scholarly journals Modelling bacterial behaviour close to a no-slip plane boundary: the influence of bacterial geometry

2010 ◽  
Vol 466 (2118) ◽  
pp. 1725-1748 ◽  
Author(s):  
H. Shum ◽  
E. A. Gaffney ◽  
D. J. Smith
Keyword(s):  
Slip Plane ◽  
Power Efficiency ◽  
Electrostatic Interactions ◽  
Plane Boundary ◽  
Geometrical Parameters ◽  
The Novel ◽  
Stable Orbit ◽  
Stable Circular Orbit ◽  
Micro Organisms ◽  
Unbounded Fluid

We describe a boundary-element method used to model the hydrodynamics of a bacterium propelled by a single helical flagellum. Using this model, we optimize the power efficiency of swimming with respect to cell body and flagellum geometrical parameters, and find that optima for swimming in unbounded fluid and near a no-slip plane boundary are nearly indistinguishable. We also consider the novel optimization objective of torque efficiency and find a very different optimal shape. Excluding effects such as Brownian motion and electrostatic interactions, it is demonstrated that hydrodynamic forces may trap the bacterium in a stable, circular orbit near the boundary, leading to the empirically observable surface accumulation of bacteria. Furthermore, the details and even the existence of this stable orbit depend on geometrical parameters of the bacterium, as described in this article. These results shed some light on the phenomenon of surface accumulation of micro-organisms and offer hydrodynamic explanations as to why some bacteria may accumulate more readily than others based on morphology.

EXPERIMENTAL AND ANALYTICAL STUDIES OF VERTICAL AXIS WIND TURBINES

2018 ◽  
pp. 51-58
Author(s):  
B. P. Khozyainov
Keyword(s):  
Wind Turbine ◽  
Flow Velocity ◽  
Wind Power ◽  
Wind Turbines ◽  
Power Efficiency ◽  
Air Flow ◽  
Geometrical Parameters ◽  
Wind Speeds ◽  
Analytical Studies ◽  
Air Flow Velocity

The article carries out the experimental and analytical studies of three-blade wind power installation and gives the technique for measurements of angular rate of wind turbine rotation depending on the wind speeds, the rotating moment and its power. We have made the comparison of the calculation results according to the formulas offered with the indicators of the wind turbine tests executed in natural conditions. The tests were carried out at wind speeds from 0.709 m/s to 6.427 m/s. The wind power efficiency (WPE) for ideal traditional installation is known to be 0.45. According to the analytical calculations, wind power efficiency of the wind turbine with 3-bladed and 6 wind guide screens at wind speedsfrom 0.709 to 6.427 is equal to 0.317, and in the range of speed from 0.709 to 4.5 m/s – 0.351, but the experimental coefficient is much higher. The analysis of WPE variations shows that the work with the wind guide screens at insignificant average air flow velocity during the set period of time appears to be more effective, than the work without them. If the air flow velocity increases, the wind power efficiency gradually decreases. Such a good fit between experimental data and analytical calculations is confirmed by comparison of F-test design criterion with its tabular values. In the design of wind turbines, it allows determining the wind turbine power, setting the geometrical parameters and mass of all details for their efficient performance.

scholarly journals Unsteady Stokes flow near boundaries: the point-particle approximation and the method of reflections

2018 ◽  
Vol 841 ◽  
pp. 883-924 ◽  
Author(s):  
A. Simha ◽  
J. Mo ◽  
P. J. Morrison
Keyword(s):  
Brownian Motion ◽  
Slip Plane ◽  
Metallic Nanoparticles ◽  
Particle Density ◽  
Point Particle ◽  
Plane Boundary ◽  
Short Time Scale ◽  
Approximation Techniques ◽  
Numerical Predictions ◽  
Particle Approximation

