CiteULike: rodney's library [1280 articles]

Confocal micro-Raman spectroscopy of single biological cells using optical trapping and shifted excitation difference techniques

Changan Xie — 2008-07-25T12:42:14-00:00

Journal of Applied Physics, Vol. 93, No. 5. (2003), pp. 2982-2986.

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Role of curcumin in health and disease.

L Pari — 2008-07-04T18:28:43-00:00

Archives of physiology and biochemistry, Vol. 114, No. 2. (April 2008), pp. 127-149.

Curcumin (diferuloylmethane) is an orange-yellow component of turmeric (Curcuma longa), a spice often found in curry powder. In recent years, considerable interest has been focused on curcumin due to its use to treat a wide variety of disorders without any side effects. It is one of the major curcuminoids of turmeric, which impart its characteristic yellow colour. It was used in ancient times on the Indian subcontinent to treat various illnesses such as rheumatism, bodyache, skin diseases, intestinal worms, diarrhoea, intermittent fevers, hepatic disorders, biliousness, urinary discharges, dyspepsia, inflammations, constipation, leukoderma, amenorrhea, and colic. Curcumin has the potential to treat a wide variety of inflammatory diseases including cancer, diabetes, cardiovascular diseases, arthritis, Alzheimer's disease, psoriasis, etc, through modulation of numerous molecular targets. This article reviews the use of curcumin for the chemoprevention and treatment of various diseases.

Metamaterials and Negative Refractive Index

DR Smith — 2006-08-07T22:08:30-00:00

Science, Vol. 305, No. 5685. (6 August 2004), pp. 788-792.

Recently, artificially constructed metamaterials have become of considerable interest, because these materials can exhibit electromagnetic characteristics unlike those of any conventional materials. Artificial magnetism and negative refractive index are two specific types of behavior that have been demonstrated over the past few years, illustrating the new physics and new applications possible when we expand our view as to what constitutes a material. In this review, we describe recent advances in metamaterials research and discuss the potential that these materials may hold for realizing new and seemingly exotic electromagnetic phenomena. 10.1126/science.1096796

Biosensing with plasmonic nanosensors

Jeffrey Anker — 2008-05-28T12:53:03-00:00

Nat Mater, Vol. 7, No. 6. (June 2008), pp. 442-453.

Magnetostatic interactions between carbon nanotubes filled with magnetic nanoparticles

Konstantin Kornev — 2008-07-03T03:28:32-00:00

Applied Physics Letters, Vol. 92, No. 23. (2008)

Theory of resonant radiation force exerted on nanostructures by optical excitation of their quantum states: From microscopic to macroscopic descriptions

Takuya Iida — 2008-07-02T20:15:29-00:00

Physical Review B (Condensed Matter and Materials Physics), Vol. 77, No. 24. (2008)

We establish a theoretical framework that provides a bridge between the microscopic to macroscopic descriptions of the radiation force (RF) under a quantum resonance condition. By using this framework, we derive an explicit analytical expression to clearly demonstrate the properties of the resonant RF on nanostructures and related novel phenomena. (i) For a single nano-object the RF drastically changes with the size, shape, and quality of a nano-object due to the spatial correlations of the internal radiation field and the matter-excited states. This property is highly advantageous in the selective manipulation of quantum properties of nano-objects. (ii) For multiple nano-objects an attractive (repulsive) interobject radiation force (IRF) arises between nano-objects under the optical excitation of a particular coupled state of their spatially separated polaritons, and we term this state as “polaritonic molecule.” This IRF can be enhanced even between the nano-objects that have a large spatial separation if there exist intermediate nano-objects even with very weak induced polarizations, and this effect is termed as “superinterobject radiation force.” In addition, we clarify that a “negative dissipative force” arises when the electronic polarization in a particular nano-object is inverted by a photomediated interaction. Since the resonant RF and IRF depend on many degrees of freedom of both nanostructures and light, they will provide a great variety of optical control methods for the collective dynamics of nanocomposite materials.

Green Fluorescent Protein in Inertially Injected Aqueous Nanodroplets

J Tang — 2008-05-09T22:57:22-00:00

Langmuir, Vol. 24, No. 9. (6 May 2008), pp. 4975-4978.

