Mohammad Islam

Survival analysis and prognostic indicators of systemic lupus erythematosus in Pakistani patients.

To aim of this study is to analyse the survival rate and prognostic indicators of systemic lupus erythematosus (SLE) in Pakistani population. A total of 198 patients with SLE diagnosed between 1992 and 2005 were reviewed retrospectively. Clinical features at presentation, subsequent evolving features, autoantibody profile, damage scores and mortality data were obtained. Prognostic factors for survival were studied by statistical analysis. Of 198 SLE patients studied, 174 were women and 24 were men. The women to men ratio was 7.2:1. Mean age at presentation was 31 years (range 14–76). Mean duration of symptoms before diagnosis was 2.8 years. Mean duration of follow-up was 34.21 months (±33.69). Mean disease duration was 15.6 years. At diagnosis, arthritis, malar rash, oral ulcers and alopecia were the commonest features. During the follow-up, the prevalence of nephritis, arthritis, neurological and hematological disease increased significantly. About 76% (n = 151) of the patients had organ damage at the time of data analysis, and renal disease was the commonest cause. Univariate analysis revealed that renal disease (P = 0.000), seizures (P = 0.048), pleural involvement (P = 0.019), alopecia (P = 0.000) and discoid lesions (P = 0.005) were predictors for damage. Multivariate model, however, revealed that only renal disease was independent risk factor for damage (P = 0.002). During the study period, 47 patients (24%) died (five due to disease-related complications and rest as a result of infections). The 3-, 5-, 10-, 15- and 20-year survival rates of our cohort were 99, 80, 77, 75 and 75%, respectively. Cox regression analysis revealed that renal involvement (P = 0.002) and infections (P = 0.004) were independent risk factors for mortality. The survival of our Pakistani SLE patients was significantly lower compared to that of the Caucasian series reported in last decade. Nephritis not only contributes to organ damage but also acts a major determinant for survival. Infection remains the commonest cause of death. Renal involvement and infections are independent risk factors for mortality. Judicious use of immunosuppressive agents is necessary to improve the short-term survival of lupus patients.

Polyamide-6-based composites reinforced with pristine or functionalized multi-walled carbon nanotubes produced using melt extrusion technique

Polyamide-6-based composites with pristine or functionalized multi-walled carbon nanotubes were produced using melt extrusion technique. After chemical functionalization, defect formation and attachment of carboxylic (−COOH) or amine (−NH2) groups on carbon nanotubes was confirmed from high-resolution transmission electron microscope and Fourier transform infra-red spectroscope studies. Carbon nanotubes incorporation promoted growth of α-form crystals with enhanced thermal stability through increase in crystallization temperature from 162 to 192℃. Dynamic mechanical thermal analysis (DMTA) indirectly pointed out to a homogeneous, uniform dispersion of nanotubes with reduction in free volume of the polymer, exhibiting a slight increase in glass transition temperature and a significant drop in coefficient of thermal expansion value. Composites containing 0.5 wt% NH2-carbon nanotubes show increases in elastic modulus and tensile strength by ∼60 and 76%, respectively. Uniform dispersion and high interfacial strength was manifested by drop in strain to failure and lack of evidence of carbon nanotubes debonding from the matrix.

Synthesis of ZnO nanostructures for low temperature CO and UV sensing.

In this paper, synthesis and results of the low temperature sensing of carbon monoxide (CO) gas and room temperature UV sensors using one dimensional (1-D) ZnO nanostructures are presented. Comb-like structures, belts and rods, and needle-shaped nanobelts were synthesized by varying synthesis temperature using a vapor transport method. Needle-like ZnO nanobelts are unique as, according to our knowledge, there is no evidence of such morphology in previous literature. The structural, morphological and optical characterization was carried out using X-ray diffraction, scanning electron microscopy and diffused reflectance spectroscopy techniques. It was observed that the sensing response of comb-like structures for UV light was greater as compared to the other grown structures. Comb-like structure based gas sensors successfully detect CO at 75 °C while other structures did not show any response.

Toughness enhancement in graphene nanoplatelet/SiC reinforced Al2O3 ceramic hybrid nanocomposites.

