Home About us Contact | |||
Observed Correlations (observed + correlation)
Selected AbstractsProviding care for an elderly parent: interactions among siblings?HEALTH ECONOMICS, Issue 9 2009Roméo Fontaine Abstract This article is focused on children providing and financing long-term care for their elderly parent. The aim of this work is to highlight the interactions that may take place among siblings when deciding whether or not to become a caregiver. We look at families with two children using data from the Survey of Health, Ageing and Retirement in Europe; our sample contains 314 dependent elderly and their 628 adult children. In order to identify the interactions between siblings, we have specified a two-person discrete game model. To estimate this model, without invoking the ,coherency' condition, we have added an endogenous selection rule to solve the incompleteness problem arising from multiplicity or absence of equilibrium. Our empirical results suggest that the three classical effects identified by Manski could potentially explain the observed correlation between the siblings' caregiving behaviour. Correlated effects alone appear to be weak. Contextual interactions and endogenous interactions reveal cross-effects. The asymmetric character of the endogenous interactions is our most striking result. The younger child's involvement appears to increase the net benefit of caregiving for the elder one, whereas the elder child's involvement decreases the net benefit of caregiving for the younger child. Copyright © 2009 John Wiley & Sons, Ltd. [source] Genome size and recombination in angiosperms: a second lookJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007J. ROSS-IBARRA Abstract Despite dramatic differences in genome size , and thus space for recombination to occur , previous workers found no correlation between recombination rate and genome size in flowering plants. Here I re-investigate these claims using phylogenetic comparative methods to test a large data set of recombination data in angiosperms. I show that genome size is significantly correlated with recombination rate across a wide sampling of species and that change in genome size explains a meaningful proportion (,20%) of variation in recombination rate. I show that the strength of this correlation is comparable with that of several characters previously linked to evolutionary change in recombination rate, but argue that consideration of processes of genome size change likely make the observed correlation a conservative estimate. And finally, although I find that recombination rate increases less than proportionally to change in genome size, several mechanistic and theoretical arguments suggest that this result is not unexpected. [source] Monitoring of mutarotation of monosaccharides by hydrophilic interaction chromatographyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 6-7 2010í Pazourek Abstract Calibration based on the "single-point calibration method", a simple exponential transformation of the response function of an evaporative light scattering detector was improved and applied to analysis of selected saccharides under hydrophilic interaction chromatography mode (a polar phase LiChrospher100 DIOL, mobile phase acetonitrile/water). The improved approach to the calibration procedure yielded a calibration curve with an excellent linearity (quality coefficient <5%). This quantitative evaluation of chromatograms of D -galactose suggested that not only anomers but even pyranose and furanose forms of the anomers could be resolved , the resulting calculations of abundance of the anomeric form strongly correlated with data from the literature obtained mostly by NMR studies (analogous results were also obtained for D -arabinose, D -glucose, and D -mannose). Because of the rapid separation (retention time less than 10,min), the observed correlation enabled to monitor anomeric conversion (mutarotation) of monosaccharides. [source] Quiescent times in gamma-ray bursts , I. An observed correlation between the durations of subsequent emission episodesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2001Enrico Ramirez-Ruiz Although more than 2000 astronomical gamma-ray bursts (GRBs) have been detected, the precise progenitor responsible for these events is unknown. The temporal phenomenology observed in GRBs can significantly constrain the different models. Here we analyse the time histories of a sample of bright, long GRBs, searching for the ones exhibiting relatively long (more than 5 per cent of the total burst duration) ,quiescent times', defined as the intervals between adjacent episodes of emission during which the gamma-ray count rate drops to the background level. We find a quantitative relation between the duration of an emission episode and the quiescent time elapsed since the previous episode. We suggest here that the mechanism responsible for the extraction and the dissipation of energy has to take place in a metastable configuration, such that the longer the accumulation period, the higher the stored energy available for the next emission