DYNAMIC FACTOR DEMANDS AND ENERGY SUBSTITUTION IN REGIONAL U.S. MANUFACTURING

Although energy substitution in U.S. manufacturing has been studied in great depth at the national level, little attention has been paid to the regional level. However, regions may differ in their use of energy for a variety of reasons. The main objective of this study is to estimate region-specific demands for energy using a dynamic model for two-digit SIC Code manufacturing sectors. We derive own and cross-price elasticities for energy for different regions and we compare them. We, thus, provide information which has implications for a region specific energy policy.Resource /Energy Economics and Policy,

Structural relaxation in silicate melts and non-Newtonian melt rheology in geologic processes

The timescale of structural relaxation in a silicate melt defines the transition from liquid (relaxed) to glassy (unrelaxed) behavior. Structural relaxation in silicate melts can be described by a relaxation time, , consistent with the observation that the timescales of both volume and shear relaxation are of the same order of magnitude. The onset of significantly unrelaxed behavior occurs 2 log10 units of time above . In the case of shear relaxation, the relaxation time can be quantified using the Maxwell relationship for a viscoelastic material; S = S/G (where S is the shear relaxation time, G is the shear modulus at infinite frequency and S is the zero frequency shear viscosity). The value of G known for SiO2 and several other silicate glasses. The shear modulus, G , and the bulk modulus, K , are similar in magnitude for every glass, with both moduli being relatively insensitive to changes in temperature and composition. In contrast, the shear viscosity of silicate melts ranges over at least ten orders of magnitude, with composition at fixed temperature, and with temperature at fixed composition. Therefore, relative to S, G may be considered a constant (independent of composition and temperature) and the value of S, the relaxation time, may be estimated directly for the large number of silicate melts for which the shear viscosity is known. For silicate melts, the relaxation times calculated from the Maxwell relationship agree well with available data for the onset of the frequency-dependence (dispersion) of acoustic velocities, the onset of non-Newtonian viscosities, the scan-rate dependence of the calorimetric glass transition, with the timescale of an oxygen diffusive jump and with the Si-O bond exchange frequency obtained from 29Si NMR studies. Using data obtained over a range of frequencies and strain-rates we illustrate the significance of relaxed versus unrelaxed behavior in laboratory experiments on silicate melts. Similarly, using strain-rate estimates for magmatic processes we evaluate the significance of the liquid-glass transition in igneous petrogenesis. Dedicated to the memory of Chris Scarf

Relative Profitability of Dynamic Walrasian Strategies

The advantage of price-taking behavior in achieving relative profitability in oligopolistic quantity competition has been much appreciated recently from economic dynamics and evolutionary game theory, respectively. The current research intends to provide a direct economic interpretation as well as intuitive justification and further to build a linkage between different perspectives. In particular, a detailed illustration of an arbitrary oligopoly that produce a homogenous product is presented. So long as the outputs of other firms are fixed and the residual demand is downward sloping, for any two identical firms whose cost functions are convex, their output space can be divided symmetrically into mutually exclusive relatively profitability regimes. Furthermore, there exist infinitely many relative-profitability reactions for each firm in such “residual” duopoly, all of which intersect at the “residual” Walrasian equilibrium. This suggests that sticking to this dynamical equilibrium output constantly (i.e., the static Walrasian strategy) turns out to be a relative-profitability strategy at each period. On the other hand, regardless of what strategies its rival may take, a firm adopting price-taking strategy or more generally defined dynamic Walrasian strategies can achieve the relative profitability if an intertemporal equilibrium is reached. The methodology adopted and the conclusions arrived clarify the confusions and misunderstandings due to the different usages of same terminologies under different frameworks and generalize the previous available results in the literature to a higher level and a broader context.Price-taking, Walrasian behavior, Relative profit, Oligopoly, Cournot, dynamic Walrasian strategy.

The transient localization scenario for charge transport in crystalline organic materials

Charge transport in crystalline organic semiconductors is intrinsically limited by the presence of large thermal molecular motions, which are a direct consequence of the weak van der Waals inter-molecular interactions. These lead to an original regime of transport called \textit{transient localization}, sharing features of both localized and itinerant electron systems. After a brief review of experimental observations that pose a challenge to the theory, we concentrate on a commonly studied model which describes the interaction of the charge carriers with inter-molecular vibrations. We present different theoretical approaches that have been applied to the problem in the past, and then turn to more modern approaches that are able to capture the key microscopic phenomenon at the origin of the puzzling experimental observations, i.e. the quantum localization of the electronic wavefuntion at timescales shorter than the typical molecular motions. We describe in particular a relaxation time approximation which clarifies how the transient localization due to dynamical molecular motions relates to the Anderson localization realized for static disorder, and allows us to devise strategies to improve the mobility of actual compounds. The relevance of the transient localization scenario to other classes of systems is briefly discussed.Comment: Accepted for publication in Advanced Functional Materials - Special issue on Organic Single Crystal

Modeling the mechanics of amorphous solids at different length and time scales

We review the recent literature on the simulation of the structure and deformation of amorphous glasses, including oxide and metallic glasses. We consider simulations at different length and time scales. At the nanometer scale, we review studies based on atomistic simulations, with a particular emphasis on the role of the potential energy landscape and of the temperature. At the micrometer scale, we present the different mesoscopic models of amorphous plasticity and show the relation between shear banding and the type of disorder and correlations (e.g. elastic) included in the models. At the macroscopic range, we review the different constitutive laws used in finite element simulations. We end the review by a critical discussion on the opportunities and challenges offered by multiscale modeling and transfer of information between scales to study amorphous plasticity.Comment: 58 pages, 14 figure

Elastic properties of proteins: insight on the folding process and evolutionary selection of native structures

We carry out a theoretical study of the vibrational and relaxation properties of naturally-occurring proteins with the purpose of characterizing both the folding and equilibrium thermodynamics. By means of a suitable model we provide a full characterization of the spectrum and eigenmodes of vibration at various temperatures by merely exploiting the knowledge of the protein native structure. It is shown that the rate at which perturbations decay at the folding transition correlates well with experimental folding rates. This validation is carried out on a list of about 30 two-state folders. Furthermore, the qualitative analysis of residues mean square displacements (shown to accurately reproduce crystallographic data) provides a reliable and statistically accurate method to identify crucial folding sites/contacts. This novel strategy is validated against clinical data for HIV-1 Protease. Finally, we compare the spectra and eigenmodes of vibration of natural proteins against randomly-generated compact structures and regular random graphs. The comparison reveals a distinctive enhanced flexibility of natural structures accompanied by slow relaxation times at the folding temperature. The fact that these properties are intimately connected to the presence and assembly of secondary motifs hints at the special criteria adopted by evolution in the selection of viable folds.Comment: Revtex 17 pages, 13 eps figure

Oil price shocks, poverty, and gender: a social accouting matrix analysis for Kenya

In a similar way to Input-Output (IO) tables, Social Accounting Matrices (SAMs) have been used in the literature mostly to assess the distributional impact of changes in production structure on household income. Yet they can also be used to assess the impact on price shocks on the cost of goods consumed by households. The key advantage of SAMs over IO tables is that the data from household surveys on the incomes and consumption patterns of various categories of households can be directly integrated into the modeling exercise in order to conduct the distributional analysis. This is illustrated with a discussion of the impact of oil price shocks in Kenya on different types of households defined according to the gender of the household head as well as poverty status. We find that due to some differences in consumption patterns, poorer households are likely to be affected more by oil price hikes than the non-poor, and that household with female heads could also be more affected than households with male heads.Input-output analysis; Social accounting matrix; Price model; Kenya; Gender