Growth and maturity of salmon sharks (Lamna ditropis) in the eastern and western North Pacific, and comments on back-calculation methods

Age and growth estimates for salmon sharks (Lamna ditropis) in the eastern North Pacific were derived from 182 vertebral centra collected from sharks ranging in length from 62.2 to 213.4 cm pre-caudal length (PCL) and compared to previously published age and growth data for salmon sharks in the western North Pacific. Eastern North Pacific female and male salmon sharks were aged up to 20 and 17 years, respectively. Relative marginal increment (RMI) analysis showed that postnatal rings form annually between January and March. Von Bertalanffy growth parameters derived from vertebral length-at-age data are L∞ =207.4 cm PCL, k=0.17/yr, and t0=−2.3 years for females (n=166), and L∞ =182.8 cm PCL, k=0.23/yr , and t0=−1.9 years for males (n=16). Age at maturity was estimated to range from six to nine years for females (median pre-caudal length of 164.7 cm PCL) and from three to five years old for males (median precaudal length of 124.0 cm PCL). Weight-length relationships for females and males in the eastern North Pacific are W=8.2 × 10_05 × L2.759 –06 × L3.383 (r2 =0.99) and W=3.2 × 10 (r2 =0.99), respectively. Our results show that female and male salmon sharks in the eastern North Pacific possess a faster growth rate, reach sexual maturity earlier, and attain greater weight-at-length than their same-sex counterparts living in the western North Pacific

Composition, Superposition, and Encapsulation in the Formal Specification of Distributed Systems

Composition, superposition, and encapsulation are important techniques that work well together for designing large distributed software systems. Composition is a symmetric operator that allows system components to communicate with each other across module boundaries. Superposition is an asymmetric relationship that allows one system component to observe the state of another. Encapsulation is the ability to define the reason about the behavior of a module in terms of a well-defined boundary between that module and its environment, while hiding the internal operations of that module. In this paper, the I/O automation model of Lynch and Tuttle is extended to permit superposition of program modules. This results in a unified model that supports composition, superposition, and encapsulation. The extended model includes a formal specification mechanism for layered systems that allows the sets of correct behaviors of each layer to be expressed in terms of the states of the layers below it. To illustrate the ideas, we use the extended model to specify the global snapshot problem and prove the correctness of the global snapshot algorithm of Chandy and Lamport

Capsules and Semantic Regions for Code Visualization and Direct Manipulation of Live Programs

JPie is a visual programming environment supporting live construction of Java applications. Class modifications, such as declaring instance variables and overriding methods, take effect immediately on existing instances of the class to encourage experimentation in an educational setting. Because programs are edited live, editing gestures must transform the program from one well-formed state to another, without intermediate ambiguous states. To accomplish this, JPie’s visual representation provides capsules, which represent logical code units, and semantic regions, which represent different aspects of a program. A capsule’s meaning depends upon its containing semantic region. Similarly, a gesture, which involves manipulation of a capsule, is interpreted on the basis of the semantic region in which it occurs. This paper describes how capsules and semantic regions visually expose the structure of JPie programs and support live program editing through natural atomic gestures

Aspects of age, growth, demographics and thermal biology of two lamniform shark species

Age and growth rates for salmon sharks (Lamna ditropis) in the eastern North Pacific (ENP) were estimated from seasonally formed bands in the vertebrae, and compared to previously published life history parameters for this species from the western North Pacific (WNP). Results of this study show that salmon sharks in the ENP achieve their maximum length at a faster rate, reach sexual maturity at an earlier age and achieve a greater weight-at-length than those in the WNP. Additionally, this dissertation shows that adult salmon sharks maintain a specific body temperature independent of changes in ambient temperature through a combination of physical and physiological means, and essentially function as homeotherms. Due to uncertainty in previous life history parameter estimates for sand tiger sharks (Carcharias taurus) in the western North Atlantic, age and growth rates were re-estimated using a larger sample size and captive individuals injected with oxytetracycline (OTC), a fluorescent skeletal marker. The results support a hypothesis that this species forms one pair of growth bands annually in the vertebral centra, whereas previous growth rate estimates were based on the formation of two bands per year. as such, the growth rate of this species is considerably slower than previously predicted and the population more susceptible to fishing mortality. Demographic analyses were conducted for salmon sharks in the ENP and WNP, and for sand tiger sharks (based on new life history parameter estimates) with uncertainty in vital rates incorporated via Monte Carlo simulations. Density-dependent compensation was included in models where fishing mortality was imposed by increasing sub-adult survivorship from output values generated by a previously published Intrinsic Rebound Potential model. The results indicate that both species are extremely vulnerable to fishing mortality and that no fishery should be implemented for sand tiger sharks or salmon sharks in the WNP. Salmon sharks in the ENP were the only population examined that indicated the potential to tolerate any fishing mortality. A comparison of growth completion rates and other life history parameters of ectothermic and endothermic sharks did not indicate that endothermic sharks achieve their maximum length at a faster rate than ectothermic sharks

