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Inverse
Kinds of Inverse Terms modified by Inverse Selected AbstractsDi-2-pyridyl Ketone Oxime in Zinc Chemistry: Inverse 12-Metallacrown-4 Complexes and Cationic Pentanuclear ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Maria Alexiou Abstract The use of di-2-pyridyl ketone oxime (Hpko)/X, "blends" (X, = PhCO2,, N3,, NCO,, acac,, NCS,) in zinc chemistry yields neutral tetranuclear and cationic pentanuclear clusters. Various synthetic procedures have led to the synthesis of compounds [Zn4(OH)2(O2CPh)2(pko)4]·3MeCN (1·3MeCN), [Zn4(OH)2(N3)2(pko)4]·4DMF (2·4DMF), [Zn4(OH)2(NCO)2(pko)4]·3DMF·H2O (3·3DMF·H2O), [Zn4(OH)2(acac)2(pko)4]·4CH2Cl2 (4·4CH2Cl2), [Zn5Cl2(pko)6][ZnCl(NCS)3]·2.5H2O·1.5MeOH (5·2.5H2O·1.5MeOH) and [Zn5(NCS)2(pko)6(MeOH)][Zn(NCS)4]·2.5H2O·MeOH (6·2.5H2O·MeOH). The structures of the six complexes have been determined by single-crystal X-ray crystallography. The tetranuclear molecules of 1,4 lie on a crystallographic inversion centre and have an inverse 12-metallacrown-4 topology. Two triply bridging hydroxides are accommodated in the centre of the metallacrown ring. The pko, ligands form a propeller configuration that imposes absolute stereoisomerism with , and , chirality. Two metal ions are in distorted O2N4 octahedral environments, whereas the rest are in severely distorted tetrahedral or trigonal bipyramidal environments. The five Zn ions of the cations of 5 and 6 are held together by six pko, ligands which adopt three different coordination modes; the chloro (5) and isothiocyanato (6) ligands are terminal. The five Zn ions define two nearly equilateral triangles sharing a common apex, and the novel Zn5 topology can be described as two "collapsed" 9-metallacrown-3 structures sharing a common Zn apex. Besides the pentanuclear cations, the structures of 5 and 6 contain slightly distorted tetrahedral [ZnCl(NCS)3]2, and [Zn(NCS)4]2, ions, respectively, with the isothiocyanato ligands binding the metal ion in a virtually linear fashion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Bone mineral density and urinary N -acetyl-,- d -glucosaminidase activity in paediatric patients with idiopathic hypercalciuriaNEPHROLOGY, Issue 2 2005SYLVA SKALOVA SUMMARY: Background: Idiopathic hypercalciuria (IH) is defined as hypercalciuria that persists after correction of dietary inbalances and has no detectable causes. Patients with IH have a higher prevalence of osteoporosis. Defective reabsorption of calcium by the renal tubule is considered a likely mechanism of IH. N -acetyl-beta- d -glucosaminidase (NAG) is a lysosomal enzyme that is a very sensitive marker of renal tubular impairment. Methods: Fifteen patients (nine boys and six girls, mean age 12.4 ± 4.0 years) with IH (urinary calcium excretion >0.1 mmol/kg per 24 h) had their bodyweight, height, body mass index (BMI), urinary NAG/creatinine ratio (U-NAG/Cr) and 24-h urinary calcium excretion (U-Ca/24 h) assessed. L1,L4 bone mineral density (BMD) was measured by dual energy X-ray absorptiometry and volumetric BMD (BMDvol) was calculated. The obtained results were expressed as Z-scores. Results: The values of basic anthropometric parameters did not differ significantly from the values of the reference population and there was a tendency to short stature, which did not reach statistical significance (P = 0.08). The values of calciuria and U-NAG/Cr were significantly higher while BMD was significantly lower when compared to the reference values (P < 0.0006, P < 0.006 and P < 0.001, respectively). Inverse and significant correlations were found between U-Ca/24 h and ,BMD, U-Ca/24 h and body height, and U-Ca/24 h and BMDvol (r = ,0.64 and ,0.70, respectively, P < 0.01; r = ,0.55, P < 0.05), while there was no correlation between U-NAG/Cr and U-Ca/24 h, nor between BMD and weight or BMD and BMI. Conclusion: Tubular impairment is highly probable in children with IH, but there is a poor relationship with the degree of calcium leakage. Idiopathic hypercalciuria should be considered as a risk factor for stunted growth and low bone mass. [source] The Mean of the Inverse of a Punctured Normal Distribution and Its ApplicationBIOMETRICAL JOURNAL, Issue 4 2004C. D. Lai Abstract The fundamental properties of a punctured normal distribution are studied. The results are applied to three issues concerning X/Y where X and Y are independent normal random variables with means ,X and ,Y respectively. First, estimation of ,X/,Y as a surrogate for E(X/Y) is justified, then the reason for preference of a weighted average, over an arithmetic average, as an estimator of ,X/,Y is given. Finally, an approximate confidence interval for ,X/,Y is provided. A grain yield data set is used to illustrate the results. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Java multithreading-based parallel approximate arrow-type inversesCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 10 2008George A. Gravvanis Abstract A new parallel shared memory Java multithreaded design and implementation of the explicit approximate inverse preconditioning, for efficiently solving arrow-type linear systems on symmetric multiprocessor systems (SMPs), is presented. A new parallel algorithm for computing a class of optimized approximate arrow-type inverse matrix is introduced. The performance on an SMP, using Java multithreading, is investigated by solving arrow-type linear systems and numerical results are given. The parallel performance of the construction of the optimized approximate inverse and the explicit preconditioned generalized conjugate gradient square scheme, using a dynamic workload scheduling, is also presented. Copyright © 2007 John Wiley & Sons, Ltd. [source] Expression and distribution of distinct variants of