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This article defines and describes the process of backing up data files, which should be undertaken by anyone who routinely uses a computer. The important points to be considered when developing a backup strategy are explained and a résumé given of the backup devices currently available.
We describe a novel optomechanical device that produces strong reflectance and polarization modulation of incident light. The structure is based on a suspended nanomechanical grating with lateral deformability, and rigorous coupled-wave analysis has been used to fully model the optical properties of the device. The grating consists of two interdigitated gratings that may be moved with respect to each other with an applied force. The structures proposed here are designed to be readily manufacturable with device processing developed for surface-micromachined microelectromechanical systems and with known microelectromechanical systems materials, such as silicon, silicon nitride, and amorphous diamond. As the spacing of the grating is changed, an anomalous diffraction effect is observed, a Wood's type anomaly in which there exists a resonance in propagating leaky modes within the grating, resulting in a dramatic change in the reflectance characteristics for slight changes in the grating. One of the unique features of this structure is that a reflected optical signal can be used to detect subangstrom in-plane motion of structures greater than 10 nm.
There is much current interest in the optical properties of semiconductor nanowires, because the cylindrical geometry and strong two-dimensional confinement of electrons, holes and photons make them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices, including lasersand nonlinear optical frequency converters. Gallium nitride (GaN) is a wide-bandgap semiconductor of much practical interest, because it is widely used in electrically pumped ultraviolet-blue light-emitting diodes, lasers and photodetectors. Recent progress in microfabrication techniques has allowed stimulated emission to be observed from a variety of GaN microstructures and films. Here we report the observation of ultraviolet-blue laser action in single monocrystalline GaN nanowires, using both near-field and far-field optical microscopy to characterize the waveguide mode structure and spectral properties of the radiation at room temperature. The optical microscope images reveal radiation patterns that correlate with axial Fabry-Perot modes (Q approximately 10(3)) observed in the laser spectrum, which result from the cylindrical cavity geometry of the monocrystalline nanowires. A redshift that is strongly dependent on pump power (45 meV microJ x cm(-2)) supports the idea that the electron-hole plasma mechanism is primarily responsible for the gain at room temperature. This study is a considerable advance towards the realization of electron-injected, nanowire-based ultraviolet-blue coherent light sources.
Currently, measuring Raman spectra of tissues of living patients online and in real time, collecting the spectra in a very short measurement time, and allowing diagnosis immediately after the spectrum is recorded from any body region, are specific advantages that fiber optic near-infrared Raman spectroscopy (NIR RS) might represent for in vivo clinical applications in dermatology. We discuss various methodological aspects and state of the art of fiber optic NIR RS in clinical and experimental dermatology to outline its present advantages and disadvantages for measuring skin in vivo, particularly its water content. Fiber optic NIR Fourier transform (FT) RS has been introduced to dermatological diagnostics to obtain information regarding the molecular composition of the skin up to several hundred micrometers below the skin surface in a relatively fast nondestructive manner. This has been especially important for probing for in vivo assessment of cutaneous (intradermal) edema in patients patch test reactions. Fiber optic NIR FT Raman spectrometers still require further technological developments and optimization, extremely accurate water concentration determination and its intensity calculation in skin tissue, and for clinical applications, a reduction of measurement time and their size. Another promising option could be the possibility of applying mobile and compact fiber optic charge-coupled device (CCD)-based equipment in clinical dermatology.
