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1

Probing the bulk viscosity of particles using aerosol optical tweezers  

NASA Astrophysics Data System (ADS)

Holographic aerosol optical tweezers can be used to trap arrays of aerosol particles allowing detailed studies of particle properties and processes at the single particle level. Recent observations have suggested that secondary organic aerosol may exist as ultra-viscous liquids or glassy states at low relative humidity, potentially a significant factor in influencing their role in the atmosphere and their activation to form cloud droplets. A decrease in relative humidity surrounding a particle leads to an increased concentration of solute in the droplet as the droplet returns to equilibrium and, thus, an increase in the bulk viscosity. We demonstrate that the timescales for condensation and evaporation processes correlate with particle viscosity, showing significant inhibition in mass transfer kinetics using ternary sucrose/sodium chloride/water droplets as a proxy to atmospheric multi-component aerosol. We go on to study the fundamental process of aerosol coagulation in aerosol particle arrays, observing the relaxation of non-spherical composite particles formed on coalescence. We demonstrate the use of bright-field imaging and elastic light scattering to make measurements of the timescale for the process of binary coalescence contrasting the rheological properties of aqueous sucrose and sodium chloride aerosol over a range of relative humidities.

Power, Rory; Bones, David L.; Reid, Jonathan P.

2012-10-01

2

Characterisation of coated aerosols using optical tweezers and neutron reflectometry  

NASA Astrophysics Data System (ADS)

Thin organic films are believed to form naturally on the surface of aerosols [1,2] and influence aerosol properties. Cloud condensation nuclei formation and chemical reactions such as aerosol oxidation are effected by the presence of thin films [3]. There is a requirement to characterise the physical properties of both the core aerosol and its organic film in order to fully understand the contribution of coated aerosols to the indirect effect. Two complementary techniques have been used to study the oxidation of thin organic films on the surface of aerosols; laser optical tweezers and neutron reflectometry. Micron sized polystyrene beads coated in oleic acid have been trapped in air using two counter propagating laser beams. Polystyrene beads are used as a proxy for solid aerosol. The trapped aerosol is illuminated with a white LED over a broadband wavelength range and the scattered light collected to produce a Mie spectrum [4]. Analysis of the Mie spectrum results in determination of the core polystyrene bead radius, the oleic acid film thickness and refractive index dispersion of the core and shell [5]. A flow of ozone gas can then be introduced into the aerosol environment to oxidise the thin film of oleic acid and the reaction followed by monitoring the changes in the Mie spectrum. The results demonstrate complete removal of the oleic acid film. We conclude that the use of a counter propagating optical trap combined with white light Mie spectroscopy can be used to study a range of organic films on different types of aerosols and their oxidation reactions. Neutron reflectometry has been used as a complementary technique to study the oxidation of monolayer films at the air-water interface in order to gain information on reaction kinetics. The oxidation of an oleic acid film at the air-water interface by the common tropospheric oxidant ozone has been studied using a Langmuir trough. Results indicate complete removal of the oleic acid film with ozone in agreement with the optical tweezers study, which confounds a previous study [6]. Findings also show complicated reaction kinetics that depend on the surface coverage of the film. Combining single particle studies using optical tweezing with macromolecular studies of thin films using neutron reflectometry provides a detailed atmospheric understanding of thin films on aerosols and their oxidation reactions. 1. Tervahattu H., Hartonen K., Kerminen V-H., Kupianen K., Aarnio P., Koskentalo T., Tuck A. and Vaida V., 2002, J. Geophys. Res. 107, 4053-4060. 2. Ellison G., Tuck A. and Vaida V., 1999, J. Geophys. Res. 104, 11633-11641. 3. King M.D., Thompson K.C., Ward A.D., 2004, JACS, 51, 16710-16711. 4. Ward A.D., Zhang M. and Hunt O., 2008, Opt. Express, 16, 16390-16403. 5. C.F. Bohren and D.R. Huffman, Absorption and Scattering of Light by Small Particles, (Wiley Scientific 1998). 6. King M.D., Rennie A.R., Thompson K.C., Fisher F.N., Dong C.C., Thomas R.K., Pfrang C., Hughes A.V., 2009, PCCP, 11, 7699-7707.

Jones, S. H.; Ward, A.; King, M. D.

2013-12-01

3

Micro-rheology and interparticle interactions in aerosols probed with optical tweezers  

NASA Astrophysics Data System (ADS)

Using optical tweezers for micro-rheological investigations of a surrounding fluid has been routinely demonstrated. In this work, we will demonstrate that rheological measurements of the bulk and surface properties of aerosol particles can be made directly using optical tweezers, providing important insights into the phase behavior of materials in confined environments and the rate of molecular diffusion in viscous phases. The use of holographic optical tweezers to manipulate aerosol particles has become standard practice in recent years, providing an invaluable tool to investigate particle dynamics, including evaporation/ condensation kinetics, chemical aging and phase transformation. When combined with non-linear Raman spectroscopy, the size and refractive index of a particle can be determined with unprecedented accuracy <+/- 0.05%). Active control of the relative positions of pairs of particles can allow studies of the coalescence of particles, providing a unique opportunity to investigate the bulk and surface properties that govern the hydrodynamic relaxation in particle shape. In particular, we will show how the viscosity and surface tension of particles can be measured directly in the under-damped regime at low viscosity. In the over-damped regime, we will show that viscosity measurements can extend close to the glass transition, allowing measurements over an impressive dynamic range of 12 orders of magnitude in relaxation timescale and viscosity. Indeed, prior to the coalescence event, we will show how the Brownian trajectories of trapped particles can yield important and unique insights into the interactions of aerosol particles.

Reid, Jonathan P.; Power, Rory M.; Cai, Chen; Simpson, Stephen H.

2014-09-01

4

Optical tweezers: 20 years on.  

PubMed

In 1986, Arthur Ashkin and colleagues published a seminal paper in Optics Letters, 'Observation of a single-beam gradient force optical trap for dielectric particles' which outlined a technique for trapping micrometre-sized dielectric particles using a focused laser beam, a technology which is now termed optical tweezers. This paper will provide a background in optical manipulation technologies and an overview of the applications of optical tweezers. It contains some recent work on the optical manipulation of aerosols and concludes with a critical discussion of where the future might lead this maturing technology. PMID:17090474

McGloin, David

2006-12-15

5

Probing the micro-rheological properties of aerosol particles using optical tweezers.  

PubMed

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >10(12) Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability. PMID:24994710

Power, Rory M; Reid, Jonathan P

2014-07-01

6

Femtosecond Optical Tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers has drawn much attention of people since recent years, which shows great advantages on biological applications due to quite straightforward ideas and simple configurations. Optical tweezers rely upon the extremely high gradient in the electric field produced near the beam waist of a tightly focused laser beam, which creates a force sufficient to trap micron-sized dielectric particles in three dimensions.(J.E. Molloy and M.J. Padgett, Light, Action: Optical Tweezers, Contemporary P)hysics, 43 241 (2002). We applied a femtosecond laser on optical tweezers as light source and got successfully ``optical trapping'' and ``optical tweezers.'' Further, due to the characters of short pulse width and extremely high intensity of laser, femtosecond optical tweezers may direct us to new optics field. Under such strong intensity many non-linear optical phenomena could be observable, such like optical Kerr effect, stimulated Raman effect and so on. Our work will shows that it may be applied into the recently proposed FAST CAR (Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman Spectroscopy) by M. Scully et. al.(M. O. Scully, G. W. Kattawar, R. P. Lucht, T. Opatrny, H. Pilloff, A. Rebane, A. V. Sokolov, and M. S. Zubairy, ``FAST CARS: Engineering a Laser Spectroscopic Technique for Rapid Identification of Bacterial Spores,'' Proceedings of NASE (2002).)

Peng, Jiahui; Wang, Lei; Sokolov, Alexei

2004-10-01

7

Optical tweezers: Theory and modelling  

NASA Astrophysics Data System (ADS)

Since their development in the 1980s, optical tweezers have become a widely used and versatile tool in many fields. Outstanding applications include the quantitative measurement of forces in cell biology and biophysics. Computational modelling of optical tweezers is a valuable tool in support of experimental work, especially quantitative applications. We discuss the theory, and the theoretical and computational modelling of optical tweezers.

Nieminen, Timo A.; du Preez-Wilkinson, Nathaniel; Stilgoe, Alexander B.; Loke, Vincent L. Y.; Bui, Ann A. M.; Rubinsztein-Dunlop, Halina

2014-10-01

8

Physics in Action: Optical Tweezers  

NSDL National Science Digital Library

This website introduces the concept of an optical tweezer, a laser trap used to manipulate objects as small as single molecules. This site lists several applications of optical tweezers and explains their application in molecular biology. Diagrams and links provide further information.

2007-07-18

9

On chip shapeable optical tweezers  

PubMed Central

Particles manipulation with optical forces is known as optical tweezing. While tweezing in free space with laser beams was established in the 1980s, integrating the optical tweezers on a chip is a challenging task. Recent experiments with plasmonic nanoantennas, microring resonators, and photonic crystal nanocavities have demonstrated optical trapping. However, the optical field of a tweezer made of a single microscopic resonator cannot be shaped. So far, this prevents from optically driven micromanipulations. Here we propose an alternative approach where the shape of the optical trap can be tuned by the wavelength in coupled nanobeam cavities. Using these shapeable tweezers, we present micromanipulation of polystyrene microspheres trapped on a silicon chip. These results show that coupled nanobeam cavities are versatile building blocks for optical near-field engineering. They open the way to much complex integrated tweezers using networks of coupled nanobeam cavities for particles or bio-objects manipulation at a larger scale. PMID:23887310

Renaut, C.; Cluzel, B.; Dellinger, J.; Lalouat, L.; Picard, E.; Peyrade, D.; Hadji, E.; de Fornel, F.

2013-01-01

10

Optical tweezers absolute calibration  

E-print Network

Optical tweezers are highly versatile laser traps for neutral microparticles, with fundamental applications in physics and in single molecule cell biology. Force measurements are performed by converting the stiffness response to displacement of trapped transparent microspheres, employed as force transducers. Usually, calibration is indirect, by comparison with fluid drag forces. This can lead to discrepancies by sizable factors. Progress achieved in a program aiming at absolute calibration, conducted over the past fifteen years, is briefly reviewed. Here we overcome its last major obstacle, a theoretical overestimation of the peak stiffness, within the most employed range for applications, and we perform experimental validation. The discrepancy is traced to the effect of primary aberrations of the optical system, which are now included in the theory. All required experimental parameters are readily accessible. Astigmatism, the dominant effect, is measured by analyzing reflected images of the focused laser spo...

Dutra, R S; Neto, P A Maia; Nussenzveig, H M

2014-01-01

11

Interferometer Control of Optical Tweezers  

NASA Technical Reports Server (NTRS)

This paper discusses progress in using spatial light modulators and interferometry to control the beam profile of an optical tweezers. The approach being developed is to use a spatial light modulator (SLM) to control the phase profile of the tweezers beam and to use a combination of the SLM and interferometry to control the intensity profile. The objective is to perform fine and calculable control of the moments and forces on a tip or tool to be used to manipulate and interrogate nanostructures. The performance of the SLM in generating multiple and independently controllable tweezers beams is also reported. Concurrent supporting research projects are mentioned and include tweezers beam scattering and neural-net processing of the interference patterns for control of the tweezers beams.

Decker, Arthur J.

2002-01-01

12

optical tweezers tractor beams  

E-print Network

tweezers (HOT) #12;setup (HOT) #12;griergroup @ nyu Dufresne group @ yale pre-calculated holograms find favourite setup... holograms. Why care? applications etc. Movies! #12;A. Ashkin, J. M. Dziedzic, J. E � flip holograms � move traps � correct for aberrations � 1D amplitude modulation #12;references A

13

Optical tweezers for confocal microscopy  

NASA Astrophysics Data System (ADS)

In confocal laser scanning microscopes (CLSMs), lasers can be used for image formation as well as tools for the manipulation of microscopic objects. In the latter case, in addition to the imaging lasers, the light of an extra laser has to be focused into the object plane of the CLSM, for example as optical tweezers. Imaging as well as trapping by optical tweezers can be done using the same objective lens. In this case, z-sectioning for 3D imaging shifts the optical tweezers with the focal plane of the objective along the optical axis, so that a trapped object remains positioned in the focal plane. Consequently, 3D imaging of trapped objects is impossible without further measures. We present an experimental set-up keeping the axial trapping position of the optical tweezers at its intended position whilst the focal plane can be axially shifted over a distance of about 15 ?m. It is based on fast-moving correctional optics synchronized with the objective movement. First examples of application are the 3D imaging of chloroplasts of Elodea densa (Canadian waterweed) in a vigorous cytoplasmic streaming and the displacement of zymogen granules in pancreatic cancer cells (AR42 J).

Hoffmann, A.; Meyer zu Hörste, G.; Pilarczyk, G.; Monajembashi, S.; Uhl, V.; Greulich, K. O.

2000-11-01

14

Characterising Conical Refraction Optical Tweezers  

E-print Network

Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focussing the conically refracted beam through a high numerical aperture microscope objective, conical refraction optical tweezers can be created, allowing for particle manipulation in both Raman spots and in the Lloyd/Poggendorff rings. We present a thorough quantification of the trapping properties of such a beam, focussing on the trap stiffness and how this varies with trap power and trapped particle location. We show that the lower Raman spot can be thought of as a single-beam optical gradient force trap, while radiation pressure dominates in the upper Raman spot, leading to optical levitation rather than trapping. Particles in the Lloyd/Poggendorff rings experience a lower trap stiffness than particles in the lower Raman spot but benefit from rotational control.

McDonald, Craig; Rafailov, Edik; McGloin, David

2014-01-01

15

Optical Tweezer as a Viscometer  

NASA Astrophysics Data System (ADS)

An optical tweezer (OT) has been widely used to study the mechanical properties of microscopic living biological systems like red blood cells. These studies are based on measurement of deformations caused by a force exerted directly or indirectly by an optical trap. The trap is usually pre-calibrated using Stokes viscous force of the suspension fluids for the biological system which is directly proportional to the viscosity of the fluids. Therefore, calibration of the trap depends on the viscosity of the fluid which depends on temperature. In this work, we have demonstrated that OT can be used to precisely measure the viscosity of biological fluids affected by temperature. Using a an infrared laser trap which is calibrated using silica sphere suspended in a distilled deionized water and measuring the power as function of escape velocity, we have measured the viscosities of a newborn and unborn bovine serum with a different concentration of antibodies.

Erenso, Daniel; Elrod, Samuel; Barns, Taylor; Farone, Anthony; Farone, Mary

2009-03-01

16

Applications of optical tweezers to optofluidics  

NASA Astrophysics Data System (ADS)

We explore the possibility of using optical tweezers to enable all optical control of optofluidic circuits. Optically trapped microspheres can be used as microlenses for optical signal switching and steering. By using cantilevers instead of microspheres we provide a method for robust and stable placement of switching elements in the optofluidic circuits. Cantilevers made of tapered optical fiber and polydimethyl siloxane are demonstrated. We also show that it is possible to use transverse optical tweezer beams to load silica beads into the hollow core photonic crystal fibers for tuning their transmission properties.

Cronin-Golomb, M.; Domachuk, P.; Mägi, E. C.; Perry, H.; Omenetto, F.; Eggleton, B. J.

2006-08-01

17

Optical Tweezers in Colloid and Interface Science David G. Grier  

E-print Network

Optical Tweezers in Colloid and Interface Science David G. Grier The James Franck Institute with radiation pressure, otherwise known as optical trapping, has emerged as a powerful experimental tool of a particular trapping technique known colloquially as ``optical tweezers.'' Even though the theory of optical

Grier, David

18

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy  

PubMed Central

Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. These techniques are described and illustrated with examples highlighting current capabilities and limitations. PMID:18511917

Neuman, Keir C.; Nagy, Attila

2012-01-01

19

Simultaneous calibration of optical tweezers spring constant and position  

E-print Network

. Howard, F. S. Pavone, F. J¨ulicher, and H. Flyvbjerg,"Calibration of optical tweezers with positional using acousto-optic deflectors," Rev. Sci. Instrum. 77, 013704 (2006). 9. K. Berg-Sørensen, L. B for optical tweezers," J. Appl. Phys. 93, 3167­3176 (2003). 10. K. Berg-Sørensen, and H. Flyvbjerg, "Power

Paris-Sud XI, Université de

20

Investigating hydrodynamic synchronisation using holographic optical tweezers  

NASA Astrophysics Data System (ADS)

Coordinated motion at low Reynolds number is widely observed in biological micro-systems, but the underlying mechanisms are often unclear. A holographic optical tweezers system is used to experimentally study this phenomenon, by employing optical forces to drive a pair of coplanar microspheres in circular orbits with a constant tangential force. In this system synchronisation is caused by hydrodynamic forces arising from the motion of the two spheres. The timescales of their synchronisation from large initial phase differences are explored and found to be dependent on how stiffly the microspheres are confined to their circular orbits. These measured timescales show good agreement with numerical simulations.

Box, Stuart; Debono, Luke; Bruot, Nicolas; Kotar, Jurij; Cicuta, Pietro; Miles, Mervyn; Hanna, Simon; Phillips, David; Simpson, Stephen

2014-09-01

21

Kinect 4 … holographic optical tweezers  

NASA Astrophysics Data System (ADS)

The 3D position and orientation of a microtool confined in multiple optical traps needs to be controlled in order for one to perform modern, challenging experiments; for example, in order to utilize it as a scanning probe and investigate the surface of optically sensitive cells. The control interface has traditionally used the keyboard/mouse combination—limiting manipulations to a series of 1D/2D transforms. In this paper we demonstrate how the Kinect can be utilized to control the position and orientation of a microtool utilizing macroscopic models.

Muhiddin, C.; Phillips, D. B.; Miles, M. J.; Picco, L.; Carberry, D. M.

2013-07-01

22

Multiplexed spectroscopy with holographic optical tweezers  

NASA Astrophysics Data System (ADS)

We have developed a multiplexed holographic optical tweezers system with an imaging spectrometer to manipulate multiple optically trapped nanosensors and detect multiple fluorescence spectra. The system uses a spatial light modulator (SLM) to control the positions of infrared optical traps in the sample so that multiple nanosensors can be positioned into regions of interest. Spectra of multiple nanosensors are detected simultaneously with the application of an imaging spectrometer. Nanosensors are capable of detecting changes in their environment such as pH, ion concentration, temperature, and voltage by monitoring changes in the nanosensors' emitted fluorescence spectra. We use streptavidin labeled quantum dots bound to the surface of biotin labeled polystyrene microspheres to measure temperature changes by observing a corresponding shift in the wavelength of the spectral peak. The fluorescence is excited at 532 nm with a wide field source.

Cibula, Matthew A.; McIntyre, David H.

2014-09-01

23

A compact holographic optical tweezers instrument  

NASA Astrophysics Data System (ADS)

Holographic optical tweezers have found many applications including the construction of complex micron-scale 3D structures and the control of tools and probes for position, force, and viscosity measurement. We have developed a compact, stable, holographic optical tweezers instrument which can be easily transported and is compatible with a wide range of microscopy techniques, making it a valuable tool for collaborative research. The instrument measures approximately 30×30×35 cm and is designed around a custom inverted microscope, incorporating a fibre laser operating at 1070 nm. We designed the control software to be easily accessible for the non-specialist, and have further improved its ease of use with a multi-touch iPad interface. A high-speed camera allows multiple trapped objects to be tracked simultaneously. We demonstrate that the compact instrument is stable to 0.5 nm for a 10 s measurement time by plotting the Allan variance of the measured position of a trapped 2 ?m silica bead. We also present a range of objects that have been successfully manipulated.

Gibson, G. M.; Bowman, R. W.; Linnenberger, A.; Dienerowitz, M.; Phillips, D. B.; Carberry, D. M.; Miles, M. J.; Padgett, M. J.

2012-11-01

24

Optical tweezers calibration with Bayesian inference  

NASA Astrophysics Data System (ADS)

We present a new method for calibrating an optical-tweezer setup that is based on Bayesian inference1. This method employs an algorithm previously used to analyze the confined trajectories of receptors within lipid rafts2,3. The main advantages of this method are that it does not require input parameters and is insensitive to systematic errors like the drift of the setup. Additionally, it exploits a much larger amount of the information stored in the recorded bead trajectory than standard calibration approaches. The additional information can be used to detect deviations from the perfect harmonic potential or detect environmental influences on the bead. The algorithm infers the diffusion coefficient and the potential felt by a trapped bead, and only requires the bead trajectory as input. We demonstrate that this method outperforms the equipartition method and the power-spectrum method in input information required (bead radius and trajectory length) and in output accuracy. Furthermore, by inferring a higher order potential our method can reveal deviations from the assumed second-order potential. More generally, this method can also be used for magnetic-tweezer calibration.

Türkcan, Silvan; Richly, Maximilian U.; Le Gall, Antoine; Fiszman, Nicolas; Masson, Jean-Baptiste; Westbrook, Nathalie; Perronet, Karen; Alexandrou, Antigoni

2014-09-01

25

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne optical tweezers from a single laser beam using diffractive optical elements. As a demonstration of this technique, we have implemented a 4 \\Theta 4 square array of optical tweezers -- the hexadeca

Grier, David

26

Optical tweezers for studying taxis in parasites  

NASA Astrophysics Data System (ADS)

In this work we present a methodology to measure force strengths and directions of living parasites with an optical tweezers setup. These measurements were used to study the parasites chemotaxis in real time. We observed behavior and measured the force of: (i) Leishmania amazonensis in the presence of two glucose gradients; (ii) Trypanosoma cruzi in the vicinity of the digestive system walls, and (iii) Trypanosoma rangeli in the vicinity of salivary glands as a function of distance. Our results clearly show a chemotactic behavior in every case. This methodology can be used to study any type of taxis, such as chemotaxis, osmotaxis, thermotaxis, phototaxis, of any kind of living microorganisms. These studies can help us to understand the microorganism sensory systems and their response function to these gradients.

de Thomaz, A. A.; Fontes, A.; Stahl, C. V.; Pozzo, L. Y.; Ayres, D. C.; Almeida, D. B.; Farias, P. M. A.; Santos, B. S.; Santos-Mallet, J.; Gomes, S. A. O.; Giorgio, S.; Feder, D.; Cesar, C. L.

2011-04-01

27

Exploring Threaded Intercalation Using Optical Tweezers  

NASA Astrophysics Data System (ADS)

Dumbbell-shaped binuclear ruthenium complexes are of interest due to their potential for use in selective chemotherapy. In bulk experiments, these complexes exhibit extremely slow binding kinetics. In contrast, single molecule studies use optical tweezers to stretch the DNA and induce much more rapid intercalation. The observed DNA force-extension curves clearly indicate an increase in DNA melting force and elongation of the DNA molecule upon drug binding, which is evidence of stabilization of the DNA and intercalation of the binuclear ruthenium complex. Hysteresis in the stretching-relaxation curves implies very slow dissociation of these molecules due to threaded intercalation. The concentration profile suggests unusually strong DNA binding affinity for the binuclear complexes compared to simple intercalators.

Paramanathan, Thayaparan; McCauley, Micah J.; Westerlund, Fredrik; Rouzina, Ioulia; Williams, Mark C.

2007-03-01

28

Exploring the mechanome with optical tweezers and single molecule fluorescence  

E-print Network

The combination of optical tweezers and single molecule fluorescence into an instrument capable of making combined, coincident measurements adds an observable dimension that allows for the examination of the localized ...

Brau, Ricardo R. (Ricardo Rafael), 1979-

2008-01-01

29

Optical shield: measuring viscosity of turbid fluids using optical tweezers.  

PubMed

The viscosity of a fluid can be measured by tracking the motion of a suspended micron-sized particle trapped by optical tweezers. However, when the particle density is high, additional particles entering the trap compromise the tracking procedure and degrade the accuracy of the measurement. In this work we introduce an additional Laguerre-Gaussian, i.e. annular, beam surrounding the trap, acting as an optical shield to exclude contaminating particles. PMID:22714199

Lee, M P; Curran, A; Gibson, G M; Tassieri, M; Heckenberg, N R; Padgett, M J

2012-05-21

30

Tunable optical tweezers for wavelength-dependent measurements  

PubMed Central

Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them. PMID:22559522

Hester, Brooke; Campbell, Gretchen K.; Lopez-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

2012-01-01

31

Tunable optical tweezers for wavelength-dependent measurements  

NASA Astrophysics Data System (ADS)

Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simply by choosing the best trapping wavelength for a given application. Here we present an optical tweezer system with wavelength tunability, for the study of resonance effects. With this system, the optical trap stiffness is measured for single trapped particles that exhibit either single or multiple extinction resonances. We include discussions of wavelength-dependent effects, such as changes in temperature, and how to measure them.

Hester, Brooke; Campbell, Gretchen K.; López-Mariscal, Carlos; Filgueira, Carly Levin; Huschka, Ryan; Halas, Naomi J.; Helmerson, Kristian

2012-04-01

32

High-Resolution Optical Tweezers for Single-Molecule Manipulation  

PubMed Central

Forces hold everything together and determine its structure and dynamics. In particular, tiny forces of 1-100 piconewtons govern the structures and dynamics of biomacromolecules. These forces enable folding, assembly, conformational fluctuations, or directional movements of biomacromolecules over sub-nanometer to micron distances. Optical tweezers have become a revolutionary tool to probe the forces, structures, and dynamics associated with biomacromolecules at a single-molecule level with unprecedented resolution. In this review, we introduce the basic principles of optical tweezers and their latest applications in studies of protein folding and molecular motors. We describe the folding dynamics of two strong coiled coil proteins, the GCN4-derived protein pIL and the SNARE complex. Both complexes show multiple folding intermediates and pathways. ATP-dependent chromatin remodeling complexes translocate DNA to remodel chromatin structures. The detailed DNA translocation properties of such molecular motors have recently been characterized by optical tweezers, which are reviewed here. Finally, several future developments and applications of optical tweezers are discussed. These past and future applications demonstrate the unique advantages of high-resolution optical tweezers in quantitatively characterizing complex multi-scale dynamics of biomacromolecules. PMID:24058311

Zhang, Xinming; Ma, Lu; Zhang, Yongli

2013-01-01

33

Systems approach to identification of feedback enhanced optical tweezers  

NASA Astrophysics Data System (ADS)

Feedback enhanced optical tweezers, based on Proportional and Integral (PI) control, are routinely used for increasing the stiffness of optical traps. Digital implementation of PI controller, using DSP or FPGA, enables easy maneuverability of feedback gains. In this paper, we report occurrence of a peak in the thermal noise power spectrum of the trapped bead as the proportional gain is cranked up, which imposes a limit on how stiff a trap can be made using position feedback. We explain the reasons for the deviant behavior in the power spectrum and present a mathematical formula to account for the anomaly, which is in very good agreement with the experimental observations. Further, we present a new method to do the closed loop system identification of feedback enhanced optical tweezers by applying a frequency chirp. The system model thus obtained greatly predicts the closed loop behavior of our feedback based optical tweezers system.

Sehgal, Hullas; Aggarwal, Tanuj; Salapaka, Murti V.

2008-08-01

34

Optical tweezers force measurements to study parasites chemotaxis  

NASA Astrophysics Data System (ADS)

In this work, we propose a methodology to study microorganisms chemotaxis in real time using an Optical Tweezers system. Optical Tweezers allowed real time measurements of the force vectors, strength and direction, of living parasites under chemical or other kinds of gradients. This seems to be the ideal tool to perform observations of taxis response of cells and microorganisms with high sensitivity to capture instantaneous responses to a given stimulus. Forces involved in the movement of unicellular parasites are very small, in the femto-pico-Newton range, about the same order of magnitude of the forces generated in an Optical Tweezers. We applied this methodology to investigate the Leishmania amazonensis (L. amazonensis) and Trypanossoma cruzi (T. cruzi) under distinct situations.

de Thomaz, A. A.; Pozzo, L. Y.; Fontes, A.; Almeida, D. B.; Stahl, C. V.; Santos-Mallet, J. R.; Gomes, S. A. O.; Feder, D.; Ayres, D. C.; Giorgio, S.; Cesar, C. L.

2009-07-01

35

Assembly of 3-dimensional structures using programmable holographic optical tweezers  

Microsoft Academic Search

The micromanipulation of objects into 3-dimensional geometries within holographic optical tweezers is carried out using modified Gerchberg-Saxton (GS) and direct binary search (DBS) algorithms to produce the hologram designs. The algorithms calculate sequences of phase holograms, which are implemented using a spatial light modulator, to reconfigure the geometries of optical traps in many planes simultaneously. The GS algorithm is able

Gavin Sinclair; Pamela Jordan; Johannes Courtial; Miles Padgett; Jon Cooper; Zsolt John Laczik

2004-01-01

36

Holographic optical tweezers in the Fresnel regime  

Microsoft Academic Search

We present a flexible setup for steering of laser tweezers using a high resolution spatial light modulator (SLM). Moving of e.g. trapped cells in the focal plane of the microscope objective is possible without the need for time consuming re-calculation of holograms. Numerous light spots or other modes like the so called \\

Alexander Jesacher; Severin Furhapter; Stefan Bernet; Monika Ritsch-Marte

2004-01-01

37

Quantum dot thermal spectroscopy for biological optical tweezer applications  

E-print Network

Quantum dot thermal spectroscopy for biological optical tweezer applications William T Ramsay1. Quantum dots can be fabricated to hold particular emission properties and can be labelled to target specific binding sites in biological samples to act as biomarkers [1]. Many quantum dots have been observed

Greenaway, Alan

38

Optical tweezers for vortex rings in Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

We study generation and stabilization of vortex rings in atomic Bose-Einstein condensates. We suggest an approach for generating vortex rings by optical tweezers—two blue-detuned optical beams forming a toroidal void in a magnetically or optically confined condensate cloud. We demonstrate that matter-wave vortex rings trapped within the void are energetically and dynamically stable. Our theoretical findings suggest a possibility for the generation, stabilization, and nondestructive manipulation of quantized vortex rings in experimentally feasible trapping configurations.

Yakimenko, A. I.; Bidasyuk, Yu. M.; Prikhodko, O. O.; Vilchinskii, S. I.; Ostrovskaya, E. A.; Kivshar, Yu. S.

2013-10-01

39

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Diffractive Optics Eric R. Dufresne)) We describe a simple method for creating multiple optical tweezers from a single laser beam using diffractive optical elements. As a demonstration of this technique, we have implemented a 4 Ã? 4 square array

Grier, David

40

Optical Tweezer Arrays and Optical Substrates Created with Di#ractive Optics Eric R. Dufresne and David G. Grier  

E-print Network

Optical Tweezer Arrays and Optical Substrates Created with Di#ractive Optics Eric R. Dufresne)) We describe a simple method for creating multiple optical tweezers from a single laser beam using di#ractive optical elements. As a demonstration of this technique, we have implemented a 4 Ã? 4 square array

Grier, David

41

Single and dual fiber nano-tip optical tweezers: trapping and analysis  

E-print Network

Single and dual fiber nano-tip optical tweezers: trapping and analysis Jean-Baptiste Decombe tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping-position adjustment," Opt. Lett. 38, 2617­2620 (2013). 15. S. K. Mondal, S. S. Pal, and P. Kapur, "Optical fiber nano

Paris-Sud XI, Université de

42

Optical manipulation and characterisation of aerosol particles using a single-beam gradient force optical trap.  

PubMed

The application of optical tweezers (a single-beam gradient force optical trap) to the manipulation and characterisation of aerosol particles is discussed in this tutorial review. Optical tweezers allow not only the indefinite control over a single droplet, but control over arrays of particles. Typical particle sizes span the 1-10 microm diameter range. When coupled with spectroscopic techniques for probing evolving particle size (with nanometre accuracy), composition, phase and mixing state, detailed investigations of the thermodynamic properties of aerosol, the kinetics of particle transformation, and the nature of interparticle forces and coagulation can be undertaken. PMID:18362982

Mitchem, Laura; Reid, Jonathan P

2008-04-01

43

Combined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for  

E-print Network

of colloidal spheres is used as a mask for a lithographic step such as illumination, deposition, or etchingCombined Optical Tweezers/Ion Beam Technique to Tune Colloidal Masks for Nanolithography Dirk L. J through a mask of colloidal particles. The use of optical tweezers combined with critical point drying

Polman, Albert

44

Speckle Optical Tweezers: Micromanipulation with Random Light Fields  

E-print Network

Current optical manipulation techniques rely on carefully engineered setups and samples. Although similar conditions are routinely met in research laboratories, it is still a challenge to manipulate microparticles when the environment is not well controlled and known a priori, since optical imperfections and scattering limit the applicability of this technique to real-life situations, such as in biomedical or microfluidic applications. Nonetheless, scattering of coherent light by disordered structures gives rise to speckles, random diffraction patterns with well-defined statistical properties. Here, we experimentally demonstrate how speckle fields can become a versatile tool to efficiently perform fundamental optical manipulation tasks such as trapping, guiding and sorting. We anticipate that the simplicity of these "speckle optical tweezers" will greatly broaden the perspectives of optical manipulation for real-life applications.

Giorgio Volpe; Lisa Kurz; Agnese Callegari; Giovanni Volpe; Sylvain Gigan

2014-03-03

45

MatLab program for precision calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the ( x, y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum. First, cross-talk between channels in 2D position measurements is tested for, and eliminated if detected. Then, the Lorentzian power spectrum that results from the Einstein-Ornstein-Uhlenbeck theory, is fitted to the low-frequency part of the experimental spectrum in order to obtain an initial guess for parameters to be fitted. Finally, a more complete theory is fitted, a theory that optionally accounts for the frequency dependence of the hydrodynamic drag force and hydrodynamic interaction with a nearby cover slip, for effects of finite sampling frequency (aliasing), for effects of anti-aliasing filters in the data acquisition electronics, and for unintended "virtual" filtering caused by the position detection system. Each of these effects can be left out or included as the user prefers, with user-defined parameters. Several tests are applied to the experimental data during calibration to ensure that the data comply with the theory used for their interpretation: Independence of x- and y-coordinates, Hooke's law, exponential distribution of power spectral values, uncorrelated Gaussian scatter of residual values. Results are given with statistical errors and covariance matrix. Program summaryTitle of program: tweezercalib Catalogue identifier: ADTV Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland. Program Summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV Computer for which the program is designed and others on which it has been tested: General computer running MatLab (MathWorks Inc.). Programming language used: MatLab (MathWorks Inc.). Uses "Optimization Toolbox" and "Statistics Toolbox". Memory required to execute with typical data: Of order 4 times the size of the data file. High speed storage required: None No. of lines in distributed program, including test data, etc.: 133 183 No. of bytes in distributed program, including test data, etc.: 1 043 674 Distribution format: tar gzip file Nature of physical problem: Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system. Method of solution: Elimination of cross-talk between quadrant photo-diode's output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects: Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for "virtual filtering" caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting. Statistical support for fit is given, with several plots suitable for inspection of consistency and quality of data and fit. Restrictions on the complexity of the problem: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate: The sampling rate should be well above the characteristic frequency of the trap,

Toli?-Nørrelykke, Iva Marija; Berg-Sørensen, Kirstine; Flyvbjerg, Henrik

2004-06-01

46

Optical tweezers for force measurements on DNA in nanopores  

NASA Astrophysics Data System (ADS)

We demonstrate the means to integrate two powerful and widely used single-molecule techniques, viz., optical tweezers and solid-state nanopores. This setup permits simultaneous spatial sampling and high-resolution force measurements of nucleic acids and proteins. First, we demonstrate the rapid spatial localization of nanopores using our custom-built inverted microscope and ionic current measurements. This is made possible by including a specialized flow cell for silicon-based nanopores with an optical window for a high-numerical aperture microscope. Subsequently, we can insert individual DNA molecules into a single nanopore and arrest the DNA during voltage-driven translocation. To detect the position of the trapped particle in the optical trap with high accuracy in the presence of the nanopore, the optical tweezers uses reflected light from the bead for detection. Consequently, we can use our setup to directly determine the force on a DNA molecule in a solid-state nanopore. Finally, we suggest a number of new experiments that become possible with this unique technique.

Keyser, U. F.; van der Does, J.; Dekker, C.; Dekker, N. H.

2006-10-01

47

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology  

NASA Technical Reports Server (NTRS)

A new method to control microparticles was developed in-house at the NASA Glenn Research Center in support of the nanotechnology project under NASA's Aerospace Propulsion and Power Base Research Program. A prototype interferometer-controlled optical tweezers was constructed to manipulate scanning probe microscope (SPM) tips. A laser beam passed through a Mach-Zehnder interferometer, and a microscope objective then produced an optical trap from the coaxial beams. The trap levitated and generated the coarse motion of a 10-mm polystyrene sphere used to simulate a SPM tip. The interference between the beams provided fine control of the forces and moments on the sphere. The interferometer included a piezoelectric-scanned mirror to modulate the interference pattern. The 10-mm sphere was observed to oscillate about 1 mm as the mirror and fringe pattern oscillated. The prototype tweezers proved the feasibility of constructing a more sophisticated interferometer tweezers to hold and manipulate SPM tips. The SPM tips are intended to interrogate and manipulate nanostructures. A more powerful laser will be used to generate multiple traps to hold nanostructures and SPM tips. The vibrating mirror in the interferometer will be replaced with a spatial light modulator. The modulator will allow the optical phase distribution in one leg of the interferometer to be programmed independently at 640 by 480 points for detailed control of the forces and moments. The interference patterns will be monitored to measure the motion of the SPM tips. Neuralnetwork technology will provide fast analysis of the interference patterns for diagnostic purposes and for local or remote feedback control of the tips. This effort also requires theoretical and modeling support in the form of scattering calculations for twin coherent beams from nonspherical particles.

Decker, Arthur J.

2002-01-01

48

Holographic optical trapping of aerosol droplets.  

PubMed

We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of some of the applications of such a technique. PMID:19516567

Burnham, D R; McGloin, D

2006-05-01

49

Holographic optical trapping of aerosol droplets.  

PubMed

We demonstrate the use of holographic optical tweezers for trapping particles in air, specifically aerosol droplets. We show the trapping and manipulation of arrays of liquid aerosols as well as the controlled coagulation of two or more droplets. We discuss the ability of spatial light modulators to manipulate airborne droplets in real time as well as highlight the difficulties associated with loading and trapping particles in such an environment. We conclude with a discussion of some of the applications of such a technique. PMID:19516568

Burnham, D R; McGloin, D

2006-05-01

50

Imaging microscopic viscosity with confocal scanning optical tweezers  

NASA Astrophysics Data System (ADS)

The techniques of confocal microscopy and optical tweezers have shown themselves to be powerful tools in biological and medical research. We combine these methods to develop a minimally invasive instrument that is capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around biopolymer-producing cells, 100 × 100 images can be taken with 0.5-?m spatial resolution in 3 min. An image of the viscosity distribution around a pullulan-producing cell of Aureobasidium pullulans is shown as an example.

Nemet, Boaz A.; Shabtai, Yossef; Cronin-Golomb, Mark

2002-02-01

51

Translation and manipulation of silicon nanomembranes using holographic optical tweezers  

PubMed Central

We demonstrate the use of holographic optical tweezers for trapping and manipulating silicon nanomembranes. These macroscopic free-standing sheets of single-crystalline silicon are attractive for use in next-generation flexible electronics. We achieve three-dimensional control by attaching a functionalized silica bead to the silicon surface, enabling non-contact trapping and manipulation of planar structures with high aspect ratios (high lateral size to thickness). Using as few as one trap and trapping powers as low as several hundred milliwatts, silicon nanomembranes can be rotated and translated in a solution over large distances. PMID:21867504

2011-01-01

52

Multiplexed force measurements on live cells with holographic optical tweezers  

PubMed Central

We describe open-loop and closed-loop multiplexed force measurements using holographic optical tweezers. We quantify the performance of our novel video-based control system in a driven suspension of colloidal particles. We demonstrate our system's abilities with the measurement of the mechanical coupling between Aplysia bag cell growth cones and beads functionalized with the neuronal cell adhesion molecule, apCAM. We show that cells form linkages which couple beads to the underlying cytoskeleton. These linkages are intermittent, stochastic and heterogeneous across beads distributed near the leading edge of a single growth cone. PMID:19365444

Mejean, Cecile O.; Schaefer, Andrew W.; Millman, Eleanor A.; Forscher, Paul; Dufresne, Eric R.

2009-01-01

53

Optical Tweezers for Sample Fixing in Micro-Diffraction Experiments  

SciTech Connect

In order to manipulate, characterize and measure the micro-diffraction of individual structural elements down to single phospholipid liposomes we have been using optical tweezers (OT) combined with an imaging microscope. We were able to install the OT system at the microfocus beamline ID13 at the ESRF and trap clusters of about 50 multi-lamellar liposomes (< 10 {mu}m large cluster). Further we have performed a scanning diffraction experiment with a 1 micrometer beam to demonstrate the fixing capabilities and to confirm the size of the liposome cluster by X-ray diffraction.

Amenitsch, H.; Rappolt, M.; Sartori, B.; Laggner, P. [Institute of Biophysics and X-ray Structure Research, Austrian Academy of Sciences, Schmiedlstr. 6, 8042 Graz (Austria); Cojoc, D.; Ferrari, E.; Garbin, V.; Di Fabrizio, E. [CNR-INFM, Lab TASC, Area di Ricerca, 34012 Basovizza (Italy); Burghammer, M.; Riekel, Ch. [ESRF, 6 rue Jules Horowitz, BP220, 38043 Grenoble Cedex (France)

2007-01-19

54

Kinect the dots: 3D control of optical tweezers  

NASA Astrophysics Data System (ADS)

Holographically generated optical traps confine micron- and sub-micron sized particles close to the center of focused light beams. They also provide a way of trapping multiple particles and moving them in three dimensions. However, in many systems the user interface is not always advantageous or intuitive especially for collaborative work and when depth information is required. We discuss and evaluate a set of multi-beam optical tweezers that utilize off the shelf gaming technology to facilitate user interaction. We use the Microsoft Kinect sensor bar as a way of getting the user input required to generate arbitrary optical force fields and control optically trapped particles. We demonstrate that the system can also be used for dynamic light control.

Shaw, Lucy; Preece, Daryl; Rubinsztein-Dunlop, Halina

2013-07-01

55

Calibration of optical tweezers based on an autoregressive model.  

PubMed

The power spectrum density (PSD) has long been explored for calibrating optical tweezers stiffness. Fast Fourier Transform (FFT) based spectral estimator is typically used. This approach requires a relatively longer data acquisition time to achieve adequate spectral resolution. In this paper, an autoregressive (AR) model is proposed to obtain the Spectrum Density using a limited number of samples. According to our method, the arithmetic model has been established with burg arithmetic, and the final prediction error criterion has been used to select the most appropriate order of the AR model, the power spectrum density has been estimated based the AR model. Then, the optical tweezers stiffness has been determined with the simple calculation from the power spectrum. Since only a small number of samples are used, the data acquisition time is significantly reduced and real-time stiffness calibration becomes feasible. To test this calibration method, we study the variation of the trap stiffness as a function of the parameters of the data length and the trapping depth. Both of the simulation and experiment results have showed that the presented method returns precise results and outperforms the conventional FFT method when using a limited number of samples. PMID:25090511

Wang, Zi-Qiang; Zhou, Jin-Hua; Zhong, Min-Cheng; Li, Di; Li, Yin-Mei

2014-07-14

56

Holographic optical tweezers and their relevance to lab on chip devices.  

PubMed

During the last decade, optical tweezers have been transformed by the combined availability of spatial light modulators and the speed of low-cost computing to drive them. Holographic optical tweezers can trap and move many objects simultaneously and their compatibility with other optical techniques, particularly microscopy, means that they are highly appropriate to lab-on-chip systems to enable optical manipulation, actuation and sensing. PMID:21327211

Padgett, Miles; Di Leonardo, Roberto

2011-04-01

57

Invited Article: A review of haptic optical tweezers for an interactive microworld exploration  

NASA Astrophysics Data System (ADS)

This paper is the first review of haptic optical tweezers, a new technique which associates force feedback teleoperation with optical tweezers. This technique allows users to explore the microworld by sensing and exerting picoNewton-scale forces with trapped microspheres. Haptic optical tweezers also allow improved dexterity of micromanipulation and micro-assembly. One of the challenges of this technique is to sense and magnify picoNewton-scale forces by a factor of 1012 to enable human operators to perceive interactions that they have never experienced before, such as adhesion phenomena, extremely low inertia, and high frequency dynamics of extremely small objects. The design of optical tweezers for high quality haptic feedback is challenging, given the requirements for very high sensitivity and dynamic stability. The concept, design process, and specification of optical tweezers reviewed here are focused on those intended for haptic teleoperation. In this paper, two new specific designs as well as the current state-of-the-art are presented. Moreover, the remaining important issues are identified for further developments. The initial results obtained are promising and demonstrate that optical tweezers have a significant potential for haptic exploration of the microworld. Haptic optical tweezers will become an invaluable tool for force feedback micromanipulation of biological samples and nano- and micro-assembly parts.

Pacoret, Cécile; Régnier, Stéphane

2013-08-01

58

The optical manipulation and characterisation of aerosol particles  

NASA Astrophysics Data System (ADS)

Aerosols play a crucial role in many areas of science, ranging from atmospheric chemistry and physics, to pharmaceutical aerosols and drug delivery to the lungs, to combustion science and spray drying. The development of new methods for characterising the properties and dynamics of aerosol particles is of crucial importance if the complex role that particles play is to be more fully understood. Optical tweezers provide a valuable new tool to address fundamental questions in aerosol science. Single or multiple particles 1-15 ?m in diameter can be manipulated for indefinite timescales. Linear and non-linear Raman and fluorescence spectroscopies can be used to probe particle composition, phase, component mixing state, and size. In particular, size can be determined with nanometre accuracy, allowing accurate measurements of the thermodynamic properties of aerosols, the kinetics of particle transformation and of light absorption. Further, the simultaneous manipulation of multiple particles in parallel optical traps provides a method for performing comparative measurements on particles of different composition. We will present some latest work in which optical tweezers are used to characterise aerosol dynamics, demonstrating that optical tweezers can find application in studies of hygroscopicity, the mixing state of different chemical components, including the phase separation of immiscible phases, and the kinetics of chemical transformation.

Reid, Jonathan P.

2008-08-01

59

Dynamic excitations in membranes induced by optical tweezers.  

PubMed Central

We present the phenomenology of transformations in lipid bilayers that are excited by laser tweezers. A variety of dynamic instabilities and shape transformations are observed, including the pearling instability, expulsion of vesicles, and more exotic ones, such as the formation of passages. Our physical picture of the laser-membrane interaction is based on the generation of tension in the bilayer and loss of surface area. Although tension is the origin of the pearling instability, it does not suffice to explain expulsion of vesicles, where we observe opening of giant pores and creeping motion of bilayers. We present a quantitative theoretical framework to understand most of the observed phenomenology. The main hypothesis is that lipid is pulled into the optical trap by the familiar dielectric effect, is disrupted, and finally is repackaged into an optically unresolvable suspension of colloidal particles. This suspension, in turn, can produce osmotic pressure and depletion forces, driving the observed transformations. PMID:9649388

Bar-Ziv, R; Moses, E; Nelson, P

1998-01-01

60

Use of optical tweezers to probe epithelial mechanosensation  

PubMed Central

Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the “ciliary hypothesis” has been difficult due the spatially distributed nature of the mechanical disturbance—several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and actin cytoskeleton exist. I report initial data using optical tweezers to manipulate individual primary cilia in an attempt to elicit a mechanotransduction response—specifically, the release of intracellular calcium. The advantage of using laser tweezers over previous work is that the applied disturbance is highly localized. I find that stimulation of a primary cilium elicits a response, while stimulation of the apical surface membrane does not. These results lend support to the hypothesis that the primary cilium mediates transduction of mechanical strain into a biochemical response in renal epithelia. PMID:20210445

Resnick, Andrew

2010-01-01

61

Use of optical tweezers to probe epithelial mechanosensation.  

PubMed

Cellular mechanosensation mechanisms have been implicated in a variety of disease states. Specifically in renal tubules, the primary cilium and associated mechanosensitive ion channels are hypothesized to play a role in water and salt homeostasis, with relevant disease states including polycystic kidney disease and hypertension. Previous experiments investigating ciliary-mediated cellular mechanosensation have used either fluid flow chambers or micropipetting to elicit a biological response. The interpretation of these experiments in terms of the "ciliary hypothesis" has been difficult due the spatially distributed nature of the mechanical disturbance-several competing hypotheses regarding possible roles of primary cilium, glycocalyx, microvilli, cell junctions, and actin cytoskeleton exist. I report initial data using optical tweezers to manipulate individual primary cilia in an attempt to elicit a mechanotransduction response-specifically, the release of intracellular calcium. The advantage of using laser tweezers over previous work is that the applied disturbance is highly localized. I find that stimulation of a primary cilium elicits a response, while stimulation of the apical surface membrane does not. These results lend support to the hypothesis that the primary cilium mediates transduction of mechanical strain into a biochemical response in renal epithelia. PMID:20210445

Resnick, Andrew

2010-01-01

62

Optical manipulation and rotation of liquid crystal drops using high-index fiber-optic tweezers  

NASA Astrophysics Data System (ADS)

We report an optical fiber tweezer based on high-index material for trapping and optical manipulation of microscale particles in water. The use of a high-index material increases the trapping force with respect to the more common silica, through tighter focusing of light. We demonstrate the potential of this simple and versatile device by trapping and rotating nematic liquid crystal drops. We monitor the rotation of the drop by detecting light modulation observed with the same fiber using backscattered light, which exhibits modulation in intensity due to the rotation of the drop; this further extends the capabilities of the fiber tweezers.

Abedin, Kazi Sarwar; Kerbage, Charles; Fernandez-Nieves, Alberto; Weitz, David A.

2007-08-01

63

Probing multiscale mechanics of collagen with optical tweezers  

NASA Astrophysics Data System (ADS)

How the molecular structure of the structural, extracellular matrix protein collagen correlates with its mechanical properties at different hierarchical structural levels is not known. We demonstrate the utility of optical tweezers to probe collagen's mechanical response throughout its assembly hierarchy, from single molecule force-extension measurements through microrheology measurements on solutions of collagen molecules, collagen fibrillar gels and gelatin. These experiments enable the determination of collagen's flexibility, mechanics, and timescales and strengths of interaction at different levels of hierarchy, information critical to developing models of how collagen's physiological function and stability are influenced by its chemical composition. By investigating how the viscoelastic properties of collagen are affected by the presence of telopeptides, protein domains that strongly influence fibril formation, we demonstrate that these play a role in conferring transient elasticity to collagen solutions.

Shayegan, Marjan; Rezaei, Naghmeh; Lam, Norman H.; Altindal, Tuba; Wieczorek, Andrew; Forde, Nancy R.

