61 research outputs found
Electronic structures of free-standing nanowires made from indirect bandgap semiconductor gallium phosphide
We present a theoretical study of the electronic structures of freestanding
nanowires made from gallium phosphide (GaP)--a III-V semiconductor with an
indirect bulk bandgap. We consider [001]-oriented GaP nanowires with square and
rectangular cross sections, and [111]-oriented GaP nanowires with hexagonal
cross sections. Based on tight binding models, both the band structures and
wave functions of the nanowires are calculated. For the [001]-oriented GaP
nanowires, the bands show anti-crossing structures, while the bands of the
[111]-oriented nanowires display crossing structures. Two minima are observed
in the conduction bands, while the maximum of the valence bands is always at
the -point. Using double group theory, we analyze the symmetry
properties of the lowest conduction band states and highest valence band states
of GaP nanowires with different sizes and directions. The band state wave
functions of the lowest conduction bands and the highest valence bands of the
nanowires are evaluated by spatial probability distributions. For practical
use, we fit the confinement energies of the electrons and holes in the
nanowires to obtain an empirical formula.Comment: 19 pages, 10 figure
Transmission blocking activity of a standardized neem (Azadirachta indica) seed extract on the rodent malaria parasite Plasmodium berghei in its vector Anopheles stephensi
<p>Abstract</p> <p>Background</p> <p>The wide use of gametocytocidal artemisinin-based combination therapy (ACT) lead to a reduction of <it>Plasmodium falciparum </it>transmission in several African endemic settings. An increased impact on malaria burden may be achieved through the development of improved transmission-blocking formulations, including molecules complementing the gametocytocidal effects of artemisinin derivatives and/or acting on <it>Plasmodium </it>stages developing in the vector. Azadirachtin, a limonoid (tetranortriterpenoid) abundant in neem (<it>Azadirachta indica</it>, Meliaceae) seeds, is a promising candidate, inhibiting <it>Plasmodium </it>exflagellation <it>in vitro </it>at low concentrations. This work aimed at assessing the transmission-blocking potential of NeemAzal<sup>®</sup>, an azadirachtin-enriched extract of neem seeds, using the rodent malaria <it>in vivo </it>model <it>Plasmodium berghei</it>/<it>Anopheles stephensi</it>.</p> <p>Methods</p> <p><it>Anopheles stephensi </it>females were offered a blood-meal on <it>P. berghei </it>infected, gametocytaemic BALB/c mice, treated intraperitoneally with NeemAzal, one hour before feeding. The transmission-blocking activity of the product was evaluated by assessing oocyst prevalence, oocyst density and capacity to infect healthy mice. To characterize the anti-plasmodial effects of NeemAzal<sup>® </sup>on early midgut stages, i.e. zygotes and ookinetes, Giemsa-stained mosquito midgut smears were examined.</p> <p>Results</p> <p>NeemAzal<sup>® </sup>completely blocked <it>P. berghei </it>development in the vector, at an azadirachtin dose of 50 mg/kg mouse body weight. The totally 138 examined, treated mosquitoes (three experimental replications) did not reveal any oocyst and none of the healthy mice exposed to their bites developed parasitaemia. The examination of midgut content smears revealed a reduced number of zygotes and post-zygotic forms and the absence of mature ookinetes in treated mosquitoes. Post-zygotic forms showed several morphological alterations, compatible with the hypothesis of an azadirachtin interference with the functionality of the microtubule organizing centres and with the assembly of cytoskeletal microtubules, which are both fundamental processes in <it>Plasmodium </it>gametogenesis and ookinete formation.</p> <p>Conclusions</p> <p>This work demonstrated <it>in vivo </it>transmission blocking activity of an azadirachtin-enriched neem seed extract at an azadirachtin dose compatible with 'druggability' requisites. These results and evidence of anti-plasmodial activity of neem products accumulated over the last years encourage to convey neem compounds into the drug discovery & development pipeline and to evaluate their potential for the design of novel or improved transmission-blocking remedies.</p
Enhanced Long-Path Electrical Conduction in ZnO Nanowire Array Devices Grown via Defect-Driven Nucleation
Vertical arrays of nanostructures have been widely used as major components in some of the most ground-breaking modern research-based devices, and ZnO nanowires have received particular attention because of their favorable electronic properties. Using a local multiprobe technique to measure the properties of individual ZnO nanowires in vertical arrays, we show for the first time that for metal-catalyzed ZnO nanowire growth the electrical contribution of individual wires to a device is highly dependent on the fate of the catalyst nanoparticle during growth. To overcome the limitations of metal-catalyzed growth, nanowires grown from a defect-driven nucleation process are shown to provide high-quality device structures with excellent long-path electrical conduction
International Society of Sports Nutrition Position Stand: Probiotics.
