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Polymer-containing solutions used across research and industry are commonly exposed to mechanically harsh fluid processes, for example shear and extensional forces during flow through porous media or rapid microdispensing of biopharmaceutical molecules. These forces are strong enough to break the covalent bonds in the polymer backbone. As this scission phenomenon can change the functional and fluid-flow properties as well as introduce reactive radicals into the solution, it must be understood and controlled. Experiments and models to date have only provided partial or qualitative insights into this behaviour. Here we build a link between the molecular-scale degradation models and the macroscale laminar flow of dilute solutions in any given geometry. A free-draining bead–rod model is used to investigate rupture events at the molecular scale. It is shown by uniaxial extension simulations of an ensemble of chains that scission can be conveniently described at the macroscopic scale as a first-order reaction whose rate is a function of the conformation tensor of the macromolecules and the velocity gradient of the flow. This approach is implemented in the finite volume code OpenFOAM by elaborating an appropriate constitutive equation for the conformation tensor. The macroscopic model is run and analysed for ultra-dilute solutions of poly(methyl methacrylate) in ethyl acetate and polyethylene oxide in water, using the geometry of an abrupt contraction flow and neglecting any viscoelastic effect. This multiscale approach bridges the gap between phenomenological observations of mechanically induced chemical degradation in large-scale applications and the rich field of molecular-scale models of macromolecules under flow.
Recent experimental studies have shown rich transition behaviour in rotating plane Couette flow (RPCF). In this paper we study the transition in supercritical RPCF theoretically by determination of equilibrium and periodic orbit tertiary states via Floquet analysis on secondary Taylor vortex solutions. Two new tertiary states are discovered which we name oscillatory wavy vortex flow (oWVF) and skewed vortex flow (SVF). We present the bifurcation routes and stability properties of these new tertiary states and, in addition, we describe a bifurcation procedure whereby a set of defected wavy twist vortices is approached. Further to this, transition scenarios at flow parameters relevant to experimental works are investigated by computation of the set of stable attractors which exist on a large domain. The physically observed flow states are shown to share features with states in our set of attractors.
We have measured the attenuation of longitudinal acoustic waves in a series of amorphous and nanocrystalline silicon films using picosecond ultrasonics. We determined the attenuation of amorphous Si to be lower than what is predicted by theories based on anharmonic interactions of the ultrasound wave with localized phonons or extended resonant modes. We determined the attenuation of nanocrystalline Si to be nearly one order of magnitude higher than amorphous Si.
There is little record of birth weight of Irish Travellers, a minority group in Ireland. Travellers are known to have higher rate of adult chronic disease and to be exposed to life-long disadvantage. The aim of this study was to establish whether the birth weight and infant mortality rate patterns in Ireland's Travellers were consistent with the developmental plasticity hypothesis. A 1-year follow-up birth cohort study was conducted with linkage data from maternity hospital records of Traveller infants born on the island of Ireland over a 12-month period to self-identifying Traveller and general Irish population mothers from the Lifeways Cross-Generation Cohort Study. The main outcome measure was the rate of birth weight <3000 g in a cohort of Traveller children. There were 987 confirmed Traveller births, 500 of whose mothers consented to linkage to their records. A social gradient was observed in the distribution of birth weight in the general population and Traveller infants constituted the highest proportion of all social classes in the birth weight range of 3 kg or less (16.3%). There was a high rate of persistent smoking among Traveller mothers (53%). After adjustment for smoking and alcohol consumption in pregnancy, the birth weight differential persisted (OR 3.5, 95% CI 1.4–8.1). Infant mortality rate at 12.0/1000 births (95% CI 5.5–19.7) was almost four times that of the general population. This analysis confirms Travellers had a greater than expected incidence of low birth weight and high infant mortality with high rates of premature adult chronic diseases from all causes already demonstrated previously.
Enhanced near band-edge (NBE) emission was observed from composite structures fabricated from a PVA coated ZnO (PVA-ZnO) nanoparticle thin film embedded with multi-walled carbon nanotubes (MWCNTs). The enhancement is attributed to the resonant coupling between the bandgap transition of the semiconductor and the surface plasmon (SP) of MWCNTs. Moreover, the PVA-ZnO/MWCNTs/PVA-ZnO composite structures show faster transient response, which is due to the carrier transportation process in the composite structure. Reductions are observed for both photocurrent to dark current ratio and intensity of photoresponsivity, demonstrating a tradeoff between the time transient response and the detectivity.
