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A broadband ultraviolet light source using GaN quantum dots formed on hexagonal truncated pyramid structures
摘要： Broadband ultraviolet (UV) emission has been achieved from the GaN quantum dots grown on different facets of hexagonal truncated pyramidal structures. The GaN-based structures include both semipolar and polar facets, on which the intrinsic piezoelectric fields and the growth rates are different. In addition, a strain is locally suppressed at the boundaries of the truncated pyramid structure. As a result, the emission wavelength of quantum dots on various facets and boundaries becomes quite different, rendering a solid-state broadband UV light source with homogenerous intensity in a wide wavelength range.
关键词： broadband ultraviolet emission,GaN quantum dots,solid-state broadband UV light source,hexagonal truncated pyramid structures
更新于2025-09-23 15:21:01
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Carbon Nanotubes - Recent Progress || Stability and Reliability of an Electrical Device Employing Highly Crystalline Single-Walled Carbon Nanotubes as a Field Emitter
摘要： Carbon nanomaterial is drawing keen interest from researchers as well as materials scientists. Carbon nanotubes (CNTs)—and their nanoscale needle shape—offering chemical stability, thermal conductivity, and mechanical strength exhibit unique properties as a quasi-one-dimensional material. Among the expected applications, field emission electron sources appear the most promising industrially and are approaching practical utilization. However, efforts to construct a field emission (FE) cathode with single-walled carbon nanotubes (SWCNTs) have so far only helped average out a non-homogeneous electron emitter plane with large FE current fluctuations and a short emission life-time because they failed to realize a stable emission current owing to crystal defects of the carbon network in CNTs. The utilization of CNTs to obtain an effective cathode, one with a stable emission and low FE current fluctuation, relies on the ability to disperse CNTs uniformly in liquid media. In particular, highly crystalline SWCNTs hold promise to obtain good stability and reliability. The author successfully manufactured highly crystalline SWCNTs-based FE lighting elements that exhibit stable electron emission, a long emission life-time, and low power consumption for electron emitters. This FE device employing highly crystalline SWCNTs has the potential for conserving energy through low power consumption in our habitats.
关键词： wet coating process,high crystallization,field emission,single-walled carbon nanotube,scratch,thin film,planar light source,cathode luminescence
更新于2025-09-23 15:21:01
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Role of light emitting diode (LED) wavelengths on increase of protein productivity and free amino acid profile of Spirulina sp. cultures
摘要： LEDs have specific wavelengths that can positively influence the production of microalga biomass and biomolecules of interest. Filling the gaps in the literature, this study evaluated the effect of different LED wavelengths and photoperiods on protein productivities and free amino acid (FAA) profile of Spirulina sp. LEB 18 cultures. The best protein productivity results were obtained in red and green LED cultures using integral and partial photoperiods, respectively. In these experiments, protein productivities increased 2 and 1.6 times, respectively, compared to the control culture using fluorescent light. Green LEDs in partial photoperiod provided also the highest concentrations of essential and non-essential FAA, about 1.8 and 2.3 times higher, respectively, than control cultures. LEDs showed to be a promising sustainable light source for increasing protein productivity and FAA concentration in Spirulina sp. LEB 18 cultures.
关键词： Photoperiod,Microalgae,Protein productivity,Cyanobacteria,Light source
更新于2025-09-23 15:21:01
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Photodynamic therapy in the treatment of oral leukoplakia: a systematic review
摘要： Objective: The aim of the present study was to systematically review the efficacy of photodynamic therapy (PDT) in the management of oral leukoplakia (OLK). Methods: This systematic review aimed to address the following focused question: “Is photodynamic therapy effective in the management of oral leukoplakia?’’ PubMed/Medline, EMBASE, ISI Web of Knowledge, OVID, CNKI, and WANFANG DATA were searched up to and including June 2018 using different combinations of the following keywords: photodynamic therapy, leukoplakia, oral dysplasia, oral precancers, and oral premalignant lesions. Results: Sixteen studies were included in the present study. A total of 352 patients was included in this review, with the age ranging from 20 to 79 years. Photosensitizers used were aminolevulinic acid, Photofrin, methylene blue, and chlorine-e6. Laser wavelength, duration of irradiation, and power density were 420 to 660 nm, 60 to 1000 seconds, and 100 to 150 mW/cm2, respectively. On the whole, the rates of complete response and partial response were 32.9% and 43.2%, and the sum was 76.1%. The follow-up period ranged from 1 month to 119 months. The recurrence rate of OLK was 0-60%. Conclusion: PDT seems to be a useful therapeutic strategy in the management of oral leukoplakia as a non-surgical treatment. Further RCTs with long follow-up period, standardized PDT parameters, and comparing efficacy of PDT with various therapies are expected to acquire definite conclusions.
