Energy requirements of lean and overweight women, assessed by indirect calorimetry

The prevalence of overweight in the developed world and the increased mortality and morbidity risk of overweight people stimulate research into the imbalance between energy intake and energy expenditure. Little information is available about the 24 hour energy expenditure and energy requirement of lean and overweight people. This thesis describes experiments on 24 hour energy expenditure, measured in whole body indirect calorimeters, energy intake and energy requirements of lean and overweight female subjects.The experiment described in chapter 2 was performed to gain an insight into the reproducibility of measurements of 24 hour energy expenditure in human subjects. Ten female subjects were measured twice over three successive 24 hour periods, under similar conditions in the calorimeter, with an interval of between 2 and 24 months. One woman lost 13 kg during the interval; her data were excluded from analysis. The data from this experiment indicate that the variability in 24 hour energy expenditure within subjects, between periods of measurements, is small under similar conditions and after sufficient adaptation to the calorimeter (within subject coefficient of variation ca 2%). The results are discussed with regard to the length of the trial and the number of subjects required to test for a difference in 24 hour energy expenditure.Chapter 3 deals with the energy requirement of lean and overweight women. The 24 hour energy expenditure of 29 lean and 18 overweight women, after 5 days on an experimental diet, was measured over 3 successive days by indirect calorimetry. The observed mean 24 hour energy expenditure was considered to be an estimate of the energy requirement as energy balance was close to zero for both groups of women. The energy requirement of the overweight subjects was higher than that of the lean subjects. However, the energy requirements of the overweight subjects, relative to fat free mass and body weight, were respectively similar to and lower than those of the lean subjects. A multiple regression analysis was performed to predict 24 hour energy expenditure (energy requirement) from variables related to the 24 hour energy expenditure. The 24 hour energy expenditure of the adult female subjects was best predicted by body weight and body fat percentage. The data on energy requirements of lean and overweight subjects are compared with data of other investigators.Chapter 4 deals with the comparison of metabolizable energy intake, during normal life, with the observed mean 24 hour energy expenditure in the calorimeter. The metabolizable energy intake was measured using a 7 day weighing record method. This method was assumed to provide an estimate of the usual energy intake required to maintain body weight (energy requirement). The 24 hour energy expenditure measurement was also considered to give an estimation of the energy requirement. The latter estimate was considered to be the most accurate. The estimated metabolizable energy intake was validated against the observed 24 hour energy expenditure for the groups of lean and overweight women. The 7 day weighing record method provided an accurate estimate of the usual energy intake of lean women. However, the use of this method to estimate usual energy intake of overweight women remains questionable.Chapter 5 describes the effect of alternating daily energy intake on energy metabolism. Theoretically one might expect that alternating the energy intake would increase 24 hour energy expenditure in comparison with a constant daily energy intake. This would result in a zero energy balance at a higher level of energy intake. The experiment was performed with two groups of subjects, each consisting of 7 females and one male. One group consumed first a diet providing a constant daily energy intake, and then a diet with an alternating daily energy intake (one day low, one day high). The other group followed the reverse protocol. Twenty-four hour energy expenditure was measured on both diets and energy balance was calculated. The result, that alternating daily energy intake does not affect energy balance, is discussed with regard to the expected theoretical effect. It is suggested that alternating energy intake might affect energy balance, if it is alternated over periods longer than one day.Chapter 6 deals with the effect of an eight week low energy intake on the energy requirements and energy metabolism of overweight women. The experiment initially involved 14 women, but because of questionable adherence to the experimental protocol by two subjects, the data of only twelve subjects are presented. Twenty-four hour energy expenditure of these subjects was measured four times. The first measurement was made when they were consuming an experimental diet that provided approximately the energy required to maintain body weight (100% diet); this was followed by a measurement after 5 days on a weightreducing experimental diet (4.2 MJ/d diet). The subjects then consumed a prescribed diet of 4.2 MJ/d during 6 weeks. After this period they were measured while still on the 4.2 MJ/d experimental diet, and then again after 5 days of refeeding on the 100% diet. The 24 hour energy expenditure of the overweight women decreased by 9% within the first week on the 4.2 MJ/d experimental diet.After 8 weeks on a low energy intake the 24 hour energy expenditure on the 4.2 MJ/d experimental diet had declined by 15%. After one week of refeeding with the 100% diet, 24 hour energy expenditure was still 10% lower than the initial value. Energy requirement of the subjects was calculated before and after weight reduction, using data on the energy balance and metabolizable energy intake on the 100% and 4.2 MJ/d diets. Energy requirement of the subjects after weight reduction had decreased by 1.2 MJ/d, which was more than would be predicted from the change in body weight and body fat percentage by the equation presented in chapter 3. It remains to be established whether this lower energy requirement than predicted (adaptation) is a consequence of the long term low energy intake or whether it is a temporary phenomenon or an indication of a low energy requirement that may have caused overweight.The general discussion follows in chapter 7. In this chapter suggestions for future research on energy expenditure and energy requirement are presented. The chapter also considers some implications of the results of the experiments presented in this thesis for the dietary management of overweight.An appendix describes in more detail the experimental diet and the calorimetric measurements

