Abstract
The properties and performance of polycrystalline materials depend critically on the properties of their grain boundaries. Polycrystalline photovoltaic materials – e.g. hybrid halide ...perovskites, copper indium gallium diselenide (CIGSe) and cadmium telluride – have already demonstrated high efficiencies and promise cost-effective electricity supply. For CIGSe-based solar cells, an efficiency above 23% has recently been achieved using an alkali-fluoride post-deposition treatment; however, its full impact and functional principle are not yet fully understood. Here, we show direct evidence for the passivation of grain boundaries in CIGSe treated with three different alkali-fluorides through a detailed study of the nanoscale optoelectronic properties. We determine a correlation of the surface potential change at grain boundaries with the open-circuit voltage, which is supported by numerical simulations. Our results suggest that heavier alkali elements might lead to better passivation by reducing the density of charged defects and increasing the formation of secondary phases at grain boundaries.
We investigated the impact of defect states on the measured forward current-voltage (<inline-formula> <tex-math notation="LaTeX">{I} </tex-math></inline-formula>-<inline-formula> <tex-math ...notation="LaTeX">{V} </tex-math></inline-formula>) curves of ion-implanted planar 4H-SiC p-i-n diodes of a different anode dimension by means of a fine-tuned numerical model. Cross sections and activation energies of defects related to the carbon vacancy (EH 6/7 and Z 1/2 ) and Titanium (Ti) impurity used in our model were experimentally identified in the diodes of the same batch. We analyzed the effect of each individual defect on the I-V curves and estimated the unknown hole capture cross sections by ensuring the optimal match between simulated and measured currents. Small discrepancies between measured and simulated forward current-voltage curves of diodes of equal shape but a different perimeter-to-area ratio has been accounted for by considering, in the simulations, the presence of a fixed positive charge at the diode surface. By using this procedure, diodes of every dimension have been simulated without the use of adjustment parameters. These results are valuable in understanding the role of defects in the I-V curves of the ion-implanted SiC diode.
This work presents a library of microgrid (MG) component models integrated in a complete university campus MG model in the Simulink/MATLAB environment. The model allows simulations on widely varying ...time scales and evaluation of the electrical, economic, and environmental performance of the MG. The models include photovoltaic (PV) generation (with MPPT control), battery storage (including charge/discharge control), loads (campus buildings and outdoor lighting), electric vehicle charging stations, and interconnections. The campus MG model is shown to be useful for (i) week-long simulations throughout the year, to analyze seasonal differences; (ii) year-long simulations for the estimation of overall economic and environmental impacts; (iii) MG islanded-mode simulations. The model is an agile tool for planning the deployment and penetration of photovoltaic plants and battery storage, with consideration of economic and environmental (carbon footprint) aspects.
In this study we perform an extensive campaign of numerical simulations of thin-film solar cell structures aimed at investigating how the conduction band offsets at buffer/window (ΔBW) and ...buffer/absorber (ΔAB) heterojunctions and the thickness and doping of the buffer layer combine to affect the performance parameters (Jsc, Voc, FF and η). For the two scenarios of ideal (i.e., without traps) and non-ideal (with traps) buffer/absorber interface, we vary ΔAB and ΔBW in the range −0.5eV to 0.5eV, and analyze, for each combination, the physical mechanisms limiting the cell performance and the way to optimize it by choosing optimal buffer doping and thickness. We show that assuming ΔAB as the main indicator for the potential performance of a cell can be misleading because ΔBW can heavily influence performance, even when ΔAB is positive (conduction band higher in the buffer than in the absorber) and near to its theoretical optimal value (0.3eV). However, we also show that ΔAB<0 (conduction band lower in the buffer than in the absorber) is usually coupled with an efficiency loss that is even worse if ΔBW>0. We verify our findings by simulating several examples of CIGS-based solar cells with different buffer layers (CdS, Zn1−xMgxO, In2S3, Zn(O,S)) taken from the literature; these comparisons confirm the validity of our results and suggest that the combination of ΔAB and ΔBW is the predominant factor in the design of high-efficiency solar cells. We finally propose simple quantitative guidelines for thin-film solar cell design and optimization.
