7,018 research outputs found
The rate of cosmic ray showers at large zenith angles: a step towards the detection of ultra-high energy neutrinos by the Pierre Auger Observatory
It is anticipated that the Pierre Auger Observatory can be used to detect
cosmic neutrinos of >10^19 eV that arrive at very large zenith angles. However
showers created by neutrino interactions close to the detector must be picked
out against a background of similar events initiated by cosmic ray nuclei. As a
step towards understanding this background, we have made the first detailed
analysis of air showers recorded at Haverah Park (an array which used similar
detectors to those planned for the Auger Observatory) with zenith angles above
60 degs. We find that the differential shower rate from 60 degs to 80 degs. can
be predicted accurately when we adopt the known primary energy spectrum above
10^17 eV and assume the QGSJET model and proton primaries. Details of the
calculation are given.Comment: 22 pages, 12 figures, to appear in Astroparticle Physic
Studi Tentang Aplikasi Kompos Ub Pada Pertumbuhan Dan Hasil Tanaman Talas (Colocasia Esculenta (L.) Schott Var. Antiquorum) Yang Ditanam Di Lahan Kering Pada Musim Kemarau
Kelompok tanaman dari umbi-umbian seperti tanaman talas memiliki potensi besar untuk dikembangkan karena dapat dimanfaatkan sebagai sumber bahan pangan alternatif yang sehat dan aman. Akan tetapi produksi umbi talas pada lahan kering masih rendah. Oleh karena itu, diperlukan upaya untuk meningkatkan produksi umbi talas pada lahan kering dengan aplikasi bahan organik. Tujuan penelitian adalah untuk mempelajari pengaruh tingkat pemupukan kompos UB pada pertumbuhan dan hasil tanaman talas dilahan kering dan menentukan tingkat pemupukan kompos UB yang optimum pada tanaman talas. Penelitian dilaksanakan dari bulan Mei â November 2014 di dusun Jetak Lor, desa Mulyoagung, Dau, Malang. Bahan yang digunakan ialah bibit tanaman talas varietas Antiquorum dan kompos UB. Penelitian menggunakan rancangan acak kelompok yang menempatkan dosis kompos UB sebagai perlakuan, terdiri dari 6 taraf yaitu: 0% (0 ton ha-1), 25% (1,51 ton ha-1), 50% (3,02 ton ha-1), 75% (4,53 ton ha-1), 100% (6,05 ton ha-1) dan 125% (7,56 ton ha-1). Hasil penelitian menunjukkan bahwa hasil panen per hektar yang lebih tinggi didapatkan pada aplikasi kompos UB dengan dosis 125%, yaitu sebesar 12,77 ton ha-1
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Rab5-mediated endosome formation is regulated at the trans-Golgi network
Early endosomes, also called sorting endosomes, are known to mature into late endosomesvia the Rab5-mediated endolysosomal trafficking pathway. Thus, early endosome existence isthought to be maintained by the continual fusion of transport vesicles from the plasmamembrane and thetrans-Golgi network (TGN). Here we show instead that endocytosis isdispensable and post-Golgi vesicle transport is crucial for the formation of endosomes andthe subsequent endolysosomal traffic regulated by yeast Rab5 Vps21p. Fittingly, all threeproteins required for endosomal nucleotide exchange on Vps21p arefirst recruited to theTGN before transport to the endosome, namely the GEF Vps9p and the epsin-relatedadaptors Ent3/5p. The TGN recruitment of these components is distinctly controlled, withVps9p appearing to require the Arf1p GTPase, and the Rab11s, Ypt31p/32p. These resultsprovide a different view of endosome formation and identify the TGN as a critical location forregulating progress through the endolysosomal trafficking pathway
MACiE: a database of enzyme reaction mechanisms.
