An investigation into solid dielectrics

Direct measurement techniques for the investigation of electrical processes in solid dielectrics are reviewed and their respective strengths and weaknesses are discussed, particularly the complementary nature of thermally stimulated current measurements. The successful design and construction of a new Thermally Stimulated Discharge Current (TSDC) Spectrometer at the University of Southampton is presented and its correct function validated with experimental measurements of the well known and often characterized synthetic polymers low density polyethylene (LDPE) and polyethylene terephtalate (PET). Results were found to correspond well to published data. First TSDC observations of filled and oil impregnated papers are presented.The second aspect of this work is the investigation of natural polymer insulation materials,specifically paper for oil-paper insulation systems. For the first time, electrical insulation papers with filler contents up to 50% were investigated. Bentonite and talcum were compared as filler materials and found to have negative and positive effects respectively.The superior electrical strength of a talcum filled kraft paper was verified, and a series of constructive modifications was undertaken to further maximise its electrical strength at comparable or improved dielectric performance. An increase in electrical breakdown strength of 20% to 30% has been observed, but the substitution of such great amounts of fiber with fillers also lead to a reduction in mechanical strength of the paper. Further trials with chemical additives were conducted to counteract this effect and polyvinyl alcohol and starch were found to enhance the paper strength. Additional trials also comprised sizing agents, guar gum and wet strength agents. Uncharged or slightly charged chemical additives provided best results with regard to dielectric performance. The significance of the trialled paper modifications is judged in light of statistical analysis

Dietary change and land use change: assessing preventable climate and biodiversity damage due to meat consumption in Germany

Land use change (LUC) is responsible for a large share of the emissions of anthropogenic greenhouse gases (GHGs) and is a major driver of global biodiversity loss. Although much of the global LUC-related CO2 emissions and biodiversity loss occur in tropical countries, the actual drivers of this LUC can be located in the global North, particularly through the import of large quantities of agricultural commodities. The aim of this study is to quantify and monetize the LUC-related impacts of the consumption of animal-based food products in Germany and subsequently explore the potential benefits of transitioning to diets with lower dependence on animal-based products. We calculate the LUC-related impacts of consumption of animal-based products in Germany through a modeling approach that combines models for land balance, emissions, and physical trade. We determine the LUC-related CO2 emissions of this consumption, as well as the deforested area and associated impacts on biodiversity loss. Following the true cost accounting approach (TCA), the LUC-related impacts are monetized to estimate the external costs of the German consumption of animal-based products. Our results show that the consumption of these products is responsible for the deforestation of 16.4 kha annually in the period between 2013 and 2016. Out of the six analyzed animal-based product groups, the largest shares of deforestation are associated with milk (35%) and pork (33%) consumption. However, beef meat consumption has the highest relative LUC-related CO2 emissions at 0.75 tCO2 per ton. The LUC-related externalities of the German meat-based product consumption incur annually societal costs of EUR 1.1 billion (plus EUR 0.5 billion for biodiversity loss). The results also show that the animal-based products imported in Germany have only slightly higher LUC-related CO2 emissions than those produced within Germany. Overall, there is a great urgency for policy measures and shifts in consumer behavior to ensure that the consumption of animal-based products in Germany does not have unacceptably high negative sustainability impacts

Percutaneous transhepatic or endoscopic ultrasound-guided biliary drainage in malignant distal bile duct obstruction using a self-expanding metal stent: Study protocol for a prospective European multicenter trial (PUMa trial)

Background Endoscopic ultrasound-guided biliary drainage (EUS-BD) was associated with better clinical success and a lower rate of adverse events (AEs) than fluoroscopy-guided percutaneous transhepatic biliary drainage (PTBD) in recent single center studies with mainly retrospective design and small case numbers (< 50). The aim of this prospective European multicenter study is to compare both drainage procedures using ultrasound-guidance and primary metal stent implantation in patients with malignant distal bile duct obstruction (PUMa Trial). Methods The study is designed as a non-randomized, controlled, parallel group, non-inferiority trial. Each of the 16 study centers performs the procedure with the best local expertise (PTBD or EUS-BD). In PTBD, bile duct access is performed by ultrasound guidance. EUS-BD is performed as an endoscopic ultrasound (EUS)-guided hepaticogastrostomy (EUS-HGS), EUS-guided choledochoduodenostomy (EUS-CDS) or EUS-guided antegrade stenting (EUS-AGS). Insertion of a metal stent is intended in both procedures in the first session. Primary end point is technical success. Secondary end points are clinical success, duration pf procedure, AEs graded by severity, length of hospital stay, re-intervention rate and survival within 6 months. The target case number is 212 patients (12 calculated dropouts included). Discussion This study might help to clarify whether PTBD is non-inferior to EUS-BD concerning technical success, and whether one of both interventions is superior in terms of efficacy and safety in one or more secondary endpoints. Randomization is not provided as both procedures are rarely used after failed endoscopic biliary drainage and study centers usually prefer one of both procedures that they can perform best

