Vezava proteinov NLP na lipidne membrane

ArticleMacrofossil calcite is of great importance for quantitative reconstructions of palaeoenvironment and palaeoseasonality. The calcite rostra of belemnites, Jurassic to Cretaceous marine invertebrates, are especially suited for such investigations, because they are comparatively large and are structured by growth bands. Despite their use in chemostratigraphic and palaeoenvironmental studies, much of the internal variability of geochemical signatures in rostra is poorly understood. Here, multiple profiles through a belemnite rostrum of Passaloteuthis bisulcata (∼183 Myr old) were analyzed for δ13C and δ18O values as well as Mg/Ca, Sr/Ca and Mn/Ca ratios. Geochemical signatures of the central 1–2 mm of the profiles indicate diagenetic cementation along the apical zone, for which original porosity of up to 40% can be inferred. The overall δ13C and δ18O values of the other, well preserved parts of the belemnite fluctuate by >1 per mil, but are nearly uniform within single growth bands. In contrast, Sr/Ca and Mg/Ca in the well-preserved parts show growth-rate and crystal-shape related variability. Close to the central apical zone, strongly bent calcite crystals are enriched in Mg (up to 70%) and Sr (up to 50%). Through the remainder of the rostrum, higher calcite precipitation rate can account for Mg depletion of ∼15% and Sr enrichment of ∼15% with respect to co-genetic calcite precipitated at a slower rate. No indication for temperature control on Mg/Ca or Sr/Ca is detected in the investigated specimen. Overall, the new findings indicate that δ13C and δ18O analyses of belemnite rostra produce consistent results regardless of the sampling area within the rostrum, and that growth rate effects on element incorporation are minor with respect to the control exerted by secular changes in seawater composition through time. Additionally, the central part of the rostrum, where strong calcite crystal bending is observed, should be avoided for sampling when studying elemental composition of the calcite for palaeoenvironmental reconstructions.Deutsche Akademie der Naturforscher Leopoldina – German National Academy of Science

Absolute Calibration of the DANCE Thermal Neutron Beam using Sodium Activation

The measurement of the neutron capture cross-section as a function of energy in the thermal range requires a precise knowledge of the absolute neutron flux. In this paper a new method of calibrating a thermal neutron beam using the controlled activation of sodium is described. The method is applied to the FP-14 Time Of Flight neutron beam line at the Los Alamos Neutron Science Center to calibrate the beam to a precision of $\pm5$%.Comment: 12 pages, 3 figures, v2 is the version accepted for publication in NIM

Reflecting optics in the diverticular eye of a deep-sea barreleye fish (Rhynchohyalus natalensis)

We describe the bi-directed eyes of a mesopelagic teleost fish, Rhynchohyalus natalensis, that possesses an extensive lateral diverticulum to each tubular eye. Each diverticulum contains a mirror that focuses light from the ventro-lateral visual field. This species can thereby visualize both downwelling sunlight and bioluminescence over a wide field of view. Modelling shows that the mirror is very likely to be capable of producing a bright, well focused image. After Dolichopteryx longipes, this is only the second description of an eye in a vertebrate having both reflective and refractive optics. Although superficially similar, the optics of the diverticular eyes of these two species of fish differ in some important respects. Firstly, the reflective crystals in the D. longipes mirror are derived from a tapetum within the retinal pigment epithelium, whereas in R. natalensis they develop from the choroidal argentea. Secondly, in D. longipes the angle of the reflective crystals varies depending on their position within the mirror, forming a Fresnel-type reflector, but in R. natalensis the crystals are orientated almost parallel to the mirror's surface and image formation is dependent on the gross morphology of the diverticular mirror. Two remarkably different developmental solutions have thus evolved in these two closely related species of opisthoproctid teleosts to extend the restricted visual field of a tubular eye and provide a well-focused image with reflective optics

Measurement of the neutron capture cross-section on argon

The use of argon as a detection and shielding medium for neutrino and dark matter experiments has made the precise knowledge of the cross section for neutron capture on argon an important design and operational parameter. Since previous measurements were averaged over thermal spectra and have significant disagreements, a differential measurement has been performed using a Time-Of-Flight neutron beam and a $\sim$4$\pi$ gamma spectrometer. A fit to the differential cross section from $0.015-0.15$\,eV, assuming a $1/v$ energy dependence, yields $\sigma^{2200} = 673 \pm 26 \text{ (stat.)} \pm 59 \text{ (sys.)}$\,mb.Comment: 5 pages, 4 figures; final version of the paper; added details and fix reference

A coumaroyl-ester-3-hydroxylase insertion mutant reveals the existence of nonredundant meta-hydroxylation pathways and essential roles for phenolic precursors in cell expansion and plant growth

