Dilute-Anion III-Nitride Semiconductor Materials and Nanostructures

In this dissertation, the work focuses on the development of the dilute-anion III-Nitride based semiconductor for device applications in visible and deep ultraviolet (UV) spectral regime. First-Principle Density-Functional Theory calculations are employed for the investigation of optoelectronic properties of the dilute-anion III-Nitride semiconductors, which includes the understanding of alloy band structures and related band parameters. Among the dilute-anion III-Nitride semiconductor material class, dilute-As GaNAs, dilute-P GaNP and dilute-As AlNAs are extensively studied in this work. The findings show that the incorporation of anion-content in the GaN or AlN alloy will result in significant changes in the electronic properties, leading to unique features as compared to the conventional III-Nitride alloys such as InGaN and AlGaN alloys. Specifically, the investigation in the electronic properties of dilute-As GaNAs and dilute-P GaNP alloys result in suppression of interband Auger recombination process – a known efficiency-limiting issue in the InGaN quantum well (QW) light emitting diode devices., Further analysis are performed to design novel active region nanostructure of InGaN / dilute-As GaNAs interface QW for visible light emission. The analysis tindicate significantly enhanced spontaneous recombination rate and optical gain across the visible spectral regime from blue to red by using InGaN / dilute-As GaNAs interface QW, as compared to conventional InGaN QW. In the case of dilute-As AlNAs semiconductor, the analysis shows that the incorporation of minute amount of As-content in the AlN alloy will result in the switching of crystal field field split-off band with the heavy hole / light hole band, potentially solving the valence band crossover issue persisting in the AlGaN deep ultraviolet light emitting devices.In addition, extensive studies have been focused in the development of Auger recombination model taking into account the interface roughness in the QW, and analytical solutions for direct Auger recombination processes including interband Auger process for semiconductors. Specifically, the developed Auger model with interface roughness are important to provide intuitive insight of the role of Auger recombination process in the semiconductor devices employing nanostructures

Development of Advanced Control for Paste Thickeners

A paste thickener produces underflow with a high solids concentration by removing water from a dilute suspension. Paste thickening technology has been gradually gaining acceptance in the mining industry. Some of the main challenges in thickening are the complex dynamics due to severe interactions between operating parameters and the existence of a large range of process time constants. Additionally, being a downstream process, paste thickeners suffer from fluctuating feed conditions from upstream processes. Furthermore, the operation of paste thickeners involves a tight operating window as the underflow properties are sensitive to small changes in concentration. The above challenges motivate this work to develop a systematic advanced control strategy, in particular, model predictive control (MPC) to effectively and efficiently regulate this complex, multivariable process. In this thesis, the sedimentation-consolidation model is adopted and analysed to identify important dynamical features and the key process parameter which will be considered in control system design. The model is then validated using industrial plant data. An extended Kalman filter is developed to estimate in real-time the key process parameter which affects thickening dynamics significantly. Through extensive simulation studies, it has been demonstrated that the proposed MPC approach can deliver a higher underflow solids concentration and a better regulated underflow removal rate. In addition to the basic MPC, several important extensions are developed based on three practical considerations. Firstly, it is illustrated that incorporating ``future'' time-varying constraints in the MPC can help deal with the control difficulty arising from the co-disposal of underflow and coarse reject, leading to improved control performance. Secondly, an MPC with a non-uniformly spaced optimisation horizon is proposed to deal with the timescale multiplicity of thickening. The proposed approach provides similar levels of performance as compared to a conventional MPC with the advantage of reduced computational complexity. A stability ensuring condition for the proposed MPC is also developed. Thirdly, an MPC is developed to control both underflow solids concentration and rake torque. The nonlinear rake torque control problem is converted into a linear MPC problem, reducing the computational complexity of the optimisation problem. Simulation studies have shown that the proposed approach can effectively control the underflow solids concentration while minimising the rake torque, potentially preventing serious operational problems such as underflow blockage

Protective coating for gabion wires against weathering elements and site conditions

Gabions are one of the most essential elements in the geotechnical field for their versatility and strength in slope stabilization. According to BS 8002:2015, gabions are rectangular large cages or baskets made of either steel wire or square welded mesh, and are usually filled with stones. Besides slope stabilization, gabions have been widely used for various purposes, including closing of river banks, road construction, landslide consolidation and hilly terrain reclamation [1]

