Blue-emitting polystyrene scintillators for plastic scintillation dosimetry

Objectives Purpose of this research was to find the best blue-emitting fluorescent substance for plastic scintillator used for gamma radiation dosimetry. Scintillator should convert gamma radiation into blue light with high efficiency. Methods Plastic scintillators with fixed concentration of various fluorescent additives, called wavelength shifters, absorbing ultraviolet light and emitting blue light were manufactured by radical bulk polymerization of styrene. Light output were measured and compared to the light output of commercial plastic scintillator. Results Performed measurements of charge Compton spectra confirmed usefulness of majority of researched substances as wavelength shifters in plastic scintillators with emission maximum at blue range of visible light. Conclusions Plastic scintillation dosimeter may be constructed from manufactured polystyrene-based scintillators. Performance of synthesized scintillators is close to commercial polystyrene scintillators.

A universal microfluidic approach for quantitative study of bacterial biofilms

Bacteria usually live in densely packed communities called biofilms, where interactions between the bacteria give rise to complex properties. Quantitative analysis is indispensable in understanding those properties. However, current biofilm culturing approaches impose various limitations to these types of analysis. Here, we developed a microfluidic approach for quantitative study of biofilms, which is universal and can be used to culture biofilms of various bacterial species. To demonstrate the advantages of this approach, we present two examples, both of which revealed new biological insights. In the first example, we explored the response of Escherichia coli biofilms to exogenous hydrogen peroxide; We found the biofilms gained resistance to H2O2, but their growth was slowed down due to the metabolic cost of maintaining the resistance; However, under oxygen limitation, H2O2 can anti-intuitively boost biofilm growth. In the second example, we explored resource retention by Pseudomonas aeruginosa biofilms; We observed a fluorescent substance within the biofilm and identified it as the siderophore pyoverdine; We further showed that the extracellular matrix component Psl acted as a retention barrier for pyoverdine, minimizing its loss into the environment and therefore potentially promoting sharing of pyoverdine within the biofilm.

Validation of Fucoxanthin from Microalgae Phaeodactylum tricornutum for the Detection of Amyloid Burden in Transgenic Mouse Models of Alzheimer’s Disease

The visualization of misfolded Aβ peptides by using fluorescence chemical dyes is very important in Alzheimer’s disease (AD) diagnosis. Here, we describe the fluorescent substance, fucoxanthin, which detects Aβ aggregates in the brain of AD transgenic mouse models. We found that fucoxanthin from the microalgae Phaeodactylum tricornutum has fluorescent excitation and emission wavelengths without any interference for Aβ interaction. Thus, we applied it to monitor Aβ aggregation in AD transgenic mouse models. Aβ plaques were visualized using fucoxanthin in the brain tissue of APP/PS1 and 5×FAD mice by histological staining with different staining methods. By comparing fucoxanthin-positive and thioflavin S-positive stained regions in the brains, we found that they are colocalized and that fucoxanthin can detect Aβ aggregates. Our finding suggests that fucoxanthin from P. tricornutum can be a new Aβ fluorescent imaging reagent in AD diagnosis.

Luminescence and tunable color properties of uniphase white-emitting Sr3B2SiO8:Tm3+/Dy3+/Eu3+ phosphors by energy transfer for UV-excited white LEDs

Multi-color single-phase white emission Sr 3 B 2 SiO 8 :Tm 3+ /Dy 3+ /Eu 3+ fluorescent powders were prepared by solid-state fritting method. The fluorescence performance of Tm 3+ , Dy 3+ and Eu 3+ ions single-activated Sr 3 B 2 SiO 8 phosphors were investigated and they exhibit desirable behaviors in their characteristic emissions. Meanwhile, the energy required for migration from Tm 3+ to Dy 3+ and from Dy 3+ to Eu 3+ in co-doped fluorescent substance was determined by the aids of steady-state and transient-state photoluminescence spectra /decay measurements. The energy transmission process from Tm 3+ to Dy 3+ and Dy 3+ to Eu 3+ has been explored to be a dipole–quadrupole interaction and a dipole-dipole interaction of the resonant type, respectively. More significantly, by tuning the molarity ratio of doping Dy 3+ /Eu 3+ ions, multicolor emission from yellow to red shall be achieved in Sr 3 B 2 SiO 8 :Dy 3+ , Eu 3+ phosphors for its potential adhibitions in solid-state lighting applications. The Sr 3 B 2 SiO 8 :Tm 3+ , Dy 3+ samples can implement white light emission by the appropriate changeable doping molar quantity of Tm 3+ and Dy 3+ , applying potentially in white LEDs. The energy migrations between co-doped rare earth ions play a decisive role in these processes.

PREPARATION OF FLUORESCENT POLYSTYRENE MICROSPHERES BY IMPROVING SWELLING PERFORMANCE BASED ON MOLECULAR WEIGHT AND SURFACE CARBOXYL GROUP CONTENT

The fluorescent microspheres are prepared by the swelling-evaporation method. The optimal swelling conditions are obtained by researching related factors, such as types and dosages of swelling agent, dosages of fluorescent substance, swelling time and swelling temperature. Considering that the structure of microspheres can influence the swelling properties, the paper mainly focuses on the effect of molecular weight and surface carboxyl group content of polystyrene microspheres on swelling properties. When the molecular weight of microspheres is 75276 g mol-1, the density of carboxyl group on their surface is 6.94×10-4 mol g-1, and the doping amount of europium complex reaches the maximum of 24.9 mg g-1 with the strongest fluorescence intensity. Meanwhile, the as-prepared fluorescent microspheres have high monodispersity, uniform particles size and high thermal stability (the decomposition temperature is 385 oC), which sets up the good foundation for biomolecule detection. So, this work provides a significant experience for the preparation of fluorescent microspheres.

