This Thesis is an embodiment of some research work carried out towards achieving faster and more reliable handover techniques in a Mobile WiMAX (Worldwide Interoperability for Microwave Access) network. Handover, also called handoff, is the critical mechanism that allows an ongoing session in a cellular mobile network like WiMAX to be seamlessly maintained without any call drop as the Mobile Station (MS) moves out of the coverage area of one base station (BS) to that of another. Mobile WiMAX supports three different types of handover mechanisms, namely, the hard handover, the Fast Base Station Switching (FBSS) and the Micro-Diversity Handover (MDHO). Out of these, the hard handover is the default handover mechanism whereas the other two are the optional schemes. Also, FBSS and MDHO provide better performance in comparison to hard handover, when it comes to dealing with the high-speed multimedia applications. However, they require a complex architecture and are very expensive to implement. So, hard handover is the commonly used technique accepted by the mobile broadband wireless user community including Mobile WiMAX users. The existing Mobile WiMAX hard handover mechanism suffers from multiple shortcomings when it comes to providing fast and reliable handovers. These shortcomings include lengthy handover decision process, lengthy and unreliable procedure of selecting the next BS, i.e., the target BS (TBS) for handover, occurrence of frequent and unwanted handovers, long connection disruption times (CDT), wastage of channel resources, etc. Out of these, reducing the handover latency and improving the handover reliability are the two issues that our present work has focused on. While the process of selecting the TBS for handover adds to the overall delay in completing the process of handover, choosing a wrong TBS for handover increases the chance of further unwanted handovers to occur or even a call drop to occur. The latter greatly hampers the reliability of a handover. In order to contribute to the solution of the above two problems of slow handover and unreliable handover, this Thesis proposes and investigates three handover techniques, which have been called Handover Techniques 1, 2 and 3, respectively. Out of these three techniques, the first two are fully MS-controlled while the third one is a dominantly serving BS-controlled. In Handover Techniques 1 and 2, which share between them some amount of commonness of ideas, the MS not only itself determines the need for a handover but also self-tracks its own independent movement with respect to the location of the (static) neighboring BSs (NBS). N both these handover techniques, the MS performs distance estimation of the NBSs from the signal strength received from the NBSs. But they (the two handover techniques) employ different kinds of “lookahead” techniques to independently choose, as the TBS, that NBS to which the MS is most likely to come nearest in the future. Being MS-controlled, both Handover Technique 1 and Handover Technique 2 put minimal handover-related workload on their respective SBSs who thus remain free to offer services to many more MSs. This interesting capability of the two handover techniques can increase the scalability of the WiMAX network considerably. In Handover Technique 3, which is a BS-controlled one with some assistance received from the MS, the SBS employs three different criteria or parameters to select the TBS. The first criterion, a novel one, is the orientation matching between the MS’s direction of motion and the geolocation of each NBS. The other two criteria are the current load of each NBS (the load provides an indication of a BS’s current QoS capabilities) and the signal strength received by the MS from each NBS. The BS assigns scores to each NBS against each of the three independent parameters and selects the TBS, which obtains the highest weighted average score among the NBSs. All three handover techniques are validated using simulation methods. While Handover Techniques 1 and 2 are simulated using Qualnet network simulator, for Handover Technique 3, we had to design, with barest minimum capability, our own simulation environment, using Python. Results of simulation showed that for Handover Techniques 1 and 2, it is possible to achieve around 45% improvement (approx) in the overall handover time by using the two proposed handover techniques. The emphasis in the simulation of the Handover Technique 3 was on studying its reliability in producing correct handovers rather than how fast handovers are. Five different arbitrary pre-defined movement paths of the MS were studied. Results showed that with orientation matching or orientation matching together with signal strength, reliability was extremely good, provided the pre-defined paths were reasonably linear. But reliability fell considerably when relatively large loads were also considered along with orientation matching and signal strength. Finally, the comparison between the proposed handover techniques in this Thesis and few other similar techniques in Mobile WiMAX proposed by other researchers showed that our techniques are better in terms providing fast, reliable and intelligent handovers in Mobile WiMAX networks, with scalability being an added feature.

