1,975 research outputs found
Drones and the Fourth Amendment: Redefining Expectations of Privacy
Drones have gained notoriety as a weapon against foreign terrorist targets; yet, they have also recently made headlines as an instrument for domestic surveillance. With their sophisticated capabilities and continuously decreasing costs, it is not surprising that drones have attracted numerous consumersâmost notably, law enforcement. Courts will likely soon have to decipher the limits on the governmentâs use of drones under the Fourth Amendment. But it is unclear where, or even whether, drones would fall under the current jurisprudence. Because of their diverse and sophisticated designs and capabilities, drones might be able to maneuver through the Fourth Amendmentâs doctrinal loopholes.
This Note advocates analyzing drones under an adapted approach to the reasonable-expectation-of-privacy test in Katz v. United States. Courts should focus more on the testâs oft-neglected first prongâwhether a person exhibited a subjective expectation of privacyâand analyze what information falls within the scope of that expectation, excluding information knowingly exposed to the plain view of the public. This analysis also considers instances when, although a subjective expectation exists, it may be impossible or implausible to reasonably exhibit that expectation, a dilemma especially relevant to an analysis of drones.
Courts that adopt the recommended analysis would have a coherent and comprehensible approach to factually dynamic cases challenging the constitutionality of drone surveillance. Until then, the constitutional uncertainties of these cases will likely linger
Use of acrylic sheet molds for elastomeric products
Molds constructed of acrylic sheet are more easily machined than metal, are transparent to ensure complete filling during injection, and have smooth surfaces free of contamination. Technique eliminates flashing on molded parts and mold release agents
Aerodynamic design trends for commercial aircraft
Recent research on advanced-configuration commercial aircraft at DFVLR is surveyed, with a focus on aerodynamic approaches to improved performance. Topics examined include transonic wings with variable camber or shock/boundary-layer control, wings with reduced friction drag or laminarized flow, prop-fan propulsion, and unusual configurations or wing profiles. Drawings, diagrams, and graphs of predicted performance are provided, and the need for extensive development efforts using powerful computer facilities, high-speed and low-speed wind tunnels, and flight tests of models (mounted on specially designed carrier aircraft) is indicated
A New Brown Dwarf Desert? A Scarcity of Wide Ultracool Binaries
We present the results of a deep-imaging search for wide companions to
low-mass stars and brown dwarfs using NSFCam on IRTF. We searched a sample of
132 M7-L8 dwarfs to magnitude limits of and ,
corresponding to secondary-primary mass ratios of . No companions
were found with separations between 2{\arcsec} to 31{\arcsec} (40 AU
to 1000 AU). This null result implies a wide companion frequency below
2.3% at the 95% confidence level within the sensitivity limits of the survey.
Preliminary modeling efforts indicate that we could have detected 85% of
companions more massive than and 50% above .Comment: 27 pages, 8 figures, 3 tables: accepted to the Astronomical Journa
Die Zyklik der Profite in der ErnÀhrungswirtschaft: Ein internationaler Vergleich.
Im Rahmen des Struktur-Verhaltens-Ergebnis-Ansatz analysiert der vorliegende Aufsatz die Determinanten und die Zyklik der Profite verschiedener Branchen der ErnĂ€hrungswirtschaft in Deutschland, den USA sowie den Niederlanden. Aus der Schwankung der Profite im Zeitablauf lassen sich, bei gegebener Marktstruktur, Hinweise auf die IntensitĂ€t des Wettbewerbs und damit das Verhalten der Unternehmen gewinnen. Die Ergebnisse der ökonometrischen Panelanalyse zeigen ausgeprĂ€gte prozyklische Schwankungen der Profite in Deutschland in hochkonzentrierten Branchen, wĂ€hrend das AusmaĂ der Schwankungen in Branchen mit niedriger Konzentration in Deutschland sowie in sĂ€mtlichen Branchen der USA gering ist. Die Beobachtungen fĂŒr Deutschland deuten auf eine Zunahme der WettbewerbsintensitĂ€t in einer Rezession hin. Die SchĂ€tzung ökonometrischer Modelle fĂŒr die Niederlande fĂŒhrt zu unbefriedigenden Ergebnissen. -- Based upon the structure-conduct-performance-approach the present paper analyses determinants of price-cost-margins over the business cycle for food industries in Germany, the USA as well as the Netherlands. Controlling for market structure variables, cyclical fluctuations in profitability are interpreted as evidence for changes in firm behaviour. The econometric panel data models reveal procyclic fluctuations of profits in highly concentrated industries in Germany. In contrast, profitability in competitive industries in Germany as well as in all US-food industries are found to be more stable over the business cycle. This observation is explicable in terms of a more aggressive behaviour of firms in boom periods. The econometric model does not adequately explain industry differences in profitability in the Netherlands.Struktur-Verhalts-Ergebnis-Ansatz,LERNER-Index,ErnĂ€hrungswirtschaft,Panelanalyse,Deutschland,Niederlande,structure-conduct-performance-approach,LERNER-index,food industries,panel data,Germany,Netherlands,USA
Millimeter-Wave Aperture Synthesis Imaging of Vega: Evidence for a Ring Arc at 95 AU
We present the first millimeter-wave aperture synthesis map of dust around a
main sequence star. A 3'' resolution image of 1.3 mm continuum emission from
Vega reveals a clump of emission 12'' from the star at PA 45 deg, consistent
with the location of maximum 850 micron emission in a lower resolution
JCMT/SCUBA map. The flux density is 4.0+/-0.9 mJy. Adjacent 1.3 mm peaks with
flux densities 3.4+/-1.0 mJy and 2.8+/-0.9 mJy are located 14'' and 13'' from
