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Secondary flows can develop in turbulent boundary layers that grow over surfaces with spanwise inhomogeneities. In this article, we demonstrate the formation of secondary flows in both experimental and numerical tests and dissect the instantaneous structure and topology of these secondary motions. We show that the formation of secondary flows is not very sensitive to the Reynolds number range investigated, and direct numerical simulations and experiments produce similar results in the mean flow as well as the dispersive and turbulent stress distributions. The numerical methods capture time-resolved features of the instantaneous flow and provide insight into the near-wall flow structures, that were previously obscured in the experimental measurements. Proper orthogonal decomposition was shown to capture the essence of the secondary flows in relatively few modes and to be useful as a filter to analyse the instantaneous flow patterns. The secondary flows are found to create extended regions of high Reynolds stress away from the wall that comprise predominantly sweeps similar to what one would expect to see near the wall and which are comparable in magnitude to the near-wall stress. Analysis of the instantaneous flow patterns reveals that the secondary flows are the result of a non-homogeneous distribution of mid-size vortices.
We study several kinds of subschemes of mixed characteristic models of Shimura varieties which admit good (partial) toroidal and minimal compactifications, with familiar boundary stratifications and formal local structures, as if they were Shimura varieties in characteristic zero. We also generalize Koecher’s principle and the relative vanishing of subcanonical extensions for coherent sheaves, and Pink’s and Morel’s formulas for étale sheaves, to the context of such subschemes.
Needle thoracostomy (NT) is a common prehospital intervention for patients in extremis or cardiac arrest due to trauma. The purpose of this study is to compare outcomes, efficacy, and complications after a change in policy related to NT in a four-county Emergency Medical Services (EMS) system with a catchment area of greater than 1.6 million people.
This is a before and after observational study of all patients who had NT performed in the Central California (USA) EMS system. The before, anterior midclavicular line (MCL) group consisted of all patients who underwent NT from May 7, 2007 through February 28, 2013. The after, midaxillary line (MAL) axillary group consisted of all patients who underwent NT from March 1, 2013 through January 30, 2016, after policy revisions changed the timing, needle size, and placement location for NT. All prehospital and hospital records where NT was performed were queried for demographics, mechanism of injury, initial status and post-NT clinical change, reported complications, and final outcome. The trauma registry was accessed to obtain Injury Severity Scores (ISS). Information was manually abstracted by study investigators and examined utilizing univariate and multivariate analyses.
Three-hundred and five trauma patients treated with NT were included in this study, of which, 169 patients (the MCL group) were treated with a 14-guage intravenous (IV) catheter at least 5.0-cm long at the second intercostal space (ICS), MCL after being placed in the ambulance; and 136 patients (the MAL group) were treated with a 10-guage IV catheter at least 9.5-cm long at the fifth ICS, MAL on scene. The mean ISS was lower in the MAL cohort (64.5 versus 69.2; P=.007). The mortality rate was 79% in both groups. The multivariate model with regard to survival supported that a lower ISS (P<.001) and reported clinical change after NT (P=.003) were significant indicators of survival. No complications from NT were reported.
Changing the timing, length of needle, and location of placement did not change mortality in patients requiring NT. Needle thoracostomy was used more frequently after the change in policy, and the MAL cohort was less injured. No increase in reported complications was noted.
WeichenthalLA, OwenS, StrohG, RamosJ. Needle Thoracostomy: Does Changing Needle Length and Location Change Patient Outcome?Prehosp Disaster Med. 2018;33(3):237–244.
We show that the automorphic étale cohomology of a (possibly noncompact) PEL-type or Hodge-type Shimura variety in characteristic zero is canonically isomorphic to the cohomology of the associated nearby cycles over most of their mixed characteristics models constructed in the literature.
Using quasi-simultaneous observations of 86 stars with known SiO maser emission, we searched for systematic differences between the strengths of the 43 and 86 GHz v=1 maser lines. Although for individual stars there is wide scatter between the line strengths spanning nearly an order of magnitude, there is no evidence of a systematic difference between these line strengths for the entire sample.
