Periodic magnetic field as a polarized and focusing thermal neutron spectrometer and monochromator.

A novel periodic magnetic field (PMF) optic is shown to act as a prism, lens, and polarizer for neutrons and particles with a magnetic dipole moment. The PMF has a two-dimensional field in the axial direction of neutron propagation. The PMF alternating magnetic field polarity provides strong gradients that cause separation of neutrons by wavelength axially and by spin state transversely. The spin-up neutrons exit the PMF with their magnetic spins aligned parallel to the PMF magnetic field, and are deflected upward and line focus at a fixed vertical height, proportional to the PMF period, at a downstream focal distance that increases with neutron energy. The PMF has no attenuation by absorption or scatter, as with material prisms or crystal monochromators. Embodiments of the PMF include neutron spectrometer or monochromator, and applications include neutron small angle scattering, crystallography, residual stress analysis, cross section measurements, and reflectometry. Presented are theory, experimental results, computer simulation, applications of the PMF, and comparison of its performance to Stern-Gerlach gradient devices and compound material and magnetic refractive prisms.

Demonstration of high-trapping efficiency and narrow energy spread in a laser-driven accelerator.

Laser-driven electron accelerators (laser linacs) offer the potential for enabling much more economical and compact devices. However, the development of practical and efficient laser linacs requires accelerating a large ensemble of electrons together ("trapping") while keeping their energy spread small. This has never been realized before for any laser acceleration system. We present here the first demonstration of high-trapping efficiency and narrow energy spread via laser acceleration. Trapping efficiencies of up to 80% and energy spreads down to 0.36% (1 sigma) were demonstrated.

X-ray focusing with compound lenses made from beryllium.

We have measured the intensity profile and transmission of x rays focused by a series of biconcave spherical unit lenses fabricated from beryllium. The use of beryllium extends the range of operation of compound refractive lenses, improving transmission, aperture size, and gain. The compound refractive lens was composed of 160 biconcave unit lenses, each with a radius of curvature of 1.9 mm. Two-dimensional focusing with a gain of 1.5 was obtained at 6.5 keV with a focal length of 93 cm. The effective aperture of the compound refractive lens was measured as 600 mum , with 9% peak transmission.

First staging of two laser accelerators.

Staging of two laser-driven, relativistic electron accelerators has been demonstrated for the first time in a proof-of-principle experiment, whereby two distinct and serial laser accelerators acted on an electron beam in a coherently cumulative manner. Output from a CO2 laser was split into two beams to drive two inverse free electron lasers (IFEL) separated by 2.3 m. The first IFEL served to bunch the electrons into approximately 3 fs microbunches, which were rephased with the laser wave in the second IFEL. This represents a crucial step towards the development of practical laser-driven electron accelerators.

Refractive lenses for coherent x-ray sources.

Incoherent x rays in the wavelength interval from approximately 0.5-2 A have been focused with refractive lenses. A single lens would have a long focal length because the refractive index of any material is close to unity; but with a stack of N lens elements the focal length is reduced by the factor N, and such a lens is termed a compound refractive lens (CRL). Misalignment of the parabolic lens elements does not alter the focusing properties and results in only a small reduction in transmission. Based on the principle of spontaneous emission amplification in a FEL wiggler, coherent x-ray sources are being developed with wavelengths of 1-1.5 A and source diameters of 50-80 mum; and the CRL can be used to provide a small, intense image. Chromatic aberration increases the image size by an amount comparable with the diffraction-limited size, and so chromatic correction is important. Pulse broadening through the lens that is due to material dispersion is negligible. The performance of a CRL used in conjunction with a coherent source is analyzed by means of the Kirchhoff integral. For typical parameters, intensity gain is 10(5)-10(6), where gain is defined as the intensity ratio in an image plane with and without the lens in place. (There may be some confusion concerning the usage of the word intensity. As employed in this manuscript, intensity, also called irradiance, refers to power per unit area. This is a commonly accepted usage for intensity, although there are places in the literature where the term radiant incidence is reserved for this definition and intensity refers to power per unit solid angle.) The image intensity is maximized when the CRL is placed 100-200 m from the source, and the diameter of the diffraction-limited spot is approximately 0.12 mum.

Body temperature of newborns: what is normal?

