1. The space use of central-place foragers, animals that forage from and return to a single central place such as a nest, burrow or sleeping site, is well documented. Limited data, however, exist for ...multiple central-place foragers that alternate among several central places. 2. The conventional view of stream-dwelling salmonids suggests that they conform to the central-place territorial model (CPTM) by (i) attacking prey and intruders from one primary foraging station, and defending (ii) small (iii) exclusive areas that (iv) increase with body size. 3. Recent studies suggest greater variability in salmonid space-use than would be expected by the CPTM, but tend to focus on the time allocated towards different activities rather than their distribution in space, especially for young-of-the-year (YOY) fish that are hard to tag and monitor in the wild. 4. In this study, the validity of CPTM was tested by mapping the daily space use of 50 YOY Atlantic salmon in a natural stream via repeated observations of tagged fish in diverse habitats, and by comparing these to earlier estimates of territory use in YOY salmonids. 5. The 50 YOY Atlantic salmon were multiple central-place foragers. All fish visited more than one foraging station (median = 12·5 stations), visited most stations (68·5%) repeatedly, showed limited fidelity to a particular station and typically attacked prey only while holding a position at a station. 6. The multiple central-place territories of the 50 fish were large (mean = 0·932 m²) compared to earlier territory size estimates (mean = 0·107 m²) for salmonids of similar size and, surprisingly, did not increase with body size. Focal fish attacked intruders from similar distances as reported earlier for much smaller territories, suggesting that large territories are less exclusively defended at any given time. 7. Overall, this study provides a new view on foraging and territoriality in stream salmonids, and on the small but diverse literature on multiple central-place foragers. Further studies, however, are needed to clarify the evolutionary benefits and population consequences of multiple central-place space-use in mobile animals.
The magnitude of variation of diel activity patterns and habitat use of wild Atlantic salmon (Salmo salar) parr was examined during the summer and autumn through a gradient of declining temperature. ...Fish were marked with passive integrated transponders and tracked using a large network of flatbed antennas. High interindividual variability was observed, as some individuals were predominantly nocturnal whereas others frequently changed their daily activity pattern. Overall fish activity decreased with decreasing temperature and increasing flow stage, but most of these changes in daily activity were observed in crepuscular periods. Parr used habitats with lower velocity at night than in the day during the summer, but not in the autumn. Furthermore, there was no difference between day and night habitats for fish that were cathemeral (active both day and night during a given day), so differences between day and night habitats were the result of individuals adopting different activity patterns. These results suggest that habitat interacts with activity pattern, as individuals using suboptimal habitats seem to increase daytime foraging to secure sufficient energy. Temporal and among-fish variability of activity patterns illustrate the dynamic nature of foraging decisions that may partly result from trade-offs experienced at the microhabitat scale.
Most studies of intrasexual mating competition have focused only on males, and have typically shown an increase in aggression and a decrease in courtship rate with increasing operational sex ratio ...(OSR), the ratio of ready-to-mate males to females. We manipulated the number of males (1, 2 or 4) and females (2, 4, 8 or 16) in a factorial design to investigate mating competition and courtship rate in Japanese medaka, a species with conventional sex roles, over a broad range of OSRs (0.0625 to 2), and in relation to the density of both sexes. As predicted, the rates of intrasexual interactions by both males and females increased with the number of competitors and decreased with the number of potential mates, whereas the rates of courtship decreased with the number of competitors and increased with the number of mates. At OSRs between 0.35 and 2, males engaged in more intrasexual interactions and courtship behaviour than females. However, females became the more competitive sex at OSRs less than 0.35, and engaged in more courtship than males at OSRs greater than 2, rather than at an OSR of 1, as predicted by conventional mating system theory. Our results indicate that OSR can predict the considerable within-sex variability in reproductive behaviour of both males and females, regardless of which sex is more competitive.
Avoiding Christian extinction Grant, James
Review (Institute of Public Affairs (Australia) : 1997),
10/2017, Letnik:
69, Številka:
3
Journal Article, Book Review
Review(s) of: The Benedict Option: A Strategy for Christians in a Post-Christian Nation, by Rod Dreher. Sentinel, March 2017, pp 272
Synthetic fractals inherently carry spatially encoded frequency information that renders them as an ideal candidate for broadband optical structures. Nowhere is this more true than in the terahertz ...(THz) band where there is a lack of naturally occurring materials with valuable optical properties. One example are perfect absorbers that are a direct step toward the development of highly sought after detectors and sensing devices. Metasurface absorbers that can be used to substitute for natural materials suffer from poor broadband performance, while those with high absorption and broadband capability typically involve complex fabrication and design and are multilayered. Here, we demonstrate a polarization-insensitive ultrathin (∼λ/6) planar metasurface THz absorber composed of supercells of fractal crosses capable of spanning one optical octave in bandwidth, while still being highly efficient. A sufficiently thick polyimide interlayer produces a unique absorption mechanism based on Salisbury screen and antireflection responses, which lends to the broadband operation. Experimental peak absorption exceeds 93%, while the average absorption is 83% from 2.82 THz to 5.15 THz. This new ultrathin device architecture, achieving an absorption-bandwidth of one optical octave, demonstrates a major advance toward a synthetic metasurface blackbody absorber in the THz band.