Abstract: We inertially inject and study the contents of optically trappable aqueous nanodroplets (hydrosomes) emulsified in a perfluorinated matrix. A new piezoelectric actuated device for production of single hydrosomes on demand is introduced. Hydrosomes containing enhanced green fluorescent protein (EGFP) were injected, optically trapped, and held at the focus of an excitation laser in a confocal microscope, and single-molecule photobleaching events were observed. The rotational diffusion time of EGFP in trapped hydrosomes was measured using time-resolved fluorescence anisotropy. In free solution, the mean rotational diffusion time was determined to be 13.8 ± 0.1 ns at 3 M and 14.0 ± 0.2 ns at 10 M. In hydrosomes, the mean rotational diffusion time was similar and determined to be 12.6 ± 1.0 ns at 3 M and 15.5 ± 1.6 ns at 10 M. We conclude that the rotational motion inside the nanodroplets is consistent with rotation in free solution and that the protein therefore does not aggregate at the water-oil interface. Protein can be confined in hydrosomes with high efficiency using this technique, which provides an alternative to surface attachment or lipid encapsulation and opens up new avenues of research using single molecules contained in fluid nanovolumes.

Developing optofluidic technology through the fusion of microfluidics and optics

Demetri Psaltis — 2006-07-28T05:50:51-00:00

Nature, Vol. 442, No. 7101. (26 July 2006), pp. 381-386.

Roughness of Microspheres for Force Measurements

PJ van Zwol — 2008-06-30T10:21:24-00:00

Langmuir (14 June 2008)

Abstract: We have investigated the morphology and surface roughness of several commercially available microspheres to determine their suitability for force measurements using the atomic force microscope. The roughness varies considerably, depending on sphere size and material, ranging from nearly ideally flat up to micrometer-sized features. Because surface roughness significantly influences the magnitude and accuracy of measurement of surface forces, the results presented here should be helpful for colloid physicists and in particular for those performing force measurements.

Interactions of Silica Surfaces

Gene Vigil — 2008-03-17T17:18:36-00:00

Journal of Colloid and Interface Science, Vol. 165, No. 2. (July 1994), pp. 367-385.

Adhesion, friction, and colloidal forces in air and aqueous salt solutions have been measured between various silica surfaces prepared by depositing amorphous but highly smooth silica films on mica. The results show four interesting and interrelated phenomena: (i) The adhesion of silica surfaces in air increases slowly with contact time, especially in humid air where the "contacting" surfaces become separated by an ~20-A-thick layer of hydrated silica or silica gel. (ii) The friction of two silica surfaces exhibits large sticking or "stiction" spikes, whose magnitude increases in the presence of water and when the surfaces are kept in contact longer before sliding. (iii) The non-DLVO repulsion commonly seen at short range (<40 A) between silica surfaces immersed in aqueous solutions is monotonically repulsive, with no oscillatory component, and is quite unlike theoretical expectations and previous measurements of forces due to solvent structure. (iv) Dynamic contact angle measurements reveal time-dependent effects which cannot be due to a fixed surface chemical heterogeneity or roughness. The results indicate that silica surfaces undergo slow structural and chemical changes during interactions with water and with each other. More specifically, we propose that the unusual interfacial and colloidal properties of silica are due, not to hydration effects, but to the presence of an ~10-Athick gel-like layer of protruding silanol and silicilic acid groups that grow on the surfaces in the presence of water. These protruding groups react chemically (sinter) with similar groups located on an opposing surface and give rise to the unusual time-dependent adhesion, friction, and non-DLVO forces observed. Concerning the effects on colloidal interactions, the surface gel-layer effectively shifts the OHP outward and adds a monotonic short-range polymer-like steric repulsion to the DLVO interaction. The mechanism proposed here is quite different from the commonly accepted one, in which modified water structure at the silica surface is believed to give rise to a repulsive "hydration force." The proposed mechanism in terms of a surface layer of silica gel is consistent with the known surface chemistry of silica and accounts for the results reported here and also for many other unusual surface and colloidal properties of silica.

