546 research outputs found
Axions and Superfluidity in Weyl Semimetals
An effective field theory (EFT) for dynamical axions in Weyl semimetals
(WSMs) is presented. A pseudoscalar axion excitation is predicted in WSMs at
sufficiently low temperatures, independently of the strength of the Weyl
fermion self-coupling. For strong fermion self-coupling the axion is the
gapless Goldstone boson of chiral spontaneous symmetry
breaking. For weak fermion self-coupling an axion is also generated at non-zero
chiral density for Weyl nodes displaced in energy, as a gapless collective mode
of correlated fermion pair excitations of the Fermi surface. This is an
explicit example of the extension of Goldstone's theorem to symmetry breaking
by the axial anomaly itself. In both cases the axion is a chiral density wave
or phason mode of the superfluid state of the WSM, and the Weyl fermions form a
chiral condensate at low temperatures. In the
presence of an applied magnetic field the axion mode becomes gapped, in analogy
to the Anderson-Higgs mechanism in a superconductor. 't Hooft anomaly matching
from ultraviolet to infrared scales is directly verified in the EFT approach.
WSMs thus provide an interesting quantum system in which superfluid, non-Fermi
liquid behavior, and a dynamical axion are predicted to follow directly from
the axial anomaly in a consistent EFT that may be tested experimentally.Comment: 50 pages, 7 figure
TEC and foF2 variations: preliminary results
Investigation of the relationship between TEC and (foF2)2 shows that although they are highly correlated, a «hysteresis» effect exists between them. The slab thickness is greater before than after mid-day for equal cos ?values. Moreover, a comparison of the calculated upper and lower quartiles of variability in TEC, foF2 and Nmax, respectively shows that the variability of TEC lies between those of foF2 and Nmax depending on the level of solar activity
TEC and foF2 variations: preliminary results
Investigation of the relationship between TEC and (foF2)2 shows that although they are highly correlated, a «hysteresis» effect exists between them. The slab thickness is greater before than after mid-day for equal cos ?values. Moreover, a comparison of the calculated upper and lower quartiles of variability in TEC, foF2 and Nmax, respectively shows that the variability of TEC lies between those of foF2 and Nmax depending on the level of solar activity
Anterior cruciate ligament reconstruction with a quadrupled hamstrings tendon autograft does not restore tibial rotation to normative levels during landing from a jump and subsequent pivoting
Aim. Recent research suggested that the anterior curciate ligament (ACL) reconstruction does not restore tibial rotation to normal levels when a bone patellar tendon bone (BPTB) graft is used during high demanding activities. Our goal was to determine if the usage of an alternative graft, as the quadrupled semitendinosus-gracilis (ST/G), restore tibial rotation to normal values in a population of athletically active individuals while performing a usual for their sport activity.
Methods. Eleven subjects, all reconstructed with an ST/G graft, were assessed in vivo, 9 months postoperatively, while they jumped off a 40 cm platform, landed on the ground and subsequently pivoted at 90 degrees. The evaluation period was identified from initial foot contact with the ground, included the pivoting of the ipsilateral leg, and was completed upon touch-down of the contralateral leg. By that time the patients had already returned to their sports activities.
Results. The maximum range of motion of the tibial rotation for the pivoting leg, during the evaluation period was found significantly (P=0.0001) larger in the reconstructed leg as compared to the intact contralateral, although both clinical and arthrometer assessments revealed restoration of anterior translation.
