A simple model for the vibrational modes in honeycomb lattices

The classical lattice dynamics of honeycomb lattices is studied in the harmonic approximation. Interactions between nearest neighbors are represented by springs connecting them. A short and necessary introduction of the lattice structure is presented. The dynamical matrix of the vibrational modes is then derived, and its eigenvalue problem is solved analytically. The solution may provide deeper insight into the nature of the vibrational modes. Numerical results for the vibrational frequencies are presented. To show that how effective our method used for the case of honeycomb lattice is, we also apply it to triangular and square lattice structures. A few suggested problems are listed in the concluding section.Comment: 9 pages, 12 figures, submitted to American Journal of Physic

Electron-Phonon Scattering in Metallic Single-Walled Carbon Nanotubes

Electron scattering rates in metallic single-walled carbon nanotubes are studied using an atomic force microscope as an electrical probe. From the scaling of the resistance of the same nanotube with length in the low and high bias regimes, the mean free paths for both regimes are inferred. The observed scattering rates are consistent with calculations for acoustic phonon scattering at low biases and zone boundary/optical phonon scattering at high biases.Comment: 4 pages, 5 figure

To What Extent Does Text Simplification Entail a More Optimized Comprehension in Human-Oriented CNLs?

International audienceThe main goal of the current study is to develop a new cockpit controlled language for future Airbus aircraft by using psycholinguistic testing to optimize pilot comprehension. Pilots are aided by cockpit messages in order to deal with different situations during aircraft operations. The current controlled languages used on the Airbus aircraft have been carefully constructed to avoid ambiguity, inaccuracy, inconsistency, and inadequacy (Spaggiari, Beaujard, Cannesson (2003)) in order to ensure the safety of the navigation, operational needs, and the adaptability of the human-computer interaction to different situations in the cockpit. However, this controlled language has several limitations, mostly due to small screen sizes (limited number of words and sentences) and is highly codified (non-conforming to natural language syntax, color-coded and so on) so that it requires prior pilot training in order to achieve fluency. As future cockpit design is under construction, we might be looking at a different flexibility margin. Our experimentation plan is to go against the tide of common CNL (Controlled Natural Language) construction, in the sense that we will not be taking natural language and simplifying it, but rather taking a highly controlled codified language (therefore theoretically most simple) and " complexifying " it (bring it closer to natural language: theoretically most complex) in order to make it more accessible, and limit prior training needs

Phonon and plasmon excitation in inelastic electron tunneling spectroscopy of graphite

The inelastic electron tunneling spectrum (IETS)of highly oriented pyrolitic graphite (HOPG) has been measured with scanning tunneling spectroscopy (STS) at 6K. The observed spectral features are in very good agreement with the vibrational density of states (vDOS) of graphite calculated from first principles. We discuss the enhancement of certain phonon modes by phonon-assisted tunneling in STS based on the restrictions imposed by the electronic structure of graphite. We also demonstrate for the first time the local excitation of surface-plasmons in IETS which are detected at an energy of 40 meV.Comment: PRB rapid communication, submitte

Risk Factors for Urinary Complications After Renal Transplantation

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73788/1/j.1600-6143.2007.01790.x.pd

Der Einfluss von Haftungsunsicherheit auf den Sorgfaltsstandard

Optimal abgestimmte Vergütungs- und Haftungsregeln regen den Arzt zu einer effizienten Ressourcenverwendung und einem angemessenen Sorgfaltsniveau an. Die nicht nur in Deutschland zu beobachtende Abkehr von der Kostenerstattung hin zu Vergütungsformen mit mehr Kostenverantwortung für den Arzt zielt vornehmlich auf eine Ressourceneinsparung. Da sie zugleich aber das Sorgfaltsniveau bedroht, sollte ein geeigneter Haftungsanreiz bestehen. Im vorliegenden Papier beschreibe ich unter prospektiver Vergütung sowie den realistischen Annahmen von Haftungsunsicherheit und Unterschieden zwischen den Ärzten in der Sorgfaltswaltung einen wohlfahrtsoptimalen Sorgfaltsstandard. Dieser entscheidet unter dem herrschenden Verschuldensprinzip über die Verurteilung eines Arztes zu Schadensersatz und definiert damit den Haftungsanreiz. Es erweist sich, dass der Standard in Abhängigkeit von den Eigenschaften der Ärzte, der Wahrscheinlichkeit gerichtlicher Fehlentscheidungen und der relativen gesellschaftlichen Belastung durch Fahrlässigkeit und Defensivmedizin größer oder kleiner als das Wohlfahrtsoptimum unter Sicherheit ist. Dieses Ergebnis steht im Kontrast zu Empfehlungen von Experten, die in Anbetracht eines steigenden Haftungsdrucks eine Absenkung der Sorgfaltsanforderungen befürworten.Optimally designed reimbursement and liability rules lead physicians to practice efficiently and carefully. The introduction of supply-side cost sharing in Germany and elsewhere should therefore be complemented by an appropriate liability incentive. Otherwise, resources are used efficiently but the level of care is too low. Under the assumptions of liability uncertainty and heterogeneous physicians I derive an optimal standard of due care. In deciding whether a physician acted negligently or not, the standard defines the liability threat of the negligence rule. Dependent on the distribution of physicians' types, probabilities of type one and type two errors in courts' judgments, and society's costs of negligence and defensive medicine, this second-best standard may well be above the first-best level of care. In contrast, medico-legal experts currently plead for a decrease of the standard of due care to cope with an increase of liability threat

The role of the chemokine receptor CXCR4 in infection with feline immunodeficiency virus

Infection with feline immunodeficiency virus (FIV) leads to the development of a disease state similar to AIDS in man. Recent studies have identified the chemokine receptor CXCR4 as the major receptor for cell culture-adapted strains of FIV, suggesting that FIV and human immunodeficiency virus (HIV) share a common mechanism of infection involving an interaction between the virus and a member of the seven transmembrane domain superfamily of molecules. This article reviews the evidence for the involvement of chemokine receptors in FIV infection and contrasts these findings with similar studies on the primate lentiviruses HIV and SIV (simian immunodeficiency virus)

Amine functionalization of cholecyst-derived extracellular matrix with generation 1 PAMAM dendrimer

This document is the unedited author's version of a Submitted Work that was subsequently accepted for publication in Biomacromolecules, copyright © American Chemical Society after peer review. To access the final edited and published work, see http://pubs.acs.org/doi/pdf/10.1021/bm701055k.A method to functionalize cholecyst-derived extracellular matrix (CEM) with free amine groups was established in an attempt to improve its potential for tethering of bioactive molecules. CEM was incorporated with Generation-1 polyamidoamine (G1 PAMAM) dendrimer by using N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide and N-hydroxysuccinimide cross-linking system. The nature of incorporation of PAMAM dendrimer was evaluated using shrink temperature measurements, Fourier transform infrared (FTIR) assessment, ninhydrin assay, and swellability. The effects of PAMAM incorporation on mechanical and degradation properties of CEM were evaluated using a uniaxial mechanical test and collagenase degradation assay, respectively. Ninhydrin assay and FTIR assessment confirmed the presence of increasing free amine groups with increasing quantity of PAMAM in dendrimer-incorporated CEM (DENCEM) scaffolds. The amount of dendrimer used was found to be critical in controlling scaffold degradation, shrink temperature, and free amine content. Cell culture studies showed that fibroblasts seeded on DENCEM maintained their metabolic activity and ability to proliferate in vitro. In addition, fluorescence cell staining and scanning electron microscopy analysis of cell-seeded DENCEM showed preservation of normal fibroblast morphology and phenotype