Songlines from Direct Collapse Seed Black Holes: Effects of X-rays on Black Hole Growth and Stellar Populations

In the last decade, the growth of supermassive black holes (SMBHs) has been intricately linked to galaxy formation and evolution and is a key ingredient in the assembly of galaxies. To investigate the origin of SMBHs, we perform cosmological simulations that target the direct collapse black hole (DCBH) seed formation scenario in the presence of two different strong Lyman-Werner (LW) background fields. These simulations include the X-ray irradiation from a central massive black hole (MBH), $\rm{H}_2$ self-shielding and stellar feedback from metal-free and metal-enriched stars. We find in both simulations that local X-ray feedback induces metal-free star formation $\sim 0.5$ Myr after the MBH forms. The MBH accretion rate reaches a maximum of $10^{-3}$ $M_{\odot}$ yr$^{-1}$ in both simulations. However, the duty cycle differs which is derived to be $6\%$ and $50\%$ for high and low LW cases, respectively. The MBH in the high LW case grows only $\sim 6\%$ in 100 Myr compared to $16\%$ in the low LW case. We find that the maximum accretion rate is determined by the local gas thermodynamics whereas the duty cycle is determined by the large scale gas dynamics and gas reservoir. We conclude that radiative feedback from the central MBH plays an important role in star formation in the nuclear regions and stifling initial MBH growth, relative to the typical Eddington rate argument, and that initial MBH growth might be affected by the local LW radiation field.Comment: 8 pages, 6 figures. Accepted for publication in ApJ, with minor changes to submitted versio

Rural Livelihoods: Interplay Between Farm Activities, Non-farm Activities and the Resource Base

A concentration of poor in rural areas has resulted in a research and policy focus on agricultural technologies and (poor) households impact on soil productivity. But farm households do not live of farming alone, non-farm activities play a principal role even in remote areas. With a unique household-level dataset covering seven regions in Africa and two in Asia we analyze (1) the importance of non-farm income in different geographical zones; (2) the role of geographical factors in determining access to non-farm employment; (3) the role of non-farm income in external input use and soil nitrogen balances. Distinguishing geographical zones based on the distance to urban areas we find the share of non-farm income increasing from 12 percent in the remote areas to 35 percent in peri-urban areas. Geographical location is found to explain a major part of the variation in individual non-farm participation, besides characteristics like education and gender. At household level we find non-farm income not playing a role of significance in explaining external input use, inorganic fertilizer use nor changes in the nitrogen balance. Households thus appear not to invest non-farm income in agriculture. This limits the contribution of non-farm income to reducing widespread soil nutrient depletion witnessed in Africa.off-farm income, rural development, micro-economics, Labor and Human Capital, Q12, D1, J43, Q24,

24 \textmu m length spin relaxation length in boron nitride encapsulated bilayer graphene

We have performed spin and charge transport measurements in dual gated high mobility bilayer graphene encapsulated in hexagonal boron nitride. Our results show spin relaxation lengths $\lambda_s$ up to 13~\textmu m at room temperature with relaxation times $\tau_s$ of 2.5~ns. At 4~K, the diffusion coefficient rises up to 0.52~m$^2$/s, a value 5 times higher than the best achieved for graphene spin valves up to date. As a consequence, $\lambda_s$ rises up to 24~\textmu m with $\tau_s$ as high as 2.9~ns. We characterized 3 different samples and observed that the spin relaxation times increase with the device length. We explain our results using a model that accounts for the spin relaxation induced by the non-encapsulated outer regions.Comment: 5 pages and 4 figure

Conformal phased array with beam forming for airborne satellite communication

For enhanced communication on board of aircraft novel antenna systems with broadband satellite-based capabilities are required. The installation of such systems on board of aircraft requires the development of a very low-profile aircraft antenna, which can point to satellites anywhere in the upper hemisphere. To this end, phased array antennas which are conformal to the aircraft fuselage are attractive. In this paper two key aspects of conformal phased array antenna arrays are addressed: the development of a broadband Ku-band antenna and the beam synthesis for conformal array antennas. The antenna elements of the conformal array are stacked patch antennas with dual linear polarization which have sufficient bandwidth. For beam forming synthesis a method based on a truncated Singular Value Decomposition is proposed

