Measuring the local pressure amplitude in microchannel acoustophoresis

Lab on a Chip ◽  
2010 ◽  
Vol 10 (5) ◽  
pp. 563 ◽  
Author(s):  
Rune Barnkob ◽  
Per Augustsson ◽  
Thomas Laurell ◽  
Henrik Bruus
Keyword(s):  
Pressure Amplitude ◽  
Local Pressure

An Attack on the Contamination Problem in the Electron Microscope

1967 ◽  
Vol 25 ◽  
pp. 368-368
Author(s):  
J. J. Kelsch ◽  
A. Holtz
Keyword(s):  
Electron Microscope ◽  
Pressure Gradient ◽  
Ionization Potential ◽  
Simple Solution ◽  
Specimen Surface ◽  
Contamination Rate ◽  
Local Pressure ◽  
High Ionization ◽  
Hydrocarbon Molecules ◽  
Contamination Problem

A simple solution to the serious problem of specimen contamination in the electron microscope is presented. This is accomplished by the introduction of clean helium into the vacuum exactly at the specimen position. The local pressure gradient thus established inhibits the migration of hydrocarbon molecules to the specimen surface. The high ionization potential of He permits the use of relatively large volumes of the gas, without interfering with gun stability. The contamination rate is reduced on metal samples by a factor of 10.

Healing venous ulcers with different modalities of leg compression

Phlebologie ◽  
2006 ◽  
Vol 35 (05) ◽  
pp. 349-355 ◽  
Author(s):  
E. O. Brizzio ◽  
G. Rossi ◽  
A. Chirinos ◽  
I. Cantero ◽  
G. Idiazabal ◽  
...  
Keyword(s):  
Wound Care ◽  
Univariate Analysis ◽  
Compression Therapy ◽  
Healing Time ◽  
Clinical Parameters ◽  
Compression Stockings ◽  
Local Pressure ◽  
Ulcer Size ◽  
Venous Ulcers ◽  
Unexpected Findings

Summary Background: Compression therapy (CT) is the stronghold of treatment of venous leg ulcers. We evaluated 5 modalities of CT in a prospective open pilot study using a unique trial design. Patients and methods: A group of experienced phlebologists assigned 31 consecutive patients with 35 venous ulcers (present for 2 to 24 months with no prior CT) to 5 different modalities of leg compression, 7 ulcers to each group. The challenge was to match the modality of CT with the features of the ulcer in order to achieve as many healings as possible. Wound care used standard techniques and specifically tailored foam pads to increase local pressure. CT modalities were either stockings Sigvaris® 15-20, 20-30, 30-40 mmHg, multi-layer bandages, or CircAid® bandaging. Compression was maintained day and night in all groups and changed at weekly visits. Study endpoints were time to healing and the clinical parameters predicting the outcome. Results: The cumulative healing rates were 71%, 77%, and 83% after 3, 6, and 9 months, respectively. Univariate analysis of variables associated with nonhealing were: previous surgery, presence of insufficient perforating and/or deep veins, older age, recurrence, amount of oedema, time of presence of CVI and the actual ulcer, and ulcer size (p <0.05-<0.001). The initial ulcer size was the best predictor of the healing-time (Pearson r=0.55, p=0.002). The modality of CT played an important role also, as 19 of 21 ulcers (90%) healed with stockings but only 8 of 14 with bandages (57%; p=0.021). Regression analysis allowed to calculate a model to predict the healing time. It compensated for the fact that patients treated with low or moderate compression stockings were at lower risk of non-healing. and revealed that healing with stockings was about twice as rapid as healing with bandages. Conclusion: Three fourths of venous ulcers can be brought to healing within 3 to 6 months. Healing time can be predicted using easy to assess clinical parameters. Irrespective of the initial presentation ulcer healing appeared more rapid with the application of stockings than with bandaging. These unexpected findings contradict current believes and require confirmation in randomised trials.

