Multiple Quantum Well AlGaAs Nanowires

This letter reports on the growth, structure and luminescent properties of individual multiple quantum well (MQW) AlGaAs nanowires (NWs). The composition modulations (MQWs) are obtained by alternating the elemental flux of Al and Ga during the molecular beam epitaxy growth of the AlGaAs wire on GaAs (111)B substrates. Transmission electron microscopy and energy dispersive X-ray spectroscopy performed on individual NWs are consistent with a configuration composed of conical segments stacked along the NW axis. Micro-photoluminescence measurements and confocal microscopy showed enhanced light emission from the MQW NWs as compared to non-segmented NWs due to carrier confinement and sidewall passivation

Equilibrium and Phase Stability of Nanoparticles

We explore the effect of size on the phase stability of nanosystems by comparing calculated trends with the annealing behavior of nanoparticles (NPs) initially in a core-shell configuration. The NPs are characterized using a variety of transmission electron microscopy (TEM) techniques. We first theoretically consider the equilibrium within a Au-Pt NP of a given size. When considering the contribution of surface and interface energies, we note the appearance of a restricted composition range of the phase diagram over which the liquid and solid phases cannot coexist in a core-shell configuration. A critical radius of ",42 nm is identified below which the NP is single-phased for any composition. It is demonstrated that both branches of the miscibility gap of the Au-Pt phase diagram shift towards the Au-rich composition with increasing curvature. The magnitude of the shift is found to be strongly correlated with the coupling of nonlinear terms entering the Gibbs energy. The main contribution to the shift arises from the composition-dependent surface energy, calculated by considering the selective adsorption of Au to the surface, evaluated using the available thermodynamic properties of the Au-Pt system. An array of TEM-related analytical methods were developed or adapted for the characterization of individual NPs. In particular, chemical maps with quantitative information from a NP with a spatial resolution of '" 1.2 nm could be achieved, with their corresponding error analysis. We introduce an algorithm to retrieve the radial elemental composition from the projected chemical map of a NP if a spherical symmetry can be assumed and test it with NPs of known structures. We also present a technique to determine the composition of a NP having one of the elements depleting during analysis, and test it experimentally with 5-20 nm Au-Ag NPs. Typically, for every Ag characteristic X-ray detected, one Ag atom is lost to knock-on damage. We discuss the detection limit of the method as a function of NP size and composition. We follow the structural evolution of a ",20 nm Au(core) Pt(shell) NP during annealing at various temperatures between 300 and 800 °e. At low temperatures, interdiffusion occurs between the core and the shell, while at temperatures abovt: ",600 °e, the configuration evolves towards one composed of Au- and Pt-rich spherical caps, separated by a relatively fiat interface. We could measure a 5-10% shift in the composition of each phase with respect to the bulk phase diagram that we assigned to capillarity effect. The shift agrees qualitatively with the calculated trends. The ratio of the surface to the interface energy is measured directly from a TEM micrograph of a segregated NP and is in close agreement with the calculated ones. This work contributes to the understanding of the phase stability of binary NPs. The prospect of extending these studies to NPs of other bimetallic systems while probing their properties seems promising, especially in view of their catalytic, magnetic and optical potential.Doctor of Philosophy (PhD

Using Automated Radio Telemetry to Track Gray Bats in Southeast Kansas

The Gray Bat (Myotis grisescens) is a federally endangered species that reaches the westernmos

Uptake and mitochondrial dysfunction of alpha-synuclein in human astrocytes, cortical neurons and fibroblasts

© 2013 Braidy et al.; licensee BioMed Central Ltd. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.The accumulation and aggregation of alpha-synuclein (α-syn) in several tissue including the brain is a major pathological hallmark in Parkinson’s disease (PD). In this study, we show that α-syn can be taken up by primary human cortical neurons, astrocytes and skin-derived fibroblasts in vitro. Our findings that brain and peripheral cells exposed to α-syn can lead to impaired mitochondrial function, leading to cellular degeneration and cell death, provides additional evidence for the involvement of mitochondrial dysfunction as a mechanism of toxicity of α-syn in human cells

