Local Departures Research Articles

New Apatite‐Type Oxide Ion Conductor, Bi2La8[(GeO4)6]O3: Structure, Properties, and Direct Imaging of Low‐Level Interstitial Oxygen Atoms Using Aberration‐Corrected Scanning Transmission Electron Microscopy

The new solid electrolyte Bi2La8[(GeO4)6]O3 is prepared and characterized by variable‐temperature synchrotron X‐ray and neutron diffraction, aberration‐corrected scanning transmission electron microscopy, and physical property measurements (impedance spectroscopy and second harmonic generation). The material is a triclinic variant of the apatite structure type and owes its ionic conductivity to the presence of oxide ion interstitials. A combination of annular bright‐field scanning transmission electron microscopy experiments and frozen‐phonon multislice simulations enables direct imaging of the crucial interstitial oxygen atoms present at a level of 8 out of 1030 electrons per formula unit of the material, and crystallographically disordered, in the unit cell. Scanning transmission electron microscopy also leads to a direct observation of the local departures from the centrosymmetric average structure determined by diffraction. As no second harmonic generation signal is observed, these displacements are non‐cooperative on the longer length scales probed by optical methods.

Imprints of massive primordial fields on large-scale structure

Attention has focussed recently on models of inflation that involve a second or more fields with a mass near the inflationary Hubble parameter H, as may occur in supersymmetric theories if the supersymmetry-breaking scale is not far from H. Quasi-single-field (QsF) inflation is a relatively simple family of phenomenological models that serve as a proxy for theories with additional fields with masses m∼ H. Since QsF inflation involves fields in addition to the inflaton, the consistency conditions between correlations that arise in single-clock inflation are not necessarily satisfied. As a result, correlation functions in the squeezed limit may be larger than in single-field inflation. Scalar non-Gaussianities mediated by the massive isocurvature field in QsF have been shown to be potentially observable. These are especially interesting since they would convey information about the mass of the isocurvature field. Here we consider non-Gaussian correlators involving tensor modes and their observational signatures. A physical correlation between a (long-wavelength) tensor mode and two scalar modes (tss), for instance, may give rise to local departures from statistical isotropy or, in other words, a non-trivial four-point function. The presence of the tensor mode may moreover be inferred geometrically from the shape dependence of the four-point function. We compute tss and stt (one soft curvature mode and two hard tensors) bispectra in QsF inflation, identifying the conditions necessary for these to “violate” the consistency relations. We find that while consistency conditions are violated by stt correlations, they are preserved by the tss in the minimal QsF model. Our study of primordial correlators which include gravitons in seeking imprints of additional fields with masses m∼ H during inflation can be seen as complementary to the recent ``cosmological collider physics'' proposal.

The land-ice contribution to 21st-century dynamic sea level rise

Abstract. Climate change has the potential to influence global mean sea level through a number of processes including (but not limited to) thermal expansion of the oceans and enhanced land ice melt. In addition to their contribution to global mean sea level change, these two processes (among others) lead to local departures from the global mean sea level change, through a number of mechanisms including the effect on spatial variations in the change of water density and transport, usually termed dynamic sea level changes. In this study, we focus on the component of dynamic sea level change that might be given by additional freshwater inflow to the ocean under scenarios of 21st-century land-based ice melt. We present regional patterns of dynamic sea level change given by a global-coupled atmosphere–ocean climate model forced by spatially and temporally varying projected ice-melt fluxes from three sources: the Antarctic ice sheet, the Greenland Ice Sheet and small glaciers and ice caps. The largest ice melt flux we consider is equivalent to almost 0.7 m of global mean sea level rise over the 21st century. The temporal evolution of the dynamic sea level changes, in the presence of considerable variations in the ice melt flux, is also analysed. We find that the dynamic sea level change associated with the ice melt is small, with the largest changes occurring in the North Atlantic amounting to 3 cm above the global mean rise. Furthermore, the dynamic sea level change associated with the ice melt is similar regardless of whether the simulated ice fluxes are applied to a simulation with fixed CO2 or under a business-as-usual greenhouse gas warming scenario of increasing CO2.

