4,321 research outputs found
On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining
Capitalizing on the recently proposed Fisher-Snedecor F composite fading
model, in this letter, we investigate the sum of independent but not
identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel
closed-form expression is derived for the moment generating function of the
instantaneous signal-to-noise ratio. Based on this, the corresponding
probability density function and cumulative distribution function of the sum of
i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently
employed in the analysis of multiple branch maximal-ratio combining (MRC).
Specifically, we investigate the impact of multipath and shadowed fading on the
outage probability and outage capacity of MRC based receivers. In addition, we
derive exact closed-form expressions for the average bit error rate of coherent
binary modulation schemes followed by an asymptotic analysis which provides
further insights into the effect of the system parameters on the overall
performance. Importantly, it is shown that the effect of multipath fading on
the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure
The role of Dark Matter interaction in galaxy clusters
We consider a toy model to analyze the consequences of dark matter
interaction with a dark energy background on the overall rotation of galaxy
clusters and the misalignment between their dark matter and baryon
distributions when compared to {\Lambda}CDM predictions. The interaction
parameters are found via a genetic algorithm search. The results obtained
suggest that interaction is a basic phenomenon whose effects are detectable
even in simple models of galactic dynamics.Comment: RevTeX 4.1, 5 pages, 3 figure
A nationwide cohort study of slipped capital femoral epiphysis
Objectives To describe the epidemiology of slipped capital femoral epiphysis (SCFE), to examine associations with childhood obesity and socioeconomic deprivation, and to explore factors associated with diagnostic delays. Design Historic cohort study using linked primary and secondary care data from the Clinical Practice Research Datalink and Hospital Episode Statistics. Setting All contacts with healthcare services, including emergency presentations, outpatient appointments, inpatient admissions and primary care visits, within the UK National Health Service. Patients All individuals <16 years old with a diagnosis of SCFE and whose electronic medical record was held by one of 650 primary care practices in the UK between 1990 and 2013. Main outcome measures Annual incidence, missed opportunities for diagnosis and diagnostic delay. Results Over the 23-year period the incidence remained constant at 4.8 (95% CI 4.4 to 5.2) cases per 100,000 0–16-year-olds. There was a strong association with socioeconomic deprivation. Predisease obesity was also strongly associated with SCFE; mean predisease z-score of body mass index was 1.43 (95% CI 1.20 to 1.68) compared with the UK reference mean. Diagnostic delays were common, with most children (75.4%) having multiple primary care contacts with relevant symptomatology, and those who presented with knee pain having significantly longer diagnostic delay (median 161 (IQR 27–278) days) than those with hip pain (20 (5–126)) or gait abnormalities (21 (7–72)). Conclusions SCFE has a strong association with both area-level socioeconomic deprivation and predisease obesity. The majority of patients with SCFE are initially misdiagnosed and those presenting with knee pain are particularly at risk
Replication-deficient Adenoviral Vector for Gene Transfer Potentiates Airway Neurogenic Inflammation
Human trials for the treatment of cystic fibrosis lung disease with adenoviral vectors have been complicated
by acute inflammatory reactions of unknown etiology. Because replicating respiratory viruses can
potentiate tachykinin-mediated neurogenic inflammatory responses in airways, we studied whether the
endotracheal administration of a replication-deficient adenoviral vector potentiated this response. The vector
Ad5CMVLacZ was administered endotracheally to rats and the leakage of Evans blue dye was used
to measure the capsaicin-induced neurogenic albumin extravasation. These studies show that neurogenic
albumin extravasation is significantly potentiated in the airways of rats after administration of Ad5CMVLacZ.