SUMMARY: MACiE (mechanism, annotation and classification in enzymes) is a publicly available web-based database, held in CMLReact (an XML application), that aims to help our understanding of the evolution of enzyme catalytic mechanisms and also to create a classification system which reflects the actual chemical mechanism (catalytic steps) of an enzyme reaction, not only the overall reaction. AVAILABILITY: http://www-mitchell.ch.cam.ac.uk/macie/.EPSRC (G.L.H. and J.B.O.M.), the BBSRC (G.J.B. and J.M.T.âCASE studentship in association with Roche Products Ltd; N.M.O.B. and J.B.O.M.âgrant BB/C51320X/1), the Chilean Governmentâs Ministerio de PlanificacioÂŽn y CooperacioÂŽn and
Cambridge Overseas Trust (D.E.A.) for funding and Unilever for supporting the Centre for Molecular Science Informatics.application note restricted to 2 printed pages web site: http://www-mitchell.ch.cam.ac.uk/macie
Pair distribution function in a two-dimensional electron gas
We calculate the pair distribution function, , in a two-dimensional
electron gas and derive a simple analytical expression for its value at the
origin as a function of . Our approach is based on solving the
Schr\"{o}dinger equation for the two-electron wave function in an appropriate
effective potential, leading to results that are in good agreement with Quantum
Monte Carlo data and with the most recent numerical calculations of . [C.
Bulutay and B. Tanatar, Phys. Rev. B {\bf 65}, 195116 (2002)] We also show that
the spin-up spin-down correlation function at the origin, , is mainly independent of the degree of spin polarization of
the electronic system.Comment: 5 figures, pair distribution dependence with distance is calculate
Astrophysical sources of high energy neutrinos
Several high energy, >100 GeV, neutrino telescopes are currently operating or
under construction. Their main motivation is the extension of the horizon of
neutrino astronomy to cosmological scales. We show that general, model
independent, arguments imply that ~1 Gton detectors are required to detect
cosmic high energy neutrino sources. Predictions of models of some of the
leading candidate sources, gamma-ray bursts and micro-quasars, are discussed,
and the question of what can be learned from neutrino observations is
addressed.Comment: Invited talk, Neutrino 2002 (Munich
Constraints on the Ultra High Energy Photon flux using inclined showers from the Haverah Park array
We describe a method to analyse inclined air showers produced by ultra high
energy cosmic rays using an analytical description of the muon densities. We
report the results obtained using data from inclined events
(60^{\circ}<\theta<80^{\circ}) recorded by the Haverah Park shower detector for
energies above 10^19 eV. Using mass independent knowledge of the UHECR spectrum
obtained from vertical air shower measurements and comparing the expected
horizontal shower rate to the reported measurements we show that above 10^19 eV
less than 48 % of the primary cosmic rays can be photons at the 95 % confidence
level and above 4 X 10^19 eV less than 50 % of the cosmic rays can be photonic
at the same confidence level. These limits place important constraints on some
models of the origin of ultra high-energy cosmic rays.Comment: 45 pages, 25 figure
Analytical expressions for the charge-charge local-field factor and the exchange-correlation kernel of a two-dimensional electron gas
We present an analytical expression for the static many-body local field
factor of a homogeneous two-dimensional electron gas, which
reproduces Diffusion Monte Carlo data and embodies the exact asymptotic
behaviors at both small and large wave number . This allows us to also
provide a closed-form expression for the exchange and correlation kernel
, which represents a key input for density functional studies of
inhomogeneous systems.Comment: 5 pages, 3 figure
Yeast Eps15-like endocytic protein Pan1p regulates the interaction between endocytic vesicles, endosomes and the actin cytoskeleton
The actin cytoskeleton plays important roles in the formation and internalization of endocytic vesicles. In yeast, endocytic vesicles move towards early endosomes along actin cables, however, the molecular machinery regulating interaction between endocytic vesicles and actin cables is poorly understood. The Eps15-like protein Pan1p plays a key role in actin-mediated endocytosis and is negatively regulated by Ark1 and Prk1 kinases. Here we show that pan1 mutated to prevent phosphorylation at all 18 threonines, pan1-18TA, displayed almost the same endocytic defect as ark1Î prk1Î cells, and contained abnormal actin concentrations including several endocytic compartments. Early endosomes were highly localized in the actin concentrations and displayed movement along actin cables. The dephosphorylated form of Pan1p also caused stable associations between endocytic vesicles and actin cables, and between endocytic vesicles and endosomes. Thus Pan1 phosphorylation is part of a novel mechanism that regulates endocytic compartment interactions with each other and with actin cables
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