Impurity effects on Fabry-Perot physics of ballistic carbon nanotubes

We present a theoretical model accounting for the anomalous Fabry-Perot pattern observed in the ballistic conductance of a single-wall carbon nanotubes. Using the scattering field theory, it is shown that the presence of a limited number of impurities along the nanotube can be identified by a measurement of the conductance and their position determined. Impurities can be made active or silent depending on the interaction with the substrate via the back-gate. The conceptual steps for designing a bio-molecules detector are briefly discussed.Comment: 4 pages, 4 figure

The CHORUS experiment: a status report

sample of 2622 fully analyzed 1 $\mu^{-}$ events, has been presented, confirming that the CHORUS proposal sensitivity for Run I \mbox{($sin^{2}2\theta_{\mu\tau}\le 3\cdot 10^{-4}$)} is reachable

Labor market regimes and monetary policy

In this paper we propose straightforward extensions of multi-union, monopolistic competition models appearing in the recent literature on the macroeconomic effects of monetary policy. We extend these models from the Stackelberg equilibrium to the Nash equilibrium under variations in labor market regime in order to evaluate propositions about non-neutrality of monetary policy.policy game monetary policy neutrality trade union monopolistic competition

Effective Lagrangian for Heavy and Light Mesons: Semileptonic Decays

We introduce an effective lagrangian including negative and positive parity heavy mesons containing a heavy quark, light pseudoscalars, and light vector resonances, with their allowed interactions, using heavy quark spin-flavour symmetry, chiral symmetry, and the hidden symmetry approach for light vector resonances. On the basis of such a lagrangian, by considering the allowed weak currents and by including the contributions from the nearest unitarity poles we calculate the form factors for semileptonic decays of $B$ and $D$ mesons into light pseudoscalars and light vector resonances. The available data, together with some additional assumptions, allow for a set of predictions in the different semileptonic channels, which can be compared with those following {}from different approaches. A discussion of non-dominant terms in our approach, which attempts at including a rather complete dynamics, will however have to wait till more abundant data become available.Comment: LaTeX (style article), 19 pages, UGVA-DPT 1992/11-790, BARI-TH/92-12

A local field emission study of partially aligned carbon-nanotubes by AFM probe

We report on the application of Atomic Force Microscopy (AFM) for studying the Field Emission (FE) properties of a dense array of long and vertically quasi-aligned multi-walled carbon nanotubes grown by catalytic Chemical Vapor Deposition on a silicon substrate. The use of nanometric probes enables local field emission measurements allowing investigation of effects non detectable with a conventional parallel plate setup, where the emission current is averaged on a large sample area. The micrometric inter-electrode distance let achieve high electric fields with a modest voltage source. Those features allowed us to characterize field emission for macroscopic electric fields up to 250 V/$\mu$m and attain current densities larger than 10$^5$ A/cm$^2$. FE behaviour is analyzed in the framework of the Fowler-Nordheim theory. A field enhancement factor $\gamma \approx$ 40-50 and a turn-on field $E_{turn-on} \sim$15 V/$\mu$m at an inter-electrode distance of 1 $\mu$m are estimated. Current saturation observed at high voltages in the I-V characteristics is explained in terms of a series resistance of the order of M$\Omega$. Additional effects as electrical conditioning, CNT degradation, response to laser irradiation and time stability are investigated and discussed

Field emission from single multi-wall carbon nanotubes

Electron field emission characteristics of individual multiwalled carbon nanotubes have been investigated by a piezoelectric nanomanipulation system operating inside a scanning electron microscopy chamber. The experimental setup ensures a high control capability on the geometric parameters of the field emission system (CNT length, diameter and anode-cathode distance). For several multiwalled carbon nanotubes, reproducible and quite stable emission current behaviour has been obtained with a dependence on the applied voltage well described by a series resistance modified Fowler-Nordheim model. A turn-on field of about 30 V/um and a field enhancement factor of around 100 at a cathode-anode distance of the order of 1 um have been evaluated. Finally, the effect of selective electron beam irradiation on the nanotube field emission capabilities has been extensively investigated.Comment: 16 pages, 5 figure

16: Long-Term Results of a Gitmo Retrospective Study on Hematopoietic Stem Cell Transplantation (HSCT) for Paroxysmal Nocturnal Hemoglobinuria (PNH)

n/

Primary Mandibular Condyle Xanthoma: Case Report and Literature Review

Bone xanthoma is a rare benign primary bone lesion histologically characterized by sheets of foamy cells which are macrophages with a cytoplasm filled with droplets of fat. It is usually associated with endocrine or metabolic diseases, in the absence of which the lesion is called primary xanthoma. Because of the lack of pathognomonic radiologic and clinical features, they require a differential diagnosis with a broad spectrum of lesions with a varying degree of malignant potential. We describe a case of primary mandibular xanthoma of a 16-year-old girl without typical cutaneous manifestations and alterations in lipid values. The temporomandibular joint involvement at the mandibular condyle is peculiar in the case described here. We present even a qualitative systematic review of the literature on primary xanthoma of the jaws in others to draw up treatment guidelines

Local probing of the field emission stability of vertically aligned multiwalled carbon nanotubes

Metallic cantilever in high vacuum atomic force microscope has been used as anode for field emission experiments from densely packed vertically aligned multi-walled carbon nanotubes. The high spatial resolution provided by the scanning probe technique allowed precise setting of the tip-sample distance in the submicron region. The dimension of the probe (curvature radius below 50nm) allowed to measure current contribution from sample areas smaller than 1um^2. The study of long-term stability evidenced that on these small areas the field emission current remains stable (within 10% fluctuations) several hours (at least up to 72 hours) at current intensities between 10-5A and 10-8A. Improvement of the current stability has been observed after performing long-time Joule heating conditioning to completely remove possible adsorbates on the nanotubes.Comment: 15 pages, 7 figure