2013-09-01

64

Dynamic properties of bacterial pili measured by optical tweezers  

E-print Network

The ability of uropathogenic Escherichia coli (UPEC) to cause urinary tract infections is dependent on their ability to colonize the uroepithelium. Infecting bacteria ascend the urethra to the bladder and then kidneys by attaching to the uroepithelial cells via the differential expression of adhesins. P pili are associated with pyelonephritis, the more severe infection of the kidneys. In order to find means to treat pyelonephritis, it is therefore of interest to investigate the properties P pili. The mechanical behavior of individual P pili of uropathogenic Escherichia coli has recently been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of ~1000 PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. We have earlier studied P pili regarding its stretching/elongation properties where we have found and characterized three different elongation regions, of which one constitute an unfolding of the quate...

Fallman, Erik; Schedin, Staffan; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

2014-01-01

65

Using Optical Tweezers to Study Cell Mechanics during Airway Reopening  

NASA Astrophysics Data System (ADS)

Patients suffering from the acute respiratory distress syndrome (ARDS) must be mechanically ventilated in order to survive. However, these ventilation protocols may generate injurious hydrodynamic stresses especially during low tidal volume (VT) ventilation when the flow of micron-sized air bubbles displace the surrounding liquid. In-vitro studies in our lab revealed that microbubble flows can severally damage lung epithelial cells (EC). The degree of injury was elevated for sub-confluent monolayers in small channel heights. Under these conditions, the micromechanics of individual EC may influence the degree of cellular injury. To investigate the role of cell mechanics, we used an oscillating Optical Tweezers (OT) technique to measure the intrinsic mechanical properties of EC before and after the flow of microbubbles. Knowledge of how the EC's micromechanical properties influence cell viability may lead to the development of novel treatment therapies that enhance the EC's ability to withstand injurious hydrodynamic stresses during ventilation treatment.

Yalcin, Huseyin; Wang, Jing; Ghadiali, Samir; Ou-Yang, H. Daniel

2006-03-01

66

Optical tweezers as manufacturing and characterization tool in microfluidics  

NASA Astrophysics Data System (ADS)

Pumping and mixing of small volumes of liquid samples are basic processes in microfluidic applications. Among the number of different principles for active transportation of the fluids microrotors have been investigated from the beginning. The main challenge in microrotors, however, has been the driving principle. In this work a new approach for a very simple magnetic driving principle has been realized. More precisely, we take advantage of optical grippers to fabricate various microrotors and introduce an optical force method to characterize the fluid flow generated by rotating the structures through magnetic actuation. The microrotors are built of silica and magnetic microspheres which are initially coated with Streptavidin or Biotin molecules. Holographic optical tweezers (HOT) are used to trap, to position, and to assemble the microspheres with the chemical interaction of the biomolecules leading to a stable binding. Using this technique, complex designs of microrotors can be realized. The magnetic response of the magnetic microspheres enables the rotation and control of the structures through an external magnetic field. The generated fluid flow around the microrotor is measured optically by inserting a probe particle next to the rotor. While the probe particle is trapped by optical forces the flow force leads to a displacement of the particle from the trapping position. This displacement is directly related to the flow velocity and can be measured and calibrated. Variations of the microrotor design and rotating speed lead to characteristic flow fields.

Köhler, J.; Ghadiri, R.; Ksouri, S. I.; Gurevich, E. L.; Ostendorf, A.

2014-09-01

67

Coherence and Raman Sideband Cooling of a Single Atom in an Optical Tweezer  

E-print Network

We investigate quantum control of a single atom in a tightly focused optical tweezer trap. We show that inevitable spatially varying polarization gives rise to significant internal-state decoherence but that this effect ...

Thompson, J. D.

68

Interrogating Biology with Force: Single Molecule High-Resolution Measurements with Optical Tweezers  

PubMed Central

Single molecule force spectroscopy methods, such as optical and magnetic tweezers and atomic force microscopy, have opened up the possibility to study biological processes regulated by force, dynamics of structural conformations of proteins and nucleic acids, and load-dependent kinetics of molecular interactions. Among the various tools available today, optical tweezers have recently seen great progress in terms of spatial resolution, which now allows the measurement of atomic-scale conformational changes, and temporal resolution, which has reached the limit of the microsecond-scale relaxation times of biological molecules bound to a force probe. Here, we review different strategies and experimental configurations recently developed to apply and measure force using optical tweezers. We present the latest progress that has pushed optical tweezers’ spatial and temporal resolution down to today’s values, discussing the experimental variables and constraints that are influencing measurement resolution and how these can be optimized depending on the biological molecule under study. PMID:24047980

Capitanio, Marco; Pavone, Francesco S.

2013-01-01

69

Measurement of interaction forces between red blood cells in aggregates by optical tweezers  

SciTech Connect

We have fabricated double-beam optical tweezers and demonstrated the possibility of their use for measuring the interaction forces between red blood cells (erythrocytes). It has been established experimentally that prolonged trapping of red blood cells in a tightly focused laser beam does not cause any visible changes in their shape or size. We have measured the interaction between red blood cells in the aggregate, deformed by optical tweezers.

Maklygin, A Yu; Priezzhev, A V; Karmenian, A; Nikitin, Sergei Yu; Obolenskii, I S; Lugovtsov, Andrei E; Kisun Li

2012-06-30

70

Optically controlled manipulation of live cells using optoelectronic tweezers  

NASA Astrophysics Data System (ADS)

Optoelectronic tweezers (OET) provides a non-invasive, low-power, optical manipulation tool for trapping, transporting, and separating microparticles, cells, and other bioparticles. The OET device uses a photosensitive layer to form "virtual electrodes" upon exposure to light, creating non-uniformities in an applied electric field. The electric field gives rise to a force known as dielectrophoresis: microparticles move as a result of the non-uniformities in the electric field imparting unequal forces on the induced dipoles of the particles. These virtual electrodes can be actuated with low optical intensities, enabling the use of incoherent light sources and direct imaging techniques to create optical manipulation patterns in real-time. In this paper, we demonstrate OET operation on live cells, including the trapping and manipulation of red and white blood cells, and the automated collection of HeLa cells. Automated size-based sorting is performed on a mixture of 15- and 20-?m-diameter polystyrene beads, and dielectric property-based separation is used to differentiate between live and dead white blood cells.

Ohta, Aaron T.; Chiou, Pei-Yu; Wu, Ming C.

2006-08-01

71

Optical nanofiber integrated into an optical tweezers for particle manipulation and in-situ fiber probing  

NASA Astrophysics Data System (ADS)

Precise control of particle positioning is desirable in many optical propulsion and sorting applications. Here, we develop an integrated platform for particle manipulation consisting of a combined optical nanofiber and optical tweezers system. Individual silica microspheres were introduced to the nanofiber at arbitrary points using the optical tweezers, thereby producing pronounced dips in the fiber transmission. We show that such consistent and reversible transmission modulations depend on both particle and fiber diameter, and may be used as a reference point for in-situ nanofiber or particle size measurement. Therefore we combine SEM size measurements with nanofiber transmission data to provide calibration for particle-based fiber assessment. We also demonstrate how the optical tweezers can be used to create a `particle jet' to feed a supply of microspheres to the nanofiber surface, forming a particle conveyor belt. This integrated optical platform provides a method for selective evanescent field manipulation of micron-sized particles and facilitates studies of optical binding and light-particle interaction dynamics.

Gusachenko, Ivan; Frawley, Mary C.; Truong, Viet. G.; Nic Chormaic, Síle

2014-09-01

72

Detection and characterization of individual intermolecular bonds using optical tweezers.  

PubMed Central

The development of scanning probe techniques has made it possible to examine protein-protein interactions at the level of individual molecular pairs. A calibrated optical tweezers, along with immunoglobulin G (IgG)-coated polystyrene microspheres, has been used to detect individual surface-linked Staphylococcus protein A (SpA) molecules and to characterize the strength of the noncovalent IgG-SpA bond. Microspheres containing, on average, less than one IgG per contact area were held in the optical trap while an SpA-coated substrate was scanned beneath them at a distance of approximately 50 nm. This geometry allows the trapped bead to make contact with the surface, from bond formation to rupture, and results in an enhancement of the force applied to a bond due to leverage supplied by the bead itself. Experiments yielded median single-bond rupture forces from 25 to 44 pN for IgG from four mammalian species, in general agreement with predictions based on free energies of association obtained from solution equilibrium constants. PMID:11371470

Stout, A L

2001-01-01

73

Particle interaction measurements using laser tweezers optical trapping.  

SciTech Connect

Laser tweezers optical trapping provides a unique noninvasive capability to trap and manipulate particles in solution at the focal point of a laser beam passed through a microscope objective. Additionally, combined with image analysis, interaction forces between colloidal particles can be quantitatively measured. By looking at the displacement of particles within the laser trap due to the presence of a neighboring particle or looking at the relative diffusion of two particles held near each other by optical traps, interparticle interaction forces ranging from pico- to femto-Newtons can be measured. Understanding interaction forces is critical for predicting the behavior of particle dispersions including dispersion stability and flow rheology. Using a new analysis method proposed by Sainis, Germain, and Dufresne, we can simultaneously calculate the interparticle velocity and particle diffusivity which allows direct calculation of the interparticle potential for the particles. By applying this versatile tool, we measure difference in interactions between various phospholipid bilayers that have been coated onto silica spheres as a new type of solid supported liposome. We measure bilayer interactions of several cell membrane lipids under various environmental conditions such as pH and ionic strength and compare the results with those obtained for empty liposomes. These results provide insight into the role of bilayer fluctuations in liposome fusion, which is of fundamental interest to liposome based drug delivery schemes.

Koehler, Timothy P.; Brinker, C. Jeffrey; Brotherton, Christopher M.; Grillet, Anne M.; Molecke, Ryan A. (University of New Mexico, Albuquerque, NM)

2008-08-01

74

Computer-automated program for calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

An optical tweezers (OT) system uses focused laser light to contain and manipulate nano-scale to micro-scale particles. Trap stiffness is the quantitative measurement of the ability to trap a particle. For some techniques, this measurement depends on an accurate knowledge of the particle's position in time. A position sensing detector (PSD) is used to track particle motion by detecting laser light from the trapping region. The PSD outputs voltages corresponding to the x- and y-coordinates of particle motion, providing a means of knowing the location of the particle in time. An OT system requires a calibration to convert the measured voltages into accurate distances. This process is time-consuming and frequently needs to be repeated, however, with the growing availability of computer-aided data acquisition and control, the complete process can now be automated, reducing time spent by researchers and increasing level of accuracy of future measurements. We have developed a program written in LabVIEW that will, after initialization, 1) via image processing, calibrate the pixel size of the camera, 2) calibrate the optical tweezer position detector by controlling a motorized mirror to move a trapped bead through a detection laser with simultaneous position detector signal measurements, 3) re-align the trap beam and the detection beam by motorized mirror control, 4) measure position data for the same trapped particle being illuminated by the detection beam, and 5) analyze the position signal via the power spectrum method and equipartition method to give two trap stiffness values for comparison. Previous automated calibration methods require additional and sometimes costly equipment as well as some precalibration of stage motion or pixel size. Here, the user only needs to input the known size of the bead (provided by the manufacturer) into the program, insert their prepared slide into their microscope, input some parameters and make selections, and click "start" in order to achieve experimental values of the camera and position detector calibrations, as well as trap stiffness. We intend to implement many other calibration techniques that require additional equipment, but have designed this initial system for use in a standard position-detection-capable OT setup as long as it has a digital camera and motorized mirror that can be controlled with LabVIEW.

Taylor, C. D.; Foley, T. W.; Chang, A. N.; Mowa, S.; Burris, J. L.; Hester, B. C.

2012-10-01

75

Mapping force of interaction between PLGA nanoparticle with cell membrane using optical tweezers  

NASA Astrophysics Data System (ADS)

Drug delivery using magnetic (Fe3O4) Poly Lactic-co-Glycolic Acid (PLGA) nanoparticles is finding increasing usage in therapeutic applications due to its biodegradability, biocompatibility and targeted localization. Since optical tweezers allow non-contact, highly sensitive force measurement, we utilized optical tweezers for studying interaction forces between the Fe3O4-PLGA nanoparticles with prostate cancer PC3 cells. Presence of Fe3O4 within the PLGA shell allowed efficient trapping of these nanoparticles in near-IR optical tweezers. The conglomerated PLGA nanoparticles could be dispersed by use of the optical tweezers. Calibration of trapping stiffness as a function of laser beam power was carried out using equipartition theorem method, where the mean square displacement was measured with high precision using time-lapse fluorescence imaging of the nanoparticles. After the trapped PLGA nanoparticle was brought in close vicinity of the PC3 cell membrane, displacement of the nanoparticle from trap center was measured as a function of time. In short time scale (< 30sec), while the force of interaction was within 0.2 pN, the force increased beyond 1pN at longer time scales (˜ 10 min). We will present the results of the time-varying force of interactions between PLGA nanoparticles with PC3 cells using optical tweezers.

Chhajed, Suyash; Gu, Ling; Homayoni, Homa; Nguyen, Kytai; Mohanty, Samarendra

2011-03-01

76

Single and dual fiber nano-tip optical tweezers: trapping and analysis  

E-print Network

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

Decombe, Jean-Baptiste; Fick, Jochen

2013-01-01

77

Single and dual fiber nano-tip optical tweezers: trapping and analysis  

NASA Astrophysics Data System (ADS)

An original optical tweezers using one or two chemically etched fiber nano-tips is developed. We demonstrate optical trapping of 1 micrometer polystyrene spheres at optical powers down to 2 mW. Harmonic trap potentials were found in the case of dual fiber tweezers by analyzing the trapped particle position fluctuations. The trap stiffness was deduced using three different models. Consistent values of up to 1 fN/nm were found. The stiffness linearly decreases with decreasing light intensity and increasing fiber tip-to-tip distance.

Decombe, Jean-Baptiste; Huant, Serge; Fick, Jochen

2013-12-01

78

Fiber-pigtailed optical tweezer for single-atom trapping and single-photon S. Garcia,1  

E-print Network

: the aspheric lens (AL) is glued to the end of a ceramic tube, the fiber inside a ferrule is glued insideFiber-pigtailed optical tweezer for single-atom trapping and single-photon generation S. Garcia,1 D demonstrate a miniature, fiber-coupled optical tweezer to trap a single atom. The same fiber is used to trap

Paris-Sud XI, Université de

79

Mechanical properties of stored red blood cells using optical tweezers  

NASA Astrophysics Data System (ADS)

We have developed a method for measuring the red blood cell (RBC) membrane overall elasticity ? by measuring the deformation of the cells when dragged at a constant velocity through a plasma fluid by an optical tweezers. The deformability of erythrocytes is a critical determinant of blood flow in the microcirculation. We tested our method and hydrodynamic models, which included the presence of two walls, by measuring the RBC deformation as a function of drag velocity and of the distance to the walls. The capability and sensitivity of this method can be evaluated by its application to a variety of studies, such as, the measurement of RBC elasticity of sickle cell anemia patients comparing homozygous (HbSS), including patients taking hydroxyrea (HU) and heterozygous (HbAS) with normal donors and the RBC elasticity measurement of gamma irradiated stored blood for transfusion to immunosupressed patients as a function of time and dose. These studies show that the technique has the sensitivity to discriminate heterozygous and homozygous sickle cell anemia patients from normal donors and even follow the course of HU treatment of Homozygous patients. The gamma irradiation studies show that there is no significant change in RBC elasticity over time for up to 14 days of storage, regardless of whether the unit was irradiated or not, but there was a huge change in the measured elasticity for the RBC units stored for more than 21 days after irradiation. These finds are important for the assessment of stored irradiated RBC viability for transfusion purposes because the present protocol consider 28 storage days after irradiation as the limit for the RBC usage.

Fontes, Adriana; Alexandre de Thomaz, Andre; de Ysasa Pozzo, Liliana; de Lourdes Barjas-Castro, Maria; Brandao, Marcelo M.; Saad, Sara T. O.; Barbosa, Luiz Carlos; Cesar, Carlos Lenz

2005-08-01

80

Dynamic properties of bacterial pili measured by optical tweezers  

NASA Astrophysics Data System (ADS)

The ability of uropathogenic Escherichia coli (UPEC) to cause urinary tract infections is dependent on their ability to colonize the uroepithelium. Infecting bacteria ascend the urethra to the bladder and then kidneys by attaching to the uroepithelial cells via the differential expression of adhesins. P pili are associated with pyelonephritis, the more severe infection of the kidneys. In order to find means to treat pyelonephritis, it is therefore of interest to investigate the properties P pili. The mechanical behavior of individual P pili of uropathogenic Escherichia coli has recently been investigated using optical tweezers. P pili, whose main part constitutes the PapA rod, composed of ~1000 PapA subunits in a helical arrangement, are distributed over the bacterial surface and mediate adhesion to host cells. We have earlier studied P pili regarding its stretching/elongation properties where we have found and characterized three different elongation regions, of which one constitute an unfolding of the quaternary (helical) structure of the PapA rod. It was shown that this unfolding takes place at an elongation independent force of 27 +/- 2 pN. We have also recently performed studies on its folding properties and shown that the unfolding/folding of the PapA rod is completely reversible. Here we present a study of the dynamical properties of the PapA rod. We show, among other things, that the unfolding force increases and that the folding force decreases with the speed of unfolding and folding respectively. Moreover, the PapA rod can be folded-unfolded a significant number of times without loosing its characteristics, a phenomenon that is believed to be important for the bacterium to keep close contact to the host tissue and consequently helps the bacterium to colonize the host tissue.

Fallman, Erik G.; Andersson, Magnus J.; Schedin, Staffan S.; Jass, Jana; Uhlin, Bernt Eric; Axner, Ove

2004-10-01

81

Semi-automated 3D assembly of multiple objects using holographic optical tweezers  

Microsoft Academic Search

The micromanipulation of objects into 2-dimensional and 3-dimensional geometries within holographic optical tweezers is carried out using a modified Gerchberg-Saxton algorithm. The modified algorithm calculates phase hologram sequences, used to reconfigure the geometries of optical traps in several planes simultaneously. The hologram sequences are calculated automatically from the initial, intermediate and final trap positions. Manipulation of multiple objects in this

Gavin S. Sinclair; Pamela Jordan; John Laczik; Johannes Courtial; Miles J. Padgett

2004-01-01

82

Two-particle quantum interference in tunnel-coupled optical tweezers.  

PubMed

The quantum statistics of atoms is typically observed in the behavior of an ensemble via macroscopic observables. However, quantum statistics modifies the behavior of even two particles. Here, we demonstrate near-complete control over all the internal and external degrees of freedom of two laser-cooled (87)Rb atoms trapped in two optical tweezers. This controllability allows us to observe signatures of indistinguishability via two-particle interference. Our work establishes laser-cooled atoms in optical tweezers as a promising route to bottom-up engineering of scalable, low-entropy quantum systems. PMID:24968938

Kaufman, A M; Lester, B J; Reynolds, C M; Wall, M L; Foss-Feig, M; Hazzard, K R A; Rey, A M; Regal, C A

2014-07-18

83

Raman Study of Mechanically Induced Oxygenation State Transition of Red Blood Cells Using Optical Tweezers  

PubMed Central

Abstract Raman spectroscopy was used to monitor changes in the oxygenation state of human red blood cells while they were placed under mechanical stress with the use of optical tweezers. The applied force is intended to simulate the stretching and compression that cells experience as they pass through vessels and smaller capillaries. In this work, spectroscopic evidence of a transition between the oxygenation and deoxygenation states, which is induced by stretching the cell with optical tweezers, is presented. The transition is due to enhanced hemoglobin-membrane and hemoglobin neighbor-neighbor interactions, and the latter was further studied by modeling the electrostatic binding of two of the protein structures. PMID:18931252

Rao, Satish; Balint, Stefan; Cossins, Benjamin; Guallar, Victor; Petrov, Dmitri

2009-01-01

84

Stress response in Caenorhabditis elegans caused by optical tweezers: wavelength, power, and time dependence.  

PubMed Central

Optical tweezers have emerged as a powerful technique for micromanipulation of living cells. Although the technique often has been claimed to be nonintrusive, evidence has appeared that this is not always the case. This work presents evidence that near-infrared continuous-wave laser light from optical tweezers can produce stress in Caenorhabditis elegans. A transgenic strain of C. elegans, carrying an integrated heat-shock-responsive reporter gene, has been exposed to laser light under a variety of illumination conditions. It was found that gene expression was most often induced by light of 760 nm, and least by 810 nm. The stress response increased with laser power and irradiation time. At 810 nm, significant gene expression could be observed at 360 mW of illumination, which is more than one order of magnitude above that normally used in optical tweezers. In the 700-760-nm range, the results show that the stress response is caused by photochemical processes, whereas at 810 nm, it mainly has a photothermal origin. These results give further evidence that the 700-760-nm wavelength region is unsuitable for optical tweezers and suggest that work at 810 nm at normal laser powers does not cause stress at the cellular level. PMID:11916877

Leitz, Guenther; Fallman, Erik; Tuck, Simon; Axner, Ove

2002-01-01

85

Quantitation of Malaria Parasite-Erythrocyte Cell-Cell Interactions Using Optical Tweezers  

E-print Network

Article Quantitation of Malaria Parasite-Erythrocyte Cell-Cell Interactions Using Optical Tweezers falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria in unraveling the blood-stage biology of malaria. BACKGROUND Most cases of severe and fatal malaria in humans

Cicuta, Pietro

86

Parallel teleoperation of holographic optical tweezers using multi-touch user interface  

Microsoft Academic Search

Holographic optical tweezers (HOT) has ability to trap and manipulate a few hundred of small particles. Previously the manipulation speed is greatly limited to the calculation speed of holograms. But recent progress in parallel computing made it possible to generate the holograms in real-time. Therefore, HOT is thought to play an important role in dexterous micromanipulation. In practical application, the

Kazuhisa Onda; Fumihito Arai

2012-01-01

87

Construction and actuation of a microscopic gear assembly formed using optical tweezers  

NASA Astrophysics Data System (ADS)

The assembly of micrometer-sized parts is an important manufacturing process; any development in it could potentially change the current manufacturing practices for micrometer-scale devices. Due to the lack of reliable microassembly techniques, these devices are often manufactured using silicon, which includes etching and depositions with little use of assembly processes. The result is the requirement of specialized manufacturing conditions with hazardous byproducts and limited applications where only simple mechanisms are allowed. Optical tweezers are non-contact type manipulators that are very suitable for assembling microparts and solve one of the most difficult problems for microassembly, which is the sticking of the physical manipulator to the micropart. Although contact type manipulators can be surface modified to be non-sticky, this involves extra preprocessing—optical tweezers do not require such additional efforts. The weakness of using optical tweezers is that the permanent assembly of parts is not possible as only very small forces can be applied. We introduce an advanced microassembly environment with the combined use of optical tweezers and a motorized microtip, where the former is used to position two parts and the latter is used to introduce deformation in the parts so that they form a strongly fitted assembly.

Kim, Jung-Dae; Lee, Yong-Gu

2013-06-01

88

Raman Study of Mechanically Induced Oxygenation State Transition of Red Blood Cells Using Optical Tweezers  

Microsoft Academic Search

Raman spectroscopy was used to monitor changes in the oxygenation state of human red blood cells while they were placed under mechanical stress with the use of optical tweezers. The applied force is intended to simulate the stretching and compression that cells experience as they pass through vessels and smaller capillaries. In this work, spectroscopic evidence of a transition between

Satish Rao; Štefan Bálint; Benjamin Cossins; Victor Guallar; Dmitri Petrov

2009-01-01

89

Femtosecond optical tweezers for in-situ control of two-photon fluorescence.  

PubMed

We perform a comparison of optical tweezing using continuous wave (cw) and femtosecond lasers. Measurement of the relative Q-values in the femtosecond and cw regimes shows that femtosecond optical tweezers are just as effective as cw optical tweezers. We also demonstrate simultaneous optical tweezing and in-situ control of two-photon fluorescence (at 400nm) from dye-doped polymer microspheres. By switching the 800 nm tweezing laser source between femtosecond and cw regimes, we turned the fluorescent signal from the tweezed particle on and off while maintaining an equivalent tweezing action. Femtosecond lasers can thus be used for optical tweezing and simultaneously utilized to induce nonlinear multi-photon processes such as two-photon excitation or even photoporation. PMID:19483818

Agate, B; Brown, C; Sibbett, W; Dholakia, K

2004-06-28

90

Fast generation of holographic optical tweezers by random mask encoding of Fourier components.  

PubMed

The random mask encoding technique of multiplexing phase-only filters can be easily adapted to the generation of holographic optical tweezers. The result is a direct, non-iterative and extremely fast algorithm that can be used for computing arbitrary arrays of optical traps. Additional benefits include the possibility of modifying any existing hologram to quickly add more trapping sites and the inexistence of ghost traps or replicas. PMID:19503542

Montes-Usategui, Mario; Pleguezuelos, Encarnación; Andilla, Jordi; Martín-Badosa, Estela

2006-03-20

91

Axial and lateral trapping efficiency of Laguerre–Gaussian modes in inverted optical tweezers  

Microsoft Academic Search

Within inverted optical tweezers we measure both the lateral and axial trapping efficiency obtained with Gaussian and high-order Laguerre–Gaussian beams. Our results confirm that, for larger particles, the axial trapping is improved by using a Laguerre–Gaussian beam but, contrary to earlier suggestions, that the lateral efficiency is unchanged. We show that this latter observation is compatible with a ray-optical model

Anna T. O'Neil; Miles J. Padgett

2001-01-01

92

Analysis of optical trap mediated aerosol coalescence  

NASA Astrophysics Data System (ADS)

The use of optical tweezers for the analysis of aerosols is valuable for understanding the dynamics of atmospherically relevant particles. However to be able to make accurate measurements that can be directly tied to real-world phenomena it is important that we understand the influence of the optical trap on those processes. One process that is seemingly straightforward to study with these techniques is binary droplet coalescence, either using dual beam traps, or by particle collision with a single trapped droplet. This binary coalescence is also of interest in many other processes that make use of dense aerosol sprays such as spray drying and the use of inhalers for drug delivery in conditions such as asthma or hay fever. In this presentation we discuss the use of high speed (~5000 frames per second) video microscopy to track the dynamics of particles as they approach and interact with a trapped aqueous droplet and develop this analysis further by considering elastic light scattering from droplets as they undergo coalescence. We find that we are able to characterize the re-equilibration time of droplets of the same phase after they interact and that the trajectories taken by airborne particles influenced by an optical trap are often quite complex. We also examine the role of parameters such as the salt concentration of the aqueous solutions used and the influence of laser wavelength.

Mistry, N. S.; Power, R.; Anand, S.; McGloin, D.; Almohamedi, A.; Downie, M.; Reid, J. P.; Hudson, A. J.

2012-10-01

93

Using optical tweezers, single molecule fluorescence and the ZIF268 protein-DNA system to probe mechanotransduction mechanisms  

E-print Network

Optical tweezers instruments use laser radiation pressure to trap microscopic dielectric beads. With the appropriate chemistry, such a bead can be attached to a single molecule as a handle, permitting the application of ...

Lee, Peter, S.M. Massachusetts Institute of Technology

2006-01-01

94

Optical tweezers for precise control of micro-bubble arrays: in situ temperature measurement  

NASA Astrophysics Data System (ADS)

We use highly a focused laser beam incident on a carbon coated coverslip to create microcavitation. Full optical control of the radii of the bubbles is attained. Multiple bubbles can also be created and their size changed independently. The dynamics of such multi-bubble systems are studied. These bubble systems generate strong flows such as Marangoni convection and also large thermal gradients. Since the size of the micro-bubbles is highly dependent on the temperature, we anticipate that these systems can be used for precise temperature control of samples. These methods are of use when the knowledge of exact and local temperature profiles are of importance. Furthermore, since bubble expansion can generate orders of magnitude more force than conventional optical tweezers, systems have application in manipulation of particles where large forces are required. We present methods based on optical tweezers for using the generated bubbles as thermal sensors and as opto-mechanical transducers.

Burns, Tristan M.; Preece, Daryl; Niemenen, Timo A.; Rubinsztein-Dunlop, Haliina

2013-09-01

95

Optical levitation and manipulation of stuck particles with pulsed optical tweezers  

NASA Astrophysics Data System (ADS)

We report on optical levitation and manipulation of microscopic particles that are stuck on a glass surface with pulsed optical tweezers. An infrared pulse laser at 1.06 ?m was used to generate a large gradient force (up to 10^-9 N) within a short duration (~45 ?s) that overcomes the adhesive interaction between the particles and the glass surface. Then a low-power continuous-wave diode laser at 785 nm was used to capture and manipulate the levitated particle. We have demonstrated that both stuck dielectric and biological micrometer-sized particles, including polystyrene beads, yeast cells, and Bacillus cereus bacteria, can be levitated and manipulated with this technique. We measured the single-pulse levitation efficiency for 2.0 ?m polystyrene beads as a function of the pulse energy and of the axial displacement from the stuck particle to the pulsed laser focus, which was as high as 88%.

Ashok Ambardekar, Amol; Li, Yong-Qing

2005-07-01

96

Measurement of macrophage adhesion using optical tweezers with backward-scattered detection  

NASA Astrophysics Data System (ADS)

Macrophages are members of the leukocyte family. Tissue damage causes inflammation and release of vasoactive and chemotactic factors, which trigger a local increase in blood flow and capillary permeability. Then, leukocytes accumulate quickly to the infection site. The leukocyte extravasation process takes place according to a sequence of events that involve tethering, activation by a chemoattractant stimulus, adhesion by integrin binding, and migrating to the infection site. The leukocyte extravasation process reveals that adhesion is an important part of the immune system. Optical tweezers have become a useful tool with broad applications in biology and physics. In force measurement, the trapped bead as a probe usually uses a polystyrene bead of 1 ?m diameter to measure adhesive force between the trapped beads and cell by optical tweezers. In this paper, using the ray-optics model calculated trapping stiffness and defined the linear displacement ranges. By the theoretical values of stiffness and linear displacement ranges, this study attempted to obtain a proper trapped particle size in measuring adhesive force. Finally, this work investigates real-time adhesion force measurements between human macrophages and trapped beads coated with lipopolysaccharides using optical tweezers with backscattered detection.

Wei, Sung-Yang; Su, Yi-Jr; Shih, Po-Chen; Yang, Shih-Mo; Hsu, Long

2010-08-01

97

Geometrical Optics of Dense Aerosols  

SciTech Connect

Assembling a free-standing, sharp-edged slab of homogeneous material that is much denser than gas, but much more rare ed than a solid, is an outstanding technological challenge. The solution may lie in focusing a dense aerosol to assume this geometry. However, whereas the geometrical optics of dilute aerosols is a well-developed fi eld, the dense aerosol limit is mostly unexplored. Yet controlling the geometrical optics of dense aerosols is necessary in preparing such a material slab. Focusing dense aerosols is shown here to be possible, but the nite particle density reduces the eff ective Stokes number of the flow, a critical result for controlled focusing. __________________________________________________

Hay, Michael J.; Valeo, Ernest J.; Fisch, Nathaniel J.

2013-04-24

98

Practical lab tool for living cells based on microstereolithography and multiple dynamic holographic optical tweezers  

Microsoft Academic Search

Recent studies have shown that the cell is mechanically differentiated both spatially and temporally, leading to a regional approach in cell behaviour essays. Most experiments are based on spatially-controlled contacts between microbeads and cells. We here propose an apparatus based on holographic optical tweezers to put on a target cell a two- or three-dimensional custom-built pattern of beads, with respect

Serge Monneret; Federico Belloni; Didier Marguet

2006-01-01

99

Practical lab tool for living cells based on microstereolithography and multiple dynamic holographic optical tweezers  

NASA Astrophysics Data System (ADS)

Recent studies have shown that the cell is mechanically differentiated both spatially and temporally, leading to a regional approach in cell behaviour essays. Most experiments are based on spatially-controlled contacts between microbeads and cells. We here propose an apparatus based on holographic optical tweezers to put on a target cell a two- or three-dimensional custom-built pattern of beads, with respect to the target cell shape, with both temporal and spatial dynamic control of each contact. In order to avoid disturbance or contact from the excess beads with the target cell, we keep the beads under isolated condition, by placing them in a confinement chamber made by microstereolithography. Our system exploits a digital display to project binary images on a photocurable resin surface, and induce space-resolved photopolymerisation reactions, constructing three-dimensional micro structures with complex shapes, including reservoirs for the filling, outlets, and confinement chambers. Combination of microfluidics, holographic optical tweezers and one supplementary single manually steerable optical tweezers leads to several experimental procedures allowing the sequential or parallel deposition of beads onto a target, with both a spatial and temporal control.

Monneret, Serge; Belloni, Federico; Marguet, Didier

2006-02-01

100

Quantitation of malaria parasite-erythrocyte cell-cell interactions using optical tweezers.  

PubMed

Erythrocyte invasion by Plasmodium falciparum merozoites is an essential step for parasite survival and hence the pathogenesis of malaria. Invasion has been studied intensively, but our cellular understanding has been limited by the fact that it occurs very rapidly: invasion is generally complete within 1 min, and shortly thereafter the merozoites, at least in in vitro culture, lose their invasive capacity. The rapid nature of the process, and hence the narrow time window in which measurements can be taken, have limited the tools available to quantitate invasion. Here we employ optical tweezers to study individual invasion events for what we believe is the first time, showing that newly released P. falciparum merozoites, delivered via optical tweezers to a target erythrocyte, retain their ability to invade. Even spent merozoites, which had lost the ability to invade, retain the ability to adhere to erythrocytes, and furthermore can still induce transient local membrane deformations in the erythrocyte membrane. We use this technology to measure the strength of the adhesive force between merozoites and erythrocytes, and to probe the cellular mode of action of known invasion inhibitory treatments. These data add to our understanding of the erythrocyte-merozoite interactions that occur during invasion, and demonstrate the power of optical tweezers technologies in unraveling the blood-stage biology of malaria. PMID:25140419

Crick, Alex J; Theron, Michel; Tiffert, Teresa; Lew, Virgilio L; Cicuta, Pietro; Rayner, Julian C

2014-08-19

101

Single-cell optoporation and transfection using femtosecond laser and optical tweezers  

PubMed Central

In this paper, we demonstrate a new single-cell optoporation and transfection technique using a femtosecond Gaussian laser beam and optical tweezers. Tightly focused near-infrared (NIR) femtosecond laser pulse was employed to transiently perforate the cellular membrane at a single point in MCF-7 cancer cells. A distinct technique was developed by trapping the microparticle using optical tweezers to focus the femtosecond laser precisely on the cell membrane to puncture it. Subsequently, an external gene was introduced in the cell by trapping and inserting the same plasmid-coated microparticle into the optoporated cell using optical tweezers. Various experimental parameters such as femtosecond laser exposure power, exposure time, puncture hole size, exact focusing of the femtosecond laser on the cell membrane, and cell healing time were closely analyzed to create the optimal conditions for cell viability. Following the insertion of plasmid-coated microparticles in the cell, the targeted cells exhibited green fluorescent protein (GFP) under the fluorescent microscope, hence confirming successful transfection into the cell. This new optoporation and transfection technique maximizes the level of selectivity and control over the targeted cell, and this may be a breakthrough method through which to induce controllable genetic changes in the cell. PMID:24049675

Waleed, Muhammad; Hwang, Sun-Uk; Kim, Jung-Dae; Shabbir, Irfan; Shin, Sang-Mo; Lee, Yong-Gu

2013-01-01

102

Template stripped double nanohole in a gold film for nano-optical tweezers.  

PubMed

Double nanohole (DNH) laser tweezers can optically trap and manipulate objects such as proteins, nanospheres, and other nanoparticles; however, precise fabrication of those DNHs has been expensive with low throughput. In this work, template stripping was used to pattern DNHs with gaps as small as 7 nm, in optically thick Au films. These DNHs were used to trap streptavidin as proof of operation. The structures were processed multiple times from the same template to demonstrate reusability. Template stripping is a promising method for high-throughput, reproducible, and cost efficient fabrication of DNH apertures for optical trapping. PMID:25407447

Zehtabi-Oskuie, Ana; Zinck, Aurora A; Gelfand, Ryan M; Gordon, Reuven

2014-12-12

103

Scanning a DNA Molecule for Bound Proteins Using Hybrid Magnetic and Optical Tweezers  

PubMed Central

The functional state of the genome is determined by its interactions with proteins that bind, modify, and move along the DNA. To determine the positions and binding strength of proteins localized on DNA we have developed a combined magnetic and optical tweezers apparatus that allows for both sensitive and label-free detection. A DNA loop, that acts as a scanning probe, is created by looping an optically trapped DNA tether around a DNA molecule that is held with magnetic tweezers. Upon scanning the loop along the ?-DNA molecule, EcoRI proteins were detected with ?17 nm spatial resolution. An offset of 33±5 nm for the detected protein positions was found between back and forwards scans, corresponding to the size of the DNA loop and in agreement with theoretical estimates. At higher applied stretching forces, the scanning loop was able to remove bound proteins from the DNA, showing that the method is in principle also capable of measuring the binding strength of proteins to DNA with a force resolution of 0.1 pN/. The use of magnetic tweezers in this assay allows the facile preparation of many single-molecule tethers, which can be scanned one after the other, while it also allows for direct control of the supercoiling state of the DNA molecule, making it uniquely suitable to address the effects of torque on protein-DNA interactions. PMID:23755219

van Loenhout, Marijn T. J.; De Vlaminck, Iwijn; Flebus, Benedetta; den Blanken, Johan F.; Zweifel, Ludovit P.; Hooning, Koen M.; Kerssemakers, Jacob W. J.; Dekker, Cees

2013-01-01

104

Raman sorting and identification of single living micro-organisms with optical tweezers  

NASA Astrophysics Data System (ADS)

We report on a novel technique for sorting and identification of single biological cells and food-borne bacteria based on laser tweezers and Raman spectroscopy (LTRS). With this technique, biological cells of different physiological states in a sample chamber were identified by their Raman spectral signatures and then they were selectively manipulated into a clean collection chamber with optical tweezers through a microchannel. As an example, we sorted the live and dead yeast cells into the collection chamber and validated this with a standard staining technique. We also demonstrated that bacteria existing in spoiled foods could be discriminated from a variety of food particles based on their characteristic Raman spectra and then isolated with laser manipulation. This label-free LTRS sorting technique may find broad applications in microbiology and rapid examination of food-borne diseases.

Xie, Changan; Chen, De; Li, Yong-Qing

2005-07-01

105

Neural Network for Image-to-Image Control of Optical Tweezers  

NASA Technical Reports Server (NTRS)

A method is discussed for using neural networks to control optical tweezers. Neural-net outputs are combined with scaling and tiling to generate 480 by 480-pixel control patterns for a spatial light modulator (SLM). The SLM can be combined in various ways with a microscope to create movable tweezers traps with controllable profiles. The neural nets are intended to respond to scattered light from carbon and silicon carbide nanotube sensors. The nanotube sensors are to be held by the traps for manipulation and calibration. Scaling and tiling allow the 100 by 100-pixel maximum resolution of the neural-net software to be applied in stages to exploit the full 480 by 480-pixel resolution of the SLM. One of these stages is intended to create sensitive null detectors for detecting variations in the scattered light from the nanotube sensors.

Decker, Arthur J.; Anderson, Robert C.; Weiland, Kenneth E.; Wrbanek, Susan Y.

2004-01-01

106

Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering.  

PubMed

In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts. PMID:24880354

Ott, Dino; Reihani, S Nader S; Oddershede, Lene B

2014-05-01

107

Crosstalk elimination in the detection of dual-beam optical tweezers by spatial filtering  

NASA Astrophysics Data System (ADS)

In dual-beam optical tweezers, the accuracy of position and force measurements is often compromised by crosstalk between the two detected signals, this crosstalk leading to systematic and significant errors on the measured forces and distances. This is true both for dual-beam optical traps where the splitting of the two traps is done by polarization optics and for dual optical traps constructed by other methods, e.g., holographic tweezers. If the two traps are orthogonally polarized, most often crosstalk is minimized by inserting polarization optics in front of the detector; however, this method is not perfect because of the de-polarization of the trapping beam introduced by the required high numerical aperture optics. Here we present a simple and easy-to-implement method to efficiently eliminate crosstalk. The method is based on spatial filtering by simply inserting a pinhole at the correct position and is highly compatible with standard back focal plane photodiode based detection of position and force. Our spatial filtering method reduces crosstalk up to five times better than polarization filtering alone. The effectiveness is dependent on pinhole size and distance between the traps and is here quantified experimentally and reproduced by theoretical modeling. The method here proposed will improve the accuracy of force-distance measurements, e.g., of single molecules, performed by dual-beam optical traps and hence give much more scientific value for the experimental efforts.

Ott, Dino; Reihani, S. Nader S.; Oddershede, Lene B.

2014-05-01

108

Optical force sensor array in a microfluidic device based on holographic optical tweezers.  

PubMed

Holographic optical tweezers (HOT) are a versatile technology, with which complex arrays and movements of optical traps can be realized to manipulate multiple microparticles in parallel and to measure the forces affecting them in the piconewton range. We report on the combination of HOT with a fluorescence microscope and a stop-flow, multi-channel microfluidic device. The integration of a high-speed camera into the setup allows for the calibration of all the traps simultaneously both using Boltzmann statistics or the power spectrum density of the particle diffusion within the optical traps. This setup permits complete spatial, chemical and visual control of the microenvironment applicable to probing chemo-mechanical properties of cellular or subcellular structures. As an example we constructed a biomimetic, quasi-two-dimensional actin network on an array of trapped polystyrene microspheres inside the microfluidic chamber. During crosslinking of the actin filaments by Mg(2+) ions, we observe the build up of mechanical tension throughout the actin network. Thus, we demonstrate how our integrated HOT-microfluidics platform can be used as a reconfigurable force sensor array with piconewton resolution to investigate chemo-mechanical processes. PMID:19224015

Uhrig, Kai; Kurre, Rainer; Schmitz, Christian; Curtis, Jennifer E; Haraszti, Tamás; Clemen, Anabel E-M; Spatz, Joachim P

2009-03-01

109

Multiplying optical tweezers force using a micro-lever  

E-print Network

. The relationship between the optical force and the spring constant can be determined by using the principle-beam gradient force optical trap for dielectric particles," Opt. Lett. 11, 288-290 (1986). 2. P. Galadja and P

Boyer, Edmond

110

Optical tweezers and cell biomechanics in macro- and nano-scale  

NASA Astrophysics Data System (ADS)

The mechanical properties of cells, as well as their dysfunction, have been implicated in many aspects of human physiology and patho-physiology. Hence, new biophysical techniques, as optical tweezers, are of great importance for biomechanical measurements in both cells and cell simulators (e.g. liposomes). Liposomes are used, among other applications, as drug delivery nanosystems in cancer therapy. In this work, experimental measurements of the optical forces exerted by line optical tweezers on trapped cells (erythrocytes) and liposomes, using the dielectrophoresis method for calibration, are presented. Folding and elongation of trapped red blood cells was observed, in the direction of the electric field of incident beam, while, upon removal of the optical trap, the red blood cells were observed to unfold to their original biconcave shape. By measuring the folding and unfolding times, membrane elasticity properties such as bending modulus were estimated. Shear and bending modulus of liposomes were also estimated by measuring the liposome deformations, induced by optical forces along the beam long axis. The optical force is quasi-linearly increased with the increase of liposome diameter. In the elasticity regime, when the laser was turned off, the liposome acquired gradually its initial shape without any hysteresis.

Serafetinides, Alexander A.; Makropoulou, Mersini; Spyratou, Ellas

2013-03-01

111

High-refractive index particles in counter-propagating optical tweezers - manipulation and forces  

NASA Astrophysics Data System (ADS)

With a tightly focused single laser beam, also called optical tweezers, particles of a few nanometers up to several micrometers in size can be trapped and manipulated in 3D. The size, shape and refractive index of such colloidal particles are of influence on the optical forces exerted on them in the trap. A higher refractive-index difference between a particle and the surrounding medium will increase the forces. The destabilizing scattering force, however, pushing the particle in the direction of the beam, increases more than the gradient force, directed towards the focus. As a consequence, particles with a certain refractive index cannot be trapped in a single-beam gradient trap, and a limit is set to the force that can be exerted. We developed an experimental setup with two opposing high-numerical objectives. By splitting the laser beam, we created counter-propagating tweezers in which the scattering forces were canceled in the axial direction and high-refractive index and metallic particles could also be trapped. With the use of a separate laser beam combined with a quadrant photodiode, accurate position detection on a trapped particle in the counter-propagating tweezers is possible. We used this to determine trap stiffnesses, and show, with measurements and calculations, an enhancement in trap stiffness of at least 3 times for high-index 1.1-micrometer-diameter titania particles as compared to 1.4-micrometer-diameter silica particles under the same conditions. The ability to exert higher forces with lower laser power finds application in biophysical experiments, where laser damage and heating play a role. The manipulation of high-index and metallic particles also has applications in materials and colloid science, for example to incorporate high-index defects in colloidal photonic crystals. We demonstrate the patterning of high-index particles onto a glass substrate. The sample cell was mounted on a high-accuracy piezo stage combined with a long-range stage with motorized actuators. Because we used image analysis of the patterned structure to accurately find back the starting position and compensate for drift of the sample, we could move far away from the patterning region. This enabled us to select particles from a separate reservoir of a mixture of particles, and, one-by-one, position them at chosen locations. By time-sharing the laser beam using acousto-optic deflectors, we created multiple counter-propagating tweezers. We trapped an array of high-refractive index particles, and were able to move those particles individually. We used such a dynamic array of counter-propagating tweezers to create line-optical tweezers in which we trapped semi-conducting high-refractive index nanorods in three dimensions. We demonstrate full 3D translational and in-plane rotational control over the rods, which could not be held in single-beam line-tweezers. The configuration of two opposing objectives was also used for simultaneous trapping with one objective and confocal imaging of the fluorescently labeled particles using the other objective. By trapping particles with a refractive index contrast in a dispersion of index-matched particles, crystallization could be induced, which was imaged in three dimensions using confocal microscopy.

van der Horst, Astrid

2006-09-01

112

Holographic optical tweezers: microassembling of shape-complementary 2PP building blocks  

NASA Astrophysics Data System (ADS)

Based on an ongoing trend in miniaturization and due to the increased complexity in MEMS-technology new methods of assembly need to be developed. Recent developments show that particularly optical forces are suitable to meet the requirements. The unique advantages of optical tweezers (OT) are attractive due to their contactless and precise manipulation forces. Spherical as well as non-spherical shaped pre-forms can already be assembled arbitrarily by using appropriate beam profiles generated by a spatial light modulator (SLM), resulting in a so called holographic optical tweezer (HOT) setup. For the fabrication of shape-complementary pre-forms, a two-photon-polymerization (2PP) process is implemented. The purpose of the process combination of 2PP and HOT is the development of an optical microprocessing platform for assembling arbitrary building blocks. Here, the optimization of the 2PP and HOT processes is described in order to allow the fabrication and 3D assembling of interlocking components. Results include the analysis of the dependence of low and high qualities of 2PP microstructures and their manufacturing accuracy for further HOT assembling processes. Besides, the applied detachable interlocking connections of the 2PP building blocks are visualized by an application example. In the long-term a full optical assembly method without applying any mechanical forces can thus be realized.

Ksouri, Sarah Isabelle; Mattern, Manuel; Köhler, Jannis; Aumann, Andreas; Zyla, Gordon; Ostendorf, Andreas

2014-09-01

113

Counter-propagating dual-trap optical tweezers based on linear momentum conservation  

SciTech Connect

We present a dual-trap optical tweezers setup which directly measures forces using linear momentum conservation. The setup uses a counter-propagating geometry, which allows momentum measurement on each beam separately. The experimental advantages of this setup include low drift due to all-optical manipulation, and a robust calibration (independent of the features of the trapped object or buffer medium) due to the force measurement method. Although this design does not attain the high-resolution of some co-propagating setups, we show that it can be used to perform different single molecule measurements: fluctuation-based molecular stiffness characterization at different forces and hopping experiments on molecular hairpins. Remarkably, in our setup it is possible to manipulate very short tethers (such as molecular hairpins with short handles) down to the limit where beads are almost in contact. The setup is used to illustrate a novel method for measuring the stiffness of optical traps and tethers on the basis of equilibrium force fluctuations, i.e., without the need of measuring the force vs molecular extension curve. This method is of general interest for dual trap optical tweezers setups and can be extended to setups which do not directly measure forces.

Ribezzi-Crivellari, M.; Huguet, J. M. [Small Biosystems Lab, Dept. de Fisica Fonamental, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona (Spain); Ritort, F. [Small Biosystems Lab, Dept. de Fisica Fonamental, Universitat de Barcelona, Avda. Diagonal 647, 08028 Barcelona (Spain); Ciber-BBN de Bioingenieria, Biomateriales y Nanomedicina, Instituto de Salud Carlos III, Madrid (Spain)

2013-04-15

114

NanoTracker: force-sensing optical tweezers for quantitative single-molecule nanomanipulation  

NASA Astrophysics Data System (ADS)

In the past decade, experiments involving the manipulation and observation of nanostructures with light using optical tweezers methodology have developed from proof-of-principle experiments to an established quantitative technique in fields ranging from (bio)physics to cell biology. With optical tweezers, microscopically small objects can be held and manipulated. At the same time, the forces exerted on the trapped objects can be accurately measured. With the Prism-Award winning NanoTracker a platform for performing experiments using specimen from single molecules to whole cells is available. With two time-continuous traps, it allows the controlled trapping and accurate tracking of nanoparticles, suspended either in a microfluidic multichannel flow chamber or even in a temperaturecontrolled open Petri dish. With its 3D detection system, particle displacements in the trap can be recorded with nanometer precision. Moreover, dynamic forces acting on the particle can be measured with better than picoNewton resolution on a microsecond time-scale. Here, we discuss design features of and measurements done with the NanoTracker platform. In particular, we show how one of the hallmarks of single-molecule biophysics, the overstretching transition of DNA, can be studied in a versatile manner and used for protein-DNA interaction mechanics. Moreover, on the lower side of the force range the other benchmark single-molecule biophysics, kinesin's 8-nm steps and stall forces, are shown to be measurable. With the NanoTracker, optical tweezers finally transcend from the labs of self-building scientists who helped the technique mature, to a turn-key system able to serve a much wider community of researchers in the life sciences.

Eggert, Helge A.; van Mameren, Joost; Wozniak, Anna; Jaehnke, Torsten

2010-02-01

115

Single beam optical vortex tweezers with tunable orbital angular momentum  

NASA Astrophysics Data System (ADS)

We propose a single beam method for generating optical vortices with tunable optical angular momentum without altering the intensity distribution. With the initial polarization state varying from linear to circular, we gradually control the torque transferred to the trapped non-absorbing and non-birefringent silica beads. The continuous transition from the maximum rotation speed to zero without changing the trapping potential gives a way to study the complex tribological interactions.

Gecevi?ius, Mindaugas; Drevinskas, Rokas; Beresna, Martynas; Kazansky, Peter G.

