Emission characteristics of a homologous series of bimesogenic liquid-crystal lasers

In this study we have fabricated eight different liquid-crystal lasers using the same gain medium but different homologues from the bimesogenic series alpha-(2',4-difluorobiphenyl-4'-yloxy)-omega-(4-cyanobiphenyl-4'-yloxy)alkanes, whereby the number of methylene units in the spacer chain varied from n=5 to n=12. To quantify the performance of these lasers, the threshold energy and the slope efficiency were extracted from the input-output characteristics of each laser. A clear odd-even effect was observed when both the excitation threshold and the slope efficiency were plotted as a function of the number of methylene units in the spacer chain. In all cases, the bimesogen lasers for which n is even exhibit lower threshold energies and higher slope efficiencies than those for which n is odd. These results are then interpreted in terms of the macroscopic physical properties of the liquid-crystalline compounds. In accordance with a previous study [S. M. Morris, A. D. Ford, M. N. Pivnenko, O. Hadeler, and H. J. Coles, Phys. Rev. E. 74, 061709 (2006)], a combination of a large birefringence and high order parameters are found, in the most part, to correlate with low-threshold energy and high slope efficiency. This indicates that the threshold and slope efficiency are dominated by the host macroscopic properties as opposed to intermolecular interactions between the dye and the liquid crystal. However, certain differences in the slope efficiency could not be explained by the birefringence and order parameter values alone. Instead, we find that the slope efficiency is further increased by increasing the elastic constants of the liquid-crystal host so as to decrease the scattering losses incurred by local distortions in the director field under high-energy optical excitation.

The clinical needs of patients with chronic gastrointestinal symptoms after pelvic radiotherapy

BACKGROUND

After radiotherapy for pelvic cancer, gastrointestinal symptoms affecting quality of life are common. How they affect daily living is unknown.

AIM

To investigate the day-to-day impact of gastrointestinal symptoms in patients after pelvic radiotherapy.

METHODS

New patients referred for gastroenterological evaluation of radiotherapy-induced symptoms were sent a questionnaire.

RESULTS

Over 15 months, 75 of 100 questionnaires were completed before the gastroenterology appointment by 45 men (median age 70) and 30 women (median age 57) treated for urological (n = 44), gynaecological (n = 27) and gastrointestinal (n = 4) cancers. Time since radiotherapy was 3 years (median) for women and 1.5 years (men). Women experienced 6 (median) symptoms whilst men experienced 4. Having someone listen to problems was often as important as treatment. Urgency, diarrhoea, pain, rectal bleeding, flatulence and bloating were particularly troublesome. 57% women and 33% men were 'very affected'. Symptoms rarely improved with time and in 33% had been present for more than 2 years. Gastrointestinal symptoms affected quality of life through change of routine (F 37%, M 22%), social limitation (F 17%, M 33%), physical limitations (F 33%, M 16%), emotional difficulties (F 47%, M 18%) and sexual problems (F 30%, M 51%).

CONCLUSIONS

Patients experience a high number of physical symptoms for long periods before referral. Clinicians must focus systematically on physical, emotional and psychosexual issues.

A randomized trial of teaching clinical skills using virtual and live standardized patients

BACKGROUND

We developed computer-based virtual patient (VP) cases to complement an interactive continuing medical education (CME) course that emphasizes skills practice using standardized patients (SP). Virtual patient simulations have the significant advantages of requiring fewer personnel and resources, being accessible at any time, and being highly standardized. Little is known about the educational effectiveness of these new resources. We conducted a randomized trial to assess the educational effectiveness of VPs and SPs in teaching clinical skills.

OBJECTIVE

To determine the effectiveness of VP cases when compared with live SP cases in improving clinical skills and knowledge.

DESIGN

Randomized trial.

PARTICIPANTS

Fifty-five health care providers (registered nurses 45%, physicians 15%, other provider types 40%) who attended a CME program.

