A real-time Global Warming Index

We propose a simple real-time index of global human-induced warming and assess its robustness to uncertainties in climate forcing and short-term climate fluctuations. This index provides improved scientific context for temperature stabilisation targets and has the potential to decrease the volatility of climate policy. We quantify uncertainties arising from temperature observations, climate radiative forcings, internal variability and the model response. Our index and the associated rate of human-induced warming is compatible with a range of other more sophisticated methods to estimate the human contribution to observed global temperature change

The effects of immediate vision on implicit hand maps

Perceiving the external spatial location of the limbs using position sense requires that immediate proprioceptive afferent signals be combined with a stored body model specifying the size and shape of the body. Longo and Haggard (Proc Natl Acad Sci USA 107:11727–11732, 2010) developed a method to isolate and measure this body model in the case of the hand in which participants judge the perceived location in external space of several landmarks on their occluded hand. The spatial layout of judgments of different landmarks is used to construct implicit hand maps, which can then be compared with actual hand shape. Studies using this paradigm have revealed that the body model of the hand is massively distorted, in a highly stereotyped way across individuals, with large underestimation of finger length and overestimation of hand width. Previous studies using this paradigm have allowed participants to see the locations of their judgments on the occluding board. Several previous studies have demonstrated that immediate vision, even when wholly non-informative, can alter processing of somatosensory signals and alter the reference frame in which they are localised. The present study therefore investigated whether immediate vision contributes to the distortions of implicit hand maps described previously. Participants judged the external spatial location of the tips and knuckles of their occluded left hand either while being able to see where they were pointing (as in previous studies) or while blindfolded. The characteristic distortions of implicit hand maps reported previously were clearly apparent in both conditions, demonstrating that the distortions are not an artefact of immediate vision. However, there were significant differences in the magnitude of distortions in the two conditions, suggesting that vision may modulate representations of body size and shape, even when entirely non-informative

Current-density functional theory of time-dependent linear response in quantal fluids: recent progress

Vignale and Kohn have recently formulated a local density approximation to the time-dependent linear response of an inhomogeneous electron system in terms of a vector potential for exchange and correlation. The vector potential depends on the induced current density through spectral kernels to be evaluated on the homogeneous electron-gas. After a brief review of their theory, the case of inhomogeneous Bose superfluids is considered, with main focus on dynamic Kohn-Sham equations for the condensate in the linear response regime and on quantal generalized hydrodynamic equations in the weak inhomogeneity limit. We also present the results of calculations of the exchange-correlation spectra in both electron and superfluid boson systems.Comment: 12 pages, 2 figures, Postscript fil

Biohydrogenation of 22:6n-3 by Butyrivibrio proteoclasticus P18

Background: Rumen microbes metabolize 22:6n-3. However, pathways of 22:6n-3 biohydrogenation and ruminal microbes involved in this process are not known. In this study, we examine the ability of the well-known rumen biohydrogenating bacteria, Butyrivibrio fibrisolvens D1 and Butyrivibrio proteoclasticus P18, to hydrogenate 22:6n-3. Results: Butyrivibrio fibrisolvens D1 failed to hydrogenate 22:6n-3 (0.5 to 32 mu g/mL) in growth medium containing autoclaved ruminal fluid that either had or had not been centrifuged. Growth of B. fibrisolvens was delayed at the higher 22:6n-3 concentrations; however, total volatile fatty acid production was not affected. Butyrivibrio proteoclasticus P18 hydrogenated 22:6n-3 in growth medium containing autoclaved ruminal fluid that either had or had not been centrifuged. Biohydrogenation only started when volatile fatty acid production or growth of B. proteoclasticus P18 had been initiated, which might suggest that growth or metabolic activity is a prerequisite for the metabolism of 22:6n-3. The amount of 22:6n-3 hydrogenated was quantitatively recovered in several intermediate products eluting on the gas chromatogram between 22:6n-3 and 22:0. Formation of neither 22:0 nor 22:6 conjugated fatty acids was observed during 22:6n-3 metabolism. Extensive metabolism was observed at lower initial concentrations of 22:6n-3 (5, 10 and 20 mu g/mL) whereas increasing concentrations of 22:6n-3 (40 and 80 mu g/mL) inhibited its metabolism. Stearic acid formation (18:0) from 18:2n-6 by B. proteoclasticus P18 was retarded, but not completely inhibited, in the presence of 22:6n-3 and this effect was dependent on 22:6n-3 concentration. Conclusions: For the first time, our study identified ruminal bacteria with the ability to hydrogenate 22:6n-3. The gradual appearance of intermediates indicates that biohydrogenation of 22:6n-3 by B. proteoclasticus P18 occurs by pathways of isomerization and hydrogenation resulting in a variety of unsaturated 22 carbon fatty acids. During the simultaneous presence of 18:2n-6 and 22:6n-3, B. proteoclasticus P18 initiated 22:6n-3 metabolism before converting 18:1 isomers into 18:0

A Lagerstätte from Australia provides insight into the nature of Miocene mesic ecosystems

