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Dark Energy: the Cosmological Challenge of the Millennium  [PDF]
T. Padmanabhan
Physics , 2004,
Abstract: Recent cosmological observations suggest that nearly seventy per cent of the energy density in the universe is unclustered and has negative pressure. Several conceptual issues related to the modeling of this component (`dark energy'), which is driving an accelerated expansion of the universe, are discussed with special emphasis on the cosmological constant as the possible choice for the dark energy. Some curious geometrical features of a universe with a cosmological constant are described and a few attempts to understand the nature of the cosmological constant are reviewed.
Ultra High Energy Cosmic Rays: The theoretical challenge  [PDF]
A. V. Olinto
Physics , 2000, DOI: 10.1016/S0370-1573(00)00028-4
Abstract: The origin of the highest-energy cosmic rays remains a mystery. The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions have strongly constrained most models proposed for the generation of these particles. An overview of the present state of theoretical proposals is presented. Astrophysical accelerators as well as top-down scenarios are reviewed along with their most general signatures. The origin and nature of these ultra-high energy particles will be tested by future observations and may indicate as well as constrain physics beyond the standard model of particle physics.
Challenge.
René-éric Dagorn
EspacesTemps.net , 2004,
Abstract: Sous le titre The Hispanic Challenge , Samuel P. Huntington propose dans le numéro de Foreign Policy de mars-avril 2004 une nouvelle démonstration du danger de sa pseudo-théorie du choc des civilisations . Quel est donc ce challenge auquel, d'après Huntington, la société américaine serait aujourd'hui confrontée ? C'est celui de l'immigration hispanique qui menace l'identité américaine, ses valeurs et son mode de vie ...
Traits to Ecosystems: The Ecological Sustainability Challenge When Developing Future Energy Crops  [PDF]
Martin Weih,Stefanie Hoeber,Friderike Beyer,Petra Fransson
Frontiers in Energy Research , 2014, DOI: 10.3389/fenrg.2014.00017
Abstract: Today, we are undertaking great efforts to improve biomass production and quality traits of energy crops. Major motivation for developing those crops is based on environmental and ecological sustainability considerations, which however often are de-coupled from the trait-based crop improvement programs. It is now time to develop appropriate methods to link crop traits to production system characteristics set by the plant and the biotic communities influencing it; and to the ecosystem processes affecting ecological sustainability. The relevant ecosystem processes involve the net productivity in terms of biomass and energy yields, the depletion of energy-demanding resources (e.g., nitrogen, N), the carbon dynamics in soil and atmosphere, and the resilience and temporal stability of the production system. In a case study, we compared aspects of N use efficiency in various varieties of an annual (spring wheat) and perennial (Salix) energy crop grown under two nutrient regimes in Sweden. For example, we found considerable variation among crops, varieties, and nutrient regimes in the energy yield per plant-internal N (megajoule per gram per year), which would result in different N resource depletion per unit energy produced.
Effects of inhomogeneities on the expansion of the Universe: a challenge to dark energy?  [PDF]
Marie-No?lle Célérier
Physics , 2012,
Abstract: The current standard model of cosmology, the LambdaCDM model, is based on the homogeneous FLRW solutions of the Einstein equations to which some perturbations are added to account for the CMB features and structure formation at large scales. This model fits rather well the observations provided 95% of the energy density budget of the Universe should be of an unknown physical nature, i.e. dark matter and dark energy. Now, the aim of a cosmological model is not merely to reproduce the observations, but also to give a physical understanding of the Universe we live in. Moreover, even if the assumption of homogeneity seems to be more or less valid at large scales, it appears to be in contradiction with observations at intermediate scales (between the scale of non linear structure formation and that where structures virialize). This is the reason why, during the last decade, a community of researchers formed whose aim was to look for the best way to take into account the influence of the inhomogeneities seen in the Universe and to construct accurate cosmological models which could possibly get rid of the dark components. This task, which is still in its infancy, is currently progressing towards promising results. Two types of methods can be found in the literature: spatial averaging of scalar quantities and use of exact inhomogeneous solutions of General Relativity. We will give here a brief report of the second one.
