Deep Defects Research Articles

Role of nanoscale compositional inhomogeneities in limiting the open circuit voltage in Cu(In,Ga)S2 solar cells

As Si-based solar cell technologies approach their theoretical efficiency limits, alternative photovoltaic systems, such as tandem solar cells, are gathering increased attention due to their potential to reach higher efficiencies by better use of the solar spectrum. Cu(In,Ga)S2 (CIGS) is a promising material for the top cell due to its large, tunable bandgap energy (Eg), stability, and already established high efficiencies. However, the deficit in open circuit voltage is still large; therefore, an improved understanding of the efficiency losses is required. Scanning electron microscopy cathodoluminescence was used to study the role of the polycrystalline nature for radiative recombination in CIGS samples of varying Cu-content. Considerable differences between neighboring grains were observed in the emission energy and the emission intensity, with significant drops in emission energy at the grain boundaries. Lateral homogeneity in the near band edge (NBE) energy was found to reduce for samples with Cu-poor compositions, with its standard deviation halving (σNBE ∼ 20 meV) compared to the more stoichiometric films (σNBE ∼ 50 meV), which corresponds to an open circuit voltage loss contribution that is nearly an order of magnitude lower. Such inhomogeneities can be attributed mainly to local variations of the Ga concentration. Hence, the differences between the samples could be explained by the different deposition times at elevated temperature allowing for different extents of homogeneity. Thus, Cu-poor films are not only favorable because of lower concentrations of deep defects but also because of reduced bandgap variations.

Thermalization and relaxation mediated by phonon management in tin-lead perovskites

Understanding and control of ultrafast non-equilibrium processes in semiconductors is key to making use of the full photon energy before relaxation, leading to new ways to break efficiency limits for solar energy conversion. In this work, we demonstrate the observation and modulation of slow relaxation in uniformly mixed tin-lead perovskites (MASnxPb1-xI3 and CsSnxPb1-xI3 nanocrystals). Transient absorption measurements reveal that slow cooling mediated by a hot phonon bottleneck effect appears at carrier densities above ~1018 cm−3 for tin-lead alloy nanocrystals, and tin addition is found to give rise to suppressed cooling. Within the alloy nanoparticles, the combination of a newly introduced high-energy band, screened Fröhlich interaction, suppressed Klemens decay and reduced thermal conductivity (acoustic phonon transport) with increased tin content contributes to the slowed relaxation. For inorganic nanocrystals where defect states couple strongly with carriers, sodium doping has been confirmed to benefit in maintaining hot carriers by decoupling them from deep defects, leading to a decreased energy-loss rate during thermalization and an enhanced hot phonon bottleneck effect. The slow cooling we observe uncovers the intrinsic photophysics of perovskite nanocrystals, with implications for photovoltaic applications where suppressed cooling could lead to hot-carrier solar cells.

Clinical outcomes of periodontal regenerative therapy with carbonate apatite granules for treatments of intrabony defects, Class II and Class III furcation involvements: A 9-month prospective pilot clinical study

IntroductionCarbonated apatite (CO3Ap) has unique properties as an alloplastic bone substitute and has been reported the safety and efficacy for bone regeneration. However, no previous studies reported the clinical application of CO3Ap for periodontal regeneration therapy. The aim of this study was to evaluate the safety and efficacy of periodontal regeneration with CO3Ap in treating intrabony defects, Class II and Class III furcation involvement (FI). MethodsA single-arm and single-center prospective pilot clinical study was performed to verify the safety and efficacy of CO3Ap in patients with periodontitis. A total of four patients with seven teeth, including three deep intrabony defects, two Class II FI, and two Class III FI, were treated with CO3Ap. The clinical parameters, including probing pocket depth (PPD), clinical attachment level (CAL), bleeding on probing (BOP), tooth mobility (Mo), Plaque index (PI), and Gingival index (GI) were evaluated at baseline, 6 months, and 9 months after the surgery. Radiographic analysis was conducted on images of dental X-ray and cone beam computed tomography (CBCT) at baseline and 9 months post-surgery. ResultsThe postoperative healing in all cases was uneventful, with no abnormal bleeding, pain, or swelling. The mean PPD reduction and CAL gain were 5.0 ± 1.0 mm, 4.5 ± 0.7 mm, 1.5 ± 0.7 mm, and 4.7 ± 1.2 mm, 4.5 ± 0.7 mm, 0.0 mm for intrabony defect, Class II and Class III FI, respectively. According to radiographic analysis, linear bone height in intrabony defects and vertical subclassification of FI in Class II FI were improved. ConclusionsThe clinical application of CO3Ap for the treatment of intrabony defects and Class II FI could be effective for periodontal regeneration, although its efficacy in treating Class III FI might be limited. Despite the limitations of this study, the findings in this study suggested that CO3Ap has the potential to be a promising bone graft substitute for periodontal regeneration.