Current Understanding of Streptococcal Urinary Tract Infection

Group B streptococcus (GBS), also known as Streptococcus agalactiae is a Gram-positive, β-hemolytic, chain-forming bacterium and a commensal within the genital tract flora in approximately 25% of healthy adult women (Campbell et al., 2000). The organism is a leading cause of serious infection in newborns, pregnant women, and older persons with chronic medical illness (Baker et al., Edwards&Baker, 2005). In neonates GBS infection most commonly causes pneumonia, meningitis, and sepsis. In addition to maternal cervicovaginal colonization and neonatal infection that can result from vertical transmission of GBS from mothers to their infants, the bacterium can also cause urinary tract infection (UTI). The spectrum of GBS UTI includes asymptomatic bacteriuria (ABU), cystitis, pyelonephritis, urethritis, and urosepsis (Bronsema et al., 1993, Edwards&Baker, 2005, Farley et al., 1993, Lefevre et al., 1991, McKenna et al., 2003, Munoz et al., 1992, Ulett et al., 2009). GBS ABU is particularly common among pregnant women, although those most at risk for cystitis due to GBS appear to be elderly individuals (Edwards&Baker, 2005, Falagas et al., 2006, Muller et al., 2006). In addition to acute and asymptomatic UTI other invasive diseases caused by GBS infection include skin infections, bacteraemia, pneumonia, arthritis, and endocarditis (Liston et al., 1979, Patil & Martin, 2010, Tissi et al., 1997, Trivalle et al., 1998). Thus, GBS is considered unique in terms of its ability to cause a spectrum of diseases in newborns and adult humans and its ability to colonize the genital tract of healthy women in a commensal-type manner..

Incorporating environmental elements in property marketing strategy in Kuala Lumpur

Half of the world population all over the countries reside in the cities. By 2050, the world proportion is likely to reach 75%. Malaysia is an urban society with majority people of the country approximately 70% living in the cities. The high demand of accommodation in the cities, and many developers supply the housing unit through condominium complex to fulfil the requirement of accommodation. Every day the number of condominium is increasing in Kuala Lumpur city. The natural green environment is decreasing with destructive impact on physical, mental illness and many problems among the people reside in the city compare to the rural. The modern developers in Kuala Lumpur facing difficulties to influence the target customers due to the lack of green environmental elements in a housing project and marketing strategy are one of the great problems to achieve the high performance of sales. Therefore, incorporate of important environmental elements in a housing project and marketing strategy to achieve the high performance of sales. The level of importance evaluates through quantitative research method with five (5) points Likert types scale. The data collected from Kuala Lumpur city area among condominium users, tenant, owner, management team and developers employees including marketing staff, managers, sales staff, and sales agents altogether 509 respondent. More than 85% respondents are agreed the environmental elements are very important at the condominium complex to have a healthy city life, and it strongly influences customers to buy or rent the apartment units. The green marketing is acting as a mediation to contribute the high performance of sales. As a result, less or no difficulty to reach the high performance of sales. In conclusion, those project has the most demanding environmental elements are more successful projects, compare to less or non-existing environmental facilities projects in Kuala Lumpur, Malaysia

Surgical Morphometry of C1 and C2 Vertebrae: A Three-Dimensional Computed Tomography Analysis of 180 Chinese, Indian, and Malay Patients

Study DesignClinical imaging study.PurposeTo study the surgical morphometry of C1 and C2 vertebrae in Chinese, Indian, and Malay patients.Overview of LiteratureC1 lateral mass and C2 pedicle screw fixation is gaining popularity. However, there is a lack of C1–C2 morphometric data for the Asian population.MethodsComputed tomography analysis of 180 subjects (60 subjects each belonging to Chinese, Indian, and Malay populations) using simulation software was performed. Length and angulations of C1 lateral mass (C1LM) and C2 pedicle (C2P) screws were assessed.ResultsThe predicted C1LM screw length was between 23.2 and 30.2 mm. The safe zone of trajectories was within 11.0°±7.7° laterally to 29.1°±6.2° medially in the axial plane and 37.0°±10.2° caudally to 20.9°±7.8° cephalically in the sagittal plane. The shortest and longest predicted C2P screw lengths were 22.1±2.8 mm and 28.5±3.2 mm, respectively. The safe trajectories were from 25.1° to 39.3° medially in the axial plane and 32.3° to 45.9° cephalically in the sagittal plane.ConclusionsC1LM screw length was 23–30 mm with the axial safe zone from 11° laterally to 29° medially and sagittal safe zone at 21° cephalically. C2P screw length was 22–28 mm with axial safe zone from 26° to 40° medially and sagittal safe zone from 32° to 46° cephalically. These data serve as an important reference for Chinese, Indian, and Malay populations during C1–C2 instrumentation

