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

The Masses Of The B-Stars In The High Galactic Latitude Eclipsing Binary IT Lib

A number of blue stars which appear to be similar to Population I B-stars in the star forming regions of the galactic disk are found more than 1 kpc from the galactic plane. Uncertainties about the true distances and masses of these high latitude B-stars has fueled a debate as to their origin and evolutionary status. The eclipsing binary IT Lib is composed of two B-stars, is approximately one kiloparsec above the galactic plane, and is moving back toward the plane. Observations of the light and velocity curves presented here lead to the conclusion that the B-stars in this system are massive young main-sequence stars. While there are several possible explanations, it appears most plausible that the IT Lib system formed in the disk about 30 million years ago and was ejected on a trajectory taking it to its present position.Comment: 26 pages, 3 figures, accepted for publication in the PASP (January 2003

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Evaluating the accuracy of two: In situ optical sensors to estimate DOC concentrations for drinking water production

Two in situ optical sensors, a single-excitation fluorescence-based sensor (fDOM) mounted on a multi-parameter EXO2 sonde (YSI), and a stand-alone, multispectral absorbance-based instrument (spectro::lyser, scan Messtechnik GmbH), were evaluated for their capability to (i) estimate river dissolved organic carbon (DOC) concentrations and (ii) provide oversight of drinking water production. The sensors were deployed between March and November 2017 in the river Fyris, which drains a mixed forested and agricultural 2003 km$^{2}$ catchment and serves as a drinking water source by managed aquifer recharge. Grab samples were collected every 2 to 3 weeks and compared with logged sensor data collected at 15 minute intervals. The fDOM probe signal was used to estimate DOC concentrations in the range of 10.4 to 24.4 mg L$^{-1}$ using linear regression (R$^{2}$ = 0.71, RMSE = 2.5 mg L$^{-1}$), after correction for temperature, turbidity and inner-filter effects. Temporal changes in DOC character associated with the mixed land use landscape, as indicated by optical indices, reduced this sensor accuracy for estimating DOC concentration. Nevertheless, humic substance concentrations, the fraction of DOC that is preferentially removed during artificial infiltration, were well captured. The spectrolyser signal was used to establish a 2-component partial least square model that captured DOC fluctuations from 10.2 to 29.4 mg L$^{-1}$ (R$^{2}$ = 0.92; RMSE = 1.3 mg L$^{-1}$). This multiple-wavelength model (220 to 720 nm) effectively handled the changes in DOC composition while accurately estimating DOC concentrations. This study explores the advantages and limitations of optical sensors for their use in managed aquifer recharge and drinking water production in relation to DOC levels

The influence of postpartum PTSD on breastfeeding: A longitudinal population-based study.

BACKGROUND: In most Western countries, breastfeeding rates are lower than what is recommended by the World Health Organization. Depression has been shown to influence breastfeeding outcomes; however, there is very little research on the role of postpartum posttraumatic stress disorder (PTSD). This study examined to what extent maternal postpartum PTSD predicted breastfeeding initiation, exclusive breastfeeding during the first 6 months, and continuation up to 1 and 2 years. METHODS: The study is part of the large, population-based Akershus Birth Cohort. Data from the hospital's birth record and questionnaire data from 8 weeks and 2 years postpartum were used (n = 1480). All breastfeeding variables significantly correlated with postpartum PTSD were entered into stepwise logistic regression analyses. RESULTS: Although most mothers (97.1%) initiated breastfeeding, considerably fewer adhered to the World Health Organization's breastfeeding guidelines about exclusive breastfeeding during the first 6 months (13.4%) or continued breastfeeding for 12 or 24 months postpartum (37.7% and 4.2%, respectively). Even after adjustment for important confounding variables, maternal postpartum PTSD was significantly associated with not initiating breastfeeding (aOR 5.98 [95% CI 1.79-19.97]). Postpartum PTSD was also significantly related to not continuing breastfeeding up to 12 months, although this association did not hold after adjusting for confounding variables. CONCLUSION: Identifying women at risk of not initiating breastfeeding is crucial to prevent a negative influence on infant development and the development of the mother-infant bond. Early screening and treatment of women at risk of developing postpartum PTSD might be a way forward

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

Spectroscopic Observations of Twenty-one Faint Cataclysmic Variables Candidates

We provide the first minimum light spectroscopic observations for 21 previously known or suspected faint cataclysmic variable candidates. The sources were selected from the Downes et al. (2001) living edition catalog and the identified candidates have minimum light magnitudes of V~18-22. We confirm 15 of the candidates to be cataclysmic variables.Comment: 10 pages, 4 figures, accepted by A&

Radial Velocity Studies of Close Binary Stars.IV

Radial-velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of ten close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), HT Vir. All systems are double-lined spectroscopic binaries with only two of them not being contact systems (SW Lyn and GSC 8-324) and with five (FI Boo, V2150 Cyg, V899 Her, EX Leo, V2377 Oph) being the recent photometric discoveries of the Hipparcos satellite project. Five of the binaries are triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, HT Vir). Three (or possibly four) companions in the triple-lined systems show radial-velocity changes during the span of our observations suggesting that these are in fact quadruple systems. Several of the studied systems are prime candidates for combined light and radial-velocity synthesis solutions.Comment: aastex5.0, 5 figures in PS; submitted to Astron.