The evolution of streams in a time-dependent potential

We study the evolution of streams in a time-dependent spherical gravitational potential. Our goal is to establish what are the imprints of this time evolution on the properties of streams as well as their observability. To this end, we have performed a suite of numerical experiments for a host system that doubles its mass during the integration time and for a variety of initial conditions. In these experiments we found that the most striking imprint is a misalignment of 10 degrees in the angular location of the apocentres of the streams compared to the static case (and to the orbit of the centre of mass), which only becomes apparent for sufficiently long streams. We have also developed an analytic model using action-angle variables which allows us to explain this behaviour and to identify the most important signature of time evolution, namely a difference in the slope defined by the distribution of particles along a stream in frequency and in angle space. Although a difference in slope can arise when the present-day potential is not correctly modelled, this shortcoming can be by-passed because in this case, streams are no longer straight lines in angle space, but depict a wiggly appearance and an implausible energy gradient. The difference in slope due to time-evolution is small, typically $\sim10^{-2}$ and its amplitude depends on the growth rate of the potential, but nonetheless we find that it could be observable if accurate full-space information for nearby long streams is available.Comment: 20 pages, 18 figures. Accepted for publication in A&

A new fitting-function to describe the time evolution of a galaxy's gravitational potential

We present a new simple functional form to model the evolution of a spherical mass distribution in a cosmological context. Two parameters control the growth of the system and this is modelled using a redshift dependent exponential for the scale mass and scale radius. In this new model, systems form inside out and the mass of a given shell can be made to never decrease, as generally expected. This feature makes it more suitable for studying the smooth growth of galactic potentials or cosmological halos than other parametrizations often used in the literature. This is further confirmed through a comparison to the growth of dark matter halos in the Aquarius simulations.Comment: 5 pages, 4 figures; example figures replaced by their correct versions. Accepted for publication in A&

On the behaviour of streams in angle and frequency spaces in different potentials

We have studied the behaviour of stellar streams in the Aquarius fully cosmological N-body simulations of the formation of Milky Way halos. In particular, we have characterised the streams in angle/frequency spaces derived using an approximate but generally well-fitting spherical potential. We have also run several test-particle simulations to understand and guide our interpretation of the different features we see in the Aquarius streams. Our goal is both to establish which deviations of the expected action-angle behaviour of streams exist because of the approximations made on the potential, but also to derive to what degree we can use these coordinates to model streams reliably. We have found that many of the Aquarius streams wrap in angle space along relatively straight lines, and also in frequency space. On the other hand, from our controlled simulations we have been able to establish that deviations from spherical symmetry, the use of incorrect potentials and the inclusion of self-gravity lead to streams in angle space to still be along relatively straight lines but also to depict wiggly behaviour whose amplitude increases as the approximation to the true potential becomes worse. In frequency space streams typically become thicker and somewhat distorted. Therefore, our analysis explains most of the features seen in the approximate angle and frequency spaces for the Aquarius streams with the exception of their somewhat `noisy' and `patchy' morphologies. These are likely due to the interactions with the large number of dark matter subhalos present in the cosmological simulations. Since the measured angle-frequency misalignments of the Aquarius streams can largely be attributed to using the wrong (spherical) potential, determining the mass growth history of these halos will only be feasible once the true potential has been determined robustly.Comment: 21 pages, 18 figures. Accepted for publication in A&

Overeducation, gender, income and life satisfaction. Panel evidence from Korea

One reason often put forward for South Korea’s rapid economic growth has been the rising level of educational attainment of its workforce. Correspondingly, the proportion of Koreans who complete tertiary education has also rapidly increased (and is also considerably higher than the OECD average). Such increases raise the possibility of overeducation if the amount of jobs which require such education do not increase at a similar pace. Among the consequences of overeducation are reduced life satisfaction and underutilised human capital. Given that Korean females are better educated than males, and they also face more discrimination in the labour market, the consequences of overeducation are likely to differ by gender. Using Korean panel data and both a subjective and objective measure of overeducation, the results are consistent with females having lower aspirations despite their high levels of education, and indicate that a more female friendly labour market could address the country’s currently underutilised human capital, for the benefit of the females themselves, as well as males, and the Korean economy

Persepsi Masyarakat terhadap Resiko Bencana Longsor di Dusun Blawong Kulon Desa Muncar Kecamatan Gemawang Kabupaten Temanggung

Dusun Blawong Kulon merupakan salah satu Dusun di Kabupaten Temanggung yang mempunyai resiko bencana longsor yang tinggi. Penelitian ini dilakukan untuk mengetahui persepsi resiko masyarakat terhadap bencana longsor. Penelitian ini bertujuan untuk a) Mengidentifikasi pengetahuan masyarakat terhadap ancaman bencana longsor b)Menganalisis persepsi resiko masyarakat terhadap ancaman bencana longsor c) Mengetahui upaya penanggulangan bencana yang dilakukan masyarakat dalam menghadapi ancaman bencana longsor. Metode kuantitatif digunakan untuk memperoleh data dengan menggunakan kuesioner dan skala likert serta menggunakan analisis statistik deskriptik dengan pemilihan sampel menggunakan probability sampling yaitu cluster sampling. Pengambilan sampel berada di delapan RT (Rumah Tangga) yang tersebar di Dusun Blawong Kulon dengan jumlah sampel 80 unit dengan unit Rumah Tangga. Hasil penelitian yang diperoleh adalah a) Penduduk Dusun Blawong Kulon mempunyai pengetahuan yang tinggi mengenai bencana longsor b) Penduduk Dusun Blawong Kulon mempunyai persepsi positif terhadap bencana longsor dengan agregat skala likert sebesar 60,8% c) dan sebanyak 51% penduduk Dusun Blawong Kulon mempunyai upaya penanggulangan bencana yang tinggi

