Time-averaged Intensity Research Articles

Induction of apoptosis and ferroptosis by a tumor suppressing magnetic field through ROS-mediated DNA damage.

Magnetic field (MF) is being used in antitumor treatment; however, the underlying biological mechanisms remain unclear. In this study, the potency and mechanism of a previously published tumor suppressing MF exposure protocol were further investigated. This protocol, characterized as a 50 Hz electromagnetic field modulated by static MF with time-average intensity of 5.1 mT, when applied for 2 h daily for over 3 consecutive days, selectively inhibited the growth of a broad spectrum of tumor cell lines including lung cancer, gastric cancer, pancreatic cancer and nephroblastoma. The level of intracellular reactive oxygen species (ROS) increased shortly after field exposure and persisted. Subsequently, pronounced DNA damage and activation of DNA repair pathways were identified both in vitro and in vivo. Furthermore, use of free radical scavenger alleviated DNA damage and partially reduced cell death. Finally, this field was found to inhibit cell proliferation, and simultaneously induced two types of programmed cell death, apoptosis and ferroptosis. In conclusion, this tumor suppressing MF could determine cell fate through ROS-induced DNA damage, inducing oxidative stress and activation of the DNA damage repair pathways, eventually lead to apoptosis and ferroptosis, as well as inhibition of tumor growth.

Flashing light does not improve photosynthetic performance and growth of green microalgae

Light attenuation in photobioreactors is a major bottleneck in microalgal production. A possible strategy for artificial light-based microalgal production to deliver light deep inside the culture is through the periodical emission of high intensity light flashes (so-called flashing light). However, our results did not show improved photosynthetic rates compared to continuous light for dilute and concentrated Tetraselmis chui cultures exposed to flashing light with various repetition rates (frequencies 0.01 Hz–1 MHz), light-dark ratios (duty cycles: 0.001–0.7) or time-averaged light intensity (50–1000 μmol s−1 m−2). Likewise, flashing light applied to Chlorella stigmatophora and T. chui batch cultures could not enhance growth. However, we observed flashing light effects at different duty cycles and frequencies, depending on cell acclimation, culture concentration, and light intensity. In conclusion, artificial flashing light does not improve microalgal biomass productivities in photobioreactors, but low frequencies (f < 50 Hz) may be still used to improve light harvesting-associated biomolecules production.

The effect of frequency on solidification characteristics of AZ80 alloy during electromagnetic DC casting

The effects of electromagnetic frequency on solidification characteristics of AZ80 magnesium alloy billet during electromagnetic Direct-chill (DC) casting were investigated experimentally. The billet with diameter 320 mm was solidified in an oscillation electromagnetic field (EMF) with the imposition of a pulse current at the frequency of 20 Hz, 30 Hz, and 40 Hz when the time-averaged current intensity was 80 A and duty cycle was 20%, from which pulse electromagnetic force was yielded. The macrostructure evolution was quantitatively examined based on the grain size and its distribution, and the conductivity was measured to evaluate the characteristics of solidified structures. The effects of electromagnetic frequency on macro- and microstructure evolution, phase composition, element segregation, and conductivity distribution were discussed in detail. It was observed that the solidified structure under pulse oscillation electromagnetic field is sensitive to the electromagnetic frequency, and there is an effective frequency range for the refinement of solidified structures. The grain size range decreases from 815 μm ∼ 951 μm (without EMF) to 408 μm ∼ 612 μm (EMF-30Hz). The segregation ratio reduced evidently at the frequency of 30 Hz. As the frequency further decreases or increases, the grain size and segregation ratio increase. Moreover, the conductivity distribution on the cross section of the billet is more uniform in the presence of EMF, which is closely related to the solidification structures.

Pyroelectric ultrasound sensor model

Ultrasound is typically measured using phase-sensitive piezoelectric sensors. Interest in phase-insensitive sensors has grown recently, with proposed applications in ultrasound attenuation tomography of the breast. The advantage of phase-insensitive imaging is that it does not suffer from degradation of image quality due to phase-aberration and narrow directional response. A numerical model of a phase-insensitive pyroelectric ultrasound sensor is presented. The model consists of three coupled components run in sequence: acoustic, thermal, and electrical. The acoustic simulation models the propagation and absorption of the incoming ultrasound wave. The negative divergence of the time-averaged acoustic intensity is used as a heat source in the thermal simulation for the time-evolution of temperature in the sensor. Both the acoustic and thermal simulations are performed using the k-Wave MATLAB toolbox with an assumption that shear waves are not supported in the medium. The final component of the model uses a pyroelectric circuit model which outputs the sensor response based on the temperature change in the sensor. The modelled pyroelectric sensor response and directional dependence are compared to empirical data. A physical model for the directionality of the sensor response is then proposed.