Perineal defect reconstruction after surgery for advanced or locally recurrent rectal cancer involving organ resection: Multiple flaps combined with lining repair.

The aim of this study was to investigate the efficacy of multiple perineal perforator flaps in repairing deep perineal defects after pelvic exenteration for locally advanced or recurrent rectal cancer. We investigated the outcomes of eight patients whose repairs involved a novel method of using an internal pudendal artery perforator (IPAP) flap combined with an inferior gluteal artery perforator (IGAP) flap. There were four male and four female patients with a mean age of 56 years (36-72 years). Bilateral IPAP flaps combined with bilateral IGAP flaps were used in five patients, unilateral IPAP flaps combined with bilateral IGAP flaps were used in two patients and bilateral IPAP flaps were used in one patient. There were no functional limitations in daily activities during the 6-month follow-up period. Our study showed that using multiple perineal perforator flaps combined with lining repair is feasible for repairing deep perineal defects in patients who have undergone rectal cancer surgery that includes pelvic exenteration.

Novel Osteochondral Biotemplate Improves Long-term Cartilage Repair Compared With Microfracture in an Ovine Model

Background: Current cartilage repair therapies do not re-create the complex mechanical interface between cartilage and bone, which is critical for long-term repair durability. New biomaterial designs that include hard tissue–soft tissue interface structures offer promise to improve clinical outcomes. Purpose/Hypothesis: The purpose of this study was to evaluate the efficacy and safety of a naturally derived osteochondral biotemplate with a novel contiguous hard tissue–soft tissue interface in an ovine model as a regenerative solution for articular cartilage defects. It was hypothesized that the osteochondral biotemplate would produce structurally superior repair tissue compared with microfracture over a 13-month period. Study Design: Controlled laboratory study. Methods: Osteochondral biotemplates were manufactured from porcine cancellous bone. Skeletally mature sheep (N = 30) were randomly allocated to 3 groups: early healing stage (euthanasia at 4 months), 6-month treatment, and 13-month treatment. In the early healing stage group, an 8 mm–diameter by 5 mm–deep osteochondral defect was created on the medial femoral condyle and treated at the time of iatrogenic injury with an osteochondral biotemplate. The contralateral limb received the same treatment 2 months later. In the 6- and 13-month treatment groups, 1 limb received the same osteochondral procedure as the early healing stage group. In the contralateral limb, an 8 mm–diameter, full-thickness cartilage defect (1-2 mm deep) was created and treated with microfracture. Cartilage repair and integration were quantitatively and qualitatively assessed with gross inspection, histological evaluation, and magnetic resonance imaging (MRI). Wilcoxon signed-rank and McNemar tests were used to compare the treatments. Results: At 6 and 13 months after treatment, the biotemplate was not present histologically. At 13 months, the biotemplate treatment demonstrated statistically higher histological scores than microfracture for integration with surrounding cartilage (biotemplate: 74 ± 31; microfracture: 28 ± 39; P = .03), type 2 collagen (biotemplate: 72 ± 33; microfracture: 40 ± 38; P = .02), total cartilage (biotemplate: 71 ± 9; microfracture: 59 ± 9; P = .01), and total integration (biotemplate: 85 ± 15; microfracture: 66 ± 20; P = .04). The osteochondral biotemplate treatment produced a notable transient nonneutrophilic inflammatory response that appeared to approach resolution at 13 months. MRI results were not statistically different between the 2 treatments. Conclusion: Even with the inflammatory response, after 13 months, the osteochondral biotemplate outperformed microfracture in cartilage regeneration and demonstrated superiority in integration between the repair tissue and host tissue as well as integration between the newly formed cartilage and the underlying bone. Clinical Relevance: This work has demonstrated the clinical potential of a novel biomaterial template to regenerate the complex mechanical interface between cartilage and the subchondral bone.

