The effect of temporally variable environmental stimuli and group size on emergence behavior

How animals trade-off food availability and predation threats is a strong determinant of animal activity and behavior; however, the majority of work on this topic has been on individual animals, despite the modulating effect the presence of conspecifics can have on both foraging and predation risk. Although these environmental factors (food and predation threat) vary spatially within habitats, they also vary temporally, and in marine habitats, this can be determined by not only the diel cycle but also the tidal cycle. Humbug damselfish, Dascyllus aruanus, live in small groups of unrelated individuals within and around branching coral heads, which they collectively withdraw into to escape a predation threat. In this study, we measured the proportion of individuals in the colony that were outside the coral head before and after they were scared by a fright stimulus and compared the responses at high tide (HT) and low tide (LT). We found that a greater proportion of the shoal emerged after the fright stimulus at HT and in larger groups than at LT or in smaller groups. We also quantified the pattern of emergence over time and discovered the rate of emergence was faster in larger shoals as time progressed. We show that shoals of fish change their behavioral response to a predation threat in accordance with the tide, exemplifying how temporally variable environmental factors can shape group movement decisions

Design of HIFU treatment plans using an evolutionary strategy

High Intensity Focused Ultrasound (HIFU) is an emerging technique for non-invasive cancer treatment where malignant tissue is destroyed by thermal ablation. Since one ablation only allows a small region of tissue to be destroyed, a series of ablations has to be conducted to treat larger volumes. To maximize the treatment outcome and prevent injuries such as skin burns, complex preoperative treatment planning is carried out to determine the focal position and sonication time for each ablation. Here, we present an evolutionary strategy to design HIFU treatment plans using a map of patient specific material properties and a realistic thermal model. The proposed strategy allows high-quality treatment plans to be designed, with the average volume of mistreated and under-treated tissue not exceeding 0.1 %

Mixtures of Charged Colloid and Neutral Polymer: Influence of Electrostatic Interactions on Demixing and Interfacial Tension

The equilibrium phase behavior of a binary mixture of charged colloids and neutral, non-adsorbing polymers is studied within free-volume theory. A model mixture of charged hard-sphere macroions and ideal, coarse-grained, effective-sphere polymers is mapped first onto a binary hard-sphere mixture with non-additive diameters and then onto an effective Asakura-Oosawa model [S. Asakura and F. Oosawa, J. Chem. Phys. 22, 1255 (1954)]. The effective model is defined by a single dimensionless parameter -- the ratio of the polymer diameter to the effective colloid diameter. For high salt-to-counterion concentration ratios, a free-volume approximation for the free energy is used to compute the fluid phase diagram, which describes demixing into colloid-rich (liquid) and colloid-poor (vapor) phases. Increasing the range of electrostatic interactions shifts the demixing binodal toward higher polymer concentration, stabilizing the mixture. The enhanced stability is attributed to a weakening of polymer depletion-induced attraction between electrostatically repelling macroions. Comparison with predictions of density-functional theory reveals a corresponding increase in the liquid-vapor interfacial tension. The predicted trends in phase stability are consistent with observed behavior of protein-polysaccharide mixtures in food colloids.Comment: 16 pages, 5 figure

Parameterization of the optical function of hydrogenated amorphous carbon by means of B-splines

ellipsometry (SE) is a non-invasive optical diagnostic that measures the change in polarization of light reflected on a thin film. To extract both the optical function and thickness of the film from SE data, a (multi-layered) model is required that describes the interaction of the incident light with the film. For amorphous materials this interaction is commonly modeled by the Tauc-Lorentz oscillator and is used to parameterize the optical function [1]. However, a fully mathematical Kramers-Kronig consistent description of the optical function by means of B-splines is also possible [2]. The B-spline parameterization requires no pre-existing knowledge about the interaction of light with the film. The layer structure for this model consists of a substrate, the bulk layer, of which the optical function is represented by Bsplines, and a roughness layer. The roughness is modeled by an effective medium approximation of 50% bulk material and 50% voids. This layer structure is verified by cross-sectional scanning electron microscopy (SEM) measurements. The roughness is in good agreement with values determined by atomic force microscopy (AFM). When the B-spline model is applied to SE data obtained during growth, it has been found that the optical function for every measured thickness is the same, thereby ascertaining the homogeneity of the bulk layer of the a-C:H. During etching of a-C:H with a hydrogen plasma, the optical function of the film - due to the homogeneity of the bulk material - can be fixed throughout the entire etch process, which enables real time in situ monitoring of the thickness evolution. Further parameterization of the dielectric function, as found by the B-spline model, by a physics-based model is possible. For a-C:H films, the bulk layer is described by two Tauc-Lorentz oscillators, from which the sp2/sp3 ratio has been, tentatively, determined from SE data up to 6.5 eV [3]. In all, the B-spline model is an accurate and fast method to determine thickness, roughness and optical constants for numerous types of thin films, including - as has been shown - hydrogenated amorphous carbon. The determined film properties can also be used as input parameters for physicsbased models

