489 research outputs found
Shallow Gas Hydrate Accumulations at a Nigerian Deepwater PockmarkâQuantities and Dynamics
The evolution of submarine pockmarks is often related to the ascent of fluid from the subsurface. For pockmarks located within the gas hydrate stability zone, methane oversaturation can result in the formation of gas hydrates in the sediment. An ~600 mâwide sea floor depression in deep waters offshore Nigeria, Pockmark A, was investigated for distributions and quantities of shallow gas hydrates, origins of hydrocarbons, and time elapsed since the last major fluid ascent event. For the first time, pressure coring of shallow sediments and drilling of more than 50 mâlong cores with the sea floor drill rig MARUMâMeBo70 were conducted in this pockmark. Unusually, high hydrate saturations of up to 51% of pore volume in the uppermost 2.5 m of sediment in the pockmark center substantiate that deepwater pockmarks are a relevant methane reservoir. Molecular and stable C and H isotopic compositions suggest that thermogenic hydrocarbons and secondary microbial methane resulting from petroleum biodegradation are injected into shallower sediments and mixed with primary microbial hydrocarbons. Two independent pore water chloride and sulfate modeling approaches suggest that a major methane migration event occurred during the past one to three centuries. A rough sea floor topography within the pockmark most likely results from combined sediment removal through ascending gas bubbles, hydrate clogging and deflection of migration pathways, gas pressure buildâup, and hydrate sea floor detachment. This study shows for the first time the chronological interrelationship between gas migration events, hydrate formation, and sea floor shaping in a deep sea pockmark
Age-related delay in information accrual for faces: Evidence from a parametric, single-trial EEG approach
Background: In this study, we quantified age-related changes in the time-course of face processing
by means of an innovative single-trial ERP approach. Unlike analyses used in previous studies, our
approach does not rely on peak measurements and can provide a more sensitive measure of
processing delays. Young and old adults (mean ages 22 and 70 years) performed a non-speeded
discrimination task between two faces. The phase spectrum of these faces was manipulated
parametrically to create pictures that ranged between pure noise (0% phase information) and the
undistorted signal (100% phase information), with five intermediate steps.
Results: Behavioural 75% correct thresholds were on average lower, and maximum accuracy was
higher, in younger than older observers. ERPs from each subject were entered into a single-trial
general linear regression model to identify variations in neural activity statistically associated with
changes in image structure. The earliest age-related ERP differences occurred in the time window
of the N170. Older observers had a significantly stronger N170 in response to noise, but this age
difference decreased with increasing phase information. Overall, manipulating image phase
information had a greater effect on ERPs from younger observers, which was quantified using a
hierarchical modelling approach. Importantly, visual activity was modulated by the same stimulus
parameters in younger and older subjects. The fit of the model, indexed by R2, was computed at
multiple post-stimulus time points. The time-course of the R2 function showed a significantly slower
processing in older observers starting around 120 ms after stimulus onset. This age-related delay
increased over time to reach a maximum around 190 ms, at which latency younger observers had
around 50 ms time lead over older observers.
