Utilizing Performance Records in Commercial Beef Herds.

4 p

Utilizing Performance Records in Commercial Beef Herds.

4 p

Understanding and Using Sire Summaries.

4 p

Understanding and Using Sire Summaries.

4 p

Wildlife and water: collective action and social capital of selected landowner associations in Texas

In Texas, landowner associations for the management of common-pool resources such as wildlife and groundwater have become increasingly popular. Successful management of white-tailed deer (Odocoileus virginianus) depends upon the collective decision-making of landowners. Likewise, aquifer reserves are a trans-boundary resource subject to the "rule of capture." Numerous factors may affect the success of common-pool associations, including property ownership and habitat characteristics, landowner demographics, and social capital. I used a mail questionnaire to explore the relationship between these factors and their effect on association activities and management practices for eight Wildlife Management Associations (WMAs) occurring within the Lower Post Oak Savannah (LPOS) and the Central Post Oak Savannah (CPOS). In addition, I compared responses of members of WMAs in CPOS to members of the Brazos Valley Water Alliance (BVWA), a groundwater association situated in the region. Compared to CPOS, members of WMAs within the LPOS belonged to much larger groups, were generally more recent landowners that met more often, raised more money using more funding methods, and tended to have longer association membership than CPOS landowners, yet they had lower social capital. CPOS landowners owned significantly more land and considered relaxation/leisure and hunting more important land uses than LPOS landowners. The smaller group size in CPOS may be the most important factor in building social capital. Intra-association trust was positively influenced by the longevity of property ownership, the number of association meetings, the percentage of males in the association, and other factors. Negative influences on trust included absentee ownership and Habitat Cover Index, which was a measure of the amount of wooded habitat present. In CPOS, members of the BVWA were part of a much larger, more heterogeneous, and more recently formed group than members of WMAs. They also placed greater importance on utilitarian aspects of their properties, as opposed to land stewardship for conservation as practiced by members of WMAs. If associations are kept small ( < 50) with more frequent meetings, greater social capital and information sharing may be achieved, which may lead to increased land stewardship practices. However, landowners may be motivated more by their shared values independent of any benefit from their association

The effect of remote sensing resolution limits on aeolian sandstone measurements and the reconstruction of ancient dune fields on Mars: Numerical experiment using the Page Sandstone, Earth

The distribution of cross‐set thicknesses is important data for reconstructing ancient aeolian dune fields from the strata they accumulated, but most aeolian strata on Mars must be observed from satellite. We hypothesize that remote sensing resolution limits will affect cross‐set thickness measurements and the dune‐field reconstructions that follow. Here we test this hypothesis using a numerical experiment mimicking the effects of satellite image resolution limits performed on a distribution of aeolian cross‐set thicknesses measured in the field from the Jurassic Page Sandstone, Arizona, USA. Page set thicknesses are exponentially distributed, representing the accumulations of dry dune fields (no water table interactions with the dunes) in a state of net‐sediment bypass. When observed from satellite, set‐thickness measurements increase as adjacent sets become indistinguishable, based on the map‐view distance between their upper and lower bounding surfaces. This is termed the exposure distance of a cross set and is a function of (1) the set thickness, (2) the dip of the outcrop surface, and (3) the number of satellite image pixels required to detect a set (detection limit). By running experiments using outcrop dips from 1° to 60° and detection limits from 0.75 to 2.50 m (3 to 10 High‐Resolution Imaging Science Experiment pixels), we find that gently sloping surfaces (< 13°) at all detection limits are associated with the least blending of adjacent sets, conserving the net‐bypass interpretation made from the true set thicknesses. Although these results are specific to the Page, they can be used as a guide for future Mars work

Electro-tactic ionic liquid droplets

Here we report for the first time electro-guided, self-propelled droplets, which are composed solely of an ionic liquid (IL), namely trihexyl(tetradecyl)phosphonium chloride ([P6,6,6,14][Cl]). These self-propelled droplets travel along an aqueous-air boundary and are guided to specific destinations within the fluidic network through the use of electro-chemically generated Cl- gradients. The direction of movement can be controlled by switching the impressed voltage (9V, ON or OFF) and polarity of the electrodes in contact with the electrolyte solution. Controlled release of surfactants has been investigated previously as a method of controlling surface tension in aqueous systems in order to achieve spontaneous movement of droplets at the air-liquid interface [1,2]. When a surfactant is released into an aqueous solution, the surface tension is lowered. Liquid flows from areas of low surface tension to areas of high surface tension, a phenomenon known as the Marangoni effect. Using stimuli-responsive surfactants, smart droplets have been designed which can solve complex mazes [1] or can be attracted or repelled by light [2], in a contactless manner. Electro-tactic movement of the droplets is due to the controlled release of the [P6,6,6,14]+, a very efficient cationic surfactant, which is a constituent of the IL droplet (Fig. 1). The asymmetric release of the cationic surfactant is controlled through modulation of the IL counter anion (Cl-) solubility, as this controls the rate of release of the cationic surfactant in order to maintain electroneutrality within the droplet. The solubility of the [P6,6,6,14]+ is limited in aqueous solutions and is dependent on the local ionic strength of the solution (Fig. 2). Therefore in ionic strength gradients there is a differential release of the surfactant from droplet boundary into the solution, which in turn results in an asymmetrical surface tension gradient around the droplet. This leads to Marangoni like flows, which propel the droplet from areas of low surface tension to areas of high surface tension. The chip used in this work was 3D printed (Objet350 Connex printer) as were the titanium mesh electrodes (Realizer SLM-50) embedded in the chip. By applying an external electric field to the solution, a [P6,6,6,14][Cl] droplet can be moved from the cathode (-) to the anode (+) (Fig. 3). The external electric field causes migration of ions, which results in concentration enrichment of ions in the proximity of the electrodes [3], Na+ at the cathode (starting position) and Cl- at the anode (destination). The resulting ion migration towards the electrodes creates an ionic strength gradient within the channel which controls the movement of the droplet. Additionally, the applied electric field causes Faradic arrangement of the charged ions within the IL droplet [3]. This also creates concentration gradients of the ions within the droplet, reinforcing the droplet movement mechanism. The electro-generation of gradients therefore provides a simple means to control the speed and direction of movement of droplets within fluidic channels in a very flexible manner