High average brightness water window source for short-exposure cryomicroscopy.

Laboratory water window cryomicroscopy has recently demonstrated similar image quality as synchrotron-based microscopy but still with much longer exposure times, prohibiting the spread to a wider scientific community. Here we demonstrate high-resolution laboratory water window imaging of cryofrozen cells with 10 s range exposure times. The major improvement is the operation of a λ=2.48 nm, 2 kHz liquid nitrogen jet laser plasma source with high spatial and temporal stability at high average brightness >1.5×10(12) ph/(s×sr×µm(2)×line), i.e., close to that of early synchrotrons. Thus, this source enables not only biological x-ray microscopy in the home laboratory but potentially other applications previously only accessible at synchrotron facilities.

Compact x-ray microscope for the water window based on a high brightness laser plasma source.

We present a laser plasma based x-ray microscope for the water window employing a high-average power laser system for plasma generation. At 90 W laser power a brightness of 7.4 x 10(11) photons/(s x sr x µm(2)) was measured for the nitrogen Lyα line emission at 2.478 nm. Using a multilayer condenser mirror with 0.3 % reflectivity 10(6) photons/(µm(2) x s) were obtained in the object plane. Microscopy performed at a laser power of 60 W resolves 40 nm lines with an exposure time of 60 s. The exposure time can be further reduced to 20 s by the use of new multilayer condenser optics and operating the laser at its full power of 130 W.

Laboratory cryo soft X-ray microscopy.

Lens-based water-window X-ray microscopy allows two- and three-dimensional (2D and 3D) imaging of intact unstained cells in their near-native state with unprecedented contrast and resolution. Cryofixation is essential to avoid radiation damage to the sample. Present cryo X-ray microscopes rely on synchrotron radiation sources, thereby limiting the accessibility for a wider community of biologists. In the present paper we demonstrate water-window cryo X-ray microscopy with a laboratory-source-based arrangement. The microscope relies on a λ=2.48-nm liquid-jet high-brightness laser-plasma source, normal-incidence multilayer condenser optics, 30-nm zone-plate optics, and a cryo sample chamber. We demonstrate 2D imaging of test patterns, and intact unstained yeast, protozoan parasites and mammalian cells. Overview 3D information is obtained by stereo imaging while complete 3D microscopy is provided by full tomographic reconstruction. The laboratory microscope image quality approaches that of the synchrotron microscopes, but with longer exposure times. The experimental image quality is analyzed from a numerical wave-propagation model of the imaging system and a path to reach synchrotron-like exposure times in laboratory microscopy is outlined.

Temporal coherence and spectral linewidth of an injection-seeded transient collisional soft x-ray laser.

The temporal coherence of an injection-seeded transient 18.9 nm molybdenum soft x-ray laser was measured using a wavefront division interferometer and compared to model simulations. The seeded laser is found to have a coherence time similar to that of the unseeded amplifier, ~1 ps, but a significantly larger degree of temporal coherence. The measured coherence time for the unseeded amplifier is only a small fraction of the pulsewidth, while in the case of the seeded laser it approaches full temporal coherence. The measurements confirm that the bandwidth of the solid target amplifiers is significantly wider than that of soft x-ray lasers that use gaseous targets, an advantage for the development of sub-picosecond soft x-ray lasers.

High-energy 13.9 nm table-top soft-x-ray laser at 2.5 Hz repetition rate excited by a slab-pumped Ti:sapphire laser.

We have demonstrated repetitive operation of a table-top lambda=13.9 nm Ni-like Ag soft-x-ray laser that generates laser pulses with 10 microJ energy. The soft-x-ray laser is enabled by a Ti:sapphire laser pumped by high-repetition-rate frequency-doubled high-energy Nd:glass slab amplifiers. Soft-x-ray laser operation at 2.5 Hz repetition rate resulted in 20 microwatt average power.

Gain-saturated 10.9 nm tabletop laser operating at 1 Hz repetition rate.

