Strong effect of the cluster environment on the size of protoplanetary discs?

Context. Most stars are born in clusters, thus the protoplanetary discs surrounding the newly formed stars might be influenced by this environment. Isolated star-disc encounters have previously been studied, and it was shown that very close encounters are necessary to completely destroy discs. However, relatively distant encounters are still able to change the disc size considerably. Aims. We quantify the importance of disc-size reduction that is due to stellar encounters in an entire stellar population. Methods. We modelled young, massive clusters of different densities using the code Nbody6 to determine the statistics of stellar encounter parameters. In a second step, we used these parameters to investigate the effect of the environments on the disc size. For this purpose, we performed a numerical experiment with an artificial initial disc size of 105 AU. Results. We quantify to which degree the disc size is more sensitive to the cluster environment than to the disc mass or frequency. We show that in all investigated clusters a large portion of discs is significantly reduced in size. After 5 Myr, the fraction of discs smaller than 1000 AU in ONC-like clusters with an average number density of 60pc$^3$, the fraction of discs smaller than 1000 AU is 65%, while discs smaller than 100 AU make up 15%. These fractions increase to 84% and 39% for discs in denser clusters like IC 348 (500pc$^3$). Even in clusters with a density four times lower than in the ONC (15pc$^3$), about 43% of all discs are reduced to sizes below 1 000 AU and roughly 9% to sizes below 100 AU. Conclusions. For any disc in the ONC that initially was larger than 1 000 AU, the probability to be truncated to smaller disc sizes as a result of stellar encounters is quite high. Thus, among other effects, encounters are important in shaping discs and potentially forming planetary systems in stellar clusters.Comment: accepted for publication in A&

From star-disc encounters to numerical solutions for a subset of the restricted three-body problem

Various astrophysical processes are known, where the fly-by of a massive object affects matter initially supported against gravity by rotation. Examples are perturbations of galaxies, protoplanetary discs or planetary systems. We approximate such events as subset of the restricted three-body problem by considering only perturbations of non-interacting low-mass objects initially on circular Keplerian orbits. In this paper we present a new parametrisation of the initial conditions of this problem. Under certain conditions the initial positions of the low-mass objects can be specified largely independent of the initial position of the perturber. Exploiting additionally the known scalings of the problem reduces the parameter space of initial conditions for one specific perturbation to two dimensions. To this two-dimensional initial condition space we have related the final properties of the perturbed trajectories of the low-mass objects from our numerical simulations. That way, maps showing the effect of the perturbation on the low-mass objects have been created, which provide a new view on the perturbation process. Comparing the maps for different mass-ratios reveals that the perturbations by low- and high-mass perturbers are dominated by different physical processes. The equal-mass case is a complicated mixture of the other two cases. Since the final properties of trajectories with similar initial conditions are usually also similar, the results of the limited number of integrated trajectories can be generalised to the full presented parameter space by interpolation. Since our results are also unique within the accuracy strived for, they constitute general numerical solutions for this subset of the restricted three-body problem. As such, they can be used to predict the evolution of real physical problems by simple transformations like scaling and without further simulations. (...)Comment: 11 pages, 8 figures, + 2 pages appendix, published by A&A; This version includes the Corrigendum (DOI: 10.1051/0004-6361/201526068e) and changes from the editing proces

Effects of inclined star-disk encounter on protoplanetary disk size

Most, if not all, young stars are initially surrounded by protoplanetary disks. Owing to the preferential formation of stars in stellar clusters, the protoplanetary disks around these stars may potentially be affected by the cluster environment. Various works have investigated the influence of stellar fly-bys on disks, although many of them consider only the effects due to parabolic, coplanar encounters often for equal-mass stars, which is only a very special case. We perform numerical simulations to study the fate of protoplanetary disks after the impact of parabolic star-disk encounter for the less investigated case of inclined up to coplanar, retrograde encounters, which is a much more common case. Here, we concentrate on the disk size after such encounters because this limits the size of the potentially forming planetary systems. In addition, with the possibilities that ALMA offers, now a direct comparison to observations is possible. Covering a wide range of periastron distances and mass ratios between the mass of the perturber and central star, we find that despite the prograde, coplanar encounters having the strongest effect on the disk size, inclined and even the least destructive retrograde encounters mostly also have a considerable effect, especially for close periastron passages. Interestingly, we find a nearly linear dependence of the disk size on the orbital inclination for the prograde encounters, but not for the retrograde case. We also determine the final orbital parameters of the particles in the disk such as eccentricities, inclinations, and semi-major axes. Using this information the presented study can be used to describe the fate of disks and also that of planetary systems after inclined encounters.Comment: 15 pages, 11 figures. Accepted for publication by Astronomy & Astrophysic

