Improved formaldehyde sensor of Zn2SnO4/SnO2 microcubes by compositional evolution and Y2O3 decoration

Zn₂SnO₄/SnO₂(ZTO/SnO₂) and Y doped Zn₂SnO₄/SnO₂(ZTO/SnO₂) microcubes were synthesized by a hydrothermal route at 130?°C and subsequently used for obtaining gas sensors. To evaluate the structure, morphology, chemical state and optical bandgap, our sensors were characterized by XRD, SEM, XPS and UV–vis analysis. Compared with sensors based on ZTO/SnO₂ microcubes, the Y doped ZTO/SnO₂ microcubes had an optimum sensing performance to 100?ppm formaldehyde (HCHO), for instance lower working temperature (210?°C) and better response (46.07). In addition, the enhanced sensing mechanism of Y doped ZTO/SnO₂ microcubes was discussed in detail.     

Effect of chlorine on the viscosities and structures of blast furnace slags

The viscosity of CaO–SiO₂–Al₂O₃–MgO–CaCl₂ slags (C/S?=?1.12) were investigated to elucidate the effects of chlorine ranging from 0.02 to 0.53?mass% on the blast furnace slags at high temperatures. Moreover, the Raman spectra of the quenched slags and the X-ray diffraction patterns of the slags cooled in air after viscosity measurement were thoroughly analysed to interpret the transformation of the structures of the slags with increasing the content of chlorine. The viscosity was found to decrease slightly with the increase of chlorine at a given temperature higher than 1673?K, and the critical temperature (T_CR) decreased from about 1660 to 1590?K simultaneously which was possibly deriving from the precipitation of Ca₂Al₂SiO₇, Ca₃Al₂(SiO₄)₃–xCl₄ x and SiO₂ in higher chlorine content. The degree of polymerisation for silicon–oxygen tetrahedra was found to decrease estimating from the decrease of the average amount of bridging oxygen calculated from the deconvolution results of the Raman spectra of the quenched slags, which provided the explanation for the decrease in viscosity. And that the apparent activation energy of the slags was commonly reduced by chlorine increasing demonstrated the decrease in the degree of polymerisation of molten slags simultaneously.     

Annual vegetation burns across the northern savanna region of Ghana: period of occurrence, area burns, nutrient losses and emissions

This study has assessed the seasonal occurrence of annual vegetation fires and defined inter-seasonally burned area for the different vegetation cover types across Ghana and the northern region of Ghana using 10-year (2001?C2010) remote sensing data. These values were used with fire induced elemental losses to estimate greenhouse gas emissions and net plant nutrient loss due to gross bush fire nutrient transfers and annual atmospheric nutrient depositions. About 21, 68, 10 and 1?% of annual burns across the northern region of Ghana take place in the months of November, December, January and February respectively. As much as 68?±?4 thousand km² (25?C32?%) and 37?±?2.6 thousand km² (46?C60?%) of dry land are annually burned across Ghana and the northern region of Ghana respectively, with 53?C56?% of the total annual burns across the country taking place in the northern region. About 10,100?C28,400 Gg of C, comprising 215?C4,700 thousand Gg of CO₂ equivalent (CO₂, CH₄) potential global warming green house gases and 48?C324 thousand Gg of local pollutants (CO, NO_x) are estimated to be released annually through bush fire occurrence across Ghana. Net negative balance for P between fire-induced nutrient transfers and, annual wet and dry nutrient deposits is of concern given the high P-sorbing mineral content of the soils. The temporal loss of P suggest an input source than wet and dry atmospheric P depositions for the sustenance of the ecosystem or predict a long term threat to regional food production.     

Design of the PIXIE cryogenic system

The Primordial Inflation Explorer (PIXIE) is a proposed mission to study the polarization of the remnant cosmic microwave background with the goal of finding and understanding primordial gravity waves. The instrument has been designed to capture this information across the entire sky by rejecting foreground signals and suppressing systematic error by multiple differencing methods. The instrument operates at a temperature very close to the cosmic microwave background of 2.7 K, while the detectors operate at 0.1 K. The PIXIE cryogenic system provides this in low Earth orbit by making use of three subsystems. Lightweight, simply deployed shields provide protection against the Earth and Sun while passively cooling wiring and instrument supports at 150 K. A mechanical cryocooler precools wires and supports at 68, 17, and 4.5 K while its compressors operate at room temperature. And finally two adiabatic demagnetization refrigerators cool the instrument from 4.5 to 2.7 K and cool the detectors to 0.1 K. Staged cooling in this manner allows a thermodynamically efficient use of relatively mature technologies that can be fully demonstrated before flight.