Unrecognized volatile and semi-volatile organic compounds from brake wear.

Motor vehicles are among the major sources of pollutants and greenhouse gases in urban areas and a transition to "zero emission vehicles" is underway worldwide. However, emissions associated with brake and tire wear will remain. We show here that previously unrecognized volatile and semi-volatile organic compounds, which have a similarity to biomass burning emissions are emitted during braking. These include greenhouse gases or, these classified as Hazardous Air Pollutants, as well as nitrogen-containing organics, nitrogen oxides and ammonia. The distribution and reactivity of these gaseous emissions are such that they can react in air to form ozone and other secondary pollutants with adverse health and climate consequences. Some of the compounds may prove to be unique markers of brake emissions. At higher temperatures, nucleation and growth of nanoparticles is also observed. Regions with high traffic, which are often disadvantaged communities, as well as commuters can be impacted by these emissions even after combustion-powered vehicles are phased out.

Effects of a hip belt on transverse plane trunk coordination and stability during load carriage.

This study examined the transverse plane kinematics of the pelvis, thorax and head while participants walked at a range of speeds on a treadmill under three load conditions: no load, with a loaded backpack with no hip belt and with a loaded backpack with a hip belt. Research has suggested that one mechanism for adapting to heavy loads carried with no hip belt is to reduce the amplitudes and relative phase of transverse plane pelvic and thoracic rotations, in order to minimize rotational torque on the loaded upper body. Transverse plane rotation amplitudes of the pelvis, thorax, backpack and head were calculated from 3D kinematic data for 12 healthy subjects, walking at speeds of 0.5, 0.9, 1.3 and 1.7 ms(-1). Relative phase relation and its variability were also computed for pelvis-thorax rotations and backpack-thorax rotations. Stability of the coordination pattern was estimated as an inverse function of the variability in relative phase. The backpack with the hip belt allowed significantly larger transverse plane rotation amplitudes, along with increased stability of the coordination pattern, than the backpack with no hip belt. Motion patterns of the backpack and thorax suggested that the backpack frame was used to assist with the deceleration and reversal of the loaded thorax, driven by the pelvis through the hip belt connection. Use of the frame in this way may have required less trunk muscle activation and allowed for improved pattern stability.

A high-resolution time-depth view of dimethylsulphide cycling in the surface sea.

Emission of the trace gas dimethylsulphide (DMS) from the ocean influences the chemical and optical properties of the atmosphere, and the olfactory landscape for foraging marine birds, turtles and mammals. DMS concentration has been seen to vary across seasons and latitudes with plankton taxonomy and activity, and following the seascape of ocean's physics. However, whether and how does it vary at the time scales of meteorology and day-night cycles is largely unknown. Here we used high-resolution measurements over time and depth within coherent water patches in the open sea to show that DMS concentration responded rapidly but resiliently to mesoscale meteorological perturbation. Further, it varied over diel cycles in conjunction with rhythmic photobiological indicators in phytoplankton. Combining data and modelling, we show that sunlight switches and tunes the balance between net biological production and abiotic losses. This is an outstanding example of how biological diel rhythms affect biogeochemical processes.

Effect of high-fat and low-fat diets on voluntary energy intake and substrate oxidation: studies in identical twins consuming diets matched for energy density, fiber, and palatability.

There remains controversy over the effects of dietary fat content on voluntary energy intake. Additionally, the question of whether there is a genetic susceptibility to overeating high-fat diets has not been resolved. To address these issues, we designed two diets: a low-fat diet providing approximately 20% of energy as fat and a high-fat diet with approximately 40% of energy as fat. The diets were matched for energy density, fiber, and palatability. In a two-phase, 18-d intervention study, voluntary energy intakes and macronutrient oxidation rates during the fasting and fed states were determined in seven pairs of identical male twins. In contrast with results of previous intervention studies, in which low-fat and high-fat diets were not matched for energy density and other associated variables, we observed no significant difference in voluntary energy intake between the low-fat and high-fat phases, and mean daily intakes were similar (10.3 and 10.7 MJ/d, respectively). Postprandial rates of fat oxidation tended to reflect fat intakes in the two dietary phases, thus helping to explain the lack of a difference in mean energy intakes. There was also a significant twin-pair similarity in differences in energy intakes between dietary phases (P = 0.013). These results suggest that dietary fat content does not have a major influence on voluntary energy intake when dietary variables usually associated with fat are controlled for and that there may be a familial influence on the effects of dietary fat content on energy intake.