This inflammatory response can be blocked by selective antagonists of the substance Preceptor
or by glucocorticoids. Therefore, (1) the acute airway inflammation observed in patients after exposure
to adenoviral vectors may exhibit a neurogenic component, which can be blocked pharmacologically, and
(2) preclinical adenoviral vector safety studies of other organs innervated by the tachykinin system, e.g.,
coronary arteries and gastrointestinal tract, should include assessment of neurogenic inflammation
Candidates for Balancing Selection in Leishmania donovani Complex Parasites
The Leishmania donovani species complex is the causative agent of visceral leishmaniasis, which cause 20–40,000 fatalities a year. Here, we conduct a screen for balancing selection in this species complex. We used 384 publicly available L. donovani and L. infantum genomes, and sequence 93 isolates of L. infantum from Brazil to describe the global diversity of this species complex. We identify five genetically distinct populations that are sufficiently represented by genomic data to search for signatures of selection. We find that signals of balancing selection are generally not shared between populations, consistent with transient adaptive events, rather than long-term balancing selection. We then apply multiple diversity metrics to identify candidate genes with robust signatures of balancing selection, identifying a curated set of 24 genes with robust signatures. These include zetatoxin, nodulin-like, and flagellum attachment proteins. This study highlights the extent of genetic divergence between L. donovani complex parasites and provides genes for further stud
An integrated approach to assess the sublethal effects of colloidal gold nanorods in tadpoles of Xenopus laevis
Gold nanorods (AuNR) have been explored for many applications, including innovative nanomedicines, which also might contribute to its increase in the environment, namely due to inadequate disposable of wastes into aquatic environments. Early-life stages of amphibians are usually aquatic and sensitive to chemical contamination. Accordingly, this study aimed to determine the sublethal effects of CTAB functionalized AuNR on Xenopus laevis tadpoles. As such, tadpoles were exposed to serial concentrations of AuNR for 72 h. A reduction in the rate of feeding (EC50 = 4 μg.L-1), snout to vent growth (EC50 = 5 μg.L-1) and weight gain (EC50 = 6 μg.L-1), was observed for AuNR-exposed tadpoles. Also, tadpoles actively avoided concentrations ≥ 4 μg.L-1 of AuNR, after 12 h of exposure. At the biochemical level, AuNR caused impairments in antioxidant and nervous system related enzymes. Exposure to CTAB alone caused a high mortality. Results indicated that CTAB functionalized AuNR may induce several sublethal effects that may compromise the organism's fitness. Avoidance behavior (which corresponds to the disappearance of organisms, thus, similar to their death), observed at concentrations matching those inducing sublethal effects, suggest that it should be considered in the risk assessment for amphibians.publishe
Tensor-Based Methods for Blind Spatial Signature Estimation in Multidimensional Sensor Arrays
The estimation of spatial signatures and spatial frequencies is crucial for several practical applications such as radar, sonar, and wireless communications. In this paper, we propose two generalized iterative estimation algorithms to the case in which a multidimensional (R-D) sensor array is used at the receiver. The first tensor-based algorithm is an R-D blind spatial signature estimator that operates in scenarios where the source’s covariance matrix is nondiagonal and unknown. The second tensor-based algorithm is formulated for the case in which the sources are uncorrelated and exploits the dual-symmetry of the covariance tensor. Additionally, a new tensor-based formulation is proposed for an L-shaped array configuration. Simulation results show that our proposed schemes outperform the state-of-the-art matrix-based and tensor-based techniques
Emission-Line Galaxy Surveys as Probes of the Spatial Distribution of Dwarf Galaxies. I. The University of Michigan Survey
Objective-prism surveys which select galaxies on the basis of line-emission
are extremely effective at detecting low-luminosity galaxies and constitute
some of the deepest available samples of dwarfs. In this study, we confirm that
emission-line galaxies (ELGs) in the University of Michigan (UM)
objective-prism survey (MacAlpine et al. 1977-1981) are reliable tracers of
large-scale structure, and utilize the depth of the samples to examine the
spatial distribution of low-luminosity (M -18.0) dwarfs relative to
higher luminosity giant galaxies (M -18.0) in the Updated Zwicky
Catalogue (Falco et al. 1999). New spectroscopic data are presented for 26 UM
survey objects. We analyze the relative clustering properties of the overall
starbursting ELG and normal galaxy populations, using nearest neighbor and
correlation function statistics. This allows us to determine whether the
activity in ELGs is primarily caused by gravitational interactions. We conclude
that galaxy-galaxy encounters are not the sole cause of activity in ELGs since
ELGs tend to be more isolated and are more often found in the voids when
compared to their normal galaxy counterparts. Furthermore, statistical analyses
performed on low-luminosity dwarf ELGs show that the dwarfs are less clustered
when compared to their non-active giant neighbors. The UM dwarf samples have
greater percentages of nearest neighbor separations at large values and lower
correlation function amplitudes relative to the UZC giant galaxy samples. These
results are consistent with the expectations of galaxy biasing.Comment: 17 pages, 4 tables, 10 figures. Accepted for publication in the Ap
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