Audenaert, Koenraad M. R.
2014-11-15
In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.
NASA Astrophysics Data System (ADS)
Audenaert, Koenraad M. R.
2014-11-01
In this paper, we study the quantum generalisation of the skew divergence, which is a dissimilarity measure between distributions introduced by Lee in the context of natural language processing. We provide an in-depth study of the quantum skew divergence, including its relation to other state distinguishability measures. Finally, we present a number of important applications: new continuity inequalities for the quantum Jensen-Shannon divergence and the Holevo information, and a new and short proof of Bravyi's Small Incremental Mixing conjecture.
Skewness of elliptic flow fluctuations
NASA Astrophysics Data System (ADS)
Giacalone, Giuliano; Yan, Li; Noronha-Hostler, Jacquelyn; Ollitrault, Jean-Yves
2017-01-01
Using event-by-event hydrodynamic calculations, we find that the fluctuations of the elliptic flow (v2) in the reaction plane have a negative skew. We compare the skewness of v2 fluctuations to that of initial eccentricity fluctuations. We show that skewness is the main effect lifting the degeneracy between higher-order cumulants, with negative skew corresponding to the hierarchy v2{4 } >v2{6 } observed in Pb+Pb collisions at the CERN Large Hadron Collider. We describe how the skewness can be measured experimentally and show that hydrodynamics naturally reproduces its magnitude and centrality dependence.
Measuring Skewness: A Forgotten Statistic?
ERIC Educational Resources Information Center
Doane, David P.; Seward, Lori E.
2011-01-01
This paper discusses common approaches to presenting the topic of skewness in the classroom, and explains why students need to know how to measure it. Two skewness statistics are examined: the Fisher-Pearson standardized third moment coefficient, and the Pearson 2 coefficient that compares the mean and median. The former is reported in statistical…
Skew resisting hydrodynamic seal
Conroy, William T.; Dietle, Lannie L.; Gobeli, Jeffrey D.; Kalsi, Manmohan S.
2001-01-01
A novel hydrodynamically lubricated compression type rotary seal that is suitable for lubricant retention and environmental exclusion. Particularly, the seal geometry ensures constraint of a hydrodynamic seal in a manner preventing skew-induced wear and provides adequate room within the seal gland to accommodate thermal expansion. The seal accommodates large as-manufactured variations in the coefficient of thermal expansion of the sealing material, provides a relatively stiff integral spring effect to minimize pressure-induced shuttling of the seal within the gland, and also maintains interfacial contact pressure within the dynamic sealing interface in an optimum range for efficient hydrodynamic lubrication and environment exclusion. The seal geometry also provides for complete support about the circumference of the seal to receive environmental pressure, as compared the interrupted character of seal support set forth in U.S. Pat. Nos. 5,873,576 and 6,036,192 and provides a hydrodynamic seal which is suitable for use with non-Newtonian lubricants.
Skew-normal antedependence models for skewed longitudinal data.
Chang, Shu-Ching; Zimmerman, Dale L
2016-06-01
Antedependence models, also known as transition models, have proven to be useful for longitudinal data exhibiting serial correlation, especially when the variances and/or same-lag correlations are time-varying. Statistical inference procedures associated with normal antedependence models are well-developed and have many nice properties, but they are not appropriate for longitudinal data that exhibit considerable skewness. We propose two direct extensions of normal antedependence models to skew-normal antedependence models. The first is obtained by imposing antedependence on a multivariate skew-normal distribution, and the second is a sequential autoregressive model with skew-normal innovations. For both models, necessary and sufficient conditions for [Formula: see text]th-order antedependence are established, and likelihood-based estimation and testing procedures for models satisfying those conditions are developed. The procedures are applied to simulated data and to real data from a study of cattle growth.
Locally adaptive document skew detection
NASA Astrophysics Data System (ADS)
Sauvola, Jaakko J.; Doermann, David S.; Pietikaeinen, Matti
1997-04-01
This paper proposes a new approach to the detection of local orientation and skew in document images. It is based on the observation that there are many documents where a single global estimate of the page skew is not sufficient. These documents require local adaptation to deal robustly with todays complex configurations of components on the page. The approach attempts to identify regions in the image which exhibit locally consistent physical properties and consistent physical properties and consistent orientation. To do this, we rapidly compute a coarse segmentation and delineate regions which differ with respect to layout and/or physical content. Each region is classified as text, graphics, mixed text/graphics, image or background using local features and additional features are extracted to estimate orientation. The local orientation decisions are propagated where appropriate to resolve ambiguity and to produce a global estimate of the skew for the page. The implementation of our algorithms is demonstrated on a set of images which have multiple regions with different orientations.
Kinematic correction for roller skewing
NASA Technical Reports Server (NTRS)
Savage, M.; Loewenthal, S. H.
1980-01-01
A theory of kinematic stabilization of rolling cylinders is developed for high-speed cylindrical roller bearings. This stabilization requires race and roller crowning to product changes in the rolling geometry as the roller shifts axially. These changes put a reverse skew in the rolling elements by changing the rolling taper. Twelve basic possible bearing modifications are identified in this paper. Four have single transverse convex curvature in the rollers while eight have rollers with compound transverse curvature composed of a central cylindrical band of constant radius surrounded by symmetric bands with both slope and transverse curvature.
Mixture of Skewed α-Stable Distributions
NASA Astrophysics Data System (ADS)
Shojaei, S. R. Hosseini; Nassiri, V.; Mohammadian, Gh. R.; Mohammadpour, A.
2011-03-01
Expectation maximization (EM) algorithm and the Bayesian techniques are two approaches for statistical inference of mixture models [3, 4]. By noting the advantages of the Bayesian methods, practitioners prefer them. However, implementing Markov chain Monte Carlo algorithms can be very complicated for stable distributions, due to the non-analytic density or distribution function formulas. In this paper, we introduce a new class of mixture of heavy-tailed distributions, called mixture of skewed stable distributions. Skewed stable distributions belongs to the exponential family and they have analytic density representation. It is shown that skewed stable distributions dominate skew stable distribution functions and they can be used to model heavy-tailed data. The class of skewed stable distributions has an analytic representation for its density function and the Bayesian inference can be done similar to the exponential family of distributions. Finally, mixture of skewed stable distributions are compared to the mixture of stable distributions through a simulations study.
Skew aberration: a form of polarization aberration.
Yun, Garam; Crabtree, Karlton; Chipman, Russell A
2011-10-15
We define a new class of aberration, skew aberration, which is a component of polarization aberration. Skew aberration is an intrinsic rotation of polarization states due to the geometric transformation of local coordinates, independent of coatings and interface polarization. Skew aberration in a radially symmetric system has the form of a circular retardance tilt plus coma aberration. Skew aberration causes undesired polarization distribution in the exit pupil. We demonstrate statistics on skew aberration of 2383 optical systems described in Code V's U.S. patent library [Code V Version 10.3 (Synopsys, 2011), pp. 22-24]; the mean skew aberration is 0.89° and the standard deviation is 1.37°. The maximum skew aberration found is 17.45° and the minimum is -11.33°. U.S. patent 2,896,506, which has ±7.01° of skew aberration, is analyzed in detail. Skew aberration should be of concern in microlithography optics and other high NA and large field of view optical systems.
Portfolio optimization with skewness and kurtosis
NASA Astrophysics Data System (ADS)
Lam, Weng Hoe; Jaaman, Saiful Hafizah Hj.; Isa, Zaidi
2013-04-01
Mean and variance of return distributions are two important parameters of the mean-variance model in portfolio optimization. However, the mean-variance model will become inadequate if the returns of assets are not normally distributed. Therefore, higher moments such as skewness and kurtosis cannot be ignored. Risk averse investors prefer portfolios with high skewness and low kurtosis so that the probability of getting negative rates of return will be reduced. The objective of this study is to compare the portfolio compositions as well as performances between the mean-variance model and mean-variance-skewness-kurtosis model by using the polynomial goal programming approach. The results show that the incorporation of skewness and kurtosis will change the optimal portfolio compositions. The mean-variance-skewness-kurtosis model outperforms the mean-variance model because the mean-variance-skewness-kurtosis model takes skewness and kurtosis into consideration. Therefore, the mean-variance-skewness-kurtosis model is more appropriate for the investors of Malaysia in portfolio optimization.
Alternating Skew Deviation from Traumatic Intracranial Hypotension
Moster, Stephen J.; Moster, Mark L.
2014-01-01
Abstract A 56-year-old woman developed progressive headache, mental status changes, and diplopia after trauma. She was diagnosed with alternating skew deviation caused by intracranial hypotension. This is the first case of alternating skew deviation reported from intracranial hypotension and perhaps a differential pressure between intracranial and intraspinal spaces plays a role in the development of these findings. PMID:27928294
Agrawal, Prateek; Chacko, Zackaria; Fortes, Elaine C. F. S.; ...
2016-05-10
We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects minimal flavor violation and is, therefore, naturally consistent with flavor constraints. We study the phenomenology of a benchmark model in whichmore » dark matter couples to right-handed charged leptons. In large regions of parameter space, the dark matter can emerge as a thermal relic, while remaining consistent with the constraints from direct and indirect detection. The collider signatures of this scenario include events with multiple leptons and missing energy. In conclusion, these events exhibit a characteristic flavor pattern that may allow this class of models to be distinguished from other theories of dark matter.« less
Agrawal, Prateek; Chacko, Zackaria; Fortes, Elaine C. F. S.; Kilic, Can
2016-05-10
We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects minimal flavor violation and is, therefore, naturally consistent with flavor constraints. We study the phenomenology of a benchmark model in which dark matter couples to right-handed charged leptons. In large regions of parameter space, the dark matter can emerge as a thermal relic, while remaining consistent with the constraints from direct and indirect detection. The collider signatures of this scenario include events with multiple leptons and missing energy. In conclusion, these events exhibit a characteristic flavor pattern that may allow this class of models to be distinguished from other theories of dark matter.
Agrawal, Prateek; Chacko, Zackaria; Fortes, Elaine C. F. S.; Kilic, Can
2016-05-10
We explore a novel flavor structure in the interactions of dark matter with the Standard Model. We consider theories in which both the dark matter candidate, and the particles that mediate its interactions with the Standard Model fields, carry flavor quantum numbers. The interactions are skewed in flavor space, so that a dark matter particle does not directly couple to the Standard Model matter fields of the same flavor, but only to the other two flavors. This framework respects minimal flavor violation and is, therefore, naturally consistent with flavor constraints. We study the phenomenology of a benchmark model in which dark matter couples to right-handed charged leptons. In large regions of parameter space, the dark matter can emerge as a thermal relic, while remaining consistent with the constraints from direct and indirect detection. The collider signatures of this scenario include events with multiple leptons and missing energy. In conclusion, these events exhibit a characteristic flavor pattern that may allow this class of models to be distinguished from other theories of dark matter.
Skew chicane based betatron eigenmode exchange module
Douglas, David
2010-12-28
A skewed chicane eigenmode exchange module (SCEEM) that combines in a single beamline segment the separate functionalities of a skew quad eigenmode exchange module and a magnetic chicane. This module allows the exchange of independent betatron eigenmodes, alters electron beam orbit geometry, and provides longitudinal parameter control with dispersion management in a single beamline segment with stable betatron behavior. It thus reduces the spatial requirements for multiple beam dynamic functions, reduces required component counts and thus reduces costs, and allows the use of more compact accelerator configurations than prior art design methods.
Variance and skewness in the FIRST survey
NASA Astrophysics Data System (ADS)
Magliocchetti, M.; Maddox, S. J.; Lahav, O.; Wall, J. V.
1998-10-01
We investigate the large-scale clustering of radio sources in the FIRST 1.4-GHz survey by analysing the distribution function (counts in cells). We select a reliable sample from the the FIRST catalogue, paying particular attention to the problem of how to define single radio sources from the multiple components listed. We also consider the incompleteness of the catalogue. We estimate the angular two-point correlation function w(theta), the variance Psi_2 and skewness Psi_3 of the distribution for the various subsamples chosen on different criteria. Both w(theta) and Psi_2 show power-law behaviour with an amplitude corresponding to a spatial correlation length of r_0~10h^-1Mpc. We detect significant skewness in the distribution, the first such detection in radio surveys. This skewness is found to be related to the variance through Psi_3=S_3(Psi_2)^alpha, with alpha=1.9+/-0.1, consistent with the non-linear gravitational growth of perturbations from primordial Gaussian initial conditions. We show that the amplitude of variance and the skewness are consistent with realistic models of galaxy clustering.
Bayesian Inference for Skewed Stable Distributions
NASA Astrophysics Data System (ADS)
Shokripour, Mona; Nassiri, Vahid; Mohammadpour, Adel
2011-03-01
Stable distributions are a class of distributions which allow skewness and heavy tail. Non-Gaussian stable random variables play the role of normal distribution in the central limit theorem, for normalized sums of random variables with infinite variance. The lack of analytic formula for density and distribution functions of stable random variables has been a major drawback to the use of stable distributions, also in the case of inference in Bayesian framework. Buckle introduced priors for the parameters of stable random variables to obtain an analytic form of posterior distribution. However, many researchers tried to solve the problem, through the Markov chain Monte Carlo methods, e.g. [8] and their references. In this paper a new class of heavy-tailed distribution is introduced, called skewed stable. This class has two main advantages: It has many inferential advantages, since it is a member of exponential family, so the Bayesian inference can be drawn similar to the exponential family of distributions and modelling skew data with stable distributions is dominated by this family. Finally, Bayesian inference for skewed stable arc compared to the stable distributions through a few simulations study.
ROTATIONAL RESPONSE OF SKEWED BRIDGE UNDER STRONG SEISMIC EXCITATIONS
NASA Astrophysics Data System (ADS)
Hirai, Yoshiyuki; Kawashima, Kazuhiko; Matsuzaki, Hiroshi
It is well known that skewed bridges tend to rotate and collapse under the strong seismic excitation. This paper clarified the requirement for rotation of skewed bridges including straight bridges considering the gap between a deck and an abutment. Then, deck rotation response of skewed bridges in which the deck can uplift from its bearings is studied. It is shown that the skewed bridges are likely to rotate more extensively, if uplift of the deck from bearings is allowed to occur.
Topological Conjugacy Between Skew Tent Maps
NASA Astrophysics Data System (ADS)
Shi, Yong-Guo; Wang, Zhihua
This paper investigates the conjugacy of any two skew tent maps. An explicit formula is given for the conjugacy. It is proved that the conjugacy is singular, Hölder continuous and not differentiable as well as its inverse. We calculate the arc-length of the conjugacy curve and the area under the conjugacy curve. We construct a sequence of functions to approximate the conjugacy, and give an estimation for the error of the approximation.
Variance and Skewness in the FIRST Survey
NASA Astrophysics Data System (ADS)
Magliocchetti, M.; Maddox, S. J.; Lahav, O.; Wall, J. V.
We investigate the large-scale clustering of radio sources by analysing the distribution function of the FIRST 1.4 GHz survey. We select a reliable galaxy sample from the FIRST catalogue, paying particular attention to the definition of single radio sources from the multiple components listed in the FIRST catalogue. We estimate the variance, Ψ2, and skewness, Ψ3, of the distribution function for the best galaxy subsample. Ψ2 shows power-law behaviour as a function of cell size, with an amplitude corresponding a spatial correlation length of r0 ~10 h-1 Mpc. We detect significant skewness in the distribution, and find that it is related to the variance through the relation Ψ3 = S3 (Ψ2)α with α = 1.9 +/- 0.1 consistent with the non-linear growth of perturbations from primordial Gaussian initial conditions. We show that the amplitude of clustering (corresponding to a spatial correlation length of r0 ~10 h-1 Mpc) and skewness are consistent with realistic models of galaxy clustering.
Dynamic Modeling from Flight Data with Unknown Time Skews
NASA Technical Reports Server (NTRS)
Morelli, Eugene A.
2016-01-01
A method for estimating dynamic model parameters from flight data with unknown time skews is described and demonstrated. The method combines data reconstruction, nonlinear optimization, and equation-error parameter estimation in the frequency domain to accurately estimate both dynamic model parameters and the relative time skews in the data. Data from a nonlinear F-16 aircraft simulation with realistic noise, instrumentation errors, and arbitrary time skews were used to demonstrate the approach. The approach was further evaluated using flight data from a subscale jet transport aircraft, where the measured data were known to have relative time skews. Comparison of modeling results obtained from time-skewed and time-synchronized data showed that the method accurately estimates both dynamic model parameters and relative time skew parameters from flight data with unknown time skews.
Inferring climate variability from skewed proxy records
NASA Astrophysics Data System (ADS)
Emile-Geay, J.; Tingley, M.
2013-12-01
Many paleoclimate analyses assume a linear relationship between the proxy and the target climate variable, and that both the climate quantity and the errors follow normal distributions. An ever-increasing number of proxy records, however, are better modeled using distributions that are heavy-tailed, skewed, or otherwise non-normal, on account of the proxies reflecting non-normally distributed climate variables, or having non-linear relationships with a normally distributed climate variable. The analysis of such proxies requires a different set of tools, and this work serves as a cautionary tale on the danger of making conclusions about the underlying climate from applications of classic statistical procedures to heavily skewed proxy records. Inspired by runoff proxies, we consider an idealized proxy characterized by a nonlinear, thresholded relationship with climate, and describe three approaches to using such a record to infer past climate: (i) applying standard methods commonly used in the paleoclimate literature, without considering the non-linearities inherent to the proxy record; (ii) applying a power transform prior to using these standard methods; (iii) constructing a Bayesian model to invert the mechanistic relationship between the climate and the proxy. We find that neglecting the skewness in the proxy leads to erroneous conclusions and often exaggerates changes in climate variability between different time intervals. In contrast, an explicit treatment of the skewness, using either power transforms or a Bayesian inversion of the mechanistic model for the proxy, yields significantly better estimates of past climate variations. We apply these insights in two paleoclimate settings: (1) a classical sedimentary record from Laguna Pallcacocha, Ecuador (Moy et al., 2002). Our results agree with the qualitative aspects of previous analyses of this record, but quantitative departures are evident and hold implications for how such records are interpreted, and
Skew quad compensation for SPEAR minibeta optics
Wille, K.
1984-06-01
With the new minibeta insertion for SPEAR the betatron coupling and the perturbations of beam optics caused by the solenoid field of the MARK III detector can't be compensated by the simple coils used so far. Therefore another scheme with four skew quads arranged in two families has been chosen. Even though this scheme doesn't compensate the effect of the solenoid on the beam completely, the residual emittance coupling is much less than 1% which should be sufficient under all running conditions. The major advantage of this concept is its simplicity.
Temperature-Compensated Clock Skew Adjustment
Castillo-Secilla, Jose María; Palomares, Jose Manuel; Olivares, Joaquín
2013-01-01
This work analyzes several drift compensation mechanisms in wireless sensor networks (WSN). Temperature is an environmental factor that greatly affects oscillators shipped in every WSN mote. This behavior creates the need of improving drift compensation mechanisms in synchronization protocols. Using the Flooding Time Synchronization Protocol (FTSP), this work demonstrates that crystal oscillators are affected by temperature variations. Thus, the influence of temperature provokes a low performance of FTSP in changing conditions of temperature. This article proposes an innovative correction factor that minimizes the impact of temperature in the clock skew. By means of this factor, two new mechanisms are proposed in this paper: the Adjusted Temperature (AT) and the Advanced Adjusted Temperature (A2T). These mechanisms have been combined with FTSP to produce AT-FTSP and A2T-FTSP Both have been tested in a network of TelosB motes running TinyOS. Results show that both AT-FTSP and A2T-FTSP improve the average synchronization errors compared to FTSP and other temperature-compensated protocols (Environment-Aware Clock Skew Estimation and Synchronization for WSN (EACS) and Temperature Compensated Time Synchronization (TCTS)). PMID:23966192
Birth delays skew developing world's fertility figures.
1999-09-01
This article explains that birth delays skew developing world's fertility figures. When successive groups of women who have delayed childbearing start having children, the rapid fertility decline stalls. Such change in the timing of childbearing skews the total fertility rate (TFR). Analysis of the tempo component of TFR trends in Taiwan suggests that tempo effects reduced its TFR by about 10% in the late 1970s and early 1990s and by about 19% in the late 1980s. In Colombia, on the basis of increasing mean maternal age at childbirth between the 1970s and the late 1980s, tempo distortions of the TFR during the most of the 1980s seem likely. Moreover, many developing countries are now experiencing rapid fertility declines that are in part attributable to tempo changes. These changes have accelerated past fertility transitions, but they also make these countries vulnerable to future stalls in fertility when the delays in childbearing end. Since fertility reductions caused by tempo effects lead to real declines in birth rates and hence in population growth, countries that wish to reduce birth rates can take actions that encourage women to delay marriage and the onset of childbearing.
[Skew deviation. Strabismological diagnosis and treatment alternatives].
Moguel-Ancheita, Silvia; Castellanos-Pérez Bolde, Carmen Guadalupe; Orozco-Gómez, Luis Porfirio
2009-01-01
We undertook this study to analyze diagnostic and treatment alternatives in patients with skew deviation (SD). This is a prospective, observational and longitudinal study of patients with SD. The study took place in a third-level medical center during the period from September 2007 to May 2008. Strabismological exploration, multidisciplinary diagnosis and treatment alternatives were analyzed. Ten patients presenting SD were studied. Diagnoses were multiple sclerosis, arteriovenous malformation, epilepsy, hydrocephalus, ischemic encephalopathy, cortical atrophy, hypoplasia of corpus callosum and thalamic hemorrhage. Psychomotor retardation was present in 80%. Other diagnoses were Cogan apraxia, Parinaud syndrome, see-saw nystagmus, Foville syndrome, and hemiplegic alterations. Related strabismuses were exotropia (5), esotropia (3), hypertropia (2), and dissociated vertical deviation (1). Lesions of II, III and VII cranial nerves were found. Complete strabological study allows a better diagnosis of the lesion and consequently relapsing disease in order to achieve a better treatment according to each patient. Optical rehabilitation and botulinum applications are especially indicated.
Incorporating covariates in skewed functional data models.
Li, Meng; Staicu, Ana-Maria; Bondell, Howard D
2015-07-01
We introduce a class of covariate-adjusted skewed functional models (cSFM) designed for functional data exhibiting location-dependent marginal distributions. We propose a semi-parametric copula model for the pointwise marginal distributions, which are allowed to depend on covariates, and the functional dependence, which is assumed covariate invariant. The proposed cSFM framework provides a unifying platform for pointwise quantile estimation and trajectory prediction. We consider a computationally feasible procedure that handles densely as well as sparsely observed functional data. The methods are examined numerically using simulations and is applied to a new tractography study of multiple sclerosis. Furthermore, the methodology is implemented in the R package cSFM, which is publicly available on CRAN.
Cracked shells under skew-symmetric loading
NASA Technical Reports Server (NTRS)
Lelale, F.
1982-01-01
A shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and antiplane elasticity solutions. Extensive results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform inplane shearing, out of plane shearing, and torsion. The effect of orthotropy on the results is also studied.
A Method for Controlling Skew on Linked Surfaces
BENZLEY,STEVEN E.; KERR,ROBERT A.; MITCHELL,SCOTT A.; WHITE,DAVID R.
1999-09-27
A new method for lessening skew in mapped meshes is presented. This new method involves progressive subdivision of a surface into loops consisting of four sides. Using these loops, constraints can then be set on the curves of the surface, which will propagate interval assignments across the surface, allowing a mesh with a better skew metric to be generated.
Analysis of carbon dioxide concentration skewness at a rural site.
Pérez, Isidro A; Sánchez, M Luisa; García, M Ángeles; Ozores, Marta; Pardo, Nuria
2014-04-01
This paper provides evidence that symmetry of CO2 concentration distribution may indicate sources or dispersive processes. Skewness was calculated by different procedures with CO2 measured at a rural site using a Picarro G1301 analyser over a two-year period. The usual skewness coefficient was considered together with fourteen robust estimators. A noticeable contrast was obtained between day and night, and skewness decreased linearly with the logarithm of the height. One coefficient was selected from its satisfactory relationship with the median concentration in daily evolution. Three analyses based on the kernel smoothing method were conducted with this coefficient to investigate its response to yearly and daily evolutions, wind direction, and wind speed. Left-skewed distributions were linked to thermal turbulence during midday, especially in spring-summer, or with high wind speeds. Almost symmetric distributions were associated with sources, such as the Valladolid City plume reinforced with spring emissions and the lack of emissions in summer in the remaining directions. Finally, right-skewed distributions were related to low wind speeds and stable stratification at night, furthered by strong emissions in spring. Skewness intervals were proposed and their average median concentrations were calculated such that the relationship between skewness and concentration depends on the analysis performed. Since some skewness coefficients may also be negative, they provide better information about sources or dispersive processes than concentration.
Learning a Novel Pattern through Balanced and Skewed Input
ERIC Educational Resources Information Center
McDonough, Kim; Trofimovich, Pavel
2013-01-01
This study compared the effectiveness of balanced and skewed input at facilitating the acquisition of the transitive construction in Esperanto, characterized by the accusative suffix "-n" and variable word order (SVO, OVS). Thai university students (N = 98) listened to 24 sentences under skewed (one noun with high token frequency) or…
Evolution of the derivative skewness for nonlinearly propagating waves.
Reichman, Brent O; Muhlestein, Michael B; Gee, Kent L; Neilsen, Tracianne B; Thomas, Derek C
2016-03-01
The skewness of the first time derivative of a pressure waveform, or derivative skewness, has been used previously to describe the presence of shock-like content in jet and rocket noise. Despite its use, a quantitative understanding of derivative skewness values has been lacking. In this paper, the derivative skewness for nonlinearly propagating waves is investigated using analytical, numerical, and experimental methods. Analytical expressions for the derivative skewness of an initially sinusoidal plane wave are developed and, along with numerical data, are used to describe its behavior in the preshock, sawtooth, and old-age regions. Analyses of common measurement issues show that the derivative skewness is relatively sensitive to the effects of a smaller sampling rate, but less sensitive to the presence of additive noise. In addition, the derivative skewness of nonlinearly propagating noise is found to reach greater values over a shorter length scale relative to sinusoidal signals. A minimum sampling rate is recommended for sinusoidal signals to accurately estimate derivative skewness values up to five, which serves as an approximate threshold indicating significant shock formation.
How Small Is Big: Sample Size and Skewness.
Piovesana, Adina; Senior, Graeme
2016-09-21
Sample sizes of 50 have been cited as sufficient to obtain stable means and standard deviations in normative test data. The influence of skewness on this minimum number, however, has not been evaluated. Normative test data with varying levels of skewness were compiled for 12 measures from 7 tests collected as part of ongoing normative studies in Brisbane, Australia. Means and standard deviations were computed from sample sizes of 10 to 100 drawn with replacement from larger samples of 272 to 973 cases. The minimum sample size was determined by the number at which both mean and standard deviation estimates remained within the 90% confidence intervals surrounding the population estimates. Sample sizes of greater than 85 were found to generate stable means and standard deviations regardless of the level of skewness, with smaller samples required in skewed distributions. A formula was derived to compute recommended sample size at differing levels of skewness.
NASA Astrophysics Data System (ADS)
Lingaiah, K.; Murthy, S. T.
Results are presented of a photoelastic study of skew plates commonly employed in machine members and structures such as parts of airplane wings, missiles, ship decks and floor slabs of skew bridges and buildings. The investigation involved skew sandwich plates made of Araldite varying in width from 80 mm to 40 mm and skew angle varying from 0 to 40 deg with a 10 x 10 mm skewed cutout located at the center of the flat plate subjected to inplane loads offset from the centroidal axis of the plates. The maximum tangential stress was found to increase at critical point A around cutout boundary on the maximum stress face of the plate as the eccentricity increases for various values of skew angles and different cutout-to-width ratios. The minimum stress occurs on the minimum stress face of the skew plate at critical point C. The stress concentration factor decreases at C with an increase in eccentricity for various values of cutout-to-width ratios and skew angles.
ERIC Educational Resources Information Center
Tabor, Josh
2010-01-01
On the 2009 AP[c] Statistics Exam, students were asked to create a statistic to measure skewness in a distribution. This paper explores several of the most popular student responses and evaluates which statistic performs best when sampling from various skewed populations. (Contains 8 figures, 3 tables, and 4 footnotes.)
Female reproductive synchrony predicts skewed paternity across primates
Nunn, Charles L.; Schülke, Oliver
2008-01-01
Recent studies have uncovered remarkable variation in paternity within primate groups. To date, however, we lack a general understanding of the factors that drive variation in paternity skew among primate groups and across species. Our study focused on hypotheses from reproductive skew theory involving limited control and the use of paternity “concessions” by investigating how paternity covaries with the number of males, female estrous synchrony, and rates of extragroup paternity. In multivariate and phylogenetically controlled analyses of data from 27 studies on 19 species, we found strong support for a limited control skew model, with reproductive skew within groups declining as female reproductive synchrony and the number of males per group increase. Of these 2 variables, female reproductive synchrony explained more of the variation in paternity distributions. To test whether dominant males provide incentives to subordinates to resist matings by extragroup males, that is, whether dominants make concessions of paternity, we derived a novel prediction that skew is lower within groups when threat from outside the group exists. This prediction was not supported as a primary factor underlying patterns of reproductive skew among primate species. However, our approach revealed that if concessions occur in primates, they are most likely when female synchrony is low, as these conditions provide alpha male control of paternity that is assumed by concessions models. Collectively, our analyses demonstrate that aspects of male reproductive competition are the primary drivers of reproductive skew in primates. PMID:19018288
Spin Hall Effects Due to Phonon Skew Scattering
NASA Astrophysics Data System (ADS)
Gorini, Cosimo; Eckern, Ulrich; Raimondi, Roberto
2015-08-01
A diversity of spin Hall effects in metallic systems is known to rely on Mott skew scattering. In this work its high-temperature counterpart, phonon skew scattering, which is expected to be of foremost experimental relevance, is investigated. In particular, the phonon skew scattering spin Hall conductivity is found to be practically T independent for temperatures above the Debye temperature TD. As a consequence, in Rashba-like systems a high-T linear behavior of the spin Hall angle demonstrates the dominance of extrinsic spin-orbit scattering only if the intrinsic spin splitting is smaller than the temperature.
Numerical simulation of the Langevin equation for skewed turbulence
Ermak, D. L.; Nasstrom, J. S.
1994-12-01
In this paper the authors present a numerical method for the generalized Langevin equation of motion with skewed random forcing for the case of homogeneous, skewed turbulence. The authors begin by showing how the analytic solution to the Langevin equation for this case can be used to determine the relationship between the particle velocity moments and the properties of the skewed random force. They then present a numerical method that uses simple probability distribution functions to simulate the effect of the random force. The numerical solution is shown to be exact in the limit of infinitesimal time steps, and to be within acceptable error limits when practical time steps are used.
4. From Skew Span to portal on span 1 looking ...
4. From Skew Span to portal on span 1 looking up grade toward the south end. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
LOOKING WEST, BETWEEN READING DEPOT BRIDGE AND SKEW ARCH BRIDGE ...
LOOKING WEST, BETWEEN READING DEPOT BRIDGE AND SKEW ARCH BRIDGE (HAER No. PA-116). - Philadelphia & Reading Railroad, Reading Depot Bridge, North Sixth Street at Woodward Street, Reading, Berks County, PA
2. Skewed view of E elevation of sugar mill looking ...
2. Skewed view of E elevation of sugar mill looking NW. - Hacienda Azurarera Santa Elena, Sugar Mill Ruins, 1.44 miles North of PR Route 2 Bridge Over Rio De La Plata, Toa Baja, Toa Baja Municipio, PR
7. William E. Barrett, Photographer, 1974. SKEWED VIEW SHOWING CHEAT ...
7. William E. Barrett, Photographer, 1974. SKEWED VIEW SHOWING CHEAT RIVER VALLEY, REMAINS OF 1887 PIER AND c. 1900 MASONRY ARCHES. - Baltimore & Ohio Railroad, Tray Run Viaduct, Spanning Tray Run, Rowlesburg, Preston County, WV
Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices
ERIC Educational Resources Information Center
Glaister, P.
2008-01-01
The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.
Systems of Differential Equations with Skew-Symmetric, Orthogonal Matrices
ERIC Educational Resources Information Center
Glaister, P.
2008-01-01
The solution of a system of linear, inhomogeneous differential equations is discussed. The particular class considered is where the coefficient matrix is skew-symmetric and orthogonal, and where the forcing terms are sinusoidal. More general matrices are also considered.
PRINCIPLE OF SKEW QUADRUPOLE MODULATION TO MEASURE BETATRON COUPLING.
LUO.Y.PILAT,F.ROSER,T.ET AL.
2004-07-05
The measurement of the residual betatron coupling via skew quadrupole modulation is a new diagnostics technique that has been developed and tested at the Relativistic Heavy Ion Collider (RHIC) as a very promising method for the linear decoupling on the ramp. By modulating the strengths of different skew quadrupole families the two eigentunes are precisely measured with the phase lock loop system. The projections of the residual coupling coefficient onto the skew quadrupole coupling modulation directions are determined. The residual linear coupling could be corrected according to the measurement. An analytical solution for skew quadrupole modulation based on Hamiltonian perturbation approximation is given, and simulation code using smooth accelerator model is also developed. Some issues concerning the practical applications of this technique are discussed.
Skewed paternity and sex allocation in hermaphroditic plants and animals.
Greeff, J. M.; Nason, J. D.; Compton, S. G.
2001-01-01
Models predict a reduced allocation to sperm when females preferentially use one of two males' sperm and the males do not know who is favoured. An analogous discounting occurs in plants when their paternity success is skewed by random, non-heritable factors such as location in the population and pollinator behaviour. We present a model that shows that skewed paternity can affect the sex allocation of hermaphrodites, that is it leads to a female-biased investment. The model highlights the close links between local mate competition and sperm competition. We use paternity data from Ficus in order to illustrate that skews in paternity success can lead to a high degree of sibling gamete competition in an apparently open breeding system. Since skews in paternity are ubiquitous in hermaphroditic plants and animals these findings should apply broadly. PMID:11600078
Generation of skewed laser pulses for laser wakefield accelerators
NASA Astrophysics Data System (ADS)
Toth, C.; Faure, J.; Geddes, C. G. R.; van Tilborg, J.; Leemans, W. P.
2002-11-01
The effect of asymmetric laser pulses on electron yield from a laser wakefield accelerator has been experimentally studied (W.P. Leemans et al., submitted to Phys. Rev. Lett.) using > 10^19 cm-3 plasmas and a 10 TW, > 45 fs, Ti:Al_2O3 laser. The non-Gaussian laser pulse shapes were controlled through non-linear chirp with a grating pair compressor. Pulses (76 fs FWHM) with a steep rise (positive skew) were found to significantly enhance the electron yield compared to pulses with a gentle rise (negative skew). These results demonstrate that laser wakefield accelerator can be optimized using skewed laser pulses. Controlling the skewness of laser pulses can be done by appropriate choice of the higher order spectral phase coefficients. Details on how this is done using non-linear chirp using grating compressor, as well as an acousto-optic system (DAZZLER) will be presented.
Interior view of skewed Baltimore truss and curved deck of ...
Interior view of skewed Baltimore truss and curved deck of Bridge No. 1363, First B&O Crossing, looking west. - Western Maryland Railway, Cumberland Extension, Pearre to North Branch, from WM milepost 125 to 160, Pearre, Washington County, MD
Skewed exponential pairwise velocities from Gaussian initial conditions
Juszkiewicz, R.; Fisher, K. B.; Szapudi, I.
1998-09-01
Using an Eulerian perturbative calculation, we show that the distribution of relative pairwise velocities which arises from gravitational instability of Gaussian density fluctuations has asymmetric (skewed) exponential tails. The negative skewness is induced by the negative mean streaming velocity of pairs (the infall prevails over expansion), while the exponential tails arise because the relative pairwise velocity is a number, not volume weighted statistic. The derived probability distribution is compared with N-body simulations and shown to provide a reasonable fit.
Skewed X inactivation in Lesch-Nyhan disease carrier females.
Torres, Rosa J; Puig, Juan G
2017-09-14
X chromosome inactivation (XCI) ratios of normal females can range from a highly skewed ratio of 0:100 to a 50:50 ratio. In several X-linked disorders, female carriers present skewed X inactivation. Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency is an X-linked disorder. Males are affected and present with the complete Lesch-Nyhan disease (LND) or with a partial phenotype (Lesch-Nyhan variant, LNV). Female carriers are usually asymptomatic. The aim of the present study was to analyze the XCI pattern of HPRT-deficiency carrier females. As a group, 75% of HPRT-deficiency carrier females presented skewed XCI. Moreover, skewed XCI is significantly more frequent in LND carriers (83%) than in LNV (0-50%, depending on the phenotype severity). The ratios of the preferentially inactivated allele of carrier females were significantly higher than the ratios of the preferentially inactivated allele of noncarrier females (89.4±15, n=52 vs 65.2±12, n=52; P<0.0001). For carrier diagnosis, the presence of skewed XCI presents a sensitivity of 75% with a specificity of 85%. In LND families, the presence of skewed XCI is more sensitive for carrier diagnosis than in LNV families; however, we believe that this test is not accurate for carrier diagnostic purposes.Journal of Human Genetics advance online publication, 14 September 2017; doi:10.1038/jhg.2017.88.
Flow in Rotating Serpentine Coolant Passages With Skewed Trip Strips
NASA Technical Reports Server (NTRS)
Tse, David G.N.; Steuber, Gary
1996-01-01
Laser velocimetry was utilized to map the velocity field in serpentine turbine blade cooling passages with skewed trip strips. The measurements were obtained at Reynolds and Rotation numbers of 25,000 and 0.24 to assess the influence of trips, passage curvature and Coriolis force on the flow field. The interaction of the secondary flows induced by skewed trips with the passage rotation produces a swirling vortex and a corner recirculation zone. With trips skewed at +45 deg, the secondary flows remain unaltered as the cross-flow proceeds from the passage to the turn. However, the flow characteristics at these locations differ when trips are skewed at -45 deg. Changes in the flow structure are expected to augment heat transfer, in agreement with the heat transfer measurements of Johnson, et al. The present results show that trips are skewed at -45 deg in the outward flow passage and trips are skewed at +45 deg in the inward flow passage maximize heat transfer. Details of the present measurements were related to the heat transfer measurements of Johnson, et al. to relate fluid flow and heat transfer measurements.
Extension of EMA to address regional skew and low outliers
Griffis, V.W.; Stedinger, J.R.; Cohn, T.A.; Bizier, P.; DeBarry, P.
2003-01-01
The recently developed expected moments algorithm [EMA] (Cohn et al. 1997) does as well as MLEs at estimating LP3 flood quantiles using systematic and historical information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B and to make use of such hydrologic information. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study illustrates the performance of an extended EMA estimator compared to estimators that employ the complete data set with and without use of regional skew, conditional probability adjustment from Bulletin 17B, and an estimator that uses probability plot regression to compute substitute values for low outliers. Estimators that use a regional skew all do better than estimators that fail to use an informative regional skewness estimator. For LP3 data, the low outlier rejection procedure results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew were generally negligible in the skew range of real interest.
Sample skewness as a statistical measurement of neuronal tuning sharpness.
Samonds, Jason M; Potetz, Brian R; Lee, Tai Sing
2014-05-01
We propose using the statistical measurement of the sample skewness of the distribution of mean firing rates of a tuning curve to quantify sharpness of tuning. For some features, like binocular disparity, tuning curves are best described by relatively complex and sometimes diverse functions, making it difficult to quantify sharpness with a single function and parameter. Skewness provides a robust nonparametric measure of tuning curve sharpness that is invariant with respect to the mean and variance of the tuning curve and is straightforward to apply to a wide range of tuning, including simple orientation tuning curves and complex object tuning curves that often cannot even be described parametrically. Because skewness does not depend on a specific model or function of tuning, it is especially appealing to cases of sharpening where recurrent interactions among neurons produce sharper tuning curves that deviate in a complex manner from the feedforward function of tuning. Since tuning curves for all neurons are not typically well described by a single parametric function, this model independence additionally allows skewness to be applied to all recorded neurons, maximizing the statistical power of a set of data. We also compare skewness with other nonparametric measures of tuning curve sharpness and selectivity. Compared to these other nonparametric measures tested, skewness is best used for capturing the sharpness of multimodal tuning curves defined by narrow peaks (maximum) and broad valleys (minima). Finally, we provide a more formal definition of sharpness using a shape-based information gain measure and derive and show that skewness is correlated with this definition.
Sample Skewness as a Statistical Measurement of Neuronal Tuning Sharpness
Samonds, Jason M.; Potetz, Brian R.; Lee, Tai Sing
2014-01-01
We propose using the statistical measurement of the sample skewness of the distribution of mean firing rates of a tuning curve to quantify sharpness of tuning. For some features, like binocular disparity, tuning curves are best described by relatively complex and sometimes diverse functions, making it difficult to quantify sharpness with a single function and parameter. Skewness provides a robust nonparametric measure of tuning curve sharpness that is invariant with respect to the mean and variance of the tuning curve and is straightforward to apply to a wide range of tuning, including simple orientation tuning curves and complex object tuning curves that often cannot even be described parametrically. Because skewness does not depend on a specific model or function of tuning, it is especially appealing to cases of sharpening where recurrent interactions among neurons produce sharper tuning curves that deviate in a complex manner from the feedforward function of tuning. Since tuning curves for all neurons are not typically well described by a single parametric function, this model independence additionally allows skewness to be applied to all recorded neurons, maximizing the statistical power of a set of data. We also compare skewness with other nonparametric measures of tuning curve sharpness and selectivity. Compared to these other nonparametric measures tested, skewness is best used for capturing the sharpness of multimodal tuning curves defined by narrow peaks (maximum) and broad valleys (minima). Finally, we provide a more formal definition of sharpness using a shape-based information gain measure and derive and show that skewness is correlated with this definition. PMID:24555451
On river-floodplain interaction and hydrograph skewness
NASA Astrophysics Data System (ADS)
Fleischmann, Ayan S.; Paiva, Rodrigo C. D.; Collischonn, Walter; Sorribas, Mino V.; Pontes, Paulo R. M.
2016-10-01
Understanding hydrological processes occurring within a basin by looking at its outlet hydrograph can improve and foster comprehension of ungauged regions. In this context, we present an extensive examination of the roles that floodplains play on driving hydrograph shapes. Observations of many river hydrographs with large floodplain influence are carried out and indicate that a negative skewness of the hydrographs is present among many of them. Through a series of numerical experiments and analytical reasoning, we show how the relationship between flood wave celerity and discharge in such systems is responsible for determining the hydrograph shapes. The more water inundates the floodplains upstream of the observed point, the more negatively skewed is the observed hydrograph. A case study is performed in the Amazon River Basin, where major rivers with large floodplain attenuation (e.g., Purus, Madeira, and Juruá) are identified with higher negative skewness in the respective hydrographs. Finally, different wetland types could be distinguished by using this feature, e.g., wetlands maintained by endogenous processes, from wetlands governed by overbank flow (along river floodplains). A metric of hydrograph skewness was developed to quantify this effect, based on the time derivative of discharge. Together with the skewness concept, it may be used in other studies concerning the relevance of floodplain attenuation in large, ungauged rivers, where remote sensing data (e.g., satellite altimetry) can be very useful.
Determining collective barrier operation skew in a parallel computer
Faraj, Daniel A.
2015-11-24
Determining collective barrier operation skew in a parallel computer that includes a number of compute nodes organized into an operational group includes: for each of the nodes until each node has been selected as a delayed node: selecting one of the nodes as a delayed node; entering, by each node other than the delayed node, a collective barrier operation; entering, after a delay by the delayed node, the collective barrier operation; receiving an exit signal from a root of the collective barrier operation; and measuring, for the delayed node, a barrier completion time. The barrier operation skew is calculated by: identifying, from the compute nodes' barrier completion times, a maximum barrier completion time and a minimum barrier completion time and calculating the barrier operation skew as the difference of the maximum and the minimum barrier completion time.
Mobile bed thickness in skewed asymmetric oscillatory sheet flows
NASA Astrophysics Data System (ADS)
Chen, Xin; Li, Yong; Wang, Fujun
2017-06-01
A new instantaneous mobile bed thickness model is presented for sediment transport in skewed asymmetric oscillatory sheet flows. The proposed model includes a basic bed load part and a suspended load part related to the Shields parameter, and takes into account the effects of mass conservation, phase-lag, and asymmetric boundary layer development, which are important in skewed asymmetric flows but usually absent in classical models. The proposed model is validated by erosion depth and sheet flow layer thickness data in both steady and unsteady flows, and applied to a new instantaneous sediment transport rate formula. With higher accuracy than classical empirical models in steady flows, the new formula can also be used for instantaneous sediment transport rate prediction in skewed asymmetric oscillatory sheet flows.
Skew flap for staged below-knee amputation in sepsis.
Matthews, Christopher O; Williams, Ian M; Lewis, Peter; McLain, A David; Twine, Christopher P
2016-04-01
Skew flap amputation was first described in the 1980s but was never as popular as the long posterior flap amputation. This report describes a staged below-knee amputation in sepsis, with pus throughout the leg and a lack of skin coverage. One benefit of skew flaps never previously published is the fact that the suture line is not directly over the tibia. Therefore, an open wound or incomplete skin coverage is not as important as in long posterior flaps where it often leads to bone exposure and revision amputation. These benefits were utilized in this case leading to stump healing.
Power and Skew Aware Point Diffusion Clock Network
NASA Astrophysics Data System (ADS)
Jung, Gunok; Kim, Chunghee; Chae, Kyoungkuk; Park, Giho; Park, Sung Bae
This letter presents point diffusion clock network (PDCN) with local clock tree synthesis (CTS) scheme. The clock network is implemented with ten times wider metal line space than typical mesh networks for low power and utilized to nine times smaller area CTS execution for minimized clock skew amount. The measurement results show that skew amount of PDCN with local CTS is reduced to 36% and latency is shrunk to 45% of the amount in a 4.81mm2 CortexA-8 core with 65nm Samsung process.
Uncertainty relations based on skew information with quantum memory
NASA Astrophysics Data System (ADS)
Ma, ZhiHao; Chen, ZhiHua; Fei, Shao-Ming
2017-01-01
We present a new uncertainty relation by defining a measure of uncertainty based on skew information. For bipartite systems, we establish uncertainty relations with the existence of a quantum memory. A general relation between quantum correlations and tight bounds of uncertainty has been presented.
Modelling psychiatric measures using Skew-Normal distributions
Counsell, N.; Cortina-Borja, M.; Lehtonen, A.; Stein, A.
2011-01-01
Data from psychiatric research frequently exhibit departures from Normality. Methods which utilise the data optimally to model the distribution directly are available. We highlight the issue of modelling skewness, resulting from screening instruments where the majority of respondents are healthy individuals and few participants have a value reflecting particular disorders. PMID:21036551
Making Skew-Resistant Fabrics For Composite Layups
NASA Technical Reports Server (NTRS)
Farley, Gary L.
1994-01-01
Fabrics used in curved composite-material structures prevented from skewing during composite layup by weaving them in modified process in which warp and fill yarns bonded together at their points of contact. (Bonding concept may prove similarly beneficial for braided and knitted fabrics.) In modified weaving process, adhesives prevent excessive shifting of warp and fill yarns with respect to each other.
Skewness and Comparability of School Based Continuous Assessment Scores
ERIC Educational Resources Information Center
Gbore, Lawrence Olu; Olabode, Abe Thomas; Olufemi, Adodo Sunday
2011-01-01
This study examined skewness as means of determining the nature of distribution of school based continuous assessment (SBCA) scores in selected subjects among Secondary Schools in Ondo State, Nigeria, to determine whether or not there is need for moderation of the SBCA Scores. This is an ex-post-facto research design involving no treatment and…
3. VIEW SOUTHEAST VIEW OF EAST PORTAL SHOWING SKEW AND ...
3. VIEW SOUTHEAST- VIEW OF EAST PORTAL SHOWING SKEW AND PORTAL BRACING. - National Docks Branch Bridge N.D.2F, Spans former Central Railroad of New Jersey , west of New Jersey Turnpike, north of Communipaw Avenue near Johnson Avenue, Jersey City, Hudson County, NJ
8. Detail, skewed portal bracing at west portal, also showing ...
8. Detail, skewed portal bracing at west portal, also showing boxed endposts, latticed upper transverse and diagonal sway bracing, laced vertical members, view to northeast, 210mm lens. - Southern Pacific Railroad Shasta Route, Bridge No. 301.85, Milepost 301.85, Pollard Flat, Shasta County, CA
Generating monthly rainfall amount using multivariate skew-t copula
NASA Astrophysics Data System (ADS)
Radi, Noor Fadhilah Ahmad; Zakaria, Roslinazairimah; Zanariah Satari, Siti
2017-09-01
This study aims to generate rainfall data in cases where the data is not available or not enough for a certain area of study. In general, the rainfall data is rightly skewed, so the multivariate skew-t copula is used as it able to model rainfall amount and capture the spatial dependence in the data. To illustrate the methodology, three rainfall stations in Kelantan are used. Firstly, the observed data is transformed to uniform unit. The Spearman’s correlation coefficient is calculated between the three stations. It is found that the correlations between the stations are significance at α = 0.05. The next step involved generating the synthetic rainfall data using the multivariate skew-t copula. The data is then transformed to uniform unit and the correlation coefficient is calculated for the generated data. Finally, the correlation coefficient of the observed and the generated data are compared. The Kolmogorov-Smirnov goodness of fit test is used to assess the fit between theoretical and empirical copula and supported by graphical representation. The results show that there is no significant difference between empirical and theoretical copula at 5% significance level. Thus, the multivariate skew-t copula is suitable to generate synthetic rainfall data that can mimic the observed rainfall data. It can also be used to present different rainfall scenarios by changing the value of the parameters in the model.
Arc voltage distribution skewness as an indicator of electrode gap during vacuum arc remelting
Williamson, R.L.; Zanner, F.J.; Grose, S.M.
1998-01-13
The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap. 4 figs.
Arc voltage distribution skewness as an indicator of electrode gap during vacuum arc remelting
Williamson, Rodney L.; Zanner, Frank J.; Grose, Stephen M.
1998-01-01
The electrode gap of a VAR is monitored by determining the skewness of a distribution of gap voltage measurements. A decrease in skewness indicates an increase in gap and may be used to control the gap.
Correcting Quadrupole Roll in Magnetic Lenses with Skew Quadrupoles
Walstrom, Peter Lowell
2014-11-10
Quadrupole rolls (i.e. rotation around the magnet axis) are known to be a significant source of image blurring in magnetic quadrupole lenses. These rolls may be caused by errors in mechanical mounting of quadrupoles, by uneven radiation-induced demagnetization of permanent-magnet quadrupoles, etc. Here a four-quadrupole ×10 lens with so-called ”Russian” or A -B B-A symmetry is used as a model problem. Existing SLAC 1/2 in. bore high-gradient quadrupoles are used in the design. The dominant quadrupole roll effect is changes in the first-order part of the transfer map (the R matrix) from the object to the image plane (Note effects on the R matrix can be of first order in rotation angle for some R-matrix elements and second order in rotation angle for other elements, as shown below). It is possible to correct roll-induced image blur by mechanically adjusting the roll angle of one or more of the quadrupoles. Usually, rotation of one quadrupole is sufficient to correct most of the combined effect of rolls in all four quadrupoles. There are drawbacks to this approach, however, since mechanical roll correction requires multiple entries into experimental area to make the adjustments, which are made according to their effect on images. An alternative is to use a single electromagnetic skew quadrupole corrector placed either between two of the quadrupoles or after the fourth quadrupole (so-called “non-local” correction). The basic feasibility of skew quadrupole correction of quadrupole roll effects is demonstrated here. Rolls of the third lens quadrupole of up to about 1 milliradian can be corrected with a 15 cm long skew quadrupole with a gradient of up to 1 T/m. Since the effect of rolls of the remaining three lens quadrupoles are lower, a weaker skew quadrupole can be used to correct them. Non-local correction of quadrupole roll effects by skew quadrupoles is shown to be about one-half as effective as local correction (i.e. rotating individual quadrupoles to zero
Quantifying Correlations via the Wigner-Yanase-Dyson Skew Information
NASA Astrophysics Data System (ADS)
Fan, Yajing; Cao, Huaixin
2016-09-01
In this paper, based on a discussion about the Wigner-Yanase-Dyson (WYD) skew information, the measure F a, α ( ρ a b ) for correlations in terms of the WYD skew information is introduced and discussed. The following conclusions are obtained. For a classical-quantum state ρ a b , F a, α ( ρ a b )=0 if and only if ρ a b is a product state; F a, α ( ρ a b ) is locally unitary invariant and convex on the set of states with the fixed marginal ρ a ; F a, α ( ρ a b ) decreases under local random unitary operation on H b ; For a quantum-classical state ρ a b , F a, α ( ρ a b ) decreases under local operation on H b ; Lastly, F a, α ( ρ a b ) is computed for the pure states and the Bell-diagonal states, respectively.
Universal relation between skewness and kurtosis in complex dynamics.
Cristelli, Matthieu; Zaccaria, Andrea; Pietronero, Luciano
2012-06-01
We identify an important correlation between skewness and kurtosis for a broad class of complex dynamic systems and present a specific analysis of earthquake and financial time series. Two regimes of non-Gaussianity can be identified: a parabolic one, which is common in various fields of physics, and a power law one, with exponent 4/3, which at the moment appears to be specific of earthquakes and financial markets. For this property we propose a model and an interpretation in terms of very rare events dominating the statistics independently on the nature of the events considered. The predicted scaling relation between skewness and kurtosis matches very well the experimental pattern of the second regime. Regarding price fluctuations, this situation characterizes a universal stylized fact.
Newspaper Coverage of Intimate Partner Violence: Skewing Representations of Risk
Carlyle, Kellie E.; Slater, Michael D.; Chakroff, Jennifer L.
2011-01-01
How media portray intimate partner violence (IPV) has implications for public perceptions and social policy. Therefore, to better understand these portrayals, this study content analyzes a nationally representative sample of newspaper coverage of IPV over a two-year-period and compares this coverage to epidemiological data in order to examine the implications of the discrepancies between coverage and social reality. Stratified media outlets across the country were used to obtain a representative sample of daily newspapers based on their designated market areas, resulting in 395 IPV-related articles. Results show that newspaper framing of IPV tends to be heavily skewed toward episodic framing. In addition, there are significant differences between our data and epidemiological estimates, particularly in the coverage of homicide and use of alcohol and illegal drugs, which may skew public perceptions of risk. Implications for public perceptions and social policy are discussed. PMID:21297889
Universal relation between skewness and kurtosis in complex dynamics
NASA Astrophysics Data System (ADS)
Cristelli, Matthieu; Zaccaria, Andrea; Pietronero, Luciano
2012-06-01
We identify an important correlation between skewness and kurtosis for a broad class of complex dynamic systems and present a specific analysis of earthquake and financial time series. Two regimes of non-Gaussianity can be identified: a parabolic one, which is common in various fields of physics, and a power law one, with exponent 4/3, which at the moment appears to be specific of earthquakes and financial markets. For this property we propose a model and an interpretation in terms of very rare events dominating the statistics independently on the nature of the events considered. The predicted scaling relation between skewness and kurtosis matches very well the experimental pattern of the second regime. Regarding price fluctuations, this situation characterizes a universal stylized fact.
TWIN SKEWED TRUSS RAILROAD BRIDGES NEAR BRIDGE STREET AT THE ...
TWIN SKEWED TRUSS RAILROAD BRIDGES NEAR BRIDGE STREET AT THE WEST END OF THE PLANT. THIS VIEW PROBABLY LOOKING NORTHWEST. BRIDGES BUILT OVER ERIE CANAL (WHICH FLOWED RIGHT THROUGH THE MIDDLE OF THE PLANT) BY AMERICAN BRIDGE COMPANY IN 1902. SINCE THIS PHOTO WAS TAKEN, NEAR BRIDGE HAS BEEN DEMOLISHED; FAR BRIDGE IS STILL IN SERVICE. - Solvay Process Company, Between Willis & Milton Avenues, Solvay, Onondaga County, NY
Estimating Incremental Costs with Skew: A Cautionary Note
Polgreen, Linnea A.; Brooks, John M.
2016-01-01
Background Cost data in healthcare are often skewed across patients. Thus researchers have used either a log transformation of the dependent variable or generalized linear models (GLMs) with log links. However, frequently these non-linear approaches produce non-linear incremental effects: the incremental effects differ at different levels of the covariates, and this can cause dramatic effects on predicted cost. Objectives To demonstrate that when modeling skewed data, log link functions or log transformations are not necessary and have unintended effects. Methods We simulated cost data using a linear model with a “treatment”, a covariate, and a specified number of observations with excessive cost (skewed data). We also used actual data from a pain-relief intervention among hip-replacement patients. We then estimated cost models using various functional approaches suggested to handle skew and calculated the incremental cost of treatment at various levels of the covariate(s). Results All of these methods provide unbiased estimates of the incremental effect of treatment on costs at the mean level of the covariate. However, in some log-based models the implied incremental treatment cost doubled between extreme low and high values of the covariate in a manner inconsistent with the underlying linear model. Conclusions Although specification checks are always needed, the potential of misleading incremental estimates resulting from log-based specifications is often ignored. In this era of cost containment and comparisons of treatment effectiveness, it is vital that researchers and policy-makers understand the limitation of the inferences that can be made using log-based models for patients whose characteristics differ from the sample mean. PMID:22762544
Estimating incremental costs with skew: a cautionary note.
Polgreen, Linnea A; Brooks, John M
2012-09-01
Cost data in healthcare are often skewed across patients. Thus, researchers have used either a log transformation of the dependent variable or generalized linear models with log links. However, frequently these non-linear approaches produce non-linear incremental effects: the incremental effects differ at different levels of the covariates, and this can cause dramatic effects on predicted cost. The aim of this study was to demonstrate that when modelling skewed data, log link functions or log transformations are not necessary and have unintended effects. We simulated cost data using a linear model with a 'treatment', a covariate and a specified number of observations with excessive cost (skewed data). We also used actual data from a pain-relief intervention among hip-replacement patients. We then estimated cost models using various functional approaches suggested to handle skew and calculated the incremental cost of treatment at various levels of the covariate(s). All of these methods provide unbiased estimates of the incremental effect of treatment on costs at the mean level of the covariate. However, in some log-based models the implied incremental treatment cost doubled between extreme low and high values of the covariate in a manner inconsistent with the underlying linear model. Although specification checks are always needed, the potential for misleading incremental estimates resulting from log-based specifications is often ignored. In this era of cost containment and comparisons of treatment effectiveness it is vital that researchers and policymakers understand the limitation of the inferences that can be made using log-based models for patients whose characteristics differ from the sample mean.
MEASURING LOCAL GRADIENT AND SKEW QUADRUPOLE ERRORS IN RHIC IRS.
CARDONA,J.; PEGGS,S.; PILAT,R.; PTITSYN,V.
2004-07-05
The measurement of local linear errors at RHIC interaction regions using an ''action and phase'' analysis of difference orbits has already been presented. This paper evaluates the accuracy of this technique using difference orbits that were taken when known gradient errors and skew quadrupole errors were intentionally introduced. It also presents action and phase analysis of simulated orbits when controlled errors are intentionally placed in a RHIC simulation model.
Incorporating Skew into RMS Surface Roughness Probability Distribution
NASA Technical Reports Server (NTRS)
Stahl, Mark T.; Stahl, H. Philip.
2013-01-01
The standard treatment of RMS surface roughness data is the application of a Gaussian probability distribution. This handling of surface roughness ignores the skew present in the surface and overestimates the most probable RMS of the surface, the mode. Using experimental data we confirm the Gaussian distribution overestimates the mode and application of an asymmetric distribution provides a better fit. Implementing the proposed asymmetric distribution into the optical manufacturing process would reduce the polishing time required to meet surface roughness specifications.
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, L.; Kalsi, M.S.
1999-02-23
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. 14 figs.
Skew and twist resistant hydrodynamic rotary shaft seal
Dietle, Lannie; Kalsi, Manmohan Singh
1999-01-01
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland.
Crack diagnostics in beams using wavelets, kurtosis and skewness
NASA Astrophysics Data System (ADS)
Kaul, Sudhir
2014-04-01
This paper presents a diagnostic technique using wavelets, kurtosis and skewness for detecting crack location and severity in beams. The first three mode shapes of a damaged beam are used for detecting crack locations in beams with varying boundary conditions. Damage due to an edge-crack is modelled by a conventional macroscopic torsional spring element. Multiple families of wavelets with varying scales and vanishing moments are used so as to distinguish between their ability to detect crack locations by using the mode shapes of the damaged beam. Crack detection is followed by determination of the crack size by using statistical measures of the mode shapes such as kurtosis and skewness. These two measures are highly sensitive to small changes in mode shapes resulting from crack initiation or crack propagation, and have been used in other fields of damage detection. Several simulations are presented to showcase the application of the proposed technique, and to highlight the differences between multiple wavelets and the parameters associated with the wavelets. The proposed diagnostic technique is also tested for robustness by adding noise to the mode shapes. The simulation results and preliminary experimental results indicate that the statistical measures of kurtosis and skewness can be used in conjunction with wavelets in order to provide a viable crack diagnostic technique for beam structures.
Kurtosis, skewness, and non-Gaussian cosmological density perturbations
NASA Technical Reports Server (NTRS)
Luo, Xiaochun; Schramm, David N.
1993-01-01
Cosmological topological defects as well as some nonstandard inflation models can give rise to non-Gaussian density perturbations. Skewness and kurtosis are the third and fourth moments that measure the deviation of a distribution from a Gaussian. Measurement of these moments for the cosmological density field and for the microwave background temperature anisotropy can provide a test of the Gaussian nature of the primordial fluctuation spectrum. In the case of the density field, the importance of measuring the kurtosis is stressed since it will be preserved through the weakly nonlinear gravitational evolution epoch. Current constraints on skewness and kurtosis of primeval perturbations are obtained from the observed density contrast on small scales and from recent COBE observations of temperature anisotropies on large scales. It is also shown how, in principle, future microwave anisotropy experiments might be able to reveal the initial skewness and kurtosis. It is shown that present data argue that if the initial spectrum is adiabatic, then it is probably Gaussian, but non-Gaussian isocurvature fluctuations are still allowed, and these are what topological defects provide.
Caste load and the evolution of reproductive skew.
Holman, Luke
2014-01-01
Reproductive skew theory seeks to explain how reproduction is divided among group members in animal societies. Existing theory is framed almost entirely in terms of selection, though nonadaptive processes must also play some role in the evolution of reproductive skew. Here I propose that a genetic correlation between helper fecundity and breeder fecundity may frequently constrain the evolution of reproductive skew. This constraint is part of a wider phenomenon that I term "caste load," which is defined as the decline in mean fitness caused by caste-specific selection pressures, that is, differential selection on breeding and nonbreeding individuals. I elaborate the caste load hypothesis using quantitative and population genetic arguments and individual-based simulations. Although selection can sometimes erode genetic correlations and resolve caste load, this may be constrained when mutations have similar pleiotropic effects on breeder and helper traits. I document evidence for caste load, identify putative genomic adaptations to it, and suggest future research directions. The models highlight the value of considering adaptation within the boundaries imposed by genetic architecture and incidentally reaffirm that monogamy promotes the evolutionary transition to eusociality.
Jet crackle: skewness transport budget and a mechanistic source model
NASA Astrophysics Data System (ADS)
Buchta, David; Freund, Jonathan
2016-11-01
The sound from high-speed (supersonic) jets, such as on military aircraft, is distinctly different than that from lower-speed jets, such as on commercial airliners. Atop the already loud noise, a higher speed adds an intense, fricative, and intermittent character. The observed pressure wave patterns have strong peaks which are followed by relatively long shallows; notably, their pressure skewness is Sk >= 0 . 4 . Direct numerical simulation of free-shear-flow turbulence show that these skewed pressure waves occur immediately adjacent to the turbulence source for M >= 2 . 5 . Additionally, the near-field waves are seen to intersect and nonlinearly merge with other waves. Statistical analysis of terms in a pressure skewness transport equation show that starting just beyond δ99 the nonlinear wave mechanics that add to Sk are balanced by damping molecular effects, consistent with this aspect of the sound arising in the source region. A gas dynamics description is developed that neglects rotational turbulence dynamics and yet reproduces the key crackle features. At its core, this mechanism shows simply that nonlinear compressive effects lead directly to stronger compressions than expansions and thus Sk > 0 .
Validation of an Acoustic Impedance Prediction Model for Skewed Resonators
NASA Technical Reports Server (NTRS)
Howerton, Brian M.; Parrott, Tony L.
2009-01-01
An impedance prediction model was validated experimentally to determine the composite impedance of a series of high-aspect ratio slot resonators incorporating channel skew and sharp bends. Such structures are useful for packaging acoustic liners into constrained spaces for turbofan noise control applications. A formulation of the Zwikker-Kosten Transmission Line (ZKTL) model, incorporating the Richards correction for rectangular channels, is used to calculate the composite normalized impedance of a series of six multi-slot resonator arrays with constant channel length. Experimentally, acoustic data was acquired in the NASA Langley Normal Incidence Tube over the frequency range of 500 to 3500 Hz at 120 and 140 dB OASPL. Normalized impedance was reduced using the Two-Microphone Method for the various combinations of channel skew and sharp 90o and 180o bends. Results show that the presence of skew and/or sharp bends does not significantly alter the impedance of a slot resonator as compared to a straight resonator of the same total channel length. ZKTL predicts the impedance of such resonators very well over the frequency range of interest. The model can be used to design arrays of slot resonators that can be packaged into complex geometries heretofore unsuitable for effective acoustic treatment.
Judd, Linda J.; Asquith, William H.; Slade, Raymond M.
1996-01-01
One technique to estimate generalized skew coefficients involved the use of regression equations developed for each of eight regions in Texas, and the other involved development of a statewide map of generalized skew coefficients. The weighted mean of the weighted mean standard errors of the regression equations for the eight regions is 0.36 log10 skew units, and the weighted mean standard error of the map is 0.35 log10 skew units. The technique based on the map is preferred for estimating generalized skew coefficients because of its smooth transition from one region of the State to another.