Seismicity along the Azores-Gibraltar region and global plate kinematics

Seismicity along the western part of the Eurasia–Nubia plate boundary displays very complex patterns. The average motion is transtensional in the Azores, dextral along the Gloria transform zone and convergent between the SW Portuguese Atlantic margin and the Ibero-Maghrebian zone. To constrain the factors controlling the seismicity, we provide a new seismotectonic synthesis using several earthquakes. We show that the study area can be divided into six different regions, with each characterised by a coherent seismicity pattern. The total seismic moment tensor and the average slip velocities are provided for each region. To determine the spatial distribution of the seismicity, we computed the slip vector for each earthquake based on its focal mechanism and compared it to the relative velocity between the Eurasian and Nubian plates, deduced from global kinematic models. Despite local departures in the Alboran Sea and near the Mid-Atlantic Ridge, we found a good correlation between these two independent vector sets. Quantitatively, the slip velocities display a linear, non-affine correlation with the norms of the relative kinematic velocities. The norms of the slip velocities also seem to depend on the tectonic regime and on the morphology of the plate boundary.

Replicated high-density genetic maps of two great tit populations reveal fine-scale genomic departures from sex-equal recombination rates.

Linking variation in quantitative traits to variation in the genome is an important, but challenging task in the study of life-history evolution. Linkage maps provide a valuable tool for the unravelling of such trait−gene associations. Moreover, they give insight into recombination landscapes and between-species karyotype evolution. Here we used genotype data, generated from a 10k single-nucleotide polymorphism (SNP) chip, of over 2000 individuals to produce high-density linkage maps of the great tit (Parus major), a passerine bird that serves as a model species for ecological and evolutionary questions. We created independent maps from two distinct populations: a captive F2-cross from The Netherlands (NL) and a wild population from the United Kingdom (UK). The two maps contained 6554 SNPs in 32 linkage groups, spanning 2010 cM and 1917 cM for the NL and UK populations, respectively, and were similar in size and marker order. Subtle levels of heterochiasmy within and between chromosomes were remarkably consistent between the populations, suggesting that the local departures from sex-equal recombination rates have evolved. This key and surprising result would have been impossible to detect if only one population was mapped. A comparison with zebra finch Taeniopygia guttata, chicken Gallus gallus and the green anole lizard Anolis carolinensis genomes provided further insight into the evolution of avian karyotypes.

Clustering Fossils from the Early Universe

Many inflationary theories introduce new scalar, vector, or tensor degrees of freedom that may then affect the generation of primordial density perturbations. Here we show how to search a galaxy (or 21-cm) survey for the imprint of primordial scalar, vector, and tensor fields. These new fields induce local departures to an otherwise statistically isotropic two-point correlation function, or equivalently, nontrivial four-point correlation functions (or trispectra, in Fourier space), that can be decomposed into scalar, vector, and tensor components. We write down the optimal estimators for these various components and show how the sensitivity to these modes depends on the galaxy-survey parameters. New probes of parity-violating early-Universe physics are also presented.

Practical considerations for sensitivity analysis after multiple imputation applied to epidemiological studies with incomplete data

BackgroundMultiple Imputation as usually implemented assumes that data are Missing At Random (MAR), meaning that the underlying missing data mechanism, given the observed data, is independent of the unobserved data. To explore the sensitivity of the inferences to departures from the MAR assumption, we applied the method proposed by Carpenter et al. (2007).This approach aims to approximate inferences under a Missing Not At random (MNAR) mechanism by reweighting estimates obtained after multiple imputation where the weights depend on the assumed degree of departure from the MAR assumption.MethodsThe method is illustrated with epidemiological data from a surveillance system of hepatitis C virus (HCV) infection in France during the 2001–2007 period. The subpopulation studied included 4343 HCV infected patients who reported drug use. Risk factors for severe liver disease were assessed. After performing complete-case and multiple imputation analyses, we applied the sensitivity analysis to 3 risk factors of severe liver disease: past excessive alcohol consumption, HIV co-infection and infection with HCV genotype 3.ResultsIn these data, the association between severe liver disease and HIV was underestimated, if given the observed data the chance of observing HIV status is high when this is positive. Inference for two other risk factors were robust to plausible local departures from the MAR assumption.ConclusionsWe have demonstrated the practical utility of, and advocate, a pragmatic widely applicable approach to exploring plausible departures from the MAR assumption post multiple imputation. We have developed guidelines for applying this approach to epidemiological studies.

