On setting up a sail

John 3:1-

Believing is seeing

Matthew 13:58

Infrared upconversion for astronomy

The basic theory of upconversion is presented, along with a brief historical summary of upconversion techniques. Upconverters were used in astronomical studies, but have met with only modest success. Upconversion will become a useful detection method for astronomy only if substantial but perhaps forseeable, improvements can be realized

Review Of Interventions For Parental Depression From Toddlerhood To Adolescence

Because of the recurrent course, significant burden, and intergenerational impact of depression, there is a great need for interventions for depressed parents and their children. This article reviews eight interventions that 1) aim to impact the functioning and well-being of 18-month to 18-year old children of depressed parents and 2) have been evaluated in controlled studies. The interventions are described and the empirical evidence of their efficacy is reviewed and critiqued. Existing research points to several promising intervention strategies, such as psychoeducation about parental depression, addressing parenting in adult depression treatment, promoting positive parent-child interactions, and teaching coping skills to children. Common limitations of the research in this area are small sample sizes, homogenous samples, and lack of replication. Implementation problems within the mental healthcare system are highlighted. Multi-component interventions seem to be a promising approach to address the complex impact parental depression has on children and the parent-child relationship. This review illustrates the need for more research on intervention models that can be implemented with children at various developmental levels

Variational analysis of self-focusing of intense ultrashort pulses in gases

By using perturbation theory we derive an expression for the electrical field of a Gaussian laser pulse propagating in a gas medium. This expression is used as a trial solution in a variational method to get quasianalytical solutions for the width, intensity and self-focusing distance of ultrashort pulse. The approximation gives an improved agreement with results of numerical simulations for a broad range of values of the input power of the pulse than previous analytical results available in the literature.Comment: 19 pages, 8 figure

A synoptic view of ionic constitution above the F-layer maximum

Ionic composition above F layer maximum from Ariel I satellite ion mass spectromete

Nitrogen geochemistry of a Cretaceous-Tertiary boundary site in New Zealand

Nitrogen in the basal layer of the K-T boundary clay at Woodside Creek, New Zealand, has an abundance of 1100 ppm, a 20-fold enrichment over Cretaceous and Tertiary values. The enrichment parallels that for Ir and elemental carbon (soot); all decrease over the next 6 mm of the boundary clay. The C/N ratio, assuming the nitrogen to be associated with organic rather than elemental carbon, is approximately 5 for the basal layer compared to 20 to 30 for the remainder of the boundary clay. The correlation between N and Ir abundances appears to persist above the boundary, implying that the N is intimately associated with the primary fallout and remained with it during the secondary redeposition processes that kept the Ir abundance relatively high into the lowermost Tertiary. Apparently the basal layer of the boundary clay represents the accumulation of a substantial quantity of N with an isotopic composition approximately 10 percent heavier than background delta value of N-15 values. If the boundary clay represents an altered impact glass from a meteorite impact than it probably denotes a time period of less than 1 year. Therefore, the changes in nitrogen geochemistry apparently occurred over a very short period of time. The high abundance of N and the correspondingly low C/N ratio may reflect enhanced preservation of organic material as a result of the rapid sweepout and burial of plankton by impact ejecta, with little or no bacterial degradation. It is conceivable that the shift in delta value of N-15 may represent an influx of nitrogen from a different source deposited contemporaneously with the impact ejecta. An interesting possibility is that it may be derived from nitrate, produced from the combustion of atmospheric nitrogen

Anomalies in Universal Intensity Scaling in Ultrarelativistic Laser-Plasma Interactions

Laser light incident on targets at intensities such that the electron dynamics is ultrarelativistic gives rise to a harmonic power spectrum extending to high orders and characterized by a relatively slow decay with the harmonic number m that follows a power law dependence, m^{-p}. Relativistic similarity theory predicts a universal value for p = 8/3 up to some cut-off m = m*. The results presented in this work suggest that under conditions in which plasma effects contribute to the emission spectrum, the extent of this contribution may invalidate the concept of universal decay. We report a decay with harmonic number in the ultrarelativistic range characterised by an index 5/3 < p < 7/3, significantly weaker than that predicted by the similarity model.Comment: 5 pages, 4 figure