Risk of gastrointestinal illness associated with the consumption of rainwater: a systematic review

The collection of rainwater for human consumption is a practice well established in many parts of the world. Much of the research to date regarding this inexpensive and sustainable source has focused on its microbiological or chemical quality and there have been no reviews of epidemiological evidence regarding actual health risks associated with rainwater consumption. Electronic bibliographic databases were searched for epidemiological studies that attempted to quantify the risk of gastrointestinal disease linked to the consumption of harvested rainwater. Online databases were searched from the oldest date up to January 2011. Both observational and experimental studies were included. In addition, reference sections of key articles were searched and authors of previous studies were contacted where appropriate. Studies were assessed for relevance independently and in duplicate. Searches returned a total of 764 articles, 13 met inclusion criteria, 5 of these were outbreak reports, and 9 were studies of other design types. Pooled subgroup analysis suggests that rainwater is associated with reduced risk of illness compared to unimproved supplies (relative risk 0.57 95% CI 0.42, 0.77). There was no significant difference in risk in the pooled analysis of studies that compared rainwater to improved water supplies (relative risk 0.82 95% CI 0.38, 1.73). However, there was heterogeneity with one study showing an excess risk of campylobacteriosis. Classification of outbreak reports determined that 4 reports were "strongly associated with rainwater" while 1 report was "probably associated with rainwater". We conclude that the evidence suggests that rainwater is safer than water from unimproved water supplies. Where feasible rainwater harvesting should be encouraged as a step toward achieving millennium development targets.     

Rhodium catalyzed chelation-assisted C-H bond functionalization reactions

Over the last several decades, researchers have achieved remarkable progress in the field of organometallic chemistry. The development of metal-catalyzed cross-coupling reactions represents a paradigm shift in chemical synthesis, and today synthetic chemists can readily access carbon-carbon and carbon-heteroatom bonds from a vast array of starting compounds. Although we cannot understate the importance of these methods, the required prefunctionalization to carry out these reactions adds cost and reduces the availability of the starting reagents. The use of C-H bond activation in lieu of prefunctionalization has presented a tantalizing alternative to classical cross-coupling reactions. Researchers have met the challenges of selectivity and reactivity associated with the development of C-H bond functionalization reactions with an explosion of creative advances in substrate and catalyst design. Literature reports on selectivity based on steric effects, acidity, and electronic and directing group effects are now numerous. Our group has developed an array of C-H bond functionalization reactions that take advantage of a chelating directing group, and this Account surveys our progress in this area. The use of chelation control in C-H bond functionalization offers several advantages with respect to substrate scope and application to total synthesis. The predictability and decreased dependence on the inherent stereoelectronics of the substrate generally result in selective and high yielding transformations with broad applicability. The nature of the chelating moiety can be chosen to serve as a functional handle in subsequent elaborations. Our work began with the use of Rh(I) catalysts in intramolecular aromatic C-H annulations, which we further developed to include enantioselective transformations. The application of this chemistry to the simple olefinic C-H bonds found in α,β-unsaturated imines allowed access to highly substituted olefins, pyridines, and piperidines. We observed complementary reactivity with Rh(III) catalysts and developed an oxidative coupling with unactivated alkenes. Further studies on the Rh(III) catalysts led us to develop methods for the coupling of C-H bonds to polarized π bonds such as those in imines and isocyanates. In several cases the methods that we have developed for chelation-controlled C-H bond functionalization have been applied to the total synthesis of complex molecules such as natural products, highlighting the utility of these methods in organic synthesis.     

Exfoliated production of single- and multi-layer graphenes and carbon nanofibres from the carbonisation of a co-polymer

Non-catalysed growth methodologies of carbon nanomaterial synthesis can represent lower costs and greener approaches and cause less damage to the nanomaterial. During the carbonisation of a polyacrylonitrile-based co-polymer, carbon nanofibres (CNFs) and single- and multi-layer graphenes (SLG and MLG) are generated. The accumulated fragmentation products of the co-polymer coalesce to form CNFs that radiate away from the monolith, whose dimensions are linked to their template growth along crests, which were formed from the out-gassing of volatile products of the polymer during the stabilisation step. The slight shrinkage of the carbonising monolith also leads to exfoliation of larger areas of the surface yielding single- and multi-layered graphenes. These results reveal a potentially useful process for the facile production of carbon nanomaterials.     

