1,721,049 research outputs found
Direct off-line two-switch forward converter with a boost PFC converter for powering of DC electromagnet systems
No full textIn this paper a switch mode power supply design for electromagnet systems is presented. It is based on a boost converter with power factor correction and a two-switch forward converter. The powered electromagnetic systems in this research are part of various electrical contact apparatus such as electromagnetic contactors, relays, circuit breakers etc. The proposed schematic works in a wide input voltage range which solve the problem with the voltage sag occurring in the energy distribution system. The proposed solution ensures stable operation of the contact equipment and the relay circuits in their industrial application.</p
CF-ABLE score as a clinical prediction rule for prognosis in cystic fibrosis (CF): validation on data from the UK CF Registry
No full textAugmentation therapy for alpha-1 antitrypsin deficiency-Not enough evidence to support its use yet!
No full textAugmentation Therapy for Alpha-1 Antitrypsin Deficiency—Not Enough Evidence to Support its Use Yet
Analysis, design, and experimental validation of a primary side current-sensing flyback converter for use in a battery management system
No full textThe purpose of the presented flyback converter is to equalise the voltage between the cells in a series string within a battery pack providing an active cell-balancing system. This would be an important part of a battery management system (BMS) for charging li-ion batteries in electric vehicles. The converter is based on primary side current sensing, where the conventional feedback circuit is omitted. The purpose of this converter is to improve efficiency by decreasing losses and to increase battery power density by decreasing the number of elements which constitute the power electronics; these are important factors for the future development of electric vehicle battery packs. Analysis of the circuit and the design procedure of the DC-DC flyback converter with primary current sensing is presented in this paper. Finally, several experimental converters have been built and tested to validate the authors’ approach
Development and validation of QOL-E© instrument for the assessment of health-related quality of life in myelodysplastic syndromes
No full textObjective: Supportive care and sustained health-related quality of life (HRQoL) are essential in the management of myelodysplastic syndromes (MDS), yet specific instruments for the measurement of HRQoL in MDS are lacking. We report on the development and validation of a psychometric questionnaire assessing HRQoL in MDS patients (QOL-E©).Methods: The questionnaire was developed in three stages. First, a Medline search and interviews in focus groups generated a list of concepts important to MDS patients. Second, pilot (derivation) study was performed in a cross-sectional sample of 52 MDS patients. Third, field (validation) testing in a clinical setting investigated psychometric properties in 147 MDS patients from six cohorts.Results: Forty-eight items were identified, and fine-tuned to a 37-item list, then a final 29-item questionnaire containing a general well-being dimension, four general health dimensions (physical, functional, social, and sexual), and disease-related dimensions (fatigue and MDS-related disturbances).Conclusion: Cognitive debriefing and psychometric analyses demonstrated good internal validity and patient acceptability. The QOL-E© is the first HRQoL instrument developed specifically for MDS patients
Cyclic patterns of incidence rate for skin malignant melanoma: association with heliogeophysical activity
No full textBackground: our previous studies revealed cyclicity in the incidence rate of skin malignant melanoma (SMM; ICD9, Dx:172) in the Czech Republic (period T=7.50?7.63 years), UK (T=11.00 years) and Bulgaria (T=12.20 years). Incidences compared with the sunspot index Rz (lag-period dT=+2, +4, +6, +10 or +12 years) have indicated that maximal rates are most likely to appear on descending slopes of the 11-year solar cycle, i.e., out of phase. We summarized and explored more deeply these cyclic variations and discussed their possible associations with heliogeophysical activity (HGA) components exhibiting similar cyclicity.Methods: annual incidences of SMM from 5 countries (Czech Republic, UK, Bulgaria, USA and Canada) over various time spans during the years 1964?1992 were analyzed and their correlations with cyclic Rz (sunspot number) and aa (planetary geomagnetic activity) indices were summarized. Periodogram regression analysis