This paper elucidates the effect of silicon carbide nanoparticles (SiCNP) and graphene nanoplatelets (GNPs), on their own and together, on the densification behavior and fracture toughness of alumina (Al2O3) ceramic matrix. This was investigated by using the high-frequency induction heat sintering (HFIHS) process. While the addition of each nanostructure caused varying degrees of grain refinement and enhancement of mechanical properties, the incorporation of as little as 0.5 wt.% GNPs along with 5.0 wt.% SiCNP promoted uniform dispersion of the latter due to the lateral surface area of the graphene nanosheets with their two-dimensional morphology. There was an associated reduction in grain size from 1500 to 300 nm upon the addition of both types of nanoscale reinforcements. Extensive electron microscopy of the as-produced nanocomposites indicated the presence of SiCNP within, as well as at, the grain boundary areas whereas the 2D GNPs anchored between neighboring grains. Fractography of the samples revealed a transition from a mixed intergranular/transgranular mode for SiCNP or GNP-reinforced nanocomposites to transgranular fracture mode for the hybrid nanocomposites with improvements in fracture toughness and microhardness by 160 and 27%, respectively, largely due to the synergic role of the nanostructured reinforcements and their distinctly different toughening mechanisms. A new toughening model is proposed for the hybrid nanocomposites by taking into consideration crack deflection and pull-out effects due to SiCNP and the atomic level slip-stick driven GNPs inter-layer slithering. It was found that the addition of GNPs facilitates SiCNP dispersion that subsequently develops dense, fine-grained microstructures after a short-cycle, pressure-assisted consolidation process.

Development of electron reflection suppression materials for improved thermionic energy converter performance using thin film deposition techniques

Nonideal electrode surfaces cause significant degree of electron reflection from collector during thermionic converter operation. The effect of the collector surface structure on the converter performance was assessed through the development of several electron reflection suppression materials using various thin film deposition techniques. The double-diode probe method was used to compare the J-V characteristics of converters with polished and modified collector surfaces for emitter temperature and cesium vapor pressure in the ranges of 900–2000K and 0.02–1.5torr, respectively. The coadsorption of cesium and oxygen with respective partial vapor pressures of ∼1.27torr and a few microtorrs reduced the emitter work function to a minimum value of 0.99eV. It was found that the collector surfaces with matte black appearance such as platinum black, voided nickel from radio-frequency plasma sputtering, and etched electroless Ni–P with craterlike pore morphology exhibited much better performance compared with poli...

Early renal damage assessed by the SLICC/ACR damage index is predictor of severe outcome in lupus patients in Pakistan

We investigated patients with systemic lupus erythematosus with the objective of assessing whether early damage accrued in systemic lupus erythematosus as measured by the SLICC/ ACR Damage Index predicts mortality in lupus patients that have been followed prospectively in a single center. Patients with systemic lupus erythematosus from Aga Khan University hospital presenting between 1992 and 2007 were included. This enabled all patients to be potentially followed for at least 10 years. Yearly SLICC/ACR Damage Index scores were determined for each patient. Early damage was defined as a score ≥1, and no damage as a score of 0 at the initial assessment. Kaplan—Meier and Log rank tests were used to compare the survival experience between those with and without damage, with all patients being assessed at 10 years. In this inception cohort 198 patients were identified and were followed for 10 years. Of these, 47 (23.7%) patients had a SLICC/ACR Damage Index score of 0 (no damage) while 151 patients (76.3%) had at least one SLICC/ACR Damage Index item scored (early damage). Mean renal damage score at 1, 5 and 10 years was 0.16, 0.34 and 0.67, respectively. Of lupus patients who exhibited renal damage at their first SLICC/ACR Damage Index assessment, 31% died within 10 years of their illness as compared with only 13% who had no early renal damage (p < 0.003). Mean renal damage score at 1 year after diagnosis was a significant predictor of death within 10 years of diagnosis (p < 0.002). Lupus (2010) 19, 1573—1578.

