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1

Probing the bulk viscosity of particles using aerosol optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

2

Optical Tweezers  

NSDL National Science Digital Library

Learn about the principles behind the optical tweezers or optical trapping experiment. Become familiar with the use of standard optics including optical alignment, and collection of data through the use of a camera-computer system. Examine the forces on a bead trapped by a laser.

2012-01-18

3

Automation of an Optical Tweezers.  

National Technical Information Service (NTIS)

Optical tweezers is a newly developed instrument, which makes possible the manipulation of micro-optical particles under a microscope. In this paper, we present the automation of an optical tweezers which consists of a modified optical tweezers, equipped ...

B. Chang L. Hsu T. Hsieh

2000-01-01

4

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

NASA Astrophysics Data System (ADS)

The use of optical trapping techniques to manipulate probe particles for performing micro-rheological measurements on a surrounding fluid is well-established. Here, we review recent advances made in the use of optical trapping to probe the rheological properties of trapped particles themselves. In particular, we review observations of the continuous transition from liquid to solid-like viscosity of sub-picolitre supersaturated solution aerosol droplets using optical trapping techniques. Direct measurements of the viscosity of the particle bulk are derived from the damped oscillations in shape following coalescence of two particles, a consequence of the interplay between viscous and surface forces and the capillary driven relaxation of the approximately spheroidal composite particle. Holographic optical tweezers provide a facile method for the manipulation of arrays of particles allowing coalescence to be controllably induced between two micron-sized aerosol particles. The optical forces, while sufficiently strong to confine the composite particle, are several orders of magnitude weaker than the capillary forces driving relaxation. Light, elastically back-scattered by the particle, is recorded with sub-100 ns resolution allowing measurements of fast relaxation (low viscosity) dynamics, while the brightfield image can be used to monitor the shape relaxation extending to times in excess of 1000 s. For the slowest relaxation dynamics studied (particles with the highest viscosity) the presence and line shape of whispering gallery modes in the cavity enhanced Raman spectrum can be used to infer the relaxation time while serving the dual purpose of allowing the droplet size and refractive index to be measured with accuracies of ±0.025% and ±0.1%, respectively. The time constant for the damped relaxation can be used to infer the bulk viscosity, spanning from the dilute solution limit to a value approaching that of a glass, typically considered to be >1012 Pa s, whilst the frequencies of the normal modes of the oscillations of the particle can be used to infer surface properties. We will review the use of optical tweezers for studying the viscosity of aerosol particles and discuss the potential use of this micro-rheological tool for probing the fundamental concepts of phase, thermodynamic equilibrium and metastability.

Power, Rory M.; Reid, Jonathan P.

2014-07-01

5

Femtosecond Optical Tweezers  

NASA Astrophysics Data System (ADS)

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

Peng, Jiahui; Wang, Lei; Sokolov, Alexei

2004-10-01

6

Optical tweezers-based immunosensor  

Microsoft Academic Search

The authors have developed an extremely sensitive immunoassay that uses optical tweezers to detect antigen-antibody bonds. An optical tweezers is used to manipulate a microscopic object with respect to a surface. The adjustable force applied by the tweezers is used to sense adhesion between the objects, which can either naturally or artificially present binding partners. This measurement can be used

B. J. Davies; R. Kishore; M.-N. Sinou; K. Helmerson; W. D. Phillips; H. H. Weetall

1998-01-01

7

Physics in Action: Optical Tweezers  

NSDL National Science Digital Library

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

2007-07-18

8

On chip shapeable optical tweezers  

PubMed Central

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

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

2013-01-01

9

On chip shapeable optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

10

On chip shapeable optical tweezers.  

PubMed

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

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

2013-01-01

11

Interferometer Control of Optical Tweezers.  

National Technical Information Service (NTIS)

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...

A. J. Decker

2002-01-01

12

Plasmon nano-optical tweezers  

Microsoft Academic Search

Conventional optical tweezers, formed at the diffraction-limited focus of a laser beam, have become a powerful and flexible tool for manipulating micrometre-sized objects. Extending optical trapping down to the nanometre scale would open unprecedented opportunities in many fields of science, where such nano-optical tweezers would allow the ultra-accurate positioning of single nano-objects. Among the possible strategies, the ability of metallic

Mathieu L. Juan; Maurizio Righini; Romain Quidant

2011-01-01

13

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

14

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

15

Quantum noise in optical tweezers  

NASA Astrophysics Data System (ADS)

Quantum enhanced sensitivity in optical tweezers based particle tracking was recently demonstrated. This has provided the necessary tool for quantum metrology to play an important role in biological measurements. Here we introduce the basic theory relevant to such optical tweezers experiments, and overview the significance of sub-shot noise limited sensitivity to practical experiments. In particular, biophysical experiments are subject to optical power constraints, which therefore limits the absolute sensitivity which is classically achievable. Quantum enhanced particle tracking can overcome this limit, and is therefore likely to play an important role in such biophysical experiments in the near future.

Taylor, Michael A.; Bowen, Warwick P.

2013-12-01

16

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

17

Optical tweezers technique and its applications  

NASA Astrophysics Data System (ADS)

Since their advent in the 1980s, optical tweezers have attracted more and more attention due to their unique non-contact and non-invasion characteristics and their wide applications in physics, biology, chemistry, medical science and nanoscience. In this paper, we introduce the basic principle, the history and typical applications of optical tweezers and review our recent experimental works on the development and application of optical tweezers technique. We will discuss in detail several technological issues, including high precision displacement and force measurement in single-trap and dual-trap optical tweezers, multi-trap optical tweezers with each trap independently and freely controlled by means of space light modulator, and incorporation of cylindrical vector optical beams to build diversified optical tweezers beyond the conventional Gaussian-beam optical tweezers. We will address the application of these optical tweezers techniques to study biophysical problems such as mechanical deformation of cell membrane and binding energy between plant microtubule and microtubule associated proteins. Finally we present application of the optical tweezers technique for trapping, transporting, and patterning of metallic nanoparticles, which can be harnessed to manipulate surface plasmon resonance properties of these nanoparticles.

Guo, HongLian; Li, ZhiYuan

2013-12-01

18

Fluorescence support in optical tweezers  

NASA Astrophysics Data System (ADS)

This paper presents the development of an installation for proves for characterization by fluorescence of micrometer and nanometer particles supported on the trapping and manipulation by optical trapping technique (optical tweezers). The system features an laser operating at 480 nm, CCD camera for image acquisition, Thor Labs micrometric table X, Y, Z for the movement of the sample and the trap in the visual field. The design includes the use of intensity modulated optical trap, with the option of being used in pulsed, opening up possibilities for the use of resonant phenomena optomechanical type for particle capture.

Animas, J. G.; Arronte, M.; Flores, T.; Ponce, L.

2013-11-01

19

Optical Tweezer as a Viscometer  

NASA Astrophysics Data System (ADS)

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

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

2009-03-01

20

Quantum limited particle sensing in optical tweezers  

SciTech Connect

Particle sensing in optical tweezers systems provides information on the position, velocity, and force of the specimen particles. The conventional quadrant detection scheme is applied ubiquitously in optical tweezers experiments to quantify these parameters. In this paper, we show that quadrant detection is nonoptimal for particle sensing in optical tweezers and propose an alternative optimal particle sensing scheme based on spatial homodyne detection. A formalism for particle sensing in terms of transverse spatial modes is developed and numerical simulations of the efficacies of both quadrant and spatial homodyne detection are shown. We demonstrate that 1 order of magnitude improvement in particle sensing sensitivity can be achieved using spatial homodyne over quadrant detection.

Tay, J.W. [Jack Dodd Centre for Photonics and Ultracold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); Hsu, Magnus T. L. [School of Mathematics and Physics, University of Queensland, St. Lucia, Queensland 4072 (Australia); Bowen, Warwick P. [Jack Dodd Centre for Photonics and Ultracold Atoms, Department of Physics, University of Otago, Dunedin (New Zealand); School of Mathematics and Physics, University of Queensland, St. Lucia, Queensland 4072 (Australia)

2009-12-15

21

Manipulation of Microobjects by Optical Tweezers  

Microsoft Academic Search

Radiation pressure from a tightly focused laser beam can be used as optical tweezers to confine, position, and transport microparticles.\\u000a Ashkin’s group first demonstrated this technique in 1986 [1]. Optical tweezers provide unique features such as remote manipulation\\u000a of micro\\/nano particles in unique features such as remote manipulation of micro\\/nano particles in liquid, noninvasive manipulation\\u000a of biological samples, precise manipulation

Shoji Maruo

22

Steerable optical tweezers for ultracold atom studies  

NASA Astrophysics Data System (ADS)

We report on the implementation of an optical tweezer system for controlled transport of ultracold atoms along a narrow, static confinement channel. The tweezer system is based on high-efficiency acousto-optical deflectors and offers two-dimensional control over beam position. This opens up the possibility for tracking the transport channel when shuttling atomic clouds along the guide, forestalling atom spilling. Multiple clouds can be tracked independently by time-shared tweezer beams addressing individual sites in the channel. The deflectors are controlled using a multichannel direct digital synthesizer, which receives instructions on a sub-microsecond time scale from a field-programmable gate array. Using the tweezer system, we demonstrate sequential binary splitting of an ultracold $\\rm^{87}Rb$ cloud into $2^5$ clouds.

Roberts, K. O.; McKellar, T.; Fekete, J.; Rakonjac, A.; Deb, A. B.; Kjærgaard, N.

2014-04-01

23

Steerable optical tweezers for ultracold atom studies.  

PubMed

We report on the implementation of an optical tweezer system for controlled transport of ultracold atoms along a narrow, static confinement channel. The tweezer system is based on high-efficiency acousto-optic deflectors and offers two-dimensional control over beam position. This opens up the possibility for tracking the transport channel when shuttling atomic clouds along it, forestalling atom spilling. Multiple clouds can be tracked independently by time-shared tweezer beams addressing individual sites in the channel. The deflectors are controlled using a multichannel direct digital synthesizer, which receives instructions on a submicrosecond time scale from a field-programmable gate array. Using the tweezer system, we demonstrate sequential binary splitting of an ultracold 87Rb cloud into 2(5) clouds. PMID:24686662

Roberts, K O; McKellar, T; Fekete, J; Rakonjac, A; Deb, A B; Kjærgaard, N

2014-04-01

24

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

25

Quantum computation architecture using optical tweezers  

SciTech Connect

We present a complete architecture for scalable quantum computation with ultracold atoms in optical lattices using optical tweezers focused to the size of a lattice spacing. We discuss three different two-qubit gates based on local collisional interactions. The gates between arbitrary qubits require the transport of atoms to neighboring sites. We numerically optimize the nonadiabatic transport of the atoms through the lattice and the intensity ramps of the optical tweezer in order to maximize the gate fidelities. We find overall gate times of a few 100 {mu}s, while keeping the error probability due to vibrational excitations and spontaneous scattering below 10{sup -3}. The requirements on the positioning error and intensity noise of the optical tweezer and the magnetic field stability are analyzed and we show that atoms in optical lattices could meet the requirements for fault-tolerant scalable quantum computing.

Weitenberg, Christof [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); Kuhr, Stefan [Max-Planck-Institut fuer Quantenoptik, Hans-Kopfermann-Strasse 1, D-85748 Garching (Germany); University of Strathclyde, Department of Physics, SUPA, Glasgow G4 0NG (United Kingdom); Moelmer, Klaus; Sherson, Jacob F. [Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C (Denmark)

2011-09-15

26

Twin-core fiber optical tweezers.  

PubMed

We present an abruptly tapered twin-core fiber optical tweezers, which is fabricated by fusing and drawing the twin-core fiber. In the twin-core fiber, the two beams are guided by the tapered fiber. At the end of the fiber tip, a larger converge angle between the two beams are made due to the abrupt tapered shape, which is formed a fast divergent optical field. The microscopic particle trapping performance of this special designed tapered twin-core fiber tip is investigated. The functionality of the proposed novel twin-core fiber optical tweezers is extended since an in-fiber integrated Mach-Zehnder interferometer has been used to control orientation of the trapped particle. The distribution of the optical field emerging from the tapered fiber tip is simulated based on the beam propagation method (BPM). By using this two-beam combination technique, a strong enough gradient forces well is obtained for microscopic particles trapping in three dimensions. The abruptly tapered twin-core fiber optical tweezers is rigid and easy to handle, especially useful for building up a multi-tweezers system for trapping and manipulating micro-scale particles. PMID:18542553

Yuan, Libo; Liu, Zhihai; Yang, Jun; Guan, Chunying

2008-03-31

27

Optical tweezers study life under tension  

PubMed Central

Optical tweezers have become one of the primary weapons in the arsenal of biophysicists, and have revolutionized the new field of single-molecule biophysics. Today’s techniques allow high-resolution experiments on biological macromolecules that were mere pipe dreams only a decade ago.

Fazal, Furqan M.; Block, Steven M.

2011-01-01

28

Interactive approach to optical tweezers control  

SciTech Connect

We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps.

Leach, Jonathan; Wulff, Kurt; Sinclair, Gavin; Jordan, Pamela; Courtial, Johannes; Thomson, Laura; Gibson, Graham; Karunwi, Kayode; Cooper, Jon; Laczik, Zsolt John; Padgett, Miles

2006-02-10

29

Interactive approach to optical tweezers control.  

PubMed

We have developed software with an interactive user interface that can be used to generate phase holograms for use with spatial light modulators. The program utilizes different hologram design techniques, allowing the user to select an appropriate algorithm. The program can be used to generate multiple beams and can be used for beam steering. We see a major application of the program to be in optical tweezers to control the position, number, and type of optical traps. PMID:16512531

Leach, Jonathan; Wulff, Kurt; Sinclair, Gavin; Jordan, Pamela; Courtial, Johannes; Thomson, Laura; Gibson, Graham; Karunwi, Kayode; Cooper, Jon; Laczik, Zsolt John; Padgett, Miles

2006-02-10

30

Nanoprobes with optical tweezers for biological applications  

NASA Astrophysics Data System (ADS)

We explore the use of sub-micron sized particles in optical tweezer traps as nanoprobes in microfluidic devices and biological cells. For applications that require high spatial resolution, the ability to suppress the particle's natural Brownian motion down to the nanometer or sub-nanometer scales is essential. However, the optical tweezer force scales with the volume of the particle making it difficult to confine and manipulate nanometer sized particles with high precision. To overcome this difficulty, we explore the possibility of using optically resonant particles as nanoprobes. The resonant particles should experience an increase in the optical tweezer force at wavelengths on the red side of the absorption resonance, resulting in a tighter confinement. We explore this phenomenon by measuring the trapping force acting on resonant particles (dye-filled polymeric and metallic particles) as a function of trapping laser wavelength and discuss the feasibility of using them as a high spatial resolution probe. In addition, we use similar particles as optically trapped nanoprobes to monitor temporal and spatial differences in an inhomogeneous environment; for example, we have developed pH-sensitive fluorescent nanoprobes for biological applications.

Kendrick, Mark; McIntyre, David; Ostroverkhova, Oksana; Bychkova, Valeriya; Shvarev, Alexey

2010-03-01

31

Optical tweezers applied to a microfluidic system.  

PubMed

We will demonstrate how optical tweezers can be combined with a microfluidic system to create a versatile microlaboratory. Cells are moved between reservoirs filled with different media by means of optical tweezers. We show that the cells, on a timescale of a few seconds, can be moved from one reservoir to another without the media being dragged along with them. The system is demonstrated with an experiment where we expose E. coli bacteria to different fluorescent markers. We will also discuss how the system can be used as an advanced cell sorter. It can favorably be used to sort out a small fraction of cells from a large population, in particular when advanced microscopic techniques are required to distinguish various cells. Patterns of channels and reservoirs were generated in a computer and transferred to a mask using either a sophisticated electron beam technique or a standard laser printer. Lithographic methods were applied to create microchannels in rubber silicon (PDMS). Media were transported in the channels using electroosmotic flow. The optical system consisted of a combined confocal and epi-fluorescence microscope, dual optical tweezers and a laser scalpel. PMID:15159778

Enger, Jonas; Goksör, Mattias; Ramser, Kerstin; Hagberg, Petter; Hanstorp, Dag

2004-06-01

32

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

33

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.

Neuman, Keir C.; Nagy, Attila

2012-01-01

34

Optical tweezers based on cylindrical vector beams  

NASA Astrophysics Data System (ADS)

Optical tweezers based on cylindrical vector beams are studied theoretically and experimentally. First, we present the basic concept of a cylindrical vector beam (CVB), whose polarization is axially symmetric to the optical axis. Second, two theoretical modes to analyze the interaction between the light beam and the particle are introduced, respectively, and some simulations have been shown. Then, the system structure and its operation principle are introduced in details, where a spatial light modulator (SLM) is used to flexibly generate the CVBs, and experimental results are also demonstrated, which show some advantages for optical manipulation of particles using CVBs.

Xu, Yongheng; Zhou, Zhehai; Zhang, Xiaolin; Zhao, Zhidan; Zhu, Lianqing

2013-10-01

35

Calibrating optical tweezers with Bayesian inference.  

PubMed

We present a new method for calibrating an optical-tweezer setup that does not depend on input parameters and is less affected by systematic errors like drift of the setup. It is based on an inference approach that uses Bayesian probability to infer the diffusion coefficient and the potential felt by a bead trapped in an optical or magnetic trap. It exploits a much larger amount of the information stored in the recorded bead trajectory than standard calibration approaches. We demonstrate that this method outperforms the equipartition method and the power-spectrum method in input information required (bead radius and trajectory length) and in output accuracy. PMID:24514731

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

2013-12-16

36

Particles sorting in micro-channel system utilizing magnetic tweezers and optical tweezers  

NASA Astrophysics Data System (ADS)

This study evaluates a method for separating magnetic microparticles in a micro channel by using embedded inverted-laser tweezers, a microflow pump, and a micro magnet. Various particles were separated using optical and/or magnetic tweezers, and were identified and counted to determine the dependence of the sorting rate on the channel flow velocity. The particle sorting experiment showed good separation results when the designed channel and magnetic tweezers were used. For magnetic particles, lower flow velocities corresponded to larger separating rates with a maximum separating rate of 81%. When the designed channel and optical tweezers were used, the polystyrene particle separating rate was as high as 94%. When both the optical tweezers and the magnetic tweezers were used, the optical tweezers were more effective in trapping polystyrene particles with flow velocities between 0.09 and 0.25 ?m/s. For flow velocities between 0.09 and 0.17 ?m/s, the separating rate for polystyrene particles reached 95% and the separating rate for magnetic particles reached 85%. This hybrid system can be applied to the separation of various particles in unknown mixtures.

Chung, Yung-Chiang; Chen, Po-Wen; Fu, Chao-Ming; Wu, Jian-Min

2013-05-01

37

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

National Technical Information Service (NTIS)

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 carbi...

A. J. Decker B. Jassemnejad R. E. Seibel K. E. Weiland

2003-01-01

38

Micromechanics of Dipolar Chains Using Optical Tweezers  

NASA Technical Reports Server (NTRS)

Here we present our initial study of the micromechanical properties of dipolar chains and columns in a magnetorheological (MR) suspension. Using dual-trap optical tweezers, we are able to directly measure the deformation of the dipolar chains parallel and perpendicular to the applied magnetic field. We observe the field dependence of the mechanical properties such as resistance to deformation, chain reorganization, and rupturing of the chains. These forms of energy dissipation are important for understanding and tuning the yield stress and rheological behavior of an MR suspension.

Furst, Eric M.; Gast, Alice P.

1999-01-01

39

Tunable Optical Tweezers for Wavelength-dependent Measurements.  

National Technical Information Service (NTIS)

Optical trapping forces depend on the difference between the trap wavelength and the extinction resonances of trapped particles. This leads to a wavelength-dependent trapping force, which should allow for the optimization of optical tweezers systems, simp...

B. Hester C. Lopez-Mariscal C. L. Filgueira G. K. Campbell R. Huschka

2012-01-01

40

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

41

Optical Tweezer Studies of Liquid Crystals Using Multiple Optical Traps  

NASA Astrophysics Data System (ADS)

We have constructed an acousto-optically scanned CW YAG laser system to generate dynamically controllable multiple optical traps. This multiple optical tweezer is being employed to probe the static and dynamic interactions of defects and textures in two and three dimensional liquid crystal (LC) systems. Results will be presented on 2D systems, where interactions between islands, thicker circular regions on few-layer thick freely suspended liquid crystal (LC) films, have been studied in the smectic C phase, in which the islands interact via the c-director orientation field. In the Smectic A phase, it has been found that the elastic interactions between islands are much smaller than in the Smectic C, and it is easy to induce coalescence using the optical tweezers. Studies of motion of suspended particles in 3D nematics and smectics will also be presented. *This research is supported by NASA Grant NAG3-2457, and NSF MRSEC Grant DMR 0213918

Pattanaporkratana, Apichart

2005-03-01

42

Transforming Mesoscopic (Bio)materials with Holographic Optical Tweezers  

NASA Astrophysics Data System (ADS)

An optical tweezer uses the forces exerted by a strongly focused beam of light to trap and move objects ranging in size from tens of nanometers to tens of micrometers. Since their introduction in 1986, optical tweezers have become a mainstay of research in biology, physical chemistry, and soft condensed matter physics. This talk highlights recent advances made possible by new classes of optical traps created with computer-designed holograms, a technique we call holographic optical trapping. Holographic optical tweezers can trap hundreds of mesoscopic objects simultaneously and move them independently in three dimensions. Arrays of optical traps can be used to continuously sort heterogeneous samples into selected fractions, a process we call optical fractionation. The same holograms can transform optical traps into optical scalpels and scissors that photochemically transform mesoscopic samples with exquisite spatial resolution. They also can impose arbitrary phase profiles onto the trapping beams, thereby creating optical vortices and related optical machines capable of actuating MEMS devices and driving mesoscale pumps and mixers. These new applications for laser light promise to take optical tweezers out of the laboratory and into real-world applications including manufacturing, diagnostics, and even consumer products. The unprecedented access to the mesoscopic world provided by holographic optical tweezers also offers revolutionary new opportunities for fundamental and applied research.

Grier, David

2004-03-01

43

MatLab program for precision calibration of optical tweezers  

Microsoft Academic Search

Optical tweezers are used as force transducers in many types of experiments. The force they exert in a given experiment is known only after a calibration. Computer codes that calibrate optical tweezers with high precision and reliability in the (x, y)-plane orthogonal to the laser beam axis were written in MatLab (MathWorks Inc.) and are presented here. The calibration is

Iva Marija Toli; Kirstine Berg-Sørensen; Henrik Flyvbjerg

44

Tunable optical tweezers for wavelength-dependent measurements  

PubMed Central

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

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

2012-01-01

45

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

46

Optical tweezers based on near infrared diode laser  

NASA Astrophysics Data System (ADS)

Emission from a single-mode 100 mW diode laser at 840 nm is used to create optical tweezers: the trapping laser beam is introduced into a microscope and focused by the objective. The microscope also allows monitoring of the motion of the trapped particles. The optical tweezers were monitored with objectives having different numerical apertures between 0.65 and 1.3. The optical trapping of polystyrene spheres with a radius between 0.11 and 7.45 micrometers and of biological objects, the flagellated alga Tetraselmis, with typical dimensions of 8 X 8 X 13 micrometers 3 were studied. The efficiency of the optical tweezers has been characterized through a parameter Q and compared with theoretical models.

Grego, S.; Arimondo, Ennio; Frediani, Carlo

1997-07-01

47

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

48

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

49

Magneto-optical tweezers built around an inverted microscope  

SciTech Connect

We present a simple experimental setup of magneto-optical tweezers built around an inverted microscope. Two pairs of coils placed around the focal point of the objective generate a planar-rotating magnetic field that is perpendicular to the stretching direction. This configuration allows us to control the rotary movement of a paramagnetic bead trapped in the optical tweezers. The mechanical design is universal and can be simply adapted to any inverted microscope and objective. The mechanical configuration permits the use of a rather large experimental cell and the simple assembly and disassembly of the magnetic attachment.

Claudet, Cyril; Bednar, Jan

2005-06-10

50

Investigating the thermodynamics of small biosystems with optical tweezers  

NASA Astrophysics Data System (ADS)

We present two examples of how single-molecule experimental techniques applied to biological systems can give insight into problems within the scope of equilibrium and nonequilibrium mesoscopic thermodynamics. The first example is the mapping of the free energy landscape of a macromolecule, the second the experimental verification of Crooks’ fluctuation theorem. In both cases the experimental setup comprises optical tweezers and DNA molecules.

Mossa, Alessandro; Huguet, Josep Maria; Ritort, Felix

2010-01-01

51

Mechanical Forces Impeding Exocytotic Surfactant Release Revealed by Optical Tweezers  

Microsoft Academic Search

The release of surfactant from alveolar type II cells is essential to lower the surface tension in the lung and to facilitate inspiration. However, the factors controlling dispersal and diffusion of this hydrophobic material are still poorly understood. Here we report that release of surfactant from the fused vesicle, termed lamellar body (LB), resisted mechanical forces applied by optical tweezers:

Wolfgang Singer; Manfred Frick; Thomas Haller; Stefan Bernet; Monika Ritsch-Marte; Paul Dietl

2003-01-01

52

Multifunctional optical tweezers using computer-generated holograms  

Microsoft Academic Search

Optical tweezers are capable of trapping microscopic particles by photon momentum transfer. The use of dynamic computer-generated holograms for beam shaping allows a high flexibility in terms of trap characteristics and features. We use a liquid crystal display (LCD) to display the holograms. Efficiency losses caused by the periodic electrode structure of the LCD have been clearly reduced by use

J. Liesener; M. Reicherter; T. Haist; H. J. Tiziani

2000-01-01

53

Optical tweezers for vortex rings in Bose-Einstein condensates  

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

54

Dual optical tweezers integrated in a four-core fiber: design and simulation  

NASA Astrophysics Data System (ADS)

We propose a novel dual optical fiber tweezers integrated in a four-core fiber which can trap, rotate and orient a micro particle immersed in a fluid medium. We design the structures and the functions of this dual optical fiber tweezers, and simulate the optical trapping forces, optical torques exerting on the micro particle. We also give out the experimental setup and the controlling method of this integrated dual optical fiber tweezers.

Zhang, Yu; Yuan, Libo; Liu, Zhihai; Yang, Jun

2013-09-01

55

Cluster formation in ferrofluids induced by holographic optical tweezers.  

PubMed

Holographic optical tweezers were used to show the interaction between a strongly focused laser beam and magnetic nanoparticles in ferrofluid. When the light intensity was high enough, magnetic nanoparticles were removed from the beam center and formed a dark ring. The same behavior was observed when focusing vortex or Bessel beams. The interactions between two or more separated rings of magnetic nanoparticles created by independent optical traps were also observed. PMID:24081086

Masajada, Jan; Bacia, Marcin; Drobczy?ski, S?awomir

2013-10-01

56

Active-passive calibration of optical tweezers in viscoelastic media  

NASA Astrophysics Data System (ADS)

In order to use optical tweezers as a force measuring tool inside a viscoelastic medium such as the cytoplasm of a living cell, it is crucial to perform an exact force calibration within the complex medium. This is a nontrivial task, as many of the physical characteristics of the medium and probe, e.g., viscosity, elasticity, shape, and density, are often unknown. Here, we suggest how to calibrate single beam optical tweezers in a complex viscoelastic environment. At the same time, we determine viscoelastic characteristics such as friction retardation spectrum and elastic moduli of the medium. We apply and test a method suggested [M. Fischer and K. Berg-Sørensen, J. Opt. A, Pure Appl. Opt. 9, S239 (2007)], a method which combines passive and active measurements. The method is demonstrated in a simple viscous medium, water, and in a solution of entangled F-actin without cross-linkers.

Fischer, Mario; Richardson, Andrew C.; Reihani, S. Nader S.; Oddershede, Lene B.; Berg-Sørensen, Kirstine

2010-01-01

57

Algorithm for computing holographic optical tweezers at video rates  

NASA Astrophysics Data System (ADS)

Digital holography enables the creation of multiple optical traps at arbitrary three-dimensional locations and spatial light modulators permit updating those holograms at video rates. However, the time required for computing the holograms makes interactive optical manipulation of several samples difficult to achieve. We introduce an algorithm for computing holographic optical tweezers that is both easy to implement and capable of speeds in excess of 10 Hz when running on a Pentium IV computer. A discussion of the pros and cons of the algorithm, a mathematical analysis of the efficiency of the resulting traps, as well as results of the three-dimensional manipulation of polystyrene micro spheres are included.

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

2006-09-01

58

Hybrid optical tweezers for dynamic micro-bead arrays  

NASA Astrophysics Data System (ADS)

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.

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

2011-08-01

59

Optical tweezers formed by pure phase pupil filter  

NASA Astrophysics Data System (ADS)

The focusing properties of vector beams have attracted great attention and quickly became the subject of extensive worldwide research due to their applications in lithography, optical storage, microscopy, material processing, and optical trapping. Focusing properties of the radially polarized beam and generalized cylindrical vector beams in high numerical aperture system with designed pure phase filter are analyzed in detail by using vector Debye diffraction theory. By utilizing diffractive optical element to partly change the polarization of vector beams, the energy density of light field in the vicinity of focus is studied by the numerical analysis. Numerical simulation result shows that optical bubbles can be obtained by changing the composition and polarization of the incident beams. At last, optical tweezers are constituted by two optical bubbles around the focus.

