To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
Our current global food system – from food production to consumption, including manufacture, packaging, transport, retail and associated businesses – is responsible for extensive negative social and environmental impacts which threaten the long-term well-being of society. This has led to increasing calls from science–policy organizations for major reform and transformation of the global food system. However, our knowledge regarding food system transformations is fragmented and this is hindering the development of co-ordinated solutions. Here, we collate recent research across several academic disciplines and sectors in order to better understand the mechanisms that ‘lock-in’ food systems in unsustainable states.
To examine the association between food choice and distress in a large national sample of American Indians/Alaska Natives (AI/AN) with type 2 diabetes.
Participants completed a sociodemographic survey, an FFQ and the Kessler-6 Distress Scale. Foods were identified as ‘healthy’ or ‘unhealthy’ using a classification grounded in the health education provided by the programme case managers; healthy and unhealthy food scores were calculated using reported intake frequencies. Pearson’s correlation coefficients for distress and food scores were calculated for all participants and by gender. Multiple linear regression models stratified by gender assessed the association between distress and food scores, controlling for sociodemographics and duration of type 2 diabetes.
Rural AI reservations and AN villages.
AI/AN (n 2484) with type 2 diabetes.
Both males (34·9 %) and females (65·1 %) had higher healthy food scores than unhealthy scores. In bivariate analysis, distress level had a significant negative correlation with healthy food scores among female participants, but the association was not significant among males. Significant positive correlations between distress and unhealthy food scores were found in both genders. In the final multivariate models, healthy food scores were not significantly related to distress; however, unhealthy food scores showed significant positive relationships with distress for both genders (females: β=0·078, P=0·0007; males: β=0·139, P<0·0001).
Health professionals working with AI/AN diagnosed with type 2 diabetes should offer food choice strategies during difficult times and recognize that males may be more likely than females to select unhealthy foods when distressed.
The skin surface of teleost fish dififers from that of higher vertebrates in that it is a living vital substrate at the margin between the water and the tissues. Its surface is continually sloughing into the water, to be replaced from the mucoid and formed elements of the epidermis. The surface, or cuticle, is altered by cyclical physiological changes in the animal, and also by pathological conditions. These, and the nature of the external medium, affect the range and the ecology of the biota of the surface. The secretions on the skin surface may also have a protective capacity. Fish epidermis is delicate and easily traumatized and there is great mobility of the Malpighian cells which allows rapid sealing of any breaches.
The general epidermal morphology of teleost fish is described and comparison made in terms of its vulnerability to ultraviolet radiation (UVR) with that of the human. Whereas human skin has a natural pigmentary photoprotective (tanning) mechanism within its epidermis, in teleosts the protective pigment layer is located primarily within the upper dermis. The potential impact of solar UV on farmed fish is discussed both in relation to water penetration of UVR and the phenomenon of photosensitisation, a condition common in higher animals and which has now been shown to induce skin lesions in fish. The results of recent investigations into photosensitisation in fish are described.
Substructure in ΛCDM provides a number of interesting puzzles. While the missing satellites problem is well-studied, there are suggestions of an opposite problem on the bright end. Subhalos large enough to host luminous satellites are uncommon, so the existence of the Large Magellanic Cloud (LMC) orbiting the Galaxy can potentially be a challenge for ΛCDM. Hence, we describe a search for analogs to an isolated galaxy pair like the Milky Way/LMC system in the SDSS and interpret these results with cosmological simulations. We note that while the LMC may not be unusual based on its luminosity, it is remarkably blue for such satellites. Thus, color may have implications for the LMC’s orbital history.
We report the synthesis of a series of highly functional metal chelated silyl- and tert-butyl-protected 2, 3-diaminomethyl norbornene derivatives. Subsequent alterations to the previously synthesized norbornene adducts afford many other derivatives containing such functionalities as alkyl, cyano, esters, and ethers. These derivatives are then subjected to ring-opening metathesis polymerization (ROMP) employing a ruthenium homogeneous catalyst to afford phase separated block polymers. The block polymers formed serve as unique templates for the formation of size controlled metal nanoclusters having a narrow dispersion. These metal nanoclusters containing diblock polymers are evaluated as unique electrical and optical materials.
