CFD Transient Simulation of an Isolator Shock Train in a Scramjet Engine

For hypersonic flight, the scramjet engine uses an isolator to contain the pre-combustion shock train formed by the pressure difference between the inlet and the combustion chamber. If this shock train were to reach the inlet, it would cause an engine unstart, disrupting the flow through the engine and leading to a loss of thrust and potential loss of the vehicle. Prior to this work, a Computational Fluid Dynamics (CFD) simulation of the isolator was needed for simulating and characterizing the isolator flow and for finding the relationship between back pressure and changes in the location of the leading edge of the shock train. In this work, the VULCAN code was employed with back pressure as an input to obtain the time history of the shock train leading location. Results were obtained for both transient and steady-state conditions. The simulation showed a relationship between back-to-inlet pressure ratios and final locations of the shock train. For the 2-D runs, locations were within one isolator duct height of experimental results while for 3-D runs, the results were within two isolator duct heights

LAGOVirtual: A Collaborative Environment for the Large Aperture GRB Observatory

We present the LAGOVirtual Project: an ongoing project to develop platform to collaborate in the Large Aperture GRB Observatory (LAGO). This continental-wide observatory is devised to detect high energy (around 100 GeV) component of Gamma Ray Bursts, by using the single particle technique in arrays of Water Cherenkov Detectors (WCD) at high mountain sites (Chacaltaya, Bolivia, 5300 m a.s.l., Pico Espejo, Venezuela, 4750 m a.s.l., Sierra Negra, Mexico, 4650 m a.s.l). This platform will allow LAGO collaboration to share data, and computer resources through its different sites. This environment has the possibility to generate synthetic data by simulating the showers through AIRES application and to store/preserve distributed data files collected by the WCD at the LAGO sites. The present article concerns the implementation of a prototype of LAGO-DR adapting DSpace, with a hierarchical structure (i.e. country, institution, followed by collections that contain the metadata and data files), for the captured/simulated data. This structure was generated by using the community, sub-community, collection, item model; available at the DSpace software. Each member institution-country of the project has the appropriate permissions on the system to publish information (descriptive metadata and associated data files). The platform can also associate multiple files to each item of data (data from the instruments, graphics, postprocessed-data, etc.).Comment: Second EELA-2 Conference Choroni, Venezuela, November 25th to 27th 200

Sex Differences in Arm Muscle Fatigability With Cognitive Demand in Older Adults

Background Muscle fatigability can increase when a stressful, cognitively demanding task is imposed during a low-force fatiguing contraction with the arm muscles, especially in women. Whether this occurs among older adults (\u3e 60 years) is currently unknown. Questions/purposes We aimed to determine if higher cognitive demands, stratified by sex, increased fatigability in older adults (\u3e 60 years). Secondarily, we assessed if varying cognitive demand resulted in decreased steadiness and was explained by anxiety or cortisol levels. Methods Seventeen older women (70 ± 6 years) and 13 older men (71 ± 5 years) performed a sustained, isometric, fatiguing contraction at 20% of maximal voluntary contraction until task failure during three sessions: high cognitive demand (high CD = mental subtraction by 13); low cognitive demand (low CD = mental subtraction by 1); and control (no subtraction). Results Fatigability was greater when high and low CD were performed during the fatiguing contraction for the women but not for the men. In women, time to failure with high CD was 16 ± 8 minutes and with low CD was 17 ± 4 minutes, both of which were shorter than time to failure in control contractions (21 ± 7 minutes; high CD mean difference: 5 minutes [95% confidence interval {CI}, 0.78–9.89], p = 0.02; low CD mean difference: 4 minutes [95% CI, 0.57–7.31], p = 0.03). However, in men, no differences were detected in time to failure with cognitive demand (control: 13 ± 5 minutes; high CD mean difference: −0.09 minutes [95% CI, −2.8 to 2.7], p = 1.00; low CD mean difference: 0.75 minutes [95% CI, −1.1 to 2.6], p = 0.85). Steadiness decreased (force fluctuations increased) more during high CD than control. Elevated anxiety, mean arterial pressure, and salivary cortisol levels in both men and women did not explain the greater fatigability during high CD. Conclusions Older women but not men showed marked increases in fatigability when low or high CD was imposed during sustained static contractions with the elbow flexor muscles and contrasts with previous findings for the lower limb. Steadiness decreased in both sexes when high CD was imposed. Clinical Relevance Older women are susceptible to greater fatigability of the upper limb with heightened mental activity during sustained postural contractions, which are the foundation of many work-related tasks

Finite-Size Scaling and Universality in the Spin 1 Quantum XY Chain

The spin-1 XY chain in a transverse field is studied using finite-size scaling. The ground state phase diagram displays a paramagnetic, an ordered ferromagnetic and an ordered oscillatory phase. The paramagnetic-ferromagnetic transition line belongs to the universality class of the 2D Ising model. Along this line, universality is confirmed for the finite-size scaling functions of several correlation lengths and for the conformal operator content.Comment: Latex 8 pages, 2 uucompressed figure