2 pp. / In the semi-arid climate of southern AZ, evaporative cooling systems are commonly used and very effective for cooling homes (swamp coolers), outdoor areas (misters), and for greenhouses used for commercial and horticultural plant production (pad-and-fan, high-pressure-fog). The purpose of this brochure is to educate users about strategies they can employ to save water and improve the performance of evaporative cooling systems. Principles of operation, a list of advantages and disadvantages, and a comparison of common systems is also included, to help users decide the best system for them.

Technological limitations have prevented interrogation and manipulation of many signaling pathways in model and living systems required for the development of diagnostic and therapeutic modalities in diseases, such as cancer. Liposome-supported plasmon resonant gold nanoshells are biologically inspired composite structures, in which the liposome allows for the encapsulation of substances, and the plasmon resonant structure facilitates rapid release of encapsulated contents upon laser light illumination. As shown in this work, we overcome current limitations in cellular manipulation using plasmon resonant gold-coated liposomes in conjunction with light-activated release to achieve accurate probing of complex cellular responses. Development toward this goal was demonstrated with four specific aims. The first specific aim was to develop a computational model of heat diffusion to investigate the light-induced heating of gold-coated liposomes. This model was used to optimize the photothermal process for release of an encapsulated payload. The second aim was to demonstrate encapsulation and on-demand release of molecules in a spectrally-controlled manner, where plasmon resonant nanoparticles only release content upon illumination with a wavelength of light matching their plasmon resonance band. The third specific aim was to demonstrate that this release mechanism can be used in a biological setting to deliver a peptide and extracellularly activate surface membrane receptors with single-cell spatial and high temporal resolution. The fourth specific aim further refined the level of spatial and temporal control of payload release using gold-coated liposomes with optical trapping to demonstrate mirco-manipulation of liposome movement and rapid content release to enable accurate perturbation of cellular functions in response to released compounds. Through this work, we have developed an experimental system with the potential for the delivery and localized release of an encapsulated agent with high spatial and temporal resolution. This on-demand release system is compatible with a broad range of molecules and uses biologically safe near-infrared light. In combination with the spectral tunability of these plasmon resonant nanoshells and spectrally-selective release, this technology may allow for interrogation of complex and diverse signaling pathways in living tissues or their models with unprecedented spatial and temporal control.

Cellulose is the most abundant renewable polymer on the planet and there is great interest in expanding its use beyond its traditional applications. However, its hydrophilicity and insolubility in most common solvent systems are obstacles to its widespread use in advanced materials. One way to counteract this is to attach hydrophobic polymer chains to cellulose: this allows the properties of the copolymer to be tailored by the molecular weight, density, and physical properties of the grafts. Two methods were used here to synthesize the graft copolymers: a ‘grafting-from’ approach, where synthetic chains were grown outward from bromoester moieties on cellulose (Cell-BiB) via Cu(0)-mediated polymerization; and a ‘grafting-to’ approach, where fully formed synthetic chains with terminal sulfide functionality were added to cellulose acetate with methacrylate functionality (CA-MAA) via thiol-ene Michael addition. The Cell-BiB was synthesized in the ionic liquid 1-butyl-3-methylimidazolium chloride and had a degree of substitution of 1.13. Polymerization from Cell-BiB proceeded at similar but slightly slower rate than an analogous non-polymeric initiator (EBiB). The average graft density of poly(methyl acrylate) chains was 0.71 chains/ring, with a maximum of 1.0 obtained. The graft density when grafting poly(methyl methacrylate) was only 0.15, and this appeared to be due to the slow initiation of BiB groups. Using EBiB to model the reaction and improve the design should allow this to be overcome. Chain extension experiments demonstrated the living behaviour of the polymer. The CA-MAA was synthesized by esterification with methacrylic acid. Reactions of CA-MAA with thiophenol and dodecanethiol resulted in quantitative addition of the thiol to the alkene. The grafts were synthesized by Cu(0)-mediated polymerization from a bifunctional initiator containing a disulfide bond, followed by reduction to sulfides. The synthetic polymers were successfully grafted to CA-MAA but the grafting yield was limited by the low sulfide functionality. Better retention of sulfide functionality is necessary for more efficient grafting. / Thesis (Master, Chemical Engineering) -- Queen's University, 2013-05-27 16:21:03.874