Lv, Wei; You, Chenglong; Wang, Mei; Yun, Maojin

2013-09-01

60

Applications of Optical Tweezers and an Integrated Force Measurement Module for Biomedical Research.  

National Technical Information Service (NTIS)

Optical tweezers are useiul for manipulating biological samples and measuring biological forces. in the present study, we have integrated a ward atter analysis (FORSA) module into the 'single-beam gradient force optical tweezers'. The entire set-up was th...

B. Liao C. Huang D. Wang J. Tsai W. L. Hwang

2000-01-01

61

All-optical constant-force laser tweezers.  

PubMed

Optical tweezers are a powerful tool for the study of single biomolecules. Many applications require that a molecule be held under constant tension while its extension is measured. We present two schemes based on scanning-line optical tweezers to accomplish this, providing all-optical alternatives to force-clamp traps that rely on electronic feedback to maintain constant-force conditions for the molecule. In these schemes, a laser beam is rapidly scanned along a line in the focal plane of the microscope objective, effectively creating an extended one-dimensional optical potential over distances of up to 8 microm. A position-independent lateral force acting on a trapped particle is created by either modulating the laser beam intensity during the scan or by using an asymmetric beam profile in the back focal plane of the microscope objective. With these techniques, forces of up to 2.69 pN have been applied over distances of up to 3.4 microm with residual spring constants of <26.6 fN/microm. We used these techniques in conjunction with a fast position measurement scheme to study the relaxation of lambda-DNA molecules against a constant external force with submillisecond time resolution. We compare the results to predictions from the wormlike chain model. PMID:15345573

Nambiar, Rajalakshmi; Gajraj, Arivalagan; Meiners, Jens-Christian

2004-09-01

62

Evidence for localized cell heating induced by infrared optical tweezers  

SciTech Connect

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 {similar_to}1.45{plus_minus}0.15 {degree}C/100 mW is observed when the vesicles are held stationary with a 1.064 {mu}m optical tweezers having a power density of {similar_to}10{sup 7} W/cm{sup 2} and a focused spot size of {similar_to}0.8 {mu}m. 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{plus_minus}0.25 {degree}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. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

Liu, Y.; Cheng, D.K.; Sonek, G.J. [Department of Electrical and Computer Engineering and Beckman Laser Institute and Medical Clinic, University of California, Irvine, California 92717 (United States); Berns, M.W.; Chapman, C.F.; Tromberg, B.J. [Department of Biophysics, and Beckman Laser Institute and Medical Clinic, University of California, Irvine, California 92717 (United States)

1995-05-01

63

Interferometer-Controlled Optical Tweezers Constructed for Nanotechnology and Biotechnology  

NASA Technical Reports Server (NTRS)

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

Decker, Arthur J.

2002-01-01

64

Single atoms in optical tweezers for quantum computing  

NASA Astrophysics Data System (ADS)

Our group is interested in neutral atom quantum computing. With this goal in mind, we have recently shown how a single rubidium atom trapped in an optical tweezer can be used to store, manipulate and measure a qubit. I will detail in this talk how we trap and observe a single atom in an optical tweezer created by focusing a far-off resonant laser down to a sub-micron waist. Our qubit is encoded on the |0>=|F =1, M=0> and |1>=|F =2, M=0> hyperfine sublevels of a rubidium 87 atom. We initialize the qubit by optical pumping. We read the state of the qubit using a state selective measurement limited by the quantum projection noise. We perform single qubit operation by driving a two-photon Raman transition. We have measured the coherence time of our qubit by Ramsey interferometry. After applying a spin-echo sequence, we have found an irreversible dephasing time of about 40 ms. To perform a computation, a feature is the ability to perform a gate between two arbitrary qubits of the register. As a first step, we have demonstrated a scheme where the qubit is transfered between two tweezers with no loss of coherence and no change in the external degrees of freedom of the atom. We have then moved the atom over distances typical of the separation between atoms in an array of dipole traps, and shown that this transport does not affect the coherence of the qubit. Finally, I will present our progress towards entangling two atoms, a key ingredient towards building a two-qubit gate.

Browaeys, Antoine

2008-05-01

65

Planar optical tweezers using tapered-waveguide junctions.  

PubMed

We demonstrate planar optical tweezers using the evanescent field of a silicon nitride tapered-waveguide junction between a singlemode waveguide and a multimode waveguide. Our experiments show that the junction embedded in a fluidic channel holds up to one and two polystyrene particles of sizes of 2.2 ?m and 1 ?m, respectively. The trapped particles are successively substituted by the incoming particles. Our experiments and numerical modeling reveal that the junction particle trapping depends on particle size and number. PMID:22825205

Cai, Hong; Poon, Andrew W

2012-07-15

66

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

67

pH microprobe manipulated in microchannels using optical tweezers  

NASA Astrophysics Data System (ADS)

SNARF-1 fluorochrome was used to functionalize 3?m diameter latex spheres making them sensitive to the pH of their environment, manifested as a change in their fluorescence. The fluorescence emission at 580nm was excited using a filtered xenon arc lamp at 515nm. A solution of functionalized latex spheres was placed between gold microelectrodes in a microfluidic channel. Optical tweezers were used to trap and manipulate the spheres in the vicinity of the microelectrodes, to map out the pH profile in the electrolyte solution, induced by passing 20 microsecond transient current pulses through the microelectrodes.

Sinclair, Gavin S.; Klauke, Norbert; Monaghan, Paul; Padgett, Miles J.; Cooper, Jon

2005-03-01

68

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

69

Moving average process underlying the holographic-optical-tweezers experiments  

NASA Astrophysics Data System (ADS)

We study statistical properties of the recordings which contain time-dependent positions of a bead trapped in optical tweezers. Analysis of such a time series indicates that the commonly accepted model, i.e., the autoregressive process of first order, is not sufficient to fit the data. We show a presence of the first-order moving average part in the dynamical model of the system. We explain origin of this part as an influence of the high frequency CCD camera on the measurements. The proposed autoregressive moving average model appears to reflect perfectly all statistical features of the high-frequency recording data.

?lezak, Jakub; Drobczy?ski, S?awomir; Weron, Karina; Masajada, Jan

2013-12-01

70

Process limitations in microassembling using holographic optical tweezers  

NASA Astrophysics Data System (ADS)

Microassembling with holographic optical tweezers (HOT) is a flexible manufacturing technology for the precise fabrication of complex microstructures. In contrast to classical direct writing techniques, here, microparticles are transported within a fluid to appropriate positions, where they are finally bound. Therefore, optical forces act against the inner friction of the fluid. This effect limits the microassembling process in the meaning of process speed. In this work we investigate these limitations depending on the applied laser power and particle size. Additionally, different to conventional optical tweezers, HOTs use spatial light modulators (SLM) to control the laser beam and the object's position. This is performed at discrete step sizes caused by successively imaging respective kinoforms on the SLM at specific refresh rates. An optimization of the step size and the applied update rate are crucial to reach maximum velocities in particle movement. Therefore, the performance of dynamic particle manipulation is investigated in individual experiments. Stable manipulation velocities of up to 114 ?m/s have been reported in our work using 6 ?m polystyrene particles and an applied laser power of 445 mW.

Ghadiri, R.; Guo, Q.; Yeoh, I.; Esen, C.; Ostendorf, A.

2012-02-01

71

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

72

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

73

Antigen detection at atomolar concentration using optical tweezers  

NASA Astrophysics Data System (ADS)

Methods that avoid intermediate amplification steps to detect protein markers of pathological disturbances would be of wide interest in the clinical environment. This is particularly the case in cancer diagnosis, where protein fragments are released into the blood by the emerging cancer cells. These fragments generate an antigen-antibody reaction, and the concentration of the antigen is known to modulate this interaction. Here we report on the development of a novel optical tweezers-based procedure to measure minute amount of antigen in a biological fluid. The force was applied on a 3?m polystyrene bead coated with Bovine Serum Albumin (BSA) attached on a 1.5 ?m diameter borosilicate rod tip coated with anti-BSA antibody. First, we verified that the binding strength was dependent on the protein concentration on the bead. We then assessed the sensitivity range by finding the minimal BSA concentration in solution that can still interfere with the bead-rod linkage. On the whole, the results demonstrated that proteinous antigen present in a biological fluid could possibly be detectable at atomolar concentration through the use of an optical tweezers.

Laliberté, Mathieu; Bordeleau, François; Marceau, Normand; Sheng, Yunlong

2009-06-01

74

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

NASA Astrophysics Data System (ADS)

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

Pacoret, Cécile; Régnier, Stéphane

2013-08-01

75

Optimization of holographic optical tweezers for multiplexed fluorescence spectroscopy  

NASA Astrophysics Data System (ADS)

We are developing a multiplexed spectroscopy technique that employs holographic optical tweezers to trap and excite multiple sensor particles. Our goal is to develop a lab-on-a-chip measurement platform for monitoring pH and other ion concentrations with high spatial resolution in a microfluidic device or within biological cells. To ensure efficient use of the available laser power required to trap multiple particles, we address three aspects of the spatial light modulator (SLM) used in the holographic technique. We measure and optimize the input and output polarizations used before and after the birefringent SLM. We reduce optical aberrations by adding appropriate Zernike polynomials to the computed hologram. We optimize the diffraction efficiency of the SLM by adjusting the gray scale input-to-output table to account for the nonlinear phase response of the SLM.

Cibula, Matthew; McIntyre, David

2012-10-01

76

Non-conservative forces in optical tweezers and Brownian vortexes  

NASA Astrophysics Data System (ADS)

Mechanical equilibrium at zero temperature does not necessarily imply thermodynamic equilibrium at finite temperature for a particle confined by a static, but non-conservative force field. Instead, the diffusing particle can enter into a steady state characterized by toroidal circulation in the probability flux, which we call a Brownian vortex. The circulatory bias in the particle's thermally-driven trajectory is not simply a deterministic response to the solenoidal component of the force, but rather reflects an interplay between advection and diffusion in which thermal fluctuations extract work from the non-conservative force field. As an example of this previously unrecognized class of stochastic machines, we consider a colloidal sphere diffusing in a conventional optical tweezer. We demonstrate both theoretically and experimentally that non-conservative optical forces bias the particle's fluctuations into toroidal vortexes whose circulation can reverse direction with temperature or laser power.

Sun, Bo; Grosberg, Alexander Y.; Grier, David G.

2010-02-01

77

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

78

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.

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

1998-01-01

79

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

80

Investigation of inclined dual-fiber optical tweezers for 3D manipulation and force sensing.  

PubMed

Optical tweezers provide a versatile tool in biological and physical researches. Optical tweezers based on optical fibers are more flexible and ready to be integrated when compared with those based on microscope objectives. In this paper, the three-dimensional (3D) trapping ability of an inclined dual-fiber optical tweezers is demonstrated. The trapping efficiency with respect to displacement is experimentally calibrated along two dimensions. The system is studied numerically using a modified ray-optics model. The spring constants obtained in the experiment are predicted by simulations. It is found both experimentally and numerically that there is a critical value for the fiber inclination angle to retain the 3D trapping ability. The inclined dual-fiber optical tweezers are demonstrated to be more robust to z-axis misalignment than the counter-propagating fiber optical tweezers, which is a special case of th former when the fiber inclination angle is 90 masculine. This inclined dual-fiber optical tweezers can serve as both a manipulator and a force sensor in integrated systems, such as microfluidic systems and lab-on-a-chip systems. PMID:19654770

Liu, Yuxiang; Yu, Miao

2009-08-01

81

Spatial measurement of spurious forces with optical tweezers  

NASA Astrophysics Data System (ADS)

The study of diffusion in a crowded and complex environment, such as inside a cell or within a porous medium, is of fundamental importance for science and technology. Combining blinking holographic optical tweezers and sub-pixel video microscopy permits one to study Brownian motion in confined geometries. In this work, in particular, we have studied the Brownian motion of two colloidal particles interacting hydrodynamically with each other. The proximity between the two microspheres induces a space-dependence in the particles diffusion coefficient and, therefore, a spurious drift. We measure this drift and evaluate the magnitude of the spurious force associated with it. We present the optoelectronic tools employed in the experiment and we discuss the experimental results.

Bordeu, Ignacio; Volpe, Giovanni; Staforelli, Juan Pablo

2013-11-01

82

Compact microscope-based 850-nm optical tweezers  

NASA Astrophysics Data System (ADS)

Emission from a single mode 100 mW laser diode at 850 nm is used for realizing optical tweezers: the laser beam is introduced into a microscope and focused by the objective into the object plane. Injection of the beam into a 40X microscope objective has been studied and the position and the size of the waist measured. The trap performance was studied as a function of the dimensions of the trapped particles. Trapping of polystyrene latex spheres of different size (from 0.2 micrometer to 6 micrometer) was observed in different conditions of laser power and transverse velocity of the spheres. Biological objects, Tetraselmis, of large dimension (around 10 micrometer) were also studied. We demonstrate the existence of an optimal range of size of the particles to be trapped. Furthermore we measure minimum trapping power required for trapping and the maximum speed of the trapped objects as a function of the dimensions.

Frediani, Carlo; Grego, S.; Guidoni, L.; Arimondo, Ennio

1996-01-01

83

Microrheology Using Optical Tweezers at the Air-Water Interface  

NASA Astrophysics Data System (ADS)

Microrheological techniques have been used successfully to determine mechanical properties of materials important in cellular structure. Also critical to cellular mechanical functions are biological membranes. Many aspects of biological membranes can be modeled using Langmuir monolayers, which are single layers surfactants at the air-water interface. The macroscopic mechanical properties of Langmuir monolayers have been extensively characterized. In contrast to macroscopic measurements, we report on experimental methods for studying the rheological properties of Langmuir monolayers on the micron scale. A water immersion optical tweezers system is used to trap ˜1 micron diameter beads in a monolayer. The passive motion of the trapped beads is recorded at high frequency and the complex shear modulus is calculated. Preliminary microrheological data of a fatty acid monolayer showing dependence on surface pressure will be presented. Experimental obstacles will also be discussed.

Boatwright, Thomas; Levine, Alex; Dennin, Michael

2010-11-01

84

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

85

Moving average process underlying the holographic-optical-tweezers experiments.  

PubMed

We study the statistical properties of recordings that contain time-dependent positions of a bead trapped in optical tweezers. Analysis of such a time series indicates that the commonly accepted model, i.e., the autoregressive process of first-order, is not sufficient to fit the data. We show the presence of a first-order moving average part in the dynamical model of the system. We explain the origin of this part as an influence of the high-frequency CCD camera on the measurements. We show that this influence evidently depends on the applied exposure time. The proposed autoregressive moving average model appears to reflect perfectly all statistical features of the high-frequency recording data. PMID:24787213

?l?zak, Jakub; Drobczy?ski, S?awomir; Weron, Karina; Masajada, Jan

2014-04-01

86

Probing multiscale mechanics of collagen with optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

87

Design and construction of a space-borne optical tweezer apparatus  

NASA Astrophysics Data System (ADS)

A compact optical tweezer package has been developed for use on a microscope to be flown on the International Space Station as part of a series of experiments in colloid crystallization. A brief introduction to the principles of single-beam optical tweezer operation will be presented, after which a detailed system layout will be shown. Special design requirements due to the spaceflight nature of the hardware will also be discussed. The tweezer apparatus is capable of trapping many particles through use of a two-axis acousto-optical deflector. The trap strength is sufficient to perform the required science (50 pN at ?n=0.2). The trap beam behaves approximately as a diffraction limited single mode Gaussian beam of numerical aperture, NA=1.4, as shown through spot size measurements and confocal-type images of the focal region. This is the first time optical tweezers will be deployed in a microgravity environment.

Resnick, Andrew

2001-11-01

88

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

89

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

Microsoft Academic Search

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.

Fabrice Merenda; Johann Rohner; Pedro Pascoal; Jean-Marc Fournier; Horst Vogel; René P. Salathé

2007-01-01

90

Cooling a Single Atom in an Optical Tweezer to Its Quantum Ground State  

NASA Astrophysics Data System (ADS)

We report cooling of a single neutral atom to its three-dimensional vibrational ground state in an optical tweezer. After employing Raman sideband cooling for tens of milliseconds, we measure via sideband spectroscopy a three-dimensional ground-state occupation of about 90%. We further observe coherent control of the spin and motional state of the trapped atom. Our demonstration shows that an optical tweezer, formed simply by a tightly focused beam of light, creates sufficient confinement for efficient sideband cooling. This source of ground-state neutral atoms will be instrumental in numerous quantum simulation and logic applications that require a versatile platform for storing and manipulating ultracold single neutral atoms. For example, these results will improve current optical-tweezer experiments studying atom-photon coupling and Rydberg quantum logic gates, and could provide new opportunities such as rapid production of single dipolar molecules or quantum simulation in tweezer arrays.

Kaufman, A. M.; Lester, B. J.; Regal, C. A.

2012-10-01

91

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

Microsoft Academic Search

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 mum diameter suspended in aqueous medium. The videos

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

2011-01-01

92

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

Microsoft Academic Search

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

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

2011-01-01

93

Advanced optical tweezers for the study of cellular and molecular biomechanics.  

PubMed

Optical tweezers are an important tool for studying cellular and molecular biomechanics. We present a robust optical tweezers device with advanced features including: multiple optical traps, acousto-optic trap steering, and back focal plane interferometry position detection. We integrate these features into an upright microscope, with no compromise to its capabilities (differential interference contrast microscopy, fluorescence microscopy, etc.). Acousto-optic deflectors (AODs) steer each beam and can create multiple time-shared traps. Position detection, force calibrations and AOD performance are presented. The system can detect subnanometer displacements and forces below 0.1 pN. PMID:12617534

Brouhard, Gary J; Schek, Henry T; Hunt, Alan J

2003-01-01

94

Particle interaction measurements using laser tweezers optical trapping.  

SciTech Connect

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

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

2008-08-01

95

Manipulation of Suspended Single Cells by Microfluidics and Optical Tweezers  

PubMed Central

Chondrocytes and osteoblasts experience multiple stresses in vivo. The optimum mechanical conditions for cell health are not fully understood. This paper describes the optical and microfluidic mechanical manipulation of single suspended cells enabled by the ?PIVOT, an integrated micron resolution particle image velocimeter (?PIV) and dual optical tweezers instrument (OT). In this study, we examine the viability and trap stiffness of cartilage cells, identify the maximum fluid-induced stresses possible in uniform and extensional flows, and compare the deformation characteristics of bone and muscle cells. These results indicate cell photodamage of chondrocytes is negligible for at least 20 min for laser powers below 30 mW, a dead cell presents less resistance to internal organelle rearrangement and deforms globally more than a viable cell, the maximum fluid-induced shear stresses are limited to ~15 mPa for uniform flows but may exceed 1 Pa for extensional flows, and osteoblasts show no deformation for shear stresses up to 250 mPa while myoblasts are more easily deformed and exhibit a modulated response to increasing stress. This suggests that global and/or local stresses can be applied to single cells without physical contact. Coupled with microfluidic sensors, these manipulations may provide unique methods to explore single cell biomechanics.

Neve, Nathalie; Kohles, Sean S.; Winn, Shelley R.; Tretheway, Derek C.

2010-01-01

96

Computer-automated program for calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

97

Multiple Optical Traps with a Single-Beam Optical Tweezer Utilizing Surface Micromachined Planar Curved Grating  

NASA Astrophysics Data System (ADS)

In this paper, we present a single-beam optical tweezer integrated with a planar curved diffraction grating for microbead manipulation. Various curvatures of the surface micromachined planar curved grating are systematically investigated. The planar curved grating was fabricated using multiuser micro-electro-mechanical-system (MEMS) processes (MUMPs). The angular separation and the number of diffracted orders were determined. Experimental results indicate that the diffraction patterns and curvature of the planar curved grating are closely related. As the curvature of the planar curved grating increases, the vertical diffraction angle increases, resulting in the strip patterns of the planar curved grating. A single-beam optical tweezer integrated with a planar curved diffraction grating was developed. We demonstrate a technique for creating multiple optical traps from a single laser beam using the developed planar curved grating. The strip patterns of the planar curved grating that resulted from diffraction were used to trap one row of polystyrene beads.

Kuo, Ju-Nan; Chen, Kuan-Yu

2010-11-01

98

Hydroxyl radical oxidation of glucose in aqueous aerosol studied in single levitated droplets by laser Raman tweezers  

NASA Astrophysics Data System (ADS)

Recent work has highlighted that cloud processing of atmospheric contaminants changes the optical properties of these clouds. Airborne particulate matter plays a crucial role in determining the climate and weather of the Earth. The chemical composition of particulate matter affects climate directly, by scattering and absorbing solar radiation, and indirectly, owing to its ability to act as cloud condensation nuclei, thus leading to an increase in cloud formation. Both the direct and indirect effects are influenced by the chemical composition of the aerosol. We present a study of oxidation of important biomass burning marker (glucose) by hydroxyl radical in single optically levitated droplets (1-20?m) using Laser Raman Tweesers. We levitate and hold the aqueous particle in the focus of an Ar-ion laser and photogenerate hydroxyl radical in the particle by a second UV laser. The Particle is subjected to a known RH. Scattered light from the trapping laser is used to provide chemical data in real time via Raman spectroscopy and brightfeild spectroscopy is used to follow the hygrodynamic size changes of the particle also in real time. The decay of glucose and hydrogen peroxide (by Raman spectroscopy) can be a fitted to a kinetic model to determine the rate constant for the reaction of hydroxyl radical with glucose as shown in the figure. Unlike our previous work (oxidation of organic particles with ozone) we see no size change and thus no change in critical supersaturation following reaction. This surprising result suggests this reaction does not alter cloud optical properties. To our knowledge this is the first time hydroxyl radical chemistry in single droplets has been studied by laser Raman tweezers. The work demonstrates that laser Raman tweezers is an excellent technique for studying the effect of oxidation reaction on the hygroscopic properties of aerosol. Loss of glucose and hydrogen peroxide from single optically levitated particle during photolysis of hydrogen peroxide by 350nm laser. Points determined by Raman spectroscopy. The decay of hydrogen peroxide and glucose can be fitted to simple kinetic model to determine rate constant of OH reacting with glucose (solid lines)

King, M. D.; Hunt, O. R.; Ward, A.

2009-12-01

99

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

100

Optical discharge in aerosols  

NASA Astrophysics Data System (ADS)

The physical fundamentals of the optical breakdown of aerosols are examined, and a theory is developed for the seed ionization processes in inert and reacting aerosols. The properties of optical discharges of various kinds generated at isolated particles are investigated, as are the characteristics of the collective breakdown mechanism. The probabilistic criteria of the breakdown and the linear transmission dynamics of an ionized atmosphere are discussed. Some results of laboratory and full-scale experiments concerned with the optical, electrodynamic, and acoustic characteristics of an extended laser spark are presented.

Kopytin, Iurii D.; Sorokin, Iurii M.; Skripkin, Aleksandr M.; Belov, N. N.; Bukatyi, V. I.

101

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

102

Analysis of RBC damage using laser tweezers Raman spectroscopy (LTRS) during femtosecond laser optical trapping  

Microsoft Academic Search

We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy (LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon absorption or second harmonic generation trapping. Femtosecond laser optical trapping

Sung-bin Ju; Jin-woo Pyo; Jae-young Jang; Seungduk Lee; Beop-Min Kim

2008-01-01

103

Grasping microscopic objects by multiple tools actuated by optical tweezers  

NASA Astrophysics Data System (ADS)

Optical tweezers is a promising manipulation tool for objects in the range of micrometers to nanometers. Although there are many reported works on manipulating objects made of different materials and objects of irregular shapes, it is more suitable for non-opaque materials and objects that are symmetrical. Furthermore, there are potential damages on the objects arising from immense heat that is produced by the laser beam. These problems can be alleviated by trapping objects (micro-handles) and using them collectively as a gripper to indirectly hold and manipulate a target object. Holding denotes equilibrium of forces exerted by the tools on a target object. However, there still is a problem with this approach. When the trapping volume is larger than the size of a tool, target objects get pulled towards the center of the trapping volume. This breaks the force equilibrium and gripping thus fails. In this paper, we report a new design of tools that can overcome this problem. The tool is a slender object with one end acting as a probe while the other end is spherical so that trapping is easy. The length of the tool is designed to be larger than the radius of the trapping volume. Thus the target object is never pulled towards the trapping center. A group of multiple identical tools will surround and push a target object at the probe tips resulting in a stable grasp.

Sung, Seung-Yong; Park, In-Yong; Lee, Jong-Hyun; Lee, Yong-Gu

2006-09-01

104

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.

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

2002-01-01

105

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

106

A computational tool to characterize particle tracking measurements in optical tweezers  

NASA Astrophysics Data System (ADS)

Here, we present a computational tool for optical tweezers which calculates the particle tracking signal measured with a quadrant detector and the shot-noise limit to position resolution. The tool is a piece of Matlab code which functions within the freely available Optical Tweezers Toolbox. It allows the measurements performed in most optical tweezer experiments to be theoretically characterized in a fast and easy manner. The code supports particles with arbitrary size, any optical fields and any combination of objective and condenser, and performs a full vector calculation of the relevant fields. Example calculations are presented which show the tracking signals for different particles, and the shot-noise limit to position sensitivity as a function of the effective condenser NA.

Taylor, Michael A.; Bowen, Warwick P.

2013-08-01

107

Resolving stable axial trapping points of nanowires in an optical tweezers using photoluminescence mapping.  

PubMed

Axially resolved microphotoluminescence mapping of semiconductor nanowires held in an optical tweezers reveals important new experimental information regarding equilibrium trapping points and trapping stability of high aspect ratio nanostructures. In this study, holographic optical tweezers are used to scan trapped InP nanowires along the beam direction with respect to a fixed excitation source and the luminescent properties are recorded. It is observed that nanowires with lengths on the range of 3-15 ?m are stably trapped near the tip of the wire with the long segment positioned below the focus in an inverted trapping configuration. Through the use of trap multiplexing we investigate the possibility of improving the axial stability of the trapped nanowires. Our results have important implication for applications of optically assisted nanowire assembly and optical tweezers based scanning probes microscopy. PMID:23394286

Wang, Fan; Toe, Wen Jun; Lee, Woei Ming; McGloin, David; Gao, Qiang; Tan, Hark Hoe; Jagadish, Chennupati; Reece, Peter J

2013-03-13

108

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

109

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

PubMed

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. PMID:24514629

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

2013-12-16

110

A microfluidic system for studies of stress response in single cells using optical tweezers  

Microsoft Academic Search

In recent years there has been a growing interest in the use of optical manipulation techniques, such as optical tweezers, in biological research as the full potential of such applications are being realized. Biological research is developing towards the study of single entities to reveal new behaviors that cannot be discovered with more traditional ensemble techniques. To be able to

Annette Granéli; Emma Eriksson; Jonas Enger; Kerstin Ramser; Mattias Goksör; Stefan Hohmann; Dag Hanstorp

2006-01-01

111

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

112

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

PubMed

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

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

2014-07-18

113

The use of optical tweezers to study sperm competition and motility in primates  

Microsoft Academic Search

Optical trapping is a non-invasive biophysical tool which has been widely applied to study physiological and biomechanical properties of cells. Using laser 'tweezers' in combination with custom-designed computer tracking algorithms, the swimming speeds and the relative swimming forces of individual sperm can be measured in real time. This combination of physical and engineering tools has been used to examine the

Jaclyn M. Nascimento; Linda Z. Shi; Stuart Meyers; Pascal Gagneux; Naida M. Loskutoff; Elliot L. Botvinick; Michael W. Berns

2008-01-01

114

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

NASA Astrophysics Data System (ADS)

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

Kim, Jung-Dae; Lee, Yong-Gu

2013-06-01

115

Noncontact microsurgery and micromanipulation of living cells with combined system femtosecond laser scalpel-optical tweezers  

NASA Astrophysics Data System (ADS)

We report on the results of using self-developed combined laser system consisting of a femtosecond laser scalpel (Cr:Forsterite seed oscillator and a regenerative amplifier, 620 nm, 100 fs, 10 Hz) and optical tweezers (cw laser, 1064 nm) for performing noncontact laser-mediated polar body (PB) and trophectoderm (TE) biopsy of early mammalian embryos. To perform PB biopsy the femtosecond laser scalpel was initially used to drill an opening in the zona pellucida, and then the PB was extracted out of the zygote with the optical tweezers. Unlike PB biopsy, TE biopsy allows diagnosing maternally-derived as well as paternally-derived defects. Moreover, as multiple TE cells can be taken from the embryo, more reliable diagnosis can be done. TE biopsy was performed by applying laser pulses to dissect the desired amount of TE cells that had just left the zona pellucida during the hatching. Optical tweezers were then used to trap and move the dissected TE cells in a prescribed way. Laser power in optical tweezers and energy of femtosecond laser pulses were thoroughly optimized to prevent cell damage and obtain high viability rates. In conclusion, the proposed techniques of laser-based embryo biopsy enable accurate, contamination-free, simple and quick microprocessing of living cells.

Il'ina, Inna V.; Sitnikov, Dmitry S.; Ovchinnikov, Andrey V.; Agranat, Mikhail B.; Khramova, Yulia V.; Semenova, Maria L.

