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We address the question of how to connect predictions by hydrodynamic models of how sea lice move in water to observable measures that count the number of lice on each fish in a cage in the water. This question is important for management and regulation of aquacultural practice that tries to maximise food production and minimise risk to the environment. We do this through a simple rule-based model of interaction between sea lice and caged fish. The model is simple: sea lice can attach and detach from a fish. The model has a novel feature, encoding what is known as a master equation producing a time-series of distributions of lice on fish that one might expect to find if a cage full of fish were placed at any given location. To demonstrate how this works, and to arrive at a rough estimate of the interaction rates, we fit a simplified version of the model with three free parameters to publicly available data about an experiment with sentinel cages in Loch Linnhe in Scotland. Our construction, coupled to the hydrodynamic models driven by surveillance data from industrial farms, quantifies the environmental impact as: what would the infection burden look like in a notional cage at any location and how does it change with time?

Many codes have been developed to study highly relativistic, magnetized flows around and inside compact objects. Depending on the adopted formalism, some of these codes evolve the vector potential $\mathbf{A}$, and others evolve the magnetic field $\mathbf{B}=\nabla\times\mathbf{A}$ directly. Given that these codes possess unique strengths, sometimes it is desirable to start a simulation using a code that evolves $\mathbf{B}$ and complete it using a code that evolves $\mathbf{A}$. Thus transferring the data from one code to another would require an inverse curl algorithm. This paper describes two new inverse curl techniques in the context of Cartesian numerical grids: a cell-by-cell method, which scales approximately linearly with the numerical grid, and a global linear algebra approach, which has worse scaling properties but is generally more robust (e.g., in the context of a magnetic field possessing some nonzero divergence). We demonstrate these algorithms successfully generate smooth vector potential configurations in challenging special and general relativistic contexts., Comment: 20 pages, 9 figures

When a gravitational wave is detected by Advanced LIGO/Virgo, sophisticated parameter estimation (PE) pipelines spring into action. These pipelines leverage approximants to generate large numbers of theoretical gravitational waveform predictions to characterize the detected signal. One of the most accurate and physically comprehensive classes of approximants in wide use is the "Spinning Effective One Body--Numerical Relativity" (SEOBNR) family. Waveform generation with these approximants can be computationally expensive, which has limited their usefulness in multiple data analysis contexts. In prior work we improved the performance of the aligned-spin approximant SEOBNR version 2 (v2) by nearly 300x. In this work we focus on optimizing the full eight-dimensional, precessing approximant SEOBNR version 3 (v3). While several v2 optimizations were implemented during its development, v3 is far too slow for use in state-of-the-art source characterization efforts for long-inspiral detections. Completion of a PE run after such a detection could take centuries to complete using v3. Here we develop and implement a host of optimizations for v3, calling the optimized approximant v3_Opt. Our optimized approximant is about 340x faster than v3, and generates waveforms that are numerically indistinguishable., Comment: 16 pages, 1 figure, 9 tables; updated to clarify science background and fix typos

Searches for gravitational-wave bursts (transient signals, typically of unknown waveform) require identification of weak signals in background detector noise. The sensitivity of such searches is often critically limited by non-Gaussian noise fluctuations which are difficult to distinguish from real signals, posing a key problem for transient gravitational-wave astronomy. Current noise rejection tests are based on the analysis of a relatively small number of measured properties of the candidate signal, typically correlations between detectors. Multivariate analysis (MVA) techniques probe the full space of measured properties of events in an attempt to maximise the power to accurately classify events as signal or background. This is done by taking samples of known background events and (simulated) signal events to train the MVA classifier, which can then be applied to classify events of unknown type. We apply the boosted decision tree (BDT) MVA technique to the problem of detecting gravitational-wave bursts associated with gamma-ray bursts. We find that BDTs are able to increase the sensitive distance reach of the search by as much as 50%, corresponding to a factor of ~3 increase in sensitive volume. This improvement is robust against trigger sky position, large sky localisation error, poor data quality, and the simulated signal waveforms that are used. Critically, we find that the BDT analysis is able to detect signals that have different morphologies to those used in the classifier training and that this improvement extends to false alarm probabilities beyond the 3{\sigma} significance level. These findings indicate that MVA techniques may be used for the robust detection of gravitational-wave bursts with a priori unknown waveform., Comment: 14 pages, 12 figures

The dispersal stages of organisms with sessile adults must be able to select habitats with suitable conditions for establishment and survival, and must also be able to reach those locations. For marine planktonic larvae, movement due to currents is often orders of magnitude greater than movement due to swimming behaviour, so transport is largely passive. Current patterns are determined by the interaction of geography with tidal forces, modified by meteorological conditions. These linkages impose an area-specific focus to connectivity studies. Yet, how geographical features and meteorological forcing combine to produce specific current patterns and resultant connectivity among populations remains unclear. In this study, we followed tracks of generic particles driven by modelled hydrodynamic currents to investigate how connectivity between evenly spaced habitat sites varies in relation to coastal topography. Larvae released from regions of high current velocity, open coastline and low local habitat availability travelled furthest but were less likely to disperse successfully. Extensive natal habitat in the vicinity of a site generally had a positive impact on the number of larvae arriving, as did low current velocities. However, relationships between numbers of arriving larvae and local geographical indices were complex, particularly at longer larval durations. Local geography alone explained up to 50% of the variance in success of larvae released and around 10% of the variation in the number of larvae arriving at each site, but coastline properties fall short of predicting dispersal measures for particular locations. The study shows that meteorological variation and broad scale current patterns interact strongly with local geography to determine connectivity in coastal areas.

