Environmental drivers of aquatic macrophyte communities in southern tropical African rivers:Zambia as a case study

The first-ever extensive macrophyte survey of Zambian rivers and associated floodplain waterbodies, conducted during 2006–2012, collected 271 samples from 228 sites, mainly located in five freshwater ecoregions of the world primarily represented in Zambia. The results supported the hypothesis that variation in macrophyte community structure (measured as species composition and diversity) in southern tropical African river systems, using Zambia as a case study area, is driven primarily by geographical variation in water physico-chemical conditions. In total, 335 macrophyte taxa were recorded, and a chronological cumulative species records curve for the dataset showed no sign of asymptoting: clearly many additional macrophyte species remain to be found in Zambian rivers. Emergent macrophytes were predominant (236 taxa), together with 26 floating and 73 submerged taxa. Several species were rare in a regional or international context, including two IUCN Red Data List species: Aponogeton rehmanii and Nymphaea divaricata. Ordination and classification analysis of the data found little evidence for temporal change in vegetation, at repeatedly-sampled sites, but strong evidence for the existence of seven groups of samples from geographically-varied study sites. These supported differing sets of vegetation (with eight species assemblages present in the sample-groups) and showed substantial inter-group differences in both macrophyte alpha-diversity, and geographically-varying physico-chemical parameters. The evidence suggested that the main environmental drivers of macrophyte community composition and diversity were altitude, stream order, shade, pH, alkalinity, NO3-N, and underwater light availability, while PO4-P showed slightly lower, but still significant variation between sample-groups

Freshwater science for the benefit of society: a perspective from early career researchers

This research brief summarises the views of a group of early career freshwater researchers on 3 questions: What are the greatest threats to freshwater resources and how will they change over the next century? Is freshwater science effectively utilised to help society adapt to these threats? How will we ensure the benefits of freshwater science are reaped by society into the future? To address these questions we reviewed the current literature and discussed our findings in a series of group meetings. We concluded that freshwater resources will be most threatened by population growth, climate change, and eutrophication in the future. We provide examples of how the utilisation of freshwater science by society is reliant on effective monitoring systems, data sharing, and effective communication of topical scientific evidence to both the public and policy makers. Developments in these fields increase the likelihood of society benefitting from past and future research in freshwater science

Cubic Re⁶⁺ (5d¹) Double Perovskites, Ba₂MgReO₆, Ba₂ZnReO₆, and Ba₂Y_2/3ReO₆: Magnetism, Heat Capacity, μSR, and Neutron Scattering Studies and Comparison with Theory

Double perovskites (DP) of the general formula Ba₂MReO₆, where M = Mg, Zn, and Y_2/3, all based on Re⁶⁺ (5d¹, t_2g¹), were synthesized and studied using magnetization, heat capacity, muon spin relaxation, and neutron-scattering techniques. All are cubic, <i>Fm</i>3̅<i>m</i>, at ambient temperature to within the resolution of the X-ray and neutron diffraction data, although the muon data suggest the possibility of a local distortion for M = Mg. The M = Mg DP is a ferromagnet, <i>T</i>_c = 18 K, with a saturation moment ∼0.3 bohr magnetons at 3 K. There are two anomalies in the heat capacity: a sharp feature at 18 K and a broad maximum centered near 33 K. The total entropy loss below 45 K is 9.68 e.u., which approaches <i>R</i> ln 4 (11.52 e.u.) supporting a <i>j</i> = 3/2 ground state. The unit cell constants of Ba₂MgReO₆ and the isostructural, isoelectronic analogue, Ba₂LiOsO₆, differ by only 0.1%, yet the latter is an anti-ferromagnet. The M = Zn DP also appears to be a ferromagnet, <i>T</i>_c = 11 K, μ_sat(Re) = 0.1 μ_B. In this case the heat capacity shows a somewhat broad peak near 10 K and a broader maximum at ∼33 K, behavior that can be traced to a smaller particle size, ∼30 nm, for this sample. For both M = Mg and Zn, the low-temperature magnetic heat capacity follows a <i>T</i>^3/2 behavior, consistent with a ferromagnetic spin wave. An attempt to attribute the broad 33 K heat capacity anomalies to a splitting of the <i>j</i> = 3/2 state by a crystal distortion is not supported by inelastic neutron scattering, which shows no transition at the expected energy of ∼7 meV nor any transition up to 100 meV. However, the results for the two ferromagnets are compared to the theory of Chen, Pereira, and Balents, and the computed heat capacity predicts the two maxima observed experimentally. The M = Y_2/3 DP, with a significantly larger cell constant (3%) than the ferromagnets, shows predominantly anti-ferromagnetic correlations, and the ground state is complex with a spin frozen component <i>T</i>_g = 16 K from both direct current and alternating current susceptibility and μSR data but with a persistent dynamic component. The low-temperature heat capacity shows a <i>T</i>¹ power law. The unit cell constant of <i>B</i> = Y_2/3 is less than 1% larger than that of the ferromagnetic Os⁷⁺ (5d¹) DP, Ba₂NaOsO₆

Using Internet and Mobile Phone Technology to Deliver an Automated Physical Activity Program: Randomized Controlled Trial

Reviewer: Dey, AnindReviewer: Johnston, SandraReviewer: Barkhuus, Louise[This item is a preserved copy and is not necessarily the most recent version. To view the current item, visit http://www.jmir.org/2007/2/e7/ ] Background: The Internet has potential as a medium for health behavior change programs, but no controlled studies have yet evaluated the impact of a fully automated physical activity intervention over several months with real-time objective feedback from a monitor. Objective: The aim was to evaluate the impact of a physical activity program based on the Internet and mobile phone technology provided to individuals for 9 weeks. Methods: A single-center, randomized, stratified controlled trial was conducted from September to December 2005 in Bedfordshire, United Kingdom, with 77 healthy adults whose mean age was 40.4 years (SD = 7.6) and mean body mass index was 26.3 (SD = 3.4). Participants were randomized to a test group that had access to an Internet and mobile phone–based physical activity program (n = 47) or to a control group (n = 30) that received no support. The test group received tailored solutions for perceived barriers, a schedule to plan weekly exercise sessions with mobile phone and email reminders, a message board to share their experiences with others, and feedback on their level of physical activity. Both groups were issued a wrist-worn accelerometer to monitor their level of physical activity; only the test group received real-time feedback via the Internet. The main outcome measures were accelerometer data and self-report of physical activity. Results: At the end of the study period, the test group reported a significantly greater increase over baseline than did the control group for perceived control (P < .001) and intention/expectation to exercise (P < .001). Intent-to-treat analyses of both the accelerometer data (P = .02) and leisure time self-report data (P = .03) found a higher level of moderate physical activity in the test group. The average increase (over the control group) in accelerometer-measured moderate physical activity was 2 h 18 min per week. The test group also lost more percent body fat than the control group (test group: −2.18, SD = 0.59; control group: −0.17, SD = 0.81; P = .04). Conclusions: A fully automated Internet and mobile phone–based motivation and action support system can significantly increase and maintain the level of physical activity in healthy adults