bluuebunny/crossref_metadata_2025 huggingface dataset:
A benchmark for reaction coordinates in the transition path ensemble
Authors: Li Wenjin , Ma Ao
Published: April 2016

The molecular mechanism of a reaction is embedded in its transition path ensemble, the complete collection of reactive trajectories. Utilizing the information in the transition path ensemble alone, we developed a novel metric, which we termed the emergent potential energy, for distinguishing reaction coordinates from the bath modes. The emergent potential energy can be understood as the average energy cost for making a displacement of a coordinate in the transition path ensemble. Where displacing a bath mode invokes essentially no cost, it costs significantly to move the reaction coordinate. Based on some general assumptions of the behaviors of reaction and bath coordinates in the transition path ensemble, we proved theoretically with statistical mechanics that the emergent potential energy could serve as a benchmark of reaction coordinates and demonstrated its effectiveness by applying it to a prototypical system of biomolecular dynamics. Using the emergent potential energy as guidance, we developed a committor-free and intuition-independent method for identifying reaction coordinates in complex systems. We expect this method to be applicable to a wide range of reaction processes in complex biomolecular systems.
MoS2 spaser
Authors: Jayasekara Charith , Premaratne Malin , Gunapala Sarath D. , Stockman Mark I.
Published: April 2016

We present a comprehensive analysis of a spaser made of a circular shaped highly doped molybdenum disulfide (MoS2) resonator. “Spaser” is an acronym for “surface plasmon amplification by stimulated emission of radiation”–a nanoscale source of surface plasmons generated by stimulated emission in a plasmonic resonator which receives energy nonradiatively. By considering localized surface plasmon modes, operation characteristics of the model are analysed, and tunability of the design is demonstrated. We find the optimum geometric and material parameters of the spaser that provides efficient outputs and carryout a comparative analysis with a similar circular spaser made of graphene. Owing to physical and chemical properties of MoS2 and the active medium, the proposed design delivers efficient outputs in terms of spaser mode energy, operating thresholds, Q-factor, and electric field amplitude. Lower operating thresholds and higher mode energies are notable advantages of the design. Owing to having many superior features to existing similar designs, this MoS2 spaser may be much suited for applications in nanoplasmonic devices.
Magnetic and magnetocaloric properties of quasi-one-dimensional Ising spin chain CoV2O6
Authors: Nandi M. , Mandal P.
Published: April 2016

We have investigated the magnetic and magnetocaloric properties of antiferromagnetic Ising spin chain CoV2O6 by magnetization and heat capacity measurements. Both monoclinic α-CoV2O6 and triclinic γ-CoV2O6 exhibit field-induced metamagnetic transitions from antiferromagnetic to ferromagnetic state via an intermediate ferrimagnetic state with 1/3 magnetization plateau. Due to the field-induced metamagnetic transitions, these systems show large conventional as well as inverse magnetocaloric effects. In α-CoV2O6, we observe field-induced complex magnetic phases and multiple magnetization plateaus below 6 K when the field is applied along c axis. Several critical temperatures and fields have been identified from the temperature and field dependence of magnetization, magnetic entropy change, and heat capacity to construct the H–T phase diagram. As compared to α-CoV2O6, γ-CoV2O6 displays a relatively simple magnetic phase diagram. Due to the large magnetic entropy change and adiabatic temperature change at low or moderate applied magnetic field, γ-CoV2O6 may be considered as a magnetic refrigerant in the low-temperature region below 20 K.
Structural and dynamical properties of chlorinated hydrocarbons studied with resonant inelastic x-ray scattering
Authors: Bohinc R. , Žitnik M. , Bučar K. , Kavčič M. , Carniato S. , Journel L. , Guillemin R. , Marchenko T. , Kawerk E. , Simon M. , Cao W.
Published: April 2016

We present a theoretical and experimental study of resonant inelastic x-ray scattering on a large group of chlorinated hydrocarbons: CH3Cl, CH2Cl2, CHCl3, CCl4, CH3CH2Cl, ClCH2CH2Cl, CH3CHCl2, CH3CCl3, C2H2Cl2-iso, C2H2Cl2-cis, C2H2Cl2-trans, and C6H5Cl. Differences in structural and dynamical properties of the molecules generated by diverse chemical environments are observed in the measured Cl(Kα) spectral maps as well as in the Cl(K) total fluorescence yield spectra. The energy position, relative intensity, and the width of the Franck-Condon distribution of low-lying σ∗ and π∗ resonances are extracted by a fitting procedure taking into account the experimental broadening. The theoretical values obtained with the transition potential and Δ Kohn-Sham methods are in good agreement with the experimental parameters indicating subtle differences due to variations in the molecular structure.
The spin relaxation of nitrogen donors in 6H SiC crystals as studied by the electron spin echo method
Authors: Savchenko D. , Shanina B. , Kalabukhova E. , Pöppl A. , Lančok J. , Mokhov E.
Published: April 2016

