Mathematical and Physical Analysis of Pressure Gradient in the Experimental Chamber for Subsequent Comparison with Optical Methods

2021 ◽  
Vol 105 (1) ◽  
pp. 601-608
Author(s):  
Robert Bayer ◽  
Anna Maxová
Keyword(s):  
Optical Methods ◽  
Experimental Chamber ◽  
Physical Analysis ◽  
Pressure Gradients ◽  
Scientific Instruments ◽  
Electronic Technology ◽  
Vacuum Chambers ◽  
University Of Technology ◽  
Flow Through ◽  
Subsequent Comparison

As a part of the research in the field of pumping vacuum chambers in the Environmental Electron Microscope, a research on supersonic flow through the Appertures is being carried out at the Department of Electrical and Electronic Technology of the Brno University of Technology in cooperation with the Institute of Scientific Instruments of the Czech Academy of Science. This paper deals with the possibility of investigating shock waves using the Shlieren optical method, which allows to observe pressure gradients as the first derivation of pressure.

Mathematical and Physical Analysis of the Effect of Conical and Detached Shock Waves at the Tip of a Static Probe in an Experimental Chamber

2021 ◽  
Vol 105 (1) ◽  
pp. 627-635
Author(s):  
Pavla Šabacká ◽  
Jiří Maxa ◽  
Anna Maxová
Keyword(s):  
Supersonic Flow ◽  
Static Pressure ◽  
Experimental Chamber ◽  
Physical Analysis ◽  
Pressure Measurements ◽  
Scientific Instruments ◽  
Electronic Technology ◽  
Vacuum Chambers ◽  
University Of Technology ◽  
Flow Through

As part of the research in the field of pumping vacuum chambers in the Environmental Electron Microscope, research on supersonic flow through apertures is being carried out at the Department of Electrical and Electronic Technology of the Brno University of Technology in cooperation with the Institute of Scientific Instruments of the CAS. This paper deals with the influence of the shape of the static probe cone design for static pressure measurements in the supersonic flow regime in the Experimental Chamber. The cone of the probe has an effect on the shape of the shock wave, which significantly influences the detected static pressure value.

Analysis of the Effect of Reflected Shock Waves in the Experimental Chamber

2021 ◽  
Vol 105 (1) ◽  
pp. 589-599
Author(s):  
Jiří Maxa ◽  
Pavla Šabacká ◽  
Robert Bayer
Keyword(s):  
Electron Microscope ◽  
Supersonic Flow ◽  
Shock Waves ◽  
Vacuum Chamber ◽  
Experimental Chamber ◽  
Scientific Instruments ◽  
Electronic Technology ◽  
Reflected Shock ◽  
University Of Technology ◽  
Flow Through

As part of the research in the field of vacuum chamber pumping in the Environmental Electron Microscope, research on supersonic flow through apertures is being carried out at the Department of Electrical and Electronic Technology of Brno University of Technology in cooperation with the Institute of Scientific Instruments of the CAS. This paper deals with the influence of reflected shock waves on the resulting flow in the pumped part of the Experimental Chamber.

scholarly journals The structure and dynamics of patch-clamped membranes: a study using differential interference contrast light microscopy.

1990 ◽  
Vol 111 (2) ◽  
pp. 599-606 ◽  
Author(s):  
M Sokabe ◽  
F Sachs
Keyword(s):  
Cell Surface ◽  
Transmural Pressure ◽  
Positive Pressure ◽  
Radius Of Curvature ◽  
Pressure Gradients ◽  
Structure And Motion ◽  
Excised Patches ◽  
Glass Interface ◽  
Pipette Tip ◽  
Flow Through

We have developed techniques for micromanipulation under high power video microscopy. We have used these to study the structure and motion of patch-clamped membranes when driven by pressure steps. Patch-clamped membranes do not consist of just a membrane, but rather a plug of membrane-covered cytoplasm. There are organelles and vesicles within the cytoplasm in the pipette tip of both cell-attached and excised patches. The cytoplasm is capable of active contraction normal to the plane of the membrane. With suction applied before seal formation, vesicles may be swept from the cell surface by shear stress generated from the flow of saline over the cell surface. In this case, patch recordings are made from membrane that was not originally present under the tip. The vesicles may break, or fuse and break, to form the gigasealed patch. Patch membranes adhere strongly to the wall of the pipette so that at zero transmural pressure the membranes tend to be normal to the wall. With transmural pressure gradients, the membranes generally become spherical; the radius of curvature decreasing with increasing pressure. Some patches have nonuniform curvature demonstrating that forces normal to the membrane may be significant. Membranes often do not respond quickly to changes in pipette pressure, probably because viscoelastic cytoplasm reduces the rate of flow through the tip of the pipette. Inside-out patches may be peeled from the walls of the pipette, and even everted (with positive pressure), without losing the seal. This suggests that the gigaseal is a distributed property of the membrane-glass interface.

