Establishing the behavioural limits for countershaded camouflage

Countershading is a ubiquitous patterning of animals whereby the side that typically faces the highest illumination is darker. When tuned to specific lighting conditions and body orientation with respect to the light field, countershading minimizes the gradient of light the body reflects by counterbalancing shadowing due to illumination, and has therefore classically been thought of as an adaptation for visual camouflage. However, whether and how crypsis degrades when body orientation with respect to the light field is non-optimal has never been studied. We tested the behavioural limits on body orientation for countershading to deliver effective visual camouflage. We asked human participants to detect a countershaded target in a simulated three-dimensional environment. The target was optimally coloured for crypsis in a reference orientation and was displayed at different orientations. Search performance dramatically improved for deviations beyond 15 degrees. Detection time was significantly shorter and accuracy significantly higher than when the target orientation matched the countershading pattern. This work demonstrates the importance of maintaining body orientation appropriate for the displayed camouflage pattern, suggesting a possible selective pressure for animals to orient themselves appropriately to enhance crypsis

Is countershading camouflage robust to lighting change due to weather?

Countershading is a pattern of coloration thought to have evolved in order to implement camouflage. By adopting a pattern of coloration that makes the surface facing towards the sun darker and the surface facing away from the sun lighter, the overall amount of light reflected off an animal can be made more uniformly bright. Countershading could hence contribute to visual camouflage by increasing background matching or reducing cues to shape. However, the usefulness of countershading is constrained by a particular pattern delivering ‘optimal’ camouflage only for very specific lighting conditions. In this study, we test the robustness of countershading camouflage to lighting change due to weather, using human participants as a ‘generic’ predator. In a simulated three-dimensional environment, we constructed an array of simple leaf-shaped items and a single ellipsoidal target ‘prey’. We set these items in two light environments: strongly directional ‘sunny’ and more diffuse ‘cloudy’. The target object was given the optimal pattern of countershading for one of these two environment types or displayed a uniform pattern. By measuring detection time and accuracy, we explored whether and how target detection depended on the match between the pattern of coloration on the target object and scene lighting. Detection times were longest when the countershading was appropriate to the illumination; incorrectly camouflaged targets were detected with a similar pattern of speed and accuracy to uniformly coloured targets. We conclude that structural changes in light environment, such as caused by differences in weather, do change the effectiveness of countershading camouflage

Two neutron decay of 16Be

Recently, the first example of two-neutron decay from the ground state of an unbound nucleus, $^{16}$Be, was seen. Three-body methods are ideal for exactly treating the degrees of freedom important for these decays. Using a basis expansion over hyperspherical harmonics and the hyperspherical R-matrix method, we construct a realistic model of $^{16}$Be in order to investigate its decay mode and the role of the two-neutron interaction. The neutron-$^{14}$Be interaction is constrained using shell model predictions. We obtain a ground state for $^{16}$Be that is over-bound by approximately 1 MeV with a width of approximately 0.23 MeV. This suggests, that for such systems, the three-body force needs to be repulsive.Comment: 4 pages, 1 figure, contribution to the proceedings for the 21st International Conference on Few Body Problems in Physics, Chicago, Illinois, US

INVESTMENT EFFECTS OF ENDOGENOUS AND EXOGENOUS DEPRECIATION: IMPROVED PASTURES IN URUGUAY

The depreciation rate for capital assets may have endogenous and exogenous components. Change in the exogenous component depends on technological change and/or environmental factors, shifts the production function, and independently affects profitability and investment. Change in the endogenous component does not. These hypotheses are tested using data on Uruguayan grass-legume pastures.Land Economics/Use,

The Synthesis and Pharmacological Evaluation of Salvinorin A Analogues as Opioid Receptor Probes

Kappa opioid (KOP) receptors have been shown to be involved in the control of several abuse related effects of central nervous system stimulants. KOP receptor agonists have been shown to modulate the activity of dopamine neurons and decrease self-administration of cocaine in a variety of species, while KOP receptor antagonists have the potential to be utilized as opioid abuse therapies and in the treatment of relapse. With this in mind, investigations were performed on the novel KOP receptor agonist neoclerodane diterpene salvinorin A. This natural product is the active component of the hallucinogenic mint plant Salvia divinorum and the first non-nitrogenous natural product having high affinity and efficacy at KOP receptors. Salvinorin A contains a furan ring, which in other furan containing natural products such as teucrin A and aflatoxin B1 has been identified to cause hepatotoxicity. In efforts to develop a more desirable pharmacological tool, structural modifications were made to salvinorin A in efforts explore the role of the furan ring in affinity and activity at KOP receptors and to reduce its potential for hepatotoxicity. Several ketone analogues were found to retain affinity at KOP receptors relative to salvinorin A and were versatile intermediates for the synthesis of other analogues. Surprisingly, benzisoxazole 187 was found to have increased affinity for MOP receptors. 2-Furanyl salvinorin A (185) was found to have similar efficacy and activity compared to salvinorin A. In addition, Captisol® was identified as a new vehicle for salvinorin A administration in pharmacological assays to eliminate some of the drawbacks of currently used vehicles. These studies assist with the identification of the pharmacophore of salvinorin A as well as the determination of structure-activity relationships, all of which will increase the potential for identification of novel opioid therapeutics

Classification and Its Risks: How Psychiatric Status Contributes to Homelessness Policy

This article examines the extent to which psychiatric classification in public policy research contributes to the equation of homelessness and mental illness. Surveys that measure psychiatric status of homeless persons are reviewed to understand whether they contribute to biased rates of mental illness among homeless persons. The relationship between psychiatric classification and the concept of need is examined and alternatives to current classification are proposed. Classification is discussed particularly in relation to policies of segmentation for single homeless adults

Line shifts in the first overtone of DF broadened by HF

Line spectra shifts in HF and in first overtone band of DF induced by HF pressure