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PubMed1982

Mechanism of active transport: free energy dissipation and free energy transduction.

The thermodynamic pathway for "chemiosmotic" free energy transduction in active transport is discussed with an ATP-driven Ca2+ pump as an illustrative example. Two innovations are made in the analysis. (i) Free energy dissipated as heat is rigorously excluded from overall free energy bookkeeping by focusing on the dynamic equilibrium state of the chemiosmotic process. (ii) Separate chemical potential terms for free energy donor and transported ions are used to keep track of the thermodynamic state of each substrate through the reaction cycle. These procedures clarify the mechanism of free energy transduction, even without step-by-step analysis. The results show that free energy exchange must occur in its entirety among protein-bound species. Imposition of conditions for an adequate rate of physiological function further indicates (i) that the standard free energy of hydrolysis of protein-bound ATP (to yield protein-bound products) needs to differ substantially from the standard free energy of hydrolysis in solution and (ii) that binding sites for the transported ions must have different affinities when facing opposite sides of the membrane. The results also demonstrate that step-by-step "basic" free energy changes (often used in the form of free energy level diagrams) are inherently unsuited for analysis of the mechanism of free energy transduction.

Adenosine Triphosphate↗
PubMed1998

Photon energy recovery: a method to improve the effective energy resolution of gamma cameras.

UNLABELLED: One of the major limitations of gamma cameras is their relatively poor energy resolution. The main practical consequence of this is that the detection of both scattered and unscattered photons in the photopeak energy window, affecting image contrast and resolution, makes the data inconsistent with the assumption of scatter-free projection data in reconstruction and attenuation correction algorithms. Here, we proposed a method to improve the effective energy resolution of scintigraphic acquisitions. This method is called photon energy recovery (PER). METHODS: Photon energy recovery is based on a spectral deconvolution analysis and uses iterative recurrent linear regressions. In practice, PER only required splitting the photopeak energy window into several subwindows and did not need list mode acquisitions. The method was fully automated. Photon energy recovery was quantitatively validated on 99mTc planar images using a Monte Carlo simulation and a real phantom and was illustrated by a bone study. RESULTS: The Monte Carlo simulation demonstrated that convergence was reached within relatively few (10-15) iterations. Photon energy recovery led to a considerable quantitative improvement because the mean error between the photopeak energy window image and the true unscattered image was equal to 8.72 s.d. (the mean error between one image and the true image was the mean of the differences between the two images; the difference is expressed as several s.d., where s.d. was the square root of the true value), whereas the mean error between the 140-keV PER image and the true unscattered image was only equal to 2.70. Moreover, the true and PER spectra were highly correlated. The real phantom data pointed out that the counts in the 140-keV PER image calculated from the images acquired "with scatter" were not very different from the true counts given by the "scatter-free" reference image. Planar pelvic bone scintigraphy demonstrated the advantages of PER because contrast increased when only unscattered photons were selected. CONCLUSION: Photon energy recovery is a stable and automated method that allows recovery of the correct value of the photon energy after a scintigraphic acquisition. Its ability to separate scattered from unscattered events has been quantitatively validated.

Algorithms↗
PubMed2000

Responses of bone turnover markers to repeated endurance running in humans under conditions of energy balance or energy restriction.

