Like Light Emitting Diodes Research Articles

Indoor photovoltaics: A numerical model of dye-sensitized solar cells based on indoor illumination for the Internet of Things applications

Since dye-sensitized solar cells (DSSC) have a suitable efficiency in the invisible region, they present a promising avenue for sustainable energy generation, particularly in the context of indoor environments where ambient lighting prevails. This paper proposes a novel numerical model tailored to assess the performance of DSSCs under indoor lighting conditions, with a specific focus on their potential application in powering Internet of Things (IoT) devices. By considering factors such as radiation intensity and spectral composition, particularly from common indoor light sources like Light Emitting Diodes (LEDs) and Fluorescent lights, the model offers insights into the efficiency and viability of DSSCs in indoor settings. Since empirical analyses are difficult and expensive, the existence of a numerical model that investigates cell behavior under indoor illumination can be beneficial for developing such cells. In conducting verifying analyses under varying lighting conditions, the study demonstrates notable efficiencies of DSSCs, with LED 3000 K illumination at 1000 lux intensity yielding the highest performance. While DSSCs may appear less economically viable in environments with readily available electricity, their potential significance lies in providing sustainable energy solutions for IoT devices, thus reducing dependency on conventional power sources and contributing to environmental sustainability. The scientific significance of this research lies in its contribution to understanding the behavior of DSSCs under indoor lighting, offering insights into their potential applications in powering IoT devices. By providing a numerical model for evaluating DSSC performance under realistic indoor conditions, this study opens avenues for further research in optimizing DSSC technology for indoor energy harvesting applications, thereby advancing the field of renewable energy and sustainable technology integration.

Triple‐Responsive Visible‐To‐Ultraviolet‐C Upconverted Photons for Multifunctional Applications

AbstractOptically upconverted materials that are capable of converting long‐wavelength low‐energy photons into short‐wavelength high‐energy light have found their applications over a broad spectrum of fields, like light‐emitting diodes (LEDs), displays, bio‐detection, etc. Despite the great advances in exploring the conventional near‐infrared‐to‐visible or even near‐infrared‐to‐ ultraviolet upconverted materials, the visible‐to‐ultraviolet‐C counterparts are far from being desired. Here, a new triple‐responsive material is introduced, i.e., Pr3+‐doped Li2SrGeO4. It has the ability to absorb the visible photons at ≈450 nm from LEDs, laser diodes (LDs), and even sunlight and emit the ultraviolet‐C (UVC) light covering the 240–280 nm wavelength range. Considering the unique characteristics of the UVC photon, the promising applications of the material are further demonstrated in several scenarios, including static/dynamic labeling under the excitation of a 450 nm LED, information encryption under excitation of sunlight, and sterilization under excitation of a 450 nm LD. The work enriches the library of optically upconverted visible‐to‐UVC materials and widens the application scenarios of these materials.

Investigating the effect of alkali metals on the structural & optoelectronic properties of hexafluorozirconate red phosphors A2ZrF6 (A = Cs, K, Na) using first-principles calculations: A prospect for warm-white LEDs (w-LEDs) applications

To meet the energy challenges of the near future, the development of environment-friendly and energy-efficient phosphors for luminescence devices like light-emitting diodes (LEDs) is the main quest of researchers nowadays. In this connection, traditional lighting devices like halogen lamps, fluorescent lamps, backlights of liquid crystal displays (LCDs), and incandescent lamps can be replaced by state-of-the-art next-generation lighting technology developed using phosphor-converted white LEDs. Hereby, we have presented a systematic study on the structural and optoelectronic properties of Zr-based phosphors A2ZrF6 (A ​= ​Cs, K, Na) for potential photoluminescence and photovoltaic applications like LEDs. The GGA and GGA ​+ ​U schemes are used for exchange and correlation energy potentials treatment to provide a comparative study on the density functional theory (DFT) based first-principles calculations. The GGA ​+ ​U approach improves bandgap values, confirming the well-known flaw of GGA-based DFT methods in underestimating band gaps in strongly correlated systems. Indirect bandgaps are found with the values 2.05, 6.415, and 7.648 ​eV for Cs2ZrF6, K2ZrF6, and Na2ZrF6, respectively. The ε2(ω) spectra show that Cs2ZrF6 absorbs the maximum number of incident photons in the visible region, whereas K2ZrF6 and Na2ZrF6 absorb the maximum of the incident photons in the near UV region. From the R(ω) spectra, we can note that A2ZrF6 (A ​= ​Cs, K, Na) are the weak reflector of incident photons in the visible and IR regions. In contrast, up to 40% of the incident photons are reflected on higher energies (above 12.0 ​eV).

