Thin Sheet Of Laser Light Research Articles

EXCIPLEX TECHNIQUE FOR SIMULTANEOUS VISUALIZATION OF THE LIQUID AND VAPOR PHASES OF PILOT-INJECTED SPRAY BY LASER-INDUCED FLUORESCENCE

An optically accessible single-cylinder compression-ignition two-stroke research engine equipped with dual-injection system, image acquisition, and control system have been designed to acquire two-dimensional images of the pilot and main diesel fuel sprays. The engine construction permits illumination of the sprays by a thin sheet of laser light from a pulsed Nd:YAG laser frequency tripled to operate at the ultraviolet wavelength of 355 nm. The liquid fuel was decane with TMPD-naphthalene dopant dispersed in it. After ultraviolet excitation by the pulsed laser, liquid fuel regions fluoresced with a spectrum centered at the wavelength of 380 nm, while vapor regions fluoresced with a spectrum centered at 470 nm. This approach, called Exciplex technique, was applied to permit simultaneous acquisition of the liquid and vapor fuel regions in the cup-in-head geometry of the combustion chamber. The results from limited conditions suggest that existence of the pilot injection affects the chamber flow field, particularly in the near-wall region, in such a way that less liquid fuel accumulation occurs with pilot injection scheme thus should reduce hydrocarbon emission. The area spreading rate of both vapor and liquid phases within the visualization plane were linear in early stages with former having a higher rate. Close to the impingement time, vapor phase area penetration is reduced to near zero, while liquid continues linearly but at slower rate than its initial value. Both air utilization and evaporization are therefore reduced. Also, based on this and work by others, the suggestion is made that to achieve optimum simultaneous reduction in soot and NOx, the timing between the pilot and main injections (dwell) should be chosen with due consideration of the interaction between the swirl flow and pilot spray and the relative magnitudes of the ignition delay period with respect to the dwell.

Light-sheet microscopy for everyone? Experience of building an OpenSPIM to study flatworm development.

BackgroundSelective plane illumination microscopy (SPIM a type of light-sheet microscopy) involves focusing a thin sheet of laser light through a specimen at right angles to the objective lens. As only the thin section of the specimen at the focal plane of the lens is illuminated, out of focus light is naturally absent and toxicity due to light (phototoxicity) is greatly reduced enabling longer term live imaging. OpenSPIM is an open access platform (Pitrone et al. 2013 and OpenSPIM.org) created to give new users step-by-step instructions on building a basic configuration of a SPIM microscope, which can in principle be adapted and upgraded to each laboratory’s own requirements and budget. Here we describe our own experience with the process of designing, building, configuring and using an OpenSPIM for our research into the early development of the polyclad flatworm Maritigrella crozieri – a non-model animal.ResultsOur OpenSPIM builds on the standard design with the addition of two colour laser illumination for simultaneous detection of two probes/molecules and dual sided illumination, which provides more even signal intensity across a specimen. Our OpenSPIM provides high resolution 3d images and time lapse recordings, and we demonstrate the use of two colour lasers and the benefits of two color dual-sided imaging. We used our microscope to study the development of the embryo of the polyclad flatworm M. crozieri. The capabilities of our microscope are demonstrated by our ability to record the stereotypical spiral cleavage pattern of M. crozieri with high-speed multi-view time lapse imaging. 3D and 4D (3D + time) reconstruction of early development from these data is possible using image registration and deconvolution tools provided as part of the open source Fiji platform. We discuss our findings on the pros and cons of a self built microscope.ConclusionsWe conclude that home-built microscopes, such as an OpenSPIM, together with the available open source software, such as MicroManager and Fiji, make SPIM accessible to anyone interested in having continuous access to their own light-sheet microscope. However, building an OpenSPIM is not without challenges and an open access microscope is a worthwhile, if significant, investment of time and money. Multi-view 4D microscopy is more challenging than we had expected. We hope that our experience gained during this project will help future OpenSPIM users with similar ambitions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12861-016-0122-0) contains supplementary material, which is available to authorized users.

