39 research outputs found
Nierenarterienstenose: Intervention oder medikamentöse Behandlung?
No full textBackground and objective: Angioplasty in patients with renal artery stenosis aims at reducing blood pressure and at improving kidney function. Its efficacy has however been questioned by recent published data. It was the aim of this retrospective study to compare angioplasty with medical treatment in an unselected patient population. Methods: Data on 109 patients were retrospectively anlysed. This cohort included all those patients admitted to the Lippe-Detmold Hospital between 1992 and 2008 for renal artery stenosis. The data included blood pressure, creatinine-based calculated glomerular filtration rate (cGFR), any renal dialysis, cardiovascular risk factors, events and survival time after transluminal renal angioplasty or drug treatment, respectively. Results: Patients who had undergone angioplasty were younger (p = 0.04), had less cardiovascular co-morbidity (p < 0.01), but a higher degree of stenosis (p < 0.01). After a median follow-up of 32.5 (angioplasty) and 36.0 months (drug treatment), respectively, a significant decrease of cGFR was recorded in drug treated patients (- 16.2 ml/min, 95%, CI - 25.7 to - 6.7) but not in the angioplasty group (- 4.5 ml/min, 95%, CI - 13.5 to 4.5). There were no other significant differences were not observed. Conclusion: Younger patients with a high degree of renal artery stenosis but without generalized atherosclerosis more frequently underwent angioplasty in clinical practice. The smaller post-angioplasty reduction in the loss of renal function in this group needs to be validated in a prospective, randomized study
Management of hepatitis C virus (HCV) infection in drug substitution programs
No full textIn Switzerland, intravenous drug use (IDU) accounts for 80% of newly acquired hepatitis C virus (HCV) infections. Early HCV treatment has the potential to interrupt the transmission chain and reduce morbidity/mortality due to decompensated liver cirrhosis and hepatocellular carcinoma. Nevertheless, patients in drug substitution programs are often insufficiently screened and treated
Analysis of cell to module losses and UV radiation hardness for passivated emitter and rear cells and modules
No full textThis work presents an experimental analysis and analytical modeling of cell to module losses for passivated emitter and rear cells (PERC), which enables to build a PERC solar module with a record efficiency of 20.2%. Further, it examines the ultraviolet radiation hardness of solar modules employing crystalline silicon (c-Si) solar cells featuring dielectric passivation layers.
Passivated emitter and rear cells are on the transition to mass production and expected to become the dominating c-Si solar cell technology in terms of market share in the next few years. Thus, it is of major importance to implement these high efficiency PERC into high efficiency solar modules. When transferring solar cells into a solar module additional recombination, optical, and resistive losses reduce the power of the solar module compared to the power of the solar cell, termed cell to module losses. In this work we study the individual recombination, optical, and resistive characteristics of various cell and module test samples. Based on our experimental results we develop an analytical model that allows to simulate the cell to module losses and reproduces the measurement results of test modules within the measurement uncertainty. We show that a reduction of the cell to module losses requires an adaptation of both, the solar cell as well as the solar module components. We employ the analytical model to improve the cell's front metalization, cell interconnection, light harvesting and cell spacing to reduce the cell to module losses for passivated emitter and rear cells and build an industrial like 60-cell sized solar module with a record power conversion efficiency of 20.2%.
Besides the efficiency, the long-term reliability of solar modules is crucial and a performance degradation of new promising technologies can impair their importance for the industry. The application of new metalization pastes that enable to contact lowly doped emitters, increases the spectral response of a PERC in the UV wavelength range. This requires the application of new encapsulation materials with enhanced UV transmittance for PERC solar modules. We report on the UV radiation hardness of solar modules featuring PERC with various silicone nitride passivation layers and employing different encapsulation polymers. Our results reveal that employing polymers with increased UV transparency results in a solar module power loss of 14%. We show that the degradation in module power is due to a reduction of the module's open circuit voltage. This loss is related to an increased charge carrier recombination in the cell, which we ascribe to a degradation of the amorphous silicon nitride (SiN) surface passivation. We develop a novel analytical model to describe the effect of high energetic photons on the solar module performance with a critical energy to deteriorate the surface passivation
Impact of Ag Pads on the Series Resistance of PERC Solar Cells
No full textAbstractScreen-printed passivated emitter and rear cells (PERC) require Ag pads on the rear side to enable solderable connections for module integration. These Ag pads are separated from the silicon by a dielectric layer to avoid recombination of minority charge carriers. The drawback of this configuration is an elongated transport path for the majority charge carriers generated above the pads. This results in an increase in series resistance. The strength of this effect depends on charge carrier generation above the Ag pads that critically depends on shading of the cell's front side. Ag pads are usually wider than the busbars or the interconnector ribbons and thus are only partially shaded. We build PERC test structures with various rear side configurations of Ag and Al screen printing as well as with and without laser contact openings (LCO). Using experiments and finite element simulations we investigate the impact of shading the Ag pads by the busbars and other means. While fully shaded regions do not increase the lumped solar cell's series resistance, unshaded Ag pads lead to an increase of about 37%
HCV treatment for prevention among people who inject drugs: Modeling treatment scale-up in the age of direct-acting antivirals.