2014-06-01

116

Direct integration of micromachined pipettes in a flow channel for single DNA molecule study by optical tweezers  

Microsoft Academic Search

We have developed a micromachined flow cell consisting of a flow channel integrated with micropipettes. The flow cell is used in combination with an optical trap setup (optical tweezers) to study mechanical and structural properties of ?-DNA molecules. The flow cell was realized using silicon micromachining including the so-called buried channel technology to fabricate the micropipettes, the wet etching of

Cristina Rusu; Oever van't Ronny; M. J. de Boer; Henri V. Jansen; J. W. Berenschot; Martin L. Bennink; Johannes S. Kanger; B. G. de Grooth; Miko Elwenspoek; Jan Greve; Jürgen Brugger; Berg van den Albert

2001-01-01

117

A new determination of the shear modulus of the human erythrocyte membrane using optical tweezers.  

PubMed Central

Optical tweezers are used to apply calibrated forces to human erythrocytes, via small silica beads bound to their membrane. The shear modulus mu of the membrane is inferred from measurements of the cell deformation in the small strain linear regime. We find the same result mu = 2.5 +/- 0.4 microN/m for both discotic and nearly spherical swollen cells. This value is smaller than the one deduced from micropipettes experiments. However the two methods do not operate in the same deformation regime and are not expected to lead to the same result. PMID:9916046

Henon, S; Lenormand, G; Richert, A; Gallet, F

1999-01-01

118

Temporal response of biological cells to high-frequency optical jumping and vibrating tweezers  

NASA Astrophysics Data System (ADS)

We analyzed the temporal responses of biological cells in the jumping and vibrating optical tweezers for tugging, wiggling and stretching the cells with the finite element method. Some new concepts were established, which might be investigated in the future experiments, such as the jumping of local stress and local strain, independently on the recovery time of the viscoelastic material and on the jumping frequency, the energy dissipation in the hysteresis cycles, the cytoplasm fluid field and its interaction with the cell membrane. The cell was modeled with full 3D structure and viscoelastic continuum materials.

Yu, Lingyao; Sheng, Yunlong

2014-09-01

119

Laser-induced fusion of human embryonic stem cells with optical tweezers  

NASA Astrophysics Data System (ADS)

We report a study on the laser-induced fusion of human embryonic stem cells (hESCs) at the single-cell level. Cells were manipulated by optical tweezers and fused under irradiation with pulsed UV laser at 355 nm. Successful fusion was indicated by green fluorescence protein transfer. The influence of laser pulse energy on the fusion efficiency was investigated. The fused products were viable as gauged by live cell staining. Successful fusion of hESCs with somatic cells was also demonstrated. The reported fusion outcome may facilitate studies of cell differentiation, maturation, and reprogramming.

Chen, Shuxun; Cheng, Jinping; Kong, Chi-Wing; Wang, Xiaolin; Han Cheng, Shuk; Li, Ronald A.; Sun, Dong

2013-07-01

120

A modular assembling platform for manufacturing of microsystems by optical tweezers  

NASA Astrophysics Data System (ADS)

Due to the increased complexity in terms of materials and geometries for microsystems new assembling techniques are required. Assembling techniques from the semiconductor industry are often very specific and cannot fulfill all specifications in more complex microsystems. Therefore, holographic optical tweezers are applied to manipulate structures in micrometer range with highest flexibility and precision. As is well known non-spherical assemblies can be trapped and controlled by laser light and assembled with an additional light modulator application, where the incident laser beam is rearranged into flexible light patterns in order to generate multiple spots. The complementary building blocks are generated by a two-photon-polymerization process. The possibilities of manufacturing arbitrary microstructures and the potential of optical tweezers lead to the idea of combining manufacturing techniques with manipulation processes to "microrobotic" processes. This work presents the manipulation of generated complex microstructures with optical tools as well as a storage solution for 2PP assemblies. A sample holder has been developed for the manual feeding of 2PP building blocks. Furthermore, a modular assembling platform has been constructed for an `all-in-one' 2PP manufacturing process as a dedicated storage system. The long-term objective is the automation process of feeding and storage of several different 2PP micro-assemblies to realize an automated assembly process.

Ksouri, Sarah Isabelle; Aumann, Andreas; Ghadiri, Reza; Prüfer, Michael; Baer, Sebastian; Ostendorf, Andreas

2013-09-01

121

Combined versatile high-resolution optical tweezers and single-molecule fluorescence microscopy.  

PubMed

Optical trapping and single-molecule fluorescence are two major single-molecule approaches. Their combination has begun to show greater capability to study more complex systems than either method alone, but met many fundamental and technical challenges. We built an instrument that combines base-pair resolution dual-trap optical tweezers with single-molecule fluorescence microscopy. The instrument has complementary design and functionalities compared with similar microscopes previously described. The optical tweezers can be operated in constant force mode for easy data interpretation or in variable force mode for maximum spatiotemporal resolution. The single-molecule fluorescence detection can be implemented in either wide-field or confocal imaging configuration. To demonstrate the capabilities of the new instrument, we imaged a single stretched ? DNA molecule and investigated the dynamics of a DNA hairpin molecule in the presence of fluorophore-labeled complementary oligonucleotide. We simultaneously observed changes in the fluorescence signal and pauses in fast extension hopping of the hairpin due to association and dissociation of individual oligonucleotides. The combined versatile microscopy allows for greater flexibility to study molecular machines or assemblies at a single-molecule level. PMID:23020384

Sirinakis, George; Ren, Yuxuan; Gao, Ying; Xi, Zhiqun; Zhang, Yongli

2012-09-01

122

Atmospheric aerosols: Their Optical Properties and Effects  

NASA Technical Reports Server (NTRS)

Measured properties of atmospheric aerosol particles are presented. These include aerosol size frequency distribution and complex retractive index. The optical properties of aerosols are computed based on the presuppositions of thermodynamic equilibrium and of Mie-theory.

1976-01-01

123

Design of hybrid optical tweezers system for controlled three-dimensional micromanipulation  

NASA Astrophysics Data System (ADS)

Three-dimensional (3D) micro/nano-manipulation using optical tweezers is a significant technique for various scientific fields ranging from biology to nanotechnology. For the dynamic handling of multiple/individual micro-objects in a true 3D working space, we present an improved hybrid optical tweezers system consisting of two multibeam techniques. These two techniques include the generalized phase contrast method with a spatial light modulator and the time-shared scanning method with a two-axis steering mirror and an electrically focus-tunable lens. Unlike our previously reported system that could only handle micro-objects in a two and half dimensional working space, the present system has high versatility for controlled manipulation of multiple micro-objects in a true 3D working space. The controlled rotation of five beads forming a pentagon, that of four beads forming a tetrahedron about arbitrary axes, and the fully automated assembly and subsequent 3D translation of micro-bead arrays are successfully demonstrated as part of the 3D manipulation experiment.

Tanaka, Yoshio; Tsutsui, Shogo; Kitajima, Hiroyuki

2013-04-01

124

Chemotaxis study using optical tweezers to observe the strength and directionality of forces of Leishmania amazonensis  

NASA Astrophysics Data System (ADS)

The displacements of a dielectric microspheres trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences. This system can measure forces on the 50 femto Newtons to 200 pico Newtons range, of the same order of magnitude of a typical forces induced by flagellar motion. The process in which living microorganisms search for food and run away from poison chemicals is known is chemotaxy. Optical tweezers can be used to obtain a better understanding of chemotaxy by observing the force response of the microorganism when placed in a gradient of attractors and or repelling chemicals. This report shows such observations for the protozoa Leishmania amazomenzis, responsible for the leishmaniasis, a serious tropical disease. We used a quadrant detector to monitor the movement of the protozoa for different chemicals gradient. This way we have been able to observe both the force strength and its directionality. The characterization of the chemotaxis of these parasites can help to understand the infection mechanics and improve the diagnosis and the treatments employed for this disease.

Pozzo, Liliana d. Y.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Ayres, Diana C.; Giorgio, Selma; Cesar, Carlos L.

2006-08-01

125

Effects of viscosity on sperm motility studied with optical tweezers  

NASA Astrophysics Data System (ADS)

The purpose of this study is to analyze human sperm motility and energetics in media with different viscosities. Multiple experiments were performed to collect motility parameters using customized computer tracking software that measures the curvilinear velocity (VCL) and the minimum laser power (Pesc) necessary to hold an individual sperm in an optical trap. The Pesc was measured by using a 1064 nm Nd:YVO4 continuous wave laser that optically traps motile sperm at a power of 450 mW in the focused trap spot. The VCL was measured frame by frame before trapping. In order to study sperm energetics under different viscous conditions sperm were labeled with the fluorescent dye DiOC6(3) to measure membrane potentials of mitochondria in the sperm midpiece. Fluorescence intensity was measured before and during trapping. The results demonstrate a decrease in VCL but an increase in Pesc with increasing viscosity. Fluorescent intensity is the same regardless of the viscosity level indicating no change in sperm energetics. The results suggest that, under the conditions tested, viscosity physically affects the mechanical properties of sperm motility rather than the chemical pathways associated with energetics.

Hyun, Nicholas; Chandsawangbhuwana, Charlie; Zhu, Qingyuan; Shi, Linda Z.; Yang-Wong, Collin; Berns, Michael W.

2012-02-01

126

Force measurement in colloidal glasses using optical tweezers  

NASA Astrophysics Data System (ADS)

Colloidal systems form the basis of many complex areas of academic and industrial research efforts. As well as contributing to the understanding of many industrially-produced substances such as paints and glues, they have also proved an excellent model thermodynamic system. Changing the properties of an ensemble of colloidal particles, chemically or otherwise, and observing the evolution of the many-body system gives insight into thermodynamic phenomena such as condensation and crystallisation. Some colloidal systems with a particle density that would place them around the dense end of the liquid-crystal coexistence region show a transition into an amorphous glassy state. Long range particle movement is prevented, while local diffusion is still allowed. Such systems are ideal candidates for exploration with optical force measurements, which allow the relatively non-intrusive manipulation of particles deep within colloidal suspensions. Careful use of refractive index matching has allowed an invisible colloidal suspension to be examined with probe particles of a similar size, but higher refractive index. The environment of particles in colloidal cages has been measured by studying the forces acting on a localised particle, as well as the forces needed to break one or more cages.

Wilson, Laurence; Besseling, Rut; Arlt, Jochen; Poon, Wilson C. K.

2005-08-01

127

Development of a two-photon polymerization and optical tweezers microscope for fabrication and manipulation of microstructures  

NASA Astrophysics Data System (ADS)

We report development of a two-photon polymerization (TPP) microscope, for micro-fabrication of microstructures, which is capable of optical manipulation by use of optical tweezers. The system is based on an inverted Nikon microscope with a tunable Ti: Sapphire femto-second (fs) laser coupled to the upper back port. While in modelocked condition, nanoparticles and wires were fabricated in photo-polymerizable synthetic materials using TPP. By axial positioning of the focused TPP laser beam, 1D-structures (for use as wave guide) were fabricated at desired height above the surface of the substrate. In the mode lock-OFF condition the same tunable laser microbeam was employed as optical tweezers to the hold the nanostructures and manipulate them even in highly viscous medium before immobilizing. Size of the TPP induced structure was found to depend on the fs laser intensity and exposure. Further, by shaping the fs laser beam to line pattern, linear 1D structures could be fabricated without scanning the beam or stage, which remain aligned along the line intensity profile due to anisotropic trapping force of the line tweezers in X and Y-directions. Use of optical tweezers with two-photon polymerization not only allowed in-situ corrective positioning of the polymerized structures, but also the integration of fluorescent microspheres (resonator/detector) with polymerized waveguide.

Ingle, Ninad; Mohanty, Samarendra K.

2011-03-01

128

Micro- and nano-particle trapping using fibered optical nano-tweezers  

NASA Astrophysics Data System (ADS)

We present the stable trapping of luminescent 300-nm cerium-doped YAG particles in aqueous suspension using a dual fiber tip optical tweezers. The particles were elaborated using a specific glycothermal synthesis route together with an original protected annealing step. We obtained harmonic trap potentials in the direction transverse to the optical fiber axes. In the longitudinal direction, the potential shows some sub-structure revealed by two peaks in the distribution statistics with a distance of about half the wavelength of the trapping laser. We calculated intensity normalized trapping stiffness of 36 pN•?m-1W-1. These results are compared to previous work of microparticle trapping and discussed thanks to numerical simulations based on finite element method.

Decombe, Jean-Baptiste; Dantelle, Géraldine; Gacoin, Thierry; Valdivia-Valero, Francisco J.; Colas des Francs, Gérard; Huant, Serge; Fick, Jochen

2014-09-01

129

Optical tweezers assisted imaging of the Z-ring in Escherichia coli: measuring its radial width  

NASA Astrophysics Data System (ADS)

Using single-beam, oscillating optical tweezers we can trap and rotate rod-shaped bacterial cells with respect to the optical axis. This technique allows imaging fluorescently labeled three-dimensional sub-cellular structures from different, optimized viewpoints. To illustrate our method we measure D, the radial width of the Z-ring in unconstricted Escherichia coli. We use cells that express FtsZ-GFP and have their cytoplasmic membrane stained with FM4-64. In a vertically oriented cell, both the Z-ring and the cytoplasmic membrane images appear as symmetric circular structures that lend themselves to quantitative analysis. We found that D ? 100 nm, much larger than expected.

Carmon, G.; Kumar, P.; Feingold, M.

2014-01-01

130

Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers  

PubMed Central

To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission. PMID:24509866

Frusawa, Hiroshi; Matsumoto, Youei

2014-01-01

131

Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers.  

PubMed

To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission. PMID:24509866

Frusawa, Hiroshi; Matsumoto, Youei

2014-01-01

132

Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers  

NASA Astrophysics Data System (ADS)

To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission.

Frusawa, Hiroshi; Matsumoto, Youei

2014-02-01

133

Extended linear detection range for optical tweezers using image-plane detection scheme  

NASA Astrophysics Data System (ADS)

Ability to measure pico- and femto-Newton range forces using optical tweezers (OT) strongly relies on the sensitivity of its detection system. We show that the commonly used back-focal-plane detection method provides a linear response range which is shorter than that of the restoring force of OT for large beads. This limits measurable force range of OT. We show, both theoretically and experimentally, that utilizing a second laser beam for tracking could solve the problem. We also propose a new detection scheme in which the quadrant photodiode is positioned at the plane optically conjugate to the object plane (image plane). This method solves the problem without need for a second laser beam for the bead sizes that are commonly used in force spectroscopy applications of OT, such as biopolymer stretching.

Hajizadeh, Faegheh; Masoumeh Mousavi, S.; Khaksar, Zeinab S.; Reihani, S. Nader S.

2014-10-01

134

Tuning the size and configuration of nanocarbon microcapsules: aqueous method using optical tweezers  

E-print Network

To date, optical manipulation techniques for aqueous dispersions have been developed that deposit and/or transport nanoparticles not only for fundamental studies of colloidal dynamics, but also for either creating photonic devices or allowing accurate control of liquids on micron scales. Here, we report that optical tweezers (OT) system is able to direct three-dimensional assembly of graphene, graphite, and carbon nanotubes (CNT) into microcapsules of hollow spheres. The OT technique facilitates both to visualize the elasticity of a CNT microcapsule and to arrange a triplet of identical graphene microcapsules in aqueous media. Furthermore, the similarity of swelling courses has been found over a range of experimental parameters such as nanocarbon species, the power of the incident light, and the suspension density. Thanks to the universality in evolutions of rescaled capsule size, we can precisely control the size of various nanocarbon microcapsules by adjusting the duration time of laser emission.

Hiroshi Frusawa; Youei Matsumoto

2014-03-05

135

Optical tweezers and non-ratiometric fluorescent-dye-based studies of respiration in sperm mitochondria  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force from the laser tweezers were measured. Human (Homo sapiens), dog (Canis lupis familiaris) and drill (Mandrillus leucophaeus) sperm were treated with DiOC6(3) to measure the membrane potential in the mitochondria-rich sperm midpieces. Sperm from all three species exhibited an increase in fluorescence when treated with the DiOC6(3). When a cyanide inhibitor (CCCP) of aerobic respiration was applied, sperm of all three species exhibited a reduction in fluorescence to pre-dye levels. With respect to VCL and escape force, the CCCP had no effect on dog or human sperm, suggesting a major reliance upon anaerobic respiration (glycolysis) for ATP in these two species. Based on the preliminary study on drill sperm, CCCP caused a drop in the VCL, suggesting potential reliance on both glycolysis and aerobic respiration for motility. The results demonstrate that optical trapping in combination with DiOC6(3) is an effective way to study sperm motility and energetics.

Chen, Timothy; Shi, Linda Z.; Zhu, Qingyuan; Chandsawangbhuwana, Charlie; Berns, Michael W.

2011-04-01

136

Stable trapping and manually controlled rotation of an asymmetric or birefringent microparticle using dual-mode split-beam optical tweezers.  

PubMed

Inserting a coverslip into half of a Gaussian laser beam at a suitable tilting angle can make the single-mode laser beam become closely spaced dual light spots at the laser focus. In this way, we can reform the conventional single-beam optical tweezers easily and construct a set of dual-mode split-beam optical tweezers, which can be used to manually rotate a trapped and twisted red blood cell around the optical axis. Furthermore, we demonstrate that the split-beam optical tweezers can also stably trap and orient a birefringent polystyrene micro strip particle, which otherwise will self rotate at a varying speed along the structural principal axes, fast spin about the optical axis in a tilting pose, or precess like a gyroscope, in the original linearly polarized single-beam optical tweezers. PMID:20639958

Sheu, Fang-Wen; Lan, Tzu-Kai; Lin, Yu-Chung; Chen, Shiung; Ay, Chyung

2010-07-01

137

Stratospheric aerosol optical depths, 1850-1990  

Microsoft Academic Search

A global stratospheric aerosol database employed for climate simulations is described. For the period 1883-1990, aerosol optical depths are estimated from optical extinction data, whose quality increases with time over that period. For the period 1850-1882, aerosol optical depths are more crudely estimated from volcanological evidence for the volume of ejecta from major known volcanoes. The data set is available

Makiko Sato; James E. Hansen; M. Patrick McCormick; James B. Pollack

1993-01-01

138

Trehalose facilitates DNA melting: a single-molecule optical tweezers study.  

PubMed

Using optical tweezers, here we show that the overstretching transition force of double-stranded DNA (dsDNA) is lowered significantly by the addition of the disaccharide trehalose as well as certain polyol osmolytes. This effect is found to depend linearly on the logarithm of the trehalose concentration. We propose an entropic driving mechanism for the experimentally observed destabilization of dsDNA that is rooted in the higher affinity of the DNA bases for trehalose than for water, which promotes base exposure and DNA melting. Molecular dynamics simulation reveals the direct interaction of trehalose with nucleobases. Experiments with other osmolytes confirm that the extent of dsDNA destabilization is governed by the ratio between polar and apolar fractions of an osmolyte. PMID:25096217

Bezrukavnikov, Sergey; Mashaghi, Alireza; van Wijk, Roeland J; Gu, Chan; Yang, Li Jiang; Gao, Yi Qin; Tans, Sander J

2014-10-01

139

Imaging microscopic fluid viscosity and velocity fields using confocal scanning optical tweezers  

NASA Astrophysics Data System (ADS)

Confocal microscopy and optical tweezers were combined to develop a minimally invasive instrument capable of making hydrodynamic measurements more rapidly than is possible with other devices. This result leads to the possibility of making scanning images of the viscosity distribution of materials around bipolymer producing cells. An image of the viscosity distribution around a pullulan producing cell of Aureobasidium pullulans is shown as an example. We present results from experiments supporting a linearized model for the motion of a trapped bead in an oscillating harmonic potential. Fluid velocity measurements are tested by comparing to an independent video based measurement. We apply the technique to obtain a 2-D map of the flow past a microscopic wedge and compare to a theoretical solution for the stream lines assuming potential flow. Since the velocity is measured simultaneously with the trap relaxation time, it requires practically no calibration and is independent of the trap stiffness and the particle size.

Nemet, Boaz A.; Harnik, Nili; Cronin-Golomb, Mark

2002-05-01

140

Accurate measurement of force and displacement with optical tweezers using DNA molecules as metrology standards  

NASA Astrophysics Data System (ADS)

Optical tweezers facilitate measurement of piconewton-level forces and nanometer-level displacements and have broad applications in biophysics and soft matter physics research. We have shown previously that DNA molecules can be used as metrology standards to define such measurements. Force-extension measurements on two DNA molecules of different lengths can be used to determine four necessary measurement parameters. Here, we show that the accuracy of determining these parameters can be improved by more than 7-fold by incorporating measurements of the DNA overstretching transition and using a multi-step data analysis procedure. This method results in very robust and precise fitting of DNA force-extension measurements to the worm-like chain model. We verify the accuracy through independent measurements of DNA stretching, DNA unzipping, and microsphere contact forces.

delToro, Damian; Smith, Douglas E.

2014-04-01

141

Optical tweezers study of viscoelastic properties in the outer hair cell plasma membrane  

NASA Astrophysics Data System (ADS)

An optical tweezers system was used to study the mechanical characteristics of the outer hair cell (OHC) lateral wall by forming plasma membrane tethers. A 2nd order generalized Kelvin model was applied to describe the viscoelastic behavior of OHC membrane tethers. The measured parameters included equilibrium tethering force, (Feq), force relaxation times (?), stiffness values (?), and coefficients of friction (?). An analysis of force relaxation in membrane tethers indicated that the force decay is a biphasic process containing both an elastic and a viscous phase. In general, we observed an overall negative trend in the measured parameters upon application of the cationic amphipath chlorpromazine (CPZ). CPZ was found to cause up to a 40 pN reduction in Feq in OHCs. A statistically significant reduction in relaxation times and coefficients of friction was also observed, suggesting an increase in rate of force decay and a decrease in plasma membrane viscosity.

Murdock, David R.; Ermilov, Sergey A.; Qian, Feng; Brownell, William E.; Anvari, Bahman

2004-06-01

142

Studies of cochlear outer hair cell membrane mechanics using optical tweezers  

NASA Astrophysics Data System (ADS)

An optical tweezers system was used to study the mechanical characteristics of outer hair cell (OHC) and human embryonic kidney (HEK) cell plasma membranes. The effect of the cationic amphipath chlorpromazine (CPZ) on the equilibrium tethering force, (Feq) force relaxation time constant,(?) and effective membrane viscosity (?eff) was measured. The Feq for the OHC lateral wall plasma membrane was ~60 pN and was unchanged by addition of CPZ. A significantly greater ? value was observed in CPZ-treated OHCs (30.5 +/- 12.6 s) than in control OHCs (19.0 +/- 13.2 s). The Feq and ? values for control HEK cells were >60% lower than the respective OHC values but increased by ~3 times following CPZ addition. Effective viscosity ranged between 1.49-1.81 pN•s/?m for CPZ-treated OHCs. This represents a decrease from reported control OHC membrane viscosities.

Murdock, David R.; Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

2003-06-01

143

Micro-rheology on (polymer-grafted) colloids using optical tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it—without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed.

Gutsche, C.; Elmahdy, M. M.; Kegler, K.; Semenov, I.; Stangner, T.; Otto, O.; Ueberschär, O.; Keyser, U. F.; Krueger, M.; Rauscher, M.; Weeber, R.; Harting, J.; Kim, Y. W.; Lobaskin, V.; Netz, R. R.; Kremer, F.

2011-05-01

144

Micro-rheology on (polymer-grafted) colloids using optical tweezers.  

PubMed

Optical tweezers are experimental tools with extraordinary resolution in positioning (± 1 nm) a micron-sized colloid and in the measurement of forces (± 50 fN) acting on it-without any mechanical contact. This enables one to carry out a multitude of novel experiments in nano- and microfluidics, of which the following will be presented in this review: (i) forces within single pairs of colloids in media of varying concentration and valency of the surrounding ionic solution, (ii) measurements of the electrophoretic mobility of single colloids in different solvents (concentration, valency of the ionic solution and pH), (iii) similar experiments as in (i) with DNA-grafted colloids, (iv) the nonlinear response of single DNA-grafted colloids in shear flow and (v) the drag force on single colloids pulled through a polymer solution. The experiments will be described in detail and their analysis discussed. PMID:21508470

Gutsche, C; Elmahdy, M M; Kegler, K; Semenov, I; Stangner, T; Otto, O; Ueberschär, O; Keyser, U F; Krueger, M; Rauscher, M; Weeber, R; Harting, J; Kim, Y W; Lobaskin, V; Netz, R R; Kremer, F

2011-05-11

145

Constructing 3D crystal templates for photonic band gap materials using holographic optical tweezers.  

PubMed

A simple and robust method is presented for the construction of 3-dimensional crystals from silica and polystyrene microspheres. The crystals are suitable for use as templates in the production of three-dimensional photonic band gap (PBG) materials. Manipulation of the microspheres was achieved using a dynamic holographic assembler (DHA) consisting of computer controlled holographic optical tweezers. Attachment of the microspheres was achieved by adjusting their colloidal interactions during assembly. The method is demonstrated by constructing a variety of 3-dimensional crystals using spheres ranging in size from 3 microm down to 800 nm. A major advantage of the technique is that it may be used to build structures that cannot be made using self-assembly. This is illustrated through the construction of crystals in which line defects have been deliberately included, and by building simple cubic structures. PMID:18711539

Benito, D C; Carberry, D M; Simpson, S H; Gibson, G M; Padgett, M J; Rarity, J G; Miles, M J; Hanna, S

2008-08-18

146

Mechanism of termination of bacteriophage DNA packaging investigated with optical tweezers  

NASA Astrophysics Data System (ADS)

The genomes of many dsDNA viruses are replicated by a mechanism that produces a long concatemer of multiple genomes. These viruses utilize multifunctional molecular motor complexes referred to as "terminases" that can excise a unit genome length of DNA and package it into preformed viral shells. Remarkably, the terminase motor can initiate packaging at the appropriate start point, translocate DNA, sense when a sufficient length has been packaged, and then switch into a mode where it arrests and cleaves the DNA to release a filled virus particle. We have recently developed an improved method to measure single phage lambda DNA packaging using dual-trap optical tweezers and pre-stalled motor-DNA-procapsid complexes. We are applying this method to test proposed mechanisms for the sensor that triggers termination; specifically a velocity-monitor model vs. energy-monitor model vs. capsid-filling monitor model.

delToro, Damian J.; Smith, Douglas E.

2012-10-01

147

Haptic guidance for improved task performance in steering microparticles with optical tweezers.  

PubMed

We report the manipulation of 4-5 mum diameter polymer microspheres floating in water using optical tweezers (OT) and a haptic device (i.e. force-reflecting robotic arm). Trapped microspheres are steered using the end-effector of a haptic device that is virtually coupled to an XYZ piezo-scanner controlling the movements of the fluid bed. To help with the manipulations, we first calculate a collision-free path for the particle and then display artificial guidance forces to the user through the haptic device to keep him/her on this path during steering. Experiments conducted with 8 subjects show almost two-fold improvements in the average path error and average speed under the guidance of haptic feedback. PMID:19547521

Basdogan, Cagatay; Kiraz, Alper; Bukusoglu, Ibrahim; Varol, Ayd?n; Do?anay, Sultan

2007-09-01

148

DNA interaction with diaminobenzidine studied with optical tweezers and dynamic light scattering.  

PubMed

We have studied the interaction of the DNA molecule with the ligand 3,3'-diaminobenzidine (DAB) by performing single molecule stretching experiments with optical tweezers and dynamic light scattering (DLS) on the DNA-DAB complexes. In the stretching experiments, the persistence and contour lengths of the complexes were measured as a function of DAB concentration, allowing one to infer the main binding mechanism and also to determine the physicochemical parameters of the interaction. In the DLS experiments, the effective size of the complexes, measured as the hydrodynamic radius, was monitored as a function of DAB concentration. We found a qualitative agreement between the results obtained from the two techniques by comparing the behaviors of the hydrodynamics radius and the radius of gyration, since this last one can be expressed as a function of the persistence and contour lengths. PMID:24164302

Reis, L A; Ramos, E B; Rocha, M S

2013-11-21

149

Determination of femto Newton forces and fluid viscosity using optical tweezers: application to Leishmania amazonensis  

NASA Astrophysics Data System (ADS)

The objective of this research is to use the displacements of a polystyrene microsphere trapped by an optical tweezers (OT) as a force transducer in mechanical measurements in life sciences. To do this we compared the theoretical optical and hydrodynamic models with experimental data under a broad variation of parameters such as fluid viscosity, refractive index, drag velocity and wall proximities. The laser power was measured after the objective with an integration sphere because normal power meters do not provide an accurate measurement for beam with high numerical apertures. With this careful laser power determination the plot of the optical force (calculated by the particle displacement) versus hydrodynamic force (calculated by the drag velocity) under very different conditions shows an almost 45 degrees straight line. This means that hydrodynamic models can be used to calibrate optical forces and vice-versa. With this calibration we observed the forces of polystyrene bead attached to the protozoa Leishmania amazonensis, responsible for a serious tropical disease. The force range is from 200 femto Newtons to 4 pico Newtons and these experiments shows that OT can be used for infection mechanism and chemotaxis studies in parasites. The other application was to use the optical force to measure viscosities of few microliters sample. Our result shows 5% accuracy measurements.

Fontes, Adriana; Giorgio, Selma; de Castro, Archimedes B., Jr.; Neto, Vivaldo M.; Pozzo, Liliana d. Y.; Marques, Gustavo P.; Barbosa, Luiz C.; Cesar, Carlos L.

2005-03-01

150

Single-molecule manipulation of double-stranded DNA using optical tweezers: Interaction studies of DNA with RecA and YOYO-1  

Microsoft Academic Search

By using optical tweezers and a specially designed flow cell with an integrated glass micropipette, we constructed a setup similar to that of Smith et al. (Science 271:795-799, 1996) in which an individual double-stranded DNA (dsDNA) molecule can be captured between two polystyrene beads. The first bead is immobilized by the optical tweezers and the second by the micropipette. Movement

Martin L. Bennink; Orlando D. Scharer; Ronald Kanaar; Kumiko Sakata-Sogawa; Juleon M. Schins; Johannes S. Kanger; Grooth de Bart G; Jan Greve

1999-01-01

151

Manipulating cell adhesions with optical tweezers for study of cell-to-cell interactions.  

PubMed

This paper presents an approach to manipulating cell adhesions using optical tweezers for cell-to-cell interactions at single cell level. A case study of investigating the adhesions between leukemia cells and bone marrow stromal cells is reported. First, the trapping force imposed on the cell is calibrated and the viability of leukemia cells after optical trapping is tested and verified. This is for demonstrating the feasibility of the proposed optical manipulation method. Second, properties of adhesions of leukemia cells K562 on stromal cells M210B4 from mouse and HS5 from human are characterized. Based on characterization results, we classify adhesions into three categories namely tightly adherent, loosely adherent or free suspending. Finally, the adhesion abilities of K562 on M210B4 and HS5 are changed by adding heparin into culture medium, which demonstrates the specificity of the adhesion. The important contribution of this paper lies in development of a dexterous cell manipulation method to characterize cell adhesion properties, which helps create a new opportunity to investigate cell-to-cell interactions at single cell level. PMID:23627055

Hu, Songyu; Gou, Xue; Han, Hochun; Leung, Anskar Y H; Sun, Dong

2013-02-01

152

The ?PIVOT: an integrated particle image velocimeter and optical tweezers instrument for microenvironment investigations.  

PubMed

A novel instrument to manipulate and characterize the mechanical environment in and around microscale objects in a fluidic environment has been developed by integrating two laser-based techniques: micron-resolution particle image velocimetry (?PIV) and optical tweezers (OT). This instrument, the ?PIVOT, enables a new realm of microscale studies, yet still maintains the individual capabilities of each optical technique. This was demonstrated with individual measurements of optical trap stiffness (?70 pN ?m(-1) for a 20 ?m polystyrene sphere and a linear relationship between trap stiffness and laser power) and fluid velocities within 436 nm of a microchannel wall. The integrated device was validated by comparing computational flow predictions to the measured velocity profile around a trapped particle in either a uniform flow or an imposed, gravity-driven microchannel flow (R(2) = 0.988, RMS error = 13.04 ?m s(-1)). Interaction between both techniques is shown to be negligible for 15 ?m to 35 ?m diameter trapped particles subjected to fluid velocities from 50 ?m s(-1) to 500 ?m s(-1) even at the highest laser power (1.45 W). The integrated techniques will provide a unique perspective toward understanding microscale phenomena including single-cell biomechanics, non-Newtonian fluid mechanics and single particle or particle-particle hydrodynamics. PMID:18953424

Nève, N; Lingwood, J K; Zimmerman, J; Kohles, S S; Tretheway, D C

2008-01-01

153

Spatially-sculpted aberrated optical tweezers for delivery of nanoparticles onto cells  

NASA Astrophysics Data System (ADS)

Nanoparticles (NP) are emerging as photochemical and photothermal agents for delivery of drugs and heat onto the targeted cells. Here, we report spatially-sculpting of transverse potential landscape by introducing aberration in the optical tweezers beam for delivery of therapeutic NP on to the prostate cancer PC3 cells. A tunable Ti-Sapphire laser beam was focused to a diffraction limited spot by use of a high numerical aperture microscope objective for optical trapping. A cylindrical lens was used to create the beam profile astigmatic, which led to spatially extended potential landscape. In order to facilitate transport of NP, Comatic potential was created by tilting of the astigmatic beam with respect to the optic axis. NPs were attracted towards the potential minima, transported along the major axis of the elliptic spot and ejected out along the direction having lower stiffness. The Carbon NPs as well as Poly Lactic-co-Glycolic Acid NPs were efficiently transported and concentrated near the PC3 cells in-vitro. The direction and the speed of transport of nano-particles could be reversed by change in tilt direction and angle. Further, by utilizing the scattering force with the asymmetric gradient force, three-dimensional transport of nanoparticles was achieved. The effect of laser beam power and size / refractive index of the nano-particles on the speed of transport will be presented.

Shivalingaiah, Shivaranjani; Chhajed, Suyash; Mohanty, Samarendra

2011-03-01

154

Cell manipulation tool with combined microwell array and optical tweezers for cell isolation and deposition  

NASA Astrophysics Data System (ADS)

Isolation from rare cells and deposition of sorted cells with high accuracy for further study are critical to a wide range of biomedical applications. In the current paper, we report an automated cell manipulation tool with combined optical tweezers and a uniquely designed microwell array, which functions for recognition, isolation, assembly, transportation and deposition of the interesting cells. The microwell array allows the passive hydrodynamic docking of cells, while offering the opportunity to inspect the interesting cell phenotypes with high spatio-temporal resolution based on the flexible image processing technique. In addition, dynamic and parallel cell manipulation in three dimensions can realize the target cell levitation from microwell and pattern assembly with multiple optical traps. Integrated with the programmed motorized stage, the optically levitated and assembled cells can be transported and deposited to the predefined microenvironment, so the tool can facilitate the integration of other on-chip functionalities for further study without removing these isolated cells from the chip. Experiments on human embryonic stem cells and yeast cells are performed to demonstrate the effectiveness of the proposed cell manipulation tool. Besides the application to cell isolation and deposition, three other biological applications with this tool are also presented.

Wang, Xiaolin; Gou, Xue; Chen, Shuxun; Yan, Xiao; Sun, Dong

2013-07-01

155

Simultaneous three-dimensional tracking of individual signals from multi-trap optical tweezers using fast and accurate photodiode detection.  

PubMed

Multiple-beam optical traps facilitate advanced trapping geometries and exciting discoveries. However, the increased manipulation capabilities come at the price of more challenging position and force detection. Due to unrivaled bandwidth and resolution, photodiode based detection is preferred over camera based detection in most single/dual-beam optical traps assays. However, it has not been trivial to implement photodiode based detection for multiple-beam optical traps. Here, we present a simple and efficient method based on spatial filtering for parallel photodiode detection of multiple traps. The technique enables fast and accurate 3D force and distance detection of multiple objects simultaneously manipulated by multiple-beam optical tweezers. PMID:25321832

Ott, Dino; Nader, S; Reihani, S; Oddershede, Lene B

2014-09-22

156

Surface charge measurements and (dis)charging dynamics of organic semiconductors in various media using optical tweezers  

NASA Astrophysics Data System (ADS)

An exciting application of optical tweezers is the measurement of the surface charge on a trapped particle, as well as its time evolution with a single charge resolution. We report on an optical tweezer-based method to measure the effective surface charge on an organic semiconductor film at microscopic scales, which offers opportunities for investigations of ion and electron transfer between organic molecules and surrounding medium. Effective charge densities of 13+/-5 elementary charges per ?m2 were observed in anthradithiophene-coated silica microspheres suspended in water, with a more than an order of magnitude reduction in charge densities upon replacing water with the 50% wt/wt glycerol/water mixture.

Grollman, Rebecca R.; Peters, Kyle; Ostroverkhova, Oksana

2014-03-01

157

Determination of fluid viscosity and femto Newton forces of Leishmania amazonensis using optical tweezers  

NASA Astrophysics Data System (ADS)

The displacements of a polystyrene microsphere trapped by an optical tweezers (OT) can be used as a force transducer for mechanical measurements in life sciences such as the measurement of forces of living microorganisms or the viscosity of local fluids. The technique we used allowed us to measure forces on the 200 femto Newtons to 4 pico Newtons range of the protozoa Leishmania amazonensis, responsible for a serious tropical disease. These observations can be used to understand the infection mechanism and chemotaxis of these parasites. The same technique was used to measure viscosities of few microliters sample with agreement with known samples better than 5%. To calibrate the force as a function of the microsphere displacement we first dragged the microsphere in a fluid at known velocity for a broad range of different optical and hydrodynamical parameters. The hydrodynamical model took into account the presence of two walls and the force depends on drag velocity, fluid viscosity and walls proximities, while the optical model in the geometric optics regime depends on the particle and fluid refractive indexes and laser power. To measure the high numerical (NA) aperture laser beam power after the objective we used an integration sphere to avoid the systematic errors of usual power meters for high NA beams. After this careful laser power measurement we obtained an almost 45 degrees straight line for the plot of the optical force (calculated by the particle horizontal displacement) versus hydrodynamic force (calculated by the drag velocity) under variation of all the parameters described below. This means that hydrodynamic models can be used to calibrate optical forces, as we have done for the parasite force measurement, or vice-versa, as we did for the viscosity measurements.

Fontes, Adriana; Giorgio, Selma; de Castro, Archimedes, Jr.; Neto, Vivaldo M.; de Y. Pozzo, Liliana; de Thomaz, Andre A.; Barbosa, Luiz C.; Cesar, Carlos L.

2005-08-01

158

Isolation of genomic DNA molecule from a single cell and control its higher order structure using optical tweezers  

NASA Astrophysics Data System (ADS)

In this report, we describe a noninvasive methodology for manipulating single Mb-size whole-genome DNA molecules. Cells were subjected to osmotic shock and the genome DNA released from the burst cells was transferred to a region of higher salt concentration between cover slips using optical tweezers. The transferred genome DNA exhibits a conformational transition from a compact state into an elongated state, accompanied by the change in its environment. Here, the applicability of optical tweezers to the on-site manipulation of giant genomic DNA is suggested. Next, to control the field environment more precisely, a flow chamber was made and similar investigations were carried out. In the flow chamber, the higher-order structure of individual chromosomal DNA molecules from a fission yeast that were folded by polyamine was changed to a partially unfolded form by transporting into a higher salt condition using optical tweezers. These promising methodologies demonstrated here may make it possible to recover an intact single whole-genome DNA from a cell and carry out further sequential investigations under a microscope.

Oana, Hidehiro; Hagiya, Isao; Washizu, Masao; Kubo, Koji; Yoshikawa, Kenichi; Atomi, Haruyuki; Imanaka, Tadayuki

2005-08-01

159

Optical tweezers and multiphoton microscopies integrated photonic tool for mechanical and biochemical cell processes studies  

NASA Astrophysics Data System (ADS)

The research in biomedical photonics is clearly evolving in the direction of the understanding of biological processes at the cell level. The spatial resolution to accomplish this task practically requires photonics tools. However, an integration of different photonic tools and a multimodal and functional approach will be necessary to access the mechanical and biochemical cell processes. This way we can observe mechanicaly triggered biochemical events or biochemicaly triggered mechanical events, or even observe simultaneously mechanical and biochemical events triggered by other means, e.g. electricaly. One great advantage of the photonic tools is its easiness for integration. Therefore, we developed such integrated tool by incorporating single and double Optical Tweezers with Confocal Single and Multiphoton Microscopies. This system can perform 2-photon excited fluorescence and Second Harmonic Generation microscopies together with optical manipulations. It also can acquire Fluorescence and SHG spectra of specific spots. Force, elasticity and viscosity measurements of stretched membranes can be followed by real time confocal microscopies. Also opticaly trapped living protozoas, such as leishmania amazonensis. Integration with CARS microscopy is under way. We will show several examples of the use of such integrated instrument and its potential to observe mechanical and biochemical processes at cell level.

de Thomaz, A. A.; Faustino, W. M.; Fontes, A.; Fernandes, H. P.; Barjas-Castro, M. d. L.; Metze, K.; Giorgio, S.; Barbosa, L. C.; Cesar, C. L.

2007-09-01

160

High-resolution detection of Brownian motion for quantitative optical tweezers experiments.  

PubMed

We have developed an in situ method to calibrate optical tweezers experiments and simultaneously measure the size of the trapped particle or the viscosity of the surrounding fluid. The positional fluctuations of the trapped particle are recorded with a high-bandwidth photodetector. We compute the mean-square displacement, as well as the velocity autocorrelation function of the sphere, and compare it to the theory of Brownian motion including hydrodynamic memory effects. A careful measurement and analysis of the time scales characterizing the dynamics of the harmonically bound sphere fluctuating in a viscous medium directly yields all relevant parameters. Finally, we test the method for different optical trap strengths, with different bead sizes and in different fluids, and we find excellent agreement with the values provided by the manufacturers. The proposed approach overcomes the most commonly encountered limitations in precision when analyzing the power spectrum of position fluctuations in the region around the corner frequency. These low frequencies are usually prone to errors due to drift, limitations in the detection, and trap linearity as well as short acquisition times resulting in poor statistics. Furthermore, the strategy can be generalized to Brownian motion in more complex environments, provided the adequate theories are available. PMID:23005790

Grimm, Matthias; Franosch, Thomas; Jeney, Sylvia

2012-08-01

161

Calibration of optical tweezers with positional detection in the back focal plane  

SciTech Connect

We explain and demonstrate a new method of force and position calibrations for optical tweezers with back-focal-plane photodetection. The method combines power spectral measurements of thermal motion and the response to a sinusoidal motion of a translation stage. It consequently does not use the drag coefficient of the trapped object as an input. Thus, neither the viscosity, nor the size of the trapped object, nor its distance to nearby surfaces needs to be known. The method requires only a low level of instrumentation and can be applied in situ in all spatial dimensions. It is both accurate and precise: true values are returned, with small error bars. We tested this experimentally, near and far from surfaces in the lateral directions. Both position and force calibrations were accurate to within 3%. To calibrate, we moved the sample with a piezoelectric translation stage, but the laser beam could be moved instead, e.g., by acousto-optic deflectors. Near surfaces, this precision requires an improved formula for the hydrodynamical interaction between an infinite plane and a microsphere in nonconstant motion parallel to it. We give such a formula.

Tolic-Noerrelykke, Simon F.; Schaeffer, Erik; Howard, Jonathon; Pavone, Francesco S.; Juelicher, Frank; Flyvbjerg, Henrik [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany) and European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy) and Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden (Germany); European Laboratory for Non-linear Spectroscopy, via Nello Carrara 1, 50019 Sesto Fiorentino, Florence (Italy); Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany); Isaac Newton Institute for Mathematical Sciences, Cambridge CB3 0EH (United Kingdom); Biosystems Department, Risoe National Laboratory, DK-4000 Roskilde (Denmark) and Danish Polymer Centre, Risoe National Laboratory, DK-4000 Roskilde (Denmark)

2006-10-15

162

An Interactive Virtual Reality Simulation for Nanoparticle Manipulation for Nanoassembly using Optical Tweezers  

NSDL National Science Digital Library

Nanotechnology and nano devices is believed to be one of the most promising steps that science is taking to the future. This paper proposes virtual reality (VR) as a tool to simulate nano particle manipulation using optical tweezers towards achieving nano- assembly for effectively handling issues such as difficulty in viewing, perceiving and controlling the nano-scale objects. The nano simulation is modeled, using virtual reality, displaying all the forces acting on nano particle during the manipulation. The simulation is developed for particles that belong to Rayleigh region and, represents interactions of OT (a laser beam) with the nano particle. The laser beam aimed on to the nano particle traps the particle by applying optical forces. The trapped particle is then moved by moving the laser beam. The proposed VR based simulation tool with its capabilities can be easily extended and used for creating an open system framework by connecting it to a real OT setup to control nano particles manipulation. In addition, a feedback system can be build to increase of precision of movement.

Bhavaraju, Krishna; Choudhury, Alamgir A.; Dwivedi, Suren; Ikonomove, Pavel

2009-10-02

163

A general method for manipulating DNA sequences from any organism with optical tweezers  

PubMed Central

Mechanical manipulation of single DNA molecules can provide novel information about DNA properties and protein–DNA interactions. Here we describe and characterize a useful method for manipulating desired DNA sequences from any organism with optical tweezers. Molecules are produced from either genomic or cloned DNA by PCR using labeled primers and are tethered between two optically trapped microspheres. We demonstrate that human, insect, plant, bacterial and viral sequences ranging from ?10 to 40 kilobasepairs can be manipulated. Force-extension measurements show that these constructs exhibit uniform elastic properties in accord with the expected contour lengths for the targeted sequences. Detailed protocols for preparing and manipulating these molecules are presented, and tethering efficiency is characterized as a function of DNA concentration, ionic strength and pH. Attachment strength is characterized by measuring the unbinding time as a function of applied force. An alternative stronger attachment method using an amino–carboxyl linkage, which allows for reliable DNA overstretching, is also described. PMID:16452295

Fuller, Derek N.; Gemmen, Gregory J.; Rickgauer, John Peter; Dupont, Aurelie; Millin, Rachel; Recouvreux, Pierre; Smith, Douglas E.

2006-01-01

164

Drug-DNA interactions at single molecule level: A view with optical tweezers  

NASA Astrophysics Data System (ADS)

Studies of small molecule--DNA interactions are essential for developing new drugs for challenging diseases like cancer and HIV. The main idea behind developing these molecules is to target and inhibit the reproduction of the tumor cells and infected cells. We mechanically manipulate single DNA molecule using optical tweezers to investigate two molecules that have complex and multiple binding modes. Mononuclear ruthenium complexes have been extensively studied as a test for rational drug design. Potential drug candidates should have high affinity to DNA and slow dissociation kinetics. To achieve this, motifs of the ruthenium complexes are altered. Our collaborators designed a dumb-bell shaped binuclear ruthenium complex that can only intercalate DNA by threading through its bases. Studying the binding properties of this complex in bulk studies took hours. By mechanically manipulating a single DNA molecule held with optical tweezers, we lower the barrier to thread and make it fast compared to the bulk experiments. Stretching single DNA molecules with different concentration of drug molecules and holding it at a constant force allows the binding to reach equilibrium. By this we can obtain the equilibrium fractional ligand binding and length of DNA at saturated binding. Fitting these results yields quantitative measurements of the binding thermodynamics and kinetics of this complex process. The second complex discussed in this study is Actinomycin D (ActD), a well studied anti-cancer agent that is used as a prototype for developing new generations of drugs. However, the biophysical basis of its activity is still unclear. Because ActD is known to intercalate double stranded DNA (dsDNA), it was assumed to block replication by stabilizing dsDNA in front of the replication fork. However, recent studies have shown that ActD binds with even higher affinity to imperfect duplexes and some sequences of single stranded DNA (ssDNA). We directly measure the on and off rates by stretching the DNA molecule to a certain force and holding it at constant force while adding the drug and then while washing off the drug. Our finding resolves the long lasting controversy of ActD binding modes, clearly showing that both the dsDNA binding and ssDNA binding converge to the same single mode. The result supports the hypothesis that the primary characteristic of ActD that contributes to its biological activity is its ability to inhibit cellular replication by binding to transcription bubbles and causing cell death.

Paramanathan, Thayaparan

165

Stratospheric aerosol optical depths, 1850-1990  

NASA Technical Reports Server (NTRS)

A global stratospheric aerosol database employed for climate simulations is described. For the period 1883-1990, aerosol optical depths are estimated from optical extinction data, whose quality increases with time over that period. For the period 1850-1882, aerosol optical depths are more crudely estimated from volcanological evidence for the volume of ejecta from major known volcanoes. The data set is available over Internet.

Sato, Makiko; Hansen, James E.; Mccormick, M. Patrick; Pollack, James B.

1993-01-01

166

Stratospheric aerosol optical depths, 1850-1990  

NASA Astrophysics Data System (ADS)

A global stratospheric aerosol database employed for climate simulations is described. For the period 1883-1990, aerosol optical depths are estimated from optical extinction data, whose quality increases with time over that period. For the period 1850-1882, aerosol optical depths are more crudely estimated from volcanological evidence for the volume of ejecta from major known volcanoes. The data set is available over Internet.

Sato, Makiko; Hansen, James E.; McCormick, M. Patrick; Pollack, James B.

