Opines stimulate induction of the vir genes of the Agrobacterium tumefaciens Ti plasmid.

Upon incubation of Agrobacterium tumefaciens A348 with acetosyringone, the vir genes encoded by the Ti (tumor-inducing) plasmid are induced. The addition of certain opines, including octopine, nopaline, leucinopine, and succinamopine, enhanced this induction 2- to 10-fold. The compounds mannopine, acetopine, arginine, pyruvate, and leucine did not stimulate the induction of the vir genes to such an extent. The enhancement of vir gene induction by opines depended on acetosyringone and the genes virA and virG. Opines stimulated the activity of the vir genes, the double-stranded cleavage of the T (transferred)-DNA at the border repeat sequences, and the production of T-strands by the bacterium. The transformation efficiency of cotton shoot tips was markedly increased by the addition of acetosyringone and nopaline at the time of infection

Reliability of fluctuation-induced transport in a Maxwell-demon-type engine

We study the transport properties of an overdamped Brownian particle which is simultaneously in contact with two thermal baths. The first bath is modeled by an additive thermal noise at temperature $T_A$. The second bath is associated with a multiplicative thermal noise at temperature $T_B$. The analytical expressions for the particle velocity and diffusion constant are derived for this system, and the reliability or coherence of transport is analyzed by means of their ratio in terms of a dimensionless P\'{e}clet number. We find that the transport is not very coherent, though one can get significantly higher currents.Comment: 14 pages, 5 figure

Can Quantum de Sitter Space Have Finite Entropy?

If one tries to view de Sitter as a true (as opposed to a meta-stable) vacuum, there is a tension between the finiteness of its entropy and the infinite-dimensionality of its Hilbert space. We invetsigate the viability of one proposal to reconcile this tension using $q$-deformation. After defining a differential geometry on the quantum de Sitter space, we try to constrain the value of the deformation parameter by imposing the condition that in the undeformed limit, we want the real form of the (inherently complex) quantum group to reduce to the usual SO(4,1) of de Sitter. We find that this forces $q$ to be a real number. Since it is known that quantum groups have finite-dimensional representations only for $q=$ root of unity, this suggests that standard $q$-deformations cannot give rise to finite dimensional Hilbert spaces, ruling out finite entropy for q-deformed de Sitter.Comment: 10 pages, v2: references added, v3: minor corrections, abstract and title made more in-line with the result, v4: published versio

Mg/Ti multilayers: structural, optical and hydrogen absorption properties

Mg-Ti alloys have uncommon optical and hydrogen absorbing properties, originating from a "spinodal-like" microstructure with a small degree of chemical short-range order in the atoms distribution. In the present study we artificially engineer short-range order by depositing Pd-capped Mg/Ti multilayers with different periodicities and characterize them both structurally and optically. Notwithstanding the large lattice parameter mismatch between Mg and Ti, the as-deposited metallic multilayers show good structural coherence. Upon exposure to H2 gas a two-step hydrogenation process occurs, with the Ti layers forming the hydride before Mg. From in-situ measurements of the bilayer thickness L at different hydrogen pressures, we observe large out-of-plane expansions of the Mg and Ti layers upon hydrogenation, indicating strong plastic deformations in the films and a consequent shortening of the coherence length. Upon unloading at room temperature in air, hydrogen atoms remain trapped in the Ti layers due to kinetic constraints. Such loading/unloading sequence can be explained in terms of the different thermodynamic properties of hydrogen in Mg and Ti, as shown by diffusion calculations on a model multilayered systems. Absorption isotherms measured by hydrogenography can be interpreted as a result of the elastic clamping arising from strongly bonded Mg/Pd and broken Mg/Ti interfaces

Magnetization study of Ni/Ag multilayers

The magnetic properties of Ni/Ag multilayers, prepared by evaporation in ultrahigh vacuum under controlled conditions, have been systematically studied by magnetic measurements. A spin-wave theory has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction Jb and surface exchange interaction JS for various Ni layer thicknesses have been obtained.The magnetic properties of Ni/Ag multilayers, prepared by evaporation in ultrahigh vacuum under controlled conditions, have been systematically studied by magnetic measurements. A spin-wave theory has been used to explain the temperature dependence of the magnetization and the approximate values for the bulk exchange interaction Jb and surface exchange interaction JS for various Ni layer thicknesses have been obtained

