Surface modifications of InAs: effect of chemical processing on electronic structure and photoluminescent properties

In this thesis, the effects of various chemical treatments on the surface modification of bulk InAs are investigated. The study focuses on the chemical processes that occur upon the exposure of the surface to sulphur-, chlorine- and bromine-containing solutions and oxygen, and the resulting changes to the electronic structure of the surface, as deduced from photoluminescence (PL) measurements, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Raman scattering and scanning electron microscopy (SEM). Three processing treatments were evaluated: i) treatment with sulphur-based solutions (Na2S:9H2O, (NH4)2S + S, [(NH4)2S / (NH4)2SO4] + S); ii) etching in halogen-based solutions (bromine-methanol and HCl: H2O); and iii) thermal oxidation. A significant overall enhancement in PL response was observed after chemical treatment or thermal oxidation, which is associated with a reduction in surface band bending. These changes correlate with the removal of the native oxide, in addition to the formation of well-ordered layers of In-S (or In-As)O as a passivating layer, indicating that electronic passivation occurs at the surface. The passivating effect on sulphide treated surfaces is unstable, however, with an increase in band bending, due to reoxidation, observed over periods of a few days. The lowest re-oxidation rate was observed for ([(NH4)2S / (NH4)2SO4] + S). Etching in HCl:H2O and Br-methanol solutions of appropriate concentrations and for moderate times (1 min) resulted in smooth and defect-free InAs surfaces. Etching completely removed the native oxides from the surface and enhanced the PL response. The adsorption of bromine and chlorine onto the InAs surface led to the formation of As-Brx , In-Brx, As-Clx and In-Clxcompounds (x = 1, 2, 3), as inferred from changes in the In 3d3/2; 5/2 and As 3d core level binding energies. The etch rate was found to decrease because of strong anisotropic effects. The improvements in surface properties were reversed, however, if the concentrations of the etchants increased or the etch time was too long. In the worst cases, pit formation and inverted pyramids with {111} side facets were observed. Surface treatments or thermal oxidisation significantly enhanced the PL intensity relative to that of the as-received samples. This was due to a reduction in the surface state density upon de-oxidation, or in some cases, to the formation of a well ordered oxide layer on the surface. The overall increase in PL intensity after treatment is ascribed to a reduction in band bending near the surface. This allows several welldefined peaks not observed or reported previously for bulk InAs (with a carrier concentration n~2x1016 cm-3), to be studied. A combination of PL and XPS measurements before and after the various treatments was used to identify the chemical nature of the impurities giving rise to bound exciton recombination in InAs (111)

APPLICATION OF 3D PRINTING IN INNOVATED DRUG DELIVERY: A REVIEW

Increasing requests for modified and personalized pharmaceutics and medical materials makes the implementation of additive manufacturing increased rapidly in recent years. 3D printing has been involved numerous advantages in case of reduction in waste, flexibility in the design, and minimizing the high cost of intended products for bulk production of. Several of 3D printing technologies have been developed to fabricate novel solid dosage forms, including selective laser sintering, binder deposition, stereolithography, inkjet printing, extrusion-based printing, and fused deposition modeling. The selection of 3D printing techniques depends on their compatibility with the printed drug products. This review intent to provide a perspective on the incentives and possible applications of 3D printed pharmaceuticals, besides a practical viewpoint on how 3D printing could be included across the pharmaceutical field

Damage Initiation in Unidirectional Polymeric Composites with Manufacturing Induced Irregularities

In this work, the initiation of the first failure event in unidirectional polymer composites subjected to different loading conditions is studied. Two energy based point failure criteria – critical dilatational and critical distortional energy densities – are considered. Local stress fields are calculated by finite element models using micromechanical simulations to evaluate damage initiation in the matrix by a brittle failure mechanism (cavitation) and by an inelastic (yielding) process. The disorder in the fiber distribution induced by manufacturing is quantified by defining the degree of nonuniformity (NU) of fiber distribution in the composite cross section. An algorithm to create simulations of the nonuniform distribution of fibers at different overall fiber volume fractions (FVFs) and different degrees of nonuniformity is developed. Representative volume elements (RVEs), with their minimum size determined on the basis of statistical analysis of interfiber distances are established for different fiber volume fractions. Under tension applied normal to the fibers, brittle cavitation is found to occur before yielding in the matrix. This first failure event is assumed to induce local debonding of the fiber/matrix interface. Effects of variables such as the degree of nonuniformity and the fiber volume fraction, as well as the ratio of matrix to fiber stiffness modulus, on the initiation of brittle cavitation are studied. Combined loading consisting of transverse tension and axial shear applied to unidirectional composites is studied next. It is found that under certain axial shear/transverse tensile stress ratios brittle cavitation requirements are fulfilled. When only axial shear is imposed, cavitation requirements are not satisfied. Instead, matrix yielding is found to occur. A parametric study of the matrix/fiber stiffness ratio shows that the mechanical strain to onset of cavitation under transverse tension increases as this ratio increases and approaches a constant value at high ratios under given fiber volume fractions and degree of nonuniformity. Also, under these conditions and under axial shear, the mechanical strain at which yielding initiates is found to increase with increasing the matrix/fiber stiffness ratio. A limited study of the effects of matrix voids was also conducted and the preliminary results showed that the presence of voids affects the initiation of brittle cavitation by altering the local stress fields near the fiber/matrix interfaces