关键词： Light source,Oral dysplasia,Oral leukoplakia,Photosensitizer,Photodynamic therapy,Oral premalignant lesions
更新于2025-09-23 15:21:01
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Development of a new multi-mode NIR laser system for photodynamic therapy
摘要： Photodynamic Therapy (PDT) has been used in various fields especially in cancer treatment. In PDT, designing a light source has vital importance in order to achieve a successful treatment. Among the light sources, Lasers are important candidates for their precise wavelengths to activate the photosensitizers (PS), coherent nature and fiber-coupled usage. In order to achieve perfect PDT treatment, the Laser light sources needs to be embedded with high stability current, temperature controllers and closed loop control systems. In this study, a novel Multi-mode PDT Laser system (MPTL) was developed with four different radiation modes. Importantly, Super Pulse Mode (SPM) was implemented for the first time among the PDT Laser systems in the open literature to minimize the thermal damage to the target tissue. The proposed system achieved high optical output stability by precise current and temperature control of the Laser resonator. The MPTL achieved high optical output stability ( ± 1mW) in the range of 0–1500 mW, high wavelength stability ( ± 1nm) at 635 nm, and high temperature stability ( ± 0.2 °C) in all radiation modes. The MPTL system with super pulse mode can be safely used for wide range of PDT clinical applications.
关键词： Pulse mode laser,Photodynamic therapy,PDT light source,NIR,Super-pulse,Laser system,Multi-mode
更新于2025-09-23 15:21:01
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Special Issue of Silicon Photonics [Scanning the Issue]
摘要： Silicon, well established as an electronics platform, was ?rst seriously explored as an optical waveguide platform in 1987 by Soref and Bennett. Light at ?ber-optic communication wavelengths can pass through crystalline silicon with very high transmission. Silicon waveguides can be made by etching into the thin crystalline silicon layer on a silicon-on-insulator wafer. Because of the high refractive index of silicon compared to the surrounding oxide, these waveguides can bend with radii less than ?ve micrometers and make compact splitters/combiners, ?lters, and polarization elements. High-speed optical modulators can be made by rapidly changing free electron and hole densities in the silicon in the optical path, and photodetectors can be made by epitaxially growing germanium on the silicon, both using electrically connected p-n junctions. The only element missing to complete an optical integration platform is an integrated light source, rendered very dif?cult because of the indirect bandgap of silicon and germanium. While to date, no practical electrically pumped light emitter has been deployed based on silicon itself, multiple hybrid and heterogeneous solutions have been reported.
关键词： integrated light source,hybrid and heterogeneous solutions,fiber-optic communication,Silicon photonics,optical waveguide
更新于2025-09-23 15:21:01
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Influence of a Light Source Installed in a Luminaire of Opal Sphere Type on the Effect of Light Pollution
摘要： The article presents the results of the studies concerning the influence of a light source installed in luminaire of opal sphere type on the light pollution effect of the night sky. It is known from literature reports that the effect of light pollution is influenced by the spectral distribution of light. Although the influence of the spectral distribution has been widely studied from different perspectives, there is still a need to study this phenomenon—for example, from the point of view of the spectral reflection properties of the ground, on which the lanterns are installed. Hence, the above-mentioned aspect was considered in the authors’ investigations. The luminaire considered has been equipped with 20 different light sources, including the latest generation of lamps (light-emitting diodes, LEDs) as well as the conventional ones. With respect to these light sources, the measurements of light distribution and spectral distribution of emitted radiation of the luminaire were performed. Having these measurement data, the simulations were carried out using the DIALux software, and the calculations were made using the specially prepared calculation tool. On the basis of the results obtained in this way this was stated that the type of light source installed in the luminaire has a significant effect on the sky glow. An important factor affecting light pollution is not only the value of the luminous flux emitted upward but also the spectral characteristics of the emitted radiation, the impact of which is most noticeable. The conclusions from the studies indicate the next steps in the analysis of the light pollution effect. These steps will be focused on extended analysis of LEDs as modern and developed light sources.