Study of the effect of ultrasound scanner settings on the level of radiation intensity by the reciprocity method

In this paper, a new method of measuring the intensity on the radiating surface of the convex sensor of the ultrasonic diagnostic scanner EDAN U50 with its various settings was proposed, based on the reciprocity method using a hydrophone calibrated with a vibration simulator. The effect of the following scanner settings on the peak-spatial average time-averaged intensity in B-mode was experimentally investigated: ultrasonic radiation frequencies, number of focuses, and number of focus positions. It was found that changing the scanner settings significantly changes the temporal parameters of the emitted bursts of pulses, which affects the result of averaging intensity over time. At the same time, an increase in the number of focuses leads to a decrease in intensity, while an increase in the focus of the positions and frequency of the radiation, on the contrary, leads to its growth. Studies have shown that the intensity value exceeds the allowable values at almost any settings of the ultrasound scanner, with the exception of the ultrasound frequency of 2.5 MHz.

An Experimental Study of Turbulent Structures in a Flat-Crested Weir-Type Fishway

Fishways can assist fish species to overcome obstacles for performing spawning, feeding, and overwintering migrations. Flow structures in a flat-crested weir-type fishway were experimentally studied. Variations of time-averaged velocity, turbulence intensity, and Reynolds stress with longitudinal and vertical directions and flow rates were analyzed. Also, flow patterns in the longitudinal profile were given. The experiments were carried out in a large scale fishway model in the Hydraulics Laboratory at Zhejiang University of Technology. Two typical flow rates corresponding to detection and preference velocities of fish species were considered. Five different horizontal planes for each flow rate were taken. Eleven transverse lines were arranged for each horizontal plane. Ten measuring points were laid along each transverse line. Three-dimensional velocity at each measuring point was measured by acoustic Doppler velocimeter (ADV). Longitudinal and vertical time-averaged velocity distributions, longitudinal turbulence intensity distribution on the different horizontal planes, vertical turbulent intensity distribution along flow depth, and Reynolds stress distributions on the different horizontal planes and on the different cross-sections in the pool of fishway were analyzed. The experimental results showed that distribution of longitudinal velocity was characterized by topology, which constituted an apparent vertical vortex. Weir flow exhibited skimming flow in the fishway pool. Peak-value range of longitudinal turbulent intensity existed. The amplitude of variation in Reynolds stress near the surface layer reached the maximum, which provided a certain hydraulic condition for fish that favor jumping near the surface layer. This study uncovers three-dimensional flow structures, especially for turbulence characteristics, which can contribute to improving the design of crested weir fishway and to assisting fish species to pass smoothly through fishway, being of potential application value.

Measurements of contact ultrasound in the workplace

Introduction. Hygienic control of the levels of contact ultrasound in the workplace should be carried out in accordance with the approved certified measurement procedures. The sanitary-epidemiological norms and rules present the requirements for the normative values and evaluation of contact ultrasound, as well as the methods of measurement of acoustic pressure and the calculation of the time-averaged peak spatial intensity. The analysis of the possibility of measurements of contact ultrasound in the workplace and in the laboratory.Results. The results showed that the presented measurement methods determine the specific power that the ultrasound source emits into a water-like gel medium, and the specific power is a technical characteristic of the ultrasonic source. This method should be used to determine the ultrasonic characteristics of the ultrasound source in the laboratory at the manufacturers, and not to assess its impact in the workplace. Measurements of contact ultrasound in the workplace are very difficult, as they require extremely complex, expensive research and unique equipment. Thus, to assess the impact of contact ultrasound on the human body in the workplace, it is advisable to use the acoustic characteristics of the contact ultrasound source obtained in the laboratory at the manufacturing plants and presented in the technical documentation.

Formin-2 drives polymerisation of actin filaments enabling segregation of apicoplasts and cytokinesis in Plasmodium falciparum.

In addition to its role in erythrocyte invasion, Plasmodium falciparum actin is implicated in endocytosis, cytokinesis and inheritance of the chloroplast-like organelle called the apicoplast. Previously, the inability to visualise filamentous actin (F-actin) dynamics had restricted the characterisation of both F-actin and actin regulatory proteins, a limitation we recently overcame for Toxoplasma (Periz et al, 2017). Here, we have expressed and validated actin-binding chromobodies as F-actin-sensors in Plasmodium falciparum and characterised in-vivo actin dynamics. F-actin could be chemically modulated, and genetically disrupted upon conditionally deleting actin-1. In a comparative approach, we demonstrate that Formin-2, a predicted nucleator of F-actin, is responsible for apicoplast inheritance in both Plasmodium and Toxoplasma, and additionally mediates efficient cytokinesis in Plasmodium. Finally, time-averaged local intensity measurements of F-actin in Toxoplasma conditional mutants revealed molecular determinants of spatiotemporally regulated F-actin flow. Together, our data indicate that Formin-2 is the primary F-actin nucleator during apicomplexan intracellular growth, mediating multiple essential functions.