Cost-Utility Analysis of Venous Thromboembolism Prophylaxis Strategies for People Undergoing Elective Total Hip and Total Knee Replacement Surgeries in the English National Health Service

Background: Major orthopedic surgery, such as elective total hip replacement (eTHR) and elective total knee replacement (eTKR), are associated with a higher risk of venous thromboembolism (VTE) than other surgical procedures. Little is known, however, about the cost-effectiveness of VTE prophylaxis strategies in people undergoing these procedures. Aim: The aim of this work was to assess the cost-effectiveness of these strategies from the English National Health Service perspective to inform NICE guideline (NG89) recommendations. Materials and Methods: Cost-utility analysis, using decision modeling, was undertaken to compare 15 VTE prophylaxis strategies for eTHR and 12 for eTKR, in addition to “no prophylaxis” strategy. The analysis complied with the NICE Reference Case. Structure and assumptions were agreed with the guideline committee. Incremental net monetary benefit (INMB) was calculated, vs. the model comparator (LMWH+ antiembolism stockings), at a threshold of £20,000/quality-adjusted life-year (QALY) gained. The model was run probabilistically. Deterministic sensitivity analyses (SAs) were undertaken to assess the robustness of the results. Results: The most cost-effective strategies were LMWH for 10 days followed by aspirin for 28 days (INMB = £530 [95% CI: -£784 to £1,103], probability of being most cost-effective = 72%) for eTHR, and foot pump (INMB = £353 [95% CI: -£101 to £665]; probability of being most cost-effective = 18%) for eTKR. There was considerable uncertainty regarding the cost-effectiveness ranking in the eTKR analysis. The results were robust to change in all SAs. Conclusions: For eTHR, LMWH (standard dose) for 10 days followed by aspirin for 28 days is the most cost-effective VTE prophylaxis strategy. For eTKR, the results are highly uncertain but foot pump appeared to be the most cost-effective strategy, followed closely by aspirin (low dose). Future research should focus on assessing cost-effectiveness of VTE prophylaxis in the eTKR population.Peer reviewe

Differential expression of sirtuins in the aging rat brain

Although there are seven mammalian sirtuins (SIRT1-7), little is known about their expression in the aging brain. To characterize the change(s) in mRNA and protein expression of SIRT1-7 and their associated proteins in the brain of "physiologically" aged Wistar rats. We tested mRNA and protein expression levels of rat SIRT1-7, and the levels of associated proteins in the brain using RT-PCR and western blotting. Our data shows that SIRT1 expression increases with age, concurrently with increased acetylated p53 levels in all brain regions investigated. SIRT2 and FOXO3a protein levels increased only in the occipital lobe. SIRT3-5 expression declined significantly in the hippocampus and frontal lobe, associated with increases in superoxide and fatty acid oxidation levels, and acetylated CPS-1 protein expression, and a reduction in MnSOD level. While SIRT6 expression declines significantly with age acetylated H3K9 protein expression is increased throughout the brain. SIRT7 and Pol I protein expression increased in the frontal lobe. This study identifies previously unknown roles for sirtuins in regulating cellular homeostasis and healthy aging.16 page(s

Characterization of sulfur and chlorine behavior during pyrolysis of biomass and waste

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Editorial: NAD+ metabolism as a novel target against infection–Volume II

