Quantization of energy and writhe in self-repelling knots

Probably the most natural energy functional to be considered for knotted strings is that given by electrostatic repulsion. In the absence of counter-charges, a charged, knotted string evolving along the energy gradient of electrostatic repulsion would progressively tighten its knotted domain into a point on a perfectly circular string. However, in the presence of charge screening self-repelling knotted strings can be stabilized. It is known that energy functionals in which repulsive forces between repelling charges grow inversely proportionally to the third or higher power of their relative distance stabilize self-repelling knots. Especially interesting is the case of the third power since the repulsive energy becomes scale invariant and does not change upon Mobius transformations (reflections in spheres) of knotted trajectories. We observe here that knots minimizing their repulsive Mobius energy show quantization of the energy and writhe (measure of chirality) within several tested families of knots.

Physical activity and energy expenditure in haemodialysis patients: an international survey.

BACKGROUND: The assessment of physical activity and energy expenditure is relevant to the care of maintenance haemodialysis (MHD) patients. In the current study, we aimed to evaluate measurements of physical activity and energy expenditure in MHD patients from different centres and countries and explored the predictors of physical activity in these patients.��METHODS: In this cross-sectional multicentre study, 134 MHD patients from four countries (France, Switzerland, Sweden and Brazil) were included. The physical activity was evaluated for 5.0 �� 1.4 days (mean �� SD) by a multisensory device (SenseWear Armband) and comprised the assessment of number of steps per day, activity-related energy expenditure (activity-related EE) and physical activity level (PAL).��RESULTS: The number of steps per day, activity-related EE and PAL from the MHD patients were compatible with a sedentary lifestyle. In addition, all parameters were significantly lower in dialysis days when compared to non-dialysis days (P < 0.001). The multivariate regression analysis revealed that diabetes and higher body mass index (BMI) predicted a lower PAL and older age and diabetes predicted a reduced number of steps.��CONCLUSIONS: The physical activity parameters of MHD patients were compatible with a sedentary lifestyle. This inactivity was worsened by aging, diabetes and higher BMI. Our results indicate that MHD patients should be encouraged by the health care team to increase their physical activity.

An energy preserving discontinouous Galerkin method for Vlasov-Poisson system

Vegeu el resum a l'inici del document de l'arxiu adjunt

Assessment of Physical Activity and Energy Expenditure by GPS Combined With Accelerometry in Real-Life Conditions.

Background: Physical activity (PA) and related energy expenditure (EE) is often assessed by means of a single technique. Because of inherent limitations, single techniques may not allow for an accurate assessment both PA and related EE. The aim of this study was to develop a model to accurately assess common PA types and durations and thus EE in free-living conditions, combining data from global positioning system (GPS) and 2 accelerometers. Methods: Forty-one volunteers participated in the study. First, a model was developed and adjusted to measured EE with a first group of subjects (Protocol I, n = 12) who performed 6 structured and supervised PA. Then, the model was validated over 2 experimental phases with 2 groups (n = 12 and n = 17) performing scheduled (Protocol I) and spontaneous common activities in real-life condition (Protocol II). Predicted EE was compared with actual EE as measured by portable indirect calorimetry. Results: In protocol I, performed PA types could be recognized with little error. The duration of each PA type could be predicted with an accuracy below 1 minute. Measured and predicted EE were strongly associated (r = .97, P < .001). Conclusion: Combining GPS and 2 accelerometers allows for an accurate assessment of PA and EE in free-living situations.

New stakeholders, spaces and instruments of analysis in the context of energy relationships: Case studies from Kazakhstan and Turkmenistan

The disintegration of the USSR brought the emergence of a new geo-energy space in Central Asia. This space arose in the context of a global energy transition, which began in the late 1970s. Therefore, this new space in a changing energy world requires both new conceptual frameworks of analysis and the creation of new analytical tools. Taking into account this fact, our paper attempts to apply the theoretical framework of the Global Commodity Chain (GCC) to the case of natural resources in Central Asia. The aim of the paper is to check if there could be any Central Asia���s geo-energy space, assuming that this space would exist if natural resources were managed with regional criteria. The paper is divided into four sections. First an introduction that describes the new global energy context within natural resources of Central Asia would be integrated. Secondly, the paper justifies why the GCC methodology is suitable for the study of the value chains of energy products. Thirdly, we build up three cases studies (oil and uranium from Kazakhstan and gas from Turkmenistan) which reveal a high degree of uncertainty over the direction these chains will take. Finally, we present the conclusions of this study that state that the most plausible scenario would be the integration of energy resources of these countries in GCC where the core of the decision-making process will be far away from the region of Central Asia. Key words: Energy transition, geo-energy space, Global Commodity Chains, Central Asia