Short-term emersion affects cardiac function and regional haemolymph distribution in the crab Cancer magister

1996 ◽  
Vol 199 (3) ◽  
pp. 569-578
Author(s):  
C Airriess ◽  
B Mcmahon
Keyword(s):  
Stroke Volume ◽  
Cardiac Function ◽  
Large Scale ◽  
Time Course ◽  
Beat Frequency ◽  
Heart Beat ◽  
Experimental Chamber ◽  
Cancer Magister ◽  
Flow Through ◽  
Cardiac Stroke Volume

Changes in cardiac function and arterial haemolymph flow associated with 6 h of emersion were investigated in the crab Cancer magister using an ultrasonic flowmeter. This species is usually found sublittorally but, owing to the large-scale horizontal water movements associated with extreme tides, C. magister may occasionally become stranded on the beach. Laboratory experiments were designed such that the emersion period was typical of those that might be experienced by this crab in its natural environment. The frequency of the heart beat began to decline sharply almost immediately after the start of the experimental emersion period. Cardiac stroke volume fell more gradually. The combined reduction in these two variables led to a maximum decrease in cardiac output of more than 70 % from the control rate. Haemolymph flow through all the arteries originating at the heart, with the exception of the anterior aorta, also declined markedly during emersion. As the water level in the experimental chamber fell below the inhalant branchial openings, a stereotypical, dramatic increase in haemolymph flow through the anterior aorta began and this continued for the duration of the emersion period. The rapid time course of the decline in heart-beat frequency and the increase in haemolymph flow through the anterior aorta suggest a neural mechanism responding to the absence of ventilatory water in the branchial chambers. These responses may be adaptations, respectively, to conserve energy by reducing the minute volume of haemolymph pumped by the heart and to protect the supply of haemolymph to cephalic elements of the central nervous system. The decline in cardiac stroke volume, which occurs more slowly over the emersion period, may be a passive result of the failure to supply sufficient O2 to meet the aerobic demands of the cardiac ganglion.

scholarly journals A homeopathic drug proving of Anthropoides paradiseus 30CH with subsequent comparison to the ethology of the substance

2018 ◽  
Author(s):  
◽  
Melissa Godfrey
Keyword(s):  
Controlled Trial ◽  
Clear Correlation ◽  
Inclusion Criteria ◽  
Two Phase ◽  
University Of Technology ◽  
Homeopathic Drug ◽  
The Common ◽  
Double Blinded ◽  
The Mind ◽  
Subsequent Comparison

Introduction The purpose of this study was to conduct a homoeopathic drug proving of Anthropoides paradiseus 30CH and to subsequently compare the symptoms derived during the proving to the ethology of the animal from which the proving substance was derived. Methodology The homoeopathic proving of Anthropoides paradiseus 30CH was conducted as a randomised double-blinded placebo-controlled trial at the Durban University of Technology on thirty participants. Twenty percent of the participants received a placebo while the remaining eighty percent received the active substance of Anthropoides paradiseus 30CH which was manufactured according to methods 6, 8a and 10 of the German Homoeopathic Pharmacopoeia. After recruitment, a two-phase consent and a comprehensive initial consultation, participants who met the inclusion criteria were accepted into this study. Powders were ingested over a two-day period and thereafter the provers were monitored for a further five weeks. During the proving period, participants subjectively recorded their experiences in a journal and were monitored by the researcher. Following the proving period, journals were collected, and the data analysis took place. The symptoms of the verum group were converted to standard repertory and materia medica formats. The symptoms were then compared to the ethology of the animal from which the substance was derived so that similarities between the behaviour of the animal and the expressed symptom picture of the provers could be assessed. Results The proving of Anthropoides paradiseus 30CH produced symptoms in keeping with five hundred and seventy-four existing rubrics, and fifty-five new rubrics were created. The majority of rubrics were represented in the MIND, NOSE, STOMACH and DREAMS sections of the repertory. The general themes of dryness, thirst, increased or decreased energy, large appetite and laterality were seen. The common sensations were itching and heaviness. The mental themes which were clearly evident were: focus, lack of concentration, isolation, sociability, music, dance, exercise, anxiety, calmness and spirituality. Correlations between the behavioural, anatomical and physiological features of Anthropoides paradisus and the symptom picture produced by provers during the proving period was clearly evident. Conclusion Clearly observable symptoms were produced in healthy individuals following the administration of Anthropoides paradiseus 30CH. A clear correlation existed between the symptomatology produced during this proving and the ethology of Anthropoides paradiseus.