Amorphous ferromagnetic alloy with the composition Fe56Co24Nb4B13Si2Cu1 was obtained by rapid quenching from the melt. Samples cut from the ribbons were annealed at 450, 550, 650 and 750 °C in a vacuum furnace. 57Fe Mössbauer spectroscopy was used to identify the phases formed based on the refined values of the hyperfine parameters. The as-quenched specimen was analyzed with a hyperfine magnetic field distribution and corresponded to an in-plane orientation of the magnetic moment directions. The sample annealed at 450 °C was found to be in a nanocrystalline state due to observation of the (FeCo)-Si alloy with the DO3 structure. The balance of the composition was represented by a metalloid-enriched amorphous grain boundary phase. In contradistinction to this, the samples annealed at 550-750 °C were totally crystallized and the new phases formed were α-(FeCo), (FeCo)2(BSi) and (FeCo)3(BSi). These findings suggest that nanocrystallization is obtained only at select processing temperatures. A new set of Mössbauer spectra was obtained by recording simultaneously the intensity transmitted by a sandwich of the sample with the stainless steel etalon, based on the dual absorber method recently introduced by us. The values of the recoilless fraction can be derived from the relative spectral areas. The f factor value dropped from 0.6 to 0.37 for the sample annealed at 450 °C, consistent with the onset of nanocrystallization in the system. For the completely crystallized specimens, the f factor maintained values close to 0.5. This indicates that the presence of quenched-in stresses may play a role in the ability of samples to undergo recoilless emission and absorption of gamma rays.
An outbreak of gastroenteritis affected 453 attendees (attack rate 28·5%) of six separate events held at a hotel in Singapore. Active case detection, case-control studies, hygiene inspections and microbial analysis of food, environmental and stool samples were conducted to determine the aetiology of the outbreak and the modes of transmission. The only commonality was the food, crockery and cutlery provided and/or handled by the hotel's Chinese banquet kitchen. Stool specimens from 34 cases and 15 food handlers were positive for norovirus genogroup II. The putative index case was one of eight norovirus-positive food handlers who had worked while they were symptomatic. Several food samples and remnants tested positive for Escherichia coli or high faecal coliforms, aerobic plate counts and/or total coliforms, indicating poor food hygiene. This large common-source outbreak of norovirus gastroenteritis was caused by the consumption of contaminated food and/or contact with contaminated crockery or cutlery provided or handled by the hotel's Chinese banquet kitchen.
A numerical investigation of two locally applied drag-reducing control schemes is carried out in the configuration of a spatially developing turbulent boundary layer (TBL). One control is designed to damp near-wall turbulence and the other induces constant mass flux in the wall-normal direction. Both control schemes yield similar local drag reduction rates within the control region. However, the flow development downstream of the control significantly differs: persistent drag reduction is found for the uniform blowing case, whereas drag increase is found for the turbulence damping case. In order to account for this difference, the formulation of a global drag reduction rate is suggested. It represents the reduction of the streamwise force exerted by the fluid on a plate of finite length. Furthermore, it is shown that the far-downstream development of the TBL after the control region can be described by a single quantity, namely a streamwise shift of the uncontrolled boundary layer, i.e. a changed virtual origin. Based on this result, a simple model is developed that allows the local drag reduction rate to be related to the global one without the need to conduct expensive simulations or measurements far downstream of the control region.
We investigate the effects of superhydrophobic surfaces (SHS) carrying streamwise grooves on the flow dynamics and the resultant drag reduction in a fully developed turbulent channel flow. The SHS is modelled as a flat boundary with alternating no-slip and free-slip conditions, and a series of direct numerical simulations is performed with systematically changing the spanwise periodicity of the streamwise grooves. In all computations, a constant pressure gradient condition is employed, so that the drag reduction effect is manifested by an increase of the bulk mean velocity. To capture the flow properties that are induced by the non-homogeneous boundary conditions the instantaneous turbulent flow is decomposed into the spatial-mean, coherent and random components. It is observed that the alternating no-slip and free-slip boundary conditions lead to the generation of Prandtl’s second kind of secondary flow characterized by coherent streamwise vortices. A mathematical relationship between the bulk mean velocity and different dynamical contributions, i.e. the effective slip length and additional turbulent losses over slip surfaces, reveals that the increase of the bulk mean velocity is mainly governed by the effective slip length. For a small spanwise periodicity of the streamwise grooves, the effective slip length in a turbulent flow agrees well with the analytical solution for laminar flows. Once the spanwise width of the free-slip area becomes larger than approximately 20 wall units, however, the effective slip length is significantly reduced from the laminar value due to the mixing caused by the underlying turbulence and secondary flow. Based on these results, we develop a simple model that allows estimating the gain due to a SHS in turbulent flows at practically high Reynolds numbers.