The advent of polymer electrolytes has provided a promising route to an all solid-state polymer battery. Such a battery would have greater safety, without potential discharge of liquid or gel electrolyte. Current battery configurations typically involve a metal anode, a solvent-plasticized polyelectrolyte, such as poly (ethylene oxide) (PEO), and a composite cathode. We have synthesized an A/B/C triblock copolymer which could have potential use as an all-solid state nanoscale polymer lithium battery. The polymeric battery was synthesized with an anode, electrolyte and cathode by synthesizing an A/B/C triblock copolymer whose microphase separation would form lamellar domains. These nanodomains contain cobalt oxide, a derivative of PEO synthesized by ring opening metathesis polymerization, and a spinel phase LiMn2O4 as the anode, electrolyte and cathode material, respectively. The first block contains cobalt oxide that stores lithium ion in a novel electrochemical reaction that allows use in a battery configuration. The second block is polyethylene oxide derived from an unsaturated crown ether, and is used for its high ionic conductivity. The third block contains LiMn2O4, which is currently being investigated as a potential cathode material because of its low toxicity and ease of preparation. The nanometer size domains in the battery can be used in unique applications in microelectronics. In addition, such size scale allows use of the battery in discrete circuits, reducing the amount of wiring necessary in conventional battery configurations.
Self-powered “smart” windows utilize an electro-optic transmittance modulator based on electrochromic (EC) thin films that exhibit reversible and controlled changes in optical properties with an applied voltage between 0.7 and 2.0 V. Existing window designs require an external electrical connection, which may be economically unfeasible. This problem is solved by the tandem photovoltaic-electrochromic device, in which a wide-gap amorphous silicon-based alloy photovoltaic device is deposited together with an electrochromic optical transmittance modulator in a monolithic device on a single substrate. In this paper, we discuss our proposed monolithic photovoltaic-electrochromic device.
We also present studies of transparent, wide-gap (1.8 to 2.2 eV) amorphous silicon-carbon thin films and p-i-n devices designed for use in the photovoltaic-electrochromic device. These photovoltaic cells can operate at low current (<1 mA/cm2) because a total injected charge of only 60 μC/cm2 will darken the EC layer to a visible transmission of 5%, but they need a high open-circuit voltage (>1.0 V) and high transparency (≈70%). We present our progress toward these design targetxxss.
In the tandem photovoltaic-electrochromic (PV-EC) device, a wide-gap, semitransparent, amorphous silicon-carbon alloy (a-SiC:H) photovoltaic device and an electrochromic optical transmittance modulator (EC device) are deposited sequentially to form a monolithic device on a single substrate. This device can be used as a “smart” window for active control of daylighting and building cooling load without an external electrical connection.
Last year we reported preliminary results on our development of a semi-transparent PV cell incorporating an a-SiC:H i-layer. Here we report our recent progress on the semitransparent PV component of a PV-EC device and development of a Li-based EC device that colors at voltages below 0.9 V. Finally, we discuss both recent progress and difficulties in integrating the two devices on one substrate.
Restoration of semi-natural grassland communities involves a combination of (1) sward disturbance to create a temporal window for establishment, and (2) target species introduction, the latter usually by seed sowing. With great regularity, particular species establish only poorly. More reliable establishment could improve outcome of restoration projects and increase cost-effectiveness. We investigated the abiotic germination niche of ten poorly establishing calcareous grassland species by simultaneously exploring the effects of moisture and light availability and temperature fluctuation on percentage germination and speed of germination. We also investigated the effects of three different pre-treatments used to enhance seed germination – cold-stratification, osmotic priming and priming in combination with gibberellic acid (GA3) – and how these affected abiotic germination niches. Species varied markedly in width of abiotic germination niche, ranging from Carex flacca with very strict abiotic requirements, to several species reliably germinating across the whole range of abiotic conditions. Our results suggest pronounced differences between species in gap requirements for establishment. Germination was improved in most species by at least one pre-treatment. Evidence for positive effects of adding GA3 to seed priming solutions was limited. In several species, pre-treated seeds germinated under a wider range of abiotic conditions than untreated seeds. Improved knowledge of species-specific germination niches and the effects of seed pre-treatments may help to improve species establishment by sowing, and to identify species for which sowing at a later stage of restoration or introduction as small plants may represent a more viable strategy.
