Numerical simulations of chromospheric hard X-ray source sizes in solar flares

X-ray observations are a powerful diagnostic tool for transport, acceleration, and heating of electrons in solar flares. Height and size measurements of X-ray footpoints sources can be used to determine the chromospheric density and constrain the parameters of magnetic field convergence and electron pitch-angle evolution. We investigate the influence of the chromospheric density, magnetic mirroring and collisional pitch-angle scattering on the size of X-ray sources. The time-independent Fokker-Planck equation for electron transport is solved numerically and analytically to find the electron distribution as a function of height above the photosphere. From this distribution, the expected X-ray flux as a function of height, its peak height and full width at half maximum are calculated and compared with RHESSI observations. A purely instrumental explanation for the observed source size was ruled out by using simulated RHESSI images. We find that magnetic mirroring and collisional pitch-angle scattering tend to change the electron flux such that electrons are stopped higher in the atmosphere compared with the simple case with collisional energy loss only. However, the resulting X-ray flux is dominated by the density structure in the chromosphere and only marginal increases in source width are found. Very high loop densities (>10^{11} cm^{-3}) could explain the observed sizes at higher energies, but are unrealistic and would result in no footpoint emission below about 40 keV, contrary to observations. We conclude that within a monolithic density model the vertical sizes are given mostly by the density scale-height and are predicted smaller than the RHESSI results show.Comment: 19 pages, 9 figures, accepted for publication in Ap

Question design in nurse-led and GP-led telephone triage for same-day appointment requests: a comparative investigation

Objective: To compare doctors’ and nurses’ communication with patients in primary care telephone triage consultations. Design: Qualitative comparative study of content and form of questions in 51 telephone triage encounters between practitioners (general practitioners (GPs)=29; nurses=22) and patients requesting a same-day appointment in primary care. Audio-recordings of nurse-led calls were synchronised with video recordings of nurse's use of computer decision support software (CDSS) during triage. Setting: 2 GP practices in Devon and Warwickshire, UK. Participants: 4 GPs and 29 patients; and 4 nurses and 22 patients requesting a same-day face-to-face appointment with a GP. Main outcome measure: Form and content of practitioner-initiated questions and patient responses during clinical assessment. Results: A total of 484 question–response sequences were coded (160 GP; 324 N). Despite average call lengths being similar (GP=4 min, 37 s, (SD=1 min, 26 s); N=4 min, 39 s, (SD=2 min, 22 s)), GPs and nurses differed in the average number (GP=5.51, (SD=4.66); N=14.72, (SD=6.42)), content and form of questions asked. A higher frequency of questioning in nurse-led triage was found to be due to nurses’ use of CDSS to guide telephone triage. 89% of nurse questions were oriented to asking patients about their reported symptoms or to wider-information gathering, compared to 54% of GP questions. 43% of GP questions involved eliciting patient concerns or expectations, and obtaining details of medical history, compared to 11% of nurse questions. Nurses using CDSS frequently delivered questions designed as declarative statements requesting confirmation and which typically preferred a ‘no problem’ response. In contrast, GPs asked a higher proportion of interrogative questions designed to request information. Conclusions: Nurses and GPs emphasise different aspects of the clinical assessment process during telephone triage. These different styles of triage have implications for the type of information available following nurse-led or doctor-led triage, and for how patients experience triage

The limits of filopodium stability

Filopodia are long, finger-like membrane tubes supported by cytoskeletal filaments. Their shape is determined by the stiffness of the actin filament bundles found inside them and by the interplay between the surface tension and bending rigidity of the membrane. Although one might expect the Euler buckling instability to limit the length of filopodia, we show through simple energetic considerations that this is in general not the case. By further analyzing the statics of filaments inside membrane tubes, and through computer simulations that capture membrane and filament fluctuations, we show under which conditions filopodia of arbitrary lengths are stable. We discuss several in vitro experiments where this kind of stability has already been observed. Furthermore, we predict that the filaments in long, stable filopodia adopt a helical shape

Years of sunlight exposure and cataract: a case-control study in a Mediterranean population.

