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1

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

2

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

3

Organic component vapor pressures and hygroscopicities of aqueous aerosol measured by optical tweezers.  

PubMed

Measurements of the hygroscopic response of aerosol and the particle-to-gas partitioning of semivolatile organic compounds are crucial for providing more accurate descriptions of the compositional and size distributions of atmospheric aerosol. Concurrent measurements of particle size and composition (inferred from refractive index) are reported here using optical tweezers to isolate and probe individual aerosol droplets over extended timeframes. The measurements are shown to allow accurate retrievals of component vapor pressures and hygroscopic response through examining correlated variations in size and composition for binary droplets containing water and a single organic component. Measurements are reported for a homologous series of dicarboxylic acids, maleic acid, citric acid, glycerol, or 1,2,6-hexanetriol. An assessment of the inherent uncertainties in such measurements when measuring only particle size is provided to confirm the value of such a correlational approach. We also show that the method of molar refraction provides an accurate characterization of the compositional dependence of the refractive index of the solutions. In this method, the density of the pure liquid solute is the largest uncertainty and must be either known or inferred from subsaturated measurements with an error of <±2.5% to discriminate between different thermodynamic treatments. PMID:25522920

Cai, Chen; Stewart, David J; Reid, Jonathan P; Zhang, Yun-Hong; Ohm, Peter; Dutcher, Cari S; Clegg, Simon L

2015-01-29

4

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

5

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

6

Optical Tweezer Assembly and Calibration  

NASA Technical Reports Server (NTRS)

An Optical Tweezer, as the name implies, is a useful tool for precision manipulation of micro and nano scale objects. Using the principle of electromagnetic radiation pressure, an optical tweezer employs a tightly focused laser beam to trap and position objects of various shapes and sizes. These devices can trap micrometer and nanometer sized objects. An exciting possibility for optical tweezers is its future potential to manipulate and assemble micro and nano sized sensors. A typical optical tweezer makes use of the following components: laser, mirrors, lenses, a high quality microscope, stage, Charge Coupled Device (CCD) camera, TV monitor and Position Sensitive Detectors (PSDs). The laser wavelength employed is typically in the visible or infrared spectrum. The laser beam is directed via mirrors and lenses into the microscope. It is then tightly focused by a high magnification, high numerical aperture microscope objective into the sample slide, which is mounted on a translating stage. The sample slide contains a sealed, small volume of fluid that the objects are suspended in. The most common objects trapped by optical tweezers are dielectric spheres. When trapped, a sphere will literally snap into and center itself in the laser beam. The PSD s are mounted in such a way to receive the backscatter after the beam has passed through the trap. PSD s used with the Differential Interference Contrast (DIC) technique provide highly precise data. Most optical tweezers employ lasers with power levels ranging from 10 to 100 miliwatts. Typical forces exerted on trapped objects are in the pico-newton range. When PSDs are employed, object movement can be resolved on a nanometer scale in a time range of milliseconds. Such accuracy, however, can only by utilized by calibrating the optical tweezer. Fortunately, an optical tweezer can be modeled accurately as a simple spring. This allows Hook s Law to be used. My goal this summer at NASA Glenn Research Center is the assembly and calibration of an optical tweezer setup in the Instrumentation and Controls Division (5520). I am utilizing a custom LabVIEW Virtual Instrument program for data collection and microscope stage control. Helping me in my assignment are the following people: Mentor Susan Wrbanek (5520), Dr. Baha Jassemnejad (UCO) and Technicians Ken Weiland (7650) and James Williams (7650). Without their help, my task would not be possible.

Collins, Timothy M.

2004-01-01

7

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

8

Undergraduate Construction of Optical Tweezers  

NASA Astrophysics Data System (ADS)

I will present a poster on the construction of optical tweezers. This will demonstrate the full process one must go through when working on a research project. First I sifted through the internet for papers and information pertaining to the tweezers. Afterwards I discussed the budget with the lab manager. Next I made purchases, however some items, such as the sample mount, needed to be custom made. These I built in the machine shop. Once the tweezers were operational I spent some time ensuring that the mirrors and lenses were adjusted just right, so that the trap performed at full strength. Finally, I used video data of the Brownian motion of trapped silica microspheres to get a reasonable estimate of the trapping stiffness with such particles. As a general note, all of this was done with the intent of leaving the tweezers for future use by other undergraduates. Because of this extra effort was taken to ensure the tweezers were as safe to use as possible. For this reason a visible LASER was chosen over an infrared LASER, in addition, the LASER was oriented parallel to the surface of the table in order to avoid stray upwards beams.

Hubbell, Lawrence

2012-10-01

9

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

E-print Network

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy force microscopy (AFM), micro-needle manipulation1, biomembrane force probe2 and flow-induced stretching

Ritort, Felix

10

Characterizing conical refraction optical tweezers  

NASA Astrophysics Data System (ADS)

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, C.; McDougall, C.; Rafailov, E.; McGloin, D.

2014-12-01

11

Characterizing conical refraction optical tweezers.  

PubMed

Conical refraction occurs when a beam of light travels through an appropriately cut biaxial crystal. By focusing 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, focusing 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. PMID:25490654

McDonald, C; McDougall, C; Rafailov, E; McGloin, D

2014-12-01

12

Multispectral optical tweezers for molecular diagnostics of single biological cells  

E-print Network

Multispectral optical tweezers for molecular diagnostics of single biological cells Author States) ABSTRACT Optical trapping of single biological cells has become an established technique Raman and Fluorescence diagnostics of biological cells. Keywords: Optical trapping, Optical tweezers

Wu, Shin-Tson

13

Optical tweezers: light for manipulating microscopic world  

NASA Astrophysics Data System (ADS)

Optical tweezers make use of a tightly focused laser beam to trap, move, guide, rotate and even sort microscopic objects solely with light. Although the basic laser tweezers, making use of a TEM00 laser beam to create a single trap point, have proved to be useful for any applications in areas ranging from physics to biology, a major breakthrough in this field came as the use of computer generated holograms enabled researchers to create multiple trap sites from single laser source (holographic optical tweezers). Coupled with microfluidic techniques, holographic optical tweezers have promised development of optical techniques for high throughput sorting of different cell types under a single micro-chip platform. The holographic methods have also helped the use of specialized laser beams like Laguerre-Gaussian beams instead of the conventional laser beam for interesting applications like orienting/rotating the trapped objects or trapping cells with minimum photodamage. Further, combining optical tweezers with Raman spectroscopy is becoming increasingly popular for studying single cell biochemistry as use of optical forces to immobilize the cells under investigations not only avoids the negative effects of fixing the cells onto substrate but also improve the quality of the recorded spectra. These advanced optical trapping techniques as outlined above along with some illustrative biophotonics applications have been explored.

Dasgupta, Raktim

2012-05-01

14

Optical manipulation of lipid and polymer nanotubes with optical tweezers  

NASA Astrophysics Data System (ADS)

Using optical tweezers and microfluidics, we stretch either the lipid or polymer membranes of liposomes or polymersomes, respectively, into long nanotubes. The membranes can be grabbed directly with the optical tweezers to produce sub-micron diameter tubes that are several hundred microns in length. We can stretch tubes up to a centimeter in length, limited only by the travel of our microscope stage. We also demonstrate the cross linking of a pulled polymer nanotube.

Reiner, Joseph E.; Kishore, Rani; Pfefferkorn, Candace; Wells, Jeffrey; Helmerson, Kristian; Howell, Peter; Vreeland, Wyatt; Forry, Samuel; Locascio, Laurie; Reyes-Hernandez, Darwin; Gaitan, Michael

2004-10-01

15

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

Microsoft Academic Search

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. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

Attila Nagy; Keir C Neuman

2008-01-01

16

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

17

"Red Tweezers": Fast, customisable hologram generation for optical tweezers  

NASA Astrophysics Data System (ADS)

Holographic Optical Tweezers (HOT) are a versatile way of manipulating microscopic particles in 3D. However, their ease of use has been hampered by the computational load of calculating the holograms, resulting in an unresponsive system. We present a program for generating these holograms on a consumer Graphics Processing Unit (GPU), coupled to an easy-to-use interface in LabVIEW (National Instruments). This enables a HOT system to be set up without writing any additional code, as well as providing a platform enabling the fast generation of other holograms. The GPU engine calculates holograms over 300 times faster than the same algorithm running on a quad core CPU. The hologram algorithm can be altered on-the-fly without recompiling the program, allowing it to be used to control Spatial Light Modulators in any situation where the hologram can be calculated in a single pass. The interface has also been rewritten to take advantage of new features in LabVIEW 2010. It is designed to be easily modified and extended to integrate with hardware other than our own.

Bowman, Richard W.; Gibson, Graham M.; Linnenberger, Anna; Phillips, David B.; Grieve, James A.; Carberry, David M.; Serati, Steven; Miles, Mervyn J.; Padgett, Miles J.

2014-01-01

18

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

19

Inserting and Manipulating DNA in a Nanopore with Optical Tweezers  

E-print Network

Chapter 8 Inserting and Manipulating DNA in a Nanopore with Optical Tweezers U. F. Keyser, J. van that a combination of optical tweezers, single solid-state nanopores, and electrophysiological ionic current the experimental procedures that are neces- sary to manipulate single biopolymers in a single nanopore, not only

Dekker, Nynke

20

Absolute calibration of forces in optical tweezers  

NASA Astrophysics Data System (ADS)

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 15 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 spot, adapting frequently employed video microscopy techniques. Combined with interface spherical aberration, it reveals a previously unknown window of instability for trapping. Comparison with experimental data leads to an overall agreement within error bars, with no fitting, for a broad range of microsphere radii, from the Rayleigh regime to the ray optics one, for different polarizations and trapping heights, including all commonly employed parameter domains. Besides signaling full first-principles theoretical understanding of optical tweezers operation, the results may lead to improved instrument design and control over experiments, as well as to an extended domain of applicability, allowing reliable force measurements, in principle, from femtonewtons to nanonewtons.

Dutra, R. S.; Viana, N. B.; Maia Neto, P. A.; Nussenzveig, H. M.

2014-07-01

21

Developing functional Optical Tweezers for Undergraduate Research  

NASA Astrophysics Data System (ADS)

Optical tweezers are useful for manipulation of microscopic materials without damage from physical contact. This project utilized a 20mW HeNe laser (wavelength 632.8nm) and a reconfigured standard teaching-laboratory microscope to form a stable diffraction limited trap. A simple method of live recording of moving particles was developed with the use of AVT SmartView and NI Vision Assistant. The physical setup was altered several times to eliminate sources of misalignment, until an optimal configuration was achieved and optical trapping and manipulation of a polystyrene microsphere was successfully recorded. Additionally, Calcite particles on the order of 1 micrometer were manipulated with the optical trap.

Dax, Tanya; Sauncy, Toni

2010-10-01

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

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

24

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

25

Optical Tweezers Array and Nimble Tweezers Probe Generated by Spatial- Light Modulator  

NASA Technical Reports Server (NTRS)

An optical tweezers is being developed at the NASA Glenn Research Center as a visiblelight interface between ubiquitous laser technologies and the interrogation, visualization, manufacture, control, and energization of nanostructures such as silicon carbide (SiC) nanotubes. The tweezers uses one or more focused laser beams to hold micrometer-sized particles called tools (sometimes called tips in atomic-force-microscope terminology). A strongly focused laser beam has an associated light-pressure gradient that is strong enough to pull small particles to the focus, in spite of the oppositely directed scattering force; "optical tweezers" is the common term for this effect. The objective is to use the tools to create carefully shaped secondary traps to hold and assemble nanostructures that may contain from tens to hundreds of atoms. The interaction between a tool and the nanostructures is to be monitored optically as is done with scanning probe microscopes. One of the initial efforts has been to create, shape, and control multiple tweezers beams. To this end, a programmable spatial-light modulator (SLM) has been used to modify the phase of a laser beam at up to 480 by 480 points. One program creates multiple, independently controllable tweezer beams whose shapes can be tailored by making the SLM an adaptive mirror in an interferometer (ref. 1). The beams leave the SLM at different angles, and an optical Fourier transform maps these beams to different positions in the focal plane of a microscope objective. The following figure shows two arrays of multiple beams created in this manner. The patterns displayed above the beam array control the intensity-to-phase transformation required in programming the SLM. Three of the seven beams displayed can be used as independently controllable beams.

Decker, Arthur J.; Jassemnejad, Baha; Seibel, Robin E.; Weiland, Kenneth E.

2003-01-01

26

Optical tweezers-assisted measurements of elastic light scattering  

NASA Astrophysics Data System (ADS)

Optical tweezers have been used in biophysical studies for over twenty years. Typical application areas are force measurements of subcellular structures and cell biomechanics. Optical tweezers can also be used to manipulate the orientation of objects. Moreover, using various beam shapes, optical tweezers allow measuring light scattering from single and multiple objects by keeping particles and cells in place during the measurement. At single cell level, light scattering yields important information about the object being studied, including its size, shape and refractive index. Also dependent scattering can be studied. In this paper, we review experimental work conducted in this area by our group and show new results relating to optical clearing phenomena at single microparticle level.

Kinnunen, M.; Tuorila, J.; Haapalainen, T.; Karmenyan, A.; Tuchin, V.; Myllylä, R.

2014-01-01

27

Mechanisms of HCV NS3 helicase monitored by optical tweezers.  

PubMed

As one of the essential enzymes for viral genome replication, the hepatitis C virus NS3 helicase is one of the best characterized RNA helicases to date in understanding the mechanistic cycles in a helicase-catalyzed strand separation reaction. Recently, single-molecule studies on NS3, in particular the use of optical tweezers with sub-base pair spatial resolution, have allowed people to examine the potential elementary steps of NS3 in unwinding the double-stranded RNA fueled by ATP binding and hydrolysis. In this chapter, I detail the essential technical elements involved in conducting a high-resolution optical tweezers study of NS3 helicase, starting from the purification of the recombinant helicase protein from E. coli to setting up a high-resolution single-molecule experiment using optical tweezers. PMID:25579590

Cheng, Wei

2015-01-01

28

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

29

Optical tweezers reveal how proteins alter replication  

NASA Astrophysics Data System (ADS)

Single molecule force spectroscopy is a powerful method that explores the DNA interaction properties of proteins involved in a wide range of fundamental biological processes such as DNA replication, transcription, and repair. We use optical tweezers to capture and stretch a single DNA molecule in the presence of proteins that bind DNA and alter its mechanical properties. We quantitatively characterize the DNA binding mechanisms of proteins in order to provide a detailed understanding of their function. In this work, we focus on proteins involved in replication of Escherichia coli (E. coli ), endogenous eukaryotic retrotransposons Ty3 and LINE-1, and human immunodeficiency virus (HIV). DNA polymerases replicate the entire genome of the cell, and bind both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) during DNA replication. The replicative DNA polymerase in the widely-studied model system E. coli is the DNA polymerase III subunit alpha (DNA pol III alpha). We use optical tweezers to determine that UmuD, a protein that regulates bacterial mutagenesis through its interactions with DNA polymerases, specifically disrupts alpha binding to ssDNA. This suggests that UmuD removes alpha from its ssDNA template to allow DNA repair proteins access to the damaged DNA, and to facilitate exchange of the replicative polymerase for an error-prone translesion synthesis (TLS) polymerase that inserts nucleotides opposite the lesions, so that bacterial DNA replication may proceed. This work demonstrates a biophysical mechanism by which E. coli cells tolerate DNA damage. Retroviruses and retrotransposons reproduce by copying their RNA genome into the nuclear DNA of their eukaryotic hosts. Retroelements encode proteins called nucleic acid chaperones, which rearrange nucleic acid secondary structure and are therefore required for successful replication. The chaperone activity of these proteins requires strong binding affinity for both single- and double-stranded nucleic acids. We use single molecule DNA stretching to show that the nucleocapsid protein (NC) of the yeast retrotransposon Ty3, which is likely to be an ancestor of HIV NC, has optimal nucleic acid chaperone activity with only a single zinc finger. We also show that the chaperone activity of the ORF1 protein is responsible for successful replication of the mouse LINE-1 retrotransposon. LINE-1 is also 17% of the human genome, where it generates insertion mutations and alters gene expression. Retrotransposons such as LINE-1 and Ty3 are likely to be ancestors of retroviruses such as HIV. Human APOBEC3G (A3G) inhibits HIV-1 replication via cytidine deamination of the viral ssDNA genome, as well as via a distinct deamination-independent mechanism. Efficient deamination requires rapid on-off binding kinetics, but a slow dissociation rate is required for the proposed deaminase-independent mechanism. We resolve this apparent contradiction with a new quantitative single molecule method, which shows that A3G initially binds ssDNA with fast on-off rates and subsequently converts to a slow binding mode. This suggests that oligomerization transforms A3G from a fast enzyme to a slow binding protein, which is the biophysical mechanism that allows A3G to inhibit HIV replication. A complete understanding of the mechanism of A3G-mediated antiviral activity is required to design drugs that disrupt the viral response to A3G, enhance A3G packaging inside the viral core, and other potential strategies for long-term treatment of HIV infection. We use single molecule biophysics to explore the function of proteins involved in bacterial DNA replication, endogenous retrotransposition of retroelements in eukaryotic hosts such yeast and mice, and HIV replication in human cells. Our quantitative results provide insight into protein function in a range of complex biological systems and have wide-ranging implications for human health.

Chaurasiya, Kathy

30

Marker-free cell discrimination by holographic optical tweezers  

NASA Astrophysics Data System (ADS)

We introduce a method for marker-free cell discrimination based on optical tweezers. Cancerous, non-cancerous, and drug-treated cells could be distinguished by measuring the trapping forces using holographic optical tweezers. We present trapping force measurements on different cell lines: normal pre-B lymphocyte cells (BaF3; "normal cells"), their Bcr-Abl transformed counterparts (BaF3-p185; "cancer cells") as a model for chronic myeloid leukaemia (CML) and Imatinib treated BaF3-p185 cells. The results are compared with reference measurements obtained by a commercial flow cytometry system.

Schaal, F.; Warber, M.; Zwick, S.; van der Kuip, H.; Haist, T.; Osten, W.

2009-06-01

31

Superresolution imaging in optical tweezers using high-speed cameras.  

PubMed

High-speed cameras are reliable alternatives for the direct characterization of optical trap force and particle motion in optical tweezers setups, replacing indirect motion measurements often performed by quadrant detectors. In the present approach, subpixel motion data of the trapped particle is retrieved from a high-speed low-resolution video sequence. Due to the richness structure of motion diversity of microscopic trapped particles, which are subjected to a Brownian motion, we propose to also use the obtained motion information for tackling the inherent lack of resolution by applying superresolution algorithms on the low-resolution image sequence. The obtained results both for trapping calibration beads and for living bacteria show that the proposed approach allows the proper characterization of the optical tweezers by obtaining the real particle motion directly from the image domain, while still providing high resolution imaging. PMID:20389339

Staforelli, Juan Pablo; Vera, Esteban; Brito, José Manuel; Solano, Pablo; Torres, Sergio; Saavedra, Carlos

2010-02-15

32

A microscopic steam engine implemented in an optical tweezer.  

PubMed

The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies. PMID:25523395

Quinto-Su, Pedro A

2014-01-01

33

A microscopic steam engine implemented in an optical tweezer  

NASA Astrophysics Data System (ADS)

The introduction of improved steam engines at the end of the 18th century marked the start of the industrial revolution and the birth of classical thermodynamics. Currently, there is great interest in miniaturizing heat engines, but so far traditional heat engines operating with the expansion and compression of gas have not reached length scales shorter than one millimeter. Here, a micrometer-sized piston steam engine is implemented in an optical tweezer. The piston is a single colloidal microparticle that is driven by explosive vapourization of the surrounding liquid (cavitation bubbles) and by optical forces at a rate between a few tens of Hertz and one kilo-Hertz. The operation of the engine allows to exert impulsive forces with optical tweezers and induce streaming in the liquid, similar to the effect of transducers when driven at acoustic and ultrasound frequencies.

Quinto-Su, Pedro A.

2014-12-01

34

A Step-by-step Guide to the Realisation of Advanced Optical Tweezers  

E-print Network

Since the pioneering work of Arthur Ashkin, optical tweezers have become an indispensable tool for contactless manipulation of micro- and nanoparticles. Nowadays optical tweezers are employed in a myriad of applications demonstrating the importance of these tools. While the basic principle of optical tweezers is the use of a strongly focused laser beam to trap and manipulate particles, ever more complex experimental set-ups are required in order to perform novel and challenging experiments. With this article, we provide a detailed step- by-step guide for the construction of advanced optical manipulation systems. First, we explain how to build a single-beam optical tweezers on a home-made microscope and how to calibrate it. Improving on this design, we realize a holographic optical tweezers, which can manipulate independently multiple particles and generate more sophisticated wavefronts such as Laguerre-Gaussian beams. Finally, we explain how to implement a speckle optical tweezers, which permit one to employ ...

Pesce, Giuseppe; Marago, Onofrio M; Jones, Philip H; Gigain, Sylvain; Sasso, Antonio; Volpe, Giovanni

2015-01-01

35

Evidence for localized cell heating induced by infrared optical tweezers.  

PubMed

The confinement of liposomes and Chinese hamster ovary (CHO) cells by infrared (IR) optical tweezers is shown to result in sample heating and temperature increases by several degrees centigrade, as measured by a noninvasive, spatially resolved fluorescence detection technique. For micron-sized spherical liposome vesicles having bilayer membranes composed of the phospholipid 1,2-diacyl-pentadecanoyl-glycero-phosphocholine (15-OPC), a temperature rise of approximately 1.45 +/- 0.15 degrees C/100 mW is observed when the vesicles are held stationary with a 1.064 microns optical tweezers having a power density of approximately 10(7) W/cm2 and a focused spot size of approximately 0.8 micron. The increase in sample temperature is found to scale linearly with applied optical power in the 40 to 250 mW range. Under the same trapping conditions, CHO cells exhibit an average temperature rise of nearly 1.15 +/- 0.25 degrees C/100 mW. The extent of cell heating induced by infrared tweezers confinement can be described by a heat conduction model that accounts for the absorption of infrared (IR) laser radiation in the aqueous cell core and membrane regions, respectively. The observed results are relevant to the assessment of the noninvasive nature of infrared trapping beams in micromanipulation applications and cell physiological studies. PMID:7612858

Liu, Y; Cheng, D K; Sonek, G J; Berns, M W; Chapman, C F; Tromberg, B J

1995-05-01

36

Trapping sub-micron Size Particles in Holographic Optical Tweezers  

NASA Astrophysics Data System (ADS)

Trapping of sub-micron size particles is of interest to the biological community as well as to nanoelectronic research and industry. We have employed spatially modified Gaussian beam to generate narrow optical traps within diffraction limitation. A spatial light modulator is addressed with the spatial frequencies of the required optical traps. The inverse Fourier transform is obtained at the trap plane of the optical tweezers. We have demonstrated the trapping of sub-micron particles in multiples traps, patterned numerically which is addressed to a spatial light modulator. The trap is vary stable and the particles are trapped for more than 120 seconds.

Dwivedi, G.; Gupta, A.; Shukla, M.; Kanaujia, S.; Yede, S.; Andrews, J. T.

2014-09-01

37

Optical manipulation of aerosol particle arrays  

NASA Astrophysics Data System (ADS)

Aerosols play a crucial role in many areas of science, ranging from atmospheric chemistry and physics, to drug delivery to the lungs, combustion science and spray drying. The development of new methods to characterise 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 over indefinite timescales using optical tweezing. Linear and non-linear Raman and fluorescence spectroscopies can be used to probe a particle's composition and size. In this paper we will report on the latest developments in the use of holographic optical trapping (HOT) to study aerosols. Although widely used to trap and manipulate arrays of particles in the condensed phase, the application of HOT to aerosols is still in its infancy. We will explore the opportunities provided by the formation of complex optical landscapes for controlling aerosol flow, for comparing the properties of multiple particles, for performing the first ever digital microfluidic operations in the aerosol phase and for examining interparticle interactions that can lead to coalescence/coagulation. Although aerosol coagulation is the primary process driving the evolution of particle size distributions, it remains very poorly understood. Using HOT, we can resolve the time-dependent motion of trapped particles and the light scattering from particles during the coalescence process.

Reid, J. P.; Haddrell, A. E.; Walker, J. S.; Power, R.; Bones, D. L.; Davies, J. F.

2011-10-01

38

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

39

A simple optical tweezers for trapping polystyrene particles  

NASA Astrophysics Data System (ADS)

Optical tweezers is an optical trap. For decades, it has become an optical tool that can trap and manipulate any particle from the very small size like DNA to the big one like bacteria. The trapping force comes from the radiation pressure of laser light which is focused to a group of particles. Optical tweezers has been used in many research areas such as atomic physics, medical physics, biophysics, and chemistry. Here, a simple optical tweezers has been constructed using a modified Leybold laboratory optical microscope. The ocular lens of the microscope has been removed for laser light and digital camera accesses. A laser light from a Coherent diode laser with wavelength ? = 830 nm and power 50 mW is sent through an immersion oil objective lens with magnification 100 × and NA 1.25 to a cell made from microscope slides containing polystyrene particles. Polystyrene particles with size 3 ?m and 10 ?m are used. A CMOS Thorlabs camera type DCC1545M with USB Interface and Thorlabs camera lens 35 mm are connected to a desktop and used to monitor the trapping and measure the stiffness of the trap. The camera is accompanied by camera software which makes able for the user to capture and save images. The images are analyzed using ImageJ and Scion macro. The polystyrene particles have been trapped successfully. The stiffness of the trap depends on the size of the particles and the power of the laser. The stiffness increases linearly with power and decreases as the particle size larger.

Shiddiq, Minarni; Nasir, Zulfa; Yogasari, Dwiyana

2013-09-01

40

Hybrid optical tweezers for dynamic micro-bead arrays.  

PubMed

Dynamic micro-bead arrays offer great flexibility and potential as sensing tools in various scientific fields. Two optical trapping techniques, the GPC method using a spatial light modulator and a mechanical scanning method using galvano mirrors, are combined in a hybrid optical tweezers system to handle dynamic micro-bead arrays. This system provides greater versatility while the GPC method creates massive micro-bead arrays in a 2D space, where the trapped beads can be manipulated smoothly and very quickly in a 3D space using the mechanical scanning method. Four typical examples are demonstrated in real time. PMID:21934908

Tanaka, Yoshio; Tsutsui, Shogo; Ishikawa, Mitsuru; Kitajima, Hiroyuki

2011-08-01

41

Research Highlights 1. Combination of single-molecule FRET & optical tweezers  

E-print Network

Research Highlights 1. Combination of single-molecule FRET & optical tweezers Understanding as little as possible. Single-molecule fluorescence resonance energy transfer (FRET) is a powerful tool to combine single-molecule FRET and optical tweezers. Prior attempts, however, exposed great technical

Hohng, Sung Chul

42

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

43

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

44

Combined holographic-mechanical optical tweezers: Construction, optimisation and calibration  

E-print Network

We have combined a spatial light modulator (SLM) and galvanometer-mounted mirrors into an optical tweezers set-up. This provides great flexibility by allowing us to create an array of traps which can be moved in a smooth and fast way. To optimise the performance we investigated the effect of incidence angle on the SLM with respect to phase and intensity response. Although it is possible to use the SLM at an incidence of 45 degrees, smaller angles give a more constant response with a full $2\\pi$ phase shift. We calibrate the traps using an active oscillatory technique and a passive probability distribution technique.

Hanes, Richard D L; Egelhaaf, Stefan U

2009-01-01

45

Mechanical properties of a giant liposome studied using optical tweezers  

NASA Astrophysics Data System (ADS)

The mechanical properties of a micrometer-sized giant liposome are studied by deforming it from the inside using dual-beam optical tweezers. As the liposome is extended, its shape changes from a sphere to a lemon shape, and finally, a tubular part is generated. The surface tension ? and the bending rigidity ? of the lipid membrane are obtained from the measured force-extension curve. In a one-phase liposome, it was found that ? increases as the charged component increases but ? remains approximately constant. In a two-phase liposome, the characteristic deformation and the force-extension curve differ from those observed for the one-phase liposome.

Shitamichi, Yoko; Ichikawa, Masatoshi; Kimura, Yasuyuki

2009-09-01

46

A tunable line optical tweezers instrument with nanometer spatial resolution.  

PubMed

We describe a simple scanning-line optical tweezers instrument for measuring pair interactions between micrometer-sized colloidal particles. Our instrument combines a resonant scanning mirror and an acousto-optic modulator. The resonant scanning mirror creates a time-averaged line trap whose effective one-dimensional intensity profile, and corresponding trapping potential energy landscape can be programmed using the acousto-optic modulator. We demonstrate control over the confining potential by designing and measuring a family of one-dimensional harmonic traps. By adjusting the spring constant, we balance scattering-induced repulsive forces between a pair of trapped particles, creating a flat potential near contact that facilitates interaction measurements. We also develop a simple method for extracting the out-of-plane motion of trapped particles from their relative brightness, allowing us to resolve their relative separation to roughly 1 nm. PMID:24784615

Rogers, W Benjamin; Crocker, John C

2014-04-01

47

Peculiarities of RBC aggregation studied by double trap optical tweezers  

NASA Astrophysics Data System (ADS)

Aggregation peculiarities of red blood cells (RBCs) in autologous plasma are studied using double trap optical tweezers technique. The positions of RBCs are controlled with submicrometer accuracy by two optical traps formed by strongly focused laser beams (?=1064 nm). Quantitative measurements of interaction forces between RBCs in pair aggregates are performed. Depending on the RBCs aggregation force, four different end-points of disaggregation induced by optical trap movement are revealed. Analysis of experimental force dependence on the distance between two RBCs during disaggregation is in a good agreement with the model of ring-shaped interaction surfaces of RBCs in pair aggregate. Aggregation velocities measured are shown to be strongly different for healthy and pathologic (System Lupus Erythematosis - SLE) blood samples.

Khokhlova, Maria D.; Lyubin, Evgeny V.; Zhdanov, Alexander G.; Rykova, Sofia Yu.; Krasnova, Tatyana N.; Sokolova, Irina A.; Fedyanin, Andrey A.

2010-04-01

48

Optical tweezers assisted quantitative phase imaging led to thickness mapping of red blood cells  

NASA Astrophysics Data System (ADS)

Quantitative phase microscopy (QPM) allows dynamic mapping of optical path length of microscopic samples with high temporal and axial resolution. However, decoupling of the geometric thickness from the refractive index in phase measurements is challenging. Here, we report use of optical tweezers combined with QPM for decoupling geometric thickness from the refractive index. This is demonstrated by orienting the microscopic sample (red blood cell) by optical tweezers and imaging the phase at various orientations. Since optical tweezers can orient wide variety of micro and nanoscopic objects, this integrated method can be employed to accurately determine their physical properties.

Cardenas, Nelson; Mohanty, Samarendra K.

2013-07-01

49

Development of optical-based array devices using imaging fiber bundles: Optical tweezer arrays, nanoscale arrays, and microelectrode arrays  

Microsoft Academic Search

The work in this dissertation describes the development of imaging fiber-based array devices, specifically the fabrication and application of an optical tweezer array, a fiber-based nanoarray, and a nanotip array. With regards for the fabrication of an optical tweezer array, this thesis describes how fiber bundles have been used as a method to create multiple beams, which are used as

Jenny M. Tam

2005-01-01

50

Probing Micromechanical Properties of Biological Cells by Oscillatory Optical Tweezers  

NASA Astrophysics Data System (ADS)

We used oscillatory optical tweezers to probe the micromechanical properties of cultured alveolar epithelial cells in vitro. The frequency-dependent viscoelasticity of these cells was measured by optical trapping and forced oscillation of either a submicron endogenous intracellular organelle (intra-cellular) or a 1.5?m silica bead attached to the cytoskeleton through trans-membrane integrin receptors (extra-cellular). Both the storage modulus and the magnitude of the complex shear modulus followed weak power-law dependence with frequency. These data are comparable to data obtained by other measurement techniques. The exponents of power-law dependence of the data from the intra- and extra- cellular measurements are similar, whereas, the differences in the magnitudes of the moluli from the two measurements are statistically significant.

Zaorski, Angela; Wei, Ming-Tzo; Yalcin, Huseyin C.; Wang, Jing; Ghadiali, Samir N.; Chiou, Arthur; Ou-Yang, H. Daniel

2008-03-01

51

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

52

Use of optical tweezers to probe epithelial mechanosensation  

NASA Astrophysics Data System (ADS)

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.

Resnick, Andrew

2010-01-01

53

Combined holographic-mechanical optical tweezers: Construction, optimization, and calibration  

SciTech Connect

A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 deg., smaller angles give a full 2{pi} phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.

Hanes, Richard D. L.; Jenkins, Matthew C.; Egelhaaf, Stefan U. [Condensed Matter Physics Laboratory, Heinrich-Heine University, 40225 Duesseldorf (Germany)

2009-08-15

54

Combined holographic-mechanical optical tweezers: Construction, optimisation and calibration  

E-print Network

A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers set-up. This provides great flexibility as the SLM creates an array of traps which can be moved smoothly and quickly with the GMM. To optimise performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 degrees, smaller angles give a full 2pi phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method.

Richard D. L. Hanes; Matthew C. Jenkins; Stefan U. Egelhaaf

2009-07-21

55

Combined holographic-mechanical optical tweezers: construction, optimization, and calibration.  

PubMed

A spatial light modulator (SLM) and a pair of galvanometer-mounted mirrors (GMM) were combined into an optical tweezers setup. This provides great flexibility as the SLM creates an array of traps, which can be moved smoothly and quickly with the GMM. To optimize performance, the effect of the incidence angle on the SLM with respect to phase and intensity response was investigated. Although it is common to use the SLM at an incidence angle of 45 degrees, smaller angles give a full 2pi phase shift and an output intensity which is less dependent on the magnitude of the phase shift. The traps were calibrated using an active oscillatory technique and a passive probability distribution method. PMID:19725658

Hanes, Richard D L; Jenkins, Matthew C; Egelhaaf, Stefan U

2009-08-01

56

Precise characterization of micro rotors in optical tweezers  

E-print Network

We present an optical tweezer based study of rotation of microscopic objects with shape asymmetry. Thermal fluctuations and rotations are simultaneously monitored through laser back scattering. The rotation results in a modulation in intensity of the back scattered light incident on a quadrant photo detector. This results in the manifestation of peaks at a fundamental rotational frequency and at integer harmonics, superimposed on a modified Lorentzian in the power spectrum. The multiple peaks indicate that the rotations are periodic but with varying angular velocity. We demonstrate the use of video microscopy for characterization of low reflectivity rotors, such as biological cells. The methods also enable a measurement of the average torque on the rotor, and in principle, can reveal information about its principal moments of inertia, and the role of hydrodynamics at micron levels

Yogesha; Sarbari Bhattacharya; Sharath Ananthamurthy

2011-02-15

57

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

58

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

59

Applications of optical tweezers and an integrated force measurement module for biomedical research  

Microsoft Academic Search

Optical tweezers are useful for manipulating biological samples and measuring biological forces. In the present study, we have integrated a forward scatter analysis (FORSA) module in the single-beam gradient force optical tweezers. The entire set-up was then incorporated onto an inverted microscope. In the FORSA module an Helium-Neon probing laser was spotted (at a slightly out-of-focus way) onto the object

Jin-Wu Tsai; Bing-Yao Liao; Chun-Cheng Huang; Wen-Liang Hwang; Da-Wei Wang; Arthur E. Chiou; Chi-Hung Lin

2000-01-01

60

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

61

Force measurements with optical tweezers inside living cells  

NASA Astrophysics Data System (ADS)

The force exerted by optical tweezers can be measured by tracking the momentum changes of the trapping beam, a method which is more general and powerful than traditional calibration techniques as it is based on first principles, but which has not been brought to its full potential yet, probably due to practical difficulties when combined with high-NA optical traps, such as the necessity to capture a large fraction of the scattered light. We show that it is possible to measure forces on arbitrary biological objects inside cells without an in situ calibration, using this approach. The instrument can be calibrated by measuring three scaling parameters that are exclusively determined by the design of the system, thus obtaining a conversion factor from volts to piconewtons that is theoretically independent of the physical properties of the sample and its environment. We prove that this factor keeps valid inside cells as it shows good agreement with other calibration methods developed in recent years for viscoelastic media. Finally, we apply the method to measuring the stall forces of kinesin and dynein in living A549 cells.

Mas, Josep; Farré, Arnau; Sancho-Parramon, Jordi; Martín-Badosa, Estela; Montes-Usategui, Mario

2014-09-01

62

Optical tweezers for free-solution label-free single bio-molecule studies  

NASA Astrophysics Data System (ADS)

Nanoaperture based trapping has developed as a significant tool among the various optical tweezer systems for trapping of very small particles down to the single nanometer range. The double nanohole aperture based trap provides a method for efficient, highly-sensitive, label-free, low-cost, free-solution single molecule trapping and detection. We use the double nanohole tweezer to understand biomolecular phenomena like protein unfolding, binding, structural conformation of DNA, protein-DNA interactions, and protein small molecule interactions.

Kotnala, Abhay; Al-Balushi, Ahmed A.; Gordon, Reuven

2014-09-01

63

Fiber optical tweezers for microscale and nanoscale particle manipulation and force sensing  

NASA Astrophysics Data System (ADS)

Optical tweezers have been an important tool in biology and physics for studying single molecules and colloidal systems. Most of current optical tweezers are built with microscope objectives, which are: i) expensive, ii) bulky and hard to integrate, iii) sensitive to environmental fluctuations, iv) limited in terms of working distances from the substrate, and v) rigid with the requirements on the substrate (transparent substrate made with glass and with a fixed thickness). These limitations of objective-based optical tweezers prevent them from being miniaturized. Fiber optical tweezers can provide a solution for cost reduction and miniaturization, and these optical tweezers can be potentially used in microfluidic systems. However, the existing fiber optical tweezers have the following limitations: i) low trapping efficiency due to weakly focused beams, ii) lack of the ability to control the positions of multiple particles simultaneously, and iii) limited functionalities. The overall objective of this dissertation work is to further the fundamental understanding of fiber optical tweezers through experimental study and modeling, and to develop novel fiber optical tweezers systems to enhance the capability and functionalities of fiber optical tweezers as microscale and nanoscale manipulators/sensors. The contributions of this dissertation work are summarized as follows. i) An enhanced understanding of the inclined dual-fiber optical tweezers (DFOTs) system has been achieved. Stable three dimensional (3D) optical trapping of a single micron-sized particle has been experimentally demonstrated. This is the first time that the trapping efficiency has been calibrated and the stiffness of the trap has been obtained in the experiments, which has been carried out by using two methods: the drag force method and power spectrum analysis. Such calibration enables the system to be used as a picoNewton-level force sensor in addition to a particle manipulator. The influence of system parameters on the trapping performance has been carefully investigated through both experimental and numerical studies. ii) Multiple traps have been created and carefully studied with the inclined DFOTs for the first time. Three traps, one 3D trap and two 2D traps, have been experimentally created at different vertical levels with adjustable separations and positions. iii) Multiple functionalities have been achieved and studied for the first time with the inclined DFOTs. Particle separation, grouping, stacking, rod alignment, rod rotation, and optical binding have been experimentally demonstrated. The multiple functionalities allow the inclined DFOTs to find applications in the study of interaction forces in colloidal systems as well as parallel particle manipulation in drug delivery systems. iv) Far-field superfocusing effect has been investigated and successfully demonstrated with a fiber-based surface plasmonic (SP) lens for the first time. A planar SP lens with a set of concentric nanoscale rings on a fiber endface has been developed. For the first time, a focus size that is comparable to the smallest achievable focus size of high NA objective lenses has been achieved with the fiber-based SP lens. The fiber-based SP lens can bridge the nanoscale particles/systems and the macroscale power sources/detectors, which has been a long standing challenge for nanophotonics. In addition to optical trapping, the fiber-based SP lens will impact many applications including high-resolution lithography, high-resolution fluorescence detection, and sub-wavelength imaging. v) Trapping ability enhanced with the fiber-based SP lens has been successfully demonstrated. With the help of the fiber-based SP lens, the trapping efficiency of fiber optical tweezers has been significantly enhanced, which is comparable with that of objective-based optical tweezers. A submicron-sized bacterium has been successfully trapped in three dimensions for the first time with optical tweezers based on single fibers.

