957 resultados para CURRENT SELF-OSCILLATION


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Based on the analysis of molecular gas dynamics, the drag and moment acting on an ellipsoid particle of revolution X-2/a(2) + Y-2/a(2) + Z(2)/c(2) = 1, as an example of nonspherical particles, are studied under the condition of free-molecular plasma flow with thin plasma sheaths. A nonzero moment which causes nonspherical particle self-oscillation and self-rotation around its own axis in the plasma flow-similar to the pitching moment in aerodynamics-is discovered for the first time. When the ratio of axis length c/a is unity, the moment is zero and the drag formula are reduced to the well-known results of spherical particles. The effects of the particle-plasma relative velocity, the plasma temperature, and the particle materials on the drag and moment are also investigated.

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With the advent of the laser in the year 1960, the field of optics experienced a renaissance from what was considered to be a dull, solved subject to an active area of development, with applications and discoveries which are yet to be exhausted 55 years later. Light is now nearly ubiquitous not only in cutting-edge research in physics, chemistry, and biology, but also in modern technology and infrastructure. One quality of light, that of the imparted radiation pressure force upon reflection from an object, has attracted intense interest from researchers seeking to precisely monitor and control the motional degrees of freedom of an object using light. These optomechanical interactions have inspired myriad proposals, ranging from quantum memories and transducers in quantum information networks to precision metrology of classical forces. Alongside advances in micro- and nano-fabrication, the burgeoning field of optomechanics has yielded a class of highly engineered systems designed to produce strong interactions between light and motion.

Optomechanical crystals are one such system in which the patterning of periodic holes in thin dielectric films traps both light and sound waves to a micro-scale volume. These devices feature strong radiation pressure coupling between high-quality optical cavity modes and internal nanomechanical resonances. Whether for applications in the quantum or classical domain, the utility of optomechanical crystals hinges on the degree to which light radiating from the device, having interacted with mechanical motion, can be collected and detected in an experimental apparatus consisting of conventional optical components such as lenses and optical fibers. While several efficient methods of optical coupling exist to meet this task, most are unsuitable for the cryogenic or vacuum integration required for many applications. The first portion of this dissertation will detail the development of robust and efficient methods of optically coupling optomechanical resonators to optical fibers, with an emphasis on fabrication processes and optical characterization.

I will then proceed to describe a few experiments enabled by the fiber couplers. The first studies the performance of an optomechanical resonator as a precise sensor for continuous position measurement. The sensitivity of the measurement, limited by the detection efficiency of intracavity photons, is compared to the standard quantum limit imposed by the quantum properties of the laser probe light. The added noise of the measurement is seen to fall within a factor of 3 of the standard quantum limit, representing an order of magnitude improvement over previous experiments utilizing optomechanical crystals, and matching the performance of similar measurements in the microwave domain.

The next experiment uses single photon counting to detect individual phonon emission and absorption events within the nanomechanical oscillator. The scattering of laser light from mechanical motion produces correlated photon-phonon pairs, and detection of the emitted photon corresponds to an effective phonon counting scheme. In the process of scattering, the coherence properties of the mechanical oscillation are mapped onto the reflected light. Intensity interferometry of the reflected light then allows measurement of the temporal coherence of the acoustic field. These correlations are measured for a range of experimental conditions, including the optomechanical amplification of the mechanics to a self-oscillation regime, and comparisons are drawn to a laser system for phonons. Finally, prospects for using phonon counting and intensity interferometry to produce non-classical mechanical states are detailed following recent proposals in literature.

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We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches-that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the reach in the usual channels for supersymmetry searches. However, the R-parity violating interactions lead to an enhancement of the final states containing isolated same-sign di-leptons and trileptons, compensating the reach loss in the fully inclusive channel. We show how the searches for displaced vertices associated to LSP decay substantially increase the coverage in supergravity parameter space, giving the corresponding reaches for two reference luminosities of 10 and 100 fb(-1) and compare with those of the R-parity conserving minimal supergravity model.

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Objective: To briefly review the clinical and biological distinctions between unipolar and bipolar depression critiquing in particular currently available depression rating scales and discuss the need for a new observer-rated scale tailored to bipolar depression.

Method: Relevant literature pertaining to the symptomatic differences between bipolar disorder and unipolar disorder as well as their measurement using existing assessment scales was identified by computerized searches and reviews of scientific journals known to the authors.