On the Classification of Real Forms of Non-Abelian Toda Theories and W-algebras

We consider conformal non-Abelian Toda theories obtained by hamiltonian reduction from Wess-Zumino-Witten models based on general real Lie groups. We study in detail the possible choices of reality conditions which can be imposed on the WZW or Toda fields and prove correspondences with sl(2,R) embeddings into real Lie algebras and with the possible real forms of the associated W-algebras. We devise a a method for finding all real embeddings which can be obtained from a given embedding of sl(2,C) into a complex Lie algebra. We then apply this to give a complete classification of real embeddings which are principal in some simple regular subalgebra of a classical Lie algebra.Comment: 42 pages, LaTeX; Minor corrections to ensure consistent conventions; some references adde

Real Forms of Non-abelian Toda Theories and their W-algebras

We consider real forms of Lie algebras and embeddings of sl(2) which are consistent with the construction of integrable models via Hamiltonian reduction. In other words: we examine possible non-standard reality conditions for non-abelian Toda theories. We point out in particular that the usual restriction to the maximally non-compact form of the algebra is unnecessary, and we show how relaxing this condition can lead to new real forms of the resulting W-algebras. Previous results for abelian Toda theories are recovered as special cases. The construction can be extended straightforwardly to deal with osp(1|2) embeddings in Lie superalgebras. Two examples are worked out in detail, one based on a bosonic Lie algebra, the other based on a Lie superalgebra leading to an action which realizes the N=4 superconformal algebra.Comment: 11 pages, LaTex; minor errors corrected, extra references adde

Production, partial cash flows and greenhouse gas emissions of simulated dairy herds with extended lactations

The transition period is the most critical period in the lactation cycle of dairy cows. Extended lactations reduce the frequency of transition periods, the number of calves and the related labour for farmers. This study aimed to assess the impact of 2 and 4 months extended lactations on milk yield and net partial cash flow (NPCF) at herd level, and on greenhouse gas (GHG) emissions per unit of fat- and protein-corrected milk (FPCM), using a stochastic simulation model. The model simulated individual lactations for 100 herds of 100 cows with a baseline lactation length (BL), and for 100 herds with lactations extended by 2 or 4 months for all cows (All+2 and All+4), or for heifers only (H+2 and H+4). Baseline lactation length herds produced 887 t (SD: 13) milk/year. The NPCF, based on revenues for milk, surplus calves and culled cows, and costs for feed, artificial insemination, calving management and rearing of youngstock, was k€174 (SD: 4)/BL herd per year. Extended lactations reduced milk yield of the herd by 4.1% for All+2, 6.9% for All+4, 1.1% for H+2 and 2.2% for H+4, and reduced the NPCF per herd per year by k€7 for All+2, k€12 for All+4, k€2 for H+2 and k€4 for H+4 compared with BL herds. Extended lactations increased GHG emissions in CO2-equivalents per t FPCM by 1.0% for All+2, by 1.7% for All+4, by 0.2% for H+2 and by 0.4% for H+4, but this could be compensated by an increase in lifespan of dairy cows. Subsequently, production level and lactation persistency were increased to assess the importance of these aspects for the impact of extended lactations. The increase in production level and lactation persistency increased milk production of BL herds by 30%. Moreover, reductions in milk yield for All+2 and All+4 compared with BL herds were only 0.7% and 1.1% per year, and milk yield in H+2 and H+4 herds was similar to BL herds. The resulting NPCF was equal to BL for All+2 and All+4 and increased by k€1 for H+2 and H+4 due to lower costs for insemination and calving management. Moreover, GHG emissions per t FPCM were equal to BL herds or reduced (0% to -0.3%) when lactations were extended. We concluded that, depending on lactation persistency, extending lactations of dairy cows can have a positive or negative impact on the NPCF and GHG emissions of milk production.</p

Low dose aspirin in the prevention of recurrent spontaneous preterm labour - the APRIL study: A multicenter randomized placebo controlled trial