Forces of a single-beam gradient laser trap on a dielectric sphere in the ray optics regime

A Ashkin — 2008-06-23T21:55:42-00:00

Biophys. J., Vol. 61, No. 2. (1 February 1992), pp. 569-582.

We calculate the forces of single-beam gradient radiation pressure laser traps, also called "optical tweezers," on micron-sized dielectric spheres in the ray optics regime. This serves as a simple model system for describing laser trapping and manipulation of living cells and organelles within cells. The gradient and scattering forces are defined for beams of complex shape in the ray-optics limit. Forces are calculated over the entire cross-section of the sphere using TEM00 and TEM01* mode input intensity profiles and spheres of varying index of refraction. Strong uniform traps are possible with force variations less than a factor of 2 over the sphere cross-section. For a laser power of 10 mW and a relative index of refraction of 1.2 we compute trapping forces as high as [~] 1.2 x 10-6 dynes in the weakest (backward) direction of the gradient trap. It is shown that good trapping requires high convergence beams from a high numerical aperture objective. A comparison is given of traps made using bright field or differential interference contrast optics and phase contrast optics.

Absorption Coefficient Imaging by Near-Field Scanning Optical Microscopy in Bacteria

Ana de Paula — 2008-05-31T17:29:43-00:00

Appl. Opt., Vol. 42, No. 16. (1 June 2003), pp. 3005-3008.

We present a method for obtaining a position-dependent absorption coefficient from near-field scanning optical transmission microscopy. We show that the optical transmission intensity can be combined with the topography, resulting into an absorption coefficient that simplifies the analysis of different materials within a sample. The method is tested with the dye rhodamine 6G, and we show some analysis in biological samples such as bacteria Klebsiella pneumoniae and Pseudomonas aeruginosa . The calculated absorption coefficient images show important details of the bacteria, in particular for P. aeruginosa , in which membrane vesicles are clearly seen.

Convective-Diffusion-Based Fluorescence Correlation Spectroscopy for Detection of a Trace Amount of E. coli in Water

De-Kui Qing — 2008-05-31T17:27:04-00:00

Appl. Opt., Vol. 42, No. 16. (1 June 2003), pp. 2987-2994.

Fluorescence correlation spectroscopy (FCS) is adapted for a new procedure to detect trace amounts of Escherichia coli in water. The present concept is based on convective diffusion rather than Brownian diffusion and employs confocal microscopy as in traditional FCS. With this system it is possible to detect concentrations as small as 1.5 × 10 5 E. coli per milliliter (2.5 × 10 −16 M). This concentration corresponds to an ~1.0-nM level of Rhodamine 6G dyes. A detailed analysis of the optical system is presented, and further improvements for the procedure are discussed.

Limited Possibility for Quantifying Mean Particle Size by Logarithmic Light-Scattering Spectroscopy

Maureen Johns — 2008-05-31T16:39:51-00:00

Appl. Opt., Vol. 42, No. 16. (1 June 2003), pp. 2968-2971.

Recent studies have shown that the slope of logarithmic scattering spectroscopy of a turbid medium is related to the sizes of the scattering particles within the turbid medium. Mie theory can be used to generate a logarithmic plot of the reduced-scattering coefficient versus wavelength. According to Nilsson et al . [Appl. Opt. 37, 1256 (1998)], the slope value of a linear fit of the logarithmic scattering spectroscopy between 600 and 1050 nm can be used for direct determination of particle size. We performed similar calculations using the Rayleigh-Gans approximation and obtained an analogous overall shape with additional sinusoidal features. Our calculations indicate a possible relationship between the slope and the particle size when the size is used to calculate the slope, namely, in the forward calculation. However, because of the sinusoidal pattern, the inverse calculation to obtain the particle size from the slope may be applied only for particles with a radius of < 0.13 μm in combination with 650–1050-nm light. Caution should be exercised when inverse calculation is performed to determine the scattering particle sizes in the range of radii > 0.13 μm, with the slope of logarithmic scattering spectroscopy within 650–1050 nm.