Nonlinear dynamics of a shell encapsulated microbubble near solid boundary in an ultrasonic field

2020 ◽  
Vol 14 (3) ◽  
pp. 7235-7243
Author(s):  
N.M. Ali ◽  
F. Dzaharudin ◽  
E.A. Alias
Keyword(s):  
Oscillation Amplitude ◽  
Ultrasonic Field ◽  
Dynamical Behaviour ◽  
Ultrasound Contrast Agents ◽  
Chaotic Behaviour ◽  
Solid Boundary ◽  
Driving Frequency ◽  
Pressure Amplitude ◽  
Radial Expansion ◽  
Therapeutic Delivery

Microbubbles have the potential to be used for diagnostic imaging and therapeutic delivery. However, the transition from microbubbles currently being used as ultrasound contrast agents to achieve its’ potentials in the biomedical field requires more in depth understanding. Of particular importance is the influence of microbubble encapsulation of a microbubble near a vessel wall on the dynamical behaviour as it stabilizes the bubble. However, many bubble studies do not consider shell encapsulation in their studies. In this work, the dynamics of an encapsulated microbubble near a boundary was studied by numerically solving the governing equations for microbubble oscillation. In order to elucidate the effects of a boundary to the non-linear microbubble oscillation the separation distances between microbubble will be varied along with the acoustic driving. The complex nonlinear vibration response was studied in terms of bifurcation diagrams and the maximum radial expansion. It was found that the increase in distance between the boundary and the encapsulated bubble will increase the oscillation amplitude. When the value of pressure amplitude increased the single bubble is more likely to exhibit the chaotic behaviour and maximum radius also increase as the inter wall-bubble distance is gradually increased. While, with higher driving frequency the maximum radial expansion decreases and suppress the chaotic behaviour.

Considerations about mass and energy flow in discontinuous evaporating crystallizers

2016 ◽  
pp. 514-516
Author(s):  
Martin Bruhns
Keyword(s):  
Energy Flow ◽  
Static Pressure ◽  
Bubble Formation ◽  
Boiling Temperature ◽  
Vapor Bubbles ◽  
Local Pressure ◽  
Heating Steam ◽  
Flow Changes ◽  
Local Superheating ◽  
Local Supersaturation

The massecuite circulates in a loop within the evaporating crystallizing vessel. The massecuite flows upwards through the heating tubes. In the room above the calandria the massecuite flow changes its direction to radial inwards and then to vertical downwards. An impeller in the central tube forces the circulation. Below the calandria the main direction of flow is radially outwards until threads of the massecuite stream enter the heating tubes in upwards direction. Within the tubes heat is transferred to the massecuite. At low temperature differences between heating steam and massecuite and higher levels of the massecuite in the crystallizer vapor bubbles are not found in the tubes. Vapor bubbles can be formed at a massecuite level in the crystallizer where the temperature of the massecuite is higher than the local boiling temperature of water, which depends on the local pressure (including the static pressure of the massecuite at this point) and the boiling point elevation of the mother liquor. The surface tension of the liquid is a resistance against the bubble formation, which has to be overcome by the local superheating i.e. the part of the enthalpy of the massecuite exceeding the local boiling temperature. The formation and the flow of the bubbles change the density of the massecuite/bubbles mixture and has an influence on the massecuite flow. The formation of a vapour bubble is connected with a local drop of the massecuite temperature which changes the local supersaturation. Today the heat transfer into the magma is quite well known but the process of bubble formation is quite unknown. Some basic considerations about the formation of bubbles and its influence on local supersaturation based on calculation of heat and mass balances and models of bubble formation are be given and discussed. Experiments for basic investigations are proposed.

scholarly journals Albuminuria intensifies the link between urinary sodium excretion and central pulse pressure in the general population: the Wakuya study

2021 ◽  
Author(s):  
Kaname Tagawa ◽  
Yusuke Tsuru ◽  
Katsumi Yokoi ◽  
Takanori Aonuma ◽  
Junichiro Hashimoto
Keyword(s):  
Cardiovascular Disease ◽  
Chronic Kidney Disease ◽  
Pulse Pressure ◽  
Augmentation Index ◽  
Sodium Intake ◽  
Urinary Sodium Excretion ◽  
Urinary Sodium ◽  
Pressure Amplitude ◽  
Excess Sodium ◽  
Central Pulse Pressure

Abstract Background Central pulse pressure is responsible for the hemodynamics of vital organs, and monitoring this parameter is important for cardiovascular disease prevention. Excess sodium intake and (micro)albuminuria (a manifestation of renal microvascular damage) are known to be strong predictors of cardiovascular disease. We sought to investigate the cross-sectional relationships among dietary sodium intake, albuminuria, and central pulse pressure in a general population cohort. Methods The subjects were 933 apparently healthy adults (mean age, 56 ± 10 years). Radial pressure waveforms were recorded with applanation tonometry to estimate mean arterial pressure, central pulse pressure, forward and backward pressure amplitudes, and augmentation index. The urinary sodium/creatinine and albumin/creatinine ratios were measured in spot urine samples. Results Both the urinary sodium/creatinine and albumin/creatinine ratios were positively correlated with central pulse pressure, even after adjusting for mean arterial pressure (P &lt; 0.001). Moreover, both ratios had a synergistic influence on increasing the central pulse pressure independent of age, sex, estimated glomerular filtration rate, hyperlipidemia, and diabetes (interaction P = 0.04). A similar synergistic influence was found on the forward pressure amplitude, but not on the backward pressure amplitude or augmentation index. The overall results were not altered when the urinary albumin/creatinine ratio was replaced with the existence of chronic kidney disease. Conclusion (Micro)albuminuria strengthens the positive association between urinary sodium excretion and central pulse pressure and systolic forward pressure. Excess sodium intake may magnify the cardiovascular risk by widening the aortic pulsatile pressure, particularly in the presence of concomitant chronic kidney disease.