Damage Initiation in Unidirectional Polymeric Composites with Manufacturing Induced Irregularities

In this work, the initiation of the first failure event in unidirectional polymer composites subjected to different loading conditions is studied. Two energy based point failure criteria – critical dilatational and critical distortional energy densities – are considered. Local stress fields are calculated by finite element models using micromechanical simulations to evaluate damage initiation in the matrix by a brittle failure mechanism (cavitation) and by an inelastic (yielding) process. The disorder in the fiber distribution induced by manufacturing is quantified by defining the degree of nonuniformity (NU) of fiber distribution in the composite cross section. An algorithm to create simulations of the nonuniform distribution of fibers at different overall fiber volume fractions (FVFs) and different degrees of nonuniformity is developed. Representative volume elements (RVEs), with their minimum size determined on the basis of statistical analysis of interfiber distances are established for different fiber volume fractions. Under tension applied normal to the fibers, brittle cavitation is found to occur before yielding in the matrix. This first failure event is assumed to induce local debonding of the fiber/matrix interface. Effects of variables such as the degree of nonuniformity and the fiber volume fraction, as well as the ratio of matrix to fiber stiffness modulus, on the initiation of brittle cavitation are studied. Combined loading consisting of transverse tension and axial shear applied to unidirectional composites is studied next. It is found that under certain axial shear/transverse tensile stress ratios brittle cavitation requirements are fulfilled. When only axial shear is imposed, cavitation requirements are not satisfied. Instead, matrix yielding is found to occur. A parametric study of the matrix/fiber stiffness ratio shows that the mechanical strain to onset of cavitation under transverse tension increases as this ratio increases and approaches a constant value at high ratios under given fiber volume fractions and degree of nonuniformity. Also, under these conditions and under axial shear, the mechanical strain at which yielding initiates is found to increase with increasing the matrix/fiber stiffness ratio. A limited study of the effects of matrix voids was also conducted and the preliminary results showed that the presence of voids affects the initiation of brittle cavitation by altering the local stress fields near the fiber/matrix interfaces

Exascale MPI-based program deadlock detection

Deadlock detection is one of the main issues of software testing in High Performance Computing (HPC) and also in exascale computing areas in the near future. Developing and testing programs for machines which have millions of cores is not an easy task. HPC program consists of thousands (or millions) of parallel processes which need to communicate with each other in the runtime. Message Passing Interface (MPI) is a standard library which provides this communication capability and it is frequently used in the HPC. Exascale programs are expected to be developed using MPI standard library. For parallel programs, deadlock is one of the expected problems. In this paper, we discussed the deadlock detection for exascale MPI-based programs where the scalability and efficiency are critical issues. The proposed method is implemented to detect and flag the processes and communication commands which are potential to cause deadlocks in a scalable and efficient manner. MPI benchmark programs were used to test the propose method

Exascale Message Passing Interface based Program Deadlock Detection

Deadlock detection is one of the main issues of software testing in High Performance Computing (HPC) and also inexascale computing areas in the near future. Developing and testing programs for machines which have millions of cores is not an easy task. HPC program consists of thousands (or millions) of parallel processes which need to communicate with each other in the runtime. Message Passing Interface (MPI) is a standard library which provides this communication capability and it is frequently used in the HPC. Exascale programs are expected to be developed using MPI standard library. For parallel programs, deadlock is one of the expected problems. In this paper, we discuss the deadlock detection for exascale MPI-based programs where the scalability and efficiency are critical issues. The proposed method detects and flags the processes and communication operations which are potential to cause deadlocks in a scalable and efficient manner. MPI benchmark programs were used to test the proposed method

