Papers by Senthil Arumugam
We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar ... more We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar vesicles by the prokaryotic tubulin homolog, FtsZ, on phase separation in freestanding lipid membranes. FtsZ has been modified to interact with the membrane through a membrane targeting sequence from the prokaryotic protein MinD. FtsZ with the attached membrane targeting sequence efficiently forms a highly interconnected network on membranes with a concentration-dependent mesh size, much similar to the eukaryotic cytoskeletal network underlying the plasma membrane. Using giant unilamellar vesicles formed from a quaternary lipid mixture, we demonstrate that the artificial membrane-associated cytoskeleton, on the one hand, suppresses large-scale phase separation below the phase transition temperature, and, on the other hand, preserves phase separation above the transition temperature. Our experimental observations support the ideas put forward in our previous simulation study: In particular, the picket fence effect on phase separation may explain why micrometer-scale membrane domains are observed in isolated, cytoskeleton-free giant plasma membrane vesicles, but not in intact cell membranes. The experimentally observed suppression of large-scale phase separation much below the transition temperatures also serves as an argument in favor of the cryoprotective role of the cytoskeleton.
Journal of Sol-Gel Science and Technology, 2015
Tungsten oxide (WO 3 ) nanoparticles have been prepared by the chemical precipitation technique. ... more Tungsten oxide (WO 3 ) nanoparticles have been prepared by the chemical precipitation technique. The powder X-ray diffraction was carried out to ascertain the crystallinity and the crystal structure associated with the assynthesized WO 3 nanoparticles. The average crystallite size of WO 3 nanoparticles was calculated by Scherrer's method and was found to be about 3 nm. The metal oxide composition and the stoichiometry of the as-synthesized WO 3 nanoparticles were assessed by energy-dispersive X-ray spectroscopy measurement. The surface morphology of WO 3 nanoparticles was characterized by field emission scanning electron microscopy analysis. The Brunauer-Emmett-Teller surface area analysis confirms that the WO 3 nanoparticles have large surface area of 240.56 m 2 g -1 and pore volume of 0.1157 cc g -1 which were essential criteria to design a dye-sensitized solar cell (DSSC). The structure of core levels W4f and O1s was explored by XPS method. The incorporation of WO 3 as a counter electrode in DSSC resulted in the power conversion efficiency of 0.98 %. Furthermore, the easy availability and environmental friendly properties of the WO 3 would be very promising to accelerate the large-scale applications of DSSC in the future. WO 3 could be a useful substitute.
Conference Proceedings. 2000 International Conference on Indium Phosphide and Related Materials (Cat. No.00CH37107), 2000
ALInAs has been grown by CBE technique for ultra-fast switching device applications. The material... more ALInAs has been grown by CBE technique for ultra-fast switching device applications. The materials were grown in the temperature range of 693-803 K and a low growth rate of 0.3 mm/h was employed in order to enhance the surface ad-atom residence time. The grown materials have excellent crystallographic and optical properties as studied by HRXRD and low temperature photoluminescence (LT PL) measurements. There is no suitable electrolyte available to successfully profile the dopants in AlInAs by ECV method. An effort has been made to develop an appropriate electrolyte for profiling AlInAs material. A number of electrolytic solutions were investigated and among the probed solutions, two different electrolytes namely HNO 3 :H 2 O 2 ::HF:H 2 O and NH 4 F have been realised. Both have very low electrolytic resistance and a low free chemical etch rate values with good I2V and C2V characteristics. Using these electrolytes, the estimated carrier concentration value were in very good agreement with independently measured HALL effect measurement values. But the ECV measured thickness value does not agree well with that of stylus profiler measurement thickness value. This discrepancy has been explained on the basis of etching properties of aluminium containing compounds during electrochemical etching process. r 2004 Published by Elsevier B.V.
