Star formation and chemical evolution in SPH simulations: a statistical approach

In Smoothed Particles Hydrodynamics (SPH) codes with a large number of particles, star formation as well as gas and metal restitution from dying stars can be treated statistically. This approach allows to include detailed chemical evolution and gas re-ejection with minor computational effort. Here we report on a new statistical algorithm for star formation and chemical evolution, especially conceived for SPH simulations with large numbers of particles, and for parallel SPH codes. For the sake of illustration, we present also two astrophysical simulations obtained with this algorithm, implemented into the Tree-SPH code by Lia & Carraro (2000). In the first one, we follow the formation of an individual disc-like galaxy, predict the final structure and metallicity evolution, and test resolution effects. In the second one we simulate the formation and evolution of a cluster of galaxies, to demonstrate the capabilities of the algorithm in investigating the chemo-dynamical evolution of galaxies and of the intergalactic medium in a cosmological context.Comment: 17 pages, 20 figures, accepted for publication on MNRA

A Parallel Tree-SPH code for Galaxy Formation

We describe a new implementation of a parallel Tree-SPH code with the aim to simulate Galaxy Formation and Evolution. The code has been parallelized using SHMEM, a Cray proprietary library to handle communications between the 256 processors of the Silicon Graphics T3E massively parallel supercomputer hosted by the Cineca Supercomputing Center (Bologna, Italy). The code combines the Smoothed Particle Hydrodynamics (SPH) method to solve hydro-dynamical equations with the popular Barnes and Hut (1986) tree-code to perform gravity calculation with a NlogN scaling, and it is based on the scalar Tree-SPH code developed by Carraro et al(1998)[MNRAS 297, 1021]. Parallelization is achieved distributing particles along processors according to a work-load criterion. Benchmarks, in terms of load-balance and scalability, of the code are analyzed and critically discussed against the adiabatic collapse of an isothermal gas sphere test using 20,000 particles on 8 processors. The code results balanced at more that 95% level. Increasing the number of processors, the load-balance slightly worsens. The deviation from perfect scalability at increasing number of processors is almost negligible up to 32 processors. Finally we present a simulation of the formation of an X-ray galaxy cluster in a flat cold dark matter cosmology, using 200,000 particles and 32 processors, and compare our results with Evrard (1988) P3M-SPH simulations. Additionaly we have incorporated radiative cooling, star formation, feed-back from SNae of type II and Ia, stellar winds and UV flux from massive stars, and an algorithm to follow the chemical enrichment of the inter-stellar medium. Simulations with some of these ingredients are also presented.Comment: 19 pages, 14 figures, accepted for publication in MNRA

Coupling Chemical Evolution with SPH

We present a new statistical algorithm of Chemical Evolution implemented into the Tree-SPH code developed by Lia & Carraro (2000 MNRAS 314, 145)

The Application of Interactive Comprehensible Written Input-Output Instruction for Teaching Writing

This study was aimed at finding out whether there was a difference on students\u27 writing ability in general as well as students\u27 aspects of writing in particular and exploringwhether there would be a difference on students\u27 prediction of Narrative and Anecdote Text as a part of Interactive Comprehensible Written Input-Output Instruction.The study involved 36 MathematicsEducation students in the first semester of academic year 2016/2017. To collect the data, the researcher administered writing testsand collected students\u27 writing drafts. Then, the data were analyzed both quantitatively and qualitatively. The results showed there was a significant difference on both students\u27 writing ability and aspects of writing after the application of this instruction. Then, there was also a difference on their prediction of two texts that it was easier for the students to predict the continuation of the story in Narrative Text rather than in Anecdote one.Penelitian ini bertujuan untuk mengetahui apakah ada perbedaan dari kemampuan menulis mahasiswa secara umum dan aspek-aspek menulis mereka secara khusus dan untuk menelusuri apakah ada perbedaan dari prediksi mahasiswa terhadap Teks Narasi dan Anekdot sebagai bagian dari Instruksi Input-Output Tertulis Terpahami yang Interaktif. Penelitian ini melibatkan 36 mahasiswa Pendidikan Matematika pada tahun ajaran 2016/2017. Untuk mengumpulkan data, penelitian mengadakan tes menulis dan mengumpulkan draft-draft tulisan mereka. Data-data tersebut kemudian dianalisa secara kuantitatif dan kualitatif. Hasil penelitian menunjukkan bahwa ada perbedaan dari kemampuan menulis mahasiswa secara umum dan aspek-aspek menulis mereka secara khusus setelah penerapan instruksi ini. Selain itu, terdapat perbedaan prediksi yang dibuat terhadap dua tekster sebut dengan lebih mudahnya mahasiswa untuk memprediksi kelanjutan cerita pada Teks Narasi dibandingkan Teks Anekdot

