Selective laser sintering (SLS) is a commercial, powder-based manufacturing process that produces parts with complicated shape and geometry based on a computer solid model. One of the major drawbacks of SLSed inter-metallic and ceramic parts is their high porosity because of the use of binder system. High porosity results in poor mechanical, electrical and thermal properties of the preform and hence renders it unsuitable for various applications. This thesis attempts to infiltrate SLSed preforms by carrying out electrochemical deposition of metal ions inside the interconnected pore network. One of the major benefits of carrying out this novel process is low processing temperature as opposed to existing methods such as melt infiltration. Low temperature reduces both energy consumption and associated carbon-footprint and also minimizes undesirable structural changes. Both conductive and non-conductive preforms may be electrochemically infiltrated, and MMCs produced by this method have potential for use in structural applications. / text

Conducting representative surveys of older people is challenging. This thesis aims to analyze a) the characteristics of individuals at risk of being underrepresented in surveys of older people, b) the systematic errors likely to occur as a result of these selections, and c) whether these systematic errors can be minimized by weighting adjustments.   In Study I, we investigated a) who would be missing from a survey that excluded those living in institutions and that did not use indirect interviews, b) how prevalence rates would be affected by these exclusions, and c) whether post-stratifying the data by sex and age (weighting adjustment) would correct for any systematic measurement error. In Study II, we compared mortality and hospitalization rates in those who responded to a postal questionnaire with rates in the target population. In addition, we tested whether a weighting variable created with a number of auxiliary variables could correct for the differences.   In Study III, we followed a longitudinal cohort sample for 43 years. By recalculating baseline characteristics at each follow-up, we investigated how the sample changed after a) selective mortality and b) survey non-participation. In Study IV, we investigated whether the systematic non-participation that is likely to occur in surveys of older people affects the association between education and health. In sum, the results of these four studies show that people in the oldest age groups, women, those of low socioeconomic position, and those with the poorest health tend to be underrepresented in surveys of older people. This systematic underrepresentation might lead to an underestimation of poor health and function, a bias that is unlikely to be corrected by weighting adjustments, and to an underestimation of health inequality between educational groups. The results also show that the selective mortality that occurs in longitudinal samples might be compounded by selective non-participation among the most disadvantaged groups. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 1: Manuscript. Paper 2: Manuscript.</p>

The lifetime of the polymer membrane ion-selective electrode is, in general, short when compared to that of the glass pH electrode. It is the manner in which the elctroactive materials are entrapped in the ion-selective membranes which accounts for this lifetime difference. In the polymer membrane electrode a high molecular weight electroactive material is dissolved in the plasticized polymer membrane. Because it is hydrophobic, this material is much more compatible with the low dielectric membrane phase than with the aqueous analyte phase. It, of course, has some solubility in the aqueous phase and, in time, leaches from the membrane. In the glass pH electrode, the electroactive material is the SiOH group which is covalently attached to the insoluble glass membrane. Because it is attached, it cannot be leached from the membrane. The purpose of this study was to investigate the possibility of covalently attaching the electroactive material to the polymer membrane in polymer membrane electrodes. In this weay, it was hoped that electrodes with much longer lifetimes could be obtained. Cation selective electrodes based on sulfonated polystyrene were investigated first. Sulfonation was accomplished by dipping polystyrene membranes into chlorosulfonic acid. Electrodes of both the conventional (i.e., with internal reference) and coated-wire types were prepared. Neither gave satisfactory response. Cation selective electrodes based on the perfluorinated, sulfonic acid containing ion exchange polymer NAFION 120® were investigated next. This material produced well-behaved Cs⁺ electrodes but electrodes responsive to larger cations (e.g., tetrapropylammonium and dodecyltri-methylammonium) could not be obtained. This may be due to ion-pairing in the membrane phase between these larger cations and the polymer bound sulfonate groups. To help answer some of the questions encountered during these investigations of electrodes based on covalently attached sulfonate groups, polymer membrane electrodes based on dinonylnaphthalenesulfonic acid were prepared and investigated. These electrodes were found to have very great selectivity for high molecular weight organic cations relative to inorganic and smaller organic cations. This type of selectivity is analogous to that obtained in ion pair solvent extraction of cations with a high molecular weight anionic species. Since a number of species of clinical, biological and toxicological interest are, at physiological pH, high molecular weight organic cations, electrodes based on dinonylnaphthalenesulfonic acid show great promise for determination of such species. An electrode for the determination of the drug phencyclidine was prepared to demonstrate the potentialities of drug analysis with this type of electrode. A microcomputer-based potentiometric analysis system was used to collect and analyze the data in this study. This system was one of the first stand-alone microcomputer systems employing a high level computer language to be described. The IMSAI 8080 Microcomputer and the computer language CONVERS were used.

