Wind induced dispersion and algal growth in shallow lakes

The objectives of this paper are (1) to present experimental measurements of wind induced, vertical dispersion in Lake Brielle, The Netherlands, and (2) to examine the utility of a euphotic—dark zone model for investigation of the effects of dispersion and sedimentation on algal growth and phosphate cycling in shallow lakes. A tracer technique was used to measure dispersion (D) caused by a moderate wind of 4 m/s. The resulting values ranged between 4 and 6 cm2/s and compared well with that predicted from theory. The latter objective was accomplished by comparing the results of a simple, two compartment model with those using a more complex, but more descriptive, finite difference model which accounts for the algal concentration gradient induced by growth, dispersion and sedimentation. Simulations showed good agreement in computation of the average euphotic and dark zone algal concentrations between the two models for D ranging from 0 to 6 cm2/s and for a sedimentation rate constant, Ks, of 0.002 and 0.02 m/h.\ud \ud The results of simulations suggest that rapid algal growth occurs most readily in calm weather when wind induced dispersion in negligible. Dispersion may also influence the rate of particulate phosphate accumulation in the sediment (due to the settling out of algal cells) and the soluble phosphate profile in the overlying water column. Field data is needed to verify the relationship between algal growth and wind induced dispersion

Psychological treatment of late-life depression:a meta-analysis of randomized controlled trials

SUMMARY Background Older meta-analyses of the effects of psychological treatments for depression in older adults have found that these treatments have large effects. However, these earlier meta-analyses also included non-randomized studies, and did not include newer high-quality randomized controlled trials. Methods We conducted a meta-analysis of randomized studies on psychological treatments for depression in older adults. Results Twenty-five studies were included, of which 17 compared a psychological intervention to a control condition (mainly waiting list and care-as-usual control groups). The quality of the included studies varied. Psychological treatments have moderate to large effects on depression in older adults (standardized mean effect size d¼0.72). Heterogeneity was very low. No differences were found between individual, group or bibliotherapy format, or between cognitive behavioral therapy and other types of psychological treatment. The effects were comparable in studies where depression was defined according to diagnostic criteria, and those in which depression was measured with self-rating questionnaires. Conclusion Although the quality of many studies was not optimal, the results of this meta-analysis support the results of earlier meta-analyses, which also included non-randomized studies. Psychological treatments are effective in the treatment of depression in older adults

Analysis of Photoassociation Spectra for Giant Helium Dimers

We perform a theoretical analysis to interpret the spectra of purely long-range helium dimers produced by photoassociation (PA) in an ultra-cold gas of metastable helium atoms. The experimental spectrum obtained with the PA laser tuned closed to the $2^3S_1\leftrightarrow 2^3P_0$ atomic line has been reported in a previous Letter. Here, we first focus on the corrections to be applied to the measured resonance frequencies in order to infer the molecular binding energies. We then present a calculation of the vibrational spectra for the purely long-range molecular states, using adiabatic potentials obtained from perturbation theory. With retardation effects taken into account, the agreement between experimental and theoretical determinations of the spectrum for the $0_u^+$ purely long-range potential well is very good. The results yield a determination of the lifetime of the $2^3P$ atomic state

Radio Astronomical Polarimetry and Point-Source Calibration

A mathematical framework is presented for use in the experimental determination of the polarimetric response of observatory instrumentation. Elementary principles of linear algebra are applied to model the full matrix description of the polarization measurement equation by least-squares estimation of non-linear, scalar parameters. The formalism is applied to calibrate the center element of the Parkes Multibeam receiver using observations of the millisecond pulsar, PSR J0437-4715, and the radio galaxy, 3C 218 (Hydra A).Comment: 8 pages, 4 figures, to be published in ApJ

Optical collisions of cold, metastable helium atoms

We have studied the optical collisions of cold, metastable helium atoms in a magneto-optical trap. We have detected the rate of Penning and associative ionization of two metastable helium atoms at a temperature of 1 mK with and without nearly resonant light. We find that the associative ionization rate is increased with more than a factor 20 due to the presence of the light field. The absolute ionization rate near resonance of (1.9±0.8)×10^(-9) cm3/s for the optical collision differs two orders of magnitude with the rate reported by Bardou et al. (Europhys. Lett. 20, 681 (1992)). Our experimental findings are in good agreement with theory. We present a simple, semi-classical model, which accounts for all the observed features

Are individual and group treatments equally effective in the treatment of depression in adults?

0.01). At follow-up no significant differences were found. Conclusions: Although individual therapy seems to be somewhat more effective than group therapy at the short term, it is not clear whether this is relevant from a clinical point of view. Because of the small number of studies and the limited quality, more research is needed to examine whether the difference between individual and group treatment is clinically relevant

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Internet-delivered cognitive-behavioral treatment is effective for insomnia. However, little is known about the beneficial effects of support. Recently we demonstrated that motivational support moderately improved the effects of Internet-delivered treatment for insomnia. In the present study, we tested whether depressive symptoms at baseline moderate the effect of support on Internet-delivered treatment for insomnia. We performed a multilevel intention-to-treat analysis on 262 participants in a randomized controlled trial. We found that baseline depressive symptoms moderated the effect of support on sleep efficiency, total sleep time, and sleep onset latency (but not on wake after sleep onset, number of nightly awakenings, or the Insomnia Severity Index). This means that for these variables, people with high levels of depressive symptoms benefit from support, whereas people with low levels of depressive symptoms improve regardless of support. The data show that baseline depression severity plays an important role in the way Internet treatments need to be delivered. These findings open up opportunities to personalize the support offered in Internet-delivered treatments. © 2014