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Log-Normal Distribution of Single Molecule Fluorescence Bursts in Micro/Nano-Fluidic Channels  [PDF]
Lazar L. Kish,Jun Kameoka,Claes G. Granqvist,Laszlo B. Kish
Physics , 2011, DOI: 10.1063/1.3648118
Abstract: The width and shape of photon burst histograms pose significant limitations to the identification of single molecules in micro/nano-fluidic channels, and the nature of these histograms is not fully understood. To reach a deeper understanding, we performed computer simulations based on a Gaussian beam intensity profile with various fluidic channel diameters and assuming (i) a deterministic (noise-free) case, (ii) photon emission/absorption noise, and (iii) photon noise with diffusion. Photon noise in narrow channels yields a Gaussian burst distribution while additional strong diffusion produces skewed histograms. We use the fluctuating residence time picture [Phys. Rev. Lett. 80, 2386-2388 (1998)] and conclude that the skewness of the photon number distribution is caused by the longitudinal diffusive component of the motion of the molecules as they traverse the laser beam. In the case of strong diffusion in narrow channels, this effect leads to a log-normal distribution. We show that the same effect can transform the separate peaks of the photon burst histograms of multiple molecule mixtures into a single log-normal shape.
Drift Estimation in Sparse Sequential Dynamic Imaging: with Application to Nanoscale Fluorescence Microscopy  [PDF]
Alexander Hartmann,Stephan Huckemann,J?rn Dannemann,Oskar Laitenberger,Claudia Geisler,Alexander Egner,Axel Munk
Statistics , 2014,
Abstract: A major challenge in many modern superresolution fluorescence microscopy techniques at the nanoscale lies in the correct alignment of long sequences of sparse but spatially and temporally highly resolved images. This is caused by the temporal drift of the protein structure, e.g. due to temporal thermal inhomogeneity of the object of interest or its supporting area during the observation process. We develop a simple semiparametric model for drift correction in SMS microscopy. Then we propose an M-estimator for the drift and show its asymptotic normality. This is used to correct the final image and it is shown that this purely statistical method is competitive with state of the art calibration techniques which require to incorporate fiducial markers into the specimen. Moreover, a simple bootstrap algorithm allows to quantify the precision of the drift estimate and its effect on the final image estimation. We argue that purely statistical drift correction is even more robust than fiducial tracking rendering the latter superfluous in many applications. The practicability of our method is demonstrated by a simulation study and by an SMS application. This serves as a prototype for many other typical imaging techniques where sparse observations with highly temporal resolution are blurred by motion of the object to be reconstructed.
H_2 Absorption and Fluorescence for Gamma Ray Bursts in Molecular Clouds  [PDF]
B. T. Draine
Physics , 1999, DOI: 10.1086/308581
Abstract: If a gamma ray burst with strong UV emission occurs in a molecular cloud, there will be observable consequences resulting from excitation of the surrounding H2. The UV pulse from the GRB will pump H2 into vibrationally-excited levels which produce strong absorption at wavelengths < 1650 A. As a result, both the prompt flash and later afterglow will exhibit strong absorption shortward of 1650 A, with specific spectroscopic features. Such a cutoff in the emission from GRB 980329 may already have been observed by Fruchter et al.; if so, GRB 980329 was at redshift 3.0 < z < 4.4 . BVRI photometry of GRB 990510 could also be explained by H2 absorption if GRB 990510 is at redshift 1.6 < z < 2.3. The fluorescence accompanying the UV pumping of the H2 will result in UV emission from the GRB which can extend over days or months, depending on parameters of the ambient medium and beaming of the GRB flash. The 7.5-13.6 eV fluorescent luminosity is \sim 10^{41.7} erg/s for standard estimates of the parameters of the GRB and the ambient medium. Spectroscopy can distinguish this fluorescent emission from other possible sources of transient optical emission, such as a supernova.
Compressible Flows in Fluidic Oscillators  [PDF]
D. Hirsch,E. C. Graff,M. Gharib
Physics , 2013,
Abstract: We present qualitative observations on the internal flow characteristics of fluidic oscillator geometries commonly referred to as sweeping jets in active flow control applications. This is part of the fluid dynamics videos.
