Evidence of the Monopolar-Dipolar Crossover Regime: A Multiscale Study of Ferroelastic Domains by In Situ Microscopy Techniques.

The elastic interaction between kinks (and antikinks) within domain walls plays a pivotal role in shaping the domain structure, and their dynamics. In bulk materials, kinks interact as elastic monopoles, dependent on the distance between walls (d-1) and typically characterized by a rigid and straight domain configuration. In this work the evolution of the domain structure is investigated, as the sample size decreases, by the means of in situ heating microscopy techniques on free-standing samples. As the sample size decreases, a significant transformation is observed: domain walls exhibit pronounced curvature, accompanied by an increase in both domain wall and junction density. This transformation is attributed to the pronounced influence of kinks, inducing sample warping, where "dipole-dipole" interactions are dominant (d-2). Moreover, a critical thickness range that delineates a crossover between the monopolar and dipolar regimens is experimentally identified and corroborated by atomic simulations. These findings are relevant for in situ TEM studies and for the development of novel devices based on free-standing ferroic thin films and nanomaterials.

The Effect of Chemical Environment and Temperature on the Domain Structure of Free-Standing BaTiO3 via In Situ STEM.

Ferroelectrics, due to their polar nature and reversible switching, can be used to dynamically control surface chemistry for catalysis, chemical switching, and other applications such as water splitting. However, this is a complex phenomenon where ferroelectric domain orientation and switching are intimately linked to surface charges. In this work, the temperature-induced domain behavior of ferroelectric-ferroelastic domains in free-standing BaTiO3 films under different gas environments, including vacuum and oxygen-rich, is studied by in situ scanning transmission electron microscopy (STEM). An automated pathway to statistically disentangle and detect domain structure transformations using deep autoencoders, providing a pathway towards real-time analysis is also established. These results show a clear difference in the temperature at which phase transition occurs and the domain behavior between various environments, with a peculiar domain reconfiguration at low temperatures, from a-c to a-a at ≈60 °C. The vacuum environment exhibits a rich domain structure, while under the oxidizing environment, the domain structure is largely suppressed. The direct visualization provided by in situ gas and heating STEM allows to investigate the influence of external variables such as gas, pressure, and temperature, on oxide surfaces in a dynamic manner, providing invaluable insights into the intricate surface-screening mechanisms in ferroelectrics.

Avalanche criticality in LaAlO[Formula: see text] and the effect of aspect ratio.

Ferroic domain dynamics, as a function of external stimuli, can be collectively described as scale-invariant avalanches characterised by a critical exponent that are sensitive to the complexity of the domain microstructure. The understanding and manipulation of these avalanches lies at the heart of developing novel applications such as neuromorphic computing. Here we combine in situ heating optical observations and mean-field analysis to investigate the collective domain behaviour in pure-ferroelastic lanthanum aluminate (LaAlO[Formula: see text]) as a function of aspect ratio, the ratio of sample length to width, where the movement of the domains is predominantly driven by thermal stresses via thermal expansion/contraction during heat cycling. Our observations demonstrate that the aspect ratio induces (1) distinctive domain microstructures at room temperature, (2) a deviation of dynamical behaviour at high temperatures and (3) critical exponent mixing in the higher aspect ratio samples that accompanies this behaviour. While the critical exponents of each aspect ratio fall within mean-field predicted values, we highlight the effect that the aspect ratio has in inducing exponent mixing. Hence, furthering our understanding towards tuning and controlling avalanches which is crucial for fundamental and applied research.

The "Standing Cone" Flap for Thumb: A Spinoff the Hypogastric Flap in Combined Defects of Dorsum of Hand and Thumb.

Background: The management of combined defects of the dorsum of the hand and the thumb can be quite challenging. The conventional teaching has been to use more than 1 flap for such discontinuous defects of the hand. Methods: We present a novel technique to provide a reliable skin cover to a concomitant second defect over thumb, which otherwise would require an additional flap, by recruiting the excess skin available after closure of the primary flap donor site of the hypogastric flap being used for the defect on the dorsum of hand. We report a case series of 5 patients wherein this technique has been used successfully. Results: The modified technique was able to successfully manage the concomitant defects of the dorsum of hand and the thumb in 1 stage. Conclusions: We find this innovation can help cover 2 separate defects on dorsum of hand and the thumb in 1 stage by utilizing just 1 flap instead of the conventional method of raising 2 flaps for such defects.

