1,246 research outputs found
First principle theory of correlated transport through nano-junctions
We report the inclusion of electron-electron correlation in the calculation
of transport properties within an ab initio scheme. A key step is the
reformulation of Landauer's approach in terms of an effective transmittance for
the interacting electron system. We apply this framework to analyze the effect
of short range interactions on Pt atomic wires and discuss the coherent and
incoherent correction to the mean-field approach.Comment: 5 pages, 3 figure
Reliable Peer-to-Peer Access for Italian Citizens to Digital Government Services on the Internet
In the delivery of e-government services to citizens it should be clear that the viewpoint cannot simply be the standard one of client-supplier commonly used to provide services on the Internet. In a modern society it has rather to be the peer-to-peer approach which is typical of democracies, where institutions are equal to citizens in front of the law. But this is not yet a widely accepted standpoint in digital government efforts going on in many advanced countries in the world.
Italian government, in its ever increasing effort to provide citizens with easier access to online government services, has instead adopted and is pursuing this symmetric approach, which is going to represent a fundamental tool in the ongoing march towards e-democracy.
In this paper we describe the organizations involved in the process and the Information Technology (IT) infrastructure enabling the effective management of the whole process while ensuring the mandatory security functions in a democratic manner. Organizational complexity lies in the distribution of responsibilities for the management of people’s personal data among the more than 8000 Italian Municipalities and the need of keeping a centralized control on all processes dealing with identity of people.
Technical complexity stems from the need of efficiently supporting this distribution of responsibilities while ensuring, at the same time, interoperability of IT-based systems independent of technical choices of the organizations involved, and fulfillment of privacy constraints. The IT architecture defined for this purpose features a clear separation between security services, provided at an infrastructure level, and application services, exposed on the Internet as Web Services
Autocrine signals increase Ovine Mesenchymal Stem Cells migration throughAquaporin-1 and CXCR4 overexpression
Sheep is a relevant large animal model that is frequently used to test innovative
tissue engineering (TE) approaches especially for bone reconstruction. Mesenchymal
stem cells (MSCs) are used in TE applications because they represent key component of
adult tissue repair. Importantly, MSCs from different species show similar characteristics,
which facilitated their application in translational studies using animal models. Nowadays,
many researches are focusing on the use of ovine mesenchymal stem cells (oMSCs) in
orthopedic preclinical settings for regenerative medicine purposes. Therefore, there is a
need to amplify our knowledge on the mechanisms underlying the behaviour of these cells.
Recently, several studies have shown that MSC function is largely dependent on factors
that MSCs release in the environment as well as in conditioned medium (CM). It has been
demonstrated that MSCs through autocrine and paracrine signals are able to stimulate
proliferation, migration and differentiation of different type of cells including themselves. In
this study, we investigated the effects of the CM produced by oMSCs on oMSCs
themselves and we explored the signal pathways involved. We observed that CM caused
an enhancement of oMSC migration. Furthermore, we found that CM increased levels of
two membrane proteins involved in cell migration, Aquaporin 1 (AQP1) and C-X-C
chemokine receptor type 4 (CXCR4), and activated Akt and Erk intracellular signal
pathways
Macroscopic polarization and band offsets at nitride heterojunctions
Ab initio electronic structure studies of prototypical polar interfaces of
wurtzite III-V nitrides show that large uniform electric fields exist in
epitaxial nitride overlayers, due to the discontinuity across the interface of
the macroscopic polarization of the constituent materials. Polarization fields
forbid a standard evaluation of band offsets and formation energies: using new
techniques, we find a large forward-backward asymmetry of the offset (0.2 eV
for AlN/GaN (0001), 0.85 eV for GaN/AlN (0001)), and tiny interface formation
energies.Comment: RevTeX 4 pages, 2 figure
First Principles Analysis of Electron-Phonon Interaction in Graphene
The electron-phonon interaction in monolayer graphene is investigated by
using density functional perturbation theory. The results indicate that the
electron-phonon interaction strength is of comparable magnitude for all four
in-plane phonon branches and must be considered simultaneously. Moreover, the
calculated scattering rates suggest an acoustic phonon contribution that is
much weaker than previously thought, revealing the role of optical phonons even
at low energies. Accordingly it is predicted, in good agreement with a recent
measurement, that the intrinsic mobility of graphene may be more than an order
of magnitude larger than the high values reported in suspended samples.Comment: 12 pages, 4 figure
Assessing the quality of heart rate variability estimated from wrist and finger PPG: A novel approach based on cross-mapping method
The non-invasiveness of photoplethysmographic (PPG) acquisition systems, together with their cost-effectiveness and easiness of connection with IoT technologies, is opening up to the possibility of their widespread use. For this reason, the study of the reliability of PPG and pulse rate variability (PRV) signal quality has become of great scientific, technological, and commercial interest. In this field, sensor location has been demonstrated to play a crucial role. The goal of this study was to investigate PPG and PRV signal quality acquired from two body locations: finger and wrist. We simultaneously acquired the PPG and electrocardiographic (ECG) signals from sixteen healthy subjects (aged 28.5 ± 3.5, seven females) who followed an experimental protocol of affective stimulation through visual stimuli. Statistical tests demonstrated that PPG signals acquired from the wrist and the finger presented different signal quality indexes (kurtosis and Shannon entropy), with higher values for the wrist-PPG. Then we propose to apply the cross-mapping (CM) approach as a new method to quantify the PRV signal quality. We found that the performance achieved using the two sites was significantly different in all the experimental sessions (p < 0.01), and the PRV dynamics acquired from the finger were the most similar to heart rate variability (HRV) dynamics
Anisotropy and NMR spectroscopy
Abstract: In this paper, different aspects concerning anisotropy in Nuclear Magnetic Resonance (NMR) spectroscopy have been reviewed. In particular, the relevant theory has been presented, showing how anisotropy stems from the dependence of internal nuclear spin interactions on the molecular orientation with respect to the external magnetic field direction. The consequences of anisotropy in the use of NMR spectroscopy have been critically discussed: on one side, the availability of very detailed structural and dynamic information, and on the other side, the loss of spectral resolution. The experiments used to measure the anisotropic properties in solid and soft materials, where, in contrast to liquids, such properties are not averaged out by the molecular tumbling, have been described. Such experiments can be based either on static low-resolution techniques or on one- and two-dimensional pulse sequences exploiting Magic Angle Spinning (MAS). Examples of applications of NMR spectroscopy have been shown, which exploit anisotropy to obtain important physico-chemical information on several categories of systems, including pharmaceuticals, inorganic materials, polymers, liquid crystals, and self-assembling amphiphiles in water. Solid-state NMR spectroscopy can be considered, nowadays, one of the most powerful characterization techniques for all kinds of solid, either amorphous or crystalline, and semi-solid systems for the obtainment of both structural and dynamic properties on a molecular and supra-molecular scale. Graphic abstract: [Figure not available: see fulltext.
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