4,520 research outputs found
KamLAND Bounds on Solar Antineutrinos and neutrino transition magnetic moments
We investigate the possibility of detecting solar electron antineutrinos with
the KamLAND experiment. These electron antineutrinos are predicted by
spin-flavor oscillations at a significant rate even if this mechanism is not
the leading solution to the SNP. KamLAND is sensitive to antineutrinos
originated from solar B neutrinos. From KamLAND negative results after
145 days of data taking, we obtain model independent limits on the total flux
of solar electron antineutrinos $\Phi({}^8 B)< 1.1-3.5\times 10^4 cm^{-2}\
s^{-1}P<0.15%\mu B< 2.3\times 10^{-21}(\Delta m^2, \tan^2\theta)\mu\lsim 3.9\times 10^{-12} \mu_BB= 50\mu\lsim 9.0\times 10^{-13} \mu_BB= 200\mu\lsim 2.0\times 10^{-13} \mu_BB= 1000$ kG at the same
statistical significance.Comment: 13 pages, 2 figure
Muon anomalous magnetic moment in supersymmetric scenarios with an intermediate scale and nonuniversality
We analyze the anomalous magnetic moment of the muon (a_{\mu}) in
supersymmetric scenarios. First we concentrate on scenarios with universal soft
terms. We find that a moderate increase of a_{\mu} can be obtained by lowering
the unification scale M_{GUT} to intermediate values 10^{10-12} GeV. However,
large values of \tan \beta are still favored. Then we study the case of
non-universal soft terms. For the usual value M_{GUT}~10^{16} GeV, we obtain
a_{\mu} in the favored experimental range even for moderate \tan \beta regions
\tan\beta ~ 5$. Finally, we give an explicit example of these scenarios. In
particular, we show that in a D-brane model, where the string scale is
naturally of order 10^{10-12} GeV and the soft terms are non universal, a_{\mu}
is enhanced with low \tan\beta.Comment: Final version to appear in Phys. Rev. D. Conventions clarified,
results in the figures improve
KamLAND, solar antineutrinos and the solar magnetic field
In this work the possibility of detecting solar electron antineutrinos
produced by a solar core magnetic field from the KamLAND recent observations is
investigated. We find a scaling of the antineutrino probability with respect to
the magnetic field profile in the sense that the same probability function can
be reproduced by any profile with a suitable peak field value. In this way the
solar electron antineutrino spectrum can be unambiguosly predicted. We use this
scaling and the negative results indicated by the KamLAND experiment to obtain
upper bounds on the solar electron antineutrino flux. We get
at 95% CL. For 90% CL this becomes
, an improvement by a factor of 3-5
with respect to existing bounds. These limits are independent of the detailed
structure of the magnetic field in the solar interior. We also derive upper
bounds on the peak field value which are uniquely determined for a fixed solar
field profile. In the most efficient antineutrino producing case, we get (95%
CL) an upper limit on the product of the neutrino magnetic moment by the solar
field MeV or for
.Comment: 15 pages. References corrected. Minor changes in the tex
Relic Neutralino Density in Scenarios with Intermediate Unification Scale
We analyse the relic neutralino density in supersymmetric models with an
intermediate unification scale. In particular, we present concrete cosmological
scenarios where the reheating temperature is as small as
MeV). When this temperature is associated to the decay of moduli fields
producing neutralinos, we show that the relic abundance increases considerably
with respect to the standard thermal production. Thus the neutralino becomes a
good dark matter candidate with 0.1\lsim \Omega h^2 \lsim 0.3, even for
regions of the parameter space where large neutralino-nucleon cross sections,
compatible with current dark matter experiments, are present. This is obtained
for intermediate scales GeV, and moduli masses
GeV. On the other hand, when the above temperature is
associated to the decay of an inflaton field, the relic abundance is too small.Comment: Latex, 11 pages, 2 figure
Experimental analysis of the addition of rice husk ash to the clayey subgrade of a road stabilized with lime
There are many studies about how the addition of lime and rice husk ash (RHA) gives the soil a better mechanical behavior, particularly on clayey soils, where usually fine particles reach more than 75%. However, the soils with a small presence of fine particles (59-60%) do not have much research. This analysis evaluates the influence that RHA has on this kind of soil stabilized with 3% of lime. After the initial mix of soil-lime, CBR increased 11.2 times its initial value; within the addition of the ash, the CBR averaged between 45-50% up until 28% of RHA was added, where the results decreased considerably. Soil workability improved and the specimens with more ash resulted in a more granular material, with a group index value 0 following the AASHTO standards. The greatest CBR record was obtained with the specimen of 16% RHA, 3% lime and soil, reaching a 51.3% CBR, 1.58g/cm3 of MDD and 16.5% of OMC. Yet, it only showed a 1.55% more resistance than the lime-soil specimen. The CBR with more presence of RHA tends to decrease its value, therefore for silica-rich clayey soils, the addition of lime by itself should be enough for an adequate performance
Adaptation to public goods cheats in Pseudomonas aeruginosa