The melanocortin 3 and 4 receptors share 58% overall amino acid identity and 76% similarity. This high level of similarity between the MC3R and the MC4R underscores the difficulties associated with developing MC3R selective ligands, and as a consequence little is known of the physiological functions of the melanocortin 3 receptor. Previous research showing the differences between endogenous non-selective ligands and melanocortin 3 receptor selective ligands are mainly within the C-terminus of the melanocortin peptide. These findings have been exploited in this research using known melanocortin 3 and 4 selective ligands modified at their respective C-termini to develop some very promising melancortin 3 selective antagonists and agonists, analog 5 ([CO(CH₂)₂CO-DNal(2')-Arg-Trp-Lys]-Gly-Lys-Pro-Val-NH₂) and analog 20 ((H-DNal(2')-c[Asp-Pr6-DPhe-Arg-Trp-Lys]-Ala-Gly-Pro-Val-NH₂) respectively. Additional studies using molecular modeling have produced further insights into the structural basis for selectivity. Finally, we have been developing a new scaffold for the melanocortin receptor using cyclic dipeptide derivatives.

Microfluidics promises to re-shape the current health-care system by transferring diagnostic tools from central laboratories to close vicinity of the patient (point-of-care). One of the most important operational steps in any diagnostic platform is sample preparation, which is the main subject in this thesis. The goal of sample preparation is to isolate targets of interest from their surroundings. The work in this thesis is based on three ways to isolate bacteria:  immune-based isolation, selective cell lysis, size-based separation. The first sample-preparation approach uses antibodies against lipopolysaccharides (LPS), which are surface molecules found on all gram-negative bacteria. There are two characteristics that make this surface molecule interesting. First, it is highly abundant: one bacterium has approximately a million LPS molecules on its cell-wall. Second, the molecule has a conserved region within all gram-negative bacteria, so using one affinity molecule to isolate disease-causing gram-negative bacteria is an attractive option, particularly from the point of view of sample preparation. The main challenge, however, is antigen accessibility. To address this, we have developed a treatment protocol that improves the capturing efficiency. The strategy behind selective cell lysis takes advantage of the differences between the blood-cell membrane and the bacterial cell-wall. These fundamental differences make it possible to lyse (destroy) blood-cells selectively while keeping the target of interest, here the bacteria, intact and, what is more important alive. Viability plays an important role in determining antibiotic susceptibility. Difference in size is another well-used characteristic for sample- separation. Inertial microfluidics can focus size-dependent particle at high flow-rates. Thus, particles of 10 µm diameter were positioned in precise streamlines within a curved channel.  The focused particles can then be collected at defined outlets.  This approach was then used to isolate white blood cells, which account for approximately 1% of the whole blood.  In such a device particles of 2µm diameter (size of bacteria) would not be focused and thereby present at every outlet. To separate bacteria from blood elasto-inertial microfluidics was used. Here, e blood components are diverted to center of the channels while smaller bacteria remain in the side streams and can subsequently be separated. / <p>QC 20141212</p>

