A new exactly integrable hypergeometric potential for the Schr\"odinger equation

We introduce a new exactly integrable potential for the Schr\"odinger equation for which the solution of the problem may be expressed in terms of the Gauss hypergeometric functions. This is a potential step with variable height and steepness. We present the general solution of the problem, discuss the transmission of a quantum particle above the barrier, and derive explicit expressions for the reflection and transmission coefficients

Pre-determining the location of electromigrated gaps by nonlinear optical imaging

In this paper we describe a nonlinear imaging method employed to spatially map the occurrence of constrictions occurring on an electrically-stressed gold nanowire. The approach consists at measuring the influence of a tightly focused ultrafast pulsed laser on the electronic transport in the nanowire. We found that structural defects distributed along the nanowire are efficient nonlinear optical sources of radiation and that the differential conductance is significantly decreased when the laser is incident on such electrically-induced morphological changes. This imaging technique is applied to pre-determined the location of the electrical failure before it occurs.Comment: 3 figure

Behaviors of susceptible-infected epidemics on scale-free networks with identical infectivity

In this article, we proposed a susceptible-infected model with identical infectivity, in which, at every time step, each node can only contact a constant number of neighbors. We implemented this model on scale-free networks, and found that the infected population grows in an exponential form with the time scale proportional to the spreading rate. Further more, by numerical simulation, we demonstrated that the targeted immunization of the present model is much less efficient than that of the standard susceptible-infected model. Finally, we investigated a fast spreading strategy when only local information is available. Different from the extensively studied path finding strategy, the strategy preferring small-degree nodes is more efficient than that preferring large-degree nodes. Our results indicate the existence of an essential relationship between network traffic and network epidemic on scale-free networks.Comment: 5 figures and 7 page

Growth of high quality, high density single-walled carbon nanotube forests on copper foils

We demonstrate the growth of high quality single-walled carbon nanotube (SWCNT) forests on commercial Cu foils by cold-wall chemical vapor deposition. Time-of-flight secondary ion mass spectrometry was employed to study the effect of annealing on the catalyst evolution with or without an AlOₓ barrier layer. X-ray photoelectron spectroscopy was used to investigate the chemical states of the catalyst and the barrier layer. SWCNT forests can be reproducibly grown on Cu foils sputter-coated with Al and Fe layers as thin as 6 nm and 0.4 nm, respectively. Al transforms into AlOₓ on exposure to air and during annealing. Most importantly, such a thin AlOₓ barrier layer ensures not only the growth of SWCNTs but also an Ohmic contact between the as grown SWCNTs and the Cu base as measured by a two-point probe station. The as-grown SWCNTs exhibit a bimodal distribution of diameters ranging from 0.6 to 4.5 nm, with two peaks centered at 0.8 nn and 2.6 nm, respectively.This work supported by Honda Research Institute USA Inc. Sugime H. acknowledges a research fellowship from the Japanese Society for the Promotion of Science (JSPS).This is the author accepted manuscript. The final version is available from Elsevier via http://dx.doi.org/10.1016/j.carbon.2015.11.04

SN 2006gy: was it really extra-ordinary?

We present an optical photometric and spectroscopic study of the very luminous type IIn SN 2006gy for a time period spanning more than one year. In photometry, a broad, bright (M_R~-21.7) peak characterizes all BVRI light curves. Afterwards, a rapid luminosity fading is followed by a phase of slow luminosity decline between day ~170 and ~237. At late phases (>237 days), because of the large luminosity drop (>3 mag), only upper visibility limits are obtained in the B, R and I bands. In the near-infrared, two K-band detections on days 411 and 510 open new issues about dust formation or IR echoes scenarios. At all epochs the spectra are characterized by the absence of broad P-Cygni profiles and a multicomponent Halpha profile, which are the typical signatures of type IIn SNe. After maximum, spectroscopic and photometric similarities are found between SN 2006gy and bright, interaction-dominated SNe (e.g. SN 1997cy, SN 1999E and SN 2002ic). This suggests that ejecta-CSM interaction plays a key role in SN 2006gy about 6 to 8 months after maximum, sustaining the late-time-light curve. Alternatively, the late luminosity may be related to the radioactive decay of ~3M_sun of 56Ni. Models of the light curve in the first 170 days suggest that the progenitor was a compact star (R~6-8 10^(12)cm, M_ej~5-14M_sun), and that the SN ejecta collided with massive (6-10M_sun), opaque clumps of previously ejected material. These clumps do not completely obscure the SN photosphere, so that at its peak the luminosity is due both to the decay of 56Ni and to interaction with CSM. A supermassive star is not required to explain the observational data, nor is an extra-ordinarily large explosion energy.Comment: 33 pages, 8 figures. Accepted by ApJ. Paper with high-resolution figures available at http://web.oapd.inaf.it/supern/sn2006gy_astroph/agnoletto_2006gy.pd