Liu, Yuxiang

2011-12-01

64

Red blood cell micromanipulation with elliptical laser beam profile optical tweezers in different osmolarity conditions  

Microsoft Academic Search

In this work optical tweezers with elliptical beam profiles have been developed in order to examine the effect of optical force on fresh red blood cells (RBC) in isotonic, hypertonic and hypotonic buffer solutions. Considering that the optical force depends essentially on the cell surface and the cytoplasmic refractive index, it is obvious that biochemical modifications associated with different states

E. Spyratou; M. Makropoulou; A. A. Serafetinides

2011-01-01

65

Membrane tether formation from outer hair cells with optical tweezers.  

PubMed Central

Optical tweezers were used to characterize the mechanical properties of the outer hair cell (OHC) plasma membrane by pulling tethers with 4.5-microm polystyrene beads. Tether formation force and tether force were measured in static and dynamic conditions. A greater force was required for tether formations from OHC lateral wall (499 +/- 152 pN) than from OHC basal end (142 +/- 49 pN). The difference in the force required to pull tethers is consistent with an extensive cytoskeletal framework associated with the lateral wall known as the cortical lattice. The apparent plasma membrane stiffness, estimated under the static conditions by measuring tether force at different tether length, was 3.71 pN/microm for OHC lateral wall and 4.57 pN/microm for OHC basal end. The effective membrane viscosity was measured by pulling tethers at different rates while continuously recording the tether force, and estimated in the range of 2.39 to 5.25 pN x s/microm. The viscous force most likely results from the viscous interactions between plasma membrane lipids and the OHC cortical lattice and/or integral membrane proteins. The information these studies provide on the mechanical properties of the OHC lateral wall is important for understanding the mechanism of OHC electromotility. PMID:11867454

Li, Zhiwei; Anvari, Bahman; Takashima, Masayoshi; Brecht, Peter; Torres, Jorge H; Brownell, William E

2002-01-01

66

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

67

Cleaved fiber optic double nanohole optical tweezers for trapping nanoparticles.  

PubMed

We demonstrate the trapping of single 20 and 40 nm polystyrene spheres at the cleaved end of a fiber optic with a double nanohole aperture in gold and without any microscope optics. An optical transmission increase of 15% indicates a trapping event for the 40 nm particle, and the jump is 2% for the 20 nm particle. This modular technique can be used to replace those used with current optical trapping setups that require complicated free space optics and frequent calibration, with one that is modular and requires no free space optics. This simple arrangement with the potential for fiber translation is of interest for future biosensor and optical nano-pipette devices. PMID:25490482

Gelfand, Ryan M; Wheaton, Skylar; Gordon, Reuven

2014-11-15

68

In situ laser power measurement at the focus of microscope objectives used in optical tweezers  

Microsoft Academic Search

We discuss measurements of the laser power at the focus of high numerical aperture objectives used in optical microscopy and optical tweezers. For a given power, the focused incident laser beam heats a small mercury bead that jumps when it reaches the boiling temperature of water, the medium used in the experiments. From the size of the mercury beads, the

N. B. Viana; M. S. Rocha; O. N. Mesquita

2005-01-01

69

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

70

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

71

Microspectroscopy and scanning microscopy in an optical tweezers system  

NASA Astrophysics Data System (ADS)

In this work we developed a setup consisting of an Optical Tweezers equipped with linear and non-linear micro-spectroscopy system to add the capabilities of manipulation and analysing captured objects. Our setup includes a homemade confocal spectrometer using a monochromator equipped with a liquid nitrogen cooled CCD. The spectroscopic laser system included a cw and a femtosecond Ti:sapphire lasers that allowed us to perform Raman, hyper-Raman, hyper-Rayleigh and two photon Excited (TPE) luminescence in particles trapped with an Nd:YAG cw laser. We obtained Raman spectra of a single trapped polystyrene microsphere and a single trapped red blood cell to evaluate the performance of our system. We also observed hyper-Rayleigh and hyper-Raman peaks for SrTiO3 with 60s integration time only. This was possible because the repetition rate of the femtosecond Ti:sapphire lasers, on the order of 80 MHz, are much higher than the few kHz typical picosecond laser repetition rate used before in hyper- Raman experiment, which required acquisition times of order of few hours. We used this system to perform scanning microscopy and to acquire TPE luminescence spectra of captured single stained microsphere and cells conjugated with quantum dots of CdS and CdTe and hyper-Rayleigh spectra of a noncaptured ZnSe microparticle. The results obtained show the potential presented by this system and fluorescent labels to perform spectroscopy in a living trapped microorganism in any neighbourhood and dynamically observe the chemical reactions changes in real time.

Fontes, Adriana; Neves, Antonio A. R.; Moreira, Wendel L.; de Thomaz, Andre A.; Barbosa, Luis C.; de Farias, Patricia M. A.; Santos, Beate S.; Ferreira, Ricardo C.; de Paula, Ana M.; Ajito, Katsuhiro; Cesar, Carlos L.

2005-08-01

72

Mechanical and electrical properties of red blood cells using optical tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers are a very sensitive tool, based on photon momentum transfer, for individual, cell by cell, manipulation and measurements, which can be applied to obtain important properties of erythrocytes for clinical and research purposes. Mechanical and electrical properties of erythrocytes are critical parameters for stored cells in transfusion centers, immunohematological tests performed in transfusional routines and in blood diseases. In this work, we showed methods, based on optical tweezers, to study red blood cells and applied them to measure apparent overall elasticity, apparent membrane viscosity, zeta potential, thickness of the double layer of electrical charges and adhesion in red blood cells.

Fontes, A.; Barjas Castro, M. L.; Brandão, M. M.; Fernandes, H. P.; Thomaz, A. A.; Huruta, R. R.; Pozzo, L. Y.; Barbosa, L. C.; Costa, F. F.; Saad, S. T. O.; Cesar, C. L.

2011-04-01

73

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; Bálint, Štefan; Cossins, Benjamin; Guallar, Victor; Petrov, Dmitri

2009-01-01

74

Red blood cell micromanipulation with elliptical laser beam profile optical tweezers in different osmolarity conditions  

NASA Astrophysics Data System (ADS)

In this work optical tweezers with elliptical beam profiles have been developed in order to examine the effect of optical force on fresh red blood cells (RBC) in isotonic, hypertonic and hypotonic buffer solutions. Considering that the optical force depends essentially on the cell surface and the cytoplasmic refractive index, it is obvious that biochemical modifications associated with different states of the cell will influence its behaviour in the optical trap. Line optical tweezers were used to manipulate simultaneously more than one red blood cell. After we have been manipulated a RBC with an elliptical laser beam profile in an isotonic or hypertonic buffer, we noticed that it rotates by itself when gets trapped by optical tweezers and undergoes folding. Further shape deformations can be observed attributed to the competition between alignment and rotational torque which are transferred by laser light to the cell. In hypotonic buffer RBCs become spherical and do not rotate or fold since the resultant force due to rays emerging from diametrically opposite points of the cell leads to zero torque. Manipulation of fresh red blood cells in isotonic solution by line optical tweezers leads to folding and elongation of trapped RBCs. Membrane elasticity properties such as bending modulus can be estimated by measuring RBC's folding time in function with laser power.

Spyratou, E.; Makropoulou, M.; Serafetinides, A. A.

2011-07-01

75

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

76

Aerosol droplet optical trap loading using surface acoustic wave nebulization.  

PubMed

We demonstrate the use of surface acoustic wave nebulization (SAWN) to load optical traps. We show that the droplets sizes produced can be tuned by altering the RF frequency applied to the devices, which leads to more control over the sizes of trapped particles. Typically the size distribution of the liquid aerosols delivered using SAWN is smaller than via a standard commercial nebulization device. The ability to trap a range of liquids or small solid particles, not readily accessible using other ultrasonic devices, is also demonstrated both in optical tweezers and dual beam fiber traps. PMID:24514593

Anand, S; Nylk, J; Neale, S L; Dodds, C; Grant, S; Ismail, M H; Reboud, J; Cooper, J M; McGloin, D

2013-12-16

77

Applications of optical tweezers and an integrated force measurement module for biomedical research  

NASA Astrophysics Data System (ADS)

Optical tweezers are useful for manipulating biological samples and measuring biological forces. In the present study, we have integrated a forward scatter analysis (FORSA) module in the single-beam gradient force optical tweezers. The entire set-up was then incorporated onto an inverted microscope. In the FORSA module an Helium-Neon probing laser was spotted (at a slightly out-of-focus way) onto the object being trapped by the infrared laser-based tweezers and generated a diffraction pattern. Imagines of the diffraction pattern were captured by a charge- coupled device (CCD), and digitized and processed by a computer. Wed demonstrated that tracking the amplified diffraction pattern war much more precise to determine the movement of the object within the trap than analyzing the minute motion of the object itself. Displacement of the object could then be translated into the force being applied by the tweezers. Also, using an algorithm developed in the lab, we were able to follow the movement of the scattering pattern at a temporal resolution close to video rate. We have used this system to investigate the binding force associate with cell-cell interactions and modular interactions. In these studies. A cell was carefully positioned to make contact with another cell or a microparticle coated with proteins of interest by optical tweezers in a well-controlled manner. During these events, we noted a progressive increase of cell adhesion at the immediate early period (i.e., a few minutes after initial contact) of cell-cell interactions. Also, binding of a disintegrin, rhodostomin, and its mutant to the counterpart integrin on the cell surface could be assessed with great convenience and accuracy. Our results demonstrated that addition of the forward scatter analysis module to convention optical tweezers provides an effective and convenient way for monitoring biological activities in situ and measuring changes of biological forces with precision.

Tsai, Jin-Wu; Liao, Bing-Yao; Huang, Chun-Cheng; Hwang, Wen-Liang; Wang, Da-Wei; Chiou, Arthur E. T.; Lin, Chi-Hung

2000-07-01

78

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

79

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

80

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

PubMed

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; Fällman, Erik; Tuck, Simon; Axner, Ove

2002-04-01

81

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; Fällman, Erik; Tuck, Simon; Axner, Ove

2002-01-01

82

Northeastern University, PHYS5318 Spring 2010, page 1 Experiment 6: Optical Tweezers  

E-print Network

. The forces that such an instrument is capable of measuring are of the order of 0.01 to 300 piconewtons (pN). While this technique has been used for over 20 years to manipulate and study the properties of micron to the study of biological systems. There are two major types of optical tweezers instruments. In the Williams

Williams, Mark C.

83

RBCs under optical tweezers as cellular motors and rockers: microfluidic applications  

NASA Astrophysics Data System (ADS)

Recently, we have reported self-rotation of normal red blood cells (RBC), suspended in hypertonic buffer, and trapped in unpolarized laser tweezers. Here, we report use of such an optically driven RBC-motor for microfluidic applications such as pumping/centrifugation of fluids. Since the speed of rotation of the RBC-motor was found to vary with the power of the trapping beam, the flow rate could be controlled by controlling the laser power. In polarized optical tweezers, preferential alignment of trapped RBC was observed. The aligned RBC (simulating a disk) in isotonic buffer, could be rotated in a controlled manner for use as a microfluidic valve by rotation of the plane of polarization of the trapping beam. The thickness of the discotic RBC could be changed by changing the osmolarity of the solution and thus the alignment torque on the RBC due to the polarization of the trapping beam could be varied. Further, in polarized tweezers, the RBCs in hypertonic buffer showed rocking motion while being in rotation. Here, the RBC rotated over a finite angular range, stopped for some time at a particular angle, and then started rotating till it was back to the aligned position and this cycle was found repetitive. This can be attributed to the fact that though the RBCs were found to experience an alignment torque to align with plane of polarization of the tweezers due to its form birefringence, it was smaller in magnitude as compared to the rotational torque due to its structural asymmetry in hypertonic solution. Changes in the laser power caused a transition from/to rocking to/from motor behavior of the RBC in a linearly polarized tweezers. By changing the direction of polarization caused by rotation of an external half wave plate, the stopping angle of rocking could be changed. Further, RBCs suspended in intermediate hypertonic buffer and trapped with polarized tweezers showed fluttering about the vertical plane.

Mohanty, Samarendra; Mohanty, Khyati; Gupta, Pradeep

2006-08-01

84

Refractive multiple optical tweezers for parallel biochemical analysis in micro-fluidics  

NASA Astrophysics Data System (ADS)

We present a multiple laser tweezers system based on refractive optics. The system produces an array of 100 optical traps thanks to a refractive microlens array, whose focal plane is imaged into the focal plane of a high-NA microscope objective. This refractive multi-tweezers system is combined to micro-fluidics, aiming at performing simultaneous biochemical reactions on ensembles of free floating objects. Micro-fluidics allows both transporting the particles to the trapping area, and conveying biochemical reagents to the trapped particles. Parallel trapping in micro-fluidics is achieved with polystyrene beads as well as with native vesicles produced from mammalian cells. The traps can hold objects against fluid flows exceeding 100 micrometers per second. Parallel fluorescence excitation and detection on the ensemble of trapped particles is also demonstrated. Additionally, the system is capable of selectively and individually releasing particles from the tweezers array using a complementary steerable laser beam. Strategies for high-yield particle capture and individual particle release in a micro-fluidic environment are discussed. A comparison with diffractive optical tweezers enhances the pros and cons of refractive systems.

Merenda, Fabrice; Rohner, Johann; Pascoal, Pedro; Fournier, Jean-Marc; Vogel, Horst; Salathé, René-Paul

2007-02-01

85

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

86

An Improved Optical Tweezers Assay for Measuring the Force Generation of Single Kinesin Molecules  

PubMed Central

Numerous microtubule-associated molecular motors, including several kinesins and cytoplasmic dynein, produce opposing forces that regulate spindle and chromosome positioning during mitosis. The motility and force generation of these motors are therefore critical to normal cell division, and dysfunction of these processes may contribute to human disease. Optical tweezers provide a powerful method for studying the nanometer motility and piconewton force generation of single motor proteins in vitro. Using kinesin-1 as a prototype, we present a set of step-by-step, optimized protocols for expressing a kinesin construct (K560-GFP) in Escherichia coli, purifying it, and studying its force generation in an optical tweezers microscope. We also provide detailed instructions on proper alignment and calibration of an optical trapping microscope. These methods provide a foundation for a variety of similar experiments. PMID:24633799

Nicholas, Matthew P.; Rao, Lu; Gennerich, Arne

2014-01-01

87

Improved direct binary search-based algorithm for generating holograms for the application of holographic optical tweezers  

NASA Astrophysics Data System (ADS)

This paper presents an improved direct binary search (DBS)-based algorithm for generating holograms to holographic optical tweezers. The simulations show that the improved algorithm greatly enhances computation speed while maintaining high hologram efficiency and high-intensity homogeneous target spots. The improved algorithm was applied to generate holographic optical tweezers in several experiments. The experiments demonstrate that real-time trap and manipulation can be realized with the improved algorithm if the number of trapped microparticles is small.

Zhao, Xudong; Li, Jing; Tao, Tao; Long, Qian; Wu, Xiaoping

2012-01-01

88

New biodiagnostics based on optical tweezers: typing red blood cells, and identification of drug resistant bacteria  

NASA Astrophysics Data System (ADS)

Measurements of optical tweezers forces on biological micro-objects can be used to develop innovative biodiagnostics methods. In the first part of this report, we present a new sensitive method to determine A, B, D types of red blood cells. Target antibodies are coated on glass surfaces. Optical forces needed to pull away RBC from the glass surface increase when RBC antigens interact with their corresponding antibodies. In this work, measurements of stripping optical forces are used to distinguish the major RBC types: group O Rh(+), group A Rh(+) and group B Rh(+). The sensitivity of the method is found to be at least 16-folds higher than the conventional agglutination method. In the second part of this report, we present an original way to measure in real time the wall thickness of bacteria that is one of the most important diagnostic parameters of bacteria drug resistance in hospital diagnostics. The optical tweezers force on a shell bacterium is proportional to its wall thickness. Experimentally, we determine the optical tweezers force applied on each bacteria family by measuring their escape velocity. Then, the wall thickness of shell bacteria can be obtained after calibrating with known bacteria parameters. The method has been successfully applied to indentify, from blind tests, Methicillinresistant Staphylococcus aureus (MRSA), including VSSA (NCTC 10442), VISA (Mu 50), and heto-VISA (Mu 3)

Chen, Jia-Wen; Lin, Chuen-Fu; Wang, Shyang-Guang; Lee, Yi-Chieh; Chiang, Chung-Han; Huang, Min-Hui; Lee, Yi-Hsiung; Vitrant, Guy; Pan, Ming-Jeng; Lee, Horng-Mo; Liu, Yi-Jui; Baldeck, Patrice L.; Lin, Chih-Lang

2013-09-01

89

Microrheology of non mulberry silk varieties by optical tweezer and video microscopy based techniques  

E-print Network

We have carried out a comparative study of the microrheological properties of silk fibroin solutions formed from a variety of silks indigenous to the Indian subcontinent. We present the measured viscoelastic moduli of Tasar silk fibroin solution using both a single and dual optical tweezer at 0.16% and 0.25% (w/v). The bandwidth of the measurements carried out using optical tweezers is extended down to the lower frequency regime by a video microscopy measurement. Further, we have measured the viscoelastic moduli of Eri and Muga varieties of silk fibroin solutions at a higher concentration (1.00% w/v) limiting the tool of measurement to video microscopy, as the reduced optical transparencies of these solutions at higher concentration preclude an optical tweezer based investigation. The choice of a higher concentration of fibroin solution of the latter silk varieties is so as to enable a comparison of the shear moduli obtained from optical methods with their corresponding fibre stiffness obtained from wide angle X-ray scattering data. We report a correlation between the microstructure and microrheological parameters of these silk varieties for the concentration of fibroin solutions studied.

Yogesha; Raghu A; Siddaraju G N; G Subramanya; Somashekar R; Sharath Ananthamurthy

2011-02-15

90

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

91

Dual-trap optical tweezers with real-time force clamp control  

NASA Astrophysics Data System (ADS)

Single molecule force clamp experiments are widely used to investigate how enzymes, molecular motors, and other molecular mechanisms work. We developed a dual-trap optical tweezers instrument with real-time (200 kHz update rate) force clamp control that can exert 0-100 pN forces on trapped beads. A model for force clamp experiments in the dumbbell-geometry is presented. We observe good agreement between predicted and observed power spectra of bead position and force fluctuations. The model can be used to predict and optimize the dynamics of real-time force clamp optical tweezers instruments. The results from a proof-of-principle experiment in which lambda exonuclease converts a double-stranded DNA tether, held at constant tension, into its single-stranded form, show that the developed instrument is suitable for experiments in single molecule biology.

Wallin, Anders E.; Ojala, Heikki; Ziedaite, Gabija; Hæggström, Edward

2011-08-01

92

Acting force comparison of microbeads and hemocytes in microchannel using optical tweezers system  

Microsoft Academic Search

An inverted-embedded optical tweezers system combining a micropump was assembled. The escaping velocities and acting forces of particles and hemocytes could be measured. After experiments and calculations, the escaping velocity of a 6 mum bead was 0.20 mum\\/s and the trapping force was 0.012 pN when the power was 5 mW. The escaping velocity of a granulocyte was 0.80 mum\\/s

Yung-Chiang Chung; Yen-Wen Hu; Tsong-Long Hwang; Po-Wen Chen; Fong-Jian Sie

2009-01-01

93

Chromosomal analysis and identification based on optical tweezers and Raman spectroscopy  

NASA Astrophysics Data System (ADS)

The ability to identify specific chromosomes with certainty has been established by the development of several cytogenetic techniques based on staining. Here, we report the use of a new optical technique, laser tweezers and Raman spectroscopy (LTRS), to capture and manipulate chromosomes in order to obtain their spectral patterns for molecular analysis without the need for staining. The purpose of this study was to obtain Raman spectroscopy patterns for chromosomes number 1, 2, and 3 and to test if the Raman spectroscopy pattern could be used to distinguish these three chromosomes. In our experiment, optical tweezers were used to capture the individual chromosomes and the Raman spectral patterns were collected for the trapped chromosomes. Then, the captured chromosome was manipulated with the optical tweezers and moved to another chamber through a micro - channel, in which the chromosomes were G banded for positive identification as chromosome number 1, 2, or 3. Generalized discriminate analysis (GDA) was used to compare the Raman signatures. This analysis revealed that chromosomes 1, 2, and 3 could be distinguished and identified based on their Raman spectra. Development of this approach will lead to more rapid automatic methods for chromosome analysis and identification without the use of prior staining. Moreover, the Raman spectral patterns may lend themselves to more detailed analysis of chromosomal structure than is currently available with standard staining protocols. Such analysis may some day be useful for rapid, automated screening and diagnosis for certain cancers.

Ojeda, Jenifer F.; Xie, Changan; Li, Yong-Qing; Bertrand, Fred E.; Wiley, John; McConnell, Thomas J.

2006-06-01

94

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

PubMed

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

95

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

96

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

NASA Astrophysics Data System (ADS)

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.

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

2014-12-01

97

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

98

Optical macro-tweezers: trapping of highly motile micro-organisms  

NASA Astrophysics Data System (ADS)

Optical micromanipulation stands for contact-free handling of microscopic particles by light. Optical forces can manipulate non-absorbing objects in a large range of sizes, e.g., from biological cells down to cold atoms. Recently much progress has been made going from the micro- down to the nanoscale. Less attention has been paid to going the other way, trapping increasingly large particles. Optical tweezers typically employ a single laser beam tightly focused by a microscope objective of high numerical aperture to stably trap a particle in three dimensions (3D). As the particle size increases, stable 3D trapping in a single-beam trap requires scaling up the optical power, which eventually induces adverse biological effects. Moreover, the restricted field of view of standard optical tweezers, dictated by the use of high NA objectives, is particularly unfavorable for catching actively moving specimens. Both problems can be overcome by traps with counter-propagating beams. Our 'macro-tweezers' are especially designed to trap highly motile organisms, as they enable three-dimensional all-optical trapping and guiding in a volume of 2 × 1 × 2 mm3. Here we report for the first time the optical trapping of large actively swimming organisms, such as for instance Euglena protists and dinoflagellates of up to 70 µm length. Adverse bio-effects are kept low since trapping occurs outside high intensity regions, e.g., focal spots. We expect our approach to open various possibilities in the contact-free handling of 50-100 µm sized objects that could hitherto not be envisaged, for instance all-optical holding of individual micro-organisms for taxonomic identification, selective collecting or tagging.

Thalhammer, G.; Steiger, R.; Bernet, S.; Ritsch-Marte, M.

2011-04-01

99

Optical Trapping of Thermo-responsive Microgel Particles by Holographic Optical Tweezers  

NASA Astrophysics Data System (ADS)

Holographic Optical Tweezers (HOT) is a technique in which the phase of trapping laser is modulated for generating steerable, multiple optical traps in a sample chamber. An indigenously developed HOT set-up at Raja Ramanna Centre for Advanced Technology, Indore has been used to trap thermo-responsive poly(N-isopropylacrylamide-co-acrylic acid) (pNIPAM-co-AAc) spherical particles of 1.6 ?m diameter suspended in aqueous medium. The videos of the trapped particles were digitally processed to track the particle positions as a function of time. From these measurements lateral trap stiffness for pNIPAM-co-AAc particles was determined as a function of trap power and temperature using Equipartition and Boltzmann Statistics methods. Both the methods gave similar results and the value for the trap stiffness at 25 °C with trapping laser power of 33 mW was estimated to be 0.14±0.01 ?N/m. Since the optical trap stiffness depends on particle size and refractive index which vary as a function of temperature the variation of the measured optical trap stiffness as a function of temperature could be used to determine the volume phase transition of the thermo-responsive microgel particles. The results should also be useful in investigating the interaction between pNIPAM-co-AAc particles trapped in different lattice configurations that can be generated using HOT.

Kannan, M. R. Rajesh; Tata, B. V. R.; Dasgupta, R.; Ahlawat, S.; Gupta, P. K.

2011-10-01

100

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

101

Optical manipulation of aerosols using surface acoustic wave nebulisation  

NASA Astrophysics Data System (ADS)

High density micron sized aerosols from liquid surfaces were generated using surface acoustic wave (SAW) nebulisation. The SAWs are made from a set of interdigitated electrodes (IDT) deposited on a lithium niobate (LiNbO3) substrate and are designed to operate around 10MHz. RF powers of ~235mW are used to achieve nebulisation. Power below this results in droplet motion across the substrate surface. The nebulisation process generated aerosols of a narrow size distribution with diameter ranging from 0.5-2 ?m. We consider ways in which these aerosols can be loaded into optical traps for further study. In particular we look at how SAW nebulisation can be used to load particles into a trap in a far more robust manner than a conventional nebuliser device. We demonstrate trapping of a range of particle types and sizes and analyse the size distribution of particles as a function of the applied frequency to the SAW device. We show that it is simpler to load, in particular, solid particles into optical traps using this technique compared to conventional nebulisation. We also consider the possibilities for loading nanoparticles into aerosol optical tweezers.

Anand, S.; Nylk, J.; Dodds, C.; Cooper, J. M.; Neale, S. N.; McGloin, D.

2011-10-01

102

Large-area manipulation of microdroplets by holographic optical tweezers based on a hybrid diffractive system.  

PubMed

We report on large-area manipulation of microdroplets by holographic optical tweezers based on a hybrid diffractive system, in which a static computer-generated hologram and a spatial light modulator (SLM) are used. The hybrid diffractive system is useful to manipulate microdroplets on distant areas with the same manner. Experimental results demonstrated that microdroplets were transported successfully in parallel with approximately equivalent velocities over the entire manipulation area. Fusion of microdroplets was also achieved at a position where the optical pattern generated by the SLM alone did not reach. PMID:22193024

Ogura, Yusuke; Kazayama, Yuki; Nishimura, Takahiro; Tanida, Jun

2011-12-01

103

New developments on the design and modeling of fiber optical tweezers  

NASA Astrophysics Data System (ADS)

The intensity profile of a focused beam of light can exert small drift forces on particles with a few microns and even smaller, which can be used to confine or manipulate them. Optical trapping has several applications, in particular it has been adopted as a powerful tool in biology, allowing, for instance to manipulate in vivo single cells. A wide variety of optical setups have been implemented to optically trap microscopic bodies, however, the single beam trap using a tightly focused Gaussian beam continues to be the most used. Recent developments introduced an alternative to bulk optical trapping systems based on lensed optical fibers. This work presents simulations showing new designs of fiber optic and 2D waveguide tweezers based on studies of the forces acting on dielectric particles immersed in media with a distinct refractive index, which take into account the refractive index and structure of the particles.

Rodrigues Ribeiro, R. S.; Jorge, P. A. S.; Guerreiro, A.

2013-11-01

104

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

105

Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes This article has been downloaded from IOPscience. Please scroll down to see the full text article.  

E-print Network

Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes This article has been.1088/0957-4484/21/24/245102 Optical-tweezer-induced microbubbles as scavengers of carbon nanotubes Hema Ramachandran1 , A K fragmentation of the bundles. Thus, microbubbles may be used for scavenging, transporting and dispersal

Sharma, Shobhona

106

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

107

The design and biological applications of dual-beam oscillating optical tweezer-based imaging cytorheometer  

NASA Astrophysics Data System (ADS)

Because of its non-invasive nature, optical tweezers have emerged as a popular tool for the studies of complex fluids and biological cells and tissues. The capabilities of optical tweezer-based experimental instruments continue to evolve for better and broader applications, through new apparatus designs and integrations with microscopic imaging techniques. In this paper, we present the design, calibration and applications of a powerful microrheometer that integrates a novel high temporal and spatial resolution dual-beam oscillating optical tweezer-based cytorheometer (DOOTC) with spinning disk confocal microscopy. The oscillating scheme detects the position of micron-size probe particles via a phase-sensitive lock-in amplifier to greatly enhance sensitivity. The dual-beam scheme ensures that the cytorheometer is insensitive to sample specimen background parameter variances, and thus enables the investigation of micromechanical properties of biological samples, which are intrinsically inhomogeneous. The cytorheometer system is demonstrated to be capable of measuring dynamic local mechanical moduli in the frequency range of 0.1-150 Hz at up to 2 data point per second and with nanometer spatial resolutions, while visualizing and monitoring structural properties in situ. We report the results of system applications in the studies of bovine skin gelatin gel, purified microtubule assemblies, and human alveolar epithelial cells. The time evolution of the storage moduli G' and the loss moduli G'' of the gel is recorded for undisturbed gel-forming process with high temporal resolution. The micromechanical modulus G* of polymerized microtubule network as a function of frequency are shown to be both inhomogeneous and anisotropic consistent with local structures revealed by confocal imaging. The mechanical properties of A549 human lung cells as a function of temperature will be reported showing significant decrease in cell stiffness at higher temperature.

Ou-Yang, H. D.; Wang, J.

2006-08-01

108

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

109

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

SciTech Connect

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; Wang Xiaolin; Sun Dong [Department of Mechanical and Biomedical Engineering, City University of Hong Kong (Hong Kong); Cheng Jinping; Han Cheng, Shuk [Department of Biology and Chemistry, City University of Hong Kong (Hong Kong); Kong, Chi-Wing [Stem Cell and Regenerative Medicine Consortium, and Departments of Medicine and Physiology, LKS Faculty of Medicine, University of Hong Kong (Hong Kong); Li, Ronald A. [Stem Cell and Regenerative Medicine Consortium, and Departments of Medicine and Physiology, LKS Faculty of Medicine, University of Hong Kong (Hong Kong); Center of Cardiovascular Research, Mount Sinai School of Medicine, New York, New York 10029 (United States)

2013-07-15

110

Quantitative characterization for dielectrophoretic behavior of biological cells using optical tweezers  

NASA Astrophysics Data System (ADS)

We report a method to precisely quantify dielectrophoretic (DEP) forces and cutoff frequencies (fc) of viable and nonviable yeast cells. The method consists of a two-step process in which generated DEP forces act upon a cell through a micro-electrode device, followed by direct measurement of DEP forces using optical tweezers. DEP behaviors of viable and nonviable yeast cells are monitored as a function of AC frequency. We believe that the proposed method can be used as a powerful platform for cell-based assays to characterize the DEP behavior of various cell types including cancer and normal cells.

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

2014-02-01

111

On chip optical tweezers for large scale trapping of microparticles  

NASA Astrophysics Data System (ADS)

We present a cost-effective and power efficient approach for on-chip large-scale trapping and sorting of particles in microchamber. Based on the Talbot self-imaging effect in Fresnel region, we make use of a 2D chessboard structure to create a 3D interconnected optical lattice near the emergent surface of the element without adopting an external optical projection configuration. The chessboard structure is designed to be a binary phase grating and fabricated with electron-beam lithography. As no focusing lens projections system is employed, the presented system enables a larger working area without sacrificing the advantage of high resolution. Theoretically the created optical lattice allows exponential size selectivity for particles sorting. We have experimentally demonstrated simultaneous trapping of hundreds of microparticles in a large regular array. Furthermore, in microfluidic chamber we proved the all-optical continuous separation of microparticles with different sizes.

Sun, Yuyang; Yuan, Xiaocong; Ong, Lin Seng; Bu, Jing

2007-02-01

112

On chip optical tweezers for large scale trapping of microparticles  

Microsoft Academic Search

We present a cost-effective and power efficient approach for on-chip large-scale trapping and sorting of particles in microchamber. Based on the Talbot self-imaging effect in Fresnel region, we make use of a 2D chessboard structure to create a 3D interconnected optical lattice near the emergent surface of the element without adopting an external optical projection configuration. The chessboard structure is

Yuyang Sun; Xiaocong Yuan; Lin Seng Ong; Jing Bu

2007-01-01

113

Magnetic tweezers to study DNA motors  

E-print Network

microscopy (AFM) · Optical tweezers · Magnetic tweezers Single molecules force microscopy techniques #12Magnetic tweezers to study DNA motors Maria Mañosas Ritort lab UB Barcelona Croquette-Bensimon lab ENS France #12;· Introduction to MT (magnetic tweezers) · Applications: 1. Tracking DNA motors: (i

Ritort, Felix

114

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

NASA Astrophysics Data System (ADS)

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.

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

2012-09-01

115

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

PubMed Central

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

2012-01-01

116

OPTICAL TWEEZERS AND THEIR APPLICATIONS IN BIOPHYSICS RESEARCH AND EDUCATION  

E-print Network

for holographic optical trapping (HOT). This allows for the creation and manipulation of multiple traps from of the thesis. Using a focused laser for local control of temperature in ice crystals is the third part of this thesis. Laser light will be absorbed in water to different degrees depending on the wavelength. The steep

Braslavsky, Ido

117

Dynamics of Interaction of RBC with optical tweezers  

NASA Astrophysics Data System (ADS)

It has recently been shown that a red blood cell (RBC) can be used as optically driven motor. The mechanism for rotation is however not fully understood. While the dependence on osmolarity of the buffer led us to conclude that the osmolarity dependent changes in shape of the cell are responsible for the observed rotation, role of ion gradients and folding of RBC to a rod shape has been invoked by Dharmadhikari et al to explain their observations. In this paper we report results of studies undertaken to understand the dynamics of a RBC when it is optically tweezed. The results obtained support our earlier conjecture that osmolarity dependent changes in shape of the cell are responsible for the observed rotation.

Mohanty, Samarendra K.; Mohanty, Khyati S.; Gupta, Pradeep Kumar

2005-06-01

118

Assembly and force measurement with SPM-like probes in holographic optical tweezers  

NASA Astrophysics Data System (ADS)

In this paper we demonstrate the optical assembly and control of scanning probe microscopy (SPM)-like probes, using holographic optical tweezers. The probes are formed from cadmium sulphide rods and silica microspheres, the latter providing explicit trapping handles. Calibration of the trap stiffness allows us to use a precise measure of probe displacement to calculate the applied forces. We demonstrate that the optically controlled probe can exert a force in excess of 60 pN, over an area of 1×10-13 m2, with a force sensitivity of 50 fN. We believe that probes similar to the ones presented here will have applications as nanotools in probing laser-sensitive cells/materials.

Ikin, L.; Carberry, D. M.; Gibson, G. M.; Padgett, M. J.; Miles, M. J.

2009-02-01

119

Evaluating cell matrix mechanics using an integrated nonlinear optical tweezer-confocal imaging system  

NASA Astrophysics Data System (ADS)

Biomechanics plays a central role in breast epithelial morphogenesis. In this study we have used 3D cultures in which normal breast epithelial cells are able to organize into rounded acini and tubular ducts, the main structures found in the breast tissue. We have identified fiber organization as a main determinant of ductal organization. While bulk rheological properties of the matrix seem to play a negligible role in determining the proportion of acini versus ducts, local changes may be pivotal in shape determination. As such, the ability to make microscale rheology measurements coupled with simultaneous optical imaging in 3D cultures can be critical to assess the biomechanical factors underlying epithelial morphogenesis. This paper describes the inclusion of optical tweezers based microrheology in a microscope that had been designed for nonlinear optical imaging of collagen networks in ECM. We propose two microrheology methods and show preliminary results using a gelatin hydrogel and collagen/Matrigel 3D cultures containing mammary gland epithelial cells.

Peng, Berney; Alonzo, Carlo A. C.; Xia, Lawrence; Speroni, Lucia; Georgakoudi, Irene; Soto, Ana M.; Sonnenschein, Carlos; Cronin-Golomb, Mark

2013-09-01

120

Laser microbeams and optical tweezers to study DNA repair and ageing  

NASA Astrophysics Data System (ADS)

Incorrect DNA repair is probably one cause of healthy ageing. Laser microbeams or optical tweezers are emerging as convenient tools in the study of repair mechanisms. Using such tools, DNA damage can be induced in a preselected volume element of a cell nucleus and at a preselected time point - an effect which is hardly to achieve with any other tool. On the other hand damage induction highly depends on a subtle combination of laser mircobeam parameters such as dose, pulse peak power and wavelength. In consequence DNA repair at the sites of damage may work differently. Furthermore, such sites are occasionally stationary, occasionally they migrate towards each other, indicating a considerable dynamics of DNA repair inside a cell nucleus. As an example for the application of optical tweezers, Erythrocyte Mediated Force Application (EMFA) is used to induce nitric oxide production in cells of the endothelium, i. e. the inner layer of (human) blood vessels. It is shown that upon stimulation by EMFA, endothelial cells initially activate the calcium homeostasis and develop calcium humps, concentration plateaus and oscillations.

Grigaravicius, Paulius; Monajembashi, Shamci; Pilarczyk, Götz; Rapp, Alexander; Greulich, Karl Otto

2007-09-01

121

Optical Tweezers Experiments Resolve Distinct Modes of DNA-Protein Binding  

PubMed Central

Optical tweezers are ideally suited to perform force microscopy experiments that isolate a single biomolecule, which then provides multiple binding sites for ligands. The captured complex may be subjected to a spectrum of forces, inhibiting or facilitating ligand activity. In the following experiments, we utilize optical tweezers to characterize and quantify DNA binding of various ligands. High Mobility Group Type B (HMGB) proteins, which bind to double-stranded DNA, are shown to serve the dual purpose of stabilizing and enhancing the flexibility of double stranded DNA. Unusual intercalating ligands are observed to thread into and lengthen the double-stranded structure. Proteins binding to both double- and single-stranded DNA, such as the alpha polymerase subunit of E. coli Pol III, are characterized and the subdomains containing the distinct sites responsible for binding are isolated. Finally, DNA binding of bacteriophage T4 and T7 single-stranded DNA (ssDNA) binding proteins are measured for a range of salt concentrations, illustrating a binding model for proteins that slide along double-stranded DNA, ultimately binding tightly to ssDNA. These recently developed methods quantify both the binding activity of the ligand as well as the mode of binding. PMID:19173290

McCauley, Micah J.; Williams, Mark C.

2009-01-01

122

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

123

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

124

Optically-driven red blood cell rotor in linearly polarized laser tweezers  

NASA Astrophysics Data System (ADS)

We have constructed a dual trap optical tweezers set-up around an inverted microscope where both the traps can be independently controlled and manipulated in all the three dimensions. Here we report our observations on rotation of red blood cells (RBCs) in a linearly polarized optical trap. Red blood cells deform and become twisted in hypertonic phosphate buffer saline and when trapped, experience an unbalanced radiation pressure force. The torque generated from the unbalanced force causes the trapped RBC to rotate. Addition of Ca^{++} ions in the solution, keeping the osmolarity same, makes the cell membranes stiffer and the cells deform less. Thus the speed of rotation of the red blood cells can be controlled, as less deformation and in turn less asymmetry in shape produces less torque under the radiation pressure resulting in slower rotation at the same laser power.

Khan, Manas; Mohanty, Samarendra K.; Sood, A. K.

2005-11-01

125

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

126

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

127

The stiffness of rabbit skeletal actomyosin cross-bridges determined with an optical tweezers transducer.  

