Comment on "Regularizing capacity of metabolic networks"

In a recent paper, Marr, Muller-Linow and Hutt [Phys. Rev. E 75, 041917 (2007)] investigate an artificial dynamic system on metabolic networks. They find a less complex time evolution of this dynamic system in real networks, compared to networks of reference models. The authors argue that this suggests that metabolic network structure is a major factor behind the stability of biochemical steady states. We reanalyze the same kind of data using a dynamic system modeling actual reaction kinetics. The conclusions about stability, from our analysis, are inconsistent with those of Marr et al. We argue that this issue calls for a more detailed type of modeling

Behaviour, practice – whatever? A theory-agnostic framework for describing and informing demand-side response

Different theoretical perspectives present diverse interpretations for why and how people may (or may not) be able to vary their electricity consumption patterns, and often propose different approaches to facilitating demand-side response (DSR). The framework set out here is suggested as a way of matching and marrying these various approaches with the goal of exploring how to achieve the maximum possible demand response which people are happy and able to provide. The framework is based around ‘electricity-relevant dimensions’, or factors which may be considered to be associated in some way with a person or people’s electricity use – activities engaged in, location, room temperature, and so on. Within each dimension, any at instant in time, certain states (such as ‘walking’ or ‘watching TV’ for activity) are more or less possible/acceptable than others for a variety of reasons. Effective DSR is understood as involving influencing adoption of those states with lower (or higher, as necessary) electricity outcomes at certain times, from a ‘phase space’ of possible options. This paper describes how the framework can be used to consider the role of DSR interventions with their roots in different theoretical positions, such as changes in material conditions or competencies (associated with social practice theory), or in the framing of messages to activate loss-aversion (behavioural economics). It is intended to prompt consideration of how such approaches (and their proponents) could work together to optimize the potential of DSR programmes and policies, and is illustrated throughout with real and hypothetical examples

L1-determined ideals in group algebras of exponential Lie groups

A locally compact group $G$ is said to be $\ast$-regular if the natural map \Psi:\Prim C^\ast(G)\to\Prim_{\ast} L^1(G) is a homeomorphism with respect to the Jacobson topologies on the primitive ideal spaces \Prim C^\ast(G) and \Prim_{\ast} L^1(G). In 1980 J. Boidol characterized the $\ast$-regular ones among all exponential Lie groups by a purely algebraic condition. In this article we introduce the notion of $L^1$-determined ideals in order to discuss the weaker property of primitive $\ast$-regularity. We give two sufficient criteria for closed ideals $I$ of $C^\ast(G)$ to be $L^1$-determined. Herefrom we deduce a strategy to prove that a given exponential Lie group is primitive $\ast$-regular. The author proved in his thesis that all exponential Lie groups of dimension $\le 7$ have this property. So far no counter-example is known. Here we discuss the example $G=B_5$, the only critical one in dimension $\le 5$

Knowing me, knowing you: the role of trust, locus of control and privacy concern in acceptance of domestic electricity demand-side response

Choosing to take part in a demand-side response (DSR) programme entails accepting external influence over one’s energy consumption patterns, such as through price or direct load control (DLC) signals. If participation is low, the programme will be ineffective. How might people’s perceptions of their relationship with the influencing entity affect the likelihood of participation? This study used a representative survey of Great Britain (N=2002) to explore the importance of trust, privacy concern and locus of control for acceptance of different approaches to influencing electricity consumption. Survey respondents were randomly shown a description of one of five DSR products (static time of use [TOU] tariff, static TOU with automated response to price changes, dynamic TOU, dynamic TOU with automated response, and DLC), framed as being offered by their electricity supplier. They then responded to a number of scales including those intended to measure trust in their supplier, privacy concern and locus of control. Controlling for demographic variables, trust in electricity supplier was significantly positively associated with acceptance of all tariffs, although the effect size was smaller for the automated TOU tariffs. The specific measure of trust in the supplier to ensure a reliable electricity supply was significantly negatively associated with acceptance of the dynamic TOU tariff. Privacy concern was significantly negatively associated with acceptance of all tariffs, with the strongest effect for the automated dynamic TOU tariff. Locus of control was a significant factor only in the case of DLC, where external locus was related to higher acceptance. These results suggest the existing low levels of trust in energy companies in the UK may present a challenge in securing uptake of DSR, and an opportunity to trusted entrants from other sectors. Automation within the home may mitigate trust concerns, but people must have confidence in the privacy of this arrangement. DLC may be viewed especially positively by people who currently perceive themselves to have little control over their energy use, but protections should be in place to ensure they are not exploited