Volumetric dimensional changes of luting cements

Indiana University-Purdue University Indianapolis (IUPUI)The luting agent is a crucial factor in the outcome of cemented fixed restorations. A new water-based cement, Ceramir C&B (CM), approved to be marketed in the US, is composed of calcium aluminate and glass ionomer. CM is a luting agent indicated for permanent cementation of cast restorations, all-zirconia or all-alumina crowns, and prefabricated metal and cast dowel and cores. The manufacturer claims that the cement has demonstrated favorable biocompatibility properties when tested in vitro and in vivo and has proven to be bioactive. The objective of this study was to evaluate volumetric dimensional changes and the amount of Ca2+ released by the new luting agent. Twenty specimens of each material, namely calcium aluminate glass ionomer, resin-modified glass ionomer, and two resin luting agents, were fabricated and weighed. The 20 specimens for all materials were divided into four groups (five samples in each group) based on storage conditions: silicone oil at 22°C and 37°C and distilled water at 22°C and 37°C. Using the manufacturers’ instructions for each material, cylindrical specimens were prepared with dimensions of 7 +0.1 mm in diameter and 2 +0.1 mm in height. A 0.01-mg resolution balance was used to determine volumetric dimensional change using an Archimedean equation. Measurements were made 30 minutes after mixing, and at the time intervals of 7 days, 14 days, 21 days, and 30 days, and after total dehydration of the specimen. Chemical analyses of the solutions were performed using atomic absorption spectroscopy to determine the Ca+2 ion concentration. Moreover, the pH values were measured to determine the OH–concentration in the solutions. The results showed that CM had the most expansion among the tested luting agents in distilled water at 22°C and 37°C, and significantly increased at higher temperature. In silicone oil, resin-modified glass ionomer shrank the most and also shrank more with the high temperature. The result of the ion concentration analysis indicated that Ca+2 and OHion release increased with increasing time and also significantly with temperature rise. In conclusion, calcium aluminate-glass ionomer exhibited the most significant dimensional change when stored in water storage. The solubility of the tested luting agents should be evaluated in the future because they were not evaluated in this study. Furthermore, to evaluate the clinical effect of the dimensional changes, the impact on the gap formation at tooth-crown margins should be determined in future work

Gibbs state sampling via cluster expansions

Gibbs states (i.e., thermal states) can be used for several applications such as quantum simulation, quantum machine learning, quantum optimization, and the study of open quantum systems. Moreover, semi-definite programming, combinatorial optimization problems, and training quantum Boltzmann machines can all be addressed by sampling from well-prepared Gibbs states. With that, however, comes the fact that preparing and sampling from Gibbs states on a quantum computer are notoriously difficult tasks. Such tasks can require large overhead in resources and/or calibration even in the simplest of cases, as well as the fact that the implementation might be limited to only a specific set of systems. We propose a method based on sampling from a quasi-distribution consisting of tensor products of mixed states on local clusters, i.e., expanding the full Gibbs state into a sum of products of local "Gibbs-cumulant" type states easier to implement and sample from on quantum hardware. We begin with presenting results for 4-spin linear chains with XY spin interactions, for which we obtain the $ZZ$ dynamical spin-spin correlation functions. We also present the results of measuring the specific heat of the 8-spin chain Gibbs state $\rho_8$.Comment: 8 pages, 8 figures, and supplementary materia

LORNOXICAM-LOADED NANOSPONGES FOR CONTROLLED ANTI-INFLAMMATORY EFFECT: IN VITRO/IN VIVO ASSESSMENT

Objective: To design a controlled topical delivery system of lornoxicam (LX) in order to enhance skin permeation and treatment efficacy. Nanosponges were selected as a novel carrier for this purpose. Methods: Nanosponges were formulated via the emulsion solvent evaporation method using ethyl cellulose (polymer) and polyvinyl alcohol (surfactant). Nanosponge dispersions were characterized for colloidal properties, entrapment efficiency and in vitro release study. The nanosponge formulation (LS1) was then incorporated into carboxymethyl cellulose sodium hydrogels and evaluated for pH, viscosity and in vitro drug release. Skin irritation was evaluated, and anti-inflammatory activity was assessed via rat hind paw edema method. Results: Nanosponges were in the nano-sized range and attained a uniform round shape with a spongy structure. LS1exhibited the highest LX release after 6 h, so it was incorporated as hydrogel. Formulated hydrogels showed acceptable physicochemical parameters (pH, drug content and rheological properties). Skin irritation testing proved LX-loaded nanosponge hydrogel formulation (G1) to be non-irritant. In vivo study revealed an enhanced anti-inflammatory activity of G1 for 6 h (p<0.001). Conclusion: The developed nanosponge hydrogel is an efficient nanocarrier for improved and controlled topical delivery of LX