1,519 research outputs found
The influence of feeding behaviour and temperature on the capacity of mosquitoes to transmit malaria
Insecticide-treated bed nets reduce malaria transmission by limiting contact between mosquito vectors and human hosts when mosquitoes feed during the night. However, malaria vectors can also feed in the early evening and in the morning when people are not protected. Here, we explored how the timing of blood feeding interacts with environmental temperature to influence the capacity of Anopheles mosquitoes to transmit the human malaria parasite Plasmodium falciparum. In laboratory experiments, we found no effect of biting time itself on the proportion of mosquitoes that became infectious (vector competence) at constant temperature. However, when mosquitoes were maintained under more realistic fluctuating temperatures, there was a significant increase in competence for mosquitoes feeding in the evening (18:00), and a significant reduction in competence for those feeding in the morning (06:00), relative to those feeding at midnight (00:00). These effects appear to be due to thermal sensitivity of malaria parasites during the initial stages of parasite development within the mosquito, and the fact that mosquitoes feeding in the evening experience cooling temperatures during the night, whereas mosquitoes feeding in the morning quickly experience warming temperatures that are inhibitory to parasite establishment. A transmission dynamics model illustrates that such differences in competence could have important implications for malaria prevalence, the extent of transmission that persists in the presence of bed nets, and the epidemiological impact of behavioural resistance. These results indicate that the interaction of temperature and feeding behaviour could be a major ecological determinant of the vectorial capacity of malaria mosquitoes
Assembly of alpha-synuclein and neurodegeneration in the central nervous system of heterozygous M83 mice following the peripheral administration of alpha-synuclein seeds
Peripheral administration (oral, intranasal, intraperitoneal, intravenous) of assembled A53T α-synuclein induced synucleinopathy in heterozygous mice transgenic for human mutant A53T α-synuclein (line M83). The same was the case when cerebellar extracts from a case of multiple system atrophy with type II α-synuclein filaments were administered intraperitoneally, intravenously or intramuscularly. We observed abundant immunoreactivity for pS129 α-synuclein in nerve cells and severe motor impairment, resulting in hindlimb paralysis and shortened lifespan. Filaments immunoreactive for pS129 α-synuclein were in evidence. A 70% loss of motor neurons was present five months after an intraperitoneal injection of assembled A53T α-synuclein or cerebellar extract with type II α-synuclein filaments from an individual with a neuropathologically confirmed diagnosis of multiple system atrophy. Microglial cells changed from a predominantly ramified to a dystrophic appearance. Taken together, these findings establish a close relationship between the formation of α-synuclein inclusions in nerve cells and neurodegeneration, accompanied by a shift in microglial cell morphology. Propagation of α-synuclein inclusions depended on the characteristics of both seeds and transgenically expressed protein
Asymmetric Dark Matter from Leptogenesis
We present a new realization of asymmetric dark matter in which the dark
matter and lepton asymmetries are generated simultaneously through two-sector
leptogenesis. The right-handed neutrinos couple both to the Standard Model and
to a hidden sector where the dark matter resides. This framework explains the
lepton asymmetry, dark matter abundance and neutrino masses all at once. In
contrast to previous realizations of asymmetric dark matter, the model allows
for a wide range of dark matter masses, from keV to 10 TeV. In particular, very
light dark matter can be accommodated without violating experimental
constraints. We discuss several variants of our model that highlight
interesting phenomenological possibilities. In one, late decays repopulate the
symmetric dark matter component, providing a new mechanism for generating a
large annihilation rate at the present epoch and allowing for mixed warm/cold
dark matter. In a second scenario, dark matter mixes with the active neutrinos,