•We simulate thin-film solar cells with a window/buffer/absorber structure.•We study the effect of conduction band offsets (CBOs) on performance.•The buffer/absorber CBO is not the sole parameter impacting on performance.•The window/buffer CBO is shown to play a major role.•When applied to published experimental data our model shows a good match.
•Stent-assisted coiling of ruptured intracranial aneurysms is a feasible option in selected cases.•Peri- and post-procedural medical treatment regimen is still controversial.•Bail-out AntiGP2b3a are ...extremely effective in achieving complete flow restoration after stent thrombosis without increasing overall complication rate.
To assess efficacy, safety and to discuss optimal medical therapy of stent-assisted coiling of ruptured intracranial aneurysms.
Ruptured intracranial aneurysms treated with stent-assisted coiling in eight different institutions were retrospectively reviewed. Medical treatment regimens varied among the centers, mainly regarding heparin administration and post-procedural single or double antiplatelet therapy. Clinical and angiographic results, including complications and outcomes were analyzed and related to the different therapies.
Sixty-one consecutive patients (male/female 23/38), aged 59.1 years (36–86) underwent stent-assisted coiling for ruptured intracranial aneurysm without antiplatelet pre-medication. Intravenous acetylsalicylic acid (ASA) 500mg was administered to all patients immediately after stent deployment. At the same time heparin was given as bolus in 15 patients (24.6%) as part of local protocol. Intravenous glycoprotein 2b/3a inhibitors (antiGP2b3a) were used as bail-out therapy for stent thrombosis. Stent thrombosis occurred in 22 patients (36.1%), of which 4 (6.5%) lead to incomplete and 18 (29.6) to complete occlusion of the stent. Heparin administration had no effect on thrombosis rate. Thrombosis resolution occurred in all cases with intravenous antiGP2b3a (7 tirofiban, 15 abciximab), without increasing overall complication rate. Single antiplatelet therapy with ASA (28 patients, 45.9%) or double antiplatelet therapy including ASA and clopidogrel (33 patients, 54.1%) were administered after procedure, depending on local protocols and on neurointerventionists’ experience. Overall complication rate, including ischemia and hemorrhage was higher in patients in which only ASA was administered (21.4% vs. 12.1%). No late stent thrombosis was seen, regardless of whether a single or double antiplatelet regimen was used. Nevertheless, the small sample size suggests caution in interpreting these results. Moreover, a possible bias may arise from the decision whether to modify the maintenance therapy or not depending on the severity of the intracranial hemorrhage in a case-by-case assessment. At three months, 34 out of 38 patients with HH grade 1-2 (89.4%), and 11 out of 23 with Hunt-Hess grade of 3-4 (47.8%) were independent (Modified Ranking Scale 0-2).
Stent assisted coiling of ruptured intracranial aneurysms is a feasible option when simple coiling is not possible. Optimal medical treatment is still controversial because balance between hemorrhagic and ischemic risks is difficult to evaluate. In our series, heparin bolus had no effect on subsequent stent thrombosis. In all cases peri-operative stent thrombosis was successfully managed using bail-out intravenous antiGP2b3a, which did not increase post-procedural hemorrhage rates. A non-significant trend towards increased complications rate was noticed in patients treated with single antiplatelet therapy versus double antiplatelet therapy.
Wide-necked brain aneurysms therapy remains a challenge for neurointerventionalists, mainly for the high recurrence rate. Low-profile stents make feasible the treatment of these aneurysms. In our ...multicenter series we analyzed clinical and angiographic results of Neuroform Atlas stent-assisted coiling.
From January 2016 to March 2017, 113 wide-necked aneurysms were discovered with CTA, MRA and DSA. The Atlas stent-assisted coiling procedures were performed under general anesthesia with sequential or jailing techniques. Six months follow-up DSA was performed to assess the recurrence rate through the modified Raymond-Roy occlusion scale (RROC). Moreover, patients were evaluated clinically to analyse the degree of disability according to the mRS. MRI was performed at 12 months evaluating both the cerebral tissue and the vessels.