The implantable miniaturized telescope (IMT) is the first intraocular magnifying system proposed for optical correction in patients with age-related macular degeneration (ARMD). The optical component is embedded in a carrying device designed as an intraocular lens that is implanted after cataract surgery. In this study, we report findings on an IMT that was explanted because of aqueous infiltration into its optic and describe the configuration of this device and the surgical technique required for its implantation. The patient, a 75-year-old male with bilateral cataract and nonexudative ARMD, underwent phacoemulsification with implantation of an IMT in the right eye. The rigid device, weighing 46.1 mg in aqueous, has an overall diameter of 13.5 mm and requires implantation through a large limbal incision. It is fixated at the 6 to 12 o'clock meridian. Follow-up examination revealed the presence of numerous droplets inside the IMT optic. The device was explanted and sent to our center for evaluation. A large fissure was found on the carrying device. However, it was unlikely the site for aqueous infiltration. Microdefects at the level of the sealing of the optical cylinder appeared to provide the opening for the inflow of aqueous that formed droplets. Based on the findings of this report the manufacturer has modified the sealing technique to avoid this complication. Current clinical trials are now ongoing to assess the efficacy of this device in providing visual rehabilitation for ARMD patients.
The optical characteristics of endoscopes can be made more effective and the quality of the image improved through incorporation in their optical systems of rod-like components. The use of rod-like components in the rigid choledochoscope helped increase three-fold the optimal efficiency by comparison with that in the formerly manufactured device provided with an optics that was made up of small thickness lenses.
Microsystems incorporate a combination of microfluidic, micromechanical, micro-optical and microelectronic components. This article, the fourth in a series exploring the impact the technology is likely to have on medical products during the next decade, looks at cochlear implants, retinal implants and devices to stimulate the optical cortex.
Based on quantum chemistry and chemical kinetics, the paper formulates basically new concepts of the possibility of controlling biochemical reactions in biological tissues by simultaneously making abnormal human visceral foci, in cancer diseases in particular, exposed to two rays via radiation and optic laser radiations. The paper also presents experimental findings of the channeling of X-ray and fluxes of charged particles along the fiber wave guides. It considers the circuit engineering of a medical endoscopic device that concurrently transmits optic laser radiation and fluxes of penetrating radiation into the viscera.
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Explore the source record for details and available documents.
This paper describes the fabrication, the characterization and the applications of a capillary electrophoresis microchip. This hybrid device (glass/PDMS) features channels and optical waveguides integrated in one common substrate. It can be used for electrophoretic separation and fluorimetric detection of molecules. The microfluidic performance of the device is demonstrated by capillary zone and gel electrophoresis of proteins.
A determination method of fluorine (F), chlorine (Cl), bromine (Br) and iodine (I) by a barrier discharge radiofrequency helium plasma-atomic emission spectroscopy was developed. A borosilicate glass was wrapped by two copper film electrodes, one of which was earthed, and the other was supplied with a radiofrequency high voltage (98 kHz, 3.2 kV), resulting in a discharge inside of the tube. An optical emission from the discharge tube was introduced to a charge-coupled device (CCD)-spectrometer through an optical fiber, and was monitored in the wavelength range of 730-960 nm. The emission lines of F (733.2 nm, 739.9 nm), Cl (833.3 nm, 837.6 nm, 858.6 nm, 894.8 nm, 912.1 nm, etc.), Br (827.2 nm, 882.5 nm, 889.8 nm, 926.5 nm, etc.) and I (905.8 nm) were observed. The linearity of the calibration was determined for F and Cl over the range of 1-10 microg, and for Br of 0.1-1 microg. The relative emission intensity was in the order of Br > I > Cl >F.
Optical simulations of a liquid crystal biosensor device are performed using an integrated optical/textural model based on the equations of nematodynamics and two optical methods: the Berreman optical matrix method [J. Opt. Soc. Am. 62, 502 (1972)] and the discretization of the Maxwell equations based on the finite difference time domain (FDTD) method. Testing the two optical methods with liquid crystal films of different degrees of orientational heterogeneities demonstrates that only the FDTD method is suitable to model this device. Basic substrate-induced texturing process due to protein adsorption gives rise to an orientation correlation function that is nearly linear with the transmitted light intensity, providing a basis to calibrate the device. The sensitivity of transmitted light to film thickness, protein surface coverage, and wavelength is established. A crossover incident light wavelength close to lambda(co) approximately 500 nm is found, such that when lambda>lambda(co) thinner films are more sensitive to the amount of protein surface coverage, while for lambda<lambda(co) the reverse holds. In addition it is found that for all wavelengths the sensitivity increases with the amount of protein coverage. The integrated device model based on FDTD optical simulations in conjunction with the Landau-de Gennes nematodynamics model provides a rational basis for further progress in liquid crystal biosensor devices.