Multiple salmonellosis outbreaks have been linked to contaminated tomatoes. We investigated a multistate outbreak of Salmonella Typhimurium infections among 190 cases. For hypothesis generation, review of patients' food histories from four restaurant-associated clusters in four states revealed that large tomatoes were the only common food consumed by patients. Two case-control studies were conducted to identify food exposures associated with infections. In a study conducted in nine states illness was significantly associated with eating raw, large, round tomatoes in a restaurant [matched odds ratio (mOR) 3·1, 95% confidence interval (CI) 1·3–7·3]. In a Minnesota study, illness was associated with tomatoes eaten at a restaurant (OR 6·3, mid-P 95% CI 1·05–50·4, P=0·046). State, local and federal regulatory officials traced the source of tomatoes to Ohio tomato fields, a growing area not previously identified in past tomato-associated outbreaks. Because tomatoes are commonly eaten raw, prevention of tomato contamination should include interventions on the farm, during packing, and at restaurants.
To describe factors associated with a rectal swab or stool sample positive for norovirus, rotavirus, or adenovirus.
Charleston Area Medical Center, a regional academic medical center in Charleston, West Virginia.
Rectal swab or stool samples were obtained from patients suspected of having viral gastroenteritis. These samples were sent to the Charleston Area Medical Center virology laboratory for testing in 2007. Viral antigen in rectal swab and stool samples is detected by use of commercially available immunoassay kits for each virus. Data were extracted from the virology laboratory database for the following 1-year time period: January 1, 2007, through December 31, 2007. When necessary, additional information was obtained from electronic administrative data on patients.
There were 2,867 rectal swab and stool samples available for viral testing. Of these samples, 1,261 (44%) were positive for a virus. Of these positive samples, 972 (77%) were positive for norovirus, 182 (14%) were positive for rotavirus, and 110 (9%) were positive for adenovirus. The patients in the youngest age group had the highest number of test results positive for all 3 viruses. When the test results for the youngest age group (0-9 years) were compared with those for all the other age groups combined (10-99 years), the proportion of positive cases was highest for the youngest age group (P<.001). There were significant seasonal trends for all 3 viruses. Multivariate analysis of norovirus showed that season, source, sex, and age were significant predictors of a positive test result. Multivariate analysis of rotavirus showed that season and source were significant predictors of a positive test result. Multivariate analysis of adenovirus showed that season and age were significant predictors of a positive test result.
We conclude (1) that these 3 viruses are common causes of gastroenteritis in Charleston, West Virginia; (2) that infants and young children are more likely to test positive for these viruses than are older individuals; (3) that norovirus was the most common cause of gastroenteritis; and (4) that there are seasonal trends for all 3 viruses.
Autism-spectrum disorder is increasingly recognised, with recent studies estimating that 1% of children in South London are affected. However, the biology of comorbid mental health problems in people with autism-spectrum disorder is poorly understood.
To investigate the brain anatomy of people with autism-spectrum disorder with and without psychosis.
We used in vivo magnetic resonance imaging and compared 30 adults with autism-spectrum disorder (14 with a history of psychosis) and 16 healthy controls.
Compared with controls both autism-spectrum disorder groups had significantly less grey matter bilaterally in the temporal lobes and the cerebellum. In contrast, they had increased grey matter in striatal regions. However, those with psychosis also had a significant reduction in grey matter content of frontal and occipital regions. Contrary to our expectation, within autism-spectrum disorder, comparisons revealed that psychosis was associated with a reduction in grey matter of the right insular cortex and bilaterally in the cerebellum extending into the fusiform gyrus and the lingual gyrus.
The presence of neurodevelopmental abnormalities normally associated with autism-spectrum disorder might represent an alternative ‘entry-point’ into a final common pathway of psychosis.
We report a case of a 70-year-old man of Asian origin with lichen sclerosus et atrophicus affecting the tonsil, which presented as a painful, enlarging, exophytic lesion mimicking squamous cell carcinoma.
We present a case report and a review of the world literature regarding lichen sclerosus et atrophicus.
Lichen sclerosus is a chronic, benign, inflammatory dermatosis of the skin and mucous membranes which mostly affects the female genitalia, presenting as white plaques with epidermal atrophy. The cause is unknown, although a number of aetiologies have been proposed. The prevalence is unknown. Women have been reported to be affected six to 10 times more than men, and the condition has no known racial preference.
Our patient illustrates a rare case of the condition lichen sclerosus et atrophicus; to our knowledge, this case represents the first report of tonsillar involvement of the condition. The case presented a diagnostic challenge.