Fermentation strategies for improving the production of bacteriocin-like inhibitory substances by Lactobacillus brevis C23 with nutrient supplementation, pH, and temperature variations

In this study, fermentation strategies were carried out for improving the production of bacteriocin-like inhibitory substances by Lactobacillus brevis C23 with nutrient supplementation, pH, and temperature variations, as well as fed-batch cultivation. The BLIS activity was highest (91.52%) in the MRS medium supplemented with 1.5% (w/v) lactose and 1% (w/v) meat extract. pH 5 augmented both the cell biomass and BLIS activity, but incubation temperature only affected growth at 37°C. Fed-batch cultivation strategy that utilized meat extract feeding would positively affect cell growth, whereas BLIS activity was enhanced by lactose feeding. The highest BLIS activity from L. brevis C23 was obtained at the 24 hr mark by feeding the culture medium with lactose (77.73%). The BLIS production of L. brevis C23 fed with meat extract followed a similar trend to lactose (74.20%). Increased BLIS activity in the final solution would reduce the downstream step such as concentrating the purified product

Poboljšanje mikrobiološke ispravnosti borovnica pomoću polimernih nanočestica s timolom

Research background. The presence of Yersinia enterocolitica on raw food products raises the concern of yersiniosis as most of the berries are consumed raw. This is a challenging issue from the food safety aspect since it could increase the occurrence of foodborne diseases among humans. Thus, it is crucial to implement an effective sanitation before the packaging. Experimental approach. This study aims to synthesize and characterize thymol-loaded polyvinyl alcohol (Thy/PVA) nanoparticles as a sanitizer for postharvest treatment of blueberries. Thy/PVA nanoparticles were characterized by spectroscopic and microscopic approaches, prior to the analyses of antimicrobial properties. Results and conclusions. The diameter size of the nanoparticles was on average 84.7 nm, with a surface charge of −11.73 mV. Based on Fourier transform infrared (FTIR) measurement, the Thy/PVA nanoparticles notably shifted to the frequency of 3275.70, 2869.66, 1651.02 and 1090.52 cm-1. A rapid burst was observed in the first hour of release study, and 74.9 % thymol was released from the PVA nanoparticles. The largest inhibition zone was displayed by methicillin-resistant Staphylococcus aureus (MRSA), followed by Y. enterocolitica and Salmonella typhi. However, amongst these bacteria, the inhibition and killing of Y. enterocolitica required a lower concentration of Thy/PVA nanoparticles. The treatment successfully reduced the bacterial load of Y. enterocolitica on blueberries by 100 %. Novelty and scientific contribution. Thymol is a plant-based chemical without reported adverse effects to humans. In this study, by using the nanotechnology method of encapsulation with PVA, we improved the stability and physicochemical properties of thymol. This nanoparticle-based sanitizer could potentially promote the postharvest microbiological safety of raw berries, which may become an alternative practice of food safety.Pozadina istraživanja. Prisutnost bakterije Yersinia enterocolitica u sirovim prehrambenim proizvodima izaziva zabrinutost zbog moguće pojave jersinioze, s obzirom na to da se bobičasto voće najčešće konzumira sirovo. S aspekta sigurnosti hrane ova bakterija predstavlja problem, jer može povećati učestalost pojave bolesti koje se prenose hranom. Stoga je neophodno provesti učinkovitu sanitaciju voća prije pakiranja. Eksperimentalni pristup. Svrha je ovoga rada bila sintetizirati i okarakterizirati nanočestice poli(vinil-alkohola) s timolom kao dezinficijensom za obradu borovnica prije pakiranja. Nanočestice su okarakterizirane pomoću spektroskopije i mikroskopije, a zatim su ispitana njihova antimikrobna svojstva. Rezultati i zaključci. Prosječni promjer nanočestica bio je 84,7 nm, s površinskim nabojem od −11,73 mV. Rezultati Fourier transformirane infracrvene spektroskopije (FTIR) pokazuju značajan pomak pika nanočestica poli(vinil-alkohola) s timolom prema frekvencijama od 3275,70; 2869,66; 1651,02 i 1090,52 cm-1. Iznenadni porast količine timola oslobođenog iz nanočestica opažen je u prvih sat vremena ispitivanja njegovog kontroliranog otpuštanja, a ukupno je otpušteno 74,9 % timola. Opažena je najveća zona inihbicije rasta bakterije Staphylococcus aureus otporne na meticilin (MRSA), a zatim bakterija Y. enterocolitica i Salmonella typhi. Međutim, za inhibiciju i ubijanje bakterija Y. enterocolitica bile su potrebne manje koncentracije nanočestica poli(vinil-alkohola) s timolom. Ovim je postupkom broj bakterija Y. enterocolitica uspješno smanjen za 100 %. Novina i znanstveni doprinos. Timol je spoj biljnog porijekla, koji ne narušava zdravlje čovjeka. U ovome smo radu inkapsulacijom u omotaču s poli(vinil-alkoholom) povećali stabilnost i poboljšali fizikalno-kemijska svojstva timola. Primjenom nanočestica tog dezinficijensa može se poboljšati mikrobiološka ispravnost sirovog bobičastog voća, što se u praksi može primijeniti za očuvanje sigurnosti hrane

