129 research outputs found
What Was Really Accomplished Today? Mathematics Content Specialists Observe a Class for Prospective K-8 Teachers
One of the important activities mathematics teacher educators engage in is the development of teachers at both the in-service and pre-service levels. Also of importance is the professional development of these professional developers. In the summer of 2004, a summer institute was held that allowed mathematics teacher educators watch the teaching of a mathematics content course for prospective K-8 teachers. This paper examines the manner in which a specific group of mathematics content specialists experienced this professional development
PF191012 Myszyniec - highest Orionid meteor ever recorded
On the night of Oct 18/19, 2012 at 00:23 UT a -14.7 mag Orionid fireball
occurred over northeastern Poland. The precise orbit and atmospheric trajectory
of the event is presented, based on the data collected by five video and one
photographic Polish Fireball Network (PFN) stations. The beginning height of
the meteor is 168.4 +\- 0.6 km which makes the PF191012 Myszyniec fireball the
highest ever observed, well documented meteor not belonging to the Leonid
shower. The ablation became the dominant source of light of the meteor at a
height of around 115 km. The thermalization of sputtered particles is suggested
to be the source of radiation above that value. The transition height of 115 km
is 10-15 km below the transition heights derived for Leonids and it might
suggest that the material of Leonids should be more fragile and have probably
smaller bulk density than in case of Orionids.Comment: 5 pages, 5 figures, accpeted for publication in Astronomy &
Astrophysic
The status of shark and ray fishery resources in the Gulf of California: applied research to improve management and conservation
Seasonal surveys were conducted during 1998–1999 in Baja California, Baja California Sur, Sonora, and Sinaloa to determine the extent and activities of artisanal elasmobranch fisheries in the Gulf of California. One hundred and forty–seven fishing sites, or camps, were documented, the majority of which (n = 83) were located in Baja California Sur. Among camps with adequate fisheries information, the great majority (85.7%) targeted elasmobranchs during some part of the year. Most small, demersal sharks and rays were landed in mixed species fisheries that also targeted demersal teleosts, but large sharks were usually targeted in directed drift gillnet or, to a lesser extent, surface longline fisheries. Artisanal fishermen were highly opportunistic, and temporally switched targets depending on the local productivity of teleost, invertebrate, and elasmobranch fishery resources. Major fisheries for small sharks ( 1.5 m, “tiburón”) were minor components of artisanal elasmobranch fisheries in Sonora and Sinaloa, but were commonly targeted during summer and early autumn in Baja California and Baja California Sur. The pelagic thresher shark (Alopias pelagicus) and silky shark (Carcharhinus falciformis) were most commonly landed in Baja California, whereas a diverse assemblage of pelagic and large coastal sharks was noted among Baja California Sur landings. Rays dominated summer landings in Baja California and Sinaloa, when elevated catch rates of the shovelnose guitarfish (Rhinobatos productus, 13.2 individuals/vessel/trip) and golden cownose ray (Rhinoptera steindachneri, 11.1 individuals/vesse/trip) primarily supported the respective fisheries. The Sonoran artisanal elasmobranch fishery was the most expansive recorded during this study, and rays (especially R. productus) dominated spring and summer landings in this state. Seasonal catch rates of small demersal sharks and rays were considerably greater in Sonora than in other surveyed states. Many tiburón populations (e.g., C. leucas, C. limbatus, C. obscurus, Galeocerdo cuvier) have likely been overfished, possibly shifting effort towards coastal populations of cazón and rays. Management recommendations, including conducting demographic analyses using available life history data, determining and protecting nursery areas, and enacting seasonal closures in areas of elasmobranch aggregation (e.g., reproduction, feeding), are proposed. Without effective, enforceable management to sustain or rebuild targeted elasmobranch populations in the Gulf of California, collapse of many fisheries is a likely outcome. (PDF contains 243 pages
El estado actual de los tiburones y rayas sujectos a explotaciĂłn comercial en el Golfo de California: una investigaciĂłn aplicada al mejoramiento de su manejo pesquero y conservaciĂłn
Se realizaron prospecciones estacionales durante 1998–1999 en Baja California, Baja California Sur, Sonora y Sinaloa para determinar la dimensiĂłn y las actividades de las pesquerĂas artesanales de elasmobranquios dentro del Golfo de California. Ciento cuarenta y siete campamentos o sitios pesqueros fueron documentados, la mayorĂa de los cuales (n= 83) fueron localizados en Baja California Sur. Entre los campamentos con informaciĂłn pesquera adecuada, la gran mayorĂa (85.7%) pescaron elasmobranquios en algĂşn momento del año. La mayorĂa de los pequeños tiburones y rayas demersales fueron capturados en pesquerĂas multiespecĂficas, las cuales tambiĂ©n tienen como objetivo teleĂłsteos, pero los grandes tiburones fueron capturados generalmente por pesquerĂas de redes agalleras a la deriva dirigidas a ellos, o en menor grado, por pesquerĂas de palangre de superficie. Los pescadores artesanales presentaron un comportamiento altamente oportunĂstico y temporalmente cambiaban de especie objetivo dependiendo de la productividad de los recursos pesqueros locales de especies de escama, invertebrados y elasmobranquios. Las mayores pesquerĂas de pequeños tiburones (≤1.5 m, “cazĂłn”) se documentaron en Baja California, Sonora, y Sinaloa durante la primavera y adicionalmente durante otoño e invierno en Sonora. Los tiburones del genero Mustelus (Mustelus spp) dominaron los desembarques de cazĂłn en los
