Nanoassisted Laser Desorption-Ionization-MS Imaging of Tumors

The ability of nanoassisted laser desorption-ionization mass spectrometry (NALDI-MS) imaging to provide selective chemical monitoring with proper spatial distribution of lipid profiles from tumor tissues after plate imprinting has been tested. NALDI-MS imaging identified and mapped several potential lipid biomarkers in a murine model of melanoma tumor (inoculation of B16/F10 cells). It also confirmed that the in vivo treatment of tumor bearing mice with synthetic supplement containing phosphoethanolamine (PHO-S) promoted an accentuated decrease in relative abundance of the tumor biomarkers. NALDI-MS imaging is a matrix-free LDI protocol based on the selective imprinting of lipids in the NALDI plate followed by the removal of the tissue. It therefore provides good quality and selective chemical images with preservation of spatial distribution and less interference from tissue material. The test case described herein illustrates the potential of chemically selective NALDI-MS imaging for biomarker discovery.     

Impact of biofouling on diffusive gradient in thin film measurements in water

The technique of diffusive gradient in thin film (DGT) is commonly used to assess metal contamination in natural waters. In this paper, we assess the effect of biofouling on DGT measured labile concentrations in water and investigate whether an additional nuclepore polycarbonate membrane on the surface of DGT devices can limit biofilm growth. Simultaneous field deployments of DGT equipped with and without the additional membrane in a canal receiving wastewater were compared. The effect of the biofilm was also assessed in controlled laboratory experiments, completed by the experimental determination of several metals diffusion coefficients in the hydrogel and membrane systems. The biofilms effect was problematic only from the 10th day of accumulation. Accumulation of some elements is highly biased by the presence of a thick biofilm (Zn, Ni, Cd). The polycarbonate membrane improved the quantification of Cd and Ni but adversely affects the quantification of Cr and Co. A kinetic model is proposed to explain the biofilm role on the DGT measurement. Depending on the metals of interest, it is possible to limit bias due to biofilms by using an additional polycarbonate membrane.     

A Novel Type of Absorber Presenting a Constant Detection Efficiency for up to 25 keV X-Ray Photons

A novel type of absorber, dedicated to cryogenic detectors, was conceived to reach a high and constant intrinsic detection efficiency (>98%) for up to 25?keV X-ray photons. The absorber consists of two layers having a different atomic number?Z. The role of the first layer (large?Z) is to make negligible the transmission through the absorber; while the second layer (medium?Z) has to reabsorb the escape photons from the first layer. A?metallic magnetic calorimeter was realized with an Au-Ag absorber. The required thicknesses of both layers were determined using Monte Carlo simulation of the efficiency. To show the advantages of such a detector, its efficiency and its energy resolution are compared to the efficiency and energy resolution of a gold absorber using a ²⁴¹Am source.     

Evaluation of solar photo-Fenton parameters on the pre-oxidation of leachates from a sanitary landfill

The main purpose of this work is to study the treatment of a leachate after preliminary aerated lagooning by a solar photo-Fenton process, using a photocatalytic reactor with compound parabolic collectors (CPCs). The influence of different process parameters in the reaction rate was evaluated, such as, the type of acid used in the acidification step (H₂SO₄, HCl, H₂SO₄ + HCl); type of iron salt (FeSO₄, FeCl₃) and respective iron concentration (60, 80, 100 and 140 mg Fe²⁺/L); temperature; and ratio of illuminated to total volume (25 L/35 L; 25 L/72 L). DOC abatement in the acidification procedure is independent of the type of acid used and temperature, and is related principally with the precipitation of humic acids. The use of HCl alone or in combination with H₂SO₄ leads to a substantially increase of the chloride ions, leading to the formation of less reactive chloride radicals when compared with sulfate radicals, decreasing the photo-Fenton reaction rate. The use of ferrous ions instead of ferric ions influenced positively the photo-Fenton reaction. Meteorological conditions favoring higher temperature of the leachate enhance the photo-Fenton reaction. Alternating dark and illumination intervals has shown a negligible effect on the illumination time needed to achieve the same mineralization, indicating that the Fenton process that takes place in dark zones is not efficient, even in the degradation of intermediate compounds resulting from the light-enhanced reaction. According to biodegradability tests, the optimum energy dose, necessary to obtain a biodegradable effluent, is 57.4 kJ_UV/L, consuming 120 mM of H₂O₂ and leading to a final DOC of 284 mg/L which corresponds to approximately 66% of mineralization.     

Effects of thermal annealing on the semi-insulating properties of radio frequency magnetron sputtering-produced germanate thin films

We report the effects of thermal annealing on the semi-insulating properties of germanate thin films produced by a radio frequency magnetron sputtering process. Electrical and physical characterizations are presented. In the case of PbO-GeO₂ films (annealed and not annealed), the electron diffraction analysis from transmission electron microscopy has shown that the amorphous structure predominates, whereas the annealed PbO-GeO₂-AgNO₃ (1 wt.%) films presented crystalline nanoparticles in the range of 1 to 9 nm composed of Pb, PbO and Ag₄GeO₄. Also, not annealed and annealed films were used to produce metal-insulator-semiconductor structures. The electrical properties of these structures were analysed from capacitance-voltage and conductance-voltage characteristics. The results showed that the significant leakage current in the accumulation region in the not annealed films can be increased by the annealing process. In addition, stable semi-insulating layers with an almost constant shifting of the capacitance-voltage characteristics are obtained when annealed PbO-GeO₂-AgNO₃ (1 wt.%) films are employed. Based on a proposed model accounting for the leakage process, the influence of this leakage on the accumulation capacitance was also established. In addition, the decrease of the dielectric constant in the presence of crystalline nanoparticles was shown. The results obtained indicate that the germanate thin films are potential passivating materials for power device applications.     

