Application of Calibration-Free Boltzmann Plot Method for Composition and Pressure Measurement in Argon Free-Burning Arcs

Plasma Chemistry and Plasma Processing - Arc plasmas have been extensively studied, experimentally and by means of modeling, due to their wide range of applications. In this article, a...     

Photoprotection by Workwear: Ultraviolet Protection Factors for Artificial Radiation from Welding Arcs

Photoprotection by clothing is one of the most effective protective measures against solar ultraviolet radiation (UVR), and the related concept of UV protection factors (UPF) for fabrics has proven itself for decades. Although immense work has been carried out regarding factors influencing textile sun protection, the idea of UPFs for artificial UVR, if necessary with different action spectra, is payed little attention. In this work, a modified UPF equation is proposed utilizing welding arcs and the ICNIRP action spectrum. These welding UPFs (wUPF) were calculated for some workwear as a function of welding power, technique and welded material. No wUPF welding power dependence existed. By means of normalized standard emission spectra, that were further clustered with regard to welding technique, it was found that the wUPF depends exclusively on the fabric’s transmittance and the ICNIRP weighting function yielding a reduced wUPF formula. Finally, a comparison of solar and welding UPFs, based on either their full or reduced equations, is discussed.     

Optical Effects Associated with Aggregates of Clusters

The effect of aggregation on the optical properties of nanometer-sized particles is studied. It is shown that for small noble metal clusters as well as for pigments of Fe₂O₃, TiN, or ZrN, the aggregation leads to changes in the color of the colloidal systems which are caused by electromagnetic coupling among the clusters in the aggregates. The model of interacting particles is shown to be helpful also for interpretation of optical properties of organic dyes with incorporated metal clusters and for interpretation of the reflectance of magnetooptical cluster systems. For soot particles it is shown that scattering and absorption are enhanced over the whole visible spectral region compared to isolated carbonaceous clusters. Finally, it is shown that the model of interacting clusters can also be applied for data interpretation in scanning near-field optical microscopy.     

Cellular Changes Associated with the Acclimation of the Intertidal Sea Anemone Actinia tenebrosa to Ultraviolet Radiation

To assess the relative importance of long‐ and short‐term cellular defense mechanisms in seasonally UV‐R‐acclimated Actinia tenebrosa (Anthozoa, Actiniidae), individuals were exposed to summer doses of PAR, UV‐A, UV‐B and enhanced UV‐B (20%) for a period of 4 days. Mycosporine‐like amino acids (MAAs) and cyclobutane pyrimidine dimer (CPD) concentrations were quantified, while oxidative damage to lipids and proteins, and the activities or levels of the antioxidant enzymes SOD, CAT, GR, GPOX and total glutathione were determined. Our results show that summer UV‐R‐acclimated individuals had a higher UV‐R tolerance, with no significant increases in CPDs levels, than winter‐acclimated sea anemones possibly due to higher MAA concentrations. Summer‐acclimated individuals showed increased lipid and protein oxidation and GPOX activity only when they were exposed to UV‐B at 20% above ambient UV‐R levels. In contrast, winter‐acclimated sea anemones showed elevated levels of oxidative damage, GPOX and SOD activities after exposure to UV‐A or UV‐B at ambient and elevated levels. Thus, this study indicates that long‐term UV‐R acclimation mechanisms such as the accumulation of MAAs could be more important than short‐term increases in antioxidant defenses with respect to reducing indirect UV‐R damage in intertidal sea anemones.     

Histopathological Changes in Liver and Heart Tissue Associated with Experimental Ultraviolet Radiation A and B Exposure on Wistar Albino Rats

This study aims to evaluate the influences of ultraviolet radiation A and B ( UVA + B) exposure on the liver and heart organs of albino rats. Female Wistar Albino rats, whose hair of the dorsal skin was shaved, were exposed to a combined UVA + B radiation for 2 h/day, for 4 weeks in order to be compared with the control group. Histopathological findings in vital organs (liver and heart) were evaluated. Tissues were fixed in 10% buffered formalin (pH = 7.2) and embedded in paraffin. The histopathological findings were examined on the H&E stained sections with light microscopy. The results show that the liver and the heart were injured in the UVA + B group. Liver tissue in the UVA + B group showed minimal vacuolation, enlargement of hepatocytes and bile duct proliferation, and the heart tissue showed hibernomas; uniform large cells resembling brown fat with coarsely granular to multivacuolated cytoplasm that is eosinophilic or pale with a small central nucleus. The number of hibernoma cases was significantly higher in the UVA + B group compared with the control group (P = 0.021). The control group showed normal liver and heart histology with normal adipose tissue in the pericardium. As a result, UVA + B exposure has toxic effects, especially on the liver and the heart of Wistar albino rats. UV radiation may cause such adverse effects in humans. Therefore, protection against the harmful effects of UV radiation is of significant importance for skin and organs.     

