Evidence for multiple processes contributing to the Perruchet effect: Response priming and associative learning.

The Perruchet effect constitutes a robust demonstration that it is possible to dissociate conditioned responding and expectancy in a random partial reinforcement design across a variety of human associative learning paradigms. This dissociation has been interpreted as providing evidence for multiple processes supporting learning, with expectancy driven by cognitive processes that lead to a Gambler's fallacy, and the pattern of conditioned responding (CRs) the result of an associative learning process. An alternative explanation is that the pattern of CRs is the result of exposure to the unconditioned stimulus (US). In three human eyeblink conditioning experiments we examined these competing explanations of the Perruchet effect by employing a differential conditioning design and varying the degree to which the two conditioned stimuli (CS) were discriminable. Across all of these experiments there was evidence for a component of the CRs being strongly influenced by recent reinforcement, in a way that was not demonstrably influenced by manipulations of CS discriminability, which suggests a response priming mechanism contributes to the Perruchet effect. However, the complete pattern of results and an analysis of the results from previously published studies are also consistent with there being an associative contribution to the effect.This research was supported by grant DP1096437 from the Australian Research Council to G. Weidemann, an ESRC Doctoral Training Grant to A. McAndrew and I. P.L. McLaren, and an EPS Study visit grant awarded to A. McAndrew

Tunable Transient Decay Times in Nonlinear Systems: Application to Magnetic Precession

The dynamical motion of the magnetization plays a key role in the properties of magnetic materials. If the magnetization is initially away from the equilibrium direction in a magnetic nanoparticle, it will precess at a natural frequency and, with some damping present, will decay to the equilibrium position in a short lifetime. Here we investigate a simple but important situation where a magnetic nanoparticle is driven non-resonantly by an oscillating magnetic field, not at the natural frequency. We find a surprising result that the lifetime of the transient motion is strongly tunable, by factors of over 10,000, by varying the amplitude of the driving field.Comment: EPL Preprin

Polyphenol- and fibre-rich dried fruits with green tea attenuate starch-derived postprandial blood glucose and insulin: a randomised, controlled, single-blind, cross-over intervention

Polyphenol- and fibre-rich foods (PFRF) have the potential to affect postprandial glycaemic responses by reducing glucose absorption, and thus decreasing the glycaemic response of foods when consumed together. A randomised, single-blind, cross-over study was conducted on sixteen healthy volunteers to test whether PFRF could attenuate postprandial blood glucose in healthy volunteers when added to a source of carbohydrate (starch in bread). This is the first study to examine the effects of a meal comprised of components to inhibit each stage of the biochemical pathway, leading up to the appearance of glucose in the blood. The volunteers were fasted and attended four visits: two control visits (bread, water, balancing sugars) and two test visits (single and double dose of PFRF) where they consumed bread, water and PFRF. Blood samples were collected at 0 (fasted), 15, 30, 45, 60, 90, 120, 150 and 180 min after consumption. The PFRF components were tested for α-amylase and α-glucosidase inhibitory potential in vitro. Plasma glucose was lower after consumption of both doses compared with controls: lower dose, change in mean incremental areas under the glucose curves (IAUC)=− 27·4 (SD 7·5) %, P< 0·001; higher dose, IAUC =− 49·0 (SD 15·3) %, P<0·001; insulin IAUC was also attenuated by − 46·9 (SD 13·4) %, P<0·01. Consistent with this, the polyphenol components of the PFRF inhibited α-amylase (green tea, strawberry, blackberry and blackcurrant) and α-glucosidase (green tea) activities in vitro. The PFRF have a pronounced and significant lowering effect on postprandial blood glucose and insulin response in humans, due in part to inhibition of α-amylase and α-glucosidase, as well as glucose transport

Validation of Aura Microwave Limb Sounder O-3 and CO observations in the upper troposphere and lower stratosphere

International audienceGlobal satellite observations of ozone and carbon monoxide from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed with emphasis on those observations in the 215–100 hPa region (the upper troposphere and lower stratosphere). The precision, resolution and accuracy of the data produced by the MLS “version 2.2” processing algorithms are discussed and quantified. O3 accuracy is estimated at ~40 ppbv +5% (~20 ppbv +20% at 215 hPa) while the CO accuracy is estimated at ~30 ppbv +30% for pressures of 147 hPa and less. Comparisons with expectations and other observations show good agreements for the O3 product, generally consistent with the systematic errors quoted above. In the case of CO, a persistent factor of ~2 high bias is seen at 215 hPa. However, the morphology is shown to be realistic, consistent with raw MLS radiance data, and useful for scientific study. The MLS CO data at higher altitudes are shown to be consistent with other observations

The UARS microwave limb sounder version 5 data set: Theory, characterization, and validation