We report the demonstration of a gain-saturated 10.9 nm tabletop soft x-ray laser operating at 1 Hz repetition rate. Lasing occurs by collisional electron impact excitation in the 4dS01-->4pP11 transition of nickel-like Te in a line-focus plasma heated by a chirped-pulse-amplification Ti:sapphire laser. With an average power of 1muW and pulse energy up to approximately 2microJ, this laser extends the ability to conduct tabletop laser experiments to a shorter wavelength.

Large area high efficiency broad bandwidth 800 nm dielectric gratings for high energy laser pulse compression.

We have demonstrated broad bandwidth large area (229 mm x 114 mm) multilayer dielectric diffraction gratings for the efficient compression of high energy 800 nm laser pulses at high average power. The gratings are etched in the top layers of an aperiodic (Nb0.5Ta0.5)2O5-SiO2 multilayer coating deposited by ion beam sputtering. The mean efficiency of the grating across the area is better than 97% at the center wavelength and remains above 96% at wavelengths between 820 nm and 780 nm. The gratings were used to compress 5.5 J pulses from a Ti:sapphire laser with an efficiency above 80 percent.

Motor neuron disease recovery associated with IV ceftriaxone and anti-Babesia therapy.

This report summarizes what we believe to be the first verifiable case of a significant and progressive motor neuron disease (MND) consistent with amyotrophic lateral sclerosis that resolved during treatment with i.v. ceftriaxone plus oral atovaquone and mefloquine. The rationale for use of these antibiotics was (i) positive testing for Borrelia burgdorferi and (ii) red blood cell ring forms consistent with Babesia species infection. The patient has continued to be free of MND signs and symptoms for 15 months, although some symptoms consistent with disseminated Borreliosis remain.

The use of digital video recorders (DVRs) for capturing digital video files for use in both The Observer and Ethovision.

Before switching a laboratory from analog to digital, for the recording of video files for use in Noldus software such as Ethovision and The Observer, researchers need to proceed with caution. There are obvious advantages in moving to digital recording for behavioral work, including increased storage capacity; no requirement to purchase video tapes; immediate search by date, time, or event; digital images are of higher quality; ability to view study sites remotely by Internet connection; and "smart" features, such as motion detection. But before you throw away your time-lapse video recorders, time code generators, and video multiplexors, there are some important cautions to take account of. Some research groups have bought digital surveillance systems on the assumption that they work with Ethovision and The Observer, only to be disappointed. The vast majority of systems depend on proprietary compression software that must then be converted to work properly in Ethovision or The Observer.

Demonstration of a desk-top size high repetition rate soft x-ray laser.

We have demonstrated a new type of high repetition rate 46.9 nm capillary discharge laser that fits on top of a small desk and that it does not require a Marx generator for its excitation. The relatively low voltage required for its operation allows a reduction of nearly one order of magnitude in the size of the pulsed power unit relative to previous capillary discharge lasers. Laser pulses with an energy of ~ 13 microJ are generated at repetition rates up to 12 Hz. About (2-3) x 10 4 laser shots can be generated with a single capillary. This new type of portable laser is an easily accessible source of intense short wavelength laser light for applications.

Evaluation of a cognitive-behavioral therapy intervention to improve body image and decrease dieting in college women.

This two-group experimental study evaluated the effectiveness of a cognitive-behavioral body image intervention, adapted from an effective clinical intervention, with normal college females. Participants included nonclinical, freshman college women who were assigned randomly to either the experimental intervention or the control group (brief educational session). Participants were assessed prior to the intervention and again 1 month later on dieting behavior, body image, fear of fat, and anxiety concerning physical appearance. Although it was hypothesized that each of these variables would be lower in the experimental group, none of these results, except for a trend for decreased dieting, were found. Overall these results of slightly reduced dieting behavior are consistent with other research targeting primary and secondary prevention. This intervention's failure to impact body image and eating behaviors of college students illustrates the continuing challenge of eating disorders prevention.