INTERVENTIONS

Participants were randomized to receive either 4 live cases (n=32) or 2 live and 2 virtual cases (n=23). Other aspects of the course were identical for both groups.

RESULTS

Participants in both groups were equivalent with respect to pre-post workshop improvement in comfort level (P=.66) and preparedness to respond (P=.61), to screen (P=.79), and to care (P=.055) for patients using the skills taught. There was no difference in subjective ratings of effectiveness of the VPs and SPs by participants who experienced both (P=.79). Improvement in diagnostic abilities were equivalent in groups who experienced cases either live or virtually.

CONCLUSIONS

Improvements in performance and diagnostic ability were equivalent between the groups and participants rated VP and SP cases equally. Including well-designed VPs has a potentially powerful and efficient place in clinical skills training for practicing health care workers.

Secular trends in desired weight of adults

CONTEXT

The prevalence of overweight and obese adults in the United States is at record levels.

OBJECTIVE

The primary purpose is to describe secular trends in desired weight among adults from 1994 to 2003, and secondarily, to examine the hypothetical impact of achieving desired weight on obesity prevalence.

DESIGN

Data were from the Behavioral Risk Factor Surveillance System (1994, 1996, 1998, 2000, 2003), a random-digit-dialed telephone survey.

SETTING

Sample included respondents from 47 states and the District of Columbia.

PARTICIPANTS

Non-institutionalized adults aged 18 years or older were included (N=703 286).

MAIN OUTCOME MEASURES

Primary outcome measures included reported weight and desired weight.

RESULTS

Means for desired weight increased 2.3 kg between 1994 and 2003, and reported weights increased 3.9 kg. The increased trend was observed across several subgroups for age, race/ethnicity and education. Within subgroups of weight status, the trend has remained relatively stable, particularly when examined in relation to the difference between reported and desired weight as a percentage of reported body weight. Generally, overweight men desired weights approximately 4.5% less than their reported weight, and obese men desired weights approximately 15% less than their reported weight for each corresponding year. For women, approximate values of desired weight were 12% less than reported weight for overweight women and 24% less for obese women. The prevalence of obesity would decrease to 4.4% if individuals weighed their desired weight.

CONCLUSIONS

Americans are shifting their desired weight upward, concomitantly with an increase in their reported body weight.

Dietary pattern as a predictor of change in BMI z-score among girls

OBJECTIVES

To describe child and adolescent dietary patterns and to determine associations between childhood dietary pattern and longitudinal change in body mass index (BMI) z-score among girls.

POPULATION AND METHODS

Healthy girls (n = 101) aged 8-12 years at baseline and 11-19 years at follow-up participated in a longitudinal study of growth and development. Participants kept 7-day dietary records at two points in time. We incorporated time of day, frequency, and amount of energy consumed (defined as percentage of total energy consumed per dietary event) when characterizing dietary patterns.

RESULTS

Girls ate an average of 4-5 times per day and consumed most energy in the afternoon and in the evening/night, rather than in the morning. After controlling for baseline BMI, the mean percentage of daily energy consumed in the evening/night was positively associated with change in BMI z-score (P = 0.039). Eating between 4.0 and 5.9 times per day overall and no more than 1.9 times in the evening/night daily were negatively associated with change in BMI z-score (P = 0.002 and 0.047, respectively), after controlling for baseline BMI z-score.

DISCUSSION

Recommendations to decrease the percentage of energy coming from the evening/night meal and the number of dietary events to no more than six times per day and two times in the evening/night should be evaluated in future longitudinal investigations.

