475 research outputs found
Planothidum audax sp. nov. (Bacillariophyta, Achnanthidiaceae), a new diatom from temporary streams in southern Portugal
emporary streams represent ca. half of the river network at the worldwide level, and in regions such as southern Europe their dominance of the landscape is evident (Larned et al. 2010, McDonough et al. 2011, Barbosa et al. 2020). Currently, these streams are receiving increased attention due to their importance as high diversity spots for algae, arthropods, plants, etc., and due to the ecosystem services they provide (Acuña et al. 2014, Datry et al. 2018b). Because of their geographical position and the land use changes in their watersheds (increased urbanization, agriculture, etc.), climate change, contamination and habitat fragmentation constitute forces threatening their integrity and ecological characteristics (Datry et al. 2018a, Bonada et al. 2020)
Localized modes at a D-brane--O-plane intersection and heterotic Alice strings
We study a system of -branes intersecting -branes and
-planes in 1+1-dimensions. We use anomaly cancellation and string dualities
to argue that there must be chiral fermion zero-modes on the -branes which
are localized near the -planes. Away from the orientifold limit we verify
this by using index theory as well as explicit construction of the zero-modes.
This system is related to F-theory on K3 and heterotic matrix string theory,
and the heterotic strings are related to Alice string defects in
Super-Yang-Mills. In the limit of large we find an
dual of the heterotic matrix string CFT.Comment: 44 pages, typos corrected, version published in JHE
Particle Dark Matter Constraints from the Draco Dwarf Galaxy
It is widely thought that neutralinos, the lightest supersymmetric particles,
could comprise most of the dark matter. If so, then dark halos will emit radio
and gamma ray signals initiated by neutralino annihilation. A particularly
promising place to look for these indicators is at the center of the local
group dwarf spheroidal galaxy Draco, and recent measurements of the motion of
its stars have revealed it to be an even better target for dark matter
detection than previously thought. We compute limits on WIMP properties for
various models of Draco's dark matter halo. We find that if the halo is nearly
isothermal, as the new measurements indicate, then current gamma ray flux
limits prohibit much of the neutralino parameter space. If Draco has a moderate
magnetic field, then current radio limits can rule out more of it. These
results are appreciably stronger than other current constraints, and so
acquiring more detailed data on Draco's density profile becomes one of the most
promising avenues for identifying dark matter.Comment: 13 pages, 6 figure
The cosmic ray positron excess and neutralino dark matter
Using a new instrument, the HEAT collaboration has confirmed the excess of
cosmic ray positrons that they first detected in 1994. We explore the
possibility that this excess is due to the annihilation of neutralino dark
matter in the galactic halo. We confirm that neutralino annihilation can
produce enough positrons to make up the measured excess only if there is an
additional enhancement to the signal. We quantify the `boost factor' that is
required in the signal for various models in the Minimal Supersymmetric
Standard Model parameter space, and study the dependence on various parameters.
We find models with a boost factor greater than 30. Such an enhancement in the
signal could arise if we live in a clumpy halo. We discuss what part of
supersymmetric parameter space is favored (in that it gives the largest
positron signal), and the consequences for other direct and indirect searches
of supersymmetric dark matter.Comment: 11 pages, 6 figures, matches published version (PRD
Factors of the epidemiological triad that influence the persistence of human papilloma virus infection in women with systemic lupus erythematosus
We studied the epidemiologic triad-related factors influencing human papilloma virus (HPV) persistence in Mexican women with systemic lupus erythematosus (SLE). Patients aged ?18 years with SLE (American College of Rheumatology criteria), with and without HPV persistence, were selected. Groups were analyzed by (1) host: clinical disease characteristics; (2) agent: (I) infectious (prevalence, incidence, HPV genotype and co-infections (?2 HPV genotypes or mycoplasmas)), (II) chemical (contraceptives and immunosuppressive drugs) and (III) physical (vitamin D deficiency) and (3) environment. A total of 121 SLE patients were selected over a two-year period. (1) Host: mean age 45.8 years and disease duration 12.7 years. (2) Agent: (I) infectious. HPV infection prevalence in the second sample was 26.4%, high-risk HPV genotypes 21.5% and co-infections 7.4%. HPV infection incidence was 13.2%, persistence 13.2% and clearance 15.7%. (II) Chemical: use of oral hormonal contraceptives 5% and immunosuppressive treatment 97.5%. (III) Physical: Vitamin D levels were similar in both groups. (3) Environment: (I) natural. A total of 60.6% of patients were residents of Puebla City. (II) Social: The mean education level was 10.9. Poverty levels were: III degree 52.4%, IV degree 28% and II degree 17%. (III) Cultural behavioral: Onset of sexual life was 20.5 years, 10% had ?3 sexual partners and 51.2% were postmenopausal. In conclusion, no factor of the epidemiologic triad was associated with HPV infection prevalence. © The Author(s) 2018
