Components Of Beta Research Articles

Spatio‐temporal patterns of eukaryotic biodiversity in shallow hard‐bottom communities from the West Antarctic Peninsula revealed by DNA metabarcoding

AbstractAimWe studied molecular eukaryotic biodiversity patterns in shallow hard‐bottom Antarctic benthic communities using community DNA metabarcoding. Polar ecosystems are extremely exposed to climate change, and benthic macroinvertebrate communities have demonstrated rapid response to a range of natural and anthropogenic pressures. However, these rich and diverse ecosystems are poorly studied, revealing how little is known about the biodiversity of the Antarctic benthos associated with hard‐bottom habitats.LocationWest Antarctic Peninsula and South Shetland Islands.MethodsUsing data collected in seven localities along the western Antarctic Peninsula, we calculated spatial patterns of alpha and beta diversities. Furthermore, we analysed temporal changes in benthic composition in one location (Deception Island) over 3 years. We calculated the temporal alpha and beta diversities to reveal changes in this community over time.ResultsWe obtained a final list of 2057 molecular operational taxonomic units. We found significant differences in benthic community composition between localities and among years. Our dataset revealed a total of 10 different kingdom‐level lineages and 34 different phyla in the samples. The most diverse phylum was Arthropoda, followed by Bacillariophyta, and Annelida, while the highest relative read abundances belonged to Annelida, Porifera and Echinodermata. Benthic community compositions changed between 2016 and 2018 in Deception Island, and decreasing species richness was the main component of temporal beta diversity.Main ConclusionsDirect sampling methods are required for monitoring these complex communities. Informative biodiversity patterns can be retrieved even though most of the benthic biodiversity found in Antarctic habitats is yet to be taxonomically described and barcoded. Hard‐bottom assemblages exhibit high spatial variability and heterogeneity, not related to depth, which represent a huge challenge for large‐scale studies in the Southern Ocean. Local patchiness and structure within these communities are probably a consequence of a combination of several biotic and abiotic factors (i.e. ice disturbance, food supply and competition).

Extreme Liquidity Risk and the Cross‐Section of Expected Returns: Evidence from China*

AbstractIn this study, we investigate whether extreme liquidity risk is priced in the China A‐shares market. We find that the market extreme liquidity risk significantly and negatively predicts market returns up to 9 months. In addition, the extreme liquidity risk beta of individual stocks commands a positive monthly premium of 0.75%. Moreover, our findings show that the extreme liquidity risk beta can subsume the tail risk beta in predicting stock returns. Furthermore, our findings show that both the potential selling pressures caused by insiders and by institutional investors significantly and positively influence an individual stock's extreme liquidity risk beta. We also find that the potential selling pressure component of the extreme liquidity risk beta significantly and positively predicts stock returns. Taken together, our evidence demonstrates that a stock's extreme liquidity risk beta provides a channel through which the stock's potential selling pressure caused by both insiders and institutional investors influences its expected return in the China A‐shares market.

Precipitation preferences alter the relative importance of herbaceous plant diversity for multifunctionality in the drylands of China

BackgroundMultiple components of biodiversity are excellent predictors of precipitation-induced changes in ecosystem function. However, the importance of differing scales (alpha versus beta) is usually overlooked in biodiversity–ecosystem multifunctionality studies. Consequently, little is known about how precipitation regulates the relationship between multifunctionality and multiple components of alpha and beta diversity.AimsWe investigated geographic patterns of herbaceous plant diversity and ecosystem multifunctionality along a precipitation gradient spanning more than 2010 km in Northwest China.MethodsWe assessed the effects of herbaceous species, phylogenetic, and functional components at different scales on multifunctionality in drylands.ResultsThe alpha diversity of species and functional beta diversity were key components explaining the variation in multifunctionality. As the main environmental factor, MAP (mean annual precipitation) affected multifunctionality by changing the mediating variables (i.e., species alpha and functional beta diversity). More importantly, a certain precipitation threshold was detected for the relationship of multifunctionality to species alpha and functional beta diversity. MAPs of approximately 158 mm and 140 mm modulated this relationship (shifting it from uncorrelated to significantly correlated).ConclusionsOur findings provide insights into previously neglected mechanisms by which diversity in herbaceous layers at different scales affects ecosystem multifunctionality. It is highlighted that MAP regulates the relationship between diversity and multifunctionality in dryland ecosystems at different scales. Further, diversity may have substantial consequences for multifunctionality where MAP is higher. These empirical results provide a comprehensive understanding of the biodiversity–multifunctionality relationship in the context of precipitation, ultimately contributing to conservation and restoration programs for multifunctionality in drylands.

