110 research outputs found
Electrical transport and ferromagnetism in Ga1-xMnxAs synthesized by ion implantation and pulsed-laser melting
We present a detailed investigation of the magnetic and magnetotransport
properties of thin films of ferromagnetic Ga1-xMnxAs synthesized using ion
implantation and pulsed-laser melting (II-PLM). The field and
temperature-dependent magnetization, magnetic anisotropy, temperature-dependent
resistivity, magnetoresistance, and Hall effect of II-PLM Ga1-xMnxAs films have
all of the characteristic signatures of the strong p-d interaction of holes and
Mn ions observed in the dilute hole-mediated ferromagnetic phase. The
ferromagnetic and electrical transport properties of II-PLM films correspond to
the peak substitutional Mn concentration meaning that the non-uniform Mn depth
distribution is unimportant in determining the film properties. Good
quantitative agreement is found with films grown by low temperature molecular
beam epitaxy (LT-MBE) and having the similar substitutional Mn_Ga composition.
Additionally, we demonstrate that II-PLM Ga1-xMnxAs films are free from
interstitial Mn_I because of the high temperature processing. At high Mn
implantation doses the kinetics of solute redistribution during solidification
alone determine the maximum resulting Mn_Ga concentration. Uniaxial anisotropy
between in-plane [-110]and [110] directions is present in II-PLM Ga1-xMnxAs
giving evidence for this being an intrinsic property of the carrier-mediated
ferromagnetic phase
Environmental challenges in the Caspian Sea and international responsibility of its littoral states
The main challenges facing the environment of the Caspian Sea include the water level rise,
environmental pollutions, the entrance of exotic species to the Caspian Sea, loss of the flora reservoirs
and eutrophication. These challenges forced the coastal states to conclude the Framework Convention
on the Protection of the Marine Environment of the Caspian Sea in 2003. The long duration of time
taken to adopt this convention and its two protocols, non-significance of two other protocols , the
competition over energy issues in the sea and conflict of opinions concerning the legal regime have
affected the level of cooperation among five coastal states in this field. This analytical-descriptive study
seeks to answer this fundamental question: “What is the responsibility of the Caspian littoral states for
environmental damage?” With the reviews, we can say that the Caspian Sea’s coastal states are
responsible individually or collectively for their own omission and actions resulting in the
environmental damages. They have to recover damages through the restitution or the compensation.
It should be noted that the speed up of argument over the legal regime may reduce the environmental
problems of the sea
Assessment of resistance and non-resistance fractions of heavy metals concentration (Fe, Mn, Cr, Ni) in surface sediments from the southern of Caspian Sea of two stations (Tonekabon and Amirabad)
This study was conducted to determine some heavy metals (Fe, Mg, Cr, Ni) of surface sediment in the southern Caspian Sea during two seasons (Summer and Winter) in 2014-2015. 36 surface sediments samples (with triplicate) were collected at two stations (Tonekabon and Bandar Amirabad). All samples were analyzed using sequential extraction to indicate natural and anthropogenic sources. The results indicated that the percentage of non-resistance fraction in Tonekabon area were measured 3.5,45.0, 22.1 and 6.0 for Fe, Mg, Cr, Ni, respectively and in Amirabad area were 23.0,2.6,1.8 and 4.0, respectively. On the other hand, the percentage of resistance fraction values were obtained 96.5, 55.0, 77.9 and 94.0 in Tonekabon, and 77.0, 97.4, 98.2, and 96.0 in Amirabad region. The chemical speciation of Fe, Mg, Cr, Ni in most sampling stations were in the order of residual> oxidisableorganic > acid-reducible >exchangeable. The order of total concentration, non-resistance and resistance fraction were observed Fe>Mn>Ni>Cr, Mn>Fe>Ni>Cr and Fe>Mn>Ni>Cr, respectively. As a conclusion, results of total concentration, resistnace and non-resistance of Fe, Mn, Ni and Cr were lower than standard and earth shell (Igeo) in this area. This is shown that surface sediments of this area were not polluted with these heavy metals and bio available fraction provides little indication of potential interactions with the biotic components present in this environment
