Surprising dissimilarities in a newly formed pair of 'identical twin' stars

The mass and chemical composition of a star are the primary determinants of its basic physical properties--radius, temperature, luminosity--and how those properties evolve with time. Thus, two stars born at the same time, from the same natal material, and with the same mass are 'identical twins,' and as such might be expected to possess identical physical attributes. We have discovered in the Orion Nebula a pair of stellar twins in a newborn binary star system. Each star in the binary has a mass of 0.41 +/- 0.01 solar masses, identical to within 2 percent. Here we report that these twin stars have surface temperatures that differ by ~300K (~10%), and luminosities that differ by ~50%, both at high confidence level. Preliminary results indicate that the stars' radii also differ, by 5-10%. These surprising dissimilarities suggest that one of the twins may have been delayed by several hundred thousand years in its formation relative to its sibling. Such a delay could only have been detected in a very young, definitively equal-mass binary system3 such as that reported here. Our findings reveal cosmic limits on the age synchronisation of young binary stars, often used as tests for the age calibrations of star-formation models.Comment: Published in Nature, 19 June 200

Bats Use Magnetite to Detect the Earth's Magnetic Field

While the role of magnetic cues for compass orientation has been confirmed in numerous animals, the mechanism of detection is still debated. Two hypotheses have been proposed, one based on a light dependent mechanism, apparently used by birds and another based on a “compass organelle” containing the iron oxide particles magnetite (Fe3O4). Bats have recently been shown to use magnetic cues for compass orientation but the method by which they detect the Earth's magnetic field remains unknown. Here we use the classic “Kalmijn-Blakemore” pulse re-magnetization experiment, whereby the polarity of cellular magnetite is reversed. The results demonstrate that the big brown bat Eptesicus fuscus uses single domain magnetite to detect the Earths magnetic field and the response indicates a polarity based receptor. Polarity detection is a prerequisite for the use of magnetite as a compass and suggests that big brown bats use magnetite to detect the magnetic field as a compass. Our results indicate the possibility that sensory cells in bats contain freely rotating magnetite particles, which appears not to be the case in birds. It is crucial that the ultrastructure of the magnetite containing magnetoreceptors is described for our understanding of magnetoreception in animals

Autism as a disorder of neural information processing: directions for research and targets for therapy

The broad variation in phenotypes and severities within autism spectrum disorders suggests the involvement of multiple predisposing factors, interacting in complex ways with normal developmental courses and gradients. Identification of these factors, and the common developmental path into which theyfeed, is hampered bythe large degrees of convergence from causal factors to altered brain development, and divergence from abnormal brain development into altered cognition and behaviour. Genetic, neurochemical, neuroimaging and behavioural findings on autism, as well as studies of normal development and of genetic syndromes that share symptoms with autism, offer hypotheses as to the nature of causal factors and their possible effects on the structure and dynamics of neural systems. Such alterations in neural properties may in turn perturb activity-dependent development, giving rise to a complex behavioural syndrome many steps removed from the root causes. Animal models based on genetic, neurochemical, neurophysiological, and behavioural manipulations offer the possibility of exploring these developmental processes in detail, as do human studies addressing endophenotypes beyond the diagnosis itself

Strong interface-induced spin-orbit coupling in graphene on WS2

Interfacial interactions allow the electronic properties of graphene to be modified, as recently demonstrated by the appearance of satellite Dirac cones in the band structure of graphene on hexagonal boron nitride (hBN) substrates. Ongoing research strives to explore interfacial interactions in a broader class of materials in order to engineer targeted electronic properties. Here we show that at an interface with a tungsten disulfide (WS2) substrate, the strength of the spin-orbit interaction (SOI) in graphene is very strongly enhanced. The induced SOI leads to a pronounced low-temperature weak anti-localization (WAL) effect, from which we determine the spin-relaxation time. We find that spin-relaxation time in graphene is two-to-three orders of magnitude smaller on WS2 than on SiO2 or hBN, and that it is comparable to the intervalley scattering time. To interpret our findings we have performed first-principle electronic structure calculations, which both confirm that carriers in graphene-on-WS2 experience a strong SOI and allow us to extract a spin-dependent low-energy effective Hamiltonian. Our analysis further shows that the use of WS2 substrates opens a possible new route to access topological states of matter in graphene-based systems.Comment: Originally submitted version in compliance with editorial guidelines. Final version with expanded discussion of the relation between theory and experiments to be published in Nature Communication

