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Diffraction Limit (diffraction + limit)
Selected AbstractsGold Nanorods: From Synthesis and Properties to Biological and Biomedical ApplicationsADVANCED MATERIALS, Issue 48 2009Xiaohua Huang Abstract Noble metal nanoparticles are capable of confining resonant photons in such a manner as to induce coherent surface plasmon oscillation of their conduction band electrons, a phenomenon leading to two important properties. Firstly, the confinement of the photon to the nanoparticle's dimensions leads to a large increase in its electromagnetic field and consequently great enhancement of all the nanoparticle's radiative properties, such as absorption and scattering. Moreover, by confining the photon's wavelength to the nanoparticle's small dimensions, there exists enhanced imaging resolving powers, which extend well below the diffraction limit, a property of considerable importance in potential device applications. Secondly, the strongly absorbed light by the nanoparticles is followed by a rapid dephasing of the coherent electron motion in tandem with an equally rapid energy transfer to the lattice, a process integral to the technologically relevant photothermal properties of plasmonic nanoparticles. Of all the possible nanoparticle shapes, gold nanorods are especially intriguing as they offer strong plasmonic fields while exhibiting excellent tunability and biocompatibility. We begin this review of gold nanorods by summarizing their radiative and nonradiative properties. Their various synthetic methods are then outlined with an emphasis on the seed-mediated chemical growth. In particular, we describe nanorod spontaneous self-assembly, chemically driven assembly, and polymer-based alignment. The final section details current studies aimed at applications in the biological and biomedical fields. [source] Single-Photon and Two-Photon Induced Photocleavage for Monolayers of an Alkyltriethoxysilane with a Photoprotected Carboxylic Ester,ADVANCED MATERIALS, Issue 23 2008Marta Álvarez The photochemical structuring of a polysiloxane monolayer protected with a photocleavable group is shown by femtosecond laser pulses in the near infrared. These experiments suggest a two-photon induced deprotection process that holds great promise for near-field monolayer photolithography far below the diffraction limit. [source] Three-Dimensional Nanonetwork Assembled in a Photopolymerized Rod ArrayADVANCED MATERIALS, Issue 23 2003H.-B. Sun One- and two-photon interferential patterning of photopolymerizable resin is demonstrated to lead to well-defined two-dimensional (2D) photonic crystal structures (which beat the diffraction limit) and also 3D nanonetworks, such as that shown in the Figure. The fiber-like features are probably formed by a novel self-assembly mechanism during drying. Applications in photonics are foreseen. [source] Application of white-beam X-ray microdiffraction for the study of mineralogical phase identification in ancient Egyptian pigmentsJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 6 2007P. A. Lynch High-brightness synchrotron X-rays together with precision achromatic focusing optics on beamline 7.3.3 at the Advanced Light Source have been applied for Laue microdiffraction analysis of mineralogical phases in Egyptian pigments. Although this task is usually performed using monochromatic X-ray diffraction, the Laue technique was both faster and more reliable for the present sample. In this approach, white-beam diffraction patterns are collected as the sample is raster scanned across the incident beam (0.8,µm × 0.8,µm). The complex Laue diffraction patterns arising from illumination of multiple grains are indexed using the white-beam crystallographic software package XMAS, enabling a mineralogical map as a function of sample position. This methodology has been applied to determine the mineralogy of colour pigments taken from the ancient Egyptian coffin of Tjeseb, a priestess of the Apis bull dating from the Third Intermediate to Late period, 25th Dynasty to early 26th Dynasty (747 to 600 BC). For all pigments, a ground layer of calcite and quartz was identified. For the blue pigment, cuprorivaite (CuCaSi4O10) was found to be the primary colouring agent with a grain size ranging from ,10 to 50,µm. In the green and yellow samples, malachite [Cu2(OH)2CO3] and goethite [FeO(OH)] were identified, respectively. Grain sizes from these pigments were significantly smaller. It was possible to index some malachite grains up to ,20,µm in size, while the majority of goethite grains displayed a nanocrystalline particle size. The inability to obtain a complete mineralogical map for goethite highlights the fact that the incident probe size is considerably larger than the grain size. This limit will continue to improve as the present trend is toward focusing optics approaching the diffraction limit (,1000× smaller beam area). [source] Investigation of dyed human hair fibres using apertureless near-field scanning optical microscopyJOURNAL OF MICROSCOPY, Issue 2 2006F. FORMANEK Summary We present the first studies of dyed human hair fibres performed with an apertureless scanning near-field optical microscope. Samples consisted of 5-µm-thick cross-sections, the hair fibres being bleached and then dyed before being cut. Hair dyed with two molecular probes diffusing deep inside the fibre or mainly spreading at its periphery were investigated at a wavelength of 655 nm. An optical resolution of about 50 nm was achieved, well below the diffraction limit; the images exhibited different optical contrasts in the cuticle region, depending