Inelastic electron tunneling via molecular vibrations in single-molecule transistors

In single-molecule transistors, we observe inelastic cotunneling features that correspond energetically to vibrational excitations of the molecule, as determined by Raman and infrared spectroscopy. This is a form of inelastic electron tunneling spectroscopy of single molecules, with the transistor geometry allowing in-situ tuning of the electronic states via a gate electrode. The vibrational features shift and change shape as the electronic levels are tuned near resonance, indicating significant modification of the vibrational states. When the molecule contains an unpaired electron, we also observe vibrational satellite features around the Kondo resonance.Comment: 5 pages, 4 figures. Supplementary information available upon reques

Experimental and theoretical characterization of microbial bioanodes formed in pulp and paper mill effluent in electrochemically controlled conditions

Microbial bioanodes were formed in pulp and paper effluent on graphite plate electrodes under constant polarization at -0.3 V/SCE, without any addition of nutriment or substrate. The bioanodes were characterized in 3-electrode set-ups, in continuous mode, with hydraulic retention times from 6 to 48 h and inlet COD from 500 to 5200 mg/L. Current densities around 4 A/m2 were obtained and voltammetry curves indicated that 6 A/m2 could be reached at +0.1 V/SCE. A theoretical model was designed, which allowed the effects of HRT and COD to be distinguished in the complex experimental data obtained with concomitant variations of the two parameters. COD removal due to the electrochemical process was proportional to the hydraulic retention time and obeyed a Michaelis–Menten law with respect to the COD of the outlet flow, with a Michaelis constant KCOD of 400 mg/L. An inhibition effect occurred above inlet COD of around 3000 mg/L

On the basis property for the root vectors of some nonselfadjoint operators

When does the root system of a nonselfadjoint operator form a Riesz basis of a Hilbert space? This question is discussed in the paper.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/24433/1/0000706.pd

N=4 Twisted Superspace from Dirac-Kahler Twist and Off-shell SUSY Invariant Actions in Four Dimensions

We propose N=4 twisted superspace formalism in four dimensions by introducing Dirac-Kahler twist. In addition to the BRST charge as a scalar counter part of twisted supercharge we find vector and tensor twisted supercharges. By introducing twisted chiral superfield we explicitly construct off-shell twisted N=4 SUSY invariant action. We can propose variety of supergauge invariant actions by introducing twisted vector superfield. We may, however, need to find further constraints to identify twisted N=4 super Yang-Mills action. We propose a superconnection formalism of twisted superspace where constraints play a crucial role. It turns out that N=4 superalgebra of Dirac-Kahler twist can be decomposed into N=2 sectors. We can then construct twisted N=2 super Yang-Mills actions by the superconnection formalism of twisted superspace in two and four dimensions.Comment: 62page

Current Exchanges and Unconstrained Higher Spins

The (Fang-)Fronsdal formulation for free fully symmetric (spinor-) tensors rests on (gamma-)trace constraints on gauge fields and parameters. When these are relaxed, glimpses of the underlying geometry emerge: the field equations extend to non-local expressions involving the higher-spin curvatures, and with only a pair of additional fields an equivalent ``minimal'' local formulation is also possible. In this paper we complete the discussion of the ``minimal'' formulation for fully symmetric (spinor-) tensors, constructing one-parameter families of Lagrangians and extending them to (A)dS backgrounds. We then turn on external currents, that in this setting are subject to conventional conservation laws and, by a close scrutiny of current exchanges in the various formulations, we clarify the precise link between the local and non-local versions of the theory. To this end, we first show the equivalence of the constrained and unconstrained local formulations, and then identify a unique set of non-local Lagrangian equations which behave in exactly the same fashion in current exchanges.Comment: 37 pages, Latex. Typos corrected, note and references added. Final version to appear in Nucl. Phys.

Lingual Lymphangioma Ablation With High Power Diode Laser: A Case Report

Introduction: Lymphangioma is a rare vascular anomaly that affects the lymphatic vessels. Its etiology is not yet clear and it usually occurs in the head and neck region. This pathology is commonly diagnosed in childhood and there is no consensus about the most effective treatment of it.Case Report: We report a case of lymphangioma located on the dorsum of the tongue in a 9-year-old boy, with the clinical appearance of small transparent vesicles similar to “frog-eggs”. The diagnosis was defined according to the clinical aspect and ultrasound images. The treatment performed consisted of two sessions of ablation with a high-power diode laser.Conclusion: High-intensity diode laser ablation was a safe and effective tool for the treatment of this lesion in the tongue, which provided the patient with a faster, efficient transoperative period and a more comfortable postoperative period.

Branes: from free fields to general backgrounds

Motivated by recent developments in string theory, we study the structure of boundary conditions in arbitrary conformal field theories. A boundary condition is specified by two types of data: first, a consistent collection of reflection coefficients for bulk fields on the disk; and second, a choice of an automorphism $\omega$ of the fusion rules that preserves conformal weights. Non-trivial automorphisms $\omega$ correspond to D-brane configurations for arbitrary conformal field theories. The choice of the fusion rule automorphism $\omega$ amounts to fixing the dimension and certain global topological features of the D-brane world volume and the background gauge field on it. We present evidence that for fixed choice of $\omega$ the boundary conditions are classified as the irreducible representations of some commutative associative algebra, a generalization of the fusion rule algebra. Each of these irreducible representations corresponds to a choice of the moduli for the world volume of the D-brane and the moduli of the flat connection on it.Comment: 56 pages, LaTeX2e. Typos corrected; two references adde

One-dimensional metallic behavior of the stripe phase in La2−x_{2-x}Srx_xCuO4_4

Using an exact diagonalization method within the dynamical mean-field theory we study stripe phases in the two-dimensional Hubbard model. We find a crossover at doping $\delta\simeq 0.05$ from diagonal stripes to vertical site-centered stripes with populated domain walls, stable in a broad range of doping, $0.05<\delta<0.17$. The calculated chemical potential shift $\propto -\delta^2$ and the doping dependence of the magnetic incommensurability are in quantitative agreement with the experimental results for doped La$_{2-x}$Sr$_x$CuO$_4$. The electronic structure shows one-dimensional metallic behavior along the domain walls, and explains the suppression of spectral weight along the Brillouin zone diagonal.Comment: 4 pages, 4 figure

Gauge Equivalence in Two--Dimensional Gravity

Two-dimensional quantum gravity is identified as a second-class system which we convert into a first-class system via the Batalin-Fradkin (BF) procedure. Using the extended phase space method, we then formulate the theory in most general class of gauges. The conformal gauge action suggested by David, Distler and Kawai is derived from a first principle. We find a local, light-cone gauge action whose Becchi-Rouet-Stora-Tyutin invariance implies Polyakov's curvature equation $\partial_{-}R=\partial_{-}^{3}g_{++}=0$, revealing the origin of the $SL(2,R)$ Kac-Moody symmetry. The BF degree of freedom turns out be dynamically active as the Liouville mode in the conformal gauge, while in the light-cone gauge the conformal degree of freedom plays that r{\^o}le. The inclusion of the cosmological constant term in both gauges and the harmonic gauge-fixing are also considered.Comment: 30 pages, KANAZAWA 93-