We present the detailed study of the spin kinetics of the nitrogen (N) donor electrons in 6H SiC wafers grown by the Lely method and by the sublimation “sandwich method” (SSM) with a donor concentration of about 1017 cm−3 at T = 10–40 K. The donor electrons of the N donors substituting quasi-cubic “k1” and “k2” sites (Nk1,k2) in both types of the samples revealed the similar temperature dependence of the spin-lattice relaxation rate (T1−1), which was described by the direct one-phonon and two-phonon processes induced by the acoustic phonons proportional to T and to T9, respectively. The character of the temperature dependence of the T1−1 for the donor electrons of N substituting hexagonal (“h”) site (Nh) in both types of 6H SiC samples indicates that the donor electrons relax through the fast-relaxing centers by means of the cross-relaxation process. The observed enhancement of the phase memory relaxation rate (Tm−1) with the temperature increase for the Nh donors in both types of the samples, as well as for the Nk1,k2 donors in Lely grown 6H SiC, was explained by the growth of the free electron concentration with the temperature increase and their exchange scattering at the N donor centers. The observed significant shortening of the phase memory relaxation time Tm for the Nk1,k2 donors in the SSM grown sample with the temperature lowering is caused by hopping motion of the electrons between the occupied and unoccupied states of the N donors at Nh and Nk1,k2 sites. The impact of the N donor pairs, triads, distant donor pairs formed in n-type 6H SiC wafers on the spin relaxation times was discussed.
Performance limits of ion extraction systems with non-circular apertures
Authors: Shagayda A. , Madeev S.
Published: April 2016

A three-dimensional computer simulation is used to determine the perveance limitations of ion extraction systems with non-circular apertures. The objective of the study is to analyze the possibilities to improve mechanical strength of the ion optics made of carbon-carbon composite materials. Non-circular grid apertures are better suited to the physical structure of carbon-carbon composite materials, than conventionally used circular holes in a hexagonal pattern, because they allow a fewer number of cut fibers. However, the slit-type accelerating systems, usually regarded as the main alternative to the conventional ion optics, have an intolerably narrow range of operating perveance values at which there is no direct ion impingement on the acceleration grid. This paper presents results of comparative analysis of a number of different ion optical systems with non-circular apertures and conventional ion optical systems with circular apertures. It has been revealed that a relatively wide perveance range without direct ion impingement may be obtained with apertures shaped as a square with rounded corners. Numerical simulations show that this geometry may have equivalent perveance range as the traditional geometry with circular apertures while being more mechanically robust. In addition, such important characteristics, as the effective transparency for both the ions and the neutral atoms, the height of the potential barrier reflecting the downstream plasma electrons and the angular divergence of the beamlet also can be very close to these parameters for the optics with circular apertures.
Deposition kinetics and characterization of stable ionomers from hexamethyldisiloxane and methacrylic acid by plasma enhanced chemical vapor deposition
Authors: Urstöger Georg , Resel Roland , Koller Georg , Coclite Anna Maria
Published: April 2016

A novel ionomer of hexamethyldisiloxane and methacrylic acid was synthesized by plasma enhanced chemical vapor deposition (PECVD). The PECVD process, being solventless, allows mixing of monomers with very different solubilities, and for polymers formed at high deposition rates and with high structural stability (due to the high number of cross-links and covalent bonding to the substrate) to be obtained. A kinetic study over a large set of parameters was run with the aim of determining the optimal conditions for high stability and proton conductivity of the polymer layer. Copolymers with good stability over 6 months' time in air and water were obtained, as demonstrated by ellipsometry, X-Ray reflectivity, and FT-IR spectroscopy. Stable coatings showed also proton conductivity as high as 1.1 ± 0.1 mS cm−1. Chemical analysis showed that due to the high molecular weight of the chosen precursors, it was possible to keep the plasma energy-input-per-mass low. This allowed limited precursor fragmentation and the functional groups of both monomers to be retained during the plasma polymerization.
Enhanced oxygen vacancy diffusion in Ta2O5 resistive memory devices due to infinitely adaptive crystal structure
Authors: Jiang Hao , Stewart Derek A.
Published: April 2016

Metal oxide resistive memory devices based on Ta2O5 have demonstrated high switching speed, long endurance, and low set voltage. However, the physical origin of this improved performance is still unclear. Ta2O5 is an important archetype of a class of materials that possess an adaptive crystal structure that can respond easily to the presence of defects. Using first principles nudged elastic band calculations, we show that this adaptive crystal structure leads to low energy barriers for in-plane diffusion of oxygen vacancies in λ phase Ta2O5. Identified diffusion paths are associated with collective motion of neighboring atoms. The overall vacancy diffusion is anisotropic with higher diffusion barriers found for oxygen vacancy movement between Ta-O planes. Coupled with the fact that oxygen vacancy formation energy in Ta2O5 is relatively small, our calculated low diffusion barriers can help explain the low set voltage in Ta2O5 based resistive memory devices. Our work shows that other oxides with adaptive crystal structures could serve as potential candidates for resistive random access memory devices. We also discuss some general characteristics for ideal resistive RAM oxides that could be used in future computational material searches.
An indicator to objectively quantify the visual impact of an offshore wind farm
Authors: Gonzalez-Rodriguez Angel G.
Published: April 2016