episode. [source] Statistical Tests for ClonalityBIOMETRICS, Issue 2 2007Colin B. Begg Summary Cancer investigators frequently conduct studies to examine tumor samples from pairs of apparently independent primary tumors with a view to determine whether they share a "clonal" origin. The genetic fingerprints of the tumors are compared using a panel of markers, often representing loss of heterozygosity (LOH) at distinct genetic loci. In this article we evaluate candidate significance tests for this purpose. The relevant information is derived from the observed correlation of the tumors with respect to the occurrence of LOH at individual loci, a phenomenon that can be evaluated using Fisher's exact test. Information is also available from the extent to which losses at the same locus occur on the same parental allele. Data from these combined sources of information can be evaluated using a simple adaptation of Fisher's exact test. The test statistic is the total number of loci at which concordant mutations occur on the same parental allele, with higher values providing more evidence in favor of a clonal origin for the two tumors. The test is shown to have high power for detecting clonality for plausible models of the alternative (clonal) hypothesis, and for reasonable numbers of informative loci, preferably located on distinct chromosomal arms. The method is illustrated using studies to identify clonality in contralateral breast cancer. Interpretation of the results of these tests requires caution due to simplifying assumptions regarding the possible variability in mutation probabilities between loci, and possible imbalances in the mutation probabilities between parental alleles. Nonetheless, we conclude that the method represents a simple, powerful strategy for distinguishing independent tumors from those of clonal origin. [source] Correlation model for spatially distributed ground-motion intensitiesEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2009Nirmal Jayaram Abstract Risk assessment of spatially distributed building portfolios or infrastructure systems requires quantification of the joint occurrence of ground-motion intensities at several sites, during the same earthquake. The ground-motion models that are used for site-specific hazard analysis do not provide information on the spatial correlation between ground-motion intensities, which is required for the joint prediction of intensities at multiple sites. Moreover, researchers who have previously computed these correlations using observed ground-motion recordings differ in their estimates of spatial correlation. In this paper, ground motions observed during seven past earthquakes are used to estimate correlations between spatially distributed spectral accelerations at various spectral periods. Geostatistical tools are used to quantify and express the observed correlations in a standard format. The estimated correlation model is also compared with previously published results, and apparent discrepancies among the previous results are explained. The analysis shows that the spatial correlation reduces with increasing separation between the sites of interest. The rate of decay of correlation typically decreases with increasing spectral acceleration period. At periods longer than 2,s, the correlations were similar for all the earthquake ground motions considered. At shorter periods, however, the correlations were found to be related to the local-site conditions (as indicated by site Vs30 values) at the ground-motion recording stations. The research work also investigates the assumption of isotropy used in developing the spatial correlation models. It is seen using the Northridge and Chi-Chi earthquake time histories that the isotropy assumption is reasonable at both long and short periods. Based on the factors identified as influencing the spatial correlation, a model is developed that can be used to select appropriate correlation estimates for use in practical risk assessment problems. Copyright © 2009 John Wiley & Sons, Ltd. [source] Interspecific relationships among growth, mortality and xylem traits of woody species from New ZealandFUNCTIONAL ECOLOGY, Issue 2 2010Sabrina E. Russo Summary 1.,Wood density is considered a key functional trait influencing the growth and survival of woody plants and has been shown to be related to a slow,fast rate-of-living continuum. Wood density is, however, an emergent trait arising from several vascular properties of wood, including the diameter and frequency of xylem conduits. 2.,We aimed to test the hypotheses that there is a set of inter-related trade-offs linked to the different functions of wood, that these trade-offs have direct consequences for tree growth and survival and that these trade-offs underlie the observed correlations between wood density and demographic rates. We evaluated the covariation between xylem anatomical traits among woody species of New Zealand and whether that covariation had the potential to constrain variation in wood density and demographic rates. 