A single-domain spectral method for black hole puncture data

We calculate puncture initial data corresponding to both single and binary black hole solutions of the constraint equations by means of a pseudo-spectral method applied in a single spatial domain. Introducing appropriate coordinates, these methods exhibit rapid convergence of the conformal factor and lead to highly accurate solutions. As an application we investigate small mass ratios of binary black holes and compare these with the corresponding test mass limit that we obtain through a semi-analytical limiting procedure. In particular, we compare the binding energy of puncture data in this limit with that of a test particle in the Schwarzschild spacetime and find that it deviates by 50% from the Schwarzschild result at the innermost stable circular orbit of Schwarzschild, if the ADM mass at each puncture is used to define the local black hole masses.Comment: 13 pages, 6 figures; published version with one important change, see Fig. 4 and the corresponding changes to the tex

Wintertime phytoplankton bloom in the subarctic Pacific supported by continental margin iron

Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 20 (2006): GB1006, doi:10.1029/2005GB002557.Heightened biological activity was observed in February 1996 in the high-nutrient low-chlorophyll (HNLC) subarctic North Pacific Ocean, a region that is thought to be iron-limited. Here we provide evidence supporting the hypothesis that Ocean Station Papa (OSP) in the subarctic Pacific received a lateral supply of particulate iron from the continental margin off the Aleutian Islands in the winter, coincident with the observed biological bloom. Synchrotron X-ray analysis was used to describe the physical form, chemistry, and depth distributions of iron in size fractionated particulate matter samples. The analysis reveals that discrete micron-sized iron-rich hot spots are ubiquitous in the upper 200 m at OSP, more than 900 km from the closest coast. The specifics of the chemistry and depth profiles of the Fe hot spots trace them to the continental margins. We thus hypothesize that iron hot spots are a marker for the delivery of iron from the continental margin. We confirm the delivery of continental margin iron to the open ocean using an ocean general circulation model with an iron-like tracer source at the continental margin. We suggest that iron from the continental margin stimulated a wintertime phytoplankton bloom, partially relieving the HNLC condition.This work was supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research (KP1202030) to J. K. B and by NSFATM-9987457 to I. F. The Advanced Light Source is supported by the Director, Office of Science, Office of Basic Energy Sciences, Division of Materials Sciences and Division of Chemical Sciences, Geosciences, and Biosciences of the U.S. Department of Energy at Lawrence Berkeley National Laboratory under contract DE-AC03-76SF00098

Nano-Scale Strain-Induced Giant Pseudo-Magnetic Fields and Charging Effects in CVD-Grown Graphene on Copper

Scanning tunneling microscopic and spectroscopic (STM/STS) studies of graphene grown by chemical vapor deposition (CVD) on copper reveal that the monolayer carbon structures remaining on copper are strongly strained and rippled, with different regions exhibiting different lattice structures and local electronic density of states (LDOS). The large and non-uniform strain induces pseudo-magnetic field up to ∼ 50 Tesla, as manifested by the integer and fractional pseudo-magnetic field quantum Hall effects (IQHE and FQHE) in the LDOS of graphene. Additionally, ridges appear along the boundaries of different lattice structures, which exhibit excess charging effects. For graphene transferred from copper to SiO_2 substrates after the CVD growth, the average strain and the corresponding charging effects and pseudo-magnetic fields become much reduced. These findings suggest the feasibility of strain-engineering of graphene-based nano-electronics

Does competition make banks riskier in dual banking system

This paper investigates competition and risk-taking behaviour of Islamic banks taking a sample of 59 Islamic banks and 149 conventional banks from 10 highly developed Islamic banking countries between 2006 and 2016. The level of competitiveness between the two types of banks is determined using Lerner index and estimations show that Islamic banks have lower market power than conventional banks. After controlling all the bank and country-specific variables, the results show that competition and risk are positively related for the overall banking system and inversely related for Islamic banks which undoubtedly emphasize that inherent difference between risk-competition relationships among these two distinct bank types. Overall, in the case of Islamic banks, the results provide evidence in favour of “competition stability view” where higher competitive market associated with fierce competition from conventional banks and its peers' reduces Islamic banks' risk-taking behaviour