Psychological, nutritional, and energy expenditure differences in college females with anorexia nervosa vs. comparable-mass controls.

This is the first study to examine psychological and behavioral variables in nonhospitalized college females with subclinical anorexia nervosa (AN) as compared to healthy college females of comparable body mass (i.e., body mass index (BMI)<19). Participants who met all DSM-IV [Diagnostic and statistical manual of mental disorders, 4th ed. (1994). Washington, DC: APA.] criteria for AN-restrictive type (except for BMI<17.5; n=11) and control participants (n=15) with comparable body mass completed psychological, nutritional, and exercise assessments. Results suggested that those with AN evidenced more general psychopathology, more eating disorder symptoms, more dieting, more compulsive exercise, and less consumption of calories compared to participants in the control group. There was no difference in macronutrient consumption. There was no significant difference in expenditure of energy, despite differences in reports of compulsive exercise. Given similar body mass, this suggests that the women with AN were experiencing an energy deficit consistent with the disorder's defining features of "fear of gaining weight or becoming fat" and provides us with more understanding of individuals with AN in their natural environment.

Development and preliminary validation of the cognitive behavioral dieting scale.

OBJECTIVE: The purpose of this research was to empirically develop the Cognitive Behavioral Dieting Scale (CBDS), a measure of current dieting. METHOD: The first study involved item generation and a procedure to boost internal consistency while reducing scale length. Study 2 involved a factor analysis and measures of scale reliability. The third study evaluated the ability of the CBDS to predict calorie intake and negative calorie balance from a 24-hr diet recall. Study 4 evaluated construct validity by comparing the CBDS to dietary restraint, body image, and health behavior self-efficacy. RESULTS: The CBDS is a 14-item scale which measures current dieting behavior and related thoughts within the past 2 weeks. Internal consistency was alpha = .95 and 2-day test-retest reliability was r = .95. This scale provides a method for operationalizing dieting, provides a construct that is different from restraint, and assess dieting behavior on a continuum. Additionally, this scale was able to predict calorie intake and negative calorie balance above and beyond the predictive ability of physical variables (i.e., body mass index BMI] and exercise calories). An additional study of construct validity showed the CBDS was related to poor body image esteem and dietary restraint, but minimally related to healthy eating self-efficacy. DISCUSSION: In conclusion, the CBDS shows promise as a valid and reliable measure of dieting behavior. This scale should have utility in future research on how current dieting relates to eating disorders, dietary restraint, and obesity.

Influence of medical school applicants' demographic and cognitive characteristics on interviewers' ratings of noncognitive traits.

BACKGROUND: Interviews are commonly used to measure noncognitive traits of medical school applicants. The present study investigated the influence of knowledge of applicants' cognitive abilities on interviewers' ratings of noncognitive traits. METHOD: Academic and demographic predictors of interview ratings of applicants' noncognitive traits were examined at the Medical University of South Carolina College of Medicine during two years: 1992, when applicants' Medical College Admission Test (MCAT) total scores and undergraduate grade-point averages (GPAs) were available to interviewers; and 1993, when MCAT and GPA data were not available. In 1992, 226 applicants met study criteria (i.e., they received ratings from three interviewers in addition to having MCAT and GPA data on file); in 1993, 245 applicants met the criteria. Step-wise regression analyses were conducted to measure the influences of seven independent variables on applicants' interview ratings. Two-way analyses of variances and t-tests were used to determine the effects of gender of applicants and interviewers. Cronbach's alpha coefficients were used as measures of interviewers' reliability. RESULTS: GPA was the best predictor for both years but accounted for double the amount of variance in interview ratings in 1992 (15.7%) compared with 1993 (7.4%). The reliability coefficients for the interviewers were .496 for 1992 and .473 for 1993. CONCLUSION: If the goal of the medical school admission interview is to assess noncognitive traits independently from academic skills, the authors recommend that MCAT and GPA data not be available to interviewers during interviews. The authors also found that gender and race influenced interview ratings in accordance with affirmative-action goals. Finally, the authors found that interview scores were only moderately reliable across different interviewers. They discuss ways to increase their reliability.