Controlled release systems aim at achieving a predictable and reproducible drug release profile over a desired time period. These controlled release formulations offer many advantages over conventional dosage forms. These advantages include: reduced dosing intervals, constant drug levels in the blood, increased patient compliance and decreased adverse effects. Complex controlled release formulations such as those with sustained release properties, often require additional steps during the production phase. The cost and economic impact associated with these complex controlled release dosage formulations often outweigh the short term benefits. Thus the development of an economic method to produce controlled release particles is of great importance especially in third world countries. In controlled release formulations the drug is often equally dispersed throughout a polymer matrix. In the presence of a thermodynamically compatible solvent, swelling occurs and the polymer releases its content to the surrounding medium. The rate of drug release can be controlled by interfering with the amount of swelling and rate of diffusion by manipulating the viscosity of the polymer matrix. Chitosan is an ideal candidate for controlled drug delivery through matrix release systems. It is a biodegradable polymer with absorption-enhancing properties. Cross-linking chitosan with different cross-linking agents allow the preparation of beads. Beads are frequently used in controlled release dosage forms as they are very flexible in dosage form development and show various advantages over single unit dosage forms. Because beads disperse freely in the gastrointestinal tract they maximize drug absorption, reduce fluctuation in peak plasma, and minimize potential side effects without lowering drug bio-availability. Chitosan beads and excipient containing chitosan beads were prepared and investigated as possible controlled release formulations. Pyrazinamide was chosen as the model drug. Chitosan beads and excipient containing chitosan beads were prepared by ionotropic gelation in tripolyphosphate. In this study chitosan/pyrazinamide beads containing pharmaceutical excipients (Ascorbic acid, Explotab and Ac-Di-Sol) were produced. The excipients were added individually and in combinations to the chitosadpyrazinamide dispersion and the beads were characterized on the basis of their morphology, solubility, fiability, drug loading capacity and swelling behaviour, as well as drug release (dissolution properties). The drug loading of the pyrazinarnide loaded chitosan beads, was 52.26 % 0.57%. It was noted that the inclusion of excipients in the beads resulted in an increase in drug loading with the combination of Ascorbic acid and Ac-Di-Sol giving the highest drug loading of 67.09 ± 0.22%. It was expected that the addition of the pharmaceutical excipients would lead to a sustained release of pyrazinamide. Dissolutions studies, however, revealed a burst release in both phosphate buffer solution (PBS) pH 5.60 and 7.40 over the first 15 minutes and the curve reached a plateau after 30 minutes. Thus, apparently the inclusion of the pharmaceutical excipients did not contribute to a sustained release of pyrazinamide over the tested period of six hours. In future studies the dissolution time can possibly be extended to a period of 24 hours. It might be possible for the remaining drug (approximately 40%) in the beads to be released over the extended period. Other polymers can also be investigated to control the release of pyrazinamide. Further studies are, however, necessary to investigate this possibility in the future. / Thesis (M.Sc. (Pharmaceutics))--North-West University, Potchefstroom Campus, 2007.

Controlled Auto-Ignition (CAI) also known as Homogeneous Charge Compression Ignition (HCCI) is increasingly seen as a very effective way of lowering both fuel consumption and emissions. Hence, it is regarded as one of the best ways to meet stringent future emissions legislation. It has however, still many problems to overcome, such as limited operating range. This combustion concept was achieved in a production type, 4-cylinder gasoline engine, in two separated tests: naturally aspirated and turbocharged. Very few modifications to the original engine were needed. These consisted basically of a new set of camshafts for the naturally aspirated test and new camshafts plus turbocharger for the boosted test. The first part of investigation shows that naturally aspirated CAI could be readily achieved from 1000 to 3500rpm. The load range, however, decreased noticeably with engine speed due to flow restrictions imposed by the low lift camshafts. Ultra-low levels of NOx emissions and reduced fuel consumption were observed. After baseline experiments with naturally aspirated operation, the capability of turbocharging for extended CAI operation was investigated. The results show that the CAI range could achieve higher load and speed with the addition of the turbocharger. The engine showed increased fuel consumption due to excessive pumping losses. Emissions, however, have been reduced substantially in comparison to the original engine. NOx levels could be reduced by up to 98% when compared to a standard SI production engine.