No full textUNLABELLED: Substantial reductions in hepatitis C virus (HCV) prevalence among people who inject drugs (PWID) cannot be achieved by harm reduction interventions such as needle exchange and opiate substitution therapy (OST) alone. Current HCV treatment is arduous and uptake is low, but new highly effective and tolerable interferon-free direct-acting antiviral (DAA) treatments could facilitate increased uptake. We projected the potential impact of DAA treatments on PWID HCV prevalence in three settings. A dynamic HCV transmission model was parameterized to three chronic HCV prevalence settings: Edinburgh, UK (25%); Melbourne, Australia (50%); and Vancouver, Canada (65%). Using realistic scenarios of future DAAs (90% sustained viral response, 12 weeks duration, available 2015), we projected the treatment rates required to reduce chronic HCV prevalence by half or three-quarters within 15 years. Current HCV treatment rates may have a minimal impact on prevalence in Melbourne and Vancouver (<2% relative reductions) but could reduce prevalence by 26% in 15 years in Edinburgh. Prevalence could halve within 15 years with treatment scale-up to 15, 40, or 76 per 1,000 PWID annually in Edinburgh, Melbourne, or Vancouver, respectively (2-, 13-, and 15-fold increases, respectively). Scale-up to 22, 54, or 98 per 1,000 PWID annually could reduce prevalence by three-quarters within 15 years. Less impact occurs with delayed scale-up, higher baseline prevalence, or shorter average injecting duration. Results are insensitive to risk heterogeneity or restricting treatment to PWID on OST. At existing HCV drug costs, halving chronic prevalence would require annual treatment budgets of US 50 million in Melbourne and Vancouver. CONCLUSION: Interferon-free DAAs could enable increased HCV treatment uptake among PWID, which could have a major preventative impact. However, treatment costs may limit scale-up, and should be addressed.<br/
Three Bypass Diodes Architecture at the Limit Publisher
No full textIn this work, we demonstrate that partial shading of one solar cell in a state-of-the-art monocrystalline photovoltaic module with three bypass diodes results in hot cells with critical peak temperatures of 164 °C. We examine two solar modules in the IEC 61215-2 MQT 09 hot-spot endurance test, one with 367.3 WP featuring 72 full-cells and the other with 388.6 WP featuring 144 half-cells. For the solar module with 72 solar cells, we measure a maximum temperature of 164 °C, which results in a degradation of the encapsulation material and increases the risk of solar module failure. The high temperature results from the hot cell effect due to the power dissipation in the reverse-biased solar cell caused by partial shading. Our experiments show that the half-cell solar module is advantageous in terms of solar cell shading compared to the full-cell solar module. Although the half-cell solar module has a higher power output than the full-cell solar module, we measure a cooler peak temperature of 150 °C. However, under certain shading conditions, the half-cell solar module can exhibit similar temperatures as the full-cell solar module. Based on our experimental results, we develop an electrical and a thermal model to predict the temperature of novel high-power solar modules with solar cells from larger silicon wafer formats in case of partial cell shading. Our predictions consider the trends of further increasing solar cell and module efficiencies, larger silicon wafer formats, and larger solar modules. We simulate a maximum peak temperature of 176 °C at the solar module's surface, which significantly increases the risk of solar module failure. Our results show that new high-power solar modules employing solar cells that are made from larger silicon wafer formats need a new protection against overheating. Three bypass diodes per solar module are no longer sufficient