Metabolic Energy Correlates of Heart Rate Variability Spectral Power Associated with a 900-Calorie Challenge  [PDF]
Richard M. Millis,Rachel E. Austin,Mark D. Hatcher,Vernon Bond,Kim L. Goring
Journal of Nutrition and Metabolism , 2011, DOI: 10.1155/2011/715361
Abstract: We studied healthy males challenged with a 900 Cal test beverage and correlated EE with the raw (ms2) and normalized units (nu) of total power (TP), low frequency/high frequency (LF/HF) and VLF spectral power of heart rate variability (HRV). The correlations were evaluated during 20 min of normal breathing (NB, control) and 20 min of paced breathing (PB) at 12 breaths?min−1 (0.2 Hz). EE was not significantly correlated with any of the HRV variables before the metabolic challenge. After the challenge, EE was positively correlated with LF/HF and with VLF; VLF was also positively correlated with LF/HF during both NB and PB. These findings suggest that EE may be a correlate of LF/HF and of VLF spectral power of HRV in healthy adolescent/young adult males. The association of lower resting energy expenditure with lower amounts of VLF spectral power may occur in individuals with predilections for obese phenotypes.
The Nishino Breathing Method and Ki-energy (Life-energy): A Challenge to Traditional Scientific Thinking  [PDF]
Tsuyoshi Ohnishi,Tomoko Ohnishi
Evidence-Based Complementary and Alternative Medicine , 2006, DOI: 10.1093/ecam/nel004
Abstract: The breathing method, which was developed and is being taught by Kozo Nishino, a Japanese Ki-expert, is for raising the levels of Ki-energy (life-energy or the vitality) of an individual. It is neither a therapy nor a healing technique. However, many of his students have experienced an improvement in their health, and in some cases, they were able to overcome health problems by themselves. Since this is an interesting subject from the standpoint of complementary and alternative medicine (CAM), we have been collaborating with Nishino to conduct a scientific investigation of his Ki-energy. We found that Nishino's Ki-energy can inhibit cell division of cancer cells, protect isolated mitochondria from heat deterioration and reduce lipid peroxidation in heat-treated mitochondria. Although Ki-energy may consist of several different energy forms, we found that at least one of them is near-infrared radiation between the wavelength range of 0.8 and 2.7 μm. Another interesting observation at his school is the Taiki-practice (paired Ki-practice). During this practice, Nishino can ‘move’ his students without any physical contact. Many of them run, jump or roll on the floor when they receive his Ki-energy. We studied this and propose that ‘information’ is conveyed through the air between two individuals by Ki-energy. This may be called a five sense-independent, life-to-life communication by Ki. All of our results suggest that we should re-evaluate the Cartesian dualism (separation of mind and body) which has been a fundamental principle of modern science for the past three centuries.
A Unified Residential Energy Cost Optimization Model for Smart Grid - Significance and Challenge  [PDF]
Muhammad Raisul Alam,Marc St-Hilaire,Thomas Kunz
Computer Science , 2015,
Abstract: This article addresses the residential energy cost optimization problem in smart grid. To date, most of the previous research only consider a partial aspect of the cost optimization problem. As a result, they fail to analyze scenarios when the interconnected components along with their properties have to be considered simultaneously. The proposed model combines these partial models into a single unified cost optimization model. Therefore, it is able to analyze scenarios which are closer to practical implementation. Furthermore, it is useful to analyze the behavior of a population (e.g., smart buildings, smart cities, etc.) and properties of the components for specific scenarios (e.g., the impact of aggregate storage capacity, etc.). It allows energy trading in microgrid which introduces a cost fairness problem. It ensures Pareto optimality among the households which guarantees that no household will be worse off to improve the cost of others. Results show that it can maintain the user preferences and can react to a demand response program by rescheduling the household loads and sources. Finally, the paper addresses the challenge of the computational complexity of the proposed model, showing that solution time increases exponentially with the problem size and proposes possible approaches to solve this.