with trigonometric approximation and phase-correlation analysis were applied.Results: previous findings on SMM for the Czech Republic, UK and Bulgaria have been validated, and cyclic patterns have been revealed for USA (T=8.63 years, P<0.05) and Canada (Ontario, T=9.91 years, P<0.10). Also, various ‘hypercycles’ were established (T=45.5, 42.0, 48.25, 34.5 and 26.5 years, respectively) describing long-term cyclic incidence patterns. The association of SMM for USA and Canada with Rz (dT=+6 and +7 years, respectively) and aa (dT=?10 and +9 years, respectively) was described. Possible interactions of cyclic non-photic influences (UV irradiation, Schumann resonance signal, low-frequency geomagnetic fluctuations) with brain waves absorbance, neuronal calcium dynamics, neuro-endocrine axis modulation, melatonin/serotonin disbalance and skin neuro-immunity impairment as likely causal pathways in melanoma appearance, were also discussed.Conclusion: the above findings on cyclicity and temporal association of SMM with cyclic environmental factors could not only allow for better forecasting models but also lead to a better understanding of melanoma aetiolog
Major vascular events after transient ischaemic attack and minor ischaemic stroke: post hoc modelling of incidence dynamics
No full textBackground: only few follow-up studies have compared the long-term risk of such major vascular events (MVE) as myocardial infarction (MI) and/or stroke following transient ischaemic attack (TIA) or minor ischaemic stroke (MIS). Estimates of relative risk and cumulative long-term occurrence of MVE may provide better information and contribute to the optimization of treatment decisions. Methods: in the current post hoc modelling study with unique data from Bulgaria, we analysed 183 consecutive patients with TIA (n = 89) or MIS (n = 94), aged >40 years, who were prospectively followed over 36 months for non-fatal or fatal MVE. The cumulative survival, hazard and risks (with 95% confidence intervals) for MVE (combined or by stratification) were calculated by Kaplan-Meier analysis and adjusted (age, sex) by multivariate Cox proportional hazard models. A set of regression models was then applied to MVE incidence (per 100 patients; 4-month intervals). Results: median follow-up was 36 months (interquartile range 30.8–36.0); no differences by age or sex were found (p > 0.05). The risk of non-fatal or fatal MVE was approximately 28% (stroke 19.7%, MI 8.2%). The adjusted cumulative risk of stroke was 0.21 versus 0.10 for MI. The odds ratio of TIA versus MIS was 0.75 (95% CI 0.43–1.32), i.e. lower for stroke (0.63, 0.31–1.25) than for MI (1.12, 0.40–3.14). The risk of non-fatal MVE was higher in MIS than in TIA (pBreslow = 0.0497), especially for non-fatal stroke (p = 0.0325). Time series regression models provided best estimates of the different outcome dynamics in TIA versus MIS (R2TIA = 0.969 with bpower = 1.04 vs. R2MIS = 0.989 with blinear = 0.84; p1-tailed = 0.04) over the study period. Conclusions: the age- and sex-adjusted cumulative 36-month hazard of MVE is higher after MIS than after TIA, but MVE fatality was higher after TIA than after MIS. Although stroke incidence was higher (up to 3 times that of MI), with the highest difference between months 8 and 18, MI fatality was always higher in absolute, relative or adjusted terms. The above alarming patterns and increasing, diverging tendencies for MVE indicate a higher long-term cumulative risk after MIS compared with TIA. These results confirm our hypothesis of a differential risk of TIA versus MIS and, at least, point toward equal importance of therapies aimed at preventing MVE in both types of preceding conditions (TIA or MIS) and the increased fatality after MI, in particular in patients with TI
Modelling, analysis and verification of a resonant llc converter as a power supply for the electromagnetic driving mechanism of an electromagnetic contactor
No full textThe paper presents model based analysis and experimental verification of a half-bridge resonant LLC converter for suppling power to the electromagnetic driving mechanism of an electromagnetic contactor. In the proposed application the convertor - powered either by AC or DC voltage - supplies the coil of the contactor with DC voltage. Analytical and experimental results presented, show several important advantages of the proposed topology: versatility in terms of input voltages – both AC and DC are accepted; stability over wide voltage range; omission of overvoltages – common to electromagnetic systems; reduced power consumption
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