Fat oxidation in response to four graded energy challenges in younger and older women.

We examined whether older individuals have an impairment in their ability to oxidize dietary fat, a factor that could help to explain age-associated weight gain. The subjects were 16 healthy younger and older women. Fat oxidation was determined by indirect calorimetry before and after consumption of four different test meals consumed > or = 5 d apart. The intervention meals contained 0, 1046, 2092, or 4184 kJ (simulating extended fasting, and consumption of a snack, a small meal, and a moderately large meal, respectively), with 35% of energy from fat. The duration of each measurement was the amount of time required for postprandial energy expenditure to return to the premeal fasting value. A total of 96 measurements were obtained, including duplicates for all meal sizes in the younger women (in the follicular and luteal phases of the menstrual cycle). Total postprandial fat oxidation increased in proportion to meal size in the younger subjects, but did not increase above that for the 2092-kJ meal in the older women. In addition, older subjects had significantly lower total fat oxidation after consumption of the 4184-kJ meal (781 compared with 1029 kJ/measurement, P < 0.02) and also significantly greater fat deposition (745 compared with 464 kJ/measurement, P < 0.02). These findings suggest that, relative to younger women, older women have a reduced ability to oxidize dietary fat when they consume large meals.

Dietary energy requirements of young and older women determined by using the doubly labeled water method.

There is little information on the effects of age on energy requirements in women. This issue was investigated in a cross-sectional study of 10 normal-weight young women aged 25.2 +/- 1.1 y (mean +/- SEM) and 10 normal-weight older women aged 74.0 +/- 1.4 y. In a 9-d study, measurements were made of free-living total energy expenditure (TEE) by using the doubly labeled water technique, body composition by using hydrodensitometry, and resting energy expenditure (REE) by using indirect calorimetry. Mean values for reported levels of strenuous activity were within the expected range in both groups (31 +/- 13 min/d in the young group and 7 +/- 2 min/d in the older group). Energy requirements expressed as the ratio of TEE to REE were 1.80 +/- 0.10 and 1.62 +/- 0.06 (P < 0.01) in the young and older group, respectively. When values for REE predicted from body weight (pREE) were used, as suggested in the current recommended dietary allowances (RDAs), the ratios of TEE to pREE in the two groups were 1.85 +/- 0.10 and 1.54 +/- 0.04 (P < 0.05). The RDAs significantly under-predicted the energy requirements of the young group (P < 0.05), but there was no significant underprediction in the older group. Although obtained in a relatively small number of subjects, these results provide no evidence to indicate that the current RDAs underestimate the energy requirements of older women, in contrast with previous observations of an underestimation of energy requirements by the RDAs in older men.

Effects of a hydrogenated form of vitamin K on bone formation and resorption.

BACKGROUND: Hydrogenation of vegetable oils affects blood lipid and lipoprotein concentrations. However, little is known about the effects of hydrogenation on other components, such as vitamin K. Low phylloquinone (vitamin K1) intake is a potential risk factor for bone fracture, although the mechanisms of this are unknown. OBJECTIVE: The objective was to compare the biological effects of phylloquinone and its hydrogenated form, dihydrophylloquinone, on vitamin K status and markers of bone formation and resorption. DESIGN: In a randomized crossover study in a metabolic unit, 15 young adults were fed a phylloquinone-restricted diet (10 microg/d) for 15 d followed by 10 d of repletion (200 microg/d) with either phylloquinone or dihydrophylloquinone. RESULTS: There was an increase and subsequent decrease in measures of bone formation (P = 0.002) and resorption (P = 0.08) after dietary phylloquinone restriction and repletion, respectively. In comparison with phylloquinone, dihydrophylloquinone was less absorbed and had no measurable biological effect on measures of bone formation and resorption. CONCLUSION: Hydrogenation of plant oils appears to decrease the absorption and biological effect of vitamin K in bone.

Evaluation of four methods for determining energy intake in young and older women: comparison with doubly labeled water measurements of total energy expenditure.