Distance running in humans has been associated with both positive and negative effects on the balance of bone remodelling. There is evidence to suggest that the negative effects may be linked to a failure to balance energy expenditure with an adequate energy intake. Energy restriction is known to reduce the synthesis and serum concentration of insulin-like growth factor 1 (IGF-1), which plays an important role in bone formation. The purpose of the present study was to compare the effects of repeated periods of prolonged treadmill running, under conditions of either energy balance or energy restriction, on markers of bone turnover and serum IGF-1 concentration in trained distance runners. Eight male distance runners [mean age 25.1 (SD 5.9) years, maximal oxygen uptake 61.8 (SD 4.9) ml x kg(-1) x min(-1)] undertook an exercise and diet regime on two separate occasions, 2 weeks apart. On each occasion they performed an intensive, 60 min treadmill run on 3 consecutive days. On one occasion their energy intake was restricted to approximately 50% of their estimated energy requirement (RES), whereas on the other occasion they remained in energy balance (BAL). The N-terminal pro-peptide of type 1 collagen (P1NP), osteocalcin and IGF-1 were measured in serum collected between 0800 and 0900 hours, when fasted and rested, on the day before and the day after each regime. The cross-linked N-telopeptides of type 1 collagen and deoxypyridinoline were measured from 24 h urine collections made on the day before and the final day of each regime and adjusted for creatinine excretion. The results showed that the serum concentration of both P1NP and IGF-1 declined by 15% (P = 0.008) and 17% (P = 0.007) respectively in response to RES, but did not change in response to BAL (P > 0.05). A strong relationship was observed between the magnitude of the reduction in the serum concentration of P1NP and IGF-1 after RES (r = 0.97; P < 0.001). There were no changes in the other bone markers in response to either regime. The results suggested that in trained distance runners, repeated periods of prolonged running do not affect the balance of bone turnover unless energy balance is simultaneously altered. These findings support the link between a negative energy balance, a reduced synthesis or serum level of IGF-1 and reduced collagen synthesis. They may also help to explain the bone remodelling imbalance that has been observed in some male and female distance runners.

Adult↗
PubMed2005

Effects of the duration of the habituation period on energy intakes from low and high energy density gruels by Burkinabè infants living in free conditions.

The present study was carried out in Ouagadougou (Burkina Faso) with the aim of determining if the duration of the habituation period (1, 5 or 10 days) to low and high energy density gruels affected the amounts consumed or the energy intakes from gruels consumed by 6-9-month-old infants. Thirty infants were chosen randomly among the eligible children in the study area and randomly assigned to two groups (S1 and S2). Each infant was given successively for 10 consecutive days two experimental gruels, each type of gruel being fed twice a day. The 15 infants in group S1 received low energy density gruel (G1) in the first period and high energy density gruel (G2) in the second, and the 15 infants in group S2 received G2 in the first period and G1 in the second. The two periods of 10 days were separated by 4 days during which the infant received his or her usual foods. The intakes of experimental gruels and other complementary foods were measured on days 1, 5 and 10 of each period. Whatever the type of gruel, the 10-day period of habituation did not result in an increase in the amounts consumed or in the energy intakes from these gruels. The amounts of G1 consumed on day 5 were significantly higher than those of G2 (9.0 vs 6.8 g/kg/meal; p = 0.044). Energy intakes from G2 were significantly higher than those from G1 on days 1 (28.8 vs 18.0 kJ/kg/meal; p = 0.0002), 5 (28.8 vs 19.2 kJ/kg/meal; p = 0.002) and 10 (25.9 vs 15.5 kJ/kg/meal; p = 0.0004). Daily frequencies of breastfeeding (approximately 5.6), water drinking (approximately 3.7) and meals with foods other than experimental gruels were relatively high and did not vary with the duration of the habituation period or the type of gruels. Whatever the type of gruel, the increase in the duration of the habituation period did not increase the amount consumed or energy intakes. The study confirmed that consumption of high energy density gruels led to a 60% increase in energy intakes in comparison with the consumption of low energy density gruels.

Breast Feeding↗
PubMed2004

Energy density and portion size: their independent and combined effects on energy intake.

The energy density (kcal/g) and the portion size (g) of foods have been identified as two properties of foods that can modulate energy intake. Recent studies have shown that when either the energy density or the portion size of foods is increased, energy intake increases. Within a meal, when both factors are increased simultaneously, their effects are independent and add together to increase energy intake. On the other hand, reducing the energy density of a first course, while increasing the volume that is consumed, leads to a decrease in energy intake at the entire meal. The mechanisms by which both factors exert their influence are not well understood but likely include cognitive and orosensory factors as well as physiological controls related to gastric distention and gastric emptying. Findings from studies in this area of research provide evidence that the energy density and the portion size of foods are important determinants of energy intake. An environment in which the food supply is ample and large portions of energy-dense foods are readily available to consumers can contribute to an overconsumption of calories.

