1,760 research outputs found
Protoplanetary gas disks in the far infrared
The physical and chemical conditions in young protoplanetary disks set the
boundary conditions for planet formation. Although the dust in disks is
relatively easily detected as a far-IR photometric ``excess'' over the expected
photospheric emission, much less is known about the gas phase. It seems clear
that an abrupt transition from massive optically thick disks (gas-rich
structures where only ~1% of the total mass is in the form of dust) to tenuous
debris disks almost devoid of gas occurs at ~10^7 years, by which time the
majority of at least the giant planets must have formed. Indeed, these planets
are largely gaseous and thus they must assemble before the gas disk dissipates.
Spectroscopic studies of the disk gas content at different evolutive stages are
thus critical. Far-IR water vapor lines and atomic fine structure lines from
abundant gas reservoirs (e.g., [OI]63um, [SI]56um, [SiII]34um) are robust
tracers of the gas in disks. Spectrometers on board Herschel will detect some
of these lines toward the closest, youngest and more massive protoplanetary
disks. However, according to models, Herschel will not reach the required
sensitivity to (1) detect the gas residual in more evolved and tenuous
transational disks that are potentially forming planets and (2) detect the gas
emission from less massive protoplanetary disks around the most numerous stars
in the Galaxy (M-type and cooler dwarfs). Both are unique goals for
SPICA/SAFARI. Besides, SAFARI will be able to detect the far-IR modes of water
ice at ~44 and ~62um, and thus allow water ice to be observed in many
protoplanetary systems and fully explore its impact on planetary formation and
evolution.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Vanderbush, Alvin W Oral History Interview: Retired Faculty and Administrators of Hope College
These records include the transcripts of oral histories conducted with retired faculty members of Hope College
Organizational Monitoring Systems and Student Academic Achievement
Organizational Monitoring Systems and Student Academic Achievement
By Adam Swinyard
The current context of K-12 education emphasizes a strong focus on standardized test results to inform school improvement planning. Concerns about this phenomena center around the methodology used to determine actions intended to improve student achievement. Some educational experts suggest many schools rely solely on test results to develop school improvement plans (SIPs). Subsequently, solutions often address symptoms rather than foundational issues. As a result, schools fall into a cycle of selecting new initiatives that do not produce sustainable improvements. The concept of becoming a learning organization by using a monitoring system to inform systems thinking is presented as an alternative approach. Although empirical evidence exists that supports OL in schools, studies on the prevalence, composition, and impact in American K-12 education is limited. This study is intended to assess the relevance of OL in the context of high stakes accountability experienced by American schools.
The findings provide evidence that organizational learning practices related to organizational monitoring is linked to student academic achievement. Multiple aspects of organizational monitoring were investigated to determine levels of statistical significance. Practices related to the collection and use of data based on school attributes were correlated with changes in the percentage of students proficient in reading and math. Results provided evidence leading to the rejection of the null hypothesis aligned to each of the research questions. Secondary analysis indicated student demographics were not a substantial confounding variable and that the research survey demonstrated a reasonable level of validity. The study supports organizational learning theory suggesting systems thinking and organizational monitoring is linked to desired organizational outcomes. Findings provided efficacious evidence that organizational learning practices related to organizational monitoring are applicable in the context of American schools
Herschel/SPIRE observations of water production rates and ortho-to-para ratios in comets
This paper presents Herschel/SPIRE (Spectral and Photometric Imaging Receiver) spectroscopic observations of several fundamental rotational ortho- and para-water transitions seen in three Jupiter-family comets and one Oort-cloud comet. Radiative transfer models that include excitation by collisions with neutrals and electrons, and by solar infrared radiation, were used to produce synthetic emission line profiles originating in the cometary coma. Ortho-to-para ratios (OPRs) were determined and used to derived water production rates for all comets. Comparisons are made with the water production rates derived using an OPR of 3. The OPR of three of the comets in this study is much lower than the statistical equilibrium value of 3; however they agree with observations of comets 1P/Halley and C/2001 A2 (LINEAR), and the protoplanetary disc TW Hydrae. These results provide evidence suggesting that OPR variation is caused by post-sublimation gas-phase nuclear-spin conversion processes. The water production rates of all comets agree with previous work and, in general, decrease with increasing nucleocentric offset. This could be due to a temperature profile, additional water source or OPR variation in the comae, or model inaccuracies
Veldman, Harold E and Pearl Oral History Interview: Old China Hands Oral History Project
This project was made possible by a grant from the Youthgrants 1n the Humanities Program of the National Endowment for the Humanities, a Federal agency established by Congress to promote research, education,and public activity in the humanities
Activities, Interests, And Opinions Of Online Shoppers And Non-Shoppers
