2,233 research outputs found
Construction and testing of a low-cost device for the collection of rainfall samples destined for stable isotope analysis
Oxygen- and hydrogen-isotope ratios in rainfall provide important hydroclimatic information, yet despite a global network of rainfall isotope measurements, significant geographical gaps exist in data coverage, with only three long-term stations spanning the southern African region. Project-based, ad hoc collections of rainfall for isotope analysis can improve this coverage. However, all rainfall samples that are destined for stable isotope analysis must be collected in such a way to avoid evaporation and resultant isotope fractionation. While such rainwater collectors are available commercially, both the product and shipping are prohibitively costly. We describe the construction of a simple rainfall collector using a design from the literature and materials that are readily available in South African hardware stores. Our rainwater collector can be constructed for the much lower cost of just under ZAR820 in comparison with the cost of ZAR9300 inclusive of shipping from commercial outlets (2022 prices). Our design modifications have the added advantage of portability, with the rainwater collector housed in a bucket with a handle. The device was tested by comparing its performance, in terms of evaporative water loss and isotopic fractionation, with that of an open bottle, using tap water in both cases. Testing confirmed that the collector prevented evaporation over a one-week period, indicating that it is suitable for weekly or more frequent sampling of rainfall. Although the design described was based on materials procured in South Africa, it could easily be adapted for construction elsewhere
Construction and testing of a low-cost device for the collection of rainfall samples destined for stable isotope analysis
Oxygen- and hydrogen-isotope ratios in rainfall provide important hydroclimatic information, yet despite a global network of rainfall isotope measurements, significant geographical gaps exist in data coverage, with only three long-term stations spanning the southern African region. Project-based, ad hoc collections of rainfall for isotope analysis can improve this coverage. However, all rainfall samples that are destined for stable isotope analysis must be collected in such a way to avoid evaporation and resultant isotope fractionation. While such rainwater collectors are available commercially, both the product and shipping are prohibitively costly. We describe the construction of a simple rainfall collector using a design from the literature and materials that are readily available in South African hardware stores. Our rainwater collector can be constructed for the much lower cost of just under ZAR820 in comparison with the cost of ZAR9300 inclusive of shipping from commercial outlets (2022 prices). Our design modifications have the added advantage of portability, with the rainwater collector housed in a bucket with a handle. The device was tested by comparing its performance, in terms of evaporative water loss and isotopic fractionation, with that of an open bottle, using tap water in both cases. Testing confirmed that the collector prevented evaporation over a one-week period, indicating that it is suitable for weekly or more frequent sampling of rainfall. Although the design described was based on materials procured in South Africa, it could easily be adapted for construction elsewhere.
Significance:
• Hydrogen and oxygen isotope composition of rainfall provides valuable climatic information.
• Rainwater collectors for stable isotope samples must prevent evaporation, as evaporation will alter the isotopic signature.
• We describe the construction and testing of a bespoke, low-cost and portable device that can be used to collect rainfall samples destined for oxygen- and hydrogen-isotope analysis without significant evaporation
Listening differently: a pedagogy for expanded listening
Mainstream education promotes a narrow conception of listening, centred on the reception and comprehension of human meanings. As such, it is ill-equipped to hear how sound propagates affects, generates atmospheres, shapes environments and enacts power. Yet these aspects of sound are vital to how education functions. We therefore argue that there is a need to expand listening in education, and suggest that listening walks could provide a pedagogy for this purpose. Using interview data in which early years practitioners reflect on a listening walk, we show how the method can: (i) produce heightened multisensory experiences of spaces; (ii) generate forms of difficulty and discomfort that produce new learning; and (iii) influence practice, particularly practitioners’ ability to empathise with young children. Listening walks function by disrupting everyday sensory habits, provoking listeners to listen anew to their own listening, in an open-ended way that is not tied to predetermined learning outcomes. The method therefore has wider pedagogic potential for rethinking education and childhood beyond rationality, representation and meaning
Effects of Subchronic Phencyclidine (PCP) Treatment on Social Behaviors, and Operant Discrimination and Reversal Learning in C57BL/6J Mice
Subchronic treatment with the psychotomimetic phencyclidine (PCP) has been proposed as a rodent model of the negative and cognitive/executive symptoms of schizophrenia. There has, however, been a paucity of studies on this model in mice, despite the growing use of the mouse as a subject in genetic and molecular studies of schizophrenia. In the present study, we evaluated the effects of subchronic PCP treatment (5 mg/kg twice daily × 7 days, followed by 7 days withdrawal) in C57BL/6J mice on (1) social behaviors using a sociability/social novelty-preference paradigm, and (2) pairwise visual discrimination and reversal learning using a touchscreen-based operant system. Results showed that mice subchronically treated with PCP made more visits to (but did not spend more time with) a social stimulus relative to an inanimate one, and made more visits and spent more time investigating a novel social stimulus over a familiar one. Subchronic PCP treatment did not significantly affect behavior in either the discrimination or reversal learning tasks. These data encourage further analysis of the potential utility of mouse subchronic PCP treatment for modeling the social withdrawal component of schizophrenia. They also indicate that the treatment regimen employed was insufficient to impair our measures of discrimination and reversal learning in the C57BL/6J strain. Further work will be needed to identify alternative methods (e.g., repeated cycles of subchronic PCP treatment, use of different mouse strains) that reliably produce discrimination and/or reversal impairment, as well as other cognitive/executive measures that are sensitive to chronic PCP treatment in mice
