609 research outputs found
Father absence and age at first birth in a western sample
Objectives: Although a large literature has shown links between âfather absenceâ during early childhood, and earlier puberty and sexual behavior in girls in Western populations, there are only a few studies which have looked at timing of reproduction, and only one of these fully incorporated childless respondents to investigate whether father absence is associated with increased hazard of becoming a parent at one time point (early) more than another. Here we sought to clarify exactly when, if at all, father absence increased the likelihood of first birth in a Western sample. Methods: An online sample of 954 women reported on their childhood living circumstances, their age of menarche, first coitus, first pregnancy, and first birth. Results: Cox regression and KaplanâMeier plots showed an increased risk of becoming a parent for father absent women in their 20s, but no overall greater likelihood of parenthood. Conclusion: These data support the suggestion that father absence is associated with an acceleration of reproductive behavior in Western samples, rather than a simple increase in likelihood of reproduction
Novel resources: opportunities for and risks to species conservation
During the Anthropocene, ongoing rapid environmental changes are exposing many species to novel resources. However, scientistsâ understanding of what novel resources are and how they impact species is still rudimentary. Here, we used a resourceâbased approach to explore novel resources. First, we conceptualized novel resource use by species along two dimensions of novelty: namely, ecosystem novelty and resource novelty. We then examined characteristics that influence a speciesâ response to a novel resource and how novel resources can affect individuals, populations, species, and communities. In addition, we discuss potential management complications associated with novel resource use by threatened species. As conservation and management embrace global environmental change, it is critical that ecologists improve the current understanding of the opportunities and risks that novel resources present to species conservation
Superconducting Properties of MgCNi3 Films
We report the magnetotransport properties of thin polycrystalline films of
the recently discovered non-oxide perovskite superconductor MgCNi3. CNi3
precursor films were deposited onto sapphire substrates and subsequently
exposed to Mg vapor at 700 C. We report transition temperatures (Tc) and
critical field values (Hc2) of MgCNi3 films ranging in thickness from 7.5 nm to
100 nm. Films thicker than ~40 nm have a Tc ~ 8 K, and an upper critical field
Hc2 ~ 14 T, which are both comparable to that of polycrystalline powders. Hall
measurements in the normal state give a carrier density, n =-4.2 x 10^22 cm^-3,
that is approximately 4 times that reported for bulk samples.Comment: submitted to PR
Rhizobacterial influence on healthy stand establishment of canola grown in Rhizoctonia solani infested fields of Saskatchewan
Non-Peer ReviewedPre-emergence seedling damping-off, seedling blight, and brown girdling root rot caused by R. solani are important diseases of canola/rape seed in western Canada. Annual yield losses in excess of 20-30% have been reported in several infected fields. Cultural control methods or resistant cultivars are currently unavailable for these diseases. Chemical fungicides have been developed for use to control the disease, but the success rate has been varied. However, the use of chemicals is becoming less acceptable from an environmental point of view. Several studies indicated that biological control using plant growth promoting
rhizobacteria may also be effective in controlling R. solani. Field plots were established in Saskatoon, Regina and Melfort, SK, in 1990, 1991 and 1992 to evaluate the potential of rhizobacterial strains as
seed treatments to increase the healthy stand of canola CV. Westar grown in R. solani infested field. The bacteria were formulated either in sterile peat or in a liquid carrier and applied to seed just before planting. Bacterized seed were mechanically planted in replicated field plots artificially infested with R. solani. Final healthy stand was measured 30 days after planting. Grain yields were determined by harvesting the plots. Seed bacterization significantly increased the final healthy stand compared to non-bacterized controls. Strains which increased stand showed in vitro antagonistic activity to not only R. solani but also other pathogens such as Pythium ultimum, Fusarium solani and F. oxysporum. Some of these strains induced root elongation of canola under laboratory conditions. Rhizosphere colonization, chemical compatibility and shelf-life of the important bacteria will be discussed
Beta Pic-like circumstellar disk gas surrounding HR 10 and HD 85905
We present high spectral resolution observations of the absorption lines of CaII and NaI associated with the circumstellar gas disk surrounding the two A-type shell stars HR 10 and HD 85905. Data taken over two four-night periods in January and November 1997 reveal substantial changes in the circumstellar absorption line profiles between successive observations of both stars. Such variable features have both blue and red-shifted velocities up to 50 km s-1 away from the central absorbing component, and are similar to those routinely observed in the [FORMULA] Pictoris system. The sporadic presence of the circumstellar absorption components observed towards both HR 10 and HD 85905 may be explained by the infalling evaporating comet model developed for the [FORMULA] Pictoris system by Beust et al. (1990). We note that variable circumstellar absorption features have also been detected in rapidly rotating A-type stars, such that they may be suffering irregular mass-loss that could give rise to similar circumstellar disks and shells
From Forbidden Coronal Lines to Meaningful Coronal Magnetic Fields
We review methods to measure magnetic fields within the corona using the
polarized light in magnetic-dipole (M1) lines. We are particularly interested
in both the global magnetic-field evolution over a solar cycle, and the local
storage of magnetic free energy within coronal plasmas. We address commonly
held skepticisms concerning angular ambiguities and line-of-sight confusion. We
argue that ambiguities are in principle no worse than more familiar remotely
sensed photospheric vector-fields, and that the diagnosis of M1 line data would
benefit from simultaneous observations of EUV lines. Based on calculations and
data from eclipses, we discuss the most promising lines and different
approaches that might be used. We point to the S-like [Fe {\sc XI}] line (J=2
to J=1) at 789.2nm as a prime target line (for ATST for example) to augment the
hotter 1074.7 and 1079.8 nm Si-like lines of [Fe {\sc XIII}] currently observed
by the Coronal Multi-channel Polarimeter (CoMP). Significant breakthroughs will
be made possible with the new generation of coronagraphs, in three distinct
ways: (i) through single point inversions (which encompasses also the analysis
of MHD wave modes), (ii) using direct comparisons of synthetic MHD or
force-free models with polarization data, and (iii) using tomographic
techniques.Comment: Accepted by Solar Physics, April 201
Do state-and-transition models derived from vegetation succession also represent avian succession in restored mine pits?