E-MAP-115 during proliferation and differentiation of human intestinal epithelial cellsCYTOSKELETON, Issue 4 2003Marie-Thérèse Vanier Abstract Epithelial cell proliferation and differentiation occur concomitant with striking remodeling of the cytoskeleton. Microtubules (MTs) play important roles in these processes, during which the MTs themselves are reorganized and stabilized by microtubule-associated proteins (MAPs). Among the proteins classified as structural MAPs, E-MAP-115 (also named ensconsin) is preferentially expressed in cells of epithelial origin. The aims of this study were, first, to determine if E-MAP-115, like other MAPs, is expressed as different isoforms during differentiation and, second, to perform a detailed analysis of the expression and distribution of any E-MAP-115 variants detected in intestinal epithelial cells during their polarization/differentiation. It was our expectation that these data would help us to develop hypotheses concerning the role of this MAP in epithelial development. We report the expression of three E-MAP-115 transcripts encoding isoforms of 115, 105, and 95 kDa; two display an expression gradient inverse to the third one as Caco-2 cells progress from proliferation through the stages of differentiation. To monitor the proteins produced from each transcript, we used purified polyclonal antibodies against synthetic peptides contained within the 115, 105, and 95 kDa isoforms to assay proliferating and differentiating CaCo-2 cells. Our results indicate that the expression and MT-binding capacity of the 115, 105, and 95 kDa isoforms vary upon proliferation/differentiation of the cells. E-MAP-115 proteins colocalize with MTs in proliferative and differentiated Caco-2 cells; in vivo, they are expressed in both crypt and villus epithelial cells where they are mainly concentrated at the apical pole of the cells. Cell Motil. Cytoskeleton 55:221,231, 2003. © 2003 Wiley-Liss, Inc. [source] A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birdsACTA ZOOLOGICA, Issue 1 2010R. L. Nudds Abstract Nudds, R. L. and Slove Davidson, J. 2010. A shortening of the manus precedes the attenuation of other wing-bone elements in the evolution of flightlessness in birds. ,Acta Zoologica (Stockholm) 91: 115,122 This is the first study to present evidence for a general pattern of wing-bone attenuation during the early stages of the evolution of flightlessness. A comparative analysis using phylogenetic independent contrasts showed that in families that contain both flighted (volant) and flightless species, the volant species have shorter wings and total-arm (humerus + ulna + manus) lengths relative to their body masses than the species within their wholly volant sister families. A shortening of the manus may typify the early stages of the evolution of flightlessness, with the humerus and ulna attenuating later, perhaps because of their role in maintaining the position of the aerodynamically important alula. A shorter wing relative to body mass was not the result of the inverse (i.e. heavier body mass relative to wing length) because mean body masses of volant members of flightless families were similar to or lower than those of their wholly volant sister families. Despite finding a common trend in the wing morphologies of volant members of flightless families, it seems unlikely that a general model of selection pressures driving the evolution of flightlessness exists. At the very least, a dichotomy between those birds that have lost the ability to fly in order to gain the ability to swim and terrestrial forms, may persist. [source] Energy input and zooplankton species richnessECOGRAPHY, Issue 6 2007Dag O. Hessen What are the relative contribution of temperature and solar irradiance as types of energy deliveries for species richness at the ecosystem level? In order to reveal this question in lake ecosystems, we assessed zooplankton species richness in 1891 Norwegian lakes covering a wide range in latitude, altitude, and lake area. Geographical variables could largely be replaced by temperature-related variables, e.g. annual monthly maximum temperature or growth season. Multivariate analysis (PCA) revealed that not only maximum monthly temperature, but also energy input in terms of solar radiation were closely associated with species richness. This was confirmed by stepwise, linear regression analysis in which lake area was also found to be significant. We tested the predictive power of the "metabolic scaling laws" for species richness by regressing Ln of species richness over the inverse of the air temperature (in Kelvin), corrected for the activation energy (eV) as predicted by the Boltzmann constant. A significant, negative slope of 0.78 for ln richness over temperature, given as 1/kT, was found, thus slightly higher than the range of slopes predicted from the scaling law (0.60,0.70). Temperature basically constrained the upper bound of species number, but it was only a modest predictor of actual richness. Both PCA-analysis and linear regression models left a large unexplained variance probably due to lake-specific properties such as catchment influence, lake productivity, food-web structure, immigration constraints or more stochastic effects. [source] Panel Data Discrete Choice Models with Lagged Dependent VariablesECONOMETRICA, Issue 4 2000Bo E. Honoré In this paper, we consider identification and estimation in panel data discrete choice models when the explanatory variable set includes strictly exogenous variables, lags of the endogenous dependent variable as well as unobservable individual-specific effects. For the binary logit model with the dependent variable lagged only once, Chamberlain (1993) gave conditions under which the model is not identified. We present a stronger