SPR based refractive index modulation of nanostructured SiO2 films grown using GLAD assisted RF sputtering technique

Low refractive index materials have always gained attention for avoiding optical losses in numerous devices like Light emitting diodes (LEDs), Distributed Bragg Reflectors (DBRs) etc. Glancing angle deposition (GLAD) has proven to be an effective method for depositing porous nanostructures with low refractive index. SiO2 has the lowest refractive index in comparison to most of the materials present in nature and is therefore utilized extensively in the fabrication of optical devices with minimum optical losses. The present work focuses on the SiO2 nanostructured thin films grown using glancing angle (GLAD) configuration in RF Sputtering technique under varying deposition conditions (glancing angle and pressure) at fixed thickness. The deposited porous SiO2 nanostructured layers have well-defined nanorods of feature size smaller than 100 nm. The refractive index corresponding to all the deposited SiO2 nanostructured films came out to be smaller than the corresponding value (1.49) mentioned in the literature for bulk SiO2. The refractive index has been observed to vary in a wide range (1.05 to 1.40). Characterization of the deposited SiO2 nanostructured films was carried out using Fourier Transform Infrared (FTIR) spectroscopy, Energy Dispersive X-Ray (EDS) analysis, and Atomic Force Microscopy (AFM) to assess the qualitative properties of the deposited nanostructured SiO2 films. Surface Plasmon Resonance (SPR) and Ellipsometry studies are performed to determine the refractive index value of the deposited nanostructured SiO2 thin films. A refractive index value as low as ∼ 1.05 at a wavelength of 633 nm is achieved for SiO2 nanostructured thin film deposited at 30 mTorr deposition pressure and 80° glancing angle.

Influence of Visible Violet, Blue and Red Light on the Development of Cataract in Porcine Lenses.

Background and Objectives: Cataract is a disease that is globally prevalent in today’s population and occurs mostly in the elderly. It is an opacity of the lens that worsens vision and can lead to blindness. One well-known risk factor of cataract is ultraviolet (UV) radiation. However, increasing exposure to modern artificial light sources like light emitting diodes (LEDs) and displays might have an impact on cataract formation due to possible high (and hidden) blue radiation. An ex-vivo study indicates that intense blue radiation causes cataract in porcine lenses. The goal of this work is the investigation whether violet or red light also lead to cataract formation in porcine lenses and to compare the impact of the different wavelengths. Materials and Methods: LEDs with wavelengths of 407 nm (violet), 463 nm (blue) and 635 nm (red) are used to irradiate ex–vivo porcine lenses with a dose of 6 kJ/cm2. Before and after irradiation the lens transmissions are measured and dark field images are taken to determine cataract formation. The same procedure is performed for unirradiated controls. Results: The results of the transmission measurements are in accordance with the results of the dark field images and state that 635 nm (red) is inducing no or only weak cataract. In comparison to the dark field images the transmission measurements exhibit stronger cataract formation for 407 nm than for 463 nm irradiation while the dark field images show similar cataract formation for both wavelengths. Conclusions: Visible light of short wavelengths cause cataract formation in porcine eyes, and it cannot be excluded that these wavelengths, which are emitted by modern LED illuminants, also pose a danger to human eyes.

Permanent Electrochemical Doping of Quantum Dot Films through Photopolymerization of Electrolyte Ions.

