Skin color-specific and spectrally-selective naked-eye dosimetry of UVA, B and C radiations.

Spectrally-selective monitoring of ultraviolet radiations (UVR) is of paramount importance across diverse fields, including effective monitoring of excessive solar exposure. Current UV sensors cannot differentiate between UVA, B, and C, each of which has a remarkably different impact on human health. Here we show spectrally selective colorimetric monitoring of UVR by developing a photoelectrochromic ink that consists of a multi-redox polyoxometalate and an e- donor. We combine this ink with simple components such as filter paper and transparency sheets to fabricate low-cost sensors that provide naked-eye monitoring of UVR, even at low doses typically encountered during solar exposure. Importantly, the diverse UV tolerance of different skin colors demands personalized sensors. In this spirit, we demonstrate the customized design of robust real-time solar UV dosimeters to meet the specific need of different skin phototypes. These spectrally-selective UV sensors offer remarkable potential in managing the impact of UVR in our day-to-day life.

Technical Note: A simulation study on the feasibility of radiotherapy dose enhancement with calcium tungstate and hafnium oxide nano- and microparticles.

PURPOSE: To assess the radiotherapy dose enhancement (RDE) potential of calcium tungstate (CaWO4 ) and hafnium oxide (HfO2 ) nano- and microparticles (NPs). A Monte Carlo simulation study was conducted to gauge their respective RDE potentials relative to that of the broadly studied gold (Au) NP. The study was warranted due to the promising clinical and preclinical studies involving both CaWO4 and HfO2 NPs as RDE agents in the treatment of various types of cancers. The study provides a baseline RDE to which future experimental RDE trends can be compared to. METHODS: All three materials were investigated in silico with the software Penetration and Energy Loss of Positrons and Electrons (PENELOPE 2014) developed by Francesc Salvat and distributed in the United States by the Radiation Safety Information Computational Center (RSICC) at Oak Ridge National Laboratory. The work utilizes the extensively studied Au NP as the "gold standard" for a baseline. The key metric used in the evaluation of the materials was the local dose enhancement factor (DEFloc ). An additional metric used, termed the relative enhancement ratio (RER), evaluates material performance at the same mass concentrations. RESULTS: The results of the study indicate that Au has the strongest RDE potential using the DEFloc metric. HfO2 and CaWO4 both underperformed relative to Au with lower DEFloc of 2-3 × and 4-100 ×, respectively. CONCLUSIONS: The computational investigation predicts the RDE performance ranking to be: Au > HfO2 > CaWO4 .

Calcium silicate-based sealers: Assessment of physicochemical properties, porosity and hydration.

OBJECTIVES: Investigation of hydration, chemical, physical properties and porosity of experimental calcium silicate-based sealers. METHODS: Experimental calcium silicate-based sealers with calcium tungstate and zirconium oxide radio-opacifiers were prepared by mixing 1g of powder to 0.3 mL of 80% distilled water and 20% propylene glycol. MTA and MTA Fillapex were used as controls. The raw materials and set sealers were characterized using a combination of scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction. Physical properties were analyzed according to ANSI/ADA. The pH and calcium ion release were assessed after 3, 24, 72 and 168 h. The porosity was assessed using mercury intrusion porosimetry. RESULTS: The analysis of hydration of prototype sealers revealed calcium hydroxide as a by-product resulting in alkaline pH and detection of calcium ion release, with high values in initial periods. The radiopacity was similar to MTA for the sealers containing high amounts of radio-opacifiers (p>0.05). Flowability was higher and film thickness was lower for resinous MTA Fillapex sealer (p<0.05). The test sealers showed water sorption and porosity similar to MTA (p>0.05). SIGNIFICANCE: The prototype sealers presented adequate hydration, elevated pH and calcium ion release. Regarding physical properties, elevated proportions of radio-opacifiers were necessary to accomplish adequate radiopacity, enhance flowability and reduce film thickness. All the tested sealers presented water sorption and porosity similar to MTA.

Assessment of color stability of white mineral trioxide aggregate angelus and bismuth oxide in contact with tooth structure.

INTRODUCTION: Dental discoloration with use of materials containing bismuth oxide has been reported. It is postulated that the discoloration is a result of chemical interaction of bismuth oxide with dentin. The aim of the study was to analyze dental color alteration and the chemical interaction of bismuth oxide with the main components present in composite (methacrylate) and in dentin (collagen). METHODS: Fifty bovine teeth were prepared and filled with white mineral trioxide aggregate (MTA) Angelus, Portland cement (PC) with 20% zirconium oxide, or PC with 20% calcium tungstate and then sealed with composite. Triple antibiotic paste and unfilled samples were the positive and negative controls, respectively. The specimens were stored in separate flasks immersed in tap water at 37°C with ambient light blocked out. The color assessment was performed with a spectrophotometer at different intervals, namely before filling and 24 hours, 15 days, and 30 days after filling. The color change and the luminosity were calculated. The statistical analysis was performed by using nonparametric Kruskal-Wallis and Dunn tests (P < .05). The interaction of the bismuth oxide, zirconium oxide, and calcium tungstate with collagen and methacrylate was assessed by placing the materials in contact, followed by color assessment. RESULTS: The analysis of color change values showed that all the materials presented color alteration after the evaluated periods. Statistically higher luminosity was verified for PC/20% zirconium oxide in comparison with white MTA Angelus (P < .05). The teeth filled with white MTA Angelus demonstrated a grayish discoloration with evident dentin staining. Bismuth oxide exhibited a color change when in contact with collagen. CONCLUSIONS: The color of white MTA Angelus was altered in contact with dental structures. Collagen, which is present in dentin matrix, reacted with bismuth oxide, resulting in a grayish discoloration. The use of an alternative radiopacifier to replace bismuth in white MTA is indicated.