This study describes a method to quantify the visual impact of an offshore wind farm, as seen from the coast. In brief, the method involves distinguishing between the visual impact due to the intrusion in the observer's vision field and the un-aesthetic effect of the arrangement unevenness. Both parameters, visual intrusion and unevenness, can be quantifiable; therefore, a final indicator for the visual impact of the wind farm can be calculated for a specific wind farm layout. Two approaches are presented to calculate the visual intrusion, which give rise to similar results. The method has been programmed and included in an application that has been tested with two known wind farm layouts, showing a complete coherence of the results given by the method. This method provides the designer with a tool that allows him to take into account the estimated visual impact of a wind farm under study. If an algorithm is used to look for the optimum location/layout for an offshore wind farm, its programmer can include this method in order to obtain a trade-off between maximum profitability and minimum visual impact.
The anisotropic redistribution of free energy for gyrokinetic plasma turbulence in a Z-pinch
Authors: Navarro Alejandro Bañón , Teaca Bogdan , Jenko Frank
Published: April 2016

For a Z-pinch geometry, we report on the nonlinear redistribution of free energy across scales perpendicular to the magnetic guide field, for a turbulent plasma described in the framework of gyrokinetics. The analysis is performed using a local flux-surface approximation, in a regime dominated by electrostatic fluctuations driven by the entropy mode, with both ion and electron species being treated kinetically. To explore the anisotropic nature of the free energy redistribution caused by the emergence of zonal flows, we use a polar coordinate representation for the field-perpendicular directions and define an angular density for the scale flux. Positive values for the classically defined (angle integrated) scale flux, which denote a direct energy cascade, are shown to be also composed of negative angular sections, a fact that impacts our understanding of the backscatter of energy and the way in which it enters the modeling of sub-grid scales for turbulence. A definition for the flux of free energy across each perpendicular direction is introduced as well, which shows that the redistribution of energy in the presence of zonal flows is highly anisotropic.
Thermoacoustic and photoacoustic characterizations of few-layer graphene by pulsed excitations
Authors: Wang Xiong , Witte Russell S. , Xin Hao
Published: April 2016

We characterized the thermoacoustic and photoacoustic properties of large-area, few-layer graphene by pulsed microwave and optical excitations. Due to its high electric conductivity and low heat capacity per unit area, graphene lends itself to excellent microwave and optical energy absorption and acoustic signal emanation due to the thermoacoustic effect. When exposed to pulsed microwave or optical radiation, distinct thermoacoustic and photoacoustic signals generated by the few-layer graphene are obtained due to microwave and laser absorption of the graphene, respectively. Clear thermoacoustic and photoacoustic images of large-area graphene sample are achieved. A numerical model is developed and the simulated results are in good accordance with the measured ones. This characterization work may find applications in ultrasound generator and detectors for microwave and optical radiation. It may also become an alternative characterization approach for graphene and other types of two-dimensional materials.
Interfacial Dzyaloshinskii-Moriya interaction, surface anisotropy energy, and spin pumping at spin orbit coupled Ir/Co interface
Authors: Kim Nam-Hui , Jung Jinyong , Cho Jaehun , Han Dong-Soo , Yin Yuxiang , Kim June-Seo , Swagten Henk J. M. , You Chun-Yeol
Published: April 2016

The interfacial Dzyaloshinskii-Moriya interaction (iDMI), surface anisotropy energy, and spin pumping at the Ir/Co interface are experimentally investigated by performing Brillouin light scattering. Contrary to previous reports, we suggest that the sign of the iDMI at the Ir/Co interface is the same as in the case of the Pt/Co interface. We also find that the magnitude of the iDMI energy density is relatively smaller than in the case of the Pt/Co interface, despite the large strong spin-orbit coupling (SOC) of Ir. The saturation magnetization and the perpendicular magnetic anisotropy (PMA) energy are significantly improved due to a strong SOC. Our findings suggest that an SOC in an Ir/Co system behaves in different ways for iDMI and PMA. Finally, we determine the spin pumping effect at the Ir/Co interface, and it increases the Gilbert damping constant from 0.012 to 0.024 for 1.5 nm-thick Co.
Carbon nanotube fiber terahertz polarizer
Authors: Zubair Ahmed , Tsentalovich Dmitri E. , Young Colin C. , Heimbeck Martin S. , Everitt Henry O. , Pasquali Matteo , Kono Junichiro
Published: April 2016