2012-05-01

116

Robot-assisted automatic cell sorting with combined optical tweezer and microfluidic chip technologies  

Microsoft Academic Search

This paper presents a robot-assisted methodology that integrates optical tweezer and microfluidic chip technologies to realize automatic cell sorting from small sample population. The microfluidic chip used for cell sorter is designed and fabricated, and the flow environment within the microfluidic channel is investigated with simulation. Two image processing methods, depending on size and fluorescence label respectively, are used to

Xiaolin Wang; Shuxun Chen; Dong Sun

2011-01-01

117

Nanomanipulation of single influenza virus using optical tweezers and dielectrophoretic force on a microfluidic chip  

Microsoft Academic Search

A major problem for analysis of bio-nanoparticles such as the influenza viruses (size is about 100 nm) is that sample concentration is low. We developed manipulation of the single virus using optical tweezers supported by dielectrophoretic concentration of the viruses in a microfluidic chip. The microfluidic chip made of poly (dimethyl siloxane) (PDMS) is useful to achieve stable manipulation of

Hisataka Maruyama; Kyosuke Kotani; Ayae Honda; Tatsuro Takahata; Fumihito Arai

2010-01-01

118

A microfluidic system for studies of stress response in single cells using optical tweezers  

NASA Astrophysics Data System (ADS)

In recent years there has been a growing interest in the use of optical manipulation techniques, such as optical tweezers, in biological research as the full potential of such applications are being realized. Biological research is developing towards the study of single entities to reveal new behaviors that cannot be discovered with more traditional ensemble techniques. To be able to study single cells we have developed a new method where a combination of micro-fluidics and optical tweezers was used. Micro-fluidic channels were fabricated using soft lithography. The channels consisted of a Y-shaped junction were two channels merged into one. By flowing different media in the two channels in laminar flow we were able to create a sharp concentration gradient at the junction. Single cells were trapped by the tweezers and the micro-fluidic system allowed fast environmental changes to be made for the cell in a reversible manner. The time required to change the surroundings of the cell was limited to how sharp mixing region the system could create, thus how far the cells had to be moved using the optical tweezers. With this new technique cellular response in single cells upon fast environmental changes could be investigated in real time. The cellular response was detected by monitoring variations in the cell by following the localization of fluorescently tagged proteins within the cell.

Granéli, Annette; Eriksson, Emma; Enger, Jonas; Ramser, Kerstin; Goksör, Mattias; Hohmann, Stefan; Hanstorp, Dag

2006-09-01

119

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.

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

2002-01-01

120

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

2006-09-01

121

Influence of multiple particles in optical tweezers on the trapping efficiency  

NASA Astrophysics Data System (ADS)

Since the early times of Arthur Ashkins groundbreaking experiments on optical tweezers, a great number of theoretical works was dedicated to this subject. Most of them treated the optical trapping of single spherical or elliptical particles. In the last years optical tweezers have become more and more a tool for assembling three dimensional structures using single microspheres as building blocks. Since all structures and particles inside the light beams influence the properties of the traps, we investigated theoretically the influence of additional single particles and particle arrays on the properties of optical traps. For this reason a geometrical optics based model is used with the inherent flexibility to be applied for various shapes and particle numbers.

Weigel, Thomas; Ghadiri, Reza; Esen, Cemal; Schweiger, Gustav; Ostendorf, Andreas

2014-02-01

122

Optical properties of red blood cells: an optical tweezer based analysis  

NASA Astrophysics Data System (ADS)

A microscopic object finds an equilibrium orientation under a laser tweezer such that a maximum of its volume lies in the region of highest electric field. Furthermore, birefringent microscopic objects show no rotational diffusion after reorienting under a linearly polarized optical trap and also are seen to follow the plane of polarization when the latter is changed using a half wave plate. We observe that a healthy human Red Blood Cell (RBC) reproduces these observations in an optical tweezer, which confirms it to be birefringent. Polarization microscopy based measurements reveal that the birefringence is confined to the cell's dimple region and the mean value of retardation for polarized green light (? = 546nm) is 9 +/- 1.5nm. We provide a simple geometrical model that attributes the birefringence to the nature of arrangement of the phospholipid molecules of the bilayer. This predicts the observed variation in the measured birefringence, from the dimple to the rim of the cell which we further show, can serve to demarcate the extent of the dimple region. This points to the value of birefringence measurements in revealing cell membrane contours. . We extend this technique to understand the birefringence of a chicken RBC, an oblate shaped cell, wherein the slow axis is identified to be coincident with the long axis of the cell. Further, we observe the birefringence to be confined to the edges of the cell. Experiments to probe the optomechanical response of the chicken RBC are in progress.

Nagesh, B. V.; Lakkegowda, Yogesha; Pratibha, R.; Praveen, P.; Bhattacharya, Sarbari; Ananthamurthy, Sharath

2014-03-01

123

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

124

Tapered fiber optical tweezers for microscopic particle trapping: fabrication and application.  

PubMed

A novel single tapered fiber optical tweezers is proposed and fabricated by heating and drawing technology. The microscopic particle tapping performance of this special designed tapered fiber probe is demonstrated and investigated. The distribution of the optical field emerging from the tapered fiber tip is numerically calculated based on the beam propagation method. The trapping force FDTD analysis results, both axial and transverse, are also given. PMID:19529686

Liu, Zhihai; Guo, Chengkai; Yang, Jun; Yuan, Libo

2006-12-11

125

An improved optical tweezers assay for measuring the force generation of single kinesin molecules.  

PubMed

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

126

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

127

Optical levitation and manipulation of stuck particles with pulsed optical tweezers  

NASA Astrophysics Data System (ADS)

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

Ashok Ambardekar, Amol; Li, Yong-Qing

2005-07-01

128

Optical tweezers induced photodamage in living cells quantified with digital holographic phase microscopy  

NASA Astrophysics Data System (ADS)

Optical tweezers are a versatile technique to manipulate living biological specimen in a contact-less way. The interaction with living cells can be performed, for example, through direct manipulation of cell organelles or by movement of an internalized particle within the cytoplasm. However, the risk of damage that the trapping beam may induce in the biological sample due to the energy deposition has to be considered. This optically induced damage or photodamage depends mainly on the wavelength of the trapping beam, the exposure time and the biological specimen that is investigated. In this work, we explore a method to analyse the photo damage in living cells in a multimodal biophotonic workstation that is based on combining a holographic optical tweezers (HOT) microscope with a self-interference digital holographic microscopy (DHM) module. A time-dependent investigation shows that no observable changes in the cell morphology are induced at room conditions with the used laser power of the trapping beam during periods of time < 20 min of laser application. In addition, results from investigations of the photodamage increasing the working temperature to 37°C demonstrate that the optical tweezers beam can provoke severe but reversible morphology changes in the cell.

Barroso Peña, Álvaro; Kemper, Björn; Woerdemann, Mike; Vollmer, Angelika; Ketelhut, Steffi; von Bally, Gert; Denz, Cornelia

2012-05-01

129

NOTE: Manufacturing micro-scale structures by an optical tweezers system controlled by five finger tips  

NASA Astrophysics Data System (ADS)

Because of the compelling need for manufacturing micro- to nano-scale structures, researchers are actively investigating new methods that are applicable for small scale manufacturing. Among them, optical tweezers that can manipulate microscopic objects using a laser are receiving key attention. Optical tweezers have been used actively in the field of science. For example, they were used for measuring mechanical characteristics on the scale of piconewtons or for manipulating and sorting large numbers of particles. However, little work has been reported on 'manufacturing' objects. In this paper, we present a new method for manufacturing micro-scale structures using micro-scale polystyrene particles. Particles will be controlled with a user interface that utilizes a human hand and glued together by the bonding force between biotin and streptavidin.

Park, In-Yong; Sung, Seung-Yong; Lee, Jong-Hyun; Lee, Yong-Gu

2007-10-01

130

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

Microsoft Academic Search

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

Serge Monneret; Federico Belloni; Didier Marguet

2006-01-01

131

Time-resolved nanoseconds dynamics of ultrasound contrast agent microbubbles manipulated and controlled by optical tweezers  

Microsoft Academic Search

Optical tweezers enable non-destructive, contact-free manipulation of ultrasound contrast agent (UCA) microbubbles, which are used in medical imaging for enhancing the echogenicity of the blood pool and to quantify organ perfusion. The understanding of the fundamental dynamics of ultrasound-driven contrast agent microbubbles is a first step for exploiting their acoustical properties and to develop new diagnostic and therapeutic applications. In

Valeria Garbin; Dan Cojoc; Enrico Ferrari; Enzo Di Fabrizio; Marlies Overvelde; Michel Versluis; Sander van der Meer; Nico de Jong; Detlef Lohse; Kishan Dholakia; Gabriel C. Spalding

2006-01-01

132

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

133

Manipulation and assembly of ZnO nanowires with single holographic optical tweezers system.  

PubMed

ZnO nanowires, characterized with high melting points, are hard to assemble together with laser fusion. In order to build micro-nano structures with ZnO nanowires, a polymer film with a low melting point and high optical transparency is introduced as a substrate for ZnO nanowires to be deposited. A holographic optical tweezers system is used not only to manipulate ZnO nanowires, but also to melt the polymer film for the fixation of ZnO nanowires. By this method, micro-nano structures composed of ZnO nanowires are produced, which can be utilized as subwavelength optical waveguides. PMID:24514119

Li, Jing; Du, Gang

2014-01-20

134

Trapping and manipulation of microscopic bubbles with a scanning optical tweezer  

NASA Astrophysics Data System (ADS)

The authors have demonstrated three-dimensional trapping of ultrasound contrast agent microbubbles using a circularly scanning optical tweezers to confine the microbubble in a time-averaged optical potential. They have measured the maximum transverse drag force that may be applied to the trapped microbubble before it escapes and found that this decreases significantly at small trap radii. They explain this in terms of the relative volumes of the microbubble and the trap and anticipate that this feature will be important in experiments involving the insonation of optically trapped microbubbles.

Jones, P. H.; Stride, E.; Saffari, N.

2006-08-01

135

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

PubMed Central

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

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

2013-01-01

136

Calibration of trapping force and response function of optical tweezers in viscoelastic media  

NASA Astrophysics Data System (ADS)

At present, a major obstacle to the quantitative application of optical tweezers as a force spectrometer in living cells is the lack of a method to calibrate the tweezers. Calibration with approved methods such as the power spectrum method (Berg-Sørensen and Flyvbjerg 2004 Rev. Sci. Instrum. 75 594; Berg-Sørensen et al 2006 Rev. Sci. Instrum. 77 063106) is not possible as the viscoelastic properties of the bio-active medium are a priori unknown. Here, we present an approach that neither requires explicit assumptions about the size of the trapped particle nor about the viscoelastic properties of the medium. Instead, the interaction between the medium and the trapped particle is described in a general manner, through velocity and acceleration memory. Our method is applicable to general, at least locally homogeneous, viscoelastic media. The procedure combines active and passive approaches by the application of Onsager's regression hypothesis. It allows extraction of the trapping stiffness ? of the optical tweezers and of the response function ?(?), which is the frequency-dependent effective inverse spring constant of the system. Finally, information about the viscoelastic properties of the medium may also be found. To test the method, we have performed simulations in which the system is driven sinusoidally. These simulations serve as an example of how to deal with real experimental data. For realistic parameters, we calibrate the trap stiffness ? with ~1% stochastic error.

Fischer, Mario; Berg-Sørensen, Kirstine

2007-08-01

137

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

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

138

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

139

Mechanical analysis of the optical tweezers in time-sharing regime.  

PubMed

Time-sharing optical tweezers is a versatile technique to realize multiple traps for manipulating biological cells and macromolecules. It has been based on an intuitive hypothesis that the trapped viscoelastic object does not "sense" blinking of the optical beam. We present a quantitative analysis using mechanical modeling and numerical simulation, showing that the local stress and strain are jumping all the time and at all locations with the jumping amplitude independent of the recovery time of the viscoelastic material and the jumping frequency. Effects of the stress and strain jumping on the object deformation and the internal energy dissipation are analyzed. PMID:24718171

Yu, Lingyao; Sheng, Yunlong

2014-04-01

140

Electrochemical detection of single microbeads manipulated by optical tweezers in the vicinity of ultramicroelectrodes.  

PubMed

Latex micrometric beads are manipulated by optical tweezers in the vicinity of an ultramicroelectrode (UME). They are optically trapped in solution and approached the electrode surface. After the electrochemical measurement, they are optically removed from the surface. The residence time of the particle on the electrode is thus controlled by the optical tweezers. The detection is based on diffusional hindrance by the insulating objects which alters the fluxes of the redox Ru(NH3)6(3+) species toward the UME and thus its mass-transfer limited current. We have optically deposited successively 1, 2, and 3 beads of 3-?m radius on the UME surface, and we have recorded the variations of the current depending on their landing locations that were optically controlled. Finally we decreased the current by partially blocking the electroactive surface with a six-bead assembly. The variation of the steady-state current and the approach curves allow for the indirect electrochemical localization of the bead in the vicinity of the UME, not only when the bead is in contact but also when it is levitated at distances lower than the UME radius. These experiments show that single particles or more complex structures may be manipulated in situ in a contactless mode near the UME surface. From comparison with simulations, the electrochemical detection affords an indirect localization of the object in the UME environment. The developed approach offers a potential application for interrogating the electrochemical activity of single cells and nanoparticles. PMID:24020821

Suraniti, Emmanuel; Kanoufi, Frédéric; Gosse, Charlie; Zhao, Xuan; Dimova, Rumiana; Pouligny, Bernard; Sojic, Neso

2013-10-01

141

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

142

3D multiple optical tweezers based on time-shared scanning with a fast focus tunable lens  

NASA Astrophysics Data System (ADS)

Three-dimensional controlled manipulation of individual micro-objects requires multiple optical tweezers that can be independently controlled in a 3D working space with high spatiotemporal resolution. Here, the author presents 3D multiple optical tweezers based on a time-shared scanning technique with an electrically focus tunable lens for axial steering and a two-axis steering mirror for lateral steering. Four typical examples of 3D controlled manipulation, including the rotation of a single bead on its axis, are demonstrated in real time. The optical system design and the control method are also described.

Tanaka, Yoshio

2013-02-01

143

Atmospheric aerosols: Their Optical Properties and Effects  

NASA Technical Reports Server (NTRS)

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

1976-01-01

144

Three-dimensional parallel particle manipulation and tracking by integrating holographic optical tweezers and engineered point spread functions.  

PubMed

We demonstrate an integrated holographic optical tweezers system with double-helix point spread function (DH-PSF) imaging for high precision three-dimensional multi-particle tracking. The tweezers system allows for the creation and control of multiple optical traps in three-dimensions, while the DH-PSF allows for high precision, 3D, multiple-particle tracking in a wide field. The integrated system is suitable for particles emitting/scattering either coherent or incoherent light and is easily adaptable to existing holographic tweezers systems. We demonstrate simultaneous tracking of multiple micro-manipulated particles and perform quantitative estimation of the lateral and axial forces in an optical trap by measuring the fluid drag force exerted on the particles. The system is thus capable of unveiling complex 3D force landscapes that make it suitable for quantitative studies of interactions in colloidal systems, biological materials, and a variety of soft matter systems. PMID:21369208

Conkey, Donald B; Trivedi, Rahul P; Pavani, Sri Rama Prasanna; Smalyukh, Ivan I; Piestun, Rafael

2011-02-28

145

Apparatus for Using Optical Tweezers to Manipulate Materials.  

National Technical Information Service (NTIS)

A method and apparatus for control of optical trap arrays and formation of particle arrays using light that is in the visible portion of the spectrum. The method and apparatus provides a laser and a time variable diffractive optical element to allow dynam...

B. A. Koss D. G. Grier E. R. Dufresne J. E. Curtis

2004-01-01

146

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.

2006-09-01

147

Force increment of twin-core fiber optical tweezers using an optimum structure radius  

NASA Astrophysics Data System (ADS)

Far-field distribution at the tip of a twin-core fiber optical tweezers is studied by using the finite-difference time-domain beam-propagation method (FDTD-BPM). Based on the Poynting vector calculations and from this distribution, the operating force on a particle at the end tip was computed. It is found that, for thin and thick radius of the cladding layer, the trapping force on micro-particles became weak. So, there is an optimum value for this parameter to have maximum force.

Rahimi-Kazerooni, Ammar; Emami, Farzin

2012-09-01

148

Surface-enhanced resonance Raman scattering in optical tweezers using co-axial second harmonic generation.  

PubMed

Silica particles were partially coated with silver, and a suitable chromophore, such that they could be simultaneously trapped within an optical tweezers system, and emit a surface-enhanced resonance Raman scattering (SERRS) response. A standard 1064 nm TEM00 mode laser was used to trap the bead whilst a frequency doubling crystal inserted into the beam gave several microwatts of 532 nm co-linear light to excite the SERRS emission. The con fi guration has clear applications in providing apparatus that can simultaneously manipulate a particle whilst obtaining surface sensitive sensory information. PMID:19495327

Jordan, Pamela; Cooper, Jon; McNay, Graeme; Docherty, Frances; Graham, Duncan; Smith, W; Sinclair, Gavin; Padgett, Miles

2005-05-30

149

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

PubMed Central

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

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

1999-01-01

150

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

151

Adding functionalities to precomputed holograms with random mask multiplexing in holographic optical tweezers.  

PubMed

In this study, we present a method designed to generate dynamic holograms in holographic optical tweezers. The approach combines our random mask encoding method with iterative high-efficiency algorithms. This hybrid method can be used to dynamically modify precalculated holograms, giving them new functionalities-temporarily or permanently-with a low computational cost. This allows the easy addition or removal of a single trap or the independent control of groups of traps for manipulating a variety of rigid structures in real time. PMID:21460909

Mas, Josep; Roth, Michelle S; Martín-Badosa, Estela; Montes-Usategui, Mario

2011-04-01

152

Probing cell biophysical behavior based on actin cytoskeleton modeling and stretching manipulation with optical tweezers  

NASA Astrophysics Data System (ADS)

This letter presents an approach to utilizing the actin cytoskeleton model and optical tweezers technology to probe the distinct underlying F-actin remodeling mechanism and showing quantitatively how cell mechanical behavior is associated with alterations in the cell functions. The structural parameters of F-actin were extracted by fitting the modeling results with the experimental results obtained by cell stretching manipulation. Alterations of cell mechanical behaviors under distinct diseased cellular stages were further interpreted. Jurkat and K562 cells were used as sample cells. This letter successfully illustrates the correlation of the cell mechanical behavior and cell functional alterations in a quantitative way.

Wang, Kaiqun; Cheng, Jinping; Han Cheng, Shuk; Sun, Dong

2013-08-01

153

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

154

Virtual Environment for Manipulating Microscopic Particles with Optical Tweezers.  

National Technical Information Service (NTIS)

In this paper, virtual reality techniques are used to define an intuitive interface to a nanoscale manipulation device. This device utilizes optical methods to focus laser light to trap and reposition nano-to-microscopic particles. The underlying physics ...

Y. G. Lee K. W. Lyons T. W. LeBrun

2003-01-01

155

Single beam optical vortex tweezers with tunable orbital angular momentum  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

156

Correction of aberration in holographic optical tweezers using a Shack-Hartmann sensor.  

PubMed

Optical aberration due to the nonflatness of spatial light modulators used in holographic optical tweezers significantly deteriorates the quality of the trap and may easily prevent stable trapping of particles. We use a Shack-Hartmann sensor to measure the distorted wavefront at the modulator plane; the conjugate of this wavefront is then added to the holograms written into the display to counteract its own curvature and thus compensate the optical aberration of the system. For a Holoeye LC-R 2500 reflective device, flatness is improved from 0.8? to ?/16 (?=532 nm), leading to a diffraction-limited spot at the focal plane of the microscope objective, which makes stable trapping possible. This process could be fully automated in a closed-loop configuration and would eventually allow other sources of aberration in the optical setup to be corrected for. PMID:23567567

López-Quesada, Carol; Andilla, Jordi; Martín-Badosa, Estela

2009-02-20

157

Dynamic and programmable cell-sorting by using microfluidics and holographic optical tweezers  

NASA Astrophysics Data System (ADS)

Cell sorting is important in quantitative analysis for cellular and molecular biology study. For this purpose, we develop an opto-electro-mechanical sorting system which integrates a holographic optical tweezers (HOT) system to a microfluidics device. This system is designed to manipulate and sort various micro objects of different sizes by an optical pattern which is dynamic and programmable. In this work, we fabricate a microchannel with a main channel and two branches with polydimethylsiloxane (PDMS) which is a biocompatible elastomer material by utilizing semiconductor micro-fabrication techniques. By using a HOT system, we also generate two linear optical traps for the manipulation of micro particles. As a result, we have demonstrated that the larger particles are guided to the second branch by the two linear optical traps while the smaller particles remain unaffected and flow into the first branch of the microchannel.

Lin, Ho-Chien; Hsu, Long

2005-08-01

158

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.

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

2012-01-01

159

A modular system architecture for agile assembly of nanocomponents using optical tweezers  

NASA Astrophysics Data System (ADS)

In order to realize the flexibility optical trapping offers as a nanoassembly tool, we need to develop natural and intuitive interfaces to assemble large quantities of nanocomponents quickly and cheaply. We propose a system to create such an interface that is scalable, inter-changeable and modular. Several prototypes are described, starting with simple interfaces that control a single trap in the optical tweezers instrument using a 3-dimensional Phantom haptic device. A networkbased approach is adopted early on, and a modular prototype is then described in detail. In such a design, individual modules developed on different platforms work independently and communicate with each other through a common language interface using the Neutral Messaging Language (NML) communication protocol. A natural user interface is implemented that can be used to create and manipulate traps interactively like in a CAD program. Modules such as image processing and automatic assembly are also added to help simplify routine assembly tasks. Drawing on lessons learned from the prototypes, a new system specification is formulated to better integrate the modules. Finally, conclusions are drawn on the overall viability and future of network-based systems for nanoassembly using optical tweezers.

Balijepalli, Arvind; LeBrun, Thomas; Gagnon, Cedric; Lee, Yong-Gu; Dagalakis, Nicholas

2005-09-01

160

Trapping volume control in optical tweezers using cylindrical vector beams.  

PubMed

We present the result of an investigation into the optical trapping of spherical microparticles using laser beams with a spatially inhomogeneous polarization direction [cylindrical vector beams (CVBs)]. We perform three-dimensional tracking of the Brownian fluctuations in the position of a trapped particle and extract the trap spring constants. We characterize the trap geometry by the aspect ratio of spring constants in the directions transverse and parallel to the beam propagation direction and evaluate this figure of merit as a function of polarization angle. We show that the additional degree of freedom present in CVBs allows us to control the optical trap strength and geometry by adjusting only the polarization of the trapping beam. Experimental results are compared with a theoretical model of optical trapping using CVBs derived from electromagnetic scattering theory in the T-matrix framework. PMID:23282827

Skelton, S E; Sergides, M; Saija, R; Iatì, M A; Maragó, O M; Jones, P H

2013-01-01

161

An interactive optical tweezers simulation for science education  

NASA Astrophysics Data System (ADS)

We developed a freely available interactive simulation of optical traps and their biological applications (phet.colorado.edu). The target audience is undergraduate majors as well as more advanced researchers. The simulation has three panels: optical traps, manipulating DNA, and measuring molecular motors. Each panel has options that allow students to interactively explore key physical ideas. For instance, viscosity can be turned off to see the critical aspect of dissipation, or time can be slowed down to see the oscillating electric field and the induced charge separation. An overview of the simulation and specific exercises suitable for an undergraduate class are discussed.

Perkins, Thomas T.; Malley, Christopher V.; Dubson, Michael A.; Perkins, Katherine K.

2010-08-01

162

Stratospheric aerosol optical depths, 1850-1990  

Microsoft Academic Search

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

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

1993-01-01

163

Two-photon fluorescence excitation in continuous-wave infrared optical tweezers  

NASA Astrophysics Data System (ADS)

We report the observation of two-photon fluorescence excitation in a continuous-wave (cw) single-beam gradient force optical trap and demonstrate its use as an in situ probe to study the physiological state of an optically confined sample. In particular, a cw Nd:YAG (1064-nm) laser is used simultaneously to confine, and excite visible fluorescence from submicrometer regions of, cell specimens. Two-photon fluorescence emission spectra are presented for motile human sperm cells and immotile Chinese hamster ovary cells that have been labeled with nucleic acid (Propidium Iodide) and pH-sensitive (Snarf) fluorescent probes. The resulting spectra are correlated to light-induced changes in the physiological state experienced by the trapped cells. This spectral technique should prove extremely useful for monitoring cellular activity and the effects of confinement by optical tweezers.

Liu, Y.; Sonek, G. J.; Berns, M. W.; Konig, K.; Tromberg, B. J.

1995-11-01

164

Amplitude-phase modulation for reducing the 0th order beam spot in holographic optical tweezers  

NASA Astrophysics Data System (ADS)

The 0-th order diffraction light in an intensity pattern produced by a hologram disturbs optical manipulation of micro-objects in dynamic holographic optical tweezers (HOT). The purpose of this study is to investigate polarization characteristics of amplitude and phase modulations in the HOT to reduce the influence of the 0-th order beam spot. Numerical simulations are conducted using a Jones matrix of the system, whose the validity is experimentally confirmed. The optimum conditions to reduce the influence of the 0-th order beam spot can be estimated on the bases of the numerical results and its effectiveness in performance of the HOT system is experimentally demonstrated by the optical manipulation of polystyrene particles.

Iwai, Toshiaki; Yamamoto, Johtaro; Doi, Yuki

2010-08-01

165

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

166

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

NASA Astrophysics Data System (ADS)

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

Tanaka, Yoshio; Tsutsui, Shogo; Kitajima, Hiroyuki

2013-04-01

167

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.

McCauley, Micah J.; Williams, Mark C.

2009-01-01

168

Auto- and cross-power spectral analysis of dual trap optical tweezer experiments using Bayesian inference  

NASA Astrophysics Data System (ADS)

The thermal fluctuations of micron-sized beads in dual trap optical tweezer experiments contain complete dynamic information about the viscoelastic properties of the embedding medium and--if present--macromolecular constructs connecting the two beads. To quantitatively interpret the spectral properties of the measured signals, a detailed understanding of the instrumental characteristics is required. To this end, we present a theoretical description of the signal processing in a typical dual trap optical tweezer experiment accounting for polarization crosstalk and instrumental noise and discuss the effect of finite statistics. To infer the unknown parameters from experimental data, a maximum likelihood method based on the statistical properties of the stochastic signals is derived. In a first step, the method can be used for calibration purposes: We propose a scheme involving three consecutive measurements (both traps empty, first one occupied and second empty, and vice versa), by which all instrumental and physical parameters of the setup are determined. We test our approach for a simple model system, namely a pair of unconnected, but hydrodynamically interacting spheres. The comparison to theoretical predictions based on instantaneous as well as retarded hydrodynamics emphasizes the importance of hydrodynamic retardation effects due to vorticity diffusion in the fluid. For more complex experimental scenarios, where macromolecular constructs are tethered between the two beads, the same maximum likelihood method in conjunction with dynamic deconvolution theory will in a second step allow one to determine the viscoelastic properties of the tethered element connecting the two beads.

von Hansen, Yann; Mehlich, Alexander; Pelz, Benjamin; Rief, Matthias; Netz, Roland R.

2012-09-01

169

Light-matter Interactions: From the Photophysics of Organic Semiconductors to High Spatial Resolution Optical Tweezer-controlled Nanoprobes  

NASA Astrophysics Data System (ADS)

Studies of light-matter interactions in organic semiconductors and in optical tweezer trapping of nanoparticles are presented. In the research related to organic semiconductor materials, a variety of novel materials and their composites have been characterized, and physical mechanisms behind their optoelectronic properties have been established. Three novel functionalized hexacene derivatives were deemed sufficiently stable to enable characterization of these materials in devices. From dark current and photocurrent measurements of the hexacene thin-films, it was determined that all three derivatives are photoconductive in the near-infrared, and space charge limited mobility values were obtained. In addition, physical mechanisms behind charge transfer, charge carrier photogeneration, and charge transport in small-molecule donor/acceptor composite films have been systematically studied. In these studies, it was determined that the charge transfer from the donor to the acceptor molecule can result in either an emissive charge transfer exciton (exciplex) or a non-emissive charge transfer exciton formation, depending on the energy difference between LUMO of the donor and the acceptor. However, the most dramatic trends in photoluminescent and photoconductive properties of the donor/acceptor composites were correlated with the separation between the donor and acceptor molecules at the donor/acceptor interface. In particular, composite films with larger separations exhibited electric field-assisted charge transfer exciton dissociation, which contributed to nanosecond time-scale photocurrents under a 500 ps pulsed photoexciation. Large donor/acceptor separation also resulted in reduced charge carrier recombination, which led to a factor of 5-10 increase in continuous wave photocurrents in certain donor/acceptor composites, as compared to those in pristine donor films. In the optical tweezer based studies, work towards the development of high spatial resolution optical tweezer controlled nanoprobes is presented. In particular, the possibility of exploiting the optical resonance of a particle to increase the optical tweezer forces acting on it within the trap has been investigated. Such an increase in the force would improve the potential spatial resolution of an optical tweezer controlled probe. Experimental results and numerical simulations on micron sized resonant dielectric particles showed a small increase in the optical forces that confine such particles within the trap, when tweezer trapping is conducted at wavelengths on the red-side of the optical resonance. Preliminary work on optical tweezer controlled ion/pH sensitive probes and on surface charge measurements is also reported.