Quantitative analysis of defect states in InGaZnO within 2 eV below the conduction band via photo-induced current transient spectroscopy

This work investigates the function of the oxygen partial pressure in photo-induced current measurement of extended defect properties related to the distribution and quantity of defect states in electronic structures. The Fermi level was adjusted by applying a negative gate bias in the TFT structure, and the measurable range of activation energy was extended to < 2.0 eV. Calculations based on density functional theory are used to investigate the changes in defect characteristics and the role of defects at shallow and deep levels as a function of oxygen partial pressure. Device characteristics, such as mobility and threshold voltage shift under a negative gate bias, showed a linear correlation with the ratio of shallow level to deep level defect density. Shallow level and deep level defects are organically related, and both defects must be considered when understanding device characteristics.

A Rab39-Klp98A-Rab35 endocytic recycling pathway is essential for rapid Golgi-dependent furrow ingression.

Ingression of the plasma membrane is an essential part of the cell topology-distorting repertoire and a key element in animal cell cytokinesis. Many embryos have rapid cleavage stages in which they are furrowing powerhouses, quickly forming and disassembling cleavage furrows on timescales of just minutes. Previous work has shown that cytoskeletal proteins and membrane trafficking coordinate to drive furrow ingression, but where these membrane stores are derived from and how they are directed to furrowing processes has been less clear. Here, we identify an extensive Rab35/Rab4>Rab39/Klp98A>trans-Golgi network (TGN) endocytic recycling pathway necessary for fast furrow ingression in the Drosophila embryo. Rab39 is present in vesiculotubular compartments at the TGN where it receives endocytically derived cargo through a Rab35/Rab4-dependent pathway. A Kinesin-3 family member, Klp98A, drives the movements and tubulation activities of Rab39, and disruption of this Rab39-Klp98A-Rab35 pathway causes deep furrow ingression defects and genomic instability. These data suggest that an endocytic recycling pathway rapidly remobilizes membrane cargo from the cell surface and directs it to the trans-Golgi network to permit the initiation of new cycles of cleavage furrow formation.

Nanostructure-Based CZGS/CZGSe Multiple Quantum Wells Could Sense Wider Solar Spectrum to Enhance Light-Harvesting Efficiency

Nanostructures in kesterite solar cells are incorporated for performance enhancement. As high recombination limits the efficiency of kesterite-based CZTS/Se solar cell, substituting Ge for Sn as Cu-Zn-Ge-S/Se (CZGS/Se) increases optical characteristics and solar cell overall performance. This research analyses MQWSC (multi-quantum-well solar cell) employing Cu-Zn-Ge-S as a barrier material and Cu-Zn-Ge-Se as a well material. Introducing quantum wells as (2, 10, 20, 30, 40, 50, 70, 100 QWs) in CZGS kesterite groups highlights the novelty of device. To enhance the performance its optic, electric, and structural characteristics are widely researched across nanostructures. An examination of the carrier dynamics of the device is carried out by varying various parameters. By introducing various loss mechanisms, including deep defect and shallow defect, the device’s worst-case operation is also evaluated. A remarkable efficiency of 29% without defect and 20% with defective states obtained from the proposed structure, which signify new route to facilitate the performance of PV (photovoltic) cells for the next generation.

Uncertainty-aware and dynamically-mixed pseudo-labels for semi-supervised defect segmentation

Deep learning-based defect segmentation is one of the important tasks of machine vision in automated inspection. Supervised learning methods have recently achieved remarkable performance on this task. However, the effectiveness of the supervised methods is limited by the scarcity and high cost of pixel-level annotation of training data. Semi-supervised learning methods have been proposed for training deep learning networks using a limited amount of labeled data along with additional unlabeled data for image segmentation. Most of these methods are based on consistency regularization and pseudo labeling, where the predictions on unlabeled samples often come with noise and are unreliable, resulting in poor segmentation performance. To alleviate this problem, we propose uncertainty-aware pseudo labels, which are generated from dynamically mixed predictions of multiple decoders that leverage a shared encoder network. The estimated uncertainty guides the pseudo-label-based supervision and regularizes the training when using the unlabeled samples. In our experiments on four public datasets for defect segmentation, the proposed method outperformed the fully supervised baseline and six state-of-the-art semi-supervised segmentation methods. We also conducted an extensive ablation study to demonstrate the effectiveness of our approach in various settings. The implementation code for this work is available at https://github.com/djene-mengistu/UAPS.

