802 research outputs found
Atomic-Layer-Deposited Al2O3 as Effective Barrier against the Diffusion of Hydrogen from SiNx:H Layers into Crystalline Silicon during Rapid Thermal Annealing
Stacks of hydrogen-lean aluminum oxide, deposited via plasma-assisted atomic-layer-deposition, and hydrogen-rich plasma-enhanced chemical vapor-deposited silicon nitride (SiNx) are applied to boron-doped float-zone silicon wafers. A rapid thermal annealing (RTA) step is performed in an infrared conveyor-belt furnace at different set-peak temperatures. The hydrogen content diffused into the crystalline silicon during the RTA step is quantified by measurements of the silicon resistivity increase due to hydrogen passivation of boron dopant atoms. These experiments indicate that there exists a temperature-dependent maximum in the introduced hydrogen content. The exact position of this maximum depends on the composition of the SiNx layer. The highest total hydrogen content, exceeding 1015âcmâ3, is introduced into the silicon bulk from silicon-rich SiNx layers with a refractive index of 2.3 (at λâ=â633ânm) at an RTA peak temperature of 800â°C, omitting the Al2O3 interlayer. Adding an Al2O3 interlayer with a thickness of 20ânm reduces the hydrogen content by a factor of four, demonstrating that Al2O3 acts as a highly effective hydrogen diffusion barrier. Measuring the hydrogen content in the silicon bulk as a function of Al2O3 thickness at different RTA peak temperatures provides the hydrogen diffusion length in Al2O3 as a function of measured temperature
The HIFI spectral survey of AFGL 2591 (CHESS). II. Summary of the survey
This paper presents the richness of submillimeter spectral features in the
high-mass star forming region AFGL 2591. As part of the CHESS (Chemical
Herschel Survey of Star Forming Regions) Key Programme, AFGL 2591 was observed
by the Herschel/HIFI instrument. The spectral survey covered a frequency range
from 480 up to 1240 GHz as well as single lines from 1267 to 1901 GHz (i.e. CO,
HCl, NH3, OH and [CII]). Rotational and population diagram methods were used to
calculate column densities, excitation temperatures and the emission extents of
the observed molecules associated with AFGL 2591. The analysis was supplemented
with several lines from ground-based JCMT spectra. From the HIFI spectral
survey analysis a total of 32 species were identified (including
isotopologues). In spite of the fact that lines are mostly quite week, 268
emission and 16 absorption lines were found (excluding blends). Molecular
column densities range from 6e11 to 1e19 cm-2 and excitation temperatures range
from 19 to 175 K. One can distinguish cold (e.g. HCN, H2S, NH3 with
temperatures below 70 K) and warm species (e.g. CH3OH, SO2) in the protostellar
envelope.Comment: Accepted to A&
Tremor pathophysiology:lessons from neuroimaging
Contains fulltext :
226036.pdf (Publisherâs version ) (Closed access)PURPOSE OF REVIEW: We discuss the latest neuroimaging studies investigating the pathophysiology of Parkinson's tremor, essential tremor, dystonic tremor and Holmes tremor. RECENT FINDINGS: Parkinson's tremor is associated with increased activity in the cerebello-thalamo-cortical circuit, with interindividual differences depending on the clinical dopamine response of the tremor. Although dopamine-resistant Parkinson's tremor arises from a larger contribution of the (dopamine-insensitive) cerebellum, dopamine-responsive tremor may be explained by thalamic dopamine depletion. In essential tremor, deep brain stimulation normalizes cerebellar overactivity, which fits with the cerebellar oscillator hypothesis. On the other hand, disconnection of the dentate nucleus and abnormal white matter microstructural integrity support a decoupling of the cerebellum in essential tremor. In dystonic tremor, there is evidence for involvement of both cerebellum and basal ganglia, although this may depend on the clinical phenotype. Finally, in Holmes tremor, different causal lesions map to a common network consisting of the red nucleus, internal globus pallidus, thalamus, cerebellum and pontomedullary junction. SUMMARY: The pathophysiology of all investigated tremors involves the cerebello-thalamo-cortical pathway, and clinical and pathophysiological features overlap among tremor disorders. We draw the outlines of a hypothetical pathophysiological axis, which may be used besides clinical features and cause in future tremor classifications
"My right-hand man" versus "We barely make use of them":change leaders talking about educational scientists in curriculum change processes-a Membership Categorization Analysis
