Wildland fire effects in silviculturally treated vs. untreated stands of New Mexico and Arizona

Stand-replacement fires, particularly in ponderosa pine (Pinus ponderosa) forests, have replaced high frequency, low-intensity historical fire regimes. We examined whether forest stands treated recently using silvicultural practices would be (1) less susceptible to stand-replacing crownfires, and (2) more ecologically and functionally resilient compared to untreated stands following extreme wildland fire. Reports detailing wildland fire behavior in treated stands remain largely anecdotal. We compared fire severity indices, fireline intensity (btu/ft/s), stand characteristics including canopy bulk density (kg/m3), and post-fire recovery indices in silviculturally treated vs. untreated forest stands in New Mexico and Arizona. Results indicated fire severity in pine-grassland forests was lowered when surface and aerial fuel loads were reduced. Specifically, as density (stems/ac) and basal area (ft2/ac) decreased and mean tree diameter (in) increased, fire severity and fireline intensity decreased. The more aggressive the treatment (i.e., where the canopy bulk density was reduced), the less susceptible forest stands were to crownfire. However, mechanical treatments where slash was scattered rendered stands susceptible to near stand-replacement type damage when wildfire occurred within 4 years of treatment. On our study sites, mechanical treatment followed by prescribed fire had the greatest impact toward mitigating fire severity (i.e., aerial and surface fuels were reduced). Treated stands were also more ecologically and functionally resilient than untreated forest stands following wildland fire

The oxidative costs of reproduction are group-size dependent in a wild cooperative breeder.

Life-history theory assumes that reproduction entails a cost, and research on cooperatively breeding societies suggests that the cooperative sharing of workloads can reduce this cost. However, the physiological mechanisms that underpin both the costs of reproduction and the benefits of cooperation remain poorly understood. It has been hypothesized that reproductive costs may arise in part from oxidative stress, as reproductive investment may elevate exposure to reactive oxygen species, compromising survival and future reproduction and accelerating senescence. However, experimental evidence of oxidative costs of reproduction in the wild remains scarce. Here, we use a clutch-removal experiment to investigate the oxidative costs of reproduction in a wild cooperatively breeding bird, the white-browed sparrow weaver, Plocepasser mahali. Our results reveal costs of reproduction that are dependent on group size: relative to individuals in groups whose eggs were experimentally removed, individuals in groups that raised offspring experienced an associated cost (elevated oxidative damage and reduced body mass), but only if they were in small groups containing fewer or no helpers. Furthermore, during nestling provisioning, individuals that provisioned at higher rates showed greater within-individual declines in body mass and antioxidant protection. Our results provide rare experimental evidence that reproduction can negatively impact both oxidative status and body mass in the wild, and suggest that these costs can be mitigated in cooperative societies by the presence of additional helpers. These findings have implications for our understanding of the energetic and oxidative costs of reproduction, and the benefits of cooperation in animal societies.This study was funded by a BBSRC David Phillips Fellowship and a Royal Society Research Grant to A.J.Y. and an NERC studentship to D.L.C. J.D.B. was supported by a Royal Society University Research Fellowship.This is the final version of the article. It first appeared from Royal Society Publishing via http://dx.doi.org/10.1098/rspb.2015.203

VLA Observations of the "Eye of the Tornado"- the High Velocity \HII Region G357.63-0.06

The unusual supernova remnant candidate G357.7-0.1 and the compact source G357.63-0.06 have been observed with the Very Large Array at 1.4 and 8.3 GHz. The H92$\alpha$ line (8.3 GHz) was detected from the compact source with a surprising velocity of about -210 km/s indicating that this source is an \HII region, is most likely located at the Galactic center, and is unrelated to the SNR. The \HI absorption line (1.4 GHz) data toward these sources supports this picture and suggests that G357.7-0.1 lies farther away than the Galactic center.Comment: Latex, 14 pages including 4 figures. Accepted to A

The Molonglo Galactic Plane Survey: I. Overview and Images

The first epoch Molonglo Galactic Plane Survey (MGPS1) is a radio continuum survey made using the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz with a resolution of 43" X 43" cosec |delta|. The region surveyed is 245 deg < l < 355 deg, |b| < 1.5 deg. The thirteen 9 deg X 3 deg mosaic images presented here are the superposition of over 450 complete synthesis observations, each taking 12 h and covering 70' X 70' cosec |delta|. The root-mean-square sensitivity over much of the mosaiced survey is 1-2 mJy/beam (1 sigma), and the positional accuracy is approximately 1" X 1" cosec |delta| for sources brighter than 20 mJy. The dynamic range is no better than 250:1, and this also constrains the sensitivity in some parts of the images. The survey area of 330 sq deg contains well over 12,000 unresolved or barely resolved objects, almost all of which are extra-galactic sources lying in the Zone of Avoidance. In addition a significant fraction of this area is covered by extended, diffuse emission associated with thermal complexes, discrete H II regions, supernova remnants, and other structures in the Galactic interstellar medium.Comment: Paper with 3 figures and 1 table + Table 2 + 7 jpg grayscales for Fig 4. Astrophysical Journal Supplement (in press) see also http://www.astrop.physics.usyd.edu.au/MGP

Immune response in a wild bird is predicted by oxidative status, but does not cause oxidative stress.

