Orbits and Masses in the multiple system LHS 1070

We present a study of the orbits of the triple system LHS1070, with the aim to determine individual masses of its components. Sixteen new relative astrometric positions of the three components in the K band were obtained with NACO at the VLT, Omega CASS at the 3.5m telescope on Calar Alto, and other high-spatial-resolution instruments. We combine them with data from the literature and fit orbit models to the dataset. We derive an improved fit for the orbit of LHS1070B and C around each other, and an estimate for the orbit of B and C around A. The orbits are nearly coplanar, with a misalignment angle of less than 10{\deg}. The masses of the three components are M_A = 0.13 - 0.16 Msun, M_B = 0.077+/-0.005 Msun, and M_C = 0.071+/-0.004 Msun. Therefore, LHS1070C is certainly, and LHS1070B probably a brown dwarf. Comparison with theoretical isochrones shows that LHS1070A is either fainter or more massive than expected. One possible explanation would be that it is a binary. However, the close companion reported previously could not be confirmed.Comment: 9 pages, 8 figures, accepted by Astronomy and Astrophysic

Schwingfestigkeit laserauftraggeschweißter legierter Stähle

Laser cladding is an established, sustainable and value-adding process. So far, merely statically loaded parts profit from its application as its impact on part properties under cyclic loads was not investigated systematically, yet. It is shown that residual stresses are the driving factor determining fatigue strength. These can neither be manipulated by process parameters nor by thermal post-processing so as to influencing fatigue strength significantly positive. Either the material combination is to be chosen so that thermal expansion of the substrate material is higher than of the coating or mechanical post-processing, i.e. by deep rolling is to be applied. Compressive residual stresses are to be induced to the interface of substrate and coating as this area is most prone to failure. Within the representative example of laser cladding of high and low alloy steel with a cobalt-based alloy higher fatigue strength could be realised as for the latter in as-cast condition

Visual orbit for the low-mass binary Gliese 22 AC from speckle interferometry

Based on 14 data points obtained with near-infrared speckle interferometry and covering an almost entire revolution, we present a first visual orbit for the low-mass binary system Gliese 22 AC. The quality of the orbit is largely improved with respect to previous astrometric solutions. The dynamical system mass is 0.592 +- 0.065 solar masses, where the largest part of the error is due to the Hipparcos parallax. A comparison of this dynamical mass with mass-luminosity relations on the lower main sequence and theoretical evolutionary models for low-mass objects shows that both probably underestimate the masses of M dwarfs. A mass estimate for the companion Gliese 22 C indicates that this object is a very low-mass star with a mass close to the hydrogen burning mass limit.Comment: Accepted by Astronomy and Astrophysics, 6 pages, 2 figure

The young, active binary star EK Draconis

EK Dra (HD 129333) is a young, active, nearby star that is orbited by a low mass companion. By combining new speckle observations with old and new radial velocity measurements we find that the orbit is highly eccentric with e=0.82\pm0.03, and we derive the true masses of both components. The masses are $0.9\pm0.1 {\rm M}_\odot$ and $0.5\pm0.1 {\rm M}_\odot$, for the primary and secondary, respectively. From high resolution spectra we derive a new $T_{\rm eff}$ of $5700\pm70$ K, and a $\log g$ of $4.37\pm0.10$, which is different to previous estimates. However, the new spectroscopic distance differs by only 5.8% to the distance derived by parallax measurement of the Hipparcos satellite and thus the stellar parameters are presumably more realistic than older determinations. We derive a somewhat higher value for the metallicity of $[Fe/H]=-0.16\pm0.07$. EK Dra turns out to be one of the few nearby young stars which will evolve similar to the sun. The precise radial velocity measurements taken in the course of this program also allows us to shed more light on to the activity of this star. In 2001 and 2002 we find a periodic signal of the radial velocity variations with a period of $2.767\pm0.005$ days which we interpret as the rotation period. This signal vanishes in 2003. However the signal can be recovered if only the spectra in which the photospheric lines are asymmetric are used. On the other hand, we do not find a close correlation between the asymmetry of photospheric lines and the radial velocity.Comment: 10 pages, 11 figures, accepted by A&

Greater Blood Pressure Variability Is Associated With Lower Cognitive Performance:The Maastricht Study