Mn L3,2 X-ray Absorption Spectroscopy And Magnetic Circular Dichroism In Ferromagnetic (Ga,Mn)P
We have measured the X-ray absorption (XAS) and X-ray magnetic circular
dichroism (XMCD) at the Mn L3,2 edges in ferromagnetic Ga1-xMnxP films for
0.018<x<0.042. Large XMCD asymmetries at the L3 edge indicate significant
spin-polarization of the density of states at the Fermi energy. The spectral
shapes of the XAS and XMCD are nearly identical with those for Ga1-xMnxAs
indicating that the hybridization of Mn d states and anion p states is similar
in the two materials. Finally, compensation with sulfur donors not only lowers
the ferromagnetic Curie temperature but also reduces the spin polarization of
the hole states.Comment: 2 pages, 1 figure; To appear in the Proceedings of the 28th
International Conference on the Physics of Semiconductors (ICPS-28, Vienna,
Austria, July 24-28, 2006
Pneumococcal Gene Complex Involved in Resistance to Extracellular Oxidative Stress
Streptococcus pneumoniae is a Gram-positive bacterium which is a member of the normal human nasopharyngeal flora but can also cause serious disease such as pneumonia, bacteremia, and meningitis. Throughout its life cycle, S. pneumoniae is exposed to significant oxidative stress derived from endogenously produced hydrogen peroxide (H2O2) and from the host through the oxidative burst. How S. pneumoniae, an aerotolerant anaerobic bacterium that lacks catalase, protects itself against hydrogen peroxide stress is still unclear. Bioinformatic analysis of its genome identified a hypothetical open reading frame belonging to the thiol-specific antioxidant (TlpA/TSA) family, located in an operon consisting of three open reading frames. For all four strains tested, deletion of the gene resulted in an approximately 10-fold reduction in survival when strains were exposed to external peroxide stress. However, no role for this gene in survival of internal superoxide stress was observed. Mutagenesis and complementation analysis demonstrated that all three genes are necessary and sufficient for protection against oxidative stress. Interestingly, in a competitive index mouse pneumonia model, deletion of the operon had no impact shortly after infection but was detrimental during the later stages of disease. Thus, we have identified a gene complex involved in the protection of S. pneumoniae against external oxidative stress, which plays an important role during invasive disease.
Bath Breakfast Project (BBP) - Examining the role of extended daily fasting in human energy balance and associated health outcomes: Study protocol for a randomised controlled trial [ISRCTN31521726]
<p>Abstract</p> <p>Background</p> <p>Current guidance regarding the role of daily breakfast in human health is largely grounded in cross-sectional observations. However, the causal nature of these relationships has not been fully explored and what limited information is emerging from controlled laboratory-based experiments appears inconsistent with much existing data. Further progress in our understanding therefore requires a direct examination of how daily breakfast impacts human health under free-living conditions.</p> <p>Methods/Design</p> <p>The Bath Breakfast Project (BBP) is a randomised controlled trial comparing the effects of daily breakfast consumption relative to extended fasting on energy balance and human health. Approximately 70 men and women will undergo extensive laboratory-based assessments of their acute metabolic responses under fasted and post-prandial conditions, to include: resting metabolic rate, substrate oxidation, dietary-induced thermogenesis and systemic concentrations of key metabolites/hormones. Physiological and psychological indices of appetite will also be monitored both over the first few hours of the day (i.e. whether fed or fasted) and also following a standardised test lunch used to assess voluntary energy intake under controlled conditions. Baseline measurements of participants' anthropometric characteristics (e.g. DEXA) will be recorded prior to intervention, along with an oral glucose tolerance test and acquisition of adipose tissue samples to determine expression of key genes and estimates of tissue-specific insulin action. Participants will then be randomly assigned either to a group prescribed an energy intake of ≥3000 kJ before 1100 each day or a group to extend their overnight fast by abstaining from ingestion of energy-providing nutrients until 1200 each day, with all laboratory-based measurements followed-up 6 weeks later. Free-living assessments of energy intake (via direct weighed food diaries) and energy expenditure (via combined heart-rate/accelerometry) will be made during the first and last week of intervention, with continuous glucose monitors worn both to document chronic glycaemic responses to the intervention and to verify compliance.