Medical records of 203 healthy full-term infants were reviewed to determine the range of axillary temperatures for newborn infants, factors that affect temperature and nursery management of infants with temperatures outside published normal ranges. The mean birth temperature was 36.5 degrees C (S.D. = 0.6 degrees C). Temperature was associated with birth weight (p<0.0005) and the presence of maternal fever (p<0.0001) but not with type of environment or time of birth. The mean temperature increased with age, rising 0.2 degrees C by 2-3 hours after birth (p<0.0001) and 0.3 degrees C by 15-20 hours (p<0.0001). Among a subset of 114 eligible neonates the mean temperature dropped 0.2 degrees C after bathing (p<0.0001). Although 17% of all temperatures measured were in the hypothermic (< or =36.3 degrees C) range, the only response recorded by nursery staff consisted of warming by modifying the environment, e.g., bundling. Blood cultures were drawn from 51 infants (25%), 43 because of maternal intrapartum antibiotic treatment for maternal fever or prolonged duration of ruptured amniotic membranes (>24 hours) and none for evaluation of abnormal temperatures. No infants had systemic infections and all were discharged in stable condition. Newborn axillary temperatures in our nursery were considerably lower than what has been previously described as "normal." Given the frequency of "hypothermia" and absence of associated illness, we believe the reference range for newborn temperatures should be expanded to include lower temperatures.

Is the routine pelvic examination needed with the advent of urine-based screening for sexually transmitted diseases?

OBJECTIVE: To determine the most cost-effective method of screening for chlamydia and gonorrhea to prevent pelvic inflammatory disease (PID) in asymptomatic sexually active adolescent females. DESIGN: Cost-effectiveness decision analysis comparing pelvic examination with cervical screening (the current national standard) with a model of urine screening with ligase chain reaction testing for Chlamydia trachomatis and Neisseria gonorrhoeae. METHODS: Four strategies using decision analysis were compared for a potential cohort of 100000 asymptomatic sexually active young women: (1) pelvic examination screening in 100%; (2) urine screening in 100%; (3) actual predicted pelvic examination screening in 70%; and (4) actual predicted urine screening in 90%. Assumptions and costs were generated from published sources. MAIN OUTCOME MEASURES: Cases of PID prevented per year and cost to prevent a case of PID. RESULTS: A total of 1750 cases of PID would be predicted to occur per year with no screening. Strategy 1 would prevent the most cases of PID (1283) at a mean cost of $10230. Strategy 2 would prevent 1215 cases of PID at a mean cost of $5093. The marginal cost to prevent an additional case of PID by strategy 1 is $101454. Strategy 3 would prevent 898 cases of PID and 1093 cases of PID would be prevented with urine screening in strategy 4. CONCLUSION: Urine-based ligase chain reaction screening is the most cost-effective strategy to detect chlamydial and gonococcal genital infection in asymptomatic sexually active adolescent females and, owing to ease of implementation, the most likely to prevent the greatest number of cases of PID.

Gender differences in physician-patient communication. Evidence from pediatric visits.

OBJECTIVE: To determine whether physician gender and patient gender influence the process of communication and parent and child satisfaction during pediatric office visits. DESIGN: Content analysis of videotaped pediatric office visits. SETTING: University-based pediatric primary care practice. SUBJECTS: Videotaped communication between 212 children, ages 4 to 14 years, parents, and physicians. Thirty-eight percent were child health supervision visits, and 62% were for the management of minor or chronic illnesses. MAIN OUTCOME MEASURES: An established coding system of physician-patient communication and measures of parent and child satisfaction with medical care. RESULTS: Female physician visits were 29% longer than those of male physicians (P < .001). Compared with male physicians, female physicians engaged in more social exchange (P < .01), more encouragement and reassurance (P < .01), more communication during the physical examination (P < .05), and more information gathering (P < .01) with children. Male and female physicians engaged in similar amounts of discussions regarding illness management. Children were more satisfied with physicians of the same gender (P < .05), while parents were more satisfied with female physicians (P < .05). CONCLUSIONS: Children communicate more with female than with male physicians and show preferences for physicians of the same gender. These findings are consistent with communication patterns in adult patients and may have a significant influence on gender disparities in health care. Efforts at improving the process and outcome of medical care should address gender differences.

Health care of children and adults with acquired immunodeficiency syndrome. A population-based analysis.

