Optical signatures of intrinsic electron localization in amorphous SiO2

We measure and analyse the optical absorption spectra of three silica glass samples irradiated with 1 MeV electrons at 80 K, where self-trapped holes are stable, and use ab initio calculations to demonstrate that these spectra contain a signature of intrinsic electron traps created as counterparts to the holes. In particular, we argue that optical absorption bands peaking at 3.7, 4.7, and 6.4 eV belong to strongly localised electrons trapped at precursor sites in amorphous structure characterized by strained Si–O bonds and O–Si–O angles greater than 132°. These results are important for our understanding of the properties of silica glass and other silicates as well as the reliability of electronic and optical devices and for luminescence dating

Novel salted anionic-cationic polymethacrylate polymer blends for sustained release of acidic and basic drugs

Background: Since a unique matrix tablet formulation that independently controls the release of various drug types is in a great demand, the objective of this research was to develop a sustained release matrix tablet as a universal dosage form using a binary mixture of the salt forms of Eudragit polymers rather than their interpolyelectrolyte complexes. Methods: Tablets were prepared by wet granulation and compressed at different compression forces, depending on drug type. Dissolution tests were conducted using USP XXII rotating paddle apparatus at 50 rpm at 37°C in consecutive pH stages. Results: Tablets containing Ibuprofen (IB) as a model acidic drug and Metronidazole (MD) as a model basic drug showed controlled/sustained release behavior. For IB tablets containing 80% Ibuprofen and 5% (w/w) polymeric combination; the time for 50% of the drug release was about 24 hours compared to 8.5 hours for plain tablets containing 80% IB. In case of MD, the drug release extended to about 7 hours for tablets containing 80% MD and 5% (w/w) polymeric combination, compared to about 1 hour for plain tablets containing 80% MD. In terms of extending the release of medications, the dissolution profiles of the tablets containing polymeric salts forms were found to be statistically superior to tablets prepared by direct compression of the polymers in their powdered base forms, and superior to tablets containing the same polymers granulated using isopropyl alcohol. Conclusion: The findings indicated the significance of combining the polymers in their salt forms in controlling the release of various drug types from matrices

Intrinsic Charge Trapping in Amorphous Oxide Films: Status and Challenges

We review the current understanding of intrinsic electron and hole trapping in insulating amorphous oxide films on semiconductor and metal substrates. The experimental and theoretical evidences are provided for the existence of intrinsic deep electron and hole trap states caused by the disorder of amorphous metal oxide films. We start from presenting the results for amorphous (a) HfO<sub>2</sub>, chosen due to the availability of highest purity amorphous films, which is vital for studying their intrinsic electronic properties. Exhaustive photo-depopulation spectroscopy (EPDS) measurements and theoretical calculations using density functional theory (DFT) shed light on the atomic nature of electronic gap states responsible for deep electron trapping observed in a-HfO<sub>2</sub>. We review theoretical methods used for creating models of amorphous structures and electronic structure calculations of amorphous oxides and outline some of the challenges in modelling defects in amorphous materials. We then discuss theoretical models of electron polarons and bi-polarons in a-HfO<sub>2</sub> and demonstrate that these intrinsic states originate from low-coordinated ions and elongated metal-oxygen bonds in the amorphous oxide network. Similarly, holes can be captured at under-coordinated O sites. We then discuss electron and hole trapping in other amorphous oxides, such as a-SiO<sub>2</sub>, a-Al<sub>2</sub>O<sub>3</sub>, a-TiO<sub>2</sub>. We propose that the presence of low-coordinated ions in amorphous oxides with electron states of significant p and d character near the conduction band minimum (CBM) can lead to electron trapping and that deep hole trapping should be common to all amorphous oxides. Finally, we demonstrate that bi-electron trapping in a-HfO<sub>2</sub> and a-SiO<sub>2</sub> weakens Hf(Si)-O bonds and significantly reduces barriers for forming Frenkel defects, neutral O vacancies and O<sup>2-</sup> ions in these materials. These results should be useful for better understanding of electronic properties and structural evolution of thin amorphous films under carrier injection conditions

The effect of nuclear deformation on level statistics

We analyze the nearest neighbor spacing distributions of low-lying 2+ levels of even-even nuclei. We grouped the nuclei into classes defined by the quadrupole deformation parameter (Beta2). We calculate the nearest neighbor spacing distributions for each class. Then, we determine the chaoticity parameter for each class with the help of the Bayesian inference method. We compare these distributions to a formula that describes the transition to chaos by varying a tuning parameter. This parameter appears to depend in a non-trivial way on the nuclear deformation, and takes small values indicating regularity in strongly deformed nuclei and especially in those having an oblate deformation.Comment: 10 Pages, 6 figure

Role of hydrogen in volatile behaviour of defects in SiO2-based electronic devices

Charge capture and emission by point defects in gate oxides of metal–oxide–semiconductor field-effect transistors (MOSFETs) strongly affect reliability and performance of electronic devices. Recent advances in experimental techniques used for probing defect properties have led to new insights into their characteristics. In particular, these experimental data show a repeated dis- and reappearance (the so-called volatility) of the defect-related signals. We use multiscale modelling to explain the charge capture and emission as well as defect volatility in amorphous SiO2 gate dielectrics. We first briefly discuss the recent experimental results and use a multiphonon charge capture model to describe the charge-trapping behaviour of defects in silicon-based MOSFETs. We then link this model to ab initio calculations that investigate the three most promising defect candidates. Statistical distributions of defect characteristics obtained from ab initio calculations in amorphous SiO2 are compared with the experimentally measured statistical properties of charge traps. This allows us to suggest an atomistic mechanism to explain the experimentally observed volatile behaviour of defects. We conclude that the hydroxyl-E′ centre is a promising candidate to explain all the observed features, including defect volatility

