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At least 325 records · Page 18Linked to original sources
PubMed2005

Study of luminescence properties of novel Er3+ single-doped and Er3+/Yb3+ co-doped tellurite glasses.

The novel Er(3+) single-doped and Er(3+)/Yb(3+) co-doped tellurite glasses were prepared. The effect of Yb(2)O(3) concentration on absorption spectra, emission spectra and upconversion spectra of glasses were measured and investigated. The emission intensity, fluorescence full width at half maximum (FWHM) and upconversion luminescence of Er(3+) go up with the increasing concentration of Yb(3+) ions. The maximum FWHM of (4)I(13/2) --> (4)I(15/2) transition of Er(3+) is approximate 77 nm for 1.41 x 10(21)ions/cm(3) concentration of Yb(3+)-doped glass. The visible upconversion emissions at about 532, 546 and 659 nm, corresponding to the (2)H(11/2) --> (4)I(15/2), (4)S(3/2) --> (4)I(15/2) and (4)F(9/2) --> (4)I(15/2) transitions of Er(3+), respectively, were simultaneously observed under the excitation at 970 nm. Subsequently, the possible upconversion mechanisms and important role of Yb(3+) on the green and red emissions were discussed and compared. The results demonstrate that this kind of tellurite glass may be a potentially useful material for developing potential amplifiers and upconversion optical devices.

Erbium↗
PubMed2004

Thermal stability, Judd-Ofelt theory analysis and spectroscopic properties of a new Er3+/Yb3+-codoped germano-tellurite glass.

The Er3+/Yb3+-codoped 70TeO2-5Li2O-10B2O3-15GeO2 glass was prepared. The thermal stability, absorption spectra, emission spectra and up-conversion spectra were measured and investigated. The Judd-Ofelt analysis based on absorption spectra was performed in order to determine the Judd-Ofelt intensity parameters Omega(t) (t = 2, 4, 6), spontaneous emission probability, radiative lifetime and branching ratios of several Er3+ transitions. It was found that this studied glass has good thermal stability, broad fluorescence full width at half maximum (FWHM), large stimulated emission cross-section and strong up-conversion emissions at about 532, 546 and 659 nm, corresponding to the 2H(11/2)-->4I(15/2), 4S(3/2)-->4I(15/2) and 4F(9/2)-->4I(15/2) transitions of Er3+, respectively under the excitation at 970 nm. The results suggest that this Er3+/Yb3+-codoped germano-tellurite glass may be a potentially useful material for developing potential amplifiers and up-conversion optical devices.

Cations, Monovalent↗
PubMed2006

Upconversion and fluorescence spectral studies of Er3+/Yb3+-codoped Bi2Q3-GeO2-Ga2Q3-Na2O glasses.

The absorption spectra and upconversion fluorescence spectra of Er3+/Yb3+-codoped natrium-gallium-germanium-bismuth glasses are measured and investigated. The intense green (533 and 549 nm) and red (672 nm) emission bands were simultaneously observed at room temperature. The quadratic dependence of the green and red emission on excitation power indicates that the two-photon absorption processes occur. The influence of Ga2C3 on upconversion intensity is investigated. The intensity of green emissions increases slowly with increasing Ga2O3 content, while the intensity of red emission increases significantly. The possible upconversion mechanisms for these glasses have also been discussed. The maximum phonon energy of the glasses determined based on the infrared (IR) spectral analysis is as low as 740 cm-1. The studies indicate that Bi2O3-GeO2-Ga2O3-Na2O glasses may be potential materials for developing upconversion optical devices.

Bismuth↗
PubMed2005

The adaptive effect of narrowing the interocular separation on the AC/A ratio.

The purpose of this study was to determine whether the response AC/A ratio could be altered when the subject's interpupillary distance (IPD) was optically halved. We measured the changes in the AC/A ratio for 10 subjects after using the optical device for 30 min. Accommodative response was measured using a Canon R-1 optometer, and vergence response was measured with an ASL 210 Eye Movement Monitor. The average AC/A ratios were 1.20+/-0.35 (SD) (MA/D) and 0.84+/-0.39 (MA/D) before and after wearing the device, respectively. The decrease in AC/A ratio was statistically significant (p=0.01). This was mainly caused by a reduction in the slope of the accommodative vergence. The results of this study suggest that the AC/A ratio can be decreased if an IPD-narrowing device is used. A possible application of this mechanism in the study of myopia is discussed.