P 227. Ultramicroscopy (UM) in neurobiology

UM is a prime example for an interdisciplinary research field invention. It enables researchers to obtain high-resolution 3D-reconstructions of organ systems in different animal models. Knowledge about the interconnections of the neuronal network to the vascular system is often essential neurobiological research. Ultramicroscopy (UM) is a light sheet based fluorescence microscopy. This novel bioimaging technique allows the 3D-visualization of cm-sized biological specimens with μm-resolution ( [Dodt et al., 2007] , [Jährling, 2011] ). Artifacts of conventional microscopy such as distortion of the tissue are avoided. It is due to optical sectioning instead of mechanical sclicing ( [Jährling and Saghafi, 2011] , [Jährling, 2011] ). In UM, a specimen is illuminated by a thin sheet of laser light, formed by one or more cylindrical lenses ( [Jährling and Saghafi, 2011] , [Jährling, 2011] ). To generate a light sheet distribution in the standard UM, we basically employ a single cylindrical lens placed in front of a variable rectangular slit aperture ( [Jährling and Saghafi, 2011] , [Jährling, 2011] ). Lectinis are proteins that bind to sugar complexes, which are attached to proteins and lipids. We employed an approach using fluorescent conjugated lectins during the transcardial perfusion of mice to contrast the endothelium building up the vascular system ( [Jährling, 2011] , [Jährling et al., 2009] ). Biological samples are prepared chemically to become as transparent as possible ( Jährling, 2011 ). In this study the architecture of the blood vessel system of whole organs of animal models is visualized ( [Jährling, 2011] , [Jährling et al., 2009] ). By combining light sheet based UM with lectin-labelling, 3D reconstructions of vascular structures of the mouse spinal cord can be generated. Alteration in optics, morphological analysis of neurobiological disorders, multiple labeling, improving histology of clearing procedure, the analysis of brain tumors are subjects of interests are subjects of interests in our future work.

A laser-supported lowerable surface setup to study the role of ground contact during stepping

We introduce a laser-supported setup to study the influence of afferent input on muscle activation during walking, using a movable ground platform. This approach allows investigating if and how the activity of stance phase muscles of an insect (e.g. stick insect) responds to a missing ground contact signal. The walking surface consists of a fixed and a lowerable part, which can be lowered to defined levels below the previous ground level at any time point during a walking sequence. As a consequence, the leg under investigation finds either a lower ground level or no ground support at all. The lowerable walking surface consists of a 49mm×34mm stainless steel surface, made slippery and equipped for tarsal contact monitoring, similar to the system that was described by Gruhn and colleagues (Gruhn et al., 2006). The setup controller allows pneumatic lowering of the surface and subsequent detection of tarsal entry into the previous ground level with the help of a thin sheet of laser light and a corresponding detector. Here, we describe basic properties of the new setup and show the results of first experiments to demonstrate its use for the study of sensory and central influences in stepping of a small animal. In the experiments, we compare the effect of ground-support (“control”) with either steps into the hole (SiH), ground support at a lower surface level, or the amputation of the tarsus on the onset of EMG activity in the flexor tibiae muscle of the stick insect.

Tissue deformation analysis using a laser based digital image correlation technique

A laser based technique for planar time-resolved measurements of tissue deformation in transparent biomedical materials with high spatial resolution is developed. The approach is based on monitoring the displacement of micrometer particles previously embedded into a semi-transparent sample as it is deformed by some form of external loading. The particles are illuminated in a plane inside the tissue material by a thin laser light sheet, and the pattern is continuously recorded by a digital camera. Image analysis yields the locally and temporally resolved sample deformation in the measurement plane without the need for any in situ measurement hardware. The applicability of the method for determination of tissue deformation and material strain during the insertion of a needle probe into a soft material sample is demonstrated by means of an in vitro trial on gelatin.