Kendrick, Mark J.

170

Effects of viscosity on sperm motility studied with optical tweezers.  

PubMed

The purpose of this study is to analyze human sperm motility and energetics in media with different viscosities. Multiple experiments were performed to collect motility parameters using customized computer tracking software that measures the curvilinear velocity (VCL) and the minimum laser power (Pesc) necessary to hold an individual sperm in an optical trap. The Pesc was measured by using a 1064 nm Nd:YVO(4) continuous wave laser that optically traps motile sperm at a power of 450 mW in the focused trap spot. The VCL was measured frame by frame before trapping. In order to study sperm energetics under different viscous conditions sperm were labeled with the fluorescent dye DiOC(6)(3) to measure membrane potentials of mitochondria in the sperm midpiece. Fluorescence intensity was measured before and during trapping. The results demonstrate a decrease in VCL but an increase in Pesc with increasing viscosity. Fluorescent intensity is the same regardless of the viscosity level indicating no change in sperm energetics. The results suggest that, under the conditions tested, viscosity physically affects the mechanical properties of sperm motility rather than the chemical pathways associated with energetics. PMID:22463031

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

2012-02-01

171

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

NASA Astrophysics Data System (ADS)

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

Ingle, Ninad; Mohanty, Samarendra K.

2011-02-01

172

Dynamics analysis and closed-loop control of biological cells in transportation using robotic manipulation system with optical tweezers  

Microsoft Academic Search

Increasing demands for both accuracy and productivity in cell manipulation highlight the need for automated process that integrates robotics and micro manipulation technologies. Optical tweezers, which use low power laser beams to trap and manipulate particles at micro\\/nano scale, have provided a revolutionary solution to manipulate biological objects in a noninvasive way. In this paper, we propose to use a

Songyu Hu; Dong Sun; Gang Feng

2010-01-01

173

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

PubMed Central

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

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

2006-01-01

174

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

175

Direct manipulation of malaria parasites with optical tweezers reveals distinct functions of Plasmodium surface proteins.  

PubMed

Plasmodium sporozoite motility is essential for establishing malaria infections. It depends on initial adhesion to a substrate as well as the continuous turnover of discrete adhesion sites. Adhesion and motility are mediated by a dynamic actin cytoskeleton and surface proteins. The mode of adhesion formation and the integration of adhesion forces into fast and continuous forward locomotion remain largely unknown. Here, we use optical tweezers to directly trap individual parasites and probe adhesion formation. We find that sporozoites lacking the surface proteins TRAP and S6 display distinct defects in initial adhesion; trap(-) sporozoites adhere preferentially with their front end, while s6(-) sporozoites show no such preference. The cohesive strength of the initial adhesion site is differently affected by actin filament depolymerization at distinct adhesion sites along the parasite for trap(-) and s6(-) sporozoites. These spatial differences between TRAP and S6 in their functional interaction with actin filaments show that these proteins have nonredundant roles during adhesion and motility. We suggest that complex protein-protein interactions and signaling events govern the regulation of parasite gliding at different sites along the parasite. Investigating how these events are coordinated will be essential for our understanding of sporozoite gliding motility, which is crucial for malaria infection. Laser tweezers will be a valuable part of the toolset. PMID:22568891

Hegge, Stephan; Uhrig, Kai; Streichfuss, Martin; Kynast-Wolf, Gisela; Matuschewski, Kai; Spatz, Joachim P; Frischknecht, Friedrich

2012-06-26

176

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.

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

1998-01-01

177

Analysis of RBC damage using laser tweezers Raman spectroscopy (LTRS) during femtosecond laser optical trapping  

NASA Astrophysics Data System (ADS)

We monitored cell viability and damage under femtosecond laser irradiation using aser weezers Raman pectroscopy (LTRS) which is becoming a powerful tool for the analysis of biological materials. Femtosecond lasers are more frequently used as a light source for optical tweezers since they enable nonlinear optical phenomena such as two-photon absorption or second harmonic generation trapping. Femtosecond laser optical trapping similar to thee CW laser optical trapping except that optical damage can be easily induced due to extremely high peak power of femtosecond pulses. We monitored the Raman signal changes as a marker for optical damage. We used red blood cell (RBC) as a target sample and first used the CW laser beams to trap the RBC from the bottom of the chamber. After the trapped RBC is moved to a desired depth, we switched the laser mode to mode-locked mode and monitored the Raman signals as a function of the laser irradiation time. It was observed that the Raman shift at 1543 cm -1 may be a good marker for optical damage both for CW and femtosecond laser trapping.

Ju, Sung-bin; Pyo, Jin-woo; Jang, Jae-young; Lee, Seungduk; Kim, Beop-Min

2008-03-01

178

Application of vertical-cavity laser-based optical tweezers for particle manipulation in microfluidic channels  

NASA Astrophysics Data System (ADS)

The combination of microfluidics and optical manipulation offers new possibilities for particle handling and sorting on a single-cell level in the field of biophotonics. We present particle manipulation in microfluidics based on vertical-cavity surface-emitting lasers (VCSELs) which constitute a new low-cost, high beam quality nanostructured laser source for optical trapping, additionally allowing easy formation of small-sized, two-dimensional laser arrays. Single devices as well as densely packed linear VCSEL arrays with a pitch of only 24 ?m are fabricated. Microfluidic channels with widths of 50 to 150 ?m forming T- and Y-junctions are made of PDMS using common soft-lithography. With a single laser, selected polystyrene particles are trapped in the inlet channel and transferred to the desired outlet branch by moving the chip relatively to the optical trap. In a second approach, a tilted, linear laser array is introduced into the setup, effectively forming an optical lattice. While passing the continuously operating tweezers array, particles are not fully trapped, but deflected by each single laser beam. Therefore, non-mechanical particle separation in microfluidics is achieved. We also show the route to ultra-miniaturization of the system avoiding any external optics. Simulations of an integrated particle deflection and sorting scheme as well as first fabrication steps for the integrated optical trap are presented.

Kroner, Andrea; Schneck, Carolin; Rinaldi, Fernando; Rösch, Rudolf; Michalzik, Rainer

2008-05-01

179

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

180

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

181

Double nanohole optical tweezers visualize protein p53 suppressing unzipping of single DNA-hairpins.  

PubMed

Here we report on the use of double-nanohole (DNH) optical tweezers as a label-free and free-solution single-molecule probe for protein-DNA interactions. Using this approach, we demonstrate the unzipping of individual 10 base pair DNA-hairpins, and quantify how tumor suppressor p53 protein delays the unzipping. From the Arrhenius behavior, we find the energy barrier to unzipping introduced by p53 to be 2 × 10(-20) J, whereas cys135ser mutant p53 does not show suppression of unzipping, which gives clues to its functional inability to suppress tumor growth. This transformative approach to single molecule analysis allows for ultra-sensitive detection and quantification of protein-DNA interactions to revolutionize the fight against genetic diseases. PMID:24940547

Kotnala, Abhay; Gordon, Reuven

2014-06-01

182

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

PubMed

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

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

2008-08-18

183

The use of optical tweezers to study sperm competition and motility in primates.  

PubMed

Optical trapping is a non-invasive biophysical tool which has been widely applied to study physiological and biomechanical properties of cells. Using laser 'tweezers' in combination with custom-designed computer tracking algorithms, the swimming speeds and the relative swimming forces of individual sperm can be measured in real time. This combination of physical and engineering tools has been used to examine the evolutionary effect of sperm competition in primates. The results demonstrate a correlation between mating type and sperm motility: sperm from polygamous (multi-partner) primate species swim faster and with greater force than sperm from polygynous (single partner) primate species. In addition, sperm swimming force linearly increases with swimming speed for each species, yet the regression relating the two parameters is species specific. These results demonstrate the feasibility of using these tools to study rapidly moving (microm s(-1)) biological cells. PMID:17650470

Nascimento, Jaclyn M; Shi, Linda Z; Meyers, Stuart; Gagneux, Pascal; Loskutoff, Naida M; Botvinick, Elliot L; Berns, Michael W

2008-03-01

184

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

PubMed

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

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

2007-09-01

185

Characterizing the rotation of non symmetric objects in an optical tweezer  

NASA Astrophysics Data System (ADS)

We present an optical tweezer based study of the rotation of microscopic objects with shape asymmetry. Thermal fluctuations and rotations are simultaneously monitored through laser back scattering. The rotation causes a modulation in intensity of the back scattered light incident on a quadrant photo detector. The resulting power spectrum is a modified Lorentzian with additional peaks located at the fundamental rotational frequency of the object and at the integer harmonics. The manifestation of these peaks reveals that the rotations are periodic but with varying angular velocity. We model our experimental results to illustrate the hydrodynamic interplay between the rotor and the surrounding medium that results in the time dependence of the angular speed of the former. Further, we demonstrate the use of video microscopy for characterization of low reflectivity rotors, such as biological cells. We propose through these studies that an analysis of these rotations can provide insights into the role of hydrodynamics at micron levels.

Yogesha; Bhattacharya, Sarbari; Ananthamurthy, Sharath

2012-05-01

186

Double nanohole optical tweezers visualize protein p53 suppressing unzipping of single DNA-hairpins  

PubMed Central

Here we report on the use of double-nanohole (DNH) optical tweezers as a label-free and free-solution single-molecule probe for protein–DNA interactions. Using this approach, we demonstrate the unzipping of individual 10 base pair DNA-hairpins, and quantify how tumor suppressor p53 protein delays the unzipping. From the Arrhenius behavior, we find the energy barrier to unzipping introduced by p53 to be 2 × 10?20 J, whereas cys135ser mutant p53 does not show suppression of unzipping, which gives clues to its functional inability to suppress tumor growth. This transformative approach to single molecule analysis allows for ultra-sensitive detection and quantification of protein–DNA interactions to revolutionize the fight against genetic diseases.

Kotnala, Abhay; Gordon, Reuven

2014-01-01

187

Measurement of the electrostatic interaction between polyelectrolyte brush surfaces by optical tweezers.  

PubMed

We demonstrated an optical tweezers method to measure the electrostatic interaction between the strong polyelectrolyte brushes, poly(2-(methacryloyloxy)ethyltrimethylammonium chloride) (PMTAC), grafted on silica particles in aqueous media. The weak electrostatic interaction was successfully detected with a resolution of less than 0.1 ?N m(-1). The apparent Debye length, including the charge distribution in the polymer brush and the surface potential, decreased as the salt concentration in the medium increased. The experimentally obtained surface charge density was much smaller than that estimated from the amount of polyelectrolyte on the surface. Furthermore, the dissociation of ionic groups was enhanced by decreasing the grafting density of the polyelectrolyte brush. The results suggest that the majority of chloride counterions was immobilized in the dense polyelectrolyte brush layer to neutralize the high charge density. PMID:24325298

Murakami, Daiki; Takenaka, Ai; Kobayashi, Motoyasu; Jinnai, Hiroshi; Takahara, Atsushi

2013-12-31

188

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

PubMed

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 microrod. The technique is also able to resolve the translational and rotational Brownian motion components of the microrod in an unperturbed trap and can be very useful in measuring translation-rotation coupling of micro-objects induced by hydrodynamic interactions. PMID:24876042

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

2014-06-01

189

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

190

Dual-trap technique for reduction of low-frequency noise in force measuring optical tweezers.  

PubMed

High-resolution long-time force measurements by optical tweezers are often limited by low-frequency (1/f) noise. A dual-trap technique is presented that can reduce such noise in the force signal. It incorporates a second trap (a reference trap) that probes the noise in the system and it is based upon the assumption that the low-frequency parts of the noise from the two traps are correlated. A subtraction of the low-frequency signal from the reference trap from the signal from the force measuring trap will therefore yield a net signal that is significantly less influenced by noise. It is shown that this dual-trap technique can reduce the noise in the force signal up to 60% depending on detection bandwidth. PMID:17228388

Klein, Markus; Andersson, Magnus; Axner, Ove; Fällman, Erik

2007-01-20

191

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.

192

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

NASA Astrophysics Data System (ADS)

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 pNpp) 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.; Phillips, D. B.; Barnes, A. C.; Drinkwater, B. W.

2014-04-01

193

Development of microfluidic system and optical tweezers for electrophysiological investigations of an individual cell  

NASA Astrophysics Data System (ADS)

We present a new approach of combining Lab-on-a-chip technologies with optical manipulation technique for accurate investigations in the field of cell biology. A general concept was to develop and combine different methods to perform advanced electrophysiological investigations of an individual living cell under optimal control of the surrounding environment. The conventional patch clamp technique was customized by modifying the open system with a gas-tight multifunctional microfluidics system and optical trapping technique (optical tweezers). The system offers possibilities to measure the electrical signaling and activity of the neuron under optimum conditions of hypoxia and anoxia while the oxygenation state is controlled optically by means of a spectroscopic technique. A cellbased microfluidics system with an integrated patch clamp pipette was developed successfully. Selectively, an individual neuron is manipulated within the microchannels of the microfluidic system under a sufficient control of the environment. Experiments were performed to manipulate single yeast cell and red blood cell (RBC) optically through the microfluidics system toward an integrated patch clamp pipette. An absorption spectrum of a single RCB was recorded which showed that laser light did not impinge on the spectroscopic spectrum of light. This is promising for further development of a complete lab-on-a-chip system for patch clamp measurements.

Alrifaiy, A.; Bitaraf, N.; Lindahl, O.; Ramser, K.

2010-08-01

194

Stratospheric aerosol optical depths, 1850-1990  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

195

Stratospheric aerosol optical depths, 1850-1990  

NASA Astrophysics Data System (ADS)

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

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

1993-12-01

196

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.

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

2008-01-01

197

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

NASA Astrophysics Data System (ADS)

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

Shivalingaiah, Shivaranjani; Chhajed, Suyash; Mohanty, Samarendra

2011-03-01

198

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

199

Power spectrum analysis for optical tweezers. II: Laser wavelength dependence of parasitic filtering, and how to achieve high bandwidth  

NASA Astrophysics Data System (ADS)

In a typical optical tweezers detection system, the position of a trapped object is determined from laser light impinging on a quadrant photodiode. When the laser is infrared and the photodiode is of silicon, they can act together as an unintended low-pass filter. This parasitic effect is due to the high transparency of silicon to near-infrared light. A simple model that accounts for this phenomenon [Berg-Sørensen et al., J. Appl. Phys. 93, 3167 (2003)] is here solved for frequencies up to 100 kHz and for laser wavelengths between 750 and 1064 nm. The solution is applied to experimental data in the same range, and is demonstrated to give this detection system of optical tweezers a bandwidth, accuracy, and precision that are limited only by the data acquisition board's bandwidth and bandpass ripples, here 96.7 kHz and 0.005 dB, respectively.

Berg-Sørensen, Kirstine; Peterman, Erwin J. G.; Weber, Tom; Schmidt, Christoph F.; Flyvbjerg, Henrik

2006-06-01

200

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

Microsoft Academic Search

Lipopolysaccharide (LPS) is one of the cell wall components of Gram-positive bacteria recognized by and interacted with receptor proteins such as CD14 on macrophage cells. Such a process plays an important role in our innate immune system. In this paper, we report the application of optical tweezers (lambda = 1064nm Gaussian beam focused by a water-immersed objective lens with N.A.

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

2006-01-01

201

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

202

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

203

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

NSDL National Science Digital Library

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

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

2009-10-02

204

Biomechanics and dynamics of red blood cells probed by optical tweezers and digital holographic microscopy  

NASA Astrophysics Data System (ADS)

Red blood cells (RBC), with their unique viscoelastic properties, can undergo large deformations during interaction with fluid flow and migration through narrow capillaries. Both local and overall viscoelastic property is important for cellular function and change in these properties indicate diseased condition. Though biomechanics of the cells have been studied using variety of physical techniques (AFM, optically-trapped anchoring beads and microcapilary aspiration) in force regime > 10pN, little is studied at low force regime <1pN. Such perturbations are not only hard to exercise on the cell membrane, but quantification of such deformations becomes extremely difficult. By application of low power optical tweezers directly on cell membrane, we could locally perturb discotic RBC along the axial direction, which was monitored dynamically by digital holographic microscopy-a real time, wide-field imaging method having nm axial resolution. The viscoelastic property of the RBC at low force regime was found to be significantly different from that of high-force regime. The results were found to be in good agreement with the simulation results obtained using finite element model of the axially-stretched RBC. The simulations and results of viscoelestic measurements will be presented.

Cardenas, Nelson; Thomas, Pattrick; Yu, Lingfeng; Mohanty, Samarendra

2011-03-01

205

A comparative study of living cell micromechanical properties by oscillatory optical tweezers.  

PubMed

Micromechanical properties of biological cells are crucial for cells functions. Despite extensive study by a variety of approaches, an understanding of the subject remains elusive. We conducted a comparative study of the micromechanical properties of cultured alveolar epithelial cells with an oscillatory optical tweezer-based cytorheometer. In this study, 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 1.5microm 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; however, the differences in the magnitudes of the moduli from the two measurements are statistically significant. PMID:18545572

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

2008-06-01

206

Combined optical tweezers and laser dissector for controlled ablation of functional connections in neural networks  

NASA Astrophysics Data System (ADS)

Regeneration of functional connectivity within a neural network after different degrees of lesion is of utmost clinical importance. To test pharmacological approaches aimed at recovering from a total or partial damage of neuronal connections within a circuit, it is necessary to develop a precise method for controlled ablation of neuronal processes. We combined a UV laser microdissector to ablate neural processes in vitro at single neuron and neural network level with infrared holographic optical tweezers to carry out force spectroscopy measurements. Simultaneous force spectroscopy, down to the sub-pico-Newton range, was performed during laser dissection to quantify the tension release in a partially ablated neurite. Therefore, we could control and measure the damage inflicted to an individual neuronal process. To characterize the effect of the inflicted injury on network level, changes in activity of neural subpopulations were monitored with subcellular resolution and overall network activity with high temporal resolution by concurrent calcium imaging and microelectrode array recording. Neuronal connections have been sequentially ablated and the correlated changes in network activity traced and mapped. With this unique combination of electrophysiological and optical tools, neural activity can be studied and quantified in response to controlled injury at the subcellular, cellular, and network level.

Difato, Francesco; Dal Maschio, Marco; Marconi, Emanuele; Ronzitti, Giuseppe; Maccione, Alessandro; Fellin, Tommasso; Berdondini, Luca; Chieregatti, Evelina; Benfenati, Fabio; Blau, Axel

2011-05-01

207

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.

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

2005-01-01

208

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers  

PubMed Central

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

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

2011-01-01

209

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

NASA Astrophysics Data System (ADS)

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

Gemmen, Gregory J.

2005-03-01

210

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

NASA Astrophysics Data System (ADS)

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

Millin, Rachel

2005-03-01

211

Cell viability in optical tweezers: high power red laser diode versus Nd:YAG laser.  

PubMed

Viability of cultivated Chinese hamster ovary cells in optical tweezers was measured after exposure to various light doses of red high power laser diodes (lambda = 670-680 nm) and a Nd:yttrium-aluminum-garnet laser (lambda = 1064 nm). When using a radiant exposure of 2.4 GJ/cm2, a reduction of colony formation up to a factor 2 (670-680 nm) or 1.6 (1064 nm) as well as a delay of cell growth were detected in comparison with nonirradiated controls. In contrast, no cell damage was found at an exposure of 340 MJ/cm2 for both wavelengths, and virtually no lethal damage at 1 GJ/cm2 applied at 1064 nm. Cell viabilities were correlated with fluorescence excitation spectra and with literature data of wavelength dependent cloning efficiencies. Fluorescence excitation maxima of the coenzymes NAD(P)H and flavins were detected at 365 and 450 nm, respectively. This is half of the wavelengths of the maxima of cell inactivation, suggesting that two-photon absorption by these coenzymes may contribute to cellular damage. Two-photon excitation of NAD(P)H and flavins may also affect cell viability after exposure to 670-680 nm, whereas one-photon excitation of water molecules seems to limit cell viability at 1064 nm. PMID:10938764

Schneckenburger, H; Hendinger, A; Sailer, R; Gschwend, M H; Strauss, W S; Bauer, M; Schütze, K

2000-01-01

212

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

2006-03-01

213

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

NASA Astrophysics Data System (ADS)

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

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

2012-10-01

214

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

215

Optical tweezers based measurement of PLGA-NP interaction with prostate cancer cells  

NASA Astrophysics Data System (ADS)

In order to quantify the binding capacities of polymeric, biodegradable and biocompatible poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NPs), conjugated with either R11 peptides or Folic Acid, the strength by detach from prostate cancer cells (PCCs) was measured via optical tweezers based measurements. Specific nanoparticle drug delivery eliminates the previously used diffuse, full-body application of potent cancer drugs by localizing drug delivery to malignant cells. Precise monitoring of NP position in the trap near the PCC membrane using a fluorescence imaging based method enabled calibration of the trap stiffness and subsequent force measurements. By defining the force with which the many diverse conjugates and coatings of different types of NPs bind the vast array of cancer cell types, chemotherapeutic drugs can be delivered in a specific manner with the optimal particle and corresponding conjugates. Further, and most significantly, the rupture force measurements will reveal whether or not targeted nanoparticles can overcome the force of blood attempting to pull the particle from designated cells. Our preliminary study revealed that the binding between PLGA-NPs and prostate cancer cells is enhanced by coating with folic acid or R11 peptides. These conjugates increase the force required to detach the particle thus allowing particles to overcome drag force of the blood in prostate capillary systems.

Blesener, Thea; Mondal, Argha; Menon, Jyothi U.; Nguyen, Kytai T.; Mohanty, Samarendra

2013-02-01

216

Microrheology of complex fluids using optical tweezers: a comparison with macrorheological measurements  

NASA Astrophysics Data System (ADS)

The increasing interest in the mechanical properties of complex systems at mesoscopic scale has recently fueled the development of new experimental techniques, collectively indicated as microrheology. Unlike bulk-based approaches (macrorheology), these new techniques make use of micrometric probes (usually microspheres) which explore the mechanical properties of the surrounding medium. In this paper we discuss the basic idea of microrheology and we will focus on one specific technique based on optical tweezers (OT). The discussion starts from Newtonian fluids to tackle the more general case of complex fluids, also showing results of these techniques on solutions of a relevant biomolecule: hyaluronic acid (HA). In particular, we study the viscoelastic properties of low molecular weight HA (155 kDa) at low ionic strength over an extended frequency range (0.1-1000 Hz) and in a wide range of concentrations (0.01-20 mg ml-1), which include both the dilute and semidilute regime. In the concentration range here explored and within the test frequencies covered by our techniques, samples prevalently exhibit a viscous behavior, the elastic contribution becoming significant at the highest concentrations. By comparing OT outcomes to those obtained by a traditional rheometer, we found that they were in good agreement in the overlapping frequency range of the two techniques, thus confirming the reliability of the microrheological approach.

Pesce, G.; DeLuca, A. C.; Rusciano, G.; Netti, P. A.; Fusco, S.; Sasso, A.

2009-03-01

217

Probing Protein Folding Kinetics with High-resolution, Stabilized Optical Tweezers  

NASA Astrophysics Data System (ADS)

Single-molecule techniques provide a powerful means of exploring molecular transitions such as the unfolding and refolding of a protein. However, the quantification of bi-directional transitions and near-equilibrium phenomena poses unique challenges, and is often limited by the detection resolution and long-term stability of the instrument. We have developed unique optical tweezers methods that address these problems, including an interference-based method for high-resolution 3D bead tracking (˜1 nm laterally, ˜0.3 nm vertically, at > 100 Hz), and a continuous autofocus system that stabilizes the trap height to within 1-2 nm longterm [1,2]. We have used our instruments to quantify the force-dependent unfolding and refolding kinetics of single protein domains (e.g. spectrin in collaboration with E. Evans). These single-molecule studies are presented, together with the accompanying probabilistic analysis that we have developed. References: 1. W.P. Wong, V. Heinrich, E. Evans, Mat. Res. Soc. Symp. Proc., 790, P5.1-P5.10 (2004). 2. V. Heinrich, W.P. Wong, K. Halvorsen, E. Evans, Langmuir, 24, 1194-1203 (2008).

Wong, Wesley; Halvorsen, Ken

2009-03-01

218

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

NASA Astrophysics Data System (ADS)

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

Wong, Wesley

2010-03-01

219

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

220

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

PubMed Central

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

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

2010-01-01

221

Combined optical tweezers/ion beam technique to tune colloidal masks for nanolithography.  

PubMed

A method is presented to control the in-plane ordering, size, and interparticle distance of nanoparticles fabricated by evaporation through a mask of colloidal particles. The use of optical tweezers combined with critical point drying gives single-particle position control over the colloidal particles in the mask. This extends the geometry of the colloidal masks from (self-organized) hexagonal to any desired symmetry and spacing. Control over the mask's hole size is achieved by MeV ion irradiation, which causes the colloids to expand in the in-plane direction, thus shrinking the size of the holes. After modification of the mask, evaporation at different angles with respect to the mask gives additional control over structure and interparticle distance, allowing nanoparticles of different materials to be deposited next to each other. We demonstrate large arrays of metal nanoparticles with dimensions in the 15-30 nm range, with control over the interparticle distance and in-plane ordering. PMID:15943464

Vossen, Dirk L J; Fific, Damir; Penninkhof, Joan; van Dillen, Teun; Polman, Albert; van Blaaderen, Alfons

2005-06-01

222

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

PubMed Central

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

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

2012-01-01

223

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

224

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

2011-04-01

225

Synthesis of information on aerosol optical properties  

Microsoft Academic Search

In a previous study (Liu et al., 2005) obtained are global scale estimates of aerosol optical depth at 0.55 ?m based on spatial and temporal variation patterns from models and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study an approach is developed to obtain information on global distribution of the single scattering albedo (?0), the

Hongqing Liu; R. T. Pinker; M. Chin; B. Holben; L. Remer

2008-01-01

226

Synthesis of information on aerosol optical properties  

Microsoft Academic Search

In a previous study (Liu et al., 2005) obtained are global scale estimates of aerosol optical depth at 0.55 mum based on spatial and temporal variation patterns from models and satellite observations, regulated by the Aerosol Robotic Network (AERONET) measurements. In this study an approach is developed to obtain information on global distribution of the single scattering albedo (omega 0),

Hongqing Liu; R. T. Pinker; M. Chin; B. Holben; L. Remer

2008-01-01

227

Controlling and characterizing the coagulation of liquid aerosol droplets  

Microsoft Academic Search

We demonstrate that optical tweezers can be used to control and characterize the coagulation and mixing state of aerosols. Liquid aerosol droplets of 2-14 mum in diameter are optically trapped and characterized by spontaneous and stimulated Raman scatterings, which together provide a unique signature of droplet size and composition. From the conventional bright field image, the size of the trapped

Jariya Buajarern; Laura Mitchem; Andrew D. Ward; N. Hendrik Nahler; David McGloin; Jonathan P. Reid

2006-01-01

228

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

229

Physiological monitoring of optically trapped cells: assessing the effects of confinement by 1064-nm laser tweezers using microfluorometry.  

PubMed Central

We report the results of microfluorometric measurements of physiological changes in optically trapped immotile Chinese hamster ovary cells (CHOs) and motile human sperm cells under continuous-wave (CW) and pulsed-mode trapping conditions at 1064 nm. The fluorescence spectra derived from the exogenous fluorescent probes laurdan, acridine orange, propidium iodide, and Snarf are used to assess the effects of optical confinement with respect to temperature, DNA structure, cell viability, and intracellular pH, respectively. In the latter three cases, fluorescence is excited via a two-photon process, using a CW laser trap as the fluorescence excitation source. An average temperature increase of < 0.1 +/- 0.30 degrees C/100 mW is measured for cells when held stationary with CW optical tweezers at powers of up to 400 mW. The same trapping conditions do not appear to alter DNA structure or cellular pH. In contrast, a pulsed 1064-nm laser trap (100-ns pulses at 40 microJ/pulse and average power of 40 mW) produced significant fluorescence spectral alterations in acridine orange, perhaps because of thermally induced DNA structural changes or laser-induced multiphoton processes. The techniques and results presented herein demonstrate the ability to perform in situ monitoring of cellular physiology during CW and pulsed laser trapping, and should prove useful in studying mechanisms by which optical tweezers and microbeams perturb metabolic function and cellular viability.

Liu, Y; Sonek, G J; Berns, M W; Tromberg, B J

1996-01-01

230

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

PubMed Central

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

Schwingel, Melanie; Bastmeyer, Martin

2013-01-01

231

Aerosol Optical Properties Observed during CHAPS  

NASA Astrophysics Data System (ADS)

During the CHAPS, the DOE Gulfstream-1 aircraft was used to make in-situ measurements of aerosol optical properties. The flight pattern was designed to allow for measurements below cloud, within the cloud layer, and above the clouds in the vicinity of Oklahoma City. Two different inlets were used on the G-1: an isokinetic inlet for sampling dry aerosols smaller than approximately 2 ?m in diameter, and a Counterflow Virtual Impactor (CVI) that excluded unactivated aerosols, but which allows cloud droplets to enter. A suite of paired instruments, including a nephelometer, Particle Soot Absorption Photometer (PSAP), and Aerosol Mass Spectrometer (AMS), was used to measure the aerosol optical properties from both sampling streams. Below the clouds, the single-scattering albedo measured inside the Oklahoma City plume was generally smaller than that observed outside of the plume. Within the cloud layer, but far from the clouds, there is little difference in the aerosol scattering measured inside and outside of the plume. These observations indicate that the vertical transport by the shallow clouds is very localized. Both aerosol extensive and intensive properties are discussed. For example, the total aerosol scattering and the mass-scattering efficiency measured inside the clouds was slightly larger for clouds that have roots within the Oklahoma City plume. Using data from the AMS in conjunction with the CVI inlet reveals that these in-cloud aerosols also have a relatively large amount of nitrate. Possible explanations for this increase nitrate will be discussed.