Fundamental discoveries in the history of science, including research from four Nobel laureates, have identified the pyrimidine nucleotide, nicotinamide adenine dinucleotide (NAD+) as an essential metabolite and the most important cross-kingdom electron carrier. While a wealth of scientific studies in the last century have highlighted the important role of NAD+ in cellular energy generation and redox biology, recent studies have provided evidence for the paramount importance of the non-redox functions of NAD+. Alteration in intracellular NAD+ concentrations is critical in several pathological conditions, including but not limited to neurodegenerative diseases, cancer, diabetes, ischemia injury, dysmetabolic diseases, and inflammatory disorders. Recent advances in our understanding of the biological functions of NAD+-consuming enzymes and the role of NAD+ biosynthetic routes have shown that targeting NAD+ metabolism has very promising potential for therapeutic treatment of infectious diseases. Bacterial resistance to antibiotics is considered one of the greatest threats to human health. Cases of antibiotic resistance are constantly emerging, and the time needed for bacteria to become resistant to newly introduced antibiotics, is getting shorter. Therefore, it is crucial to identify antimicrobials with new mechanism of action to use as therapeutic tools. In this context, modulation of host NAD+ metabolism by the activation or inhibition of key enzymes could influence NAD+ signaling pathways in pathogens and their ability to colonize host cells. Further, the discovery of the enzymes involved in NAD+ turnover in the host during infection could increase our knowledge of bacterial pathogenesis and may be relevant for the development of targeted drug therapies against antibiotic resistant bacteria. However, detailed mechanisms by which NAD+ acts as a regulator and how we can target NAD+ metabolism during microbial infections is still poorly understood

Electromyographic Analysis of Hip Muscle Activity Comparing Maximal Voluntary Contraction to Manual Muscle Test Grades

Introduction: The purpose of this study was to investigate the relationship between muscle activity during three manual muscle tests (MMT) and muscle activity during a maximal voluntary contraction (MVC) of the same muscle. Subjects: Eleven female subjects voluntarily participated in this study. All participants were physical therapy students under the age of 30, nonpregnant, and without recent history of musculoskeletal injury. Methods: Electromyographic (EMG) data was collected by placing surface electrodes over each participant\u27s right tensor fasciae latae (TFL) and gluteus medius (GM) muscle. The EMG data from each muscle was transmitted by Noraxont TeleMy02400 G2 telemetry to a computer equipped with MyoResearch XP 1.07 software. EMG data was collected while each participant performed a MVC and a Normal (5), Fair (3) , and Poor (2) Grade MMT test for each muscle, respectively. Results: EMG data analysis produced an average percentage of MVC for MMT of GM and TFL using Grades 5, 3, and 2 as follows: 91.7%; 32.3%; 20.7%. Conclusion: This study shows the percentage of MVC EMG activity elicited by MMT of Grades 5, 3, and 2 for TFL and GM. These percentages could possibly be used by clinicians as an inferred benchmark of muscle activity elicited by patients achieving these MMT scores; referenced as a percentage of MVC in normal functioning muscle

Management policies to handle multi queuing systems in a service oriented organization : a study of the Henri Bourassa driver licensing office in the City of Montreal

Service operations are often characterized as a seemingly endless series of waiting lines and servers. Almost every interaction between a consumer and the organization providing the service involves waiting in a queue. Capacity management is one response to the cry for a service performance improvement during the past decade. It represents the ability to balance demand and the capability of the service delivery system to satisfy the demand. A review of the literature reveals that an integrated approach of management strategies (demand and resources) is desirable. A feasible set of management policies to handle multi-tandem queuing systems characterized by stochastic demand is presented in this paper. This type of system is common in many high customer contact (HCC) service related organizations. An extensive study of the city of Montreal driver licensing office (Henri Bourrassa Complex) was conducted and explored. A GPSS/H based simulation model was developed and employed to manipulate various policy variables (demand management, labor assignment and job flexibility) in an effort to provide options for increased system efficiency. The use of simulation analysis permits the incorporation of complex system characteristics, therefore providing a realistic representation of the effects of possible management actions. Customer arrival patterns during a three week period in January and July were compared using this model. Using a full-factorial design and given the statistical analysis, it was evident that a deterministic customer arrival rates produce significantly shorter mean system transit times. The results also revealed that job flexibility policy as well as the moving server model have been the most effective in decreasing the customer waiting time in the system and reducing servers idle tim