High resolution airborne radiometric and magnetic studies of ilesha and its environs, southwestern Nigeria

The study of the nature of distribution of natural radioelements in Ilesha and its environs with its geological structure has been studied using aeroradiometric data. Aeromagnetic data have also been subjected to three automated gradient techniques to delineate the sub-surface structure of the study area. From the study, it can be found that maximum values of “eU” (ppm) and “eTh” (ppm) fall within the branded gneiss, whereas the maximum value of K (%) falls within porphyritic granite regions. eTh had the highest radioactive content. The environmental dose rate of Ilesha was between 0.1817 and 3.9296 msv/yr. Although there were extreme values, but the mean dose rate was 0.522 ± 0.310 msv/yr (within acceptable safe limit of 1.0 msv/yr). eU/K, eU/eTh and eTh/K ratios were analysed for enrichment or depletion of radioisotopes. eU/eTh >1 showed uranium depletion, while eTh >2 showed eTh enrichment. The magnetic intensity values ranged from -79.41 to 140.93 nT. The horizontal gradient method (HGM) and analytic signal amplitude (ASA) revealed that depth to magnetic sources ranged from 0.478 to 4.112 km and 0.348 to 2.551 km, respectively, whereas local wavenumber (LWN) depth ranged from 0.478 to 5.48 km, which overestimated those compared using HGM and ASA functions. The apparent susceptibility ranged from -0.00325 to 0.00323 SI, showing that ferromagnetic and diamagnetic mineral ranges control apparent susceptibility in Ilesha.

Costs of reproduction and carry-over effects in breeding albatrosses

We investigated the physiology of two closely related albatross species relative to their breeding strategy: black-browed albatrosses (Thalassarche melanophris) breed annually, while grey-headed albatrosses (T. chrysostoma) breed biennially. From observations of breeding fate and blood samples collected at the end of breeding in one season and feather corticosterone levels (fCort) sampled at the beginning of the next breeding season, we found that in both species some post-breeding physiological parameters differed according to breeding outcome (successful, failed, deferred). Correlations between post-breeding physiology and fCort, and links to future breeding decisions, were examined. In black-browed albatrosses, post-breeding physiology and fCort were not significantly correlated, but fCort independently predicted breeding decision the next year, which we interpret as a possible migratory carry-over effect. In grey-headed albatrosses, post-breeding triglyceride levels were negatively correlated with fCort, but only in females, which we interpret as a potential cost of reproduction. However, this potential cost did not carry-over to future breeding in the grey-headed albatrosses. None of the variables predicted future breeding decisions. We suggest that biennial breeding in the grey-headed albatrosses may have evolved as a strategy to buffer against the apparent susceptibility of females to negative physiological costs of reproduction. Future studies are needed to confirm this.

Local avian density influences risk of mortality from window strikes

Up to a billion birds die per year in North America as a result of striking windows. Both transparent and reflective glass panes are a cause for concern, misleading birds by either acting as invisible, impenetrable barriers to desired resources, or reflecting those resources over a large surface area. A high number of window strikes occur during migration, but little is known about the factors of susceptibility, or whether particular avian taxa are more vulnerable than others. We report on a study of window strikes and mist-netting data at the Virginia Zoological Park (Norfolk, Virginia, USA), conducted in the autumn of 2013 and 2014. We focused on three factors likely to contribute to an individual’s predisposition to collide with windows: (i) taxonomic classification, (ii) age, and (iii) migrant vs. resident status. Thrushes, dominated by the partial migrant American Robin (Turdus migratorius), were significantly less likely to strike glass than be sampled in mist nets (χ2= 9.21, p = 0.002), while wood-warblers (Parulidae) were more likely to strike than expected (χ2= 13.55, p < 0.001). The proportion of juveniles striking windows (45.4%) was not significantly different (χ2= 0.05, p = 0.827) than the population of juvenile birds naturally occurring at the zoo (48.8%). Migrants, however, were significantly more susceptible to window strikes than residents (χ2= 6.35, p = 0.012). Our results suggest that resident birds are able to learn to avoid and thus reduce their likelihood of striking windows; this intrinsic risk factor may help explain the apparent susceptibility of certain taxa to window strikes.

Geophysical models of the Montresor metasedimentary belt and its environs, central Nunavut, Canada

Recent identification of hydrothermally altered rocks and breccia in the underexplored Montresor belt of Paleoproterozoic metasedimentary rocks suggests the possible presence of undiscovered mineralization. This study examines potential field data from the region with the goal of identifying subsurface features that could be associated with or serve as vectors to mineralization (subsurface alteration zones, faulting and (or) igneous intrusions). Gravity data were used to model regional and local geological features using known geology and physical properties from the study area and environs as constraints, and documents dense intrusive bodies underlying the Paleoproterozoic sequences. Maps of transformed apparent magnetic susceptibility values outline corridors of weak magnetization that correspond to observed zones of non-magnetic breccia and epidote–hematite–quartz alteration. Imputing the apparent susceptibility and rock property information into a magnetic forward model defines the geometry of this alteration zone, which is best explained as a northerly dipping non-magnetic or demagnetized, metasomatized intrusive sheet. The presence of previously undocumented igneous intrusions, their association with demagnetized hydrothermal breccia, and the continuity of the demagnetized zone suggests additional prospective areas within the region. This geological–geophysical framework for the nature and geometry of the Montresor belt and its surrounds highlights the importance of integrated modelling for areas with limited data.

Mapping of apparent magnetic susceptibility and the identification of fractures: A case study from the Eye-Dashwa Lakes pluton, Atikokan, Ontario

In situ magnetic-susceptibility measurements are only possible on outcrops, which are often limited by overburden and water bodies. An alternative approach is to derive an apparent susceptibility map from total-magnetic-intensity (TMI) surveys, which was done in this study for the Eye-Dashwa Lakes pluton near Atikokan, Ontario. Susceptibility logs of cores directly link alteration to systematic changes in the amount and composition of magnetic minerals. The surficial distribution of alteration zones was originally estimated from a limited number of in situ magnetic-susceptibility measurements. Here, through forward modeling of the TMI data set, susceptibility data are used to validate the apparent susceptibility data set. The modeling accounts for the bathymetric surface of all lakes that cover the area. A two-step process of bulk and local-scale modeling was used to estimate apparent susceptibility patterns. Bulk magnetic susceptibility is used as an indicator of overall alteration content, and local-scale apparent magnetic-susceptibility values are computed using a forward-modeling routine. The new apparent magnetic data set indicates northwest and northeast linears, which are the same as those seen in previous studies.

Unexpected Enzyme TEM-126: Role of Mutation Asp179Glu

ABSTRACT The clinical isolate Escherichia coli CF884 exhibited low-level resistance to ceftazidime (4 μg/ml) by a positive double-disk synergy test and apparent susceptibility to cefuroxime, cefotaxime, cefepime, cefpirome, and aztreonam. The enzyme implicated in this phenotype was a novel 180-kb plasmid-encoded TEM-type extended-spectrum β-lactamase designated TEM-126 which harbors the mutations Asp179Glu and Met182Thr. TEM-126 exhibited significant hydrolytic activity (k cat, 2 s−1) and a Km value of 82 μM against ceftazidime. Molecular dynamics simulations suggested that the substitution Asp179Glu induces subtle conformational changes to the omega loop which may favor the insertion of ceftazidime in the binding site and the correct positioning of the crucial residue Glu166. Overall, these results highlight the remarkable plasticity of TEM enzymes, which can expand their activity against ceftazidime by the addition of one carbon atom in the side chain of residue 179.