Contrast effects : incentive value of N-lengths

E.J. Capaldi has developed a sequential explanation of the partial reinforcement effect. The central assumption of this explanation is that non reinforced trials occasion a specific and distinctive internal stimulus and that this stimulus is progressively modified by successive non reinforcements. In this experiment, forty, male albino Holtzman rats traversed a straight alley runway under different patterns of partial reinforcement. Group One received an N3-length, i.e., three successive non-reinforced trials followed by a reinforced trial. Group Two received an N1-length, i.e., one non-reinforced trial followed by a reinforced trial. Group Three received an N3-length for the first ten days of acquisition training and was then shifted to an N1-length for the last five days of acquisition training. Group Four received an N1-length for the first ten days of acquisition training and an N3-length for the last five days of acquisition training. All groups received five days of extinction training. The results indicate that partial reinforcement patterns not only effect extinction performance but also effect acquisition performance in extended training

Fortnightly modulation of the estuarine circulation in Juan de Fuca Strait

Riverine discharge into the Strait of Georgia sets up a well-defined estuarine circulation within Juan de Fuca Strait, the main path for the freshwater outflow to the continental shelf. At the landward end of Juan de Fuca Strait, the water flows through narrow channels in which strong tidal currents are known to induce significant mixing of the water column, and a spring-neap modulation of the estuarine exchange. A three-dimensional prognostic numerical model has been developed to study the circulation around Vancouver Island, British Columbia. In a series of simulations, the estuarine circulation within Juan de Fuca Strait is established by the Fraser River freshwater discharge. A fortnightly modulation is imposed on the mixing over the various sills to simulate the spring-neap tidal mixing regime. The resulting variation in the estuarine circulation is found to be largely limited to the eastern section of Juan de Fuca Strait, in the vicinity of the sills. Data from current meter moorings and surface salinity data from lighthouse stations compare favorably with the model results. The effect of local wind forcing on the estuarine exchange is also examined. The model is capable of simulating those rare events during which a concurrence of river freshet, neap tide and northwest wind allows a stronger pulse of fresh surface water to escape relatively unmixed into the eastern end of Juan de Fuca Strait. The disturbance then propagates along the northern shore of the strait as a first mode internal Kelvin wave. Finally, the effect of the fortnightly modulation on the export of freshwater onto the continental shelf is examined. It is found that small amplitude coastal trapped waves are generated near the mouth of Juan de Fuca. However, this fortnightly signal is weak in comparison to the energetic wind-induced variations typically found over the shelf

Microscopic theory for the glass transition in a system without static correlations

We study the orientational dynamics of infinitely thin hard rods of length L, with the centers-of-mass fixed on a simple cubic lattice with lattice constant a.We approximate the influence of the surrounding rods onto dynamics of a pair of rods by introducing an effective rotational diffusion constant D(l),l=L/a. We get D(l) ~ [1-v(l)], where v(l) is given through an integral of a time-dependent torque-torque correlator of an isolated pair of rods. A glass transition occurs at l_c, if v(l_c)=1. We present a variational and a numerically exact evaluation of v(l).Close to l_c the diffusion constant decreases as D(l) ~ (l_c-l)^\gamma, with \gamma=1. Our approach predicts a glass transition in the absence of any static correlations, in contrast to present form of mode coupling theory.Comment: 6 pages, 3 figure

Systematic review of the clinical effectiveness and cost-effectiveness, and economic evaluation, of denosumab for the treatment of bone metastases from solid tumours

Peer reviewedPublisher PD

Gestational weight gain and its effect on birth outcomes in sub-Saharan Africa: Systematic review and meta-analysis.