Sizes of protoplanetary discs after star-disc encounters

Most stars do not form in isolation, but as part of a star cluster or association. These young stars are initially surrounded by protoplanetary discs. In these cluster environments tidal interactions with other cluster members can alter the disc properties. Besides the disc frequency, its mass, angular momentum, and energy, in particular the disc's size is prone to being changed by a passing star. So far the change in disc size was only investigated for a small number of very specific encounters. Several studies investigated the effect of the cluster environment on the sizes of planetary systems, like our own solar system, based on a generalisation of information from this limited sample. We performed numerical simulations covering the wide parameter space typical for young star clusters, to test the validity of this approach. Here the sizes of discs after encounters are presented, based on a size definition which is comparable to that one used in observational studies. We find that, except for encounters between equal-mass stars, the usually applied estimates are insufficient. They tend to severely overestimate the remaining disc size. We show that the disc size after an encounter can be described by a relatively simple dependence on the periastron distance and the mass ratio of the encounter partners. This knowledge allows, for example, to pin down the types of encounter possibly responsible for the structure of today's solar system.Comment: 7 pages, 4 figures, + 2 pages Online material, accepted by A&

Creating retrogradely orbiting planets by prograde stellar fly-bys

Several planets have been found that orbit their host star on retrograde orbits (spin-orbit angle {\phi} > 90{\deg}). Currently, the largest measured projected angle between the orbital angular momentum axis of a planet and the rotation axis of its host star has been found for HAT-P-14b to be $\approx$ 171{\deg}. One possible mechanism for the formation of such misalignments is through long-term interactions between the planet and other planetary or stellar companions. However, with this process, it has been found to be difficult to achieve retrogradely orbiting planets, especially planets that almost exactly counter-orbit their host star ({\phi} $\approx$ 180{\deg}) such as HAT-P-14b. By contrast, orbital misalignment can be produced efficiently by perturbations of planetary systems that are passed by stars. Here we demonstrate that not only retrograde fly-bys, but surprisingly, even prograde fly-bys can induce retrograde orbits. Our simulations show that depending on the mass ratio of the involved stars, there are significant ranges of planetary pre-encounter parameters for which counter-orbiting planets are the natural consequence. We find that the highest probability to produce counter-orbiting planets ($\approx$ 20%) is achieved with close prograde, coplanar fly-bys of an equal-mass perturber with a pericentre distance of one-third of the initial orbital radius of the planet. For fly-bys where the pericentre distance equals the initial orbital radius of the planet, we still find a probability to produce retrograde planets of $\approx$ 10% for high-mass perturbers on inclined (60{\deg} < i < 120{\deg}) orbits. As usually more distant fly-bys are more common in star clusters, this means that inclined fly-bys probably lead to more retrograde planets than those with inclinations < 60{\deg}. (...)Comment: 13 pages, 9 figures, + 2 pages appendix, accepted by A&

What can we learn from consumer reports on psychiatric adverse drug reactions with antidepressant medication? Experiences from reports to a consumer association