Hydrogen generation using solar energy will require the development of efficient electrocatalysts for proton reduction. This article discusses the important role that proton movement plays in hydrogenase enzymes and potential devices for solar generation. Studies of hydrogenase enzymes provide many important design principles for the development of simpler molecular catalysts. These principles are illustrated with examples from the literature and from the authors’ laboratories. In particular, pendant bases incorporated in the second coordination sphere of catalytic molecules play a number of important roles that are crucial to efficient catalysis. These roles include acting as relays to move protons between the metal center and solution, promoting intra- and intermolecular proton transfer reactions, coupling proton and electron transfer reactions, assisting heterolytic cleavage of hydrogen, and stabilizing critical reaction intermediates. The importance of controlling proton movement on the molecular scale underscores the importance of a similar degree of control in devices designed for the solar production of hydrogen or any fuel generation process involving multiple electrons and protons.
Since Hubble first resolved stars in external galaxies and confirmed that these ‘island universes’ were beyond the realm of our own MilkyWay Galaxy, astronomers have sought to understand the properties of galaxies over many orders of magnitude in luminosity and distance from the Milky Way. To deal with the various morphologies of observed galaxies, Hubble proposed a classification in which galaxies are broadly identified as variations of spirals, ellipticals and irregulars. Although galaxies are observed with widely varying morphologies, the mass of most of them appears to be dominated by an unseen dark matter component, as was shown by Vera Rubin, Ken Freeman and others using measurements of gas clouds in spiral galaxies in the 1970s. Since these early studies, observations of the mass distributions of many galaxies have been studied, with results showing that the ratio of dark matter to luminous matter varies from galaxy to galaxy; the largest clusters of galaxies and the smallest known dwarf galaxies have the highest ratio of dark to luminous matter.
It is now known that even though galaxies with brightness similar to that of the Milky Way dominate the luminosity distribution of galaxies, by far the most numerous galaxies in the Universe are dwarf galaxies, which fall under Hubble's irregular category. The first recorded discovery of a dwarf galaxy came perhaps as early as the tenth century in the Persian astronomer Al-Sufi's Book of Fixed Stars.
We show initial results from our ongoing HST/ACS GHOSTS survey of the resolved stellar envelopes of 14 nearby, massive disk galaxies. In hierarchical galaxy formation the stellar halos and thick disks of galaxies are formed by accretion of minor satellites and therefore contain valuable information about the (early) assembly process of galaxies. We detect for the first time the very small halo of NGC 4244, a low mass edge-on galaxy. We find that massive galaxies have very extended halos, with equivalent surface brightnesses of 28-29 V-mag arcsec−2 at 20-30 kpc from the disk. The old RGB stars of the thick disk in the NGC 891 and NGC 4244 edge-on galaxies truncate at the same radius as the young thin disk stars, providing insights into the formation of both disk truncations and thick disks. We furthermore present the stellar populations of a very low surface brightness stream around M83, the first such a stream resolved into stars beyond those of the Milky Way and M31.
Seeds and phytoplankton can be extremely mobile, but usually we are interested in surveying plants that cannot move. Sessile plants are usually arranged over a substrate (soil, sediment, etc.) and can be found, identified and examined at leisure. This characteristic means that, in many ways, it is much easier to census plants than it is to census other organisms and estimates of, e.g., density, species number and composition and distribution of a species are more accurate for plants. A second characteristic of plants, however, causes problems in deciding how best to characterise the abundance of species. Plant species, and even individuals within a species, in a community can differ enormously in size. An English wood may contain oak trees 30 m tall and with a canopy diameter of 40 m, in contrast to herbs, grasses and oak seedlings in the understorey, which are only a few centimetres in height. Even in a grassland where all plants are a few centimetres tall, there will be huge differences in the horizontal spread of individuals, from a few millimetres to several metres. While the standard measure of abundance of animals, a count of individuals, can be used for plants, this variety in plant size will mean that counts ignore a large amount of information about the community. For instance, there may be equal numbers of individuals of two species in your study area but the species with a larger average size will have a greater importance for the ecological processes.