Cytochromes P450 monooxygenases from the CYP98 family catalyze the meta-hydroxylation step in the phenylpropanoid biosynthetic pathway. The ref8 Arabidopsis (Arabidopsis thaliana) mutant, with a point mutation in the CYP98A3 gene, was previously described to show developmental defects, changes in lignin composition, and lack of soluble sinapoyl esters. We isolated a T-DNA insertion mutant in CYP98A3 and show that this mutation leads to a more drastic inhibition of plant development and inhibition of cell growth. Similar to the ref8 mutant, the insertion mutant has reduced lignin content, with stem lignin essentially made of p-hydroxyphenyl units and trace amounts of guaiacyl and syringyl units. However, its roots display an ectopic lignification and a substantial proportion of guaiacyl and syringyl units, suggesting the occurrence of an alternative CYP98A3-independent meta-hydroxylation mechanism active mainly in the roots. Relative to the control, mutant plantlets produce very low amounts of sinapoyl esters, but accumulate flavonol glycosides. Reduced cell growth seems correlated with alterations in the abundance of cell wall polysaccharides, in particular decrease in crystalline cellulose, and profound modifications in gene expression and homeostasis reminiscent of a stress response. CYP98A3 thus constitutes a critical bottleneck in the phenylpropanoid pathway and in the synthesis of compounds controlling plant development. CYP98A3 cosuppressed lines show a gradation of developmental defects and changes in lignin content (40% reduction) and structure (prominent frequency of p-hydroxyphenyl units), but content in foliar sinapoyl esters is similar to the control. The purple coloration of their leaves is correlated to the accumulation of sinapoylated anthocyanins

Experimental Evaluation of Subgraph Isomorphism Solvers

International audienceSubgraph Isomorphism (SI) is an NP-complete problem which is at the heart of many structural pattern recognition tasks as it involves finding a copy of a pattern graph into a target graph. In the pattern recognition community, the most well-known SI solvers are VF2, VF3, and RI. SI is also widely studied in the constraint programming community, and many constraint-based SI solvers have been proposed since Ullman, such as LAD and Glasgow, for example. All these SI solvers can solve very quickly some large SI instances, that involve graphs with thousands of nodes. However, McCreesh et al. have recently shown how to randomly generate SI instances the hardness of which can be controlled and predicted, and they have built small instances which are computationally challenging for all solvers. They have also shown that some small instances, which are predicted to be easy and are easily solved by constraint-based solvers, appear to be challenging for VF2 and VF3. In this paper, we widen this study by considering a large test suite coming from eight benchmarks. We show that, as expected for an NP-complete problem, the solving time of an instance does not depend on its size, and that some small instances coming from real applications are not solved by any of the considered solvers. We also show that, if RI and VF3 can solve very quickly a large number of easy instances, for which Glasgow or LAD need more time, they fail at solving some other instances that are quickly solved by Glasgow or LAD, and they are clearly outperformed by Glasgow on hard instances. Finally, we show that we can easily combine solvers to take benefit of their complementarity

Orbital pacing and secular evolution of the Early Jurassic carbon cycle

Cyclic variations in Earth’s orbit drive periodic changes in the ocean–atmosphere system at a time scale of tens to hundreds of thousands of years. The Mochras δ13CTOC record illustrates the continued impact of long-eccentricity (405-ky) orbital forcing on the carbon cycle over at least ∼18 My of Early Jurassic time and emphasizes orbital forcing as a driving mechanism behind medium-amplitude δ13C fluctuations superimposed on larger-scale trends that are driven by other variables such as tectonically determined paleogeography and eruption of large igneous provinces. The dataset provides a framework for distinguishing between internal Earth processes and solar-system dynamics as the driving mechanism for Early Jurassic δ13C fluctuations and provides an astronomical time scale for the Sinemurian Stage

Astronomical constraints on the duration of the Early Jurassic Pliensbachian Stage and global climatic fluctuations

The Early Jurassic was marked by multiple periods of major global climatic and palaeoceanographic change, biotic turnover and perturbed global geochemical cycles, commonly linked to large igneous province volcanism. This epoch was also characterised by the initial break-up of the super-continent Pangaea and the opening and formation of shallow-marine basins and ocean gateways, the timing of which are poorly constrained. Here, we show that the Pliensbachian Stage and the Sinemurian–Pliensbachian global carbon-cycle perturbation (marked by a negative shift in δ13Cδ13C of 2–4‰2–4‰), have respective durations of ∼8.7 and ∼2 Myr. We astronomically tune the floating Pliensbachian time scale to the 405 Kyr eccentricity solution (La2010d), and propose a revised Early Jurassic time scale with a significantly shortened Sinemurian Stage duration of 6.9±0.4 Myr6.9±0.4 Myr. When calibrated against the new time scale, the existing Pliensbachian seawater 87Sr/86Sr record shows relatively stable values during the first ∼2 Myr of the Pliensbachian, superimposed on the long-term Early Jurassic decline in 87Sr/86Sr. This plateau in 87Sr/86Sr values coincides with the Sinemurian–Pliensbachian boundary carbon-cycle perturbation. It is possibly linked to a late phase of Central Atlantic Magmatic Province (CAMP) volcanism that induced enhanced global weathering of continental crustal materials, leading to an elevated radiogenic strontium flux to the global ocean