1,047 research outputs found
Education Reform for the Digital Era
Will the digital-learning movement repeat the mistakes of the charter-school movement? How much more successful might today's charter universe look if yesterday's proponents had focused on the policies and practices needed to ensure its quality, freedom, and resources over the long term? What mistakes might have been avoided? Damaging scandals forestalled? Missed opportunities seized
The use of non-vacuum electron beam (NVEB) technology as an universal manufacturing process for welding and cutting of high-strength steels
This publication presents the advantages of NVEB technology as an universal tool for material processing based on our investigations on welding and cutting of high-strength S960QL, S1100 and S1300 steels. In this work, the effect of welding cooling time t8/5 on the microstructure of the heat-affected zone (HAZ) and mechanical properties of the joints were investigated. The new process NVEB-cutting with a local suction produces extremely high cutting speeds, up to 17 m/min with high quality edges, render this method a significant development for new NVEB-applications. To demonstrate the capabilities of the non-vacuum electron beam as a universal tool for the technological process chain, the samples of steel S1100QL were made, while cutting and welding was carried out by one machine basement. The experimental results will be shown and discussed
Charter School Funding: Inequityâs Next Frontier
Of all the controversies swirling around the nationâs charter schools, none is more hotly contested than the debate over funding. Charter opponents charge that] these autonomous public schools are draining scarce resources from public school districts. Proponents, by contrast, complain that charter schools do not get their fair share of public education dollars
Modeling the Lukewarm Corino Phase: Is L1527 Unique?
Sakai et al. have observed long-chain unsaturated hydrocarbons and cyanopolyynes in the low-mass star-forming region L1527, and have attributed this result to a gas-phase ion-molecule chemistry, termed warm carbon-chain chemistry, which occurs during and after the evaporation of methane from warming grains. The source L1527 is an envelope surrounding a Class 0/I protostar with regions that possess a slightly elevated temperature of â30 K. The molecules detected by Sakai et al. are typically associated only with dark molecular clouds, and not with the more evolved hot corino phase. In order to determine whether L1527 is chemically distinct from a dark cloud, we compute models including various degrees of heating. The results indicate that the composition of L1527 is somewhat more likely to be due to warm carbon-chain chemistry than to be a remnant of a colder phase. If so, the molecular products provide a signature of a previously uncharacterized early phase of low-mass star formation, which can be characterized as a "lukewarm" corino. We also include predictions for other molecular species that might be observed toward candidate lukewarm corino sources. Although our calculations show that unsaturated hydrocarbons and cyanopolyynes can be produced in the gas phase as the grains warm up to 30 K, they also show that such species do not disappear rapidly from the gas as the temperature reaches 200 K, implying that such species might be detected in hot corinos and hot cores
Monopolelike probes for quantitative magnetic force microscopy: calibration and application
A local magnetization measurement was performed with a Magnetic Force
Microscope (MFM) to determine magnetization in domains of an exchange coupled
[Co/Pt]/Co/Ru multilayer with predominant perpendicular anisotropy. The
quantitative MFM measurements were conducted with an iron filled carbon
nanotube tip, which is shown to behave like a monopole. As a result we
determined an additional in-plane magnetization component of the multilayer,
which is explained by estimating the effective permeability of the sample
within the \mu*-method.Comment: 3 pages, 3 figure
Detection of a dense clump in a filament interacting with W51e2
In the framework of the Herschel/PRISMAS Guaranteed Time Key Program, the
line of sight to the distant ultracompact HII region W51e2 has been observed
using several selected molecular species. Most of the detected absorption
features are not associated with the background high-mass star-forming region
and probe the diffuse matter along the line of sight. We present here the
detection of an additional narrow absorption feature at ~70 km/s in the
observed spectra of HDO, NH3 and C3. The 70 km/s feature is not uniquely
identifiable with the dynamic components (the main cloud and the large-scale
foreground filament) so-far identified toward this region. The narrow
absorption feature is similar to the one found toward low-mass protostars,
which is characteristic of the presence of a cold external envelope. The
far-infrared spectroscopic data were combined with existing ground-based
observations of 12CO, 13CO, CCH, CN, and C3H2 to characterize the 70 km/s
component. Using a non-LTE analysis of multiple transitions of NH3 and CN, we
estimated the density (n(H2) (1-5)x10^5 cm^-3) and temperature (10-30 K) for
this narrow feature. We used a gas-grain warm-up based chemical model with
physical parameters derived from the NH3 data to explain the observed
abundances of the different chemical species. We propose that the 70 km/s
narrow feature arises in a dense and cold clump that probably is undergoing
collapse to form a low-mass protostar, formed on the trailing side of the
high-velocity filament, which is thought to be interacting with the W51 main
cloud. While the fortuitous coincidence of the dense clump along the line of
sight with the continuum-bright W51e2 compact HII region has contributed to its
non-detection in the continuum images, this same attribute makes it an
