The DCU laser ion source.

Laser ion sources are used to generate and deliver highly charged ions of various masses and energies. We present details on the design and basic parameters of the DCU laser ion source (LIS). The theoretical aspects of a high voltage (HV) linear LIS are presented and the main issues surrounding laser-plasma formation, ion extraction and modeling of beam transport in relation to the operation of a LIS are detailed. A range of laser power densities (I approximately 10(8)-10(11) W cm(-2)) and fluences (F=0.1-3.9 kJ cm(-2)) from a Q-switched ruby laser (full-width half-maximum pulse duration approximately 35 ns, lambda=694 nm) were used to generate a copper plasma. In "basic operating mode," laser generated plasma ions are electrostatically accelerated using a dc HV bias (5-18 kV). A traditional einzel electrostatic lens system is utilized to transport and collimate the extracted ion beam for detection via a Faraday cup. Peak currents of up to I approximately 600 microA for Cu(+) to Cu(3+) ions were recorded. The maximum collected charge reached 94 pC (Cu(2+)). Hydrodynamic simulations and ion probe diagnostics were used to study the plasma plume within the extraction gap. The system measured performance and electrodynamic simulations indicated that the use of a short field-free (L=48 mm) region results in rapid expansion of the injected ion beam in the drift tube. This severely limits the efficiency of the electrostatic lens system and consequently the sources performance. Simulations of ion beam dynamics in a "continuous einzel array" were performed and experimentally verified to counter the strong space-charge force present in the ion beam which results from plasma extraction close to the target surface. Ion beam acceleration and injection thus occur at "high pressure." In "enhanced operating mode," peak currents of 3.26 mA (Cu(2+)) were recorded. The collected currents of more highly charged ions (Cu(4+)-Cu(6+)) increased considerably in this mode of operation.

Polarization control in two-color above-threshold ionization of atomic helium.

Two-color multiphoton ionization of atomic helium was investigated by combining extreme ultraviolet (XUV) radiation from the Free Electron Laser in Hamburg with an intense synchronized optical laser. In the photoelectron spectrum, lines associated with direct ionization and above-threshold ionization show strong variations of their amplitudes as a function of both the intensity of the optical dressing field and the relative orientation of the linear polarization vectors of the two fields. The polarization dependence provides direct insight into the symmetry of the outgoing electrons in above-threshold ionization. In the high field regime, the monochromaticity of the XUV radiation enables the unperturbed observation of nonlinear processes in the optical field.

Dynamically and quasiforbidden transitions in photoionization of open-shell atoms: a combined experimental and theoretical study.

Completely fine-structure-resolved photoelectron spectra produced from sodium atoms selectively excited into the Na* 2p(6)3p (2)P(1/2) and (2)P(3/2) states were obtained using a third generation synchrotron source in conjunction with laser pumping and high-resolution spectrometry. The spectra show dramatically different behaviors. The strong variations observed in the regions of the Na+ 2p(5)3p (1,3)L(J) photolines and the Na+ 2p(5)4p (1,3)L(J) shakeup satellites are explained within a generalized geometrical model, accounting for the intermediate angular momentum coupling in the ionic states.

Popular diets: correlation to health, nutrition, and obesity.