PubMed Central

Muscle contraction is brought about by the cyclical interaction of myosin with actin coupled to the breakdown of ATP. The current view of the mechanism is that the bound actomyosin complex (or "cross-bridge") produces force and movement by a change in conformation. This process is known as the "working stroke." We have measured the stiffness and working stroke of a single cross-bridge (kappa xb, dxb, respectively) with an optical tweezers transducer. Measurements were made with the "three bead" geometry devised by Finer et al. (1994), in which two beads, supported in optical traps, are used to hold an actin filament in the vicinity of a myosin molecule, which is immobilized on the surface of a third bead. The movements and forces produced by actomyosin interactions were measured by detecting the position of both trapped beads. We measured, and corrected for, series compliance in the system, which otherwise introduces large errors. First, we used video image analysis to measure the long-range, force-extension property of the actin-to-bead connection (kappa con), which is the main source of "end compliance." We found that force-extension diagrams were nonlinear and rather variable between preparations, i.e., end compliance depended not only upon the starting tension, but also upon the F-actin-bead pair used. Second, we measured kappa xb and kappa con during a single cross-bridge attachment by driving one optical tweezer with a sinusoidal oscillation while measuring the position of both beads. In this way, the bead held in the driven optical tweezer applied force to the cross-bridge, and the motion of the other bead measured cross-bridge movement. Under our experimental conditions (at approximately 2 pN of pretension), connection stiffness (kappa con) was 0.26 +/- 0.16 pN nm-1. We found that rabbit heavy meromyosin produced a working stroke of 5.5 nm, and cross-bridge stiffness (kappa xb) was 0.69 +/- 0.47 pN nm-1. PMID:9726944

Veigel, C; Bartoo, M L; White, D C; Sparrow, J C; Molloy, J E

1998-01-01

128

Condensation transition in DNA-polyaminoamide dendrimer fibers studied using optical tweezers  

E-print Network

When mixed together, DNA and polyaminoamide (PAMAM) dendrimers form fibers that condense into a compact structure. We use optical tweezers to pull condensed fibers and investigate the decondensation transition by measuring force-extension curves (FECs). A characteristic plateau force (around 10 pN) and hysteresis between the pulling and relaxation cycles are observed for different dendrimer sizes, indicating the existence of a first-order transition between two phases (condensed and extended) of the fiber. The fact that we can reproduce the same FECs in the absence of additional dendrimers in the buffer medium indicates that dendrimers remain irreversibly bound to the DNA backbone. Upon salt variation FECs change noticeably confirming that electrostatic forces drive the condensation transition. Finally, we propose a simple model for the decondensing transition that qualitatively reproduces the FECs and which is confirmed by AFM images.

F. Ritort; S. Mihardja; S. B. Smith; C. Bustamante

2006-05-30

129

Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers  

PubMed Central

We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the “killing time” of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision. PMID:25657879

Samadi, Akbar; Zhang, Chensong; Chen, Joseph; Reihani, S. N. S.; Chen, Zhigang

2014-01-01

130

Simultaneous detection of rotational and translational motion in optical tweezers by measurement of backscattered intensity  

NASA Astrophysics Data System (ADS)

We describe a simple yet powerful technique of simultaneously measuring both translational and rotational motion of mesoscopic particles in optical tweezers by measuring the backscattered intensity on a quadrant photodiode (QPD). While the measurement of translational motion by taking the difference of the backscattered intensity incident on adjacent quadrants of a QPD is well-known, we demonstrate that rotational motion can be measured very precisely by taking the difference between the diagonal quadrants. The latter measurement eliminates the translational component entirely, and leads to a detection sensitivity of around 50 mdeg at S/N of 2 for angular motion of a driven micro-rod. The technique is also able to resolve the translational and rotational Brownian motion components of the micro-rod in an unperturbed trap, and can be very useful in measuring translation-rotation coupling of micro-objects induced by hydrodynamic interactions.

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

2014-06-01

131

Optical tweezers as a force sensor for separating dielectrophoresis and AC electroosmosis forces  

NASA Astrophysics Data System (ADS)

Forces experienced by colloidal particles in an AC electric field such as dielectrophoresis (DEP) and AC electro-osmosis (ACEO) have been widely investigated for their application in microfluidic devices. In order to provide a more complete theoretical basis for such AC electrokinetic mechanisms, we propose a method to quantify the two forces upon one individual particle using optical tweezers as a force transducer and lock-in phase sensitive detection technique to allow high selectivity. Using this method, we isolated the ACEO force from the DEP force for charged polystyrene sphere in deionized (DI) water. ACEO free DEP crossover frequencies and a comprehensive 2D-mapping of the frequency dependent ACEO forces are presented in this paper.

Wang, Jingyu; Ou-Yang, H. Daniel

2010-08-01

132

Evaluating the toxic effect of an antimicrobial agent on single bacterial cells with optical tweezers.  

PubMed

We implement an optical tweezers technique to assess the effects of chemical agents on single bacterial cells. As a proof of principle, the viability of a trapped Escherichia coli bacterium is determined by monitoring its flagellar motility in the presence of varying concentrations of ethyl alcohol. We show that the "killing time" of the bacterium can be effectively identified from the correlation statistics of the positional time series recorded from the trap, while direct quantification from the time series or associated power spectra is intractable. Our results, which minimize the lethal effects of bacterial photodamage, are consistent with previous reports of ethanol toxicity that used conventional culture-based methods. This approach can be adapted to study other pairwise combinations of drugs and motile bacteria, especially to measure the response times of single cells with better precision. PMID:25657879

Samadi, Akbar; Zhang, Chensong; Chen, Joseph; Reihani, S N S; Chen, Zhigang

2015-01-01

133

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

134

High-resolution, long-term characterization of bacterial motility using optical tweezers  

NASA Astrophysics Data System (ADS)

We present a single-cell motility assay, which allows the quantification of bacterial swimming in a well-controlled environment, for durations of up to an hour and with a temporal resolution greater than the flagellar rotation rates of approximately 100 Hz. The assay is based on an instrument combing optical tweezers, light and fluorescence microscopy, and a microfluidic chamber. Using this device we characterized the long-term statistics of the run-tumble time series in individual Escherichia coli cells. We also quantified higher-order features of bacterial swimming, such as changes in velocity and reversals of swimming direction. Additionally, we investigated the effects of flagella number on swimming parameters including speed and tumble frequency.

Mears, Patrick J.; Min, Taejin L.; Chubiz, Lon M.; Rao, Christopher V.; Golding, Ido; Chemla, Yann R.

2010-03-01

135

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

136

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

137

Rapid feedback control and stabilization of an optical tweezers with a budget microcontroller  

NASA Astrophysics Data System (ADS)

Laboratories ranging the scientific disciplines employ feedback control to regulate variables within their experiments, from the flow of liquids within a microfluidic device to the temperature within a cell incubator. We have built an inexpensive, yet fast and rapidly deployed, feedback control system that is straightforward and flexible to implement from a commercially available Arduino Due microcontroller. This is in comparison with the complex, time-consuming and often expensive electronics that are commonly implemented. As an example of its utility, we apply our feedback controller to the task of stabilizing the main trapping laser of an optical tweezers. The feedback controller, which is inexpensive yet fast and rapidly deployed, was implemented from hacking an open source Arduino Due microcontroller. Our microcontroller based feedback system can stabilize the laser intensity to a few tenths of a per cent at 200 kHz, which is an order of magnitude better than the laser's base specifications, illustrating the utility of these devices.

Nino, Daniel; Wang, Haowei; Milstein, Joshua N.

2014-09-01

138

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

139

Development of optical-based array devices using imaging fiber bundles: Optical tweezer arrays, nanoscale arrays, and microelectrode arrays  

NASA Astrophysics Data System (ADS)

The work in this dissertation describes the development of imaging fiber-based array devices, specifically the fabrication and application of an optical tweezer array, a fiber-based nanoarray, and a nanotip array. With regards for the fabrication of an optical tweezer array, this thesis describes how fiber bundles have been used as a method to create multiple beams, which are used as optical traps. By coupling a single beam into an imaging fiber bundle, the light energy is distributed across the face of the fiber bundle. Each illuminated individual fiber in the array propagates light to the distal face of the bundle, where light focusing elements at the end of each fiber focus the laser light and form optical traps. These optical traps are capable of capturing and arraying microspheres in parallel. The number of optical traps is determined by the number of fibers in the optical fiber bundle and is capable of creating a dense array (˜104 traps/mm2) of optical tweezers. This dissertation also describes the fabrication of fiber bundle-based nanoarrays with two different size formats---one with 700 nm array elements and one with 300 nm array elements. These arrays have an ultra-high packing density in that they contain 1 x 106 or 4.5 x 10 6 array elements/mm2. Current fiber bundle-based arrays have micron feature sizes and a high packing density, up to 5 x 10 4 fibers/mm2. These nanoarrays have feature sizes at least 4 times smaller than the micron-sized arrays used and contain up to 4.5 x 106 fibers/mm2. Nanofiber bundles were chemically etched to create nanowells into which sensors were deposited. The number of sensor elements in these arrays provides enough sensing positions such that they could be used to screen an entire genome while also moving towards the concept of a universal array. In addition, this high density of sensors allows for a large number of replicates, leading to an improvement in the signal to noise ratio. An improvement on creating nanoapertures that was originally developed by Paul Pantano, a former postdoctoral fellow in the Walt lab, is also discussed in this thesis. The original technique employed a mechanical puller that heated and pulled a fiber bundle, which was then polished and etched to create nanowells. Although effective, the technique was difficult to reproduce. (Abstract shortened by UMI.)

Tam, Jenny M.

140

Measurements of the force fields within an acoustic standing wave using holographic optical tweezers  

SciTech Connect

Direct measurement of the forces experienced by micro-spheres in an acoustic standing wave device have been obtained using calibrated optical traps generated with holographic optical tweezers. A micro-sphere, which is optically trapped in three dimensions, can be moved through the acoustic device to measure forces acting upon it. When the micro-sphere is subjected to acoustic forces, it's equilibrium position is displaced to a position where the acoustic forces and optical forces are balanced. Once the optical trapping stiffness has been calibrated, observation of this displacement enables a direct measurement of the forces acting upon the micro-sphere. The measured forces are separated into a spatially oscillating component, attributed to the acoustic radiation force, and a constant force, attributed to fluid streaming. As the drive conditions of the acoustic device were varied, oscillating forces (>2.5 pN{sub pp}) and streaming forces (<0.2 pN) were measured. A 5??m silica micro-sphere was used to characterise a 6.8?MHz standing wave, ??=?220??m, to a spatial resolution limited by the uncertainty in the positioning of the micro-sphere (here to within 2?nm) and with a force resolution on the order of 10 fN. The results have application in the design and testing of acoustic manipulation devices.

Bassindale, P. G.; Drinkwater, B. W. [Faculty of Engineering, Queens building, University of Bristol, Bristol BS8 1TR (United Kingdom); Phillips, D. B. [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Barnes, A. C. [Department of Physics, H.H.Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol BS8 1TL (United Kingdom)

2014-04-21

141

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

142

Optical tweezers for synchrotron radiation probing of trapped biological and soft matter objects in aqueous environments.  

PubMed

Investigations of single fragile objects manipulated by optical forces with high brilliance X-ray beams may initiate the development of new research fields such as protein crystallography in an aqueous environment. We have developed a dedicated optical tweezers setup with a compact, portable, and versatile geometry for the customary manipulation of objects for synchrotron radiation applications. Objects of a few micrometers up to a few tens of micrometers size can be trapped for extended periods of time. The selection and positioning of single objects out of a batch of many can be performed semi-automatically by software routines. The performance of the setup has been tested by wide-angle and small-angle X-ray scattering experiments on single optically trapped starch granules, using a synchrotron radiation microbeam. We demonstrate here for the first time the feasibility of microdiffraction on optically trapped protein crystals. Starch granules and insulin crystals were repeatedly raster-scanned at about 50 ms exposure/raster-point up to the complete loss of the structural order. Radiation damage in starch granules results in the appearance of low-angle scattering due to the breakdown of the polysaccharide matrix. For insulin crystals, order along the densely packed [110] direction is preferentially maintained until complete loss of long-range order. PMID:21542583

Santucci, Silvia C; Cojoc, Dan; Amenitsch, Heinz; Marmiroli, Benedetta; Sartori, Barbara; Burghammer, Manfred; Schoeder, Sebastian; DiCola, Emanuela; Reynolds, Michael; Riekel, Christian

2011-06-15

143

Combining digital holographic microscopy and optical tweezers: a new route in microfluidic  

NASA Astrophysics Data System (ADS)

An optical configuration is realized to obtain quantitative phase-contrast maps able to characterize particles floating in a microfluidic chamber by interference microscopy. The novelty is the possibility to drive the sample and measure it thorough the same light path. That is realized by an optical setup made of two light beams coming from the same laser source. One beam provides the optical forces for driving the particle along the desired path and, at same time, it works as object beam in the digital holographic microscope (DHM). The second one acts as reference beam, allowing recording of an interference fringe pattern (i.e., the digital hologram) in an out-of-focus image plane. This work finds application in the field of micromanipulation as, the devise developed allows to operate in microfluidic chambers driving samples flowing in very small volumes. Recently, the field of optical particle micro-manipulation has had rapid growth, due to Optical Tweezers development. A particle is trapped or moved along certain trajectories according to the intensity and phase distribution of the laser beam used. Here, particles freely floating are driven by optical forces along preferential directions and then analyzed by a DHM to numerically calculate their phase-contrast signature. The improvement is that one laser source is employed for making two jobs: driving and analyze the sample. We use two slightly off-axis laser beams coming from a single laser source. The interference between them gives the possibility to record in real-time a sequence of digital holograms, while one of the beam creates the driving force. By this method, a great amount of particles can be analyzed by a real-time recording of DH movies. This allows one to examine each particle at time and characterize it. The optical configuration and the working method are illustrated. Experimental results are shown for polymeric particles and in-vitro.

Miccio, L.; Memmolo, P.; Merola, F.; Paturzo, M.; Finizio, A.; Grilli, S.; Ferraro, P.

2012-04-01

144

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

145

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

PubMed Central

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 (R2 = 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

146

Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces.  

PubMed

Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level. PMID:22463027

Khokhlova, Maria D; Lyubin, Eugeny V; Zhdanov, Alexander G; Rykova, Sophia Yu; Sokolova, Irina A; Fedyanin, Andrey A

2012-02-01

147

Normal and system lupus erythematosus red blood cell interactions studied by double trap optical tweezers: direct measurements of aggregation forces  

NASA Astrophysics Data System (ADS)

Direct measurements of aggregation forces in piconewton range between two red blood cells in pair rouleau are performed under physiological conditions using double trap optical tweezers. Aggregation and disaggregation properties of healthy and pathologic (system lupus erythematosis) blood samples are analyzed. Strong difference in aggregation speed and behavior is revealed using the offered method which is proposed to be a promising tool for SLE monitoring at single cell level.

Khokhlova, Maria D.; Lyubin, Eugeny V.; Zhdanov, Alexander G.; Rykova, Sophia Yu.; Sokolova, Irina A.; Fedyanin, Andrey A.

2012-02-01

148

3D manipulation and visualization of in-vitro cells by optical tweezers and digital holographic microscopy  

NASA Astrophysics Data System (ADS)

We present the possibility to trap cells (mouse fibroblasts, bovine spermatozoa and diatoms), to manage their position and to induce rotation, by using optical tweezers. The aim is to place them in desired positions, in order to record holographic images in a microscope configuration. Then we are able to recover the 3D shape and to calculate the biovolume of the cells starting from the reconstructed quantitative phase maps (QPMs).

Merola, F.; Miccio, L.; Memmolo, P.; Di Caprio, G.; Coppola, G.; Netti, P.; Ferraro, P.

2014-03-01

149

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

150

Manipulating CD4+ T cells by optical tweezers for the initiation of cell-cell transfer of HIV-1  

PubMed Central

Cell-cell interactions through direct contact are very important for cellular communication and coordination – especially for immune cells. The human immunodeficiency virus type I (HIV-1) induces immune cell interactions between CD4+ cells to shuttle between T cells via a virological synapse. A goal to understand the process of cell-cell transmission through virological synapses is to determine the cellular states that allow a chance encounter between cells to become a stable cell-cell adhesion. Here we demonstrate the use of optical tweezers to manipulate uninfected primary CD4+ T cells near HIV Gag-iGFP transfected Jurkat T cells to probe the determinants that induce stable adhesion. When combined with fast 4D confocal fluorescence microscopy, optical tweezers can be utilized to not only facilitate cell-cell contact, but to also allow one to simultaneously track the formation of a virological synapse, and ultimately to enable us to precisely determine all events preceding virus transfer. HIV-1 infected T cell (green) decorated with uninfected primary T cells (red) by manipulating the primary cells with an optical tweezers system PMID:20301121

McNerney, Gregory P.; Hübner, Wolfgang; Chen, Benjamin K.; Huser, Thomas

2011-01-01

151

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

152

Haptic Manipulation of Microspheres Using Optical Tweezers Under the Guidance of Artificial Force Fields  

E-print Network

Using optical tweezers and a haptic device, microspheres having diameters ranging from 3 to 4 um (floating in a fluid solution) are manipulated in order to form patterns of coupled optical microresonators by assembling the spheres via chemical binding. For this purpose, biotin-coated microspheres trapped by a laser beam are steered and chemically attached to an immobilized streptavidin-coated sphere (i.e. anchor sphere) one by one using an XYZ piezo scanner controlled by a haptic device. The positions of all spheres in the scene are detected using a CCD camera and a collision-free path for each manipulated sphere is generated using the potential field approach. The forces acting on the manipulated particle due to the viscosity of the fluid and the artificial potential field are scaled and displayed to the user through the haptic device for better guidance and control during steering. In addition, a virtual fixture is implemented such that the desired angle of approach and strength are achieved during the bind...

Bukusoglu, Ibrahim; Kiraz, Alper; Kurt, Adnan

2007-01-01

153

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

154

Holographic optical tweezers combined with back-focal-plane displacement detection.  

PubMed

A major problem with holographic optical tweezers (HOTs) is their incompatibility with laser-based position detection methods, such as back-focal-plane interferometry (BFPI). The alternatives generally used with HOTs, like high-speed video tracking, do not offer the same spatial and temporal bandwidths. This has limited the use of this technique in precise quantitative experiments. In this paper, we present an optical trap design that combines digital holography and back-focal-plane displacement detection. We show that, with a particularly simple setup, it is possible to generate a set of multiple holographic traps and an additional static non-holographic trap with orthogonal polarizations and that they can be, therefore, easily separated for measuring positions and forces with the high positional and temporal resolutions of laser-based detection. We prove that measurements from both polarizations contain less than 1% crosstalk and that traps in our setup are harmonic within the typical range. We further tested the instrument in a DNA stretching experiment and we discuss an interesting property of this configuration: the small drift of the differential signal between traps. PMID:24514607

Marsà, Ferran; Farré, Arnau; Martín-Badosa, Estela; Montes-Usategui, Mario

2013-12-16

155

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

156

Spectrin-Level Modeling of the Cytoskeleton and Optical Tweezers Stretching of the Erythrocyte  

PubMed Central

We present a three-dimensional computational study of whole-cell equilibrium shape and deformation of human red blood cell (RBC) using spectrin-level energetics. Random network models consisting of degree-2, 3, …, 9 junction complexes and spectrin links are used to populate spherical and biconcave surfaces and intermediate shapes, and coarse-grained molecular dynamics simulations are then performed with spectrin connectivities fixed. A sphere is first filled with cytosol and gradually deflated while preserving its total surface area, until cytosol volume consistent with the real RBC is reached. The equilibrium shape is determined through energy minimization by assuming that the spectrin tetramer links satisfy the worm-like chain free-energy model. Subsequently, direct stretching by optical tweezers of the initial equilibrium shape is simulated to extract the variation of axial and transverse diameters with the stretch force. At persistence length p = 7.5 nm for the spectrin tetramer molecule and corresponding in-plane shear modulus ?0 ? 8.3 ?N/m, our models show reasonable agreement with recent experimental measurements on the large deformation of RBC with optical tweezers. We find that the choice of the reference state used for the in-plane elastic energy is critical for determining the equilibrium shape. If a position-independent material reference state such as a full sphere is used in defining the in-plane energy, then the bending modulus ? needs to be at least a decade larger than the widely accepted value of 2 × 10?19 J to stabilize the biconcave shape against the cup shape. We demonstrate through detailed computations that this paradox can be avoided by invoking the physical hypothesis that the spectrin network undergoes constant remodeling to always relax the in-plane shear elastic energy to zero at any macroscopic shape, at some slow characteristic timescale. We have devised and implemented a liquefied network structure evolution algorithm that relaxes shear stress everywhere in the network and generates cytoskeleton structures that mimic experimental observations. PMID:15749778

Li, J.; Dao, M.; Lim, C. T.; Suresh, S.

2005-01-01

157

Optical rotor capable of controlling clockwise and counterclockwise rotation in optical tweezers by displacing the trapping position.  

PubMed

A clockwise rotor and a counterclockwise rotor (a clockwise rotor placed upside down) are linked on the optical axis to control the rotation direction in optical tweezers by displacing the trapping (focus) position. The dependence of optical torque on the trapping position of this linked rotor is analyzed using an upward-directed focused beam as illumination, via an objective lens with a numerical aperture of 1.4, using a ray optics model under the condition that laser light is incident to not only the lower surfaces, but also to the side surfaces of both rotors. The rotation rate in water is also simulated for an SU-8 linked rotor with 20 microm diameter at a laser power of 200 mW, with rotor thickness as a parameter, by balancing the optical torque with the drag force evaluated using computational fluid dynamics. It is confirmed that the rotation direction changes from clockwise to counterclockwise with the displacement of the trapping position, that almost the same rotation speed is possible in both directions, and that both speeds increase, reach a maximum at a rotor thickness of 9 microm, and then decrease as the thickness increases. PMID:20357886

Ukita, Hiroo; Kawashima, Hiroki

2010-04-01

158

Force unfolding kinetics of RNA using optical tweezers. II. Modeling experiments  

E-print Network

By exerting mechanical force it is possible to unfold/refold RNA molecules one at a time. In a small range of forces, an RNA molecule can hop between the folded and the unfolded state with force-dependent kinetic rates. Here, we introduce a mesoscopic model to analyze the hopping kinetics of RNA hairpins in an optical tweezers setup. The model includes different elements of the experimental setup (beads, handles and RNA sequence) and limitations of the instrument (time lag of the force-feedback mechanism and finite bandwidth of data acquisition). We investigated the influence of the instrument on the measured hopping rates. Results from the model are in good agreement with the experiments reported in the companion article (1). The comparison between theory and experiments allowed us to infer the values of the intrinsic molecular rates of the RNA hairpin alone and to search for the optimal experimental conditions to do the measurements. We conclude that long handles and soft laser traps represent the best conditions to extract rate estimates that are closest to the intrinsic molecular rates. The methodology and rationale presented here can be applied to other experimental setups and other molecules.

M. Manosas; J. -D. Wen; P. T. X. Li; S. B. Smith; C. Bustamante; I. Tinoco, Jr.; F. Ritort

2007-07-04

159

Elasticity of the red cell membrane and its relation to hemolytic disorders: an optical tweezers study.  

PubMed Central

We have used optical tweezers to study the elasticity of red cell membranes; force was applied to a bead attached to a permeabilized spherical ghost and the force-extension relation was obtained from the response of a second bead bound at a diametrically opposite position. Interruption of the skeletal network by dissociation of spectrin tetramers or extraction of the actin junctions engendered a fourfold reduction in stiffness at low applied force, but only a twofold change at larger extensions. Proteolytic scission of the ankyrin, which links the membrane skeleton to the integral membrane protein, band 3, induced a similar effect. The modified, unlike the native membranes, showed plastic relaxation under a prolonged stretch. Flaccid giant liposomes showed no measurable elasticity. Our observations indicate that the elastic character is at least as much a consequence of the attachment of spectrin as of a continuous membrane-bound network, and they offer a rationale for formation of elliptocytes in genetic conditions associated with membrane-skeletal perturbations. The theory of Parker and Winlove for elastic deformation of axisymmetric shells (accompanying paper) allows us to determine the function BH(2) for the spherical saponin-permeabilized ghost membranes (where B is the bending modulus and H the shear modulus); taking the literature value of 2 x 10(-19) Nm for B, H then emerges as 2 x 10(-6) Nm(-1). This is an order of magnitude higher than the value reported for intact cells from micropipette aspiration. Reasons for the difference are discussed. PMID:10585930

Sleep, J; Wilson, D; Simmons, R; Gratzer, W

1999-01-01

160

Studying red blood cell agglutination by measuring membrane viscosity with optical tweezers  

NASA Astrophysics Data System (ADS)

The red blood cell (RBC) viscoelastic membrane contains proteins and glycoproteins embedded in a fluid lipid bilayer that are responsible for cell agglutination. Manipulating RBCs rouleaux with a double optical tweezers, we observed that the cells slide easily one over the others but are strongly connected by their edges. An explanation for this behavior could be the fact that when the cells slide one over the others, proteins are dragged through the membrane. It confers to the movement a viscous characteristic that is dependent of the velocity between the RBCs and justifies why is so easy to slide them apart. Therefore, in a first step of this work, by measuring the force as a function of the relative velocity between two cells, we confirmed this assumption and used this viscous characteristic of the RBC rouleaux to determine the apparent membrane viscosity of the cell. As this behavior is related to the proteins interactions, we can use the apparent membrane viscosity to obtain a better understanding about cell agglutination. Methods related to cell agglutination induced by antigen-antibody interactions are the basis of most of tests used in transfusion centers. Then, in a second step of this work, we measured the apparent membrane viscosity using antibodies. We observed that this methodology is sensitive to different kinds of bindings between RBCs. Better comprehension of the forces and bindings between RBCs could improve the sensibility and specificity of the hemagglutination reactions and also guides the development of new potentiator substances.

Fernandes, Heloise P.; Fontes, Adriana; de Thomaz, André A.; Barbosa, Luiz C.; Barjas-Castro, Maria L.; Cesar, Carlos L.

2007-09-01

161

Mechanics of protein-DNA interaction studied with ultra-fast optical tweezers  

NASA Astrophysics Data System (ADS)

The lac operon is a well known example of gene expression regulation, based on the specific interaction of Lac repressor protein (LacI) with its target DNA sequence (operator). LacI and other DNA-binding proteins bind their specific target sequences with rates higher than allowed by 3D diffusion alone. Generally accepted models predict a combination of free 3D diffusion and 1D sliding along non-specific DNA. We recently developed an ultrafast force-clamp laser trap technique capable of probing molecular interactions with sub-ms temporal resolution, under controlled pN-range forces. With this technique, we tested the interaction of LacI with two different DNA constructs: a construct with two copies of the O1 operator separated by 300 bp and a construct containing the native E.coli operator sequences. Our measurements show at least two classes of LacI-DNA interactions: long (in the tens of s range) and short (tens of ms). Based on position along the DNA sequence, the observed interactions can be interpreted as specific binding to operator sequences (long events) and transient interactions with nonspecific sequences (short events). Moreover, we observe continuous sliding of the protein along DNA, passively driven by the force applied with the optical tweezers.

Monico, Carina; Tempestini, Alessia; Vanzi, Francesco; Pavone, Francesco S.; Capitanio, Marco

2014-05-01

162

Force measuring optical tweezers system for long time measurements of P pili stability  

NASA Astrophysics Data System (ADS)

A force-measuring optical tweezers instrumentation and long time measurements of the elongation and retraction of bacterial fimbriae from Uropathogenic E. coli (UPEC) under strain are presented. The instrumentation is presented in some detail. Special emphasis is given to measures taken to reduce the influence of noise and drifts in the system and from the surrounding, which makes long term force measurements possible. Individual P pili from UPEC bacteria were used as a biological model system for repetitive unfolding and refolding cycles of bacterial fimbriae under equilibrium conditions. P pili have evolved into a three-dimensional helix-like structure, the PapA rod, that can be successively and significantly elongated and/or unfolded when exposed to external forces. The instrumentation is used for characterization of the force-vs.-elongation response of the PapA rod of individual P pili, with emphasis on the long time stability of the forced unfolding and refolding of the helical structure of the PapA rod. The results show that the PapA rod is capable of withstanding extensive strain, leading to a complete unfolding of the helical structure, repetitive times during the life cycle of a bacterium without any noticeable alteration of the mechanical properties of the P pili. This function is believed to be importance for UPEC bacteria in vivo since it provides a close contact to a host cell (which is an initial step of invasion) despite urine cleaning attempts.

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

2006-02-01

163

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

164

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

165

STED nanoscopy combined with optical tweezers reveals protein dynamics on densely covered DNA (presentation video)  

NASA Astrophysics Data System (ADS)

Dense coverage of DNA by proteins is a ubiquitous feature of cellular processes such as DNA organization, replication and repair. We present a single-molecule approach capable of visualizing individual DNA-binding proteins on densely covered DNA and in the presence of high protein concentrations. Our approach combines optical tweezers with multicolor confocal and stimulated emission depletion (STED) fluorescence microscopy. Proteins on DNA are visualized at a resolution of 50 nm, a sixfold resolution improvement over that of confocal microscopy. High temporal resolution (<50 ms) is ensured by fast one-dimensional beam scanning. Individual trajectories of proteins translocating on DNA can thus be distinguished and tracked with high precision. We demonstrate our multimodal approach by visualizing the assembly of dense nucleoprotein filaments with unprecedented spatial resolution in real time. Experimental access to the force-dependent kinetics and motility of DNA-associating proteins at biologically relevant protein densities is essential for linking idealized in vitro experiments with the in vivo situation.

Heller, Iddo; Sitters, Gerrit; Broekmans, Onno D.; Farge, Géraldine; Menges, Carolin; Wende, Wolfgang; Hell, Stefan W.; Peterman, Erwin J.; Wuite, Gijs J.

2014-09-01

166

On-chip pH measurement using functionalized gel-microbeads positioned by optical tweezers.  

PubMed

This paper demonstrates local pH measurement in a microchip using a pH-sensing gel-microbead. To achieve this, the gel-microbead made of a hydrophilic photo-crosslinkable resin was functionalized with the pH indicator bromothymol blue (BTB). The primary constituent of this photo-crosslinkable resin is poly(ethylene glycol). Gel-microbeads impregnated with BTB were obtained by stirring the mixture solution, which was composed of the resin, BTB, and an electrolyte solution. The gel-microbead is polymerized by UV illumination. The polymerized gel-microbead can be manipulated by optical tweezers and made to adhere to a glass surface. The local pH was measured from the color of the gel-microbead impregnated with BTB by calibrated color information in the YCrCb color space. We succeeded in measuring the local pH value using the pH-sensing gel-microbead by manipulating and positioning it at the desired point in the microchip. PMID:18231676

Maruyama, Hisataka; Arai, Fumihito; Fukuda, Toshio

2008-02-01

167

Uncoiling mechanism of Klebsiella pneumoniae type 3 pili measured by using optical tweezers  

NASA Astrophysics Data System (ADS)

Pili are bacterial appendages that play many important roles in bacterial behaviors, physiology and interaction with hosts. Via pili, bacteria are able to adhere to, migrate onto, and colonize on host cells, mechanically. Different from the most studied type 1 and P type pili, which are rigid and thick with an average of 6~7 nm in diameter, type 3 pili are relatively tiny (3-5 nm in diameter) and flexible, and their biophysical properties remains unclear. By using optical tweezers, we found that the elongation processes of type 3 pili are divided into three phases: (1) elastic elongation, (2) uncoiling elongation, and (3) intrinsic elongation, separately. Besides, the uncoiling force of the recombinant pili displayed on the surface of E. coli [pmrkABCD V1F] is measured 20 pN in average stronger than that of E. coli [pmrkABCD V1]. This suggests that pilin MrkF is involved in determining the mechanical properties of the type 3 pili.

Chen, Feng-Jung; Chan, Chia-Han; Liu, Kuo-Liang; Huang, Ying-Jung; Peng, Hwei-Ling; Chang, Hwan-You; Yew, Tri-Rung; Hsu, Ken Y.; Hsu, Long

2007-09-01

168

A New Optical Aerosol Spectrometer  

NASA Technical Reports Server (NTRS)

An optical particle spectrometer capable of measuring aerosol particle size distributions from 0.02 to 100 micrometers has been developed. This instrument combines several optical methods in one, in-situ configuration; it can provide continuous data collection to encompass the wide dynamic size ranges and concentrations found in studies of modeled planetary atmospheres as well as terrestrial air quality research. Currently, the system is incorporated into an eight liter capacity spherical pressure vessel that is appropriate both for flowthrough and for in-situ particle generation. The optical sizing methods include polarization ratio, The scattering, and forward scattering detectors, with illumination from a fiber-coupled, Argon-ion laser. As particle sizes increase above 0.1 micrometer, a customized electronics and software system automatically shifts from polarization to diffraction-based measurements as the angular scattering detectors attain acceptable signal-to-noise ratios. The number concentration detection limits are estimated to be in the part-per-trillion (ppT by volume) range, or roughly 1000 submicron particles per cubic centimeter. Results from static experiments using HFC134A (approved light scattering gas standard), flow-through experiments using sodium chloride (NaCl) and carbon particles, and dynamic 'Tholin' (photochemical produced particles from ultraviolet (UV)-irradiated acetylene and nitrogen) experiments have been obtained. The optical spectrometer data obtained with particles have compared well with particle sizes determined by electron microscopy. The 'Tholin' tests provided real-time size and concentration data as the particles grew from about 30 nanometers to about 0.8 micrometers, with concentrations ranging from ppT to ppB, by volume. Tests are still underway, to better define sizing accuracy and concentration limits, these results will be reported.

Fonda, Mark; Malcolmson, Andrew; Bonin, Mike; Stratton, David; Rogers, C. Fred; Chang, Sherwood (Technical Monitor)

1998-01-01

169

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

170

Wavefront analysis and optimization from conventional liquid crystal displays for low-cost holographic optical tweezers and digital holographic microscopy  

NASA Astrophysics Data System (ADS)

In different study fields the manipulation and imaging of micro-sized particles is essential. The use of holographic optical tweezers (HOT) and digital holographic microscopy (DHM) facilitates this task in a non-mechanical way by providing the proper computer generated hologram and the required amount of light. Electrically addressed spatial light modulators (EASLM) found in holographic optical tweezers are typically of the reflective liquid crystal on silicon (LCoS) type which can achieve a phase shift of more than 2? but they are expensive. Similar components like transmissive twisted nematic liquid crystal displays (TN-LCD) are produced in large quantities, their optical characteristics improve rapidly and they are inexpensive. Under certain circumstances these devices can be used instead of expensive spatial light modulators. Consumer grade objectives are not always well corrected for spherical aberration. In that case conventional liquid crystal displays can also compensate these undesired optical effects. For this purpose software-corrected computer generated holograms are calculated. Procedures to analyze and compensate different parameters of a conventional low-cost liquid crystal display, e.g. phase shift evaluation and aberration correction of objectives by Zernike polynomials approximation are explained. The applied software compensation of the computer generated hologram has shown significant improvement of the focus quality. An important price reduction of holographic devices could be achieved by replacing special optical elements if correction algorithms for conventional liquid crystal displays are provided.

Weber, Andreas; Ortega Clavero, Valentin; Schröder, Werner

2011-05-01

171

Aerosol optical depth measurements during the Aerosols99 experiment  

NASA Astrophysics Data System (ADS)

The Aerosols99 cruise took place during the period from January 14 to February 8, 1999, on the R/V Ronald Brown. The cruise track was almost a straight line in the southeast direction from Norfolk, Virginia, to Cape Town, South Africa, and afforded the opportunity to sample several different aerosol regimes over the North and South Atlantic. Handheld sunphotometers, a shadowband radiometer (FRSR), and a LIDAR were used to measure the aerosol optical depth (AOD) during the cruise. The AOD and angstrom exponent ? (spectral dependence of the AOD) varied strongly between regimes. Maritime regions typically had AOD (500 nm) of approximately 0.10±0.03, with ? around 0.3±0.3. An African dust event was encountered in which the AOD (500 nm) averaged 0.29±0.05 with an ? of 0.36±0.13. At the Intertropical Convergence Zone (ITCZ), no measurements were obtained because of cloudiness; however, after the ITCZ we encountered a biomass burning aerosol with high average AOD (500 nm) of 0.36±0.13, and a high ? (0.88±0.30). Farther south the aerosol went back to the low levels of a typical marine aerosol.

Voss, Kenneth J.; Welton, Ellsworth J.; Quinn, Patricia K.; Frouin, Robert; Miller, Mark; Reynolds, R. Michael

2001-09-01

172

Force unfolding kinetics of RNA using optical tweezers. I. Effects of experimental variables on measured results  

E-print Network

Experimental variables of optical tweezers instrumentation that affect RNA folding/unfolding kinetics were investigated. A model RNA hairpin, P5ab, was attached to two micron-sized beads through hybrid RNA/DNA handles; one bead was trapped by dual-beam lasers and the other was held by a micropipette. Several experimental variables were changed while measuring the unfolding/refolding kinetics, including handle lengths, trap stiffness, and modes of force applied to the molecule. In constant-force mode where the tension applied to the RNA was maintained through feedback control, the measured rate coefficients varied within 40% when the handle lengths were changed by 10 fold (1.1 to 10.2 Kbp); they increased by two- to three-fold when the trap stiffness was lowered to one third (from 0.1 to 0.035 pN/nm). In the passive mode, without feedback control and where the force applied to the RNA varied in response to the end-to-end distance change of the tether, the RNA hopped between a high-force folded-state and a low-force unfolded-state. In this mode, the rates increased up to two-fold with longer handles or softer traps. Overall, the measured rates remained with the same order-of-magnitude over the wide range of conditions studied. In the companion paper (1), we analyze how the measured kinetics parameters differ from the intrinsic molecular rates of the RNA, and thus how to obtain the molecular rates.

J. -D. Wen; M. Manosas; P. T. X. Li; S. B. Smith; C. Bustamante; F. Ritort; I. Tinoco Jr

2007-07-04

173

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

174

Three-Dimensional Optical Trapping of a Plasmonic Nanoparticle using Low Numerical Aperture Optical Tweezers.  

PubMed

It was previously believed that larger metal nanoparticles behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, several groups have recently reported successful optical trapping of gold and silver particles as large as 250?nm. We offer a possible explanation based on the fact that metal nanoparticles naturally occur in various non-spherical shapes and their optical properties differ significantly due to changes in localized plasmon excitation. We demonstrate experimentally and support theoretically three-dimensional confinement of large gold nanoparticles in an optical trap based on very low numerical aperture optics. We showed theoretically that the unique properties of gold nanoprisms allow an increase of trapping force by an order of magnitude at certain aspect ratios. These results pave the way to spatial manipulation of plasmonic nanoparticles using an optical fibre, with interesting applications in biology and medicine. PMID:25630432

Brzobohatý, Oto; Šiler, Martin; Trojek, Jan; Chvátal, Lukáš; Karásek, Vít?zslav; Paták, Aleš; Pokorná, Zuzana; Mika, Filip; Zemánek, Pavel

2015-01-01

175

Three-Dimensional Optical Trapping of a Plasmonic Nanoparticle using Low Numerical Aperture Optical Tweezers  

PubMed Central

It was previously believed that larger metal nanoparticles behave as tiny mirrors that are pushed by the light beam radiative force along the direction of beam propagation, without a chance to be confined. However, several groups have recently reported successful optical trapping of gold and silver particles as large as 250?nm. We offer a possible explanation based on the fact that metal nanoparticles naturally occur in various non-spherical shapes and their optical properties differ significantly due to changes in localized plasmon excitation. We demonstrate experimentally and support theoretically three-dimensional confinement of large gold nanoparticles in an optical trap based on very low numerical aperture optics. We showed theoretically that the unique properties of gold nanoprisms allow an increase of trapping force by an order of magnitude at certain aspect ratios. These results pave the way to spatial manipulation of plasmonic nanoparticles using an optical fibre, with interesting applications in biology and medicine. PMID:25630432

Brzobohatý, Oto; Šiler, Martin; Trojek, Jan; Chvátal, Lukáš; Karásek, Vít?zslav; Paták, Aleš; Pokorná, Zuzana; Mika, Filip; Zemánek, Pavel

2015-01-01

176

New calibration method for position detector for simultaneous measurements of force constants and local viscosity in optical tweezers  

NASA Astrophysics Data System (ADS)

We present a new method to calibrate a quadrant photodiode used as position detector to monitor latex beads trapped in optical tweezers. The method combines the dragging Stoke's force with the thermal noise analysis (power spectral density (PSD)) of the Brownian motion of the trapped bead. Position detector calibrations used in other similar methods normally utilise a bead attached to the coverslip: the voltage-position calibration factor is found by translating the bead across the waist of a laser beam. The so determined calibration factor is then assumed to be the same when beads are investigated in the optical trap. This procedure presents some drawbacks since attached beads can be affected by proximity effects due to the coverslip glass surface which alter the position sensor response itself. On the contrary, our method is able to provide, simultaneously, the calibration factor, the trap stiffness, and the local viscosity of the medium making use of a single trapped bead.

