Influence of Temperature on the Conformational Guided Physical Properties of Ultrathin Films of PLLA

Poly (L lactic acid) (PLLA) ultrathin films of various thicknesses were prepared by spin coating method and investigated by using vibrational spectroscopic techniques such as FTIR and Raman. The analysis has been done in two parts: first one is verification of structural mode to understand the visibility of characteristic band to confirm the PLLA structure; where interestingly, as the thickness of the film increased, the structural features were found to be more explicit. The second part of the study was to observe the features of the film having been annealed for 1 h in two separate temperatures, one at specific annealing temperature 120 °C and the other at 160 °C to enable PLLA chains to reorient to get crystallized from its soften state at two such specific temperatures. The isothermal crystallization behavior of PLLA film at 120 °C and 160 °C from the melt was monitored by FTIR as well as Raman spectroscopies. More importantly, the band at 921 cm-1 corresponds to α crystalline phase of PLLA has been observed even in this ultrathin film with the effective application of temperature as selected in this study.Defence Science Journal, Vol. 64, No. 3, May 2014, pp. 309-313, DOI:http://dx.doi.org/10.14429/dsj.64.732

Study of magnetic nanowires of amorphous Co20_{20}Fe60_{60}B20_{20} prepared by oblique angle deposition on nanorippled substrate

An array of magnetic nanowires of amorphous Co$_{20}$Fe$_{60}$B$_{20}$ alloy has been prepared by oblique angle deposition of material on nanorippled substrate. The angle of incidence is chosen such that the deposition takes place on only one facet of the nanoripples. Grazing incidence small angle x-ray scattering measurement has been done in order to characterize the morphology of the nanowires. It is found that the oblique angle deposition results in columnar growth, and each individual nanowire consists of nanocolumns having average diameter of 7 nm and a tilt angle of 37° with respect to the surface normal. Azimuthal angle dependence of longitudinal magneto-optical Kerr effect measurement shows that the nanowires possess a well-defined uniaxial magnetic anisotropy with the easy axis of magnetization tilted by an angle of 25° with respect to the direction of the ripples. The magnetization follows the Stoner-Wohlfarth model with a very narrow distribution in the direction of easy axis. It is suggested that, tilt of the easy axis can be understood in terms of the interplay of two shape anisotropy terms corresponding to the ensemble of strongly interacting nanocolumns through magnetostatic dipolar interaction, and the overall shape of a nanowire

Structure-function correlations in sputter deposited gold/fluorocarbon multilayers for tuning optical response

A new strategy to nanoengineer gold/fluorocarbon multilayer (ML) nanostructures is reported. We have investigated the morphological changes occurring at the metal–polymer interface in ML structures with varying volume fraction of gold (Au) and the kinetic growth aspect of the microscale properties of nano-sized Au in plasma polymer fluorocarbon (PPFC). Investigations were carried out at various temperatures and annealing times by means of grazing incidence small-angle and wide-angle X-ray scattering (GISAXS and GIWAXS). We have fabricated a series of MLs with varying volume fraction (0.12, 0.27, 0.38) of Au and bilayer periodicity in ML structure. They show an interesting granular structure consisting of nearly spherical nanoparticles within the polymer layer. The nanoparticle (NP) morphology changes due to the collective effects of NPs diffusion within ensembles in the in-plane vicinity and interlayer with increasing temperature. The in-plane NPs size distinctly increases with increasing temperature. The NPs become more spherical, thus reducing the surface energy. Linear growth of NPs with temperature and time shows diffusion-controlled growth of NPs in the ML structure. The structural stability of the multilayer is controlled by the volume ratio of the metal in polymer. At room temperature, UV-Vis shows a blue shift of the plasmon peak from 560 nm in ML Au/PTFE_1 to 437 nm in Au/PTFE_3. We have identified the fabrication and postdeposition annealing conditions to limit the local surface plasmon resonance (LSPR) shift from ΔλLSPR = 180 nm (Au/PTFE_1) to ΔλLSPR = 67 nm (Au/PTFE_3 ML)) and their optical response over a wide visible wavelength range. A variation in the dielectric constant of the polymer in presence of varying Au inclusion is found to be a possible factor affecting the LSPR frequency. Our findings may provide insights in nanoengineering of ML structure that can be useful to systematically control the growth of NPs in polymer matrix

Anomalous Behavior of Magnetic Anisotropy of Amorphous Co40_{40}Fe43_{43}B17_{17} Thin Film Sandwiched Between Mo Layers

