Unified model of voltage/current mode control to predict saddle-node bifurcation

A unified model of voltage mode control (VMC) and current mode control (CMC) is proposed to predict the saddle-node bifurcation (SNB). Exact SNB boundary conditions are derived, and can be further simplified in various forms for design purpose. Many approaches, including steady-state, sampled-data, average, harmonic balance, and loop gain analyses are applied to predict SNB. Each approach has its own merits and complement the other approaches.Comment: Submitted to International Journal of Circuit Theory and Applications on December 23, 2010; Manuscript ID: CTA-10-025

Peroxisome Proliferator-Activated Receptor alpha (PPAR alpha) down-regulation in cystic fibrosis lymphocytes

Background: PPARs exhibit anti-inflammatory capacities and are potential modulators of the inflammatory response. We hypothesized that their expression and/or function may be altered in cystic fibrosis (CF), a disorder characterized by an excessive host inflammatory response. Methods: PPARα, β and γ mRNA levels were measured in peripheral blood cells of CF patients and healthy subjects via RT-PCR. PPARα protein expression and subcellular localization was determined via western blot and immunofluorescence, respectively. The activity of PPARα was analyzed by gel shift assay. Results: In lymphocytes, the expression of PPARα mRNA, but not of PPARβ, was reduced (-37%; p < 0.002) in CF patients compared with healthy persons and was therefore further analyzed. A similar reduction of PPARα was observed at protein level (-26%; p < 0.05). The transcription factor was mainly expressed in the cytosol of lymphocytes, with low expression in the nucleus. Moreover, DNA binding activity of the transcription factor was 36% less in lymphocytes of patients (p < 0.01). For PPARα and PPARβ mRNA expression in monocytes and neutrophils, no significant differences were observed between CF patients and healthy persons. In all cells, PPARγ mRNA levels were below the detection limit. Conclusion: Lymphocytes are important regulators of the inflammatory response by releasing cytokines and antibodies. The diminished lymphocytic expression and activity of PPARα may therefore contribute to the inflammatory processes that are observed in CF

Bifurcation Boundary Conditions for Switching DC-DC Converters Under Constant On-Time Control

Sampled-data analysis and harmonic balance analysis are applied to analyze switching DC-DC converters under constant on-time control. Design-oriented boundary conditions for the period-doubling bifurcation and the saddle-node bifurcation are derived. The required ramp slope to avoid the bifurcations and the assigned pole locations associated with the ramp are also derived. The derived boundary conditions are more general and accurate than those recently obtained. Those recently obtained boundary conditions become special cases under the general modeling approach presented in this paper. Different analyses give different perspectives on the system dynamics and complement each other. Under the sampled-data analysis, the boundary conditions are expressed in terms of signal slopes and the ramp slope. Under the harmonic balance analysis, the boundary conditions are expressed in terms of signal harmonics. The derived boundary conditions are useful for a designer to design a converter to avoid the occurrence of the period-doubling bifurcation and the saddle-node bifurcation.Comment: Submitted to International Journal of Circuit Theory and Applications on August 10, 2011; Manuscript ID: CTA-11-016

Identification of hip fracture patients from radiographs using Fourier analysis of the trabecular structure: a cross-sectional study

Peer reviewedPublisher PD

Context and Crowding in Perceptual Learning on a Peripheral Contrast Discrimination Task: Context-Specificity in Contrast Learning

Perceptual learning is an improvement in sensitivity due to practice on a sensory task and is generally specific to the trained stimuli and/or tasks. The present study investigated the effect of stimulus configuration and crowding on perceptual learning in contrast discrimination in peripheral vision, and the effect of perceptual training on crowding in this task. 29 normally-sighted observers were trained to discriminate Gabor stimuli presented at 9° eccentricity with either identical or orthogonally oriented flankers with respect to the target (ISO and CROSS, respectively), or on an isolated target (CONTROL). Contrast discrimination thresholds were measured at various eccentricities and target-flanker separations before and after training in order to determine any learning transfer to untrained stimulus parameters. Perceptual learning was observed in all three training stimuli; however, greater improvement was obtained with training on ISO-oriented stimuli compared to CROSS-oriented and unflanked stimuli. This learning did not transfer to untrained stimulus configurations, eccentricities or target-flanker separations. A characteristic crowding effect was observed increasing with viewing eccentricity and decreasing with target-flanker separation before and after training in both configurations. The magnitude of crowding was reduced only at the trained eccentricity and target-flanker separation; therefore, learning for contrast discrimination and for crowding in the present study was configuration and location specific. Our findings suggest that stimulus configuration plays an important role in the magnitude of perceptual learning in contrast discrimination and suggest context-specificity in learning