Forecasting stock market volatility: Do realized skewness and kurtosis help?
NASA Astrophysics Data System (ADS)
Mei, Dexiang; Liu, Jing; Ma, Feng; Chen, Wang
2017-09-01
In this study, we investigate the predictability of the realized skewness (RSK) and realized kurtosis (RKU) to stock market volatility, that has not been addressed in the existing studies. Out-of-sample results show that RSK, which can significantly improve forecast accuracy in mid- and long-term, is more powerful than RKU in forecasting volatility. Whereas these variables are useless in short-term forecasting. Furthermore, we employ the realized kernel (RK) for the robustness analysis and the conclusions are consistent with the RV measures. Our results are of great importance for portfolio allocation and financial risk management.
Correlating the skewness and kurtosis of baryon number distributions
NASA Astrophysics Data System (ADS)
Fu, Wei-jie; Pawlowski, Jan M.
2016-05-01
The skewness and the kurtosis of the baryon number distributions are computed within QCD-improved low energy effective models including quantum thermal and density fluctuations. The results are compared with the Beam Energy Scan experiment at RHIC. The theoretical results agree with the experimental measurements up to errors, for the collision energy √{s }≥19.6 GeV . For smaller collision energies a discrepancy between theoretical and experimental results develops. This discrepancy partially relates to the lack of precision of the current setup for small collision energies. It is outlined how this deficiency can be overcome.
Effect of Resonator Axis Skew on Normal Incidence Impedance
NASA Technical Reports Server (NTRS)
Parrott, Tony L.; Jones, Michael G.; Homeijer, Brian
2003-01-01
High by-pass turbofan engines have fewer fan blades and lower rotation speeds than their predecessors. Consequently, the noise suppression at the low frequency end of the noise spectra has become an increasing concern. This has led to a renewed emphasis on improving noise suppression efficiency of passive, duct liner treatments at the lower frequencies. For a variety of reasons, passive liners are comprised of locally-reacting, resonant absorbers. One reason for this design choice is to satisfy operational and economic requirements. The simplest liner design consists of a single layer of honeycomb core sandwiched between a porous facesheet and an impervious backing plate. These resonant absorbing structures are integrated into the nacelle wall and are very ef- ficient over a limited bandwidth centered on their resonance frequency. Increased noise suppression bandwidth and greater suppression at lower frequencies is typically achieved for conventional liners by increasing the liner depth and incorporating thin porous septa into the honeycomb core. However, constraints on liner depth in modern high by-pass engine nacelles severely limit the suppression bandwidth extension to lower frequencies. Also, current honeycomb core liners may not be suitable for irregular geometric volumes heretofore not considered. It is of interest, therefore, to find ways to circumvent liner depth restrictions and resonator cavity shape constraints. One way to increase effective liner depth is to skew the honeycomb core axis relative to the porous facesheet surface. Other possibilities are to alter resonator cavity shape, e.g. high aspect ratio, narrow channels that possibly include right angle bends, 180. channel fold-backs, and splayed channel walls to conform to irregular geometric constraints. These possibilities constitute the practical motivation for expanding impedance modeling capability to include unconventional resonator orientations and shapes. The work reported in this paper is
Skew And Twist Resistant Hydrodynamic Rotary Shaft Seal
Dietle, Lannie; Kalsi, Manmohan Singh
2000-03-14
A hydrodynamically lubricated squeeze packing type rotary shaft seal suitable for lubricant retention and environmental exclusion which incorporates one or more resilient protuberances which and cooperate with the gland walls to hold the seal straight in its installation groove in unpressurized and low pressure lubricant retention applications thereby preventing skew-induced wear caused by impingement of abrasive contaminants present in the environment, and which also serve as radial bearings to prevent tipping of the seal within its installation gland. Compared to prior art, this invention provides a dramatic reduction of seal and shaft wear in abrasive environments and provides a significant increase in seal life.
Pattern formation of underwater sand ripples with a skewed drive.
Bundgaard, F; Ellegaard, C; Scheibye-Knudsen, K; Bohr, T; Sams, T
2004-12-01
In this paper we present an experimental study of the dynamics of underwater sand ripples when a regular pattern of ripples is subjected to a skewed oscillatory flow, i.e., one not perpendicular to the direction of the ripple crests. Striking patterns with new, superposed ripples on top of the original ones occur very quickly with a characteristic angle, which is, in general, not perpendicular to the flow. A slower, more complex transition then follows, leading to the final state where the ripples are again perpendicular to the flow. We investigate the variation of the superposed pattern as a function of the direction, amplitude, and frequency of the drive, and as a function of the viscosity (by changing the temperature). We quantify the dynamics of the entire transition process and finally study the grain motion around idealized (solid) skewed ripples. This leads to a characteristic mean path of a single particle. The path has a shape close to a parallelogram, with no apparent connection to the pattern of real, superposed ripples. On the other hand, a thin layer of sand sprinkled on the solid ripples leads to qualitatively similar patterns.
Tissue-specific patterns of allelically-skewed DNA methylation
Marzi, Sarah J.; Meaburn, Emma L.; Dempster, Emma L.; Lunnon, Katie; Paya-Cano, Jose L.; Smith, Rebecca G.; Volta, Manuela; Troakes, Claire; Schalkwyk, Leonard C.; Mill, Jonathan
2016-01-01
ABSTRACT While DNA methylation is usually thought to be symmetrical across both alleles, there are some notable exceptions. Genomic imprinting and X chromosome inactivation are two well-studied sources of allele-specific methylation (ASM), but recent research has indicated a more complex pattern in which genotypic variation can be associated with allelically-skewed DNA methylation in cis. Given the known heterogeneity of DNA methylation across tissues and cell types we explored inter- and intra-individual variation in ASM across several regions of the human brain and whole blood from multiple individuals. Consistent with previous studies, we find widespread ASM with > 4% of the ∼220,000 loci interrogated showing evidence of allelically-skewed DNA methylation. We identify ASM flanking known imprinted regions, and show that ASM sites are enriched in DNase I hypersensitivity sites and often located in an extended genomic context of intermediate DNA methylation. We also detect examples of genotype-driven ASM, some of which are tissue-specific. These findings contribute to our understanding of the nature of differential DNA methylation across tissues and have important implications for genetic studies of complex disease. As a resource to the community, ASM patterns across each of the tissues studied are available in a searchable online database: http://epigenetics.essex.ac.uk/ASMBrainBlood. PMID:26786711
Approximate Median Regression for Complex Survey Data with Skewed Response
Fraser, Raphael André; Lipsitz, Stuart R.; Sinha, Debajyoti; Fitzmaurice, Garrett M.; Pan, Yi
2016-01-01
Summary The ready availability of public-use data from various large national complex surveys has immense potential for the assessment of population characteristics using regression models. Complex surveys can be used to identify risk factors for important diseases such as cancer. Existing statistical methods based on estimating equations and/or utilizing resampling methods are often not valid with survey data due to complex survey design features. That is, stratification, multistage sampling and weighting. In this paper, we accommodate these design features in the analysis of highly skewed response variables arising from large complex surveys. Specifically, we propose a double-transform-both-sides (DTBS) based estimating equations approach to estimate the median regression parameters of the highly skewed response; the DTBS approach applies the same Box-Cox type transformation twice to both the outcome and regression function. The usual sandwich variance estimate can be used in our approach, whereas a resampling approach would be needed for a pseudo-likelihood based on minimizing absolute deviations (MAD). Furthermore, the approach is relatively robust to the true underlying distribution, and has much smaller mean square error than a MAD approach. The method is motivated by an analysis of laboratory data on urinary iodine (UI) concentration from the National Health and Nutrition Examination Survey. PMID:27062562
Free vibration analysis of skewed open circular cylindrical shells
NASA Astrophysics Data System (ADS)
Kandasamy, Selvakumar; Singh, Anand V.
2006-03-01
In this paper, a numerical study is presented for the free vibration of skewed open circular cylindrical deep shells. The formulation considers first-order shear deformation theory of shells and includes rotary inertia and shear deformation so that thin-to-moderately thick shells can be analyzed. A set of grid points, the number of which depends upon the orders of the polynomials chosen for the displacement and rotation components, on the middle surface of the shell is defined first. For a particular displacement component, the field functions are derived corresponding to each node from the above-mentioned set of points and are used in the Rayleigh-Ritz method to calculate frequencies and mode shapes. Convergence study with reference to the order of the polynomials used for the displacement fields was performed first. Numerical results obtained from the present method are compared with those from the finite element method and very good agreement is observed. Additional results are presented and discussed in this paper for skewed panels clamped at the curved edges and free at the straight parallel edges.
Crossover ensembles of random matrices and skew-orthogonal polynomials
Kumar, Santosh; Pandey, Akhilesh
2011-08-15
Highlights: > We study crossover ensembles of Jacobi family of random matrices. > We consider correlations for orthogonal-unitary and symplectic-unitary crossovers. > We use the method of skew-orthogonal polynomials and quaternion determinants. > We prove universality of spectral correlations in crossover ensembles. > We discuss applications to quantum conductance and communication theory problems. - Abstract: In a recent paper (S. Kumar, A. Pandey, Phys. Rev. E, 79, 2009, p. 026211) we considered Jacobi family (including Laguerre and Gaussian cases) of random matrix ensembles and reported exact solutions of crossover problems involving time-reversal symmetry breaking. In the present paper we give details of the work. We start with Dyson's Brownian motion description of random matrix ensembles and obtain universal hierarchic relations among the unfolded correlation functions. For arbitrary dimensions we derive the joint probability density (jpd) of eigenvalues for all transitions leading to unitary ensembles as equilibrium ensembles. We focus on the orthogonal-unitary and symplectic-unitary crossovers and give generic expressions for jpd of eigenvalues, two-point kernels and n-level correlation functions. This involves generalization of the theory of skew-orthogonal polynomials to crossover ensembles. We also consider crossovers in the circular ensembles to show the generality of our method. In the large dimensionality limit, correlations in spectra with arbitrary initial density are shown to be universal when expressed in terms of a rescaled symmetry breaking parameter. Applications of our crossover results to communication theory and quantum conductance problems are also briefly discussed.
Tissue-specific patterns of allelically-skewed DNA methylation.
Marzi, Sarah J; Meaburn, Emma L; Dempster, Emma L; Lunnon, Katie; Paya-Cano, Jose L; Smith, Rebecca G; Volta, Manuela; Troakes, Claire; Schalkwyk, Leonard C; Mill, Jonathan
2016-01-01
While DNA methylation is usually thought to be symmetrical across both alleles, there are some notable exceptions. Genomic imprinting and X chromosome inactivation are two well-studied sources of allele-specific methylation (ASM), but recent research has indicated a more complex pattern in which genotypic variation can be associated with allelically-skewed DNA methylation in cis. Given the known heterogeneity of DNA methylation across tissues and cell types we explored inter- and intra-individual variation in ASM across several regions of the human brain and whole blood from multiple individuals. Consistent with previous studies, we find widespread ASM with > 4% of the ∼220,000 loci interrogated showing evidence of allelically-skewed DNA methylation. We identify ASM flanking known imprinted regions, and show that ASM sites are enriched in DNase I hypersensitivity sites and often located in an extended genomic context of intermediate DNA methylation. We also detect examples of genotype-driven ASM, some of which are tissue-specific. These findings contribute to our understanding of the nature of differential DNA methylation across tissues and have important implications for genetic studies of complex disease. As a resource to the community, ASM patterns across each of the tissues studied are available in a searchable online database: http://epigenetics.essex.ac.uk/ASMBrainBlood.
Approximate median regression for complex survey data with skewed response.
Fraser, Raphael André; Lipsitz, Stuart R; Sinha, Debajyoti; Fitzmaurice, Garrett M; Pan, Yi
2016-12-01
The ready availability of public-use data from various large national complex surveys has immense potential for the assessment of population characteristics using regression models. Complex surveys can be used to identify risk factors for important diseases such as cancer. Existing statistical methods based on estimating equations and/or utilizing resampling methods are often not valid with survey data due to complex survey design features. That is, stratification, multistage sampling, and weighting. In this article, we accommodate these design features in the analysis of highly skewed response variables arising from large complex surveys. Specifically, we propose a double-transform-both-sides (DTBS)'based estimating equations approach to estimate the median regression parameters of the highly skewed response; the DTBS approach applies the same Box-Cox type transformation twice to both the outcome and regression function. The usual sandwich variance estimate can be used in our approach, whereas a resampling approach would be needed for a pseudo-likelihood based on minimizing absolute deviations (MAD). Furthermore, the approach is relatively robust to the true underlying distribution, and has much smaller mean square error than a MAD approach. The method is motivated by an analysis of laboratory data on urinary iodine (UI) concentration from the National Health and Nutrition Examination Survey. © 2016, The International Biometric Society.
Multiple mating and reproductive skew in Trinidadian guppies.
Becher, S A; Magurran, A E
2004-05-22
Male offspring production in promiscuously mating species is typically more skewed than female offspring production. It is therefore advantageous for males to seek as many mating partners as possible. However, given the documented benefits of polyandry we expect females, as well as males, to mate multiply. We tested these ideas using Trinidadian guppies, Poecilia reticulata. Fishes were collected from the wild, housed in groups of 10 males and 10 females and allowed to reproduce freely over a period of three months. We used hypervariable microsatellite loci to identify the parents of 840 offspring and to quantify the variance in mating success. As anticipated, and in line with the Bateman gradient, there was greater skew in the number of progeny produced by males. By contrast, we found no sex difference in mating partner number over the duration of the experiment. A median of two males fathered each brood and there was marked turnover in the identities of the sires of successive broods. Female partner turnover was, however, less than expected under random mating. We suggest that partner switching over time, as well as polyandry within broods, could contribute to the maintenance of genetic diversity in guppy populations.
Natural vibrations of shear deformable cantilevered skewed trapezoidal and triangular thick plates
NASA Astrophysics Data System (ADS)
McGee, O. G.; Butalia, T. S.
1992-12-01
The efficacy of higher-order shear deformable, C exp 0, continuous, Lagrangian isoparametric plate finite element analyses has been demonstrated on cantilevered skewed (parallelogram) thick plates. The present work extends the method to include skewed thick plates having trapezoidal and triangular planforms. Extensive and accurate nondimensional frequency tables and graphical charts are presented for a series of trapezoidal plates showing the effect of aspect ratio, chord ratio, thickness ratio, and skew angle. The need for the present higher-order shear deformable plate finite element method for skewed trapezoidal plate vibrations increases as the skew angle increases and as the aspect ratio, chord ratio, and thickness ratio decreases. Some theoretical and experimental data hitherto published for delta and skewed triangular cantilevered plates are compared with results obtained using the present finite element method.
Severe Skew Foot Deformity in a Patient With Freeman-Sheldon Syndrome
Kaissi, Ali Al; Klaushofer, Klaus; Grill, Franz
2011-01-01
We report on a 3-year-old boy with the full phenotypic features of Freeman Sheldon syndrome (FSS). Severe skew foot deformity has been recognized as additional skeletal abnormality. Parents were first degree cousins, raising the possibility of autosomal recessive pattern of inheritance. To the best of our knowledge this is the first report of severe skew foot deformity in a patient with (FSS). Keywords Freeman-Sheldon syndrome; Skew foot deformity; Metatarsus adductus PMID:22383916
Increased skewing of X chromosome inactivation in Rett syndrome patients and their mothers.
Knudsen, Gun Peggy S; Neilson, Tracey C S; Pedersen, June; Kerr, Alison; Schwartz, Marianne; Hulten, Maj; Bailey, Mark E S; Orstavik, Karen Helene
2006-11-01
Rett syndrome is a largely sporadic, X-linked neurological disorder with a characteristic phenotype, but which exhibits substantial phenotypic variability. This variability has been partly attributed to an effect of X chromosome inactivation (XCI). There have been conflicting reports regarding incidence of skewed X inactivation in Rett syndrome. In rare familial cases of Rett syndrome, favourably skewed X inactivation has been found in phenotypically normal carrier mothers. We have investigated the X inactivation pattern in DNA from blood and buccal cells of sporadic Rett patients (n=96) and their mothers (n=84). The mean degree of skewing in blood was higher in patients (70.7%) than controls (64.9%). Unexpectedly, the mothers of these patients also had a higher mean degree of skewing in blood (70.8%) than controls. In accordance with these findings, the frequency of skewed (XCI > or =80%) X inactivation in blood was also higher in both patients (25%) and mothers (30%) than in controls (11%). To test whether the Rett patients with skewed X inactivation were daughters of skewed mothers, 49 mother-daughter pairs were analysed. Of 14 patients with skewed X inactivation, only three had a mother with skewed X inactivation. Among patients, mildly affected cases were shown to be more skewed than more severely affected cases, and there was a trend towards preferential inactivation of the paternally inherited X chromosome in skewed cases. These findings, particularly the greater degree of X inactivation skewing in Rett syndrome patients, are of potential significance in the analysis of genotype-phenotype correlations in Rett syndrome.
Skewness and shock formation in laboratory-scale supersonic jet data.
Gee, Kent L; Neilsen, Tracianne B; Atchley, Anthony A
2013-06-01
Spatial properties of noise statistics near unheated, laboratory-scale supersonic jets yield insights into source characteristics and near-field shock formation. Primary findings are (1) waveforms with positive pressure skewness radiate from the source with a directivity upstream of maximum overall level and (2) skewness of the time derivative of the pressure waveforms increases significantly with range, indicating formation of shocks during propagation. These results corroborate findings of a previous study involving full-scale engine data. Further, a comparison of ideally and over-expanded laboratory data show that while derivative skewness maps are similar, waveform skewness maps are substantially different for the two cases.
NASA Astrophysics Data System (ADS)
Liu, Yufang; Zhang, Weiguo; Fu, Junhui
2016-11-01
This paper presents the Binomial Markov-switching Multifractal (BMSM) model of asset returns with Skewed t innovations (BMSM-Skewed t for short), which considers the fat tails, skewness and multifractality in asset returns simultaneously. The parameters of BMSM-Skewed t model can be estimated by Maximum Likelihood (ML) methods, and volatility forecasting can be accomplished via Bayesian updating. In order to evaluate the performance of BMSM-Skewed t model, BMSM model with Normal innovations (BMSM-N), BMSM model with Student-t innovations (BMSM-t) and GARCH(1,1) models (GARCH-N, GARCH-t and GARCH-Skewed t) are chosen for comparison. Through empirical studies on Shanghai Stock Exchange Composite Index (SSEC), we find that for sample estimation, BMSM models outperform the GARCH(1,1) models through BIC and AIC rules, and BMSM-Skewed t performs the best among all the models due to its fat tails, skewness and multifractality. In addition, BMSM-Skewed t model dominates other models at most forecasting horizons for out-of-sample volatility forecasts in terms of MSE, MAE and SPA test.
Bandyopadhyay, Dipankar; Lachos, Victor H.; Castro, Luis M.; Dey, Dipak K.
2012-01-01
Often in biomedical studies, the routine use of linear mixed-effects models (based on Gaussian assumptions) can be questionable when the longitudinal responses are skewed in nature. Skew-normal/elliptical models are widely used in those situations. Often, those skewed responses might also be subjected to some upper and lower quantification limits (viz. longitudinal viral load measures in HIV studies), beyond which they are not measurable. In this paper, we develop a Bayesian analysis of censored linear mixed models replacing the Gaussian assumptions with skew-normal/independent (SNI) distributions. The SNI is an attractive class of asymmetric heavy-tailed distributions that includes the skew-normal, the skew-t, skew-slash and the skew-contaminated normal distributions as special cases. The proposed model provides flexibility in capturing the effects of skewness and heavy tail for responses which are either left- or right-censored. For our analysis, we adopt a Bayesian framework and develop a MCMC algorithm to carry out the posterior analyses. The marginal likelihood is tractable, and utilized to compute not only some Bayesian model selection measures but also case-deletion influence diagnostics based on the Kullback-Leibler divergence. The newly developed procedures are illustrated with a simulation study as well as a HIV case study involving analysis of longitudinal viral loads. PMID:22685005
O'Connell, Megan E; Tuokko, Holly; Kadlec, Helena
2011-04-01
Demographic corrections for cognitive tests should improve classification accuracy by reducing age or education biases, but empirical support has been equivocal. Using a simulation procedure, we show that creating moderate or extreme skewness in cognitive tests compromises the classification accuracy of demographic corrections, findings that appear replicated within clinical data for the few neuropsychological test scores with an extreme degree of skew. For most neuropsychological tests, the dementia classification accuracy of raw and demographically corrected scores was equivalent. These findings suggest that the dementia classification accuracy of demographic corrections is robust to slight degrees of skew (i.e., skewness <1.5).
Measures of kurtosis and skewness of INGARCH model
NASA Astrophysics Data System (ADS)
Mohamad, Nurul Najihah; Mohamed, Ibrahim; Thavaneswaran, A.; Yahya, Mohd Sahar
2014-07-01
Recently there has been a growing interest in time series of counts/integer-valued time series. The time series under the hypothesis of homogeneous variance becomes unrealistic in many situations because the variance tend to change with level. Important models such as ACP (autoregressive conditional Poisson) models and integer valued GARCH models have been proposed in the literature. Ghahramani and Thavaneswaran [1] studied the moment properties of ACP models using martingale transformation. However the forecasting for count process has not been studied in the literature. Using a martingale transformation, Thavaneswaran et al. [2] studied the volatility forecasts for GARCH models. In this paper, first we derive closed form expressions for skewness and kurtosis for count processes via martingale transformation then we study the joint forecasts for integer-valued count models with errors following Poisson.
Soft bounds on diffusion produce skewed distributions and Gompertz growth
NASA Astrophysics Data System (ADS)
Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco
2014-09-01
Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.
Soft bounds on diffusion produce skewed distributions and Gompertz growth.
Mandrà, Salvatore; Lagomarsino, Marco Cosentino; Gherardi, Marco
2014-09-01
Constraints can affect dramatically the behavior of diffusion processes. Recently, we analyzed a natural and a technological system and reported that they perform diffusion-like discrete steps displaying a peculiar constraint, whereby the increments of the diffusing variable are subject to configuration-dependent bounds. This work explores theoretically some of the revealing landmarks of such phenomenology, termed "soft bound." At long times, the system reaches a steady state irreversibly (i.e., violating detailed balance), characterized by a skewed "shoulder" in the density distribution, and by a net local probability flux, which has entropic origin. The largest point in the support of the distribution follows a saturating dynamics, expressed by the Gompertz law, in line with empirical observations. Finally, we propose a generic allometric scaling for the origin of soft bounds. These findings shed light on the impact on a system of such "scaling" constraint and on its possible generating mechanisms.
Evolution of cooperation and skew under imperfect information.
Akçay, Erol; Meirowitz, Adam; Ramsay, Kristopher W; Levin, Simon A
2012-09-11
The evolution of cooperation in nature and human societies depends crucially on how the benefits from cooperation are divided and whether individuals have complete information about their payoffs. We tackle these questions by adopting a methodology from economics called mechanism design. Focusing on reproductive skew as a case study, we show that full cooperation may not be achievable due to private information over individuals' outside options, regardless of the details of the specific biological or social interaction. Further, we consider how the structure of the interaction can evolve to promote the maximum amount of cooperation in the face of the informational constraints. Our results point to a distinct avenue for investigating how cooperation can evolve when the division of benefits is flexible and individuals have private information.
Cracked shells under skew-symmetric loading. [Reissner theory
NASA Technical Reports Server (NTRS)
Delale, F.
1981-01-01
The general problem of a shell containing a through crack in one of the principal planes of curvature and under general skew-symmetric loading is considered. By employing a Reissner type shell theory which takes into account the effect of transverse shear strains, all boundary conditions on the crack surfaces are satisfied separately. Consequently, unlike those obtained from the classical shell theory, the angular distributions of the stress components around the crack tips are shown to be identical to the distributions obtained from the plane and anti-plane elasticity solutions. Results are given for axially and circumferentially cracked cylindrical shells, spherical shells, and toroidal shells under uniform in-plane shearing, out of plane shearing, and torsion. The problem is formulated for specially orthostropic materials, therefore, the effect of orthotropy on the results is also studied.
Quantum coherence via skew information and its polygamy
NASA Astrophysics Data System (ADS)
Yu, Chang-shui
2017-04-01
Quantifying coherence is a key task in both quantum-mechanical theory and practical applications. Here, a reliable quantum coherence measure is presented by utilizing the quantum skew information of the state of interest subject to a certain broken observable. This coherence measure is proven to fulfill all the criteria (especially the strong monotonicity) recently introduced in the resource theories of quantum coherence. The coherence measure has an analytic expression and an obvious operational meaning related to quantum metrology. In terms of this coherence measure, the distribution of the quantum coherence, i.e., how the quantum coherence is distributed among the multiple parties, is studied and a corresponding polygamy relation is proposed. As a further application, it is found that the coherence measure forms the natural upper bounds for quantum correlations prepared by incoherent operations. The experimental measurements of our coherence measure as well as the relative-entropy coherence and lp-norm coherence are studied finally.
Renormalized cumulants and velocity derivative skewness in Kolmogorov turbulence
NASA Astrophysics Data System (ADS)
Singha, Tapas; Dutta, Kishore; Nandy, Malay K.
2017-03-01
We apply a renormalized perturbative scheme to the Navier–Stokes equation for an incompressible isotropic turbulent velocity field. This allows us to obtain the renormalized expressions for second- and third-order cumulants of the velocity derivative directly from the corresponding Feynman diagrams. The resulting expressions are integrated numerically by excluding and including the dissipation range assuming Kolmogorov and Pao’s phenomenological expressions for the energy spectrum. The ensuing values for skewness are found to be S = ‑0.647 (when the dissipation range is excluded) and S=-0.682 (when the dissipation is included). These estimated values are compared with various experimental, numerical and theoretical results.
Restoring the skew quadrupole moment in the Tevatron dipoles
Harding, D.J.; Bauer, P.C.; Blowers, J.N.; DiMarco, J.; Glass, H.D.; Hanft, R.W.; Carson, J.A.; Robotham, W.F.; Tartaglia, M.A.; Tompkins, J.C.; Velev, G.; /Fermilab
2005-05-01
In early 2003 it was realized that mechanical changes in the Tevatron dipoles had led to a deterioration of the magnetic field quality that was hindering operation of the accelerator. After extensive study, a remediation program was started in late 2003 that will continue through 2005. The mechanical and magnetic effects are discussed. The readjustment process and experience are reported, along with other observations on aging magnets. In January 2003 two lines of inquiry converged, leading to the recognition that the severe betatron coupling that was hindering operation of the Tevatron could be explained by a systematic shift on the skew quadrupole field in the dipole magnets of the same size expected from observed mechanical movement of the coils inside the magnet yokes [1]. This paper reports on subsequent magnet studies that were conducted in parallel with additional beam studies and accelerator modeling [2] exploring the feasibility of the eventual remediation effort [3].
Prototyping and Characterization of an Adjustable Skew Angle Single Gimbal Control Moment Gyroscope
2015-03-01
learning, and never give up on your dreams . xvi THIS PAGE INTENTIONALLY LEFT BLANK 1 I. INTRODUCTION A. BACKGROUND AND MOTIVATION The advancements...is a highly intrusive and impractical means for skew angle adjustment. In order to implement CMG arrays like a box-array which uses a 90° skew angle
Torque ripple minimization in a doubly salient permanent magnet motors by skewing the rotor teeth
NASA Astrophysics Data System (ADS)
Sheth, N. K.; Sekharbabu, A. R. C.; Rajagopal, K. R.
2006-09-01
This paper presents the effects of skewing the rotor teeth on the performance of an 8/6 doubly salient permanent magnet motor using a simple method, which utilizes the results obtained from the 2-D FE analysis. The optimum skewing angle is obtained as 12-15° for the least ripple torque without much reduction in the back-emf.
Testing reproductive skew models in a communally breeding bird, the pukeko, Porphyrio porphyrio
Jamieson, I. G.
1997-01-01
Recent attempts to explain variation among social species in the degree to which reproduction is shared among group members are focused on what are known as reproductive skew models. Reproduction within social groups can vary from an even distribution among all adults (i.e. low skew) to complete monopolization by a dominant individual (high skew). Three critical predictions derived from these models have remained largely untested: (1) reduced chances of independent breeding due to strong ecological constraints results in high reproductive skew; (2) the lower the genetic relatedness within social groups the lower the skew; and, counter-intuitively, (3) dominance-related aggression will be more prevalent in social groups composed of close kin where reproductive skew is predicted to be high. Here I test these predictions by comparing two populations of the communally breeding pukeko (Porphyrio porphyrio), which show extremes in social organization, namely social groups consisting of close kin versus groups made up of unrelated breeders. I report evidence from both cobreeding males and females in support of the above predictions. The results also indicate that low reproductive skew among unrelated group members may be prevalent in social species that possess weapons that can inflict serious injury in situations where reproductive competition may escalate to fighting. The consistency between these results and those from studies of social insects suggests that reproductive skew models may represent a unifying framework for understanding the factors shaping complex animal societies.
Bandyopadhyay, Dipankar; Lachos, Victor H.; Abanto-Valle, Carlos A.; Ghosh, Pulak
2010-01-01
Bivariate clustered (correlated) data often encountered in epidemiological and clinical research are routinely analyzed under a linear mixed model framework with underlying normality assumptions of the random effects and within-subject errors. However, such normality assumptions might be questionable if the data-set particularly exhibit skewness and heavy tails. Using a Bayesian paradigm, we use the skew-normal/independent (SNI) distribution as a tool for modeling clustered data with bivariate non-normal responses in a linear mixed model framework. The SNI distribution is an attractive class of asymmetric thick-tailed parametric structure which includes the skew-normal distribution as a special case. We assume that the random effects follows multivariate skew-normal/independent distributions and the random errors follow symmetric normal/independent distributions which provides substantial robustness over the symmetric normal process in a linear mixed model framework. Specific distributions obtained as special cases, viz. the skew-t, the skew-slash and the skew-contaminated normal distributions are compared, along with the default skew-normal density. The methodology is illustrated through an application to a real data which records the periodontal health status of an interesting population using periodontal pocket depth (PPD) and clinical attachment level (CAL). PMID:20740568
Assessment of seismic performance of skew reinforced concrete box girder bridges
NASA Astrophysics Data System (ADS)
Abdel-Mohti, Ahmed; Pekcan, Gokhan
2013-12-01
The seismic vulnerability of highway bridges remains an important problem and has received increased attention as a consequence of unprecedented damage observed during several major earthquakes. A significant number of research studies have examined the performance of skew bridges under service and seismic loads. The results of these studies are particularly sensitive to modeling assumptions in view of the interacting parameters. In the present study, three-dimensional improved beam-stick models of two-span highway bridges with skew angles varying from 0° to 60° are developed to investigate the seismic response characteristics of skew box girder bridges. The relative accuracy of beam-stick models is verified against counterpart finite element models. The effect of various parameters and conditions on the overall seismic response was examined such as skew angle, ground motion intensity, soil condition, abutment support conditions, bridge aspect ratio, and foundation-base conditions. The study shows that the improved beam-stick models can be used to conduct accurate nonlinear time history analysis of skew bridges. Skew angle and interacting parameters were found to have significant effect on the behavior of skewed highway bridges. Furthermore, the performance of shear keys may have a predominant effect on the overall seismic response of the skew bridges.
Optimization of a magnetic disk drive actuator with small skew actuation
NASA Astrophysics Data System (ADS)
He, Zhimin; Ong, Eng Hong; Guo, Guoxiao
2002-05-01
Currently the utilization of the voice-coil motor for actuating read/write head elements in magnetic hard disk drives results in a skewed actuation, which necessitates an involved microjogging process and thus a complicated servo system. Furthermore, in perpendicular recording systems, a small skew actuation will relax the requirement on pole trimming. This article presents a magnetic hard disk drive actuator and suspension assembly with small skew actuation. In the present study, the distance from the actuator pivot to the read/write head is chosen so that the skew angle variation is minimized. After that, the suspension head is assembled to the actuator arm at a slant angle with respect to the actuator longitudinal direction to achieve an absolute small skew actuation. Finite element modeling and experimental measurements reveal that there are no significant changes of the actuator assembly dynamic performance with and without the slant angle.
Optimizing head/media electrical characterization in the presence of skew at high track density
NASA Astrophysics Data System (ADS)
Wang, Wen Yao; Huo, Hong; Tan, Victor MH
2006-08-01
The skew angle causes a discrepancy in determining the reader-to-writer offset (RWO) when using different periodical patterns in track profile tests. It also separates the peak overwrite (OW) from the peak high frequency amplitude HFA, (1 T periodical pattern) on corresponding track profiles. Furthermore, higher track density and larger skew angle exacerbate the skew effect and induce more RWO error, thus impacting the parametric performance optimization. Simulation studies are used to interpret the skew effect on the RWO determination and OW cross-track characteristics. Based on experimental investigations and simulation analyses, using the HFA, track profile for deriving the optimal RWO is proposed for spin-stand tests. Actual parametric characterization has proven that the optimal RWO minimized the skew effect and the RWO error, thus improving the parametric performance and reducing the test variation. The method is beneficial and necessary for the high track density characterization.
Assessment of seismic responses of skewed bridges with bidirectional collision effect
NASA Astrophysics Data System (ADS)
Wu, G.; You, X.; Hui, Y. X.
2017-06-01
Unbonded laminated elastomeric bearings have been used widely for skewed highway bridges in China. This type bearing is likely to slip during an earthquake, which will lead to large girder displacement and collision phenomenon. In order to discuss the effect of different collision models and design parameters on the seismic response of skewed bridges in China, 3D beam-stick models of three-span highway bridges with skew angles varying from 0°to 60°are developed in this paper. The results show that the collision effect is the principal contributor to girder rotation. The collision model considered nonlinear property in this paper can capture the irregular behavior of skewed bridges correctly. The uneven collision phenomenon will be more obvious for changing the initial gap of shear keys, and the overall seismic responses are likely to become complicated. Then, an appropriate gap is recommended to reduce the seismic damage of skewed bridges.
Ishido, Naoko; Inoue, Naoya; Watanabe, Mikio; Hidaka, Yoh
2015-01-01
Background: Autoimmune thyroid diseases (AITDs) predominantly develop in females. One of two X chromosomes is randomly inactivated by methylation in each female cell, but it has been reported that skewed X chromosome inactivation (XCI) may be associated with the development of autoimmune diseases. To clarify the significance of skewed XCI in the prognosis and development of AITD, we investigated the proportion of skewed XCI in female patients with AITD. Methods: We analyzed the degree of XCI skewing in 120 female patients with AITD (77 patients with Graves' disease [GD] and 43 patients with Hashimoto's disease [HD]) and 49 female controls in DNA from peripheral blood mononuclear cells (PBMC). We performed XCI analysis by digesting inactive DNA with a methylation-sensitive restriction enzyme (HpaII) followed by a polymerase chain reaction (PCR) assay for the polymorphic CAG repeat of the androgen receptor gene and electrophoresis of the PCR products. Results: The proportion of skewed XCI (≥65% skewing) was not significantly different between AITD patients and control subjects but was higher in patients with intractable GD (66.7%) than those with GD in remission (25.0%, p=0.0033) and control subjects (32.6%, p=0.0038). When the cutoff value for XCI skewing was relaxed, the proportion of skewed XCI (≥60% skewing) was higher in patients with severe HD (76.5%) than in those with mild HD (41.2%, p=0.0342). Conclusions: Skewed XCI is related to the prognosis of AITD, particularly the intractability of GD. PMID:25338305
Skewness of cloud droplet spectrum and an improved estimation for its relative dispersion
NASA Astrophysics Data System (ADS)
Liu, Yu; Lu, Chunsong; Li, Weiliang
2017-02-01
The relative dispersion of the cloud droplet spectrum is a very important parameter in describing and modeling cloud microphysical processes. Based on the definition of skewness as well as theoretical and data analyses, a linear fitting relationship ( α = 2.91 ɛ-0.59) between skewness ( α) and relative dispersion ( ɛ) is established and a new method is developed to estimate the relative dispersion of the cloud droplet spectrum. The new method does not depend on any assumption of a particular distribution for the cloud droplet spectrum and has broader applicability than the previous methods. Comparisons of the three methods for the relative dispersion with the observed data supported the following conclusions. (1) The skewness of the cloud droplet spectrum is asymmetrically distributed. An assumption of zero skewness in quantifying the relative dispersion inevitably results in relatively large deviations from the observations. Errors of the estimated relative dispersion due to the omission of the skewness term are not solely related to the skewness, but rather to the product of the skewness and relative dispersion. (2) The use of the assumption that the cloud droplet spectrum takes a gamma distribution is similar to the assumption that the skewness is twice the relative dispersion. This leads to a better accuracy in estimating the relative dispersion than that with zero skewness assumption. (3) Comparisons with observations show that the new method is more accurate than the one under gamma distribution assumption and is the best among all the three methods. (4) It is believed that finding a better correlation between the skewness and the relative dispersion would further reduce the deviations for the estimated relative dispersion.
Skew redundant MEMS IMU calibration using a Kalman filter
NASA Astrophysics Data System (ADS)
Jafari, M.; Sahebjameyan, M.; Moshiri, B.; Najafabadi, T. A.
2015-10-01
In this paper, a novel calibration procedure for skew redundant inertial measurement units (SRIMUs) based on micro-electro mechanical systems (MEMS) is proposed. A general model of the SRIMU measurements is derived which contains the effects of bias, scale factor error and misalignments. For more accuracy, the effect of lever arms of the accelerometers to the center of the table are modeled and compensated in the calibration procedure. Two separate Kalman filters (KFs) are proposed to perform the estimation of error parameters for gyroscopes and accelerometers. The predictive error minimization (PEM) stochastic modeling method is used to simultaneously model the effect of bias instability and random walk noise on the calibration Kalman filters to diminish the biased estimations. The proposed procedure is simulated numerically and has expected experimental results. The calibration maneuvers are applied using a two-axis angle turntable in a way that the persistency of excitation (PE) condition for parameter estimation is met. For this purpose, a trapezoidal calibration profile is utilized to excite different deterministic error parameters of the accelerometers and a pulse profile is used for the gyroscopes. Furthermore, to evaluate the performance of the proposed KF calibration method, a conventional least squares (LS) calibration procedure is derived for the SRIMUs and the simulation and experimental results compare the functionality of the two proposed methods with each other.
Vibration suppression of a skew cantilever plate using PZT patches
NASA Astrophysics Data System (ADS)
Pai, Perngjin F.; Rommel, Bernd; Naser, Ahmad S.; Schulz, Mark J.
1998-07-01
We investigate the control of steady-state vibrations of a cantilevered skew isotropic plate by using nonlinear saturation phenomena and PZT (lead zirconate titanate) patches as sensors and actuators. Modal testing and finite- element analysis are performed to study the bending- torsional dynamic characteristics due to the non-rectangular plate geometry. The control method uses linear second-order controllers coupled to the plate via quadratic terms to establish energy bridges between the plate and controllers. Each linear second-order controller is designed to have a 1:2 internal resonance with one of the plate vibration modes and hence is able to exchange energy with the plate at or around the specific modal frequency. Because of quadratic nonlinearities and 1:2 internal resonances, saturation phenomena exist and are used to suppress modal vibrations. To test this control technique in an efficient and systematic way, we built a digital control system that consists of SIMULINK modeling software and a dSPACE DS1102 controller in a pentium computer. Both numerical and experimental results show that this nonlinear control method is robust in suppression steady-state resonant vibrations without significant spill-over effects.
Statistics on Cannabis Users Skew Perceptions of Cannabis Use
Burns, Rachel M.; Caulkins, Jonathan P.; Everingham, Susan S.; Kilmer, Beau
2013-01-01
Collecting information about the prevalence of cannabis use is necessary but not sufficient for understanding the size, dynamics, and outcomes associated with cannabis markets. This paper uses two data sets describing cannabis consumption in the United States and Europe to highlight (1) differences in inferences about sub-populations based on the measure used to quantify cannabis-related activity; (2) how different measures of cannabis-related activity can be used to more accurately describe trends in cannabis usage over time; and (3) the correlation between frequency of use in the past-month and average grams consumed per use-day. Key findings: focusing on days of use instead of prevalence shows substantially greater increases in U.S. cannabis use in recent years; however, the recent increase is mostly among adults, not youth. Relatively more rapid growth in use days also occurred among the college-educated and Hispanics. Further, data from a survey conducted in seven European countries show a strong positive correlation between frequency of use and quantity consumed per day of use, suggesting consumption is even more skewed toward the minority of heavy users than is suggested by days-of-use calculations. PMID:24223560
NASA Technical Reports Server (NTRS)
Nypan, L. J.
1980-01-01
Measurements of roller skewing in a 118 mm bore roller bearing operating at shaft speeds to 12000 rpm are reported. High speed motion pictures of a modified roller were taken through a derotation prism to record skewing as the roller moved through loaded and unloaded regions of the bearing. Subsequent frame by frame measurement of the photographic film provided information on roller skewing. Radial and tangential skew amplitudes of .4 to .5 degrees were observed with .5 degree misalignment.
Fieremans, Nathalie; Van Esch, Hilde; Holvoet, Maureen; Van Goethem, Gert; Devriendt, Koen; Rosello, Monica; Mayo, Sonia; Martinez, Francisco; Jhangiani, Shalini; Muzny, Donna M.; Gibbs, Richard A.; Lupski, James R.; Vermeesch, Joris R.; Marynen, Peter; Froyen, Guy
2016-01-01
Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males due to the hemizygous state of their X chromosome. Carrier females are generally unaffected due to the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analysed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6%) had extreme skewing (>90%), which is significantly higher than observed in the general population (3.6%; p=0.029). Whole exome sequencing of 19 females with extreme skewing revealed causal variants in 6 females in the XLID genes DDX3X, NHS, WDR45, MECP2 and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in 3 of these patients. Moreover, variants likely accounting for skewing only, were detected in MED12, HDAC8 and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients. PMID:27159028
Fieremans, Nathalie; Van Esch, Hilde; Holvoet, Maureen; Van Goethem, Gert; Devriendt, Koenraad; Rosello, Monica; Mayo, Sonia; Martinez, Francisco; Jhangiani, Shalini; Muzny, Donna M; Gibbs, Richard A; Lupski, James R; Vermeesch, Joris R; Marynen, Peter; Froyen, Guy
2016-08-01
Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males because of the hemizygous state of their X chromosome. Carrier females are generally unaffected because of the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analyzed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6%) had extreme skewing (>90%), which is significantly higher than observed in the general population (3.6%; P = 0.029). Whole-exome sequencing of 19 females with extreme skewing revealed causal variants in six females in the XLID genes DDX3X, NHS, WDR45, MECP2, and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in three of these patients. Moreover, variants likely accounting for skewing only were detected in MED12, HDAC8, and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients. © 2016 WILEY PERIODICALS, INC.
Log Pearson type 3 quantile estimators with regional skew information and low outlier adjustments
NASA Astrophysics Data System (ADS)
Griffis, V. W.; Stedinger, J. R.; Cohn, T. A.
2004-07-01
The recently developed expected moments algorithm (EMA) [, 1997] does as well as maximum likelihood estimations at estimating log-Pearson type 3 (LP3) flood quantiles using systematic and historical flood information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study compares the performance of Bulletin 17B using the entire sample with and without regional skew with estimators that use regional skew and censor low outliers, including an extended EMA estimator, the conditional probability adjustment (CPA) from Bulletin 17B, and an estimator that uses probability plot regression (PPR) to compute substitute values for low outliers. Estimators that neglect regional skew information do much worse than estimators that use an informative regional skewness estimator. For LP3 data the low outlier rejection procedure generally results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew are generally modest in the skewness range of real interest. Samples contaminated to model actual flood data demonstrate that estimators which give special treatment to low outliers significantly outperform estimators that make no such adjustment.
Log Pearson type 3 quantile estimators with regional skew information and low outlier adjustments
Griffis, V.W.; Stedinger, J.R.; Cohn, T.A.
2004-01-01
[1] The recently developed expected moments algorithm (EMA) [Cohn et al., 1997] does as well as maximum likelihood estimations at estimating log-Pearson type 3 (LP3) flood quantiles using systematic and historical flood information. Needed extensions include use of a regional skewness estimator and its precision to be consistent with Bulletin 17B. Another issue addressed by Bulletin 17B is the treatment of low outliers. A Monte Carlo study compares the performance of Bulletin 17B using the entire sample with and without regional skew with estimators that use regional skew and censor low outliers, including an extended EMA estimator, the conditional probability adjustment (CPA) from Bulletin 17B, and an estimator that uses probability plot regression (PPR) to compute substitute values for low outliers. Estimators that neglect regional skew information do much worse than estimators that use an informative regional skewness estimator. For LP3 data the low outlier rejection procedure generally results in no loss of overall accuracy, and the differences between the MSEs of the estimators that used an informative regional skew are generally modest in the skewness range of real interest. Samples contaminated to model actual flood data demonstrate that estimators which give special treatment to low outliers significantly outperform estimators that make no such adjustment.
Why are Upward EP-flux and Temperature Positively Skewed in the Stratosphere?
NASA Astrophysics Data System (ADS)
Watt-Meyer, O.; Kushner, P. J.
2016-12-01
Polar stratospheric temperatures are positively skewed, with a typical value of skewness of 0.64 in Northern Hemisphere winter, an asymmetry that determines the character of ozone climate coupling and stratosphere-troposphere interactions. This skewness is often attributed to the fact that temperatures are bounded from below by a radiative limit while dynamical wave-driving events like sudden warmings can drive significantly larger positive anomalies. However, recent research has shown that both strong vortex and weak vortex conditions can involve large wave activity flux anomalies, which suggests that the temperature skewness may be at least partially dynamically controlled. Here, we examine the positive skewness of upward wave activity flux itself as a driver of the temperature distribution. Explaining the skewness of the upward wave activity flux distribution can be done by appealing to the ideas of linear interference. In this framework, heat fluxes are decomposed into a linear term (LIN) that measures the coherence of the wave anomaly and the climatology and an additional nonlinear term (NONLIN) that depends only on the wave anomaly. We demonstrate that there is a strong nonlinear dependence between LIN and NONLIN for wave-1 fluxes: the NONLIN term tends to be large and positive given either a negative or positive LIN term. This has implications for the skewness of upward wave activity flux because the two terms cancel when LIN is negative but reinforce each other when LIN is positive, leading to the positive skewness of upward wave activity flux. This idea is tested by constructing a toy statistical model of wave interference in the lower stratosphere, and it is shown that the westward tilt of the climatology is the key ingredient to obtaining a positively skewed upward EP-flux distribution. Finally, a stochastic model that simulates the relationship between upward EP-flux and temperature in the stratosphere is used to determine the connection between the
GPDs at non-zero skewness in ADS/QCD model
NASA Astrophysics Data System (ADS)
Rinaldi, Matteo
2017-08-01
We study Generalized Parton Distribution functions (GPDs) usually measured in hard exclusive processes and encoding information on the three dimensional partonic structure of hadrons and their spin decomposition, for non-zero skewness within the AdS/QCD formalism. To this aim the canonical scheme to calculate GPDs at zero skewness has been properly generalized. Furthermore, we show that the latter quantities, in this non-forward regime, are sensitive to non-trivial details of the hadronic light front wave function, such as a kind of parton correlations usually not accessible in studies of form factors and GPDs at zero skewness.
Sensitivity of odd-harmonic amplitudes to open quotient and skewing quotient in glottal airflow.
Titze, Ingo R
2015-01-01
It is well known that a half-sinusoid has no odd harmonics other than the fundamental. If glottal flow in phonation were to approximate this exact waveshape, which is generally unlikely, some misperception of pitch and loss of vowel intelligibility would occur. The sensitivity of the glottal waveshape to this special shape is explored by systematically varying two parameters, open quotient and skewing quotient. Mild asymmetry (open quotient below 0.45 or above 0.55 and/or skewing quotient greater than 2.0) equalizes the odd-even harmonic series. Singers and speakers avoid the exact symmetry by skewing the flow pulse with source-filter interaction.
Optimal platform skewing for Space Shuttle inertial measurement unit redundancy management
NASA Technical Reports Server (NTRS)
Rasmussen, M. C.
1980-01-01
Constraints are applied to a general quaternion which describes the skewing between platforms of the Space Shuttle IMU. Once a skewing is derived, the use of the failure magnitude to threshold ratio makes possible predictions of the identification sensitivities for various failure modes. This in turn simplifies analyses and identifies portions of the flight envelope where second failure coverage is lacking. The square root of 6 and square root of 2 skewings have been baselined for use during nominal entry; the realignment software will be used on orbit to reskew the IMUs to the optimal configuration.
NASA Astrophysics Data System (ADS)
Ding, Song; Tian, GuiYun; Dobmann, Gerd; Wang, Ping
2017-01-01
Skewness of Magnetic Barkhausen Noise (MBN) signal is used as a new feature for applied stress determination. After experimental studies, skewness presents its ability for measuring applied tensile stress compared with conventional feature, meanwhile, a non-linear behavior of this new feature and an independence of the excitation conditions under compressive stress are found and discussed. Effective damping during domain wall motion influencing the asymmetric shape of the MBN statistical distribution function is discussed under compressive and tensile stress variation. Domain wall (DW) energy and distance between pinning edges of the DW are considered altering the characteristic relaxation time, which is the reason for the non-linear phenomenon of skewness.
Genetic Architecture of Skewed X Inactivation in the Laboratory Mouse
Calaway, John D.; Lenarcic, Alan B.; Didion, John P.; Wang, Jeremy R.; Searle, Jeremy B.; McMillan, Leonard; Valdar, William; Pardo-Manuel de Villena, Fernando
2013-01-01
X chromosome inactivation (XCI) is the mammalian mechanism of dosage compensation that balances X-linked gene expression between the sexes. Early during female development, each cell of the embryo proper independently inactivates one of its two parental X-chromosomes. In mice, the choice of which X chromosome is inactivated is affected by the genotype of a cis-acting locus, the X-chromosome controlling element (Xce). Xce has been localized to a 1.9 Mb interval within the X-inactivation center (Xic), yet its molecular identity and mechanism of action remain unknown. We combined genotype and sequence data for mouse stocks with detailed phenotyping of ten inbred strains and with the development of a statistical model that incorporates phenotyping data from multiple sources to disentangle sources of XCI phenotypic variance in natural female populations on X inactivation. We have reduced the Xce candidate 10-fold to a 176 kb region located approximately 500 kb proximal to Xist. We propose that structural variation in this interval explains the presence of multiple functional Xce alleles in the genus Mus. We have identified a new allele, Xcee present in Mus musculus and a possible sixth functional allele in Mus spicilegus. We have also confirmed a parent-of-origin effect on X inactivation choice and provide evidence that maternal inheritance magnifies the skewing associated with strong Xce alleles. Based on the phylogenetic analysis of 155 laboratory strains and wild mice we conclude that Xcea is either a derived allele that arose concurrently with the domestication of fancy mice but prior the derivation of most classical inbred strains or a rare allele in the wild. Furthermore, we have found that despite the presence of multiple haplotypes in the wild Mus musculus domesticus has only one functional Xce allele, Xceb. Lastly, we conclude that each mouse taxa examined has a different functional Xce allele. PMID:24098153
Genetic architecture of skewed X inactivation in the laboratory mouse.
Calaway, John D; Lenarcic, Alan B; Didion, John P; Wang, Jeremy R; Searle, Jeremy B; McMillan, Leonard; Valdar, William; Pardo-Manuel de Villena, Fernando
2013-01-01
X chromosome inactivation (XCI) is the mammalian mechanism of dosage compensation that balances X-linked gene expression between the sexes. Early during female development, each cell of the embryo proper independently inactivates one of its two parental X-chromosomes. In mice, the choice of which X chromosome is inactivated is affected by the genotype of a cis-acting locus, the X-chromosome controlling element (Xce). Xce has been localized to a 1.9 Mb interval within the X-inactivation center (Xic), yet its molecular identity and mechanism of action remain unknown. We combined genotype and sequence data for mouse stocks with detailed phenotyping of ten inbred strains and with the development of a statistical model that incorporates phenotyping data from multiple sources to disentangle sources of XCI phenotypic variance in natural female populations on X inactivation. We have reduced the Xce candidate 10-fold to a 176 kb region located approximately 500 kb proximal to Xist. We propose that structural variation in this interval explains the presence of multiple functional Xce alleles in the genus Mus. We have identified a new allele, Xce(e) present in Mus musculus and a possible sixth functional allele in Mus spicilegus. We have also confirmed a parent-of-origin effect on X inactivation choice and provide evidence that maternal inheritance magnifies the skewing associated with strong Xce alleles. Based on the phylogenetic analysis of 155 laboratory strains and wild mice we conclude that Xce(a) is either a derived allele that arose concurrently with the domestication of fancy mice but prior the derivation of most classical inbred strains or a rare allele in the wild. Furthermore, we have found that despite the presence of multiple haplotypes in the wild Mus musculus domesticus has only one functional Xce allele, Xce(b). Lastly, we conclude that each mouse taxa examined has a different functional Xce allele.
Skewness in large-scale structure and non-Gaussian initial conditions
NASA Technical Reports Server (NTRS)
Fry, J. N.; Scherrer, Robert J.
1994-01-01
We compute the skewness of the galaxy distribution arising from the nonlinear evolution of arbitrary non-Gaussian intial conditions to second order in perturbation theory including the effects of nonlinear biasing. The result contains a term identical to that for a Gaussian initial distribution plus terms which depend on the skewness and kurtosis of the initial conditions. The results are model dependent; we present calculations for several toy models. At late times, the leading contribution from the initial skewness decays away relative to the other terms and becomes increasingly unimportant, but the contribution from initial kurtosis, previously overlooked, has the same time dependence as the Gaussian terms. Observations of a linear dependence of the normalized skewness on the rms density fluctuation therefore do not necessarily rule out initially non-Gaussian models. We also show that with non-Gaussian initial conditions the first correction to linear theory for the mean square density fluctuation is larger than for Gaussian models.
Skew in CG content near the transcription start site in Arabidopsis thaliana.
Tatarinova, Tatiana; Brover, Vyacheslav; Troukhan, Maxim; Alexandrov, Nickolai
2003-01-01
We have discovered a novel statistical feature of Arabidopsis thaliana genome that remarkably correlates with a position of transcription start site--CG skew peak. We hypothesize that the phenomenon can be explained by the higher mutability of unprotected cytosines.
A skewed PDF combustion model for jet diffusion flames. [Probability density function (PDF)
Abou-Ellail, M.M.M.; Salem, H. )
1990-11-01
A combustion model based on restricted chemical equilibrium is described. A transport equation for the skewness of the mixture fraction is derived. It contains two adjustable constants. The computed values of the mean mixture fraction (f) and its variance and skewness (g and s) for a jet diffusion methane flame are used to obtain the shape of a shewed pdf. The skewed pdf is split into a turbulent part (beta function) and a nonturbulent part (delta function) at f = 0. The contribution of each part is directly related to the values of f, g, and s. The inclusion of intermittency in the skewed pdf appreciably improves the numerical predictions obtained for a turbulent jet diffusion methane flame for which experimental data are available.
12. Underside of Skew SpanHot Metal system on right, toward ...
12. Underside of Skew Span-Hot Metal system on right, toward Rocker Bent. - Monongahela Connecting Railroad Company, Hot Metal Bridge, Spanning Monongahela River at mile post 3.1, Pittsburgh, Allegheny County, PA
Cloud Fingerprinting: Using Clock Skews To Determine Co Location Of Virtual Machines
2016-09-01
NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS CLOUD FINGERPRINTING: USING CLOCK SKEWS TO DETERMINE CO-LOCATION OF VIRTUAL MACHINES by...9/17/2016 4. TITLE AND SUBTITLE CLOUD FINGERPRINTING: USING CLOCK SKEWS TO DETERMINE CO- LOCATION OF VIRTUAL MACHINES 5. FUNDING NUMBERS 6. AUTHOR(S...hardware hosting virtual machines for multiple businesses and organizations. Current cloud security methods, such as Amazon’s Virtual Private Cloud, have
Some results on circulant and skew circulant type matrices with k-Fibonacci sequences
NASA Astrophysics Data System (ADS)
Zhang, Ying
2017-02-01
In this paper, we consider the circulant matrices, skew circulant matrices and skew left circulant matrices with k-Fibonacci sequences. We compute their eigenvalues by diagonalizing these matrices. Furthermore, the maximum column sum matrix norms, the maximum row sum matrix norms, the Frobenius norms, the spectral norms, and the bounds for the spread of these matrices are given with the properties of k-Fibonacci sequences.
An Adaptive Method for Reducing Clock Skew in an Accumulative Z-Axis Interconnect System
NASA Technical Reports Server (NTRS)
Bolotin, Gary; Boyce, Lee
1997-01-01
This paper will present several methods for adjusting clock skew variations that occur in a n accumulative z-axis interconnect system. In such a system, delay between modules in a function of their distance from one another. Clock distribution in a high-speed system, where clock skew must be kept to a minimum, becomes more challenging when module order is variable before design.
NASA Technical Reports Server (NTRS)
Majumdar, A. K.
1979-01-01
Expressions are derived for higher-order skewness and excess coefficients using central moments and cumulants up to 8th order. These coefficients are then calculated for three probability distributions: (1) Log-normal, (2) Rice-Nakagami, and (3) Gamma distributions. Curves are given to shown the variation of skewness with excess coefficients for these distributions. These curves are independent of the particular distribution parameters. This method is useful for studying fluctuating phenomena, which obey non-Gaussian statistics.
Effect of skew angle on second harmonic guided wave measurement in composite plates
NASA Astrophysics Data System (ADS)
Cho, Hwanjeong; Choi, Sungho; Lissenden, Cliff J.
2017-02-01
Waves propagating in anisotropic media are subject to skewing effects due to the media having directional wave speed dependence, which is characterized by slowness curves. Likewise, the generation of second harmonics is sensitive to micro-scale damage that is generally not detectable from linear features of ultrasonic waves. Here, the effect of skew angle on second harmonic guided wave measurement in a transversely isotropic lamina and a quasi-isotropic laminate are numerically studied. The strain energy density function for a nonlinear transversely isotropic material is formulated in terms of the Green-Lagrange strain invariants. The guided wave mode pairs for cumulative second harmonic generation in the plate are selected in accordance with the internal resonance criteria - i.e., phase matching and non-zero power flux. Moreover, the skew angle dispersion curves for the mode pairs are obtained from the semi-analytical finite element method using the derivative of the slowness curve. The skew angles of the primary and secondary wave modes are calculated and wave propagation simulations are carried out using COMSOL. Numerical simulations revealed that the effect of skew angle mismatch can be significant for second harmonic generation in anisotropic media. The importance of skew angle matching on cumulative second harmonic generation is emphasized and the accompanying issue of the selection of internally resonant mode pairs for both a unidirectional transversely isotropic lamina and a quasi-isotropic laminate is demonstrated.
Mapping of quantitative trait loci using the skew-normal distribution*
Fernandes, Elisabete; Pacheco, António; Penha-Gonçalves, Carlos
2007-01-01
In standard interval mapping (IM) of quantitative trait loci (QTL), the QTL effect is described by a normal mixture model. When this assumption of normality is violated, the most commonly adopted strategy is to use the previous model after data transformation. However, an appropriate transformation may not exist or may be difficult to find. Also this approach can raise interpretation issues. An interesting alternative is to consider a skew-normal mixture model in standard IM, and the resulting method is here denoted as skew-normal IM. This flexible model that includes the usual symmetric normal distribution as a special case is important, allowing continuous variation from normality to non-normality. In this paper we briefly introduce the main peculiarities of the skew-normal distribution. The maximum likelihood estimates of parameters of the skew-normal distribution are obtained by the expectation-maximization (EM) algorithm. The proposed model is illustrated with real data from an intercross experiment that shows a significant departure from the normality assumption. The performance of the skew-normal IM is assessed via stochastic simulation. The results indicate that the skew-normal IM has higher power for QTL detection and better precision of QTL location as compared to standard IM and nonparametric IM. PMID:17973340
Skewed X-chromosome inactivation in patients with esophageal carcinoma
2013-01-01
Abstract Skewed X-chromosome inactivation (SXCI) was found in some apparently healthy females mainly from Western countries. It has been linked to development of ovarian, breast and pulmonary carcinomas. The present study aimed to observe the SXCI frequencies in apparently healthy Chinese females and patients with esophageal carcinoma. DNA was extracted from the peripheral blood cells from 401 Chinese females without a detectable tumor and 143 female patients with esophageal carcinoma. Exon 1 of androgen receptor (AR) gene was amplified, and the products of different CAG alleles were resolved on denaturing polyacrylamide gels and visualized after silver staining. The corrected ratios (CR) of the products before and after HpaII digestion were calculated. As to the healthy females, when CR ≥ 3 was used as a criterion, SXCI was found in two (4.3%) of the 46 neonates, 13 (7.8%) of the 166 younger adults (16–50 years) and 37 (25.7%) of the 144 elderly females (51–96 years), with the frequency higher in the elderly subjects than in the two former groups (P < 0.05). When a more stringent criterion (CR ≥ 10) was used, SXCI was found in one (2.2%), two (1.2%) and 16 (11.1%) of the subjects in the three age groups, respectively, itsfrequency being higher in the elderly than in the younger age groups (P < 0.05). Occurrence of SXCI was detected in both the patients and controls at similar frequencies. However, the phenomenon, as defined as CR ≥ 3, was more frequent in the patients aging <40 years (35.7%) compared to the corresponding reference group (7.6%, P = 0.006). When CR ≥ 10 was adopted, the frequencies were 7.1% and 1.2%, respectively. Their difference did not attain statistical significance (P = 0. 217). SXCI also occurs in apparently healthy Chinese females, and is associated with age. It may be considered as a predisposing factor for the early development of esophageal carcinoma. Virtual slides The virtual slide(s) for this
Static performance investigation of a skewed-throat multiaxis thrust-vectoring nozzle concept
NASA Technical Reports Server (NTRS)
Wing, David J.
1994-01-01
The static performance of a jet exhaust nozzle which achieves multiaxis thrust vectoring by physically skewing the geometric throat has been characterized in the static test facility of the 16-Foot Transonic Tunnel at NASA Langley Research Center. The nozzle has an asymmetric internal geometry defined by four surfaces: a convergent-divergent upper surface with its ridge perpendicular to the nozzle centerline, a convergent-divergent lower surface with its ridge skewed relative to the nozzle centerline, an outwardly deflected sidewall, and a straight sidewall. The primary goal of the concept is to provide efficient yaw thrust vectoring by forcing the sonic plane (nozzle throat) to form at a yaw angle defined by the skewed ridge of the lower surface contour. A secondary goal is to provide multiaxis thrust vectoring by combining the skewed-throat yaw-vectoring concept with upper and lower pitch flap deflections. The geometric parameters varied in this investigation included lower surface ridge skew angle, nozzle expansion ratio (divergence angle), aspect ratio, pitch flap deflection angle, and sidewall deflection angle. Nozzle pressure ratio was varied from 2 to a high of 11.5 for some configurations. The results of the investigation indicate that efficient, substantial multiaxis thrust vectoring was achieved by the skewed-throat nozzle concept. However, certain control surface deflections destabilized the internal flow field, which resulted in substantial shifts in the position and orientation of the sonic plane and had an adverse effect on thrust-vectoring and weight flow characteristics. By increasing the expansion ratio, the location of the sonic plane was stabilized. The asymmetric design resulted in interdependent pitch and yaw thrust vectoring as well as nonzero thrust-vector angles with undeflected control surfaces. By skewing the ridges of both the upper and lower surface contours, the interdependency between pitch and yaw thrust vectoring may be eliminated
The past, present and future of reproductive skew theory and experiments.
Nonacs, Peter; Hager, Reinmar
2011-05-01
A major evolutionary question is how reproductive sharing arises in cooperatively breeding species despite the inherent reproductive conflicts in social groups. Reproductive skew theory offers one potential solution: each group member gains or is allotted inclusive fitness equal to or exceeding their expectation from reproducing on their own. Unfortunately, a multitude of skew models with conflicting predictions has led to confusion in both testing and evaluating skew theory. The confusion arises partly because one set of models (the 'transactional' type) answer the ultimate evolutionary question of what ranges of reproductive skew can yield fitness-enhancing solutions for all group members. The second set of models ('compromise') give an evolutionarily proximate, game-theoretic evolutionarily stable state (ESS) solution that determines reproductive shares based on relative competitive abilities. However, several predictions arising from compromise models require a linear payoff to increased competition and do not hold with non-linear payoffs. Given that for most species it may be very difficult or impossible to determine the true relationship between effort devoted to competition and reproductive share gained, compromise models are much less predictive than previously appreciated. Almost all skew models make one quantitative prediction (e.g. realized skew must fall within ranges predicted by transactional models), and two qualitative predictions (e.g. variation in relatedness or competitive ability across groups affects skew). A thorough review of the data finds that these three predictions are relatively rarely supported. As a general rule, therefore, the evolution of cooperative breeding appears not to be dependent on the ability of group members to monitor relatedness or competitive ability in order to adjust their behaviour dynamically to gain reproductive share. Although reproductive skew theory fails to predict within-group dynamics consistently, it does
Handling Data Skew in MapReduce Cluster by Using Partition Tuning
Zhou, Yanjie; Zhou, Bing; Shi, Lei
2017-01-01
The healthcare industry has generated large amounts of data, and analyzing these has emerged as an important problem in recent years. The MapReduce programming model has been successfully used for big data analytics. However, data skew invariably occurs in big data analytics and seriously affects efficiency. To overcome the data skew problem in MapReduce, we have in the past proposed a data processing algorithm called Partition Tuning-based Skew Handling (PTSH). In comparison with the one-stage partitioning strategy used in the traditional MapReduce model, PTSH uses a two-stage strategy and the partition tuning method to disperse key-value pairs in virtual partitions and recombines each partition in case of data skew. The robustness and efficiency of the proposed algorithm were tested on a wide variety of simulated datasets and real healthcare datasets. The results showed that PTSH algorithm can handle data skew in MapReduce efficiently and improve the performance of MapReduce jobs in comparison with the native Hadoop, Closer, and locality-aware and fairness-aware key partitioning (LEEN). We also found that the time needed for rule extraction can be reduced significantly by adopting the PTSH algorithm, since it is more suitable for association rule mining (ARM) on healthcare data.