on the nature of the dye. Our results suggest that the dye that remains confined at the hair periphery is mainly located at its surface and in the endocuticle. [source] 20-W average power, high repetition rate, nanosecond pulse with diffraction limit from an all-fiber MOPA systemMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2008Songtao Du Abstract In this article, we report an all-fiber master oscillator power amplifier (MOPA) system, which can provide high repetition rate and nanosecond pulse with diffraction-limit. The system was constructed using a (2 + 1) × 1 multimode combiner. The Q-Switched, LD pumped Nd:YVO4 solid-state laser was used as master oscillator. The 976-nm fiber-coupled module is used as pump source. A 10-m long China-made Yb3+ -doped D-shape double-clad large-mode-area fiber was used as amplifier fiber. The MOPA produced as much as 20-W average power with nanosecond pulse and near diffraction limited. The pulse duration is maintained at about 15 ns during 50,175 kHz. The system employs a simple and compact architecture and is therefore suitable for the use in practical applications such as scientific and military airborne LIDAR and imaging. Based on this system, the amplification performances of the all-fiber amplifier is investigated. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2546,2549, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23770 [source] IR spectroscopy of COmosphere dynamics with the CO ?rst overtone bandASTRONOMISCHE NACHRICHTEN, Issue 6 2010T.A. Schad Abstract We discuss observations of the weak ?rst overtone (,, = 2) CO absorption band near 2300 nm with the U.S. National Solar Observatory Array Camera (NAC), a modern mid-infrared detector. This molecular band provides a thermal diagnostic that forms lower in the atmosphere than the stronger fundamental band near 4600 nm. The observed center-to-limb increase in CO line width qualitatively agrees with the proposed higher temperature shocks or faster plasma motions higher in the COmosphere. The spatial extent of chromospheric shock waves is currently at or below the diffraction limit of the available CO lines at existing telescopes. Five minute period oscillations in line strength and measured Doppler shifts are consistent with the p-mode excitation of the photospheric gas. We also show recent efforts at direct imaging at 4600 nm. We stress that future large-aperture solar telescopes must be teamed with improved, dynamic mid-infrared instruments, like the NAC, to capitalize on the features that motivate such facilities (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Purification, crystallization and X-ray diffraction analysis of a recombinant Fab that recognizes a human blood-group antigenACTA CRYSTALLOGRAPHICA SECTION D, Issue 4 2004Shuh-Chyung Song The NNA7 Fab fragment recognizes the human glycopeptide N blood-group antigen and has a high affinity for N-type glycophorin A (GPA). To provide insight into how antibodies recognize glycopeptide antigens, soluble Fab fragments were expressed in Escherichia coli, purified and crystallized using the hanging-drop vapor-diffusion method at 293,K. The best crystals were obtained from solutions of PEG monomethyl ether 5000 containing 4,8,mM yttrium chloride (YCl3). This rare-earth ion, which could be substituted with various lanthanides, changed the habit of crystals from multinucleated rods with a diffraction limit of 4.25,Å resolution to a diamond-shaped morphology that grew as single crystals and diffracted X-rays to 1.75,Å resolution. Data were collected that indicated that the crystals belonged to space group P212121, with unit-cell parameters a = 57.9, b = 77.1, c = 118.1,Å and one Fab fragment per asymmetric unit. A molecular-replacement solution has been obtained and 86% of the molecule was fitted by use of an automated refinement procedure (ARP). [source] Purification, crystallization and preliminary crystallographic analysis of a thermostable endonuclease IV from Thermotoga maritimaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 12 2009Ronny C. Hughes The DNA-repair enzyme endonuclease IV from the thermophilic bacterium Thermotoga maritima MSB8 (reference sequence NC_000853) has been expressed in Escherichia coli and crystallized for X-ray analysis. T. maritima endonuclease IV is a 287-amino-acid protein with 32% sequence identity to E. coli endonuclease IV. The protein was purified to homogeneity and was crystallized using the sitting-drop vapor-diffusion method. The protein crystallized in space group P61, with one biological molecule in the asymmetric unit, corresponding to a Matthews coefficient of 2.39,Å3,Da,1 and 47% solvent content. The unit-cell parameters of the crystals were a = b = 123.2, c = 35.6,Å. Microseeding and further optimization yielded crystals with an X-ray diffraction limit of 2.36,Å. A single 70° data set was collected and processed, resulting in an overall Rmerge and a completeness of 9.5% and 99.3%, respectively. [source] Crystallization and preliminary X-ray diffraction analyses of several forms of the CfaB major subunit of enterotoxigenic Escherichia coli CFA/I fimbriaeACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 3 2009Yong-Fu Li Enterotoxigenic Escherichia coli (ETEC), a major global cause of diarrhea, initiates the pathogenic process via fimbriae-mediated attachment to the small intestinal epithelium. A common prototypic ETEC fimbria, colonization factor antigen I (CFA/I), consists of a tip-localized minor adhesive subunit CfaE and the stalk-forming major subunit CfaB, both of which are necessary for fimbrial assembly. To elucidate the structure