关键词： light pollution,light color,lighting,light source,spectral distribution,sky glow
更新于2025-09-23 15:19:57
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Rapid identification of wood species by near-infrared spatially resolved spectroscopy (NIR-SRS) based on hyperspectral imaging (HSI)
摘要： Conventional near-infrared (NIR) spectroscopy has shown its potential to separate wood species non-destructively based on the aggregate effect of light absorption and scattering values. However, wood has an aligned microstructure, and there is a large refractive index (RI) mismatch between the wood cell wall substance (n≈1.55) and the cell lumen (air≈1.0, water≈1.33). Light scattering is dominant over absorption μ′ (cid:31)( ) a in wood, and this fact can be utilized for complex classification purposes. In this study, an NIR hyperspectral imaging (HSI) camera combined with one focused halogen light source (? 1 mm) was designed to evaluate the light scattering patterns of five softwood (SW) and 10 hardwood (HW) species in the wavelength range from 1002 to 2130 nm. Several parameters were combined to improve the data quality, such as image histogram plots of defined spaced bins (associated with diffuse reflectance values of light), variance calculation on the frequency (the number of pixels in each bin) of each histogram and the principal component analysis (PCA) of all the variance values at each wavelength. The identification accuracy of the quadratic discriminant analysis (QDA) under the five-fold cross-validation method was 94.1%, based on the first three principal component (PC) scores.
关键词： spatially resolved spectroscopy,light scattering characteristics,wood species identification,hardwood,quadratic discriminant analysis (QDA),near-infrared hyperspectral imaging camera,principal component analysis (PCA),softwood,halogen spot-light source
更新于2025-09-19 17:15:36
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In the Right Light: Photodynamic Inactivation of Microorganisms Using a LED-Based Illumination Device Tailored for the Antimicrobial Application
摘要： Drug-resistant bacteria threaten the health of people world-wide and cause high costs to their health systems. According to Scientific American, the number of regrettable fatalities due to the bacteria that are resistant to conventional antibiotics will sum up to 300 million until 2050 if the problem is not tackled immediately. Photodynamic Inactivation (PDI) has proven effective against microorganisms irrespective of their resistance to conventional treatment, but for the translation into clinical practice, economic, homogenous and powerful light sources holding approval as medical devices are needed. In this study we present two novel light emitting diode (LED)-based lamps (Repuls7PDI-red and Repuls7PDI-blue) tailored for application in PDI and demonstrate their photodynamic efficiency upon using either methylene blue (MB), a photoactive compound widely used in PDI, or Sodium Magnesium Chlorophyllin (CHL), a water-soluble derivative of chlorophyll, which holds approval as food additive E140, against bacteria and fungi. Gram+ Staphylococcus aureus, Gram? Escherichia coli and the yeast Candida albicans serve as model systems. Repuls7PDI-red emits a wavelength of 635 nm and an intensity of 27.6 ± 2.4 mW·cm?2 at a distance of 13.5 cm between the light source and the target, while the Repuls7PDI-blue allows an exposure at 433 nm (within the range of violet light) (6.4 ± 0.5 mW·cm?2 at 13.5 cm). Methylene blue was photoactivated with the Repuls7PDI-red at 635 nm (25.6 J·cm?2) and allows for photokilling of E. coli by more than 6 log10 steps at a concentration of 10 μM MB. Using equal parameters, more than 99.99999% of S. aureus (20 μM MB) and 99.99% of C. albicans (50 μM MB) were killed. If blue light (Repuls7PDI-blue, 433 nm, 6.6 J·cm2) is used to trigger the production of reactive oxygen species (ROS), a photoinactivation of S. aureus (5 μM CHL, CFU reduction > 7 log10) and C. albicans (>7 log10) below the detection limit is achieved. PDI based on CHL (10 μM) using red light activation reduces the number of viable S. aureus by more than 6 log10. Our data prove that both LED-based light sources are applicable for Photodynamic Inactivation. Their easy-to-use concept, high light output and well-defined wavelength might facilitate the translation of PDI into clinical practice.
关键词： light emitting diode,photosensitizers,Photodynamic Inactivation,light source,natural substances
更新于2025-09-19 17:13:59
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Optimal LED Filtering for Fluorescence Microscopy
摘要： LED illumination systems for fluorescence microscopy offer a wealth of benefits in comparison to traditional mercury and metal halide lamps, including ease of use, improved stability, and enhanced control. To fully realize these benefits, it is important to ensure that optical filters are configured correctly, which often can be confusing. However, without the correct filter configuration, experimental conditions can be suboptimal, and results may therefore be inaccurate. This article looks at optical filter setup in more depth, explaining the purpose and benefits of optimal LED filtering.
关键词： fluorophores,LED light source,optical filters,illumination systems,fluorescence
更新于2025-09-19 17:13:59