424 research outputs found
X-ray imaging of spin currents and magnetisation dynamics at the nanoscale
Understanding how spins move in time and space is the aim of both fundamental
and applied research in modern magnetism. Over the past three decades, research
in this field has led to technological advances that have had a major impact on
our society, while improving the understanding of the fundamentals of spin
physics. However, important questions still remain unanswered, because it is
experimentally challenging to directly observe spins and their motion with a
combined high spatial and temporal resolution. In this article, we present an
overview of the recent advances in X-ray microscopy that allow researchers to
directly watch spins move in time and space at the microscopically relevant
scales. We discuss scanning X-ray transmission microscopy (STXM) at resonant
soft X-ray edges, which is available at most modern synchrotron light sources.
This technique measures magnetic contrast through the X-ray magnetic circular
dichroism (XMCD) effect at the resonant absorption edges, while focusing the
X-ray radiation at the nanometre scale, and using the intrinsic pulsed
structure of synchrotron-generated X-rays to create time-resolved images of
magnetism at the nanoscale. In particular, we discuss how the presence of spin
currents can be detected by imaging spin accumulation, and how the
magnetisation dynamics in thin ferromagnetic films can be directly imaged. We
discuss how a direct look at the phenomena allows for a deeper understanding of
the the physics at play, that is not accessible to other, more indirect
techniques. Finally, we present an overview of the exciting opportunities that
lie ahead to further understand the fundamentals of novel spin physics,
opportunities offered by the appearance of diffraction limited storage rings
and free electron lasers.Comment: 21 pages, 10 figure
Understanding the mechanism of binding between Gab2 and the C terminal SH3 domain from Grb2
Gab2 is a large disordered protein that regulates several cellular signalling
pathways and is overexpressed in different forms of cancer. Because of its disordered
nature, a detailed characterization of the mechanisms of recognition between Gab2
and its physiological partners is particularly difficult. Here we provide a detailed
kinetic characterization of the binding reaction between Gab2 and the C-terminal
SH3 domain of the growth factor receptor-bound protein 2 (Grb2). We demonstrate
that Gab2 folds upon binding following an induced fit type mechanism, whereby
recognition is characterized by the formation of an intermediate, in which Gab2 is
primarily disordered. In this scenario, folding of Gab2 into the bound conformation
occurs only after binding. However, an alanine scanning of the proline residues of
Gab2 suggests that the intermediate contains some degree of native-like structure,
which might play a role for the recognition event to take place. The results, which
represent a fundamental step forward in the understanding of this functional proteinprotein interaction, are discussed on the light of previous structural works on these
proteins
Total Cost of Ownership of melting furnaces: application of a prototypal model to aluminum die casting producers
After reviewing current literature on the Total Cost of Ownership (TCO) methodology and its application to manufacturing contexts, we propose an application of this methodology to secondary aluminum melting furnaces. A prototypal calculation model is created and tested through three case studies of aluminum die casting companies. We illustrate the model structure and input data used to calculate the studied furnaces TCO. At last, results of the model test are presented and possible developments of the prototypal model are briefly discussed
Power and linewidth of propagating and localized modes in nanocontact spin-torque oscillators
Integrated power and linewidth of a propagating and a self-localized spin
wave modes excited by spin-polarized current in an obliquely magnetized
magnetic nanocontact are studied experimentally as functions of the angle
between the external bias magnetic field and the nanocontact plane.
It is found that the power of the propagating mode monotonically increases with
, while the power of the self-localized mode has a broad maximum near
deg, and exponentially vanishes near the critical angle
deg, at which the localized mode disappears. The linewidth of
the propagating mode in the interval of angles deg, where only
this mode is excited, is adequtely described by the existing theory, while in
the angular interval where both modes can exist the observed linewidth of both
modes is substantially broadened due to the telegraph switching between the
modes. Numetical simulations and an approximate analytical model give good
semi-quantitative description of the observed results.Comment: 8 pages, 6 figure
Experimental evidence of self-localized and propagating spin wave modes in obliquely magnetized current-driven nanocontacts
Through detailed experimental studies of the angular dependence of spin wave
excitations in nanocontact-based spin-torque oscillators, we demonstrate that
two distinct spin wave modes can be excited, with different frequency,
threshold currents and frequency tuneability. Using analytical theory and
micromagnetic simulations we identify one mode as an exchange-dominated
propagating spin wave, and the other as a self-localized nonlinear spin wave
bullet. Wavelet-based analysis of the simulations indicates that the apparent
simultaneous excitation of both modes results from rapid mode hopping induced
by the Oersted field.Comment: 5 pages, 3 figure
Usefulness of an app in improving oral hygiene compliance in adolescent orthodontic patients
Objective: To evaluate the influence of an app-based approach in a protocol for domestic oral hygiene maintenance in a group of adolescent patients wearing fixed multibracket appliances. Materials and Methods: Eighty adolescent patients scheduled to start an orthodontic multibracket treatment were randomly divided into two groups of 40. Plaque index (PI), gingival index (GI), white spots (WS), and caries presence were recorded in all patients, and they were instructed regarding domestic oral hygiene maintenance on the day of braces application (t0) and every 3 months (t1, t2, t3, t4) during the first year of treatment. Study group (SG) patients were enrolled in a WhatsApp chat room-based competition and instructed to share monthly with the other participants two selfphotographs (selfies) showing their oral hygiene status. Results: SG patient participation in the chat room was regular and active throughout the observation period. At t3, t3, and t4, SG patients had significantly lower values of both PI and GI and a lower incidence of new WS and caries, compared with the control group. Conclusion: Integration of new "social" technologies in a standard oral hygiene motivation protocol is effective in improving compliance of adolescent patients and in improving their oral health status during orthodontic multibracket treatment
Numerical modelling of wave propagation phenomena in thermo-poroelastic media via discontinuous Galerkin methods
We present and analyze a high-order discontinuous Galerkin method for the
space discretization of the wave propagation model in thermo-poroelastic media.