Efficient coupling of dynamic electro-optical and heat-transport models for high-power broad-area semiconductor lasers

In this work, we discuss the modeling of edge-emitting high-power broad-area semiconductor lasers. We demonstrate an efficient iterative coupling of a slow heat transport (HT) model defined on multiple vertical–lateral laser cross-sections with a fast dynamic electro-optical (EO) model determined on the longitudinal–lateral domain that is a projection of the device to the active region of the laser. Whereas the HT-solver calculates temperature and thermally-induced refractive index changes, the EO-solver exploits these distributions and provides time-averaged field intensities, quasi-Fermi potentials, and carrier densities. All these time-averaged distributions are used repetitively by the HT-solver for the generation of the heat sources entering the HT problem solved in the next iteration step.

COMPUTATIONAL FLUID DYNAMICS METHOD FOR THE ANALYSIS OF HYDRODYNAMICS PERFORMANCE OF MANGROVE ROOT MODELS

Mangroves play a prominent role in obstructing water currents in riverbanks, shorelines, and coastal areas. Mangrove roots have a significant contribution to the resiliency of the vegetation structure. In this work, the flow characteristics past a cluster of circular cylinders (patch), which represents the mangrove roots, are investigated. Numerical simulations were conducted for five patch porosities (φ = 86% to 96%) for Reynolds number ranging from 2000 to 10,000. The complex two-dimensional flow structure of the cylinder wake is reasonably captured and time-averaged streamwise velocity, vorticity, and turbulence intensity are presented. A comparison is made between flow around one cylinder and a patch of cylinders with the same diameter to determine the impact of the patch porosity. Based on the results, unlike for a canonical cylinder, the patch porosity gives a rise in the Strouhal number but drops drag coefficient. We found that blockage parameter for a patch decreases with porosity for all Reynolds numbers. A von Karman vortex sheet is predicted behind the patch with a periodicity which agrees well with experiment. In addition, the vorticity field for the least porous patch reveals a delay in the formation of von Karman vortex street due to the small vortices in the near wake, whereas the vortices evolve in the far wake and produce swirling flow.

Wake flow modification behind a square cylinder using control rods

In the present study, flow behind a square cylinder is investigated using control rods. The control rods are placed in the shear layer and studied using particle image velocimetry, hotwire anemometry and flow visualization techniques. Experiments are conducted in a low-speed wind tunnel for three different Reynolds numbers 485, 805 and 1290. However, detailed analysis of flow is only presented at a Reynolds number of 485. The aim is to modify the wake behind a square cylinder for possible suppression of vortex Street and drag reduction. The control rod diameter is kept constant as 0.2 times of the cylinder diameter. Depending upon the gap between control rods and the cylinder, the flow structure, vortex dynamics, the distance of the shear layer roll up behind the cylinder is modified. An attempt is made to correlate the different flow structures with corresponding drag forces. Several parameters such as time-averaged drag coefficient, Strouhal number, recirculation length, fluctuating velocity, turbulence intensity, and Reynolds stress are measured. To understand the flow phenomena and its intricate structure, flow visualization images are also captured in the same setup with smoke visualization. Maximum up to 22% drag reduction is observed at a particular control rod position.

Real-time study of high-cycle fatigue damage using the averaged speckle dynamics

The theory of the method permitting a study of damage accumulation in high-cycle fatigue of reflecting and transparent objects using the time-averaged speckle images is briefly discussed. The formulas that relate the relative displacement vector of the scattering centres to the time-average intensity and the temporal autocorrelation function of this intensity at some observation point are presented. A technique identifying the component of the relative displacement vector as local plastic deformations emerge during fatigue testing is discussed. The issue of real-time recording and processing of the speckle images using the conventional personal computers and special-purpose video systems with function-oriented processors based on homogenous computing environment is discussed. Processors with homogenous architecture allow assurance of the highest possible image processing performance within the order of 10-teraflops/s. The specimens, the optical system, the equipment for fatigue testing, the USB camera and the software used in high-cycle fatigue experiments are discussed. The possibilities and prospects for application of this technique and equipment in evaluation of the remaining life of some object types are discussed.