In recent years, there have been tremendous advances in wireless & mobile communications, including wireless radio techniques, networking protocols, and mobile devices. It is expected that different broadband wireless access technologies, e.g., WiFi (IEEE 802.11) and WiMAX (IEEE 802.16) will coexist in the future. In the meantime, multimedia applications have experienced an explosive growth with increasing user demands. Nowadays, people expect to receive high-speed video, audio, voice and web services even when being mobile. The key question that needs to be answered, then, is how do we ensure that users always have the "best" network performance with the "lowest" costs in such complicated situations? The latest IEEE 802.11n standards attains rates of more than 100 Mbps by introducing innovative enhancements at the PHY and MAC layer, e.g. MIMO and Frame Aggregation, respectively. However, in this thesis we demonstrate that frame aggregation's performance adheres due to the EDCA scheduler's priority mechanism and consequently resulting in the network's poor overall performance. Short waiting times for high priority flows into the aggregation queue resolves to poor channel utilization. A Delayed Channel Access algorithm was designed to intentionally postpone the channel access procedure so that the number of packets in a formed frame can be increased and so will the network's overall performance. However, in some cases, the DCA algorithm has a negative impact on the applications that utilize the TCP protocol, especially the when small TCP window sizes are engaged. So, the TCP process starts to refrain from sending data due to delayed acknowledgements and the overall throughput drops. In this thesis, we address the above issues by firstly demonstrating the potential performance benefits of frame aggregation over the next generation wireless networks. The efficiency and behaviour of frame aggregation within a single queue, are mathematically analysed with the aid of a M=G[a;b]=1=K model. Results show that a trade-off choice has to be taken into account over minimizing the waiting time or maximizing utilization. We also point out that there isn't an optimum batch collection rule which can be assumed as generally valid but individual cases have to be considered separately. Secondly, we demonstrate through extensive simulations that by introducing a method, the DCA algorithm, which dynamically determines and adapts batch collections based upon the traffic's characteristics, QoS requirements and server's maximum capacity, also improves e ciency. Thirdly, it is important to understand the behaviour of the TCP ows over the WLAN and the influence that DCA has over the degrading performance of the TCP protocol. We investigate the cause of the problem and provide the foundations of designing and implementing possible solutions. Fourthly, we introduce two innovative proposals, one amendment and one extension to the original DCA algorithm, called Adaptive DCA and Selective DCA, respectively. Both solutions have been implemented in OPNET and extensive simulation runs over a wide set of scenarios show their effectiveness over the network's overall performance, each in its own way.

On 1 June 2010, a new Block Exemption Regulation (BER) and new Guidelines that affect the practical use of selective distribution systems enter into force. The BER exempts vertical agreements, such as selective distribution agreements, from the prohibition of Article 101 (1) TFEU. It is significant for individual market players to obtain knowledge of what impact the new BER and the new Guidelines have for the practical use of selective distribution systems. The Commission has amended the new BER and the new Guidelines in the light of the development the last decade. Two main changes are noticed that affect the content of the new legislative documents. Firstly, it is established that many distributors have obtained larger market shares. Secondly, it is stated that Internet sales have increased largely. The basic principles of the new versions of the BER and the Guidelines are identical with the former versions but the present changes are although noticeable for companies and their selective distribution systems. The new BER contains a new market share rule that is more restrictive than the corresponding rule in the former BER. However, the new market share rule is not an expression of a less tolerant approach towards selective distribution systems; rather an amendment necessary due to the development of distributors’ market shares. The growth of distribution in the Internet the last ten years is reflected in the new Guidelines. The Commission’s approach towards the Internet as a distribution method seems in general to be positive. It is noticeable that the Commission wants that parties of selective distribution agreements shall be able to benefit from all the positive effects of online sales at the same time as the Commission tries to preserve the positive effects of selective distribution. This thesis describes and examines the practical use of selective distribution systems. Different reasons for companies to use selective distribution systems and effects of the new BER and Guidelines are in particular examined.

