Joint Analysis Of Data Research Articles

The accuracy of statistical estimates in genetic studies of aging can be significantly improved

The sample size of the data used in genetic studies is often a factor limiting the accuracy of statistical estimates. In this paper we suggest a new approach to evaluation of genetic influence on risk of development of aging-related health disorders. The approach results in substantial improvement of the accuracy of statistical estimates without an increase in the size of the genetic sample. The approach is based on the joint analysis of data from the genetic samples and easily accessible non-genetic data, such as data collected in epidemiological, demographic, and longitudinal studies of human aging and aging-related pathologies.

Combined Analysis of Women's Health Initiative Observational and Clinical Trial Data on Postmenopausal Hormone Treatment and Cardiovascular Disease

Circumstances in which both randomized controlled trial and observational study data are available provide an important opportunity to identify biases and improve study design and analysis procedures. In addition, joint analyses of data from the two sources can extend clinical trial findings. The US Women's Health Initiative includes randomized controlled trials of use of estrogen by posthysterectomy women and of estrogen plus progestin by women with a uterus, along with corresponding observational study components. In this paper, for coronary heart disease, stroke, and venous thromboembolism, results are first presented from joint analysis of estrogen clinical trial and observational study data to show that residual bias patterns are similar to those previously reported for estrogen plus progestin. These findings support certain combined analyses of the observational data on estrogen and the estrogen plus progestin clinical trial and observational study data to give adjusted observational study estimates of estrogen treatment effects. The resulting treatment effect estimates are compared with corresponding clinical trial estimates, and parallel analyses are also presented for estrogen plus progestin. An application to postmenopausal hormone treatment effects on coronary heart disease among younger women is also provided.

Handedness in Twins: Joint Analysis of Data From 35 Samples

Simultaneous analysis of handedness data from 35 samples of twins (with a combined sample size of 21,127 twin pairs) found a small but significant additive genetic effect accounting for 25.47% of the variance (95% confidence interval [CI] 15.69-29.51%). No common environmental influences were detected (C = 0.00; 95% CI 0.00-7.67%), with the majority of the variance, 74.53%, explained by factors unique to the individual (95% CI 70.49-78.67%). No significant heterogeneity was observed within studies that used similar methods to assess handedness, or across studies that used different methods. At an individual level the majority of studies had insufficient power to reject a purely unique environmental model due to insufficient power to detect familial aggregation. This lack of power is seldom mentioned within studies, and has contributed to the misconception that twin studies of handedness are not informative.

Handedness in Twins: Joint Analysis of Data From 35 Samples

AbstractSimultaneous analysis of handedness data from 35 samples of twins (with a combined sample size of 21,127 twin pairs) found a small but significant additive genetic effect accounting for 25.47% of the variance (95% confidence interval [CI] 15.69–29.51%). No common environmental influences were detected (C = 0.00; 95% CI 0.00–7.67%), with the majority of the variance, 74.53%, explained by factors unique to the individual (95% CI 70.49–78.67%). No significant heterogeneity was observed within studies that used similar methods to assess handedness, or across studies that used different methods. At an individual level the majority of studies had insufficient power to reject a purely unique environmental model due to insufficient power to detect familial aggregation. This lack of power is seldom mentioned within studies, and has contributed to the misconception that twin studies of handedness are not informative.

Constraints on the sound speed of dark energy

We have studied constraints on the equation of state, $w$, and speed of sound, ${c}_{s}$, of the dark energy from a joint analysis of data from the cosmic microwave background, large scale structure and type-Ia supernovae. We find that current observations have no significant sensitivity to ${c}_{s}$. However, there is a slight difference between models in which there are no dark energy perturbations and models in which dark energy behaves as a fluid. Assuming that there are no dark energy perturbations shifts the allowed region for $w$ to slightly higher values. At present models with and without dark energy perturbations provide roughly equally good fits to observations, but the difference is potentially important for future parameter estimations. Finally, we have also performed error forecasts for future measurements of ${c}_{s}$.

Unexpected burst of solar activity recorded by neutron monitors during October–November 2003

During the extreme burst of solar activity in October–November 2003, a series of outstanding events distinguished by their magnitude and peculiarities were recorded by the ground based neutron monitor network. The biggest and most productive in 23rd solar cycle active region 486 generated the most significant series of solar flares among of which the flare X28/3B on November 4, 2003 was the mostly powerful over the history of X-ray solar observations. The fastest arrival of the interplanetary disturbance from the Sun after the flare event in August 1972 and the highest solar wind velocity and IMF intensity were observed during these events. In one-week period three ground level enhancements (GLEs) of solar cosmic rays were recorded by neutron monitor network (28, 29 October and 2 November 2003). Maximum proton energy in these events seems to be ranged from 5 to 10 GeV. Joint analysis of data from ground level stations (neutron monitors) and satellite measurements allows the estimation of the particle path length, the onset time of the injection on the Sun and some other proton flux characteristics.