Cain, Meghan K; Zhang, Zhiyong; Yuan, Ke-Hai
2016-10-17
Nonnormality of univariate data has been extensively examined previously (Blanca et al., Methodology: European Journal of Research Methods for the Behavioral and Social Sciences, 9(2), 78-84, 2013; Miceeri, Psychological Bulletin, 105(1), 156, 1989). However, less is known of the potential nonnormality of multivariate data although multivariate analysis is commonly used in psychological and educational research. Using univariate and multivariate skewness and kurtosis as measures of nonnormality, this study examined 1,567 univariate distriubtions and 254 multivariate distributions collected from authors of articles published in Psychological Science and the American Education Research Journal. We found that 74 % of univariate distributions and 68 % multivariate distributions deviated from normal distributions. In a simulation study using typical values of skewness and kurtosis that we collected, we found that the resulting type I error rates were 17 % in a t-test and 30 % in a factor analysis under some conditions. Hence, we argue that it is time to routinely report skewness and kurtosis along with other summary statistics such as means and variances. To facilitate future report of skewness and kurtosis, we provide a tutorial on how to compute univariate and multivariate skewness and kurtosis by SAS, SPSS, R and a newly developed Web application.
Modeling absolute differences in life expectancy with a censored skew-normal regression approach.
Moser, André; Clough-Gorr, Kerri; Zwahlen, Marcel
2015-01-01
Parameter estimates from commonly used multivariable parametric survival regression models do not directly quantify differences in years of life expectancy. Gaussian linear regression models give results in terms of absolute mean differences, but are not appropriate in modeling life expectancy, because in many situations time to death has a negative skewed distribution. A regression approach using a skew-normal distribution would be an alternative to parametric survival models in the modeling of life expectancy, because parameter estimates can be interpreted in terms of survival time differences while allowing for skewness of the distribution. In this paper we show how to use the skew-normal regression so that censored and left-truncated observations are accounted for. With this we model differences in life expectancy using data from the Swiss National Cohort Study and from official life expectancy estimates and compare the results with those derived from commonly used survival regression models. We conclude that a censored skew-normal survival regression approach for left-truncated observations can be used to model differences in life expectancy across covariates of interest.
Generalized Skew Coefficients of Annual Peak Flows for Rural, Unregulated Streams in West Virginia
Atkins, John T.; Wiley, Jeffrey B.; Paybins, Katherine S.
2009-01-01
Generalized skew was determined from analysis of records from 147 streamflow-gaging stations in or near West Virginia. The analysis followed guidelines established by the Interagency Advisory Committee on Water Data described in Bulletin 17B, except that stations having 50 or more years of record were used instead of stations with the less restrictive recommendation of 25 or more years of record. The generalized-skew analysis included contouring, averaging, and regression of station skews. The best method was considered the one with the smallest mean square error (MSE). MSE is defined as the following quantity summed and divided by the number of peaks: the square of the difference of an individual logarithm (base 10) of peak flow less the mean of all individual logarithms of peak flow. Contouring of station skews was the best method for determining generalized skew for West Virginia, with a MSE of about 0.2174. This MSE is an improvement over the MSE of about 0.3025 for the national map presented in Bulletin 17B.
Modeling absolute differences in life expectancy with a censored skew-normal regression approach
Clough-Gorr, Kerri; Zwahlen, Marcel
2015-01-01
Parameter estimates from commonly used multivariable parametric survival regression models do not directly quantify differences in years of life expectancy. Gaussian linear regression models give results in terms of absolute mean differences, but are not appropriate in modeling life expectancy, because in many situations time to death has a negative skewed distribution. A regression approach using a skew-normal distribution would be an alternative to parametric survival models in the modeling of life expectancy, because parameter estimates can be interpreted in terms of survival time differences while allowing for skewness of the distribution. In this paper we show how to use the skew-normal regression so that censored and left-truncated observations are accounted for. With this we model differences in life expectancy using data from the Swiss National Cohort Study and from official life expectancy estimates and compare the results with those derived from commonly used survival regression models. We conclude that a censored skew-normal survival regression approach for left-truncated observations can be used to model differences in life expectancy across covariates of interest. PMID:26339544
Skew-Symmetric Splitting and Stability of High Order Central Schemes
NASA Astrophysics Data System (ADS)
Sjögreen, Björn; Yee, H. C.; Kotov, Dmitry
2017-05-01
Skew-symmetric splittings of the inviscid flux derivative for high order central schemes are studied and developed to improve their numerical stability without added high order numerical dissipation for long time wave propagations and long time integration of compressible turbulent flows. For flows containing discontinuities and multiscale turbulence fluctuations the Yee & Sjogreen [33] and Kotov et al. [15, 14] high order nonlinear filter approach is utilized in conjunction with the skew-symmetric form of high order central schemes. Due to the incomplete hyperbolic nature of the conservative ideal magnetohydrodynamics (MHD) governing equations, not all of the skew-symmetric splittings for gas dynamics can be extended to the ideal MHD. For the MHD the Ducros et al. [6] variants are constructed. In addition, four formulations of the MHD are considered: (a) the conservative MHD, (b) the Godunov/Powell non-conservative form, (c) the Janhunen MHD with magnetic field source terms [13], and (d) a MHD with source terms of [3]. The different formulation of the equations in conjunction with the variants of Ducros et al. type skew-symmetric splitting will be shown to have a strong effect on the stability of non-dissipative approximations. Representative test cases for both smooth flows and problems containing discontinuities for the ideal MHD are included. The results illustrate the improved stability by using the skew-symmetric splitting as part of the central base scheme instead of the pure high order central scheme.
Skewness and transformations of Farnsworth-Munsell 100-hue test scores.
Dain, S J
1998-11-01
In the past, suggested transformations of Farnsworth-Munsell 100-Hue Test (FM 100-Hue) test scores distributions have been limited to a square root transformation. In this study, the choice of transformations of total error scores (TES) are considered by identifying a possible source of skewness. Several distributions of FM100-Hue Test TES were assessed for skewness (third moment). The error score (ES) distributions for the 85 individual caps in each of the populations were also analysed for skewness (Figs. 3 and 4). There is no single transformation which will normalise all TES distributions. The single cap ES distributions with low mean ES (such as those achieved normals and, for some regions of the test, by anomalous trichromats and dichromats) are symmetrical because most subjects can organise the cap perfectly (and could do even better given smaller colour differences). The distributions of ESs where the mean ES is in the moderate range (such as those achieved by diabetics) are skewed because some ESs at the lower end of the range represent performance which could also be better than the test allows. ES distributions with a high mean (such as random distributions and some regions of the test by congenital dichromats) are symmetrical being unaffected by the limitations of the test. TES distributions of diabetics are asymmetrical and comprise skewed cap ES distributions. A suggestion for a transformation is made.
Algorithms to get the maximum operation frequency for skew-tolerant clocking schemes
NASA Astrophysics Data System (ADS)
Guerrero, D.; Bellido, M.; Juan, J.; Millan, A.; Ruiz, P.; Ostua, E.; Viejo, J.
2005-06-01
Nowadays it is not possible to neglect the delay of interconnection lines. The die size is rising very fast, and the delay of the interconnection lines grows quadrically with it. Also, the fact that the gate delay keeps getting smaller increases the importance of the delay of the interconnection lines. The delay of the clock lines is specially important: If the clock skew is underestimated and the clocking scheme is not properly designed, then the system may not work under any clock frequency. In this paper we evaluate the timing performance of three skew-tolerant clocking schemes. These schemes are the well known Master-Slave clocking scheme (MS) and two schemes developed by the authors: Parallel Alternating Latches Clocking Scheme (PALACS) and four-phase Parallel Alternating Latches Clocking Scheme (four-phase PALACS). To carry out these analysis, the authors introduce new algorithms to obtain the clock waveforms required by a synchronous sequential circuit. Separated algorithms were developed for every clocking scheme. The algorithms take a set of timing parameters as input and generate a chronogram of the circuit trying to minimise the clock period but ensuring the timing restrictions of the circuit are met for a given clock skew. Using these algorithms is it possible to draw a representation of the computation frequency as a function of the clock skew for every clock scheme. Once we have estimated the timing parameters and the skew, these representations can help us to choose the best clocking scheme for our design.
Eggert, Anne-Katrin; Otte, Tobias; Müller, Josef K
2008-11-07
Proximate mechanisms underlying reproductive skew are obscure in many animals that breed communally. Here, we address causes of reproductive skew in brood-parasitic associations of burying beetles (Nicrophorus vespilloides). Male and female burying beetles feed and defend their larvae on buried carcasses. When several females locate the same small carcass, they engage in violent physical altercations. The subordinate then acts as an intraspecific brood parasite, laying eggs, but not providing care. The dominant female largely monopolizes access to the carcass; she alone provides parental care and her share of the brood is much larger than the subordinate's. On larger carcasses, subordinates have greater access to the carcass than on small ones, and reproductive skew is reduced. Differential fecundity, ovicide and larvicide have been suggested as causes of skew on small carcasses. Here, we report the results of the experiments pertaining to the first two of these potential mechanisms. Ovicide did not significantly contribute to reproductive skew on small carcasses, but differential fecundity did. Fecundity differences were due to dominance status, not body size per se. Fecundity differences disappeared when supplemental food was available, suggesting that reduced access to the carcass limits fecundity by causing nutritional deficiencies. Supplemental food prevented such nutritional deficiencies and allowed subordinates to produce as many eggs as dominants. Apparently, aggressive behaviour by dominants functions in the context of reproductive competition, limiting subordinate reproduction by preventing food intake on the carcass.
Effect of skewing the rotor teeth on the performance of doubly salient permanent magnet motors
NASA Astrophysics Data System (ADS)
Sheth, N. K.; Sekharbabu, A. R. C.; Rajagopal, K. R.
2006-04-01
This paper presents the effects of skewing the rotor teeth on the performance characteristics such as flux linkage, back emf, phase inductance, and reluctance torque of an 8/6 doubly salient permanent magnet motor using a simple method, which utilizes the results obtained from the two-dimensional finite element analysis. The optimum skewing angle is obtained as 12°-15° for the least ripple torque without much reduction in the back emf. Skewing the rotor teeth of an 8/6 doubly salient permanent magnet motor by 12°-15° will reduce the total harmonic distortion of the back emf profile to 29.69% from the original value of 44.69%. The reduction in the amplitude of the back emf in this case will be 18.79% only.
Perceived quality of wood images influenced by the skewness of image histogram
NASA Astrophysics Data System (ADS)
Katsura, Shigehito; Mizokami, Yoko; Yaguchi, Hirohisa
2015-08-01
The shape of image luminance histograms is related to material perception. We investigated how the luminance histogram contributed to improvements in the perceived quality of wood images by examining various natural wood and adhesive vinyl sheets with printed wood grain. In the first experiment, we visually evaluated the perceived quality of wood samples. In addition, we measured the colorimetric parameters of the wood samples and calculated statistics of image luminance. The relationship between visual evaluation scores and image statistics suggested that skewness and kurtosis affected the perceived quality of wood. In the second experiment, we evaluated the perceived quality of wood images with altered luminance skewness and kurtosis using a paired comparison method. Our result suggests that wood images are more realistic if the skewness of the luminance histogram is slightly negative.
NASA Astrophysics Data System (ADS)
Fan, Ya-Jing; Cao, Huai-Xin; Meng, Hui-Xian; Chen, Liang
2016-12-01
The uncertainty principle in quantum mechanics is a fundamental relation with different forms, including Heisenberg's uncertainty relation and Schrödinger's uncertainty relation. In this paper, we prove a Schrödinger-type uncertainty relation in terms of generalized metric adjusted skew information and correlation measure by using operator monotone functions, which reads, U_ρ ^{(g,f)}(A)U_ρ ^{(g,f)}(B)≥ f(0)^2l/k| Corr_ρ ^{s(g,f)}(A,B)| ^2 for some operator monotone functions f and g, all n-dimensional observables A, B and a non-singular density matrix ρ . As applications, we derive some new uncertainty relations for Wigner-Yanase skew information and Wigner-Yanase-Dyson skew information.
Leiva, David; Solanas, Antonio; Salafranca, Lluís
2008-05-01
In the present article, we focus on two indices that quantify directionality and skew-symmetrical patterns in social interactions as measures of social reciprocity: the directional consistency (DC) and skew-symmetry indices. Although both indices enable researchers to describe social groups, most studies require statistical inferential tests. The main aims of the present study are first, to propose an overall statistical technique for testing null hypotheses regarding social reciprocity in behavioral studies, using the DC and skew-symmetry statistics (Phi) at group level; and second, to compare both statistics in order to allow researchers to choose the optimal measure depending on the conditions. In order to allow researchers to make statistical decisions, statistical significance for both statistics has been estimated by means of a Monte Carlo simulation. Furthermore, this study will enable researchers to choose the optimal observational conditions for carrying out their research, since the power of the statistical tests has been estimated.
Skewness in CMB temperature fluctuations from curved cosmic (super-)strings
Yamauchi, Daisuke; Sendouda, Yuuiti; Yoo, Chul-Moon; Naruko, Atsushi; Sasaki, Misao; Takahashi, Keitaro E-mail: sendouda@yukawa.kyoto-u.ac.jp E-mail: keitaro@a.phys.nagoya-u.ac.jp E-mail: misao@yukawa.kyoto-u.ac.jp
2010-05-01
We compute the one-point probability distribution function of small-angle cosmic microwave background temperature fluctuations due to curved cosmic (super-)strings with a simple model of string network by performing Monte Carlo simulations. Taking into account of the correlation between the curvature and the velocity of string segments, there appear non-Gaussian features, specifically non-Gaussian tails and a skewness, in the one-point pdf. The obtained sample skewness for the conventional field-theoretic cosmic strings is g{sub 1} ≈ −0.14, which is consistent with the result reported by Fraisse et al. We also discuss the dependence of the pdf on the intercommuting probability. We find that the standard deviation of the Gaussian part increases and non-Gaussian features are suppressed as the intercommuting probability decreases. For sufficiently small intercommuting probability, the skewness is given by ∼< (a few) × 10{sup −2}.
Watermann, J.; McNamara, A.G. ); Sofko, G.J.; Koehler, J.A. )
1989-06-01
Some 7,700 radio aurora spectra obtained from a six link 50-MHz CW radar network set up on the Canadian prairies were analyzed with respect to the distributions of mean Doppler shift, spectral width and skewness. A comparison with recently published SABRE results obtained at 153 MHz shows substantial differences in the distributions which are probably due to different experimental and geophysical conditions. The spectra are mostly broad with mean Doppler shifts close to zero (type II spectra). The typical groupings of type I and type III spectra are clearly identified. All types appear to be in general much more symmetric than those recorded with SABRE, and the skewness is only weakly dependent on the sign of the mean Doppler shift. Its distribution peaks near zero and shows a weak positive correlation with the type II Doppler shifts while the mostly positive type I Doppler shifts are slightly negatively correlated with the skewness.
Generation of time histories with a specified auto spectral density, skewness, and kurtosis
Smallwood, D.O.
1996-02-01
Some dynamic environments are characterized by time histories that are not Gaussian. A more accurate simulation of these environments can be generated if a realization of a non Gaussian time history can be reproduced which has a specified auto spectral density (also called power spectral density) and a specified skewness and kurtosis (not necessarily the skewness and kurtosis of a Gaussian time history). The mean square of the waveform is reproduced if the spectrum is reproduced. Modern waveform reproduction techniques can be used to reproduce the realized waveform on an electrodynamic or electrohydraulic shaker. A method is presented for the generation of realizations of zero mean non Gaussian random time histories with a specified auto spectral density, skewness, and kurtosis. Kurtosis, defined in this paper as E[{chi}{sup 4}]/E{sup 2}[{chi}{sup 2}], greater than 3 can be realized. Realizations of the random process are generated with a generalization of shot noise.
Modeling the effects of wave skewness and beach cusps on littoral sand transport
Haas, K.A.; Check, L.A.; Hanes, D.M.
2008-01-01
A process-based numerical modeling system is utilized for predicting littoral sand transport. The intent is to examine conditions slightly more complex than linear waves impinging upon a plane beach. Two factors that we examine are wave skewness and longshore varying bathymetry. An empirical model is used for calculating the skewed bottom wave orbital velocity. The advection of sediment due to the skewed wave velocity is larger and in the direction of the waves, opposite to the results with sinusoidal wave velocities, due to the increase in the bottom shear stress under the wave crests. The model system is also applied to bathymetry containing beach cusps. When the wave field has relatively weak longshore wave power, the currents and the littoral transport exhibit significant longshore variability, thereby altering the overall mean littoral transport.
Evolution of Quantitative Traits under a Migration-Selection Balance: When Does Skew Matter?
Débarre, Florence; Yeaman, Sam; Guillaume, Frédéric
2015-10-01
Quantitative-genetic models of differentiation under migration-selection balance often rely on the assumption of normally distributed genotypic and phenotypic values. When a population is subdivided into demes with selection toward different local optima, migration between demes may result in asymmetric, or skewed, local distributions. Using a simplified two-habitat model, we derive formulas without a priori assuming a Gaussian distribution of genotypic values, and we find expressions that naturally incorporate higher moments, such as skew. These formulas yield predictions of the expected divergence under migration-selection balance that are more accurate than models assuming Gaussian distributions, which illustrates the importance of incorporating these higher moments to assess the response to selection in heterogeneous environments. We further show with simulations that traits with loci of large effect display the largest skew in their distribution at migration-selection balance.
Julià, Olga; Vidal-Mas, Jaume; Panikov, Nicolai S.; Vives-Rego, Josep
2010-01-01
We report a skew-Laplace statistical analysis of both flow cytometry scatters and cell size from microbial strains primarily grown in batch cultures, others in chemostat cultures and bacterial aquatic populations. Cytometry scatters best fit the skew-Laplace distribution while cell size as assessed by an electronic particle analyzer exhibited a moderate fitting. Unlike the cultures, the aquatic bacterial communities clearly do not fit to a skew-Laplace distribution. Due to its versatile nature, the skew-Laplace distribution approach offers an easy, efficient, and powerful tool for distribution of frequency analysis in tandem with the flow cytometric cell sorting. PMID:20592754
Julià, Olga; Vidal-Mas, Jaume; Panikov, Nicolai S; Vives-Rego, Josep
2010-01-01
We report a skew-Laplace statistical analysis of both flow cytometry scatters and cell size from microbial strains primarily grown in batch cultures, others in chemostat cultures and bacterial aquatic populations. Cytometry scatters best fit the skew-Laplace distribution while cell size as assessed by an electronic particle analyzer exhibited a moderate fitting. Unlike the cultures, the aquatic bacterial communities clearly do not fit to a skew-Laplace distribution. Due to its versatile nature, the skew-Laplace distribution approach offers an easy, efficient, and powerful tool for distribution of frequency analysis in tandem with the flow cytometric cell sorting.
Elevated Mortality among Birds in Chernobyl as Judged from Skewed Age and Sex Ratios
Møller, Anders Pape; Bonisoli-Alquati, Andrea; Rudolfsen, Geir; Mousseau, Timothy A.
2012-01-01
Background Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions. Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in male-skewed adult sex ratios. Methodology/Principal Finding We estimated the effects of low-dose radiation on adult survival rates in birds by determining age ratios of adults captured in mist nets during the breeding season in relation to background radiation levels around Chernobyl and in nearby uncontaminated control areas. Age ratios were skewed towards yearlings, especially in the most contaminated areas, implying that adult survival rates were reduced in contaminated areas, and that populations in such areas could only be maintained through immigration from nearby uncontaminated areas. Differential mortality in females resulted in a strongly male-skewed sex ratio in the most contaminated areas. In addition, males sang disproportionately commonly in the most contaminated areas where the sex ratio was male skewed presumably because males had difficulty finding and acquiring mates when females were rare. The results were not caused by permanent emigration by females from the most contaminated areas because none of the recaptured birds had changed breeding site, and the proportion of individuals with morphological abnormalities did not differ significantly between the sexes for areas with normal and higher levels of contamination. Conclusions/Significance These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation. Such skewed age ratios towards yearlings in contaminated areas are consistent with the hypothesis that an area exceeding 30,000 km2 in
Elevated mortality among birds in Chernobyl as judged from skewed age and sex ratios.
Møller, Anders Pape; Bonisoli-Alquati, Andrea; Rudolfsen, Geir; Mousseau, Timothy A
2012-01-01
Radiation has negative effects on survival of animals including humans, although the generality of this claim is poorly documented under low-dose field conditions. Because females may suffer disproportionately from the effects of radiation on survival due to differences in sex roles during reproduction, radiation-induced mortality may result in male-skewed adult sex ratios. We estimated the effects of low-dose radiation on adult survival rates in birds by determining age ratios of adults captured in mist nets during the breeding season in relation to background radiation levels around Chernobyl and in nearby uncontaminated control areas. Age ratios were skewed towards yearlings, especially in the most contaminated areas, implying that adult survival rates were reduced in contaminated areas, and that populations in such areas could only be maintained through immigration from nearby uncontaminated areas. Differential mortality in females resulted in a strongly male-skewed sex ratio in the most contaminated areas. In addition, males sang disproportionately commonly in the most contaminated areas where the sex ratio was male skewed presumably because males had difficulty finding and acquiring mates when females were rare. The results were not caused by permanent emigration by females from the most contaminated areas because none of the recaptured birds had changed breeding site, and the proportion of individuals with morphological abnormalities did not differ significantly between the sexes for areas with normal and higher levels of contamination. These findings are consistent with the hypothesis that the adult survival rate of female birds is particularly susceptible to the effects of low-dose radiation, resulting in male skewed sex ratios at high levels of radiation. Such skewed age ratios towards yearlings in contaminated areas are consistent with the hypothesis that an area exceeding 30,000 km(2) in Chernobyl's surroundings constitutes an ecological trap that
Multivariate skew- t approach to the design of accumulation risk scenarios for the flooding hazard
NASA Astrophysics Data System (ADS)
Ghizzoni, Tatiana; Roth, Giorgio; Rudari, Roberto
2010-10-01
The multivariate version of the skew- t distribution provides a powerful analytical description of the joint behavior of multivariate processes. It enjoys valuable properties: from the aptitude to model skewed as well as leptokurtic datasets to the availability of moments and likelihood analytical expressions. Moreover, it offers a wide range of extremal dependence strength, allowing for upper and lower tail dependence. The idea underneath this work is to employ the multivariate skew- t distribution to provide an estimation of the joint probability of flood events in a multi-site multi-basin approach. This constitutes the basis for the design and evaluation of flood hazard scenarios for large areas in terms of their intensity, extension and frequency, i.e. those information required by civil protection agencies to put in action mitigation strategies and by insurance companies to price the flooding risk and to evaluate portfolios. Performances of the skew- t distribution and the corresponding t copula function, introduced to represent the state of the art for multivariate simulations, are discussed with reference to the Tanaro Basin, North-western Italy. To enhance the characteristics of the correlation structure, three nested and non-nested gauging stations are selected with contributing areas from 1500 to 8000 km 2. A dataset of 76 trivariate flood events is extracted from a mean daily discharges database available for the time period from January 1995 to December 2003. Applications include the generation of multivariate skew- t and t copula samples and models' comparison through the principle of minimum cross-entropy, here revised for the application to multivariate samples. Copula and skew- t based scenario return period estimations are provided for the November 1994 flood event, i.e. the worst on record in the 1801-2001 period. Results are encouraging: the skew- t distribution seems able to describe the joint behavior, being close to the observations. Marginal
Analysis of axially non-uniform loss distribution in 3-phase induction motor considering skew effect
Kown, B.I.; Kim, B.T.; Jun, C.S.; Park, S.C. )
1999-05-01
This paper discusses the phenomena of the axially non-uniform distribution of magnetic flux densities and losses in a 3-phase squirrel cage induction motor of which the rotor bars are skewed. A 2-dimensional complex finite element method taking account of the effects of the skewed rotor bars is utilized for the analysis of characteristics such as copper and iron losses and the loss distributions are examined. The summing up values of non-uniform losses resulted from the finite element analysis are compared with measurement values.
Rhiel, G Steven
2010-02-01
In 2007, Rhiel presented a technique to estimate the coefficient of variation from the range when sampling from skewed distributions. To provide an unbiased estimate, a correction factor (a(n)) for the mean was included. Numerical correction factors for a number of skewed distributions were provided. In a follow-up paper, he provided a proof he claimed showed the correction factor was independent of the mean and standard deviation, making the factors useful as these parameters vary; however, that proof did not establish independence. Herein is a proof which establishes the independence.
The dissipation-range spectrum and the velocity-derivative skewness in turbulent flows
NASA Technical Reports Server (NTRS)
Smith, L. M.; Reynolds, W. C.
1991-01-01
A dynamical equation for the energy dissipation rate is used together with a model spectrum to predict the velocity derivative skewness at a high Reynolds number. The objective is to determine the best choice of the exponent, m, so that the resulting model spectrum can be used to estimate statistical properties of the fine scales of turbulence. Skewness data suggest that m = 2 is the best model for laboratory-scale flows and m = 1 is a poor model for a broad range of Reynolds numbers.
The Use of the Skew T, Log P Diagram in Analysis and Forecasting. Revision
1990-03-01
65 O 006 6063 10 1i 0 i 6 110 I1 FA*RtNEPIT TEMPCRATUX( SCALE Figure 3. Isatherms an the Skew-T Chert. in parts of water vapor per 1000 parts of dry...2 no 1000200 .p 47, 46 46 so III U $3 04 UT so s7 U 0s s .o es so t5 10050 Figure 7. Ttcdmm Socoles an Owe Skew-T Churt. * 2-7 0* ~ ~ ~ ~~~V orj or
Bounded Skew High-Order Resolution Schemes for the Discrete Ordinates Method
NASA Astrophysics Data System (ADS)
Coelho, P. J.
2002-01-01
The discrete ordinates method for the solution of the radiative heat transfer equation suffers from two main shortcomings, namely ray effects and numerical smearing. Spatial discretization, which is the cause of numerical smearing, constitutes the subject of the present work. Bounded skew high-order resolution schemes are applied to the discrete ordinate equations and compared with standard bounded high-order resolution schemes (CLAM, MUSCL, and SMART), as well as with the step scheme. Calculations are performed for two- and three-dimensional enclosures with transparent, emitting-absorbing, and emitting-absorbing-scattering media. One of the walls of the enclosure is hot, while the others are cold. The results demonstrate that the bounded skew high-order schemes are more accurate than the bounded high-order ones, regardless of the radiative properties of the medium. The improved accuracy is more significant for the radiation intensity along directions oblique to the coordinate lines, but it is also observed for the incident radiation. The difference between the results of the skewed and the standard schemes is attenuated as the optical thickness of the medium increases. A drawback of the skewed schemes is their higher computational requirements, associated with an increased number of iterations required for convergence.
Large-Scale Age-Dependent Skewed Sex Ratio in a Sexually Dimorphic Avian Scavenger
Lambertucci, Sergio A.; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando
2012-01-01
Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed. PMID:23029488
Skewness and Kurtosis as Applied to a Portfolio in the Korean Stock Market
NASA Astrophysics Data System (ADS)
Ahn, Tae-Sung
2009-04-01
A well diversified portfolio is critical to prudent investment in a stock market. To lessen risk in a volatile market, portfolios should minimize dispersion. This paper analyzes skewness and kurtosis of businesses listed on Korean stock markets, e.g., KOSPI and KOSDAQ. It looks at distribution using the Gauss function, and examines how mean and variance can be applied in building a portfolio.
An analytical algorithm for skew-slit imaging geometry with nonuniform attenuation correction.
Huang, Qiu; Zeng, Gengsheng L
2006-04-01
The pinhole collimator is currently the collimator of choice in small animal single photon emission computed tomography (SPECT) imaging because it can provide high spatial resolution and reasonable sensitivity when the animal is placed very close to the pinhole. It is well known that if the collimator rotates around the object (e.g., a small animal) in a circular orbit to form a cone-beam imaging geometry with a planar trajectory, the acquired data are not sufficient for an exact artifact-free image reconstruction. In this paper a novel skew-slit collimator is mounted instead of the pinhole collimator in order to significantly reduce the image artifacts caused by the geometry. The skew-slit imaging geometry is a more generalized version of the pinhole imaging geometry. The multiple pinhole geometry can also be extended to the multiple-skew-slit geometry. An analytical algorithm for image reconstruction based on the tilted fan-beam inversion is developed with nonuniform attenuation compensation. Numerical simulation shows that the axial artifacts are evidently suppressed in the skew-slit images compared to the pinhole images and the attenuation correction is effective.
On Some Confidence Intervals for Estimating the Mean of a Skewed Population
ERIC Educational Resources Information Center
Shi, W.; Kibria, B. M. Golam
2007-01-01
A number of methods are available in the literature to measure confidence intervals. Here, confidence intervals for estimating the population mean of a skewed distribution are considered. This note proposes two alternative confidence intervals, namely, Median t and Mad t, which are simple adjustments to the Student's t confidence interval. In…
The curious anomaly of skewed judgment distributions and systematic error in the wisdom of crowds.
Nash, Ulrik W
2014-01-01
Judgment distributions are often skewed and we know little about why. This paper explains the phenomenon of skewed judgment distributions by introducing the augmented quincunx (AQ) model of sequential and probabilistic cue categorization by neurons of judges. In the process of developing inferences about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can be inferred from how skewed their judgment distributions are, and in what direction they tilt. This implies not just that judgment distributions are shaped by cues, but that judgment distributions are cues themselves for the wisdom of crowds. The AQ model also predicts that judgment variance correlates positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support, and implications are discussed with reference to three central ideas on collective intelligence, these being Galton's conjecture on the distribution of judgments, Muth's rational expectations hypothesis, and Page's diversity prediction theorem.
Consistent paternity skew through ontogeny in Peron's tree frog (Litoria peronii).
Sherman, Craig D H; Wapstra, Erik; Olsson, Mats
2009-12-14
A large number of studies in postcopulatory sexual selection use paternity success as a proxy for fertilization success. However, selective mortality during embryonic development can lead to skews in paternity in situations of polyandry and sperm competition. Thus, when assessment of paternity fails to incorporate mortality skews during early ontogeny, this may interfere with correct interpretation of results and subsequent evolutionary inference. In a previous series of in vitro sperm competition experiments with amphibians (Litoria peronii), we showed skewed paternity patterns towards males more genetically similar to the female. Here we use in vitro fertilizations and sperm competition trials to test if this pattern of paternity of fully developed tadpoles reflects patterns of paternity at fertilization and if paternity skews changes during embryonic development. We show that there is no selective mortality through ontogeny and that patterns of paternity of hatched tadpoles reflects success of competing males in sperm competition at fertilization. While this study shows that previous inferences of fertilization success from paternity data are valid for this species, rigorous testing of these assumptions is required to ensure that differential embryonic mortality does not confound estimations of true fertilization success.
Influence of pressure gradient on streamwise skewness factor in turbulent boundary layer
NASA Astrophysics Data System (ADS)
Dróżdż, Artur
2014-08-01
The paper shows an effect of favourable and adverse pressure gradients on turbulent boundary layer. The skewness factor of streamwise velocity component was chosen as a measure of the pressure gradient impact. It appears that skewness factor is an indicator of convection velocity of coherent structures, which is not always equal to the average flow velocity. The analysis has been performed based upon velocity profiles measured with hot-wire technique in turbulent boundary layer with pressure gradient corresponding to turbomachinery conditions. The results show that the skewness factor decreases in the flow region subjected to FPG and increases in the APG conditions. The changes of convection velocity and skewness factor are caused by influence of large-scale motion through the mechanism called amplitude modulation. The large-scale motion is less active in FPG and more active in APG, therefore in FPG the production of vortices is random (there are no high and low speed regions), while in the APG the large-scale motion drives the production of vortices. Namely, the vortices appear only in the high-speed regions, therefore have convection velocity higher than local mean velocity. The convection velocity affects directly the turbulent sweep and ejection events. The more flow is dominated by large-scale motion the higher values takes both the convection velocity of small-scale structures and sweep events induced by them.
Using social parasitism to test reproductive skew models in a primitively eusocial wasp
Green, Jonathan P.; Cant, Michael A.; Field, Jeremy
2014-01-01
Remarkable variation exists in the distribution of reproduction (skew) among members of cooperatively breeding groups, both within and between species. Reproductive skew theory has provided an important framework for understanding this variation. In the primitively eusocial Hymenoptera, two models have been routinely tested: concessions models, which assume complete control of reproduction by a dominant individual, and tug-of-war models, which assume on-going competition among group members over reproduction. Current data provide little support for either model, but uncertainty about the ability of individuals to detect genetic relatedness and difficulties in identifying traits conferring competitive ability mean that the relative importance of concessions versus tug-of-war remains unresolved. Here, we suggest that the use of social parasitism to generate meaningful variation in key social variables represents a valuable opportunity to explore the mechanisms underpinning reproductive skew within the social Hymenoptera. We present a direct test of concessions and tug-of-war models in the paper wasp Polistes dominulus by exploiting pronounced changes in relatedness and power structures that occur following replacement of the dominant by a congeneric social parasite. Comparisons of skew in parasitized and unparasitized colonies are consistent with a tug-of-war over reproduction within P. dominulus groups, but provide no evidence for reproductive concessions. PMID:24990668
Lu, Xiaosun; Huang, Yangxin
2014-07-20
It is a common practice to analyze complex longitudinal data using nonlinear mixed-effects (NLME) models with normality assumption. The NLME models with normal distributions provide the most popular framework for modeling continuous longitudinal outcomes, assuming individuals are from a homogeneous population and relying on random-effects to accommodate inter-individual variation. However, the following two issues may standout: (i) normality assumption for model errors may cause lack of robustness and subsequently lead to invalid inference and unreasonable estimates, particularly, if the data exhibit skewness and (ii) a homogeneous population assumption may be unrealistically obscuring important features of between-subject and within-subject variations, which may result in unreliable modeling results. There has been relatively few studies concerning longitudinal data with both heterogeneity and skewness features. In the last two decades, the skew distributions have shown beneficial in dealing with asymmetric data in various applications. In this article, our objective is to address the simultaneous impact of both features arisen from longitudinal data by developing a flexible finite mixture of NLME models with skew distributions under Bayesian framework that allows estimates of both model parameters and class membership probabilities for longitudinal data. Simulation studies are conducted to assess the performance of the proposed models and methods, and a real example from an AIDS clinical trial illustrates the methodology by modeling the viral dynamics to compare potential models with different distribution specifications; the analysis results are reported.
Large-scale age-dependent skewed sex ratio in a sexually dimorphic avian scavenger.
Lambertucci, Sergio A; Carrete, Martina; Donázar, José Antonio; Hiraldo, Fernando
2012-01-01
Age-dependent skewed sex ratios have been observed in bird populations, with adult males generally outnumbering females. This trend is mainly driven by higher female mortality, sometimes associated with anthropogenic factors. Despite the large amount of work on bird sex ratios, research examining the spatial stability of adult sex ratios is extremely scarce. The Andean condor (Vultur gryphus) is the only bird of prey with strong sexual dimorphism favouring males (males are 30% heavier than females). By examining data from most of its South-American range, we show that while the juvenile sex ratio is balanced, or even female-skewed, the sex ratio becomes increasing male-skewed with age, with adult males outnumbering females by >20%, and, in some cases by four times more. This result is consistent across regions and independent of the nature of field data. Reasons for this are unknown but it can be hypothesized that the progressive disappearance of females may be associated with mortality caused by anthropogenic factors. This idea is supported by the asymmetric habitat use by the two sexes, with females scavenging in more humanized areas. Whatever the cause, male-skewed adult sex ratios imply that populations of this endangered scavenger face higher risks of extinction than previously believed.
NASA Astrophysics Data System (ADS)
Dehghan, Mehdi; Hajarian, Masoud
2012-08-01
A matrix P is called a symmetric orthogonal if P = P T = P -1. A matrix X is said to be a generalised bisymmetric with respect to P if X = X T = PXP. It is obvious that any symmetric matrix is also a generalised bisymmetric matrix with respect to I (identity matrix). By extending the idea of the Jacobi and the Gauss-Seidel iterations, this article proposes two new iterative methods, respectively, for computing the generalised bisymmetric (containing symmetric solution as a special case) and skew-symmetric solutions of the generalised Sylvester matrix equation ? (including Sylvester and Lyapunov matrix equations as special cases) which is encountered in many systems and control applications. When the generalised Sylvester matrix equation has a unique generalised bisymmetric (skew-symmetric) solution, the first (second) iterative method converges to the generalised bisymmetric (skew-symmetric) solution of this matrix equation for any initial generalised bisymmetric (skew-symmetric) matrix. Finally, some numerical results are given to illustrate the effect of the theoretical results.
Development of a Skewed Pipe Shear Connector for Precast Concrete Structures
Kim, Sang-Hyo; Choi, Jae-Gu; Park, Sejun; Lee, Hyunmin; Heo, Won-Ho
2017-01-01
Joint connection methods, such as shear key and loop bar, improve the structural performance of precast concrete structures; consequently, there is usually decreased workability or constructional efficiency. This paper proposes a high-efficiency skewed pipe shear connector. To resist shear and pull-out forces, the proposed connectors are placed diagonally between precast concrete segments and a cast-in-place concrete joint part on a girder. Design variables (such as the pipe diameter, length, and insertion angle) have been examined to investigate the connection performance of the proposed connector. The results of our testing indicate that the skewed pipe shear connectors have 50% higher ductility and a 15% higher ratio of maximum load to yield strength as compared to the corresponding parameters of the loop bar. Finite element analysis was used for validation. The resulting validation indicates that, compared to the loop bar, the skewed pipe shear connector has a higher ultimate shear and pull-out resistance. These results indicate that the skewed pipe shear connector demonstrates more idealized behavior than the loop bar in precast concrete structures. PMID:28772887
Development of a Skewed Pipe Shear Connector for Precast Concrete Structures.
Kim, Sang-Hyo; Choi, Jae-Gu; Park, Sejun; Lee, Hyunmin; Heo, And Won-Ho
2017-05-13
Joint connection methods, such as shear key and loop bar, improve the structural performance of precast concrete structures; consequently, there is usually decreased workability or constructional efficiency. This paper proposes a high-efficiency skewed pipe shear connector. To resist shear and pull-out forces, the proposed connectors are placed diagonally between precast concrete segments and a cast-in-place concrete joint part on a girder. Design variables (such as the pipe diameter, length, and insertion angle) have been examined to investigate the connection performance of the proposed connector. The results of our testing indicate that the skewed pipe shear connectors have 50% higher ductility and a 15% higher ratio of maximum load to yield strength as compared to the corresponding parameters of the loop bar. Finite element analysis was used for validation. The resulting validation indicates that, compared to the loop bar, the skewed pipe shear connector has a higher ultimate shear and pull-out resistance. These results indicate that the skewed pipe shear connector demonstrates more idealized behavior than the loop bar in precast concrete structures.
The Curious Anomaly of Skewed Judgment Distributions and Systematic Error in the Wisdom of Crowds
Nash, Ulrik W.
2014-01-01
Judgment distributions are often skewed and we know little about why. This paper explains the phenomenon of skewed judgment distributions by introducing the augmented quincunx (AQ) model of sequential and probabilistic cue categorization by neurons of judges. In the process of developing inferences about true values, when neurons categorize cues better than chance, and when the particular true value is extreme compared to what is typical and anchored upon, then populations of judges form skewed judgment distributions with high probability. Moreover, the collective error made by these people can be inferred from how skewed their judgment distributions are, and in what direction they tilt. This implies not just that judgment distributions are shaped by cues, but that judgment distributions are cues themselves for the wisdom of crowds. The AQ model also predicts that judgment variance correlates positively with collective error, thereby challenging what is commonly believed about how diversity and collective intelligence relate. Data from 3053 judgment surveys about US macroeconomic variables obtained from the Federal Reserve Bank of Philadelphia and the Wall Street Journal provide strong support, and implications are discussed with reference to three central ideas on collective intelligence, these being Galton's conjecture on the distribution of judgments, Muth's rational expectations hypothesis, and Page's diversity prediction theorem. PMID:25406078
Progress in understanding the renormalization group skewness and kappa-epsilon models
NASA Technical Reports Server (NTRS)
Smith, Leslie M.; Reynolds, W. C.
1991-01-01
The immediate goal is to understand and validate the Yakhot-Orszag model of the velocity-derivative skewness and model equation for the rate of energy dissipation epsilon. A summary of a more detailed manuscript in preparation is presented. The purpose is to clarify some limitations of the theory by careful examination of key assumptions and approximations, and thereby to encourage its improvement.
Tan, Kun; An, Lei; Miao, Kai; Ren, Likun; Hou, Zhuocheng; Tao, Li; Zhang, Zhenni; Wang, Xiaodong; Xia, Wei; Liu, Jinghao; Wang, Zhuqing; Xi, Guangyin; Gao, Shuai; Sui, Linlin; Zhu, De-Sheng; Wang, Shumin; Wu, Zhonghong; Bach, Ingolf; Chen, Dong-bao; Tian, Jianhui
2016-01-01
Dynamic epigenetic reprogramming occurs during normal embryonic development at the preimplantation stage. Erroneous epigenetic modifications due to environmental perturbations such as manipulation and culture of embryos during in vitro fertilization (IVF) are linked to various short- or long-term consequences. Among these, the skewed sex ratio, an indicator of reproductive hazards, was reported in bovine and porcine embryos and even human IVF newborns. However, since the first case of sex skewing reported in 1991, the underlying mechanisms remain unclear. We reported herein that sex ratio is skewed in mouse IVF offspring, and this was a result of female-biased peri-implantation developmental defects that were originated from impaired imprinted X chromosome inactivation (iXCI) through reduced ring finger protein 12 (Rnf12)/X-inactive specific transcript (Xist) expression. Compensation of impaired iXCI by overexpression of Rnf12 to up-regulate Xist significantly rescued female-biased developmental defects and corrected sex ratio in IVF offspring. Moreover, supplementation of an epigenetic modulator retinoic acid in embryo culture medium up-regulated Rnf12/Xist expression, improved iXCI, and successfully redeemed the skewed sex ratio to nearly 50% in mouse IVF offspring. Thus, our data show that iXCI is one of the major epigenetic barriers for the developmental competence of female embryos during preimplantation stage, and targeting erroneous epigenetic modifications may provide a potential approach for preventing IVF-associated complications. PMID:26951653
Yue, Yang; Zhang, Bo; Wang, Qiang; Lofland, Rob; O'Neil, Jason; Anderson, Jon
2016-03-21
Dual-polarization quadrature amplitude modulation (DP-QAM) is one of the feasible paths towards 100-Gb/s, 400-Gb/s and 1-Tb/s optical fiber communications systems. For DP-QAM transmitter, the time mismatch between the in-phase and quadrature (IQ) or x-polarized and y-polarized (XY) tributary channels is known as the IQ or XY skew. Large uncompensated IQ or XY skew can significantly degrade the optical fiber communications system performance. Sometimes, time-interleaved return-to-zero (RZ) DP signal is preferred with lower nonlinear polarization scattering induced penalty. In this work, detection and alignment of DP-QAM transmitter IQ and XY skews using reconfigurable interference is experimentally demonstrated. For IQ skew detection, a total dynamic range of 26.4 dB is achieved with ~1-dB power change for 0.5-ps skew from well alignment. For XY skew detection, it shows 23.2-dB dynamic range, and ~1.5-dB power change is achieved for 1-ps XY skew. Fast detection algorithm for arbitrary skew is also proposed and experimentally verified. The scheme is compatible with different modulation formats, flexible data sequences, and variable waveforms.
Wikberg, Eva C; Jack, Katharine M; Fedigan, Linda M; Campos, Fernando A; Yashima, Akiko S; Bergstrom, Mackenzie L; Hiwatashi, Tomohide; Kawamura, Shoji
2017-01-01
Reproductive skew in multimale groups may be determined by the need for alpha males to offer reproductive opportunities as staying incentives to subordinate males (concessions), by the relative fighting ability of the alpha male (tug-of-war) or by how easily females can be monopolized (priority-of-access). These models have rarely been investigated in species with exceptionally long male tenures, such as white-faced capuchins, where female mate choice for novel unrelated males may be important in shaping reproductive skew. We investigated reproductive skew in white-faced capuchins at Sector Santa Rosa, Costa Rica, using 20 years of demographic, behavioural and genetic data. Infant survival and alpha male reproductive success were highest in small multimale groups, which suggests that the presence of subordinate males can be beneficial to the alpha male, in line with the concession model's assumptions. None of the skew models predicted the observed degree of reproductive sharing, and the probability of an alpha male producing offspring was not affected by his relatedness to subordinate males, whether he resided with older subordinate males, whether he was prime aged, the number of males or females in the group or the number of infants conceived within the same month. Instead, the alpha male's probability of producing offspring decreased when he was the sire of the mother, was weak and lacked a well-established position and had a longer tenure. Because our data best supported the inbreeding avoidance hypothesis and female choice for strong novel mates, these hypotheses should be taken into account in future skew models.
Reynolds, Pamela L; Bruno, John F
2012-01-01
Widespread overharvesting of top consumers of the world's ecosystems has "skewed" food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions.
Reproductive skew and relatedness in social groups of European badgers, Meles meles.
Dugdale, Hannah L; Macdonald, David W; Pope, Lisa C; Johnson, Paul J; Burke, Terry
2008-04-01
Reproductive skew is a measure of the proportion of individuals of each sex that breed in a group and is a valuable measure for understanding the evolution and maintenance of sociality. Here, we provide the first quantification of reproductive skew within social groups of European badgers Meles meles, throughout an 18-year study in a high-density population. We used 22 microsatellite loci to analyse within-group relatedness and demonstrated that badger groups contained relatives. The average within-group relatedness was high (R = 0.20) and approximately one-third of within-group dyads were more likely to represent first-order kin than unrelated pairs. Adult females within groups had higher pairwise relatedness than adult males, due to the high frequency of extra-group paternities, rather than permanent physical dispersal. Spatial clustering of relatives occurred among neighbouring groups, which we suggest was due to the majority of extra-group paternities being attributable to neighbouring males. Reproductive skew was found among within-group candidate fathers (B = 0.26) and candidate mothers (B = 0.07), but not among breeding individuals; our power to detect skew in the latter was low. We use these results to evaluate reproductive skew models. Although badger society best fits the assumptions of the incomplete-control models, our results were not consistent with their predictions. We suggest that this may be due to female control of paternity, female-female reproductive suppression occurring only in years with high food availability resulting in competition over access to breeding sites, extra-group paternity masking the benefits of natal philopatry, and/or the inconsistent occurrence of hierarchies that are linear when established.
NASA Astrophysics Data System (ADS)
Bayat, M.; Daneshjoo, F.; Nisticò, N.
2017-01-01
In this study the probable seismic behavior of skewed bridges with continuous decks under earthquake excitations from different directions is investigated. A 45° skewed bridge is studied. A suite of 20 records is used to perform an Incremental Dynamic Analysis (IDA) for fragility curves. Four different earthquake directions have been considered: -45°, 0°, 22.5°, 45°. A sensitivity analysis on different spectral intensity meas ures is presented; efficiency and practicality of different intensity measures have been studied. The fragility curves obtained indicate that the critical direction for skewed bridges is the skew direction as well as the longitudinal direction. The study shows the importance of finding the most critical earthquake in understanding and predicting the behavior of skewed bridges.
NASA Astrophysics Data System (ADS)
Yue, Yang; Zhang, Bo; Wang, Qiang; Lofland, Rob; O'Neil, Jason; Anderson, Jon
2016-02-01
DP-QAM is one of the feasible paths towards 100Gbps, 400Gbps and 1Tbps optical communications systems. For DPQAM transmitter, the time mismatch between the XY tributary channels is known as the XY skew. Large uncompensated XY skew can significantly degrade the system performance. Sometimes, time-interleaved return-to-zero DP signal is preferred with lower nonlinear polarization scattering induced penalty. In this work, XY skew detection and alignment of dual-polarization optical quadrature amplitude transmitter using reconfigurable interference is experimentally demonstrated with >23-dB dynamic range. ~1.5-dB power change is achieved for 1-ps XY skew. Fast detecting scheme for arbitrary skew measurement is also experimentally verified. The scheme is compatible with different modulation formats, data sequences, and waveforms.
Consequences of a male takeover on mating skew in wild Sanje mangabeys.
Fernández, David
2016-01-28
Among primate species living in multimale-multifemale groups, the number of receptive females may determine the rank of the lowest male that copulates (priority of access model, or PoA [Altmann SA. 1962. A field study of the sociobiology of rhesus monkeys, Macaca mulatta. Annals of the New York Academy of Sciences 102:338-435]). Factors, such as temporary instability in the hierarchy and female behavior can, however, affect high-ranking males' ability to monopolize females, reducing mating skew and causing the hierarchy to depart from predictions of PoA. Here, I use behavioral data collected over a 22-month period on a wild group of Sanje mangabeys (Cercocebus sanjei) to examine the effect of a takeover by two immigrating males who became α and β in the hierarchy, and of female behavior on male mating skew. Data on male agonistic interactions were collected on nine males using ad libitum observations, while information on male mating success (i.e., daily proportion of ejaculatory copulations with the focal female) was collected through focal follows of 12 sexually receptive females. Before the takeover, the hierarchy was stable and highly skewed, with the α-male monopolizing up to 75% of copulations. At this time, however, mating skew did not follow the predictions of PoA. During the takeover, from the time one of the newly immigrant males replaced the α until the second immigrant male became the new β, the stability of the hierarchy dropped significantly and mating was no longer skewed. Accordingly, the top two ranking males at that time (i.e., the new α and former β) accounted for only 33% of copulations. After the takeover, rank stability increased, and mating skew followed the PoA. Female mating solicitations also had a significant positive effect on male mating success, and may have contributed to the deviation from the PoA. This study demonstrates that temporary rank instability decreases high-ranking males' ability to monopolize copulations, causing a
Construction engineering of steel tub-girder bridge systems for skew effects
NASA Astrophysics Data System (ADS)
Jimenez Chong, Juan Manuel
Closed structural sections, such as those having circular, rectangular or trapezoidal shape, possess high rotational rigidity when compared to open sections such as I-girders. The high torsional rigidity of closed sections makes them ideal for use in highly curved bridges. In this case, the geometry of the bridge results in large torsional forces. Because of structural efficiency and economy reasons, most of these closed-section bridges consist of a trapezoidal cross-section, with a top concrete slab and bottom and side steel plates. The slab is cast after the steel is erected and thus a system of internal diaphragms and braces is necessary to stabilize the system during erection. During the steel erection and the early stages of the concrete deck placement, the section can be considered as quasi-closed as the top concrete flange has not been cast or is not yet effective. During steel erection, undetermined and/or large torsional forces and/or displacements may result in fit-up problems requiring large stresses to overcome. During concrete deck placement, the undetermined displacements can affect the control of the deck thickness and the final deck geometry, such as the alignment of deck joints and the matching of stages in phased constructions projects. Due to the interactions between their various components, the behavior of curved and skewed tub-girder bridges is significantly more complex than that of straight bridges. When skewed supports are used in tub-girders, the interaction of the girder bending rotations and the displacement constraints induced by the skewed support diaphragms causes twisting of the girders at the supports. These twist rotations introduce additional torques into the system. Both curvature and skew can cause design and construction difficulties, especially at the supports, where the corresponding steel dead load deflections and the large torsional stiffness of the girders may lead to large fit-up forces. Currently, the general
Muon Tracking Studies in a Skew Parametric Resonance Ionization Cooling Channel
Sy, Amy; Afanaciev, Andre; Derbenev, Yaroslav S.; Johnson, Rolland; Morozov, Vasiliy
2015-09-01
Skew Parametric-resonance Ionization Cooling (SPIC) is an extension of the Parametric-resonance Ionization Cooling (PIC) framework that has previously been explored as the final 6D cooling stage of a high-luminosity muon collider. The addition of skew quadrupoles to the PIC magnetic focusing channel induces coupled dynamic behavior of the beam that is radially periodic. The periodicity of the radial motion allows for the avoidance of unwanted resonances in the horizontal and vertical transverse planes, while still providing periodic locations at which ionization cooling components can be implemented. A first practical implementation of the magnetic field components required in the SPIC channel is modeled in MADX. Dynamic features of the coupled correlated optics with and without induced parametric resonance are presented and discussed.
Tang, An-Min; Tang, Nian-Sheng
2015-02-28
We propose a semiparametric multivariate skew-normal joint model for multivariate longitudinal and multivariate survival data. One main feature of the posited model is that we relax the commonly used normality assumption for random effects and within-subject error by using a centered Dirichlet process prior to specify the random effects distribution and using a multivariate skew-normal distribution to specify the within-subject error distribution and model trajectory functions of longitudinal responses semiparametrically. A Bayesian approach is proposed to simultaneously obtain Bayesian estimates of unknown parameters, random effects and nonparametric functions by combining the Gibbs sampler and the Metropolis-Hastings algorithm. Particularly, a Bayesian local influence approach is developed to assess the effect of minor perturbations to within-subject measurement error and random effects. Several simulation studies and an example are presented to illustrate the proposed methodologies.
Optimization Of Mean-Semivariance-Skewness Portfolio Selection Model In Fuzzy Random Environment
NASA Astrophysics Data System (ADS)
Chatterjee, Amitava; Bhattacharyya, Rupak; Mukherjee, Supratim; Kar, Samarjit
2010-10-01
The purpose of the paper is to construct a mean-semivariance-skewness portfolio selection model in fuzzy random environment. The objective is to maximize the skewness with predefined maximum risk tolerance and minimum expected return. Here the security returns in the objectives and constraints are assumed to be fuzzy random variables in nature and then the vagueness of the fuzzy random variables in the objectives and constraints are transformed into fuzzy variables which are similar to trapezoidal numbers. The newly formed fuzzy model is then converted into a deterministic optimization model. The feasibility and effectiveness of the proposed method is verified by numerical example extracted from Bombay Stock Exchange (BSE). The exact parameters of fuzzy membership function and probability density function are obtained through fuzzy random simulating the past dates.
Skewing of immune cell cytokine production by mediators from adipocytes and endothelial cells
Vielma, Silvana A; Klein, Richard L; Levingston, Corinne A; Young, M Rita I
2014-01-01
Since adipose tissue is composed of adipocytes as well as other cell types including endothelial cells, this study sought to determine how mediators from adipocytes and from endothelial cells impact on immune cell production of cytokines. A minimalistic design was used in which media conditioned by adipocytes or by endothelial cells were added individually or as a mixture to normal spleen cells. Media from adipocytes or endothelial cells each stimulated spleen cell production of Th1 cytokines, Th2 cytokines, most of the measured inflammatory cytokines, and some chemokines. However, a mixture of media conditioned by adipocytes and by endothelial cells inhibited production of Th1 cytokines and skewed reactivity toward a Th2 and inflammatory phenotype. Adiponectin, but not leptin, was shown to contribute to the skewing of immune responsiveness to endothelial cell-derived mediators. PMID:24719786
Truck loading positions for maximum live load girder moment in skewed integral bridges
NASA Astrophysics Data System (ADS)
Yalcin, O. Fatih
2015-12-01
In this study, the effect of the longitudinal and transverse truck positions on the distribution of live load moment among the girders of skewed integral abutment bridges (SIBs) is investigated. For this purpose, three dimensional finite element models (FEMs) of several single-span SIBs are built and analyzed. In the analyses, bridges with various skew angles under all possible single and double truck loading positions both in longitudinal and transverse directions are considered. An automated analysis procedure managed by a visual basic program is developed to obtain the structural models and apply the wheel loads of trucks. The finite element analyses (FEA) results are then used to find the most critical loading cases of single truck and adjacent two trucks for the live load moment in the girders of SIBs. The results revealed that, the trucks should be placed nearby the midline of the bridge deck in a diagonal manner.
Verbruggen, Frederick; Chambers, Christopher D; Logan, Gordon D
2013-03-01
The stop-signal paradigm is a popular method for examining response inhibition and impulse control in psychology, cognitive neuroscience, and clinical domains because it allows the estimation of the covert latency of the stop process: the stop-signal reaction time (SSRT). In three sets of simulations, we examined to what extent SSRTs that were estimated with the popular mean and integration methods were influenced by the skew of the reaction time distribution and the gradual slowing of the response latencies. We found that the mean method consistently overestimated SSRT. The integration method tended to underestimate SSRT when response latencies gradually increased. This underestimation bias was absent when SSRTs were estimated with the integration method for smaller blocks of trials. Thus, skewing and response slowing can lead to spurious inhibitory differences. We recommend that the mean method of estimating SSRT be abandoned in favor of the integration method.
Research on the optimal structure configuration of dither RLG used in skewed redundant INS
NASA Astrophysics Data System (ADS)
Gao, Chunfeng; Wang, Qi; Wei, Guo; Long, Xingwu
2016-05-01
The actual combat effectiveness of weapon equipment is restricted by the performance of Inertial Navigation System (INS), especially in high reliability required situations such as fighter, satellite and submarine. Through the use of skewed sensor geometries, redundant technique has been applied to reduce the cost and improve the reliability of the INS. In this paper, the structure configuration and the inertial sensor characteristics of Skewed Redundant Strapdown Inertial Navigation System (SRSINS) using dithered Ring Laser Gyroscope (RLG) are analyzed. For the dither coupling effects of the dither gyro, the system measurement errors can be amplified either the individual gyro dither frequency is near one another or the structure of the SRSINS is unreasonable. Based on the characteristics of RLG, the research on coupled vibration of dithered RLG in SRSINS is carried out. On the principle of optimal navigation performance, optimal reliability and optimal cost-effectiveness, the comprehensive evaluation scheme of the inertial sensor configuration of SRINS is given.
Dip and anisotropy effects on flow using a vertically skewed model grid.
Hoaglund, John R; Pollard, David
2003-01-01
Darcy flow equations relating vertical and bedding-parallel flow to vertical and bedding-parallel gradient components are derived for a skewed Cartesian grid in a vertical plane, correcting for structural dip given the principal hydraulic conductivities in bedding-parallel and bedding-orthogonal directions. Incorrect-minus-correct flow error results are presented for ranges of structural dip (0 < or = theta < or = 90) and gradient directions (0 < or = phi < or = 360). The equations can be coded into ground water models (e.g., MODFLOW) that can use a skewed Cartesian coordinate system to simulate flow in structural terrain with deformed bedding planes. Models modified with these equations will require input arrays of strike and dip, and a solver that can handle off-diagonal hydraulic conductivity terms.
Skew-Quad Parametric-Resonance Ionization Cooling: Theory and Modeling
Afanaciev, Andre; Derbenev, Yaroslav S.; Morozov, Vasiliy; Sy, Amy; Johnson, Rolland P.
2015-09-01
Muon beam ionization cooling is a key component for the next generation of high-luminosity muon colliders. To reach adequately high luminosity without excessively large muon intensities, it was proposed previously to combine ionization cooling with techniques using a parametric resonance (PIC). Practical implementation of PIC proposal is a subject of this report. We show that an addition of skew quadrupoles to a planar PIC channel gives enough flexibility in the design to avoid unwanted resonances, while meeting the requirements of radially-periodic beam focusing at ionization-cooling plates, large dynamic aperture and an oscillating dispersion needed for aberration corrections. Theoretical arguments are corroborated with models and a detailed numerical analysis, providing step-by-step guidance for the design of Skew-quad PIC (SPIC) beamline.
Remaining useful life prediction for an adaptive skew-Wiener process model
NASA Astrophysics Data System (ADS)
Huang, Zeyi; Xu, Zhengguo; Ke, Xiaojie; Wang, Wenhai; Sun, Youxian
2017-03-01
Predicting the remaining useful life for operational devices plays a critical role in prognostics and health management. As the models based on the stochastic processes are widely used for characterizing the degradation trajectory, an adaptive skew-Wiener model, which is much more flexible than traditional stochastic process models, is proposed to model the degradation drift of industrial devices. To make full use of the prior knowledge and the historical information, an on-line filtering algorithm is proposed for state estimation, a two-stage algorithm is adopted to estimate unknown parameters as well. For remaining useful life prediction, a novel result is presented with an explicit form based on the closed skew normal distribution. Finally, sufficient Monte Carlo simulations and an application for ball bearings in rotating electrical machines are used to validate our approach.
A reciprocity law and the skew Pieri rule for the symplectic group
NASA Astrophysics Data System (ADS)
Howe, Roger; Lávička, Roman; Lee, Soo Teck; Souček, Vladimír
2017-03-01
We use the theory of skew duality to show that decomposing the tensor product of k irreducible representations of the symplectic group Sp2 m=Sp2 m(ℂ ) is equivalent to branching from Sp2n to Sp2 n1×⋯ ×Sp2 nk , where n ,n1,… ,nk are positive integers such that n =n1+⋯ +nk and the njs depend on m as well as the representations in the tensor product. Using this result and a work of Lepowsky, we obtain a skew Pieri rule for Sp2m, i.e., a description of the irreducible decomposition of the tensor product of an irreducible representation of the symplectic group Sp2m with a fundamental representation.
Higher reproductive skew among birds than mammals in cooperatively breeding species.
Raihani, Nichola J; Clutton-Brock, Tim H
2010-10-23
While competition for limited breeding positions is a common feature of group life, species vary widely in the extent to which reproduction is shared among females ('reproductive skew'). In recent years, there has been considerable debate over the mechanisms that generate variation in reproductive skew, with most evidence suggesting that subordinates breed when dominants are unable to prevent them from doing so. Here, we suggest that viviparity reduces the ability of dominant females to control subordinate reproduction and that, as a result, dominant female birds are more able than their mammal counterparts to prevent subordinates from breeding. Empirical data support this assertion. This perspective may increase our understanding of how cooperative groups form and are stabilized in nature.
Research on the Multi-variable Optimization of Forward-skewed Blade
NASA Astrophysics Data System (ADS)
Yang, Bo; Gu, Chuan Gang
2011-12-01
This is a study of the multi-variable optimization of the forward-skewed blade by means of the Genetic Algorithms combined with an improved Hierarchical Fair Competition model. In this optimization scheme, the Bezier curves were used to describe the airfoil profiles, numerical simulations were adopted to estimate the aerodynamic performance of the axial-flow machine and a specific fitness function was put forwards to evaluate the fitness level of every individual. In order to testify the optimization algorithms and to study the effects of the forward-skewed blades on the fan performance, a series of comparative experiments and calculations were carried out to illustrate the performance difference between the optimized and the other three fans.
Olfactory learning skews mushroom body output pathways to steer behavioral choice in Drosophila
Owald, David; Waddell, Scott
2015-01-01
Learning permits animals to attach meaning and context to sensory stimuli. How this information is coded in neural networks in the brain, and appropriately retrieved and utilized to guide behavior, is poorly understood. In the fruit fly olfactory memories of particular value are represented within sparse populations of odor-activated Kenyon cells (KCs) in the mushroom body ensemble. During learning reinforcing dopaminergic neurons skew the mushroom body network by driving zonally restricted plasticity at synaptic junctions between the KCs and subsets of the overall small collection of mushroom body output neurons. Reactivation of this skewed KC-output neuron network retrieves memory of odor valence and guides appropriate approach or avoidance behavior. PMID:26496148
Changing skewness: an early warning signal of regime shifts in ecosystems.
Guttal, Vishwesha; Jayaprakash, Ciriyam
2008-05-01
Empirical evidence for large-scale abrupt changes in ecosystems such as lakes and vegetation of semi-arid regions is growing. Such changes, called regime shifts, can lead to degradation of ecological services. We study simple ecological models that show a catastrophic transition as a control parameter is varied and propose a novel early warning signal that exploits two ubiquitous features of ecological systems: nonlinearity and large external fluctuations. Either reduced resilience or increased external fluctuations can tip ecosystems to an alternative stable state. It is shown that changes in asymmetry in the distribution of time series data, quantified by changing skewness, is a model-independent and reliable early warning signal for both routes to regime shifts. Furthermore, using model simulations that mimic field measurements and a simple analysis of real data from abrupt climate change in the Sahara, we study the feasibility of skewness calculations using data available from routine monitoring.
Homoclinic snaking in plane Couette flow: bending, skewing, and finite-size effects
NASA Astrophysics Data System (ADS)
Gibson, John; Schneider, Tobias
2016-11-01
Invariant solutions of shear flows have recently been extended from spatially periodic solutions in minimal flow units to spatially localized solutions on extended domains. One set of spanwise-localized solutions of plane Couette flow exhibits homoclinic snaking, a process by which steady-state solutions grow additional structure smoothly at their fronts when continued parametrically. In this talk, we present a numerical study of the snaking solutions, generalizing beyond the fixed streamwise wavelength of previous studies. We find a number of new solution features, including bending, skewing, and finite-size effects. We establish the parameter regions over which snaking occurs and show that the finite-size effects of the traveling-wave solution are due to a coupling between its fronts and interior that results from its shift-reflect symmetry. A new winding solution of plane Couette flow is derived from a strongly-skewed localized equilibrium.
Expanding the mission plan for large scale telescope systems via skew path optical conditioners
NASA Astrophysics Data System (ADS)
Savastinuk, John; Palmer, Troy A.; Alexay, Christopher
2017-05-01
We describe a case study in which a telescope system, originally designed for a large format, visible camera, needed MWIR imaging capabilities while maintaining its original setup. The dedicated telescope system was adapted to share its existing optics with a new imaging module via a skew path concept. The challenges of non-rotationally symmetric design are explored along with an explanation of the methodology used to analyze and address the unique configuration.