OBJECTIVE: To examine the association between a range of health and nutrition indicators and popular diets. DESIGN: The Continuing Survey of Food Intake by Individuals (CSFII) 1994-1996 data were used to examine the relationship between prototype popular diets and diet quality as measured by the healthy eating index (HEI), consumption patterns, and body mass index (BMI). The prototype diets included vegetarian (no meat, poultry, or fish on day of survey) and non-vegetarian. The nonvegetarian group was further subdivided into low carbohydrate (less than 30% of energy from carbohydrate), medium (30% to 55%), and high (greater than 55% of energy). Within the high carbohydrate group, participants were classified as having Pyramid or non-Pyramid eating patterns. The Pyramid group was defined as 30% or less of energy from fat and at least one serving from the five major food groups in the USDA Food Guide Pyramid. Finally, the non-Pyramid group was further subdivided into low fat (less than 15% of energy from fat) and moderate fat (15% to 30% of energy from fat). In addition, a review of the published scientific literature was conducted; all studies identified were included in the review. SUBJECTS: 10,014 adults, aged 19 years and older, from the 1994-1996 CSFII were included in the analyses of extant data. More than 200 individual studies were included in the review of the literature. RESULTS: Analyses of the CSFII indicate that diet quality as measured by HEI was highest for the high carbohydrate Pyramid group (82.9) and lowest for the low carbohydrate group (44.6). Energy intakes were low for the vegetarians (1,606 kcals) and high carbohydrate/low fat group (1360 kcals). BMIs were lowest for women in the vegetarian group (24.6) and the high carbohydrate/low fat group (24.4); for men, the lowest BMIs were observed for vegetarians (25.2) and the high carbohydrate Pyramid group (25.2). Review of the literature suggests that weight loss is independent of diet composition. Energy restriction is the key variable associated with weight reduction in the short term. CONCLUSIONS: Diets that are high in carbohydrate and low to moderate in fat tend to be lower in energy. The lowest energy intakes were observed for those on a vegetarian diet. The diet quality as measured by HEI was highest for the high carbohydrate groups and lowest for the low carbohydrate groups. The BMIs were significantly lower for men and women on the high carbohydrate diet; the highest BMIs were noted for those on a low carbohydrate diet.

Dietary-fat intake in the US population.

OBJECTIVE: This article looks at the food group choices by individuals grouped based on fat intake, saturated fat intake, and use of lowfat foods. METHODS: Food consumption data from USDA's National Food Consumption Surveys (NFCS) and the Continuing Survey of Food Intakes by Individuals (CSFII) were used to look at changes in the mean energy, percent calories from fat and saturated-fat and total-fat intakes over time. USDA's 1995 CSFII data were used to evaluate the diets of individuals grouped based on percent calories from fat and use of low-fat foods. Individuals six to 50 years old who had complete food intake records were included and five age-gender classifications were used. RESULTS: The percent of calories from total fat and saturated fat have steadily declined over the last 30 years, and the amount of fat in the diet has increased from 1989 to 1995. Those whose diets met the Dietary Guidelines Recommendations for fat and saturated fat had lower fat intakes. Except for adult males, those with low-fat diets had higher intakes of total-food amount. Also, lower saturated-fat intakes were associated with lower energy intakes. In general, high-fruit-and-grain-products consumption were seen in groups with low-fat intake. For those who included low-fat foods in their diets and also had low-fat intakes, rice and pasta were the major foods of choice for calories. Fried potatoes were one of the main sources of calories for high-fat groups. CONCLUSION: The study showed individuals whose diets included low-fat foods are more likely to have a diet that meets the dietary guidelines recommendations for fat and saturated fat.

The Healthy Eating Index: design and applications.

OBJECTIVE: To develop an index of overall diet quality. DESIGN: The Healthy Eating Index (HEI) was developed based on a 10-component system of five food groups, four nutrients, and a measure of variety in food intake. Each of the 10 components has a score ranging from 0 to 10, so the total possible index score is 100. METHODS/SUBJECTS: Data from the 1989 and 1990 Continuing Survey of Food Intake by Individuals were used to analyze the HEI for a representative sample of the US population. STATISTICAL ANALYSES PERFORMED: Frequencies, correlation coefficients, means. RESULTS: The mean HEI was 63.9; most people scored neither very high nor very low. No one component of the index dominated the HEI score. People were most likely to do poorly in the fruit, saturated fat, grains, vegetable, and total fat categories. The HEI correlated positively and significantly with most nutrients; as the total HEI increased, intake for a range of nutrients also increased. DISCUSSION/CONCLUSIONS: The HEI is a useful index of overall diet quality of the consumer. The US Department of Agriculture will use the HEI to monitor changes in dietary intake over time and as the basis of nutrition promotion activities for the population.