Observations of CME-related phenomena in a wide spectral range

We study pre-eruptive, eruptive, and post-eruptive phenomena related to a CME that occurred on November 23, 2000 by means of joint analyses of data from various spectral ranges. Almost all known CME-associated phenomena were observed during this event, i.e., a filament eruption, solar flare, dimmings, and a post-eruptive arcade formation. Following a chain of events observed in various spectral ranges, we find that the event occurred in an activity complex consisting of active regions 9231 and 9238, and that it was triggered by a magnetic flux emergence, which caused a flare in AR 9231. In turn, the flare triggered activation and eruption of the filament followed by the CME and the flare in AR 9238 in which the post-eruptive arcade was observed. We discuss some characteristics of the flare and CME and also estimate the magnetic field strength in the coronal arcade to be about 200 G from spatially resolved polarization measurements in microwaves with radio telescopes. In this particular case, the only significant emission mechanism is optically thin free-free emission, and the possible contribution of nonthermal emissions cannot change our estimate of the magnetic field strength in the corona. However, generally one should make sure that the nonthermal contribution cannot be important in similar cases; otherwise, the magnetic field can be well overestimated. Here, we specifically address the identification technique of the radio emission mechanism.

Cosmological constraints on the dark energy equation of state and its evolution

We have calculated constraints on the evolution of the equation of state of the dark energy,w(z), from a joint analysis of data from the cosmic microwave background, large scalestructure and type-Ia supernovae. In order to probe the time evolution ofw we propose a new, simple parametrization ofw, which has the advantage of being transparent and simple to extend tomore parameters as better data become available. Furthermore it is wellbehaved in all asymptotic limits. Based on this parametrization we find thatw(z = 0) = −1.43−0.38+0.16 anddw/dz(z = 0) = 1.0−0.8+1.0. For aconstant w we find that -1.34 ⩽ w ⩽ -0.79 at 95% CL. Thus, allowing for a time-varyingw shifts the best fitpresent day value of w down. However, even though models with time variation inw yielda lower χ2 than pure ΛCDM models, they do not have a better goodness-of-fit. Rank correlationtests on supernova data also do not show any need for a time-varyingw.

Solar cyclicity during the Maunder minimum

A multifaceted statistical study of all available data on solar activity during the Maunder minimum (1645–1715) is presented. The data include European telescope observations, Asian sunspot observations using the unaided eye, concentrations of cosmogeneous isotopes, and catalogues of polar aurorae. Joint analyses of data on the cosmogeneous isotopes 10Be and 14C are a promising source of information on solar activity in the past. The dates of relative sunspot maxima during the Maunder minimum are consistent with the idea that there were chaotic bursts of solar activity randomly distributed in time during this interval. The available evidence that the 11-year cyclicity was preserved in 1645–1715 are worthy of attention but require additional deep study and verification. No convincing evidence for a 22-year periodicity of the occurrence of sunspots during the Maunder minimum has been found.

SE—Structures and Environment: The Penman–Monteith Evapotranspiration Equation as an Element in Greenhouse Ventilation Design

Transpiration is a major cooling mechanism of greenhouse crop canopies. The larger this energy dissipation component, the smaller the required ventilation rate. The evaporation coefficient, namely the fraction of the radiation load dissipated as latent heat, is therefore an important ventilation design parameter, of which designers have currently no more than qualitative knowledge. In an attempt to overcome this difficulty, the present study proposes to incorporate the Penman–Monteith evapotranspiration equation into the standard ventilation design formula. With this modification the design adapts automatically not only to different radiation loads and temperatures, but also to different humidity conditions. The new design formula can be modified for greenhouses with an evaporative cooling system, and either air temperature or crop temperature may be used as the design criterion. The applicability of this approach depends on the availability of reliable bulk Penman–Monteith coefficients, which may be improved by a joint analysis of data from different climatic regions.