Accommodation, Ocular↗
PubMed2005

Age and FSH effects in fluorescence spectra from the cervix: an exploratory analysis.

INTRODUCTION: Real-time optical technologies that could diagnose cervical cancer could improve the detection of cervical cancer. Our group is studying the technology assessment of optical devices in the screening and diagnosis of cervical neoplasias. METHODS: We have conducted a diagnostic trial in 850 patients with referral Papanicolaou smears showing ASCUS or greater. Each colposcopically abnormal site and two normal sites were measured with fluorescence and reflectance spectroscopy and then biopsied. Each site generates a fluorescence excitation emission matrix that has a 3-dimensional map with peaks and valleys. RESULTS: The early exploration of these data is presented and shows an effect of age, Follicle Stimulating Hormone or FSH, and, curiously, of their interaction. We have examined other biographical variables like smoking, HPV positivity, grade of CIN, device used, probe used, race, ethnicity, gravidity, parity, previous treatments, and others. None are significant predictors of this finding of increased intensity, except age and FSH. CONCLUSIONS: The effect of age supports the work done on fresh tissue slices in trying to better understand the biology of fluorescence. The effect of FSH is not a surrogate for age, but an independently significant effect, for which we currently do not have an explanation. We are exploring if FSH is a surrogate for estrogenization by measuring estradiol levels and calculating the BMI.

Age Factors↗
PubMed1997

VATS for complete dissection of LIMA in minimally invasive coronary artery bypass grafting.

BACKGROUND: The aim of this work is to report our initial experience with minimally invasive coronary artery bypass grafting, using video-assisted thoracic surgery (VATS) to facilitate the operation and provide complete dissection of the left internal mammary artery (LIMA). METHODS: Of 44 scheduled patients, 43 patients, 30 (69.8%) male, ranging in age from 31 to 83 years (60.8 +/- 12.0 years), with a severe lesion in the anterior descending artery, were operated upon. An 8-cm left anterior minithoracotomy was performed at the fourth intercostal space. Through this incision the optical device for video-assisted thoracic surgery as well as the surgical instruments were placed to provide complete LIMA dissection. This permits dissection until the subclavian region, allowing for anastomosis without tension or distortion. Bypass circulation was not used, and the cardiac rate was decreased with the use of intravenous beta-blockers. For LIMA-to-anterior descending artery anastomosis, proximal and distal tourniquets were used and 1.5 mg/kg of heparin was administered intravenously. RESULTS: Video-assisted thoracic surgery provided a complete dissection of LIMA. The 43 patients presented satisfactory postoperative progress, being released from the hospital between 2 and 12 days after their operation, with a mean of 4 days. The patients have remained asymptomatic during a period that ranged from 1 to 13 months (6.3 +/- 3.5 months). During the follow-up, there was one death as a result of stroke and pneumonia 2 months after the release from the hospital. CONCLUSIONS: The use of video-assisted thoracic surgery through thoracotomy allows the LIMA dissection without the necessity of other incisions. The procedure also permitted more ample dissection of LIMA when compared with minithoracotomy without video-assisted thoracic surgery.

Adult↗
PubMed1982

The prognosis for keratoplasty in keratoconus.

The long-term results in 326 eyes grafted for phakic keratoconus by the same surgeon were reviewed. All consecutive grafts performed for this disease with a minimum of five-year follow-up were included in the study. The mean follow-up was 11.3 years, with a range of 5 to 34 years. Ninety percent of grafts remained clear, 3% were nebulous but retained 20/40 vision, and 7% failed. Donor age was available for 188 of the 326 grafts. No relationship was found between donor age and long-term graft clarity even when older (more than 70 years) donor tissue was used. The visual acuity was measured with the patient's preferred optical device worn daily. Seventy-three percent of eyes achieved 20/40 or better vision after their initial graft.

Adolescent↗
PubMed2000

Supported membranes on soft polymer cushions: fabrication, characterization and applications.

