Gallium arsenide field effect transistors microstrip integrated circuit dielectric resonator oscillators

Bibliography: leaves 175-177.This thesis is concerned with Gallium Arsenide Metal Semiconductor Field Effect Transistor Microstrip Integrated Circuit Dielectric Resonator Oscillators (GaAs MESFET MIC DROs) - the different types, their design and their performance compared to other high Q factor (ie narrowband) microwave oscillators. The thesis has three major objectives. The first is to collate the information required to build microwave DROs. The second is to present the practical results obtained from Dielectric Resonator Bandreject and Bandpass filters (DR BRFs and DR BPFs). The last is to present and compare results from a DR stabilised microstrip oscillator and three types of series feedback DROs. Narrowband oscillators are usually evaluated in terms of their frequency stability, reliability, size, cost, efficiency and output power characteristics. In terms of these parameters DROs outperform Gunn cavity oscillators and are only bettered by crystal locked sources in terms of frequency temperature stability and long-term stability. The components of a GaAs MESFET MIC DRO possess ideal properties for the construction of a narrowband source with the exception of the long term stability of the GaAs MESFET. GaAs MESFET•DROs have the best published DRO results for efficiency, output power, power temperature stability and external Q factor. Basic oscillator theory derived by Kurokawa can be applied to both negative resistance and feedback oscillators. Impedance locus, device-line and operating point concepts provide a convenient framework for understanding hysteresis in microwave oscillators. The work by Kurokawa can also be translated into the S-parameter domain which has proved convenient for the design of microwave oscillators

Delirium screening in the intensive care unit using emerging QEEG techniques : A pilot study

This work was supported by an Alzheimer’s Society grant (project grant number AS-PG-14-039 to BP) and a British Journal of Anaesthesia / Royal College of Anaesthetists funded John Snow Anaesthesia iBSc Award (to AH).Peer reviewedPublisher PD

Stochastic Streams: Sample Complexity vs. Space Complexity

We address the trade-off between the computational resources needed to process a large data set and the number of samples available from the data set. Specifically, we consider the following abstraction: we receive a potentially infinite stream of IID samples from some unknown distribution D, and are tasked with computing some function f(D). If the stream is observed for time t, how much memory, s, is required to estimate f(D)? We refer to t as the sample complexity and s as the space complexity. The main focus of this paper is investigating the trade-offs between the space and sample complexity. We study these trade-offs for several canonical problems studied in the data stream model: estimating the collision probability, i.e., the second moment of a distribution, deciding if a graph is connected, and approximating the dimension of an unknown subspace. Our results are based on techniques for simulating different classical sampling procedures in this model, emulating random walks given a sequence of IID samples, as well as leveraging a characterization between communication bounded protocols and statistical query algorithms

Illness patterns prior to diagnosis of lymphoma : Analysis of UK medical records

Background: Increased understanding of the relationship between lymphomas and co-morbidities is likely to provide valuable insights into the natural history of these disorders. Methods: 761 cases with lymphoma (310 diffuse large B-cell [DLBCL]; 226 follicular [FL]; and 225 Hodgkin [HL]) and 761 unaffected age and sex matched controls were recruited and their histories of infection and non-infection diagnoses in primary care records were compared using negative binomial regression. Results: No differences were observed between the infectious illness patterns of DLBCL and FL cases and their matched controls over the 15 years preceding lymphoma diagnosis. A marked excess of infectious illness episodes was recorded for HL cases compared to their controls; evident at least a decade prior to HL diagnosis. For non-infectious consultations an excess of case over control visits emerged 4-6 years before DLBCL and FL diagnosis; no specific co-morbidity associations were found. No case-control differences for non-infectious conditions were apparent for HL. Conclusion: There are substantial variations in patterns of illness prior to diagnosis of the three lymphoma subtypes examined. The excess of infectious diagnoses prior to HL may point to underlying immune abnormality, but there was no suggestion of this for DLBCL and FL where a generalized excess of non-infectious conditions was evident. (C) 2010 Elsevier Ltd. All rights reserved

Heritage, health and place:The legacies of local community-based heritage conservation on social wellbeing

Geographies of health challenge researchers to attend to the positive effects of occupying, creating and using all kinds of spaces, including 'green space' and more recently 'blue space'. Attention to the spaces of community-based heritage conservation has largely gone unexplored within the health geography literature. This paper examines the personal motivations and impacts associated with people's growing interest in local heritage groups. It draws on questionnaires and interviews from a recent study with such groups and a conceptual mapping of their routes and flows. The findings reveal a rich array of positive benefits on the participants' social wellbeing with/in the community. These include personal enrichment, social learning, satisfaction from sharing the heritage products with others, and less anxiety about the present. These positive effects were tempered by needing to face and overcome challenging effects associated with running the projects thus opening up an extension to health-enabling spaces debates

Electronic adherence monitoring identifies severe preschool wheezers who are steroid responsive.