Acoustic Streaming in a Soft Tissue Microenvironment

We demonstrated that sound can push fluid through a tissue-mimicking material. Although acoustic streaming in tissue has been proposed as a mechanism for biomedical ultrasound applications, such as neuromodulation and enhanced drug penetration, streaming in tissue or acoustic phantoms has not been directly observed. We developed a material that mimics the porous structure of tissue and used a dye and a video camera to track fluid movement. When applied above an acoustic intensity threshold, a continuous focused ultrasound beam (spatial peak time average intensity: 238 W/cm2, centre frequency: 5 MHz) was found to push the dye axially, that is, in the direction of wave propagation and in the radial direction. Dye clearance increased with ultrasound intensity and was modelled using an adapted version of Eckart's acoustic streaming velocity equation. No microstructural changes were observed in the sonicated region when assessed using scanning electron microscopy. Our study indicates that acoustic streaming can occur in soft porous materials and provides a mechanistic basis for future use of streaming for therapeutic or diagnostic purposes.

Gas-heating phenomenon in a nanosecond pulse discharge in atmospheric-pressure air and its application for high-speed flow control

The interaction between the gas-heating phenomenon in a pulsed discharge in atmospheric-pressure air and the separated shear layer in the flow around the airfoil is discussed. The first half of the paper details the development of the modeling for gas heating in a pulsed discharge in atmospheric-pressure air and reviews recent research results. Particular attention is paid to the processes of fast and slow gas heating. In the latter half of the paper, the experimental results of the high-speed Schlieren visualization are presented and the interaction between the nanosecond-pulse-driven dielectric-barrier-discharge plasma actuator (ns-DBDPA) actuation and the density field is discussed, based on the periodic and time-averaged components of the Schlieren signal intensity. The time-averaged intensity of the contrast of the Schlieren signal that originates in the separated shear layer changes according to the normalized actuation frequency of ns-DBDPA, F+. As F+ increases from 0.1 to 2, the periodic component of the Schlieren signal intensity increases, resulting in a decrease in the time-averaged contrast of the Schlieren signal. When F+ > 2, the heated air caused by ns-DBDPA actuation is accumulated along the separated shear layer, resulting in an increase in the time-averaged contrast of the Schlieren signal.

Experimental investigation of a robust algorithm for unambiguous source directionalization by sharks

All fish can detect the three vector components of particle motion, enabling them to determine source bearing, but particle motion alone cannot resolve which direction is towards the source and which direction is away (i.e., there is a 180° ambiguity). However, fish with swim bladders can also detect acoustic pressure which enables such fish to resolve this 180° ambiguity. Proposed processing algorithms, though, often employ unrealistic restrictions such as sinusoidal time dependence and free-field conditions. We propose a robust algorithm for determining the unambiguous source direction by a fish that can detect acoustic pressure. The method is based on the time-averaged acoustic intensity vector (the time-integral of the product of pressure and particle velocity). This non-oscillatory quantity points in the direction of energy flow and hence directly away from the source. The algorithm has the advantage of being applicable to signals with any time dependence, in any propagation environment. For sharks, which do not have swim bladders, we hypothesize that the vertical component of particle acceleration can be substituted for pressure, provided that the shark is sufficiently close to the water surface. We test the validity of this hypothesis by determining the direction to the source for reef noise, a biologically relevant signal, and boat noise in a range-varying shallow water environment.

Near field scattering measurements using acoustic vector sensors

The objective of this research is to measure and characterize acoustic energy flow surrounding underwater objects in the near field condition. To accomplish this, we employ prototype acoustic vector sensors which simultaneously measure acoustic pressure and three-dimensional acoustic particle acceleration at a singular point, allowing for precise vector field measurements. In March of 2018, a test at the U.S. Navy’s Dodge Pond Test Facility examined the intensity field surrounding hollow spheres at low ka (wavenumber × radius) values. Phase differences between varying acoustic path lengths from reflected, scattered, and creeping waves result in interference patterns around the object. Various intensity processing techniques are used to reconstruct the acoustic field. Instantaneous intensity describes the time-dependent energy flux of the field and can be divided into active (real) and reactive (imaginary) components, which represent physically real elements. Time-averaged intensity shows energy transport and can be visualized in the form of acoustic streamlines.

Blinking Suppression in Highly Excited CdSe/ZnS Quantum Dots by Electron Transfer under Large Positive Gibbs (Free) Energy Change.