set of conditions under which the parameters of the model are identified. The identification result suggests estimators of the model, and we show that these are consistent and asymptotically normal, although their rate of convergence is slower than the inverse of the square root of the sample size. We also consider identification in the semiparametric case where the logit assumption is relaxed. We propose an estimator in the spirit of the conditional maximum score estimator (Manski (1987)) and we show that it is consistent. In addition, we discuss an extension of the identification result to multinomial discrete choice models, and to the case where the dependent variable is lagged twice. Finally, we present some Monte Carlo evidence on the small sample performance of the proposed estimators for the binary response model. [source] Xenoestrogenic gene exression: Structural features of active polycyclic aromatic hydrocarbonsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 4 2002T. Wayne Schultz Abstract Estrogenicity was assessed using the Saccharomyces cerevisiae -based Lac-Z reporter assay and was reported as the logarithm of the inverse of the 50% molar ,-galactosidase activity (log[EC50,1]). In an effort to quantify the relationship between molecular structure of polycyclic aromatic hydrocarbons (PAHs) and estrogenic gene expression, a series of PAHs were evaluated. With noted exceptions, the results of these studies indicate that the initial two-dimensional structural warning for estrogenicity, the superpositioning of a hydroxylated aromatic system on the phenolic A-ring of 17-,-estradiol, can be extended to the PAHs. This two-dimensional-alignment criterion correctly identified estrogenicity of 22 of the 29 PAHs evaluated. Moreover, the estrogenic potency of these compounds was directly related to the size of the hydrophobic backbone. The seven compounds classified incorrectly by this structural feature were either dihydroxylated naphthalenes or aromatic nitrogen-heterocyclic compounds; all such compounds were false positives. Results with dihydroxylated naphthalenes reveal derivatives that were nonestrogenic when superimposed on the phenolic A-ring of 17-,-estradiol had the second hydroxyl group in the position of the C-ring or were catechol-like in structure. Structural alerts for nitrogen-heterocyclic compounds must take into account the position of the hydroxyl group and the in-ring nitrogen atom; compounds with the hydroxyl group and nitrogen atom involved with the same ring were observed to be nonactive. [source] Di-2-pyridyl Ketone Oxime in Zinc Chemistry: Inverse 12-Metallacrown-4 Complexes and Cationic Pentanuclear ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Maria Alexiou Abstract The use of di-2-pyridyl ketone oxime (Hpko)/X, "blends" (X, = PhCO2,, N3,, NCO,, acac,, NCS,) in zinc chemistry yields neutral tetranuclear and cationic pentanuclear clusters. Various synthetic procedures have led to the synthesis of compounds [Zn4(OH)2(O2CPh)2(pko)4]·3MeCN (1·3MeCN), [Zn4(OH)2(N3)2(pko)4]·4DMF (2·4DMF), [Zn4(OH)2(NCO)2(pko)4]·3DMF·H2O (3·3DMF·H2O), [Zn4(OH)2(acac)2(pko)4]·4CH2Cl2 (4·4CH2Cl2), [Zn5Cl2(pko)6][ZnCl(NCS)3]·2.5H2O·1.5MeOH (5·2.5H2O·1.5MeOH) and [Zn5(NCS)2(pko)6(MeOH)][Zn(NCS)4]·2.5H2O·MeOH (6·2.5H2O·MeOH). The structures of the six complexes have been determined by single-crystal X-ray crystallography. The tetranuclear molecules of 1,4 lie on a crystallographic inversion centre and have an inverse 12-metallacrown-4 topology. Two triply bridging hydroxides are accommodated in the centre of the metallacrown ring. The pko, ligands form a propeller configuration that imposes absolute stereoisomerism with , and , chirality. Two metal ions are in distorted O2N4 octahedral environments, whereas the rest are in severely distorted tetrahedral or trigonal bipyramidal environments. The five Zn ions of the cations of 5 and 6 are held together by six pko, ligands which adopt three different coordination modes; the chloro (5) and isothiocyanato (6) ligands are terminal. The five Zn ions define two nearly equilateral triangles sharing a common apex, and the novel Zn5 topology can be described as two "collapsed" 9-metallacrown-3 structures sharing a common Zn apex. Besides the pentanuclear cations, the structures of 5 and 6 contain slightly distorted tetrahedral [ZnCl(NCS)3]2, and [Zn(NCS)4]2, ions, respectively, with the isothiocyanato ligands binding the metal ion in a virtually linear fashion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Overexpression of GAP-43 modifies the distribution of the receptors for myelin-associated growth-inhibitory proteins in injured Purkinje axonsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2009Simona Foscarin Abstract Neurons with enhanced intrinsic growth capabilities can elongate their axons into non-permissive territories, but the mechanisms that enable the outgrowing processes to overcome environmental inhibition are largely unknown. To address this issue, we examined adult mouse Purkinje cells that overexpress the axonal growth-associated protein GAP-43. After injury, these neurons exhibit sprouting along the intracortical neuritic course and at the severed stump in the white matter. To determine whether GAP-43-overexpressing Purkinje cells are responsive to extrinsic inhibitory cues, we investigated the content and subcellular localization of major receptors for myelin-associated inhibitory proteins, PlexinB1 and the Nogo receptor (NgR) with the related co-receptors LINGO-1 and p75. Expression of these molecules, estimated by measuring perikaryal immunostaining intensity and Western blot, was not different in wild-type or transgenic mice, and it was not overtly modified after axotomy. Following injury, however, the content of