of industrial and urban manufactured products.&nbsp

    A Comparative Femtosecond Coherence Study of the Unligated Monomeric Hemeproteins Myoglobin and Leghemoglobin

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    Impulsive optical excitation has been performed on wild type, unligated leghemoglobin for the first time to compare the induced vibrational coherence with that observed in myoglobin. Both proteins were excited at the Soret maxima and probed at red and blue edges of the Soret band. The resulting kinetic traces were modulated by low-frequency vibrations. Leghemoglobin shows a decrease in vibrational amplitude compared with myoglobin. The possible cause for the amplitude differences is discussed in terms of contributions from both ground- and excited-state vibrational coherences and ground-state heterogeneity

    Interaction of Glutathione S-Transferase with Hypericin:  A Photophysical Study

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    The photophysics of hypericin have been studied in its complex with two different isoforms, A1-1 and P1-1, of the protein glutathione S-transferase (GST). One molecule of hypericin binds to each of the two GST subunits. Comparisons are made with our previous results for the hypericin/human serum albumin complex (Photochem. Photobiol. 1999, 69, 633−645). Hypericin binds with high affinity to the GSTs:  0.65 μM for the A1-1 isoform and 0.51 μM for the P1-1 isoform (Biochemistry 2004, 43, 12761−12769). The photophysics and activity of hypericin are strongly modulated by the binding protein. Intramolecular hydrogen-atom transfer is suppressed in both cases. Most importantly, while there is significant singlet oxygen generation from hypericin bound to GST A1-1, binding to GST P1-1 suppresses singlet oxygen generation to almost negligible levels. The data are rationalized in terms of a simple model in which the hypericin photophysics depends entirely upon the decay of the triplet state by two competing processes, quenching by oxygen to yield singlet oxygen and ionization, the latter of these two are proposed to be modulated by A1-1 and P1-1

    EFFECT OF PESTICIDES ON MICROBIAL TRANSFORMATION OF SULPHUR IN SOIL

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    to investigate the effect of pesticides, on the microbial transformation of sulphur (S) in soil. Insecticide (Endosulfan), fungicide (Dithane M-45), herbicide (2,4-D) were added to the soil at their recommended doses, respectively and their effect on the proliferation and potentiality of thiosulphate oxiding bacteria, aryl sulphatase, available and total sulphur were investigated in soil. The results of the present investigation revealed that insecticide, endosulfan effectuated a significant detrimental effect on some microbiological, biochemical and chemical properties in soil whereas fungicide, dithane M-45 caused a significant detrimental influence during the later stages in spite of stimulating influence at early stages incubation period. However, herbicide, 2,4-D, brought about a beneficial influence on the microbiological, biochemical and chemical properties in soil. Among the pesticides used in the study, the performance of the herbicide was favorable in all respect

    Phase diagram of a strongly disordered s-wave superconductor, NbN, close to the metal-insulator transition

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    We present a phase diagram as a function of disorder in three-dimensional NbN thin films, as the system enters the critical disorder for the destruction of the superconducting state. The superconducting state is investigated using a combination of magnetotransport and tunneling spectroscopy measurements. Our studies reveal 3 different disorder regimes. At low disorder the (k_{F}l~10-4), the system follows the mean field Bardeen-Cooper-Schrieffer behavior where the superconducting energy gap vanishes at the temperature where electrical resistance appears. For stronger disorder (k_{F}l<4) a "pseudogap" state emerges where a gap in the electronic spectrum persists up to temperatures much higher than Tc, suggesting that Cooper pairs continue to exist in the system even after the zero resistance state is destroyed. Finally, very strongly disordered samples (k_{F}l<1) exhibit a pronounced magnetoresistance peak at low temperatures, suggesting that localized Cooper pairs continue to survive in the system even after the global superconducting ground state is completely destroyed.Comment: pdf file with figures (Modified Version

    Phase diagram and upper critical field of homogenously disordered epitaxial 3-dimensional NbN films

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    We report the evolution of superconducting properties with disorder, in 3-dimensional homogeneously disordered epitaxial NbN thin films. The effective disorder in NbN is controlled from moderately clean limit down to Anderson metal-insulator transition by changing the deposition conditions. We propose a phase diagram for NbN in temperature-disorder plane. With increasing disorder we observe that as kFl-->1 the superconducting transition temperature (Tc) and minimum conductivity (sigma_0) go to zero. The phase diagram shows that in homogeneously disordered 3-D NbN films, the metal-insulator transition and the superconductor-insulator transition occur at a single quantum critical point at kFl~1.Comment: To appear in Journal of Superconductivity and Novel Magnetism (ICSM2010 proceedings
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