Conventional, commercially available terahertz (THz) polarizers are made of uniformly and precisely spaced metallic wires. They are fragile and expensive, with performance characteristics highly reliant on wire diameters and spacings. Here, we report a simple and highly error-tolerant method for fabricating a freestanding THz polarizer with nearly ideal performance, reliant on the intrinsically one-dimensional character of conduction electrons in well-aligned carbon nanotubes (CNTs). The polarizer was constructed on a mechanical frame over which we manually wound acid-doped CNT fibers with ultrahigh electrical conductivity. We demonstrated that the polarizer has an extinction ratio of ∼−30 dB with a low insertion loss (<0.5 dB) throughout a frequency range of 0.2–1.1 THz. In addition, we used a THz ellipsometer to measure the Müller matrix of the CNT-fiber polarizer and found comparable attenuation to a commercial metallic wire-grid polarizer. Furthermore, based on the classical theory of light transmission through an array of metallic wires, we demonstrated the most striking difference between the CNT-fiber and metallic wire-grid polarizers: the latter fails to work in the zero-spacing limit, where it acts as a simple mirror, while the former continues to work as an excellent polarizer even in that limit due to the one-dimensional conductivity of individual CNTs.
Saturated ideal kink/peeling formations described as three-dimensional magnetohydrodynamic tokamak equilibrium states
Authors: Cooper W. A. , Brunetti D. , Duval B. P. , Faustin J. M. , Graves J. P. , Kleiner A. , Patten H. , Pfefferlé D. , Porte L. , Raghunathan M. , Reimerdes H. , Sauter O. , Tran T. M.
Published: April 2016

Free boundary magnetohydrodynamic equilibrium states with spontaneous three dimensional deformations of the plasma-vacuum interface are computed for the first time. The structures obtained have the appearance of saturated ideal external kink/peeling modes. High edge pressure gradients yield toroidal mode number n = 1 corrugations for a high edge bootstrap current and larger n distortions when this current is small. Deformations in the plasma boundary region induce a nonaxisymmetric Pfirsch-Schlüter current driving a field-aligned current ribbon consistent with reported experimental observations. A variation in the 3D equilibrium confirms that the n = 1 mode is a kink/peeling structure. We surmise that our calculated equilibrium structures constitute a viable model for the edge harmonic oscillations and outer modes associated with a quiescent H-mode operation in shaped tokamak plasmas.
Dry seeds and environmental extremes: consequences for seed lifespan and germination
Authors: Visscher Anne M. , Seal Charlotte E. , Newton Rosemary J. , Frances Alba Latorre , Pritchard Hugh W.
Published: April 2016

In the context of climate change, food security and long-term human space missions, it is important to understand which species produce seeds that can tolerate extreme environmental conditions. Here we consider dry seed survival of extreme conditions encountered in both natural and artificially controlled environments. Considerable overlap exists between the two: for example, ultra-dry and anoxic conditions can be artificially imposed during seed storage and also occur naturally in the vacuum of space environments. Aside from ultra-drying and anoxia, dry seeds of many species may experience extremely high temperatures due to heat from wildfires or when exposed to solar heat in biomes such as deserts. In addition, seeds can be irradiated by UV-A and UV-B at the surface of the Earth and by the shorter wavelengths of UV-C in outer space. We focus on the effects of these extreme environmental conditions on dry seed lifespan and germination. Although it is clear that seeds from particular plant species and families can tolerate exposures to ultra-drying, high temperatures (at least 32 families) or UV radiation with minimal consequences for subsequent germination ability, further research is needed to elucidate many of the mechanisms underlying extreme tolerance of these environmental conditions found on Earth or in space.
Assessing the potential to combine attitude tracking and health campaign evaluation surveys
Authors: Hollier Lauren P. , Pettigrew Simone , Minto Carolyn , Slevin Terry , Strickland Mark
Published: April 2016

Issue addressed

Online surveys are becoming increasingly popular in health research because of the low cost and fast completion time. A large proportion of online survey costs are allocated to setup and administration expenses, which suggests that conducting fewer, longer surveys would be a cost‐effective approach. The current study assessed whether the incorporation of a health campaign evaluation survey within a longitudinal attitudes and behaviours tracking survey produced different outcomes compared with the separate administration of the evaluation survey.

Methods

Data were collected via an online panel, with 688 respondents completing the combined survey and 657 respondents completing the evaluation‐only survey. Regression analyses were conducted to examine whether survey type was related to the campaign evaluation results.

Results

Those who completed the combined survey perceived the campaign advertisement to be more personally relevant than those completing the evaluation‐only survey. There were no differences in results relating to campaign awareness and reported behavioural change as a result of campaign exposure.

Conclusions

There were minimal differences between results obtained from combining an attitude/behaviour tracking survey with a campaign evaluation survey. Any priming or order effects were limited to respondents' cognitive responses to the advertisement.

So what?