Conclusion: Using a component-free ERP analysis that provides a precise timing of the visual
system sensitivity to image structure, the current study demonstrates that older observers
accumulate face information more slowly than younger subjects. Additionally, the N170 appears to
be less face-sensitive in older observers
Genotyping of Infectious Laryngotracheitis Virus (ILTV) isolates from Western Canadian provinces of Alberta and British Columbia based on partial Open Reading Frame (ORF) a and b
Infectious laryngotracheitis virus (ILTV) causes an acute upper respiratory disease in
chickens called infectious laryngotracheitis (ILT). Live attenuated vaccines are effective in disease
control; however, they have residual virulence, which makes them able to replicate, cause disease
and revert to the original virulent form. Information is scarce on the molecular nature of ILTV that is
linked to ILT in Canada. This study aims to determine whether isolates originating from ILT cases in
Western Canada are a wild type or vaccine origin. Samples submitted for the diagnosis of ILT between
2009â2018 were obtained from Alberta (AB, n = 46) and British Columbia (BC, n = 9). For genotyping,
a Sanger sequencing of open reading frame (ORF) a and b was used. A total of 27 from AB, and 5 from
BC samples yielded a fragment of 1751 base pairs (bp). Three of the BC samples classified as group
IV (CEO vaccine strains) and 2 as group V (CEO revertant). Of the AB samples, 22 samples clustered with group V, 3 with group VI (wild type), and 2 with group VII, VIII, and IX (wild type). Overall,
17 non-synonymous single nucleotide polymorphisms (SNPs) were detected. Further studies are
underway to ascertain the virulence and transmission potential of these isolates
Analysis of whole-genome sequences of infectious laryngotracheitis virus isolates from poultry flocks in Canada : evidence of recombination
Infectious laryngotracheitis virus (ILTV) is a herpes virus that causes an acute respiratory disease of poultry known as infectious laryngotracheitis (ILT). Chicken embryo origin (CEO) and tissue culture origin (TCO) live attenuated vaccines are routinely used for the control of ILT. However, vaccine virus is known to revert to virulence, and it has been recently shown that ILT field viral strains can undergo recombination with vaccinal ILTV and such recombinant ILT viruses possess greater transmission and pathogenicity potential. Based on complete or partial genes of the ILTV genome, few studies genotyped ILTV strains circulating in Canada, and so far, information is scarce on whole-genome sequencing or the presence of recombination in Canadian ILTV isolates. The objective of this study was to genetically characterize the 14 ILTV isolates that originated from three provinces in Canada (Alberta, British Columbia and Quebec). To this end, a phylogenetic analysis of 50 ILTV complete genome sequences, including 14 sequences of Canadian origin, was carried out. Additional phylogenetic analysis of the unique long, unique short and inverted repeat regions of the ILTV genome was also performed. We observed that 71%, 21% and 7% of the ILTV isolates were categorized as CEO revertant, wild-type and TCO vaccine-related, respectively. The sequences were also analyzed for potential recombination events, which included evidence in the British Columbia ILTV isolate. This event involved two ILTV vaccine (CEO) strains as parental strains. Recombination analysis also identified that one ILTV isolate from Alberta as a potential parental strain for a United States origin ILTV isolate. The positions of the possible recombination breakpoints were identified. These results indicate that the ILTV wild-type strains can recombine with vaccinal strains complicating vaccine-mediated control of ILT. Further studies on the pathogenicity of these ILTV strains, including the recombinant ILTV isolate are currently ongoing
Evaluation of recombinant Herpesvirus of Turkey Laryngotracheitis (rHVT-LT) Vaccine against Genotype VI Canadian Wild-Type Infectious Laryngotracheitis Virus (ILTV) Infection
In Alberta, infectious laryngotracheitis virus (ILTV) infection is endemic in backyard
poultry flocks; however, outbreaks are only sporadically observed in commercial flocks. In addition
to ILTV vaccine revertant strains, wild-type strains are among the most common causes of infectious
laryngotracheitis (ILT). Given the surge in live attenuated vaccine-related outbreaks, the goal of this
study was to assess the efficacy of a recombinant herpesvirus of turkey (rHVT-LT) vaccine against a
genotype VI Canadian wild-type ILTV infection. One-day-old specific pathogen-free (SPF) White
Leghorn chickens were vaccinated with the rHVT-LT vaccine or mock vaccinated. At three weeks
of age, half of the vaccinated and the mock-vaccinated animals were challenged. Throughout the
experiment, weights were recorded, and feather tips, cloacal and oropharyngeal swabs were collected
for ILTV genome quantification. Blood was collected to isolate peripheral blood mononuclear
cells (PBMC) and quantify CD4+ and CD8+ T cells. At 14 dpi, the chickens were euthanized, and
respiratory tissues were collected to quantify genome loads and histological examination. Results
showed that the vaccine failed to decrease the clinical signs at 6 days post-infection. However, it
was able to significantly reduce ILTV shedding through the oropharyngeal route. Overall, rHVT-LT
produced a partial protection against genotype VI ILTV infection
Editorial : Solving Complex Ocean Challenges Through Interdisciplinary Research: Advances from Early Career Marine Scientists
Non peer reviewe
Pathogenic and transmission potential of wildtype and chicken embryo origin (CEO) vaccine revertant infectious laryngotracheitis virus
Infectious laryngotracheitis (ILT) is an infectious upper respiratory tract disease that
impacts the poultry industry worldwide. ILT is caused by an alphaherpesvirus commonly referred
to as infectious laryngotracheitis virus (ILTV). Vaccination with live attenuated vaccines is practiced
regularly for the control of ILT. However, extensive and improper use of live attenuated vaccines
is related to vaccine viruses reverting to virulence. An increase in mortality and pathogenicity has
been attributed to these vaccine revertant viruses. Recent studies characterized Canadian ILTV
strains originating from ILT outbreaks as related to live attenuated vaccine virus revertants. However,
information is scarce on the pathogenicity and transmission potential of these Canadian isolates.
