Ultraviolet (UV) disinfection is an early discovered technology that is currently and widely used for water treatment and food hygiene treatment. A newly emerging technology of UV disinfection, that ...is, UV light-emitting diodes (UV-LEDs), has aroused considerable research attention. UV-LEDs feature numerous advantages compared with traditional UV mercury vapor lamps and are expected to replace traditional UV lamps. Researchers currently perform studies to obtain data and develop methods for UV-LED water treatment systems. This article analyzes the latest research status and discusses the types of inactivation factors, such as the wavelength selectivity of UV light source, control of UV dose, effect of inactivation rate constant (K) (cm2/mJ), working mode of water sample, external auxiliary system, and UV sensitivity of pathogenic bacteria in water. The wavelengths of approximately 260 and 280 nm normally feature strong inactivation characteristics. When compared with the approximately 260 nm wavelength chip, the around 280 nm wavelength chip proves to be a better choice as its higher wavelength light power can result in faster disinfection capacity of bacteria. UV dose can also be used as the reference value for disinfection of drinking water, whereas the inactivation rate constant (K) (cm2/mJ) varies with different microorganism internal structures. Changing the working mode or adding an auxiliary system can also enhance the inactivation effect in water treatment system settings. In addition, we can compare the inactivation capacities of several pathogens as follows: ΦX174 > Escherichia coli > T type bacteriophage >Bacillus subtilis > MS2 or Qβ > human adenovirus. The in-depth investigation and discussion of inactivation factors and the mechanism of action in UV-LEDs water treatment systems will establish a more efficient UV-LED disinfection method in the future, provide a guiding direction, and promote the standardization and normalization of pathogen inactivation mechanism in UV-LED water treatment systems.
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•The latest researches on ultraviolet light-emitting diodes (UV-LEDs) for water disinfection are reviewed.•The disinfection mechanism by UV-LEDs is discussed in detail.•The influence rule of UV-LED light source system parameters is illustrated.•The influence rule of UV-LED water treatment system settings is also presented.•Conclusions and future suggestions for UV-LEDs water disinfection are proposed.
Current and emerging treatments for vitiligo Rodrigues, Michelle, MBBS(Hons), FACD; Ezzedine, Khaled, MD, PhD; Hamzavi, Iltefat, MD ...
Journal of the American Academy of Dermatology,
07/2017, Volume:
77, Issue:
1
Journal Article
Peer reviewed
Clinicians should be aware that vitiligo is not merely a cosmetic disease and that there are safe and effective treatments available for vitiligo. It is important to recognize common and uncommon ...presentations and those with active disease, as well as their implications for clinical management; these were discussed in the first article in this continuing medical education series. Existing treatments include topical and systemic immunosuppressants, phototherapy, and surgical techniques, which together may serve to halt disease progression, stabilize depigmented lesions, and encourage repigmentation. We discuss how to optimize the currently available treatments and highlight emerging treatments that may improve treatment efficacy in the future.
Light‐emitting diodes with emission wavelengths between 230 and 240 nm are grown on AlN substrates and characterized optically and electrically. Optimized doping of the n‐AlGaN with Si has resulted ...in a mean forward voltage at 200 mA of 9 V. The electroluminescence spectra is demonstrated to be free of long wavelength parasitic emission. An envelope function in the output power versus peak wavelength is shown, demonstrating the increasing dominance of in‐plane emission at shorter wavelengths as light extraction becomes more difficult. However, variations in device structure show that further optimization of the structure for carrier confinement and injection efficiency are also able to push performance beyond the current state of the art.
In this work UVC LEDs with emitting wavelengths as low as 230 nm and packaged powers averaging 0.1 mW are demonstrated. The shift in emission polarization across the wavelength region is displayed as a continuous function via photoluminescence. The lowest forward voltages to date at these wavelengths are achieved, and power output over time is investigated to demonstrate commercial feasibility.
•Ultraviolet-induced NO removal by Fe(II)EDTA with exposed (001) facets nF-TiO2.•NO was removed through catalytic oxidation-complexation synergism.•NO is mainly converted into NO3–, NO2–, NH4+, N2, ...and N2O.•UV/Fe(Ⅱ)EDTA/5F-TiO2 system shows great potential for practical applications.