PlexinB1 was significantly reduced in GAP-43-overexpressing neurites. Furthermore, in the same axons the distribution of both PlexinB1 and NgR was altered, being inverse to that of GAP-43. Labelling for the two receptors was conspicuously reduced on the axonal surface and it was almost undetectable in the outgrowing sprouts, which showed strong GAP-43 immunoreactivity. These observations indicate that although GAP-43 overexpression does not modify the expression of receptors for myelin-associated inhibitory factors, it interferes with their subcellular localization and exposure on the neuritic membrane. Therefore, GAP-43 promotes axon growth by multiple synergistic mechanisms that potentiate the intrinsic motility of the elongating processes, while reducing their sensitivity to environmental inhibition. [source] Enamel microhardness and bond strengths of self-etching primer adhesivesEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2 2010Olabisi A. Adebayo Adebayo OA, Burrow MF, Tyas MJ, Adams GG, Collins ML. Enamel microhardness and bond strengths of self-etching primer adhesives. Eur J Oral Sci 2010; 118: 191,196. © 2010 The Authors. Journal compilation © 2010 Eur J Oral Sci The aim of this study was to determine the relationship between enamel surface microhardness and microshear bond strength (,SBS). Buccal and lingual mid-coronal enamel sections were prepared from 22 permanent human molars and divided into two groups, each comprising the buccal and lingual enamel from 11 teeth, to analyze two self-etching primer adhesives (Clearfil SE Bond and Tokuyama Bond Force). One-half of each enamel surface was tested using the Vickers hardness test with 10 indentations at 1 N and a 15-s dwell time. A hybrid resin composite was bonded to the other half of the enamel surface with the adhesive system assigned to the group. After 24 h of water storage of specimens at 37º°C, the ,SBS test was carried out on a universal testing machine at a crosshead speed of 1 mm min,1 until bond failure occurred. The mean ,SBS was regressed on the mean Vickers hardness number (VHN) using a weighted regression analysis in order to explore the relationship between enamel hardness and ,SBS. The weights used were the inverse of the variance of the ,SBS means. Neither separate correlation analyses for each adhesive nor combined regression analyses showed a significant correlation between the VHN and the ,SBS. These results suggest that the ,SBS of the self-etch adhesive systems are not influenced by enamel surface microhardness. [source] GENES WITH SOCIAL EFFECTS ARE EXPECTED TO HARBOR MORE SEQUENCE VARIATION WITHIN AND BETWEEN SPECIESEVOLUTION, Issue 7 2009Timothy A. Linksvayer The equilibrium sequence diversity of genes within a population and the rate of sequence divergence between populations or species depends on a variety of factors, including expression pattern, mutation rate, nature of selection, random drift, and mating system. Here, we extend population genetic theory developed for maternal-effect genes to predict the equilibrium polymorphism within species and sequence divergence among species for genes with social effects on fitness. We show how the fitness effects of genes, mating system, and genetic system affect predicted gene polymorphism. We find that, because genes with indirect social effects on fitness effectively experience weaker selection, they are expected to harbor higher levels of polymorphism relative to genes with direct fitness effects. The relative increase in polymorphism is proportional to the inverse of the genetic relatedness between individuals expressing the gene and their social partners that experience the fitness effects of the gene. We find a similar pattern of more rapid divergence between populations or species for genes with indirect social effects relative to genes with direct effects. We focus our discussion on the social insects, organisms with diverse indirect genetic effects, mating and genetic systems, and we suggest specific examples for testing our predictions with emerging sociogenomic tools. [source] Fiscal Decentralisation and Empowerment: Evolving Concepts and Alternative Measures,FISCAL STUDIES, Issue 4 2008Jameson Boex H11; H70; H72 Abstract Decentralisation reforms are among the most common and significant public sector reforms, particularly in developing and transitional countries around the world. Despite the importance of the topic to policy practitioners and academic researchers alike and the extensive empirical research on the topic, there is consensus in the literature that the measures of decentralisation that are currently used are unsatisfactory. In response, we propose an alternative measure of fiscal decentralisation based on the notion that decentralisation is more than simply the inverse of centralisation. Following Bahl (2005), we consider fiscal decentralisation as ,the empowerment of people by the [fiscal] empowerment of their local governments'. Accordingly, we develop a measure of fiscal empowerment that allows us to quantify fiscal decentralisation as the gain in empowerment due to devolution and we analyse the proposed measures of empowerment and decentralisation for a cross-section of developing, transitional and industrialised countries. [source] Quantum measurement and informationFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 2-3 2003Z. Hradil The operationally defined invariant information introduced by Brukner and Zeilinger is related to the problem of estimation of quantum states. It quantifies how the estimated states differ in average from the true states in the sense of Hilbert-Schmidt norm. This information evaluates the quality of the measurement and data treatment adopted. Its ultimate limitation is given by the trace of inverse