OBJECTIVES: To compare the use of medical services by pediatric and adult patients with acquired immunodeficiency syndrome (AIDS) in the 6 months before and after the diagnosis of AIDS when demand for care is often high and to study the influence of human immunodeficiency virus specialty care on survival of pediatric patients. DESIGN: Retrospective analysis of Medicaid files. SETTING: New York State Medicaid Program. PATIENTS: A cohort identified as having AIDS from 1985 through 1990 and enrolled on Medicaid from birth or 1 year or more before diagnosis. Because of differing prognoses, 3 groups were studied by age at the time that AIDS was diagnosed: infants younger than 6 months, children aged 6 months to 12 years, and adults aged 13 to 60 years. MAIN OUTCOME MEASURES: Frequencies of any service use and, among users, monthly rates of services. From Cox proportional hazards models, the adjusted hazard of death for human immunodeficiency virus specialty ambulatory care. RESULTS: Nearly all infants (n = 122) were hospitalized before and after the diagnosis of AIDS was made--the most of all groups. After diagnosis, only 81% of older children (n = 612) were hospitalized vs 93% of infants and 90% of adults (n = 5602). Hospitalized children had a median of only 3.3 inpatient days per month vs 12.3 and 7.8 inpatient days for infants and adults, respectively. Of older children, 45% used the emergency department vs 33% of adults. Human immunodeficiency virus specialty care for infants and children was associated with a 40% lower risk of death after the diagnosis of AIDS. CONCLUSIONS: In this AIDS cohort, infants had the greatest use of inpatient care, and older children used the emergency department more than adults. The finding of improved survival for infants and children with human immunodeficiency virus specialty care warrants further study in more recent years.

Free-electron laser oscillator in a symmetrical, confocal resonator.

A tapered wiggler is used in a free-electron laser (FEL) oscillator to improve the saturation efficiency. During signal buildup the tapered wiggler does not provide optimum phase synchronism between the electron beam and the electromagnetic wave, resulting in an appreciable loss in small-signal gain. If the taper is too large, the decrease in gain during buildup may preclude the onset of oscillation. This problem can be ameliorated with a multicomponent wiggler, which is a combination of a uniform wiggler and a tapered section. During buildup gain is primarily contributed by the linear element, and at high power levels the gain and efficiency are enhanced by the taper. Ideally, one would like to have a uniform wiggler at small-signal levels and then be able to substitute a taper at saturation. Placing the FEL in a symmetrical confocal resonator approaches this desired effect automatically.

Evaluation of urine-based screening strategies to detect Chlamydia trachomatis among sexually active asymptomatic young males.

OBJECTIVE: To evaluate the performances of diagnostic screening tests alone or in combination to detect asymptomatic chlamydial urethral infection in young males. DESIGN: Comparisons of the performance profiles of the following chlamydia screening strategies were done: urethral culture; identification of polymorphonucleocytes (PMNs) on spun first-void urine (FVU); urinary leukocyte esterase test (LET) on unspun FVU; chlamydial enzyme immunoassay (EIA) applied to FVU sediment; combining LET on unspun FVU followed by EIA with or without direct fluorescent antibody (DFA) confirmation on FVU sediment; and combining PMNs on spun FVU followed by EIA with or without DFA confirmation. SETTING: General clinics at a youth detention center, university-based teen clinic, college health service, and a military screening clinic. PATIENTS: A total of 618 males aged 12 to 35 years (mean, 17 years) were recruited as a convenience sample; site participation rates ranged from 50% to 80%. Eligible subjects were sexually active, denied symptoms of urethritis, and had taken no antibiotics in the prior 2 weeks. MAIN OUTCOME MEASURES: Sensitivity, specificity, and positive and negative predictive values of each test strategy's ability to detect Chlamydia trachomatis infection, and cost to confirm each positive case. RESULTS: With a 7% prevalence of chlamydial infection, tissue culture had a sensitivity of only 61%. However, two strategies yielded significantly better performance profiles compared with the others: EIA confirmed by DFA test with a sensitivity of 84%, a specificity of 100%, and a cost to identify each positive case of $434; and PMNs followed by EIA confirmed by DFA test with a sensitivity of 78%, a specificity of 100%, and a cost to identify each positive case of $199. The LET followed by EIA-DFA had a similar performance profile to the PMN test strategies. CONCLUSIONS: A combination of a nonspecific screening of FVU for PMNs or LET followed by specific testing with EIA with DFA confirmation has superior clinical and cost-effective performance for detecting asymptomatic C trachomatis urethritis in young males compared with other strategies. However, an evaluation of the medical, fiscal, and psychological benefits and risks associated with a specific screening strategy for sexually transmitted diseases must be made before adopting a specific strategy for a particular population.

Noninvasive digital energy subtraction angiography with a channeling-radiation x-ray source.