1993-12-01

167

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers  

PubMed Central

Single-molecule techniques for stretching DNA of contour lengths less than a kilobase are fraught with experimental difficulties. However, many interesting biological events such as histone binding and protein-mediated looping of DNA1,2, occur on this length scale. In recent years, the mechanical properties of DNA have been shown to play a significant role in fundamental cellular processes like the packaging of DNA into compact nucleosomes and chromatin fibers3,4. Clearly, it is then important to understand the mechanical properties of short stretches of DNA. In this paper, we provide a practical guide to a single-molecule optical tweezing technique that we have developed to study the mechanical behavior of DNA with contour lengths as short as a few hundred basepairs. The major hurdle in stretching short segments of DNA is that conventional optical tweezers are generally designed to apply force in a direction lateral to the stage5,6, (see Fig. 1). In this geometry, the angle between the bead and the coverslip, to which the DNA is tethered, becomes very steep for submicron length DNA. The axial position must now be accounted for, which can be a challenge, and, since the extension drags the microsphere closer to the coverslip, steric effects are enhanced. Furthermore, as a result of the asymmetry of the microspheres, lateral extensions will generate varying levels of torque due to rotation of the microsphere within the optical trap since the direction of the reactive force changes during the extension. Alternate methods for stretching submicron DNA run up against their own unique hurdles. For instance, a dual-beam optical trap is limited to stretching DNA of around a wavelength, at which point interference effects between the two traps and from light scattering between the microspheres begin to pose a significant problem. Replacing one of the traps with a micropipette would most likely suffer from similar challenges. While one could directly use the axial potential to stretch the DNA, an active feedback scheme would be needed to apply a constant force and the bandwidth of this will be quite limited, especially at low forces. We circumvent these fundamental problems by directly pulling the DNA away from the coverslip by using a constant force axial optical tweezers7,8. This is achieved by trapping the bead in a linear region of the optical potential, where the optical force is constant-the strength of which can be tuned by adjusting the laser power. Trapping within the linear region also serves as an all optical force-clamp on the DNA that extends for nearly 350 nm in the axial direction. We simultaneously compensate for thermal and mechanical drift by finely adjusting the position of the stage so that a reference microsphere stuck to the coverslip remains at the same position and focus, allowing for a virtually limitless observation period. PMID:22025209

Raghunathan, Krishnan; Milstein, Joshua N.; Meiners, Jens -Christian

2011-01-01

168

Femtosecond single optical fiber tweezers enabled two-photon fluorescence excitation of trapped microscopic objects  

NASA Astrophysics Data System (ADS)

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber femto second optical tweezers and its use in two-photon fluorescence (TPF) excitation of trapped fluorescent particles. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Trapping depth of few cm was achieved inside colloidal sample with TPF from the trapped particle being visible to the naked eye. Furthermore, the fiber optic trapping was so stable that the trapped particle could be moved in 3D even by holding the fiber in hand and slow maneuvering of the same. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. The theoretical simulation of fiber optical microbeam profiles emerging from the axicon tip and trapping force estimations was found to be in good agreement with the experimentally observed stiffness and TPF patterns. Apart from miniaturization capability into lab-on- a-chip micro-fluidic devices, the proposed non-invasive micro axicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting and ablation as well as for two-photon fluorescence excitation of motile sample which will revolutionize biophysics and research in material science.

Mishra, Yogeshwar N.; Pinto, Mervyn; Ingle, Ninad; Mohanty, Samarendra K.

2011-03-01

169

DNA condensation by TmHU studied by optical tweezers, AFM and molecular dynamics simulations  

PubMed Central

The compaction of DNA by the HU protein from Thermotoga maritima (TmHU) is analysed on a single-molecule level by the usage of an optical tweezers-assisted force clamp. The condensation reaction is investigated at forces between 2 and 40 pN applied to the ends of the DNA as well as in dependence on the TmHU concentration. At 2 and 5 pN, the DNA compaction down to 30% of the initial end-to-end distance takes place in two regimes. Increasing the force changes the progression of the reaction until almost nothing is observed at 40 pN. Based on the results of steered molecular dynamics simulations, the first regime of the length reduction is assigned to a primary level of DNA compaction by TmHU. The second one is supposed to correspond to the formation of higher levels of structural organisation. These findings are supported by results obtained by atomic force microscopy. PMID:22210966

Olbrich, Carsten; Brutzer, Hergen; Salomo, Mathias; Kleinekathofer, Ulrich; Keyser, Ulrich F.; Kremer, Friedrich

2010-01-01

170

Optical tweezers reveal a dynamic mechanical response of cationic peptide-DNA complexes  

NASA Astrophysics Data System (ADS)

Nonviral carriers have been developed to deliver nucleic acids by forming nanoscale complexes; however, there has been limited success in achieving high transfection efficiency. Our hypothesis is that a factor affecting gene delivery efficiency is the mechanical response of the condensed complex. To begin to test this hypothesis, we directly measured the mechanical properties of DNA-carrier complexes using optical tweezers. Histidine-lysine (HK) polymer, Asparagine-lysine (NK) polymer and poly-L-lysine were used to form complexes with a single DNA molecule. As carriers were introduced, a sudden decrease in DNA extension occurrs at a force level which is defined as critical force (Fc). Fc is carrier and concentration dependent. Pulling revealed reduction in DNA extension length for HK-DNA complexes. The characteristics of force profiles vary by agent and can be dynamically manipulated by changes in environmental conditions such as ionic strength of the buffer as well as pH. Heparin can remove cationic reagents which are otherwise irreversibly bound to DNA. The implications for optimizing molecular interactions to enhance transfection efficiency will be discussed.

Lee, Amy; Zheng, Tai; Sucayan, Sarah; Chou, Szu-Ting; Tricoli, Lucas; Hustedt, Jason; Kahn, Jason; Mixson, A. James; Seog, Joonil

2013-03-01

171

Induction of sustained glycolytic oscillations in single yeast cells using microfluidics and optical tweezers  

NASA Astrophysics Data System (ADS)

Yeast glycolytic oscillations have been studied since the 1950s in cell free extracts and in intact cells. Until recently, sustained oscillations have only been observed in intact cells at the population level. The aim of this study was to investigate sustained glycolytic oscillations in single cells. Optical tweezers were used to position yeast cells in arrays with variable cell density in the junction of a microfluidic flow chamber. The microfluidic flow chambers were fabricated using soft lithography and the flow rates in the different inlet channels were individually controlled by syringe pumps. Due to the low Reynolds number, the solutions mixed by diffusion only. The environment in the junction of the chamber could thus be controlled by changing the flow rates in the inlet channels, with a complete change of environment within 2 s. The optimum position of the cell array was determined by simulations, to ensure complete coverage of the intended solution without any concentration gradients over the cell array. Using a DAPI filter set, the NADH auto fluorescence could be monitored in up to 100 cells simultaneously. Sustained oscillations were successfully induced in individual, isolated cells within specific flow rates and concentrations of glucose and cyanide. By changing the flow rates without changing the surrounding solution, it was found that the cell behavior was dependent on the concentration of chemicals in the medium rather than the flow rates in the range tested. Furthermore, by packing cells tightly, cell-to-cell interaction and synchronization could be studied.

Gustavsson, Anna-Karin; Adiels, Caroline B.; Goksör, Mattias

2012-10-01

172

Single-molecule kinetics under force: probing protein folding and enzymatic activity with optical tweezers  

NASA Astrophysics Data System (ADS)

Weak non-covalent bonds between and within single molecules govern many aspects of biological structure and function (e.g. DNA base-paring, receptor-ligand binding, protein folding, etc.) In living systems, these interactions are often subject to mechanical forces, which can greatly alter their kinetics and activity. My group develops and applies novel single-molecule manipulation techniques to explore and quantify these force-dependent kinetics. Using optical tweezers, we have quantified the force-dependent unfolding and refolding kinetics of different proteins, including the cytoskeletal protein spectrin in collaboration with E. Evans's group [1], and the A2 domain of the von Willebrand factor blood clotting protein in collaboration with T. Springer's group [2]. Furthermore, we have studied the kinetics of the ADAMTS13 enzyme acting on a single A2 domain, and have shown that physiolgical forces in the circulation can act as a cofactor for enzymatic cleavage, regulating hemostatic activity [2]. References: 1. E. Evans, K. Halvorsen, K. Kinoshita, and W.P. Wong, Handbook of Single Molecule Biophysics, P. Hinterdorfer, ed., Springer (2009). 2. X. Zhang, K. Halvorsen, C.-Z. Zhang, W.P. Wong, and T.A. Springer, Science 324 (5932), 1330-1334 (2009).

Wong, Wesley

2010-03-01

173

A survey of DNA looping and cleavage properties of different restriction enzymes using optical tweezers  

NASA Astrophysics Data System (ADS)

Of the more than 3500 known Type II REases, a small but growing number have been identified that require two copies of the enzyme's recognition site for activity. Each site is bound to one enzyme subunit, and the two subunits come together by thermodynamic DNA looping to form an active multimer that cleaves the DNA. When Ca^++ is replaced with Mg^++ however, the multimers usually ``staple'' the recognition sites together trapping the DNA loops. Using force measuring optical tweezers, we investigate the behavior of 16 different two-site REases from the Type IIe, Type IIf, and Type IIs subsets on single DNA molecules in the presence of Mg^++, Ca^++, and EDTA. We show that one-site and two-site REases may be rapidly discerned. By measuring the force needed to disrupt the loops in the presence of Ca^++, we elucidate various binding behaviors amongst the two-site REases, probing DNA-enzyme and/or enzymatic subunit-subunit affinity. For one enzyme, HpaII, the effect of [Ca^++] on activity is studied in detail.

Millin, Rachel

2005-03-01

174

Thermodynamic DNA Looping by a Two-Site Restriction Endonuclease Studied using Optical Tweezers  

NASA Astrophysics Data System (ADS)

Many enzyme-DNA interactions involve multimeric protein complexes that bind at two distant sites such that the DNA is looped. An example is the type IIe restriction enzyme Sau3AI, which requires two recognition sites to cleave the DNA. Here we study this process at the single DNA level using force measuring optical tweezers. We characterize cleavage rates of single DNA molecules in the presence of Sau3AI as a function of enzyme concentration, incubation time, and the fractional extension of the DNA molecule. Activity is completely inhibited by tensions of a few picoNewtons. By replacing Mg^2+ with Ca^2+, the Sau3AI dimers form but do not cleave the DNA, thus trapping DNA loops. We are able to pull apart these loops, measuring the force needed and the length of DNA released for each. We also characterize the number and length distributions of these loops as a function of incubation time and DNA fractional extension. The results of these studies are discussed in the context of a Brownian dynamics model of DNA looping.

Gemmen, Gregory J.

2005-03-01

175

The elasticity of single titin molecules using a two-bead optical tweezers assay.  

PubMed

Titin is responsible for the passive elasticity of the muscle sarcomere. The mechanical properties of skeletal and cardiac muscle titin were characterized in single molecules using a novel dual optical tweezers assay. Antibody pairs were attached to beads and used to select the whole molecule, I-band, A-band, a tandem-immunoglobulin (Ig) segment, and the PEVK region. A construct from the PEVK region expressing >25% of the full-length skeletal muscle isoform was chemically conjugated to beads and similarly characterized. By elucidating the elasticity of the different regions, we showed directly for the first time, to our knowledge, that two entropic components act in series in the skeletal muscle titin I-band (confirming previous speculations), one associated with tandem-immunoglobulin domains and the other with the PEVK region, with persistence lengths of 2.9 nm and 0.76 nm, respectively (150 mM ionic strength, 22 degrees C). Novel findings were: the persistence length of the PEVK component rose (0.4-2.7 nm) with an increase in ionic strength (15-300 mM) and fell (3.0-0.3 nm) with a temperature increase (10-60 degrees C); stress-relaxation in 10-12-nm steps was observed in the PEVK construct and hysteresis in the native PEVK region. The region may not be a pure random coil, as previously thought, but contains structured elements, possibly with hydrophobic interactions. PMID:15298915

Leake, Mark C; Wilson, David; Gautel, Mathias; Simmons, Robert M

2004-08-01

176

The Elasticity of Single Titin Molecules Using a Two-Bead Optical Tweezers Assay  

PubMed Central

Titin is responsible for the passive elasticity of the muscle sarcomere. The mechanical properties of skeletal and cardiac muscle titin were characterized in single molecules using a novel dual optical tweezers assay. Antibody pairs were attached to beads and used to select the whole molecule, I-band, A-band, a tandem-immunoglobulin (Ig) segment, and the PEVK region. A construct from the PEVK region expressing >25% of the full-length skeletal muscle isoform was chemically conjugated to beads and similarly characterized. By elucidating the elasticity of the different regions, we showed directly for the first time, to our knowledge, that two entropic components act in series in the skeletal muscle titin I-band (confirming previous speculations), one associated with tandem-immunoglobulin domains and the other with the PEVK region, with persistence lengths of 2.9 nm and 0.76 nm, respectively (150 mM ionic strength, 22°C). Novel findings were: the persistence length of the PEVK component rose (0.4–2.7 nm) with an increase in ionic strength (15–300 mM) and fell (3.0–0.3 nm) with a temperature increase (10–60°C); stress-relaxation in 10–12-nm steps was observed in the PEVK construct and hysteresis in the native PEVK region. The region may not be a pure random coil, as previously thought, but contains structured elements, possibly with hydrophobic interactions. PMID:15298915

Leake, Mark C.; Wilson, David; Gautel, Mathias; Simmons, Robert M.

2004-01-01

177

Optical tweezers reveal relationship between microstructure and nanoparticle penetration of pulmonary mucus  

PubMed Central

In this study, the mobility of nanoparticles in mucus and similar hydrogels as model systems was assessed to elucidate the link between microscopic diffusion behavior and macroscopic penetration of such gels. Differences in particle adhesion to mucus components were strongly dependent on particle coating. Particles coated with 2 kDa PEG exhibited a decreased adhesion to mucus components, whereas chitosan strongly increased the adhesion. Despite such mucoinert properties of PEG, magnetic nanoparticles of both coatings did not penetrate through native respiratory mucus, resisting high magnetic forces (even for several hours). However, model hydrogels were, indeed, penetrated by both particles in dependency of particle coating, obeying the theory of particle mobility in an external force field. Comparison of penetration data with cryogenic scanning EM images of mucus and the applied model systems suggested particularly high rigidity of the mucin scaffold and a broad pore size distribution in mucus as reasons for the observed particle immobilization. Active probing of the rigidity of mucus and model gels with optical tweezers was used in this context to confirm such properties of mucus on the microscale, thus presenting the missing link between micro- and macroscopical observations. Because of high heterogeneity in the size of the voids and pores in mucus, on small scales, particle mobility will depend on adhesive or inert properties. However, particle translocation over distances larger than a few micrometers is restricted by highly rigid structures within the mucus mesh. PMID:23091027

Kirch, Julian; Schneider, Andreas; Abou, Berengere; Hopf, Alexander; Schaefer, Ulrich F.; Schneider, Marc; Schall, Christian; Wagner, Christian; Lehr, Claus-Michael

2012-01-01

178

On chip single-cell separation and immobilization using optical tweezers and thermosensitive hydrogel.  

PubMed

A novel approach appropriate for rapid separation and immobilization of a single cell by concomitantly utilizing laser manipulation and locally thermosensitive hydrogelation is proposed in this paper. We employed a single laser beam as optical tweezers for separating a target cell and locating it adjacent to a fabricated, transparent micro heater. Simultaneously, the target cell is immobilized or partially entrapped by heating the thermosensitive hydrogel with the micro heater. The state of the thermosensitive hydrogel can be switched from sol to gel and gel to sol by controlling the temperature through heating and cooling by the micro heater. After other unwanted cells are removed by the high-speed cleaning flow in the microchannel, the entrapped cell is successfully isolated. It is possible to collect the immobilized target cell for analysis or culture by switching off the micro heater and releasing the cell from the entrapment. We demonstrated that the proposed approach is feasible for rapid manipulation, immobilization, cleaning, isolation and extraction of a single cell. The experimental results are shown here. PMID:16286972

Arai, Fumihito; Ng, Chinaik; Maruyama, Hisataka; Ichikawa, Akihiko; El-Shimy, Haitham; Fukuda, Toshio

2005-12-01

179

Optical tweezers reveal force plateau and internal friction in PEG-induced DNA condensation.  

PubMed

The simplified artificial environments in which highly complex biological systems are studied do not represent the crowded, dense, salty, and dynamic environment inside the living cell. Consequently, it is important to investigate the effect of crowding agents on DNA. We used a dual-trap optical tweezers instrument to perform force spectroscopy experiments at pull speeds ranging from 0.3 to 270 ?m/s on single dsDNA molecules in the presence of poly(ethylene glycol) (PEG) and monovalent salt. PEG of sizes 1,500 and 4,000 Da condensed DNA, and force-extension data contained a force plateau at approximately 1 pN. The level of the force plateau increased with increasing pull speed. During slow pulling the dissipated work increased linearly with pull speed. The calculated friction coefficient did not depend on amount of DNA incorporated in the condensate, indicating internal friction is independent of the condensate size. PEG300 had no effect on the dsDNA force-extension curve. The force plateau implies that condensation induced by crowding agents resembles condensation induced by multivalent cations. PMID:24477280

Ojala, Heikki; Ziedaite, Gabija; Wallin, Anders E; Bamford, Dennis H; Hæggström, Edward

2014-03-01

180

Effect of salicylate on outer hair cell plasma membrane viscoelasticity: studies using optical tweezers  

NASA Astrophysics Data System (ADS)

The plasma membrane (PM) of mammalian outer hair cells (OHCs) generates mechanical forces in response to changes in the transmembrane electrical potential. The resulting change in the cell length is known as electromotility. Salicylate (Sal), the anionic, amphipathic derivative of aspirin induces reversible hearing loss and decreases electromotile response of the OHCs. Sal may change the local curvature and mechanical properties of the PM, eventually resulting in reduced electromotility or it may compete with intracellular monovalent anions, particularly Cl-, which are essential for electromotility. In this work we have used optical tweezers to study the effects of Sal on viscoelastic properties of the OHC PM when separated from the underlying composite structures of the cell wall. In this procedure, an optically trapped microsphere is brought in contact with PM and subsequently pulled away to form a tether. We measured the force exerted on the tether as a function of time during the process of tether growth at different pulling rates. Effective tether viscosity, steady-state tethering force extrapolated to zero pulling rate, and the time constant for tether growth were estimated from the measurements of the instantaneous tethering force. The time constant for the tether growth measured for the OHC basal end decreased 1.65 times after addition of 10 mM Sal, which may result from an interaction between Sal and cholesterol, which is more prevalent in the PM of OHC basal end. The time constants for the tether growth calculated for the OHC lateral wall and control human embryonic kidney cells as well as the other calculated viscoelastic parameters remained the same after Sal perfusion, favoring the hypothesis of competitive inhibition of electromotility by salicylate.

Ermilov, Sergey A.; Brownell, William E.; Anvari, Bahman

2004-06-01

181

Optical tweezers for single molecule force spectroscopy on bacterial adhesion organelles  

NASA Astrophysics Data System (ADS)

Instrumentation and methodologies for single molecule force spectroscopy on bacterial adhesion organelles by the use of force measuring optical tweezers have been developed. A thorough study of the biomechanical properties of fimbrial adhesion organelles expressed by uropathogenic E. coli, so-called pili, is presented. Steady-state as well as dynamic force measurements on P pili, expressed by E. coli causing pyelonephritis, have revealed, among other things, various unfolding and refolding properties of the helical structure of P pili, the PapA rod. Based on these properties an energy landscape model has been constructed by which specific biophysical properties of the PapA rod have been extracted, e.g. the number of subunits, the length of a single pilus, bond lengths and activation energies for bond opening and closure. Moreover, long time repetitive measurements have shown that the rod can be unfolded and refolded repetitive times without losing its intrinsic properties. These properties are believed to be of importance for the bacteria's ability to maintain close contact with host cells during initial infections. The results presented are considered to be of importance for the field of biopolymers in general and the development of new pharmaceuticals towards urinary tract infections in particular. The results show furthermore that the methodology can be used to gain knowledge of the intrinsic biomechanical function of adhesion organelles. The instrumentation is currently used for characterization of type 1 pili, expressed by E. coli causing cystitis, i.e. infections in the bladder. The first force spectrometry investigations of these pili will be presented.

Andersson, Magnus; Axner, Ove; Uhlin, Bernt Eric; Fällman, Erik

2006-08-01

182

Force Mapping during the Formation and Maturation of Cell Adhesion Sites with Multiple Optical Tweezers  

PubMed Central

Focal contacts act as mechanosensors allowing cells to respond to their biomechanical environment. Force transmission through newly formed contact sites is a highly dynamic process requiring a stable link between the intracellular cytoskeleton and the extracellular environment. To simultaneously investigate cellular traction forces in several individual maturing adhesion sites within the same cell, we established a custom-built multiple trap optical tweezers setup. Beads functionalized with fibronectin or RGD-peptides were placed onto the apical surface of a cell and trapped with a maximum force of 160 pN. Cells form adhesion contacts around the beads as demonstrated by vinculin accumulation and start to apply traction forces after 30 seconds. Force transmission was found to strongly depend on bead size, surface density of integrin ligands and bead location on the cell surface. Highest traction forces were measured for beads positioned on the leading edge. For mouse embryonic fibroblasts, traction forces acting on single beads are in the range of 80 pN after 5 minutes. If two beads were positioned parallel to the leading edge and with a center-to-center distance less than 10 µm, traction forces acting on single beads were reduced by 40%. This indicates a spatial and temporal coordination of force development in closely related adhesion sites. We also used our setup to compare traction forces, retrograde transport velocities, and migration velocities between two cell lines (mouse melanoma and fibroblasts) and primary chick fibroblasts. We find that maximal force development differs considerably between the three cell types with the primary cells being the strongest. In addition, we observe a linear relation between force and retrograde transport velocity: a high retrograde transport velocity is associated with strong cellular traction forces. In contrast, migration velocity is inversely related to traction forces and retrograde transport velocity. PMID:23372781

Schwingel, Melanie; Bastmeyer, Martin

2013-01-01

183

Direct measurement of the dielectrophoresis forces acting on micro-objects using optical tweezers and a simple microfluidic chip  

NASA Astrophysics Data System (ADS)

We constructed a reliable frequency-dependent dielectrophoretic (DEP) force measurement system based on optical tweezers and a microfluidic chip. Using this system, we directly measured the frequency-dependent DEP forces acting on polystyrene beads while varying various parameters, which were all verified by theoretical simulations. We also investigated the DEP characteristics of non-functionalized and carboxyl-functionalized polystyrene beads in solutions with different conductivities by associating the measured crossover frequencies with a theoretical DEP model. This system can be used as a quantifying tool for surface conductance assays by characterizing the DEP forces acting on micro-objects in various experimental conditions.

Park, In Soo; Park, Se Hee; Yoon, Dae Sung; Lee, Sang Woo; Kim, Beop-Min

2014-09-01

184

Microfluidic growth chambers with optical tweezers for full spatial single-cell control and analysis of evolving microbes.  

PubMed

Single-cell analysis in microfluidic systems has opened up new possibilities in biotechnological research enabling us to deal with large eukaryotic cells and even small bacteria. In particular, transient investigations in laminar flow or diffusive environments can be performed to unravel single cell behaviour. Up to now, most systems have been limited with respect to precise cell inoculation and sampling methods. Individual cell selection and manipulations have now been made possible by combining laser tweezers with microfluidic cell cultivation environments specifically tailored for micrometre-sized bacteria. Single cells were optically seeded into various micrometre-sized growth sites arranged in parallel. During cultivation, single-cell elongation, morphology and growth rates were derived from single cells and microcolonies of up to 500 cells. Growth of irradiated bacteria was not impaired by minimizing the exposed laser dosage as confirmed by exceptional growth rates. In fact, Escherichia coli exhibited doubling times of less than 20min. For the first time, a filamentous Escherichia coli WT (MG1655) was safely relocated from its growing microcolony by laser manipulations. The cell was transferred to an empty cultivation spot allowing single-cell growth and morphology investigations. Contrary to previous discussions, the filamentous E. coli exhibited normal cell morphology and division after a few generations. This combination of optical tweezers and single-cell analysis in microfluidics adds a new degree of freedom to microbial single-cell analysis. PMID:24041615

Probst, Christopher; Grünberger, Alexander; Wiechert, Wolfgang; Kohlheyer, Dietrich

2013-12-01

185

Single-cell adhesion probed in-situ using optical tweezers: A case study with Saccharomyces cerevisiae  

NASA Astrophysics Data System (ADS)

A facile method of using optical trapping to measure cell adhesion forces is presented and applied to the adhesion of Saccharomyces cerevisiae on glass, in contact with solutions of different compositions. Trapping yeast cells with optical tweezers (OT) is not perturbed by cell wall deformation or cell deviation from a spherical shape. The trapping force calibration requires correction not only for the hydrodynamic effect of the neighboring wall but also for spherical aberrations affecting the focal volume and the trap stiffness. Yeast cells trapped for up to 5 h were still able to undergo budding but showed an increase of doubling time. The proportion of adhering cells showed the expected variation according to the solution composition. The detachment force varied in the same way. This observation and the fact that the detachment stress was exerted parallel to the substrate surface point to the role of interactions involving solvated macromolecules. Both the proportion of adhering cells and the removal force showed a distribution which, in our experimental conditions, must be attributed to a heterogeneity of surface properties at the cell level or at the subcellular scale. As compared with magnetic tweezers, atomic force microscopy, and more conventional ways of studying cell adhesion (shear-flow cells), OT present several advantages that are emphasized in this paper.

Castelain, Mickaël; Rouxhet, Paul G.; Pignon, Frédéric; Magnin, Albert; Piau, Jean-Michel

2012-06-01

186

A strategy for characterizing the mixing state of immiscible aerosol components and the formation of multiphase aerosol particles through coagulation.  

PubMed

We demonstrate that the coagulation of two aerosol droplets of different chemical composition can be studied directly through the unique combination of optical tweezers and Raman spectroscopy. Multiple optical traps can be established, allowing the manipulation of multiple aerosol droplets. Spontaneous Raman scattering allows the characterization of droplet composition and mixing state, permitting the phase segregation of immiscible components in multiphase aerosol to be investigated with spatial resolution. Stimulated Raman scattering allows the integrity of the droplet and uniformity of refractive index to be probed. The combination of these spectroscopic probes with optical tweezers is shown to yield unprecedented detail in studies of the coagulation of decane and water droplets. PMID:16836313

Mitchem, Laura; Buajarern, Jariya; Ward, Andrew D; Reid, Jonathan P

2006-07-20

187

A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells  

Microsoft Academic Search

The dynamics of cell surface membrane proteins plays an important role in cell-cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where optical tweezers are used to trap cells and precisely control in space and time the initiation of interactions

M. I. Snijder-Van As; B. Rieger; B. H. G. M. Joosten; V. Subramaniam; C. G. Figdor; J. S. Kanger

2009-01-01

188

Optical Tweezers and Optical Trapping Improved for Future Automated Micromanipulation and Characterization  

NASA Technical Reports Server (NTRS)

Optical trap arrays are being developed at the NASA Glenn Research Center for holding, manipulating, and optically interrogating arrays of nanotube sensors. The trap arrays, for example, might be used to arrange arrays of chemical sensors for insertion onto a chip in liquid, air, and vacuum environments. Neural-network-controlled spatial light modulators (SLMs) are to generate and control the trap positions and trap profiles in three dimensions.

Wrbanek, Susan Y.; Decker, Arthur J.

2005-01-01

189

Using optical tweezers for measuring the interaction forces between human bone cells and implant surfaces: System design and force calibration  

NASA Astrophysics Data System (ADS)

Optical tweezers were used to study the interaction and attachment of human bone cells to various types of medical implant materials. Ideally, the implant should facilitate cell attachment and promote migration of the progenitor cells in order to decrease the healing time. It is therefore of interest, in a controlled manner, to be able to monitor the cell adhesion process. Results from such studies would help foresee the clinical outcome of integrating medical implants. The interactions between two primary cell culture models, human gingival fibroblasts and bone forming human osteoblast cells, and three different implant materials, glass, titanium, and hydroxyapatite, were studied. A novel type of optical tweezers, which has a newly designed quadrant detector and a powerful 3W laser was constructed and force calibrated using two different methods: one method in which the stiffness of the optical trap was obtained by monitoring the phase lag between the trap and the moved object when imposing a forced oscillation on the trapped object and another method in which the maximum trapping force was derived from the critical velocity at which the object escapes the trap. Polystyrene beads as well as cells were utilized for the calibrations. This is the first time that cells have been used directly for these types of force calibrations and, hence, direct measurements of forces exerted on cells can be performed, thus avoiding the difficulties often encountered when translating the results obtained from cell measurements to the calibrations obtained with reference materials. This more straightforward approach represents an advantage in comparison to established methods.

Andersson, Martin; Madgavkar, Ashwin; Stjerndahl, Maria; Wu, Yanrong; Tan, Weihong; Duran, Randy; Niehren, Stefan; Mustafa, Kamal; Arvidson, Kristina; Wennerberg, Ann

2007-07-01

190

Optical modeling of stratopheric aerosols - Present status  

NASA Technical Reports Server (NTRS)

A stratospheric aerosol optical model is developed which is based on a size distribution conforming to direct measurements. Additional constraints are consistent with large data sets of independently measured macroscopic aerosol properties such as mass and backscatter. The period under study covers background as well as highly disturbed volcanic conditions and an altitude interval ranging from the tropopause to about 30 km. The predictions of the model are used to form a basis for interpreting and intercomparing several diverse types of stratospheric aerosol measurement.

Rosen, J. M.; Hofmann, D. J.

1986-01-01

191

Applying combined optical tweezers and fluorescence microscopy technologies to manipulate cell adhesions for cell-to-cell interaction study.  

PubMed

Cell-to-cell interactions are important for the regulation of various cell activities, such as proliferation, differentiation, and apoptosis. This paper presents an approach to studying cell-to-cell interactions at a single-cell level through manipulating cell adhesions with optical tweezers. Experiments are performed on leukemia cancer cells and stromal cells to demonstrate the feasibility of this method. After the adhesion properties of leukemia cells on stromal cells are characterized, fluorescence intensity is used as a label to study the Wnt signaling pathway of leukemia cells. The activities of the Wnt signaling pathway of K562 cells on M210B4 and HS5 cells are examined based on fluorescence analysis. The reliability of the fluorescence imaging is confirmed through comparison with traditional flow cytometry analysis. The proposed approach will offer new avenues to investigate otherwise inaccessible mechanisms in cell-to-cell interactions. PMID:23549881

Gou, Xue; Han, Ho Chun; Hu, Songyu; Leung, Anskar Y H; Sun, Dong

2013-08-01

192

The interaction of lipopolysaccharide-coated polystyrene particle with membrane receptor proteins on macrophage measured by optical tweezers  

NASA Astrophysics Data System (ADS)

Lipopolysaccharide (LPS) is one of the cell wall components of Gram-positive bacteria recognized by and interacted with receptor proteins such as CD14 on macrophage cells. Such a process plays an important role in our innate immune system. In this paper, we report the application of optical tweezers (? = 1064nm Gaussian beam focused by a water-immersed objective lens with N.A. = 1.0) to the study of the dynamics of the binding of a LPS-coated polystyrene particle (diameter = 1.5?m) onto the plasma membrane of a macrophage cell. We demonstrated that the binding rate increased significantly when the macrophage cell was pre-treated with the extract of Reishi polysaccharides (EORP) which has been shown to enhance the cell surface expression of CD14 (receptor of LPS) on macrophage cells.

Wei, Ming-Tzo; Hua, Kuo-Feng; Hsu, Jowey; Karmenyan, Artashes; Hsu, Hsien-Yeh; Chiou, Arthur

2006-08-01

193

Optical measurement of medical aerosol media parameters  

NASA Astrophysics Data System (ADS)

The problem of aerosol media parameters measurements are presented in the work and these media are used for the treatment of the patients with bronchial asthma moreover we show the results of the development and the concentration and dispersity of the particles for the long-term monitoring under such conditions when the aggressive surroundings are available. The system for concentration measurements is developed, which consists of two identical photometers permitting to carry out the measurements of the transmission changes and the light dispersion depending on the concentration of the particles. The given system permits to take into account the error, connected with the deposition of the salt particles on the optical windows and the mirrors in the course of the long-term monitoring. For the controlling of the dispersity of the aggressive media aerosols the optical system is developed and used for the non-stop analysis of the Fure-spectra of the aerosols which deposit on the lavsan film. The registration of the information is performed with the help of the rule of the photoreceivers or CCD-chamber which are located in the Fure- plane. With the help of the developed optical system the measurements of the concentration and dispersity of the rock-salt aerosols were made in the medical mines of Solotvino (Ukraine) and in the artificial chambers of the aerosol therapy.

Sharkany, Josif P.; Zhytov, Nikolay B.; Sichka, Mikhail J.; Lemko, Ivan S.; Pintye, Josif L.; Chonka, Yaroslav V.

2000-07-01

194

Aerosol optical thickness and atmospheric path radiance  

NASA Technical Reports Server (NTRS)

Simultaneous measurements from the ground of the spectral optical thickness and the atmospheric path radiance from over 30 sites located in many parts of the world and affected by several different aerosol types are reported. These measurements are used to derive the relationship between the optical thickness and the path radiance for a single viewing and illumination geometry and to discuss its implications on remote sensing observations. It is shown that simple measurements performed from the ground can yield empirical relationships that can be used to check some of the common but not validated assumptions about the particle homogeneity, sphericity, composition, and size distribution used in remote sensing models and in estimates of the radiative effects of aerosol. The results are used to test concepts of atmospheric corrections and remote sensing of aerosol from space.

Kaufman, Yoram J.

1993-01-01

195

Trapping and two-photon fluorescence excitation of microscopic objects using ultrafast single-fiber optical tweezers  

NASA Astrophysics Data System (ADS)

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample.

Mishra, Yogeshwar N.; Ingle, Ninad; Mohanty, Samarendra K.

2011-10-01

196

Trapping and two-photon fluorescence excitation of microscopic objects using ultrafast single-fiber optical tweezers.  

PubMed

Analysis of trapped microscopic objects using fluorescence and Raman spectroscopy is gaining considerable interest. We report on the development of single fiber ultrafast optical tweezers and its use in simultaneous two-photon fluorescence (TPF) excitation of trapped fluorescent microscopic objects. Using this method, trapping depth of a few centimeters was achieved inside a colloidal sample with TPF from the trapped particle being visible to the naked eye. Owing to the propagation distance of the Bessel-like beam emerging from the axicon-fiber tip, a relatively longer streak of fluorescence was observed along the microsphere length. The cone angle of the axicon was engineered so as to provide better trapping stability and high axial confinement of TPF. Trapping of the floating objects led to stable fluorescence emission intensity over a long period of time, suitable for spectroscopic measurements. Furthermore, the stability of the fiber optic trapping was confirmed by holding and maneuvering the fiber by hand so as to move the trapped fluorescent particle in three dimensions. Apart from miniaturization capability into lab-on-a-chip microfluidic devices, the proposed noninvasive microaxicon tipped optical fiber can be used in multifunctional mode for in-depth trapping, rotation, sorting, and ablation, as well as for two-photon fluorescence excitation of a motile sample. PMID:22029347

Mishra, Yogeshwar N; Ingle, Ninad; Mohanty, Samarendra K

2011-10-01

197

Using a new aerosol relative optical thickness concept to identify aerosol particle species  

NASA Astrophysics Data System (ADS)

We developed an aerosol relative optical thickness concept and then established an effective aerosol particle recognition model by analyzing variations in aerosol optical thicknesses in Beijing between 2001 and 2006. The accuracy of the model was verified using inverse calculations. The aerosol particle types and size distributions were assessed for several typical atmospheric phenomena, and the characteristic relative optical thicknesses for several typical aerosols were identified. Finally, we analyzed annual variations in the aerosol particle species in several eastern Asian cities using the model.

Yuan, Yuan; Shuai, Yong; Li, Xiao-Wei; Liu, Bin; Tan, He-Ping

2014-12-01

198

An emerging ground-based aerosol climatology: Aerosol optical depth from AERONET  

Microsoft Academic Search

Long-term measurements by the AERONET program of spectral aerosol optical depth, precipitable water, and derived Angstrom exponent were analyzed and compiled into an aerosol optical properties climatology. Quality assured monthly means are presented and described for 9 primary sites and 21 additional multiyear sites with distinct aerosol regimes representing tropical biomass burning, boreal forests, midlatitude humid climates, midlatitude dry climates,

B. N. Holben; D. Tanré; A. Smirnov; T. F. Eck; I. Slutsker; N. Abuhassan; W. W. Newcomb; J. S. Schafer; B. Chatenet; F. Lavenu; Y. J. Kaufman; J. Vande Castle; A. Setzer; B. Markham; D. Clark; R. Frouin; R. Halthore; A. Karneli; N. T. O'Neill; C. Pietras; R. T. Pinker; K. Voss; G. Zibordi

2001-01-01

199

A new technique for high sensitive detection of rotational motion in optical tweezers by a differential measurement of backscattered intensity  

NASA Astrophysics Data System (ADS)

Asymmetric particles, such as biological cells, often experience torque under optical tweezers due to birefringence or unbalanced scattering forces, which makes precise determination of the torque crucial for calibration and control of the particles. The estimate of torque relies on the accurate measurement of rotational motion, which has been achieved by various techniques such as measuring the intensity fluctuations of the forward scattered light, or the polarization component orthogonal to the trapping light polarization in plasmonic nanoparticles and vaterite crystals. Here we present a simple yet high sensitive technique to measure rotation of such an asymmetric trapped particle by detecting the light backscattered onto a quadrant photodiode, and subtracting the signals along the two diagonals of the quadrants. This automatically suppresses the common mode translational signal obtained by taking the difference signal of the adjacent quadrants, while amplifying the rotational signal. Using this technique, we obtain a S/N of 200 for angular displacement of a trapped micro-rod by 5 degrees, which implies a sensitivity of 50 mdeg with S/N of 2. The technique is thus independent of birefringence and polarization properties of the asymmetric particle and depends only on the scattering cross-section.

Roy, Basudev; Bera, Sudipta K.; Mondal, Argha; Banerjee, Ayan

2014-09-01

200

Laser microbeams for DNA damage induction, optical tweezers for the search on blood pressure relaxing drugs: contributions to ageing research  

NASA Astrophysics Data System (ADS)

One essential cause of human ageing is the accumulation of DNA damages during lifetime. Experimental studies require quantitative induction of damages and techniques to visualize the subsequent DNA repair. A new technique, the "immuno fluorescent comet assay", is used to directly visualize DNA damages in the microscope. Using DNA repair proteins fluorescently labeled with green fluorescent protein, it could be shown that the repair of the most dangerous DNA double strand breaks starts with the inaccurate "non homologous end joining" pathway and only after 1 - 1 ½ minutes may switch to the more accurate "homologous recombination repair". One might suggest investigating whether centenarians use "homologous recombination repair" differently from those ageing at earlier years and speculate whether it is possible, for example by nutrition, to shift DNA repair to a better use of the error free pathway and thus promote healthy ageing. As a complementary technique optical tweezers, and particularly its variant "erythrocyte mediated force application", is used to simulate the effects of blood pressure on HUVEC cells representing the inner lining of human blood vessels. Stimulating one cell induces in the whole neighbourhood waves of calcium and nitric oxide, known to relax blood vessels. NIFEDIPINE and AMLODIPINE, both used as drugs in the therapy of high blood pressure, primarily a disease of the elderly, prolong the availability of nitric oxide. This partially explains their mode of action. In contrast, VERAPAMILE, also a blood pressure reducing drug, does not show this effect, indicating that obviously an alternative mechanism must be responsible for vessel relaxation.

Grigaravicius, P.; Monajembashi, S.; Hoffmann, M.; Altenberg, B.; Greulich, K. O.

2009-08-01

201

Studies of viral DNA packaging motors with optical tweezers: a comparison of motor function in bacteriophages ?29, ?, and T4  

NASA Astrophysics Data System (ADS)

A key step in the assembly of many viruses is the packaging of double-stranded DNA into a viral procapsid (an empty protein shell) by the action of an ATP-powered portal motor complex. We have developed methods to measure the packaging of single DNA molecules into single viral proheads in real time using optical tweezers. We can measure DNA binding and initiation of translocation, the DNA translocation dynamics, and the filling of the capsid against resisting forces. In addition to studying bacteriophage ?29, we have recently extended these methods to study the E. coli bacteriophages ? and T4, two important model systems in molecular biology. The three systems have different capsid sizes/shapes, genome lengths, and biochemical and structural differences in their packaging motors. Here, we compare and contrast these three systems. We find that all three motors translocate DNA processively and generate very large forces, each exceeding 50 piconewtons, ~20x higher force than generated by the skeletal muscle myosin 2 motor. This high force generation is required to overcome the forces resisting the confinement of the stiff, highly charged DNA at high density within the viral capsids. However, there are also striking differences between the three motors: they exhibit different DNA translocation rates, degrees of static and dynamic disorder, responses to load, and pausing and slipping dynamics.

Smith, Douglas E.; Fuller, Derek N.; Raymer, Dorian M.; Rickgauer, Peter; Grimes, Shelley; Jardine, Paul J.; Anderson, Dwight L.; Catalano, Carlos E.; Kottadiel, Vishal; Rao, Venigalla B.

2007-09-01

202

DNA looping and cleavage by restriction enzymes studied by manipulation of single DNA molecules with optical tweezers  

NASA Astrophysics Data System (ADS)

Looping and cleavage of single DNA molecules by the two-site restriction endonuclease Sau3AI were measured with optical tweezers. A DNA template containing many recognition sites was used, permitting loop sizes from ~10 to 10,000 basepairs. At high enzyme concentration cleavage events were detected within 5 seconds and nearly all molecules were cleaved within 5 minutes. Activity decreased ~10-fold as the DNA tension was increased from 0.03 to 0.7 pN. Substituting Ca 2+ for Mg 2+ blocked cleavage, permitting measurement of stable loops. At low tension, the initial rates of cleavage and looping were similar (~0.025 s -1 at 0.1 pN), suggesting that looping is rate limiting. Short loops formed more rapidly than long loops. The optimum size decreased from ~250 to 45 bp and the average number of loops (in 1 minute) from 4.2 to 0.75 as tension was increased from 0.03 to 0.7 pN. No looping was detected at 5 pN. These findings are in qualitative agreement with recent theoretical predictions considering only DNA mechanics, but we observed weaker suppression with tension and smaller loop sizes. Our results suggest that the span and elasticity of the protein complex and protein-induced DNA bending and wrapping play an important role.

Smith, Douglas E.; Gemmen, Gregory J.; Millin, Rachel

2006-08-01

203

Mechanism of a viral DNA packaging motor studied by characterization of biochemical mutants via optical tweezers measurements  

NASA Astrophysics Data System (ADS)

Optical tweezers measurements were employed to directly observe viral DNA packaging in wild type and packaging mutants of bacteriophage lambda. Several key findings are reported here: DNA packaging by purified wild type lambda motors was measured for the first time, showing nearly identical behavior in packaging DNA to crude extracts of terminase components. A slow packaging lambda mutant, T194M, was found to package DNA at ~10× slower velocity than wild type. Meanwhile another packaging mutant Y46F was found to package DNA slower than the wild type (60-70% the velocity of the wild type velocity) as well as slipping >10x more frequently (per length of DNA) than wild type. Another mutant (K84A) showed slower packaging (60-70% the velocity of wildtype), but displayed slipping and pausing behavior similar to wild type. Finally the pausing and slipping dependence on length of DNA packaged of the various terminases studied was discovered, suggesting further structural defects of the mutants that are detrimental to translocation. These studies confirm the location of an ATPase center in the N-terminal portion of gpA which is responsible for translocation of dsDNA.

Tsay, James M.; Sippy, Jean; Feiss, Michael; Smith, Douglas E.

2008-08-01

204

A Polypeptide-DNA Hybrid with Selective Linking Capability Applied to Single Molecule Nano-Mechanical Measurements Using Optical Tweezers  

PubMed Central

Many applications in biosensing, biomaterial engineering and single molecule biophysics require multiple non-covalent linkages between DNA, protein molecules, and surfaces that are specific yet strong. Here, we present a novel method to join proteins and dsDNA molecule at their ends, in an efficient, rapid and specific manner, based on the recently developed linkage between the protein StrepTactin (STN) and the peptide StrepTag II (ST). We introduce a two-step approach, in which we first construct a hybrid between DNA and a tandem of two STs peptides (tST). In a second step, this hybrid is linked to polystyrene bead surfaces and Maltose Binding Protein (MBP) using STN. Furthermore, we show the STN-tST linkage is more stable against forces applied by optical tweezers than the commonly used biotin-Streptavidin (STV) linkage. It can be used in conjunction with Neutravidin (NTV)-biotin linkages to form DNA tethers that can sustain applied forces above 65 pN for tens of minutes in a quarter of the cases. The method is general and can be applied to construct other surface-DNA and protein-DNA hybrids. The reversibility, high mechanical stability and specificity provided by this linking procedure make it highly suitable for single molecule mechanical studies, as well as biosensing and lab on chip applications. PMID:23336001

Tans, Sander J.

2013-01-01

205

Aerosol optical depth characteristics in Yinchuan area  

NASA Astrophysics Data System (ADS)

Sand dust aerosol is the main component of aerosol in troposphere atmosphere of East Asia, which can produce the extensive influence on the ecosystem, atmosphere environment and atmosphere chemistry through intensive sand dust weather process. For investigation of the aerosol optical depth (AOD) and its temporal-spatial evolution over this area, a series of observation experiments were carried out by a sun photometer CE-318 located at Beifang University of Nationality( 106°E, 38°29'N ), Yinchuan Ningxia province of China from September 2012 to April 2013 and many direct solar radiation datum were obtained. The experiments results were analyzed in detail and some conclusions are obtained as follows: (1) For daily evolution of AOD, the variation trend are divided into four types: ?the AOD values are relatively steady in whole day; ? the AOD values increase from morning to afternoon; ? the AOD values are greater at noon than that in the morning and afternoon; ?there is a peak in the variation trends of AOD from 9:00~12:00 in the morning, but it is small at other time. (2) For month evolution, the minimum AOD average value appears in September and the maximum one appears in April. (3) For the seasonal changes trend, the average AOD values in the April are bigger than that in the autumn. (4) In addition, during the observation period, one dust weather process was observed and the change characteristic of AOD of dust aerosol was obtained and analyzed.

Zhang, Yaya; Mao, Jiandong; Rao, Zhimin; Zhang, Fan

2013-08-01

206

Are electron tweezers possible?  

PubMed

Positively answering the question in the title, we demonstrate in this work single electron beam trapping and steering of 20-300nm solid Al nanoparticles generated inside opaque submicron-sized molten Al-Si eutectic alloy spheres. Imaging of solid nanoparticles and liquid alloy in real time was performed using energy filtering in an analytical transmission electron microscope (TEM). Energy-filtering TEM combined with valence electron energy-loss spectroscopy enabled us to investigate in situ nanoscale transformations of the internal structure, temperature dependence of plasmon losses, and local electronic and optical properties under melting and crystallization of individual binary alloy particles. For particles below 20nm in size, enhanced vibrations of the dynamic solid-liquid interface due to instabilities near the critical threshold were observed just before melting. The obtained results indicate that focused electron beams can act as a tool for manipulation of metal nanoparticles by transferring linear and angular mechanical momenta. Such thermally assisted electron tweezers can be utilized for touchless manipulation and processing of individual nano-objects and potentially for fabrication of assembled nanodevices with atomic level sensitivity and lateral resolution provided by modern electron optical systems. This is by three orders of magnitude better than for light microscopy utilized in conventional optical tweezers. New research directions and potential applications of trapping and tracking of nano-objects by focused electron beams are outlined. PMID:21946000

Oleshko, Vladimir P; Howe, James M

2011-11-01

207

Contribution of different aerosol species to the global aerosol extinction optical thickness: Estimates from model results  

Microsoft Academic Search

We combine global distributions of aerosol loading resulting from transport models for soil dust, sulfate, sea salt, and carbonaceous aerosol. From the aerosol distributions we estimate optical thickness and compare them with Sun photometer measurements and satellite retrievals, thereby revealing problems with both model results and comparisons with such measurements. Globally, sulfate, dust, and carbonaceous particles appear to contribute equally

Ina Tegen; Peter Hollrig; Mian Chin; Inez Fung; Daniel Jacob; Joyce Penner

1997-01-01

208

tweezercalib 2.1: Faster version of MatLab package for precise calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

New version program summaryTitle of program: tweezercalib Catalogue identifier:ADTV_v2_1 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV_v2_1 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:no No. of lines in distributed program, including test data, etc.: 134 188 No. of bytes in distributed program, including test data, etc.: 1 050 368 Distribution format: tar.gz Programming language: MatLab (Mathworks Inc.), standard license Computer:General computer running MatLab (Mathworks Inc.) Operating system:Windows2000, Windows-XP, Linux RAM:Of order four times the size of the data file Classification:3, 4.14, 18, 23 Catalogue identifier of previous version: ADTV_v2_0 Journal reference of previous version: Comput. Phys. Comm. 174 (2006) 518 Does the new version supersede the previous version?: yes Nature of problem:Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system. The theoretical underpinnings of the procedure may be found in Ref. [3]. Solution method:Elimination of cross-talk between quadrant photo-diodes, output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects; Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for "virtual filtering" caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting with custom written routines based on Refs. [1,2]. Statistical support for fit is given, with several plots facilitating inspection of consistency and quality of data and fit. Reasons for the new version:Recent progress in the field has demonstrated a better approximation of the formula for the theoretical power spectrum with corrections due to frequency dependence of motion and distance to a surface nearby. Summary of revisions:The expression for the theoretical power spectrum when accounting for corrections to Stokes law, P(f), has been updated to agree with a better approximation of the theoretical spectrum, as discussed in Ref. [4] The units of the kinematic viscosity applied in the program is now stated in the input window. Greek letters and exponents are inserted in the input window. The graphical output has improved: The figures now bear a meaningful title and four figures that test the quality of the fit are now combined in one figure with four parts. Restrictions: Data should be positions of bead doing Brownian motion while held by optical tweezers. For high precision in final results, data should be time series measured over a long time, with sufficiently high experimental sampling rate; The sampling rate should be well above the characteristic frequency of the trap, the so-called corner frequency. Thus, the sampling frequency should typically be larger than 10 kHz. The Fast Fourier Transform used works optimally when the time series contain 2 data points, and long measurement time is obtained with n>12-15. Finally, the optics should be set to ensure a harmonic trapping potential in the range of positions visited by the bead. The fitting procedure checks for harmonic potential. Running time:seconds ReferencesJ. Nocedal, Y.x. Yuan, Combining trust region and line search techniques, Technical Report OTC 98/04, Optimization Technology Center, 1998. W.H. Press, B.P. Flannery, S.A. Teukolsky, W.T. Vetterling, Numerical Recipes. The Art of Scientific Computing, Cambridge University Press, Cambridge, 1986. (The theoretical underpinnings for the procedure) K. Berg

Hansen, Poul Martin; Tolic-Nørrelykke, Iva Marija; Flyvbjerg, Henrik; Berg-Sørensen, Kirstine

2006-10-01

209

Optical Properties of Titan's Aerosol Analogues  

NASA Astrophysics Data System (ADS)

In the upper Titan's atmosphere its main constituents, CH4 and N2, are photolyzed and radiolyzed by solar photons and magnetospheric electrons. The primary products of these chemical interactions evolve to heavier organic compounds which are likely to associate to form the haze layers observed on Titan's upper atmosphere. Different theories and models have been used to explain the physical, chemical and optical properties of the haze material, but only with limited success. Among the parameters involved in these models, the complex refractive index is one of the most critical due to the influence that chemical composition and structural organization of the solid have on the n and k values. As part of a continued systematical study for the synthesis and characterization of Titan's aerosol analogues initiated in our group, we have subjected mixtures of CH4 in N2 to laser irradiation to produce layer of aerosol analogues. A set of optical properties values directly calculated from the transmission and reflectance curves, as well as a chemical characterization, by tandem mass spectroscopy, of the laboratory analogues will be presented. Our experimental protocol avoids some of the difficulties usually faced on laboratory simulations (over-irradiation, contamination with atmospheric oxygen, accurate ratio of initial gas mixture), porosity influences will also be discussed. The optical values can be used to determine how the chemical and optical properties of these aerosols influence the matching with the observed geometric albedo spectrum and how they participate in the radiative equilibrium processes in Titan's atmosphere. They will certainly help in the interpretation of the observations made by the Huygens descend through Titan's atmosphere last January and in all the new information about Titan generated since then. Financial support from CONACyT (40449) and PROMEP (103.5/03/1134) is acknowledged. SIRJ acknowledges a travel grant from PIFI 3.2.