of Fisher information matrix. [source] Scaling of body temperature in mammals and birdsFUNCTIONAL ECOLOGY, Issue 1 2008Andrew Clarke Summary 1We examine variation associated with phylogeny in the scaling of body temperature in endotherms, using data from 596 species of mammal and 490 species of bird. 2Among higher groups of mammals there is statistically significant scaling of body temperature with mass in Marsupialia (positive), Ferae and Ungulata (both negative). In mammalian orders where data are available for at least 10 species, scaling is negative in three orders (Carnivora, Erinaceomorpha and Artiodactyla), positive in one (Chiroptera) and not significant in seven others. There is no relationship apparent between the scaling of body temperature and the existence of gut fermentation. As expected, monotremes exhibit the lowest body temperatures, but within marsupials diprotodonts have a mean body temperature higher than several placental groups; the traditional ranking of body temperatures in the sequence monotremes , marsupials , placentals is thus misleading. 3In birds, scaling relationships are significant only for Ciconiiformes (strongly negative) and Passeriformes (weakly positive). 4When allowance is made for phylogenetic effects, there is no significant relationship between temperature in body mass in mammals overall, but an inverse and almost significant relationship in birds. 5This study indicates a complex relationship between body mass, body temperature and metabolic rate in mammals and birds, mediated through ecology. [source] Joint full-waveform analysis of off-ground zero-offset ground penetrating radar and electromagnetic induction synthetic data for estimating soil electrical propertiesGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 3 2010D. Moghadas SUMMARY A joint analysis of full-waveform information content in ground penetrating radar (GPR) and electromagnetic induction (EMI) synthetic data was investigated to reconstruct the electrical properties of multilayered media. The GPR and EMI systems operate in zero-offset, off-ground mode and are designed using vector network analyser technology. The inverse problem is formulated in the least-squares sense. We compared four approaches for GPR and EMI data fusion. The two first techniques consisted of defining a single objective function, applying different weighting methods. As a first approach, we weighted the EMI and GPR data using the inverse of the data variance. The ideal point method was also employed as a second weighting scenario. The third approach is the naive Bayesian method and the fourth technique corresponds to GPR,EMI and EMI,GPR sequential inversions. Synthetic GPR and EMI data were generated for the particular case of a two-layered medium. Analysis of the objective function response surfaces from the two first approaches demonstrated the benefit of combining the two sources of information. However, due to the variations of the GPR and EMI model sensitivities with respect to the medium electrical properties, the formulation of an optimal objective function based on the weighting methods is not straightforward. While the Bayesian method relies on assumptions with respect to the statistical distribution of the parameters, it may constitute a relevant alternative for GPR and EMI data fusion. Sequential inversions of different configurations for a two layered medium show that in the case of high conductivity or permittivity for the first layer, the inversion scheme can not fully retrieve the soil hydrogeophysical parameters. But in the case of low permittivity and conductivity for the first layer, GPR,EMI inversion provides proper estimation of values compared to the EMI,GPR inversion. [source] Revised Pacific M-anomaly geomagnetic polarity timescaleGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2010Masako Tominaga SUMMARY The current M-anomaly geomagnetic polarity timescale (GPTS) is mainly based on the Hawaiian magnetic lineations in the Pacific Ocean. M-anomaly GPTS studies to date have relied on a small number of magnetic profiles, a situation that is not ideal because any one profile contains an uncertain amount of geologic ,noise' that perturbs the magnetic field signal. Compiling a polarity sequence from a larger array of magnetic profiles is desirable to provide greater consistency and repeatability. We present a new compilation of the M-anomaly GPTS constructed from polarity models derived from magnetic profiles crossing the three lineation sets (Hawaiian, Japanese and Phoenix) in the western Pacific. Polarity reversal boundary locations were estimated with a combination of inverse and forward modelling of the magnetic profiles. Separate GPTS were established for each of the three Pacific lineation sets, to allow examination of variability among the different lineation sets, and these were also combined to give a composite timescale. Owing to a paucity of reliable direct dates of the M-anomalies on ocean crust, the composite model was time calibrated with only two ages; one at each end of the sequence. These two dates are 125.0 Ma for the base of M0r and 155.7 Ma for the base of M26r. Relative polarity block widths from the three lineation sets are similar, indicating a consistent Pacific-wide spreading regime. The new GPTS model shows slightly different spacings of polarity blocks, as compared with previous GPTS, with less variation in block width. It appears that the greater polarity chron irregularity in older models is mostly an artifact of modelling a small number of magnetic profiles. The greater averaging of polarity chron boundaries in our model gives a GPTS that is statistically more robust than prior GPTS models and a superior foundation for Late Jurassic,Early Cretaceous geomagnetic