This is the author accepted manuscript. The final version is available from the Royal Society via the DOI in this record.Cooperation in nature is ubiquitous, but is susceptible to social cheats who pay little or no cost of cooperation yet reap the benefits. The effect such cheats have on reducing population productivity suggests that there is selection for cooperators to mitigate the adverse effects of cheats. While mechanisms have been elucidated for scenarios involving a direct association between producer and cooperative product, it is less clear how cooperators may suppress cheating in an anonymous public goods scenario, where cheats cannot be directly identified. Here, we investigate the real-time evolutionary response of cooperators to cheats when cooperation is mediated by a diffusible public good: the production of iron-scavenging siderophores by Pseudomonas aeruginosa. We find that siderophore producers evolved in thepresence of a high frequency of non-producing cheats were fitter in the presence of cheats, at no obvious cost to population productivity. A novel morphotype independently evolved and reached higher frequencies in cheat-adapted versus control populations, exhibiting reduced siderophore production but increased production of pyocyanin - an extracellular toxin that can also increase the availability of soluble iron. This suggests that cooperators may have mitigated the negative effects of cheats by downregulating siderophore production and upregulating an alternative iron-acquisition public good. More generally, the study emphasises that cooperating organisms can rapidly adapt to the presence of anonymous cheats without necessarily
incurring fitness costs in the environment they evolve in.The work was funded by AXA research fund, NERC, BBSRC and the Royal Society to AB and a University of Exeter PhD studentship to SOB
Initial Scales, Supersymmetric Dark Matter and Variations of Neutralino-Nucleon Cross Sections
The neutralino-nucleon cross section in the context of the MSSM with universal soft supersymmetry-breaking terms is compared with the limits from dark matter detectors. Our analysis is focussed on the stability of the corresponding cross sections with respect to variations of the initial scale for the running of the soft terms, finding that the smaller the scale is, the larger the cross sections become. For example, by taking GeV rather than , which is a more sensible election, in particular in the context of some superstring models, we find extensive regions in the parameter space with cross sections in the range of -- pb, i.e. where current dark matter experiments are sensitive. For instance, this can be obtained for \tan\beta\gsim 3
Dysflective cones: Visual function and cone reflectivity in long-term follow-up of acute bilateral foveolitis.
PURPOSE:Confocal adaptive optics scanning laser ophthalmoscope (AOSLO) images provide a sensitive measure of cone structure. However, the relationship between structural findings of diminished cone reflectivity and visual function is unclear. We used fundus-referenced testing to evaluate visual function in regions of apparent cone loss identified using confocal AOSLO images. METHODS:A patient diagnosed with acute bilateral foveolitis had spectral-domain optical coherence tomography (SD-OCT) (Spectralis HRA + OCT system [Heidelberg Engineering, Vista, CA, USA]) images indicating focal loss of the inner segment-outer segment junction band with an intact, but hyper-reflective, external limiting membrane. Five years after symptom onset, visual acuity had improved from 20/80 to 20/25, but the retinal appearance remained unchanged compared to 3 months after symptoms began. We performed structural assessments using SD-OCT, directional OCT (non-standard use of a prototype on loan from Carl Zeiss Meditec) and AOSLO (custom-built system). We also administered fundus-referenced functional tests in the region of apparent cone loss, including analysis of preferred retinal locus (PRL), AOSLO acuity, and microperimetry with tracking SLO (TSLO) (prototype system). To determine AOSLO-corrected visual acuity, the scanning laser was modulated with a tumbling E consistent with 20/30 visual acuity. Visual sensitivity was assessed in and around the lesion using TSLO microperimetry. Complete eye examination, including standard measures of best-corrected visual acuity, visual field tests, color fundus photos, and fundus auto-fluorescence were also performed. RESULTS:Despite a lack of visible cone profiles in the foveal lesion, fundus-referenced vision testing demonstrated visual function within the lesion consistent with cone function. The PRL was within the lesion of apparent cone loss at the fovea. AOSLO visual acuity tests were abnormal, but measurable: for trials in which the stimulus remained completely within the lesion, the subject got 48% correct, compared to 78% correct when the stimulus was outside the lesion. TSLO microperimetry revealed reduced, but detectible, sensitivity thresholds within the lesion. CONCLUSIONS AND IMPORTANCE:Fundus-referenced visual testing proved useful to identify functional cones despite apparent photoreceptor loss identified using AOSLO and SD-OCT. While AOSLO and SD-OCT appear to be sensitive for the detection of abnormal or absent photoreceptors, changes in photoreceptors that are identified with these imaging tools do not correlate completely with visual function in every patient. Fundus-referenced vision testing is a useful tool to indicate the presence of cones that may be amenable to recovery or response to experimental therapies despite not being visible on confocal AOSLO or SD-OCT images
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