Electrical conductivity and defect disorder of tantalum‐doped TiO2

The present work reports the electrical properties of polycrystalline Ta‐doped TiO₂ (0.39 at.% Ta) determined in situ at elevated temperatures (1173‐1323 K) in the gas phase of controlled oxygen activity (10^?12 Pa to 10⁵ Pa). The effect of oxygen activity on the electrical conductivity and thermoelectric power of TiO₂ is discussed in terms of defect disorder, including (1) the intrinsic electronic disorder that is governed by electronic compensation in the strongly reducing regime, (2) the extrinsic electronic disorder that is governed by electronic charge compensation in the reducing regime, and (3) the extrinsic ionic disorder that is governed by ionic compensation in the oxidizing regime. It is shown that tantalum ions are incorporated into the titanium sublattice of TiO₂ leading to the formation of donor‐type energy levels. The Arrhenius‐type plot of the electrical conductivity data leads to the determination of the formation enthalpy terms. The obtained results are considered in terms of the effect of tantalum and oxygen activity on the defect disorder and the associated key performance‐related properties in the light‐induced partial water oxidation.     

Electrochemical Desulfurization of Waste Gases in a Batch Reactor

To meet the increasing need for reduction of exhaust emissions from stationary sources, many technologies have been developed to remove SO2 from flue gas. In this study the anodic oxidation of sulfur dioxide in aqueous solutions of sulfuric acid with a unique reactor design and electrode configuration has been investigated. An electrochemical absorption column larger than laboratory scale was employed. A titanium rod cathode and platinum expanded mesh anode separated by a cation exchange membrane were used as electrodes in the cylindrical electrochemical reactor. The effects of current densities of 10, 1, and 0.1?Am?2, initial SO2 concentrations of 500, 2,500, and 5,000?ppm, gas flow rates of 0.75, 1.5, and 5?L min?1, sulfuric acid concentrations of 1, 5, and 10%(w), gas composition, and electrolysis time on removal efficiency, current efficiency, energy consumption, and mass transfer coefficient were reported. Removal efficiency of 94% was obtained with a high current efficiency of 94%, energy consumption of 2.22×10?2?kW?hm?3, and mass transfer coefficient of 5.9×10?5?ms?1 without additives or pretreatment. At the current densities of 0.1, 1, and 10?Am?2, the removal efficiencies were 10, 94, and 98%, respectively. Removal efficiency was observed to decrease as inlet SO2 concentration, gas flow rate, and electrolyte concentration increased. The presence of CO2 in the gas mixture led to a decrease in the SO2 removal efficiency. During electrochemical absorption of SO2 into the H2SO4 solution, the concentration of acid is increased from 5 to 10%. At the end of the studies, electrochemical desulfurization succeeded in meeting the regulation requirement, and the absorbing liquid remained in a reusable form.     

Determining the duration of Ixodes scapularis (Acari: Ixodidae) attachment to tick-bite victims

The duration of tick attachment is one factor associated with risk for human infection caused by several tick-borne pathogens. We measured tick engorgement indices at known time intervals after tick attachment and used these indices to determine the length of time that ticks were attached to tick-bite victims in selected Rhode Island and Pennsylvania communities where the agents of Lyme disease and human babesiosis occur. The total body length and width as well as the length and width of the scutum were measured on nymphal and adult female Ixodes scapularis Say removed from laboratory animals at 0, 12, 24, 36, 48, 60, and 72 h after their attachment. Three engorgement indices were calculated at each time interval. In addition, engorgement indices measurements were recorded for 504 ticks submitted to a commercial laboratory for pathogen detection testing between 1990 and 1992. No detectable change was observed in the average engorgement indices for either nymphal or adult ticks between 0 and 24 h of attachment using any of the engorgement indices. After 24 h of tick attachment, all engorgement indices continuously increased: average indices for nymphs attached 36, 48, and 60 h were significantly different from those attached < or = 24 h and from each other. Similarly, average engorgement indices for adult ticks attached < or = 36 h were significantly different from those attached for 48 h or more. More than 60% of tick-bite victims removed adult ticks by 36 h of attachment, but only 10% found and removed the smaller nymphal ticks within the first 24 h of tick feeding. The duration of tick attachment may serve as a useful predictor of risk for acquiring various infections, such as Lyme disease and babesiosis, transmitted by I. scapularis. Regression equations developed herein correlate tick engorgement indices with duration of feeding. A table containing specific engorgement index prediction intervals calculated for both nymphs and adults will allow the practitioner or clinical laboratory to use easily measured tick engorgement indices to predict transmission risk by determining the duration of feeding by individual ticks.     

