Methods of Determining the Numbers and Availability of Ringed Seals in the Eastern Canadian Arctic

Discusses procedures for making local estimates of population density and prospective catch of the Eskimo hunters. A method is outlined for counting seals from ships in open water; and for determining population density by the amount and quality of fast ice, with regard to complexity of the coastline. From hunting trips in various parts of the Eastern Arctic, average daily catch to be expected is estimated at 3.6 seals from a boat in summer on a complex coast and 1.4 on an open coast, 2.8 on the ice before the peak of the spring basking season, and 6.8 at the peak. From these and other calculable variables, such as loss of kill by sinking, weather conditions, etc., an equation is formulated for predicting the potential annual catch of a hunter in a given region

[Photodissociation of Acetylene and Acetone using Step-Scan Time-Resolved FTIR Emission Spectroscopy]

The photodissociation of acetylene and acetone was investigated as a function of added quenching gas pressures using step-scan time-resolved FTIR emission spectroscopy. Its main components consist of Bruker IFS88, step-scan Fourier Transform Infrared (FTIR) spectrometer coupled to a flow cell equipped with Welsh collection optics. Vibrationally excited C2H radicals were produced from the photodissociation of acetylene in the unfocused experiments. The infrared (IR) emission from these excited C2H radicals was investigated as a function of added argon pressure. Argon quenching rate constants for all C2H emission bands are of the order of 10(exp -13)cc/molecule.sec. Quenching of these radicals by acetylene is efficient, with a rate constant in the range of 10(exp -11) cc/molecule.sec. The relative intensity of the different C2H emission bands did not change with the increasing argon or acetylene pressure. However, the overall IR emission intensity decreased, for example, by more than 50% when the argon partial pressure was raised from 0.2 to 2 Torr at fixed precursor pressure of 160mTorr. These observations provide evidence for the formation of a metastable C2H2 species, which are collisionally quenched by argon or acetylene. Problems encountered in the course of the experimental work are also described

Associatively-mediated stopping: training stimulus-specific inhibitory control

This is the author accepted manuscript. The final version is available from Springer Verlag via the DOI in this record.Response inhibition is often considered to be a deliberate act of cognitive control. However, our and other research suggests that by repeatedly pairing stimuli with an inhibitory response, inhibition can become automatized. Currently, relatively little research has focused on the nature of the associative structure that underpins stimulus-specific inhibitory training. This paper investigated what associations can be learnt in stop-signal training tasks, distinguishing between indirect priming of the stop signal and direct activation of a stop response. We employed a novel paradigm, where colored cues are stochastically paired with a number of stop-signals, and demonstrated that cues consistently paired with stopping reduced commission errors and slowed reaction times. Furthermore, we showed that manipulating the pairings between stimuli and stop signals, in a manner that favored the formation of stimulus-stop associations, produced enhanced stop learning effects on reaction time, but not probability of responding. Our results suggest that perceptual processes supporting signal detection (priming) as well as inhibitory processes are involved in inhibitory control training, and that inhibition training may benefit from reducing the contingency between stimuli and stop-signals.Economic and Social Research CouncilER

Associatively-mediated stopping: training stimulus-specific inhibitory control (dataset)

Behavioural data, R analysis scripts, and documentation for two behavioural experiments described in "Associatively-mediated stopping: training stimulus-specific inhibitory control". To be published in Learning & Behavior (2015). Available in ORE at: https://ore.exeter.ac.uk/repository/handle/10871/18061Behavioural data, R analysis scripts, and documentation for two behavioural experiments described in "Associatively-Mediated Stopping: Training Stimulus-Specific Inhibitory Control". To be published in Learning & Behavior (2015).ESRCER

The inhibitory control reflex (article)

publication-status: Acceptedtypes: ArticleThis is an open access article that is freely available in ORE or from the publisher's web site. Please cite the published version.Related dataset available in ORE at: http://hdl.handle.net/10871/15358 (see link above)Response inhibition is typically considered a hallmark of deliberate executive control. In this article, we review work showing that response inhibition can also become a ‘prepared reflex’, readily triggered by information in the environment, or after sufficient training, a ‘learned reflex’ triggered by the retrieval of previously acquired associations between stimuli and stopping. We present new results indicating that people can learn various associations, which influence performance in different ways. To account for previous findings and our new results, we present a novel architecture that integrates theories of associative learning, Pavlovian conditioning, and executive response inhibition. Finally, we discuss why this work is also relevant for the study of ‘intentional inhibition’.ESR

Genotype-specific lesion growth rates in stargardt disease

Reported growth rates (GR) of atrophic lesions in Stargardt disease (STGD1) vary widely. In the present study, we report the longitudinal natural history of patients with confirmed bial-lelic ABCA4 mutations from five genotype groups: c.6079C \u3e T, c.[2588G \u3e C;5603A \u3e T], c.3113C \u3e T, c.5882G \u3e A and c.5603A \u3e T. Fundus autofluorescence (AF) 30◦ × 30◦ images were manually seg-mented for boundaries of definitely decreased autofluorescence (DDAF). The primary outcome was the effective radius GR across five genotype groups. The age of DDAF formation in each eye was calculated using the x-intercept of the DDAF effective radius against age. Discordance between age at DDAF formation and symptom onset was compared. A total of 75 eyes from 39 STGD1 patients (17 male [44%]; mean ± SD age 45 ± 19 years; range 21–86) were recruited. Patients with c.3113C \u3e T or c.6079C \u3e T had a significantly faster effective radius GR at 0.17 mm/year (95% CI 0.12 to 0.22; p \u3c 0.001 and 0.14 to 0.21; p \u3c 0.001) respectively, as compared to those patients harbouring c.5882G \u3e A at 0.06 mm/year (95% CI 0.03–0.09), respectively. Future clinical trial design should consider the effect of genotype on the effective radius GR and the timing of DDAF formation relative to symptom onset

Sibling concordance in symptom onset and atrophy growth rates in Stargardt disease using ultra-widefield fundus autofluorescence

Purpose: To investigate concordance in symptom onset, area of dark autofluorescence (DAF), and growth rate (GR) between Stargardt disease siblings at an age-matched time point. Methods: In this retrospective longitudinal study of sibling pairs with identical biallelic ABCA4 variants, age at symptom onset, best-corrected visual acuity, atrophy area, and effective radius of DAF on ultra-widefield fundus autofluorescence were recorded. Absolute intersibling differences for both eyes were compared with absolute interocular differences using the Mann-Whitney test. Results: Overall 39 patients from 19 families were recruited. In 16 families, age-matched best-corrected visual acuity and DAF were compared between siblings. In 8 families, DAF GR was compared. The median (range) absolute difference in age at symptom onset between siblings was 3 (0-35) years. Absolute intersibling differences in age-matched best-corrected visual acuity were greater than interocular differences (P = 0.01). Similarly, absolute intersibling differences in DAF area and radius were greater than interocular differences (P = 0.04 for area and P = 0.001 for radius). Differences between absolute interocular and intersibling GR were not statistically significant (P = 0.44 for area GR and P = 0.61 for radius GR). Conclusion: There was significant discordance in age-matched best-corrected visual acuity and DAF beyond the expected limits of interocular asymmetry. Lack of significant intersibling differences in GR warrants further investigation