Microstructure-mechanical-tribological property correlation of multistage spark plasma sintered tetragonal ZrO2

We report here the development of dense yttria-stabilized t-ZrO₂ ceramics with more uniform and finer grain sizes and concomitantly better mechanical and tribological properties via multistage spark plasma sintering (SPS). The dense tetragonal ZrO₂ ceramics were obtained by adopting three different SPS heating cycles, designed on the basis of fundamental sintering theory. The suppression of grain growth to nanosize regime (～100–150 nm), along with the development of more uniform grain size distribution was achieved with multistage sintering (MSS), as compared to normal single stage sintering (SSS). Finer microstructural scale, along with superior hardness also led to improved fretting wear resistance for the ZrO₂ samples processed via MSS. Based on the experimental results and analysis, a correlation has been established between the SPS processing schemes, microstructural development and mechanical as well as tribological properties of the tetragonal ZrO₂. The effectiveness of MSS to produce tetragonal ZrO₂ ceramics with better mechanical and tribological properties was confirmed at two different levels of yttria content (3 and 2 mol%).     

Estimate of solid flow rate from pressure measurement in circulating fluidized bed

A method is described to estimate solid mass flow rate based on measurement of pressure drop in horizontal section of circulating fluid bed (CFB). A theoretical model was derived based on momentum balance equation and used to predict the solids flow rate. Several approaches for formulating such models are compared and contrasted. A correlation was developed that predicts the solids flow rate as a function of pressure drop measured in the horizontal section of piping leading from the top of the riser to the cyclone, often referred to as the cross-over. Model validation data was taken from literature data and from steady state, cold flow, CFB tests results of five granular materials with various sizes and densities in which the riser was operated in core-annular and dilute flow regimes. Experimental data were taken from a 0.20 m ID cross-over piping and compared to literature data generated in a 0.10 m ID cross-over pipe. The solids mass flow rate data were taken from statistically designed experiments over a wide range of Froude number , load ratio , Euler number , density ratio , Reynolds number , and Archimedes number . Several correlations were developed and tested to predict the solids mass flux based on measuring pressure drop in the horizontal section of CFB. It was found that load ratio is a linear function of the Euler number and that each of these expressions all worked quite well (R² > 95%) for the data within the range of conditions from which the coefficients were estimated.     

Electrochemical Determination of the Activity of Na2O in the Pyrochlore Phase of the Sb2O4-NaSbO3 System

Activity of Na₂O in the pyrochlore phase of the system Sb₂O₄-NaSbO₃ has been measured as a function of temperature in the range 1073–1412 K by electromotive force (emf) measurements of the following solid-state electrochemical cells:
The solid electrolyte used in the above electrochemical cells is Na-ß-Al₂O₃, which is an excellent sodium-ion conductor in the temperature range of the measurements. From the measured reversible emf, the activity of Na₂O in the Sb₂O₄-NaSbO₃ system has been calculated. The temperature dependence of the logarithm of the activity of Na₂O in various two-phase regions of the Sb₂O₄-NaSbO₃ system can be represented as
No thermodynamic data have been reported earlier in the literature for the system Sb₂O₄-NaSbO₃, and the present data constitute the first thermodynamic information.     

An electrochemical study on deformed galvanneal steel sheets

Corrosion behavior of deformed galvanneal steel sheets has been evaluated as a function of their degree of deformation under four different strain paths namely, biaxial, uniaxial (drawing), plane strain and tensile mode. A correlation between the degree of deformation and the loss in the extent of corrosion protection offered by these coatings in 3.5 wt.% NaCl solution has been established by carrying out electrochemical studies such as potentiodynamic polarization and electrochemical impedance spectroscopy. An almost linear relation has been found to exist between the effective strain applied to the specimen and damage caused to the coating. While uniaxial, plane strain and tensile modes of deformation have been found to affect the coating corrosion resistance almost to the same extent, the biaxial deformation has been found to cause a greater damage to the coating.     

Hydrogen Sulfide and Substance P Levels in Patients with Escherichia coli and Klebsiella pneumoniae Bacteraemia

Hydrogen sulfide (H₂S) and substance P (SP) are known from animal models and in vitro studies as proinflammatory mediators. In this study, peripheral blood concentrations of H₂S and SP were measured in patients with Escherichia coli or Klebsiella pneumoniae bacteraemia. Fifty patients were recruited from general wards at Christchurch Hospital, during 2020–2021. Samples from age- and sex-matched healthy subjects previously recruited as controls for studies of cardiovascular disease were used as controls. The concentrations of H₂S were higher than controls on day 0, day 1, and day 2, and SP was higher than controls on all 4 days. The concentrations of H₂S were highest on day 0, whereas SP concentrations were higher on day 2 than other days. Interleukin-6 and C-reactive protein were significantly higher on day 0 and day 1, respectively. The concentrations of H₂S and SP did not differ between 15 non-septic (SIRS 0-1) and the 35 septic subjects (SIRS ≥ 2). Substance P concentrations were higher in subjects with abdominal infection than urinary tract infections on day 0 (p = 0.0002) and day 1 (p = 0.0091). In conclusion, the peak H₂S concentrations precede the SP peak in patients with Gram-negative bacteraemia, but this response varies with the site of infection.     

A comparison of multiple behavior models in a simulation of the aftermath of an improvised nuclear detonation

We describe a large-scale simulation of the aftermath of a hypothetical 10kT improvised nuclear detonation at ground level, near the White House in Washington DC. We take a synthetic information approach, where multiple data sets are combined to construct a synthesized representation of the population of the region with accurate demographics, as well as four infrastructures: transportation, healthcare, communication, and power. In this article, we focus on the model of agents and their behavior, which is represented using the options framework. Six different behavioral options are modeled: household reconstitution, evacuation, healthcare-seeking, worry, shelter-seeking, and aiding & assisting others. Agent decision-making takes into account their health status, information about family members, information about the event, and their local environment. We combine these behavioral options into five different behavior models of increasing complexity and do a number of simulations to compare the models.     

Towards Quantification of Functional Breast Images Using Dedicated SPECT With Non-Traditional Acquisition Trajectories

Quantification of radiotracer uptake in breast lesions can provide valuable information to physicians in deciding patient care or determining treatment efficacy. Physical processes (e.g., scatter, attenuation), detector/collimator characteristics, sampling and acquisition trajectories, and reconstruction artifacts contribute to an incorrect measurement of absolute tracer activity and distribution. For these experiments, a cylinder with three syringes of varying radioactivity concentration, and a fillable 800 mL breast with two lesion phantoms containing aqueous (99m)Tc pertechnetate were imaged using the SPECT sub-system of the dual-modality SPECT-CT dedicated breast scanner. SPECT images were collected using a compact CZT camera with various 3D acquisitions including vertical axis of rotation, 30° tilted, and complex sinusoidal trajectories. Different energy windows around the photopeak were quantitatively compared, along with appropriate scatter energy windows, to determine the best quantification accuracy after attenuation and dual-window scatter correction. Measured activity concentrations in the reconstructed images for syringes with greater than 10 μCi /mL corresponded to within 10% of the actual dose calibrator measured activity concentration for ±4% and ±8% photopeak energy windows. The same energy windows yielded lesion quantification results within 10% in the breast phantom as well. Results for the more complete complex sinsusoidal trajectory are similar to the simple vertical axis acquisition, and additionally allows both anterior chest wall sampling, no image distortion, and reasonably accurate quantification.