Temperature Mediated Morphological Transition during Drying of Spray Colloidal Droplets.

Understanding how a tiny dilute evaporative colloidal spray droplet gets transformed into a microgranule with a characteristic morphology is crucial from scientific as well as technological points of view. In the present work, it is demonstrated that the morphology and the size distribution of the microcapsules can be tuned simply by adjusting the drying temperature. Shape and size of the capsules are quantified at four different drying temperatures. It is shown that the morphology transits gradually from sphere to toroid with increasing temperature keeping the average volume-fraction of the correlated nanoparticles nearly unaffected for the synthesized granules. A plausible mechanism for the chronological pathway of such morphological transformation is illustrated. Computer simulation corroborates the experimentally observed morphological transition. The variation in hollowness and buckling tendency of the capsules are elucidated by scattering and imaging techniques.

Colloidal Nanoparticle Interaction Transition during Solvent Evaporation Investigated by in-Situ Small-Angle X-ray Scattering.

In-situ scanning small-angle X-ray scattering (SAXS) experiments have been performed to probe the drying of a single suspended droplet of silica colloids. It has been demonstrated that the formation of a nanoparticle shell during drying can be confirmed just by measuring the temporal evolution of the spatial transmission profile across the drying droplet. The shrinkage of the droplet stops once the shell is formed. The temporal dependence of the shell thickness and droplet radius has been estimated by quantitative analysis of the functionality of the transmission profiles. It is revealed that the position of the correlation peak originating from interactions between silica nanoparticles evolves linearly during the initial stage of drying and exhibits sigmoidal growth behavior in later stages. The interaction between colloidal particles in different drying stages has been investigated. We provide experimental confirmation of the transition from repulsive interaction to a capillary-driven short-range attraction during shell formation. The present work demonstrates that in-situ scanning SAXS on a suspended droplet is an invaluable technique for monitoring the dynamic self-organization of colloids as it probes the drying of complex fluids without the interference of a substrate.

An experimental and theoretical study of the gas phase kinetics of atomic chlorine reactions with CH3NH2, (CH3)2NH, and (CH3)3N.

The rate coefficients for the reactions of Cl((2)PJ) with methylamine (R1), dimethylamine (R2) and trimethylamine (R3) have been measured using the laser flash photolysis - resonance fluorescence technique as a function of temperature (274-435 K) and pressure (25-400 Torr N2). The experimental data are well-represented by the following temperature- and pressure-independent rate coefficients (10(10) × k/cm(3) molecule(-1) s(-1)): kR1 = 2.90 ± 0.44, kR2 = 3.89 ± 0.58, kR3 = 3.68 ± 0.55; the uncertainties are estimates of accuracy at the 95% confidence level. Potential energy surfaces (PES) for the reactions have been characterized at the MP2/cc-pVTZ level and improved single point energies of stationary points obtained in CCSD(T)-F12a calculations. The PES for all reactions are characterized by the formation of pre and post reaction complexes and submerged barriers. Rate coefficients for the reactions were calculated as a function of temperature and pressure using a master equation model based on the coupled cluster theory results. The calculated rate coefficients are in good agreement with experiment; the overall rate coefficients are relatively insensitive to variations of the barrier heights within typical chemical accuracy, but the predicted branching ratios vary significantly. The inclusion of tunnelling has no effect.

Redox decomposition of silver citrate complex in nanoscale confinement: an unusual mechanism of formation and growth of silver nanoparticles.

We demonstrate for the first time the intrinsic role of nanoconfinement in facilitating the chemical reduction of metal ion precursors with a suitable reductant for the synthesis of metal nanoparticles, when the identical reaction does not occur in bulk solution. Taking the case of citrate reduction of silver ions under the unusual condition of [citrate]/[Ag(+)] ≫ 1, it has been observed that the silver citrate complex, stable in bulk solution, decomposes readily in confined nanodomains of charged and neutral matrices (ion-exchange film and porous polystyrene beads), leading to the formation of silver nanoparticles. The evolution of growth of silver nanoparticles in the ion-exchange films has been studied using a combination of (110m)Ag radiotracer, small-angle X-ray scattering (SAXS) experiments, and transmission electron microscopy (TEM). It has been observed that the nanoconfined redox decomposition of silver citrate complex is responsible for the formation of Ag seeds, which thereafter catalyze oxidation of citrate and act as electron sink for subsequent reduction of silver ions. Because of these parallel processes, the particle sizes are in the bimodal distribution at some stages of the reaction. A continuous seeding with parallel growth mechanism has been revealed. Based on the SAXS data and radiotracer kinetics, the growth mechanism has been elucidated as a combination of continuous autoreduction of silver ions on the nanoparticle surfaces and a sudden coalescence of nanoparticles at a critical number density. However, for a fixed period of reduction, the size, size distribution, and number density of thus-formed Ag nanoparticles have been found to be dependent on physical architecture and chemical composition of the matrix.