Permanent Magnet Skew Quadrupoles for the Low Emittance LER Lattice of PEP-II
Decker, F.-J.; Anderson, S.; Kharakh, D.; Sullivan, M.; /SLAC
2011-07-05
The vertical emittance of the low energy ring (LER) in the PEP-II B-Factory was reduced by using skew quadrupoles consisting of permanent magnet material. The advantages over electric quadrupoles or rotating existing normal quadrupoles are discussed. To assure a high field quality, a Biot-Savart calculation was used to cancel the natural 12-pole component by using different size poles over a few layers. A magnetic measurement confirmed the high quality of the magnets. After installation and adjusting the original electric 12 skew and 16 normal quadrupoles the emittance contribution from the region close to the interaction point, which was the biggest part in the original design, was considerably reduced. To strengthen the vertical behavior of the LER beam, a low emittance lattice was developed. It lowered the original vertical design emittance from 0.54 nm-rad to 0.034 nm-rad. In order to achieve this, additional skew quadrupoles were required to bring the coupling correction out of the arcs and closer to the detector solenoid in the straight (Fig. 1). It is important, together with low vertical dispersion, that the low vertical emittance is not coupled into the horizontal, which is what we get if the coupling correction continues into the arcs. Further details of the lattice work is described in another paper; here we concentrate on the development of the permanent skew (PSK) quadrupole solution. Besides the permanent magnets there are two other possibilities, using electric magnets or rotating normal quadrupoles. Electric magnets would have required much more additional equipment like magnets stands, power supply, and new vacuum chamber sections. Rotating existing quadrupoles was also not feasible since they are mostly mounted together with a bending magnet on the same support girder.
Measuring skewness of red blood cell deformability distribution by laser ektacytometry
NASA Astrophysics Data System (ADS)
Nikitin, S. Yu; Priezzhev, A. V.; Lugovtsov, A. E.; Ustinov, V. D.
2014-08-01
An algorithm is proposed for measuring the parameters of red blood cell deformability distribution based on laser diffractometry of red blood cells in shear flow (ektacytometry). The algorithm is tested on specially prepared samples of rat blood. In these experiments we succeeded in measuring the mean deformability, deformability variance and skewness of red blood cell deformability distribution with errors of 10%, 15% and 35%, respectively.
Effects of Skew Angle on Simple Span Bridge Decks under Simulated Truck Loading.
1984-01-01
for the Bending Plate Parallelogram ( BPP ) element which is used in this study. Zienkiewicz [20] shows it is not possible for a simple polynomial...expres- sion to ensure full compatibility when only one displacement and two rotations are prescribed at the nodes. However, experience [20] with the BPP ...the Bending Plate Parallelogram ( BPP ) which is very well suited to skew plate analysis. The BPP uses a fourth order transverse displacement expansion
Measuring skewness of red blood cell deformability distribution by laser ektacytometry
Nikitin, S Yu; Priezzhev, A V; Lugovtsov, A E; Ustinov, V D
2014-08-31
An algorithm is proposed for measuring the parameters of red blood cell deformability distribution based on laser diffractometry of red blood cells in shear flow (ektacytometry). The algorithm is tested on specially prepared samples of rat blood. In these experiments we succeeded in measuring the mean deformability, deformability variance and skewness of red blood cell deformability distribution with errors of 10%, 15% and 35%, respectively. (laser biophotonics)
Efficient skew-angle cladding-pumped tunable narrow-linewidth Yb-doped fiber laser.
Jelger, Pär; Laurell, Fredrik
2007-12-15
A skew-angle cladding-pumped tunable Yb-doped fiber laser is presented. The laser was tunable over more than 30 nm, from 1022 to 1055 nm, by employing a volume Bragg grating in a retroreflector configuration as one of the cavity delimiters. Output powers in excess of 4.3 W were recorded with a spectral bandwidth of 5 GHz and an M(2) value below 1.3 over the whole tuning range.
Lau, A W; Brown, C J; Peñaherrera, M; Langlois, S; Kalousek, D K; Robinson, W P
1997-01-01
The inactivation of one X chromosome in females is normally random with regard to which X is inactivated. However, exclusive or almost-exclusive inactivation of one X may be observed in association with some X-autosomal rearrangements, mutations of the XIST gene, certain X-linked diseases, and MZ twinning. In the present study, a methylation difference near a polymorphism in the X-linked androgen-receptor gene was used to investigate the possibility that nonrandom X inactivation is increases in fetuses and newborns that are associated with confined placental mosaicism (CPM) involving an autosomal trisomy. Extreme skewing was observed in 7 (58%) of 12 cases with a meiotic origin of the trisomy, but in none of 10 cases examined with a somatic origin of the trisomy, and in only 1 (4%) of 27 control adult females. In addition, an extremely skewed X-inactivation pattern was observed in 3 of 10 informative cases of female uniparental disomy (UPD) of chromosome 15. This may reflect the fact that a proportion of UPD cases arise by "rescue" of a chromosomally abnormal conceptus and are therefore associated with CPM. A skewed pattern of X inactivation in CPM cases is hypothesized to result from a reduction in the size of the early-embryonic cell pool, because of either poor early growth or subsequent selection against the trisomic cells. Since approximately 2% of pregnancies detected by chorionic villus sampling are associated with CPM, this is likely a significant contributor to both skewed X inactivation observed in the newborn population and the expression of recessive X-linked diseases in females. Images Figure 1 PMID:9399909
Reynolds, Pamela L.; Bruno, John F.
2012-01-01
Widespread overharvesting of top consumers of the world’s ecosystems has “skewed” food webs, in terms of biomass and species richness, towards a generally greater domination at lower trophic levels. This skewing is exacerbated in locations where exotic species are predominantly low-trophic level consumers such as benthic macrophytes, detritivores, and filter feeders. However, in some systems where numerous exotic predators have been added, sometimes purposefully as in many freshwater systems, food webs are skewed in the opposite direction toward consumer dominance. Little is known about how such modifications to food web topology, e.g., changes in the ratio of predator to prey species richness, affect ecosystem functioning. We experimentally measured the effects of trophic skew on production in an estuarine food web by manipulating ratios of species richness across three trophic levels in experimental mesocosms. After 24 days, increasing macroalgal richness promoted both plant biomass and grazer abundance, although the positive effect on plant biomass disappeared in the presence of grazers. The strongest trophic cascade on the experimentally stocked macroalgae emerged in communities with a greater ratio of prey to predator richness (bottom-rich food webs), while stronger cascades on the accumulation of naturally colonizing algae (primarily microalgae with some early successional macroalgae that recruited and grew in the mesocosms) generally emerged in communities with greater predator to prey richness (the more top-rich food webs). These results suggest that trophic skewing of species richness and overall changes in food web topology can influence marine community structure and food web dynamics in complex ways, emphasizing the need for multitrophic approaches to understand the consequences of marine extinctions and invasions. PMID:22693549
Neutrino exotica in the skew E6 left-right model
NASA Astrophysics Data System (ADS)
Ma, Ernest
2000-11-01
With the particle content of the 27 representation of E6, a skew left-right supersymmetric gauge model was proposed many years ago, with a variety of interesting phenomenological implications. The neutrino sector of this model offers a natural framework for obtaining small Majorana masses for νe, νμ, and ντ, with the added bonus of accommodating 2 light sterile neutrinos.
Effect of phase response curve skew on synchronization with and without conduction delays
Canavier, Carmen C.; Wang, Shuoguo; Chandrasekaran, Lakshmi
2013-01-01
A central problem in cortical processing including sensory binding and attentional gating is how neurons can synchronize their responses with zero or near-zero time lag. For a spontaneously firing neuron, an input from another neuron can delay or advance the next spike by different amounts depending upon the timing of the input relative to the previous spike. This information constitutes the phase response curve (PRC). We present a simple graphical method for determining the effect of PRC shape on synchronization tendencies and illustrate it using type 1 PRCs, which consist entirely of advances (delays) in response to excitation (inhibition). We obtained the following generic solutions for type 1 PRCs, which include the pulse-coupled leaky integrate and fire model. For pairs with mutual excitation, exact synchrony can be stable for strong coupling because of the stabilizing effect of the causal limit region of the PRC in which an input triggers a spike immediately upon arrival. However, synchrony is unstable for short delays, because delayed inputs arrive during a refractory period and cannot trigger an immediate spike. Right skew destabilizes antiphase and enables modes with time lags that grow as the conduction delay is increased. Therefore, right skew favors near synchrony at short conduction delays and a gradual transition between synchrony and antiphase for pairs coupled by mutual excitation. For pairs with mutual inhibition, zero time lag synchrony is stable for conduction delays ranging from zero to a substantial fraction of the period for pairs. However, for right skew there is a preferred antiphase mode at short delays. In contrast to mutual excitation, left skew destabilizes antiphase for mutual inhibition so that synchrony dominates at short delays as well. These pairwise synchronization tendencies constrain the synchronization properties of neurons embedded in larger networks. PMID:24376399
NASA Astrophysics Data System (ADS)
Denner, Fabian; van Wachem, Berend G. M.
2015-10-01
Total variation diminishing (TVD) schemes are a widely applied group of monotonicity-preserving advection differencing schemes for partial differential equations in numerical heat transfer and computational fluid dynamics. These schemes are typically designed for one-dimensional problems or multidimensional problems on structured equidistant quadrilateral meshes. Practical applications, however, often involve complex geometries that cannot be represented by Cartesian meshes and, therefore, necessitate the application of unstructured meshes, which require a more sophisticated discretisation to account for their additional topological complexity. In principle, TVD schemes are applicable to unstructured meshes, however, not all the data required for TVD differencing is readily available on unstructured meshes, and the solution suffers from considerable numerical diffusion as a result of mesh skewness. In this article we analyse TVD differencing on unstructured three-dimensional meshes, focusing on the non-linearity of TVD differencing and the extrapolation of the virtual upwind node. Furthermore, we propose a novel monotonicity-preserving correction method for TVD schemes that significantly reduces numerical diffusion caused by mesh skewness. The presented numerical experiments demonstrate the importance of accounting for the non-linearity introduced by TVD differencing and of imposing carefully chosen limits on the extrapolated virtual upwind node, as well as the efficacy of the proposed method to correct mesh skewness.
Deterioration of the skew quadrupole moment in Tevatron dipoles over time
Syphers, M.J.; Harding, D.J.; /Fermilab
2005-05-01
During the 20 years since it was first commissioned, the Fermilab Tevatron has developed strong coupling between the two transverse degrees of freedom. A circuit of skew quadrupole magnets is used to correct for coupling and, though capable, its required strength has increased since 1983 by more than an order of magnitude. In more recent years changes to the Tevatron for colliding beams operation have altered the skew quadrupole corrector distribution and strong local coupling become evident, often encumbering routine operation during the present physics run. Detailed magnet measurements were performed on each individual magnet during construction, and in early 2003 it was realized that measurements could be performed on the magnets in situ which could determine coil movements within the iron yoke since the early 1980's. It was discovered that the superconducting coils had become vertically displaced relative to their yokes since their construction. The ensuing systematic skew quadrupole field introduced by this displacement accounts for the required corrector settings and observed beam behavior. An historical account of the events leading to this discovery and progress toward its remedy are presented.
Coalescence times and FST under a skewed offspring distribution among individuals in a population.
Eldon, Bjarki; Wakeley, John
2009-02-01
Estimates of gene flow between subpopulations based on F(ST) (or N(ST)) are shown to be confounded by the reproduction parameters of a model of skewed offspring distribution. Genetic evidence of population subdivision can be observed even when gene flow is very high, if the offspring distribution is skewed. A skewed offspring distribution arises when individuals can have very many offspring with some probability. This leads to high probability of identity by descent within subpopulations and results in genetic heterogeneity between subpopulations even when Nm is very large. Thus, we consider a limiting model in which the rates of coalescence and migration can be much higher than for a Wright-Fisher population. We derive the densities of pairwise coalescence times and expressions for F(ST) and other statistics under both the finite island model and a many-demes limit model. The results can explain the observed genetic heterogeneity among subpopulations of certain marine organisms despite substantial gene flow.
Buffeting response of long-span cable-supported bridges under skew winds. Part 1: theory
NASA Astrophysics Data System (ADS)
Zhu, L. D.; Xu, Y. L.
2005-03-01
A finite-element-based framework for buffeting analysis of long-span cable-supported bridges under skew winds is developed in the frequency domain utilizing the linear quasi-steady theory and the strip theory of aerodynamics in conjunction with the pseudo excitation method. A set of universal expressions for six components of buffeting forces is first derived in association with oblique cross-sections of bridge components, in which the buffeting forces are formed with respect to the wind coordinate system and then converted to those with respect to the structural coordinate system. Skew mean wind and three orthogonal components of velocity fluctuations can thus be easily handled without any further decomposition. The coherence between velocity fluctuations of wind turbulence at any two arbitrary spatial points is considered in the global wind coordinate system rather than in the global structural coordinate system. Aeroelastic stiffness and damping matrices due to self-excited forces are then taken into consideration in terms of the 18 flutter derivatives with respect to the oblique cross-sections. The pseudo-excitation method is finally employed to solve efficiently the fully coupled 3D buffeting problem of long-span cable-supported bridges under skew winds with the effects of multi-modes and spatial modes, inter-mode coupling and aerodynamic coupling, and the interaction among major bridge components being naturally included.
Skewed X-inactivation in a family with DLG3-associated X-linked intellectual disability.
Gieldon, Laura; Mackenroth, Luisa; Betcheva-Krajcir, Elitza; Rump, Andreas; Beck-Wödl, Stefanie; Schallner, Jens; Di Donato, Nataliya; Schröck, Evelin; Tzschach, Andreas
2017-09-01
Mutations in DLG3 are a rare cause of non-syndromic X-linked intellectual disability (XLID) (MRX90, OMIM *300189). Only ten DLG3 mutations have been reported to date. The majority of female heterozygous mutation carriers was healthy and had random X-inactivation patterns. We report on an XLID family with a novel DLG3 mutation. The 12-year-old male index patient had moderate intellectual disability (ID) and dysmorphic features. The mutation was also present in four female relatives. A maternal aunt had moderate ID and significantly skewed X-inactivation favorably inactivating the normal DLG3 allele. The proband's healthy mother also had skewed X-inactivation but in the opposite direction (i.e., inactivation of the mutated allele). Two other female relatives had intermediate cognitive phenotypes and random X-inactivation. This family broadens the mutational and phenotypical spectrum of DLG3-associated XLID and demonstrates that heterozygous female mutation carriers can be as severely affected as males. Reports of additional families will be needed to elucidate the causes of unfavorable skewing in female XLID patients. © 2017 Wiley Periodicals, Inc.
NASA Astrophysics Data System (ADS)
Aminian, Manuchehr; Bernardi, Francesca; Camassa, Roberto; McLaughlin, Richard M.
2015-10-01
We study the role geometry plays in the emergence of asymmetries in diffusing passive scalars advected by pressure-driven flows in ducts and pipes of different aspect ratios. We uncover nonintuitive, multi-time-scale behavior gauged by a new statistic, which we term "geometric skewness" SG, which measures instantaneously forming asymmetries at short times due to flow geometry. This signature distinguishes elliptical pipes of any aspect ratio, for which SG=0 , from rectangular ducts whose SG is generically nonzero, and, interestingly, shows that a special duct of aspect ratio ≈0.533 35 behaves like a circular pipe as its geometric skewness vanishes. Using a combination of exact solutions, novel short-time asymptotics, and Monte Carlo simulations, we establish the relevant time scales for plateaus and extrema in the evolution of the skewness and kurtosis for our class of geometries. For ducts limiting to channel geometries, we present new exact, single-series formulas for the first four moments on slices used to benchmark Monte Carlo simulations.
Oliva, Michele; Dunand, Christophe
2007-01-01
Arabidopsis seedlings growing on inclined agar surfaces exhibit characteristic root behaviours called 'waving' and 'skewing': the former consists of a series of undulations, whereas the latter is a deviation from the direction of gravity. Even though the precise basis of these growth patterns is not well understood, both gravity and the contact between the medium and the root are considered to be the major players that result in these processes. The influence of these forces on root surface-dependent behaviours can be verified by growing seedlings at different gel pitches: plants growing on vertical plates present roots with slight waving and skewing when compared with seedlings grown on plates held at minor angles of < 90 degrees . However, other factors are thought to modulate root growth on agar; for instance, it has been demonstrated that the presence and concentration of certain compounds in the medium (such as sucrose) and of drugs able to modify the plant cell cytoskeleton also affect skewing and waving. The recent discovery of an active role of ethylene on surface-dependent root behaviour, and the finding of new mutants showing anomalous growth, pave the way for a more detailed description of these phenomena.
Measurement of primordial non-Gaussianity using the WMAP 5-year temperature skewness power spectrum
Smidt, Joseph; Amblard, Alexandre; Serra, Paolo; Cooray, Asantha
2009-12-15
We constrain the primordial non-Gaussianity parameter of the local model f{sub NL} using the skewness power spectrum associated with the two-to-one cumulant correlator of cosmic microwave background temperature anisotropies. This bispectrum-related power spectrum was constructed after weighting the temperature map with the appropriate window functions to form an estimator that probes the multipolar dependence of the underlying bispectrum associated with the primordial non-Gaussianity. We also estimate a separate skewness power spectrum sensitive more strongly to unresolved point sources. When compared to previous attempts at measuring the primordial non-Gaussianity with WMAP data, our estimators have the main advantage that we do not collapse information to a single number. When model fitting the two-to-one skewness power spectrum, we make use of bispectra generated by the primordial non-Gaussianity, radio point sources, and lensing-secondary correlation. We analyze Q, V, and W-band WMAP 5-year data using the KQ75 mask out to l{sub max}=600. Using V and W-band data and marginalizing over model parameters related to point sources and lensing-secondary bispectrum, our overall and preferred constraint on f{sub NL} is 11.0{+-}23.7 at the 68% confidence level (-36.4
Townsend, Andrea K.; Clark, Anne B.; McGowan, Kevin J.; Lovette, Irby J.
2009-01-01
Understanding the benefits of cooperative breeding for group members of different social and demographic classes requires knowledge of their reproductive partitioning and genetic relatedness. From 2004-2007, we examined parentage as a function of relatedness and social interactions among members of 21 American crow (Corvus brachyrhynchos) family groups. Paired female breeders monopolized maternity of all offspring in their broods, whereas paired male breeders sired 82.7% of offspring, within-group auxiliary males sired 6.9% of offspring, and extragroup males sired 10.4% of offspring. Although adult females had fewer opportunities for direct reproduction as auxiliaries than males, they appeared to have earlier opportunities for independent breeding. These different opportunities for direct reproduction probably contributed to the male biased adult auxiliary sex ratio. Patterns of reproductive partitioning and conflict among males were most consistent with a synthetic reproductive skew model, in which auxiliaries struggled with breeders for a limited reproductive share, beyond which breeders could evict them. Counter to a frequent assumption of reproductive skew models, female breeders appeared to influence paternity, although their interests might have agreed with the interests of their paired males. Unusual among cooperative breeders, close inbreeding and incest occurred in this population. Incest avoidance between potential breeders did not significantly affect reproductive skew. PMID:20126287
Free vibration of composite skewed cylindrical shell panel by finite element method
NASA Astrophysics Data System (ADS)
Haldar, Salil
2008-03-01
In this paper a composite triangular shallow shell element has been used for free vibration analysis of laminated composite skewed cylindrical shell panels. In the present element first-order shear deformation theory has been incorporated by taking transverse displacement and bending rotations as independent field variables. The interpolation function used to approximate transverse displacement is one order higher than for bending rotations. This has made the element free from locking in shear. Two types of mass lumping schemes have been recommended. In one of the mass lumping scheme the effect of rotary inertia has been incorporated in the element formulations. Free vibration of skewed composite cylindrical shell panels having different thickness to radius ratios ( h/R=0.01-0.2), length to radius ratios ( L/R), number of layers and fiber orientation angles have been analyzed following the shallow shell method. The results for few examples obtained in the present analysis have compared with the published results. Some new results of composite skewed cylindrical shell panels have been presented which are expected to be useful to future research in this direction.
A Bayesian estimate of the concordance correlation coefficient with skewed data.
Feng, Dai; Baumgartner, Richard; Svetnik, Vladimir
2015-01-01
Concordance correlation coefficient (CCC) is one of the most popular scaled indices used to evaluate agreement. Most commonly, it is used under the assumption that data is normally distributed. This assumption, however, does not apply to skewed data sets. While methods for the estimation of the CCC of skewed data sets have been introduced and studied, the Bayesian approach and its comparison with the previous methods has been lacking. In this study, we propose a Bayesian method for the estimation of the CCC of skewed data sets and compare it with the best method previously investigated. The proposed method has certain advantages. It tends to outperform the best method studied before when the variation of the data is mainly from the random subject effect instead of error. Furthermore, it allows for greater flexibility in application by enabling incorporation of missing data, confounding covariates, and replications, which was not considered previously. The superiority of this new approach is demonstrated using simulation as well as real-life biomarker data sets used in an electroencephalography clinical study. The implementation of the Bayesian method is accessible through the Comprehensive R Archive Network. Copyright © 2015 John Wiley & Sons, Ltd.
Deflection and stress analysis of stiffened orthotropic skew panels under uniform transverse loading
NASA Astrophysics Data System (ADS)
Tripathy, A. K.; Pang, Su-Seng
Skew plates with different orientations behave in a manner quite different from those of rectangular plates. An analysis has been carried out for the deflections and stresses of plates with various skew angles subjected to uniformly distributed tranverse loads. It has been thought that the excess deflection at the rear tip of a cantilever plate can be reduced by applying stiffeners along the length of the plate. These stiffeners can also reduce the stresses at the root drastically. The skin-stringer connections in aircraft can be treated as a problem of this type. An investigation has been carried out on the stress and deflection characteristics of stiffened parallelogramic plates with different skew angles. The numerical solution with assumed displacement function was developed using a finite element analysis. Experiments using aluminum and Scotchply composite laminates were conducted to verify the results. Cantilever and simply supported boundary conditions were included in the analysis, and an optimized angular stiffener for a particular swept-back panel was achieved.
Joint skewness and its application in unsupervised band selection for small target detection.
Geng, Xiurui; Sun, Kang; Ji, Luyan; Tang, Hairong; Zhao, Yongchao
2015-04-15
Few band selection methods are specially designed for small target detection. It is well known that the information of small targets is most likely contained in non-Gaussian bands, where small targets are more easily separated from the background. On the other hand, correlation of band set also plays an important role in the small target detection. When the selected bands are highly correlated, it will be unbeneficial for the subsequent detection. However, the existing non-Gaussianity-based band selection methods have not taken the correlation of bands into account, which generally result in high correlation of obtained bands. In this paper, combining the third-order (third-order tensor) and second-order (correlation) statistics of bands, we define a new concept, named joint skewness, for multivariate data. Moreover, we also propose an easy-to-implement approach to estimate this index based on high-order singular value decomposition (HOSVD). Based on the definition of joint skewness, we present an unsupervised band selection for small target detection for hyperspectral data, named joint skewness band selection (JSBS). The evaluation results demonstrate that the bands selected by JSBS are very effective in terms of small target detection.
Aminian, Manuchehr; Bernardi, Francesca; Camassa, Roberto; McLaughlin, Richard M
2015-10-09
We study the role geometry plays in the emergence of asymmetries in diffusing passive scalars advected by pressure-driven flows in ducts and pipes of different aspect ratios. We uncover nonintuitive, multi-time-scale behavior gauged by a new statistic, which we term "geometric skewness" S^{G}, which measures instantaneously forming asymmetries at short times due to flow geometry. This signature distinguishes elliptical pipes of any aspect ratio, for which S^{G}=0, from rectangular ducts whose S^{G} is generically nonzero, and, interestingly, shows that a special duct of aspect ratio ≈0.53335 behaves like a circular pipe as its geometric skewness vanishes. Using a combination of exact solutions, novel short-time asymptotics, and Monte Carlo simulations, we establish the relevant time scales for plateaus and extrema in the evolution of the skewness and kurtosis for our class of geometries. For ducts limiting to channel geometries, we present new exact, single-series formulas for the first four moments on slices used to benchmark Monte Carlo simulations.
Joint Skewness and Its Application in Unsupervised Band Selection for Small Target Detection
Geng, Xiurui; Sun, Kang; Ji, Luyan; Tang, Hairong; Zhao, Yongchao
2015-01-01
Few band selection methods are specially designed for small target detection. It is well known that the information of small targets is most likely contained in non-Gaussian bands, where small targets are more easily separated from the background. On the other hand, correlation of band set also plays an important role in the small target detection. When the selected bands are highly correlated, it will be unbeneficial for the subsequent detection. However, the existing non-Gaussianity-based band selection methods have not taken the correlation of bands into account, which generally result in high correlation of obtained bands. In this paper, combining the third-order (third-order tensor) and second-order (correlation) statistics of bands, we define a new concept, named joint skewness, for multivariate data. Moreover, we also propose an easy-to-implement approach to estimate this index based on high-order singular value decomposition (HOSVD). Based on the definition of joint skewness, we present an unsupervised band selection for small target detection for hyperspectral data, named joint skewness band selection (JSBS). The evaluation results demonstrate that the bands selected by JSBS are very effective in terms of small target detection. PMID:25873018
Coil Creep and Skew-Quadrupole Field Components in the Tevatron
Annala, G.; Harding, D.J.; Syphers, M.J.; /Fermilab
2011-07-11
During the start-up of Run II of the Tevatron Collider program, several issues surfaced which were not present, or not seen as detrimental, during Run I. These included the repeated deterioration of the closed orbit requiring orbit smoothing every two weeks or so, the inability to correct the closed orbit to desired positions due to various correctors running at maximum limits, regions of systematically strong vertical dipole corrections, and the identification of very strong coupling between the two transverse degrees-of-freedom. It became apparent that many of the problems being experienced operationally were connected to a deterioration of the main dipole magnet alignment, and remedial actions were undertaken. However, the alignment alone was not enough to explain the corrector strengths required to handle transverse coupling. With one exception, strong coupling had generally not been an issue in the Tevatron during Run I. Based on experience with the Main Ring, the Tevatron was designed with a very strong skew quadrupole circuit to compensate any quadrupole alignment and skew quadrupole field errors that might present themselves. The circuit was composed of 48 correctors placed evenly throughout the arcs, 8 per sector, evenly placed in every other cell. Other smaller circuits were installed but not initially needed or commissioned. These smaller circuits were composed of individual skew quadrupole correctors on either side of the long straight sections. These circuits were tuned by first bringing the horizontal and vertical tunes near each other. The skew quadrupoles were then adjusted to minimize tune split, usually to less than 0.003. Initially, the main skew quad circuit (designated T:SQ) could accomplish this global decoupling with only 4% of its possible current, and the smaller circuits were not required at all. The start-up of Run Ib was complicated by what was later discovered to be a rolled triplet quadrupole magnet in one of the Interaction Regions
Observations of intra-wave suspended sediment transport under acceleration-skewed oscillatory flow
NASA Astrophysics Data System (ADS)
Ruessink, G.; Michallet, H.; Hurther, D.; Silva, P.
2008-12-01
In the nearshore, waves transform from skewed shoaling waves to asymmetric breaking waves. Velocity skewness, such as found beneath Stokes second-order waves, generally results in a net onshore sediment transport. Recent numerical studies and limited experimental laboratory data have demonstrated the potential importance of acceleration skewness to onshore sediment transport beneath asymmetric, 'saw- tooth' waves. Here, we investigate new full-scale laboratory tunnel experiments under sheetflow conditions in which regular oscillatory sawtooh flow with varying degrees of acceleration skewness and velocity skewness were generated over a mobile bed. In all experiments the velocity amplitude was 1.2 m/s, the wave period was 7 s, and the bed was composed of well-sorted, fine to medium sand (d50 = 200~μm). In several experiments a counter-current of 0.4 m/s was imposed to imitate undertow. We deployed (1) a 2-MHz Acoustical Doppler Velocimeter Profiler (ADVP) to obtain vertical profiles of (phase-averaged) horizontal and vertical oscillatory and turbulent flow with a temporal and vertical resolution of 50 Hz and 3 mm, respectively, and (2) a triple-frequency Acoustical Backscatter Sensor to obtain vertical profiles of (phase-averaged) suspended sediment concentration with a temporal and vertical resolution of 10 Hz and 5 mm, respectively. Under waves with acceleration skewness only, we observed two concentration peaks, which at the top of the sheetflow layer were approximately in phase with the free-stream velocity. As the concentration peak following the rapid acceleration towards maximum onshore flow was slightly larger than the concentration peak under maximum offshore flow, the depth-integrated and wave-averaged suspended transport was directed onshore. While most sediment stirred during the onshore flow phase had settled back to the bed before flow reversal, some sediment stirred during the offshore flow phase persisted into the onshore flow phase, thus providing
NASA Technical Reports Server (NTRS)
Weick, Fred E; Harris, Thomas A
1934-01-01
This report covers the sixth of a series of investigations in which various lateral control devices are compared with particular reference to their effectiveness at high angles of attack. The present report deals with flap-type ailerons hinged about axes having an angle with respect to the leading and trailing edges of the wing. Tests were made on four different skewed ailerons, including two different angles of skew and two sizes of ailerons. At the high angles of attack, all the skewed ailerons tested were slightly inferior with respect to rolling and yawing moments to straight ailerons having the same span and average chord. Computations indicate that the skewed ailerons are also inferior with respect to hinge moments.
Ng, Benjamin; Cai, Wenju; Walsh, Kevin
2014-01-01
A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming. PMID:25112717
Using skew-logistic probability density function as a model for age-specific fertility rate pattern.
Asili, Sahar; Rezaei, Sadegh; Najjar, Lotfollah
2014-01-01
Fertility rate is one of the most important global indexes. Past researchers found models which fit to age-specific fertility rates. For example, mixture probability density functions have been proposed for situations with bi-modal fertility patterns. This model is less useful for unimodal age-specific fertility rate patterns, so a model based on skew-symmetric (skew-normal) pdf was proposed by Mazzuco and Scarpa (2011) which was flexible for unimodal and bimodal fertility patterns. In this paper, we introduce skew-logistic probability density function as a better model: its residuals are less than those of the skew-normal model and it can more precisely estimate the parameters of the model.
Ng, Benjamin; Cai, Wenju; Walsh, Kevin
2014-08-12
A positive Indian Ocean Dipole (IOD) tends to have stronger cold sea surface temperature anomalies (SSTAs) over the eastern Indian Ocean with greater impacts than warm SSTAs that occur during its negative phase. Two feedbacks have been suggested as the cause of positive IOD skewness, a positive Bjerknes feedback and a negative SST-cloud-radiation (SCR) feedback, but their relative importance is debated. Using inter-model statistics, we show that the most important process for IOD skewness is an asymmetry in the thermocline feedback, whereby SSTAs respond to thermocline depth anomalies more strongly during the positive phase than negative phase. This asymmetric thermocline feedback drives IOD skewness despite positive IODs receiving greater damping from the SCR feedback. In response to global warming, although the thermocline feedback strengthens, its asymmetry between positive and negative IODs weakens. This behaviour change explains the reduction in IOD skewness that many models display under global warming.
Orstavik, K.H.; Orstavik, R.E.; Eiklid, K.; Tranebjaerg, L.
1996-07-12
A new X-linked recessive deafness syndrome was recently reported and mapped to Xq22 (Mohr-Tranebjaeerg syndrome). In addition to deafness, the patients had visual impairment, dystonia, fractures, and mental deterioration. The female carriers did not have any significant manifestations of the syndrome. We examined X chromosome inactivation in 8 obligate and 12 possible carriers by using a polymerase chain reaction analysis of the methylation-dependent amplification of the polymorphic triplet repeat at the androgen receptor locus. Seven of 8 obligate carriers and 1 of 5 carriers by linkage analysis had an extremely skewed pattern in blood DNA not found in 30 normal females. The X inactivation pattern in fibroblast DNA from 2 of the carriers with the extremely skewed pattern was also skewed but to a lesser degree than in blood DNA. One obligate carrier had a random X inactivation pattern in both blood and fibroblast DNA. A selection mechanism for the skewed pattern is therefore not likely. The extremely skewed X inactivation in 8 females of 3 generations in this family may be caused by a single gene that influences skewing of X chromosome inactivation. 22 refs., 2 figs., 1 tab.
Godler, David E; Inaba, Yoshimi; Schwartz, Charles E; Bui, Quang M; Shi, Elva Z; Li, Xin; Herlihy, Amy S; Skinner, Cindy; Hagerman, Randi J; Francis, David; Amor, David J; Metcalfe, Sylvia A; Hopper, John L; Slater, Howard R
2015-07-01
Methylation of the fragile X mental retardation 1 (FMR1) exon 1/intron 1 boundary positioned fragile X related epigenetic element 2 (FREE2), reveals skewed X-chromosome inactivation (XCI) in fragile X syndrome full mutation (FM: CGG > 200) females. XCI skewing has been also linked to abnormal X-linked gene expression with the broader clinical impact for sex chromosome aneuploidies (SCAs). In this study, 10 FREE2 CpG sites were targeted using methylation specific quantitative melt analysis (MS-QMA), including 3 sites that could not be analysed with previously used EpiTYPER system. The method was applied for detection of skewed XCI in FM females and in different types of SCA. We tested venous blood and saliva DNA collected from 107 controls (CGG < 40), and 148 FM and 90 SCA individuals. MS-QMA identified: (i) most SCAs if combined with a Y chromosome test; (ii) locus-specific XCI skewing towards the hypomethylated state in FM females; and (iii) skewed XCI towards the hypermethylated state in SCA with 3 or more X chromosomes, and in 5% of the 47,XXY individuals. MS-QMA output also showed significant correlation with the EpiTYPER reference method in FM males and females (P < 0.0001) and SCAs (P < 0.05). In conclusion, we demonstrate use of MS-QMA to quantify skewed XCI in two applications with diagnostic utility.
Social queuing in animal societies: a dynamic model of reproductive skew
Kokko, H.; Johnstone, R. A.
1999-01-01
Previously developed models of reproductive skew have overlooked one of the main reasons why subordinates might remain in a group despite restricted opportunities to breed: the possibility of social queuing, i.e. acquiring dominant status in the future. Here, we present a dynamic ESS model of skew in animal societies that incorporates both immediate and future fitness consequences of the decisions taken by group members, based on their probability of surviving from one season to the next (when post-breeding survival probabilities drop to zero, our analysis reduces to the model produced by Reeve and Ratnieks in 1993, which considered only a single breeding season). This allows us to compare the delayed benefits of philopatry and the immediate opportunities for independent breeding. We show that delayed benefits greatly reduce the need for dominants to offer reproductive concessions to retain subordinates peacefully in the group. Moreover, this effect is strong enough that differences in survival have a much greater impact on the group structure than differences in other parameters, such as relatedness. When the possibility of acceding to dominant status is taken into account, groups where the dominant completely monopolizes reproduction can be stable, even if they consist of unrelated individuals, and even if subordinates have a reasonably high probability of winning a fight for dominance. Finally, we show that stable groups are possible even if association leads to a decrease in current productivity. Subordinates may still stand to gain from group membership under these circumstances, as acquiring breeding positions by queuing may be more efficient than the attempt to establish a new territory. At the same time, the dominant may be unable to exclude unwelcome subordinates, may enjoy increased survival when they are present, or may gain indirect benefits from allowing relatives to stay and queue for dominance. We conclude that reproductive skew in animal groups
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
1992-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass, heat transfer model with both radially inward and outward flow. Trip strips, skewed at 45 deg to the flow direction, were machined on the leading and trailing surfaces of the radial coolant passages. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges which are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. The heat transfer coefficients on surfaces, where the heat transfer decreased with rotation and buoyancy, decreased to as low as 40 percent of the value without rotation. However, the maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels previously obtained with the smooth wall models. It was concluded that (1) both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer in models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design information.
Measuring skew in average surface roughness as a function of surface preparation
NASA Astrophysics Data System (ADS)
Stahl, Mark T.
2015-08-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo® white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.
Extrinsic spin Hall effect induced by resonant skew scattering in graphene.
Ferreira, Aires; Rappoport, Tatiana G; Cazalilla, Miguel A; Castro Neto, A H
2014-02-14
We show that the extrinsic spin Hall effect can be engineered in monolayer graphene by decoration with small doses of adatoms, molecules, or nanoparticles originating local spin-orbit perturbations. The analysis of the single impurity scattering problem shows that intrinsic and Rashba spin-orbit local couplings enhance the spin Hall effect via skew scattering of charge carriers in the resonant regime. The solution of the transport equations for a random ensemble of spin-orbit impurities reveals that giant spin Hall currents are within the reach of the current state of the art in device fabrication. The spin Hall effect is robust with respect to thermal fluctuations and disorder averaging.
The Universal Patient Centeredness Questionnaire: scaling approaches to reduce positive skew
Bjertnaes, Oyvind; Iversen, Hilde Hestad; Garratt, Andrew M
2016-01-01
Purpose Surveys of patients’ experiences typically show results that are indicative of positive experiences. Unbalanced response scales have reduced positive skew for responses to items within the Universal Patient Centeredness Questionnaire (UPC-Q). The objective of this study was to compare the unbalanced response scale with another unbalanced approach to scaling to assess whether the positive skew might be further reduced. Patients and methods The UPC-Q was included in a patient experience survey conducted at the ward level at six hospitals in Norway in 2015. The postal survey included two reminders to nonrespondents. For patients in the first month of inclusion, UPC-Q items had standard scaling: poor, fairly good, good, very good, and excellent. For patients in the second month, the scaling was more positive: poor, good, very good, exceptionally good, and excellent. The effect of scaling on UPC-Q scores was tested with independent samples t-tests and multilevel linear regression analysis, the latter controlling for the hierarchical structure of data and known predictors of patient-reported experiences. Results The response rate was 54.6% (n=4,970). Significantly lower scores were found for all items of the more positively worded scale: UPC-Q total score difference was 7.9 (P<0.001), on a scale from 0 to 100 where 100 is the best possible score. Differences between the four items of the UPC-Q ranged from 7.1 (P<0.001) to 10.4 (P<0.001). Multivariate multilevel regression analysis confirmed the difference between the response groups, after controlling for other background variables; UPC-Q total score difference estimate was 8.3 (P<0.001). Conclusion The more positively worded scaling significantly lowered the mean scores, potentially increasing the sensitivity of the UPC-Q to identify differences over time and between providers. However, none of the groups exhibited large positive skew and ceiling effects, implying that such effects might not be a big
Measuring Skew in Average Surface Roughness as a Function of Surface Preparation
NASA Technical Reports Server (NTRS)
Stahl, Mark T.
2015-01-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces grinding saving both time and money and allows the science requirements to be better defined. In this study various materials are polished from a fine grind to a fine polish. Each sample's RMS surface roughness is measured at 81 locations in a 9x9 square grid using a Zygo white light interferometer at regular intervals during the polishing process. Each data set is fit with various standard distributions and tested for goodness of fit. We show that the skew in the RMS data changes as a function of polishing time.
Measuring Skew in Average Surface Roughness as a Function of Surface Preparation
NASA Technical Reports Server (NTRS)
Stahl, Mark
2015-01-01
Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.
Emergence of heavy-tailed skew distributions from the heat equation
NASA Astrophysics Data System (ADS)
Choi, ByoungSeon; Kang, Hyuk; Choi, M. Y.
2017-03-01
It is well known that the symmetric Gaussian function, called the fundamental solution, serves as the Green's function of the heat equation. In reality, on the other hand, distribution functions obtained empirically often differ from the Gaussian function. This study presents a new solution of the heat equation, satisfying localized initial conditions like the Gaussian fundamental solution. The new solution corresponds to a hetero-mixture distribution, which generalizes the Gaussian distribution function to a skewed and heavy-tailed distribution, and thus provides a candidate for the empirical distribution functions.
A variational Bayesian approach for inverse problems with skew-t error distributions
NASA Astrophysics Data System (ADS)
Guha, Nilabja; Wu, Xiaoqing; Efendiev, Yalchin; Jin, Bangti; Mallick, Bani K.
2015-11-01
In this work, we develop a novel robust Bayesian approach to inverse problems with data errors following a skew-t distribution. A hierarchical Bayesian model is developed in the inverse problem setup. The Bayesian approach contains a natural mechanism for regularization in the form of a prior distribution, and a LASSO type prior distribution is used to strongly induce sparseness. We propose a variational type algorithm by minimizing the Kullback-Leibler divergence between the true posterior distribution and a separable approximation. The proposed method is illustrated on several two-dimensional linear and nonlinear inverse problems, e.g. Cauchy problem and permeability estimation problem.
Skewed X-chromosome inactivation in female carriers of dyskeratosis congenita
Devriendt, K.; Matthijs, G.; Legius, E.
1997-03-01
In this study, we report on a family with X-linked dyskeratosis congenita (DC). Linkage analysis with markers in the factor VIII gene at Xq28 yielded a LOD score of 2 at a recombination of 0. Clinical manifestations of DC, such as skin lesions following the Blaschko lines, were present in two obligate carrier females. Highly skewed X inactivation was observed in white blood cells, cultured skin fibroblasts, and buccal mucosa from female carriers of DC in this family. This suggests a critical role for the DC gene in bone marrow-cell and fibroblast-cell proliferation. 23 refs., 4 figs., 1 tab.
On the Complex Symmetric and Skew-Symmetric Operators with a Simple Spectrum
NASA Astrophysics Data System (ADS)
Zagorodnyuk, Sergey M.
2011-02-01
In this paper we obtain necessary and sufficient conditions for a linear bounded operator in a Hilbert space H to have a three-diagonal complex symmetric matrix with non-zero elements on the first sub-diagonal in an orthonormal basis in H. It is shown that a set of all such operators is a proper subset of a set of all complex symmetric operators with a simple spectrum. Similar necessary and sufficient conditions are obtained for a linear bounded operator in H to have a three-diagonal complex skew-symmetric matrix with non-zero elements on the first sub-diagonal in an orthonormal basis in H.
NASA Astrophysics Data System (ADS)
Luo, Shunlong; Sun, Yuan
2017-08-01
Quantifications of coherence are intensively studied in the context of completely decoherent operations (i.e., von Neuamnn measurements, or equivalently, orthonormal bases) in recent years. Here we investigate partial coherence (i.e., coherence in the context of partially decoherent operations such as Lüders measurements). A bona fide measure of partial coherence is introduced. As an application, we address the monotonicity problem of K -coherence (a quantifier for coherence in terms of Wigner-Yanase skew information) [Girolami, Phys. Rev. Lett. 113, 170401 (2014), 10.1103/PhysRevLett.113.170401], which is introduced to realize a measure of coherence as axiomatized by Baumgratz, Cramer, and Plenio [Phys. Rev. Lett. 113, 140401 (2014), 10.1103/PhysRevLett.113.140401]. Since K -coherence fails to meet the necessary requirement of monotonicity under incoherent operations, it is desirable to remedy this monotonicity problem. We show that if we modify the original measure by taking skew information with respect to the spectral decomposition of an observable, rather than the observable itself, as a measure of coherence, then the problem disappears, and the resultant coherence measure satisfies the monotonicity. Some concrete examples are discussed and related open issues are indicated.
Hölder properties of perturbed skew products and Fubini regained
NASA Astrophysics Data System (ADS)
Ilyashenko, Yu; Negut, A.
2012-08-01
In 2006, Gorodetski proved that central fibres of perturbed skew products are Hölder continuous with respect to the base point. In this paper, we give an explicit estimate of this Hölder exponent. Moreover, we extend Gorodetski's result from the case when the fibre maps are close to the identity to a much wider class of maps that satisfy the so-called modified dominated splitting condition. In many cases (for example, in the case of skew products over the solenoid or over linear Anosov diffeomorphisms of the torus), the Hölder exponent is close to 1. This allows one to overcome the so-called Fubini nightmare, in some sense. Namely, we prove that the union of central fibres that are strongly atypical from the point of view of ergodic theory, has Lebesgue measure zero despite the lack of absolute continuity of the holonomy map for the central foliation. This result is based on a new kind of ergodic theorem, which we call special. To prove our main result, we revisit the theory of Hirsch, Pugh and Shub, and estimate the contraction constant of the graph transform map.
NASA Astrophysics Data System (ADS)
Ziman, Timothy; Gu, Bo; Maekawa, Sadamichi
2017-01-01
The spin Hall effect is affected by the Coulomb interaction as well as spin-spin correlations in metals. Here we examine the enhancement in the effect caused by resonant skew scattering induced by electron correlations. For single-impurity scattering, local Coulomb correlations may significantly change the observed spin Hall angle. There may be additional effects because of the special atomic environment close to a surface — extra degeneracies compared to the bulk, enhanced correlations that move the relative d- or f-levels, and interference effects coming from the lower local dimension. Our results may explain the very large spin Hall angle observed in CuBi alloys. We discuss the impact on the spin Hall effect from cooperative effects, firstly in an itinerant ferromagnet where there is an anomaly near the Curie temperature originating from high-order spin fluctuations. The second case considered is a metallic spin glass, where exchange via slowly fluctuating magnetic moments may lead to the precession of an injected spin current. This decreases the net spin-charge conversion from skew scattering at temperatures below a value three or four times the freezing temperature.
Chen, Jichun; Bryant, Mark A.; Dent, James J.; Sun, Yu; Desierto, Marie J.; Young, Neal S.
2015-01-01
A deletion of telomerase RNA component (Terc−/−) in C57BL/6 (B6) mice resulted in hematopoietic lineage skewing with increased neutrophils and CD11b+ myeloid cells and decreased red blood cells and CD45R+ B lymphocytes when animals reach ages older than 12 months. There was no decline in bone marrow (BM) c-Kit+Sca-1+Lin− (KSL) cells in old Terc−/− mice, and the lineage skewing phenomenon was not transferred when BM cells from old Terc−/− donors were transplanted into young B6 recipients. Necropsy and histological examinations found minimal to no change in the lung, spleen and liver but detected severe epithelia degeneration, ulceration and infection in small and large intestines, leading to enteritis, typhlitis and colitis in old Terc−/− mice. In a mouse model of dextran-sulfate-sodium-induced typhlitis and colitis, development of intestinal pathology was associated with increases in neutrophils and CD11b+ myeloid cells and a decrease in CD45R+ B cells, similar to those observed in old Terc−/− mice. Treatment of 11–13 month old Terc−/− mice with antibiotic trimethoprim-sulfa water reduced neutrophils and myeloid cells and increased B lymphocytes in the blood, indicating that mitigation of intestinal infection and inflammation could alleviate hematological abnormalities in old Terc−/− animals. PMID:26523501
Chen, Jichun; Bryant, Mark A; Dent, James J; Sun, Yu; Desierto, Marie J; Young, Neal S
2015-12-01
A deletion of a telomerase RNA component (Terc(-/-)) in C57BL/6 (B6) mice resulted in hematopoietic lineage skewing with increased neutrophils and CD11b(+) myeloid cells and decreased red blood cells and CD45R(+) B lymphocytes when animals reach ages older than 12 months. There was no decline in bone marrow (BM) c-Kit(+)Sca-1(+)Lin(-) (KSL) cells in old Terc(-/-) mice, and the lineage skewing phenomenon was not transferred when BM cells from old Terc(-/-) donors were transplanted into young B6 recipients. Necropsy and histological examinations found minimal to no change in the lung, spleen and liver but detected severe epithelia degeneration, ulceration and infection in small and large intestines, leading to enteritis, typhlitis and colitis in old Terc(-/-) mice. In a mouse model of dextran-sulfate-sodium-induced typhlitis and colitis, development of intestinal pathology was associated with increases in neutrophils and CD11b(+) myeloid cells and a decrease in CD45R(+) B cells, similar to those observed in old Terc(-/-) mice. Treatment of 11-13 month old Terc(-/-) mice with antibiotic trimethoprim-sulfa water reduced neutrophils and myeloid cells and increased B lymphocytes in the blood, indicating that mitigation of intestinal infection and inflammation could alleviate hematological abnormalities in old Terc(-/-) animals.
Pronounced reproductive skew in a natural population of green swordtails, Xiphophorus helleri.
Tatarenkov, Andrey; Healey, Christiane I M; Grether, Gregory F; Avise, John C
2008-10-01
For many species in nature, a sire's progeny may be distributed among a few or many dams. This poses logistical challenges--typically much greater across males than across females--for assessing means and variances in mating success (number of mates) and reproductive success (number of progeny). Here we overcome these difficulties by exhaustively analyzing a population of green swordtail fish (Xiphophorus helleri) for genetic paternity (and maternity) using a suite of highly polymorphic microsatellite loci. Genetic analyses of 1476 progeny from 69 pregnant females and 158 candidate sires revealed pronounced skews in male reproductive success both within and among broods. These skews were statistically significant, greater than in females, and correlated in males but not in females with mating success. We also compare the standardized variances in swordtail reproductive success to the few such available estimates for other taxa, notably several mammal species with varied mating systems and degrees of sexual dimorphism. The comparison showed that the opportunity for selection on male X. helleri is among the highest yet reported in fishes, and it is intermediate compared to estimates available for mammals. This study is one of a few exhaustive genetic assessments of joint-sex parentage in a natural fish population, and results are relevant to the operation of sexual selection in this sexually dimorphic, high-fecundity species.
Skewness and kurtosis as indicators of non-Gaussianity in galactic foreground maps
Ben-David, Assaf; Jackson, Andrew D.; Hausegger, Sebastian von E-mail: s.vonhausegger@nbi.dk
2015-11-01
Observational cosmology is entering an era in which high precision will be required in both measurement and data analysis. Accuracy, however, can only be achieved with a thorough understanding of potential sources of contamination from foreground effects. Our primary focus will be on non-Gaussian effects in foregrounds. This issue will be crucial for coming experiments to determine B-mode polarization. We propose a novel method for investigating a data set in terms of skewness and kurtosis in locally defined regions that collectively cover the entire sky. The method is demonstrated on two sky maps: (i) the SMICA map of Cosmic Microwave Background fluctuations provided by the Planck Collaboration and (ii) a version of the Haslam map at 408 MHz that describes synchrotron radiation. We find that skewness and kurtosis can be evaluated in combination to reveal local physical information. In the present case, we demonstrate that the statistical properties of both maps in small local regions are predominantly Gaussian. This result was expected for the SMICA map. It is surprising that it also applies for the Haslam map given its evident large scale non-Gaussianity. The approach described here has a generality and flexibility that should make it useful in a variety of astrophysical and cosmological contexts.
Near and Far Field Acoustic Pressure Skewness in a Heated Supersonic Jet
NASA Astrophysics Data System (ADS)
Gutmark, Ephraim; Mora, Pablo; Kastner, Jeff; Heeb, Nick; Kailasanath, Kailas; Liu, Junhui; University of Cincinnati Collaboration; Naval Research Laboratory Collaboration
2012-11-01
The dominant component of turbulent mixing noise in high speed jets is the Mach wave radiation generated by large turbulent structures in the shear layer The Over-All Sound Pressure Level (OASPL) in the far field peaks in a direction near the Mach wave angle. ``Crackle'' is another important component of high speed jet noise. Crackle cannot be recognized in the spectrum of the acoustic pressure signal, but it appears in the temporal waveform of the pressure as sharply rising peaks. Skewness levels of the pressure and dP/dt have been used as a measure of crackle in high specific thrust engines and rockets. In this paper, we focus on recognizing a technique that identifies the impact of different test conditions on the near-field and far-field statistics of the pressure and dP/dt signals of a supersonic jet with a design Mach number of Md=1.5 produced by a C-D conical nozzle. Cold and hot jets, T0=300K and 600K, are tested at over, design, and under-expanded conditions, with NPRs=2.5, 3.671, 4.5, respectively. Second, Third and Forth order statistics are examined in the near and far fields. Rms, skewness and kurtosis intensity levels and propagation are better identified in the dP/dt than in the pressure signal. Statistics of the dP/dt demonstrate to be a better measure for crackle. Project funded by ONR grant.
Analyzing Fish Condition Factor Index Through Skew-Gaussian Information Theory Quantifiers
NASA Astrophysics Data System (ADS)
Contreras-Reyes, Javier E.
2016-06-01
Biological-fishery indicators have been widely studied. As such the condition factor (CF) index, which interprets the fatness level of a certain species based on length and weight, has been investigated, too. However, CF has been studied without considering its temporal features and distribution. In this paper, we analyze the CF time series via skew-gaussian distributions that consider the asymmetry produced by extreme events. This index is characterized by a threshold autoregressive model and corresponds to a stationary process depending on the shape parameter of the skew-gaussian distribution. Then we use the Jensen-Shannon (JS) distance to compare CF by length classes. This distance has mathematical advantages over other divergences such as Kullback-Leibler and Jeffrey’s, and the triangular inequality property. Our results are applied to a biological catalogue of anchovy (Engraulis ringens) from the northern coast of Chile, for the period 1990-2010 that consider monthly CF time series by length classes and sex. We find that for high values of shape parameter, JS distance tends to be more sensible to detect discrepancies than Jeffrey’s divergence. In addition, the body condition of male anchovies with higher lengths coincides with the ending of the moderate-strong El Niño event 91-92 and for both males and females, the smaller lengths coincide with the beginning of the strong El Niño event 97-98.
About the infinite dimensional skew and obliquely reflected Ornstein-Uhlenbeck process
NASA Astrophysics Data System (ADS)
Röckner, Michael; Trutnau, Gerald
2015-12-01
Based on an integration by parts formula for closed and convex subsets Γ of a separable real Hilbert space H with respect to a Gaussian measure, we first construct and identify the infinite dimensional analogue of the obliquely reflected Ornstein-Uhlenbeck process (perturbed by a bounded drift B) by means of a Skorokhod type decomposition. The variable oblique reflection at a reflection point of the boundary ∂Γ is uniquely described through a reflection angle and a direction in the tangent space (more precisely through an element of the orthogonal complement of the normal vector) at the reflection point. In case of normal reflection at the boundary of a regular convex set and under some monotonicity condition on B, we prove the existence and uniqueness of a strong solution to the corresponding SDE. Subsequently, we consider an increasing sequence (Γαk)k∈ℤ of closed and convex subsets of H and the skew reflection problem at the boundaries of this sequence. We present concrete examples and obtain as a special case the infinite dimensional analogue of the p-skew reflected Ornstein-Uhlenbeck process.
Héroux, Julie; Moodie, Erica E. M.; Strumpf, Erin; Coyle, Natalie; Tousignant, Pierre; Diop, Mamadou
2017-01-01
Evaluating the impacts of clinical or policy interventions on health care utilization requires addressing methodological challenges for causal inference while also analyzing highly skewed data. We examine the impact of registering with a Family Medicine Group (FMG), an integrated primary care model in Quebec, on hospitalization and emergency department visits using propensity scores to adjust for baseline characteristics and marginal structural models to account for time-varying exposure. We also evaluate the performance of different marginal structural GLMs in the presence of highly skewed data and conduct a simulation study to determine the robustness of different GLMs to distributional model mis-specification. Although the simulations found that the zero-inflated Poisson likelihood performed the best overall, the negative binomial likelihood gave the best fit for both outcomes in the real dataset. Our results suggest that registration to a FMG for all three years caused a small reduction in the number of emergency room visits, and no significant change in the number of hospitalizations in the final year. PMID:24167024
Experimental and modeling study of the flow over a skewed bump
NASA Astrophysics Data System (ADS)
Ching, David S.; Elkins, Christopher J.; Eaton, John K.
2016-11-01
Three-dimensional separated flows can be very sensitive to geometry and inlet conditions, such that a small change in the geometry or the upstream boundary layer could cause the flow structure to change drastically. This study examines the geometric sensitivity of a skewed bump with axis ratio 4/3 by changing the angle of the bump with respect to the flow. The three-dimensional, three-component mean velocity field was acquired using Magnetic Resonance Velocimetry (MRV) for several bump angles. The flow is dominated by large coherent vortices in the wake. For a symmetric case, two counter-rotating vortices exist in the wake, but when the bump is skewed relative to the oncoming flow one vortex structure is much stronger and overwhelms the other vortex. A comparison to RANS simulations found that the RANS simulations predict the velocity fields with reasonable accuracy within the separation bubble, but are very inaccurate downstream of reattachment. Using a time-resolved MRV sequence, the shedding frequency of the wake was determined for two bump angles. Hot-wire anemometry confirmed the shedding frequencies found from the MRV data and observed that the shedding frequency is sensitive to the bump angle at low bump angles, but is insensitive at high bump angles. Funding provided by the Office of Naval Research.
Maximum Parsimony and the Skewness Test: A Simulation Study of the Limits of Applicability
Määttä, Jussi; Roos, Teemu
2016-01-01
The maximum parsimony (MP) method for inferring phylogenies is widely used, but little is known about its limitations in non-asymptotic situations. This study employs large-scale computations with simulated phylogenetic data to estimate the probability that MP succeeds in finding the true phylogeny for up to twelve taxa and 256 characters. The set of candidate phylogenies are taken to be unrooted binary trees; for each simulated data set, the tree lengths of all (2n − 5)!! candidates are computed to evaluate quantities related to the performance of MP, such as the probability of finding the true phylogeny, the probability that the tree with the shortest length is unique, the probability that the true phylogeny has the shortest tree length, and the expected inverse of the number of trees sharing the shortest length. The tree length distributions are also used to evaluate and extend the skewness test of Hillis for distinguishing between random and phylogenetic data. The results indicate, for example, that the critical point after which MP achieves a success probability of at least 0.9 is roughly around 128 characters. The skewness test is found to perform well on simulated data and the study extends its scope to up to twelve taxa. PMID:27035667
Fuel cell plates with skewed process channels for uniform distribution of stack compression load
Granata, Jr., Samuel J.; Woodle, Boyd M.
1989-01-01
An electrochemical fuel cell includes an anode electrode, a cathode electrode, an electrolyte matrix sandwiched between electrodes, and a pair of plates above and below the electrodes. The plate above the electrodes has a lower surface with a first group of process gas flow channels formed thereon and the plate below the electrodes has an upper surface with a second group of process gas flow channels formed thereon. The channels of each group extend generally parallel to one another. The improvement comprises the process gas flow channels on the lower surface of the plate above the anode electrode and the process gas flow channels on the upper surface of the plate below the cathode electrode being skewed in opposite directions such that contact areas of the surfaces of the plates through the electrodes are formed in crisscross arrangements. Also, the plates have at least one groove in areas of the surfaces thereof where the channels are absent for holding process gas and increasing electrochemical activity of the fuel cell. The groove in each plate surface intersects with the process channels therein. Also, the opposite surfaces of a bipolar plate for a fuel cell contain first and second arrangements of process gas flow channels in the respective surfaces which are skewed the same amount in opposite directions relative to the longitudinal centerline of the plate.
Skew ocular deviation: a catastrophic sign on MRI of fetal glioblastoma.
Chuang, Yu-Ming; Guo, Wan-Yuo; Ho, Donald Ming-Tak; Wong, Tai-Tong; Hung, Jeng-Hsiu; Chen, Shu-Jen; Sheu, Ming-Huei; Chang, Cheng-Yen
2003-06-01
We report the prenatal observation of fetal ocular skew deviation in a case of a glioblastoma found prenatally at 33 weeks' gestation by MRI. The fetal MRI, obtained by half-Fourier single-shot turbo spin echo (HASTE) pulse sequences, showed a tumor (80 mm in maximum diameter) in the right deep cerebral hemisphere with extension to the mid-cranial fossa and tentorial hiatus in addition to severe hydrocephalus. On coronal MR images a vertical dysconjugated gaze was recognized. One week after the MRI, frequent delayed deceleration prompted an emergency cesarean section. The baby was born with left hemiparesis and central neurogenic hyperventilation, which evolved into decerebrate rigidity and apneustic breathing within 2 h. Post-mortem examination revealed a glioblastoma in the right deep hemisphere, a tumor with brain stem involvement, and transtentorial herniation. We suggest, therefore, that recognition of ocular skew deviation on fetal MR images would indicate brain stem involvement and poor postnatal prognosis. Early recognition of the catastrophic sign would lead to proper management.
Random sampling of skewed distributions implies Taylor’s power law of fluctuation scaling
Cohen, Joel E.; Xu, Meng
2015-01-01
Taylor’s law (TL), a widely verified quantitative pattern in ecology and other sciences, describes the variance in a species’ population density (or other nonnegative quantity) as a power-law function of the mean density (or other nonnegative quantity): Approximately, variance = a(mean)b, a > 0. Multiple mechanisms have been proposed to explain and interpret TL. Here, we show analytically that observations randomly sampled in blocks from any skewed frequency distribution with four finite moments give rise to TL. We do not claim this is the only way TL arises. We give approximate formulae for the TL parameters and their uncertainty. In computer simulations and an empirical example using basal area densities of red oak trees from Black Rock Forest, our formulae agree with the estimates obtained by least-squares regression. Our results show that the correlated sampling variation of the mean and variance of skewed distributions is statistically sufficient to explain TL under random sampling, without the intervention of any biological or behavioral mechanisms. This finding connects TL with the underlying distribution of population density (or other nonnegative quantity) and provides a baseline against which more complex mechanisms of TL can be compared. PMID:25852144
Comment on "Universal relation between skewness and kurtosis in complex dynamics"
NASA Astrophysics Data System (ADS)
Celikoglu, Ahmet; Tirnakli, Ugur
2015-12-01
In a recent paper [M. Cristelli, A. Zaccaria, and L. Pietronero, Phys. Rev. E 85, 066108 (2012), 10.1103/PhysRevE.85.066108], the authors analyzed the relation between skewness and kurtosis for complex dynamical systems, and they identified two power-law regimes of non-Gaussianity, one of which scales with an exponent of 2 and the other with 4 /3 . They concluded that the observed relation is a universal fact in complex dynamical systems. In this Comment, we test the proposed universal relation between skewness and kurtosis with a large number of synthetic data, and we show that in fact it is not a universal relation and originates only due to the small number of data points in the datasets considered. The proposed relation is tested using a family of non-Gaussian distribution known as q -Gaussians. We show that this relation disappears for sufficiently large datasets provided that the fourth moment of the distribution is finite. We find that kurtosis saturates to a single value, which is of course different from the Gaussian case (K =3 ), as the number of data is increased, and this indicates that the kurtosis will converge to a finite single value if all moments of the distribution up to fourth are finite. The converged kurtosis value for the finite fourth-moment distributions and the number of data points needed to reach this value depend on the deviation of the original distribution from the Gaussian case.
Using Skewness and the First-Digit Phenomenon to Identify Dynamical Transitions in Cardiac Models
Seenivasan, Pavithraa; Easwaran, Soumya; Sridhar, Seshan; Sinha, Sitabhra
2016-01-01
Disruptions in the normal rhythmic functioning of the heart, termed as arrhythmia, often result from qualitative changes in the excitation dynamics of the organ. The transitions between different types of arrhythmia are accompanied by alterations in the spatiotemporal pattern of electrical activity that can be measured by observing the time-intervals between successive excitations of different regions of the cardiac tissue. Using biophysically detailed models of cardiac activity we show that the distribution of these time-intervals exhibit a systematic change in their skewness during such dynamical transitions. Further, the leading digits of the normalized intervals appear to fit Benford's law better at these transition points. This raises the possibility of using these observations to design a clinical indicator for identifying changes in the nature of arrhythmia. More importantly, our results reveal an intriguing relation between the changing skewness of a distribution and its agreement with Benford's law, both of which have been independently proposed earlier as indicators of regime shift in dynamical systems. PMID:26793114
Inter-population variation in multiple paternity and reproductive skew in the guppy.
Neff, Bryan D; Pitcher, Trevor E; Ramnarine, Indar W
2008-06-01
We use microsatellite loci to detail the multiple paternity patterns in broods from 10 wild populations of the guppy (Poecilia reticulata) found in Northern Trinidad. The populations span two major drainages comprising the Caroni and the Oropouche, and include sites that are characterized by either high or low predation. Across the populations the frequency of multiple paternity is high with 95% (range: 70%-100%) of broods having multiple sires. Broods have an average of 3.5 sires (range: 1-9) and a mixed-model analysis suggests that broods from high predation sites have marginally more sires than do those from low predation sites, but this is true only in the Oropouche drainage. There is no difference in sire number between predation sites in the Caroni drainage. Brood size, but not female body length, is correlated with the number of sires and the correlation cannot be attributed solely to the stochastic process associated with sperm competition and a 'fair raffle'. Within broods there is significant skew in reproductive success among males, which may reflect variation in sperm competitiveness or female choice. There is, however, no difference in the skew among populations from different predation regimes or drainages. Finally, high predation populations were characterized by increased genetic variability at the microsatellite loci, suggesting a larger effective population size. We discuss explanations for the high degree of multiple paternity but the general lack of any major differences among broods from ecologically different populations.
Homoclinic snaking in plane Couette flow: bending, skewing and finite-size effects
NASA Astrophysics Data System (ADS)
Gibson, J. F.; Schneider, T. M.
2016-05-01
Invariant solutions of shear flows have recently been extended from spatially periodic solutions in minimal flow units to spatially localized solutions on extended domains. One set of spanwise-localized solutions of plane Couette flow exhibits homoclinic snaking, a process by which steady-state solutions grow additional structure smoothly at their fronts when continued parametrically. Homoclinic snaking is well understood mathematically in the context of the one-dimensional Swift-Hohenberg equation. Consequently, the snaking solutions of plane Couette flow form a promising connection between the largely phenomenological study of laminar-turbulent patterns in viscous shear flows and the mathematically well-developed field of pattern-formation theory. In this paper we present a numerical study of the snaking solutions, generalizing beyond the fixed streamwise wavelength of previous studies. We find a number of new solution features, including bending, skewing, and finite-size effects. We show that the finite-size effects result from the shift-reflect symmetry of the traveling wave and establish the parameter regions over which snaking occurs. A new winding solution of plane Couette flow is derived from a strongly skewed localized equilibrium.
