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Search Results: 1 - 10 of 18557 matches for " Samim Ali "
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Use of ultrasound attenuation spectroscopy to determine the size distribution of clay tactoids in aqueous suspensions
Samim Ali,Ranjini Bandyopadhyay
Physics , 2014, DOI: 10.1021/la402478h
Abstract: The dispersion processes of aqueous samples of clay are studied using ultrasound attenuation spectroscopy. The attenuation spectra that are acquired in the frequency range $10-100$ MHz are used to determine the particle size distributions (PSDs) for different concentrations and ages of the clay suspensions. Our analysis, using equivalent spherical diameter (ESD) for circular discs under Stokes drag in samples of concentrations greater than 1.5\% w/v, shows that a substantial fraction of the aggregates in suspension are actually tactoids that are composed of more than one platelet. This is in contrast to the general belief that clay disperses into individual platelets in the concentration range where their suspensions exhibit glassy behavior. We conclude that the incomplete fragmentation of the clay tactoids arises from the rapid enhancement of the inter-tactoid Coulombic repulsion.
Effect of electrolyte on the microstructure and yielding of aqueous dispersions of colloidal clay
Samim Ali,Ranjini Bandyopadhyay
Physics , 2015,
Abstract: Na-montmorillonite is a natural clay mineral and is available in abundance in nature. The aqueous dispersions of charged and anisotropic platelets of this mineral exhibit non-ergodic kinetically arrested states ranging from soft glassy phases dominated by interparticle repulsions to colloidal gels stabilized by salt induced attractive interactions. When the salt concentration in the dispersing medium is varied systematically, viscoelasticity and yield stress of the dispersion show non-monotonic behavior at a critical salt concentration, thus signifying a morphological change in the dispersion microstructures. We directly visualize the microscopic structures of these kinetically arrested phases using cryogenic scanning electron microscopy. We observe the existence of honeycomb-like network morphologies for a wide range of salt concentrations. The transition of the gel morphology, dominated by overlapping coin (OC) and house of cards (HoC) associations of clay particles at low salt concentrations to a new network structure dominated by face-face coagulation of platelets, is observed across the critical salt concentration. We further assess the stability of these gels under gravity using electroacoustics. This study, performed for concentrated clay dispersions for a wide concentration range of externally added salt, is useful in our understanding of many geophysical phenomena that involve the salt induced aggregation of natural clay minerals.
Urinary Level of CA19-9 as a Tumor Marker in Urothelial Carcinoma of the Bladder
Keya Pal,Suparna Roy,Samim Ali Mondal,Uttara Chatterjee
Urology Journal , 2011,
Abstract: Purpose: To diagnose the urothelial carcinoma of the bladder by measuringCA19-9 level in the urine. Materials and Methods: This study was conducted on 47 patients with histopathologically confirmed urothelial cancer and 50 control subjects. Theurinary level of CA19-9 was measured in both groups by enzyme-linke dimmunosorbent assay after concentration of urine with Bio-Gel dry beads. Urine cytology was also done in both controls and patients. Results: The mean urinary level of CA19-9 was 194.59 ± 110.56 u/mL in patients and 11.67 ± 8.42 u/mL in controls (P = .0001). The mean urinary level of CA19-9 in patients with low-grade and high-grade bladder cancer was 206.56 ± 114.56 u/mL and 174.80 ± 94.06 u/mL, respectively(P = .56). Urine cytology by Papanicolaou stain was mostly negative. Conclusion: It can be concluded that CA19-9 may be a useful non-invasivetest to diagnose the urothelial carcinoma of the bladder.
Beauty97 Conference Summary
Samim Erhan
Physics , 1998, DOI: 10.1016/S0168-9002(98)00382-9
Abstract: CP-violation is one of the least understood phenomena in our field. There are major experimental programs in all high energy laboratories around the world which will hopefully remedy this within the next decade. The study of CP-violating effects in B meson decays will allow stringent tests of the Standard Model to be made and may point the way to New Physics. The Beauty97 conference provided a forum for these experiments to discuss their physics potential and experimental challenges relating to these studies. This paper reviews the ongoing and future experimental B-physics projects. I will summarize the status and future plans of these projects, as well as the highlights of the physics and key R&D results presented at the conference. At the end, a critical comparison of the CP-violation B experiments will be given.
Whether WTP Is Affected By Some Other Factors? A Case Study On Durgapur
Sk Samim Ferdows
Journal of Knowledge Management, Economics and Information Technology , 2012,
Abstract: Industrialization process is the one of the vital key element of any developing country. It has two impacts. One is the benefit and the other is cost. While it is necessary for occupational transformation of the economy, in terms of employment and growth of the economy, but it has also substantial impact on environmental degradation, resource depletion and related social costs. In this research paper, the objective the study is to examine the how WTP is affected by the other factors in Durgapur.
