Maximum likelihood estimation of local stellar kinematics

Context. Kinematical data such as the mean velocities and velocity dispersions of stellar samples are useful tools to study galactic structure and evolution. However, observational data are often incomplete (e.g., lacking the radial component of the motion) and may have significant observational errors. For example, the majority of faint stars observed with Gaia will not have their radial velocities measured. Aims. Our aim is to formulate and test a new maximum likelihood approach to estimating the kinematical parameters for a local stellar sample when only the transverse velocities are known (from parallaxes and proper motions). Methods. Numerical simulations using synthetically generated data as well as real data (based on the Geneva-Copenhagen survey) are used to investigate the statistical properties (bias, precision) of the method, and to compare its performance with the much simpler "projection method" described by Dehnen & Binney (1998). Results. The maximum likelihood method gives more correct estimates of the dispersion when observational errors are important, and guarantees a positive-definite dispersion matrix, which is not always obtained with the projection method. Possible extensions and improvements of the method are discussed.Comment: 7 pages, 2 figures. Accepted for publication in Astronomy & Astrophysic

Size Control in the Nanoprecipitation Process of Stable Iodine (127I) Using Microchannel Reactor—Optimization by Artificial Neural Networks

In this study, nanosuspension of stable iodine (127I) was prepared by nanoprecipitation process in microfluidic devices. Then, size of particles was optimized using artificial neural networks (ANNs) modeling. The size of prepared particles was evaluated by dynamic light scattering. The response surfaces obtained from ANNs model illustrated the determining effect of input variables (solvent and antisolvent flow rate, surfactant concentration, and solvent temperature) on the output variable (nanoparticle size). Comparing the 3D graphs revealed that solvent and antisolvent flow rate had reverse relation with size of nanoparticles. Also, those graphs indicated that the solvent temperature at low values had an indirect relation with size of stable iodine (127I) nanoparticles, while at the high values, a direct relation was observed. In addition, it was found that the effect of surfactant concentration on particle size in the nanosuspension of stable iodine (127I) was depended on the solvent temperature. © 2015, American Association of Pharmaceutical Scientists

Effectiveness of a psychoeducation program on the quality of life in patients with coronary heart disease: A clinical trial

Aim The present study was conducted to evaluate effectiveness of a psychoeducation program (PEP) on the quality of life in patients with coronary heart disease (CHD). Background CHD affects patients' quality of life. PEPs may be useful to help patients reach maximum functional health. Methods A pretest–posttest controlled clinical trial was conducted on a study population of 70 CHD patients, who were selected through convenience sampling and randomly allocated to either the intervention or the control group. The MacNew Quality of Life Questionnaire in heart disease was completed by participants twice: first as a pretest, and then in a follow-up posttest. Results After the intervention, the quality of life (QOL) score was 157.97 ± 25.51 in the intervention group and 105.03 ± 8.38 in the control group, making for a significant difference (p < 0. 05). Conclusion Based on the findings, PEPs helped CHD patients improve their quality of life through reducing tension, relieving their negative emotions, and improving their social relationships. © 2016 Elsevier Inc