Buosciolo, A.; Pesce, G.; Sasso, A.

2004-02-01

177

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

178

Development and applications of an optical tweezer-based microrheometer: case studies of biomaterials and living cells  

NASA Astrophysics Data System (ADS)

The investigation of mechanical properties of living biological cells and biomaterials is challenging because they are inhomogeneous and anisotropic at microscopic scales, and often time-dependent over a broad time scale. Through three case studies of biomaterials and living cells, we demonstrate that a novel, oscillating optical tweezer-based imaging microrheometer developed recently in our laboratory has overcome many technical barriers posed by the complexity of biological systems. In this paper, we present the working principle, system setup and calibration of the imaging microrheometer, and report the groundbreaking results of the three applications: gelation dynamics of cross-linkable hyaluronan acid (HA) hydrogels; Mechanical in-homogeneity and anisotropy in purified microtubule networks; and effects of drug treatment and temperature variation on the mechanical properties of in vitro human alveolar epithelial cells. In each case, micro beads inserted in the materials, or attached to the cell membrane were used as probes for optical trapping. The probe particle was set into a forced harmonic oscillation by oscillating optical tweezers. Position sensing optics and phase lock-in signal processing allow the determination of the amplitude and phase shift of the particle motion at high sensitivity. The complex mechanical modulus G * is then calculated from the amplitude and the phase shift. The rheometer system is capable of measuring dynamic local mechanical moduli in the broad frequency range of 1.3-1000 Hz at a sampling rate of 2 data point per second across a wide dynamic range (1~20,000 dyne/cm2). Integration of the rheometer system with spinning disk confocal microscopy enables the study of micromechanical properties and the microstructure of the sample simultaneously. Combination of dual-axis, piezo-electric activated mirror and 2-D position sensing detector gives the rheometer system the capability of investigating mechanical anisotropy in highly structured biological samples.

Wang, Jing; Yalcin, Huseyin; Lengel, Angela; Hewitt, Corey; Ou-Yang, H. Daniel

2007-02-01

179

Silicon-on-insulator multimode-interference waveguide-based arrayed optical tweezers (SMART) for two-dimensional microparticle trapping and manipulation.  

PubMed

We demonstrate two-dimensional optical trapping and manipulation of 1 ?m and 2.2 ?m polystyrene particles in an 18 ?m-thick fluidic cell at a wavelength of 1565 nm using the recently proposed Silicon-on-insulator Multimode-interference (MMI) waveguide-based ARrayed optical Tweezers (SMART) technique. The key component is a 100 ?m square-core silicon waveguide with mm length. By tuning the fiber-coupling position at the MMI waveguide input facet, we demonstrate various patterns of arrayed optical tweezers that enable optical trapping and manipulation of particles. We numerically simulate the physical mechanisms involved in the arrayed trap, including the optical force, the heat transfer and the thermal-induced microfluidic flow. PMID:23389134

Lei, Ting; Poon, Andrew W

2013-01-28

180

Calibrating bead displacements in optical tweezers using acousto-optic deflectors  

SciTech Connect

Displacements of optically trapped particles are often recorded using back-focal-plane interferometry. In order to calibrate the detector signals to displacements of the trapped object, several approaches are available. One often relies either on scanning a fixed bead across the waist of the laser beam or on analyzing the power spectrum of movements of the trapped bead. Here, we introduce an alternative method to perform this calibration. The method consists of very rapidly scanning the laser beam across the solvent-immersed, trapped bead using acousto-optic deflectors while recording the detector signals. It does not require any knowledge of solvent viscosity and bead diameter, and works in all types of samples, viscous or viscoelastic. Moreover, it is performed with the same bead as that used in the actual experiment. This represents marked advantages over established methods.

Vermeulen, Karen C.; Mameren, Joost van; Stienen, Ger J.M.; Peterman, Erwin J.G.; Wuite, Gijs J.L.; Schmidt, Christoph F. [Laser Centre and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands); Laboratory for Physiology, Institute for Cardiovascular Research, VU Medical Center, Van der Boechorststraat 7, 1081 BT Amsterdam (Netherlands); Laser Centre and Department of Physics and Astronomy, Vrije Universiteit Amsterdam, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)

2006-01-15

181

Comparative study of methods to calibrate the stiffness of a single-beam gradient-force optical tweezers over various laser trapping powers.  

PubMed

Optical tweezers have become an important instrument in force measurements associated with various physical, biological, and biophysical phenomena. Quantitative use of optical tweezers relies on accurate calibration of the stiffness of the optical trap. Using the same optical tweezers platform operating at 1064 nm and beads with two different diameters, we present a comparative study of viscous drag force, equipartition theorem, Boltzmann statistics, and power spectral density (PSD) as methods in calibrating the stiffness of a single beam gradient force optical trap at trapping laser powers in the range of 0.05 to 1.38 W at the focal plane. The equipartition theorem and Boltzmann statistic methods demonstrate a linear stiffness with trapping laser powers up to 355 mW, when used in conjunction with video position sensing means. The PSD of a trapped particle's Brownian motion or measurements of the particle displacement against known viscous drag forces can be reliably used for stiffness calibration of an optical trap over a greater range of trapping laser powers. Viscous drag stiffness calibration method produces results relevant to applications where trapped particle undergoes large displacements, and at a given position sensing resolution, can be used for stiffness calibration at higher trapping laser powers than the PSD method. PMID:25375348

Sarshar, Mohammad; Wong, Winson T; Anvari, Bahman

2014-11-01

182

Comparative study of methods to calibrate the stiffness of a single-beam gradient-force optical tweezers over various laser trapping powers  

NASA Astrophysics Data System (ADS)

Optical tweezers have become an important instrument in force measurements associated with various physical, biological, and biophysical phenomena. Quantitative use of optical tweezers relies on accurate calibration of the stiffness of the optical trap. Using the same optical tweezers platform operating at 1064 nm and beads with two different diameters, we present a comparative study of viscous drag force, equipartition theorem, Boltzmann statistics, and power spectral density (PSD) as methods in calibrating the stiffness of a single beam gradient force optical trap at trapping laser powers in the range of 0.05 to 1.38 W at the focal plane. The equipartition theorem and Boltzmann statistic methods demonstrate a linear stiffness with trapping laser powers up to 355 mW, when used in conjunction with video position sensing means. The PSD of a trapped particle's Brownian motion or measurements of the particle displacement against known viscous drag forces can be reliably used for stiffness calibration of an optical trap over a greater range of trapping laser powers. Viscous drag stiffness calibration method produces results relevant to applications where trapped particle undergoes large displacements, and at a given position sensing resolution, can be used for stiffness calibration at higher trapping laser powers than the PSD method.

Sarshar, Mohammad; Wong, Winson T.; Anvari, Bahman

2014-11-01

183

Rotation rate of a three-wing rotor illuminated by upward-directed focused beam in optical tweezers  

NASA Astrophysics Data System (ADS)

The optical torque and the trapping position (focal point) in optical tweezers are analyzed for upward-directed focused laser illumination using a ray optics model, considering that laser light is incident at not only the lower surface but also the side surface of a 3-wing rotor. The viscous drag force due to the pressure and the shearing stress on all surfaces of the rotor is evaluated using computational fluid dynamics. The rotation rate is simulated in water by balancing the optical torque with the drag force, resulting in 500 rpm for an SU-8 rotor with 20 ?m diameter at a laser power of 200 mW. The trapping position is estimated to be 7.6 ?m in the rotor with an upward-directed laser at 200 mW via an objective lens having a numerical aperture of 1.4. Both the rotation rate and the trapping position agree well with the values obtained in the experiment.

Ukita, Hiroo; Ohnishi, Takakazu; Nonohara, Yasunari

2008-03-01

184

Using optical tweezers to examine the chemotactic force to a single inflammatory cell--eosinophil stimulated by chemoattractants prepared from Toxocara Canis larvae  

NASA Astrophysics Data System (ADS)

Granulocytes are a group of white blood cells belonging to the innate immune system in human and in murine in which eosinophils play an important role in worm infection-induced inflammation. The migration of these cells is well characterized and has been separated into four steps: rolling, adhesion, transendothelial migration, and chemotaxis, however, the physical characteristics of the chemotactic force to eosinophils from worm component remain largely unknown. Note that optical tweezers are featured in the manipulation of a single cell and the measurement of biological forces. Therefore, we propose to use optical tweezers to examine the chemotactic force to a eosinophil from a T. canis lavae preparation in terms of distance during the migration of eosinophil.

Shih, Po-Chen; Su, Yi-Jr; Chen, Ke-Min; Jen, Lin-Ni; Liu, Cheng-tzu; Hsu, Long

2005-08-01

185

Hyperspectral aerosol optical depths from TCAP flights  

NASA Astrophysics Data System (ADS)

4STAR (Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research), a hyperspectral airborne Sun photometer, acquired aerosol optical depths (AOD) at 1 Hz during all July 2012 flights of the Two-Column Aerosol Project. Root-mean-square differences from Aerosol Robotic Network 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 Department of Energy Gulfstream 1 with 4STAR) and lidar (on NASA B200) extinction measurements within 0.01, 0.03, 0.01, 0.02, 0.02, and 0.02 at 355, 450, 532, 550, 700, and 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 and 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, Y.; Johnson, R. R.; Flynn, C. J.; Russell, P. B.; Schmid, B.; Redemann, J.; Dunagan, S. E.; Kluzek, C. D.; Hubbe, J. M.; Segal-Rosenheimer, M.; Livingston, J. M.; Eck, T. F.; Wagener, R.; Gregory, L.; Chand, D.; Berg, L. K.; Rogers, R. R.; Ferrare, R. A.; Hair, J. W.; Hostetler, C. A.; Burton, S. P.

2013-11-01

186

Aerosol Optical Depth Measurements in the Southern Ocean Within the Framework of Maritime Aerosol Network  

NASA Astrophysics Data System (ADS)

Aerosol production sources over the World Ocean and various factors determining aerosol spatial and temporal distribution are important for understanding the Earth's radiation budget and aerosol-cloud interactions. The Maritime Aerosol Network (MAN) as a component of AERONET has been collecting aerosol optical depth data over the oceans since 2006. A significant progress has been made in data acquisition over areas that previously had very little or no coverage. Data collection included intensive study areas in the Southern Ocean and off the coast of Antarctica including a number of circumnavigation cruises in high southern latitudes. It made an important contribution to MAN and provided a valuable reference point in atmospheric aerosol optical studies. The paper presents results of this international and multi-agency effort in studying aerosol optical properties over Southern Ocean and adjacent areas. The ship-borne aerosol optical depth measurements offer an excellent opportunity for comparison with global aerosol transport models, satellite retrievals and provide useful information on aerosol distribution over the World Ocean. A public domain web-based database dedicated to the MAN activity can be found at http://aeronet.gsfc.nasa.gov/new_web/maritime_aerosol_network.html.

Smirnov, A.; Holben, B. N.; Sayer, A. M.; Sakerin, S. M.; Radionov, V. F.; Courcoux, Y.; Broccardo, S. P.; Evangelista, H.; Croot, P. L.; Disterhoft, P.; Piketh, S.; Milinevsky, G. P.; O'Neill, N. T.; Slutsker, I.; Giles, D. M.

2013-12-01

187

THEMIS Observations of Atmospheric Aerosol Optical Depth  

NASA Technical Reports Server (NTRS)

The Mars Odyssey spacecraft entered into Martian orbit in October 2001 and after successful aerobraking began mapping in February 2002 (approximately Ls=330 deg.). Images taken by the Thermal Emission Imaging System (THEMIS) on-board the Odyssey spacecraft allow the quantitative retrieval of atmospheric dust and water-ice aerosol optical depth. Atmospheric quantities retrieved from THEMIS build upon existing datasets returned by Mariner 9, Viking, and Mars Global Surveyor (MGS). Data from THEMIS complements the concurrent MGS Thermal Emission Spectrometer (TES) data by offering a later local time (approx. 2:00 for TES vs. approx. 4:00 - 5:30 for THEMIS) and much higher spatial resolution.

Smith, Michael D.; Bandfield, Joshua L.; Christensen, Philip R.; Richardson, Mark I.

2003-01-01

188

Magnetic tweezers for the measurement of twist and torque.  

PubMed

Single-molecule techniques make it possible to investigate the behavior of individual biological molecules in solution in real time. These techniques include so-called force spectroscopy approaches such as atomic force microscopy, optical tweezers, flow stretching, and magnetic tweezers. Amongst these approaches, magnetic tweezers have distinguished themselves by their ability to apply torque while maintaining a constant stretching force. Here, it is illustrated how such a "conventional" magnetic tweezers experimental configuration can, through a straightforward modification of its field configuration to minimize the magnitude of the transverse field, be adapted to measure the degree of twist in a biological molecule. The resulting configuration is termed the freely-orbiting magnetic tweezers. Additionally, it is shown how further modification of the field configuration can yield a transverse field with a magnitude intermediate between that of the "conventional" magnetic tweezers and the freely-orbiting magnetic tweezers, which makes it possible to directly measure the torque stored in a biological molecule. This configuration is termed the magnetic torque tweezers. The accompanying video explains in detail how the conversion of conventional magnetic tweezers into freely-orbiting magnetic tweezers and magnetic torque tweezers can be accomplished, and demonstrates the use of these techniques. These adaptations maintain all the strengths of conventional magnetic tweezers while greatly expanding the versatility of this powerful instrument. PMID:24894412

Lipfert, Jan; Lee, Mina; Ordu, Orkide; Kerssemakers, Jacob W J; Dekker, Nynke H

2014-01-01

189

Hyperspectral aerosol optical depths from TCAP flights  

NASA Astrophysics Data System (ADS)

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.

Schmid, B.; Shinozuka, Y.; Johnson, R.; Flynn, C. J.; Russell, P. B.; Redemann, J.; Dunagan, S.; Kluzek, C.; Hubbe, J.; Segal-Rosenhaimer, M.; Livingston, J. M.; Eck, T. F.; Wagener, R.; Gregory, L.; Chand, D.; Berg, L. K.; Rogers, R. R.; Ferrare, R. A.; Hair, J. W.; Hostetler, C. A.; Burton, S. P.

2013-12-01

190

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

191

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

192

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

193

Multiwavelength multistatic optical scattering for aerosol characterization  

NASA Astrophysics Data System (ADS)

The main focus of this research is the development of a technique to remotely characterize aerosol properties, such as particle size distribution, concentration, and refractive index as a function of wavelength, through the analysis of optical scattering measurements. The proposed technique is an extension of the multistatic polarization ratio technique that has been developed by prior students at the Penn State Lidar Lab to include multiple wavelengths. This approach uses the ratio of polarized components of the scattering phase functions at multiple wavelengths across the visible region of the electromagnetic spectrum to extract the microphysical and optical properties of aerosols. The scattering intensities at each wavelength are vertically separated across the face of the imager using a transmission diffraction grating, so that scattering intensities for multiple wavelengths at many angles are available for analysis in a single image. The ratio of the scattering phase function intensities collected using parallel and perpendicular polarized light are formed for each wavelength and analysis of the ratio is used to determine the microphysical properties of the aerosols. One contribution of the present work is the development of an inversion technique based on a genetic algorithm that retrieves lognormal size distributions from scattering measurements by minimizing the squared error between measured polarization ratios and polarization ratios calculated using the Mie solution to Maxwell's equations. The opportunities and limitations of using the polarization ratio are explored, and a genetic algorithm is developed to retrieve single mode and trimodal lognormal size distributions from multiwavelength, angular scattering data. The algorithm is designed to evaluate particles in the diameter size range of 2 nm to 60 im, and uses 1,000 linear spaced diameters within this range to compute the modeled polarization ratio. The algorithm returns geometric mean radii and geometric standard deviations within 2% of the correct value when inverting a single lognormal probability size distribution from simulated polarization ratios that include random Gaussian noise added to limit the signal-to-noise ratio to 25. The genetic algorithm performed reasonably well when retrieving results using a single complex refractive index for all three wavelengths while finding the lognormal particle size parameters. Three inversion runs of the algorithm on simulated noisy data showed that the algorithm could retrieved a trimodal size distribution and a single complex refractive index that produced a very good fit between the simulated noisy polarization ratios and the forward-calculated polarization ratios. A significant contribution of the present work is a set of tests conducted at the Environmental Protection Agency's (EPA) Aerosol Test Facility (ATF), which is a controlled environment, where direct measurements of the size distribution and concentration of the scattering volume are available. The aerosol size distribution results obtained from inversion of the measured scattering phase functions, a lognormal size distribution with a geometric mean diameter of ˜450 nm and a geometric standard deviation of ˜1.3, compare favorably with measurements from an aerodynamic particle sizer and a condensation particle counter. This is one of the first large scale experiments where a comparison between multistatic inversion results and known properties of the interrogated volume of aerosols are made under controlled conditions. The eventual goal is to develop a prototype sensor and an analysis approach to provide an important and useful tool to better define the atmospheric aerosol properties.

Brown, Andrea M.

194

Towards 3D modelling and imaging of infection scenarios at the single cell level using holographic optical tweezers and digital holographic microscopy.  

PubMed

The analysis of dynamic interactions of microorganisms with a host cell is of utmost importance for understanding infection processes. We present a biophotonic holographic workstation that allows optical manipulation of bacteria by holographic optical tweezers and simultaneously monitoring of dynamic processes with quantitative multi-focus phase imaging based on self-interference digital holographic microscopy. Our results show that several bacterial cells, even with non-spherical shape, can be aligned precisely on the surface of living host cells and localized reproducibly in three dimensions. In this way a new label-free multipurpose device for modelling and quantitative analysis of infection scenarios at the single cell level is provided. PMID:22700281

Kemper, Björn; Barroso, Álvaro; Woerdemann, Mike; Dewenter, Lena; Vollmer, Angelika; Schubert, Robin; Mellmann, Alexander; von Bally, Gert; Denz, Cornelia

2013-03-01

195

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

196

Using the OMI Aerosol Index and Absorption Aerosol Optical Depth to evaluate the NASA MERRA Aerosol Reanalysis  

NASA Astrophysics Data System (ADS)

A radiative transfer interface has been developed to simulate the UV Aerosol Index (AI) from the NASA Goddard Earth Observing System version 5 (GEOS-5) aerosol assimilated fields. The purpose of this work is to use the AI and Aerosol Absorption Optical Depth (AAOD) derived from the Ozone Monitoring Instrument (OMI) measurements as independent validation for the Modern Era Retrospective analysis for Research and Applications Aerosol Reanalysis (MERRAero). MERRAero is based on a version of the GEOS-5 model that is radiatively coupled to the Goddard Chemistry, Aerosol, Radiation, and Transport (GOCART) aerosol module and includes assimilation of Aerosol Optical Depth (AOD) from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. Since AI is dependent on aerosol concentration, optical properties and altitude of the aerosol layer, we make use of complementary observations to fully diagnose the model, including AOD from the Multi-angle Imaging SpectroRadiometer (MISR), aerosol retrievals from the Aerosol Robotic Network (AERONET) and attenuated backscatter coefficients from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) mission to ascertain potential misplacement of plume height by the model. By sampling dust, biomass burning and pollution events in 2007 we have compared model produced AI and AAOD with the corresponding OMI products, identifying regions where the model representation of absorbing aerosols was deficient. As a result of this study over the Saharan dust region, we have obtained a new set of dust aerosol optical properties that retains consistency with the MODIS AOD data that were assimilated, while resulting in better agreement with aerosol absorption measurements from OMI. The analysis conducted over the South African and South American biomass burning regions indicates that revising the spectrally-dependent aerosol absorption properties in the near-UV region improves the modeled-observed AI comparisons. Finally, during a period where the Asian region was mainly dominated by anthropogenic aerosols, we have performed a qualitative analysis in which the specification of anthropogenic emissions in GEOS-5 is adjusted to provide insight into discrepancies observed in AI comparisons.

Buchard, V.; da Silva, A. M.; Colarco, P. R.; Darmenov, A.; Randles, C. A.; Govindaraju, R.; Torres, O.; Campbell, J.; Spurr, R.

2014-12-01

197

The study of adhesive forces between the type-3 fimbriae of Klebsiella pneumoniae and collagen-coated surfaces by using optical tweezers  

NASA Astrophysics Data System (ADS)

Adherence to host cells by a bacterial pathogen is a critical step for establishment of infection. It will contribute greatly to the understanding of bacterial pathogenesis by studying the biological force between a single pair of pathogen and host cell. In our experiment, we use a calibrated optical tweezers system to detach a single Klebsiella pneumoniae, the pathogen, from collagen, the host. By gradually increasing the laser power of the optical tweezers until the Klebsiella pneumoniae is detached from the collagen, we obtain the magnitude of the adhesive force between them. This happens when the adhesive force is barely equal to the trapping force provided by the optical tweezers at that specific laser power. This study is important because Klebsiella pneumoniae is an opportunistic pathogen which causes suppurative lesions, urinary and respiratory tract infections. It has been proved that type 3 fimbrial adhesin (mrkD) is strongly associated with the adherence of Klebsiella pneumoniae. Besides, four polymorphic mrkD alleles: namely, mrkDv1, v2, v3, and v4, are typed by using RFLP. In order to investigate the relationship between the structure and the function for each of these variants, DNA fragments encoding the major fimbrial proteins mrkA, mrkB, mrkC are expressed together with any of the four mrkD adhesins in E. coli JM109. Our study shows that the E. coli strain carrying the mrkDv3 fimbriae has the strongest binding activity. This suggests that mrkDv3 is a key factor that enhances the adherence of Klebsiella Pneumoniae to human body.

Chan, Chiahan; Fan, Chia-chieh; Huang, Ying-Jung; Peng, Hwei-Ling; Long, Hsu

2004-10-01

198

Retrieval of aerosol optical thickness over snow using AATSR observations  

Microsoft Academic Search

Remote sensing of aerosols experiences lack of products over very bright surfaces, such as deserts and snow, due to difficulties with the subtraction of the surface reflection contribution, when a small error in accounting for surface reflectance can cause a large error in retrieved aerosol optical thickness (AOT). Cloud screening over bright surface is also not easy because of low

Larysa Istomina; Wolfgang von Hoyningen-Huene; Vladimir Rozanov; Alexander Kokhanovsky; John P. Burrows

2010-01-01

199

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

200

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

201

Simulating Aerosol Optical Properties With the Aerosol Simulation Program (ASP): Closure Studies Using ARCTAS Data  

NASA Astrophysics Data System (ADS)

The scattering and absorption of ultraviolet and visible radiation by aerosols can significantly alter actinic fluxes and photolysis rates. Accurate modeling of aerosol optical properties is thus essential to simulating atmospheric chemistry, air quality, and climate. Here we evaluate the aerosol optical property predictions of the Aerosol Simulation Program (ASP) with in situ data on aerosol scattering and absorption gathered during the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) campaign. The model simulations are initialized with in situ data on the aerosol size distribution and composition. We perform a set of sensitivity studies (e.g., internal vs. external mixture, core-in-shell versus Maxwell-Garnett, fraction of the organic carbon mass that is light-absorbing "brown carbon," etc.) to determine the model framework and parameters most consistent with the observations. We compare the ASP results to the aerosol optical property lookup tables in FAST-JX and suggest improvements that will better enable FAST-JX to simulate the impact of aerosols on photolysis rates and atmospheric chemistry.

Alvarado, M. J.; Macintyre, H. L.; Bian, H.; Chin, M.; Wang, C.

2012-12-01

202

A method for an approximate determination of a polymer-rich-domain concentration in phase-separated poly(N-isopropylacrylamide) aqueous solution by means of confocal Raman microspectroscopy combined with optical tweezers.  

PubMed

The paper demonstrates that a confocal Raman microspectroscope combined with optical tweezers is a promising technique to estimate polymer concentration in polymer-rich domain in phase-separated-aqueous polymer solution. The sample polymer is poly-(N-isopropylacrylamide) (PNIPAM) that is well-known as a representative thermo-responsive polymer. Optical tweezers can selectively trap the polymer-rich domain at the focal point in non-contact and non-intrusive modes. Such situation allows us to determine polymer concentration in the domain, which has been unclear due to a lack of appropriate analytical technique. It is applicable for a variety of other thermo-responsive polymers. PMID:25479874

Shoji, Tatsuya; Nohara, Riku; Kitamura, Noboru; Tsuboi, Yasuyuki

2015-01-01

203

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

204

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

205

Seasonal Variability of Aerosol Optical Depth over Indian Subcontinent  

E-print Network

Seasonal Variability of Aerosol Optical Depth over Indian Subcontinent Anup K. Prasad1,2 , Ramesh P University, Fairfax, VA, 22030, USA * corresponding author - ramesh@iitk.ac.in Abstract- Ganga basin extends

Singh, Ramesh P.

206

Using optical tweezers for the characterization of polyelectrolyte solutions with very low viscoelasticity.  

PubMed

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

Pommella, Angelo; Preziosi, Valentina; Caserta, Sergio; Cooper, Jonathan M; Guido, Stefano; Tassieri, Manlio

2013-07-23

207

Complex field-induced nematic defect structures in Laguerre-Gaussian optical tweezers  

NASA Astrophysics Data System (ADS)

Complex optical field-induced defect structures are presented in nematic and chiral nematic liquid crystals, as imprinted by Laguerre-Gaussian (LG) laser beams. Our modeling study is based on the phenomenological free energy approach, which dielectrically couples the nematic optical axis with the polarization of the LG beams. The symmetry of the presented structures proves to be conditioned by the beam helical indices. The beam intensity, strength of the nematic elastic constant, and local intensity-induced control of the nematic order via absorption of the light are demonstrated as possible mechanisms for producing, imprinting, and tuning of the field-induced complex defect structures in achiral and chiral nematics.

Žumer, Slobodan; Porenta, Tine; Ravnik, Miha

2012-10-01

208

Reducing Need for Collocated Ground and Satellite based Observations in Statistical Aerosol Optical Depth Estimation  

E-print Network

prediction of Aerosol Optical Density (AOD) which is defined as the amount of loss a beam of light incurs of solar radiation. An important metric of aerosol's concentration in the atmosphere is Aerosol OpticalReducing Need for Collocated Ground and Satellite based Observations in Statistical Aerosol Optical

Vucetic, Slobodan

209

Variations in stratospheric aerosol optical depth during northern warmings  

NASA Technical Reports Server (NTRS)

In this paper, the properties of the stratospheric aerosol optical depth (above 50 mbar) have been studied by using aerosol extinction profiles (at 1 micron) derived from the Stratospheric Aerosol Measurement and Stratospheric Aerosol and Gas Experiment (SAGE) during warming periods in the Northern Hemisphere. It is shown that, during the disturbed periods in winter, low values of aerosol optical depth (less than 0.0002) are found within the low-pressure system(s) (at the 30-mbar pressure surface), while high values are found outside. Similar characteristics are found to exist for the simultaneously observed SAGE O3 and NO2 columnar density distributions. Strong longitudinal gradients are shown with the low values within and wherever the vortex exists. This characteristic is maintained during and after the circumpolar vortex is disturbed, even after breakdown, indicating an isolation of the material within the vortex.

Wang, P.-H.; Mccormick, M. P.

1985-01-01

210

Optical tweezers applied to a microfluidic system Jonas Enger, Mattias Goksr, Kerstin Ramser, Petter Hagberg and Dag Hanstorp*  

E-print Network

- osmotic flow can be used to control the transport of the cells together with their surrounding media.20. Lithographic methods were applied to create microchannels in rubber silicon (PDMS). Media were transported tweezers can be applied in automated single cell-sorting using peripheral blood as a model system.12

211

Estimating aerosol light-scattering enhancement from dry aerosol optical properties at different sites  

NASA Astrophysics Data System (ADS)

Microphysical and optical properties of aerosol particles are strongly dependent on the relative humidity (RH). Knowledge of the effect of RH on aerosol optical properties is of great importance for climate forcing calculations and for comparison of in-situ measurements with satellite and remote sensing retrievals. The scattering enhancement factor, f(RH), is defined as the ratio of the scattering coefficient at a high and reference RH. Predictive capability of f(RH) for use in climate models would be enhanced if other aerosol parameters could be used as proxies to estimate hygroscopic growth. Toward this goal, we explore the relationship between aerosol light-scattering enhancement and dry aerosol optical properties such as the single scattering albedo (SSA) and the scattering Ångström exponent (SAE) at multiple sites around the world. The measurements used in this study were conducted by the US Department of Energy at sites where different aerosol types predominate (pristine marine, polluted marine, dust dominated, agricultural and forest environments, among others). In all cases, the scattering enhancement decreases as the SSA decreases, that is, as the contribution of absorbing particles increases. On the other hand, for marine influenced environments the scattering enhancement clearly increases as the contribution of coarse particles increases (SAE decreases), evidence of the influence of hygroscopic coarse sea salt particles. For other aerosol types the relationship between f(RH) and SAE is not so straightforward. Combining all datasets, f(RH) was found to exponentially increase with SSA with a high correlation coefficient.

Titos, Gloria; Jefferson, Anne; Sheridan, Patrick; Andrews, Elisabeth; Lyamani, Hassan; Ogren, John; Alados-Arboledas, Lucas

2014-05-01

212

Validation of MODIS Aerosol Optical Depth Retrieval Over Land  

NASA Technical Reports Server (NTRS)

Aerosol optical depths are derived operationally for the first time over land in the visible wavelengths by MODIS (Moderate Resolution Imaging Spectroradiometer) onboard the EOSTerra spacecraft. More than 300 Sun photometer data points from more than 30 AERONET (Aerosol Robotic Network) sites globally were used in validating the aerosol optical depths obtained during July - September 2000. Excellent agreement is found with retrieval errors within (Delta)tau=+/- 0.05 +/- 0.20 tau, as predicted, over (partially) vegetated surfaces, consistent with pre-launch theoretical analysis and aircraft field experiments. In coastal and semi-arid regions larger errors are caused predominantly by the uncertainty in evaluating the surface reflectance. The excellent fit was achieved despite the ongoing improvements in instrument characterization and calibration. This results show that MODIS-derived aerosol optical depths can be used quantitatively in many applications with cautions for residual clouds, snow/ice, and water contamination.

Chu, D. A.; Kaufman, Y. J.; Ichoku, C.; Remer, L. A.; Tanre, D.; Holben, B. N.; Einaudi, Franco (Technical Monitor)

2001-01-01

213

A microfluidic system in combination with optical tweezers for analyzing rapid and reversible cytological alterations in single cells upon environmental changes.  

PubMed

We report on the development of an experimental platform where epi-fluorescence microscopy and optical tweezers are combined with a microfluidic system to enable the analysis of rapid cytological responses in single cells. The microfluidic system allows two different media to be merged in a Y-shaped channel. Microscale channel dimensions ensure purely laminar flow and, as a result, an environmental gradient can be created between the two media. Optical tweezers are used to move a single trapped cell repeatedly between the different environments. The cell is monitored continuously by fluorescence microscopy during the experiment. In a first experiment on yeast (Saccharomyces cerevisiae) we observed changes in cell volume as the cell was moved between environments with different osmolarity. This demonstrated that the platform allowed analysis of cytological alterations on a time scale shorter than 0.2 s. In a second experiment we observed the spatial migration of the Yap1p transcription factor fused to GFP as a cell was moved from an environment of low to high oxidative capacity. The system is universal allowing the response to numerous environmental changes to be studied on the sub second time scale in a variety of model cells. We intend to use the platform to study how the age of cells, their progression through the cell cycle, or their genetic landscape, alter their capacity (kinetics and amplitude) to respond to environmental changes. PMID:17180207

Eriksson, Emma; Enger, Jonas; Nordlander, Bodil; Erjavec, Nika; Ramser, Kerstin; Goksör, Mattias; Hohmann, Stefan; Nyström, Thomas; Hanstorp, Dag

2007-01-01

214

INDOEX aerosol optical depths and radiative forcing derived from AVHRR  

NASA Astrophysics Data System (ADS)

The Indian Ocean Experiment (INDOEX) had as a primary objective determining the radiative forcing due to anthropogenic aerosols over climatologically significant space and time scales: the Indian Ocean during the winter monsoon, January-March. During the winter monsoon, polluted, low-level air from the Asian subcontinent blows over the Arabian Sea and Indian Ocean. As part of INDOEX, aerosol optical depths were derived from Advanced Very High Resolution Radiometer (AVHRR) data for the cloud- free ocean regions. The AVHRR radiances were first calibrated using the interior zone of the Antarctic and Greenland ice sheets, which proved to be radiometrically stable calibration targets. Optical depths were derived by matching the observed radiances to radiances calculated for a wide range of optical depths and viewing geometry. Optical depths derived with the AVHRR were compared with those derived with NASA's Aerosol Robotic Network (AERONET) CIMEL instrument at the Center for Clouds, Chemistry, and Climate's Kaashidhoo Observatory, as well as with other surface and shipboard observations taken in the INDOEX region. The retrieved and surface- based optical depths agreed best for a new 2-channel, 2- aerosol model scheme in which the AVHRR observations at 0.64 and 0.84 microns were used to determine relative amounts of marine and polluted continental aerosol and then the resulting aerosol mixture was used to derive the optical depths. Broadband radiative transfer calculations for the mixture of marine and polluted continental aerosols were combined with the 0.64 and 0.84-micron AVHRR radiances to determine the radiative forcing due to aerosols in the INDOEX region. Monthly composites of aerosol optical depth and top of the atmosphere, surface, and atmospheric radiative forcing were derived from calibrated AVHRR radiances for January-March 1996-2000. An inter-annual variability in the magnitude and spatial extent of high value regions is noted for derived optical depths and radiative forcing, with highest values reached in 1999, particularly in the Bay of Bengal which during the IFP was covered by plumes from Indochina. Frequency distributions of the optical depth for 1° x 1° latitude-longitude regions are well represented by gamma distribution functions. The day-to-day and year-to-year variability of the optical depth for such regions is correlated with the long term average optical depth. Interannual variability of the monthly mean optical depths for such regions is found to be as large as the day to day.

Tahnk, William Richard

2001-08-01

215

A force measurement instrument for optical tweezers based on the detection of light momentum changes  

NASA Astrophysics Data System (ADS)

In this work, we present and discuss several developments implemented in an instrument that uses the detection of the light momentum change for measuring forces in an optical trap. A system based on this principle provides a direct determination of this magnitude regardless of the positional response of the sample under the effect of an external force, and it is therefore to be preferred when in situ calibrations of the trap stiffness are not attainable or are difficult to achieve. The possibility to obtain this information without relying upon a harmonic model of the force is more general and can be used in a wider range of situations. Forces can be measured on non-spherical samples or non-Gaussian beams, on complex and changing environments, such as the interior of cells, or on samples with unknown properties (size, viscosity, etc.). However, the practical implementation of the method entails some difficulties due to the strict conditions in the design and operation of an instrument based on this method. We have focused on some particularly conflicting points. We developed a process and a mechanism to determine and systematically set the correct axial position of the device. We further analyzed and corrected the non-uniform transmittance of the optical system and we finally compensated for the variations in the sensor responsivity with temperature. With all these improvements, we obtained an accuracy of ~5% in force measurements for samples of different kinds.

Farré, Arnau; Marsà, Ferran; Montes-Usategui, Mario

2014-09-01

216

Unzipping DNA with optical tweezers: high sequence sensitivity and force flips.  

PubMed Central

Force measurements are performed on single DNA molecules with an optical trapping interferometer that combines subpiconewton force resolution and millisecond time resolution. A molecular construction is prepared for mechanically unzipping several thousand-basepair DNA sequences in an in vitro configuration. The force signals corresponding to opening and closing the double helix at low velocity are studied experimentally and are compared to calculations assuming thermal equilibrium. We address the effect of the stiffness on the basepair sensitivity and consider fluctuations in the force signal. With respect to earlier work performed with soft microneedles, we obtain a very significant increase in basepair sensitivity: presently, sequence features appearing at a scale of 10 basepairs are observed. When measured with the optical trap the unzipping force exhibits characteristic flips between different values at specific positions that are determined by the base sequence. This behavior is attributed to bistabilities in the position of the opening fork; the force flips directly reflect transitions between different states involved in the time-averaging of the molecular system. PMID:11867467

Bockelmann, U; Thomen, Ph; Essevaz-Roulet, B; Viasnoff, V; Heslot, F

2002-01-01

217

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

218

Plasma etching of single fine particle trapped in Ar plasma by optical tweezers  

NASA Astrophysics Data System (ADS)

Physical and chemical interactions between plasmas and nano-featured surfaces are one important issue in the plasma processing. Here we optically trap single fine particle levitated at plasma/sheath boundary with an infrared laser to realize in-situ analysis of such interactions. We have measured time evolution of the diameter of the single fine particle in Ar plasma. The trapped particle was etched at an etching rate of 1 nm/min in Ar plasma. We also obtained a Raman peak at around 2950 cm-1 corresponding to C-H bonds in the single fine particle in Ar plasma. The results open a new possibility to observe directly interactions between plasma and single fine particle.

Ito, T.; Koga, K.; Yamashita, D.; Kamataki, K.; Itagaki, N.; Uchida, G.; Shiratani, M.

2014-06-01

219

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

220

Independent trapping and manipulation of microparticles using dexterous acoustic tweezers  

SciTech Connect

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., E-mail: c.r.p.courtney@bath.ac.uk [Department of Mechanical Engineering, University of Bath, Bath (United Kingdom); Demore, Christine E. M.; Wu, Hongxiao; Cochran, Sandy [Institute of Medical Science and Technology, University of Dundee, Dundee (United Kingdom); Grinenko, Alon; Wilcox, Paul D.; Drinkwater, Bruce W. [Department of Mechanical Engineering, University of Bristol, Bristol (United Kingdom)

2014-04-14

221

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

222

In situ optical measurements of hydrofluoric acid aerosols  

Microsoft Academic Search

HF aerosol measurements were obtained in a specially developed flow chamber with a cross-section of 8 Ã 16 feet, and approximately 140 feet long. The primary objective was to determine the extent of HF aerosol mist formation in a potential accidental release of HF. A newly developed in situ optical instrument (PCSV-P) was used to obtain on-line measurements of the

D. J. Holve; T. L. Harvill; K. W. Schatz; R. P. Koopman; NJ Princeton

1989-01-01

223

Magnetic Tweezers: Micromanipulation and Force Measurement at the Molecular Level  

Microsoft Academic Search

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

Charlie Gosse; Vincent Croquette

2002-01-01

224

Maritime component in aerosol optical models derived from Aerosol Robotic Network data  

NASA Astrophysics Data System (ADS)

Aerosol optical properties above the oceans vary considerably, depending on contributions of major aerosol components, i.e., urban/industrial pollution, desert dust, biomass burning, and maritime. The optical characterization of these aerosols is fundamental to the parameterization of radiative forcing models as well as to the atmospheric correction of ocean color imagery. We present a model of the maritime aerosol component derived using Aerosol Robotic Network (AERONET) data from three island locations: Bermuda (Atlantic Ocean), Lanai, Hawaii (Pacific Ocean), and Kaashidhoo, Maldives (Indian Ocean). To retrieve the maritime component, we have considered the data set with aerosol optical depth at a wavelength 500 nm less than 0.15 and Angstrom parameter ? less than 1. The inferred maritime component in the columnar size distribution, which was found to be very similar for the three study sites, is bimodal with a fine mode at an effective radius (reff) ˜ 0.11-0.14 ?m and a coarse mode reff of ˜1.8-2.1 ?m. The results are comparable with size distributions reported in the literature. The refractive index is spectrally independent and estimated to be 1.37-0.001i (single-scattering albedo is about 0.98), based on the single-component homogenous particle composition assumption. Fractional contributions of the fine and coarse modes to the computed ?a (500 nm) are within the range of ?fine ˜ 0.03-0.05 and ?coarse ˜ 0.05-0.06 correspondingly. Angstrom parameters vary from ˜0.8 to 1.0 computed in the UV-visible (340-670 nm) and from 0.4 to 0.5 estimated in the near IR (870-2130 nm) spectral ranges. Aerosol phase functions are very similar for all three sites considered. The maritime aerosol component presented in this paper can serve as a candidate model in atmospheric correction algorithms.