Soft biofunctional and biocompatible interfaces on solids designed by the deposition of ultrathin soft polymer films or supported membranes have numerous scientific and practical applications. These include the immobilization of glycolipids, membrane receptors and proteins to generate models of cell and tissue surfaces. Powerful surface-sensitive techniques can be applied to study protein-protein recognition processes at membranes and the control of cell adhesion by the interplay of specific 'lock-and-key' forces and universal interfacial forces. Potential practical applications include the design of smart biosensors based on electro-optical devices and the fabrication of biofunctional surfaces for the stimulation of cell proliferation and tissue growth, or for the suppression of apoptosis.

Biosensing Techniques↗
PubMed1997

A new data-acquisition system for the measurement of the net water flux across epithelia.

We describe a computer-based data-acquisition system designed for the measurement of net water flux across epithelia. It is based on the detection of a liquid meniscus position in a capillary tube using an electro-optical device. Then the data are digitized, transferred to the computer main memory and saved in a file. The advantages of the system are: (a) to measure net water transfer with an accuracy of 50 nl; (b) to switch from absorptive to secretory conditions in real time; (c) data are directly digitized to be analytically, graphically and statistically treated; (d) the specially developed software allows change of time intervals for data acquirement and the scale in graphic events; (e) the software also allows recall to the monitor screen of graphics from previous tests or to print them on paper; (f) a simple mechanical structure, saving maintenance and time; and (g) high reliability.

Animals↗
PubMed2005

[Ocular biometry using Orbscan].

Orbscan is a recent optical device that combines the Placido disk of the videokeratoscope and a scanning slit. The scanning slit measures the elevation of both the corneal surface (anterior and posterior) and the anterior iris-lens surface. Biometric measures of the anterior segment such as corneal thickness, anterior chamber depth, corneal diameter, and iridocorneal angle are obtained using spatial coordinates of various ocular surfaces. Orbscan is not only a corneal topograph but a versatile device capable of measuring the biometry of the anterior segment of the eye.

Biometry↗
PubMed1991

Attack of the sand brier.

Corneal foreign bodies represent one of the more common sources of eye-related trauma presenting to emergency and primary care physicians. Presented is the case of a man in whom the diagnosis was overlooked because a magnifying optical device was not used.

Adult↗
PubMed2003

Three-dimensional morphometry of the femoral condyles.

OBJECTIVE: The present study describes the geometry of the three-dimensional articular surfaces of the human femoral condyles based on measurements of surface coordinates. DESIGN: The purpose was not to obtain a complex representation of one single condyle, but to describe the femoral condyles using simple geometric parameters based on measurements using a number of specimens. BACKGROUND: In joint modeling, a representative knee joint geometry is often desired which requires an approximation of the irregular joint geometry while taking into account interspecimen variations. METHODS: An optical device was used to measure the condylar articular surfaces of 12 human femurs in the femorotibial contact region. The sagittal profiles were reconstructed by means of two circular arcs and the radial profiles by means of one circular arc. RESULTS: The results provide the geometric parameters necessary for the three-dimensional reconstruction of the articular surfaces of the femoral condyles. The results indicate that the medial and lateral condyles of the distal femur are significantly asymmetric in a number of morphological features. CONCLUSION: The primary application of the results is expected to be in the formulation of finite element models of the knee joint for static contact problems. RELEVANCE: Numerical models of the knee joint are being widely used to study the mechanics of the joint. However, formulation of such models demands a prior knowledge of the complex three-dimensional geometry of the articular surfaces of the natural joint to establish the input parameters of the model.

Adult↗
PubMed1998

Blood volume regulation during hemodialysis.