3.,Several xylem traits were strongly correlated with each other, but wood density was not correlated with any of them. We also found no significant relationships between wood density and growth or mortality rate. Instead, growth was strongly related to xylem traits associated with hydraulic capacity (conduit diameter and a conductivity index) and to maximum height, whereas mortality rate was strongly correlated only with maximum height. The diameter and frequency of conduits exhibited a significant negative relationship, suggesting a trade-off, which restricted variation in wood density and growth rate, but not mortality rate. 4.,Our results suggest, for woody species in New Zealand, that growth rate is more closely linked to xylem traits determining hydraulic conductance, rather than wood density. We also found no evidence that denser woods conferred higher survival, or that risk of cavitation caused by wide conduits increased mortality. 5.,In summary, we found little support for the idea that wood density is a good proxy for position along a fast,slow rate-of-living continuum. Instead, the strong, negative relationship between vessel diameter and frequency may constrain the realized diversity of demographic niches of tree species in New Zealand. Trade-offs in function therefore have the potential to shape functional diversity and ecology of forest communities by linking selection on structure and function to population-level dynamics. [source] Chromosome organization and gene control: It is difficult to see the picture when you are inside the frameJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2006Pernette J. Verschure Abstract The organization of the genome in the nucleus is related to its function. The functional compartmentalization of the genome is described at the nuclear, chromosomal, subchromosomal, nucleosomal, and DNA sequence level. These descriptions originate from the techniques that were used for analysis. The different levels of compartmentalization are not easily reconciled, because the techniques applied to identify genome compartmentalization generally cannot be performed in combination. We have obtained a large body of information on individual "actors" and "scenes" in the nucleus regarding genome compartmentalization, but we still do not understand how and by what pieces of equipment the "actors" play their game. The next challenge is to understand the combined operation of the various levels of functional genome organization in the nucleus, that is, how do the epigenetic and genetic levels act together. In this paper, I will highlight some of the general features and observations of functional organization of the eukaryotic genome in interphase nuclei and discuss the concepts and views based on observed correlations between genome organization and function. I will reflect on what is to be expected from this field of research when the functional levels of genome compartmentalization are integrated. In this context I will draw attention to what might be needed to improve our understanding. J. Cell. Biochem. © 2006 Wiley-Liss, Inc. [source] Theoretical studies on the structure and protonation of Cu(II) complexes of a series of tripodal aliphatic tetraamines: Good correlations with the experimental dataJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2010Sadegh Salehzadeh Abstract DFT(B3LYP) studies on first protonation step of a series of Cu(II) complexes of some tripodal tetraamines with general formula N[(CH2)nNH2][(CH2)mNH2][(CH2)pNH2] (n = m = p = 2, tren; n = 3, m = p = 2, pee; n = m = 3, p = 2, ppe; n = m = 3, tpt; n = 2, m = 3, p = 4, epb; and n = m = 3, p = 4; ppb) are reported. First, the gas-phase proton macroaffinity of all latter complexes was calculated with considering following simple reaction: [Cu(L)]2+(g) + H+(g) , [Cu(HL)]3+(g). The results showed that there is a good correlation between the calculated proton macroaffinities of all complexes with their stability constants in solution. Then, we tried to determine the possible reliable structures for microspecies involved in protonation process of above complexes. The results showed that, similar to the solid state, the [Cu(L)(H2O)]2+ and [Cu(HL)(H2O)2]3+ are most stable species for latter complexes and their protonated form, respectively, at gas phase. We found that there are acceptable correlations between the formation constants of above complexes with both the , and , of following reaction: [Cu(L)(H2O)]2+(g) + H+(g) + H2O(g) , [Cu(HL)(H2O)2]3+(g). The , of the latter reaction can be defined as a theoretically solvent,proton macroaffinity of reactant complexes because they have gained one proton and one molecule of the solvent. The unknown formation constant of [Cu(epb)]2+ complex was also predicted from the observed correlations. In addition, the first proton affinity of all complexes was studied in solution using DPCM and CPCM methods. It was shown that there is an acceptable correlation between the solvent,proton affinities of [Cu(L)(H2O)]2+ complexes with formation constants of [Cu(HL)(H2O)2]3+ complexes in solution. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010 [source] Surface-sensitive reflection-mode EXAFS from layered sample systems: the influence of surface and interface roughnessJOURNAL OF SYNCHROTRON RADIATION, Issue 4 2009P. Keil The calculation of reflection-mode grazing-incidence X-ray absorption spectra from single surfaces and (multi-)layered systems is studied here. In particular, the influence of the surface and interface roughness was investigated in detail. Simulations of grazing-incidence reflection-mode EXAFS spectra using a simple Fresnel theory neglecting any effect of roughness are compared with the Névot,Croce model and the elaborated distorted-wave Born approximation which both include surface and interface roughness. Data are presented for clean gold surfaces, where the strong influence of the surface roughness on the resulting spectra is demonstrated. Furthermore, in the case of layered systems, the influence of both the outer (air or vacuum side) surface roughness and the inner interface roughness on the reflection-mode EXAFS spectra is evaluated. The practical consequences of the observed correlations are discussed, and a quantitative data analysis of a copper sample that was oxidized in ambient air for several months is shown, including the evaluation of specular reflectivity profiles at fixed energy. [source] The link between the masses and central stellar populations of S0 galaxiesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008A. G. Bedregal ABSTRACT Using high signal-to-noise ratio VLT/FORS2 long-slit spectroscopy, we have studied the properties of the central stellar populations and dynamics of a sample of S0 galaxies in the Fornax cluster. The central absorption-line indices in these galaxies correlate well with the central velocity dispersions (,0) in accordance with what previous studies found for elliptical galaxies. However, contrary to what it is usually assumed for cluster ellipticals, the observed correlations seem to be driven by systematic age and ,-element abundance variations, and not changes in overall metallicity. We also found that the observed scatter in the index,,0 relations can be partially explained by the rotationally supported nature of these systems. Indeed, even tighter correlations exist between the line indices and the maximum circular velocity of the galaxies. This study suggests that the dynamical mass is the physical property driving these correlations, and for S0 galaxies such masses have to be estimated assuming a large degree of rotational support. The observed trends imply that the most massive S0s have the shortest star formation time-scales and the oldest stellar populations. [source] Life in the last lane: star formation and chemical evolution in an extremely gas rich dwarfMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 2 2008Ayesha Begum ABSTRACT We present an analysis of H i, H, and oxygen abundance data for NGC 3741. This galaxy has a very extended gas disc (,8.8 times the Holmberg radius), and a dark-to-luminous (i.e. stellar) mass ratio of ,149, which makes it one of the ,darkest' dwarf irregular galaxies known. However, its ratio of baryon (i.e. gas + stellar) mass to dark mass is typical of that in galaxies. Our new high-resolution H i images of the galaxy show evidence for a large-scale (purely gaseous) spiral arm and central bar. From our H i data, a rotation curve can be derived out to ,37,44 disc scalelengths in the J and B bands, respectively. This is just slightly short of the radius at which one would expect a Navarro,Frenk,White type rotation curve to start falling. The galaxy has an integrated star formation rate (SFR) of ,0.0034 M, yr,1, while the average SFR within the optical disc is ,0.0049 M, yr,1 kpc,2. Despite the gaseous spiral feature and the ongoing star formation, we find that the global gas density in NGC 3741 is significantly lower than the Toomre instability criterion. This is consistent with the behaviour seen in other dwarf galaxies. We also find that the SFR is consistent with that expected from the observed correlations between H i mass and SFR and the global Kennicutt,Schmidt law, respectively. We measure the oxygen abundance to be 12 + log(O/H) = 7.66 ± 0.10, which is consistent with that expected from the metallicity,luminosity relation, despite its extreme gas mass ratio. We also examine the issue of chemical evolution of NGC 3741 in the context of the closed-box model of chemical evolution. The effective oxygen yield of NGC 3741 is consistent with recent model estimates of closed-box yields, provided one assumes that the gas has been efficiently mixed all the way to the edge of the H i disc (i.e. greater than eight times the optical radius). This seems a priori unlikely. On the other hand, using a sample of galaxies with both interferometric H i maps and chemical abundance measurements, we find that the effective yield is anticorrelated with the total dynamical mass, as expected in leaky box models. [source] The SAURON project , IV.MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 4 2006The mass-to-light ratio, lenticular galaxies, the Fundamental Plane