The results suggest that health practitioners with limited resources available for tracking and evaluation research may be able to maximise outcomes by administering fewer, longer surveys.
Low functional redundancy and high variability in Sargassum browsing fish populations in a subtropical reef system
Authors: Gilby Ben L. , Tibbetts Ian R. , Stevens Tim
Published: April 2016

Establishing levels of functional redundancy in browsing fish populations among sampling periods and across spatial gradients is important in understanding coral reef functioning. We used baited video techniques to determine functional redundancy and variability in browsing herbivores within no-take marine protected areas (MPAs) and reference fished sites across two sampling periods and four reef types (scaling from high to low coral cover) in Moreton Bay, Australia (~27°S, 153°E). We hypothesised higher herbivore abundance and browsing rates in MPAs due to protection from fishing, but lower functional redundancy in Moreton Bay generally than in tropical reefs. The function of Sargassum browsing in Moreton Bay is conducted by a single species (rabbitfish Siganus fuscescens), which is unlikely to browse at ecologically significant rates. Siganus fuscescens abundance was variable between reef types, sampling periods and individual sites, such that their abundance and browsing rates were not higher within MPAs. Similar spatial and temporal variability was found for fish community structure, indicating that other functional roles might not be influenced by MPA protection in Moreton Bay. We highlight the importance of accounting for variability in fish communities and ecosystem processes across spatial and temporal periods in considering the influence of no-take MPAs.
Inflammatory and neuropathic cold allodynia are selectively mediated by the neurotrophic factor receptor GFRα3
Authors: Lippoldt Erika K. , Ongun Serra , Kusaka Geoffrey K. , McKemy David D.
Published: April 2016

Significance

There are few effective treatments for chronic cold pain induced by tissue damage, nerve injury, or chemotherapeutic polyneuropathies. Here, we show that the specific artemin receptor, glial cell line-derived neurotrophic factor family of receptors-α3, is absolutely required for injury-induced cold pain, and we show results of a specific transduction pathway that can be targeted selectively to treat cold pain.
Genomic tools and plant genes to mitigate impacts of climate change and extreme environments.
Authors: De Pace C.
Published: April 2016

This review outlines a conceptual framework that links climate-related risk components (hazard, exposure and vulnerability) to the genetics and genomics tools used for developing new crop varieties to promote adaptation to extreme weather events and to mitigate risks related to the effects of climate change. The establishment of templates for identifiable features or markers on the genome to refine genetic maps for monogenic traits - especially those related to stress resistance in plant model species - has benefited plant genome projects from early on. Genomics has facilitated the discovery of genes affecting quantitative, or continuous, traits for enhancing yield in low-input sustainable agriculture. Genomics and genomic tools developed in model species favour translational approaches when searching for orthologous genes in diploid crop species or diploid relatives of polyploid crop species. Discovering genetic variation through focused identification of germplasm from extreme environments, and generating genetic variation by mutagenesis and 'genome editing', will facilitate targeted induction of new alleles and adaptation to the effects of climate change. Genetic marker-aided transfer and shuffling alleles by introgression breeding and publically accepted plant transformation methodologies, will accelerate precise breeding and release of crop cultivars that will greatly benefit adaptation to and mitigation of risks related to climate change.
Prevention of enterotoxigenic
Escherichia coli
infections in pigs by dairy-based nutrition.
Authors: Sugiharto S. , Jensen B. B. , Jensen K. H. , Lauridsen C.
Published: April 2016

Postweaning diarrhoea (PWD) is a significant enteric disease causing considerable economic losses for the pig industry. Among several aetiological risk factors, enterotoxigenic
Escherichia coli
(ETEC) is considered to be a major cause. After being routinely used for several decades to control bacterial disease outbreaks in piglets, the use of antibiotics at subtherapeutic concentrations has been banned in the European Union because of the increasing prevalence of resistance to antibiotics in pigs. The removal of in-feed antibiotics from piglet diets has negative economic consequences as it dramatically increases the rate of morbidity and mortality due to ETEC as well as the use of antibiotics for therapeutic purposes. Other than subtherapeutic antibiotics, zinc oxide (ZnO) has been reported to ameliorate and/or prevent the development of PWD in piglets, but its excretion may have negative impacts on the environment. Thus, other alternatives that can control ETEC infections in piglets postweaning will be of great advantage. A number of nutritional strategies have been proposed as alternative means of preventing ETEC infections, of which feeding dairy-based products to piglets could be one of such strategies. It is apparent that colostrum, milk and milk fractions such as whey and casein contain several biologically active compounds with anti-microbial and immunomodulatory properties. Recently, these dairy products and their isolated compounds such as lactoferrin and oligosaccharides have been employed as anti-infective agents against ETEC infections in piglets postweaning. The dairy by-products (e.g. whey or whey permeate) may also be fermented to further improve the anti-infective potential of the products. Overall, the anti-infective activities of dairy-based products against ETEC could be attributed to the improvement of the intestinal barrier functions, microbial ecosystem and immunity of the piglets.
Integration of Complex Data Sources to Provide Biologic Insight into Pulmonary Vascular Disease (2015 Grover Conference Series)
Authors: Brittain Evan L. , Chan Stephen Y.
Published: April 2016

