Effect of aging on the reinforcement efficiency of carbon nanotubes in epoxy matrix

The reinforcement efficiency of carbon nanotubes (CNTs) in epoxy matrix was investigated in the elastic regime. Cyclic uniaxial tensile tests were performed at constant strain amplitude and increasing maximum strain. Post-curing of the epoxy and its composite at a temperature close to the glass transition temperature allowed us to explore the effect of aging on the reinforcement efficiency of CNT. It is found that the reinforcement efficiency is compatible with a mean field mixture rule of stress reinforcement by random inclusions. It also diminishes when the maximum strain increased and this effect is amplified by aging. The decrease of elastic modulus with increasing cyclic maximum strain is quite similar to the one observed for filled elastomers with increasing strain amplitude, a phenomenon often referred as the Payne effect

Osmoregulatory bicarbonate secretion exploits H(+)-sensitive haemoglobins to autoregulate intestinal O2 delivery in euryhaline teleosts

This is the final version of the article. Available from Springer Verlag via the DOI in this record.Marine teleost fish secrete bicarbonate (HCO3 (-)) into the intestine to aid osmoregulation and limit Ca(2+) uptake by carbonate precipitation. Intestinal HCO3 (-) secretion is associated with an equimolar transport of protons (H(+)) into the blood, both being proportional to environmental salinity. We hypothesized that the H(+)-sensitive haemoglobin (Hb) system of seawater teleosts could be exploited via the Bohr and/or Root effects (reduced Hb-O2 affinity and/or capacity with decreasing pH) to improve O2 delivery to intestinal cells during high metabolic demand associated with osmoregulation. To test this, we characterized H(+) equilibria and gas exchange properties of European flounder (Platichthys flesus) haemoglobin and constructed a model incorporating these values, intestinal blood flow rates and arterial-venous acidification at three different environmental salinities (33, 60 and 90). The model suggested red blood cell pH (pHi) during passage through intestinal capillaries could be reduced by 0.14-0.33 units (depending on external salinity) which is sufficient to activate the Bohr effect (Bohr coefficient of -0.63), and perhaps even the Root effect, and enhance tissue O2 delivery by up to 42 % without changing blood flow. In vivo measurements of intestinal venous blood pH were not possible in flounder but were in seawater-acclimated rainbow trout which confirmed a blood acidification of no less than 0.2 units (equivalent to -0.12 for pHi). When using trout-specific values for the model variables, predicted values were consistent with measured in vivo values, further supporting the model. Thus this system is an elegant example of autoregulation: as the need for costly osmoregulatory processes (including HCO3 (-) secretion) increases at higher environmental salinity, so does the enhancement of O2 delivery to the intestine via a localized acidosis and the Bohr (and possibly Root) effect.Underlying research materials, i.e. raw data, is accessible by contacting the corresponding author, Dr. Rod Wilson at [email protected]. This research was supported by BBSRC and NERC grants (BB/D005108/1 and NE/H010041/1) to RWW and an NSERC Discovery grant to CJB. We would like to thank Jan Shears for excellent technical support and fish husbandry

Irreversible reorganization in a supercooled liquid originates from localised soft modes

The transition of a fluid to a rigid glass upon cooling is a common route of transformation from liquid to solid that embodies the most poorly understood features of both phases1,2,3. From the liquid perspective, the puzzle is to understand stress relaxation in the disordered state. From the perspective of solids, the challenge is to extend our description of structure and its mechanical consequences to materials without long range order. Using computer simulations, we show that the localized low frequency normal modes of a configuration in a supercooled liquid are causally correlated to the irreversible structural reorganization of the particles within that configuration. We also demonstrate that the spatial distribution of these soft local modes can persist in spite of significant particle reorganization. The consequence of these two results is that it is now feasible to construct a theory of relaxation length scales in glass-forming liquids without recourse to dynamics and to explicitly relate molecular properties to their collective relaxation.Comment: Published online: 20 July 2008 | doi:10.1038/nphys1025 Available from http://www.nature.com/nphys/journal/v4/n9/abs/nphys1025.htm

Spatially and genetically distinct African trypanosome virulence variants defined by host interferon-g response

We describe 2 spatially distinct foci of human African trypansomiasis in eastern Uganda. The Tororo and Soroti foci of <i>Trypanosoma brucei rhodesiense</i> infection were genetically distinct as characterized by 6 microsatellite and 1 minisatellite polymorphic markers and were characterized by differences in disease progression and host-immune response. In particular, infections with the Tororo genotype exhibited an increased frequency of progression to and severity of the meningoencephalitic stage and higher plasma interferon (IFN)–γ concentration, compared with those with the Soroti genotype. We propose that the magnitude of the systemic IFN-γ response determines the time at which infected individuals develop central nervous system infection and that this is consistent with the recently described role of IFN-γ in facilitating blood-brain barrier transmigration of trypanosomes in an experimental model of infection. The identification of trypanosome isolates with differing disease progression phenotypes provides the first field-based genetic evidence for virulence variants in T. <i>brucei rhodesiense</i>

