Static Wettability of Differently Mechanically Treated and Amphiphobic-Coated Aluminium Surfaces

Wettability, roughness and surface treatment methods are essential for the majority of practical applications, where liquid–solid surface interactions take place. The present study experimentally investigated the influence of different mechanical surface treatment methods on the static wettability of uncoated and amphiphobic-coated aluminium alloy (AlMg3) samples, specially focusing on the interaction between surface finishing and coating. Five different surfaces were prepared: as-received substrate, polished, sandpapered, fleece-abraded and sandblasted. After characterisation, the samples were spray-coated using an amphiphobic coating. The characterisation of the uncoated and coated samples involved measurements of the roughness parameters and the apparent contact angles of demineralized water and rapeseed oil. The coating was initially characterised regarding its adhesion to the sample and elevated temperature stability. The applied surface treatments resulted in the scattered sample roughness in the range of Sa = 0.3–15.8 µm, water contact angles of θap,w = 78°–106° and extremely low oil contact angles. Coating the samples more than doubled the surface roughness to Sa = 13.3–29 µm, whereas the initial surface treatment properties (structure, anisotropy, etc.) were entirely repressed by the coating properties. Coating led the water contact angles to increase to θap,w_coated = 162°–173° and even more pronounced oil contact angles to increase to θap,o_coated = 139°–150°, classifying the surfaces as superhydrophobic and oleophobic

The role of wall deposition and re‐entrainment in swirl spray dryers

A new experimental method is outlined to study fouling in spray dryers and similar devices. In essence, it makes the deposits traceable so that one can quantify the material that comes off the walls, how long it remains there and how the deposits agglomerate with particles in the air. This paper investigates a countercurrent swirl spray dryer of detergent and provides sound evidence that fouling is a dynamic process: clusters form and break at the walls renewing an active layer of deposits. Remarkably, the wall generates >20% of the product and most of the large granules, and increases drastically the residence time of the powder. The assumptions of current numerical models are clearly invalid (i.e. particles rebound at the wall or deposit indefinitely). Several re-entrainment mechanisms and their times scales are identified in this work, and accordingly, a new general framework to describe fouling in spray dryers is proposed

Deposition and wear of deposits in swirl spray driers: The equilibrium exchange rate and the wall-borne residence time

Wall deposits are omnipresent in many particle technology operations, such as spray drying and granulation processes. Their impact has been long recognized and is typically considered detrimental to the process performance. Counter-current spray drying units, such as those used in the manufacture of detergents, make use of strong swirling flows which leads to substantial multi-layered deposits at the walls. However their relation to the rest of the process has never been studied in detail. The work presented here discusses the generation of the structure at the walls and how it interacts with the air-borne population of particles. A tracer experiment is outlined that permits one to track the release of material from the deposits and differentiate the origin of aggregates in the product, as being generated either by the atomization or through the erosion of deposits. Monitoring of the wall and analysis of the release rate of the tracer has permitted identification of a dynamic equilibrium between the rates of deposition and re-entrainment, and quantification of the exchange rate above 12-20% of the full production. The age of the re-entrained material, indicative of the time the granules remain resident at the wall, appears much higher than expected for an air-borne trajectory. Such observations suggests that the description of the spray drying process exclusively in terms of the air-borne condition of particles is incomplete, at least in relation to the manufacture of detergents in swirl assisted systems. Focus should be paid to the wall-borne condition of the product, for it is seen to govern the generation of large granule sizes and dominate the residence time and drying kinetics of a significant part of the product

Cardiovascular disease risk and central and peripheral responses to exercise in individuals with spinal cord injury

Introduction: Persons with spinal cord injury (SCI) are often physically inactive and as such are at increased risk of cardiovascular morbidity. Fortunately, exercise training in SCI can provide improve health-related physical fitness and alleviate medical complications associated with deconditioning. To optimize health-related fitness gains of exercise in SCI and maximize the potential for chronic disease prevention it is necessary to understand the acute responses (central and peripheral) to exercise. Purposes: The primary purposes of this research were to: 1) determine the contribution of central/peripheral limitations to exercise capacity and 2) examine vascular health in SCI. Methods: Seven persons with paraplegia and seven able-bodied (AB) individuals participated in two testing days. Testing day one consisted of incremental arm crank ergometry to exhaustion with measures of cardiac output, muscle oxygenation, and expired gas and ventilatory parameters. Testing day two involved the measurement of arterial compliance and endothelial function. Results: There was a significant difference for small artery compliance between SCI and AB(6.9±3.7 versus 10.5±1.7ml mmHg⁻¹x100, p< 0.05). Arm total haemoglobin increased significantly throughout exercise. Arm oxygenation decreased until 60% of maximal wattage after which values did not change. Though non-significant, the large effect size (eta²=.142) suggests a trend for higher aerobic power in AB (28.6±5.7mL.kg⁻¹min-1)than in SCI (23.7±2.77mL.kg⁻¹min⁻¹)due to a trend for higher cardiac output values in AB (18.0±5.7L.min⁻¹)than SCI (15.8±3.4L.min⁻¹)at maximal exercise. Conclusions: Small artery compliance is lower in SCI than AB. Leveling off of deoxygenated haemoglobin with total haemoglobin increasing throughout exercise suggests a peripheral limitation to arm ergometry in both groups. A trend for higher cardiac output in AB suggests a central limitation in SCI.Education, Faculty ofKinesiology, School ofGraduat

Physical activity during inpatient spinal cord injury rehabilitation

Introduction Rehabilitation activities of a sufficient intensity are necessary for optimal recovery in individuals with spinal cord injury (SCI). Optimizing rehabilitation and activity prescription requires quantification of physical activity and its predictors during this time. Purpose To determine, during inpatient rehabilitation, the: 1) reliability and validity of measures of physical activity. 2) level of physical activity using objective and self-report measures. 3) level of cardiovascular stress experienced during physical therapy (PT) and occupational therapy (OT). 4) variables associated with greater time spent at higher heart rate during PT. 5) number of active movement repetitions occurring during PT and OT. Methods Design: A test retest design was used to determine the reliability of physical activity measures. A longitudinal observation design was used to determine movement repetitions and physical activity levels. A cross-sectional observational design was used to determine the level of cardiovascular stress. Subjects: Participants (n=108) were recruited from consecutive admissions to rehabilitation. Results Good reliability for accelerometry and step counts, and moderate reliability for self-report, was demonstrated. Validity was demonstrated for wrist accelerometry and step counts but not self-report physical activity. For most groups and variables, no changes occurred during therapy time from admission to discharge. Outside of therapy all groups increased from admission to discharge in accelerometer measured activity kilocounts but not self-report minutes, where the majority of time was spent in leisure time sedentary activity (~4.5 hours). The average time spent at a heart rate within the cardiovascular training zone was 6.0±9.0 minutes in PT and lower in OT. Lower spasticity, higher exercise self-efficacy, and better orthostatic tolerance correlated with a greater amount of time within a cardiovascular training zone. Average repetitions for PT and OT combined did not exceed 300 for the upper or lower extremity. Most repetition variables remained unchanged over the inpatient rehabilitation stay while clinical outcomes improved significantly. Conclusions Individuals report that a large amount of time is spent engaged in higher intensity activities. Measurement of heart rate during therapy sessions shows little time is spent at intensities sufficient to accrue cardiovascular benefits. Repetitions in therapy are low compared to the motor learning literature.Medicine, Faculty ofGraduat