scholarly journals Comparative Assessment of Tubular Ceramic, Spiral Wound, and Hollow Fiber Membrane Microfiltration Module Systems for Milk Protein Fractionation

Foods ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. 692
Author(s):  
Roland Schopf ◽  
Florian Schmidt ◽  
Johanna Linner ◽  
Ulrich Kulozik
Keyword(s):  
Hollow Fiber ◽  
Milk Protein ◽  
Hollow Fiber Membrane ◽  
Comparative Assessment ◽  
Transmission Factor ◽  
Transmembrane Pressure ◽  
Protein Fractionation ◽  
Flow Conditions ◽  
Local Pressure ◽  
Spiral Wound

The fractionation efficiency of hollow fiber membranes (HFM) for milk protein fractionation was compared to ceramic tubular membranes (CTM) and spiral wound membranes (SWM). HFM combine the features of high membrane packing density of SWM and the more defined flow conditions and better control of membrane fouling in the open flow channel cross-sections of CTM. The aim was to comparatively analyze the effect of variations in local pressure and flow conditions while using single industrially sized standard modules with similar dimensions and module footprints (module diameter and length). The comparative assessment with varied transmembrane pressure was first applied for a constant feed volume flow rate of 20 m3 h−1 and, secondly, with the same axial pressure drop along the modules of 1.3 bar m−1, similar to commonly applied crossflow velocity and wall shear stress conditions at the industrial level. Flux, transmission factor of proteins (whey proteins and serum caseins), and specific protein mass flow per area membrane and per volume of module installed were determined as the evaluation criteria. The casein-to-whey protein ratios were calculated as a measure for protein fractionation effect. Results obtained show that HFM, which so far are under-represented as standard module types in industrial dairy applications, appear to be a competitive alternative to SWM and CTM for milk protein fractionation.

scholarly journals Design and Optimization of a Centrifugal Pump for Slurry Transport Using the Response Surface Method

Machines ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 60
Author(s):  
Khaled Alawadhi ◽  
Bashar Alzuwayer ◽  
Tareq Ali Mohammad ◽  
Mohammad H. Buhemdi
Keyword(s):  
Response Surface ◽  
Centrifugal Pump ◽  
Industrial Applications ◽  
Pump Efficiency ◽  
Optimized Design ◽  
Centrifugal Pumps ◽  
Local Pressure ◽  
Design And Optimization ◽  
Geometry Characteristic ◽  
Line Design

Since centrifugal pumps consume a mammoth amount of energy in various industrial applications, their design and optimization are highly relevant to saving maximum energy and increasing the system’s efficiency. In the current investigation, a centrifugal pump has been designed and optimized. The study has been carried out for the specific application of transportation of slurry at a flow rate of 120 m3/hr to a head of 20 m. For the optimization process, a multi-objective genetic algorithm (MOGA) and response surface methodology (RSM) have been employed. The process is based on the mean line design of the pump. It utilizes six geometric parameters as design variables, i.e., number of vanes, inlet beta shroud, exit beta shroud, hub inlet blade draft, Rake angle, and the impeller’s rotational speed. The objective functions employed are pump power, hydraulic efficiency, volumetric efficiency, and pump efficiency. In this reference, five different software packages, i.e., ANSYS Vista, ANSYS DesignModeler, response surface optimization software, and ANSYS CFX, were coupled to achieve the optimized design of the pump geometry. Characteristic maps were generated using simulations conducted for 45 points. Additionally, erosion rate was predicted using 3-D numerical simulations under various conditions. Finally, the transient behavior of the pump, being the highlight of the study, was evaluated. Results suggest that the maximum fluctuation in the local pressure and stresses on the cases correspond to a phase angle of 0°–30° of the casing that in turn corresponds to the maximum erosion rates in the region.

