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At least 1,657 records · Page 92Linked to original sources
PubMed2006

The smart Petri dish: a nanostructured photonic crystal for real-time monitoring of living cells.

The intensity of light scattered from a porous Si photonic crystal is used to monitor physiological changes in primary rat hepatocytes. The cells are seeded on the surface of a porous Si photonic crystal that has been filled with polystyrene and treated with an O2 plasma. Light resonant with the photonic crystal is scattered by the cell layer and detected as an optical peak with a charge-coupled-device spectrometer. It is demonstrated that exposure of hepatocytes to the toxins cadmium chloride or acetaminophen leads to morphology changes that cause a measurable increase in scattered intensity. The increase in signal occurs before traditional assays are able to detect a decrease in viability, demonstrating the potential of the technique as a complementary tool for cell viability studies. The scattering method presented here is noninvasive and can be performed in real time, representing a significant advantage compared to other techniques for in vitro monitoring of cell morphology.

Animals↗
PubMed1997

High order DNA structure as inferred by optical fluorimetry and scanning calorimetry.

New quantitative insights on the native high order chromatin-DNA structure existing within interphase nuclei are obtained by monitoring the effects of two common well-characterized fixatives, glutaraldehyde and ethanol/acetic acid mixture, at the level of the intranuclear DNA distribution and structures. Reproducible distinct levels of DNA fluorescence intensity and their intranuclear distribution are apparent in unfixed and fixed thymocytes by using DAPI and quantitative optical microscopy based on a charge coupled device. The fluorescent histograms correlated with the calorimetric thermograms on the very same thymocytes fixed and unfixed, establish an unequivocal baseline for the different levels of structural organization of the chromatin within the intact nucleus; namely their number, DNA packing ratio and fiber diameter. A systematic comparison among all the numerous models, being so far proposed for the quinternary and quaternary levels of DNA folding, to identifies the rope or ribbon-like and the chromonema as the ones that best fit with the in situ distribution.

Animals↗
PubMed2001

[Image analysis and Sheimpflug photography of anterior segment of the eye--a review].

BACKGROUND: Light scattering properties of the cornea and lens change in relation to age. This process is influenced by noxious factors which may induce the formation of cataracts. Four different camera types based on the Scheimpflug principle have been developed for documentation and evaluation of light scattering in the eye. Topcon SL-45. Zeiss SLC, Oxford CASE 2000, Nidek EAS 1000. Only the SL-45 and EAS 1000, however, have found a wider application in clinical and experimental studies. MATERIAL AND METHODS: Documentation of the eye with a Scheimpflug system is performed in a dark room after mydriasis induction. The rotating axis of the camera is aligned to the optical axis of the eye with fixation devices. Four meridians have been found appropriate for routine documentation. Image analysis is based on peak height and distance evaluation of 2 layers in the cornea and 10 layers in the lens. Standardization devices allow correction of technical differences in the recording process. RESULTS: Evaluation of the ageing properties of the lens has evidenced typical density developments for each individual layer, the cortex increasing in density earlier than the nucleus. Cataract classification using a Scheimpflug camera provides an objective characterization of cataract type and progression. The outcome of surgical procedures changing the refractive power of the eye can be evaluated with a Scheimpflug camera as well. Its application in studies dealing with the ocular effects of Quinolones and HMG-CoA-reductase inhibitors, has demonstrated that Scheimpflug photography is the method of choice for establishment of a safety profile for a new drug. CONCLUSIONS: Scheimpflug photography has proven to be ideal for objective documentation of the anterior eye segment in human and animal eyes, although both documentation and image analysis demand technical expertise to be reproducible.

Adult↗
PubMed1986

Resting myosin cross-bridge configuration in frog muscle thick filaments.

