Natural resource scarcity and technological change

Nonrenewable natural resources, such as aluminum and crude oil, exist only in fixed amounts on Earth. Consequently, some observers are concerned that natural resource scarcity will eventually limit future economic growth and human well-being. Others remain optimistic that technological change will overcome geophysical scarcity. Brown and Wolk examine the evidence for natural resource scarcity and find that over the past century reliance on free markets has promoted sufficient technological change to overcome geophysical scarcity for most nonrenewable natural resources. Rather than rising--as would result from increased scarcity--the relevant real prices of most nonrenewable natural resources have fallen. Although declines in real prices have moderated since World War II, the authors find little evidence of increased scarcity in the postwar era. Increased reliance on markets during the closing decades of the twentieth century is cause for optimism that these trends will continue in the twenty-first.

Acute toxicity and effects of methanolic extract of Moringa oleifera flower on haematological parameters of Wistar rats

Methanolic extract of Moringa oleifera flowers was investigated for its acute toxicity and effects on haematological parameters of Wistar rats. The acute toxicity study to determine the LD50 was evaluated using Lorke’s method. It involves first and second phases with six rats each phase. The rats were divided into three groups of two rats each of the phase. In the first, they were administered 10, 100 and 1000 mg/kg of the extract intraperitonially while in the second phase, they were administered 1600, 2900 and 5000 mg/kg and then observed for 24 hours. The haematological study was carried out according to standard procedures. Twenty (20) rats were divided into 4 groups with five rats in each group. The rats in groups B, C and D were treated orally with the methanolic extract of Moringa oleifera flowers using 200 mg/kg, 400 mg/kg, and 800 mg/kg respectively for 21 days while group A that served as control were administered sterile water for injection at 0.5 ml/kg. Blood sample was taken from all the rats and used to establish the baseline values prior to treatments with the extract. Blood samples were collected at the end of every week and analyzed for haematological values. The administration of the extract at the dose of 5000 mg/kg intraperitoneally to the rats resulted in death but was safe at the dose of 2900 mg/kg. This indicated that the LD50 is below 5000 mg/kg. There were significant increases (p<0.05) in red blood cells, haemoglobin concentration and the packed cell volume values in all treated groups when compared to the baseline values (control group). There were also significant (p<0.05) decrease and variation in the neutrophilic values and an increase in the lymphocytic values of the differential leukocytes counts. This research has revealed that the methanolic extract of Moringa oleifera flowers increased significantly the red blood cells, packed cell volume, haemoglobin concentration and lymphocytosis in Wistar rats

Strongly correlated fermions with nonlinear energy dispersion and spontaneous generation of anisotropic phases

Using the bosonization approach we study fermionic systems with a nonlinear dispersion relation in dimension d>2. We explicitly show how the band curvature gives rise to interaction terms in the bosonic version of the model. Although these terms are perturbatively irrelevant in relation to the Landau Fermi liquid fixed point, they become relevant perturbations when instabilities take place. Using a coherent state path integral technique we built up the effective action that governs the dynamics of the Fermi surface fluctuations. We consider the combined effect of fermionic interactions and band curvature on possible anisotropic phases triggered by negative Landau parameters. In particular we study in some detail the phase diagram for the isotropic/nematic/hexatic quantum phase transition.Comment: RevTeX4, 9 pages, 2 eps figures, Final version as appeared in Phys.Rev.

"Does god play dice with corrugations?": environmental effects on growth

Corrugation growth has perplexed many researchers for several decades with remaining challenges including its reliable prediction in the field. In the present paper, the effect of environmental variations on corrugation growth is investigated using field measurements and mechanics-based modelling. Statistically significant relationships between average daily rainfall, humidity and the growth of rail corrugation were investigated using meterological and railway site field monitoring of a metropolitan network test site with a recurring rail corrugation of about 95mm wavelength. Corrugation growth rate (G) was determined by systematically measuring the longitudinal rail profile with a Corrugation Analysis Trolley (CAT) on the 240m radius, narrow gauge, concrete-sleepered curve. Both roughness generated and weld initiated profile growths were investigated. The weather data was obtained from records held by the Bureau of Meteorology. The modelling is developed to provide insight and mechanics based analysis of the field corrugation growth under changes in environmental conditions and vehicle speed variability. Results show a strong correlation between variations in rainfall and corrugation growth that is consistent with changes in steady state wear. Changes in contact patch geometry and the damage mechanism as the corrugation amplitude grows are shown to have substantial but slower effects on growth. The results are used to explain observed changes in corrugation growth rate under variable speed control at the same site

Self-Similarity in Random Collision Processes

Kinetics of collision processes with linear mixing rules are investigated analytically. The velocity distribution becomes self-similar in the long time limit and the similarity functions have algebraic or stretched exponential tails. The characteristic exponents are roots of transcendental equations and vary continuously with the mixing parameters. In the presence of conservation laws, the velocity distributions become universal.Comment: 4 pages, 4 figure