Fast, label-free tracking of single viruses and weakly scattering nanoparticles in a nano-fluidic optical fiber  [PDF]
Sanli Faez,Yoav Lahini,Stefan Weidlich,Rees F. Garmann,Katrin Wondraczek,Matthias Zeisberger,Markus A. Schmidt,Michel Orrit,Vinothan N. Manoharan
Physics , 2015,
Abstract: High-speed tracking of single particles is a gateway to understanding physical, chemical, and biological processes at the nanoscale. It is also a major experimental challenge, particularly for small, nanometer-scale particles. Although methods such as confocal or fluorescence microscopy offer both high spatial resolution and high signal-to-background ratios, the fluorescence emission lifetime limits the measurement speed, while photobleaching and thermal diffusion limit the duration of measurements. Here we present a tracking method based on elastic light scattering that enables long-duration measurements of nanoparticle dynamics at rates of thousands of frames per second. We contain the particles within a single-mode silica fiber containing a sub-wavelength, nano-fluidic channel and illuminate them using the fiber's strongly confined optical mode. The diffusing particles in this cylinderical geometry are continuously illuminated inside the collection focal plane. We show that the method can track unlabeled dielectric particles as small as 20 nm as well as individual cowpea chlorotic mottle virus (CCMV) virions - 4.6 megadaltons in size - at rates of over 2 kHz for durations of tens of seconds. Our setup is easily incorporated into common optical microscopes and extends their detection range to nanometer-scale particles and macromolecules. The ease-of-use and performance of this technique support its potential for widespread applications in medical diagnostics and micro total analysis systems.
Strangely behaving fluidic oscillator  [cached]
Tesa? V.,Peszynski K.
EPJ Web of Conferences , 2013, DOI: 10.1051/epjconf/20134501074
Abstract: Fluidic oscillators became recently of increasing importance for a number of applications. Two alternative variants have been known so far: (a) feedback-loop configurations, with Strouhal number invariance and (b) configurations with a resonator and frequency not dependent on flow rate. Authors tested an oscillator of seemingly quite conventional two-loop design. Surprisingly, its properties fit to neither of the two established categories. Its Strouhal number is not constant and the frequency of oscillation is flow-rate dependent. There is, so far, no reasonable physical explanation for this strange behaviour.
Determination of Optimum Conditions for X-Ray Fluorescence Analysis Using Coupling Equations  [PDF]
Antonina Nikonovna Smagunova, Oyuntsetseg Bolormaa, Sergei Dimitrovich Pan’kov
Journal of Analytical Sciences, Methods and Instrumentation (JASMI) , 2012, DOI: 10.4236/jasmi.2012.22015
Abstract: Coupling equations used to calculate the chemical composition of substances by X-ray fluorescence analysis can be classified as empirical, theoretical or semi-empirical based on the method for determining the coefficients of the calibration function. The advantages and disadvantages of each class of equations are discussed. Recommendations for the selecting the optimum conditions for determining empirical correction coefficients and their control during analysis are provided.
Large scale simulations of solar type III radio bursts: flux density, drift rate, duration and bandwidth  [PDF]
H. Ratcliffe,E. P. Kontar,H. A. S. Reid
Physics , 2014, DOI: 10.1051/0004-6361/201423731
Abstract: Non-thermal electrons accelerated in the solar corona can produce intense coherent radio emission, known as solar type III radio bursts. This intense radio emission is often observed from hundreds of MHz in the corona down to the tens of kHz range in interplanetary space. It involves a chain of physical processes from the generation of Langmuir waves to nonlinear processes of wave-wave interaction. We develop a self-consistent model to calculate radio emission from a non-thermal electron population over large frequency range, including the effects of electron transport, Langmuir wave-electron interaction, the evolution of Langmuir waves due to non-linear wave-wave interactions, Langmuir wave conversion into electromagnetic emission, and finally escape of the electromagnetic waves. For the first time we simulate escaping radio emission over a broad frequency range from 500~MHz down to a few MHz and infer key properties of the radio emission observed: the onset (starting) frequency, {identification as fundamental or harmonic emission}, peak flux density, instantaneous frequency bandwidth, and timescales for rise and decay. Comparing with the observations, these large scale simulations enable us to identify the processes governing the key type III solar radio burst characteristics.
Fluidic Elements based on Coanda Effect
Constantin OLIVOTTO
INCAS Bulletin , 2010, DOI: 10.13111/2066-8201.2010.2.4.21
Abstract: This paper contains first some definitions and classifications regarding the fluidic elements. Thegeneral current status is presented, nominating the main specific elements based on the Coanda effect developedspecially in Romania. In particularly the development of an original bistable element using industrial compressedair at industrial pressure supply is presented. The function of this element is based on the controlled attachmentof the main jet at a curved wall through the Coanda effect. The methods used for particular calculation andexperiments are nominated. The main application of these elements was to develop a specific execution element:a fluidic step–by-step motor based on the Coanda effect.
"Master and Slave" fluidic amplifier cascade  [cached]
Tesa? Václav
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122501093
Abstract: No-moving-part fluidics recently found interesting application in generation of gas microbubbles by oscillating the inlet flow of the gas into the aerator. The oscillation frequency has to be high and this calls for small size of the oscillator. On the other hand, most microbubble applications require a large total gas flow. This calls for large fluidic device – a les expensive alternative than “numbering up” (several oscillators in parallel). The contradiction of the large and small scale is solved by the “MASTER & SLAVE” fluidic circuit: large output device controlled by a small oscillator. Paper discusses basic problems encountered in designing the circuit which requires matching the characteristics of the two devices.
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