In all the procedures it was feasible to navigate the Neuroform Atlas to the goal vessel and deploy the stent across the aneurysmal neck. Intra-procedural complications account for the 6.2% (7/113). The immediate occlusion rate was RROC 1 in 88%, 2 in 9% and 3 in 3% of cases. The 6 months clinical data showed mRS Score 0–1 in 96.5% of patients; 3 patients died of complications related to SAH. The 12 months follow-up showed RROC of 1 in 82%, 2 in 13% and 3 in 5% of cases. No aneurysm has been retreated.
In our multicenter experience the Neuroform Atlas stent assisted-coiling has shown to be a safe and effective technique for the treatment of wide-necked intracranial aneurysms with encouraging clinical and angiographic results.
The rehabilitation of paretic stroke patients uses a wide range of intervention programs to improve the function of impaired upper limb. A new rehabilitative approach, called action observation ...therapy (AOT) is based on the discovery of mirror neurons and has been used to improve the motor functions of adult stroke patients and children with cerebral palsy. Recently, virtual reality (VR) has provided the potential to increase the frequency and effectiveness of rehabilitation treatment by offering challenging and motivating tasks. METHODS: The purpose of the present project is to design a randomized controlled six-month follow-up trial (RCT) to evaluate whether action observation (AO) added to standard VR (AO + VR) is effective in improving upper limb function in patients with stroke, compared with a control treatment consisting of observation of naturalistic scenes (CO) without any action content, followed by VR training (CO + VR).
AO + VR treatment may provide an addition to the rehabilitative interventions currently available for recovery after stroke and could be utilized within standard sensorimotor training or in individualized tele-rehabilitation.
The trial has been prospectively registered on ClinicalTrials.gov. NCT05163210 . 17 December 2021.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Structural defects such as voids and compositional inhomogeneities may affect the performance of Cu(In,Ga)Se
2
(CIGS) solar cells. We analyzed the morphology and elemental distributions in ...co-evaporated CIGS thin films at the different stages of the CIGS growth by energy-dispersive x-ray spectroscopy in a transmission electron microscope. Accumulation of Cu-Se phases was found at crevices and at grain boundaries after the Cu-rich intermediate stage of the CIGS deposition sequence. It was found, that voids are caused by Cu out-diffusion from crevices and GBs during the final deposition stage. The Cu inhomogeneities lead to non-uniform diffusivities of In and Ga, resulting in lateral inhomogeneities of the In and Ga distribution. Two and three-dimensional simulations were used to investigate the impact of the inhomogeneities and voids on the solar cell performance. A significant impact of voids was found, indicating that the unpassivated voids reduce the open-circuit voltage and fill factor due to the introduction of free surfaces with high recombination velocities close to the CIGS/CdS junction. We thus suggest that voids, and possibly inhomogeneities, limit the efficiency of solar cells based on three-stage co-evaporated CIGS thin films. Passivation of the voids' internal surface may reduce their detrimental effects.
Issues remain on the optimal management of subarachnoid hemorrhage (SAH) patients once they are admitted to the referring center, before and after the aneurysm treatment. To address these issues, we ...created a consensus of experts endorsed by the Italian Society of Anesthesia and Intensive Care (SIAARTI). In this manuscript, we aim to provide a list of experts' recommendations regarding the early management of SAH patients from hospital admission, in a center with neurosurgical/neuro-endovascular facilities, until securing of the bleeding aneurysm.
A multidisciplinary consensus panel composed of 24 physicians selected for their established clinical and scientific expertise in the acute management of SAH patients with different background (anesthesia/intensive care, neurosurgery, and interventional neuroradiology) was created. A modified Delphi approach was adopted.
Among 19 statements discussed. The consensus was reached on 18 strong recommendations. In one case, consensus could not be agreed upon and no recommendation was provided.
This consensus provides practical recommendations for the management of SAH patients in hospitals with neurosurgical/neuroendovascular facilities until aneurysm securing. It is intended to support clinician's decision-making and not to mandate a standard of practice.
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