Exhaled Air and Aerosolized Droplet Dispersion During Application of a Jet Nebulizer

BackgroundAs part of our influenza pandemic preparedness, we studied the dispersion distances of exhaled air and aerosolized droplets during application of a jet nebulizer to a human patient simulator (HPS) programmed at normal lung condition and different severities of lung injury.MethodsThe experiments were conducted in a hospital isolation room with a pressure of − 5 Pa. Airflow was marked with intrapulmonary smoke. The jet nebulizer was driven by air at a constant flow rate of 6 L/min, with the mask reservoir filled with sterile water and attached to the HPS via a nebulizer mask. The exhaled leakage jet plume was revealed by a laser light sheet and images captured by high-definition video. Smoke concentration in the plume was estimated from the light scattered by smoke and droplet particles.FindingsThe maximum dispersion distance of smoke particles through the nebulizer side vent was 0.45 m lateral to the HPS at normal lung condition (oxygen consumption, 200 mL/min; lung compliance, 70 mL/cm H2O), but it increased to 0.54 m in mild lung injury (oxygen consumption, 300 mL/min; lung compliance, 35 mL/cm H2O), and beyond 0.8 m in severe lung injury (oxygen consumption, 500 mL/min; lung compliance, 10 mL/cm H2O). More extensive leakage through the side vents of the nebulizer mask was noted with more severe lung injury.InterpretationHealth-care workers should take extra protective precaution within at least 0.8 m from patients with febrile respiratory illness of unknown etiology receiving treatment via a jet nebulizer even in an isolation room with negative pressure.

Simultaneous measurement method of size and 3D velocity components of droplets in a spray field illuminated with a thin laser-light sheet

A measurement technique to simultaneously obtain the size and 3D velocity components of droplets in a spray field illuminated by a thin laser-light sheet has been proposed. This technique is based on the optical processes of in-focus and out-of-focus imaging of spray droplets using a stereoscopic camera arrangement. The patterns obtained by this technique represent the distributions of glare-point pairs and defocused images with interference fringes generated by the imaging of reflection and first-order refraction rays scattered from each droplet illuminated by the laser light. The size of a droplet is evaluated by the glare-point separation and the fringe order of the interferogram. The velocity of each droplet is obtained by 3D particle tracking velocimetry (3D-PTV) based on the tracking of the glare-point pair and the defocused image generated by a droplet. For this technique, the three-dimensional optical arrangement corresponding to the scattering angle and the stereo-viewing angle, and the algorithm for stereoscopic matching of both images have been developed. The accuracy of this technique for the size and 3D velocity measurements was evaluated by applying a calibration technique, and the feasibility of this technique has been confirmed by applying it to the measurements of a spray field issuing from a swirl nozzle. From the results obtained, it has been verified that the error in the size measurement is within 1.5% and that for the velocity measurement is less than 3%.

Preliminary results of the sounding rocket experiment on wetting and coalescence prevention by Marangoni effect

This paper deals with the microgravity experiment on droplets, wetting and coalescence prevention, performed on the MAXUS 5 sounding rocket launched in April 2003 from the base ESRANGE located in Kiruna—Sweden. The aim of the experiment was to study wetting and coalescence prevention phenomena, induced by thermal Marangoni flows in drops bounded by a non isothermal immiscible liquid matrix. A failure in the on-board procedure occurred just after lift off, so the automatic experimental sequence did not start, but PI's switched to the manual mode and managed to run the experiment by telescience operative mode directly from Naples. A hemispherical drop of silicone oil was formed under microgravity conditions in a matrix of Fluorinert. The drop was anchored to a moving metallic disk ( 10 mm diameter) held at controlled temperature. A temperature gradient was initially established in the liquid matrix controlling the temperature of a fixed plate. During the experiment, a thin liquid film (about 100 μm thick) could be observed at sufficiently large temperature difference between the moving drop and the fixed disk (wetting prevention). The decreasing of the film thickness, as expected, was detected when the thermal gradient was reduced until wetting occurred at a “critical” temperature difference. A similar behaviour was observed during the non-coalescence study (coalescence prevention). For the different conditions investigated, the Marangoni flows in the meridian plane of the drop were detected by two CCD cameras (with different fields of view) looking at the tracers particles illuminated by an orthogonal thin laser light sheet. The paper reports the preliminary results of the microgravity experiment and a number of numerical simulations aimed at explaining and correlating the experimental findings.

