Angular Momentum Changes Due to Direct Impact Accretion in a Simplified Binary System

We model a circular mass-transferring binary system to calculate the exchange of angular momentum between stellar spins and the orbit due to direct impact of the mass transfer stream onto the surface of the accretor. We simulate mass transfer by calculating the ballistic motion of a point mass ejected from the $L_1$ point of the donor star, conserving the total linear and angular momentum of the system, and treating the stars as uniform density spheres with main sequence radii determined by their masses. We show that, contrary to previous assumptions in the literature, direct impact does not always act as a sink of orbital angular momentum and may in fact increase it by facilitating the transfer of angular momentum from the spin of the donor to the orbit. Here, we show an example of the exchange of angular momentum, as well as a measure of the orbital angular momentum changes for a variety of binary star systems with main sequence components.Comment: 2 pages, 2 figures, Conference Proceedings for the International Conference on Binaries, Mykonos, Greece. Updated Version of Fig. 1b, correcting a scaling error. Results remain unchanged, but the numerical scaling factors have been decrease

Evolutionary Channels for the Formation of Double Neutron Stars

We analyze binary population models of double-neutron stars and compare results to the accurately measured orbital periods and eccentricities of the eight known such systems in our Galaxy. In contrast to past similar studies, we especially focus on the dominant evolutionary channels (we identify three); for the first time, we use a detailed understanding of the evolutionary history of three double neutron stars as actual constraints on the population models. We find that the evolutionary constraints derived from the double pulsar are particularly tight, and less than half of the examined models survive the full set of constraints. The top-likelihood surviving models yield constraints on the key binary evolution parameters, but most interestingly reveal (i) the need for electron-capture supernovae from relatively low-mass degenerate, progenitor cores, and (ii) the most likely evolutionary paths for the rest of the known double neutron stars. In particular, we find that J1913+16 likely went through a phase of Case BB mass transfer, and J1906+0746 and J1756-2251 are consistent with having been formed in electron-capture supernovae.Comment: 17 pages, 9 figure

Algorithms for deterministic balanced subspace identification

New algorithms for identification of a balanced state space representation are proposed. They are based on a procedure for the estimation of impulse response and sequential zero input responses directly from data. The proposed algorithms are more efficient than the existing alternatives that compute the whole Hankel matrix of Markov parameters. It is shown that the computations can be performed on Hankel matrices of the input–output data of various dimensions. By choosing wider matrices, we need persistency of excitation of smaller order. Moreover, this leads to computational savings and improved statistical accuracy when the data is noisy. Using a finite amount of input–output data, the existing algorithms compute finite time balanced representation and the identified models have a lower bound on the distance to an exact balanced representation. The proposed algorithm can approximate arbitrarily closely an exact balanced representation. Moreover, the finite time balancing parameter can be selected automatically by monitoring the decay of the impulse response. We show what is the optimal in terms of minimal identifiability condition partition of the data into “past” and “future”

Medication adherence among Turkish type-2 diabetics in Belgium: results from a qualitative study

Abstract title: Medication adherence among Turkish type-2 diabetics in Belgium: results from a qualitative study. Aim: Prevalence of diabetes in Belgium is 2 to 3 times higher among people from Turkish descent. Medication adherence, an essential element of the diabetic regimen, appears to be lower among nonwhite ethnic groups. This study identifies factors influencing medication adherence among Turkish type-2 diabetics living in Belgium. Methods: Since this topic hasn’t been studied before we conducted an explorative, qualitative study using semi-structured in-depth interviews with the aid of an interpreter. The topicslist was based on insights from the literature and conversations with Turkish diabetics and health care workers and was slightly adjusted after the first interviews. 21 Turkish type-2 diabetics living in Belgium were selected using theoretical sampling. Respondent’s most recent HbA1c-values were also collected. Interviews lasted between 2 and 5 hours, were audio-taped, fully transcribed and translated. Thematic analysis was conducted by the first two authors with different educational backgrounds (sociologist/pharmacist). The first phase was a detailed, thematic analysis of the individual cases, in the second phase an analysis across cases, distinguishing adherers from non-adherers, identified factors influencing medication adherence. NVivo 8 was used for managing, coding and analysing the qualitative data. Results: Factors influencing medication adherence among type-2 diabetics from Turkish descent include knowledge of and attitudes towards diabetes and antidiabetics, health and medication beliefs, social support from health care providers and family members, the nature of the patient-provider relationship, perceptions of health care worker’s expertise and social roles in daily life. A typology was constructed identifying different constellations of factors that distinguish adherers from non-adherers. Implications for clinical practice are discussed. Conclusion: This qualitative study identifies factors influencing medication adherence among type-2 Turkish diabetics living in Belgium and provides a typology, distinguishing adherers from non-adherers, that may guide clinical practice. Results from this qualitative study will be tested in a future, quantitative study

Medication adherence among Turkish type-2 diabetics in Belgium: results from a qualitative study

Abstract title: Medication adherence among Turkish type-2 diabetics in Belgium: results from a qualitative study. Aim: Prevalence of diabetes in Belgium is 2 to 3 times higher among people from Turkish descent. Medication adherence, an essential element of the diabetic regimen, appears to be lower among nonwhite ethnic groups. This study identifies factors influencing medication adherence among Turkish type-2 diabetics living in Belgium. Methods: Since this topic hasn’t been studied before we conducted an explorative, qualitative study using semi-structured in-depth interviews with the aid of an interpreter. The topicslist was based on insights from the literature and conversations with Turkish diabetics and health care workers and was slightly adjusted after the first interviews. 21 Turkish type-2 diabetics living in Belgium were selected using theoretical sampling. Respondent’s most recent HbA1c-values were also collected. Interviews lasted between 2 and 5 hours, were audio-taped, fully transcribed and translated. Thematic analysis was conducted by the first two authors with different educational backgrounds (sociologist/pharmacist). The first phase was a detailed, thematic analysis of the individual cases, in the second phase an analysis across cases, distinguishing adherers from non-adherers, identified factors influencing medication adherence. NVivo 8 was used for managing, coding and analysing the qualitative data. Results: Factors influencing medication adherence among type-2 diabetics from Turkish descent include knowledge of and attitudes towards diabetes and antidiabetics, health and medication beliefs, social support from health care providers and family members, the nature of the patient-provider relationship, perceptions of health care worker’s expertise and social roles in daily life. A typology was constructed identifying different constellations of factors that distinguish adherers from non-adherers. Implications for clinical practice are discussed. Conclusion: This qualitative study identifies factors influencing medication adherence among type-2 Turkish diabetics living in Belgium and provides a typology, distinguishing adherers from non-adherers, that may guide clinical practice. Results from this qualitative study will be tested in a future, quantitative study