Metabolic Energy Correlates of Heart Rate Variability Spectral Power Associated with a 900-Calorie Challenge  [PDF]
Richard M. Millis,Rachel E. Austin,Mark D. Hatcher,Vernon Bond,Kim L. Goring
Journal of Nutrition and Metabolism , 2011, DOI: 10.1155/2011/715361
Abstract: We studied healthy males challenged with a 900 Cal test beverage and correlated EE with the raw (ms2) and normalized units (nu) of total power (TP), low frequency/high frequency (LF/HF) and VLF spectral power of heart rate variability (HRV). The correlations were evaluated during 20?min of normal breathing (NB, control) and 20?min of paced breathing (PB) at 12 breaths min?1 (0.2?Hz). EE was not significantly correlated with any of the HRV variables before the metabolic challenge. After the challenge, EE was positively correlated with LF/HF and with VLF; VLF was also positively correlated with LF/HF during both NB and PB. These findings suggest that EE may be a correlate of LF/HF and of VLF spectral power of HRV in healthy adolescent/young adult males. The association of lower resting energy expenditure with lower amounts of VLF spectral power may occur in individuals with predilections for obese phenotypes. 1. Introduction Sympathetic regulatory mechanisms are at the nexus of nutrition, metabolism, and obesity. Heart rate variability spectral power (HRVSP) measurements of respiratory sinus arrhythmia are noninvasive indicators of the autonomic influences on heart rate regulation. Advances in knowledge of obese phenotypes have been impeded by the lack of noninvasive technologies for measuring the impact of body fat on regulatory mechanisms. However, this impediment has effectively been overcome by the advent of heart rate variability (HRV) analyses for elucidating autonomic mechanisms [1] which make it possible to differentiate a wide variety of conditions with common autonomic etiologies [2–6]. Previous studies have shown correlations between increments in vagal signaling and high-frequency (HF) HRVSP during controlled (paced) breathing [7–9], and paced breathing has often been used to limit the influence of HF HRVSP on the low-frequency/high-frequency spectral power ratio (LF/HF), a commonly used index of sympathetic influences. Although the percentage of body fat may be a determinant of HRVSP measured at rest [10, 11], the influence of body fat on HRV measurements was found to be nil when performed at rest and significant only during an autonomic challenge [12]. We have demonstrated positive correlations of LF/HF with the respiratory quotient (RQ) before and after feeding [13] and negative correlations with the percentage of body fat in healthy young adult/adolescent African American males after overnight fasting and the latter only during 5?min periods of spontaneous, uncontrolled breathing and not during 5?min periods of paced breathing at 12
Presentation of the Second Big Challenge Symposium - The Big Challenge of Cosmological Understanding: Gravitation, Dark Matter and Dark Energy. Towards New Scenarios  [PDF]
Christian Corda
Physics , 2010, DOI: 10.1063/1.3498619
Abstract: This Symposium is devoted to the Memory of Lev Kofman, June-17-1957-November-12-2009. The accelerated expansion of the Universe, which is today observed, shows that cosmological dynamics is dominated by the so-called Dark Energy field which provides a large negative pressure. This is the standard picture, in which such new ingredient is considered as a source of the right hand side of the field equations. It should be some form of non-clustered non-zero vacuum energy which, together with the clustered Dark Matter, drives the global dynamics. This is the so-called "concordance model" (ACDM) which gives, in agreement with the Cosmic Microwave Background Radiation (CMBR), dim Lyman Limit Systems (LLS) and type la supernovae (SNeIa) data, a good framework to understand the today observed Universe. However, it presents several shortcomings as the well known "coincidence" and "cosmological constant" problems . An alternative approach is to have a better understanding of the energy concept in General Relativity and also to change the left hand side of the field equations, and check if observed cosmic dynamics can be achieved by extending general relativity. In this different context, it is not required to search candidates for Dark Energy and Dark Matter, which till now have not been found. Rather, one can only stand on the "observed" ingredients: curvature and baryon matter, to account for the observations. Considering this point of view, one can think of that gravity is not scale-invariant. The goal of this Symposium is to obtain a tapestry of the present status of theory and observations concerning Gravitation and Dark Universe.
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