1,940 research outputs found
Effects of vitamin e and zinc supplementation on antioxidants in beta thalassemia major patients
Objective: In beta thalassemic patients, tissue damage occurs due to oxidative stress and it happens because of the accumulation of iron in the body. This study was conducted to determine the effect of zinc and vitamin E supplementation on antioxidant status in beta-thalassemic major patients. Methods: This double blind randomized clinical trial was carried out on 120 beta thalassemic patients older than 18 years. Patients were randomly categorized in four groups. Zinc (50mg/day) and vitamin E (400mg/day) supplements were administered for former and latter group, respectively. In the third group both supplements were administered in similar doses. The fourth (control) group received no supplement. The effect of supplementations on serum zinc and vitamin E, superoxide dismutase (SOD), glutathione peroxidase (GPX), total antioxidant capacity (TAC) and body mass index (BMI) were measured at the beginning and the end of the study. Findings: Serum zinc levels in group 1 and 3 were significantly increased (P<0.007 and P<0.005, respectively). Serum vitamin E levels in group 2 and 3 were also increased significantly (P<0.001). Mean GPX activity in group1, 2 and 3 decreased significantly (P<0.015, P<0.032 and P<0.029, respectively). Mean SOD activity and TAC did not show significant change after supplementation. BMI had significant increase in all treated groups (P<0.001). Conclusion: Our results suggest that beta thalassemic patients have enhanced oxidative stress and administration of selective antioxidants may preclude oxidative damage. © 2011 by Pediatrics Center of Excellence, Children's Medical Center, Tehran University of Medical Sciences, All rights reserved
Non-Fourier heat transport in metal-dielectric core-shell nanoparticles under ultrafast laser pulse excitation
Relaxation dynamics of embedded metal nanoparticles after ultrafast laser
pulse excitation is driven by thermal phenomena of different origins the
accurate description of which is crucial for interpreting experimental results:
hot electron gas generation, electron-phonon coupling, heat transfer to the
particle environment and heat propagation in the latter. Regardingthis last
mechanism, it is well known that heat transport in nanoscale structures and/or
at ultrashort timescales may deviate from the predictions of the Fourier law.
In these cases heat transport may rather be described by the Boltzmann
transport equation. We present a numerical model allowing us to determine the
electron and lattice temperature dynamics in a spherical gold nanoparticle core
under subpicosecond pulsed excitation, as well as that of the surrounding shell
dielectric medium. For this, we have used the electron-phonon coupling equation
in the particle with a source term linked with the laser pulse absorption, and
the ballistic-diffusive equations for heat conduction in the host medium.
Either thermalizing or adiabatic boundary conditions have been considered at
the shell external surface. Our results show that the heat transfer rate from
the particle to the matrix can be significantly smaller than the prediction of
Fourier's law. Consequently, the particle temperature rise is larger and its
cooling dynamics might be slower than that obtained by using Fourier's law.
This difference is attributed to the nonlocal and nonequilibrium heat
conduction in the vicinity of the core nanoparticle. These results are expected
to be of great importance for analyzing pump-probe experiments performed on
single nanoparticles or nanocomposite media
Targeting a channel coating by using magnetic field and magnetic nanofluids
In this paper, the magnetic nanofluids and magnetic field are used to provide a coating around the wall of a channel. The magnetic field is induced by the direct current wire. Iron oxide is used as magnetic nanoparticles. A finite volume method is used to solve the Navier–Stokes equations, and the Eulerian–Lagrangian approach is employed to track the magnetic nanoparticles. The effects of magnetic strength, the position of current wire, and the diameter of magnetic nanoparticles on the trajectory of magnetic nanoparticles and coating efficiency are investigated by providing contours and diagrams. The results show that the length of coating decreases by about 55% with the increase in the particle diameter in the range of 500 nm to 1 μm. Further, the coating efficiency, defined as the ratio of the number of trapped particles on the wall to the number of injected particles at the inlet of the channel, improves by increasing the magnetic strength and decreasing the vertical position of the current wire
Analytic approximate solutions for unsteady boundary-layer flow and heat transfer due to a stretching sheet by homotopy analysis method
In this work, the homotopy analysis method is applied to study the unsteady boundary-layer flow and heat transfer due to a stretching sheet. The analytic solutions of the system of nonlinear ordinary differential equations are constructed in the series form. The convergence of the obtained series solutions is carefully analyzed. The velocity and temperature profiles are shown and the influence of non-dimensional parameter on the heat transfer is discussed in detail. The validity of our solutions is verified by the numerical results
A Case for Redundant Arrays of Hybrid Disks (RAHD)
