Wide Area Uniform Illumination Scheme Using LED Matrix for Optogenetic Cardiac Pacing

Control of heart rhythm is vital in the case of arrhythmia. Cardiac optogenetics is a promising technique to replace electrical stimulation in a next generation of pacemakers and defibrillators. Therefore, further research towards optimizing light delivery methods is essential. A major requirement is the uniform stimulation of all cells in the area of interest while reducing side effects such as photodamage. Here, a 2 × 2 blue (470 nm, InGaN-based) light-emitting diode (LED) optoelectronic module for uniform ex vivo cardiac muscle illumination is demonstrated. It satisfies two important requirements in optogenetics, which are high illumination homogeneity and high irradiance. CCD camera images show an average 90% homogeneity over the central illumination area of close to 38 mm2 at 1 cm distance from the light source. The module is used to perform physiological experiments on channelrhodopsin 2-expressing Langendorff-perfused mouse hearts. Successful ventricular pacing is obtained for an optical power density threshold below 2 mW/mm2 with light pulses as short as 1 ms. For 10 ms long pulses, the threshold was below 0.2 mW/mm2. The large homogeneous illumination area enabled optogenetic pacing with less than half the optical power of previous attempts with smaller areas of 2 mm2 and thus, presumably, will result in less phototoxicity.

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An ANN-Based Adaptive Predistorter for LED Nonlinearity in Indoor Visible Light Communications

Electronics ◽

10.3390/electronics10080948 ◽

2021 ◽

Vol 10 (8) ◽

pp. 948

Author(s):

Jenn-Kaie Lain ◽

Yan-He Chen

Keyword(s):

Visible Light ◽

Light Emitting Diode ◽

Optical Power ◽

Visible Light Communication ◽

Universal Function ◽

Visible Light Communications ◽

Least Mean Square ◽

Training Sequences ◽

Led Nonlinearity ◽

Electrical Source

By modulating the optical power of the light-emitting diode (LED) in accordance with the electrical source and using a photodetector to convert the corresponding optical variation back into electrical signals, visible light communication (VLC) has been developed to achieve lighting and communications simultaneously, and is now considered one of the promising technologies for handling the continuing increases in data demands, especially indoors, for next generation wireless broadband systems. During the process of electrical-to-optical conversion using LEDs in VLC, however, signal distortion occurs due to LED nonlinearity, resulting in VLC system performance degradation. Artificial neural networks (ANNs) are thought to be capable of achieving universal function approximation, which was the motivation for introducing ANN predistortion to compensate for LED nonlinearity in this paper. Without using additional training sequences, the related parameters in the proposed ANN predistorter can be adaptively updated, using a feedback replica of the original electrical source, to track the LED time-variant characteristics due to temperature variation and aging. Computer simulations and experimental implementation were carried out to evaluate and validate the performance of the proposed ANN predistorter against existing adaptive predistorter schemes, such as the normalized least mean square predistorter and the Chebyshev polynomial predistorter.

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&[mu]-Watt Enhanced Electroluminescent Power of Silicon Nanocrystal Light-Emitting Diodes Made on Nano-Scale Silicon-Tip-Array Substrate

MRS Proceedings ◽

10.1557/proc-0989-a10-05 ◽

2007 ◽

Vol 989 ◽

Author(s):

Gong-Ru Lin ◽

Chun-Jung Lin

Keyword(s):

Light Emitting Diode ◽

Optical Power ◽

Oxide Semiconductor ◽

Si Substrate ◽

Light Emitting ◽

Pillar Array ◽

Turn On ◽

Air Interface ◽

Order Of Magnitude ◽

Etching Mask

AbstractA Si nanocrystal based metal-oxide-semiconductor light-emitting diode (MOSLED) on Si nano-pillar array is preliminarily demonstrated. Rapid self-aggregation of Ni nanodots on Si substrate covered with a thin SiO2 buffered layer is employed as the etching mask for obtaining Si nano-pillar array. Dense Ni nanodots with size and density of 30 nm and 2.8×10 cm-2, respectively, can be formatted after rapid thermal annealing at 850°C for 22 s. The nano-roughened Si surface contributes to both the relaxation of total-internal reflection at device-air interface and the Fowler-Nordheim tunneling enhanced turn-on characteristics, providing the MOSLED a maximum optical power of 0.7 uW obtained at biased current of 375 uA. The optical intensity, turn-on current, power slope and external quantum efficiency of the MOSLED are 140 μW/cm2, 5 uA, 2+-0.8 mW/A and 1×10-3, respectively, which is almost one order of magnitude larger than that of a same device made on smooth Si substrate.