Results
: Bipolar depression is distinct from unipolar depression in terms of phenomenology and clinical characteristics. These distinguishing features can be used to identify bipolarity in patients that present with recurrent depressive episodes. This is important because current self-report and observer-rated scales are optimized for unipolar depression, and hence limited in their ability to accurately assess bipolar depression.

Conclusion
: The development of a specific bipolar depression rating scale will improve the assessment of bipolar depression in both research and clinical settings and assist the development of better treatments and interventions.

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This thesis includes a literature review that summarises the types of psychological research that have been conducted into gratitude, including the research conceptualising and developing assessments around it and exploring its associations with wellbeing, personality, social interaction, and health. The review focuses specifically on the research examining the relationship of gratitude to anxiety, depression and sleep, providing an outline of current theories about the relationship of positive affect to wellbeing, and a summary of the evidence to date. It is noted that there is comparatively little research on the impact of gratitude on anxiety and sleep but promising findings about the role of gratitude in the treatment of depression. Taken together, it is argued, the current research supported the need for trials of gratitude interventions specifically with clinical populations. Finally, the review looks at the literature of experimental interventions using gratitude. Particular emphasis is given to what has been learnt through these trials that might guide the focus and design of future research.

There follows the report of a randomized wait-list controlled pre-post trial of a gratitude diary intended to extend the research into the efficacy of gratitude diaries in the treatment of clinical populations with depression, anxiety and sleep difficulties. It was hypothesised that after completing a brief gratitude diary for three weeks, participants would have lower scores on measures of depression, anxiety, and perceived sleep difficulties, and higher scores on a measure of life satisfaction. These results were also expected to be evident at three-week follow-up. In a randomised waitlist-controlled trial with repeated measures pre-, post- and follow-up design, participants (N=109, from Australia) aged 18-64 years with a current self-reported diagnosis of an anxiety disorder and/or depression, took part in a self-help study via the internet. After completing the diary participants had lower scores on measures of depression, anxiety and perceived sleep difficulties and higher scores on a measure of subjective wellbeing than immediately pre-intervention. In addition, they had improved scores on a measure of stress. At three-week follow-up scores on depression and perceived sleep difficulties were no longer significantly different from pre-intervention, however improvements for subjective wellbeing and stress at post-intervention were maintained. At follow-up scores for anxiety had not only been maintained but had improved significantly beyond post-intervention results. This trial provides support for the use of gratitude diaries as a short-term intervention with a clinical population. Different patterns of anxiety and depression scores raise the possibility that gratitude interventions work differently to address depression and anxiety symptoms and provide support for the idea that gratitude interventions may have sustainable effects on anxiety symptoms.

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We study the collider phenomenology of bilinear R-parity violating supergravity, the simplest effective model for supersymmetric neutrino masses accounting for the current neutrino oscillation data. At the CERN Large Hadron Collider the center-of-mass energy will be high enough to probe directly these models through the search for the superpartners of the Standard Model (SM) particles. We analyze the impact of R-parity violation on the canonical supersymmetry searches-that is, we examine how the decay of the lightest supersymmetric particle (LSP) via bilinear R-parity violating interactions degrades the average expected missing momentum of the reactions and show how this diminishes the reach in the usual channels for supersymmetry searches. However, the R-parity violating interactions lead to an enhancement of the final states containing isolated same-sign di-leptons and trileptons, compensating the reach loss in the fully inclusive channel. We show how the searches for displaced vertices associated to LSP decay substantially increase the coverage in supergravity parameter space, giving the corresponding reaches for two reference luminosities of 10 and 100 fb(-1) and compare with those of the R-parity conserving minimal supergravity model.

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In a former study, taste disturbances after tonsillectomy seemed to be more frequent than expected. Eight percent of patients reported subjective taste disorders 6 months after tonsillectomy. Fifteen patients from the initial trial, who reported taste disorders after tonsillectomy, were contacted again for this long-term follow-up. A telephone interview using the same questionnaire addressing the current self-estimate of taste function was performed. At 32 ± 10 months following surgery, two (0.9%) patients still reported suffering from taste disturbance. This long-term follow-up study shows that dysgeusia following tonsillectomy occurs in approximately 1% of patients. These data should be considered when patients are informed about complications after tonsillectomy.