Vacuum Bubble in an Inhomogeneous Cosmology

We study the propagation of bubbles of new vacuum in a radially inhomogeneous Lemaitre-Tolman-Bondi background that includes a cosmological constant. This exemplifies the classical evolution of a tunneling bubble through a metastable state with curvature inhomogeneities, and will be relevant in the context of the Landscape. We demand that the matter profile in the LTB background satisfy the weak energy condition. For sample profiles that satisfy this restriction, we find that the evolution of the bubble (in terms of the physically relevant coordinates intrinsic to the shell) is largely unaffected by the prsence of local inhomogeneities. Our setup should also be a useful toy model for capturing the effects of ambient inhomogeneities on an inflating region.Comment: 31 pages, 21(!) figures, v2: minor changes, figures re-sized (might require zoom on some systems), references adde

Development of three dimensional constitutive theories based on lower dimensional experimental data

Most three dimensional constitutive relations that have been developed to describe the behavior of bodies are correlated against one dimensional and two dimensional experiments. What is usually lost sight of is the fact that infinity of such three dimensional models may be able to explain these experiments that are lower dimensional. Recently, the notion of maximization of the rate of entropy production has been used to obtain constitutive relations based on the choice of the stored energy and rate of entropy production, etc. In this paper we show different choices for the manner in which the body stores energy and dissipates energy and satisfies the requirement of maximization of the rate of entropy production that leads to many three dimensional models. All of these models, in one dimension, reduce to the model proposed by Burgers to describe the viscoelastic behavior of bodies.Comment: 23 pages, 6 figure

Vortices, Q-balls and Domain Walls on Dielectric M2-branes

We study BPS solitons in N=6 U(N) \times U(N) Chern-Simons-matter theory deformed by an F-term mass. The F-term mass generically breaks N=6 supersymmetry down to N=2. At vacua, M2-branes are polarized into a fuzzy S^3 forming a spherical M5-brane with topology \mathbf{R}^{1,2} \times S^3. The polarization is interpreted as Myers' dielectric effect caused by an anti-self-dual 4-form flux T_4 in the eleven-dimensional supergravity. Assuming a polarized M2-brane configuration, the model effectively reduces to the well-known abelian Chern-Simons-Higgs model studied in detail by Jackiw-Lee-Weinberg. We find that the potential for the fuzzy S^3 radius agrees with the one calculated from the M5-brane point of view at large N. This effective model admits not only BPS topological vortex and domain wall solutions but also non-topological solitons that keep 1/4 of the manifest N=2 supersymmetry. We also comment on the reduction of our configuration to ten dimensions.Comment: references added, minor modification

Studies on Tensile Characteristics of Kevlar/Jute/ Syntactic Foam Hybrid Sandwich Composites

In this study, a structured approach combining Taguchi experimental design and analysis of variance (ANOVA) is used to investigate the effects of skin material choice, material density, and percentage of reinforcement on the tensile properties of Kelvar/jute/synthetic foam hybrid sandwich composites. By deliberately changing these variables and examining how they affect tensile strength, modulus, and other important qualities, the goal is to maximize the mechanical performance of these composites. This work gives helpful insights into the interaction of these variables and their contribution to the overall tensile behavior of the composites through a series of carefully planned experiments and statistical studies. While ANOVA aids in quantifying the importance of individual components and interactions, the Taguchi approach makes it easier to identify the ideal parameter values. Making a substantial addition to the field of materials science and engineering, this combined method provides a solid framework for improving the design and engineering of lightweight, high-strength sandwich composites with customized features

Hybrid photonic crystal light-emitting diode renders 123% color conversion effective quantum yield

Colloidal quantum dots (QDs) have emerged as promising color conversion light emitters for solid-state lighting applications [Nat. Photonics 7, 13 (2012) [CrossRef] due to their emission tunability and near-unity photoluminescence quantum yields. In the current commercial LEDs, QDs are dispersed into an encapsulation layer in a far-field architecture, where the majority of the light emitted by the LED remains trapped within the epitaxy due to total internal reflection, drastically reducing the out-coupling efficiency. In this paper, we demonstrate a photonic quasi-crystal hybrid LED geometry that allows QD emitters to be placed in close proximity to the multiple quantum wells (MQWs) of the active area. This architecture greatly improves the coupling between MQWs and QDs, simultaneously allowing for a non-radiative resonant energy transfer between the MQWs and the QDs and near-field radiative coupling of trapped (guided) modes in the LED to the emitters. In this configuration, we demonstrate record-breaking effective quantum yields reaching 123% for single-color conversion LEDs and 110% for white light-emitting devices