Frustrated classical Heisenberg and XY models in two dimensions with nearest-neighbor biquadratic exchange: exact solution for the ground-state phase diagram.

The ground-state phase diagram is determined exactly for the frustrated classical Heisenberg model plus nearest-neighbor biquadratic exchange interactions on a two-dimensional lattice. A square- and a rhombic-symmetry version are considered. There appear ferromagnetic, incommensurate-spiral, "up-up-down-down" (UUDD), and canted ferromagnetic states, a nonspiral coplanar state that is an ordered vortex lattice, plus a noncoplanar ordered state (a "conical vortex lattice"). In the rhombic case, which adds biquadratic terms to the Heisenberg model used widely for insulating manganites, the UUDD state found is the E-type state observed; this, along with accounting essentially for the variety of ground states observed in these materials, shows that this model probably contains the long-sought mechanism behind the UUDD state.

Thermally or magnetically induced polarization reversal in the Multiferroic CoCr2O4.

We report the unexpected evolution, with thermal and magnetic-field (H) variations, of the interrelation between the polarization P, magnetization M, and spiral wave vector Q in CoCr2O4, which has a ferrimagnetic conical-spiral magnetic order. For example, P suddenly jumps and changes its sign at the magnetic lock-in transition (T_{L}) with thermal variation, or with isothermal variation of H (without changing its direction) at T_{L}, which surprisingly occurs without change in spiral handedness (i.e., the sign of Q). The presence of multiple spiral sublattices may be behind this unusual behavior.

Non-Stoner continuum in the double exchange model.

Exact diagonalization studies of the double exchange model indicate the existence of continuum states in the single-spin-flip channel that overlap the magnons at very low energies (approximately 10(-2) eV) and extend to high energies (approximately eV). This picture differs dramatically from the prevalent view, where there are the magnons, plus the Stoner continuum at the high-energy scale, with nothing in between. The relevance of these new continuum states to inelastic neutron scattering and optical properties is discussed.

Physical and psychological changes with vigorous exercise in sedentary primigravidae.

PURPOSE: The present study examined the effects of exercise on physical and psychological variables in sedentary primigravidae (PRA). METHODS: A total of nine women randomly assigned to an exercise (E) (mean age = 31.3 +/- 3.1 yr) and six subjects randomly assigned to a control (C) group (mean age = 27.8 +/- 3.1 yr) fulfilled all requirements for the study. Exercise included a variety of exercise activities performed to a target heart rate of 150-156 beats x min(-1), three times per week for 15 wk. RESULTS: Results showed no significant differences between E and C groups in physical characteristics initially. A repeated measures ANOVA showed a significant group effect (P < 0.05) and a significant group by time interaction (P = 0.001) with the E group showing a significantly longer amount of time on the PWC150 test than the C group. There was no significant group, time, or group by time interaction for lactate accumulation. This occurred, despite the fact that the E group spent 56% longer on the PWC150 test and the C group spent 30% less time on the same test at the conclusion of the study. Finally, the E group in comparison to the C group showed more favorable improvements in several items related to health and well-being on the Body Cathexis Scale. There were no significant differences between E and C groups in any pregnancy outcome measures. All babies were delivered healthy at term. CONCLUSIONS: These data suggest that a vigorous exercise program can lead to significant improvements in aerobic fitness at similar lactate concentrations compared to a control group and can be well tolerated by low risk sedentary PRA without any deleterious effects occurring to herself or unborn child.

Fitness, diet and coronary risk factors in a sample of southeastern U.S. children.

