7,945 research outputs found
Role of Cerebellar Interpositus Nucleus in the Genesis and Control of Reflex and Conditioned Eyelid Responses
The role of cerebellar circuits in the acquisition of new motor abilities is still a matter of intensive debate. To establish the contribution of posterior interpositus nucleus (PIN) to the performance and/or acquisition of reflex and classically conditioned responses (CRs) of the eyelid, the effects of microstimulation and/or pharmacological inhibition by muscimol of the nucleus were investigated in conscious cats. Microstimulation of the PIN in naive animals evoked ramp-like eyelid responses with a wavy appearance, without producing any noticeable plastic functional change in the cerebellar and brainstem circuits involved. Muscimol microinjections decreased the amplitude of reflex eyeblinks evoked by air puffs, both when presented alone or when paired with a tone as conditioned stimulus (CS). In half-conditioned animals, muscimol injections also decreased the amplitude and damped the typical wavy profile of CRs, whereas microstimulation of the same sites increased both parameters. However, neither muscimol injections nor microstimulation modified the expected percentage of CRs, suggesting a major role of the PIN in the performance of eyelid responses rather than in the learning process. Moreover, the simultaneous presentation of CS and microstimulation in well trained animals evoked CRs similar in amplitude to the added value of those evoked by the two stimuli presented separately. In contrast, muscimol-injected animals developed CRs to paired CS and microstimulation presentations, larger than those evoked by the two stimuli when presented alone. It is concluded that the PIN contributes to the enhancement of both reflex and conditioned eyelid responses and to the damping of resonant properties of neuromuscular elements controlling eyelid kinematics
Statistical properties of the dark matter haloes of dwarf galaxies and correlations with the environment
According to the now strongly supported concordance CDM model,
galaxies may be grossly described as a luminous component embedded in a dark
matter halo. The density profile of these mass dominating haloes may be
determined by N - body simulations which mimic the evolution of the tiny
initial density perturbations during the process leading to the structures we
observe today. Unfortunately, when the effect of baryons is taken into account,
the situation gets much more complicated due to the difficulties in simulating
their physics. As a consequence, a definitive prediction of how dark matter
haloes should presently look like is still missing. We revisit here this issue
from an observational point of view devoting our attention to dwarf galaxies.
Being likely dark matter dominated, these systems are ideal candidates to
investigate the present day halo density profiles and check whether dark matter
related quantities correlate with the stellar ones or the environment. By
fitting a large sample of well measured rotation curves, we infer constraints
on both halo structural parameters (such as the logarithmic slope of the
density profile and its concentration) and derived quantities (e.g., the mass
fraction and the Newtonian acceleration) which could then be used to constrain
galaxy formation scenarios. Moreover, we investigate whether the halo
properties correlates with the environment the galaxy lives in thus offering a
new tool to deepen our understanding of galaxy formation.Comment: 14 pages, 8 tables, 5 figures, accepted for publication on MNRA
Phthalocyanines: Alternative Sensitizers of TiO2 to be Used in Photocatalysis
Currently, titanium dioxide is a most researched semiconductor in photocatalysis field; however, practical applications of TiO2 are limited due to high band gap (3.2 eV). In last decades, researchers implemented several strategies to improve photoactivity of TiO2 in visible electromagnetic spectrum. Titanium dioxide (TiO2) sensitization for absorption of naturals and/or synthetics organic dyes is an important research subject in the field, and it is an efficient method to develop practical application in waste treatment. In this chapter, we review main theoretical aspects of sensitization process of TiO2 by phthalocyanines and its effect in photocatalytic properties. In the last section, we review reports of photocatalytic systems
Flexible membranes anchored to the ground for slope stabilisation: Numerical modelling of soil slopes using SPH
An alternative modelling for flexible membranes anchored to the ground for soil slope stabilisation is presented using Smoothed-Particle Hydrodynamics to model the unstable ground mass in a soil slope, employing a dynamic solve engine. A regression model of pressure normal to the ground, qsim, and also membrane deflection, fsim, have been developed using Design of Experiment. Finally, a comparison between the pressure obtained from numerical simulation and from a limit equilibrium analysis considering infinite slope has been carried out, showing differences in the results, mainly due to the membrane stiffness.The realization of this research paper has been possible thanks to the funding of the following entities: SODERCAN (Sociedad para el Desarrollo de Cantabria), ConsejerÃa de Obras Públicas del Gobierno de Cantabria, Iberotalud S.L., Malla Talud Cantabria S.L. and Contratas Iglesias S.L.