Annals of Medicine and Surgery, 2015
The estimated prevalence of Sensory Neural Hearing Loss (SNHL) in patients less than 18 years of ... more The estimated prevalence of Sensory Neural Hearing Loss (SNHL) in patients less than 18 years of age is 6 per 1000. Roughly 50% of cases of congenital SNHL can be linked to a genetic cause, with approximately 30% being syndromic and the remaining 70% being non-syndromic. The term "syndromic" implies the presence of other distinctive clinical features in addition to hearing loss. The aim of our study was to find the distribution of various Syndromic associations in patients with profound deafness, presented at Madras ENT Research foundation, Chennai and to formulate a management protocol for these patients and to discuss in detail about the clinical features of commonly encountered syndromic deafness. Our retrospective study was aimed at describing the various Syndromic associations seen in patients with congenital profound deafness. Information was collected from the medical records. At our centre all patients undergo a comprehensive evaluation. The distribution, etiological factors and management protocol for various syndromes are here presented. Out of 700 patients with congenital profound deafness all patients with Syndromic associations (n = 35) were studied. 5% of profoundly deaf candidates were found to be syndromic. Most common syndrome in our series was found to be congenital rubella syndrome followed by Jervell and Lange-Nielsen syndrome. Congenital deafness is an associated feature of many syndromes. Detailed history taking with comprehensive evaluation is mandatory to rule out the associated syndromes. Diagnosis must be confirm by a genetic study. Multidisciplinary approach is essential for appropriate diagnosis and management.
Journal of Materials Science: Materials in Electronics, 2015
Titanium dioxide nanorods/nanoparticles (NR/ NP) were prepared via hydrothermal process. The crys... more Titanium dioxide nanorods/nanoparticles (NR/ NP) were prepared via hydrothermal process. The crystallographic information of prepared samples was confirmed with PXRD, which shows anatase phase with small fraction of brookite phase. The FESEM results indicate that the formed nanostructures are having both nanorods and nanoparticles. From the HRTEM results, the lattice images of nanostructures were clearly observed, which indicates that these nanostructures possess high degrees of crystallinity. From the distance between the adjacent lattice fringes, we can assign the lattice plane on the nanostructures. The nanoparticles showed lattice spacing of 0.35 nm for the (101) plane of the anatase phase. BET analysis shows that the surface area of the sample is 37.97 m 2 /g. In the BJH approach, multiple pores are observed (2.6, 4.7 and 7.3 nm) in the structure. The obtained porous NR/NP nanostructure was applied to DSSC. The solar energy conversion efficiency (g) of the NR/NP based DSSC was about 2.12 % with J sc of 5.56 mA/cm 2 , V oc of 0.61 V and FF of 62.87 %.
Biophysical journal, Jan 10, 2015
We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar ... more We study the effect of a minimal cytoskeletal network formed on the surface of giant unilamellar vesicles by the prokaryotic tubulin homolog, FtsZ, on phase separation in freestanding lipid membranes. FtsZ has been modified to interact with the membrane through a membrane targeting sequence from the prokaryotic protein MinD. FtsZ with the attached membrane targeting sequence efficiently forms a highly interconnected network on membranes with a concentration-dependent mesh size, much similar to the eukaryotic cytoskeletal network underlying the plasma membrane. Using giant unilamellar vesicles formed from a quaternary lipid mixture, we demonstrate that the artificial membrane-associated cytoskeleton, on the one hand, suppresses large-scale phase separation below the phase transition temperature, and, on the other hand, preserves phase separation above the transition temperature. Our experimental observations support the ideas put forward in our previous simulation study: In particula...
Optics & Laser Technology, 2014
and sharing with colleagues.
Essays in Biochemistry, 2015
The understanding of lipid membranes and their organization has undergone significant development... more The understanding of lipid membranes and their organization has undergone significant development with better techniques and therefore more resolved experiments. Many new factors and organizing principles have been discovered, and interplay between these factors is expected to result in rich functional behaviours. The major factors regulating the lateral membrane heterogeneity, apart from the well-studied phase separation, are cytoskeleton pinning, clustering of lipids and curvature. These factors are effective means to create membrane domains that provide rich biological functionality. We review the recent advances and concepts of membrane heterogeneity organization by curvature, cytoskeleton and clustering proteins.