Correlation Functions for Diffusion-Limited Annihilation, A + A -> 0

The full hierarchy of multiple-point correlation functions for diffusion-limited annihilation, A + A -> 0, is obtained analytically and explicitly, following the method of intervals. In the long time asymptotic limit, the correlation functions of annihilation are identical to those of coalescence, A + A -> A, despite differences between the two models in other statistical measures, such as the interparticle distribution function

Radiology AI Deployment and Assessment Rubric (RADAR) to bring value-based AI into radiological practice

Objective: To provide a comprehensive framework for value assessment of artificial intelligence (AI) in radiology. Methods: This paper presents the RADAR framework, which has been adapted from Fryback and Thornbury’s imaging efficacy framework to facilitate the valuation of radiology AI from conception to local implementation. Local efficacy has been newly introduced to underscore the importance of appraising an AI technology within its local environment. Furthermore, the RADAR framework is illustrated through a myriad of study designs that help assess value. Results: RADAR presents a seven-level hierarchy, providing radiologists, researchers, and policymakers with a structured approach to the comprehensive assessment of value in radiology AI. RADAR is designed to be dynamic and meet the different valuation needs throughout the AI’s lifecycle. Initial phases like technical and diagnostic efficacy (RADAR-1 and RADAR-2) are assessed pre-clinical deployment via in silico clinical trials and cross-sectional studies. Subsequent stages, spanning from diagnostic thinking to patient outcome efficacy (RADAR-3 to RADAR-5), require clinical integration and are explored via randomized controlled trials and cohort studies. Cost-effectiveness efficacy (RADAR-6) takes a societal perspective on financial feasibility, addressed via health-economic evaluations. The final level, RADAR-7, determines how prior valuations translate locally, evaluated through budget impact analysis, multi-criteria decision analyses, and prospective monitoring.Conclusion: The RADAR framework offers a comprehensive framework for valuing radiology AI. Its layered, hierarchical structure, combined with a focus on local relevance, aligns RADAR seamlessly with the principles of value-based radiology. Critical relevance statement: The RADAR framework advances artificial intelligence in radiology by delineating a much-needed framework for comprehensive valuation. </p

Instantons and Matter in N=1/2 Supersymmetric Gauge Theory

We extend the instanton calculus for N=1/2 U(2) supersymmetric gauge theory by including one massless flavor. We write the equations of motion at leading order in the coupling constant and we solve them exactly in the non(anti)commutativity parameter C. The profile of the matter superfield is deformed through linear and quadratic corrections in C. Higher order corrections are absent because of the fermionic nature of the back-reaction. The instanton effective action, in addition to the usual 't Hooft term, includes a contribution of order C^2 and is N=1/2 invariant. We argue that the N=1 result for the gluino condensate is not modified by the presence of the new term in the effective action.Comment: 33 pages, harvmac; v2: minor changes, added references; v3: added analysis of the instanton measure in section

Prevalence of Upper Limb Pain in Spinal Cord Injury: A Systematic Review

A systematic review was undertaken to evaluate and critically appraise literature pertaining to prevalence and treatment of upper limb pain in the spinal cord injured (SCI) population using manual wheelchair. Data extraction tables were compiled, then an in-depth data on the types of injury, level of injury, type of wheelchair used, type of treatment sought and the impact on Activities of Daily Living were recorded. A Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies tool was used to critically appraise the quality of studies included in this review. 994 papers in total were screened, 46 full text studies were assessed with 14 studies included in the final synthesis: four cohort studies and ten cross-sectional studies. Shoulder pain was the most common type of pain reported (30–71%) followed by wrist, hand, and elbow. Functional limitations reported because of upper limb pain included interference with mobilizing, transferring, and Activities of Daily Living, primarily personal care tasks. There is clear evidence that upper limb pain is prevalent in the SCI manual wheelchair using population which impacts on functional tasks. Further research is required to explore the perceptions of those with upper limb pain and techniques used to manage pain

On the physico-mechanical, electrical and dielectric properties of mullite-glass composites

Mullite-glass composites were obtained by solid-state reactive sintering of kaolinite clay and kaolin waste mixtures with waste additions up to 100 wt%. The structural and microstructural analysis of starting powders and sintered samples were evaluated by X-ray diffractometry (XRD) and field-emission scanning electron microscopy (FESEM). The mechanical properties were evaluated by measuring the flexural strength of sintered bodies. Electrical properties of the composites were assessed by impedance spectroscopy (at 30 °C and from 400 to 700 °C) in air. A viscous flux mechanism resulting from the glassy phase filled up the open porosity and increased the mechanical strength. Electrical conductivity, dielectric constant and dielectric loss were strongly dependent on the microstructural features, namely glassy phase and porosity. The activation energies (0.89–0.99 eV) for electrical conduction were lower than typical literature values of mullite-based materials. The results indicated that the herein synthesized mullite-glass composites with up to 53.6 wt% mullite are promising low-cost materials for electronics-related applications.publishe