18,828 research outputs found
Ethnography, ethics and ownership of data
© The Author(s) 2019. Establishing trust and obtaining informed consent with participants is reliant upon on a process whereby unequally positioned agents constantly re-negotiate (mis)trust and consent during ethnographic encounters. All research has been increasingly subject to an intensification in ethical regulation, within a context whereby Eurocentric norms and ethical guidelines arguably diminish individual accountability under the guise of quasi-contractual relationships. This phenomenon has particular implications for ethnography and its management of ethics, given its intimate, longitudinal and receptive nature. Two expert ethnographers working with children and young people draw upon their work to reveal how issues of informed consent and data ownership can shift and be a source of tension and unequal power dynamics. The ethnographer requires autonomy while managing ethics soundly in situ to work within the messiness and unpredictability of participants’ everyday lives
Turnaround Time Between ILLiad’s Odyssey and Ariel Delivery Methods: A Comparison
Interlibrary loan departments are frequently looking for ways to reduce turnaround time. The advent of electronic delivery in the past decade has greatly reduced turnaround time for articles, but recent developments in this arena have the potential to decrease that time even further. The ILLiad ILL management system has an electronic delivery component, Odyssey, with a Trusted Sender setting that allows articles to be sent to patrons without borrowing staff intervention, provided the lending library is designated as a Trusted Sender, or this feature is enabled for all lenders. Using the tracking data created by the ILLiad management system, the turnaround time for two delivery methods, Ariel and Odyssey, was captured for two different academic institutions. With the Trusted Sender setting turned on, Odyssey delivery was faster than Ariel for the institutions studied
Invariant states and rates of Convergence for a critical fluid model of a processor sharing queue
This paper contains an asymptotic analysis of a fluid model for a heavily
loaded processor sharing queue. Specifically, we consider the behavior of
solutions of critical fluid models as time approaches \infty. The main theorems
of the paper provide sufficient conditions for a fluid model solution to
converge to an invariant state and, under slightly more restrictive
assumptions, provide a rate of convergence. These results are used in a related
work by Gromoll for establishing a heavy traffic diffusion approximation for a
processor sharing queue
Effect of Carex rostrata on seasonal and interannual variability in peatland methane emissions
Peatlands are a large natural source of atmospheric methane (CH4), and the sedge Carex rostrata plays a critical role in the production, oxidation, and transport of CH4 in these systems. This 4 year clipping experiment examined the changes in CH4 emissions from a temperate peatland after removing all aboveground C. rostrata biomass. Methane fluxes, dissolved CH4, and environmental variables were measured during spring, summer, and fall from 2008 to 2011. Clipping and removing the C. rostrata leaves and stems caused an immediate decrease in CH4 emissions that persisted over 4 years of this study. There was a strong seasonal trend in CH4 flux, with the largest treatment effects occurring during the fall months when the sedges were senescing. As expected, there was a strong positive correlation between C. rostrata green-leaf area and CH4 flux, implying that the presence of C. rostrata increases CH4 emissions from this peatland. Large interannual variability in vegetation distribution and biomass, water table depth, and temperature was observed in this study, indicating the importance of multiyear studies for understanding the interactions among these factors to determine how they could be incorporated into biogeochemical models to predict CH4 emissions under changing environmental conditions
The effect of P2O5 on the viscosity of haplogranitic liquid
The effect of P2O5 on the viscosity of a haplogranitic (K2O-Na2O-Al2O3-SiO2) liquid has been determined at 1 atm pressure in the temperature interval of 700 - 1650°C. Viscosity measurements of a haplogranite, haplogranite + 5.1 wt.% P2O5 and haplogranite + 9.5 wt.% P2O5 have been performed using the concentric cylinder and micropenetration methods. The viscosity of haplogranite liquid decreases with the addition of P2O5 at all temperatures investigated. The viscosity decrease is nonlinear, with the strongest decrease exhibited at low P2O5 concentration. The temperature-dependence of the viscosity of all the investigated liquids is Arrhenian, as is the case for P2O5 liquid. The Arrhenian activation energy is slightly lower in the P2O5-bearing liquids than in the P2O5-free haplogranite with the result that the effect of P2O5 on viscosity is a (weak) function of temperature. At temperatures corresponding to the crystallization of phosphorus-rich granitic and pegmatitic systems the addition of 1 wt.% of P2O5 decreases the viscosity 0.2 log10 units. The effect of P2O5 on haplogranitic melt viscosity is much less than that for B2O3, F2O−1 on the same melt composition (Dingwell et al., 1992 and this study). This implies that P2O5 concentration gradients in high-silica melts during, for example, phosphate mineral growth or dissolution in granitic magmas, will not significantly influence melt viscosity