Comparative endocrinology of the insulin-like growth factor-binding protein

Emerging early in chordate evolution, the IGF-regulatory axis diverged from an insulin-like predecessor into a vertebrate regulatory system specializing in cell growth activation and allied anabolic functions. Essential to the divergence of the IGF and insulin systems was an early presence of soluble IGF-binding proteins (IGFBPs), which bind IGF peptides at much higher affinity than that of the insulin receptor but at comparable affinities to that of the IGF receptor. IGFBPs have no homology with IGF receptors. Instead, IGFBPs are a derived group of proteins within a superfamily of cysteine-rich growth factors, whose members are found throughout the animal taxa. While blocking IGF actions through the insulin receptor is a fundamental role, IGFBPs evolved within the vertebrate line into centralized, 'integrators' of the endocrine growth-regulatory apparatus. IGFBPs have substantial influences on the distribution and bioavailability of IGF peptides in the cellular and physiological environments, but they have a variety of other properties. The six principal mammalian IGFBPs exhibit an array of specialized properties that appear to be derived from a complex evolutionary history (including cell membrane association, interaction with proteins that post-translationally modify them, direct IGF-independent effects on cells, and others) and they are regulated by a diversity of 'outside' factors (e.g. other hormones, metabolic status, stress). Thus, IGFBPs are multifunctional integrators having diverse physiological 'agendas'. Much less is known about IGFBPs and their properties in the other vertebrate taxa. Increasingly, however, it is being recognized that they play equally important endocrine roles, in both conserved and non-conserved ways, when compared with those currently defined in mammals. This review highlights selected 'comparative aspects' in current IGFBP research, in an attempt to view this essential group of endocrine regulators from a wider, biological perspective.

High serum retinyl esters are not associated with reduced bone mineral density in the Third National Health And Nutrition Examination Survey, 1988-1994

Hypervitaminosis A is sometimes associated with abnormalities of calcium metabolism and bone mineral status. A recent study found a negative association between reported dietary vitamin A intake and bone mineral density (BMD). Some segments of the U.S. population have high fasting serum retinyl ester concentrations, a physiological marker that may reflect high and possibly excessive vitamin A intake. We examined the association between fasting serum retinyl esters and BMD in the Third National Health and Nutrition Examination Survey, 1988-1994 (NHANES III), a large, nationally representative sample of the U.S. population. BMD was measured for the femoral neck, trochanter, intertrochanter, and total hip on all nonpregnant participants aged > or = 20 years; 5,790 participants also had complete data on fasting serum retinyl esters and covariates including age, body mass index (BMI), smoking, alcohol consumption, dietary supplement use, diabetes, physical activity, and, among women, parity, menopausal status, and the use of oral contraceptives or estrogen-replacement therapy. The sample included non-Hispanic white, non-Hispanic black, and Mexican American men and women. We examined the association between fasting serum retinyl esters and BMD at each site, controlling for covariates with multiple linear regression. We examined the association with osteopenia and osteoporosis with multiple logistic regression. Although the prevalences of high fasting serum retinyl esters concentration and low BMD were both substantial in this sample, there were no significant associations between fasting serum retinyl esters and any measure of bone mineral status.

Serum retinyl esters are not associated with biochemical markers of liver dysfunction in adult participants in the third National Health and Nutrition Examination Survey (NHANES III), 1988--1994

BACKGROUND

Serum retinyl ester concentrations are elevated in hypervitaminosis A. It was suggested that retinyl esters >10% of total serum vitamin A indicate potential hypervitaminosis, but this cutoff was derived from small clinical samples that may not be representative of the general population.

OBJECTIVE

We sought to examine the distribution of serum retinyl ester concentrations and associations between retinyl ester concentrations and biochemical markers of liver dysfunction in a nationally representative sample.

DESIGN

We assessed the associations between serum retinyl ester concentrations and 5 biochemical indexes of liver dysfunction by using multivariate linear and multiple logistic regression techniques and controlling for age, sex, use of supplements containing vitamin A, alcohol consumption, smoking status, and use of exogenous estrogens in 6547 adults aged > or =18 y in the third National Health and Nutrition Examination Survey (NHANES III), 1988--1994.

RESULTS

Thirty-seven percent of the sample had serum retinyl ester concentrations >10% of total serum vitamin A and 10% of the sample had serum retinyl esters >15% of total vitamin A. We found no associations between serum retinyl ester concentrations and 1) concentrations of any biochemical variable (multiple linear regression) or 2) risk of having biochemical variables above the reference range (multiple logistic regression). We did not find a serum retinyl ester value with statistically significant sensitivity and specificity for predicting increases in biochemical indexes of liver dysfunction.