Neonatal adaptation of energy and protein metabolism

During the last decade, the development of "bedside" investigative methods, including indirect calorimetry, nutritional balance and stable isotope techniques, have given a new insight into energy and protein metabolism in the neonates. Neonates and premature infants especially, create an unusual opportunity to study the metabolic adaptation to extrauterine life because their physical environment can be controlled, their energy intake and energy expenditure can be measured and the link between their protein metabolism and the energetics of their postnatal growth can be assessed with accuracy. Thus, relatively abstract physiological concepts such as the postnatal timecourse of heat production, energy cost of growth, energy cost of physical activity, thermogenic effect of feeding, efficiency of protein gain, metabolic cost of protein gain and protein turnover have been quantified. These results show that energy expenditure and heat production rates increase postnatally from average values of 40 kcal/kgxday during the first week to 60 kcal/kgxday in the third week. This increase parellels nutritional intakes as well as the rate of weight gain. The thermogenic effect of feeding and the physical activity are relatively low and account only for an average of 5% each of the total heat production. The cost of protein turnover is the highest energy demanding process. The fact that nitrogen balance becomes positive within 72 hours after birth places the newborn in a transitional situation of dissociated balance between energy and protein metabolism: dry body mass and fat decrease while there is a gain in protein and increase in supine length. This particular situation ends during the second postnatal week and soon thereafter the rate of weight gain matches the statural growth. The goals of the following review are to summarize recent data on the physiological aspects of energy and protein metabolism directly related to the extrauterine adaptation, to describe experimental approaches which recently were adapted to the newborns in order to get "bedside results" and to discuss how far these results can help everyday's neonatal practice.

The neurobiological basis of prefrontal cortex impairment in the phencyclidine model of schizophrenia : convergent reduction of synaptic glutamate release, energy metabolism and cognitive performance

