Dynamics of Micropollutant Adsorption to Polystyrene Surfaces Probed by Angle-Resolved Second Harmonic Scattering

Angle-resolved second harmonic scattering is used to probe the adsorption dynamics of aqueous cationic and anionic dye molecules onto polystyrene surfaces. The adsorptions of malachite green to negatively charged polystyrene and naphthol yellow S to positively charged polystyrene are both highly favorable, with Î"GAds values of -10.9 ± 0.2 and -10.27 ± 0.09 kcal/mol, respectively. A competitive displacement methodology was employed to obtain values for the adsorption free energies of various smaller neutral organic molecules, including the important micropollutant ascorbic acid, caffeine, and pentoxifylline. For charged adsorbers, electrostatic interactions appear to significantly contribute to adsorption behavior. However, electrostatic repulsion does not necessarily deter the adsorption of molecules with large uncharged moieties (e.g., surfactants). In these cases, the mechanism of adsorption is dominated by van der Waals interactions, with the surface charge playing a relatively minor role

Carbon cycling in a tidal freshwater marsh ecosystem: a carbon gas flux study

A process-based carbon gas flux model was developed to calculate total macrophyte and microalgal production, and community and belowground respiration, for a Peltandra virginica dominated tidal freshwater marsh in Virginia. The model was based on measured field fluxes of CO2 and CH,, scaled to monthly and annual rates using empirically derived photosynthesis versus irradiance, and respiration versus temperature relationships. Because the gas exchange technique measures whole system gas fluxes and therefore includes turnover and seasonal translocation, estimates of total macrophyte production will be more accurate than those calculated from biomass harvests. One Limitation of the gas flux method is that gaseous carbon fluxes out of the sediment may underestimate true belowground respiration if sediment-produced gases are transported through plant tissues to the atmosphere. Therefore we measured gross nitrogen mineralization (converted to carbon units using sediment C/N ratios and estimates of bacterial growth efficiency) as a proxy for belowground carbon respiration. We estimated a total net macrophyte production of 536 to 715 g C m(-2) yr(-1), with an additional 59 g C m(-2) yr(-1) fixed by sediment microalgae. Belowground respiration calculated from nitrogen mineralization was estimated to range from 516 to 323 g C m(-2) yr(-1) versus 75 g C m(-2) yr(-1) measured directly with sediment chambers. Methane flux (72 g C m(-2) yr(-1)) accounted for 11 to 13 % of total belowground respiration. Gas flux results were combined with biomass harvest and Literature data to create a conceptual mass balance model of macrophyte-influenced carbon cycling. Spring and autumn translocation and re-translocation are critical in controlling observed seasonal patterns of above and belowground biomass accumulation. Annually, a total of 270 to 477 g C m(-2) of macrophyte tissue is available for deposition on the marsh surface as detritus or export from the marsh as particulate or dissolved carbon

Dynamic variation of supernatant quality in a dairy shed waste stabilisation pond system

An intensive monitoring program of a standard two-stage dairy shed waste stabilisation pond system was undertaken to determine the incidence and extent of spatial and temporal variation of basic physio-chemical parameters, and to shed light on the longer term dynamic nature of in-pond conditions. The anaerobicâfacultative pond system, located in a remote rural area, treats wastewater from the hosing down and hydraulic flushing of the milking parlour and holding yard at the farm dairy shed. A number of multi-parameter water quality field monitoring probes were permanently deployed at various locations within the two ponds to enable continuous measurement of temperature, pH, conductivity and dissolved oxygen. In addition, profiling of the supernatant of both ponds was undertaken at different times of the year to examine vertical variation of the same parameters. Continuous monitoring revealed spatial homogeneity in EC and pH levels in the upper metre of both ponds. Physio-chemical parameters also appear to change uniformly across the ponds in response to external stimuli such as rainfall. Neither pond, however, exhibits homogeneity down the profile of the supernatant. Seasonal stratification is prevalent in the facultative pond suggesting poor vertical mixing, while the anaerobic pond is notably affected by sludge accumulation. A long-term pattern of rising conductivity in both ponds indicated accumulation of dissolved salt species in the system due to recirculation of reclaimed effluent for hydraulic flushing of the dairy shed. In the facultative pond, diurnal fluctuations in dissolved oxygen, oxidation-reduction potential and turbidity during warmer months of the year closely followed temperature swings. The extensive data collected in this study provides a detailed picture of the physio-chemical dynamics of two-stage stabilisation pond systems treating dairy shed wastewater