Complexity of case mix in a regional allergy service

<p>Abstract</p> <p>Background</p> <p>Currently in the United Kingdom (UK), there is a mismatch between limited financial resources and the large proportion of patients with suspected allergies actually being referred to specialist allergy clinics. To better understand the case mix of patients being referred, we audited referrals to a regional allergy service over an 8 year period.</p> <p>The main source of data was consultant letters to General Practitioners (GP) summarising the diagnosis of patients, archived from January 2002 to September 2009. Letters were reviewed, extracting the clinic date, doctor seen, gender, date of birth, postcode, GP, and diagnoses. Diagnoses were classified into seven groups and illustrative cases for each group noted.</p> <p>Findings</p> <p>Data from 2,028 new referrals with suspected allergy were analysed. The largest group of patients (43%) were diagnosed with a type I hypersensitivity. The other diagnostic groups were chronic idiopathic (spontaneous) urticaria (35%), suspected type I hypersensitivity but no allergen identified (8%), idiopathic (spontaneous) angioedema (8%), physical urticaria (2.5%), non-allergic symptoms (1.6%), type IV hypersensitivity (0.8%) and ACE inhibitor sensitivity (0.5%). Two thirds of patients seen were female with a higher percentage of female patients in the non type-I hypersensitivity group (71%) than the type 1 hypersensitivity (66%) (χ²= 5.1, 1df, <it>p = 0.024</it>). The type 1 hypersensitivity patients were younger than other patients (38 Vs 46 years, t = -10.8, <it>p < 0.001</it>)</p> <p>Conclusions</p> <p>This study highlights the complexity of specialist allergy practice and the large proportion of patients referred with non-type I hypersensitivities, chronic idiopathic (spontaneous) urticaria being by far the largest group. Such information is critical to inform commissioning decisions, define referral pathways and in primary care education.</p

Characterization of Films with Thickness Less than 10 nm by Sensitivity-Enhanced Atomic Force Acoustic Microscopy

We present a method for characterizing ultrathin films using sensitivity-enhanced atomic force acoustic microscopy, where a concentrated-mass cantilever having a flat tip was used as a sensitive oscillator. Evaluation was aimed at 6-nm-thick and 10-nm-thick diamond-like carbon (DLC) films deposited, using different methods, on a hard disk for the effective Young's modulus defined as E/(1 - ν2), where E is the Young's modulus, and ν is the Poisson's ratio. The resonant frequency of the cantilever was affected not only by the film's elasticity but also by the substrate even at an indentation depth of about 0.6 nm. The substrate effect was removed by employing a theoretical formula on the indentation of a layered half-space, together with a hard disk without DLC coating. The moduli of the 6-nm-thick and 10-nm-thick DLC films were 392 and 345 GPa, respectively. The error analysis showed the standard deviation less than 5% in the moduli

Comparison of primary care experiences among adults in general outpatient clinics and private general practice clinics in Hong Kong