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This synthesis of the literature provides descriptive analysis and outlines current self-management interventions for African Americans with type 2 diabetes. Specifically, this study describes and explores the design of those studies whose interventions have been shown to lower HbA1C levels in this population by at least 0.5% points, an improvement that provides approximately 10% reduction in long term complications from this disease.^ Results. In total, 37 articles were reviewed and 17 articles met inclusion criteria for analysis. Analysis of each study's methodology and results was performed and selected studies with interventions that resulted in improvements in HbA1C outcomes equal to 0.5% or greater for both group 1 and 2 were summarized by intervention type in table format. Descriptive analysis, outlining the number and characteristics of proximal and distal mediating components addressed in Group 1 studies, was performed in order to determine whether mediating components may have had some relation to effectiveness of intervention on outcome HbA1C. Descriptive analysis revealed that no particular design is substantially more effective than another among Behavioral studies although, there may be an advantage in using culturally sensitive, group interventions that address greater numbers of distal mediating components. Among Process studies, structured approaches (i.e. algorithm care and scheduled follow up), as well as utilization of specialty and group care are represented as effective for African American populations. ^ Conclusions. It may be summarized that by targeting behavior and addressing provider delivery (i.e. algorithm use, group care, home care, and provider follow up) in this population, a greater yield in outcome improvements may be accomplished. However, many gaps exist in a review process that stratifies results and focuses on identifying group specific intervention successes and failures. Further research in different populations will aid researchers and practitioners in discovering the best evidence, and identifying models that could be utilized in practice to achieve the best diabetes management for at risk groups.^

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The aim of this study was to identify Spanish stakeholders’ views on the relationship between childhood obesity and the marketing and advertising of food and beverages aimed at children in Spain, as well as on the corresponding of regulations. We performed a qualitative study based on semi-structured interviews with Stakeholders/Key Informants (KI) from 13 organisations: experts (2), consumer advocates (1), public health advocates (2), food manufacturers (2), advertising advocates (1), government representatives (1), child/family/school advocates (2) and media (1). The variables studied were Prevalence of childhood obesity and its relationship to marketing/advertising and Regulation of marketing. In order to identify the most relevant arguments (pearls) in the discourses, a blind independent analysis by four members of the research team was performed. We found that the prevalence of childhood obesity was perceived to be higher than the European average. Self-regulation was identified as the main form of marketing control. Only food manufacturers and advertising agencies considered voluntary action and supervisory procedures to be effective. The other stakeholders advocated state control through legislation and non-state actions such as external assessment and sanctions. Despite the divergence of opinion between stakeholders, there was agreement on the need to improve supervision and to ensure compliance with current self-regulatory codes in Spain.

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Clear qualitative changes have taken place in relations between the European Union and its Eastern neighbours over the past year. The European Neighbourhood Policy (ENP) has been playing a significant part in the context of these changes. In the cases of Moldova and Ukraine, which are the countries interested in enhancing co-operation with the EU, the ENP has provided a formula that allows taking steps to implement this objective. The ENP has also contributed to "outlining an alternative" to Belarus' current self-isolation. However, the ENP has first of all given a clear message to Russia by specifying the EU's interests and objectives concerning Eastern Europe. The ENP has clearly stated that the EU wants to build democracy and a free market in those countries, and has signalled that the European Union intends to discuss the issues concerning the countries directly with them, and not through Moscow's offices.

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BACKGROUND: The Multimedia Activity Recall for Children and Adults (MARCA) is a computerized recall instrument that records use of time during 24 hr the previous day and has been developed to address limitations of current self-report physical activity measures for those in advanced age. METHODS: Test-retest reliability and convergent validity of the adult MARCA were assessed in a sample of 45 advanced-age adults (age 84.9 SD ± 1.62 yr) as a subsample of the Life and Living in Advanced-Age Cohort Study New Zealand (LiLACS NZ). Test-retest methods required participants to recall the previous day's activity using the MARCA twice within the same day. Convergent validity was assessed against accelerometry. RESULTS: Test-retest reliability was high, with ICCs greater than .99 for moderate to vigorous physical activity (MVPA) and physical activity level (PAL). Compared with accelerometry, the MARCA demonstrated validity comparable to other self-report instruments with Spearman's coefficients of .34 and .59 for time spent in nonsedentary physical activity and PAL. CONCLUSION: The MARCA is a valid and reliable self-report tool for physical activity behaviors in advanced-age adults.