Problems of particle dynamics involving unsteady Stokes flows in confined geometries are typically harder to solve than their steady counterparts. Approximation techniques are often the only resort. Felderhof (see e.g. J. Phys. Chem. B, vol. 109 (45), 2005, pp. 21406–21412; J. Fluid Mech., vol. 637, 2009, pp. 285–303) has developed a point-particle approximation framework to solve such problems, especially in the context of Brownian motion. Despite excellent agreement with past experiments, this framework produces unsteady drag coefficients that depend on particle density. This is inconsistent, since the problem can be formulated mathematically without any reference to the particle’s density. We address this inconsistency in our work. Upon implementing our modifications, the framework passes consistency checks that it previously failed. Further, it is not obvious that such an approximation should work for short-time-scale motion. We investigate its validity by deriving it from a general formalism based on integral equations through a series of systematic approximations. We also compare results from the point-particle framework against a calculation performed using the method of reflections, for the specific case of a sphere near a full-slip plane boundary. We find from our analysis that the reasons for the success of the point-particle approximation are subtle and have to do with the nature of the unsteady Oseen tensor. Finally, we provide numerical predictions for Brownian motion near a full-slip and a no-slip plane wall based on the point-particle approximation as used by Felderhof, our modified point-particle approximation and the method of reflections. We show that our modifications to Felderhof’s framework would become significant for systems of metallic nanoparticles in liquids.

An Analysis of Power Characteristics of Oil-Free Scroll Vacuum Pumps

2020 ◽  
pp. 37-43
Author(s):  
A.V. Tyurin ◽  
A.V. Burmistrov ◽  
A.A. Raykov ◽  
S.I. Salikeev
Keyword(s):  
Mathematical Model ◽  
Power Efficiency ◽  
High Speed ◽  
Pressure Sensors ◽  
Operating Conditions ◽  
Total Power ◽  
Radial Clearance ◽  
Geometrical Parameters ◽  
Power Characteristics ◽  
Indicator Power

This paper presents an analysis of the indicator power of an oil-free scroll vacuum pump based on the indicator diagrams obtained through high-speed pressure sensors. These values are compared with the results of calculations using a mathematical model of the pump working process. It is shown that the divergence of the calculated results and experimental values does not exceed 4%, which confirms the adequacy of the developed mathematical model. The total power of the scroll pump exceeds the indicator power by more than 2 times due to the friction losses between the face seals and disks of the reciprocal scroll elements, friction losses in the stuffing box seals and rolling bearings, as well as due to the coefficient of efficiency of the motor. The influence of the radial clearance between the scroll elements on the power consumption is considered. It is shown that at low pressures nearing the ultimate pressure, the power increases with the increased clearance, while at inlet pressures exceeding 40 kPa it decreases. The performed analysis can be used for selecting the optimal geometrical parameters of the scroll elements and increasing power efficiency of the pump depending on specific operating conditions.

scholarly journals Paenibacillus favisporus sp. nov., a xylanolytic bacterium isolated from cow faeces

2004 ◽  
Vol 54 (1) ◽  
pp. 59-64 ◽  
Author(s):  
Encarna Velázquez ◽  
Trinidad de Miguel ◽  
Margarita Poza ◽  
Raúl Rivas ◽  
Ramón Rosselló-Mora ◽  
...  
Keyword(s):  
Novel Species ◽  
Hydrolytic Enzymes ◽  
Gas Production ◽  
Cow Dung ◽  
Rrna Gene ◽  
The Novel ◽  
Closely Related Species ◽  
Main Fatty Acid ◽  
Phenylalanine Deaminase ◽  
Micro Organisms