Semiconductor quantum dots with stable photoluminescence are necessary for next generation optoelectronic and photovoltaic devices. Photoluminescence intensity fluctuations of cadmium and lead chalcogenide quantum dots have been extensively investigated since the first observation of blinking in CdSe nanocrystals in 1996. In a quantum dot, blinking originates from stochastic photocharging, nonradiative Auger recombination, and delayed neutralization. So far, blinking is suppressed by defect passivation, electron transfer, and shell preparation, but without any deep insight into free energy change of electron transfer. We report real-time detection of significant blinking suppression for CdSe/ZnS quantum dots exposed to N, N-dimethylaniline, which is accompanied by a considerable increase in the time-averaged photoluminescence intensity of quantum dots. Although the Gibbs (free) energy change (Δ Get = +2.24 eV), which is estimated electrochemically and from density functional theory calculations, is unfavorable for electron transfer from N, N-dimethylaniline to a quantum dot in the minimally excited (band-edge) state, electron transfer is obvious when a quantum dot is highly excited. Nonetheless, Δ Get crosses from the positive to negative scale as the solvent dielectric constant exceeds 5, favoring electron transfer from N, N-dimethylaniline to a quantum dot excited to the band-edge state. Based on single-molecule photoluminescence and ensemble electron transfer studies, we assign blinking suppression to the transfer of an electron from N, N-dimethylaniline to the hot hole state of a quantum dot. In addition to blinking suppression by electron transfer, complete removal of blinking is limited by short-living OFF states induced by the negative trion.

Theoretical Estimation of Optimal Parameters for Maximum Fluorescence under Pulsed Excitation.

We present a detailed theoretical study on choosing optimum excitation parameters for maximizing the fluorescence yield. Using a model system, we show how the time-averaged emission (fluorescence) is modulated as the excitation conditions are changed from continuous wave excitation to pulsed excitation with various combinations of pulse widths and pulse repetition-rates for the same time-averaged excitation intensity. We conclude that depending on the excitation intensity, different pulse parameters are required for generating maximum fluorescence output. Our method can be implemented for other more sophisticated models without much difficulty.

The effects of bed form roughness on total suspended load via the Lattice Boltzmann Method

• 3D LBM simulation of turbulent flow over bed forms with different roughnesses. • LBM is extended with Smagorinsky and free surface models for open channel flow. • The commonly adopted flat-bed assumptions may lead to an overestimation of total suspended load. • The total suspended load is linearly proportional to the friction factor . Bed forms in natural rivers and man-made channels provide the dominant contribution to overall flow resistance and hence significantly affect sediment transport rate. Many laboratory experiments and field observations have been conducted on bed forms, and it was found that theoretical flat-bed assumptions do not give the correct estimation for the total suspended load (TSL). In this study, we present a systematic numerical investigation of turbulent open-channel flows over bed forms using the Lattice Boltzmann Method (LBM). A static Smagorinsky model is incorporated into LBM to account for turbulence, and the dynamic interface between fluid and air is captured by a free-surface model. The time-averaged flow velocity, turbulence intensity and Reynolds shear stress in LBM simulations show an excellent agreement with the available experimental data. In addition, the coherent flow structures induced by the bed forms qualitatively agree with previous numerical results from Large Eddy Simulations based the Navier–Stokes equations. We then proceed to investigate the effects of bed form roughness, quantified by the total friction factor f T , on sediment transport. It is found that the prediction of the TSL based on the theoretical flat-bed assumptions may lead to an overestimation of up to 30%, depending on the bed form roughness. In addition, the normalized TSL is linearly proportional to f T and nearly inversely proportional to the ratio of downward settling velocity and upward turbulence induced diffusion. Our work proposes a general law linking these quantities to estimate the TSL, which has the potential for a more efficient and accurate engineering design of man-made channels and improved river management.

Hilbert–Huang transform based advanced Bessel fringe generation and demodulation for full-field vibration studies of specular reflection micro-objects

The Hilbert-Huang transform working principle is used to develop advanced single-frame and two-frame Bessel fringe pattern generation and demodulation algorithms especially tailored to enhance full-field vibration studies using time-averaged interferometry. The Bessel fringe pattern, named as the Besselogram, is understood as calculated amplitude modulation/contrast variation map of the time-averaged interferogram intensity distribution. Proposed Besselogram processing techniques are computationally fast and robust to fringe pattern imperfections and environmental disturbances encountered in interferometric studies of vibrating micro-objects. The advanced fast adaptive bidimensional empirical mode decomposition scheme is employed to filter interferograms, Bessel fringes and their phase maps. Reported Bessel fringe pattern analysis method possesses unique ability to determine both vibration phase and amplitude distribution maps from a single time-averaged interferogram. Comprehensive numerical simulations corroborate advantageous features of proposed methods. Experimental evaluation performed for two resonant modes of a silicon micro-membrane is enclosed for completeness of the analysis.