Inner-outer interactions in a rough-wall turbulent boundary layer

The primary goal of the present effort is to enhance the current understanding of inner-outer interactions in rough-wall turbulent boundary layers. These interactions were recently established over smooth-wall turbulent boundary layers as modulating interactions, where the outer layer large scales amplitude and frequency modulate the near-wall small scales. Given that the outer layer dynamics responsible for these modulations are identical in most high-Reynolds-number (Re) rough-wall flows as well, similar modulation interactions are are explored to identify the similarities and differences of these interactions and establish a spatio-temporal description of the same. This is particularly important given the engineering significance of the flows over rough walls. This work was performed as two parts. In the first part, high temporal-resolution boundary layer hot-wire measurements were made in a wind tunnel, that fully resolved all dynamical scales temporally at fixed points in the flow. Flows over smooth and rough walls were investigated, with the latter being a complex topography indicative of a realistic roughness commonly encountered in engineering applications. Single- and two-probe measurements provided a dual perspective on the large scales, and enabled analysis of analytical techniques commonly employed. With these measurements, it was found that the nature of amplitude and frequency modulation occur even over this complex topography, and that the structure is very similar to that observed in smooth-wall flow. Further, the simultaneous two-probe measurements enabled the investigation of predictive models, which interestingly suggested a possibly stronger modulation in rough-wall flow compared to the smooth-wall case. A `quasi-steady, quasi-homogenous' theory previously developed for smooth-wall flow showed promising predictions of the calibrations constants even in rough-wall flow, lending additional support to the mechanisms speculating that the small scales respond in a quasi-steady manner, irrespective of the origin, to the large scales. With these inner-outer interactions established, the second part of the current work aimed to develop a spatio-temporal description of the modulating mechanisms using high frame-rate particle-image velocimetry (PIV). The experiments, performed in a refractive-index-matched flow facility, enabled the measurements very close to the surface without being impeded by the near-wall reflections that are common in smooth- and rough-wall PIV experiments. Following a preliminary demonstration of the relevant physics observed via point measurements, a representative large-scale structure was defined using conditional averaging. The associated changes to the small-scale turbulence close to the wall indicated similar modulation interactions, and provided a spatial tool to investigate the same. Further, the large-scale -small-scale interaction structure lended support to the speculations made on the same using hot-wire measurements in the current work and in the recent literature for smooth- and rough-wall flow. These experiments identify and emphasize the significance of inner-outer interactions over rough-wall flows, and the necessity to accurately model them to enhance the fidelity of any high Re simulations over rough walls

Coaxial Jets with Disparate Viscosity: Mixing and Laminarization Characteristics

Mixing of fluids in a coaxial jet is studied under four distinct viscosity ratios, m = 1, 10, 20 and 40, using highly resolved large-eddy simulations (LES), particle image velocimetry and planar laser-induced fluorescence. The accuracy of predictions is tested against data obtained by the simultaneous experimental measurements of velocity and concentration fields. For the highest and lowest viscosity ratios, standard RANS models with unclosed terms pertaining to viscosity variations are employed. We show that the standard Reynolds-averaged Navier-Stokes (RANS) approach with no explicit modelling for variable-viscosity terms is not applicable whereas dynamic LES models provide high-quality agreement with the measurements. To identify the underlying mixing physics and sources of discrepancy in RANS predictions, two distinct mixing modes are defined based on the viscosity ratio. Then, for each mode, the evolution of mixing structures, momentum budget analysis with emphasis on variable-viscosity terms, analysis of the turbulent activity and decay of turbulence are investigated using highly resolved LES data. The mixing dynamics is found to be quite distinct in each mixing mode. Variable viscosity manifests multiple effects that are working against each other. Viscosity gradients induce additional instabilities while increasing overall viscosity decreases the effective Reynolds number leading to laminarization of the turbulent jet, explaining the lack of dispersion and turbulent diffusion. Momentum budget analysis reveals that variable-viscosity terms are significant to be neglected. The scaling of the energy spectrum cascade suggests that in the TLL mode the unsteady laminar shedding is responsible for the eddies observed

Comparison of soybean Cultivars enriching Cd and the application foreground of the low-accumulating Cultivar in production

