X-ray laser pulses at the Fourier transform limit

The temporal output of a Ni-like Ag x-ray laser of wavelength 13.9 nm has been recorded using a streak camera with ultrashort (700 fs) temporal resolution. We present a model to calculate the degree of coherence and Fourier transform limit of x-ray laser pulses produced by amplified spontaneous emission and relate the results from the model to previous interferometric measurements of the coherence length of the same Ni-like Ag x-ray laser and our measured duration of temporal output. Our modeling shows that the interferometer and streak camera results are consistent and close to the Fourier transform limit at longer gain medium lengths

The Effects of Isoprene Emission from Native and Invasive Trees on Local Air Quality

Biogenic volatile organic compounds (BVOC) are the second-most abundant reactive gasses emitted into the atmosphere by the biosphere. Isoprene is a BVOC produced by the process of photosynthesis from vegetation and is emitted from plant leaves. Isoprene is a hydrocarbon that combines with oxides of nitrogen in the atmosphere to create ozone in the troposphere, an air pollutant. Invasive trees alter ecosystems and affect native tree populations. Invasive tree species in the Chicagoland area are outcompeting native tree species and expanding rapidly. The effect of isoprene emissions on air quality is a well-researched area in the atmospheric science community, however, the differing isoprene emission patterns between invasive and native trees in the Chicagoland area have not been studied in the literature. From the experiment, it was conclusive that there was no statistical difference in isoprene emissions between the most abundant native and invasive tree species in the same ecosystem, and hence an impact of invasive species on air quality was not demonstrated. However, it was clear that European buckthorn, invasive to Illinois, was a strong isoprene emitter

Experiments and Simulations of short-pulse laser-pumped extreme ultraviolet lasers

Recent experimental work on the development of extreme ultraviolet lasers undertaken using as the pumping source the VULCAN laser at the Rutherford Appleton Laboratory is compared to detailed simulations. It is shown that short duration (similar topicosecond) pumping can produce X-ray laser pulses of a few picosecond duration and that measurement of the emission from the plasma can give an estimate of the duration of the gain coefficient. The Ehybrid fluid and atomic physics code developed at the University of York is used to simulate X-ray laser gain and plasma emission. Two postprocessors to the Ehybrid code are utilized: 1) to raytrace the X-ray laser beam amplification and refraction and 2) to calculate the radiation emission in the kiloelectronvolt photon energy range. The raytracing and spectral simulations are compared, respectively, to measured X-ray laser output and the output of two diagnostics recording transverse X-ray emission. The pumping laser energy absorbed in the plasma is examined by comparing the simulations to experimental results. It is shown that at high pumping irradiance (>10(15) Wcm(-2)), fast electrons are produced by parametric processes in the preformed long scale-length plasmas. These fast electrons do not pump the population inversion and so pumping efficiency is reduced at high irradiance

Studies in Glycosuria and diabetes in non-white populations of the Transvaal part 2: Indians

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Autogenous Brachial—Brachial Fistula for Vein Access. Haemodynamic Factors Predicting Outcome and 1 Year Clinical Data

AbstractTwo-stage autogenous brachial vein–brachial artery access (ABBA) has been proposed as an option where adequate superficial vein is not available for the creation of conventional haemodialysis fistulae.MethodsThis report depicts the clinical outcome of a series of 17 consecutive patients who underwent ABBA in a single centre. Of the 17 patients, nine had had at least one previous arterioventricular (AV) fistula or graft, and eight were new to haemodialysis. Patencies were assessed using the Kaplan–Meier survival analysis.ResultsIn 14 patients, the brachial vein was transposed (82%) and the time to transposition ranged from 4 to 26 weeks (median time: 6 weeks). The functional patency rate was 45.75% at 12 months. After stage one, all fistulas that went on to develop well had a brachial vein flow of at least 900mlmin−1, and this was significantly higher than in fistulas that failed to develop (p=0.005). The maturation rate in our study was 65% and the median time to cannulation of the fistula was 8weeks from the stage 1. Of the 17 patients, 12 (71%) experienced at least one complication. Ten (59%) demonstrated moderate-to-severe stenoses; eight of which necessitated angioplasty and/or percutaneous mechanical thrombolysis.ConclusionsABBA was characterised by a high incidence of complications and a long period to achieve maturation. Despite close monitoring and a high rate of secondary interventions, the patency rate was low. With this experience, we now only consider it an alternative in patients without adequate superficial veins, who have had failed grafts or where there is a very high risk of infection

