A simple variational approach to the quantum Frenkel-Kontorova model

We present a simple and complete variational approach to the one-dimensional quantum Frenkel-Kontorova model. Dirac's time-dependent variational principle is adopted together with a Hatree-type many-body trial wavefunction for the atoms. The single-particle state is assumed to have the Jackiw-Kerman form. We obtain an effective classical Hamiltonian for the system which is simple enough for a complete numerical solution for the static ground state of the model. Numerical results show that our simple approach captures the essence of the quantum effects first observed in quantum Monte Carlo studies.Comment: 12 pages, 2 figure

Trans-esophageal endobronchial ultrasound-guided needle aspiration (EUS-B-NA) : a road map for the chest physician

The endobronchial ultrasound (EBUS) scope has been increasingly used in the gastrointestinal tract (EUS-B). Scientific data proves its efficacy and safety to provide a complete lung cancer staging, when combined with EBUS-TBNA, and in the diagnosis of para-esophageal lesions. There are multiple barriers to start performing EUS-B but probably the most important ones are related to knowledge and training, so new operators should follow a structured training curriculum. This review aims to reflect the best current knowledge regarding EUS-B and provide a road map to assist those who are incorporating the technique into their clinical practice

PLA/WOOD BIOCOMPOSITES: IMPROVING COMPOSITE STRENGTH BY CHEMICAL TREATMENT OF THE FIBERS

A resol type phenolic resin was prepared for the impregnation of wood particles used for the reinforcement of PLA. A preliminary study showed that the resin penetrates wood with rates depending on the concentration of the solution and on temperature. Treatment with a solution of 1 wt% resin resulted in a considerable increase of composite strength and decrease of water absorption. Composite strength improved as a result of increased inherent strength of the wood, but interfacial adhesion might be modified as well. When wood was treated with resin solutions of larger concentrations, the strength of the composites decreased, first slightly, then drastically to a very small value. A larger amount of resin results in a thick coating on wood with inferior mechanical properties. At large resin contents the mechanism of deformation changes; the thick coating breaks very easily leading to the catastrophic failure of the composites at very small loads

Composite absorbing potentials

The multiple scattering interferences due to the addition of several contiguous potential units are used to construct composite absorbing potentials that absorb at an arbitrary set of incident momenta or for a broad momentum interval.Comment: 9 pages, Revtex, 2 postscript figures. Accepted in Phys. Rev. Let

Court changes could salvage the Democrats

Editorial columns by David R. Bowen, U.S. Representative from Mississippi (D)\u27 1973-1983.https://scholarsjunction.msstate.edu/db-columns/1016/thumbnail.jp

TRANSITION IN AGRICULTURE – REVIEW ON SUBSIDY AND CUSTOM RATES EFFECTS IN APPLE PRODUCTION IN BOSNIA AND HERZEGOVINA

Kada govorimo o poljoprivredi u tranziciji, mislimo na poljoprivredu tranzicijskih zemalja, odnosno zemalja Srednje i Istočne Europe. Taj razvoj promatra se sa stajališta Europske unije, kako bi se uvidjele mogućnosti i ograničenja koja donosi pristupanje zemalja Srednje i Istočne Europe Uniji, ali i sa stajališta tranzicijskih zemalja. U ovoj analizi istražujemo neke posljedice promjena u poljoprivrednoj politici u slučaju Bosne i Hercegovine. Spoznaje bi trebale pomoći u prepoznavanju strateških smjernica za lokalni razvoj poljoprivrede i sela unutar sadašnjeg i budućeg okvira poljoprivrednih politika Bosne i Hercegovine. Prilagodbom poljoprivrednog sektora, ali i poljoprivredne politike treba poboljšati konkurentnost domaće poljoprivrede. Stoga u ovom radu primjenjujemo cost-benefi t analizu u ocjeni posljedica promjene subvencija i carinskih stopa u specifi čnom slučaju podizanja novih nasada i proizvodnje jabuka, odnosno u ocjeni prednosti i ograničenja poljoprivrede. Rezultati analize daju objektivniju sliku domaćeg poljoprivrednog sektora u međunarodnom okruženju.Speaking about transition in agriculture, we think on agriculture in transition countries, that is Central and Eastern European Countries. Such development is observed from the perspective of the European Union, discussing about possibilities as well as restrictions brought with accession of the CEECs to the Union, but also from the CEECs point of view. In this analysis we examine some consequences of changes in agricultural policy in the case of Bosnia and Herzegovina. The general conception should help in recognizing strategical guidelines for local development of agriculture and rural areas within the current and coming frame of Bosnia and Herzegovina. By the process of adjusting the agricultural sector, but also the agricultural policy, it should be improved competitiveness of domestic agriculture. That is why in this paper we use the cost-benefi t analysis in estimation the consequences of changes in subsidies and custom rates in specifi c case of construction new plantations and production of apples, that is in evaluation advantages and limitations of agriculture. The results of the analysis provide more objective illustration of domestic agricultural sector in internatioal environment