Anomalous behavior of magnetic anisotropy in Co$_{40}$Fe$_{43}$B$_{17}$ film sandwiched between Mo layers has been observed as a function of thermal annealing at different temperatures. The as-deposited amorphous film exhibits a uniaxial magnetic anisotropy, the origin of which can be traced to quenched-in stresses. With thermal annealing up to 300 °C, anisotropy remains unchanged. We observe an anomalous magnetic reversal near the hard axis (HA) in the samples annealed at 350 °C and above. The anomaly of the occurrence of nonuniform magnetization near HA can be explained in terms of distribution of easy magnetization direction, as evidenced by the ripple domain structure in Kerr microscopy images

Synthesis of glycinamides using protease immobilized magnetic nanoparticles

In the present investigation, Bacillus subtilis was isolated from slaughterhouse waste and screened for the production of protease enzyme. The purified protease was successfully immobilized on magnetic nanoparticles (MNPs) and used for the synthesis of series of glycinamides. The binding and thermal stability of protease on MNPs was confirmed by FTIR spectroscopy and TGA analysis. The surface morphology of MNPs before and after protease immobilization was carried out using SEM analysis. XRD pattern revealed no phase change in MNPs after enzyme immobilization. The processing parameters for glycinamides synthesis viz. temperature, pH, and time were optimized using Response Surface Methodology (RSM) by using Design Expert (9.0.6.2). The maximum yield of various amides 2 butyramidoacetic acid (AMD-1,83.4%), 2-benzamidoacetic acid (AMD-2,80.5%) and 2,2′((carboxymethyl) amino)-2-oxoethyl)-2-hydroxysuccinyl)bis(azanediyl))diacetic acid (AMD-3,80.8%) formed was observed at pH-8, 50 °C and 30 min. The synthesized immobilized protease retained 70% of the initial activity even after 8 cycles of reuse

Portable mini-chamber for temperature dependent studies using small angle and wide angle x-ray scattering

The present work describes the design and performance of a vacuum compatible portable mini chamber for temperature dependent GISAXS and GIWAXS studies of thin films and multilayer structures. The water cooled body of the chamber allows sample annealing up to 900 K using ultra high vacuum compatible (UHV) pyrolytic boron nitride heater, thus making it possible to study the temperature dependent evolution of structure and morphology of two-dimensional nanostructured materials. Due to its light weight and small size, the chamber is portable and can be accommodated at synchrotron facilities worldwide. A systematic illustration of the versatility of the chamber has been demonstrated at beamline P03, PETRA-III, DESY, Hamburg, Germany. Temperature dependent grazing incidence small angle x-ray scattering (GISAXS) and grazing incidence wide angle x-ray scattering (GIWAXS) measurements were performed on oblique angle deposited Co/Ag multilayer structure, which jointly revealed that the surface diffusion in Co columns in Co/Ag multilayer enhances by increasing temperature from RT to ∼573 K. This results in a morphology change from columnar tilted structure to densely packed morphological isotropic multilaye

High-stress abrasive wear response of 0.2% carbon dual phase steel : Effects of microstructural features and experimental conditions

Effects of heat treatment on the high-stress abrasive wear response of 0.2% carbon steel have been investigated at varying applied loads, abrasive (SiC) sizes and sliding distances. The heat treatment involved intercritical annealing at three different temperatures between Ac-1 and Ac-3 followed by ice water quenching in order to produce a dual phase microstructure consisting of varying quantities of ferrite plus martensite. The wear rate increased monotonically with applied load irrespective of the heat treatment schedule. Further, the wear rate increased drastically when the abrasive size was increased from 15 to 27 mu m; a further increase in the abrasive size led to only a marginal increase in the wear rate. In general, the wear rate decreased with increasing sliding distance and attained a nearly stable value at longer sliding distances. Increasing intercritical annealing temperature resulted into higher martensite content, thereby leading to reduced wear rate. However, the extent of reduction in wear rate with martensite content has been found to change with the applied load and abrasive size. The present investigation clearly suggests that it is quite possible to attain desired combinations of bulk hardness and microstructure (ferrite plus martensite) that could greatly control abrasive wear properties in low carbon steel. The observed wear response of the samples has been explained on the basis of microconstituent-abrasive interaction during the course of abrasive action, degradation of the abrasive particles and the nature of various microconstituents, i.e. mechanical properties. (c) 2007 Elsevier B.V. All rights reserved.Peer reviewe

CsrA Regulates Translation of the Escherichia coli Carbon Starvation Gene, cstA, by Blocking Ribosome Access to the cstA Transcript