Position statement: The International Society of Sports Nutrition (ISSN) provides an objective and critical review of the mechanisms and use of probiotic supplementation to optimize the health, performance, and recovery of athletes. Based on the current available literature, the conclusions of the ISSN are as follows: 1)Probiotics are live microorganisms that, when administered in adequate amounts, confer a health benefit on the host (FAO/WHO).2)Probiotic administration has been linked to a multitude of health benefits, with gut and immune health being the most researched applications.3)Despite the existence of shared, core mechanisms for probiotic function, health benefits of probiotics are strain- and dose-dependent.4)Athletes have varying gut microbiota compositions that appear to reflect the activity level of the host in comparison to sedentary people, with the differences linked primarily to the volume of exercise and amount of protein consumption. Whether differences in gut microbiota composition affect probiotic efficacy is unknown.5)The main function of the gut is to digest food and absorb nutrients. In athletic populations, certain probiotics strains can increase absorption of key nutrients such as amino acids from protein, and affect the pharmacology and physiological properties of multiple food components.6)Immune depression in athletes worsens with excessive training load, psychological stress, disturbed sleep, and environmental extremes, all of which can contribute to an increased risk of respiratory tract infections. In certain situations, including exposure to crowds, foreign travel and poor hygiene at home, and training or competition venues, athletes' exposure to pathogens may be elevated leading to increased rates of infections. Approximately 70% of the immune system is located in the gut and probiotic supplementation has been shown to promote a healthy immune response. In an athletic population, specific probiotic strains can reduce the number of episodes, severity and duration of upper respiratory tract infections.7)Intense, prolonged exercise, especially in the heat, has been shown to increase gut permeability which potentially can result in systemic toxemia. Specific probiotic strains can improve the integrity of the gut-barrier function in athletes.8)Administration of selected anti-inflammatory probiotic strains have been linked to improved recovery from muscle-damaging exercise.9)The minimal effective dose and method of administration (potency per serving, single vs. split dose, delivery form) of a specific probiotic strain depends on validation studies for this particular strain. Products that contain probiotics must include the genus, species, and strain of each live microorganism on its label as well as the total estimated quantity of each probiotic strain at the end of the product's shelf life, as measured by colony forming units (CFU) or live cells.10)Preclinical and early human research has shown potential probiotic benefits relevant to an athletic population that include improved body composition and lean body mass, normalizing age-related declines in testosterone levels, reductions in cortisol levels indicating improved responses to a physical or mental stressor, reduction of exercise-induced lactate, and increased neurotransmitter synthesis, cognition and mood. However, these potential benefits require validation in more rigorous human studies and in an athletic population
Infliximab in treatment of idiopathic refractory childhood pyoderma gangrenosum (PG)
Farhad Salehzadeh,1 Yusef Mohammadikebar,2 Afsaneh Enteshary,2 Omid Ghanbarpour,1 Mehrdad Mirzarahimi11Department of Pediatric, Bouali Children’s Hospital, Ardabil University of Medical Sciences (ARUMS), Ardabil, Iran; 2Department of Internal Medicine, Emam Khomeini Hospital, Ardabil University of Medical Sciences (ARUMS), Ardabil, IranAbstract: We report a case of refractory idiopathic childhood pyoderma gangrenosum in a young boy who had suffered from this disease since 3 years of age. He had unfavorable responses and intermittent relapses under different combinations of cytotoxic and steroid therapies. Although there was not much information available about infliximab use for biologic and childhood pyoderma gangrenosum, eventually we decided to use infliximab in this patient. Infliximab showed a dramatic response and resulted in full recovery during 2 years’ follow-up.Keywords: pyoderma gangrenosum, infliximab, childhoo
