3,076 research outputs found
Quasi-Spherical Light Cones of the Kerr Geometry
Quasi-spherical light cones are lightlike hypersurfaces of the Kerr geometry
that are asymptotic to Minkowski light cones at infinity. We develop the
equations of these surfaces and examine their properties. In particular, we
show that they are free of caustics for all positive values of the Kerr radial
coordinate r. Useful applications include the propagation of high-frequency
waves, the definition of Kruskal-like coordinates for a spinning black hole and
the characteristic initial-value problem.Comment: LaTeX, 14 pages, 2 figure
Aplikasi Web Monitoring Realisasi Anggaran Biaya Operasional Pada PT. Pertamina Ep Region Jawa
PT. Pertamina EP Region Jawa adalah Perusahaan yang menyelenggarakan kegiatan USAha di sektor hulu bidang minyak dan gas bumi, meliputi eksplorasi dan eksploitasi. Untuk menjalankan segala kegiatan USAha maka dibutuhkan dana untuk membiayainya. Dalam hal ini kebutuhan dana dituangkan didalam suatu perencanaan yang dinamakan anggaran. GM (General Manager) selaku pimpinan dan MK (Manajer Keuangan) selaku penanggung jawab keuangan Perusahaan tentunya mempunyai peran dalam pengawasan realisasi dari anggaran yang telah disetujui (master anggaran) agar tidak ada penyimpangan dalam pelaksanaanya, salah satunya yaitu dalam bentuk laporan. Laporan tersebut diharapkan dapat memberikan gambaran sudah sejauh mana dana dari master anggaran tersebut telah terealisasi dan apakah dana tersebut benar-benar digunakan secara maksimal dalam pelaksanannya atau tidak. Namun terkadang ketika GM (General Manager) atau MK (Manajer Keuangan) membutuhkan laporan tersebut sewaktu-waktu, fungsi atau divisi yang dimintai laporan tersebut baru menyusunnya. Hal tersebut dikarenakan dalam penyusunanya harus sesuai dengan apa yang dibutuhkan GM ataupun MK sehingga memakan waktu dalam proses pembuatan laporan tersebut. Adapun metode yang digunakan dalam membuat aplikasi ini adalah metode waterfall. Bagian yang terlibat adalah GM (General Manager), MK (Manajer Keuangan) dan kepala fungsi. Aplikasi ini memberikan dan mendapatkan informasi mengenai master anggaran dan realisasi dari anggaran yang telah disetujui dalam bentuk laporan perbulan, pertahun dan kumulatif
Inspiral, merger and ring-down of equal-mass black-hole binaries
We investigate the dynamics and gravitational-wave (GW) emission in the
binary merger of equal-mass black holes as obtained from numerical relativity
simulations. Results from the evolution of three sets of initial data are
explored in detail, corresponding to different initial separations of the black
holes. We find that to a good approximation the inspiral phase of the evolution
is quasi-circular, followed by a "blurred, quasi-circular plunge", then merger
and ring down. We present first-order comparisons between analytical models of
the various stages of the merger and the numerical results. We provide
comparisons between the numerical results and analytical predictions based on
the adiabatic Newtonain, post-Newtonian (PN), and non-adiabatic resummed-PN
models. From the ring-down portion of the GW we extract the fundamental
quasi-normal mode and several of the overtones. Finally, we estimate the
optimal signal-to-noise ratio for typical binaries detectable by GW
experiments.Comment: 47 pages, 34 figures, full abstract in paper, revtex4, accepted by
PRD, miscellaneous revisions throughout pape
Reproducibility of visual-field asymmetries:Nine replication studies investigating lateralization of visual information processing
Numerous behavioral studies suggest that the processing of various types of visual stimuli and features may be more efficient in either the left or the right visual field. However, not all of these visual-field asymmetries (VFAs) have been observed consistently. Moreover, it is typically unclear whether a failure to observe a particular VFA can be ascribed to certain characteristics of the participants and stimuli, to a lack of statistical power, or to the actual absence of an effect. To increase our understanding of lateralization of visual information processing, we have taken a rigorous methodological and statistical approach to examine the reproducibility of various previously reported VFAs. We did so by performing (near-)exact replications of nine representative previous studies, aiming for sufficient power to detect the effects of interest, and taking into consideration all relevant dependent variables (reaction times and error rates). Following Bayesian analyses –on our data alone as well as on the combined evidence from the original and replication studies– we find precise and reliable evidence that support VFAs in the processing of faces, emotional expressions, global and local information, words, and in the distribution of spatial attention. In contrast, we find less convincing evidence for VFAs in processing of high and low spatial frequencies. Finally, we find no evidence for VFAs in categorical perception of color and shape oddballs, and in the judgments of categorical and coordinate spatial relations. We discuss our results in the light of their implications for theories of visual lateralization
Spatial variability of CO \u3c inf\u3e 2 uptake in polygonal tundra: Assessing low-frequency disturbances in eddy covariance flux estimates
The large spatial variability in Arctic tundra complicates the representative assessment of CO2 budgets. Accurate measurements of these heterogeneous landscapes are, however, essential to understanding their vulnerability to climate change. We surveyed a polygonal tundra lowland on Svalbard with an unmanned aerial vehicle (UAV) that mapped ice-wedge morphology to complement eddy covariance (EC) flux measurements of CO2. The analysis of spectral distributions showed that conventional EC methods do not accurately capture the turbulent CO2 exchange with a spatially heterogeneous surface that typically features small flux magnitudes. Nonlocal (low-frequency) flux contributions were especially pronounced during snowmelt and introduced a large bias of -46 gCm-2 to the annual CO22 budget in conventional methods (the minus sign indicates a higher uptake by the ecosystem). Our improved flux calculations with the ogive optimization method indicated that the site was a strong sink for CO2 in 2015 (82 gCm2). Due to differences in light-use efficiency, wetter areas with lowcentered polygons sequestered 47% more CO2 than drier areas with flat-centered polygons. While Svalbard has experienced a strong increase in mean annual air temperature of more than 2K in the last few decades, historical aerial photographs from the site indicated stable ice-wedge morphology over the last 7 decades. Apparently, warming has thus far not been sufficient to initiate strong ice-wedge degradation, possibly due to the absence of extreme heat episodes in the maritime climate on Svalbard. However, in Arctic regions where ice-wedge degradation has already initiated the associated drying of landscapes, our results suggest a weakening of the CO2 sink in polygonal tundra