of elliptical, the virial mass estimator ABSTRACT We investigate the well-known correlations between the dynamical mass-to-light ratio (M/L) and other global observables of elliptical (E) and lenticular (S0) galaxies. We construct two-integral Jeans and three-integral Schwarzschild dynamical models for a sample of 25 E/S0 galaxies with SAURON integral-field stellar kinematics to about one effective (half-light) radius Re. They have well-calibrated I -band Hubble Space Telescope WFPC2 and large-field ground-based photometry, accurate surface brightness fluctuation distances, and their observed kinematics is consistent with an axisymmetric intrinsic shape. All these factors result in an unprecedented accuracy in the M/L measurements. We find a tight correlation of the form (M/L) = (3.80 ± 0.14) × (,e/200 km s,1)0.84±0.07 between the M/L (in the I band) measured from the dynamical models and the luminosity-weighted second moment ,e of the LOSVD within Re. The observed rms scatter in M/L for our sample is 18 per cent, while the inferred intrinsic scatter is ,13 per cent. The (M/L),,e relation can be included in the remarkable series of tight correlations between ,e and other galaxy global observables. The comparison of the observed correlations with the predictions of the Fundamental Plane (FP), and with simple virial estimates, shows that the ,tilt' of the FP of early-type galaxies, describing the deviation of the FP from the virial relation, is almost exclusively due to a real M/L variation, while structural and orbital non-homology have a negligible effect. When the photometric parameters are determined in the ,classic' way, using growth curves, and the ,e is measured in a large aperture, the virial mass appears to be a reliable estimator of the mass in the central regions of galaxies, and can be safely used where more ,expensive' models are not feasible (e.g. in high-redshift studies). In this case the best-fitting virial relation has the form (M/L)vir= (5.0 ± 0.1) ×Re,2e/(LG), in reasonable agreement with simple theoretical predictions. We find no difference between the M/L of the galaxies in clusters and in the field. The comparison of the dynamical M/L with the (M/L)pop inferred from the analysis of the stellar population, indicates a median dark matter fraction in early-type galaxies of ,30 per cent of the total mass inside one Re, in broad agreement with previous studies, and it also shows that the stellar initial mass function varies little among different galaxies. Our results suggest a variation in M/L at constant (M/L)pop, which seems to be linked to the galaxy dynamics. We speculate that fast-rotating galaxies have lower dark matter fractions than the slow-rotating and generally more-massive ones. If correct, this would suggest a connection between the galaxy assembly history and the dark matter halo structure. The tightness of our correlation provides some evidence against cuspy nuclear dark matter profiles in galaxies. [source] LINK BETWEEN DOMESTIC R&D AND INFLOW OF FDI: A GAME-THEORETIC ANALYSISPACIFIC ECONOMIC REVIEW, Issue 2 2008Hamid Beladi Further, the existing theoretical explanations of such empirical results appear to be inadequate. This study presents an alternative game-theoretic explanation for the observed correlations. The results show that the seemingly contradictory observed mixed correlations can be explained in an encompassing model in terms of the multinationals' competitive and interactive assessment of the efficiency and expenditure consequences that domestic R&D could generate for the undertaking domestic competitors. [source] Crucial stages of protein folding through a solvable model: Predicting target sites for enzyme-inhibiting drugsPROTEIN SCIENCE, Issue 8 2002Cristian Micheletti Abstract An exactly solvable model based on the topology of a protein native state is applied to identify bottlenecks and key sites for the folding of human immunodeficiency virus type 1 (HIV-1) protease. The predicted sites are found to correlate well with clinical data on resistance to Food and Drug Administration-approved drugs. It has been observed that the effects of drug therapy are to induce multiple mutations on the protease. The sites where such mutations occur correlate well with those involved in folding bottlenecks identified through the deterministic procedure proposed in this study. The high statistical significance of the observed correlations suggests that the approach may be promisingly used in conjunction with traditional techniques to identify candidate locations for drug attacks. [source] Dietary and physiological controls on the hydrogen and oxygen isotope ratios of hair from mid-20th century indigenous populationsAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Gabriel J. Bowen Abstract A semimechanistic model has recently been proposed to explain observed correlations between the H and O isotopic composition of hair from modern residents of the USA and the isotopic composition of drinking water, but the applicability of this model to hair from non-USA and preglobalization populations