Diet↗
PubMed1996

Comparison of multiple-pass 24-hour recall estimates of energy intake with total energy expenditure determined by the doubly labeled water method in young children.

OBJECTIVE: This study determined the accuracy of the multiple-pass 24-hour recall method for estimating energy intake in young children by comparing it with measurements of total energy expenditure made using the doubly labeled water method. DESIGN: Three multiple-pass 24-hour recalls were obtained over a 14-day period to estimate mean energy intake. Total energy expenditure was measured over the same 14-day period under free-living conditions using the doubly labeled water technique. SUBJECTS/SETTING: Twenty-four children between the ages of 4 and 7 years were tested at the General Clinical Research Center/Sims Obesity Nutrition Research Center at the University of Vermont. STATISTICAL ANALYSIS: t Tests, paired t tests, Pearson product-moment correlation coefficients, pairwise comparison to show relative bias and limits of agreement, and regression analysis were used to test the relationships among study variables. RESULTS: No difference was found between 3-day mean energy intake and total energy expenditure for the group (t = 2.07, P = .65). The correlation between individual measures of energy intake and total energy expenditure was not statistically significant (r = .25, P = .24). CONCLUSIONS: Data from 3 days of multiple-pass 24-hour recalls were sufficient to make valid group estimates of energy intake. The method was not precise for individual measurements of energy intake.

Body Composition↗
PubMed2005

Consequences of inadequate food energy and negative energy balance in humans.

Energy deficiency is probably best measured in adults by the body mass index (BMI). Acute energy deficiency (AED) is associated with body weight loss, along with changes in body composition, as well as a reduced BMR and physical activity. Chronic energy deficiency (CED) is an inadequacy in food to which individuals adapt, at some cost. Individuals with this have never 'lost' weight: they have simply grown less. They adapt to the decreased food energy by reductions in their total energy expenditure (TEE), linked mainly to a lower body size, and to their physical activity. It seems unlikely that enhanced metabolic efficiency contributes substantially to energy saving in CED. Supplementation of energy deficient individuals is accompanied by significant fat deposition; this may have deleterious consequences. Women in many developing countries achieve a successful outcome to pregnancy in spite of being chronically undernourished. Reductions in basal metabolism and behavioural changes in the form of diminished physical activity could meet most of the extra energy needed for pregnancy. Milk energy output is maintained within the expected range in undernourished lactating mothers. Energy deficiency in children is best measured by height-for-age for stunting, and weight-for-height for wasting. Deficits in behavioural and functional parameters in children exist with undernutrition, and can be reduced by early nutritional supplementation along with the appropriate environment.

Adaptation, Physiological↗
PubMed1998

Total energy expenditure and physical activity as assessed by the doubly labeled water method in Swedish adolescents in whom energy intake was underestimated by 7-d diet records.

Swedish children and adolescents may be adopting a sedentary lifestyle with low energy expenditures and intakes, but no quantitative data are available. The purpose of the present study in 50 adolescents aged 15 y was to investigate whether assessment of total energy expenditure (TEE) and physical activity level (PAL) by the doubly labeled water method and indirect calorimetry and estimation of energy intake by a 7-d diet record would indicate physical inactivity. The boys' (n = 25) mean weight was 112% and the girls' (n = 25) was 109% of Swedish reference values from 1976; the mean height of both boys and girls was 102% of those reference values. Mean TEE in the boys and girls, 13.82 +/- 1.90 and 10.70 +/- 1.59 MJ/d, and mean PAL (TEE/basal metabolic rate), 1.89 +/- 0.16 and 1.79 +/- 0.22, respectively, were nonsignificantly higher than corresponding figures from other published studies. Mean energy intake as a percentage of TEE was 81.9 +/- 17.9% in the boys and 78.3 +/- 16.4% in the girls. Significant negative correlations were found both between energy intake as a percentage of TEE and percentage body fat and between energy intake as a percentage of TEE and body mass index. These results add to the evidence that 7-d diet records underestimate energy intake in adolescents, particularly those with a tendency for overweight and increased body fat. The results support indications of a trend of increasing body weight and height in Swedish adolescents, but conflict with the presumptions of low physical activity, low energy expenditure, and low energy intake. These results support the view that current recommendations for energy intake during adolescence are too low.

