1,730 research outputs found
On the role of galactic magnetic halo in the ultra high energy cosmic rays propagation
The study of propagation of Ultra High Energy Cosmic Rays (UHECR) is a key
step in order to unveil the secret of their origin. Up to now it was considered
only the influence of the galactic and the extragalactic magnetic fields. In
this article we focus our analysis on the influence of the magnetic field of
the galaxies standing between possible UHECR sources and us. Our main approach
is to start from the well known galaxy distribution up to 120 Mpc. We use the
most complete galaxy catalog: the LEDA catalog. Inside a sphere of 120 Mpc
around us, we extract 60130 galaxies with known position. In our simulations we
assign a Halo Dipole magnetic Field (HDF) to each galaxy. The code developed is
able to retro-propagate a charged particle from the arrival points of UHECR
data across our galaxies sample. We present simulations in case of Virgo
cluster and show that there is a non negligible deviation in the case of
protons of eV, even if the value is conservative. Then
special attention is devoted to the AGASA triplet where we find that NGC3998
and NGC3992 could be possible candidates as sources.Comment: Version accepted from ApJ, 5 figure
Midinfrared Conductivity in Orientationally Disordered Doped Fullerides
The coupling between the intramolecular vibrational modes and the doped
conduction electrons in is studied by a calculation of the
electronic contributions to the phonon self energies. The calculations are
carried out for an orientationally ordered reference solid with symmetry and for a model with quenched orientational disorder on the
fullerene sites. In both cases, the dispersion and symmetry of the renormalized
modes is governed by the electronic contributions. The current current
correlation functions and frequency dependent conductivity through the
midinfrared are calculated for both models. In the disordered structures, the
renormalized modes derived from even parity intramolecular phonons are resonant
with the dipole excited single particle spectrum, and modulate the predicted
midinfrared conductivity. The spectra for this coupled system are calculated
for several recently proposed microscopic models for the electron phonon
coupling, and a comparison is made with recent experimental data which
demonstrate this effect.Comment: 32 pages + 9 postscript figures (on request), REVTeX 3.
Aversive Counterconditioning Attenuates Reward Signaling in the Ventral Striatum
Appetitive conditioning refers to the process of learning cue-reward associations and is mediated by the mesocorticolimbic system. Appetitive conditioned responses are difficult to extinguish, especially for highly salient reward such as food and drugs. We investigate whether aversive counterconditioning can alter reward reinstatement in the ventral striatum in healthy volunteers using functional magnetic resonance imaging (fMRI). In the initial conditioning phase, two different stimuli were reinforced with a monetary reward. In the subsequent counterconditioning phase, one of these stimuli was paired with an aversive shock to the wrist. In the following extinction phase, none of the stimuli were reinforced. In the final reinstatement phase, reward was reinstated by informing the participants that the monetary gain could be doubled. Our fMRI data revealed that reward signaling in the ventral striatum and ventral tegmental area following reinstatement was smaller for the stimulus that was counterconditioned with an electrical shock, compared to the non-counterconditioned stimulus. A functional connectivity analysis showed that aversive counterconditioning strengthened striatal connectivity with the hippocampus and insula. These results suggest that reward signaling in the ventral striatum can be attenuated through aversive counterconditioning, possibly by concurrent retrieval of the aversive association through enhanced connectivity with hippocampus and insula
Do pilocarpine drops help dry mouth in palliative care patients: A protocol for an aggregated series of n-of-1 trials
Background: It is estimated that 39,000 Australians die from malignant disease yearly. Of these, 60% to 88% of advanced cancer patients suffer xerostomia, the subjective feeling of mouth dryness. Xerostomia has significant physical, social and psychological consequences which compromise function and quality of life. Pilocarpine is one treatment for xerostomia. Most studies have shown some variation in individual response to pilocarpine, in terms of dose used, and timing and extent of response.We will determine a population estimate of the efficacy of pilocarpine drops (6 mg) three times daily compared to placebo in relieving dry mouth in palliative care (PC) patients. A secondary aim is to assess individual patients' response to pilocarpine and provide reports detailing individual response to patients and their treating clinician. Methods/Design. Aggregated n-of-1 trials (3 cycle, double blind, placebo-controlled crossover trials using standardized measures of effect). Individual trials will identify which patients respond to the medication. To produce a population estimate of a treatment effect, the results of all cycles will be aggregated. Discussion. Managing dry mouth with treatment supported by the best possible evidence will improve functional status of patients, and improve quality of life for patients and carers. Using n-of-1 trials will accelerate the rate of accumulation of high-grade evidence to support clinical therapies used in PC. Trial registration. Australia and New Zealand Clinical Trial Registry Number: 12610000840088. © 2013 Nikles et al.; licensee BioMed Central Ltd
Nonperturbative approach to the Hubbard model in C60 cluster
We propose a computational scheme for the Hubbard model in the C60 cluster in
which the interaction with the Fermi sea of charges added to the neutral
molecule is switched on sequentially. This is applied to the calculation of the
balance of charging energies, within a low-energy truncation of the space of
states which produces moderate errors for an intermediate range of the
interaction strength.Comment: 5 pages, Revtex, 2 figure
In-Situ Infrared Transmission Study of Rb- and K-Doped Fullerenes
We have measured the four IR active molecular vibrations in
as a function of doping . We observe
discontinuous changes in the vibrational spectra showing four distinct phases
(presumably , and 6). The and modes
show the largest changes shifting downward in frequency in four steps as the
doping increases. Several new very weak modes are visible in the phase
and are possibly Raman modes becoming weakly optically active. We present
quantitative fits of the data and calculate the electron-phonon coupling of the
IR mode.Comment: 3 pages, Figure 1 included, 3 more figures available by request.
REVTEX v3.0 IRC60DO
Community inclusion of wheelchair users during the long-term recovery phase following the 2010/2011 Canterbury earthquakes
Research exploring how people living with disability experience community inclusion during the medium to long-term recovery following natural disasters is scant. Yet such information is vital to ensure that recovering communities are inclusive of all members within the population. This study explored the perspectives of people with specific functional needs, wheelchair users, regarding their experience of community inclusion in the four years following the 2010/2011 earthquakes in Christchurch, New Zealand. Thirteen adult wheelchair users were interviewed one-to-one and then invited to attend a group interview. The group interview presented a summary of the interview data for discussion to help clarify and prioritise elements of community inclusion. All data were subjected to thematic analysis. Four interrelated themes described the key elements of the participants’ experience of community post-earthquakes: 1) earthquakes magnified barriers, 2) community inclusion requires energy, 3) social connections are important, and 4) an unprecedented opportunity for change. Findings emphasized the need for recovery energies at a local and national level to move from conceptualizing disability in terms of individual vulnerability, to instead, focusing on reducing environmental barriers that inhibit community inclusion. Of critical importance is creating pathways for people who experience disability to be co-creators of this change
Orientational Melting in Carbon Nanotube Ropes
Using Monte Carlo simulations, we investigate the possibility of an
orientational melting transition within a "rope" of (10,10) carbon nanotubes.
When twisting nanotubes bundle up during the synthesis, orientational
dislocations or twistons arise from the competition between the anisotropic
inter-tube interactions, which tend to align neighboring tubes, and the torsion
rigidity that tends to keep individual tubes straight. We map the energetics of
a rope containing twistons onto a lattice gas model and find that the onset of
a free "diffusion" of twistons, corresponding to orientational melting, occurs
at T_OM > 160 K.Comment: 4 page LaTeX file with 3 figures (10 PostScript files
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