Low-Temperature Expansions and Correlation Functions of the Z_3-Chiral Potts Model

Using perturbative methods we derive new results for the spectrum and correlation functions of the general Z_3-chiral Potts quantum chain in the massive low-temperature phase. Explicit calculations of the ground state energy and the first excitations in the zero momentum sector give excellent approximations and confirm the general statement that the spectrum in the low-temperature phase of general Z_n-spin quantum chains is identical to one in the high-temperature phase where the role of charge and boundary conditions are interchanged. Using a perturbative expansion of the ground state for the Z_3 model we are able to gain some insight in correlation functions. We argue that they might be oscillating and give estimates for the oscillation length as well as the correlation length.Comment: 17 pages (Plain TeX), BONN-HE-93-1

Effect of pre-treatment with catecholamines on cold preservation and ischemia/reperfusion-injury in rats

Treatment of organ donors with catecholamines reduces acute rejection episodes and improves long-term graft survival after renal transplantation. The aim of this study was to investigate the effect of catecholamine pre-treatment on ischemia/reperfusion (I/R)- and cold preservation injury in rat kidneys. I/R-injury was induced by clamping the left kidney vessels for 60 min along with a contralateral nephrectomy. Cold preservation injury was induced by storage of the kidneys for 24 h at +4°C in University of Wisconsin solution, followed by syngeneic transplantation. Rats were pre-treated with either dopamine (DA), dobutamine (DB), or norepinephrine (2, 5, and 10 μg/kg/min, each group) intravenously via an osmotic minipump for 24 h before I/R- and cold preservation injury. Pre-treatment with DA (2 or 5 μg/kg/min) and DB (5 μg/kg/min) improved recovery of renal function after I/R-injury and dose dependently reduced mononuclear and major histocompatibility complex class II-positive cells infiltrating the kidney after I/R-injury. One day after I/R-injury, upregulation of transforming growth factor (TGF)-β 1 and 2 and phosphorylation of p42/p44 mitogen-activated protein kinases was observed in kidneys of animals treated with DA or DB. DA (5 μg/kg/min) and DB (5 μg/kg/min) pre-treatment reduced endothelial cell damage after 24 h of cold preservation. Only DA pre-treatment improved renal function and reduced renal inflammation after 24 h of cold preservation and syngeneic transplantation. Our results demonstrate a protective effect of pre-treatment with catecholamines on renal inflammation and function after I/R- or cold preservation injury. This could help to explain the potent organoprotective effects of catecholamine pre-treatment observed in human kidney transplantation

Lived Experiences of American Adults who Survive COVID-19: Implications for Physical Activity and Interpersonal Stress

Introduction: The cumulative number of COVID-19 cases has surpassed 579 million globally. Symptoms during and after COVID-19 infection vary from mild cold symptoms to severe multisystem illness. Given the wide range of symptom presentations and complications post COVID-19, the purpose of this study was to describe the lived experience of American adults surviving COVID-19. Method: This study employed an exploratory qualitative description design. Semi-structured interviews were conducted with a sample of 35 individuals, [white (94%), female (71%), mean age = 43.7 years], with proximity to a university in an urban Midwest American city. Interviews occurred between May and August 2021, three or more months after participants tested positive for COVID-19. Results: Forty percent of the 35 participants experienced prolonged COVID-19 symptoms impacting their lifestyle. Four themes characterized the impacts of the post COVID-19 condition on the lives of the participants within the context of a global pandemic: (a) disruptions in health & well-being, (b) persistent uncertainty, (c) disruptions in interpersonal relationships, (d) beneficent outcomes and adaptation. Discussion: This study of COVID-19 has identified important implications for physical activity and interpersonal stress. Prolonged COVID-19 symptoms led to disruptions in the health, well-being, and interpersonal relationships of participants. Healthcare professionals need to attend to symptoms post COVID-19, assess interpersonal functioning, and provide guidance on physical activity. Future studies are recommended to track consequences of COVID-19’s impact on long-term health and well-being

Severe anal bleeding in Proteus syndrome: a case report

Proteus syndrome was originally described by Cohen and Hayden in 1979. The disorder was named Proteus syndrome by Wiedmann and colleagues in 1983 after Proteus, the giant Greek god of the sea. Proteus syndrome is a rare, sporadic, congenital polymorphic condition. Approximately 200 cases have been reported in the literature, but none has been associated with anal bleeding from hemorrhoids. We describe the case of a 21-year-old man with Proteus syndrome with severe anal bleeding. A hemorrhoidectomy was assumed to be too risky because of the massive venous abnormalities seen on CT. The patient was successfully treated by Doppler-guided haemorrhoidal artery ligation (DG-HAL). Six months after surgery, the patient has had no further episodes of anal bleeding