15,757 research outputs found
Dual regimes of ion migration in high repetition rate femtosecond laser inscribed waveguides
Ion migration in high repetition rate femtosecond laser inscribed waveguides
is currently being reported in different optical glasses. For the first time we
discuss and experimentally demonstrate the presence of two regimes of ion
migration found in laser written waveguides. Regime-I, corresponds to the
initial waveguide formation mainly via light element migration (in our case
atomic weight < 31u), whereas regime-II majorly corresponds to the movement of
heavy elements. This behavior brings attention to a problem which has never
been analyzed before and that affects laser written active waveguides in which
active ions migrate changing their local spectroscopic properties. The
migration of active ions may in fact detune the pre-designed optimal values of
active photonic devices. This paper experimentally evidences this problem and
provides solutions to avert it.Comment: 4 pages, 5 figure
Magnetic transitions in Pr2NiO4 single crystal
The magnetic properties of a stoichiometric Pr2NiO4 single crystal have been examined by means of the temperature dependence of the complex ac susceptibility and the isothermal magnetization in fields up to 200 kOe at T=4.2 K. Three separate phases have been identified and their anisotropic character has been analyzed. A collinear antiferromagnetic phase appears first between TN = 325 K and Tc1 = 115 K, where the Pr ions are polarized by an internal magnetic field. At Tc1 a first modification of the magnetic structure occurs in parallel with a structural phase transition (Bmab to P42/ncm). This magnetic transition has a firstâorder character and involves both the outâofâplane and the inâplane spin components (magnetic modes gx and gxcyfz, respectively). A second magnetic transition having also a firstâorder character is also clearly identified at Tc2 = 90 K which corresponds to a spin reorientation process (gxcyfz to cxgyaz magnetic modes). It should be noted as well that the outâofâphase component of Ïac shows a peak around 30 K which reflects the coexistence of both magnetic configurations in a wide temperature interval. Finally, two fieldâinduced transitions have been observed at 4.2 K when the field is directed along the c axis. We propose that the highâfield anomaly arises from a metamagnetic transition of the weak ferromagnetic component, similarly to La2CuO4
Phenomenology of double deeply virtual Compton scattering in the era of new experiments
We revisit the phenomenology of the deep exclusive electroproduction of a
lepton pair, i.e. double deeply virtual Compton scattering (DDVCS), in view of
new experiments planned in the near future. The importance of DDVCS in the
reconstruction of generalized parton distributions (GPDs) in their full
kinematic domain is emphasized. Using Kleiss-Stirling spinor techniques, we
provide the leading order complex amplitudes for both DDVCS and Bethe-Heithler
sub-processes. Such a formulation turns out to be convenient for practical
implementation in the PARTONS framework and EpIC Monte Carlo generator that we
use in simulation studies.Comment: 21 pages, 13 figure
Prospects for GPDs extraction with Double DVCS
Double deeply virtual Compton scattering (DDVCS) is the process where an
electron scatters off a nucleon and produces a lepton pair. The main advantage
of this process in contrast with deeply virtual and timelike Compton
scatterings (DVCS and TCS) is the possibility of directly measuring GPDs for
at leading order in (LO). We present a new calculation
of the DDVCS amplitude based on the methods developed by R. Kleiss and W. J.
Stirling in the 1980s. These techniques produce expressions for amplitudes that
are perfectly suited for implementation in numerical simulations. Via the
PARTONS software, the correctness of this new formulation has been tested by
comparing the DVCS and TCS limits of DDVCS with independent calculations of
DVCS and TCS.Comment: 5 pages, 4 figures, proceedings for the XXIX Cracow Epiphany
Conferenc
EURONU WP6 2009 yearly report: Update of the physics potential of Nufact, superbeams and betabeams
Many studies in the last ten years have shown that we can measure the unknown
angle theta13, discover leptonic CP violation and determine the neutrino
hierarchy in more precise neutrino oscillation experiments, searching for the
subleading channel nue -> numu in the atmospheric range. In this first report
of WP6 activities the following new results are reviewed: (1) Re-evaluation of
the physics reach of the upcoming generation of experiments to measure theta13
and delta; (2) New tools to explore a larger parameter space as needed beyond
the standard scenario; (3) Neutrino Factory: (a) evaluation of the physics
reach of a Nufact regards sterile neutrinos; (b) evaluation of the physics
reach of a Nufact as regards non-standard interactions; (c) evaluation of the
physics reach of a Nufact as regards violation of unitarity; (d) critical
assessment on long baseline tau-detection at Nufact; (e) new physics searches
at a near detector in a Nufact; (4) Beta-beams: (a) choice of ions and location
for a gamma = 100 CERN-based beta-beam; (b) re-evaluation of atmospheric
neutrino background for the gamma = 100 beta-beam scenario; (c) study of a two
baseline beta-beam; (d) measuring absolute neutrino mass with beta-beams; (e)
progress on monochromatic beta-beams; (5) Update of the physics potential of
the SPL super-beam. Eventually, we present an updated comparison of the
sensitivity to theta13, delta and the neutrino mass hierarchy of several of the
different proposed facilities.Comment: 2009 Yearly report of the Working Package 6 (Physics) of the EUROnu
FP7 EU project. 55 pages, 21 figures
Recent Technological Developments on LGAD and iLGAD Detectors for Tracking and Timing Applications
This paper reports the last technological development on the Low Gain
Avalanche Detector (LGAD) and introduces a new architecture of these detectors
called inverse-LGAD (iLGAD). Both approaches are based on the standard
Avalanche Photo Diodes (APD) concept, commonly used in optical and X-ray
detection applications, including an internal multiplication of the charge
generated by radiation. The multiplication is inherent to the basic n++-p+-p
structure, where the doping profile of the p+ layer is optimized to achieve
high field and high impact ionization at the junction. The LGAD structures are
optimized for applications such as tracking or timing detectors for high energy
physics experiments or medical applications where time resolution lower than 30
ps is required. Detailed TCAD device simulations together with the electrical
and charge collection measurements are presented through this work.Comment: Keywords: silicon detectors, avalanche multiplication, timing
detectors, tracking detectors. 8 pages. 8 Figure
Structure-function mapping of a heptameric module in the nuclear pore complex.
