609 research outputs found
Materials characterization on efforts for ablative materials
Experimental efforts to develop a new procedure to measure char depth in carbon phenolic nozzle material are described. Using a Shor Type D Durometer, hardness profiles were mapped across post fired sample blocks and specimens from a fired rocket nozzle. Linear regression was used to estimate the char depth. Results are compared to those obtained from computed tomography in a comparative experiment. There was no significant difference in the depth estimates obtained by the two methods
Neural Mechanism of a Sex-Specific Risk Variant for Posttraumatic Stress Disorder in the Type I Receptor of the Pituitary Adenylate Cyclase Activating Polypeptide
AbstractBackgroundPosttraumatic stress disorder (PTSD) is a frequent anxiety disorder with higher prevalence rates in female patients than in male patients (2.5:1). Association with a single nucleotide polymorphism (rs2267735) in the gene ADCYAP1R1 encoding the type I receptor (PAC1-R) of the pituitary adenylate cyclase activating polypeptide has been reported with PTSD in female patients. We sought to identify the neural correlates of the described PAC1-R effects on associative learning.MethodsIn a reverse genetic approach, we examined two independent healthy samples (N1 = 112, N2 = 73) using functional magnetic resonance imaging during cued and contextual fear conditioning. Skin conductance responses and verbal self-reports of arousal, valence, and contingency were recorded.ResultsWe found that PAC1-R modulates the blood oxygenation level–dependent response of the hippocampus. Specifically, we observed decreased hippocampal activity during contextual, but not during cued, fear conditioning in female participants carrying the PAC1-R risk allele. We observed no significant differences in conditionability for skin conductance responses, verbal reports, or activation in other brain regions between the genotype groups in female participants.ConclusionsOur results suggest that impaired contextual conditioning in the hippocampal formation may mediate the association between PAC1-R and PTSD symptoms. Our findings potentially identify a missing link between the involvement of PAC1-R in PTSD and the well-established structural and functional hippocampal deficits in these patients
Use of gene expression profiling to identify candidate genes for pretherapeutic patient classification in acute appendicitis
Background:
Phlegmonous and gangrenous appendicitis represent independent pathophysiological entities with different clinical courses ranging from spontaneous resolution to septic disease. However, reliable predictive methods for these clinical phenotypes have not yet been established. In an attempt to provide pathophysiological insights into the matter, a genomewide gene expression analysis was undertaken in patients with acute appendicitis.
Methods:
Peripheral blood mononuclear cells were isolated and, after histological confirmation of PA or GA, analysed for genomewide gene expression profiling using RNA microarray technology and subsequent pathway analysis.
Results:
Samples from 29 patients aged 7–17 years were included. Genomewide gene expression analysis was performed on 13 samples of phlegmonous and 16 of gangrenous appendicitis. From a total of 56 666 genes, 3594 were significantly differently expressed. Distinct interaction between T and B cells in the phlegmonous appendicitis group was suggested by overexpression of T cell receptor α and β subunits, CD2, CD3, MHC II, CD40L, and the B cell markers CD72 and CD79, indicating an antiviral mechanism. In the gangrenous appendicitis group, expression of genes delineating antibacterial mechanisms was found.
Conclusion:
These results provide evidence for different and independent gene expression in phlegmonous and gangrenous appendicitis in general, but also suggest distinct immunological patterns for the respective entities. In particular, the findings are compatible with previous evidence of spontaneous resolution in phlegmonous and progressive disease in gangrenous appendicitis
Magnetic fields in solar plage regions: insights from high-sensitivity spectropolarimetry
Plage regions are patches of concentrated magnetic field in the Sun's
atmosphere where hot coronal loops are rooted. While previous studies have shed
light on the properties of plage magnetic fields in the photosphere, there are
still challenges in measuring the overlying chromospheric magnetic fields,
which are crucial to understanding the overall heating and dynamics. Here, we
utilize high-sensitivity, spectropolarimetric data obtained by the four-meter
Daniel K. Inouye Solar Telescope (DKIST) to investigate the dynamic environment
and magnetic field stratification of an extended, decaying plage region. The
data show strong circular polarization signals in both plage cores and
surrounding fibrils. Notably, weak linear polarization signals clearly
differentiate between plage patches and the fibril canopy, where they are
relatively stronger. Inversions of the Ca II 8542 spectra show
an imprint of the fibrils in the chromospheric magnetic field, with typical
field strength values ranging from 200-300 G in fibrils. We confirm the
weak correlation between field strength and cooling rates in the lower
chromosphere. Additionally, we observe supersonic downflows and strong velocity
gradients in the plage periphery, indicating dynamical processes occurring in
the chromosphere. These findings contribute to our understanding of the
magnetic field and dynamics within plages, emphasizing the need for further
research to explore the expansion of magnetic fields with height and the
three-dimensional distribution of heating rates in the lower chromosphere.Comment: 17 pages, 8 figures, accepted for publication in ApJ
Insight into the solar plage chromosphere with DKIST
The strongly coupled hydrodynamic, magnetic, and radiation properties of the
plasma in the solar chromosphere makes it a region of the Sun's atmosphere that
is poorly understood. We use data obtained with the high-resolution Visible
Broadband Imager (VBI) equipped with an H filter and the Visible
Spectro-Polarimeter (ViSP) at the Daniel K. Inouye Solar Telescope to
investigate the fine-scale structure of the plage chromosphere. To aid the
interpretation of the VBI imaging data, we also analyze spectra from the
CHROMospheric Imaging Spectrometer on the Swedish Solar Telescope. The analysis
of spectral properties, such as enhanced line widths and line depths explains
the high contrast of the fibrils relative to the background atmosphere
demonstrating that H is an excellent diagnostic for the enigmatic
fine-scale structure of the chromosphere. A correlation between the parameters
of the H line indicates that opacity broadening created by overdense
fibrils could be the main reason for the spectral line broadening observed
frequently in chromospheric fine-scale structures. Spectropolarimetric
inversions of the ViSP data in the Ca II 8542 {\AA} and Fe I 6301/6302 {\AA}
lines are used to construct semiempirical models of the plage atmosphere.
Inversion outputs indicate the existence of dense fibrils in the Ca II 8542
{\AA} line. The analyses of the ViSP data show that the morphological
characteristics, such as orientation, inclination and length of fibrils are
defined by the topology of the magnetic field in the photosphere. Chromospheric
maps reveal a prominent magnetic canopy in the area where fibrils are directed
towards the observer.Comment: 17 pages, 11 figures, accepted in Ap
Das NDICEA-Modell zur Abbildung der Stickstoffdynamik im ökologischen Gemüsebau
Der NDICEA-Ansatz zur Stickstoffmodellierung kombiniert Bewirtschaftungs- und Wetterdaten, um den Umsatz organischer Substanzen zu berechnen. Die Ergebnisse der Modellierung des ökologischen Gartenbaus unterstreichen den Einfluss der Bodenbearbeitung auf die Stickstoffmineralisierung
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