and chronologic studies. [source] Non-double-couple mechanisms in the seismicity preceding the 1991,1993 Etna volcano eruptionGEOPHYSICAL JOURNAL INTERNATIONAL, Issue 2 2001A. Saraò Summary The temporal evolution of the complete source moment tensor is investigated for 28 earthquakes that occurred at Mt Etna in the period August 1990,December 1991 preceding the biggest eruption of the last three centuries. We perform several tests to check the robustness of the results of inversion considering different frequency ranges and different groups of stations. As well as the selection of good-quality data, the error analysis, statistically significant at the 95 per cent confidence level, is employed to validate the findings of the inversion and to distinguish between physical solutions and artefacts of modelling. For events between 0.3 and 10 km depth, strike-slip mechanisms prevail on normal, inverse and dip-slip mechanisms; this is possibly due to the dyke-induced stress dominating the overall stress field at the surface, producing a continuous switch of the tensile and compressive axes. The regional E,W tension prevails at depth, as indicated by the prevalence of normal mechanisms. An increment of the non-double-couple components is observed immediately before the eruption and can be related to movements of fluids, even though, for some events, the complex interaction between tectonic stress and volcanic activity cannot be excluded. The source time functions retrieved are in general simple and short but some show complexities, as one would expect in volcanic seismicity. From the seismic scalar moment found, we extrapolate an empirical moment,magnitude relation that we compare with other relations proposed for the same area and computed for the duration magnitude and the equivalent Wood,Anderson magnitude. [source] Interval velocity and thickness estimate from wide-angle reflection dataGEOPHYSICAL PROSPECTING, Issue 4 2001Roberto De Franco A method to estimate interval velocities and thickness in a horizontal isotropic layered medium from wide-angle reflection traveltime curves is presented. The method is based on a relationship between the squared reflection traveltime differences and the squared offset differences relative to two adjacent reflectors. The envelope of the squared-time versus offset-difference curves, for rays with the same ray parameter, is a straight line, whose slope is the inverse of the square of the interval velocity and whose intercept is the square of the interval time. The method yields velocity and thickness estimates without any knowledge of the overlying stratification. It can be applied to wide-angle reflection data when either information on the upper crust and/or refraction control on the velocity is not available. Application to synthetic and real data shows that the method, used together with other methods, allows us to define a reliable 1D starting model for estimating a depth profile using either ray tracing or another technique. [source] Can the tropical conservatism hypothesis explain temperate species richness patterns?GLOBAL ECOLOGY, Issue 4 2009An inverse latitudinal biodiversity gradient in the New World snake tribe Lampropeltini ABSTRACT Aim, A latitudinal gradient in species richness, defined as a decrease in biodiversity away from the equator, is one of the oldest known patterns in ecology and evolutionary biology. However, there are also many known cases of increasing poleward diversity, forming inverse latitudinal biodiversity gradients. As only three processes (speciation, extinction and dispersal) can directly affect species richness in areas, similar factors may be responsible for both classical (high tropical diversity) and inverse (high temperate diversity) gradients. Thus, a modified explanation for differential species richness which accounts for both patterns would be preferable to one which only explains high tropical biodiversity. Location, The New World. Methods, We test several proposed ecological, temporal, evolutionary and spatial explanations for latitudinal diversity gradients in the New World snake tribe Lampropeltini, which exhibits its highest biodiversity in temperate regions. Results, We find that an extratropical peak in species richness is not explained by latitudinal variation in diversification rate, the mid-domain effect, or Rapoport's rule. Rather, earlier colonization and longer duration in the temperate zones allowing more time for speciation to increase biodiversity, phylogenetic niche conservatism limiting tropical dispersal and the expansion of the temperate zones in the Tertiary better explain inverse diversity gradients in this group. Main conclusions, Our conclusions are the inverse of the predictions made by the tropical conservatism hypothesis to explain higher biodiversity near the equator. Therefore, we suggest that the processes invoked are not intrinsic to the tropics but are dependent on historical biogeography to determine the distribution of species richness, which we refer to as the ,biogeographical conservatism hypothesis'. [source] The Value of Subsidence Data in Ground Water Model CalibrationGROUND WATER, Issue 4 2008Tingting Yan The accurate estimation of aquifer parameters such as transmissivity and specific storage is often an important objective during a ground water modeling investigation or aquifer resource evaluation. Parameter estimation is often accomplished with changes in hydraulic head data as the key and most abundant type of observation. The availability and accessibility of global positioning system and interferometric synthetic aperture radar data in heavily pumped alluvial basins can provide important subsidence observations that can greatly aid parameter estimation. The aim of this investigation