thus presenting a distinct method to populate sterile neutrino dark matter
through leptogenesis. At late times, oscillations and dark matter decays lead
to interesting indirect detection signals.Comment: 32 pages + appendix, references added, minor change
Asymmetric Origin for Gravitino Relic Density in the Hybrid Gravity-Gauge Mediated Supersymmetry Breaking
We propose the hybrid gravity-gauge mediated supersymmetry breaking where the
gravitino mass is about several GeV. The strong constraints on supersymmetry
viable parameter space from the CMS and ATLAS experiments at the LHC can be
relaxed due to the heavy colored supersymmetric particles, and it is consistent
with null results in the dark matter (DM) direct search experiments such as
XENON100. In particular, the possible maximal flavor and CP violations from the
relatively small gravity mediation may naturally account for the recent LHCb
anomaly. In addition, because the gravitino mass is around the asymmetric DM
mass, we propose the asymmetric origin of the gravitino relic density and solve
the cosmological coincident problem on the DM and baryon densities \Omega_{\rm
DM}:\Omega_{B}\approx 5:1. The gravitino relic density arises from asymmetric
metastable particle (AMP) late decay. However, we show that there is no AMP
candidate in the minimal supersymmetric Standard Model (SM) due to the robust
gaugino/Higgsino mediated wash-out effects. Interestingly, AMP can be realized
in the well motivated supersymmetric SMs with vector-like particles or
continuous U(1)_R symmetry. Especially, the lightest CP-even Higgs boson mass
can be lifted in the supersymmetric SMs with vector-like particles.Comment: RevTex4, 21 pages, 1 figure, minor corrections, JHEP versio
Warped Radion Dark Matter
Warped scenarios offer an appealing solution to the hierarchy problem. We
consider a non-trivial deformation of the basic Randall-Sundrum framework that
has a KK-parity symmetry. This leads to a stable particle beyond the Standard
Model, that is generically expected to be the first KK-parity odd excitation of
the radion field. We consider the viability of the KK-radion as a DM candidate
in the context of thermal and non-thermal production in the early universe. In
the thermal case, the KK-radion can account for the observed DM density when
the radion decay constant is in the natural multi-TeV range. We also explore
the effects of coannihilations with the first KK excitation of the RH top, as
well as the effects of radion-Higgs mixing, which imply mixing between the
KK-radion and a KK-Higgs (both being KK-parity odd). The non-thermal scenario,
with a high radion decay constant, can also lead to a viable scenario provided
the reheat temperature and the radion decay constant take appropriate values,
although the reheat temperature should not be much higher than the TeV scale.
Direct detection is found to be feasible if the DM has a small (KK-parity odd)
Higgs admixture. Indirect detection via a photon signal from the galactic
center is an interesting possibility, while the positron and neutrino fluxes
from KK-radion annihilations are expected to be rather small. Colliders can
probe characteristic aspects of the DM sector of warped scenarios with
KK-parity, such as the degeneracy between the radion and the KK-radion (DM)
modes.Comment: 43 pages, 16 figures; added reference
Lorentz Violation in Warped Extra Dimensions
Higher dimensional theories which address some of the problematic issues of
the Standard Model(SM) naturally involve some form of -dimensional
Lorentz invariance violation (LIV). In such models the fundamental physics
which leads to, e.g., field localization, orbifolding, the existence of brane
terms and the compactification process all can introduce LIV in the higher
dimensional theory while still preserving 4-d Lorentz invariance. In this
paper, attempting to capture some of this physics, we extend our previous
analysis of LIV in 5-d UED-type models to those with 5-d warped extra
dimensions. To be specific, we employ the 5-d analog of the SM Extension of
Kostelecky et. al. ~which incorporates a complete set of operators arising from
spontaneous LIV. We show that while the response of the bulk scalar, fermion
and gauge fields to the addition of LIV operators in warped models is
qualitatively similar to what happens in the flat 5-d UED case, the gravity
sector of these models reacts very differently than in flat space.