Nitric acid (HNO3) is a major player in processes controlling the springtime depletion of polar ozone. It is the main constituent of the Polar Stratospheric Clouds (PSCs) and a primary reservoir for reactive nitrogen. Potential variations in the stratospheric circulation and temperature may alter the extent and duration of PSCs activity, influencing the future ozone levels significantly. Monitoring HNO3 and its long-term variability, especially in polar region, is then crucial for better understanding issues related to ozone decline and expected recovery. In this study we present an intercomparison between ground based HNO3 measurements, carried out by means of the Ground-Based Millimeter-wave Spectrometer (GBMS), and two satellite data sets produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments. In particular, we compare UARS MLS measurements (1991-1999) with those carried out by the GBMS at South Pole, Antarctica (90°S), Fall of 1993 and 1995. A similar intercomparison is made between Aura MLS HNO3 observations (2004 - to date) and GBMS measurements obtained during the period February 2004 - March 2007, at the mid-latitudes/high altitudes station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), and during polar winters 2008/09 and 2009/2010 at Thule Air Base (76.5°N 68.8°W), Greenland. We assess systematic differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels (θ) spanning the range 465 – 960 K. The UARS data set advected to the South Pole shows a low bias, within 20% for all θ levels but the 960 K, with respect to GBMS measurements. A very good agreement, within 5%, is obtained between Aura and GBMS observations at Testa Grigia, while larger differences, possibly due to latitude dependent effects, are observed over Thule. These differences are under further investigations but a preliminary comparison over Thule among MLS v3, GBMS, and ACE-FTS measurements suggests that GBMS measurements carried out during winter 2009 might not be reliable. These comparisons have been performed in the framework of the NASA JPL GOZCARDS project, which is aimed at developing a long-term, global data record of the relevant stratospheric constituents in the context of ozone decline. GBMS has been selected in GOZCARDS since its HNO3 dataset, although sampling different latitudes in different years, is the only one spanning a sufficiently long time interval for cross-calibrating HNO3 measurements by the UARS and Aura MLS experiments

A new 147-56 hPa water vapor product from the UARS Microwave Limb Sounder

Measurements of H2O in the tropopause region have been obtained by production of a new data set from the Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite (UARS). A modified version of the retrieval scheme used to produce upper tropospheric humidity (UTH) from the MLS 203 GHz radiometer was applied to the MLS 183 GHz radiometer measurements to produce useful H2O data at 147, 121, 100, 83, 68, and 56 hPa. These new data, for the first 18 months of the UARS mission when the MLS 183 GHz radiometer was operational, fill an important “gap” around 100 hPa where previous MLS H2O data were generally not useful. Characteristics of the new data set are discussed and compared with National Oceanic and Atmospheric Administration (NOAA), Climate Monitoring and Diagnostics Laboratory (CMDL) frost-point hygrometer, and UARS Halogen Occultation Experiment (HALOE) measurements

The roles of convection, extratropical mixing, and in-situ freeze-drying in the Tropical Tropopause Layer

Mechanisms for transporting and dehydrating air across the tropical tropopause layer (TTL) are investigated with a conceptual two dimensional (2-D) model. The 2-D TTL model combines the Holton and Gettelman cold trap dehydration mechanism (Holton and Gettelman, 2001) with the two column convection model of Folkins and Martin (2005). We investigate 3 possible transport scenarios through the TTL: 1) slow uniform ascent across the level of zero radiative heating without direct convective mixing, 2) convective mixing of H&lt;sub&gt;2&lt;/sub&gt;O vapor at 100% relative humidity with respect to ice (RHi) with no ice retention, and 3) convective mixing of extremely subsaturated air (100% RHi following the moist adiabatic temperature above the level of neutral buoyancy) with sufficient ice retention such that total H&lt;sub&gt;2&lt;/sub&gt;O is 100%RHi. The three mechanisms produce similar seasonal cycles for H&lt;sub&gt;2&lt;/sub&gt;O that are in good quantitative agreement with the Aura Microwave Limb Sounder (MLS) measurements. We use Aura MLS measurement of CO and Atmospheric Chemistry Experiment-Fourier Transform Spectrometer measurement of HDO to distinguish among the transport mechanisms. Model comparisons with the observations support the view that H&lt;sub&gt;2&lt;/sub&gt;O is predominantly controlled by regions having the lowest cold point tropopause temperature but the trace species CO and HDO support the convective mixing of dry air and lofted ice. The model provides some insight into the processes affecting the long term trends observed in stratospheric H&lt;sub&gt;2&lt;/sub&gt;O

Polar processing and development of the 2004 Antarctic ozone hole: First results from MLS on Aura

The Microwave Limb Sounder (MLS) on Aura is providing an extensive data set on stratospheric winter polar processing, including the first daily global observations of HCl, together with simultaneous measurements of ClO, HNO3, H2O, O3, N2O, and temperature (among others). We present first results charting the evolution of these quantities during the 2004 Antarctic late winter. MLS observations of chlorine deactivation and ozone loss during this period are shown to be consistent with results from the SLIMCAT chemical transport model

Validation of Aura Microwave Limb Sounder HCl measurements

The Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura satellite has provided daily global HCl profiles since August 2004. We provide a characterization of the resolution, random and systematic uncertainties, and known issues for the version 2.2 MLS HCl data. The MLS sampling allows for comparisons with many (similar to 1500 to more than 3000) closely matched profiles from the Halogen Occultation Experiment (HALOE) and Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). These data sets provide HCl latitudinal distributions that are, overall, very similar to those from (coincident) MLS profiles, although there are some discrepancies in the upper stratosphere between the MLS and HALOE gradients. As found in previous work, MLS and ACE HCl profiles agree very well (within similar to 5%, on average), but the MLS HCl abundances are generally larger (by 10-20%) than HALOE HCl. The bias versus HALOE is unlikely to arise mostly from MLS, as a similar systematic bias (of order 15%) is not observed between average MLS and balloon-borne measurements of HCl, obtained over Fort Sumner, New Mexico, in 2004 and 2005. At the largest pressure (147 hPa) for MLS HCl, a high bias (similar to 0.2 ppbv) is apparent in analyses of low to midlatitude data versus in situ aircraft chemical ionization mass spectrometry (CIMS) HCl measurements from the Aura Validation Experiment (AVE) campaigns in 2004, 2005, and 2006; this bias is also observed in comparisons of MLS and aircraft HCl/O-3 correlations. Good agreement between MLS and CIMS HCl is obtained at 100 to 68 hPa. The recommended pressure range for MLS HCl is from 100 to 0.15 hPa.</p