The nuclear pore complex (NPC) is a multiprotein assembly that serves as the sole mediator of nucleocytoplasmic exchange in eukaryotic cells. In this paper, we use an integrative approach to determine the structure of an essential component of the yeast NPC, the ~600-kD heptameric Nup84 complex, to a precision of ~1.5 nm. The configuration of the subunit structures was determined by satisfaction of spatial restraints derived from a diverse set of negative-stain electron microscopy and protein domain-mapping data. Phenotypic data were mapped onto the complex, allowing us to identify regions that stabilize the NPC's interaction with the nuclear envelope membrane and connect the complex to the rest of the NPC. Our data allow us to suggest how the Nup84 complex is assembled into the NPC and propose a scenario for the evolution of the Nup84 complex through a series of gene duplication and loss events. This work demonstrates that integrative approaches based on low-resolution data of sufficient quality can generate functionally informative structures at intermediate resolution
COVID-19 and Sick Leave: An Analysis of the Ibermutua Cohort of Over 1,651,305 Spanish Workers in the First Trimester of 2020
Objectives: The worldwide SARS-COV2 pandemic has impacted the health of workers and companies. The aim is to quantify it according to sick leave. Methods: Using ICD-9 codes, we analyzed Ibermutua records of all sick leaves during the first trimester of 2020, compared to during the same months of 2017, 2018, and 2019. We stratified the analysis by causes, patient sex, activity sectors, and regional data. All sick leaves were adjusted by the number of Ibermutua-affiliated persons in each period. Results: In March 2020, there was an unprecedented (116%) increase in total sick leaves, mainly due to infectious and respiratory diseases. Men and women were equally affected. All activity sectors were impacted, with the highest increase (457%) observed among health-related workers, especially due to contagious disease. The incidences of sick leaves were heterogeneous among different regions. Cost-analysis of sick leaves during the first trimester of 2020 compared with in previous years showed 40.3% increment (mean 2,813 vs. 2,005 euro per 100 affiliated workers). Conclusions: The SARS-COV2 pandemic is having a huge impact on workers' health, as shown by data regarding sick leaves in March 2020. This is associated with greater economic burden for companies, both due to the cost associated with sick leaves and the losses in productivity due to confinement
Bio-inspired computational memory model of the Hippocampus: an approach to a neuromorphic spike-based Content-Addressable Memory
The brain has computational capabilities that surpass those of modern
systems, being able to solve complex problems efficiently in a simple way.
Neuromorphic engineering aims to mimic biology in order to develop new systems
capable of incorporating such capabilities. Bio-inspired learning systems
continue to be a challenge that must be solved, and much work needs to be done
in this regard. Among all brain regions, the hippocampus stands out as an
autoassociative short-term memory with the capacity to learn and recall
memories from any fragment of them. These characteristics make the hippocampus
an ideal candidate for developing bio-inspired learning systems that, in
addition, resemble content-addressable memories. Therefore, in this work we
propose a bio-inspired spiking content-addressable memory model based on the
CA3 region of the hippocampus with the ability to learn, forget and recall
memories, both orthogonal and non-orthogonal, from any fragment of them. The
model was implemented on the SpiNNaker hardware platform using Spiking Neural
Networks. A set of experiments based on functional, stress and applicability
tests were performed to demonstrate its correct functioning. This work presents
the first hardware implementation of a fully-functional bio-inspired spiking
hippocampal content-addressable memory model, paving the way for the
development of future more complex neuromorphic systems.Comment: 15 pages, 5 figures, journal, Spiking Neural Networ
Use of Native Grassland in Small-Scale Dairy Systems in the Highlands of Central Mexico. A Case Study
Small-scale dairy systems in Mexico comprise 78% of specialized dairy farms and provide 37% of national production. They are small farms with herds 3-35 cows plus replacements, and rely on family labour (Posadas-DomĂnguez et al., 2014).
In the highlands, many farms have native grasslands, grazed during the rainy season, and supplemented with other feeds as maize straw, maize grain and maize ears. Native grasslands have not been studied in this context. This is a case study on the use of native grassland in a small-scale dairy farm. The objective was to determine how native grasslands are integrated in feeding milking dairy cows, and the feeding costs involved
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