The accuracy and precision of four different food intake assessment methods were evaluated in young and older women by comparing reported energy intakes with doubly labeled water measurements total energy expenditure (TEE). A study lasting 8 d was conducted in 10 young women aged 25.2+/-1.1 y (-x+/-SEM) and in 10 older women aged 74.0+/-1.4 y. Free-living TEE was measured over 7 d and food consumption was determined from weighed food intake data (7 d), a 24-h food recall (in duplicate), and two different food-frequency questionnaires [Fred Hutchinson Cancer Research Center (FHCRC)/Block and Willett, both in duplicate]. In addition, body composition was determined by using hydrodensitometry, and strenuous physical activity and the extent of dietary restraint were determined by questionnaire. In young women, 24-h recall gave mean energy intakes that were closest to measures of TEE (-0.34+/-3.71 MJ/d compared with TEE, P=0.178), and energy intakes by food-frequency questionnaires were the only intake data that correlated significantly with individual values for TEE (P<0.05). In older women, food-frequency questionnaires gave mean energy intakes that were closest to measured TEE (+0.53+/-2.95 MJ/d with the Willett questionnaire and -1.19+/-3.02 MJ/d with FHCRC/Block questionnaire). No energy intake data from this group correlated significantly with values for TEE. The 7-d weighed dietary intakes were significantly lower than measured TEE in both young and older women (-2.0 MJ/d in young and older women combined, P<0.001), and did not correlate significantly with values for TEE, although they did most closely mirror the mean difference in TEE between the young and older women (2.30 MJ/d for TEE and 2.11 MJ/d for 7-d weighed intake). These data suggest that none of the methods studied gave accurate estimates of the usual energy requirements of individual subjects. In addition, the results suggest that for some types of studies, simple methods for assessing group mean dietary intake may actually give more accurate information than weighed dietary intakes.

Dietary vitamin K1 and stability of oral anticoagulation: proposal of a diet with constant vitamin K1 content.

Case reports cited in Medline or Biological Abstracts (1966-1996) were reviewed to evaluate the impact of vitamin K1 dietary intake on the stability of anticoagulant control in patients using coumarin derivatives. Reported nutrient-drug interactions cannot always be explained by the vitamin K1 content of the food items. However, metabolic data indicate that a consistent dietary intake of vitamin K is important to attain a daily equilibrium in vitamin K status. We report a diet that provides a stable intake of vitamin K1 equivalent to the current U.S. Recommended Dietary Allowance, using food composition data derived from high-performance liquid chromatography. Inconsistencies in the published literature indicate that prospective clinical studies should be undertaken to clarify the putative dietary vitamin K1-coumarin interaction. The dietary guidelines reported here may be used in such studies.

The role of energy expenditure in energy regulation: findings from a decade of research.

The role of energy expenditure in energy regulation remains a subject of continuing controversy. New data have emerged from studies conducted over the last decade demonstrating that energy expenditure is a critical factor contributing to successful energy regulation in normal individuals, as well as to the disregulation of energy balance that characterizes obesity. Reduced energy expenditure appears to facilitate weight gain in individuals susceptible to obesity and also appears to reduce the extent of body energy loss during undereating in both lean and obese individuals. The magnitude of the reduction in energy expenditure during, and perhaps after, weight loss is greater than expected on the basis of the reduction in body weight and appears to occur in response to undefined underlying determinants of energy regulation. In addition, exercise intervention studies and cross-sectional investigations of the relationship between energy expenditure for physical activity and body composition demonstrate an apparent equilibration between physical activity and body fat content. This equilibration is suggestive of a direct influence of physical activity on the underlying metabolic determinants of energy balance.

Dietary fiber and weight regulation.

The influence of dietary fiber on energy regulation remains controversial. This review summarizes published studies on the effects of dietary fiber on hunger, satiety, energy intake, and body composition in healthy individuals. Under conditions of fixed energy intake, the majority of studies indicate that an increase in either soluble or insoluble fiber intake increases postmeal satiety and decreases subsequent hunger. When energy intake is ad libitum, mean values for published studies indicate that consumption of an additional 14 g/day fiber for >2 days is associated with a 10% decrease in energy intake and body weight loss of 1.9 kg over 3.8 months. Furthermore, obese individuals may exhibit a greater suppression of energy intake and body weight loss (mean energy intake in all studies was reduced to 82% by higher fiber intake in overweight/obese people versus 94% in lean people; body weight loss was 2.4 kg versus 0.8 kg). These amounts are very similar to the mean changes in energy intake and body weight changes observed when dietary fat content is lowered from 38% to 24% of energy intake in controlled studies of nonobese and obese subjects. The observed changes in energy intake and body weight occur both when the fiber is from naturally high-fiber foods and when it is from a fiber supplement. In view of the fact that mean dietary fiber intake in the United States is currently only 15 g/day (i.e., approximately half the American Heart Association recommendation of 25-30 g/day), efforts to increase dietary fiber in individuals consuming <25 g/day may help to decrease the currently high national prevalence of obesity.