Quantum dots (QDs) are considered for devices like light-emitting diodes (LEDs) and photodetectors as a result of their tunable optoelectronic properties. To utilize the full potential of QDs for optoelectronic applications, control over the charge carrier density is vital. However, controlled electronic doping of these materials has remained a long-standing challenge, thus slowing their integration into optoelectronic devices. Electrochemical doping offers a way to precisely and controllably tune the charge carrier concentration as a function of applied potential and thus the doping levels in QDs. However, the injected charges are typically not stable after disconnecting the external voltage source because of electrochemical side reactions with impurities or with the surfaces of the QDs. Here, we use photopolymerization to covalently bind polymerizable electrolyte ions to polymerizable solvent molecules after electrochemical charge injection. We discuss the importance of using polymerizable dopant ions as compared to nonpolymerizable conventional electrolyte ions such as LiClO4 when used in electrochemical doping. The results show that the stability of charge carriers in QD films can be enhanced by many orders of magnitude, from minutes to several weeks, after photochemical ion fixation. We anticipate that this novel way of stable doping of QDs will pave the way for new opportunities and potential uses in future QD electronic devices.

Calculation of Net Emission Coefficient for High Intensity Discharge Lamps

There is still great interest in studying high intensity discharge (HID) lamps despite the great development of other light sources like light emitting diodes (LEDs). Basic equations and numerical formulations allow calculating important terms such as the net emission coefficient (NEC) that plays an important role in understanding the radiation behaviour of these lamps. These lamps are considered to be at high pressure and the produced plasma was found to be at local thermodynamic equilibrium (LTE). The volume of the lamp is meshed into small cells and the total number of cells represents a compromise between correct results and calculation time. Each cell has its own local absorption and emission coefficient that applies to its position in the discharge. Line profile is calculated by two profiles convolution: one is Lorentz’s and the second one is a quasi-static profile. Ray tracing technique is used to resolve the radiation transport for the visible and ultra violet (UV) spectrum. The NEC is thus calculated and compared with other models for a pure mercury discharge. In addition, additional photometric properties of the lamp are obtained.

Interference analysis and MUI-cancellation in DCO-OFDMA-based IM/DD systems for VLC

The arresting virtue of Visible Light Communication (VLC) to expedite illumination and communication contemporaneously by exploiting sustainable and energy-efficient illuminating devices like Light Emitting Diodes (LEDs) in an indoor environment, enables it to resemble like a small scale cellular communication network providing data access to multiple users within its vicinity. This emphasizes to assure efficacious synchronization between the transmitter and receiver. Consequently, there is an urge to address the synchronization aspects in optical orthogonal frequency division multiple access (OOFDMA) reconcilable with Intensity Modulated (IM)/Direct Detection (DD) systems for VLC. Moreover, in an uplink scenario the existence of frequency offsets (FO) which emanates due to the existence of Doppler shift and symbol time offset (STO) leads to interference among the users as well induces to interfere with the desired user leading to most detrimental aspect called multiuser interference (MUI). This paper derives the analytical expressions for the deterioration of signal to interference noise ratio (SINR) in DC-Biased optical-OFDMA (DCO-OFDMA) system in view of the existence of STO. Furthermore, a modified version of single user detection (SUD) scheme and certain modified versions of synchronization algorithms to mitigate the effects of STO are illustrated for DCO-OFDMA flexible to be implemented for VLC Networks. In addition, Cramer Rao Lower Bound (CRLB) is derived for FO and STO estimators using joint parameter estimation for the uplink scenario and is verified through simulations.

Removal of 4-chlorophenol by visible-light photocatalysis using ammonium iron(II) sulfate-doped nano-titania

Halogenated aromatic compounds are toxic and carcinogenic. This is the case of 4-chlorophenol (4-CP), a priority pollutant found in large amounts in industrial wastewater effluents from pharmaceutical, dye, pulp and paper industries. Long term exposure to 4-CP even at low-concentration is associated to endocrine disruption. Photocatalysis is a promising advanced oxidation process that attains complete degradation of organic pollutants. The use of UV lamps undermines actual photocatalysis application due to the electrical energy requirements. In this frame, the development of visible light photoactive catalysts can overcome these challenges allowing the implementation using affordable light sources like light emitting diodes (LEDs) or natural sunlight. This work is to present the synthesis and use of an alternative photocatalyst that provided eight-fold increase on 4-CP degradation in comparison to commercial TiO2 Degussa P-25. Almost complete removal (99.20%) was achieved with synthesized Fe/N/S-doped TiO2 at 1.0 g L−1 of photocatalyst dose and pH 7.0 for treating 10 ppm of 4-CP.The first-order rate constant, kLH, and Langmuir adsorption constant, KLH, were calculated with values of 0.429 min−1 and 2.326 ppm−1, respectively. The Fe/N/S-TiO2. photocatalysts showed an excellent stability maintaining their performance during four cycles of recovery/reuse.

