Metric gravity theories and cosmology. I. Physical interpretation and viability

We critically review some concepts underlying current applications of gravity theories with Lagrangians depending on the full Riemann tensor to cosmology. We argue that it is impossible to reconstruct the underlying Lagrangian from the observational data: the Robertson-Walker spacetime is so simple and "flexible" that any cosmic evolution may be fitted by infinite number of Lagrangians. Confrontation of a solution with the astronomical data is obstructed by the existence of many frames of dynamical variables and the fact that initial data for the gravitational triplet depend on which frame is minimally coupled to ordinary matter. Prior to any application it is necessary to establish physical contents and viability of a given gravity theory.Comment: 29 pages. The previous version is divided in two separate papers. The first four chapters, expanded and modified, form the present paper. The title and abstract are adequately modified, some recent references added. The main conclusions remain unchanged. The second part will also appear in Class. Qu. Gra

Dissipative particle dynamics study of solvent mediated transitions in pores decorated with tethered polymer brushes in the form of stripes

We study self-assembly of a binary mixture of components A and B confined in a slit-like pore with the walls modified by the stripes of tethered brushes made of beads of a sort A. The emphasis is on solvent mediated transitions between morphologies when the composition of the mixture varies. For certain limiting cases of the pore geometry we found that an effective reduction of the dimensionality may lead to a quasi one- and two-dimensional demixing. The change of the environment for the chains upon changing the composition of the mixture from polymer melt to a good solvent conditions provides explanation for the mechanism of development of several solvent mediated morphologies and, in some cases, for switching between them. We found solvent mediated lamellar, meander and in-lined cylinder phases. Quantitative analysis of morphology structure is performed considering brush overlap integrals and gyration tensor components.Comment: 14 pages, 12 figure

Ultra-sensitive surface absorption spectroscopy using sub-wavelength diameter optical fibers

The guided modes of sub-wavelength diameter air-clad optical fibers exhibit a pronounced evanescent field. The absorption of particles on the fiber surface is therefore readily detected via the fiber transmission. We show that the resulting absorption for a given surface coverage can be orders of magnitude higher than for conventional surface spectroscopy. As a demonstration, we present measurements on sub-monolayers of 3,4,9,10-perylene-tetracarboxylic dianhydride (PTCDA) molecules at ambient conditions, revealing the agglomeration dynamics on a second to minutes timescale.Comment: 4 pages, Fig.1a corrected y-axis, p.2 minor text changes to facilitate the understanding of eq. 4 and

Comparison of trace metal bioavailabilities in European coastal waters using mussels from Mytilus edulis

Mussels from Mytilus edulis complex were used as biomonitors of the trace metals Fe, Mn, Pb, Zn, and Cu at 17 sampling sites to assess the relative bioavailability of metals in coastal waters around the European continent. Because accumulated metal concentrations in a given area can differ temporally, data were corrected for the effect of season before large-scale spatial comparisons were made. The highest concentration of Fe was noted in the North Sea and of Mn in the Baltic. Increased tissue concentrations of Pb were recorded in the mussels from the Bay of Biscay and the Baltic Sea. Low concentrations of metals were determined in the mussels from the Mediterranean Sea and the Northern Baltic. Relatively low geographic variations of Cu and Zn indicate that mussels are able to partially regulate accumulated body concentrations, which means Cu and Zn are, to some extent, independent of environmental concentrations

Government Drug Testing: A Question of Reasonableness

The 1980s were noted for the escalation of the war on drugs. The dominant public perception was that drug use is a hideous evil that must be stopped, even at a great cost of public resources and personal liberties. Parents, politicians, and law enforcement officials rallied to battle drug use.2 Tremendous expenses and limited victories did not slow the war on drugs.\u27It cannot be disputed that drug abuse is widespread. More than seventy million Americans have experimented with illegal drugs, and twenty-three million currently use an illegal drug.4 The costs to society include drug-related crimes, accidents, lost productivity, increased health costs, and personal suffering.\u27 Drug users\u27 employers bear a large portion of the costs resulting from lost productivity, accidents, illnesses,and related expenses. Some employers have responded by requiring employees to be tested for drug use. The federal government, the Nation\u27s largest employer, is leading the way in drug testing.8 Serious fourth amendment issues arise, however, when the government forces employees to submit to drug testing as a condition of employment. The typical urinalysis of a government employee constitutes a search without a warrant, probable cause, or individualized suspicion that a particular employee violated a law or even a workplace rule. Nevertheless, the United States Supreme Court in 1989 upheld government drug testing programs in National Treasury Employees Union v. Von Raab and Skinner v. Railway Labor Executives\u27 Association.\u27 These cases were among a flood of recent federal and state court decisions allowing mandatory testing of federal, state, and municipal employees and private employees in pervasively regulated industries. These rulings have led several commentators to note that a drug exception to the fourth amendment may be emerging.\u27 Part II of this Note details the executive branch\u27s efforts to per-form drug tests on its employees and on private employees in pervasively regulated industries. Part III traces the Supreme Court\u27s recent erosion of traditional fourth amendment protections against search and seizure. Part IV describes the Supreme Court\u27s analysis of the executive branch\u27s efforts at drug testing. Part V examines the analytical structure that courts use to determine the constitutionality of drug testing by the government. Part VI traces judicial trends in unsettled legal areas. Finally, Part VII concludes that the Court\u27s reasonableness balancing test provides no concrete limit on government searches

The dynamical equivalence of modified gravity revisited

We revisit the dynamical equivalence between different representations of vacuum modified gravity models in view of Legendre transformations. The equivalence is discussed for both bulk and boundary space, by including in our analysis the relevant Gibbons-Hawking terms. In the f(R) case, the Legendre transformed action coincides with the usual Einstein frame one. We then re-express the R+f(G) action, where G is the Gauss-Bonnet term, as a second order theory with a new set of field variables, four tensor fields and one scalar and study its dynamics. For completeness, we also calculate the conformal transformation of the full Jordan frame R+f(G) action. All the appropriate Gibbons-Hawking terms are calculated explicitly.Comment: 17 pages; v3: Revised version. New comments added in Sections 3 & 5. New results added in Section 6. Version to appear in Class. Quantum Gravit