Nicotinic receptor components of amyloid beta 42 proteome regulation in human neural cells

Alzheimer’s disease (AD) is associated with chronic neurodegeneration often accompanied by elevated levels of the neurotoxic peptide amyloid-beta 1–42 (Aβ42) in the brain. Studies show that extracellular Aβ42 binds to various cell surface receptors including the human α7 nicotinic acetylcholine receptor (nAChR) and activates pathways of neurotoxicity leading to cell death. The α7 nAChR is thus considered a promising drug target for therapy against neurodegenerative disease such as AD. In this study, we use mass spectrometry-based label-free precursor ion quantification to identify proteins and pathways that are changed by a 72-hour treatment with Aβ42 or Aβ42 in the presence of the α7 nAChR blocker, α-bungarotoxin (Bgtx) in the human neuroblastoma SH-SY5Y cell line. Bioinformatic gene ontology enrichment analysis was used to identify and characterize proteins and pathways altered by Aβ42 presentation. The results support evidence on the involvement of mitochondrial proteins in Aβ42 responses and define potential mechanisms of α7 nAChR mediated amyloid toxicity. These findings can inform pharmacological strategies for drug design and treatment against amyloid disease.

Correlation and the omitted variable: A tale of two prices

AbstractWe offer a new perspective on the low‐beta anomaly by acknowledging the omitted‐variable problem in the correlation component of beta: Correlation is “plagued” by firm size (the omitted variable) to exhibit a negative price. Once isolating the size impact, a hidden positive price emerges for the size‐orthogonalized component of correlation. Further analyses suggest that (a) the positive price of the size‐orthogonalized component is not due to mispricing, supporting the return comovement‐based pricing channel; (b) the negative price of the size‐explained component is related to illiquidity and coskewness.; (c) the omitted‐variable problem also applies to the pricing of beta.

Experimental analyses of diversity partitioning in southern hemisphere algal communities.

Understanding how biodiversity and its components of alpha, beta, and gamma vary over spatial and temporal scales and across communities is crucial to mitigating stressors of ecosystems. Marine communities present several problems in partitioning diversity over fine spatial scales, such as tidal zones, and temporal scales relating to seasonal occurrences of species and recovery responses to impacts. This study uses an experimental approach to test disturbance effects on beta diversity in algal communities in southern New Zealand. Dominant canopies in mid-shore Hormosira banksii and low-shore Durvillaea poha communities were removed and diversity metrics assessed, including additive partitioning, permutational dispersion, and nestedness and turnover analyses. Over 2years, 258 species were found. Species richness was greater where canopies remained intact in Hormosira communities compared to removal plots, but, in Durvillaea communities, controls and removals had similar richness. In both communities, β-diversity was 1.5-3.9 times greater than α-diversity, with the temporal component βt being 1.2-2.4 × greater than the spatial component. Hormosira communities exhibited high nestedness, with species in removal plots being a subset of those in controls. In Durvillaea communities, however, turnover was high and nestedness low, because removal plots had a different species assemblage than controls. Multivariate analyses showed that species occurrences and abundances remained different in controls and removals in both communities over 2years. Differences in diversity components between communities were related to environmental differences to which they are exposed, including desiccation and wave forces, and the relative importance of facilitation and competition in the different communities.