Vascular pattern and diagnostic accuracy of contrast-enhanced ultrasound (CEUS) in spleen alterations

BACKGROUND: Contrast-enhanced ultrasound (CEUS) has been used as an additional imaging technique in order to clarify rare focal splenic lesions (FSL). CEUS is a safe and cost-effective modality for assessment of perfusion. OBJECTIVE: To validate contrast enhancement pattern and evaluate the diagnostic accuracy of CEUS in unclear FSL. METHODS: CEUS examinations of the spleen in 50 patients between 2012 and 2018 were included in the study. Examinations were performed using B-mode, colour-coded Doppler ultrasound (CCDS) and CEUS after injection of sulphur hexafluoride microbubbles and interpreted in consensus by two experienced radiologists. Reference standard was defined as histopathological report and clinical course (treatment response, long term follow up). RESULTS: All patients were successfully examined by CEUS without an adverse reaction. CEUS presented the correct differentiation of benign and malignant alterations in 49/50 (98%). Lesion washout was found in all malignant but also 16.7% of all benign lesions. Matched to the histopathological report and clinical follow up, CEUS represented a sensitivity of 100% (95%-CI, 57-100), a specificity of 98% (95%-CI, 88-100), a positive predictive value (PPV) of 83% (95%-CI, 44-97) and a negative predictive value (NPV) of 100% (95%-CI, 92-100). CONCLUSION: CEUS may provide additional information by visualization of dynamic contrast enhancement pattern to differentiate benign and malignant lesions. Nevertheless, established criteria for malignancy (early enhancement or washout) in FSL should be considered with caution since they are also found in benign lesions

Nuclear structure of 82Kr and 82Se relevant for neutrinoless double-beta decay

Nuclear Resonance Fluorescence (NRF) experiments on the nuclei 82Kr and 82Se were performed, that are a candidates for a mother-daughter pair for the hypothetical neutrinoless double-beta (0νββ) decay. The experiment aimed at providing high-precision data to benchmark theoretical calculations of the nuclear matrix elements involved in this exotic decay mode. We have investigated the excitation energy range from 2.3MeV to 4.2MeV, where the nuclear scissors mode is expected to be located in nuclei of this mass region. Our experiment was able to constrain decay branches of the scissors mode down to a level of a few percents, comparable to previous experiments on heavy deformed 0νββ decay candidates. Reduced transition strengths of the magnetic dipole-excited states have been determined by a method that exploits the non-resonant background in the NRF spectra. They are compared to a calculation within the nuclear shell model for 82Se, which reveals their mixed orbital and spin character, hinting at a more complex microscopic structure of low-lying 1+ states

Nuclear structure of

Nuclear Resonance Fluorescence (NRF) experiments on the nuclei 82Kr and 82Se were performed, that are a candidates for a mother-daughter pair for the hypothetical neutrinoless double-beta (0νββ) decay. The experiment aimed at providing high-precision data to benchmark theoretical calculations of the nuclear matrix elements involved in this exotic decay mode. We have investigated the excitation energy range from 2.3MeV to 4.2MeV, where the nuclear scissors mode is expected to be located in nuclei of this mass region. Our experiment was able to constrain decay branches of the scissors mode down to a level of a few percents, comparable to previous experiments on heavy deformed 0νββ decay candidates. Reduced transition strengths of the magnetic dipole-excited states have been determined by a method that exploits the non-resonant background in the NRF spectra. They are compared to a calculation within the nuclear shell model for 82Se, which reveals their mixed orbital and spin character, hinting at a more complex microscopic structure of low-lying 1+ states