Contaminated soil collected from an agricultural field was used to compare Cd enrichment among 20 soybean cultivars to explore their application foregrounds in safe production. The results showed that Cd concentration in beans of 20 soybean cultivars was from 0.23 mg kg-1 to 2.33 mg kg-1 when Cd concentration in soil was 1.98 mg kg-1. Cd enrichment factors of 19 cultivars were lower than 1. Cd translocation factors of all cultivars were lower than 1. As for background soil with 0.15 mg kg-1 Cd, the concentrations of Cd in beans of two soybean cultivars were higher than 0.10 mg kg-1 (an agricultural trade standard of non-pollution food for soybean of China, NY5310-2005). Thus, the use of a low-accumulation soybean cultivar in Cd-contaminated soil should be done carefully and with reserve. Keywords: Cd, soybean cultivar, enrichment factor, phytoremediation, safe productio

Highly Sensitive and Cost-Effective Portable Sensor for Early Gastric Carcinoma Diagnosis

Facile and efficient early detection of cancer is a major challenge in healthcare. Herein we developed a novel sensor made from a polycarbonate (PC) membrane with nanopores, followed by sequence-specific Oligo RNA modification for early gastric carcinoma diagnosis. In this design, the gastric cancer antigen CA72-4 is specifically conjugated to the Oligo RNA, thereby inhibiting the electrical current through the PC membrane in a concentration-dependent manner. The device can determine the concentration of cancer antigen CA72-4 in the range from 4 to 14 U/mL, possessing a sensitivity of 7.029 µAU−1mLcm−2 with a linear regression (R2) of 0.965 and a lower detection limit of 4 U/mL. This device has integrated advantages including high specificity and sensitivity and being simple, portable, and cost effective, which collectively enables a giant leap for cancer screening technologies towards clinical use. This is the first report to use RNA aptamers to detect CA72-4 for gastric carcinoma diagnosi

Increasing outdoor host-seeking in Anopheles gambiae over 6 years of vector control on Bioko Island.

BACKGROUND: Vector control through indoor residual spraying (IRS) has been employed on Bioko Island, Equatorial Guinea, under the Bioko Island Malaria Control Project (BIMCP) since 2004. This study analyses the change in mosquito abundance, species composition and outdoor host-seeking proportions from 2009 to 2014, after 11 years of vector control on Bioko Island. METHODS: All-night indoor and outdoor human landing catches were performed monthly in the Bioko Island villages of Mongola, Arena Blanca, Biabia and Balboa from 2009 to 2014. Collected mosquitoes were morphologically identified and a subset of Anopheles gambiae sensu lato (s.l.) were later identified molecularly to their sibling species. Mosquito collection rates, species composition and indoor/outdoor host-seeking sites were analysed using generalized linear mixed models to assess changes in mosquito abundance and behaviour. RESULTS: The overall mosquito collection rate declined in each of the four Bioko Island villages. Anopheles coluzzii and Anopheles melas comprised the An. gambiae s.l. mosquito vector population, with a range of species proportions across the four villages. The proportion of outdoor host-seeking An. gambiae s.l. mosquitoes increased significantly in all four villages with an average increase of 58.8 % [57.9, 59.64 %] in 2009 to 70.0 % [67.8, 72.0 %] in 2014. Outdoor host-seeking rates did not increase in the month after an IRS spray round compared to the month before, suggesting that insecticide repellency has little impact on host-seeking behaviour. CONCLUSION: While vector control on Bioko Island has succeeded in substantial reduction in overall vector biting rates, populations of An. coluzzii and An. melas persist. Host-seeking behaviour has changed in these An. gambiae s.l. populations, with a shift towards outdoor host-seeking. During this study period, the proportion of host-seeking An. gambiae s.l. caught outdoors observed on Bioko Island increased to high levels, exceeding 80 % in some locations. It is possible that there may be a genetic basis underlying this large shift in host-seeking behaviour, in which case outdoor feeding could pose a serious threat to current vector control programmes. Currently, the BIMCP is preparing for this potential challenge by testing source reduction as a complementary control effort that also targets outdoor transmission

Variable response of three Trifolium repens ecotypes to soil flooding by seawater.

