Crack Growth Studies in a welded Ni-base superalloy

It is well known that the introduction of sustained tensile loads during high-temperature fatigue (dwell-fatigue) significantly increases the crack propagation rates in many superalloys. One such superalloy is the Ni-Fe based Alloy 718, which is a high-strength corrosion resistant alloy used in gas turbines and jet engines. As the problem is typically more pronounced in fine-grained materials, the main body of existing literature is devoted to the characterization of sheets or forgings of Alloy 718. However, as welded components are being used in increasingly demanding applications, there is a need to understand the behavior. The present study is focused on the interaction of the propagating crack with the complex microstructure in Alloy 718 weld metal during cyclic and dwell-fatigue loading at 550 °C and 650 °C

A Pilot Study into the Value of 3-D Sketch Modelling at Key Stage 3

Modelling is fundamental to design and technology. From the initial image in the mind, a cognitive model, right the way through until the final product designers use models. They can use drawings or sketches, 2- D modelling, 3-D sketch modelling or mock ups, mathematical and/or computer models, and prototypes. This paper is an account of a pilot study into the value of the use of one type of model, the 3-D sketch model, when used by Key Stage 3 pupils when designing a product to be made in the area known in the English National Curriculum as resistant materials. The pilot study was conducted at a rural comprehensive community college. The researchers first reviewed the extent of the use of 3-D sketch models by pupils in Year 9. They found that little use was made of this way of developing design ideas and solving problems. In conjunction with the school staff a revised approach to a resistant materials project was set up to include the use o

Room temperature plasticity in sub-micrometer thermally grown oxide scales

Thermally grown oxides (TGOs) are generally considered to be brittle, capable of sustaining very limited plastic deformation before fracture. As they are prone to exhibit different forms of defects, the fracture toughness, typically measured to be some 1–2 MPa m1/2 [1], is typically reached well before sufficiently high stresses to induce plasticity can be applied [2]. This is particularly true at room temperature, where possible low-stress thermally activated creep mechanisms are suppressed. However, the occurrence of plasticity in e.g. Al2O3 single crystals at room temperature can occur for samples in the micrometer range [3]. Most measurements of the deformation of TGOs have been made on relatively thick scales, (\u3e1 micrometer), which are limited by the fracture originating from inherent defects. Furthermore, the studies have been limited in resolution and sensitivity, as the scales were adherent to the substrates and tested as a composite. Recently, micro-mechanical testing has been introduced as a method to evaluate mechanical behavior of TGOs on a ferritic/martensitic steel [4], where micro-cantilever bending was used to test specimen extracted from different layers in a 5–10 micrometers thick oxide. Still, the cantilever cross-section was typically several micrometers, and the very similar fracture stresses for notched and un-notched cantilevers seems to indicate that the deformation is still limited by inherent defects. Please click Additional Files below to see the full abstract

Is There a Cell-to-Cell Contact Effect on the X-Ray Dose-Survival Response of Mammalian Cells?

While a cell-to-cell contact effect has been reported for a Chinese hamster subline V79-171B, this was not observed for another subline V79 171-S. Therefore, we tested whether the cell-to-cell contact effect on cell survival depended on the cell line or the experimental conditions used. We have cultured and compared both sublines under identical conditions. Both sublines, cultured in Eagle\u27s minimal essential medium (MEM) with 15% serum, bad nearly identical cell doubling times and radiosensitivities. For both sublines, the survival of spheroid and monolayer cells subcultured immediately after irradiation were nearly the same, i.e., a radio-protective contact effect for spheroid cells was absent. Under conditions favorable for the repair of radiation induced damage, cell survival was higher for cells in monolayers than for cells in spheroids. Potentially lethal damage (PLD) repair and sublethal damage (SLD) repair were present in both sublines. However, the magnitude of expression of PLD by hypertonic saline was higher for monolayer than for spheroid cells. We conclude that: 1) the reported differences between V79 sublines (contact effect on survival) appear to be dependent on differences between experimental conditions rather than on cell type; 2) delayed plating technique does not detect PLD repair in round spheroid cells; and 3) detection of repair by split dose is independent of cell shape and/or two-or three-dimensional culture conditions

A Critical Examination of Empowerment Discourse in Medical Tourism: The Case of the Dental Tourism Industry in Los Algodones, Mexico

Background  Medical tourism is a term used to describe the phenomenon of individuals intentionally traveling across national borders to privately purchase medical care. The medical tourism industry has been portrayed in the media as an “escape valve” providing alternative care options as a result of vast economic asymmetries between the global north and global south and the flexible regulatory environment in which care is provided to medical tourists. Discourse suggesting the medical tourism industry necessarily enhances access to medical care has been employed by industry stakeholders to promote continued expansion of the industry; however, it remains unknown how this discourse informs industry practices on the ground. Using case study methodology, this research examines the perspectives and experiences of industry stakeholders working and living in a dental tourism industry site in northern Mexico to develop a better understanding of the ways in which common discourses of the industry are taken up or resisted by various industry stakeholders and the possible implications of these practices on health equity. Results  Interview discussions with a range of industry stakeholders suggest that care provision in this particular location enables international patients to access high quality dental care at more affordable prices than typically available in their home countries. However, interview participants also raised concerns about the quality of care provided to medical tourists and poor access to needed care amongst local populations. These concerns disrupt discourses about the positive health impacts of the industry commonly circulated by industry stakeholders positioned to profit from these unjust industry practices. Conclusions  We argue in this paper that elite industry stakeholders in our case site took up discourses of medical tourism as enhancing access to care in ways that mask health equity concerns for the industry and justify particular industry activities despite health equity concerns for these practices. This research provides new insight into the ways in which the medical tourism industry raises ethical concern and the structures of power informing unethical practices