The effects of age on postprandial thermogenesis at four graded energetic challenges: findings in young and older women.

There remains controversy over the effect of age on postprandial thermogenesis, with some studies observing decreased postprandial thermogenesis in older subjects and other studies finding no effect of age. We investigated this issue in 8 young (25.2+/-1.8 years) and 8 older (72.2+/-2.1 years) healthy glucose-tolerant women with normal thyroid hormone status. Repeated measures of the thermic effect of feeding (TEF) were obtained following consumption of test meals containing 0, 1046, 2092, and 4184 kilojoules (kJ) by using indirect calorimetry. TEF at each meal size was determined once in the older subjects and twice in the younger subjects (during follicular and luteal phases of the menstrual cycle) for a total of 96 measurements. There was a positive dose-response between meal size and TEF (p < .001) that was not significantly affected by age group. The best single predictor of TEF expressed as a percentage of meal energy content was waist-to-hip ratio (R2=67.416, p < .02). These results indicate that aging is not associated with decreased TEF in the absence of factors such as a hypothyroid state or glucose intolerance.

Effects of a 6-week hypocaloric diet on changes in body composition, hunger, and subsequent weight regain in healthy young and older adults.

Recent studies have suggested a short-term impairment in the regulation of food intake in older adults, but further studies are needed to determine if a longer-term impairment exists and to identify underlying causes. Changes in body weight and composition were measured over a 6-week underfeeding study and a 6-month follow-up period in healthy young (n = 23) and older (OLD, n = 18) men and women. The young adults were either normal weight (YNW, n = 12) or overweight (YOW, n = 11). Energy intakes during underfeeding were 896 +/- 18 (SEM) kcal less than weight-maintenance energy requirements determined prior to underfeeding. In addition, changes in perceived hunger during underfeeding were monitored in a subgroup (n = 19). OLD and YOW subjects lost significantly more weight during underfeeding than did YNW subjects (p = .025 and .000, respectively), and they did not gain back significant weight in the 6-month follow-up. In addition, OLD subjects reported a significantly lower frequency of hunger during underfeeding (p = .05). There was no significant difference among groups in the relationship between weight lost and fat-free mass lost. Healthy OLD adults have an impaired ability to regulate food intake over at least 6 months following underfeeding compared with YNW adults, and a reduction in their perceived frequency of hunger may be a contributing factor.

Blood glucose and hormonal responses to small and large meals in healthy young and older women.

Blood glucose regulation in the fasting and fed states has important implications for health. In addition, the ability to maintain normal blood glucose homeostasis may be an important determinant of an individual's capacity to regulate food intake. We tested the hypothesis that aging is associated with an impairment in the ability to maintain normal blood glucose homeostasis following the consumption of large meals but not small ones, a factor that could help to explain age-related impairments in the control of food intake and energy regulation. The subjects were eight healthy younger women (25 +/- 2 years, SD) and eight healthy older women (72 +/- 2 years) with normal body weight and glucose tolerance. Following a 36-h period when diet and physical activity were controlled, subjects consumed test meals containing 0, 1046, 2092, and 4184 kJ (simulating extended fasting, and consumption of a snack, a small meal, and a moderately large meal), with 35% of energy from fat, 48% from carbohydrate, and 17% from protein. Each subject consumed each of the test meals on a separate occasion. Serial blood samples were collected at baseline and during 5 h after consumption of the meals. Measurements were made of circulating glucose, insulin, glucagon, free fatty acids, and triglycerides. There was no significant difference between young and older women in their hormone and metabolite responses to fasting and consumption of the 1046-kJ meal. However, following consumption of 2092 and 4148 kJ, older individuals showed exaggerated responses and a delayed return to premeal values for glucose (p = .023), insulin (p = .010), triglycerides (p = .023), and the ratio of insulin to glucagon (p = .026). In conclusion, these results suggest an impairment in the hormonal and metabolite responses to large meals in older women.

Head and neck cancer in the elderly.

One hundred fifty-nine patients, 80 years of age or older, with cancer of the head and neck were reviewed. Patients tolerated head and neck resection well and an absolute survival of 36 months for all treated patients and 41 months for all surgically treated patients suggests the efforts are worthwhile. Treatment offered the elimination of uncontrolled cancer in 68% of the patients. Prompt and adequate treatment reduces time, effort, cost, and the actual suffering of the patients. There is little justification for therapeutic nihilism even in the elderly patient.

