1,257 research outputs found
Hemodynamic and inotropic effects of endothelin-1 in vivo
Endothelin-1 (ET-1) is known to have strong vasoactive properties. Contradictory results have been reported with regard to its inotropic effects. This study examined the dose-dependent (500, 1000, 2500, 5000 and 10,000 ng ET-1/kg vs. NaCl controls) hemodynamic and inotropic effects of ET-1 in 53 open-chest rats during and after a 7-min infusion. Besides measurements in the intact circulation the myocardial function was examined by isovolumic registrations independent of peripheral vascular effects. A transient ET-1 induced (500, 1000, 2500, 5000 ng ET-1/kg) decrease of the left ventricular systolic pressure (LVSP) and the mean aortic pressure (AoPmean) was followed by a dose-related rise of these pressures (LVSP: -1%, -1%, +8%, +16% vs. preinfusion values; AoPmean: -11%, +9%, +39%, +52%). Heart rate (HR) was not influenced by ET-1. Due to the dose-dependent decrease of the stroke volume (SV) the cardiac output (CO) was reduced (CO: -8%, -23%, -40%, -50%). After an initial vasodilatation ET-1 elevates the total peripheral resistance (TPR: -1%, +49%, +139%, +215%) dose-dependently. 10,000 ng ET-1/kg was a lethal dose resulting in cardiac failure within minutes (low output). Since the maximum of the isovolumic LVSP (peak LVSP) and the corresponding dP/dtmax (peak dP/dtmax) were unchanged under ET-1, the isovolumic measurements do not indicate a positive inotropic effect of ET-1 in vivo in contrast to published results of in vitro experiments. It may be possible that a direct positive inotropic effect of ET-1 observed in in vitro studies is counterbalanced in vivo by an indirect negative inotropic effect due to the coronary-constrictive effect of ET-1
Real-time Monitoring of High-speed Spindle Operations Using Infrared Data Transmission
AbstractHigh-performance cutting is carried out with high cutting and feed speeds. Particularly, the use of heavy cutting tools (e.g. in planing machines), it is important to monitor the clamping and balance condition of the mounted tool, as well as the process forces. Therefore, a real-time monitoring system for high-speed operations based on the IrDA protocol was developed. It could be shown that infrared data transmission systems allow shorter reaction times compared to conventional wireless LAN applications. The presented monitoring system provides a reaction time of 7.14 ms at a bandwidth of 42.5 kHz and a data rate of 4.1 MBit/s
Probing the centre of the large circumstellar disc in M17
We investigated the nature of the hitherto unresolved elliptical infrared
emission in the centre of the ~20000 AU disc silhouette in M 17. We combined
high-resolution JHKsL'M' band imaging carried out with NAOS/CONICA at the VLT
with [Fe II] narrow band imaging using SOFI at the NTT. The analysis is
supported by Spitzer/GLIMPSE archival data and by already published SINFONI/VLT
Integral Field Spectroscopy data. For the first time, we resolve the elongated
central infrared emission into a point-source and a jet-like feature that
extends to the northeast in the opposite direction of the recently discovered
collimated H2 jet. They are both orientated almost perpendicular to the disc
plane. In addition, our images reveal a curved southwestern emission nebula
whose morphology resembles that of the previously detected northeastern one.