Experiment K-6-08. Biochemical and histochemical observations of vastus medialis

Muscles of the hindlimb in the rat have been used to demonstrate the effects of unloading in weightlessness and in animal models used to mimic weightlessness. The vastus medialis (VM) is discussed here. Samples were obtained from rats exposed to weightlessness for 12 days in Cosmos 1887 (Experiment K-6-08, coordinated by Dr. V.S. Oganov). The principal objective of this study was to ascertain if the vastus medialis responded to 12 days of microgravity exposure. The loss in muscle mass is greatest, -43 percent, when comparing F vs B, and least, -13 percent, when comparing F vs. V. Taken at face value these differences may be misleading. Due to the variability of the muscle weight in the basal group, these muscle mass losses may be exaggerated. In terms of percent water, there were no differences between the flight and the control groups. In spite of the limited sample, researchers conclude that muscle mass changes in the VM are not significant. Although some of the morphological parameters suggest a small degree of atrophy in the vastus medialis, the biochemical analyses (protein, RNA and DNA) suggest that these may be minimal and functionally nonsignificant. The relatively similar CS and LDH activities of VM from F and various control groups, as well as the lack of difference in LPL activity between F and S rats, suggests that there is little or no effect on the oxidative or glycolytic function of this muscle. Since the VM is chiefly a mixed fast twitch muscle, these metabolic indices of energy production are relatively unchanged. The results of VM studies are in agreement with previous observations of another type II fast twitch muscle, the EDL, from SL-3 rats which did not respond markedly to weightlessness and whole body suspension

Cosmological perturbations on local systems

We study the effect of cosmological expansion on orbits--galactic, planetary, or atomic--subject to an inverse-square force law. We obtain the laws of motion for gravitational or electrical interactions from general relativity--in particular, we find the gravitational field of a mass distribution in an expanding universe by applying perturbation theory to the Robertson-Walker metric. Cosmological expansion induces an ($\ddot a/a) \vec r$ force where $a(t)$ is the cosmological scale factor. In a locally Newtonian framework, we show that the $(\ddot a/a) \vec r$ term represents the effect of a continuous distribution of cosmological material in Hubble flow, and that the total force on an object, due to the cosmological material plus the matter perturbation, can be represented as the negative gradient of a gravitational potential whose source is the material actually present. We also consider the effect on local dynamics of the cosmological constant. We calculate the perihelion precession of elliptical orbits due to the cosmological constant induced force, and work out a generalized virial relation applicable to gravitationally bound clusters.Comment: 10 page

Imaging of the relative saturation current density and sheet resistance of laser doped regions via photoluminescence

We present an approach to characterize the relative saturation current density (J oe) and sheet resistance (RSH) of laser doped regions on silicon wafers based on rapid photoluminescence (PL) imaging. In the absence of surface passivation layers, the RSH of laser doped regions using a wide range of laser parameters is found to be inversely proportional to the PL intensity (I PL ). We explain the underlying mechanism for this correlation, which reveals that, in principle, I PL is inversely proportional to J oe at any injection level. The validity of this relationship under a wide range of typical experimental conditions is confirmed by numerical simulations. This method allows the optimal laser parameters for achieving low RSH and J oe to be determined from a simple PL image.The authors acknowledge financial support from the Australian Solar Institute (ASI)/Australian Renewable Energy Agency (ARENA) under the ANU PV Core project, Postdoctoral Fellowship and Australia-Germany Collaborative Solar Research and Development projects. The authors also acknowledge support from the Australian Government’s NCRIS/EIF funding programs for access to Heavy Ion Accelerator Facilities at the Australian National University

A Uniqueness Theorem for Constraint Quantization

This work addresses certain ambiguities in the Dirac approach to constrained systems. Specifically, we investigate the space of so-called ``rigging maps'' associated with Refined Algebraic Quantization, a particular realization of the Dirac scheme. Our main result is to provide a condition under which the rigging map is unique, in which case we also show that it is given by group averaging techniques. Our results comprise all cases where the gauge group is a finite-dimensional Lie group.Comment: 23 pages, RevTeX, further comments and references added (May 26. '99