Steady-state and perturbed rhythmical movements: a dynamical analysis.

This study examined rhythmic finger movements in the steady state and when momentarily perturbed in order to derive their qualitative dynamical properties. Movement frequency, amplitude, and peak velocity were stable under perturbation, signaling the presence of an attractor, and the topological dimensionality of that attractor was approximately equal to one. The strength of the attractor was constant with increasing movement frequency, and the Fourier spectra of the steady-state trials showed an alternating harmonic pattern. These results are consistent with a previously derived nonlinear oscillator model. However, the oscillation was phase advanced by perturbation overall, and a consistent phase-dependent, phase-shift pattern occurred, which is inconsistent with the model. The overall phase advance also shows that any central pattern generator responsible for generating the rhythm must be nontrivially modulated by the limb being controlled.

Space-time behavior of single and bimanual rhythmical movements: data and limit cycle model.

How do space and time relate in rhythmical tasks that require the limbs to move singly or together in various modes of coordination? And what kind of minimal theoretical model could account for the observed data? Earlier findings for human cyclical movements were consistent with a nonlinear, limit cycle oscillator model (Kelso, Holt, Rubin, & Kugler, 1981) although no detailed modeling was performed at that time. In the present study, kinematic data were sampled at 200 samples/second, and a detailed analysis of movement amplitude, frequency, peak velocity, and relative phase (for the bimanual modes, in phase and antiphase) was performed. As frequency was scaled from 1 to 6 Hz (in steps of 1 Hz) using a pacing metronome, amplitude dropped inversely and peak velocity increased. Within a frequency condition, the movement's amplitude scaled directly with its peak velocity. These diverse kinematic behaviors were modeled explicitly in terms of low-dimensional (nonlinear) dissipative dynamics, with linear stiffness as the only control parameter. Data and model are shown to compare favorably. The abstract, dynamical model offers a unified treatment of a number of fundamental aspects of movement coordination and control.

Soluble fiber and energy regulation. Current knowledge and future directions.

Soluble dietary fiber is a potentially important factor determining our ability to maintain a stable energy balance and avoid obesity. However, clinical metabolic investigations have given conflicting results on the effects of soluble fiber on energy regulation, perhaps for the reasons that a) other dietary components that affect energy regulation have not always be controlled adequately and b) in the past it has been hard to ensure that subjects are consistently compliant with the dietary requirements of soluble fiber protocols. The recent development of techniques for assessing dietary compliance in metabolic studies, combined with increased control of non-fiber dietary variables that influence energy intake, should help ensure more consistent findings in future investigations.

Skill acquisition and development: the roles of state-, parameter, and graph dynamics.

The development of motor skills can be portrayed as a dynamical process that involves three types of dynamics: state dynamics, parameter dynamics, and graph dynamics. The time scales associated with each type of dynamics are discussed, and an outline is provided of the role played by each type in the developing organism. In particular, the role of parameter dynamics and graph dynamics in producing qualitative, bifurcational changes in behavior is described. It is concluded that all three types of dynamics are required for a complete description of skill acquisition and development.

A dynamical model of locomotion in spastic hemiplegic cerebral palsy: influence of walking speed.

OBJECTIVE: The objective of this study was to assess the capability of an escapement-driven inverted pendulum with springs and damping model to estimate the effects of impairments (e.g. spasticity, muscle weakness) on the dynamics and patterns of locomotion of children with spastic cerebral palsy. METHODS: Kinematic data of six children with spastic hemiplegic cerebral palsy and six matched, typically developing children were collected at five different self-selected overground walking speeds ('very slow' to 'very fast'). Changes in forcing, stiffness and gravitational potentials were estimated during the stance phase of each leg according to the model's equation of motion. RESULTS: Significantly greater stiffness and decreased forcing was observed in the more affected limbs of children with spastic hemiplegic cerebral palsy and compared to typically developing peers. The forcing term of the non-affected limb was greater than that of the matched typically developing children. CONCLUSIONS: Results support the claim that disabled individuals with losses in dynamic resources (stiffness, muscle forcing capability) exploit and develop the remaining resources in their adapted gait patterns. It was suggested that clinical interventions aimed at normalizing a gait pattern may be contraindicated, and that rehabilitation might be more effective if focused at the level of dynamics. RELEVANCE: Pattern formation is seen as an optimal solution based on the individuals' action capabilities and dynamic properties under environmental and task demands. This perspective could lead to the development of interventions that address these dynamic variables with the objective of improving the functional capabilities of children with cerebral palsy.