Berg, L. K.; Berkowitz, C. M.; Ogren, J. A.; Andrews, E.; Hubbe, J. M.; Lee, Y.; Yu, X.

2008-12-01

232

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

PubMed

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

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

2006-07-20

233

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

National Technical Information Service (NTIS)

Optical trap arrays are being developed at the NASA Glenn Research Center for holding, manipulating, and optically interrogating arrays of nanotube sensors. The trap arrays, for example, might be used to arrange arrays of chemical sensors for insertion on...

S. Y. Wrbanek A. J. Decker

2005-01-01

234

Mechanical characterization of human red blood cells under different osmotic conditions by robotic manipulation with optical tweezers.  

PubMed

The physiological functions of human red blood cells (RBCs) play a crucial role to human health and are greatly influenced by their mechanical properties. Any alteration of the cell mechanics may cause human diseases. The osmotic condition is an important factor to the physiological environment, but its effect on RBCs has been little studied. To investigate this effect, robotic manipulation technology with optical tweezers is utilized in this paper to characterize the mechanical properties of RBCs in different osmotic conditions. The effectiveness of this technology is demonstrated first in the manipulation of microbeads. Then the optical tweezers are used to stretch RBCs to acquire the force-deformation relationships. To extract cell properties from the experimental data, a mechanical model is developed for RBCs in hypotonic conditions by extending our previous work , and the finite element model is utilized for RBCs in isotonic and hypertonic conditions. Through comparing the modeling results to the experimental data, the shear moduli of RBCs in different osmotic solutions are characterized, which shows that the cell stiffness increases with elevated osmolality. Furthermore, the property variation and potential biomedical significance of this study are discussed. In conclusion, this study indicates that the osmotic stress has a significant effect on the cell properties of human RBCs, which may provide insight into the pathology analysis and therapy of some human diseases. PMID:20176536

Tan, Youhua; Sun, Dong; Wang, Jinzhi; Huang, Wenhao

2010-07-01

235

Optical manipulation and characterisation of aerosol droplets  

Microsoft Academic Search

Aerosol droplets are trapped and manipulated with a single-beam gradient-force optical trap for timescales of hours. By coupling the optical trap with cavity enhanced Raman scattering, the size of the trapped droplet can be determined with nanometre accuracy and high time resolution. This allows the evolution in droplet size and composition to be monitored during the growth or evaporation of

Jonathan P. Reid; Laura Mitchem; Rebecca J. Hopkins; Andrew D. Ward

2005-01-01

236

Aerosol optical depth measuring network - project description  

NASA Astrophysics Data System (ADS)

The Finnish Meteorological Institute (FMI), in collaboration with Servicio Meteorológico Nacional (SMN), Argentina, is constructing a network for aerosol optical depth (AOD) measurements. Measurements are to be started in the summer 2003 with three sunphotometers, model PFR, Davos. One of them will be sited in Marambio (64°S), Antarctica, and the rest two in the Observatory of Jokioinen (61°N) and Sodankylä GAW station (67°N), Finland. Each instrument consists of a precision filter radiometer and a suntracker. Due to the harsh climate conditions special solutions had to be introduced to keep the instrument warm and free from snow. Aerosol optical depth measured at Pallas-Sodankylä GAW station can be compared with estimated aerosol extinction, which is calculated from ground base aerosol scattering and absorption coefficient measurements.

Aaltonen, A.; Koskela, K.; Lihavainen, L.

2003-04-01

237

Dye lasing in optically manipulated liquid aerosols.  

PubMed

We report lasing in airborne, rhodamine B-doped glycerol-water droplets with diameters ranging between 7.7 and 11.0 ?m, which were localized using optical tweezers. While being trapped near the focal point of an infrared laser, the droplets were pumped with a Q-switched green laser. Our experiments revealed nonlinear dependence of the intensity of the droplet whispering gallery modes (WGMs) on the pump laser fluence, indicating dye lasing. The average wavelength of the lasing WGMs could be tuned between 600 and 630 nm by changing the droplet size. These results may lead to new ways of probing airborne particles, exploiting the high sensitivity of stimulated emission to small perturbations in the droplet laser cavity and the gain medium. PMID:23938905

Karadag, Y; Aas, M; Jonáš, A; Anand, S; McGloin, D; Kiraz, A

2013-05-15

238

Measuring nanoscale interactions and dynamics of DNA-grafted colloids with line optical tweezers  

NASA Astrophysics Data System (ADS)

Much of the excitement regarding nanotechnology stems from the idea of "bottom-up" self-assembly: the possibility of spontaneously growing complex structures or devices out of molecular scale components rather than using conventional microfabrication. Realizing such goals requires a reliable method for inducing specific interactions between multiple particle species. The preferred method for inducing such interactions is to use hybridization, the sequence-specific assembly of single stranded DNA grafted onto the particles into double strands. Linking bridges of DNA can either glue two objects together strongly or cause them to weakly and reversibly adhere. While the strong adhesion limit has been studied, the weak reversible interactions required for equilibrium self-assembly and annealing remain poorly characterized, hindering experimental and theoretical progress. All previous attempts to assemble non-DNA objects using DNA interactions have created highly disordered aggregates rather than the hoped for crystal-like structures. Here we report the first direct measurements of such DNA-induced colloidal interactions, as well as the first colloidal crystals assembled using them. The pair interactions measured with our optical tweezer method can be modeled in detail by well-known statistical physics and chemistry, boding well for their application to directed self-assembly. The microspheres' binding dynamics, however, have a surprising power-law scaling that can significantly slow annealing and crystallization. We separated effects due to multiple bridge kinetics from those due to individual DNA hybridization by adjusting the microspheres' DNA surface density. The process of DNA hybridization requires the traversing of a multitude of intermediate steps to get from two random coil oligonucleotides to a tidy duplex DNA. We probed the nature of these intermediate states by measuring the lifetime distribution of single 16-bp duplexes subject to thermal dissociation under effectively zero tension. Unlike comparable single molecule experiments performed at finite tension, we find an unusual stretched exponential lifetime distribution, suggesting that thermal dissociation proceeds via a number of competing intermediate pathways. Similar measurements with higher DNA density indicate that multiple-bridged states are highly unstable, indicating that the duplexes are extremely force sensitive. Our power-law kinetics are a likely consequence of the exquisite force sensitivity and nonexponential dissociation kinetics of the DNA bridges.

Biancaniello, Paul Louis

239

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

Microsoft Academic Search

The purpose of this study is to investigate how the mitochondrial membrane potential affects sperm motility using laser tweezers and a non-ratiometric fluorescent probe, DiOC6(3). A 1064 nm Nd:YVO4 continuous wave laser was used to trap motile sperm at a power of 450 mW in the trap spot. Using customized tracking software, the curvilinear velocity (VCL) and the escape force

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

2011-01-01

240

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

NASA Technical Reports Server (NTRS)

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

Wrbanek, Susan Y.; Decker, Arthur J.

2005-01-01

241

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

242

Maritime Aerosol Optical Model Based on the Aerosol Robotic Network (AERONET) Measurements  

Microsoft Academic Search

The quality of bio-optical products of satellite ocean color sensors is strongly dependent on the accuracy of atmospheric correction algorithms. Atmospheric correction of ocean color imagery requires better aerosol modeling. Aerosol optical properties over the oceans vary considerably. In order to simulate aerosol optical conditions over the oceans three major sources should be considered, which we can define in terms

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

2001-01-01

243

Annual distributions and sources of Arctic aerosol components, aerosol optical depth, and aerosol absorption  

NASA Astrophysics Data System (ADS)

forcing by aerosols and tropospheric ozone could play a significant role in recent Arctic warming. These species are in general poorly accounted for in climate models. We use the GEOS-Chem global chemical transport model to construct a 3-D representation of Arctic aerosols and ozone that is consistent with observations and can be used in climate simulations. We focus on 2008, when extensive observations were made from different platforms as part of the International Polar Year. Comparison to aircraft, surface, and ship cruise observations suggests that GEOS-Chem provides in general a successful year-round simulation of Arctic black carbon (BC), organic carbon (OC), sulfate, and dust aerosol. BC has major fuel combustion and boreal fire sources, OC is mainly from fires, sulfate has a mix of anthropogenic and natural sources, and dust is mostly from the Sahara. The model is successful in simulating aerosol optical depth (AOD) observations from Aerosol Robotics Network stations in the Arctic; the sharp drop from spring to summer appears driven in part by the smaller size of sulfate aerosol in summer. The anthropogenic contribution to Arctic AOD is a factor of 4 larger in spring than in summer and is mainly sulfate. Simulation of absorbing aerosol optical depth (AAOD) indicates that non-BC aerosol (OC and dust) contributed 24% of Arctic AAOD at 550 nm and 37% of absorbing mass deposited to the snow pack in 2008. Open fires contributed half of AAOD at 550 nm and half of deposition to the snowpack.

Breider, Thomas J.; Mickley, Loretta J.; Jacob, Daniel J.; Wang, Qiaoqiao; Fisher, Jenny A.; Chang, Rachel. Y.-W.; Alexander, Becky

2014-04-01

244

Optical measurement of medical aerosol media parameters  

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

245

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

246

Aerosol optical thickness and atmospheric path radiance  

NASA Technical Reports Server (NTRS)

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

Kaufman, Yoram J.

1993-01-01

247

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

NASA Astrophysics Data System (ADS)

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

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

2006-09-01

248

Atmospheric Aerosol Optical Properties in the Persian Gulf  

Microsoft Academic Search

Aerosol optical depth measurements over Bahrain acquired through the ground-based Aerosol Robotic Network (AERONET) are analyzed. Optical depths obtained from ground-based sun\\/sky radiometers showed a pronounced temporal trend, with a maximum dust aerosol loading observed during the March-July period. The aerosol optical depth probability distribution is rather narrow with a modal value of about 0.25. The Ångström parameter frequency distribution

Alexander Smirnov; Brent N. Holben; Oleg Dubovik; Norm T. O'Neill; Thomas F. Eck; Douglas L. Westphal; Andreas K. Goroch; Christophe Pietras; Ilya Slutsker

2002-01-01

249

Comparison of simulated and observed aerosol optical depth  

Microsoft Academic Search

A variety of measurements have been used to evaluate the treatment of aerosol radiative properties and radiative impacts of aerosols simulated by the Model for Integrated Research on Atmospheric Global Exchanges (MIRAGE). This paper focuses on comparisons of simulated and measured aerosol optical depth (AOD). When the analyzed relative humidity is used to calculate aerosol water uptake in MIRAGE, the

Nels Laulainen; Steven Ghan; Richard Easter; Rahul Zaveri

2000-01-01

250

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

Microsoft Academic Search

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

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

2001-01-01

251

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

NASA Astrophysics Data System (ADS)

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

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

2011-10-01

252

Titan aerosols - Optical properties and vertical distribution  

NASA Astrophysics Data System (ADS)

An analysis of Titan's solar phase variation as a function of wavelength together with the continuum geometric albedo makes it possible to set limits on the real part of the refractive index and on the average particle size of the aerosol component of Titan's atmosphere of between about 1.5 and 2.0 and between 0.20 microns and about 0.35 microns, respectively. If the real part of the refractive index is known the average particle size can be determined to within a few percent, and varies inversely with the real part of the refractive index. Using this information in a two-layer model of a methane-aerosol atmosphere and comparing the result with Titan's visible and near-infrared methane spectrum leads to the conclusion that the top layer of Titan's atmosphere contains 0.01 km atm of methane and 2.5 extinction optical depths of aerosol, while the data are consistent with a bottom layer containing 2.2 km atm of methane and about 7.5 aerosol optical depths for a real part of the refractive index equal to 1.7 and an average particle size of 0.25 microns.

Rages, K.; Pollack, J. B.

1980-01-01

253

tweezercalib 2.0: Faster version of MatLab package for precise calibration of optical tweezers  

NASA Astrophysics Data System (ADS)

We present a vectorized version of the MatLab (MathWorks Inc.) package tweezercalib for calibration of optical tweezers with precision. The calibration is based on the power spectrum of the Brownian motion of a dielectric bead trapped in the tweezers. Precision is achieved by accounting for a number of factors that affect this power spectrum, as described in vs. 1 of the package [I.M. Toli?-Nørrelykke, K. Berg-Sørensen, H. Flyvbjerg, Matlab program for precision calibration of optical tweezers, Comput. Phys. Comm. 159 (2004) 225-240]. The graphical user interface allows the user to include or leave out each of these factors. Several "health tests" are applied to the experimental data during calibration, and test results are displayed graphically. Thus, the user can easily see whether the data comply with the theory used for their interpretation. Final calibration results are given with statistical errors and covariance matrix. New version program summaryTitle of program: tweezercalib Catalogue identifier: ADTV_v2_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/ADTV_v2_0 Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Reference in CPC to previous version: I.M. Toli?-Nørrelykke, K. Berg-Sørensen, H. Flyvbjerg, Comput. Phys. Comm. 159 (2004) 225 Catalogue identifier of previous version: ADTV Does the new version supersede the original program: Yes Computer for which the program is designed and others on which it has been tested: General computer running MatLab (Mathworks Inc.) Operating systems under with the program has been tested: Windows2000, Windows-XP, Linux Programming language used: MatLab (Mathworks Inc.), standard license Memory required to execute with typical data: Of order four times the size of the data file High speed storage required: none No. of lines in distributed program, including test data, etc.: 135 989 No. of bytes in distributed program, including test data, etc.: 1 527 611 Distribution format: tar. gz Nature of physical problem: Calibrate optical tweezers with precision by fitting theory to experimental power spectrum of position of bead doing Brownian motion in incompressible fluid, possibly near microscope cover slip, while trapped in optical tweezers. Thereby determine spring constant of optical trap and conversion factor for arbitrary-units-to-nanometers for detection system. Method of solution: Elimination of cross-talk between quadrant photo-diode's output channels for positions (optional). Check that distribution of recorded positions agrees with Boltzmann distribution of bead in harmonic trap. Data compression and noise reduction by blocking method applied to power spectrum. Full accounting for hydrodynamic effects: Frequency-dependent drag force and interaction with nearby cover slip (optional). Full accounting for electronic filters (optional), for "virtual filtering" caused by detection system (optional). Full accounting for aliasing caused by finite sampling rate (optional). Standard non-linear least-squares fitting. Statistical support for fit is given, with several plots facilitating inspection of consistency and quality of data and fit. Summary of revisions: A faster fitting routine, adapted from [J. Nocedal, Y.x. Yuan, Combining trust region and line search techniques, Technical Report OTC 98/04, Optimization Technology Center, 1998; W.H. Press, B.P. Flannery, S.A. Teukolsky, W.T. Vetterling, Numerical Recipes. The Art of Scientific Computing, Cambridge University Press, Cambridge, 1986], is applied. It uses fewer function evaluations, and the remaining function evaluations have been vectorized. Calls to routines in Toolboxes not included with a standard MatLab license have been replaced by calls to routines that are included in the present package. Fitting parameters are rescaled to ensure that they are all of roughly the same size (of order 1) while being fitted. Generally, the program package has been updated to comply with MatLab, vs. 7.0, and optimized for speed. Restrictions on the complexity of the prob

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

2006-03-01

254

Intercomparison of CALIOP and MODIS aerosol optical depth retrievals  

NASA Astrophysics Data System (ADS)

The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) is carried on the CALIPSO satellite and has acquired global aerosol profiles since June 2006. CALIPSO is flown in formation with the Aqua satellite as part of the A-train satellite constellation, so that a large number of coincident aerosol observations are available from CALIOP and the MODIS-Aqua instrument. This study compares column aerosol optical depth at 0.532 ?m derived from CALIOP aerosol profiles with MODIS-Aqua 0.55 ?m aerosol optical depth over the period June 2006 through August 2008. The study is based on the CALIOP Version 2 Aerosol Layer Product and MODIS Collection 5. While CALIOP is first and foremost a profiling instrument, this comparison of column aerosol optical depth provides insight into quality of CALIOP aerosol data. It is found that daytime aerosol optical depth from the CALIOP Version 2 product has a small global mean bias relative to MODIS Collection 5. Regional biases, of both signs, are larger and biases are seen to vary somewhat with season. In northern mid-latitudes, aerosol optical depth from CALIOP is lower, on average, than from MODIS. This may be partly due to a latitude-dependent calibration error in Version 2 CALIOP Level 1 daytime 0.532 ?m profiles. This comparison of CALIOP and MODIS also provides insight into possible biases in the MODIS aerosol optical depth product due to cloud masking and errors in modeling land surface reflectance.

Kittaka, C.; Winker, D. M.; Vaughan, M. A.; Omar, A.; Remer, L. A.

2010-08-01

255

Forces between blank surfaces as measured by the colloidal probe technique and by optical tweezers--a comparison.  

PubMed

The well-established atomic force microscopy (AFM)-based colloidal probe technique (CPT) and optical tweezers (OT) are combined to measure the interaction forces between blank SiO(2) surfaces in aqueous ionic solutions (CaCl(2)) of varying concentration at pH 7. Spherical colloids (SiO(2), diameter approximately 4.63 +/- 0.05 microm) taken out of the same batch are used by both methods. In the case of CPT, a single colloid is glued to a cantilever, and the interaction forces with a plain SiO(2) surface are determined in dependence on the concentration of the surrounding medium. For the OT studies, two colloids (one fixed to a micropipet by capillary action, the other held with the optical trap) are approached to each other in nanometer steps, and the resulting forces are measured for the same media as in the CPT experiment. Both techniques fit well to each other and enable one to cover interaction energies ranging from 10(-5) to 1 mN/m. The experimental data are well described by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory revealing that the effective surface charge density changes slightly with concentration. PMID:19769349

Elmahdy, Mahdy M; Drechsler, Astrid; Gutsche, Christof; Synytska, Alla; Uhlmann, Petra; Kremer, Friedrich; Stamm, Manfred

2009-11-17

256

Evaluation of ACCMIP simulated aerosol concentrations and aerosol optical depths over China  

NASA Astrophysics Data System (ADS)

The ACCMIP (Atmospheric Chemistry & Climate Model Intercomparison Project) simulated aerosol concentrations and aerosol optical depths (AODs) over China are evaluated using ground measurements in order to understand regional radiative forcing and climatic effect of aerosols. Comparisons of simulated aerosol concentrations in 12 ACCMIP models with ground-based observations from the Atmosphere Watch Network sites under China Meteorological Administration (CAWNET) indicate that the ACCMIP models underestimate concentrations of all major aerosol species, including sulfate, nitrate, ammonium, black carbon, and organic carbon. On an annual mean basis, the multi-model averaged concentrations of sulfate, nitrate, ammonium, black carbon, and organic carbon are underestimated by 63%, 72%, 55%, 51%, and 55%, respectively. While the observed concentrations of all aerosol species were generally high in winter and low in summer, the models could reproduce seasonal variation of nitrate but did not capture well the seasonal variations of other aerosol species. Over AERONET sites in China, the multi-model mean aerosol optical depths and absorption aerosol optical depths are found to be underestimated by 20% and 55%, respectively. These analyses indicate that current global models may underestimate aerosol radiative forcing and hence the cooling of aerosols over China. Because of the enormous importance of China as a source of aerosols, accurate simulations of aerosol levels in China are called for.

Chang, W.; Liao, H.

2013-12-01

257

Aerosol Optical Depth Determinations for BOREAS  

NASA Technical Reports Server (NTRS)

Automated tracking sun photometers were deployed by NASA/Ames Research Center aboard the NASA C-130 aircraft and at a ground site for all three Intensive Field Campaigns (IFCs) of the Boreal Ecosystem-Atmosphere Study (BOREAS) in central Saskatchewan, Canada during the summer of 1994. The sun photometer data were used to derive aerosol optical depths for the total atmospheric column above each instrument. The airborne tracking sun photometer obtained data in both the southern and northern study areas at the surface prior to takeoff, along low altitude runs near the ground tracking sun photometer, during ascents to 6-8 km msl, along remote sensing flightlines at altitude, during descents to the surface, and at the surface after landing. The ground sun photometer obtained data from the shore of Candle Lake in the southern area for all cloud-free times. During the first IFC in May-June ascents and descents of the airborne tracking sun photometer indicated the aerosol optical depths decreased steadily from the surface to 3.5 kni where they leveled out at approximately 0.05 (at 525 nm), well below levels caused by the eruption of Mt. Pinatubo. On a very clear day, May 31st, surface optical depths measured by either the airborne or ground sun photometers approached those levels (0.06-0.08 at 525 nm), but surface optical depths were often several times higher. On June 4th they increased from 0.12 in the morning to 0.20 in the afternoon with some evidence of brief episodes of pollen bursts. During the second IFC surface aerosol optical depths were variable in the extreme due to smoke from western forest fires. On July 20th the aerosol optical depth at 525 nm decreased from 0.5 in the morning to 0.2 in the afternoon; they decreased still further the next day to 0.05 and remained consistently low throughout the day to provide excellent conditions for several remote sensing missions flown that day. Smoke was heavy for the early morning of July 24th but cleared partially by 10:30 local time and cleared fully by 11:30. Heavy smoke characterized the rest of the IFC in both study areas.

Wrigley, R. C.; Livingston, J. M.; Russell, P. B.; Guzman, R. P.; Ried, D.; Lobitz, B.; Peterson, David L. (Technical Monitor)

1994-01-01

258

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

259

Comparison between radiation forces upon nanoparticles in continuous laser tweezers and in pulsed laser tweezers  

Microsoft Academic Search

It is easier to obtain high energy in very short period through pulse laser than through continuous laser. And in the field of biology, especially in researching the active cells by optical tweezers, the traditional continuous laser employed in the tweezers are inclined to hurt even kill the cells. So, substituting the traditional continuous laser by pulsed laser is one

XiaoYu Liu; Feng Wang

2010-01-01

260

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

261

Geometrical optics of dense aerosols: forming dense plasma slabs.  

PubMed

Assembling a freestanding, sharp-edged slab of homogeneous material that is much denser than gas, but much more rarefied 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 field, 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 finite particle density reduces the effective Stokes number of the flow, a critical result for controlled focusing. PMID:24237567

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

2013-11-01

262

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

NASA Astrophysics Data System (ADS)

Looping and cleavage of single DNA molecules by the two-site restriction endonuclease Sau3AI were measured with optical tweezers. A DNA template containing many recognition sites was used, permitting loop sizes from ~10 to 10,000 basepairs. At high enzyme concentration cleavage events were detected within 5 seconds and nearly all molecules were cleaved within 5 minutes. Activity decreased ~10-fold as the DNA tension was increased from 0.03 to 0.7 pN. Substituting Ca2+ for Mg2+ blocked cleavage, permitting measurement of stable loops. At low tension, the initial rates of cleavage and looping were similar (~0.025 s-1 at 0.1 pN), suggesting that looping is rate limiting. Short loops formed more rapidly than long loops. The optimum size decreased from ~250 to 45 bp and the average number of loops (in 1 minute) from 4.2 to 0.75 as tension was increased from 0.03 to 0.7 pN. No looping was detected at 5 pN. These findings are in qualitative agreement with recent theoretical predictions considering only DNA mechanics, but we observed weaker suppression with tension and smaller loop sizes. Our results suggest that the span and elasticity of the protein complex and protein-induced DNA bending and wrapping play an important role.

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

2006-09-01

263

Probing the effect of elevated cholesterol on the mechanical properties of membrane-cytoskeleton by optical tweezers  

NASA Astrophysics Data System (ADS)

The composition of the cell membrane and the surrounding physiological factors determine the nature and dynamics of membrane-cytoskeleton coupling. Mechanical strength of a cell is mainly derived from such coupling. In this article, we investigate the effect of extra cellular cholesterol on the membrane-cytoskelaton connectivity of single cell endothelium and consequent remodeling of its mechanical properties. Using optical tweezers as a force probe, we have measured membrane stiffness (km), membrane microviscosity (?eff ) and the two-dimensional shear modulus (G'(f)) as a function of extracellular cholesterol in the range of 0.1mM to 6mM. We find that membrane stiffness and shear modulus are dependent on cholesterol-induced membrane-cytoskeletal organization. Further, by disrupting the membranecytoskeletal connectivity with Cytochalasin D, an actin delpolymerizing molecule, we recover pure membrane behaviour devoid of any cytoskeleton attachment. However, behaviour of ?eff was found to be unaffected by disruption of membrane-cytoskeleton organization. We infer that cholesterol is playing a distinct role in modulating membrane organization and membrane-cytoskeleton connectivity independently. We further discuss implications of our approach in characterizing cellular mechanics.

Rajkumar, Arun S.; Muley, Ajit; Chatterjee, Suvro; Jaffar Ali, B. M.

2010-08-01

264

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

PubMed Central

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

Tans, Sander J.

2013-01-01

265

Computational modelling of optical tweezers with many degrees of freedom using dynamic simulation: cylinders, nanowires, and multiple particles  

NASA Astrophysics Data System (ADS)

Computational tasks such as the calculation and characterization of the optical force acting on a sphere are relatively straightforward in a Gaussian beam trap. Resulting properties of the trap such as the trap strength, spring constants, and equilibrium position can be easily determined. More complex systems with non-spherical particles or multiple particles add many more degrees of freedom to the problem. Extension of the simple methods used for single spherical particles could result in required computational time of months or years. Thus, alternative methods must be used. One powerful tool is to use dynamic simulation: model the dynamics and motion of a particle or particles within the trap. We demonstrate the use of dynamic simulation for non-spherical particles and multi-particle systems. Using a hybrid discrete dipole approximation (DDA) and T-matrix method, we find plausible equilibrium positions and orientations of cylinders of varying size and aspect ratio. Orientation landscapes revealing different regimes of behaviour for micro-cylinders and nanowires with different refractive indices trapped with beams of differing polarization are also presented. This investigation provides a solid background in both the function and properties of micro-cylinders and nanowires trapped in optical tweezers. This method can also be applied to particles with other shapes. We also investigate multiple-particle trapping, which is quite different from single particle systems, as they can include effects such as optical binding. We show that equilibrium positions, and the strength of interactions between particles can be found in systems of two and more particles.

Cao, Yongyin; Stilgoe, Alexander B.; Stroet, Martin; Loke, Vincent L. Y.; Chen, Lixue; Nieminen, Timo A.; Rubinsztein-Dunlop, Halina

2012-10-01

266

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

267

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

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

268

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

269

Path Radiance Technique for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

270

Path Radiance Technique for Retrieving Aerosol Optical Thickness Over Land  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

271

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

272

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

NASA Technical Reports Server (NTRS)

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

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

2007-01-01

273

Near infrared optical tweezers and nanosecond ablation on yeast and algae cells  

NASA Astrophysics Data System (ADS)

In recent years, lasers for optical trapping and micromanipulation of microscopic particles or cells and sub cellular structures, both in vivo and in vitro, have gained remarkable interest in biomedical research and applications. Although the principles and the mechanisms of pulsed laser ablation have been well described for macroscopic interventions, the microbeam operation under microscopic guidance necessitates further investigation. In this work, we present the research and development efforts towards a pulsed ultraviolet microbeam laser system, the design and realization efforts towards a near infrared laser trapping device and the results obtained on yeast cells and algae by the combined system. We investigated the optical dissection of the cells versus the presence of optical trapping forces and the presence of rhodamine dye. We characterized the optical ablation of the cell walls and resulting cavitation as plasma formation effects which create shock waves due to their occurrence only in nanosecond pulse irradiation mode. We estimated the minimum energy of the microbeam for optical dissection of yeast cell, under the influence of optical trapping forces, as lower as 3 ?J, while in the presence of rhodamine as lower as 2 ?J. Lastly, using the techniques of optical microsurgery we demonstrated the minimum energy value for sub cellular dissection on an algae cell equal to 27 ?J.

Kotsifaki, D. G.; Makropoulou, M.; Serafetinides, A.

2013-03-01

274

P6F-4 A Theoretical Time-Course Study of Acoustic Tweezers  

Microsoft Academic Search

Single beam based optical tweezers has been applied to many biomedical applications in trapping macromolecules and cells. Due to the finite penetration ability of laser in tissue and only utilization in opaque particles, these limitations reduce the potential of optical tweezers in-vivo performance. Consequently, some researchers theoretically demonstrated to manipulate micro-size particles by acoustic tweezers to avoid mentioned problems. To

Hsiao-Chun Ting; Chih-Kuang Yeh

2007-01-01

275

Parallel Transport of Biological Cells using Individually Addressable VCSEL Arrays as Optical Tweezers.  

National Technical Information Service (NTIS)

We have demonstrated the use of vertical cavity surface emitting lasers (VCSELs) for optical trapping and active manipulation of live biological cells and microspheres.We have experimentally verified that the Laguerre Gaussian laser mode output from the V...