scholarly journals Seasonal food habits of the four-horned antelope (Tetracerus quadricornis de Blainville, 1816) in tropical deciduous forests of Aravalli mountain range, Rajasthan, Western India

2020 ◽  
Vol 81 (1) ◽  
Author(s):  
Ramchandra Meghwal ◽  
Chhaya Bhatnagar ◽  
Vijay Kumar Koli
Keyword(s):  
Plant Species ◽  
Forest Fires ◽  
Habitat Management ◽  
Fleshy Fruit ◽  
Feeding Strategies ◽  
Western India ◽  
Mountain Range ◽  
Local Pressure ◽  
Dendrocalamus Strictus ◽  
Helicteres Isora

Abstract Background Feeding strategies assessment of endangered species during food limited seasons is important in order to understand their niche and advise effective habitat management steps. We assessed the four-horned antelope (Tetracerus quadricornis) seasonal diet from April 2014 to March 2015, in three wildlife sanctuaries in western India, namely, Sitamata, Kumbhalgarh, and Phulwari-ki-nal Wildlife Sanctuaries. Opportunistic focal animal sampling method was used in five 1 km paths in each sanctuary to take feeding observations. Each transect was walked three times a day (morning 06:00-10:00 h; mid-day 10:00-14:00 h; evening 15:00-18:00 h), 1 day a month, during 12 months, with a total of 540 surveys divided between 15 paths. The diet data was categorized into different plant categories. Results A total of 532 feeding records from 85 animal sightings were noted with a mean (± SD) of 14.78 ± 10.04 feeding records/month. Feeding was observed on 63 plant species belonging to 23 families. The highest feeding records noted were on trees (60.91%) in the diet followed by shrubs (20.49%), grasses (16.92%), forbs (1.50%), and climbers (0.18%) respectively. Most of the plant species consumed were from Fabaceae (n = 17) and Poaceae (n = 12) families. The overall browse-grass ratio was 83.08-16.92% (88.02-11.98% for Sitamata WLS; 82.11-17.89% for Kumbhalgarh WLS; 79.10-20.90% for Phulwari-ki-nal WLS). Leaves were the most consumed part of the plants (64.10%), followed by dry fruit (16.55%), fleshy fruit (13.34%), flowers (2.82%), buds (2.06%), and twigs (1.13%) respectively. Use of fleshy fruits, dry fruits, and trees showed significant seasonal dietary difference (P < 0.05) in all three sanctuaries. Conclusions Tetracerus quadricornis was found to consume more browse species than grasses. We recommend conservation and promotion of natural plant regeneration, in particular for the plant species that were the most consumed by four-horned antelope, namely, Aristida adscensionis, Dendrocalamus strictus, Dichrostachys cinerea, Acacia leucophloea, Butea monosperma, Helicteres isora, Ziziphus nummularia, and Ziziphus xylopyrus. Conservation of grassland patches, minimizing local pressure, and planning, construction, and maintenance of fire lines prior to timing of forest fires would help to protected T. quadricornis habitat in all three sanctuaries.

Effects of the staggered blades on unsteady pressure pulsations and flow structures of a centrifugal pump

2021 ◽  
pp. 095765092098732
Author(s):  
Ning Zhang ◽  
Bo Gao ◽  
Chao Li ◽  
Dan Ni ◽  
Guoping Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Pulsation ◽  
Second Harmonic ◽  
Simulation Method ◽  
Pump Efficiency ◽  
Pressure Amplitude ◽  
Pressure Pulsations ◽  
Unsteady Pressure ◽  
Negative Effect

Effects of the staggered blades on unsteady pressure pulsations of a centrifugal pump with a specific speed ns=147 are investigated by the numerical simulation method. The obtained results are compared with the original blades. To clarify the resulting effects, eight monitoring points are used to extract pressure signals at three typical working conditions, and component at the blade passing frequency fBPF is emphasized. Results show that the pump efficiency and head will be reduced by the staggered blades, and at the nominal flow rate, the reduction is about 1.5% from comparison with the original blades. For all the eight points, the staggered blades contribute to the reduction of pressure amplitudes at fBPF when the pump works at three flow rates. The averaged reduction is 15.5% at the nominal flow rate. However, the negative effect on the second harmonic of fBPF will be caused by the staggered blades, and the corresponding pressure amplitude will increase at 2fBPF. It means that the pressure pulsation energy will be redistributed among the discrete components in pressure spectrum by the staggered blades. From the TKE distribution, it is found that the TKE values on the blade pressure side will be significantly affected by the staggered blades.

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