The immune system provides vital protection against pathogens, but extensive evidence suggests that mounting immune responses can entail survival and fecundity costs. The physiological mechanisms that underpin these costs remain poorly understood, despite their potentially important role in shaping life-histories. Recent studies involving laboratory models highlight the possibility that oxidative stress could mediate these costs, as immune-activation can increase the production of reactive oxygen species leading to oxidative stress. However, this hypothesis has rarely been tested in free-ranging wild populations, where natural oxidative statuses and compensatory strategies may moderate immune responses and their impacts on oxidative status. Furthermore, the possibility that individuals scale their immune responses according to their oxidative status, conceivably to mitigate such costs, remains virtually unexplored. Here, we experimentally investigate the effects of a phytohaemagglutinin (PHA) immune-challenge on oxidative status in wild male and female white-browed sparrow weavers, Plocepasser mahali. We also establish whether baseline oxidative status prior to challenge predicts the scale of the immune responses. Contrary to previous work on captive animals, our findings suggest that PHA-induced immune-activation does not elicit oxidative stress. Compared with controls (n = 25 birds), PHA-injected birds (n = 27 birds) showed no evidence of a differential change in markers of oxidative damage or enzymatic and non-enzymatic antioxidant protection 24 hours after challenge. We did, however, find that the activity of a key antioxidant enzyme (superoxide dismutase, SOD) prior to immune-activation predicted the scale of the resulting swelling: birds with stronger initial SOD activity subsequently produced smaller swellings. Our findings (i) suggest that wild birds can mount immune responses without suffering from systemic oxidative stress, and (ii) lend support to biomedical evidence that baseline oxidative status can impact the scale of immune responses; a possibility not yet recognised in ecological studies of immunity

Supramolecular Complexation of Carbon Nanostructures by Crown Ethers

Since their discovery, crown ethers as well as the most recent carbon nanostructures, namely fullerenes, carbon nanotubes, and graphene, have received a lot of attention from the chemical community. Merging these singular chemical structures by noncovalent forces has provided a large number of unprecedented supramolecular assemblies with new geometric and electronic properties whose more representative examples are presented in this Synopsis organized according to the different nature of the carbon nanostructures

Microjansky radio sources in DC0107-46 (Abell 2877)

The cluster DC0107-46 (Abell 2877) lies within the Phoenix Deep Survey, made at 1.4 GHz with the Australia Telescope Compact Array. Of 89 known optical cluster members, 70 lie within the radio survey area. Of these 70 galaxies, 15 (21%) are detected, with luminosities as faint as 10^20 W/Hz. Spectroscopic observations are available for 14/15 of the radio-detected cluster galaxies. Six galaxies show only absorption features and are typical low-luminosity AGN radio sources. One galaxy hosts a Seyfert 2 nucleus, two are star-forming galaxies, and the remaining five may be star-forming galaxies, AGNs, or both.Comment: 14 pages, 3 figures, Accepted by ApJS (v128n2p JUN 2000 issue

Proteomic Analysis Reveals CACN-1 Is a Component of the Spliceosome in Caenorhabditis elegans

Cell migration is essential for embryonic development and tissue formation in all animals. cacn-1 is a conserved gene of unknown molecular function identified in a genome-wide screen for genes that regulate distal tip cell migration in the nematode worm Caenorhabditis elegans. In this study we take a proteomics approach to understand CACN-1 function. To isolate CACN-1−interacting proteins, we used an in vivo tandem-affinity purification strategy. Tandem-affinity purification−tagged CACN-1 complexes were isolated from C. elegans lysate, analyzed by mass spectrometry, and characterized bioinformatically. Results suggest significant interaction of CACN-1 with the C. elegans spliceosome. All of the identified interactors were screened for distal tip cell migration phenotypes using RNAi. Depletion of many of these factors led to distal tip cell migration defects, particularly a failure to stop migrating, a phenotype commonly seen in cacn-1 deficient animals. The results of this screen identify eight novel regulators of cell migration and suggest CACN-1 may participate in a protein network dedicated to high-fidelity gonad development. The composition of proteins comprising the CACN-1 network suggests that this critical developmental module may exert its influence through alternative splicing or other post-transcriptional gene regulation