Optics and Photonics Research Papers (original) (raw)

Top Papers
Most Cited Papers
Most Downloaded Papers
Newest Papers
People
- by
- •
- Optics, Biomedical Engineering, Photochemistry, Computer Security

The restoration of anterior teeth is a difficult task, even for an experienced operator. Currently there are many different ceramic systems that can be used to achieve highly esthetic results. These include metal-ceramics with porcelain margins, Dicor, In-Ceram, Cerestore, Hi-Ceram, IPS-Empress, Cerapearl, Optec, and CAD/CAM ceramics. While metal-ceramics have been used for more than four decades, the quest for a material that transmits and refracts light like a natural tooth has inspired research into all-ceramic restorations. The purpose of this paper is to briefly discuss the properties of each of the above-mentioned materials and clinically evaluate the optical behavior of: (1) metal-ceramic crowns with castings 2 mm short of the shoulder preparation and 360-degree porcelain margins; (2) In-Ceram Spinell restorations; and (3) IPS Empress restorations, and to compare these with metal-ceramic crowns with copings to the shoulder preparation and 180-degree porcelain margins. Light t...

- by Konstantinos Michalakis
- •
- Dentistry, Computer Aided Design, Dental Materials, Ceramics
- by Carmen Puliafito
- •
- Optical coherence tomography, Porphyrins, Tomography, Photodynamic Therapy
- by Joohwan Kim
- •
- Mechanical Engineering, Electrochemistry, Liquid Crystals, Polymers
- by Devon Murphy
- •
- Materials Science, Fluorescence Microscopy, Glass, Medicine
- by Claudia Muñoz
- •
- Physical Chemistry, Dentistry, Biomedical Engineering, Dental Materials

Keratometry is currently achieved by projecting a circular mire onto the patient's cornea and analyzing the size and shape of its reflected image. The projection mires are decisive for the precision of the measurement. We have previously developed a keratometric module for slit lamps, and the development of four projection mires are presented. Mire 1 is composed of optical fibers and electrical cables; Mire 2, 48 LEDs; Mire 3, optical fibers and no electrical cables; and Mire 4, mechanical parts--cable free. Mires 2-4 provide accurate keratometry measurements at slit lamps. Mire 4 is the most adequate for the clinical environment.

- by Liliane Ventura
- •
- Mechanical Engineering, Ophthalmology, Research Design, Cornea
- by Pablo Artal
- •
- Adaptive Optics, Humans, Contrast sensitivity, Cataract
- by Patrick Tekavec
- •
- Engineering, Mathematics, Physical Chemistry, Electronics
- by feng zhang
- •
- Pharmacology, Biochemistry, Bioinformatics, Evolutionary Biology

Bifunctional DNA oligonucleotides serve as templates for chromophoric silver clusters and as recognition sites for target DNA strands, and communication between these two components is the basis of an oligonucleotide sensor. Few-atom silver clusters exhibit distinct electronic spectra spanning the visible and near-infrared region, and they are selectively synthesized by varying the base sequence of the DNA template. In these studies, a 16-base cluster template is adjoined with a 12-base sequence complementary to the target analyte, and hybridization induces structural changes in the composite sensor that direct the conversion between two spectrally and stoichiometrically distinct clusters. Without its complement, the sensor strand selectively harbors ~7 Ag atoms that absorb at 400 nm and fold the DNA host. Upon association of the target with its recognition site, the sensor strand opens to expose the cluster template that has the binding site for ~11 Ag atoms, and absorption at 720 nm with relatively strong emission develops in lieu of the violet absorption. Variations in the length and composition of the recognition site and the cluster template indicate that these types of dual-component sensors provide a general platform for near-infrared-based detection of oligonucleotides in challenging biological environments.

- by Austin Herbst
- •
- Chemical Engineering, Analytical Chemistry, Nanotechnology, DNA
- by Asha Chaubey
- •
- Analytical Chemistry, Biomedical Engineering, Health Care, Environmental Monitoring
- by Anna Köhler
- •
- Chemistry, Electronics, Quantum Theory, Organic Semiconductors
- by Robertus J.m. Klein Gebbink
- •
- Chemistry, Photochemistry, Self Assembly, Porphyrins
- by Tony Ng
- •
- Materials Engineering, Condensed Matter Physics, Microscopy, Fluorescence Microscopy
- by Pablo Artal
- •
- Humans, Follow-up studies, Cataract, Clinical Sciences

A technique for accurate superimposition of computerized perimetry data onto the corresponding retinal locations seen on fundus photographs was developed. The technique was designed to take into account: 1) that the photographic field of view of the fundus camera varies with ametropia-dependent camera focusing 2) possible distortion by the fundus camera, and 3) that corrective lenses employed during perimetry magnify or minify the visual field. The technique allowed an overlay of perimetry data of the central 60 degrees of the visual field onto fundus photographs with an accuracy of 0.5 degree. The correlation of localized retinal morphology to localized retinal function was therefore limited by the spatial resolution of the computerized perimetry, which was 2.5 degrees in the Dicon AP-2500 perimeter employed for this study. The theoretical assumptions of the technique were confirmed by comparing visual field records to fundus photographs from patients with morphologically well-defined non-functioning lesions in the retina.

