Radio planetary nebulae in the Magellanic Clouds     

M. D. Filipovi&#;  M. Cohen  W. A. Reid  J. L. Payne  Q. A. Parker  E. J. Crawford  I. S. Boji&#;i&#;  A. Y. De Horta  A. Hughes  J. Dickel  F. Stootman 《Monthly notices of the Royal Astronomical Society》2009,399(2):769-777

We report the extragalactic radio-continuum detection of 15 planetary nebulae (PNe) in the Magellanic Clouds (MCs) from recent Australia Telescope Compact Array+Parkes mosaic surveys. These detections were supplemented by new and high-resolution radio, optical and infrared observations which helped to resolve the true nature of the objects. Four of the PNe are located in the Small Magellanic Cloud (SMC) and 11 are located in the Large Magellanic Cloud (LMC). Based on Galactic PNe the expected radio flux densities at the distance of the LMC/SMC are up to ∼2.5 and ∼2.0 mJy at 1.4 GHz, respectively. We find that one of our new radio PNe in the SMC has a flux density of 5.1 mJy at 1.4 GHz, several times higher than expected. We suggest that the most luminous radio PN in the SMC (N S68) may represent the upper limit to radio-peak luminosity because it is approximately three times more luminous than NGC 7027, the most luminous known Galactic PN. We note that the optical diameters of these 15 Magellanic Clouds (MCs) PNe vary from very small (∼0.08 pc or 0.32 arcsec; SMP L47) to very large (∼1 pc or 4 arcsec; SMP L83). Their flux densities peak at different frequencies, suggesting that they may be in different stages of evolution. We briefly discuss mechanisms that may explain their unusually high radio-continuum flux densities. We argue that these detections may help solve the 'missing mass problem' in PNe whose central stars were originally  1–8 M_⊙  . We explore the possible link between ionized haloes ejected by the central stars in their late evolution and extended radio emission. Because of their higher than expected flux densities, we tentatively call this PNe (sub)sample –'Super PNe'.  相似文献   

Making local futures tangible—Synthesizing, downscaling, and visualizing climate change scenarios for participatory capacity building   总被引：1，自引：0，他引：1  

Alison Shaw  Stephen Sheppard  Sarah Burch  David Flanders  Arnim Wiek  Jeff Carmichael  John Robinson  Stewart Cohen 《Global Environmental Change》2009,19(4):447-463

Local in its causes and global in its impacts, climate change still poses an unresolved challenge for scientists, politicians, entrepreneurs, and citizens. Climate change research is largely global in focus, aims at enhanced understanding, and is driven by experts, all of which seem to be insufficient to anchor climate change action in regional and local contexts. We present results from a participatory scenario study conducted in collaboration with the municipality of Delta in SW British Columbia, Canada. This study applies a participatory capacity building approach for climate change action at the local level where the sources of emissions and the mechanisms of adaptation reside and where climate change is meaningful to decision-makers and stakeholders alike. The multi-scale scenario approach consists of synthesizing global climate change scenarios, downscaling them to the regional and local level, and finally visualizing alternative climate scenarios out to 2100 in 3D views of familiar, local places. We critically discuss the scenarios produced and the strengths and weaknesses of the approach applied.  相似文献   

Agricultural Chemical News     

Stuart Cohen 《Ground Water Monitoring & Remediation》1995,15(3):80-81

  相似文献   

Agricultural Chemical News     

Stuart Cohen 《Ground Water Monitoring & Remediation》1995,15(4):206-207

  相似文献   

An example of fingerprint detection of greenhouse climate change     

DJ Karoly  JA Cohen  GA Meehl  JFB Mitchell  AH Oort  RJ Stouffer  RT Wetherald 《Climate Dynamics》1994,10(1-2):97-105