Journal of Rare Earths, 2014
ABSTRACT The perovskite-like NaMgF3 polycrystalline powder samples, pure and rare earth doped, we... more ABSTRACT The perovskite-like NaMgF3 polycrystalline powder samples, pure and rare earth doped, were synthesized by conventional solid state reaction method. The perovskite material was doped with 0.2 mol.% of EuF3 and CeF3 impurity. Phase purity of synthesized compounds was analyzed by powder X-ray diffraction technique. The thermoluminescence response of polycrystalline samples showed a linear response up to 12 Gy and then became sub linear at higher doses. The order of kinetics (b), activation energy (E) and other trapping parameters were calculated using peak shape method and variable heating rate method. From glow curve analysis the symmetric factor was calculated. The glow curve showed two peaks at 404 and 488 K, and both of them confirmed the thermoluminescence in the phosphor, which obeyed second-order kinetics. The experimental resulted showed that this phosphor could have potential applications in radiation dosimetry.
ABSTRACT The perovskite-like KMgF3 polycrystalline compounds were synthesized by standard solid s... more ABSTRACT The perovskite-like KMgF3 polycrystalline compounds were synthesized by standard solid state reaction technique. Phase purity of the synthesized compounds was analyzed by powder X-ray diffraction technique. Single crystals of (0.2 mol% of EuF3 and CeF3) Co-doped KMgF3 have been grown from melt by using a vertical Bridgman-Stockbarger method. Thermoluminescence (TL) characteristics of KMgF3 samples doped with Eu2+ and Ce3+ have been studied after β-ray irradiation. At ambient conditions the photoluminescence spectra consisted of sharp line peaked of Eu2+ at 360 nm attributed to the f → f transition (6P7/2→8S7/2) could only be observed due to the energy transfer from Ce3+ to Eu2+.
Materials Research Bulletin, 2012
Unidirectional h0 1 0i TGS single crystal of diameter 35 mm and length 80 mm was grown by Sankara... more Unidirectional h0 1 0i TGS single crystal of diameter 35 mm and length 80 mm was grown by Sankaranarayanan-Ramasamy (SR) method. Nearly two times higher d 33 value has been obtained for the SR grown TGS crystal compared to conventional grown TGS. The etch pit density of SEST and SR method grown TGS crystal is 2.1 Â 10 2 cm À2 and 1.5 Â 10 2 cm À2 respectively. The values of hardness were found to be 152 kg/mm 2 for SR grown TGS and 108 kg/mm 2 for SEST grown TGS crystal. The average laser damage threshold obtained on the SEST grown TGS crystal was 29 mJ/cm 2 whereas a high damage threshold of 39 mJ/cm 2 was obtained for the SR grown crystal. The SR method grown TGS has 5% higher transmittance as against conventional method grown crystal. Dielectric study showed higher dielectric permittivity and lower dielectric loss in SR grown TGS crystal. ß Fig. 5. (a) Bundles of solvent inclusions; (b) Growth bands on chemically polished TGS crystal surface; (c) Micro-cracks obtained in as grown TGS crystal; (d) Milky opaques near the solvent inclusions, and (e) Various types of defects observed in conventional SEST grown TGS seed crystal. M. Senthil Pandian et al. / Materials Research Bulletin xxx (2012) xxx-xxx 6 G Model MRB-5557; No. of Pages 11 Please cite this article in press as: M. Senthil Pandian, et al., Mater.
International Journal of Pediatric Otorhinolaryngology, 2014
Obstructive Sleep Apnea (OSA) is a common medical problem in adults that is becoming increasingly... more Obstructive Sleep Apnea (OSA) is a common medical problem in adults that is becoming increasingly recognized in children. It occurs in the pediatric age group, from newborns to teens. More recently, many specialists have estimated OSA prevalence to be between 5 and 6%. However, in syndromic children, the prevalence of OSA can be from 50 to 100%, having a significant effect on their Quality-of-Life. As they are a challenging population for management, it is essential to evaluate them thoroughly before planning appropriate intervention. To compare the efficacy of Adenotonsillectomy (T&A) and Continuous Positive Airway Pressure (CPAP) in syndromic children [Down syndrome (DS) and Mucopolysaccharidoses (MPS)] with Obstructive Sleep Apnea (OSA). In a prospective, randomized, cohort comparative study, 124 syndromic children (DS and MPS) aged between 6 and 12 years were recruited from a private MPS support group and the Down Syndrome Society, Chennai. A standard assessment was performed on all children who entered the study including a full overnight Polysomnogram (PSG), Epworth Sleepiness Scale-Children (ESS-C) and Quality-of-Life (QOL) tool OSA-18. The children with positive PSG who consented for the study (n = 80) were randomly distributed to two groups, T&A group & CPAP group. The children were followed up with repeat PSG, clinical evaluation, ESS-C and Quality-of-Life (QOL) tool OSA-18 for a period of 1 year. Follow-up was available for 73 syndromic children. Both the groups, T&A group and CPAP group, showed statistically significant (p < 0.05) improvement in Apnea-Hypoapnea Index (AHI), ESS-C, QOL from the intervention. In our study, T&A showed equal outcome compared to CPAP. The contrasting feature between the two groups was that CPAP use gave immediate sustained improvement while T&A gave gradual progressive improvement of symptoms over a period of 1 year. On average, T&A gives equal outcomes as CPAP and it can be suggested as a first-line treatment in this group of syndromic children.
