554 research outputs found

    Linear instabilities of a two-layer geostrophic surface front near a wall

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    The development of linear instabilities on a geostrophic surface front in a two-layer primitive equation model on an ƒ-plane is studied analytically and numerically using a highly accurate differential shooting method. The basic state is composed of an upper layer in which the mean flow has a constant potential vorticity, and a quiescent lower layer that outcrops between a vertical wall and the surface front (defined as the line of intersection between the interface that separates the two layers and the ocean\u27s surface). The characteristics of the linear instabilities found in the present work confirm earlier results regarding the strong dependence of the growth rate (σi) on the depth ratio r (defined as the ratio between the total ocean depth and the upper layer\u27s depth at infinity) for r ≥ 2 and their weak dependence on the distance L between the surface front and the wall. These earlier results of the large r limit were obtained using a much coarser, algebraic, method and had a single maximum of the growth rate curve at some large wavenumber k. Our new results, in the narrow range of 1.005 ≤ r ≤ 1.05, demonstrate that the growth rate curve displays a second lobe with a local (secondary) maximum at a nondimensional wavenumber (with the length scale given by the internal radius of deformation) of 1.05. A new fitting function 0.183 r-0.87is found for the growth rate of the most unstable wave (σimax ) for r ranging between 1.001 and 20, and for L \u3e 2 Rd (i.e.where the effect of the wall becomes negligible). Therefore, σimax converges to a finite value for |r — 1 | \u3c\u3c 1 (infinitely thin lower layer). This result differs from quasi-geostrophic, analytic solutions that obtain for the no wall case since the QG approximation is not valid for very thin layers. In addition, an analytical solution is derived for the lower-layer solutions in the region between the wall and the surface front where the upper layer is not present. The weak dependence of the growth rate on L that emerges from the numerical solution of the eigenvalue problem is substantiated analytically by the way L appears in the boundary conditions at the surface front. Applications of these results for internal radii of deformation of 35– 45 km show reasonable agreement with observed meander characteristics of the Gulf Stream downstream of Cape Hatteras. Wavelengths and phase speeds of (180 –212 km, 39 –51 km/day) in the vicinity of Cape Hatteras were also found to match with the predicted dispersion relationships for the depth-ratio range of 1+ \u3c r \u3c 2

    Structure of 12Be: intruder d-wave strength at N=8

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    The breaking of the N=8 shell-model magic number in the 12Be ground state has been determined to include significant occupancy of the intruder d-wave orbital. This is in marked contrast with all other N=8 isotones, both more and less exotic than 12Be. The occupancies of the 0 hbar omega neutron p1/2-orbital and the 1 hbar omega, neutron d5/2 intruder orbital were deduced from a measurement of neutron removal from a high-energy 12Be beam leading to bound and unbound states in 11Be.Comment: 5 pages, 2 figure

    Submesoscale dispersion in the vicinity of the Deepwater Horizon spill

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    Reliable forecasts for the dispersion of oceanic contamination are important for coastal ecosystems, society and the economy as evidenced by the Deepwater Horizon oil spill in the Gulf of Mexico in 2010 and the Fukushima nuclear plant incident in the Pacific Ocean in 2011. Accurate prediction of pollutant pathways and concentrations at the ocean surface requires understanding ocean dynamics over a broad range of spatial scales. Fundamental questions concerning the structure of the velocity field at the submesoscales (100 meters to tens of kilometers, hours to days) remain unresolved due to a lack of synoptic measurements at these scales. \textcolor{black} {Using high-frequency position data provided by the near-simultaneous release of hundreds of accurately tracked surface drifters, we study the structure of submesoscale surface velocity fluctuations in the Northern Gulf Mexico. Observed two-point statistics confirm the accuracy of classic turbulence scaling laws at 200m−-50km scales and clearly indicate that dispersion at the submesoscales is \textit{local}, driven predominantly by energetic submesoscale fluctuations.} The results demonstrate the feasibility and utility of deploying large clusters of drifting instruments to provide synoptic observations of spatial variability of the ocean surface velocity field. Our findings allow quantification of the submesoscale-driven dispersion missing in current operational circulation models and satellite altimeter-derived velocity fields.Comment: 9 pages, 6 figure

    The Interplay Between Attentional Strategies and Language Processing in High-functioning Adults with Autism Spectrum Disorder

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    This study examined the hypothesis of an atypical interaction between attention and language in ASD. A dual-task experiment with three conditions was designed, in which sentences were presented that contained errors requiring attentional focus either at (a) low level, or (b) high level, or (c) both levels of language. Speed and accuracy for error detection were measured from 16 high-functioning adults with ASD, and 16 matched controls. For controls, there was an attentional cost of dual level processing for low level performance but not for high level performance. For participants with ASD, there was an attentional cost both for low level and for high level performance. These results suggest a compensatory strategic use of attention during language processing in ASD

    Increased brain age in adults with Prader-Willi syndrome.