Hybrid Hard Disk Drive was originally concepted by Samsung, which incorporates a Flash memory in a magnetic disk. The combined ultra-high-density benefits of magnetic storage and the low-power and fast read access of NAND technology inspires us to construct Redundant Arrays of Hybrid Disks (RAHD) to offer a possible alternative to today’s Redundant Arrays of Independent Disks (RAIDs) and/or Massive Arrays of Idle Disks (MAIDs). We first design an internal management system (including Energy-Efficient Control) for hybrid disks. Three traces collected from real systems as well as a synthetic trace are then used to evaluate the RAHD arrays. The trace-driven experimental results show: in the high speed mode, a RAHD outplays the purely-magnetic-disk-based RAIDs by a factor of 2.4–4; in the energy-efficient mode, a RAHD4/5 can save up to 89% of energy at little performance degradationPeer reviewe
Catalase epitopes vaccine design for Helicobacter pylori: A bioinformatics approach
Bioinformatics tools are helpful for epitopes prediction directly from the genomes of pathogens in order to design a vaccine. Epitopes are sub-sequences of proteins (8 to 10 mer peptides) which bind to MHC to interact with the T cell receptors and stimulate immune responses. Finding a suitable vaccine against Helicobacter pylori is necessary, because of high prevalence of the infection (25 to 90%). Moreover, this bacteria has been classified as a grade I carcinogen by WHO since 1994. Catalase, an important enzyme in the virulence of H. pylori, could be a suitable candidate for vaccine design because it is highly conserved, which is important for the survival of H. pylori; it is expressed in high level and it is exposed on the surface of the bacteria. In this study, we designed epitope-based vaccine for catalase specific regions of H. pylori by means of immunobioinformatic tools. H. pylori (26695) catalase has been compared with human catalase in order to select specific regions. Afterwards, epitopes of catalase were determined by propred software. Among predicted epitopes, three epitopes were selected including, MVNKDVKQTT, VLLQSTWFL and FHPFDVTKI. Three candidates out of 51catalase antigen epitopes had the highest score for reactivating with MHC II MHC in propred software. The candidate epitopes for vaccine design should be rather a composition of considering epitopes: MVNKDVKQTTKKVLLQSTWFLKKFHPFDVTKI. In this manner, 39 of 51 alleles of MHC class ІІ were involved and stimulated T-cell responses. We believe prediction of catalase epitopes by the immunoinformatics tools would be valuable for developing new immuoprophylatic strategy against H. pylori infection.Key words: Helicobacter pylori, catalase, epitopes
A concise review on the role of nanoparticles upon the productivity of solar desalination systems
In recent years, nanofluids have been widely used to improve the performance of various energy systems due to their favourable thermo-physical and optical characteristics. In particular, solar distillation, as an affordable and reliable technique to provide freshwater, has benefited from nanofluid technology. This article performs a review of the literature on the implementation of nanofluid technology in active and passive solar distillation systems. The progress made and the existing challenges are discussed, and some conclusions and suggestions are made for future research. The review indicates that the daily productivities of solar distillation systems enhance by using nanofluid and increasing the volume fraction of nanoparticles. However, long-term operational stability and life cycle assessment remain critical issues. These factors should be considered for future research in this field
Progress in phase change nano-emulsions for energy applications-A concise review
Thermal energy storage and transport are central to the wide application of renewable energy. With excellent storage capacities, latent heat storage is more promising than sensible one. Phase change materials are the primary storage materials for latent heat storage. Phase change nanoemulsions are developed for latent heat storage in flow systems that can be used as heat transport and thermal storage purposes, offering improved heat transfer, pumping power, and higher storage capacities. This review is focused on the new advances in phase change nanoemulsions for energy applications. The phase change nanoemulsions are introduced and their features and classification are provided. The preparation methods and thermophysical properties of these nanostructured phase changeable fluids are discussed and, material synthesis and property characterization are covered. Finally, the applications of this class of fluids in different energy systems are reviewed. The major barriers to the applications of phase change nanoemulsions, including instability and high degree of super-cooling, are discussed
Analytical modeling of MHD flow over a permeable rotating disk in the presence of soret and dufour effects: Entropy analysis.
The main concern of the present article is to study steady magnetohydrodynamics (MHD) flow, heat transfer and entropy generation past a permeable rotating disk using a semi numerical/analytical method named Homotopy Analysis Method (HAM). The results of the present study are compared with numerical quadrature solutions employing a shooting technique with excellent correlation in special cases. The entropy generation equation is derived as a function of velocity, temperature and concentration gradients. Effects of flow physical parameters including magnetic interaction parameter, suction parameter, Prandtl number, Schmidt number, Soret and Dufour number on the fluid velocity, temperature and concentration distributions as well as entropy generation number are analysed and discussed in detail. Results show that increasing the Soret number or decreasing the Dufour number tends to decrease the temperature distribution while the concentration distribution is enhanced. The averaged entropy generation number increases with increasing magnetic interaction parameter, suction parameter, Prandtl number, and Schmidt number
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