Hemodialysis (HD)-induced hypotension may be precipitated by severe hypovolemia. To avoid the appearance of destabilizing hypovolemias, we have developed a biofeedback control system for intradialytic blood volume (BV)-changes modeling. The system, incorporated in a dialysis machine, is based on a multivariable closed-loop control with a dependent output variable, the BV changes, and two independent control variables, the ultrafiltration rate (Qf) and dialysate conductivity (DC). The relative BV changes occurring during HD are measured by an optical device. The Qf and DC are continuously adjusted by the control model during the treatment to minimize any discrepancies between the ideal targets for the BV, the patient's body weight reductions, and the experimentally obtained results. The system manages three kinds of errors: in BV changes, the total weight loss, and the sodium balance. The latter is controlled by a dedicated kinetic model that continuously calculates the equivalent DC and, by the end of the session, tends to make the sodium balance the same as the one obtained in conventional HD with constant DC. This system's capacity to improve intradialytic hemodynamic tolerance has been assessed in a crossover study of eight highly symptomatic patients. Conventional HD (CHD; period A) was compared with blood volume-controlled dialysis sessions (BV-CHD; period B) following a protocol with an A1-B-A2 sequence, with each period lasting 1 month. A lower decrease in BV (-10.6%) was obtained during BV-CHD (period B) compared with CHD (-12.3% in period A1 and -12.5% in period A2). The predialysis to postdialysis systolic arterial pressure changes were lower in period B (-12.4%) than in period A (-20% in A1 and -17.5% in A2; P < 0.05) despite similar total Qf and mean treatment times. A significant reduction in the number of severe hypotensive episodes (three in period B v 26 in period A1 and 16 in period A2; P < 0.05) and the overall incidence of complaints, especially of muscular cramps, was found in BV-CHD. These results were reflected in a reduced need for therapeutically administered isotonic saline in each session (60 mL in B v160 mL in A1 and 95 mL in A2; P < 0.05). In conclusion, the proposed biofeedback system for intradialytic BV control may be useful to avoid severe hypovolemic states, to stabilize BV by modeling its trend, and to avoid reaching individual critical BV thresholds in hypotension-prone patients.

Blood Pressure↗
PubMed2002

BEM simulation of Wien filters.

The boundary element method can provide accurate solutions to the electromagnetic problem in numerical simulations of electron optics devices. In this paper, we describe our approach, which applies a subsectional-bases method to generate a boundary division, representing the shape and behaviour of the Wien filter precisely. We investigate by direct ray tracing the origin of the second-order geometrical aberrations of this filter and propose new designs to reduce them.

Journal Article↗
PubMed1999

The determination of three subcutaneous adipose tissue compartments in non-insulin-dependent diabetes mellitus women with artificial neural networks and factor analysis.

The optical device LIPOMETER allows for non-invasive, quick, precise and safe determination of subcutaneous fat distribution, so-called subcutaneous adipose tissue topography (SAT-Top). In this paper, we show how the high-dimensional SAT-Top information of women with type-2 diabetes mellitus (non-insulin-dependent diabetes mellitus (NIDDM)) and a healthy control group can be analysed and represented in low-dimensional plots by applying factor analysis and special artificial neural networks. Three top-down sorted subcutaneous adipose tissue compartments are determined (upper trunk, lower trunk, legs). NIDDM women provide significantly higher upper trunk obesity and significantly lower leg obesity ('apple' type), as compared with their healthy control group. Further, we show that the results of the applied networks are very similar to the results of factor analysis.

Adipose Tissue↗
PubMed1998

Role of ophthalmic nurses with visually impaired patients.

In 1987, it was estimated that over 13 million people in the world were visually impaired, and more than 27 to 35 million were classified as blind. Greater than 6 million visually impaired people live in the United States. There are many causes of visual impairment, including age-related macular degeneration, cataracts, glaucoma, diabetic retinopathy, autoimmune deficiency syndrome, and trauma. Some patients may be helped or visual loss delayed with surgery. Many may have dramatic visual improvement with optical devices, large-print publications, and improved lighting. The ophthalmic nurse may assist in accurately assessing the patient's vision and identifying his or her lifestyle and ability to function independently. Assisting the patient to overcome psychosocial and economic barriers and helping to obtain assistance is critical to enable patients to function independently. Ophthalmic nurses may be instrumental in increasing patients' awareness of community resources and services available to those who are visually impaired.

Activities of Daily Living↗
PubMed2002

Crystal of semiconducting quantum dots built on covalently bonded t5 [in(28)cd(6)s(54)](-12): the largest supertetrahedral cluster in solid state.

Periodic array of nanoparticles is essential for practical applications in optical devices. Periodic dot arrays often exhibit very interesting collective phenomenon. We report a periodic crystal of InCdS pseudo-T5 nanocluster, the largest supertetrahedral cluster found thus far in solid state. Each InCdS cluster behaves like a nanoparticle with the same size. Unlike the array of colloidal dots in which the dot-dot separation is large ( approximately 5 nm), the neighboring T5 clusters in [In28Cd6S54].[(CH3)4N]12[(HSCH2COOH)2]3.5 crystal form a natural point contact by sharing covalently bonded S atoms. Both experimental and theoretical studies show that this crystal is a semiconductor with a band gap of 3.0 eV.

Journal Article↗