Magnetic field measurements near RF induction heaters

We discuss initial magnetic field strength measurements made around radiofrequency (RF) induction heaters. These measurements were made with a monitor developed for the National Institute for Occupational Safety and Health (NIOSH) by the National Bureau of Standards (NBS). The monitor has a dynamic range of .01 to 10,000 A2/m2, a frequency range of 300 kHz to 100 MHz, an isotropic response (+/- .3 dB) with three mutally orthogonal loop antennas that have the ability to measure and display each of three orthogonal magnetic field components, a high probe burnout protection level of 20,000 A2/m2, and an accuracy of +/- 1.0 dB at 13 calibration frequencies. The portable survey monitor was used to measure the magnetic field strengths in the vicinity of 16 RF induction heaters. Typically these induction heaters are operated continuously for several hours. The maximum field strengths (without duty factor correction) ranged from 15 to 4,500 A2/m2 and were measured 5 to 51 cm from the loop applicators of the induction heaters. At locations commonly occupied by workers (ie, approximately 30 to 76 cm from heaters), the fields ranged from .01 to 300 A2/m2 (without duty factor correction).     

Synthesis of Large Surface‐Area g‐C3N4 Comodified with MnOx and Au‐TiO2 as Efficient Visible‐Light Photocatalysts for Fuel Production

Herein, this study successfully fabricates porous g‐C₃N₄‐based nanocomposites by decorating sheet‐like nanostructured MnO_x and subsequently coupling Au‐modified nanocrystalline TiO₂. It is clearly demonstrated that the as‐prepared amount‐optimized nanocomposite exhibits exceptional visible‐light photocatalytic activities for CO₂ conversion to CH₄ and for H₂ evolution, respectively by ≈28‐time (140 µmol g^?1 h^?1) and ≈31‐time (313 µmol g^?1 h^?1) enhancement compared to the widely accepted outstanding g‐C₃N₄ prepared with urea as the raw material, along with the calculated quantum efficiencies of ≈4.92% and 2.78% at 420 nm wavelength. It is confirmed mainly based on the steady‐state surface photovoltage spectra, transient‐state surface photovoltage responses, fluorescence spectra related to the produced ?OH amount, and electrochemical reduction curves that the exceptional photoactivities are comprehensively attributed to the large surface area (85.5 m² g^?1) due to the porous structure, to the greatly enhanced charge separation and to the introduced catalytic functions to the carrier‐related redox reactions by decorating MnO_x and coupling Au‐TiO₂, respectively, to modulate holes and electrons. Moreover, it is suggested mainly based on the photocatalytic experiments of CO₂ reduction with isotope ¹³CO₂ and D₂O that the produced ?CO₂ and ?H as active radicals would be dominant to initiate the conversion of CO₂ to CH₄.     

Blue light (470 nm) effectively inhibits bacterial and fungal growth

Blue light (470 nm) LED antimicrobial properties were studied alone against bacteria and with or without the food grade photosensitizer, erythrosine (ERY) against filamentous fungi. Leuconostoc mesenteroides (LM), Bacillus atrophaeus (BA) or Pseudomonas aeruginosa (PA) aliquots were exposed on nutrient agar plates to Array 1 (AR1, 0·2 mW cm^?2) or Array 2 (AR2, 80 mW cm^?2), which emitted impure or pure blue light (0–300 J cm^?2), respectively. Inoculated control (room light only) plates were incubated (48 h) and colonies enumerated. The antifungal properties of blue light combined with ERY (11·4 and 22·8 μmol l^?1) on Penicillium digitatum (PD) and Fusarium graminearum (FG) conidia were determined. Conidial controls consisted of: no light, room light‐treated conidia and ERY plus room light. Light‐treated (ERY + blue light) conidial samples were exposed only to AR2 (0–100 J cm^?2), aliquots spread on potato dextrose agar plates, incubated (48 h, 30°C) and colonies counted. Blue light alone significantly reduced bacterial and FG viability. Combined with ERY, it significantly reduced PD viability. Blue light is lethal to bacteria and filamentous fungi although effectiveness is dependent on light purity, energy levels and microbial genus.

Significance and Impact of the Study

Light from two arrays of different blue LEDs significantly reduced bacterial (Leuconostoc mesenteroides, Bacillus atrophaeus and Pseudomonas aeruginosa) viabilities. Significant in vitro viability loss was observed for the filamentous fungi, Penicillium digitatum and Fusarium graminearum when exposed to pure blue light only plus a photosensitizer. F. graminearum viability was significantly reduced by blue light alone. Results suggest that (i) the amount of significant loss in bacterial viability observed for blue light that is pure or with traces of other wavelengths is genus dependent and (ii) depending on fungal genera, pure blue light is fungicidal with or without a photosensitizer.     

The effect of 100 Hz magnetic field combined with X-ray on hepatoma-implanted mice

Our previous cellular experiments demonstrated that 100 Hz magnetic field (MF) was effective at enhancing apoptosis of liver cancer cells BEL‐7402 induced by X‐ray irradiation. This study was performed to further explore the possible synergism between 100 Hz MF and X‐ray in treatment of hepatoma‐implanted Balb/c mice. 100 Hz MF exposure with a mean flux density of 0.7 mT was performed inside an energized solenoid coil. Six MV X‐ray irradiation was generated using a linear accelerator. Tumor growth and survival of mice implanted with H22 cells were evaluated by measuring the tumor diameters and overall days of survival. Six groups treated with 100 Hz MF or X‐ray alone or a combination of MF and X‐ray were examined. Furthermore, the effects of different numbers of MF exposure periods on tumor growth and mice survival were examined when combined with 4 Gy X‐ray. Data referring to overall survival days and tumor diameters of the above groups were compared using log‐rank test and Student's t‐test. Our results showed that five periods of combined 100 Hz MFs and 4 Gy X‐ray could significantly extend the overall days of survival and reduce the tumor size compared to MF or X‐ray alone. Also, a greater number of 100 Hz MF exposure periods could further improve the survival and inhibit tumor growth in hepatoma‐implanted mice when combined with 4 Gy X‐ray. In conclusion, these findings suggested that 100 Hz MF could possibly synergize with 4 Gy X‐ray in terms of survival improvement and tumor inhibition in hepatoma‐implanted mice. Bioelectromagnetics 32:322–324, 2011. © 2011 Wiley‐Liss, Inc.     

Photodynamic Damage to Yeast Subcellular Organelles Induced by Elevated Levels of Endogenous Protoporphyrin IX

The 2,2"-dipyridyl-induced accumulation of protoporphyrin IX in Saccharomyces cerevisiae cells was shown to be accompanied by the photoinhibition of cell respiration and the enhancement of the photoinduced permeability of plasma membranes to the fluorescent dye primuline. The visible-light illumination (at 400–600 nm) of the mitochondria and plasma membranes isolated from yeast cells with a high level of endogenous protoporphyrin IX intensified lipid peroxidation in these subcellular organelles. Comparative studies showed that the rad 52 mutant cells, which are deficient in the postreplicative recombinational DNA repair system, are considerably more sensitive to the inactivating action of visible light than are the wild-type cells and the rad 3 mutant cells, which are deficient in the excision DNA repair system. The contribution of photodynamic damage to the yeast subcellular organelles to the lethal photodynamic effect is discussed.