Ferrous ethylenediaminetetraacetate (Fe(II)EDTA) accompanied by regeneration is thought to be a very efficient method to remove nitric oxide (NO) from flue gas. However, Fe(II)EDTA regeneration requires a large amount of regenerant consumption. For this purpose, anatase titanium dioxide with exposed (001) facets by fluorination (nF-TiO2) was synthesized and combined with Fe(II)EDTA solution for NO removal with ultraviolet light (UV). The result showed that 5F-TiO2 with approximately 30 % (001) facets exposed can significantly promote NO removal of Fe(II)EDTA under UV irradiation, with an average removal efficiency of up to 94.83 % over a 60-minute period. The mechanism study indicated that the excellent removal performance of 5F-TiO2 was mainly because the moderate co-exposure of its (001) and (101) facets could greatly suppress the electron hole recombination rate, accelerate the Fe(Ⅱ)EDTA/Fe(III)EDTA cycle, and form catalytic oxidation-complexation synergism denitrification. Under this synergistic effect, NO from simulated flue gas was mainly transformed to NO3–, NO2–, NH4+, N2, and N2O. Subsequently, NO removal performance using UV/Fe(Ⅱ)EDTA/5F-TiO2 under different parameters demonstrated that appropriate oxygen concentration (3 vol%), suitable 5F-TiO2 mass (0.5 g), low temperature (30 ℃), and weak acidic environment (pH = 4) were favorable for NO removal. The kinetics demonstrated that NO removal by the UV/Fe(Ⅱ)EDTA/5F-TiO2 system was a pseudo-first-order process. Finally, UV/Fe(II)EDTA/5F-TiO2 denitrification technology shows great potential in practical applications. This work offers a new route for the greenandlow-costapplication of Fe(Ⅱ)EDTA denitrification in flue gas treatment.
Epitaxially grown high crystalline quality InGaN/AlGaN multiple quantum structures on patterned sapphire with silica array (PSSA) have been successfully demonstrated. In comparison to conventional ...epilayers grown on patterned sapphire substrate (PSS), we observed a reduced threading dislocation density in the films grown on PSSA, attributing to the preferable vertical growth mode and reduced misfit at the coalescence boundary. Furthermore, a significant enhancement in light extraction efficiency can be achieved from InGaN/AlGaN-based ultraviolet light-emitting diodes (UVLEDs) built on PSSA owing to the large refractive index contrast between the epilayers and PSSA. More photons can escape from the top and bottom of the device, which was confirmed by numerically modeling light propagation within such device architecture. Benefiting from the reduced threading dislocation density and enhanced light extraction efficiency, the external quantum efficiency (EQE) of the fabricated UVLEDs on PSSA was more than two times higher than that of devices on the conventional flat sapphire substrate and it was additionally enhanced by 26.1% in comparison to the devices fabricated on PSS under an injection current of 150 mA. Therefore, the successful demonstration of UVLED on PSSA provides an unprecedented opportunity in achieving higher electroluminescence performance in future solid-state UV light sources.
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•Patterned sapphire with silica array (PSSA) was demonstrated a prominent substrate for highly efficient UVLEDs.•AlGaN epilayers grown on PSSA showed preferable vertical growth mode and reduced misfit at coalescence boundary.•PSSA enlarged the index contrast between epilayer and substrate, which facilitated more efficient light extraction.
Different strategies have been developed over the years to improve the safety of foods without compromising on their quality. Ultraviolet (UV) light has shown potential to meet these expectations. ...However, due to environmental and safety concerns regarding the use of UV mercury lamps, UV-light emitting diode (LED) devices have emerged more recently, which may be more suited to applications in the food industry. Thus, further evaluation of UV-LED technology is required.
In this review, challenges involving the application of UV-LED technology as a disinfection strategy in the food chain are described. Stress-related mechanisms induced by UV light exposure in microorganisms and their potential consequences are reviewed. Moreover, other future challenges associated with the inactivation of foodborne pathogens and spoilage microorganisms are considered, together with the impact of the application of UV-LED technology on the quality of food.