Coherent beam combination of multiple fibres can be used to overcome limitations such as the power handling capability of single fibre configurations. In such a scheme, the focal intensity profile is ...critically dependent upon the relative phase of each fibre and so precise control over the phase of each fibre channel is essential. Determining the required phase compensations from the focal intensity profile alone (as measured via a camera) is extremely challenging with a large number of fibres as the phase information is obfuscated. Whilst iterative methods exist for phase retrieval, in practice, due to phase noise within a fibre laser amplification system, a single step process with computational time on the scale of milliseconds is needed. Here, we show how a neural network can be used to identify the phases of each fibre from the focal intensity profile, in a single step of ~ 10 ms, for a simulated 3-ring hexagonal close-packed arrangement, containing 19 separate fibres and subsequently how this enables bespoke beam shaping. In addition, we show that deep learning can be used to determine whether a desired intensity profile is physically possible within the simulation. This, coupled with the demonstrated resilience against simulated experimental noise, indicates a strong potential for the application of deep learning for coherent beam combination.
Abstract
Most experimental tests of mating systems theory have been conducted in the laboratory, using operational sex ratios (ratio of ready-to-mate male to ready-to-mate female) that are often not ...representative of natural conditions. Here, we first measured the range of adult sex ratio (proportion of adult males to adult females; ASR) in two populations of Trinidadian guppies (Poecilia reticulata) differing in ambient predation risk (high vs. low). We then explored, under semi-wild conditions, the effect of ASR (i.e., 0.17, 0.50, 0.83) on mating competition patterns in these populations. ASR in the wild was female-biased and did not significantly differ between the two populations. The range of ASR in our experiment was representative of natural ASRs. As expected, we observed an increase in intrasexual aggression rates in both sexes as the relative abundance of competitors increased. In support of the risky competition hypothesis, all measured behaviors had lower rates in a high versus low predation-risk population, likely due to the costs of predation. In terms of mating tactics, a male-biased ASR did not lead males to favor forced mating over courtship, indicating that males did not compensate for the cost of competition by switching to a less costly alternative mating tactic. Overall, this study highlights the need for field experiments using natural ranges of ASRs to test the validity of mating systems theory in a more complex, ecologically relevant context.
Precision metabolomics and quantification for cost-effective rapid diagnosis of disease are the key goals in personalized medicine and point-of-care testing. At present, patients are subjected to ...multiple test procedures requiring large laboratory equipment. Microelectronics has already made modern computing and communications possible by integration of complex functions within a single chip. As More than Moore technology increases in importance, integrated circuits for densely patterned sensor chips have grown in significance. Here, we present a versatile single complementary metal-oxide-semiconductor chip forming a platform to address personalized needs through on-chip multimodal optical and electrochemical detection that will reduce the number of tests that patients must take. The chip integrates interleaved sensing subsystems for quadruple-mode colorimetric, chemiluminescent, surface plasmon resonance, and hydrogen ion measurements. These subsystems include a photodiode array and a single photon avalanche diode array with some elements functionalized to introduce a surface plasmon resonance mode. The chip also includes an array of ion sensitive field-effect transistors. The sensor arrays are distributed uniformly over an active area on the chip surface in a scalable and modular design. Bio-functionalization of the physical sensors yields a highly selective simultaneous multiple-assay platform in a disposable format. We demonstrate its versatile capabilities through quantified bio-assays performed on-chip for glucose, cholesterol, urea, and urate, each within their naturally occurring physiological range.
1. How individuals within a population distribute themselves across resource patches of varying quality has been an important focus of ecological theory. The ideal free distribution predicts equal ...fitness amongst individuals in a 1 : 1 ratio with resources, whereas resource defence theory predicts different degrees of monopolization (fitness variance) as a function of temporal and spatial resource clumping and population density. 2. One overlooked landscape characteristic is the spatial distribution of resource patches, altering the equitability of resource accessibility and thereby the effective number of competitors. While much work has investigated the influence of morphology on competitive ability for different resource types, less is known regarding the phenotypic characteristics conferring relative ability for a single resource type, particularly when exploitative competition predominates. 3. Here we used young-of-the-year rainbow trout (Oncorhynchus mykiss) to test whether and how the spatial distribution of resource patches and population density interact to influence the level and variance of individual growth, as well as if functional morphology relates to competitive ability. Feeding trials were conducted within stream channels under three spatial distributions of nine resource patches (distributed, semi-clumped and clumped) at two density levels (9 and 27 individuals). 4. Average trial growth was greater in high-density treatments with no effect of resource distribution. Within-trial growth variance had opposite patterns across resource distributions. Here, variance decreased at low-population, but increased at high-population densities as patches became increasingly clumped as the result of changes in the levels of interference vs. exploitative competition. Within-trial growth was related to both pre- and post-trial morphology where competitive individuals were those with traits associated with swimming capacity and efficiency: larger heads/bodies/caudal fins and less angled pectoral fins. 5. The different degrees of within-population growth variance at the same density level found here, as a function of spatial resource distribution, provide an explanation for the inconsistencies in within-site growth variance and population regulation often noted with regard to density dependence in natural landscapes.
•Sequential search problem is formulated as a combinatorial multi-armed bandit.•We consider a novel setting with action-dependent filtering of Poisson rewards.•A new upper confidence bound approach ...based on martingale inequalities is proposed.•We derive order-optimal upper bounds on the regret of the approach.•We verify its strong performance and robustness in extensive numerical experiments.
We consider the problem of sequentially choosing observation regions along a line, with an aim of maximising the detection of events of interest. Such a problem may arise when monitoring the movements of endangered or migratory species, detecting crossings of a border, policing activities at sea, and in many other settings. In each case, the key operational challenge is to learn an allocation of surveillance resources which maximises successful detection of events of interest. We present a combinatorial multi-armed bandit model with Poisson rewards and a novel filtered feedback mechanism - arising from the failure to detect certain intrusions - where reward distributions are dependent on the actions selected. Our solution method is an upper confidence bound approach and we derive upper and lower bounds on its expected performance. We prove that the gap between these bounds is of constant order, and demonstrate empirically that our approach is more reliable in simulated problems than competing algorithms.
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