Ramirez, Sandra I.; Contreras, G.; Agarwal, V.

2006-09-01

210

Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the UK  

NASA Astrophysics Data System (ADS)

Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the UK. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA observed in urban plumes compared to regional aerosol (0.85 versus 0.9-0.95). We attribute these differences to the presence of relatively rapidly formed secondary aerosol, primarily OOA and ammonium nitrate, which must be taken into account in radiative forcing calculations.

McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

2011-05-01

211

Black carbon aerosol mixing state, organic aerosols and aerosol optical properties over the United Kingdom  

NASA Astrophysics Data System (ADS)

Black carbon (BC) aerosols absorb sunlight thereby leading to a positive radiative forcing and a warming of climate and can also impact human health through their impact on the respiratory system. The state of mixing of BC with other aerosol species, particularly the degree of internal/external mixing, has been highlighted as a major uncertainty in assessing its radiative forcing and hence its climate impact, but few in situ observations of mixing state exist. We present airborne single particle soot photometer (SP2) measurements of refractory BC (rBC) mass concentrations and mixing state coupled with aerosol composition and optical properties measured in urban plumes and regional pollution over the United Kingdom. All data were obtained using instrumentation flown on the UK's BAe-146-301 large Atmospheric Research Aircraft (ARA) operated by the Facility for Airborne Atmospheric Measurements (FAAM). We measured sub-micron aerosol composition using an aerosol mass spectrometer (AMS) and used positive matrix factorization to separate hydrocarbon-like (HOA) and oxygenated organic aerosols (OOA). We found a higher number fraction of thickly coated rBC particles in air masses with large OOA relative to HOA, higher ozone-to-nitrogen oxides (NOx) ratios and large concentrations of total sub-micron aerosol mass relative to rBC mass concentrations. The more ozone- and OOA-rich air masses were associated with transport from continental Europe, while plumes from UK cities had higher HOA and NOx and fewer thickly coated rBC particles. We did not observe any significant change in the rBC mass absorption efficiency calculated from rBC mass and light absorption coefficients measured by a particle soot absorption photometer despite observing significant changes in aerosol composition and rBC mixing state. The contributions of light scattering and absorption to total extinction (quantified by the single scattering albedo; SSA) did change for different air masses, with lower SSA observed in urban plumes compared to regional aerosol (0.85 versus 0.9-0.95). We attribute these differences to the presence of relatively rapidly formed secondary aerosol, primarily OOA and ammonium nitrate, which must be taken into account in radiative forcing calculations.

McMeeking, G. R.; Morgan, W. T.; Flynn, M.; Highwood, E. J.; Turnbull, K.; Haywood, J.; Coe, H.

2011-09-01

212

Leishmania amazonensis chemotaxis under glucose gradient studied by the strength and directionality of forces measured with optical tweezers  

NASA Astrophysics Data System (ADS)

Chemotaxis is the mechanism microorganisms use to sense the environment surrounding them and to direct their movement towards attractive, or away from the repellent, chemicals. The biochemical sensing is almost the only way for communication between unicellular organisms. Prokaryote and Eukaryote chemotaxis has been mechanically studied mainly by observing the directionality and timing of the microorganisms movements subjected to a chemical gradient, but not through the directionality and strength of the forces it generates. To observe the vector force of microorganisms under a chemical gradient we developed a system composed of two large chambers connected by a tiny duct capable to keep the chemical gradient constant for more than ten hours. We also used the displacements of a microsphere trapped in an Optical Tweezers as the force transducer to measure the direction and the strength of the propulsion forces of flagellum of the microorganism under several gradient conditions. A 9?m diameter microsphere particle was trapped with a Nd:YAG laser and its movement was measured through the light scattered focused on a quadrant detector. We observed the behavior of the protozoa Leishmania amazonensis (eukaryote) under several glucose gradients. This protozoa senses the gradient around it by swimming in circles for three to five times following by tumbling, and not by the typical straight swimming/tumbling of bacteria. Our results also suggest that force direction and strength are also used to control its movement, not only the timing of swimming/tumbling, because we observed a higher force strength clearly directed towards the glucose gradient.

de Ysasa Pozzo, Liliana; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz Carlos; Ayres, Diana Copi; Giorgio, Selma; Cesar, Carlos Lenz

2007-02-01

213

Determining the binding mode and binding affinity constant of tyrosine kinase inhibitor PD153035 to DNA using optical tweezers  

SciTech Connect

Research highlights: {yields} PD153035 is a DNA intercalator and intercalation occurs only under very low salt concentration. {yields} The minimum distance between adjacent bound PD153035 {approx} 11 bp. {yields} Binding affinity constant for PD153035 is 1.18({+-}0.09) x 10{sup 4} (1/M). {yields} The change of binding free energy of PD153035-DNA interaction is -5.49 kcal mol{sup -1} at 23 {+-} 0.5 {sup o}C. -- Abstract: Accurately predicting binding affinity constant (K{sub A}) is highly required to determine the binding energetics of the driving forces in drug-DNA interactions. Recently, PD153035, brominated anilinoquinazoline, has been reported to be not only a highly selective inhibitor of epidermal growth factor receptor but also a DNA intercalator. Here, we use a dual-trap optical tweezers to determining K{sub A} for PD153035, where K{sub A} is determined from the changes in B-form contour length (L) of PD153035-DNA complex. Here, L is fitted using a modified wormlike chain model. We found that a noticeable increment in L in 1 mM sodium cacodylate was exhibited. Furthermore, our results showed that K{sub A} = 1.18({+-}0.09) x 10{sup 4} (1/M) at 23 {+-} 0.5 {sup o}C and the minimum distance between adjacent bound PD153035 {approx} 11 bp. We anticipate that by using this approach we can determine the complete thermodynamic profiles due to the presence of DNA intercalators.

Cheng, Chih-Ming [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Lee, Yuarn-Jang [Section of Infectious Diseases, Department of Internal Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan (China)] [Section of Infectious Diseases, Department of Internal Medicine, Taipei Medical University Hospital, Taipei 110, Taiwan (China); Wang, Wei-Ting [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Hsu, Chien-Ting [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China) [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Tsai, Jing-Shin [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China) [School of Dental Technology, Taipei Medical University, Taipei 110, Taiwan (China); Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); Wu, Chien-Ming [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China)] [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Hsinchu 30043, Taiwan (China); Ou, Keng-Liang [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China) [Institute of Biomedical Materials and Engineering, Taipei Medical University, Taipei 110, Taiwan (China); Research Center for Biomedical Implants and Microsurgery Devices, Taipei Medical University, Taipei 110, Taiwan (China); and others

2011-01-07

214

Single-molecule manipulation of double-stranded DNA using optical tweezers: interaction studies of DNA with RecA and YOYO-1.  

PubMed

By using optical tweezers and a specially designed flow cell with an integrated glass micropipette, we constructed a setup similar to that of Smith et al. (Science 271:795-799, 1996) in which an individual double-stranded DNA (dsDNA) molecule can be captured between two polystyrene beads. The first bead is immobilized by the optical tweezers and the second by the micropipette. Movement of the micropipette allows manipulation and stretching of the DNA molecule, and the force exerted on it can be monitored simultaneously with the optical tweezers. We used this setup to study elongation of dsDNA by RecA protein and YOYO-1 dye molecules. We found that the stability of the different DNA-ligand complexes and their binding kinetics were quite different. The length of the DNA molecule was extended by 45% when RecA protein was added. Interestingly, the speed of elongation was dependent on the external force applied to the DNA molecule. In experiments in which YOYO-1 was added, a 10-20% extension of the DNA molecule length was observed. Moreover, these experiments showed that a change in the applied external force results in a time-dependent structural change of the DNA-YOYO-1 complex, with a time constant of approximately 35 s (1/e2). Because the setup provides an oriented DNA molecule, we determined the orientation of the transition dipole moment of YOYO-1 within DNA by using fluorescence polarization. The angle of the transition dipole moment with respect to the helical axis of the DNA molecule was 69 degrees +/- 3. PMID:10404969

Bennink, M L; Schärer, O D; Kanaar, R; Sakata-Sogawa, K; Schins, J M; Kanger, J S; de Grooth, B G; Greve, J

1999-07-01

215

Antibody-Antigen assay design for combined optical tweezers and fluorescence  

E-print Network

The recent development in combined optical trapping and fluorescence technology promises to enable unbindinig force studies of receptor-ligand interactions, whose specificity play a crucial role in the function of many ...

Ta, Jenny, 1982-

2004-01-01

216

Quantitative comparison of aerosol optical depth (AOD) and aerosol indirect effects in three polluted Asian cities  

NASA Astrophysics Data System (ADS)

Advances in satellite technology and ground based measurement techniques have resulted in vast amount of data on aerosol and cloud parameters. Aerosol indirect effects are characterized by the effects of aerosol on cloud radiative properties. This being a subject of significant interest for climate change and human health effects, many computational and satellite data analysis studies have been made to understand this mechanism. However, most of the studies are made on understanding the global effects. In this work we attempt to understand the local effects by making quantitative analysis of aerosol and its indirect effects in three polluted Asian cities. We analyze aerosol optical depth (AOD) data from MODIS (Moderate Resolution Imaging Spectroradiometer) and MISR (Multiangle Imaging SpectroRadiometer), aerosol extinction optical depth, absorption optical depth, and aerosol index (AI) data from OMI (Ozone Monitoring Instrument) and compare with AOD data of AERONET (Aerosol Robotic Network) at Beijing, China; Dalanzadgad, Mongolia; and Kanpur, India. Cloud parameters from MODIS data are correlated with aerosol optical depth. Seasonal variation of aerosol optical depth and its effect on cloud radiative properties are discussed. Large differences in AOD are observed in the measurements by different instruments. The differences in the results of indirect effects indicate considerable influence of local environment.

Das, B.; Ahn, C.; Torres, O.; Durbin, P.

2008-12-01

217

Measurements of Semi-volatile Aerosol and Its Effect on Aerosol Optical Properties During Southern Oxidant and Aerosol Study  

NASA Astrophysics Data System (ADS)

Semi-volatile compounds, including particle-bound water, comprise a large part of aerosol mass and have a significant influence on aerosol lifecycle and its optical properties. Understanding the properties of semi-volatile compounds, especially those pertaining to gas/aerosol partitioning, is of critical importance for our ability to predict concentrations and properties of ambient aerosol. A set of state-of-the-art instruments was deployed at the SEARCH site near Centerville, AL during the Southern Oxidant and Aerosol Study (SOAS) campaign in summer 2013 to measure the effect of temperature and relative humidity on aerosol size distribution, composition and optical properties. Light scattering and absorption by temperature- and humidity-conditioned aerosols was measured using three photo-acoustic extinctiometers (PAX) at three wavelengths (405 nm, 532 nm, and 870 nm). In parallel to these measurements, a long residence time temperature-stepping thermodenuder and a variable residence time constant temperature thermodenuder in combination with three SMPS systems and an Aerosol Chemical Speciation Monitor (ACSM) were used to assess aerosol volatility and kinetics of aerosol evaporation. It was found that both temperature and relative humidity have a strong effect on aerosol optical properties. The variable residence time thermodenuder data suggest that aerosol equilibrated fairly quickly, within 2 s, in contrast to other ambient observations. Preliminary analysis show that approximately 50% and 90% of total aerosol mass evaporated at temperatures of 100 C and 180C, respectively. Evaporation varied substantially with ambient aerosol loading and composition and meteorology. During course of this study, T50 (temperatures at which 50% aerosol mass evaporates) varied from 60 C to more than 120 C.

Khlystov, A.; Grieshop, A. P.; Saha, P.; Subramanian, R.

2013-12-01

218

Fiber-integrated optical nano-tweezer based on a bowtie-aperture nano-antenna at the apex of a SNOM tip.  

PubMed

We propose a new concept of fiber-integrated optical nano-tweezer on the basis of a single bowtie-aperture nano-antenna (BNA) fabricated at the apex of a metal-coated SNOM tip. We demonstrate 3D optical trapping of 0.5 micrometer latex beads with input power which does not exceed 1 mW. Optical forces induced by the BNA on tip are then analyzed numerically. They are found to be 10(3) times larger than the optical forces of a circular aperture of the same area. Such a fiber nanostructure provides a new path for manipulating nano-objects in a compact, flexible and versatile architecture and should thus open promising perspectives in physical, chemical and biomedical domains. PMID:24787888

El Eter, Ali; Hameed, Nyha M; Baida, Fadi I; Salut, Roland; Filiatre, Claudine; Nedeljkovic, Dusan; Atie, Elie; Bole, Samuel; Grosjean, Thierry

2014-04-21

219

Using Optical Tweezers for the Characterization of Polyelectrolyte Solutions with Very Low Viscoelasticity  

PubMed Central

Recently, optical tweezing has been used to provide a method for microrheology addressed to measure the rheological properties of small volumes of samples. In this work, we corroborate this emerging field of microrheology by using these optical methods for the characterization of polyelectrolyte solutions with very low viscoelasticity. The influence of polyelectrolyte (i.e., polyacrylamide, PAM) concentration, specifically its aging, of the salt concentration is shown. The close agreement of the technique with classical bulk rheological measurements is demonstrated, illustrating the advantages of the technique. PMID:23786307

2013-01-01

220

Project of Aerosol Optical Depth Change in South America  

E-print Network

GEOG478 Project of Aerosol Optical Depth Change in South America Lan Luo, Ling-Wei Huang April 3 2008 #12;Countries Map of South America #12;Aerosol Optical Depth Change of South American During 2001 to 2006 #12;Statistics of Aerosol in 13 Countries Annually South America 0 0.1 0.2 0.3 0.4 0.5 0.6 Mean

Frank, Thomas D.

221

Computer-Generated Holographic Optical Tweezer Arrays Eric R. Dufresne(1)  

E-print Network

by optical intensity gradients. Dielectric particles polarized by the light's electric field are drawn up to a tight focus with a high numerical aperture lens. Microscope objective lenses of- fer an ideal to an objective lens' back aperture (B) by lenses L1 and L2 and focused into a trapping array. OP denotes

Grier, David

222

Hyperspectral Aerosol Optical Depths from TCAP Flights  

SciTech Connect

4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), the world’s first hyperspectral airborne tracking sunphotometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two Column Aerosol Project (TCAP). Root-mean square differences from AERONET ground-based observations were 0.01 at wavelengths between 500-1020 nm, 0.02 at 380 and 1640 nm and 0.03 at 440 nm in four clear-sky fly-over events, and similar in ground side-by-side comparisons. Changes in the above-aircraft AOD across 3-km-deep spirals were typically consistent with integrals of coincident in situ (on DOE Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, 0.02 at 355, 450, 532, 550, 700, 1064 nm, respectively, despite atmospheric variations and combined measurement uncertainties. Finer vertical differentials of the 4STAR measurements matched the in situ ambient extinction profile within 14% for one homogeneous column. For the AOD observed between 350-1660 nm, excluding strong water vapor and oxygen absorption bands, estimated uncertainties were ~0.01 and dominated by (then) unpredictable throughput changes, up to +/-0.8%, of the fiber optic rotary joint. The favorable intercomparisons herald 4STAR’s spatially-resolved high-frequency hyperspectral products as a reliable tool for climate studies and satellite validation.

Shinozuka, Yohei; Johnson, Roy R.; Flynn, Connor J.; Russell, P. B.; Schmid, Beat; Redemann, Jens; Dunagan, Stephen; Kluzek, Celine D.; Hubbe, John M.; Segal-Rosenheimer, Michal; Livingston, J. M.; Eck, T.; Wagener, Richard; Gregory, L.; Chand, Duli; Berg, Larry K.; Rogers, Ray; Ferrare, R. A.; Hair, John; Hostetler, Chris A.; Burton, S. P.

2013-11-13

223

Quantifying the response of the ORAC aerosol optical depth retrieval for MSG SEVIRI to aerosol model assumptions  

E-print Network

Quantifying the response of the ORAC aerosol optical depth retrieval for MSG SEVIRI to aerosolRed Imager (MSG SEVIRI) to changes in the aerosol properties used in the dust aerosol model, using data from retrieval for MSG SEVIRI to aerosol model assumptions, J. Geophys. Res., 116, D05208, doi:10.1029/2010JD

Oxford, University of

224

Climatology of Aerosol Optical Properties in Southern Africa  

NASA Technical Reports Server (NTRS)

A thorough regionally dependent understanding of optical properties of aerosols and their spatial and temporal distribution is required before we can accurately evaluate aerosol effects in the climate system. Long term measurements of aerosol optical depth, Angstrom exponent and retrieved single scattering albedo and size distribution, were analyzed and compiled into an aerosol optical properties climatology for southern Africa. Monitoring of aerosol parameters have been made by the AERONET program since the middle of the last decade in southern Africa. This valuable information provided an opportunity for understanding how aerosols of different types influence the regional radiation budget. Two long term sites, Mongu in Zambia and Skukuza in South Africa formed the core sources of data in this study. Results show that seasonal variation of aerosol optical thicknesses at 500 nm in southern Africa are characterized by low seasonal multi-month mean values (0.11 to 0.17) from December to May, medium values (0.20 to 0.27) between June and August, and high to very high values (0.30 to 0.46) during September to November. The spatial distribution of aerosol loadings shows that the north has high magnitudes than the south in the biomass burning season and the opposite in none biomass burning season. From the present aerosol data, no long term discernable trends are observable in aerosol concentrations in this region. This study also reveals that biomass burning aerosols contribute the bulk of the aerosol loading in August-October. Therefore if biomass burning could be controlled, southern Africa will experience a significant reduction in total atmospheric aerosol loading. In addition to that, aerosol volume size distribution is characterized by low concentrations in the non biomass burning period and well balanced particle size contributions of both coarse and fine modes. In contrast high concentrations are characteristic of biomass burning period, combined with significant dominance of fine mode particles.

Queface, Antonio J.; Piketh, Stuart J.; Eck, Thomas F.; Tsay, Si-Chee

2011-01-01

225

Path Radiance Technique for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from short-wave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Department of Energy's Atmospheric Radiation Measurement) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 pm) during the first Landsat IOP (Intensive Observation Period). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 pm and band 3 at 0.66 pm agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Tsay, S.-C.; Wen, G.; Cahalan, R. F.; Oreopoulos, L.

1999-01-01

226

Path Radiance Technique for Retrieving Aerosol Optical Thickness Over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Department of Energy's Atmospheric Radiation Measurement) program on September 27,1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 microns) during the first Landsat Intensive Observation Period (IOP). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 micron and band 3 at 0.66 micron agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Tsay, S.-C.; Wen, G.; Cahalan, R. F.; Oreopoulos, L.

1999-01-01

227

Path radiance technique for retrieving aerosol optical thickness over land  

SciTech Connect

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a ''path radiance'' method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the ''dark object'' approach to extract the aerosol signal. This method uses the signature of the correlation of visible and middle-IR reflectance at the surface and couples the correlation with the atmospheric effect. We have applied this method to a Landsat TM (Thematic Mapper) image acquired over the Oklahoma southern Great Plains site of the Department of Energy Atmospheric Radiation Measurement (ARM) program on September 27, 1997, a very clear day (aerosol optical thickness of 0.07 at 0.5 {mu}m) during the first Landsat Intensive Observation Period. The retrieved mean aerosol optical thickness for TM band 1 at 0.49 {mu}m and band 3 at 0.66 {mu}m agree very well with the ground-based Sun photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method. (c) 1999 American Geophysical Union.

Wen, Guoyong [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)] [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); Tsay, Si-Chee [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States)] [NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Cahalan, Robert F. [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States) [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States); NASA Goddard Space Flight Center, Greenbelt, Maryland (United States); Oreopoulos, Lazaros [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)] [Joint Center for Earth Systems Technology, University of Maryland, Baltimore County, Catonsville (United States)

1999-12-27

228

Size distribution of near-surface aerosols and its relation to the columnar aerosol optical depths  

NASA Astrophysics Data System (ADS)

Simultaneous data on Aerosol Optical Depth (AOD) and size segregated, near-surface, aerosol mass concentration was obtained from a Multi wavelength Solar Radiometer (MWR) and Quartz Crystal Microbalance Impactor (QCM), respectively. These were used to examine the association between near-surface aerosol properties and columnar AOD. The spectral AODs were approximated to the Ångström relation ?p=??-?, and the wavelength exponent ? and turbidity coefficient ? have been obtained. In general, ? was found to be well associated with the relative abundance of accumulation mode aerosols (estimated from the simultaneous QCM data) while ? followed the variations of the coarse mode aerosol mass concentration; the association being closer during periods of continental airmass.

Pillai, P.; Krishna Moorthy, K.

2004-10-01

229

To Study the Effect of Paclitaxel on the Cytoplasmic Viscosity of Murine Macrophage Immune Cell RAW 264.7 Using Self-Developed Optical Tweezers System  

NASA Astrophysics Data System (ADS)

In recent years, optical tweezers have become one of the tools to measure the mechanical properties of living cells. In this study, we first constructed an optical tweezers to investigate the cytoplasmic viscosity of immune cells. In addition to measuring viscosity of cells in a normal condition, we also treated cells with anti-cancer drug, Paclitaxel, and in order to study its effect on the cytoplasmic viscosity. The results showed that the viscosity decreased dramatically during the first 3 h. After 3 h, the change started to slow down and it remained nearly flat by the end of the experiment. In addition, we used the confocal laser scanning microscope to observe the cytoskeleton of the cell after drug treatment for 3 and 5 h, respectively, and found that actin filaments were disrupted and that the nucleus had disintegrated in some drug-treated cells, similar to the process of apoptosis. This study presents a new way for measuring the changes in cytoplasmic viscosity, and to determine if a cell is going into apoptosis as a result of a drug treatment.

Chen, Ying-chun; Wu, Chien-ming

2012-12-01

230

Optical closure study on light-absorbing aerosols  

NASA Astrophysics Data System (ADS)

The in situ measurement of atmospheric aerosol optical properties is an important component of quantifying climate change. In particular, the in-situ measurement of the aerosol single-scattering albedo (SSA), which is the ratio of aerosol scattering to aerosol extinction, is identified as a key challenge in atmospheric sciences and climate change research. Ideally, the complete set of aerosol optical properties is measured through optical closure studies which simultaneous measure aerosol extinction, scattering and absorption coefficients. The recent development of new optical instruments have made real-time in situ optical closure studies attainable, however, many of these instruments are state-of-the-art but not practical for routine monitoring. In our studies we deployed a suit of well-established and recently developed instruments including the cavity attenuated phase shift (CAPS) method for aerosol light extinction, multi-angle absorption photometer (MAAP) and particle soot absorption photometer (PSAP) for aerosol light absorption, and an integrating nephelometer (NEPH) for aerosol light scattering measurements. From these directly measured optical properties we calculated light absorption from extinction minus scattering (difference method), light extinction from scattering plus absorption, and aerosol single-scattering albedo from combinations CAPS + MAAP, NEPH + PSAP, NEPH + MAAP, CAPS + NEPH. Closure studies were conducted for laboratory-generated aerosols composed of various mixtures of black carbon (Regal 400R pigment black, Cabot Corp.) and ammonium sulphate, urban aerosol (Billerica, MA), and background aerosol (Storm Peak Lab.). Key questions addressed in our closure studies are: (1) how well can we measure aerosol light absorption by various methods, and (2) how well can we measure the aerosol single-scattering albedo by various instrument combinations? In particular we investigated (3) whether the combination of a CAPS and NEPH provides a reasonable approach for determining aerosol absorption using the difference method, and (4) whether this comparison provides any indication that the PSAP and/or MAAP measurements of absorption have artifacts by organic condensation as suggested in the literature. The results presented here contribute to the ongoing efforts of assessing measurement methods suitable for the monitoring of aerosol optical properties.

Petzold, Andreas; Bundke, Ulrich; Freedman, Andrew; Onasch, Timothy B.; Massoli, Paola; Andrews, Elizabeth; Hallar, Anna G.

2014-05-01

231

Global Aerosol Optical Models and Lookup Tables for the New MODIS Aerosol Retrieval over Land  

NASA Technical Reports Server (NTRS)

Since 2000, MODIS has been deriving aerosol properties over land from MODIS observed spectral reflectance, by matching the observed reflectance with that simulated for selected aerosol optical models, aerosol loadings, wavelengths and geometrical conditions (that are contained in a lookup table or 'LUT'). Validation exercises have showed that MODIS tends to under-predict aerosol optical depth (tau) in cases of large tau (tau greater than 1.0), signaling errors in the assumed aerosol optical properties. Using the climatology of almucantur retrievals from the hundreds of global AERONET sunphotometer sites, we found that three spherical-derived models (describing fine-sized dominated aerosol), and one spheroid-derived model (describing coarse-sized dominated aerosol, presumably dust) generally described the range of observed global aerosol properties. The fine dominated models were separated mainly by their single scattering albedo (omega(sub 0)), ranging from non-absorbing aerosol (omega(sub 0) approx. 0.95) in developed urban/industrial regions, to neutrally absorbing aerosol (omega(sub 0) approx.90) in forest fire burning and developing industrial regions, to absorbing aerosol (omega(sub 0) approx. 0.85) in regions of savanna/grassland burning. We determined the dominant model type in each region and season, to create a 1 deg. x 1 deg. grid of assumed aerosol type. We used vector radiative transfer code to create a new LUT, simulating the four aerosol models, in four MODIS channels. Independent AERONET observations of spectral tau agree with the new models, indicating that the new models are suitable for use by the MODIS aerosol retrieval.

Levy, Robert C.; Remer, Loraine A.; Dubovik, Oleg

2007-01-01

232

An optical tweezer actuated, nanoaperture-grid based Optofluidic Microscope implementation method.  

PubMed

We report a novel grid based Optofluidic Microscope (OFM) method where a closely spaced 2D grid of nanoapertures (diameter = 100 nm, separation = 2.5 mum) provided patterned illumination. We achieved a one-to-one mapping of the light transmissions through the nanoapertures onto a high-speed CCD camera. By optically tweezing a targeted sample across the grid in a controlled fashion and recording the time varying light reception from the nanoapertures, we were able to generate high-resolution images of the sample. The achievable resolution limit of the prototype was ~ 110 nm (Sparrow's criterion) under optimal conditions. We demonstrated the technique by imaging polystyrene beads and pollen spores. PMID:19550927

Heng, Xin; Hsiao, Edward; Psaltis, Demetri; Yang, Changhuei

2007-12-10

233

Surface charge and hydrodynamic coefficient measurements of {\\it Bacillus subtilis} spore by Optical Tweezers  

E-print Network

In this work we report on the simultaneous measurement of the hydrodynamic coefficient and the electric charge of single {\\it Bacillus subtilis} spores. The latter has great importance in protein binding to spores and in the adhesion of spores onto surfaces. The charge and the hydrodynamic coefficient were measured by an accurate procedure based on the analysis of the motion of single spores confined by an optical trap. The technique has been validated using charged spherical polystyrene beads. The excellent agreement of our results with the expected values demonstrates the quality of our procedure. We measured the charge of spores of {\\it B. subtilis} purified from a wild type strain and from two isogenic mutants characterized by an altered spore surface. Our technique is able to discriminate the three spore types used, by their charge and by their hydrodynamic coefficient which is related to the hydrophobic properties of the spore surface.

Giuseppe Pesce; Giulia Rusciano; Antonio Sasso; Rachele Isticato; Teja Sirec; Ezio Ricca

2014-03-18

234

Path Radiance Techniques for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

The key issue in retrieving aerosol optical thickness over land from shortwave satellite radiances is to identify and separate the signal due to scattering by a largely transparent aerosol layer from the noise due to reflection by the background surface, where the signal is relatively uniform compared to the highly inhomogeneous surface contribution. Sensitivity studies in aerosol optical thickness retrievals reveal that the apparent reflectance at the top of the atmosphere is very susceptible to the surface reflectance, especially when aerosol optical thickness is small. Uncertainties associated with surface reflectance estimation can greatly amplify the error of the aerosol optical thickness retrieval. To reduce these uncertainties, we have developed a "path radiance" method to retrieve aerosol optical thickness over land by extending the traditional technique that uses the "dark object" approach to extract the aerosol signal. This method uses the signature of the correlation of visible and mid-IR reflectance at the surface, and couples the correlation with the atmospheric effect. We have applied this method to a TM (Landsat Thematic Mapper) image acquired over the Oklahoma Southern Great Plains (SGP) site of DoE's ARM (Atmospheric Radiation Measurement) program on September 27, 1997, a very clear day during the first Landsat IOP (Intensive Observation Period). The retrieved mean aerosol optical thickness for TM band 1 at 0.49 micrometers and band 3 at 0.66 micrometers agree very well with the ground-based sun-photometer measurements at the ARM site. The ability to retrieve small aerosol optical thickness (such as 0.07 at 0.5 micrometers as in the example considered here) makes this path radiance technique promising. More importantly, the path radiance is relatively insensitive to surface inhomogeneity. The retrieved mean path radiances in reflectance units have very small standard deviations for both TM blue and red bands. This small variability of path radiance further supports the current aerosol retrieval method.

Wen, Guoyong; Tsay, Si-Chee; Cahalan, Robert F.; Oreopoulos, Lazaros

1999-01-01

235

Independent trapping and manipulation of microparticles using dexterous acoustic tweezers  

NASA Astrophysics Data System (ADS)

An electronically controlled acoustic tweezer was used to demonstrate two acoustic manipulation phenomena: superposition of Bessel functions to allow independent manipulation of multiple particles and the use of higher-order Bessel functions to trap particles in larger regions than is possible with first-order traps. The acoustic tweezers consist of a circular 64-element ultrasonic array operating at 2.35 MHz which generates ultrasonic pressure fields in a millimeter-scale fluid-filled chamber. The manipulation capabilities were demonstrated experimentally with 45 and 90-?m-diameter polystyrene spheres. These capabilities bring the dexterity of acoustic tweezers substantially closer to that of optical tweezers.

Courtney, Charles R. P.; Demore, Christine E. M.; Wu, Hongxiao; Grinenko, Alon; Wilcox, Paul D.; Cochran, Sandy; Drinkwater, Bruce W.

2014-04-01

236

Aerosol optical properties during coagulation and condensation in multimodal aerosol size distribution  

NASA Astrophysics Data System (ADS)

The aerosols in the atmosphere continuously change their size and composition through the dynamic processes such as coagulation or condensation. For example, the Brownian motion of particles, turbulence, presence of a shear field, aerosol particle growth with the accretion of monomers on existing particle, and external forces such as gravity and electrical forces could cause coagulation. This means that the change of the size distribution due to coagulation and condensation process affect Ångstrom exponent. For this reasons, the aerosol dynamics play an important role in estimating optical properties such as Ångstrom exponent. Usually, the atmospheric aerosol shows the multimodal distribution (such as bimodal or three modal distribution). In this study, the change of the Ångstrom exponent for polydispersed aerosol size distribution during the aerosol dynamic processes was investigated. Multimodal Log-normal aerosol size distribution was assumed and the sensitive analysis of the Ångstrom exponent during the coagulation and condensation process was performed. The sensitivities of coarse mode particles are analyzed in order to find the effect of dust particles on optical properties with large particle size such as Asian dust. This study also investigated the sensitivity of aerosol refractive index to analyze the Angstrom exponent due to aerosol composition change during the aerosol dynamic process. The results showed that the Ångstrom exponent changes sensitively as a function of multimodal size distribution and refractive index.

Jung, C.; Park, R.; Kim, Y.

2012-12-01

237

Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model  

NASA Astrophysics Data System (ADS)

This study estimates the emission fluxes of a range of aerosol species and one aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. These improvements are larger over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 15 Tg yr-1, 119 Tg yr-1 for particulate organic matter, 17 Pg yr-1 for sea salt, 83 TgS yr-1 for SO2 and 1383 Tg yr-1 for desert dust. They represent a difference of +45 %, +40 %, +26 %, +13 % and -39 % respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

Huneeus, N.; Chevallier, F.; Boucher, O.

2012-05-01

238

Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model  

NASA Astrophysics Data System (ADS)

The emission fluxes of a range of aerosol species and aerosol precursor are estimated at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The assimilation system has been applied to the entire year 2002 and its performance is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. The estimated emission flux for black carbon is 14.5 Tg/yr, 119 Tg/yr for organic matter, 17 Pg/yr for sea salt, 82.7 TgS/yr for SO2 and 1383 Tg/yr for desert dust. They represent a difference of +45%, +40%, +26%, +13% and -39% respectively, with respect to the a priori values. The system has been applied to the year 2005 with similar performance in the reduction of the RMS and bias and increase in correlation. The study will be extended by applying it to the year 2010. The estimated fluxes corresponding to the years 2002, 2005 and 2010 will be presented and compared with different top-down and bottom-up estimates.

Huneeus, N.; Chevallier, F.; Boucher, O.

2012-04-01

239

Estimating aerosol emissions by assimilating observed aerosol optical depth in a global aerosol model  

NASA Astrophysics Data System (ADS)

This study estimates the emission fluxes of a range of aerosol species and aerosol precursor at the global scale. These fluxes are estimated by assimilating daily total and fine mode aerosol optical depth (AOD) at 550 nm from the Moderate Resolution Imaging Spectroradiometer (MODIS) into a global aerosol model of intermediate complexity. Monthly emissions are fitted homogenously for each species over a set of predefined regions. The performance of the assimilation is evaluated by comparing the AOD after assimilation against the MODIS observations and against independent observations. The system is effective in forcing the model towards the observations, for both total and fine mode AOD. Significant improvements for the root mean square error and correlation coefficient against both the assimilated and independent datasets are observed as well as a significant decrease in the mean bias against the assimilated observations. The assimilation is more efficient over land than over ocean. The impact of the assimilation of fine mode AOD over ocean demonstrates potential for further improvement by including fine mode AOD observations over continents. The Angström exponent is also improved in African, European and dusty stations. The estimated emission flux for black carbon is 14.5 Tg yr-1, 119 Tg yr-1 for organic matter, 17 Pg yr-1 for sea salt, 82.7 TgS yr-1 for SO2 and 1383 Tg yr-1 for desert dust. They represent a difference of +45%, +40%, +26%, +13% and -39% respectively, with respect to the a priori values. The initial errors attributed to the emission fluxes are reduced for all estimated species.

Huneeus, N.; Chevallier, F.; Boucher, O.

2012-01-01

240

Modelling of aerosol optical depth variability at regional scale  

Microsoft Academic Search

Monitoring of aerosol optical depth (AOD) is of particular importance due to the significant role of aerosols in the atmospheric radiative budget. AOD is a key parameter in studies related to global climatology, atmospheric pollutants, forest fires, and for performing atmospheric corrections on remotely sensed imagery of surface scenes. Up to now the two standard techniques used for retrieving AOD

M. Aube; N. T. O'Neill; A. Royer

2000-01-01

241

Climatology of Aerosol Optical Depth over the United States  

Microsoft Academic Search

Information on the optical properties of aerosols over extended areas is needed for estimating their radiative effects, for correctly computing surface radiative fluxes by methods of remote sensing, as inputs to climate models, as well as for the evaluation of satellite based estimates of this parameter. To respond to such needs, several attempts have been made to obtain aerosol climatologies,

H. Liu; R. T. Pinker; B. N. Holben; J. Ballabrera; T. Eck; A. Smirnov

2002-01-01

242

Aerosol Optical Depth Value-Added Product Report  

SciTech Connect

This document describes the process applied to retrieve aerosol optical depth (AOD) from multifilter rotating shadowband radiometers (MFRSR) and normal incidence multifilter radiometers (NIMFR) operated at the ARM Climate Research Facility’s ground-based facilities.

Koontz, A; Hodges, G; Barnard, J; Flynn, C; Michalsky, J

2013-03-17

243

Hydrodynamic slip on DNA observed by optical tweezers-controlled translocation experiments with solid-state and lipid-coated nanopores.  

PubMed

We use optical tweezers to investigate the threading force on a single dsDNA molecule inside silicon-nitride nanopores between 6 and 70 nm in diameter, as well as lipid-coated solid-state nanopores. We observe a strong increase of the threading force for decreasing nanopore size that can be attributed to a significant reduction in the electroosmotic flow (EOF), which opposes the electrophoresis. Additionally, we show that the EOF can also be reduced by coating the nanopore wall with an electrically neutral lipid bilayer, resulting in an 85% increase in threading force. All experimental findings can be described by a quantitative theoretical model that incorporates a hydrodynamic slip effect on the DNA surface with a slip length of 0.5 nm. PMID:24935198

Galla, Lukas; Meyer, Andreas J; Spiering, Andre; Sischka, Andy; Mayer, Michael; Hall, Adam R; Reimann, Peter; Anselmetti, Dario

2014-07-01

244

The complex folding behavior of HIV-1-protease monomer revealed by optical-tweezer single-molecule experiments and molecular dynamics simulations.  

PubMed

We have used optical tweezers and molecular dynamics simulations to investigate the unfolding and refolding process of a stable monomeric form of HIV-1-protease (PR). We have characterized the behavior under tension of the native state (N), and that of the ensemble of partially folded (PF) conformations the protein visits en route to N, which collectively act as a long-lived state controlling the slow kinetic phase of the folding process. Our results reveal a rich network of unfolding events, where the native state unfolds either in a two-state manner or by populating an intermediate state I, while the PF state unravels through a multitude of pathways, underscoring its structural heterogeneity. Refolding of mechanically denatured HIV-1-PR monomers is also a multiple-pathway process. Molecular dynamics simulations allowed us to gain insight into possible conformations the protein adopts along the unfolding pathways, and provide information regarding possible structural features of the PF state. PMID:25194276

Caldarini, M; Sonar, P; Valpapuram, I; Tavella, D; Volonté, C; Pandini, V; Vanoni, M A; Aliverti, A; Broglia, R A; Tiana, G; Cecconi, C

2014-12-01

245

Identification of stepped changes of binding affinity during interactions between the disintegrin rhodostomin and integrin ?IIb?3 in living cells using optical tweezers  

NASA Astrophysics Data System (ADS)

Integrin receptors serve as both mechanical links and signal transduction mediators between the cell and its environment. Experimental evidence demonstrates that conformational changes and lateral clustering of the integrin proteins may affect their binding to ligands and regulate downstream cellular responses; however, experimental links between the structural and functional correlations of the ligand-receptor interactions are not yet elucidated. In the present report, we utilized optical tweezers to measure the dynamic binding between the snake venom rhodostomin, coated on a microparticle and functioned as a ligand, and the membrane receptor integrin alpha(IIb)beta(3) expressed on a Chinese Hamster Ovary (CHO) cell. A progressive increase of total binding affinity was found between the bead and CHO cell in the first 300 sec following optical tweezers-guided contact. Further analysis of the cumulative data revealed the presence of "unit binding force" presumably exerted by a single rhodostomin-integrin pair. Interestingly, two such units were found. Among the measurements of less total binding forces, presumably taken at the early stage of ligand-receptor interactions, a unit of 4.15 pN per molecule pair was derived. This unit force dropped to 2.54 pN per molecule pair toward the later stage of interactions when the total binding forces were relatively large. This stepped change of single molecule pair binding affinity was not found when mutant rhodostomin proteins were used as ligands (a single unit of 1.81 pN per pair was found). These results were interpreted along with the current knowledge about the conformational changes of integrins during the "molecule activation" process.

Hsieh, Chia-Fen; Chang, Bo-Jui; Pai, Chyi-Huey; Chen, Hsuan-Yi; Chi, Sien; Hsu, Long; Tsai, Jin-Wu; Lin, Chi-Hung

2004-10-01

246

Closure Evaluation of Laboratory Aerosols Optical and Hygroscopic Properties  

NASA Astrophysics Data System (ADS)

Closure analysis of the optical and hygroscopic properties of selected pure inorganic aerosol (e.g., ammonium sulfate and sodium chloride), pure organic aerosol (e.g., glutaric acid and succinic acid), and two inorganic and organic aerosol mixtures will be evaluated. Focus will be on the effect of particulate organic matter (POM) content on an aerosol's optical hygroscopicity. The Mie-Lorentz light scattering ("BHMIE") code is used to predict the total light scattering and backscattering coefficients (?sp and ?bsp, respectively) at given RH values. The "BHMIE" code uses measured aerosol particle number size distributions by Hygroscopic Tandem Differential Mobility Analyzer (H-TDMA), and refractive indices as major model inputs. As a subset of the optical closure study, another closure on the real refractive indices of the aerosols will also be completed by comparing results from the partial molar refraction (PMR) approach to the experimentally determined values using two independent optical devices - ellipsometer and refractometer at different sub-saturated solute mass concentrations. Meanwhile, a scanning relative humidity (RH) nephelometry system, humidograph, is used to measure ?bsp and ?bsp at controlled RH values between 35% and 85%. Comparisons of the extensive aerosol optical properties, ?sp and ?bsp, and intensive derived ones, such as hygroscopic response in ?sp (f?sp), single scattering albedo ( ?), Ångström exponent (å), and hemispheric backscatter fraction (b) at select RH values will be made to accomplish the closure evaluations. In addition, particle growth (g(RH)), effect of temperature (T) and RH uncertainties and sample heating on measurements of aerosol optical properties will also be quantified.

Wang, W.; Rood, M.

2006-12-01

247

Assessment of Error in Aerosol Optical Depth Measured by AERONET Due to Aerosol Forward Scattering  

NASA Technical Reports Server (NTRS)

We present an analysis of the effect of aerosol forward scattering on the accuracy of aerosol optical depth (AOD) measured by CIMEL Sun photometers. The effect is quantified in terms of AOD and solar zenith angle using radiative transfer modeling. The analysis is based on aerosol size distributions derived from multi-year climatologies of AERONET aerosol retrievals. The study shows that the modeled error is lower than AOD calibration uncertainty (0.01) for the vast majority of AERONET level 2 observations, 99.53%. Only 0.47% of the AERONET database corresponding mostly to dust aerosol with high AOD and low solar elevations has larger biases. We also show that observations with extreme reductions in direct solar irradiance do not contribute to level 2 AOD due to low Sun photometer digital counts below a quality control cutoff threshold.

Sinyuk, Alexander; Holben, Brent N.; Smirnov, Alexander; Eck, Thomas F.; Slustsker, Ilya; Schafer, Joel S.; Giles, David M.; Sorokin, Michail

2013-01-01

248

Jet Assisted Aerosol Chemical Vapor Deposition for Optical Fiber Synthesis  

Microsoft Academic Search

Various kinds of high quality optical fibers are routinely fabricated by the modified chemical vapor deposition (MCVD), in which fine particles are generated through the oxidation of chemical precursor and deposited in a silica tube reactor. Efficiency, rate, and uniformity of particle deposition determine the quality and cost of optical fibers; therefore efforts to enhance aerosol deposition performance should be

Mansoo Choi; Choonkeun Hong; Kong Hoon Lee

2002-01-01

249

Tube length-assisted optimized aerosol trapping  

NASA Astrophysics Data System (ADS)

Trapping a single aerosol using optical tweezers could be of great importance for environmental sciences. Though a single nanoparticle as small as 10 nm is successfully trapped in aqueous media using optical tweezers, due to spherical aberration only large clusters of nanoparticles were stably trapped in air. In this paper we provide our theoretical and experimental results on optimized trapping of aerosols as small as 400 nm in radius by the introduction of an extra spherical aberration source in order to minimize the total spherical aberration of the system. Our method allows for trapping of high refractive index particles such as polystyrene beads in air. It also provides considerably large trappable depth range which endows in-depth trapping. Our theoretical and experimental results are in very good agreement.

Taheri, S. Mohammad-Reza; Sadeghi, Mohammad; Madadi, Ebrahim; S. Reihani, S. Nader

2014-10-01

250

Strategies for Improved CALIPSO Aerosol Optical Depth Estimates  

NASA Technical Reports Server (NTRS)

In the spring of 2010, the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) project will be releasing version 3 of its level 2 data products. In this paper we describe several changes to the algorithms and code that yield substantial improvements in CALIPSO's retrieval of aerosol optical depths (AOD). Among these are a retooled cloud-clearing procedure and a new approach to determining the base altitudes of aerosol layers in the planetary boundary layer (PBL). The results derived from these modifications are illustrated using case studies prepared using a late beta version of the level 2 version 3 processing code.

Vaughan, Mark A.; Kuehn, Ralph E.; Tackett, Jason L.; Rogers, Raymond R.; Liu, Zhaoyan; Omar, A.; Getzewich, Brian J.; Powell, Kathleen A.; Hu, Yongxiang; Young, Stuart A.; Avery, Melody A.; Winker, David M.; Trepte, Charles R.

2010-01-01

251

Global Aerosol Radiative Forcing Derived from Sea WiFS-Inferred Aerosol Optical Properties  

NASA Technical Reports Server (NTRS)

Aerosol optical properties inferred from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) radiance measurements are used to compute the aerosol shortwave radiative forcing using a radiative transfer model. The aerosol optical thickness at the wavelength of 865-nm is taken from the SeaWIFS archive. It is found that the nominal optical thickness over oceans ranges from 0.1 to 0.2. Using a maritime aerosol model and the radiances measured at the various SeaWiFS channels, the Angstrom exponent is determined to be 0.2174, the single-scattering albedo to be 0.995, and the asymmetry factor to be 0.786. The radiative transfer model has eight bands in the visible and ultraviolet spectral regions and three bands in the near infrared. It includes the absorption due to aerosols, water vapor, carbon dioxide, and oxygen, and the scattering due to aerosols and gases (Rayleigh scattering). The radiative forcing is computed over global oceans for four months (January, April, July, and October, 1998) to represent four seasons. It is found that the aerosol radiative forcing is large and changes significantly with seasons near the continents with large-scale forest fires and desert dust. Averaged over oceans and the four months, the aerosol radiative forcing is approximately 7 W/sq m at the top of the atmosphere. This large radiative forcing is expected to have a significant cooling effect on the Earth's climate as implied from simulations of a number of general circulation models.

Chou, Ming-Dah; Chan, Pui-King; Wang, Menghua

1999-01-01

252

Columnar aerosol optical properties at AERONET sites in central eastern Asia and aerosol transport to the tropical mid-Pacific  

Microsoft Academic Search

The column-integrated optical properties of aerosol in the central eastern region of Asia and midtropical Pacific were investigated based on Sun\\/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites in these regions. Characterization of aerosol properties in the Asian region is important due to the rapid growth of both population and economic activity, with associated increases in fossil fuel

T. F. Eck; B. N. Holben; O. Dubovik; A. Smirnov; P. Goloub; H. B. Chen; B. Chatenet; L. Gomes; X.-Y. Zhang; S.-C. Tsay; Q. Ji; D. Giles; I. Slutsker

2005-01-01

253

Aerosol optical properties in the ABL over arctic sea ice from airborne aerosol lidar measurements  

NASA Astrophysics Data System (ADS)

Between 2009 and 2013 aerosols, sea ice properties and meteorological variables were measured during several airborne campaigns covering a wide range of the western Arctic Ocean. The campaigns were carried out with the aircraft Polar 5 of the German Alfred-Wegener-Institute (AWI) during spring and summer periods. Optical properties of accumulation mode aerosol and clouds were measured with the nadir looking AMALi aerosol lidar covering the atmospheric boundary layer and the free troposphere up to 3000m, while dropsondes provided coincident vertical profiles of meteorological quantities. Based on these data we discuss the vertical distribution of aerosol backscatter in and above the atmospheric boundary layer and its dependence on relative humidity, dynamics and underlying sea ice properties. We analyze vertical profiles of lidar and coincident dropsonde measurements from various locations in the European and Canadian Arctic from spring and summer campaigns. Sea ice cover is derived from modis satellite and aircraft onboard camera images. The aerosol load in the arctic atmospheric boundary layer shows a high variability. Various meteorological parameters and in particular boundary layer properties are discussed with their respective influence on aerosol features. To investigate the effect of the frequency and size of open water patches on aerosol properties, we relate the profiles to the sea ice properties influencing the atmosphere in the upwind region.

Schmidt, Lukas; Neuber, Roland; Ritter, Christoph; Maturilli, Marion; Dethloff, Klaus; Herber, Andreas

2014-05-01

254

Aerosol Radiative Forcing Derived From SeaWIFS - Retrieved Aerosol Optical Properties  

NASA Technical Reports Server (NTRS)

To understand climatic implications of aerosols over global oceans, the aerosol optical properties retrieved from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) are analyzed, and the effects of the aerosols on the Earth's radiation budgets (aerosol radiative forcing, ARF) are computed using a radiative transfer model. It is found that the distribution of the SeaWiFS-retrieved aerosol optical thickness is distinctively zonal. The maximum in the equatorial region coincides with the Intertropical Convergence Zone, and the maximum in the Southern Hemispheric high latitudes coincides with the region of prevailing westerlies. The minimum aerosol optical thickness is found in the subtropical high pressure regions, especially in the Southern Hemisphere. These zonal patterns clearly demonstrate the influence of atmospheric circulation on the oceanic aerosol distribution. Over global oceans, aerosols reduce the annual mean net downward solar flux by 5.4 W m-2 at the top of the atmosphere and by 6.1 W m-2 at the surface. The largest ARF is found in the tropical Atlantic, Arabian Sea, Bay of Bengal, the coastal regions of Southeast and East Asia, and the Southern Hemispheric high latitudes. During the period of the Indonesian big fires (September-December 1997), the cooling due to aerosols is greater than 15 W m-2 at the top of the atmosphere and greater than 30 W m(exp -1) at the surface in the vicinity of the maritime continents. The atmosphere receives extra solar radiation by greater than 15 W m(exp -1) over a large area. These large changes in radiative fluxes are expected to have enhanced the atmospheric stability, weakened the atmospheric circulation, and augmented the drought condition during that period. It would be very instructive to simulate the regional climatic. The model-calculated clear sky solar flux at the top of the atmosphere is compared with that derived from the Clouds and the Earth's Radiant Energy System (CERES). The net downward solar flux of CERES is systematically larger than the model calculations by -3 W M-2. In the equatorial region, the CERES-derived net downward solar flux is even larger than the model calculations without including aerosols. It is possible that the CERES incorrectly identified regions of high humidity and high aerosol concentration as being cloud contaminated and, hence, overestimated the clear sky net downward solar flux.