UV-LEDs have been shown to inactivate a wide range of foodborne pathogens and spoilage microorganisms. However, there are limited studies assessing the effectiveness of UV-LED on products to enhance food safety. Additionally, further studies are required to explore the impact of sublethal exposure to UV-LEDs and the potential consequences of UV-LED exposure in different microorganisms at various wavelengths. Furthermore, UV-LEDs can negatively affect some physicochemical attributes of food. Thus, more attention should be paid to the underlying mechanism of quality changes induced by UV-LEDs.
•Challenges in applying UV-LED in food for microbial inactivation are reviewed.•The impact of UV-LED on food quality attributes is discussed.•Microbial stress-related mechanisms when exposed to UV-LED light are reviewed.•A better understanding of DNA-repair mechanisms induced by UV-LED is required.•The effect of UV-LED on food safety and quality requires further investigation.
Contact with continuous belt conveyors during processing results in opportunities for pathogenic and spoilage microorganisms to contaminate meat products. The objective of this project is to ...investigate the germicidal response on the surface of food-grade conveyor belt materials treated with pulsed ultraviolet (PUV) light. Four conveyor belt types including: a stainless-steel chain-link belt, a polytetrafluoroethylene (PTFE)-coated fabric belt, a solid pliable polymer belt, and a rigid-linked polymer belt, were evaluated for the inactivation of Escherichia coli K12-NSR strain and lactic acid bacteria (LAB). Prior to bacterial inoculation, samples were classified as soiled or unsoiled, based on the presence or absence of pork intramuscular fluid on the surfaces of the conveyor samples. Using a variable speed conveyor, equipped with a Xenon flashlamp positioned 10-cm above the surface, each belt sample was exposed to PUV light at three fixed conveyor speeds: 3.05, 15.24, and 30.48 cm/sec, resulting in a total energy exposure of 3.31, 0.66 and 0.33 J/cm
2
, respectively. For samples inoculated with E. coli K12-NSR, the surface condition (soiled or unsoiled) by treatment interaction was significant for microbial inactivation on the surface of the rigid polymer linked belt (P < 0.05). For samples inoculated with the LAB cocktail, the same interaction was significant for the PTFE-coated fabric belt and the solid pliable polymer belt (P < 0.05). Microbial reduction ranged from 0.74 to 5.04 log
10
CFU/cm
2
for E. coli K12-NSR and 0.63 to 4.61 Log
10
CFU/cm
2
for LAB for the evaluated treatment parameters. The results of this project demonstrate that PUV light is an effective means of decontamination for conveyor belts during food processing.
Planar vacuum‐fluorescent‐display devices emitting polarized UV‐C, blue, and green light are demonstrated using immiscible Al1−xInxN nanostructures grown in nonpolar m‐directions. Despite the ...presence of high concentration of nonradiative recombination centers, the Al1−xInxN nanostructures emit polarized light with the luminescence lifetimes of 22–32 ps at 300 K. This defect‐resistant radiative performance suggests supernormal localized characteristics of electron–hole pairs.
Water is one of the most essential elements of life. Despite many studies on the physical and chemical properties of water, many features are still not yet understood. Here, we consider the negative ...electrical potential in the water adjacent to the Nafion membrane. The electrical potential becomes more negative closer to the membrane, a feature that might arise from the special water structure (interfacial water) next to Nafion. Evidence has shown that the water was characterized by a UV absorbance at ∼270 nm. We hypothesized that such radiant energy might contribute to the electrical potential of the interfacial water. Here, the effect of exposure to light on this potential, at wavelengths of 275 nm, 370 nm and 650 nm was studied. The electrical potential became more negative under 275 nm wavelength UV light, while other two wavelengths had negligible effects. The result fits well with the ∼270 nm wavelength absorption peak reported in previous studies. Potentially, the absorbed UV energy helps fuel the ‘water battery’. The findings shed light on the mechanism underlying the character of interfacial water adjacent to hydrophilic surfaces.
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