During a search for xylan-degrading micro-organisms, a sporulated bacterium was recovered from recent and old cow dung and rectal samples. The isolates were identified as members of a novel species of the genus Paenibacillus, based on 16S rRNA gene sequences. According to the results of phylogenetic analysis, the most closely related species was Paenibacillus azoreducens. Phenotypic and chemotaxonomic analyses and DNA–DNA hybridization experiments also showed that the isolates belonged to a novel species of the genus Paenibacillus. The novel species is a facultatively anaerobic, motile, Gram-variable, sporulated rod. The spores of this rod-shaped micro-organism occur in slightly swollen sporangia and are honeycomb-shaped. The main fatty acid is anteiso-branched C15 : 0. Growth was observed with many carbohydrates, including xylan, as the only carbon source and gas production was not observed from glucose. The novel species produces a wide variety of hydrolytic enzymes, such as xylanases, cellulases, amylases, gelatinase, urease and β-galactosidase. On the contrary, it does not produce caseinase, phenylalanine deaminase or lysine decarboxylase. According to the data obtained in this work, the strains belong to a novel species, for which the name Paenibacillus favisporus sp. nov. is proposed (type strain, GMP01T=LMG 20987T=CECT 5760T).

Design optimization of a fluidized bed with a novel air chamber using the CFD-Taguchi method

2021 ◽  
pp. 095440622110293
Author(s):  
Fei Wang ◽  
Hao Yan ◽  
Yishan Zeng ◽  
Wei Xu ◽  
Haozhou Zang ◽  
...  
Keyword(s):  
Taguchi Method ◽  
Fluidized Bed ◽  
Gas Flow ◽  
Interaction Mechanism ◽  
Splitter Plate ◽  
Geometrical Parameters ◽  
The Novel ◽  
Residual Rate ◽  
Air Chamber ◽  
Level 1

The gas–solid fluidized bed is the key structure of industrial fluidization, and it is widely used in fields such as chemical reactors and industrial material conveying. To study the uniformity of velocity distribution ( Vu) in a fluidized bed and clarify the interaction mechanism between the geometric structure of the air chamber and the gas flow, in this paper, 16 novel chamber structures for powder unloading were designed based on the Taguchi method. Computational fluid dynamics was used to simulate the different chamber schemes, and the effects of various geometric factors on the response were analyzed based on the Taguchi method. The effect of the novel optimization model for powder unloading was verified by tests. The results show that the optimal combination of geometrical parameters is air chamber capacity ( V) at level 4, separation ratio ( K) at level 1 and clearance of splitter plate ( δ) at level 1, and δ has the greatest effect on the Vu1 and Vu2 in the fluidized bed. With the increase in δ and K, the velocity of the airflow away from the inlet side increases, and the area of the vortex near the splitter plate increases. Compared with the baseline model, the fluidized bed with the novel air chamber can effectively reduce the residual rate of powder unloading.

scholarly journals iDirac: a field-portable instrument for long-term autonomous measurements of isoprene and selected VOCs

2020 ◽  
Vol 13 (2) ◽  
pp. 821-838 ◽  
Author(s):  
Conor G. Bolas ◽  
Valerio Ferracci ◽  
Andrew D. Robinson ◽  
Mohammed I. Mead ◽  
Mohd Shahrul Mohd Nadzir ◽  
...  
Keyword(s):  
Power Efficiency ◽  
Modular Design ◽  
Limit Of Detection ◽  
The Novel ◽  
Relative Standard ◽  
New Instrument ◽  
Instrument Control ◽  
Gas Consumption ◽  
And Performance ◽  
Dual Column

Abstract. The iDirac is a new instrument to measure selected hydrocarbons in the remote atmosphere. A robust design is central to its specifications, with portability, power efficiency, low gas consumption and autonomy as the other driving factors in the instrument development. The iDirac is a dual-column isothermal oven gas chromatograph with photoionisation detection (GC-PID). The instrument is designed and built in-house. It features a modular design, with the novel use of open-source technology for accurate instrument control. Currently configured to measure biogenic isoprene, the system is suitable for a range of compounds. For isoprene measurements in the field, the instrument precision (relative standard deviation) is ±10 %, with a limit of detection down to 38 pmol mol−1 (or ppt). The instrument was first tested in the field in 2015 during a ground-based campaign, and has since shown itself suitable for deployment in a variety of environments and platforms. This paper describes the instrument design, operation and performance based on laboratory tests in a controlled environment as well as during deployments in forests in Malaysian Borneo and central England.