Both nebulae are located at a distance of 1500 AU from the disc centre. We
describe the infrared point-source in terms of a protostar that is embedded in
circumstellar material producing a visual extinction of 60 <= Av <= 82. The
observed Ks band magnitude is equivalent to a stellar mass range of 2.8 Msun <=
Mstar <= 8 Msun adopting conversions for a main-sequence star. Altogether, we
suggest that the large M 17 accretion disc is forming an intermediate to
high-mass protostar. Part of the accreted material is expelled through a
symmetric bipolar jet/outflow.Comment: 6 pages, 3 figures, accepted by MNRAS (16 May 2008
Radial Velocity Studies of Close Binary Stars.III
Radial velocity measurements and simple sine-curve fits to the orbital
velocity variations are presented for the third set of ten contact binary
systems: CN And, HV Aqr, AO Cam, YY CrB, FU Dra, RZ Dra, UX Eri, RT LMi, V753
Mon, OU Ser. All systems but two are contact, double-line spectroscopic
binaries with four of them (YY CrB, FU Dra, V753 Mon, OU Ser) being the recent
discoveries of the Hipparcos satellite project. The most interesting object is
V753 Mon with the mass-ratio closest to unity among all contact systems (q =
0.970 pm 0.003) and large total mass ((M1+M2)sin^3i = 2.93 pm 0.06). Several of
the studied systems are prime candidates for combined light and radial-velocity
synthesis solutions.Comment: submitted for publication in Astronomical Journal; 3 figures, 2
table
Learning high-order interactions for polygenic risk prediction
Within the framework of precision medicine, the stratification of individual genetic susceptibility based on inherited DNA variation has paramount relevance. However, one of the most relevant pitfalls of traditional Polygenic Risk Scores (PRS) approaches is their inability to model complex high-order non-linear SNP-SNP interactions and their effect on the phenotype (e.g. epistasis). Indeed, they incur in a computational challenge as the number of possible interactions grows exponentially with the number of SNPs considered, affecting the statistical reliability of the model parameters as well. In this work, we address this issue by proposing a novel PRS approach, called High-order Interactions-aware Polygenic Risk Score (hiPRS), that incorporates high-order interactions in modeling polygenic risk. The latter combines an interaction search routine based on frequent itemsets mining and a novel interaction selection algorithm based on Mutual Information, to construct a simple and interpretable weighted model of user-specified dimensionality that can predict a given binary phenotype. Compared to traditional PRSs methods, hiPRS does not rely on GWAS summary statistics nor any external information. Moreover, hiPRS differs from Machine Learning-based approaches that can include complex interactions in that it provides a readable and interpretable model and it is able to control overfitting, even on small samples. In the present work we demonstrate through a comprehensive simulation study the superior performance of hiPRS w.r.t. state of the art methods, both in terms of scoring performance and interpretability of the resulting model. We also test hiPRS against small sample size, class imbalance and the presence of noise, showcasing its robustness to extreme experimental settings. Finally, we apply hiPRS to a case study on real data from DACHS cohort, defining an interaction-aware scoring model to predict mortality of stage II-III Colon-Rectal Cancer patients treated with oxaliplatin
Mid - infrared interferometry of massive young stellar objects II Evidence for a circumstellar disk surrounding the Kleinmann - Wright object
The formation scenario for massive stars is still under discussion. To
further constrain current theories, it is vital to spatially resolve the
structures from which material accretes onto massive young stellar objects
(MYSOs). Due to the small angular extent of MYSOs, one needs to overcome the
limitations of conventional thermal infrared imaging, regarding spatial
resolution, in order to get observational access to the inner structure of
these objects.We employed mid - infrared interferometry, using the MIDI
instrument on the ESO /VLTI, to investigate the Kleinmann - Wright Object, a
massive young stellar object previously identified as a Herbig Be star
precursor. Dispersed visibility curves in the N- band (8 - 13 {\mu}m) have been
obtained at 5 interferometric baselines. We show that the mid - infrared
emission region is resolved. A qualitative analysis of the data indicates a non
- rotationally symmetric structure, e.g. the projection of an inclined disk. We
employed extensive radiative transfer simulations based on spectral energy
distribution fitting. Since SED - only fitting usually yields degenerate
results, we first employed a statistical analysis of the parameters provided by
the radiative transfer models. In addition, we compared the ten best - fitting
self - consistent models to the interferometric observations. Our analysis of
the Kleinmann - Wright Object suggests the existence of a circumstellar disk of
0.1M\odot at an intermediate inclination of 76\circ, while an additional dusty
envelope is not necessary for fitting the data. Furthermore, we demonstrate
that the combination of IR interferometry with radiative transfer simulations
has the potential to resolve ambiguities arising from the analysis of spectral
energy distributions alone.Comment: 12 pages, 22 figures accepted for publication in A&
Variable stars in the Open Cluster M11 (NGC 6705)
V-band time-series CCD photometric observations of the intermediate-age open
cluster M11 were performed to search for variable stars. Using these
time-series data, we carefully examined light variations of all stars in the
observing field. A total of 82 variable stars were discovered, of which 39
stars had been detected recently by Hargis et al. (2005). On the basis of
observational properties such as variable period, light curve shape, and
position on a color-magnitude diagram, we classified their variable types as 11
delta Scuti-type pulsating stars, 2 gamma Doradus-type pulsating stars, 40 W
UMa-type contact eclipsing binaries, 13 Algol-type detached eclipsing binaries,
and 16 eclipsing binaries with long period. Cluster membership for each
variable star was deduced from the previous proper motion results (McNamara et
al. 1977) and position on the color-magnitude diagram. Many pulsating stars and
eclipsing binaries in the region of M11 are probable members of the cluster.Comment: 23 pages, 9 figures, 3 tables, and accepted for publication in PAS
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