Perovskite solar cells: short lifetime and hysteresis behaviour of current–voltage characteristics

Perovskite solar cells have shown an impressive efficiency improvement over the past ~ 10 years achieving ~ 23% to date. However, the lifetime and instability of device characteristics are real issues to understand and solve before scaling up and commercialisation of these devices. Researchers have attempted to understand the hysteresis behaviour of current–voltage (I–V) curves in terms of mechanisms such as migration of several ions across the device and the effects of electronic defects during measurements. This review contributes to this scientific debate by presenting similar behaviour observed and reported for devices based on inorganic semiconductors. In established inorganic semiconductor thin film solar cells, both short lifetime and hysteresis have been observed, described and understood in terms of effects of numerous electronic defect levels. Therefore, the situation may be very similar and it is important to identify and reduce defects to remove this un-desirable behaviour from perovskite solar cells. After considering the wealth of experimental results reported in the literature, the conclusion made is the dominating mechanism of I–V hysteresis is due to electronic defects available within the device structure. Suggestions have been made for potential researchers to experimentally investigate the phenomenon in order to finally put an end to this debate. As the defect levels and their concentrations are reduced, the initial efficiency, stability and the lifetime of perovskite solar cells should improve further, beyond the current situation

Open Social Learning Network

This paper considers the affordances of social networking theories and tools to build new and effective e-learning practices. We argue that “connectivism” (social networking applied to learning and knowledge contexts) can lead to a reconceptualization of learning in which formal and non-formal learning can be integrated as to build a potentially lifelong learning activities to be experienced in “personal learning environments”. In order to provide a guide in the design, development and improvement both of personal learning environments and in the related learning activities we provide a knowledge flow model called Open Social Learning Network (OSLN) —a hybrid of the LMS and the personal learning environment (PLE)—is proposed as an alternative learning technology environment with the potential to leverage the affordances of the Web to improve learning dramatically and  highlighting the stages of learning and the related enabling conditions. The derived model is applied in a possible scenario of formal learning in order to show how the learning process can be designed according to the presented theory. Keywords: Open Social Learning Network OSLN, Learning Theory, Connectivism, Networked Learnin, Collaboration Technologies, Collaborative Learning and Relationship Classification.

The influence of V addition on the structure, mechanical properties, and oxidation behaviour of TiAlSiN coatings deposited by DC magnetron sputtering

The influence of V content on the morphology, structure, hardness (H) and reduced Young's modulus (E), adhesion, and oxidation resistance of TiAlSiN coatings is investigated. The coatings were produced by DC reactive magnetron sputtering, with increasing V contents from 0, 4.8 and 11.0 at.%. All coatings exhibit a fcc type structure. The coating with 4.8 at.% of V shows the highest values of H and E, whereas the values are similar for the reference coating and the coating with 11.0 at.% of V. The coatings adhere well to the substrates and show a dense and compact columnar growth extending from the adhesive interlayer to the top surface of the coatings. The dynamic thermal gravimetric oxidation curves reveal that V additions decreases the onset point of oxidation significantly and degrades the oxidation resistance of the coatings. A dual oxide layer is formed on the top surface of the reference coating: an outer porous Ti–Al–O rich layer with plate-like features on the top, which classified to TiO2 (rutile and anatase) and Al2O3 phases, and an inner Ti–Si–O rich layer with Al depletion that identified as mixture of amorphous Si–O and Ti–Si–O protective oxides. The diffusion of V to the top surface governs the oxidation process of the V-containing coatings, i.e. increasing V concentration leads to disrupt the formation of the protective continuous oxide layers easily.This research is sponsored by national funds through FCT e Fundação para a Ciência e a Tecnologia, under the projects: UIDB/00285/2020, SMARTLUBdref. “POCI-01-0145-FEDER-031-807”. MCTool21 project “Manufacturing of cutting tools for the 21st century: from nano-scale material design to numerical process simulation” (reference: POCI-01-0247-FEDER-045940), co-financed by the European Regional Development Fund, through Portugal 2020 (PT2020), and by the Competitiveness and Internationalization Operational Programme (COMPETE 2020).info:eu-repo/semantics/publishedVersio

Solving The Problem of Adaptive E-Learning By Using Social Networks

This paper propose an enhanced E-Learning Social Network Exploiting Approach focused around chart model and clustering algorithm, which can consequently gathering dispersed e-learners with comparative premiums and make fitting suggestions, which can at last upgrade the collective learning among comparable e-learners. Through closeness revelation, trust weights overhaul and potential companions change, the algorithm actualized a programmed adjusted trust association with progressively upgraded fulfillments. Keywords: Relations, Adaptive E-Learning, Clustering , Social Network , E-learning ,  and Collaborative Learnin