Smirnov, A.; Holben, B. N.; Dubovik, O.; Frouin, R.; Eck, T. F.; Slutsker, I.

2003-01-01

225

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

226

Optical extinction of highly porous aerosol following atmospheric freeze drying  

NASA Astrophysics Data System (ADS)

glassy particles are a potentially significant but unexplored component of atmospheric aerosol that can form by aerosol processing through the ice phase of high convective clouds. The optical properties of porous glassy aerosols formed from a freeze-dry cycle simulating freezing and sublimation of ice particles were measured using a cavity ring down aerosol spectrometer (CRD-AS) at 532 nm and 355 nm wavelength. The measured extinction efficiency was significantly reduced for porous organic and mixed organic-ammonium sulfate particles as compared to the extinction efficiency of the homogeneous aerosol of the same composition prior to the freeze-drying process. A number of theoretical approaches for modeling the optical extinction of porous aerosols were explored. These include effective medium approximations, extended effective medium approximations, multilayer concentric sphere models, Rayleigh-Debye-Gans theory, and the discrete dipole approximation. Though such approaches are commonly used to describe porous particles in astrophysical and atmospheric contexts, in the current study, these approaches predicted an even lower extinction than the measured one. Rather, the best representation of the measured extinction was obtained with an effective refractive index retrieved from a fit to Mie scattering theory assuming spherical particles with a fixed void content. The single-scattering albedo of the porous glassy aerosols was derived using this effective refractive index and was found to be lower than that of the corresponding homogeneous aerosol, indicating stronger relative absorption at the wavelengths measured. The reduced extinction and increased absorption may be of significance in assessing direct, indirect, and semidirect forcing in regions where porous aerosols are expected to be prevalent.

Adler, Gabriela; Haspel, Carynelisa; Moise, Tamar; Rudich, Yinon

2014-06-01

227

Relationship between chemical transformations and optical properties of aerosols  

NASA Astrophysics Data System (ADS)

The optical properties of complex aerosols, important in determining their radiative forcing in the atmosphere and, subsequently, their impact on climate, are extensively examined. There is an abundance of natural and anthropogenic organic compounds in the atmosphere that can be released as primary aerosols or form secondary organic aerosols (SOAs) via photocchemical reactions with OH, NO3, and O3. SOAs can undergo further processing in the atmosphere with oxidative species, changing the chemical, physical, and optical properties of the particles. Absorbing aerosol components include nitrated aromatics, aromatic polycarboxylic acids, phenols, polycyclic aromatic hydrocarbons, and nitrated inorganics. Many of these species have been found in atmospheric particles. Some of them are strong absorbers at long UV wavelengths. Such aerosols may affect downward UV irradiances in urban location and may be important for predicting smog evolution in urban areas. It is possible that such species can form by reactions of NOx with organic aerosols. Using cavity ring down spectrometry and aerosol mass spectrometry we show for the first time that after exposure to NOx, aerosols coated by PAHs undergo a large change in the extinction efficiency as a result of a chemical reaction. The main product peak is mononitrated-BaP (m/z 267 and m/z 297). Its product formation is accompanied by a subsequent decrease in reactant peak (m/z 252), which appears to be mirrored by the increase in Qext with time. This study supports Mark Jacobson’s suggestion that aerosol aging downwind from urban location due to the coupling with NOx chemistry may lead to increased light extinction due to more absorption at longer wavelengths. This process may have implications for regional processes.

Lu, J.; Rudich, Y.; Flores, M.

2010-12-01

228

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

229

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

230

optical tweezers tractor beams  

E-print Network

. and Ormos P., Appl Phys Lett, 78, 249­251, 2001. plane polarized + static movies movie movie #12;sorting P.C. Splading and K. Dholakia, Nature 426, 421 (2003) protein capsules (2 and 4 ) #12;beyond plane waves

231

In situ optical measurements of hydrofluoric acid aerosols  

SciTech Connect

HF aerosol measurements were obtained in a specially developed flow chamber with a cross-section of 8 {times} 16 feet, and approximately 140 feet long. The primary objective was to determine the extent of HF aerosol mist formation in a potential accidental release of HF. A newly developed in situ optical instrument (PCSV-P) was used to obtain on-line measurements of the aerosol. A total of 86 usable aerosol data sets were obtained during the test period. As many as 10 data sets were acquired for an 11 minute duration HF release. Briefly summarizing the results, the PCSV-P measured predominately submicron aerosols at the exit of the sharp-edged orifice. The aerosol then grew to larger particles at the outlet of the flow chamber. This result points to the formation of an aerosol through vaporization-condensation as opposed to a conventional shear spray. Temperature, humidity, release pressure, radial position in the plume, and type of acid did not appear to have an significant effect in the measured size distributions for the range of conditions investigated. 7 refs., 23 figs., 2 tabs.

Holve, D.J.; Harvill, T.L.; Schatz, K.W.; Koopman, R.P. (INSITEC, San Ramon, CA (USA); Mobil Research and Development Corp., Princeton, NJ (USA); Lawrence Livermore National Lab., CA (USA))

1989-09-01

232

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

233

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

234

The deconvolution of aerosol backscattered optical pulses to obtain system-independent aerosol signatures  

NASA Astrophysics Data System (ADS)

Means are discussed for extracting system-independent aerosol signatures from aerosol backscatter measurements obtained with a specific pencil beam active optical detection system. Such signatures are required before the backscatter data can be applied to various proposed optical fuze designs for determining their aerosol vulnerability and to the investigation of aerosol discrimination schemes. The measurement system, which has been used in numerous experiments to probe such aerosols as weather clouds and military smokes, is a short pulse GaAs laser probe (pulse width + or - 10 nanoseconds whose range sensitivity extends from near the system to beyond 10 meters. A computationally fast numerical deconvolution algorithm is devised together with a comprehensive supporting analysis. Both indicate that severe signal-to-noise ratio constraints apply to the achievement of meaningful superresolution. While the signal-to-noise ratios typical of recent measurements are likely to satisfy the severe constraints discovered, many of the earlier data are too noisy and thus require other signature determination methods.

McGuire, D.; Conner, M.

1981-06-01

235

Correction to “Hyperspectral Aerosol Optical Depths from TCAP Flights”  

SciTech Connect

In the paper “Hyperspectral aerosol optical depths from TCAP flights” by Y. Shinozuka et al. (Journal of Geophysical Research: Atmospheres, 118, doi:10.1002/2013JD020596, 2013), Tables 1 and 2 were published with the column heads out of order. Tables 1 and 2 are published correctly here. The publisher regrets the error.

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.

2014-02-16

236

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

237

Role of Aerosols in Governing Optical Depth of Marine Low-level Clouds  

Microsoft Academic Search

Marine low-level clouds have a significant cooling effect on the earth radiation budget. Their optical properties are influenced by aerosols through complex interactions involving aerosol properties as initial condensation nuclei (CN), increases in CN concentration due to anthropogenic activities, aerosol activation to cloud droplets, and cloud dynamics. The aerosol indirect effect on global climate change by altering cloud microphysics is

Y. Feng; V. Ramanathan

2006-01-01

238

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

239

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

240

Improving Radiative Assessments of Aerosol Chemical, Physical and Optical Properties Through Aerosol Volatility Studies Over Optically Effective Sizes  

Microsoft Academic Search

In order to interpret in-situ and satellite observations of complex aerosol mixtures such as those encountered during ACE-ASIA and TRACE-P as well as to model them, optical effects due to each component of particles in a given size needs to be determined. Here we present recently refined techniques applied to particles with optically effective sizes over 0.1 - 14 mum.

Y. Shinozuka; A. Clarke; S. Howell; V. Kapustin

2002-01-01

241

Effect of black carbon on the optical properties and climate forcing of sulfate aerosols  

Microsoft Academic Search

We study the optical properties of anthropogenic sulfate aerosols containing black carbon using a recently developed exact solution of the scattering problem for a spherical particle (sulfate aerosol) containing an eccentrically located spherical inclusion (black carbon). We present the expression for the change of planetary albedo due to addition of an absorbing, but optically thin aerosol layer and estimate the

Petr Chýlek; Gorden Videen; Dat Ngo; Ronald G. Pinnick; James D. Klett

1995-01-01

242

Diurnal variability of dust aerosol optical thickness and Angstrom exponent over dust source regions in China  

E-print Network

Diurnal variability of dust aerosol optical thickness and Angstro¨m exponent over dust source of Sunphotometer Aerosol Optical Thickness (AOT) data collected near the Taklamakan and Gobi dust source regions (Dunhuang, 40.09°N, 94.41°E) in China; we examine the diurnal and seasonal change of dust aerosol properties

Wang, Jun

243

Investigation of aerosol optical properties for remote sensing through DRAGON (distributed regional aerosol gridded observation networks) campaign in Korea  

NASA Astrophysics Data System (ADS)

Aerosols in the atmosphere, including dust and pollutants, scatters/absorbs solar radiation and change the microphysics of clouds, thus influencing the Earth's energy budget, climate, air quality, visibility, agriculture and water circulation. Pollutants have also been reported to threaten the human health. The present research collaborated with the U.S. NASA and the U.S. Aerosol Robotic Network (AERONET) is to study the aerosol characteristics in East Asia and improve the long-distance transportation monitoring technology by analyzing the observations of aerosol characteristics in East Asia during Distributed Regional Aerosol Gridded Observation Networks (DRAGON) Campaign (March 2012-May 2012). The sun photometers that measure the aerosol optical characteristics were placed evenly throughout the Korean Peninsula and concentrated in Seoul and the metropolitan area. Observation data are obtained from the DRAGON campaign and the first year (2012) observation data (aerosol optical depth and aerosol spatial distribution) are analyzed. Sun photometer observations, including aerosol optical depth (AOD), are utilized to validate satellite observations from Geostationary Ocean Color Imager (GOCI) and Moderate Resolution Imaging Spectroradiometer (MODIS). Additional analysis is performed associated with the Northeast Asia, the Korean Peninsula in particular, to determine the spatial distribution of the aerosol.

Lim, Jae-Hyun; Ahn, Joon Young; Park, Jin-Soo; Hong, You-Deok; Han, Jin-Seok; Kim, Jhoon; Kim, Sang-Woo

2014-11-01

244

Derivation of Aerosol Columnar Mass from MODIS Optical Depth  

NASA Technical Reports Server (NTRS)

In order to verify performance, aerosol transport models (ATM) compare aerosol columnar mass (ACM) with those derived from satellite measurements. The comparison is inherently indirect since satellites derive optical depths and they use a proportionality constant to derive the ACM. Analogously, ATMs output a four dimensional ACM distribution and the optical depth is linearly derived. In both cases, the proportionality constant requires a direct intervention of the user by prescribing the aerosol composition and size distribution. This study introduces a method that minimizes the direct user intervention by making use of the new aerosol products of MODIS. A parameterization is introduced for the derivation of columnar aerosol mass (AMC) and CCN concentration (CCNC) and comparisons between sunphotometer, MODIS Airborne Simulator (MAS) and in-measurements are shown. The method still relies on the scaling between AMC and optical depth but the proportionality constant is dependent on the MODIS derived r$_{eff}$,\\eta (contribution of the accumulation mode radiance to the total radiance), ambient RH and an assumed constant aerosol composition. The CCNC is derived fkom a recent parameterization of CCNC as a function of the retrieved aerosol volume. By comparing with in-situ data (ACE-2 and TARFOX campaigns), it is shown that retrievals in dry ambient conditions (dust) are improved when using a proportionality constant dependent on r$ {eff}$ and \\eta derived in the same pixel. In high humidity environments, the improvement inthe new method is inconclusive because of the difficulty in accounting for the uneven vertical distribution of relative humidity. Additionally, two detailed comparisons of AMC and CCNC retrieved by the MAS algorithm and the new method are shown. The new method and MAS retrievals of AMC are within the same order of magnitude with respect to the in-situ measurements of aerosol mass. However, the proposed method is closer to the in-situ measurements than the MODIS retrievals. The retrievals of CCNC are also within the same order of magnitude for both methods. The new method is applied to an actual MODIS retrieval and although no in-situ data is available to compare, it is shown that the proposed method yields more credible values than the MODIS retrievals. In addition, recent data available from the PRIDE (Puerto Rico Dust Experiment, July 2000) will be shown by comparing sunphotometer, MODIS and in-situ data.

Gasso, Santiago; Hegg, Dean A.

2003-01-01

245

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

246

Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements  

Microsoft Academic Search

Sensitivity studies are conducted regarding aerosol optical property retrieval from radiances measured by ground-based Sun-sky scanning radiometers of the Aerosol Robotic Network (AERONET). These studies focus on testing a new inversion concept for simultaneously retrieving aerosol size distribution, complex refractive index, and single-scattering albedo from spectral measurements of direct and diffuse radiation. The perturbations of the inversion resulting from random

O. Dubovik; A. Smirnov; B. N. Holben; M. D. King; Y. J. Kaufman; T. F. Eck; I. Slutsker

2000-01-01

247

Investigating Molecular Level Stress-Strain Relationships in Entangled F-Actin Networks by Combined Force-Measuring Optical Tweezers and Fluorescence Microscopy  

NASA Astrophysics Data System (ADS)

Actin is an important cytoskeletal protein involved in cell structure and motility, cancer invasion and metastasis, and muscle contraction. The intricate viscoelastic properties of filamentous actin (F-actin) networks allow for the many dynamic roles of actin, thus warranting investigation. Exploration of this unique stress-strain/strain-rate relationship in complex F-actin networks can also improve biomimetic materials engineering. Here, we use optical tweezers with fluorescence microscopy to study the viscoelastic properties of F-actin networks on the microscopic level. Optically trapped microspheres embedded in various F-actin networks are moved through the network using a nanoprecision piezoelectric stage. The force exerted on the microspheres by the F-actin network and subsequent force relaxation are measured, while a fraction of the filaments in the network are fluorescent-labeled to observe filament deformation in real-time. The dependence of the viscoelastic properties of the network on strain rates and amplitudes as well as F-actin concentration is quantified. This approach provides the much-needed link between induced force and deformation over localized regimes (tens of microns) and down to the single molecule level.

Lee, Kent; Henze, Dean; Robertson-Anderson, Rae M.

2013-03-01

248

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

249

Quantifying Aerosol Direct Effects from Broadband Irradiance and Spectral Aerosol Optical Depth Observations  

SciTech Connect

We 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

2014-05-16

250

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

251

Aerosol physical and optical properties and their relationship to aerosol composition in the free troposphere at Izaña, Tenerife, Canary Islands, during July 1995  

Microsoft Academic Search

Aerosol physical, optical, and chemical properties were measured at 2360 m above sea level over the Canary Islands during July 1995. Five aerosol size modes were observed. Nucleation aerosols 160 Mm-1 at relative humidities <30%. The lowest scattering was in air masses from the northwest whose aerosols were mostly pollutants. Air masses with North African mineral dust had the highest

H. Maring; D. L. Savoie; M. A. Izaguirre; C. McCormick; R. Arimoto; J. M. Prospero; C. Pilinis

2000-01-01

252

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

253

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

254

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 in aerosol properties at these locations. In this study, we present the results of a trend analysis at selected stations with long data records. In addition to commonly studied parameters such as aerosol optical depth (AOD) and Ångström exponent (AE), we also focus on inversion products including absorption aerosol optical depth (ABS), single-scattering albedo (SSA) and the absorption Ångström exponent (AAE). Level 2.0 quality assured data are the primary source. However, due to the scarcity of level 2.0 inversion products resulting from the strict AOD quality control threshold, we have also analyzed level 1.5 data, with some quality control screening to provide a reference for global results. Two statistical methods are used to detect and estimate the trend: the Mann-Kendall test associated with Sen's slope and linear least-squares fitting. The results of these statistical tests 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, while significant (>90%) increases in these two parameters are found for North India and the Arabian Peninsula. The AE trends turn out to be different for North America and Europe, with increases for the former and decreases for the latter, suggesting opposite changes in fine/coarse-mode fraction. For level 2.0 inversion parameters, Beijing and Kanpur both experienced an increase in SSA. Beijing also shows a reduction in ABS, while the SSA increase for Kanpur is mainly due the increase in scattering aerosols. Increased absorption and reduced SSA are found at Solar_Village. At level 1.5, most European and North American sites also show positive SSA and negative ABS trends, although the data are more uncertain. The AAE trends are less spatially coherent due to large uncertainties, except for a robust increase at three sites in West Africa, which suggests a possible reduction in black carbon. Overall, the trends do not exhibit obvious seasonality for the majority of parameters and stations.

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

2014-11-01

255

Optical conveyors: Active tractor beams for colloids, emulsions and aerosols  

NASA Astrophysics Data System (ADS)

A tractor beam is a travelling wave that transports material back to its source. We experimentally demonstrate such a beam by coherently superposing coaxial Bessel beams. These optical conveyors have periodic intensity variations along their axes that act as highly effective optical traps for micrometer-scale objects. Varying the Bessel beams' relative phase shifts the traps axially and thereby selectively transports trapped objects either downstream or upstream along the length of the beam. The same methods used to project a single optical conveyor can project arrays of independent optical conveyors, allowing bidirectional motion. This opens up new possibilities for three dimensional transport of colloids, emulsion droplets and aerosol particles with sub-micrometer resolution over ranges extending to 50 micrometers and potentially beyond.

Ruffner, David; Grier, David

2013-03-01

256

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 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 Morocco Niger Nigeria Senegal Sierra Leone Togo Tunisia Western Sahara #12;Southern Africa MISR vs AERONET

Frank, Thomas D.

257

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

258

Intensive Airborne and Surface Measurements of Aerosol Microphysical and Optical Properties and Influences on Shortwave Radiation  

NASA Astrophysics Data System (ADS)

Knowledge of pertinent aerosol optical properties (e.g. optical thickness, single scatter albedo, backscatter fraction) is required to accurately calculate aerosol forcing. The Department of Energy (DOE) Atmospheric Radiation Measurement (ARM) program has been systematically measuring aerosol properties at the surface and limited measurements aloft from light aircraft. Lidar and airborne in-situ measurements show that much of the aerosol at the ARM Southern Great Plains (SGP) site is aloft, often in layers decoupled from the surface, raising questions of the representativeness of surface aerosol properties for such calculations. Initial comparisons of aerosol optical thickness and aerosol extinction, two key aerosol properties, have revealed discrepancies among the lidar, Sun photometer, and airborne in situ measurements. Detailed measurements of aerosol optical properties are required to resolve these discrepancies, as well as to more completely characterize the aerosol optical, microphysical, and chemical properties at the surface and above the SGP site required for accurately computing radiative fluxes. Such well-characterized data would permit a more detailed evaluation of the performance of radiative transfer models to compute flux profiles and heating rates. In an effort to acquire these data, ARM will conduct an Aerosol Intensive Operational Period (IOP) in May 2003 at the ARM Southern Great Plains (SGP) site in north central Oklahoma. This experiment will use ground and airborne measurements of aerosol absorption, scattering, and extinction over the ARM SGP site to characterize the routine ARM aerosol measurements, and help resolve differences between measurements and models of diffuse irradiance at the surface. The assessments of aerosol optical thickness and aerosol absorption will be carried out in conjunction with measurements of downwelling direct and diffuse irradiance as a function of wavelength and altitude. The IOP will carry out a variety of closure experiments on aerosol optical properties and their radiative influence. Measurements of the aerosol chemical composition and size distribution will allow testing of the ability to reconstruct optical properties from these measurements. Additional effort will be directed toward measurement of cloud condensation nucleus concentration as a function of supersaturation and relating CCN concentration to aerosol composition and size distribution. This relation is central to description of the aerosol indirect effect. This poster describes the airborne and surface instruments that will be used in this IOP and the use of these data to conduct specific closure experiments relating to aerosol optical properties, radiative fluxes, and cloud condensation nuclei.

Ferrare, R. A.; Schwartz, S.; Ogren, J.; Schmid, B.; Ghan, S.; Daum, P.; Feingold, G.

2002-12-01

259

Hygroscopic and optical properties of organic sea salt aerosol and consequences for climate forcing  

E-print Network

by the evaporation of sea spray from wind induced white caps, sea salt occurs in aerosol with diameter Dp > 0.13 mmHygroscopic and optical properties of organic sea salt aerosol and consequences for climate forcing of incoming solar radiation by sea salt aerosol is strongly dependent on relative humidity (RH) since

Russell, Lynn

260

Nephelometer derived and directly measured aerosol optical depth of the atmospheric boundary layer  

Microsoft Academic Search

The aerosol optical depth of the atmospheric boundary layer was determined both from direct solar irradiance measurements and from vertical extrapolation of ground-based nephelometry, during a period with cloudless skies and high aerosol mass loadings in the Netherlands. The vertical profile of the aerosol was obtained from lidar measurements. From humidity controlled nephelometry at the ground and humidity profiles from

J. P. Veefkind; J. C. H. van der Hage; H. M. ten Brink

1996-01-01

261

Optical and microphysical properties of atmospheric aerosols in Moldova  

NASA Astrophysics Data System (ADS)

Measurements of aerosol properties in Kishinev, Moldova are being carried out within the framework of the international AERONET program managed by NASA/GSFC since 1999. Direct solar and sky diffuse radiances are measured by using of sunphotometer Cimel-318. Aerosol optical properties are retrieved from measured radiances by using of smart computational procedures developed by the AERONET's team. The instrument is situated at the ground-based solar radiation monitoring station giving the opportunity to make simultaneous spectral (win sunphotometer) and broadband (with the set of sensors from radiometric complex) solar radiation. Detailed description of the station and investigations in progress can be found at the http://arg.phys.asm.md. Ground station is placed in an urban environment of Kishinev city (47.00N; 28.56E; 205 m a.s.l). Summary of aerosol optical and microphysical properties retrieved from direct solar and diffuse sky radiance observations at Moldova site from September 1999 to June 2009 are presented below. Number of measurements (total): 1695 Number of measurements (for ?o, n, k): 223 Range of aerosol optical depth (AOD) @440 nm: 0.03 < ?(440) < 2.30, < ?(440)>=0.25 Range of Ångström parameter < ?440_870 >: 0.14 < ? < 2.28 Asymmetry factor (440/670/870/1020): 0.70/0.63/0.59/0.58 ±0.04 Refraction (n) and absorption (k) indices@440 nm: 1.41 ± 0.06; 0.009 ± 0.005 Single scattering albedo < ?o >(440/670/870/1020): 0.93/0.92/0.90/0.89 ±0.04 Parameters of volume particle size distribution function: (fine mode) volume median radius r v,f , ?m: 0.17 ± 0.06 particle volume concentration Cv,f, ?m3/?m2: 0.04 ± 0.03 (coarse mode) volume median radius rv,c , ?m: 3.08 ± 0.64 particle volume concentration Cv,c, ?m3/?m2: 0.03 ± 0.03 Climatic norms of AOD@500 nm and Ångström parameter < ?440_870 > at the site of observation are equal to 0.21 ± 0.06 and 1.45 ± 0.14, respectively. The aerosol type in Moldova may be considered as 'urban-industrial and mixed' in accordance with the classification of aerosol type models systematized and developed by AERONET team (O.Dubovik et al., 2002, J. Atmosph. Sci., 59, 590-608) on the basis of datasets acquired from worldwide observations at the network of sunphotometers. It should be noted the presence of increased value of absorption index and reduced values of albedo. This may be due to influence of absorptive aerosols (soot). These aerosols are originated from local dust sources and exhausts from intensive urban traffic, from sources of biomass and household garbage burning both in and around the city, and from long-range transport over regions with high loading of aerosols (dust, smoke).

Aculinin, Alexandr; Smicov, Vladimir

2010-05-01

262

Optoelectronic tweezers for microparticle and cell manipulation  

NASA Technical Reports Server (NTRS)

An optical image-driven light induced dielectrophoresis (DEP) apparatus and method are described which provide for the manipulation of particles or cells with a diameter on the order of 100 .mu.m or less. The apparatus is referred to as optoelectric tweezers (OET) and provides a number of advantages over conventional optical tweezers, in particular the ability to perform operations in parallel and over a large area without damage to living cells. The OET device generally comprises a planar liquid-filled structure having one or more portions which are photoconductive to convert incoming light to a change in the electric field pattern. The light patterns are dynamically generated to provide a number of manipulation structures that can manipulate single particles and cells or groups of particles/cells. The OET preferably includes a microscopic imaging means to provide feedback for the optical manipulation, such as detecting position and characteristics wherein the light patterns are modulated accordingly.

Wu, Ming Chiang (Inventor); Chiou, Pei Yu (Inventor); Ohta, Aaron T. (Inventor)

2009-01-01

263

Accuracy assessments of aerosol optical properties retrieved from Aerosol Robotic Network (AERONET) Sun and sky radiance measurements  

NASA Astrophysics Data System (ADS)

Sensitivity studies are conducted regarding aerosol optical property retrieval from radiances measured by ground-based Sun-sky scanning radiometers of the Aerosol Robotic Network (AERONET). These studies focus on testing a new inversion concept for simultaneously retrieving aerosol size distribution, complex refractive index, and single-scattering albedo from spectral measurements of direct and diffuse radiation. The perturbations of the inversion resulting from random errors, instrumental offsets, and known uncertainties in the atmospheric radiation model are analyzed. Sun or sky channel miscalibration, inaccurate azimuth angle pointing during sky radiance measurements, and inaccuracy in accounting for surface reflectance are considered as error sources. The effects of these errors on the characterization of three typical and optically distinct aerosols with bimodal size distributions (weakly absorbing water-soluble aerosol, absorbing biomass-burning aerosol, and desert dust) are considered. The aerosol particles are assumed in the retrieval to be polydispersed homogeneous spheres with the same complex refractive index. Therefore we also examined how inversions with such an assumption bias the retrievals in the case of nonspherical dust aerosols and in the case of externally or internally mixed spherical particles with different refractive indices. The analysis shows successful retrieval of all aerosol characteristics (size distribution, complex refractive index, and single-scattering albedo), provided the inversion includes the data combination of spectral optical depth together with sky radiances in the full solar almucantar (with angular coverage of scattering angles up to 100° or more). The retrieval accuracy is acceptable for most remote sensing applications even in the presence of rather strong systematic or random uncertainties in the measurements. The major limitations relate to the characterization of low optical depth situations for all aerosol types, where high relative errors may occur in the direct radiation measurements of aerosol optical depth. Also, the results of tests indicate that a decrease of angular coverage of scattering (scattering angles of 75° or less) in the sky radiance results in the loss of practical information about refractive index. Accurate azimuth angle pointing is critical for the characterization of dust. Scattering by nonspherical dust particles requires special analysis, whereby approximation of the aerosol by spheres allows us to derive single-scattering albedo by inverting spectral optical depth together with sky radiances in the full solar almucantar. Inverting sky radiances measured in the first 40° scattering angle only, where nonspherical effects are minor, results in accurate retrievals of aerosol size distributions of nonspherical particles.

Dubovik, O.; Smirnov, A.; Holben, B. N.; King, M. D.; Kaufman, Y. J.; Eck, T. F.; Slutsker, I.

2000-04-01

264

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

265

Relations between Optically Derived Aerosol Parameters, Humidity, and Air-Quality Data in an Urban Atmosphere.  

NASA Astrophysics Data System (ADS)

This paper deals with diurnal and mensual correlations between ground-based atmospheric observations of columnar and surface optical parameters, standard surface humidity parameters, and surface air-quality data. The implications of a significant portion of small, Rayleigh-free optical depths being attributable to continuum water vapor absorption are analyzed in terms of the impact on the computation of aerosol optical depth and Ångström spectral coefficients in relatively clear atmospheres. Multiwavelength correlation analysis between aerosol optical depth and precipitable water indicators (surface vapor pressure or vertically integrated precpitable water) yielded a systematic, inverse-wavelength type of dependency in the extracted slopes (apparent attenuation coefficients) that was suggestive of a simple correlation between precipitable water and the accumulation-mode number density of the aerosols. On a diurnal basis, increasing trends in aerosol optical depth were negatively correlated with surface relative humidity and thus resulted either from variations in the nature or abundance of dry aerosol or possibly from convection-induced increases in relative humidity at higher altitudes in the aerosol scattering layer. The diurnal trend in aerosol optical depth plus the limited correlation between surface volume extinction coefficients derived from visibility measurements and relative humidity indicated that the aerosol optical scale height, on a diurnal basis, varied in an inverse fashion with surface relative humidity. Correlations between diurnally averaged aerosol optical depths and 24-h averaged surface sulfate measurements indicated the potential of satellite-based pollution monitoring using passive remote sensing data.

O'Neill, N. T.; Royer, A.; Coté, P.; McArthur, L. J. B.

1993-09-01

266

Optical Properties of Smoke Aerosol Over Los Alamos, New Mexico, Derived From AERONET  

NASA Astrophysics Data System (ADS)

Significant amounts of atmospheric aerosols are annually generated from wildfires and biomass burning events. Smoke aerosol, from biomass combustion, is a leading source of natural and anthropogenic pollution affecting Earth's radiation budget. Recent improvements in the detailed knowledge of smoke aerosol optical properties have reduced uncertainties in the role of biomass burning on climate forcing. The increase in smoke aerosol knowledge has been largely advanced with data acquired through the global network of AERONET (http://aeronet.gsfc.nasa.gov/index.html) sun/sky radiometers. Previous studies using AERONET data have revealed variability in smoke aerosol properties generated from different biomes throughout the world. Here we present AERONET measurements over Los Alamos, New Mexico to assess the influence of smoke aerosol over a region where seasonal variations in biomass burning occur regularly and research on smoke aerosol properties has remained minimal. During June of 2005, a series of wildfires resulted in heavy aerosol loading throughout the Southwestern United States. Significant variations in aerosol optical thickness were observed during this period over the Los Alamos AERONET site (35.87 N, 106.33 W). Computed back trajectories using the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model (https://www.arl.noaa.gov/ready/hysplit4.html) revealed advection of smoke aerosol from fire sites in Arizona, Nevada, Utah, and New Mexico. Aerosol optical depth, size distribution, and single scattering albedo measurements from AERONET at Los Alamos were analyzed for this period and compared to periods not dominated by the presence of smoke aerosol. Results indicated that the influence of smoke aerosol increased aerosol optical thickness by a factor of five at 440nm, and resulted in bimodal size distributions dominated by fine mode accumulation particles. Single scattering albedo values were typically .95 on days dominated by smoke aerosol. Relationships among single scattering albedo and size distributions will be further discussed.

Altmann, G.; Henderson, B.; Dubey, M.; Petr, C.; Porch, W.

2005-12-01

267

Radiative Effects of Dust Aerosols, Natural Cirrus Clouds and Contrails: Broadband Optical Properties and Sensitivity Studies  

E-print Network

This dissertation aims to study the broadband optical properties and radiative effects of dust aerosols and ice clouds. It covers three main topics: the uncertainty of dust optical properties and radiative effects from the dust particle shape...

Yi, Bingqi

2013-07-09

268

Aerosols optical depth enhancement in presence of clouds  

NASA Astrophysics Data System (ADS)

Moderate Resolution Imaging Spectrometer (MODIS) observations at 550 nm are used to estimate aerosol optical depth (AOD) enhancement in presence of clouds. Daily 10x10 km observations from eleven years of MODIS-Terra (MOD04_L2) are processed to determine the enhancement defined as the difference between AOD at high (0.8-0.9) and low (0.1-0.2) cloud fraction (CF). The analysis is performed globally over the oceans at 2.5degx2.5deg resolution. First results indicate that the enhancement in AOD is observed in the presence of higher cloud fraction. The elevated AOD at higher CF is not distributed uniformly but shows regional and latitudinal patterns in different seasons. The highest enhancement in AOD is observed near the aerosol source regions indicating that the source of this enhancement is less likely due to cloud contamination. The spring (MAM) and summer (JJA) seasons show higher enhancement in AOD over the northern hemisphere. The normalized enhancement in AOD at these CF is highest in the tropics and subtropics. We hypothesize that the most of the enhancement in AOD is a result of the hygroscopic swelling of the aerosol in the relatively more humid air accompanying partially cloudy conditions. Since the MODIS AOD observations are widely used for climate research and other applications, a consideration of these cloud-dependent enhancements can help improve our understanding on aerosol-cloud interactions. Seasonal and geographical variations in AOD in the presence of low and high CFs will be studied and possible explanations using models will be discussed.

Chand, D.; Wang, M.; Ghan, S.; Ovchinnikov, M.; McFarlane, S.; Riihimaki, L.; Wood, R.

2011-12-01

269

The Smallest Tweezers in the World  

ERIC Educational Resources Information Center

A pair of fine tweezers and a steady hand may well be enough to pick up a grain of sand, but what would you use to hold something hundreds of times smaller still, the size of only one micron? The answer is to use a device that is not mechanical in nature but that relies instead on the tiny forces that light exerts on small particles: "optical

Lewalle, Alexandre

2008-01-01

270

Two steps forward, one step back: determining XPD helicase mechanism by single-molecule fluorescence and high-resolution optical tweezers  

PubMed Central

XPD-like helicases constitute a prominent DNA helicase family critical for many aspects of genome maintenance. These enzymes share a unique structural feature, an auxiliary domain stabilized by an iron-sulphur (FeS) cluster, and a 5?-3? polarity of DNA translocation and duplex unwinding. Biochemical analyses alongside two single-molecule approaches, total internal reflection fluorescence microscopy and high-resolution optical tweezers, have shown how the unique structural features of XPD helicase and its specific patterns of substrate interactions tune the helicase for its specific cellular function and shape its molecular mechanism. The FeS domain forms a duplex separation wedge and contributes to an extended DNA binding site. Interaction within this site position the helicase in an orientation to unwind the duplex, control the helicase rate, and verify the integrity of the translocating strand. Consistent with its cellular role, processivity of XPD is limited and is defined by an idiosyncratic stepping kinetics. DNA duplex separation occurs in single base pair steps punctuated by frequent backward steps and conformational rearrangements of the protein-DNA complex. As such, the helicase in isolation mainly stabilizes spontaneous base pair opening and exhibits a limited ability to unwind stable DNA duplexes. The presence of a cognate ssDNA binding protein converts XPD into a vigorous helicase by destabilizing the upstream dsDNA as well as by trapping the unwound strands. Remarkably, the two proteins can co-exist on the same DNA strand without competing for binding. The current model of the XPD unwinding mechanism will be discussed along with possible modifications to this mechanism by the helicase interacting partners and unique features of such bio-medically important XPD-like helicases as FANCJ (BACH1), RTEL1 and CHLR1 (DDX11). PMID:24560558

Spies, Maria

2014-01-01

271

Two steps forward, one step back: determining XPD helicase mechanism by single-molecule fluorescence and high-resolution optical tweezers.  

PubMed

XPD-like helicases constitute a prominent DNA helicase family critical for many aspects of genome maintenance. These enzymes share a unique structural feature, an auxiliary domain stabilized by an iron-sulphur (FeS) cluster, and a 5'-3' polarity of DNA translocation and duplex unwinding. Biochemical analyses alongside two single-molecule approaches, total internal reflection fluorescence microscopy and high-resolution optical tweezers, have shown how the unique structural features of XPD helicase and its specific patterns of substrate interactions tune the helicase for its specific cellular function and shape its molecular mechanism. The FeS domain forms a duplex separation wedge and contributes to an extended DNA binding site. Interactions within this site position the helicase in an orientation to unwind the duplex, control the helicase rate, and verify the integrity of the translocating strand. Consistent with its cellular role, processivity of XPD is limited and is defined by an idiosyncratic stepping kinetics. DNA duplex separation occurs in single base pair steps punctuated by frequent backward steps and conformational rearrangements of the protein-DNA complex. As such, the helicase in isolation mainly stabilizes spontaneous base pair opening and exhibits a limited ability to unwind stable DNA duplexes. The presence of a cognate ssDNA binding protein converts XPD into a vigorous helicase by destabilizing the upstream dsDNA as well as by trapping the unwound strands. Remarkably, the two proteins can co-exist on the same DNA strand without competing for binding. The current model of the XPD unwinding mechanism will be discussed along with possible modifications to this mechanism by the helicase interacting partners and unique features of such bio-medically important XPD-like helicases as FANCJ (BACH1), RTEL1 and CHLR1 (DDX11). PMID:24560558

Spies, Maria

2014-08-01

272

Optical modeling of aerosol extinction for remote sensing in the marine environment  

NASA Astrophysics Data System (ADS)

A microphysical model is presented for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01-100 ?m particles in different geographic sites. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of the ASDF and its dependence on meteorological parameters, altitudes above sea level (H), fetch (X), wind speed (U) and relative humidity (RH) are investigated. The spectral profiles of the aerosol extinction coefficients calculated by MaexPro (Marine Aerosol Extinction Profiles) are in good agreement with observational data and the numerical results obtained from the Navy Aerosol Model (NAM) and the Advanced Navy Aerosol Model (ANAM). Moreover, MaexPro was found to be an accurate and reliable tool for investigation of the optical properties of atmospheric aerosols.

Kaloshin, G. A.

2013-05-01

273

Influence of Observed Diurnal Cycles of Aerosol Optical Depth on Aerosol Direct Radiative Effect  

NASA Technical Reports Server (NTRS)

The diurnal variability of aerosol optical depth (AOD) can be significant, depending on location and dominant aerosol type. However, these diurnal cycles have rarely been taken into account in measurement-based estimates of aerosol direct radiative forcing (ADRF) or aerosol direct radiative effect (ADRE). The objective of our study was to estimate the influence of diurnal aerosol variability at the top of the atmosphere ADRE estimates. By including all the possible AERONET sites, we wanted to assess the influence on global ADRE estimates. While focusing also in more detail on some selected sites of strongest impact, our goal was to also see the possible impact regionally.We calculated ADRE with different assumptions about the daily AOD variability: taking the observed daily AOD cycle into account and assuming diurnally constant AOD. Moreover, we estimated the corresponding differences in ADREs, if the single AOD value for the daily mean was taken from the the Moderate Resolution Imaging Spectroradiometer (MODIS) Terra or Aqua overpass times, instead of accounting for the true observed daily variability. The mean impact of diurnal AOD variability on 24 h ADRE estimates, averaged over all AERONET sites, was rather small and it was relatively small even for the cases when AOD was chosen to correspond to the Terra or Aqua overpass time. This was true on average over all AERONET sites, while clearly there can be much stronger impact in individual sites. Examples of some selected sites demonstrated that the strongest observed AOD variability (the strongest morning afternoon contrast) does not typically result in a significant impact on 24 h ADRE. In those cases, the morning and afternoon AOD patterns are opposite and thus the impact on 24 h ADRE, when integrated over all solar zenith angles, is reduced. The most significant effect on daily ADRE was induced by AOD cycles with either maximum or minimum AOD close to local noon. In these cases, the impact on 24 h ADRE was typically around 0.1-0.2W/sq m (both positive and negative) in absolute values, 5-10% in relative ones.

Arola, A.; Eck, T. F.; Huttunen, J.; Lehtinen, K. E. J.; Lindfors, A. V.; Myhre, G.; Smirinov, A.; Tripathi, S. N.; Yu, H.

