Performance Investigation of Transcritical Carbon Dioxide Refrigeration Cycle

AbstractCO2 has low critical pressure and temperature. This gives an opportunity CO2 cycles to work in a transcritical nature where heat rejection and absorption are done at supercritical and subcritical conditions, respectively. However, this characteristic posed some performance issues for CO2 refrigeration cycle such as the pressure and temperature of CO2 becomes independent of one another above the critical point thus specifying the operating conditions would be tough. It is also important to identify the optimum cooler pressure and control it; in order to get high cycle coefficient of performance (COP). Thus, the objective of this paper is to investigate the performance of a transcritical CO2 compression refrigeration cycle for different parameters and evaluate its COP. To achieve that, a refrigeration cycle was modeled using thermodynamic concepts. Then, the model was simulated for various parameters that were manipulated to investigate the cycle performance. Maintaining other operating parameters constant the highest COP was 3.24 at 10MPa gas cooler pressure. It was also observed that the cycle is suitable for air-condition application than refrigeration cycle, as COP increases when the evaporator temperature increases. Simulations were conducted using EXCEL developed program. The results can be used in the design of CO2 refrigeration cycle

Development of novel clinical examination scales for the measurement of disease severity in Creutzfeldt-Jakob disease

OBJECTIVE: To use a robust statistical methodology to develop and validate clinical rating scales quantifying longitudinal motor and cognitive dysfunction in sporadic Creutzfeldt-Jakob disease (sCJD) at the bedside. METHODS: Rasch analysis was used to iteratively construct interval scales measuring composite cognitive and motor dysfunction from pooled bedside neurocognitive examinations collected as part of the prospective National Prion Monitoring Cohort study, October 2008-December 2016.A longitudinal clinical examination dataset constructed from 528 patients with sCJD, comprising 1030 Motor Scale and 757 Cognitive Scale scores over 130 patient-years of study, was used to demonstrate scale utility. RESULTS: The Rasch-derived Motor Scale consists of 8 items, including assessments reliant on pyramidal, extrapyramidal and cerebellar systems. The Cognitive Scale comprises 6 items, and includes measures of executive function, language, visual perception and memory. Both scales are unidimensional, perform independently of age or gender and have excellent inter-rater reliability. They can be completed in minutes at the bedside, as part of a normal neurocognitive examination. A composite Examination Scale can be derived by averaging both scores. Several scale uses, in measuring longitudinal change, prognosis and phenotypic heterogeneity are illustrated. CONCLUSIONS: These two novel sCJD Motor and Cognitive Scales and the composite Examination Scale should prove useful to objectively measure phenotypic and clinical change in future clinical trials and for patient stratification. This statistical approach can help to overcome obstacles to assessing clinical change in rapidly progressive, multisystem conditions with limited longitudinal follow-up

BioLPG for Clean Cooking in Sub-Saharan Africa: Present and Future Feasibility of Technologies, Feedstocks, Enabling Conditions and Financing

Energy supply for clean cooking is a priority for Sub-Saharan Africa (SSA). Liquefied petroleum gas (LPG, i.e., propane or butane or a mixture of both) is an economically efficient, cooking energy solution used by over 2.5 billion people worldwide and scaled up in numerous low- and middle-income countries (LMICs). Investigation of the technical, policy, economic and physical requirements of producing LPG from renewable feedstocks (bioLPG) finds feasibility at scale in Africa. Biogas and syngas from the circular economic repurposing of municipal solid waste and agricultural waste can be used in two groundbreaking new chemical processes (Cool LPG or Integrated Hydropyrolysis and Hydroconversion (IH2)) to selectively produce bioLPG. Evidence about the nature and scale potential of bioLPG presented in this study justifies further investment in the development of bioLPG as a fuel that can make a major contribution toward enabling an SSA green economy and universal energy access. Techno-economic assessments of five potential projects from Ghana, Kenya and Rwanda illustrate what might be possible. BioLPG technology is in the early days of development, so normal technology piloting and de-risking need to be undertaken. However, fully developed bioLPG production could greatly reduce the public and private sector investment required to significantly increase SSA clean cooking capacity

All Data are Wrong, but Some are Useful? Advocating the Need for Data Auditing

<p>In a recent article from the <i>Annals of Applied Statistics</i>, Cox discussed the main phases of applied statistical research ranging from clarifying study objectives to final data analysis and interpreting results. As an incidental remark to these main phases, we advocate that beyond <i>cleaning</i> and <i>preprocessing</i> the data, it is a good practice to <i>audit</i> the data to determine if they can be trusted at all. A case study based on Ghanaian Official Fishery Statistics is used to illustrate this need, with Benford's law being the tool used to carrying out the data audit. Supplementary materials for this article are available online.</p

Gymnura poecilura Longtail Butterfly Ray

The Longtail Butterfly Ray (Gymnura poecilura) is a medium-sized (to at least 104 cm disc width) coastal ray that is widespread in the Indian and Northwestern Pacific Oceans from the Red Sea and Arabian/Persian Gulf to southern Japan. It is demersal in on the continental shelf at depths of 0–75 m. Its meat is considered to be of good quality and is consumed locally and traded internationally. There is a long history of overfishing of inshore populations and fishing pressure remains high, and may be rising, across the species’ entire range

Assessment of quality of care given to diabetic patients at Jimma University Specialized Hospital diabetes follow-up clinic, Jimma, Ethiopia