Simulation of the upper urinary system.

The ureter and its peristalsis motions have long been of significant interest in biomechanics. In this article we review experimental, theoretical, and numerical studies of the behavior of the ureter together with its mechanical properties, emphasizing studies that contain information of importance in building a virtual simulation tool of the complete ureter that includes its complex geometry, nonlinear material properties, and interaction with urine flow. A new technique to model the contraction of a ureter, which directly applies wall forces to model pacemaker activities, is presented. The required further steps to capture the full complex movement of the peristalsis are discussed, aiming to construct a computational platform that will provide a reliable tool to assist in the investigation and design of material devices (stents) for the renal system.

Swine production impact on residential ambient air quality.

Numerous residents in agricultural areas are concerned about the impact that the swine industry may have on the ambient air quality. They assume there is a risk because there is limited information on the airborne contaminant that may originate from these facilities. The objective of the project was to assess the impact of swine production on ambient air quality related to public health in farming communities. Of the six chosen communities, three were considered not to be in a swine production area, whereas the three others were considered to be within a swine production area. Data were collected during three periods in spring and summer 2006. Ammonia and hydrogen sulfide concentrations were monitored on a continuous basis whereas odor concentrations and intensities were monitored twice a week. Odor concentrations were measured by dynamic olfactometry and odor intensities were determined by trained odor assessors. Public health was evaluated by survey questionnaires sent to a sample of residents in each of the six communities. Average NH(3) concentrations ranged from 6.9 to 12.6 ppb for nonexposed communities and from 8.9 to 18.3 ppb for exposed communities. Average H(2)S concentrations ranged from 1.1 to 1.5 ppb for nonexposed communities and from 1.1 to 1.6 ppb for exposed communities. For a community in a swine production area, ambient NH(3) and H(2)S concentrations were found to be higher than those communities not in a swine production area; however, that difference was not significant and they were within air quality standards for public health and safety. Odor concentrations showed no significant difference between the nonexposed and exposed communities and between evening and morning periods. Odor intensities were found to be significantly higher in the communities within swine production areas. More research will be required to fully understand the correlation between specific physical symptoms from residents and the presence of odors from swine production.

Development of an integrated sensor to measure odors.

Odorous air samples collected from several sources were presented to an olfactometer, an electronic nose, a hydrogen sulfide (H(2)S) detector and an ammonia (NH(3)) detector. The olfactometry measurements were used as the expected values while measurements from the other instrumentation values became input variables. Five hypotheses were established to relate the input variables and the expected values. Both linear regression and artificial neural network analyses were used to test the hypotheses. Principal component analysis was utilized to reduce the dimensionality of the electronic nose measurements from 33 to 3 without significant loss of information. The electronic nose or the H(2)S detector can individually predict odor concentration measurements with similar accuracy (R(2) = 0.46 and 0.50, respectively). Although the NH(3) detector alone has a very poor relationship with odor concentration measurements, combining the H(2)S and NH(3) detectors can predict odor concentrations more accurately (R(2) = 0.58) than either individual instrument. Data from the integration of the electronic nose, H(2)S, and NH(3) detectors produce the best prediction of odor concentrations (R(2) = 0.75). With this accuracy, odor concentration measurements can be confidently represented by integrating an electronic nose, and H(2)S and NH(3) detectors.

[Variation in the structure of the periphytic community that colonizes artificial substrata in the Medellín river (Colombia)]. / Variación estructural de la comunidad perifítica colonizadora de sustratos artificiales en la zona de ritral del río Medellín, Colombia.