CONCLUSIONS

The prevalence of serum retinyl ester concentrations >10% of the total vitamin A concentration in the NHANES III sample was substantially higher than expected but elevated retinyl ester concentrations were not associated with abnormal liver function.

C-reactive protein and body mass index in children: findings from the Third National Health and Nutrition Examination Survey, 1988-1994

OBJECTIVES

To examine the relationship between C-reactive protein (CRP) concentration and body mass index (BMI) in children.

STUDY DESIGN

With the use of data from 5305 children aged 6 to 18 years in the Third National Health and Nutrition Examination Survey (1988 to 1994), a cross-sectional health survey, we examined whether CRP concentrations were elevated among overweight children.

RESULTS

Among children whose BMI was below the age- and sex-specific 15th percentile, 6.6% of boys and 10.7% of girls had an elevated CRP concentration (>2.1 mg/L) compared with 24.2% of boys and 31.9% of girls whose BMI was > or =95th percentile. After adjustment was done for age, sex, race or ethnicity, poverty income ratio, high-density lipoprotein cholesterol concentration, white blood cell count, and history of chronic bronchitis, the adjusted odds of having an elevated CRP concentration were 2.20 (95% CI 1.30, 3.75) for children with a BMI of 85th to <95th percentile and 4.92 (95% CI 3.39, 7.15) for children with a BMI of > or =95th percentile compared with children who had a BMI of 15th to <85th percentile. The associations did not differ significantly by age, sex, or race or ethnicity.

CONCLUSIONS

In a large representative sample of US children, CRP concentration was significantly elevated among children with a BMI > or=85th percentile, thus confirming previous findings of this association in children and extending previous research in adults to children. Excess body weight may be associated with a state of chronic low-grade inflammation in children.

Serum retinol distributions in residents of the United States: third National Health and Nutrition Examination Survey, 1988-1994

BACKGROUND

Inadequate vitamin A status has been a potential nutritional problem for some segments of the US population, particularly children and the poor.

OBJECTIVE

We evaluated serum retinol concentration by using population-representative data from 16058 participants aged 4 to >/=90 y in the third National Health and Nutrition Examination Survey, 1988-1994.

DESIGN

We used multivariate regression to examine the simultaneous associations of sociodemographic, biologic, and behavioral factors with serum retinol concentration.

RESULTS

In children, serum retinol concentrations were greater with greater age, body mass index, serum lipids, and the use of supplements containing vitamin A. In adults, male sex, serum lipids, alcohol consumption, and age were positively associated with serum retinol concentration in most racial/ethnic strata. Household income was not associated with serum retinol concentration in children; associations were inconsistent in adults. The prevalence of serum retinol <0.70 micromol/L was very low in all strata; the prevalence of serum retinol <1.05 micromol/L was 16.7-33.9% in children aged 4-8 y and 3.6-14.2% in children aged 9-13 y, depending on sex and racial/ethnic group. The prevalence of serum retinol<1.05 micromol/L was higher in non-Hispanic black and Mexican American children than in non-Hispanic white children; these differences remained significant (P < 0.0001) after covariates were controlled for. Among adults, nonwhite women were significantly (P < 0.0001) more likely than white women to have serum retinol <1.05 micromol/L after covariates were controlled for.

CONCLUSIONS

Clinically low serum retinol concentration is uncommon in US residents aged > or = 4 y, although racial/ethnic and socioeconomic differences in serum retinol concentration still exist.

Beverage choices affect adequacy of children's nutrient intakes

OBJECTIVE

To assess the relationship between beverage choices and the adequacy of nutrient intakes among children and adolescents.

DESIGN

Beverages reported in 24-hour recall records were classified as milk, 100% juice, fruit-flavored drinks, or carbonated sodas. Recommended intakes were based on Recommended Dietary Allowances or Dietary Reference Intakes.