High renin and prorenin in plasma and pleural exudate of a patient with the ovarian hyperstimulation syndrome
We present the case of a 35-year-old woman with a severe ovarian hyperstimulation syndrome (OHSS) as a complication of ovulation induction for primary infertility. The clinical picture showed massively enlarged ovaries, pleural effusion and haemoconcentration. She needed a thoracentesis for evacuation of the large pleural effusion. High levels of renin and prorenin were observed in plasma and pleural exudate
Gravitational collapse in 2+1 dimensional AdS spacetime
We present results of numerical simulations of the formation of black holes
from the gravitational collapse of a massless, minimally-coupled scalar field
in 2+1 dimensional, axially-symmetric, anti de-Sitter (AdS) spacetime. The
geometry exterior to the event horizon approaches the BTZ solution, showing no
evidence of scalar `hair'. To study the interior structure we implement a
variant of black-hole excision, which we call singularity excision. We find
that interior to the event horizon a strong, spacelike curvature singularity
develops. We study the critical behavior at the threshold of black hole
formation, and find a continuously self-similar solution and corresponding
mass-scaling exponent of approximately 1.2. The critical solution is universal
to within a phase that is related to the angle deficit of the spacetime.Comment: 31 pages, 20 figures, LaTeX. Replaced with version to be published in
Phys. Rev.
Event-related fMRI responses in the human frontal eye fields in a randomized pro- and antisaccade task
We examined whether the frontal eye fields (FEF) are involved in the suppression of reflexive saccades. Simultaneous recording of horizontal eye movements and functional magnetic resonance imaging enabled us to perform a randomized pro- and antisaccade task and to sort blood oxygenation level dependent (BOLD) time series on the basis of task performance. Saccadic reaction time distributions were comparable across tasks indicating a similar effort in preprocessing of the saccades. Furthermore, we found similar BOLD activation in FEF during both correctly performed pro- and antisaccades. Frontal eye field activation started prior to target presentation and saccade generation. While we observed only few erroneous antisaccades, these were associated with a decrease in BOLD activity prior to target presentation, and increased BOLD activity after target presentation relative to correctly performed antisaccades. These findings are consistent with a role of the FEF in the suppression of reflexive saccades. The increase in activity after target presentation for antisaccade errors can only be indirectly linked to such a role but may also reflect activity related to the generation of a correction saccade. Frontal eye field BOLD activity may further represent general arousal, preparatory set, shortterm memory, or salience-map related activity
Towards a unified understanding of lateralized vision:A large-scale study investigating principles governing patterns of lateralization using a heterogeneous sample
While functional lateralization of the human brain has been a widely studied topic in the past decades, few studies to date have gone further than investigating lateralization of single, isolated processes. With the present study, we aimed to arrive at a more unified view by investigating lateralization patterns in face and word processing, and associated lower-level visual processing. We tested a large and heterogeneous participant group, and used a number of tasks that had been shown to produce replicable indices of lateralized processing of visual information of different types and complexity. Following Bayesian statistics, group-level analyses showed the expected right hemisphere (RH) lateralization for face, global form, low spatial frequency processing, and spatial attention, and left hemisphere (LH) lateralization for visual word and local feature processing. Compared to right-handed individuals, lateralization patterns of left-handed and especially those who are RH-dominant for language deviated from this 'typical' pattern. Our results support the notion that face and word processes come to be lateralized to homologue areas of the two hemispheres, under influence of the RHand LH-specializations in global form, local feature, and low and high spatial frequency processing. As such, we present a more unified understanding of lateralized vision, providing evidence for the input asymmetry and causal complementarity principles of lateralized visual information processing. The absence of correlations between spatial attention and lateralization of the other processes supports the notion of their independent lateralization, conform the statistical complementarity principle. (C) 2020 The Author(s). Published by Elsevier Ltd
An Axisymmetric Gravitational Collapse Code
We present a new numerical code designed to solve the Einstein field
equations for axisymmetric spacetimes. The long term goal of this project is to
construct a code that will be capable of studying many problems of interest in
axisymmetry, including gravitational collapse, critical phenomena,
investigations of cosmic censorship, and head-on black hole collisions. Our
objective here is to detail the (2+1)+1 formalism we use to arrive at the
corresponding system of equations and the numerical methods we use to solve
them. We are able to obtain stable evolution, despite the singular nature of
the coordinate system on the axis, by enforcing appropriate regularity
conditions on all variables and by adding numerical dissipation to hyperbolic
equations.Comment: 19 pages, 9 figure
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