R��SUM�� : Le traitement r��p��t�� �� la phencyclidine (PCP), un bloqueur du r��cepteur NMDA (NMDAR), reproduit chez les rongeurs une partie de la symptomatologie typique de la schizophr��nie. Le blocage prolong�� du NMDAR par la PCP mime une hypofunction du NMDAR, une des principales alt��rations suppos��es exister dans les cerveaux des patients schizophr��niques. Le but de notre ��tude ��tait d'examiner les cons��quences neurochimiques, m��taboliques et fonctionnelles du traitement r��p��t�� �� la phencyclidine in vivo, au niveau du cortex pr��frontal (cpf), une r��gion c��r��brale qui joue un r��le dans les d��ficits cognitifs observ��s chez les patients schizophr��niques. Pour r��pondre �� cette question, les rats ou les souris ont re��u chaque jour une injection soit de PCP (5 mg/kg), soit de solution saline, pendant 7 ou 14 jours. Les animaux ont ensuite ��t�� sacrifi��s au moins 24 heures apr��s le dernier traitement. Des tranches aigu��s du cpf ont ��t�� pr��par��es rapidement, puis stimul��es avec une concentration ��lev��e de KCI, de mani��re �� induire une lib��ration de glutamate �� partir des terminaisons synaptiques excitatrices. Les r��sultats montrent que les tranches du cpf des animaux trait��s �� la PCP ont lib��r�� une quantit�� de glutamate significativement inf��rieure par rapport �� celles des animaux contr��le. Ce d��ficit de lib��ration a persist�� 72 heures apr��s la fin du traitement, tandis qu'il n'��tait pas observ�� dans le cortex visuel primaire, une autre r��gion corticale. En outre, le traitement avec des antipsychotiques, l'halop��ridol ou l'olanzapine, a supprim�� le d��ficit induit par la PCP. Le m��me d��ficit de lib��ration a ��t�� remarqu�� sur des synaptosomes obtenus �� partir du cpf des animaux trait��s �� la phenryclidine. Cette observation indique que la PCP induit une modification plastique adaptative du m��canisme qui contr��le la lib��ration du glutamate dans les terminaisons synaptiques. Nous avons d��couvert que cette modification implique la sous-r��gulation d'un NMDAR pr��synaptique, qui serait dou�� d'un r��le d'autor��cepteur stimulateur de la lib��ration du glutamate. Gr��ce �� des tests comportementaux conduits en parall��le et r��alis��s pour ��valuer la fonctionnalit�� du cpf, nous avons observ�� chez les souris trait��es �� la PCP une flexibilit�� comportementale r��duite lors d'un test de discrimination de stimuli visuels/tactiles. Le d��ficit cognitif ��tait encore pr��sent 4 jours apr��s la derni��re administration de PCP. La technique de l'autoradiographie quantitative du [14C]2-deoxyglucose a permis d'associer ce d��ficit �� une r��duction de l'activit�� m��tabolique c��r��brale pendant le d��roulement du test, particuli��rement au niveau du cpf. Dans l'ensemble, nos r��sultats sugg��rent que le blocage prolong�� du NMDAR lors de l'administration r��p��t��e de PCP produit un d��ficit de lib��ration du glutamate au niveau des terminaisons synaptiques excitatrices du cpf. Un tel d��ficit pourrait ��tre provoqu�� par la sousr��gulation d'un NMDAR pr��synaptique, qui aurait une fonction de stimulateur de lib��ration; la transmission excitatrice du cpf s'en trouverait dans ce cas r��duite. Ce r��sultat est en ligne avec l'activit�� m��tabolique et fonctionnelle r��duite du cpf et l'observation de d��ficits cognitifs induits lors de l'administration de la PCP. ABSTRACT : Sub-chronic treatment with phencyclidine (PCP), an NMDA receptor (NMDAR) channel blocker, reproduces in rodents part of the symptomatology associated to schizophrenia in humans. Prolonged pharmacological blockade of NMDAR with PCP mimics NMDAR hypofunction, one of the main alterations thought to take place in the brains of schizophrenics. Our study was aimed at investigating the neurochemical, metabolic and behavioral consequences of repeated PCP administration in vivo, focusing on the functioning of the prefrontal cortex (pfc), a brain region highly relevant for the cognitive deficits observed in schizophrenic patients. Rats or mice received a daily administration of either PCP (5 mg/kg) or saline for 7 or 14 days. At least 24 hours after the last treatment the animals were sacrificed. Acute slices of the pfc were quickly prepared and challenged with high KCl to induce synaptic glutamate release. Pfc slices from PCP-treated animals released significantly less glutamate than slices from salinetreated animals. The deficit persisted 72 hours after the end of the treatment, while it was not observed in another cortical region: the primary visual cortex. Interestingly, treatment with antipsychotic drugs, either haloperidol or olanzapine, reverted the glutamate release defect induced by PCP treatment. The same release defect was observed in synaptosomes prepared from the pfc of PCP-treated animals, indicating that PCP induces a plastic adaptive change in the mechanism controlling glutamate release in the glutamatergic terminals. We discovered that such change most likely involves the down-regulation of a newly identified, pre-synaptic NMDAR with stimulatory auto-receptor function on glutamate release. In parallel sets of behavioral experiments challenging pfc function, mice sub-chronically treated with PCP displayed reduced behavioral flexibility (reversal learning) in a visual/tactile-cued discrimination task. The cognitive deficit was still evident 4 days after the last PCP administration and was associated to reduced brain metabolic activity during the performance of the behavioral task, notably in the pfc, as determined by [14C]2-deoxyglucose quantitative autoradiography. Clverall, our findings suggest that prolonged NMDAR blockade by repeated PCP administration results in a defect of glutamate release from excitatory afferents in the pfc, possibly ascribed to down-regulation of apre-synaptic stimulatory NMDAR. Deficient excitatory neurotransmission in the pfc is consistent with the reduced metabolic and functional activation of this area and the observed PCP-induced cognitive deficits.

Association of irisin with fat mass, resting energy expenditure, and daily activity in conditions of extreme body mass index.