Alpha Beta Risk and Stock Returns—A Decomposition Analysis of Idiosyncratic Volatility with Conditional Models

The variance of stock returns is decomposed based on a conditional Fama–French three-factor model instead of its unconditional counterpart. Using time-varying alpha and betas in this model, it is evident that four additional risk terms must be considered. They include the variance of alpha, the variance of the interaction between the time-varying component of beta and factors, and two covariance terms. These additional risk terms are components that are included in the idiosyncratic risk estimate using an unconditional model. By investigating the relation between the risk terms and stock returns, we find that only the variance of the time-varying alpha is negatively associated with stock returns. Further tests show that stock returns are not affected by the variance of time-varying beta. These results are consistent with the findings in the literature identifying return predictability from time-varying alpha rather than betas.

CAPM, components of beta and the cross section of expected returns

Abstract This paper demonstrates that a conditional version of the Capital Asset Pricing Model (CAPM) explains the cross section of expected returns, just as well as the three factor model of Fama and French. This is achieved by measuring beta (systematic risk) with short-, medium- and long-run components. The short-run component of beta is computed from daily returns over the prior year, while the medium-run beta component is from daily returns over the prior 5 years, and the long-run component from monthly returns over the prior 10 years.

A meta‐analysis of nestedness and turnover components of beta diversity across organisms and ecosystems

AbstractAimThe number of studies investigating the nestedness and turnover components of beta diversity has increased substantially, but our general understanding of the drivers of turnover and nestedness remains elusive. Here, we examined the effects of species traits, spatial extent, latitude and ecosystem type on the nestedness and turnover components of beta diversity.LocationGlobal.Time period1968–2017.Major taxa studiedFrom bacteria to mammals.MethodsFrom the 99 studies that partition total beta diversity into its turnover and nestedness components, we assembled 269 and 259 data points for the pairwise and multiple site beta‐diversity metrics, respectively. Our data covered a broad variation in species dispersal type, body size and trophic position. The data were from freshwater, marine and terrestrial realms, and encompassed geographical areas from the tropics to near polar regions. We used linear modelling as a meta‐regression tool to analyse the data.ResultsPairwise turnover, multiple site turnover and total beta diversity all decreased significantly with latitude. In contrast, multiple site nestedness showed a positive relationship with latitude. Beta‐diversity components did not generally differ among the realms. The turnover component and total beta diversity increased with spatial extent, whereas nestedness was scale invariant for pairwise metrics. Multiple site beta‐diversity components did not vary with spatial extent. Surprisingly, passively dispersed organisms had lower turnover and total beta diversity than flying organisms. Body size showed a relatively weak relationship with beta diversity but had important interactions with trophic position, thus also affecting beta diversity via interactive effects. Producers had significantly higher average pairwise turnover and total beta diversity than carnivores.Main conclusionsThe present results provide evidence that species turnover, being consistently the larger component of total beta diversity, and nestedness are related to the latitude of the study area and intrinsic organismal features. We showed that two beta‐diversity components had generally opposing patterns with regard to latitude. We highlight that beta‐diversity partition may give additional insights into the underlying causes of spatial variability in biotic communities compared with total beta diversity alone.

Generalized Single-Index Models: The EFM Approach

Generalized single-index models are natural extensions of linear models and circumvent the so-called curse of dimensionality. They are becoming increasingly popular in many scientific fields including biostatistics, medicine, economics and finan- cial econometrics. Estimating and testing the model index coefficients beta is one of the most important objectives in the statistical analysis. However, the commonly used assumption on the index coefficients, beta = 1, represents a non-regular problem: the true index is on the boundary of the unit ball. In this paper we introduce the EFM ap- proach, a method of estimating functions, to study the generalized single-index model. The procedure is to first relax the equality constraint to one with (d - 1) components of beta lying in an open unit ball, and then to construct the associated (d - 1) estimating functions by projecting the score function to the linear space spanned by the residuals with the unknown link being estimated by kernel estimating functions. The root-n consistency and asymptotic normality for the estimator obtained from solving the re- sulting estimating equations is achieved, and a Wilk's type theorem for testing the index is demonstrated. A noticeable result we obtain is that our estimator for beta has smaller or equal limiting variance than the estimator of Carroll et al. (1997). A fixed point iterative scheme for computing this estimator is proposed. This algorithm only involves one-dimensional nonparametric smoothers, thereby avoiding the data sparsity problem caused by high model dimensionality. Numerical studies based on simulation and on applications suggest that this new estimating system is quite powerful and easy to implement.