Premature death among primary care patients with a history of self-harm

PURPOSE Self-harm is a public health problem that requires a better understanding of mortality risk. We undertook a study to examine premature mortality in a nationally representative cohort of primary care patients who had harmed themselves. METHODS During 2001–2013, a total of 385 general practices in England contributed data to the Clinical Practice Research Datalink with linkage to Office for National Statistics mortality records. We identified 30,017 persons aged 15 to 64 years with a recorded episode of self-harm. We estimated the relative risks of all-cause and cause-specific natural and unnatural mortality using a comparison cohort of 600,258 individuals matched on age, sex, and general practice. RESULTS We found an elevated risk of dying prematurely from any cause among the self-harm cohort, especially in the first year of follow-up (adjusted hazard ratio for that year, 3.6; 95% CI, 3.1–4.2). In particular, suicide risk was especially high during the first year (adjusted hazard ratio, 54.4; 95% CI, 34.3–86.3); although it declined sharply, it remained much higher than that in the comparison cohort. Large elevations of risk throughout the follow-up period were also observed for accidental, alcohol-related, and drug poisoning deaths. At 10 years of follow-up, cumulative incidence values were 6.5% (95% CI, 6.0%–7.1%) for all-cause mortality and 1.3% (95% CI, 1.2%–1.5%) for suicide. CONCLUSIONS Primary care patients who have harmed themselves are at greatly increased risk of dying prematurely by natural and unnatural causes, and especially within a year of a first episode. These individuals visit clinicians at a relatively high frequency, which presents a clear opportunity for preventive action. Primary care patients with myriad comorbidities, including self-harming behavior, mental disorder, addictions, and physical illnesses, will require concerted, multipronged, multidisciplinary collaborative care approaches

Open-source bandstructure models of interdiffusion, impurity and exciton states for the QWWAD v1.4 simulation suite

The vast majority of high-quality software for simulating semiconductor nanostructures (e.g., [1]) is supplied under a proprietary license and its source code cannot be studied, modified or redistributed by its users. The open-source project, Quantum Wells, Wires and Dots (QWWAD) [2] is a free, non-commercial community-focused resource, which accompanies the new 4th edition of the eponymous textbook [3]. Previously described features in QWWAD include numerical Schrodinger/Poisson solvers in generic 1D potentials [e.g., Fig. 1(a)], quasi-analytical and empirical pseudopotential calculations of the band-structure in quantum wires and dots, and scattering calculations for interactions with impurities, phonons, interface roughness, alloy disorder and carrier–carrier processes. We describe new tools, included in the latest release (QWWAD v1.4), for modelling the perturbed quantum-confined states within 2D heterostructures resulting from interdiffusion, impurities and excitonic contribution

A dynamic network approach for the study of human phenotypes

The use of networks to integrate different genetic, proteomic, and metabolic datasets has been proposed as a viable path toward elucidating the origins of specific diseases. Here we introduce a new phenotypic database summarizing correlations obtained from the disease history of more than 30 million patients in a Phenotypic Disease Network (PDN). We present evidence that the structure of the PDN is relevant to the understanding of illness progression by showing that (1) patients develop diseases close in the network to those they already have; (2) the progression of disease along the links of the network is different for patients of different genders and ethnicities; (3) patients diagnosed with diseases which are more highly connected in the PDN tend to die sooner than those affected by less connected diseases; and (4) diseases that tend to be preceded by others in the PDN tend to be more connected than diseases that precede other illnesses, and are associated with higher degrees of mortality. Our findings show that disease progression can be represented and studied using network methods, offering the potential to enhance our understanding of the origin and evolution of human diseases. The dataset introduced here, released concurrently with this publication, represents the largest relational phenotypic resource publicly available to the research community.Comment: 28 pages (double space), 6 figure

Energy drink use, problem drinking and drinking motives in a diverse sample of Alaskan college students

Background. Recent research has identified the use of caffeinated energy drinks as a common, potentially risky behaviour among college students that is linked to alcohol misuse and consequences. Research also suggests that energy drink consumption is related to other risky behaviours such as tobacco use, marijuana use and risky sexual activity. Objective. This research sought to examine the associations between frequency of energy drink consumption and problematic alcohol use, alcohol-related consequences, symptoms of alcohol dependence and drinking motives in an ethnically diverse sample of college students in Alaska. We also sought to examine whether ethnic group moderated these associations in the present sample of White, Alaska Native/American Indian and other ethnic minority college students. Design. A paper-and-pencil self-report questionnaire was completed by a sample of 298 college students. Analysis of covariance (ANCOVA) was used to examine the effects of energy drink use, ethnic group and energy drink by ethnic group interactions on alcohol outcomes after controlling for variance attributed to gender, age and frequency of binge drinking. Results. Greater energy drink consumption was significantly associated with greater hazardous drinking, alcohol consequences, alcohol dependence symptoms, drinking for enhancement motives and drinking to cope. There were no main effects of ethnic group, and there were no significant energy drink by ethnic group interactions. Conclusion. These findings replicate those of other studies examining the associations between energy drink use and alcohol problems, but contrary to previous research we did not find ethnic minority status to be protective. It is possible that energy drink consumption may serve as a marker for other health risk behaviours among students of various ethnic groups