A Search for Ionized Gas in the Draco and Ursa Minor Dwarf Spheroidal Galaxies

The Wisconsin H Alpha Mapper has been used to set the first deep upper limits on the intensity of diffuse H alpha emission from warm ionized gas in the Local Group dwarf spheroidal galaxies (dSphs) Draco and Ursa Minor. Assuming a velocity dispersion of 15 km/s for the ionized gas, we set limits for the H alpha intensity of less or equal to 0.024 Rayleighs and less or equal to 0.021 Rayleighs for the Draco and Ursa Minor dSphs, respectively, averaged over our 1 degree circular beam. Adopting a simple model for the ionized interstellar medium, these limits translate to upper bounds on the mass of ionized gas of approximately less than 10% of the stellar mass, or approximately 10 times the upper limits for the mass of neutral hydrogen. Note that the Draco and Ursa Minor dSphs could contain substantial amounts of interstellar gas, equivalent to all of the gas injected by dying stars since the end of their main star forming episodes more than 8 Gyr in the past, without violating these limits on the mass of ionized gas.Comment: 10 pages, 2 figures, AASTeX two-column format. Accepted for publication in The Astrophysical Journa

Optimasi Basis Krim Ekstrak Etanol Daun Kawista (Limonia Acidissima L.) Sebagai Antibakteri Staphylococcus Aureus

SARI Daun kawista diketahui mengandung senyawa flavonoid, tannin, dan alkaloid yang dapat menghambat pertumbuhan Staphylococcus aureus. Penggunaan emulgid dan parafin cair dalam sediaan krim sebagai emulgator dan pelembut diharapkan mampu meningkatkan aktivitas antibakteri Staphylococcus aureus dan karakteristik fisik krim yang memenuhi syarat.Penelitian ini bertujuan untuk mengetahui pengaruh dan menentukan formula optimal dengan komponen emulgid dan parafin cair dalam krim ekstrak etanol daun kawista (Limonia acidissima L.) pada karakteristik fisik dan aktivitas antibakteri Staphylococcus aureus dengan metode Simplex Lattice Design. Ekstrak etanol daun kawista didapatkan dengan cara remaserasi menggunakan pelarut etanol 70%. Ekstrak kental diuji aktivitas antibakteri Staphylococcus aureus dengan metode difusi sumuran kemudian konsentrasi ekstrak yang optimal diformulasikan dalam sediaan krim. Berdasarkan Design Expert 9.0.6.2 Trial, didapatkan formula optimal dengan perbandingan konsentrasi emulgid dan parafin cair sebesar 24,848%:5,152%. Hasil pengujian formula optimal didapatkan rerata diameter zona hambat bakteri 11,50 mm, daya sebar 6,49 cm, viskositas 4480 cps, dan pH 5,46 dimana hasil tersebut berbeda tidak signifikan terhadap hasil prediksi Design Expert 9.0.6.2 Trial

Clausius' Virial vs. Total Potential Energy in the dynamics of a two-component system

In a gravitational virialized bound system built up of two components, one of which is embedded in the other, the Clausius' virial energy of one subcomponent is not, in general, equal to its total potential energy, as occurs in a single system without external forces. This is the main reason for the presence, in the case of two non-coinciding concentric spheroidal subsystems, of a minimum (in absolute value) in the Clausius' virial of the inner component B, when it assumes a special configuration characterized by a value of its semi-major axis we have named "tidal radius". The physical meaning, connected with its appearance, is to introduce a scale length on the gravity field of the inner subsystem, which is induced from the outer one. Its relevance in the galaxy dynamics has been stressed by demonstrating that some of the main features of the Fundamental Plane may follow as consequence of its existence. More physical insight into the dynamics of a two component system may be got by looking at the location of this scale length inside the plots of the potential energies of each subsystem and of the whole system and by also taking into account the trend of the anti-symmetric residual-energy, that is the difference between the tidal and the interaction-energy of each component. Some thermodynamical arguments related to the inner component are also added to prove as special is the "tidal radius configuration". Moreover the role of the divergency at the center of the two subsystems in obtaining this scale length is considered. For the sake of simplicity the analysis has been performed in the case of a frozen external component even if this constraint does not appear to be too relevant in order to preserve the main results.Comment: New Astronomy, accepte

Pengaruh Hedonic Shopping Motivation Terhadap Impulse Buying Pada Toko Online: Studi Pada Toko Online Zalora

Online shopping, including shopping for fashion goods, has become a trend in Indonesia. One of buyer's motivations to do online-fashion-shopping is hedonic shopping motivation. This research aims to examine the influence of hedonic shopping motivation on impulse buying process. Using 100 buyers of Zalora (an online shop) as the respondents, this study confirms that hedonic shopping motivation has a significant influence on the impulse buying process