The development of microgels/nanogels for drug delivery applications

Jung Oh — 2008-05-29T04:31:34-00:00

Progress in Polymer Science, Vol. 33, No. 4. (April 2008), pp. 448-477.

Microgels/nanogels are crosslinked polymeric particles, which can be considered as hydrogels if they are composed of water soluble/swellable polymer chains. They possess high water content, biocompatibility, and desirable mechanical properties. They offer unique advantages for polymer-based drug delivery systems (DDS): a tunable size from nanometers to micrometers, a large surface area for multivalent bioconjugation, and an interior network for the incorporation of biomolecules. Present and future microgel applications require a high degree of control over properties. They include stability for prolonged circulation in the blood stream, novel functionality for further bioconjugation, controlled particle size with uniform diameter, and biodegradability for sustained release of drugs for a desired period of time and facile removal of empty devices. This review describes the recent developments of microgel/nanogel particles as drug delivery carriers for biological and biomedical applications. Various synthetic strategies for the preparation of microgels/nanogels are detailed, including photolithographic and micromolding methods, continuous microfluidics, modification of biopolymers, and heterogeneous free radical and controlled/living radical polymerizations.

Encapsulation of methylene blue in polyacrylamide nanoparticle platforms protects its photodynamic effectiveness

Wei Tang — 2008-05-13T04:04:09-00:00

Biochemical and Biophysical Research Communications, Vol. 369, No. 2. (2 May 2008), pp. 579-583.

The ability to prevent methylene blue (MB), a photosensitizer, from being reduced by plasma reductases will greatly improve its efficacy in photodynamic therapy (PDT) applications. We have developed a delivery approach for PDT by encapsulating MB using nanoparticle platforms (NPs). The 30-nm polyacrylamide-based NPs provide protection for the embedded MB against reduction by diaphorase enzymes. Furthermore, our data shows the matrix-protected MB efficiently induces photodynamic damage to tumor cells. The unprecedented results demonstrate the significant in vitro photodynamic effectiveness of MB when encapsulated within NPs, which promises to open new opportunities for MB in its in vivo and clinical studies.

Synthesis and Characterization of Fluorescently Doped Mesoporous Nanoparticles for Two-Photon Excitation

Valérie Lebret — 2008-05-13T03:58:28-00:00

Chem. Mater., Vol. 20, No. 6. (25 March 2008), pp. 2174-2183.

Abstract: The template-directed synthesis of mesoporous silica nanoparticles doped with water-soluble fluorescent dyes optimized for two-photon excitation is described. Two structurally related symmetrical two-photon dyes that possess pyridinium acceptor endgroups conjugated to a fluorenyl core are synthesized by Heck coupling. These dyes display bright fluorescence (¦ H 0.35) under both one- (µ H 6 × 104 M1 cm1) and two-photon excitation (Ã2 H 1000 GM) and were successfully encapsulated in silica nanoparticles via immobilization through noncovalent interactions. The nanoparticles present a mean diameter of 100 nm and a hexagonal network of mesopores as shown by TEM. Interestingly, the photophysical characteristics of the dyes are retained upon their immobilization into the silica matrix, leading to fluorescent silica nanoparticles with giant/unprecedented TPA cross-section (1 × 107 GM). Such nanospheres represent attractive nanoplatforms for the development of biotargeted biocompatible luminescent tracers.

Iridium-complex-functionalized Fe3O4/SiO2 core/shell nanoparticles: a facile three-in-one system in magnetic resonance imaging, luminescence imaging, and photodynamic therapy.

CW Lai — 2008-05-13T03:52:32-00:00

Small (Weinheim an der Bergstrasse, Germany), Vol. 4, No. 2. (February 2008), pp. 218-224.

Highly uniform Fe3O4/SiO2 core/shell nanoparticles functionalized by phosphorescent iridium complexes (Ir) have been strategically designed and synthesized. The Fe3O4/SiO2(Ir) nanocomposite demonstrates its versatility in various applications: the magnetic core provides the capability for magnetic resonance imaging and the great enhancement of the spin-orbit coupling in the iridium complex makes it well suited for phosphorescent labeling and simultaneous singlet oxygen generation to induce apoptosis.