Evidence for xi- and t-dependent damping of the Pomeron Flux in the proton
Samim Erhan,Peter E. Schlein
Physics , 1998, DOI: 10.1016/S0370-2693(98)00405-5
Abstract: We show that a triple-Regge parametrization of inclusive single diffraction agrees with the data in the following two domains: (a) xi > 0.03 at all t, (b) |t| > 1 GeV^2 at all xi. Since the triple-Regge parametrization fails when applied to the full xi-t range of the total single-diffractive cross section, we conclude that damping occurs only at low-xi and low-|t|. We give a (``toy'') parametrization of the damping factor, D(xi), valid at low-|t|, which describes the diffractive differential cross-section (dsig/dt) data at the ISR and roughly accounts for the observed s-dependence of diffractive total cross-section up to Tevatron energies. However, an effective damping factor calculated for the CDF fitted function for dsig/dxidt at sqrt(s} = 1800 GeV and |t| = 0.05 GeV^2, suggests that, at fixed-xi, damping increases as s increases. We conjecture that, in the regions where the triple-Regge formalism describes the data and there is no evidence of damping, factorization is valid and the Pomeron-flux-factor may be universal. With the assumption that the observed damping is due to multi-Pomeron exchange, our results imply that the recent UA8 demonstration that the effective Pomeron trajectory flattens for |t| > 1 GeV$^2 is evidence for the onset of the perturbative 2-gluon pomeron. Our damping results may also shed some light on the self-consistency of recent measurements of hard-diffractive jet production cross sections in the UA8, CDF and ZEUS experiments.
Inelastic diffraction data and the effective Pomeron trajectory
Samim Erhan,Peter E. Schlein
Physics , 1999, DOI: 10.1016/S0370-2693(00)00467-6
Abstract: A further analysis of inelastic diffraction data at the ISR and SPS-Collider confirms the relatively flat s-independent pomeron trajectory in the high-|t| domain, 1-2 GeV^2, reported earlier by the UA8 Collaboration. At |t| = 1.5 GeV^2, alpha = 0.92 +/- 0.03 is in agreement with the trajectories found in diffractive photoproduction of vector mesons at HERA. This suggests a universal fixed Pomeron trajectory at high-|t|. We also show that a triple-Regge Pomeron-exchange parametrization fit to the data requires an s-dependent (effective) Pomeron trajectory intercept, alpha(0), which decreases with increasing s, as expected from unitarization (multi-Pomeron-exchange) calculations. alpha(0) = 1.10 at the lowest ISR energy, 1.03 at the SPS-Collider and perhaps smaller at the Tevatron.
Synthesis and characterization of gold nanorods and their application for photothermal cell damage
Samim M,Prashant CK,Dinda AK,Maitra AN
International Journal of Nanomedicine , 2011,
Abstract: Mohd Samim1, CK Prashant2, AK Dinda2, AN Maitra3, Indu Arora41Department of Chemistry, Hamdard University, Hamdard Nagar; 2Department of Pathology, All India Institute of Medical Sciences, New Delhi; 3Department of Chemistry, University of Delhi, Delhi, India; 4Department of Biomedical Sciences, Shaeed Rajguru College of Applied Sciences, University of Delhi, Delhi, IndiaBackground: Gold nanorods show a surface plasmon resonance (SPR) band at the near infra-red (NIR) region which enables them to produce heat on irradiation with a NIR laser. As a result of this, gold nanorods have the potential to be used as thermal therapeutic agents for selective damage to cancer cells, bacterial cells, viruses, and DNA.Methods: Gold nanorods with an aspect ratio of approximately 5 were prepared by exploiting the normal micellar route of a water/dioctyl sulfosuccinate (Aerosol-T)/hexane system. The shape and size of the gold nanorods were characterized by surface plasmon bands at 520 nm and 980 nm, and by atomic force microscopy and transmission electron microscopy.Results: The length of the gold nanorods was 100 nm and their diameter was 20 nm. X-ray diffraction analysis demonstrated that the gold nanorods formed were metallic in nature. The gold nanorods showed good photothermolysis activity.Conclusion: Gold nanorods injected subcutaneously and irradiated with 980 nm laser caused injury to rat tissue, demonstrating that gold nanorods may be used to kill cancerous cells in tumor tissue.Keywords: nanorods, gold, micellar system, photothermolysis
A wire chamber for educational purposes
Saime Gurbuz,Gokhan Unel,Samim Erhan
Physics , 2014,
Abstract: Gaseous detectors with sense wires are still in use today in small experiments as well as modern ones as those at the LHC. This short note is about the construction of a small wire chamber with limited resources, which could be used both as an educational tool and also as a tracker in small experiments. The particular detector type selected for this work is the so called "Delay Wire Chamber": it has only two output channels per plane and can be made fully gas tight for educational operations. The design can be made with free software tools, and the construction can be achieved by relatively simple means.
Nonlinear Stokes Mueller Polarimetry
Masood Samim,Serguei Krouglov,Virginijus Barzda
Physics , 2015,
Abstract: The Stokes Mueller polarimetry is generalized to include nonlinear optical processes such as second- and third-harmonic generation, sum- and difference-frequency generations. The overall algebraic form of the polarimetry is preserved, where the incoming and outgoing radiations are represented by column vectors and the intervening medium is represented by a matrix. Expressions for the generalized nonlinear Stokes vector and the Mueller matrix are provided in terms of coherency and correlation matrices, expanded by higher-dimensional analogues of Pauli matrices. In all cases, the outgoing radiation is represented by the conventional $4\times 1$ Stokes vector, while dimensions of the incoming radiation Stokes vector and Mueller matrix depend on the order of the process being examined. In addition, relation between nonlinear susceptibilities and the measured Mueller matrices are explicitly provided. Finally, the approach of combining linear and nonlinear optical elements is discussed within the context of polarimetry.
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