The osteological paradox addresses how well interpretations of past population health generated from human skeletal remains reflect the health of the living population from which they were drawn. Selective mortality and hidden heterogeneity in frailty are particularly relevant when assessing childhood health in the past, as subadults are the most vulnerable group in a population and are therefore less likely to fully represent the health of those who survived. The ability of subadults to represent the health of those who survived is tested here by directly comparing interpretations of childhood stress based on non-survivors (subadults aged 6-20,14 females and 9 males) to those based on retrospective analyses of survivors (adults aged 21-46, 26 females and 27 males). Non-survivors and survivors were directly matched by birth year, using the Coimbra Identified Skeletal Collection; therefore interpretations of childhood stress reflect a shared childhood. Long bone and vertebral canal growth, linear enamel hypoplasia, cribra orbitalia, porotic hyperostosis, scurvy indicators and periosteal bone reactions were assessed for both groups. Overall, long bone growth generates the same interpretation of health for both non-survivors and survivors, and both groups exhibit the same range of stress (mild to severe), but the pattern of stress experienced in childhood differs between the two groups. Female survivors reveal different timing of stress episodes and a higher degree of stress than female non-survivors. Male survivors exhibit less stress than male non-survivors. These different patterns suggest that interpretations based solely on non-survivors would under-represent the stress experienced by female survivors and over-represent the stress experienced by male survivors, further demonstrating the importance of addressing issues of selective mortality. In addition, these different patterns suggest that hidden heterogeneity of frailty may be sex specific where males are more vulnerable to stress and females more able to develop resistance to stress and survive.

The osteological paradox addresses how well interpretations of past population health generated from human skeletal remains reflect the health of the living population from which they were drawn. Selective mortality and hidden heterogeneity in frailty are particularly relevant when assessing childhood health in the past, as subadults are the most vulnerable group in a population and are therefore less likely to fully represent the health of those who survived. The ability of subadults to represent the health of those who survived is tested here by directly comparing interpretations of childhood stress based on non-survivors (subadults aged 6-20,14 females and 9 males) to those based on retrospective analyses of survivors (adults aged 21-46, 26 females and 27 males). Non-survivors and survivors were directly matched by birth year, using the Coimbra Identified Skeletal Collection; therefore interpretations of childhood stress reflect a shared childhood. Long bone and vertebral canal growth, linear enamel hypoplasia, cribra orbitalia, porotic hyperostosis, scurvy indicators and periosteal bone reactions were assessed for both groups. Overall, long bone growth generates the same interpretation of health for both non-survivors and survivors, and both groups exhibit the same range of stress (mild to severe), but the pattern of stress experienced in childhood differs between the two groups. Female survivors reveal different timing of stress episodes and a higher degree of stress than female non-survivors. Male survivors exhibit less stress than male non-survivors. These different patterns suggest that interpretations based solely on non-survivors would under-represent the stress experienced by female survivors and over-represent the stress experienced by male survivors, further demonstrating the importance of addressing issues of selective mortality. In addition, these different patterns suggest that hidden heterogeneity of frailty may be sex specific where males are more vulnerable to stress and females more able to develop resistance to stress and survive.

In this thesis, a low-profile, high-gain, ultra-wideband (UWB) planar dipole antenna is presented for radar imaging applications. The antenna is loaded with open complementary double concentric split-hexagonal-ring resonators (LC tank) and chip resistors, and backed with a novel double-layer FSS reflector for gain enhancement. A broadband microstrip to parallel-plate transformer is designed as the feeding structure of the antenna to provide impedance matching and balanced-to-unbalanced transition. The measurement results show the proposed antenna operates over the frequency bandwidth of 0.65-3.8 GHz with S11< -10 dB (VSWR) and smooth gains in the range of 6.2-9 dBi.