94 research outputs found
Broken Ergodicity in classically chaotic spin systems
A one dimensional classically chaotic spin chain with asymmetric coupling and
two different inter-spin interactions, nearest neighbors and all-to-all, has
been considered. Depending on the interaction range, dynamical properties, as
ergodicity and chaoticity are strongly different. Indeed, even in presence of
chaoticity, the model displays a lack of ergodicity only in presence of all to
all interaction and below an energy threshold, that persists in the
thermodynamical limit. Energy threshold can be found analytically and results
can be generalized for a generic XY model with asymmetric coupling.Comment: 6 pages, 3 figure
Facial Asymmetry Detected with 3D Methods in Orthodontics: A Systematic Review
Background: Historically, the development of two-dimensional (2D) imaging techniques forerun that of three-dimensional (3D) ones. Some 2D methods are still considered valid and effective to diagnose facial asymmetry but 3D techniques may provide more precise and accurate measurements.
Objective: The aim of this work is to analyze the accuracy and reliability of the imaging techniques available for the diagnosis of facial asymmetry in orthodontics and find the most reliable.
Methods: A search strategy was implemented using PubMed (National Library of Medicine, NCBI).
Results: A total of 3201 papers were identified in electronic searches. 90 articles, available in full text, were included in the qualitative synthesis consisting of 8 reviews on the diagnosis of facial asymmetry, 22 in vivo and in vitro studies on 2D methods and 60 in vivo and in vitro studies on 3D methods to quantify the asymmetry.
Conclusion: 2D techniques include X-ray techniques such as posterior-anterior cephalogram, which still represents the first level exam in the diagnosis of facial asymmetry. 3D techniques represent the second level exam in the diagnosis of facial asymmetry. The most current used techniques are CBCT, stereophotogrammetry, laser scanning, 3D optical sensors and contact digitization. The comparison between bilateral parameters (linear distances, angles, areas, volumes and contours) and the calculation of an asymmetry index represent the best choices for clinicians who use CBCT. The creation of a color-coded distance map seems to represent the most accurate, reliable and validated methods for clinicians who use stereophotogrammetry, laser scanning and 3D optical sensors
Evidence of vectorial photoelectric effect on Copper
Quantum Efficiency (QE) measurements of single photon photoemission from a
Cu(111) single crystal and a Cu polycrystal photocathodes, irradiated by 150
fs-6.28 eV laser pulses, are reported over a broad range of incidence angle,
both in s and p polarizations. The maximum QE (\simeq 4\times10^{-4}) for
polycrystalline Cu is obtained in p polarization at an angle of incidence
{\theta} = 65deg. We observe a QE enhancement in p polarization which can not
be explained in terms of optical absorption, a phenomenon known as vectorial
photoelectric effect. Issues concerning surface roughness and symmetry
considerations are addressed. An explanation in terms of non local conductivity
tensor is proposed.Comment: 3 pages, 3 figure
Short-wavelength four wave mixing experiments using single and two-color schemes at FERMI
The development of ultra-bright extreme ultraviolet (EUV) and X-ray free electron laser (FEL) sources has enabled the extension of wave-mixing approaches into the short wavelength regime. Such a class of experiments relies upon nonlinear interactions among multiple light pulses offering a unique tool for exploring the dynamics of ultrafast processes and correlations between selected excitations at relevant length and time scales adding elemental and site selectivity as well. Besides the availability of a suitable photon source, the implementation of wave mixing methodology requires efforts in developing the instrumental set-up. We have realized at the FERMI FEL two dedicated set-ups to handle multiple FEL beams with preselected parameters in a non-collinear fashion and control their interaction sequence at the target. These unique apparatuses, combined with the exceptional characteristics of the seeded FERMI FEL, have allowed us to make the first steps into this field and further advances are foreseen in the near future
2015 ACVIM Small Animal Consensus Statement on Seizure Management in Dogs
This report represents a scientific and working clinical consensus statement on seizure management in dogs based on current literature and clinical expertise. The goal was to establish guidelines for a predetermined, concise, and logical sequential approach to chronic seizure management starting with seizure identification and diagnosis (not included in this report), reviewing decisionâmaking, treatment strategies, focusing on issues related to chronic antiepileptic drug treatment response and monitoring, and guidelines to enhance patient response and quality of life. Ultimately, we hope to provide a foundation for ongoing and future clinical epilepsy research in veterinary medicine
Towards jitter-free pump-probe measurements at seeded free electron laser facilities