Fine-scale patterns of odor encounter by the antennules of mantis shrimp tracking turbulent plumes in wave-affected and unidirectional flow.

Many marine animals track odor plumes to their source. Although studies of plume-tracking behavior have been performed in unidirectional flow, benthic animals such as crustaceans live in coastal habitats characterized by waves. We compared signal encounters by odor-plume-tracking stomatopods (mantis shrimp) in wave-affected and unidirectional flow in a flume. Stomatopods are small enough that we can study their natural behavior in a flume. They sample odors by flicking their antennules. A thin sheet of laser light illuminating an odor plume labeled with dye [planar laser induced fluorescence (PLIF) technique] permitted us to measure the instantaneous odor concentration encountered by the animal's chemosensory organs (antennules) while it tracked the plume. We simultaneously measured behavior and the high-resolution odor signal at the spatial and temporal scale of the animal. We found that the navigating animal encountered odor filaments more often in wave-affected flow than in unidirectional flow. Odor filaments along the animals' antennules were significantly wider and of higher concentration in waves than in unidirectional flow.

Image processing of underwater multispectral imagery

Capturing in situ fluorescence images of marine organisms presents many technical challenges. The effects of the medium, as well as the particles and organisms within it, are intermixed with the desired signal. Methods for extracting and preparing the imagery for analysis are discussed in reference to a novel underwater imaging system called the low-light-level underwater multispectral imaging system (LUMIS). The instrument supports both uni- and multispectral collections, each of which is discussed in the context of an experimental application. In unispectral mode, LUMIS was used to investigate the spatial distribution of phytoplankton. A thin sheet of laser light (532 nm) induced chlorophyll fluorescence in the phytoplankton, which was recorded by LUMIS. Inhomogeneities in the light sheet led to the development of a beam-pattern-correction algorithm. Separating individual phytoplankton cells from a weak background fluorescence field required a two-step procedure consisting of edge detection followed by a series of binary morphological operations. In multispectral mode, LUMIS was used to investigate the bio-assay potential of fluorescent pigments in corals. Problems with the commercial optical-splitting device produced nonlinear distortions in the imagery. A tessellation algorithm, including an automated tie-point-selection procedure, was developed to correct the distortions. Only pixels corresponding to coral polyps were of interest for further analysis. Extraction of these pixels was performed by a dynamic global-thresholding algorithm.

Optical patternation: a technique for three-dimensional aerosol diagnostics

A novel technique based on optical patternation is described for three-dimensional diagnostic studies of aerosols used in analytical spectroscopies. The aerosol is illuminated with a thin laser light sheet to capture images of the fluorescence and Lorenz-Mie light-scattering signals from the aerosol field with a charge-coupled detector. These measurements allow for the rapid and nonintrusive elucidation of two-dimensional spray structures, planar mass distributions, and spatial droplet size distributions. The ratio of the fluorescence image to the Lorenz-Mie image is then utilized to construct a spatially resolved map of the volume-to-surface area mean of the aerosol (Sauter mean diameter). Three-dimensional maps of spray structure, mass distribution, and droplet size distribution are obtained for the entire aerosol field by image stacking. The technique is applied to the measurement of the droplet size over the aerosol field at distances of 5-30 mm from the nebulizer tip where droplet sizes ranged from 6 to 12 microm for a direct injection high efficiency nebulizer used in inductively coupled plasma spectrometries.

Performance evaluation of an optical flow technique applied to particle image velocimetry using the VSJ Standard Images

A Dynamic Programming based Optical Flow technique has been applied to the Particle Image Velocimetry (PIV) problem. It has been used for the extraction of dense velocity fields in a planar section of a fluid flow illuminated by a thin laser light sheet. Two (in-plane) components of the velocity vectors can be recovered using a single camera and all three components can be recovered using two or three cameras. Quantitative performance tests have been carried out on calibrated synthetic image sequences from the PIV Standard Project of the Visualization Society of Japan (VSJ). Results are presented for the 2D flow based sequences (STD01 to STD08 Standard Images) and the 3D flow based sequences (STD301, STD302, STD331 and STD337 Standard Images). The RMS error is within the 2-3% range and within the 4-8% range for recovery of the two-component and the three-component velocity vectors respectively.