Adipose Tissue↗
PubMed1996

Effects of immune challenge, dietary energy density, and source of energy on performance and immunity in weanling pigs.

The objective of this study was to investigate the effects of nutrient density and dietary energy source on performance and immune function of weanling pigs that were either challenged or not challenged with Escherichia coli lipopolysaccharide (LPS). A basal diet was formulated to contain 14 g CP/MJ DE and 7 g lysine/100 g CP. Sulfur amino acids, threonine and tryptophan were kept constant relative to lysine. Experimental diets were mixed using 70 parts basal diet and either 30 parts starch or an isocaloric amount (14 parts) of lard. Diets were fed either for ad libitum intake or on a pair-feeding basis to evaluate effects of diet nutrient density or source of energy, respectively. On d 9 and 25, pigs were challenged i.m. with either 1 mL of a LPS solution or a control solution. Lymphocyte blastogenesis was measured 2 d after the LPS administration and antibody response to sheep red blood cells (SRBC) or ovalbumin was determined 3 d after challenge. No interactive effects on performance were observed between LPS challenge and energy density or source of energy (P > .10). Injection of LPS tended to reduce feed intake and daily gain (P < .10), but not efficiency of feed or energy utilization. Addition of fat to the diets improved feed efficiency and efficiency of energy utilization for gain (P < .05). No consistent effects of LPS challenge, energy density, or source of energy were observed for lymphocyte blastogenesis. Antibody response to ovalbumin, but not to SRBC, was decreased by fat (P < .05). Results indicate that increasing energy density of the diet did not alter the performance depression due to LPS challenge. Addition of fat to the diet improved feed efficiency and efficiency of energy conversion but may depress the humoral immune response. Effects of fat on the immune response may depend on the immune status of the pig.

Aging↗
PubMed2000

Energy balance of lactating primiparous sows as affected by feeding level and dietary energy source.

The effects of feeding level and major dietary energy source used during lactation on sow milk composition, piglet body composition, and energy balance of sows were determined. During a 21-d lactation, 48 primiparous sows were fed either a Fat-rich (134.9 g/kg fat; 196.8 g/kg carbohydrate) or a Starch-rich (33.2 g/kg fat; 380.9 g/kg carbohydrate) diet at either a High (44 MJ NE/d; 1,050 g protein/d) or a Low (33 MJ NE/d; 790 g protein/d) feeding level. Within each feeding level, the two diets were fed to provide an isocaloric and isonitrogenous intake. At the Low feeding level, no differences in milk production, milk composition, or piglet body composition were found as a result of feeding the two dietary energy sources. However, at the High feeding level, sows fed the Fat-rich diet produced higher milk fat (8.4 vs 6.9%) and milk energy (5.38 vs 4.77 kJ/g) concentrations and a higher piglet body fat concentration (152.1 vs 135.4 g/kg) than sows fed the Starch-rich diet. At the Low feeding level, the energy balance (d 6 to d 20) of the sows was similar when fed either the Fat- or the Starch-rich diet (-558 and -515 kJ x BW(-.75) x d(-1)), but at the High feeding level, the energy balance was more negative in sows fed the Fat than those fed the Starch-rich diet (-544 vs -372 kJ x BW(-.75) x d(-1)). This suggests that at the High feeding level, dietary energy in the form of fat is preferentially used for milk fat synthesis, resulting in growth and in fatter piglets. Alternatively, at the High feeding level, Starch as the major energy source is used only for growth of the piglets, as confirmed by protein deposition, and also results in a less-negative energy balance for the sows. From this experiment, it can be concluded that effects of substituting cornstarch for fat in the diet of lactating sows on milk composition, piglet body composition, and energy balance of the sows are dependent on feeding level.