Weighted skewness and kurtosis unbiased by sample size and Gaussian uncertainties
NASA Astrophysics Data System (ADS)
Rimoldini, Lorenzo
2014-07-01
Central moments and cumulants are often employed to characterize the distribution of data. The skewness and kurtosis are particularly useful for the detection of outliers, the assessment of departures from normally distributed data, automated classification techniques and other applications. Estimators of higher order moments that are robust against outliers are more stable but might miss characteristic features of the data, as in the case of astronomical time series exhibiting brief events like stellar bursts or eclipses of binary systems, while weighting can help identify reliable measurements from uncertain or spurious outliers. Furthermore, noise is an unavoidable part of most measurements and their uncertainties need to be taken properly into account during the data analysis or biases are likely to emerge in the results, including basic descriptive statistics. This work provides unbiased estimates of the weighted skewness and kurtosis moments and cumulants, corrected for biases due to sample size and Gaussian noise, under the assumption of independent data. A comparison of biased and unbiased weighted estimators is illustrated with simulations as a function of sample size and signal-to-noise ratio, employing different data distributions and weighting schemes related to measurement uncertainties and the sampling of the signal. Detailed derivations and figures of simulation results are presented in the Appendices available online.
Mills, Candice M; Grant, Meridith G
2009-09-01
The current experiment examines if and when children consider the possibility of relationships skewing judgments when evaluating judgments in different contexts. Eighty-seven 6-year-olds, 8-year-olds, 10-year-olds, and adults heard stories about judges who made decisions matching or mismatching possible relationship biases (e.g. a judge choosing a friend or an enemy as the winner) in contests with objective or subjective criteria. While even 6-year-olds distinguished between subjective and objective contests, neither children nor adults focused on the objectivity of the contest criteria when evaluating a judge's claims. Instead, by age 8, if not earlier, children focused on relationships, trusting judgments that mismatched someone's relationship biases and discounting judgments that matched someone's relationship biases. The findings also suggested that children are better at recognizing that a judgment may have been biased than predicting that one will be, and that they may understand that negative relationships may skew judgments before positive ones.
Few Skewed Disks Found in First Closure-Phase Survey of Herbig Ae/Be Stars
NASA Astrophysics Data System (ADS)
Monnier, J. D.; Berger, J.-P.; Millan-Gabet, R.; Traub, W. A.; Schloerb, F. P.; Pedretti, E.; Benisty, M.; Carleton, N. P.; Haguenauer, P.; Kern, P.; Labeye, P.; Lacasse, M. G.; Malbet, F.; Perraut, K.; Pearlman, M.; Zhao, M.
2006-08-01
Using the three-telescope IOTA interferometer on Mount Hopkins, we report results from the first near-infrared (λ=1.65 μm) closure-phase survey of young stellar objects (YSOs). These closure phases allow us to unambiguously detect departures from centrosymmetry (i.e., skew) in the emission pattern from YSO disks on the scale of ~4 mas, expected from generic ``flared disk'' models. Six of 14 targets showed small, yet statistically significant nonzero closure phases, with largest values from the young binary system MWC 361-A and the (pre-main-sequence?) Be star HD 45677. Our observations are quite sensitive to the vertical structure of the inner disk, and we confront the predictions of the ``puffed-up inner wall'' models of Dullemond, Dominik, & Natta (DDN). Our data support disk models with curved inner rims because the expected emission appears symmetrically distributed around the star over a wide range of inclination angles. In contrast, our results are incompatible with the models possessing vertical inner walls because they predict extreme skewness (i.e., large closure phases) from the near-IR disk emission that is not seen in our data. In addition, we also present the discovery of mysterious H-band ``halos'' (~5%-10% of light on scales 0.01"-0.50") around a few objects, a preliminary ``parametric imaging'' study for HD 45677, and the first astrometric orbit for the young binary MWC 361-A.
NASA Astrophysics Data System (ADS)
Farag, Marwa H.; Hoenders, Bernhard J.; Knoester, Jasper; Jansen, Thomas L. C.
2017-06-01
The effect of Gaussian dynamics on the line shapes in linear absorption and two-dimensional correlation spectroscopy is well understood as the second-order cumulant expansion provides exact spectra. Gaussian solvent dynamics can be well analyzed using slope line analysis of two-dimensional correlation spectra as a function of the waiting time between pump and probe fields. Non-Gaussian effects are not as well understood, even though these effects are common in nature. The interpretation of the spectra, thus far, relies on complex case to case analysis. We investigate spectra resulting from two physical mechanisms for non-Gaussian dynamics, one relying on the anharmonicity of the bath and the other on non-linear couplings between bath coordinates. These results are compared with outcomes from a simpler log-normal dynamics model. We find that the skewed spectral line shapes in all cases can be analyzed in terms of the log-normal model, with a minimal number of free parameters. The effect of log-normal dynamics on the spectral line shapes is analyzed in terms of frequency correlation functions, maxline slope analysis, and anti-diagonal linewidths. A triangular line shape is a telltale signature of the skewness induced by log-normal dynamics. We find that maxline slope analysis, as for Gaussian dynamics, is a good measure of the solvent dynamics for log-normal dynamics.
Heat transfer in rotating serpentine passages with trips skewed to the flow
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.; Yeh, F. C.
1992-01-01
Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large scale, multi-pass heat transfer model with both radially inward and outward flow. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature, rotation number, Reynolds number, and radius-to-passage hydraulic diameter ratio. Results were correlated and compared to previous results from similar stationary and rotating models with smooth walls and with trip strips normal to the flow direction. It was concluded that (1) both Coriolis and buoyancy must be considered in turbine blade cooling designs with trip strips, (2) the effects of rotation are markedly different depending upon the flow direction, and (3) the heat transfer with skewed trip strips is less sensitive to buoyancy than the heat transfer models with either smooth or normal trips. Therefore, skewed trip strips rather than normal trip strips are recommended and geometry-specific tests are required for accurate design.
Sardeshmukh, Prashant D.
2015-03-15
The probability distributions of large-scale atmospheric and oceanic variables are generally skewed and heavy-tailed. We argue that their distinctive departures from Gaussianity arise fundamentally from the fact that in a quadratically nonlinear system with a quadratic invariant, the coupling coefficients between system components are not constant but depend linearly on the system state in a distinctive way. In particular, the skewness arises from a tendency of the system trajectory to linger near states of weak coupling. We show that the salient features of the observed non-Gaussianity can be captured in the simplest such nonlinear 2-component system. If the system is stochastically forced and linearly damped, with one component damped much more strongly than the other, then the strongly damped fast component becomes effectively decoupled from the weakly damped slow component, and its impact on the slow component can be approximated as a stochastic noise forcing plus an augmented nonlinear damping. In the limit of large time-scale separation, the nonlinear augmentation of the damping becomes small, and the noise forcing can be approximated as an additive noise plus a correlated additive and multiplicative noise (CAM noise) forcing. Much of the diversity of observed large-scale atmospheric and oceanic probability distributions can be interpreted in this minimal framework.
Buffeting response of long-span cable-supported bridges under skew winds. Part 2: case study
NASA Astrophysics Data System (ADS)
Xu, Y. L.; Zhu, L. D.
2005-03-01
The finite-element-based framework for buffeting analysis of long-span cable-supported bridges under skew winds has been presented in Part 1 of this paper. The framework is now applied to the Tsing Ma Suspension Bridge in Hong Kong as a case study. The wind velocities and bridge responses measured by the Wind and Structural Health Monitoring System (WASHMS) of the bridge during Typhoon Sam in 1999 are first analyzed to find the skew wind characteristics surrounding the bridge, the modal damping ratios and acceleration responses of the bridge. The buffeting responses of the bridge under skew winds during Typhoon Sam are then computed using the wind characteristics and modal damping ratios measured from the field and the aerodynamic coefficients and flutter derivatives of the bridge deck and tower measured from the wind tunnel under skew winds. The computed acceleration responses of the bridge deck and cable are finally compared with the responses measured from the field. The comparison is found to be satisfactory in general and the case study forms a good practical demonstration for the verification of the proposed method for buffeting analysis of long-span cable-supported bridges under skew winds.
Gentilini, Davide; Garagnani, Paolo; Pisoni, Serena; Bacalini, Maria Giulia; Calzari, Luciano; Mari, Daniela; Vitale, Giovanni; Franceschi, Claudio; Di Blasio, Anna Maria
2015-08-01
In this study we applied a new analytical strategy to investigate the relations between stochastic epigenetic mutations (SEMs) and aging. We analysed methylation levels through the Infinium HumanMethylation27 and HumanMethylation450 BeadChips in a population of 178 subjects ranging from 3 to 106 years. For each CpG probe, epimutated subjects were identified as the extreme outliers with methylation level exceeding three times interquartile ranges the first quartile (Q1-(3 x IQR)) or the third quartile (Q3+(3 x IQR)). We demonstrated that the number of SEMs was low in childhood and increased exponentially during aging. Using the HUMARA method, skewing of X chromosome inactivation (XCI) was evaluated in heterozygotes women. Multivariate analysis indicated a significant correlation between log(SEMs) and degree of XCI skewing after adjustment for age (β = 0.41; confidence interval: 0.14, 0.68; p-value = 0.0053). The PATH analysis tested the complete model containing the variables: skewing of XCI, age, log(SEMs) and overall CpG methylation. After adjusting for the number of epimutations we failed to confirm the well reported correlation between skewing of XCI and aging. This evidence might suggest that the known correlation between XCI skewing and aging could not be a direct association but mediated by the number of SEMs.
Zolal, Amir; Juratli, Tareq A; Linn, Jennifer; Podlesek, Dino; Sitoci Ficici, Kerim Hakan; Kitzler, Hagen H; Schackert, Gabriele; Sobottka, Stephan B; Rieger, Bernhard; Krex, Dietmar
2016-05-01
Objective To determine the value of apparent diffusion coefficient (ADC) histogram parameters for the prediction of individual survival in patients undergoing surgery for recurrent glioblastoma (GBM) in a retrospective cohort study. Methods Thirty-one patients who underwent surgery for first recurrence of a known GBM between 2008 and 2012 were included. The following parameters were collected: age, sex, enhancing tumor size, mean ADC, median ADC, ADC skewness, ADC kurtosis and fifth percentile of the ADC histogram, initial progression free survival (PFS), extent of second resection and further adjuvant treatment. The association of these parameters with survival and PFS after second surgery was analyzed using log-rank test and Cox regression. Results Using log-rank test, ADC histogram skewness of the enhancing tumor was significantly associated with both survival (p = 0.001) and PFS after second surgery (p = 0.005). Further parameters associated with prolonged survival after second surgery were: gross total resection at second surgery (p = 0.026), tumor size (0.040) and third surgery (p = 0.003). In the multivariate Cox analysis, ADC histogram skewness was shown to be an independent prognostic factor for survival after second surgery. Conclusion ADC histogram skewness of the enhancing lesion, enhancing lesion size, third surgery, as well as gross total resection have been shown to be associated with survival following the second surgery. ADC histogram skewness was an independent prognostic factor for survival in the multivariate analysis.
Xing, Dongyuan; Huang, Yangxin; Chen, Henian; Zhu, Yiliang; Dagne, Getachew A; Baldwin, Julie
2017-08-01
Semicontinuous data featured with an excessive proportion of zeros and right-skewed continuous positive values arise frequently in practice. One example would be the substance abuse/dependence symptoms data for which a substantial proportion of subjects investigated may report zero. Two-part mixed-effects models have been developed to analyze repeated measures of semicontinuous data from longitudinal studies. In this paper, we propose a flexible two-part mixed-effects model with skew distributions for correlated semicontinuous alcohol data under the framework of a Bayesian approach. The proposed model specification consists of two mixed-effects models linked by the correlated random effects: (i) a model on the occurrence of positive values using a generalized logistic mixed-effects model (Part I); and (ii) a model on the intensity of positive values using a linear mixed-effects model where the model errors follow skew distributions including skew- t and skew-normal distributions (Part II). The proposed method is illustrated with an alcohol abuse/dependence symptoms data from a longitudinal observational study, and the analytic results are reported by comparing potential models under different random-effects structures. Simulation studies are conducted to assess the performance of the proposed models and method.
Smits, Iris A M; Timmerman, Marieke E; Stegeman, Alwin
2016-05-01
Maximum likelihood estimation of the linear factor model for continuous items assumes normally distributed item scores. We consider deviations from normality by means of a skew-normally distributed factor model or a quadratic factor model. We show that the item distributions under a skew-normal factor are equivalent to those under a quadratic model up to third-order moments. The reverse only holds if the quadratic loadings are equal to each other and within certain bounds. We illustrate that observed data which follow any skew-normal factor model can be so well approximated with the quadratic factor model that the models are empirically indistinguishable, and that the reverse does not hold in general. The choice between the two models to account for deviations of normality is illustrated by an empirical example from clinical psychology.
Numerical Investigation of Sediment Suspension Above Plane Bed Under Skewed Grouping Waves
NASA Astrophysics Data System (ADS)
Finn, J.; Li, M.; Apte, S.
2016-12-01
Sediment suspension above a plane bed under oscillatory flow is of particular importance to coastal engineering in terms of understanding the influence of surface waves on beach and estuary transport processes. Existing studies, however, largely focus a on single representative wave condition and the randomness of natural waves are not taken into account. The present study aims to investigate wave grouping effects together with wave skewness on near bed boundary layer processes and sediment suspension using a newly developed three dimensional, multiphase, Euler-Lagrange point-particle model, e.g. Finn et al (2016). The sediment in the model is treated as a collection of Lagrangian particles that respond to both hydrodynamic and inter-particle forces, and particle motion is coupled to the near-bed hydrodynamics through the volume filtered Navier Stokes equations, which are solved in a finite volume LES framework at near-particle scale. The experiment by Bhawanin et al (2014) was used to validate the model's prediction on hydrodynamics and turbulence characteristics above boundary layer. Figure 1 shows the computed streamwise flow velocity within the wave group under a velocity-skewed signal in comparison with the measured values at different levels above the bed. The corresponding turbulence kinetic energy distribution under the wave group show similar level of agreement. The signature of waves with different strength within the group is clearly seen in the TKE distribution close to the bed. Subsequently, the Euler-Lagrange point-particle model was activated to investigate sediment suspension under the complex grouped waves. The particle size was chosen as 0.46mm sand. Initial examination of the model results reveals the immediate resuspension of sediment under large waves within the group and rapid drop of concentration under smaller waves, largely due to the coarse grain size and short wave period used in the test. However, the signature of near-bed turbulence on
Skart: A skewness- and autoregression-adjusted batch-means procedure for simulation analysis
NASA Astrophysics Data System (ADS)
Tafazzoli Yazdi, Ali
We discuss Skart, an automated batch-means procedure for constructing a skewness- and autoregression-adjusted confidence interval (CI) for the steady-state mean of a simulation output process in either discrete time (i.e., observation-based statistics) or continuous time (i.e., time-persistent statistics). Skart is a sequential procedure designed to deliver a CI that satisfies user-specified requirements concerning not only the CI's coverage probability but also the absolute or relative precision provided by its half-length. Skart exploits separate adjustments to the half-length of the classical batchmeans CI so as to account for the effects on the distribution of the underlying Student's t-statistic that arise from skewness (nonnormality) and autocorrelation of the batch means. The skewness adjustment is based on a modified Cornish-Fisher expansion for the classical batch-means Student's t -ratio, and the autocorrelation adjustment is based on an autoregressive approximation to the batch-means process for sufficiently large batch sizes. Skart also delivers a point estimator for the steady-state mean that is approximately free of initialization bias. The duration of the associated warm-up period (i.e., the statistics clearing time) is based on iteratively applying von Neumann's randomness test to spaced batch means with progressively increasing batch sizes and interbatch spacer sizes. In an experimental performance evaluation involving a wide range of test processes, Skart compared favorably with other simulation analysis methods---namely, its predecessors ASAP3, WASSP, and SBatch as well as ABATCH, LBATCH, the Heidelberger-Welch procedure, and the Law-Carson procedure. Specifically, Skart exhibited competitive sampling efficiency and substantially closer conformance to the given CI coverage probabilities than the other procedures. Also presented is a nonsequential version of Skart, called N-Skart, in which the user supplies a single simulation-generated series of
Mangold, Alexandra; Trenkwalder, Katharina; Ringler, Max; Hödl, Walter; Ringler, Eva
2015-09-03
Reproductive skew, the uneven distribution of reproductive success among individuals, is a common feature of many animal populations. Several scenarios have been proposed to favour either high or low levels of reproductive skew. Particularly a male-biased operational sex ratio and the asynchronous arrival of females is expected to cause high variation in reproductive success among males. Recently it has been suggested that the type of benefits provided by males (fixed vs. dilutable) could also strongly impact individual mating patterns, and thereby affecting reproductive skew. We tested this hypothesis in Hyalinobatrachium valerioi, a Neotropical glass frog with prolonged breeding and paternal care. We monitored and genetically sampled a natural population in southwestern Costa Rica during the breeding season in 2012 and performed parentage analysis of adult frogs and tadpoles to investigate individual mating frequencies, possible mating preferences, and estimate reproductive skew in males and females. We identified a polygamous mating system, where high proportions of males (69 %) and females (94 %) reproduced successfully. The variance in male mating success could largely be attributed to differences in time spent calling at the reproductive site, but not to body size or relatedness. Female H. valerioi were not choosy and mated indiscriminately with available males. Our findings support the hypothesis that dilutable male benefits - such as parental care - can favour female polyandry and maintain low levels of reproductive skew among males within a population, even in the presence of direct male-male competition and a highly male-biased operational sex ratio. We hypothesize that low male reproductive skew might be a general characteristic in prolonged breeders with paternal care.
NASA Astrophysics Data System (ADS)
Obaya, Rafael; Sanz, Ana M.
2016-10-01
We determine sufficient conditions for uniform and strict persistence in the case of skew-product semiflows generated by solutions of non-autonomous families of cooperative systems of ODEs or delay FDEs in terms of the principal spectrums of some associated linear skew-product semiflows which admit a continuous separation. Our conditions are also necessary in the linear case. We apply our results to a noncooperative almost periodic Nicholson system with a patch structure, whose persistence turns out to be equivalent to the persistence of the linearized system along the null solution.
Kerr Effect from Diffractive Skew Scattering in Chiral px±i py Superconductors
NASA Astrophysics Data System (ADS)
König, Elio J.; Levchenko, Alex
2017-01-01
We calculate the temperature dependent anomalous ac Hall conductance σH(Ω ,T ) for a two-dimensional chiral p -wave superconductor. This quantity determines the polar Kerr effect, as it was observed in Sr2RuO4 [J. Xia et al., Phys. Rev. Lett. 97, 167002 (2006)]. We concentrate on a single band model with an arbitrary isotropic dispersion relation subjected to rare, weak impurities treated in the Born approximation. As we explicitly show by detailed computation, previously omitted contributions to the extrinsic part of an anomalous Hall response, physically originating from diffractive skew scattering on quantum impurity complexes, appear to the leading order in the impurity concentration. By direct comparison with published results from the literature we demonstrate the relevance of our findings for the interpretation of the Kerr effect measurements in superconductors.
Uncertainty Relation on Generalized Skew Information with aMonotone Pair
NASA Astrophysics Data System (ADS)
Liu, Jun-Tong; Wang, Qing-Wen; Li, Lei
2017-08-01
In this paper, we first define a generalized ( f, g)-skew information |I_{ ρ }^{(f, g)} |(A) and two related quantity |J_{ ρ }^{(f, g)} |(A) and |U_{ ρ }^{(f, g)} |(A) for any non-Hermitian Hilbert-Schmidt operator A and a density operator ρ on a Hilbert space H and discuss some properties of them. And then, we obtain the following uncertainty relation in terms of |U_{ ρ }^{(f, g)} |(A): |U_{ ρ}^{(f, g)}|(A)|U_{ ρ}^{(f, g)}|(B)≥ β_{(f, g)}|Tr( f(ρ)g(ρ)[A, B]0)|2, which is a generalization of a known uncertainty relation in Ko and Yoo (J. Math. Anal. Appl. 383, 208-214, 11).
Marks, Steve; Prestemon, Soren; Robin, David; Schlueter, Ross D.; Steier, Christoph; Wolski, Andrew; Jung, Jin-Young; Chubar, Oleg
2005-11-29
Three elliptically polarizing undulators (EPU) are installed and operational at the Advanced Light Source (ALS); the most recent was installed in April 2005. Operational experience has shown a variation in electron beam size which correlates with the EPU's magnetic quadrant shifts used to vary polarization. Storage ring electron dynamics studies pointed to the existence of a shift dependent skew quadrupole (SQ) component generated within the EPUs. Detailed magnetic and mechanical measurements demonstrated that the field errors were the result of systematic individual magnetic block displacements which vary with quadrant shift. This paper will discuss the results of electron dynamics studies, magnetic and mechanical measurements, design modifications planned for future EPUs to eliminate the SQ source, and the design and implementation of SQ compensation coils.
Haemophilia B in a female caused by skewed inactivation of the normal X-chromosome.
Espinós, C; Lorenzo, J I; Casaña, P; Martínez, F; Aznar, J A
2000-10-01
Hemophilia B (factor IX deficiency) is an X-linked recessive disorder with a prevalence of 1:30,000 male births, which rarely affects females. A missense mutation T38R (6488C>G) of the factor IX (FIX) gene was characterized in a young female with moderate-to-severe hemophilia B. She is heterozygous for this mutation, which she inherited from her carrier mother. Analysis of the methyl-sensitive HpaII sites in the first exon of the human androgen-receptor locus indicated a de novo skewed X-chromosomal inactivation. This indicates that the paternal X-chromosome carrying her normal FIX gene is the inactive one, which has led to the phenotypic expression of hemophilia B in this patient.
Obliterable of graphics and correction of skew using Hough transform for mobile captured documents
NASA Astrophysics Data System (ADS)
Chethan, H. K.; Kumar, G. Hemantha
2011-10-01
CBDA is an emerging field in Computer Vision and Pattern Recognition. In recent technology camera are incorporated to several electronic equipments and are very interesting and thus playing a vital role by replacing scanner with hand held imaging devices like Digital Cameras, Mobile phones and gaming devices attached with these camera. The goal of the work is to remove graphics from the document which plays a vital role in recognition of characters from the mobile captured documents. In this paper we have proposed a novel method for separating or removal of graphics like logos, animations other than the text from the document and method to reduce noise and finally textual content skew is estimated and corrected using Hough Transform. The experimental results show the efficacy compared to the result of well known existing methods.
Separation of variables in anisotropic models and non-skew-symmetric elliptic r-matrix
NASA Astrophysics Data System (ADS)
Skrypnyk, Taras
2017-05-01
We solve a problem of separation of variables for the classical integrable hamiltonian systems possessing Lax matrices satisfying linear Poisson brackets with the non-skew-symmetric, non-dynamical elliptic so(3)⊗ so(3)-valued classical r-matrix. Using the corresponding Lax matrices, we present a general form of the "separating functions" B( u) and A( u) that generate the coordinates and the momenta of separation for the associated models. We consider several examples and perform the separation of variables for the classical anisotropic Euler's top, Steklov-Lyapunov model of the motion of anisotropic rigid body in the liquid, two-spin generalized Gaudin model and "spin" generalization of Steklov-Lyapunov model.
A cylindrical shell with an axial crack under skew-symmetric loading.
NASA Technical Reports Server (NTRS)
Yuceoglu, U.; Erdogan, F.
1973-01-01
The skew-symmetric problem for a cylindrical shell containing an axial crack is considered. It is assumed that the material has a special orthotropy - namely, that the shear modulus may be evaluated from the measured Young's moduli and Poisson ratios and is not an independent material constant. The problem is solved within the confines of an eighth-order linearized shallow shell theory. As numerical examples, the torsion of an isotropic cylinder and that of a specially orthotropic cylinder (titanium) are considered. The membrane and bending components of the stress intensity factor are calculated and are given as functions of a dimensionless shell parameter. In the torsion problem for the axially cracked cylinder the bending effects appear to be much more significant than that found for the circumferentially cracked cylindrical shell. Also, as the shell parameter increases, unlike the results found in the pressurized shell, the bending stresses around crack ends do not change sign.
A novel generalized normal distribution for human longevity and other negatively skewed data.
Robertson, Henry T; Allison, David B
2012-01-01
Negatively skewed data arise occasionally in statistical practice; perhaps the most familiar example is the distribution of human longevity. Although other generalizations of the normal distribution exist, we demonstrate a new alternative that apparently fits human longevity data better. We propose an alternative approach of a normal distribution whose scale parameter is conditioned on attained age. This approach is consistent with previous findings that longevity conditioned on survival to the modal age behaves like a normal distribution. We derive such a distribution and demonstrate its accuracy in modeling human longevity data from life tables. The new distribution is characterized by 1. An intuitively straightforward genesis; 2. Closed forms for the pdf, cdf, mode, quantile, and hazard functions; and 3. Accessibility to non-statisticians, based on its close relationship to the normal distribution.
Wigner-Yanase skew information and entanglement generation in quantum measurement
NASA Astrophysics Data System (ADS)
Banik, Manik; Deb, Prasenjit; Bhattacharya, Samyadeb
2017-04-01
The first step of quantum measurement procedure is known as premeasurement, during which correlation is established between the system and the measurement apparatus. Such correlation may be classical or nonclassical in nature. One compelling nonclassical correlation is entanglement, a useful resource for various quantum information theoretic protocols. Quantifying the amount of entanglement, generated during quantum measurement, therefore, seeks importance from practical ground, and this is the central issue of the present paper. Interestingly, for a two-level quantum system, we obtain that the amount of entanglement, measured in term of negativity, generated in premeasurement process can be quantified by two factors: skew information, which quantifies the uncertainty in the measurement of an observable not commuting with some conserved quantity of the system, and mixedness parameter of the system's initial state.
A Novel Generalized Normal Distribution for Human Longevity and other Negatively Skewed Data
Robertson, Henry T.; Allison, David B.
2012-01-01
Negatively skewed data arise occasionally in statistical practice; perhaps the most familiar example is the distribution of human longevity. Although other generalizations of the normal distribution exist, we demonstrate a new alternative that apparently fits human longevity data better. We propose an alternative approach of a normal distribution whose scale parameter is conditioned on attained age. This approach is consistent with previous findings that longevity conditioned on survival to the modal age behaves like a normal distribution. We derive such a distribution and demonstrate its accuracy in modeling human longevity data from life tables. The new distribution is characterized by 1. An intuitively straightforward genesis; 2. Closed forms for the pdf, cdf, mode, quantile, and hazard functions; and 3. Accessibility to non-statisticians, based on its close relationship to the normal distribution. PMID:22623974
Higher reproductive skew among birds than mammals in cooperatively breeding species
Raihani, Nichola J.; Clutton-Brock, Tim H.
2010-01-01
While competition for limited breeding positions is a common feature of group life, species vary widely in the extent to which reproduction is shared among females (‘reproductive skew’). In recent years, there has been considerable debate over the mechanisms that generate variation in reproductive skew, with most evidence suggesting that subordinates breed when dominants are unable to prevent them from doing so. Here, we suggest that viviparity reduces the ability of dominant females to control subordinate reproduction and that, as a result, dominant female birds are more able than their mammal counterparts to prevent subordinates from breeding. Empirical data support this assertion. This perspective may increase our understanding of how cooperative groups form and are stabilized in nature. PMID:20236970
Flight demonstration of redundancy management algorithms for a skewed array of inertial sensors
NASA Technical Reports Server (NTRS)
Morrell, F. R.; Bailey, M. L.; Motyka, P. R.
1988-01-01
Flight test results for two fault-tolerance algorithms developed for a redundant strapdown inertial measurement unit consisting of four 2-DOF gyros and accelerometers mounted on the faces of a semioctahedron are presented. Although both algorithms provided timely detection and isolation of flight control level failures, the generalized likelihood test algorithm provided more timely detection and isolation of low-level sensor failures than the edge vector test algorithm. The generalized likelihood test produced a false isolation for the case of a dual low-level failure applied to the sensitive axes of an accelerometer. Both of the algorithms were shown to provide dual fail-operational performance for the skewed array of inertial sensors.
Dynamics of a Skew Tent Map in the Nonlinear Frobenius-Perron Equation
NASA Astrophysics Data System (ADS)
Katsuragi, Daisuke
Return maps of the mean field in globally coupled map lattices (GCML) with a large system size were compared with those at the limit in a large system size. We adopted a nonlinear Frobenius-Perron equation (NFPE) for the limit in the large system size, and used a skew tent map as a chaotic map to simplify calculations in the NFPE. The return maps of the mean field for direct numerical calculations in the GCML usually fluctuate from those for numerical calculations in the NFPE. However, at some coupling strengths, there are totally different return maps between the GCML and the NFPE. We show that this strongly depends on the initial conditions at some coupling strengths.
Xiao, Gang; Wang, Xuanjun; Sheng, Jun; Lu, Shengjun; Yu, Xuezhong; Wu, Jennifer D
2015-02-20
Expression of surface NKG2D ligand MIC on tumor cells is deemed to stimulate NK and co-stimulate CD8 T cell anti-tumor immunity. Human cancer cells however frequently adopt a proteinase-mediated shedding strategy to generate soluble MIC (sMIC) to circumvent host immunity. High levels of sMIC have been shown to correlate with advanced disease stages in cancer patients. The underlying mechanism is currently understood as systemic downregulation of NKG2D expression on CD8 T and NK cells and perturbing NK cell periphery maintenance. Herein we report a novel mechanism by which sMIC poses immune suppressive effect on host immunity and tumor microenvironment. We demonstrate that sMIC facilitates expansion of myeloid-derived suppressor cells (MDSCs) and skews macrophages to the more immune suppressive alternative phenotype through activation of STAT3. These findings further endorse that sMIC is an important therapeutic target for cancer immunotherapy.
Separation of variables in anisotropic models and non-skew-symmetric elliptic r-matrix
NASA Astrophysics Data System (ADS)
Skrypnyk, Taras
2016-11-01
We solve a problem of separation of variables for the classical integrable hamiltonian systems possessing Lax matrices satisfying linear Poisson brackets with the non-skew-symmetric, non-dynamical elliptic so(3)⊗ so(3) -valued classical r-matrix. Using the corresponding Lax matrices, we present a general form of the "separating functions" B(u) and A(u) that generate the coordinates and the momenta of separation for the associated models. We consider several examples and perform the separation of variables for the classical anisotropic Euler's top, Steklov-Lyapunov model of the motion of anisotropic rigid body in the liquid, two-spin generalized Gaudin model and "spin" generalization of Steklov-Lyapunov model.
A missing model in reproductive skew theory: the bordered tug-of-war.
Reeve, Hudson Kern; Shen, Sheng-Feng
2006-05-30
Models of reproductive skew can be classified into two groups: transactional models, in which group members yield shares of reproduction to each other in return for cooperation, and tug-of-war models, in which group members invest group resources in a tug-of-war over their respective reproductive shares. We synthesize these two models to yield a "bordered tug-of-war" model in which the internal tug-of-war is limited ("bordered") by the requirement that group members must achieve a certain amount of reproduction lest they pursue a noncooperative option leading to group breakup. Previous attempts to synthesize these two models did not allow for the fact that the tug-of-war will affect group output, which in turn feeds back on the reproductive payments required by group members to remain cooperative. The bordered tug-of-war model, which does not assume complete reproductive control by any individual and allows for conflict within groups, predicts that the degree of within-group selfishness will increase as the noncooperative options become less attractive, e.g., as ecological constraints on solitary breeding increase. When the noncooperative option involves fighting for the group resource (e.g., territory) and leaving if the fight is lost, the subordinate's overall share of reproduction is predicted to be independent of its relatedness to the dominant and to increase the greater its probability of winning the fight, the less the value of the territory, and the greater its personal payoff for leaving. The unique predictions of the bordered tug-of-war model may fit skew data from a number of species, including meerkats, lions, and wood mice.
Th1-skewed tissue responses to a mycolyl glycolipid in mycobacteria-infected rhesus macaques
Morita, Daisuke; Miyamoto, Ayumi; Hattori, Yuki; Komori, Takaya; Nakamura, Takashi; Igarashi, Tatsuhiko; Harashima, Hideyoshi; Sugita, Masahiko
2013-11-08
Highlights: •Glucose monomycolate (GMM) is a marker glycolipid for active tuberculosis. •Tissue responses to GMM involved up-regulation of Th1-attracting chemokines. •Th1-skewed local responses were mounted at the GMM-injected tissue. -- Abstract: Trehalose 6,6′-dimycolate (TDM) is a major glycolipid of the cell wall of mycobacteria with remarkable adjuvant functions. To avoid detection by the host innate immune system, invading mycobacteria down-regulate the expression of TDM by utilizing host-derived glucose as a competitive substrate for their mycolyltransferases; however, this enzymatic reaction results in the concomitant biosynthesis of glucose monomycolate (GMM) which is recognized by the acquired immune system. GMM-specific, CD1-restricted T cell responses have been detected in the peripheral blood of infected human subjects and monkeys as well as in secondary lymphoid organs of small animals, such as guinea pigs and human CD1-transgenic mice. Nevertheless, it remains to be determined how tissues respond at the site where GMM is produced. Here we found that rhesus macaques vaccinated with Mycobacterium bovis bacillus Calmette–Guerin mounted a chemokine response in GMM-challenged skin that was favorable for recruiting T helper (Th)1 T cells. Indeed, the expression of interferon-γ, but not Th2 or Th17 cytokines, was prominent in the GMM-injected tissue. The GMM-elicited tissue response was also associated with the expression of monocyte/macrophage-attracting CC chemokines, such as CCL2, CCL4 and CCL8. Furthermore, the skin response to GMM involved the up-regulated expression of granulysin and perforin. Given that GMM is produced primarily by pathogenic mycobacteria proliferating within the host, the Th1-skewed tissue response to GMM may function efficiently at the site of infection.
Colony size is linked to paternity frequency and paternity skew in yellowjacket wasps and hornets.
Loope, Kevin J; Chien, Chun; Juhl, Michael
2014-12-30
The puzzle of the selective benefits of multiple mating and multiple paternity in social insects has been a major focus of research in evolutionary biology. We examine paternity in a clade of social insects, the vespine wasps (the yellowjackets and hornets), which contains species with high multiple paternity as well as species with single paternity. This group is particularly useful for comparative analyses given the wide interspecific variation in paternity traits despite similar sociobiology and ecology of the species in the genera Vespula, Dolichovespula and Vespa. We describe the paternity of 5 species of yellowjackets (Vespula spp.) and we perform a phylogenetically controlled comparative analysis of relatedness, paternity frequency, paternity skew, colony size, and nest site across 22 vespine taxa. We found moderate multiple paternity in four small-colony Vespula rufa-group species (effective paternity 1.5 - 2.1), and higher multiple paternity in the large-colony Vespula flavopilosa (effective paternity ~3.1). Our comparative analysis shows that colony size, but not nest site, predicts average intracolony relatedness. Underlying this pattern, we found that greater colony size is associated with both higher paternity frequency and reduced paternity skew. Our results support hypotheses focusing on the enhancement of genetic diversity in species with large colonies, and run counter to the hypothesis that multiple paternity is adaptively maintained due to sperm limitation associated with large colonies. We confirm the patterns observed in taxonomically widespread analyses by comparing closely related species of wasps with similar ecology, behavior and social organization. The vespine wasps may be a useful group for experimental investigation of the benefits of multiple paternity in the future.
Ultra-High Energy Cosmic Rays: Composition, Early Air Shower Interactions, and Xmax Skewness
NASA Astrophysics Data System (ADS)
Stapleton, James
The composition of Ultra-High Energy Cosmic Rays (UHECRs) is still not completely understood, and must be inferred from Extended Air Shower (EAS), particle cascades which they initiate upon entering the atmosphere. The atmospheric depth at which the shower contains the maximum number of particles ( Xmax) is the most composition-sensitive property of the air shower, but its interpretation is hindered by intrinsic statistical fluctuations in EAS development which cause distinct compositions to produce overlapping Xmax distributions as well as our limited knowledge at these energies of hadronic physics which strongly impacts the Xmax distribution's shape. These issues ultimately necessitate a variety of complementary approaches to interpreting UHECR composition from Xmax data. The current work advances these approaches by connecting X max skewness to the uncertainties above. The study of X max has historically focused only on the mean and standard deviation of its distribution, but skewness is shown here to be strongly related to both the statistical fluctuations in EAS development as well as the least-understood hadronic cross-sections in the air shower. This leads into a treatment of the Exponentially-Modified Gaussian (EMG) distribution, whose little-known properties make it very useful for Xmax analysis and for data analysis in general. A powerful method emerges which uses only descriptive statistics in a robust check for energy-dependent changes in UHECR mass or EAS development. The application of these analyses to X max data provides tantalizing clues concerning issues of critical importance, such as the relationship between Xmax and the 'ankle' break in the UHECR energy spectrum, or the inferred properties of the UHECR mass distribution and its strong dependence on hadronic model systematics.
Low paternity skew and the influence of maternal kin in an egalitarian, patrilocal primate
Strier, Karen B.; Chaves, Paulo B.; Mendes, Sérgio L.; Fagundes, Valéria; Di Fiore, Anthony
2011-01-01
Levels of reproductive skew vary in wild primates living in multimale groups depending on the degree to which high-ranking males monopolize access to females. Still, the factors affecting paternity in egalitarian societies remain unexplored. We combine unique behavioral, life history, and genetic data to evaluate the distribution of paternity in the northern muriqui (Brachyteles hypoxanthus), a species known for its affiliative, nonhierarchical relationships. We genotyped 67 individuals (22 infants born over a 3-y period, their 21 mothers, and all 24 possible sires) at 17 microsatellite marker loci and assigned paternity to all infants. None of the 13 fathers were close maternal relatives of females with which they sired infants, and the most successful male sired a much lower percentage of infants (18%) than reported for the most successful males in other species. Our findings of inbreeding avoidance and low male reproductive skew are consistent with the muriqui's observed social and sexual behavior, but the long delay (≥2.08 y) between the onset of male sexual behavior and the age at which males first sire young is unexpected. The allocation of paternity implicates individual male life histories and access to maternal kin as key factors influencing variation in paternal—and grandmaternal—fitness. The apparent importance of lifelong maternal investment in coresident sons resonates with other recent examinations of maternal influences on offspring reproduction. This importance also extends the implications of the “grandmother hypothesis” in human evolution to include the possible influence of mothers and other maternal kin on male reproductive success in patrilocal societies. PMID:22065786
A missing model in reproductive skew theory: The bordered tug-of-war
Reeve, Hudson Kern; Shen, Sheng-Feng
2006-01-01
Models of reproductive skew can be classified into two groups: transactional models, in which group members yield shares of reproduction to each other in return for cooperation, and tug-of-war models, in which group members invest group resources in a tug-of-war over their respective reproductive shares. We synthesize these two models to yield a “bordered tug-of-war” model in which the internal tug-of-war is limited (“bordered”) by the requirement that group members must achieve a certain amount of reproduction lest they pursue a noncooperative option leading to group breakup. Previous attempts to synthesize these two models did not allow for the fact that the tug-of-war will affect group output, which in turn feeds back on the reproductive payments required by group members to remain cooperative. The bordered tug-of-war model, which does not assume complete reproductive control by any individual and allows for conflict within groups, predicts that the degree of within-group selfishness will increase as the noncooperative options become less attractive, e.g., as ecological constraints on solitary breeding increase. When the noncooperative option involves fighting for the group resource (e.g., territory) and leaving if the fight is lost, the subordinate's overall share of reproduction is predicted to be independent of its relatedness to the dominant and to increase the greater its probability of winning the fight, the less the value of the territory, and the greater its personal payoff for leaving. The unique predictions of the bordered tug-of-war model may fit skew data from a number of species, including meerkats, lions, and wood mice. PMID:16717185
Prolonged Activation of Invariant Natural Killer T Cells and TH2-Skewed Immunity in Stroke Patients.
Wong, Connie H Y; Jenne, Craig N; Tam, Patrick P; Léger, Caroline; Venegas, Andres; Ryckborst, Karla; Hill, Michael D; Kubes, Paul
2017-01-01
Infection is highly prevalent and contribute significantly to mortality of stroke patients. In addition to the well described robust systemic lymphocytopenia and skewed T helper 2 (TH2)-immunity after stroke, emerging experimental evidence demonstrate that the development of infection poststroke is attributed by the activation of invariant natural killer T (iNKT) cells. In this prospective study, we examined the levels of a broad spectrum of inflammatory mediators, the activation status of iNKT cell in the blood of patients with various degree of stroke severity, and investigate whether these parameters differ in patients who later develop poststroke infections. We obtained blood from stroke patients and matching controls to perform flow cytometry and multiplex measurement of inflammatory mediators. Our data suggest a pronounced activation of iNKT cells in stroke patients as compared with matched Healthy and Hospital control patients. The magnitude of iNKT activation is positively correlated with the severity of stroke, supporting the hypothesis that iNKT cells may contribute in the modulation of the host immune response after stroke-associated brain injury. In addition, stroke severity is closely correlated with decreased TH1/TH2 ratio, increased production of interleukin (IL)-10, with infected stroke patients showing exacerbated production of IL-10. Stroke triggers a robust and sustained shift in systemic immunity in patients, including specific lymphopenia, robust activation of iNKT cells, systemic production of IL-10, and a prolonged TH2-skewed immunity, all are potential contributors to severe immune suppression seen in patients after stroke. Future studies with large sample size will provide potential causality relationship insights.
Faerch, Mia; Corydon, Thomas J; Rittig, Søren; Christensen, Jane H; Hertz, Jens Michael; Jendle, Johan
2010-11-01
To establish the clinical phenotype and genetic background in a family with diabetes insipidus. The subjects were a sister and brother, aged 34 and 27 years, respectively, with a history of polyuria since infancy. Clinical testing confirmed a diagnosis of congenital nephrogenic diabetes insipidus (CNDI) in both. Samples of purified genomic DNA were analysed. The sequence of the entire coding region of the AQP2 gene as well as the AVPR2 gene was determined. Sequence analysis revealed no variations in the AQP2 gene. A missense variation in exon 2 of the AVPR2 gene (g.685G>A), predicting a p.Asp85Asn substitution, was identified in the X-chromosome of the affected male and one allele in the sister and the asymptomatic mother. The p.Asp85Asn variation in AVPR2 is known to cause CNDI, and has previously been described as inducing a partial phenotype treatable with dDAVP. However, in this family dDAVP had no influence on urine osmolality, whereas combination therapy with indomethacin and hydrochlorothiazide increased urine osmolality to 299 mosm/l in the proband. A skewed X-inactivation pattern (93%) occurring in the normal X allele was recognized in the sister. This study demonstrates the effect of skewed X-chromosome inactivation associated with X-linked CNDI. Polydipsia in early childhood could be due to X-linked CNDI despite affecting both genders. The significant heterogeneity in the clinical phenotype in CNDI carries a risk of diagnostic misinterpretation and emphasizes the need for genetic characterization. Treatment combining indomethacin and hydrochlorothiazide results in a marked response on both urine output and urine osmolality.
Skewing the T-cell repertoire by combined DNA vaccination, host conditioning, and adoptive transfer.
Jorritsma, Annelies; Bins, Adriaan D; Schumacher, Ton N M; Haanen, John B A G
2008-04-01
Approaches for T-cell-based immunotherapy that have shown substantial effects in clinical trials are generally based on the adoptive transfer of high numbers of antigen-specific cells, and the success of these approaches is thought to rely on the high magnitude of the tumor-specific T-cell responses that are induced. In this study, we aimed to develop strategies that also yield a T-cell repertoire that is highly skewed toward tumor recognition but do not rely on ex vivo generation of tumor-specific T cells. To this end, the tumor-specific T-cell repertoire was first expanded by DNA vaccination and then infused into irradiated recipients. Subsequent vaccination of the recipient mice with the same antigen resulted in peak CD8(+) T-cell responses of approximately 50%. These high T-cell responses required the presence of antigen-experienced tumor-specific T cells within the graft because only mice that received cells of previously vaccinated donor mice developed effective responses. Tumor-bearing mice treated with this combined therapy showed a significant delay in tumor outgrowth, compared with mice treated by irradiation or vaccination alone. Furthermore, this antitumor effect was accompanied by an increased accumulation of activated and antigen-specific T cells within the tumor. In summary, the combination of DNA vaccination with host conditioning and adoptive transfer generates a marked, but transient, skewing of the T-cell repertoire toward tumor recognition. This strategy does not require ex vivo expansion of cells to generate effective antitumor immunity and may therefore easily be translated to clinical application.
An Euler-Lagrangian Numerical Study for Bed Armoring under skewed-asymmetric waves
NASA Astrophysics Data System (ADS)
Hsu, T. J.; Cheng, Z.; Rafati, Y.; Chauchat, J.; Bateman, S. P.; Calantoni, J.
2016-12-01
To better predict morphological evolution subject to extreme events, this study aims to improve sediment transport formulations for regional-scale coastal evolution models. The most commonly adopted assumptions in the existing sediment transport formulations are uniform grain properties (e.g., grain size, grain shape) and bottom-stress-based parameterizations. In this study we adopt a fully coupled Euler-Lagrangian numerical modeling framework to study the effects of bed armoring and grain shape on wave-induced sediment transport, particularly for highly energetic wave condition. The Eulerian two-phase model for small-scale sediment transport, sedFoam is coupled with the Discrete Element Model (DEM) solver LIGGGHTS, in which, mixed grain sizes and non-spherical particle shapes can be directly implemented. For the fluid turbulence, a modified k-w model is adopted. To better represent medium and fine sand transport, an eddy-interaction module is incorporated to model turbulent suspension while a lubrication correction is added for intergranular interaction. The model is used to study sheet flow sediment transport under skewed-asymmetric wave for a wide range of grain size distributions. Preliminary results suggest that the model can reproduce net onshore transport subject to skewed-asymmetric waves. However, the amount of onshore transport is highly dependent on the grain size distribution. The armoring effect appears to be more pronounced during the more energetic phase with higher bottom shear stress and horizontal pressure gradient. For wider grain size distribution, the net onshore transport can be reduced by as much as a factor two.
Ibbotson, Paul
2013-01-01
We use the Google Ngram database, a corpus of 5,195,769 digitized books containing ~4% of all books ever published, to test three ideas that are hypothesized to account for linguistic generalizations: verbal semantics, pre-emption and skew. Using 828,813 tokens of un-forms as a test case for these mechanisms, we found verbal semantics was a good predictor of the frequency of un-forms in the English language over the past 200 years—both in terms of how the frequency changed over time and their frequency rank. We did not find strong evidence for the direct competition of un-forms and their top pre-emptors, however the skew of the un-construction competitors was inversely correlated with the acceptability of the un-form. We suggest a cognitive explanation for this, namely, that the more the set of relevant pre-emptors is skewed then the more easily it is retrieved from memory. This suggests that it is not just the frequency of pre-emptive forms that must be taken into account when trying to explain usage patterns but their skew as well. PMID:24399991
NASA Astrophysics Data System (ADS)
Pipień, M.
2008-09-01
We present the results of an application of Bayesian inference in testing the relation between risk and return on the financial instruments. On the basis of the Intertemporal Capital Asset Pricing Model, proposed by Merton we built a general sampling distribution suitable in analysing this relationship. The most important feature of our assumptions is that the skewness of the conditional distribution of returns is used as an alternative source of relation between risk and return. This general specification relates to Skewed Generalized Autoregressive Conditionally Heteroscedastic-in-Mean model. In order to make conditional distribution of financial returns skewed we considered the unified approach based on the inverse probability integral transformation. In particular, we applied hidden truncation mechanism, inverse scale factors, order statistics concept, Beta and Bernstein distribution transformations and also a constructive method. Based on the daily excess returns on the Warsaw Stock Exchange Index we checked the empirical importance of the conditional skewness assumption on the relation between risk and return on the Warsaw Stock Market. We present posterior probabilities of all competing specifications as well as the posterior analysis of the positive sign of the tested relationship.
ERIC Educational Resources Information Center
Cooper, David
2015-01-01
The paper looks closely at student enrolment trends through a case study of South African "race" enrolment data, including some hypotheses about how student social class has influenced these trends. First, data on 1988-1998 enrolments showing a "skewed revolution" in student africanisation are summarised. Then, using 2000-2012…
Ibbotson, Paul
2013-01-01
We use the Google Ngram database, a corpus of 5,195,769 digitized books containing ~4% of all books ever published, to test three ideas that are hypothesized to account for linguistic generalizations: verbal semantics, pre-emption and skew. Using 828,813 tokens of un-forms as a test case for these mechanisms, we found verbal semantics was a good predictor of the frequency of un-forms in the English language over the past 200 years-both in terms of how the frequency changed over time and their frequency rank. We did not find strong evidence for the direct competition of un-forms and their top pre-emptors, however the skew of the un-construction competitors was inversely correlated with the acceptability of the un-form. We suggest a cognitive explanation for this, namely, that the more the set of relevant pre-emptors is skewed then the more easily it is retrieved from memory. This suggests that it is not just the frequency of pre-emptive forms that must be taken into account when trying to explain usage patterns but their skew as well.
ERIC Educational Resources Information Center
Cooper, David
2015-01-01
The paper looks closely at student enrolment trends through a case study of South African "race" enrolment data, including some hypotheses about how student social class has influenced these trends. First, data on 1988-1998 enrolments showing a "skewed revolution" in student africanisation are summarised. Then, using 2000-2012…
Veilleux, Andrea G.; Stedinger, Jery R.; Eash, David A.
2012-01-01
This paper summarizes methodological advances in regional log-space skewness analyses that support flood-frequency analysis with the log Pearson Type III (LP3) distribution. A Bayesian Weighted Least Squares/Generalized Least Squares (B-WLS/B-GLS) methodology that relates observed skewness coefficient estimators to basin characteristics in conjunction with diagnostic statistics represents an extension of the previously developed B-GLS methodology. B-WLS/B-GLS has been shown to be effective in two California studies. B-WLS/B-GLS uses B-WLS to generate stable estimators of model parameters and B-GLS to estimate the precision of those B-WLS regression parameters, as well as the precision of the model. The study described here employs this methodology to develop a regional skewness model for the State of Iowa. To provide cost effective peak-flow data for smaller drainage basins in Iowa, the U.S. Geological Survey operates a large network of crest stage gages (CSGs) that only record flow values above an identified recording threshold (thus producing a censored data record). CSGs are different from continuous-record gages, which record almost all flow values and have been used in previous B-GLS and B-WLS/B-GLS regional skewness studies. The complexity of analyzing a large CSG network is addressed by using the B-WLS/B-GLS framework along with the Expected Moments Algorithm (EMA). Because EMA allows for the censoring of low outliers, as well as the use of estimated interval discharges for missing, censored, and historic data, it complicates the calculations of effective record length (and effective concurrent record length) used to describe the precision of sample estimators because the peak discharges are no longer solely represented by single values. Thus new record length calculations were developed. The regional skewness analysis for the State of Iowa illustrates the value of the new B-WLS/BGLS methodology with these new extensions.
James, Patrick M A; Janes, Jasmine K; Roe, Amanda D; Cooke, Barry J
2016-08-01
Through their influence on effective population sizes, sex ratio skew affects population dynamics. We examined spatial variation in female-biased sex ratios in the mountain pine beetle (Dendroctonus ponderosae Hopkins) outbreak in western Canada to better understand how environmental context affects sex ratio skew. Our specific objectives were to: 1) characterize spatial variation in mountain pine beetle sex ratio; 2) test previously asserted hypotheses that beetle sex ratio varies with tree diameter and year in outbreak; and 3) develop predictive models of sex ratio skew for larval and adult populations. Using logistic regression, we modeled the probability that an individual beetle (n = 2,369) was female as a function of multiple environmental variables across 34 stands in British Columbia and Alberta, Canada. We identified a consistent female-biased sex ratio with significantly greater skew in adults (2:1, n = 713) than in larvae (1.76:1, n = 1,643). We found that the proportion of larval females increased with decreasing tree size and with outbreak age. However, adults did not respond to tree size and larvae did not respond to outbreak age. Predictive models differed between larvae and adults. All identified models perform well and included predictors related to weather, tree diameter, and year in outbreak. Female-biased sex ratios appear to originate from differential male mortality during development rather than from sex-biased oviposition, suggesting sex ratio skew is not the cause of outbreaks, but rather a consequence. © The Authors 2016. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Mynard, Jonathan P; Steinman, David A
2013-05-01
Given evidence that fully developed axisymmetric flow may be the exception rather than the rule, even in nominally straight arteries, maximum velocity (V(max)) can lie outside the Doppler sample volume (SV). The link between V(max) and derived quantities, such as volume flow (Q), may therefore be more complex than commonly thought. We performed idealized virtual Doppler ultrasound on data from image-based computational fluid dynamics (CFD) models of the normal human carotid artery and investigated how velocity profile skewing and choice of sample volume affected V(max) waveforms and derived Q variables, considering common assumptions about velocity profile shape (i.e., Poiseuille or Womersley). Severe velocity profile skewing caused substantial errors in V(max) waveforms when using a small, centered SV, although peak V(max) was reliably detected; errors with a long SV covering the vessel diameter were orientation dependent but lower overall. Cycle-averaged Q calculated from V(max) was typically within ±15%, although substantial skewing and use of a small SV caused 10%-25% underestimation. Peak Q derived from Womersley's theory was generally accurate to within ±10%. V(max) pulsatility and resistance indexes differed from Q-based values, although the Q-based resistance index could be predicted reliably. Skewing introduced significant error into V(max)-derived Q waveforms, particularly during mid-to-late systole. Our findings suggest that errors in the V(max) and Q waveforms related to velocity profile skewing and use of a small SV, or orientation-dependent errors for a long SV, could limit their use in wave analysis or for constructing characteristic or patient-specific flow boundary conditions for model studies.
NASA Astrophysics Data System (ADS)
Sawetsakulanond, Budhapon; Kinnares, Vijit
This paper presents analysis and investigation of the skew effect on behavior and performance of a three-phase, 220/380V, 8.7/5.0A, Δ/Y connected, 4 poles, 2.2kW self-excited induction generator (SEIG) with different angles rotor skewing. A 2D finite element analysis (2D-FEA) is used to consider core loss, flux density and circuit parameters. Analysis of excitation capacitor values for the SEIG based on a steady-state equivalent circuit model including rotor skew effect is given. Skewed rotor slots with angle of 0° (non-skew), 5° and 10° for the SEIGs are employed. Testing and performance comparisons under steady-state operation with a pure resistive load have been conducted. Obtained results can be guidelines and recommendations for development of effective wind induction generators.
NPIP: A skew line needle configuration optimization system for HDR brachytherapy
Siauw, Timmy; Cunha, Adam; Berenson, Dmitry; Atamtuerk, Alper; Hsu, I-Chow; Goldberg, Ken; Pouliot, Jean
2012-07-15
Purpose: In this study, the authors introduce skew line needle configurations for high dose rate (HDR) brachytherapy and needle planning by integer program (NPIP), a computational method for generating these configurations. NPIP generates needle configurations that are specific to the anatomy of the patient, avoid critical structures near the penile bulb and other healthy structures, and avoid needle collisions inside the body. Methods: NPIP consisted of three major components: a method for generating a set of candidate needles, a needle selection component that chose a candidate needle subset to be inserted, and a dose planner for verifying that the final needle configuration could meet dose objectives. NPIP was used to compute needle configurations for prostate cancer data sets from patients previously treated at our clinic. NPIP took two user-parameters: a number of candidate needles, and needle coverage radius, {delta}. The candidate needle set consisted of 5000 needles, and a range of {delta} values was used to compute different needle configurations for each patient. Dose plans were computed for each needle configuration. The number of needles generated and dosimetry were analyzed and compared to the physician implant. Results: NPIP computed at least one needle configuration for every patient that met dose objectives, avoided healthy structures and needle collisions, and used as many or fewer needles than standard practice. These needle configurations corresponded to a narrow range of {delta} values, which could be used as default values if this system is used in practice. The average end-to-end runtime for this implementation of NPIP was 286 s, but there was a wide variation from case to case. Conclusions: The authors have shown that NPIP can automatically generate skew line needle configurations with the aforementioned properties, and that given the correct input parameters, NPIP can generate needle configurations which meet dose objectives and use as many
Epicenter estimation using erroneous crustal model(s) and skew regional networks
NASA Astrophysics Data System (ADS)
Jih, Rong-Song
1999-06-01
A simple, hybrid procedure is proposed for seismic location at regional distances when (1) the crustal model is not known, (2) the seismic network is not calibrated, and (3) the azimuthal coverage of recording stations is poor. Among all parameters related to event location, the backazimuth estimated with a skew, large-aperture network appears to be the least sensitive to the model error—under these difficult yet realistic conditions. This observation leads to a hypothesis that epicenters could be better constrained through triangulation using backazimuths derived from two skew, large-aperture subnetworks or arrays. If two subnetworks can be found such that the corresponding backazimuths are sufficiently apart (say, they intersect at an angle of 20° or larger), the resulting absolute mislocation associated with the intersection point is often less than 18 km, which is the permissible location accuracy as quoted in the Comprehensive Nuclear Test Ban Treaty (CTBT). The origin time and source depth can then be obtained from a standard location procedure with the approximate epicenter held fixed. If the network cannot be partitioned to provide two `good' backazimuths, then the conventional location procedure (which feeds on the phase picks altogether) can still be used. The proposed algorithm is tested with three events: (1) U.S. explosion Salmon of Oct. 22, 1964, (2) Kola explosion of Sept. 29, 1996, and (3) Pakistani event of April 28, 1991. The absolute location error associated with this hybrid method is typically comparable to or, in many cases, better than that of the conventional method. Furthermore, this new approach also offers a measurable quantity which positively flags when the location is more likely to be good—even for regions that are not calibrated. These features could have important implications for the CTBT implementation as the proposed algorithm can readily be used in areas previously not well studied as an ad hoc procedure on problem events
A Unique Dermal Dendritic Cell Subset That Skews the Immune Response toward Th2
Hashimoto, Shin-ichi; Nagai, Shigenori; Hattori, Masahira; Irimura, Tatsuro
2013-01-01
Dendritic cell (DC) subsets in the skin and draining lymph nodes (LNs) are likely to elicit distinct immune response types. In skin and skin-draining LNs, a dermal DC subset expressing macrophage galactose-type C-type lectin 2 (MGL2/CD301b) was found distinct from migratory Langerhans cells (LCs) or CD103+ dermal DCs (dDCs). Lower expression levels of Th1-promoting and/or cross-presentation-related molecules were suggested by the transcriptome analysis and verified by the quantitative real-time PCR analysis in MGL2+ dDCs than in CD103+ dDCs. Transfer of MGL2+ dDCs but not CD103+ dDCs from FITC-sensitized mice induced a Th2-type immune response in vivo in a model of contact hypersensitivity. Targeting MGL2+ dDCs with a rat monoclonal antibody against MGL2 efficiently induced a humoral immune response with Th2-type properties, as determined by the antibody subclass. We propose that the properties of MGL2+ dDCs, are complementary to those of CD103+ dDCs and skew the immune response toward a Th2-type response. PMID:24039898
NASA Technical Reports Server (NTRS)
Eberlein, A. J.; Lahm, T. G.
1976-01-01
The degree to which flight-critical failures in a strapdown laser gyro tetrad sensor assembly can be isolated in short-haul aircraft after a failure occurrence has been detected by the skewed sensor failure-detection voting logic is investigated along with the degree to which a failure in the tetrad computer can be detected and isolated at the computer level, assuming a dual-redundant computer configuration. The tetrad system was mechanized with two two-axis inertial navigation channels (INCs), each containing two gyro/accelerometer axes, computer, control circuitry, and input/output circuitry. Gyro/accelerometer data is crossfed between the two INCs to enable each computer to independently perform the navigation task. Computer calculations are synchronized between the computers so that calculated quantities are identical and may be compared. Fail-safe performance (identification of the first failure) is accomplished with a probability approaching 100 percent of the time, while fail-operational performance (identification and isolation of the first failure) is achieved 93 to 96 percent of the time.
Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments
Adel, Mustafa; Elbehery, Ali H. A.; Aziz, Sherry K.; Aziz, Ramy K.; Grossart, Hans-Peter; Siam, Rania
2016-01-01
The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 109 bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer. PMID:27596223
Tumour cell conditioned medium reveals greater M2 skewing of macrophages in the absence of properdin
Al‐Rayahi, Izzat A.M.; Browning, Michael J.
2017-01-01
Abstract Introduction The tumour microenvironment is shaped by the interaction of immune, non immune, and tumour cells present in close proximity. Tumour cells direct the development of a locally immune suppressed state, affecting the activity of anti tumour T cells and preparing the escape phase of tumour development. Macrophages in the tumour typically develop into so‐called tumour associated macrophages with a distinct profile of activities which lead to a reduction in inflammation and antigen presentation. The direct impact of tumour cell conditioned medium on the activity profile of macrophages in dependence of their complement component expression has not yet been investigated. Methods In our in vitro study, macrophages differentiated from bone marrows of properdin deficient and wildtype mice were stimulated with conditioned medium of a syngeneic tumour cell line, B16F10, a mouse melanoma subline. Results In comparison with macrophages from wildtype mice, those from congenic properdin deficient mice showed skewing towards M2 profile, encompassing mRNA expression for genes involved in arginine metabolism, production of type 2 cytokines, and relatively lower surface expression of molecules needed for antigen presentation. Conclusions These data suggest that properdin insufficiency promotes a tumour environment that helps the tumour evade the immune response. PMID:28250926
SIU-based modification in Kelley's measure of skewness to achieve gains in efficiency
NASA Astrophysics Data System (ADS)
Habibullah, Saleha Naghmi; Shan-E-Fatima, Syeda
2015-02-01
The importance of accurate modeling of life-lengths of components and systems cannot be over-emphasized. Some well-known distributions such as the Birnbaum Saunders distribution extensively used in Reliability Theory are known to fulfill the self-inversion property, the term `Self-Inverse at Unity' (`SIU') implying that, for a random variable X, the distribution of 1/ X is identical to the distribution of X. Very recently, it has been demonstrated the advantage that can be drawn from the SIU property by proposing a modification to the well-known formula of the empirical cumulative distribution function to obtain an estimator of the cumulative distribution function that is more efficient than the empirical cumulative distribution function in situations where the parent population can be assumed to be SIU. Subsequently, a number of papers have appeared proposing SIU-based modifications to the formulae of well-known estimators of central tendency, dispersion and kurtosis that are likely to yield gains in efficiency on account of an approach very similar to the one adopted for the modification of the formula of the empirical cumulative distribution function. In this paper, we propose SIU-based modification to Kelley's Measure of Skewness and, through a simulation study, demonstrate the potential of the proposed formula in improving the efficiency of the estimation process which, obviously, has important implications for accurate modeling of life-data encountered in various branches of engineering.
Robustness of S1 statistic with Hodges-Lehmann for skewed distributions
NASA Astrophysics Data System (ADS)
Ahad, Nor Aishah; Yahaya, Sharipah Soaad Syed; Yin, Lee Ping
2016-10-01
Analysis of variance (ANOVA) is a common use parametric method to test the differences in means for more than two groups when the populations are normally distributed. ANOVA is highly inefficient under the influence of non- normal and heteroscedastic settings. When the assumptions are violated, researchers are looking for alternative such as Kruskal-Wallis under nonparametric or robust method. This study focused on flexible method, S1 statistic for comparing groups using median as the location estimator. S1 statistic was modified by substituting the median with Hodges-Lehmann and the default scale estimator with the variance of Hodges-Lehmann and MADn to produce two different test statistics for comparing groups. Bootstrap method was used for testing the hypotheses since the sampling distributions of these modified S1 statistics are unknown. The performance of the proposed statistic in terms of Type I error was measured and compared against the original S1 statistic, ANOVA and Kruskal-Wallis. The propose procedures show improvement compared to the original statistic especially under extremely skewed distribution.
A Timing Estimation Method Based-on Skewness Analysis in Vehicular Wireless Networks
Cui, Xuerong; Li, Juan; Wu, Chunlei; Liu, Jian-Hang
2015-01-01
Vehicle positioning technology has drawn more and more attention in vehicular wireless networks to reduce transportation time and traffic accidents. Nowadays, global navigation satellite systems (GNSS) are widely used in land vehicle positioning, but most of them are lack precision and reliability in situations where their signals are blocked. Positioning systems base-on short range wireless communication are another effective way that can be used in vehicle positioning or vehicle ranging. IEEE 802.11p is a new real-time short range wireless communication standard for vehicles, so a new method is proposed to estimate the time delay or ranges between vehicles based on the IEEE 802.11p standard which includes three main steps: cross-correlation between the received signal and the short preamble, summing up the correlated results in groups, and finding the maximum peak using a dynamic threshold based on the skewness analysis. With the range between each vehicle or road-side infrastructure, the position of neighboring vehicles can be estimated correctly. Simulation results were presented in the International Telecommunications Union (ITU) vehicular multipath channel, which show that the proposed method provides better precision than some well-known timing estimation techniques, especially in low signal to noise ratio (SNR) environments. PMID:26580628
White, Jonah
2011-01-01
Objectives. Few studies have considered the sociohistorical intersection of environmental injustice and gentrification; a gap addressed by this case study of Seattle, Washington. This study explored the advantages of integrating air toxic risk screening with gentrification research to enhance proximity and health equity analysis methodologies. It was hypothesized that Seattle's industrial air toxic exposure risk was unevenly dispersed, that gentrification stratified the city's neighborhoods, and that the inequities of both converged. Methods. Spatial characterizations of air toxic pollution risk exposures from 1990 to 2007 were combined with longitudinal cluster analysis of census block groups in Seattle, Washington, from 1990 to 2000. Results. A cluster of air toxic exposure inequality and socioeconomic inequity converged in 1 area of south central Seattle. Minority and working class residents were more concentrated in the same neighborhoods near Seattle's worst industrial pollution risks. Conclusions. Not all pollution was distributed equally in a dynamic urban landscape. Using techniques to examine skewed riskscapes and socioeconomic urban geographies provided a foundation for future research on the connections among environmental health hazard sources, socially vulnerable neighborhoods, and health inequity. PMID:21836115
Inhibition of RORγT Skews TCRα Gene Rearrangement and Limits T Cell Repertoire Diversity.