Photosensitiser-loaded biodegradable polymeric micelles: Preparation, characterisation and in vitro PDT efficacy

Cristianne Rijcken — 2008-03-12T19:00:37-00:00

Journal of Controlled Release, Vol. 124, No. 3. (20 December 2007), pp. 144-153.

The application of photosensitisers (PSs) in photodynamic therapy (PDT) is often hampered by their hydrophobicity, as this complicates their formulation and results in an unfavourable biodistribution. Consequently, there is an urgent need for novel delivery vehicles for PSs. In this paper, the loading and stability of thermosensitive mPEG-b-p(HPMAm-Lac2) micelles with a hydrophobic solketal-substituted phthalocyanine (Si(sol)2Pc) photosensitiser were studied. It was shown that the Si(sol)2Pc could be loaded efficiently in the micelles (diameter 75 nm) up to a concentration of ~ 2 mg/mL. UV/Vis and fluorescence spectroscopy showed that at low concentrations (<= 0.05 [mu]M, 0.45 mg/mL polymer), the PS was molecularly dissolved in the micellar core, whereas it was present in an aggregated form at higher concentrations. In B16F10 and 14C cells, the photocytotoxicity of Si(sol)2Pc-loaded micelles (PS < 0.05 [mu]M) was similar to free PS, i.e. IC50 of 3.0 +/- 0.2 nM (10% serum). The cellular uptake of high-loaded micelles (10 [mu]M Si(sol)2Pc) was low and independent of the serum concentration. The nanoaggregates of Si(sol)2Pc loaded in the micellar core were only released upon hydrolysis-induced micellar dissociation, which was observed after 5.5 h at pH 8.7 at 37 [degree sign]C. The stability of the high-loaded micellar Si(sol)2Pc formulation also in the presence of serum, the controlled release of the PS upon micellar disintegration and the high photodynamic activity of Si(sol)2Pc make these micelles interesting for future in vivo studies.

Nanoparticle-Based Photosensitizers under CW Infrared Excitation

Yanyan Guo — 2008-03-12T18:55:50-00:00

Chemistry of Materials, Vol. 19, No. 25. (11 December 2007), pp. 6071-6072.

Photophysical, electrochemical characteristics and cross-linking of STAT-3 protein by an efficient bifunctional agent for fluorescence image-guided photodynamic therapy

Yihui Chen — 2008-03-12T18:42:44-00:00

Photochemical & Photobiological Sciences, Vol. 6, No. 12. (2007), pp. 1257-1267.

Biodegradable, polymeric nanoparticle delivery systems for cancer therapy

Eric Pridgen — 2008-03-12T16:59:55-00:00

Nanomedicine, Vol. 2, No. 5. (October 2007), pp. 669-680.

Nanotechnology has the potential to impact the treatment of cancer significantly. This review will explore how this potential is beginning to be realized through the design of polymeric nanoparticle delivery systems. Current research is focused on developing biocompatible nanoparticles capable of targeting specific cancer markers and delivering imaging and therapeutic agents for the detection and treatment of cancer, resulting in a number of preclinical and clinical applications. More sophisticated nanoparticle designs are now in development, including particles able to release multiple drugs for enhanced treatment efficacy and targeted, multifunctional particles capable of combining imaging and drug release.

Mathematical Modeling of Ultraviolet Germicidal Irradiation for Air Disinfection

WJ Kowalski — 2008-02-15T12:12:51-00:00

Quantitative Microbiology, Vol. 2, No. 3. (1 October 2000), pp. 249-270.

A comprehensive treatment of the mathematical basis for modeling the disinfection process for air using ultraviolet germicidal irradiation (UVGI). A complete mathematical description of the survival curve is developed that incorporates both a two stage inactivation curve and a shoulder. A methodology for the evaluation of the three-dimensional intensity fields around UV lamps and within reflective enclosures is summarized that will enable determination of the UV dose absorbed by aerosolized microbes. The results of past UVGI studies on airborne pathogens are tabulated. The airborne rate constant for Bacillus subtilis is confirmed based on results of an independent test. A re-evaluation of data from several previous studies demonstrates the application of the shoulder and two-stage models. The methods presented here will enable accurate interpretation of experimental results involving aerosolized microorganisms exposed to UVGI and associated relative humidity effects

Inactivation of microorganisms in a flow-through photoreactor with an immobilized TiO2 layer

Lenka Belháová — 2008-02-14T13:39:03-00:00

Journal of Chemical Technology & Biotechnology, Vol. 74, No. 2. (1999), pp. 149-154.