Chou, Mong-Dah; Chan, Pui-King; Wang, Menghua; Einaudi, Franco (Technical Monitor)

2000-01-01

255

Optical Properties of Aerosol in Seoul from MODIS and Skyradiometer Measurements  

E-print Network

1 Optical Properties of Aerosol in Seoul from MODIS and Skyradiometer Measurements Ja-Ho Koo, Jhoon University, Seoul, Korea #12;2 Contents · Introduction · Site and Instrument · Time series of Aerosol Optical Properties ­ June peak of Aerosol Optical Depth (AOD) in 2006 ­ AOD trend retrieved from MODIS measurement

Wang, Yuhang

256

Retrieval of Aerosol Optical Properties under Thin Cirrus from MODIS  

NASA Technical Reports Server (NTRS)

Retrieval of aerosol optical properties using shortwave bands from passive satellite sensors, such as MODIS, is typically limited to cloud-free areas. However, if the clouds are thin enough (i.e. thin cirrus) such that the satellite-observed reflectance contains signals under the cirrus layer, and if the optical properties of this cirrus layer are known, the TOA reflectance can be corrected for the cirrus layer to be used for retrieving aerosol optical properties. To this end, we first correct the TOA reflectances in the aerosol bands (0.47, 0.55, 0.65, 0.86, 1.24, 1.63, and 2.12 micron for ocean algorithm and 0.412, 0.47, and 0.65 micron for deep blue algorithm) for the effects of thin cirrus using 1.38 micron reflectance and conversion factors that convert cirrus reflectance in 1.38 micron band to those in aerosol bands. It was found that the conversion factors can be calculated by using relationships between reflectances in 1.38 micron band and minimum reflectances in the aerosol bands (Gao et al., 2002). Refer to the example in the figure. Then, the cirrus-corrected reflectance can be calculated by subtracting the cirrus reflectance from the TOA reflectance in the optically thin case. A sensitivity study suggested that cloudy-sky TOA reflectances can be calculated with small errors in the form of simple linear addition of cirrus-only reflectances and clear-sky reflectances. In this study, we correct the cirrus signals up to TOA reflectance at 1.38 micron of 0.05 where the simple linear addition is valid without extensive radiative transfer simulations. When each scene passes the set of tests shown in the flowchart, the scene is corrected for cirrus contamination and passed into aerosol retrieval algorithms.

Lee, Jaehwa; Hsu, Nai-Yung Christina; Bettenhausen, Corey; Sayer, Andrew Mark.

2014-01-01

257

MODIS Aerosol Optical Depth retrieval over South America: sensitivity on modeled aerosol from improved AERONET regional climatology  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols affect climate directly, through absorption and scattering of solar radiation, and indirectly, altering cloud formation mechanisms and properties. The radiation balance is a critical component of climate system and an increase in aerosol concentration causes a net change in radiation budget. Estimating aerosol direct radiative forcing combines, as input to radiative transfer codes, aerosol optical and microphysical models obtained through surface remote sensing and aerosol optical depth (AOD) from satellite data. Besides information on aerosol, atmospheric and surface conditions play also significant role along the estimation process. The purpose of this work is to study the sensitivity of AOD MODIS retrievals over South America to regional aerosol properties from AERONET ground-based data, and to typical atmospheric and surface conditions observed from satellite. Since May 2007, INPE counts on a regional system of aerosol retrieval from MODIS, based on NASA/GSFC algorithms. A new version of this product is under development, with changes on aerosol properties assumed inside the retrieval. Long-term measurements (1999-2006) from 9 AERONET sites over South America were used by LFA (Laboratory of Atmospheric Physics, USP) to produce a new set of regional aerosol models, allowing better characterization of aerosol types over this region. These models were combined with AOD from MODIS data as input to SBDART. The obtained results show that sensitivity of retrieved AOD on modeled microphysical and optical properties is much larger than that on atmospheric vertical profile. For instance, differences between the typical single scattering albedo observed at different AERONET sites create large discrepancies on regional scale MODIS retrievals. The results allow us to conclude that improvements on aerosol optical and microphysical modeling inside MODIS aerosol retrievals are critical in order to obtain a much more reliable tool on estimating aerosol radiative forcing. The use of AERONET climatology to produce regional aerosol models appears as a key method to this goal.

Pires, C.; Correia, A. L.; Paixao, M.

2007-12-01

258

Aerosol Optical Depth over Africa retrieved from AATSR  

NASA Astrophysics Data System (ADS)

Aerosols produced over the African continent have important consequences for climate. In particular, large amounts of desert dust are produced over the Sahara and transported across the North Atlantic where desert dust deposition influences the eco system by iron fertilization, and further North over Europe with outbreaks as far as Scandinavia. Biomass burning occurs in most of the African continent south of the Sahara and causes a net positive radiating forcing resulting in local warming of the atmosphere layers. These effects have been studied during large field campaigns. Satellites can systematically provide information on aerosols over a large area such as Africa and beyond. To this end, we retrieved the Aerosol Optical Depth (AOD) at three wavelengths (555nm, 670nm, and 1600nm) over Africa from the reflectance measured at the top of the atmosphere by the AATSR (Advances Along Track Scanning Radiometer) flying on ENVISAT, for one year (1 May 2008 to 30 April 2009) to obtain information on the seasonal and spatial behaviour of the AOD, episodes of high AOD events and connect the retrieved AOD with the ground-based aerosol measurements. The AOD retrieval algorithm, which is applied to cloud-free pixels over land, is based on the comparison of the measured and modeled reflectance at the top of the atmosphere (TOA). The algorithm uses look-up-tables (LUTs) to compute the modeled TOA reflectance. For AOD retrieval, an aerosol in the atmosphere is assumed to be an external mixture of fine and coarse mode particles. The two aerosol types are mixed such that the spectral behavior of the reflectance due to aerosol best fits the measurements. Comparison with AERONET (Aerosol Roboric NETwork), which is a network of ground-based sun photometers which measure atmospheric aerosol properties, shows good agreement but with some overestimation of the AATSR retrieved AOD. Different aerosol models have been used to improve the comparison. The lack of AERONET stations in Africa, its location in similar-type environments, while Africa is a continent with desert-to-rainforest lands with steppe, savanna, woodlands in between, makes it difficult to select the most appropriate aerosol types in the retrieval. We aim to find the connection of the aerosol types used in retrieval with the seasonality (rainy season, dry season, biomass burning season) and air mass transport (e.g., transport of Sahara dust).

Sogacheva, Larisa; de Leeuw, Gerrit; Kolmonen, Pekka; Sundström, Anu-Maija; Rodriques, Edith

2010-05-01

259

A hybrid total internal reflection fluorescence and optical tweezers microscope to study cell adhesion and membrane protein dynamics of single living cells.  

PubMed

The dynamics of cell surface membrane proteins plays an important role in cell-cell interactions. The onset of the interaction is typically not precisely controlled by current techniques, making especially difficult the visualization of early-stage dynamics. We have developed a novel method where optical tweezers are used to trap cells and precisely control in space and time the initiation of interactions between a cell and a functionalized surface. This approach is combined with total internal reflection fluorescence microscopy to monitor dynamics of membrane bound proteins. We demonstrate an accuracy of approximately 2 s in determining the onset of the interaction. Furthermore, we developed a data analysis method to determine the dynamics of cell adhesion and the organization of membrane molecules at the contact area. We demonstrate and validate this approach by studying the dynamics of the green fluorescent protein tagged membrane protein activated leukocyte cell adhesion molecule expressed in K562 cells upon interaction with its ligand CD6 immobilized on a coated substrate. The measured cell spreading is in excellent agreement with existing theoretical models. Active redistribution of activated leukocyte cell adhesion molecule is observed from a clustered to a more homogenous distribution upon contact initiation. This redistribution follows exponential decay behaviour with a characteristic time of 35 s. PMID:19196415

Snijder-Van As, M I; Rieger, B; Joosten, B; Subramaniam, V; Figdor, C G; Kanger, J S

2009-01-01

260

A Study on the Optical Properties of Aerosols above the Forest by Remote Sensing  

Microsoft Academic Search

Aerosol retrieval by remote sensing technique is one of the promising method in understanding the chemical and optical properties, column load, and spatial distribution of aerosols. However, though the current technique in use is quite successful about aerosols over ocean with small water-leaving radiances, quantitative retrieval of aerosols over land mass is not yet satisfactory. We try to develop a

J. Bian

2004-01-01

261

Retrieval of aerosol optical thickness over land surfaces from top-of-atmosphere radiance  

Microsoft Academic Search

Aerosol remote sensing requires techniques enabling the determination of aerosol optical thickness (AOT) over land surfaces, because the most important sources (continental aerosols, anthropogenic aerosols, biomass burning, desert dust, volcano eruptions and others) are on continents. Here a retrieval method for the AOT over land surfaces from top-of-atmosphere (TOA) radiance using nadir looking instruments of the ocean color type (like

W. von Hoyningen-Huene; M. Freitag; J. B. Burrows

2003-01-01

262

Using molecular tweezers to move and image nanoparticles.  

PubMed

The ability to manipulate nanoparticles is significant in nanoscale science and technology. As sizes of the objects scale down to the sub-10 nm regime, it imposes a great challenge for the conventional optical tweezers. There has been much effort to explore alternative manipulation methods including using nanostructures, electron beams, scanning probes, etc. In this paper, an overview of the latest advances in trapping and manipulation of nanoparticles with a focus on the emergent electron tweezers is provided. PMID:23592008

Zheng, Haimei

2013-05-21

263

Variability of aerosol optical thickness and atmospheric turbidity in Tunisia  

NASA Astrophysics Data System (ADS)

The aerosol optical thickness (AOT) ?a computed from the spectral sun photometer in Thala (Tunisia) exhibited variability ranging from approximately 0.03 to greater than 2.0 at 870 nm for March-October 2001. These measurements are compared to the aerosol optical thickness computed in Ouagadougou (Burkina-Faso), Banizoumbou (Niger), IMC Oristano (Sardinia) and Rome Tor Vergata (Italy). Analysis of ?a data from this observation network suggests that there is a high temporal and spatial variability of ?a in the different sites. The Angström wavelength exponent ? was found to vary with the magnitude of the aerosol optical thickness, with values as high as 1.5 for very low ?a, and values of -0.1 for high ?a situations. The relationship between the two parameters ?a and ? is investigated. Values of the turbidity coefficient ? have been determined in Thala (Tunisia) for 8 months in 2001 based on a direct fitting method of the Angström power law expression using sun photometer data. The monthly averaged values of the turbidity coefficient ? vary between 0.15 and 0.33. The months of July and October experienced the highest turbidity, while April experienced the lowest aerosol loading on average. The turbidity shows a maximum and minimum values for the Southwest and the Northwest wind directions, respectively. The single scattering albedo ?o for the 870 nm wavelength obtained from solar aureole data in Thala is analysed according to the particles' origin.

Masmoudi, M.; Chaabane, M.; Medhioub, K.; Elleuch, F.

264

Aerosol optical depth determination from ground based irradiance ratios  

SciTech Connect

The atmospheric optical depth serves as an input parameter to atmospheric correction procedures in remote sensing and as an index of atmospheric opacity or constituent columnar abundance for meteorological applications. Its measurement, typically performed by means of a small field of view radiometer centered on the solar disk, is sensitive to the absolute calibration accuracy of the instrument. In this paper a simple technique is presented which permits the extraction of aerosol optical depth from the ratio of total to direct irradiance measurements. An error analysis performed on the results of radiative transfer simulations and field measurements indicates that the technique generates values of aerosol optical depth which are sufficiently accurate for many applications. This method thus represents a useful alternative to standard sunphotometer measurements.

Miller, J. R.; O'Neill, N. T.; Boyer, A.

1989-08-01

265

Effect of Dust and Anthropogenic Aerosols on Columnar Aerosol Optical Properties over Darjeeling (2200 m asl), Eastern Himalayas, India  

PubMed Central

Background The loading of atmospheric particulate matter (aerosol) in the eastern Himalaya is mainly regulated by the locally generated anthropogenic aerosols from the biomass burning and by the aerosols transported from the distance sources. These different types of aerosol loading not only affect the aerosol chemistry but also produce consequent signature on the radiative properties of aerosol. Methodology/Principal Findings An extensive study has been made to study the seasonal variations in aerosol components of fine and coarse mode aerosols and black carbon along with the simultaneous measurements of aerosol optical depth on clear sky days over Darjeeling, a high altitude station (2200 masl) at eastern Himalayas during the year 2008. We observed a heavy loading of fine mode dust component (Ca2+) during pre-monsoon (Apr – May) which was higher by 162% than its annual mean whereas during winter (Dec – Feb), the loading of anthropogenic aerosol components mainly from biomass burning (fine mode SO42? and black carbon) were higher (76% for black carbon and 96% for fine mode SO42?) from their annual means. These high increases in dust aerosols during pre-monsoon and anthropogenic aerosols during winter enhanced the aerosol optical depth by 25 and 40%, respectively. We observed that for every 1% increase in anthropogenic aerosols, AOD increased by 0.55% during winter whereas for every 1% increase in dust aerosols, AOD increased by 0.46% during pre-monsoon. Conclusion/Significance The natural dust transport process (during pre-monsoon) plays as important a role in the radiation effects as the anthropogenic biomass burning (during winter) and their differential effects (rate of increase of the AOD with that of the aerosol concentration) are also very similar. This should be taken into account in proper modeling of the atmospheric environment over eastern Himalayas. PMID:22792264

Chatterjee, Abhijit; Ghosh, Sanjay K.; Adak, Anandamay; Singh, Ajay K.; Devara, Panuganti C. S.; Raha, Sibaji

2012-01-01

266

Recent trends in aerosol optical properties derived from AERONET measurements  

NASA Astrophysics Data System (ADS)

The Aerosol Robotic Network (AERONET) has been providing high-quality retrievals of aerosol optical properties from the surface at worldwide locations for more than a decade. Many sites have continuous and consistent records for more than 10 years, which enables the investigation of long-term trends of aerosol properties at these locations. In this study, we present trend analysis of AERONET data at 63 selected locations. In addition to commonly studied parameters such as Aerosol Optical Depth (AOD) and Ångström Exponent (AE), we also focus on Absorption Aerosol Optical Depth (ABS), Scattering Optical Depth (SCT), Single Scattering Albedo (SSA) and the Absorption Ångström Exponent (AAE). Two statistical methods are used to detect and estimate the trend: Mann-Kendall test associated with Sen's slope and linear least square fitting. Their results agree well in terms of the significance of the trend for the majority of the cases. The results indicate that Europe and North America experienced a uniform decrease in AOD and SCT, while significant (> 90%) increases of these two parameters are found for Kanpur, India. Most of European and North American sites also show negative trends for ABS, as well as three East Asian stations. The reduction in ABS results in positive SSA trends for these locations. The increase of SCT also leads to a positive SSA trend for Kanpur. Negative SSA trends are mostly found over South America, Australia and a few West European stations, which are mainly attributed to the increase of absorption. Fewer stations are found with significant trends for AE and AAE. In general, the trends do not exhibit obvious seasonality for the majority of the parameters and stations.

Li, J.; Carlson, B. E.; Dubovik, O.; Lacis, A. A.

2014-06-01

267

Contribution of particulate water to the measured aerosol optical properties of aged aerosol  

NASA Astrophysics Data System (ADS)

Measurements of aged aerosol scattering in the Eastern Mediterranean at ambient and low relative humidity (RH) are combined with measurements of its size composition distribution and its aerosol water content to gain insights about its hygroscopic and optical properties. The particle water uptake above 60% RH can be explained by the water absorption by the inorganic particulate matter in this sulphate rich environment. However, the particles were supersaturated aqueous solutions at low RH and this water cannot be explained just by the water associated with their inorganic components in a metastable state. We estimate that approximately 20% of this water may be contributed by the aged organic particulate matter. A semi-empirical equation is derived allowing the estimation of the aged aerosol Volume Growth Factor (VGF) from the ratios of scattering at ambient and low RH. The predictions of the equation are in good agreement with the measurement dataset obtained during the study.

Pilinis, Christodoulos; Charalampidis, Panagiotis E.; Mihalopoulos, Nikolaos; Pandis, Spyros N.

2014-01-01

268

Investigation of the transformation of aerosol microphysical characteristics by thermo-optical method  

Microsoft Academic Search

This paper is devoted to the analysis of thermo-optical characteristics of atmospheric aerosol particles obtained at artificial heating of sampled aerosol. The change in the particle size distribution and in the optical constants of the aerosol matter at heating up to 250°C is studied. The volatility factor in temperature range 25 to 100°C is determined as function of the particle's

Mikhail V. Panchenko; Svetlana A. Terpugova; Mikhail A. Sviridenkov

2004-01-01

269

Optical characterization of continental and biomass-burning aerosols over Bozeman, Montana: A case study of the aerosol direct effect  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol optical properties were observed from 21 to 27 September 2009 over Bozeman, Montana, during a transitional period in which background polluted rural continental aerosols and well-aged biomass-burning aerosols were the dominant aerosol types of extremely fresh biomass-burning aerosols resulting from forest fires burning in the northwestern United States and Canada. Aerosol optical properties and relative humidity profiles were retrieved using an eye-safe micropulse water vapor differential absorption lidar (DIAL) (MP-DIAL), a single-channel backscatter lidar, a CIMEL solar radiometer as part of the Aerosol Robotic Network (AERONET), a ground-based integrating nephelometer, and aerosol products from Moderate Resolution Imaging Spectroradiometer (MODIS) Terra and Aqua. Aerosol optical depths (AODs) measured during the case study ranged between 0.03 and 0.17 (0.015 and 0.075) at 532 nm (830 nm) as episodic combinations of fresh and aged biomass-burning aerosols dominated the optical depth of the pristinely clean background air. Here, a pristinely clean background refers to very low AOD conditions, not that the aerosol scattering and absorption properties are necessarily representative of a clean aerosol type. Diurnal variability in the aerosol extinction to backscatter ratio (Sa) of the background atmosphere derived from the two lidars, which ranged between 55 and 95 sr (50 and 90 sr) at 532 nm (830 nm), showed good agreement with retrievals from AERONET sun and sky measurements over the same time period but were consistently higher than some aerosol models had predicted. Sa measured during the episodic smoke events ranged on average from 60 to 80 sr (50 to 70 sr) at 532 nm (830 nm) while the very fresh biomass-burning aerosols were shown to exhibit significantly lower Sa ranging between 20 and 40 sr. The shortwave direct radiative forcing that was due to the intrusion of biomass-burning aerosols was calculated to be on average -10 W/m2 and was shown to compare favorably with regional-scale forcing calculations using MODIS-Terra and AERONET data in an effort to assess the accuracy of estimating the regional-scale aerosol direct radiative forcing effect using aerosol optical properties measured from a single rural site such as Bozeman, Montana.

Nehrir, Amin R.; Repasky, Kevin S.; Reagan, John A.; Carlsten, John L.

2011-11-01

270

Aerosol deposition for optical and electroceramic applications  

Microsoft Academic Search

A new technique for the fabrication of substrates for optical planar waveguides, fiber optics, and thin films of electroceramic capacitors has been developed. We dope multi-component elements (Si, Ge, B, Al, Na, Ga, Zn, P, and rare earths) into glass waveguide on the Si wafers. Pyrex (SiOsb2-Bsb2Osb3-Alsb2Osb3-Nasb2O, n = 1.4696) based glasses are very promising candidates for rare-earth doped host,

Chih-Hung Wei

1997-01-01

271

Study of formation and convective transport of aerosols using optical diagnostic technique  

E-print Network

The characteristics of liquid and solid aerosols have been intensively investigated by means of optical diagnostic techniques. Part I describes the characteristics of liquid aerosol formation formed by heat transfer fluids (HTFs) from bulk liquids...

Kim, Tae-Kyun

2004-09-30

272

Cloud-Driven Changes in Aerosol Optical Properties - Final Technical Report  

SciTech Connect

The optical properties of aerosol particles are the controlling factors in determining direct aerosol radiative forcing. These optical properties depend on the chemical composition and size distribution of the aerosol particles, which can change due to various processes during the particles’ lifetime in the atmosphere. Over the course of this project we have studied how cloud processing of atmospheric aerosol changes the aerosol optical properties. A counterflow virtual impactor was used to separate cloud drops from interstitial aerosol and parallel aerosol systems were used to measure the optical properties of the interstitial and cloud-scavenged aerosol. Specifically, aerosol light scattering, back-scattering and absorption were measured and used to derive radiatively significant parameters such as aerosol single scattering albedo and backscatter fraction for cloud-scavenged and interstitial aerosol. This data allows us to demonstrate that the radiative properties of cloud-processed aerosol can be quite different than pre-cloud aerosol. These differences can be used to improve the parameterization of aerosol forcing in climate models.

Ogren, John A.; Sheridan, Patrick S.; Andrews, Elisabeth

2007-09-30

273

Quantifying aerosol direct effects from broadband irradiance and spectral aerosol optical depth observations  

NASA Astrophysics Data System (ADS)

outline a methodology using broadband and spectral irradiances to quantify aerosol direct effects on the surface diffuse shortwave (SW) irradiance. Best Estimate Flux data span a 13 year timeframe at the Department of Energy Atmospheric Radiation Measurement Program's Southern Great Plains (SGP) site. Screened clear-sky irradiances and aerosol optical depth (AOD), for solar zenith angles ? 65°, are used to estimate clear-sky diffuse irradiances. We validate against detected clear-sky observations from SGP's Basic Radiation System (BRS). BRS diffuse irradiances were in accordance with estimates, producing a root-mean-square error and mean bias errors of 4.0 W/m2 and -1.4 W/m2, respectively. Absolute differences show 99% of estimates within ±10 W/m2 (10%) of the mean BRS observations. Clear-sky diffuse estimates are used to derive quantitative estimates of aerosol radiative effects, represented as the aerosol diffuse irradiance (ADI). ADI is the contribution of diffuse SW to global SW, attributable to scattering of atmospheric transmission by natural plus anthropogenic aerosols. Estimated slope for the ADI as a function of AOD indicates an increase of ~22 W/m2 in diffuse SW for every 0.1 increase in AOD. Such significant increases in the diffuse fraction could possibly increase photosynthesis. Annual mean ADI is 28.2 W/m2, and heavy aerosol loading at SGP provides up to a maximum increase of 120 W/m2 in diffuse SW over background conditions. With regard to seasonal variation, the mean diffuse forcings are 17.2, 33.3, 39.0, and 23.6 W/m2 for winter, spring, summer, and fall, respectively.

Creekmore, Torreon N.; Joseph, Everette; Long, Charles N.; Li, Siwei

2014-05-01

274

Optical and Chemical Characterization of Aerosols Produced from Cooked Meats  

NASA Astrophysics Data System (ADS)

Cooking processes can release a variety compounds into the air immediately above a cooking surface. The distribution of compounds will largely depend on the type of food that is being processed and the temperatures at which the food is prepared. High temperatures release compounds from foods like meats and carry them away from the preparation surface into cooler regions where condensation into particles can occur. Aerosols formed in this manner can impact air quality, particularly in urban areas where the amount of food preparation is high. Reported here are the results of laboratory experiments designed to optically and chemically characterize aerosols derived from cooking several types of meats including ground beef, salmon, chicken, and pork both in an inert atmosphere and in synthetic air. The laboratory-generated aerosols are studied using a laminar flow cell that is configured to accommodate simultaneous optical characterization in the mid-infrared and collection of particles for subsequent chemical analysis by gas chromatography. Preliminary optical results in the visible and ultra-violet will also be presented.

Niedziela, R. F.; Foreman, E.; Blanc, L. E.

2011-12-01

275

Columnar Aerosol Optical Properties during "El Arenosillo 2004 Summer Campaign"  

SciTech Connect

A detailed analysis of the microphysical and radiative columnar aerosol parameters has been carried out for data collected during the “El Arenosillo 2004” summer campaign. These data are derived from a Cimel sun-photometer, as part of the PHOTONS-AERONET network at the El Arenosillo site in south-western Spain, over the period 1 June to 31 October 2004. The aim of this campaign was to obtain a more complete set of data on aerosol microphysical, optical/radiative, and chemical properties for use in closure studies. Previous papers addressed the climatology of the AOD-alpha parameters at this site. In this paper, we focus on the characterization of the particle size distribution and associated microphysical parameters, such as volume concentration, effective radius, etc., in order to define the features and ranges of these physical parameters associated with both fine and coarse particle modes. The requirement of high AOD values for using the optical inversion technique puts significant constraints on the estimation of these parameters and, thus, necessitates great care in the analysis. As a result, only the characterizations for desert dust events are considered reliable. Moreover, summer 2004 had the most frequent desert dust intrusions, including the most intense event, ever recorded at the El Arensillo site. We summarize the results for the intensive summer campaign in terms of the range of values of the physical and optical parameters of the mixed aerosol types present in this area of Spain.

Prats, N.; Cachorro, V. E.; Sorribas, M.; Mogo, S.; Berjon, A.; Toledano, C.; de Frutos, A. M.; de la Rosa, J.; Laulainen, Nels S.; de la Morena, B. A.

2008-04-14

276

Preliminary results of a non-spherical aerosol method for the retrieval of the atmospheric aerosol optical properties  

Microsoft Academic Search

There is experimental evidence that the non-sphericity of certain atmospheric particles can cause scattering properties different from those predicted by standard Mie theory. Numerous studies indicate the need to consider the presence of non-spherical particles in modeling the optical properties of atmospheric aerosols. On the other hand, natural aerosols show a great variety of shapes, making difficult a realistic choice

F. J. Olmo; A. Quirantes; A. Alcántara; H. Lyamani; L. Alados-Arboledas

2006-01-01

277

Spatial and temporal variations of aerosols around Beijing in summer 2006: 2. Local and column aerosol optical properties  

Microsoft Academic Search

Model calculations were conducted using the Weather Research and Forecasting model coupled with chemistry (WRF-chem) for the region around Beijing, China, in the summer of 2006, when the CAREBeijing-2006 intensive campaign was conducted. In this paper, we interpret aerosol optical properties in terms of aerosol mass concentrations and their chemical compositions by linking model calculations with measurements. The model calculations

Hitoshi Matsui; Makoto Koike; Yutaka Kondo; Nobuyuki Takegawa; Jerome D. Fast; U. Pöschl; R. M. Garland; M. O. Andreae; A. Wiedensohler; N. Sugimoto; T. Zhu

2010-01-01

278

In situ aerosol profiles over the Southern Great Plains cloud and radiation test bed site: 1. Aerosol optical properties  

Microsoft Academic Search

Aerosol optical properties were measured over the Southern Great Plains (SGP) cloud and radiation test bed site using a light aircraft (Cessna C-172N). The aircraft flew level legs at altitudes between 500 m and 3500 m several times per week over the course of 2 years in order to obtain a statistically representative data set of in situ aerosol vertical

Elisabeth Andrews; Patrick J. Sheridan; John A. Ogren; Richard Ferrare

2004-01-01

279

Africa Aerosol Optical Depth Obtained From MISR  

E-print Network

OpticalDepth Central African Republic Chad Djibouti Egypt Ethiopia Libya Kenya Somalia Sudan Uganda #12;Southern Africa Madagascar Malawi Mozambique Namibia Rwanda South Africa Swaziland Tanzania, United Republic of Zaire Zambia Ethiopia Libya Kenya Somalia Sudan Uganda #12;Southern Africa 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 Mean Seasonal

Frank, Thomas D.

280

Nanoscale Molecular Tweezers  

NSDL National Science Digital Library

The featured molecules for this month are drawn from the "Research Advances" column by Angela G. King, and represent some of the structures from the research on molecular tweezers (published in J. Am. Chem. Soc. 2004, 126, 8124). The structures below are based on the figure on page 1690 showing two types of receptors that switch between U and W shapes upon coordination of soft metal cations, acting in the manner of mechanical tweezers. When viewing these molecules in Chime you must render in ball and stick or space filling modes in order to see the incorporated metal ions. In several cases the torsion angles connecting the anthracene substituents to the rest of the molecule are not well defined and have been drawn as either coplanar or orthogonal to the central ring system. At a moderate level of theory, the torsion angle in those instances where it has been set to 90° displays a broad minimum ranging for 50?130°.

281

On factors controlling marine boundary layer aerosol optical depth  

NASA Astrophysics Data System (ADS)

spray aerosol is one of the largest natural contributors to the global aerosol loading and thus plays an important role in the global radiative budget through both direct and indirect effects. Previous studies have shown either strong or weak relationships between marine boundary layer (MBL) aerosol optical depth (?) and the near-surface wind speed. However, the marine ? is influenced by a wide range of factors. This study attempts to examine extra contributing factors beyond wind to better characterize MBL ? variations over the global ocean by using 4 year A-train data (2006-2010). The results show that among many factors controlling MBL ?, surface wind speed and MBL depth are the two most important factors. This suggests that not only mechanical production of sea spray particles driven by near-surface wind processes but also vertical redistribution driven by turbulent and shallow convective mixing in the MBL controls MBL ? variations. A new two-parameter parameterization of ? was derived based on satellite measurements. Evaluations with independent data show that the new parameterization improves the prediction of MBL ?. The comparisons between the Fu-Liou radiative transfer model calculations and Aqua Clouds and the Earth's Radiant Energy System observations showed that the new parameterization improves the estimation of aerosol radiative forcing.

Luo, Tao; Yuan, Renmin; Wang, Zhien

2014-03-01

282

Optical Properties of Mixed Black Carbon, Inorganic and Secondary Organic Aerosols  

SciTech Connect

Summarizes the achievements of the project, which are divided into four areas: 1) Optical properties of secondary organic aerosols; 2) Development and of a polar nephelometer to measure aerosol optical properties and theoretical approaches to several optical analysis problems, 3) Studies on the accuracy of measurements of absorbing carbon by several methods, and 4) Environmental impacts of biodiesel.

Paulson, S E

2012-05-30

283

Aerosol optical depth, aerosol composition and air pollution during summer and winter conditions in Budapest.  

PubMed

The dependence of aerosol optical depth (AOD) on air particulate concentrations in the mixing layer height (MLH) was studied in Budapest in July 2003 and January 2004. During the campaigns gaseous (CO, SO(2), NO(x), O(3)), solid components (PM(2.5), PM(10)), as well as ionic species (ammonium, sulfate and nitrate) were measured at several urban and suburban sites. Additional data were collected from the Budapest air quality monitoring network. AOD was measured by a ground-based sun photometer. The mixing layer height and other common meteorological parameters were recorded. A linear relationship was found between the AOD and the columnar aerosol burden; the best linear fit (R(2)=0.96) was obtained for the secondary sulfate aerosol due to its mostly homogeneous spatial distribution and its optically active size range. The linear relationship is less pronounced for the PM(2.5) and PM(10) fractions since local emissions are very heterogeneous in time and space. The results indicate the importance of the mixing layer height in determining pollutant concentrations. During the winter campaign, when the boundary layer decreases to levels in between the altitudes of the sampling stations, measured concentrations showed significant differences due to different local sources and long-range transport. In the MLH time series unexpected nocturnal peaks were observed. The nocturnal increase of the MLH coincided with decreasing concentrations of all pollutants except for ozone; the ozone concentration increase indicates nocturnal vertical mixing between different air layers. PMID:17570465

Alföldy, B; Osán, J; Tóth, Z; Török, S; Harbusch, A; Jahn, C; Emeis, S; Schäfer, K

2007-09-20

284

Optical Properties of Fine/Coarse Mode Aerosol Mixtures  

NASA Astrophysics Data System (ADS)

Several regions of the earth exhibit seasonal mixtures of fine and coarse mode sized aerosol types, which are challenging to characterize from satellite remote sensing. Over land the coarse mode size aerosols (radius >1 micron) originate primarily from arid regions, which generate airborne soil dust, and the dominant fine mode sources are gases and particulates from urban/industrial emissions and from biomass burning. AERONET sun-sky radiometer almucantar retrievals from several years are analyzed for the urban sites of Beijing, China and Kanpur, India (in the Ganges floodplain) where seasonal coarse mode dust particles mix with fine mode pollution aerosol, predominately in the spring. As increasingly more absorbing fine mode pollutants are added to the dust aerosol at both sites, the single scattering albedo (SSA) of the mixtures at 675 nm through 1020 nm decrease as the fine mode fraction of AOD increases, while the 440 nm SSA is relatively constant. Additionally we compare multi-year data from Ilorin, Nigeria where desert dust from the Sahara and Sahel mix with fine mode biomass-burning aerosols. The volume size distribution retrievals from this site often shows tri-modality (third mode centered at 0.6 micron radius), which suggests a different particle source than found for most other arid region AERONET sites, which typically have bi-modal distributions. Comparison of mid-visible single scattering albedo obtained from in situ aircraft measurements during DABEX to multi-year means from the Ilorin site AERONET retrievals show close agreement (within 0.03 or less) over a wide range of Angstrom exponent (0.3 to 1.5). Observed differences in the spectral SSA as a function of fine mode fraction of the optical depth between all three sites are discussed and occur due to differences in absorption for both modes and also due to fine mode particle size dynamics.

Eck, T. F.; Holben, B. N.; Siniuk, A.; Pinker, R. T.; Goloub, P.; Chen, H.; Chatenet, B.; Li, Z.; Singh, R.; Tripathi, S. N.; Dubovik, O.; Giles, D. M.; Martins, J.; Reid, J. S.; O'Neill, N. T.; Smirnov, A.

2009-12-01

285

Can satellite-derived aerosol optical depth quantify the surface aerosol radiative forcing?  

NASA Astrophysics Data System (ADS)

Aerosols play an important role in the climate of the Earth through aerosol radiative forcing (ARF). Nowadays, aerosol particles are detected, quantified and monitored by remote sensing techniques using low Earth orbit (LEO) and geostationary (GEO) satellites. In the present article, the use of satellite-derived AOD (aerosol optical depth) products is investigated in order to quantify on a daily basis the ARF at the surface level (SARF). By daily basis we mean that an average SARF value is computed every day based upon the available AOD satellite measurements for each station. In the first part of the study, the performance of four state-of-art different AOD products (MODIS-DT, MODIS-DB, MISR, and SEVIRI) is assessed through comparison against ground-based AOD measurements from 24 AERONET stations located in Europe and Africa during a 6-month period. While all AOD products are found to be comparable in terms of measured value (RMSE of 0.1 for low and average AOD values), a higher number of AOD estimates is made available by GEO satellites due to their enhanced frequency of scan. Experiments show a general lower agreement of AOD estimates over the African sites (RMSE of 0.2), which show the highest aerosol concentrations along with the occurrence of dust aerosols, coarse particles, and bright surfaces. In the second part of this study, the lessons learned about the confidence in aerosol burden derived from satellites are used to estimate SARF under clear sky conditions. While the use of AOD products issued from GEO observations like SEVIRI brings improvement in the SARF estimates with regard to LEO-based AOD products, the resulting absolute bias (13 W/m2 in average when AERONET AOD is used as reference) is judged to be still high in comparison with the average values of SARF found in this study (from - 25 W/m2 to - 43 W/m2) and also in the literature (from - 10 W/m2 to - 47 W/m2).

Xu, Hui; Ceamanos, Xavier; Roujean, Jean-Louis; Carrer, Dominique; Xue, Yong

2014-12-01

286

Simulations of the Aerosol Index and the Absorption Aerosol Optical Depth and Comparisons with OMI Retrievals During ARCTAS-2008 Campaign  

NASA Technical Reports Server (NTRS)

We have computed the Aerosol Index (AI) at 354 nm, useful for observing the presence of absorbing aerosols in the atmosphere, from aerosol simulations conducted with the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) module running online the GEOS-5 Atmospheric GCM. The model simulates five aerosol types: dust, sea salt, black carbon, organic carbon and sulfate aerosol and can be run in replay or data assimilation modes. In the assimilation mode, information's provided by the space-based MODIS and MISR sensors constrains the model aerosol state. Aerosol optical properties are then derived from the simulated mass concentration and the Al is determined at the OMI footprint using the radiative transfer code VLIDORT. In parallel, model derived Absorption Aerosol Optical Depth (AAOD) is compared with OMI retrievals. We have focused our study during ARCTAS (June - July 2008), a period with a good sampling of dust and biomass burning events. Our ultimate goal is to use OMI measurements as independent validation for our MODIS/MISR assimilation. Towards this goal we document the limitation of OMI aerosol absorption measurements on a global scale, in particular sensitivity to aerosol vertical profile and cloud contamination effects, deriving the appropriate averaging kernels. More specifically, model simulated (full) column integrated AAOD is compared with model derived Al, this way identifying those regions and conditions under which OMI cannot detect absorbing aerosols. Making use of ATrain cloud measurements from MODIS, C1oudSat and CALIPSO we also investigate the global impact on clouds on OMI derived Al, and the extent to which GEOS-5 clouds can offer a first order representation of these effects.

2010-01-01

287

The Optical Constants of Several Atmospheric Aerosol Species: Ammonium Sulfate, Aluminum Oxide, and Sodium Chloride  

Microsoft Academic Search

The optical constants of substances composing atmospheric aerosols are required to evaluate properly the effects of aerosols on the earth's radiation balance. We briefly review techniques for determining optical constants and also discuss pitfalls in using measured optical constants to simulate the optical constants of the real particles found in the atmosphere. We then compile the optical constants of (NH4hSO4,

Owen B. Toon; James B. Pollack; Bishun N. Khare

1976-01-01

288

Optical Tweezers-Assisted Cross-Correlation Analysis for a Non-intrusive Fluid Temperature Measurement in Microdomains  

NASA Astrophysics Data System (ADS)

An image-based approach to predict the fluid temperature in microfluidic flow cell is presented. We apply Fourier-based cross-correlation processing to determine the lateral displacement of the optically trapped bead; therefore, both the mean square displacement (MSD) and the diffusion coefficient (D) can be obtained. On the other hand, applying the Stokes-Einstein equation, together with Faxen's law correction, the theoretical relation showed that D is proportional to (T/?), where T and ? are temperature and temperature-dependent fluid viscosity, respectively. Hence, the fluid temperature can be determined by MSD-based thermometry.

Cheng, Chih-Ming; Chang, Ming-Chih; Chang, Yu-Fen; Wang, Wei-Ting; Hsu, Chien-Ting; Tsai, Jing-Shin; Liu, Chia-Yeh; Wu, Chien-Ming; Ou, Keng-Liang; Yang, Tzu-Sen

2012-06-01

289

Investigation of aerosol optical properties in Bangkok and suburbs  

NASA Astrophysics Data System (ADS)

Aerosol optical depth and Angstrom coefficients for three sites in Bangkok and suburbs are examined: Silpakorn University at Nakhon Pathom, NP (13.82°N, 100.04°E), the Asian Institute of Technology at Phatum Thani, AIT (14.08°N, 100.62°E) and the Thai Meteorological Department at Bangkok, BK (13.73°N, 100.57°E). Sunphotometers have been used to measure direct normal spectral irradiance at these sites for a period of 2 years (2004-2005). Cloudless conditions were selected and Bouguer’s law was employed to obtain aerosol optical depth. All three sites exhibit strong seasonal variations, with the highest values occurring at the height of the dry season in April, and the lowest occurring during the rainy season in July. April turbidity conditions are very high, as evidenced by maximum 500 nm optical depths of between 1.4 to 2.0 that were measured at all three locations. The Angstrom exponent ? also showed a marked seasonal change, with highest values at the height of the dry season.

Janjai, S.; Suntaropas, S.; Nunez, M.

2009-05-01

290

Characteristics of spectral aerosol optical depths over India during ICARB  

NASA Astrophysics Data System (ADS)

Spectral aerosol optical depth (AOD) measurements, carried out regularly from a network of observatories spread over the Indian mainland and adjoining islands in the Bay of Bengal and Arabian Sea, are used to examine the spatio-temporal and spectral variations during the period of ICARB (March to May 2006). The AODs and the derived Ångström parameters showed considerable variations across India during the above period. While at the southern peninsular stations the AODs decreased towards May after a peak in April, in the north Indian regions they increased continuously from March to May. The Ångström coefficients suggested enhanced coarse mode loading in the north Indian regions, compared to southern India. Nevertheless, as months progressed from March to May, the dominance of coarse mode aerosols increased in the columnar aerosol size spectrum over the entire Indian mainland, maintaining the regional distinctiveness. Compared to the above, the island stations showed considerably low AODs, so too the northeastern station Dibrugarh, indicating the prevalence of cleaner environment. Long-range transport of aerosols from tshe adjoining regions leads to remarkable changes in the magnitude of the AODs and their wavelength dependencies during March to May. HYSPLIT back-trajectory analysis shows that enhanced long-range transport of aerosols, particularly from the west Asia and northwest coastal India, contributed significantly to the enhancement of AOD and in the flattening of the spectra over entire regions; if it is the peninsular regions and the island Minicoy are more impacted in April, the north Indian regions including the Indo Gangetic Plain get affected the most during May, with the AODs soaring as high as 1.0 at 500 nm. Over the islands, the Ångström exponent ( ?) remained significantly lower (˜1) over the Arabian Sea compared to Bay of Bengal (BoB) (˜1.4) as revealed by the data respectively from Minicoy and Port Blair. Occurrences of higher values of ?, showing dominance of accumulation mode aerosols, over BoB are associated well with the advection, above the boundary layer, of fine particles from the east Asian region during March and April. The change in the airmass to marine in May results in a rapid decrease in ? over the BoB.

Beegum, S. Naseema; Moorthy, K. Krishna; Nair, Vijayakumar S.; Babu, S. Suresh; Satheesh, S. K.; Vinoj, V.; Reddy, R. Ramakrishna; Gopal, K. Rama; Badarinath, K. V. S.; Niranjan, K.; Pandey, Santosh Kumar; Behera, M.; Jeyaram, A.; Bhuyan, P. K.; Gogoi, M. M.; Singh, Sacchidanand; Pant, P.; Dumka, U. C.; Kant, Yogesh; Kuniyal, J. C.; Singh, Darshan

2008-07-01

291

TRANSFORMATION OF PHYSICAL, CHEMICAL AND OPTICAL PROPERTIES OF BLACK CARBON AEROSOL PARTICLES  

E-print Network

) particle shape determination as a function of fuel-to-air ratio including observations of structuralTRANSFORMATION OF PHYSICAL, CHEMICAL AND OPTICAL PROPERTIES OF BLACK CARBON AEROSOL PARTICLES Cross, physical, and optical properties of aerosol particles containing black carbon are necessary to improve

292

Kriging interpolation method and its application in retrieval of MODIS aerosol optical depth  

Microsoft Academic Search

Dense Dark Vegetation algorithm (DDV) is effectively used in retrieval of aerosol optical depth (AOD) from satellite images over land. However, the algorithm is only suitable for low albedo areas such as water and dense vegetation areas. The purpose of this paper is mainly to retrieve aerosol optical depth over none DDV pixels by using the kriging interpolation method, we

Chao Yu; Liangfu Chen; Lin Su; Meng Fan; Shenshen Li

2011-01-01

293

High aerosol optical depth biomass burning events: A comparison of optical properties for different source regions  

NASA Astrophysics Data System (ADS)

The optical properties of aerosols such as smoke from biomass burning vary due to aging processes and these particles reach larger sizes at high concentrations. We compare the spectra of aerosol optical depth (?a), column-integrated volume size distributions, refractive indices, and single scattering albedo retrieved from AERONET observations for four selected events of very high smoke optical depth (?a ~ 2 at 500 nm). Two case studies are from tropical biomass burning regions (Brazil and Zambia) and two are cases of boreal forest and peat fire smoke transported long distances to sites in the US and Moldova. Smoke properties for these extreme events can be significantly different from those reported in more typical plumes. In particular, large differences in smoke fine mode particle radius (~0.17 to 0.25 ?m) and single scattering albedo (~0.88 to 0.99 at 440 nm) were observed as a result of differences in fuels burned, combustion phase, and aging.

Eck, T. F.; Holben, B. N.; Reid, J. S.; O'Neill, N. T.; Schafer, J. S.; Dubovik, O.; Smirnov, A.; Yamasoe, M. A.; Artaxo, P.

2003-10-01

294

Evaluation of sulfate aerosol optical depths over the North Atlantic and comparison with satellite observations  

SciTech Connect

It has been postulated that scattering of sunlight by aerosols can significantly reduce the amount of solar energy absorbed by the climate system. Aerosol measurement programs alone cannot provide all the information needed to evaluate the radiative forcing due to anthropogenic aerosols. Thus, comprehensive global-scale aerosol models, properly validated against surface-based and satellite measurements, are a fundamental tool for evaluating the impacts of aerosols on the planetary radiation balance. Analyzed meteorological fields from the European Centre for Medium-Range Weather Forecasts are used to drive a modified version of the PNL Global Chemistry Model, applied to the atmospheric sulfur cycle. The resulting sulfate fields are used to calculate aerosol optical depths, which in turn are compared to estimates of aerosol optical depth based on satellite observations.

Berkowitz, C.M.; Ghan, S.J. [Pacific Northwest Lab., Richland, WA (United States); Benkovitz, C.M.; Wagener, R.; Nemesure, S.; Schwartz, S.E. [Brookhaven National Lab., Upton, NY (United States)

1993-11-01

295

Preliminary results of the aerosol optical depth retrieval in Johor, Malaysia  

NASA Astrophysics Data System (ADS)

Monitoring of atmospheric aerosols over the urban area is important as tremendous amounts of pollutants are released by industrial activities and heavy traffic flow. Air quality monitoring by satellite observation provides better spatial coverage, however, detailed aerosol properties retrieval remains a challenge. This is due to the limitation of aerosol retrieval algorithm on high reflectance (bright surface) areas. The aim of this study is to retrieve aerosol optical depth over urban areas of Iskandar Malaysia; the main southern development zone in Johor state, using Moderate Resolution Imaging Spectroradiometer (MODIS) 500 m resolution data. One of the important steps is the aerosol optical depth retrieval is to characterise different types of aerosols in the study area. This information will be used to construct a Look Up Table containing the simulated aerosol reflectance and corresponding aerosol optical depth. Thus, in this study we have characterised different aerosol types in the study area using Aerosol Robotic Network (AERONET) data. These data were processed using cluster analysis and the preliminary results show that the area is consisting of coastal urban (65%), polluted urban (27.5%), dust particles (6%) and heavy pollution (1.5%) aerosols.

Lim, H. Q.; Kanniah, K. D.; Lau, A. M. S.

2014-02-01

296

Model analysis of influences of aerosol mixing state upon its optical properties in East Asia  

NASA Astrophysics Data System (ADS)

The air quality model system RAMS (Regional Atmospheric Modeling System)-CMAQ (Models-3 Community Multi-scale Air Quality) coupled with an aerosol optical/radiative module was applied to investigate the impact of different aerosol mixing states (i.e., externally mixed, half externally and half internally mixed, and internally mixed) on radiative forcing in East Asia. The simulation results show that the aerosol optical depth (AOD) generally increased when the aerosol mixing state changed from externally mixed to internally mixed, while the single scattering albedo (SSA) decreased. Therefore, the scattering and absorption properties of aerosols can be significantly affected by the change of aerosol mixing states. Comparison of simulated and observed SSAs at five AERONET (Aerosol Robotic Network) sites suggests that SSA could be better estimated by considering aerosol particles to be internally mixed. Model analysis indicates that the impact of aerosol mixing state upon aerosol direct radiative forcing (DRF) is complex. Generally, the cooling effect of aerosols over East Asia are enhanced in the northern part of East Asia (Northern China, Korean peninsula, and the surrounding area of Japan) and are reduced in the southern part of East Asia (Sichuan Basin and Southeast China) by internal mixing process, and the variation range can reach ±5 W m-2. The analysis shows that the internal mixing between inorganic salt and dust is likely the main reason that the cooling effect strengthens. Conversely, the internal mixture of anthropogenic aerosols, including sulfate, nitrate, ammonium, black carbon, and organic carbon, could obviously weaken the cooling effect.

Han, Xiao; Zhang, Meigen; Zhu, Lingyun; Xu, Liren

2013-07-01

297

Interpretation of Aerosol Optical and Morphological Properties during the Carbonaceous Aerosols and Radiative Effects Study in Sacramento, June 2010  

NASA Astrophysics Data System (ADS)

The Sacramento Carbonaceous Aerosols and Radiative Effects Study (CARES) utilized two ground sites T0 and T1 along with an aircraft platform to characterize carbonaceous aerosol chemical and physical properties and their evolution. The T0 site was chosen within the Sacramento metropolitan area for measuring primary and secondary aerosols generated in the city. The T1 site was chosen East of Sacramento on the Sierra foothill to study the evolution and processing of the Sacramento aerosol plume and to assess the characteristics of the background air. To reach T1, the Sacramento aerosols traveled often over the Blodgett Forest resulting in significant aging due coagulation, condensation, and photochemical processes. The ground sites were chosen for this unique and reoccurring transport pattern of the aerosols. The campaign took place in June 2010. Six Integrated Photoacoustic/Nephelometer Spectrometers (IPNSs) were installed at the sites to simultaneously record aerosol light scattering and absorption data. The optical properties of the aerosols were measured at 355nm (ultraviolet), 375nm (ultraviolet), 405nm (blue), 532nm (green), and 781nm (red). In conjugation with the IPNSs, aerosol filters for electron microscopy analysis were collected at each site; these were examined using a field emission scanning electron microscope to study the aerosol morphology. The origins of the air masses did vary daily, but a few general trends emerged. The processing of the IPNS data with a wavelet denoising technique greatly enhanced the signal to noise ratio of the measurements enabling a better understanding of the aerosol optical properties for various airmasses with different characteristics. Typically signals at both sites were lower than expected, however the processed signals from T0 clearly showed a daily rise and dilution of the Sacramento plume. Using the processed signals from both sites the transportation of the Sacramento plume was detectable. The IPNS data were compared with morphological descriptors derived from the electron microscopy analysis to elucidate the effects of aging on the aerosols properties. In particular we are elucidating the effect of organic coatings as well as secondary organic formations on the optical properties of aerosols in a mixed urban-forested environment.

Gorkowski, K.; Mazzoleni, C.; China, S.; Sharma, N.; Flowers, B. A.; Dubey, M. K.; Gyawali, M. S.; Arnott, W. P.; Zaveri, R. A.

2010-12-01

298

Field Studies of Broadband Aerosol Optical Extinction in the Ultraviolet Spectral Region  

NASA Astrophysics Data System (ADS)

Aerosols influence the Earth's radiative budget by scattering and absorbing incoming solar radiation. The optical properties of aerosols vary as a function of wavelength, but few measurements have reported the wavelength dependence of aerosol extinction cross sections and complex refractive indices. In the case of brown carbon, its wavelength-dependent absorption in the ultraviolet spectral region has been suggested as an important component of aerosol radiative forcing. We describe a new field instrument to measure aerosol optical extinction as a function of wavelength, using cavity enhanced spectroscopy with a broadband light source. The instrument consists of two broadband channels which span the 360-390 and 385-420 nm spectral regions using two light emitting diodes (LED) and a grating spectrometer with charge-coupled device (CCD) detector. We deployed this instrument during the Fire Lab at Missoula Experiment during Fall 2012 to measure biomass burning aerosol, and again during the Southern Oxidant and Aerosol Study in summer 2013 to measure organic aerosol in the Southeastern U.S. In both field experiments, we determined aerosol optical extinction as a function of wavelength and can interpret this together with size distribution and composition measurements to characterize the aerosol optical properties and radiative forcing.

Washenfelder, R. A.; Attwood, A.; Brock, C. A.; Brown, S. S.