Guo, Yanxia; MacIsaac, Kenzie D; Chen, Yi; Miller, Richard J; Jain, Renu; Joyce-Shaikh, Barbara; Ferguson, Heidi; Wang, I-Ming; Cristescu, Razvan; Mudgett, John; Engstrom, Laura; Piers, Kyle J; Baltus, Gretchen A; Barr, Kenneth; Zhang, Hongjun; Mehmet, Huseyin; Hegde, Laxminarayan G; Hu, Xiao; Carter, Laura L; Aicher, Thomas D; Glick, Gary; Zaller, Dennis; Hawwari, Abbas; Correll, Craig C; Jones, Dallas C; Cua, Daniel J
2016-12-20
Recent studies have elucidated the molecular mechanism of RORγT transcriptional regulation of Th17 differentiation and function. RORγT was initially identified as a transcription factor required for thymopoiesis by maintaining survival of CD4(+)CD8(+) (DP) thymocytes. While RORγ antagonists are currently being developed to treat autoimmunity, it remains unclear how RORγT inhibition may impact thymocyte development. In this study, we show that in addition to regulating DP thymocytes survival, RORγT also controls genes that regulate thymocyte migration, proliferation, and T cell receptor (TCR)α selection. Strikingly, pharmacological inhibition of RORγ skews TCRα gene rearrangement, limits T cell repertoire diversity, and inhibits development of autoimmune encephalomyelitis. Thus, targeting RORγT not only inhibits Th17 cell development and function but also fundamentally alters thymic-emigrant recognition of self and foreign antigens. The analysis of RORγ inhibitors has allowed us to gain a broader perspective of the diverse function of RORγT and its impact on T cell biology. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.
Ancient human disturbances may be skewing our understanding of Amazonian forests
McMichael, Crystal N. H.; Matthews-Bird, Frazer; Farfan-Rios, William; Feeley, Kenneth J.
2017-01-01
Although the Amazon rainforest houses much of Earth’s biodiversity and plays a major role in the global carbon budget, estimates of tree biodiversity originate from fewer than 1,000 forest inventory plots, and estimates of carbon dynamics are derived from fewer than 200 recensus plots. It is well documented that the pre-European inhabitants of Amazonia actively transformed and modified the forest in many regions before their population collapse around 1491 AD; however, the impacts of these ancient disturbances remain entirely unaccounted for in the many highly influential studies using Amazonian forest plots. Here we examine whether Amazonian forest inventory plot locations are spatially biased toward areas with high probability of ancient human impacts. Our analyses reveal that forest inventory plots, and especially forest recensus plots, in all regions of Amazonia are located disproportionately near archaeological evidence and in areas likely to have ancient human impacts. Furthermore, regions of the Amazon that are relatively oversampled with inventory plots also contain the highest values of predicted ancient human impacts. Given the long lifespan of Amazonian trees, many forest inventory and recensus sites may still be recovering from past disturbances, potentially skewing our interpretations of forest dynamics and our understanding of how these forests are responding to global change. Empirical data on the human history of forest inventory sites are crucial for determining how past disturbances affect modern patterns of forest composition and carbon flux in Amazonian forests. PMID:28049821
Ancient human disturbances may be skewing our understanding of Amazonian forests.
McMichael, Crystal N H; Matthews-Bird, Frazer; Farfan-Rios, William; Feeley, Kenneth J
2017-01-17
Although the Amazon rainforest houses much of Earth's biodiversity and plays a major role in the global carbon budget, estimates of tree biodiversity originate from fewer than 1,000 forest inventory plots, and estimates of carbon dynamics are derived from fewer than 200 recensus plots. It is well documented that the pre-European inhabitants of Amazonia actively transformed and modified the forest in many regions before their population collapse around 1491 AD; however, the impacts of these ancient disturbances remain entirely unaccounted for in the many highly influential studies using Amazonian forest plots. Here we examine whether Amazonian forest inventory plot locations are spatially biased toward areas with high probability of ancient human impacts. Our analyses reveal that forest inventory plots, and especially forest recensus plots, in all regions of Amazonia are located disproportionately near archaeological evidence and in areas likely to have ancient human impacts. Furthermore, regions of the Amazon that are relatively oversampled with inventory plots also contain the highest values of predicted ancient human impacts. Given the long lifespan of Amazonian trees, many forest inventory and recensus sites may still be recovering from past disturbances, potentially skewing our interpretations of forest dynamics and our understanding of how these forests are responding to global change. Empirical data on the human history of forest inventory sites are crucial for determining how past disturbances affect modern patterns of forest composition and carbon flux in Amazonian forests.
Macrophage skewing by Phd2 haplodeficiency prevents ischaemia by inducing arteriogenesis.
Takeda, Yukiji; Costa, Sandra; Delamarre, Estelle; Roncal, Carmen; Leite de Oliveira, Rodrigo; Squadrito, Mario Leonardo; Finisguerra, Veronica; Deschoemaeker, Sofie; Bruyère, Françoise; Wenes, Mathias; Hamm, Alexander; Serneels, Jens; Magat, Julie; Bhattacharyya, Tapan; Anisimov, Andrey; Jordan, Benedicte F; Alitalo, Kari; Maxwell, Patrick; Gallez, Bernard; Zhuang, Zhen W; Saito, Yoshihiko; Simons, Michael; De Palma, Michele; Mazzone, Massimiliano
2011-10-09
PHD2 serves as an oxygen sensor that rescues blood supply by regulating vessel formation and shape in case of oxygen shortage. However, it is unknown whether PHD2 can influence arteriogenesis. Here we studied the role of PHD2 in collateral artery growth by using hindlimb ischaemia as a model, a process that compensates for the lack of blood flow in case of major arterial occlusion. We show that Phd2 (also known as Egln1) haplodeficient (Phd2(+/-)) mice displayed preformed collateral arteries that preserved limb perfusion and prevented tissue necrosis in ischaemia. Improved arteriogenesis in Phd2(+/-) mice was due to an expansion of tissue-resident, M2-like macrophages and their increased release of arteriogenic factors, leading to enhanced smooth muscle cell (SMC) recruitment and growth. Both chronic and acute deletion of one Phd2 allele in macrophages was sufficient to skew their polarization towards a pro-arteriogenic phenotype. Mechanistically, collateral vessel preconditioning relied on the activation of canonical NF-κB pathway in Phd2(+/-) macrophages. These results unravel how PHD2 regulates arteriogenesis and artery homeostasis by controlling a specific differentiation state in macrophages and suggest new treatment options for ischaemic disorders.
Polyandry and paternity skew in natural and experimental populations of Drosophila serrata.
Frentiu, Francesca D; Chenoweth, Stephen F
2008-03-01
Many species engage in polyandry, resulting in the potential for sexual selection to continue post-copulation through sperm competition and/or cryptic female choice. The relative importance of pre- vs. post-copulatory processes remains unknown for most species despite this information being fundamental for understanding the evolutionary consequences of sexual selection. The Australian fruit fly Drosophila serrata has become a prominent model system for studying precopulatory sexual selection, such as mating preferences and their influence on the evolution of sexually selected traits. Here, we investigated polyandry and the potential for post-copulatory sexual selection in this species using indirect paternity analysis. We genotyped 21 wild-caught and 19 laboratory-reared mothers and their offspring (a total of 787 flies) at six microsatellite loci and found extensive polyandry, with all broods surveyed having at least two sires. Female remating rates were higher than in other Drosophila surveyed to date and no significant differences were found between laboratory and field populations. Additionally, we found evidence for biased sperm usage in several broods of D. serrata. Paternity skew occurred more frequently in broods from the field population than the laboratory one, suggesting differences between the two environments in the level of post-copulatory sexual selection. Our data suggest that D. serrata represents a promising system for studying the interaction between pre- and post-copulatory sexual selection in driving the evolution of sexually selected phenotypes.
DISCOVERY OF RED-SKEWED K {sub {alpha}} IRON LINE IN Cyg X-2 WITH SUZAKU
Shaposhnikov, Nikolai E-mail: Lev.Titarchuk@nrl.navy.mil E-mail: plaurent@cea.fr
2009-07-10
We report on the Suzaku observation of neutron star (NS) low-mass X-ray binary Cygnus X-2 which reveals a presence of the iron K {sub {alpha}} emission line. The line profile shows a significant red wing. This discovery increases the number of NS sources where red-skewed iron lines were observed and strongly suggests that this phenomenon is common not only in black holes but also in other types of accreting compact objects. We examine the line profile in terms of models which attribute its production to the relativistic effects due to reflection of X-ray radiation from a cold accretion disk and also as a result of the line formation in the extended wind/outflow configuration. Both models are able to adequately represent the observed line profile. We consider the results of line modeling in the context of subsecond variability. While we were unable to conclusively disqualify one of the models, we find that the wind paradigm has several advantages over the relativistic disk reflection model.
NASA Astrophysics Data System (ADS)
Hirotsuka, Isao; Tsuboi, Kazuo
The capacitor motor (CRM) is widely used to drive industrial equipments and electric home appliances. Recently, the reduction in the vibration and noise of the CRM has become increasingly important from the standpoint of environmental improvement. However, the electromagnetic vibration of the CRM under load has not been analyzed sufficiently. Therefore, we have studied the electromagnetic vibration of CRM for the purpose of reducing it. In a previous paper, the relationships for a backward magnetic field, the equivalent circuit current, and the vibration of the CRM were clarified. The present paper theoretically and experimentally discusses the effect of the slot combination and skewed slot on the electromagnetic vibration of CRM under load. The primary conclusions are as follows: (1) In the case of 4-pole and 6-pole CRMs, the dominant electromagnetic vibration of CRMs was theoretically attributed to three types of electromagnetic force waves. Two types of electromagnetic force waves are generated: one wave is generated by the interaction of two forward magnetic fluxes, such as those of a three-phase squirrel-cage induction motor, and the other wave is generated under the influence of a backward magnetic flux. (2) The characteristics of dominant electromagnetic vibration depending on load and running capacitor were classified theoretically and experimentally into three types based on the characteristics of the electromagnetic force wave and equivalent circuit current. (3) The influences of magnetic saturation in dominant electromagnetic vibration were verified experimentally and their causes were clarified theoretically in relation to electromagnetic force waves.
Th2 skewing by activation of Nrf2 in CD4+ T cells1
Rockwell, Cheryl E.; Zhang, Mingcai; Fields, Patrick E.; Klaassen, Curtis D.
2012-01-01
Nuclear factor erythroid 2 related factor 2 (Nrf2) is a transcription factor that mediates the upregulation of a battery of cytoprotective genes in response to cell stress. Recent studies have shown that Nrf2 also modulates immune responses and exhibits anti-inflammatory activity. In this report, we demonstrate that a common food preservative, tBHQ, can activate Nrf2 in T cells, as evidenced by Nrf2 binding to the antioxidant response element (ARE) and the subsequent upregulation of Nrf2 target genes. The activation of Nrf2 suppresses IFNγ production, while inducing the production of the Th2 cytokines, IL-4, IL-5, and IL-13. Nrf2 activation also suppresses T-bet DNA binding and promotes GATA-3 DNA binding. Collectively, the present studies suggest that Nrf2 activation skews CD4+ T cells toward Th2 differentiation and thus represents a novel regulatory mechanism in CD4+ T cells. Further studies will be needed to determine whether the commercial use of Nrf2 activators as food preservatives promotes food allergies in humans. PMID:22250088
Dodla, Ramana; Wilson, Charles J.
2013-01-01
We investigate why electrically coupled neuronal oscillators synchronize or fail to synchronize using the theory of weakly coupled oscillators. Stability of synchrony and antisynchrony is predicted analytically and verified using numerical bifurcation diagrams. The shape of the phase response curve (PRC), the shape of the voltage time course, and the frequency of spiking are freely varied to map out regions of parameter spaces that hold stable solutions. We find that type-1 and type-2 PRCs can both hold synchronous and antisynchronous solutions, but the shape of the PRC and the voltage determine the extent of their stability. This is achieved by introducing a five-piecewise linear model to the PRC, and a three-piecewise linear model to the voltage time course, and then analyzing the resultant eigenvalue equations that determine the stability of the phase-locked solutions. A single time parameter defines the skewness of the PRC, and another single time parameter defines the spike width and frequency. Our approach gives a comprehensive picture of the relation between the PRC shape, voltage time course and the stability of the resultant synchronous and antisynchronous solutions. PMID:23777519
Properties of the Subantarctic Front and Polar Front from the skewness of sea level anomaly
NASA Astrophysics Data System (ADS)
Shao, Andrew E.; Gille, Sarah T.; Mecking, Sabine; Thompson, LuAnne
2015-07-01
The region of the Southern Ocean that encompasses the Subantarctic Front (SAF) to the north and the Polar Front (PF) to the south contains most of the transport of the Antarctic Circumpolar Current. Here skewness of sea level anomaly (SLA) from 1992 to 2013 is coupled with a meandering Gaussian jetw model to estimate the mean position, meridional width, and the percent variance that each front contributes to total SLA variability. The SAF and PF have comparable widths (85 km) in the circumpolar average, but their widths differ significantly in the East Pacific Basin (85 and 60 km, respectively). Interannual variability in the positions of the SAF and PF are also estimated using annual subsets of the SLA data from 1993 to 2012. The PF position has enhanced variability near strong topographic features such as the Kerguelen Plateau, the Campbell Plateau east of New Zealand, and downstream of Drake Passage. Neither the SAF nor the PF showed a robust meridional trend over the 20 year period. The Southern Annular Mode was significantly correlated with basin-averaged SAF and PF positions in the East Pacific and with the PF south of Australia. A correlation between the PF and the basin-scale wind stress curl anomaly was also found in the western extratropical Pacific but not in other basins.
NASA Astrophysics Data System (ADS)
Tang, S. L.; Antonia, R. A.; Djenidi, L.; Danaila, L.; Zhou, Y.
2016-09-01
The transport equation for the mean scalar dissipation rate ɛ ¯ θ is derived by applying the limit at small separations to the generalized form of Yaglom's equation in two types of flows, those dominated mainly by a decay of energy in the streamwise direction and those which are forced, through a continuous injection of energy at large scales. In grid turbulence, the imbalance between the production of ɛ ¯ θ due to stretching of the temperature field and the destruction of ɛ ¯ θ by the thermal diffusivity is governed by the streamwise advection of ɛ ¯ θ by the mean velocity. This imbalance is intrinsically different from that in stationary forced periodic box turbulence (or SFPBT), which is virtually negligible. In essence, the different types of imbalance represent different constraints imposed by the large-scale motion on the relation between the so-called mixed velocity-temperature derivative skewness ST and the scalar enstrophy destruction coefficient Gθ in different flows, thus resulting in non-universal approaches of ST towards a constant value as Reλ increases. The data for ST collected in grid turbulence and in SFPBT indicate that the magnitude of ST is bounded, this limit being close to 0.5.
Normal and skewed phosphorene nanoribbons in combined magnetic and electric fields
NASA Astrophysics Data System (ADS)
Arsoski, Vladimir V.; Grujić, Marko M.; Čukarić, Nemanja A.; Tadić, Milan Ž.; Peeters, François M.
2017-09-01
The energy spectrum and eigenstates of single-layer black phosphorus nanoribbons in the presence of a perpendicular magnetic field and an in-plane transverse electric field are investigated by means of a tight-binding method, and the effect of different types of edges is examined analytically. A description based on a continuum model is proposed using an expansion of the tight-binding model in the long-wavelength limit. The wave functions corresponding to the flatband part of the spectrum are obtained analytically and are shown to agree well with the numerical results from the tight-binding method for both narrow (10 nm) and wide (100 nm) nanoribbons. Analytical expressions for the critical magnetic field at which Landau levels are formed and the ranges of wave numbers in the dispersionless flatband segments in the energy spectra are derived. We examine the evolution of the Landau levels when an in-plane lateral electric field is applied, and we determine analytically how the edge states shift with magnetic field. For wider nanoribbons, the conductance is shown to have a characteristic staircase shape in combined magnetic and electric fields. Some of the stairs in zigzag and skewed armchair nanoribbons originate from edge states that are found in the band gap.
Application of derivative matrices of skew rays to design of compound dispersion prisms.
Lin, Psang Dain
2016-09-01
Numerous optimization methods have been developed in recent decades for optical system design. However, these methods rely heavily on ray tracing and finite difference techniques to estimate the derivative matrices of the rays. Consequently, the accuracy of the results obtained from these methods is critically dependent on the incremental step size used in the tuning stage. To overcome this limitation, the present study proposes a comprehensive methodology for the design of compound dispersion prisms based on the first- and second-order derivative matrices of skew rays. The proposed method facilitates the analysis and design of prisms with respect to arbitrary system variables and provides an ideal basis for automatic prism design applications. Four illustrative examples are given. It is shown that the optical quantities required to evaluate the prism performance can be extracted directly from the proposed derivative matrices. In addition, it is shown in this study that the single-element 3D prism can have the same deviation angle and spectral dispersion as the 2D compound prism.
Evaluation of skew-planar antenna for UAV communication at 2.4 GHz band
NASA Astrophysics Data System (ADS)
Prakoso, T.; Yaqin, A. A.; Ibrahim; Santoso, I.; Triwiyatno, A.; Riyadi, M. A.
2017-04-01
Skew-planar antenna is suitable for unmanned aerial vehicles (UAVs) since it has circular polarization (avoiding polarization-mismatched), omnidirectional radiation pattern (low pointing loss) thus comply with maneuver angles of UAV, and also small size. Investigation with electromagnetic simulations shows that tilt angle and coaxial length are the most sensitive parameters. Modified design with 55° tilt angle (original design: 45°) and 100 mm coaxial length (original: 60 mm) potentially provides wider bandwidth (400 MHz vs. 290 MHz), better impedance-matched (|S11|: -47.1 dB vs. -13.6 dB), and better gain (1.98 dBi vs 1.61 dBi). The antenna is predicted capable to support service distance of 3 km in 2.4 GHz band if used with communication module with 18 dBm transmit power and -100 dBm receiver sensitivity. Therefore, the modified antenna is suitable to be applied in UAV.
Radillo, Oriano
2014-01-01
Procalcitonin (PCT) is one of the best diagnostic and prognostic markers in clinical practice, widely used to evaluate the evolution of bacterial infections. Although it is mainly produced by thyroid, during sepsis almost all the peripheral tissues are involved in PCT production. Parenchymal cells have been suggested as the main source of PCT expression; however the contribution of macrophages is not clear yet. In response to environmental cues, tissue macrophages acquire distinct functional phenotypes, ranging from proinflammatory (M1) to anti-inflammatory (M2) phenotype. Macrophages at the fetal-maternal interface show immunosuppressive M2-like activities required for the maintenance of immunological homeostasis during pregnancy. This study aims to clarify the ability to synthesise PCT of fully differentiated (M0), polarized (M1/M2) macrophages and those cultured either in the presence of first trimester gravid serum (GS) or pregnancy hormones. We found out that M1 macrophages upregulate PCT expression following LPS stimulation compared to M0 and M2. The GS downregulates PCT expression in macrophages, skewing them towards an M2-like phenotype. This effect seems only partially mediated by the hormonal milieu. Our findings strengthen the key role of macrophages in counteracting inflammatory stimuli during pregnancy, suggesting PCT as a possible new marker of M1-like macrophages. PMID:24733960
Rami, Damiano; La Bianca, Martina; Agostinis, Chiara; Zauli, Giorgio; Radillo, Oriano; Bulla, Roberta
2014-01-01
Procalcitonin (PCT) is one of the best diagnostic and prognostic markers in clinical practice, widely used to evaluate the evolution of bacterial infections. Although it is mainly produced by thyroid, during sepsis almost all the peripheral tissues are involved in PCT production. Parenchymal cells have been suggested as the main source of PCT expression; however the contribution of macrophages is not clear yet. In response to environmental cues, tissue macrophages acquire distinct functional phenotypes, ranging from proinflammatory (M1) to anti-inflammatory (M2) phenotype. Macrophages at the fetal-maternal interface show immunosuppressive M2-like activities required for the maintenance of immunological homeostasis during pregnancy. This study aims to clarify the ability to synthesise PCT of fully differentiated (M0), polarized (M1/M2) macrophages and those cultured either in the presence of first trimester gravid serum (GS) or pregnancy hormones. We found out that M1 macrophages upregulate PCT expression following LPS stimulation compared to M0 and M2. The GS downregulates PCT expression in macrophages, skewing them towards an M2-like phenotype. This effect seems only partially mediated by the hormonal milieu. Our findings strengthen the key role of macrophages in counteracting inflammatory stimuli during pregnancy, suggesting PCT as a possible new marker of M1-like macrophages.
The Impact of male reproductive skew on kin structure and sociality in multi-male groups.
Widdig, Anja
2013-01-01
Patterns of within-group relatedness are expected to affect the prospects for cooperation among group members through kin selection. It has long been established that dispersal patterns determine the availability of kin and there is ample evidence of matrilineal kin biases in social behavior across primate species. However, in 1979, Jeanne Altmann(1) suggested that mating patterns also influence the structure of within-group relatedness; high male reproductive skew and the frequent replacement of breeding males leads to relatively high levels of paternal relatedness and age-structured paternal sibships within groups. As a consequence of frequent replacement of breeding males, relatedness among offspring of a given female will be reduced to the half- rather than full-sibling level. Depending on the number of sires and degree of relatedness among mothers, members of the same birth cohort may be as closely related as maternal siblings. If animals are able to recognize their paternal kin and exhibit biases in favor of them, this may influence the distribution of cooperation and the intensity of competition within groups of primates. Here, I summarize the evidence that serves as the basis for Altmann's predictions and review evidence regarding whether or not the availability of paternal kin also leads to paternal kin bias among primates.
Bacterial clearance reverses a skewed T-cell repertoire induced by Salmonella infection.
Leyva-Rangel, Jessica P; de Los Angeles Hernández-Cueto, Maria; Galan-Enriquez, Carlos-Samuel; López-Medina, Marcela; Ortiz-Navarrete, Vianney
2015-09-01
Salmonella typhimurium invades the spleen, liver, and peripheral lymph nodes and has recently been detected in the bone marrow and thymus, resulting in a reduced thymic size and a decline in the total number of thymic cells. A specific deletion of the double-positive cell subset has been characterized, yet the export of mature T cells to the periphery remains normal. We analyzed Salmonella pathogenesis regarding thymic structure and the T-cell maturation process. We demonstrate that, despite alterations in the thymic structure, T-cell development is maintained during Salmonella infection, allowing the selection of single-positive T-cell clones expressing particular T-cell receptor beta chains (TCR-Vβ). Moreover, the treatment of infected mice with an antibiotic restored the normal thymic architecture and thymocyte subset distribution. Additionally, the frequency of TCR-Vβ usage after treatment was comparable to that in non-infected mice. However, bacteria were still recovered from the thymus after 1 month of treatment. Our data reveal that a skewed T-cell developmental process is present in the Salmonella-infected thymus that alters the TCR-Vβ usage frequency. Likewise, the post-treatment persistence of Salmonella reveals a novel function of the thymus as a potential reservoir for this infectious agent.
The male handicap: male-biased mortality explains skewed sex ratios in brown trout embryos
Labbé, L.
2016-01-01
Juvenile sex ratios are often assumed to be equal for many species with genetic sex determination, but this has rarely been tested in fish embryos due to their small size and absence of sex-specific markers. We artificially crossed three populations of brown trout and used a recently developed genetic marker for sexing the offspring of both pure and hybrid crosses. Sex ratios (SR = proportion of males) varied widely one month after hatching ranging from 0.15 to 0.90 (mean = 0.39 ± 0.03). Families with high survival tended to produce balanced or male-biased sex ratios, but SR was significantly female-biased when survival was low, suggesting that males sustain higher mortality during development. No difference in SR was found between pure and hybrid families, but the existence of sire × dam interactions suggests that genetic incompatibility may play a role in determining sex ratios. Our findings have implications for animal breeding and conservation because skewed sex ratios will tend to reduce effective population size and bias selection estimates. PMID:27928001
Zinc Induces Dendritic Cell Tolerogenic Phenotype and Skews Regulatory T Cell-Th17 Balance.
George, Mariam Mathew; Subramanian Vignesh, Kavitha; Landero Figueroa, Julio A; Caruso, Joseph A; Deepe, George S
2016-09-01
Zinc (Zn) is an essential metal for development and maintenance of both the innate and adaptive compartments of the immune system. Zn homeostasis impacts maturation of dendritic cells (DCs) that are important in shaping T cell responses. The mechanisms by which Zn regulates the tolerogenic phenotype of DCs remain largely unknown. In this study, we investigated the effect of Zn on DC phenotype and the generation of Foxp3(+) regulatory T cells (Tregs) using a model of Histoplasma capsulatum fungal infection. Exposure of bone marrow-derived DCs to Zn in vitro induced a tolerogenic phenotype by diminishing surface MHC class II (MHCII) and promoting the tolerogenic markers, programmed death-ligand (PD-L)1, PD-L2, and the tryptophan degrading enzyme, IDO. Zn triggered tryptophan degradation by IDO and kynurenine production by DCs and strongly suppressed the proinflammatory response to stimulation by TLR ligands. In vivo, Zn supplementation and subsequent H. capsulatum infection supressed MHCII on DCs, enhanced PD-L1 and PD-L2 expression on MHCII(lo) DCs, and skewed the Treg-Th17 balance in favor of Foxp3(+) Tregs while decreasing Th17 cells. Thus, Zn shapes the tolerogenic potential of DCs in vitro and in vivo and promotes Tregs during fungal infection.
Zinc Induces Dendritic Cell Tolerogenic Phenotype and Skews Regulatory T cell – Th17 Balance
George, Mariam Mathew; Vignesh, Kavitha Subramanian; Landero Figueroa, Julio A.; Caruso, Joseph A.; Deepe, George S.
2016-01-01
Zn is an essential metal for development and maintenance of both the innate and adaptive compartments of the immune system. Zn homeostasis impacts maturation of dendritic cells (DCs) that are important in shaping T cell responses. The mechanism by which Zn regulates the tolerogenic phenotype of DCs remains largely unknown. In this study, we investigated the effect of Zn on DC phenotype and the generation of forkhead box P3 (FoxP3+) regulatory T cells (Tregs) using a model of Histoplasma capsulatum fungal infection. Exposure of bone marrow derived DCs to Zn in vitro induced a tolerogenic phenotype by diminishing surface major histocompatibility complex (MHC)II and promoting the tolerogenic markers, programmed death-ligand (PD-L)1, PD-L2 and the tryptophan degrading enzyme, indoleamine 2,3 dioxygenase (IDO). Zn triggered tryptophan degradation by IDO and kynurenine production by DCs and strongly suppressed the proinflammatory response to stimulation by toll like receptor (TLR) ligands. In vivo, Zn supplementation and subsequent H. capsulatum infection supressed MHCII on DCs, enhanced PD-L1 and PD-L2 expression on MHCIIlo DCs and skewed the Treg - Th17 balance in favour of FoxP3+ Tregs while decreasing Th17 cells. Thus, Zn shapes the tolerogenic potential of DCs in vitro and in vivo and promotes Tregs during fungal infection. PMID:27465530
Viruses-to-mobile genetic elements skew in the deep Atlantis II brine pool sediments.
Adel, Mustafa; Elbehery, Ali H A; Aziz, Sherry K; Aziz, Ramy K; Grossart, Hans-Peter; Siam, Rania
2016-09-06
The central rift of the Red Sea has 25 brine pools with different physical and geochemical characteristics. Atlantis II (ATIID), Discovery Deeps (DD) and Chain Deep (CD) are characterized by high salinity, temperature and metal content. Several studies reported microbial communities in these brine pools, but few studies addressed the brine pool sediments. Therefore, sediment cores were collected from ATIID, DD, CD brine pools and an adjacent brine-influenced site. Sixteen different lithologic sediment sections were subjected to shotgun DNA pyrosequencing to generate 1.47 billion base pairs (1.47 × 10(9) bp). We generated sediment-specific reads and attempted to annotate all reads. We report the phylogenetic and biochemical uniqueness of the deepest ATIID sulfur-rich brine pool sediments. In contrary to all other sediment sections, bacteria dominate the deepest ATIID sulfur-rich brine pool sediments. This decrease in virus-to-bacteria ratio in selected sections and depth coincided with an overrepresentation of mobile genetic elements. Skewing in the composition of viruses-to-mobile genetic elements may uniquely contribute to the distinct microbial consortium in sediments in proximity to hydrothermally active vents of the Red Sea and possibly in their surroundings, through differential horizontal gene transfer.
A Timing Estimation Method Based-on Skewness Analysis in Vehicular Wireless Networks.
Cui, Xuerong; Li, Juan; Wu, Chunlei; Liu, Jian-Hang
2015-11-13
Vehicle positioning technology has drawn more and more attention in vehicular wireless networks to reduce transportation time and traffic accidents. Nowadays, global navigation satellite systems (GNSS) are widely used in land vehicle positioning, but most of them are lack precision and reliability in situations where their signals are blocked. Positioning systems base-on short range wireless communication are another effective way that can be used in vehicle positioning or vehicle ranging. IEEE 802.11p is a new real-time short range wireless communication standard for vehicles, so a new method is proposed to estimate the time delay or ranges between vehicles based on the IEEE 802.11p standard which includes three main steps: cross-correlation between the received signal and the short preamble, summing up the correlated results in groups, and finding the maximum peak using a dynamic threshold based on the skewness analysis. With the range between each vehicle or road-side infrastructure, the position of neighboring vehicles can be estimated correctly. Simulation results were presented in the International Telecommunications Union (ITU) vehicular multipath channel, which show that the proposed method provides better precision than some well-known timing estimation techniques, especially in low signal to noise ratio (SNR) environments.
Gluten-containing grains skew gluten assessment in oats due to sample grind non-homogeneity.
Fritz, Ronald D; Chen, Yumin; Contreras, Veronica
2017-02-01
Oats are easily contaminated with gluten-rich kernels of wheat, rye and barley. These contaminants are like gluten 'pills', shown here to skew gluten analysis results. Using R-Biopharm R5 ELISA, we quantified gluten in gluten-free oatmeal servings from an in-market survey. For samples with a 5-20ppm reading on a first test, replicate analyses provided results ranging <5ppm to >160ppm. This suggests sample grinding may inadequately disperse gluten to allow a single accurate gluten assessment. To ascertain this, and characterize the distribution of 0.25-g gluten test results for kernel contaminated oats, twelve 50g samples of pure oats, each spiked with a wheat kernel, showed that 0.25g test results followed log-normal-like distributions. With this, we estimate probabilities of mis-assessment for a 'single measure/sample' relative to the <20ppm regulatory threshold, and derive an equation relating the probability of mis-assessment to sample average gluten content.
Titarchuk, Lev; Laurent, Philippe E-mail: plaurent@cea.fr
2009-08-01
We perform the analysis of the iron K{sub {alpha}} lines detected in three sources representing three types of accreting compact sources: cataclysmic variable (CV) GK Per, neutron star (NS) Serpens X-1, and black hole (BH) GX 339-4. We find, using data from Epic-PN Camera onboard XMM-Newton observatory, that the iron K{sub {alpha}} emission line in GK Per has a noticeable red-skewed profile. We compare the GK Per asymmetric line with the red-skewed lines observed by XMM-Newton in Serpens X-1 and GX 339-4. The observation of the K{sub {alpha}} emission with red-skewed features in CV GK Per cannot be related to the redshift effects of General Relativity (GR). Therefore, if the mechanism of the K{sub {alpha}}-line formation is the same in CVs, NSs, and BHs then it is evident that the GR effects would be ruled out as a cause of red skewness of K{sub {alpha}} line. The line reprocessing in an outflowing wind has been recently suggested as an alternative model for a broad red-shifted iron line formation. In the framework of the outflow scenario the red-skewed iron line is formed in the strong extended wind due to its illumination by the radiation emanating from the innermost part of the accreting material. The outflow is a common phenomenon for CVs, NSs, and BHs. In this paper, we demonstrate that the asymmetric shapes of the lines detected from these CV, NS, and BH sources are well described with the wind (outflow) model. Furthermore we find by analyzing Rossi X-Ray Timing Explorer(RXTE) observations that when the strong red-skewed iron line is observed in GX 339-4 the high-frequency variability is strongly suppressed. While this fact is hard to reconcile with the relativistic models, it is consistent with the outflowing gas washing out high-frequency modulations of the radiation presumably originated in the innermost part of the source.
Mathematical models of the simplest fuzzy PI/PD controllers with skewed input and output fuzzy sets.
Mohan, B M; Sinha, Arpita
2008-07-01
This paper unveils mathematical models for fuzzy PI/PD controllers which employ two skewed fuzzy sets for each of the two-input variables and three skewed fuzzy sets for the output variable. The basic constituents of these models are Gamma-type and L-type membership functions for each input, trapezoidal/triangular membership functions for output, intersection/algebraic product triangular norm, maximum/drastic sum triangular conorm, Mamdani minimum/Larsen product/drastic product inference method, and center of sums defuzzification method. The existing simplest fuzzy PI/PD controller structures derived via symmetrical fuzzy sets become special cases of the mathematical models revealed in this paper. Finally, a numerical example along with its simulation results are included to demonstrate the effectiveness of the simplest fuzzy PI controllers.
Raynaud, M; Moizard, M P; Dessay, B; Briault, S; Toutain, A; Gendrot, C; Ronce, N; Moraine, C
2000-04-01
It has been demonstrated in several X-linked disorders, both with and without mental retardation, that the X-inactivation process plays a significant role in the expression of X-linked diseases in females. Moreover, in some disorders extremely skewed inactivation of the X chromosome is constant in carriers, and this is thought to result from a proliferation or a survival advantage for cells expressing the normal allele at this locus over cells expressing the mutated allele. X-linked mental retardation (XLMR) is heterogeneous, and cloning and characterization of the mutated genes are in progress. XLMR can be expressed in carrier females but often with milder manifestations. We report the systematic study of the X-inactivation profile of obligate carriers and other females in 19 multiplex XLMR pedigrees, using leucocyte-extracted DNA. Extremely skewed profiles were observed in carriers in three of 19 families.
Lin, Psang Dain
2014-05-10
In a previous paper [Appl. Opt.52, 4151 (2013)], we presented the first- and second-order derivatives of a ray for a flat boundary surface to design prisms. In this paper, that scheme is extended to determine the Jacobian and Hessian matrices of a skew ray as it is reflected/refracted at a spherical boundary surface. The validity of the proposed approach as an analysis and design tool is demonstrated using an axis-symmetrical system for illustration purpose. It is found that these two matrices can provide the search direction used by existing gradient-based schemes to minimize the merit function during the optimization stage of the optical system design process. It is also possible to make the optical system designs more automatic, if the image defects can be extracted from the Jacobian and Hessian matrices of a skew ray.
Ning, S. A.; Hayman, G.; Damiani, R.; Jonkman, J.
2014-12-01
Blade element momentum methods, though conceptually simple, are highly useful for analyzing wind turbines aerodynamics and are widely used in many design and analysis applications. A new version of AeroDyn is being developed to take advantage of new robust solution methodologies, conform to a new modularization framework for National Renewable Energy Laboratory's FAST, utilize advanced skewed-wake analysis methods, fix limitations with previous implementations, and to enable modeling of highly flexible and nonstraight blades. This paper reviews blade element momentum theory and several of the options available for analyzing skewed inflow. AeroDyn implementation details are described for the benefit of users and developers. These new options are compared to solutions from the previous version of AeroDyn and to experimental data. Finally, recommendations are given on how one might select from the various available solution approaches.
NASA Astrophysics Data System (ADS)
Taylor, Peter; Massey, Richard; Jauzac, Mathilde; Courbin, Frédéric; Harvey, David; Joseph, Rémy; Robertson, Andrew
2017-07-01
Simulations of self-interacting dark matter predict that dark matter should lag behind galaxies during a collision. If the interaction is mediated by a high-mass force carrier, the distribution of dark matter can also develop asymmetric dark matter tails. To search for this asymmetry, we compute the gravitational lensing properties of a mass distribution with a free skewness parameter. We apply this to the dark matter around the four central galaxies in cluster Abell 3827. In the galaxy whose dark matter peak has previously been found to be offset, we tentatively measure a skewness s = 0.23^{+0.05}_{-0.22} in the same direction as the peak offset. Our method may be useful in future gravitational lensing analyses of colliding galaxy clusters and merging galaxies.
Chai, High Seng; Bailey, Kent R
2008-08-15
The problem of analyzing a continuous variable with a discrete component is addressed within the framework of the mixture model proposed by Moulton and Halsey (Biometrics 1995; 51:1570-1578). The model can be generalized by the introduction of the log-skew-normal distribution for the continuous component, and the fit can be significantly improved by its use, while retaining the interpretation of regression parameter estimates. Simulation studies and application to a real data set are used for demonstration.
Foo, Suan-Sin; Chen, Weiqiang; Chan, Yen; Bowman, James W; Chang, Lin-Chun; Choi, Younho; Yoo, Ji Seung; Ge, Jianning; Cheng, Genhong; Bonnin, Alexandre; Nielsen-Saines, Karin; Brasil, Patrícia; Jung, Jae U
2017-08-21
Blood CD14(+) monocytes are frontline immunomodulators categorized into classical, intermediate or non-classical subsets, and subsequently differentiated into M1 pro- or M2 anti-inflammatory macrophages on stimulation. Although the Zika virus (ZIKV) rapidly establishes viraemia, the target cells and immune responses, particularly during pregnancy, remain elusive. Furthermore, it is unknown whether African- and Asian-lineage ZIKV have different phenotypic impacts on host immune responses. Using human blood infection, we identified CD14(+) monocytes as the primary target for African- or Asian-lineage ZIKV infection. When immunoprofiles of human blood infected with ZIKV were compared, a classical/intermediate monocyte-mediated M1-skewed inflammation by the African-lineage ZIKV infection was observed, in contrast to a non-classical monocyte-mediated M2-skewed immunosuppression by the Asian-lineage ZIKV infection. Importantly, infection of the blood of pregnant women revealed an enhanced susceptibility to ZIKV infection. Specifically, Asian-lineage ZIKV infection of pregnant women's blood led to an exacerbated M2-skewed immunosuppression of non-classical monocytes in conjunction with a global suppression of type I interferon-signalling pathway and an aberrant expression of host genes associated with pregnancy complications. Also, 30 ZIKV(+) sera from symptomatic pregnant patients showed elevated levels of M2-skewed immunosuppressive cytokines and pregnancy-complication-associated fibronectin-1. This study demonstrates the differential immunomodulatory responses of blood monocytes, particularly during pregnancy, on infection with different lineages of ZIKV.Both African and epidemic strains of Zika virus are shown to target CD14(+) monocytes, which are more susceptible in pregnant women, but African strains are associated with inflammatory responses, and epidemic strains with immunotolerance.
NASA Astrophysics Data System (ADS)
Ma, Wenyong; Liu, Qingkuan; Du, Xiaoqing; Liu, Xiaobing
2017-08-01
The mechanism of large-amplitude aeroelastic vibrations of cylindrical bodies in the critical Reynolds number range are still unclear. This study concerns the aerodynamic forces acting on elliptical cylinders and the induced galloping instability resulting from skew flows (i.e., the direction of the flow is angled 0°-45° with respect to the central axis of the cylinder) for Reynolds numbers in the range of 37-235 k. The effects of the critical Reynolds number and the skew angle on the aerodynamic forces and the galloping instability are investigated with pressure wind tunnel tests. In all of the cases investigated in the present study, a sharp decrease in the lift coefficient with increasing angle of attack and a reduction in the drag coefficient at the critical Reynolds number could be responsible for the galloping instability. Variations in the torque coefficient leads to a torsional aerodynamic instability at the critical Reynolds number. Furthermore, the skew flow cause a critical flow state at lower Reynolds numbers. One possible reason for this behavior is that the longer effective cross section allows the flow to reattach.
Passow, Courtney N.; Delclos, Pablo J.; Kindsvater, Holly K.; Jones, Adam G.; Rosenthal, Gil G.
2015-01-01
Just as mating patterns can promote speciation or hybridization, the presence of hybridization can shape mating patterns within a population. In this study, we characterized patterns of multiple mating and reproductive skew in a naturally hybridizing swordtail fish species, Xiphophorus birchmanni. We quantified multiple mating using microsatellite markers to genotype embryos from 43 females collected from 2 wild populations. We also used a suite of single-nucleotide polymorphism markers to categorize females and their inferred mates as either parental X. birchmanni or as introgressed individuals, which carried alleles from a sister species, X. malinche. We found that parental and introgressed X. birchmanni females mated multiply with both parental and introgressed males. We found no difference in mating patterns or reproductive skew between parental and introgressed X. birchmanni females. However, nonintrogressed X. birchmanni males mated more often with large, fecund females. These females also had the greatest levels of skew in fertilization success of males. Thus, our results show that X. birchmanni has a polygynandrous mating system and that introgression of X. malinche alleles has only subtle effects on mating patterns in this species. PMID:25433083
Huang, Yangxin; Dagne, Getachew
2012-09-01
It is a common practice to analyze complex longitudinal data using semiparametric nonlinear mixed-effects (SNLME) models with a normal distribution. Normality assumption of model errors may unrealistically obscure important features of subject variations. To partially explain between- and within-subject variations, covariates are usually introduced in such models, but some covariates may often be measured with substantial errors. Moreover, the responses may be missing and the missingness may be nonignorable. Inferential procedures can be complicated dramatically when data with skewness, missing values, and measurement error are observed. In the literature, there has been considerable interest in accommodating either skewness, incompleteness or covariate measurement error in such models, but there has been relatively little study concerning all three features simultaneously. In this article, our objective is to address the simultaneous impact of skewness, missingness, and covariate measurement error by jointly modeling the response and covariate processes based on a flexible Bayesian SNLME model. The method is illustrated using a real AIDS data set to compare potential models with various scenarios and different distribution specifications.
NASA Astrophysics Data System (ADS)
Murphy, Andrew; Aref, Thomas; Coskun, Ulas; Weinberg, Phillip; Levchenko, Alex; Vakaryuk, Victor; Bezryadin, Alexey
2013-03-01
We study statistical properties of the switching current in superconductor-graphene-superconductor proximity junctions and superconductor-nanowire-superconductor devices. The fluctuations of the switching current are related to Little's phase slips, generated by thermal and quantum fluctuations of the superconducting order parameter. The study focuses on higher moments of the statistical probability distributions of the switching current. Namely we study the skewness, which defines the asymmetry of the distribution, and kurtosis, which is a measure of the ``peakedness.'' The skewness is defined as sk= m3 /m23 / 2 where m2 is the second moment of the distribution, called the variance, and m3 is the third moment. Kurtosis is defined as kur= m4 /m22 , where m4 is the fourth moment of the distribution. It is known that for Gaussian distributions sk=0 and kur=3. On our devices we find, in most cases, sk ~ -1 and kur ~ 5. These results are in agreement with numerical simulations as well as an analytic model. Finally we present preliminary experimental results for a two-nanowire device. We have found that the standard deviation, skewness and kurtosis of the switching current distributions in these devices vary periodically with magnetic field.
Grinsted, L; Bilde, T
2013-03-01
Reproductive partitioning is a key component of social organization in groups of cooperative organisms. In colonies of permanently social spiders of the genus Stegodyphus less than half of the females reproduce, while all females, including nonreproducers, perform suicidal allo-maternal care. Some theoretical models suggest that reproductive skew is a result of contest competition within colonies, leading to size hierarchies where only the largest females become reproducers. We investigated the effect of competition on within-group body size variation over six months in S. dumicola, by manipulating food level and colony size. We found no evidence that competition leads to increased size asymmetry within colonies, suggesting that contest competition may not be the proximate explanation for reproductive skew. Within-colony body size variation was high already in the juvenile stage, and did not increase over the course of the experiment, suggesting that body size variation is shaped at an early stage. This might facilitate task specialization within colonies and ensure colony-level reproductive output by early allocation of reproductive roles. We suggest that reproductive skew in social spiders may be an adaptation to sociality selected through inclusive fitness benefits of allo-maternal care as well as colony-level benefits maximizing colony survival and production.
Řlepokura, Katarzyna Anna
2016-02-01
β-NH4[(MeO)2cDHAP] (where cDHAP is cyclic dihydroxyacetone phosphate) has been investigated by X-ray crystallography in the temperature range 350-100 K. Three reversible single-crystal-to-single-crystal phase transitions have been examined and four phases (high-, room-, medium- and low-temperature phase, HTP, RTP, MTP and LTP, respectively) have been structurally determined: HTP (at 350 K, P2(1)/a, Z = 24), RTP (290 K, P1, Z = 12), MTP (205 K, P2(1)/a, Z = 4) and LTP (100 K, P1, Z = 24). Various puckering modes of the 1,3,2-dioxaphosphorinane ring of the organic cyclic phosphate anion have been revealed in the crystal: chair and skew. The chair ↔ skew ring flipping, which has been shown to take place during the phase transitions, results in various populations of skew and chair conformers in different phases. The flexibility in the coordination geometry of ammonium cations is considered to assist in the conformational flexibility of the dioxaphosphorinane ring.
Juang, K W; Lee, D Y; Ellsworth, T R
2001-01-01
The spatial distribution of a pollutant in contaminated soils is usually highly skewed. As a result, the sample variogram often differs considerably from its regional counterpart and the geostatistical interpolation is hindered. In this study, rank-order geostatistics with standardized rank transformation was used for the spatial interpolation of pollutants with a highly skewed distribution in contaminated soils when commonly used nonlinear methods, such as logarithmic and normal-scored transformations, are not suitable. A real data set of soil Cd concentrations with great variation and high skewness in a contaminated site of Taiwan was used for illustration. The spatial dependence of ranks transformed from Cd concentrations was identified and kriging estimation was readily performed in the standardized-rank space. The estimated standardized rank was back-transformed into the concentration space using the middle point model within a standardized-rank interval of the empirical distribution function (EDF). The spatial distribution of Cd concentrations was then obtained. The probability of Cd concentration being higher than a given cutoff value also can be estimated by using the estimated distribution of standardized ranks. The contour maps of Cd concentrations and the probabilities of Cd concentrations being higher than the cutoff value can be simultaneously used for delineation of hazardous areas of contaminated soils.
Paczolt, Kimberly A; Passow, Courtney N; Delclos, Pablo J; Kindsvater, Holly K; Jones, Adam G; Rosenthal, Gil G
2015-01-01
Just as mating patterns can promote speciation or hybridization, the presence of hybridization can shape mating patterns within a population. In this study, we characterized patterns of multiple mating and reproductive skew in a naturally hybridizing swordtail fish species, Xiphophorus birchmanni. We quantified multiple mating using microsatellite markers to genotype embryos from 43 females collected from 2 wild populations. We also used a suite of single-nucleotide polymorphism markers to categorize females and their inferred mates as either parental X. birchmanni or as introgressed individuals, which carried alleles from a sister species, X. malinche. We found that parental and introgressed X. birchmanni females mated multiply with both parental and introgressed males. We found no difference in mating patterns or reproductive skew between parental and introgressed X. birchmanni females. However, nonintrogressed X. birchmanni males mated more often with large, fecund females. These females also had the greatest levels of skew in fertilization success of males. Thus, our results show that X. birchmanni has a polygynandrous mating system and that introgression of X. malinche alleles has only subtle effects on mating patterns in this species.
Fieremans, Nathalie; Bauters, Marijke; Belet, Stefanie; Verbeeck, Jelle; Jansen, Anna C; Seneca, Sara; Roelens, Filip; De Baere, Elfride; Marynen, Peter; Froyen, Guy
2014-11-01
Xq28 microduplications of MECP2 are a prominent cause of a severe syndromic form of intellectual disability (ID) in males. Females are usually unaffected through near to complete X-inactivation of the aberrant X chromosome (skewing). In rare cases, affected females have been described due to random X-inactivation. Here, we report on two female patients carrying de novo MECP2 microduplications on their fully active X chromosomes. Both patients present with ID and additional clinical features. Mono-allelic expression confirmed complete skewing of X-inactivation. Consequently, significantly enhanced MECP2 mRNA levels were observed. We hypothesize that the cause for the complete skewing is due to a more harmful mutation on the other X chromosome, thereby forcing the MECP2 duplication to become active. However, we could not unequivocally identify such a second mutation by array-CGH or exome sequencing. Our data underline that, like in males, increased MECP2 dosage in females can contribute to ID too, which should be taken into account in diagnostics.
Flow Style Investigation and Noise Reduction of a Cross-Flow Fan with Varied Rotor-Skew-Angle Rotor
NASA Astrophysics Data System (ADS)
Tsai, Go-Long; Tu, Tsung-Hsien; Li, Tung-Chen; Wang, Kuang-Hsieng
The purpose of this study was investigating the noise emission, flow-style, fan’s performance regarding to cross-fan with three different rotor-skew angle (RSA) rotors. The special flow visualization setups for both vertical and parallel investigation of smoke slice were used to overcome the blind sight of a Laser-Doppler or a particle-tracking velocimeter, and the three-dimensional flow differences were confirmed with streamline images. The experimental results indicated that RSA-5, which is a rotor with a nearly a pitch skew within blade’s two end shrouds, has a lower sound emission and little pressure drops relative to that of no skew angle case, RSA-0. RSA-10, two pitches twisting case, also has a better acoustics quietness than that of RSA-0, but it excited undesired noise in a high frequency components around 2-4kHz. In this work, for a compromise between flow and acoustics performances, RSA-5 shows the most suitable design for cross-flow fan rotor.
Ji, Ting; Xu, Jing-Jing; Mace, Ruth
2014-03-01
Here we argue that models developed to examine cooperation and conflict in communal breeders, using a "tug-of-war" model of reproductive skew generated by incomplete control, are an appropriate way to model human kinship systems. We apply such models to understand the patterns of effort put into competition between father and son and between brothers in conflict over family resources in a patrilineal kinship system. Co-resident kin do not necessarily emerge with equal shares of the cake in terms of reproductive output. The models show that, depending on the efficiency with which they can gain more control of the resource, on the marriage system, and on the relatedness of the partners in conflict, individuals can do better to help their relatives breed rather than fight each other for the resources needed to reproduce. The models show that when a son's father is still breeding with his mother, sons should not compete for any share of reproduction. However, under polygyny, increased effort is spent on father/son and brother/brother conflict. Fathers will win the majority of reproduction if dominant to sons (in contrast to the finding that daughters-in-law win in conflict over mothers-in-law in patrilocal kinship systems, which has been suggested as explaining the evolution of menopause). Hence who wins in the sharing of reproduction depends not just on which sex disperses but also on the relative competitive ability of all individuals to exploit family resources. Anthropologists have long argued that cultural norms can reduce conflict. These formal evolutionary models help us to quantify the effects of reproductive conflict in families, throwing light on the evolutionary basis not just of patterns of reproductive scheduling, but also human kinship and marriage systems.
Skewness and flatness factors of the longitudinal velocity derivative in wall-bounded flows
NASA Astrophysics Data System (ADS)
Djenidi, Lyazid; Antonia, Robert A.; Talluru, Murali K.; Abe, Hiroyuki
2017-06-01
Hot-wire measurements are carried out in turbulent boundary layers over smooth and rough walls in order the assess the behavior of the skewness (S ) and flatness (F ) factors of the longitudinal velocity derivative as y , the distance from the wall, increases. The measurements are complemented by direct numerical simulations of a smooth wall turbulent channel flow. It is observed that, as the distance to the wall increases, S and F vary significantly before approaching a constant in the outer layer of the boundary layer. Further, S and F exhibit a nontrivial dependence on the Taylor microscale Reynolds number (Reλ). For example, in the region below about 0.2 δ (δ is the boundary layer thickness) where Reλ varies significantly, S and F strongly vary with Reλ and can be multivalued at a given Reλ. In the outer region, between 0.3 δ and 0.6 δ , S , F , and Reλ remain approximately constant. The channel flow direct numerical simulation data for S and F exhibit a similar behavior. These results point to the ambiguity that can arise when assessing the Reλ dependence of S and F in wall shear flows. In particular, the multivaluedness of S and F can lead to erroneous conclusions if y /δ is known only poorly, as is the case for the atmospheric shear layer (ASL). If the laboratory turbulent boundary layer is considered an adequate surrogate to the neutral ASL, then the behavior of S and F in the ASL is expected to be similar to that reported here.
Androgen receptor blockade using flutamide skewed sex ratio of litters in mice
Gharagozlou, Faramarz; Youssefi, Reza; Vojgani, Mehdi; Akbarinejad, Vahid; Rafiee, Ghazaleh
2016-01-01
Maternal testosterone has been indicated to affect sex ratio of offspring. The present study was conducted to elucidate the role of androgen receptor in this regard by blockade of androgen receptor using flutamide in female mice. Mice were randomly assigned to two experimental groups. Mice in the control (n = 20) and treatment (n = 20) groups received 8 IU equine chorionic gonadotropin (eCG) followed by human chorionic gonadotropin (hCG) injection (8 IU) 47 hr later. In addition, mice in the control and treatment groups received four injections of ethanol-saline vehicle and flutamide solution (2.50 mg), respectively, started from 1 hr before eCG injection until hCG injection at 12-hr intervals. Conception rate was not different between the treatment (18/20: 90.00%) and control (19/20: 95.00%) groups (p > 0.05). Litter size was higher in the treatment (8.22 ± 0.26) than control (7.21 ± 0.28) group (p < 0.05). Male sex ratio was lower in the flutamide-treated mice (67/148: 45.30%) as compared with the untreated ones (80/137: 58.40%; odds ratio = 1.69; p < 0.05). In conclusion, the results showed that androgen receptor blockade could skew sex ratio of offspring toward females implying that the effect of testosterone on sex ratio might be through binding to androgen receptor. In addition, the blockade of androgen receptor using flutamide appeared to enhance litter size. PMID:27482363
Serotonin skews human macrophage polarization through HTR2B and HTR7.
de las Casas-Engel, Mateo; Domínguez-Soto, Angeles; Sierra-Filardi, Elena; Bragado, Rafael; Nieto, Concha; Puig-Kroger, Amaya; Samaniego, Rafael; Loza, Mabel; Corcuera, María Teresa; Gómez-Aguado, Fernando; Bustos, Matilde; Sánchez-Mateos, Paloma; Corbí, Angel L
2013-03-01
Besides its role as a neurotransmitter, serotonin (5-hydroxytryptamine, 5HT) regulates inflammation and tissue repair via a set of receptors (5HT(1-7)) whose pattern of expression varies among cell lineages. Considering the importance of macrophage polarization plasticity for inflammatory responses and tissue repair, we evaluated whether 5HT modulates human macrophage polarization. 5HT inhibited the LPS-induced release of proinflammatory cytokines without affecting IL-10 production, upregulated the expression of M2 polarization-associated genes (SERPINB2, THBS1, STAB1, COL23A1), and reduced the expression of M1-associated genes (INHBA, CCR2, MMP12, SERPINE1, CD1B, ALDH1A2). Whereas only 5HT(7) mediated the inhibitory action of 5HT on the release of proinflammatory cytokines, both 5HT(2B) and 5HT(7) receptors mediated the pro-M2 skewing effect of 5HT. In fact, blockade of both receptors during in vitro monocyte-to-macrophage differentiation preferentially modulated the acquisition of M2 polarization markers. 5HT(2B) was found to be preferentially expressed by anti-inflammatory M2(M-CSF) macrophages and was detected in vivo in liver Kupffer cells and in tumor-associated macrophages. Therefore, 5HT modulates macrophage polarization and contributes to the maintenance of an anti-inflammatory state via 5HT(2B) and 5HT(7), whose identification as functionally relevant markers for anti-inflammatory/homeostatic human M2 macrophages suggests their potential therapeutic value in inflammatory pathologies.
S1 statistic with Hodges-Lehmann in two groups case for skewed distribution
NASA Astrophysics Data System (ADS)
Yin, Lee Ping; Yahaya, Sharipah Soaad Syed; Ahad, Nor Aishah
2015-12-01
This study is focused on the modification of S1 statistic, a procedure for testing the equality of groups, by replacing median with Hodges-Lehmann estimator as the location measure in two groups case under skewed distribution. The modification is also extended to the default scale estimator of Hodges-Lehmann, S1(HL) and robust scale estimator, MADn, S1(MADn). The purpose of the modifications is to improve the robustness of the statistic. To test the strengths and weaknesses of S1(HL) and S1(MADn), a simulation study was conducted. Several variables such as the shape of distributions, balanced and unbalanced group sizes, equal and unequal variances and nature of pairings were manipulated to create various conditions for the data. Since the distribution of S1 statistic is unknown, bootstrap method was used for data generation. According to Guo and Luh, a test statistic is considered robust if its empirical error rate does not exceed 0.075 when α = 0.05. Refer to the results obtained, S1(HL) and S1(MADn) can be considered as robust due to all error rates fall below 0.075 for balanced and unbalanced design in each distribution. t-test and Mann-Whitney are the chosen methods for comparison purpose. For balanced design, t-test and Mann-Whitney shown better results compare to S1(HL) and S1(MADn). However, for unbalanced design especially in negative pairing, S1(MADn) is the most appropriate method to be used across three distributions.
NASA Astrophysics Data System (ADS)
Ghotbi, Abdoulreza
This study aims to investigate the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction (SSI) due to near-fault ground motions. Both deterministic (i.e., pushover and nonlinear dynamic analyses) and probabilistic approaches were utilized. A set of response sensitivity analyses was performed considering various skew angles, column elements, and soil properties for bridge considered both as fixed-base and SSI models. It has been observed that as the skew angle increased, the bridge responded more severely to the ground motion. For instance, the deck rotation and shear-keys displacement increased with an increase in the skew angle. A modal pushover analysis was also performed in conjunction with the nonlinear dynamic analysis. It has been found that combining the bridge responses for various modes of vibration resulted in a relatively accurate seismic response compared to the nonlinear dynamic analysis while saving time and analysis cost, to a great extent. A probabilistic analysis was also performed considering record-to-record variability in ground motion, and a set of probabilistic seismic demand and fragility plots was generated. The effects of change in the skew angle and also SSI were studied to see various bridge responses. The damage probability increased especially with respect to deck rotation as the skew angle increased. The SSI had a decreasing effect on the overall response of the bridge with pile foundation.
Weber, Claudia C; Hurst, Laurence D
2010-12-01
Recent evidence suggests that germline transcription may affect both protein evolutionary rates, possibly mediated by repair processes, and recombination rates, possibly mediated by chromatin and epigenetic modification. Here, we test these propositions in Drosophila melanogaster. The challenge for such analyses is to provide defendable measures of germline gene expression. Intronic AT skew is a good candidate measure as it is thought to be a consequence, at least in part, of transcription-coupled repair. Prior evidence suggests that intronic AT skew in D. melanogaster is not affected by proximity to intron extremities and differs between transcribed DNA and flanking sequence. We now also establish that intronic AT skew is a defendable proxy for germline expression as (a) it is more similar than expected by chance between introns of the same gene (which is not accounted for by physical proximity), (b) is correlated with male germline expression, and (c) is more pronounced in broadly expressed genes. Furthermore, (d) a trend for intronic skew to differ between 3' and 5' ends of genes is particular to broadly expressed genes. Finally, (e) controlling for physical distance, introns of proximate genes are most different in skew if they have different tissue specificity. We find that intronic AT skew, employed as a proxy for germline transcription, correlates neither with recombination rates nor with the rate of protein evolution. We conclude that there is no prima facie evidence that germline expression modulates recombination rates or monotonically affects protein evolution rates in D. melanogaster.
Young, J.S.; Brain, K.L.; Cunnane, T.C.
2007-01-01
The skewed amplitude distribution of spontaneous excitatory junction potentials (sEJPs) in the mouse vas deferens and other electrically-coupled smooth muscle syncytia has been attributed to electrically-attenuated depolarizations resulting from the spontaneous release of quantized packets of ATP acting on remote smooth muscle cells (SMCs). However, in the present investigation surface SMCs of the mouse isolated vas deferens were poorly electrically coupled, with input resistances (176±18 MΩ, range: 141–221 MΩ, n=4) similar to those of dissociated cells. Furthermore, the amplitude of evoked EJPs was more variable in surface compared with deeper SMCs (F test, F=17.4, P<0.0001). Using simultaneous electrophysiology and confocal microscopy to investigate these poorly-coupled cells, it is shown that α-latrotoxin-stimulated sEJPs correlate, in timing (median delay ranged from −30 to −57 ms, P<0.05 in all experiments, n=5) and amplitude (Pearson product moment correlation, ρ>0.55 and P<0.001), with purinergic neuroeffector Ca2+ transients (NCTs) in SMCs. The temporal correlation between sEJPs of widely ranging amplitude with NCTs in the impaled SMC demonstrates that all sEJPs could arise from neurotransmitter action on the impaled cell and that the skewed distribution of sEJPs can be explained by the variable effect of packets of ATP on a single SMC. The amplitude correlation of sEJPs and NCTs argues against the attenuation of electrical signal amplitude along the length of a single SMC. The skewed sEJP amplitude distribution arising from neurotransmitter release on single SMCs is consistent with a broad neurotransmitter packet size distribution at sympathetic neuroeffector junctions. PMID:17208381
Young, J S; Brain, K L; Cunnane, T C
2007-03-02
The skewed amplitude distribution of spontaneous excitatory junction potentials (sEJPs) in the mouse vas deferens and other electrically-coupled smooth muscle syncytia has been attributed to electrically-attenuated depolarizations resulting from the spontaneous release of quantized packets of ATP acting on remote smooth muscle cells (SMCs). However, in the present investigation surface SMCs of the mouse isolated vas deferens were poorly electrically coupled, with input resistances (176+/-18 MOmega, range: 141-221 MOmega, n=4) similar to those of dissociated cells. Furthermore, the amplitude of evoked EJPs was more variable in surface compared with deeper SMCs (F test, F=17.4, P<0.0001). Using simultaneous electrophysiology and confocal microscopy to investigate these poorly-coupled cells, it is shown that alpha-latrotoxin-stimulated sEJPs correlate, in timing (median delay ranged from -30 to -57 ms, P<0.05 in all experiments, n=5) and amplitude (Pearson product moment correlation, rho>0.55 and P<0.001), with purinergic neuroeffector Ca2+ transients (NCTs) in SMCs. The temporal correlation between sEJPs of widely ranging amplitude with NCTs in the impaled SMC demonstrates that all sEJPs could arise from neurotransmitter action on the impaled cell and that the skewed distribution of sEJPs can be explained by the variable effect of packets of ATP on a single SMC. The amplitude correlation of sEJPs and NCTs argues against the attenuation of electrical signal amplitude along the length of a single SMC. The skewed sEJP amplitude distribution arising from neurotransmitter release on single SMCs is consistent with a broad neurotransmitter packet size distribution at sympathetic neuroeffector junctions.
Burnham, Bryan R; Cilento, James J; Hanley, Bridget
2015-08-01
Priming of pop-out (PoP), or intertrial priming, is the finding that responding to a singleton target is faster when a target's defining feature (e.g., color) and nontarget features are repeated between trials than when the target and nontarget features switch between trials. Facilitated responding may reflect priming's influence on selection, that is, implicitly encoded features speed the selection of a matching target. In contrast, PoP effects may also reflect intertrial priming's influence on postselection processes, where episodic retrieval of a previous target is facilitated when its features match the current target. Lamy, Yashar, and Ruderman Attention, Perception, & Psychophysics, 73, 2160-2167 (2011) proposed a hybrid, dual-stage model that assumes intertrial priming influences both selection and postselection retrieval. To provide support for intertrial priming influencing more than one cognitive process, we examined priming's influence on the shift, skew, and dispersion of RT distributions in PoP tasks by fitting the exponential-Gaussian function to the RTs. Three experiments demonstrated that PoP effects at the level of mean RT were associated with changes in both the shift and skew of the underlying RT distributions. Importantly, Experiments 2 and 3 showed that manipulations intended to influence selection or postselection processes produced corresponding changes in the contributions of the distribution shift and skew to the PoP effects on mean RT. The results suggest more than one process is influenced by intertrial priming in visual search tasks, but readers should be cautious about relating specific processes to specific exponential-Gaussian parameters.
Holvoet, Sébastien; Zuercher, Adrian W; Julien-Javaux, Françoise; Perrot, Marie; Mercenier, Annick
2013-01-01
Pre-clinical and clinical studies have evaluated the efficacy of probiotics in allergy. However, predictive in vitro systems for rational strain selection are still missing. We developed a novel in vitro screening system for the characterization of probiotics with anti-allergic potential. In this model, human peripheral blood mononuclear cells (PBMC) from healthy donors (n = 68) were skewed towards a Th2 cytokine phenotype by culture with IL-4 and anti-CD40, to resemble cells from allergic donors. Th2-skewed cells were then co-cultured with probiotics; a total of 35 strains were tested. Levels of IFN-γ, IL-10, IL-5 and 7 additional cytokines in culture supernatants were determined by ELISA or multiplex assay. Gene expression was assessed by real-time PCR. For validation, splenocytes from ovalbumin-primed mice and PBMC from grass-allergic donors were restimulated with respective antigen and co-cultured with probiotics, and cytokine profiles were correlated. Culture with IL-4 and anti-CD40 antibody induced secretion of IL-5 from PBMC, indicative of induction of a Th2 phenotype. Cytokine profiles induced by probiotics were strain specific even though species- and genus-specific clustering was observed for many strains by principal component analysis. This was paralleled by mRNA levels of the corresponding genes such as increased Tbet and reduced GATA-3 gene expression. Cytokine profiles induced by probiotics in PBMC stimulated with IL-4 and anti-CD40 correlated with those obtained from allergen-stimulated murine splenocytes or human PBMC from grass-allergic donors. Cytokine profiling of probiotic strains with IL-4-/anti-CD40-stimulated PBMC allowed to determine the effect of probiotics on Th2-skewed cells and thus to classify probiotic strains with anti-allergic potential. Copyright © 2013 S. Karger AG, Basel.