2013-01-01

274

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

275

Validation of MODIS aerosol optical depth over the Mediterranean Coast  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols, due to their high spatial and temporal variability, are considered one of the largest sources of uncertainty in different processes affecting visibility, air quality, human health, and climate. Among their effects on climate, they play an important role in the energy balance of the Earth. On one hand they have a direct effect by scattering and absorbing solar radiation; on the other, they also have an impact in precipitation, modifying clouds, or affecting air quality. The application of remote sensing techniques to investigate aerosol effects on climate has advanced significatively over last years. In this work, the products employed have been obtained from the Moderate Resolution Imaging Spectroradiometer (MODIS). MODIS is a sensor located onboard both Earth Observing Systems (EOS) Terra and Aqua satellites, which provide almost complete global coverage every day. These satellites have been acquiring data since early 2000 (Terra) and mid 2002 (Aqua) and offer different products for land, ocean and atmosphere. Atmospheric aerosol products are presented as level 2 products with a pixel size of 10 x 10 km2 in nadir. MODIS aerosol optical depth (AOD) is retrieved by different algorithms depending on the pixel surface, distinguishing between land and ocean. For its validation, ground based sunphotometer data from AERONET (Aerosol Robotic Network) has been employed. AERONET is an international operative network of Cimel CE318 sky-sunphotometers that provides the most extensive aerosol data base globally available of ground-based measurements. The ground sunphotometric technique is considered the most accurate for the retrieval of radiative properties of aerosols in the atmospheric column. In this study we present a validation of MODIS C051 AOD employing AERONET measurements over different Mediterranean coastal sites centered over an area of 50 x 50 km2, which includes both pixels over land and ocean. The validation is done comparing spatial statistics from MODIS with corresponding temporal statistics from AERONET, as proposed by Ichoku et al. (2002). Eight Mediterranean coastal sites (in Spain, France, Italy, Crete, Turkey and Israel) with available AERONET and MODIS data have been used. These stations have been selected following QA criteria (minimum 1000 days of level 2.0 data) and a maximum distance of 8 km from the coast line. Results of the validation over each site show analogous behaviour, giving similar results regarding to the accuracy of the algorithms. Greatest differences are found for the AOD obtained over land, especially for drier regions, where the surface tends to be brighter. In general, the MODIS AOD has better a agreement with AERONET retrievals for the ocean algorithm than the land algorithm when validated over coastal sites, and the agreement is within the expected uncertainty estimated for MODIS data. References: - C. Ichoku et al., "A spatio-temporal approach for global validation and analysis of MODIS aerosol products", Geophysical Research Letters, 219, 12, 10.1029/2001GL013206, 2002.

Díaz-Martínez, J. Vicente; Segura, Sara; Estellés, Víctor; Utrillas, M. Pilar; Martínez-Lozano, J. Antonio

2013-04-01

276

Observations and projections of visibility and aerosol optical thickness (1956–2100) in the Netherlands: impacts of time-varying aerosol composition and hygroscopicity  

NASA Astrophysics Data System (ADS)

Time series of visibility and aerosol optical thickness for the Netherlands have been constructed for 1956–2100 based on observations and aerosol mass scenarios. Aerosol optical thickness from 1956 to 2013 has been reconstructed by converting time series of visibility to visible extinction which in turn are converted to aerosol optical thickness using an appropriate scaling depth. The reconstruction compares closely with remote sensing observations of aerosol optical thickness between 1960 and 2013. It appears that aerosol optical thickness was relatively constant over the Netherlands in the years 1955–1985. After 1985, visibility has improved, while at the same time aerosol optical thickness has decreased. Based on aerosol emission scenarios for the Netherlands three aerosol types have been identified: (1) a constant background consisting of sea salt and mineral dust, (2) a hydrophilic anthropogenic inorganic mixture, and (3) a partly hydrophobic mixture of black carbon (BC) and organic aerosols (OAs). A reduction in overall aerosol concentration turns out to be the most influential factor in the reduction in aerosol optical thickness. But during 1956–1985, an upward trend in hydrophilic aerosols and associated upward trend in optical extinction has partly compensated the overall reduction in optical extinction due to the reduction in less hydrophilic BC and OAs. A constant optical thickness ensues. This feature highlights the influence of aerosol hygroscopicity on time-varying signatures of atmospheric optical properties. Within the hydrophilic inorganic aerosol mixture there is a gradual shift from sulfur-based (1956–1985) to a nitrogen-based water aerosol chemistry (1990 onwards) but always modulated by the continual input of sodium from sea salt. From 2013 to 2100, visibility is expected to continue its increase, while at the same time optical thickness is foreseen to continue to decrease. The contribution of the hydrophilic mixture to the aerosol optical thickness will increase from 30% to 35% in 1956 to more than 70% in 2100. At the same time the contribution of black and organic aerosols will decrease by more than 80%.

Boers, R.; van Weele, M.; van Meijgaard, E.; Savenije, M.; Siebesma, A. P.; Bosveld, F.; Stammes, P.

2015-01-01

277

Kinetically Lockedin Colloidal Transport in an Array of Optical Tweezers Pamela T. Korda, Michael B. Taylor, # and David G. Grier  

E-print Network

, and macromolecules. Depending on the balance of forces, a particle driven across a corrugated potential energy 11111 11111 11111 Beam [01] [10] q flow Ar Laser Resin Ion Exchange Dichroic Mirror Sample Chamber beams formed by a di#ractive optical element (DOE) are transferred by a telescope to the input pupil

Grier, David

278

Optical properties of absorbing and non-absorbing aerosols retrieved by cavity ring down (CRD) spectroscopy  

NASA Astrophysics Data System (ADS)

Application of cavity ring down (CRD) spectrometry for measuring the optical properties of pure and mixed laboratory-generated aerosols is presented. The extinction coefficient (?ext), extinction cross section (?ext) and extinction efficiency (Qext) were measured for polystyrene spheres (PSS), ammonium sulphate ((NH4)2(SO4), sodium chloride (NaCl), glutaric acid (GA), and Rhodamine-590 aerosols. The refractive indices of the different aerosols were retrieved by comparing the measured extinction efficiency of each aerosol type to the extinction predicted by Mie theory. Aerosols composed of sodium chloride and glutaric acid in different mixing ratios were used as model for mixed aerosols of two non-absorbing materials, and their extinction and complex refractive index were derived. Aerosols composed of Rhodamine-590 and ammonium sulphate in different mixing ratios were used as model for mixing of absorbing and non-absorbing species, and their optical properties were derived. The refractive indices of the mixed aerosols were also calculated by various optical mixing rules. We found that for non-absorbing mixtures, the linear rule, Maxwell-Garnett rule, and extended effective medium approximation (EEMA), give comparable results, with the linear mixing rule giving a slightly better fit than the others. Overall, calculations for the mixed aerosols are not as good as for single component aerosols. For absorbing mixtures, the differences between the refractive indices calculated using the mixing rules and those retrieved by CRD are generally higher.

Abo Riziq, A.; Erlick, C.; Dinar, E.; Rudich, Y.

2007-03-01

279

Optical properties of absorbing and non-absorbing aerosols retrieved by cavity ring down (CRD) spectroscopy  

NASA Astrophysics Data System (ADS)

Application of cavity ring down (CRD) spectrometry for measuring the optical properties of pure and mixed laboratory-generated aerosols is presented. The extinction coefficient (?ext), extinction cross section (?ext) and extinction efficiency (Qext) were measured for polystyrene spheres (PSS), ammonium sulphate ((NH4)2(SO4)), sodium chloride (NaCl), glutaric acid (GA), and Rhodamine-590 aerosols. The refractive indices of the different aerosols were retrieved by comparing the measured extinction efficiency of each aerosol type to the extinction predicted by Mie theory. Aerosols composed of sodium chloride and glutaric acid in different mixing ratios were used as model for mixed aerosols of two non-absorbing materials, and their extinction and complex refractive index were derived. Aerosols composed of Rhodamine-590 and ammonium sulphate in different mixing ratios were used as model for mixing of absorbing and non-absorbing species, and their optical properties were derived. The refractive indices of the mixed aerosols were also calculated by various optical mixing rules and a core plus shell Mie model. We found that for non-absorbing mixtures, the linear rule, Maxwell-Garnett rule, extended effective medium approximation (EEMA), and core plus shell model give comparable results, with the linear mixing rule giving a slightly better fit than the others. Overall, calculations for the mixed aerosols are not as good as for single component aerosols. For absorbing mixtures, the differences between the refractive indices calculated using the mixing rules and those retrieved by CRD are generally higher.

Riziq, A. A.; Erlick, C.; Dinar, E.; Rudich, Y.

2006-11-01

280

Deriving atmospheric visibility from satellite retrieved aerosol optical depth  

NASA Astrophysics Data System (ADS)

Atmospheric visibility is a measure that reflects different physical and chemical properties of the atmosphere. In general, poor visibility conditions come along with risks for transportation (e.g. road traffic, aviation) and can negatively impact human health since visibility impairment often implies the presence of atmospheric pollution. Ambient pollutants, particulate matter, and few gaseous species decrease the perceptibility of distant objects. Common estimations of this parameter are usually based on human observations or devices that measure the transmittance of light from an artificial light source over a short distance. Such measurements are mainly performed at airports and some meteorological stations. A major disadvantage of these observations is the gap between the measurements, leaving large areas without any information. As aerosols are one of the most important factors influencing atmospheric visibility in the visible range, the knowledge of their spatial distribution can be used to infer visibility with the so called Koschmieder equation, which relates visibility and atmospheric extinction. In this study, we evaluate the applicability of satellite aerosol optical depth (AOD) products from the Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) to infer atmospheric visibility on large spatial scale. First results applying AOD values scaled with the planetary boundary layer height are promising. For the comparison we use a full automated and objective procedure for the estimation of atmospheric visibility with the help of a digital panorama camera serving as ground truth. To further investigate the relation between the vertical measure of AOD and the horizontal visibility data from the Aerosol Robotic Network (AERONET) site Laegeren (Switzerland), where the digital camera is mounted, are included as well. Finally, the derived visibility maps are compared with synoptical observations in central Europe.

Riffler, M.; Schneider, Ch.; Popp, Ch.; Wunderle, S.

2009-04-01

281

Observations of Stratospheric Aerosols by Balloon-borne Optical Particle Counter at Bandung, Indonesia  

Microsoft Academic Search

The campaign of stratospheric aerosol measurement by balloon-borne optical particle counter was conducted four times from April 1997 to March 1999 at Bandung, Indonesia (6.9°S, 107.6°E). Within a few kilometers above the tropopause low aerosol mixing ratios were observed. The layer of relatively small aerosols (size ranges from 0.15 ?m to 0.25 ?m and from 0.25 ?m to 0.4 ?m

Takatsugu Matsumura; Masahiko Hayashi; Motowo Fujiwara; Katsuji Matsunaga; Motoaki Yasui; Slamet Saraspriya; Timbul Manik; Agus Suripto

2001-01-01

282

CALIPSO and MODIS Observations of Increases in Aerosol Optical Depths near Marine Stratocumulus  

NASA Astrophysics Data System (ADS)

Aerosols not only affect droplet sizes and number concentrations in marine stratocumulus but in turn the near cloud environment gives rise to changes in the aerosol particle concentrations and sizes. In addition, the clouds serve as reflectors that illuminate the adjacent cloud-free air. This extra illumination leads to overestimates of aerosol optical depths and fine mode fractions retrieved from multispectral satellite imagery. Large cloud-free ocean regions bounded on both ends, or if sufficiently large (>100 km), on at least one end by layers of marine stratocumulus, as deduced from CALIPSO lidar returns, were examined to deduce the effects of the clouds on the properties of nearby aerosols. CALIPSO aerosol optical depths composited for more than a year and covering the global oceans, 60°S-60°N, reveal that the fractional increase in aerosol optical depth in going from a cloud-free 5-km region more than 10 to 15 km from a cloud boundary to one adjacent the clouds is 10%-15% at both 532 and 1064 nm for both daytime and nighttime observations. All of the changes are statistically significant at the 90% confidence level or greater. The associated reduction in the 532/1064 Ånsgtröm Exponent is 0.023 for the nighttime observations, but owing to a poorer signal to noise ratio, no change in the Exponent is detected for the daytime observations. For comparison, the MODIS aerosol optical depths collocated with the daytime CALIPSO optical depths suggest that the fractional increases in aerosol optical depths in going from a cloud-free 10-km region 15 km from a cloud boundary to one adjacent the clouds is about 5% at both 550 and 850 nm. The associated reduction in the 550/850 Ånsgtröm Exponent is 0.053. The changes in aerosol properties die away within 10 to 20 km from the marine stratocumulus. The increases in aerosol scattering and reductions in Ånsgtröm Exponent suggest that near the clouds, the aerosol particles become larger. The fine mode fraction found in the MODIS aerosol retrievals decreases as clouds are approached. Cloud contamination of the aerosol retrievals for the 5-km CALIPSO and 10-km MODIS observations adjacent the cloud might explain the observed changes. The fall in the 532-nm aerosol optical depth between cloud-free regions 7.5 and 12.5 km from the cloud boundaries, however, is statistically significant for the daytime CALIPSO observations, suggesting that the changes are caused by factors other than cloud contamination. These findings are placed in context with estimates of the changes in aerosol properties based on aircraft measurements and analyses of satellite observations reported by others.

Coakley, J. A.; Tahnk, W. R.

2009-12-01

283

Aerosol optical properties over the midcontinental United States  

NASA Technical Reports Server (NTRS)

Solar and sky radiation measurements were analyzed to obtain aerosol properties such as the optical thickness and the size distribution. The measurements were conducted as part of the First International Satellite Land Surface Climatology Project Field Experiment during the second intensive field campaign (IFC) from June 25 to July 14, 1987, and the fifth IFC from July 25 to August 12, 1989, on the Konza Prairie near Manhattan, Kansas. Correlations with climatological and meteorological parameters show that during the period of observations in 1987, two types of air masses dominated the area: an air mass with low optical thickness and low temperature air associated with a northerly breeze, commonly referred to as the continental air, and an air mass with a higher optical thickness and higher temperature air associated with a southerly wind which we call 'Gulf air'. The size distributions show a predominance of the larger size particles in 'Gulf air'. Because of the presence of two contrasting air masses, correlations with parameters such as relative humidity, specific humidity, pressure, temperature, and North Star sky radiance reveal some interesting aspects. In 1989, clear distinctions between continental and Gulf air cannot be made; the reason for this will be discussed.

Halthore, Rangasayi N.; Markham, Brian L.; Ferrare, Richard A.; Aro, Theo. O.

1992-01-01

284

A methodology to retrieve self-consistent aerosol optical properties using common aircraft measurements  

Microsoft Academic Search

Aerosol optical properties that include the extinction coefficient, single scattering albedo, and asymmetry factor are needed to calculate the radiative effects of aerosols. However, measurements of these properties are typically limited to a few wavelengths, and direct measurements of the asymmetry factor are not available. We describe and evaluate a retrieval methodology that uses commonly collected aircraft-based measurements to derive

Brian I. Magi; Qiang Fu; Jens Redemann

2007-01-01

285

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

286

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

287

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

288

Satellite-observed patterns in stratus microphysics, aerosol optical thickness, and shortwave radiative forcing  

Microsoft Academic Search

A long-term global daily data set of satellite-derived radiances has been applied over oceans to investigate the effect of aerosol particles on marine stratus cloud physical parameters and cloud shortwave radiative forcing. Tropospheric aerosol can indirectly influence cloud reflectance and radiative forcing by acting as cloud condensation nuclei, thus modifying the droplet size distribution and cloud optical properties. The NOAA

Melanie A. Wetzel; Larry L. Stowe

1999-01-01

289

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

290

Global sea surface temperatures and cloud clearing for aerosol optical depth estimates  

Microsoft Academic Search

Multichannel sea surface tempratures (MCSSTs) have been produced operationally on a global basis from AVHRR data since November 1981. Although the basic technique has been unchanged for over S years, refinements and modifications to handle special situations (e.g. volcanic and sandstorm aerosols) are under development and a cross-product (nonlinear) procedure for atmospheric corrections has been tested. The aerosol optical depth

E. PAUL McCLAIN

1989-01-01

291

Use of Brewer ozone spectrophotometer for aerosol optical depth measurements on ultraviolet region  

Microsoft Academic Search

The Brewer ozone spectrophotometer has been mainly used for automated measurements of total ozone and SO2 and global UV-B radiation. However, the power of this scientific instrument allows to perform another kind of interesting measurements in the UV region of the solar spectra, as for example the aerosol optical depth. This work shows a simple method to retrieve the aerosol

F. Carvalho; D. Henriques

2000-01-01

292

Latitudinal distribution of the aerosol optical depth over oceans in southern hemisphere  

NASA Astrophysics Data System (ADS)

Latitudinal distribution of the aerosol optical depth (AOD) of the atmosphere over ocean in southern hemisphere is considered on the basis of data of long-term measurements (AERONET MAN). It is shown that the aerosol turbidity of the atmosphere decreases with increasing latitude in Atlantic, Indian, and Pacific oceans. Simple linear relationships are proposed to describe the latitudinal distribution of AOD.

Kabanov, Dmitry M.; Gulev, Sergey K.; Holben, Brent N.; Radionov, Vladimir F.; Sakerin, Sergey M.; Smirnov, Alexander

2014-11-01

293

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

294

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

295

Aerosol Optical Properties Measured Onboard the Ronald H. Brown During ACE Asia as a Function of Aerosol Chemical Composition and Source Region  

NASA Technical Reports Server (NTRS)

During the ACE Asia intensive field campaign conducted in the spring of 2001 aerosol properties were measured onboard the R/V Ronald H. Brown to study the effects of the Asian aerosol on atmospheric chemistry and climate in downwind regions. Aerosol properties measured in the marine boundary layer included chemical composition; number size distribution; and light scattering, hemispheric backscattering, and absorption coefficients. In addition, optical depth and vertical profiles of aerosol 180 deg backscatter were measured. Aerosol within the ACE Asia study region was found to be a complex mixture resulting from marine, pollution, volcanic, and dust sources. Presented here as a function of air mass source region are the mass fractions of the dominant aerosol chemical components, the fraction of the scattering measured at the surface due to each component, mass scattering efficiencies of the individual components, aerosol scattering and absorption coefficients, single scattering albedo, Angstrom exponents, optical depth, and vertical profiles of aerosol extinction. All results except aerosol optical depth and the vertical profiles of aerosol extinction are reported at a relative humidity of 55 +/- 5%. An over-determined data set was collected so that measured and calculated aerosol properties could be compared, internal consistency in the data set could be assessed, and sources of uncertainty could be identified. By taking into account non-sphericity of the dust aerosol, calculated and measured aerosol mass and scattering coefficients agreed within overall experimental uncertainties. Differences between measured and calculated aerosol absorption coefficients were not within reasonable uncertainty limits, however, and may indicate the inability of Mie theory and the assumption of internally mixed homogeneous spheres to predict absorption by the ACE Asia aerosol. Mass scattering efficiencies of non-sea salt sulfate aerosol, sea salt, submicron particulate organic matter, and dust found for the ACE Asia aerosol are comparable to values estimated for ACE 1, Aerosols99, and INDOEX. Unique to the ACE Asia aerosol was the large mass fractions of dust, the dominance of dust in controlling the aerosol optical properties, and the interaction of dust with soot aerosol.

Quinn, P. K.; Coffman, D. J.; Bates, T. S.; Welton, E. J.; Covert, D. S.; Miller, T. L.; Johnson, J. E.; Maria, S.; Russell, L.; Arimoto, R.

2004-01-01

296

Investigation of the optical and cloud forming properties of pollution, biomass burning, and mineral dust aerosols  

E-print Network

the optical and cloud forming properties of a range of ambient aerosol types measured in a number of different locations. The tool used for most of these analyses is a differential mobility analyzer / tandem differential mobility analyzer (DMA / TDMA) system...

Lee, Yong Seob

2006-08-16

297

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 ...

298

The impact of aerosol optical depth assimilation on aerosol forecasts and radiative effects during a wild fire event over the United States  

NASA Astrophysics Data System (ADS)

The Gridpoint Statistical Interpolation three-dimensional variational data assimilation (DA) system coupled with the Weather Research and Forecasting/Chemistry (WRF/Chem) model was utilized to improve aerosol forecasts and study aerosol direct and semi-direct radiative feedbacks during a US wild fire event. Assimilation of MODIS total 550 nm aerosol optical depth (AOD) retrievals clearly improved WRF/Chem forecasts of surface PM2.5 and organic carbon (OC) compared to the corresponding forecasts without aerosol data assimilation. The scattering aerosols in the fire downwind region typically cooled layers both above and below the aerosol layer and suppressed convection and clouds, which led to an average of 2% precipitation decrease during the fire week. This study demonstrated that, even with no input of fire emissions, AOD DA improved the aerosol forecasts and allowed a more realistic model simulation of aerosol radiative effects.

Chen, D.; Liu, Z.; Schwartz, C. S.; Lin, H.-C.; Cetola, J. D.; Gu, Y.; Xue, L.

2014-11-01

299

Aerosol Optical Depth Trends in Switzerland from 1995 - 2010  

NASA Astrophysics Data System (ADS)

Accurate and long-term measurements of aerosol optical depth (AOD) serve as an important contribution to studies assessing the effect of aerosols on climate change. In this study re-calibrated and updated AOD climatologies are reported for two sites in Switzerland for 1995 - 2010, (Davos, 1580 m and Jungfraujoch, 3580 m), as well as a new data-set for an urban site Bern (560 m asl). At Davos and Jungfraujoch AOD observations were conducted using an SPM2000 sun-photometer system until 2003 and with precision filter radiometers (PFR) from 1999 onwards, while continuous AOD measurements were conducted at Bern over the 1998 - 2006 period with SPM2000. In order to homogenize these diverse data-sets, procedures and algorithms of the GAW-PFR (Global Atmosphere Watch - Precision Filter Radiometer, WMO) program to derive AOD are used here. GAW-PFR procedures and algorithms use: 1) in-situ air pressure data, ii) in-situ or satellite ozone data, 3) commonly-used algorithms for cloud-screening, airmass calculation etc. The AOD average for the available 1-month data-set was 0.026 (± 0.013; ± 1 stdev) at Jungfraujoch, 0.069 (± 0.037) at Davos and 0.174 (± 0.054) at Bern illustrating the typical increase in average AOD with decreasing altitude due to surface aerosol sources, and to boundary layer/free troposphere dynamics. A trend analysis was performed using the seasonal Kendall test, and Sen's slope estimator on logarithmized AOD data. The seasonal Kendall test is an extension of the Mann-Kendall test, a non-parametric technique which determines if a monotonic increasing or de-creasing long-term trend exists. As AOD data are log-normally distributed, the logarithm of AOD was used for analysis. Statistically significant linear trends was found only at Jungfraujoch while for Davos and Bern even though no statistically significant trends were observed, significant trends during certain months were detected (e.g. during May, July, and December for Bern). Factors which could mask the true AOD trends at all three Swiss stations are further discussed. The influence of Pinatubo on AOD in Switzerland after 1994 was examined using the SAGE stratospheric AOD database and the volcanic component was modeled with an exponential decay and subtracted from Jungfraujoch and Davos data-sets. Further, the influence of boundary layer conditions to Jungfraujoch measurements, which are generally representative of undisturbed conditions in the lower Free Troposphere, was assessed and the trends of the undisturbed free troposphere AOD measurements were calculated. Finally, the effect of the North Atlantic Oscillation on the AOD datasets was examined.

Nyeki, S.; Halios, C.; Eleftheriadis, K.; Wehrli, C.; Groebner, J.

2011-12-01

300

Climatological Aspects of the Optical Properties of Fine/Coarse Mode Aerosol Mixtures  

NASA Technical Reports Server (NTRS)

Aerosol mixtures composed of coarse mode desert dust combined with fine mode combustion generated aerosols (from fossil fuel and biomass burning sources) were investigated at three locations that are in and/or downwind of major global aerosol emission source regions. Multiyear monitoring data at Aerosol Robotic Network sites in Beijing (central eastern China), Kanpur (Indo-Gangetic Plain, northern India), and Ilorin (Nigeria, Sudanian zone of West Africa) were utilized to study the climatological characteristics of aerosol optical properties. Multiyear climatological averages of spectral single scattering albedo (SSA) versus fine mode fraction (FMF) of aerosol optical depth at 675 nm at all three sites exhibited relatively linear trends up to 50% FMF. This suggests the possibility that external linear mixing of both fine and coarse mode components (weighted by FMF) dominates the SSA variation, where the SSA of each component remains relatively constant for this range of FMF only. However, it is likely that a combination of other factors is also involved in determining the dynamics of SSA as a function of FMF, such as fine mode particles adhering to coarse mode dust. The spectral variation of the climatological averaged aerosol absorption optical depth (AAOD) was nearly linear in logarithmic coordinates over the wavelength range of 440-870 nm for both the Kanpur and Ilorin sites. However, at two sites in China (Beijing and Xianghe), a distinct nonlinearity in spectral AAOD in logarithmic space was observed, suggesting the possibility of anomalously strong absorption in coarse mode aerosols increasing the 870 nm AAOD.

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

2010-01-01

301

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

302

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

303

Aerosol optical depth measurements and their impact on surface levels of ultraviolet-B radiation  

NASA Astrophysics Data System (ADS)

Surface measurements of total and diffuse UV irradiance at the seven narrowband wavelength channels of the ultraviolet multifilter rotating shadow-band radiometer (UVMFR) were used to determine total column ozone and aerosol optical depth for two 6-month periods in 1997 and 1999 at a site in the Blue Ridge Mountains of North Carolina. The retrieved column ozone displayed a seasonal dependence and consistent agreement with the Total Ozone Mapping Spectrometer (TOMS). The mean ratio of retrieved ozone to TOMS ozone was 0.98 with standard deviations of 0.02 and 0.01 for 1997 and 1999, respectively. Aerosol optical depth at 317, 325, 332, and 368 nm was derived for a 6-month period of 1999. The seasonal trend exhibited is influenced by the persistent summertime haze that occurs in the region. The retrieved aerosol optical depths are used as input in a radiative transfer model to investigate the effect of their realistic values on the calculation of the UV index (UVI) forecasted by the National Weather Service. The percentage change in calculated surface erythemally weighted UV (versus calculations using the standard UVI aerosol inputs) ranges from a 4% increase to a nearly 50% decrease, dependent upon the aerosol optical depth and amount of absorption by aerosols. Based on our measurements, it was found that during the summertime the UV index can deviate by up to -5 index units from the forecast using the standard aerosol inputs.

Wenny, B. N.; Saxena, V. K.; Frederick, J. E.

2001-01-01

304

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

305

How safe is gamete micromanipulation by laser tweezers?  

NASA Astrophysics Data System (ADS)

Laser tweezers, used as novel sterile micromanipulation tools of living cells, are employed in laser-assisted in vitro fertilization (IVF). For example, controlled spermatozoa transport with 1064 nm tweezers to human egg cells has been performed in European clinics in cases of male infertility. The interaction of approximately 100 mW near infrared (NIR) trapping beams at MW/cm2 intensity with human gametes results in low mean less than 2 K temperature increases and less than 100 pN trapping forces. Therefore, photothermal or photomechanical induced destructive effects appear unlikely. However, the high photon flux densities may induce simultaneous absorption of two NIR photons resulting in nonlinear interactions. These nonlinear interactions imply non-resonant two-photon excitation of endogenous cellular chromophores. In the case of less than 800 nm tweezers, UV- like damage effects may occur. The destructive effect is amplified when multimode cw lasers are used as tweezer sources due to longitudinal mode-beating effects and partial mode- locking. Spermatozoa damage within seconds using 760 nm traps due to formation of unstable ps pulses in a cw Ti:Sa ring laser is demonstrated. We recommend the use of greater than or equal to 800 nm traps for optical gamete micromanipulation. To our opinion, further basic studies on the influence of nonlinear effects of laser tweezers on human gamete are necessary.

Koenig, Karsten; Tromberg, Bruce J.; Tadir, Yona; Berns, Michael W.

1998-04-01

306

Aerosol optical properties and radiative effects over Manora Peak in the Himalayan foothills: seasonal variability and role of transported aerosols.  

PubMed

The higher altitude regions of Himalayas and Tibetan Plateau are influenced by the dust and black carbon (BC) aerosols from the emissions and long-range transport from the adjoining areas. In this study, we present impacts of advection of polluted air masses of natural and anthropogenic emissions, on aerosol optical and radiative properties at Manora Peak (~2000m amsl) in central Himalaya over a period of more than two years (February 2006-May 2008). We used the most updated and comprehensive data of chemical and optical properties available in one of the most climatically sensitive region, the Himalaya, to estimate atmospheric radiative forcing and heating rate. Aerosol optical depth (AOD) was found to vary from 0.04 to 0.45 with significantly higher values in summer mainly due to an increase in mineral dust and biomass burning aerosols due to transport. In contrast, single scattering albedo (SSA) varied from 0.74 to 0.88 with relatively lower values during summer, suggesting an increase in absorbing BC and mineral dust aerosols. As a result, a large positive atmospheric radiative forcing (about 28±5 Wm(-2)) and high values of corresponding heating rate (0.80±0.14 Kday(-1)) has been found during summer. During the entire observation period, radiative forcing at the top of the atmosphere varied from -2 to +14 Wm(-2) and from -3 to -50 Wm(-2) at the surface whereas atmospheric forcing was in the range of 3 to 65 Wm(-2) resulting in a heating rate of 0.1-1.8 Kday(-1). PMID:25261819

Srivastava, A K; Ram, K; Singh, Sachchidanand; Kumar, Sanjeev; Tiwari, S

2015-01-01

307

On the variation of aerosol properties over Finland based on the optical columnar measurements  

NASA Astrophysics Data System (ADS)

Long-range aerosol transport over Finland has been studied using ground-based sunphotometer measurements of aerosol optical properties. Cimel sunphotometers were used at an urban site (Helsinki), a rural site (Hyytiälä) and a semiurban site (Kuopio) and PFR sunphotometer measurements were made at two rural sites, Jokioinen and Sodankylä. The CIMEL measurements are part of the AERONET (Aerosol robotic network) network and Jokioinen and Sodankylä are GAW-PFR (Global Atmosphere Watch-Precision Filter Radiometer) Associate Stations. Sunphotometers provide information on local columnar aerosol properties such as aerosol optical depth (AOD) and Ångström exponent (ÅE) that were used to investigate the aerosol content and aerosol type in this region. A set of representative event days, i.e. days with high turbidity, covering the time period between March 2006 and June 2010 has been selected for further analysis. For these days the AOD results were combined with air mass back trajectories to provide information about the air mass origin, especially for cases with moderate turbidity produced by long-range transported aerosols from mid latitudes to Finland. As expected, episodes with high AOD are connected with the transport of polluted air masses originating from the east or southeast or from industrial areas in Central Europe. We distinguished events with long range transported air pollution from cases where pollution was accumulated in the area due to the local meteorological factors.

Aaltonen, V.; Rodriguez, E.; Kazadzis, S.; Arola, A.; Amiridis, V.; Lihavainen, H.; de Leeuw, G.

2012-10-01

308

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

309

Aerosol optical hygroscopicity measurements during the 2010 CARES Campaign  

NASA Astrophysics Data System (ADS)

Measurements of the effect of water uptake on particulate light extinction or scattering made at two locations during the 2010 CARES study around Sacramento, CA are reported. The observed influence of water uptake, characterized through the dimensionless optical hygroscopicity parameter ?, is compared with calculations constrained by observed particle size distributions and size-dependent particle composition. A closure assessment has been carried out that allowed for determination of the average hygroscopic growth factors (GF) at 85% relative humidity and the dimensionless hygroscopicity parameter ? for oxygenated organic aerosol (OA) and for supermicron particles, yielding ? = 0.1-0.15 and 0.9-1.0, respectively. The derived range of oxygenated OA ? values are in line with previous observations. The relatively large values for supermicron particles is consistent with substantial contributions of sea salt-containing particles in this size range. Analysis of time-dependent variations in the supermicron particle hygroscopicity suggest that atmospheric processing, specifically chloride displacement by nitrate and the accumulation of secondary organics on supermicron particles, can lead to substantial depression of the observed GF.

Atkinson, D. B.; Radney, J. G.; Lum, J.; Kolesar, K. R.; Cziczo, D. J.; Pekour, M. S.; Zhang, Q.; Setyan, A.; Zelenyuk, A.; Cappa, C. D.

2014-12-01

310

Spatiotemporal modeling of irregularly spaced Aerosol Optical Depth data  

PubMed Central

Many advancements have been introduced to tackle spatial and temporal structures in data. When the spatial and/or temporal domains are relatively large, assumptions must be made to account for the sheer size of the data. The large data size, coupled with realities that come with observational data, make it difficult for all of these assumptions to be met. In particular, air quality data are very sparse across geographic space and time, due to a limited air pollution monitoring network. These “missing” values make it diffcult to incorporate most dimension reduction techniques developed for high-dimensional spatiotemporal data. This article examines aerosol optical depth (AOD), an indirect measure of radiative forcing, and air quality. The spatiotemporal distribution of AOD can be influenced by both natural (e.g., meteorological conditions) and anthropogenic factors (e.g., emission from industries and transport). After accounting for natural factors influencing AOD, we examine the spatiotemporal relationship in the remaining human influenced portion of AOD. The presented data cover a portion of India surrounding New Delhi from 2000 – 2006. The proposed method is demonstrated showing how it can handle the large spatiotemporal structure containing so much missing data for both meteorologic conditions and AOD over time and space. PMID:24470786

Oleson, Jacob J.; Kumar, Naresh; Smith, Brian J.

2012-01-01

311

Vertical distribution of the spectral aerosol optical depth in the Arctic from 1993 to 1996  

NASA Astrophysics Data System (ADS)

During the period from summer 1993 to spring 1996, 51 profiles of spectral aerosol optical depth were measured with airborne Sun photometers throughout the Arctic. This period was influenced by volcanic aerosols after the Pinatubo eruption and the removal of volcanic material from the stratosphere into the troposphere. By 1996, stratospheric aerosol concentration has decreased to pre-Pinatubo levels. Mean values of aerosol optical depth have changed during the period from 1993 to 1996 from 0.09 to 0.02 at 403 nm and from 0.065 to 0.01 at 1041nm/1057 nm, respectively. Size spectra of stratospheric aerosol also show the influence of volcanic aerosols. A bimodal distribution was found with main radius modes at 0.1 ?m to 0.3 ?m and 0.75 ?m to 0.9 ?m. The typical vertical distribution of tropospheric aerosols in the Arctic in this time period and inferred size spectra are presented. The seasonal change in the spectral aerosol optical depth with a minimum in summer and high values in spring is shown, as well as the high extinction and distinct layering of Arctic haze up into the free troposphere. Size spectra of Arctic haze also change with height and show, in addition to particles with radii smaller than 0.1 ?m, main radius modes between 0.1 ?m and 0.2 ?m and between 1 ?m and 2 ?m. Possible influence of tropospheric aerosols on the radiation balance is also discussed for the spring and summer season. While in summer the influence on the radiation balance of the very small amount of tropo-spheric aerosols is negligible, in spring, haze layers with high extinction can result in a slight warming.

Nagel, Dagmar; Herber, Andreas; Thomason, Larry W.; Leiterer, Ullrich

1998-01-01

312

Improved method to retrieve aerosol optical properties from combined elastic backscatter and Raman lidar data  

NASA Astrophysics Data System (ADS)

An improved method that has the potential to improve the retrieval of aerosol optics properties (backscatter/extinction coefficients) from elastic-Raman lidar data is presented. Aerosol backscatter coefficients can be retrieved by choosing the reference height at near-range rather than conventional far-range when the signal-to-noise ratios are low at the far-range or aloft aerosol layers and clouds appear there. Significant retrieval errors in aerosol backscatter coefficients caused by large uncertainties of the aerosol reference value at far-range can be reduced. To avoid the ill-posed retrievals of aerosol extinction from the conventional Raman method, the new method derives the aerosol extinction and lidar ratio with the constrained Fernald inversions by independent aerosol backscatter coefficients from above proposed method. The numerical simulations demonstrated that the proposed method provides good accuracy and resolution of aerosol profile retrievals. And the method is also applied to elastic-Raman lidar measurements at the Hampton University, Hampton, Virginia.

Su, Jia; Wu, Yonghua; McCormick, M. Patrick; Lei, Liqiao; Lee, Robert B.

2014-07-01

313

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

314

Synthesis of information on aerosol optical properties Hongqing Liu,1  

E-print Network

revealed a significant decrease in sur- face solar heating due to the presence of absorbing aerosols, which and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study spectral dependence derived from AERONET retrievals. The asymmetry parameter over the solar spectrum

Chin, Mian

315

Regional Aerosol Optical Depth Characteristics from Satellite Observations: ACE-1, TARFOX and ACE-2 Results  

NASA Technical Reports Server (NTRS)

Analysis of the aerosol properties during 3 recent international field campaigns ACE-1, TARFOX and ACE-2 are described using satellite retrievals from NOAA AVHRR data. Validation of the satellite retrieval procedure is performed with airborne, shipboard, and land-based sunphotometry during ACE-2. The intercomparison between satellite and surface optical depths has a correlation coefficient of 0.93 for 630 nm wavelength and 0.92 for 860 nm wavelength, The standard error of estimate is 0.025 for 630 nm wavelength and 0.023 for 860 nm wavelength. Regional aerosol properties are examined in composite analysis of aerosol optical properties from the ACE-1, TARFOX and ACE-2 regions. ACE-1 and ACE-2 regions have strong modes in the distribution of optical depth around 0.1, but the ACE-2 tails toward higher values yielding an average of 0.16 consistent with pollution and dust aerosol intrusions. The TARFOX region has a noticeable mode of 0.2, but has significant spread of aerosol optical depth values consistent with the varied continental aerosol constituents off the eastern North American Coast.

Durkee, P. A.; Nielsen, K. E.; Smith, P. J.; Russell, P. B.; Schmid, B.; Livingston, J. M.; Holben, B. N.; Tomasi, C.; Vitale, V.; Collins, D.

1999-01-01

316

Comparative Optical Measurements of Airspeed and Aerosols on a DC-8 Aircraft  

NASA Technical Reports Server (NTRS)

NASA Dryden supported a cooperative flight test program on the NASA DC-8 aircraft in November 1993. This program evaluated optical airspeed and aerosol measurement techniques. Three brassboard optical systems were tested. Two were laser Doppler systems designed to measure free-stream-referenced airspeed. The third system was designed to characterize the natural aerosol statistics and airspeed. These systems relied on optical backscatter from natural aerosols for operation. The DC-8 aircraft carried instrumentation that provided real-time flight situation information and reference data on the aerosol environment. This test is believed to be the first to include multiple optical airspeed systems on the same carrier aircraft, so performance could be directly compared. During 23 hr of flight, a broad range of atmospheric conditions was encountered, including aerosol-rich layers, visible clouds, and unusually clean (aerosol-poor) regions. Substantial amounts of data were obtained. Important insights regarding the use of laser-based systems of this type in an aircraft environment were gained. This paper describes the sensors used and flight operations conducted to support the experiments. The paper also briefly describes the general results of the experiments.

Bogue, Rodney; McGann, Rick; Wagener, Thomas; Abbiss, John; Smart, Anthony

1997-01-01

317

[Aerosol optical thickness of the atmospheric aerosol over Taihu Lake and its features: results of in-site measurements].  

PubMed

Based on the data measured in situ by an automatic sun tracking photometer (CE-318), the aerosol optical thickness (AOT) and the corresponding Angström coefficient alpha of the atmospheric aerosol over Taihu Lake from November 2005 to October 2010 were collected. The results showed that high values of AOT over Taihu Lake were measured in summer (June to July) whereas low values were detected in autumn and winter (October to January). However, the low and high values of a appeared in spring (March to April) and in autumn (September to November), respectively. The variations of AOT and a over Taihu Lake may be related to weather patterns in this region. Based on the frequency distribution, AOT (500 nm) had only one peak value, with a maximum frequency of 0.4-0.6 and a yearly average value of 0.80, accounting for 26% of the total sample. Calculated from the mean AOT (500 nm), the solar radiation reduction was reduced by at least 50% by the atmospheric aerosol, resulting in more turbid atmosphere in this region and consequently heavy fog and haze. There were two peak values of the Angström coefficient alpha, with the maximum frequency ranging from 1.1-1.3 and 1.3-1.5 and a yearly average value of 1.17, accounting for 30% of the total sample. Significant variations were also observed in the daily average values of AOT (500 nm) and a, indicating the coexistence of different types of aerosols over Taihu Lake. The mean value of AOT (500 nm) declined when a increased. To sum up, values of AOT (500 nm) over Taihu Lake changed greatly with time, and the aerosol should be classified as an urban-industrial aerosol. PMID:23002586

Rao, Jia-Wang; Ma, Rong-Hua; Duan, Hong-Tao; Jiang, Guang-Jia; Shang, Lin-Lin; Zhou, Lin

2012-07-01

318

First measurements of aerosol optical depth and Angstrom exponent number from AERONET's Kuching site  

NASA Astrophysics Data System (ADS)

We report our first measurements, over the 2011 dry season period, of aerosol optical depth, Angstrom exponent number and its fine mode counterpart obtained from photometric measurements at AERONET's newest site located at the city of Kuching, Sarawak, East Malaysia. This site was set up as part of the collaborative efforts of the Seven South East Asian Studies (7SEAS) regional aerosol measurements initiative. Located at the converging zone between peninsular Malaysia and the land masses of Sumatra, Borneo, Java and Sulawesi, this site is expected to provide first hand evidence about the physical and optical characteristics of the regional aerosol environment, specially during the biomass burning months. Moreover, given its relative proximity to our Singapore radiation measurement super-site, Kuching is expected to provide further insight on aerosol transport pathways caused by seasonal winds transporting smoke to other parts of the maritime continent and the South Asia region.

