5,057 research outputs found
Magellanic Cloud Periphery Carbon Stars IV: The SMC
The kinematics of 150 carbon stars observed at moderate dispersion on the
periphery of the Small Magellanic Cloud are compared with the motions of
neutral hydrogen and early type stars in the Inter-Cloud region. The
distribution of radial velocities implies a configuration of these stars as a
sheet inclined at 73+/-4 degrees to the plane of the sky. The near side, to the
South, is dominated by a stellar component; to the North, the far side contains
fewer carbon stars, and is dominated by the neutral gas. The upper velocity
envelope of the stars is closely the same as that of the gas. This
configuration is shown to be consistent with the known extension of the SMC
along the line of sight, and is attributed to a tidally induced disruption of
the SMC that originated in a close encounter with the LMC some 0.3 to 0.4 Gyr
ago. The dearth of gas on the near side of the sheet is attributed to ablation
processes akin to those inferred by Weiner & Williams (1996) to collisional
excitation of the leading edges of Magellanic Stream clouds. Comparison with
pre LMC/SMC encounter kinematic data of Hardy, Suntzeff, & Azzopardi (1989) of
carbon stars, with data of stars formed after the encounter, of Maurice et al.
(1989), and Mathewson et al. (a986, 1988) leaves little doubt that forces other
than gravity play a role in the dynamics of the H I.Comment: 30 pages; 7 figures, latex compiled, 1 table; to appear in AJ (June
2000
Hamilton Standard Q-fan demonstrator dynamic pitch change test program, volume 1
Tests of a full scale variable pitch fan engine to obtain data on the structural characteristics, response times, and fan/core engine compatibility during transient changes in blade angle, fan rpm, and engine power is reported. Steady state reverse thrust tests with a take off nozzle configuration were also conducted. The 1.4 meter diameter, 13 bladed controllable pitch fan was driven by a T55 L 11A engine with power and blade angle coordinated by a digital computer. The tests demonstrated an ability to change from full forward thrust to reverse thrust in less than one (1) second. Reverse thrust was effected through feather and through flat pitch; structural characteristics and engine/fan compatibility were within satisfactory limits
Peeping at chaos: Nondestructive monitoring of chaotic systems by measuring long-time escape rates
One or more small holes provide non-destructive windows to observe
corresponding closed systems, for example by measuring long time escape rates
of particles as a function of hole sizes and positions. To leading order the
escape rate of chaotic systems is proportional to the hole size and independent
of position. Here we give exact formulas for the subsequent terms, as sums of
correlation functions; these depend on hole size and position, hence yield
information on the closed system dynamics. Conversely, the theory can be
readily applied to experimental design, for example to control escape rates.Comment: Originally 4 pages and 2 eps figures incorporated into the text; v2
has more numerical results and discussion: now 6 pages, 4 figure
Coupling atmospheric mercury isotope ratios and meteorology to identify sources of mercury impacting a coastal urban‐industrial region near Pensacola, Florida, USA
Identifying the anthropogenic and natural sources of mercury (Hg) emissions contributing to atmospheric mercury on local, regional, and global scales continues to be a grand challenge. The relative importance of various direct anthropogenic emissions of mercury, in addition to natural geologic sources and reemission of previously released and deposited mercury, differs regionally and temporally. In this study, we used local‐scale, mesoscale, and synoptic‐scale meteorological analysis to couple the isotopic composition of ambient atmospheric mercury with potential sources of mercury contributing to a coastal urban‐industrial setting near a coal‐fired power plant in Pensacola, Florida, USA. We were able to broadly discern four influences on the isotopic composition of ambient atmospheric mercury impacting this coastal urban‐industrial region: (1) local to regional urban‐industrial anthropogenic emissions (mean δ202Hg = 0.44 ± 0.05‰, 1SD, n = 3), (2) marine‐influenced sources derived from the Gulf of Mexico (mean δ202Hg = 0.77 ± 0.15‰, 1SD, n = 4), (3) continental sources associated with north‐northwesterly flows from within the planetary boundary layer (mean δ202Hg = 0.65 ± 0.04‰, 1SD, n = 3), and (4) continental sources associated with north‐northeasterly flows at higher altitudes (i.e., 2000 m above ground level; mean δ202Hg = 1.10 ± 0.21‰, 1SD, n = 8). Overall, these data, in conjunction with previous studies, suggest that the background global atmospheric mercury pool is characterized by moderately positive δ202Hg values; that urban‐industrial emissions drive the isotopic composition of ambient atmospheric mercury toward lower δ202Hg values; and that air‐surface exchange dynamics across vegetation and soils of terrestrial ecosystems drive the isotopic composition of ambient atmospheric mercury toward higher positive δ202Hg values. The data further suggest that mass‐independent fractionation (MIF) of both even‐mass‐ and odd‐mass‐number isotopes, likely generated by photochemical reactions in the atmosphere or during reemission from terrestrial and aquatic ecosystems, can be obscured by mixing with anthropogenic emissions having different MIF signatures.Key PointsIsotopic composition of TGM differed among meteorologically identified sourcesBackground atmospheric TGM displayed moderately positive δ202Hg valuesAnthropogenic emissions drive TGM isotopic composition to lower δ202Hg valuesPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136364/1/gbc20349-sup-0001-Supplementary.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136364/2/gbc20349.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136364/3/gbc20349_am.pd