Background: Although physical inactivity has been linked with numerous chronic health conditions and overall mortality, the majority of English adults report insufficient physical activity. To increase population physical activity levels, researchers have called for more community-level interventions. To evaluate these complex public health interventions, innovative study designs are required. The aim of this thesis was to evaluate whether a community-level physical activity intervention—‘Devon Active Villages’—increased the activity levels of rural communities. Methods: The Devon Active Villages intervention provided villages with 12 weeks of physical activity opportunities for all age groups. Community engagement helped tailor activity programmes for each village; communities were then supported for a further 12 months. 128 rural villages from south-west England were randomised to receive the intervention in one of four time periods, as part of a stepped wedge cluster randomised controlled trial. Data collection consisted of a postal survey of a random sample of adults (≥18 years), at baseline, and after each of the four intervention periods. The primary outcome of interest was the proportion of adults who reported sufficient physical activity to meet the current guidelines (≥150mins of moderate-and-vigorous, or ≥75mins of vigorous-intensity activity per week). The number of minutes spent in moderate-and-vigorous activity per week was analysed as a secondary outcome. Using data from all five periods, a comparison of study outcomes between intervention and control arms was performed, allowing for time period (as a fixed effect), and the random effect induced by correlation of outcomes (clustering) within villages. Additionally, the baseline data were analysed separately using logistic and linear regression models to examine the correlates of physical activity behaviour in rural adults. Results: Baseline study: 2415 adults completed the postal survey (response rate 37.7%). The following factors both increased the odds of meeting the recommended activity guidelines and were associated with more leisure-time physical activity: being male, in good health, greater commitment to being more active, favourable activity social norms, greater physical activity habit, and recent use of recreational facilities. In addition, there was evidence that younger age, lower body mass index, having a physical occupation, dog ownership, inconvenience of public transport, and using recreational facilities outside the local village were associated with greater reported leisure-time physical activity. Main study: 10,412 adults (4693 intervention, 5719 control) completed the postal survey (response rate 32.2%). The intervention did not increase the odds of adults meeting the physical activity guideline, although there was weak evidence of an increase in the minutes of moderate-and-vigorous-intensity activity per week. The ineffectiveness of the intervention may have been due to its low penetration—only 16% of intervention participants reported being aware of the intervention, and just 4% reported participating in intervention events. Conclusions: Baseline study: This study highlights potentially important correlates of physical activity that could be the focus of interventions targeting rural populations, and demonstrates the need to examine rural adults separately from their urban counterparts. Main study: A community-level physical activity intervention providing tailored physical activity opportunities to rural villages did not improve physical activity levels in adults. Greater penetration of such interventions needs to be achieved for them to have any chance of increasing the prevalence of physical activity at the community level.

Background Patients who experience a stroke or transient ischemic attack (TIA) are at high risk of recurrent stroke, but little is known about temporal trends in unselected populations. Reports of low adherence to recommended treatments indicate a need for enhanced secondary preventive follow-up to achieve the full potential of evidence-based treatments. In addition, socioeconomic factors have been associated with poor health outcomes in a variety of contexts. Therefore, it is important to assess the implementation and results of secondary prevention in different socioeconomic groups. Aims The aims of this thesis were to assess temporal trends in ischemic stroke recurrence and evaluate the implementation and results of a nurse-led, telephone-based follow-up program to improve blood pressure (BP) and low-density lipoprotein cholesterol (LDL-C) levels after stroke/TIA. Methods In study I, we collected baseline data for unique patients with an ischemic stroke event between 1998 and 2009 (n=196 765) from the Swedish Stroke Register (Riksstroke). Recurrent ischemic stroke events within 1 year were collected from the Swedish National Inpatient Register (IPR) and the cumulative incidence was compared between four time periods using the Kaplan-Meier survival analysis and the logrank test. Implementation (study II) and 1-year results (study III-IV) for the secondary preventive follow-up were studied in the NAILED (Nurse-based Age-independent Intervention to Limit Evolution of Disease) study. Between 1 Jan 2010 and 31 Dec 2013, the baseline characteristics of consecutive patients admitted to Östersund Hospital for acute stroke or TIA were collected prospectively (n=1776). Consenting patients in a condition permitting telephone-based follow-up were randomized to nurse-led, telephone-based follow-up or follow-up according to usual care. Follow-up was cunducted at 1 and 12 months after discharge and the intervention included BP and LDL-C measurements, titration of medication, and lifestyle counseling. In study II, we analyzed factors associated with non-participation in the randomized phase of the NAILED study, including association with education level. In addition, we compared the 1-year prognosis in terms of cumulative survival between participants and non-participants. In study III, we compared differences in BP and LDL-C levels between the intervention and control groups during the first year of follow-up and, in study IV, in relation to level of education (low, ≤10 years; high, >10 years). Results The cumulative 1-year incidence of recurrent ischemic stroke decreased from 15.0% to 12.0%. Among surviving stroke and TIA patients, 53.1% were included for randomization, 35.7% were excluded mainly due to physical or cognitive disability, and 11.2% declined participation in the randomized phase. A low level of education was independently associated with exclusion, as well as the patient’s decision to abstain from randomization. Excluded patients had a more than 12-times higher risk of death within 1 year than patients who were randomized. After 1 year of follow-up, the mean systolic BP, diastolic BP, and LDL-C levels were 3.3 mmHg (95% CI 0.3 to 6.3), 2.3 mmHg (95% CI 0.5 to 4.2), and 0.3 mmol/L (95% CI 0.1 to 0.4) lower in the intervention group than among controls. Among participants with values above the treatment goal at baseline, the differences in systolic BP and LDL-C levels were more pronounced (8.0 mmHg, 95% CI 4.0 to 12.1; 0.6 mmol/L, 95% CI 0.4 to 0.9). In the intervention group, participants with a low level of education achieved similar or larger improvements in BP and LDL-C than participants with a high level of education. In the control group, BP remained unaltered and the LDL-C levels increased among participants with a low level of education. Conclusion The 1-year risk of ischemic stroke recurrence decreased in Sweden between 1998 and 2010. Nurse-led, telephone-based secondary preventive follow-up is feasible in just over half of the survivors of acute stroke and TIA and achieve better than usual care in terms of BP and LDL-C levels, and equality in BP improvements across groups defined by education level. However, a large proportion of stroke survivors are in a general condition precluding this form of follow-up, and their prognosis in terms of 1-year survival is poor. Patients with a low education level are over-represented within this group and among patients declining randomization for secondary preventive follow-up.

