3,454 research outputs found
On The Nature of Variations in the Measured Star Formation Efficiency of Molecular Clouds
Measurements of the star formation efficiency (SFE) of giant molecular clouds
(GMCs) in the Milky Way generally show a large scatter, which could be
intrinsic or observational. We use magnetohydrodynamic simulations of GMCs
(including feedback) to forward-model the relationship between the true GMC SFE
and observational proxies. We show that individual GMCs trace broad ranges of
observed SFE throughout collapse, star formation, and disruption. Low measured
SFEs (<<1%) are "real" but correspond to early stages, the true "per-freefall"
SFE where most stars actually form can be much larger. Very high (>>10%) values
are often artificially enhanced by rapid gas dispersal. Simulations including
stellar feedback reproduce observed GMC-scale SFEs, but simulations without
feedback produce 20x larger SFEs. Radiative feedback dominates among mechanisms
simulated. An anticorrelation of SFE with cloud mass is shown to be an
observational artifact. We also explore individual dense "clumps" within GMCs
and show that (with feedback) their bulk properties agree well with
observations. Predicted SFEs within the dense clumps are ~2x larger than
observed, possibly indicating physics other than feedback from massive (main
sequence) stars is needed to regulate their collapse.Comment: Fixed typo in the arXiv abstrac
Fragmentos de floresta riparia em áreas de cultivo de arroz sob diferentes manejos : diferenças através diversidade de himenópteros parasitoides
Hymenopteran parasitoids are important biological control agents in agroecosystems, and their diversity can be increased with habitat heterogeneity. Thus, the purpose of the study is to evaluate the influence of distance of rice-growing areas from natural fragment, type of crop management (organic and conventional) and crop stages (vegetative and reproductive stages) on parasitoids family diversity. The work took place in two irrigated rice crops, one with organic management (O.M.) and another one with conventional management (C.M.), in the municipality of Nova Santa Rita, RS, Brazil, during the 2013/2014 and 2014/2015 seasons. The parasitoids were collected with Malaise trap arranged at different distances in relation to the native vegetation surrounding the rice crop in both places. Specimens were collected twice a month from seeding until the rice harvest. Average abundance between management, distances and rice development were compared. The most abundant families were Platygastridae, Mymaridae, Encyrtidae, Eulophidae and Trichogrammatidae. Parasitoid average abundance was significantly higher on OM only in the second season. There was a negative correlation between distance from native vegetation and parasitoid abundance in C.M. areas. There were differences in the composition of the parasitoid assembly between the phenological stages of rice.Os himenĂłpteros parasitoides sĂŁo importantes agentes de controle biolĂłgico em agroecossistemas com sua diversidade variando de acordo com a heterogeneidade de habitat. Nesse sentido, o objetivo deste trabalho foi avaliar a influĂŞncia da distância de áreas com fragmentos de vegetação natural das áreas de cultivo de arroz, o tipo de manejo (orgânico ou convencional) e os estágios da cultura (vegetativo e reprodutivo) na diversidade de famĂlias de parasitoides. O trabalho foi conduzido em duas áreas com plantio de arroz irrigado, uma com manejo orgânico (MO) e outra com manejo convencional (CM), no municĂpio de Nova Santa Rita, RS, Brasil, durante a safra 2013/2014 e 2014/2015. Os parasitoides foram coletados com armadilha Malaise colocadas sob diferentes distâncias em relação a vegetação nativa circundante ao cultivo em ambas as áreas. Os espĂ©cimes foram coletados duas vezes ao mĂŞs da semeadura atĂ© a colheita. Foram comparadas a abundância mĂ©dia entre os manejos, distâncias e estágio de desenvolvimento do arroz. As famĂlias mais abundantes foram Platygastridae, Mymaridae, Encyrtidae, Eulophidae e Trichogrammatidae com suas abundâncias variando ao longo da safra. A abundância mĂ©dia de parasitoides foi significativamente maior no MO somente na segunda safra. Houve uma correlação negativa entre a distância da vegetação nativa e a abundância de parasitoides. Houve diferença na composição da assembleia de parasitoides entre os estágios fenolĂłgicos do arroz
Developing a Rapid Assessment Program for Student Success in Clinical Education