Clear images of myosin filaments have been seen in shadowed freeze-fracture replicas of single fibers of relaxed frog semitendinosus muscles rapidly frozen using a dual propane jet freezing device. These images have been analyzed by optical diffraction and computer averaging and have been modelled to reveal details of the myosin head configuration on the right-handed, three-stranded helix of cross-bridges. Both the characteristic 430-A and 140-150-A repeats of the myosin cross-bridge array could be seen. The measured filament backbone diameter was 140-160 A, and the outer diameter of the cross-bridge array was 300 A. Evidence is presented that suggests that the observed images are consistent with a model in which both of the heads of one myosin molecule tilt in the same direction at an angle of approximately 50-70 degrees to the normal to the filament long axis and are slewed so that they lie alongside each other and their radially projected density lies along the three right-handed helical tracks. Any perturbation of the myosin heads away from their ideal lattice sites needed to account for x-ray reflections not predicted for a perfect helix must be essentially along the three helical tracks of cross-bridges. Little trace of the presence of non-myosin proteins could be seen.

Animals↗
PubMed1995

Analysis of signal propagation in optically coupled detectors for digital mammography: I. Phosphor screens.

The angular emission of light from turbid phosphor screens has been measured and modelled. As a first approximation, turbid phosphor screens have traditionally been modelled as Lambertian sources; however, Giakoumakis et al have previously shown that light emission from turbid phosphor screens is in fact more forward peaked. In this article, we extend the theory of Giakoumakis to include turbid phosphor screens that incorporate a transparent overcoat. The refractive index of the optical coupling medium in contact with the overcoat is shown to have a direct effect on both light output and angular emission from the screen. It was found that simple laws of refraction adequately describe this phenomenon. To model the angular emission of light from such phosphor screens, a term was included to describe the refraction from the overcoat into the adjacent coupling medium. The data obtained are required to calculate the propagation of the signal in a digital mammography detector in which a phosphor screen is optically coupled to a charge-coupled device (CCD) image array.

Biophysical Phenomena↗
PubMed1998

Experimental 193-nm excimer laser trephination with divergent cut angles in penetrating keratoplasty.

PURPOSE: To study the morphologic properties of divergent cut angles after nonmechanical trephination for penetrating keratoplasty in donors and recipients and to assess its implications for donor-recipient stability in an experimental porcine model. METHODS: An excimer laser 193-nm corneal trephination was performed in 30 enucleated porcine eyes by using a modified "open mask" (stainless steel sheet 10CrNi18), to obtain round donor buttons and corresponding recipient beds 7 mm in diameter at the level of Bowman's layer. An automated globe-rotation device allowed different cut angles toward the optical axis. Three cut angles were intended: 0 degrees, 15 degrees divergent, and 35 degrees divergent. Quality of the cuts was assessed by means of histology and scanning electron microscopy (SEM). In a different setting, after alignment of the donor button and corresponding recipient bed in an artificial anterior chamber, intracameral pressure was increased stepwise, modifying the height of a bottle of balanced saline solution connected to the chamber. Criterion for "instability" was the movement of the donor button in all four quadrants during observation with a surgical microscope (x12). RESULTS: Reproducible cut angles and smooth cut surfaces of donors and recipients were confirmed by histologic and SEM evaluation. Macroscopically, a good alignment of a divergent donor button in a corresponding recipient bed was achieved. Instability of the donor buttons occurred with a water column niveau at 2 cm in the 0 degrees cut, at 3 cm in 15 degrees divergent cuts, and at 4.5 cm in 35 degrees divergent cuts. CONCLUSION: The stability of a corneal donor button in a recipient bed seems to increase in proportion with the degree of divergence of the trephination angle. Considering the good histologic quality and macroscopic alignment obtained, divergent cut angles may allow a reduction of sutures, assuring a water-tight wound closure in penetrating keratoplasty.

Animals↗
PubMed2004

Light therapy in the treatment of acne vulgaris.

