3,931 research outputs found
Job desirability of the university professorate in the field of educational leadership
Journal ArticleThis survey research study uses job choice theory to assess recent educational leadership doctoral graduates' perceptions of the desirability of the educational administration professorate. Results reveal attractive and unattractive aspects of professorial work as well as those job attributes that are most strongly related to candidates' assessment of overall job desirability and job intentions
A Review of Shark Control in Hawaii with Recommendations for Future Research
In an attempt to allay public fears and to reduce the risk of shark
attack, the state government of Hawaii spent over 182 per shark.
The programs furnished information on diet, reproduction, and distribution of
sharks in Hawaii, but research efforts of the programs had a number of shortcomings.
Analysis of the biological data gathered was not directed toward
the tiger shark, Galeocerdo cuvier (Peron & LeSueur), which is responsible for
most attacks in Hawaii. Reliable estimates of shark populations in Hawaii
cannot be made based on catch data from control programs because of sampling
biases. Most of the information gained from the control programs was not
published in reviewed journals and is not readily available to the scientific
community. The ability of the control programs to reduce shark populations
and to remove large sharks from coastal waters appears to have been stated with
more confidence than is warranted, considering seasonal changes observed in
shark abundance and variable fishing effort. Shark control programs do not
appear to have had measurable effects on the rate of shark attacks in Hawaiian
waters. Implementation of large-scale control programs in the future in Hawaii
may not be appropriate. Increased understanding of the behavior and biology
of target species is necessary for evaluation of the effectiveness of small-scale
control efforts, such as selective fishing after an attack. Acoustic telemetry,
conventional tagging, and studies on population dynamics concentrating primarily
on the tiger shark may be used to obtain data about activity patterns,
distribution, and population parameters, providing information useful for reducing
the risk of shark attack in Hawaii and elsewhere
Voter Model with Time dependent Flip-rates
We introduce time variation in the flip-rates of the Voter Model. This type
of generalisation is relevant to models of ageing in language change, allowing
the representation of changes in speakers' learning rates over their lifetime
and may be applied to any other similar model in which interaction rates at the
microscopic level change with time. The mean time taken to reach consensus
varies in a nontrivial way with the rate of change of the flip-rates, varying
between bounds given by the mean consensus times for static homogeneous (the
original Voter Model) and static heterogeneous flip-rates. By considering the
mean time between interactions for each agent, we derive excellent estimates of
the mean consensus times and exit probabilities for any time scale of flip-rate
variation. The scaling of consensus times with population size on complex
networks is correctly predicted, and is as would be expected for the ordinary
voter model. Heterogeneity in the initial distribution of opinions has a strong
effect, considerably reducing the mean time to consensus, while increasing the
probability of survival of the opinion which initially occupies the most slowly
changing agents. The mean times to reach consensus for different states are
very different. An opinion originally held by the fastest changing agents has a
smaller chance to succeed, and takes much longer to do so than an evenly
distributed opinion.Comment: 16 pages, 6 figure
Young Lives and Imagined Futures: Insights from Archived Data
On 15th November 2010, Timescapes and the UK Data Archive (UKDA) hosted a seminar âYoung Lives and Imagined Futures: Analysing and Re-Analysing Narrative Data on Young Lives.â The seminar investigated data on young peopleâs orientationto their future lives. In addition to engaging with time and young lives, the seminar also explored methodologies for primary and secondary analysis of historical and contemporary datasets. In this working paper we bring together two papers from this event: Graham Crow and Dawn Lyonâs âTurning points in work and family life in the imagined futures of young people on Sheppey in 1978â and Mandy Winterton and Sarah Irwinâs âYoungstersâ expectations and context: secondary analysis and interpretationâ. These papers are significant together because they both draw on secondary analysis projects, constructing new insight from archived data collected by others and for other purposes. These two papers draw heavily on similar kinds of data to explore young peopleâs lives and imagined futures, although in very different ways. Yet it is worth noting that they were never pre-designed to sit so readily side by side. There was no discussion between the authors at any point. It was entirely fortuitous that they offered, by the extent of their similarities and difference, stimulating insight about the possibilities of qualitative secondary analysis when placed side by side. Before introducing these two papers, we provide some insight into the context of the day. We can only map below the nature and diversity of the research that was presented and cannot do justice here to the complexity and richness of the research that was offered
Finite-size scaling of the error threshold transition in finite population
The error threshold transition in a stochastic (i.e. finite population)
version of the quasispecies model of molecular evolution is studied using
finite-size scaling. For the single-sharp-peak replication landscape, the
deterministic model exhibits a first-order transition at , where is the probability of exact replication of a molecule of length , and is the selective advantage of the master string. For
sufficiently large population size, , we show that in the critical region
the characteristic time for the vanishing of the master strings from the
population is described very well by the scaling assumption \tau = N^{1/2} f_a
\left [ \left (Q - Q_c) N^{1/2} \right ] , where is an -dependent
scaling function.Comment: 8 pages, 3 ps figures. submitted to J. Phys.
Stochasticity and evolutionary stability
In stochastic dynamical systems, different concepts of stability can be
obtained in different limits. A particularly interesting example is
evolutionary game theory, which is traditionally based on infinite populations,
where strict Nash equilibria correspond to stable fixed points that are always
evolutionarily stable. However, in finite populations stochastic effects can
drive the system away from strict Nash equilibria, which gives rise to a new
concept for evolutionary stability. The conventional and the new stability
concepts may apparently contradict each other leading to conflicting
predictions in large yet finite populations. We show that the two concepts can
be derived from the frequency dependent Moran process in different limits. Our
results help to determine the appropriate stability concept in large finite
populations. The general validity of our findings is demonstrated showing that
the same results are valid employing vastly different co-evolutionary
processes
Random copying in space
Random copying is a simple model for population dynamics in the absence of
selection, and has been applied to both biological and cultural evolution. In
this work, we investigate the effect that spatial structure has on the
dynamics. We focus in particular on how a measure of the diversity in the
population changes over time. We show that even when the vast majority of a
population's history may be well-described by a spatially-unstructured model,
spatial structure may nevertheless affect the expected level of diversity seen
at a local scale. We demonstrate this phenomenon explicitly by examining the
random copying process on small-world networks, and use our results to comment
on the use of simple random-copying models in an empirical context.Comment: 26 pages, 11 figures. Based on invited talk at AHRC CECD Conference
on "Cultural Evolution in Spatially Structured Populations" at UCL, September
2010. To appear in ACS - Advances in Complex System
Destruction of the Mott Insulating Ground State of Ca_2RuO_4 by a Structural Transition
We report a first-order phase transition at T_M=357 K in single crystal
Ca_2RuO_4, an isomorph to the superconductor Sr_2RuO_4. The discontinuous
decrease in electrical resistivity signals the near destruction of the Mott
insulating phase and is triggered by a structural transition from the low
temperature orthorhombic to a high temperature tetragonal phase. The magnetic
susceptibility, which is temperature dependent but not Curie-like decreases
abruptly at TM and becomes less temperature dependent. Unlike most insulator to
metal transitions, the system is not magnetically ordered in either phase,
though the Mott insulator phase is antiferromagnetic below T_N=110 K.Comment: Accepted for publication in Phys. Rev. B (Rapid Communications
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