Conclusion. It was concluded that ACL reconstruction with an ST/G graft does not restore tibial rotation to normal levels during this high demanding activity. It seems that new surgical techniques are needed to better replicate the actual anatomy and function of the natural ACL in order to address this problem
Intelligent dual curve-driven tool path optimization and virtual CMM inspection for sculptured surface CNC machining
This paper investigates the profitability of a dualâcurve driven surface finish tool path under the concept
of optimizing crucial machining parameters such as toroidal endâmill diameter, lead angle and tilt angle. Surface
machining error as well as tool path time are treated as optimization objectives under a multiâcriteria sense, whilst
a central composite design is conducted to obtain experimental outputs for examination and, finally, fit a full
quadratic model considered as the fitness function for process optimization by means of a genetic algorithm. A
benchmark sculptured surface given as a secondâorder parametric equation was tested and simulated using a
cuttingâedge manufacturing modeling software and best parameters recommended by the genetic algorithm were
implemented for validation. Further assessment involves the virtual inspection to selected profile sections on the
part. It was shown that the approach can produce dualâcurve driven tool trajectories capable of eliminating sharp
scallop heights, maximizing machining strip widths as well as maintaining smoothness quality and machining
efficiency
COPERNICUS KNOWLEDGE and INNOVATION HUBS
Copernicus, the European Space program ensures free data availability and the organisational and financial framework to provide standardized information products in its service domains atmosphere, marine, land monitoring, climate change, emergency management and human security. A key to success to the market uptake process is knowledge exchange among all actors from the various sectors involved, notably research and educational institutions, industry, and the public sector. As a successful instrument to foster and stimulate this exchange, maximize the impact and additionally boost related capacity building and training activities, the Copernicus Academy has been anchored in the European Space Strategy. The present paper highlights some key activities to leverage the potential of this dynamically growing network of experts from universities and research institutions, public and private organizations, companies, stakeholders, and increase the benefit to its members. The vision of establishing both physical implementations of regional Copernicus hubs and virtual Copernicus hubs, built on key elements of the European Innovation strategy, is discussed. Regional hubs, attached e.g. to centres of excellence, are essential to meet local needs for exchange and training to boost the user uptake. The increasing importance of virtual hubs is becoming evident as a critical means to maximise synergies among actors in the rapidly advancing technological areas. Proposed technical elements demonstrate innovative solutions to visualize and facilitate easy harvesting of the Copernicus Academy membeĆs expertise for different stakeholder and the public, and show cast possibilities of active involvement and exchange within the network
Development of an IoT Based Smart Campus: Wide Shuttle Tracking System
Vehicle tracking systems are a versatile technology which enables commuters to
determine the location of the buses in real-time. Bus operators can also deploy it for
fleet management purposes. In this work, an integrated, embedded GPS-GSM vehicle
tracking system is designed and implemented. The application enables passengers to
view the location of bus shuttles in real-time. It also allows bus managers to ascertain
the driver behaviour and observe the past and present locations of the bus shuttle. The
system has been designed to provide more functionalities with some modifications and
additional hardware, such as Accident detection, Fire detection systems and Fuel
monitoring. The location of buses can be accessed by the users either using the SMS
request option or logging into the mobile application developed for this purpose. Upon
receipt of a location request, the tracking system sends feedback which includes both
the latitude and longitude coordinates of the vehicle and also a link that enables the display of the bus location of a google map. The location is also logged onto a server
managed by the bus operators to monitor the bus activities
Scale without Conformal Invariance at Three Loops
We carry out a three-loop computation that establishes the existence of scale
without conformal invariance in dimensional regularization with the MS scheme
in d=4-epsilon spacetime dimensions. We also comment on the effects of scheme
changes in theories with many couplings, as well as in theories that live on
non-conformal scale-invariant renormalization group trajectories. Stability
properties of such trajectories are analyzed, revealing both attractive and
repulsive directions in a specific example. We explain how our results are in
accord with those of Jack & Osborn on a c-theorem in d=4 (and d=4-epsilon)
dimensions. Finally, we point out that limit cycles with turning points are
unlike limit cycles with continuous scale invariance.Comment: 21 pages, 3 figures, Erratum adde
Associations of sedentary behaviour, physical activity, blood pressure and anthropometric measures with cardiorespiratory fitness in children with cerebral palsy
Background - Children with cerebral palsy (CP) have poor cardiorespiratory fitness in comparison to their peers with typical development, which may be due to low levels of physical activity. Poor cardiorespiratory fitness may contribute to increased cardiometabolic risk. Purpose - The aim of this study was to determine the association between sedentary behaviour, physical activity and cardiorespiratory fitness in children with CP. An objective was to determine the association between cardiorespiratory fitness, anthropometric measures and blood pressure in children with CP. Methods- This study included 55 ambulatory children with CP [mean (SD) age 11.3 (0.2) yr, range 6-17 yr; Gross Motor Function Classification System (GMFCS) levels I and II]. Anthropometric measures (BMI, waist circumference and waist-height ratio) and blood pressure were taken. Cardiorespiratory fitness was measured using a 10 m shuttle run test. Children were classified as low, middle and high fitness according to level achieved on the test using reference curves. Physical activity was measured by accelerometry over 7 days. In addition to total activity, time in sedentary behaviour and light, moderate, vigorous, and sustained moderate-to-vigorous activity (â„10 min bouts) were calculated. Results - Multiple regression analyses revealed that vigorous activity (ÎČ = 0.339, p<0.01), sustained moderate-to-vigorous activity (ÎČ = 0.250, p<0.05) and total activity (ÎČ = 0.238, p<0.05) were associated with level achieved on the shuttle run test after adjustment for age, sex and GMFCS level. Children with high fitness spent more time in vigorous activity than children with middle fitness (p<0.05). Shuttle run test level was negatively associated with BMI (r2 = -0.451, p<0.01), waist circumference (r2 = -0.560, p<0.001), waist-height ratio (r2 = -0.560, p<0.001) and systolic blood pressure (r2 = -0.306, p<0.05) after adjustment for age, sex and GMFCS level. Conclusions - Participation in physical activity, particularly at a vigorous intensity, is associated with high cardiorespiratory fitness in children with CP. Low cardiorespiratory fitness is associated with increased cardiometabolic risk
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