BACKGROUND: Over the past decade, lasers and light-based systems have become a common modality to treat a wide variety of skin-related conditions, including acne vulgaris. In spite of the various oral and topical treatments available for the treatment of acne, many patients fail to respond adequately or may develop side effects. Therefore, there is a growing demand by patients for a fast, safe, and side-effect-free novel therapy. OBJECTIVES: To address the role of light therapy in the armamentarium of treatments for acne vulgaris, to discuss photobiology aspects and biomedical optics, to review current technologies of laser/light-based devices, to review the clinical experience and results, and to outline clinical guidelines and treatment considerations. RESULTS: Clinical trials show that 85% of the patients demonstrate a significant quantitative reduction in at least 50% of the lesions after four biweekly treatments. In approximately 20% of the cases, acne eradication may reach 90%. At 3 months after the last treatment, clearance is approximately 70% to 80%. The nonrespondent rate is 15% to 20%. CONCLUSIONS: Laser and light-based therapy is a safe and effective modality for the treatment of mild to moderate inflammatory acne vulgaris. Amelioration of acne by light therapy, although comparable to the effects of oral antibiotics, offers faster resolution and fewer side effects and leads to patient satisfaction.

Acne Vulgaris↗
PubMed1967

Spectrophotometric cell sorter.

A new device can physically separate cells of predetermined optical properties, from large populations of cells in suspension.

Carcinoma↗
PubMed1997

Imaging of Lactobacillus brevis single cells and microcolonies without a microscope by an ultrasensitive chemiluminescent enzyme immunoassay with a photon-counting television camera.

An ultrasensitive chemiluminescent enzyme immunoassay (CLEIA) was developed for the rapid detection and quantification of Lactobacillus brevis contaminants in beer and pitching yeast (Saccharomyces cerevisiae slurry collected for reinoculation). L. brevis cells trapped on a 47-mm nucleopore membrane (0.4-micron pore size) were reacted with a peroxidase-labelled Lactobacillus group E antibody and then subjected to an enhanced CLEIA analysis with 4-iodophenol as the enhancer. The combination of a nucleopore membrane with low background characteristics that enables the antigen-antibody reaction to proceed through the pores of the membrane and a labelled antibody prepared by the maleimide hinge method with minimal nonspecific binding characteristics was essential to minimize background in the detection of single cells. An ultrahigh sensitive charge-coupled device (CCD) camera equipped with a fiber optics image intensifier permitted the imaging of single cells. A clear correlation existed between the number of luminescent spots observed and the plate count [y (CLEIA) = 0.990x (plate count) + 15.9, where n = 7, r = 0.993, and P < 0.001]. Microscopic observation confirmed that the luminescent spots were produced by single cells. This assay could be used to detect approximately 20 L. brevis cells in 633 ml of beer within 4 h. Our ultrasensitive CLEIA could also be used to detect microcolonies approximately 20 microns in diameter which had formed on a membrane after 15 to 18 h of incubation. This method, which we called the microcolony immunoluminescence (MIL) method, increased the signal-to-noise ratio dramatically. The MIL method could be used to detect a 10(0) level of L. brevis contamination in 633 ml of beer and a 1/10(8) level of L. brevis contamination in pitching yeast within 1 day (15 to 18 h to form microcolonies and 2 h for CLEIA).

Beer↗
PubMed1987

Microscope ocular fundus photography.

The ocular of any microscope may be used for the purpose of photography through the device if the camera utilizes the given optical conditions like an observer eye concerning aperture and focal length.

Equipment Design↗
PubMedDate not supplied

Imagequest. A model self-assessment and self-teaching program for cytopathology.

OBJECTIVE: To develop a low-cost program for providing self-assessment and training for cytopathologists. STUDY DESIGN: Using an optical microscope with a color charge coupled device connected to a personal computer equipped with an ISA bus frame grabber, images were digitized. After the selection of proper images, they were attached to 100 questions with a single answer and five options each. For every question, references accompanied the answer. A colorful score and sounds were played while each question and its corresponding answer were on the screen in order to stimulate the learning process. RESULTS: A low-cost, attractive, effective program for providing self-assessment and training for cytopathologists was developed. CONCLUSION: The use of a high-level programming language permits the creation of a simple, assisted, programmable interface with accessibility for upgrades and customization for every pathologist. This feature permits the insertion of new questions, an essential feature to preserve the usefulness of the program for the future.

Cell Biology↗
PubMed1994

Noninvasive optical diagnosis of bacteria causing otitis media.