Evaluation of the beta energy spectrum from a distributed uranium mill tailings source.

The beta energy spectra from uranium mill tailings, 90Sr with different absorber thicknesses, and a uranium metal slab were measured and compared to select an appropriate beta source for calibrating a personal dosimeter to measure shallow dose equivalent when exposed to uranium mill tailings. The measured beta energy spectrum from the 90Sr source, with a 111 mg cm-2 cover thickness, was selected as a possible calibration source for a personnel dosimeter. The dose equivalent rate to the skin at 1 cm from a distributed tailings source of infinite thickness, with a 226Ra activity of 56 Bq g-1 (1.5 x 10(3) pCi g-1), was measured to be 0.024 mSv h-1 (2.4 mrem h-1).

A multiyear quality control study of alpha-track radon monitors.

Quality control exposures of commercial alpha-track radon monitors have been conducted approximately weekly at the U.S. Department of Energy (DOE) Grand Junction Projects Office since early 1987 in support of DOE remedial action programs. The results of these exposures provide a historical record of the comparative performances of these radon monitors.

Half-lives of 214Pb and 214Bi.

New measurements on chemically separated samples of 214Bi have yielded a mean half-life value of 19.71 +/- 0.02 min, where the error quoted is twice the standard deviation of the mean based on 23 decay runs. This result provides strong support for the historic 19.72 +/- 0.04 min half-life value and essentially excludes the 19.9-min value, both reported in previous studies. New measurements of the decay rate of 222Rn progeny activity initially in radioactive equilibrium have yielded a value of 26.89 +/- 0.03 min for the half-life of 214Pb, where the error quoted is twice the standard deviation of the mean based on 12 decay runs. This value is 0.1 min longer than the currently accepted 214Pb half-value of 26.8 min.

Year-to-year variations in annual average indoor 222Rn concentrations.

Annual average indoor 222Rn concentrations in 40 residences in and around Grand Junction, CO, have been measured repeatedly since 1984 using commercial alpha-track monitors (ATM) deployed for successive 12-mo time periods. Data obtained provide a quantitative measure of the year-to-year variations in the annual average Rn concentrations in these structures over this 6-y period. A mean coefficient of variation of 25% was observed for the year-to-year variability of the measurements at 25 sampling stations for which complete data were available. Individual coefficients of variation at the various stations ranged from a low of 7.7% to a high of 51%. The observed mean coefficient of variation includes contributions due to the variability in detector response as well as the true year-to-year variation in the annual average Rn concentrations. Factoring out the contributions from the measured variability in the response of the detectors used, the actual year-to-year variability of the annual average Rn concentrations was approximately 22%.

Comparative performance of short-term diffusion barrier charcoal canisters and long-term alpha-track monitors for indoor 222Rn measurements.

The accuracy and precision of indoor 222Rn measurements obtained with the use of diffusion barrier charcoal canisters (DBCC) under actual field conditions were determined by comparing the integrated average of 26 successive 7-d exposures of DBCC in each of 16 occupied residences over a 6-mo period with simultaneous measurements using four types of commercially available alpha-track monitors (ATM) and one type of scintillation chamber continuous 222Rn monitor. The results suggest that properly calibrated DBCCs provide very good estimates of the integrated 222Rn concentrations in residential structures over the standard 1-wk exposure period despite the occurrence of large diurnal variations in the actual 222Rn concentrations. The results also suggest that a relatively small number of 1-wk DBCC measurements at selected times throughout the calendar year would provide estimates of the annual average indoor 222Rn concentrations that compare favorably with single long-term ATM measurements.