of CFA/I at atomic resolution, three recombinant proteins were generated consisting of fusions of the minor and major subunits (CfaEB) and of two (CfaBB) and three (CfaBBB) repeats of the major subunit. Crystals of CfaEB diffracted X-rays to 2.1,Å resolution and displayed the symmetry of space group P21. CfaBB exhibited a crystal diffraction limit of 2.3,Å resolution and had the symmetry of space group P21212. CfaBBB crystallized in the monoclinic space group C2 and diffracted X-rays to 2.3,Å resolution. These structures were determined using the molecular-replacement method. [source] The purification, crystallization and preliminary structural characterization of FAD-dependent monooxygenase PhzS, a phenazine-modifying enzyme from Pseudomonas aeruginosaACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 10 2006Neelakshi Gohain The blue chloroform-soluble bacterial metabolite pyocyanin (1-hydroxy-5-methyl-phenazine) contributes to the survival and virulence of Pseudomonas aeruginosa, an important Gram-negative opportunistic pathogen of humans and animals. Little is known about the two enzymes, designated PhzM and PhzS, that function in the synthesis of pyocyanin from phenazine-1-carboxylic acid. In this study, the FAD-dependent monooxygenase PhzS was purified and crystallized from lithium sulfate/ammonium sulfate/sodium citrate pH 5.5. Native crystals belong to space group C2, with unit-cell parameters a = 144.2, b = 96.2, c = 71.7,Å, , = , = 90, , = 110.5°. They contain two monomers of PhzS in the asymmetric unit and diffract to a resolution of 2.4,Å. Seleno- l -methionine-labelled PhzS also crystallizes in space group C2, but the unit-cell parameters change to a = 70.6, b = 76.2, c = 80.2,Å, , = , = 90, , = 110.5° and the diffraction limit is 2.7,Å. [source] Make them Blink: Probes for Super-Resolution MicroscopyCHEMPHYSCHEM, Issue 12 2010Jan Vogelsang Dr. Abstract In recent years, a number of approaches have emerged that enable far-field fluorescence imaging beyond the diffraction limit of light, namely super-resolution microscopy. These techniques are beginning to profoundly alter our abilities to look at biological structures and dynamics and are bound to spread into conventional biological laboratories. Nowadays these approaches can be divided into two categories, one based on targeted switching and readout, and the other based on stochastic switching and readout of the fluorescence information. The main prerequisite for a successful implementation of both categories is the ability to prepare the fluorescent emitters in two distinct states, a bright and a dark state. Herein, we provide an overview of recent developments in super-resolution microscopy techniques and outline the special requirements for the fluorescent probes used. In combination with the advances in understanding the photophysics and photochemistry of single fluorophores, we demonstrate how essentially any single-molecule compatible fluorophore can be used for super-resolution microscopy. We present examples for super-resolution microscopy with standard organic fluorophores, discuss factors that influence resolution and present approaches for calibration samples for super-resolution microscopes including AFM-based single-molecule assembly and DNA origami. [source] Super-Resolution Imaging of DNA Labelled with Intercalating DyesCHEMPHYSCHEM, Issue 13 2009Cristina Flors Dr. Imaging DNA: DNA intercalating cyanine dyes provide a simple and convenient method to image DNA topology by means of fluorescence microscopy with a spatial resolution better than the diffraction limit of light (see picture). [source] Magnifying Superlenses and other Applications of Plasmonic Metamaterials in Microscopy and SensingCHEMPHYSCHEM, Issue 4 2009Igor I. Smolyaninov Dr. Abstract Every last detail: New advances in the construction of metamaterials enable the creation of artificial optical media, whose use in microscopy can provide resolution that is not determined by the conventional diffraction limit. The picture shows a superposition of an AFM image of a plasmonic metamaterial onto the corresponding optical image obtained using a conventional optical microscope. Over the past century, the resolution of conventional optical microscopes, which rely on optical waves that propagate into the far field, has been limited because of diffraction to a value of the order of a half-wavelength (,0/2) of the light used. Although immersion microscopes have slightly improved resolution, of the order of ,0/2n, the increased resolution is limited by the small range of refractive indices n of available transparent materials. However, now we are experiencing a quick demolition of the diffraction limit in optical microscopy. In the last few years, numerous nonlinear optical microscopy techniques based on photoswitching and saturation of fluorescence have demonstrated far-field resolution of 20 to 30 nm. In a parallel development, recent progress in metamaterials has demonstrated that artificial optical media can be created, whose use in microscopy can provide resolution that is not determined by the conventional diffraction limit. The resolution of linear immersion microscopes based on such metamaterials is only limited by losses, which can be minimized by appropriate selection of the constituents of the metamaterials used and by the wavelength(s) used for imaging. It is also feasible to compensate for losses by adding gain to the structure. Thus, optical microscopy is quickly moving towards resolution of around 10 nm, which should bring about numerous revolutionary advances in lithography and imaging. [source] | ||||||||||