The match/mismatch hypothesis and the feeding success of fish larvae in ice-covered southeastern Hudson Bay

We studied the synchronism between the seasonal occurrence of fish larvae and their prey in ice-covered southeastern Hudson Bay, Canada, in spring 1988, 1989 and 1990. Arctic cod #Boreogadus saida and sand lance #Ammodytes sp. larvae hatched several weeks before ice break-up and fed primarily on copepod nauplii. The timing of 50% yolk resorption was the same every year (11 to 18 May for Arctic cod and 5 to 11 June for sand lance) but the availability of copepod nauplii varied substantially between years, both in magnitude (7-fold) and timing (4 to 6 wk). Interannual differences in the under-ice abundance of nauplii were linked to variations in the abundance of female cyclopoid copepods, and appeared unrelated to the timing of the ice-algal or phytoplankton blooms. Interannual differences (2- to 4-fold) in the feeding success of fish larvae (percent feeding incidence at length and mean feeding ratio at length) were related to the availability of copepod nauplii. Consistent with the match/mismatch hypothesis, the fixity of the spawning season in relation to a variable cycle of prey abundance accounted for the observed variations in feeding success and apparent growth (length at date) of fish larvae. Yet, in this particular ecosystem, a match or mismatch between Arctic cod or sand lance larvae and their prey may depend more on the dynamics of cyclopoid copepods during the previous winter than on the timing of the spring algal blooms. (Résumé d'auteur

Springtime sensible heat, nutrients and phytoplankton in the northwater Polynya, Canadian Arctic

Sampling was conducted in the Northwater Polynya (between 70°20' and 77°20'N), on 17 and 19 May 1991. At each of the 14 sampling stations, CTD profiles were recorded from surface to bottom and nutrients and phytoplankton were determined at four depths down to 30 m. The presence, between 220 and 400 m, of water temperatures > 0°C is an indication that, in winter, the West Greenland Current enters the Northwater along the Greenland coast. The worm water is progressively mixed as it moves northward and eastward. It was thus hypothesized that sensible heat is as an important factor in keeping the Northwater open. Measured chemical and biological variables were quite homogeneous on the vertical down to 30 m and they showed longitudinal gradients. From east to west, the average concentrations of nutrients increased (phosphate from 0.5 to 1.4, nitrate from 3.7 to 10.8, and silicate from 6.8 to 34.2 mmol/m3), whereas the areal concentrations of phytoplankton decreased (from 47 to 9 x 10 to the ninth power cells/m2 and from 506 to 50 mg Chla/m2). Nutrient ratios indicated possible silicon deficiency in the easternmost part of the polynya. Diatoms dominated cell numbers (greater or equal to 87% at all stations). Concentrations of the three nutrients were inversely correlated with both Chla and cell numbers. The Y-intercepts of regressions of Chla on nutrients provided an estimate of potential maximum biomass in the upper 30 m, which was ca. 600 mg Chla/m2, or lower if there was silicon limitation. The overall picture was that of a diatom bloom, moving westward and progressively exhausting the nutrients. Initiation of the bloom appeared to have been linked to the absence of sea ice. A source of heat for this would have been the above sensible-heat process. (Résumé d'auteur

Impact of freshwater on a subarctic coastal ecosystem under seasonal sea ice (southeastern Hudson Bay, Canada) : 3. Feeding success of marine fish larvae

We monitored the feeding success (percent feeding incidence at length and mean feeding ratio at length) of Arctic cod (#Boreogadus saida) and sand lance (#Ammodytes sp. larvae in relation to prey density, light, temperature and potential predator density under the ice cover of southeastern Hudson Bay in the spring of 1988, 1989 and 1990. Both prey density and light limited larval fish feeding. The relationship between feeding success and actual food availability (nauplii density x irradiance) was adequately described by an Ivlev function which explained 64 and 76% of the variance in Arctic cod and sand lance feeding success respectively. By affecting both prey density and irradiance, the thickness of the Great Whale River plume (as defined by the depth of the 25 isohaline) was the main determinant of prey availability. Arctic cod and sand lance larvae stopped feeding when the depth of the 25 isohaline exceeded 9 m. Limitation of feeding success attributable to freshwater inputs occurred exclusively in 1988, the only time when the depth of the 25 isohaline exceeded the 9 m threshold. The close dependence of larval fish feeding success on the timing of the freshet and plume dynamics suggests a direct link between climate and survival of Arctic cod and sand lance larvae. The actual impact of climate fluctuations and/or hydro-electric developments on recruitment will depend on the fraction of the larval dispersal area of the two species that is affected by river plumes. (Résumé d'auteur

Virginia Community College System Online Student Success: Best Practices and Sustainable Change