Probing evaporation induced assembly across a drying colloidal droplet using in situ small-angle X-ray scattering at the synchrotron source.

Colloidal particles in a tiny drying droplet are forced to assemble due to attractive capillary forces. Jamming of the particles throughout the droplet remains either isotropic or anisotropic depending upon the drying kinetics and the physicochemical environment. In this work, we explore the dynamical evolution of such an assembly process across a single evaporative droplet by in situ scanning small-angle scattering using a micro-focused X-ray beam at the synchrotron source. A methodology has been elucidated to differentiate quantitatively between the isotropic and the anisotropic jamming process. Switching of jamming behaviour depending on the initial particle volume fraction in the droplet has been demonstrated. Three distinct stages of assembly, associated with droplet shrinkage, have been revealed even during isotropic jamming. This is in contrast to the drying of a pure liquid droplet under diffusion limited evaporation. It has been established that such in situ scattering measurements can also be used to estimate the temporal evolutions of the viscosity of a drying suspension as well as the diffusivity of nanoparticles in a droplet.

Investigation of nanolevel molecular packing and its role in thermo-mechanical properties of PVA-fMWCNT composites: positron annihilation and small angle X-ray scattering studies.

Carbon based nanofillers have shown phenomenal improvements in thermo-mechanical properties of poly vinyl alcohol (PVA) based nanocomposites depending on their interaction with PVA molecules and dispersion in the polymer matrix. In the present study, PVA based nanocomposites with amino-functionalized multi-wall carbon nanotubes (fMWCNTs, 0.2, 0.4, 0.8 and 1.0 wt%) were prepared by a simple casting method from aqueous solution. The relative increase in Young's modulus with 0.4% fMWCNTs was observed to be comparable with that for PVA-nanodiamond composite films which have been shown to have higher strength compared to nanotube and graphene oxide based nanocomposites. In order to investigate the nanolevel molecular packing (sub-nano level free volumes and nano level lamellar structure) and its role in thermal and mechanical properties, positron annihilation spectroscopy and small angle scattering have been used. The crystallinity and morphology of the samples were characterized using X-ray diffraction and scanning electron microscopy. The studies showed that interfacial interaction between PVA molecules and functionalities on the surface of fMWCNTs results in the formation of an ordered structure of PVA molecules which enhances load transfer between the PVA matrix and fMWCNTs leading to improved mechanical properties. The thermal properties of the composites were observed to be unaffected at the studied filler concentration.

Association of Posterior Reversible Encephalopathy Syndrome (PRES) with Preeclampsia with Severe Symptoms and Eclampsia in South East Part of Bangladesh.