Performance Analysis of DST-Based Intensity Modulated/Direct Detection (IM/DD) Systems for VLC

The dual functionality of assuring ‘illumination’ and “communication” contemporaneously by relying on sustainable and energy-efficient opto-electronic devices like light emitting diodes (LEDs) has enabled visible light communication to garner the attraction of research era. This paper proposes a discrete sine transform (DST)-based optical orthogonal frequency division multiplexing (OFDM) system bestowing as the simplest and alternative multicarrier scheme complying the requirements of intensity modulated and direct detection systems. Moreover, this paper addresses the most vital issue like peak to average power ratio (PAPR) that emerges principally due to the limited dynamic range of LEDs when exploiting DC-biased optical OFDM (DCO-OFDM). Therefore, this paper imparts DST spreading to DST-based DCO-OFDM (DST-S-DCO-OFDM), and consequently, the PAPR performance is compared with other PAPR reduction schemes for the same system. Furthermore, in order to serve multiple subscribers with high-data rates as well as to significantly reduce the amount of PAPR of the multicarrier system, this work investigates a DST-based single carrier frequency division multiple access (DST-SC-FDMA) and derives the mathematical analysis of the time-domain signal formats for different subcarrier mapping strategies like DST-based optical interleaved frequency division multiple access (DST-OIFDMA) and optical localized frequency division multiple access (DST-OLFDMA). The simulated results evidences that the reduction in PAPR for DST-S-DCO-OFDM is more predominant when compared with other PAPR reduction schemes and among the multiple access schemes, the DST-OIFDMA is more power efficient upon comparison with DST-OLFDMA. However, both the schemes exhibit a significant reduction in PAPR when compared with DST-based optical OFDM (DST-OOFDMA).

Concurrent illumination and communication: A survey on Visible Light Communication

The exceptional increase in the mobile data traffic leads to over exploitation of the radio frequency (RF) spectrum making it to become overcrowded. This necessitates relying on novel technology like Visible Light Communication (VLC) which utilizes cost-effective and solid-state illuminating devices like Light Emitting Diodes (LEDs). The stunning notability of enabling contemporaneous illumination and communication has driven VLC to become a revolutionary alternative to RF. This survey provides an elaborate analysis of the VLC system model, optical channel environment, modulation techniques, detailed analysis on different variants of optical orthogonal frequency division multiplexing (OOFDM), and other modulation formats like carrier-less amplitude and phase modulation (CAP) and multi-band CAP (m-CAP) which bestows with the most feasible solution for VLC in the perspective of spectral, power and computational efficiency. In addition, multiple access schemes like orthogonal frequency division multiple access (OFDMA), non orthogonal multiple access (NOMA) is also the focus of this survey. Furthermore, the research advancements in enabling organic LEDs (OLEDs) and superluminescent diodes (SLDs) to penetrate the solid state lighting (SSL) industry is also highlighted. This survey provides insights about the programmable test beds facilitating real time application and signifies how VLC can be amalgamated with both the lighting infrastructure and intelligent transportation system (ITS) in smart cities. In addition, certain research challenges to be addressed is also the part of this survey.

Effects of frequency and timing offsets in DCT-based multiple access system for VLC

Abstract Visible light communication (VLC) has gained a significant momentum in the recent times due to its distinctive characteristics of imparting concurrent ‘illumination’ and ‘communication’ by exploiting sustainable and energy-efficient opto-electronic devices like light emitting diodes (LEDs). Consequently, by utilizing the already installed LED lighting fixtures a small scale cellular communication network can be created within an indoor environment imparting economic and ubiquitous data transmission services to multitude of roaming mobile stations within the proximity of LEDs. Therefore, it is vital to address the detrimental aspects like carrier frequency offset (CFO) and symbol time offset (STO) which emanates predominantly in an uplink scenario. This paper evaluates the performance of DC offset optical fast orthogonal frequency division multiple access (DCO-FOFDMA) system in the presence of both CFO and STO and accomplishes a thorough mathematical analysis emphasizing the different interferences like inter carrier (ICI) and multi user interferences (MUI) emanating due to different timing disparities and frequency discrepancies. The simulation results evidences that, with the increase in sensitivity of CFO and timing misalignments, the system performance drastically deteriorates thereby hindering the detection capability of multiple users operating at the same time. In order to estimate the STO, synchronization algorithms like Maximum Likelihood (ML) and Classen are imposed to the developed system model. Additionally, Cramer Rao Lower Bound (CRLB) is derived for the estimation of CFO and STO.

