Transition of Transient Channel Flow with High Reynolds Number Ratios

Large-eddy simulations of turbulent channel flow subjected to a step-like acceleration have been performed to investigate the effect of high Reynolds number ratios on the transient behaviour of turbulence. It is shown that the response of the flow exhibits the same fundamental characteristics described in He & Seddighi (J. Fluid Mech., vol. 715, 2013, pp. 60–102 and vol. 764, 2015, pp. 395–427)—a three-stage response resembling that of the bypass transition of boundary layer flows. The features of transition are seen to become more striking as the Re-ratio increases—the elongated streaks become stronger and longer, and the initial turbulent spot sites at the onset of transition become increasingly sparse. The critical Reynolds number of transition and the transition period Reynolds number for those cases are shown to deviate from the trends of He & Seddighi (2015). The high Re-ratio cases show double peaks in the transient response of streamwise fluctuation profiles shortly after the onset of transition. Conditionally-averaged turbulent statistics based on a λ_2-criterion are used to show that the two peaks in the fluctuation profiles are due to separate contributions of the active and inactive regions of turbulence generation. The peak closer to the wall is attributed to the generation of “new” turbulence in the active region, whereas the peak farther away from the wall is attributed to the elongated streaks in the inactive region. In the low Re-ratio cases, the peaks of these two regions are close to each other during the entire transient, resulting in a single peak in the domain-averaged profile

DNS study of a pipe flow following a step increase in flow rate

Direct numerical simulation (DNS) is conducted to study the transient flow in a pipe following a near-step increase of flow rate from an initial turbulent flow. The results are compared with those of the transient flow in a channel reported in He and Seddighi (2013). It is shown that the flow again exhibits a laminar–turbulent transition, similar to that in a channel. The behaviours of the flow in a pipe and a channel are the same in the near-wall region, but there are significant differences in the centre of the flow. The correlation between the critical Reynolds number and free stream turbulence previously established for a channel flow has been shown to be applicable to the pipe flow. The responses of turbulent viscosity, vorticity Reynolds number, and budget terms are analysed. Some significant differences have been found to exist between the developments of the vorticity Reynolds number in the pipe and channel flows

Extramedullary hematopoiesis presenting as a compressive cord and cerebral lesion in a patient without a significant hematologic disorder: a case report

<p>Abstract</p> <p>Introduction</p> <p>Intracranial or spinal compressive lesions due to extramedullary hematopoiesis have been reported in the medical literature. Most of the reported cases are extradural lesions or, on rare occasions, foci within another neoplasm such as hemangioblastoma, meningioma or pilocytic astrocytoma. Often these cases occur in patients with an underlying hematological disorder such as acute myelogenic leukemia, myelofibrosis, or other myelodysplastic syndromes. Such lesions have also been reported in thalassemia major.</p> <p>Case presentation</p> <p>We report the case of a 43-year-old Iranian woman in whom extramedullary hematopoiesis presented as a compressive cord lesion and then later as an intracranial lesion.</p> <p>Conclusions</p> <p>To the best of our knowledge, we document the first reported case of sacral, lumbar, thoracic and cranial involvement in the same patient with extramedullary hematopoiesis, which seems both rare and remarkable.</p

Study of deterministic systems in epidemic diseases.

This article presents the deterministic system for susceptible-infective model for HIV. In this paper the homotopy analysis method is employed to compute an exact analytical approximation to the solution of the deterministic system for this model. We do a comparison between this method and Runge-Kutta method

Pharmacokinetics of intravenous and subcutaneous cefovecin in alpacas

The purpose of this study was to determine the pharmacokinetics of cefovecin after intravenous and subcutaneous dose of 8 mg/kg to alpacas. Bacterial infections requiring long‐term antibiotic therapy such as neonatal bacteremia, pneumonia, peritonitis, dental, and uterine infections are a significant cause of morbidity and mortality in this species. However, few antimicrobials have been evaluated and proven to have favorable pharmacokinetics for therapeutic use. Most antimicrobials that are currently used require daily injections for many days. Cefovecin is a long‐acting cephalosporin that is formulated for subcutaneous administration, and its long‐elimination half‐life allows for 14‐day dosing intervals in dogs and cats. The properties of cefovecin may be advantageous for medical treatment of camelids due to its broad spectrum, route of administration, and long duration of activity. Pharmacokinetic evaluation of antimicrobial drugs in camelids is essential for the proper treatment and prevention of bacterial disease, and to minimize development of antibiotic resistant bacterial strains due to inadequate antibiotic concentrations. Cefovecin mean half‐life, volume of distribution at steady‐state, and clearance after intravenous administration were 10.3 h, 86 mL/kg, and 7.07 mL·h/kg. The bioavailability was 143%, while half‐life, Cmax, and Tmax were 16.9 h, 108 μg/mL, and 2.8 h following subcutaneous administration. In the absence of additional microbial susceptibility data for alpaca pathogens, the current cefovecin dosage regimen prescribed for dogs (8 mg/kg SC every 14 days) may need to be optimized for the treatment of infections in this species

Distribution into the quadrupole mass filter with round rods.

Potential field distribution of a quadrupole mass filter with circular cross-section electrodes is described. At first, using superposition principle, we calculate potential around a round rod which is subjected to a given potential. By standard separation method, we then able to obtain the potential distribution into the quadrupole mass filter with circular rods. The results are compared with those obtained with a conventional hyperbolic rod set. Also, the results show that, for the same equivalent operating point in two stability diagrams (having the same βy) the associated modulated secular ion frequencies behavior are the same

A Safe Home? A Qualitative Study into the Experiences of Adolescents Growing Up in the Dutch Area Impacted by Earthquakes Induced by Gas Extraction

For decades, the Netherlands has experienced minor earthquakes due to gas extraction. This study aims to obtain insight into the experiences of adolescents and the impact of these earthquakes on their well-being and living environment. Focus groups were held with 24 adolescents, and interviews were held with 3 adolescents (N = 27; M = 15 years). Through qualitative analysis, we identified six themes. The adolescents shared experiences of anxiety related to the earthquakes and their consequences and considered these to be a normal part of their life. Anxiety and feelings of endangerment not only related to their own experiences but were also connected to the impact of earthquakes on their social environment, such as the restoration of buildings. Several sources of support (e.g., talking, social cohesion) were mentioned to deal with the negative consequences of the earthquakes. A lack of trust in the government was an additional main theme, with adolescents mentioning several needs, potentially relevant to policymakers in the Netherlands. Growing up in the gas extraction area of Groningen had many consequences on the adolescents in the study, who felt inhibited from expressing feelings of anxiety and fear. To support their needs, interventions at the individual, family, educational, societal, and policy levels are recommended. View Full-Tex