Specifically, we show that LIV in this warped case leads to a non-zero bulk
mass for the 5-d graviton and so the would-be zero mode, which we identify as
the usual 4-d graviton, must necessarily become massive. The origin of this
mass term is the simultaneous existence of the constant non-zero
curvature and the loss of general co-ordinate invariance via LIV in the 5-d
theory. Thus warped 5-d models with LIV in the gravity sector are not
phenomenologically viable.Comment: 14 pages, 4 figs; discussion added, algebra repaire
Risk factors for high anti-HHV-8 antibody titers (≥1:51,200) in black, HIV-1 negative South African cancer patients: a case control study
Background: Infection with human herpesvirus 8 (HHV-8) is the necessary causal agent in the
development of Kaposi's sarcoma (KS). Infection with HIV-1, male gender and older age all increase
risk for KS. However, the geographic distribution of HHV-8 and KS both prior to the HIV/AIDS
epidemic and with HIV/AIDS suggest the presence of an additional co-factor in the development of
KS.
Methods: Between January 1994 and October 1997, we interviewed 2576 black in-patients with
cancer in Johannesburg and Soweto, South Africa. Blood was tested for antibodies against HIV-1
and HHV-8 and the study was restricted to 2191 HIV-1 negative patients. Antibodies against the
latent nuclear antigen of HHV-8 encoded by orf73 were detected with an indirect
immunofluorescence assay. We examined the relationship between high anti-HHV-8 antibody
titers (≥1:51,200) and sociodemographic and behavioral factors using unconditional logistic
regression models. Variables that were significant at p = 0.10 were included in multivariate analysis.
Results: Of the 2191 HIV-1 negative patients who did not have Kaposi's sarcoma, 854 (39.0%)
were positive for antibodies against HHV-8 according to the immunofluorescent assay. Among
those seropositive for HHV-8, 530 (62.1%) had low titers (1:200), 227 (26.6%) had medium titers
(1:51,200) and 97 (11.4%) had highest titers (1:204,800). Among the 2191 HIV-1 negative patients,
the prevalence of high anti-HHV-8 antibody titers (≥1:51,200) was independently associated with
increasing age (ptrend = 0.04), having a marital status of separated or divorced (p = 0.003), using
wood, coal or charcoal as fuel for cooking 20 years ago instead of electricity (p = 0.02) and
consuming traditional maize beer more than one time a week (p = 0.02; p-trend for increasing
consumption = 0.05) although this may be due to chance given the large number of predictors
considered in this analysis.
Conclusions: Among HIV-negative subjects, patients with high anti-HHV-8 antibody titers are
characterized by older age. Other associations that may be factors in the development of high anti-
HHV-8 titers include exposure to poverty or a low socioeconomic status environment and
consumption of traditional maize beer. The relationship between these variables and high anti-
HHV-8 titers requires further, prospective study
The flavor puzzle in multi-Higgs models
We reconsider the flavor problem in the models with two Higgs doublets. By
studying two generation toy models, we look for flavor basis independent
constraints on Yukawa couplings that will give us the mass hierarchy while
keeping all Yukawa couplings of the same order. We then generalize our findings
to the full three generation Standard Model. We find that we need two
constraints on the Yukawa couplings to generate the observed mass hierarchy,
and a slight tuning of Yukawa couplings of order 10%, much less than the
Standard Model. We briefly study how these constraints can be realized, and
show how flavor changing currents are under control for mixing in
the near-decoupling limit.Comment: 26 pages, typos are corrected, references are added, the final
versio
Is Emotion Recognition Impaired in Individuals with Autism Spectrum Disorders?
Researchers have argued that individuals with autism spectrum disorders (ASDs) use an effortful “systematizing” process to recognize emotion expressions, whereas typically developing (TD) individuals use a more holistic process. If this is the case, individuals with ASDs should show slower and less efficient emotion recognition, particularly for socially complex emotions. We tested this account by assessing the speed and accuracy of emotion recognition while limiting exposure time and response window. Children and adolescents with ASDs showed quick and accurate recognition for most emotions, including pride, a socially complex emotion, and no differences emerged between ASD and TD groups. Furthermore, both groups trended toward higher accuracy when responding quickly, even though systematizing should promote a speed-accuracy trade-off for individuals with ASDs
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