is to evaluate the value of spatial and temporal subsidence data for automatically estimating parameters with and without observation error using UCODE-2005 and MODFLOW-2000. A synthetic conceptual model (24 separate cases) containing seven transmissivity zones and three zones each for elastic and inelastic skeletal specific storage was used to simulate subsidence and drawdown in an aquifer with variably thick interbeds with delayed drainage. Five pumping wells of variable rates were used to stress the system for up to 15 years. Calibration results indicate that (1) the inverse of the square of the observation values is a reasonable way to weight the observations, (2) spatially abundant subsidence data typically produce superior parameter estimates under constant pumping even with observation error, (3) only a small number of subsidence observations are required to achieve accurate parameter estimates, and (4) for seasonal pumping, accurate parameter estimates for elastic skeletal specific storage values are largely dependent on the quantity of temporal observational data and less on the quantity of available spatial data. [source] Joint effects of coffee consumption and serum gamma-glutamyltransferase on the risk of liver cancer,HEPATOLOGY, Issue 1 2008Gang Hu Only three Japanese prospective studies have suggested an inverse association between coffee drinking and liver cancer risk. No prospective studies on the association between serum gamma-glutamyltransferase (GGT) and liver cancer risk have been reported. We aimed to determine the single and joint associations of coffee consumption and serum GGT with the risk of primary liver cancer. Study cohorts included 60,323 Finnish participants who were 25-74 years of age and free of any cancer at baseline. During a median follow-up period of 19.3 years (interquartile range: 9.3-29.2 years), 128 participants were diagnosed with an incident liver cancer. The multivariable-adjusted (age, sex, alcohol consumption, education, smoking, diabetes and chronic liver disease at baseline and during follow-up, and body mass index) hazards ratios of liver cancer in participants who drank 0-1, 2-3, 4-5, 6-7, and ,8 cups of coffee daily were 1.00, 0.66, 0.44, 0.38, and 0.32 (P for trend = 0.003), respectively. Further adjustment for serum GGT in subgroup analysis affected the results only slightly. The multivariable-adjusted and coffee-adjusted hazard ratio of liver cancer for the highest versus the lowest quartile of serum GGT was 3.13 (95% confidence interval = 1.22-8.07). The multivariable-adjusted inverse association between coffee consumption and liver cancer risk persisted when stratified by baseline factors: age more/less than 50 years, current smoker/never smoked/ever smoked, alcohol drinker/never drinker, obese/nonobese, and the highest/lowest three quartiles of serum GGT. A combination of very low coffee consumption and high level of serum GGT was associated with nearly nine-fold increased risk. Conclusion: Coffee drinking has an inverse and graded association with the risk of liver cancer. High serum GGT is associated with an increased risk of liver cancer. (HEPATOLOGY 2008.) [source] Nonlinear transient dynamic analysis by explicit finite element with iterative consistent mass matrixINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 3 2009Shen Rong Wu Abstract Various mass matrices in the explicit finite element analyses of nonlinear transient dynamic problems are investigated. The matrices are obtained as a linear combination of lumped and consistent mass matrices. An iterative procedure to calculate the inverse of the consistent and the mixed mass matrices in the framework of explicit finite element method is presented. The convergence of the iterative procedure is proved. The inverse of the consistent and mixed mass matrices is approximated by the iteration and is used to compare the results from the lumped mass matrix. For the impact of a structural component and a vehicle, some difference in the results by using coarse mesh is observed. For the component using fine mesh, no significant difference is found. Copyright © 2008 John Wiley & Sons, Ltd. [source] Special decompositions for eigenproblems in structural mechanicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2006A. Kaveh Abstract The main objective of this paper is to study those matrices which can be written as the sum of two Kronecker products. Special decompositions are proposed. Applications are extended to the eigensolution of problems from structural mechanics. It is also shown how the analysis of structures can be performed without finding the inverse of the structural matrices. Copyright © 2006 John Wiley & Sons, Ltd. [source] Numerical stability of unsteady stream-function vorticity calculationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 6 2003E. Sousa Abstract The stability of a numerical solution of the Navier,Stokes equations is usually approached by con- sidering the numerical stability of a discretized advection,diffusion equation for either a velocity component, or in the case of two-dimensional flow, the vorticity. Stability restrictions for discretized advection,diffusion equations are a very serious constraint, particularly when a mesh is refined in an explicit scheme, so an accurate understanding of the numerical stability of a discretization procedure is often of equal or greater practical importance than concerns with accuracy. The stream-function vorticity formulation provides two equations, one an advection,diffusion equation for vorticity and the other a Poisson equation between the vorticity and the stream-function. These two equations are usually not coupled when considering numerical stability. The relation between the stream-function and the