Comparison of different solar-assisted air conditioning systems for Australian office buildings

© 2017 by the authors. This study has investigated the feasibility of three different solar-assisted air conditioning systems for typical medium-sized office buildings in all eight Australian capital cities using the whole building energy simulation software EnergyPlus. The studied solar cooling systems include: solar desiccant-evaporative cooling (SDEC) system, hybrid solar desiccant-compression cooling (SDCC) system, and solar absorption cooling (SAC) system. A referenced conventional vapor compression variable-air-volume (VAV) system has also been investigated for comparison purpose. The technical, environmental, and economic performances of each solar cooling system have been evaluated in terms of solar fraction (SF), system coefficient of performance (COP), annual HVAC (heating, ventilation, and air conditioning) electricity consumption, annual CO2 emissions reduction, payback period (PBP), and net present value (NPV). The results demonstrate that the SDEC system consumes the least energy in Brisbane and Darwin, achieving 56.9% and 82.1% annual energy savings, respectively, compared to the conventional VAV system, while for the other six cities, the SAC system is the most energy efficient. However, from both energy and economic aspects, the SDEC system is more feasible in Adelaide, Brisbane, Darwin, Melbourne, Perth, and Sydney because of high annual SF and COP, low yearly energy consumption, short PBP and positive NPV, while for Canberra and Hobart, although the SAC system achieves considerable energy savings, it is not economically beneficial due to high initial cost. Therefore, the SDEC system is the most economically beneficial for most of Australian cities, especially in hot and humid climates. The SAC system is also energy efficient, but is not as economic as the SDEC system. However, for Canberra and Hobart, reducing initial cost is the key point to achieve economic feasibility of solar cooling applications

Parametric analysis of design parameter effects on the performance of a solar desiccant evaporative cooling system in brisbane, Australia

© 2017 by the authors. Solar desiccant cooling is widely considered as an attractive replacement for conventional vapor compression air conditioning systems because of its environmental friendliness and energy efficiency advantages. The system performance of solar desiccant cooling strongly depends on the input parameters associated with the system components, such as the solar collector, storage tank and backup heater, etc. In order to understand the implications of different design parameters on the system performance, this study has conducted a parametric analysis on the solar collector area, storage tank volume, and backup heater capacity of a solid solar desiccant cooling system for an office building in Brisbane, Australia climate. In addition, a parametric analysis on the outdoor air humidity ratio control set-point which triggers the operation of the desiccant wheel has also been investigated. The simulation results have shown that either increasing the storage tank volume or increasing solar collector area would result in both increased solar fraction (SF) and system coefficient of performance (COP), while at the same time reduce the backup heater energy consumption. However, the storage tank volume is more sensitive to the system performance than the collector area. From the economic aspect, a storage capacity of 30 m3/576 m2 has the lowest life cycle cost (LCC) of 405,954 for the solar subsystem. In addition, 100 kW backup heater capacity is preferable for the satisfaction of the design regeneration heating coil hot water inlet temperature set-point with relatively low backup heater energy consumption. Moreover, an outdoor air humidity ratio control set-point of 0.008 kgWater/kgDryAir is more reasonable, as it could both guarantee the indoor design conditions and achieve low backup heater energy consumption

Physical and hydrodynamic characteristics of a dairy shed waste stabilisation pond system