A. L. Birkbeck B. Shao M. Gross M. Ozhan R. A. Flynn

2005-01-01

276

An algorithm for improved control of trap intensities in holographic optical tweezers  

NASA Astrophysics Data System (ADS)

The use of phase only spatial light modulators for holographic optical trapping results in the appearance of ghost orders, creating unwanted traps with uncontrolled intensity and causing variations in the intensity of the desired traps. By introducing dummy areas in the diffraction plane during the hologram optimization, the intensity in the ghost orders can be significantly reduced. By directing a variable fraction of the light to the dummy area, the optical power in the traps can be controlled independently and kept constant also while moving traps to different arrangements. We present and evaluate an algorithm for hologram generation which utilizes dummy areas and allows arbitrary spot positioning in three dimensions. The method enables the use of holographic optical trapping for applications requiring precise control of the intensity in traps, such as optical force measurement.

Persson, Martin; Engström, David; Goksör, Mattias

2012-10-01

277

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

278

Potential-well model in acoustic tweezers  

Microsoft Academic Search

Standing-wave acoustic tweezers are popularly used for non-invasive and non-contact particle manipulation. Because of their good penetration in biological tissue, they also show promising prospects for in vivo applications. According to the concept of an optical vortex, we propose an acoustics-vortex- based trapping model of acoustic tweezers. A four-element 1-MHz planar transducer was used to generate 1-MHz sine waves at

Shih-Tsung Kang; Chih-Kuang Yeh

2010-01-01

279

Shaping of the trapping volume in optical tweezers using cylindrical vector beams  

NASA Astrophysics Data System (ADS)

We present the result of an investigation into the optical trapping of micropaticles using laser beams with a spatially inhomogeneous polarization (cylindrical vector beams). We perform three-dimensional tracking of the Brownian fluctuations in position of a trapped particle and extract the trap spring constants. We characterize the trap geometry by the aspect ratio of spring constants in the directions transverse and parallel to the beam propagation direction and evaluate this figure of merit as a function of polarization angle. We show that the additional degree of freedom present in cylindrical vector beams (CVBs) allows us to control the optical trap strength and geometry by adjusting the polarization of the trapping beam only. Experimental results are compared with a theoretical model of optical trapping using CVBs derived from electromagnetic scattering theory in the T-matrix framework.

Skelton, Susan E.; Sergides, Marios; Donato, Maria G.; Vasi, Sebastiano; Sayed, Rania; Gucciardi, Pietro G.; Saija, Rosalba; Iat?, Maria A.; Maragó, Onofrio M.; Jones, Philip H.

2012-10-01

280

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

PubMed Central

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

2013-01-01

281

Path Radiance Techniques for Retrieving Aerosol Optical Thickness over Land  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

282

Seasonal variability of aerosol optical depth over indian subcontinent  

Microsoft Academic Search

Ganga basin extends 2000 km E-W and about 400 km N-S and is bounded by Himalayas in the north. This basin is unequivocally found to be affected by high aerosols optical depth (AOD) (>0.6) throughout the year. Himalayas restricts movement of aerosols toward north and as a result dynamic nature of aerosol is seen over the Ganga basin. High AOD

Anup K. Prasad; Ramesh P. Singh; Ashbindu Singh; Menas Kafatos

2005-01-01

283

Quantification of high-efficiency trapping of nanoparticles in a double nanohole optical tweezer.  

PubMed

We measure the dynamics of 20 nm polystyrene particles in a double nanohole trap to determine the trap stiffness for various laser powers. Both the autocorrelation analysis of Brownian fluctuations and the trapping transient analysis provide a consistent value of ? 0.2 fN/nm stiffness for 2 mW of laser power, which is similar to theoretical calculations for aperture trapping. As expected, the stiffness increases linearly with laser power. This is comparable to the stiffness obtained for conventional optical traps for trapping, but for ten times smaller dielectric particles and less power. This approach will allow us to quantitatively evaluate future aperture-based optical traps, with the goal of studying the folding dynamics of smaller proteins (? 10 kDa) and small-molecule interactions. PMID:24404888

Kotnala, Abhay; Gordon, Reuven

2014-02-12

284

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

285

Electro-optical Detection of External Mixtures in Aerosols  

Microsoft Academic Search

A measurement technique was developed that has the capability to resolve externally mixed particles of different refractive indices within the range expected for and observed in atmospheric aerosols. Measurements of laboratory aerosols showed that for a specified geometric size, absorbing particles could be sized either larger or smaller than nonabsorbing particles by an optical particle counter and that the difference

Jost Heintzenberg; Hans-Christen Hansson

1990-01-01

286

Optical properties of aerosol over a South European urban environment  

Microsoft Academic Search

Aerosol optical depths (AODs) and single scattering albedos (SSAs) were derived from in situ aircraft measurements of scattering and absorption coefficients at 550 nm. These values were compared to the AODs and SSAs derived from the sun photometer (CIMEL) data of the Aerosol Robotic Network (AERONET) site, in Thessaloniki, Greece, between 18 and 21 July 2006. The aircraft-obtained AODs were

Kyriaki Kelektsoglou; Spyridon Rapsomanikis; Evangelos T. Karageorgos; Ioannis Kosmadakis

2012-01-01

287

Optical properties of aerosol over a South European urban environment  

Microsoft Academic Search

Aerosol optical depths (AODs) and single scattering albedos (SSAs) were derived from in situ aircraft measurements of scattering and absorption coefficients at 550 nm. These values were compared to the AODs and SSAs derived from the sun photometer (CIMEL) data of the Aerosol Robotic Network (AERONET) site, in Thessaloniki, Greece, between 18 and 21 July 2006. The aircraft-obtained AODs were

Kyriaki Kelektsoglou; Spyridon Rapsomanikis; Evangelos T. Karageorgos; Ioannis Kosmadakis

2011-01-01

288

Machine Learning and Bias Correction of MODIS Aerosol Optical Depth  

Microsoft Academic Search

Machine-learning approaches (neural networks and support vector machines) are used to explore the reasons for a persistent bias between aerosol optical depth (AOD) retrieved from the MODerate resolution Imaging Spectroradiometer (MODIS) and the accurate ground-based Aerosol Robotic Network. While this bias falls within the expected uncertainty of the MODIS algorithms, there is room for algorithm improvement. The results of the

D. J. Lary; L. A. Remer; D. MacNeill; B. Roscoe; S. Paradise

2009-01-01

289

Optical and microphysical properties of atmospheric aerosols in Moldova  

Microsoft Academic Search

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

Alexandr Aculinin; Vladimir Smicov

2010-01-01

290

Laboratory Comparison of Aerosol Optical Property Measurement Techniques  

NASA Astrophysics Data System (ADS)

Aerosol particles influence the global radiative balance with their optical properties, i.e., the ability of scattering and/or absorbing the incoming solar radiation (aerosol direct effect). Because this ability depends on aerosol characteristics such as composition, size distribution and mixing state, it is critical to link aerosol optical,physical and chemical properties to emissions for better assessing the regional and global impact of different aerosol types. During 2006, NOAA ERSL/CSD performed a series of laboratory based comparison studies to address the performance, uncertainties, and biases of both existing and newly developed instruments to measure aerosol optical properties. These investigations included measurements of extinction using cavity ring-down spectrometers (CRD-AES),scattering by a TSI nephelometer, and absorption by a Photoacoustic spectrometer (PAS) and a Radiance Research Particle Soot Absorption Photometer (PSAP). In this work we compare the optical properties derived for several aerosol types and mixtures by using various combinations of CRD-AES, nephelometer, and PSAP measurements. Our results indicate that such properties significantly depend on composition and mixing state of aerosols. We complete the study with top-of-the-atmosphere radiative forcing estimates and we compare the newly obtained values with what has been reported in past calculations.

Massoli, P.; Baynard, T.; Lack, D.; Ravishankara, A.; Lovejoy, E.

2006-12-01

291

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

NASA Astrophysics Data System (ADS)

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

Chen, Ying-chun; Wu, Chien-ming

2012-12-01

292

Optical properties of aerosols of mixed composition  

Microsoft Academic Search

A model is developed which relates the reduction in visual air quality to the chemical and physical properties of airborne aerosol particles. The aerosols are considered to be inhomogeneous and to have a mixed chemical composition which varies with particle size. The water content of the aerosol particles is derived from a semi-empirical application of the thermodynamic equations for particle

C. S. Sloane

1984-01-01

293

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

294

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

295

Studying biomechanics at the single-molecule level with optical tweezers  

NASA Astrophysics Data System (ADS)

Lasers have found significant roles in today's world. One of their applications is trapping microscopic objects, which has helped scientists to understand mechanical processes involved in protein and DNA mechanics, structure, and interaction kinetics. We use the optical trapping technique to study mechanical properties of short proteins that play a vital role in providing structural support for the body. Elastin and collagen are two important structural proteins: we study their mechanical response to an applied force, and try to understand how it relates to their biological roles. The goals are to reveal how changes chemical compositions at the molecular scale affect mechanical properties, and relate these to macroscopic changes that can lead to serious and sometimes lethal diseases.

Rezaei, Naghmeh; Forde, Nancy; Wieczorek, Andrew

2012-10-01

296

Surface charge and hydrodynamic coefficient measurements of Bacillus subtilis spore by optical tweezers.  

PubMed

In this work we report on the simultaneous measurement of the hydrodynamic coefficient and the electric charge of single 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 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. PMID:24583259

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

2014-04-01

297

Rate-dependent dynamics of cellular membranes probed by laser tweezers and optical displacement sensing  

NASA Astrophysics Data System (ADS)

In this study, we investigated nanomechanical properties of cell membranes in response to elongation at different rates. Membrane nanotubes (tethers) were pulled at different pulling rates by an optically-trapped fluorescent microsphere as recorded and analyzed for low (1 ?m/s) and high (100 ?m/s) pulling rates. The force relaxation response of membrane nanotubes exhibited a bi-phasic behavior including fast and slow relaxation processes at low and high pulling rates. The fast and slow force relaxation time constants were 0.388+/-0.21 s and 11.74+/-3.35 s, in response to pulling rate of 1 ?m/s, respectively and significantly decreased at higher pulling rates. These reductions in the time constants are suggestive of reduced viscous effects and weakened adhesions between the membrane and the cytoskeleton during rapid pulling.

Khatibzadeh, Nima; Spector, Alexander A.; Brownell, William E.; Anvari, Bahman

2014-02-01

298

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

299

Spatiotemporal Analysis of Cell Response to a Rigidity Gradient: A Quantitative Study Using Multiple Optical Tweezers  

PubMed Central

Abstract We investigate the dynamic response of single cells to weak and local rigidities, applied at controlled adhesion sites. Using multiple latex beads functionalized with fibronectin, and each trapped in its own optical trap, we study the reaction in real time of single 3T3 fibroblast cells to asymmetrical tensions in the tens of pN · ?m?1 range. We show that the cell feels a rigidity gradient even at this low range of tension, and over time develops an adapted change in the force exerted on each adhesion site. The rate at which force increases is proportional to trap stiffness. Actomyosin recruitment is regulated in space and time along the rigidity gradient, resulting in a linear relationship between the amount of recruited actin and the force developed independently in trap stiffness. This time-regulated actomyosin behavior sustains a constant and rigidity-independent velocity of beads inside the traps. Our results show that the strengthening of extracellular matrix-cytoskeleton linkages along a rigidity gradient is regulated by controlling adhesion area and actomyosin recruitment, to maintain a constant deformation of the extracellular matrix.

Allioux-Guerin, Myriam; Icard-Arcizet, Delphine; Durieux, Christiane; Henon, Sylvie; Gallet, Francois; Mevel, Jean-Claude; Masse, Marie-Jo; Tramier, Marc; Coppey-Moisan, Maite

2009-01-01

300

Closure Evaluation of Laboratory Aerosols Optical and Hygroscopic Properties  

NASA Astrophysics Data System (ADS)

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

Wang, W.; Rood, M.

2006-12-01

301

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

NASA Technical Reports Server (NTRS)

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

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

2013-01-01

302

Spectral aerosol optical depth variation with different types of aerosol at Gwangju, Korea  

Microsoft Academic Search

Simultaneous ground-based measurements of aerosol chemical composition and atmospheric aerosol optical depth (AOD) in the UV and visible regions were carried out at Gwangju (35.13°N, 126.50°E), Korea during a biomass burning period, October 4 November 12, 2002. An Asian dust event and biomass burning events were observed during the study period. The correlation coefficients (R) between AOD and PM2.5 and

Jeong E. Kim; Seong Y. Ryu; Zhuanshi He; Young J. Kim

2006-01-01

303

Spectral aerosol optical depth variation with different types of aerosol at Gwangju, Korea  

Microsoft Academic Search

Simultaneous ground-based measurements of aerosol chemical composition and atmospheric aerosol optical depth (AOD) in the UV and visible regions were carried out at Gwangju (35.13°N, 126.50°E), Korea during a biomass burning period, October 4–November 12,2002. An Asian dust event and biomass burning events were observed during the study period. The correlation coefficients (R) between AOD and PM2.5 and PM10 mass

Jeong E. Kim; Seong Y. Ryu; Zhuanshi He; Young J. Kim

2006-01-01

304

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

PubMed

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

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

2014-07-01

305

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

306

Workplace aerosol mass concentration measurement using optical particle counters.  

PubMed

Direct-reading aerosol measurement usually uses the optical properties of airborne particles to detect and measure particle concentration. In the case of occupational hygiene, mass concentration measurement is often required. Two aerosol monitoring methods are based on the principle of light scattering: optical particle counting (OPC) and photometry. The former analyses the light scattered by a single particle, the latter by a cloud of particles. Both methods need calibration to transform the quantity of scattered light detected into particle concentration. Photometers are simpler to use and can be directly calibrated to measure mass concentration. However, their response varies not only with aerosol concentration but also with particle size distribution, which frequently contributes to biased measurement. Optical particle counters directly measure the particle number concentration and particle size that allows assessment of the particle mass provided the particles are spherical and of known density. An integrating algorithm is used to calculate the mass concentration of any conventional health-related aerosol fraction. The concentrations calculated thus have been compared with simultaneous measurements by conventional gravimetric sampling to check the possibility of field OPC calibration with real workplace aerosols with a view to further monitoring particle mass concentration. Aerosol concentrations were measured in the food industry using the OPC GRIMM® 1.108 and the CIP 10-Inhalable and CIP 10-Respirable (ARELCO®) aerosol samplers while meat sausages were being brushed and coated with calcium carbonate. Previously, the original OPC inlet had been adapted to sample inhalable aerosol. A mixed aerosol of calcium carbonate and fungi spores was present in the workplace. The OPC particle-size distribution and an estimated average particle density of both aerosol components were used to calculate the mass concentration. The inhalable and respirable aerosol fractions calculated from the OPC data are closely correlated with the results of the particle size-selective sampling using the CIP 10. Furthermore, the OPC data allow calculation of the thoracic fraction of workplace aerosol (not measured by sampling), which is interesting in the presence of allergenic particles like fungi spores. The results also show that the modified COP inlet adequately samples inhalable aerosol in the range of workplace particle-size distribution. PMID:22009365

Görner, Peter; Simon, Xavier; Bémer, Denis; Lidén, Göran

2012-02-01

307

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

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

308

Trends in aerosol optical depth for cities in India  

NASA Astrophysics Data System (ADS)

Recent analysis of trends in global short-wave radiation measured with pyranometers in major cities in India support a decrease in solar radiation in many of those cities since 1990. Since direct and diffuse radiation measurements include cloud effects, spring and summer dust and the variable summer monsoon rains, we concentrate in this paper on wintertime (November-February) aerosol optical depth measurements. The aerosol optical depth is derived from cloud-free turbidity measurements beginning in the 1960s and more recent sun photometer direct aerosol optical depth measurements. We compare the sun photometer derived trends with the pyranometer-derived trends using a radiative transfer model. These results are then compared to total ozone mapping spectrometer (TOMS) satellite-derived regional aerosol optical depths from 1980 to 2000. The results show that inclusion of the earlier turbidity measurements helps to establish an increasing regional turbidity trend. However, most of the increasing trend is confined to the larger cities in the Ganges River Basin of India (mainly Calcutta and New Delhi) with other cities showing a much less increase. Regional satellite data show that there is an increasing trend in aerosol off the coast of India and over the Ganges River Basin. The increase over the Ganges River Basin is consistent with population trends over the region during 1980-2000.

Porch, William; Chylek, Petr; Dubey, Mavendra; Massie, Steven

309

Measuring Aerosol Optical Properties with the Ozone Monitoring Instrument (OMI)  

NASA Technical Reports Server (NTRS)

The Ozone Monitoring Instrument (OMI) is the Dutch-Finnish contribution to the NASA EOS-Aura mission scheduled for launch in January 2004. OM1 is an imaging spectrometer that will measure the back-scattered Solar radiance between 270 an 500 nm. With its relatively high spatial resolution (13x24 sq km at nadir) and daily global coverage. OM1 will make a major contribution to our understanding of atmospheric chemistry and to climate research. OM1 will provide data continuity with the TOMS instruments. One of the pleasant surprises of the TOMS data record was its information on aerosol properties. First, only the absorbing aerosol index, which is sensitive to elevated lay- ers of aerosols such as desert dust and smoke aerosols, was derived. Recently these methods were further improved to yield aerosol optical thickness and single scattering albedo over land and ocean for 19 years of TOMS data (1979-1992,1997-2002), making it one of the longest and most valuable time series for aerosols presently available. Such long time series are essential to quantify the effect of aerosols on the Earth& climate. The OM1 instrument is better suited to measure aerosols than the TOMS instruments because of the smaller footprint, and better spectral coverage. The better capabilities of OMI will enable us to provide an improved aerosol product, but the knowledge will also be used for further analysis of the aerosol record from TOMS. The OM1 aerosol product that is currently being developed for OM1 combines the TOMS experience and the multi-spectral techniques that are used in the visible and near infrared. The challenge for this new product is to provide aerosol optical thickness and single scattering albedo from the near ultraviolet to the visible (330-500 nm) over land and ocean. In this presentation the methods for deriving the OM1 aerosol product will be presented. Part of these methods developed for OM1 can already be applied to TOMS data and results of such analysis will be shown.

Veefkind, J. P.; Torres, O.; Syniuk, A.; Decae, R.; deLeeuw, G.

2003-01-01

310

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

Microsoft Academic Search

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

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

2005-01-01

311

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

SciTech Connect

Weather Research and Forecasting (WRF)-chem model calculations were conducted to study aerosol optical properties around Beijing, China, during the Campaign of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing-2006) period. In this paper, we interpret aerosol optical properties in terms of aerosol mass concentrations and their chemical compositions by linking model calculations with measurements. In general, model calculations reproduced observed features of spatial and temporal variations of various surface and column aerosol optical parameters in and around Beijing. Spatial and temporal variations of aerosol absorption, scattering, and extinction coefficient corresponded well to those of elemental carbon (primary aerosol), sulfate (secondary aerosol), and the total aerosol mass concentration, respectively. These results show that spatial and temporal variations of the absorption coefficient are controlled by local emissions (within 100 km around Beijing during the preceding 24 h), while those of the scattering coefficient are controlled by regional-scale emissions (within 500 km around Beijing during the preceding 3 days) under synoptic-scale meteorological conditions, as discussed in our previous study of aerosol mass concentration. Vertical profiles of aerosol extinction revealed that the contribution of secondary aerosols and their water uptake increased with altitude within the planetary boundary layer, leading to a considerable increase in column aerosol optical depth (AOD) around Beijing. These effects are the main factors causing differences in regional and temporal variations between particulate matter (PM) mass concentration at the surface and column AOD over a wide region in the northern part of the Great North China Plain.

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

2010-11-23

312

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

313

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

314

Toward Investigating Optically Trapped Organic Aerosols with CARS Microspectroscopy  

NASA Astrophysics Data System (ADS)

The Intergovernmental Panel on Climate Change notes the huge uncertainty in the effect that atmospheric aerosols play in determining overall global temperature, specifically in their ability to nucleate clouds. To better understand aerosol chemistry, the novel coupling of gradient force optical trapping with broad bandwidth coherent anti-Stokes Raman scattering (CARS) spectroscopy is being developed to study single particles suspended in air. Building on successful designs employed separately for the techniques, this hybrid technology will be used to explain how the oxidation of organic compounds changes the chemical and physical properties of aerosols. By trapping the particles, an individual aerosol can be studied for up to several days. Using a broad bandwidth pulse for one of the incident beams will result in a Raman vibrational spectrum from every laser pulse. Combined with signal enhancement due to resonance and coherence of nonlinear CARS spectroscopy, this technique will allow for acquisition of data on the millisecond time scale, facilitating the study of dynamic processes. This will provide insights on how aerosols react with and absorb species from the gas phase. These experiments will increase understanding of aerosol oxidation and growth mechanisms and the effects that aerosols have on our atmosphere and climate. Progress in efforts developing this novel technique to study model systems is presented.

Voss, L. F.

2009-12-01

315

Optical properties of aerosols of mixed composition  

NASA Astrophysics Data System (ADS)

A model is developed which relates the reduction in visual air quality to the chemical and physical properties of airborne aerosol particles. The aerosols are considered to be inhomogeneous and to have a mixed chemical composition which varies with particle size. The water content of the aerosol particles is derived from a semi-empirical application of the thermodynamic equations for particle growth. The model is valid for all ranges of relative humidity. The light scattering and absorption coefficients are calculated using Mie theory extended to concentric sphere scatterers. The core of each particle, which is primarily taken to be nonvolatile carbon, is enclosed in a water-soluble exterior. The soluble layer responds to changes in the relative humidity by absorbing (or releasing) water. The model predictions are in excellent agreement with experimental measurements made in Denver in the fall of 1978.

Sloane, C. S.

316

Estimates of effective aerosol optical depths from spectral solar radiation measurements  

Microsoft Academic Search

This study reports a 37-year long record of direct beam spectral irradiance measurements made in Athens, Greece. An analysis of aerosol effects on the spectral distribution of solar radiation through effective optical depths, are presented. Thus, spectrally resolved aerosol optical depths were calculated and analyzed for the period 1954–1990. Summertime aerosol optical depths were found to be larger than winter

C. P. Jacovides; P. Kassomenos; N. A. Kaltsunides

1996-01-01

317

Reproducing the optical properties of fine desert dust aerosols using ensembles of simple model particles  

Microsoft Academic Search

Single scattering optical properties are calculated for a proxy of fine dust aerosols at a wavelength of 0.55?m. Spherical and spheroidal model particles are employed to fit the aerosol optical properties and to retrieve information about the physical parameters characterising the aerosols. It is found that spherical particles are capable of reproducing the scalar optical properties and the forward peak

Michael Kahnert

2004-01-01

318

Background Maritime Aerosol: Their Optical Thickness and Scattering Properties  

NASA Technical Reports Server (NTRS)

The effect of human induced change in the aerosol concentration and properties, or the aerosol response to climate change (e.g. droughts producing fires or dust) should be measured relative to a "background aerosol". How to define this background aerosol, so that it is both measurable and useful? Here we use 10 stations located in the Pacific, Atlantic and Indian Oceans to answer this question. Using a data set of the spectral optical thickness measured by the Aerosol Robotic network (AERONET), extending 1-3 years, we find the background conditions for these stations. The oceanic background aerosol is the result of ocean emission and spray, and some residual long lived continental aerosol. Its source is very broadly spread and is expected to vary little in time. Pollution or dust sources are from specific locations, emitted and transported to the measuring site in specific combination of meteorological conditions. Therefore they are expected to vary with time. It follows that the background aerosol can be identified as the median for conditions with small variations. To define the background we compute the median of N consequent measurements. We use N=50 that in average cloudy conditions corresponds to 2-3 days of measurements and N=100 (4-5 days). Most high polluted or dusty conditions correspond to data sequences with high standard deviation (greater than 0.02 in optical thickness) and are excluded. From the remaining N point running medians with low standard deviations we derive again the median. This excludes those rare cases of pollution or dust that is stable during the N measurements. The results show that the background aerosol over the Pacific Ocean is characterize by optical thickness of 0.055 at 500 nm and Angstrom exponent of 0.74. Over the Atlantic Ocean the values are 0.070 and 1.1 respectively, with little influence of the assumed value of N (50 or 100). The derivation of the background uses 20,000 and 5000 medians respectively that passed the criteria. The contribution of coarse and fine aerosol to the background aerosol is also calculated.

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

2001-01-01

319

Retrieval of aerosol optical properties for cloudy scenes from METOP  

NASA Astrophysics Data System (ADS)

The retrieval of aerosol optical properties is an important task for industry and climate forecasting. An ideal instrument should include observations with moderate spectral and high spatial resolutions for a wide range of wavelengths (from the UV to the TIR), measurements of the polarization state at different wavelengths and measurements of the same scene for different observation geometries. As such an ideal instrument is currently unavailable the usage of different instruments on one satellite platform is an alternative choice. We present the Polar Multi sensor Aerosol Product (PMAp) which is delivered as operational GOME-2 product starting in February 2014. The algorithms retrieve aerosol optical depth, further aerosol classifications like volcanic ash and cloud properties (geometric cloud fraction, cloud optical depth) combining different METOP instruments like GOME-2, AVHRR and IASI. These instruments provide high spatial resolution (AVHRR), moderate and high spectral resolution in the UV/VIS range (GOME-2), measurements in the infrared (AVHRR, IASI) and the determination of the polarization state (GOME-2). The multi-sensor approach allows a simultaneous retrieval of aerosol and cloud properties for GOME pixels with cloud coverage smaller than 30%. We demonstrate the benefit of our approach by verifications and comparisons to other data products (e.g. AERONET, MODIS/Terra).

Grzegorski, Michael; Poli, Gabriele; Holdak, Andriy; Lang, Ruediger; Munro, Rosemary

2014-05-01

320

Seasonal variability of aerosol optical properties in Darwin, Australia  

NASA Astrophysics Data System (ADS)

This paper investigates the annual cycle in aerosol optical thickness (AOT) and Angstrom exponent in Darwin, Australia, a coastal site in the Tropical Warm Pool where the major aerosol sources are biomass burning and sea salt. We have used radiometer measurements from the Tropical Western Pacific Atmospheric Radiation Measurement facility for the period March 2002-June 2003. Strong seasonal cycles in AOT and Angstrom exponent were observed, peaking during the burning season (May-November). Investigation of the spectral dependence of optical thickness showed that the Angstrom formula can be satisfactorily fitted to the AOT data during the burning season but not on summer and autumn afternoons due to the presence of sea salt aerosols.

Bouya, Zahra; Box, Gail P.; Box, Michael A.

2010-06-01

321

Nighttime Aerosol Optical Depth Variability From Astronomical Photometry  

Microsoft Academic Search

A technique for determination of the short-term (6 minutes intervals) variability of the aerosol optical depth (AOD) during nighttime from broadband visible measurements of star irradiances during clear nights was developed for the instrument called the Whole Sky Imager (WSI), placed at the Atmospheric Radiation Measurement (ARM) observation site in Oklahoma. The AOD is inferred indirectly from simultaneous observations of

I. C. Musat; R. G. Ellingson

2006-01-01

322

Trends in aerosol optical depth for cities in India  

Microsoft Academic Search

Recent analysis of trends in global short-wave radiation measured with pyranometers in major cities in India support a decrease in solar radiation in many of those cities since 1990. Since direct and diffuse radiation measurements include cloud effects, spring and summer dust and the variable summer monsoon rains, we concentrate in this paper on wintertime (November–February) aerosol optical depth measurements.

William Porch; Petr Chylek; Mavendra Dubey; Steven Massie

2007-01-01

323

Optical Properties and Associated Hygroscopicity of Clay Aerosols  

Microsoft Academic Search

Airborne mineral dust particles contribute a significant fraction to the total aerosol mass, thus they make a substantial contribution to the Earth's radiative budget by direct scattering and absorption of radiation. Quantifying their contribution is complicated by the variability of optical properties as a function of water uptake. To improve understanding, we directly measured the relative humidity (RH) dependence of

Alexis Rae Attwood; Margaret E. Greenslade

2010-01-01

324

Spectral aerosol optical depth variation with different types of aerosol at Gwangju, Korea  

NASA Astrophysics Data System (ADS)

Simultaneous ground-based measurements of aerosol chemical composition and atmospheric aerosol optical depth (AOD) in the UV and visible regions were carried out at Gwangju (35.13°N, 126.50°E), Korea during a biomass burning period, October 4 November 12, 2002. An Asian dust event and biomass burning events were observed during the study period. The correlation coefficients (R) between AOD and PM2.5 and PM10 mass concentration during the study period are 0.58±0.15 and 0.52±0.14, respectively. Aerosol optical properties (AOD and Ångström exponent) and chemical characteristics were presented for selected days and their impacts on aerosol loading were examined. Both fine and coarse mode particle mass concentrations increased on biomass burning day resulting in high AOD values. The simultaneous occurrence of Asian dust and biomass burning resulted in the highest AOD of 1.20 at 311 nm and the lowest Ångström exponent of 0.42 in the visible range. When both transported urban pollutants and land dust aerosols affected the air quality over the study area, AOD and surface PM mass concentration increased 18 60% and 230 890%, respectively.

Kim, Jeong E.; Ryu, Seong Y.; He, Zhuanshi; Kim, Young J.