The ethanolamide metabolite of DHA, docosahexaenoylethanolamine, shows immunomodulating effects in mouse peritoneal and RAW264.7 macrophages: evidence for a new link between fish oil and inflammation

Several mechanisms have been proposed for the positive health effects associated with dietary consumption of long-chain n-3 PUFA (n-3 LC-PUFA) including DHA (22 : 6n-3) and EPA (20 : 5n-3). After dietary intake, LC-PUFA are incorporated into membranes and can be converted to their corresponding N-acylethanolamines (NAE). However, little is known on the biological role of these metabolites. In the present study, we tested a series of unsaturated NAE on the lipopolysaccharide (LPS)-induced NO production in RAW264.7 macrophages. Among the compounds tested, docosahexaenoylethanolamine (DHEA), the ethanolamide of DHA, was found to be the most potent inhibitor, inducing a dose-dependent inhibition of NO release. Immune-modulating properties of DHEA were further studied in the same cell line, demonstrating that DHEA significantly suppressed the production of monocyte chemotactic protein-1 (MCP-1), a cytokine playing a pivotal role in chronic inflammation. In LPS-stimulated mouse peritoneal macrophages, DHEA also reduced MCP-1 and NO production. Furthermore, inhibition was also found to take place at a transcriptional level, as gene expression of MCP-1 and inducible NO synthase was inhibited by DHEA. To summarise, in the present study, we showed that DHEA, a DHA-derived NAE metabolite, modulates inflammation by reducing MCP-1 and NO production and expression. These results provide new leads in molecular mechanisms by which DHA can modulate inflammatory processes

The Response of Metal Rich Gas to X-Ray Irradiation from a Massive Black Hole at High Redshift: Proof of Concept

Observational studies show that there is a strong link between the formation and evolution of galaxies and the growth of supermassive black holes (SMBH) at their centers. However, the underlying physics of this observed relation is poorly understood. In order to study the effects of X-ray radiation on the surroundings of the black hole, we implement X-ray Dominated Region (XDR) physics into Enzo and use the radiation transport module Moray to calculate the radiative transfer for a polychromatic spectrum. In this work, we investigate the effects of X-ray irradiation, produced by a central massive black hole (MBH) with a mass of M = 5x10^4 M_(solar), on ambient gas with solar and zero metallicity. We find that in the solar metallicity case, due to high opacity of the metals, the energy deposition rate in the central region (< 20 pc) is high and hence the temperatures in the center are on the order of 10^(5-7) K. Moreover, due to the cooling ability and high intrinsic opacity of solar metallicity gas, column densities of 10^(24) cm^(-2) are reached at a radius of 20 pc from the MBH. These column densities are about 3 orders of magnitudes higher than in the zero metallicity case. Furthermore, in the zero metallicity case an X-ray induced H II region is formed already after 5.8 Myr. This causes a significant outflow of gas (~8x10^6 M_(solar) from the central region, with the gas reaching outflow velocities up to ~100 km s^(-1). At later times, ~23 Myr after we insert the MBH, we find that the solar metallicity case also develops an X-ray induced H II region, but delayed by ~17 Myr.Comment: 27 pages, 11 figures. Resubmitted to Ap

Design of a ring resonator-based optical beam forming network for phased array receive antennas