2013-12-01

299

Baseline Maritime Aerosol: Methodology to Derive the Optical Thickness and Scattering Properties  

NASA Technical Reports Server (NTRS)

Satellite Measurements of the global distribution of aerosol and their effect on climate should be viewed in respect to a baseline aerosol. In this concept, concentration of fine mode aerosol particles is elevated above the baseline by man-made activities (smoke or urban pollution), while coarse mode by natural processes (e.g. dust or sea-spray). Using 1-3 years of measurements in 10 stations of the Aerosol Robotic network (ACRONET we develop a methodology and derive the optical thickness and properties of this baseline aerosol for the Pacific and Atlantic Oceans. Defined as the median for periods of stable optical thickness (standard deviation < 0.02) during 2-6 days, the median baseline aerosol optical thickness over the Pacific Ocean is 0.052 at 500 am with Angstrom exponent of 0.77, and 0.071 and 1.1 respectively, over the Atlantic Ocean.

Kaufman, Yoram J.; Smirnov, Alexander; Holben, Brent N.; Dubovik, Oleg; Einaudi, Franco (Technical Monitor)

2001-01-01

300

Retrieval of Aerosol Optical Depth Above Clouds from OMI Observations: Sensitivity Analysis, Case Studies  

NASA Technical Reports Server (NTRS)

A large fraction of the atmospheric aerosol load reaching the free troposphere is frequently located above low clouds. Most commonly observed aerosols above clouds are carbonaceous particles generally associated with biomass burning and boreal forest fires, and mineral aerosols originated in arid and semi-arid regions and transported across large distances, often above clouds. Because these aerosols absorb solar radiation, their role in the radiative transfer balance of the earth atmosphere system is especially important. The generally negative (cooling) top of the atmosphere direct effect of absorbing aerosols, may turn into warming when the light-absorbing particles are located above clouds. The actual effect depends on the aerosol load and the single scattering albedo, and on the geometric cloud fraction. In spite of its potential significance, the role of aerosols above clouds is not adequately accounted for in the assessment of aerosol radiative forcing effects due to the lack of measurements. In this paper we discuss the basis of a simple technique that uses near-UV observations to simultaneously derive the optical depth of both the aerosol layer and the underlying cloud for overcast conditions. The two-parameter retrieval method described here makes use of the UV aerosol index and reflectance measurements at 388 nm. A detailed sensitivity analysis indicates that the measured radiances depend mainly on the aerosol absorption exponent and aerosol-cloud separation. The technique was applied to above-cloud aerosol events over the Southern Atlantic Ocean yielding realistic results as indicated by indirect evaluation methods. An error analysis indicates that for typical overcast cloudy conditions and aerosol loads, the aerosol optical depth can be retrieved with an accuracy of approximately 54% whereas the cloud optical depth can be derived within 17% of the true value.

Torres, O.; Jethva, H.; Bhartia, P. K.

2012-01-01

301

Spatial variation of aerosol optical properties in North China Plain  

NASA Astrophysics Data System (ADS)

The column-integrated optical properties of aerosol in Beijing and Xianghe situated at North China Plain were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites. Only version 2 and level 2 quality-assured data were presented and analyzed in this paper. Time intervals differ for the two sites, with Beijing having 9 years of data (Mar.-May, 2001; Apr., 2002-Dec., 2011),while Xianghe having 6 years of data (Mar.-Apr., 2001;Sep., 2004-Dec.,2011). Monthly mean 500 nm AOT values reach a maximum in June (0.95) and exceed 0.55 from March through September, and the minimum values occur during the late fall and winter months of November through February at Beijing. The monthly mean AOT values at Xianghe are very close to those measured at Beijing. The absolute differences of AOT between the two sites are less than 0.1 except in June and July. The reason of large difference in June and July is the frequently cloud contamination in summer result in the monthly means over the two sites computed from a large number of measurements of different date. The monthly averaged AOT with the same date in June and July are re-computed and the absolute difference of AOT between Beijing and Xianghe reduced to 0.01 and 0.03 in June and July respectively. The monthly mean Angstrom Exponent (AE) in Beijing and Xianghe sites are very close, with the absolute difference less than 0.075. The monthly mean AE in the two sites varied between ~1.0 and ~1.3 except in spring (March-May), therefore clearly dominated by fine mode aerosol for most of the year. All monthly averaged SSA at Beijing showed much lower value as compared to Xianghe though the seasonal variations are similar for the two sites, which indicates that aerosol absorption is greater in Beijing. All monthly averaged imaginary part of refractive index at Beijing has much higher value than Xianghe. The absolute differences of SSA between the two sites range from 0.016 to 0.037 except that the difference in September is only 0.0005. All the significant differences but September exceed the 95% confidence level based on t-test technique. This very large difference in SSA over a relatively small distance (~70 km) suggests the significant variability in aerosol absorption between Beijing and Xianghe and the reasons for this difference should be investigated.

Fan, Xuehua

2013-04-01

302

Magnetic Tweezers for the Measurement of Twist and Torque  

E-print Network

1 Magnetic Tweezers for the Measurement of Twist and Torque Authors: Jan n.h.dekker@tudelft.nl Corresponding author: Nynke H. Dekker Keywords: magnetic tweezers, magnetic torque tweezers, freely-orbiting magnetic tweezers, twist, torque

Dekker, Nynke

303

ModelE2-TOMAS development and evaluation using aerosol optical depths, mass and number concentrations  

NASA Astrophysics Data System (ADS)

The TwO-Moment Aerosol Sectional microphysics model (TOMAS) has been integrated into the state-of-the-art general circulation model, GISS ModelE2. TOMAS has the flexibility to select a size resolution as well as the lower size cutoff. A computationally efficient version of TOMAS is used here, which has 15 size bins covering 3 nm to 10 ?m aerosol dry diameter. For each bin, it simulates the total aerosol number concentration and mass concentrations of sulphate, pure elementary carbon (hydrophobic), mixed elemental carbon (hydrophilic), hydrophobic organic matter, hydrophilic organic matter, sea salt, mineral dust, ammonium, and aerosol-associated water. This paper provides a detailed description of the ModelE2-TOMAS model and evaluates the model against various observations including aerosol precursor gas concentrations, aerosol mass and number concentrations, and aerosol optical depths. Additionally, global budgets in ModelE2-TOMAS are compared with those of other global aerosol models, and the TOMAS model is compared to the default aerosol model in ModelE2, which is a bulk aerosol model. Overall, the ModelE2-TOMAS predictions are within the range of other global aerosol model predictions, and the model has a reasonable agreement with observations of sulphur species and other aerosol components as well as aerosol optical depth. However, ModelE2-TOMAS (as well as the bulk aerosol model) cannot capture the observed vertical distribution of sulphur dioxide over the Pacific Ocean possibly due to overly strong convective transport. The TOMAS model successfully captures observed aerosol number concentrations and cloud condensation nuclei concentrations. Anthropogenic aerosol burdens in the bulk aerosol model running in the same host model as TOMAS (ModelE2) differ by a few percent to a factor of 2 regionally, mainly due to differences in aerosol processes including deposition, cloud processing, and emission parameterizations. Larger differences are found for naturally emitted aerosols such as sea salt and mineral dust. With TOMAS, ModelE2 has three different aerosol models (the bulk aerosol model and modal-based aerosol microphysics model, MATRIX) and allows exploration of the uncertainties associated with aerosol modelling within the same host model, NASA GISS ModelE2.

Lee, Y. H.; Adams, P. J.; Shindell, D. T.

2014-09-01

304

Influences of external vs. core-shell mixing on aerosol optical properties at various relative humidities.  

PubMed

Aerosol optical properties of external and core-shell mixtures of aerosol species present in the atmosphere are calculated in this study for different relative humidities. Core-shell Mie calculations are performed using the values of radii, refractive indices and densities of aerosol species that act as core and shell, and the core-shell radius ratio. The single scattering albedo (SSA) is higher when the absorbing species (black carbon, BC) is the core, while for a sulfate core SSA does not vary significantly as the BC in the shell dominates the absorption. Absorption gets enhanced in core-shell mixing of absorbing and scattering aerosols when compared to their external mixture. Thus, SSA is significantly lower for a core-shell mixture than their external mixture. SSA is more sensitive to core-shell ratio than mode radius when BC is the core. The extinction coefficient, SSA and asymmetry parameter are higher for external mixing when compared to BC (core)-water soluble aerosol (shell), and water soluble aerosol (core)-BC (shell) mixtures in the relative humidity range of 0 to 90%. Spectral SSA exhibits the behaviour of the species which acts as a shell in core-shell mixing. The asymmetry parameter for an external mixture of water soluble aerosol and BC is higher than BC (core)-water soluble aerosol (shell) mixing and increases as function of relative humidity. The asymmetry parameter for the water soluble aerosol (core)-BC (shell) is independent of relative humidity as BC is hydrophobic. The asymmetry parameter of the core-shell mixture decreases when BC aerosols are involved in mixing, as the asymmetry parameter of BC is lower. Aerosol optical depth (AOD) of core-shell mixtures increases at a higher rate when the relative humidity exceeds 70% in continental clean and urban aerosol models, whereas AOD remains the same when the relative humidity exceeds 50% in maritime aerosol models. The SSA for continental aerosols varies for core-shell mixing of water soluble aerosol (core)-shell (BC) when compared to their external mixture, while the SSA for maritime aerosols does not vary significantly for different mixing scenarios because of the dominance of sea salt aerosols. Thus, these results confirm that aerosol mixing can modify the physical and optical characteristics of aerosols, which vary as a function of relative humidity. These calculations will be useful in parameterising the effect of core-shell vs. external mixing of aerosols in global climate models, and in the evaluation of aerosol radiative effects. PMID:23563501

Ramachandran, S; Srivastava, Rohit

2013-05-01

305

Characterization of aerosol optical depth, aerosol mass concentration, UV irradiance and black carbon aerosols over Indo-Gangetic plains, India, during fog period  

NASA Astrophysics Data System (ADS)

Every year during winter months (December-January) fog formation over Indo-Gangetic plains (IGP) of Indian region is believed to create numerous hazards. The present study addresses variations in aerosol optical properties, aerosol mass concentration and their impact on solar irradiance for pre-during-post fog conditions of December 2004 over IGP, India. Continuous measurements on aerosol optical depth (AOD), total aerosol mass concentration, black carbon (BC) aerosols, UVery and UVA were carried out for pre, during and post fog periods over study site of Allahabad, India, during December 2004 as a part of Aerosol Land Campaign-II conducted by Indian Space Research Organization (ISRO). High aerosol mass concentrations were observed during fog and post-fog periods. Accumulation mode particle loading was found to be high during pre-fog period and coarse mode particle loading was observed to be high during fog and post-fog periods. Considerable reduction in UVery and UVA irradiance was observed during fog period compared with pre and post-fog periods . Analysis of NOAA-HYSPLIT model runs suggested that enhanced biomass burning episodes down-wind to the study area increased the concentration of AOD and BC.

Badarinath, K. V. S.; Kharol, Shailesh Kumar; Kiran Chand, T. R.; Latha, K. Madhavi

2011-02-01

306

Recent Advances in Optical Tweezers  

E-print Network

. Biochem. 2008. 77:205­28 First published online as a Review in Advance on February 28, 2008 The Annual Review of Biochemistry is online at biochem.annualreviews.org This article's doi: 10.1146/annurev.biochem.77.043007.090225 Copyright c 2008 by Annual Reviews. All rights reserved 0066

Ritort, Felix

307

Relationship between column aerosol optical properties and surface aerosol gravimetric concentrations during the Distributed Regional Aerosol Gridded Observation Network - Northeast ASIA 2012 campaign  

NASA Astrophysics Data System (ADS)

One of the main objectives of Distributed Regional Aerosol Gridded Observation Network (DRAGON) campaign in Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) mission is to understand the relationship between the column optical properties of the atmosphere and the surface level air quality in terms of aerosols and gases. This study aims to identify the important parameters that affecting the relationship between those variables during the DRAGON - northeast Asia 2012 campaign. Column aerosol optical properties from ten Cimel sun photometers at DRAGON sites in Seoul, MODIS (Moderate Resolution Imaging Spectroradiometer), and GOCI (Geostationary Ocean Color Imager) and particulate matter (PM10) sampling from 40 NIER (National Institute of Environmental Research of South Korea) measurement sites in Seoul during the period of 1st March - 31th May 2012 were employed in this study. The key parameters in relationship between aerosol optical depth (AOD) and PM are reported to be aerosol vertical profile and hygroscopicity of the aerosols. The meteorological conditions including relative humidity, surface temperature, and wind speed that could affect those parameters were investigated.

Jeong, U.; Kim, J.; Seo, S.; Choi, M.; Kim, W. V.; Holben, B. N.; Lee, S.; Kim, J.

2012-12-01

308

Columnar optical properties of tropospheric aerosol by combined lidar and sunphotometer measurements at Taipei, Taiwan  

Microsoft Academic Search

Vertical extinction profiles and columnar optical properties (optical depth, Angstrom exponent, lidar ratio, and particle depolarization) of aerosols were obtained by simultaneous measurements with a depolarization lidar and a sunphotometer at Taipei, Taiwan from February 2004 to January 2006. Columnar optical depths are high in Feb–Apr (0.61–0.75) by sunphotometer measurements. Lidar measurements show the contribution of aerosols in the free

Wei-Nai Chen; Yi-Wei Chen; Charles C. K. Chou; Shih-Yang Chang; Po-Hsiung Lin; Jen-Ping Chen

2009-01-01

309

Seasonal characteristics of chemically apportioned aerosol optical properties at Seoul and Gosan, Korea  

Microsoft Academic Search

Seasonal variations of aerosol optical properties in Seoul (polluted urban site) and Gosan (coastal background site), Korea, with an emphasis on the relative humidity were investigated using ground-based aerosol measurements and optical model calculations. The mass fraction of elemental carbon was 9–20%, but the optical contribution of these particles to light extinction was higher, up to 33–55% in Seoul. In

Sihye Lee; Young Sung Ghim; Sang-Woo Kim; Soon-Chang Yoon

2009-01-01

310

Satellite and ground-based study of optical properties of 1997 Indonesian forest fire aerosols  

Microsoft Academic Search

Optical properties of biomass burning aerosols in the event of Indonesian forest fires in 1997 were studied by ground-based sky radiometry and satellite remote sensing with AVHRR and TOMS radiometers. The AVHRR-derived optical thickness distribution agreed with the distribution of TOMS-derived UV-absorbing aerosol index and with the optical thickness measured by sky radiometry and sunphotometry. The single scattering albedo of

Teruyuki Nakajima; Akiko Higurashi; Nobuo Takeuchi; Jay R. Herman

1999-01-01

311

Aeronet-based Microphysical and Optical Properties of Smoke-dominated Aerosol near Source Regions and Transported over Oceans, and Implications for Satellite Retrievals of Aerosol Optical Depth  

NASA Technical Reports Server (NTRS)

Smoke aerosols from biomass burning are an important component of the global aerosol cycle. Analysis of Aerosol Robotic Network (AERONET) retrievals of size distribution and refractive index reveals variety between biomass burning aerosols in different global source regions, in terms of aerosol particle size and single scatter albedo (SSA). Case studies of smoke transported to coastal/island AERONET sites also mostly lie within the range of variability at near-source sites. Two broad families of aerosol properties are found, corresponding to sites dominated by boreal forest burning (larger, broader fine mode, with midvisible SSA 0.95), and those influenced by grass, shrub, or crop burning with additional forest contributions (smaller, narrower particles with SSA 0.88-0.9 in the midvisible). The strongest absorption is seen in southern African savanna at Mongu (Zambia), with average SSA 0.85 in the midvisible. These can serve as candidate sets of aerosol microphysicaloptical properties for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean are often insufficiently absorbing to represent these biomass burning aerosols. A corollary of this is an underestimate of AOD in smoke outflow regions, which has important consequences for applications of these satellite datasets.

Sayer, A. M.; Hsu, N. C.; Eck, T. F.; Smirnov, A.; Holben, B. N.

2013-01-01

312

Measurement of Aerosol Optical Property in Hong Kong Rural Area  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols play an important role in climate change and visibility impairment. The evidence of the role in climate change is required for monitoring the extinction, absorption, scattering coefficient and single scattering albedo in different sites around world. In the southern China public attention are focusing on severe regional visibility problem and its connection to regional air pollution. Black carbon (BC) is a form of atmospheric aerosol and can reduce visibility through absorption of solar radiation and it is an important primary aerosol cause global warming. Here, we presented the 2-year measurements (2011-2013) of aerosol optical properties, using aethalometer and nephelometer to measure scattering (Bsp), absorption coefficient (Bab), single scattering albedo (SSA) and scattering angstrom exponent (?s) in Hong Kong rural area (Hok Tsui) and determine the Hong Kong regional pollution status. The mean Bsp, Bab, ?s and SSA during the sampling period is 110.84±89.19, 15.09±9.85 Mm-1, 1.0±0.42 and 0.84±0.11, respectively. Scattering coefficient and absorption coefficient are both ~22% higher than the median. The significant seasonal variation of absorption and scattering coefficient is observed, which was lower in spring (12.87±7.5 and 91.30±73.3) and summer (10.84±10.1 and 65.24±75.2) seasons but has higher value in autumn (16.79±8.9 and 124.23±82.4) and winter (18.74±10.3 and 157.27±98.8) seasons. Similar as scattering and absorption value, in spring and summer, the SSA is lower than the value measured in autumn and winter seasons, indicates that absorption coefficient play an important role in spring and summer seasons than in autumn and winter seasons. Compared to scattering and absorption coefficient data reported by [1] in HT, 14 years ago, the annual scattering coefficient is increased about ~106% and absorption coefficient decreased ~11%. The main reason for absorption coefficient decreasing relies on BC concentration significantly decreased. In addition, the value of SSA is 0.8 in 2011 compared with 0.7 in 2001and it could estimate that secondary pollution increasing greatly.

GAO, Yuan; Lee, Shun-cheng; Huang, Yu; Lai, Senchao

2014-05-01

313

Measurements of the chemical, physical, and optical properties of single aerosol particles  

Microsoft Academic Search

Knowledge of aerosol physical, chemical, optical properties is essential for judging the effect that particulates have on human health, climate and visibility. The aerosol time-of-flight mass spectrometer (ATOFMS) is capable of measuring, in real-time, the size and chemical composition of atmospheric aerosols. This was exemplified by the recent deployments of the ATOFMS to Mexico City and Riverside. The ATOFMS provided

Ryan Christopher Moffet

2007-01-01

314

Improvement of MISR aerosol optical properties over the contiguous United States using GOCART Data  

NASA Astrophysics Data System (ADS)

Abstract-- With a unique multiangle design, the Multi-angle Imaging SpectroRadiometer (MISR) can potentially provide more reliable Aerosol Optical Depth (AOD), particularly over land, compared with single-angle satellite instruments. MISR also provides particle information, including Angström exponent (ANG) and single scattering albedo. However, uncertainties in retrieved aerosol composition increase if many conflicting mixtures successfully pass the operational MISR aerosol retrieval acceptance criteria. We present a post-processing technique that couples Goddard Chemistry Aerosol Radiation and Transport Model (GOCART) simulations with MISR observations to improve MISR aerosol retrievals. By constraining MISR mixtures' ANG and compositions with corresponding GOCART predictions, we recalculated MISR aerosol optical properties over the contiguous U.S. from 2006 to 2009. Compared with the MISR operational product, the correlation coefficient (r) between our ANG and AERONET ground-based sunphotometer observations is improved from 0.26 (MISR) to 0.52. Regression analysis for the absorbing AOD against AERONET data also shows MISR significantly overestimates it by a factor of 3. Our method was able to reduce this bias by up to 50%. Analysis of calibrated MISR-retrieved aerosol microphysical properties showed that on average, inorganic aerosol has the highest AOD (0.089) nationally, followed by absorbing non-dust species (0.031), and dust (0.014). Retrieval uncertainties associated with the errors in GOCART simulations and the sensitivities by using different distinguishing thresholds were also analyzed using ground measurements. Keywords--MISR; Aerosol Optical Properties; GOCART; AERONET

Li, S.; Chen, L.; Chin, M.; Garay, M. J.; Liu, Y.

2013-12-01

315

El Chichón – influence on aerosol optical depth and direct, diffuse and total solar irradiances at Vancouver, B.C  

Microsoft Academic Search

Solar radiation data for Vancouver, B.C. were used to determine the increase in aerosol optical depth and the changes in the total, direct, diffuse and net short?wave radiation fluxes associated with the presence of aerosol that originated from the eruption of El Chichón (Mexico) in April 1982. The aerosol optical depth increased by 400% resulting in reductions of 33% in

John E. Hay; Robert Darby

1984-01-01

316

Aerosol optical depth spatio-temporal characterization over the Canadian BOREAS domain  

Microsoft Academic Search

A complete set of Advanced Very High Resolution Radiometer (AVHRR) data (75 images) is used to retrieve aerosol optical depth (AOD) over dense vegetation and over lake water in the visible AVHRR channel. The present approach for remote sensing of aerosols from the National Oceanic and Atmospheric Administration (NOAA)-11 AVHRR sensor is based on the detection of atmospherically dominated signals

C. Bertrand; A. Royer

2004-01-01

317

Image-based derivation of aerosol optical depth to correct the atmospheric effect for satellite image  

Microsoft Academic Search

An image-based atmospheric correction model for a satellite image is proposed. By assuming Junge size distributed aerosol in the atmosphere and feeding back the new Junge parameter, not only the aerosol optical depth but also the Junge parameter, single scattering albedo and phase function can be iteratively derived and converged from digital counts of dense-dark vegetation (DDV) in the green

C. H. Liu; A. J. Chen; G. R. Liu

1995-01-01

318

Modeling of Aerosol Optical Depth Variability during the 1998 Canadian Forest Fire Smoke Event  

Microsoft Academic Search

Monitoring of aerosol optical depth (AOD) is of particular importance due to the significant role of aerosols in the atmospheric radiative budget. Up to now the two standard techniques used for retrieving AOD are; (i) sun photometry which provides measurements of high temporal frequency and sparse spatial frequency, and (ii) satellite based approaches such as based DDV (Dense Dark Vegetation)

M. Aubé; A. Royer; D. Lavoué

2003-01-01

319

A modeling approach for aerosol optical depth analysis during forest fire events  

Microsoft Academic Search

Measurements of aerosol optical depth (AOD) are important indicators of aerosol particle behavior. Up to now the two standard techniques used for retrieving AOD are; (i) sun photometry which provides measurements of high temporal frequency and sparse spatial frequency, and (ii) satellite based approaches such as DDV (Dense Dark Vegetation) based inversion algorithms which yield AOD over dark targets in

Martin P. Aubé; Normand T. O'Neill; Alain Royer; David Lavoué

2004-01-01

320

Retrieval method for aerosol optical depth over Fuzhou based on MODIS data  

Microsoft Academic Search

Aerosol optical depth (AOD) was an important factor in the aerosol research, the AOD over Fuzhou city was retrieved based on MODIS data of November 11th, 2006, and a test of sensitivity to AOD and the surface reflectance were made for the planetary albedo of three channels of MODIS ( red channel, blue channel and mid-infrared channel) by 6S (

Weihua Pan; Chungui Zhang; Hui Chen; Jiajin Chen

2011-01-01

321

Retrieval of aerosol optical depth in vicinity of broken clouds from reflectance ratios: case study  

Microsoft Academic Search

A recently developed reflectance ratio (RR) method for the retrieval of aerosol optical depth (AOD) is evaluated using extensive airborne and ground-based data sets collected during the Cloud and Land Surface Interaction Campaign (CLASIC) and the Cumulus Humilis Aerosol Processing Study (CHAPS), which took place in June 2007 over the US Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) Southern

E. Kassianov; M. Ovchinnikov; L. K. Berg; S. A. McFarlane; C. Flynn; R. Ferrare; C. Hostetler; M. Alexandrov

2010-01-01

322

Aerosol size distributions and optical properties found in the marine boundary layer over the Atlantic Ocean  

Microsoft Academic Search

Measurements and analyses of the aerosol size distribution and optical properties found in the marine boundary layer (MBL) during the 1983 USNS Lynch cruise from Charleston, South Carolina, to Scotland via Canary Islands are presented. The data given are the most extensive and accurate measurements of the submicron marine aerosol size distribution to date and are supplemented by extensive meteorological

W. A. Hoppel; J. W. Fitzgerald; G. M. Frick; R. E. Larson; E. J. Mack

1990-01-01

323

Wavelength dependence of the optical depth of biomass burning, urban, and desert dust aerosols  

Microsoft Academic Search

The Angstrom wavelength exponent alpha, which is the slope of the logarithm of aerosol optical depth (taua) versus the logarithm of wavelength (lambda), is commonly used to characterize the wavelength dependence of taua and to provide some basic information on the aerosol size distribution. This parameter is frequently computed from the spectral measurements of both ground-based sunphotometers and from satellite

T. F. Eck; B. N. Holben; J. S. Reid; O. Dubovik; A. Smirnov; N. T. O'Neill; I. Slutsker; S. Kinne

1999-01-01

324

Using Artificial Sky Glow to Retrieve Night Time Aerosol Optical Depth  

Microsoft Academic Search

Measuring the Aerosol Optical Depth (AOD) is of particular importance in monitoring aerosol contributions to global radiative forcing. Most measuring methods are based on direct or indirect observation of sunlight and thus are only available for use during daylight hours. Attempts have been made to measure AOD behavior at night from star photometry, and more recently moon photometry. Star photometry

M. Aubé; N. T. O'Neill; J.-D. Giguère; A. Royer

2009-01-01

325

Anthropogenic and natural contributions to regional trends in aerosol optical depth, 1980-2006  

Microsoft Academic Search

Understanding the roles of human and natural sources in contributing to aerosol concentrations around the world is an important step toward developing efficient and effective mitigation measures for local and regional air quality degradation and climate change. In this study we test the hypothesis that changes in aerosol optical depth (AOD) over time are caused by the changing patterns of

David G. Streets; Fang Yan; Mian Chin; Thomas Diehl; Natalie Mahowald; Martin Schultz; Martin Wild; Ye Wu; Carolyne Yu; Forschungszentrum

2009-01-01

326

Anthropogenic and natural contributions to regional trends in aerosol optical depth, 1980–2006  

Microsoft Academic Search

Understanding the roles of human and natural sources in contributing to aerosol concentrations around the world is an important step toward developing efficient and effective mitigation measures for local and regional air quality degradation and climate change. In this study we test the hypothesis that changes in aerosol optical depth (AOD) over time are caused by the changing patterns of

David G. Streets; Fang Yan; Mian Chin; Thomas Diehl; Natalie Mahowald; Martin Schultz; Martin Wild; Ye Wu; Carolyne Yu

2009-01-01

327

A flexible inversion algorithm for retrieval of aerosol optical properties from Sun and sky radiance measurements  

Microsoft Academic Search

The problem of deriving a complete set of aerosol optical properties from Sun and sky radiance measurements is discussed. Algorithm development is focused on improving aerosol retrievals by means of including a detailed statistical optimization of the influence of noise in the inversion procedure. The methodological aspects of such an optimization are discussed in detail and revised according to both

Oleg Dubovik; Michael D. King

2000-01-01

328

Latitudinal variation of spectral optical thickness and columnar size distribution of the El Chichon stratospheric aerosol layer  

NASA Technical Reports Server (NTRS)

Measurements are presented for the spectral optical thickness of El Chichon's stratospheric aerosol layer, obtained during an airborne latitudinal survey in April and May of 1983. Columnar aerosol size distributions of the stratosphere are derived by inverting the aerosol optical thickness measurements as a function of wavelength and from spectral aerosol depth measurements obtained during an airborne survey in October and November 1982. Spectral optical thickness data and the derived size distributions from both airborne missions show latitidunal regions with similar characteristics. Airborne solar radiometer measurements are shown to be useful in studies of the latitudinal variations of optical and related particle size characteristics of the stratospheric aerosol layer.

Spinhirne, J. D.; King, M. D.

1985-01-01

329

Effects of atmospheric water on the optical properties of soot aerosols with different mixing states  

NASA Astrophysics Data System (ADS)

Soot aerosols have become the second most important contributor to global warming after carbon dioxide in terms of direct forcing, which is the dominant absorber of visible solar radiation. The optical properties of soot aerosols depend strongly on the mixing mechanism of black carbon with other aerosol components and its hygroscopic properties. In this study, the effects of atmospheric water on the optical properties of soot aerosols have been investigated using a superposition T-matrix method that accounts for the mixing mechanism of soot aerosols with atmospheric water. The dramatic changes in the optical properties of soot aerosols were attributed to its different mixing states with atmospheric water (externally mixed, semi-embedded mixed, and internally mixed). Increased absorption is accompanied by a larger increase in scattering, which is reflected by the increased single scattering albedo. The asymmetry parameter also increased when increasing the atmospheric water content. Moreover, atmospheric water intensified the radiative absorption enhancement attributed to the mixing states of the soot aerosols, with values ranging from 1.5 to 2.5 on average at 0.870 ?m. The increased absorption and scattering ability of soot aerosols, which is attributed to atmospheric water, exerted an opposing effect on climate change. These findings should improve our understanding of the effects of atmospheric water on the optical properties of soot aerosols and their effects on climate. The mixing mechanism for soot aerosols and atmospheric water is important when evaluating the climate effects of soot aerosols, which should be explicitly considered in radiative forcing models.

Cheng, Tianhai; Gu, Xingfa; Wu, Yu; Chen, Hao

2014-11-01

330

A COMPARISON OF AEROSOL OPTICAL DEPTH SIMULATED USING CMAQ WITH SATELLITE ESTIMATES  

EPA Science Inventory

Satellite data provide new opportunities to study the regional distribution of particulate matter. The aerosol optical depth (AOD) - a derived estimate from the satellite measured irradiance, can be compared against model derived estimate to provide an evaluation of the columnar ...

331

Characteristic aerosol optical depths during the Harmattan season on sub-Sahara Africa  

NASA Technical Reports Server (NTRS)

Aerosol optical depths were derived from sun photometer measurements in three narrow bands centered at 500, 675 and 875 nm, taken at Ilorin, Nigeria, located in sub-Saharan Africa. Selected results will be presented on the diurnal, seasonal, and interannual variability of spectral aerosol optical depth for two Harmattan seasons, during 1987-1989. At 500 nm values between 0.9-1.6 were quite common while the averages were between 1-1.2.

Pinker, Rachel T.; Idemudia, G.; Aro, T. O.

1994-01-01

332

Characteristic aerosol optical depths during the Harmattan Season on sub-Sahara Africa  

NASA Astrophysics Data System (ADS)

Aerosol optical depths were derived from sun photometer measurements in three narrow bands centered at 500, 675 and 875 nm, taken at Ilorin, Nigeria, located in sub-Saharan Africa. Selected results will be presented on the diurnal, seasonal, and interannual variability of spectral aerosol optical depth for two Harmattan seasons, during 1987-1989. At 500 nm values between 0.9-1.6 were quite common while the averages were between 1-1.2.

Pinker, Rachel T.; Idemudia, G.; Aro, T. O.

1994-04-01

333

Assimilation of POLDER aerosol optical thickness into the LMDz-INCA model: Implications for the Arctic aerosol burden  

NASA Astrophysics Data System (ADS)

The large spatial and temporal variability of atmospheric aerosol load makes it a challenge to quantify aerosol effect on climate. This study is one of the first attempts to apply data assimilation for the analysis of global aerosol distribution. Aerosol optical thickness (AOT) observed from the Polarization and Directionality of the Earth Reflectances (POLDER) spaceborne instrument are assimilated into a three-dimensional chemistry model. POLDER capabilities to distinguish between fine and coarse AOT are used to constrain them separately in the model. Observation and model errors are a key component of such a system and are carefully estimated on a regional basis using some of the high-quality surface observations from the Aerosol Robotic Network (AERONET). Other AERONET data provide an independent evaluation of the a posteriori fields. Results for the fine mode show improvements, in terms of reduction of root-mean-square errors, in most regions with the largest improvements found in the Mediterranean Sea and Eurasia. We emphasize the results for the Arctic, where there is growing evidence of a strong aerosol impact on climate, but a lack of regional and continuous aerosol monitoring. The a posteriori fields noticeably well reproduce the winter-spring "Arctic Haze" peak measured in Longyearbyen (15°E, 78°N) and typical seasonal variations in the Arctic region, where AOT increase by up to a factor of three between a posteriori and a priori. Enhanced AOT are found over a longer period in spring 2003 than in 1997, suggesting that the large Russian fires in 2003 have influenced the Arctic aerosol load.

Generoso, S.; BréOn, F.-M.; Chevallier, F.; Balkanski, Y.; Schulz, M.; Bey, I.

2007-01-01

334

Temporal and Spatial Variability of Aerosol Optical Properties in the UAE  

NASA Astrophysics Data System (ADS)

In this investigation we analyze measured spectral aerosol optical depth and retrieved aerosol size distributions and spectral single scattering albedo in the United Arab Emirates (UAE) and adjacent Arabian Gulf. A meso-scale network of several ground-based Aerosol Robotic Network (AERONET) sun-sky radiometers in the UAE from August to October 2004 (during the UAE2 field campaign) provides a unique opportunity to examine the spatial distribution and temporal variability of remotely sensed aerosol optical properties. The geographical location of the UAE includes strong regional desert dust aerosol sources, and also strong fine mode pollution particle sources from petroleum and natural gas processing facilities. This variability of atmospheric particle type and size in conjunction with highly variable regional meteorology results in some observations that are dominated by coarse mode desert dust, others dominated by fine mode pollution, and most that are a mixture of the two aerosol types. Retrievals of aerosol size distributions and single scattering albedo are made with a newly improved algorithm assuming spheroid particle shape and with improved earth surface albedo input from MODIS products. This study attempts to quantify aerosol optical properties dynamics in the late summer season in the UAE.

Eck, T. F.; Holben, B. N.; Dubovik, O.; Smirnov, A.; Sinyuk, A.; Reid, J. S.; Giles, D.; Schafer, J. S.; Sorokin, M.; Newcomb, W. W.

2005-12-01

335

Aerosols in GEOS-5: simulations of the UV Aerosol Index and the Aerosol Absorption Optical Depth and comparisons with OMI retrievals.  

NASA Astrophysics Data System (ADS)

GEOS-5 is the latest version of the NASA Global Modeling and Assimilation Office (GMAO) earth system model. GEOS-5 contains components for atmospheric circulation and composition (including data assimilation), ocean circulation and biogeochemistry, and land surface processes. In addition to traditional meteorological parameters, GEOS-5 includes modules representing the atmospheric composition, most notably aerosols and tropospheric/stratospheric chemical constituents, taking explicit account of the impact of these constituents on the radiative processes of the atmosphere. The assimilation of Aerosol Optical Depth (AOD) in GEOS-5 involves very careful cloud screening and homogenization of the observing system by means of a Neural Net scheme that translates MODIS radiances into AERONET calibrated AOD. These measurements are further quality controlled using an adaptive buddy check scheme, and assimilated using the Local Displacement Ensemble (LDE) methodology. For this analysis, GEOS-5 runs at a nominal 50km horizontal resolution with 72 vertical layers (top at ~85km). GEOS-5 is driven by daily biomass burning emissions derived from MODIS fire radiative power retrievals. We present a summary of our efforts to simulate the UV Aerosol Index (AI) at 354 nm from aerosol simulations by performing a radiative transfer calculation. We have compared model produced AI with the corresponding OMI measurements, identifying regions where the model representation of absorbing aerosols were deficient. Separately, model derived Absorption Aerosol Optical Depth (AAOD) is compared with OMI retrievals. Making use of CALIPSO measurements we have also investigated the impact of the altitude of the aerosol layer on OMI derived AI trying to ascertain misplacement of plume height by the model.

Buchard-Marchant, Virginie; da Silva, Arlindo; Colarco, Peter; Darmenov, Anton; Govindaraju, Ravi

2013-04-01

336

Measurements of Aerosol Vertical Profiles and Optical Properties during INDOEX 1999 Using Micro-Pulse Lidars  

NASA Technical Reports Server (NTRS)

Micro-pulse lidar systems (MPL) were used to measure aerosol properties during the Indian Ocean Experiment (INDOEX) 1999 field phase. Measurements were made from two platforms: the NOAA ship RN Ronald H. Brown, and the Kaashidhoo Climate Observatory (KCO) in the Maldives. Sunphotometers were used to provide aerosol optical depths (AOD) needed to calibrate the MPL. This study focuses on the height distribution and optical properties (at 523 nm) of aerosols observed during the campaign. The height of the highest aerosols (top height) was calculated and found to be below 4 km for most of the cruise. The marine boundary layer (MBL) top was calculated and found to be less than 1 km. MPL results were combined with air mass trajectories, radiosonde profiles of temperature and humidity, and aerosol concentration and optical measurements. Humidity varied from approximately 80% near the surface to 50% near the top height during the entire cruise. The average value and standard deviation of aerosol optical parameters were determined for characteristic air mass regimes. Marine aerosols in the absence of any continental influence were found to have an AOD of 0.05 +/- 0.03, an extinction-to-backscatter ratio (S-ratio) of 33 +/- 6 sr, and peak extinction values around 0.05/km (near the MBL top). The marine results are shown to be in agreement with previously measured and expected values. Polluted marine areas over the Indian Ocean, influenced by continental aerosols, had AOD values in excess of 0.2, S-ratios well above 40 sr, and peak extinction values approximately 0.20/km (near the MBL top). The polluted marine results are shown to be similar to previously published values for continental aerosols. Comparisons between MPL derived extinction near the ship (75 m) and extinction calculated at ship-level using scattering measured by a nephelometer and absorption using a PSAP were conducted. The comparisons indicated that the MPL algorithm (using a constant S-ratio throughout the lower troposphere) calculates extinction near the surface in agreement with the ship-level measurements only when the MBL aerosols are well mixed with aerosols above. Finally, a review of the MPL extinction profiles showed that the model of aerosol vertical extinction developed during an earlier INDOEX field campaign (at the Maldives) did not correctly describe the true vertical distribution over the greater Indian Ocean region. Using the average extinction profile and AOD obtained during marine conditions, a new model of aerosol vertical extinction was determined for marine atmospheres over the Indian Ocean. A new model of aerosol vertical extinction for polluted marine atmospheres was also developed using the average extinction profile and AOD obtained during marine conditions influenced by continental aerosols.

Welton, Ellsworth J.; Voss, Kenneth J.; Quinn, Patricia K.; Flatau, Piotr J.; Markowicz, Krzysztof; Campbell, James R.; Spinhirne, James D.; Gordon, Howard R.; Johnson, James E.; Starr, David OC. (Technical Monitor)

2001-01-01

337

Manipulation and characterization of aqueous sodium dodecyl sulfate/sodium chloride aerosol particles.  

PubMed

Aerosol optical tweezers coupled with Raman spectroscopy can allow the detailed investigation of aerosol dynamics. We describe here measurements of the evolving size, composition, and phase of single aqueous aerosol droplets containing the surfactant sodium dodecyl sulfate and the inorganic salt sodium chloride. Not only can the evolving wet particle size be probed with nanometer accuracy, but we show that the transition to a metastable microgel particle can be followed, demonstrating that optical tweezers can be used to manipulate both spherical and non-spherical aerosol particles. Further, through the simultaneous manipulation and characterization of two aerosol droplets of different composition in two parallel optical traps, the phase behavior of a surfactant-doped particle and a surfactant-free droplet can be compared directly in situ. We also illustrate that the manipulation of two microgel particles can allow studies of the coagulation and interaction of two solid particles. Finally, we demonstrate that such parallel measurements can permit highly accurate comparative measurements of the evolving wet particle size of a surfactant-doped droplet with a surfactant-free droplet. PMID:18044858

Buajarern, Jariya; Mitchem, Laura; Reid, Jonathan P

2007-12-20

338

Estimation of cloud condensation nuclei concentration from aerosol optical quantities: influential factors and uncertainties  

NASA Astrophysics Data System (ADS)

Large-scale measurements of cloud condensation nuclei (CCN) are difficult to obtain on a routine basis, whereas aerosol optical quantities are more readily available. This study investigates the relationship between CCN and aerosol optical quantities for some distinct aerosol types using extensive observational data collected at multiple Atmospheric Radiation Measurement (ARM) Climate Research Facility (CRF) sites around the world. The influences of relative humidity (RH), aerosol hygroscopicity (fRH) and single scattering albedo (SSA) on the relationship are analyzed. Better relationships are found between aerosol optical depth (AOD) and CCN at the Southern Great Plains (US), Ganges Valley (India) and Black Forest sites (Germany) than those at the Graciosa Island (the Azores) and Niamey (Niger) sites, where sea salt and dust aerosols dominate, respectively. In general, the correlation between AOD and CCN decreases as the wavelength of the AOD measurement increases, suggesting that AOD at a shorter wavelength is a better proxy for CCN. The correlation is significantly improved if aerosol index (AI) is used together with AOD. The highest correlation exists between CCN and aerosol scattering coefficients (?sp) and scattering AI measured in situ. The CCN-AOD (AI) relationship deteriorates with increasing RH. If RH exceeds 75%, the relationship where AOD is used as a proxy for CCN becomes invalid, whereas a tight ?sp-CCN relationship exists for dry particles. Aerosol hygroscopicity has a weak impact on the ?sp-CCN relationship. Particles with low SSA are generally associated with higher CCN concentrations, suggesting that SSA affects the relationship between CCN concentration and aerosol optical quantities. It may thus be used as a constraint to reduce uncertainties in the relationship. A significant increase in ?sp and decrease in CCN with increasing SSA is observed, leading to a significant decrease in their ratio (CCN / ?sp) with increasing SSA. Parameterized relationships are developed for estimating CCN, which account for RH, particle size, and SSA.

Liu, Jianjun; Li, Zhanqing

2014-01-01

339

Determination of motility forces on isolated chromosomes with laser tweezers.  

PubMed

Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064?nm laser trap. The minimum force required to move a single chromosome was determined to be ?0.8-5?pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ?0.01-0.02. These results confirm theoretical force calculations of ?0.1-12?pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5-15?µm in media with 1-7?cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens. PMID:25359514

Khatibzadeh, Nima; Stilgoe, Alexander B; Bui, Ann A M; Rocha, Yesenia; Cruz, Gladys M; Loke, Vince; Shi, Linda Z; Nieminen, Timo A; Rubinsztein-Dunlop, Halina; Berns, Michael W

2014-01-01

340

Determination of motility forces on isolated chromosomes with laser tweezers  

NASA Astrophysics Data System (ADS)

Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064 nm laser trap. The minimum force required to move a single chromosome was determined to be ~0.8-5 pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ~0.01-0.02. These results confirm theoretical force calculations of ~0.1-12 pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5-15 µm in media with 1-7 cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens.

Khatibzadeh, Nima; Stilgoe, Alexander B.; Bui, Ann A. M.; Rocha, Yesenia; Cruz, Gladys M.; Loke, Vince; Shi, Linda Z.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

2014-10-01

341

Determination of motility forces on isolated chromosomes with laser tweezers  

PubMed Central

Quantitative determination of the motility forces of chromosomes during cell division is fundamental to understanding a process that is universal among eukaryotic organisms. Using an optical tweezers system, isolated mammalian chromosomes were held in a 1064?nm laser trap. The minimum force required to move a single chromosome was determined to be ?0.8–5?pN. The maximum transverse trapping efficiency of the isolated chromosomes was calculated as ?0.01–0.02. These results confirm theoretical force calculations of ?0.1–12?pN to move a chromosome on the mitotic or meiotic spindle. The verification of these results was carried out by calibration of the optical tweezers when trapping microspheres with a diameter of 4.5–15?µm in media with 1–7?cP viscosity. The results of the chromosome and microsphere trapping experiments agree with optical models developed to simulate trapping of cylindrical and spherical specimens. PMID:25359514

Khatibzadeh, Nima; Stilgoe, Alexander B.; Bui, Ann A. M.; Rocha, Yesenia; Cruz, Gladys M.; Loke, Vince; Shi, Linda Z.; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina; Berns, Michael W.

2014-01-01

342

Multialtitude airborne observations of insolation effects of forest fire smoke aerosols at BOREAS: Estimates of aerosol optical parameters  

NASA Astrophysics Data System (ADS)

Forest fire disturbance, as part of the natural cycle of the boreal ecosystem renewal, proved a significant factor in the acquisition scheduling of optical remote imagery at the northern study site of the Boreal Ecosystem-Atmosphere Study (BOREAS), conducted in northern/central Canada during the July/August months of 1994. One such episode, between July 28 and 31, was due entirely to smoke transported over the study site from nearby and distant downwind fires. Noon insolation was reduced from 800 W/m2 on July 28 to 680 W/m2 on July 31 and incident PAR radiation from 320 to 250 W/m2. During the July 31 smoke episode the compact airborne spectrographic imager (CASI) was flown at 150, 300, 900, 1500, and 3200 m agl over a forested site, while measuring the scene-reflected radiance as well as upwelling and downwelling irradiances in the spectral range 403 and 916 nm (2.5 nm resolution). These multialtitude observations of upwelling and downwelling irradiance and the hemispherical reflectance are used to estimate at two wavelengths, 550 and 672 nm, the vertical profiles of aerosol optical depth, attenuation coefficient, and single-scattering albedo representative of the smoke aerosols encountered at BOREAS. For smoke aerosols from distant fires (high altitude) the single-scattering albedo was 0.9 and the attenuation coefficient was 0.32 km-1 at 672 nm, whereas for smoke aerosols from nearby fires, values of 0.6 and 0.60 km-1 were found. This is qualitatively consistent with differences expected for distant primarily sulfate aerosols and higher soot aerosols for nearby flaming fires.

Miller, John R.; O'Neill, Norman T.

1997-12-01

343

Effect of Wind Speed on Aerosol Optical Depth over Remote Oceans, Based on Data from the Maritime Aerosol Network  

NASA Technical Reports Server (NTRS)

The Maritime Aerosol Network (MAN) has been collecting data over the oceans since November 2006. The MAN archive provides a valuable resource for aerosol studies in maritime environments. In the current paper we investigate correlations between ship-borne aerosol optical depth (AOD) and near-surface wind speed, either measured (onboard or from satellite) or modeled (NCEP). According to our analysis, wind speed influences columnar aerosol optical depth, although the slope of the linear regression between AOD and wind speed is not steep (approx. 0.004 - 0.005), even for strong winds over 10m/s. The relationships show significant scatter (correlation coefficients typically in the range 0.3 - 0.5); the majority of this scatter can be explained by the uncertainty on the input data. The various wind speed sources considered yield similar patterns. Results are in good agreement with the majority of previously published relationships between surface wind speed and ship-based or satellite-based AOD measurements. The basic relationships are similar for all the wind speed sources considered; however, the gradient of the relationship varies by around a factor of two depending on the wind data used

Smirnov, A.; Sayer, A. M.; Holben, B. N.; Hsu, N. C.; Sakerin, S. M.; Macke, A.; Nelson, N. B.; Courcoux, Y.; Smyth, T. J.; Croot, P.; Quinn, P. K.; Sciare, J.; Gulev, S. K.; Piketh, S.; Losno, R.; Kinne, S.; Radionov, V. F.

2012-01-01

344

Sensitivity of Multiangle Imaging to the Optical and Microphysical Properties of Biomass Burning Aerosols  

NASA Technical Reports Server (NTRS)

The treatment of biomass burning (BB) carbonaceous particles in the Multiangle Imaging SpectroRadiometer (MISR) Standard Aerosol Retrieval Algorithm is assessed, and algorithm refinements are suggested, based on a theoretical sensitivity analysis and comparisons with near-coincident AERONET measurements at representative BB sites. Over the natural ranges of BB aerosol microphysical and optical properties observed in past field campaigns, patterns of retrieved Aerosol Optical Depth (AOD), particle size, and single scattering albedo (SSA) are evaluated. On the basis of the theoretical analysis, assuming total column AOD of 0.2, over a dark, uniform surface, MISR can distinguish two to three groups in each of size and SSA, except when the assumed atmospheric particles are significantly absorbing (mid-visible SSA approx.0.84), or of medium sizes (mean radius approx.0.13 pin); sensitivity to absorbing, medium-large size particles increases considerably when the assumed column AOD is raised to 0.5. MISR Research Aerosol Retrievals confirm the theoretical results, based on coincident AERONET inversions under BB-dominated conditions. When BB is externally mixed with dust in the atmosphere, dust optical model and surface reflection uncertainties, along with spatial variability, contribute to differences between the Research Retrievals and AERONET. These results suggest specific refinements to the MISR Standard Aerosol Algorithm complement of component particles and mixtures. They also highlight the importance for satellite aerosol retrievals of surface reflectance characterization, with accuracies that can be difficult to achieve with coupled surface-aerosol algorithms in some higher AOD situations.

Chen, Wei-Ting; Kahn, Ralph A.; Nelson, David; Yau, Kevin; Seinfeld, John H.

2008-01-01

345

Aerosol optical properties in the Marine Environment during the TCAP-I campaign  

NASA Astrophysics Data System (ADS)

The role of direct radiative forcing by atmospheric aerosol is one of the largest sources of uncertainty in predicting climate change. Much of this uncertainty comes from the limited knowledge of observed aerosol optical properties. In this presentation we discuss derived aerosol optical properties based on measurements made during the summer 2012 Two-Column Aerosol Project-I (TCAP) campaign and relate these properties to the corresponding chemical and physical properties of the aerosol. TCAP was designed to provide simultaneous, in-situ observations of the size distribution, chemical properties, and optical properties of aerosol within and between two atmospheric columns over the Atlantic Ocean near the eastern seaboard of the United States. These columns are separated by 200-300 km and were sampled in July 2012 during a summer intensive operation period (IOP) using the U.S. Department of Energy's Gulfstream-1 (G-1) and NASA's B200 aircraft, winter IOP using G-1 aircraft in February 2013, and the surface-based DOE Atmospheric Radiation Measurement (ARM) Mobile Facility (AMF) located on Cape Cod. In this presentation we examine the spectral dependence of the aerosol optical properties measured from the aircraft over the TCAP-I domain, with an emphasis on in-situ derived intensive properties measured by a 3-? Nephelometer, a Particle Soot Absorption Photometer (PSAP), a humidograph (f(RH)), and a Single Particle Soot Photometer (SP2). Preliminary results indicate that the aerosol are more light-absorbing as well as more hygroscopic at higher altitudes (2-4 km) compared to the corresponding values made within residual layers near the surface (0-2 km altitude). The average column (0-4 km) single scattering albedo (?) and hygroscopic scattering factor (F) are found to be ~0.96 and 1.25, respectively. Additional results on key aerosol intensive properties such as the angstrom exponent (å), asymmetry parameter (g), backscattering fraction (b), and gamma parameter (?) will be presented and discussed.

