13,895 research outputs found
Unsustainable Sustainability: Do Policies that Increase Environmental Quality Exacerbate Income Inequality?
International pressure to meet climate and sustainability goals are mounting. Countries attempting to industrialize in the age of sustainability are tasked with industrializing using low-carbon practices. The transition to a “green” economy requires elimination of some jobs and skillsets that may upset social equality. This paper empirically examines the hypothesis that policies aimed at increased environmental performance promote increased income inequality in developing countries. Because existing literature firmly supports the hypothesis that lower income inequality leads to higher environmental performance, this paper develops a simultaneous equations model (SEM) to estimate the hypothesized endogenous relationship using two stage least squares (2SLS) estimation with an instrumental variable. While the instrumental variables employed were not per se valid, the 2SLS estimation results for the sample of developing countries reflects a positive and practically large, though statistically insignificant effect of air quality on income inequality
Diffractive X-ray Telescopes
Diffractive X-ray telescopes using zone plates, phase Fresnel lenses, or
related optical elements have the potential to provide astronomers with true
imaging capability with resolution several orders of magnitude better than
available in any other waveband. Lenses that would be relatively easy to
fabricate could have an angular resolution of the order of micro-arc-seconds or
even better, that would allow, for example, imaging of the distorted space-
time in the immediate vicinity of the super-massive black holes in the center
of active galaxies What then is precluding their immediate adoption? Extremely
long focal lengths, very limited bandwidth, and difficulty stabilizing the
image are the main problems. The history, and status of the development of such
lenses is reviewed here and the prospects for managing the challenges that they
present are discussed.Comment: 46 pages, 15 figures, invited review paper to be published in a
special issue on "X-Ray Focusing: Techniques and Applications" of the online
journal "X-Ray Optics & Instrumentation
X-ray interferometry with transmissive beam combiners for ultra-high angular resolution astronomy
Interferometry provides one of the possible routes to ultra-high angular
resolution for X-ray and gamma-ray astronomy. Sub-micro-arc-second angular
resolution, necessary to achieve objectives such as imaging the regions around
the event horizon of a super-massive black hole at the center of an active
galaxy, can be achieved if beams from parts of the incoming wavefront separated
by 100s of meters can be stably and accurately brought together at small
angles. One way of achieving this is by using grazing incidence mirrors. We
here investigate an alternative approach in which the beams are recombined by
optical elements working in transmission. It is shown that the use of
diffractive elements is a particularly attractive option. We report
experimental results from a simple 2-beam interferometer using a low-cost
commercially available profiled film as the diffractive elements. A
rotationally symmetric filled (or mostly filled) aperture variant of such an
interferometer, equivalent to an X-ray axicon, is shown to offer a much wider
bandpass than either a Phase Fresnel Lens (PFL) or a PFL with a refractive lens
in an achromatic pair. Simulations of an example system are presented.Comment: To be published in "Experimental Astronomy
Passive instrumentation and stimuli generation for Saturn IB equipment checkout. Volume I - Summary technical report Final technical report, 26 Jun. 1965 - 31 May 1966
Passive instrumentation and stimuli generation for Saturn IB equipment checkout - nondestructive testin
Implementations guidelines, airborne evaluation equipment, advanced system checkout design, phase B Final report, 29 Jun. 1965 - 29 Jul. 1966
Airborne checkout equipment functions and implementation for Saturn IVB stage and instrument uni
The New Eclipsing Cataclysmic Variable SDSS 154453+2553
The cataclysmic variable SDSS154453+2553 was recently identified in the Sloan
Digital Sky Survey. We obtained spectra and photometry at the MDM Observatory,
which revealed an eclipse with a 6.03 hour period. The H{\alpha} emission line
exhibits a strong rotational disturbance during eclipse, indicating that it
arises in an accretion disk. A contribution from an M-type companion is also
observed. Time-series photometry during eclipse gives an ephemeris of
2454878.0062(15) + 0.251282(2)E. We present spectroscopy through the orbit and
eclipse photometry. Our analysis of the secondary star indicates a distance of
800 {\pm} 180 pc.Comment: 6 pages, 3 figures, Accepted for publication in PAS
Positrons in the Galaxy: Their Births, Marriages and Deaths
High energy (approximately GeV) positrons are seen within cosmic rays and observation of a narrow line at 511 keV shows that positrons are annihilating in the galaxy after slowing down to approximately keV energies or less. Our state of knowledge of the origin of these positrons, of the formation of positronium 'atoms', and of the circumstances of their annihilation or escape from the galaxy are reviewed and the question of whether the two phenomena are linked is discussed
Fluctuating Inhibitory Inputs Promote Reliable Spiking at Theta Frequencies in Hippocampal Interneurons
Theta-frequency (4–12 Hz) rhythms in the hippocampus play important roles in learning and memory. CA1 interneurons located at the stratum lacunosum-moleculare and radiatum junction (LM/RAD) are thought to contribute to hippocampal theta population activities by rhythmically pacing pyramidal cells with inhibitory postsynaptic potentials. This implies that LM/RAD cells need to fire reliably at theta frequencies in vivo. To determine whether this could occur, we use biophysically based LM/RAD model cells and apply different cholinergic and synaptic inputs to simulate in vivo-like network environments. We assess spike reliabilities and spiking frequencies, identifying biophysical properties and network conditions that best promote reliable theta spiking. We find that synaptic background activities that feature large inhibitory, but not excitatory, fluctuations are essential. This suggests that strong inhibitory input to these cells is vital for them to be able to contribute to population theta activities. Furthermore, we find that Type I-like oscillator models produced by augmented persistent sodium currents (INaP) or diminished A-type potassium currents (IA) enhance reliable spiking at lower theta frequencies. These Type I-like models are also the most responsive to large inhibitory fluctuations and can fire more reliably under such conditions. In previous work, we showed that INaP and IA are largely responsible for establishing LM/RAD cells’ subthreshold activities. Taken together with this study, we see that while both these currents are important for subthreshold theta fluctuations and reliable theta spiking, they contribute in different ways – INaP to reliable theta spiking and subthreshold activity generation, and IA to subthreshold activities at theta frequencies. This suggests that linking subthreshold and suprathreshold activities should be done with consideration of both in vivo contexts and biophysical specifics
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