Successful management of the struggling student in the clinic relies heavily on the early identification of clinical performance deficits. CIs who directly observe student performance, actions and behaviors should aim for early and precise identification of difficulties, which should lead to initial discussions with the student. If the student\u27s struggles require involvement from the educational institution, the CI should promptly contact and collaborate with the DCE. Early communication with the DCE is beneficial, as they can provide support for CIs overwhelmed by the difficulties that accompany working with a challenging student. The DCE provides guidance on determining the depth of deficiencies, the student’s needs, and options for remediation. The Rapid Student Assessment and Review (R-STAR) Program was designed to facilitate a thorough and timely review of students’ Clinical Performance Instruments (CPIs)through partnership with expert clinical education faculty. With the increasing number of students in programs and the competing demands on Clinical Instructors (CIs), the successful management of the struggling student in the clinic relies heavily on the early identification of clinical performance deficits. Judicious review of CPI ratings and narratives is essential to identify discrepancies between the scores given and narrative comments. The R-STAR Program utilizes clinical partners who were carefully selected and specifically trained to review and provide feedback to students and CIs, while identifying those individuals with issues requiring the DCE to prioritize and address. This session describes how to develop an efficient and effective program that may be implemented to help facilitate the timely management of student assessments in clinical education to enhance success
World Species of the Genus Chromoteleia Ashmead (Hymenoptera, Platygastridae, Scelioninae)
The genus Chromoteleia was originally described by William H. Ashmead (1893), based on the colorful type species Chromoteleia semicyanea from the Caribbean island of Saint Vincent. Currently, six species have been recorded from the New World and a single species from Africa. One fossil species, C. theobaldi Maneval, was reported from Baltic amber (from 40~60 mya), but the status of this species is not clear. These creatures are parasites of insect eggs, but which host they attack is still unclear. Since its original description Chromoteleia has never been comprehensively reviewed. In this study, a total of 27 species are recognized worldwide, of which 21 are new to science. All species are described and illustrated. Several important morphological characters are provided for the identification of the species of Chromoteleia and the geographical distribution records of the genus are expanded to 29 countries in Central and South America, the Caribbean, and Africa. The documentation of the species diversity is crucial to the understanding of the evolution and interrelationships in this genus, as well as informing conservation policies
Calixomeria, a new genus of Sceliotrachelinae (Hymenoptera, Platygastridae) from Australia
Calixomeria lasallei gen. n. et sp. n. is described as a new genus and species of Sceliotrachelinae. Calixomeria most closely resembles genera of the Aphanomerus-cluster but possesses several characters that readily separate it from other sceliotracheline genera. The key of Masner and Huggert (1989) is modified to accommodate Calixomeria, and the relationship of the genus to other members of the subfamily is discussed
New species of Idris Förster (Hymenoptera, Platygastroidea) from southeast Asia, parasitoids of the eggs of pholcid spiders (Araneae, Pholcidae)
Four new species of the genus Idris Förster (Hymenoptera: Platygastroidea), reared from the eggs of pholcid spiders (Araneae: Pholcidae) in southeast Asia are described on the basis of external morphology and the barcode region of the mitochondrial COI gene. The new species and their hosts are: I. badius Johnson &amp; Chen, sp. n. (ex Nipisa phyllicola (Deeleman-Reinhold), Panjange hamiguitan Huber), I. balteus Johnson &amp; Chen, sp. n. (ex Panjange camiguin Huber), I. curtus Johnson &amp; Chen, sp. n. (ex Calapnita nunezae Huber, Panjange camiguin Huber, Tissahamia bukittimah (Huber), Uthina luzonica Simon), and I. fusciceps (ex Belisana khaosok Huber)
The Amateur Sky Survey Mark III Project
The Amateur Sky Survey (TASS) is a loose confederation of amateur and
professional astronomers. We describe the design and construction of our Mark
III system, a set of wide-field drift-scan CCD cameras which monitor the
celestial equator down to thirteenth magnitude in several passbands. We explain
the methods by which images are gathered, processed, and reduced into lists of
stellar positions and magnitudes. Over the period October, 1996, to November,
1998, we compiled a large database of photometric measurements. One of our
results is the "tenxcat" catalog, which contains measurements on the standard
Johnson-Cousins system for 367,241 stars; it contains links to the light curves
of these stars as well.Comment: 20 pages, including 4 figures; additional JPEG files for Figures 1,
2. Submitted to PAS
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