FNDC5/irisin has been recently postulated as beneficial in the treatment of obesity and diabetes because it is induced in muscle by exercise, increasing energy expenditure. However, recent reports have shown that WAT also secretes irisin and that circulating irisin is elevated in obese subjects. The aim of this study was to evaluate irisin levels in conditions of extreme BMI and its correlation with basal metabolism and daily activity. The study involved 145 female patients, including 96 with extreme BMIs (30 anorexic (AN) and 66 obese (OB)) and 49 healthy normal weight (NW). The plasma irisin levels were significantly elevated in the OB patients compared with the AN and NW patients. Irisin also correlated positively with body weight, BMI, and fat mass. The OB patients exhibited the highest REE and higher daily physical activity compared with the AN patients but lower activity compared with the NW patients. The irisin levels were inversely correlated with daily physical activity and directly correlated with REE. Fat mass contributed to most of the variability of the irisin plasma levels independently of the other studied parameters. Conclusion. Irisin levels are influenced by energy expenditure independently of daily physical activity but fat mass is the main contributing factor.

International regimes as knowledge syndicates? Energy and trends of global governance

El poder de l'Estat i la sobirania tradicional s'est�� deteriorant de manera constant, sobretot en termes de la provisi�� de certs b��ns p��blics fonamentals. Els Estats, en particular, s��n incapa��os de manejar el coneixement i la informaci�� que ��s essencial per mantenir la competitivitat i la sostenibilitat en una economia interdependent. Estructures fiables de la governan��a mundial i la cooperaci�� internacional estan lluny de ser establertes. Energia com a problema a les agendes p dels governs, les empreses privades i la societat civil ��s un exemple manifest d'aquesta din��mica.. L'actual sistema de governan��a mundial d'energia implica accions pol��tiques disperses per actors divers. L'Ag��ncia Internacional de l'Energia t�� un paper destacat, per�� est�� debilitat per la seva composici�� limitada i basada en el coneixement- epist��mic en lloc del material o executiu. Aquest treball sost�� que ni la mida ni nombre de membres disponibles estan dificultant la governabilitat mundial d'energia. M��s aviat, l'energia ��s una s��rie de b��ns p��blics que es troben als llimbs, on els estats no poden pagar la seva disposici��, aix�� com els diversos interessos impedir l'establiment d'una autoritat internacional. Despr��s de la introducci�� de la teoria del r��gim internacional i el concepte de coneixement basats en les comunitats epist��miques, l'article revisa l'estat actual de la governabilitat de l'energia mundia. A continuaci�� es presenta una comparaci�� d'aquesta estructura amb els r��gims de govern nacional i regional, d'una banda, i amb r��gims globals ambientals i de salut, de l'altra

Perspectives on the green construction of the new European Energy Policy

The EU has been one of the main actors involved in the construction process of an international climate change regime, adopting it as an identity sign in the international arena. This activism has reverted in the European political agenda and in the one of its Members States. Therefore, climate change has become a driver for the EU growing participation in energy policy and for its governance evolution. In this context, much attention has been paid to the climate and energy policies integration agreed after the 2007 spring European Council. Apparently, this decision meant a decisive step towards the incorporation of the environmental variable in the energy policy-making. Moreover, the Action Plan [2007-2009] ���Energy Policy for Europe��� outlined priority actions in a variety of energy-related areas, implying the new European Energy Policy commencement. Against this background, there is still much left to understand about its formulation and its further development. Rooted on the Environmental Policy Integration approach, this paper traces the increasing proximity between environment and energy policies in order to understand the green contribution to the European Energy Policy construction.

The EU ���2020 Energy Initiative���: The post-Lisbon pattern of change in EU energy policy

El novembre de 2010, la Comissi�� Europea ha finalment donat a con��ixer la seva "Energia 2020 Comunicaci��", un document estrat��gic en el marc m��s ampli del programa "Europa 2020". Una estrat��gia per al desenvolupament sostenible intel �� ligent, i creixement inclusiu posa les bases d'un nou enfocament a la pol��tica d'energia a la UE. En el marc d'Europa 2020, la Iniciativa d'Energia recopila els resultats que ja s'han obtingut a trav��s de la Estrat��gia de Lisboa 2000-2010, s'identifiquen les defici��ncies del passat i i introdueix nous objectius ambiciosos per a la UE en mat��ria de pol��tica energ��tica.