vorticity is linear and so has, in principle, an exact inverse. This allows an algebraic method to link the interior and the boundary vorticity into a single iteration scheme. In this work, we derive a global time-iteration matrix for the combined system. When applied to a model problem, this matrix formulation shows differences between the numerical stability of the full system equations and that of the discretized advection,diffusion equation alone. It also gives an indication of how the wall vorticity discretization affects stability. Despite the added algebraic complexity, it is straightforward to use MATLAB to carry out all the matrix operations. Copyright © 2003 John Wiley & Sons, Ltd. [source] On the inverse of generalized ,-matrices with singular leading termINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2006N. A. Dumont Abstract An algorithm is introduced for the inverse of a ,-matrix given as the truncated series A0,i,A1,,2A2+i,3A3+,4A4+···+O(,n+1) with square coefficient matrices and singular leading term A0. Moreover, A1 may be conditionally singular and no restrictions are made for the remaining terms. The result is a ,-matrix given as a unique, truncated series of the same error order. Motivation for this problem is the evaluation of the frequency-dependent stiffness matrix of general boundary or macro-finite elements in the frame of a hybrid variational formulation that is based on a flexibility matrix F expressed as a truncated power series of the circular frequency ,. Copyright © 2005 John Wiley & Sons, Ltd. [source] An efficient diagonal preconditioner for finite element solution of Biot's consolidation equationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 4 2002K. K. Phoon Abstract Finite element simulations of very large-scale soil,structure interaction problems (e.g. excavations, tunnelling, pile-rafts, etc.) typically involve the solution of a very large, ill-conditioned, and indefinite Biot system of equations. The traditional preconditioned conjugate gradient solver coupled with the standard Jacobi (SJ) preconditioner can be very inefficient for this class of problems. This paper presents a robust generalized Jacobi (GJ) preconditioner that is extremely effective for solving very large-scale Biot's finite element equations using the symmetric quasi-minimal residual method. The GJ preconditioner can be formed, inverted, and implemented within an ,element-by-element' framework as readily as the SJ preconditioner. It was derived as a diagonal approximation to a theoretical form, which can be proven mathematically to possess an attractive eigenvalue clustering property. The effectiveness of the GJ preconditioner over a wide range of soil stiffness and permeability was demonstrated numerically using a simple three-dimensional footing problem. This paper casts a new perspective on the potentialities of the simple diagonal preconditioner, which has been commonly perceived as being useful only in situations where it can serve as an approximate inverse to a diagonally dominant coefficient matrix. Copyright © 2002 John Wiley & Sons, Ltd. [source] A high-order mass-lumping procedure for B-spline collocation method with application to incompressible flow simulationsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 12 2003O. Botella Abstract This paper presents new developments of the staggered spline collocation method for cost-effective solution to the incompressible Navier,Stokes equations. Maximal decoupling of the velocity and the pressure is obtained by using the fractional step method of Gresho and Chan, allowing the solution to sparse elliptic problems only. In order to preserve the high-accuracy of the B-spline method, this fractional step scheme is used in association with a sparse approximation to the inverse of the consistent mass matrix. Such an approximation is constructed from local spline interpolation method, and represents a high-order generalization of the mass-lumping technique of the finite-element method. A numerical investigation of the accuracy and the computational efficiency of the resulting semi-consistent spline collocation schemes is presented. These schemes generate a stable and accurate unsteady Navier,Stokes solver, as assessed by benchmark computations. Copyright © 2003 John Wiley & Sons, Ltd. [source] A rapidly converging filtered-error algorithm for multichannel active noise controlINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 7 2007A. P. Berkhoff Abstract In this paper, a multichannel adaptive control algorithm is described which has good convergence properties while having relatively small computational complexity. This complexity is similar to that of the filtered-error algorithm. In order to obtain these properties, the algorithm is based on a preprocessing step for the actuator signals using a stable and causal inverse of the minimum-phase part of the transfer path between actuators and error sensors, the secondary path. The latter algorithm is known from the literature as postconditioned filtered-error algorithm, which improves convergence rate for the case that the minimum-phase part of the secondary path increases the eigenvalue spread. However, the convergence rate of this algorithm suffers from delays in the adaptation path because adaptation rates have to be reduced for larger delays. The contribution of this paper is to modify the postconditioned filtered-error scheme in such a way that the adaptation rate can be set to a higher value. Consequently, the scheme also provides good convergence if the system contains significant delays. Furthermore, a regularized extension of the scheme is given which can be used to limit the actuator signals. Copyright © 2006 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||