X-ray free electron lasers (FEL) coupled with optical lasers have opened unprecedented opportunities for studying ultrafast dynamics in matter. The major challenge in pump-probe experiments using FEL and optical lasers is synchronizing the arrival time of the two pulses. Here we report a technique that benefits from the seeded-FEL scheme and uses the optical seed laser for nearly jitter-free pump-probe experiments. Timing jitter as small as 6 fs has been achieved and confirmed by measurements of FEL-induced transient reflectivity changes of Si3N4 using both collinear and non-collinear geometries. Planned improvements of the experimental set-up are expected to further reduce the timing jitter between the two pulses down to fs level
High-resolution ptychographic imaging at a seeded free-electron laser source using OAM beams
Electromagnetic waves possessing orbital angular momentum (OAM) are powerful
tools for applications in optical communications, new quantum technologies and
optical tweezers. Recently, they have attracted growing interest since they can
be harnessed to detect peculiar helical dichroic effects in chiral molecular
media and in magnetic nanostructures. In this work, we perform single-shot per
position ptychography on a nanostructured object at a seeded free-electron
laser, using extreme ultraviolet OAM beams of different topological charge
order generated with spiral zone plates. By controlling , we
demonstrate how the structural features of OAM beam profile determine an
improvement of about 30% in image resolution with respect to conventional
Gaussian beam illumination. This result extends the capabilities of coherent
diffraction imaging techniques, and paves the way for achieving time-resolved
high-resolution (below 100 nm) microscopy on large area samples.Comment: M. Pancaldi and F. Guzzi contributed equally to this wor
International Veterinary Epilepsy Task Force consensus proposal: Medical treatment of canine epilepsy in Europe
In Europe, the number of antiepileptic drugs (AEDs) licensed for dogs has grown considerably over the last years. Nevertheless, the same questions remain, which include, 1) when to start treatment, 2) which drug is best used initially, 3) which adjunctive AED can be advised if treatment with the initial drug is unsatisfactory, and 4) when treatment changes should be considered. In this consensus proposal, an overview is given on the aim of AED treatment, when to start long-term treatment in canine epilepsy and which veterinary AEDs are currently in use for dogs. The consensus proposal for drug treatment protocols, 1) is based on current published evidence-based literature, 2) considers the current legal framework of the cascade regulation for the prescription of veterinary drugs in Europe, and 3) reflects the authorsâ experience. With this paper it is aimed to provide a consensus for the management of canine idiopathic epilepsy. Furthermore, for the management of structural epilepsy AEDs are inevitable in addition to treating the underlying cause, if possible
Surface and bulk contribution to Cu(111) quantum efficiency
The quantum efficiency (QE) of Cu(111) is measured for different impinging light angles with photon energies just above the work function. We observe that the vectorial photoelectric effect, an enhancement of the QE due to illumination with light with an electric vector perpendicular to the sample surface, is stronger in the more surface sensitive regime. This can be explained by a contribution to photoemission due to the variation in the electromagnetic potential at the surface. The contributions of bulk and surface electrons can then be determined
Symmetry-Resolved CO Desorption and Oxidation Dynamics on O/Ru(0001) Probed at the C K-edge by Ultrafast X-Ray Spectroscopy
We report on carbon monoxide desorption and oxidation induced by 400 nm femtosecond laser excitation on the O/Ru(0001) surface probed by time-resolved x-ray absorption spectroscopy (TR-XAS) at the carbon K-edge. The experiments were performed under constant background pressures of CO (6 Ă 10â8 Torr) and O2 (3 Ă 10â8 Torr). Under these conditions, we detect two transient CO species with narrow 2Ï* peaks, suggesting little 2Ï* interaction with the surface. Based on polarization measurements, we find that these two species have opposing orientations: (1) CO favoring a more perpendicular orientation and (2) CO favoring a more parallel orientation with respect to the surface. We also directly detect gas-phase CO2 using a mass spectrometer and observe weak signatures of bent adsorbed CO2 at slightly higher x-ray energies than the 2Ï* region. These results are compared to previously reported TR-XAS results at the O K-edge, where the CO background pressure was three times lower (2 Ă 10â8 Torr) while maintaining the same O2 pressure. At the lower CO pressure, in the CO 2Ï* region, we observed adsorbed CO and a distribution of OCâO bond lengths close to the CO oxidation transition state, with little indication of gas-like CO. The shift toward âgas-likeâ CO species may be explained by the higher CO exposure, which blocks O adsorption, decreasing O coverage and increasing CO coverage. These effects decrease the CO desorption barrier through dipoleâdipole interaction while simultaneously increasing the CO oxidation barrier
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