The purpose of this study was to evaluate the relationship between physical fitness variables and nutrient intake to coronary risk factors (CRF) in a sample of children living in the Southeastern U.S. A total of 22 sixth-grade children of whom 10 were boys (mean age = 11.83 +/- 0.3) and 12 were girls (mean age 11.7 +/- 0.3) volunteered for this study. Results indicated that boys in comparison to girls weighed more (54.0 +/- 10.8 kg versus 42.1 +/- 8.0 kg; p < 0.05), had a higher body mass index (BMI) (23.6 +/- 2.7 versus 20.2 +/- 3.3; p < 0.05), a higher lean body mass (37.8 +/- 6.0 kg versus 30.7 +/- 3.8 kg; p < 0.01), and a higher systolic blood pressure (115.7 +/- 11.1 versus 106.4 +/- 8.1; p < .0001). There were, however, no significant gender differences in serum lipoproteins or nutrient intake. Stepwise multiple regression analyses indicated that physical fitness variables which included VO2max, one-mile run for time, grip strength, and leg strength could significantly predict resting diastolic blood pressure (DBP) (F = 3.06; p < 0.05) and percent body fat (F = 4.98; p < 0.01) in children. Analysis of food intake revealed that total and saturated fat, and carbohydrate intake could predict serum triglycerides (TG) (F = 5.18; p = 0.01) while total kilocalorie, fat, and carbohydrate intake could significantly predict percent body fat (F = 3.42; p < 0.03). These findings may be clinically relevant since both serum triglyceride levels and percent body fat were well above the 50th percentile according to U.S. norms. In summary, the present study showed that measurements of muscular strength in addition to aerobic fitness are associated with DBP and percent body fat in children. Furthermore, it is recommended that nutrient intake be used when evaluating CRF in children due to its ability to predict TG and percent body fat.

Lack of effect of delta F508 mutation on aerobic capacity in patients with cystic fibrosis.

OBJECTIVE: As aerobic exercise capacity, as defined by VO2max, is associated with patient functioning and possibly prognosis in cystic fibrosis (CF), correlations between VO2max phenotype and genotype may be of value. DESIGN: Retrospective clinical series. SETTING: Cystic fibrosis referral clinic. PATIENTS: Convenience sample of 35 patients with CF consecutively referred for exercise testing. MAIN OUTCOME MEASURES: Blood samples were examined for mutations of cystic fibrosis transmembrane regulator (CFTR), Height, wight, pulmonary function, resting-energy expenditure, VO2max, and other exercise variables were assessed in each referred patient. RESULTS: Statistical comparison of 10 patients who were homozygous for the dF508 mutation of CFTR with 20 patients heterozygous for dF508 revealed no significant differences for height, weight, pulmonary function, resting-energy expenditure, VO2max, or any other exercise variables. CONCLUSIONS: These results imply a limited effect of the mutation status on overall patient functioning and prognosis. Future identification of more rare CFTR mutations and other genes and subsequent classification of patients in a manner reflective of the cellular physiology may lead to different results.

Effect of obesity on injury risk in high school football players.

Little is known about the relative injury risk of obese adolescent football players. Two high school varsity teams were followed prospectively for injuries after measurement of height, weight, and triceps and subscapular skinfolds during the preseason. Certified athletic trainers who were present at all practices recorded all injuries that required a player to miss at least one practice or game. In all, 98 players were enrolled in the study. Twenty-eight injuries were documented in 24 different players. There were 27 (28%) players with the sum of skinfolds > or = 95th percentile for age; eight of them had nine injuries. The overall prevalence of injuries per player per season was 0.28 for players < or = 95th percentile and 0.33 for players above this percentile (not significant). High body mass (body weight > 90 kg) was associated with a 2.5 times higher relative risk of injury. While this study did not find evidence for an overall higher injury rate in overly fat high school football players, an alarmingly high incidence of obesity was found in this athletic population.

Exercise-induced bronchospasm in nonasthmatic obese children.

The frequency, degree, and pattern of bronchial reactivity to exercise were compared in 13 obese and 14 control children, ages 6 to 10 years, with no history of asthma. Spirometry was performed before and every three minutes after a seven-minute exercise challenge on a treadmill. There were 11 obese children and 6 controls who had at least a 15% fall in at least one of three monitored pulmonary function parameters (P < .05). The group mean percentage falls in FEV1 and FEF25%-75% were significantly greater in the obese group than in the controls. The pattern of bronchospasm, occurring soon after the exercise challenge, is consistent with that found in the known asthmatic population. A significant correlation was found between triceps skin-fold thickness and degree of fall in FEF25%-75% (r = .55, P < .005). This study demonstrated that significantly greater frequency and degree of bronchospasm of the smaller airways occur in obese children, partially related to the amount of subcutaneous fat. Whether exercise-induced bronchospasm leads to exercise avoidance and obesity or whether obesity causes or enhances bronchial hyperreactivity to exercise requires further study.

Effects of acute inhalation of the bronchodilator, albuterol, on power output.

