5,755 research outputs found
Identification of a recurring bacterial contaminant in a spacecraft watering system
Bacterial contaminant in Biosatellite water syste
The Butz Stops Here: Why the Food Movement Needs to Rethink Agricultural History
From the 1890s to the 1930s, rural Americans played a vital role in radical leftist politics. While specialists know this history well, the public tends to know a folk history, written by figures associated with contemporary food movements. This folk history rests on several key myths, which cover different periods of modern history from the New Deal to the present. This essay challenges these myths to reveal the causes and extent of the suffering endured by rural families in the 20th century, which in turn, decimated the populist left. A reconsideration of the history of agricultural policy will help food-system reformers develop a more radical and effective vision for rural Americ
The Manchester occulting mask imager (MOMI) - first results on the environment of P Cygni
The design and first use of the Manchester occulting mask imager (MOMI) is
described. This device, when combined with the Cassegrain or Ritchey-Chretien
foci of large telescopes, is dedicated to the imagery of faint line emission
regions around bright central sources.
Initial observations, with MOMI on the Nordic Optical telescope (NOT), of the
V=4.8 mag P~Cygni environment, have revealed a ~5~arcmin long [NII] 6584A
emitting filament projecting from the outer nebular shell of this luminous blue
variable (LBV) star. The presence of a mono-polar lobe older than both the
inner (22 arcsec diameter) and outer (1.6 arcmin diameter) shells is suggested.Comment: 4 pages, 4 figures, accepted MNRAS 1998 June 1
Myths and Realities of American Political Geography
The division of America into red states and blue states misleadingly suggests that states are split into two camps, but along most dimensions, like political orientation, states are on a continuum. By historical standards, the number of swing states is not particularly low, and America's cultural divisions are not increasing. But despite the flaws of the red state/blue state framework, it does contain two profound truths. First, the heterogeneity of beliefs and attitudes across the United States is enormous and has always been so. Second, political divisions are becoming increasingly religious and cultural. The rise of religious politics is not without precedent, but rather returns us to the pre-New Deal norm. Religious political divisions are so common because religious groups provide politicians the opportunity to send targeted messages that excite their base.
The Causes and Consequences of Land Use Regulation: Evidence from Greater Boston
Over the past 30 years, eastern Massachusetts has seen a remarkable combination of rising home prices and declining supply of new homes. The reductions in new supply don't appear to reflect a real lack of land, but instead reflect a response to man-made restrictions on development. In this paper, we examine the land-use regulations in greater Boston. There has been a large increase in the number of new regulations, which differ widely over space. Few variables, other than historical density and abundant recreational water, reliably predict these regulations. High lot sizes and other regulations are associated with less construction. The regulations boost prices by decreasing density, but density levels seem far too low to maximize total land value.
Myths and Realities of American Political Geography
The division of America into red states and blue states misleadingly suggests that states are split into two camps, but along most dimensions, like political orientation, states are on a continuum. By historical standards, the number of swing states is not particularly low, and America's cultural divisions are not increasing. But despite the flaws of the red state/blue state framework, it does contain two profound truths. First, the heterogeneity of beliefs and attitudes across the United States is enormous and has always been so. Second, political divisions are becoming increasingly religious and cultural. The rise of religious politics is not without precedent, but rather returns us to the pre-New Deal norm. Religious political divisions are so common because religious groups provide politicians the opportunity to send targeted messages that excite their base.
Near-Infrared InGaAs Detectors for Background-limited Imaging and Photometry
Originally designed for night-vision equipment, InGaAs detectors are
beginning to achieve background-limited performance in broadband imaging from
the ground. The lower cost of these detectors can enable multi-band
instruments, arrays of small telescopes, and large focal planes that would be
uneconomical with high-performance HgCdTe detectors. We developed a camera to
operate the FLIR AP1121 sensor using deep thermoelectric cooling and
up-the-ramp sampling to minimize noise. We measured a dark current of 163-
s pix, a read noise of 87- up-the-ramp, and a well depth of
80k-. Laboratory photometric testing achieved a stability of 230 ppm
hr, which would be required for detecting exoplanet transits. InGaAs
detectors are also applicable to other branches of near-infrared time-domain
astronomy, ranging from brown dwarf weather to gravitational wave follow-up.Comment: Submitted to Proc. SPIE, Astronomical Telescopes + Instrumentation
(2014
Synthetic dimensions in ultracold molecules: quantum strings and membranes
Synthetic dimensions alter one of the most fundamental properties in nature,
the dimension of space. They allow, for example, a real three-dimensional
system to act as effectively four-dimensional. Driven by such possibilities,
synthetic dimensions have been engineered in ongoing experiments with ultracold
matter. We show that rotational states of ultracold molecules can be used as
synthetic dimensions extending to many - potentially hundreds of - synthetic
lattice sites. Microwaves coupling rotational states drive fully controllable
synthetic inter-site tunnelings, enabling, for example, topological band
structures. Interactions leads to even richer behavior: when molecules are
frozen in a real space lattice with uniform synthetic tunnelings, dipole
interactions cause the molecules to aggregate to a narrow strip in the
synthetic direction beyond a critical interaction strength, resulting in a
quantum string or a membrane, with an emergent condensate that lives on this
string or membrane. All these phases can be detected using measurements of
rotational state populations.Comment: 5-page article + 4 figures + references; 7 pages + 4 figures in
Supplemen
Precision of a Low-Cost InGaAs Detector for Near Infrared Photometry
We have designed, constructed, and tested an InGaAs near-infrared camera to
explore whether low-cost detectors can make small (<1 m) telescopes capable of
precise (<1 mmag) infrared photometry of relatively bright targets. The camera
is constructed around the 640x512 pixel APS640C sensor built by FLIR
Electro-Optical Components. We designed custom analog-to-digital electronics
for maximum stability and minimum noise. The InGaAs dark current halves with
every 7 deg C of cooling, and we reduce it to 840 e-/s/pixel (with a
pixel-to-pixel variation of +/-200 e-/s/pixel) by cooling the array to -20 deg
C. Beyond this point, glow from the readout dominates. The single-sample read
noise of 149 e- is reduced to 54 e- through up-the-ramp sampling. Laboratory
testing with a star field generated by a lenslet array shows that 2-star
differential photometry is possible to a precision of 631 +/-205 ppm (0.68
mmag) hr^-0.5 at a flux of 2.4E4 e-/s. Employing three comparison stars and
de-correlating reference signals further improves the precision to 483 +/-161
ppm (0.52 mmag) hr^-0.5. Photometric observations of HD80606 and HD80607 (J=7.7
and 7.8) in the Y band shows that differential photometry to a precision of 415
ppm (0.45 mmag) hr^-0.5 is achieved with an effective telescope aperture of
0.25 m. Next-generation InGaAs detectors should indeed enable Poisson-limited
photometry of brighter dwarfs with particular advantage for late-M and L types.
In addition, one might acquire near-infrared photometry simultaneously with
optical photometry or radial velocity measurements to maximize the return of
exoplanet searches with small telescopes.Comment: Accepted to PAS
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