Morphology and thermal conductivity of model organic aerogels

The intersection volume of two independent 2-level cut Gaussian random fields is proposed to model the open-cell microstructure of organic aerogels. The experimentally measured X-ray scattering intensity, surface area and solid thermal conductivity of both polymeric and colloidal organic aerogels can be accounted for by the model.Comment: 5 pages. RevTex with 4 encapsulated figures. Higher resolution figures have been submitted for publication. To be published in Phys. Rev. E (Rapid Comm.). email, [email protected]

Determining fPAR and leaf area index of several land cover classes in the Pot River and Tsitsa River catchments of the Eastern Cape, South Africa

Determining the quantum (both annual maxima and minima) and the temporal variation in the leaf area index (LAI), and the fraction of photosynthetically active radiation (fPAR), are three fundamental biophysical characteristics of the plant canopy that should parameterise ecophysiological models of water use (evapotranspiration) and carbon sequestration. Although Earth observation provides values and time series for both these parameters, in-field validation of these values is necessary. Following a very wet summer season, we conducted field surveys of several land cover classes within two quaternary catchments in the Eastern Cape province, South Africa, to determine maximum values of LAI and fPAR that occur within each of these land cover classes. To assist in up-scaling these point measures to the landscape, we present a regression relationship between Landsat 8 NDVI and LAI measured using an Accupar Ceptometer (r2 = 0.92). Peak wet season LAI varied from extremely high (>7.0) under the canopy of invasive black wattle (Acacia mearnsii) trees to ~2.0 under the canopy of a Eucalyptus plantation. Ungrazed native grassland displayed an intermediate LAI value of 3.84. The black wattle stand absorbed 97% of the available PAR, whereas the mature Eucalyptus plantation only absorbed 66% of PAR.Keywords: agroforestry, ecosystem ecology, remote sensin

Exploring the invasion of rangelands by Acacia mearnsii (black wattle): biophysical characteristics and management implications

Australian acacias have spread to many parts of the world. In South Africa, species such as A. mearnsii and A. dealbata are invasive. Consequently, more effort has focused on their clearing. In a context of increasing clearing costs, it is crucial to develop innovative ways of managing invasions. Our aim was to understand the biophysical properties of A. mearnsii in grasslands as they relate to grass production and to explore management implications. Aboveground biomass (AGB) of A. mearnsii was determined using a published allometric equation in invaded grasslands of the northern Eastern Cape, South Africa. The relationships among the A. mearnsii leaf area index (LAI), normalised difference vegetation index (NDVI) and AGB were investigated. The influence of A. mearnsii LAI and terrain slope on grass cover was also investigated. Strong linear relationships between NDVI, LAI and AGB were developed. Acacia mearnsii canopy adversely impacted grass production more than terrain slope (p < 0.05) and when LAI approached 2.1, grass cover dropped to below 10% in infested areas. Reducing A. mearnsii canopy could promote grass production while encouraging carbon sequestration. Given the high AGB and clearing costs, it may be prudent to adopt the ‘novel ecosystems’ approach in managing infested landscapes.Keywords: grassland, invasive plants, landscape ecology, rangeland conditio

“Do you still trust me?” Effects of Personality on Changes in Trust during an Experimental Task with a Human or Robot Partner

In the current study, we investigated the effects of dispositional variables on self-reported trust and suspicion perceptions of one’s partner in a maze-running task. Dispositional variables affect the extent to which people perceive and encode information in their environment. Prior research has shown that dispositional variables interact with situational variables in expressing behaviors. In order to test the effects of three dispositional variables (i.e., dispositional trust, dispositional distrust, and dispositional suspicion) on self-reported trust and suspicion perceptions towards a partner (a human or a Nao robot), we ran two discontinuous growth models. Overall, we found that participants’ trust towards their partner decreased when the partner engaged in untrustworthy behaviors as expected. In addition, changes in trust perceptions towards the partner were predicted by participants’ level of dispositional trust. These results have implications for studying the effects of dispositional variables on context-dependent trust perceptions within the trust process

Could you please pay attention?’ Comparing in-person and MTurk Responses on a Computer Code Review Task

The current study examined the differences in data quality across two environments (i.e., in a laboratory and online via Amazon’s Mechanical Turk) on a computer code review task. Researchers and practitioners often collect data online for the sake of convenience, as well as for obtaining a more generalizable sample of participants. The lack of social contact between the researchers and participants, however, may result in less effort dedicated to the experimental task resulting in poor quality data. The results of the current study showed that data quality—at least when measuring the individual difference variables—was drastically worsened when the experimental task was presented online. In contrast, we observed little differences in the experimental task perceptions across the two samples. Rather, participants spent significantly less time examining the computer code when completing the experiment online. The current study has implications for the effects of using online platforms (like MTurk) to collect experimental data

Effects of Acoustic Coupling Layer Electrical Conducitivity on Pulsed Electroacoustic Measurements

The spatial resolution of Pulsed Electroacoustic (PEA) measurements can be limited by the acoustic thickness of the coupling material coupling the sample to the detector assembly. Our investigations studied the effect of adhesive material and thickness to optimize the quality of the PEA signal

Investigating the Effect of Trust Manipulations on Affect over Time in Human-Human versus Human-Robot Interactions

The current study explored the influence of trust and distrust behaviors on affect over time. We examined the differences in affect when participants (N=97) were paired with a human or a robot while playing amodified version of the investorgame. Results indicated that there were no differences in affect between partner types when the partner performed a trustful behavior. When the partner performed a distrustful behavior, positive affect was higher for human partners than for robot partners. When robot partners performed a distrustful behavior, negative affect had a steeper incline compared to human partners. These findings suggest that people are more sensitive to distrust behaviors that are performed by a robot over a human