Hence, in this study, the pathogenicity and transmission potential of two wildtype ILTVs and a
chicken embryo origin (CEO) vaccine revertant ILTV of Canadian origin were evaluated. To this
end, 3-week-old specific pathogen-free chickens were experimentally infected with each of the ILTV
isolates and compared to uninfected controls. Additionally, naĂŻve chickens were exposed to the
experimentally infected chickens to mimic naturally occurring infection. Pathogenicity of each of
these ILTV isolates was evaluated by the severity of clinical signs, weight loss, mortality, and lesions
observed at the necropsy. The transmission potential was evaluated by quantification of ILTV genome
loads in oropharyngeal and cloacal swabs and tissue samples of the experimentally infected and
contact-exposed chickens, as well as in the capacity to produce ILT in contact-exposed chickens.
We observed that the CEO vaccine revertant ILTV isolate induced severe disease in comparison
to the two wildtype ILTV isolates used in this study. According to ILTV genome load data, CEO
vaccine revertant ILTV isolate was successfully transmitted to naĂŻve contact-exposed chickens in
comparison to the tested wildtype ILTV isolates. Overall, the Canadian origin CEO vaccine revertant
ILTV isolate possesses higher virulence, and dissemination potential, when compared to the wildtype
ILTV isolates used in this study. These findings have serious implications in ILT control in chickens
UBVRI Light Curves of 44 Type Ia Supernovae
We present UBVRI photometry of 44 type-Ia supernovae (SN Ia) observed from
1997 to 2001 as part of a continuing monitoring campaign at the Fred Lawrence
Whipple Observatory of the Harvard-Smithsonian Center for Astrophysics. The
data set comprises 2190 observations and is the largest homogeneously observed
and reduced sample of SN Ia to date, nearly doubling the number of
well-observed, nearby SN Ia with published multicolor CCD light curves. The
large sample of U-band photometry is a unique addition, with important
connections to SN Ia observed at high redshift. The decline rate of SN Ia
U-band light curves correlates well with the decline rate in other bands, as
does the U-B color at maximum light. However, the U-band peak magnitudes show
an increased dispersion relative to other bands even after accounting for
extinction and decline rate, amounting to an additional ~40% intrinsic scatter
compared to B-band.Comment: 84 authors, 71 pages, 51 tables, 10 figures. Accepted for publication
in the Astronomical Journal. Version with high-res figures and electronic
data at http://astron.berkeley.edu/~saurabh/cfa2snIa
Fifteen new risk loci for coronary artery disease highlight arterial-wall-specific mechanisms
Coronary artery disease (CAD) is a leading cause of morbidity and mortality worldwide. Although 58 genomic regions have been associated with CAD thus far, most of the heritability is unexplained, indicating that additional susceptibility loci await identification. An efficient discovery strategy may be larger-scale evaluation of promising associations suggested by genome-wide association studies (GWAS). Hence, we genotyped 56,309 participants using a targeted gene array derived from earlier GWAS results and performed meta-analysis of results with 194,427 participants previously genotyped, totaling 88,192 CAD cases and 162,544 controls. We identified 25 new SNP-CAD associations (P < 5 Ă 10(-8), in fixed-effects meta-analysis) from 15 genomic regions, including SNPs in or near genes involved in cellular adhesion, leukocyte migration and atherosclerosis (PECAM1, rs1867624), coagulation and inflammation (PROCR, rs867186 (p.Ser219Gly)) and vascular smooth muscle cell differentiation (LMOD1, rs2820315). Correlation of these regions with cell-type-specific gene expression and plasma protein levels sheds light on potential disease mechanisms
- âŠ