Salinas, Santo V.; Chew, Boon N.; Mohamad, M.; Mahmud, M.; Liew, Soo C.

2013-10-01

319

Airborne in situ characterization of dry urban aerosol optical properties around complex topography  

NASA Astrophysics Data System (ADS)

In situ data from the 1997 Southern California Ozone Study—NARSTO were used to describe the aerosol optical properties in an urban area whose aerosol distribution is modified as the aerosols are advected over the surrounding topography. The data consist of measurements made with a nephelometer and absorption photometer onboard the Center for Interdisciplinary Remotely-Piloted Aircraft Studies (CIRPAS) Pelican aircraft. The cases investigated in this study include vertical profiles flown over coastal sites as well as sites located along some important mountain ranges in southern California. The vertical distribution of the aerosol in the Los Angeles Basin showed a complex configuration, directly related with the local meteorological circulations and the surrounding topography. High spatial and temporal variability in air pollutant concentrations within a relatively small area was found, as indicated by the aerosol scattering and absorption coefficient data. The results suggest that in areas with such complex terrain, a high spatial resolution is required in order to adequately describe the aerosol optical quantities. Principal components analysis (PCA) has been applied to aerosol chemical samples in order to identify the major aerosol types in the Los Angeles Basin. The technique yielded four components that accounted for 78% of the variance in the data set. These were indicative of marine aerosols, urban aerosols, trace elements and secondary aerosol components of traffic emissions and agricultural activities. A Monte Carlo radiation transfer model has been employed to simulate the effects that different aerosol vertical profiles have on the attenuation of solar energy. The cases examined were selected using the results of the PCA and in situ data were used to describe the atmospheric optical properties in the model. These investigations comprise a number of sensitivity tests to evaluate the effects on the results of the location of the aerosol layers as well as the vertical resolution of the Monte Carlo model. NARSTO, originally the North American Research Strategy for Tropospheric Ozone, is a public/private partnership whose membership spans government, utilities, industry, and academia throughout Canada, Mexico, and the United States. Its primary mission is to coordinate and enhance policy-relevant scientific research and assessment of tropospheric ozone behavior and provides a cross-organization planning process for scientific investigations.

Targino, Admir Créso; Noone, Kevin J.

2006-02-01

320

The ground-based lidar combined with sunphotometer for aerosol optical depth retrieval  

NASA Astrophysics Data System (ADS)

Aerosol particles are important components of the earth-atmosphere system, not only affecting atmospheric visibility of the earth's surface from space, but also be an important element to the occurrence of cloud that aerosol particles serve as the primary source of cloud condensation nuclei(CCN). Remote sensing of aerosol properties from space/satellite can reveal the tendency of temporal-spatial distribution in global scale, however, whose precision can't satisfy the request of quantitative remote sensing. Thus, in this paper proposes the method combined sunphotometer (passive measurements) and Lidar (active remote sensing measurements) developed by Wuhan University to retrieve the aerosol optical depth. The primary results show that the proposed method improved the precision of aerosol optical depth effectively. Furthermore, long-term atmospheric and aerosol data could be obtained by consecutive Lidar and sunphotometer observations. Also these data will be used for emending the existing atmospheric model and aerosol type, and make them more compliant for China area application.

Mao, Feiyue; Gong, Wei; Zhu, Zhongmin; Li, Pingxiang

2008-10-01

321

Radiative properties of desert aerosols by optical ground-based measurements at solar wavelengths  

Microsoft Academic Search

Radiation measurements were made during April and May 1986 at M'bour (16.9 deg W, 14.3 deg N), 80 km south of Dakar, Senegal. The goal was to derive the optical properties of desert aerosols from ground-based measurements in order to validate satellite monitoring of these aerosols. The results of a ground truth experiment are presented. The measurements were performed during

D. Tanre; C. Devaux; M. Herman; R. Santer; J. Y. Gac

1988-01-01

322

Aerosol physical, chemical and optical properties observed in the ambient atmosphere during haze pollution conditions  

NASA Astrophysics Data System (ADS)

Aerosol’s properties in the ambient atmosphere may differ significantly from sampling results due to containing of abundant water content. We performed sun-sky radiometer measurements in Beijing during 2011 and 2012 winter to obtain distribution of spectral and angular sky radiance. The measurements are then used to retrieve aerosol physical, chemical and optical properties, including single scattering albedo, size distribution, complex refractive indices and aerosol component fractions identified as black carbon, brown carbon, mineral dust, ammonium sulfate-like components and water content inside particle matters. We found that during winter haze condition aerosol is dominated by fine particles with center radius of about 0.2 micron. Fine particles contribute about 93% to total aerosol extinction of solar light, and result in serious decrease of atmospheric visibility during haze condition. The percentage of light absorption of haze aerosol can up to about 10% among its total extinction, much higher than that of unpolluted conditions, that causes significant radiative cooling effects suppressing atmospheric convection and dispersion of pollutants. Moreover, the average water content occupies about one third of the ambient aerosol in volume which suggests the important effect of ambient humidity in the formation of haze pollution.

Li, Zhengqiang; Xie, Yisong; Li, Donghui; Li, Kaitao; Zhang, Ying; Li, Li; Lv, Yang; Qie, Lili; Xu, Hua

323

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

324

Modeling of microphysics and optics of aerosol particles in the marine environments  

NASA Astrophysics Data System (ADS)

We present a microphysical model for the surface layer marine and coastal atmospheric aerosols that is based on long-term observations of size distributions for 0.01-100 ?m particles. The fundamental feature of the model is a parameterization of amplitudes and widths for aerosol modes of the aerosol size distribution function (ASDF) as functions of fetch and wind speed. The shape of ASDF and its dependence on meteorological parameters, height above sea level (H), fetch (X), wind speed (U) and relative humidity (RH), are investigated. At present, the model covers the ranges H = 0 - 25 m, U = 3 - 18 km s-1, X ? 120 km and RH = 40 - 98%. The latest version of the Marine Aerosol Extinction Profiles model (MaexPro) is described and applied for the computation and analysis of the spectral profiles of aerosol extinction coefficients ?(?) in the wavelength band ? = 0.2-12 ?m. MaexPro is based on the aforementioned aerosol model assuming spherically shaped aerosol particles and the well-known Mie theory. The spectral profiles of ?(?) calculated by MaexPro are in good agreement with observational data and the numerical results. Moreover, MaexPro was found to be an accurate and reliable tool for investigating the optical properties of atmospheric aerosols.

Kaloshin, Gennady

2013-05-01

325

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

326

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

327

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 allowed "thermal spectral analysis (TSA)" and wavelength (?)-dependent organic-carbon (OC)-elemental-carbon (EC) measurements. Optical sensing was calibrated with transfer standards traceable to absolute R and T measurements, adjusted for loading effects to report spectral light absorption (as absorption optical depth (?a, ?)), and verified using diesel exhaust samples. 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 infrared to the near ultraviolet 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. J.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

2015-01-01

328

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

NASA Astrophysics Data System (ADS)

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 new method to make the aerosol retrieval over land more accurate than ever before. A sensitivity analysis of reflectance shows that wrong selection of spectral reflectance model results in quite a large difference in retrieved aerosol characteristics. Therefore, a well¡Csuited surface reflectance model is needed to be created. We conducted aerosol and radiation measurements coupled with in situ forest reflectance measurements in sync with satellite radiance measurements by EOS Terra and Aqua from the top of the atmosphere. The experimental site is located in a forest with an extensive and uniform area covered with deciduous trees commonly existing in Japan. The ground-based measurements include Andersen impactor samplings, radiometric measurements with OPC, a sunphotometer and a telephotometer. Forest reflectance was measured with a spectral radiometer covering visible and near infrared above the forest canopy level from a tower standing in the forest. Reflectance was measured directionally, and was found to show no major bi-directional dependency, assuring us that Lambert reflectance model is sufficient for calculation in this particular type of forest. The sampled spectral reflectances were averaged to be 0.0414 at 0.55 ? m. For satellite aerosol retrieval, visible and near infrared bands in MODIS sensors were employed. MODTRAN code was used in radiative transfer in the aerosol-laden atmosphere. Several different types of aerosol were examined, and a rural aerosol model with similar size distribution and composition to the aerosols, which are estimated from OPC measurements and Andersen samplings, was used as an input for the radiative transfer calculation. Absorption coefficients were calculated from the data obtained from a separate carbon sampling. The column aerosol optical depth was obtained to be 0.309 at 0.50 ? m, which is similar to the value derived from sunphotometer.

Bian, J.

2004-12-01

329

A study of aerosol optical properties during ozone pollution episodes in 2013 over Shanghai, China  

NASA Astrophysics Data System (ADS)

Aerosol optical property is essential to the tropospheric ozone formation mechanism while it was rarely measured in ozone-rich environment for a specific study. With the retrieved products of the sun-photometer, a comparative investigation was conducted on aerosol optical depth (AOD), single scattering albedo (SSA) and size distribution during ozone-polluted episodes and clean background. Contrary to expectations, aerosol loading was found to be positively-correlated with ozone concentration: daily averaged AOD at 500 nm in ozone episodes (~ 0.78) displayed 2.4 times higher than that in clean days (~ 0.32). Large Ångström exponent (~ 1.51) along with heavy aerosol loading indicated a considerable impact of fine particles on optical extinction. The dynamic diurnal fluctuation of these parameters also implied a complex interaction between aerosols and photo-chemical reactions. The bimodal lognormal distribution pattern for aerosol size spectra exhibited in both ozone-polluted and clean days. The occurrence of maximum volume concentration (~ 0.28) in fine mode (radius < 0.6 ?m) was observed at 3 p.m. (local time), when ozone was substantially generated. Pronounced scattering feature of aerosol was reproduced in high-concentration ozone environment. SSA tended to increase continuously from morning (~ 0.91 at 440 nm) to afternoon (~ 0.99), which may be associated with secondary aerosol formation. The scattering aerosol (with moderately high aerosol loading) may favor the ozone formation through increasing solar flux in boundary layer. Utilizing the micro-pulse lidar (MPL), a more developed planet boundary layer (PBL, top height ~ 1.96 km) was discovered during ozone-polluted days than clean condition (~ 1.4 km). In episodes, the maximum extinction ratio (~ 0.5 km- 1) was presented at a height of 1.2 km in the late afternoon. The humidity profile by sounding also showed the extreme value at this altitude. It suggested that optical extinction was mainly attributed to the aerosol in middle PBL, where the intense photochemical reactions and hydroscopic growth may occur.

Shi, Chanzhen; Wang, Shanshan; Liu, Rui; Zhou, Rui; Li, Donghui; Wang, Wenxin; Li, Zhengqiang; Cheng, Tiantao; Zhou, Bin

2015-02-01

330

Statistical Estimation of the Atmospheric Aerosol Absorption Coefficient Based on the Data of Optical Measurements  

SciTech Connect

The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms.

Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.

2005-03-18

331

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

332

Boundary layer aerosol characteristics at Mahabubnagar during CAIPEEX-IGOC: modeling the optical and radiative properties.  

PubMed

An Integrated Ground Observational Campaign (IGOC) was conducted at Mahabubnagar--a tropical rural station in the southern peninsular India, under the Cloud Aerosol Interaction and Precipitation Enhancement Experiment (CAIPEEX) program during the period from July to November 2011. Measured chemical composition and carbonaceous aerosols from PM2.5 samples were used in an aerosol optical model to deduce crucial aerosol optical properties, which were then used in a radiative transfer model for radiative forcing estimations. The model derived aerosol optical depth (AOD at 500 nm), varied from 0.13 to 0.76 (mean of 0.40 ± 0.18) whereas Ångström exponent (AE) between 0.10 and 0.65 (mean of 0.33 ± 0.17) suggests relative dominance of coarse particles over the station. On the other hand, single scattering albedo (SSA at 500 nm) was found to vary from 0.78 to 0.92 (mean of 0.87 ± 0.04) during the measurement period. The magnitude of absorption Ångström exponent (AAE), varied from 0.83 to 1.33 (mean of 1.10 ± 0.15), suggests mixed type aerosols over the station. Aerosol direct radiative forcing was estimated and found to vary from -8.9 to -49.3 W m(-2) (mean of -27.4 ± 11.8 W m(-2)) at the surface and +9.7 to +44.5 W m(-2) (mean of +21.3 ± 9.4 W m(-2)) in the atmosphere during the course of measurements. The atmospheric forcing was observed to be ~30% higher during October (+ 29 ± 9 W m(-2)) as compared to August (+21 ± 7 W m(-2)) when the station is mostly influenced by continental polluted aerosols. The result suggests an additional atmospheric heating rate of 0.24 K day(-1) during October, which may be crucial for various boundary layer processes in favorable atmospheric conditions. PMID:24103256

Srivastava, A K; Bisht, D S; Tiwari, S

2014-01-15

333

Satellite study over Europe to estimate the single scattering albedo and the aerosol optical depth  

NASA Astrophysics Data System (ADS)

Aerosol particles have a significant effect on the Earth climate on regional and global scales by perturbing the radiation balance both directly due to scattering and absorption of solar radiation and indirectly due to their effect on cloud macroscopic and microphysical properties (IPCC 2007 [1]). One of the main contributors to the radiative effect of aerosols is the Single Scattering Albedo (SSA). One of the research topics is the uncertainty in estimating and improving the SSA value. In radiative transfer studies, single scattering albedo is the ratio of scattering optical depth and the total optical depth of the atmosphere. The SSA and the Aerosol Optical Depth (AOD) are two of the main parameters to estimate aerosol radiative forcing. In this study we show results of the SSA and the AOD at 0.555 ?m retrieved from Advanced Along Track Scanning Radiometer (AATSR) data, with focus on forest fires over Europe. The retrieval results are validated using AERONET AOD level 2.0 data and the SSA is compared with the AERONET level 2.0 inversion product. The SSA is a new AATSR product; it is obtained with a new method, based on aerosol Look-Up Tables (LUT), for selected aerosol size distribution, with given refractive index. The LUTs are used together with the contribution in the AOD fraction of absorbing and non-absorbing aerosol particles. The SSA can be applied in different studies like the computation of scattering phase function, the characterization of aerosol particles and in radiative transfer models. Preliminary results show a good agreement between the AOD at 0.555 ?m from AERONET and AATSR with a correlation coefficient of up to 0.86.

Rodríguez, E.; Kolmonen, P.; Sundström, A.-M.; Sogacheva, L.; Virtanen, T.; de Leeuw, G.

2013-05-01

334

Airborne Sunphotometry of Aerosol Optical Depth and Columnar Water Vapor During ACE-Asia  

NASA Technical Reports Server (NTRS)

During the Intensive Field Campaign (IFC) of the Aerosol Characterization Experiment - Asia (ACE-Asia), March-May 2001, the 6-channel NASA Ames Airborne Tracking Sunphotometer (AATS-6) operated during 15 of the 19 research flights aboard the NCAR C- 130, while its 14-channel counterpart (AATS- 14) was flown successfully on all 18 research flights of a Twin Otter aircraft operated by the Center for Interdisciplinary Remotely Piloted Aircraft Studies (CIRPAS), Monterey, CA. ACE-Asia was the fourth in a series of aerosol characterization experiments and focused on aerosol outflow from the Asian continent to the Pacific basin. Each ACE was designed to integrate suborbital and satellite measurements and models so as to reduce the uncertainty in calculations of the climate forcing due to aerosols. The Ames Airborne Tracking Sunphotometers measured solar beam transmission at 6 (380-1021 nm, AATS-6) and 14 wavelengths (353-1558 nm, AATS-14) respectively, yielding aerosol optical depth (AOD) spectra and column water vapor (CWV). Vertical differentiation in profiles yielded aerosol extinction and water vapor concentration. The wavelength dependence of AOD and extinction indicates that supermicron dust was often a major component of the aerosol. Frequently this dust-containing aerosol extended to high altitudes. For example, in data flights analyzed to date 34 +/- 13% of full-column AOD(525 nm) was above 3 km. In contrast, only 10 +/- 4% of CWV was above 3 km. In this paper, we will show first sunphotometer-derived results regarding the spatial variation of AOD and CWV, as well as the vertical distribution of aerosol extinction and water vapor concentration. Preliminary comparison studies between our AOD/aerosol extinction data and results from: (1) extinction products derived using in situ measurements and (2) AOD retrievals using the Multi-angle Imaging Spectro-Radiometer (MISR) aboard the TERRA satellite will also be presented.

Redemann, Jens; Schmid, B.; Russell, P. B.; Livingston, J. M.; Eilers, J. A.; Ramirez, S. A.; Kahn, R.; Hipskind, R. Stephen (Technical Monitor)

2001-01-01

335

Differences in the OC/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis  

EPA Science Inventory

Thermal-optical analysis (TOA) is typically used to measure the OC/EC (organic carbon/elemental carbon) and EC/TC (elemental carbon/total carbon) ratios in source and atmospheric aerosols. The present study utilizes a dual-optical carbon aerosol analyzer to examine the effects of...

336

Variability in aerosol optical and physical characteristics over the Bay of Bengal and the Arabian Sea deduced from Ångström exponents  

Microsoft Academic Search

Spectral distribution of aerosol optical depths (AODs) measured in the 0.4–0.875 ?m wavelength region using a Sun photometer over Bay of Bengal and Arabian Sea during the 2006 premonsoon season are analyzed to obtain more interesting information on the physical and optical characteristics of aerosols. Examination of spectral AODs measured over the Bay of Bengal and the Arabian Sea by

Sumita Kedia; S. Ramachandran

2009-01-01

337

Variations in optical properties of aerosols on monsoon seasonal change and estimation of aerosol optical depth using ground-based meteorological and air quality data  

NASA Astrophysics Data System (ADS)

In this study, the optical properties of aerosols in Penang, Malaysia were analyzed for four monsoonal seasons (northeast monsoon, pre-monsoon, southwest monsoon, and post-monsoon) based on data from the AErosol RObotic NETwork (AERONET) from February 2012 to November 2013. The aerosol distribution patterns in Penang for each monsoonal period were quantitatively identified according to the scattering plots of the aerosol optical depth (AOD) against the Angstrom exponent. A modified algorithm based on the prototype model of Tan et al. (2014a) was proposed to predict the AOD data. Ground-based measurements (i.e., visibility and air pollutant index) were used in the model as predictor data to retrieve the missing AOD data from AERONET because of frequent cloud formation in the equatorial region. The model coefficients were determined through multiple regression analysis using selected data set from in situ data. The predicted AOD of the model was generated based on the coefficients and compared against the measured data through standard statistical tests. The predicted AOD in the proposed model yielded a coefficient of determination R2 of 0.68. The corresponding percent mean relative error was less than 0.33% compared with the real data. The results revealed that the proposed model efficiently predicted the AOD data. Validation tests were performed on the model against selected LIDAR data and yielded good correspondence. The predicted AOD can beneficially monitor short- and long-term AOD and provide supplementary information in atmospheric corrections.

Tan, F.; Lim, H. S.; Abdullah, K.; Yoon, T. L.; Holben, B.

2014-07-01

338

Contribution of ammonium nitrate to aerosol optical depth and direct radiative forcing by aerosols over East Asia  

NASA Astrophysics Data System (ADS)

This study focused on the contribution of ammonium nitrate (NH4NO3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, CTM-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique, over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties, the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH4NO3 to AOD and DRF by aerosols (?AOD and ?DRF) were estimated for four seasons of 2006 over East Asia. Both ?AOD and ?DRF showed seasonal variations over East Asia within the ranges between 4.7% (summer) and 31.3% (winter) and between 4.7% (summer) and 30.7% (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6% and 15.3%. Under all-sky conditions, ?DRF varied between 3.6% (summer) and 24.5% (winter), showing annual average contribution of 12.1% over East Asia. These annual average contributions of NH4NO3 to AOD and DRF are almost comparable to the annual average mass fractions of NH4NO3 to PM2.5 and PM10 (17.0% and 14.0%, respectively). ?AOD and ?DRF were even larger in the locations where NH3 and NOx emission rates are strong like the Central East China (CEC) region and Sichuan basin. For example, under clear-sky conditions, both ?AOD and ?DRF over the CEC region range between 6.9% (summer) and 47.9% (winter) and between 6.7% (summer) and 47.5% (winter), respectively. Based on this analysis, it was concluded that both ?DRF and ?DRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.

Park, R. S.; Lee, S. J.; Shin, S.-K.; Song, C. H.

2013-07-01

339

Contribution of ammonium nitrate to aerosol optical depth and direct radiative forcing by aerosols over East Asia  

NASA Astrophysics Data System (ADS)

This study focused on the contribution of ammonium nitrate (NH4NO3) to aerosol optical depth (AOD) and direct radiative forcing (DRF) by aerosols over an East Asian domain. In order to evaluate the contribution, chemistry-transport model (CTM)-estimated AOD was combined with satellite-retrieved AOD, utilizing a data assimilation technique, over East Asia for the entire year of 2006. Using the assimilated AOD and CTM-estimated aerosol optical properties, the DRF by aerosols was estimated over East Asia via a radiative transfer model (RTM). Both assimilated AOD and estimated DRF values showed relatively good agreements with AOD and DRF by aerosols from AERONET. Based on these results, the contributions of NH4NO3 to AOD and DRF by aerosols (?AOD and ?DRF) were estimated for the four seasons of 2006 over East Asia. Both ?AOD and ?DRF showed seasonal variations over East Asia within the ranges between 4.7% (summer) and 31.3% (winter) and between 4.7% (summer) and 30.7% (winter), respectively, under clear-sky conditions, showing annual average contributions of 15.6% and 15.3%. Under all-sky conditions, ?DRF varied between 3.6% (summer) and 24.5% (winter), showing annual average contribution of 12.1% over East Asia. These annual average contributions of NH4NO3 to AOD and DRF are almost comparable to the annual average mass fractions of NH4NO3 in PM2.5 and PM10 (17.0% and 14.0%, respectively). ?AOD and ?DRF were even larger in the locations where NH3 and NOx emission rates are strong, such as the central East China (CEC) region and Sichuan Basin. For example, under clear-sky conditions, both ?AOD and ?DRF over the CEC region range between 6.9% (summer) and 47.9% (winter) and between 6.7% (summer) and 47.5% (winter), respectively. Based on this analysis, it was concluded that both ?AOD and ?DRF cannot be ignored in East Asian air quality and radiative forcing studies, particularly during winter.

Park, R. S.; Lee, S.; Shin, S.-K.; Song, C. H.

2014-02-01

340

Aerosol optical parameters in Kazakhstan for the summer and autumn seasons  

NASA Astrophysics Data System (ADS)

Measurements of direct and diffuse solar radiation in cloudless atmosphere were conducted in 1984 and 1996 - 1998 in South-Eastern Kazakhstan (not far from Almaty city) during the period July - October. The day sky spectrophotometer, operating in 8 spectral bands within the interval 0.42 - 22.2 microns, was used. Aerosol phase function was inverted from diffuse radiance in the solar almucantar using proposed earlier adjustment method. Aerosol optical depth was calculated by long Bouguer method for solar zenith angles 30 degree(s) - 80 degree(s) (both a.m. and p.m.) under condition of stability of atmospheric optical transparency during 1 and more hours.

Petelina, Svetlana V.; Egorova, Lilya A.; Glushko, Viktor N.

1999-11-01

341

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

342

Airborne measurements of optical properties of tropospheric aerosols over an urban area  

NASA Astrophysics Data System (ADS)

Aircraft measurements of aerosol sizes, intensities of direct-solar and circumsolar (aureole) radiations, and upward and downward fluxes of solar radiation were carried out over Nagoya, a typical urban area in Japan, using an optical particle counter, an aureolemeter, and spectral pyranometers, respectively. Vertical profiles of optical thicknesses and volume spectra of aerosols were retrieved by inverting measured aureole intensities. The obtained values were utilized to estimate the absorption indices of aerosols from the downward flux measurements. The results are summarized as follows: (1) the concentration and the vertical stratification of tropospheric aerosols vary considerably day by day, (2) bimodal volume spectra of aerosols with radii smaller and larger than about 0.5 microns generally prevail in the troposphere, and (3) estimated values of the imaginary index of refraction of tropospheric columnar aerosols are within the range of 0.005-0.014 in the visible region and 0.008-0.020 in the NIR region. Corresponding values for the haze layer are slightly larger.

Tanaka, Masayuki; Hayasaka, Tadahiro; Nakajima, Teruyuki

1990-06-01

343

A Comparison of Aerosol Optical, Microphysical, and Chemical Measurements between LAX and Long Beach Harbor  

NASA Astrophysics Data System (ADS)

In the summer of 2008, measurements of aerosols were made on-board the NASA DC-8 over the state of California, as part of the second phase of the Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) on behalf of the California Air resources Board (CARB). The DC-8 made four flights, between 18 June and 26 June, totaling 33 hours, to examine California’s atmosphere to better understand the chemical dynamics of smog and greenhouse gases over the state. The NASA DC-8 had a suite of aerosol instruments, capable of measuring the number concentrations, optical properties, and size distributions of aerosols between 0.003 and 1500 um. In this presentation, we will compare aerosol observations made at two areas within the Los Angeles Basin, Los Angeles International airport (LAX) and Long Beach Harbor. LAX is in the middle of the second most populated metropolitan area in the United States and is the fifth busiest airport in the world, while Long Beach Harbor (20 miles south of LAX) is the world’s 2nd busiest container port. Initial results suggest a greater aerosol loading and additional presence of ultrafine aerosols during the week due to vehicular emissions. We will also present analysis of aerosol observations as a function of time of day from the four missed approaches at LAX and four over flights of Long Beach Harbor.

Thornhill, K. L.; Anderson, B. E.; Chen, G.; Winstead, E.; Ziemba, L. D.; Beyersdorf, A. J.; Diskin, G. S.; Nenes, A.; Lathem, T. L.; Arctas Science Team

2010-12-01

344

The use of a stage diffusion cut-off in aerosol optical investigations  

NASA Astrophysics Data System (ADS)

A controlled cut-off of the natural aerosol size spectrum was applied to nephelometric measurements in order to test the reliability of the retrieval of aerosol microstructure from nephelometer data. The cut-off was carried out using a 4-stage diffusion battery. It was shown that transformation of the aerosol size distribution obtained by solving the inverse problem for measured directed scattering coefficients at scattering angles of 45° and 90° and the degree of linear polarization at 90° corresponds to theoretical calculations for different stages of the diffuse battery in the particle size range from 0.07 to 0.4 ?m. It was also established that inversion of the difference between the optical characteristics of non-cut and cut aerosol gives the difference between size distributions.

Kozlov, Valerii S.; Kozlov, A. S.; Ankilov, A. N.; Baklanov, A. M.; Panchenko, Mikhail V.; Sviridenkov, Mikhail A.; Terpugova, Svetlana A.

2004-02-01

345

Characteristics of the aerosol climatology over Finland based on the optical columnar properties  

NASA Astrophysics Data System (ADS)

We have studied the long-range aerosol transport over Finland using ground-based sunphotometric and satellite based aerosol optical properties' measurements. More specifically, we have used data from two satellite sensors: the Advanced Along Track Scanning Radiometer (AATSR) flying on ENVISAT and the MODIS instrument onboard Terra. In addition data from three. Cimel sunphotometers were used at: an urban (Helsinki), a rural (Hyytiälä), and a semiurban (Kuopio) sites all being part of AERONET network, supported by PFR measurements at two rural sites, Jokioinen and Sodankylä. AATSR and MODIS provided information on the regional distribution of aerosol properties whereas sunphotometers provided information on local columnar aerosol properties (e.g. Aerosol Optical Depth). Sunphotometric AOD data were used to validate the satellite retrievals, as well as to provide information on other microphysical parameters such as the aerosol single scattering albedo, size distribution, and refractive index. The wind speed and direction, jointly with the air mass back trajectories for specific cases of aerosol transportation over Finland were used to determine aerosol gradients in along-wind situations. Depending on the prevailing air masses, Finland (boreal forest, subarctic zone) is characterized by maritime - causing warm, clean weather - and continental climate, accounting for moderately cold in winter, and hot in summer. Our initial expectation is that pollution events are connected with polluted air masses originating from east or southeast as well as industrial areas in Central Europe. Pollution events observed in spring in Helsinki are often related to the removal of the sanding material or inversion situations. We distinguished the events with long transported air pollution from cases with accumulation of the pollution due to the local meteorological factors. We chose a set of representative event days covering the overall time period between June 2006 and August 2009.

Aaltonen, Veijo; Rodriguez, Edith; Stylianos, Kazadzis; Larisa, Sogacheva; Antti, Arola; de Leeuw, Gerrit

2010-05-01

346

Variation of aerosol optical properties from AERONET observation at Mt. Muztagh Ata, Eastern Pamirs  

NASA Astrophysics Data System (ADS)

Using data from the ground-based remote sensing Aerosol Robotic Network (AERONET), aerosol optical properties, including aerosol optical depth (AOD), Ångström exponent (?), and volume size distribution were investigated for the period June to December 2011 at Mt. Muztagh Ata (Muztagata), Eastern Pamirs. The monthly average values of AOD (500 nm) and ? (440-870 nm) varied from 0.08 ± 0.02 to 0.16 ± 0.11, and from 0.56 ± 0.06 to 0.93 ± 0.28, respectively. The daily AOD averages 0.14 ± 0.07, with the maximum (0.5) occurring in August and the minimum (0.05) occurring in November. A small increase in AOD is expected with a noticeable decrease in the ? value. The daily ? averages 0.70 ± 0.27, and most exponents are less than 1, indicating the majority of larger aerosol particles. The volume size distribution of aerosol particles shows bimodal log-normal characteristics, with a fine mode radius of 0.2 ?m and a coarse mode radius of 3 ?m. The MODIS AOD and AERONET AOD display a similar variation, while the former is always noticeably higher than the latter with a difference of 0.1-0.4, indicating that the MODIS data might overestimate the aerosol load. Our results indicate that high aerosol volume concentration occurs in summer with the dominance of coarse particles over Muztagh Ata. The low AOD shows a clean atmosphere in this region, revealing that it is an atmospheric background site for continental aerosol monitoring.

Yan, Ni; Wu, Guangjian; Zhang, Xuelei; Zhang, Chenglong; Xu, Tianli; Lazhu

2015-02-01

347

Observations of rapid aerosol optical depth enhancements in the vicinity of polluted cumulus clouds  

NASA Astrophysics Data System (ADS)

During the July 2011 Deriving Information on Surface conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field experiment in Maryland, significant enhancements in Aerosol Robotic Network (AERONET) sun-sky radiometer measured aerosol optical depth (AOD) were observed in the immediate vicinity of non-precipitating cumulus clouds on some days. Both measured Ångström exponents and aerosol size distribution retrievals made before, during and after cumulus development often suggest little change in fine mode particle size; therefore, implying possible new particle formation in addition to cloud processing and humidification of existing particles. In addition to sun-sky radiometer measurements of large enhancements of fine mode AOD, lidar measurements made from both ground-based and aircraft-based instruments during the experiment also measured large increases in aerosol signal at altitudes associated with the presence of fair weather cumulus clouds. These data show modifications of the aerosol vertical profile as a result of the aerosol enhancements at and below cloud altitudes. The airborne lidar data were utilized to estimate the spatial extent of these aerosol enhancements, finding increased AOD, backscatter and extinction out to 2.5 km distance from the cloud edge. Furthermore, in situ measurements made from aircraft vertical profiles over an AERONET site during the experiment also showed large increases in aerosol scattering and aerosol volume after cloud formation as compared to before. The 15-year AERONET database of AOD measurements at the Goddard Space Flight Center (GSFC), Maryland site, was investigated in order to obtain a climatological perspective of this phenomenon of AOD enhancement. Analysis of the diurnal cycle of AOD in summer showed significant increases in AOD from morning to late afternoon, corresponding to the diurnal cycle of cumulus development.

Eck, T. F.; Holben, B. N.; Reid, J. S.; Arola, A.; Ferrare, R. A.; Hostetler, C. A.; Crumeyrolle, S. N.; Berkoff, T. A.; Welton, E. J.; Lolli, S.; Lyapustin, A.; Wang, Y.; Schafer, J. S.; Giles, D. M.; Anderson, B. E.; Thornhill, K. L.; Minnis, P.; Pickering, K. E.; Loughner, C. P.; Smirnov, A.; Sinyuk, A.

2014-11-01

348

Effects of Transport and Processing on Aerosol Chemical and Optical Properties Across the Gulf of Maine  

NASA Astrophysics Data System (ADS)

NEAQS-ITCT 2004 took place in July and August to study natural and anthropogenic emissions from North America including the processing of gas and particle phase species during transport over the North Atlantic and the resulting impact on air quality and climate. During the experiment, measurements were made onboard the NOAA RV Ronald H. Brown with a ship track that extended from the coast along Cape Cod, MA, Boston, MA and Portland, ME, east into the Gulf of Maine and out to Chebogue Point, Nova Scotia. Although measurements on the ship were not made in a true Lagrangian sense, they reveal information about the effects of transport and processing on aerosol chemical and optical properties. Photochemical age based on measured toluene to benzene ratios can be used in this region to indicate 'younger' versus 'older' aerosol. This approach, coupled with FLEXPART estimates of source contributions and age, reveals that continental aerosol becomes more acidic as it ages with transport over the Gulf of Maine. The increasing acidity is due to the conversion of SO2 to SO4= with no further significant input of NH3 in the well-capped marine boundary layer to neutralize the aerosol. In addition, as the aerosol ages, the organic mass fraction decreases while the organics that are present become more oxidized. These same chemical features were observed in aerosol transported from the Ohio River Valley and beyond. In contrast, recently formed aerosol from urban centers along the Eastern Seaboard are neutralized, have a higher organic content, and the organics are less oxidized. The impact of the observed range of aerosol acidity, organic mass fraction, and degree of oxidation of the organic matter on the f(RH) of the aerosol will be described. Here, f(RH) refers to the dependence of light extinction on relative humidity.

Quinn, P.; Bates, T.; Baynard, T.; Onasch, T.; Coffman, D.; Covert, D.; Worsnop, D.; Goldan, P.; Kuster, B.; Degouw, J.; Stohl, A.

2005-12-01

349

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

350

Trends in sulfate and organic aerosol mass in the Southeast U.S.: Impact on aerosol optical depth and radiative forcing  

NASA Astrophysics Data System (ADS)

of SO2 in the United States have declined since the early 1990s, resulting in a decrease in aerosol sulfate mass in the Southeastern U.S. of -4.5(±0.9)% yr-1 between 1992 and 2013. Organic aerosol mass, the other major aerosol component in the Southeastern U.S., has decreased more slowly despite concurrent emission reductions in anthropogenic precursors. Summertime measurements in rural Alabama quantify the change in aerosol light extinction as a function of aerosol composition and relative humidity. Application of this relationship to composition data from 2001 to 2013 shows that a -1.1(±0.7)% yr-1 decrease in extinction can be attributed to decreasing aerosol water mass caused by the change in aerosol sulfate/organic ratio. Calculated reductions in extinction agree with regional trends in ground-based and satellite-derived aerosol optical depth. The diurnally averaged summertime surface radiative effect has changed by 8.0 W m-2, with 19% attributed to the decrease in aerosol water.

Attwood, A. R.; Washenfelder, R. A.; Brock, C. A.; Hu, W.; Baumann, K.; Campuzano-Jost, P.; Day, D. A.; Edgerton, E. S.; Murphy, D. M.; Palm, B. B.; McComiskey, A.; Wagner, N. L.; Sá, S. S.; Ortega, A.; Martin, S. T.; Jimenez, J. L.; Brown, S. S.

2014-11-01

351

A new method of measuring aerosol optical properties from digital twilight photographs  

NASA Astrophysics Data System (ADS)

An optimal-estimation algorithm for inferring aerosol optical properties from digital twilight photographs is proposed. The sensitivity of atmospheric components and surface characteristics to brightness and color of twilight sky is investigated, and the results suggest that tropospheric and stratospheric aerosol optical thickness (AOT) are sensitive to condition of the twilight sky. The coarse-fine particle volume ratio is moderately sensitive to the sky condition near the horizon under a clean-atmosphere condition. A radiative transfer model that takes into account a spherical-shell atmosphere, refraction, and multiple scattering is used as a forward model. Error analysis shows that the tropospheric and stratospheric AOT can be retrieved without significant bias. Comparisons with results from other ground-based instruments exhibit reasonable agreement on AOT. A case study suggests that the AOT retrieval method can be applied to atmospheric conditions with varying aerosol vertical profiles and vertically inhomogeneous species in the troposphere.

Saito, M.; Iwabuchi, H.

2015-01-01

352

Water tweezers for pariticles gagging  

Microsoft Academic Search

In recent years, the microfabrication has grown rapidly, and one of the key technique and important basis is pariticle trapping and manipulation. Now, it develops mostly on light, electricity and plasma to make it. The text raises a fire-new concept of “water tweezers”: when fistulous micro water-jet acts on the face of pariticle, the block of viscosity that causes a

Xiaomin Cheng; Ye Xu; Lin Zhou; Guoliang Zhang; Naiyu Shen

2010-01-01

353

Estimation of aerosol columnar size distribution and optical thickness from the angular distribution of radiance exiting the atmosphere: simulations  

NASA Astrophysics Data System (ADS)

We report the results of simulations in which an algorithm developed for estimation of aerosol optical properties from the angular distribution of radiance exiting the top of the atmosphere over the oceans [Appl. Opt. 33, 4042 (1994)] is combined with a technique for carrying out radiative transfer computations by synthesis of the radiance produced by individual components of the aerosol-size distribution [Appl. Opt. 33, 7088 (1994)], to estimate the aerosol-size distribution by retrieval of the total aerosol optical thickness and the mixing ratios for a set of candidate component aerosol-size distributions. The simulations suggest that in situations in which the true size-refractive-index distribution can actually be synthesized from a combination of the candidate components, excellent retrievals of the aerosol optical thickness and the component mixing ratios are possible. An exception is the presence of strongly absorbing aerosols. The angular distribution of radiance in a single spectral band does not appear to contain sufficient information to separate weakly from strongly absorbing aerosols. However, when two spectral bands are used in the algorithm, retrievals in the case of strongly absorbing aerosols are improved. When pseudodata were simulated with an aerosol-size distribution that differed in functional form from the candidate components, excellent retrievals were still

Wang, Menghua; Gordon, Howard R.

