scholarly journals Acoustic Biosensor for Discrimination of Pathogens according to the Gram Principle

Proceedings ◽  
2020 ◽  
Vol 60 (1) ◽  
pp. 57
Author(s):  
Vladislav Lemozerskii ◽  
Tatiana Zimina ◽  
Alena Gagarina
Keyword(s):  
Acoustic Waves ◽  
Sharp Decrease ◽  
Resonance Curve ◽  
Bifidobacterium Bifidum ◽  
Staining Procedure ◽  
Biomedical Analysis ◽  
Resonance Effects ◽  
Gram Staining ◽  
Resonance Frequencies ◽  
External Acoustic Field

The microacoustic methods of biomedical analysis, implemented on piezoelectric crystals and ceramics, are becoming increasingly popular due to the fact of their potential for integration into laboratories-on-a-chip, biochips, and biosensors as functional elements of biosensors. An important stage in diagnostics of infectious diseases is the identification of pathogens. One possible applications of such a sensor is an alternative to the time- and labor-consuming Gram method of discriminating bacteria according to the composition of their cell walls. Thus, bacteria, which in a Gram staining procedure do not decolor after application of the dye solution, are classified as Gram-positive (G(+)). They are surrounded with a thick peptidoglycan layer that is pulpy and dampens acoustic waves. While Gram-negative (G(–)) bacteria, which acquire a red color in a Gram procedure, are covered with a thin and springy layer, demonstrating resonance effects when interacting with acoustic fields. Thus, G(+) and G(–), which are differently colored in Gram procedures, also react differently to an external acoustic field: for G(–) bacteria, this was a sharp decrease in the Q-factor of the “resonator–suspension” system and a shift of the resonance curve to lower frequencies. While for G(+) bacteria, although a certain shift of the resonance curve was also observed, the bandwidth of the resonance curve practically did not change. This effect was studied for L. acidophilus (G(+)) and Escherichia coli (G(–)) bacilli with quarts resonators of 4 MHz, 5 MHz, and 10 MHz. The biosensor was tested using Lactobacillus fermentum, E. coli M-17, Bifidobacterium bifidum, Burkholderia cepacian, and Staphylococcus aureus. At this stage, it has been demonstrated that the method is particularly effective for discriminating bacteria of a similar shape, such as, for example, cocci. The discrimination of the Gram factor for cocci and bacilli was less accurate and needs further studies for selection of precise resonance frequencies.

ON LOGARITHMIC ASYMPTOTICS OF STOCHASTIC RESONANCE FREQUENCIES

2003 ◽  
Vol 03 (01) ◽  
pp. 55-71
Author(s):  
S. C. CARMONA ◽  
M. I. FREIDLIN
Keyword(s):  
Dynamical Systems ◽  
Stochastic Resonance ◽  
Small Amplitude ◽  
Large Deviation ◽  
Large Deviation Theory ◽  
Resonance Effects ◽  
Resonance Frequencies ◽  
Logarithmic Asymptotics ◽  
The Relationship ◽  
Deviation Theory

Stochastic resonance effects due to arbitrarily small amplitude deterministic perturbations in dynamical systems with noise are studied. The concept of Log-Asymptotic Resonance Frequency is introduced and the relationship between its existence and some types of symmetries in the stochastic system is established; the spectrum of this kind of frequencies is determined. These symmetries are defined through the quasi-deterministic approximation of the system. The large deviation theory gives the basic machinery for this analysis.

Convective Scaling of Intrinsic Thermo-Acoustic Eigenfrequencies of a Premixed Swirl Combustor

2017 ◽  
Author(s):  
Alp Albayrak ◽  
Thomas Steinbacher ◽  
Thomas Komarek ◽  
Wolfgang Polifke
Keyword(s):  
Flow Velocity ◽  
Acoustic Waves ◽  
Feedback Loop ◽  
Feedback Mechanism ◽  
Bulk Flow ◽  
Axial Position ◽  
Low Frequencies ◽  
Swirl Combustor ◽  
Acoustic Modes ◽  
Resonance Frequencies

For velocity sensitive premixed flames, intrinsic thermoacoustic (ITA) feedback results from flow-flame-acoustic interactions as follows: perturbations of velocity upstream of the flame result in modulations of the heat release rate, which in turn generate acoustic waves that travel in the downstream as well as the upstream direction. The latter perturb again the upstream velocity, and thus close the ITA feedback loop. This feedback mechanism exhibits resonance frequencies that are not related to acoustic eigenfrequencies of a combustor and generates — in additional to acoustic modes — so-called ITA modes. In this work spectral distributions of the sound pressure level (SPL) observed in a perfectly premixed, swirl stabilized combustion test rig are analyzed. Various burner configurations and operating points are investigated. Spectral peaks in the SPL data for stable as well as for unstable cases are interpreted with the help of a newly developed simple criterion for the prediction of burner intrinsic ITA modes. This criterion extends the known −π measure for the flame transfer function (FTF) by including the burner acoustic. This way, the peaks in the SPL spectra are identified to correspond to either ITA or acoustic modes. It is found that ITA modes are prevalent in this particular combustor. Their frequencies change significantly with the power rating (bulk flow velocity) and the axial position of the swirler, but are insensitive to changes in the length of the combustion chamber. It is argued that the resonance frequencies of the ITA feedback loop are governed by convective time scales. For that reason, they arise at rather low frequencies, which scale with the bulk flow velocity.