CsrA is a global regulator that binds to two sites in the glgCAP leader transcript, thereby blocking ribosome access to the glgC Shine-Dalgarno sequence. The upstream CsrA binding site (GCACACGGAU) was used to search the Escherichia coli genomic sequence for other genes that might be regulated by CsrA. cstA contained an exact match that overlapped its Shine-Dalgarno sequence. cstA was previously shown to be induced by carbon starvation and to encode a peptide transporter. Expression of a cstA′-′lacZ translational fusion in wild-type and csrA mutant strains was examined. Expression levels in the csrA mutant were approximately twofold higher when cells were grown in Luria broth (LB) and 5- to 10-fold higher when LB was supplemented with glucose. It was previously shown that cstA is regulated by the cyclic AMP (cAMP)-cAMP receptor protein complex and transcribed by Εσ(70). We investigated the influence of σ(S) on cstA expression and found that a σ(S) deficiency resulted in a threefold increase in cstA expression in wild-type and csrA mutant strains; however, CsrA-dependent regulation was retained. The mechanism of CsrA-mediated cstA regulation was also examined in vitro. Cross-linking studies demonstrated that CsrA is a homodimer. Gel mobility shift results showed that CsrA binds specifically to cstA RNA, while coupled-transcription-translation and toeprint studies demonstrated that CsrA regulates CstA synthesis by inhibiting ribosome binding to cstA transcripts. RNA footprint and boundary analyses revealed three or four CsrA binding sites, one of which overlaps the cstA Shine-Dalgarno sequence, as predicted. These results establish that CsrA regulates translation of cstA by sterically interfering with ribosome binding

Clinical and Autoimmune Profile of Scleroderma Patients from Western India

Background. Systemic sclerosis (SSc, scleroderma) is a disorder characterized by fibrosis of skin and visceral organs. Pathogenesis of scleroderma is complex and is incompletely understood as yet. Autoantibodies in SSc represent a serologic hallmark which have clinical relevance, with diagnostic and prognostic potential. Objectives. To study distribution of clinical manifestations and to identify frequency of autoantibodies among subtypes of scleroderma patients from Western India. Methodology. One hundred and ten scleroderma patients were clinically classified according to the American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) criteria. All these patients were in active stage of disease. Clinical manifestations were recorded at the time of presentation. Autoantibodies were tested in them by indirect immunofluorescence test and ELISA. Immunoglobulin levels were estimated by nephelometer. These parameters were further correlated with clinical presentation of the disease. Results. Scleroderma patients had M : F ratio of 1 : 10 where mean age at evaluation was 34.7±10.7 years and a mean disease duration was 43.7±35 months. Clinical subtypes showed that 45 patients (40.9%) had diffused cutaneous (dcSSc) lesions, 32 patients (29.1%) had limited cutaneous (lcSSc) lesions, and 33 patients (30%) had other autoimmune overlaps. The overall frequency of ANA in SSc patients studied was 85.5%. The frequency of anti-Scl70, anti-centromere, anti-endothelial cell antibodies (AECA), and anti-keratinocyte antibodies (AKA) was 62.7%, 22.7%, 30%, and 40.9%, respectively. Anti-Scl70 antibodies were significantly high (75.6% versus 46.9%) among dcSSc patients (P<0.0115) whereas anti-centromere antibodies were significantly high (9% versus 38%) among lcSSc patients when these two subtypes were compared (P<0.0044). Conclusion. This study supports that there are geoepidemiological variations among scleroderma patients for their clinical presentation, autoantibody profile, and immune parameters across the country

High-Stress Abrasive Wear Response of 0.2% Carbon Dual Phase Steel: Effects of Microstructural Features and Experimental Conditions.

Effects of heat treatment on the high-stress abrasive wear response of 0.2% carbon steel have been investigated at varying applied loads, abrasive (SiC) sizes and sliding distances. The heat treatment involved intercritical annealing at three different temperatures between Ac1 and Ac3 followed by ice water quenching in order to produce a dual phase microstructure consisting of varying quantities of ferrite plus martensite. The wear rate increased monotonically with applied load irrespective of the heat treatment schedule. Further, the wear rate increased drastically when the abrasive size was increased from 15 to 27 �m; a further increase in the abrasive size led to only a marginal increase in the wear rate. In general, the wear rate decreased with increasing sliding distance and attained a nearly stable value at longer sliding distances.Increasing intercritical annealing temperature resulted into higher martensite content, thereby leading to reduced wear rate. However, the extent of reduction in wear rate with martensite content has been found to change with the applied load and abrasive size. The present investigation clearly suggests that it is quite possible to attain desired combinations of bulk hardness and microstructure (ferrite plus martensite) that could greatly control abrasive wear properties in low carbon steel. The observed wear response of the samples has been explained on the basis of microconstituent–abrasive interaction during the course of abrasive action, degradation of the abrasive particles and the nature of various microconstituents, i.e. mechanical properties