Optical sensors for determining phenolic compounds with different structures

The literature data published in 1993–2012 on the development and application of optical sensors for the determination of phenolic compounds of various structures are summarized. The design, analytical characteristics, and advantages and disadvantages of the existing optical sensors are reviewed, and some examples of using optical sensors in the analysis of real samples, including those from field experiments, are considered in detail.     

A New Method of Surface Preparation for High Spatial Resolution EPMA/SEM with an Argon Ion Beam

A novel specimen preparation method has been devised utilizing an Ar ion beam with a masking plate and an apparatus for this method has been developed for the preparation of good quality cross sections for high spatial resolution microscopy and microanalysis. This apparatus is defined as a Cross-section Polisher. The method overcomes most of the drawbacks inherent in the traditional method of mechanical grinding and polishing and enabled us to prepare good quality cross sections with much larger areas than those prepared by a focused ion beam method, essentially retaining the excellent characteristics of the latter method. Microstructural observations of corrosion morphology and chemical analysis of corrosion products in a corrosion-resistant alloy (Alloy 825) with a thermal field emission type electron probe X-ray microanalyzer are reported to show the power of the Cross-section Polisher.     

Rare-earth Doped Nanoparticles with Narrow NIR-II Emission for Optical Imaging with Reduced Autofluorescence

Fluorescence imaging in the second near-infrared region(900-1700 nm, NIR-II) with a high resolution and penetration depth due to the significantly reduced tissue scattering and autofluorescence has emerged as a useful tool in biomedical fields. Recently, many efforts have been devoted to the development of fluorophores with an emission band covering the long-wavelength end of NIR-II region(1500-1700 nm) to eliminate the autofluorescence. Alternatively, we believe imaging with a narrow bandwidth could also reduce the autofluorescence. As a proof of concept, NaYF₄:Yb,Nd@NaYF₄ downconversion nanoparticles(DCNPs) with sharp NIR-II emission were synthesized. The luminescence of DCNPs showed a half-peak width of 49 nm centered at 998 nm, which was perfectly matched with a (1000±25) nm bandpass filter. With this filter, we were able to retain most of the emissions from the nanoparticles, while the autofluorescence was largely reduced. After PEGylation, the DCNPs exhibited great performance for blood vessel and tumor imaging in living mice with significantly reduced autofluorescence and interference signals. This work provided an alternative way for the low-autofluorescence imaging and emphasized the importance of narrow emitting rare-earth doped nanoparticles for NIR-II imaging.     

Aerogels Based on Calcium Alginate and Silicon Dioxide and Modified with Carbon Nanotubes for Selective Sorption of Argon from a Mixture with Oxygen

Russian Journal of Applied Chemistry - Two kinds of aerogels, those based on silicon dioxide and on calcium aginate, modified with multiwalled carbon nanotubes, were synthesized by the...     

Radiation synthesis of chitosan beads grafted with acrylic acid for metal ions sorption

Radiation-induced grafting of acrylic acid onto chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of cobalt-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted material was performed by FTIR spectroscopy and the swelling measurements at different pHs. The grafting yield increased with the increase in dose, it reached 80% at 40 kGy irradiation dose.The removal of Pb and Cd ions from aqueous solutions was investigated with both ungrafted and grafted chitosan beads. The sorption behavior of the sorbents was examined through pH, kinetics and equilibrium measurements. Grafted chitosan beads presented higher sorption capacity for both metal ions than unmodified chitosan beads.     

Integration of Metal-Organic Frameworks with Bi-Nanoprobes as Dual-Emissive Ratiometric Sensors for Fast and Highly Sensitive Determination of Food Hazards

Functional nanoprobes which detect specific food hazards quickly and simply are still in high demand in the field of food-safety inspection research. In the present work, a dual-emission metal-organic framework-based ratiometric fluorescence probe was integrated to detect Cu²⁺ and Pb²⁺ with rapidness and ease. Specifically, quantum dots (QDs) and carbon quantum dots (CQDs) were successfully embedded into zeolitic imidazolate framework-67 (ZIF-67) to function as a novel ratiometric fluorescent sensing composite. The ratiometric fluorescence signal of CQDs/QDs@ZIF-67 was significantly aligned with the concentration of metal ions to give an extremely low detection limit of 0.3324 nM. The highly sensitive and selective CQDs/QDs@ZIF-67 composite showed potential for the rapid and cost-effective detection of two metal ions.     