Increased response/recovery lifetimes and reinforcement of polyaniline nanofiber films using carbon nanotubes

We have prepared high surface area, conductive, mechanically robust, responsive polyaniline–carbon nanotube composite films. These were produced by filtration from dilute dispersions of polyaniline nanofibers and single-walled carbon nanotubes. Unlike polyaniline alone, these composites are mechanically stable, maintain large intractable surfaces and exhibit greatly enhanced response/recovery behavior to changes in their local environment. This is illustrated by exposing the films to ammonia.     

The development of canola oil based bio‐resins

Bio‐based resins made from vegetable oils offer a sustainable alternative to petroleum‐based thermoset resins. The thermosetting resin systems we have developed from epoxidized canola oil and the polyurethanes we have produced from canola oil‐based polyols show promise as cost‐effective materials incorporating a high renewable content. Here we outline the use of canola oil based bio‐resins in composite boards, and in polyurethane adhesive and insulating foam applications.     

Energy and the environment: Pipeline petulance

The president's decision in January to “defer” (i.e., cancel) the Keystone Pipeline project pending yet more environmental review is perhaps the best known of the administration's politically driven environmental policy decisions.     

Multi-channel microstrip transceiver arrays using harmonics for high field MR imaging in humans

Radio-frequency (RF) transceiver array design using primary and higher order harmonics for in vivo parallel magnetic resonance imaging imaging (MRI) and spectroscopic imaging is proposed. The improved electromagnetic decoupling performance, unique magnetic field distributions and high-frequency operation capabilities of higher-order harmonics of resonators would benefit transceiver arrays for parallel MRI, especially for ultrahigh field parallel MRI. To demonstrate this technique, microstrip transceiver arrays using first and second harmonic resonators were developed for human head parallel imaging at 7T. Phantom and human head images were acquired and evaluated using the GRAPPA reconstruction algorithm. The higher-order harmonic transceiver array design technique was also assessed numerically using FDTD simulation. Compared with regular primary-resonance transceiver designs, the proposed higher-order harmonic technique provided an improved g-factor and increased decoupling among resonant elements without using dedicated decoupling circuits, which would potentially lead to a better parallel imaging performance and ultimately faster and higher quality imaging. The proposed technique is particularly suitable for densely spaced transceiver array design where the increased mutual inductance among the elements becomes problematic. In addition, it also provides a simple approach to readily upgrade the channels of a conventional primary resonator microstrip array to a larger number for faster imaging.     

LaAlO<Subscript>3</Subscript>/SrTiO<Subscript>3</Subscript> Epitaxial Heterostructures by Atomic Layer Deposition

Thin films of LaAlO₃ were deposited on TiO₂-terminated (100) SrTiO₃ crystals by atomic layer deposition (ALD), using tris(iso-propylcyclopentadienyl)lanthanum and trimethyl aluminum precursors. Water was used as the oxidizer. The film composition was shown to be controlled by the ratio of La/Al precursor pulses during ALD, with near-stoichiometric LaAlO₃ resulting at precursor pulse ratios of 4/1 to 5/1. Films near the stoichiometric LaAlO₃ composition were shown to crystallize on subsequent annealing to form epitaxial LaAlO₃/SrTiO₃ heterostructures. Electrical characterization of these structures was done by two-terminal direct-current (DC) current–voltage scans at room temperature and under high-vacuum conditions. The results show electrical conductivity for the ALD-deposited epitaxial LaAlO₃/SrTiO₃ heterostructures, which turns on for thickness above four unit cells for the LaAlO₃ film.     

Spatially oversampled TDC with digital resolution enhancement

A digital resolution enhancement technique for time-to-digital converters (TDC) is proposed. This involves a simultaneous multi-channel measurement of a time interval with low complexity TDC of varying low resolutions. The coarse outputs of each converter are digitally post-processed to obtain an output whose precision is much better than that of the individual converters. Three post-processing algorithms are proposed and their limitations in presence of converter non-idealities are analyzed. A prototype system with 8 channels is implemented in 90 nm CMOS. 40MS/s output of each channel is algorithmically combined to obtain over 2.2–3X measured improvement in the resolution in 4/6/8 channel modes, validating the system principle. The chip occupies 0.3 mm² and draws up to a maximum of 4 mA from a 1.2 V supply.