Household and preschooler vitamin A consumption in southwestern Kenya.

This study examined the effects of an income-generating policy to expand the commercialization of subsistence agriculture in southwestern Kenya on household and preschooler macro- and micronutrient consumption. A representative sample of 617 household was included, and all preschoolers under the age of 6 y (1677) residing in these households were included in the study. Results of this analysis indicate that although increases in household income do result in improved household level vitamin A consumption, increases in household income are not significantly associated with the intake of dietary vitamin A by preschoolers. The analysis suggests that although increases in household income have some very positive effects on household food security and household micronutrient consumption, other community-based health, sanitation and nutrition interventions are needed to address the dietary needs of individuals within the household.

A prenatal screening system for use in a community-based setting.

An obstetrical risk and a nutritional risk screening system were developed and implemented in Massachusetts to be used for the identification of high-risk pregnant women. Components of the obstetrical risk score include age, parity, length of interconceptual periods, a pregravid weight-for-height index, and prior history of miscarriages and low birth weight (LBW) infants. The nutritional risk screening system is based on a modified food frequency using four food groups--meat and their alternates, milk, bread and cereal, and fruits and vegetables. Results from this study on 910 WIC and 418 non-WIC pregnant women indicate that women classified as at high obstetrical risk had a significantly higher incidence of LBW infants than women in the low-risk group. However, the nutritional risk score had no predictive value in identifying those women likely to produce LBW infants.

The effect of WIC supplemental feeding on birth weight: a case-control analysis.

Extant data from prenatal patients in Massachusetts were analyzed to evaluate the effects of WIC supplemental feeding on birth outcomes. A total of 418 pairs of WIC and non-WIC women were directly matched for racial/ethnic group, age, parity, marital status, and income. Participation in WIC supplemental feeding appears to have a positive effect on pregnancy outcome. Participation in WIC is associated with a 107 g increase in mean birth weight (p = 0.012) and a 4.0% decrease in the incidence of low birth weight (p = 0.059). Teenage, Black, and Hispanic women show similar, if not stronger, benefits.

Evaluation of the effect of WIC supplemental feeding on birth weight.

This study examined the impact of pregnant women's participation in a WIC supplemental feeding program on the birth weight of infants. Data on 1,328 WIC and non-WIC participants were collected from a retrospective review of medical and/or nutrition records. Participation of women in WIC was associated with a positive and significant increment in birth weight of their infants.

Effect of WIC supplemental feeding on hemoglobin and hematocrit of prenatal patients.

The present study was designed to assess the effect of WIC food supplementation on the hematological status of pregnant women as measured by hemoglobin and hematocrit values. Although the baseline hematological status of the WIC and non-WIC pregnant women was similar, the final values for the WIC participants were significantly higher than those for the non-participants. Analyses from the present study reveal that participation in the WIC program was associated with a positive and significant increase in the final hemoglobin and hematocrit measurements of pregnant women.

Laser-produced continua for absorption spectroscopy in the VUV and XUV.

Recent work has shown that with appropriate targets, laser-produced plasmas provide clean essentially linefree continua suitable for absorption spectroscopy from 40 to 2000 A. A systematic study of the continua emitted by the elements from samarium to ytterbium is reported, and their use in absorption spectroscopy is demonstrated. The temporal profiles of the continuum pulses at different wavelengths are studied with a photomultiplier system and are found to have essentially the same halfwidths as the pulse from the exciting Q-switched ruby laser (~25 nsec). Pulse heights are shown to be reproducible to 15% or better. Ambient gases, at least at pressures up to several Torr, do not affect the emission mechanism. A comparison with other continuum sources at XUV wavelengths (i.e., BRV, synchrotron) is made, and possible future developments are outlined.