Size Control of CH3NH3PbBr3 perovskite Quantum Dots Via Ostwald Anti-Ripening

「 Introduction 」 Organic-inorganic perovskite crystals have been aggressively applied to perovskite solar cells due to their attractive properties such as long carrier diffusion, am-bipolar conductivity, broad color-tunability, and their small exciton binding energy1. These perovskite crystals have been also applied to various applications like light-emitting diodes (LED), photodetectors, field effect transistors, and lasers due to perovskite crystals can be simply prepared from low-cost precursors with simple solution processes1. These tremendous potential for various applications with high performance are based on perovskite electro-optical features and they are expected to be used as an alternative semiconductor material to silicon and compound materials. Recently, bright luminescence properties from methylammonium lead tri-bromide (MAPbBr3) perovskite quantum dots (PeQDs) have been reported owing to the development of methods for preparing these PeQDs. Zhang et al. developed a ligand-assisted reprecipitation (LARP) inspired by the reprecipitation method for preparing organic and nano / micro crystals2. LARP can simply obtain MAPbX3(X = I, Br, and Cl) PeQDs through mixing a solution dissolving precursors and poor solvent. Although synthesis methods representative for LARP with narrow size-distributions are of particular interest for the successful implementation of PeQDs into LED with narrow emission, size-controlled PeQDs by nanometers have not been developed. In this work, we report on Ostwald ripening as a size-tunable technique for MAPbBr3PeQDs using LARP. 「 Experimental 」 Size-controlled synthesis of MAPbBr3PeQDs, and a simple strategy is as follows; a precursor solution was dropped into poor solvent followed by centrifuged to remove large-sized MAPbBr3crystals. Herein, MAPbBr3PeQD dispersions were aged at the 50℃using water bath to accelerate Ostwald ripening in MAPbBr3PeQD dispersions. Finally, we obtained size-controlled MAPbBr3PeQDs through centrifugation to remove grown MAPbBr3crystals. 「 Results and Discussion 」 MAPbBr3PeQD dispersions can be clearly observed that as aging time increases, PL peaks are blue shifted from 517 nm to 456 nm through aging for 4 hours. The emission colors irradiated UV lamp at 254 nm of MAPbBr3PeQD dispersions also changed from green to cyan and deep blue , while these dispersions close to be color less. When MAPbBr3PeQD dispersion is aged 1 hour, compared with an initial MAPbBr3PeQD dispersion, maximum PL peak was not clearly blue shift (ΔE = 42 meV) because of mean QD sizes were not drastically changed and also these square shape is maintained. In contrast, MAPbBr3PeQD dispersion is aged for 2 hours, a maximum PL peak drastically blue shifted from 508 nm to 489 nm. Because morphologies of samples such as sizes and shapes were completely changed from square to spherical with 7.2 nm size , result in PL energy extremely change (ΔE = 95 meV). Moreover, as further aging times increases, their mean QD sizes down to approach 5.3 nm by aging at the 50℃for 4 hours, in which clearly appear increasing band gap of MAPbBr3PeQDs due to quantum confinement effect. 「 References 」 1) B. R. Sutherland, et al., Nature, 2016, 10, 295-302. 2) F. Zhang, et al., ACS Nano, 2015, 9, 4533-4542.

When Fluorescent Proteins Meet White Light-Emitting Diodes.