Currently, the identification of the bacteria responsible for acute otitis media requires a painful invasive procedure: tympanocentesis. To develop a rapid and noninvasive technique for bacterial diagnosis, the fluorescence profiles of four common pathogens and the optical characteristics of the tympanic membrane have been investigated. Each bacterium produces a unique in vitro fluorescence profile when measured in a saline suspension. Also, spectrally resolved transmission measurements from the chinchilla tympanic membrane demonstrate an optical window that will transmit sufficient light for in vivo measurement of the fluorescence profiles. Thus, we have established the precept for a fluorescence-based bacterial diagnosis technique to be used in otitis media. This paper presents the theory, optical data, and a discussion of the device engineering involved in the technique.

Animals↗
PubMed2006

Tunable Bragg filters based on polymer swelling.

We report on the optical properties of Bragg mirrors and filters fabricated from photo-cross-linked standard optical polymers. The transmittance spectra of these devices in the visible to near-infrared spectral range were measured. We demonstrate efficient tuning of the filter peak of the polymer Bragg filters over several hundred nanometers by adding organic solvents to the surrounding atmosphere of the filter. This represents what we believe to be a novel tuning principle for Bragg filters relying on the use of polymeric materials.

Journal Article↗
PubMed2006

Single-frequency Sb-based distributed-feedback lasers emitting at 2.3 microm above room temperature for application in tunable diode laser absorption spectroscopy.

GaInAsSb/GaAlAsSb/GaSb distributed-feedback (DFB) laser diodes based on a type I active region were fabricated by molecular beam epitaxy at the Centre d'Electronique et de Micro-Optoélectronique de Montpellier (CEM2). The DFB processing was done by Nanoplus Nanosystems and Technologies GmbH. The devices work in the continuous-wave regime above room temperature around an emission wavelength of 2.3 microm with a side-mode suppression ratio greater than 25 dB and as great as 10 mW of output power. The laser devices are fully characterized in terms of optical and electrical properties. Their tuning properties made them adaptable to tunable diode laser absorption spectroscopy because they exhibit more than 220 GHz of continuous tuning by temperature or current. The direct absorption of CH4 is demonstrated to be possible with high spectral selectivity.

Journal Article↗
PubMed2005

Implementation of a graded-index medium by use of subwavelength structures with graded fill factor.

We present a novel configuration for the implementation of subwavelength-based graded-index devices. The proposed concept is based on the etching of one-dimensional subwavelength gratings into a high-index slab waveguide to achieve the desired effective index distribution. A graded-index profile can be achieved by gradually modifying the duty ratio of the grating along the horizontal axis, while the beam is confined in the vertical direction by the slab waveguide. On the basis of this concept, novel graded-index lenses and waveguides are both proposed and characterized numerically by use of finite-difference time-domain and finite-element analysis. The proposed devices can be used for guiding, imaging, optical signal processing, mode matching, coupling, and other applications while offering the intrinsic advantages of on-chip integration such as miniaturization, eliminating the need to align each component separately, and compatibility with standard microfabrication techniques for manufacturability.

Journal Article↗
PubMed2004

Chaotic ray dynamics in an optical cavity with a beam splitter.

We investigate the ray dynamics in an optical cavity when a ray-splitting mechanism is present. The cavity is a conventional two-mirror stable resonator, and the ray splitting is achieved by inserting an optical beam splitter perpendicular to the cavity axis. Using Hamiltonian optics, we show that such a simple device presents surprisingly rich chaotic ray dynamics.

Journal Article↗
PubMed2006

Highly efficient optical coupling and transport phenomena in chains of dielectric microspheres.

Using the generalized multiparticle Mie theory, we investigate optical coupling and transport through chains of dielectric microspheres. We identify two distinct coupling mechanisms of optical transport in terms of the coupling efficiency between neighboring microspheres, namely, evanescent coupling and nanojet coupling. We demonstrate that perfect whispering gallery mode propagation through a chain of evanescently coupled microspheres can be achieved. However, optical coupling and transport through a chain of nanojet-inducing microspheres is less efficient due to the radiative nature of photonic nanojets. Understanding these two optical coupling mechanisms is critical for selecting appropriate microspheres to build coupled resonator optical waveguides and other photon-manipulation devices for effective and low-loss guiding of photons.

Journal Article↗