A procedure to evaluate the effect of lag-time in studying length structure and growth rate of young fish: the case of <i>Phycis blennoides</i> Brunnich, 1768 (Osteichthyes: Gadiformes) in the Central Mediterranean

The joint analysis of data from different programs represents a good opportunity to improve knowledge about the condition of any exploited populations. This note investigates the influence of lag-time in sample characteristics (growth rate and recruitment) by following a simple and quick exploratory procedure. In order to illustrate this approach, the Greater Fork-beard (Phycis blennoides Brunnich, 1768), a species with discrete recruitment pattern and available to the capture process in the first years of life, was considered . The length-frequency distributions (LFD), obtained during five spring (MEDITS - International) and successive autumn (GRUND - Italian) bottom trawl surveys, conducted from 1994 to 1998, in the Strait of Sicily and Southern Tyrrhenian Sea (Mediterranean) were analysed. The procedure was divided into three steps. Firstly, the LFD were analysed in order to estimate the mean length of the first component in each survey. Secondly, for each survey, the difference between the standardized mean lengths of the first components in the LFD of the two areas was compared with the corresponding lag-time in order to assess any systematic temporal effect in recruitment periodicity. Thirdly, for each area, the absolute and instantaneous growth rates between the spring and autumn surveys of the same year were computed on the base of the lag-time, to evaluate any difference in growth rate between the areas. The results show that the earlier the surveys begin in the Strait of Sicily, the smaller is the difference in mean length. Since the growth rates between the two areas are practically indistinguishable, the higher mean lengths observed in samples from the Strait of Sicily mainly reflect the lag-time. The reference mean growth rate found (1.03 and 0.93 cm per month in the Strait of Sicily and Southern Tyrrhenian Sea, respectively) agreed with the literature. In spring, the recruits of 0 group represent up to 90% of the whole trawl catch, and the smallest length class observed (4.5-5.0 cm) is close to the size of transition from the pelagic to the demersal one. The proposed exploratory procedure shows that systematic differences between the two investigated sub-areas in mean size and growth rate suggested by actual data are strongly reduced after having included the lag-time in the analysis.

Experimental and Numerical Verification of Similarity Concept for Dispersion of Car Exhaust Gases in Urban Street Canyons

In urban conditions, car exhaust gases are often emitted inside poorly ventilated street canyons. One may suppose however that moving cars can themselves produce a certain ventilation effect in addition to natural air motions. Such ventilation mechanism is not sufficiently studied so far. A similarity criterion relating the vehicle- and wind-induced components of turbulent motion in an urban street canyon was proposed in 1982 by E. J. Plate for wind tunnel modelling purposes. The present study aims at further evaluation of the criterion and its applicability for a variety of wind and traffic conditions. This is accomplished by joint analyses of data from numerical simulations and wind tunnel measurements.

Ion balance equation in the atmosphere

Cosmic rays are the main source of ions in the atmosphere at altitudes of 5–35 km. The flux of cosmic rays in the atmosphere depends on the site of observation and is controlled by the geomagnetic field. Except for the rare cases of solar proton events and Forbush decreases, cosmic ray flux varies slowly with changes of solar activity level. Thus there is quasi‐stationary equilibrium between the ion production and recombination processes. Usually, the equation q=αn2 is used to describe this equilibrium state, where q is the ion production rate, n is the ion concentration, and α is Thompson's coefficient of recombination. However, the joint analysis of data on ion concentration and cosmic ray fluxes observed at various latitudes shows that there is a linear relationship between ion production rate and ion concentration, q=βn, where β is the linear coefficient of ion recombination.

RESEARCH ON THE GULF STREAM FRONTAL ZONE USING SYNTHETIC-APERTURE RADAR OF THE ALMAZ-1 SPACECRAFT AND CONTACT SHIPBOARD MEASUREMENTS

The results of a joint analysis of data recorded quasisynchronously in the Gulf Stream frontal zone by a radar with a synthetic aperture radar (SAR) carried aboard the Almaz-I spacecraft and the Akademik Vernadskiy research ship (contact measurements) are presented. It is shown that the dark linear structures visible on SAR images are radar images of zones of current convergence, in which surfactants are accumulated, suppressing cm-length ripples. In the case of wave propagation in the same direction as the current, the effects of refraction and reflection of surface waves, leading to the formation of regions of concentration of waves at the current boundaries and in the wave “shadow” region, are detected and investigated.

Bow shock analysis at comets Halley and Grigg‐Skjellerup

The interaction of an active comet with the solar wind is effected by the pickup of heavy cometary ions over extended regions of space. It was predicted before any spacecraft encounters with comets that a bow shock would form at a critical point in the mass‐loaded flow. Here we present an analysis of the results from Giotto's encounters of comets Halley and Grigg‐Skjellerup on the plasma structure of the bow shock regions at the two comets. This is achieved in a joint analysis of data on solar wind and cometary ions, magnetic field, and electrons. We find that these mass‐loading shocks are among the most complex in the solar system with heavy cometary ions dominating the component pressures. Results of Mach number calculations at Halley support earlier interpretations that bow shocks were, indeed, seen with possible solar wind disturbance inbound. At Grigg‐Skjellerup, Mach number results support the interpretation of a “wave” inbound and a “shock” outbound; both features also occur near to the expected location for a bow shock. A weak correlation between magnetic field strength and electron density is noted at the Grigg‐Skjellerup outbound shock in agreement with quasi‐perpendicular hybrid simulations.