Structurally compromised teeth. Part II: A novel approach to peripheral build up procedures.

To introduce the "Peripheral Build-Up technique - PBUt" as a foundation restoration strategy for structurally compromised teeth (SCT). Several strategies have been proposed over time (cervical marginal relocation, doughnut, and preformed ring techniques) to enable the management of restorative procedures in challenging situations such as the presence of deep subgingival defects. The PBUt is a versatile, completely additive direct technique that share some strategical concepts with these techniques to approach critical clinical situations while supplying a wider field of application thanks to distinct operative expedients. The clamp insertion modality, the extension of the proximal wall and the matrix customization/stabilization strategies adopted in PBUt endorse the possibility to manage the most apical and peripheral border of the residual tooth structure when located up to >1.5 mm above the bone crest. The periodontal response has to be then monitored over time. Moreover, thanks to the peripheral and apically-extended addictive approach, it allows a massive preservation of residual sound tooth structure and improves the resistance and retentive physical/geometrical features of the abutment tooth. The PBUt operative workflow is herein explained. The Peripheral-Build-Up technique (PBUt) advocates some innovative clinical restorative steps for the management of SCT with coronal and deep subgingival defects.

Studying the effectiveness of deep active learning in software defect prediction

Accurate prediction of defective software modules is of great importance for prioritizing quality assurance efforts, reasonably allocating testing resources, reducing costs and improving software quality. Several studies have used machine learning to predict software defects. However, complex structures and imbalanced class distributions in software defect data make learning an effective defect prediction model challenging. In this article, two deep learning-based defect prediction models using static code metrics are proposed. In order to enhance the learning process and improve the performance of the proposed models, pool-based active learning is employed. In this regard, the possibility of using active learning to mitigate the need for a large amount of labeled data in the process of building deep learning models is investigated. To deal with imbalanced distribution of software modules between defective and non-defective classes, Near-Miss under-sampling and KNN, with different number of neighbors, are used. The reason for choosing them is their good performance in binary classification problems. Experiments are performed on two well-known, publicly available datasets, GitHub Bug Dataset and public Unified Bug Dataset for java projects. The evaluation results reveal the effectiveness of our proposed models in comparison to the traditional machine learning algorithms. In the conducted investigations on the Unified Bug Dataset, at the file level, the value of F-measure and AUC criteria have improved by 13 and 11 percent, respectively and at the class level, the values have improved by 14 and 11 percent, respectively.

Efficient and bending durable flexible Cu2ZnSn(S,Se)4 solar cells achieved by Ga doping stress regulation

Ga-doped CZTSSe is achieved by evaporating Ga layer in precursor combined with subsequent selenization to balance the efficiency and bending durability of flexible CZTSSe solar cells in this paper. Ga doping can simultaneously alleviate the residual stress and reinforce the microstructure of CZTSSe, retaining the original lattice structure of CZTSSe and suppressing Sn-related deep level defects. The gratifying residual stress reduction from -5.31 GPa to -3.82 GPa with decreased porosity from 6.24% to 3.24% of CZTSSe thin film spontaneously promotes the device performance after evaporating the 20 nm Ga layer. A desirable efficiency enhancement from 2.61% to 5.04% with preferable bending durability of flexible device is achieved, which strategy provides substantial assistance for the potential application of flexible solar cells.

Cs2TiI6 (Cs2TiIxBr6-x) Halide Perovskite Solar Cell and Its Point Defect Analysis.

This work presents a comprehensive numerical study for designing a lead-free, all-inorganic, and high-performance solar cell based on Cs2TiI6 halide perovskite with all-inorganic carrier transport layers. A rigorous ab initio density-functional theory (DFT) calculation is performed to identify the electronic and optical properties of Cs2TiI6 and, upon extraction of the existing experimental data of the material, the cell is designed and optimized to the degree of practical feasibility. Consequently, a theoretical power conversion efficiency (PCE) of 21.17% is reported with inorganic TiO2 and CuI as carrier transport layers. The calculated absorption coefficient of Cs2TiI6 reveals its enormous potential as an alternative low-bandgap material for different solar cell applications. Furthermore, the role of different point defects and the corresponding defect densities on cell performance are investigated. It is found that the possible point defects in Cs2TiI6 can form both the shallow and deep defect states, with deep defect states having a prominent effect on cell performance. For both defect states, the cell performance deteriorates significantly as the defect density increases, which signifies the importance of high-quality material processing for the success of Cs2TiI6-based perovskite solar cell technology.