Betawi Ulama's Perception of The XXI Century Against Contraception Law Controversy in Population Control

Legal issues regarding contraception and population control efforts to limit births and reduce overcrowding have not been without controversy. Differences in using naqli arguments and scientific, medical, and even political arguments make the discourse on family planning still hotly debated. This research will identify how Betawi Ulama's response in the XXI century to the law on the use of contraceptives and birth control through population control, along with the arguments and legal methods, they used to analyze the factors behind it and collect theoretical and empirical data related to social impacts/implications, from the Betawi Ulama's response to enacting the law on contraception and population control. The conclusion of this study will explain the positions, thoughts, and religious perspectives of Betawi Ulama in understanding various problems of Islamic law. Tend to think that is exclusive, inclusive, or moderate, especially in addressing the controversies of family planning law? This study took the capital city of DKI Jakarta as the sampling location, considering that the densest population in the country is in Jakarta, and it is very heterogeneous in terms of diversity and community characteristics. Population census data in 2010 shows that the capital city of DKI Jakarta is the largest city with the most populous population in Indonesia, around 9.6 million people. This research uses logical thinking, analysis with logic, induction, deduction, analogy, comparison and the like. The data in this study will be obtained through observation techniques, in-depth interviews with resource persons, and documentation

General practitioners\u27 knowledge and approach to chronic kidney disease in Karachi, Pakistan

Due to lack of adequate number of formally trained nephrologists, many patients with chronic kidney disease (CKD) are seen by general practitioners (GPs). This study was designed to assess the knowledge of the GPs regarding identification of CKD and its risk factors, and evaluation and management of risk factors as well as complications of CKD. We conducted a cross-sectional survey of 232 randomly selected GPs from Karachi during 2011. Data were collected on a structured questionnaire based on the kidney disease outcomes and quality initiative recommendations on screening, diagnosis, and management of CKD. A total of 235 GPs were approached, and 232 consented to participate. Mean age was 38.5 ± 11.26 years; 56.5% were men. Most of the GPs knew the traditional risk factors for CKD, i.e., diabetes (88.4%) and hypertension (80%), but were less aware of other risk factors. Only 38% GPs were aware of estimated glomerular filtration rate in evaluation of patients with CKD. Only 61.6% GPs recognized CKD as a risk factor for cardiovascular disease. About 40% and 29% GPs knew the correct goal systolic and diastolic blood pressure, respectively. In all, 41% GPs did not know when to refer the patient to a nephrologist. Our survey identified specific gaps in knowledge and approach of GPs regarding diagnosis and management of CKD. Educational efforts are needed to increase awareness of clinical practice guidelines and recommendations for patients with CKD among GPs, which may improve management and clinical outcomes of this population

Complication rate and diagnostic yield of percutaneous native kidney biopsies: A 10-year experience at a Tertiary Care Hospital in Pakistan

The use of an automated biopsy device, and real-time ultrasound for percutaneous kidney biopsies (PKBs) has improved the likelihood of obtaining adequate tissue for diagnosis and also has reduced the complications associated with the procedure. We aimed to determine the frequency and type of complications associated with PKB and to determine the diagnostic yield. It was a retrospective file-based review of cases who underwent PKB of native kidney between January 2003 and December 2013 at the Aga Khan University Hospital in Karachi, Pakistan. PKBs were performed by trained nephrologists or radiologists using an automated device with a 16/18-gauge needle under real-time ultrasound. The data obtained included age, gender, clinical and histopathological diagnosis, and complications associated with the procedure (minor: hematuria, local infections, and hematoma; major: transfusions, severe infections, surgery, nephrectomy, arteriography, embolism, and death. Yield of the procedure was based on the number of glomeruli obtained. Patients having major complications were compared with the patients who had minor or no complications. A total of 433 native kidney biopsies were performed. The mean age of the patients was 41 ± 15.9 years, and 58% of the patients were male. The main histological findings were membranoproliferative glomerulonephritis (17.6%) followed by focal and segmental glomerulosclerosis (16.4%) and interstitial nephritis (13.9%). Majority of the procedures were performed by nephrologists (67.4%). The overall complication rate was 14.2%. Among those, 21 patients (4.8%) had a major complication while the others had minor complications. Of those who had a major complication, 17 patients required blood transfusion(s) and had hematuria or a major hematoma, three had prolonged hospitalization \u3e24 hours, and one patient required surgical intervention. Only 10 procedures (2.3%) had inadequate tissue to establish the histopathologic diagnosis. PKB under real-time ultrasound guidance is a safe and efficacious procedure to establish the histological diagnosis of the renal disease