Agent-based Social Psychology: from Neurocognitive Processes to Social Data

Moral Foundation Theory states that groups of different observers may rely on partially dissimilar sets of moral foundations, thereby reaching different moral valuations. The use of functional imaging techniques has revealed a spectrum of cognitive styles with respect to the differential handling of novel or corroborating information that is correlated to political affiliation. Here we characterize the collective behavior of an agent-based model whose inter individual interactions due to information exchange in the form of opinions are in qualitative agreement with experimental neuroscience data. The main conclusion derived connects the existence of diversity in the cognitive strategies and statistics of the sets of moral foundations and suggests that this connection arises from interactions between agents. Thus a simple interacting agent model, whose interactions are in accord with empirical data on conformity and learning processes, presents statistical signatures consistent with moral judgment patterns of conservatives and liberals as obtained by survey studies of social psychology.Comment: 11 pages, 4 figures, 2 C codes, to appear in Advances in Complex System

Effect of a Motivational Interviewing–Based Intervention on Initiation of Mental Health Treatment and Mental Health After an Emergency Department Visit Among Suicidal Adolescents

Abstract IMPORTANCE Emergency department (ED) visits present opportunities to identify and refer suicidal youth for outpatient mental health care, although this practice is not routine. OBJECTIVE To examine whether a motivational interviewing–based intervention increases linkage of adolescents to outpatient mental health services and reduces depression symptoms and suicidal ideation in adolescents seeking emergency care for non–mental health–related concerns who screen positive for suicide risk. DESIGN, SETTING, AND PARTICIPANTS In this randomized clinical trial, adolescents aged 12 to 17 years who screened positive on the Ask Suicide Screening Questions (ASQ) during a nonpsychiatric ED visit at 2 academic pediatric EDs in Ohio were recruited from April 2013 to July 2015. Intention-totreat analyses were performed from September 2018 to October 2019. INTERVENTIONS The Suicidal Teens Accessing Treatment After an Emergency Department Visit (STAT-ED) intervention included motivational interviewing to target family engagement, problem solving, referral assistance, and limited case management. The enhanced usual care (EUC) intervention consisted of brief mental health care consultation and referral. MAIN OUTCOMES AND MEASURES Primary outcomes were mental health treatment initiation and attendance within 2 months of ED discharge and suicidal ideation (assessed by the Suicidal Ideation Questionnaire JR) and depression symptoms (assessed by the Center for Epidemiologic Studies– Depression scale) at 2 and 6 months. Exploratory outcomes included treatment initiation and attendance and suicide attempts at 6 months. RESULTS A total of 168 participants were randomized and 159 included in the intention-to-treat analyses (mean [SD] age, 15.0 [1.5] years; 126 [79.2%] female; and 80 [50.3%] white). Seventy-nine participants were randomized to receive the STAT-ED intervention and 80 to receive EUC. At 2 months, youth in the STAT-ED group had similar rates of mental health treatment initiation compared with youth in the EUC group as assessed by parent report (29 [50.9%] vs 22 [34.9%]; adjusted odds ratio [OR], 2.08; 95% CI, 0.97-4.45) and administrative data from mental health care agencies (19 [29.7%] vs 11 [19.3%]; adjusted OR, 1.77; 95% CI, 0.76-4.15). At 2 months, youth in the STAT-ED group and the EUC group had similar rates of treatment attendance (1 appointment: 6 [9.7%] vs 2 [3.6%]; adjusted OR, 2.97; 95% CI, 0.56-15.73; 2 appointments: 10 [16.1%] vs 7 [12.7%]; adjusted OR, 1.43; 95% CI, 0.50-4.11). There were no significant group × time differences in suicidal ideation (F = 0.28; P = .72) and depression symptoms (F = 0.49; P = .60) during the 6-month follow-up period. In exploratory analyses, at 6 months, STAT-ED participants had significantly higher rates of agencyreported mental health treatment initiation (adjusted OR, 2.48; 95% CI, 1.16-5.28) and more completed appointments (t99.7 = 2.58; P = .01). CONCLUSIONS AND RELEVANCE This study’s findings indicate that no differences were found on any primary outcome by study condition. However, STAT-ED was more efficacious than EUC at increasing mental health treatment initiation and attendance at 6 months. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT01779414 JAMA Network Open. 2019;2(12):e1917941. doi:10.1001/jamanetworkopen.2019.1794