Over the last decades, fluorescent proteins (FPs) have been extensively employed for imaging and tracing in cell biology and medicine. However, their application for lighting devices like light-emitting diodes (LEDs) and lasers has recently started. The interest of FPs is the result of their good photoluminescence features (high emission efficiency with a narrow spectrum and a high photon-flux saturation), good photostability, sustainable production by bacteria, and eco-friendly recycling. Their low stability at high temperatures as well as the need for an aqueous environment have, however, strongly limited their use in optoelectronics. This has recently been circumvented with new coating systems that are paving the way for the entrance of FPs into the LED field. In this Minireview, we summarize the first steps taken by a few groups towards the development of bio-hybrid white LEDs (Bio-HWLEDs) with a focus on using FPs as color down-converters, highlighting the state of the art and challenges associated with this emerging field.

A low PAPR multicarrier and multiple access schemes for VLC

The omnipresence of solid-state illuminating devices like Light Emitting Diodes (LEDs) has driven Visible Light Communication (VLC) to acquire mammoth eminence. However, the limited dynamic range of LEDs leads to deleterious non-linear distortion when employing the high data rate multicarrier modulation technique like optical orthogonal frequency division multiplexing (OOFDM) resulting in high Peak to Average Power Ratio (PAPR). Furthermore, since VLC has profound applicability in a cellular network, there is an urge to investigate different PAPR mitigation techniques. In this paper, Discrete Cosine Transform-Spread-Fast-Optical OFDM (DCT-S-FOOFDM) is proposed and compared with other PAPR reduction schemes like Partial Transmit Sequence (PTS), clipping and filtering techniques. This work focuses on imparting Discrete Fourier Transform (DFT)-spreading for Optical Orthogonal Frequency Division Multiple Access (OOFDMA) and DCT-spreading for Fast Optical Orthogonal Frequency Division Multiple Access (FOOFDMA) system to reduce PAPR. Here, an elaborate mathematical analysis of the time-domain signal is accomplished for Asymmetrically clipped DC biased-Optical-Interleaved FDMA (ADO-IFDMA), Asymmetrically clipped-Optical-Localized FDMA (ACO-LFDMA), Fast-Optical-IFDMA (F-O-IFDMA) and Fast-Optical-LFDMA (F-O-LFDMA). The simulated result analysis emphasizes that PAPR is reduced significantly by employing DCT-Spreading in FOOFDM. Among the multiple access schemes, PAPR reduction in F-O-IFDMA is superior than F-O-LFDMA and outperforms FOOFDMA.

Growing and Drying <i>Spirulina/</i><i>Arthrospira</i> for Producing Food and Nutraceuticals: A Review

Microalgae-cianobacteriaArthrospira(trade nameSpirulina) are cultivated worldwide due to its nutritional and therapeutic qualities. The aim of this review is to summary production parameters affecting quality ofArthrospira. The biochemical composition of microalgae foodstuff is mostly determined by growing conditions, e.g. growth media, light intensity, temperature as well as drying method and conditions. This review showed that prospective directions for optimization of costs to cultivateArthrospiraindoors are: effective use of light, e.g., using effective artificial light sources like light emitting diodes (LED) in color with regards to necessary component inArthrospira; mixotropic growth using growth media from food processing by-product/waste; and selection ofArthrospirastrain according to available temperature. Common methods of algae drying for food and nutraceuticals are solar drying, convective drying, spray drying, lyophilization. The drying method and regime can greatly affect the amount of biologically active compounds and organoleptic quality.

Modeling of light-emitting diode wavefronts for the optimization of transmission holograms.

The objective of applying transmission holograms in automotive headlamp systems requires the adaptation of holograms to divergent and polychromatic light sources like light-emitting diodes (LEDs). In this paper, four different options to describe the scalar light waves emitted by a typical automotive LED are regarded. This includes a new approach to determine the LED's wavefront from interferometric measurements. Computer-generated holograms are designed considering the different LED approximations and recorded into a photopolymer. The holograms are reconstructed with the LED and the resulting images are analyzed to evaluate the quality of the wave descriptions. In this paper, we show that our presented new approach leads to better results in comparison to other wave descriptions. The enhancement is evaluated by the correlation between reconstructed and ideal images. In contrast to the next best approximation, a spherical wave, the correlation coefficient increased by 0.18% at 532nm, 1.69% at 590nm, and 0.75% at 620nm.