PARTICIPANTS

Four thousand seventy children aged 2 to 5, 6 to 11, and 12 to 17 years participating in the 1994-96 Continuing Survey of Food Intakes by Individuals.

STATISTICAL ANALYSIS

The likelihood of achieving recommended intakes of selected nutrients on the day of recall was assessed with multiple logistic regression including ounces of milk, juice, fruit-flavored drinks, and carbonated sodas in the model while controlling for sex, age in years, race/ethnic group, household income, and total energy intake.

RESULTS

Milk consumption was positively (P<.0001) associated with the likelihood of achieving recommended vitamin A, folate, vitamin B(12), calcium, and magnesium intakes in all age strata. Juice consumption was positively (P< or =. 001) associated with achieving recommended vitamin C and folate intakes in all age strata and magnesium intakes among children aged 6 years and older. Carbonated soda consumption was negatively (P< or =. 01) associated with achieving vitamin A intake in all age strata, calcium in children younger than 12 years, and magnesium in children aged 6 years and older.

CONCLUSION

Beverage choice can have a significant effect on the nutrient adequacy of the diets of children and adolescents.

A rapid food screener to assess fat and fruit and vegetable intake

BACKGROUND

The U.S. Preventive Services Task Force recommends that Americans lower dietary fat and cholesterol intake and increase fiber and fruit/vegetables to reduce prevalence of heart disease, cancer, stroke, hypertension, obesity, and non-insulin-dependent diabetes mellitus in the United States. To provide preventive services to all, a rapid, inexpensive, and valid method of assessing dietary intake is needed.

METHODS

We used a one-page food intake screener based on national nutrition data. Respondents can complete and score the screener in a few minutes and can receive immediate, brief feedback. Two hundred adults self-administered the food screener. We compared fat, fiber, and fruit/vegetable intake estimates derived from the screener with estimates from a full-length, 100-item validated questionnaire.

RESULTS

The screener was effective in identifying persons with high-fat intake, or low-fruit/vegetable intake. We found correlations of 0.6-0.7 (p<0. 0001) for total fat, saturated fat, cholesterol, and fruit/vegetable intake. The screener could identify persons with high percentages of calories from fat, total fat, saturated fat, or cholesterol, and persons with low intakes of vitamin C, fiber, or potassium.

CONCLUSIONS

This screener is a useful tool for quickly monitoring patients' diets. The health care provider can use it as a prelude to brief counseling or as the first stage of triage. Persons who score poorly can be referred for more extensive evaluation by low-cost paper-and-pencil methods. Those who still have poor scores at the second stage ultimately can be referred for in-person counseling.

A controlled trial of exercise training in older coronary patients

BACKGROUND

This study compared the effects of a formal exercise conditioning program of 3 and 12 months duration to spontaneous recovery in a population of older, post-coronary event patients.

METHODS

Indices of peak exercise and submaximal exercise performance such as oxygen consumption, treadmill work capacity, minute ventilation, heart rate, and systolic blood pressure were assessed before and after conditioning in 60 post-myocardial infarction and post-coronary bypass surgery patients (mean age 68 +/- 5 years) and compared to measures of fitness in a usual care control group (n = 23, mean age 68 +/- 5 years).

RESULTS

Maximal treadmill work capacity increased by 47% in the intervention group at 3 months compared to no improvement in the usual care control group. However, both groups increased peak oxygen consumption similarly at 3 and 12 months, increasing by 16% and 20% in the intervention group at 3 and 12 months and by 7% and 14% in the control group (p = n.s.). Only the exercise training group manifested submaximal indices of conditioning such as a lower heart rate and minute ventilation at a standard workload.

CONCLUSION

While spontaneous improvements in peak oxygen consumption are seen in older coronary patients in the months following a coronary event, a formal exercise training program results in significantly greater increases in peak exercise capacity and in peak and submaximal exercise efficiency.