Scalable spin squeezing in a dipolar Rydberg atom array

The standard quantum limit bounds the precision of measurements that can be achieved by ensembles of uncorrelated particles. Fundamentally, this limit arises from the non-commuting nature of quantum mechanics, leading to the presence of fluctuations often referred to as quantum projection noise. Quantum metrology relies on the use of non-classical states of many-body systems in order to enhance the precision of measurements beyond the standard quantum limit. To do so, one can reshape the quantum projection noise -- a strategy known as squeezing. In the context of many-body spin systems, one typically utilizes all-to-all interactions (e.g. the one-axis twisting model) between the constituents to generate the structured entanglement characteristic of spin squeezing. Motivated by recent theoretical work, here we explore the prediction that short-range interactions -- and in particular, the two-dimensional dipolar XY model -- can also enable the realization of scalable spin squeezing. Working with a dipolar Rydberg quantum simulator of up to 100 atoms, we demonstrate that quench dynamics from a polarized initial state lead to spin squeezing that improves with increasing system size up to a maximum of -3.5 dB (prior to correcting for detection errors, or approximately -5 dB after correction). Finally, we present two independent refinements: first, using a multistep spin-squeezing protocol allows us to further enhance the squeezing by approximately 1 dB, and second, leveraging Floquet engineering to realize Heisenberg interactions, we demonstrate the ability to extend the lifetime of the squeezed state by freezing its dynamics.Comment: 12 pages, 10 figure

Three-Dimensional Simulations of Kelvin-Helmholtz Instability in Settled Dust Layers in Protoplanetary Disks

As dust settles in a protoplanetary disk, a vertical shear develops because the dust-rich gas in the midplane orbits at a rate closer to true Keplerian than the slower-moving dust-depleted gas above and below. A classical analysis (neglecting the Coriolis force and differential rotation) predicts that Kelvin-Helmholtz instability occurs when the Richardson number of the stratified shear flow is below roughly one-quarter. However, earlier numerical studies showed that the Coriolis force makes layers more unstable, whereas horizontal shear may stabilize the layers. Simulations with a 3D spectral code were used to investigate these opposing influences on the instability in order to resolve whether such layers can ever reach the dense enough conditions for the onset of gravitational instability. I confirm that the Coriolis force, in the absence of radial shear, does indeed make dust layers more unstable, however the instability sets in at high spatial wavenumber for thicker layers. When radial shear is introduced, the onset of instability depends on the amplitude of perturbations: small amplitude perturbations are sheared to high wavenumber where further growth is damped; whereas larger amplitude perturbations grow to magnitudes that disrupt the dust layer. However, this critical amplitude decreases sharply for thinner, more unstable layers. In 3D simulations of unstable layers, turbulence mixes the dust and gas, creating thicker, more stable layers. I find that layers with minimum Richardson numbers in the approximate range 0.2 -- 0.4 are stable in simulations with horizontal shear.Comment: 33 pages, 11 figures (5 color, low-resolution versions), Submitted to The Astrophysical Journal, see http://www.physics.sfsu.edu/~barranco for higher resolution color figures and associated avi animation file