1,979 research outputs found
Scanning tunneling microscopy and photoemission studies of self-organised Ag nanostructures on the N-modified Cu(001) surface
There has been a strong interest in methods of creating nanometer scale structures and in particular forming one and two-dimensional electron confinement structures. Self -organisation has been recognised as a promising way for growing large nanostructure domains with sufficiently regular size and spacing as required for the observation of quantum well states. We investigated the electronic properties and the morphology of Ag nano structures on c(2 x 2)-N/Cu(001) surface. This system is an example of epitaxial growth confined on nanoscale regions due to the occurrence of an adsorbate induced reconstruction. Using a combination of Scanning Tunneling Microscopy and Angle Resolved Photoemission Spectroscopy techniques we were able to determine the morphology and the growth mode of Ag on N -modified Cu(001) surface and the occurrence of quantum size effects in the electron properties of Ag nanostripes and nanoislands, evidenced in the observation of quantum well states
Estimation of fluence rate and absorbed dose rate due to gas bremsstrahlung from electron storage rings
Abstract Bremsstrahlung produced in electron storage rings by interactions with residual gas has been studied in the energy range 100–1000 MeV using the PLUKA code. Photon spectra and quantitative estimates of fluence rate and tissue absorbed dose rate are given. Simple equations are proposed for the fluence rate and the absorbed dose rate according to the results obtained
Symmetrization Techniques in Image Deblurring
This paper presents a couple of preconditioning techniques that can be used
to enhance the performance of iterative regularization methods applied to image
deblurring problems with a variety of point spread functions (PSFs) and
boundary conditions. More precisely, we first consider the anti-identity
preconditioner, which symmetrizes the coefficient matrix associated to problems
with zero boundary conditions, allowing the use of MINRES as a regularization
method. When considering more sophisticated boundary conditions and strongly
nonsymmetric PSFs, the anti-identity preconditioner improves the performance of
GMRES. We then consider both stationary and iteration-dependent regularizing
circulant preconditioners that, applied in connection with the anti-identity
matrix and both standard and flexible Krylov subspaces, speed up the
iterations. A theoretical result about the clustering of the eigenvalues of the
preconditioned matrices is proved in a special case. The results of many
numerical experiments are reported to show the effectiveness of the new
preconditioning techniques, including when considering the deblurring of sparse
images
Symbol Based Convergence Analysis in Block Multigrid Methods with applications for Stokes problems
The main focus of this paper is the study of efficient multigrid methods for
large linear system with a particular saddle-point structure. In particular, we
propose a symbol based convergence analysis for problems that have a hidden
block Toeplitz structure. Then, they can be investigated focusing on the
properties of the associated generating function , which
consequently is a matrix-valued function with dimension depending on the block
of the problem. As numerical tests we focus on the matrix sequence stemming
from the finite element approximation of the Stokes equation. We show the
efficiency of the methods studying the hidden block structure of
the obtained matrix sequence proposing an efficient algebraic multigrid method
with convergence rate independent of the matrix size. Moreover, we present
several numerical tests comparing the results with different known strategies
Intermuscular pocket for subcutaneous implantable cardioverter defibrillator: Single-center experience
AbstractThe subcutaneous implantable cardioverter defibrillator (S-ICD) is a novel device now accepted in clinical practice for treating ventricular arrhythmias. In 14 consecutive patients, S-ICD devices were placed in the virtual space between the anterior surface of the serratus anterior muscle and the posterior surface of the latissimus dorsi muscle. During a mean follow up of 9 months, no dislocations, infections, hematoma formations, or skin erosions were observed. Intermuscular implantation of the S-ICD could be a reliable, safe, and appealing alternative to the standard subcutaneous placement
The Rare Book Collection of the Library of the Italian National Institute of Health: from the past to the present
The Library of the Istituto Superiore di SanitĂ (ISS), the Italian National Institute of Health, is the main library for public health and biomedical research in Italy and holds a small but valuable special collection of ancient books. Known as the Rare Book Collection, this fund consists of over 1200 scientific printed volumes published between the XVI and the XIX century. The purpose of this paper is to illustrate the challenges and the process undertaken by the Library to share and digitalize this Collection
Preliminary Report on the Study of Beam-Induced Background Effects at a Muon Collider
Physics at a multi-TeV muon collider needs a change of perspective for the
detector design due to the large amount of background induced by muon beam
decays. Preliminary studies, based on simulated data, on the composition and
the characteristics of the particles originated from the muon decays and
reaching the detectors are presented here. The reconstruction performance of
the physics processes and has been investigated
for the time being without the effect of the machine induced background. A
preliminary study of the environment hazard due to the radiation induced by
neutrino interactions with the matter is presented using the FLUKA simulation
program
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