Animals↗
PubMed1992

Predictions of energy intake and energy allowance of patients with Duchenne muscular dystrophy and their validity.

Patients with Duchenne muscular dystrophy are so malnourished that energy supplementation is crucial. Their degree of energy deficiency was assessed as difference between their energy intake and their energy allowance, which were deduced from easily measured parameters. A significant, negative relationship was found between the basal metabolic rate (BMR) (Y, %, BMR/standard BMR) and body weight (X, %, body weight/standard body weight) in the patients, from which the formula for the BMR was deduced to be Y = -1.116X + 174.5 (n = 202, r = -0.72, p less than 0.001). Thus, it is possible to estimate the energy allowance for individual patients by a factorial procedure from the presumed BMR and a factor for physical activity. In addition, their energy intake was calculated from a constant protein-energy % (14.6%) in their diet and nitrogen intake which was deduced from a significant positive correlation between their nitrogen intake (Y, mg/kg/day) and their nitrogen excretion in 24 h urine samples (X, mg/kg/day). This correlation conformed to the equation Y = 1.053X + 32.4 (n = 267, r = +0.76, p less than 0.001). The validities of the above predictions for energy intake and allowance were examined by plotting the degree of energy deficiency (% ratio of presumed intake/presumed allowance) against the concentrations of retinal binding protein, prealbumin and transferrin in the serum, because rapid turnover proteins are sensitive to energy deficiency. Significant positive correlations were obtained with both variables, suggesting that these predictions were valid.

Adolescent↗
PubMed1995

Dietary energy intake, energy expenditure and activity pattern among selected rural and urban poor in Bangladesh.

Rural-urban and seasonal differences in energy balance were studied among selected free living subjects, chosen from the poor population groups in Bangladesh. Individual dietary energy intakes were estimated by a combination of 24 hours recall and weighing method. Time allocation to various occupational and non-occupational activities were recorded by observation and questioning, and energy expenditures were calculated by using FAO/WHO/UNU guidelines. The male working adults in both the population groups studied were found to be in negative energy balance in both the seasons observed. In Jan-Feb when employment opportunities for the rural poor were few all age and sex groups were in negative energy balance, and when employment opportunities improved during May-June the situation reversed except for the male working adults. In urban areas, on the other hand, all age and sex groups, except the male working adults were in positive energy balance in both the seasons. Rural children under 10 years, had significantly higher energy expenditure (P < 0.023) than their urban counterparts. Seasonal difference in energy expenditure among the rural male adults is quite high. In the urban group there was no such seasonal difference. Apparently very high rural-urban difference in energy expenditure of the male adults (18-30 y) in season 1 may be attributed to very high energy demanding activities in which the observed subjects in rural areas were engaged during this season. Compared to their urban counterparts rural male adults (18-30 yrs.) were found to be devoted significantly higher time in occupational and heavy household activities.

Adolescent↗
PubMed1998

Effects of exercise on appetite control: loose coupling between energy expenditure and energy intake.

The relationship between physical activity and energy intake (food consumption) can take a number of forms, depending on the intensity, duration and frequency of the activity, and upon the degrees of fitness and physiological status of the individual. At extremes of energy expenditure such as those found in long distance cyclists, voluntary energy intake may be sufficient to balance the enormous daily expenditure; this is due to an entraining effect. Under more normal situations, there is a widely held belief that physical activity is a poor strategy for losing weight, since the energy expended drives up hunger and food intake to compensate for the energy deficit incurred. Recent studies in both normal weight and obese individuals show that substantial periods of exercise do not increase hunger and do not drive up food intake. Comparisons between sedentary and normally active individuals, or between enforced periods of rest or strenuous activity, generate little or no effect on levels of hunger or daily energy intake, indicating a rather loose physiological coupling between energy expenditure and food intake. This view generates an optimistic view of the role of exercise in weight loss and weight control, as it indicates that intake is not automatically driven up to compensate for energy expended. Reasons why physical activity often produces disappointing effects, rise from inappropriate food choices, a desire for self-reward after exercise and misjudgements about the relative rates at which energy can be expended (by exercise) or taken in (by eating). This means that physical activity will be most beneficial for weight control, if carried out in conjunction with a low energy dense diet or with judicious control of eating.