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Reduction of Thermal Resistance and Optical Power Loss Using Thin-Film Light-Emitting Diode (LED) Structure

IEEE Transactions on Industrial Electronics ◽

10.1109/tie.2015.2443106 ◽

2015 ◽

Vol 62 (11) ◽

pp. 6925-6933 ◽

Cited By ~ 5

Author(s):

Huan Ting Chen ◽

Yuk Fai Cheung ◽

Hoi Wai Choi ◽

Siew Chong Tan ◽

S. Y. Hui

Keyword(s):

Thin Film ◽

Thermal Resistance ◽

Power Loss ◽

Light Emitting Diode ◽

Optical Power ◽

Light Emitting

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A simple design of uniform LED illumination using catadioptric collimator and freeform lenslet array

Lighting Research and Technology ◽

10.1177/14771535211052451 ◽

2021 ◽

pp. 147715352110524

Author(s):

DT Vu ◽

H Vu ◽

S Shin ◽

NM Kieu ◽

TQ Tien ◽

...

Keyword(s):

Energy Consumption ◽

Light Emitting Diode ◽

Optical Path Length ◽

Light Emitting ◽

Simple Strategy ◽

Area Of Interest ◽

Lenslet Array ◽

Freeform Optics ◽

Receiver Plane ◽

Indoor Lighting

We introduce a compact lenslet array principle that takes advantage of freeform optics to deploy a light distributor, beneficial for highly efficient, inexpensive, low energy consumption light-emitting diode (LED) lighting system. We outline here a simple strategy for designing the freeform lens that makes use of an array of the identical plano-convex lenslet. The light is redistributed from such lenslet, hinging on the principle of optical path length conservation, and then delivered to the receiver plane. The superimposing of such illumination area from every lenslet occurs on the receiver plane, in which the non-uniform illumination area located in the boundary should have the same dimension as the size of the freeform lenslet array. Such an area, insofar, is negligible due to their small size, which is the crux of our design, representing a large departure from the former implementations. Based on simulations that assess light performance, the proposed design exhibited the compatibility for multiple radiation geometries and off-axis lighting without concern for the initial radiation pattern of the source. As simulated, the LED light source integrated with such proposed freeform lenslet array revealed high luminous efficiency and uniformity within the illumination area of interest were above 70% and 85%, respectively. Such novel design was then experimentally demonstrated to possess a uniformity of 75% at hand, which was close to the simulation results. Also, proposed indoor lighting was implemented in comparison with the commercial LED downlight and LED panel, whereby the energy consumption, number of luminaires and illumination performance were assessed to show the advantage of our simplified model.

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N-face GaN substrate roughening for improved performance GaN-on-GaN LED

Microelectronics International ◽

10.1108/mi-02-2021-0011 ◽

2021 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

Ezzah Azimah Alias ◽

Muhammad Esmed Alif Samsudin ◽

Steven DenBaars ◽

James Speck ◽

Shuji Nakamura ◽

...

Keyword(s):

Quantum Efficiency ◽

External Quantum Efficiency ◽

Light Emitting Diode ◽

Optical Power ◽

Ammonium Hydroxide ◽

Content Type ◽

Light Emitting ◽

Gan Led ◽

Improved Performance ◽

Substrate Roughening

Purpose This study aims to focus on roughening N-face (backside) GaN substrate prior to GaN-on-GaN light-emitting diode (LED) growth as an attempt to improve the LED performance. Design/methodology/approach The N-face of GaN substrate was roughened by three different etchants; ammonium hydroxide (NH4OH), a mixture of NH4OH and H2O2 (NH4OH: H2O2) and potassium hydroxide (KOH). Hexagonal pyramids were successfully formed on the surface when the substrate was subjected to the etching in all cases. Findings Under 30 min of etching, the highest density of pyramids was obtained by NH4OH: H2O2 etching, which was 5 × 109 cm–2. The density by KOH and NH4OH etchings was 3.6 × 109 and 5 × 108 cm–2, respectively. At standard operation of current density at 20 A/cm2, the optical power and external quantum efficiency of the LED on the roughened GaN substrate by NH4OH: H2O2 were 12.3 mW and 22%, respectively, which are higher than its counterparts. Originality/value This study demonstrated NH4OH: H2O2 is a new etchant for roughening the N-face GaN substrate. The results showed that such etchant increased the density of the pyramids on the N-face GaN substrate, which subsequently resulted in higher optical power and external quantum efficiency to the LED as compared to KOH and NH4OH.

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Real-Time Optical Monitoring of Endotracheal Tube Displacement

Biosensors ◽

10.3390/bios10110174 ◽

2020 ◽

Vol 10 (11) ◽

pp. 174

Author(s):

Ramzan Ullah ◽

Karl Doerfer ◽

Pawjai Khampang ◽

Faraneh Fathi ◽

Wenzhou Hong ◽

...