the star at PA 67 deg and 18 deg, respectively. An arc-like bridge connects the
two strongest peaks. There is an additional 2.4 +/-0.8 mJy peak to the SW 11''
from the star at PA 215 deg and a marginal detection, 1.4+/-0.5 mJy, at the
stellar position, consistent with photospheric emission. An extrapolation from
the 850 micron flux, assuming F_{1.3mm-0.85mm} proportional to lambda^{-2.8},
agrees well with the total detected flux for Vega at 1.3 mm, and implies a dust
emissivity index, beta, of 0.8. We conclude that we have detected all but a
very small fraction of the dust imaged by SCUBA in our aperture synthesis map
and that these grains are largely confined to segments of a ring of radius 95
AU.Comment: 4 pages, 1 figure, 1 table, accepted for publication in Astrophysical
Journal Letter
Keck Imaging of Binary L Dwarfs
We present Keck near-infrared imaging of three binary L dwarf systems, all of
which are likely to be sub-stellar. Two are lithium dwarfs, and a third
exhibits an L7 spectral type, making it the coolest binary known to date. All
have component flux ratios near 1 and projected physical separations between 5
and 10 AU, assuming distances of 18 to 26 pc from recent measurements of
trigonometric parallax. These surprisingly similar binaries represent the sole
detections of companions in ten L dwarf systems which were analyzed in the
preliminary phase of a much larger dual-epoch imaging survey. The detection
rate prompts us to speculate that binary companions to L dwarfs are common,
that similar-mass systems predominate, and that their distribution peaks at
radial distances in accord both with M dwarf binaries and with the radial
location of Jovian planets in our own solar system. To fully establish these
conjectures against doubts raised by biases inherent in this small preliminary
survey, however, will require quantitative analysis of a larger volume-limited
sample which has been observed with high resolution and dynamic range.Comment: LaTex manuscript in 13 pages, 3 postscript figures, Accepted for
publication in the Letters of the Astrophysical Journal; Postscript pre-print
version available at: http://www.hep.upenn.edu/PORG/papers/koerner99a.p
Natural frequencies of cantilevered triangular tapered plates
Call number: LD2668 .T4 1966 K78Master of Scienc
Correlation of Early Outcomes and Intradiscal Interleukin-6 Expression in Lumbar Fusion Patients.
OBJECTIVE: To determine if there is correlation between intradiscal levels of interleukin-6 (IL-6) and early outcome measures in patients undergoing lumbar fusion for painful disc degeneration.
METHODS: Intervertebral disc tissue was separated into annulus fibrosus/nucleus pulposus and cultured separately in vitro in serum-free medium (Opti-MEM). Conditioned media was collected after 48 hours. The concentration of IL-6 was quantified using enzyme-linked immunosorbent assay. Pearson correlation coefficients quantified relationships between IL-6 levels and pre- and postoperative visual analogue scale (VAS) back pain and Oswestry Disability Index (ODI), as well as change in VAS/ODI.
RESULTS: Sixteen discs were harvested from 9 patients undergoing anterior lumbar interbody fusion (mean age, 47.4 years; range, 21-70 years). Mean preoperative and 6-month postoperative VAS were 8.1 and 3.7, respectively. Mean preoperative and postoperative ODI were 56.2 and 25.6, respectively. There were significant positive correlations between IL-6 expression and postoperative VAS (Ï = 0.38, p = 0.048) and ODI (Ï = 0.44, p = 0.02). No significant correlations were found between intradiscal IL-6 expression and preoperative VAS (Ï = -0.12, p = 0.54). Trends were seen associating IL-6 expression and change in VAS/ODI (Ï = -0.35 p = 0.067; Ï = -0.34, p = 0.08, respectively). A trend associated IL-6 and preoperative ODI (Ï = 0.36, p = 0.063).
CONCLUSION: The direct association between IL-6 expression and VAS/ODI suggests patients with elevated intradiscal cytokine expression may have worse early outcomes than those with lower expression of IL-6 after surgery for symptomatic disc degeneration
A Single Circumbinary Disk in the HD 98800 Quadruple System
We present sub-arcsecond thermal infrared imaging of HD 98800, a young
quadruple system composed of a pair of low-mass spectroscopic binaries
separated by 0.8'' (38 AU), each with a K-dwarf primary. Images at wavelengths
ranging from 5 to 24.5 microns show unequivocally that the optically fainter
binary, HD 98800B, is the sole source of a comparatively large infrared excess
upon which a silicate emission feature is superposed. The excess is detected
only at wavelengths of 7.9 microns and longer, peaks at 25 microns, and has a
best-fit black-body temperature of 150 K, indicating that most of the dust lies
at distances greater than the orbital separation of the spectroscopic binary.
We estimate the radial extent of the dust with a disk model that approximates
radiation from the spectroscopic binary as a single source of equivalent
luminosity. Given the data, the most-likely values of disk properties in the
ranges considered are R_in = 5.0 +/- 2.5 AU, DeltaR = 13+/-8 AU, lambda_0 =
2(+4/-1.5) microns, gamma = 0+/-2.5, and sigma_total = 16+/-3 AU^2, where R_in
is the inner radius, DeltaR is the radial extent of the disk, lambda_0 is the
effective grain size, gamma is the radial power-law exponent of the optical
depth, tau, and sigma_total is the total cross-section of the grains. The range
of implied disk masses is 0.001--0.1 times that of the moon. These results show
that, for a wide range of possible disk properties, a circumbinary disk is far
more likely than a narrow ring.Comment: 11 page Latex manuscript with 3 postscript figures. Accepted for
publication in Astrophysical Journal Letters. Postscript version of complete
paper also available at
http://www.hep.upenn.edu/PORG/web/papers/koerner00a.p
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