1995-10-01

354

Characterizing Aerosol Distributions and Optical Properties Using the NASA Langley High Spectral Resolution Lidar  

SciTech Connect

The objective of this project was to provide vertically and horizontally resolved data on aerosol optical properties to assess and ultimately improve how models represent these aerosol properties and their impacts on atmospheric radiation. The approach was to deploy the NASA Langley Airborne High Spectral Resolution Lidar (HSRL) and other synergistic remote sensors on DOE Atmospheric Science Research (ASR) sponsored airborne field campaigns and synergistic field campaigns sponsored by other agencies to remotely measure aerosol backscattering, extinction, and optical thickness profiles. Synergistic sensors included a nadir-viewing digital camera for context imagery, and, later in the project, the NASA Goddard Institute for Space Studies (GISS) Research Scanning Polarimeter (RSP). The information from the remote sensing instruments was used to map the horizontal and vertical distribution of aerosol properties and type. The retrieved lidar parameters include profiles of aerosol extinction, backscatter, depolarization, and optical depth. Products produced in subsequent analyses included aerosol mixed layer height, aerosol type, and the partition of aerosol optical depth by type. The lidar products provided vertical context for in situ and remote sensing measurements from other airborne and ground-based platforms employed in the field campaigns and was used to assess the predictions of transport models. Also, the measurements provide a data base for future evaluation of techniques to combine active (lidar) and passive (polarimeter) measurements in advanced retrieval schemes to remotely characterize aerosol microphysical properties. The project was initiated as a 3-year project starting 1 January 2005. It was later awarded continuation funding for another 3 years (i.e., through 31 December 2010) followed by a 1-year no-cost extension (through 31 December 2011). This project supported logistical and flight costs of the NASA sensors on a dedicated aircraft, the subsequent analysis and archival of the data, and the presentation of results in conferences, workshops, and publications. DOE ASR field campaigns supported under this project included - MAX-Mex /MILAGRO (2006) - TexAQS 2006/GoMACCS (2006) - CHAPS (2007) - RACORO (2009) - CARE/CalNex (2010) In addition, data acquired on HSRL airborne field campaigns sponsored by other agencies were used extensively to fulfill the science objectives of this project and the data acquired have been made available to other DOE ASR investigators upon request.

Hostetler, Chris; Ferrare, Richard

2013-02-14

355

AERONET-based models of smoke-dominated aerosol near source regions and transported over oceans, and implications for satellite retrievals of aerosol optical depth  

NASA Astrophysics Data System (ADS)

Smoke aerosols from biomass burning are an important component of the global aerosol system. Analysis of Aerosol Robotic Network (AERONET) retrievals of aerosol microphysical/optical parameters at 10 sites 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 observed at coastal/island AERONET sites also mostly lie within the range of variability at the near-source sites. Differences between sites tend to be larger than variability at an individual site, although optical properties for some sites in different regions can be quite similar. Across the sites, typical midvisible SSA ranges from ~ 0.95-0.97 (sites dominated by boreal forest or peat burning, typically with larger fine-mode particle radius and spread) to ~ 0.88-0.9 (sites most influenced by grass, shrub, or crop burning, typically smaller fine-mode particle radius and spread). The tropical forest site Alta Floresta (Brazil) is closer to this second category, although with intermediate SSA ~ 0.92. The strongest absorption is seen in southern African savannah at Mongu (Zambia), with average midvisible SSA ~ 0.85. Sites with stronger absorption also tend to have stronger spectral gradients in SSA, becoming more absorbing at longer wavelengths. Microphysical/optical models are presented in detail so as to facilitate their use in radiative transfer calculations, including extension to UV (ultraviolet) wavelengths, and lidar ratios. One intended application is to serve as candidate optical models for use in satellite aerosol optical depth (AOD) retrieval algorithms. The models presently adopted by these algorithms over ocean often have insufficient absorption (i.e. too high SSA) to represent these biomass burning aerosols. The underestimates in satellite-retrieved AOD in smoke outflow regions, which have important consequences for applications of these satellite data sets, are consistent with the level of underestimated absorption.

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

2014-10-01

356

Atmospheric optical and radiative e!ects of anthropogenic aerosol constituents from India  

Microsoft Academic Search

A box model has been used to compare the burdens, optical depths and direct radiative forcing from anthropogenic PM 2.5 aerosol constituents over the Indian subcontinent. A PM 2.5 emission inventory from India for 1990, compiled for the \\

M. Shekar Reddy; Chandra Venkataraman

2000-01-01

357

Features and effects of aerosol optical depth observed at Mauna Loa Hawaii: 1982-1992  

Microsoft Academic Search

Spectral aerosol optical depth, taua, observed at Mauna Loa, Hawaii, for the past 11 years is analyzed for background variations and the effects of two major volcanic eruptions: El Chichón in 1982 and Mount Pinatubo in 1991. A previously known annual variation and near-background levels are present in the record. The data are of high accuracy, being primarily obtained from

Ellsworth G. Dutton; Patrick Reddy; Steve Ryan; John J. DeLuisi

1994-01-01

358

MISR aerosol optical depth retrievals over southern Africa during the SAFARI?2000 Dry Season Campaign  

Microsoft Academic Search

This paper presents, for the first time, retrievals of aerosol optical depths from Multi-angle Imaging Spectro- Radiometer (MISR) observations over land. Application of the MISR operational algorithm to data taken over southern Africa during the SAFARI-2000 dry season campaign yields results that compare favorably with coincident surface-based measurements taken by the AERONET radiometer network.

D. J. Diner; W. A. Abdou; C. J. Bruegge; J. E. Conel; K. A. Crean; B. J. Gaitley; M. C. Helmlinger; R. A. Kahn; J. V. Martonchik; S. H. Pilorz; B. N. Holben

2001-01-01

359

LIDAR Measurements of the Vertical Distribution of Aerosol Optical and Physical Properties over Central Asia  

EPA Science Inventory

The vertical structure of aerosol optical and physical properties was measured by Lidar in Eastern Kyrgyzstan, Central Asia, from June 2008 to May 2009. Lidar measurements were supplemented with surface-based measurements of PM2.5 and PM10 mass and chemical ...

360

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 radiance, can be compared against model estimates to provide an evaluation of the columnar ae...

361

Differences in the OC\\/EC Ratios that Characterize Ambient and Source Aerosols due to Thermal-Optical Analysis  

Microsoft Academic Search

Different thermal-optical methods used to measure OC\\/EC and EC\\/TC ratios in atmospheric aerosols often produce significantly different results due to variations within the temperature programming and optical techniques of each method. To quantify the thermal and optical effects on these ratios, various source (residential cookstoves and diesel exhaust) and atmospheric (rural and urban) aerosols were analyzed using 3 thermal protocols:

Bernine Khan; Michael D. Hays; Chris Geron; James Jetter

2012-01-01

362

Long-term observations of aerosol optical properties at Wuhan, an urban site in Central China  

NASA Astrophysics Data System (ADS)

Aerosol optical properties including aerosol optical depth (AOD), Ångström exponent (?), single scattering albedo (SSA), aerosol size distribution and refractive index at urban Wuhan in Central China are investigated based on the measurements from a CIMEL sun-photometer during 2007-2013. AOD500 nm is found to be relatively high all year round and the highest value 1.52 occurs in June 2012 and the lowest (0.57) in November 2012. ? shows a significant monthly variation, with the highest value in June 2010 (1.71) and the lowest value (0.78) in April 2012. Analysis of AOD and ? frequencies indicate that this region is populated with fine-mode particles. Monthly variations of SSA for total, fine and coarse-mode particles are closely related to the aerosol hygroscopic growth, fossil fuel and biomass burning. The aerosol volume size distributions (bi-modal pattern) show distinct differences in particle radius for different seasons, the radius for fine-mode particles generally increase from spring to summer month, for example, the highest peak is around radius 0.15 ?m in March, while the peak radius is around 0.25 ?m in June. Finally, monthly statistics of real and imaginary parts of the complex refractive index are analyzed, the highest averages of real (1.50) and imaginary parts (0.0395) are found in spring and autumn, respectively at wavelength 440-1020 nm.

Wang, Lunche; Gong, Wei; Xia, Xiangao; Zhu, Jun; Li, Jun; Zhu, Zhongmin

2015-01-01

363

Aerosol optical chromatography and measurements of light extinction by single particles  

NASA Astrophysics Data System (ADS)

To resolve some of the significant uncertainties in the impact of aerosols on global climate, new tools are required to probe light scattering and absorption by aerosol particles. Ideally, such tools should allow direct measurements on individual particles over extended periods of time, providing data to better constrain the optical properties of aerosol, how they depend on the environmental conditions (relative humidity and temperature) and how they change with time. Here, we present a new technique using a combination of a Bessel beam to manipulate individual particles and cavity ringdown spectroscopy for ultrasensitive measurements of the optical extinction. We show that particles can be spatially separated along the propagation direction of a Bessel beam according to their size and refractive index when confined by a Bessel beam core and a counter-propagating gas flow, referred to as optical chromatography. The time-dependent position of a particle is shown to be a consequence of the differing size dependencies of the forces arising from Stokes drag and radiation pressure. We also show that particles captured in a Bessel beam can be moved in and out of an optical cavity formed by two highly reflective mirrors. The time constant for the ringdown in light coupled within the cavity can then be used to measure the optical cross-section of the individual particle with high accuracy. An individual particle can be captured indefinitely and its change in optical cross-section measured with change in environmental conditions.

Reid, Jonathan P.; Mason, Bernard J.; Cotterell, Michael I.; Preston, Thomas C.; Orr-Ewing, Andrew J.

2014-09-01

364

A novel method to retrieve Aerosol Optical Thickness from high-resolution optical satellite images  

NASA Astrophysics Data System (ADS)

Aerosol Optical Thickness (AOT) data has many important applications including atmospheric correction of satellite imagery and monitoring of particulate matter air pollution. Current data products are generally available at a kilometre-scale resolution, but many applications require far higher resolutions. For example, particulate matter concentrations vary on a metre-scale, and thus data products at a similar scale are required to provide accurate assessments of particle densities and allow effective monitoring of air quality and analysis of local air quality effects on health. A novel method has been developed which retrieves per-pixel AOT values from high-resolution (~30m) satellite data. This method is designed to work over a wide range of land covers - including both bright and dark surfaces - and requires only standard visible and near-infrared data, making it applicable to a range of data from sensors such as Landsat, DMC, SPOT and Pleiades. The method is based upon an extension of the Haze Optimized Transform (HOT). The HOT was originally designed for assessing areas of thick haze in satellite imagery by calculating a ';haziness' value for each pixel in an image as the distance from a ';Clear Line' in feature space, defined by the high correlation between visible bands. Here, we adapt the HOT method and use it to provide AOT data instead. Significant extensions include Monte Carlo estimation of the ';Clear Line', object-based correction for land cover, and Bayesian estimation of AOT from the haziness values through radiative transfer modelling. This novel method will enable many new applications of AOT data that were impossible with previously available low-resolution data, and has the potential to contribute significantly to our understanding of the air quality on health, the accuracy of satellite image atmospheric correction and the role of aerosols in the climate system.

Wilson, R. T.; Milton, E. J.; Nield, J. M.

2013-12-01

365

A Comparison of Aerosol Optical Property Measurements Made During the DOE Aerosol Intensive Operating Period and Their Effects on Regional Climate  

NASA Technical Reports Server (NTRS)

The amount of radiant energy an aerosol absorbs has profound effects on climate and air quality. It is ironic that aerosol absorption coefficient is one of the most difficult to measure aerosol properties. One of the main purposes of the DOE Aerosol Intensive Operating Period (IOP) flown in May, 2003 was to assess our ability to measure absorption coefficient in situ. This paper compares measurements of aerosol optical properties made during the IOP. Measurements of aerosol absorption coefficient were made by Particle Soot Absorption Photometer (PSAP) aboard the CIRPAS Twin-Otter (U. Washington) and on the DOE Cessna 172 (NOAA-C,MDL). Aerosol absorption coefficient was also measured by a photoacoustic instrument (DRI) that was operated on an aircraft for the first time during the IOP. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-AkC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. Absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Measurements of absorption coefficient from all of these instruments during appropriate periods are compared. During the IOP, several significant aerosol layers were sampled aloft. These layers are identified in the remote (AATS-14) as well as in situ measurements. Extinction profiles measured by Cadenza are compared to those derived from the Ames Airborne Tracking Sunphotometer (AATS-14, NASA-ARC). The regional radiative impact of these layers is assessed by using the measured aerosol optical properties in a radiative transfer model.

Strawa, Anthony W.; Hallar, A. G.; Arnott, W. P.; Covert, D.; Elleman, R.; Ogren, J.; Schmid, B.; Luu, A.

2004-01-01

366

Retrieval of Aerosol Optical Depth over Hong Kong by using MTSAT-1R  

NASA Astrophysics Data System (ADS)

Aerosols suspended in atmosphere have an effect on regional air quality as well as climate change, where monitoring of sources, distribution and transport are very important to understand. There have been numerous studies to retrieve aerosol optical depth (AOD) from geostationary orbit (GEO) satellite. In this study, AOD at 550 nm over Hong Kong is retrieved by using single visible channel of MTSAT-1R. The uncertainty of this algorithm comes mainly from characterizing surface reflectance and assuming aerosol model. Surface reflectance is estimated from the clear-sky composite with the assumption that there is at least one clear sky condition and surface conditions do not change for certain periods of time. Aerosol optical properties are obtained from long term observation of AERONET (AErosol ROboric NETwork) at the sites of the Hong Kong Polytechnic University(HPU) and Hok Tsui(HT) for different seasons, which are applied to calculate look-up tables (LUT). The retrieved AODs are compared with values from MODIS (within 30 minutes) for a year of 2006. The results are compared for the two different aerosol model of HPU and HT, where the results with the HPU model show better correlation than those with the HT. The results show seasonal dependence, showing better correlation during spring and fall than summer and winter. The correlation coefficient is larger than 0.6 except for winter season, and the slope between AOD from MODIS and MTSAT-1R is close to 1.0 except for summer. Due to relatively high RH condition over Hong Kong, understanding and consideration about RH effects are needed to improve AOD accuracy. Also, improvement in characterizing aerosol model and cloud masking are expected to decrease the uncertainties further.

Kim, M.; Kim, J.; Yoon, J.; Chan, P.; Nichol, J.; Wong, C. S.

2009-12-01

367

Sensitivity of Multiangle Imaging to Optical and Microphysical Properties of Biomass Burning Aerosols  

NASA Astrophysics Data System (ADS)

The Multiangle Imaging Spectroradiometer (MISR) provides unique multiangle, multi-spectral global tropospheric aerosol data. To improve the retrieval algorithm of MISR for biomass burning (BB) aerosols, the microphysical and optical properties of BB particles are summarized from the literature of past field experiments, and variations with vegetation type, plume age, and fire phase are identified. Based on the review, a theoretical sensitivity study is carried out to examine the MISR retrieval algorithm's ability to discriminate among component particles in the two-dimensional space of spherical particles covering the observed range of BB size distribution (mean volume-weighted geometric diameter, Dpg,V, from 0.15 to 0.63 ?m) and Single Scattering Albedo (SSA at 550 nm, ?0,550, from 0.83 to 0.93). For a column Aerosol Optical Depth (AOD) of 0.5, over a dark, uniform surface, MISR can distinguish two to three groups in size and SSA, except when the atmospheric particles are very absorbing (?0,550~0.74) and have Dpg,V smaller then 0.36 ?m. In BB field case studies over Alta Floresta, Brazil and Mongu, Zambia, our analysis indicates that, in retrievals having AOD ? 0.4 over a relatively uniform land surface, MISR can separate small, absorbing particles from ones in other size and SSA categories. The uncertainty and interpretation of the retrieval depends on AOD as well as surface properties, which in our field study are derived using a forward radiative transfer model constrained by AERONET aerosol inversion products on clean days before and after the hazy day. The scarcity of good cases indicates the importance of aerosol measurements with coordinated BB field campaigns and long-tem monitoring networks to help refine satellite aerosol retrievals, which, in turn, will benefit future aerosol research.

Chen, W.; Kahn, R. A.; Li, W.; Seinfeld, J. H.

2005-12-01

368

Quantitative Constraints on Aerosol Optical Properties Over Dark Water from MISR Multi-angle Imaging  

NASA Astrophysics Data System (ADS)

Prior to the NASA Earth Observing System (EOS) satellite launchs, a broad picture of global aerosol distributions was already emerging, from the combination of earlier in situ and satellite measurements with transport modeling. One goal of the instruments aboard the EOS satellites is to quantitatively improve our knowledge of the aerosol radiative impacts and transport budgets developed from the pre-launch picture, by better constraining aerosol amounts and types, globally. To address this goal, details of low-light-level instrument calibration, as well as assumed aerosol properties and other attributes of the satellite aerosol retrieval algorithms, must be understood, within a few percent accuracy. We identified 14 occasions when the Multi-angle Imaging SpectroRadiometer (MISR) instrument aboard the EOS Terra satellite took high-quality data over islands hosting operational AERONET sun photometers, under relatively cloud-free conditions, at times when aerosol optical thickness (AOT), AOT variability, wind speed, and ocean surface reflectance were low. We simulated top-of-atmosphere equivalent reflectances in all 36 MISR channels using AERONET-derived AOT and particle properties, and compared with MISR radiance products. The details of these comparisons raise interesting questions that bear upon the quality of satellite instrument calibration, the nature of data sets required to validate satellite aerosol retrieval algorithms, and about the combinations of measurements needed routinely to achieve quantitative improvements in the aerosol picture over global oceans. This work is performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

Kahn, R. A.; Li, W.; Bruegge, C. J.; Diner, D. J.; Martonchik, J. V.; Gaitley, B. J.; Dubovik, O.; Holben, B.; Smirnov, A.

2003-12-01

369

Lidar profiling of aerosol optical properties from Paris to Lake Baikal (Siberia)  

NASA Astrophysics Data System (ADS)

In June 2013, a ground-based mobile lidar performed the 10 000 km ride from Paris to Ulan-Ude, near Lake Baikal, profiling for the first time aerosol optical properties all the way from Western Europe to central Siberia. The instrument was equipped with N2-Raman and depolarization channels that enabled an optical speciation of aerosols in the low and middle troposphere. The backscatter-to-extinction ratio (BER) and particle depolarization ratio (PDR) at 355 nm have been retrieved. The BER in the lower boundary layer (300-700 m) was found to be 0.017 ± 0.009 sr-1 in average during the campaign, with slightly higher values in background conditions near Lake Baikal (0.021 ± 0.010 sr-1 in average) corresponding to dust-like particles. PDR values observed in Russian cities (>1.7%) are higher than the ones measured in European cities (<1.3%) due to the lifting of terrigenous aerosols by traffic on roads with a bad tarmac. Biomass burning layers from grassland or/and forest fires in southern Russia exhibit BER values ranging from 0.010 to 0.015 sr-1 and from 2 to 3% for the PDR. Desert dust aerosols originating from the Caspian and Aral seas regions were characterized for the first time, with a BER (PDR) of 0.022 sr-1 (21%) for pure dust, and 0.011 sr-1 (15%) for a mix between dust and biomass burning. The lidar observations also showed that this dust event extended over 2300 km and lasted for ~6 days. Measurements from the Moderate Resolution Imaging Spectrometer (MODIS) show that our results are comparable in terms of aerosol optical thickness (between 0.05 and 0.40 at 355 nm) with the mean aerosol load encountered throughout our route.

Dieudonné, E.; Chazette, P.; Marnas, F.; Totems, J.; Shang, X.

2014-11-01

370

Characterizing the Spatial and Temporal Distribution of Aerosol Optical Thickness Over the Atlantic Basin Utilizing GOES-8 Multispectral Data  

NASA Technical Reports Server (NTRS)

In recent years, modeling and analysis efforts have suggested that the direct and indirect radiative effects of both anthropogenic and natural aerosols play a major role in the radiative balance of the earth and are an important factor in climate change calculations. The direct effects of aerosols on radiation and indirect effects on cloud properties are not well understood at this time. In order to improve the characterization of aerosols within climate models it is important to accurately parameterize aerosol forcing mechanisms at the local, regional, and global scales. This includes gaining information on the spatial and temporal distribution of aerosols, transport regimes and mechanisms, aerosol optical thickness, and size distributions. Although there is an expanding global network of ground measurements of aerosol optical thickness and size distribution at specific locations, satellite data must be utilized to characterize the spatial and temporal extent of aerosols and transport regimes on regional and global scales. This study was part of a collaborative effort to characterize aerosol radiative forcing over the Atlantic basin associated with the following three major aerosol components in this region: urban/sulfate, Saharan dust, and biomass burning. In-situ ground measurements obtained by a network of sun photometers during the Smoke Clouds and Radiation Experiment in Brazil (SCAR-B) and the Tropospheric Aerosol Radiative Forcing Observational Experiment (TARFOX) were utilized to develop, calibrate, and validate a Geostationary Operational Environmental Satellite (GOES)-8 aerosol optical thickness (AOT) product. Regional implementation of the GOES-8 AOT product was used to augment point source measurements to gain a better understanding of the spatial and temporal distributions of Atlantic basin aerosols during SCAR-B and TARFOX.

Fox, Robert; Prins, Elaine Mae; Feltz, Joleen M.

2001-01-01

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

Aerosol optical and microphysical retrievals from a hybrid multiwavelength lidar data set - DISCOVER-AQ 2011  

NASA Astrophysics Data System (ADS)

Retrievals of aerosol microphysical properties (effective radius, volume and surface-area concentrations) and aerosol optical properties (complex index of refraction and single-scattering albedo) were obtained from a hybrid multiwavelength lidar data set for the first time. In July 2011, in the Baltimore-Washington DC region, synergistic profiling of optical and microphysical properties of aerosols with both airborne (in situ and remote sensing) and ground-based remote sensing systems was performed during the first deployment of DISCOVER-AQ. The hybrid multiwavelength lidar data set combines ground-based elastic backscatter lidar measurements at 355 nm with airborne High-Spectral-Resolution Lidar (HSRL) measurements at 532 nm and elastic backscatter lidar measurements at 1064 nm that were obtained less than 5 km apart from each other. This was the first study in which optical and microphysical retrievals from lidar were obtained during the day and directly compared to AERONET and in situ measurements for 11 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 in such discrepancies.

Sawamura, P.; Müller, D.; Hoff, R. M.; Hostetler, C. A.; Ferrare, R. A.; Hair, J. W.; Rogers, R. R.; Anderson, B. E.; Ziemba, L. D.; Beyersdorf, A. J.; Thornhill, K. L.; Winstead, E. L.; Holben, B. N.

2014-09-01

373

Estimation of aerosol optical depth over Dehradun (India) using simple model for atmospheric radiative transfer in multiple scattering approximation  

NASA Astrophysics Data System (ADS)

Aerosol optical depth retrieval over land surface using remote sensing employs the use of radiative transfer simulations and/or simultaneous measurements of atmospheric parameters at the time of satellite pass. Also, an accurate estimate of land surface parameters is also required in order to separate the atmospheric component from the land surface reflectance reaching at-sensor. In addition to empirical and semi-empirical approaches, amongst the most widely used methods to retrieve the aerosol properties from satellite measurements are radiative transfer codes used in either forward or inverse modes. As most of them are computationally complex, henceforth, efforts are made to formulate approximate models. In this study, we have tried to estimate aerosol optical depth using one such established physically based model, namely, SMART (Simple Model for Atmospheric Radiative Transfer) code in multiple scattering approximation for aerosols over first band (0.52-0.59 ?m) of RESOURCESAT-AWiFS sensor. The aim of the analysis was to find out an approach to decouple aerosol effects from Top of atmosphere signals recorded by AWiFS sensor using multiple scattering approximations for aerosols. The model is first calibrated for aerosol asymmetry parameter for one dataset each of summer and winter seasons respectively and subsequently validated for 4 different datasets (2 summer and 2 winter) against the MODIS atmosphere product for aerosol optical depth. The results show that the difference between simulated vs. MODIS AOD fall within MODIS expected errors for the aerosol product.

Mehta, M.

2014-11-01

374

Significance of nitrogen dioxide absorption in estimating aerosol optical depth and size distributions  

NASA Astrophysics Data System (ADS)

Concurrent measurements of spectral direct beam solar radiation and columnar NO2 content at a suburban site, McMaster Unversity, in Hamilton, Ontario, were used to determine the effect of NO2 absorption upon aerosol optical depths, derived size distributions, and the columnar particle number density and mass. Aerosol optical depths were reduced by 22-47, 12-25, 3-6 percent and 1 percent at wavelengths of 400, 500, 610 and 670 nm, respectively, when the gaseous absorption was included. The smaller reductions refer to average NO2 amounts, and the larger to high amounts. Columnar number density was reduced by 51-95 percent and mass by 13-26 percent. At high NO2 amounts, the inclusion of NO2 absorption narrowed the size distribution derived from median optical depths and changed it from bimodal to unimodal.

Schroeder, R.; Davies, J. A.

1987-06-01

375

GROUND BASED LIDAR OBSERVATIONS OF AEROSOL AND CIRRUS CLOUDS OPTICAL PROPERTIES IN CENTRAL AMAZON DURING THE DRY SEASON  

E-print Network

to perform continuous measurements of aerosols and water vapor and aiming to study and monitor the atmosphereGROUND BASED LIDAR OBSERVATIONS OF AEROSOL AND CIRRUS CLOUDS OPTICAL PROPERTIES IN CENTRAL AMAZON Paulo, São Paulo, S.P., Brazil E-mail: hbarbosa@if.usp.br A permanent UV Raman Lidar station, designed

Barbosa, Henrique

376

Comparison of optical properties of nitrate and sulfate aerosol and the direct radiative forcing due to nitrate in China  

E-print Network

Comparison of optical properties of nitrate and sulfate aerosol and the direct radiative forcing due to nitrate in China H. Zhang a, , Z. Shen a,b , X. Wei a,c , M. Zhang d , Z. Li e,f a Laboratory the direct radiative forcing (DRF) due to nitrate aerosols. Ensuing errors have not been rigorously evaluated

Li, Zhanqing

377

Light pollution modelling and detection in a heterogeneous environment: toward a night-time aerosol optical depth retreival method  

Microsoft Academic Search

Tracking the Aerosol Optical Depth (AOD) is of particular importance in monitoring aerosol contributions to global radiative forcing. Until now, the two standard techniques used for retrieving AOD were; (i) sun photometry, and (ii) satellite-based approaches, such as based DDV (Dense Dark Vegetation) inversion algorithms. These methods are only available for use during daylight time since they are based on

M. Aube; L. Franchomme-Fosse; P. Robert-Staehler; V. Houle

2005-01-01

378

Retrieval of optical depth and particle size distribution of tropospheric and stratospheric aerosols by means of Sun photometry  

Microsoft Academic Search

Aerosol optical depth measurements by means of ground-based Sun photometry were made in Bern, Switzerland during two and a half years primarily to provide quantitative corrections for atmospheric effects in remotely sensed data in the visible and near-infrared spectral region. An investigation of the spatial variability of tropospheric aerosol was accomplished in the summer of 1994 in the Swiss Central

B. Schmid; C. Maetzler; A. Heimo; N. Kampfer

1997-01-01

379

Biomass burning and pollution aerosol over North America: Organic components and their influence on spectral optical properties and humidification response  

Microsoft Academic Search

Thermal analysis of aerosol size distributions provided size resolved volatility up to temperatures of 400°C during extensive flights over North America (NA) for the INTEX\\/ICARTT experiment in summer 2004. Biomass burning and pollution plumes identified from trace gas measurements were evaluated for their aerosol physiochemical and optical signatures. Measurements of soluble ionic mass and refractory black carbon (BC) mass, inferred

A. Clarke; C. McNaughton; V. Kapustin; Y. Shinozuka; S. Howell; J. Dibb; J. Zhou; B. Anderson; V. Brekhovskikh; H. Turner; M. Pinkerton

2007-01-01

380

MODIS Aerosol Optical Depth Bias Adjustment Using Machine Learning Algorithms  

NASA Technical Reports Server (NTRS)

To monitor the earth atmosphere and its surface changes, satellite based instruments collect continuous data. While some of the data is directly used, some others such as aerosol properties are indirectly retrieved from the observation data. While retrieved variables (RV) form very powerful products, they don't come without obstacles. Different satellite viewing geometries, calibration issues, dynamically changing atmospheric and earth surface conditions, together with complex interactions between observed entities and their environment affect them greatly. This results in random and systematic errors in the final products.

Albayrak, Arif; Wei, Jennifer; Petrenko, Maksym; Lary, David; Leptoukh, Gregory

2011-01-01

381

Implications of Satellite Swath Width on Global Aerosol Optical Thickness Statistics  

NASA Technical Reports Server (NTRS)

We assess the impact of swath width on the statistics of aerosol optical thickness (AOT) retrieved by satellite as inferred from observations made by the Moderate Resolution Imaging Spectroradiometer (MODIS). We sub-sample the year 2009 MODIS data from both the Terra and Aqua spacecraft along several candidate swaths of various widths. We find that due to spatial sampling there is an uncertainty of approximately 0.01 in the global, annual mean AOT. The sub-sampled monthly mean gridded AOT are within +/- 0.01 of the full swath AOT about 20% of the time for the narrow swath sub-samples, about 30% of the time for the moderate width sub-samples, and about 45% of the time for the widest swath considered. These results suggest that future aerosol satellite missions with only a narrow swath view may not sample the true AOT distribution sufficiently to reduce significantly the uncertainty in aerosol direct forcing of climate.

Colarco, Peter; Kahn, Ralph; Remer, Lorraine; Levy, Robert; Welton, Ellsworth

2012-01-01

382

In situ observations of aerosol physical and optical properties in northern India  

NASA Astrophysics Data System (ADS)

The southern Asia, including India, is exposed to substantial quantities of particulate air pollution originating mainly from fossil fuel combustion and biomass burning. Besides serious adverse health effects, these aerosols cause a large reduction of solar radiation at the surface accompanied by a substantial atmospheric heating, which is expected to have significant influences on the air temperature, crop yields, livestock and water resources over the southern Asia. The various influences by aerosols in this region depend crucially on the development of aerosol emissions from household, industrial, transportation and biomass burning sectors. The main purpose of this study is to investigate several measured aerosol optical and physical properties. We take advantage of observations from two measurement stations which have been established by the Finnish Meteorological Institute and The Energy and Resources Institute. Another station is on the foothills of Himalayas, in Mukteshwar, about 350 km east of New Delhi at elevation about 2 km ASL. This site is considered as a rural background site. Measurements of aerosol size distribution (7-500 nm), PM10, PM2.5, aerosol scattering and absorption coefficients and weather parameters have been conducted since 2006. Another station is located at the outskirts of New Delhi, in Gual Pahari, about 35 km south of city centre. It is considered as an urban background site. Measurements of aerosol size distribution (7 nm- 10 ?m), PM10, PM2.5, aerosol scattering and absorption coefficients, aerosol optical depth, aerosol vertical distribution (LIDAR), aerosol filter sampling for chemical characterization and weather parameters were conducted between 2008 and 2010. On the overall average PM10 and PM2.5 values were about 3-4 times higher in Gual Pahari than in Mukteshwar as expected, 216 and 126 ?g m^-3, respectively. However, difference depended much on the season, so that during winter time PM10 and PM2.5 concentrations were about 9 and 6 times higher in Gual Pahari than in Mukteshwar. During the pre-monsoon the concentrations in Gual Pahari were only twofold compared to Mukteshwar. The monsoon cleans the atmosphere from particulate matter so that PM10 and PM2.5 concentrations reduced to more than half compared to pre-monsoon values. We also found a very clear diurnal cycle on both station, except during the monsoon season. However the phase of the cycle was different between stations. This annual and diurnal variation is controlled besides emissions by evolution of boundary layer and transport of aerosols from Indo- Gangetic plains to the background site in Mukteshwar. Basically all measured aerosol properties behaved similarly. We also analyzed the data to observe the so called elevated heat pump hypothesis and trends in long term aerosol properties, although six years of data is not enough to make solid conclusions.

Lihavainen, H.; Hyvarinen, A.; Hooda, R. K.; Raatikainen, T. E.; Sharma, V.; Komppula, M.

2012-12-01

383

Common summertime total cloud cover and aerosol optical depth weekly variabilities over Europe: Sign of the aerosol indirect effects?  

NASA Astrophysics Data System (ADS)

In this study, the summer total cloud cover (TCC) weekly cycle over Europe is investigated using MODIS and ISCCP satellite data in conjunction with aerosol optical depth (AOD) MODIS data. Spatial weekly patterns are examined at a 1° × 1° (MODIS) and 250 × 250 km2 (ISCCP) resolution. Despite the noise in the TCC weekly cycle patterns, their large-scale features show similarities with the AOD550 patterns. Regions with a positive (higher values during midweek) weekly cycle appear over Central Europe, while a strong negative (higher values during weekend) weekly plume appears over the Iberian Peninsula and the North-Eastern Europe. The TCC weekly variability exhibits a very good agreement with the AOD550 weekly variability over Central, South-Western Europe and North-Eastern Europe and a moderate agreement for Central Mediterranean. The MODIS derived TCC weekly variability shows reasonable agreement with the independent ISCCP observations, thus supporting the credibility of the results. TCC and AOD550 correlations exhibit a strong slope for the total of the 6 regions investigated in this work with the slopes being higher for regions with common TCC-AOD550 weekly variabilities. The slope is much stronger for AOD550 values less than 0.2 for Central and South-Western Europe, in line with previous studies around the world. Possible scenarios that could explain the common weekly variability of aerosols and cloud cover through the aerosol indirect effects are discussed here also taking into account the weekly variability appearing in ECA&D E-OBS rainfall data.

Georgoulias, A. K.; Kourtidis, K. A.; Alexandri, G.; Rapsomanikis, S.; Sanchez-Lorenzo, A.

2015-02-01

384

Consistency of Global Modis Aerosol Optical Depths over Ocean on Terra and Aqua Ceres SSF Datasets  

NASA Technical Reports Server (NTRS)

Aerosol retrievals over ocean from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Terra and Aqua platforms are available from the Clouds and the Earth's Radiant Energy System (CERES) Single Scanner Footprint (SSF) datasets generated at NASA Langley Research Center (LaRC). Two aerosol products are reported side-by-side. The primary M product is generated by sub-setting and remapping the multi-spectral (0.47-2.1 micrometer) MODIS produced oceanic aerosol (MOD04/MYD04 for Terra/Aqua) onto CERES footprints. M*D04 processing uses cloud screening and aerosol algorithms developed by the MODIS science team. The secondary AVHRR-like A product is generated in only two MODIS bands 1 and 6 (on Aqua, bands 1 and 7). The A processing uses the CERES cloud screening algorithm, and NOAA/NESDIS glint identification, and single-channel aerosol retrieval algorithms. The M and A products have been documented elsewhere and preliminarily compared using 2 weeks of global Terra CERES SSF Edition 1A data in which the M product was based on MOD04 collection 3. In this study, the comparisons between the M and A aerosol optical depths (AOD) in MODIS band 1 (0.64 micrometers), tau(sub 1M) and tau(sub 1A) are re-examined using 9 days of global CERES SSF Terra Edition 2A and Aqua Edition 1B data from 13 - 21 October 2002, and extended to include cross-platform comparisons. The M and A products on the new CERES SSF release are generated using the same aerosol algorithms as before, but with different preprocessing and sampling procedures, lending themselves to a simple sensitivity check to non-aerosol factors. Both tau(sub 1M) and tau(sub 1A) generally compare well across platforms. However, the M product shows some differences, which increase with ambient cloud amount and towards the solar side of the orbit. Three types of comparisons conducted in this study - cross-platform, cross-product, and cross-release confirm the previously made observation that the major area for improvement in the current aerosol processing lies in a more formalized and standardized sampling (and most importantly, cloud screening) whereas optimization of the aerosol algorithm is deemed to be an important yet less critical element.

Ignatov, Alexander; Minnis, Patrick; Miller, Walter F.; Wielicki, Bruce A.; Remer, Lorraine

2006-01-01

385

Production of aerosols by optical catapulting: Imaging, performance parameters and laser-induced plasma sampling rate  

NASA Astrophysics Data System (ADS)

Optical catapulting (OC) is a sampling and manipulation method that has been extensively studied in applications ranging from single cells in heterogeneous tissue samples to analysis of explosive residues in human fingerprints. Specifically, analysis of the catapulted material by means of laser-induced breakdown spectroscopy (LIBS) offers a promising approach for the inspection of solid particulate matter. In this work, we focus our attention in the experimental parameters to be optimized for a proper aerosol generation while increasing the particle density in the focal region sampled by LIBS. For this purpose we use shadowgraphy visualization as a diagnostic tool. Shadowgraphic images were acquired for studying the evolution and dynamics of solid aerosols produced by OC. Aluminum silicate particles (0.2-8 ?m) were ejected from the substrate using a Q-switched Nd:YAG laser at 1064 nm, while time-resolved images recorded the propagation of the generated aerosol. For LIBS analysis and shadowgraphy visualization, a Q-switched Nd:YAG laser at 1064 nm and 532 nm was employed, respectively. Several parameters such as the time delay between pulses and the effect of laser fluence on the aerosol production have been also investigated. After optimization, the particle density in the sampling focal volume increases while improving the aerosol sampling rate till ca. 90%.

Abdelhamid, M.; Fortes, F. J.; Fernández-Bravo, A.; Harith, M. A.; Laserna, J. J.

2013-11-01

386

Total volcanic stratospheric aerosol optical depths and implications for global climate change  

NASA Astrophysics Data System (ADS)

the cooling effect of recent volcanoes is of particular interest in the context of the post-2000 slowing of the rate of global warming. Satellite observations of aerosol optical depth above 15 km have demonstrated that small-magnitude volcanic eruptions substantially perturb incoming solar radiation. Here we use lidar, Aerosol Robotic Network, and balloon-borne observations to provide evidence that currently available satellite databases neglect substantial amounts of volcanic aerosol between the tropopause and 15 km at middle to high latitudes and therefore underestimate total radiative forcing resulting from the recent eruptions. Incorporating these estimates into a simple climate model, we determine the global volcanic aerosol forcing since 2000 to be -0.19 ± 0.09 Wm-2. This translates into an estimated global cooling of 0.05 to 0.12°C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km.

Ridley, D. A.; Solomon, S.; Barnes, J. E.; Burlakov, V. D.; Deshler, T.; Dolgii, S. I.; Herber, A. B.; Nagai, T.; Neely, R. R.; Nevzorov, A. V.; Ritter, C.; Sakai, T.; Santer, B. D.; Sato, M.; Schmidt, A.; Uchino, O.; Vernier, J. P.

2014-11-01

387

AVHRR remote sensing of aerosol optical properties in the Persian Gulf region, summer 1991  

NASA Astrophysics Data System (ADS)

Satellite remote sensing is studied in this paper for retrieving aerosol parameters, i.e., aerosol optical thickness at 0.5 ?m ?0.5, size exponent p, and absorption index ?, from channel 1 and 2 radiances of the NOAA 11 advanced very high resolution radiometer (AVHRR) in the Persian Gulf region in the summer of 1991. Results of the remote sensing are compared with ground-based values obtained from solar radiation measurements with a sunphotometer and a pyranometer in Bushehr, Iran. It is found that tuning the calibration coefficients of AVHRR and introduction of a suitable aerosol absorption are needed for a good agreement between satellite-derived and ground-based values of ?0.5. The aerosol absorption index is also retrieved with two methods, i.e., simultaneous analyses with ground-based ?0.5 and p, and the Fraser-Kaufman method. Retrieved values of the aerosol single-scattering albedo are ??0.75 and 0.70 from the two methods, respectively, for the Kuwait oil-fire smoke layer. The single scattering albedo of another case, which is regarded as a sand-dust layer, is estimated to be ??0.76 with the Fraser-Kaufman method.

Nakajima, Teruyuki; Higurashi, Akiko

1997-07-01

388

Variability in Aerosol Optical and Physical Properties at a Coastal Industrial City in India, deduced from OMI and MODIS data  

NASA Astrophysics Data System (ADS)

Many cities in India have gone through industrial revolution due to the priorities put by the State and Central Governments for economical growth. Bhubaneswar is one of the cities in the eastern part of India (85.8 E and 20.2 N) that has been the center of industrial activities since 1990s. A number of industries such as thermal power plants, sponge iron plants and housing developments have resulted changes in the land cover and in the slow deterioration of air quality affecting public health and reduced visibility. The primary purpose of this study is to understand the variability in aerosol optical and physical properties in Bhubaneswar using remote sensing data produced by OMI (Ozone Monitoring Instrument) and MODIS (Moderate Resolution Imaging Spectroradiometer). We have analyzed the data for Aerosol Extiction Optical Depth (AOD), Aerosol Absorption Optical Depth (AAOD), UV Aerosol Index and Cloud Fraction from OMI and Aerosol Small Mode Fraction, Aerosol Optical Depth