In this paper we present electro-osmotic (EO) flow within a more traditional fluid mechanics framework. Specifically, the modified Bernoulli equation (viz. the energy equation, the mechanical energy equation, the pipe flow equation, etc.) is shown to be applicable to EO flows if an electrical potential energy term is also included. The form of the loss term in the modified Bernoulli equation is unaffected by the presence of an electric field; i.e., the loss term still represents the effect of wall shear stress, which can be represented via a friction factor. We show that that the friction factor for pure EO flow (no applied pressure gradient) varies inversely with the Reynolds number based on the Debeye length of the electric double layer. Expressions for friction factor for combined laminar pressure-driven and EO flow are also given. These are shown to be functions of Reynolds number and geometry, as well as the relative strength of the applied electric field to the applied pressure gradient.

An analysis of English-as-a-Second-Language (ESL) textbooks published in the United States from the 1950s through the 1980s focuses on incidental but pervasive social messages contained in their content, including restriction to middle class populations and values, stereotyped sex roles, lack of visibility of minorities, negative messages about minority groups, and treatment of some socially sensitive topics such as divorce. Substantial changes, most of them positive, are found in the content of ESL textbooks over this period. Social and political factors influencing this change are examined, and additional goals held by some for these materials are discussed. It is concluded that, judged by today's standards, ESL textbooks of the 1950s can be faulted on grounds of both accuracy and fairness. However, some tension exists between accuracy and fairness in portrayal of members of society; when accuracy and fairness come into conflict, the tendency is often for accuracy to yield to fairness. Current textbooks portray U.S. society more accurately than in the past by including much greater social diversity. Contains 30 references. (MSE)

A discussion of authentic materials for English-as-a-Second-Language (ESL) instruction focuses on the necessary balance between authenticity and comprehensibility. A variety of definitions of authentic materials offered in the literature are considered, and then compared with published ESL materials that are claimed to be authentic. A new definition is proposed: materials are authentic if they are unaltered language data and are produced by and for native speakers of a common language and not for second language learners of that language. The assumption that all authentic materials are acquisition-rich input, either immediately comprehensible or comprehensible after a process of negotiation of meaning, is then examined. It is argued that while comprehension is a necessary and customary requisite to acquisition, it does not necessarily lead to comprehension, and it is the responsibility of the classroom teacher to make language samples useful. Teachers are invited to consider their motivations for using authentic language, and whether "contrived" language samples can be at least as valid and useful learning materials as those drawn directly from authentic sources. A brief bibliography is included. (MSE)

Selected reasons for resistance to change in education are discussed, the kinds of resulting behaviors are noted, and suggestions for plausible means of overcoming this resistance are offered. Though the search for excellence and innovation in education are desirable, they are often not sustained for any appreciable period of time and the innovations are often used in a limited manner. The use of computers in higher education is a recent example of this process in operation. Though computers have been widely applied, the potential has not been realized. Cost, lack of access to good software, and teacher resistance to the approach threaten the widespread implementation of computers. Resistance to change is discussed in detail, and resistant behaviors are explained. Such behavior becomes evident when there is an attempt to introduce new methods of instruction in education. Both aggressive (directly attacking) and subtle (stalling for time) resistant behavior is found. Various steps for overcoming resistance are "unfreezing" the old attitude, changing, and refreezing the new attitude. Each faculty member's needs must be considered. Information regarding the innovation must go to all necessary people in a form that is uniquely meaningful to each. Some people may fear economic or job loss or loss of job status because of the innovation, so those introducing the innovation must be aware of these fears and must act in a nonalienating way. Information must focus on things in which the change will and will not result. Too often, the individual will progress to the point of using the innovation, but not in a way that optimizes its potential. This individual must learn to network with others and engage in mutual sharing of ideas and potential uses. Success is based on individual efforts resulting from personal commitment to change. Contains 25 references. (SM)

Discusses critical issues facing the languages across the curriculum (LAC) movement. These include benefits to students derived from LAC offerings, effective curriculum design and teaching methods, benefits of LAC to teachers in other fields, and justification of the costs of long-term institutional support. (40 references) (CK)

The two types of programs investigated were required basic activity-based physical education and required conceptually-based physical education, both in small Christian colleges. Surveys indicated that real differences between the groups were small in respect to knowledge, attitudes, and habits. (SM)