Towards safe shearography inspection of thick composites with controlled surface temperature heating

Thick glass fiber-reinforced polymer (GFRP) composites, e.g. thickness of more than 50 mm, are increasingly used in a wide variety of industries, particularly in the marine and wind energy sectors. Defect detection and characterisation in these composites remain appealing challenges due to the material complexity and the presence of various manufacturing and in-service defects. In this study, we propose a novel shearography method with controlled surface temperature (CST) heating for deep defect detection (i.e., 15 mm depth and more) in thick GFRP laminates. The proposed CST heating has been developed based on analytical solutions to control the maximum surface temperature of a test object during shearography inspection. Numerical and experimental studies have been performed to analyse the defect behaviour and defect detection under various heating scenarios, a topic which is rarely reported for thick composites with shearography. Compared with conventional shearography, the CST shearography method maximises heating energy input with a controlled and stable maximum surface temperature for deep defect detection. Results indicate an enhancement of about 27% in defect signal for the defect at 15 mm depth in comparison to conventional heating. The results also provide insight for implementing an efficient inspection in terms of the inspection duration and the number of datasets. This study makes a step towards safe, quantitative and predictable inspection of deep defects in thick composites.

Progress in Evaluation of Deep Artificial Defects from Sweep-Frequency Eddy-Current Testing Signals.

The article discusses the practical application of the method of electromagnetic non-destructive investigation of austenitic materials. To identify and evaluate deep artificial defects, the sweep-frequency eddy current method with harmonic excitation is used. The objects of interest are the surface electric-discharged machined notches, with a defined geometry, fabricated in a plate with a thickness of 30 mm. An innovative eddy current probe with a separate excitation and detection circuit is used for the investigation. The achieved results clearly demonstrate the robustness and potential of the method, especially for deep defects in thick material. By using the fifth probe in connection with the frequency sweeping of eddy currents, it is possible to reliably detect artificial defects up to 24 ± 0.5 mm deep by using low-frequency excitation signals. An important fact is that the measuring probe does not have to be placed directly above the examined defect. The experimental results achieved are presented and discussed in this paper. The conducted study can serve, for example, as an input database of defect signals with a defined geometry to increase the convergence of learning networks and for the prediction of the geometry of real (fatigue and stress-corrosion) defects.

A "T.E.S.T." hydrogel bioadhesive assisted by corneal cross-linking for in situ sutureless corneal repair.

Corneal transplantation is an effective clinical treatment for corneal diseases, which, however, is limited by donor corneas. It is of great clinical value to develop bioadhesive corneal patches with functions of "Transparency" and "Epithelium & Stroma generation", as well as "Suturelessness" and "Toughness". To simultaneously meet the "T.E.S.T." requirements, a light-curable hydrogel is designed based on methacryloylated gelatin (GelMA), Pluronic F127 diacrylate (F127DA) & Aldehyded Pluronic F127 (AF127) co-assembled bi-functional micelles and collagen type I (COL I), combined with clinically applied corneal cross-linking (CXL) technology for repairing damaged cornea. The patch formed after 5min of ultraviolet irradiation possesses transparent, highly tough, and strongly bio-adhesive performance. Multiple cross-linking makes the patch withstand deformation near 600% and exhibit a burst pressure larger than 400mmHg, significantly higher than normal intraocular pressure (10-21mmHg). Besides, the slower degradation than GelMA-F127DA&AF127 hydrogel without COL I makes hydrogel patch stable on stromal beds in vivo, supporting the regrowth of corneal epithelium and stroma. The hydrogel patch can replace deep corneal stromal defects and well bio-integrate into the corneal tissue in rabbit models within 4 weeks, showing great potential in surgeries for keratoconus and other corneal diseases by combining with CXL.