Ascorbate electro-oxidation by modified electrodes: Polypyrrole and polypyrrole/Ni(OH)2 composite thin films

The present paper describes the utilization of polypyrrole and the composite of polypyrrole doped with nickel hydroxide modified electrodes toward the catalytic oxidation of ascorbate. Films were potentiostatically deposited onto a glassy carbon surface and Fluor-doped tin oxide glass for different times. The physical characterization was performed using the low angle X-ray diffraction technique. Furthermore, the films were electrochemically characterized using cyclic voltammetry. The X-ray diffraction results show the existence of different polymorphic phases of nickel hydroxide in the polymer matrix, and the β-Ni(OH)₂ phase appears to be dominant. The cyclic voltammetry profile in KOH solution shows the presence of two redox peaks that are related to the Ni^II/Ni^III and Ni^III/Ni^II couples, at approximately 0.5 and 0.35 V, respectively. The reversible electro-oxidation of ascorbate was observed on the surface of the polypyrrole and composite films. The analytical curves obtained using voltammetric techniques show a linear relationship between the faradaic current and the increase of the ascorbic acid concentration. The sensitivity of these films, which is obtained from the slope of the analytical curves, shows that the composite film is more electroactive than the polypyrrole film: 133.4 mA L mol^− 1 cm^− 2 and 83.8 mA L mol^− 1 cm^− 2, respectively. The rate constants of the catalytic ascorbate electro-oxidation were also reported, where the mean values were found to be 217.74 M^− 1 s^− 1 and 54.37 M^− 1 s^− 1, for the composite and polypyrrole films, respectively. The low cost of polypyrrole doped with Ni(OH)₂ composite electrodes presents a more selective and high sensitivity to determine ascorbic acid concentration.     

NIR luminescent Er/Yb co-doped SiO2–ZrO2 nanostructured planar and channel waveguides: Optical and structural properties

Optical and structural properties of planar and channel waveguides based on sol–gel Er³⁺ and Yb³⁺ co-doped SiO₂–ZrO₂ are reported. Microstructured channels with high homogeneous surface profile were written onto the surface of multilayered densified films deposited on SiO₂/Si substrates by a femtosecond laser etching technique. The densification of the planar waveguides was evaluated from changes in the refractive index and thickness, with full densification being achieved at 900 °C after annealing from 23 up to 500 min, depending on the ZrO₂ content. Crystal nucleation and growth took place together with densification, thereby producing transparent glass ceramic planar waveguides containing rare earth-doped ZrO₂ nanocrystals dispersed in a silica-based glassy host. Low roughness and crack-free surface as well as high confinement coefficient were achieved for all the compositions. Enhanced NIR luminescence of the Er³⁺ ions was observed for the Yb³⁺-codoped planar waveguides, denoting an efficient energy transfer from the Yb³⁺ to the Er³⁺ ion.     

Acoustically driven photon antibunching in nanowires

The oscillating piezoelectric field of a surface acoustic wave (SAW) is employed to transport photoexcited carriers, as well as to spatially control exciton recombination in GaAs-based nanowires (NWs) on a subns time scale. The experiments are carried out in core-shell NWs transferred to a SAW delay line on a LiNbO(3) crystal. Carriers generated in the NW by a focused laser spot are acoustically transferred to a second location, leading to the remote emission of subns light pulses synchronized with the SAW phase. The dynamics of the carrier transport, investigated using spatially and time-resolved photoluminescence, is well-reproduced by computer simulations. The high-frequency contactless manipulation of carriers by SAWs opens new perspectives for applications of NWs in opto-electronic devices operating at gigahertz frequencies. The potential of this approach is demonstrated by the realization of a high-frequency source of antibunched photons based on the acoustic transport of electrons and holes in (In,Ga)As NWs.     

Preparation of nanocomposites resin from seed Pterodon emarginatus doped maghemite nanoparticles

Electrical characterization and magnetic nanocomposite resin seeds Pterodon emarginatus (PE) doped with nanoparticles of maghemite and treated by different chemical processes is reported in this paper. The pure PE resin showed semiconducting characteristics probably the presence of natural iron oxide in its molecular structure. The analysis of M?ssbauer spectra pure resin showed two magnetic sites presented on measurements made at temperature of 300 K. Six "LEDs" to have been doped maghemite nanoparticles forming concentrations of 2.6 x 10(15) to 1.56 x 10(16) particles/cm2 forming the LED-PEMN. In the presence of the applied current versus voltage (0 to 0.9 V) LED-PEMN shown semiconducting properties. In the presence of frequency versus voltage sample of pure resin and LED features small decrease. While samples of LED-PEMN suffers loss frequency linearly with concentration and voltage. The pure PE resin shows high resistance to the applied voltage while the LED-PEMN is observed linear increase with the strength and concentration of nanoparticles of maghemite.     

Tuning the conditions for the deposition of nanocrystalline diamond by hot filament chemical vapour deposition

Although large focus has been placed into the deposition of nanocrystalline and ultra-nanocrystalline diamond films, most of this research uses microwave plasma assisted CVD systems. However, the growth conditions used in microwave systems cannot be directly used in hot-filament CVD systems. This paper, aims to enlarge the knowledge of the diamond film depositing process. H2/CH4/Ar gas mixtures have been used to deposit micro, nano and ultra-nanocrystalline diamond films by hot-filament CVD systems. Additionally, the distance between the filaments array and the substrate was varied, in order to observe its effect and consequently the effect of a lower substrate temperature in the nucleation density and deposition. All the samples were characterized for microstructure and quality, using scanning electron microscopy and Raman spectroscopy.