is unknown. Here we test the model against data from hair samples collected during the 1930s,1950s from populations of five continents. Although C and N isotopes confirm that the samples represent a much larger range of dietary "space" than the modern USA residents, the model is able to reproduce the observed ,2H and ,18O values given reasonable adjustments to 2 model parameters: the fraction of dietary intake derived from locally produced foods and the fraction of keratin H fixed during the in vivo synthesis of amino acids. The model is most sensitive to the local dietary intake, which appears to constitute between 60% and 80% of diet among the groups sampled. The isotopic data are consistent with a trophic-level effect on protein H isotopes, which we suggest primarily reflects mixing of 2H-enriched water and 2H-depleted food H in the body rather than fractionation during biosynthesis. Samples from Inuit groups suggest that humans with marine-dominated diets can be identified on the basis of coupled ,2H and ,18O values of hair. These results indicate a dual role for H and O isotopic measurements of keratin, including both biological (diet, physiology) and environmental (geographic movement, paleoclimate) reconstruction. Am J Phys Anthropol, 2009. © 2009 Wiley-Liss, Inc. [source] Long-Term Performance of Clarion 1.0 Cochlear Implant Users,THE LARYNGOSCOPE, Issue 7 2007Chad V. Ruffin BS Abstract Objective/Hypothesis: To evaluate the long-term performance of adult Clarion 1.0 cochlear implant users. Study Design: This was a retrospective, longitudinal study evaluating word discrimination in quiet for 31 adult cochlear implant patients with preimplantation sentence scores of less than 10%. Methods: The length of the study was 135 months with a mean follow-up length of 93 (median, 96) months. For the duration of the study, all subjects used the Clarion 1.0 cochlear implant with speech processors programmed for the use of the continuous interleaved sampling strategy. Results: There was no significant growth or decline in speech perception after 24 months postimplantation unless adverse medical events were experienced. Age at implantation was significantly and substantially negatively correlated (,11% word score per decade, r = 0.68) with most recent score, maximum score, time to maximum score, range of performance, 24- to 130-month mean score, and for any longitudinal data point tested: 3 to 6 months, 6 months, 1 year, 2 years, 5 years, and 10 years. There were no age-related declines in performance. There were no observed correlations between duration of deafness and any of the variables listed above. Conclusions: The lack of correlation between duration of deafness and performance in a cohort without residual hearing suggests the presence of a strong correlation between age and speech performance with a cochlear implant. That the cochlear implant is a safe therapy for the treatment of profound deafness is supported by the stability of scores through the 10-year study period as well as a zero rate of device failures or explantation. [source] North atlantic oscillatiodannular mode: Two paradigms,one phenomenonTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 564 2000John M. Wallace Abstract The North Atlantic Oscillation (NAO), as defined in the studies of Sir Gilbert Walker ca. 1930, and the zonal-index cycle, as elaborated by investigators at the Massachusetts Institute of Technology some twenty years later, are different interpretations of the same entity, whose time variations are well represented by the leading principal component of the northern hemisphere sea-level pressure field. The NAO paradigm envisions this phenomenon as involving a unique teleconnection pattern in the Atlantic sector that varies on interannual and longer time-scales in association with large-scale atmosphere-ocean interaction. In contrast, the zonal-index-cycle paradigm posits the existence of independent, fundamentally zonally symmetric (or ,annular') modes of variability in the northern and southern hemispheres, both of which fluctuate on intraseasonal as well as interannual time-scales. Spontaneous interactions between the zonally symmetric flow and the eddies are viewed as being largely responsible for the variability of the annular modes at the higher frequencies, and a variety of different mechanisms including, but by no means limited to, atmosphere-ocean interaction are viewed as potentially capable of forcing them at the lower frequencies. The NAO and ,annular mode' paradigms offer contradictory interpretations of the causal linkages that are responsible for the observed correlations between North Atlantic climate variability and variations in a diverse array of zonally averaged quantities. They suggest different research agendas and they evoke quite different images in the popular press. It is argued that the two paradigms cannot be equally valid and that it is in the interests of the community to come to a consensus as to which of them is more appropriate. Rules of evidence are proposed as a basis for making that decision. [source] |