Histopathological changes and antioxidant responses in common carp (Cyprinus carpio) exposed to copper nanoparticles

This is the author accepted manuscript. The final version is available from Taylor & Francis via the DOI in this recordDespite the rapid increase of nanotechnology in a wide array of industrial sectors, the biosafety profile of nanomaterials remains undefined. The accelerated use of nanomaterials has increased the potential discharge of nanomaterials into the environment in different ways. The aquatic environment is mainly susceptible as it is likely to act as an ultimate sink for all contaminants. Therefore, this study assessed the toxicological impacts of waterborne engineered copper nanoparticles (Cu-NPs) on histology, lipid peroxidation (LPO), catalase (CAT), and glutathione (GSH) levels in the gills of common carp (Cyprinus carpio). Nanoparticles were characterized by XRD and SEM techniques. Before starting the sub-acute toxicity testing, 96 h LC50 of Cu-NPs for C. carpio was calculated as 4.44 mg/l. Then based on LC50, C. carpio of 40–45 g in weight were exposed to three sub-lethal doses of waterborne engineered Cu-NPs (0 or 0.5 or 1 or 1.5 mg/l) for a period of 14 days. The waterborne Cu-NPs have appeared to induce alterations in gill histology and oxidative stress parameters in a dose-dependent manner. The gill tissues showed degenerative secondary lamellae, necrotic lamella, fused lamella, necrosis of the primary and secondary lamella, edema, complete degeneration, epithelial lifting, degenerative epithelium, and hyperplasia in a dose-dependent manner. In the gill tissues, waterborne Cu-NPs caused a decreased level of CAT and elevated levels of LPO, and GSH in the fish exposed to the highest dose of 1.5 mg Cu-NPs/l of water. Our results indicate that the exposure to waterborne Cu-NPs was toxic to the aquatic organisms as shown by the oxidative stresses and histological alterations in C. carpio, a freshwater fish of good economic value

Feasibility of state of the art PET/CT systems performance harmonisation

Purpose The objective of this study was to explore the feasibility of harmonising performance for PET/CT systems equipped with time-of-flight (ToF) and resolution modelling/point spread function (PSF) technologies. A second aim was producing a working prototype of new harmonising criteria with higher contrast recoveries than current EARL standards using various SUV metrics. Methods Four PET/CT systems with both ToF and PSF capabilities from three major vendors were used to acquire and reconstruct images of the NEMA NU2-2007 body phantom filled conforming EANM EARL guidelines. A total of 15 reconstruction parameter sets of varying pixel size, post filtering and reconstruction type, with three different acquisition durations were used to compare the quantitative performance of the systems. A target range for recovery curves was established such that it would accommodate the highest matching recoveries from all investigated systems. These updated criteria were validated on 18 additional scanners from 16 sites in order to demonstrate the scanners' ability to meet the new target range. Results Each of the four systems was found to be capable of producing harmonising reconstructions with similar recovery curves. The five reconstruction parameter sets producing harmonising results significantly increased SUVmean (25%) and SUVmax (26%) contrast recoveries compared with current EARL specifications. Additional prospective validation performed on 18 scanners from 16 EARL accredited sites demonstrated the feasibility of updated harmonising specifications. SUVpeak was found to significantly reduce the variability in quantitative results while producing lower recoveries in smaller ( Conclusions Harmonising PET/CT systems with ToF and PSF technologies from different vendors was found to be feasible. The harmonisation of such systems would require an update to the current multicentre accreditation program EARL in order to accommodate higher recoveries. SUVpeak should be further investigated as a noise resistant alternative quantitative metric to SUVmax

Plane Localization in 3-D Fetal Neurosonography for Longitudinal Analysis of the Developing Brain.

The parasagittal (PS) plane is a 2-D diagnostic plane used routinely in cranial ultrasonography of the neonatal brain. This paper develops a novel approach to find the PS plane in a 3-D fetal ultrasound scan to allow image-based biomarkers to be tracked from prebirth through the first weeks of postbirth life. We propose an accurate plane-finding solution based on regression forests (RF). The method initially localizes the fetal brain and its midline automatically. The midline on several axial slices is used to detect the midsagittal plane, which is used as a constraint in the proposed RF framework to detect the PS plane. The proposed learning algorithm guides the RF learning method in a novel way by: 1) using informative voxels and voxel informative strength as a weighting within the training stage objective function, and 2) introducing regularization of the RF by proposing a geometrical feature within the training stage. Results on clinical data indicate that the new automated method is more reproducible than manual plane finding obtained by two clinicians