verA Gene is Involved in the Step to Make the Xanthone Structure of Demethylsterigmatocystin in Aflatoxin Biosynthesis

In the biosynthesis of aflatoxin, verA, ver-1, ordB, and hypA genes of the aflatoxin gene cluster are involved in the pathway from versicolorin A (VA) to demethylsterigmatocystin (DMST). We herein isolated each disruptant of these four genes to determine their functions in more detail. Disruptants of ver-1, ordB, and hypA genes commonly accumulated VA in their mycelia. In contrast, the verA gene disruptant accumulated a novel yellow fluorescent substance (which we named HAMA) in the mycelia as well as culture medium. Feeding HAMA to the other disruptants commonly caused the production of aflatoxins B1 (AFB1) and G1 (AFG1). These results indicate that HAMA pigment is a novel aflatoxin precursor which is involved at a certain step after those of ver-1, ordB, and hypA genes between VA and DMST. HAMA was found to be an unstable substance to easily convert to DMST and sterigmatin. A liquid chromatography-mass spectrometry (LC-MS) analysis showed that the molecular mass of HAMA was 374, and HAMA gave two close major peaks in the LC chromatogram in some LC conditions. We suggest that these peaks correspond to the two conformers of HAMA; one of them would be selectively bound on the substrate binding site of VerA enzyme and then converted to DMST. VerA enzyme may work as a key enzyme in the creation of the xanthone structure of DMST from HAMA.

Enhanced Red Fluorescence Emissions of [Ru(bpy)3]Cl2 in DNA Complexes

The research on molecular devices, fluorescent labels and fluorescent probes based on the interaction between biomolecular DNA and fluorescent dyes has been paid more attention at home and abroad. In this paper, the luminescence properties of the [Ru(bpy)3]Cl2 complex itself were investigated, and the luminescence properties of the [Ru(bpy)3]Cl2 complex under the interaction of the solution and the film were observed by association of the DNA complex with the [Ru(bpy)3]Cl2 complex. The results showed that [Ru(bpy)3]Cl2 emitted red light with its main emission peak wavelength was 610nm, and its fluorescence intensity was the highest when the concentration of solution substance was 10mmol/L. When doped with DNA solution in [Ru(bpy)3]Cl2 complex, a small amount of fluorescent dye [Ru(bpy)3]Cl2 can be used to achieve a higher luminous intensity At the same time, the fluorescent dye [Ru(bpy)3]Cl2 doped with DNA solution reached a higher luminous intensity in the thin-film state. This experiment provides an important experimental basis for the application of fluorescent substance [Ru(bpy)3]Cl2 in luminescent thin films.

Ultraviolet Fluorescence in the Assessment of Quality in the Mixing of Granular Material

The aim of the study was to determine the possibility of using ultraviolet fluorescence to evaluate the quality of the mixing process of industrial feed. A laboratory funnel-flow mixer was used for the mixing process. The studies were carried out using three different feeds for pigs. A key component in the form of ground grains of yellow maize covered with the fluorescent substance Rhodamine B was introduced into the mixer before the mixing process began. After the illumination of the sample by UV lamps, the images were taken with a digital camera. The images were analyzed in Patan® software. The information obtained on the percentage content of the key component was used for further calculations. At the same time, the tracer content was determined using the control method (weight method). The comparison of the results obtained by the two methods (statistical comparative analysis) did not indicate significant differences. Therefore, the usefulness of the proposed method to track the share of the key component by inducing it to glow in the ultraviolet light has been proven. The introduced tracer is also one of the components of the feed, which translates into the possibility of observing the material having the characteristics of a mixed material.

Detection of Directivity of Fluorescence From a Mixed Specimen Which Consists of Micro Particles Attached Different Fluorescent Substances Using a Light Waveguide Incorporated Optical TAS

A resin-based optical total analysis system (O-TAS) which consists both of microfluidic channels and light waveguides [1] is thought to be one of the most promising components in developing a “ubiquitous human healthcare system” in the near future. Along with this technology trend, we have already developed a transparent epoxy-resin-based optical TAS chip which has a specially prepared light waveguide structure of radially arranged configuration at an intersection portion with a microfluidic channel, in order to detect directivity of fluorescence from fluorescent substance attached micro particles [2],[3]. Schematic diagram of the optical TAS is shown in Figure 1. In the latest research, utilizing an AC modulated laser source and time-series averaging function on detected signal waveforms, we could have successfully obtained directivities of fluorescence from 5-μm-diameter particles with higher signal to noise (S/N) ratio [3].

Method for Visualizing Fractures Induced by Laboratory-Based Hydraulic Fracturing and Its Application to Shale Samples

A better understanding of the process of stimulation by hydraulic fracturing in shale gas and oil reservoirs is necessary for improving resource productivity. However, direct observation of hydraulically stimulated regions including induced fractures has been difficult. In the present study, we develop a new approach for directly visualizing regions of shale specimens impregnated by fluid during hydraulic fracturing. The proposed laboratory method uses a thermosetting resin mixed with a fluorescent substance as a fracturing fluid. After fracturing, the resin is fixed within the specimens by heating, and the cut sections are then observed under ultraviolet light. Based on brightness, we can then distinguish induced fractures and their surrounding regions impregnated by the fluid from other regions not reached by the fluid. Polarization microscope observation clearly reveals the detailed structures of tortuous or branched fractures on the micron scale and interactions between fractures and constituent minerals. The proposed experimental and observation method is useful for understanding the process of stimulation by hydraulic fracturing and its relationship with microscopic rock characteristics, which is important for fracturing design optimization in shale gas and oil resource development.