The authors wish also to acknowledge the support provided by the GICONSIME Research Group of the University of Oviedo and the GITECO Research Group of the University of Cantabria. We also thank Swanson Analysis Inc. for the use of the ANSYS Academic program
Broken R-parity, stop decays, and neutrino physics
We discuss the phenomenology of the lightest stop in models where R-parity is
broken by bilinear superpotential terms. In this class of models we consider
scenarios where the R-parity breaking two-body decay ~t_1->\tau^+b competes
with the leading three-body decays such as ~t_1->W^+b~\chi^0_1. We demonstrate
that the R-parity violating decay can be sizable and in some parts of the
parameter space even the dominant one. Moreover we discuss the expectations for
\~t_1->\mu^+b and ~t_1->e^+b. The recent results from solar and atmospheric
neutrinos suggest that these are as important as the tau bottom mode. The
\~t_1->l^+b decays are of particular interest for hadron colliders, as they may
allow a full mass reconstruction of the lighter stop. Moreover these decay
modes allow cross checks on the neutrino mixing angle involved in the solar
neutrino puzzle complementary to those possible using neutralino decays. For
the so--called small mixing angle or SMA solution ~t_1->e^+b should be
negligible, while for the large mixing angle type solutions all ~t_1->l^+b
decays should have comparable magnitude.Comment: 51 pages, 6 figures, LaTeX2e and RevTeX4, published versio
Clinical debriefing during the COVID-19 pandemic: hurdles and opportunities for healthcare teams
The COVID-19 pandemic and the subsequent pressures on healthcare staff and resources have exacerbated the need for clinical teams to reflect and learn from workplace experiences. Surges in critically ill patients, the impact of the disease on the workforce and long term adjustments in work and life have upturned our normality. Whilst this situation has generated a new 'connectedness' within healthcare workers, it also continues to test our resilience. An international multi-professional collaboration has guided the identification of ongoing difficulties to effective communication and debriefing, as well as emerging opportunities to promote a culture of dialogue. This article outlines pandemic related barriers and new possibilities categorising them according to task management, teamwork, situational awareness and decision making. It describes their direct and indirect impact on clinical debriefing and signposts towards solutions to overcome challenges and, building on new bridges, advance team conversations that allow us to learn, improve and support each other. This pandemic has brought clinical professionals together; nevertheless, it is essential to invest in further developing and supporting cohesive teams. Debriefing enables healthcare teams and educators to mitigate stress, build resilience and promote a culture of continuous learning and patient care improvement
On the universality of density profiles
We use the secondary infall model described in Del Popolo (2009), which takes
into account the effect of dynamical friction, ordered and random angular
momentum, baryons adiabatic contraction and dark matter baryons interplay, to
study how in- ner slopes of relaxed LCDM dark matter (DM) halos with and
without baryons (baryons+DM, and pure DM) depend on redshift and on halo mass.
We apply the quoted method to structures on galactic scales and clusters of
galaxies scales. We find that the inner logarithmic density slope, of dark
matter halos with baryons has a significant dependence on halo mass and
redshift with slopes ranging from 0 for dwarf galaxies to 0.4 for objects of M
= 10^13M_solar and 0.94 for M = 10^15M_solar clusters of galaxies. Structures
slopes increase with increasing redshift and this trend reduces going from
galaxies to clusters. In the case of density profiles constituted just of dark
matter the mass and redshift dependence of slope is very slight. In this last
case, we used the Merrit et al. (2006) analysis who compared N-body density
profiles with various parametric models finding systematic variation in profile
shape with halo mass. This last analysis suggests that the galaxy-sized halos
obtained with our model have a different shape parameter, i.e. a different mass
distribution, than the cluster-sized halos, obtained with the same model. The
results of the present paper argue against universality of density profiles
constituted by dark matter and baryons and confirm claims of a systematic
variation in profile shape with halo mass, for dark matter halos.Comment: 11 pages, 5 figure
Searching for R-Parity Violation at Run-II of the Tevatron
We present an outlook for possible discovery of supersymmetry with broken
R-parity at Run II of the Tevatron. We first present a review of the literature
and an update of the experimental bounds. In turn we then discuss the following
processes: 1. Resonant slepton production followed by R-parity violating decay,
(a) via and (b) via . 2. How to distinguish resonant slepton
production from or production. 3. Resonant slepton production
followed by the decay to neutralino LSP, which decays via . 4. Resonant
stop production followed by the decay to a chargino, which cascades to the
neutralino LSP. 5. Gluino pair production followed by the cascade decay to
charm squarks which decay directly via . 6. Squark pair production
followed by the cascade decay to the neutralino LSP which decays via
. 7. MSSM pair production followed by the cascade decay to the LSP
which decays (a) via , (b) via , and (c) via ,
respectively. 8. Top quark and top squark decays in spontaneous R-parity
violation.Comment: 39 pages, 51 figures, LaTex, reqires aipproc2.sty and axodraw.sty. To
be published in the Physics at Run II Workshop: Supersymmetry/Higgs. Text has
been edited by H. Dreiner. Author list on front page has been correcte
Charged lepton Flavor Violation in Supersymmetry with Bilinear R-Parity Violation
The simplest unified extension of the Minimal Supersymmetric Standard Model
with bi-linear R-parity violation naturally predicts a hierarchical neutrino
mass spectrum, suitable to explain atmospheric and solar neutrino fluxes. We
study whether the individual violation of the lepton numbers L_{e,mu,tau} in
the charged sector can lead to measurable rates for BR(mu->e gamma)and
$BR(tau-> mu gamma). We find that some of the R-parity violating terms that are
compatible with the observed atmospheric neutrino oscillations could lead to
rates for mu->e gamma measurable in projected experiments. However, the Delta
m^2_{12} obtained for those parameters is too high to be compatible with the
solar neutrino data, excluding therefore the possibility of having measurable
rates for mu->e gamma in the model.Comment: 29 pages, 8 figures. Constraint from solar neutrino data included,
conclusions changed respect v
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