BACKGROUND AND AIMS: Despite concerns about the impact of rising sea levels and storm surge events on coastal ecosystems, there is remarkably little information on the response of terrestrial coastal plant species to seawater inundation. The aim of this study was to elucidate responses of a glycophyte (white clover, Trifolium repens) to short-duration soil flooding by seawater and recovery following leaching of salts. METHODS: Using plants cultivated from parent ecotypes collected from a natural soil salinity gradient, the impact of short-duration seawater soil flooding (8 or 24 h) on short-term changes in leaf salt ion and organic solute concentrations was examined, together with longer term impacts on plant growth (stolon elongation) and flowering. KEY RESULTS: There was substantial Cl(-) and Na(+) accumulation in leaves, especially for plants subjected to 24 h soil flooding with seawater, but no consistent variation linked to parent plant provenance. Proline and sucrose concentrations also increased in plants following seawater flooding of the soil. Plant growth and flowering were reduced by longer soil immersion times (seawater flooding followed by drainage and freshwater inputs), but plants originating from more saline soil responded less negatively than those from lower salinity soil. CONCLUSIONS: The accumulation of proline and sucrose indicates a potential for solute accumulation as a response to the osmotic imbalance caused by salt ions, while variation in growth and flowering responses between ecotypes points to a natural adaptive capacity for tolerance of short-duration seawater soil flooding in T. repens. Consequently, it is suggested that selection for tolerant ecotypes is possible should the predicted increase in frequency of storm surge flooding events occur

Constant time algorithms for some geometric intersection problems on processor arrays with reconfigurable bus systems

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to [email protected], referencing the URI of the item.Includes bibliographical references.Not availabl

Structure of turbulent channel flow perturbed by cylindrical roughness elements

The current study investigates the structural modifications imposed in fully-developed turbulent channel flow by an isolated, wall-mounted circular cylinder. The cylinder height is chosen to specifically extend into the logarithmic layer of the flow in order to study its perturbation of the larger flow scales that embody a significant fraction of the turbulent kinetic energy. Hot-wire measurements were made in the wake of the wall-mounted circular cylinder at multiple wall-normal and streamwise positions. Mean streamwise statistics (mean velocity and Reynolds normal stress) and pre-multiplied spectra of perturbed and unperturbed flow were computed, and influence of the cylinder on these statistics were analyzed. The influence of such perturbations on the inner-outer interactions of the channel flow were also investigated. Besides the mean velocity deficit in the wake of the cylinder, a new peak in streamwise Reynolds normal stress away from the wall was observed, coupled with the suppression of the near-wall peak native to the incoming unperturbed flow. Pre-multiplied spectra elaborated on these energy modifications, specifically the occurrence of an energy peak corresponding to a wavelength (λx) ~ 0.45 times the channel half-height (h), an attenuation of large-scale energy close to the wall, and a tertiary peak at two-third's the cylinder height corresponding to a length scale of λx ~ 10h. Further, amplitude modulation effects of the large-scale motions on small scales close to the wall, representative of inner-outer interactions, was found to be greatly enhanced in the near-wall region. All the perturbations were found to decay with streamwise distance downstream towards the unperturbed flow. A clear persistence of the structures at the aforementioned tertiary peak, similar to the wavelengths of the very large scale motions (VLSMs) in canonical wall turbulence, tends to suggest an environment in turbulent flows preferring structures of such wavelengths. Possible mechanisms for the observed suppression of near-wall cycle and the enhanced inner-outer interactions are suggested. The influence of cylinder aspect ratio on the characteristics of perturbed flow are evaluated, and a distinction in wake structure is identified. The necessity of future studies to further understand these significant attributes of perturbation response and recovery of the turbulent wall bounded flows is highlighted

Acute Liver Failure

Acute liver failure is a rare but often catastrophic illness affecting the liver and multiple organ systems. Patients with acute liver failure require a multidisciplinary approach for adequate management. With improved critical care and the availability of liver transplantation, survival has significantly improved. Hepatic encephalopathy, cerebral edema and infections are the most common complications of acute liver failure. The evaluation requires a diligent search for a specific etiology of the liver failure, since certain causes may respond well to specific pharmacological therapies. Acetaminophen and non-acetaminophen drug-induced hepatotoxicity account for more than 50% of cases of acute liver failure. Assessment of prognosis frequently (at least on a daily basis) by using various prognostic tools, allows the treating team to decide whether or not to proceed with urgent liver transplantation. Artificial liver support devices are still in evaluation and not ready for use in clinical practice. While it is determined whether or not there is sufficient hepatic regeneration, the care of the patient with acute liver failure revolves around managing the dysfunction of multiple extra hepatic systems