Posterior reversible encephalopathy syndrome (PRES) is a pathology seen not only in precelampsia with severe symptoms and eclampsia but in a varicty of diseases/ conditions. With the availability of neuroimaging, it is possible to know the exact underlying Central nervous system (CNS) pathology in preeclampsia with severe symptoms and eclampsia and thus therapy can be targeted. Preeclampsia with severe symptoms and eclampsia remains to be an important cause of maternal morbidity and mortality in both the developing and developed world. The objective of this study was to evaluate the association of Posterior reversible encephalopathy syndrome (PRES) by MRI (Magnetic resonance imaging) with preeclampsia with severe symptoms and eclampsia in south east part of Bangladesh. This cross-sectional observational study was performed among women suffering from preeclampsia with severe symptoms and eclampsia who attended at Obstetrics & Gynaecology department of Chittagong Medical College Hospital (CMCH), Bangladesh from January 2021 to June 2021. According to inclusion/exclusion criteria 50 samples were taken by convenient sampling for this study. A detail history was taken and complete general physical and gynecological examination was performed. Required data was collected through preset questionnaire. Neuroimaging reports were reviewed by both neurologist and radiologist. Data was analyzed by using windows based computer software device, SPSS 25.0. Results obtained from this study will be used to make a statement regarding aggressive management for cerebral vasospasm in severe preeclampsia and eclamptia related PRES. PRES has been reported to be reversible but late recognition or incorrect treatment can cause irreversible brain damage. Institution of early treatment leads to resolution of symptoms without any neurologic deficit and thus reduces maternal morbidity and mortality. PRES is a cliniconeuroradiologic entity. This study can aware doctors regarding prompt diagnosis of PRES in peripartum period among patient suffering from preeclampsia with severe symptoms and eclampsia by imaging aside clinical findings. A conclusive decision can be made to improve the outcome in this potentially life threatening but reversible condition.

Control of buckling in colloidal droplets during evaporation-induced assembly of nanoparticles.

Micrometric grains of anisotropic morphology have been achieved by evaporation-induced self-assembly of silica nanoparticles. The roles of polymer concentration and its molecular weight in controlling the buckling behavior of drying droplets during assembly have been investigated. Buckled doughnut grains have been observed in the case of only silica colloid. Such buckling of the drying droplet could be arrested by attaching poly(ethylene glycol) on the silica surface. The nature of buckling in the case of only silica as well as modified silica colloids has been explained in terms of theory of homogeneous elastic shell under capillary pressure. However, it has been observed that colloids, modified by polymer with relatively large molecular weight, gives rise to buckyball-type grains at higher concentration and could not be explained by the above theory. It has been demonstrated that the shell formed during drying of colloidal droplet in the presence of polymer becomes inhomogeneous due to the presence of soft polymer rich zones on the shell that act as buckling centers, resulting in buckyball-type grains.

One-step fabrication of thermally stable TiO2/SiO2 nanocomposite microspheres by evaporation-induced self-assembly.

The evaporation-induced self-assembly of mixed colloids has been employed to synthesize microspheres of TiO(2)/SiO(2) nanocomposites. Small-angle neutron/X-ray scattering and scanning electron microscopy experiments reveal the hierarchical morphology of the microspheres. Although the internal structure of the microspheres, consisting of solely silica nanoparticles, gets significantly modified with time because of the reduction in the high specific surface area by internal coalescence, the same for the composite microspheres remains stable over an aging time of 1 year. Such temporal stability of the composite microspheres is attributed to the inhibition of coalescence of the silica nanoparticles in the presence of titania nanoparticles. X-ray diffraction and thermogravimetric results show the improved thermal stability of the composite grains against the anatase-to-rutile phase transition. Such thermal stability is attributed to the suppression of the growth of titania nanoparticles in the presence of silica nanoparticles. The UV-vis results indicate the confinement effect of the TiO(2) nanoparticles in the silica matrix. A plausible mechanism has been elucidated for the formation of microspheres with different morphology during self-assembly.

Clinical Profile and Immediate Outcome of Pyogenic Meningitis in Children.