<p>Abstract</p> <p>Background</p> <p>Sub-Saharan Africa is currently enduring the heaviest global burden of diabetes and diabetes care in such resource poor countries is far below standards. This study aims to describe the gaps in the care of Ethiopian diabetic patients at Jimma University Specialized Hospital.</p> <p>Methods</p> <p>329 diabetic patients were selected as participants in the study, aged 15 years or greater, who have been active in follow-up for their diabetes for more than 1 year at the hospital. They were interviewed for their demographic characters and relevant clinical profiles. Their charts were simultaneously reviewed for characters related to diabetes and related morbidities. Descriptive statistics was used for most variables and Chi-square test, where necessary, was used to test the association among various variables. P-value of < 0.05 was used as statistical significance.</p> <p>Results</p> <p>Blood glucose determination was done for 98.5% of patients at each of the last three visits, but none ever had glycosylated haemoglobin results. The mean fasting blood sugar (FBS) level was 171.7 ± 63.6 mg/dl and 73.1% of patients had mean FBS levels above 130 mg/dl. Over 44% of patients have already been diagnosed to be hypertensive and 64.1% had mean systolic BP of > 130 and/or diastolic > 80 mmHg over the last three visits. Diabetes eye and neurologic evaluations were ever done for 42.9% and 9.4% of patients respectively. About 66% had urine test for albumin, but only 28.2% had renal function testing over the last 5 years. The rates for lipid test, electrocardiography, echocardiography, or ultrasound of the kidneys during the same time were < 5% for each. Diabetic neuropathy (25.0%) and retinopathy (23.1%) were the most common chronic complications documented among those evaluated for complications.</p> <p>Conclusions</p> <p>The overall aspects of diabetes care at the hospital were far below any recommended standards. Hence, urgent action to improve care for patients with diabetes is mandatory. Future studies examining patterns and prevalence of chronic complications using appropriate parameters is strongly recommended to see the true burden of diabetes.</p

Estimating the Worldwide Extent of Illegal Fishing

Illegal and unreported fishing contributes to overexploitation of fish stocks and is a hindrance to the recovery of fish populations and ecosystems. This study is the first to undertake a world-wide analysis of illegal and unreported fishing. Reviewing the situation in 54 countries and on the high seas, we estimate that lower and upper estimates of the total value of current illegal and unreported fishing losses worldwide are between $10 bn and$23.5 bn annually, representing between 11 and 26 million tonnes. Our data are of sufficient resolution to detect regional differences in the level and trend of illegal fishing over the last 20 years, and we can report a significant correlation between governance and the level of illegal fishing. Developing countries are most at risk from illegal fishing, with total estimated catches in West Africa being 40% higher than reported catches. Such levels of exploitation severely hamper the sustainable management of marine ecosystems. Although there have been some successes in reducing the level of illegal fishing in some areas, these developments are relatively recent and follow growing international focus on the problem. This paper provides the baseline against which successful action to curb illegal fishing can be judged

Estimating the unreported catch of Eritrean Red Sea fisheries

Unreported catches from three major fisheries in the Eritrean Red Sea were investigated in order to estimate the impact of the total extraction of fish from the ecosystem, which will help the assessment of the resource and its management. The fisheries target small pelagics, demersal finfish and shrimps, and were chosen for their major contribution to the total Eritrean catch, economic importance and/or significant contribution to unreported catch. The analysis covers the period from 1950 to 2004, subdivided into five-year blocks. Factors that provide incentives to fishers to misreport were obtained by examining the historical development of the fisheries; analysis was based on interpolations, guided by these incentives, between independent quantitative estimates of unreported catch (‘anchor points'). Errors were estimated using a Monte Carlo sampling technique. The fishery industry in Eritrea operated smoothly from the mid-1950s to the end of 1960s, when it was disrupted by political instability. Fishing operations were normalised again at the beginning of the 1990s. Of the three fisheries, the small pelagic fishery has the least unreported catch — a maximum of 5% of the total extracted. The total catch from the three fisheries has been under-reported on average by 21%. Keywords: Eritrean fisheries, interpolation, Red Sea, time-series catch, unreported catchAfrican Journal of Marine Science 2007 29(1): 55–6

Biomimicking natural nanopatterned topology by 3D laser lithography

Natural nanopatterned surfaces (nNPS) present on insect wings have demonstrated bactericidal activity [1, 2]. Fabricated nanopatterned surfaces (fNPS) derived by characterization of these wings have also shown superior bactericidal activity [2]. However bactericidal NPS topologies vary in both geometry and chemical characteristics of the individual features in different insects and fabricated surfaces, rendering it difficult to ascertain the optimum geometrical parameters underling bactericidal activity. This situation calls for the adaptation of new and emerging techniques, which are capable of fabricating and characterising comparable structures to nNPS from biocompatible materials. In this research, CAD drawn nNPS representing an area of 10 μm x10 μm was fabricated on a fused silica glass by Nanoscribe photonic professional GT 3D laser lithography system using two photon polymerization lithography. The glass was cleaned with acetone and isopropyl alcohol thrice and a drop of IP-DIP photoresist from Nanoscribe GmbH was cast onto the glass slide prior to patterning. Photosensitive IP-DIP resist was polymerized with high precision to make the surface nanopatterns using a 780 nm wavelength laser. Both moving-beam fixedsample (MBFS) and fixed-beam moving-sample (FBMS) fabrication approaches were tested during the fabrication process to determine the best approach for the precise fabrication of the required nanotopological pattern. Laser power was also optimized to fabricate the required fNPS, where this was changed from 3mW to 10mW to determine the optimum laser power for the polymerization of the photoresist for fabricating FNPS..