Background According to the World Health Organization (WHO) the cost of adverse drug reactions   (ADRs) in the general population is high and under-reporting by health professionals   is a well-recognized problem. Another way to increase ADR reporting is to let the   consumers themselves report directly to the authorities. In Sweden it is mandatory   for prescribers to report serious ADRs to the Medical Products Agency (MPA), but there   are no such regulations for consumers. The non-profit and independent organization   Consumer Association for Medicines and Health, KILEN has launched the possibility   for consumers to report their perceptions and experiences from their use of medicines   in order to strengthen consumer rights within the health care sector. This study aimed   to analyze these consumer reports. Methods All reports submitted from January 2002 to April 2009 to an open web site in Sweden   where anyone could report their experience with the use of pharmaceuticals were analyzed   with focus on common psychiatric side effects related to antidepressant usage. More   than one ADR for a specific drug could be reported. Results In total 665 reports were made during the period. 442 reports concerned antidepressant   medications and the individual antidepressant reports represented 2392 ADRs and 878   (37%) of these were psychiatric ADRs. 75% of the individual reports concerned serotonin-reuptake   inhibitor (SSRI) and the rest serotonin-norepinephrine reuptake inhibitor (SNRI).   Women reported more antidepressant psychiatric ADRs (71%) compared to men (24%). More   potentially serious psychiatric ADRs were frequently reported to KILEN and withdrawal   symptoms during discontinuation were also reported as a common issue. Conclusions The present study indicates that consumer reports may contribute with important information   regarding more serious psychiatric ADRs following antidepressant treatment. Consumer   reporting may be considered a complement to traditional ADR reporting

Honori & amori posthumo Viri Admodum generosi maximeqve strenui Domini D. Thomæ de Jagow, In Scharpenhufe, aulosen, Stresow & Cruden Haereditarii Gravissimi optimeqve meriti ... Ipso solemni Exsequiarum die XVII. Mensis Martii Ann. M. DCC VII. hoc, quicquid est Monumenti, consecravit ac posuit lugentissimo animo Andreas Breslow, Past. Crüd.

Autopsie nach Exemplar der ULB Sachsen-AnhaltVorlageform des Erscheinungsvermerks: Gustroviæ Typis Johannis Lembkii, Sereniss. Princ. Typograph

Chinese my trauma recovery, a web-based intervention for traumatized persons in two parallel samples: randomized controlled trial

Background: Guided self-help interventions for PTSD (post-traumatic stress disorder) are a promising tool for the dissemination of contemporary psychological treatment. Objective: This study investigated the efficacy of the Chinese version of the My Trauma Recovery (CMTR) website. Methods: In an urban context, 90 survivors of different trauma types were recruited via Internet advertisements and allocated to a randomized controlled trial (RCT) with a waiting list control condition. In addition, in a rural context, 93 survivors mainly of the 2008 Sichuan earthquake were recruited in-person for a parallel RCT in which the website intervention was conducted in a counseling center and guided by volunteers. Assessment was completed online on a professional Chinese survey website. The primary outcome measure was the Post-traumatic Diagnostic Scale (PDS); secondary outcome measures were Symptom Checklist 90-Depression (SCL-D), Trauma Coping Self-Efficacy Scale (CSE), Post-traumatic Cognitive Changes (PCC), and Social Functioning Impairment (SFI) questionnaires adopted from the My Trauma Recovery website. Results: For the urban sample, findings indicated a significant group×time interaction in post-traumatic symptom severity (F1,88=7.65, P=.007). CMTR reduced post-traumatic symptoms significantly with high effect size after one month of treatment (F1,45=15.13, Cohen’s d=0.81, P<.001) and the reduction was sustained over a 3-month follow-up (F1,45=17.29, Cohen’s d=0.87, P<.001). In the rural sample, the group×time interaction was also significant in post-traumatic symptom severity (F1,91=5.35, P=.02). Post-traumatic symptoms decreased significantly after treatment (F1,48=43.97, Cohen’s d=1.34, P<.001) and during the follow-up period (F1,48=24.22, Cohen’s d=0.99, P<.001). Additional outcome measures (post-traumatic cognitive changes, depression) indicated a range of positive effects, in particular in the urban sample (group×time interactions: F1,88=5.32-8.37, all Ps<.03), contributing to the positive evidence for self-help interventions. Differences in the effects in the two RCTs are exploratorily explained by sociodemographic, motivational, and setting feature differences between the two samples. Conclusions: These findings give support for the short-term efficacy of CMTR in the two Chinese populations and contribute to the literature that self-help Web-based programs can be used to provide mental health help for traumatized persons. Trial Registration: Australia New Zealand Clinical Trials Registry (ANZCTR): ACTRN12611000951954; https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?ACTRN=12611000951954 (Archived by WebCite at http://www.webcitation.org/6G7WyNODk)