BACKGROUND: We aimed to investigate the relation between sunlight exposure and risk of cataract. METHODS: We carried out a frequency-matched case-control study of 343 cases and 334 controls attending an ophthalmology outpatient clinic at a primary health-care center in a small town near Valencia, Spain. All cases were diagnosed as having a cataract in at least one eye based on the Lens Opacification Classification system (LOCS II). Controls had no opacities in either eye. All cases and controls were interviewed for information on outdoor exposure, "usual" diet, history of severe episodes of diarrhea illness, life-style factors and medical and socio-demographic variables. Blood antioxidant vitamin levels were also analyzed. We used logistic regression models to estimate sex and age-adjusted odds ratios (ORs) by quintiles of years of occupational outdoor exposure, adjusting for potential confounders such as smoking, alcohol consumption, serum antioxidants and education. RESULTS: No association was found between years of outdoor exposure and risk of cataract. However, exploratory analyses suggested a positive association between years of outdoor exposure at younger ages and risk of nuclear cataract later in life. CONCLUSION: Our study does not support an association with cataract and sunlight exposure over adult life

Optic nerve head segmentation

Reliable and efficient optic disk localization and segmentation are important tasks in automated retinal screening. General-purpose edge detection algorithms often fail to segment the optic disk due to fuzzy boundaries, inconsistent image contrast or missing edge features. This paper presents an algorithm for the localization and segmentation of the optic nerve head boundary in low-resolution images (about 20 /spl mu//pixel). Optic disk localization is achieved using specialized template matching, and segmentation by a deformable contour model. The latter uses a global elliptical model and a local deformable model with variable edge-strength dependent stiffness. The algorithm is evaluated against a randomly selected database of 100 images from a diabetic screening programme. Ten images were classified as unusable; the others were of variable quality. The localization algorithm succeeded on all bar one usable image; the contour estimation algorithm was qualitatively assessed by an ophthalmologist as having Excellent-Fair performance in 83% of cases, and performs well even on blurred image

Computer Components and Systems

Contains research objectives.U.S. Navy Bureau of Ships under Contracts NObsr 72716 and NObsr 7760

Discharge Education for Residents: A Study of Trainee Preparedness for Hospital Discharge

BACKGROUND: Safe hospital discharges have become a major focus in the national discussion on transitions of care and care coordination. Education on the hospital discharge process is evolving as the needs of trainees are better understood. PURPOSE: This study is a cross-sectional survey of residents in a Midwestern residency program about their confidence in safely discharging patients from the hospital, including how they have or have not learned to do so. METHODS: An anonymous paper questionnaire was distributed to a convenience sample of interns and residents at a weekly meeting of the residency program. RESULTS: Most residents reported a general confidence in their abilities to safely discharge patients from the hospital; however, further probing revealed that their confidence breaks down when required to competently perform specific tasks of the discharge process such as activity restrictions or facilitation of home care. More than 50% of house staff surveyed responded that their education in many specific aspects of the discharge process are lacking. CONCLUSION: Interdisciplinary care education, and the discharge summary in particular, warrant further scrutiny as a care transition tool and means of teaching safe hospital discharge to trainees. We present a questionnaire that may serve useful as an anonymous tool to gauge residents' educational needs

THE DETERMINANTS OF FOOD STAMP PROGRAM PARTICIPATION

Food Security and Poverty,

Multidisciplinary Projects: A Modern Technique in Engineering Education

The multidisciplinary project laboratory course has been developed for the purpose of preparing young engineers to deal successfully with the complex practical problems associated with todays\u27 technology. Students undertake a realistic engineering project which they pursue from inception to completion. Such a program fosters logical planning, ingenuity and creativity, constructive cooperation with related disciplines, technical responsibility, and a systematic approach to problem solving. The multidisciplinary project technique used in the Mechanical and Aerospace Engineering Department at Rutgers University is discussed in terms of a project example and benefits derived from the course