Chand, D.; Berg, L. K.; Barnard, J.; Berkowitz, C. M.; Burton, S. P.; Chapman, E. G.; Comstock, J. M.; Fast, J. D.; Ferrare, R. A.; Connor, F. J.; Hair, J. W.; Hostetler, C. A.; Hubbe, J.; Kluzek, C.; Mei, F.; Pekour, M. S.; Sedlacek, A. J.; Schmid, B.; Shilling, J. E.; Shinozuka, Y.; Tomlinson, J. M.; Wilson, J. M.; Zelenyuk-Imre, A.

2013-12-01

346

Variability of Aerosol Optical Properties from Long-term  

E-print Network

Aerosol Forcing Forest fires in Canada on June 10, 1997. #12;NOAA Aerosol Network South PoleSouth Pole Photometer · Principle of operation is to measure the change in light transmission through a filter on which light extinction and light scattering. · Instrument exhibits a significant response to nonabsorbing

Delene, David J.

347

Seasonal Variability of Aerosol Optical Depth over Indian Subcontinent  

E-print Network

) in this region. Indo- Asian aerosols have impact on radiative forcing that cause negative forcing (cooling. Singh1,3,* , Ashbindu Singh2 , and Menas Kafatos3 1 Department of Civil Engineering, Indian Institute]. Aerosols are responsible for lowering of land surface temperature i.e. cooling effect which restricts

Singh, Ramesh P.

348

Biogenic aerosols from Amazonia: Composition, size distributions and optical properties  

NASA Astrophysics Data System (ADS)

Amazonia is an excellent laboratory to study atmospheric processes that are characteristic of natural conditions, as they existed prior to the impact of industrialization on the regional and global atmosphere. Biogenic aerosols dominate the particle population in Amazonia, showing a strong link between forest biology and atmospheric composition. In the fine fraction, aerosols are mostly secondary organic particles formed from biogenic emissions of trace gases, with a contribution of primary particles. In the coarse mode, primary biogenic particles dominates the picture. Aerosols have been continuously measured at the TT34 LBA tower at the ZF2 ecological station about 55 Km North of Manaus since January 2008. Fine mode aerosol mass concentration is very low in Amazonia, with PM2.5 of about 1.3×0.7 ?g m-3 and 3.4×2.0 ?g m-3 in the wet and dry seasons, respectively. In terms of particle number concentrations a median value of 220 cm-3 in the wet season and 2,200 cm-3 in the dry season were observed. An aerosol chemical speciation monitor (ACSM) was deployed in 2013, and it shows that organic aerosol account to 81% to the non-refractory PM1 aerosol loading at TT34, while in the dry season, a high 93% content of organic particles was observed. Size distribution shows the occurrence of bursts of particles with about 20 nanometers at night time, possibly associated with biological process. Very few events of new particle formation are observed. Aerosol light scattering and absorption coefficients at the TT34 site were low during the wet season, increasing by a factor of 5, approximately, in the dry season due to long range transport of biomass burning aerosols reaching the forest site. Aerosol single scattering albedo (SSA) ranged from 0.84 in the wet season up to 0.91 in the dry, indicating a surprising high absorption in the wet season, associated with biogenic particles.

Rizzo, L. V.; Artaxo, P. P.; Brito, J. F.; Barbosa, H. M.; Andreae, M. O.; Martin, S. T.

2013-12-01

349

AEROSOL EFFECTS ON SATELLITE RETRIEVALS OF CLOUD OPTICAL PROPERTIES IN THE SOUTH ATLANTIC OCEAN  

E-print Network

AEROSOL EFFECTS ON SATELLITE RETRIEVALS OF CLOUD OPTICAL PROPERTIES IN THE SOUTH ATLANTIC OCEAN optical depth and effective radius are shown to be underestimated in the South Atlantic Ocean, where layer is elevated above a liquid cloud in the South Atlantic Ocean. Both absorbing and scattering

Wisconsin at Madison, University of

350

A Method For Retrieving Water Vapor Columnar Content And Aerosol Optical Thickness  

Microsoft Academic Search

The capability to monitor and predict the physical characteristics of the atmosphere has been largely improved last decades. Aerosol optical thickness (AOT) and precipitable water vapor amount (W) are crucial atmospheric parameters in the understanding of atmospheric dynamics, as well as for the atmospheric correction of optical remote sensing images to be employed for land and water management. The objective

C. Bassani; R. M. Cavalli; V. Estelle´s; J. L. Go´mez-Amo; J. A. Marti´nez-Lozano; S. Pignatti; M. P. Utrillas

2006-01-01

351

Detection of Biomass in New York City Aerosols: Light Scattering and Optical Fluorescence Techniques  

Microsoft Academic Search

Optical spectroscopy is an ideal method for detecting bacteria and spores in real time. Optical fluorescence spectroscopy examination of New York City aerosols is used to quantify the mass of bacteria spores present in air masses collected at 14 liters\\/minute onto silica fiber filters, and on silica fiber ribbons using an Environmental Beta Attenuation Monitor manufactured by MetOne Instruments configured

M. Niebauer; A. Alimova; A. Katz; M. Xu; E. Rudolph; J. Steiner; R. R. Alfano

2005-01-01

352

Separating real and apparent effects of cloud, humidity, and dynamics on aerosol optical thickness near cloud edges  

Microsoft Academic Search

Aerosol optical thickness (AOT) is one of aerosol parameters that can be measured on a routine basis with reasonable accuracy from Sun-photometric observations at the surface. However, AOT-derived near clouds is fraught with various real effects and artifacts, posing a big challenge for studying aerosol and cloud interactions. Recently, several studies have reported correlations between AOT and cloud cover, pointing

Myeong-Jae Jeong; Zhanqing Li

2010-01-01

353

Aerosol Optical Depth Retrievals From High-Resolution Commercial Satellite Imagery Over Areas of High Surface Reflectance  

Microsoft Academic Search

The advancement and proliferation of high-resolution commercial imaging satellites presents a new opportunity for overland aerosol characterization. Current aerosol optical depth retrieval methods typically fail over areas with high surface reflectance, such as urban areas and deserts, since the upwelling radiance due to scattering by aerosols is small compared to the radiance resulting from surface reflection. The method proposed here

D. A. Vincent; K. E. Nielsen; P. A. Durkee; J. S. Reid

2005-01-01

354

A multi-angle aerosol optical depth retrieval algorithm for geostationary satellite data over the United States  

Microsoft Academic Search

Aerosol optical depth (AOD) retrieval from geostationary satellites has high temporal resolution compared to the polar orbiting satellites and thus enables us to monitor aerosol motion. However, current Geostationary Operational Environmental Satellites (GOES) have only one visible channel for retrieving aerosol and hence the retrieval accuracy is lower than those from the multichannel polar-orbiting satellite instruments such as the Moderate

H. Zhang; A. Lyapustin; Y. Wang; S. Kondragunta; I. Laszlo; P. Ciren; R. M. Hoff

2011-01-01

355

Lidar profiling of aerosol optical and microphysical properties from space: overview, review, and outlook  

NASA Astrophysics Data System (ADS)

The potential of spaceborne lidar to monitor aerosol layering and mixing with high vertical resolution is reviewed. An overview is presented on aerosol lidar techniques of past, present, and future NASA and ESA lidar missions. The potential of a standard backscatter lidar (LITE, 1994), a backscatter/polarization lidar (CALIPSO, since 2006), a polarization High Spectral Resolution Lidar (HSRL, ATLID, EARTHCARE), and of a multiwavelength polarization HSRL are discussed regarding their ability to derive height profiles of optical and microphysical properties of aerosols and to resolve aerosol types and mixtures as a function of height. The important role of ground-truth activities is emphasized. Measurement examples taken with ground-based lidars illustrate that these systems provide a detailed characterization of complex aerosol scenarios in contrast to the snapshot-like observations with spaceborne lidars.

Ansmann, A.; Müller, D.; Wandinger, U.; Mamouri, R. E.

2013-08-01

356

Influence of molecular scattering models on aerosol optical properties measured by high spectral resolution lidar.  

PubMed

The influence of molecular scattering models on aerosol optical properties measured by high spectral resolution lidar (HSRL) is experimentally investigated and theoretically evaluated. The measurements analyzed in this study were made during three field campaigns by the German Aerospace Center airborne HSRL. The influence of the respective theoretical model on spaceborne HSRL retrievals is also estimated. Generally, the influence on aerosol extinction coefficient can be neglected for both airborne and spaceborne HSRLs. However, the influence on aerosol backscatter coefficient depends on aerosol concentration and is larger than 3% (6%) at ground level for airborne (spaceborne) HSRLs, which is considerable for the spaceborne HSRL, especially when the aerosol concentration is low. A comparison of the HSRL measurements and coordinated ground-based sunphotometer measurements shows that the influence of the model is observable and comparable to the measurement error of the lidar system. PMID:19767932

Liu, Bing-Yi; Esselborn, Michael; Wirth, Martin; Fix, Andreas; Bi, De-Cang; Ehret, Gerhard

2009-09-20

357

MODIS Aerosol Optical Depth Bias Adjustment Using Machine Learning Algorithms  

NASA Astrophysics Data System (ADS)

Over the past decade, global aerosol observations have been conducted by space-borne sensors, airborne instruments, and ground-base network measurements. Unfortunately, quite often we encounter the differences of aerosol measurements by different well-calibrated instruments, even with a careful collocation in time and space. The differences might be rather substantial, and need to be better understood and accounted for when merging data from many sensors. The possible causes for these differences come from instrumental bias, different satellite viewing geometries, calibration issues, dynamically changing atmospheric and the surface conditions, and other "regressors", resulting in random and systematic errors in the final aerosol products. In this study, we will concentrate on the subject of removing biases and the systematic errors from MODIS (both Terra and Aqua) aerosol product, using Machine Learning algorithms. While we are assessing our regressors in our system when comparing global aerosol products, the Aerosol Robotic Network of sun-photometers (AERONET) will be used as a baseline for evaluating the MODIS aerosol products (Dark Target for land and ocean, and Deep Blue retrieval algorithms). The results of bias adjustment for MODIS Terra and Aqua are planned to be incorporated into the AeroStat Giovanni as part of the NASA ACCESS funded AeroStat project.

Albayrak, A.; Wei, J. C.; Petrenko, M.; Lary, D. J.; Leptoukh, G. G.

2011-12-01

358

Characteristics of spectral optical depths and size distributions of aerosols over tropical oceanic regions  

NASA Astrophysics Data System (ADS)

The characteristics of atmospheric aerosols and their dependence on meterological parameters over different marine environments are examined using columnar size distributions retrieved from spectral optical depth estimates over coastal and remote regions of the Arabian sea and equatorial Indian Ocean. In the near coastal regions, the aerosol size distribution is dependent on surface wind direction, showing the influence of proximity to the continent under continental wind conditions. Marine aerosols dominate and the large particle mode becomes well established in the far coastal and remote ocean environments. The optical depths and size parameters depend on surface wind speed. The overall aerosol loading decreases and the relative concentration of coarse particle increases as one moves to oceanic regions farther from the coast. The implications of these findings are discussed.

Moorthy, K. K.; Satheesh, S. K.; Murthy, B. V. K.

1998-06-01

359

Retrieval of Aerosol Optical Thickness (AOT) and its Relationship to Air Pollution Particulate Matter (PM10)  

Microsoft Academic Search

This paper presents a transmittance measurements technique collected by using FieldSpec HandHeld (Fieldspec HH) spectroradiometer to derive the aerosol optical thickness (AOT) in the atmosphere at 550 nm to improve the particulate matters of less than 10 micron (PM10) concentrations mapping. The concentrations of PM10 at selected locations were measured simultaneously with the atmospheric transmittance measurements using DustTrak Aerosol Monitor

Nadzri Othman; Mohd Zubir Matjafri; Hwee San Lim; Khiruddin Abdullah

2009-01-01

360

Comparison of MISR and AERONET aerosol optical depths over desert sites  

Microsoft Academic Search

Comparisons of the Multi-angle Imaging SpectroRadiometer (MISR) aerosol optical depths (AOD) with those of the AErosol RObotic NETwork (AERONET) were made at four desert sites, covering a two-year time period from December 2000 to November 2002. The two data sets show good correlation with no obvious systematic biases or trends, demonstrating MISR's ability to retrieve reliable visible and near infrared

J. V. Martonchik; D. J. Diner; R. Kahn; B. Gaitley; B. N. Holben

2004-01-01

361

Ultraviolet high-spectral-resolution Doppler lidar for measuring wind field and aerosol optical properties  

Microsoft Academic Search

An ultraviolet incoherent Doppler lidar that incorporates the high-spectral-resolution (HSR) technique has been developed for measuring the wind field and aerosol optical properties in the troposphere. An injection seeded and tripled Nd:YAG laser at an ultraviolet wavelength of 355 nm was used in the lidar system. The HRS technique can resolve the aerosol Mie backscatter and the molecular Rayleigh backscatter

Masaharu Imaki; Takao Kobayashi

2005-01-01

362

Remote sensing of aerosol optical characteristics in sub-Sahel, West Africa  

NASA Astrophysics Data System (ADS)

We have determined the characteristics of sub-Sahelian aerosols from a 2-year record of continuous ground-based measurements, made at the University of Ilorin, Ilorin (08°19'N, 04°20'E), Nigeria, in cooperation with the Aerosol Robotic Network. Observations of spectral aerosol optical depths during the dusty harmattan season indicate more than a twofold increase, when compared to other seasons. Retrieved columnar volume size distributions show the existence of bimodality with a dominant coarse mode. The retrieved size distributions were grouped according to different ranges of aerosol optical depths to characterize the aerosols for this particular region. Monthly means of retrieved single-scattering albedos show a sharp decrease from ˜0.95 to ˜0.85 at 500 nm from the preharmattan to the harmattan season when biomass burning is also practiced, increasing the presence of absorbing aerosols. On the basis of these comprehensive observations, we propose to augment existing desert aerosol models, as presented in the literature, to better characterize the dust outbreak season in West Africa, which is quite prolonged and overlaps with the biomass burning season.

Pandithurai, G.; Pinker, R. T.; Dubovik, O.; Holben, B. N.; Aro, T. O.

2001-11-01

363

Retrieval of aerosol optical characteristics from polarization measurements of reflected solar radiation above the oceans  

NASA Technical Reports Server (NTRS)

The reflected near infrared solar radiation observed from space above the oceans is due mainly to the atmosphere scattering, as the ocean surface is nearly black. The molecular Rayleigh contribution is also minimized at infrared wavelengths and it can be evaluated. It is shown that the degree of polarization is much more sensitive to the aerosol properties than the radiance. Measurements of polarization at two wavelengths and with an angular scanning are simulated and an inversion algorithm is proposed. It aims at finding an 'equivalent aerosol model', which reproduces the optical thickness and the asymmetry factor of the actual aerosol at all wavelengths in the solar spectrum.

Santer, R.; Herman, M.; Lenoble, J.

1982-01-01

364

A Global Survey of Shipboard Measurements of Aerosol Optical Properties over the Oceans  

NASA Astrophysics Data System (ADS)

Marine aerosols contribute to the global albedo in two ways: direct scattering of incoming solar radiation to space (the direct effect) and modulation of the scattering properties of marine clouds (the indirect effect). The shortwave scattering and absorption characteristics of the marine atmosphere vary widely in space and time due to the variety of aerosol types, aerosol concentrations, and cloud structures that can be present. Aerosols over the oceans may originate from a variety of sources. Some are locally produced by wind-wave interaction while others are advected over great distances by the wind. In clear skies, advected continental aerosols can have a significantly different radiative impact than those that are locally produced. In cloudy skies, continental aerosol can cause modifications to the cloud droplet distribution in marine boundary layer clouds. Therefore, it is important to understand the spatial, temporal, and physical characteristics of aerosol over the world's oceans. Although information about aerosol optical properties over the world's oceans is critical, shipboard sun photometer measurements of these properties are relatively sparse. As part of our NASA SIMBIOS work and with additional support from the Department of Energy's (DOE) Atmospheric Radiation Program (ARM) program, the number of shipboard measurements has increased exponentially due to the development of a marine version of the Fast-Rotating, Shadow-band spectral Radiometer (FRSR). This instrument makes continuous, semi-automated shipboard measurements of the direct-normal, diffuse, and global irradiance in seven channels (415 nm, 500 nm, 610 nm, 660 nm, 862 nm, 936 nm, and broadband) and does not require a mechanically stabilized platform, thereby making it cost effective and reliable. The aerosol optical thickness is computed continuously from the direct-normal component of irradiance using calibration constants obtained using the Langley technique. The FRSR has been deployed on numerous cruises of opportunity (over 20) and is semi-permanently deployed on several operational research vessels. The data base of cruises has reasonable global coverage and the current FRSR data base contains years of data. In addition to routine cruises, the FRSR database includes data from the following field experiments: Aerosols99, INDOEX, Nauru99, and ACE-Asia. The FRSR data base have been analyzed for the purpose of classifying the various aerosol regimes over the world's oceans and quantifying the aerosol optical properties in these regimes. Uncertainties in the measurements have been quantified and are used as filtering criteria. Data from the instrument, after significant processing, are combined with aerosol chemical classifications, when available, to provide a unique view of aerosol structure over the world's oceans. Different aerosol regimes have been identified and their characteristics determined from the FRSR measurements. The FRSR can distinguish differences between the aerosol radiative properties, namely the aerosol optical thickness, the angstrom exponent, and the diffuse irradiance, in different aerosol regimes. Differences in the aerosol characteristics in different regimes are delineated in the FRSR data and interesting patterns are documented.

Miller, M. A.; Reynolds, R. M.; Quinn, P.; Bartholomew, M. J.

2001-12-01

365

Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol  

NASA Astrophysics Data System (ADS)

A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405-980 nm) for monitoring spectral reflectance (R) and transmittance (T) of filter samples allows "thermal spectral analysis (TSA)" and wavelength (?)-dependent organic carbon (OC)-elemental carbon (EC) measurements. Optical sensing is calibrated with transfer standards traceable to absolute R and T measurements and adjusted for loading effects to determine spectral light absorption (as absorption optical depth [?a, ?]) using diesel exhaust samples as a reference. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~635 nm) for pyrolysis adjustment. TSA provides additional information that evaluates black carbon (BC) and brown carbon (BrC) contributions and their optical properties in the near-IR to the near-UV parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

Chen, L.-W. A.; Chow, J. C.; Wang, X. L.; Robles, J. A.; Sumlin, B.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

2014-09-01

366

Aerosol optical properties and types over the tropical urban region of Hyderabad, India  

NASA Astrophysics Data System (ADS)

India is densely populated, industrialized and in the recent years has witnessed an impressive economic development. Aerosols over and around India not only affect the Indian monsoon but also the global climate. The growing population coupled with revolution in industry has resulted in higher demands for energy and transport. With more and more urbanization the usage pattern of fossil and bio-fuels are leading to changes in aerosol properties, which may cause changes in precipitation and can decelerate the hydrological cycle. Over urban areas of India aerosol emissions from fossil fuels such as coal, petrol and diesel oil dominate. Further-more, the Indian subcontinent exhibits different land characteristics ranging from vegetated areas and forests to semiarid and arid environments and tall mountains. India experiences large seasonal climatic variations, which result in extreme temperatures, rainfall and relative humidity. These meteorological and climatic features introduce large variabilities in aerosol op-tical and physico-chemical characteristics at spatial and temporal scales. In the present study, seasonal variations in aerosol properties and types were analysed over tropical urban region of Hyderabad, India during October 2007-September 2008 using MICROTOPS II sun photometer measurements. Higher aerosol optical depth (AOD) values are observed in premonsoon, while the variability of the ?ngstrüm exponent (?) seems to be more pronounced with higher values A in winter and premonsoon and lower in the monsoon periods. The AOD at 500 nm (AOD500 ) is very large over Hyderabad, varying from 0.46±0.17 in postmonsoon to 0.65±0.22 in premon-soon periods. A discrimination of the different aerosol types over Hyderabad is also attempted using values of AOD500 and ?380-870. Such discrimination is rather difficult to interpret since a single aerosol type can partly be identified only under specific conditions (e.g. anthropogenic emissions, biomass burning or dust outbreaks), while the presence of mixed aerosols, without dominance of the coarse or accumulation mode is the usual situation. According to the analysis the three individual components of differing origin, composition and optical characteristics are, a) an urban/industrial aerosol type composed of aerosols produced locally and all year round by combustion activities in the city or long-range transported (mainly in spring) biomass burning, b) an aerosol type of mineral origin raised by the wind in the deserts (mainly in premonsoon) or constitutes coarse-mode aerosols under high relative humidity conditions mainly in the monsoon period, and c) an aerosol type with a marine influence under background conditions occurred in monsoon and postmonsoon periods. Nevertheless, the mixed or undetermined aerosol type dominates with percentages varying from 44.3% (premonsoon) to 72.9% (postmonsoon). Spec-tral AOD and ? data are analyzed to obtain information about the adequacy of the simple use of the ?ngstrüm exponent for characterizing the aerosols. This is achieved by taking advantage A of the spectral variation of lnAOD vs ln?, the so-called curvature. The results show that the spectral curvature can be effectively used as a tool for aerosol types discrimination, since the fine-mode aerosols exhibit negative curvature, while the coarse-mode particles positive. The present study is among the first over Hyderabad focusing on the seasonal pattern of aerosol properties and types and aiming at associating them with local emissions, regional climatology and long-range transport. Keywords: AOD, aerosol types; sun photometer; back trajectories; Hyderabad; India

Kharol, Shailesh Kumar; Kaskaoutis, D. G.; Rani Sharma, Anu; Kvs, Badarinath; Kambezidis, H. D.

367

Spatial and temporal variations of aerosol optical depth in China during the period from 2003 to 2006  

Microsoft Academic Search

Spatial and temporal variations of aerosol optical depth (AOD, or ?) in China were investigated using MODIS-derived aerosol data for a period of 2003–2006. The geographical distribution patterns of 4-year mean AOD for total, ?0.55 (AOD at 0.55 ?m), fine, ?0.55-fine, and coarse, ?0.55-coarse, aerosols over China were addressed. These results indicate that the distribution of aerosol was largely affected

Bengang Li; Huishi Yuan; Nan Feng; Shu Tao

2010-01-01

368

Airborne high spectral resolution lidar for profiling aerosol optical properties.  

PubMed

A compact, highly robust airborne High Spectral Resolution Lidar (HSRL) that provides measurements of aerosol backscatter and extinction coefficients and aerosol depolarization at two wavelengths has been developed, tested, and deployed on nine field experiments (over 650 flight hours). A unique and advantageous design element of the HSRL system is the ability to radiometrically calibrate the instrument internally, eliminating any reliance on vicarious calibration from atmospheric targets for which aerosol loading must be estimated. This paper discusses the design of the airborne HSRL, the internal calibration and accuracy of the instrument, data products produced, and observations and calibration data from the first two field missions: the Joint Intercontinental Chemical Transport Experiment--Phase B (INTEX-B)/Megacity Aerosol Experiment--Mexico City (MAX-Mex)/Megacities Impacts on Regional and Global Environment (MILAGRO) field mission (hereafter MILAGRO) and the Gulf of Mexico Atmospheric Composition and Climate Study/Texas Air Quality Study II (hereafter GoMACCS/TexAQS II). PMID:19104525

Hair, Johnathan W; Hostetler, Chris A; Cook, Anthony L; Harper, David B; Ferrare, Richard A; Mack, Terry L; Welch, Wayne; Isquierdo, Luis Ramos; Hovis, Floyd E

2008-12-20

369

Development of a polarization optical particle counter capable of aerosol type classification  

NASA Astrophysics Data System (ADS)

We developed a polarization optical particle counter (POPC) for measuring the concentrations of aerosol types, which were classified using polarization information from particle-scattered light. Polarization sensors that detect P and S polarization components of scattered light were placed at a scattering angle of 120°. The polarization ratio is calculated as the ratio of the S component to the sum of the S and P components, and it is used to help distinguish proposed aerosol types. The POPC field observation was conducted in Fukuoka, located in the western part of Japan, in 2012. The classification rule for three aerosol types (mineral dust, air pollution, and sea-salt particles) was determined empirically on the basis of measurements during typical conditions dominated by each aerosol type. The mass concentration of each aerosol type was estimated from the POPC measurement with some assumptions. The results indicate independent seasonal variation in each aerosol mass concentration. Using black carbon as an indicator of anthropogenic aerosols, we show a correlation of 0.770 with our estimated pollution aerosol type.

Kobayashi, Hiroshi; Hayashi, Masahiko; Shiraishi, Koichi; Nakura, Yoshinobu; Enomoto, Takayuki; Miura, Kazuhiko; Takahashi, Hiroshi; Igarashi, Yasuhito; Naoe, Hiroaki; Kaneyasu, Naoki; Nishizawa, Tomoaki; Sugimoto, Nobuo

2014-11-01

370

Anomalies in Sea Spray Aerosol Optical Properties Detected by NASA High Spectral Resolution Lidar  

NASA Astrophysics Data System (ADS)

Data from a NASA flight mission over the Azores Archipelago off the western coast of Africa are analyzed to identify anomalies in sea spray aerosol optical properties associated with ocean biological production. The weeklong flight campaign began October 11, 2012 and focused on the sampling of clean marine air with little contamination from other sources like African dust or continental pollution. The NASA High Spectral Resolution Lidar (HSRL) has a laser that emits a pulse at two wavelengths (0.532 and 1.064 ?m) and a receiver that measures the backscattered radiation as a function of altitude. From this instrument, three important optical properties relevant to our study are derived: the aerosol lidar ratio, color ratio, and depolarization ratio, analysis of which can give insight into aerosol type, size, and shape respectively. To analyze the optical properties of aerosols within the marine boundary layer, one needs to accurately predict the boundary layer height and the presence of clouds in the optical path of the HSRL. Therefore, this study first introduces a new cloud-screening algorithm and then applies a boundary layer detection algorithm to filter the aerosol sample. Our analysis for the cloud free regions revealed statistically significant anomalies in particle depolarization ratio (?>10%) that were well correlated with surface chlorophyll-a concentrations (R?0.5) detected by NASA's MODerate Imaging Spectroradiometer (MODIS). Other parameters such as the lidar ratio and color ratio that are influenced by the aerosol size distribution and physiochemical properties will also be discussed. This study suggests that HSRL is suitable for exploring the effects of ocean biological production on clean marine aerosol optical properties.

Dawson, K. W.; Meskhidze, N.; Hu, Y.

2013-12-01

371

Magnetic Tweezers Instrumentation: We have used magnetic tweezers to study chromatin assembly and disassembly and RNA  

E-print Network

Magnetic Tweezers Instrumentation: We have used magnetic tweezers to study chromatin assembly and disassembly and RNA transcription. Magnetic tweezers surface magnetic bead F DNA external magnets F =kBT l/> l F x surface Instrumental set-up video camera beam condenser hollow bearing with magnet 90x oil

Leuba, Sanford

372

Controlling and characterizing the coagulation of liquid aerosol droplets.  

PubMed

We demonstrate that optical tweezers can be used to control and characterize the coagulation and mixing state of aerosols. Liquid aerosol droplets of 2-14 mum in diameter are optically trapped and characterized by spontaneous and stimulated Raman scatterings, which together provide a unique signature of droplet size and composition. From the conventional bright field image, the size of the trapped droplet can be estimated and compared with that determined from stimulated Raman scattering, and the motion of the particle within the trapping plane can be recorded. A maximum of four droplets can be manipulated in tandem by forming multiple optical traps through rapid beam steering. The coagulation of two droplets can be studied directly by controlling two droplets. The limiting conditions under which optical forces and capillary forces dominate the aerosol coagulation event are explored by varying the relative optical trap strengths and characterizing the coagulation of different droplet sizes. Finally, we demonstrate that the coagulation of different aerosol components can be compared and the mixing state of the final coagulated droplet can be investigated. In particular, we compare the outcome of the coagulation of an aqueous sodium chloride aerosol droplet with a second aqueous droplet, with an ethanol droplet or with a decane droplet. PMID:16999489

Buajarern, Jariya; Mitchem, Laura; Ward, Andrew D; Nahler, N Hendrik; McGloin, David; Reid, Jonathan P

2006-09-21

373

Aerosol Optical Properties of Smoke from the Las Conchas Wildfire, Los Alamos, NM  

NASA Astrophysics Data System (ADS)

The Las Conchas wildfire in Northern New Mexico started on June, 26 2011 and spread rapidly, eventually burning an area of 634 km2 (245 mi2). Due to the close proximity to the fire, the Los Alamos National Laboratory (LANL) was shut down and the town evacuated for several days. Immediately after LANL reopened (7/6/2011) the Earth and Environmental Sciences Division (EES-14) attained unique measurements of the smoke by sampling the ambient air. Three Integrated Photoacoustic/Nephelometer Spectrometers (DMT Inc.) were set up to measure aerosol light absorption and scattering coefficients. A University of Northwest Switzerland thermodenuder was used to remove compounds that are volatile at temperatures up to 200C. The aerosol's optical properties were measured before and after denuding the sample at 405nm (blue), 532nm (green), 781nm (red), and for non-denuded particles also at 375nm (ultraviolet). The aerosol size distributions were measured after the denuder with a Laser Aerosol Spectrometer (LAS, TSI Inc.) and black carbon was measured with a Single Particle Soot Photometer (SP2, DMT Inc.). Additionally, ambient measurements of Total Particulate Matter (PM2.5 and PM10) were collected continuously at the LANL air monitoring stations. These measurements are used in conjunction with numerical simulations to determine the bulk optical properties of the aerosol. Aerosols in wildfire smoke are composed of organic and black carbon (soot) particles that are formed during wood combustion and pyrolysis. The optical properties of the smoke particles are complex and lead to large uncertainties in assessing the global climate. During the measurement period, the Las Conchas fire provided very high particle concentrations (up to 200 ?g/m3) that were exploited to investigate their optical properties. By heating the particles to temperatures ranging from 75 to 200C in the denuder, volatile organics were removed and the optical properties of the remaining particles were measured. Denuding of the aerosols, removed the outer organic coatings leaving behind the inner core of black carbon (soot) and any compounds that did not volatize completely. By simultaneously measuring the optical properties of the non-denuded as well as the denuded aerosol, we can study how the coatings affect the optical properties. The absorption coefficient measurements showed that coatings can cause an increase or decrease in absorption. The photoacoustic measurements were also combined with SP2 measurements to gain a mechanistic understanding of the effect of composition on the mass light absorption cross-sections of carbonaceous aerosols emitted by fires.

Gorkowski, K.; Dubey, M. K.; Flowers, B. A.; Aiken, A. C.; Klein, B. Z.; Mazzoleni, C.; Sharma, N.; China`, S.

2011-12-01

374

Sensitivity of spectral reflectance to aerosol optical properties in UV and visible wavelength range: Preparatory study for aerosol retrieval from Geostationary Environmental Monitoring Spectrometer (GEMS)  

NASA Astrophysics Data System (ADS)

Asia, with its rapid increase in industrialization and population, has been receiving great attention as one of important source regions of pollutants including aerosols and trace gases. Since the spatio-temporal distribution of the pollutants varies rapidly, demands to monitor air quality in a geostationary satellite have increased recently. In these perspectives, the Ministry of Environment of Korea initiated a geostationary satellite mission to launch the Geostationary Environmental Monitoring Spectrometer (GEMS) onboard the GEO-KOMPSAT in 2017-2018 timeframe. From the Ozone Monitoring Instrument (OMI) measurements, it has been found that the low surface reflectance and strong interaction between aerosol absorption and molecular scattering in UV wavelength range can be advantageous in retrieving aerosol optical properties, such as aerosol optical thickness (AOT) and optical type (or single scattering albedo), over the source regions as well as ocean areas. In addition, GEMS is expected to have finer spatial resolution compared to OMI (13 x 24 km2 at nadir), thereby less affected by sub-pixel clouds. In this study, we present sensitivity of spectral reflectance to aerosol optical properties in ultraviolet (UV) and visible wavelength range for a purpose to retrieve aerosol optical properties from GEMS. The so called UV-VIS algorithm plans to use spectral reflectance in 350-650 nm. The algorithm retrieves AOT and aerosol type using an inversion method, which adopts pre-calculated lookup table (LUT) for a set of assumed aerosol models. For the aerosol models optimized in Asia areas, the inversion data of Aerosol Robotic Network (AERONET) located in the target areas are selectively used to archive aerosol optical properties. As a result, major aerosol types representing dust, polluted dust, and absorbing/non-absorbing anthropogenic aerosols are constructed and used for the LUT calculations. We analyze the effect of cloud contamination on the retrieved AOT by comparing the results from different spatial resolutions (7.5 x 7.5 km2, 5 x 5 km2, 2.5 x 7.5 km2, 1.25 x 3.75 km2). In addition, improved methodology to obtain aerosol products using hyper-spectral UV-VIS measurements is discussed.

KIM, M.; Kim, J.; Lee, J.

2011-12-01

375

Stratospheric aerosol optical depth observed by the Stratospheric Aerosol and Gas Experiment 2: Decay of the El Chichon and Ruiz volcanic perturbations  

Microsoft Academic Search

The decay of the El Chichon perturbation to the optical depth of stratospheric aerosols at 1.02 μm, and 0.453 μm is calculated from the Stratospheric Aerosol and Gas Experiment II (SAGE II) data set for the period December 1984 to December 1988. It is found that the perturbed optical depths at middle and higher latitudes of both hemispheres exhibited an

G. K. Yue; M. P. McCormick; E. W. Chiou

1991-01-01

376

Optical and microphysical properties of severe haze and smoke aerosol measured by integrated remote sensing techniques in Gwangju, Korea  

E-print Network

Optical and microphysical properties of severe haze and smoke aerosol measured by integrated remote October 2008 Accepted 21 October 2008 Keywords: Haze Raman lidar Satellite Single-scattering albedo a b s t r a c t Aerosol optical and microphysical parameters from severe haze events observed in October

Li, Zhanqing

377

Evaluation of SIMBADA measurements of marine reflectance and aerosol optical thickness during ACE-Asia and AOPEX  

Microsoft Academic Search

The SIMBADA radiometer was designed to check the radiometric calibration of satellite ocean-color sensors and evaluate the atmospheric correction of ocean-color imagery. It measures marine reflectance and aerosol optical thickness in 11 spectral bands covering the spectral range 350 to 870 nm. Aerosol optical thickness is obtained by viewing the sun disk and marine reflectance by viewing the ocean surface

Robert Frouin; Hubert Loisel; Antoine Poteau

2010-01-01

378

Estimating trace gas and aerosol emissions over South America: Relationship between fire radiative energy released and aerosol optical depth observations  

NASA Astrophysics Data System (ADS)

Contemporary human activities such as tropical deforestation, land clearing for agriculture, pest control and grassland management lead to biomass burning, which in turn leads to land-cover changes. However, biomass burning emissions are not correctly measured and the methods to assess these emissions form a part of current research area. The traditional methods for estimating aerosols and trace gases released into the atmosphere generally use emission factors associated with fuel loading and moisture characteristics and other parameters that are hard to estimate in near real-time applications. In this paper, fire radiative power (FRP) products were extracted from Moderate Resolution Imaging Spectroradiometer (MODIS) and from the Geostationary Operational Environmental Satellites (GOES) fire products and new South America generic biomes FRE-based smoke aerosol emission coefficients were derived and applied in 2002 South America fire season. The inventory estimated by MODIS and GOES FRP measurements were included in Coupled Aerosol-Tracer Transport model coupled to the Brazilian developments on the Regional Atmospheric Modeling System (CATT-BRAMS) and evaluated with ground truth collected in Large Scale Biosphere-Atmosphere Smoke, Aerosols, Clouds, rainfall, and Climate (SMOCC) and Radiation, Cloud, and Climate Interactions (RaCCI). Although the linear regression showed that GOES FRP overestimates MODIS FRP observations, the use of a common external parameter such as MODIS aerosol optical depth product could minimize the difference between sensors. The relationship between the PM 2.5?m (Particulate Matter with diameter less than 2.5 ?m) and CO (Carbon Monoxide) model shows a good agreement with SMOCC/RaCCI data in the general pattern of temporal evolution. The results showed high correlations, with values between 0.80 and 0.95 (significant at 0.5 level by student t test), for the CATT-BRAMS simulations with PM 2.5?m and CO.

Pereira, Gabriel; Freitas, Saulo R.; Moraes, Elisabete Caria; Ferreira, Nelson Jesus; Shimabukuro, Yosio Edemir; Rao, Vadlamudi Brahmananda; Longo, Karla M.

2009-12-01

379

CALIOP and AERONET Aerosol Optical Depth Comparisons: One Size Fits None  

NASA Technical Reports Server (NTRS)

We compare the aerosol optical depths (AOD) retrieved from backscatter measurements of the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aboard the Cloud Aerosol Lidar Infrared Pathfinder Satellite Observations (CALIPSO) satellite with coincident Aerosol Robotic Network (AERONET) measurements. Overpass coincidence criteria of +/- 2 h and within a 40 km radius are satisfied at least once at 149 globally distributed AERONET sites from 2006 to 2010. Most data pairs (>80%) use AERONET measurements acquired +/- 30 min of the overpass. We examine the differences in AOD estimates between CALIOP and AERONET for various aerosol, environmental, and geographic conditions. Results show CALIOP AOD are lower than AERONET AOD especially at low optical depths as measured by AERONET (500 nm AOD<0.1). Furthermore, the median relative AOD difference between the two measurements is 25% of the AERONET AOD for AOD>0.1. Differences in AOD between CALIOP and AERONET are possibly due to cloud contamination, scene inhomogeneity, instrument view angle differences, CALIOP retrieval errors, and detection limits. Comparison of daytime to nighttime number of 5 km 60m (60m in the vertical) features detected by CALIOP show that there are 20% more aerosol features at night. We find that CALIPSO and AERONET do not agree on the cloudiness of scenes. Of the scenes that meet the above coincidence criteria, CALIPSO finds clouds in more than 45% of the coincident atmospheric columns AERONET classifies as clear.

Omar, A. H.; Winker, D. M.; Tackett, J. L.; Giles, D. M.; Kar, J.; Liu, Z.; Vaughan, M. A.; Powell, K. A.; Trepte, C. R.

2013-01-01

380

Estimation of cloud condensation nuclei concentration from aerosol optical quantities: influential factors and uncertainties  

NASA Astrophysics Data System (ADS)

Cloud condensation nuclei (CCN) is a key variable for understanding cloud formation, but it is hard to obtain on large scales on a routine basis, whereas aerosol optical quantities are more readily available. This study presents an in-depth investigation on the relationship between CCN and aerosol optical quantities in regions of distinct aerosol types using extensive measurements collected at multiple Atmospheric Radiation Measurement (ARM) Climate Research Facility (CRF) sites around the world. The influences of relative humidity (RH), aerosol hygroscopicity (fRH) and single scattering albedo (SSA) on the relationship are analyzed. Better relationships are found between aerosol optical depth (AOD) and CCN at the Southern Great Plains (US), Ganges Valley (India) and Black Forest sites (Germany) than those at the Graciosa Island and Niamey (Niger) sites, where sea salt and dust aerosols dominate, respectively. In general, the correlation between AOD and CCN decreases as the wavelength of AOD measurement increases, suggesting that AOD measured at a shorter wavelength is a better proxy of CCN. The correlation is significantly improved if aerosol index (AI) is used together with AOD. The highest correlation exists between CCN and aerosol scattering coefficients (?sp) and scattering AI measured in-situ. The CCN-AOD (AI) relationship deteriorates with increasing RH. If RH exceeds 75%, the relationship becomes almost invalid for using AOD as a CCN proxy, whereas a tight ?sp-CCN relationship exists for dry particles. Aerosol hygroscopicity has a weak impact on the ?sp-CCN relationship. Particles with low SSA are generally associated with higher CCN concentrations, suggesting that SSA affects the relationship between CCN concentration and aerosol optical quantities. It may thus be used as a constraint to reduce uncertainties in the relationship. A significant increase in ?sp and decrease in CCN with increasing SSA is observed, leading to a significant decrease in their ratio (CCN/?sp) with increasing SSA. The relationships and major influential factors are parameterization for improving CCN estimation with varying amount of information on RH, particle size and SSA.

Liu, J.; Li, Z.

2013-09-01

381

Magnetic tweezers: micromanipulation and force measurement at the molecular level.  

PubMed Central

Cantilevers and optical tweezers are widely used for micromanipulating cells or biomolecules for measuring their mechanical properties. However, they do not allow easy rotary motion and can sometimes damage the handled material. We present here a system of magnetic tweezers that overcomes those drawbacks while retaining most of the previous dynamometers properties. Electromagnets are coupled to a microscope-based particle tracking system through a digital feedback loop. Magnetic beads are first trapped in a potential well of stiffness approximately 10(-7) N/m. Thus, they can be manipulated in three dimensions at a speed of approximately 10 microm/s and rotated along the optical axis at a frequency of 10 Hz. In addition, our apparatus can work as a dynamometer relying on either usual calibration against the viscous drag or complete calibration using Brownian fluctuations. By stretching a DNA molecule between a magnetic particle and a glass surface, we applied and measured vertical forces ranging from 50 fN to 20 pN. Similarly, nearly horizontal forces up to 5 pN were obtained. From those experiments, we conclude that magnetic tweezers represent a low-cost and biocompatible setup that could become a suitable alternative to the other available micromanipulators. PMID:12023254

Gosse, Charlie; Croquette, Vincent

2002-01-01

382

Retrieval of optical and microphysical properties of aerosols from a hybrid multiwavelength lidar dataset  

NASA Astrophysics Data System (ADS)

Over the past decade the development of inversion techniques for the retrievals of aerosol microphysical properties (e.g. effective radius, volume and surface-area concentrations) and aerosol optical properties (e.g. complex index of refraction and single scattering albedo) from multiwavelength lidar systems brought a new perspective in the study of the vertical distribution of aerosols. In this study retrievals of such parameters were obtained from a hybrid multiwavelength lidar dataset for the first time. In July of 2011, in the Baltimore-Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne in-situ and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar dataset combines elastic ground-based measurements at 355 nm with airborne High Spectral Resolution Lidar (HSRL) measurements at 532 nm and elastic measurements at 1064 nm that were obtained less than 5 km apart of each other. This was the first study to our knowledge in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in-situ measurements for eleven cases. Good agreement was observed between lidar and AERONET retrievals. Larger discrepancies were observed between lidar retrievals and in-situ measurements obtained by the aircraft and aerosol hygroscopic effects are believed to be the main factor of such discrepancies.

Sawamura, Patricia

383

Evaluating the impact of aerosol particles above cloud on cloud optical depth retrievals from MODIS  

NASA Astrophysics Data System (ADS)

two different operational Aqua Moderate Resolution Imaging Spectroradiometer (MODIS) cloud optical depth (COD) retrievals (0.86 versus 1.6 µm), we evaluate the impact of above-cloud smoke aerosol particles on near-IR (0.86 µm) COD retrievals. Aerosol Index (AI) from the collocated Ozone Monitoring Instrument (OMI) are used to identify above-cloud aerosol particle loading over the southern Atlantic Ocean, including both smoke and dust from the African subcontinent. Collocated Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation data constrain cloud phase and provide contextual above-cloud aerosol optical depth. The frequency of occurrence of above-cloud aerosol events is depicted on a global scale for the spring and summer seasons from OMI and Cloud Aerosol Lidar with Orthogonal Polarization. Seasonal frequencies for smoke-over-cloud off the southwestern Africa coastline reach 20-50% in boreal summer. We find a corresponding low COD bias of 10-20% for standard MODIS COD retrievals when averaged OMI AI are larger than 1. No such bias is found over the Saharan dust outflow region off northern Africa, since both MODIS 0.86 and 1.6 µm channels are vulnerable to radiance attenuation due to dust particles. A similar result is found for a smaller domain, in the Gulf of Tonkin region, from smoke advection over marine stratocumulus clouds and outflow into the northern South China Sea in spring. This study shows the necessity of accounting for the above-cloud aerosol events for future studies using standard MODIS cloud products in biomass burning outflow regions, through the use of collocated OMI AI and supplementary MODIS 1.6 µm COD products.

Alfaro-Contreras, Ricardo; Zhang, Jianglong; Campbell, James R.; Holz, Robert E.; Reid, Jeffrey S.

2014-05-01

384

Microphysical properties of transported biomass burning aerosols in coastal regions, and application to improving retrievals of aerosol optical depth from SeaWiFS data  

NASA Astrophysics Data System (ADS)

Due to the limited measurement capabilities of heritage and current spaceborne passive imaging radiometers, algorithms for the retrieval of aerosol optical depth (AOD) and related quantities must make assumptions relating to aerosol microphysical properties and surface reflectance. Over the ocean, surface reflectance can be relatively well-modelled, but knowledge of aerosol properties can remain elusive. Several field campaigns and many studies have examined the microphysical properties of biomass burning (smoke) aerosol. However, these largely focus on properties over land and near to the source regions. In coastal and open-ocean regions the properties of transported smoke may differ, due to factors such as aerosol aging, wet/dry deposition, and mixture with other aerosol sources (e.g. influence of maritime, pollution, or mineral dust aerosols). Hence, models based on near-source aerosol observations may be less representative of such transported smoke aerosols, introducing additional uncertainty into satellite retrievals of aerosol properties. This study examines case studies of transported smoke from select globally-distributed coastal and island Aerosol Robotic Network (AERONET) sites. These are used to inform improved models for over-ocean transported smoke aerosol for AOD retrievals from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS). These models are used in an updated version of the SeaWiFS Ocean Aerosol Retrieval (SOAR) algorithm, which has been combined with the Deep Blue algorithm over land to create a 13-year (1997-2010) high-quality record of AOD over land and ocean. Applying these algorithms to other sensors will enable the creation of a long-term global climate data record of spectral AOD.

Sayer, A. M.; Hsu, N. C.; Bettenhausen, C.

2013-05-01

385

Synthesis of information on aerosol optical properties Hongqing Liu,1  

E-print Network

and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study), the asymmetry parameter (g), and the normalized extinction coefficient over shortwave (SW) spectrum. Since space. The single scattering albedo is generated by extending GOCART w0 at 0.55 mm to the entire SW spectrum using

Chin, Mian

386

Combined active-passive remote sensing of aerosol optical properties  

Microsoft Academic Search

Recent assessments of global climate change conclude that the radiative effect of aerosols is one of the largest uncertainties in our ability to predict future climate change. A myriad of new sensors and satellite missions are being designed to address this major question confronting credible prediction of climate change. The NASA Langley Airborne A-Band Spectrometer (LAABS) is a recently developed

Michael Pitts; Chris Hostetler; John Hair; Rich Ferrare; Jeng-Hwa Yee

2004-01-01

387

Long-term trends in aerosol optical characteristics in the Po Valley, Italy  

NASA Astrophysics Data System (ADS)

Aerosol properties have been monitored by ground-based in situ and remote sensing measurements at the station for atmospheric research located in Ispra, on the edge of the Po Valley, for almost one decade. In situ measurements are performed according to Global Atmosphere Watch recommendations, and quality is assured through the participation in regular inter-laboratory comparisons. Sun-photometer data are produced by the Aerosol Robotic Network (AERONET). Data show significant decreasing trends over the 2004-2010 period for a number of variables, including particulate matter (PM) mass concentration, aerosol scattering, backscattering and absorption coefficients, and aerosol optical thickness (AOT). In situ measurement data show no significant trends in the aerosol backscatter ratio, but they do show a significant decreasing trend of about -0.7 ± 0.3% yr-1 in the aerosol single scattering albedo (SSA) in the visible light range. Similar trends are observed in the SSA retrieved from sun-photometer measurements. Correlations appear between in situ PM mass concentration and aerosol scattering coefficient, on the one hand, and elemental carbon (EC) concentration and aerosol absorption coefficient, on the other hand. However, no increase in the EC / PM ratio was observed, which could have explained the decrease in SSA. The application of a simple approximation to calculate the direct radiative forcing by aerosols suggests a significant diminution in their cooling effect, mainly due to the decrease in AOT. Applying the methodology we present to those sites, where the necessary suite of measurements is available, would provide important information to inform future policies for air-quality enhancement and fast climate change mitigation.

Putaud, J. P.; Cavalli, F.; Martins dos Santos, S.; Dell'Acqua, A.

2014-09-01

388

Intercomparison of aerosol optical parameters from WALI and R-MAN510 aerosol Raman lidars in the framework of HyMeX campaign  

NASA Astrophysics Data System (ADS)

The HyMeX program (Hydrological cycle in Mediterranean eXperiment) aims at improving our understanding of hydrological cycle in the Mediterranen and at a better quantification and forecast of high-impact weather events in numerical weather prediction models. The first Special Observation Period (SOP1) took place in September/October 2012. During this period two aerosol Raman lidars have been deployed at Menorca Island (Spain) : one Water-vapor and Aerosol Raman LIdar (WALI) operated by LSCE/CEA (Laboratoire des Sciences du Climat et de l'Environnement/Commissariat à l'Energie Atomique) and one aerosol Raman and dual-polarization lidar (R-Man510) developed and commercialized by LEOSPHERE company. Both lidars have been continuously running during the campaign and have provided information on aerosol and cloud optical properties under various atmospheric conditions (maritime background aerosols, dust events, cirrus clouds...). We will present here the results of intercomparisons between R-Man510, and WALI aerosol lidar systems and collocated sunphotometer measurements. Limitations and uncertainties on the retrieval of extinction coefficients, depolarization ratio, aerosol optical depths and detection of atmospheric structures (planetary boundary layer height, aerosol/cloud layers) will be discussed according atmospheric conditions. The results will also be compared with theoretical uncertainty assessed with direct/inverse model of lidar profiles.

Boytard, Mai-Lan; Royer, Philippe; Chazette, Patrick; Shang, Xiaoxia; Marnas, Fabien; Totems, Julien; Bizard, Anthony; Bennai, Baya; Sauvage, Laurent

2013-04-01

389

China Collection 2.0: The aerosol optical depth dataset from the synergetic retrieval of aerosol properties algorithm  

NASA Astrophysics Data System (ADS)

A wide range of data products have been published since the operation of the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's TERRA and AQUA satellites. Based on DarkTarget and DeepBlue method, NASA has published Aerosol Optical Depth (AOD) products Collection 5.0 and Collection 5.1 at 10 km spatial resolution. The Collection 6.0 will be published soon with spatial resolution of 3 km. Although validated globally, regional and systematic errors are still found in the MODIS-retrieved AOD products. This is especially remarkable for bright heterogeneous land surface, such as mainland China. In order to solve the aerosol retrieval problem over heterogeneous bright land surface, the Synergetic Retrieval of Aerosol Properties algorithm (SRAP) has been developed based on the synergetic use of the MODIS data of TERRA and AQUA satellites. Using the SRAP algorithm, we produced AOD dataset-China Collection 2.0, dated from August 2002 to August 2012, and compared the AOD results with AErosol Robotic NETwork (AERONET) and Chinese Meteorological Administration Aerosol Remote Sensing Network (CARSNET) measurements. We find that 62% of China Collection 2.0 AOD values are within an expected error (EE) range of ±(0.05 + 20%) and that 56% are within an EE range of ±(0.05 + 15%) when compared with AERONET-obse