Comparison of light emitting diode and compact fluorescent lamp phototherapy in treatment of neonatal hyperbilirubinemia

Background: High levels of total serum bilirubin can cause life threatening complications in neonates requiring management either with phototherapy or exchange blood transfusion. Most commonly used modality of phototherapy is with blue light. There are many bulbs like fluorescent tubes, halogen spotlights etc. Due to disadvantages of the available bulbs, newer method like light-emitting diodes (LEDs) has been investigated as possible alternatives as they produce low heat, has a longer life span with lower energy consumption and rapid reduction of serum bilirubin level. The aim was to compare the efficacy between phototherapy equipped with light emitting diode (LED) to compact fluorescent lamp (CFL) in the treatment of neonatal hyperbilirubinemia among neonates.Methods: A hospital-based intervention study was conducted among 50 neonates born in the hospital during the study period, with gestational age more than equal to 35 weeks, being breastfed and healthy in a private medical college teaching hospital in Dakshina Kannada district from August to September 2016. Following ethical committee clearance the neonates looking icteric by clinical examination were randomly allocated to receive CFL or LED phototherapy. Baseline, 24 hour total serum bilirubin and rectal temperature was measured. Results: A total of 50 neonates were randomly allocated into two groups with almost similar characteristics between the two groups with respect to gender, type of delivery and gestational age. The mean bilirubin values (in mg/dl) among neonates in the CFL group and LED group were 14.8 and 15.6 respectively and post 24 hour values were 11.54 and 10.68 respectively. The mean difference in the reduction in the bilirubin values before and after receiving phototherapy between the two groups were significant (p <0.001). The increase in temperature was lesser among LED treatment group.Conclusions: LED therapy is better than the CFL therapy in terms of mean reduction in the total serum bilirubin after a fixed duration of time and lesser raise in temperature among the neonates.

Optimization of signal-to-noise-plus-distortion ratio for dynamic-range-limited nonlinearities

Many components used in signal processing and communication applications, such as power amplifiers and analog-to-digital converters, are nonlinear and have a finite dynamic-range. The nonlinearity associated with these devices distorts the input, which can degrade the overall system performance. Signal-to-noise-plus-distortion ratio (SNDR) is a common metric to quantify the performance degradation. One way to mitigate nonlinear distortions is by maximizing the SNDR. In this paper, we analyze how to maximize the SNDR of the nonlinearities in optical wireless communication (OWC) systems. Specifically, we answer the question of how to optimally predistort a double-sided memory-less nonlinearity that has both a “turn-on” value and a maximum “saturation” value. We show that the SNDR-maximizing response given the constraints is a double-sided limiter with a certain linear gain and a certain bias value. Both the gain and the bias are functions of the probability density function (PDF) of the input signal and the noise power. We also find a lower bound of the nonlinear system capacity, which is given by the SNDR and an upper bound determined by dynamic signal-to-noise ratio (DSNR). An application of the results herein is to design predistortion linearization of nonlinear devices like light emitting diodes (LEDs).

Comparative evaluation of marginal adaptation between nanocomposites and microhybrid composites exposed to two light cure units

Recent advances in resin adhesives and restorative materials, as well as an increased demand for esthetics, have lead to the introduction of newer resin-based composites like nanocomposites and light-curing units like light emitting diodes (LEDs). The present study was conducted to evaluate the effect of conventional quartz tungsten halogen (QTH) curing unit and blue LED on marginal adaptation of microhybrid composite (Filtek Z250) and nanocomposite (Filtek Z350) resins. Eighty Class V cavities were prepared on, extracted human premolars and were divided into four groups of 20 each. The four groups were designed according to the restorative resin and light cure unit used microhybrid/QTH, nanocomposites/QTH, microhybrid/LED and nanocomposites/LED. After thermocycling and immersion in 2% Basic Fuschin dye solution, the teeth were sectioned and dye penetration was observed under a stereomicroscope at 20X magnification. All the samples were scored and results were analyzed using the "Kruskal Wallis and Mann Whitney tests" with "Wilcoxone correction." The results revealed least microleakage in microhybrid composites exposed to QTH and maximum in nanocomposites exposed to LED. Microhybrid composites exhibited lesser microleakage than nanocomposite resins.