CARACTERISTICS OF TIME AND FREQUENCY EEG PATTERN IN CHILDREN AND ADOLESCENTS LIVING IN THE NORTH IN DIFFERENT AGE PERIODS

Features of CNS development have been investigated in children and adolescents living under the severe ecological conditions in the North of Russia. The original method for estimating a time structure of the EEG frequency components interrelations was used to study the dynamics of maturation of bioelectrical brain activity pattern and age-related changes of the interplay between the main EEG rhythms. It was found that the statistical structure of the interaction of the frequency components of EEG is undergoing a significant restructuring with age and has certain topography and gender differences. The period from 7 to 18 years of age is marked by decrease the probability of interaction of wave components of the main EEG frequency bands with components of delta and theta bands while simultaneously increasing interaction with the components of beta and alpha2 frequency bands. The dynamics of studied indices EEG manifested in the parietal, temporal and occipital regions of the cerebral cortex to the greatest extent. The largest sex-related differences in the EEG parameters occur in puberty. Functional core of the wave components interaction that maintain the structure of the frequency-temporal EEG pattern is formed to 16-18 years in girls in alpha2-beta1 range, while in boys - in alpha1-alpha2 range. Intensity of age-related rearrangements of the EEG pattern reflects the gradual maturation of electrogenesis in different brain structures and has individual features due to both genetic and environmental factors. Obtained quantitative indicators of formation with age of dynamic relationships between basic EEG rhythms permit to reveal children with disturbed or delayed development of the central nervous system.

CAPM, Components of Beta and the Cross Section of Expected Returns

This paper demonstrates that a conditional version of the Capital Asset Pricing Model (CAPM) explains the cross section of expected returns, just as well as the three factor model of Fama and French. This is achieved by measuring beta (systematic risk) with short-, medium- and long-run components. The short-run component of beta is computed from daily returns over the prior year, while the medium-run beta component is from daily returns over the prior 5 years, and the long-run component from monthly returns over the prior 10 years.

Cash Flow and Discount Rate Risk in Up and Down Markets: What Is Actually Priced?

AbstractWe test whether asymmetric preferences for losses versus gains affect the prices of cash flow versus discount rate risk. We construct a return decomposition distinguishing cash flow and discount rate betas in up and down markets. Using U.S. data, we find that downside cash flow and discount rate betas carry the largest premia. Downside cash flow risk is priced consistently across different samples, periods, and return decomposition methods. It is the only component of beta with significant out-of-sample predictive ability. Downside cash flow premia mainly occur for small stocks, while large stocks are compensated for symmetric cash-flow-related risk.

CAPM, Components of Beta and the Cross Section of Expected Returns

This paper demonstrates that a conditional version of the Capital Asset Pricing Model (CAPM) explains the cross section of expected returns, just as well as the three factor model of Fama and French. This is achieved by measuring beta (systematic risk) with short-, medium- and long-run components. The short-run component of beta is computed from daily returns over the prior year. While the medium-run beta component is from daily returns over the prior 5 years and the long-run component from monthly returns over the prior 10 years. More immediate changes in risk such as changes in portfolio characteristics are captured in the short-run beta component, whereas, more slowly changing risk due to the business cycle is captured in the medium- and long-run beta components.