2006-09-01

325

Aerosol optical properties during the Lindenberg Aerosol Characterization Experiment (LACE 98)  

NASA Astrophysics Data System (ADS)

The optical properties of atmospheric aerosol particles were measured close to ground level using different methods at Lindenberg/Falkenberg (Germany) during the Lindenberg Aerosol Characterization Experiment (LACE 98), 13 July 1998 to 14 August 1998 [, 2002]. The experimental setup consisted of (a) an aerosol photometer, which measured a complete set of aerosol optical properties, such as extinction, scattering, and absorption coefficients, single scattering albedo, apparent complex refractive index, asymmetry parameter of the phase function of scattering, and apparent volume soot content, (b) an integrating plate, which measured the absorption coefficient, and (c) a nephelometer and (d) a particle soot absorption photometer (PSAP) for measurements of scattering and absorption coefficients. All these measurements were performed under dry conditions. A telephotometer and a horizontal lidar were used to determine the aerosol extinction coefficient under ambient conditions. This paper presents a closure study of the different measurement methods. An empirical correction function for the PSAP is introduced and compared with a semiempirical correction function previously introduced by [1999]. A detailed model of humidity effects on the extinction coefficient is presented using "coated sphere" calculations based on measured input values of the size distribution, the chemical composition, the growth factor at 90% relative humidity, the water-soluble fraction of particulate materials, the temperature, and the relative humidity. Model calculations allowed an intercomparison of measured values of particles in the dry state and at ambient relative humidity and showed good agreement.

Bundke, U.; HäNel, G.; Horvath, H.; Kaller, W.; Seidl, S.; Wex, H.; Wiedensohler, A.; Wiegner, M.; Freudenthaler, V.

2002-11-01

326

A portable optical particle counter system for measuring dust aerosols  

Microsoft Academic Search

A portable battery-operated optical particle counter\\/multichannel analyzer system has been developed for the number size distribution and number concentration measurement of light-absorbing irregular-shaped dust particles. An inertial impactor technique has been used to obtain calibration curves by relating the magnitude of the optical counter's signal to the particle's aerodynamic or Stokes' diameter. These calibrations have been made for aerosols of

VIRGIL A. MARPLE; KENNETH L. RUBOW

1978-01-01

327

A theoretical time-course model of acoustic tweezers: Pulse-wave mode  

Microsoft Academic Search

The optical tweezers has been a very useful tool in biological research. However, due to finite penetration depth in optics, it is only utilized for transparent particle. This limitation reduces its potential of in-vivo manipulation. The idea of acoustic tweezers with better penetration ability than optics was recently proposed. In this paper, a novel pulse-wave mode is theoretically demonstrated to

Shih-Tsung Kang; Chih-Kuang Yeh

2008-01-01

328

Aerosol optical depth trends over different regions of India  

NASA Astrophysics Data System (ADS)

Seasonal and annual mean trends in aerosol optical depths (AODs) for the last decade are derived using MODerate resolution Imaging Spectroradiometer (MODIS) Level 2 10 km × 10 km remote sensing data over different locations in India. AODs have increased across India in the last decade. AOD trends exhibit spatial, seasonal and annual mean variations. Annual mean AODs have increased by >40% during 2000-2009 in Jaipur, Hyderabad and Bengaluru. The increase in AODs over Hyderabad and Bengaluru, major high-tech cities, can be ascribed to the increase in urbanization. An increase in AODs over New Delhi where manmade aerosols are dominant can be attributed to an increase in the amount of aerosols from fossil fuel and biomass burning, while an increasing trend in AODs in the northeast, indicates an increase in the amount of aerosols produced from biomass burning and forest fires. AODs decreased in the high altitude sites of Shimla and Dehradun. AODs and wind speeds increased over Jaipur, while they decreased in Trivandrum during the last decade. An increase in wind speeds led to an increase in soil derived dust particles over Jaipur, an arid site, while a decrease in wind speeds over Trivandrum, contributed to a decrease in sea spray aerosols thereby causing a decrease in AOD. Annual rainfall increased by ?1% in most locations. Both AODs and rainfall have increased in the last decade over most study locations. These findings become important and useful in the context of regional and global climate change due to aerosols.

Ramachandran, S.; Kedia, Sumita; Srivastava, Rohit

2012-03-01

329

COMPARISON OF PREDICTED AND MEASURED AEROSOL OPTICAL AND PHYSICAL PROPERTIES IN AUSTRALIAN CITIES  

Microsoft Academic Search

Summary Comprehensive information on the optical and physical properties of aerosol particles is important for evaluating or estimating the effects of aerosol on air quality, visibility degradation and radiative forcing. The determination of extinction of light by ambient aerosol particles can be achieved successfully by the accurate estimation of aerosol refractive index using observed and modelled size-resolved chemical composition data.

Yoshiteru Iinuma; Gail P. Box; John L. Gras; Melita Keywood; Gregory Ayers

330

Thin film-coated plastic optical fiber probe for aerosol chemical sensing applications  

Microsoft Academic Search

The increasing importance of aerosols in understanding environmental processes as well as the general use of aerosol technologies has led to great interest in aerosol characterization. Thus, we present the development of a thin film-coated plastic optical fiber probe for aerosol chemical composition sensing. To prepare the sensor probe, a small length of cladding was removed from the middle portion

Atul Kulkarni; Jun-Ho Lee; Jae-Do Nam; Taesung Kim

2010-01-01

331

Aerosol characteristics at a high-altitude location in central Himalayas: Optical properties and radiative forcing  

Microsoft Academic Search

Collocated measurements of the mass concentrations of aerosol black carbon (BC) and composite aerosols near the surface were carried out along with spectral aerosol optical depths (AODs) from a high-altitude station, Manora Peak in central Himalayas, during a comprehensive aerosol field campaign in December 2004. Despite being a pristine location in the Shivalik Ranges of central Himalayas and having a

P. Pant; P. Hegde; U. C. Dumka; Ram Sagar; S. K. Satheesh; K. Krishna Moorthy; Auromeet Saha; M. K. Srivastava

2006-01-01

332

Variations in the aerosol optical properties and types over the tropical urban site of Hyderabad, India  

Microsoft Academic Search

Aerosol measurements over the tropical urban site of Hyderabad, India, provide a way of determining the variability of the aerosol characteristics over a duration of 1 year (October 2007 to September 2008). The meteorological pattern over India, mainly driven by the regional monsoons, has a great effect on the amount and size distribution of the aerosols. Higher aerosol optical depth

D. G. Kaskaoutis; K. V. S. Badarinath; Shailesh Kumar Kharol; Anu Rani Sharma; H. D. Kambezidis

2009-01-01

333

Preliminary evaluation of S-NPP VIIRS aerosol optical thickness  

NASA Astrophysics Data System (ADS)

Visible Infrared Imaging Radiometer Suite (VIIRS) is the next-generation polar-orbiting operational environmental sensor with a capability for global aerosol observations. The VIIRS aerosol Environmental Data Record (EDR) is expected to continue the decade-long successful multispectral aerosol retrieval from the NASA's Earth Observing System Moderate Resolution Imaging Spectroradiometer (MODIS) for scientific research and applications. Since the launch of the Suomi National Polar-orbiting Partnership (S-NPP), the VIIRS aerosol calibration/validation team has been continuously monitoring, evaluating, and improving the performance of VIIRS aerosol retrievals. In this study, the VIIRS aerosol optical thickness (AOT) at 550 nm EDR at current Provisional maturity level is evaluated by comparing it with MODIS retrievals and measurements from the Aerosol Robotic Network (AERONET) and the Maritime Aerosol Network (MAN). The VIIRS global mean AOT at 550 nm differs from that of MODIS by approximately -0.01 over ocean and 0.03 over land (0.00 and -0.01 for the collocated retrievals) but shows larger regional biases. Global validation with AERONET and with MAN measurements shows biases of 0.01 over ocean and -0.01 over land, with about 64% and 71% of retrievals falling within the expected uncertainty range established by MODIS over ocean (±(0.03 + 0.05AOT)) and over land (±(0.05 + 0.15AOT)), respectively. The VIIRS retrievals over land exhibit slight overestimation over vegetated surfaces and underestimation over soil-dominated surfaces. These results show that the VIIRS AOT at 550 nm product provides a solid global data set for quantitative scientific investigations and environmental monitoring.

Liu, Hongqing; Remer, Lorraine A.; Huang, Jingfeng; Huang, Ho-Chun; Kondragunta, Shobha; Laszlo, Istvan; Oo, Min; Jackson, John M.

2014-04-01

334

Measurements of Multispectral Aerosol Optical Depth At Mace Head, Ireland  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols affect the Earths climate both directly by scattering and absorb- ing solar radiation and indirectly by modifying the optical and microphysical proper- ties of clouds. On a global scale, the radiative effect of aerosols is believed to result in an atmospheric cooling which is comparable and of opposite sign to the radiative forcing caused by greenhouse gases (GHG). Since aerosol concentrations are highly variable in space and time, an assessment of the overall impact of aerosols on the climate system requires a characterization of aerosol properties and their controlling factors on a regional scale. In this contribution we present results of the measurements of aerosol radiative properties at a coastal North Atlantic site. A unique platform for studying marine aerosols is the Global Atmospheric Watch (GAW) atmospheric re- search station at Mace Head, located on the west coast of Ireland. The research station can be designated as clean marine in character due to its location. Since March 2000, measurements of the column-integrated light-extinction have been conducted in Mace Head for deriving the aerosol optical depth (AOD). The measurements are performed with a Precision Filter Radiometer (PFR), developed at the World Radiation Center, Davos, Switzerland. Columnar light-extinction is recorded every 2 min at four differ- ent wavelengths (862, 500, 412, and 368 nm) with a bandwidth of 5 nm. The results presented in this contribution are based on photometer data covering a period of al- most 2 years. Over this period the mean value of AOD at 500 nm is calculated to be 0.12 and thus lying within the range of AOD data published for measurements in the marine atmosphere. However, the AOD standard deviations in all spectral channels show a magnitude comparable to the average values and therefore indicating a high variability within the 2 min AOD data. The mean Angstroem exponent amounts to a value of 0.87 highlighting the contribution of larger particles to the columnar aerosol light extinction at Mace Head. The time series will be subject to further analysis re- garding the influence of air mass history on AOD and the impact of sea salt aerosols on the light extinction.

Kleefeld, C.; Jennings, S. G.; Wehrli, C.

335

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.

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

2012-01-01

336

Recent trends in aerosol optical properties derived from AERONET measurements  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

337

Tropospheric aerosols in the Mediterranean: 1. Microphysical and optical properties  

NASA Astrophysics Data System (ADS)

Measurements of the aerosol properties were carried out at the island of Lampedusa, in the Mediterranean, in May 1999, as part of the Photochemical Activity and Ultraviolet Radiation modulating factors II campaign. Data from ground-based lidar and Sun photometer, and particle counters aboard an instrumented ultralight aircraft, are used in this study. Three different cases, when all the measurements were available in cloud-free conditions, were identified to derive the aerosol microphysical and optical properties. In one of these cases (18 May) the airmasses originated from Africa, and were loaded with a large amount of desert dust. In the other two cases (25 May and 27 May) the airmasses passed over Europe before reaching Lampedusa from North. The microphysical and optical properties of the aerosol strongly depend on the origin of the airmasses. The amount of particles in the 1-6 ?m range of radii and the average aerosol surface area per unit volume are larger in the desert dust case than on 25 May and 27 May. The real part of the refractive index of the desert dust at 532 nm is between 1.52 and 1.58; its imaginary part is 5-7 × 10-3 and the single scattering albedo is about 0.7-0.75. The aerosol layer of 18 May closest to the surface, that probably contains a mixture of desert dust and marine aerosol, displays a smaller imaginary part (1.2 × 10-3) and a larger single scattering albedo (0.91). The aerosols originating from the North Atlantic and Europe have a real part of the refractive index between 1.35 and 1.49, and an imaginary part ranging from 8 × 10-4 to 1.8 × 10-2; the single scattering albedo at 532 nm (0.78-0.95) is larger than for desert dust values. The smallest value of the single scattering albedo (0.69) corresponds to an airmass originating from North, characterized by a large imaginary part of the refractive index. The asymmetry factor of the desert dust appears consistently larger for the desert dust (0.75-0.8) than for the other cases (0.61-0.72). The extinction-to-backscattering ratio, also derived from the measurements, is about 40 sr for the desert dust, and between 60 and 81 sr for the aerosol of northern origin. Simple estimates of the aerosol average direct shortwave radiative forcing at the top of the atmosphere indicate that all considered aerosol types induce a cooling. The radiative forcing per unit optical depth of the aerosol originating from North is about -37 Wm-2 over ocean and -(12-17) Wm-2 over land, while is -29 Wm-2 over ocean and -8 Wm-2 over land for desert dust. The largest forcing is however produced by the desert aerosols that generally display a considerably larger optical depth.

di Iorio, T.; di Sarra, A.; Junkermann, W.; Cacciani, M.; Fiocco, G.; Fuã, D.

2003-05-01

338

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

339

Sensitivity of aerosol to assumed optical properties over Asia using a global aerosol model and AERONET  

NASA Astrophysics Data System (ADS)

Key variables required for aerosol direct radiative forcing estimates are aerosol optical thickness (AOT), Ångström Exponent (AE) and single scattering albedo (SSA), which are determined not only by aerosol amount but also by physical and optical parameters such as size distribution, hygroscopicity, mixing state of the particles, and refractive index especially of absorbing particles such as black carbon (BC) and dust. As the values of these parameters are often assumed in climate models, we investigate how the variations in these prescribed parameters can explain the differences in AOT, AE and SSA between the simulation by an aerosol global model and the ground-based remote sensing observation, AERONET. We conclude that the differences between our simulations and AERONET observations of AOT, AE and SSA are larger than sampling errors but can be generally explained by the uncertainty of the assumed parameters, although some simulations have clear biases that may be caused by errors in both emission and transport by the model. The uncertainty of sulfate sizes significantly dominates the uncertainty of AOT, AE and SSA, whereas the uncertainty of dust refractive indices and mixing states of organic carbon and BC is dominates the uncertainty of SSA.

Goto, D.; Schutgens, N. A. J.; Nakajima, T.; Takemura, T.

2011-09-01

340

Aerosol particle vertical distributions and optical properties over Singapore  

NASA Astrophysics Data System (ADS)

As part of the Seven Southeast Asian Studies (7SEAS) program, an Aerosol Robotic Network (AERONET) sun photometer and a Micro-Pulse Lidar Network (MPLNET) instrument have been deployed at Singapore to study the regional aerosol environment of the Maritime Continent (MC). Using coincident AERONET Level 2.0 and MPLNET Level 2.0a data from 24 September 2009 to 31 March 2011, the seasonal variability of aerosol particle vertical distributions and optical properties is examined. On average, the bulk (˜65%) of aerosol extinction is found below 1.5 km with substantial aerosol loading (˜35%) above. Possibly due to the transition from El Niño to La Niña conditions and subsequent reduction in fire events, the MPLNET mean integrated aerosol extinction is observed to be the lowest for July-September 2010, which coincides with the typical MC biomass burning season. On the other hand, the highest mean integrated extinctions are derived for January-March 2010 and 2011, which can be attributed to off-season MC biomass burning smoke and anthropogenic pollution. The seasonal lidar ratios also show higher occurrences ?60 sr, which are indicative of biomass burning smoke, for October 2009-June 2010, but such occurrences decrease from July 2010 to March 2011 when La Niña conditions prevail. In addition, principal component analysis (PCA) identifies five primary aerosol vertical profile types over Singapore, i.e. strongly-capped/deep near-surface layer (SCD; 0-1.35 km), enhanced mid-level layer (EML; 1.35-2.4 km), enhanced upper-level layer (EUL; 2.4-3.525 km), deep contiguous layer (DCL; 3.525-4.95 km) and deep multi-layer (DML; >4.95 km). PCA also identifies an off-season MC biomass burning smoke event from 22 February to 8 March 2010, which is subsequently examined in detail.

Chew, Boon Ning; Campbell, James R.; Salinas, Santo V.; Chang, Chew Wai; Reid, Jeffrey S.; Welton, Ellsworth J.; Holben, Brent N.; Liew, Soo Chin

2013-11-01

341

Heterogeneous Photochemistry and Optical Properties of Mineral Dust Aerosol  

NASA Astrophysics Data System (ADS)

It is now widely recognized that heterogeneous reactions of mineral dust aerosol with trace atmospheric gases impact the chemical balance of the atmosphere and the physicochemical properties of these particles. Field studies using single particle analysis, have now shown that the chemistry is mineralogy specific and follows the trends expected from laboratory studies. These laboratory studies, which were initiated over a decade ago, have focused on the nighttime chemistry of mineral dust aerosol which is really only ``half'' the story. This talk will focus on two aspects of solar light interaction with mineral dust aerosol. First, the heterogeneous photochemistry of adsorbed chromophores (e.g. nitrate ion) and light absorbing components of mineral dust (iron oxides and titanium dioxide) is discussed. These heterogeneous photochemical reactions are poorly understood and laboratory studies to better quantify these reactions in order to determine the impact on the chemical balance of the atmosphere are needed, as will be discussed. Second, the optical properties of mineral dust aerosol measured by extinction infrared spectroscopy and visible light scattering show that shape effects are extremely important for mineral dust aerosol.

Grassian, Vicki

2012-02-01

342

Evaluation of aerosol measurements from SAGE II, HALOE, and balloonborne optical particle counters  

Microsoft Academic Search

Stratospheric aerosol measurements from the University of Wyoming balloonborne optical particle counters (OPCs), the Stratospheric Aerosol and Gas Experiment (SAGE) II, and the Halogen Occultation Experiment (HALOE) were compared in the period 1982-2000, when measurements were available. The OPCs measure aerosol size distributions, and HALOE multiwavelength (2.45-5.26 mum) extinction measurements can be used to retrieve aerosol size distributions. Aerosol extinctions

Mark Hervig; Terry Deshler

2002-01-01

343

Evaluation of aerosol measurements from SAGE II, HALOE, and balloonborne optical particle counters  

Microsoft Academic Search

Stratospheric aerosol measurements from the University of Wyoming balloonborne optical particle counters (OPCs), the Stratospheric Aerosol and Gas Experiment (SAGE) II, and the Halogen Occultation Experiment (HALOE) were compared in the period 1982–2000, when measurements were available. The OPCs measure aerosol size distributions, and HALOE multiwavelength (2.45–5.26 ?m) extinction measurements can be used to retrieve aerosol size distributions. Aerosol extinctions

Mark Hervig; Terry Deshler

2002-01-01

344

Investigating the potential applications of a Raman tweezer system  

NASA Astrophysics Data System (ADS)

This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (e=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman spectra obtained from optically trapped samples of polystyrene fluorescent orange, amine-modified latex beads. In addition, I explored the Raman spectra of bulk cytochrome c mixed with or injected onto Ag aggregates for SERs enhancement.

Wray, John Casey

345

Seasonal variability of aerosol optical depth over Indian subcontinent  

USGS Publications Warehouse

Ganga basin extends 2000 km E-W and about 400 km N-S and is bounded by Himalayas in the north. This basin is unequivocally found to be affected by high aerosols optical depth (AOD) (>0.6) throughout the year. Himalayas restricts movement of aerosols toward north and as a result dynamic nature of aerosol is seen over the Ganga basin. High AOD in this region has detrimental effects on health of more than 460 million people living in this part of India besides adversely affecting clouds formation, monsoonal rainfall pattern and Normalized Difference Vegetation Index (NDVI). Severe drought events (year 2002) in Ganga basin and unexpected failure of monsoon several times, occurred in different parts of Indian subcontinent. Significant rise in AOD (18.7%) over the central part of basin (Kanpur region) have been found to cause substantial decrease in NDVI (8.1%) since 2000. A negative relationship is observed between AOD and NDVI, magnitude of which differs from region to region. Efforts have been made to determine general distribution of AOD and its dominant departure in recent years spatially using Moderate Resolution Imaging Spectroradiometer (MODIS) data. The seasonal changes in aerosol optical depth over the Indo-Gangetic basin is found to very significant as a result of the increasing dust storm events in recent years. ?? 2005 IEEE.

Prasad, A. K.; Singh, R. P.; Singh, A.; Kafatos, M.

2005-01-01

346

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

Microsoft Academic Search

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, SO2, NOx, O3), solid components (PM2.5, PM10), as well as ionic species (ammonium, sulfate and nitrate) were measured at several urban and suburban sites. Additional data were collected

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

2007-01-01

347

Comparison of the accuracy of aerosol refractive index measurements from single particle and ensemble techniques.  

PubMed

The ability of two techniques, aerosol cavity ring down spectroscopy (A-CRDS) and optical tweezers, to retrieve the refractive index of atmospherically relevant aerosol was compared through analysis of supersaturated sodium nitrate at a range of relative humidities. Accumulation mode particles in the diameter range 300-600 nm were probed using A-CRDS, with optical tweezer measurements performed on coarse mode particles several micrometers in diameter. A correction for doubly charged particles was applied in the A-CRDS measurements. Both techniques were found to retrieve refractive indices in good agreement with previously published results from Tang and Munkelwitz, with a precision of ±0.0012 for the optical tweezers and ±0.02 for the A-CRDS technique. The coarse mode optical tweezer measurements agreed most closely with refractive index predictions made using a mass-weighted linear mixing rule. The uncertainty in the refractive index retrieved by the A-CRDS technique prevented discrimination between predictions using both mass-weighted and volume-weighted linear mixing rules. No efflorescence or kinetic limitations on water transport between the particle and the gas phase were observed at relative humidities down to 14%. The magnitude of the uncertainty in refractive index retrieved using the A-CRDS technique reflects the challenges in determining particle optical properties in the accumulation mode, where the extinction efficiency varies steeply with particle size. PMID:22856537

Mason, Bernard J; King, Simon-John; Miles, Rachael E H; Manfred, Katherine M; Rickards, Andrew M J; Kim, Jin; Reid, Jonathan P; Orr-Ewing, Andrew J

2012-08-23

348

A theoretical potential-well model of acoustic tweezers  

Microsoft Academic Search

Standing wave acoustic tweezers have been popularly used in non-invasive and non-contact particle manipulation. With better penetration ability in biological tissue, acoustic tweezers has the promising potential for in-vivo study. However, the dual-beam configuration has many limits on operation and system setup. A single-beam trapping model is thus preferable. According to the concept of optical vortex, we propose an acoustics-vortex

Shih-Tsung Kang; Chih-Kuang Yeh

2009-01-01

349

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

350

Influence of aerosol hygroscopic growth parameterization on aerosol optical depth and direct radiative forcing over East Asia  

NASA Astrophysics Data System (ADS)

The influence of aerosol hygroscopic growth parameterization on aerosol optical depth (AOD) and aerosol direct radiative forcing (ADRF) over East Asia is investigated by using an online coupled regional climate-chemistry/aerosol model (RIEMS-Chemaero) focusing on the period of summer 2006. Three aerosol hygroscopic growth schemes are tested in this study. Model performances are evaluated with ground observations and satellite retrievals. Comparison with observations of aerosol concentration demonstrates that the model is able to reproduce the spatial and temporal variations of aerosol components over East Asia. Model comparison with AOD measurements shows that AOD is best predicted by the aerosol hygroscopic growth scheme developed based on observations in China (Case B), and the aerosol hygroscopic growth affects AOD simulation significantly. In this study, the domain and seasonal mean AOD, ADRF at the top of the atmosphere, and ADRF at the surface over East Asia are estimated to be 0.31, ? 9 W/m2, and ? 29 W/m2 by Case B, respectively. Compared with Case B, the estimations from Case A (scheme from CCM3 radiation package) differ by + 71%, + 100%, and + 17%, respectively, while those from Case C (? parameterization) differ by ? 16%, + 11%, and ? 17%. The large differences in AOD and ADRF among cases suggest the necessity to develop appropriate hygroscopic growth parameterization with geographical characteristics in climate model for estimating regional aerosol optical properties and radiative effects.

Li, Jiawei; Han, Zhiwei; Zhang, Renjian

2014-04-01

351

Estimation of Aerosol Optical Thickness of Multi-Layered Aerosol Using Satellite Data during ACE-Asia  

NASA Astrophysics Data System (ADS)

Characterization of the aerosol optical thickness (AOT) and other optical properties is one of the key objectives of satellite observations of atmospheric environment. The quality of satellite aerosol retrieval depends critically upon the modeling accuracy of the physical and optical properties of aerosol such as single scattering albedo, phase function, refractive index, size distribution, and vertical profile. Manny current satellite aerosol retrieval algorithms use a standard vertical aerosol profile assumed in radiative transfer models. LIDAR measurements during ACE-Asia IOP showed that the aerosol profile of Asian dust was multi-layered. SeaWiFS and MODIS data over Gosan, Jeju Island, Korea which was the ACE-Asia super site (33d17m N, 126d09m E) were used in this analysis along with collocated LIDAR data. Results of satellite data analysis shows that accuracy of SeaWiFS AOT was influenced by the presence of multi-layer aerosol. The results of this study will allow better interpretation of satellite aerosol retrievals and characterization of the radiative impacts of aerosol on atmospheric radiation budget. Acknowledgments This work was supported in part by the Korea Science and Engineering Foundation (KOSEF) through the Advanced Environmental Monitoring Research Center (ADEMRC) at Kwangju Institute of Science and Technology (K-JIST)

Kim, Y. J.; Lee, K. H.; Hong, C. S.; Hoyningen-Huene, W. V.

2003-12-01

352

Evaluating UVA aerosol optical depth using a smartphone camera.  

PubMed

This research evaluates a smartphone complementary metal oxide semiconductor (CMOS) image sensor's ability to detect and quantify incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies revealed that the consumer grade CMOS sensor has inherent UVA sensitivities, despite attenuating effects of the lens. Narrow bandpass and neutral density filters were used to protect the image sensor and to not allow saturation of the solar images produced. Observations were made on clear days, free from clouds. The results of this research demonstrate that there is a definable response to changing solar irradiance and aerosol optical depth can be measured within 5% and 10% error margins at 380 and 340 nm respectively. The greater relative error occurs at lower wavelengths (340 nm) due to increased atmospheric scattering effects, particularly at higher air masses and due to lower signal to noise ratio in the image sensor. The relative error for solar irradiance was under 1% for observations made at 380 nm. The results indicate that the smartphone image sensor, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate solar UVA irradiance and aerosol optical depth. PMID:23581749

Igoe, Damien P; Parisi, Alfio V; Carter, Brad

2013-01-01

353

Nighttime Aerosol Optical Depth Variability From Astronomical Photometry  

NASA Astrophysics Data System (ADS)

A technique for determination of the short-term (6 minutes intervals) variability of the aerosol optical depth (AOD) during nighttime from broadband visible measurements of star irradiances during clear nights was developed for the instrument called the Whole Sky Imager (WSI), placed at the Atmospheric Radiation Measurement (ARM) observation site in Oklahoma. The AOD is inferred indirectly from simultaneous observations of extinction of stars having different colors (spectra) and different elevations above the horizon, and takes into account the other sources for starlight attenuation in the atmosphere which might be present and which are measured by other instruments at the site at compatible timescales (e.g., precipitable water vapor content, columnar ozone amount, observed atmospheric stratification). The total error of the new method is a combination of the absolute star flux measurement error with the WSI and a systematic error in the models assumed for the other atmospheric components causing the starlight extinction. The relative error in the aerosol optical depth determined through this method is found to be below 4%. For the validation of the results, the comparison of the aerosol optical depth measured with the Lidar at 10 minutes intervals (at 355nm) with the AOD determined from WSI (in visible) shows a good agreement for the data in the interval studied (1999-2003).

Musat, I. C.; Ellingson, R. G.

2006-12-01

354

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

SciTech Connect

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

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

2008-04-14

355

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

Microsoft Academic Search

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

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

2010-01-01

356

Aerosol optical depth increase in partly cloudy conditions  

NASA Astrophysics Data System (ADS)

Remote sensing observations of aerosol from surface and satellite instruments are extensively used for atmospheric and climate research. From passive sensors, the apparent cloud-free atmosphere in the vicinity of clouds often appears to be brighter than further away from the clouds, leading to an increase in the retrieved aerosol optical depth (?). Mechanisms contributing to this enhancement or increase, including contamination by undetected clouds, hygroscopic growth of aerosol particles, and meteorological conditions, have been debated in recent literature, but the extent to which each of these factors influence the observed enhancement (??) is poorly known. Here we used 11 years of daily global observations at 10 × 10 km2 resolution from the MODIS on the NASA Terra satellite to quantify ? as a function of cloud fraction (CF). Our analysis reveals that, averaged over the globe, the clear sky ? is enhanced by ?? = 0.05 in cloudy conditions (CF = 0.8-0.9). This enhancement in ?? corresponds to relative enhancement of 25% in cloudy conditions (CF = 0.8-0.9) compared with relatively clear conditions (CF = 0.1-0.2). Unlike the absolute enhancement ??, the relative increase in ?is rather consistent in all seasons and is 25-35% in the subtropics and 15-25% at mid and higher latitudes. Using a simple Gaussian probability density function model to connect cloud cover and the distribution of relative humidity, we argue that much of the enhancement is consistent with aerosol hygroscopic growth in the humid environment surrounding clouds. Consideration of these cloud-dependent?effects will facilitate understanding aerosol-cloud interactions and reduce the uncertainty in estimates of aerosol radiative forcing by global climate models.