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    Prader-Willi syndrome (PWS) is the most common genetic obesity syndrome, with associated learning difficulties, neuroendocrine deficits, and behavioural and psychiatric problems. As the life expectancy of individuals with PWS increases, there is concern that alterations in brain structure associated with the syndrome, as a direct result of absent expression of PWS genes, and its metabolic complications and hormonal deficits, might cause early onset of physiological and brain aging. In this study, a machine learning approach was used to predict brain age based on grey matter (GM) and white matter (WM) maps derived from structural neuroimaging data using T1-weighted magnetic resonance imaging (MRI) scans. Brain-predicted age difference (brain-PAD) scores, calculated as the difference between chronological age and brain-predicted age, are designed to reflect deviations from healthy brain aging, with higher brain-PAD scores indicating premature aging. Two separate adult cohorts underwent brain-predicted age calculation. The main cohort consisted of adults with PWS (n = 20; age mean 23.1 years, range 19.8-27.7; 70.0% male; body mass index (BMI) mean 30.1 kg/m2, 21.5-47.7; n = 19 paternal chromosome 15q11-13 deletion) and age- and sex-matched controls (n = 40; age 22.9 years, 19.6-29.0; 65.0% male; BMI 24.1 kg/m2, 19.2-34.2) adults (BMI PWS vs. control P = .002). Brain-PAD was significantly greater in PWS than controls (effect size mean ± SEM +7.24 ± 2.20 years [95% CI 2.83, 11.63], P = .002). Brain-PAD remained significantly greater in PWS than controls when restricting analysis to a sub-cohort matched for BMI consisting of n = 15 with PWS with BMI range 21.5-33.7 kg/m2, and n = 29 controls with BMI 21.7-34.2 kg/m2 (effect size +5.51 ± 2.56 years [95% CI 3.44, 10.38], P = .037). In the PWS group, brain-PAD scores were not associated with intelligence quotient (IQ), use of hormonal and psychotropic medications, nor severity of repetitive or disruptive behaviours. A 24.5 year old man (BMI 36.9 kg/m2) with PWS from a SNORD116 microdeletion also had increased brain PAD of 12.87 years, compared to 0.84 ± 6.52 years in a second control adult cohort (n = 95; age mean 34.0 years, range 19.9-55.5; 38.9% male; BMI 28.7 kg/m2, 19.1-43.1). This increase in brain-PAD in adults with PWS indicates abnormal brain structure that may reflect premature brain aging or abnormal brain development. The similar finding in a rare patient with a SNORD116 microdeletion implicates a potential causative role for this PWS region gene cluster in the structural brain abnormalities associated primarily with the syndrome and/or its complications. Further longitudinal neuroimaging studies are needed to clarify the natural history of this increase in brain age in PWS, its relationship with obesity, and whether similar findings are seen in those with PWS from maternal uniparental disomy

    Comparing farm biosecurity and antimicrobial use in high-antimicrobial-consuming broiler and pig farms in the Belgian-Dutch border region