Internet shopping represents the launch of a new industry with corresponding levels of praise and concern. It is both the “golden child” for innovative net users, and the “evil empire” for anxious brick-and-mortar retailers. Online purchasing is growing at a dramatic rate yet the expectation for an explosion of Internet shopping has not occurred; its market share is small, at just under two percent of total U.S. retail spending. This study has been designed to explore why online shopping is growing so fast among some households, and so slowly among others. It focuses on characterizing the fundamental motivators or satisfiers of e-retail shopping, along with its dis-satisfiers and de-motivators. And it examines lifestyles of both Web shoppers and non-shoppers to find that these are not homogeneous groups at all, but discrete market segments, each seeking distinctive benefits from the Internet. It examines the lifestyle characteristics of online households. By means of a U.S. national probability sample of online heads-of-households, this descriptive research provides a lifestyle perspective of who is using the Internet to shop, who does not shop, and why. It is hypothesized and shown that, compared with online non-shoppers, online shoppers are younger, wealthier, have higher computer literacy, spend more time on their computer, spend more time on the Internet, and find online shopping to be easier and more entertaining. It is further reported that shoppers and non-shoppers are involved in different online activities, and have different attitudes and opinions toward the Internet and online use. Each group is profiled and marketing implications are discussed
In-flight calibration of the Herschel-SPIRE instrument
SPIRE, the Spectral and Photometric Imaging REceiver, is the Herschel Space Observatory's submillimetre camera and spectrometer. It contains a three-band imaging photometer operating at 250, 350 and 500 μm, and an imaging Fourier-transform spectrometer (FTS) covering 194–671 μm (447-1550 GHz). In this paper we describe the initial approach taken to the absolute calibration of the SPIRE instrument using a combination of the emission from the Herschel telescope itself and the modelled continuum emission from solar system objects and other astronomical targets. We present the photometric, spectroscopic and spatial accuracy that is obtainable in data processed through the “standard” pipelines. The overall photometric accuracy at this stage of the mission is estimated as 15% for the photometer and between 15 and 50% for the spectrometer. However, there remain issues with the photometric accuracy of the spectra of low flux sources in the longest wavelength part of the SPIRE spectrometer band. The spectrometer wavelength accuracy is determined to be better than 1/10th of the line FWHM. The astrometric accuracy in SPIRE maps is found to be 2 arcsec when the latest calibration data are used. The photometric calibration of the SPIRE instrument is currently determined by a combination of uncertainties in the model spectra of the astronomical standards and the data processing methods employed for map and spectrum calibration. Improvements in processing techniques and a better understanding of the instrument performance will lead to the final calibration accuracy of SPIRE being determined only by uncertainties in the models of astronomical standards
New accurate measurement of 36ArH+ and 38ArH+ ro-vibrational transitions by high resolution IR absorption spectroscopy
The protonated Argon ion, ArH, has been identified recently in
the Crab Nebula (Barlow et al. 2013) from Herschel spectra. Given the
atmospheric opacity at the frequency of its =1-0 and =2-1 rotational
transitions (617.5 and 1234.6 GHz, respectively), and the current lack of
appropriate space observatories after the recent end of the Herschel mission,
future studies on this molecule will rely on mid-infrared observations. We
report on accurate wavenumber measurements of ArH and
ArH rotation-vibration transitions in the =1-0 band in the
range 4.1-3.7 m (2450-2715 cm). The wavenumbers of the (0)
transitions of the =1-0 band are 2612.501350.00033 and
2610.701770.00042 cm () for ArH and
ArH, respectively. The calculated opacity for a gas thermalized at
a temperature of 100 K and a linewidth of 1 km.s of the (0) line is
(ArH). For column densities of
ArH larger than cm, significant absorption
by the (0) line can be expected against bright mid-IR sources
Carinae's Dusty Homunculus Nebula from Near-Infrared to Submillimeter Wavelengths: Mass, Composition, and Evidence for Fading Opacity
Infrared observations of the dusty, massive Homunculus Nebula around the
luminous blue variable Carinae are crucial to characterize the mass-loss
history and help constrain the mechanisms leading to the Great Eruption. We
present the 2.4 - 670 m spectral energy distribution, constructed from
legacy ISO observations and new spectroscopy obtained with the {\em{Herschel
Space Observatory}}. Using radiative transfer modeling, we find that the two
best-fit dust models yield compositions which are consistent with CNO-processed
material, with iron, pyroxene and other metal-rich silicates, corundum, and
magnesium-iron sulfide in common. Spherical corundum grains are supported by
the good match to a narrow 20.2 m feature. Our preferred model contains
nitrides AlN and SiN in low abundances. Dust masses range from 0.25 to
0.44 but 45 in both cases due to an
expected high Fe gas-to-dust ratio. The bulk of dust is within a 5
7 central region. An additional compact feature is detected at 390 m.
We obtain = 2.96 10 , a 25\% decline from
an average of mid-IR photometric levels observed in 1971-1977. This indicates a
reduction in circumstellar extinction in conjunction with an increase in visual
brightness, allowing 25-40\% of optical and UV radiation to escape from the
central source. We also present an analysis of CO and CO through lines, showing that the abundances are consistent with
expectations for CNO-processed material. The [C~{\sc{ii}}] line is
detected in absorption, which we suspect originates in foreground material at
very low excitation temperatures.Comment: Accepted in Ap
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