Appetite↗
PubMed1993

Measurements of total energy expenditure provide insights into the validity of dietary measurements of energy intake.

The quantification of errors inherent in methods of measuring dietary intake has been handicapped by the absence of independent markers for testing their validity. The doubly labeled water technique permits a precise measure of energy expenditure in free-living persons. Because energy expenditure must equal energy intake in populations in energy balance, this technique may be used to validate the assessment of energy intake. A series of studies demonstrated good agreement between mean energy intake and mean energy expenditure when food intake was recorded by observers or when it was self-reported by normal-weight, self-selected, highly motivated volunteer subjects using weighed records. However, in randomly recruited men and women, energy intake by weighed records was 82% and 81%, of energy expenditure, respectively, indicating underestimation of habitual intake. Men and women in the lowest third of reported intake recorded energy expenditure of only 69% and 61%, respectively. Reported intake of obese and previously obese women was only 73% and 64% of expenditure, whether measured by weighed record or by diet history, confirming suspicions that these subjects misrepresented their intake. Acceptable weighed records were obtained from 7- and 9-year-olds whereas 15- and 18-year-olds underestimated intake. Diet histories taken from the same children tended to overestimate intake. These studies suggest that, ideally, all dietary studies should include independent measures of validity.

Adolescent↗
PubMed2001

An evaluation of energy intakes and the ratio of energy intake to estimated basal metabolic rate (EI/BMRest) in the North/South Ireland Food Consumption Survey.

OBJECTIVE: To examine energy intakes (EI), their ratio to estimated basal metabolic rate (BMR(est) and the contribution of food groups to energy intake in the North/South Ireland Food Consumption Survey. DESIGN AND SETTING: Random sample of adults from the populations of Northern Ireland and the Republic of Ireland. Food intake data were collected using a 7-day food diary. Body weight and height were measured and EI/BMR(est) was calculated from reported energy intake and estimated basal metabolic rate. Dieting practices were assessed as part of a self-administered questionnaire. RESULTS: Mean energy intake in men was 11.0 MJ and in women was 7.6 MJ, which is comparable to reported energy intakes in Northern Ireland and the Republic of Ireland over a decade ago. Mean EI/BMR(est) was 1.38. This increased to 1.42 after the exclusion of dieters and those who were unwell, but still remained less than the established cut-off of 1.53. EI/BMR(est) was significantly (P<0.05) higher in men than in women and decreased significantly (P<0.05) with increasing BMI in both sexes. The four food groups that contributed 50% of energy in men and women were meat and meat products, breads and rolls, potatoes and potato products, and biscuits, cakes, pastries and puddings. CONCLUSIONS: Energy intakes have not changed remarkably in Northern Ireland or the Republic of Ireland in the last 10 years, but the mean EI/BMR(est) of 1.38 suggests that energy underreporting occurred. EI/BMR(est) was lower in women and in the overweight/obese. Additional multivariate analysis of the data is needed to identify more clearly subgroups of the population reporting lower than expected energy intakes and to evaluate the effect of low energy reporting on the consumption of various foods and food groups.

Adolescent↗
PubMed1993

[Effect of the starch sources barley, corn and potatoes and their ration portions on nutrient digestibility and energy utilization in ruminants. 3. Energy utilization in cattle].