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    As antimicrobial resistance is a worldwide problem, threatening both livestock and public health, understanding the drivers for resistance in different settings and countries is essential. Therefore, 30 pig and 30 poultry farms with country-specific high antimicrobial use (AMU) were recruited in the Belgian-Dutch border region. Information regarding production parameters, farm characteristics, biosecurity, and AMU was collected. On average, more biosecurity measures were implemented on Dutch farms, compared to Belgian farms in both animal species. In addition, more opportunities were found to increase the level of internal biosecurity compared to external biosecurity in both countries. AMU, quantified as treatment incidence (TI), differed marginally significant between broiler farms in Belgium and the Netherlands (median BE: 8; NL: 3), whereas in weaned piglets (median BE: 45 and NL: 14) and finishing pigs (median BE: 5 and NL: 1), there was a substantial difference in AMU between farms from both countries. Overall, Dutch farms showed less between-farm variation in TI than did Belgian farms. In both poultry and pig production, the majority of antimicrobials used were extended-spectrum penicillins (BE: 32 and 40%; NL: 40 and 24% for poultry and pigs, respectively). Compared to Belgian farms, Dutch poultry farms used high amounts of (fluoro)quinolones (1 and 15% of total AMU, respectively). None of the production parameters between broiler farms differed significantly, but in pig production, weaning age in Belgian farms (median: 23) was lower than in Dutch farms (median: 27). These results indicate considerable room for improvement in both countries and animal species. Farm-specific preventive strategies can contribute to lowering the risk for animal disease and hence the need for AMU

    Reducing pain in children with cancer at home:a feasibility study of the KLIK pain monitor app

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    Purpose This study assessed adherence to, feasibility of, and barriers and facilitators of implementation of an app developed to monitor and follow-up with pain in children with cancer at home. Methods Children (8-18 years) receiving cancer treatment (all diagnoses) or their parents (of children aged 0-7 years) used the KLIK Pain Monitor app for 3 weeks. Pain was assessed twice daily using an 11-point numeric rating scale (NRS-11) (ranging from 0 to 10). Healthcare professionals (HCP's) from the hospital's Pediatric Pain Service were instructed to follow-up with clinically significant pain scores (>= 4) within 120 min (scores 4-6) or 30 min (scores 7-10). Adherence, feasibility, and implementation outcomes were assessed using questionnaires, app log data, and interviews. Results Twenty-seven children (M age = 7.3 years, 51.8% male) and six HCP's participated. Sixty-three percent (N = 17) of families used the app on a daily basis during three weeks, and 18.5% (N = 5) reported pain scores twice daily during that time (family adherence). Twelve out of 27 children (44.4%) reported a clinically significant pain score at least once. In 70% (14/20) of clinically significant pain scores, HCP's followed-up with families within the set timeframe (HCP adherence). Outcomes reveal feasibility for the majority of app functions (i.e., positive evaluation by >= 70% families/HCP's), and non-feasible aspects could be resolved. Identified barriers and facilitators were used to improve future implementation efforts. Conclusion Use of the KLIK Pain Monitor app seems feasible. Future research will determine its effectiveness in reducing pain in children with cancer at home

    High expression of Cathepsin E in tissues but not blood of patients with Barrett’s esophagus and adenocarcinoma

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    Background Cathepsin E (CTSE), an aspartic proteinase, is differentially expressed in the metaplasia–dysplasia–neoplasia sequence of gastric and colon cancer. We evaluated CTSE in Barrett’s esophagus (BE) and cancer because increased CTSE levels are linked to improved survival in several cancers, and other cathepsins are up-regulated in BE and esophageal adenocarcinoma (EAC). Methods A total of 273 pretreatment tissues from 199 patients were analyzed [31 normal squamous esophagus (NE), 29 BE intestinal metaplasia, 31 BE with dysplasia (BE/D), 108 EAC]. CTSE relative mRNA expression was measured by real-time polymerase chain reaction, and protein expression was measured by immunohistochemistry. CTSE serum levels were determined by enzyme-linked immunosorbent assay. Results Median CTSE mRNA expression levels were ≥1,000-fold higher in BE/intestinal metaplasia and BE/D compared to NE. CTSE levels were significantly lower in EAC compared to BE/intestinal metaplasia and BE/D, but significantly higher than NE levels. A similar expression pattern was present in immunohistochemistry, with absent staining in NE, intense staining in intestinal metaplasia and dysplasia, and less intense EAC staining. CTSE serum analysis did not discriminate patient groups. In a uni- and multivariable Cox proportional hazards model, CTSE expression was not significantly associated with survival in patients with EAC, although CTSE expression above the 25th percentile was associated with a 41 % relative risk reduction for death (hazard ratio 0.59, 95 % confidence interval 0.27–1.26, p = 0.17). Conclusions CTSE mRNA expression is up-regulated more than any known gene in Barrett intestinal metaplasia and dysplasia tissues. Protein expression is similarly highly intense in intestinal metaplasia and dysplasia tissues
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