A laboratory flow-through photoreactor with an immobilized layer of TiO2 (total volume of the liquid 5000 cm 3, photoactive area 60 cm long and 30 cm wide; irradiation source UV lamps Eversun, Osram, light intensity from 0.9 to 6.2×10-9 Einstein cm-2 s -1) was tested for the inactivation of Escherichia coli (strain DH5?) and bacteriophage ?NM1149. The kinetics of the deactivation were approximately first order and the initial reaction rate depended on the light intensity. At maximum intensity, the rate constants of the bacteria and viruses inactivation were 2.3×10-4 and 7.2×10-4 s-1, respectively. Bacterial inactivation was also accomplished with solar excitation.© 1999 Society of Chemical Industry

Curvefitting Imaginary Components of Optical Properties: Restrictions on the Lineshape Due to Causality

Dale Keefe — 2008-02-12T01:14:00-00:00

Journal of Molecular Spectroscopy, Vol. 205, No. 2. (February 2001), pp. 261-268.

The Kramers-Kronig transformation has been extensively applied in optical spectroscopy to calculate the real component of an optical quantity from the imaginary component, such as the real refractive index from the imaginary component, or vice versa. In this paper, the traditional proof of the Kramers-Kronig transformation, and its application to the complex refractive index, complex dielectric constant, and complex molar polarizability, are reviewed. Often the imaginary components of these quantities are fitted with standard lineshapes such as the Gaussian, Lorentzian, or Classical Damped Harmonic Oscillator (CDHO) lineshapes. It is shown that the usual Gaussian and Lorentzian lineshapes do not meet the physical criteria of these imaginary components nor the conditions of the Kramers-Kronig transformation since they are not odd functions of wavenumber. However, the CDHO lineshape meets the physical criteria of the imaginary components of these optical quantities and the Kramers-Kronig transformation. Modifications are presented that make the Gaussian and Lorentzian odd. The Gaussian decays so fast that the modification is not needed in practice; however, the Lorentzian is much slower to decay and thus modification is necessary whenever fitting peaks below ~250 cm-1. Since the computational difference between the usual Lorentzian and modified Lorentzian is negligible, the author recommends that only the modified Lorentzian be used when fitting bands with a Lorentzian lineshape.

Optical Absorption Characteristics of Pink Ruby

DC Cronemeyer — 2008-02-12T01:12:36-00:00

J. Opt. Soc. Am., Vol. 56, No. 12. (1 December 1966), 1703.

Fifth-order corrected electromagnetic field components for a fundamental Gaussian beam

JP Barton — 2008-02-12T01:08:12-00:00

Journal of Applied Physics, Vol. 66, No. 7. (1989), pp. 2800-2802.

The discrete-dipole approximation and its application to interstellar graphite grains

BT Draine — 2008-02-12T01:04:37-00:00

Astrophys. J., Vol. 333 (October 1988), pp. 848-872.

The discrete dipole approximation (DDA), a flexible method for computing scattering of radiation by particles of arbitrary shape, is extended to incorporate the effects of radiative reaction and to allow for possible anisotropy of the dielectric tensor of the material. Formulas are given for the evaluation of extinction, absorption, scattering, and polarization cross sections. A simple numerical algorithm based on the method of conjugate gradients is found to provide an efficient and robust method for obtaining accurate solutions to the scattering problem. The method works well for absorptive, as well as dielectric, grain materials. Two validity criteria for the DDA are presented. The DDA is then used to compute extinction cross sections for spherical graphite grains and to calculate extinction cross sections for nonspherical graphite grains with three different geometries. It is concluded that the interstellar 2175 A extinction feature could be produced by small graphite grains which should have aspect ratios not far from unity.

