A review on the complementarity of renewable energy sources: concept, metrics, application and future research directions

It is expected, and regionally observed, that energy demand will soon be covered by a widespread deployment of renewable energy sources. However, the weather and climate driven energy sources are characterized by a significant spatial and temporal variability. One of the commonly mentioned solutions to overcome the mismatch between demand and supply provided by renewable generation is a hybridization of two or more energy sources in a single power station (like wind-solar, solar-hydro or solar-wind-hydro). The operation of hybrid energy sources is based on the complementary nature of renewable sources. Considering the growing importance of such systems and increasing number of research activities in this area this paper presents a comprehensive review of studies which investigated, analyzed, quantified and utilized the effect of temporal, spatial and spatio-temporal complementarity between renewable energy sources. The review starts with a brief overview of available research papers, formulates detailed definition of major concepts, summarizes current research directions and ends with prospective future research activities. The review provides a chronological and spatial information with regard to the studies on the complementarity concept.Comment: 34 pages 7 figures 3 table

Acute hospitalisation needs of adults admitted to public facilities in the Cape Town Metro district

INTRODUCTION: Public health care delivery in South Africa aims to provide equitable access at the most appropriate level of care. We studied to what extent the acute health care needs of adults admitted to public hospitals in the Cape Town Metropole were being appropriately met. METHODS: A retrospective study was conducted of the hospital records of adults admitted to medical beds in public hospitals in Cape Town between August and November 2008. Intensive care unit patients were not included. RESULTS: Of 802 beds in use, the estimated occupancy was at least 95%. The average time elapsed since admission was 7.9 days; 94.3% of medical admissions were acute; 45% were severely to critically ill on admission; and co-morbid disease was present in 78.1%. Of all admissions, 31.9% were HIV-positive, and 17% had active tuberculosis. At least 396 (51.6%) patients were deemed to have required specialist or subspecialist consultation to expedite appropriate care; 386 (50.3%) accessed the appropriate level of medical care required; 339 (44.2%) accessed a more sophisticated level of care than required; and 42 (5.5%) did not access an adequate level of care. CT scan and ultrasound accounted for 59% of all restricted tests done. CONCLUSIONS: Our findings support the plan to provide more primary care hospital facilities in the metropolitan area. Most patients needing specialised care are accessing such care, and most patients accessing a higher level of care than needed can be addressed by ensuring that they first access primary care and are referred according to protocols

Systematic approach towards reliable estimation of abdominal aortic aneurysm size by ultrasound imaging and CT

Background: The management of abdominal aortic aneurysm (AAA) is fully dictated by AAA size, but there are no uniform measurement guidelines, and systematic differences exist between ultrasound- and CT-based size estimation. The aim of this study was to devise a uniform ultrasound acquisition and measurement protocol, and to test whether harmonization of ultrasound and CT readings is feasible. Methods: A literature review was undertaken to evaluate evidence for ultrasound-based measurement of AAA. A protocol for measuring AAA was then developed, and intraobserver and interobserver reproducibility was tested. Finally, agreement between ultrasound readings and CT-based AAA diameters was evaluated. This was an observational study of patients with a small AAA who participated in two pharmaceutical intervention trials. Results: Based on a literature review, an ultrasound acquisition and reading protocol was devised. Evaluation of the protocol showed an intraobserver repeatability of 1.6 mm (2s.d.) and an interobserver intraclass correlation coefficient (ICC) of 0.97. Comparison of protocolled ultrasound readings and local CT readings indicated a good correlation (r = 0.81), but a systematic +4.1-mm difference for CT. Harmonized size readings for ultrasound imaging and CT increased the correlation (r = 0.91) and reduced the systematic difference to +1.8 mm by CT. Interobserver reproducibility of protocolized CT measurements showed an ICC of 0.94 for the inner-to-inner method and 0.96 for the outer-to-outer method. Conclusion: The absence of harmonized size acquisition and reading guidelines results in overtreatment and undertreatment of patients with AAA. This can be avoided by the implementation of standardized ultrasound acquisition and a harmonized reading protocol for ultrasound- and CT-based readings

A new concurrent chemotherapy with vinorelbine and mitomycin C in combination with radiotherapy in patients with locally advanced squamous cell carcinoma of the head and neck

Objective: The purpose of this pilot study was to evaluate the feasibility and toxicity of concurrent chemotherapy with vinorelbine and mitomycin C in combination with accelerated radiotherapy (RT) in patients with locally advanced cancer of the head and neck. Patients and Methods: Between January 2003 and March 2004, 15 patients with T4/N2-3 squamous cell carcinoma (12/15) and with N3 cervical lymph node metastases of carcinoma of unknown primary (3/15) were treated with chemotherapy and simultaneous accelerated RT. Results: 11 patients completed therapy without interruption or dose reduction. Grade 3 - 4 acute mucosal toxicity was observed in 9/15 patients, grade 4 hematologic toxicity in 6/15 patients. At a median follow-up of 7.5 months, 2 patients have died of intercurrent disease, 2 patients have experienced local relapse; 5 patients are alive with no evidence of disease at the primary tumor site. Discussion: The described regimen is highly effective, but led to remarkable side effects

Gender plays no role in student ability to perform on computer-based examinations