Treatment of descemetocele with deep keratotomy combined with a nictitating membrane flap in a dog

A 10-year-old, spayed female, Maltese dog presented with a 2-day history of severe left eye squint. Slit-lamp biomicroscopy showed a deep corneal defect stained into a doughnut shape together with hypopyon in the anterior chamber. Based on these results, a diagnosis of descemetocele and uveitis in the left eye was made. Deep keratotomy combined with a nictitating membrane flap effectively resolved the descemetocele without complications. The surgical procedures performed on this patient were easy and effective, and could be used as an alternative to graft surgery for descemetocele treatment.

Dual gene-activated dermal scaffolds regulate angiogenesis and wound healing by mediating the coexpression of VEGF and angiopoietin-1.

The vascularization of dermal substitutes is a key challenge in efforts to heal deep skin defects. In this study, dual gene-activated dermal scaffolds (DGADSs-1) were fabricated by loading nanocomposite particles of polyethylenimine (PEI)/multiple plasmid DNAs (pDNAs) encoding vascular endothelial growth factor and angiopoietin-1 at a ratio of 1:1. In a similar manner, DGADSs-2 were loaded with a chimeric plasmid encoding both VEGF and Ang-1. In vitro studies showed that both types of DGADSs released PEI/pDNA nanoparticles in a sustained manner; they demonstrated effective transfection ability, leading to upregulated expression of VEGF and Ang-1. Furthermore, both types of DGADSs promoted fibroblast proliferation and blood vessel formation, although DGADSs-1 showed a more obvious promotion effect. A rat full-thickness skin defect model showed that split-thickness skin transplanted using a one-step method could achieve full survival at the 12th day after surgery in both DGADSs-1 and DGADSs-2 groups, and the vascularization time of dermal substitutes was significantly shortened. Compared with the other three groups of scaffolds, the DGADSs-1 group had significantly greater cell infiltration, collagen deposition, neovascularization, and vascular maturation, all of which promoted wound healing. Thus, compared with single-gene-activated dermal scaffolds, DGADSs show greater potential for enhancing angiogenesis. DGADSs with different loading modes also exhibited differences in terms of angiogenesis; the effect of loading two genes (DGADSs-1) was better than the effect of loading a chimeric gene (DGADSs-2). In summary, DGADSs, which continuously upregulate VEGF and Ang-1 expression, offer a new functional tissue-engineered dermal substitute with the ability to activate vascularization.

Therapy of pathological scars.

A scar develops following the appearance of a deep tissue defect as part of the physiological wound healing process. The initial inflammatory response is followed by proliferation of connective tissue cells, which form fibrosis as a final tissue substitute. Disorders can occur at all stages of the process and are most commonly manifested as impaired wound healing or the formation of atrophic and hypertrophic scars or keloids. The focus of this article is on the treatment of pathologic scars, which are an indication for therapy due to functional limitations, complaints, and stigmatization, among other reasons. Conservative medical, physical, surgical and laser therapeutic approaches are pursued. The basis for this is an understanding of the pathophysiological mechanisms and factors influencing the choice of therapy, as well as an interdisciplinary and interprofessional therapeutic approach.

Clinical experience of free superficial temporal fascia flap/anterolateral femoral fascial flap combined with skin grafting in repairing deep tissue defects of special parts of extremities

The deep tissue defects of extremities are prone to cause the exposure of tendons, blood vessels, nerves, and bones, which are commonly repaired with free flaps in clinical practice. However, for special parts such as fingers, toes, posterior ankles, anterior tibias, and dorsum of feet, the appearances are usually bulky after being repaired with free flaps and need lipectomy operations, which bring great physiological, psychological, and economic burden to patients. As the fascia flap is soft and thin with reliable blood supply and strong anti-infection ability, the free fascia flap combined with skin grafting offers some advantages in repairing the above-mentioned wounds. However, its clinical application is severely limited due to the complexity of surgical operation and the difficulty in observing blood supply after operation. In recent years, our team has carried out a lot of work and accumulated rich experience in repairing deep tissue defects of special parts of extremities with free superficial temporal fascia flap/anterolateral femoral fascial flap combined with skin grafting. From the clinical perspective, this paper mainly introduces the anatomy and harvesting method of free superficial temporal fascia flap/anterolateral femoral fascial flap, as well as the advantages, difficulties, and precautions of clinical application, for reference of peers.