With investigations on the influence of different starch origins (barley, maize and raw potatoes) and different portions of the starch origins in the rations (50, 25 and 10% of the net energy fat, cattle (NEFr) content of the rations) on the energy utilization of rations a contribution was made to the development of the energetic feed evaluation within Rostock NEF-system. The experiments were carried out with fattened oxen using the methods of total metabolism technique and duodenal passage measurement by means of reentrant fistula. The nutrition levels amounted to 1.7 and 1.1 of energy maintenance requirement. The utilization of metabolizable energy for deposition of the 9 rations-including 3 variants of starch origins barley, maize and raw potatoes with parts in the rations of 50, 25 and 10%--was measured as 65, 61 and 59%, 61, 60 and 58% as well as 59, 61 and 55%. The energy maintenance requirement amounted to 526 kJ ME/kg LM 0.75.d. The gradations of energy utilization are caused by the connection between energy concentration and utilization of rations in ruminants. With comparable parts of the rations the different starch sources had no relevant influence on the energy utilization of the rations. Despite a wide range of starch plus water soluble carbohydrates (WSC) intake between 896 and 3426 g/animal.d no correlation between the kind of digestion (fermentative or enzymatic) of starch and WSC and the energy utilization of the rations was measurable, because the part of the ruminal digestion amounted to 86.0 and 97.2%. The result presented for the energy and nitrogen metabolism measurements are in good agreement with results of former experiments with 92 rations.

Animal Feed↗
PubMed1995

[Energy and nitrogen metabolism of pregnant and lactating sows and suckling piglets. 7. Energy and nitrogen metabolism in suckling piglets].

In 23 litters, each with 10 or 11 piglets, the energy and nitrogen metabolism was measured on base of 218 body analyses in suckling piglets and on base of 96 total metabolism experiments in early weaned piglets, combined with 134 body analyses. The studies were carried out as part of a complex experimental program for the factorial derivation of energy and protein requirement of piglets and for measuring the milk production of lactating sows. The energy maintenance requirement of suckling piglets (sow's milk nutrition, I) and of early weaned piglets (sow's milk replacement on the basis of cow's milk, II) amounted to 468 (I) and 451 kJ (II) metabolizable energy per kg LW0.75 . d, the utilization of of metabolizable energy for energy deposition to 70(I) and 72% (II). With mean live weight gains (LWG) of 161 and 162 g per animal and day the cost per kg LWG amounted to 19.9 and 20.4 MJ gross energy, 19.3 and 19.4 MJ metabolizable energy as well as 14.4 and 14.2 MJ net energy-fat in suckling and early weaned piglets resp. The mean energy content of the LWG amounted to 8.9 (I) and to 7.9 MJ/kg (II).

Animals↗
PubMed1995

An improved energy-range relationship for high-energy electron beams based on multiple accurate experimental and Monte Carlo data sets.

A theoretically based analytical energy-range relationship has been developed and calibrated against well established experimental and Monte Carlo calculated energy-range data. Only published experimental data with a clear statement of accuracy and method of evaluation have been used. Besides published experimental range data for different uniform media, new accurate experimental data on the practical range of high-energy electron beams in water for the energy range 10-50 MeV from accurately calibrated racetrack microtrons have been used. Largely due to the simultaneous pooling of accurate experimental and Monte Carlo data for different materials, the fit has resulted in an increased accuracy of the resultant energy-range relationship, particularly at high energies. Up to date Monte Carlo data from the latest versions of the codes ITS3 and EGS4 for absorbers of atomic numbers between four and 92 (Be, C, H2O, PMMA, Al, Cu, Ag, Pb and U) and incident electron energies between 1 and 100 MeV have been used as a complement where experimental data are sparse or missing. The standard deviation of the experimental data relative to the new relation is slightly larger than that of the Monte Carlo data. This is partly due to the fact that theoretically based stopping and scattering cross-sections are used both to account for the material dependence of the analytical energy-range formula and to calculate ranges with the Monte Carlo programs. For water the deviation from the traditional energy-range relation of ICRU Report 35 is only 0.5% at 20 MeV but as high as -2.2% at 50 MeV. An improved method for divergence and ionization correction in high-energy electron beams has also been developed to enable use of a wider range of experimental results.

Electrons↗