Time-averaged total force on a dipolar sphere in an electromagnetic field

PC Chaumet — 2008-02-12T01:02:13-00:00

Opt. Lett., Vol. 25, No. 15. (2000), pp. 1065-1067.

We establish the time-averaged total force on a subwavelength-sized particle in a time-harmonic-varying field. Our analysis is not restricted to the spatial dependence of the incident field. We discuss the addition of the radiative reaction term to the polarizability to deal correctly with the scattering force. As an illustration, we assess the degree of accuracy of several previously established polarizability models.

Stability of radiation-pressure particle traps: an optical Earnshaw theorem

A Ashkin — 2008-02-12T00:59:26-00:00

Opt. Lett., Vol. 8, No. 10. (1 October 1983), 511.

Three-dimensional pH microprobing with an optically-manipulated fluorescent particle

Keiji Sasaki — 2008-02-12T00:55:08-00:00

Chemistry Letters, Vol. 25, No. 2. (1996), 141.

Stimulated Optical Radiation in Ruby

TH Maiman — 2007-02-14T01:28:15-00:00

Nature, Vol. 187, No. 4736. (1960), pp. 493-494.

Tangential Forces between Nontouching Colloidal Particles

D Velegol — 2008-02-12T00:33:46-00:00

Physical Review Letters, Vol. 83, No. 6. (1999), 1243.

By measuring the orientation of colloidal doublets suspended in water under the opposing alignment forces of gravity and electrophoresis; we observed tangential forces between nontouching particles. We found a new phenomenon of time-dependent switching between “slipping” (no tangential force) and “sticking” (tangential forces producing rigid-body behavior of the doublet) for heterodoublets of silica/polystyrene. Tangential forces between particle surfaces across a fluid gap and their transient nature are important to the dynamics of colloidal suspensions and the evolution of floc morphology.

A self-assembled microlensing rotational probe

James Brody — 2008-02-12T00:27:43-00:00

Applied Physics Letters, Vol. 74, No. 1. (1999), pp. 144-146.

Pump-probe imaging of femtosecond pulsed laser ablation of silicon with thermally grown oxide films

Joel Mcdonald — 2008-02-12T00:25:35-00:00

Journal of Applied Physics, Vol. 102, No. 6. (2007)

The effect of the in-plane demagnetizing field on films with weak perpendicular magnetic anisotropy

Oscar de Abril — 2008-02-12T00:23:04-00:00

Journal of Applied Physics, Vol. 100, No. 6. (2006)

Magnetophoresis of microspheres covered by magnetic nanoparticles

X Zhao — 2008-02-12T00:21:04-00:00

Journal of Applied Physics, Vol. 102, No. 5. (2007)

Into the Big Blue yonder

Robert Buderi — 2008-02-11T03:55:27-00:00

Technol. Rev., Vol. 102, No. 4. (1999), pp. 46-53.

Condensed Matter Physics in a Market Economy

John Rowell — 2008-02-11T02:37:56-00:00

Physics Today, Vol. 45, No. 5. (1992), pp. 40-47.

In 1991 I attended my 30th consecutive March meeting of The American Physical Society, held in Cincinnati. This anniversary made me reflect on the changes I have seen in the field since I listened to my first ten-minute talk in Baltimore in 1962. I believe it was obvious to many in Cincinnati that there is a malaise affecting our field that was not present 30 or even 10 years ago. By “our field,” I mean what is variously called solid-state physics, condensed matter physics, materials physics and materials science.

The foundation of the silicon age

IM Ross — 2008-02-11T01:56:34-00:00

Physics Today, Vol. 50 (December 1997), pp. 34-39.

Not Available

Strategic Curiosity: Semiconductor Physics in the 1950s

Henry Ehrenreich — 2008-02-11T01:35:50-00:00

Physics Today, Vol. 48, No. 1. (1995), pp. 28-34.

