8,995 research outputs found
On the polarimetric variability of bright O-type stars
Polarimetric data associated with multi-parameter observational campaigns of selected bright O-type stars and their variable winds, are analysed in relation to the outcomes of the UV and optical spectroscopic studies. For the stars ξ Per and λ Cep, individual measurement uncertainties are Δρ~±0.0002 with nightly mean uncertainties of Δρ~±0.00007. Although variability is apparent on a night-to-night basis, with differences in δρ~0.0002, no correlations are found between these and the periodic behaviours associated with the stellar Si IV and H α lines. Similar polarimetric variability is seen in the data for the standard star ø Cas used as a reference in this observing campaign. It is suggested that all of these low level fluctuations are not intrinsic to the stars but are engendered by structured instrumental polarization in the diffraction pattern and depolarization effects in combination with inconsistent target acquisition and with variable seeing conditions in the Earth's atmosphere. Reassessment of older data for λ Cep from Hayes (1978) also supports this thesis
The impact of boundary conditions on CO2 capacity estimation in aquifers
The boundary conditions of an aquifer determine the extent to which fluids (including formation water
and CO2) and pressure can be transferred into adjacent geological formations, either laterally or vertically.
Aquifer boundaries can be faults, lithological boundaries, formation pinch-outs, salt walls, or outcrop. In
many cases compliance with regulations preventing CO2 storage influencing areas outside artificial
boundaries defined by non-geological criteria (international boundaries; license limits) may be necessary.
A bounded aquifer is not necessarily a closed aquifer.
The identification of an aquiferâs boundary conditions determines how CO2 storage capacity is estimated
in the earliest screening and characterization stages. There are different static capacity estimation methods
in use for closed systems and open systems. The method used has a significant impact on the final
capacity estimate.
The recent EU Directive (2009/31/EC) stated that where more than one storage site within a single
âhydraulic unitâ (bounded aquifer volume) is being considered, the characterization process should
account for potential pressure interactions. The pressure interplay of multiple sites (or even the pressure
footprint of just one site) is heavily influenced by boundary conditions
Surface modification of a polyether-urethane with RGD-containing peptides for enhanced cell attachment and signalling
Abstract of article examining the chemical modification of polyurethane with RGD-containing peptides offers a means of encouraging the adhesion, spreading and proliferation of cells cultured on its surface. This study assesses the efficacy of a modification procedure using surface analysis techniques and preliminary cell culture studies
The role of the family in child and adolescent posttraumatic stress following attendance at an emergency department
Objective: To evaluate the role of family factors in posttraumatic stress symptomatology (PTSS) in children and adolescents who have attended an emergency department following assaults or motor vehicle accident. Methods: Children and their parents completed self-report questionnaires and semistructured interviews relating to their psychopathology and cognitive styles at 2-4 weeks and 6 months after trauma. Results: Parental depression was correlated with child PTSS at each assessment point. Less consistent findings were observed for family functioning. Parental endorsement of worry was a correlate of child PTSS at each assessment and a mediator between parental depression and child PTSS. Conclusions: A role for family factors, in particular parental depression and parental endorsement of worry, in the development of child PTSS is supported. Weaknesses of the study are discussed, and suggestions for future research are given
The legal protection of the marine environment : is Jamaica ready for a serious pollution incident?
SGMA in the Field: Early Efforts at Defining Sustainability in Californiaâs Critically Overdrafted Basins
How can paediatric epilepsy services best be delivered in secondary care?