The application of complex data sources to pulmonary vascular diseases is an emerging and promising area of investigation. The use of ‐omics platforms, in silico modeling of gene networks, and linkage of large human cohorts with DNA biobanks are beginning to bear biologic insight into pulmonary hypertension. These approaches to high‐throughput molecular phenotyping offer the possibility of discovering new therapeutic targets and identifying variability in response to therapy that can be leveraged to improve clinical care. Optimizing the methods for analyzing complex data sources and accruing large, well‐phenotyped human cohorts linked to biologic data remain significant challenges. Here, we discuss two specific types of complex data sources—gene regulatory networks and DNA‐linked electronic medical record cohorts—that illustrate the promise, challenges, and current limitations of these approaches to understanding and managing pulmonary vascular disease.
Comparison of the measurement standards of the length unit in the field of roundness deviations measurements
Authors: Lysenko V G , Kupko V S , Makarevich V B
Published: April 2016

A trilateral comparison has been performed in the subject field of roundness measurement. The comparison was pilot by VNIIMS, Russia and took place between February 2014 and August 2014. The circulated standards were a roundness transfer standard in the form of a glass hemisphere and a magnification standard often referred to as a 'Flick' standard. Data from the roundness standard were processed using a Gaussian filter and a bandpass up to 50 undulations per revolution to provide a measured value of Roundness Deviation (RONt). For the magnification standard, data were also filtered and the fitted element was the circumscribed circle together with the deviation of the valleys (RONv). The results of comparisons show the correspondence of measurement uncertainties to the declared values and the compared measurement standards are equivalent.

Main text

To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.

The final report has been peer-reviewed and approved for publication by the CCL, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).
Symmetric cubic surfaces and 𝐆₂ character varieties
Authors: Boalch Philip , Paluba Robert
Published: April 2016

We will consider a two dimensional “symmetric” subfamily of the four dimensional family of Fricke cubic surfaces. The main result is that such symmetric cubic surfaces arise as character varieties for the exceptional group of type

G
2

G_2

. Further, this symmetric family will be related to the fixed points of the triality automorphism of

Spin
⁡
(
8
)

\operatorname {Spin}(8)

, and an example involving the finite simple group of order

6048
6048

inside

G
2

G_2

will be considered.
Evaluation of Rheological Properties of Four Italian Rice Samples and Starch Thereof by RVA and FTIR Spectroscopy Supported by Double Two‐Dimensional Correlation Analysis: Evidence of Lipid–Carbohydrate Interactions
Authors: Acquistucci Rita , Melini Valentina , Cecconi Sabrina , Mecozzi Mauro
Published: April 2016

In this paper four rice samples and purified starch thereof characterized by different genetic background, amylose content, and gelatinization behavior were considered. They were examined with respect to chemical composition and pasting properties. To explain differences observed in the Rapid Visco Analyzer (RVA) curves, Fourier transform infrared spectroscopy (FTIR) was also used to characterize the rice and starch samples. Double two‐dimensional correlation analysis (D2DCORR), a powerful chemometric tool not commonly used in food analysis, was applied to FTIR spectra to support the interpretation of FTIR results. Finally, a study by FTIR spectroscopy was performed to characterize the lipid components extracted from some rice and starch samples. Rice samples showed different pasting properties owing to genetic characteristics, although these differences were mostly evident in the samples of starch thereof. However, the most interesting differences among samples were evidenced in the lipid component related to lipid–carbohydrate interactions, as resulted from the FTIR spectra and D2DCORR analysis.
Analysis of Fatty Acids in Kernel, Flour, and Oil Samples of Maize by NIR Spectroscopy Using Conventional Regression Methods
Authors: Egesel Cem Ömer , Kahrıman Fatih , Ekinci Neslihan , Kavdır İsmail , Büyükcan M. Burak
Published: April 2016

High cost and painstaking procedures associated with fatty acid analyses of maize kernel necessitate the use of alternative methods. NIR spectroscopy offers advantages in this respect for a variety of areas such as plant breeding, food and feed industries, and biofuel production, in which different forms of maize kernel (e.g., intact kernel, flour, or oil) are used as material. We investigated the possibility of estimating maize oil quality traits by using different samples (intact kernel, flour, and oil) and conventional regression methods (multiple linear regression [MLR] and partial least squares regression [PLSR]) applied to their NIR spectra. MLR and PLSR calibration models were developed for oleic acid, linoleic acid, oleic/linoleic acid ratios, total monounsaturated fatty acid, total polyunsaturated fatty acid (PUFA), and total saturated fatty acid by analyzing 120 maize samples. Robustness in terms of prediction accuracy of the models developed here was tested with a reserved set of samples (n = 30). The results suggested that fatty acids could be possibly estimated by calibrations developed from flour and oil samples with a high degree of accuracy, whereas intact samples did not offer satisfactory results. PLSR and MLR methods gave better results in flour and oil samples, respectively. PUFA was the trait that was most successfully estimated from both flour (for the PLSR model, standard error of the estimate [SEP] of 1.78%, relative performance to deviation [RPD] of 3.09, R2 = 0.93) and oil (for the MLR model, SEP of 0.85%, RPD of 6.52, R2 = 0.98) samples. We concluded that sample type and chemometric method should be handled as important factors in calibration development, and the effects of these factors may vary depending on the trait being analyzed.
Understanding modern extinctions in marine ecosystems: the role of palaeoecological data
Authors: Kosnik Matthew A. , Kowalewski Michał
Published: April 2016