When I arrived at the General Electric Research Laboratory at the beginning of 1955, fresh from a PhD at Cornell, I was greeted by my supervisor, Leroy Apker, who looked after the semiconductor section of the general physics department. I asked him to suggest some research topics that might be germane to the interests of the section. He said that what I did was entirely up to me. After recovering from my surprise, I asked, “Well, how are you going to judge my performance at the end of the year?” He replied, “Oh, I'll just call up the people at Bell and ask them how they think you are doing.” Viewed from today's environment, what is particularly hard to understand about this conversation is how an industrial laboratory, responsible to the operating units of the company and to the stockholders, could afford to take such a relaxed view.

Edison and the Pure Science Ideal in 19th-Century America

David Hounshell — 2008-02-11T00:36:43-00:00

Science, Vol. 207, No. 4431. (8 February 1980), pp. 612-617.

Between 1878 and 1882, key members of the American scientific community played an important role in Thomas A. Edison's work on electric lighting. Impressed by his abilities, these scientists came to regard Edison as a peer and led him to see himself as a scientific man. But Edison's high standing among scientists and the American public and his professed self-image as a scientist provoked America's noted experimental physicist, Henry A. Rowland, to make a "Plea for pure science" before the American Association for the Advancement of Science in 1883. 10.1126/science.207.4431.612

Science and Technology

George Wise — 2008-02-11T00:27:06-00:00

The Role of Science in Our Society

Burton Richter — 2008-02-10T23:36:23-00:00

Physics Today, Vol. 48, No. 9. (1995), pp. 43-47.

Science, particularly physics, has been in a relatively privileged position in the United States since the end of World War II. Support by the government has been generous, and those of us whose careers have spanned the period since World War II have, until recently, seen research funding increasing in real terms. Our support rested on two assumptions: Science would improve the lives of the citizens, and science would make us secure in a world that seemed very dangerous because of the US-USSR confrontation.

Beyond Basic and Applied

Roger Pielke — 2008-02-10T23:31:55-00:00

Physics Today, Vol. 51, No. 2. (1998), pp. 42-46.

Science policy implements a social contract. In the US since World War II, this arrangement has amounted to society—through government—giving science both money and relative autonomy while, in return, reaping the practical benefits that inevitably result. The arrangement once may have been appropriate, but it no longer is; we now need a new understanding of how science serves national needs.

What Future Will We Choose for Physics?

Sol Gruner — 2008-02-10T22:44:41-00:00

Physics Today, Vol. 48, No. 12. (1995), pp. 25-30.

Science in the United States is in a time of pain and uncertainty. The pain is felt most acutely by young scientists, who are having great difficulty establishing their careers. The uncertainty about the duration and outcome of the current situation stems from its roots in ponderous events of recent history—the end of the cold war, industrial downsizing, government deficits and demographic trends. Although budget difficulties and lack of jobs plague most of the sciences, the atmosphere of uncertainty about the future is palpably different from one profession to the next. Our concern here is with the profession of physics.

Why Do They Leave Physics?

Philip Anderson — 2008-02-10T22:43:01-00:00

Vol. 52, No. 9. (September 1999), 11.

Changing

Leo Kadanoff — 2008-02-10T22:29:50-00:00

Physics Today, Vol. 52, No. 12. (1999), pp. 11-14.

Discussion with Einstein on Epistemological Problems in Atomic Physics

Niels Bohr — 2008-02-10T20:59:49-00:00

Uspekhi fizicheskikh nauk, Vol. 66, No. 4. (1958), pp. 571-598.

The Effect of World War II on the Development of Knowledge in the Physical Sciences [and Discussion]

Edward Bullard — 2008-02-10T20:15:03-00:00

Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences (1934-1990), Vol. 342, No. 1631. (15 April 1975), pp. 519-536.

The first effect of the outbreak of war in 1939 was greatly to reduce work in pure science and to direct effort to projects relevant to the war. After the war there was a very rapid expansion to a level much exceeding that of the 1930s. The work done during the war in nuclear physics, electronics, instrumentation, radar and rocketry was the basis of this expansion. Successes during the war had given science a new image with the public and with the government; money and facilities were available for fundamental science on a scale more than 10 times that of pre-war days. Wartime work had also had a profound effect on the expectations and style of work of physicists. They had learnt how to obtain and handle large resources.