Bond risk, bond return volatility, and the term structure of interest rates

Abstract This paper explores the time variation in the bond risk, as measured by the covariation of bond returns with stock returns and consumption growth, and in the volatility of bond returns. A robust stylized fact in empirical finance is that the spread between the yields on long- and short-term bonds forecasts future excess returns on bonds at varying horizons positively; in addition, the short-term nominal interest rate forecasts both the stock return volatility and the exchange rate volatility positively. This paper presents evidence that movements in both the short-term nominal interest rate and the yield spread are positively related to changes in the subsequent realized bond risk and bond return volatility. The yield spread appears to proxy for business conditions, while the short rate appears to proxy for inflation and economic uncertainty. A decomposition of bond betas into a real cash flow risk component and a discount rate risk component shows that yield spreads have offsetting effects in each component. A widening yield spread is correlated with a reduced cash-flow (or inflationary) risk for bonds, but it is also correlated with a larger discount rate risk for bonds. The short rate only forecasts the discount rate component of the bond beta.

Nonlinear Optical Properties of Stacked Conjugated Systems

We study linear and nonlinear optical properties of two push-pull polyenes stacked in head to head (HtH) and head to tail (HtT) configurations, at different stacking angles within the Pariser-Parr-Pople model using exact diagonalization method. By varying the stacking angle between the polyenes, we find that the optical gap varies marginally, but transition dipoles show large variations. We find that the dominant first-order hyperpolarizability component beta(XXX) for HtH arrangement and beta(YYY) for HtT arrangement strongly depend on the distance of separation between molecules, while the other smaller component beta(XYY) for HtH arrangement and beta(XXY) for HtT arrangement) does not show this variation with distance. We find that the beta(XXX) for HtH configuration shows a maximum at an angle away from 0, in contrast with the oriented gas model. This angle varies with distance between the polyenes, and at large distance it falls to 0. The ratio of all components of beta of a dimer to monomer is less than two for HtH configuration for all angles. But for HtT configurations the ratio of the dominant beta component is greater than two at large angles. Our ZINDO study on two monomers (4-hydroxy-4'-nitroazobenzene) connected in a nonconjugative fashion shows a linear increase in vertical bar(beta) over right arrow (av)vertical bar without much red shift in optical gap. There is a linear increase in vertical bar(beta) over right arrow (av)vertical bar with increase in number of monomers connected nonconjugatively without resulting in a red shift in optical gap.

Some Identification Problems in the Cointegrated Vector Autoregressive Model

An analysis of some identification problems in the cointegrated VAR is given. We give a new criteria for identification by linear restrictions on individual relations which is equivalent to the rank condition. We compare the asymptotic distribution of the estimators of alpha and beta when they are identified by linear restrictions on alpha and when they are identified by linear restrictions on alpha in which case a component of beta is asymptotically Gaussian. Finally we discuss identification of shocks by introducing the contemporaneous and permanent effect of a shock and the distinction between permanent and transitory shocks, which allows one to identify permanent shocks from the long-run variance and transitory shocks from the short-run variance.

Peroxisome Proliferator-Activated Receptor Gamma Promotes Lymphocyte Survival Via a Mitochondrial Pathway Mediated by GSK-3 Beta.

Peroxisome proliferator-activated receptor (PPAR) gamma is a nuclear hormone receptor involved in maintaining glucose and fatty acid homeostasis. Besides its metabolic functions, the receptor has also been implicated in tumorigenesis. Ligands of PPAR gamma induce apoptosis in several types of tumor cells including lymphomas, leading to the proposal that these ligands may be used as anti-cancer agents. However, apoptosis induction requires high doses of ligands, suggesting the effect may not be receptor-dependent. Previously, we reported that PPAR gamma is expressed in human primary T cell lymphoma tissues and activation of PPAR gamma with low doses of ligands protects lymphoma cells from serum starvation-induced apoptosis. The prosurvival effect of PPAR gamma is linked to its actions on mitochondria. In serum-deprived cells, PPAR gamma attenuates the decline in ATP, reduces mitochondrial hyperpolarization and limits the amount of reactive oxygen species (ROS) in favor of cell survival (Yang et al, Am J Pathol , 170, 722–32, 2007). In the current study, we investigated the molecular mechanisms by which PPAR gamma maintains mitochondria homeostasis. We demonstrated that PPAR gamma modulates the activities of two key components of Wnt signaling pathway, Fzd4 and GSK-3 beta. The receptor up-regulates the mRNA expression of Fzd4, a cell surface receptor of Wnt, through a conserved PPAR-response element (PPRE) in the promoter region of the Fzd4 gene. Moreover, PPAR gamma suppresses the activation of GSK-3 beta, a downstream inhibitory serine/threonine kinase, by maintaining its phosphorylation at serine 9 and decreasing its association with mitochondria. Downregulation of GSK-3 beta activity results in maintenance of mitochondrial membrance potential and suppression of ROS production in growth factor-deprived cells. Our studies revealed a novel interaction between PPAR gamma and Wnt signaling in lymphocyte survival. Since Wnt signaling plays an important role in tumorigenesis, our studies highlight the need for further investigation into the role of PPAR gamma in cancer prior to widespread use of its agonists as anticancer therapeutics.