INTRODUCTION:An increased metabolic demand during pregnancy is fulfilled by gaining sufficient gestational weight. Women who gain inadequate-weight are at a high-risk of premature birth or having a baby with low-birth weight. However, women who gain excessive-weight are at a high-risk of having a baby with macrosomia. The aim of this review was to determine the distribution of gestational weight gain and its association with birth-outcomes in Sub-Saharan Africa. METHODS:For this systematic review and meta-analysis, we performed a literature search using PubMed, Medline, Embase, Scopus, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) databases. We searched grey-literature from Google and Google Scholar, and region-specific journals from the African Journals Online (AJOL) database. We critically appraised the included studies using the Effective Public Health Practice Project Quality Assessment Tool for Quantitative Studies. Two independent reviewers evaluated the quality of the studies and extracted the data. We calculated pooled relative-risks (RR) with 95% confidence intervals. RESULTS:Of 1450 retrieved studies, 26 met the inclusion criteria. Sixteen studies classified gestational weight gain according to the United States Institute of Medicine recommendations. The percentage adequate amount of gestational weight ranged from 3% to 62%. The percentage of inadequate weight was >50% among nine studies. Among underweight women, the percentage of women who gained inadequate gestational weight ranged from 67% to 98%. Only two studies were included in the meta-analyses to evaluate the association of gestational weight gain with pre-eclampsia and macrosomia. No difference was observed among women who gained inadequate and adequate gestational weight regarding experiencing pre-eclampsia (RR, 0.71; 95% CI: 0.22, 2.28, P = 0.57). Excessive gestational weight gain was not significantly associated with macrosomia compared to adequate weight gain (RR, 0.68; 95% CI: 0.38, 1.22, P = 0.20). CONCLUSION:A substantial proportion of sub-Saharan African women gain inadequate gestational weight particularly high among underweight women. Future interventions would need to design effective pre-pregnancy weight management strategies

North Pacific internal tides from the Aleutian Ridge: Altimeter observations and modeling

Internal tides radiating into the North Pacific from the Aleutian Ridge near Amukta Pass are examined using 7 years of Topex/Poseidon altimeter data. The observations show coherent southward phase propagation at the M2 frequency over a distance of at least 1100 km into the central Pacific. Barotropic and baroclinic models are applied to study this internal tidal signal. Results from the barotropic model show that the strongest cross-slope volume and energy fluxes occur in the vicinity of Amukta Pass, helping to establish this region as an important site for baroclinic energy conversion along the eastern half of the ridge. A two-dimensional version of the Princeton Ocean Model is used to simulate internal tide generation and propagation. A comparison between the altimeter data south of the ridge and the sea-surface signature of the internal tide signal of the model shows good agreement for the phase, both close to the source and well into the far field. Comparison of the phase between model and data also provides evidence for wave refraction. This occurs due to the slow modulation of wavelength associated with the variation in the Coriolis parameter encountered as the internal tide propagates southward. The model results suggest that the net rate of conversion of barotropic to baroclinic energy is about 1.8 GW in the vicinity of Amukta Pass. This represents about 6% of the local barotropic energy flux across the ridge and perhaps 1% of global baroclinic conversion

Midwives' and obstetricians' perspectives about pregnancy related weight management in Ethiopia: A qualitative study.

BackgroundMidwives and obstetricians are key maternity care providers; they are the most trusted source of information regarding nutrition and gestational weight gain. However, their views, practices and perceived barriers to managing pregnancy related weight gain have not been studied in Ethiopia. The aim of this study was to explore midwives' and obstetricians' observations and perspectives about gestational weight gain and postpartum weight management in Ethiopia.MethodsWe conducted face-to-face interviews with 11 midwives and 10 obstetricians, from January 2019 to March 2019. All interview data were transcribed verbatim. We analysed the data using thematic analysis with an inductive approach.ResultsWe identified three themes and associated subthemes. Midwives and obstetricians had limited knowledge of the optimal gestational weight gain. Almost all participants were unaware of the presence of the Institute of Medicine recommendations for optimal weight gain in pregnancy. According to the study participants, women in Ethiopia do not want to gain weight during pregnancy, but do want to gain weight after the birth. Counselling about gestational weight gain and postpartum weight management was not routinely provided for pregnant women. This is mostly because gestational weight gain counselling was not considered to be a priority by maternity care providers in Ethiopia.ConclusionsThe limited knowledge of and low attention to pregnancy related weight management by midwives and obstetricians in this setting needs appropriate intervention. Adapting a guideline for pregnancy weight management and integrating it into antenatal care is essential