Channeling radiation could provide a viable source for digital energy subtraction angiography (DESA). A signal to noise ratio (SNR) of 6.2 for a resolution of 0.5 mm x 0.5 mm could be achieved using a 6-mA 100-ms 20-MeV electron-beam pulse and a diamond channeling crystal as the x-ray source. This article investigates the choice of a DESA contrast agent and the parameters of a channeling-radiation x-ray source to develop a channeling-radiation DESA imaging system. The production of dual-energy peaks, the maximum available x-ray flux, the advantages of an area exposure, the necessity of a mosaic Bragg-crystal filter to reduce patient dose, the optimal energy separation of the peaks for a quasi-monochromatic x-ray source, and the reduction of the signal from bone are discussed, leading to estimated SNRs and image resolution for a channeling-radiation imaging system. The computer analysis developed to calculate the image quality is also discussed.

Psychosocial problems during child health supervision visits: eliciting, then what?

An explicit goal of child health supervision visits is to gather information and provide guidance about the psychosocial problems of children and families. The purpose of this study was to determine the extent to which parents had opportunities to express psychosocial concerns and the nature of physicians' responses to these concerns during health supervision visits. The authors analyzed videotapes of child health supervision visits by 34 children aged 5-12 years to 34 pediatric and family medicine residents. Coding systems with acceptable interobserver reliability were developed to assess (1) the nature of opportunities provided to express concerns, (2) categories of psychosocial problems expressed by parents and children, and (3) the nature of physicians' responses. In 88% of the child health supervision visits, opportunities were created by the physician to discuss psychosocial concerns or were spontaneously raised by the parent or child. In half of the visits, parents or children expressed a total of 30 psychosocial concerns. Psychosocial problems raised included conduct/behavior problems (47%), insecurity (13%), family, sibling, or social problems (13%), learning difficulties (10%), somatization (7%), and other (10%). Physicians' responses to these psychosocial concerns were as follows: 17% ignored the concern; 43% asked further exploratory questions but provided no information, reassurance, or guidance; 3% reassured the parent; 27% responded with psychosocial information and/or action; 3% responded with medical information and/or action; and 7% responded with a combination of these latter two modes of actions. Pediatric residents were more likely to respond to more disruptive behavioral concerns (r = .60, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Increasing patient knowledge, satisfaction, and involvement: randomized trial of a communication intervention.

A brief educational intervention to promote effective communication between physicians, children, and parents during pediatric office visits was designed and tested. A randomized clinical trial involving 141 children (5- to 15-year-olds) tested the effectiveness of the intervention to improve the process and outcome of medical care. The intervention was contained in three brief videotapes (one each for parents, physicians, and patients) and in accompanying written materials. Materials were designed to build skills and motivation for increased child competence and participation during pediatric medical visits. Control subjects saw health education videotapes and received materials comparable in length with those of experimental subjects. Postintervention medical visit process was analyzed using videotapes of visits. Visit outcomes, assessed with standardized instruments and interviews, included children's rapport with physicians, children's anxiety, children's preference for an active health role, children's recall of information, parents' satisfaction with the medical visit, and physician satisfaction. Results indicated that physicians in the intervention group, compared with their counterparts in the control group, more often included children in discussions of medical recommendations (50% vs 29%, t = 2.39, P less than .05); that children in the intervention group, compared with control children, recalled more medication recommendations (77% vs 47%, P less than .01) and reported greater satisfaction and preference for an active health role; and that the intervention and control groups did not differ in parent satisfaction, physician satisfaction, or child anxiety. The results suggest that a brief educational intervention administered during waiting room time can positively impact physician-child rapport and children's preference for an active role in health and their acquisition of medical information.

Patterns of fecal coliform contamination in day-care centers.

During a six-month period, on four separate occasions, six licensed day-care centers had cultures taken from environmental surfaces as well as the hands of children and teachers. Fecal coliforms were recovered from 64 (9.5%) of the 675 surfaces sampled. Recovery rate was not influenced by a center's socioeconomic status, time of year, or presence of children who were not toilet trained. Recovery rates did differ significantly in different areas, with the kitchen showing a relatively high recovery rate (19%), and toys and toilets showing remarkably low rates (2% and 4%). Centers with formal hand-washing procedures had lower recovery rates than those without such practices. We also demonstrated a high recovery rate from hands of staff (16%); 6% of children had positive cultures. Contamination of hands and classroom objects is a potential source for the transmission of enteric diseases for children in day-care centers. A program directed at reducing contamination would be important in preventing the spread of diarrheal illness.