Abstract. Background. The main goal of Hong Kong's publicly-funded general outpatient clinics (GOPCs) is to provide primary medical services for the financially vulnerable. The objective of the current study was to compare the primary care experiences of GOPC users and the users of care provided by private general practitioners (GPs) in Hong Kong via a territory-wide telephone survey. Methods. One thousand adults in Hong Kong aged 18 and above were interviewed by a telephone survey. The modified Chinese translated Primary Care Assessment Tool was used to collect data on respondents' primary care experience. Results. Our results indicated that services provided by GOPC were more often used by female, older, poorer, chronically-ill and less educated population. GOPC participants were also more likely to have visited a specialist or used specialist services (69.7% vs. 52.0%; p < 0.001), although this difference in utilization of specialist services disappeared after adjusting for age (55.7% vs. 52.0%, p = 0.198). Analyses were also performed to asses the relationship between healthcare settings (GOPCs versus private GPs) and primary care quality. Private GP patients achieved higher overall PCAT scores largely due to better accessibility (Mean: 6.88 vs. 8.41, p < 0.001) and person-focused care (Mean: 8.37 vs. 11.69, p < 0.001). Conclusions. Our results showed that patients primarily receiving care from private GPs in Hong Kong reported better primary care experiences than those primarily receiving care from GOPCs. This was largely due to the greater accessibility and better interpersonal relationships offered by the private GPs. As most patients use both GOPCs and private GPs, their overall primary care experiences may not be as different as the findings of this study imply. © 2010 Wong et al; licensee BioMed Central Ltd.link_to_subscribed_fulltex

Male reproductive health and environmental xenoestrogens

EHP is a publication of the U.S. government. Publication of EHP lies in the public domain and is therefore without copyright. Research articles from EHP may be used freely; however, articles from the News section of EHP may contain photographs or figures copyrighted by other commercial organizations and individuals that may not be used without obtaining prior approval from both the EHP editors and the holder of the copyright. Use of any materials published in EHP should be acknowledged (for example, "Reproduced with permission from Environmental Health Perspectives") and a reference provided for the article from which the material was reproduced.Male reproductive health has deteriorated in many countries during the last few decades. In the 1990s, declining semen quality has been reported from Belgium, Denmark, France, and Great Britain. The incidence of testicular cancer has increased during the same time incidences of hypospadias and cryptorchidism also appear to be increasing. Similar reproductive problems occur in many wildlife species. There are marked geographic differences in the prevalence of male reproductive disorders. While the reasons for these differences are currently unknown, both clinical and laboratory research suggest that the adverse changes may be inter-related and have a common origin in fetal life or childhood. Exposure of the male fetus to supranormal levels of estrogens, such as diethlylstilbestrol, can result in the above-mentioned reproductive defects. The growing number of reports demonstrating that common environmental contaminants and natural factors possess estrogenic activity presents the working hypothesis that the adverse trends in male reproductive health may be, at least in part, associated with exposure to estrogenic or other hormonally active (e.g., antiandrogenic) environmental chemicals during fetal and childhood development. An extensive research program is needed to understand the extent of the problem, its underlying etiology, and the development of a strategy for prevention and intervention.Supported by EU Contract BMH4-CT96-0314

'Being there' for women with metastatic breast cancer: a pan-European patient survey

BACKGROUND: Understanding their experiences of diagnosis is integral to improving the quality of care for women living with advanced/metastatic breast cancer. METHODS: A survey, initiated in March 2011, was conducted in two stages. First, the views of 47 breast cancer-related patient groups in eight European countries were sought on standards of breast cancer care and unmet needs of patients. Findings were used to develop a patient-centric survey to capture personal experiences of advanced breast cancer to determine insights into the ‘trade-off' between extending overall survival and side effects associated with its treatment. The second online survey was open to women with locally advanced or metastatic breast cancer, or their carers, and responders were recruited through local patient groups. Data were collected via anonymous local language questionnaires. RESULTS: The online stage II survey received a total of 230 responses from 17 European countries: 94% of respondents had locally advanced or metastatic breast cancer and 6% were adult carers. Although the overall experience of care was generally good/excellent (77%), gaps were still perceived in terms of treatment choice and information provision. Treatment choice for patients was felt to be lacking by 32% of responders. In addition, 68% of those who responded would have liked more information about future medical treatments and research, with 57% wishing to receive this information from their oncologist. Two-thirds (66%) of women with advanced breast cancer, or their carers, believed life-extending treatment to be important so that they can spend more time with family and friends, and 67% said that the treatment was worthwhile, despite potential associated side effects. CONCLUSION: These findings show a continuing need to provide women with advanced breast cancer with better information and emphasise the importance that these patients often place on prolonging survival