A tale of one city: intra-institutional variations in migrating VLE platform

City University London committed in 2009 to make Moodle the Virtual Learning Environment (VLE) at the core of a new Strategic Learning Environment (SLE) comprised of VLE, externally facing website and related systems such as video streaming and virtual classrooms. Previously, the WebCT VLE had been separate from most of the other systems at the institution with very limited connections to other tools. Each of the schools within the institution was able to pursue their own strategy and timeframe for the migration and embedding of Moodle within their subject areas, within an absolute limit of 2 years. This paper outlines the approaches taken by the various schools, highlighting similarities and differences, and draws out common aspects from the project to make recommendations for institutions seeking to undertake similar migrations

How an improved implementation of H2 self-shielding influences the formation of massive stars and black holes

High redshift quasars at z>6 have masses up to ~$10^9$ M$_\odot$. One of the pathways to their formation includes direct collapse of gas, forming a supermassive star, precursor of the black hole seed. The conditions for direct collapse are more easily achievable in metal-free haloes, where atomic hydrogen cooling operates and molecular hydrogen (H2) formation is inhibited by a strong external UV flux. Above a certain value of UV flux (J_crit), the gas in a halo collapses isothermally at ~$10^4$ K and provides the conditions for supermassive star formation. However, H2 can self-shield, reducing the effect of photodissociation. So far, most numerical studies used the local Jeans length to calculate the column densities for self-shielding. We implement an improved method for the determination of column densities in 3D simulations and analyse its effect on the value of J_crit. This new method captures the gas geometry and velocity field and enables us to properly determine the direction-dependent self-shielding factor of H2 against photodissociating radiation. We find a value of J_crit that is a factor of two smaller than with the Jeans approach (~2000 J_21 vs. ~4000 J_21). The main reason for this difference is the strong directional dependence of the H2 column density. With this lower value of J_crit, the number of haloes exposed to a flux >J_crit is larger by more than an order of magnitude compared to previous studies. This may translate into a similar enhancement in the predicted number density of black hole seeds.Comment: 14 pages, 12 figures, published in MNRA

NAO und Vorhersagbarkeit / NAO and predictability

Ein Überblick über die Güte heutiger NAO-Vorhersagen und Vorhersagbarkeit der NAO an sich wird gegeben. Der Einfluss der wesentlichen Prozesse auf die Vorhersagegüte auf saisonal-interannualen und dekadischen Zeitskalen wird zusammengetragen. Auf den saisonal-interannualen Zeitskalen ist vor allem die Wärmekapazität und der Wärmetransport der oberen Schichten des Nordatlantik von Bedeutung für den Anstieg der NAO-Vorhersagegüte. Statistische Modelle sowie gekoppelte Atmosphäre-Ozean-Ensemble-Vorhersagesysteme weisen für die beiden letzten Dekaden des 20 Jahrhunderts eine Vorhersagegüte von etwa 15 % auf. Die Vorhersagegüte über die letzten 50 Jahre liegt jedoch unter 10 %. Auf dekadischen Zeitskalen bildet die atlantische meridionale Umwälzbewegung eine Grundlage für die Vorhersagen des dekadischen Klimas in der atlantischen Region. A review of the NAO prediction and predictability is given. The impact of basic processes governing the NAO variability and their feasibility to enhance prediction skill on seasonal-to-interannual and decadal timescales is investigated. On seasonal-to-interannual timescales heat content and transport of the North Atlantic upper layer ocean can be essential to increase winter NAO prediction skill. Statistical models and coupled atmosphere-ocean ensemble prediction systems suggest a positive skill of about 15% for the latest decades in the 20th century. The prediction skill for the last 50 years, however, is below 10%. On decadal timescales particularly the meridional overturning circulation provides the basis for forecasts of the decadal climate over the North Atlantic region

Effects of turbulence and rotation on protostar formation as a precursor to seed black holes

Context. The seeds of the first supermassive black holes may have resulted from the direct collapse of hot primordial gas in $\gtrsim 10^4$ K haloes, forming a supermassive or quasistar as an intermediate stage. Aims. We explore the formation of a protostar resulting from the collapse of primordial gas in the presence of a strong Lyman-Werner radiation background. Particularly, we investigate the impact of turbulence and rotation on the fragmentation behaviour of the gas cloud. We accomplish this goal by varying the initial turbulent and rotational velocities. Methods. We performed 3D adaptive mesh refinement simulations with a resolution of 64 cells per Jeans length using the ENZO code, simulating the formation of a protostar up to unprecedentedly high central densities of $10^{21}$ cm$^{-3}$, and spatial scales of a few solar radii. To achieve this goal, we employed the KROME package to improve modelling of the chemical and thermal processes. Results. We find that the physical properties of the simulated gas clouds become similar on small scales, irrespective of the initial amount of turbulence and rotation. After the highest level of refinement was reached, the simulations have been evolved for an additional ~5 freefall times. A single bound clump with a radius of $2 \times 10^{-2}$ AU and a mass of ~$7 \times 10^{-2}$ M$_{\odot}$ is formed at the end of each simulation, marking the onset of protostar formation. No strong fragmentation is observed by the end of the simulations, regardless of the initial amount of turbulence or rotation, and high accretion rates of a few solar masses per year are found. Conclusions. Given such high accretion rates, a quasistar of $10^5$ M$_{\odot}$ is expected to form within $10^5$ years.Comment: 18 pages, 7 figures, fixed typos, added references and clarified some details; accepted for publication in A&