Background: Preterm birth (birth before 37 weeks of gestation) is a major problem in obstetrics and affects an estimated 15 million pregnancies worldwide annually. A history of previous preterm birth is the strongest risk factor for preterm birth, and recurrent spontaneous preterm birth affects more than 2.5 million pregnancies each year. A recent meta-analysis showed possible benefits of the use of low dose aspirin in the prevention of recurrent spontaneous preterm birth. We will assess the (cost-)effectiveness of low dose aspirin in comparison with placebo in the prevention of recurrent spontaneous preterm birth in a randomized clinical trial. Methods/design: Women with a singleton pregnancy and a history of spontaneous preterm birth in a singleton pregnancy (22-37 weeks of gestation) will be asked to participate in a multicenter, randomized, double blinded, placebo controlled trial. Women will be randomized to low dose aspirin (80 mg once daily) or placebo, initiated from 8 to 16 weeks up to maximal 36 weeks of gestation. The primary outcome measure will be preterm birth, defined as birth at a gestational age (GA) < 37 weeks. Secondary outcomes will be a composite of adverse neonatal outcome and maternal outcomes, including subgroups of prematurity, as well as intrauterine growth restriction (IUGR) and costs from a healthcare perspective. Preterm birth will be analyzed as a group, as well as separately for spontaneous or indicated onset. Analysis will be performed by intention to treat. In total, 406 pregnant women have to be randomized to show a reduction of 35% in preterm birth from 36 to 23%. If aspirin is effective in preventing preterm birth, we expect that there will be cost savings, because of the low costs of aspirin. To evaluate this, a cost-effectiveness analysis will be performed comparing preventive treatment with aspirin with placebo. Discussion: This trial will provide evidence as to whether or not low dose aspirin is (cost-) effective in reducing recurrence of spontaneous preterm birth. Trial registration: Clinical trial registration number of the Dutch Trial Register: NTR 5675. EudraCT-registration number: 2015-003220-31

Phenomenology of the Lense-Thirring effect in the Solar System

Recent years have seen increasing efforts to directly measure some aspects of the general relativistic gravitomagnetic interaction in several astronomical scenarios in the solar system. After briefly overviewing the concept of gravitomagnetism from a theoretical point of view, we review the performed or proposed attempts to detect the Lense-Thirring effect affecting the orbital motions of natural and artificial bodies in the gravitational fields of the Sun, Earth, Mars and Jupiter. In particular, we will focus on the evaluation of the impact of several sources of systematic uncertainties of dynamical origin to realistically elucidate the present and future perspectives in directly measuring such an elusive relativistic effect.Comment: LaTex, 51 pages, 14 figures, 22 tables. Invited review, to appear in Astrophysics and Space Science (ApSS). Some uncited references in the text now correctly quoted. One reference added. A footnote adde

Horizontal Branch Stars: The Interplay between Observations and Theory, and Insights into the Formation of the Galaxy

We review HB stars in a broad astrophysical context, including both variable and non-variable stars. A reassessment of the Oosterhoff dichotomy is presented, which provides unprecedented detail regarding its origin and systematics. We show that the Oosterhoff dichotomy and the distribution of globular clusters (GCs) in the HB morphology-metallicity plane both exclude, with high statistical significance, the possibility that the Galactic halo may have formed from the accretion of dwarf galaxies resembling present-day Milky Way satellites such as Fornax, Sagittarius, and the LMC. A rediscussion of the second-parameter problem is presented. A technique is proposed to estimate the HB types of extragalactic GCs on the basis of integrated far-UV photometry. The relationship between the absolute V magnitude of the HB at the RR Lyrae level and metallicity, as obtained on the basis of trigonometric parallax measurements for the star RR Lyrae, is also revisited, giving a distance modulus to the LMC of (m-M)_0 = 18.44+/-0.11. RR Lyrae period change rates are studied. Finally, the conductive opacities used in evolutionary calculations of low-mass stars are investigated. [ABRIDGED]Comment: 56 pages, 22 figures. Invited review, to appear in Astrophysics and Space Scienc

Strategies and performance of the CMS silicon tracker alignment during LHC Run 2

The strategies for and the performance of the CMS silicon tracking system alignment during the 2015–2018 data-taking period of the LHC are described. The alignment procedures during and after data taking are explained. Alignment scenarios are also derived for use in the simulation of the detector response. Systematic effects, related to intrinsic symmetries of the alignment task or to external constraints, are discussed and illustrated for different scenarios