Self-assembled hierarchical nanostructures composed of novel chalcopyrite nanosheets for photovoltaic properties

Self-assembled nanostructures of CulnGaSe2 (CIGS) comprising of nanosheets with sheet thickness of 20 nm have been developed via one-step electrochemically alloying technique. These self-assembled nanoplates exhibit highly intersecting behavior and transform from CuSe to CIGS as the reduction potential was varied. The morphological analysis indicated that the process resulted in a progression of crystallites to a series of heavy dense intersecting nanoplates. Further analyses revealed that the nanostructures keep their integrity on heat treatment. The structure confirms the inclusion of Indium and Gallium at higher reduction potentials and its transition from pseudoamorphous to polycrystalline structure. A strong correlation between reduction potential, and the composition was established. The spectroscopic and optical spectra clearly prove that the direct band gap for the as-grown and annealed thin films, and appropriate for solar cell applications. These self-assembled dense interweaved nanoplates structure have not been observed previously in CIGS semiconductor system and have potential implications forenergy applications.

Poly(3-methylthiophene)/graphene composite: in-situ synthesis and its electrochemical characterization

Poly(3-methylthiophene)/Graphene composites (G-PMT) and poly(3-methylthiophene) (PMT) were synthesized by in-situ chemical oxidative polymerization and investigated as electrode material for supercapacitors. The interaction between graphene and polymer chains was characterized by Fourier Transform Infrared (FTIR) spectroscopy. The morphology of the nanocomposites was characterized by Scanning Electron Microscopy (SEM) and High Resolution Transmission Electron Microscopy (TEM). The thermal stability of the composite and the polymer was studied by Thermogravimetric Analysis (TGA) which shows G-PMT has higher thermal stability than PMT. The electrochemical properties were investigated by Cyclic Voltammetry (CV), Cyclic Charging-discharging tests (CC) and Electrochemical Impedance Spectroscopy (EIS) in a three-electrode system. G-PMT resulted in higher specific capacitance of 240 F/g. The specific capacitance retention after 500 cycles on G-PMT was also higher compared with PMT. These results indicate that G-PMT has good electrochemical performance than PMT hence it is useful for the making of electrode in supercapacitor application.

Particulate matter characterization by gray level co-occurrence matrix based support vector machines

An efficient and highly reliable automatic selection of optimal segmentation algorithm for characterizing particulate matter is presented in this paper. Support vector machines (SVMs) are used as a new self-regulating classifier trained by gray level co-occurrence matrix (GLCM) of the image. This matrix is calculated at various angles and the texture features are evaluated for classifying the images. Results show that the performance of GLCM-based SVMs is drastically improved over the previous histogram-based SVMs. Our proposed GLCM-based approach of training SVM predicts a robust and more accurate segmentation algorithm than the standard histogram technique, as additional information based on the spatial relationship between pixels is incorporated for image classification. Further, the GLCM-based SVM classifiers were more accurate and required less training data when compared to the artificial neural network (ANN) classifiers.

Laparoscopic slit mesh repair of parastomal hernia using a designated mesh: long-term results

BACKGROUND

Parastomal hernia (PH) is a frequent complication of colorectal surgery, which incidence reaches 55% of all stoma formation. Currently, there is no definitive strategy for its repair. This study was designed to assess the outcome in patients who underwent laparoscopic PH repair using a slit mesh/keyhole technique.

METHODS

We undertook a retrospective case review of all patients who underwent laparoscopic PH repair with a designed slit mesh/keyhole between 2005 and 2010. Three ports were placed opposite the stoma site, and careful adhesiolysis and hernia content reduction were performed. The parastomal fascial defect was measured and covered with a designated mesh. Fixation of the mesh was achieved with concentric tacks and transcutaneous Prolene suture. Recurrence was diagnosed after examination of patients by two surgeons or by imaging demonstrating an indolent hernia.

RESULTS

Twenty-nine laparoscopic PH mesh repairs were performed with an average age of 63.5 (range 42-81, median 64) years to treat paracolostomy hernia in 18 of 29 cases (62.1%), para-ileostomy hernia in 10 of 29 cases (34.5%), and for an ileal conduit site hernia in 1 of 29 cases (3.4%). The average operative time was 179 (range, 80-300; median, 180) min. Two operations (6.9%) were converted to an open approach. Early postoperative complications were documented in four patients (13.8%), including one elderly patient with severe comorbidities who died from postoperative sepsis (mortality rate, 3.4%). Only one late complication was recorded (3.4%). The average hospital stay was 4.7 (range, 1-19; median, 3) days. Average follow-up time was 28 (range, 12-53; median, 30) months. Recurrence of the hernia was found in 13 of 28 patients (46.4%).

CONCLUSIONS

Laparoscopic slit mesh/keyhole repair is feasible, although it is a complex surgery reflected by extended operative time. The high recurrence rate suggests that technical improvement of the method is essential.

Metastatic angiosarcoma presenting as diffuse alveolar hemorrhage

Angiosarcoma is a rare malignant neoplasm of the vascular or lymphatic endothelium. Diffuse alveolar hemorrhage is a rare presenting manifestation of angiosarcoma. We describe a case of pulmonary metastasis of angiosarcoma who presented with diffuse alveolar hemorrhage as initial manifestation.

Effect of the number of stacking layers on the characteristics of quantum-dash lasers

A theoretical model is evaluated to investigate the characteristics of InAs/InP quantum dash (Qdash) lasers as a function of the stack number. The model is based on multimode carrier-photon rate equations and accounts for both inhomogeneous and homogeneous broadenings of the optical gain. The numerical results show a non monotonic increase in the threshold current density and a red shift in the lasing wavelength on increasing the stack number, which agrees well with reported experimental results. This observation may partly be attributed to an increase of inhomogeneity in the active region.

A new approach to simulate characterization of particulate matter employing support vector machines

This paper, for the first time, applies the support vector machines (SVMs) paradigm to identify the optimal segmentation algorithm for physical characterization of particulate matter. Size of the particles is an essential component of physical characterization as larger particles get filtered through nose and throat while smaller particles have detrimental effect on human health. Typical particulate characterization processes involve image reading, preprocessing, segmentation, feature extraction, and representation. Of these various steps, knowledge based selection of optimal image segmentation algorithm (from existing segmentation algorithms) is the key for accurately analyzing the captured images of fine particulate matter. Motivated by the emerging machine-learning concepts, we present a new framework for automating the selection of optimal image segmentation algorithm employing SVMs trained and validated with image feature data. Results show that the SVM method accurately predicts the best segmentation algorithm. As well, an image processing algorithm based on Sobel edge detection is developed and illustrated.