Online learning has an increasingly greater presence in the higher education landscape. Students are able to earn a degree in fully online programs and take courses in modalities that offer the necessary convenience to balance multiple life priorities. The flexibility that online courses offer is valuable for adult learners with young children, students with disabilities including invisible and non-physical disabilities, or populations who must work to support families while pursuing an education. For these populations, community colleges play an important role in providing access to education as they enroll a greater number of adult students and have a higher percentage of minority students for whom having an online option is important. This broad mission of access is both commendable and challenging. The challenge is how to ensure success and increase completion while navigating a switch to online learning. This mixed method study combines three pieces of data and information to develop a sustainable online student success plan for the Virginia Community College System (VCCS). First, the study includes a literature review on best practices related to online student success and sustainable change management. Second, the study provides a detailed examination of student success web portals deployed by institutions. And lastly, the study included a survey and focus group interviews with VCSS administrators, faculty, and staff. The findings led to recommendations for a sustainable implementation plan to ensure online student success

Factors that Influence Teachers’ Views on Standardized Tests

The central aim of this study was to explore K-12 teachers’ (N = 183) attitudes about standardized tests as a function of experience, instructional level, student population, and type of school. The Teachers’ Views on Standardized Tests Questionnaire was developed to assess teachers’ perceptions of the impact of standardized tests on practice. All survey items were intended to measure a facet of teachers’ attitudes regarding the necessity of standardized tests and their influence on best practices. Findings from this study indicated that special education and inclusion teachers viewed standardized tests as more negatively influencing instruction than general education teachers. There were also significant differences by instructional level and type of school (i.e., public vs. independent). Compared to elementary teachers, middle and high school teachers’ views were more negative, and public school educators perceived standardized assessments as having a more negative influence on instruction than teachers in independent schools. Finally, elementary school teachers reported that the standards of learning were more appropriate in contrast to middle and high school teachers

Mediation of supersymmetry breaking in extra dimensions

We review the mechanisms of supersymmetry breaking mediation that occur in sequestered models, where the visible and the hidden sectors are separated by an extra dimension and communicate only via gravitational interactions. By locality, soft breaking terms are forbidden at the classical level and reliably computable within an effective field theory approach at the quantum level. We present a self-contained discussion of these radiative gravitational effects and the resulting pattern of soft masses, and give an overview of realistic model building based on this set-up. We consider both flat and warped extra dimensions, as well as the possibility that there be localized kinetic terms for the gravitational fields.Comment: LaTex, 15 pages; brief review prepared for MPLA. v2: minor correction

FW propagation and absorption in reactor plasmas in the ICR frequency range at the quasiperpendicular propagation

On the base of the numerical model, taking into account the strong transverse and longitudinal dispersion of plasma, the absorption and dispersion of the Fast Mode of fast magnetosonic wave (FW) near ICR harmonics ω=nωci at the quasiperpendicular propagation regime were investigated. It was shown that in the region of small longitudinal refractive index values NII there appears the additional absorption that provides the value of optical thickness τ being constant in the entire region of additional absorption. At first and second harmonics the additional absorption can be interesting for FW plasma heating in the reactor-size devices. For higher harmonics it can be important for HF diagnostic purposes and for investigation of astrophysical plasmas.Дисперсия и поглощение быстрой моды быстрой магнитозвуковой волны (БВ) в области ионных циклотронных гармоник ω=nωci исследованы на основе численной модели, учитывающей сильную продольную и поперечную дисперсии плазмы. Показано, что в области малых продольных замедлений появляется дополнительное поглощение, которое обеспечивает постоянное значение оптической толщи во всей области проявления дополнительного поглощения. На первой и второй гармониках такое поглощение может быть интересно для нагрева реакторной плазмы. Для более высоких гармоник оно может быть важным для ВЧ-диагностики, а также для исследования астрофизической плазмы.Дисперсія і поглинання швидкої моди швидкої магнітозвукової хвилі (ШХ) в області іонних циклотронних гармонік ω=nωci досліджені на основі чисельної моделі, що враховує сильну поздовжню і поперечну дисперсії плазми. Показано, що в області малих поздовжніх уповільнень з'являється додаткове поглинання, яке забезпечує постійне значення оптичної товщі у всій області прояви додаткового поглинання. На першій і другій гармоніках таке поглинання може бути цікавим для нагріву реакторної плазми. Для більш високих гармонік воно може бути важливим для ВЧ-діагностики, а також для дослідження астрофізичної плазми

The impact of poor metabolic health on aggressive breast cancer: adipose tissue and tumor metabolism

Obesity and type 2 diabetes are chronic metabolic diseases that impact tens to hundreds of millions of adults, especially in developed countries. Each condition is associated with an elevated risk of breast cancer and with a poor prognosis after treatment. The mechanisms connecting poor metabolic health to breast cancer are numerous and include hyperinsulinemia, inflammation, excess nutrient availability, and adipose tissue dysfunction. Here, we focus on adipose tissue, highlighting important roles for both adipocytes and fibroblasts in breast cancer progression. One potentially important mediator of adipose tissue effects on breast cancer is the fibroblast growth factor receptor (FGFR) signaling network. Among the many roles of FGFR signaling, we postulate that key mechanisms driving aggressive breast cancer include epithelial-to-mesenchymal transition and cellular metabolic reprogramming. We also pose existing questions that may help better understand breast cancer biology in people with obesity, type 2 diabetes, and poor metabolic health

ACQUIRING SEISMIC DATA IN THE NORTH-EAST OF ITALY: THE OGS-CRS EXPERIENCE IN USING THE ANTELOPE SOFTWARE SUITE

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