On the duration of long GRBs: effects of black hole spin

In the frame of the collapsar model for long gamma ray bursts (GRBs), we investigate the formation of a torus around a spinning BH and we check what rotational properties a progenitor star must have in order to sustain torus accretion over relatively long activity periods. We also study the time evolution of the BH spin parameter. We take into account the coupling between BH mass, its spin parameter and the critical specific angular momentum of accreting gas, needed for the torus to form. The large BH spin reduces the critical angular momentum which in turn can increase the GRB duration with respect to the Schwarzschild BH case. We quantify this effect and estimate the GRB durations in three cases: when a hyper accreting torus operates or a BH spins very fast or both. We show under what conditions a given progenitor star produces a burst that can last as short as several seconds and as long as several hundred of seconds. Our models indicate that it is possible for a single collapse to produce three kinds of jets: (1) a very short, lasting between a fraction of a second and a few seconds, 'precursor' jet, powered only by a hyper accreting torus before the BH spins up, (2) an 'early' jet, lasting several tens of seconds and powered by both hyper accretion and BH rotation, and (3) a 'late' jet, powered only by the spinning BH.Comment: 13 pages; 9 figures; ApJ in pres

Kpi form factors and final state interactions in D+ --> K- pi+ pi+ decays

We present a model for the decay D+ --> K- pi+ pi+. The weak interaction part of this reaction is described using the effective weak Hamiltonian in the factorisation approach. Hadronic final state interactions are taken into account through the Kpi scalar and vector form factors fulfilling analyticity, unitarity and chiral symmetry constraints. The model has only two free parameters that are fixed from experimental branching ratios. We show that the modulus and phase of the S wave thus obtained agree nicely with experiment up to 1.55 GeV. We perform Monte Carlo simulations to compare the predicted Dalitz plot with experimental analyses. Allowing for a global phase difference between the S and P waves of -65 degrees, the Dalitz plot of the D+ --> K- pi+ pi+ decay, the Kpi invariant mass spectra and the total branching ratio due to S-wave interactions are well reproduced.Comment: 24 pages, 4 figures, REVTeX style. A discussion on the isospin 2 component has been included. Two references added. Published in Phys. Rev.

Uniform high irradiance source

New 50 Kw xenon short arc lamp mounted within elliptical collector provides irradiance levels up to 4.4 x 10 to the 7th power watts/sq m with non-uniformity ratio of 3.30. Energy mixer or light pipe between lamp source and target improves non-uniformity to required ratio

Evidence for chaotic behaviour in pulsar spin-down rates

We present evidence for chaotic dynamics within the spin-down rates of 17 pulsars originally presented by Lyne et al. Using techniques that allow us to re-sample the original measurements without losing structural information, we have searched for evidence of a strange attractor in the time series of frequency derivatives for each of the 17 pulsars. We demonstrate the effectiveness of our methods by applying them to a component of the Lorenz and R\"ossler attractors that were sampled with similar cadence to the pulsar time series. Our measurements of correlation dimension and Lyapunov exponent show that the underlying behaviour appears to be driven by a strange attractor with approximately three governing non-linear differential equations. This is particularly apparent in the case of PSR B1828$-$11 where a correlation dimension of 2.06\pm0.03 and a Lyapunov exponent of $(4.0\pm0.3)\times10^{-4}$ inverse days were measured. These results provide an additional diagnostic for testing future models of this behaviour.Comment: 15 pages, 18 figures, 2 tables, Accepted to MNRA

KEDUDUKAN AHLI WARIS NON MUSLIM DALAM KEWARISAN ISLAM (STUDI KASUS PUTUSAN NOMOR : 1578/PDT.G/2010/PA.JT)

Salah satu pembahasan dalam ilmu mawaris adalah pembahasan tentang penghalang dalam kewarisan. Penghalang dalam kewarisan ada tiga penyebabnya yaitu pembunuhan yang disengaja, beda agama dan perbudakan. Beda agama adalah apabila antara ahli waris dan pewaris salah satunya beragama Islam dan yang lain tidak beragama Islam. Tentang perbedaan agama antara pewaris dan ahli waris, dapat menggugurkan hak seseorang untuk mewarisi harta peninggalan. Rumusan masalah dalam penelitian ini ialah bagaimana kedudukan ahli waris non muslim dalam kewarisan Islam dan apakah pertimbangan Hakim dalam putusan nomor : 1578/Pdt.G/2010/PA.JT telah sesuai dengan hukum Islam serta Kompilasi Hukum Islam. Metode pendekatan yang digunakan peneliti adalah library research (yurudis normatif). Yaitu suatu pendekatan alternatif yang menganalisa bahan-bahan pustaka di bidang hukum yang norma- normanya tertulis dan spesifikasi penelitian deskriptis analitis, yaitu dengan menggunakan metode dan teori ilmu-ilmu sosial tentang hukum untuk membantu peneliti dalam melakukan analisis. Hasil dari penelitian ini diperoleh kesimpulan yakni : (1) Hukum Islam menegaskan prinsip dalam kewarisan bahwa ahli waris non muslim tidak mempunyai kedudukan untuk mewarisi harta dari pewaris muslim, sebagaimana yang telah diatur dalam Al-Qur’an, Hadits serta Kompilasi Hukum Islam. (2) Dalam pertimbangan hakim Pengadilan Agama Jakarta Timur dianggap telah terjadi kekeliruan mengenai pemahaman tentang kompetensi absolut Pengadilan Negeri Jakarta Timur yang menetapkan masalah kewarisan Islam, karena pada dasarnya yang mempunyai kewenangan absolut ialah Pengadilan Agama Jakarta Timur. Hal tersebut menimbulkan dasar penolakan hakim Pengadilan Agama menolak gugatan perkara ahli waris, yang menyebabkan ahli waris non muslim memperoleh kembali hak kewarisannya. Hasil dari putusan tersebut ditinjau secara sudut pandang Islam sangat bertentangan dengan Al- Qur’an dan Hadits serta ketentuan menurut perspektif Kompilasi Hukum Islam, bahwa mengenai sistem kewarisan Islam tidak mengakui ahli waris non muslim sebagai ahli waris dari pewaris muslim

Vapor grown silicon dioxide improves transistor base-collector junctions

Vapor grown silicon dioxide layer protects base-collector junction in silicon planar transistors during the emitter diffusion process. This oxide fills in any imperfections that exist in the thermally grown oxide layer and is of greater thickness than that layer. This process is used to deposit protective silicon dioxide coatings on optical surfaces

Aircrew oxygen system

Closed-loop rebreather system which includes pilot provides oxygen for use in aircraft by safe, reliable method of low weight and size and reduces expense of ground equipment. Water electrolysis generated oxygen is fed into rebreather loop which allows nitrogen elimination and water and carbon dioxide removal