Ancient hydrothermal seafloor deposits in Eridania basin on Mars

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/ licenses/by/4.0/. The file attached is the Published/publisher’s pdf version of the article

Construction and in vivo assembly of a catalytically proficient and hyperthermostable de novo enzyme

Although catalytic mechanisms in natural enzymes are well understood, achieving the diverse palette of reaction chemistries in re-engineered native proteins has proved challenging. Wholesale modification of natural enzymes is potentially compromised by their intrinsic complexity, which often obscures the underlying principles governing biocatalytic efficiency. The maquette approach can circumvent this complexity by combining a robust de novo designed chassis with a design process that avoids atomistic mimicry of natural proteins. Here, we apply this method to the construction of a highly efficient, promiscuous, and thermostable artificial enzyme that catalyzes a diverse array of substrate oxidations coupled to the reduction of H2O2. The maquette exhibits kinetics that match and even surpass those of certain natural peroxidases, retains its activity at elevated temperature and in the presence of organic solvents, and provides a simple platform for interrogating catalytic intermediates common to natural heme-containing enzymes

Distant agricultural landscapes

This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. The final publication is available at Springer via http://dx.doi.org/10.1007/s11625-014-0278-0This paper examines the relationship between the development of the dominant industrial food system and its associated global economic drivers and the environmental sustainability of agricultural landscapes. It makes the case that the growth of the global industrial food system has encouraged increasingly complex forms of “distance” that separate food both geographically and mentally from the landscapes on which it was produced. This separation between food and its originating landscape poses challenges for the ability of more localized agricultural sustainability initiatives to address some of the broader problems in the global food system. In particular, distance enables certain powerful actors to externalize ecological and social costs, which in turn makes it difficult to link specific global actors to particular biophysical and social impacts felt on local agricultural landscapes. Feedback mechanisms that normally would provide pressure for improved agricultural sustainability are weak because there is a lack of clarity regarding responsibility for outcomes. The paper provides a brief illustration of these dynamics with a closer look at increased financialization in the food system. It shows that new forms of distancing are encouraged by the growing significance of financial markets in global agrifood value chains. This dynamic has a substantial impact on food system outcomes and ultimately complicates efforts to scale up small-scale local agricultural models that are more sustainable.The Trudeau Foundation || Social Sciences and Humanities Research Council of Canad

Hypertension persisting after pre-eclampsia: a prospective cohort study at Mulago Hospital, Uganda.

BACKGROUND: Pre-eclampsia/eclampsia usually resolves after delivery but sometimes hypertension persists and cardiovascular disease develops later. Our objective was to determine the incidence and maternal socio-demographic and obstetric risk factors for persistence of hypertension in women with pre-eclampsia/eclampsia. METHODS: This was a prospective cohort study conducted from July 2009 to June 2011 at Mulago Hospital labour ward and postnatal clinics. We followed up 188 women admitted with pre-eclampsia/eclampsia until 3 months after delivery. Data was collected using interviewer-administered questionnaires, examination of participants and review of medical records. Stata (version12) software was used for data analysis. Univariable analysis was used to compute the relative risk of persistent hypertension at the 95% confidence level. This was followed by multivariable logistic regression analysis to determine factors independently associated with persistence of hypertension. RESULTS: 64 (34%) out of the 188 women analysed had persistent hypertension three months after delivery. Maternal age, gestational age at delivery and parity were predictors of persistent hypertension. CONCLUSION: The proportion of women with pre-eclampsia/eclampsia at risk of persistent hypertension at three months after delivery was high, with nearly one of three mothers remaining hypertensive. Follow up of mothers who develop pre-eclampsia is important so that early diagnosis and management of chronic hypertension can be made to avoid long term morbidity and mortality

Improving pulse crops as a source of protein, starch and micronutrients

Pulse crops have been known for a long time to have beneficial nutritional profiles for human diets but have been neglected in terms of cultivation, consumption and scientific research in many parts of the world. Broad dietary shifts will be required if anthropogenic climate change is to be mitigated in the future, and pulse crops should be an important component of this change by providing an environmentally sustainable source of protein, resistant starch and micronutrients. Further enhancement of the nutritional composition of pulse crops could benefit human health, helping to alleviate micronutrient deficiencies and reduce risk of chronic diseases such as type 2 diabetes. This paper reviews current knowledge regarding the nutritional content of pea (Pisum sativum L.) and faba bean (Vicia faba L.), two major UK pulse crops, and discusses the potential for their genetic improvement