Meningitis literally means inflammation of the meninges. It is mostly caused by bacteria, virus, fungus and protozoa and pyogenic meningitis constitutes a serious neurological disorder associated with significant morbidity and mortality in developing countries. This study was carried out to evaluate the clinical presentation and immediate outcome of pyogenic meningitis in children. This was a prospective observational study and conducted at department of Paeditrics in Cumilla Medical College Hospital, Cumilla, Bangladesh from July 2014 to June 2015. Total 50 children were diagnosed as pyogenic meningitis fulfilling the inclusion criteria was included in this study. Cases were enrolled purposively. Immediately after admission through history and clinical examination, complete blood count, random blood sugar, Cerebrospinal fluid (CSF) examination and blood culture was done in all patients. For statistical analysis chi-square test was done and significance of analysis was made when p value <0.05. This study includes patients aged between 2 months to 12 years and male female ratio was 1.5:1. Several risk factors like male sex (60.0%), age below one year (42.0%), Protein energy malnutrition (PEM) (30.0%), not exclusively breastfed (44.0%) were identified. Common presenting complaints were fever (100.0%), convulsion (96.0%), altered consciousness (42.0%) and vomiting (38.0%). Common physical signs were neck rigidity (56.0%), Kernig's sign (26.0%) and bulged fontanelle (34.0%). CSF was hazy in 54.0%, clear in 38.0% and turbid in 08.0% cases, CSF protein was more than 100mg/dl in 90.0% of the cases and glucose was less than 40mg/dl in most of the cases (94.0%). Streptococcus Pneumoniae (49.0%) followed by Neisseria Meningitidis (38.0%) were the two most commonly isolated organism responsible for pyogenic meningitis. Mortality rate during hospital stay was 18.0% and complications developed in 18.0% of cases. To avoid maltreatment in our resource limited setting due to failure of identifying organism, this study might help to administer appropriate antibiotics against organism and to reduce morbidity and mortality in meningitis. This study revealed less mortality rate in our country than neighbors and severe malnutrition important risk factors for the burden of pyogenic meningitis. It requires large scale multicentre studies to establish the whole scenario of Bangladesh.

Origin of buckling phenomenon during drying of micrometer-sized colloidal droplets.

The origin of the buckling of micrometer-sized colloidal droplets during evaporation-induced self-assembly (EISA) has been elucidated using electron microscopy and small-angle neutron scattering. Doughnut-like assembled grains with varying aspect ratios are formed during EISA at different physicochemical conditions. It has been revealed that this phenomenon is better explained by an existing hypothesis based on the formation of a viscoelastic shell of nanoparticles during drying than by other existing hypotheses based on the inertial instability of the initial droplets and hydrodynamic instability due to thermocapillary forces. This conclusion was further supported by the arrest of buckling through modification of the colloidal interaction in the initial dispersion.

Buckling-driven morphological transformation of droplets of a mixed colloidal suspension during evaporation-induced self-assembly by spray drying.

Morphological transformation during evaporation-induced self-assembly of a mixed colloidal suspension in micrometric droplets has been investigated. It has been demonstrated that a buckling-driven shape transition of drying droplets of mixed colloidal suspension takes place during evaporation-induced self-assembly. Further, it is also shown that the distortion modulations get significantly amplified with enhancement in volume fraction of anisotropic soft colloidal component of the mixed colloids. It has been argued that the reduction in elastic modulus of formed shell, at the boundary of a drying droplet, and the anisotropic nature of one of the colloidal components facilitate the deformation process. Hierarchical structures of these assembled colloidal grains have been probed using electron microscopy and scattering techniques.

Decoration of carbon nanotubes with metal nanoparticles by wet chemical method: a small-angle neutron scattering study.

Multi-wall carbon nanotubes have been synthesized by catalytic chemical vapour deposition method. Attempts have been made to decorate the walls of these nanotubes with various metal nanoparticles (Ni, Cu and Fe) after functionalizing the nanotubes walls by wet chemical method. Small-Angle Neutron Scattering data reveals chain cluster type morphology of the carbon nanotubes. Transmission electron microscopy, Energy dispersive analysis of X-rays and Small-Angle Neutron Scattering measurements show that decoration of nanotube walls by metallic nano-particles could be realized for Ni and Cu nano-particles. Further, wall decoration by nano-particles of Fe could not be achieved by wet chemical method due to strong agglomeration behavior of Fe nano-particles.

Optimization of parameters by Taguchi method for controlling purity of carbon nanotubes in chemical vapour deposition technique.

The process parameters (viz. temperature of synthesis, type of catalyst, concentration of catalyst and type of catalyst-support material) for controlling purity of carbon nanotubes synthesized by catalytic chemical vapour deposition of acetylene have been optimized by analyzing the experimental results using Taguchi method. It has been observed that the catalyst-support material has the maximum (59.4%) and the temperature of synthesis has the minimum effect (2.1%) on purity of the nanotubes. At optimum condition (15% ferrocene supported on carbon black at the synthesis temperature of 700 degrees C) the purity of nanotubes was found out to be 96.2% with yield of 1900%. Thermogravimetry has been used to assess purity of nanotubes. These nantubes have been further characterized by scanning electron microscopy, transmission electron microscopy and Raman Spectroscopy. Small angle neutron scattering has been used to find out their average inner and outer diameter using an appropriate model. The nanotubes are well crystallized but with wide range of diameter varying between 20-150 nm.

