Amplitude ambiguities in pseudoscalar meson photoproduction

We consider the problem of determining amplitudes from observables for the case of pseudoscalar meson photoproduction. We find a number of surprisingly simple constraints which give necessary conditions for a complete set of measurements. These results contradict one of the selection rules derived previously.Comment: 7 page

Direction to an internet support group compared with online expressive writing for people with depression and anxiety: a randomized trial

BACKGROUND: Depression and anxiety are common, often comorbid, conditions, and Internet support groups for them are well used. However, little rigorous research has been conducted on the outcome of these groups. OBJECTIVE: This study aimed to evaluate the efficacy of an Internet support group in reducing depression and anxiety, and increasing social support and life satisfaction. METHODS: A randomized trial compared direction to an existing Internet support group for depression and anxiety with an online expressive writing condition. A total of 863 (628 female) United Kingdom, United States, and Canadian volunteers were recruited via the Internet. Online, self-report measures of depression, anxiety, social support, and satisfaction with life were administered at baseline, 3, and 6 months. RESULTS: All four outcomes - depression, anxiety, social support, and satisfaction with life - improved over the 6 months of the study (all P <.001). There was no difference in outcome between the two conditions: participants responded similarly to the expressive writing and the Internet support group. Engagement with the Internet support group was low, it had high 6-month attrition (692/795, 87%) and low adherence, and it received mixed and often negative feedback. The main problems reported were a lack of comfort and connection with others, negative social comparisons, and the potential for receiving bad advice. Expressive writing had lower attrition (194/295, 65%) and participants reported that it was more acceptable. CONCLUSIONS: Until further evidence accumulates, directing people with depression and anxiety to Internet support groups cannot be recommended. On the other hand, online expressive writing seems to have potential, and its use for people with depression and anxiety warrants further investigation. TRIAL REGISTRATION: TRIAL REGISTRATION: Clinicaltrials.gov NCT01149265; https://clinicaltrials.gov/ct2/show/NCT01149265 (Archived by WebCite at http://www.webcitation.org/6hYISlNFT)

Acculturation and physical activity among immigrants: a systematic review

Aim: The acculturation process presents numerous challenges that could benefit or adversely affect immigrants' health practices. The goal of this review was to present a systematic summary of studies examining the relationship between acculturation and physical activity among immigrants and ethnic minority populations. Subjects and methods: Systematic review based on 44 original studies found in electronic databases (Psychinfo/Psyndex, Eric, Pubmed/Medline, Web of Science, SportDiscus). Studies were eligible if they were written in English, German or French, incorporated a measure of acculturation and physical activity, exercise, or sport as independent and dependent variables, and provided statistical information to judge the level of significance. The 44 studies found included 760,242 participants. A narrative synthesis was performed. Causality of effects was examined based on seven criteria: consistency, strength of associations, specificity of effects, temporality, gradient, plausibility and experimental evidence. Results: Acculturation was associated with higher leisure time physical activity in 57% of all studies (even after controlling for potential confounds), independent of participants' gender, age and ethnic background. The main limitations of this review are that findings were not weighted for sample size and that publication biases might have contributed to an overestimation of the relationships. Conclusion: Prevention programs aimed at stimulating participation in physical activity among immigrants should give priority to individuals with low acculturation levels and it should consider culturally specific beliefs and constraints. Additionally, prevention programs could make an effort to promote acculturation among immigrants. Future studies should use longitudinal designs which include objective assessments of physical activity and which use multidimensional and bidirectional definitions of acculturatio

An experiment to assess the effects of diatom dissolution on oxygen isotope ratios

Rationale: Current studies which use the oxygen isotope composition from diatom silica (δ18Odiatom) as a palaeoclimate proxy assume that the δ18Odiatom value reflects the isotopic composition of the water in which the diatom formed. However, diatoms dissolve post mortem, preferentially losing less silicified structures in the water column and during/after burial into sediments. The impact of dissolution on δ18Odiatom values and potential misinterpretation of the palaeoclimate record are evaluated. Methods: Diatom frustules covering a range of ages (6 samples from the Miocene to the Holocene), environments and species were exposed to a weak alkaline solution for 48 days at two temperatures (20 °C and 4 °C), mimicking natural dissolution post mucilage removal. Following treatment, dissolution was assessed using scanning electron microscope images and a qualitative diatom dissolution index. The diatoms were subsequently analysed for their δ18O values using step-wise fluorination and isotope ratio mass spectrometry. Results: Variable levels of diatom dissolution were observed between the six samples; in all cases higher temperatures resulted in more frustule degradation. Dissolution was most evident in younger samples, probably as a result of the more porous nature of the silica. The degree of diatom dissolution does not directly equate to changes in the isotope ratios; the δ18Odiatom value was, however, lower after dissolution, but in only half the samples was this reduction outside the analytical error (2σ analytical error = 0.46‰). Conclusions: We have shown that dissolution can have a small negative impact on δ18Odiatom values, causing reductions of up to 0.59‰ beyond analytical error (0.46‰) at natural environmental temperatures. These findings need to be considered in palaeoenvironmental reconstructions using δ18Odiatom values, especially when interpreting variations in these values of <1‰

A Randomised Controlled Trial Comparing an Online Support Group to Expressive Writing for Depression and Anxiety