Cationic liposome-mediated expression of HIV-regulated luciferase and diphtheria toxin a genes in HeLa cells infected with or expressing HIV

HIV-regulated expression of the diphtheria toxin A fragment gene (HIV-DT-A) is a potential gene therapy approach to AIDS. Since cationic liposomes are safe and non-immunogenic for in vivo gene delivery, we examined whether LipofectAMINE or DMRIE reagent could mediate the transfection of HIV-DT-A (pTHA43) or the HIV-regulated luciferase gene (pLUCA43) into HIV-infected or uninfected HeLa cells. pLUCA43 was expressed at a 103-fold higher level in HeLa/LAV cells than in uninfected HeLa cells, while the extent of expression of RSV-regulated luciferase was the same in both cell lines. Co-transfection of HeLa cells with pTHA43 and the proviral HIV clone, HXBΔBgl, resulted in complete inhibition of virus production. In contrast, the delivery of HIV-DT-A to chronically infected HeLa/LAV or HeLa/IIIB cells, or to HeLa CD4+ cells before infection, did not have a specific effect on virus production, since treatment of cells with control plasmids also reduced virus production. This reduction could be ascribed to cytotoxicity of the reagents. The efficiency of transfection, as measured by the percentage of cells expressing β-gal, was ~5%. Thus, cationic liposome mediated transfection was too inefficient to inhibit virus production when the DT-A was delivered by cationic liposomes to chronically- or de novo-infected cells. However, when both the virus and DT-A genes were delivered into the same cells by cationic liposomes, DT-A was very effective at inhibiting virus production. Our results indicate that the successful use of cationic liposomes for gene therapy will require the improvement of their transfection efficiency

Metodología de detección Gliclazida en muestras biológicas

Aim: This research is dedicated to development of a methodology for the determination of gliclazide in biological samples for analytical diagnostics of lethal overdose caused by the drug. Materials and Methods: TLC method: chromatographic plates Merck silica gel 60 F254 10×10 cm in size, mobile phase - ethyl acetate, visualization reagent 1% vanillin solution or 5% solution of chloral hydrate. HPLC method: liquid chromatograph «Milichrom-A-02» with UV detecting (RF); Prontosil-120-5-C18- AQ reverse-phase column Ø2×75 mm in diameter, 5 μm grains (Bischoff Analysetechnik und Geräte GmbH, Germany); Gradient elution with a mixture of two eluents (eluent A – [0.2 M solution LiClO4 – 0.005 M solution of HClO4] and eluent B - acetonitrile); Wavelength 230 nm. Results: Methodology for the determination of gliclazide in biological samples is developed. It includes an effective method of gliclazide isolation from the objects of the study, specific and selective chromatographic detection methods and quantitative determination of toxicity in the extracts that had been received. It was established that while using TLC method gliclazide was assigned an Rf value of 0,48±0,01; detection limit is 3.0 μg. When applying HPLC method gliclazide holding time was 7.80 min (RSD = 0.13%), detection limit was 0.050 μg / ml, limit of the quantitative determination was 0.157 μg/ml, linearity of the procedure was in the range of 0.1-20.0 μg/ml. Under the developed conditions, gliclazide was determined at 17.48 ± 1.32 μg/ml (RSD = 6.06%). Conclusions: Results of the study indicate that methodology for the determination of gliclazide in biological samples that was developed can be used for analytical diagnostics of lethal overdose caused by the drug.Objetivo: Desarrollar un método de detección de gliclazida en muestras biológicas para el diagnóstico analítico de los fallecimientos por sobredosis del fármaco. Materiales y métodos: Método de CCF: placas para cromatografía Merck silica gel 60 F254 de 10×10 cm de tamaño, fase móvil - acetato de etilo, revelador - solución al 1% de vainillina o solución al 5% de hidrato de cloral. Método de HPLC: cromatógrafo líquido «Milihrom-A-02» con detección de UV (Rusia); columna de fase inversa Prontosil-120-5-C18-AQ de Ø2 x 75 mm, con graneado de 5 mm («Bischoff Analysetechnik und Geräte GmbH», Alemania); elución gradiente con una mezcla de dos eluyentes (eluyente A - [0,2 M solución de LiClO4 - solución de HClO 0,005 M4] y eluyente B - acetonitrilo); la longitud de onda es de 230 nm. Resultados y discusión: Se desarrolló una metodología de determinación de la gliclazida en muestras biológicos, que incluye un método eficaz de aislar la gliclazida de los objetos de estudio, unos métodos cromatográficos específicos y selectivos de detección y cuantificación de la sustancia tóxica en los extractos obtenidos. Se constató que al aplicarse el método de CCF la gliclazida ha sido identificada de acuerdo con el valor Rf 0,48±0,01; el límite de detección es de 3,0 μg. Al aplicarse el método de HPLC se constató lo siguiente: el tiempo de retención de la gliclazida es de 7,80 min (RSD=0,13%), el límite de detección es de 0,050 μg/ml, el límite de cuantificación es de 0,157 μg/ml, la linealidad del método está en el intervalo de 0,1-20,0 μg/ml. En condiciones diseñadas la gliclazida se detectó a un nivel de 17,48±1,32μg/ml (RSD=6,06%). Conclusiones. Los resultados obtenidos confirman que la metodología desarrollada de detección de la gliclazida en muestras biológicos es adecuada para el diagnóstico analítico de los fallecimientos por sobredosis del fármaco.The research work performed in the manuscript is done on the funding of National University of Pharmacy (Ukraine