Lentiviral-mediated gene delivery holds significant promise for sustained gene expression within living systems. Vesicular stomatitis virus glycoprotein-pseudotyped human immunodeficiency virus type 1-based lentiviral vectors can be used to introduce transgenes in a broad spectrum of dividing as well as nondividing cells. In the current study, we construct a lentiviral vector carrying two reporter genes separated by an internal ribosomal entry site and utilize that virus in delivering both genes into neuroblastoma cells in cell culture and into cells implanted in living mice. We utilize two reporter genes, a mutant herpes simplex virus type 1 (HSV1) sr39tk as a reporter gene compatible with positron emission tomography (PET) and a bioluminescent optical reporter gene, firefly luciferase (Fluc), to image expression in living mice by an optical charge-coupled device (CCD) camera. By using this lentivirus, neuroblastoma (N2a) cells are stably transfected and a high correlation (R(2) = 0.91) between expressions of the two reporter genes in cell culture is established. Imaging of both reporter genes using microPET and optical CCD camera in living mice is feasible, with the optical approach being more sensitive, and a high correlation (R(2) = 0.86) between gene expressions is again observed in lentiviral-infected N2a tumor xenografts. Indirect imaging of HSV1-sr39tk suicide gene therapy utilizing Fluc is also feasible and can be detected with increased sensitivity by using the optical CCD. These preliminary results validate the use of lentiviral vectors carrying reporter genes for multimodality imaging of gene expression and should have many applications, including imaging of xenografts, metastasis, and cell trafficking as well as noninvasive monitoring of lentiviral-mediated gene delivery and expression.
We report an all solid-state polarization-state generator that uses magneto-optic polarization rotators. The device can generate either five or six distinctive polarization states uniformly across a Poincaré sphere with repeatability better than 0.1 degrees. It is ideal for polarization analysis, swept-wavelength measurement, and monitoring of polarization-related parameters and signal-to-noise ratios of optical networks.
The present study aimed at the determination of changes of tooth-colored cervical restorations in vivo using an optical 3-dimensional laser scanning device. The study was performed on 197 cervical restorations placed on incisors, canines, and premolars. Four different tooth-colored restoration materials, a composite, a polyacid-modified resin composite, and two resin-modified glass ionomer cements, were used for the restoration of the lesions. For the determination of changes, images were taken at baseline and 15, 24 and 36 months after the placement of the fillings using a 3D-laser scanning device. The images were superimposed automatically, and digital subtraction was made by a specially developed image analysis software. The total substance loss on the entire filling surface at 36 months for the resin-modified glass ionomer Photac-Fil was 44 (+/-23) microm, for Fuji II LC 45 (+/-26) microm, for Dyract 71 (+/-47) microm and for Tetric 18 (+/-12) microm. Differentiating between the class of lesion, a higher wear rate was observed at 36 months on restorations which had been placed in erosion/non-carious cervical cavities (66 (+/-33) microm). In conclusion, the composite material demonstrated a distinctly lower surface wear rate over time in comparison to the resin-modified glass ionomer cements and the polyacid-modified resin composite.
We present a study of the sidewall surface quality inside microchannels fabricated in fused silica glass by femtosecond laser pulses and chemical etching. Multiple combinations of laser exposure and etching solution parameters were examined. Results of scanning electron microscopy, atomic force microscopy, and optical reflection analyses of the surfaces are presented. The results obtained demonstrate the feasibility of optical quality surface fabrication, which in turn demonstrates the feasibility of fabricating complex integrated devices containing microfluidic channels and optical waveguides in the glass substrates.