This study was designed to examine the effects of acute inhalation of the bronchodilator, albuterol (Proventil, Schering Corp.), on high intensity power output. Fifteen healthy nonasthmatic subjects (eight male, seven female, 18-33 yr) performed four supramaximal 15-s rides on a bicycle ergometer. Rides were arranged in pairs with a 10-min rest interval. Each pair of rides was preceded by a 5-min warm-up. Sessions were separated by a minimum of 48 h. The study design was fully randomized and double blind. Ten minutes prior to each pair of rides subjects inhaled two metered doses (180 micrograms) of albuterol (A) or a placebo (P). Individual ANOVAs revealed a significant difference between the A and P treatment for peak power (A = 886.6 W, P = 858.3 W) and fatigue (A = 27.2%, P = 24.4%). Mean changes in FEF25-75% (A = 0.712, P = 0.040 l.s-1), FEV1.0 (A = 0.188, P = 0.007 l), and PEF (A = 0.573, P = -0.155 l.s-1) were also statistically significant; however, these changes did not correlate to the anaerobic performance changes. No significant differences were found between treatments for heart rate increases resulting from the power test (A = 56.73 bpm, P = 53.20 bpm). These results indicate an ergogenic effect of the bronchodilator on short-term power output independent of impact on respiratory smooth muscle, with no effect on cardiac response.

Obesity in a high school football candidate: a case presentation.

A 14-yr-old male presented for medical clearance to play fall football for his high school team. He had stayed out of the prior spring football practice sessions after a shoulder injury on the first day of practice, but indicated no other positive responses to the standard medical questionnaire. He was severely overweight with height of 180 cm, weight 133.4 kg, and his estimated body fat was 36%. His examination was otherwise not revealing. He demonstrated poor aerobic fitness, exercise-induced bronchospasm, residual left shoulder weakness, and a dyslipoproteinemia on further medical evaluation. He was disqualified on an empirical basis, the attending physician making the clinical decision that it would be of greater harm than good for this adolescent to participate. However, there is little data and no established guidelines for this type of situation. The overweight football athlete is a challenge to the sports medicine team, both in managing the condition and in determining athletic eligibility.

Impact of CF summer camp.

In two consecutive years, patients with cystic fibrosis were studied at the beginning and end of a nine-day summer camp program to assess the program's effects on weight gain and pulmonary function. The camp experience includes daily exercise and a high-protein and high-fat diet. There were a total of 58 children between 6 and 12 years of age (42 different patients) and 10 adult counselors from 19 to 30 years of age (eight different patients). On the first and eighth days patients were weighed, sputum cultures were collected, and spirometry was performed. In year 2, peak expiratory flow rate was monitored daily. Also in year 2, campers and counselors with CF were prescreened by sputum culture and excluded from camp if they had Pseudomonas cepacia in their sputum. Only one candidate screened was positive before camp. In year 1, no significant group changes in pulmonary function were identified. In year 2, significant increases on post-camp testing were found for FEF 25%-75% and PEF. Mean body weight for all patients increased significantly, by 0.4 kg in year 1 and 0.9 kg in year 2 (p less than .05). In year 1, a total of nine patients acquired a new organism in their follow-up sputum culture, including five who acquired a new Pseudomonas species. There was no intra-cabin pattern of spread. Four patients were positive for P. cepacia on day 1 culture. No new subjects acquired this organism on follow-up examination. In year 2, only one subject had P. cepacia on the first camp collection; he alone was positive on day 9.(ABSTRACT TRUNCATED AT 250 WORDS)

Use of exercise in the management of cystic fibrosis: short communication about a survey of cystic fibrosis referral centers.

A survey of 47 cystic fibrosis referral centers was conducted to study the use of exercise in the management of patients with cystic fibrosis (CF). A questionnaire with 5 brief questions concerning the prescription and application of exercise therapy was sent to the first 47 centers (38.5%) listed in the 1988 CF Foundation Directory, and 46 (97.9%) were returned. While all but one of the respondents recommend exercise at least to selected patients, and while 80.4% of the centers refer patients to summer camp programs, only 43.5% offer exercise stress testing and only 21.7% offer an exercise program for their patients. Most of the respondents who recommend exercise prescribe aerobic exercise, swimming being the most frequently chosen type. Although there is a large discrepancy between those centers that acknowledge the benefits of exercise and those that have arranged for regularly available exercise services, inroads have been made in utilizing this therapeutic tool for patients with CF.