Constraints on the evolution of Taranaki Fault from thermochronology and basin analysis: Implications for the Taranaki Fault play

Taranaki Fault is the major structure defining the eastern margin of Taranaki Basin and marks the juxtaposition of basement with the Late Cretaceous-Paleogene succession in the basin. Although the timing of the basement over-thrusting on Taranaki Fault and subsequent marine onlap on to the basement block are well constrained as having occurred during the Early Miocene, the age of formation of this major structure, its character, displacement history and associated regional vertical movement during the Late Cretaceous- Recent are otherwise poorly known. Here we have applied (i) apatite fission track thermochronology to Mesozoic basement encountered in exploration holes and in outcrop to constrain the amount and timing of Late Cretaceous-Eocene exhumation of the eastern side of the fault, (ii) basin analysis of the Oligocene and Miocene succession east of the fault to establish the late-Early Miocene - Early Pliocene subsidence history, and (iii), regional porosity-bulk density trends in Neogene mudstone to establish the late uplift and tilting of eastern Taranaki Basin margin, which may have been associated with the main period of charge of the underlying Taranaki Fault play. We make the following conclusions that may be useful in assessing the viability of the Taranaki Fault play. (1) Mid-Cretaceous Taniwha Formation, intersected in Te Ranga-1 was formerly extensive across the western half of the Kawhia Syncline between Port Waikato and Awakino. (2) Taranaki Fault first formed as a normalfault during the Late Cretaceous around 85±10 Ma, and formed the eastern boundary of the Taranaki Rift-Transform basin. (3) Manganui Fault, located onshore north of Awakino, formed as a steeply east dipping reverse fault and accommodated about four km of displacement during the mid-Cretaceous. (4) Uplift and erosion, involving inversion of Early Oligocene deposits, occurred along the Herangi High during the Late Oligocene. This may have been associated with initial reverse movement on Taranaki Fault. (5) During the Early Miocene (Otaian Stage) the Taranaki and Manganui Faults accommodated the westward transport of Murihiku basement into the eastern margin of Taranaki Basin, but the amount of topography generated over the Herangi High can only have been a few hundred metres in elevation. (6) The Altonian (19-16 Ma) marked the start of the collapse of the eastern margin of Taranaki Basin that lead during the Middle Miocene to the eastward retrogradation of the continental margin wedge into the King Country region. During the Late Miocene, from about 11 Ma, a thick shelf-slope continental margin wedge prograded northward into the King Country region and infilled it (Mt Messenger, Urenui, Kiore and Matemateaonga Formations). (7) During the Pliocene and Pleistocene the whole of central New Zealand, including the eastern margin of Taranaki Basin, became involved in long wavelength up-doming with 1-2 km erosion of much of the Neogene succession in the King Country region. This regionally elevated the Taranaki Fault play into which hydrocarbons may have migrated from the Northern Graben region

Strength Reduction in Electrical and Elastic Networks

Particular aspects of problems ranging from dielectric breakdown to metal insu- lator transition can be studied using electrical o elastic networks. We present an expression for the mean breakdown strength of such networks.First, we intro- duce a method to evaluate the redistribution of current due to the removal of a finite number of elements from a hyper-cubic network of conducatances.It is used to determine the reduction of breakdown strength due to a fracture of size $\kappa$.Numerical analysis is used to show that the analogous reduction due to random removal of elements from electrical and elastic networks follow a similar form.One possible application, namely the use of bone density as a diagnostic tools for osteorosporosis,is discussed.Comment: one compressed file includes: 9 PostScrpt figures and a text fil