Media outlets and their moguls: why concentrated individual or family ownership is bad for editorial independence
This article investigates the levels of owner influence in 211 different print and broadcast outlets in 32 different European media markets. Drawing on the literature from industrial organisation, it sets out reasons why we should expect greater levels of influence where ownership of individual outlets is concentrated; where it is concentrated in the hands of individuals or families; and where ownership groups own multiple outlets in the same media market. Conversely, we should expect lower levels of influence where ownership is dispersed between transnational companies. The articles uses original data on the ownership structures of these outlets, and combines it with reliable expert judgments as to the level of owner influence in each of the outlets. These hypotheses are tested and confirmed in a multilevel regression model of owner influence. The findings are relevant for policy on ownership limits in the media, and for the debate over transnational versus local control of media
Au-Ag template stripped pattern for scanning probe investigations of DNA arrays produced by Dip Pen Nanolithography
We report on DNA arrays produced by Dip Pen Nanolithography (DPN) on a novel
Au-Ag micro patterned template stripped surface. DNA arrays have been
investigated by atomic force microscopy (AFM) and scanning tunnelling
microscopy (STM) showing that the patterned template stripped substrate enables
easy retrieval of the DPN-functionalized zone with a standard optical
microscope permitting a multi-instrument and multi-technique local detection
and analysis. Moreover the smooth surface of the Au squares (abput 5-10
angstrom roughness) allows to be sensitive to the hybridization of the
oligonucleotide array with label-free target DNA. Our Au-Ag substrates,
combining the retrieving capabilities of the patterned surface with the
smoothness of the template stripped technique, are candidates for the
investigation of DPN nanostructures and for the development of label free
detection methods for DNA nanoarrays based on the use of scanning probes.Comment: Langmuir (accepted
Strengthening of the net section of steel elements under tensile loads with bonded CFRP strips
Abstract : The use of CFRP is increasingly common as a solution for the strengthening of structures, but the majority of research and applications have focused on the retrofit of concrete structures. The application of CFRP adhesively bonded to enhance the load carrying capacity of metallic elements has been widely studied in the aeronautical industry but is also a promising technique for the civil engineering area. This paper presents an experimental study to verify the effectiveness of the use of CFRP for the strengthening of the net section of steel elements under tensile loading. A series of tensile tests were conducted with different bond lengths, different number of layers and different surface preparation of steel elements in double lap joints and steel plates. The ultimate load, the failure mode and the effective bond length for CFRP strengthened specimens were determined. The results showed that using CFRP sheets for the strengthening against net area failure provides no gain on the ultimate state, provides a small gain at the elastic limit, and provides a larger gain if the designer accepts to increase the capacity from the elastic limit to the debondig limit
COMPARISON OF WHITE-CLAWED CRAYFISH POPULATIONS IN IRISH AND FRENCH STREAMS, WITH COMMENTS ON ITS FUTURE SURVIVAL IN EUROPE
White-clawed crayfish Austropotamobius pallipes (Lereboullet) populations remain strong in Ireland across a range of river and lake habitats, but the species is in decline elsewhere in Europe where it is sympatric with alien species. From comparison of published French and Irish studies, we suggest that in the changed European context the long-term health and survival of this species requires the maintenance of Ireland’s no-go status for non-indigenous crayfish
Remarks on Renormalization of Black Hole Entropy
We elaborate the renormalization process of entropy of a nonextremal and an
extremal Reissner-Nordstr\"{o}m black hole by using the Pauli-Villars
regularization method, in which the regulator fields obey either the
Bose-Einstein or Fermi-Dirac distribution depending on their spin-statistics.
The black hole entropy involves only two renormalization constants. We also
discuss the entropy and temperature of the extremal black hole.Comment: 14 pages, revtex, no figure
Zwitterionic Si-C-Si-P and Si-P-Si-P four-membered rings with two-coordinate phosphorus atoms.
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