Blockade of avidity and focal clustering of β 2-integrin by cysteinyl leukotriene antagonism attenuates eosinophil adhesion

Cysteinyl leukotriene (cysLT) antagonism attenuates migration of eosinophils into airways during immune challenge in human subjects and animal models. The intracellular signaling mechanism by which this occurs has not been elucidated. We sought to determine the relative efficacy and mechanism by which 5-lipoxygenase (5-LO) inhibition and cysLT(1) receptor (cysLT(1)R) antagonism block beta(2)-integrin adhesion in isolated human eosinophils in vitro. Human blood eosinophils were isolated by means of immunomagnetic separation. Upregulation of CD11b expression, active conformation of CD11b, and focal clustering of beta(2)-integrin caused by IL-5, eotaxin-1 or leukotriene (LT) B(4) was assessed by means of flow cytometry and confocal microscopy. The effect and mechanism of cysLT(1)R or 5-LO blockade on these components of beta(2)-integrin adhesion were determined. Montelukast, a cysLT(1)R antagonist, and AA861, a 5-LO enzyme inhibitor, blocked (1) avidity of beta(2)-integrin, (2) beta(2)-integrin-mediated adhesion to intercellular adhesion molecule 1, and (3) focal clustering of CD11b elicited by LTB(4). However, adhesion caused by either IL-5 or eotaxin-1 was not attenuated for eosinophils pretreated with either montelukast or AA861. Our data demonstrate that (1) LTB(4) causes autocrine upregulation of adhesion through secretion of cysLTs, and (2) blockade of cysLT(1)R blocks the avidity and focal clustering of CD11b/CD18 for eosinophils activated by LTB(4) but not by IL-5 or eotaxin-1. Unlike cysLT-induced adhesion, adhesion caused by IL-5 or eotaxin-1 is not regulated through the cysLT(1)R, suggesting that cysLTs have specific but limited potential to upregulate eosinophil adhesion.

Enhancement of Quadratic Nonlinearity via Multiple Hydrogen-Bonded Supramolecular Complex Formation

The formation and quadratic nonlinearity of a multiple hydrogen-bonded 1:1 supramolecular complex 1.2 between the 2,6-diaminopyridine-based Lambda-shaped molecule, 1, and ferrocenyl barbituric acid, 2, in solution have been investigated by the hyper-Rayleigh scattering (HRS) and NMR techniques. A 6-fold increase in the molecular hyperpolarizability (beta) of the complex 1.2 over the sum of the molecular hyperpolarizabilities of the components 1 and 2 is seen. Such a significant enhancement in beta is attributed to the alignment of the molecular dipoles of 1 and 2 in the 2D plane leading to the creation of a large dipole moment in the plane of the supramolecular complex. Depolarized HRS experiments led to the determination of the in-plane polarization components of beta of the supramolecular complex 1.2. The component of beta in the direction of the dipole moment is large. This investigation exemplifies the role of multiple hydrogen bonds in stabilizing a 2D supramolecular architecture leading to a large enhancement of molecular nonlinearity.