Establishing baseline data on the abundance of threatened shark species is critical for monitoring site- and region-specific population tends over time. This is of particular importance for monitoring sharks at remote locations or in regions where there are no reliable data on shark numbers, fishing effort and current population status. Through establishing a standardized recreational SCUBA diver observation programme, this study examined the number, size and sex-composition of grey reef sharks, Carcharhinus amblyrhynchos, on a remote coral reef system off the Red Sea coast of Sudan. In addition, placard tags were attached to individual sharks to examine coarse scale residency and movement patterns and to determine the effectiveness of this technique. Over a 4.5 month period (December 2007–April 2008), a mean (±SE) of 5.9 ± 0.3 grey reef sharks were observed per diving day with peak numbers of sharks associated with temperatures of 26–26.9°C and strong currents. Estimated mean (±SE) total length of observed sharks was 1.9 ± 0.03 m identifying that most animals were mature. Female sharks were dominant on the site and pregnant females were recorded. Placard tagged sharks (N = 4) were observed by recreational SCUBA divers throughout the study period (23.1%, 20.0%, 16.9% and 3.1% of total observation diving days) indicating sporadic site attachment. The placard tags remained intact and were free of fouling for a total of 175 days. The numbers of grey reef sharks seen on this Red Sea coral complex suggest a healthy, relatively unexploited population. This study demonstrates that the recreational diver community, which forms a large pool of skilled volunteers, can generate baseline data on shark numbers at regularly dived sites and provide insights into the ecology of the observed species. Modification of placard tags, including attachment to the dorsal fin and time corrodible release systems may provide an inexpensive and accepted tool for monitoring individual shark residency and movement patterns. Engaging the recreational SCUBA diver community in a standardized scientific monitoring programme has the potential to monitor trends in shark populations over large spatial and temporal scales.
We have fabricated polysilicon (poly-Si) thin film transistors (TFTs) using a standard 4-mask sequence, with self-aligned ion implantation for source and drain doping. The active layer was obtained by solid phase crystallisation of high purity Si2H6-deposited amorphous Si, whereas the gate oxide was synthesised by a novel plasma deposition technique, namely distributed electron cyclotron resonance plasma enhanced chemical vapour deposition (DECR PECVD). We have obtained high carrier mobilities (70 cm2V−1s−1 for electrons and 40 cm2V−1s−1 for holes) with an excellent uniformity and without the need for a post-hydrogenation treatment. Moreover, we show that the TFT characteristics are practically insensitive to hot carrier effects.
Neonatal tetanus (NT) elimination, <1 case per 1000 live births (LB), was assessed at district level in Zimbabwe using a combined lot quality assurance–cluster sampling survey (LQA–CS). Three of the highest risk districts were selected. NT was considered eliminated if fewer than a specified number of NT deaths (proxy for NT cases) were found in the sample determined using operating characteristic curves and tables. TT2+ vaccine coverage was measured in mothers who gave birth 1–13 months before the survey and women aged 15–49 years. NT was considered as eliminated, TT2+ coverage was 78% (95% CI 71–82%) in women aged 15–49 and 83% (95% CI 76–89%) in mothers. The survey cost US$ 30000 excluding costs of consultants. NT incidence was below the elimination threshold (<1/1000 LB) in the surveyed districts and probably in all districts. LQA–CS is a practical, relatively cost effective field method which can be applied in an African setting to assess NT elimination status.
We show that the problem of designing RNA sequences
that can fold into multiple stable secondary structures
can be transformed into a combinatorial optimization problem
that can be solved by means of simple heuristics. Hence
it is feasible to design RNA switches with prescribed structural
alternatives. We discuss the theoretical background and
present an efficient tool that allows the design of various
types of switches. We argue that both the general properties
of the sequence structure map of RNA secondary structures
and the ease with which our design tool finds bistable
RNAs strongly indicates that RNA switches are easily accessible
in evolution. Thus conformational switches are yet another
function for which RNA can be employed.
We describe and test two process models of candidate evaluation. The memory-based model holds that evaluations are dependent on the mix of pro and con information retrieved from memory. The impression-driven model holds that evaluations are formed and updated “on-line” as information is encountered. The results provide evidence for the existence of stereotyping and projection biases that render the mix of evidence available in memory a nonveridical representation of the information to which subjects were exposed. People do not rely on the specific candidate information available in memory. Rather, consistent with the logic of the impression-driven processing model, an “on-line” judgment formed when the information was encountered best predicts candidate evaluation. The results raise both methodological and substantive challenges to how political scientists measure and model the candidate evaluation process.
The evidence for the production of tecali (travertine) vessels at Tollan, Hidalgo, Mexico is examined and some possible secondary uses for the resultant waste materials are considered. An attempt is also made to show how artifact reuse can confuse the archaeological record, possibly leading to false conclusions.