estados norteños, mientras que los tiburones martillo juveniles (Sphyrna lewini) sostuvieron la pesquerĂa en Sinaloa. Los grandes tiburones (> 1.5 m, “tiburĂłn”) fueron componente menor de las pesquerĂas artesanales de elasmobranquios en Sonora y Sinaloa, pero comĂşnmente fueron capturados en verano y principios de otoño en Baja California y Baja California Sur. El tiburĂłn zorro pelágico (Alopias pelagicus) y el tiburĂłn piloto (Carcharhinus falciformis) fueron comĂşnmente desembarcados en Baja California, mientras que un diverso ensamble de tiburones pelágicos y grandes costeros fueron observados en los desembarques de Baja California Sur. Las rayas dominaron los desembarques en verano en Baja California y Sinaloa, sostenidas principalmente por elevadas tasas de captura de la guitarra comĂşn (Rhinobatos productus, 13.2 individuos/embarcaciĂłn/viaje) y del tecolote (Rhinoptera steindachneri, 11.1 individuos/embarcaciĂłn/viaje). La pesquerĂa de rayas de Sonora fue la más extensamente documentada durante este estudio y las rayas (especialmente R. productus) dominaron los desembarques en primavera y verano en este estado. Las tasas de captura estacionales de pequeños tiburones demersales y rayas fueron considerablemente mayores en Sonora que en los otros estados prospectados. Numerosas poblaciones de tiburĂłn
(p. ej. C. leucas, C. limbatus, C. obscurus, Galeocerdo cuvier) han sido probablemente sobreexplotados, lo que posiblemente este causando un cambio en el esfuerzo hacia las poblaciones de cazĂłn y rayas costeros. Se proponen recomendaciones de manejo, incluyendo conducir análisis demográficos empleando la informaciĂłn de historias de vida disponible, localizando y protegiendo áreas de crianza e implementando temporadas de veda estacional en las áreas de mayor concentraciĂłn de elasmobranquios (p. ej. alimentaciĂłn, reproducciĂłn). Sin un manejo pesquero efectivo, vigilado, para sostener o reconstruir las poblaciones de elasmobranquios sujetas a explotaciĂłn comercial dentro del Golfo de California, el colapso de las pesquerĂas es un evento probable. (PDF contains 261 pages
Isospin dependence of relative yields of and mesons at 1.528 AGeV
Results on and meson production in Ru +
Ru and Zr + Zr collisions at a beam kinetic
energy of 1.528 GeV, measured with the FOPI detector at GSI-Darmstadt, are
investigated as a possible probe of isospin effects in high density nuclear
matter. The measured double ratio ()/() is
compared to the predictions of a thermal model and a Relativistic Mean Field
transport model using two different collision scenarios and under different
assumptions on the stiffness of the symmetry energy. We find a good agreement
with the thermal model prediction and the assumption of a soft symmetry energy
for infinite nuclear matter while more realistic transport simulations of the
collisions show a similar agreement with the data but also exhibit a reduced
sensitivity to the symmetry term.Comment: 5 pages, 3 figures. accepted for publication in Phys. Rev.
Charged pion production in Ru+Ru collisions at 400A and 1528A MeV
We present transverse momentum and rapidity spectra of charged pions in
central Ru + Ru collisions at 400 and 1528 MeV. The data exhibit enhanced
production at low transverse momenta compared to the expectations from the
thermal model that includes the decay of -resonances and thermal
pions. Modification of the -spectral function and the Coulomb
interaction are necessary to describe the detailed shape of the transverse
momentum spectra. Within the framework of the thermal model, the freeze-out
radii of pions are similar at both beam energies. The IQMD model reproduces the
shapes of the transverse momentum and rapidity spectra of pions, but the
predicted absolute yields are larger than in the measurements, especially at
lower beam energy.Comment: 12 pages, 11 figure
Two-proton small-angle correlations in central heavy-ion collisions: a beam-energy and system-size dependent study
Small-angle correlations of pairs of protons emitted in central collisions of
Ca + Ca, Ru + Ru and Au + Au at beam energies from 400 to 1500 MeV per nucleon
are investigated with the FOPI detector system at SIS/GSI Darmstadt.
Dependences on system size and beam energy are presented which extend the
experimental data basis of pp correlations in the SIS energy range
substantially. The size of the proton-emitting source is estimated by comparing
the experimental data with the output of a final-state interaction model which
utilizes either static Gaussian sources or the one-body phase-space
distribution of protons provided by the BUU transport approach. The trends in
the experimental data, i.e. system-size and beam energy dependences, are well
reproduced by this hybrid model. However, the pp correlation function is found
rather insensitive to the stiffness of the equation of state entering the
transport model calculations.Comment: 9 pages, 8 figures, accepted at Eur. Phys. Journ.
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