AbstractObjective: To produce practical evidence-based guidelines for the management of paediatric epilepsy in secondary care settings. Design: Question-specific systematic literature review and local service audit. Main outcome measures: Grade of recommendation for specific management issues. Results: There is little good quality research to support many existing epilepsy guidelines for secondary care. Conclusion: Practical guidelines for the provision of childrenâs epilepsy services can be evidence influenced but until more relevant research is undertaken, not evidence based
The geology and genesis of the iron skarns of the Turgai belt, northwestern Kazakhstan
The magnetite deposits of the Turgai belt (Kachar, Sarbai and Sokolov), in the Valerianovskoe zone of the southern Urals, Kazakhstan, contain a combined resource of over 3 Gt of iron oxide ore. The deposits are hosted by carbonate sediments and volcaniclastic rocks of the Carboniferous Valerianovka Supergroup, and are spatially related to the gabbroic to granitoid composition intrusive rocks of the SarbaiâSokolov intrusive series. The magnetite deposits are developed dominantly as metasomatic replacement of limestone, but also, to a lesser extent, of volcanic rocks. Pre-mineralisation metamorphism and alteration resulted in the formation of wollastonite and the silicification of limestone. Magnetite mineralisation is associated with the development of a high temperature skarn assemblage of diopside, grossularâandradite garnet, actinolite, epidote and apatite. Sub-economic copper-bearing sulphide mineralisation overprints the magnetite mineralisation and is associated with deposition of hydrothermal calcite and the formation of an extensive sodium alteration halo dominated by albite and scapolite. Chlorite formation accompanies this stage and further later stage hydrothermal overprints. The replacement has in places resulted in preservation of primary features of the limestone, including fossils and sedimentary structures in magnetite, skarn calc-silicates and sulphides.
Analysis of ReâOs isotopes in molybdenite indicates formation of the sulphide mineral assemblage at 336.2 Âą 1.3 Ma, whilst UâPb analyses of titanite from the skarn alteration assemblage suggests skarn alteration at 326.6 Âą 4.5 Ma with re-equilibration of isotope systematics down to ~ 270 Ma. Analyses of mineral assemblages, fluid inclusion microthermometry, O and S isotopes suggest initial mineralisation temperatures in excess of 600 °C from hypersaline brines (45â50 wt.% NaCl eq.), with subsequent cooling and dilution of fluids to around 150 °C and 20 wt.% NaCl eq. by the time of calcite deposition in late stage sulphide-bearing veins. δ18O in magnetite (â 1.5 to + 3.5â°) and skarn forming silicates (+ 5 to + 9â°), δ18O and δ13C in limestone and skarn calcite (δ18O + 5.4 to + 26.2â°; δ13C â 12.1 to + 0.9â°) and δ34S in sulphides (â 3.3 to + 6.6â°) and sulphates (+ 4.9 to + 12.9â°) are all consistent with the interaction of a magmatic-equilibrated fluid with limestone, and a dominantly magmatic source for S. All these data imply skarn formation and mineralisation in a magmaticâhydrothermal system that maintained high salinity to relatively late stages resulting in the formation of the large Na-alteration halo. Despite the reported presence of evaporites in the area there is no evidence for evaporitic sulphur in the mineralising system.
These skarns show similarities to some members of the iron oxideâapatite and iron oxideâcopper gold deposit classes and the model presented here may have implications for their genesis. The similarity in age between the Turgai deposits and the deposits of the Magnitogorsk zone in the western Urals suggests that they may be linked to similar magmatism, developed during post-orogenic collapse and extension following the continentâcontinent collision, which has resulted in the assembly of Laurussian terranes with the Uralide orogen and the Kazakh collage of the Altaids or Central Asian Orogenic Belt. This model is preferred to the model of simultaneous formation of very similar deposits in arc settings at either side of an open tract of oceanic crust forming part of the Uralian ocean
Growing Guava for Processing
This bulletin covers the many aspects of growing guava suitable for processing in Hawaii
Transmission Losses in Left-handed Materials
We numerically analyze the origin of the transmission losses in left-handed
structures. Our data confirms that left handed structures can have very good
transmission properties, in spite of the expectable dispersion of their
effective permeability and refraction index. The large permittivity of the
metallic components improves the transmission. High losses, observed in recent
experiments, could be explained by the absorption of the dielectric board
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