Extraction of fresh banana waste juice as non-cellulosic and non-food renewable feedstock for direct lipase production

The bulk availability of banana waste in the world has made a move towards the development of alternative novel renewable sugars in present study as the pressed juice from banana frond and pseudostem was found to contain high level of renewable sugars such as glucose, sucrose and fructose. By using a simple sugarcane press, the glucose content in the banana frond juice was 16.6 g/L, which accounts for 55% of the total fermentable sugars. From the results, the lipase production reached ∼200 U/mL in medium comprising banana frond juice and banana pseudostem juice, comparable to basal medium with glucose (206.3 U/mL) as carbon source in basal media. As banana pseudostem possesses high content of starch, microwave heating pretreatment showed 36% enhancement of glucose content (10.4 g/L) in juice as compared to direct pressed juice (7.78 g/L). This result indicates that banana waste juice can be used as an alternative fermentable carbon source for lipase production and has potential as a fermentable carbon source

Abundant copy-number loss of CYCLOPS and STOP genes in gastric adenocarcinoma

Background Gastric cancer, a leading cause of cancer death worldwide, has been little studied compared with other cancers that impose similar health burdens. Our goal is to assess genomic copy-number loss and the possible functional consequences and therapeutic implications thereof across a large series of gastric adenocarcinomas. Methods We used high-density single-nucleotide polymorphism microarrays to determine patterns of copy-number loss and allelic imbalance in 74 gastric adenocarcinomas. We investigated whether suppressor of tumorigenesis and/or proliferation (STOP) genes are associated with genomic copy-number loss. We also analyzed the extent to which copy-number loss affects Copy-number alterations Yielding Cancer Liabilities Owing to Partial losS (CYCLOPS) genes–genes that may be attractive targets for therapeutic inhibition when partially deleted. Results The proportion of the genome subject to copy-number loss varies considerably from tumor to tumor, with a median of 5.5 %, and a mean of 12 % (range 0–58.5 %). On average, 91 STOP genes were subject to copy-number loss per tumor (median 35, range 0–452), and STOP genes tended to have lower copy-number compared with the rest of the genes. Furthermore, on average, 1.6 CYCLOPS genes per tumor were both subject to copy-number loss and downregulated, and 51.4 % of the tumors had at least one such gene. Conclusions The enrichment of STOP genes in regions of copy-number loss indicates that their deletion may contribute to gastric carcinogenesis. Furthermore, the presence of several deleted and downregulated CYCLOPS genes in some tumors suggests potential therapeutic targets in these tumors.Singapore. Ministry of Health (Duke-NUS Signature Research Programs)Singapore. Agency for Science, Technology and ResearchSingapore-MIT Allianc