971 research outputs found
Transition probabilities in OH A 2 sigma + - X 2 pi i: Bands with v prime = 0 and 1, v double prime = 0 to 4
Experimental results for relative vibrational band transition probabilities for v prime = 0 and 1, and v double prime = 0 to 4 in the A-X electronic system of OH are presented. The measurements, part of a larger set involving v prime = 0 to 4 and v double prime = 0 to 6, were made using spectrally dispersed laser-induced fluorescence (LIF) in the burnt gases of a flame. These Einstein coefficients will be useful in dynamics experiments for quantitative LIF determinations of OH radical concentrations in high v double prime
An interoperable signaling solution between SIP and H.323
The Session Initiation Protocol and H.323 dominate the Voice over IP world. These signaling protocols are responsible for call setup and call tear down by IP telephony solutions. This project analyses and discusses the underlying H.323 and SIP interoperability issues and intends to build a scalable solution for the interoperability of these protocols. The gateway maps the call sequences between the two protocols. A test scenario establishes a barrage of call setup and tear down requests to test the scalability of any H.323/SIP interoperability solution.Telkom Siemens, THRI
An Interoperable signaling solution for IP-based Next Generation Networks
Current VoIP signaling protocols are interoperable with the PSTN SS7 via H.323-to-SS7 or SIP-to-SS7 gateways. As we move toward the Next Generation Network, the PSTN falls away and we work toward carrier-grade VoIP interoperability between H.323, SIP, and other future VoIP signaling protocols. This paper present a Work in Progress to design and implement a solution based on the Internet Protocol itself.Telkom, Siemens, THRI
Students’ Perspectives on Social Studies Teachers’ Views on Immigration and Nationalism
This mixed-methods study examines students’ perspectives on their high school social studies teachers’ views and pedagogy surrounding the issues of immigration, nationalism, and patriotism within the classroom. The article is based within the framework of critical pedagogy, particularly critical nationalism. The sample (N=58) comes from students enrolled in an introductory education course at a university in the American Southeast. The quantitative data revealed students believed their teachers tended towards more inclusive views towards immigration overall, but they were more exclusive towards undocumented immigration. They also tended to have high levels of patriotism and more moderate levels of nationalism. The qualitative data revealed a lack of discussion on immigration, which related to a larger fear of discussing contemporary issues of controversy within the classroom. This study has strong relevance for both educators and teachers educators in critically and thoroughly examining issues such as nationalism and immigration particularly in more conservative settings like the American Southeast where these topics are often given little more than a cursory overview.
Ages of young stars
Determining the sequence of events in the formation of stars and planetary
systems and their time-scales is essential for understanding those processes,
yet establishing ages is fundamentally difficult because we lack direct
indicators. In this review we discuss the age challenge for young stars,
specifically those less than ~100 Myr old. Most age determination methods that
we discuss are primarily applicable to groups of stars but can be used to
estimate the age of individual objects. A reliable age scale is established
above 20 Myr from measurement of the Lithium Depletion Boundary (LDB) in young
clusters, and consistency is shown between these ages and those from the upper
main sequence and the main sequence turn-off -- if modest core convection and
rotation is included in the models of higher-mass stars. Other available
methods for age estimation include the kinematics of young groups, placing
stars in Hertzsprung-Russell diagrams, pulsations and seismology, surface
gravity measurement, rotation and activity, and lithium abundance. We review
each of these methods and present known strengths and weaknesses. Below ~20
Myr, both model-dependent and observational uncertainties grow, the situation
is confused by the possibility of age spreads, and no reliable absolute ages
yet exist. The lack of absolute age calibration below 20 Myr should be borne in
mind when considering the lifetimes of protostellar phases and circumstellar
material.Comment: Accepted for publication as a chapter in Protostars and Planets VI,
University of Arizona Press (2014), eds. H. Beuther, R. Klessen, C.
Dullemond, Th. Hennin
Low-mass members of the young cluster IC 4665 and pre-main-sequence lithium depletion
We have used fibre spectroscopy to establish cluster membership and examine
pre-main-sequence (PMS) lithium depletion for low-mass stars (spectral types F
to M) in the sparse young (~30 Myr) cluster IC 4665. We present a filtered
candidate list of 40 stars that should contain 75 per cent of single cluster
members with V of 11.5 to 18 in the central square degree of the cluster.