Peran Pengkhotbah Terhadap Minat Jemaat Menghadiri Ibadah Raya Di Gereja Injili Agape Makassar

Tujuan penulisan ini adalah menjelaskan sejauh mana Peran Pengkhotbah Terhadap Minat Jemaat Menghadiri Ibadah Raya Di Gereja Injili Agape Makassar. Adapun metode yang penulis gunakan dalam penelitian ini adalah metode kualitatif deskriptif dengan cara mengalami (mengamati secara partisipatif), dengan menyelediki, mewancarai, bertujuan untuk menggambarkan secara utuh dan mendalam tentang realitas sosial dan berbagai fenomena yang terjadi. Dari hasil penelitian ini maka penulis menarik beberapa kesimpulan. Pertama, menjadi seorang pengkhotbah adalah tugas dan tanggung jawab yang paling mulia dari Tuhan Yesus Kristus. Oleh sebab itu seorang pengkhotbah tidak hanya menerima kepercayaan itu saja, tetapi dapat menjalankannya sebaik-baiknya sesuai dengan kebenaran firman Tuhan. Kedua, kehadiran jemaat dapat dipengaruhi oleh bagaimana caranya pengkhotbah mempersiapkan dirinya dan mempersiapkan khotbahnya serta bagaimana cara pengkhotbah dapat menguraikan kebenaran firman Tuhan sesuai dengan kebutuhan jemaat yang dilayaninya dan yang lain adalah perkunjungan kepada jemaat. Ketiga, kebanyakan jemaat kurang memahami bahasa inggris sehingga mereka sulit untuk memahami setiap kebenaran firman Tuhan yang disampaikan oleh pengkhotbah, hal inilah yang menyebabkan jemaat malas hadir untuk mengikuti ibadah

Kim Jiyoung, Born 1982, and the Labour Market: Overeducation, Gender, Income and Life Satisfaction. Panel evidence from Korea.

One reason often put forward for South Korea’s rapid economic growth has been the rising level of educational attainment of its workforce. Correspondingly, the proportion of Koreans who complete tertiary education has also rapidly increased (and is also considerably higher than the OECD average). Such increases raise the possibility of overeducation if the amount of jobs which require such education do not increase at a similar pace. Among the consequences of overeducation are reduced life satisfaction and underutilised human capital. Given that Korean females are better educated than males, and they also face more discrimination in the labour market, the consequences of overeducation are likely to differ by gender. Using Korean panel data and both a subjective and objective measure of overeducation, the results are consistent with females having lower aspirations despite their high levels of education, and indicate that a more female friendly labour market could address the country’s currently underutilised human capital, for the benefit of the females themselves, as well as males, and the Korean economy

The Performance of Fertility Awareness-based Method Apps Marketed to Avoid Pregnancy

INTRODUCTION: In recent years there has been an explosion in the development of medical apps, with more than 40,000 apps now available. Nearly 100 apps allow women to track their fertility and menstrual cycles and can be used to avoid or achieve pregnancy. Apps offer a convenient way to track fertility biomarkers. However, only some use evidence-based fertility awareness-based methods (FABMs), which with ideal use have rates of effectiveness similar to those of commonly used forms of hormonal birth control. Since having a baby or preventing a pregnancy are important responsibilities, it is critical that women and couples have access to reliable, evidence-based apps that allow them to accurately track their fertility. METHODS: We developed a tool to evaluate and rate fertility apps. This tool is specifically designed to help couples avoid pregnancy. RESULTS: Results showed that the majority of fertility apps are not based on evidence-based FABMs or include a disclaimer discouraging use for avoiding pregnancy. However, at least 1 app in each FABM category (except symptohormonal methods) had a perfect score on accuracy. CONCLUSION: Relying solely on an app to use an FABM, without appropriate training in the method, may not be sufficient to prevent pregnancy

Synthesis, Characterization and Study of Antibacterial Activity of a New Schiff Base Ligand and Its Complexes with Co(II), Ni(II), Cu(II), Cd(II) and Hg(II) Metal Ions

Some coordination complexes of Co(??), Ni(??), Cu(??), Cd(??) and Hg(??) are reacted in ethanol with Schiff base ligand derived from of 2,4,6- trihydroxybenzophenone and 3-aminophenol using microwave irradiation and then reacted with metal salts in ethanol as a solvent in 1:2 ratio (metal: ligand). The ligand [H4L] is characterized by FTIR, UV-Vis, C.H.N, 1H-NMR,13C-NMR, and mass spectra. The metal complexes are characterized by atomic absorption, infrared spectra, electronic spectra, molar conductance, (C.H.N for Ni(??) complex) and magnetic moment measurements. These measurements indicate that the ligand coordinates with metal (??) ion in a tridentate manner through the nitrogen and oxygen atoms of the ligand, octahedral structures are suggested for these complexes. Antibacterial activity of the ligand [H4L] and its complexes are studied against (gram positive) and (gram negative) bacteria [Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus and Bacillus]. The proposed structure of the complexes using the program, Chem office (2006) and the general formula has been given for the prepared ligand complexes K2[M(H2L)2]