Microscale fracture of chromia scales

High temperature materials such as superalloys rely on the formation of a protective surface oxide scale for prevention of corrosion. Such materials undergo periods of varying thermal and mechanical loads during operation, which can lead to cracking of the surface oxide. This exposes the material to corrosion, and can also act as stress concentrations, which affects the life of the underlying material. It is therefore necessary to consider the mechanical integrity of these scales while estimating material life. Several models have been developed in which fracture mechanics is utilized to estimate failure. But there is a lack of data such as fracture strains and elastic modulus for oxide scales. Conventional mechanical testing methods such as tensile and bending tests have been modified to obtain mechanical data, but it mainly applies to thick oxide scales (several µm thick). These methods are also limited with respect to isolating substrate and residual stress effects. For advanced materials, where the oxide formation kinetics are low, new methods are required in order to assess the mechanical properties. Please click Additional Files below to see the full abstract

Reward system and temporal pole contributions to affective evaluation during a first person shooter video game

<p>Abstract</p> <p>Background</p> <p>Violent content in video games evokes many concerns but there is little research concerning its rewarding aspects. It was demonstrated that playing a video game leads to striatal dopamine release. It is unclear, however, which aspects of the game cause this reward system activation and if violent content contributes to it. We combined functional Magnetic Resonance Imaging (fMRI) with individual affect measures to address the neuronal correlates of violence in a video game.</p> <p>Results</p> <p>Thirteen male German volunteers played a first-person shooter game (<it>Tactical Ops: Assault on Terror</it>) during fMRI measurement. We defined success as eliminating opponents, and failure as being eliminated themselves. Affect was measured directly before and after game play using the Positive and Negative Affect Schedule (PANAS). Failure and success events evoked increased activity in visual cortex but only failure decreased activity in orbitofrontal cortex and caudate nucleus. A negative correlation between negative affect and responses to failure was evident in the right temporal pole (rTP).</p> <p>Conclusions</p> <p>The deactivation of the caudate nucleus during failure is in accordance with its role in reward-prediction error: it occurred whenever subject missed an expected reward (being eliminated rather than eliminating the opponent). We found no indication that violence events were directly rewarding for the players. We addressed subjective evaluations of affect change due to gameplay to study the reward system. Subjects reporting greater negative affect after playing the game had less rTP activity associated with failure. The rTP may therefore be involved in evaluating the failure events in a social context, to regulate the players' mood.</p

Transferrin lipoplex-mediated suicide gene therapy of oral squamous cell carcinoma in an immunocompetent murine model and mechanisms involved in the antitumoral response

Suicide gene therapy has been used for the treatment of a variety of cancers. We reported previously the in vitro efficacy of the Herpes Simplex Virus Thymidine kinase (HSV-tk)/ganciclovir (GCV) system to mediate cytotoxicity in oral squamous cancer cells, using transferrin (Tf)-lipoplexes, prepared from cationic liposomes composed of 1,2-dioleoyl-3-(trimethylammonium) propane (DOTAP) and cholesterol. In the present study, we evaluated the antitumoral efficacy mediated by this lipoplex formulation in two suicide gene therapy strategies, HSV-tk/GCV and cytosine deaminase (CD)/5-fluorocytosine (5-FC), using a syngeneic, orthotopic murine model for head and neck squamous cell carcinoma. The cellular and molecular events associated with the antitumoral response elicited by both the therapeutic approaches were investigated by analyzing tumor cell death, tumor-infiltrating immune cells and tumor cytokine microenvironment. Significant tumor reduction was achieved upon intratumoral delivery of HSV-tk or CD genes mediated by Tf-lipoplexes, followed by intraperitoneal injection of GCV or 5-FC, respectively. Enhanced apoptosis, the recruitment of NK cells, CD4 and CD8 T-lymphocytes and an increase in the levels of several cytokines/chemokines were observed within the tumors. These observations suggest that suicide gene therapy with lipoplexes modifies the tumor microenvironment, and leads to the recruitment of immune effector cells that can act as adjuvants in reducing the tumor size. © 2009 Nature Publishing Group All rights reserved