Description of a dust particle detection system and measurements of particulate contamination from shock, gate valve, and ion pump under ultrahigh vacuum conditions

Dust particle contamination is known to be responsible for reduced quality and yield in microelectronic processing. However it may also limit the operation of particle accelerators as a result of beam lifetime reduction or enhanced field emission in radio-frequency accelerating cavities. Intrinsic dust contamination from sources such as valves or ion pumps has not yet been studied due to the inability of commercial particle counters to be able to detect across large cross sections under ultrahigh vacuum (UHV) conditions. This motivated the development of the dust particle detector described here which is able to quantify, in situ, the level of contamination on a representative part of a vacuum vessel. This system operates under UHV conditions and measures flashes of scattered light from free falling dust particles as they cross a thin laser light sheet across a 100 mm diam vacuum vessel. A calibration using microspheres of known diameter has allowed estimation of the particle size from the scattered signal amplitude. Measurements of particulate contamination generated by shocks onto the vessel walls are presented and determination of the height of origin of dust particles from their transit time across the irradiation sheet is discussed. Measurements of dust particle release right to operation of an all-metal gate valve are also presented in the form of time resolved measurements of dust occurrence during the open/close cycles of the valve, as well as histograms of the particle size distribution. A partial self-cleaning effect is witnessed during the first 10 operation cycles following valve installation. The operation of an ion pump has also been investigated and revealed that, in our conditions, particles were released only at pump startup.

Videogrammetric Methods in Velocimetry

Photogrammetry has been successfully applied in surveying and mapping for a long time. New imaging techniques, digital data acquisition and storage and powerful computing facilities transformed photogrammetry into videogrammetry, a technique applied in many fields for precise and reliable position measurements. Two applications of videogrammetry in fluid mechanics are presented in this article. Both are at their present stage of development suited for three-dimensional velocity measurements in liquids. One is based on tracking particles seeded in the liquid by using three to four synchronized video-cameras (PTV). It allows one to determine accurately the velocity vectors at a large number of points inside a thick observation volume and also to follow the trajectories of these particles for sufficiently long time periods. It is especially well suited for Lagrangian measurements in flows. The other tracks small three-dimensional patterns in flows of liquids tagged by fluorescent dye (LIFV). The three-dimensional Laser Induced Fluorescence images needed are obtained by sweeping rapidly a thin laser-light sheet with simultaneous imaging using a high speed solid-state camera. The method yields the shift and deformations of the liquid volumes associated with these patterns and allows one to determine velocity vectors and their derivatives simultaneously and accurately at a large number of points inside the observation volume. This review article includes 100 references.

Pollutant dispersal downstream of a hill in different wind conditions

Abstract Pollutant dispersion has been investigated experimentally in a wind tunnel over a flat terrain interrupted by a two-dimensional hill of height equal to two times the elevation of the source. Three conditions were simulated for the incoming wind. All the measurements have been made using light scattering from the smoke-traced plume illuminated by a thin laser-light sheet. The global instantaneous and mean concentration fields, both in the longitudinal and in the transversal cross-sections, have been measured using a CCD TV camera connected to a tape recorder and then using digital image analysis. The local fluctuations in concentration, at predefined position in the plume have been measured using a focused photodiode with high-frequency response. With these techniques mean and instantaneous concentration profiles as a function of the different flow conditions, as well as the probability density distribution and the frequency spectra of the concentration fluctuations were obtained.

