Heterogeneity in Autonomic Arousal Level in Perseverative Worry: The Role of Cognitive Control and Verbal Thought.

One puzzle in high worry and generalized anxiety disorder (GAD) is the heterogeneity in the level of autonomic arousal symptoms seen among affected individuals. While current models agree that worry persists, in part, because it fosters avoidance of unpleasant internal experiences, they disagree as to whether worry does so by suppressing activation of autonomic arousal or by fostering persistent autonomic hyperarousal. Our Cognitive Control Model predicts that which pattern of autonomic arousal occurs depends on whether or not a worrier has sufficient cognitive control capacity to worry primarily in a verbal versus imagery-based manner. Because this model has been supported by only one study to date, the present study sought to replicate and extend that study's findings. Results from an online survey in an unselected sample of over 900 college students provide further support for our model's central tenet and initial support for its prediction that higher effortful control is associated with a higher percentage of verbal thought during worry. Finally, we report tentative evidence that autonomic arousal symptoms in worry and GAD vary as a function of individual differences in cognitive control capacity because higher capacity is linked to a greater predominance of verbal thought during worry.

The lakes of Titan.

The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for the presence of lakes on the surface of Titan, obtained during the Cassini Radar flyby of Titan on 22 July 2006 (T16). The radar imaging polewards of 70 degrees north shows more than 75 circular to irregular radar-dark patches, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. The radar-dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes, including associated channels and location in topographic depressions. Some of the lakes do not completely fill the depressions in which they lie, and apparently dry depressions are present. We interpret this to indicate that lakes are present in a number of states, including partly dry and liquid-filled. These northern-hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface 'liquid methane' table.

Titan Radar Mapper observations from Cassini's T3 fly-by.

Cassini's Titan Radar Mapper imaged the surface of Saturn's moon Titan on its February 2005 fly-by (denoted T3), collecting high-resolution synthetic-aperture radar and larger-scale radiometry and scatterometry data. These data provide the first definitive identification of impact craters on the surface of Titan, networks of fluvial channels and surficial dark streaks that may be longitudinal dunes. Here we describe this great diversity of landforms. We conclude that much of the surface thus far imaged by radar of the haze-shrouded Titan is very young, with persistent geologic activity.

The sand seas of Titan: Cassini RADAR observations of longitudinal dunes.

The most recent Cassini RADAR images of Titan show widespread regions (up to 1500 kilometers by 200 kilometers) of near-parallel radar-dark linear features that appear to be seas of longitudinal dunes similar to those seen in the Namib desert on Earth. The Ku-band (2.17-centimeter wavelength) images show approximately 100-meter ridges consistent with duneforms and reveal flow interactions with underlying hills. The distribution and orientation of the dunes support a model of fluctuating surface winds of approximately 0.5 meter per second resulting from the combination of an eastward flow with a variable tidal wind. The existence of dunes also requires geological processes that create sand-sized (100- to 300-micrometer) particulates and a lack of persistent equatorial surface liquids to act as sand traps.

Cassini radar views the surface of Titan.

The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

Evaluation of Colilert and Enterolert defined substrate methodology for wastewater applications.

This study evaluated the utility of defined substrate methodology (DSM) for the enumeration of indicator bacteria in wastewater applications. Two commercial products, Colilert and Enterolert systems (Idexx Laboratories, Westbrook, Maine), were evaluated for variation, false-positive results, and method correlation in both surface waters and treated wastewater effluent. The DSM tests performed as well or better than the traditional methodology. The Colilert total coliform test was also evaluated for its utility in estimating fecal coliforms by incubation at 44.5 +/- 0.2 degrees C. The modified DSM total coliform test correlated well to membrane filtration (Pearson correlation coefficient 0.8) for two different sample groups, demonstrating its utility as a screening tool to estimate fecal coliform densities.