Keyword(s):

Endotracheal Tube ◽

Real Time ◽

Near Infrared ◽

Ex Vivo ◽

Light Emitting Diode ◽

Clinical Care ◽

Cost Effective ◽

Infrared Light ◽

In Vivo Experiments

Proper ventilation of a patient with an endotracheal tube (ETT) requires proper placement of the ETT. We present a sensitive, noninvasive, operator-free, and cost-effective optical sensor, called Opt-ETT, for the real-time assessment of ETT placement and alerting of the clinical care team should the ETT become displaced. The Opt-ETT uses a side-firing optical fiber, a near-infrared light-emitting diode, two photodetectors with an integrated amplifier, an Arduino board, and a computer loaded with a custom LabVIEW program to monitor the position of the endotracheal tube inside the windpipe. The Opt-ETT generates a visual and audible warning if the tube moves over a distance set by the operator. Displacement prediction is made using a second-order polynomial fit to the voltages measured from each detector. The system is tested on ex vivo porcine tissues, and the accuracy is determined to be better than 1.0 mm. In vivo experiments with a pig are conducted to test the performance and usability of the system.

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Factors influencing the use of leadless or transvenous pacemakers: results of the European Heart Rhythm Association Prospective Survey

EP Europace ◽

10.1093/europace/euz357 ◽

2020 ◽

Vol 22 (4) ◽

pp. 667-673 ◽

Cited By ~ 1

Author(s):

Serge Boveda ◽

Eloi Marijon ◽

Radoslaw Lenarczyk ◽

Konstantinos E Iliodromitis ◽

Francisco Marin ◽

...

Keyword(s):

Heart Rhythm ◽

Cardiac Pacing ◽

Cardiac Resynchronization ◽

Standards Of Care ◽

Ventricular Pacing ◽

Risk Of Infection ◽

Prospective Survey ◽

Leadless Pacemaker ◽

Factors Influencing ◽

Double Chamber

Abstract To study the proportion of leadless pacemaker (LL-PM) implants and the factors influencing the choice of LL-PM vs. transvenous pacemaker (TV-PM) across tertiary centres in Europe with routine availability of the LL-PM. A European Heart Rhythm Association (EHRA) prospective snapshot survey using electronically distributed questionnaire sent to participating centres. Participating tertiary cardiac pacing centres prospectively included consecutive patients implanted between November 2018 and January 2019. Questions covered standards of care and policies used for patient management, focusing particularly on the reasons for choosing LL-PM vs. TV-PM. Overall, 21 centres from four countries (France, Netherlands, Spain, and Italy) participated, with eventual data from 798 patients (n = 472, 59% male). With 69 implants, LL-PM represented only 9% of all implants and 36% of the single-chamber pacing group; double-chamber transvenous pacemakers were implanted in 528 patients and biventricular (cardiac resynchronization pacemaker) in 79. The two major reasons reported in favour of LL-PM implantation were an anticipated high risk of infection or low rate of ventricular pacing. Compared to TV-PM, LL-PM patients were more often male (74% vs. 54%, P = 0.009), with greater proportion of valvular heart disease (45% vs. 35%, P = 0.01) and atrial fibrillation (AF; 65% vs. 23%, P < 0.0001), with significantly more comorbidities (≥ one comorbidity, 66% vs. 52%, P = 0.02). This contemporary multicentre European survey shows that LL-PM constitutes a small proportion of all PM implants. Patients implanted with LL-PM were more likely to have AF and a high anticipated risk of infection.

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Do cardiologists follow the European guidelines for cardiac pacing and resynchronization therapy? Results of the European Heart Rhythm Association survey

EP Europace ◽

10.1093/europace/euu395 ◽

2014 ◽

Vol 17 (1) ◽

pp. 148-151 ◽

Cited By ~ 10

Author(s):

E. Sciaraffia ◽

N. Dagres ◽

A. Hernandez-Madrid ◽

A. Proclemer ◽

D. Todd ◽

...

Keyword(s):

Heart Rhythm ◽

Cardiac Pacing ◽

Resynchronization Therapy ◽

European Guidelines

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Evaluation of bone mineral density through radiographic optical densitometry in 42 canine femures

Clínica Veterinária ◽

10.46958/rcv.2021.xxvi.n.150.p.64-69 ◽

2021 ◽

Vol XXVI (150) ◽

pp. 64-69

Author(s):

Bianca Marfil Dias ◽

Anderson F. de Souza ◽

André Luis do V. De Zoppa

Keyword(s):

Bone Mineral Density ◽

Bone Mineral ◽

Ex Vivo ◽

Mineral Density ◽

Trend Function ◽

Tissue Samples ◽

Area Of Interest ◽

Atypical Values ◽

Biomechanical Tests ◽

Densitometric Data

This study evaluates the bone mineral density of 42 canine femurs using radiographic optical densitometry and validates radiographic optical densitometry as a parameter to standardize bone tissue samples used in biomechanical tests, contributing to the diagnosis of osteoporosis in dogs. The ImageJ 1.46r® program was used for the radiographic optical densitometry. After selecting the aluminum steps and the area of interest in the femur, the data obtained were stored in a table and converted into mm/Al using the MS Excel® trend function. Statistical analysis demonstrated the absence of atypical values (outiliers) in the samples analyzed. The samples evaluated were homogeneous and the densitometric data obtained may contribute to reducing the scarcity of densitometric references in the veterinary literature. Ex vivo biomechanical studies may benefit from the method used in this study to standardize their sample when evaluating bone mineral density, validating their respective projects

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