CfA4: LIGHT CURVES FOR 94 TYPE Ia SUPERNOVAE

We present multi-band optical photometry of 94 spectroscopically-confirmed Type Ia supernovae (SN Ia) in the redshift range 0.0055 to 0.073, obtained between 2006 and 2011. There are a total of 5522 light curve points. We show that our natural system SN photometry has a precision of roughly 0.03 mag or better in BVr'i', 0.06 mag in u', and 0.07 mag in U for points brighter than 17.5 mag and estimate that it has a systematic uncertainty of 0.014, 0.010, 0.012, 0.014, 0.046, and 0.073 mag in BVr'i'u'U, respectively. Comparisons of our standard system photometry with published SN Ia light curves and comparison stars reveal mean agreement across samples in the range of ~0.00-0.03 mag. We discuss the recent measurements of our telescope-plus-detector throughput by direct monochromatic illumination by Cramer et al (in prep.). This technique measures the whole optical path through the telescope, auxiliary optics, filters, and detector under the same conditions used to make SN measurements. Extremely well-characterized natural-system passbands (both in wavelength and over time) are crucial for the next generation of SN Ia photometry to reach the 0.01 mag accuracy level. The current sample of low-z SN Ia is now sufficiently large to remove most of the statistical sampling error from the dark energy error budget. But pursuing the dark-energy systematic errors by determining highly-accurate detector passbands, combining optical and near-infrared (NIR) photometry and spectra, using the nearby sample to illuminate the population properties of SN Ia, and measuring the local departures from the Hubble flow will benefit from larger, carefully measured nearby samples.

Rotational tunneling in CH4 II: Disorder effects

Transitions within the tunneling multiplet of CH(4) in phase II have been measured in an experiment at the backscattering instrument BASIS of the Neutron Source SNS. They all involve transitions from or to T-states. A statistical model is put forward which accounts for local departures from tetrahedral symmetry at the sites of ordered molecules. Different from previous work, in which discrete sets of overlap matrix elements have been studied, now large numbers of elements as well as the ensemble of T-states are considered. The observed neutron spectra can be explained rather well, all based on the pocket state formalism of A. Hüller [Phys. Rev. B 16, 1844 (1977)]. A completely new result is the observation and simulation of transitions between T-states, which give rise to a double peaked feature close to the elastic position and which reflect the disorder in the system. CH(2)D(2) molecules in the CH(4) matrix are largely responsible for the disorder and an interesting topic for their own sake. The simple model presented may lend itself to a broader application.

Simultaneous confidence bands for nonparametric regression with functional data

We consider nonparametric regression in the context of functional data, that is, when a random sample of functions is observed on a fine grid. We obtain a functional asymptotic normality result that can provide simultaneous confidence bands (SCB) for various estimation and inference tasks. Applications to a SCB procedure for the regression function and to a goodness-of-fit test for curvilinear regression models are proposed. The first one has improved accuracy over other available methods, while the second can detect local departures from a parametric shape, as opposed to the usual goodness-of-fit tests which only track global depar- tures. A numerical study of the SCB procedures and an illustration with a speech data set are provided.

BUSDM – an algorithm for the bottom-up search of departures from a model

Searching for regions of the input space where a statistical model is inappropriate is useful in many applications. The study proposes an algorithm for finding local departures from a regression-type prediction model. The algorithm returns low-dimensional hypercubes where the average prediction error clearly departs from zero. The study describes the developed algorithm, and shows successful applications on the simulated and real data from the steel plate production. The algorithms that have been originally developed for searching regions of the high-response value from the input space are reviewed and considered as alternative methods for locating model departures. The proposed algorithm succeeds in locating the model departure regions better than the compared alternatives. The algorithm can be utilized in sequential follow-up of a model as time goes along and new data are observed.

On the Analytic Wavelet Transform

An exact and general expression for the analytic wavelet transform of a real-valued signal is constructed, resolving the time-dependent effects of non-negligible amplitude and frequency modulation. The analytic signal is first locally represented as a modulated oscillation, demodulated by its own instantaneous frequency, and then Taylor-expanded at each point in time. The terms in this expansion, called the instantaneous modulation functions, are time-varying functions which quantify, at increasingly higher orders, the local departures of the signal from a uniform sinusoidal oscillation. Closed-form expressions for these functions are found in terms of Bell polynomials and derivatives of the signal's instantaneous frequency and bandwidth. The analytic wavelet transform is shown to depend upon the interaction between the signal's instantaneous modulation functions and frequency-domain derivatives of the wavelet, inducing a hierarchy of departures of the transform away from a perfect representation of the signal. The form of these deviation terms suggests a set of conditions for matching the wavelet properties to suit the variability of the signal, in which case our expressions simplify considerably. One may then quantify the time-varying bias associated with signal estimation via wavelet ridge analysis, and choose wavelets to minimize this bias.