A partial molar volume for B 2 O 3 in haplogranitic melt
The densitiesa nd thermal expansivitieso f boron-bearingh aplogranitic glassesa nd Iiquids have been determined using a combination of scanning .florimetry and dilatomelry. B2O3 reduces the density of haplogranitic liquids (at 750'C) from 2.295 t 0.006 g cm-r to 2.237 + 0.005 g cm-3 wirh the addition of 8.92 wt. Vo 82o,. These densities have been converted into molar volumes in the binary system haplogranite - BrO3. The partial molar volume of 8203, calculated from a linear fit to the data at 750oC, is ,10.30 + 0.77 cmr mole-r in these melts. This value compares with a molar volume of pure B2O3 at this temperature of M.36 x. 0.22 cm3 mole-l (Napolitano et ol. 1965), indicating a negative excess volume of mixing along the haplogranite - B2O3 join. In comparison, at l3moc, the addition ot Na2O to B2O3 reduces the panial molar volume of B2O3 from 46.6 to 32.3 cm3 mole-r ar 45 molego Na2O (Riebling 1966).T he densityr esultsr eported here, along with the viscosity-reducinge ffect of B2O3o n granitic melts (Dingwell et al, 1992),s hould both significantlya cceleratep rocesseso f crystal-melt fractionation and facilitate the evolution of extremely fractionated igneous systems
The effect of F on the density of haplogranite melt
The densities and thermal expansivities of F-bearing haplogranitic glasses and liquids
have been investigated using a combination of scanning calorimetry and dilatometry.
F2O-1 reduces the density of haplogranitic liquids (at 750 °C) from 2.295 + 0.006 g/cm3
to 2.261 + 0.005 g/cm3 with the addition of 4.55 wt% F (0.33% per wt% of F added). The
expansivities of the liquids increase with the addition of F2O-1 from 29.9 +- 3.0 x l0 -6/°C to 53.1 +- 1.4 x l0 -6/°C (at 750°C).
Densities have been converted into molar volumes based on the haplogranite and F2O-1
components. The partial molar volume of F2O-1 has been calculated at 750°C to be 14.2
+- 1.3 cm3/mol in these melts. This value is close to the molar volume per O for several
components of silicate melts. F and O have similar ionic and covalent radii, and thus the
substitution of two F for one O yields approximately the volume change expected, assuming
no secondaryc onsequencesfo r the averagec oordination number of cations. This is
despite evidence from quenched melts that [6]Al exists in these compositions.
F is significantly more effective (per wt% added) than B2O3 in reducing the density of
haplogranitic melt. The effect of F on density reported here should complement the viscosity-
reducing effect of F2O-1 on granitic melts in significantly acceleratingg ravity-driven
processes of crystal-melt fractionation in F-rich igneous systems
Temperature-dependent thermal expansivities of silicate melts: The system anorthite-diopside
The temperature-dependent thermal expansivities of melts along the join anorthite-diopside have been determined on glassy and liquid samples using a combination of calorimetry, dilatometry, and Pt double bob Archimedean densitometry.
Supercooled liquid volumes and molar thermal expansivities were determined using scanning calorimetric and dilatometric measurements of properties in the glass region and their behavior at the glass transition. The extraction of low-temperature liquid molar expansivities from dilatometry /calorimetry is based on an assumed equivalence of the relaxation of volume and enthalpy at the glass transition using a method developed and tested by Webb et al. (1992). This method corrects for transient effects at the glass transition which can lead to serious overestimates of liquid thermal expansivity from “peak” values. Superliquidus volumes were determined using double Pt bob Archimedean densitometry at temperatures up to 1650°C.
The resulting data for liquid volumes near glass transition temperatures (810–920°C) and at superliquidus temperatures (1400–1650°C) are combined to yield thermal expansivities over the entire supercooled and stable liquid range. The molar expansivities are, in general, temperature dependent. The temperature-dependence of thermal expansivity increases from anorthite to diopside composition. The thermal expansivity of anorthite is essentially temperature independent, whereas that of diopside decreases by 50% between 800 and 1500°C, with the consequence that the thermal expansivities of the liquids in the anorthite-diopside system converge at high temperature
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