BACKGROUND: To see if there is a difference in performance when students switch from traditional paper-and-pencil examinations to computer-based examinations, and to determine whether there are gender differences in student performance in these two examination formats. METHODS: This study involved first year medical students at the University of Illinois at Urbana-Champaign over three Academic Years 2002–03/2003–04 and 2003–05. Comparisons of student performance by overall class and gender were made. Specific comparisons within courses that utilized both the paper-and-pencil and computer formats were analyzed. RESULTS: Overall performance scores for students among the various Academic Years revealed no differences between exams given in the traditional pen-and-paper and computer formats. Further, when we looked specifically for gender differences in performance between these two testing formats, we found none. CONCLUSION: The format for examinations in the courses analyzed does not affect student performance. We find no evidence for gender differences in performance on exams on pen-and-paper or computer-based exams

Medical students who decompress during the M-1 year outperform those who fail and repeat it: A study of M-1 students at the University of Illinois College of Medicine at Urbana-Champaign 1988–2000

BACKGROUND: All medical schools must counsel poor-performing students, address their problems and assist them in developing into competent physicians. The objective of this study was to determine whether students with academic deficiencies in their M-1 year graduate more often, spend less time to complete the curriculum, and need fewer attempts at passing USMLE Step 1 and Step 2 by entering the Decompressed Program prior to failure of the M-1 year than those students who fail the M-1 year and then repeat it. METHOD: The authors reviewed the performance of M-1 students in the Decompressed Program and compared their outcomes to M-1 students who failed and fully repeated the M-1 year. To compare the groups upon admission, t-Tests comparing the Cognitive Index of students and MCAT scores from both groups were performed. Performance of the two groups after matriculation was also analyzed. RESULTS: Decompressed students were 2.1 times more likely to graduate. Decompressed students were 2.5 times more likely to pass USMLE Step 1 on the first attempt than the repeat students. In addition, 46% of those in the decompressed group completed the program in five years compared to 18% of the repeat group. CONCLUSION: Medical students who decompress their M-1 year prior to M-1 year failure outperform those who fail their first year and then repeat it. These findings indicate the need for careful monitoring of M-1 student performance and early intervention and counseling of struggling students

Public transport policy in the Netherlands

Dutch public transport as a part of transport policy.Institute of Transport and Logistics Studies. Faculty of Economics and Business. The University of Sydne

The potential of sodium-glucose cotransporter 2 inhibitors for the treatment of systemic right ventricular failure in adults with congenital heart disease

AimsGiven the compelling evidence on the effectiveness of sodium-glucose cotransporter 2 inhibitors (SGLT2i) in the conventional heart failure population, SGLT2i deserve exploration in systemic right ventricular (sRV) failure. The initial experience with dapagliflozin in sRV failure patients is described, with a focus on tolerability and short-term effects on clinical outcomes.Methods and resultsTen patients (70% female, median age 50 years [46.5-52]) with symptomatic sRV failure who received dapagliflozin 10 mg per day on top of optimal medical therapy between 04-2021 and 01-2023 were included. Within 4 weeks, no significant changes in blood pressure, electrolytes, or serum glucose occurred. Creatinine and estimated glomerular filtration rate (eGFR) showed a slight decline (88 & PLUSMN; 17 to 97 & PLUSMN; 23 & mu;mol/L, p = 0.036, and 72 & PLUSMN; 14 vs. 66 & PLUSMN; 16 ml/min/1.73m(2), p = 0.020, respectively). At 6 months follow-up (n = 8), median NT-proBNP decreased significantly from 736.6 [589.3-1193.3] to 531.6 [400.8-1018] ng/L (p = 0.012). Creatinine and eGFR recovered to baseline levels. There were no significant changes in echocardiographic systolic sRV or left ventricular function. New York Heart Association class improved significantly in 4 out of 8 patients (p = 0.046), who also showed an improvement in the 6-minute walk test or bicycle exercise test performance. One female patient developed an uncomplicated urinary tract infection. No patients discontinued treatment.ConclusionDapagliflozin was well-tolerated in this small cohort of sRV failure patients. While the early results on the reduction of NT-proBNP and clinical outcome parameters are encouraging, large-scale prospective studies are warranted to thoroughly evaluate the effects of SGLT2i in the growing sRV failure population

Recurrence of ventricular arrhythmias in ischaemic secondary prevention implantable cardioverter defibrillator recipients: long-term follow-up of the Leiden out-of-hospital cardiac arrest study (LOHCAT)

Aims to assess the long-term rate of mortality and the recurrence of potentially life-threatening ventricular arrhythmias in secondary prevention implantable cardioverter defibrillator (ICD) patients and to construct a model for baseline risk stratification.Methods and resultsSince 1996, all patients with ischaemic heart disease, receiving ICD therapy for secondary prevention of sudden death, were included in the current study. Patients were evaluated at implantation and during long-term follow-up. A total of 456 patients were included in the analysis and followed for 54 ± 35 months. During follow-up, 100 (22) patients died and ICD therapy was noted in 216 (47) patients, of which 138 (30) for fast, potentially life-threatening ventricular arrhythmia. Multivariate analysis revealed a history of atrial fibrillation or flutter (AF), ventricular tachycardia as presenting arrhythmia, and wide QRS and poor left ventricular ejection fraction as independent predictors of life-threatening ventricular arrhythmias. The strongest predictor was AF with a hazard ratio of 2.1 (95 confidence interval 1.3-3.2). On the basis of the available clinical data, it was not possible to identify a group which exhibited no risk on recurrence of potentially life-threatening ventricular arrhythmias.ConclusionIschaemic secondary prevention ICD recipients exhibit a high recurrence rate of potentially life-threatening ventricular arrhythmias. Factors that increase risk can be identified but, even with these factors, it was not possible to distinguish a recurrence-free group