Degradable Vanadium Disulfide Nanostructures with Unique Optical and Magnetic Functions for Cancer Theranostics

Multifunctional biodegradable inorganic theranostic nano‐agents are of great interest to the field of nanomedicine. Upon lipid modification, VS₂ nanosheets could be converted into ultra‐small VS₂ nanodots encapsulated inside polyethylene glycol (PEG) modified lipid micelles. Owing to paramagnetism, high near‐infrared (NIR) absorbance, and chelator‐free ^99mTc⁴⁺ labeling of VS₂, such VS₂@lipid‐PEG nanoparticles could be used for T1‐weighted magnetic resonance (MR), photoacoustic (PA),and single photon emission computed tomography (SPECT) tri‐modal imaging guided photothermal ablation of tumors. Importantly, along with the gradual degradation of VS₂, our VS₂@lipid‐PEG nanoparticles exhibit effective body excretion without appreciable toxicity. The unique advantages of VS₂ nanostructures with highly integrated functionalities and biodegradable behaviors mean they are promising for applications in cancer theranostics.     

Optical cell with a temperature-control unit for a vacuum-ultraviolet circular dichroism spectrophotometer.

We constructed an assembled-type MgF2 cell that can function under a high vacuum (10(-4) Pa), and is capable of measuring the vacuum-ultraviolet circular dichroism (VUVCD) spectrum in a wavelength region down to 140 nm for aqueous solutions. Its path length can be adjusted by various spacers in the range from 1.3 to 50 microm. The temperature-control unit of the cell was also constructed with a Peltier thermoelectric element to keep the temperature of a sample within an accuracy of +/- 1 degrees C in the temperature range from -30 to 70 degrees C. The optical cell and the temperature-control unit were confirmed to have good performance by monitoring the VUVCD spectra of ammonium d-camphor-10-sulfonate and myoglobin aqueous solutions. This cell is available not only for VUVCD spectroscopy, but also for vacuum-ultraviolet absorption measurements.     

高灵敏度二氧化硫光纤传感器的研究

以奎宁为荧光试剂,通过改变传感液膜的组成及采用非稳态测量法,研制成功高灵敏度的二氧化硫光纤传感器,该传感器的线性响应范围为3.1×10^-7～7.8×10^-5mol/L,检测限达1.6×10^-7mol/L.研究了内充液中NaHSO₃浓度、内充液层厚度对该光纤传感器动态响应信号的影响,用该传感器测定了葡萄酒中游离二氧化硫的含量,结果令人满意.     

Radiation grafting of ionically crosslinked alginate/chitosan beads with acrylic acid for lead sorption

Radiation-induced grafting of acrylic acid onto alginate/chitosan beads was performed in solution at a dose rate of 20.6 Gy/min of Co-60 gamma rays. The effect of absorbed dose on grafting yield was investigated. The characterization of the grafted and un-grafted beads was performed by FTIR spectroscopy and the swelling measurements at different pHs was studied. It is found that as the pH value increases the swelling degree increases up to pH 6 but with further increase in pH value the swelling decreases. Also, it is noticed that the grafting yield increased with increase the irradiation dose. Both un-grafted and grafted alginate/chitosan beads were examined as sorbents for the removal of Pb ions from aqueous solutions. The sorption behavior of the sorbents was examined through pH, and equilibrium measurements. Grafted alginate/chitosan beads presented higher sorption capacity for Pb ions than un-grafted beads.     

The Sol-Gel Process for Nano-Technologies: New Nanocomposites with Interesting Optical and Mechanical Properties

Various nanocomposite systems have been synthesized by sol-gel routes. For this reason, prefabricated nanoparticles (SiO2 sols or boehmite powder) have been dispersed after surface modification in sol-gel-derived organically modified or polymeric ligand matrices. In all cases, a significant effect on dispersibility by surface modification could be observed. After curing, the mechanical or optical properties depend strongly on the dispersion and surface modification. Using these results, composites to be used in chip coupling and as hard coatings on polycarbonate and CR 39 have been developed.     

吡啶二亚胺过渡金属配合物的二阶非线性光学性质

采用密度泛函理论(DFT) B3LYP方法,对8个吡啶二亚胺配合物的几何结构、电子光谱和二阶非线性光学(NLO)性质进行了计算和分析.结果表明,配合物的极化率受副配体和中心金属离子的影响不大,副配体对配合物二阶NLO系数的影响也不明显.随金属离子d电子数的增加,配合物二阶NLO系数(β)有所减小,同一族金属离子随半径增大,其配合物相应的βtot值增加.配合物中的金属离子起到供电子作用时,配合物最大振子强度下的跃迁能较小,其相应的βtot值较大.