Health professions education scholarship units (HPESUs) are increasingly becoming a standard for medical schools worldwide without having much information about their value and role in actual educational practices, particularly of those who work in these units, the educational scientists. We conducted a linguistic analysis, called Membership Categorization Analysis, of interviews with leaders of recent curriculum changes to explore how they talk about educational scientists in relation to these processes. The analysis was conducted on previously collected interview data with nine change leaders of major undergraduate medical curriculum change processes in the Netherlands. We analyzed how change leaders categorize HPESUs and educational scientists (use of category terms) and what they say about them (predicates). We noticed two ways of categorizing educational scientists, with observable different predicates. Educational scientists categorized by their first name were suggested to be closer to the change process, more involved in decisional practices and positively described, whereas those described in more generic terms were represented in terms of relatively passive and unspecified activities, were less explicit referenced for their knowledge and expertise and were predominantly factually or negatively described. This study shows an ambiguous portrayal of educational scientists by leaders of major curriculum change processes. Medical schools are challenged to establish medical curricula in consultation with a large, diverse and interdisciplinary stakeholder group. We suggest that it is important to invest in interpersonal relationships to strengthen the internal collaborations and make sure people are aware of each other's existence and roles in the process of curriculum development
Hot gas and dust in a protostellar cluster near W3(OH
We used the IRAM Interferometer to obtain sub-arcsecond resolution
observations of the high-mass star-forming region W3(OH) and its surroundings
at a frequency of 220 GHz. With the improved angular resolution, we distinguish
3 peaks in the thermal dust continuum emission originating from the hot core
region about 6 arcsec (0.06 pc) east of W3(OH). The dust emission peaks are
coincident with known radio continuum sources, one of which is of non-thermal
nature. The latter source is also at the center of expansion of a powerful
bipolar outflow observed in water maser emission. We determine the hot core
mass to be 15 solar masses based on the integrated dust continuum emission.
Simultaneously many molecular lines are detected allowing the analysis of the
temperature structure and the distribution of complex organic molecules in the
hot core. From HNCO lines, spanning a wide range of excitation, two 200 K
temperature peaks are found coincident with dust continuum emission peaks
suggesting embedded heating sources within them.Comment: 12 pages, 3 figure
Early warning signals and critical transitions in psychopathology:challenges and recommendations
Empirical evidence is mounting that monitoring momentary experiences for the presence of early warning signals (EWS) may allow for personalized predictions of meaningful symptom shifts in psychopathology. Studies aiming to detect EWS require intensive longitudinal measurement designs that center on individuals undergoing change. We recommend that researchers: (a) define criteria for relevant symptom shifts a priori to allow specific hypothesis testing; (b) balance the observation period length and high-frequency measurements with participant burden by testing ambitious designs with pilot studies; (c) choose variables that are meaningful to their patient group and facilitate replication by others. Thoroughly considered designs are necessary to assess the promise of EWS as a clinical tool to detect, prevent or encourage impending symptom changes in psychopathology
FIRI - a Far-Infrared Interferometer
Half of the energy ever emitted by stars and accreting objects comes to us in
the FIR waveband and has yet to be properly explored. We propose a powerful
Far-InfraRed Interferometer mission, FIRI, to carry out high-resolution imaging
spectroscopy in the FIR. This key observational capability is essential to
reveal how gas and dust evolve into stars and planets, how the first luminous
objects in the Universe ignited, how galaxies formed, and when super-massive
black holes grew. FIRI will disentangle the cosmic histories of star formation
and accretion onto black holes and will trace the assembly and evolution of
quiescent galaxies like our Milky Way. Perhaps most importantly, FIRI will
observe all stages of planetary system formation and recognise Earth-like
planets that may harbour life, via its ability to image the dust structures in
planetary systems. It will thus address directly questions fundamental to our
understanding of how the Universe has developed and evolved - the very