Study on unsteady gas jet and wall impingement jet ? Comparison experimental results with numerical analysis by discrete vortex method

Abstract Generally speaking, it is very difficult to observe the growing process of large scaled vortices in a transient gas jet. The vortices have great effect on the mechanism of mixture formation between the jet itself and the surroundings. The objective of the study presented here is the clarification of this mechanism in both cases of a free jet and a jet impinging on a flat wall by means of the flow visualization of 21) image taken by thin sheet of laser light in the experiments and the numerical analysis by the discrete vortex method. The mechanism of the vortex growth and the coherent structure of vortices entraining the surroundings are observed in the case of the free jet. In the wall impinging jet, the structure inside the jet is divided into four regions, that is, free jet region, impingement region, wall jet region and wall jet vortex region. The results of the numerical analysis agree qualitatively well with the experimental data.

Numerical Analysis of Transient Gas Jet and Wall Impinging Jet by Discrete Vortex Method.

Generally speaking, it is very difficult to clarify the growth process of large-scale vortices in a transient gas jet. The vortices have a great effect on the mechanism of mixture formation between the jet itself and the surroundings. The objective of the study presented here is the clarification of this mechanism in both a free jet and a jet impinging on a flat wall by means of the flow visualization of 2D images obtain by a thin sheet of laser light in experiments and numerical analysis by the discrete vortex method. The mechanism of the vortex growth and the coherent structure of vortices entraining the surroundings are clarified in the case of a free jet. In the wall impinging jet, the structure inside the jet is divided into three regions, namely, free jet region, impingement region and wall-main jet region. The results of the numerical analysis agree qualitatively with the experimental data.

Flow visualization in floating zone crystal growth - a videotape movie

Flow visualization during floating zone crystal growth has been conducted for the first time. Floating zone growth of 6 mm diameter NaNO 3 single crystals was carried out using a ring heater made of a thin Pt wire. The flow patterns in the melt were revealed by tracer particles illuminated by a thin laser light sheet, i.e., the laser light-cut technique. A color super-VHS videotape movie was made. Thermocapillary convection, forced convection and the shapes of both the growth and feed fronts were all clearly shown. The forced convection was induced by fast feed-rod rotation, crystal rotation and feed/crystal counterrotation. These results confirmed those predicted by computer simulation. A limited number of the videotape copies will be available upon request as the photographs shown in the present report are far less clear than the videotape itself.

Simultaneous no and temperature imaging measurements in turbulent nonpremixed flames

A quantitative laser-induced fluorescence imaging technique was developed with sufficient sensitivity to detect low NO concentration levels present in turbulent flames. For this linear fluorescence technique, quenching and population corrections are necessary for quantitative NO imaging. A correction procedure was developed that utilizes temperature measurements and flamelet or distributed reaction model results. The model results showed that the quenching correction can be related to temperature. Simultaneously with NO imaging, Rayleigh scattering imaging was used to determine the temperature. The measured temperature was combined with model results to estimate the quenching and population corrections for the NO signal. Analysis showed that this data reduction methodology has less than 10% error and the total error is within 25%. The imaging setup uses a multipass cell, to create a thin sheet of laser light, and a 0.8/f collection optics for the NO signal. The in-flame detectability of the imaging system is 1 ppm. To validate the technique, NO was measured and compared at two different rotational levels. Imaging results were also compared with NO{sub x} probe and thermocouple temperature measurements. The results of different measurement methods compared well, thus confirming the validity of the technique. The technique was applied to the flame initiationmore » zone of lifted turbulent non-premixed-methane flames. NO was found to correspond closely to the temperature field. As the turbulence altered the structure of the temperature field, NO was similarly altered. Distributed reaction model results were favorably compared to the imaging data. This further supports the validity of both experimental and model results.« less

Visualization of Unsteady Impinging Spray by Means of Exciplex Fluorescence Method.

An unsteady single spray of n-decane which was miscible with a small quantity of exciplex-forming dopants was impinged on a flat wall with high temperature at a normal angle in a quiescent atmosphere in the experiment presented here. It was possible to generate fluorescent emissions from vapor and liquid phase in this evaporating and impinging spray, when a thin sheet of laser light from Nd : YAG laser was passing through the cross section containing the central axis of this spray. Then, clear 2-D images of vapor and liquid in the spray were acquired by this method distance between the outlet of the injection nozzle and the wall.