</p> <p>Trial registration</p> <p>Current Controlled Trials <a href="http://www.controlled-trials.com/ISRCTN31521726">ISRCTN31521726</a>.</p
Dietary factors associated with metabolic syndrome in Brazilian adults
<p>Abstract</p> <p>Background</p> <p>Metabolic Syndrome (MS) is defined as the association of numerous factors that increase cardiovascular risk and diet is one of the main factors related to increase the MS in the population. This study aimed to evaluate the association of diet on the presence of MS in an adult population sample.</p> <p>Methodology</p> <p>305 adults were clinically screened to participate in a lifestyle modification program. Anthropometric assessments included waist circumference (WC), body fat and calculated BMI (kg/m<sup>2</sup>) and muscle-mass index (MMI kg/m<sup>2</sup>). Dietary intake was estimated by 24 h dietary recall. Fasting blood was used for biochemical analysis. MS was diagnosed using NCEP-ATPIII (2001) criteria with adaptation for glucose (≥ 100 mg/dL). Logistic regression (Odds ratio) was performed in order to determine the odds ratio for developing MS according to dietary intake.</p> <p>Results</p> <p>An adequate intake of fruits, OR = 0.52 (CI:0.28-0.98), and an intake of more than 8 different items in the diet (variety), OR = 0.31 (CI:0.12-0.79) showed to be a protective factor against a diagnosis of MS. Saturated fat intake greater than 10% of total caloric value represented a risk for MS diagnosis, OR = 2.0 (1.04-3.84).</p> <p>Conclusion</p> <p>Regarding the dietary aspect, a risk factor for MS was higher intake of saturated fat, and protective factors were high diet variety and adequate fruit intake.</p
Comparison of diet consumption, body composition and lipoprotein lipid values of Kuwaiti fencing players with international norms
<p>Abstract</p> <p>Background</p> <p>No published data is currently available that describes the dietary patterns or physiological profiles of athletes participating on the Kuwaiti national fencing team and its potential impact on health and physical performance. The purpose of this investigation was to: 1) collect baseline data on nutrient intake 2) collect, analyze and report baseline for body composition, plasma lipid and lipoprotein concentrations during the competitive season, 3) compare the results with the international norms, 4) and provide necessary health and nutritional information in order to enhance the athletes' performance and skills.</p> <p>Methods</p> <p>Fifteen national-class fencers 21.5 ± 2.6 years of age participated in this study. Food intake was measured using a 3-day food record. Body composition was estimated using both the BOD POD and Body Mass Index (BMI). Total blood lipid profiles and maximum oxygen consumption was measured for each of the subjects during the competitive season.</p> <p>Results</p> <p>The results of the present study showed significant differences in dietary consumption in comparison with the recommended dietary allowances (RDA). The blood lipids profile and body composition (BMI and % body fat) were in normal range in comparison with international norms However, the average VO<sub>2 max </sub>value was less than the value of the other fencers.</p> <p>Conclusion</p> <p>Due to the results of the research study, a dietary regimen can be designed that would better enhance athletic performance and minimize any health risks associated with nutrition. Percent body fat and BMI will also be categorized for all players. In addition, the plasma blood tests will help to determine if any of the players have an excessive level of lipids or any blood abnormalities. The outcomes of present study will have a direct impact on the players health and therefore their skills and athletic performance.</p
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