Modelling dependency networks to inform data structures in BIM and smart cities

The pervasive deployment of "smart city" and "smart building" projects in cities world-wide is driving innovation on many fronts including; technology, telematics, engineering and entrepreneurship. This paper focuses on the technical and engineering perspectives of BIM and smart cities, by extending building and urban morphology studies as to respond to the challenges posed by Big Data, and smart infrastructure. The proposed framework incorporates theoretical and modelling descriptions to verify how network-based models can act as the backbone skeletal representation of both building and urban complexity, and yet relate to environmental performance and smart infrastructure. The paper provides some empirical basis to support data information models through building dependency networks as to represent the relationships between different existing and smart infrastructure components. These dependency networks are thought to inform decisions on how to represent building and urban data sets in response to different social and environmental performance requirements, feeding that into void and solid descriptions of data maturity models. It is concluded that network-based models are fundamental to comprehend and represent the complexity of cities and inform urban design and public policy practices, in the design and operation phases of infrastructure projects

Numerical estimation and experimental verification of optimal parameter identification based on modern optimization of a three phase induction motor

The parameters of electric machines play a substantial role in the control system which, in turn, has a great impact on machine performance. In this paper, a proposed optimal estimation method for the electrical parameters of induction motors is presented. The proposed method uses the particle swarm optimization (PSO) technique. Further, it also considers the influence of temperature on the stator resistance. A complete experimental setup was constructed to validate the proposed method. The estimated electrical parameters of a 3.8-hp induction motor are compared with the measured values. A heat run test was performed to compare the effect of temperature on the stator resistance based on the proposed estimation method and the experimental measurements at the same conditions. It is shown that acceptable accuracy between the simulated results and the experimental measurements has been achieved

Antiretroviral therapy, CD4, viral load, and disease stage in HIV patients in Saudi Arabia: a 2001–2013 cross-sectional study

Introduction: The incidence of HIV/AIDS is increasing worldwide and in the Middle East. In this study, we analyzed the use of antiretroviral therapy (ART), the patterns of CD4 and viral load (VL), and stage of presentation. Methodology: Laboratory variables, ART use, and CD4 count were obtained and analyzed retrospectively. Results: A total of 997 cases from eight HIV/AIDS care providers were included. Of the total cases, 274 (28.3%) had a CD4 count of 5 log10. Of the total cases, 50% were on highly active antiretroviral therapy (HAART), and the majority of cases were asymptomatic (70%). Of those patients on ART, 247 (39.5%) took tenofovir/emtricitabine combined with either efavirenz (147; 14.7%) or lopinavir/ritonavir (100; 10%), and 158 (15.8%) were on lamivudine and zidovudine with either efavirenz (32; 3.2%) or lopinavir/ritonavir (126; 12.6%). Other combinations were used in 70 (7%) patients. The mean (± standard deviation) of baseline CD4 and viral load were 401 cells/mm3 (322 cells/mm3) and 4.6 log1010 (1.3 log10), respectively. At diagnosis, 72% of patients were asymptomatic; 50% had AIDS and 20% had CD4 count < 350. Conclusions: ART use was in line with international guidelines, but the number of patients receiving ART was lower than expected. Large proportions of cases presented late with AIDS at diagnosis or had CD4 < 350. Further data is needed to evaluate the medical care of patients with HIV/AIDS in the Kingdom of Saudi Arabia

Rates of Soft Ground Tunneling in Vicinity of Existing Structures

Soft ground tunneling in the vicinity of existing structures is a major challenge to tunneling engineers. Tunneling works cause inevitable ground movements that may lead to unrecoverable damages to adjacent structures. Tunneling rates significantly affect such risks. However, a guideline that determines appropriate tunneling rates and accounts for the effects of tunneling on the structures existing in the vicinity is not available. Tunneling records in terms of TBM advance speed (AS), utilization factor (U), and advance rate (AR) for tunnels constructed without causing significant risks on the existing structures are presented in the paper.These records are discussed for different types of existing structures.Ranges of these records for tunneling without causing detrimental effects on different types existing structures are recommended.Useful observations are also made on the variation of these records with the ground type and composition and the precautions to be adopted to mitigate the tunneling risks on existing structures

Specific Cellular Immune Response and Cytokine Patterns in Patients Coinfected with Hepatitis C Virus and Schistosoma mansoni

Patients coinfected with hepatitis C virus (HCV) and Schistosoma mansoni show high incidence of viral persistence and accelerated fibrosis. To determine whether immunological mechanisms are responsible for this alteration in the natural history of HCV, the HCV-specific peripheral CD4+ T cell responses and cytokines were analyzed in patients with chronic hepatitis C monoinfection, S. mansoni monoinfection, or HCV and S. mansoni coinfection. An HCV-specific CD4+ proliferative response to at least 1 HCV antigen was detected in 73.3% of patients infected with HCV, compared with 8.6% of patients coinfected with HCV and S. mansoni. Stimulation with HCV antigens produced a type 1 cytokine profile in patients infected with HCV alone, compared with a type 2 predominance in patients coinfected with HCV and S. mansoni. In contrast, there was no difference in response to schistosomal antigens in patients infected with S. mansoni alone, compared with those coinfected with HCV and S. mansoni. These findings suggest that the inability to generate an HCV-specific CD4+/Th1 T cell response plays a role in the persistence and severity of HCV infection in patients with S. mansoni coinfectio