Insights into semiconductor nanowire conductivity using electrodeposition
Copper (Cu) and iron (Fe) electrical contacts to gallium arsenide (GaAs) and indium arsenide (InAs) nanowires (NWs) have been fabricated via electrodeposition. For undoped or low carbon-doped (10 17/cm 3), p-type GaAs NWs, Cu or Fe nucleate and grow only on the gold catalyst at the NW tip, avoiding the sidewalls. Metal growth is limited by the Au contact resistance due to thick sidewall depletion layers. For InAs NWs and heavier-doped, core-shell (undoped core-C-doped shell) GaAs NWs, metal nucleation and growth occurs on the sidewalls as well as on the gold catalyst limited now by the ion electrolyte diffusivity. \ua9 2012 IOP Publishing Ltd.Peer reviewed: YesNRC publication: Ye
A systematic survey of centrality measures for protein-protein interaction networks
Abstract Background Numerous centrality measures have been introduced to identify “central” nodes in large networks. The availability of a wide range of measures for ranking influential nodes leaves the user to decide which measure may best suit the analysis of a given network. The choice of a suitable measure is furthermore complicated by the impact of the network topology on ranking influential nodes by centrality measures. To approach this problem systematically, we examined the centrality profile of nodes of yeast protein-protein interaction networks (PPINs) in order to detect which centrality measure is succeeding in predicting influential proteins. We studied how different topological network features are reflected in a large set of commonly used centrality measures. Results We used yeast PPINs to compare 27 common of centrality measures. The measures characterize and assort influential nodes of the networks. We applied principal component analysis (PCA) and hierarchical clustering and found that the most informative measures depend on the network’s topology. Interestingly, some measures had a high level of contribution in comparison to others in all PPINs, namely Latora closeness, Decay, Lin, Freeman closeness, Diffusion, Residual closeness and Average distance centralities. Conclusions The choice of a suitable set of centrality measures is crucial for inferring important functional properties of a network. We concluded that undertaking data reduction using unsupervised machine learning methods helps to choose appropriate variables (centrality measures). Hence, we proposed identifying the contribution proportions of the centrality measures with PCA as a prerequisite step of network analysis before inferring functional consequences, e.g., essentiality of a node
Exciton Kinetics, Quantum Efficiency, and Efficiency Droop of Monolayer MoS<sub>2</sub> Light-Emitting Devices
We
have investigated the quantum efficiency of monolayer MoS<sub>2</sub> light-emitting devices through detailed temperature and power-dependent
photoluminescence studies and rate equation analysis. The internal
quantum efficiency can reach 45 and 8.3% at 83 and 300 K, respectively.
However, efficiency droop is clearly measured with increasing carrier
injection due to the unusually large Auger recombination coefficient,
which is found to be ∼10<sup>–24</sup> cm<sup>6</sup>/s at room temperature, nearly 6 orders of magnitude higher than
that of conventional bulk semiconductors. The significantly elevated
Auger recombination in the emerging two-dimensional (2D) semiconductors
is primarily an indirect process and is attributed to the abrupt bounding
surfaces and the enhanced correlation, mediated by magnified Coulomb
interactions, between electrons and holes confined in a 2D structure
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