Palaeohydraulics revisited: palaeoslope estimation in coarse‐grained braided rivers

Methods for estimating palaeoslope from fluvial deposits have been available for some time, but new data and improved understanding of the relevant physical processes afford the possibility of improving existing methods, and the emerging field of quantitative stratigraphy provides a new context for the results. Here we focus on deriving palaeoslope estimates for coarse‐grained fluvial deposits. These estimates can be used in basin analyses to constrain the magnitude of the slope change necessary for a given deflection of palaeocurrents, to constrain temporal and spatial variation in basin subsidence rate, and to provide a surface datum for use in sediment‐backstripping calculations. The algorithm we derive to estimate palaeoslope applies to rivers that self‐adjust through variations in channel width to maintain a temporally and spatially averaged bed shear stress equal to some constant multiple of the critical shear stress for initial motion of bed sediment. Data from modern coarse‐grained rivers with minimal bank cohesion and form resistance suggest that this boundary shear stress is equal to about 1.4 times the critical shear stress for movement of the median‐sized clast of the surface layer. The key sedimentological criteria for recognition of systems appropriate for this type of analysis are: (1) field relations suggesting that channel banks formed in effectively noncohesive gravel (i.e. free of clay‐size sediment and plant roots); (2) absence of significant volumes of dune‐derived cross‐stratification; and (3) absence of indicators of extremely rapid, flash‐flood‐type deposition. The basic input data for a palaeoslope calculation are spatially averaged estimates of palaeodepth and median grain size. The most important aspect of data collection is that the depth and grain‐size estimates should be determined independently by random sampling over the whole outcrop. Joint analysis of data from appropriate modern rivers and of errors associated with palaeodepth and grain‐size estimates indicates that in coarse‐grained braided‐river deposits, palaeoslope can be estimated to within a factor of 2.

Analysis of Bivariate Accelerated Life Test Data for the Bivariate Exponential Distribution

SYNOPTIC ABSTRACTAccelerated life testing of a product is commonly used to reduce test time and costs. Accelerated testing is achieved by subjecting the test units to conditions that are more severe than the typical ones. The results obtained at the more severe conditions are then extrapolated to typical conditions to obtain an estimate of life distribution under typical conditions. This problem is considered when the product is a 2-component system with the bivariate exponential distribution of Marshall and Olkin (1967); our interest is the joint analysis of data with two failure times.

On a bivariate accelerated life test

Accelerated life testing of a product is commonly used to reduce test time and costs. Accelerated testing is achieved by subjecting the test units to conditions that at more severe than the normal ones. The results obtained at the more severe conditions are then extrapolated to normal conditions to obtain an estimate of life distribution under normal condition. This problem is considered when the product is a 2-component system with lifetimes following the bivariate exponential distribution of Block and Basu (1974). Here our interest is in the joint analysis of data with two failure times.

Molecular potential functions from joint analysis of gas electron diffraction and spectroscopic data

A joint analysis of electron diffraction and spectroscopic data is carried out for BF 3, PBr 3, AsBr 3, SbCl 3, SeO 2 and ClO 2 in terms of the harmonic force fields. The scheme of analysis was extended to include the following spectroscopic observables: vibrational frequencies, rotational, Coriolis coupling and centrifugal distortion constants and, whenever available, those for the isotopic species. For ClO 2 a simplified anharmonic analysis was also performed, the anharmonic spectroscopic observables being involved in this case. Compelling evidence has been presented that the conventional harmonic approximation for the force field in terms of rectilinear internal coordinates yields the simplest satisfactory representation of diffraction and spectroscopic observations. However, a consistently better fit to experimental data was found when natural curvilinear internal coordinates were used. It is shown here that for the systems considered the joint analysis of data from various sources ensures that reliable and accurate values for equilibrium distances and force field parameters are obtained. The optimized values of spectroscopic constants, structural and force field parameters obtained are presented and compared with those available from the literature.

Influence of crystallization temperature on the structure of growth surfaces of epitaxial gallium arsenide layers in the system GaAs-AsCl3-H2

Thus, joint analysis of data on the growth rate and the structure of the growth surface of epitaxial GaAs layers made it possible to obtain quantitative characteristics of the surface processes (tangential velocity of steps, average diffusion length of adsorbed particles, reaction time at a kink, density and average height of growth steps) and their dependence on the deposition temperature. The absence of qualitative changes in the microrelief in the passage from region I to region II [1] confirms that the two ranges of temperatures are kinetic while the motion of the growth steps is controlled by surface processes. For the 〈111〉A pole this consists primarily of surface-diffusion limitations while for the 〈111〉B consists of limitations on the reaction rate at the steps.