State-and-transition models are increasingly used as a tool to inform management of post-disturbance succession and effective conservation of biodiversity in production landscapes. However, if they are to do this effectively, they need to represent faunal, as well as vegetation, succession. We assessed the congruence between vegetation and avian succession by sampling avian communities in each state of a state-and-transition model used to inform management of post-mining restoration in a production landscape in southwestern Australia. While avian communities differed significantly among states classified as on a desirable successional pathway, they did not differ between desirable and deviated states of the same post-mining age. Overall, we concluded there was poor congruence between vegetation and avian succession in this state-and-transition model. We identified four factors that likely contributed to this lack of congruence, which were that long-term monitoring of succession in restored mine pits was not used to update and improve models, states were not defined based on ecological processes and thresholds, states were not defined by criteria that were important in structuring the avian community, and states were not based on criteria that related to values in the reference community. We believe that consideration of these four factors in the development of state-and-transition models should improve their ability to accurately represent faunal, as well as vegetation, succession. Developing state-and-transition models that better incorporate patterns of faunal succession should improve the ability to manage post-disturbance succession across a range of ecosystems for biodiversity conservation
Ecological and financial impacts of illegal bushmeat trade in Zimbabwe
Under conditions of political instability and
economic decline illegal bushmeat hunting has emerged
as a serious conservation threat in Zimbabwe. Following
settlement of game ranches by subsistence farming communities,
wildlife populations have been eradicated over
large areas. In several areas still being managed as game
ranches illegal hunting is causing further declines of
wildlife populations (including threatened species such as
the wild dog Lycaon pictus and black rhinoceros Diceros
bicornis), threatening the viability of wildlife-based land
uses. From August 2001 to July 2009 in SaveÂŽ Valley
Conservancy 10,520 illegal hunting incidents were recorded,
84,396 wire snares removed, 4,148 hunters caught,
2,126 hunting dogs eliminated and at least 6,454 wild
animals killed. Estimated future financial losses from illegal
hunting in the Conservancy exceed USD 1.1 million year-1.
Illegal huntersâ earnings account for 0.31â0.52% of the
financial losses that they impose and the bushmeat trade is
an inefficient use of wildlife resources. Illegal hunting
peaks during the late dry season and is more frequent
close to the boundary, near areas resettled during land
reform and close to water. Illegal hunting with dogs peaks
during moonlight periods. Our study highlights several
management and land-use planning steps required to
maximize the efficacy of anti-poaching and to reduce the
likelihood of high impacts of illegal hunting. Anti-poaching
efforts should be aligned with the regular temporal and
spatial patterns of illegal hunting. Leases for hunting and
tourism concessions should ensure minimum adequate
investment by operators in anti-poaching. Reserve designers
should minimize the surface area to volume ratio of parks.
Fences should not be constructed using wire that can be
made into snares. Land reform involving game ranches
should integrate communities in wildlife-based land uses and ensure spatial separation between land for wildlife and
human settlement. Means are required to create stakeholdings
for communities in wildlife and disincentives for
illegal hunting.TRAFFIC Southern and East Africa, the
European Union, Wilderness Trust, Chicago Board of
Trade and the supporters of the African Wildlife Conservation
Fund.http://journals.cambridge.orgab201
Hsp70 in mitochondrial biogenesis
The family of hsp70 (70 kilodalton heat shock protein) molecular chaperones plays an essential and diverse role in cellular physiology, Hsp70 proteins appear to elicit their effects by interacting with polypeptides that present domains which exhibit non-native conformations at distinct stages during their life in the cell. In this paper we review work pertaining to the functions of hsp70 proteins in chaperoning mitochondrial protein biogenesis. Hsp70 proteins function in protein synthesis, protein translocation across mitochondrial membranes, protein folding and finally the delivery of misfolded proteins to proteolytic enzymes in the mitochondrial matrix
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