Successive laser-induced breakdowns in atmospheric pressure air and premixed ethane–air mixtures

Two successive focused laser pulses are employed to experimentally simulate laser-induced breakdown plasmas at high repetition rates. We find that energy absorption of the second laser pulse by the plasma produced by the first laser pulse is enhanced slightly when the time interval between the pulses is shorter than several tens of nanoseconds but falls to almost zero when the time interval is between a few hundreds of nanoseconds and several tens of microseconds. This behavior is attributed to gas heating by the first breakdown event. In premixed ethane–air mixtures, we identify another strong reduction in the second laser pulse absorption when this pulse coincides with the heat released by combustion, typically milliseconds after the first laser pulse. The fuel–air equivalence ratio (?) and base flow speed are also varied in this study. The results show that the window of reduced absorption coinciding with heat release due to combustion is narrowed when the base flow speed is increased, and also under fuel lean and fuel rich conditions. These results suggest that the use of pulsed high frequency laser breakdowns for premixed combustion stabilization is optimized when laser pulse repetition rates below a certain frequency (e.g., 500 Hz at the conditions that ? is 1 and the base flow speed is 4.9 m/s) to maximize laser energy coupling and for improved anchoring of the flame base.     

Secluded maternity areas for parturient dairy cows offer protection from herd members

Use of individual maternity pens for dairy cows is recommended to ensure undisturbed calving and postpartum transfer of colostrum to calves, but management of these pens is a challenge due to difficulty predicting the time of calving. If group-housed cows, however, have the opportunity to calve in a secluded area of a group pen, this may limit disturbance of the dam and her newborn, especially if this area is fitted with a gate preventing other cows from entering. The aims of this study were to assess effects of cows calving inside a secluded area versus cows calving in the group area on maternal behavior and social interaction between dam and herd members during the first postpartum hour, calf's latency to stand, number of calves suckling an alien cow, and the dam's acute response to separation from the calf. This was investigated in pens consisting of a central group area with access to 6 secluded areas with or without a mechanical push gate allowing only 1 cow access at a time. At least 2 wk before expected calving, 60 Danish Holstein multiparous cows were assigned alternately, in groups of 6, to a group pen with 6 gated secluded areas or a group pen with 6 ungated secluded areas. The effects of treatment (gated, ungated) and calving place chosen within treatment (secluded area, group area) on maternal behavior, interactions with herd members, maternal response to separation, and calf latency to stand were investigated. Irrespective of whether cows calved in a secluded area or not and whether the secluded area was gated or not, cows spent, on average, 39 (±7.9) min of the first hour after calving licking their calves. When calving in a gated secluded area, the cows interacted less with herd members than when calving in the group area (0.5, 28, 18, and 33 min/h for gated/secluded, gated/group, ungated/secluded, and ungated/group areas, respectively), and no calves suckled an alien cow within the first hour after birth. In addition, the longer the calf stayed with the dam, the longer the dam stood with her head out of the pen after removal of the calf. Calf's latency to stand after calving was unaffected by treatment and calving place (mean = 39 min; range = 8–243 min). The results show that dam and calf can be protected from disturbances when cows calve in a secluded maternity area, especially if the secluded maternity area is fitted with a gate preventing other cows form entering.     

Oxidation of P92 steel weldment between 600 and 800 °C in air

P92 alloy with a composition of Fe-9.1Cr-0.5Mo-1.7W (wt.%) was welded, and its oxidation behavior was studied at 600, 700 and 800 °C for up to 6 months in air. The oxidation resistance decreased in the order of the base metal, weld metal, and the heat affected zone. The morphology and the composition of the scales formed on these samples were similar. The scales were either uniform in thickness or nodular. The scales consisted mainly of Fe₂O₃. As oxidation progressed, thick, nodular oxide scales formed. The alloying elements such as Cr, W, and Mn tended to incorporate in the lower part of the oxide scale.