Asphericity Can Cause Nonuniform Lithium Intercalation in Battery Active Particles

Uniform intercalation is desired to enable next-generation Li-ion batteries. While we expect nonuniformity in materials undergoing a phase change, single-phase intercalation materials such as nickel manganese cobalt oxide are believed to lithiate uniformly at the particle/electrolyte interface. However, recent imaging reveals nonuniform lithiation. Motivated by this discrepancy, we examine if aspherical particle shape can cause such nonuniformity since the conventional belief is based on spherical particle theory. We obtain real particle geometries using rapid lab-based X-ray computed tomography and subsequently perform physics-based calculations accounting for electrochemical reactions at the particle/electrolyte interface and lithium transport inside the particle bulk. The aspherical geometry breaks the symmetry and causes nonuniform reaction distribution. Such nonuniformity is exacerbated as the particle becomes more aspherical. The proposed mechanism represents a fundamental limit on achievable lithiation uniformity in aspherical particles in the absence of other mechanisms causing inhomogeneity, such as grain structure, nonuniform carbon-binder coating, etc

Development of a core–shell composite hydrogel for 3D bioprinting

Recently, 3D printing has become popular in the field of tissue engineering, where materials and biology are combined with the aim of producing functional tissues for regenerative medicine therapies and for in vitro disease and toxicology models. However, current 3D printing techniques are not able to produce functional tissue-engineered constructs that are physiologically-relevant in the long-term. Challenges arise when combining desired mechanical properties with biological properties in a single construct. Often, cell-supportive materials lack mechanical stability and mechanically-robust materials are unable to support cell growth and function. In addition, many native tissues and organs are heterogeneous, with graded properties. The recapitulation of these factors will help to produce more physiologically-relevant tissue replacements and in vitro models with better predictability. This thesis seeks to combine biological and mechanical properties in a single core–shell strand: a mechanically-robust shell hydrogel encapsulating biologically active cell-laden core. This body of work has been split into three sections, the assessment of a hybrid material for use in the shell, the production of 3D printed constructs with core–shell strands, and the incorporation of gradients into these printed constructs. First, the mechanical properties of a poly(ethylene glycol) diacrylate (PEGDA)/alginate hybrid hydrogel was assessed using tensile testing. The hybrid hydrogels demonstrated synergy in their mechanical properties in a composition-dependent manner. In the second part of this thesis, a coaxial printing method was developed by combining a coaxial needle with a commercial extrusion-based 3D printer. Extruded strands displayed distinct core and shell regions and were able to support cell viability and function for up to 6 weeks. In the final part of this thesis, gradients were incorporated into the shell of core–shell strands. Both soluble factors gradients and stiffness gradients were characterised, and their longevity within these printed constructs was studied. In summary, core–shell strands have been shown to be a viable method to combine optimal mechanical and biological properties in a single construct. The core–shell technique could be made more complex with the addition of gradients, bringing printed constructs closer to their in vivo counterparts. With further research, this technique will help to create more physiologically-relevant tissue engineered constructs, which can drive research a step closer towards better disease models and future therapies

A quantum probability account of individual differences in causal reasoning

We use quantum probability (QP) theory to investigate individual differences in causal reasoning. By analyzing data sets from Rehder (2014) on comparative judgments, and from Rehder & Waldmann (2016) on absolute judgments, we show that a QP model can both account for individual differences in causal judgments, and why these judgments sometimes violate the properties of causal Bayes nets. We implement this and previously proposed models of causal reasoning (including classical probability models) within the same hierarchical Bayesian inferential framework to provide a detailed comparison between these models, including computing Bayes factors. Analysis of the inferred parameters of the QP model illustrates how these can be interpreted in terms of putative cognitive mechanisms of causal reasoning. Additionally, we implement a latent classification mechanism that identifies subcategories of reasoners based on properties of the inferred cognitive process, rather than post hoc clustering. The QP model also provides a parsimonious explanation for aggregate behavior, which alternatively can only be explained by a mixture of multiple existing models. Investigating individual differences through the lens of a QP model reveals simple but strong alternatives to existing explanations for the dichotomies often observed in how people make causal inferences. These alternative explanations arise from the cognitive interpretation of the parameters and structure of the quantum probability model