Role of bilirubin as antioxidant in neonatal jaundice and effect of ethanolic extract of sweet lime peel on experimentally induced jaundice in rat.

Bilirubin above a threshold level is toxic to human system and is excreted in urinary and through gastrointestinal tract. The role of bilirubin as antioxidant is debatable. This paper aims at elucidating the role of bilirubin as an antioxidant in neonatal jaundice patients. It is observed that bilirubin up to 6 mg/dl in blood acts as an antioxidant and above 12.5 mg/dl is strongly prooxidant. Phototherapy is the accepted therapeutic management of neonatal jaundice and has been shown to enhance the oxidative stress. Approaches have been taken to formulate a herbal medication which will reduce bilirubin level in the neonates without inducing additional damages. The ethanolic extract of sweet lime peel, administered orally at a dose of 72 microg is found to reduce the oxidative stress in erythrocytes of phenylhydrazine-induced jaundiced rats treated with phototherapy.

Small-angle neutron scattering investigations on sintering behavior of combustion synthesized La0.8Sr0.2CrO3.

Pore morphology of La0.8Sr0.2CrO3 (LSC) powder compacts, sintered between 1200 degrees C and 1450 degrees C for a fixed time, has been characterized by small-angle neutron scattering (SANS) in the scattering wave vector 'q' range, 0.003-0.17 nm(-1) of a double crystal based instrument. Scattering profile of green compact exhibits fractal scaling at two regions of 'q' with magnitudes of fractal dimensionality 1.8 and 2.36. Scattering profiles of sintered pellets have been modeled assuming a random distribution of near spherical pores in the solid matrix. Estimated pore size distributions of sintered pellets indicate decrease in pore volume has taken place by progressive elimination of smallest pores and growth of relatively larger pores with increasing sintering temperature. SANS results are supplemented by light scattering measurement and TEM image of powder and SEM image of the fracture surface of sintered pellet.

Role of virulence plasmid of Aeromonas hydrophila in the pathogenesis of ulcerative disease syndrome in Clarias batrachus.

Pathogenic Aeromonas hydrophila (strain VB21), a multiple-drug resistance strain contains a plasmid of about 21 kb. After curing of plasmid, the isolates became sensitive to antimicrobials, to which they were earlier resistant. The cured bacteria exhibited significant alterations in their surface structure, growth profile and virulence properties, and failed to cause ulcerative disease syndrome (UDS) when injected into the Indian catfish Clarias batrachus. Routine biochemical studies revealed that the plasmid curing did not alter the biochemical properties of the bacteria. After transformation of the plasmid into cured A. hydrophila the bacterium regained its virulence properties and induced all the characteristic symptoms of UDS when injected into fish. Thus, the plasmid plays a pivotal role in the phenotype, growth and virulence of A. hydrophila and pathogenesis of aeromonad UDS.

Porous nano-structured micro-granules from silica-milk bi-colloidal suspension: Synthesis and characterization.

Synthesis and characterization of nano-structured porous granules, with fairly defined morphology and porosity, is crucial because such granules are widely utilized for various technological applications. However, an easy, one-step, economic synthesis protocol for large scale production is extremely desirable. In the present work, we have reported the synthesis and characterization of the nano-structured micro-granules using aerosol drying of bi-colloidal suspension of nano-silica and milk. Removal of soft organic component from the granules results in formation of meso and macro pores with moderate specific surface area. Granule morphology and porosity depends strongly on the concentration ratio of the individual components in the drying aerosol as well as the interaction between them.

Limitation of glucose oxidase method of glucose estimation in jaundiced neonates.

The most widely used method for estimation of plasma glucose is that adopted by Trinder's using glucose oxidase-peroxidase (GOD-POD) system. This method gives much lower blood glucose values with blood samples of neonatal jaundice (plasma bilirubin level > 10 mg/dL) of age 10 +/- 5 daysthan with samples of neonates of the same age group without jaundice or older children suffering from other diseases like acute respiratory distress, septicemia.