Catalytic conversion of cellulose to ethylene glycol over a low-cost binary catalyst of Raney Ni and tungstic acid.

Following our previous report on the selective transformation of cellulose to ethylene glycol (EG) over a binary catalyst composed of tungstic acid and Ru/C, we herein report a new low-cost but more effective binary catalyst by using Raney nickel in place of Ru/C (Raney Ni+H(2 WO(4) ). In addition to tungstic acid, other W compounds were also investigated in combination with Raney Ni. The results showed that the EG yield depended on the W compound: H(4)SiW(12)O(40)

A microbiological assessment of polymer and conventional carbide burs in caries removal.

PURPOSE: The purpose of this study was to compare the caries removal efficiency of polymer burs (Smartburs) and conventional carbide burs microbiologically. METHODS: Twenty-four patients participated, each presenting 2 active carious lesions on the occlusal surfaces of primary molars. Sample-taking and caries-removal were done in the following order: (1) first sample (from the carious dentin); (2) caries removal (with a Smartbur or carbide bur); and (3) second sample (from the caries-free dentin), respectively. The samples were processed in a laboratory and spread on various media. The colonies on the agar plates were counted, and then numbers of CFU/ml were calculated. RESULTS: There were no statistically significant differences between the numbers of CFU/ml in the carious dentin before preparation, comparing the Smartbur group and carbide bur group for all the media used (P>.05). There were statistically significant differences in the numbers of CFU/ml before and after preparation comparing both types of burs for all the media used (P<.05). There were no statistically significant differences in the reductions of the numbers of CFU/ml, comparing the 2 preparation instruments (P>.05). CONCLUSION: The polymer burs were found as effective as the conventional carbide burs microbiologically in caries removal.

Assessment of the interaction between a synthetic epitope of troponin C and its specific antibody using a label-free faradaic impedimetric immunosensor and alpha-Keggin silicotungstic heteropolyacid as a redox probe.

The development of an immunosensor for the direct probing of the interaction between a cysteine-modified synthetic peptide, which corresponds to the epitope cTnC-89-98 of troponin C, and its specific antibody is described. Following immobilization of the peptide onto gold electrodes through the formation of a self-assembled monolayer, the alteration of the interfacial properties of the electrodes upon peptide-antibody interaction was traced by faradaic electrochemical impedance spectroscopy (EIS) using a silicotungstic heteropolyacid, H(4)SiO(4).12WO(3), as a redox probe. The electrochemical behaviour of the redox probe was evaluated with cyclic voltammetry and EIS. The effect of milk protein or 4-mercaptophenol, which was used as post-blocking agents, on the performance of the immunosensor, was investigated. Treatment with 4-mercaptophenol resulted in immunoeffective electrodes that successfully tested in anti-serum samples. An optimum dilution ratio of the samples, where the effect of the matrix on the measuring signal is negligible, was also determined.

Direct, efficient, and inexpensive formation of alpha-hydroxyketones from olefins by hydrogen peroxide oxidation catalyzed by the 12-tungstophosphoric acid/cetylpyridinium chloride system.

The direct ketohydroxylation of a variety of 1-aryl-1-alkenes with H2O2, catalyzed by the inexpensive 12-tungstophosphoric acid/cetylpyridinium chloride system under very mild conditions, was achieved. Various acyloins were obtained in good yields and high regioselectivies.

Thick, segmented CdWO4-photodiode detector for cone beam megavoltage CT: a Monte Carlo study of system design parameters.

Megavoltage (MV) imaging detectors have been the focus of research by many groups in recent years. We have been working with segmented CdWO4 crystals in contact with photodiodes in our lab. The present study uses both x-ray and optical photon transport Monte Carlo simulations to analyze the effects of scintillation crystal height, septa material, beam divergence, and beam spectrum on the modulation transfer function, MTF(f) and zero frequency detective quantum efficiency, DQE(0), of a theoretical area detector. The theoretical detector is comprised of tall, segmented CdWO4 crystals and two dimensional photodiode arrays with a pitch of 1 mm and a fill factor of 72%. Increasing the crystal height above 10 mm does not result in an improvement in the DQE(0) if the reflection coefficient of the septa is less than 0.8. For a reflection coefficient of 0.975 for the septa, there is a continual gain in the DQE(0) up to 30 mm tall crystals. Similar calculations show that employing a 3.5 MV beam without a flattening filter increases the DQE(0) for 20 mm tall crystals by 9% compared to a typical 6 MV beam with a flattening filter. The severe degradations due to beam divergence on MTF(f) are quantified and suggest the use of focused detectors in MV imaging. It is found that when the effect of optical photons is considered, the presence of divergence can appear as a shift in the location of the input signal as well as loss of spatial resolution.