Contribution of the large hepatic veins to postsinusoidal vascular resistance

1992 ◽  
Vol 262 (1) ◽  
pp. G14-G22 ◽  
Author(s):  
R. Maass-Moreno ◽  
C. F. Rothe
Keyword(s):  
Transition Point ◽  
Venous Pressure ◽  
Primary Site ◽  
The Other ◽  
Hepatic Veins ◽  
Pressure Gradients ◽  
Double Lumen ◽  
Pentobarbital Sodium ◽  
Anesthetized Dogs ◽  
Flow Through

We tested the hypothesis that the larger (greater than 2 mm ID) hepatic veins are the primary site of the portal-to-caval venous pressure gradient in the dog. Double-lumen catheters were inserted through the caval wall into hepatic veins of pentobarbital sodium-anesthetized dogs. One lumen opened at the end, and the other to the side. Each catheter was advanced until stopped and then it was withdrawn. The pressure at either port dropped from 87 +/- 31 to 13 +/- 11% of the portal-to-caval pressure difference as each moved past a transition point (TP). The location of the TP depended on the catheter diameter. Intraportal histamine or norepinephrine, 4 and 2.6 micrograms.min-1.kg body wt-1 respectively, augmented only the pressure measured upstream to the TP. A mathematical model of flow through a vessel with a catheter inside predicted a marked increase in resistance when the ratio of catheter OD to vessel ID exceeded approximately 0.6. Autopsy revealed ratios greater than 0.6 upstream to the TP. A hydraulic model confirmed that this effect caused the appearance of the TP. Given the depth (11.7 cm) at which near caval pressures could be found, even during histamine administration, we conclude that the major pressure gradients in the canine liver must lie upstream to the large hepatic veins.

scholarly journals Effects of Wall Ventilation on the Shock-wave/Viscous-Layer Interactions in a Mach 2.2 Intake

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 208 ◽  
Author(s):  
Humrutha Gunasekaran ◽  
Thillaikumar Thangaraj ◽  
Tamal Jana ◽  
Mrinal Kaushik
Keyword(s):  
High Speed ◽  
Static Pressure ◽  
Normal Shock ◽  
Pressure Gradients ◽  
Dual Mode ◽  
Contraction Ratio ◽  
Cavity Configuration ◽  
Flow Through ◽  
Flow Compressor ◽  
Surface Covering

In order to achieve proficient combustion with the present technologies, the flow through an aircraft intake operating at supersonic and hypersonic Mach numbers must be decelerated to a low-subsonic level before entering the combustion chamber. High-speed intakes are generally designed to act as a flow compressor even in the absence of mechanical compressors. The reduction in flow velocity is essentially achieved by generating a series of oblique as well as normal shock waves in the external ramp region and also in the internal isolator region of the intake. Thus, these intakes are also referred to as mixed-compression intakes. Nevertheless, the benefits of shock-generated compression do not arise independently but with enormous losses because of the shockwave and boundary layer interactions (SBLIs). These interactions should be manipulated to minimize or alleviate the losses. In the present investigation a wall ventilation using a new cavity configuration (having a cross-section similar to a truncated rectangle with the top wall covered by a thin perforated surface is deployed underneath the cowl-shock impinging point of the Mach 2.2 mixed-compression intake. The intake is tested for four different contraction ratios of 1.16, 1.19, 1.22, and 1.25, with emphasis on the effect of porosity, which is varied at 10.6%, 15.7%, 18.8%, and 22.5%. The introduction of porosity on the surface covering the cavity has been proved to be beneficial in decreasing the wall static pressure substantially as compared to the plain intake. A maximum of approximately 24.2% in the reduction in pressure at the upstream proximal location of 0.48 L is achieved in the case of the wall-ventilated intake with 18.8% porosity, at the contraction ratio of 1.19. The Schlieren density field images confirm the efficacy of the 18.8% ventilation in stretching the shock trains and in decreasing the separation length. At the contraction ratios of 1.19, 1.22, and 1.25 (‘dual-mode’ contraction ratios), the controlled intakes with higher porosity reduce the pressure gradients across the shockwaves and thereby yields an ‘intake-start’ condition. However, for the uncontrolled intake, the ‘unstart’ condition emerges due to the formation of a normal shock at the cowl lip. Additionally, the cowl shock in the ‘unstart’ intake is shifted upstream because of higher downstream pressure.

Simulations of coastal upwelling on the Sydney Continental Shelf

2000 ◽  
Vol 51 (6) ◽  
pp. 577 ◽  
Author(s):  
Patrick Marchesiello ◽  
Mark T. Gibbs ◽  
Jason H. Middleton
Keyword(s):  
Boundary Layer ◽  
Coastal Upwelling ◽  
Deep Ocean ◽  
Bottom Boundary Layer ◽  
Return Flow ◽  
Pressure Gradients ◽  
Bottom Boundary ◽  
Eastern Australia ◽  
Flow Through ◽  
Good Agreement

Two-dimensional numerical simulations of the response of the coastal waters of Sydney, south-eastern Australia, to idealized upwelling-favourable winds are presented. The spin up of the upwelling circulation is investigated, in particular the structure of the nearshore circulation. The intensity of the final upwelling state is found to be strongly linked to the activation of the return flow through the bottom boundary layer, which is also related to the strength of imposed alongshore pressure gradients. Results from a simulation of upwelling forced by a deep-ocean alongshore-current jet also show the final upwelling state to be weak in comparison with upwelling states produced by the action of the local wind stress. Bottom boundary layer shut-down in the presence of such a forcing jet is also discussed. A simulation of a real upwelling event was also performed and good agreement was found between the simulation and observations from a field experiment performed during summer 1994 in the Sydney coastal ocean.

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