Chand, Duli; Wood, Robert; Ghan, Steven J.; Wang, Minghuai; Ovchinnikov, Mikhail; Rasch, Philip J.; Miller, Steven; Schichtel, Bret; Moore, Tom

2012-09-01

357

Single-sided lateral-field and phototransistor-based optoelectronic tweezers  

NASA Technical Reports Server (NTRS)

Described herein are single-sided lateral-field optoelectronic tweezers (LOET) devices which use photosensitive electrode arrays to create optically-induced dielectrophoretic forces in an electric field that is parallel to the plane of the device. In addition, phototransistor-based optoelectronic tweezers (PhOET) devices are described that allow for optoelectronic tweezers (OET) operation in high-conductivity physiological buffer and cell culture media.

Ohta, Aaron (Inventor); Chiou, Pei-Yu (Inventor); Hsu, Hsan-Yin (Inventor); Jamshidi, Arash (Inventor); Wu, Ming-Chiang (Inventor); Neale, Steven L. (Inventor)

2011-01-01

358

Direct measurements of the axial displacement and evolving size of optically trapped aerosol droplets  

Microsoft Academic Search

The axial displacement of optically tweezed liquid aerosol droplets has been studied directly through the application of side imaging at 90 to the trapping laser beam. In conjunction with imaging in the plane of the optical trap and cavity-enhanced Raman spectroscopy (CERS), the optical forces experienced by a trapped aerosol have been interrogated. By varying the power of the trapping

K J Knox; J P Reid; K L Hanford; A J Hudson; L Mitchem

2007-01-01

359

Direct measurements of the axial displacement and evolving size of optically trapped aerosol droplets  

Microsoft Academic Search

The axial displacement of optically tweezed liquid aerosol droplets has been studied directly through the application of side imaging at 90° to the trapping laser beam. In conjunction with imaging in the plane of the optical trap and cavity-enhanced Raman spectroscopy (CERS), the optical forces experienced by a trapped aerosol have been interrogated. By varying the power of the trapping

K. J. Knox; J. P. Reid; K. L. Hanford; A. J. Hudson; L. Mitchem

2007-01-01

360

Validation of MODIS retrieval aerosol optical depth and an investigation of aerosol transport over Mohal in north western Indian Himalaya  

Microsoft Academic Search

This study deals with the optical properties of aerosols during 2007 over Mohal (31.9º N, 77.12º E) in north western Indian Himalaya, investigated using ground-based measurements and multi-satellite data. The daily average (mean ± standard deviation) aerosol optical depth (AOD) at 500 nm, Ångström exponent and turbidity coefficient values were 0.2 ± 0.1, 1.1 ± 0.3 and 0.1 ± 0.1,

Raj Paul Guleria; Jagdish Chandra Kuniyal; Pan Singh Rawat; Harinder Kumar Thakur; Manum Sharma; Nand Lal Sharma; Pitamber Prasad Dhyani; Mahavir Singh

2012-01-01

361

Aerosol optical properties at Lampedusa (Central Mediterranean). 1. Influence of transport and identification of different aerosol types  

Microsoft Academic Search

Aerosol optical depth and Ångström exponent were obtained from multi filter rotating shadowband radiometer (MFRSR) observations carried out at the island of Lampedusa, in the Central Mediterranean, in the period July 2001-September 2003. The average aerosol optical depth at 495.7 nm, tau, is 0.24±0.14; the average Ångström exponent, alpha, is 0.86±0.63. The observed values of tau range from 0.03 to

G. Pace; A. di Sarra; D. Meloni; S. Piacentino; P. Chamard

2006-01-01

362

Aerosol optical properties at Lampedusa (Central Mediterranean). 2. Determination of single scattering albedo at two wavelengths for different aerosol types  

Microsoft Academic Search

Aerosol optical properties were retrieved from direct and diffuse spectral irradiance measurements made by a multi-filter rotating shadowband radiometer (MFRSR) at the island of Lampedusa (35.5° N, 12.6° E), in the Central Mediterranean, in the period July 2001-September 2003. In a companion paper (Pace et al., 2006) the aerosol optical depth (AOD) and Ångström exponent were used together with airmass

D. Meloni; A. di Sarra; G. Pace; F. Monteleone

2006-01-01

363

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

364

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

365

Microphysical and optical properties of aerosol particles in urban zone during ESCOMPTE  

Microsoft Academic Search

Microphysical and optical properties of the main aerosol species on a peri-urban site have been investigated during the ESCOMPTE experiment. Ammonium sulfate (AS), nitrate (N), black carbon (BC), particulate organic matter (POM), sea salt (SS) and mineral aerosol (D) size distributions have been used, associated with their refractive index, to compute, from the Mie theory, the key radiative aerosol properties

M. Mallet; J. C. Roger; S. Despiau; O. Dubovik; J. P. Putaud

2003-01-01

366

Tropospheric Aerosol Optical Thickness from the GOCART Model and Comparisons with Satellite and Sun Photometer Measurements  

Microsoft Academic Search

The Georgia Institute of Technology-Goddard Global Ozone Chemistry Aerosol Radiation and Transport (GOCART) model is used to simulate the aerosol optical thickness for major types of tropospheric aerosols including sulfate, dust, organic carbon (OC), black carbon (BC), and sea salt. The GOCART model uses a dust emission algorithm that quantifies the dust source as a function of the degree of

Mian Chin; Paul Ginoux; Stefan Kinne; Omar Torres; Brent N. Holben; Bryan N. Duncan; Randall V. Martin; Jennifer A. Logan; Akiko Higurashi; Teruyuki Nakajima

2002-01-01

367

Physical and optical properties of aerosols over an urban location in western India: Seasonal variabilities  

Microsoft Academic Search

We present results on various physical and optical properties of aerosols measured over Ahmedabad, an urban location in western India, from 2002 to 2005 and discuss their seasonal and interannual variabilities. Aerosol parameters which have been studied include AOD spectra, aerosol mass concentration, size distribution, BC concentration, wavelength dependency in absorption, scattering coefficient, single scattering albedo and their vertical distribution

Dilip Ganguly; A. Jayaraman; H. Gadhavi

2006-01-01

368

Relation between optical and chemical properties of dust aerosol over Beijing, China  

Microsoft Academic Search

Characteristics of optical and chemical properties of dust aerosol over Beijing and their relation were studied in the spring dust season, 2006 to understand the impact of dust and anthropogenic aerosol on the regional climate. Two dust plumes (DS1 and DS2) were identified with contrasting physicochemical properties. Strong absorbing of aerosol at 439 nm was observed, probably due to the

Kan Huang; Guoshun Zhuang; Yanfen Lin; Juan Li; Yele Sun; Wenjie Zhang; Joshua S. Fu

2010-01-01

369

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

370

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 (NH4)2SO4,

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

1976-01-01

371

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

372

Aerosol Characteristics at a High Altitude Location in Central Himalayas: Optical Properties and Radiative Forcing  

Microsoft Academic Search

Collocated measurements of the mass concentrations of aerosol black carbon\\u000a(BC) and composite aerosols near the surface were carried out along with\\u000aspectral aerosol optical depths (AODs) from a high altitude station, Manora\\u000aPeak in Central Himalayas, during a comprehensive aerosol field campaign in\\u000aDecember 2004. Despite being a pristine location in the Shivalik Ranges of\\u000aCentral Himalayas, and having

P. Pant; P. Hegde; U. C. Dumka; Ram Sagar; S. K. Satheesh; K. Krishna Moorthy

2006-01-01

373

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

NASA Astrophysics Data System (ADS)

The column-integrated optical properties of aerosol in the central eastern region of Asia and midtropical Pacific were investigated based on Sun/sky radiometer measurements made at Aerosol Robotic Network (AERONET) sites in these regions. Characterization of aerosol properties in the Asian region is important due to the rapid growth of both population and economic activity, with associated increases in fossil fuel combustion, and the possible regional and global climatic impacts of related aerosol emissions. Multiyear monitoring over the complete annual cycle at sites in China, Mongolia, South Korea, and Japan suggest spring and/or summer maximum in aerosol optical depth (?a) and a winter minimum; however, more monitoring is needed to establish accurate climatologies. The annual cycle of Angstrom wavelength exponent (?) showed a springtime minimum associated with dust storm activity; however, the monthly mean ?440-870 was >0.8 even for the peak dust season at eastern Asian sites suggesting that fine mode pollution aerosol emitted from population centers in eastern Asia dominates the monthly aerosol optical influence even in spring as pollution aerosol mixes with coarse mode dust originating in western source regions. Aerosol optical depth peaks in spring in the tropical mid-Pacific Ocean associated with seasonal shifts in atmospheric transport from Asia, and ˜35% of the springtime ?a500 enhancement occurs at altitudes above 3.4 km. For predominately fine mode aerosol pollution cases, the average midvisible (˜550 nm) single scattering albedo (?0) at two continental urban sites in China averaged ˜0.89, while it was significantly higher, ˜0.93, at two relatively rural coastal sites in South Korea and Japan. Differences in fine mode absorption between these regions may result from a combination of factors including aerosol aging during transport, relative humidity differences, sea salt at coastal sites, and fuel type and combustion differences in the two regions. For cases where ?a was predominately coarse mode dust aerosol in the spring of 2001, the absorption was greater in eastern Asia compared to the source regions, with ?0 at Dunhuang, China (near to the major Taklamakan dust source), ˜0.04 higher than at Beijing at all wavelengths, and Anmyon, South Korea, showing an intermediate level of absorption. Possible reasons for differences in dust absorption magnitude include interactions between dust and fine mode pollution aerosol and also variability of dust optical properties from different source regions in China and Mongolia.

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

2005-03-01

374

Investigation of aerosol optical properties in Bangkok and suburbs  

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

375

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

Microsoft Academic Search

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,

V. N. Uzhegov; V. S. Kozlov; M. V. Panchenko; Yu. A. Pkhalagov; V. V. Polkin; S. A. Terpugova; V. P. Shmargunov; E. P. Yausheva

2005-01-01

376

Aerosol Size Distributions Obtained by Inversions of Spectral Optical Depth Measurements  

Microsoft Academic Search

Columnar aerosol size distributions have been inferred by numerically,inverting particulate optical depth measurements as a function of wavelength. An inversion formula which explicitly includes the magnitude of the measurement variances is derived and applied to optical depth measurements obtained in Tucson with a solar radiometer. It is found that the individual size distributions of the aerosol particles (assumed spher- ical),

Michael D. King; Dale M. Byrne; Benjamin M. Herman; John A. Reagan

1978-01-01

377

Aerosol optical depth during episodes of Asian dust storms and biomass burning at Kwangju, South Korea  

Microsoft Academic Search

Spectral daily aerosol optical depths (?a?) estimated from a multi-filter radiometer over Kwangju were analyzed from January 1999 to August 2001 (total of 277 days). Optical depths obtained showed a pronounced temporal trend, with maximum dust loading observed during spring time and biomass burning aerosol in early summer and autumn of each year. Result indicates that ?a501nm increased from spring

K. O Ogunjobi; Z He; K. W Kim; Y. J Kim

2004-01-01

378

Retrieval of aerosol optical thickness over snow using AATSR observations  

NASA Astrophysics Data System (ADS)

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 contrast between clouds and surface in visible range of spectrum, and additional infrared chan-nels are not always available. Luckily, AATSR instrument onboard ENVISAT has necessary features to solve both of these problems. In current work we present an improved version of discussed earlier [1,2] dual-view algorithm to retrieve AOT over snow. The retrieval algorithm still consists of cloud screening, based on spectral shape analysis of AATSR pixel in order to extract clear snow pixels, and of AOT retrieval over snow and water. Current version of AOT retrieval over open ocean now contains improved accounting for ocean reflectance (in previous version the ocean was assumed to be absolutely black). The AOT retrieval over snow has been improved to account more accurately for the bidirectional features of the surface reflection function. For this we now use the approach described in [4] instead of [3], which has been used in the previous version of the retrieval. The accuracy of both approaches [3] and [4] has been evaluated via comparison to forward radiative-transfer model for the case of a very bright surface. The new algorithm has been applied to various scenes in European Arctic and Alaska in different scales, up to global AOT maps. The correspondence of AOT over snow to AOT over water is quite good, which proves the reliability of the retrieval. The algorithm has been validated against AERONET and other Arctic ground based AOT data and shows reasonably good correlation. The presented cloud screening method has been validated via comparison to MODIS cloud mask and Micro Pulse Lidar data. 1. L.G. Istomina, W. Von Hoyningen-Huene, A.A.Kokhanovsky, V.V. Rozanov, M. Schreier, K. Dethloff, M.Stock, R. Treffeisen, A. Herber, J.P.Burrows (2008). Sensitivity study of the dual-view algorithm for aerosol optical thickness retrieval over snow and ice, Proceedings of the 2nd MERIS/(A)ATSR User Workshop, 22-26 September 2008, ESRIN, Frascati, Italy. 2. L.G. Istomina, W. Von Hoyningen-Huene, A.A. Kokhanovsky, J.P. Burrows (2009) Retrieval of aerosol optical thickness in Arctic region using dual-view AATSR observations, Proceedings of ESA Atmospheric Science Conference, 9-11 September 2009, Barcelona, Spain. 3. Y.R. Kaufman, D. Tanre, H.R. Gordon, T. Nakajima, J. Lenoble, R. Frouin, H. Grassl, B.M. Herman, M.D. King, P.M. Teillet (1997) Passive remote sensing of tropospheric aerosol and atmorpheric correction for the aerosol effect. J. Geophys. Res. 102, 16.815-16.830 4. D.Tanre, M. Herman, P.Y.Deschamps, A. De Leffe (1979) Atmosperic modeling for space measurements of ground reflectances, including bidirectional properties. Appl. Optics, 18, 21. 3587-3594

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

379

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

NASA Astrophysics Data System (ADS)

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 ?m. These provide constraints on the real and imaginary refractive indices, as required for both scattering and absorbing particles. We will also demonstrate the application of this approach to ACE-Asia and TRACE-P data. The size distribution during ACE-Asia was measured by Optical Particle Counter (OPC, custom LAS-X, Particle Measurement Systems) with thermal analysis at 150°C and 300°C that inferred the volatile and refractory components of the particles. Calibrations of this optical measurement based upon wide-angle scattering provided the optically effective diameters of particles sized by the OPC rather than physical diameters. This allows direct Mie modeling of optical properties and reduces related uncertainties common to instruments that size particles based on other techniques (eg. aerodynamic - problematic for nonspherical particles and uncertain refractive index; forward scattering instruments - uncertain for large aerosol and very sensitive to refractive index ; impactors - uncertainties due to size cuts and inversions and refractive index; etc.). These optically effective size distributions are then used in the following manner: 1) Integration of optical sizes over scattering angles seen by a nephelometer provides a direct closure without having to make estimated nephelometer truncation corrections. For large particle dust events these approaches indicate that standard truncation corrections for nephelometer data appear to underestimate required corrections. 2) Volatility is related to concurrently measured soluble species (PILS-particle in liquid sampler, R. Weber) providing chemical characterization and associated refractive indices for the volatile component. This also allows correction of effective optical sizes to actual physical sizes if needed. 3) Submicrometer refractory (300°C) component is linked to the absorbing soot and dust components to refine effective refractive index for this size class. 4) The calculated optical properties enable us to provide a constrained estimate of the actual refractive indices of the dust and soot components through comparison with direct measurements of scattering by nephelometer and absorption by Particle Soot Absorption Photometer (PSAP). 5) If measurements such as f(RH) are available, this size-resolved volatility can also be used to predict this humidity response and confirming the approach for modeling properties at ambient humidity as required for closure and satellite comparisons.

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

2002-12-01

380

Comparison of CALIOP and MODIS aerosol optical depths for aerosol types over the ocean  

NASA Astrophysics Data System (ADS)

The aerosol optical depth (AOD) obtained by vertical integration of the CALIOP (The Cloud-Aerosol Lidar with Orthogonal Polarization) level 2 aerosol extinction coefficient at 532 nm is compared with AOD from MODIS (The Moderate Resolution Imaging Spectroradiometer)-Aqua level 2 product at 550 nm for five aerosol subtypes (clean marine, dust, polluted dust, polluted continental, and biomass burning) identified by CALIOP algorithm over the ocean from June 2006 to December 2010. The mean AOD of MODIS (0.108±0.081) for all collocated dataset is 61% higher than that of CALIOP (0.067±0.074). The difference of AOD between CALIOP and MODIS for five aerosol types and potential reasons for the difference are discussed. (i) Clean marine: For the clean marine, which accounts for 84% of total collocated dataset, the mean AOD of MODIS (0.107±0.066) is almost twice higher than CALIOP (0.056±0.041) having strong latitude dependency related with surface wind speed over the ocean. The difference of AOD increases up to ~0.074 (MODIS AOD minus CALIOP AOD) at 52°S where the surface wind speed is maximum, while the difference is ~0.030 at 32°S where the surface wind speed is minimum. (ii) Dust: The difference of AOD between two sensors for dust (~12.4%) is smallest among five aerosols types but shows regional variation. CALIOP AOD is similar or even slightly higher than MODIS AOD for the dust from Saharan and Arabian deserts, whereas CALIOP AOD for the Asian dust is much less than MODIS AOD. This result suggests that the Asian dust is often mixed with polluted aerosols, thus the lidar ratio for the Asian dust would be higher than current value used in CALIOP algorithm. The difference of AOD for dust also shows distinguishable dependency on the layer mean of particulate depolarization ratio (?). The lidar ratio for dust should increase as ? increases to reduce the AOD difference between two sensors. (iii) Polluted dust and polluted continental: The differences of AOD for polluted dust and polluted continental show similar results; the number of collocated datasets is still high over the remote ocean far from their source region, and CALIOP AOD is overestimated compared to MODIS for most part of the ocean. One of possible reasons for the difference is misclassification of clean marine as polluted dust and polluted continental in CALIOP algorithm. (iv) Biomass burning: The uncertainty on the determination of base altitude for the biomass burning layer is thought to be one of the main reasons for the underestimation of CALIOP AOD because all the biomass burning layers are elevated layers in the CALIOP algorithm. Moreover, for more than 70% of biomass burning cases, the marine boundary layer is excluded for the aerosol extinction retrieval.

Kim, M.; Yoon, S.; Kim, S.; Omar, A. H.

2012-12-01

381

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

382

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

NASA Astrophysics Data System (ADS)

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

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

2003-10-01

383

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

NASA Technical Reports Server (NTRS)

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

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

2012-01-01

384

Hemoglobin degradation in human erythrocytes with long-duration near-infrared laser exposure in Raman optical tweezers  

NASA Astrophysics Data System (ADS)

Near-infrared laser (785-nm)-excited Raman spectra from a red blood cell, optically trapped using the same laser beam, show significant changes as a function of trapping duration even at trapping power level of a few milliwatts. These changes in the Raman spectra and the bright-field images of the trapped cell, which show a gradual accumulation of the cell mass at the trap focus, suggest photoinduced aggregation of intracellular heme. The possible role of photoinduced protein denaturation and hemichrome formation in the observed aggregation of heme is discussed.

Dasgupta, Raktim; Ahlawat, Sunita; Verma, Ravi Shanker; Uppal, Abha; Gupta, Pradeep Kumar

2010-09-01

385

Albedo Measurements and Optical Sizing of Single Aerosol Particles  

Microsoft Academic Search

Aerosols play an important role in global climate change by their interactions with incoming solar radiation and outgoing longwave radiation from the planetary surface. The climate effects of aerosols depend on their scattering and absorption properties. This article describes the development of an instrument (ASTER: Aerosol Scattering To Extinction Ratio) that simultaneously measures the scattering and extinction of single aerosol

Todd J. Sanford; Daniel M. Murphy; David S. Thomson; Richard W. Fox

2008-01-01

386

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

387

Validation of stratospheric aerosol and gas experiments 1 and 2 satellite aerosol optical depth measurements using surface radiometer data  

NASA Technical Reports Server (NTRS)

The stratospheric aerosol measurement 2, stratospheric aerosol and gas experiment (SAGE) 1, and SAGE 2 series of solar occultation satellite instruments were designed for the study of stratospheric aerosols and gases and have been extensively validated in the stratosphere. They are also capable, under cloud-free conditions, of measuring the extinction due to aerosols in the troposphere. Such tropospheric extinction measurements have yet to be validated by appropriate lidar and in situ techniques. In this paper published atmospheric aerosol optical depth measurements, made from high-altitude observatories during volcanically quiet periods, have been compared with optical depths calculated from local SAGE 1 and SAGE 2 extinction profiles. Surface measurements from three such observatories have been used, one located in Hawaii and two within the continental United States. Data have been intercompared on a seasonal basis at wave-lenths between 0.5 and 1.0 micron and found to agree within the range of measurement errors and expected atmospheric variation. The mean rms difference between the optical depths for corresponding satellite and surface measured data sets is 29%, and the mean ratio of the optical depths is 1.09.

Kent, G. S.; Mccormick, M. P.; Wang, P.-H.

1994-01-01

388

Climatology of aerosol optical properties at ACRF sites in the tropical warm pool region  

NASA Astrophysics Data System (ADS)

long-term multifilter rotating shadowband radiometer measurements at three Atmospheric Radiation Measurements Climate Research Facility sites of Darwin, Nauru, and Manus have been processed to develop the climatology of aerosols in the tropical warm pool region at the interannual, seasonal, and diurnal temporal scales. Due to their unique geolocations and associated large-scale circulation patterns, aerosols at the Nauru site exhibit background oceanic characteristics (strongly correlated with the sea surface wind), aerosols at the Darwin site show strong influences by biomass-burning aerosols, particularly in the dry season, and aerosols at the Manus site have climatologic characteristics in between the Darwin and Nauru sites. There are no obvious trends of aerosol loading for past decades at all three sites. El Niño/Southern Oscillation has its impacts on aerosol optical depth, as well as particle size and composition, at all three sites. Madden-Julian Oscillation modulates aerosol optical depth at the Manus and Nauru sites along the equator but has no apparent impact at the Darwin site. The annual or seasonal variation of aerosols is closely linked with Indo-Australian monsoons, exhibiting wet and dry season differences. The aerosol loading is significant lower with relatively larger particles in the wet season than in the dry season. There are significant diurnal cycles in both aerosol optical depth and Angstrom exponent at the Darwin site: low values of aerosol optical depth and Angstrom exponent in the midday and the two peaks in the early morning and late afternoon. There are noticeable changes between the dry and wet seasons. The amplitude of diurnal variation during La Niña periods is greater than that during El Niño periods. However, there are no significant diurnal variations of aerosol loading at the Manus and Nauru sites.

Yin, Bangsheng; Min, Qilong

2013-03-01

389

Quantitative retrieval of aerosol optical thickness from FY-2 VISSR data  

NASA Astrophysics Data System (ADS)

Atmospheric aerosol, as particulate matter suspended in the air, exists in a variety of forms such as dust, fume and mist. It deeply affects climate and land surface environment in both regional and global scales, and furthermore, lead to be hugely much influence on human health. For the sake of effectively monitoring it, many atmospheric aerosol observation networks are set up and provide associated informational services in the wide world, as well-known Aerosol robotic network (AERONET), Canadian Sunphotometer Network (AeroCan) and so forth. Given large-scale atmospheric aerosol monitoring, that satellite remote sensing data are used to inverse aerosol optical depth is one of available and effective approaches. Nowadays, special types of instruments aboard running satellites are applied to obtain related remote sensing data of retrieving atmospheric aerosol. However, atmospheric aerosol real-timely or near real-timely monitoring hasn't been accomplished. Nevertheless, retrievals, using Fengyun-2 VISSR data, are carried out and the above problem resolved to certain extent, especially over China. In this paper, the authors have developed a new retrieving model/mode to retrieve aerosol optical depth, using Fengyun-2 satellite data that were obtained by the VISSR aboard FY-2C and FY-2D. A series of the aerosol optical depth distribution maps with high time resolution were able to obtained, is helpful for understanding the forming mechanism, transport, influence and controlling approach of atmospheric aerosol.

Bai, Linyan; Xue, Yong; Cao, Chunxiang; Feng, Jianzhong; Zhang, Hao; Guang, Jie; Wang, Ying; Li, Yingjie; Mei, Linlu; Ai, Jianwen

2009-09-01

390

Development of algorithm for retrieving aerosol optical properties from Geostationary Environmental Monitoring Spectrometer (GEMS)  

NASA Astrophysics Data System (ADS)

A scanning UV-Visible Spectrometer, GEMS (Geostationary Environment Spectrometer) is planned to be launched in 2018 onboard a geostationary satellite, GeoKOMPSAT(Geostationary Korea Multi-Purpose SATellite by KARI(Korea Aerospace Research Institute). The hyper-spectral data which have finer resolution in both respects of time and space measured from GEMS is expected to contribute to better scientific understanding on the distribution and optical properties of aerosol over Asia. In this study, we present UV-VIS algorithm using multiple-wavelength reflectance in 350-500 nm to retrieve the aerosol optical properties such as aerosol optical depth (AOD) and aerosol type. The algorithm adopts inversion method and pre-calculated look-up table (LUT) for a set of assumed aerosol models which are analyzed from inversion data of Aerosol Robotic Network (AERONET) located in the target areas. Major aerosol types representing dust and absorbing/non-absorbing anthropogenic aerosols are constructed and used for the calculation of LUT. The algorithm is tested with measured reflectance from OMI, a provisional data stand in for GEMS measurement, and retrieved AOD and aerosol type show reasonable distribution. Also, additional improvement to obtain aerosol products using hyper-spectral UV-VIS measurements is discussed.

KIM, M.; Kim, J.; Lee, H.

2012-12-01

391

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

392

Aerosol optical depth during episodes of Asian dust storms and biomass burning at Kwangju, South Korea  

NASA Astrophysics Data System (ADS)

Spectral daily aerosol optical depths (? a ?) estimated from a multi-filter radiometer over Kwangju were analyzed from January 1999 to August 2001 (total of 277 days). Optical depths obtained showed a pronounced temporal trend, with maximum dust loading observed during spring time and biomass burning aerosol in early summer and autumn of each year. Result indicates that ? a501 nm increased from spring average of 0.45±0.02 to values >0.7 on 7 April 2000, and 13 April 2001. Daily mean spectral variations in the Ångström exponents ? were also computed for various episode periods under consideration. A dramatic change in ? value is noted especially at high aerosol optical depth when coarse mode aerosol dominates over the influence of accumulation-mode aerosol. High values of ? a ? associated with high values of ? in early June and October are characteristics of smoke aerosol predominantly from biomass burning aerosol. Also, volume size distribution is investigated for different pollution episodes with result indicating that the peak in the distribution of the coarse mode volume radius and fine mode particles of dust and biomass-burning aerosol respectively increases as aerosol optical depth increases at Kwangju. Air-mass trajectory were developed on 7-8 April and 19-20 October, 2000 to explain the transport of Asian dust particle and biomass burning to Kwangju.

Ogunjobi, K. O.; He, Z.; Kim, K. W.; Kim, Y. J.

393

Aerosol optical properties over east Asia determined from ground-based sky radiation measurements  

Microsoft Academic Search

Aerosol optical properties (aerosol optical thickness, Ångström exponent, size distribution, and single scattering albedo) over east Asia were examined using long-term measurements of sky radiation at Mandalgovi, Dunhuang, Yinchuan, and Sri-Samrong sites of the Skyradiometer Network (SKYNET). Also included were sky radiation measurements at Anmyon, Gosan in Korea, and Amami-Oshima in Japan during April for examining optical properties of Asian

Do-Hyeong Kim; Byung-Ju Sohn; Teruyuki Nakajima; Tamio Takamura; Toshihiko Takemura; Byoung-Cheol Choi; Soon-Chang Yoon

2004-01-01

394

Measurement of Aerosol Optical Property in Hong Kong Rural Area  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

395

Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer  

NASA Astrophysics Data System (ADS)

The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm?1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

2014-06-01

396

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

397

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

Microsoft Academic Search

Application of cavity ring down (CRD) spectrometry for measuring the optical properties of pure and mixed laboratory-generated aerosols is presented. The extinction coefficient (alphaext), extinction cross section (sigmaext) 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

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

2007-01-01

398

Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source  

NASA Astrophysics Data System (ADS)

A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands are selected from the continuous spectrum of the laser (ranging from 400-2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

Sharma, N.; Arnold, I. J.; Moosmüller, H.; Arnott, W. P.; Mazzoleni, C.

2013-12-01

399

Photoacoustic and nephelometric spectroscopy of aerosol optical properties with a supercontinuum light source  

NASA Astrophysics Data System (ADS)

A novel multi-wavelength photoacoustic-nephelometer spectrometer (SC-PNS) has been developed for the optical characterization of atmospheric aerosol particles. This instrument integrates a white light supercontinuum laser with photoacoustic and nephelometric spectroscopy to measure aerosol absorption and scattering coefficients at five wavelength bands (centered at 417, 475, 542, 607, and 675 nm). These wavelength bands were selected from the continuous spectrum of the laser (ranging from 400-2200 nm) using a set of optical interference filters. Absorption and scattering measurements on laboratory-generated aerosol samples were performed sequentially at each wavelength band. To test the instrument we measured the wavelength dependence of absorption and scattering coefficients of kerosene soot and common salt aerosols. Results were favorably compared to those obtained with a commercial 3-wavelength photoacoustic and nephelometer instrument demonstrating the utility of the SC light source for studies of aerosol optical properties at selected wavelengths. Here, we discuss instrument design, development, calibration, performance and experimental results.

Sharma, N.; Arnold, I. J.; Moosmüller, H.; Arnott, W. P.; Mazzoleni, C.

2013-07-01

400