scholarly journals Improving the Cellular Uptake of Biomimetic Magnetic Nanoparticles

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 766
Author(s):  
Federica Vurro ◽  
Ylenia Jabalera ◽  
Silvia Mannucci ◽  
Giulia Glorani ◽  
Alberto Sola-Leyva ◽  
...  
Keyword(s):  
Magnetic Nanoparticles ◽  
Electrostatic Interactions ◽  
Ph Value ◽  
Cell Uptake ◽  
The Novel ◽  
Tat Peptide ◽  
Ph Values ◽  
Cell Internalization ◽  
Drug Nanocarriers

Magnetococcus marinus magnetosome-associated protein MamC, expressed as recombinant, has been proven to mediate the formation of novel biomimetic magnetic nanoparticles (BMNPs) that are successful drug nanocarriers for targeted chemotherapy and hyperthermia agents. These BMNPs present several advantages over inorganic magnetic nanoparticles, such as larger sizes that allow the former to have larger magnetic moment per particle, and an isoelectric point at acidic pH values, which allows both the stable functionalization of BMNPs at physiological pH value and the molecule release at acidic (tumor) environments, simply based on electrostatic interactions. However, difficulties for BMNPs cell internalization still hold back the efficiency of these nanoparticles as drug nanocarriers and hyperthermia agents. In the present study we explore the enhanced BMNPs internalization following upon their encapsulation by poly (lactic-co-glycolic) acid (PLGA), a Food and Drug Administration (FDA) approved molecule. Internalization is further optimized by the functionalization of the nanoformulation with the cell-penetrating TAT peptide (TATp). Our results evidence that cells treated with the nanoformulation [TAT-PLGA(BMNPs)] show up to 80% more iron internalized (after 72 h) compared to that of cells treated with BMNPs (40%), without any significant decrease in cell viability. This nanoformulation showing optimal internalization is further characterized. In particular, the present manuscript demonstrates that neither its magnetic properties nor its performance as a hyperthermia agent are significantly altered due to the encapsulation. In vitro experiments demonstrate that, following upon the application of an alternating magnetic field on U87MG cells treated with BMNPs and TAT-PLGA(BMNPs), the cytotoxic effect of BMNPs was not affected by the TAT-PLGA enveloping. Based on that, difficulties shown in previous studies related to poor cell uptake of BMNPs can be overcome by the novel nanoassembly described here.

scholarly journals The Reentrant Four-Layer Quasi-Elliptic Bandstop Filter

Electronics ◽  
2019 ◽  
Vol 8 (1) ◽  
pp. 81 ◽  
Author(s):  
Victor V. Atuchin ◽  
Anatoly P. Gorbachev ◽  
Vladimir A. Khrustalev ◽  
Natalya V. Tarasenko
Keyword(s):  
Transmission Lines ◽  
Stop Band ◽  
Microwave Frequency ◽  
Geometrical Parameters ◽  
Floating Potential ◽  
The Novel ◽  
Printed Circuit ◽  
Metallic Body ◽  
Bandstop Filter ◽  
Transverse Electromagnetic

The novel microwave quasi-elliptic bandstop filter, which uses the initially uncoupled strip transmission lines, is considered in this work. The proposed filter is based on the reentrant structure, where the metallic body with a floating potential is asymmetric. Generally speaking, the internal and external dielectric fillings must have their unequal relative permittivities. As a result, additional symmetrical reflection zeros are reached at the lower and upper pass bands of the stop band leading to the quasi-elliptic function response that improves the filter selectivity. The general transverse electromagnetic (TEM) circuit model for the proposed filter in terms of a series connection of the multi-ports is presented and then used to predict the initial electrical and geometrical parameters. An experimental printed circuit prototype has been manufactured and evaluated to validate the design concept. The measured filter parameters correlate well with the simulation-derived ones and that increases the degree of freedom in the fabrication of microwave frequency selective components.

