Population assessment of the vermilion snapper, Rhomboplites aurorubens, from the Southeastern United States

Changes in the age structure and population size of vermilion snapper, Rhornboplites aurorubens, from North Carolina through the Florida Keys were examined using records of landings and size frequencies of fish from commercial, recreational, and headboat fisheries from 1986-1996. Population size in numbers at age was estimated for each year by applying separable virtual population analysis (SVPA) to the landings in numbers at age. SVPA was used to estimate annual, age-specific fishing mortality (F) for four levels of natural mortality (M = 0.20, 0.25, 0.30, and 0.35). Although landings of vermilion snapper for the three fisheries have declined, minimum fish size regulations have resulted in an increase in the mean size of fish landed. Age at entry and age at full recruitment were age-1 andage-3 fDr 1986-1991, compared with age-1 and age-4, respectively, for 1992-1996. Levels of mortality from fishing (F) ranged from 0.38 - 0.61 for the entire period. Current spawning potential ratio (SPR) is 21% or 27% depending on the natural mortality estimate. SPR could be raised to 30% or 40% with a reduction in F, or by increasing the age at entry to the fisheries. The latter could be enhanced now if fishermen, particularly recreational, comply with minimum size regulations. However, released fish mortality, modeled in the assessment at 27%, will continue to make the achievement of 30% and 40% SPR more difficult. (PDF contains 63 pages

Identifying research priorities to advance climate services

Climate services involve the timely production, translation, and delivery of useful climate data, information, and knowledge for societal decision-making. They rely on a range of expertise and are underpinned by research in climate and related sciences, sectoral applications (e.g., agriculture, water, health, energy, disasters), and a number of social science fields, including political science, sociology, anthropology, and economics. Feedback and engagement between these research communities and the communities involved in developing and/or using climate services is thus critical, ensuring that climate services are built on the best available science and providing researchers with guidance regarding priority challenges in the development of climate services that should warrant their attention. This paper reports the results of an international survey to gauge community perspective on research priorities for climate services, highlighting several areas in which respondents agree on the need for future work. The survey results indicate an overarching interest in research that can better connect climate information to users, particularly around the communication of climate information, the mapping of climate information needs, and the evaluation and prioritization of capacity building efforts. They also reveal significant interest in climate research to advance the skill of forecasts at subseasonal-to-seasonal scales – considered more broadly useful to decision makers than information at the end-of-century timescale – and to identify the drivers of extreme events. To support climate-related research, survey respondents underscore the need to continually develop and maintain the observational network. In analyzing these results, the paper offers guidance to researchers and to other members of the climate services community that may find these priorities useful in directing their own work to address the challenges posed by climate variability and change

Sums of two squares and a power

We extend results of Jagy and Kaplansky and the present authors and show that for all $k\geq 3$ there are infinitely many positive integers $n$, which cannot be written as $x^2+y^2+z^k=n$ for positive integers $x,y,z$, where for $k\not\equiv 0 \bmod 4$ a congruence condition is imposed on $z$. These examples are of interest as there is no congruence obstruction itself for the representation of these $n$. This way we provide a new family of counterexamples to the Hasse principle or strong approximation.Comment: 6 pages, to appear in the memorial volume "From Arithmetic to Zeta-Functions - Number Theory in Memory of Wolfgang Schwarz

Smart Materials as Intelligent Insulation

In order to provide a robust infrastructure for the transmission and distribution of electrical power, understanding and monitoring equipment ageing and failure is of paramount importance. Commonly, failure is associated with degradation of the dielectric material; therefore the introduction of a smart moiety into the material is a potentially attractive means of continual condition monitoring. It is important that any introduction of smart groups into the dielectric does not have any detrimental effect on the desirable electrical and mechanical properties of the bulk material. Initial work focussed on the introduction of fluorophores into a model dielectric system. Fluorescence is known to be a visible effect even at very low concentrations of active fluorophores and therefore was thought well suited to such an application. It was necessary both to optimise the active fluorophore itself and to determine the most appropriate manner in which to introduce the fluorophores into the insulating system. This presentation will describe the effect of introducing fluorophores into polymeric systems on the dielectric properties of the material and the findings thus far [1]. Alternative smart material systems will also be discussed along with the benefits and limitations of smart materials as electric field sensors

Performance Evaluation and Optimization of Math-Similarity Search

Similarity search in math is to find mathematical expressions that are similar to a user's query. We conceptualized the similarity factors between mathematical expressions, and proposed an approach to math similarity search (MSS) by defining metrics based on those similarity factors [11]. Our preliminary implementation indicated the advantage of MSS compared to non-similarity based search. In order to more effectively and efficiently search similar math expressions, MSS is further optimized. This paper focuses on performance evaluation and optimization of MSS. Our results show that the proposed optimization process significantly improved the performance of MSS with respect to both relevance ranking and recall.Comment: 15 pages, 8 figure

The narrow-line quasar NAB 0205+024 observed with XMM-Newton

The XMM-Newton observation of the narrow-line quasar NAB 0205+024 reveals three striking differences since it was last observed in the X-rays with ASCA. Firstly, the 2-10 keV power-law is notably steeper. Secondly, a hard X-ray flare is detected, very similar to that seen in I Zw 1. Thirdly, a strong and broad emission feature is detected with the bulk of its emission redward of 6.4 keV, and extending down to ~5 keV in the rest frame. The most likely explanation for the broad feature is neutral iron emission emitted from a narrow annulus of an accretion disc close to the black hole. The hard X-ray flare could be the mechanism which illuminates this region of the disc, allowing for the emission line to be detected. The combination of effects can be understood in terms of the `thundercloud' model proposed by Merloni & Fabian.Comment: 7 pages. Accepted for publication in MNRA

Kilohertz Quasi-Periodic Oscillation Peak Separation is not Constant in the Atoll Source 4U 1608-52

We present new Rossi X-ray Timing Explorer observations of the low-mass X-ray binary 4U 1608-52 during the decay of its 1998 outburst. We detect by a direct FFT method the existence of a second kilohertz quasi-periodic oscillation (kHz QPO) in its power density spectrum, previously only seen by means of the sensitivity-enhancing `shift and add' technique. This result confirms that 4U 1608-52 is a twin kHz QPO source. The frequency separation between these two QPO decreased significantly, from 325.5 +/- 3.4 Hz to 225.3 +/- 12.0 Hz, as the frequency of the lower kHz QPO increased from 470 Hz to 865 Hz, in contradiction with a simple beat-frequency interpretation. This change in the peak separation of the kHz QPOs is closely similar to that previously seen in Sco X-1, but takes place at a ten times lower average luminosity. We discuss this result within the framework of models that have been proposed for kHz QPO. Beat frequency models where the peak separation is identified with the neutron star spin rate, as well as the explanations previously proposed to account for the similar behavior of the QPOs in Sco X-1, are strongly challenged by this result.Comment: To appear in ApJL. AAS LaTex v4.0 (6 pages plus 3 postscript figures