Impact of the absolute rutile fraction on TiO2 visible-light absorption and visible-light-promoted photocatalytic activity

Titanium dioxide is by far the most used semiconductor material for photocatalytic applications. Still, it is transparent to visible-light. Recently, it has been proved that a type-II band alignment for the rutile − anatase mixture would improve visible-light absorption. In this research paper we thoroughly characterised the real crystalline and amorphous phases of synthesised titanias – thermally treated at different temperatures to get distinct ratios of anatase-rutile-amorphous fraction – as well as that of three commercially available photocatalytic nano-TiO2. Optical spectroscopy showed that even a small fraction of rutile (2 wt%) is able to shift to lower energies the apparent optical band gap of an anatase-rutile mixed phase. But is this enough to attain a real photocatalytic activity promoted by merely visible-light? We tried to give an answer to that question. Photocatalytic activity was assessed in the liquid- and gas-solid phase (employing rhodamine B and 4-chlorophenol, and isopropanol, respectively, as the organic substances to degrade) using a light source irradiating exclusively in the visible-range. Photocatalytic activity results in the liquid-solid phase showed that a high surface hydroxylation led to specimen with superior visible light-promoted catalytic activity – i.e. dye and ligand-to-metal charge transfer complexes sensitisation effects, not photocatalysis sensu-strictu. On the other hand, the gas-solid phase results showed that a higher amount of the absolute rutile fraction (around 10 wt%), together with less recombination of the charge carriers, were more effective for both visible-light absorption and a “real” visible-light promoted photocatalytic oxidation of isopropanol.publishe

Parallel updating cellular automaton models of driven diffusive Frenkel-Kontorova-type systems

Three cellular automaton (CA) models of increasing complexity are introduced to model driven diffusive systems related to the generalized Frenkel-Kontorova (FK) models recently proposed by Braun [Phys.Rev.E58, 1311 (1998)]. The models are defined in terms of parallel updating rules. Simulation results are presented for these models. The features are qualitatively similar to those models defined previously in terms of sequentially updating rules. Essential features of the FK model such as phase transitions, jamming due to atoms in the immobile state, and hysteresis in the relationship between the fraction of atoms in the running state and the bias field are captured. Formulating in terms of parallel updating rules has the advantage that the models can be treated analytically by following the time evolution of the occupation on every site of the lattice. Results of this analytical approach are given for the two simpler models. The steady state properties are found by studying the stable fixed points of a closed set of dynamical equations obtained within the approximation of retaining spatial correlations only upto two nearest neighboring sites. Results are found to be in good agreement with numerical data.Comment: 26 pages, 4 eps figure

Tunable linear and quadratic optomechanical coupling for a tilted membrane within an optical cavity: theory and experiment

We present an experimental study of an optomechanical system formed by a vibrating thin semi-transparent membrane within a high-finesse optical cavity. We show that the coupling between the optical cavity modes and the vibrational modes of the membrane can be tuned by varying the membrane position and orientation. In particular we demonstrate a large quadratic dispersive optomechanical coupling in correspondence with avoided crossings between optical cavity modes weakly coupled by scattering at the membrane surface. The experimental results are well explained by a first order perturbation treatment of the cavity eigenmodes.Comment: 10 pages, 6 figure