Because anthropogenic impacts on ecological systems pre-date the oldest scientific observations, historical documents and archaeological records, understanding modern extinctions requires additional data sources that extend further back in time. Palaeoecological records, which provide quantitative proxy records of ecosystems prior to human impact, are essential for understanding recent extinctions and future extinction risks. Here we critically review the value of the most recent fossil record in contributing to our understanding of modern extinctions and illustrate through case studies how naturally occurring death assemblages and Holocene sedimentary records provide context to the plight of marine ecosystems. While palaeoecological data are inherently restricted censuses of past communities (manipulative experiments are not possible), they yield quantitative records over temporal scales that are beyond the reach of ecology. Only by including palaeoecological data is it possible to fully assess the role of long-term anthropogenic processes in driving modern extinction risk.
Time-calibrated models support congruency between Cretaceous continental rifting and titanosaurian evolutionary history
Authors: Gorscak Eric , O‘Connor Patrick M.
Published: April 2016

Recent model-based phylogenetic approaches have expanded upon the incorporation of extinct lineages and their respective temporal information for calibrating divergence date estimates. Here, model-based methods are explored to estimate divergence dates and ancestral ranges for titanosaurian sauropod dinosaurs, an extinct and globally distributed terrestrial clade that existed during the extensive Cretaceous supercontinental break-up. Our models estimate an Early Cretaceous (approx. 135 Ma) South American origin for Titanosauria. The estimated divergence dates are broadly congruent with Cretaceous geophysical models of supercontinental separation and subsequent continental isolation while obviating the invocation of continuous Late Cretaceous continental connections (e.g. ephemeral land bridges). Divergence dates for mid-Cretaceous African and South American sister lineages support semi-isolated subequatorial African faunas in concordance with the gradual northward separation between South America and Africa. Finally, Late Cretaceous Africa may have linked Laurasian lineages with their sister South American lineages, though the current Late Cretaceous African terrestrial fossil record remains meagre.
Quantitative analysis of harmonic convergence in mosquito auditory interactions
Authors: Aldersley Andrew , Champneys Alan , Homer Martin , Robert Daniel
Published: April 2016

This article analyses the hearing and behaviour of mosquitoes in the context of inter-individual acoustic interactions. The acoustic interactions of tethered live pairs ofAedes aegyptimosquitoes, from same and opposite sex mosquitoes of the species, are recorded on independent and unique audio channels, together with the response of tethered individual mosquitoes to playbacks of pre-recorded flight tones of lone or paired individuals. A time-dependent representation of each mosquito's non-stationary wing beat frequency signature is constructed, based on Hilbert spectral analysis. A range of algorithmic tools is developed to automatically analyse these data, and used to perform a robust quantitative identification of the ‘harmonic convergence’ phenomenon. The results suggest that harmonic convergence is an active phenomenon, which does not occur by chance. It occurs for live pairs, as well as for lone individuals responding to playback recordings, whether from the same or opposite sex. Male–female behaviour is dominated by frequency convergence at a wider range of harmonic combinations than previously reported, and requires participation from both partners in the duet. New evidence is found to show that male–male interactions are more varied than strict frequency avoidance. Rather, they can be divided into two groups: convergent pairs, typified by tightly bound wing beat frequencies, and divergent pairs, that remain widely spaced in the frequency domain. Overall, the results reveal that mosquito acoustic interaction is a delicate and intricate time-dependent active process that involves both individuals, takes place at many different frequencies, and which merits further enquiry.
Coalescent models for developmental biology and the spatio-temporal dynamics of growing tissues
Authors: Smadbeck Patrick , Stumpf Michael P. H.
Published: April 2016

Development is a process that needs to be tightly coordinated in both space and time. Cell tracking and lineage tracing have become important experimental techniques in developmental biology and allow us to map the fate of cells and their progeny. A generic feature of developing and homeostatic tissues that these analyses have revealed is that relatively few cells give rise to the bulk of the cells in a tissue; the lineages of most cells come to an end quickly. Computational and theoretical biologists/physicists have, in response, developed a range of modelling approaches, most notably agent-based modelling. These models seem to capture features observed in experiments, but can also become computationally expensive. Here, we develop complementary genealogical models of tissue development that trace the ancestry of cells in a tissue back to their most recent common ancestors. We show that with both bounded and unbounded growth simple, but universal scaling relationships allow us to connect coalescent theory with the fractal growth models extensively used in developmental biology. Using our genealogical perspective, it is possible to study bulk statistical properties of the processes that give rise to tissues of cells, without the need for large-scale simulations.
Monodominance in tropical forests: modelling reveals emerging clusters and phase transitions
Authors: Kazmierczak Martin , Backmann Pia , Fedriani José M. , Fischer Rico , Hartmann Alexander K. , Huth Andreas , May Felix , Müller Michael S. , Taubert Franziska , Grimm Volker , Groeneveld Jürgen
Published: April 2016