The study of Earth's magnetism (1269–1950): A foundation by Peregrinus and subsequent development of geomagnetism and paleomagnetism

This paper summarizes the histories of geomagnetism and paleomagnetism (1269–1950). The role of Peregrinus is emphasized. In the sixteenth century a debate on local versus global departures of the field from that of an axial dipole pitted Gilbert against Le Nautonier. Regular measurements were undertaken in the seventeenth century. At the turn of the nineteenth century, de Lamanon, de Rossel, and von Humboldt discovered the decrease of intensity as one approaches the equator. Around 1850, three figures of rock magnetism were Fournet (remanent and induced magnetizations), Delesse (remagnetization in a direction opposite to the original), and Melloni (direction of lava magnetization acquired at time of cooling). Around 1900, Brunhes discovered magnetic reversals. In the 1920s, Chevallier produced the first magnetostratigraphy and hypothesized that poles had undergone enormous displacements. Matuyama showed that the Earth's field had reversed before the Pleistocene. Our review ends in the 1940s, when exponential development of geomagnetism and paleomagnetism starts.

Analysis of Mass Transfer with Reversible Chemical Reaction

An approximate analytical technique is presented for solving nonlinear differential equations that govern steady-state mass transfer with reversible reaction. Its essential feature, which K. A. Smith devised to analyze membrane transport with rapid reaction, is linearization of the kinetics on the assumption of small local departures from equilibrium. It is shown here to yield precise estimates of enhancement factors for absorption and effectiveness factors for catalysis over complete ranges of operating regimes, from exceedingly slow reaction to instantaneous reaction.

Carbon isotope variability across the Ediacaran Yangtze platform in South China: Implications for a large surface-to-deep ocean δ13C gradient

New isotope data obtained from relatively conformable, carbonate-rich strata of the Ediacaran Yangtze platform in South China reveal substantial δ 13C variability. In platform sections, four negative δ 13C anomalies with a nadir down to ≤− 8‰ (PDB) are present in the interval between the cap carbonate level (∼ 635 Ma) and the Precambrian/Cambrian boundary (∼ 542 Ma), while in slope and basinal sections, δ 13C values are negative through the entire Doushantuo Formation (∼ 635–551 Ma). If these δ 13C values are close to their primary seawater signature, they imply a strong (≥ 10‰) surface-to-deep ocean δ 13C gradient that is consistent with long-term deep ocean anoxia and the presence of a large dissolved organic carbon (DOC) reservoir. The two prominent negative δ 13C excursions within the Doushantuo Formation above the cap carbonate level are associated with shoaling and local exposure of the platform. The anomalies may thus record remineralization of a large oceanic DOC pool via sulfate reduction that transferred 13C-depleted carbon from the oceanic DOC reservoir to the surface ocean during regression. Inconsistencies in Ediacaran δ 13C profiles globally and variations in South China in particular highlight the need for further evaluation of local departures in δ 13C from an inferred average seawater signature.

Stream temperature and the potential growth and survival of juvenile Oncorhynchus mykiss in a southern California creek

Summary1. We asked whether an increase in food supply in the field would increase the ability of fish populations to withstand climate warming, as predicted by certain bioenergetic models and aquarium experiments.2. We subsidised the in situ food supply of wild juvenile steelhead (Oncorhynchus mykiss) in a small stream near the species’ southern limit. High‐quality food (10% of fish biomass per day) was added to the drift in eight in‐stream enclosures along a naturally‐occurring thermal gradient.3. The temperatures during the experiment were well below the upper thermal limit for the species (means of enclosures ranged from 15.1 to 16.5 °C). Food supplements had no discernible effect on survival, but raised mean (± SD) specific growth rate substantially, from 0.038 ± 0.135 in controls to 2.28 ± 0.51 in feeding treatments. Food supplements doubled the variation in growth among fish.4. The mean and variance of water temperature were correlated across the enclosures, and were therefore transformed into principal component scores T1 (which expressed the stream‐wide correlation pattern) and T2 (which expressed local departures from the pattern). Even though T1 accounted for 96% of the variation in temperature mean and variance, it was not a significant predictor of fish growth. T2 was a significant predictor of growth. The predicted time to double body mass in an enclosure with a large T2 score (cool‐variable) was half that in an enclosure with a low T2 score (warm‐stable).5. Contrary to expectation, temperature effects were neutral, at least with respect to the main axis of variation among enclosures (cool‐stable versus warm‐variable). Along the orthogonal axis (cool‐variable versus warm‐stable), the effect was opposite from expectations, probably because of temperature variation. Subtle patterns of temperature heterogeneity in streams can be important to potential growth of O. mykiss.