Little is known about adherence to inhaled corticosteroids (ICS) in preschool children with troublesome wheeze. Children with aeroallergen senitization, or those reporting multiple trigger wheeze (MTW), are more likely to respond to ICS. We hypothesized that adherence to ICS and symptom control are only positively related in atopic children, or those reporting MTW. Patients aged 1 to 5 years with recurrent wheeze prescribed ICS were recruited from a tertiary respiratory clinic. Clinical phenotype and aeroallergen senitization were determined, and adherence assessed using an electronic monitoring device (Smartinhaler). Symptom control (test for respiratory and asthma control in kids [TRACK]), quality of life (PACQLQ), airway inflammation (offline exhaled nitric oxide) were assessed at baseline and follow-up. Forty-eight children (mean age 3.7 years; SD, 1.2) were monitored for a median of 112 (interquartile range [IQR], 91-126) days. At baseline n = 29 reported episodic viral wheeze and n = 19 reported MTW. Twenty-four out of 48 (50%) wheezers had suboptimal ICS adherence (<80%). Median adherence was 64% (IQR, 38-84). There was a significant increase in TRACK and PACQLQ in the group as a whole, unrelated to adherence. In subgroup analysis only atopic wheezers with moderate or good adherence ≥ 60% had a significant increase in TRACK. There was no relationship between clinical phenotype, and adherence or TRACK. In this pilot study, overall adherence to ICS was suboptimal and was positively related to symptom control in atopic wheezers only. Assessments of adherence are important in preschool troublesome wheezers before therapy escalation to help identify those with an ICS responsive phenotype

Parvalbumin-positive interneurons of the prefrontal cortex support working memory and cognitive flexibility

We were supported by the Biotechnology and Biological Sciences Research Council grant BB/H001123/1 (P.W.), the Medical Research Council grants G0601498 and G1100546/2 (P.W.), Tenovus Scotland Grant G09/17 (A.J.M.) and the University of Aberdeen (P.W.). We thank O. Tüscher for discussion, P. Teismann and the microscopy core facility at the University of Aberdeen for the use of microscopy equipment, L. Strachan, A. Plano, S. Deiana for help with behavioral testing.Peer reviewedPublisher PD

Pandemic H1N1 Influenza A Viruses Are Resistant to the Antiviral Activities of Innate Immune Proteins of the Collectin and Pentraxin Superfamilies

Abstract Acquired immune responses elicited to recent strains of seasonal H1N1 influenza viruses provide limited protection against emerging A(H1N1) pandemic viruses. Accordingly, pre-existing or rapidly induced innate immune defenses are of critical importance in limiting early infection. Respiratory secretions contain proteins of the innate immune system, including members of the collectin and pentraxin superfamilies. These mediate potent antiviral activity and act as an initial barrier to influenza infection. In this study, we have examined the sensitivity of H1N1 viruses, including pandemic virus strains, for their sensitivity to collectins (surfactant protein [SP]-D and mannose-binding lectin [MBL]) and to the pentraxin PTX3. Human SP-D and MBL inhibited virus-induced hemagglutinating activity, blocked the enzymatic activity of the viral neuraminidase, and neutralized the ability of H1N1 viruses to infect human respiratory epithelial cells in a manner that correlated with the degree of glycosylation in the globular head of the hemagglutinin. Recent seasonal H1N1 viruses expressed three to four N-glycosylation sequons on the head of hemagglutinin and were very sensitive to inhibition by SP-D or MBL, whereas A(H1N1) pandemic viruses expressed a single N-glycosylation sequon and were resistant to either collectin. Of interest, both seasonal and pandemic H1N1 viruses were resistant to PTX3. Thus, unlike recent seasonal H1N1 strains of influenza virus, A(H1N1) pandemic viruses are resistant to the antiviral activities of innate immune proteins of the collectin superfamily

S-Nitrosylation of Surfactant Protein-D Controls Inflammatory Function

The pulmonary collectins, surfactant proteins A and D (SP-A and SP-D) have been implicated in the regulation of the innate immune system within the lung. In particular, SP-D appears to have both pro- and anti-inflammatory signaling functions. At present, the molecular mechanisms involved in switching between these functions remain unclear. SP-D differs in its quaternary structure from SP-A and the other members of the collectin family, such as C1q, in that it forms large multimers held together by the N-terminal domain, rather than aligning the triple helix domains in the traditional “bunch of flowers” arrangement. There are two cysteine residues within the hydrophobic N terminus of SP-D that are critical for multimer assembly and have been proposed to be involved in stabilizing disulfide bonds. Here we show that these cysteines exist within the reduced state in dodecameric SP-D and form a specific target for S-nitrosylation both in vitro and by endogenous, pulmonary derived nitric oxide (NO) within a rodent acute lung injury model. S-nitrosylation is becoming increasingly recognized as an important post-translational modification with signaling consequences. The formation of S-nitrosothiol (SNO)-SP-D both in vivo and in vitro results in a disruption of SP-D multimers such that trimers become evident. SNO-SP-D but not SP-D, either dodecameric or trimeric, is chemoattractive for macrophages and induces p38 MAPK phosphorylation. The signaling capacity of SNO-SP-D appears to be mediated by binding to calreticulin/CD91. We propose that NO controls the dichotomous nature of this pulmonary collectin and that posttranslational modification by S-nitrosylation causes quaternary structural alterations in SP-D, causing it to switch its inflammatory signaling role. This represents new insight into both the regulation of protein function by S-nitrosylation and NO's role in innate immunity