Meeus, Sofie; Honnay, Olivier; Brys, Rein; Jacquemyn, Hans
2012-01-01
Background and Aims In heterostylous plant species, skewed morph ratios are not uncommon and may arise from a range of factors. Despite the recognized importance of skewed morph ratios on overall reproductive success within populations, little is known about the impact of skewed morph ratios on population genetic diversity and differentiation in heterostylous species. This study specifically aimed to clarify the effect of population size and morph bias on population genetic diversity and differentiation in the temperate forest herb Pulmonaria officinalis. This species is characterized by a distylous breeding system and shows morph-specific differences in reproductive success. Methods Genetic diversity was determined for 27 P. officinalis populations in northern Belgium by using eight recently developed microsatellite markers. Multiple regressions were used to assess the relationship between genetic diversity, morph bias and population size, and FST-values were calculated for short- and long-styled morphs separately to study genetic differentiation as a function of morph type. Key Results For all genetic measures used, morph bias was more important in explaining patterns of genetic diversity than population size, and in all cases patterns of population genetic diversity followed a quadratic function, which showed a symmetrical decrease in genetic diversity with increasing morph bias. However, probably due to the reproductive advantage of L-morphs relative to S-morphs, maximum genetic diversity was found in populations showing an excess of L-morphs (60·7 % L-morph). On the other hand, no significant difference in pairwise genetic distances between populations was observed between L- (0·107) and S-morphs (0·106). Conclusions Our results indicate that significant deviations from equal morph ratios not only affect plant reproductive success but also population genetic diversity of heterostylous plant species. Hence, when defining conservation measures for populations
NASA Technical Reports Server (NTRS)
Sorenson, R. L.; Steger, J. L.
1983-01-01
An algorithm for generating computational grids about arbitrary three-dimensional bodies is developed. The elliptic partial differential equation (PDE) approach developed by Steger and Sorenson and used in the NASA computer program GRAPE is extended from two to three dimensions. Forcing functions which are found automatically by the algorithm give the user the ability to control mesh cell size and skewness at boundary surfaces. This algorithm, as is typical of PDE grid generators, gives smooth grid lines and spacing in the interior of the grid. The method is applied to a rectilinear wind-tunnel case and to two body shapes in spherical coordinates.
Tay, Richard
2016-03-01
The binary logistic model has been extensively used to analyze traffic collision and injury data where the outcome of interest has two categories. However, the assumption of a symmetric distribution may not be a desirable property in some cases, especially when there is a significant imbalance in the two categories of outcome. This study compares the standard binary logistic model with the skewed logistic model in two cases in which the symmetry assumption is violated in one but not the other case. The differences in the estimates, and thus the marginal effects obtained, are significant when the assumption of symmetry is violated.
Chronopoulos, D
2017-01-01
A systematic expression quantifying the wave energy skewing phenomenon as a function of the mechanical characteristics of a non-isotropic structure is derived in this study. A structure of arbitrary anisotropy, layering and geometric complexity is modelled through Finite Elements (FEs) coupled to a periodic structure wave scheme. A generic approach for efficiently computing the angular sensitivity of the wave slowness for each wave type, direction and frequency is presented. The approach does not involve any finite differentiation scheme and is therefore computationally efficient and not prone to the associated numerical errors. Copyright © 2016 Elsevier B.V. All rights reserved.
Parrett, Charles; Veilleux, Andrea; Stedinger, J.R.; Barth, N.A.; Knifong, Donna L.; Ferris, J.C.
2011-01-01
Improved flood-frequency information is important throughout California in general and in the Sacramento-San Joaquin River Basin in particular, because of an extensive network of flood-control levees and the risk of catastrophic flooding. A key first step in updating flood-frequency information is determining regional skew. A Bayesian generalized least squares (GLS) regression method was used to derive a regional-skew model based on annual peak-discharge data for 158 long-term (30 or more years of record) stations throughout most of California. The desert areas in southeastern California had too few long-term stations to reliably determine regional skew for that hydrologically distinct region; therefore, the desert areas were excluded from the regional skew analysis for California. Of the 158 long-term stations used to determine regional skew, 145 have minimally regulated annual-peak discharges, and 13 stations are dam sites for which unregulated peak discharges were estimated from unregulated daily maximum discharge data furnished by the U.S. Army Corp of Engineers. Station skew was determined by using an expected moments algorithm (EMA) program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual peak-discharge data. The Bayesian GLS regression method previously developed was modified because of the large cross correlations among concurrent recorded peak discharges in California and the use of censored data and historical flood information with the new expected moments algorithm. In particular, to properly account for these cross-correlation problems and develop a suitable regression model and regression diagnostics, a combination of Bayesian weighted least squares and generalized least squares regression was adopted. This new methodology identified a nonlinear function relating regional skew to mean basin elevation. The regional skew values ranged from -0.62 for a mean basin elevation of zero to 0.61 for a mean basin elevation
Paik, Wooyul; Choi, Choong Gon; Kim, Sang Joon
2016-01-01
Objective To determine whether pre-operative perfusion skewness and kurtosis derived from normalized cerebral blood volume (nCBV) histograms are associated with progression-free survival (PFS) of patients after partial resection of newly diagnosed glioblastoma. Materials and Methods A total of 135 glioblastoma patients who had undergone partial resection of tumor (resection of < 50% of pre-operative tumor volume or surgical biopsy) confirmed with immediate postsurgical MRI and examined with both conventional MRI and dynamic susceptibility contrast (DSC) perfusion MRI before the surgery were retrospectively reviewed in this study. They had been followed up post-surgical chemoradiotherapy for tumor progression. Using histogram analyses of nCBV derived from pre-operative DSC perfusion MRI, patients were sub-classified into the following four groups: positive skewness and leptokurtosis (group 1); positive skewness and platykurtosis (group 2); negative skewness and leptokurtosis (group 3); negative skewness and platykurtosis (group 4). Kaplan-Meier analysis and multivariable Cox proportional hazards regression analysis were performed to determine whether clinical and imaging covariates were associated with PFS or overall survival (OS) of these patients. Results According to the Kaplan-Meier method, median PFS of group 1, 2, 3, and 4 was 62, 51, 39, and 41 weeks, respectively, with median OS of 82, 77, 77, and 72 weeks, respectively. In multivariable analyses with Cox proportional hazards regression, pre-operative skewness/kurtosis pattern (hazard ratio: 2.98 to 4.64; p < 0.001), Karnofsky performance scale score (hazard ratio: 1.04; p = 0.003), and post-operative tumor volume (hazard ratio: 1.04; p = 0.02) were independently associated with PFS but not with OS. Conclusion Higher skewness and kurtosis of nCBV histogram before surgery were associated with longer PFS in patients with newly diagnosed glioblastoma after partial tumor resection. PMID:26798224
Rosen, Allison B; Aizcorbe, Ana; Ryu, Alexander J; Nestoriak, Nicole; Cutler, David M; Chernew, Michael E
2013-05-01
Bundled payment entails paying a single price for all services delivered as part of an episode of care for a specific condition. It is seen as a promising way to slow the growth of health care spending while maintaining or improving the quality of care. To implement bundled payment, policy makers must set base payment rates for episodes of care and update the rates over time to reflect changes in the costs of delivering care and the components of care. Adopting the fee-for-service paradigm of adjusting payments with uniform update rates would be fair and accurate if costs increased at a uniform rate across episodes. But our analysis of 2003 and 2007 US commercial claims data showed spending growth to be highly skewed across episodes: 10 percent of episodes accounted for 82.5 percent of spending growth, and within-episode spending growth ranged from a decline of 75 percent to an increase of 323 percent. Given that spending growth was much faster for some episodes than for others, a situation known as skewness, policy makers should not update episode payments using uniform update rates. Rather, they should explore ways to address variations in spending growth, such as updating episode payments one by one, at least at the outset.
Dreassi, Emanuela; Petrucci, Alessandra; Rocco, Emilia
2014-01-01
Linear-mixed models are frequently used to obtain model-based estimators in small area estimation (SAE) problems. Such models, however, are not suitable when the target variable exhibits a point mass at zero, a highly skewed distribution of the nonzero values and a strong spatial structure. In this paper, a SAE approach for dealing with such variables is suggested. We propose a two-part random effects SAE model that includes a correlation structure on the area random effects that appears in the two parts and incorporates a bivariate smooth function of the geographical coordinates of units. To account for the skewness of the distribution of the positive values of the response variable, a Gamma model is adopted. To fit the model, to get small area estimates and to evaluate their precision, a hierarchical Bayesian approach is used. The study is motivated by a real SAE problem. We focus on estimation of the per-farm average grape wine production in Tuscany, at subregional level, using the Farm Structure Survey data. Results from this real data application and those obtained by a model-based simulation experiment show a satisfactory performance of the suggested SAE approach. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Henry, MaLinda D.; Hankerson, Sarah J.; Siani, Jennifer M.; French, Jeffrey A.; Dietz, James M.
2013-01-01
Across taxa, cooperative breeding has been associated with high reproductive skew. Cooperatively breeding golden lion tamarins (Leontopithecus rosalia) were long thought to have a monogynous mating system in which reproduction was limited to a single dominant female. Subordinates with few reproductive opportunities delayed dispersal and remained in the natal group to provide alloparental care to siblings, thus allowing dominant reproductive females to meet the energetic needs associated with high rates of reproduction and successful infant rearing. The goal of this study was to re-assess monogyny in wild golden lion tamarin groups based upon pregnancy diagnoses that used non-invasive enzyme immunoassay for progesterone and cortisol, combined with weekly data on individual weight gain, bi-annual physical examinations noting pregnancy and lactation status and daily behavioral observations. We established quantitative and qualitative criteria to detect and determine the timing of pregnancies that did not result in the birth of infants. Pregnancy polygyny occurred in 83% of golden lion tamarin groups studied. The loss of 64% of subordinate pregnancies compared to only 15% by dominant females limited reproductive success mainly to dominant females, thus maintaining high reproductive skew in female golden lion tamarins. Pregnancy loss by subordinate adults did not appear to result from dominant interference in subordinate hormonal mechanisms, but more likely resulted from subordinate abandonment of newborn infants to mitigate dominant aggression. PMID:23454002
Chen, Jiaqing; Huang, Yangxin
2015-09-10
In longitudinal studies, it is of interest to investigate how repeatedly measured markers in time are associated with a time to an event of interest, and in the mean time, the repeated measurements are often observed with the features of a heterogeneous population, non-normality, and covariate measured with error because of longitudinal nature. Statistical analysis may complicate dramatically when one analyzes longitudinal-survival data with these features together. Recently, a mixture of skewed distributions has received increasing attention in the treatment of heterogeneous data involving asymmetric behaviors across subclasses, but there are relatively few studies accommodating heterogeneity, non-normality, and measurement error in covariate simultaneously arose in longitudinal-survival data setting. Under the umbrella of Bayesian inference, this article explores a finite mixture of semiparametric mixed-effects joint models with skewed distributions for longitudinal measures with an attempt to mediate homogeneous characteristics, adjust departures from normality, and tailor accuracy from measurement error in covariate as well as overcome shortages of confidence in specifying a time-to-event model. The Bayesian mixture of joint modeling offers an appropriate avenue to estimate not only all parameters of mixture joint models but also probabilities of class membership. Simulation studies are conducted to assess the performance of the proposed method, and a real example is analyzed to demonstrate the methodology. The results are reported by comparing potential models with various scenarios.
Lamontagne, Jonathan R.; Stedinger, Jery R.; Berenbrock, Charles; Veilleux, Andrea G.; Ferris, Justin C.; Knifong, Donna L.
2012-01-01
Flood-frequency information is important in the Central Valley region of California because of the high risk of catastrophic flooding. Most traditional flood-frequency studies focus on peak flows, but for the assessment of the adequacy of reservoirs, levees, other flood control structures, sustained flood flow (flood duration) frequency data are needed. This study focuses on rainfall or rain-on-snow floods, rather than the annual maximum, because rain events produce the largest floods in the region. A key to estimating flood-duration frequency is determining the regional skew for such data. Of the 50 sites used in this study to determine regional skew, 28 sites were considered to have little to no significant regulated flows, and for the 22 sites considered significantly regulated, unregulated daily flow data were synthesized by using reservoir storage changes and diversion records. The unregulated, annual maximum rainfall flood flows for selected durations (1-day, 3-day, 7-day, 15-day, and 30-day) for all 50 sites were furnished by the U.S. Army Corps of Engineers. Station skew was determined by using the expected moments algorithm program for fitting the Pearson Type 3 flood-frequency distribution to the logarithms of annual flood-duration data. Bayesian generalized least squares regression procedures used in earlier studies were modified to address problems caused by large cross correlations among concurrent rainfall floods in California and to address the extensive censoring of low outliers at some sites, by using the new expected moments algorithm for fitting the LP3 distribution to rainfall flood-duration data. To properly account for these problems and to develop suitable regional-skew regression models and regression diagnostics, a combination of ordinary least squares, weighted least squares, and Bayesian generalized least squares regressions were adopted. This new methodology determined that a nonlinear model relating regional skew to mean basin elevation
NASA Astrophysics Data System (ADS)
Ghotbi, Abdoul R.
2014-09-01
The seismic behavior of skewed bridges has not been well studied compared to straight bridges. Skewed bridges have shown extensive damage, especially due to deck rotation, shear keys failure, abutment unseating and column-bent drift. This research, therefore, aims to study the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction (SSI) due to near-fault ground motions. Due to several sources of uncertainty associated with the ground motions, soil and structure, a probabilistic approach is needed. Thus, a probabilistic methodology similar to the one developed by the Pacific Earthquake Engineering Research Center (PEER) has been utilized to assess the probability of damage due to various levels of shaking using appropriate intensity measures with minimum dispersions. The probabilistic analyses were performed for various bridge configurations and site conditions, including sand ranging from loose to dense and clay ranging from soft to stiff, in order to evaluate the effects. The results proved a considerable susceptibility of skewed bridges to deck rotation and shear keys displacement. It was also found that SSI had a decreasing effect on the damage probability for various demands compared to the fixed-base model without including SSI. However, deck rotation for all types of the soil and also abutment unseating for very loose sand and soft clay showed an increase in damage probability compared to the fixed-base model. The damage probability for various demands has also been found to decrease with an increase of soil strength for both sandy and clayey sites. With respect to the variations in the skew angle, an increase in skew angle has had an increasing effect on the amplitude of the seismic response for various demands. Deck rotation has been very sensitive to the increase in the skew angle; therefore, as the skew angle increased, the deck rotation responded accordingly
NASA Astrophysics Data System (ADS)
Bor, Sheau-Shong; Yang, Tai-Lin; Yang, Shui-Yuan
1992-05-01
The monostatic radar cross-sectional spectra of rotating multiple skew-plated metal fan blades are investigated. The theoretical treatment of such a slowly rotating and electrically large scatterer is based on the quasi-stationary method together with physical optics/physical theory of diffraction (PO/PTD) equivalent current techniques. Only the θθ polarization case is considered here, but the \\psi\\psi polarization case can be treated in the same way. This solution is applicable to any observation angle, and is represented by such a general form as one which enables us to treat a similar scatterer with multiple blades and with different skew angles. Three rotating skew-plated blades are taken as an example, and the agreements between the theoretical and experimental results are satisfactory.
Lyu, Cuicui; Shen, Jun; Zhang, Jianping; Xue, Feng; Liu, Xiaofan; Liu, Wei; Fu, Rongfeng; Zhang, Liyan; Li, Huiyuan; Zhang, Donglei; Zhang, Xiaobing; Cheng, Tao; Yang, Renchi; Zhang, Lei
2017-07-01
Skewed X chromosome inactivation (XCI) is a rare reason for hemophilia B in females. It is indefinite whether X chromosome reactivation (XCR) would occur when cells of hemophilia B patients with skewed XCI were reprogrammed into induced pluripotent stem cells (iPSCs). In this study, we investigated a female hemophilia B patient with a known F9 gene mutation: c.676C>T, p.Arg226Trp. We demonstrated that skewed XCI was the pathogenesis of the patient, and we successfully generated numerous iPSC colonies of the patient from peripheral blood mononuclear cells (PBMNCs), which was the first time for generating hemophilia-specific iPSCs from PBMNCs. Then we detected the XCI state of these iPSCs. Ninety-two iPSC lines were picked for XCI analysis. All of them retained an inactive X chromosome, which could be proved by amplification of the androgen receptor gene and XIST (X inactivation-specific transcript), expression of H3K27me3, and existence of XIST clouds in XIST RNA fluorescence in situ hybridization (FISH) analysis. We attempted to obtain iPSC lines with the wild-type F9 gene on the active X chromosome for further disease treatment. But it turned out that the patient's iPSCs were still skewed such as the somatic cells with 92 iPSC lines having mutant F9 on the active X chromosome. In conclusion, skewed XCI is one reason for hemophilia in females. PBMNCs are excellent somatic cell resources for hemophilia patients to do reprogramming. More attentions should be paid to generate naive iPSCs with two active X chromosomes for further clinical disease treatment. The state of skewed XCI is retained in the iPSCs from a female with hemophilia B.
Efremova, L S
2013-11-30
We use the notions of the Ω-function and functions suitable to it, to give a detailed proof of a decomposition theorem for the space of C{sup 1}-smooth skew products of interval maps whose quotient maps have complicated dynamics and satisfy the additional condition of Ω-stability with respect to the C{sup 1}-norm. In our theorem, the space of C{sup 1}-smooth skew products is decomposed into a union of four nonempty, pairwise disjoint subspaces. We give examples of maps contained in each of the four subspaces. Bibliography: 46 titles.
NASA Astrophysics Data System (ADS)
Roman, H. E.; Porto, M.; Dose, C.
2008-10-01
We analyze daily log-returns data for a set of 1200 stocks, taken from US stock markets, over a period of 2481 trading days (January 1996-November 2005). We estimate the degree of non-stationarity in daily market volatility employing a polynomial fit, used as a detrending function. We find that the autocorrelation function of absolute detrended log-returns departs strongly from the corresponding original data autocorrelation function, while the observed leverage effect depends only weakly on trends. Such effect is shown to occur when both skewness and long-time memory are simultaneously present. A fractional derivative random walk model is discussed yielding a quantitative agreement with the empirical results.
Study of Row Phase Dependent Skew Quadrupole Fields in Apple-II Type EPUs at the ALS
Steier, C.; Marks, S.; Prestemon, Soren; Robin, David; Schlueter, Ross; Wolski, Andrzej
2004-05-07
Since about 5 years, Apple-II type Elliptically Polarizing Undulators (EPU) have been used very successfully at the ALS to generate high brightness photon beams with arbitrary polarization. However, both EPUs installed so far cause significant changes of the vertical beamsize, especially when the row phase is changed to change the polarization of the photons emitted. Detailed measurements indicate this is caused by a row phase dependent skew quadrupole term in the EPUs. Magnetic measurements revealed the same effect for the third EPU to be installed later this year. All measurements to identify and quantify the effect with beam will be presented, as well as some results of magnetic bench measurements and numeric field simulations.
NASA Astrophysics Data System (ADS)
Herschbach, Christian; Fedorov, Dmitry V.; Mertig, Ingrid; Gradhand, Martin; Chadova, Kristina; Ebert, Hubert; Ködderitzsch, Diemo
2013-11-01
We present a detailed analysis of the skew-scattering contribution to the spin Hall conductivity using an extended version of the resonant scattering model of Fert and Levy [Phys. Rev. Lett.PRLTAO0031-900710.1103/PhysRevLett.106.157208 106, 157208 (2011)]. For 5d impurities in a Cu host, the proposed phase shift model reproduces the corresponding first-principles calculations. Crucial for that agreement is the consideration of two scattering channels related to p and d impurity states since the discussed mechanism is governed by a subtle interplay between the spin-orbit and potential scattering in both angular-momentum channels. It is shown that the potential scattering strength plays a decisive role for the magnitude of the spin Hall conductivity.
NASA Astrophysics Data System (ADS)
Guszejnov, Dávid; Lazányi, Nóra; Bencze, Attila; Zoletnik, Sándor
2013-11-01
This paper is aimed to contribute to the scientific discussions that have been triggered by the experimental observation of a quadratic relation between the kurtosis and skewness of turbulent fluctuations present in fusion plasmas and other nonlinear physical systems. In this paper, we offer a general statistical model which attributes the observed K =aS2+b relation to the varying intermittency of the experimental signals. The model is a two random variable model constructed to catch the essential intermittent feature of the real signal. One of the variables is the amplitude of the underlying intermittent event (e.g., turbulent structure) while the other is connected to the intermittency level of the system. This simple model can attribute physical meaning to the a and b coefficients, as they characterize the spatio-temporal statistics of intermittent events. By constructing a particle-conserving Gaussian model for the underlying coherent structures, the experimentally measured a and b coefficients could be adequately reproduced.
Influence of complex disorder on skew-scattering Hall effects in L 10 -ordered FePt alloy
NASA Astrophysics Data System (ADS)
Zimmermann, Bernd; Long, Nguyen H.; Mavropoulos, Phivos; Blügel, Stefan; Mokrousov, Yuriy
2016-08-01
We show by first-principles calculations that the skew-scattering anomalous Hall and spin Hall angles of L 10 -ordered FePt drastically depend on different types of disorder. A different sign of the anomalous Hall angle is obtained when slightly deviating from the stoichiometric ratio towards the Fe-rich side as compared to the Pt-rich side. For stoichiometric samples, short-range ordering of defects has a profound effect on the Hall angles and can change them by a factor of 2 as compared to the case of uncorrelated disorder. This might explain the vast range of anomalous Hall angles measured in experiments, which undergo different preparation procedures and thus might differ in their crystallographic quality.
NASA Astrophysics Data System (ADS)
Zhang, Shuyuan; Liu, Min; Liu, Wen; Li, Zhaofeng; Liu, Yusheng; Wang, Xiaodong; Yang, Fuhua
2017-10-01
Light trapping is essential to improve the performance of thin film solar cells. In this paper, we performed a parametric optimization of double-sided skewed nanopyramid arrays that act as a light trapping scheme to increase light absorption in thin-film c-Si solar cells. Our theoretical optimization reveals that the short-circuit current density in a solar cell, employing only 1 μm silicon could reach as high as 38.57 mA cm‑2, which is 17% and 245% higher than that of the Yablonovitch limit and planar-film counterparts, respectively. Furthermore, we analyzed the underlying physics of the light absorption enhancement through electric field intensity profiles.
Carvalho, Karina I; Melo, Karina M; Bruno, Fernanda R; Snyder-Cappione, Jennifer E; Nixon, Douglas F; Costa-Carvalho, Beatriz T; Kallas, Esper G
2010-09-09
Common variable immunodeficiency disorder (CVID) is the commonest cause of primary antibody failure in adults and children, and characterized clinically by recurrent bacterial infections and autoimmune manifestations. Several innate immune defects have been described in CVID, but no study has yet investigated the frequency, phenotype or function of the key regulatory cell population, natural killer T (NKT) cells. We measured the frequencies and subsets of NKT cells in patients with CVID and compared these to healthy controls. Our results show a skewing of NKT cell subsets, with CD4+ NKT cells at higher frequencies, and CD8+ NKT cells at lower frequencies. However, these cells were highly activated and expression CD161. The NKT cells had a higher expression of CCR5 and concomitantly expression of CCR5+CD69+CXCR6 suggesting a compensation of the remaining population of NKT cells for rapid effector action.
Leong, Josiah K.; Pestilli, Franco; Wu, Charlene C.; Samanez-Larkin, Gregory R.; Knutson, Brian
2016-01-01
SUMMARY Individuals sometimes show inconsistent risk preferences, including excessive attraction to gambles featuring small chances of winning large amounts (called “positively skewed” gambles). While functional neuroimaging research indicates that nucleus accumbens (NAcc) and anterior insula (AIns) activity inversely predict risky choice, structural connections between these regions have not been described in humans. By combining diffusion-weighted MRI with tractography, we identified the anatomical trajectory of white-matter tracts projecting from the AIns to the NAcc and statistically validated these tracts using Linear Fascicle Evaluation (LiFE) and virtual lesions. Coherence of the right AIns-NAcc tract correlated with reduced preferences for positively skewed gambles. Further, diminished NAcc activity during gamble presentation mediated the association between tract structure and choice. These results identify an unreported tract connecting the AIns to the NAcc in humans and support the notion that structural connections can alter behavior by influencing brain activity as individuals weigh uncertain gains against uncertain losses. PMID:26748088
NASA Astrophysics Data System (ADS)
Ohlberger, Mario; Smetana, Kathrin
2016-09-01
In this article we introduce a procedure, which allows to recover the potentially very good approximation properties of tensor-based model reduction procedures for the solution of partial differential equations in the presence of interfaces or strong gradients in the solution which are skewed with respect to the coordinate axes. The two key ideas are the location of the interface either by solving a lower-dimensional partial differential equation or by using data functions and the subsequent removal of the interface of the solution by choosing the determined interface as the lifting function of the Dirichlet boundary conditions. We demonstrate in numerical experiments for linear elliptic equations and the reduced basis-hierarchical model reduction approach that the proposed procedure locates the interface well and yields a significantly improved convergence behavior even in the case when we only consider an approximation of the interface.
Skew scattering dominated anomalous Hall effect in Co x (MgO)100‑x granular thin films
NASA Astrophysics Data System (ADS)
Zhang, Qiang; Wen, Yan; Zhao, Yuelei; Li, Peng; He, Xin; Zhang, Junli; He, Yao; Peng, Yong; Yu, Ronghai; Zhang, Xixiang
2017-10-01
We investigated the mechanism(s) of the anomalous Hall effect (AHE) in magnetic granular materials by fabricating 100 nm-thick thin films of Co x (MgO)100‑x with a Co volume fraction of 34 ⩽ x ⩽ 100 using co-sputtering at room temperature. We measured the temperature dependence of longitudinal resistivity ({{ρ }xx} ) and anomalous Hall resistivity ({{ρ }AHE} ) from 5 K to 300 K in all samples. We found that when x decreases from 100 to 34, the values of {{ρ }xx} and {{ρ }AHE} respectively increased by about four and three orders in magnitude. By linearly fitting the data, obtained at 5 K, of anomalous Hall coefficient ({{R}s} ) and of {{ρ }xx} to log({{R}s})∼ γ log({{ρ }xx}) , we found that our results perfectly fell on a straight line with a slope of γ = 0.97 ± 0.02. This fitting value of γ in {{R}s}\\propto ρ xxγ ~ clearly suggests that skew scattering dominated the AHE in this granular system. To explore the effect of the scattering on the AHE, we performed the same measurements on annealed samples. We found that although both {{ρ }xx} and {{ρ }AHE} significantly reduced after annealing, the correlation between them was almost the same, which was confirmed by the fitted value, γ = 0.99 ± 0.03. These data strongly suggest that the AHE originates from the skew scattering in Co–MgO granular thin films no matter how strong the scattering of electrons by the interfaces and defects is. This observation may be of importance to the development of spintronic devices based on MgO.
Ryder, Thomas B.; Parker, Patricia G.; Blake, John G.; Loiselle, Bette A.
2009-01-01
Variance in reproductive success among individuals is a defining characteristic of many social vertebrates. Yet, our understanding of which male attributes contribute to reproductive success is still fragmentary in most cases. Male–male reproductive coalitions, where males jointly display to attract females, are of particular interest to evolutionary biologists because one male appears to forego reproduction to assist the social partner. By examining the relationship between social behaviour and reproductive success, we can elucidate the proximate function of coalitions in the context of mate choice. Here, we use data from a 4-year study of wire-tailed manakins (Pipra filicauda) to provide molecular estimates of reproductive skew and to test the hypothesis that male–male social interactions, in the context of coordinated displays, positively influence a male's reproductive success. More specifically, we quantify male–male social interactions using network metrics and predict that greater connectivity will result in higher relative reproductive success. Our data show that four out of six leks studied had significant reproductive skew, with success apportioned to very few individuals in each lek. Metrics of male social affiliations derived from our network analysis, especially male connectivity, measured as the number of males with whom the focal male has extended interactions, were strong predictors of the number of offspring sired. Thus, network connectivity is associated with male fitness in wire-tailed manakins. This pattern may be the result of shared cues used by both sexes to assess male quality, or the result of strict female choice for coordinated display behaviour. PMID:19324732
NASA Astrophysics Data System (ADS)
Guillet, T.; Teyssier, R.; Colombi, S.
2010-06-01
We study the dissipative effects of baryon physics on cosmic statistics at small scales using a cosmological simulation of a (50Mpch-1)3 volume of universe. The MareNostrum simulation was performed using the adaptive mesh refinement (AMR) code RAMSES, and includes most of the physical ingredients which are part of the current theory of galaxy formation, such as metal-dependent cooling and UV heating, subgrid modelling of the interstellar medium, star formation and supernova feedback. We reran the same initial conditions for a dark matter only universe, as a reference point for baryon-free cosmic statistics. In this paper, we present the measured small-scale amplification of σ2 and S3 due to baryonic physics and their interpretation in the framework of the halo model. As shown in recent studies, the effect of baryons on the matter power spectrum can be accounted for at scales k <~ 10hMpc-1 by modifying the halo concentration parameter. We propose to extend this result by using a composite halo profile, which is a linear combination of a Navarro, Frenk and White profile for the dark matter component and an exponential disc profile mimicking the baryonic component at the heart of the halo. This halo profile form is physically motivated and depends on two parameters, the mass fraction f d of baryons in the disc and the ratio λd of the disc's characteristic scale to the halo's virial radius. We find this composite profile to reproduce both the small-scale variance and skewness boosts measured in the simulation up to k ~ 102hMpc-1 for physically meaningful values of the parameters f d and λd. Although simulations like the one presented here usually suffer from various problems when compared to observations, our modified halo model could be used as a fitting model to improve the determination of cosmological parameters from weak lensing convergence spectra and skewness measurements.
Ghaffari, A; Homaeinezhad, M R; Khazraee, M; Daevaeiha, M M
2010-04-01
In this study, a simple mathematical-statistical based metric called Multiple Higher Order Moments (MHOM) is introduced enabling the electrocardiogram (ECG) detection-delineation algorithm to yield acceptable results in the cases of ambulatory holter ECG including strong noise, motion artifacts, and severe arrhythmia(s). In the MHOM measure, important geometric characteristics such as maximum value to minimum value ratio, area, extent of smoothness or being impulsive and distribution skewness degree (asymmetry), occult. In the proposed method, first three leads of high resolution 24-h holter data are extracted and preprocessed using Discrete Wavelet Transform (DWT). Next, a sample to sample sliding window is applied to preprocessed sequence and in each slid, mean value, variance, skewness, and kurtosis of the excerpted segment are superimposed called MHOM. The MHOM metric is then used as decision statistic to detect and delineate ECG events. To show advantages of the presented method, it is applied to MIT-BIH Arrhythmia Database, QT Database, and T-Wave Alternans Database and as a result, the average values of sensitivity and positive predictivity Se = 99.95% and P+ = 99.94% are obtained for the detection of QRS complexes, with the average maximum delineation error of 6.1, 4.1, and 6.5 ms for P-wave, QRS complex, and T-wave, respectively showing marginal improvement of detection-delineation performance. In the next step, the proposed method is applied to DAY hospital high resolution holter data (more than 1,500,000 beats including Bundle Branch Blocks--BBB, Premature Ventricular Complex--PVC, and Premature Atrial Complex-PAC) and average values of Se = 99.97% and P+ = 99.95% are obtained for QRS detection. In summary, marginal performance improvement of ECG events detection-delineation process, reliable robustness against strong noise, artifacts, and probable severe arrhythmia(s) of high resolution holter data can be mentioned as important merits and capabilities
Alvarez-Mora, Maria Isabel; Rodriguez-Revenga, Laia; Feliu, Aina; Badenas, Celia; Madrigal, Irene; Milà, Montserrat
2016-01-01
Fragile-X-associated tremor/ataxia syndrome (FXTAS) is a late-onset multisystem neurological disorder characterized by intention tremor and cerebellar ataxia. We hypothesized that in FMR1 premutation females with FXTAS, a normal X chromosome might more frequently be inactivated; therefore, the aim of this study was to determine the relationship between skewed X chromosome inactivation (XCI) and FXTAS. We studied the XCI patterns of cases of FMR1 premutation in 10 women with FXTAS and 21 without FXTAS. The distribution of XCI patterns in the FXTAS and no-FXTAS groups showed differences regarding the allele presenting severe skewed XCI. In the FXTAS group, all cases preferentially inactivated the non-expanded X chromosome, whereas in the no-FXTAS group, all inactivated the expanded X chromosome. Nevertheless, no significant differences were found on comparing XCI frequencies among FMR1 premutation carriers with and without FXTAS. As expected, we found statistically significant differences in the skewed XCI on comparing FMR1 premutation women and controls. Although the reduced sample size and blood XCI patterns are two limitations of this study, our results suggest that the skewed XCI of the normal FMR1 allele may be a risk factor for the development of FXTAS. Furthermore, our findings also support the protective effect of the expression of a normal FMR1 allele. © 2015 S. Karger AG, Basel.
McFadden, J P; Thyssen, J P; Basketter, D A; Puangpet, P; Kimber, I
2015-03-01
During the last 50 years there has been a significant increase in Western societies of atopic disease and associated allergy. The balance between functional subpopulations of T helper cells (Th) determines the quality of the immune response provoked by antigen. One such subpopulation - Th2 cells - is associated with the production of IgE antibody and atopic allergy, whereas, Th1 cells antagonize IgE responses and the development of allergic disease. In seeking to provide a mechanistic basis for this increased prevalence of allergic disease, one proposal has been the 'hygiene hypothesis', which argues that in Westernized societies reduced exposure during early childhood to pathogenic microorganisms favours the development of atopic allergy. Pregnancy is normally associated with Th2 skewing, which persists for some months in the neonate before Th1/Th2 realignment occurs. In this review, we consider the immunophysiology of Th2 immune skewing during pregnancy. In particular, we explore the possibility that altered and increased patterns of exposure to certain chemicals have served to accentuate this normal Th2 skewing and therefore further promote the persistence of a Th2 bias in neonates. Furthermore, we propose that the more marked Th2 skewing observed in first pregnancy may, at least in part, explain the higher prevalence of atopic disease and allergy in the first born.
Heine-Suñer, D; Torres-Juan, L; Morlà, M; Busquets, X; Barceló, F; Picó, G; Bonilla, L; Govea, N; Bernués, M; Rosell, J
2003-10-01
Fragile X syndrome is the most common form of inherited mental retardation. It is caused by the increase in length of a stretch of CGG triplet repeats within the FMR1 gene. A full mutation (> 200 repeats) leads to methylation of the CpG island and silencing of the FMR1 gene. We present here two sisters that are compound heterozygotes for a full mutation and a 53 repeat intermediate allele, one of them showing mental retardation and clinical features of an affected male (speech delay, hyperactivity, large ears, prominent jaw, gaze aversion), while the other is borderline normal (mild delay). Southern blot and FMRP expression analysis showed that the sister with mental retardation had the normal FMR1 gene totally methylated and no detectable protein, while her sister had 70% of her cells with the normal FMR1 gene unmethylated and normal FMRP levels. We found that the observed phenotypic differences between both sisters who are cytogenetically normal, are caused by extreme skewed X-chromosome inactivation. Analysis of the extended family showed that most of the other female family members that carry a pre-mutation or a full mutation showed some degree of skewing in their X-chromosome inactivation. The presence of several family members with skewed X inactivation and the direction and degree of skewing is inconsistent with a mere selection during development, and suggests a genetic origin for this phenomenon.
NASA Astrophysics Data System (ADS)
Meng, L.; Stock, J.
2008-12-01
Plate tectonics study based on total field marine magnetic anomalies measured by proton precession magnetometers has always been challenging in the equatorial area due to the relatively smaller amplitude of the anomaly and larger diurnal variations of the magnetic field resulting from the varying current of the ionosphere including the effect of the electrojet. Previous investigation of the magnetic anomalies in the equatorial Pacific has been used to study the paleomagnetic pole of the Pacific plate. However, the skewness of the magnetic data was low in coherence and accuracy, and the anomaly pattern is unable to be determined between the Clipperton fracture zone and the modern equator. Here we corrected a set of shipboard magnetic profiles using Comprehensive Model : Phase 4 ( CM4 ) which is designed to estimate the Near- Earth magnetic field by sources in the Earth's core, ionosphere and magnetosphere. We use the CM4 model to remove the diurnal variation of the ionosphere magnetic field which reduces the long-wavelength component of noise in magnetic data. In this study we deskewed more than 40 ship magnetic data sets in the central Pacific, including the Nathaniel B Palmer cruise NBP0207, by comparing the data profile with zero- skewness synthetics. The magnetic profiles are then mapped on a satellite gravity map along with their skewness values. Theoretical models show that for a ridge trending 170 degrees from north, a sudden ~90 degree change in skewness occurs when the magnetized crust moves across the paleo-equator. On the map we were able to identify that the skewness generally decreases systematically as the latitude increases. Despite the noisy data, we located positions where the ridge crossed the paleo-equator at the time of creation of the individual magnetic isochrons. The track of the paleo-equator moves southward relative to the Pacific plate during chron 32-25 time. The track of the paleo-equatorial crossing also has implications for constraints
Nakashima, J; Liao, F; Sparks, J A; Tang, Y; Blancaflor, E B
2014-01-01
Before plants can be effectively utilised as a component of enclosed life-support systems for space exploration, it is important to understand the molecular mechanisms by which they develop in microgravity. Using the Biological Research in Canisters (BRIC) hardware on board the second to the last flight of the Space Shuttle Discovery (STS-131 mission), we studied how microgravity impacts root growth in Arabidopsis thaliana. Ground-based studies showed that the actin cytoskeleton negatively regulates root gravity responses on Earth, leading us to hypothesise that actin might also be an important modulator of root growth behaviour in space. We investigated how microgravity impacted root growth of wild type (ecotype Columbia) and a mutant (act2-3) disrupted in a root-expressed vegetative actin isoform (ACTIN2). Roots of etiolated wild-type and act2-3 seedlings grown in space skewed vigorously toward the left, which was unexpected given the reduced directional cue provided by gravity. The left-handed directional root growth in space was more pronounced in act2-3 mutants than wild type. To quantify differences in root orientation of these two genotypes in space, we developed an algorithm where single root images were converted into binary images using computational edge detection methods. Binary images were processed with Fast Fourier Transformation (FFT), and histogram and entropy were used to determine spectral distribution, such that high entropy values corresponded to roots that deviated more strongly from linear orientation whereas low entropy values represented straight roots. We found that act2-3 roots had a statistically stronger skewing/coiling response than wild-type roots, but such differences were not apparent on Earth. Ultrastructural studies revealed that newly developed cell walls of space-grown act2-3 roots were more severely disrupted compared to space-grown wild type, and ground control wild-type and act2-3 roots. Collectively, our results provide
Discovery of the Red-Skewed K-alpha Iron Line in Cyg X-2 with Suzaku
NASA Technical Reports Server (NTRS)
Shaposhnikov, Nikolai; Titarchuk, Lev; Laurent, Philippe
2008-01-01
We report on the Suzaku observation of neutron star low-mass X-ray binary Cygnus X-2 which reveals strong iron K-alpha emission line. The line profile shows a prominent red wing extending down to 4 keV. This discovery increases the number of neutron star sources where red-skewed iron lines were observed and strongly suggests that this phenomenon is common not only in black holes but also in other types of compact objects. We examine the line profile by fitting it with the model which attributes its production to the relativistic effects due to disk reflection of X-ray radiation. We also apply an alternative model where the red wing is a result of down-scattering effect of the first order with respect to electron velocity in the wind outflow. Both models describe adequately the observed line profile. However, the X-ray variability in a state similar to that in the Suzaku observation which we establish by analysing RXTE observation favors the wind origin of the line formation.
Palmieri, Erika M; Menga, Alessio; Martín-Pérez, Rosa; Quinto, Annamaria; Riera-Domingo, Carla; De Tullio, Giacoma; Hooper, Douglas C; Lamers, Wouter H; Ghesquière, Bart; McVicar, Daniel W; Guarini, Attilio; Mazzone, Massimiliano; Castegna, Alessandra
2017-08-15
Glutamine-synthetase (GS), the glutamine-synthesizing enzyme from glutamate, controls important events, including the release of inflammatory mediators, mammalian target of rapamycin (mTOR) activation, and autophagy. However, its role in macrophages remains elusive. We report that pharmacologic inhibition of GS skews M2-polarized macrophages toward the M1-like phenotype, characterized by reduced intracellular glutamine and increased succinate with enhanced glucose flux through glycolysis, which could be partly related to HIF1α activation. As a result of these metabolic changes and HIF1α accumulation, GS-inhibited macrophages display an increased capacity to induce T cell recruitment, reduced T cell suppressive potential, and an impaired ability to foster endothelial cell branching or cancer cell motility. Genetic deletion of macrophagic GS in tumor-bearing mice promotes tumor vessel pruning, vascular normalization, accumulation of cytotoxic T cells, and metastasis inhibition. These data identify GS activity as mediator of the proangiogenic, immunosuppressive, and pro-metastatic function of M2-like macrophages and highlight the possibility of targeting this enzyme in the treatment of cancer metastasis. Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.
Guszejnov, Dávid; Lazányi, Nóra; Bencze, Attila; Zoletnik, Sándor
2013-11-15
This paper is aimed to contribute to the scientific discussions that have been triggered by the experimental observation of a quadratic relation between the kurtosis and skewness of turbulent fluctuations present in fusion plasmas and other nonlinear physical systems. In this paper, we offer a general statistical model which attributes the observed K=aS{sup 2}+b relation to the varying intermittency of the experimental signals. The model is a two random variable model constructed to catch the essential intermittent feature of the real signal. One of the variables is the amplitude of the underlying intermittent event (e.g., turbulent structure) while the other is connected to the intermittency level of the system. This simple model can attribute physical meaning to the a and b coefficients, as they characterize the spatio-temporal statistics of intermittent events. By constructing a particle-conserving Gaussian model for the underlying coherent structures, the experimentally measured a and b coefficients could be adequately reproduced.
St. John, Lisa S.; de Lima, Marcos; McMannis, John; Rosinski, Steven; McNiece, Ian; Bryan, Susan G.; Kaur, Indreshpal; Martin, Sean; Wieder, Eric D.; Worth, Laura; Cooper, Laurence J. N.; Petropoulos, Demetrios; Molldrem, Jeffrey J.; Champlin, Richard E.; Shpall, Elizabeth J.
2007-01-01
Advances in immune assessment, including the development of T-cell receptor excision circle (TREC) assays of thymopoiesis, cytokine-flow cytometry assays of T-cell function, and higher-order phenotyping of T-cell maturation subsets have improved our understanding of T-cell homeostasis. Limited data exist using these methods to characterize immune recovery in adult cord blood (CB) transplant recipients, in whom infection is a leading cause of mortality. We now report the results of a single-center prospective study of T-cell immune recovery after cord blood transplantation (CBT) in a predominantly adult population. Our primary findings include the following: (1) Prolonged T lymphopenia and compensatory expansion of B and natural killer (NK) cells was evident; (2) CB transplant recipients had impaired functional recovery, although we did observe posttransplantation de novo T-cell responses to cytomegalovirus (CMV) in a subset of patients; (3) Thymopoietic failure characterized post-CBT immune reconstitution, in marked contrast to results in other transplant recipients; and (4) Thymopoietic failure was associated with late memory T-cell skewing. Our data suggest that efforts to improve outcomes in adult CB transplant recipients should be aimed at optimizing T-cell immune recovery. Strategies that improve the engraftment of lymphoid precursors, protect the thymus during pretransplant conditioning, and/or augment the recovery of thymopoiesis may improve outcomes after CBT. PMID:17671230
Komanduri, Krishna V; St John, Lisa S; de Lima, Marcos; McMannis, John; Rosinski, Steven; McNiece, Ian; Bryan, Susan G; Kaur, Indreshpal; Martin, Sean; Wieder, Eric D; Worth, Laura; Cooper, Laurence J N; Petropoulos, Demetrios; Molldrem, Jeffrey J; Champlin, Richard E; Shpall, Elizabeth J
2007-12-15
Advances in immune assessment, including the development of T-cell receptor excision circle (TREC) assays of thymopoiesis, cytokine-flow cytometry assays of T-cell function, and higher-order phenotyping of T-cell maturation subsets have improved our understanding of T-cell homeostasis. Limited data exist using these methods to characterize immune recovery in adult cord blood (CB) transplant recipients, in whom infection is a leading cause of mortality. We now report the results of a single-center prospective study of T-cell immune recovery after cord blood transplantation (CBT) in a predominantly adult population. Our primary findings include the following: (1) Prolonged T lymphopenia and compensatory expansion of B and natural killer (NK) cells was evident; (2) CB transplant recipients had impaired functional recovery, although we did observe posttransplantation de novo T-cell responses to cytomegalovirus (CMV) in a subset of patients; (3) Thymopoietic failure characterized post-CBT immune reconstitution, in marked contrast to results in other transplant recipients; and (4) Thymopoietic failure was associated with late memory T-cell skewing. Our data suggest that efforts to improve outcomes in adult CB transplant recipients should be aimed at optimizing T-cell immune recovery. Strategies that improve the engraftment of lymphoid precursors, protect the thymus during pretransplant conditioning, and/or augment the recovery of thymopoiesis may improve outcomes after CBT.
De novo interstitial direct duplication of Xq21.1q25 associated with skewed X-inactivation pattern.
Tachdjian, G; Aboura, A; Benkhalifa, M; Creveaux, I; Foix-Hélias, L; Gadisseux, J F; Boespflug-Tanguy, O; Mohammed, M; Labrune, P
2004-12-15
Genotype-phenotype correlation in women with an abnormal phenotype associated with a duplication of the long arm of the X chromosome remains unclear. We report on prenatal diagnosis and follow-up of a girl with an Xq duplication and dysmorphic features. The abnormal phenotype included growth retardation, hypotonia, and nystagmus. In order to improve the resolution of the cytogenetic analysis, we used both conventional and array-based comparative genomic hybridization to perform a global molecular cytogenetic analysis of the genome. These molecular cytogenetic analyses showed a direct duplication Xq21.1 --> q25 without other chromosomal abnormalities. This duplication was originating from the paternal X chromosome. Moreover, a skewed X-inactivation pattern was observed leading to a partial functional disomy of the chromosomal region Xq21.1q25. This report and review of the literature suggest that functional disomy for chromosome X could explain the abnormal phenotype. In prenatal diagnosis, this can have implication for patient management and genetic counseling.
Dawar, Swati; Shahrin, Nur Hezrin; Sladojevic, Nikolina; D'Andrea, Richard J; Dorstyn, Loretta; Hiwase, Devendra K; Kumar, Sharad
2016-01-01
The apoptotic cysteine protease caspase-2 has been shown to suppress tumourigenesis in mice and its reduced expression correlates with poor prognosis in some human malignancies. Caspase-2-deficient mice develop normally but show ageing-related traits and, when challenged by oncogenic stimuli or certain stress, show enhanced tumour development, often accompanied by extensive aneuploidy. As stem cells are susceptible to acquiring age-related functional defects because of their self-renewal and proliferative capacity, we examined whether loss of caspase-2 promotes such defects with age. Using young and aged Casp2−/− mice, we demonstrate that deficiency of caspase-2 results in enhanced aneuploidy and DNA damage in bone marrow (BM) cells with ageing. Furthermore, we demonstrate for the first time that caspase-2 loss results in significant increase in immunophenotypically defined short-term haematopoietic stem cells (HSCs) and multipotent progenitors fractions in BM with a skewed differentiation towards myeloid progenitors with ageing. Caspase-2 deficiency leads to enhanced granulocyte macrophage and erythroid progenitors in aged mice. Colony-forming assays and long-term culture-initiating assay further recapitulated these results. Our results provide the first evidence of caspase-2 in regulating HSC and progenitor differentiation, as well as aneuploidy, in vivo. PMID:27906175
Hashemi, Hassan; Beiranvand, Asghar; Khabazkhoob, Mehdi; Fotouhi, Akbar
2014-01-01
Purpose: The purpose of this study is to determine the distribution of corneal topography patterns in Tehran. Materials and Methods: In this population-based study, a total of 442 individuals were randomly selected by cluster sampling for complete ophthalmologic examination. A total of 404 (788 eyes) met the inclusion criteria and were enrolled in this study. Orbscan II (Bausch and Lomb Surgical, Salt Lake City, USA) was used to determine the anterior segment indices and axial power maps for each eye. Results: On the basis of the axial power maps, the symmetric bowtie (SB) (29.0%) and asymmetric bowtie with inferior steepening (16.7%) patterns were the most prevalent and the irregular (3.3%) and superior steepening (1.5%) patterns the least prevalent. Asymmetric bowtie pattern with a skewed radial axis (AB-SRAX) was seen in 7.6% of eyes. These cases had both thinner and steeper corneas compared with round and SB ones (P < 0.014 and P < 0.006). Maximum anterior elevation in 5 mm zone, of AB-SRAX corneas were higher than other patterns (P < 0.01) except for superior steepened and inferior steepened ones. Conclusions: The distribution of corneal topographic patterns in Iranians seems like other Asian population on the whole. The 7.6% prevalence of AB-SRAX patterns may be a warning on keratoconus prevalence in our population. This is in line with recent regional reports. PMID:24669150
NASA Technical Reports Server (NTRS)
Johnson, B. V.; Wagner, J. H.; Steuber, G. D.
1993-01-01
An experimental program was conducted to investigate heat transfer and pressure loss characteristics of rotating multipass passages, for configurations and dimensions typical of modem turbine blades. This experimental program is one part of the NASA Hot Section Technology (HOST) Initiative, which has as its overall objective the development and verification of improved analysis methods that will form the basis for a design system that will produce turbine components with improved durability. The objective of this program was the generation of a data base of heat transfer and pressure loss data required to develop heat transfer correlations and to assess computational fluid dynamic techniques for rotating coolant passages. The experimental work was broken down into two phases. Phase 1 consists of experiments conducted in a smooth wall large scale heat transfer model. A detailed discussion of these results was presented in volume 1 of a NASA Report. In Phase 2 the large scale model was modified to investigate the effects of skewed and normal passage turbulators. The results of Phase 2 along with comparison to Phase 1 is the subject of this Volume 2 NASA Report.
Huang, Yangxin; Chen, Ren; Dagne, Getachew
2011-01-01
In recent years, various mixed-effects models have been suggested for estimating viral decay rates in HIV dynamic models for complex longitudinal data. Among those models are linear mixed-effects (LME), nonlinear mixed-effects (NLME), and semiparametric nonlinear mixed-effects (SNLME) models. However, a critical question is whether these models produce coherent estimates of viral decay rates, and if not, which model is appropriate and should be used in practice. In addition, one often assumes that a model random error is normally distributed, but the normality assumption may be unrealistic, particularly if the data exhibit skewness. Moreover, some covariates such as CD4 cell count may be often measured with substantial errors. This paper addresses these issues simultaneously by jointly modeling the response variable with skewness and a covariate process with measurement errors using a Bayesian approach to investigate how estimated parameters are changed or different under these three models. A real data set from an AIDS clinical trial study was used to illustrate the proposed models and methods. It was found that there was a significant incongruity in the estimated decay rates in viral loads based on the three mixed-effects models, suggesting that the decay rates estimated by using Bayesian LME or NLME joint models should be interpreted differently from those estimated by using Bayesian SNLME joint models. The findings also suggest that the Bayesian SNLME joint model is preferred to other models because an arbitrary data truncation is not necessary; and it is also shown that the models with a skew-normal distribution and/or measurement errors in covariate may achieve reliable results when the data exhibit skewness. PMID:22848189
Rea, A.H.; Tortorelli, R.L.
1997-01-01
This digital report contains two digital-map grids of data that were used to develop peak-flow regression equations in Tortorelli, 1997, 'Techniques for estimating peak-streamflow frequency for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 97-4202. One data set is a grid of mean annual precipitation, in inches, based on the period 1961-90, for Oklahoma. The data set was derived from the PRISM (Parameter-elevation Regressions on Independent Slopes Model) mean annual precipitation grid for the United States, developed by Daly, Neilson, and Phillips (1994, 'A statistical-topographic model for mapping climatological precipitation over mountainous terrain:' Journal of Applied Meteorology, v. 33, no. 2, p. 140-158). The second data set is a grid of generalized skew coefficients of logarithms of annual maximum streamflow for Oklahoma streams less than or equal to 2,510 square miles in drainage area. This grid of skew coefficients is taken from figure 11 of Tortorelli and Bergman, 1985, 'Techniques for estimating flood peak discharges for unregulated streams and streams regulated by small floodwater retarding structures in Oklahoma,' U.S. Geological Survey Water-Resources Investigations Report 84-4358. To save disk space, the skew coefficient values have been multiplied by 100 and rounded to integers with two significant digits. The data sets are provided in an ASCII grid format.
Sharma, Amit; Kaut, Oliver; Pavlova, Anna; Fröhlich, Holger; Ahmad, Ashar; Schmitt, Ina; El-Maarri, Osman; Oldenburg, Johannes; Wüllner, Ullrich
2017-09-01
Parkinson's disease (PD) is a degenerative disorder of the nervous system and the cause of the majority of sporadic cases is unknown. Females are relatively protected from PD as compared with males and linkage studies suggested a PD susceptibility locus on the X chromosome. To determine a putative association of skewed X-chromosome inactivation (XCI) and PD, we examined XCI patterns using a human androgen receptor gene-based assay (HUMARA) and did not identify any association of skewed or random X inactivation with clinical heterogeneity among female PD patients. In addition, we sought to determine methylation-specific changes at the X-inactive specific transcript (XIST) locus, which is known to be responsible for initiating X inactivation. We observed a trend towards hypomethylation in the gene body region of the XIST locus in PD females which did not reach significance. Furthermore, we extended our analysis of DNA methylation across the entire X-chromosome which revealed no methylation-specific differences between PD females and healthy controls. Thus, we propose that skewed XCI and methylation levels on the entire X chromosome did not reveal changes which could account for the decreased PD susceptibility in females or suitable to use as a biomarker. Copyright © 2017 Elsevier Inc. All rights reserved.
Woodward, K; Kirtland, K; Dlouhy, S; Raskind, W; Bird, T; Malcolm, S; Abeliovich, D
2000-06-01
Pelizaeus-Merzbacher disease (PMD) is an X-linked recessive disease caused by coding sequence mutations in the PLP gene, sub-microscopic duplications of variable sizes including the PLP gene or very rarely deletions of the PLP gene. We analysed the X inactivation pattern in blood of PMD female carriers with duplications and with point mutations. In the majority of duplication carriers (7/11), the X chromosome bearing the duplication was preferentially inactivated, whereas a random pattern of X inactivation was detected in point mutation carriers (3/3), a deletion carrier (1/1), affected females (4/4) who did not have a recognised mutation and normal control females. However 2/5 non-carrier female relatives of patients with a duplication, had skewed X inactivation. The skewed pattern of inactivation observed in most duplication carriers and not in mutation carriers suggests a) that there is selection against those cells in which the duplicated X chromosome is active and b) other expressed sequences within the duplicated region rather than mutant PLP may be responsible. Since the skewed X inactivation did not segregate with the disease in two families and the pattern of X inactivation was variable among the duplication carriers, the pattern X inactivation is an unsuitable diagnostic tool for female carriers of PMD.
NASA Astrophysics Data System (ADS)
Allentoft, Morten E.; Bunce, Michael; Scofield, R. Paul; Hale, Marie L.; Holdaway, Richard N.
2010-03-01
Ancient DNA was isolated from the bones of 267 individuals of the extinct New Zealand moa (Aves: Dinornithiformes) from two late Holocene deposits [Pyramid Valley (PV) and Bell Hill Vineyard (BHV)] located 5.7 km apart in North Canterbury, South Island. The two sites' combined fossil record cover the last 3000 years of pre-human New Zealand and mitochondrial DNA confirmed that four species ( Dinornis robustus, Euryapteryx curtus, Emeus crassus, and Pachyornis elephantopus) were sympatric in the region. However, the relative species compositions in the two deposits differed significantly with D. robustus and E. crassus being most abundant at PV while E. curtus outnumbered the other three moa taxa combined at BHV. A subsample of 227 individuals had sufficient nuclear DNA preservation to warrant the use of molecular sexing techniques, and the analyses uncovered a remarkable excess of females in both deposits with an overall male to female ratio of 1:5.1. Among juveniles of E. curtus, the only species which was represented by a substantial fraction of juveniles, the sex ratio was not skewed (10 ♂, 10 ♀), suggesting that the observed imbalance arose as a result of differential mortality during maturation. Surprisingly, sex ratios proved significantly different between sites with a 1:2.2 ratio at BHV ( n = 90) and 1:14.2 at PV ( n = 137). Given the mobility of large ratites, and the proximity of the two fossil assemblages in space and time, these differences in taxonomic and gender composition indicate that moa biology and the local environment have affected the fossil representation dramatically and several possible explanations are offered. Apart from adding to our understanding of moa biology, these discoveries reinforce the need for caution when basing interpretation of the fossil record on material from a single site.
NASA Astrophysics Data System (ADS)
Disrattakit, P.; Chanphana, R.; Chatraphorn, P.
2017-10-01
Time varying skewness (S) and kurtosis (Q) of height distribution of (2 + 1) -dimensional larger curvature (LC) model with and without noise reduction techniques (NRTs) are investigated in both transient and steady state regimes. In this work, effects of the multiple hit NRT (m > 1 NRT) and the long surface diffusion length NRT (ℓ > 1 NRT) on the surface morphologies and characteristics of S and Q are studied. In the early growth time, plots of S and Q versus time of the m > 1 morphologies show pronounced oscillation indicating the layer by layer growth. Our results show that S = 0 and Q < 0 at every half layer while S = 0 and Q > 0 at every complete layer. The results are confirmed by the same plots of the results from the Das Sarma-Tamborenea (DT) model. The ℓ > 1 LC model, on the other hand, has no evidence of the layer by layer growth mode due to the rapidly damped oscillation of S and Q. In the steady state, the m > 1 and ℓ > 1 NRTs affect weakly on the values of S and Q and the mounded morphologies of the film. This lead to the evidence of universality of S and Q in the steady state of the LC models with various m and ℓ. The finite size effect on the values of S and Q is found to be very weak in the LC model. By extrapolating to L → ∞, we obtain SL→∞ ≈ 0.05 and QL→∞ ≈ - 0.62 which are in agreement with the NRTs results.
ERIC Educational Resources Information Center
Bausell, R. Barker
1995-01-01
This editorial provides an informal review of "The Bell Curve" (Herrnstein and Murray, 1994). The book, packaged as scientific writing, is an attack on affirmative action and on government attempts to foster egalitarianism. It is a political treatise that assumes that racial differences in intelligence are valid and genetic. (SLD)
Takimoto, Hiroaki; Kato, Hanano; Kaneko, Masahiro; Kumazawa, Yoshio
2008-01-01
We showed in a previous study that hot-water extracts of Agaricus blazei (Agaricus extracts) had anti-tumor activity to Meth A fibrosarcoma, but it remains unclear whether the Agaricus extracts ameliorate the skewed balance of type-1 T helper (Th1) and type-2 T helper (Th2) cells. We examined whether Agaricus extracts effect the skewed Th1/Th2 balance in tumor-bearing and asthma-induced mice. When Meth A-bearing mice were given orally either Agaricus extracts or water once a day starting 5 days after tumor implantation, spleen T cells, prepared from tumor-bearing mice treated with Agaricus extracts, in response to anti-CD3 monoclonal antibody produced significantly higher levels of interferon gamma (IFN-gamma) than that of controls. The mRNA expression of IFN-gamma-inducing protein 10 and the frequency of CD69(+) or CD49d(+) cells, among activated T cells infiltrated into tumors, significantly increased in Agaricus-treated mice, compared with those of tumor-controls. In asthma-induced mice, treatment with the Agaricus extracts caused significant downregulation of OVA-specific antibody responses of IgG1 and IgE but not of IgG2a, and significantly decreased total cell numbers, levels of interleukin 5, and eosinophil numbers in bronchial alveolar lavage fluids. IFN-gamma production by anti-CD3-stimulated spleen cells, obtained from Agaricus-treated mice, significantly increased. Our results strongly suggest that oral administration of Agaricus extracts ameliorates the Th1/Th2 balance from the Th2-skewed conditions.
Wang, Jian; Yu, Robert; Shete, Sanjay
2014-09-01
X-chromosome inactivation (XCI) is the process in which one of the two copies of the X-chromosome in females is randomly inactivated to achieve the dosage compensation of X-linked genes between males and females. That is, 50% of the cells have one allele inactive and the other 50% of the cells have the other allele inactive. However, studies have shown that skewed or nonrandom XCI is a biological plausibility wherein more than 75% of cells have the same allele inactive. Also, some of the X-chromosome genes escape XCI, i.e., both alleles are active in all cells. Current statistical tests for X-chromosome association studies can either account for random XCI (e.g., Clayton's approach) or escape from XCI (e.g., PLINK software). Because the true XCI process is unknown and differs across different regions on the X-chromosome, we proposed a unified approach of maximizing likelihood ratio over all biological possibilities: random XCI, skewed XCI, and escape from XCI. A permutation-based procedure was developed to assess the significance of the approach. We conducted simulation studies to compare the performance of the proposed approach with Clayton's approach and PLINK regression. The results showed that the proposed approach has higher powers in the scenarios where XCI is skewed while losing some power in scenarios where XCI is random or XCI is escaped, with well-controlled type I errors. We also applied the approach to the X-chromosomal genetic association study of head and neck cancer.
Ulrich, Rolf; Miller, Jeff
2015-12-01
Simonsohn, Nelson, and Simmons (2014) have suggested a novel test to detect p-hacking in research, that is, when researchers report excessive rates of "significant effects" that are truly false positives. Although this test is very useful for identifying true effects in some cases, it fails to identify false positives in several situations when researchers conduct multiple statistical tests (e.g., reporting the most significant result). In these cases, p-curves are right-skewed, thereby mimicking the existence of real effects even if no effect is actually present.
NASA Astrophysics Data System (ADS)
Ginzburg, Irina
2017-01-01
The effect of the heterogeneity in the soil structure or the nonuniformity of the velocity field on the modeled resident time distribution (RTD) and breakthrough curves is quantified by their moments. While the first moment provides the effective velocity, the second moment is related to the longitudinal dispersion coefficient (kT) in the developed Taylor regime; the third and fourth moments are characterized by their normalized values skewness (Sk) and kurtosis (Ku), respectively. The purpose of this investigation is to examine the role of the truncation corrections of the numerical scheme in kT, Sk, and Ku because of their interference with the second moment, in the form of the numerical dispersion, and in the higher-order moments, by their definition. Our symbolic procedure is based on the recently proposed extended method of moments (EMM). Originally, the EMM restores any-order physical moments of the RTD or averaged distributions assuming that the solute concentration obeys the advection-diffusion equation in multidimensional steady-state velocity field, in streamwise-periodic heterogeneous structure. In our work, the EMM is generalized to the fourth-order-accurate apparent mass-conservation equation in two- and three-dimensional duct flows. The method looks for the solution of the transport equation as the product of a long harmonic wave and a spatially periodic oscillating component; the moments of the given numerical scheme are derived from a chain of the steady-state fourth-order equations at a single cell. This mathematical technique is exemplified for the truncation terms of the two-relaxation-time lattice Boltzmann scheme, using plug and parabolic flow in straight channel and cylindrical capillary with the d2Q9 and d3Q15 discrete velocity sets as simple but illustrative examples. The derived symbolic dependencies can be readily extended for advection by another, Newtonian or non-Newtonian, flow profile in any-shape open-tabular conduits. It is
Ginzburg, Irina
2017-01-01
The effect of the heterogeneity in the soil structure or the nonuniformity of the velocity field on the modeled resident time distribution (RTD) and breakthrough curves is quantified by their moments. While the first moment provides the effective velocity, the second moment is related to the longitudinal dispersion coefficient (k_{T}) in the developed Taylor regime; the third and fourth moments are characterized by their normalized values skewness (Sk) and kurtosis (Ku), respectively. The purpose of this investigation is to examine the role of the truncation corrections of the numerical scheme in k_{T}, Sk, and Ku because of their interference with the second moment, in the form of the numerical dispersion, and in the higher-order moments, by their definition. Our symbolic procedure is based on the recently proposed extended method of moments (EMM). Originally, the EMM restores any-order physical moments of the RTD or averaged distributions assuming that the solute concentration obeys the advection-diffusion equation in multidimensional steady-state velocity field, in streamwise-periodic heterogeneous structure. In our work, the EMM is generalized to the fourth-order-accurate apparent mass-conservation equation in two- and three-dimensional duct flows. The method looks for the solution of the transport equation as the product of a long harmonic wave and a spatially periodic oscillating component; the moments of the given numerical scheme are derived from a chain of the steady-state fourth-order equations at a single cell. This mathematical technique is exemplified for the truncation terms of the two-relaxation-time lattice Boltzmann scheme, using plug and parabolic flow in straight channel and cylindrical capillary with the d2Q9 and d3Q15 discrete velocity sets as simple but illustrative examples. The derived symbolic dependencies can be readily extended for advection by another, Newtonian or non-Newtonian, flow profile in any-shape open-tabular conduits. It is
NASA Technical Reports Server (NTRS)
Wilson, Michael J.; Sherwin, Blake D.; Hill, J. Collin; Addison, Graeme; Battaglia, Nick; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Duenner, Rolando; Fowler, Joseph W.; Gralla, Megan, B.; Hajian, Amir; Halpern, Mark; Hilton, Matt; Hincks, Adam D.; Hlozek, Renee; Huffenberger, Kevin; Hughes, John P.; Kosowsky, Arthur; Louis, Thibaut; Marriage, Tobias A.; Marsden, Danica; Menanteau, Felipe; Wollack, Ed
2012-01-01
We present a detection of the unnormalized skewness (T(sup )(sup 2)(n(circumflex)) induced by the thermal Sunyaev-Zel'dovich (tSZ) effect in filtered Atacama Cosmology Telescope (ACT) 148 GHz cosmic microwave background temperature maps. Contamination due to infrared and radio sources is minimized by template subtraction of resolved sources and by constructing a mask using outlying values in the 218 GHz (tSZ-null) ACT maps. We measure (T(sup )(sup 3) (n(circumflex)) = -31 plus or minus 6 micro-K(sup 3) (measurement error only) or plus or minus 14 micro-K(sup 3) (including cosmic variance error) in the filtered ACT data, a 5sigma detection. We show that the skewness is a sensitive probe of sigma(sub 8), and use analytic calculations and tSZ simulations to obtain cosmological constraints from this measurement. From this signal alone we infer a value of sigma(sub 8) = 0.78 sup +0.03 sub -0.04 (68% C.L.) sup +0.05 sub -0.16. Our results demonstrate that measurements of nonGaussianity can be a useful method for characterizing the tSZ effect and extracting the underlying cosmological information.
