Swept-wavelength mid-infrared fiber laser for real-time ammonia gas sensing

The mid-infrared (mid-IR) spectral region holds great promise for new laser-based sensing technologies, based on measuring strong mid-IR molecular absorption features. Practical applications have been limited to date, however, by current low-brightness broadband mid-IR light sources and slow acquisition-time detection systems. Here, we report a new approach by developing a swept-wavelength mid-infrared fiber laser, exploiting the broad emission of dysprosium and using an acousto-optic tunable filter to achieve electronically controlled swept-wavelength operation from 2.89 to 3.25 {\mu}m (3070-3460 cm^-1). Ammonia (NH3) absorption spectroscopy is demonstrated using this swept source with a simple room-temperature single-pixel detector, with 0.3 nm resolution and 40 ms acquisition time. This creates new opportunities for real-time high-sensitivity remote sensing using simple, compact mid-IR fiber-based technologies.Comment: Invited article for APL Photonic

Does poverty cause conflict? Isolating the causal origins of the conflict trap

Does poverty cause civil conflict? A considerable literature seeks to answer this question, yet concerns about reverse causality threaten the validity of extant conclusions. To estimate the impact of poverty on conflict and to determine whether the relationship between them is causal, it is necessary to identify a source of exogenous variation in poverty. We do this by introducing a robust instrument for poverty: a time-varying measure of international inequalities. We draw upon existing theories about the structural position of a country in the international economic network—specifically, the expectation that countries in the core tend to be wealthier and those on the periphery struggle to develop. This instrument is plausibly exogenous and satisfies the exclusion restriction, which suggests that it affects conflict only through its influence upon poverty. Instrumental variables probit regression is employed to demonstrate that the impact of poverty upon conflict appears to be causal

The Peculiar Velocities of Local Type Ia Supernovae and their Impact on Cosmology

We quantify the effect of supernova Type Ia peculiar velocities on the derivation of cosmological parameters. The published distant and local Ia SNe used for the Supernova Legacy Survey first-year cosmology report form the sample for this study. While previous work has assumed that the local SNe are at rest in the CMB frame (the No Flow assumption), we test this assumption by applying peculiar velocity corrections to the local SNe using three different flow models. The models are based on the IRAS PSCz galaxy redshift survey, have varying beta = Omega_m^0.6/b, and reproduce the Local Group motion in the CMB frame. These datasets are then fit for w, Omega_m, and Omega_Lambda using flatness or LambdaCDM and a BAO prior. The chi^2 statistic is used to examine the effect of the velocity corrections on the quality of the fits. The most favored model is the beta=0.5 model, which produces a fit significantly better than the No Flow assumption, consistent with previous peculiar velocity studies. By comparing the No Flow assumption with the favored models we derive the largest potential systematic error in w caused by ignoring peculiar velocities to be Delta w = +0.04. For Omega_Lambda, the potential error is Delta Omega_Lambda = -0.04 and for Omega_m, the potential error is Delta Omega_m < +0.01. The favored flow model (beta=0.5) produces the following cosmological parameters: w = -1.08 (+0.09,-0.08), Omega_m = 0.27 (+0.02,-0.02) assuming a flat cosmology, and Omega_Lambda = 0.80 (+0.08,-0.07) and Omega_m = 0.27 (+0.02,-0.02) for a w = -1 (LambdaCDM) cosmology.Comment: 4 pages, 2 figures, 1 table, accepted for publication in ApJ Letter

Potential Impact of Country-of-Origin Labeling on Beef Industry Structure

International Relations/Trade, Livestock Production/Industries,

Identification of wood energy resources in central Michigan

Existing biomass studies were compiled for determining their applicability in measuring forest biomass in an entirely new way. Over sixty tree-weight tables were prepared from existing tables or formulas. An estimate of forest biomass was made on a defined area by using Landsat Satellite data analysis, existing forest cover type maps and actual weighting of the entire biomass. Control plots were cruised for normal volume data and weight data, harvested and weighed to determine actual tonnage yields

Scorodite precipitation in the presence of antimony

publisher: Elsevier articletitle: Scorodite precipitation in the presence of antimony journaltitle: Chemical Geology articlelink: http://dx.doi.org/10.1016/j.chemgeo.2015.04.013 content_type: article copyright: Copyright © 2015 The Authors. Published by Elsevier B.V.© 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license. The attached file is the published version of the article