The proposed scheme supports general polytopal grids. Stability analysis and
-version error estimates in suitable energy norms are derived for the
semi-discrete problem. The fully-discrete scheme is then obtained based on
employing an implicit Newmark- time integration scheme. A wide set of
numerical simulations is reported, both for the verification of the theoretical
estimates and for examples of physical interest. A comparison with the results
of the poroelastic model is provided too, highlighting the differences between
the predictive capabilities of the two models
An efficient tool for the assisted design of SAR ADCs capacitive DACs
The optimal design of SAR ADCs requires the accurate estimate of nonlinearity and parasitic capacitance effects in the feedback charge redistribution DAC. Since both contributions depend on the specific array topology, complex calculations, custom modeling and heavy simulations in common circuit design environments are often required. This paper presents a MATLAB-based numerical environment to assist the design of the charge redistribution DACs adopted in SAR ADCs. The tool performs both parametric and statistical simulations taking into account capacitive mismatch and parasitic capacitances computing both differential and integral nonlinearity (DNL, INL). An excellent agreement is obtained with the results of circuit simulators (e.g. Cadence Spectre) featuring up to 10^4 shorter simulation time, allowing statistical simulations that would be otherwise impracticable. The switching energy and SNDR degradation due to static nonlinear effects are also estimated. Simulations and measurements on three designed and two fabricated prototypes confirm that the proposed tool can be used as a valid instrument to assist the design of a charge redistribution SAR ADC and to predict its static and dynamic metrics
Incisal apical root resorption evaluation after low-friction orthodontic treatment using two-dimensional radiographic imaging and trigonometric correction
BACKGROUND:
Root resorption shall be taken into consideration during every orthodontic treatment, and it can be effected by the use of different techniques, such as the application of low friction mechanics. However, its routinely assessment on orthopantomography has limitations related to distortions and changes in dental inclination.
AIM:
The aim of this investigation was to evaluate the severity of apical root resorption of maxillary and mandibular incisors after low-friction orthodontic treatment, using the combination of panoramic and lateral radiographs, and applying a trigonometric correction.
SETTINGS AND DESIGN:
A hospital based Retrospective study at the orthodontic Department (Dental School, University of Brescia, Spedali Civili di Brescia, Brescia, Italy).
MATERIALS AND METHODS:
Ninety-three subjects (53 females and 40 males; mean age, 14 years) with mild teeth crowding were treated without extractions by the same operator using a low-friction fixed appliance following an integrated straight wire (ISW) protocol. The pre- and post-treatment tooth lengths of the maxillary and mandibular incisors were measured on panoramic radiographs. A trigonometric factor of correction for the pre-treatment length was calculated based on the difference between the pre and post-treatment incisal inclination on lateral cephalograms.
STATISTICAL ANALYSIS:
The changes in lengths were investigated using the Student's t-test for paired values (p<0.05).
RESULTS:
Maxillary central incisors showed no changes (0.3%, 0.6%), maxillary lateral incisors showed a small increase (1.4%, 1.8%) that was attributed to the completion of root development in younger patients, mandibular central and lateral incisors underwent slight resorption (-3.1%, -3.4%). A statistically significant difference was found for the mandibular incisors but not for the maxillary ones.
CONCLUSION:
In patients with mild crowding and consequent low amount of root movement, a low-friction orthodontic treatment can lead to slight apical root resorption, mainly involving lower incisors. The use of a trigonometric correction in the panoramic radiograph analysis may reduce the limitations of this 2D evaluation
NTMpy: An open source package for solving coupled parabolic differential equations in the framework of the three-temperature model
The NTMpy code package allows for simulating the one-dimensional thermal
response of multilayer samples after optical excitation, as in a typical
pump-probe experiment. Several Python routines are combined and optimized to
solve coupled heat diffusion equations in one dimension, on arbitrary piecewise
homogeneous material stacks, in the framework of the so-called
three-temperature model. The energy source deposited in the material is
modelled as a light pulse of arbitrary cross-section and temporal profile. A
transfer matrix method enables the calculation of realistic light absorption in
presence of scattering interfaces as in multilayer samples. The open source
code is fully object-oriented to enable a user-friendly and intuitive interface
for adjusting the physically relevant input parameters. Here, we describe the
mathematical background of the code, we lay out the workflow, and we validate
the functionality of our package by comparing it to commercial software, as
well as to experimental transient reflectivity data recorded in a pump-probe
experiment with femtosecond light pulses
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