Weekly samples were taken from microscope glass slides attached to acrylic substrata were placed at subsuperficial level in two sampling stations in the higher section of the Medellin river, Colombia, from January through March 1998. Diversity and evenness varied with time (Friedman p<0.05). There were spatial differences in biomass, productivity, diversity and evenness (Friedman p<0.05). Total biomass and productivity increased with the time of colonization at station 1. Station 2, with four times more water flow, had lower diversity and mean evenness values. During the colonization process the were 76 species (22 families). The Chrysophyta, mainly diatoms, were the most abundant (56% of the total), followed by Clorophyta (29%), Cyanophyta (11%) and Cryptophyta (4%).

Preliminary investigation of air bubbling and dietary sulfur reduction to mitigate hydrogen sulfide and odor from swine waste.

When livestock manure slurry is agitated, the sudden release of hydrogen sulfide (H(2)S) can raise concentrations to dangerous levels. Low-level air bubbling and dietary S reduction were evaluated as methods for reducing peak H(2)S emissions from swine (Sus scrofa) manure slurry samples. In a first experiment, 15-L slurry samples were stored in bench-scale digesters and continuously bubbled with air at 0 (control), 5, or 10 mL min(-1) for 28 d. The 5-L headspace of each digester was also continuously ventilated at 40 mL min(-1) and the mean H(2)S concentration in the outlet air was <10 microL L(-1). On Day 28, the slurry was agitated suddenly. The peak H(2)S concentration exceeded instrument range (>120 microL L(-1)) from the control treatment, and was 47 and 3.4 microL L(-1) for the 5 and 10 mL min(-1) treatments, respectively. In a second experiment, individually penned barrows were fed rations with dietary S concentrations of 0.34, 0.24, and 0.15% (w/w). Slurry derived from each diet was bubbled with air in bench-scale digesters, as before, at 10 mL min(-1) for 12 d and the mean H(2)S concentration in the digester outlet air was 11 microL L(-1). On Day 12, the slurry was agitated but the H(2)S emissions did not change significantly. Both low-level bubbling of air through slurry and dietary S reduction appear to be viable methods for reducing peak H(2)S emissions from swine manure slurry at a bench scale, but these approaches must be validated at larger scales.

Respiratory symptoms and lung function in poultry confinement workers in Western Canada.

OBJECTIVE: To determine whether poultry production methods impact respiratory health, and whether poultry farmers have more respiratory symptoms and lower lung function than comparison control groups. DESIGN: Cross-sectional study. SETTING: Provinces of Saskatchewan, Alberta and Manitoba during the winters of 1997 to 1999. POPULATION: Three hundred three poultry workers, 241 grain farmers and 206 nonfarming control subjects were studied. Poultry workers were further classified according to the poultry housing type in which they worked, ie, workers who worked with poultry raised on the floor (floor-based operations), which included broiler/roaster, broiler/breeder and turkey operations (n=181), and workers who worked with poultry raised in a caged setting (cage-based operations), which included egg operations (n=122). INTERVENTIONS: Subjects completed a respiratory health questionnaire, which included questions on the poultry operation and work habits, and participated in lung function testing. MAIN RESULTS: Overall, this study indicated that poultry workers report greater prevalences of current and chronic respiratory symptoms than control populations, and that the type of production method (cage-based versus floor-based) appears to influence the prevalence of respiratory symptoms and lung function values. Workers from cage-based operations report greater prevalences of current cough and wheeze, as well as lower mean values for forced expiratory volume in the first second (FEV1), forced expiratory flow at 25% to 75% of vital capacity (FEF25-75) and FEV1/FVC than workers from floor-based facilities. Workers from cage-based facilities also reported greater prevalences of current and chronic cough and phlegm, as well as significantly lower FEF25-75 and FEV1/FVC values than nonfarming control subjects. Furthermore, grain farmers had lower FVC and FEV1 values than nonfarmers. CONCLUSIONS: The results suggest that the type of poultry production system (ie, floor- versus cage-based) appears to have an effect on the respiratory response of workers from these facilities. Further studies are required to understand the physiological mechanisms of respiratory dysfunction and the relationships concerning workplace exposure among poultry workers.