Extraction of biological hydroxyapatite from tuna fish bone for biomedical applications

Natural hydroxyapatite (HAp) is known for its common use in biomedical applications including in orthopaedic and implantation. HAp can be extracted from natural resources such as eggshells, fish bones and coral. Annually, it is found that huge amount of tuna fish bones was thrown away and being wasted as results from great consumption of tuna fish. In this study, tuna fish bones were extracted and characterised to be used in biomedical applications. Specifically, tuna fish bones were cleaned, and calcined at high temperature of 700 °C, 900 °C and 1100 °C. Powders calcined at 700 °C showed pure HAp compared to powders calcined at 900 °C and 1100 °C which showed the presence of β-TCP. As temperature rising, the morphology of the powders also changes from spherical-shaped to irregular-shaped indicated the substitution of phosphate and calcium from the β-TCP which also influenced the ratio of Ca/P obtained. In this study, powders calcined at 700 °C obtained optimum Ca/P ratio of 1.60. Moreover, EDS analysis showed the presence of tracer elements such as Ca, Mg, Sr Na, K and Zn in all calcined samples. These elements can help improve the biocompatibility of the HAp and beneficial for biomedical applications

A UV flux constraint on the formation of direct collapse black holes

The ability of metal free gas to cool by molecular hydrogen in primordial halos is strongly associated with the strength of ultraviolet (UV) flux produced by the stellar populations in the first galaxies. Depending on the stellar spectrum, these UV photons can either dissociate $\rm H_{2}$ molecules directly or indirectly by photo-detachment of $\rm H^{-}$ as the latter provides the main pathway for $\rm H_{2}$ formation in the early universe. In this study, we aim to determine the critical strength of the UV flux above which the formation of molecular hydrogen remains suppressed for a sample of five distinct halos at $z>10$ by employing a higher order chemical solver and a Jeans resolution of 32 cells. We presume that such flux is emitted by PopII stars implying atmospheric temperatures of $\rm 10^{4}$~K. We performed three-dimensional cosmological simulations and varied the strength of the UV flux below the Lyman limit in units of $\rm J_{21}$. Our findings show that the value of $\rm J_{21}^{crit}$ varies from halo to halo and is sensitive to the local thermal conditions of the gas. For the simulated halos it varies from 400-700 with the exception of one halo where $\rm J_{21}^{crit} \geq 1500$. This has important implications for the formation of direct collapse black holes and their estimated population at z > 6. It reduces the number density of direct collapse black holes by almost three orders of magnitude compared to the previous estimates.Comment: 10 pages, 6 figures, matches the accepted version to ber published in MNRAS, higher resolution version is available at http://www.astro.physik.uni-goettingen.de/~mlatif/Jcrit.pd

Evaluasi Aspek Keselamatan Kegiatan Metalografi Di Instalasi Elemen Bakar Eksperimental

─Telah dilakukan evaluasi aspek keselamatan kegiatan metalografi di Instalasi Elemen Bakar Eksperimental. Tujuan dari kegiatan ini untuk mengetahui aspek keselamatan dari kegiatan metalografi di IEBE. Pengukuran kontaminasi dilakukan terhadap meja preparasi, peralatan metalografi yang berpotensi terkontaminasi, kemudian penanganan limbah cair dan padat serta pelaksanaan dekontaminasi pada meja kerja preparasi, atau lokasi penempatan sampel hasil metalografi. Hasil pengukuran pada titik pantau yang variatif, didapatkan hasil yang tertinggi yaitu pada titik pantau 1, lebih tinggi dari titik pengukuran yang lain. Dari hasil rata-rata pada titik pantau 1 (satu) didapatkan hasil pengukuran (0,245 ± 0,014 Bq/cm2), sedangkan pada titik pantau 2 (dua) didapat hasil pengukuran (0,228 ± 0,008 Bq/cm2), titik pengukuran 3 (tiga) didapat hasil pengukuran (0,238 ± 0,006550 Bq/cm2)dan titik pantau 4 (empat) didapatkan hasil pengukuran (0,232 ± 0,035 Bq/cm2). Pengukuran tingkat kontaminasi pasca deko pada titik pantau 1 didapat rata-rata 0,245 ± 0,014 Bq/cm2. Pasca dekontaminasi kontaminasi dapat diturunkan menjadi 0,018 ± 0,007 Bq/cm2. Pengukuran kontaminasi juga dilakukan pada peralatan metalografi dan didapatkan hasil pengukuran terendah 0,049 Bq/cm2, sedangkan tertinggi 0,059 Bq/cm2 dengan rata-rata 0,054 ± 0,005 Bq/cm2 Sedangkan pada titik pantau lainnya lebih rendah. Dari kegiatan metalografi ini dipastikan dapat menghasilkan dua jenis limbah baik limbah padat maupun limbah cair. Dari hasil limbah padat yang didapatkan akan ditampung pada wadah limbah yang tersedia, sedangkan untuk limbah cair dilakukan analisa kandungan uraniumnya, apabila terdapat kandungan uranium lebih besar 50 ppm maka akan dilakukan pemungutan kembali. Secara keseluruhan kegiatan metalografi di IEBE sudah terpenuhi dari aspek keselamatan dan tidak menyimpang dari kaidah dan norma keselamatan yang ada