appropriate source for absorption studies and in particular for ice studies of
star-forming regions.Comment: Accepted for publication in A&
The chemistry of C3 & Carbon Chain Molecules in DR21(OH)
(Abridged) We have observed velocity resolved spectra of four ro-vibrational
far-infrared transitions of C3 between the vibrational ground state and the
low-energy nu2 bending mode at frequencies between 1654--1897 GHz using HIFI on
board Herschel, in DR21(OH), a high mass star forming region. Several
transitions of CCH and c-C3H2 have also been observed with HIFI and the IRAM
30m telescope. A gas and grain warm-up model was used to identify the primary
C3 forming reactions in DR21(OH). We have detected C3 in absorption in four
far-infrared transitions, P(4), P(10), Q(2) and Q(4). The continuum sources MM1
and MM2 in DR21(OH) though spatially unresolved, are sufficiently separated in
velocity to be identified in the C3 spectra. All C3 transitions are detected
from the embedded source MM2 and the surrounding envelope, whereas only Q(4) &
P(4) are detected toward the hot core MM1. The abundance of C3 in the envelope
and MM2 is \sim6x10^{-10} and \sim3x10^{-9} respectively. For CCH and c-C3H2 we
only detect emission from the envelope and MM1. The observed CCH, C3, and
c-C3H2 abundances are most consistent with a chemical model with
n(H2)\sim5x10^{6} cm^-3 post-warm-up dust temperature, T_max =30 K and a time
of \sim0.7-3 Myr. Post warm-up gas phase chemistry of CH4 released from the
grain at t\sim 0.2 Myr and lasting for 1 Myr can explain the observed C3
abundance in the envelope of DR21(OH) and no mechanism involving
photodestruction of PAH molecules is required. The chemistry in the envelope is
similar to the warm carbon chain chemistry (WCCC) found in lukewarm corinos.
The observed lower C3 abundance in MM1 as compared to MM2 and the envelope
could be indicative of destruction of C3 in the more evolved MM1. The timescale
for the chemistry derived for the envelope is consistent with the dynamical
timescale of 2 Myr derived for DR21(OH) in other studies.Comment: 11 Pages, 6 figures, accepted for publication in A&
New Theoretical Results Concerning the Interstellar Abundance of Molecular Oxygen
The low abundance of molecular oxygen in cold cores of interstellar clouds poses a continuing problem to modelers of the chemistry of these regions. In chemical models O_2 is formed principally by the reaction between O and OH, which has been studied experimentally down to 39 K. It remains possible that the rate coefficient of this reaction at 10 K is considerably less than its measured value at 39 K, which might inhibit the production of O_2 and possibly bring theory and observation closer together over a wider range of times. Two theoretical determinations of the rate coefficient for the O + OH reaction at temperatures down to 10 K have been undertaken recently; both results show that the rate coefficient is indeed lower at 10 K than at 39 K, although they differ in the magnitude of the decrease. Here we show, using gas-phase models, how the calculated interstellar O_2 abundance in cold cores is affected by a decrease in the rate coefficient. We also consider its effect on other species. Our major finding is that for standard O-rich abundances, the calculated abundance of O_2 in cold cores is sufficiently low to explain observations only at early times regardless of the value of k_1 in the range investigated here. For C-rich abundances, on the other hand, late-time solutions can also be possible
Probing Ionization Energies for Trace Gas Identification: The Micro Photo Electron Ionization Detector (PEID)
Micro gas sensors detect the presence of substances, but can hardly identify them. We developed a novel approach of probing referenceable ionization energies. It extends the photoionization principle towards tunable energies via replacement of photons by accelerated photo electrons. The device comprises UV-LED illumination, an atmospherically stable photoelectron emission layer with a nano-vacuum electronics accelerator realized in thin film technology and charged particle measurement. A voltage variation at the accelerator provides electrons of tunable energies. We were able to prove that variable electron energies can be used for substance detection. The resulting system reaches ambient conditions operability. The actual limitations and challenges are discussed
Impaired sustained attention and executive dysfunction:bipolar disorder versus depression-specific markers of affective disorders
Objective - To identify neurocognitive measures that could be used as objective markers of bipolar disorder. Methods - We examined executive function, sustained attention and short-term memory as neurocognitive domains in 18 participants with bipolar disorder in euthymic state (Beuth), 14 in depressed state (Bdep), 20 with unipolar depression (Udep) and 28 healthy control participants (HC). We conducted four-group comparisons followed by relevant post hoc analyses. Results - Udep and Bdep, but not Beuth showed impaired executive function (p = 0.045 and p = 0.046, respectively). Both Bdep and Beuth, but not Udep, showed impaired sustained attention (p = 0.001 and p = 0.045, respectively). The four groups did not differ significantly on short-term memory. Impaired sustained attention and executive dysfunction were not associated with depression severity, duration of illness and age of illness onset. Only a small number of abnormal neurocognitive measures were associated with medication in Bdep and Beuth. Conclusion - Impaired sustained attention appears specific to bipolar disorder and present in both Beuth and Bdep; it may represent an objective marker of bipolar disorder. Executive dysfunction by contrast, appears to be present in Udep and Bdep and likely represents a marker of depression
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