Background: The Internet enables people to help each other out with their problems, regardless of time or geographical location. Countless online forums or support groups exist, including for psychological problems. Objective: This study examined the efficacy of an online support group (OSG) in reducing depression and anxiety, and increasing perceived social support. Randomised controlled trials (RCTs) of online interventions face several challenges, including the choice of a control group. Our study compared an OSG with an online expressive writing task, where participants wrote about their thoughts and feelings, often upsetting ones, for a minimum of five minutes every two weeks over the course of the study. Participants submitted their writings, but received no feedback. Methods: 6-month RCT in which participants were directed either to (1) take part in an OSG (Psych Central); or (2) complete an online expressive writing task. 863 (628 female) UK, US and Canadian volunteers were recruited via the Internet. Using a 2:1 ratio, 568 were randomised to the OSG condition (at 6 months 103, 82% attrition) and 295 randomised to the expressive writing condition (at 6 months: 101, 65% attrition). Standard measures (Center for Epidemiologic Studies Depression Scale; Generalized Anxiety Disorder 7-item; Medical Outcomes Study Social Support Survey; Satisfaction with Life Scale) were administered at intake, 3 months and 6 months. Results: All four outcome variables showed a significant time effect (depression: F(2,201) = 35.00, p < 0.001; social support: F(2,201) = 12.29, p < 0.001; satisfaction with life: F(2,201) = 16.67, p < 0.001; anxiety: F(2,201) = 13.39, p < 0.001) but there were no significant interactions with group, thus showing no differences between conditions (depression: F(2,201) = 1.57, p = 0.21; social support: F(2,201) = 0.59, p = 0.56; satisfaction with life: F(2,201) = 0.19, p = 0.91; anxiety: F(2,201) = 1.09, p = 0.34). The expressive writing condition showed lower drop-out. Within the OSG condition, the mean number of times the OSG was accessed in the first fortnight was twice, and this fell to less than once in the final fortnight of the study period. We split the OSG group into low and high engagers, and compared just high engagers to the expressive writing condition: there were still no significant group effects. Engagement was predicted by high expectation of the intervention’s utility, but not demographic factors. Conclusions: Participants in both the OSG and expressive writing conditions showed similar improvements over time. The expressive writing condition, chosen as a control, was more effective than expected and participants reported it was highly acceptable. Engagement with the OSG was low, it had higher attrition and lower adherence, and it received mixed and often negative feedback. This raises questions about the effectiveness of OSGs for this population. While expressive writing has been demonstrated to have some efficacy over short periods (3-5 days), it has not been used in this manner previously and its use as an online intervention warrants further investigation

Design and Characterization of 1.8-3.2 THz Schottky-based Harmonic Mixers

A room-temperature Schottky diode-based WM-86 (WR-0.34) harmonic mixer was developed to build high-resolution spectrometers, and multi-pixel receivers in the THz region for applications such as radio astronomy, plasma diagnostics, and remote sensing. The mixer consists of a quartz-based Local Oscillator (LO), Intermediate-Frequency (IF) circuits, and a GaAs-based beam-lead THz circuit with an integrated diode. Measurements of the harmonic mixer were performed using a 2 THz solid-state source and 2.6906 THz QCL. A conversion loss of 27 dB for the 3rd harmonic mixing and a conversion loss of 30 dB for the 4th harmonic mixing was achieved. This is the first development of a wideband WM-86 (WR-0.34) harmonic mixer with planar Schottky diode integrated on a beam-lead THz circuit that uses a lower LO harmonic factor for 1.8-3.2 THz RF frequency. Furthermore, this result represents the best Schottky-based mixer in this frequency range

Grazing protozoa and the evolution of the Escherichia coli O157:H7 Shiga toxin-encoding prophage

Humans play little role in the epidemiology of Escherichia coli O157:H7, a commensal bacterium of cattle. Why then does E. coli O157:H7 code for virulence determinants, like the Shiga toxins (Stxs), responsible for the morbidity and mortality of colonized humans? One possibility is that the virulence of these bacteria to humans is coincidental and these virulence factors evolved for and are maintained for other roles they play in the ecology of these bacteria. Here, we test the hypothesis that the carriage of the Stx-encoding prophage of E. coli O157:H7 increases the rate of survival of E. coli in the presence of grazing protozoa, Tetrahymena pyriformis. In the presence but not the absence of Tetrahymena, the carriage of the Stx-encoding prophage considerably augments the fitness of E. coli K-12 as well as clinical isolates of E. coli O157 by increasing the rate of survival of the bacteria in the food vacuoles of these ciliates. Grazing protozoa in the environment or natural host are likely to play a significant role in the ecology and maintenance of the Stx-encoding prophage of E. coli O157:H7 and may well contribute to the evolution of the virulence of these bacteria to colonize humans

Ambiguities in the partial-wave analysis of pseudoscalar-meson photoproduction

Ambiguities in pseudoscalar-meson photoproduction, arising from incomplete experimental data, have analogs in pion-nucleon scattering. Amplitude ambiguities have important implications for the problems of amplitude extraction and resonance identification in partial-wave analysis. The effect of these ambiguities on observables is described. We compare our results with those found in earlier studies.Comment: 12 pages of text. No figure