Tropical forests are highly diverse ecosystems, but within such forests there can be large patches dominated by a single tree species. The myriad presumed mechanisms that lead to the emergence of such monodominant areas is currently the subject of intensive research. We used the most generic of these mechanisms, large seed mass and low dispersal ability of the monodominant species, in a spatially explicit model. The model represents seven identical species with long-distance dispersal of small seeds, competing with one potentially monodominant species with short-distance dispersal of large seeds. Monodominant patches emerged and persisted only for a narrow range of species traits; these results have the characteristic features of phase transitions. Additional mechanisms may explain monodominance in different ecological contexts, but our results suggest that percolation-like phenomena and phase transitions might be pervasive in this type of system.
Cities and regions in Britain through hierarchical percolation
Authors: Arcaute Elsa , Molinero Carlos , Hatna Erez , Murcio Roberto , Vargas-Ruiz Camilo , Masucci A. Paolo , Batty Michael
Published: April 2016

Urban systems present hierarchical structures at many different scales. These are observed as administrative regional delimitations which are the outcome of complex geographical, political and historical processes which leave almost indelible footprints on infrastructure such as the street network. In this work, we uncover a set of hierarchies in Britain at different scales using percolation theory on the street network and on its intersections which are the primary points of interaction and urban agglomeration. At the larger scales, the observed hierarchical structures can be interpreted as regional fractures of Britain, observed in various forms, from natural boundaries, such as National Parks, to regional divisions based on social class and wealth such as the well-known North–South divide. At smaller scales, cities are generated through recursive percolations on each of the emerging regional clusters. We examine the evolution of the morphology of the system as a whole, by measuring the fractal dimension of the clusters at each distance threshold in the percolation. We observe that this reaches a maximum plateau at a specific distance. The clusters defined at this distance threshold are in excellent correspondence with the boundaries of cities recovered from satellite images, and from previous methods using population density.
Understanding the group dynamics and success of teams
Authors: Klug Michael , Bagrow James P.
Published: April 2016

Complex problems often require coordinated group effort and can consume significant resources, yet our understanding of how teams form and succeed has been limited by a lack of large-scale, quantitative data. We analyse activity traces and success levels for approximately 150 000 self-organized, online team projects. While larger teams tend to be more successful, workload is highly focused across the team, with only a few members performing most work. We find that highly successful teams are significantly more focused than average teams of the same size, that their members have worked on more diverse sets of projects, and the members of highly successful teams are more likely to be core members or ‘leads’ of other teams. The relations between team success and size, focus and especially team experience cannot be explained by confounding factors such as team age, external contributions from non-team members, nor by group mechanisms such as social loafing. Taken together, these features point to organizational principles that may maximize the success of collaborative endeavours.
Sex differences in social focus across the life cycle in humans
Authors: Bhattacharya Kunal , Ghosh Asim , Monsivais Daniel , Dunbar Robin I. M. , Kaski Kimmo
Published: April 2016

Age and gender are two important factors that play crucial roles in the way organisms allocate their social effort. In this study, we analyse a large mobile phone dataset to explore the way life history influences human sociality and the way social networks are structured. Our results indicate that these aspects of human behaviour are strongly related to age and gender such that younger individuals have more contacts and, among them, males more than females. However, the rate of decrease in the number of contacts with age differs between males and females, such that there is a reversal in the number of contacts around the late 30s. We suggest that this pattern can be attributed to the difference in reproductive investments that are made by the two sexes. We analyse the inequality in social investment patterns and suggest that the age- and gender-related differences we find reflect the constraints imposed by reproduction in a context where time (a form of social capital) is limited.
Fatal diseases and parasitoids: from competition to facilitation in a shared host
Authors: Hajek Ann E. , van Nouhuys Saskya
Published: April 2016

Diverse parasite taxa share hosts both at the population level and within individual hosts, and their interactions, ranging from competitive exclusion to facilitation, can drive community structure and dynamics. Emergent pathogens have the potential to greatly alter community interactions. We found that an emergent fungal entomopathogen dominated pre-existing lethal parasites in populations of the forest defoliating gypsy moth,Lymantria dispar. The parasite community was composed of the fungus and four parasitoid species that only develop successfully after they kill the host, and a virus that produces viable propagules before the host has died. A low-density site was sampled over 17 years and compared with 66 sites across a range of host densities, including outbreaks. The emergent fungal pathogen and competing parasitoids rarely co-infected host individuals because each taxa must kill its host. The virus was not present at low host densities, but successfully co-infected with all other parasite species. In fact, there was facilitation between the virus and one parasitoid species hosting a polydnavirus. This newly formed parasite community, altered by an emergent pathogen, is shaped both by parasite response to host density and relative abilities of parasites to co-inhabit the same host individuals.