Optical emission spectroscopy investigation of an ultra-short laser induced titanium plasma reheated by a ns laser pulse

The dynamics of a titanium plasma species, induced in air by coupling a fs-ablating laser pulse with an orthogonal ns-reheating laser source placed at the fixed distance of 1.0 mm from the target surface, has been followed by temporally resolved emission spectroscopy. The temporal evolutions of plasma features such as excitation temperatures and electron densities have been evaluated by using two different laser energies of the first fs-ablating laser pulse (0.8 mJ and 3.0 mJ). Optimum inter-pulse delay times, experimentally determined, of 250 μs and 500 μs were used for the fs laser energy of 3.0 mJ and 0.8 mJ, respectively. By experimental inspections of the main plasma species electronic transitions so obtained, a strong enhancement was evaluated up to one and two orders of magnitude for Ti(I) and Ti(II), respectively. Independently from the fs laser energy employed, the plasma features showed the same temporal behaviour implying that the ns-reheating characteristics of this process belong to the reheating mechanism itself. The experimental results have been discussed and the excited species evolutions and elementary processes involved, as well as, the local thermodynamic equilibrium departures, have been outlined.

Algorithms for bounded-influence estimation

Bounded-influence estimation is a well developed and useful theory. It provides fairly efficient estimators which are robust to outliers and local model departures. However, its use has been limited thus far, mainly because of computational difficulties. A careful implementation in modern statistical software can effectively overcome the numerical problems of bounded-influence estimators. The proposed approach is based on general methods for solving estimating equations, together with suitable methods developed in the statistical literature, such as the delta algorithm and nested iterations. The focus is on Mallows estimation in generalized linear models and on optimal bias-robust estimation in models for independent data, such as regression models with asymmetrically distributed errors.

Calcretes from a Late Quaternary interfluve in the Ganga Plains, India: Carbonate types and isotopic systems in a monsoonal setting

Calcretes are abundant in Late Quaternary channel and floodplain strata of the southern Ganga plains. In a key section at Kalpi, pedogenic carbonates (nodules, rhizoconcretions, and powdery carbonate) are present within aggradational floodplain deposits, where they correspond to relatively high monsoonal precipitation and river discharge. In contrast, groundwater carbonate has cemented degradational surfaces (discontinuities), which correspond with periods of relatively low precipitation. Mixed groundwater and pedogenic calcretes are present in the deposits of small interfluve channels, and reworked nodules line degradational surfaces and locally fill channels. Most carbonates show alpha fabrics that include floating textures, shrinkage crack fills, and grain coatings. The predominance of alpha fabrics is unexpected, but is characteristic of calcretes across dryland and seasonal parts of northern India, where soil formation led to only weakly developed or poorly preserved beta fabrics. Interpretation of δ 13C and δ 18O values of bulk and microdrilled calcrete samples suggests relatively little variation in precipitation and vegetation types through the sampled interval at Kalpi. Floodplain deposits were vegetated with a mixture of C 4 and C 3 plants (predominantly C 4), with a higher proportion of C 3 plants associated with channel deposits. This apparent lack of variation is surprising because the sampled interval represents at least 60,000 years of Marine Isotope Stages 3–5, during which climate models suggest that Asia experienced radical fluctuations in monsoon intensity and precipitation. Some of the apparent lack of variation may be explained by preferential preservation of aggradational strata that represent relatively active monsoonal periods, as well as by the mixing of drier floodplain (C 4) and riparian (C 3) vegetation. However, local departures from the regionally based climate model cannot be ruled out. A modest upsection increase in C 4 plants may represent increased aridity and lower atmospheric CO 2. Isotopic analysis of organic matter from floodplain pedogenic nodules suggests a higher C 3 plant contribution than carbonate-based data would suggest. The preserved organic matter may reflect the annual average biomass in the soil, whereas carbonate formation may have taken place mainly during the drier season when respiration of C 4 plants was more important. In interfluve settings such as Kalpi, seasonality may strongly affect the C 3–C 4 system, with preferential preservation of only part of the biomass.

Regional residual plots for assessing the fit of linear regression models

An intuitively appealing lack-of-fit test to assess the adequacy of a regression model is introduced together with a graphical diagnostic tool. The graphical method itself includes a formal testing procedure, and, it is particularly useful to detect the location of lack-of-fit. The procedure is based on regional residuals, using subsets of the space of the independent variables. A simulation study shows that, the proposed procedures in simple linear regression have similar power as those of some popular classical lack-of-fit tests. In case of local departures from the hypothesized regression model, the new tests are shown to be more powerful. Therefore, when it becomes difficult to discriminate between systematic deviations and noise, regional residual plots are very helpful in formally locating areas of lack-of-fit in the predictor space. Data examples illustrate the ability of the new methods to detect and to locate lack-of-fit.