Clark, Jeremy S C; Kaczmarczyk, Mariusz; Mongiało, Zbigniew; Ignaczak, Paweł; Czajkowski, Andrzej A; Klęsk, Przemysław; Ciechanowicz, Andrzej
2013-08-01
Gompertz-related distributions have dominated mortality studies for 187 years. However, nonrelated distributions also fit well to mortality data. These compete with the Gompertz and Gompertz-Makeham data when applied to data with varying extents of truncation, with no consensus as to preference. In contrast, Gaussian-related distributions are rarely applied, despite the fact that Lexis in 1879 suggested that the normal distribution itself fits well to the right of the mode. Study aims were therefore to compare skew-t fits to Human Mortality Database data, with Gompertz-nested distributions, by implementing maximum likelihood estimation functions (mle2, R package bbmle; coding given). Results showed skew-t fits obtained lower Bayesian information criterion values than Gompertz-nested distributions, applied to low-mortality country data, including 1711 and 1810 cohorts. As Gaussian-related distributions have now been found to have almost universal application to error theory, one conclusion could be that a Gaussian-related distribution might replace Gompertz-related distributions as the basis for mortality studies.
Cazzola, M; May, A; Bergamaschi, G; Cerani, P; Rosti, V; Bishop, D F
2000-12-15
X-linked sideroblastic anemia (XLSA) is caused by mutations in the erythroid-specific 5-aminolevulinic acid synthase (ALAS2) gene. An elderly woman who presented with an acquired sideroblastic anemia is studied. Molecular analysis revealed that she was heterozygous for a missense mutation in the ALAS2 gene, but she expressed only the mutated gene in reticulocytes. Her 2 daughters and a granddaughter were heterozygous for this mutation, had normal hemoglobin levels, and expressed the normal ALAS2 gene in reticulocytes. A grandson with a previous diagnosis of thalassemia intermedia was found to be hemizygous for the ALAS2 mutation. Treatment with pyridoxine completely corrected the anemia both in the proband and her grandson. All women who were analyzed in this family showed skewed X-chromosome inactivation in leukocytes, which indicated a hereditary condition associated with unbalanced lyonization. Because the preferentially active X chromosome carried the mutant ALAS2 allele, acquired skewing in the elderly likely worsened the genetic condition and abolished the normal ALAS2 allele expression in the proband. (Blood. 2000;96:4363-4365)
Hassan, Y.A.
1985-02-01
The upwind finite difference scheme used in the COMMIX-1A code to approximate the convective transport term was shown to contribute more artificial diffusivity to the computed temperature field than the total physical diffusivity that could be inferred from experimental observations of the thermal mixing processes. With aim to reduce such numerical error, a new finite difference scheme called the mass-flow-weighted skew-upwind approach was developed, incorporated in COMMIX-1A, and evaluated by comparison with known analytical solutions and experimental data. This report describes the follow-on activities pursued to demonstrate the applicability of the new finite difference scheme to simulations of pressurized thermal shock events. These activities include benchmarking the code against the Creare one-fifth-scale test 51 and simulating mixing in the full-scale cold leg and downcomer of a Babcock and Wilcox plant using both the upwind and the mass-flow-weighted skew-upwind finite difference scehmes. The new scheme is shown to considerably reduce the amount of artifical diffusivity contributed to the computed temperature field by the convective term approximation.
Lewis, Eric M; Singla, Manav; Sergeant, Susan; Koty, Patrick P.; McPhail, Linda C.
2008-01-01
Chronic Granulomatous Disease (CGD) is characterized by defects in the superoxide producing enzyme NADPH oxidase causing phagocytes to improperly clear invading pathogens. Here we report findings of a late presenting 16 year old female with X-linked CGD. The patient presented with community-acquired pneumonia, but symptoms persisted for 2 weeks during triple antimicrobial coverage. Cultures revealed Aspergillus fumigatus which was resolved through aggressive voriconazole treatment. Neutrophil studies revealed NADPH oxidase activity and flavocytochrome b558 levels that were 4–8% of controls and suggested carrier status of the mother. We found a null mutation in the CYBB gene (c.252insAG) predicting an aberrant gp91phox protein (p.Cys85fsX23) in the heterozygous state. Methylation analysis demonstrated extremely skewed X chromosome inactivation favoring the maternally inherited defective gene. In conclusion, a novel mutation in the CYBB gene and an extremely skewed X-inactivation event resulted in the rare expression of the CGD phenotype in a carrier female. PMID:18774749
Lewis, Eric M; Singla, Manav; Sergeant, Susan; Koty, Patrick P; McPhail, Linda C
2008-11-01
Chronic granulomatous disease (CGD) is characterized by defects in the superoxide producing enzyme NADPH oxidase causing phagocytes to improperly clear invading pathogens. Here we report findings of a late presenting 16-year-old female with X-linked CGD. The patient presented with community-acquired pneumonia, but symptoms persisted for 2 weeks during triple antimicrobial coverage. Cultures revealed Aspergillus fumigatus which was resolved through aggressive voriconazole treatment. Neutrophil studies revealed NADPH oxidase activity and flavocytochrome b(558) levels that were 4-8% of controls and suggested carrier status of the mother. We found a null mutation in the CYBB gene (c.252insAG) predicting an aberrant gp91(phox) protein (p.Cys85fsX23) in the heterozygous state. Methylation analysis demonstrated extremely skewed X chromosome inactivation favoring the maternally inherited defective gene. In conclusion, a novel mutation in the CYBB gene and an extremely skewed X-inactivation event resulted in the rare expression of the CGD phenotype in a carrier female.
NASA Astrophysics Data System (ADS)
Kubota, Kenji; Yoshiura, Shintaro; Shimabukuro, Hayato; Takahashi, Keitaro
2016-08-01
The redshifted 21 cm-line signal from neutral hydrogen in the intergalactic medium (IGM) gives a direct probe of the epoch of reionization (EoR). In this paper, we investigate the potential of the variance and skewness of the probability distribution function of the 21 cm brightness temperature for constraining EoR models. These statistical quantities are simple, easy to calculate from the observed visibility, and thus suitable for the early exploration of the EoR with current telescopes such as the Murchison Widefield Array (MWA) and LOw Frequency ARray (LOFAR). We show, by performing Fisher analysis, that the variance and skewness at z = 7-9 are complementary to each other to constrain the EoR model parameters such as the minimum virial temperature of halos which host luminous objects, ionizing efficiency, and mean free path of ionizing photons in the IGM. Quantitatively, the constraining power highly depends on the quality of the foreground subtraction and calibration. We give a best case estimate of the constraints on the parameters, neglecting the systematics other than the thermal noise.
Olson, Scott A.; with a section by Veilleux, Andrea G.
2014-01-01
This report provides estimates of flood discharges at selected annual exceedance probabilities (AEPs) for streamgages in and adjacent to Vermont and equations for estimating flood discharges at AEPs of 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent (recurrence intervals of 2-, 5-, 10-, 25-, 50-, 100-, 200-, and 500-years, respectively) for ungaged, unregulated, rural streams in Vermont. The equations were developed using generalized least-squares regression. Flood-frequency and drainage-basin characteristics from 145 streamgages were used in developing the equations. The drainage-basin characteristics used as explanatory variables in the regression equations include drainage area, percentage of wetland area, and the basin-wide mean of the average annual precipitation. The average standard errors of prediction for estimating the flood discharges at the 50-, 20-, 10-, 4-, 2-, 1-, 0.5-, and 0.2-percent AEP with these equations are 34.9, 36.0, 38.7, 42.4, 44.9, 47.3, 50.7, and 55.1 percent, respectively. Flood discharges at selected AEPs for streamgages were computed by using the Expected Moments Algorithm. To improve estimates of the flood discharges for given exceedance probabilities at streamgages in Vermont, a new generalized skew coefficient was developed. The new generalized skew for the region is a constant, 0.44. The mean square error of the generalized skew coefficient is 0.078. This report describes a technique for using results from the regression equations to adjust an AEP discharge computed from a streamgage record. This report also describes a technique for using a drainage-area adjustment to estimate flood discharge at a selected AEP for an ungaged site upstream or downstream from a streamgage. The final regression equations and the flood-discharge frequency data used in this study will be available in StreamStats. StreamStats is a World Wide Web application providing automated regression-equation solutions for user-selected sites on streams.
NASA Astrophysics Data System (ADS)
Shikakhwa, M. S.; Al-Qaq, E.
2010-09-01
The Aharonov-Casher (AC) Hamiltonian with the inclusion of the {\\triangledown}^{\\!\\!\\!\\!\\!\\!\\smash{\\raise2pt\\\\ssty\\rightharpoonup}} \\cdot \\skew2\\vec{E} term, which introduces a new singular interaction at the origin, is considered. Proceeding within the framework of the model of a finite-radius filament that is shrunk to zero at the end, the effect of the inclusion of this term on the original AC cross section is investigated. While the inclusion of this term gives rise to components of the radial wavefunctions that are irregular at the origin, it is found that the original AC cross section is the same whether one includes it or not, and regardless of whether the resulting singular interaction is attractive or repulsive. The underlying physics is discussed, and the physical equivalence with the spin one-half AB case is established.
Healy, Richard W.; Rice, Cynthia A.; Bartos, Timothy T.
2012-01-01
The Powder River Structural Basin is one of the largest producers of coal-bed natural gas (CBNG) in the United States. An important environmental concern in the Basin is the fate of groundwater that is extracted during CBNG production. Most of this produced water is disposed of in unlined surface impoundments. A 6-year study of groundwater flow and subsurface water and soil chemistry was conducted at one such impoundment, Skewed Reservoir. Hydrologic and geochemical data collected as part of that study are contained herein. Data include chemistry of groundwater obtained from a network of 21 monitoring wells and three suction lysimeters and chemical and physical properties of soil cores including chemistry of water/soil extracts, particle-size analyses, mineralogy, cation-exchange capacity, soil-water content, and total carbon and nitrogen content of soils.
Chatterjee, Siddhartha; Gunnels, John A
2011-11-08
A method and structure of distributing elements of an array of data in a computer memory to a specific processor of a multi-dimensional mesh of parallel processors includes designating a distribution of elements of at least a portion of the array to be executed by specific processors in the multi-dimensional mesh of parallel processors. The pattern of the designating includes a cyclical repetitive pattern of the parallel processor mesh, as modified to have a skew in at least one dimension so that both a row of data in the array and a column of data in the array map to respective contiguous groupings of the processors such that a dimension of the contiguous groupings is greater than one.
Shimizu, Jun; Kaneko, Fumio; Suzuki, Noboru
2013-01-01
Behcet's disease (BD) is a multisystemic inflammatory disease and is characterized by recurrent attacks on eyes, brain, skin, and gut. There is evidence that skewed T-cell responses contributed to its pathophysiology in patients with BD. Recently, we found that Th17 cells, a new helper T (Th) cell subset, were increased in patients with BD, and both Th type 1 (Th1) and Th17 cell differentiation signaling pathways were overactivated. Several researches revealed that genetic polymorphisms in Th1/Th17 cell differentiation signaling pathways were associated with the onset of BD. Here, we summarize current findings on the Th cell subsets, their contribution to the pathogenesis of BD and the genetic backgrounds, especially in view of IL-12 family cytokine production and pattern recognition receptors of macrophages/monocytes. PMID:24490076
Lin, Psang Dain; Wu, Wei
2011-08-01
The second-order derivative of a scalar function with respect to a variable vector is known as the Hessian matrix. We present a computational scheme based on the principles of differential geometry for determining the Hessian matrix of a skew ray as it travels through a prism system. A comparison of the proposed method and the conventional finite difference (FD) method is made at last. It is shown that the proposed method has a greater inherent accuracy than FD methods based on ray-tracing data. The proposed method not only provides a convenient means of investigating the wavefront shape within complex prism systems, but it also provides a potential basis for determining the higher order derivatives of a ray by further taking higher order differentiations.
NASA Astrophysics Data System (ADS)
Horner-Johnson, Benjamin C.; Gordon, Richard G.
2010-09-01
We test the fixed hot spot and fixed spin axis hypotheses through a paleomagnetic investigation of the skewness of crossings of magnetic anomaly 12r (32 Ma B.P.) between the Galapagos and Clarion fracture zones on the Pacific plate. We focus on this region for three reasons. First, numerical experiments show that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma B.P. paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal-to-noise ratios. Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm a-1) above which anomalous skewness is negligible. The new pole (83.5°N, 44.6°E) has compact 95% confidence limits (ellipse with major semiaxis length of 3.1° toward 84° clockwise from north and minor semiaxis length of 1.2°) and is not subject to the biases inherent in other methods for estimating Pacific plate paleomagnetic poles. The pole differs significantly by ≈5° from the pole predicted if the Pacific hot spots have been fixed with respect to the spin axis, thus demonstrating, for the first time from paleomagnetic data, that Pacific hot spots have moved relative to the spin axis since the formation of the elbow in the Hawaiian-Emperor chain. The pole is consistent, however, with previously published paleomagnetic poles in a reference frame fixed relative to Indo-Atlantic hot spots. Thus, the new results require no motion between Pacific and Indo-Atlantic hot spots since 32 Ma B.P. Instead, superimposed on whatever motion occurs between hot spots, as expected for true polar wander.
NASA Astrophysics Data System (ADS)
Alhamadi, Mohd A. Wahed
1992-01-01
A three dimensional finite element (3D-FE) method for the computation of global distributions of 30 magnetic fields in electric machines containing permanent magnets is presented. The formulation of this 3D-FE method is based on a coupled magnetic vector potential - magnetic scalar potential (CMVP-MSP) approach. In this CMVP-MSP method, the modeling and formulations of permanent magnet volumes, suited to first and second order MVP 3D-FE environments as well as first order MSP 3D-FE environment, are developed in this dissertation. The development of the necessary 3D-FE grids and algorithms for the application of the CMVP -MSP method to an example brushless dc motor, whose field is three dimensional due to the skewed permanent magnet mounts on its rotor, is also given here. It should be mentioned that the entire volume of the case-study machine from one end to another is considered in the global magnetic field computations. A complete set of results of application of the CMVP-MSP method to the computation of the global 3D field distributions and associated motor parameters under no-load and load conditions are presented in this dissertation. In addition, a complete simulation of the dynamic performance of the motor drive system using the parameters obtained from the 3D-FE field solutions are presented for no-load and various other load conditions. All the above mentioned results are experimentally verified by corresponding oscillograms obtained in the laboratory. These results are also compared with results obtained from motor parameters based on various 2D-FE approaches, showing that for certain types of skewed permanent magnet mounts, 3D-FE based parameters can make significant qualitative and quantitative improvements in motor-drive simulation results.
Jayawardena, Uthpala A; Ratnasooriya, Wanigasekara D; Wickramasinghe, Deepthi D; Udagama, Preethi V
2016-10-01
Immune cell and cytokine profiles in relation to metal exposure though much studied in mammals has not been adequately investigated in amphibians, due mainly to lack of suitable reagents for cytokine profiling in non-model species. However, interspecies cross reactivity of cytokines permitted us to assay levels of IFNγ, TNFα, IL6 and IL10in a common anuran, the Indian green frog (Euphlyctis hexadactylus), exposed to heavy metals (Cd, Cr, Cu, Zn and Pb, at ~5ppm each) under field and laboratory settings in Sri Lanka. Enumeration of immune cells in blood and melanomacrophages in the liver, assay of serum and hepatic cytokines, and Th1/Th2 cytokine polarisation were investigated. Immune cell counts indicated overall immunosuppression with decreasing total WBC and splenocyte counts while neutrophil/lymphocyte ratio increased with metal exposure, indicating metal mediated stress. Serum IL6 levels of metal exposed frogs reported the highest (~9360pg/mL) of all cytokines tested. Significantly elevated IFNγ production (P<0.05) was evident in heavy metal exposed frogs. Th1/Th2 cytokine ratio in both serum and liver tissue homogenates was Th1 skewed due to significantly higher production of pro-inflammatory cytokines, IFNγ in serum and TNFα in the liver (P<0.01).Metal mediated aggregations of melanomacrophages in the liver were positively and significantly (P<0.05) correlated with the hepatic expression of TNFα, IL6 and IL10 activity. Overall, Th1 skewed response may well be due to oxidative stress mediated nuclear factor κ-light chain enhancer of activated B cells (NFκB) which enhances the transcription of pro-inflammatory cytokines. Xenobiotic stress has recently imposed an unprecedented level of threat to wildlife, particularly to sensitive species such as amphibians. Therefore, understanding the interactions between physiological stress and related immune responses is fundamental to conserve these environmental sentinels in the face of emerging eco
Sisdelli, Luiza; Vidi, Angela Cristina; Moysés-Oliveira, Mariana; Di Battista, Adriana; Bortolai, Adriana; Moretti-Ferreira, Danilo; da Silva, Magnus R Dias; Melaragno, Maria Isabel; Carvalheira, Gianna
2016-02-01
X-chromosome inactivation occurs randomly in normal female cells. However, the inactivation can be skewed in patients with alterations in X-chromosome. In balanced X-autosome translocations, normal X is preferentially inactivated, while in unbalanced X alterations, the aberrant X is usually inactivated. Here, we present a novel strategy to verify the skewed X inactivation pattern through the incorporation of 5-ethynyl-2'-deoxyuridine (EdU) into cells, in 11 patients: five carriers of balanced X-autosome translocations and six of unbalanced X-chromosome alterations. Since EdU is a labeled nucleoside analog of thymidine, its incorporation during DNA synthesis can reveal late replication regions and the inactive X-chromosome. All EdU findings were validated by the human androgen receptor gene (HUMARA) assay. The late replication regions were easily and quickly visualized in all cells, where inactive Xs are marked with strong green fluorescence. It was observed that the normal X-chromosome was preferentially inactivated in patients with balanced X-autosome translocations; while the aberrant X-chromosome was inactivated in most cells from patients with unbalanced alterations. By performing the fluorescence-based EdU assay, the differences between the active and inactive X-chromosomes are more easily recognizable than by classic cytogenetic methods. Furthermore, EdU incorporation allows the observation of the late replication regions in autosomal segments present in X derivatives from X-autosome translocations. Therefore, EdU assay permits an accurate and efficient cytogenetic evaluation of the X inactivation pattern with a low-cost, easy to perform and highly reproducible technique.
NASA Astrophysics Data System (ADS)
Ismagilov, R. S.
1988-02-01
Two problems in measure theory are considered: that of the tail C*-algebra of a random walk on a group, and that of ergodicity of a skew-product action. These problems are solved in a uniform way by using Banach algebras and harmonic analysis on a group. Bibliography: 22 titles.
Al-Saaidi, Rasha; Rasmussen, Torsten B.; Palmfeldt, Johan; Nissen, Peter H.; Beqqali, Abdelaziz; Hansen, Jakob; Pinto, Yigal M.; Boesen, Thomas; Mogensen, Jens; Bross, Peter
2013-11-15
heterozygosity for the nonsense mutation causes NMD degradation of the mutant transcripts blocking expression of the truncated mutant protein and an additional trans effect on lamin A protein levels expressed from the wild type allele. We discuss the possibility that skewing of the lamin A to lamin C ratio may contribute to ensuing processes that destabilize cardiomyocytes and trigger cardiomyopathy - Highlights: • We study disease mechanisms in DCM patients carrying PTC mutations in the LMNA gene. • The mutant transcript is degraded by the nonsense mediated mRNA decay system. • Skewed lamin A to lamin C protein ratio expressed from the wild type allele. • We suggest a combined pathomechanism: haploinsuffiency plus lamin A/C imbalance.
Avettand-Fenoël, Véronique; Nembot, Georges; Mélard, Adeline; Blanc, Catherine; Lascoux-Combe, Caroline; Slama, Laurence; Allegre, Thierry; Allavena, Clotilde; Yazdanpanah, Yazdan; Duvivier, Claudine; Katlama, Christine; Goujard, Cécile; Seksik, Bao Chau Phung; Leplatois, Anne; Molina, Jean-Michel; Meyer, Laurence; Autran, Brigitte; Rouzioux, Christine
2013-01-01
Optimizing therapeutic strategies for an HIV cure requires better understanding the characteristics of early HIV-1 spread among resting CD4+ cells within the first month of primary HIV-1 infection (PHI). We studied the immune distribution, diversity, and inducibility of total HIV-DNA among the following cell subsets: monocytes, peripheral blood activated and resting CD4 T cells, long-lived (naive [TN] and central-memory [TCM]) and short-lived (transitional-memory [TTM] and effector-memory cells [TEM]) resting CD4+T cells from 12 acutely-infected individuals recruited at a median 36 days from infection. Cells were sorted for total HIV-DNA quantification, phylogenetic analysis and inducibility, all studied in relation to activation status and cell signaling. One month post-infection, a single CCR5-restricted viral cluster was massively distributed in all resting CD4+ subsets from 88% subjects, while one subject showed a slight diversity. High levels of total HIV-DNA were measured among TN (median 3.4 log copies/million cells), although 10-fold less (p = 0.0005) than in equally infected TCM (4.5), TTM (4.7) and TEM (4.6) cells. CD3−CD4+ monocytes harbored a low viral burden (median 2.3 log copies/million cells), unlike equally infected resting and activated CD4+ T cells (4.5 log copies/million cells). The skewed repartition of resting CD4 subsets influenced their contribution to the pool of resting infected CD4+T cells, two thirds of which consisted of short-lived TTM and TEM subsets, whereas long-lived TN and TCM subsets contributed the balance. Each resting CD4 subset produced HIV in vitro after stimulation with anti-CD3/anti-CD28+IL-2 with kinetics and magnitude varying according to subset differentiation, while IL-7 preferentially induced virus production from long-lived resting TN cells. In conclusion, within a month of infection, a clonal HIV-1 cluster is massively distributed among resting CD4 T-cell subsets with a flexible inducibility, suggesting that
NASA Astrophysics Data System (ADS)
Gordon, R. G.; Horner-Johnson, B. C.
2010-12-01
Prior studies have shown that Pacific hotspots and Indo-Atlantic hotspots have moved in approximate unison relative to the spin axis since 65 Ma B.P. [Morgan, 1981; Gordon and Cape, 1981; Gordon, 1982] and since 56 Ma B.P. [Petronotis et al., 1994], which is most simply interpreted as true polar wander. In contrast, Pacific hotspots and Indo-Atlantic hotspots give conflicting results for 72 Ma B.P. and for 81 Ma B.P., which may indicate motion between Pacific hotspots and Indo-Atlantic hotspots [Tarduno and Cottrell, 1997; Petronotis et al., 1999; Tarduno et al., 2003]. Thus it is important to estimate Pacific plate apparent polar wander (APW) for more time intervals. From such estimates the APW of Pacific hotspots can be inferred and compared with that of Indo-Atlantic hotspots [e.g., Besse and Courtillot 2002]. Here we present a study of the skewness of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones. We chose this region for several reasons: First, numerical experiments, like those conducted by Acton and Gordon [1991], indicate that magnetic profiles between the Galapagos and Clarion fracture zones should contain the most information about the Pacific plate paleomagnetic pole for chron C12r (32 Ma B.P.). Second, in these two spreading rate corridors, spreading half rates range from 72 to 86 mm/a and therefore have negligible anomalous skewness, given that they exceed ≈50 mm/a [Roest et al., 1992; Dyment et al. 1994]. Third, vector aeromagnetic profiles are available for analysis. One of the challenges to interpreting magnetic anomalies in low latitudes where the anomalies strike nearly north-south is the very low amplitude of the signal relative to the noise, the latter of which can be especially intense near the present magnetic equator due to the amplification of diurnal variation by the equatorial electrojet. Previously we showed that vector aeromagnetic profiles record low-latitude Pacific plate
Homma, Tetsuya; Kato, Atsushi; Bhushan, Bharat; Norton, James E.; Suh, Lydia A.; Carter, Roderick G.; Gupta, Dave S.
2016-01-01
Aspergillus fumigatus (AF) infection and sensitization are common and promote Th2 disease in individuals with asthma. Innate immune responses of bronchial epithelial cells are now known to play a key role in determination of T cell responses upon encounter with inhaled pathogens. We have recently shown that extracts of AF suppress JAK-STAT signaling in epithelial cells and thus may promote Th2 bias. To elucidate the impact of AF on human bronchial epithelial cells, we tested the hypothesis that AF can modulate the response of airway epithelial cells to favor a Th2 response and explored the molecular mechanism of the effect. Primary normal human bronchial epithelial (NHBE) cells were treated with AF extract or fractionated AF extract before stimulation with poly I:C or infection with human rhinovirus serotype 16 (HRV16). Expression of CXCL10 mRNA (real-time RT-PCR) and protein (ELISA) were measured as markers of IFN-mediated epithelial Th1–biased responses. Western blot was performed to evaluate expression of IFN regulatory factor-3 (IRF-3), NF-κB, and tyrosine-protein phosphatase nonreceptor type 11 (PTPN11), which are other markers of Th1 skewing. Knockdown experiments for protease-activated receptor-2 (PAR-2) and PTPN11 were performed to analyze the role of PAR-2 in the mechanism of suppression by AF. AF and a high-molecular-weight fraction of AF extract (HMW-AF; > 50 kD) profoundly suppressed poly I:C– and HRV16-induced expression of both CXCL10 mRNA and protein from NHBE cells via a mechanism that relied upon PAR-2 activation. Both AF extract and a specific PAR-2 activator (AC-55541) suppressed the poly I:C activation of phospho–IRF-3 without affecting activation of NF-κB. Furthermore, HMW-AF extract enhanced the expression of PTPN11, a phosphatase known to inhibit IFN signaling, and concurrently suppressed poly I:C–induced expression of both CXCL10 mRNA and protein from NHBE cells. These results show that exposure of bronchial epithelial cells to AF
Young, M Rita I; Levingston, Corinne A; Johnson, Sara D
2016-05-15
While immune suppression is a hallmark of head and neck squamous cell carcinoma (HSNCC), the immunological impact of premalignant oral lesions, which often precedes development of HNSCC, is unknown. The present study assessed the changes in splenic and draining lymph node CD4(+) cell populations and their production of select cytokines that occur in mice with carcinogen-induced premalignant oral lesions and the changes that occur as lesions progress to oral cancer. These studies found skewing toward Th1 and Th17-type phenotypes in the spleen and lymph nodes of mice with premalignant oral lesions and a shift to Treg as lesions progress to cancer. Since the role of Th17 cells in the progression from premalignant lesions to cancer is not clear, studies determined the immunological and clinical effect of treating mice bearing premalignant oral lesions with a TGF-β type 1 receptor inhibitor plus IL-23 as an approach to sustain the Th17 phenotype. These studies showed that the treatment approach not only sustained the Th17 phenotype, but also increased distal spleen cell and regional lymph node cell production of other stimulatory/inflammatory mediators and slowed premalignant lesion progression to cancer. © 2016 UICC.
DeGabriel, Jane L.; Moore, Ben D.; Foley, William J.; Johnson, Christopher N.
2014-01-01
Differences in predation risk may exert strong selective pressures on life history strategies of populations. We investigated the potential for predation to shape male mating strategies in an arboreal folivore, the common brushtail possum (Trichosurus vulpecula Kerr). We predicted that possums in a tropical population exposed to high natural levels of predation would grow faster and reproduce earlier compared to those in temperate populations with lower predation. We trapped a population of possums in eucalypt woodland in northern Australia each month to measure life history traits and used microsatellites to genotype all individuals and assign paternity to all offspring. We observed very high levels of male-biased predation, with almost 60% of marked male possums being eaten by pythons, presumably as a result of their greater mobility due to mate-searching. Male reproductive success was also highly skewed, with younger, larger males fathering significantly more offspring. This result contrasts with previous studies of temperate populations experiencing low levels of predation, where older males were larger and the most reproductively successful. Our results suggest that in populations exposed to high levels of predation, male possums invest in increased growth earlier in life, in order to maximise their mating potential. This strategy is feasible because predation limits competition from older males and means that delaying reproduction carries a risk of failing to reproduce at all. Our results show that life histories are variable traits that can match regional predation environments in mammal species with widespread distributions. PMID:25372294
DeGabriel, Jane L; Moore, Ben D; Foley, William J; Johnson, Christopher N
2014-01-01
Differences in predation risk may exert strong selective pressures on life history strategies of populations. We investigated the potential for predation to shape male mating strategies in an arboreal folivore, the common brushtail possum (Trichosurus vulpecula Kerr). We predicted that possums in a tropical population exposed to high natural levels of predation would grow faster and reproduce earlier compared to those in temperate populations with lower predation. We trapped a population of possums in eucalypt woodland in northern Australia each month to measure life history traits and used microsatellites to genotype all individuals and assign paternity to all offspring. We observed very high levels of male-biased predation, with almost 60% of marked male possums being eaten by pythons, presumably as a result of their greater mobility due to mate-searching. Male reproductive success was also highly skewed, with younger, larger males fathering significantly more offspring. This result contrasts with previous studies of temperate populations experiencing low levels of predation, where older males were larger and the most reproductively successful. Our results suggest that in populations exposed to high levels of predation, male possums invest in increased growth earlier in life, in order to maximise their mating potential. This strategy is feasible because predation limits competition from older males and means that delaying reproduction carries a risk of failing to reproduce at all. Our results show that life histories are variable traits that can match regional predation environments in mammal species with widespread distributions.
van der Weerd, Kim; Dik, Willem A.; Schrijver, Benjamin; Schweitzer, Dave H.; Langerak, Anton W.; Drexhage, Hemmo A.; Kiewiet, Rosalie M.; van Aken, Maarten O.; van Huisstede, Astrid; van Dongen, Jacques J.M.; van der Lelij, Aart-Jan; Staal, Frank J.T.; van Hagen, P. Martin
2012-01-01
Obesity is associated with local T-cell abnormalities in adipose tissue. Systemic obesity-related abnormalities in the peripheral blood T-cell compartment are not well defined. In this study, we investigated the peripheral blood T-cell compartment of morbidly obese and lean subjects. We determined all major T-cell subpopulations via six-color flow cytometry, including CD8+ and CD4+ T cells, CD4+ T-helper (Th) subpopulations, and natural CD4+CD25+FoxP3+ T-regulatory (Treg) cells. Moreover, molecular analyses to assess thymic output, T-cell proliferation (T-cell receptor excision circle analysis), and T-cell receptor-β (TCRB) repertoire (GeneScan analysis) were performed. In addition, we determined plasma levels of proinflammatory cytokines and cytokines associated with Th subpopulations and T-cell proliferation. Morbidly obese subjects had a selective increase in peripheral blood CD4+ naive, memory, natural CD4+CD25+FoxP3+ Treg, and Th2 T cells, whereas CD8+ T cells were normal. CD4+ and CD8+ T-cell proliferation was increased, whereas the TCRB repertoire was not significantly altered. Plasma levels of cytokines CCL5 and IL-7 were elevated. CD4+ T-cell numbers correlated positively with fasting insulin levels. The peripheral blood T-cell compartment of morbidly obese subjects is characterized by increased homeostatic T-cell proliferation to which cytokines IL-7 and CCL5, among others, might contribute. This is associated with increased CD4+ T cells, with skewing toward a Treg- and Th2-dominated phenotype, suggesting a more anti-inflammatory set point. PMID:22228716
Abdel-Hamid, Ahmed A M; Firgany, Alaa El-Din L
2016-07-01
Hydroxychloroquine (HCQ) has been demonstrated to reduce the risk to develop diabetes mellitus (DM). However no previous experimental study had investigated its effect on the structure of the endocrine pancreas, islets of Langerhans (IOL), in insulin resistance (IR). In addition, the mechanism by which HCQ can prevent DM is not well understood. In this study, we hypothesized that the possible favorable outcome of HCQ may be partly achieved by its molecular effect on the endothelial stress markers as well as on the imparied balance of the adipokines that usually accompanies IR. A total of 54 rats were divided equally into; control, high fat diet (HFD) and HFD+HCQ groups (received standard chow, HFD and HFD+HCQ respectively). After 12 weeks, samples from pancreas as well as visceral adipose tissue (VAT) were histologically studied for the consequent changes. In the HFD group, there were mild degenerative changes and expansion of the IOL accompanied with a significantly increased (p<0.05) β-cell area%, mass, proliferation and neogenesis as well as a significantly decreased (p<0.05) α-cell area% compared with the other groups. On combining HCQ with HFD, reversal of these changes along with correction of the impaired adipokines levels (leptin, adiponectin, resistin, visfatin and lipocalin-2) and significant decrease (p<0.05) of the vascular endothelial stress markers (sE-selectin, sICAM and sVICAM) were manifested compared with the HFD group. Therefore, HCQ favorable effects in IR may be attributed to relieving of the endothelial stress as well as normalization of the skewed balance of adipokines.
Haegel, Hélène; Thioudellet, Christine; Hallet, Rémy; Geist, Michel; Menguy, Thierry; Le Pogam, Fabrice; Marchand, Jean-Baptiste; Toh, Myew-Ling; Duong, Vanessa; Calcei, Alexandre; Settelen, Nathalie; Preville, Xavier; Hennequi, Marie; Grellier, Benoit; Ancian, Philippe; Rissanen, Jukka; Clayette, Pascal; Guillen, Christine; Rooke, Ronald; Bonnefoy, Jean-Yves
2013-01-01
Cancer progression has been associated with the presence of tumor-associated M2-macrophages (M2-TAMs) able to inhibit anti-tumor immune responses. It is also often associated with metastasis-induced bone destruction mediated by osteoclasts. Both cell types are controlled by the CD115 (CSF-1R)/colony-stimulating factor-1 (CSF-1, M-CSF) pathway, making CD115 a promising target for cancer therapy. Anti-human CD115 monoclonal antibodies (mAbs) that inhibit the receptor function have been generated in a number of laboratories. These mAbs compete with CSF-1 binding to CD115, dramatically affecting monocyte survival and preventing osteoclast and macrophage differentiation, but they also block CD115/CSF-1 internalization and degradation, which could lead to potent rebound CSF-1 effects in patients after mAb treatment has ended. We thus generated and selected a non-ligand competitive anti-CD115 mAb that exerts only partial inhibitory effects on CD115 signaling without blocking the internalization or the degradation of the CD115/CSF-1 complex. This mAb, H27K15, affects monocyte survival only minimally, but downregulates osteoclast differentiation and activity. Importantly, it inhibits monocyte differentiation to CD163(+)CD64(+) M2-polarized suppressor macrophages, skewing their differentiation toward CD14(-)CD1a(+) dendritic cells (DCs). In line with this observation, H27K15 also drastically inhibits monocyte chemotactic protein-1 secretion and reduces interleukin-6 production; these two molecules are known to be involved in M2-macrophage recruitment. Thus, the non-depleting mAb H27K15 is a promising anti-tumor candidate, able to inhibit osteoclast differentiation, likely decreasing metastasis-induced osteolysis, and able to prevent M2 polarization of TAMs while inducing DCs, hence contributing to the creation of more efficient anti-tumor immune responses.
Mehta, Akanksha; Malek-Jones, Matthew; Bolyakov, Alexander; Mielnik, Anna; Schlegel, Peter N; Paduch, Darius A
2012-01-01
Klinefelter syndrome (KS) remains the most common, yet often undiagnosed, chromosomal aberration in men. Early diagnosis and treatment can improve the health of patients with KS. The aim of this study was to evaluate the inactivation pattern of supernumerary X chromosomes. The secondary aim was to design a reliable and cost-effective molecular test for detection of X chromosome disomy. Methylation-specific polymerase chain reaction (M-PCR), with primers for familial mental retardation (FMR1) and X chromosome inactive-specific transcript (XIST) genes, was used to detect the presence of X chromosome disomy in men. Seventeen fertile males, 12 females, and 35 males with KS (28 with 47,XXY karyotype, and 7 with 47,XXY/46,XY mosaics) were included in the study. Results of the karyotype were compared with the results of semiquantitative M-PCR. Inactivation of X chromosomes was measured by XIST/FMR-1 methylation ratio. Differences in the methylation patterns of FMR1 and XIST genes between 46,XY men and men with X chromosome disomy allowed for rapid detection of the presence of an additional X chromosome, achieving 100% sensitivity and specificity using M-PCR. The methylated:unmethylated FMR1 amplicon ratio allowed the detection of 1 additional X chromosome per 100 normal XY cells (1% of XX/XY mosaicism). In our series, 50% of 47,XXY men showed skewed inactivation of the X chromosome. Men with KS can have incomplete inactivation of supernumerary X chromosomes. M-PCR is a sensitive, specific, fast, and relatively inexpensive test for the diagnosis of X chromosome disomy.
Djae, Tanalou; Bravin, Matthieu N; Garnier, Cédric; Doelsch, Emmanuel
2017-04-01
Parameterizing speciation models by setting the percentage of dissolved organic matter (DOM) that is reactive (% r-DOM) toward metal cations at a single 65% default value is very common in predictive ecotoxicology. The authors tested this practice by comparing the free copper activity (pCu(2+) = -log10 [Cu(2+) ]) measured in 55 soil sample solutions with pCu(2+) predicted with the Windermere humic aqueous model (WHAM) parameterized by default. Predictions of Cu toxicity to soil organisms based on measured or predicted pCu(2+) were also compared. Default WHAM parameterization substantially skewed the prediction of measured pCu(2+) by up to 2.7 pCu(2+) units (root mean square residual = 0.75-1.3) and subsequently the prediction of Cu toxicity for microbial functions, invertebrates, and plants by up to 36%, 45%, and 59% (root mean square residuals ≤9 %, 11%, and 17%), respectively. Reparametrizing WHAM by optimizing the 2 DOM binding properties (i.e., % r-DOM and the Cu complexation constant) within a physically realistic value range much improved the prediction of measured pCu(2+) (root mean square residual = 0.14-0.25). Accordingly, this WHAM parameterization successfully predicted Cu toxicity for microbial functions, invertebrates, and plants (root mean square residual ≤3.4%, 4.4%, and 5.8%, respectively). Thus, it is essential to account for the real heterogeneity in DOM binding properties for relatively accurate prediction of Cu speciation in soil solution and Cu toxic effects on soil organisms. Environ Toxicol Chem 2017;36:898-905. © 2016 SETAC. © 2016 SETAC.
van der Weerd, Kim; Dik, Willem A; Schrijver, Benjamin; Schweitzer, Dave H; Langerak, Anton W; Drexhage, Hemmo A; Kiewiet, Rosalie M; van Aken, Maarten O; van Huisstede, Astrid; van Dongen, Jacques J M; van der Lelij, Aart-Jan; Staal, Frank J T; van Hagen, P Martin
2012-02-01
Obesity is associated with local T-cell abnormalities in adipose tissue. Systemic obesity-related abnormalities in the peripheral blood T-cell compartment are not well defined. In this study, we investigated the peripheral blood T-cell compartment of morbidly obese and lean subjects. We determined all major T-cell subpopulations via six-color flow cytometry, including CD8+ and CD4+ T cells, CD4+ T-helper (Th) subpopulations, and natural CD4+CD25+FoxP3+ T-regulatory (Treg) cells. Moreover, molecular analyses to assess thymic output, T-cell proliferation (T-cell receptor excision circle analysis), and T-cell receptor-β (TCRB) repertoire (GeneScan analysis) were performed. In addition, we determined plasma levels of proinflammatory cytokines and cytokines associated with Th subpopulations and T-cell proliferation. Morbidly obese subjects had a selective increase in peripheral blood CD4+ naive, memory, natural CD4+CD25+FoxP3+ Treg, and Th2 T cells, whereas CD8+ T cells were normal. CD4+ and CD8+ T-cell proliferation was increased, whereas the TCRB repertoire was not significantly altered. Plasma levels of cytokines CCL5 and IL-7 were elevated. CD4+ T-cell numbers correlated positively with fasting insulin levels. The peripheral blood T-cell compartment of morbidly obese subjects is characterized by increased homeostatic T-cell proliferation to which cytokines IL-7 and CCL5, among others, might contribute. This is associated with increased CD4+ T cells, with skewing toward a Treg- and Th2-dominated phenotype, suggesting a more anti-inflammatory set point.
Liu, Zhuyun; Keegan, Brian; Gazzinelli-Guimarães, Ana Clara; Fujiwara, Ricardo T.; Briggs, Neima; Jones, Kathryn M.; Strych, Ulrich; Beaumier, Coreen M.; Bottazzi, Maria Elena; Zhan, Bin
2017-01-01
egg challenge that associates with a Th2-skewed immune response, suggesting that rAS16 could be a feasible vaccine candidate against ascariasis. PMID:28708895
Wei, Junfei; Versteeg, Leroy; Liu, Zhuyun; Keegan, Brian; Gazzinelli-Guimarães, Ana Clara; Fujiwara, Ricardo T; Briggs, Neima; Jones, Kathryn M; Strych, Ulrich; Beaumier, Coreen M; Bottazzi, Maria Elena; Hotez, Peter J; Zhan, Bin
2017-07-01
Ascariasis remains the most common helminth infection in humans. As an alternative or complementary approach to global deworming, a pan-anthelminthic vaccine is under development targeting Ascaris, hookworm, and Trichuris infections. As16 and As14 have previously been described as two genetically related proteins from Ascaris suum that induced protective immunity in mice when formulated with cholera toxin B subunit (CTB) as an adjuvant, but the exact protective mechanism was not well understood. As16 and As14 were highly expressed as soluble recombinant proteins (rAs16 and rAs14) in Pichia pastoris. The yeast-expressed rAs16 was highly recognized by immune sera from mice infected with A. suum eggs and elicited 99.6% protection against A. suum re-infection. Mice immunized with rAs16 formulated with ISA720 displayed significant larva reduction (36.7%) and stunted larval development against A. suum eggs challenge. The protective immunity was associated with a predominant Th2-type response characterized by high titers of serological IgG1 (IgG1/IgG2a > 2000) and high levels of IL-4 and IL-5 produced by restimulated splenocytes. A similar level of protection was observed in mice immunized with rAs16 formulated with alum (Alhydrogel), known to induce mainly a Th2-type immune response, whereas mice immunized with rAs16 formulated with MPLA or AddaVax, both known to induce a Th1-type biased response, were not significantly protected against A. suum infection. The rAs14 protein was not recognized by A. suum infected mouse sera and mice immunized with rAs14 formulated with ISA720 did not show significant protection against challenge infection, possibly due to the protein's inaccessibility to the host immune system or a Th1-type response was induced which would counter a protective Th2-type response. Yeast-expressed rAs16 formulated with ISA720 or alum induced significant protection in mice against A. suum egg challenge that associates with a Th2-skewed immune response
Green, Mark P; Spate, Lee D; Parks, Tina E; Kimura, Koji; Murphy, Clifton N; Williams, Jim E; Kerley, Monty S; Green, Jonathan A; Keisler, Duane H; Roberts, R Michael
2008-01-01
Background Evolutionary theory suggests that in polygynous mammalian species females in better body condition should produce more sons than daughters. Few controlled studies have however tested this hypothesis and controversy exists as to whether body condition score or maternal diet is in fact the determining factor of offspring sex. Here, we examined whether maternal diet, specifically increased n-6 polyunsaturated fatty acid (PUFA) intake, of ewes with a constant body condition score around the time of conception influenced sex ratio. Methods Ewes (n = 44) maintained in similar body condition throughout the study were assigned either a control (C) diet or one (F) enriched in rumen-protected PUFA, but otherwise essentially equivalent, from four weeks prior to breeding until d13 post-estrus. On d13, conceptuses were recovered, measured, cultured to assess their capacity for interferon-tau (IFNT) production and their sex determined. The experiment was repeated with all ewes being fed the F diet to remove any effects of parity order on sex ratio. Maternal body condition score (BCS), plasma hormone and metabolite concentrations were also assessed throughout the study and related to diet. Results In total 129 conceptuses were recovered. Ewes on the F diet produced significantly more male than female conceptuses (proportion male = 0.69; deviation from expected ratio of 0.5, P < 0.001). Conceptus IFNT production was unaffected by diet (P > 0.1), but positively correlated with maternal body condition score (P < 0.05), and was higher (P < 0.05) in female than male conceptuses after 4 h culture. Maternal plasma hormone and metabolite concentrations, especially progesterone and fatty acid, were also modulated by diet. Conclusion These results provide evidence that maternal diet, in the form of increased amounts of rumen-protected PUFA fed around conception, rather than maternal body condition, can skew the sex ratio towards males. These observations may have implications to
NASA Astrophysics Data System (ADS)
Zheng, L.; Gordon, R. G.; Horner-Johnson, B. C.
2011-12-01
Pacific plate apparent polar wander between 67 Ma and 44 Ma determined from the analysis of the skewness of both vector and scalar magnetic anomalies due to seafloor spreading The apparent polar wander (APW) path for the Pacific plate is important to the study of Pacific plate motions and their relation to circum-Pacific tectonics. It can be used to discriminate between alternative plate motion circuits, determine the motion of Pacific hotspots relative to the paleomagnetic axis, and test the fixed hotspot hypothesis. The pioneering investigations of Jean Francheteau and his colleagues of Pacific plate APW through the analysis of magnetic anomalies over seamounts helped to demonstrate that the Pacific plate has had substantial northward motion relative to the spin axis since Cretaceous time. We also investigate the APW of the Pacific plate through analysis of magnetic anomalies. Instead of anomalies over seamounts, however, we investigate the skewness (asymmetry) of magnetic anomalies due to seafloor spreading. In prior work, skewness analysis of shipboard magnetic profiles has been used to determine Pacific paleomagnetic poles for chron 25r (57 Ma B.P.; Petronotis et al., 1994), chron 27r to 31n (62 to 69 Ma B.P.; Acton and Gordon, 1991) and chron 32n (72 Ma B.P.; Petronotis and Gordon, 1999). Recently, vector aeromagnetic data from low paleolatitudes, combined with shipboard profiles from low paleolatitudes, were used to determine a paleomagnetic pole with compact confidence limits for anomaly 12r (32 Ma B.P.; Horner-Johnson and Gordon, 2010). Here we use the low-paleolatitude shipboard- and vector aero-magnetic profiles to determine new paleomagnetic poles for the Pacific plate. A new feature of our analysis is a correction for the spreading-rate dependence of anomalous skewness (Koivisto et al. 2011). We estimate anomalous skewness as a function of spreading rate for each anomaly by creating many synthetic profiles using the model of Dyment and Arkani
NASA Technical Reports Server (NTRS)
Kolbe, Carl D; Tinling, Bruce E
1948-01-01
Results of wind-tunnel tests of a semispan model of a triangular wing of aspect ratio 2 with a skewed wing-tip flap are presented. Lift, drag, pitching-moment, and hinge-moment data are included for subsonic Mach numbers up to 0.95. The flap showed extremely high hinge moments and low effectiveness as a longitudinal control. Although less affected by compressibility, this flap is indicated to be inferior to a constant-chord flap when applied to this triangular wing.
NASA Astrophysics Data System (ADS)
Toomey, D. R.; Hooft, E. E.
2007-12-01
, whereas average crustal densities are expected to be less near axial depth minima or where off-axis seafloor depth shoals in the rise-parallel direction. Our modeling results, in combination with seismic observations and simple calculations, can be used to infer the origin of rise-parallel, segment-scale variations in crustal density. We attribute segment-scale variations in crustal density to magmatic differentiation that results from a skew between the axes of mantle upwelling and plate spreading. We use seismic imaging of crustal thickness and upper mantle structure combined with gravity data to provide novel constraints on the temporal evolution of mantle upwelling beneath the EPR and to infer that axial sites of intense volcanic and hydrothermal activity can persist for 105 to 106 years.
NASA Astrophysics Data System (ADS)
Toomey, D. R.; Hooft, E. E.
2004-12-01
, whereas average crustal densities are expected to be less near axial depth minima or where off-axis seafloor depth shoals in the rise-parallel direction. Our modeling results, in combination with seismic observations and simple calculations, can be used to infer the origin of rise-parallel, segment-scale variations in crustal density. We attribute segment-scale variations in crustal density to magmatic differentiation that results from a skew between the axes of mantle upwelling and plate spreading. We use seismic imaging of crustal thickness and upper mantle structure combined with gravity data to provide novel constraints on the temporal evolution of mantle upwelling beneath the EPR and to infer that axial sites of intense volcanic and hydrothermal activity can persist for 105 to 106 years.
Ghiglione, Yanina; Falivene, Juliana; Ruiz, María Julia; Laufer, Natalia; Socías, María Eugenia; Cahn, Pedro; Giavedoni, Luis; Sued, Omar; Gherardi, María Magdalena; Salomón, Horacio; Turk, Gabriela
2014-01-01
The important role of the CD8+ T-cells on HIV control is well established. However, correlates of immune protection remain elusive. Although the importance of CD8+ T-cell specificity and functionality in virus control has been underscored, further unraveling the link between CD8+ T-cell differentiation and viral control is needed. Here, an immunophenotypic analysis (in terms of memory markers and Programmed cell death 1 (PD-1) expression) of the CD8+ T-cell subset found in primary HIV infection (PHI) was performed. The aim was to seek for associations with functional properties of the CD8+ T-cell subsets, viral control and subsequent disease progression. Also, results were compared with samples from Chronics and Elite Controllers. It was found that normal maturation of total and HIV-specific CD8+ T-cells into memory subsets is skewed in PHI, but not at the dramatic level observed in Chronics. Within the HIV-specific compartment, this alteration was evidenced by an accumulation of effector memory CD8+ T (TEM) cells over fully differentiated terminal effector CD8+ T (TTE) cells. Furthermore, higher proportions of total and HIV-specific CD8+ TEM cells and higher HIV-specific TEM/(TEM+TTE) ratio correlated with markers of faster progression. Analysis of PD-1 expression on total and HIV-specific CD8+ T-cells from PHI subjects revealed not only an association with disease progression but also with skewed memory CD8+ T-cell differentiation. Most notably, significant direct correlations were obtained between the functional capacity of CD8+ T-cells to inhibit viral replication in vitro with higher proportions of fully-differentiated HIV-specific CD8+ TTE cells, both at baseline and at 12 months post-infection. Thus, a relationship between preservation of CD8+ T-cell differentiation pathway and cell functionality was established. This report presents evidence concerning the link among CD8+ T-cell function, phenotype and virus control, hence supporting the instauration of
NASA Astrophysics Data System (ADS)
Horner-Johnson, B. C.; Gordon, R. G.
2007-12-01
In recent years, some researchers have asserted that there has been no motion of the Pacific hotspots relative to the spin axis since the age (ca. 47 Ma) of the elbow in the Hawaiian-Emperor chain (e.g., Tarduno et al. 2003). In contrast, the apparent polar wander of the Indo-Atlantic hotspots shows distinct motion of the hotspots relative to the spin axis over the same time interval (e.g., Morgan 1981; Besse and Courtillot 2002). If this latter shift is due to true polar wander, one would expect to see a similar shift of Pacific hotspots relative to the spin axis. Here we present critical new data and analyses to test these distinctly different hypotheses. Specifically, we present results of an investigation of the skewness of magnetic anomaly crossings of anomaly 12r between the Galapagos and Clipperton and between the Clipperton and Clarion fracture zones on the Pacific plate. We chose to focus on these adjacent regions for three reasons. First, numerical experiments showed that these crossings, of all those available from the Pacific plate, should contain the most information about the location of the 32 Ma paleomagnetic pole for the Pacific plate. Second, many of the available crossings are from vector aeromagnetic profiles, which have superior signal to noise ratios (Horner-Johnson and Gordon, 2003). Third, the rate of seafloor spreading recorded in these crossings exceeds the threshold (half rate of 50 mm/yr) above which no anomalous skewness occurs. Moreover, for the first time, we combine uncertainties in plate- hotspot rotations (Andrews et al. 2005) with paleomagnetic uncertainties to obtain the total uncertainties of our new paleomagnetic pole reconstructed into the Pacific hotspot frame of reference. The results show significant and unambiguous motion of Pacific hotspots relative to the spin axis since 32 Ma. Moreover, when the 32 Ma Pacific plate paleomagnetic pole is reconstructed into the Pacific hotspot reference frame, it is consistent with the
Ackerman, Margaret E; Dugast, Anne-Sophie; McAndrew, Elizabeth G; Tsoukas, Stephen; Licht, Anna F; Irvine, Darrell J; Alter, Galit
2013-05-01
While development of an HIV vaccine that can induce neutralizing antibodies remains a priority, decades of research have proven that this is a daunting task. However, accumulating evidence suggests that antibodies with the capacity to harness innate immunity may provide some protection. While significant research has focused on the cytolytic properties of antibodies in acquisition and control, less is known about the role of additional effector functions. In this study, we investigated antibody-dependent phagocytosis of HIV immune complexes, and we observed significant differences in the ability of antibodies from infected subjects to mediate this critical effector function. We observed both quantitative differences in the capacity of antibodies to drive phagocytosis and qualitative differences in their FcγR usage profile. We demonstrate that antibodies from controllers and untreated progressors exhibit increased phagocytic activity, altered Fc domain glycosylation, and skewed interactions with FcγR2a and FcγR2b in both bulk plasma and HIV-specific IgG. While increased phagocytic activity may directly influence immune activation via clearance of inflammatory immune complexes, it is also plausible that Fc receptor usage patterns may regulate the immune response by modulating downstream signals following phagocytosis--driving passive degradation of internalized virus, release of immune modulating cytokines and chemokines, or priming of a more effective adaptive immune response.
Mantile, Francesca; Trovato, Maria; Santoni, Andrea; Barba, Pasquale; Ottonello, Simone; De Berardinis, Piergiuseppe; Prisco, Antonella
2014-01-01
The development of active immunotherapy for Alzheimer's disease (AD) requires the identification of immunogens that can ensure a high titer antibody response toward Aβ, while minimizing the risks of adverse reactions. Multimeric protein (1–11)E2 induces a robust and persistent antibody response to Aβ in mice, when formulated in Freund's adjuvant. The goal of this translational study was to evaluate the immunogenicity of (1–11)E2 formulated in alum (Alhydrogel 2%), or in a squalene oil-in-water emulsion (AddaVax), or without adjuvant. A IgG1-skewed isotype distribution was observed for the anti-Aβ antibodies generated in mice immunized with either the non-adjuvanted or the adjuvanted vaccine, indicating that (1–11)E2 induces a Th2-like response in all tested conditions. Both Alhydrogel 2% and AddaVax enhanced the titer and avidity of the anti-Aβ response elicited by (1–11)E2. We conclude that (1–11)E2 is a promising candidate for anti-Aβ immunization protocols that include alum or squalene-oil-in-water emulsion, or no adjuvant. PMID:24983378
Yanagita, Manabu; Kobayashi, Ryohei; Murakami, Shinya
2009-10-09
Macrophages (M{Phi}s) exhibit functional heterogeneity and plasticity in the local microenvironment. Recently, it was reported that M{Phi}s can be divided into proinflammatory M{Phi}s (M{Phi}1) and anti-inflammatory M{Phi}s (M{Phi}2) based on their polarized functional properties. Here, we report that nicotine, the major ingredient of cigarette smoke, can modulate the characteristics of M{Phi}1. Granulocyte-macrophage colony-stimulating factor-driven M{Phi}1 with nicotine (Ni-M{Phi}1) showed the phenotypic characteristics of M{Phi}2. Like M{Phi}2, Ni-M{Phi}1 exhibited antigen-uptake activities. Ni-M{Phi}1 suppressed IL-12, but maintained IL-10 and produced high amounts of MCP-1 upon lipopolysaccharide stimulation compared with M{Phi}1. Moreover, we observed strong proliferative responses of T cells to lipopolysaccharide-stimulated M{Phi}1, whereas Ni-M{Phi}1 reduced T cell proliferation and inhibited IFN-{gamma} production by T cells. These results suggest that nicotine can change the functional characteristics of M{Phi} and skew the M{Phi}1 phenotype to M{Phi}2. We propose that nicotine is a potent regulator that modulates immune responses in microenvironments.
Zaborsky, Nadja; Gassner, Franz Josef; Asslaber, Daniela; Reinthaler, Petra; Denk, Ursula; Flenady, Sabine; Hofbauer, Josefina Piñón; Danner, Barbara; Rebhandl, Stefan; Harrer, Andrea; Geisberger, Roland; Greil, Richard; Egle, Alexander
2016-01-01
Chronic lymphocytic leukemia develops within a complex network driven by genetic mutations and microenvironmental interactions. Among the latter a complex interplay with the immune system is established by the clone. Next to a proposed recruitment of support from T and myeloid cells, potential anti-CLL immune reactions need to be subverted. By using TCL1 mice as a CLL model, we show that TCR-Vβ7+ NK1.1+ T cells are overrepresented in this disease model and constitute a main subset of peripheral CD3+ cells with biased TCR usage, showing that these cells account for a major part for T cell skewing in TCL1 mice. Moreover, we show that overrepresentation is dependent on CD1d expression in TCL1 mice, implicating that these cells belong to a NKT-like cell fraction which are restricted to antigen presented by the MHC-like surface marker CD1d. Accordingly, we observed a high fraction of CD161+ cells within overrepresented T cells in CLL patients and we found downregulation of CD1d on the surface of CLL cells, both in TCL1 mice and patients. Finally, we show that in TCL1 mice, CD1d deficiency resulted in shortened overall survival. Our results point to an interaction between CLL and CD161+ T cells that may represent a novel therapeutic target for immune modulation. PMID:27385215
Mantile, Francesca; Trovato, Maria; Santoni, Andrea; Barba, Pasquale; Ottonello, Simone; De Berardinis, Piergiuseppe; Prisco, Antonella
2014-01-01
The development of active immunotherapy for Alzheimer's disease (AD) requires the identification of immunogens that can ensure a high titer antibody response toward Aβ, while minimizing the risks of adverse reactions. Multimeric protein (1-11)E2 induces a robust and persistent antibody response to Aβ in mice, when formulated in Freund's adjuvant. The goal of this translational study was to evaluate the immunogenicity of (1-11)E2 formulated in alum (Alhydrogel 2%), or in a squalene oil-in-water emulsion (AddaVax), or without adjuvant. A IgG1-skewed isotype distribution was observed for the anti-Aβ antibodies generated in mice immunized with either the non-adjuvanted or the adjuvanted vaccine, indicating that (1-11)E2 induces a Th2-like response in all tested conditions. Both Alhydrogel 2% and AddaVax enhanced the titer and avidity of the anti-Aβ response elicited by (1-11)E2. We conclude that (1-11)E2 is a promising candidate for anti-Aβ immunization protocols that include alum or squalene-oil-in-water emulsion, or no adjuvant.
Yang, Xi; Hoshino, Akihiro; Taga, Takashi; Kunitsu, Tomoaki; Ikeda, Yuhachi; Yasumi, Takahiro; Yoshida, Kenichi; Wada, Taizo; Miyake, Kunio; Kubota, Takeo; Okuno, Yusuke; Muramatsu, Hideki; Adachi, Yuichi; Miyano, Satoru; Ogawa, Seishi; Kojima, Seiji; Kanegane, Hirokazu
2015-04-01
X-linked lymphoproliferative disease (XLP) is a rare inherited immunodeficiency that often leads to hemophagocytic lymphohistiocytosis (HLH). XLP can be classified as XLP1 or XLP2, caused by mutations in SH2D1A and XIAP, respectively. In women, X-chromosome inactivation (XCI) of most X-linked genes occurs on one of the X chromosomes in each cell. The choice of which X chromosome remains activated is generally random, although genetic differences and selective advantage may cause one of the X chromosomes to be preferentially inactivated. Here we describe three patients with pancytopenia, including one female patient, in a Japanese family with a novel XIAP mutation. All three patients exhibited deficient XIAP protein expression, impaired NOD2/XIAP signaling, and augmented activation-induced cell death. In the female patient, the paternally derived X chromosome was non-randomly and exclusively inactivated in her peripheral blood and hair root cells. In contrast to asymptomatic females, this patient exhibied non-random XCI skewed towards the wild-type XIAP allele. This is the first report of a female patient with incomplete HLH resulting from a heterozygous XIAP mutation in association with non-random XCI.
Lu, Tao; Wang, Min; Liu, Guangying; Dong, Guang-Hui; Qian, Feng
2016-01-01
It is well known that there is strong relationship between HIV viral load and CD4 cell counts in AIDS studies. However, the relationship between them changes during the course of treatment and may vary among individuals. During treatments, some individuals may experience terminal events such as death. Because the terminal event may be related to the individual's viral load measurements, the terminal mechanism is non-ignorable. Furthermore, there exists competing risks from multiple types of events, such as AIDS-related death and other death. Most joint models for the analysis of longitudinal-survival data developed in literatures have focused on constant coefficients and assume symmetric distribution for the endpoints, which does not meet the needs for investigating the nature of varying relationship between HIV viral load and CD4 cell counts in practice. We develop a mixed-effects varying-coefficient model with skewed distribution coupled with cause-specific varying-coefficient hazard model with random-effects to deal with varying relationship between the two endpoints for longitudinal-competing risks survival data. A fully Bayesian inference procedure is established to estimate parameters in the joint model. The proposed method is applied to a multicenter AIDS cohort study. Various scenarios-based potential models that account for partial data features are compared. Some interesting findings are presented.
Dugast, Anne-Sophie; McAndrew, Elizabeth G.; Tsoukas, Stephen; Licht, Anna F.; Irvine, Darrell J.; Alter, Galit
2013-01-01
While development of an HIV vaccine that can induce neutralizing antibodies remains a priority, decades of research have proven that this is a daunting task. However, accumulating evidence suggests that antibodies with the capacity to harness innate immunity may provide some protection. While significant research has focused on the cytolytic properties of antibodies in acquisition and control, less is known about the role of additional effector functions. In this study, we investigated antibody-dependent phagocytosis of HIV immune complexes, and we observed significant differences in the ability of antibodies from infected subjects to mediate this critical effector function. We observed both quantitative differences in the capacity of antibodies to drive phagocytosis and qualitative differences in their FcγR usage profile. We demonstrate that antibodies from controllers and untreated progressors exhibit increased phagocytic activity, altered Fc domain glycosylation, and skewed interactions with FcγR2a and FcγR2b in both bulk plasma and HIV-specific IgG. While increased phagocytic activity may directly influence immune activation via clearance of inflammatory immune complexes, it is also plausible that Fc receptor usage patterns may regulate the immune response by modulating downstream signals following phagocytosis—driving passive degradation of internalized virus, release of immune modulating cytokines and chemokines, or priming of a more effective adaptive immune response. PMID:23468489
Soloviova, Kateryna; Puliaiev, Maksym; Haas, Mark; Dalgard, Clifton L.; Schaefer, Brian C.; Via, Charles S.
2015-01-01
Using the parent-into-F1 model of induced lupus and (C57Bl/6xDBA2) F1 mice as hosts, we compared the inherent lupus-inducing properties of the two parental strain CD4 T cells. To control for donor CD4 recognition of alloantigen, we used H-2d identical DBA/2 and B10.D2 donor T cells. We demonstrate that these two normal, non-lupus prone parental strains exhibit two different T cell activation pathways in vivo. B10.D2 CD4 T cells induce a strong Th1/CMI pathway characterized by IL-2/IFN-g expression, help for CD8 CTL, skewing of DC subsets towards CD8a DC, coupled with reduced CD4Tfh cells and transient B cell help. By contrast, DBA/2 CD4 T cells exhibit a reciprocal, lupus-inducing pathway characterized by poor IL-2/IFN-g expression, poor help for CD8 CTL, skewing of DC subsets towards pDC coupled with greater CD4 Tfh cells, prolonged B cell activation, autoantibody formation, and lupus-like renal disease. Additionally, two distinct in vivo splenic gene expression signatures were induced. In vitro analysis of TCR signaling revealed defective DBA CD4 T cell induction of NF-κB, reduced degradation of IκBα and increased expression of the NF-κB regulator A20. Thus, attenuated NF-κB signaling may lead to diminished IL-2 production by DBA CD4 T cells. These results indicate that intrinsic differences in donor CD4 IL-2 production and subsequent immune skewing could contribute to lupus susceptibility in humans. Therapeutic efforts to skew immune function away from excessive help for B cells and towards help for CTL may be beneficial. PMID:26320249
Archer, Hayley; Evans, Julie; Leonard, Helen; Colvin, Lyn; Ravine, David; Christodoulou, John; Williamson, Sarah; Charman, Tony; Bailey, Mark E S; Sampson, Julian; de Klerk, Nicholas; Clarke, Angus
2007-01-01
Introduction Rett syndrome (RTT) is an X‐linked dominant neurodevelopmental disorder that is usually associated with mutations in the MECP2 gene. The most common mutations in the gene are p.R168X and p.T158M. The influence of X‐chromosome inactivation (XCI) on clinical severity in patients with RTT with these mutations was investigated, taking into account the extent and direction of skewing. Methods Female patients and their parents were recruited from the UK and Australia. Clinical severity was measured by the Pineda Severity and Kerr profile scores. The degree of XCI and its direction relative to the X chromosome parent of origin were measured in DNA prepared from peripheral blood leucocytes, and allele‐specific polymerase chain reaction was used to determine the parental origin of mutation. Combining these, the percentage of cells expected to express the mutant allele was calculated. Results Linear regression analysis was undertaken for fully informative cases with p.R168X (n = 23) and p.T158M (n = 20) mutations. A statistically significant increase in clinical severity with increase in the proportion of active mutated allele was shown for both the p.R168X and p.T158M mutations. Conclusions XCI may vary in neurological and haematological tissues. However, these data are the first to show a relationship between the degree and direction of XCI in leucocytes and clinical severity in RTT, although the clinical utility of this in giving a prognosis for individual patients is unclear. PMID:16905679