The Giant Magellan Telescope (GMT) primary mirror consists of seven 8.4 m light-weight honeycomb mirrors that are being manufactured at the Richard F. Caris Mirror Lab (RFCML), University of Arizona. In order to manufacture the largest and most aspheric astronomical mirrors various high precision fabrication technologies have been developed, researched and implemented at the RFCML. The unique 8.4 m (in mirror diameter) capacity fabrication facilities are fully equipped with large optical generator (LOG), large polishing machine (LPM), stressed lap, rigid conformal lap (RC lap) and their process simulation/optimization intelligence called MATRIX. While the core capability and key manufacturing technologies have been well demonstrated by completing the first GMT off-axis segment, there have been significant hardware and software level improvements in order to improve and enhance the GMT primary mirror manufacturing efficiency. The new and improved manufacturing technology plays a key role to realize GMT, the next generation extremely large telescope enabling new science and discoveries, with high fabrication efficiency and confidence.

In today’s drug discovery, the number of candidate drugs based on new molecular entities with poor aqueous solubility is increasing. Since poor aqueous solubility of an active pharmaceutical ingredients (APIs) is associated with low bioavailability and thus limite their therapeutic effect, this is often a great challenge in the development of new drugs when oral administration is the preferred route of administration. A number of different strategies have been developed to circumvent this problem where salt formulations of an API is the most widely employed method. However, new strategies are needed since there is no one solution that solves this issue for all substances. In recent time, the concept of stabilizing poorly soluble APIs in their amorphous form has gained a lot of attention since amorphous compounds exhibit a higher apparent solubility compared to their crystalline counterparts. Amorphous substances are prone to crystallize if left in a non-constricted environment and thus need to be stabilized if the amorphous state is to be conserved until administration. Inorganic mesoporous materials have been proposed as an interesting type of excipients that can conserve the amorphous state of APIs. In this work, the focus was to investigate the possibilities of using a mesoporous type of magnesium carbonate to stabilize the amorphous state of different APIs. Due to the nanometer sized pores in the material, complete conservation of amorphous APIs was obtained. This resulted in both an increase in in vitro release rate and a higher solubility of the substances which may translate to both a faster onset of action and an improved therapeutic effect of the APIs in a clinical situation. The long term stability of formulations was also investigated showing promising results. The results presented in this work show that mesoporous magnesium carbonate represents an interesting type of excipient for oral formulations of APIs with poor aqueous solubility. / <p>Felaktigt ISBN 978-91-554-9702-6 i tryck version.</p>