Reduced precipitation in the Miocene triggered the geographic contraction of rainforest ecosystems around the world. In Australia, this change was particularly pronounced; mesic rainforest ecosystems that once dominated the landscape transformed into the shrublands, grasslands, and deserts of today. A lack of well-preserved fossils has made it difficult to understand the nature of Australian ecosystems before the aridification. Here, we report on an exceptionally well-preserved rainforest biota from New South Wales, Australia. This Konservat-Lagerstätte hosts a rich diversity of microfossils, plants, insects, spiders, and vertebrate remains preserved in goethite. We document evidence for several species interactions including predation, parasitism, and pollination. The fossils are indicative of an oxbow lake in a mesic rainforest and suggest that rainforest distributions have shifted since the Miocene. The variety of fossils preserved, together with high fidelity of preservation, allows for unprecedented insights into the mesic ecosystems that dominated Australia during the Miocene

Quantifying the improvement of surrogate indices of hepatic insulin resistance using complex measurement techniques

We evaluated the ability of simple and complex surrogate-indices to identify individuals from an overweight/obese cohort with hepatic insulin-resistance (HEP-IR). Five indices, one previously defined and four newly generated through step-wise linear regression, were created against a single-cohort sample of 77 extensively characterised participants with the metabolic syndrome (age 55.6±1.0 years, BMI 31.5±0.4 kg/m2; 30 males). HEP-IR was defined by measuring endogenous-glucose-production (EGP) with [6–62H2] glucose during fasting and euglycemic-hyperinsulinemic clamps and expressed as EGP*fasting plasma insulin. Complex measures were incorporated into the model, including various non-standard biomarkers and the measurement of body-fat distribution and liver-fat, to further improve the predictive capability of the index. Validation was performed against a data set of the same subjects after an isoenergetic dietary intervention (4 arms, diets varying in protein and fiber content versus control). All five indices produced comparable prediction of HEP-IR, explaining 39–56% of the variance, depending on regression variable combination. The validation of the regression equations showed little variation between the different proposed indices (r2 = 27–32%) on a matched dataset. New complex indices encompassing advanced measurement techniques offered an improved correlation (r = 0.75, P<0.001). However, when validated against the alternative dataset all indices performed comparably with the standard homeostasis model assessment for insulin resistance (HOMA-IR) (r = 0.54, P<0.001). Thus, simple estimates of HEP-IR performed comparable to more complex indices and could be an efficient and cost effective approach in large epidemiological investigations

Achieving temperature-size changes in a unicellular organism.

The temperature-size rule (TSR) is an intraspecific phenomenon describing the phenotypic plastic response of an organism size to the temperature: individuals reared at cooler temperatures mature to be larger adults than those reared at warmer temperatures. The TSR is ubiquitous, affecting >80% species including uni- and multicellular groups. How the TSR is established has received attention in multicellular organisms, but not in unicells. Further, conceptual models suggest the mechanism of size change to be different in these two groups. Here, we test these theories using the protist Cyclidium glaucoma. We measure cell sizes, along with population growth during temperature acclimation, to determine how and when the temperature-size changes are achieved. We show that mother and daughter sizes become temporarily decoupled from the ratio 2:1 during acclimation, but these return to their coupled state (where daughter cells are half the size of the mother cell) once acclimated. Thermal acclimation is rapid, being completed within approximately a single generation. Further, we examine the impact of increased temperatures on carrying capacity and total biomass, to investigate potential adaptive strategies of size change. We demonstrate no temperature effect on carrying capacity, but maximum supported biomass to decrease with increasing temperature

Endogenous cholinergic inputs and local circuit mechanisms govern the phasic mesolimbic dopamine response to nicotine

Nicotine exerts its reinforcing action by stimulating nicotinic acetylcholine receptors (nAChRs) and boosting dopamine (DA) output from the ventral tegmental area (VTA). Recent data have led to a debate about the principal pathway of nicotine action: direct stimulation of the DAergic cells through nAChR activation, or disinhibition mediated through desensitization of nAChRs on GABAergic interneurons. We use a computational model of the VTA circuitry and nAChR function to shed light on this issue. Our model illustrates that the α4β2-containing nAChRs either on DA or GABA cells can mediate the acute effects of nicotine. We account for in vitro as well as in vivo data, and predict the conditions necessary for either direct stimulation or disinhibition to be at the origin of DA activity increases. We propose key experiments to disentangle the contribution of both mechanisms. We show that the rate of endogenous acetylcholine input crucially determines the evoked DA response for both mechanisms. Together our results delineate the mechanisms by which the VTA mediates the acute rewarding properties of nicotine and suggest an acetylcholine dependence hypothesis for nicotine reinforcement.Peer reviewe

An ultraviolet-optical flare from the tidal disruption of a helium-rich stellar core

The flare of radiation from the tidal disruption and accretion of a star can be used as a marker for supermassive black holes that otherwise lie dormant and undetected in the centres of distant galaxies. Previous candidate flares have had declining light curves in good agreement with expectations, but with poor constraints on the time of disruption and the type of star disrupted, because the rising emission was not observed. Recently, two `relativistic' candidate tidal disruption events were discovered, each of whose extreme X-ray luminosity and synchrotron radio emission were interpreted as the onset of emission from a relativistic jet. Here we report the discovery of a luminous ultraviolet-optical flare from the nuclear region of an inactive galaxy at a redshift of 0.1696. The observed continuum is cooler than expected for a simple accreting debris disk, but the well-sampled rise and decline of its light curve follows the predicted mass accretion rate, and can be modelled to determine the time of disruption to an accuracy of two days. The black hole has a mass of about 2 million solar masses, modulo a factor dependent on the mass and radius of the star disrupted. On the basis of the spectroscopic signature of ionized helium from the unbound debris, we determine that the disrupted star was a helium-rich stellar core.Comment: To appear in Nature on May 10, 201