scholarly journals Characterization of clinical isolates previously identified as Oerskovia turbata: proposal of Cellulosimicrobium funkei sp. nov. and emended description of the genus Cellulosimicrobium

2006 ◽  
Vol 56 (4) ◽  
pp. 801-804 ◽  
Author(s):  
June M. Brown ◽  
Arnold G. Steigerwalt ◽  
Roger E. Morey ◽  
Maryam I. Daneshvar ◽  
Leslie-Joy Romero ◽  
...  
Keyword(s):  
Sequence Similarity ◽  
Clinical Isolates ◽  
Rrna Gene ◽  
The Novel ◽  
Phenotypic Properties ◽  
Dna Reassociation ◽  
Cellulosimicrobium Cellulans ◽  
Definition Of ◽  
Taxonomic Studies ◽  
Micro Organisms

Taxonomic studies were performed on 13 clinical isolates (ten of which were epidemiologically related) that had been previously identified as Oerskovia turbata. Comparative phylogenetic analysis, based on 16S rRNA gene sequences, indicated that the isolates are closely related to Cellulosimicrobium cellulans with sequence similarity values ranging from 99·5 to 99·8 %. Chemotaxonomic results (fatty acid profiles and menaquinones) supported the inclusion of these isolates in the genus Cellulosimicrobium. The DNA G+C content was 74·5 mol%. The results of DNA–DNA reassociation, whole-cell sugars (with galactose as the characteristic whole sugar) and phenotypic properties, including antimicrobial resistance, indicated that these isolates are representatives of a novel species of the genus Cellulosimicrobium. The name Cellulosimicrobium funkei sp. nov. is proposed for the novel strains, with strain W6122T (=ATCC BAA-886T=DSM 16025T=CCUG 50705T) as the type strain. The definition of this novel Cellulosimicrobium species will assist in the understanding of the epidemiology and clinical significance of these micro-organisms.

Optimal pitching schedules for a cycloidal rotor in hovering

2016 ◽  
Vol 88 (5) ◽  
pp. 623-635
Author(s):  
Andrea Andrisani ◽  
Diego Angeli ◽  
Antonio Dumas
Keyword(s):  
Power Efficiency ◽  
Geometrical Parameters ◽  
Mean Power ◽  
Content Type ◽  
Computational Fluid Dynamics Cfd ◽  
The Mean ◽  
Sinusoidal Functions ◽  
Definition Of ◽  
Propulsion Concept ◽  
Practical Implications

Purpose The purpose of this paper is to define an optimal pitching profile for the blades of a cycloidal rotor which minimizes the mean power consumption for a given mean thrust of the rotor. Design/methodology/approach A simple analytical model of the kinematics and aerodynamics of a cycloidal rotor is defined first to obtain expressions for thrust and power depending on the pitching profile and geometrical parameters of the rotor. Then, Lagrange optimization is applied to obtain the optimal pitching schedule under hovering conditions. Finally, results of the theoretical analysis are compared with those of a two-dimensional computational fluid dynamics (CFD) model. Findings Results of the optimization suggest that the optimal profile is a combination of sinusoidal functions. It is shown that the adoption of the optimal pitching schedule could improve the power efficiency of the rotor by approximately 25 per cent. Practical implications The possibility to increase the efficiency of a cycloidal rotor by acting on its pitching schedule could be a significant factor of success for this alternative propulsion concept. Originality/value The present work represents the first attempt at a definition of an optimal pitching profile for a cycloidal rotor. Moreover, although being carried out on the basis of simplified analytical considerations, the present investigation sets a methodological framework which could be successfully applied to the design of similar kinds of systems.

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