Whilst F- and G-type stars in IC 4665 have depleted little or no lithium, the
K- and early M-type stars have depleted more Li than expected when compared
with similar stars in other clusters of known age. An empirical age estimate
based on Li-depletion among the late-type stars of IC 4665 would suggest it is
older than 100 Myr. This disagrees entirely with ages determined either from
the nuclear turn-off, from isochronal matches to low-mass stars or from the
re-appearance of lithium previously found in much lower mass stars (the
``lithium depletion boundary''). We suggest that other parameters besides age,
perhaps composition or rotation, are very influential in determining the degree
of PMS Li-depletion in stars with M greater than 0.5 Msun. Further work is
required to identify and assess the effects of these additional parameters,
particularly to probe conditions at the interface between the sub-photospheric
convection zone and developing radiative core. Until then, PMS Li depletion in
F- to early M-type stars cannot be confidently used as a precise age indicator
in young clusters, kinematic groups or individual field stars.Comment: Accepted for publication in MNRA
X-ray Emission From Nearby M-dwarfs: the Super-saturation Phenomenon
A rotation rate and X-ray luminosity analysis is presented for rapidly
rotating single and binary M-dwarf systems. X-ray luminosities for the majority
of both single & binary M-dwarf systems with periods below days
(equatorial velocities, V 6 km~s) are consistent with the
current rotation-activity paradigm, and appear to saturate at about
of the stellar bolometric luminosity. The single M-dwarf data show tentative
evidence for the super-saturation phenomenon observed in some ultra-fast
rotating ( 100 km~s) G & K-dwarfs in the IC 2391, IC 2602 and Alpha
Persei clusters. The IC 2391 M star VXR60b is the least X-ray active and most
rapidly rotating of the short period (P 2 days) stars considered
herein, with a period of 0.212 days and an X-ray activity level about 1.5 sigma
below the mean X-ray emission level for most of the single M-dwarf sample. For
this star, and possibly one other, we cautiously believe that we have
identified the first evidence of super-saturation in M-dwarfs. If we are wrong,
we demonstrate that only M-dwarfs rotating close to their break up velocities
are likely to exhibit the super-saturation effect at X-ray wavelengths.Comment: 12 pages, 4 figures, accepted by MNRA
The Overcoming Disadvantage in Early Childhood Study: Evaluation of the Australian Literacy and Numeracy Foundation’s Early Language and Literacy Program. Summary report
This report provides a summary of the completed Overcoming Disadvantage in Early Childhood (ODEC) longitudinal research study. The study was designed to evaluate the Australian Literacy and Numeracy Foundation’s (ALNF) Early Language and Literacy (EL&L) program by answering the research question: What is the effect of the EL&L program on the development of language and literacy skills in preschool aged children? An integral component of this study was the development of the Early Language and Literacy Developmental Index (ELLDI), a new tool to measure oral language and literacy learning. The development of the ELLDI was based on the recognised need for a fit for purpose early childhood best practice measure of oral language and literacy. This summary report highlights the demonstrated capacity of the EL&L program to close the language and literacy achievement gap for children who participate in the program, particularly those from disadvantaged backgrounds. It also encapsulates the successful development of the ELLDI and the ELLDI scale to accurately measure and map children’s language and literacy development, to inform teaching and learning
The Overcoming Disadvantage in Early Childhood Study: Evaluation of the Australian Literacy and Numeracy Foundation’s Early Language and Literacy Program. Final Report
The Overcoming Disadvantage in Early Childhood (ODEC) study is a longitudinal evaluation of the Australian Literacy and Numeracy Foundation’s (ALNF) Early Language and Literacy (EL&L) program. The study was designed to answer the research question: What is the effect of the EL&L program on the development of language and literacy skills in preschool aged children? An integral component of this study was to develop a new measure of oral language and literacy - the Early Language and Literacy Developmental Index (ELLDI). The ELLDI was developed in recognition of the need for a best practice measure of oral language and literacy that was fit for purpose. This report documents the sum of work completed across the duration of the study from 2018-2022. The design of the study was based on the principles of a longitudinal outcome evaluation and had three components: a) design of the outcome measure: the ELLDI; b) interim results and recommendations; and c) final results, recommendations and reporting
High carbon burial rates by small ponds in the landscape
Temperate ponds may be important sinks and sources of greenhouse gases but just how quickly ponds bury carbon (C) is poorly understood. We derived – to the best of our knowledge – the first organic carbon (OC) burial rates for small ponds of known age by digging out the whole sediment from ponds, and determined that the average C burial rate was 142 g m −2 yr −1 , with a range of 79–247 g m −2 yr −1 , depending on the ponds' vegetation. Burial rates in the ponds were 20–30 times higher than rates estimated for many other habitat types, such as woodlands or grasslands, and higher than those of other natural wetlands. Although small ponds occupy a very small proportion of the landscape as compared to these other habitats, their high OC burial rates result in comparable annual OC burial overall. Ponds are easy to create, can fit in with other land uses, and are a globally ubiquitous habitat. Our results indicate that ponds have the potential to be a very useful additional tool for mitigating C emissions
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