The Strategic value of European renewable energy promotion policy

Encara falta per fer possible una transformaci�� estrat��gica d'Europa del sistema d'energia, per�� el que ��s de la mateixa import��ncia com a objectius a llarg termini de la FER i Reduccions de GEH s��n vinculants i forts objectius d'efici��ncia energ��tica, no nom��s per 2020, per�� tamb�� per al 2030, 2040 i 2050, com aquesta for��a ajudaria a fixar l'augment de les energies renovables en el total d'energia consum i per reduir el total Emissions de GEH d'Europa en general, i les del sector de l'energia en particular, encara sent un dels majors emissors de gasos d'efecte hivernacle de tots els sectors. La refosa Directiva, prevista per 2011/12 ha de ser un bones finestres d'oportunitat per finalment establir objectius vinculants d'efici��ncia energ��tica, l'��nic pilar que encara falta en la for��a energia interdependents i estrat��gia sobre el clima de la UE, basat en la reducci�� de gasos d'efecte hivernacle i i l'efici��ncia energ��tica.

Energy-nitrogen balances and protein turnover in small and appropriate for gestational age low birthweight infants.

The aim of the present study was to compare, under the same nursing conditions, the energy-nitrogen balance and the protein turnover in small for gestational age (SGA) and appropriate for gestational age (AGA) low birthweight infants. We compared 8 SGA's (mean +/- s.d.: gestational age 35 +/- 2 weeks, birthweight 1520 +/- 330 g) to 11 AGA premature infants (32 +/- 2 weeks, birthweight 1560 +/- 240 g). When their rate of weight gain was above 15 g/kg/d (17.6 +/- 3.0 and 18.2 +/- 2.6 g/kg/d, mean postnatal age 18 +/- 10 and 20 +/- 9 d respectively) they were studied with respect to their metabolizable energy intake, their energy expenditure, their energy and protein gain and their protein turnover. Energy balance was assessed by the difference between metabolizable energy and energy expenditure as measured by indirect calorimetry. Protein gain was calculated from the amount of retained nitrogen. Protein turnover was estimated by a stable isotope enrichment technique using repeated nasogastric administration of 15N-glycine for 72 h. Although there was no difference in their metabolizable energy intakes (110 +/- 12 versus 108 +/- 11 kcal/kg/d), SGA's had a higher rate of resting energy expenditure (64 +/- 8 versus 57 +/- 8 kcal/kg/d, P less than 0.05). Protein gain and composition of weight gain was very similar in both groups (2.0 +/- 0.4 versus 2.1 +/- 0.4 g protein/kg/d; 3.5 +/- 1.1 versus 3.3 +/- 1.4 g fat/kg/d in SGA's and AGA's respectively). However, the rate of protein synthesis was significantly lower in SGA's (7.7 +/- 1.6 g/kg/d) as compared to AGA's (9.7 +/- 2.8 g/kg/d; P less than 0.05). It is concluded that SGA's have a more efficient protein gain/protein synthesis ratio since for the same weight and protein gains, SGA's show a 20 per cent slower protein turnover. They might therefore tolerate slightly higher protein intakes. Postconceptional age seems to be an important factor in the regulation of protein turnover.

Horizontal, but not vertical, biotic interactions affect fine-scale plant distribution patterns in a low-energy system

Studies of species range determinants have traditionally focused on abiotic variables (typically climatic conditions), and therefore the recent explicit consideration of biotic interactions represents an important advance in the field. While these studies clearly support the role of biotic interactions in shaping species distributions, most examine only the influence of a single species and/or a single interaction, failing to account for species being subject to multiple concurrent interactions. By fitting species distribution models (SDMs), we examine the influence of multiple vertical (i.e., grazing, trampling, and manuring by mammalian herbivores) and horizontal (i.e., competition and facilitation; estimated from the cover of dominant plant species) interspecific interactions on the occurrence and cover of 41 alpine tundra plant species. Adding plant-plant interactions to baseline SDMs (using five field-quantified abiotic variables) significantly improved models' predictive power for independent data, while herbivore-related variables had only a weak influence. Overall, abiotic variables had the strongest individual contributions to the distribution of alpine tundra plants, with the importance of horizontal interaction variables exceeding that of vertical interaction variables. These results were consistent across three modeling techniques, for both species occurrence and cover, demonstrating the pattern to be robust. Thus, the explicit consideration of multiple biotic interactions reveals that plant-plant interactions exert control over the fine-scale distribution of vascular species that is comparable to abiotic drivers and considerably stronger than herbivores in this low-energy system.