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The behavior of room temperature self-sustained current oscillations resulting from sequential resonance tunneling in a doped weakly-coupled GaAs/AlAs superlattice (SL) is investigated under hydrostatic pressure. From atmosphere pressure to 6.5 kbar, oscillations exist in the whole plateau of the I-V curve and oscillating characteristics are affected by the pressure. When hydrostatic pressure is higher than 6.5 kbar, the current oscillations are completely suppressed although a current plateau still can be seen in the I-V curve. The plateau disappears when the pressure is close to 13.5 kbar. As the main effect of hydrostatic pressure is to lower the X point valley with respect to Gamma point valley, the disappearance of oscillation and the plateau shrinkage before Gamma - X resonance takes place are attributed to the increases of thermoionic emission and nonresonant tunneling components determined by the lowest Gamma - X barrier height in GaAs/AlAs SL structure.

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The multi-level current reinjection concept described in literature is well-known to produce high quality AC current waveforms in high power and high voltage self-commutating current source converters. This paper proposes a novel reinjection circuitry which is capable of producing a 7-level reinjection current. It is shown that this reinjection current effectively increases the pulse number of the converter to 72. The use of PSCAD/EMTDC simulation validates the functionality of the proposed concept illustrating its effectiveness on both AC and DC sides of the converter.

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There is a growing awareness of the high levels of psychological distress being experienced by law students and the practising profession in Australia. In this context, a Threshold Learning Outcome (TLO) on self-management has been included in the six TLOs recently articulated as minimum learning outcomes for all Australian graduates of the Bachelor of Laws degree (LLB). The TLOs were developed during 2010 as part of the Australian Learning and Teaching Council’s (ALTC’s) project funded by the Australian Government to articulate ‘Learning and Teaching Academic Standards’. The TLOs are the result of a comprehensive national consultation process led by the ALTC’s Discipline Scholars: Law, Professors Sally Kift and Mark Israel.1 The TLOs have been endorsed by the Council of Australian Law Deans (CALD) and have received broad support from members of the judiciary and practising profession, representative bodies of the legal profession, law students and recent graduates, Legal Services Commissioners and the Law Admissions Consultative Committee. At the time of writing, TLOs for the Juris Doctor (JD) are also being developed, utilising the TLOs articulated for the LLB as their starting point but restating the JD requirements as the higher order outcomes expected of graduates of a ‘Masters Degree (Extended)’, this being the award level designation for the JD now set out in the new Australian Qualifications Framework.2 As Australian law schools begin embedding the learning, teaching and assessment of the TLOs in their curricula, and seek to assure graduates’ achievement of them, guidance on the implementation of the self-management TLO is salient and timely.

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Objective: Attention deficit hyperactivity disorder (ADHD) is a life-long condition, but because of its historical status as a self-remitting disorder of childhood, empirically validated and reliable methods for the assessment of adults are scarce. In this study, the validity and reliability of the Wender Utah Rating Scale (WURS) and the Adult Problem Questionnaire (APQ), which survey childhood and current symptoms of ADHD, respectively, were studied in a Finnish sample. Methods: The self-rating scales were administered to adults with an ADHD diagnosis (n = 38), healthy control participants (n = 41), and adults diagnosed with dyslexia (n = 37). Items of the self-rating scales were subjected to factor analyses, after which the reliability and discriminatory power of the subscales, derived from the factors, were examined. The effects of group and gender on the subscales of both rating scales were studied. Additionally, the effect of age on the subscales of the WURS was investigated. Finally, the diagnostic accuracy of the total scores was studied. Results: On the basis of the factor analyses, a four-factor structure for the WURS and five-factor structure for the APQ had the best fit to the data. All of the subscales of the APQ and three of the WURS achieved sufficient reliability. The ADHD group had the highest scores on all of the subscales of the APQ, whereas two of the subscales of the WURS did not statistically differ between the ADHD and the Dyslexia group. None of the subscales of the WURS or the APQ was associated with the participant's gender. However, one subscale of the WURS describing dysthymia was positively correlated with the participant's age. With the WURS, the probability of a correct positive classification was .59 in the current sample and .21 when the relatively low prevalence of adult ADHD was taken into account. The probabilities of correct positive classifications with the APQ were .71 and .23, respectively. Conclusions: The WURS and the APQ can provide accurate and reliable information of childhood and adult ADHD symptoms, given some important constraints. Classifications made on the basis of the total scores are reliable predictors of ADHD diagnosis only in populations with a high proportion of ADHD and a low proportion of other similar disorders. The subscale scores can provide detailed information of an individual's symptoms if the characteristics and limitations of each domain are taken into account. Improvements are suggested for two subscales of the WURS.