questions posed by ESA's Cosmic Vision.Comment: Proposal developed by a large team of astronomers from Europe, USA
and Canada and submitted to the European Space Agency as part of "Cosmic
Vision 2015-2025
Heterodyne Receiver for Origins
The Heterodyne Receiver for Origins (HERO) is the first detailed study of a heterodyne focal plane array receiver for space applications. HERO gives the Origins Space Telescope the capability to observe at very high spectral resolution (R = 107) over an unprecedentedly large far-infrared (FIR) wavelengths range (111 to 617 ÎŒm) with high sensitivity, with simultaneous dual polarization and dual-frequency band operation. The design is based on prior successful heterodyne receivers, such as Heterodyne Instrument for the Far-Infrared /Herschel, but surpasses it by one to two orders of magnitude by exploiting the latest technological developments. Innovative components are used to keep the required satellite resources low and thus allowing for the first time a convincing design of a large format heterodyne array receiver for space. HERO on Origins is a unique tool to explore the FIR universe and extends the enormous potential of submillimeter astronomical spectroscopy into new areas of astronomical research
High-Resolution Continuum Imaging at 1.3 and 0.7 cm of the W3 IRS 5 Region
High-resolution images of the hypercompact HII regions (HCHII) in W3 IRS 5
taken with the Very Large Array (VLA) at 1.3 and 0.7 cm are presented. Four
HCHII regions were detected with sufficient signal-to-noise ratios to allow the
determination of relevant parameters such as source position, size and flux
density. The sources are slightly extended in our ~0.2 arcsecond beams; the
deconvolved radii are less than 240 AU. A comparison of our data with VLA
images taken at epoch 1989.1 shows proper motions for sources IRS 5a and IRS
5f. Between 1989.1 and 2002.5, we find a proper motion of 210 mas at a position
angle of 12 deg for IRS 5f and a proper motion of 190 mas at a position angle
of 50 deg for IRS 5a. At the assumed distance to W3 IRS 5, 1.83 +/- 0.14 kpc,
these offsets translate to proper motions of ~135 km/s and ~122 km/s$
respectively. These sources are either shock ionized gas in an outflow or
ionized gas ejected from high mass stars. We find no change in the positions of
IRS 5d1/d2 and IRS 5b; and we show through a comparison with archival NICMOS
2.2 micron images that these two radio sources coincide with the infrared
double constituting W3 IRS 5. These sources contain B or perhaps O stars. The
flux densities of the four sources have changed compared to the epoch 1989.1
results. In our epoch 2002.5 data, none of the spectral indicies obtained from
flux densities at 1.3 and 0.7 cm are consistent with optically thin free-free
emission; IRS 5d1/d2 shows the largest increase in flux density from 1.3 cm to
0.7 cm. This may be an indication of free-free optical depth within an ionized
wind, a photoevaporating disk, or an accretion flow. It is less likely that
this increase is caused by dust emission at 0.7 cm.Comment: 13 pages, 3 figures To be published in The Astrophysical Journa
Urinary 1-Hydroxypyrene Levels in Workers Exposed to Polycyclic Aromatic Hydrocarbon from Rubber Wood Burning
AbstractBackgroundUrinary 1-hydroxypyrene (1-OHP) was selected as a biomarker of polycyclic aromatic hydrocarbons (PAHs) to explore the accumulation level in the bodies of workers at rubber smoke sheet factories in southern Thailand.MethodsSpot urine samples were taken from four groups of workers from June 2006 to November 2007. The nonexposure or control groups included habitual cigarette smokers and nonsmokers. The other two groups were workers exposed to particle-bound PAHs from rubber wood smoke and they were nonsmokers. All spot urine samples were analyzed for 1-OHP and creatinine levels.ResultsThe mean ± standard deviation urinary 1-OHP in the control group of habitual smokers and the nonsmokers was 0.24 ± 0.16 Όmol/mol creatinine and not-detected to 0.14 Όmol/mol creatinine, respectively. In the workers, the 1-OHP levels on workdays had no significant difference from the 1-OHP levels on the days off. The yearly average 1-OHP level was 0.76 ± 0.41 Όmol/mol creatinine whereas the average 1-OHP level during 10 consecutive workdays was 1.06 ± 0.29 Όmol/mol creatinine (p > 0.05).ConclusionThe urinary 1-OHP levels of workers exposed to PAHs were high. The accumulation of 1-OHP in the body was not clear although the workers had long working hours with few days off during their working experience. Therefore, a regular day off schedule and rotation shift work during high productive RSS should be set for RSS workers
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