Exclusion limits on the WIMP-nucleon cross-section from the Cryogenic Dark Matter Search
The Cryogenic Dark Matter Search (CDMS) employs low-temperature Ge and Si
detectors to search for Weakly Interacting Massive Particles (WIMPs) via their
elastic-scattering interactions with nuclei while discriminating against
interactions of background particles. For recoil energies above 10 keV, events
due to background photons are rejected with >99.9% efficiency, and surface
events are rejected with >95% efficiency. The estimate of the background due to
neutrons is based primarily on the observation of multiple-scatter events that
should all be neutrons. Data selection is determined primarily by examining
calibration data and vetoed events. Resulting efficiencies should be accurate
to about 10%. Results of CDMS data from 1998 and 1999 with a relaxed
fiducial-volume cut (resulting in 15.8 kg-days exposure on Ge) are consistent
with an earlier analysis with a more restrictive fiducial-volume cut.
Twenty-three WIMP candidate events are observed, but these events are
consistent with a background from neutrons in all ways tested. Resulting limits
on the spin-independent WIMP-nucleon elastic-scattering cross-section exclude
unexplored parameter space for WIMPs with masses between 10-70 GeV c^{-2}.
These limits border, but do not exclude, parameter space allowed by
supersymmetry models and accelerator constraints. Results are compatible with
some regions reported as allowed at 3-sigma by the annual-modulation
measurement of the DAMA collaboration. However, under the assumptions of
standard WIMP interactions and a standard halo, the results are incompatible
with the DAMA most likely value at >99.9% CL, and are incompatible with the
model-independent annual-modulation signal of DAMA at 99.99% CL in the
asymptotic limit.Comment: 40 pages, 49 figures (4 in color), submitted to Phys. Rev. D;
v.2:clarified conclusions, added content and references based on referee's
and readers' comments; v.3: clarified introductory sections, added figure
based on referee's comment
Whole genome sequencing of Shigella sonnei through PulseNet Latin America and Caribbean: advancing global surveillance of foodborne illnesses
Objectives Shigella sonnei is a globally important diarrhoeal pathogen tracked through the surveillance network PulseNet Latin America and Caribbean (PNLA&C), which participates in PulseNet International. PNLA&C laboratories use common molecular techniques to track pathogens causing foodborne illness. We aimed to demonstrate the possibility and advantages of transitioning to whole genome sequencing (WGS) for surveillance within existing networks across a continent where S. sonnei is endemic. Methods We applied WGS to representative archive isolates of S. sonnei (n = 323) from laboratories in nine PNLA&C countries to generate a regional phylogenomic reference for S. sonnei and put this in the global context. We used this reference to contextualise 16 S. sonnei from three Argentinian outbreaks, using locally generated sequence data. Assembled genome sequences were used to predict antimicrobial resistance (AMR) phenotypes and identify AMR determinants. Results S. sonnei isolates clustered in five Latin American sublineages in the global phylogeny, with many (46%, 149 of 323) belonging to previously undescribed sublineages. Predicted multidrug resistance was common (77%, 249 of 323), and clinically relevant differences in AMR were found among sublineages. The regional overview showed that Argentinian outbreak isolates belonged to distinct sublineages and had different epidemiologic origins. Conclusions Latin America contains novel genetic diversity of S. sonnei that is relevant on a global scale and commonly exhibits multidrug resistance. Retrospective passive surveillance with WGS has utility for informing treatment, identifying regionally epidemic sublineages and providing a framework for interpretation of prospective, locally sequenced outbreaks
Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector
A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results
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