Catalytic growth of multi-walled carbon nanotubes using NiFe2O4 nanoparticles and incorporation into epoxy matrix for enhanced mechanical properties

Abstract Mechanical properties of multi-walled carbon nanotubes (CNT) reinforced epoxy nanocomposites, with and without any structural defect, were investigated using different weight percent values of pristine and covalently functionalized CNT. First, nickel ferrite (NiFe2O4) catalyst nanoparticles were prepared using the co-precipitate method followed by CNT growth via chemical vapor deposition, using acetylene as carbon feedstock. Through a combination of magnetic stirring and ultrasound vibration treatments in acetone, pristine, COOH-, or NH2-functionalized CNTs at 0.15, 0.60, 1.10 and 1.50 wt% were added to the Epon 828 epoxy. During each stage, extensive materials characterization was carried out using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) and thermogravimetric analysis (TGA)/differential thermal analysis (DTA) techniques. Tensile testing of the specimens revealed an increase in the elastic modulus and tensile strength values with maximum increase registered in the case of nanocomposites made from 1.1 wt% CNT-NH2 (+73%) or CNT-COOH (67%) addition. The energy absorbed during impact testing also increased by 86% upon addition of 1.50 wt% CNT-NH2. The presence of a small notch in the nanocomposite specimens yielded superior mechanical properties to those of the neat epoxy. Such enhancement in the mechanical properties can be attributed to better CNT dispersion in the nanocomposites and good interfacial bonding, as confirmed from microstructural examination of the fractured surfaces.

Synthesis and characterization of Al2O3 and SiO2 films with fluoropolymer content using rf-plasma magnetron sputtering technique

Pure and molecularly mixed inorganic films for protection against atomic oxygen in lower earth orbit were prepared using radio-frequency (rf) plasma magnetron sputtering technique. Alumina (Al2O3) and silica (SiO2) films with average grain size in the range of 30–80nm and fully dense or dense columnar structure were synthesized under different conditions of pressure and power. Simultaneous oxide sputtering and plasma polymerization (PP) of hexafluoropropylene (HFP) led to the formation of molecularly mixed films with fluoropolymer content. The degree of plasma polymerization was strongly influenced by total chamber pressure and the argon to HFP molar ratio (nAr∕nM). An order of magnitude increase in pressure due to argon during codeposition changed the plasma-polymerization mechanism from radical-chain- to radical-radical-type processes. Subsequently, a shift from linear CH2 group based chain polymerization to highly disordered fluoropolymer content with branching and cross-linking was observed. Fourier t...

Removal of micrometer size morphological defects and enhancement of ultraviolet emission by thermal treatment of Ga-doped ZnO nanostructures.

Mixed morphologies of Ga-doped Zinc Oxide (ZnO) nanostructures are synthesized by vapor transport method. Systematic scanning electron microscope (SEM) studies of different morphologies, after periodic heat treatments, gives direct evidence of sublimation. SEM micrographs give direct evidence that morphological defects of nanostructures can be removed by annealing. Ultra Violet (UV) and visible emission depends strongly on the annealing temperatures and luminescent efficiency of UV emission is enhanced significantly with each subsequent heat treatment. X-Ray diffraction (XRD) results suggest that crystal quality improved by annealing and phase separation may occur at high temperatures.

SOLUTION PROCESSING OF CADMIUM SULFIDE BUFFER LAYER AND ALUMINUM-DOPED ZINC OXIDE WINDOW LAYER FOR THIN FILMS SOLAR CELLS

Cadmium sulfide (CdS) and aluminum-doped zinc oxide (Al:ZnO) thin films are used as buffer layer and front window layer, respectively, in thin film solar cells. CdS and Al:ZnO thin films were produced using chemical bath deposition (CBD) and sol–gel technique, respectively. For CBD CdS, the effect of bath composition and temperature, dipping time and annealing temperature on film properties was investigated. The CdS films are found to be polycrystalline with metastable cubic crystal structure, dense, crack-free surface morphology and the crystallite size of either few nanometers or 12–17 nm depending on bath composition. In case of CdS films produced with 1:2 ratio of Cd and S precursors, spectrophotometer studies indicate quantum confinement effect, owing to extremely small crystallite size, with an increase in Eg value from 2.42 eV (for bulk CdS) to ~ 3.76 eV along with a shift in the absorption edge toward ~ 330 nm wavelength. The optimum annealing temperature is 400°C beyond which film properties deteriorate through S evaporation and CdO formation. On the other hand, Al:ZnO films prepared via spin coating of precursor sols containing 0.90–1.10 at.% Al show that, with an increase in Al concentration, the average grain size increases from 28 nm to 131 nm with an associated decrease in root-mean-square roughness. The minimum value of electrical resistivity, measured for the films prepared using 0.95 at.% Al in the precursor sol, is ~ 2.7 × 10-4 Ω ⋅ cm. The electrical resistivity value rises upon further increase in Al doping level due to introduction of lattice defects and Al segregation to the grain boundary area, thus limiting electron transport through it.