International Journal of Modern Physics B, 2003
WSPC Journals Online,WorldSciNet.
The plasma membrane of cells can be viewed as a highly dynamic, regulated, heterogeneous environm... more The plasma membrane of cells can be viewed as a highly dynamic, regulated, heterogeneous environment with multiple functions. It constitutes the boundary of the cell, encapsulating all its components. Proteins interact with the membrane in many ways to accommodate essential processes, such as membrane trafficking, membrane protrusions, cytokinesis, signaling, and cell-cell communication. A vast amount of literature has already fostered our current understanding of membrane-protein interactions. However, many phenomena still remain to be understood, e.g., the exact mechanisms of how certain proteins cause or assist membrane transformations. Systems biology aims to predict biological processes on the basis of the set of molecules involved. Many key processes arise from interactions with the lipid membrane. Protein interactome maps do not consider such specific interactions, and thus cannot predict precise outcomes of the interactions of the involved proteins. These can only be inferred from experimental approaches. We describe examples of how an emergent behavior of protein-membrane interactions has been demonstrated by the use of minimal systems. These studies contribute to a deeper understanding of protein interactomes involving membranes and complement other approaches of systems biology.
Bacterial cell division initiates with the formation of a ring-like structure at the cell center ... more Bacterial cell division initiates with the formation of a ring-like structure at the cell center composed of the tubulin homolog FtsZ (the Z-ring), which acts as a scaffold for the assembly of the cell division complex, the divisome. Previous studies have suggested that the divisome is initially composed of FtsZ polymers stabilized by membrane anchors FtsA and ZipA, which then recruit the remaining division proteins. The MinCDE proteins prevent the formation of the Z-ring at poles by oscillating from pole to pole, thereby ensuring that the concentration of the Z-ring inhibitor, MinC, is lowest at the cell center. We show that prior to septum formation, the early-division proteins ZipA, ZapA, and ZapB, along with FtsZ, assemble into complexes that counter-oscillate with respect to MinC, and with the same period. We propose that FtsZ molecules distal from high concentrations of MinC form relatively slowly diffusing filaments that are bound by ZapAB and targeted to the inner membrane by ZipA or FtsA. These complexes may facilitate the early stages of divisome assembly at midcell. As MinC oscillates toward these complexes, FtsZ oligomerization and bundling are inhibited, leading to shorter or monomeric FtsZ complexes, which become less visible by epifluorescence microscopy because of their rapid diffusion.
Materials Research Bulletin, 2014
ABSTRACT Potassium hydrogen phthalate single crystals have been grown by conventional and Sankara... more ABSTRACT Potassium hydrogen phthalate single crystals have been grown by conventional and Sankaranarayanan-Ramasamy method. Dye inclusion crystals have attracted researchers in the context of crystal growth for applications in solid state lasers. The effect of crystal violet as dopant on the characteristic properties of KAP crystal was studied. Thermal stability of the crystals is tested using TG-DTA. There is only one endothermic peak which indicates the decomposition point. The optical transparency of the crystals was identified from the UV-vis spectrum. The mechanical strength of the crystals has been measured by Vickers micro hardness. The dielectric, piezoelectric and luminescence study is carried out for both pure and dye doped KAP crystals. The photoluminescence spectrum of the KAP induced by the dye-doping reveals an emission band peaking at 595 nm.
Materials Research Bulletin, 2012
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Papers by Senthil Arumugam