- by Toke Bek
- •
- Photography, Humans, Diabetic Retinopathy, Lenses
- by Joanna Cygler
- •
- Biomedical Engineering, Medical Physics, Radiotherapy, Radiometry
- by antony jeevarajan
- •
- Bioengineering, Biotechnology, Multidisciplinary, Cell Culture
- by Nicholas Goddard
- •
- Analytical Chemistry, Biomedical Engineering, Electrochemistry, Nanotechnology
- by B. Rouhani
- •
- Acoustics, Materials Science, Optics, Silicon
- by Jean-jacques Greffet
- •
- Nanotechnology, Multidisciplinary, Quantum Dots, Gold
- by Laurent Markey
- •
- Photonic Integrated Circuits, Computer Aided Design, Computer Simulation, Surface Plasmons
- by Vimal Thilak
- •
- Mechanical Engineering, Algorithms, Image Processing, Remote Sensing
- by Hamayun Zafar
- •
- Dentistry, Electronics, Temporomandibular Joint, Humans
- by Maciej Wojtkowski and +1
- •
- Optical coherence tomography, Fourier Analysis, Humans, Automation
- by Álvaro M Pons
- •
- Clinical Sciences, Optometry and Ophthalmology, Optics and Photonics, Visual Fields
- by Nanguang Chen
- •
- Quantum Physics, Microscopy, Optical coherence tomography, Optical physics
- by Toni Laurila
- •
- Engineering, Polymers, Dental Materials, Humans
- by Manuel Nieto-Vesperinas
- •
- Humans, Diffusion, Optical physics, Theoretical Models
- by Thomas Laue
- •
- Thermodynamics, Biology, Medicine, Quantitative analysis
- by Peter Gunter
- •
- Terahertz spectroscopy, Terahertz, Optical physics, Cesium
- by Peter Lanzerstorfer and +1
- •
- Fluorescence, Fluorescence Microscopy, Nanoparticles, Fluorescent Dyes and Reagents
- by arafa aly and +1
- •
- Transmission, Photonic Band Gap Materials, Optics and Photonics
- by Frans Groen
- •
- Microscopy, Flow Cytometry, Multidisciplinary, Optics and Photonics
- by Donald Tan
- •
- Myopia, Cornea, Higher Order Thinking, Refractive Error
- by Michael McKenna
- •
- Strength & Conditioning, Skeletal muscle biology, Adolescent, Humans
- by Jay Pepose
- •
- Optometry, Cornea, Biometry, Cataract surgery
- by hung bui
- •
- Skeletal muscle biology, Muscle strength, Humans, Female
- by Akihiro Ohira
- •
- Ophthalmology, Surgery, Treatment, Radiation Protection
- by Ivo Que
- •
- Physiology, Nanoparticles, Fluorescent Dyes and Reagents, Near Infrared
- by Sergei a. Vinogradov
- •
- Biochemistry, Analytical Chemistry, Kinetics, Microcirculation

Pulse oximeters are known to be inaccurate in the presence of elevated concentrations of carboxyhemoglobin and methemoglobin. This paper attempts to alleviate some of the confusion that exists between fractional and functional saturation, and to clarify the comparison of each with SpO2. A series of theoretical relationships between pulse oximeter reading (SpO2) and actual oxygen saturation (both fractional and functional) is derived using simple absorption theory. The theoretical relationships are checked using an experimental in vitro test system. This consists of a blood circuit containing a model finger, capable of simulating the pulsatile transmission signals through a real finger. Theoretical predictions and experimental results are compared and are found to agree well in the presence of carboxyhemoglobin, but less well with methemoglobin. Possible reasons are discussed.

- by John Moyle
- •
- Biomedical Engineering, Carbon Dioxide, Humans, Calibration
- by Vasudevan lakshminarayanan
- •
- Ancient History, Physiological Optics, Egypt, Humans

We report on a photodetector in which colloidal quantum dots directly bridge nanometer-spaced electrodes. Unlike in conventional quantum-dot thin film photodetectors, charge mobility no longer plays a role in our quantum-dot junctions as charge extraction requires only two individual tunnel events. We find an efficient photoconductive gain mechanism with external quantum efficiencies of 38 electrons-per-photon in combination with response times faster than 300 ns. This compact device-architecture may open up new routes for improved photodetector performance in which efficiency and bandwidth do not go at the cost of one another.

- by Val Zwiller and +2
- •
- Photochemistry, Nanotechnology, Confocal Microscopy, Multidisciplinary

We have simulated diffuse reflectance spectra of skin by assuming a wavelength-independent scattering coefficient for the different skin tissues and using the known wavelength dependence of the absorption coefficient of oxy- and deoxyhaemoglobin and water. A stochastic Monte Carlo method is used to convert the wavelength-dependent absorption coefficient and wavelength-independent scattering coefficient into reflected intensity. The absorption properties of skin tissues in the visible and near-infrared spectral regions are estimated by taking into account the spatial distribution of blood vessels, water and melanin content within distinct anatomical layers. The geometrical peculiarities of skin histological structure, degree of blood oxygenation and the haematocrit index are also taken into account. We demonstrate that when the model is supplied with reasonable physical and structural parameters of skin, the results of the simulation agree reasonably well with the results of in vivo ...

- by Igor Meglinski
- •
- Algorithms, Biomedical Engineering, Monte Carlo, Near Infrared

The Dutch merchant and naturalist Anton van Leeuwenhoek is considered to be the father of optic microscopy and the precursor of bacteriology. Among others, he discovered and studied the spermatozoon.

- by Maria Tzetis
- •
- Microbiology, Microscopy, Cell Biology, Humans
- by Desiree O'Leary
- •
- Humans, Radiologic Technology, Clinical Sciences, Optics and Photonics