As an example of the technique of fingerprint detection of greenhouse climate change, a multivariate signal or fingerprint of the enhanced greenhouse effect is defined using the zonal mean atmospheric temperature change as a function of height and latitude between equilibrium climate model simulations with control and doubled CO₂ concentrations. This signal is compared with observed atmospheric temperature variations over the period 1963 to 1988 from radiosonde-based global analyses. There is a significant increase of this greenhouse signal in the observational data over this period.These results must be treated with caution. Upper air data are available for a short period only, possibly too short to be able to resolve any real greenhouse climate change. The greenhouse fingerprint used in this study may not be unique to the enhanced greenhouse effect and may be due to other forcing mechanisms. However, it is shown that the patterns of atmospheric temperature change associated with uniform global increases of sea surface temperature, with El NinoSouthern Oscillation events and with decreases of stratospheric ozone concentrations individually are different from the greenhouse fingerprint used here.  相似文献   

Agricultural Chemical News     

Stuart Cohen 《Ground Water Monitoring & Remediation》1994,14(3):97-98

  相似文献   

EPA Letter     

Stuart Cohen 《Ground Water Monitoring & Remediation》1994,14(4):117-119

  相似文献   

Seismic reflection and refraction investigations of Lake Kinneret - central Jordan Valley, Israel     

Zvi Ben-Avraham  Avihu Ginzburg  Zvi Yuval 《Tectonophysics》1981,80(1-4):165-181

Seismic reflection and refraction studies in Lake Kinneret, which is located in the northern part of the Dead Sea Rift have been carried out. In the seismic reflection work several instruments including sparker, boomer and air guns were used. The acoustic penetration was limited, giving information on the uppermost sediments only. In the seismic refraction study the energy source was seismic explosives charges placed below the water table in shotholes located onshore at either end of two lines. The seismic signals were picked up by hydrophones and transmitted to the shore-based recording stations by special radio transmitters.

The seismic refraction profiles show different sedimentary structures at various parts of the lake. The layer underlying the top sedimentary sequence is of higher seismic velocity in the northern section than in the southern section. This suggests a difference in the stratigraphic section between the two parts. Unconformities and faults which account for the structures observed here probably exist under the lake.

The shallow reflection data indicate active tectonic processes in this area. Folds and faults have been observed in the uppermost sediments. The most deformed areas are along the margins but some deformation also occurs at the center of the lake in its deepest portion. The area is also seismically active.  相似文献   

m-Benzene disulfonic acid (BDS) as a superior accompanying acid for routine silicate rock analysis     

R.S. Cohen  P. Hemmes  J.H. Puffer 《Chemical Geology》1975,16(4):307-309

We recommend that m-benzene disulfonic acid (BDS) be used with hydrofluoric acid during the dissolution of silicate rocks and minerals for purposes of routine analysis of RO and R₂O groups and trace elements. This recommendation is based on several properties that make it superior to the alternative acids. These properties include: (1) a relatively high boiling point (resulting in more effective removal of HF and silica); (2) the high solubility of virtually all salts of BDS; (3) the non-complexing characteristics of BDS salts; (4) the thermal stability of BDS (resulting in very slight degassing at elevated temperatures, thus reducing splattering); and (5) the safety of BDS compared with highly oxidizing acids such as perchloric.  相似文献   

Assessment of downstream trends in channel gradient, total and specific stream power: a GIS approach     

Ivars Reinfelds  Tim Cohen  Paul Batten  Gary Brierley 《Geomorphology》2004,60(3-4):403-416

Geographic Information Systems (GIS) analyses of Digital Elevation Models (DEMs) coupled with catchment area based discharge estimation techniques provide a relatively simple means of modelling contiguous downstream trends in channel gradient, total stream power, and in riverscapes conducive to regime analysis, also specific stream power. For a small, high relief, coastal catchment in SE Australia, good agreement was obtained between channel gradients derived from a 25 m cell-size DEM and field survey equivalents over distances of several kilometres, indicating that channel gradients derived from DEMs can have a reasonable degree of absolute as well as relative accuracy over multi-kilometre reach scales. Assessment of downstream rates of change in channel gradient and specific stream power across four river systems suggests that some of the river reaches most responsive to high magnitude floods occur in zones where these variables rapidly decrease downstream. Modelling of downstream trends in channel gradient, total and specific stream power from catchment-wide DEMs has potential to provide a framework with which to investigate conceptual and empirical models between channel gradient, stream power and the form and dynamics of river systems.  相似文献