A novel squint-free ring resonator-based optical beam forming network (OBFN) for phased array antennas (PAA) is proposed. It is intended to provide broadband connectivity to airborne platforms via geostationary satellites. In this paper, we present the design of the OBFN and its control system. Our goal is to deliver large bandwidth Ku-band connectivity between antennas, mount conformal to the airplane fuselage and on a geostationary satellite, respectively.This way it would be possible to bring live DVB-S television to airplane passengers. In this paper, we present recent research conducted on a 4 × 1 ring resonator-based OBFN test set-up. This OBFN has four optical input ports and one optical output port. It is tuned to provide the desired signal combination with optimal constructive interference between the modulated input signals from the PAA. Therefore, combining circuitry and delay elements are required. The OBFN is tuned by electrically heating tunable true time delay (TTD) elements. These are built using optical ring resonators (ORRs). By cascading multiple ORRs with different resonance frequencies, it is possible to create a TTD with a large bandwidth. Optical beam forming is used because it provides advantages over traditional beam forming methods. These advantages are: large bandwidth, EMI resistance, and, when integrated onto a single chip, compactness and low costs. The OBFN is created using planar optical waveguide technology and consists of the following building blocks: waveguides, Mach-Zehnder interferometers, (MZIs) couplers and ORRs. The tuning of the OBFN is done by an electronic control system using a microcontroller. Communication with a PC is possible using USB. To our knowledge, this is the first integrated ORR-based OBFN circuit for PAA satellite reception

HNC, HCN and CN in Seyfert galaxies

Bright HNC 1--0 emission has been found towards several Seyfert galaxies. This is unexpected since traditionally HNC is a tracer of cold (10 K) gas, and the molecular gas of luminous galaxies like Seyferts is thought to have bulk kinetic temperatures surpassing 50 K. In this work we aim to distinguish the cause of the bright HNC and to model the physical conditions of the HNC and HCN emitting gas. We have used SEST, JCMT and IRAM 30m telescopes to observe HNC 3-2 and HCN 3-2 line emission in a selection of 5 HNC-luminous Seyfert galaxies. We estimate and discuss the excitation conditions of HCN and HNC in NGC 1068, NGC 3079, NGC 2623 and NGC 7469, based on the observed 3-2/1-0 line intensity ratios. We also observed CN 1-0 and 2-1 emission and discuss its role in photon and X-ray dominated regions. HNC 3-2 was detected in 3 galaxies (NGC 3079, NGC 1068 and NGC 2623). HCN 3-2 was detected in NGC 3079, NGC 1068 and NGC 1365. The HCN 3-2/1-0 ratio is lower than 0.3 only in NGC 3079, whereas the HNC 3-2/1-0 ratio is larger than 0.3 only in NGC 2623. The HCN/HNC 1-0 and 3-2 line ratios are larger than unity in all the galaxies. The HCN/HNC 3-2 line ratio is lower than unity only in NGC 2623, similar to Arp 220, Mrk 231 and NGC 4418. In three of the galaxies the HNC emissions emerge from gas of densities n<10^5 cm^3, where the chemistry is dominated by ion-neutral reactions. In NGC 1068 the emission of HNC emerges from lower (<10^5 cm^3) density gas than HCN (>10^5 cm^3). Instead, the emissions of HNC and HCN emerge from the same gas in NGC 3079. The observed HCN/HNC and CN/HCN line ratios favor a PDR scenario, rather than an XDR one. However, the N(HNC)/N(HCN) column density ratios obtained for NGC 3079 can be found only in XDR environments.Comment: Accepted for publication in A&A. A selection of this paper will be presented as a poster in the FIR workshop 2007, held at Bad Honnef, Germany. High resolution figures in original paper. 16 pages, 8 figure

Tracing star formation in galaxies with molecular line and continuum observations

We report our recent progress on extragalactic spectroscopic and continuum observations, including HCN(J=1-0), HCO$^+$(J=1-0), and CN(N=1-0) imaging surveys of local Seyfert and starburst galaxies using the Nobeyama Millimeter Array, high-J CO observations (J=3-2 observations using the Atacama Submillimeter Telescope Experiment (ASTE) and J=2-1 observations with the Submillimeter Array) of galaxies, and $\lambda$ 1.1 mm continuum observations of high-z violent starburst galaxies using the bolometer camera AzTEC mounted on ASTE.Comment: 6 pages, 5 figures, To appear in proceedings of "Far-Infrared and Submillimeter Emission of the Interstellar Medium", EAS Publication Series, Bad Honnef, November 2007, Eds. C. Kramer, S. Aalto, R. Simon. See http://www.nro.nao.ac.jp/~f0212kk/FIR07/kk-ver20.pdf for a version with high resolution figure