Realistic boundary conditions for stochastic simulations of reaction-diffusion processes
Many cellular and subcellular biological processes can be described in terms
of diffusing and chemically reacting species (e.g. enzymes). Such
reaction-diffusion processes can be mathematically modelled using either
deterministic partial-differential equations or stochastic simulation
algorithms. The latter provide a more detailed and precise picture, and several
stochastic simulation algorithms have been proposed in recent years. Such
models typically give the same description of the reaction-diffusion processes
far from the boundary of the simulated domain, but the behaviour close to a
reactive boundary (e.g. a membrane with receptors) is unfortunately
model-dependent. In this paper, we study four different approaches to
stochastic modelling of reaction-diffusion problems and show the correct choice
of the boundary condition for each model. The reactive boundary is treated as
partially reflective, which means that some molecules hitting the boundary are
adsorbed (e.g. bound to the receptor) and some molecules are reflected. The
probability that the molecule is adsorbed rather than reflected depends on the
reactivity of the boundary (e.g. on the rate constant of the adsorbing chemical
reaction and on the number of available receptors), and on the stochastic model
used. This dependence is derived for each model.Comment: 24 pages, submitted to Physical Biolog
Influence of the Fermi Surface Morphology on the Magnetic Field-Driven Vortex Lattice Structure Transitions in YBaCuO0, 0.15
We report small-angle neutron scattering measurements of the vortex lattice
(VL) structure in single crystals of the lightly underdoped cuprate
superconductor YBa2Cu3O6.85. At 2 K, and for fields of up to 16 T applied
parallel to the crystal c-axis, we observe a sequence of field-driven and
first-order transitions between different VL structures. By rotating the field
away from the c-axis, we observe each structure transition to shift to either
higher or lower field dependent on whether the field is rotated towards the
[100] or [010] direction. We use this latter observation to argue that the
Fermi surface morphology must play a key role in the mechanisms that drive the
VL structure transitions. Furthermore, we show this interpretation is
compatible with analogous results obtained previously on lightly overdoped
YBa2Cu3O7. In that material, it has long-been suggested that the high field VL
structure transition is driven by the nodal gap anisotropy. In contrast, the
results and discussion presented here bring into question the role, if any, of
a nodal gap anisotropy on the VL structure transitions in both YBa2Cu3O6.85 and
YBa2Cu3O7
Sequential effects in two-choice reaction time tasks: decomposition and synthesis of mechanisms
Performance on serial tasks is influenced by first- and higher-order sequential effects, respectively due to the immediately previous and earlier trials. As response-to-stimulus interval (RSI) increases, the pattern of reaction times transits from a benefit-only mode, traditionally ascribed to automatic facilitation (AF), to a cost-benefit mode, due to strategic expectancy (SE). To illuminate the sources of such effects, we develop a connectionist network of two mutually-inhibiting neural decision units subject to feedback from previous trials. A study of separate biasing mechanisms shows that residual decision unit activity can lead only to first-order AF, but higher-order AF can result from strategic priming mediated by conflict-monitoring, which we instantiate in two distinct versions. A further mechanism mediates expectation-related biases that grow during RSI toward saturation levels determined by weighted repetition (or alternation) sequence lengths. Equipped with these mechanisms, the network, consistent with known neurophysiology, accounts for several sets of behavioral data over a wide range of RSIs. The results also suggest that practice speeds up all the mechanisms rather than adjusting their relative strengths
Comparison of Quality-of-Life Instruments in Adults with Strabismus
To compare two health-related quality of life (HRQOL) questionnaires in adults with strabismus: the new AS-20 (developed specifically for adult strabismus) and the NEI VFQ-25 (VFQ-25)
The differential effect of instructions on dysphoric and nondysphoric persons
The experimenters investigated whether dysphoric and
nondysphoric persons differentially exhibited the traditional instruction-induced schedule-insensitivity effect (rule-governed behavior).
Dysphoric and nondysphoric participants were given instructions to
perform a matching-to-sample task (four blocks, 40 trials each). The
instructions in the first half of the study were correct and in the second
half, incorrect. Participants were assigned to one of two instructional
control conditions in which they read the instruction either privately
(tracking condition) or out loud to the experimenter (pliance condition).
Dysphoric individuals demonstrated greater schedule sensitivity (less
rule-governed behavior) than did nondysphoric persons. No other
differences were found. Results indicate that deficits in rule-governed
behavior may contribute to depression; however, this experiment did
not incorporate procedures to directly test the role of rule-governed
experiential avoidance
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