Waste stabilization pond systems are widely used to treat animal wastes under highly variable hydraulic loading regimes. These systems have received limited research attention with regard to their hydrodynamic behaviour and the potential impact of shock hydraulic loading on their performance. In this study a two-stage dairy shed waste stabilisation pond system was topographically surveyed to determine the physical shape and the theoretical hydraulic retention time (HRT) of each pond, as well as the extent of sludge accumulation in the primary pond. The primary pond was then subjected to a series of drogue tracking runs whereby weighted floating survey targets with submerged âsailsâ were tracked during their movement through the pond at times of peak flow in order to characterise the hydrodynamic behaviour of the pond. The full capacity volumes of the primary and secondary ponds were calculated to be 1285m3 and 2391m3, respectively. Sludge had been accumulating in the primary pond at a rate of 0.73m3/d over a period of 2.4 years and this has reduced the active treatment volume of the pond to 657m3. Based on mean outflow, the HRTs of the ponds were 40 d and 137 d, respectively. The drogue runs revealed a vortexlike mixing pattern within the pond with higher velocities around the perimeter of the pond between the inlet and outlet, and lower velocities in the centre of the pond. In-pond velocities seemed relatively high in comparison with those from other drogue studies of larger ponds and the surging inflow caused the formation of a flow âjetâ that potentially contributed to significant short-circuiting. The range of influence of this flow jet, however, was limited to within 15m of the inlet, suggesting that short-circuiting would be likely to occur only under certain high inflow conditions

Neuromuscular Function of the Knee Joint Following Knee Injuries: Does It Ever Get Back to Normal? A Systematic Review with Meta-Analyses.

BACKGROUND: Neuromuscular deficits are common following knee injuries and may contribute to early-onset post-traumatic osteoarthritis, likely mediated through quadriceps dysfunction. OBJECTIVE: To identify how peri-articular neuromuscular function changes over time after knee injury and surgery. DESIGN: Systematic review with meta-analyses. DATA SOURCES: PubMed, Web of Science, Embase, Scopus, CENTRAL (Trials). ELIGIBILITY CRITERIA FOR SELECTING STUDIES: Moderate and high-quality studies comparing neuromuscular function of muscles crossing the knee joint between a knee-injured population (ligamentous, meniscal, osteochondral lesions) and healthy controls. Outcomes included normalized isokinetic strength, muscle size, voluntary activation, cortical and spinal-reflex excitability, and other torque related outcomes. RESULTS: A total of 46 studies of anterior cruciate ligament (ACL) and five of meniscal injury were included. For ACL injury, strength and voluntary activation deficits were evident (moderate to strong evidence). Cortical excitability was not affected at < 6 months (moderate evidence) but decreased at 24+ months (moderate evidence). Spinal-reflex excitability did not change at < 6 months (moderate evidence) but increased at 24+ months (strong evidence). We also found deficits in torque variability, rate of torque development, and electromechanical delay (very limited to moderate evidence). For meniscus injury, strength deficits were evident only in the short-term. No studies reported gastrocnemius, soleus or popliteus muscle outcomes for either injury. No studies were found for other ligamentous or chondral injuries. CONCLUSIONS: Neuromuscular deficits persist for years post-injury/surgery, though the majority of evidence is from ACL injured populations. Muscle strength deficits are accompanied by neural alterations and changes in control and timing of muscle force, but more studies are needed to fill the evidence gaps we have identified. Better characterisation and therapeutic strategies addressing these deficits could improve rehabilitation outcomes, and potentially prevent PTOA. TRIAL REGISTRATION NUMBER: PROSPERO CRD42019141850

Assessing Cognitive Processing and Human Factors Challenges in NextGen Air Traffic Control Tower Team Operations

Previous research of Terminal Radar Control Facilities and Standard Terminal Automation Replacement Systems interactions by the authors examined how combined NextGen digitized technology affects air traffic controller functions. Applying their updated SHELL model, human factors implications on the Tower Team before and after implementing NextGen technology were examined, focusing on cognitive loading and automated functions affecting each team member. A survey examined where cognitive difficulties occur when controllers are responsible for multiple screen views, remote airfields or helipads, and digitized cameras and blind spots. Scanning challenges were identified where local traffic, ground operations, and data converge onto one screen, and when attention is diverted to distant screens. Also studied were automatic aircraft handoffs and potential for missed handoffs, and, assessing changes from voice communication to text messaging for human error. Findings indicated a necessity for controllers to manage balanced tasking, vigilance pacing, and resource management