An increasing number of individuals will face age-related cognitive difficulties because life expectancy has increased. It is, therefore, important to identify modifiable risk factors for cognitive impairment. Very short-term to mid-term blood pressure variability (BPV) may be such a factor because it may cause cerebral ischemia. To this end, we investigated whether greater systolic and diastolic BPV are cross-sectionally associated with memory function (n=1804), information processing speed (n=1793), and executive function (n=1780) in 40- to 75-year-old individuals from The Maastricht Study. A composite BPV-index was derived by standardizing within-visit, 24-hour, and 7-day BPV. We performed linear regression with adjustments for age, sex, educational level, 24-hour systolic or diastolic pressure, and cardiovascular risk factors. We found that a 1-SD greater systolic BPV was not associated with information processing speed (β [SD difference], -0.10; 95% CI, -0.14 to 0.06), or executive function (-0.09; 95% CI, -0.20 to 0.02) but was marginally associated with lower memory function (-0.11; 95% CI, -0.21 to 0.00). A 1-SD greater diastolic BPV was associated with lower information processing speed (-0.10; 95% CI, -0.20 to -0.00) and executive function (-0.12; 95% CI, -0.22 to -0.01) and marginally associated with lower memory function (-0.09; 95% CI, -0.20 to 0.01). These effects on cognitive performance are equivalent to ≈3 additional years of aging. In conclusion, greater very short-term to mid-term diastolic and, to a lesser extent, systolic BPV may be a modifiable risk factor for cognitive deterioration in 40- to 75-year-old, community-dwelling individuals

On the universal outcome of star-formation: Is there a link between stars and brown-dwarfs?

(abridged) The recent evidence obtained by Briceno et al. that star-formation in Taurus-Auriga (TA) may be producing significantly fewer brown dwarfs (BDs) per star than the ONC is investigated by setting up a realistic model stellar plus BD population and explicitly taking into account a high binary proportion and dynamical evolution in the TA groups and the ONC. The Briceno result is reproduced almost exactly despite an identical IMF in both systems because many BD-BD and star-BD binaries are disrupted in the ONC thus freeing BDs, while the TA groups remain unevolved dynamically. However, the resulting populations do not have the correct star-star, star-BD and expecially BD-BD binary properties, even if a variable BD IMF is allowed for. The conclusion is therefore that BDs need to be added as a separate population which has its own binary properties. Such an extra population can have various origins which are briefly discussed in this contribution but more fully in an associated paper.Comment: MNRAS, accepted, 23 pages, 14 figures, LaTeX, two references adde

Exercise SBP response and incident depressive symptoms: The Maastricht Study

Objective : An exaggerated exercise SBP, which is potentially modifiable, may be associated with incident depressive symptoms via an increased pulsatile pressure load on the brain. However, the association between exaggerated exercise SBP and incident depressive symptoms is unknown. Therefore, we examined whether exaggerated exercise SBP is associated with a higher risk of depressive symptoms over time. Methods : We used longitudinal data from the population-based Maastricht Study, with only individuals free of depressive symptoms at baseline included (n = 2121; 51.3% men; age 59.5 +/- 8.5 years). Exercise SBP was measured at baseline with a submaximal exercise cycle test. We calculated a composite score of exercise SBP based on four standardized exercise SBP measures: SBP at moderate workload, SBP at peak exercise, SBP change per minute during exercise and SBP 4 min after exercise. Clinically relevant depressive symptoms were determined annually at follow-up and defined as a Patient Health Questionnaire score of at least 10. Results : After a mean follow-up of 3.9 years, 175 participants (8.3%) had incident clinically relevant depressive symptoms. A 1 SD higher exercise SBP composite score was associated with a higher incidence of clinically relevant depressive symptoms [hazard ratio: 1.27 (95% confidence interval: 1.04-1.54)]. Results were adjusted for age, sex, education level, glucose metabolism status, lifestyle, cardiovascular risk factors, resting SBP and cardiorespiratory fitness. Conclusion : A higher exercise SBP response is associated with a higher incidence of clinically relevant depressive symptoms

Millennial-scale ocean climate variability

Marine sediment cores that span the last 50,000 years frequently show considerable variability in sediment and biogeochemical variables. In the North Atlantic, a series of massive iceberg and meltwater events (Heinrich events) were sourced from Hudson Strait and the Laurentide Ice Sheet with a periodicity of ~7.2 ky and had significant impacts on the Atlantic meridional overturning circulation and the global hydrological and biogeochemical cycles. Some marine proxies show higher frequency, abrupt events, that may match the Dansgaard-Oeschger (D-O) oscillations. Predictable millennial-scale periodicities and associated forcings have proved elusive, and an observed ~1.5 ky cycle may be linked to stochastic resonance.01500/2014, 04326/2020info:eu-repo/semantics/publishedVersio