scholarly journals Experimental and Numerical Assessment of Local Resonance Phenomena in 3D-Printed Acoustic Metamaterials

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
D. Roca ◽  
T. Pàmies ◽  
J. Cante ◽  
O. Lloberas-Valls ◽  
J. Oliver
Keyword(s):  
Acoustic Waves ◽  
Unit Cell ◽  
Material Structure ◽  
Cell Design ◽  
Acoustic Metamaterials ◽  
Local Resonance ◽  
Resonance Phenomena ◽  
Resonance Frequencies ◽  
Characteristic Wavelength ◽  
3D Printed

Abstract The so-called locally resonant acoustic metamaterials (LRAMs) are a new kind of artificially engineered materials capable of attenuating acoustic waves. As the name suggests, this phenomenon occurs in the vicinity of internal frequencies of the material structure and can give rise to acoustic bandgaps. One possible way to achieve this is by considering periodic arrangements of a certain topology (unit cell), smaller in size than the characteristic wavelength. In this context, a computational model based on a homogenization framework has been developed from which one can obtain the aforementioned resonance frequencies for a given LRAM unit cell design in the sub-wavelength regime, which is suitable for low-frequency applications. Aiming at validating both the proposed numerical model and the local resonance phenomena responsible for the attenuation capabilities of such materials, a 3D-printed prototype consisting of a plate with a well selected LRAM unit cell design has been built and its acoustic response to normal incident waves in the range between 500 and 2000 Hz has been tested in an impedance tube. The results demonstrate the attenuating capabilities of the proposed design in the targeted frequency range for normal incident sound pressure waves and also establish the proposed formulation as the fundamental base for the computational design of 3D-printed LRAM-based structures.

scholarly journals Effect of heat-staining procedure on the Gram staining properties of mycobacteria.

1991 ◽  
Vol 46 (2) ◽  
pp. 533-539
Author(s):  
Masahiro NAKAMURA ◽  
Yumiko HARANO ◽  
Toshihiko KOGA
Keyword(s):  
Staining Procedure ◽  
Gram Staining

scholarly journals Microfluidic Jetting Deformation and Pinching-off Mechanism in Capillary Tubes by Using Traveling Surface Acoustic Waves

Actuators ◽  
2020 ◽  
Vol 9 (1) ◽  
pp. 5 ◽  
Author(s):  
Yulin Lei ◽  
Hong Hu ◽  
Jian Chen ◽  
Peng Zhang
Keyword(s):  
Acoustic Waves ◽  
Capillary Tube ◽  
Surface Acoustic Waves ◽  
Liquid Volume ◽  
Rf Power ◽  
Single Droplet ◽  
Research Attention ◽  
Number Range ◽  
Drop On Demand ◽  
Resonance Frequencies

To date, there has been little research attention paid to jetting deformation and pinching-off of microfluidic flows induced by the surface acoustic wave (SAW) mechanism. Further, such studies were almost limited to one sessile drop actuation without any confinement mechanisms. Such a scenario is likely attributable to the mechanism’s relatively poor controllability, the difficulty of maintaining the fluid loading position and issues related to stability and repeatability. In this paper, a novel SAW-microfluidic jetting system with a vertical capillary tube was designed, accompanied by a large number of experiments investigating the single droplet jetting mechanism with different device dimensions, resonance frequencies and radio frequency (RF) power capabilities. The study began with the whole jetting deformation and droplet pinching off through the use of a microscope with a high-speed camera, after which the results were discussed to explain the droplet jetting mechanism in a vertical capillary tube. After that, the study continued with experimental and theoretical examinations for high-quality single droplet jetting conditions. Jetting characterization parameters, including threshold RF power, resonance frequency, liquid volume, pinching off droplet dimensions, were thoroughly analyzed. Lastly, the Weber number range, a significant parameter in SAW-microfluidic jetting, was verified, and the pinching off microdroplet dimension was analyzed and compared via experiments. The significance of this study lies in the realization of microfluidic drop-on-demand based on SAW technology.

MOTION OF A RIGID SPHERE IN AN ACOUSTIC WAVE FIELD

Geophysics ◽  
1945 ◽  
Vol 10 (1) ◽  
pp. 91-109 ◽  
Author(s):  
Alfred Wolf
Keyword(s):  
Acoustic Waves ◽  
Response Curve ◽  
Wave Length ◽  
Elastic Solid ◽  
Rigid Sphere ◽  
Resonance Effects ◽  
First Order ◽  
Solid Media ◽  
The Waves ◽  
Scattering Of Acoustic Waves

A rigid sphere in the field of plane acoustic waves in a fluid or in an elastic solid medium is subjected to harmonic forces in the direction of propagation of the waves, and proportional to their amplitude. The response curve is a function of the ratio of the circumference of the sphere to the wave length, and of the ratio of the mass of the sphere to the mass of the displaced medium. In an elastic solid, Poisson’s ratio must also be included among the variables. The response curve in fluids decreases continuously with decreasing wave length. In elastic solid media, the response curve has a maximum which is due to resonance effects. In general, the greater the mass of the sphere the smaller the response except in the neighborhood of resonance in elastic solid media. The scattering of acoustic waves by a rigid sphere is determined. The potential of scattered waves is developed in a series of spherical harmonics; it is shown that only the first order coefficients are affected by the motion of the sphere.

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