An Incremental Distributed Algorithm for Computing Biconnected Components

This paper describes a distributed algorithm for computing the biconnected components of a dynamically changing graph. Our algorithm has a worst case communication complexity of O(b + c) messages for an edge insertion and O(b\u27 + c) messages for an edge removal, and a worst case time complexity of O(c) for both operations, where c is the maximum number of biconnected components in any of the connected components during the operation, b is the number of nodes in the biconnected component containing the new edge, and bprime is the number of nodes in the biconnected component in which the update request is being processed. The algorithm is presented in two stages. First, a serial algorithm is presented in which topology updates occur one at a time. Then, building on the serial algorithm, an algorithm is presented in which concurrent update requests are serialized within each connected component. The problem is motivated by the need to implement casual ordering of messages efifciently in a dynamically changing communication structure

Dynamic Reconfiguration with I/O Abstraction

Dynamic reconfiguration is explored in the context of I/O abstraction, a new programming model that defines the communication structure of a system in terms of connections among well-defined data interfaces for the modules in the system. The properties of I/O abstraction, particularly the clear separation of computation from communication and the availability of a module\u27s state information, help simplify the reconfiguration strategy. Both logical and physical reconfiguration are discussed, with an emphasis on a new module migration mechanism that (1) takes advantage of the underlying I/O abstraction model, (2) avoids the expense and complication of state extraction techniques, (3) minimizes the amount of code required for migration and confines that code to a separate section of the program, and (4) is designed to permit migration across heterogeneous hosts and to allow replacemnt of one implementation by another, even if the new implementation is written in another programming language. The flexibility of the migration mechanism is illustrated by presenting three different paradigms for constructing reconfiguration modules that are supported by this new mechanism. A uniform specification mechanism is provided for both logical and physical reconfiguration

Formal Specification of a Dynamically Configurable Distributed System

The Programmers\u27 Playground is a programming environment that supports end-user construction of distributed multimedia applications. The system implements a new programming model that is based, in part, upon ideas from the formal I/O automaton model of Lynch and Tuttle. Important features of The Programmers\u27 Playground are a separation of communication and computation and graphical support for dynamic reconfiguration. This paper provides a formal specification of the Playground programming model and runtime system in terms of the I/O automaton model on which it is based. Exploiting the compositionality properties of the I/O automaton model, the formal specification is describd as a composition of several modules. A behavioral specification of each module is presented, followed by an I/O automaton that implements each specification. We present the specification in two stages, a centralized specification that captures the allowable behaviors, and then a detailed distributed implementation

End-User Visualization and Manipulation of Distributed Aggregate Data

Aggregate visualization and manipulation enables the viewing and interaction of dynamically changing data sets in a graphically meaningful way. However, off-the-shelf applications typically provide only limited ways to view static aggregates and generally do not support manipulation of aggregate data through the resulting visualization. To be fully dynamic, an aggregate visualization should be customizable to suit the individual's needs and should allow end-users to modify the data through direct manipulation. This paper describes a software system that empowers end-users to create interactive aggregate visualizations through a visual language interface. Included are mechanisms for specifying how aggregate data is processed from multiple sources of a distributed application, providing functionality similar to project, select, join, and cross product of relational databases. This approach gives end-users the power to create customized, interactive visualizations of dynamically changing ..

Learning Curve Management in Educational Programming Environments

Beginning programmers are best served by integrateddevelopment environments that adapt to their growingsophistication as programmers. To this end, we propose fourdesign goals for learning curve management in educationalprogramming environments. We provide pedagogicaljustification for each goal, describe possible supporting featuresets, and discuss the extent to which these goals have beenachieved in some current environments, particularly JPie, ourinteractive environment for live construction of Java applications

Run-time Modification of the Class Hierarchy in a Live Java Development Environment

Class hierarchy design is central to object-oriented software development. However, it is sometimes difficult for developers to anticipate all the implications of a design until implementation is underway. To support experimentation with different designs, we extend prior work on live development environments to allow run-time modification of the class hierarchy. The result is a more fluid object-oriented development process, in which immediate feedback from the executing program can be used to guide hierarchy design. This paper presents a framework and developer support for run-time modification of class inheritance relations in JPie, a live visual programming environment for Java. Most notably, the framework supports class reloading without modification of the Java Virtual Machine