Search Results (26)

This study proposes an extension of Seasonal Autoregressive Integrated Moving Average models with exogenous regressors (SARIMAX) by incorporating skew-normal and zero-inflated skew-normal error structures to better accommodate asymmetry and excess zeros in time series data. The proposed framework demonstrates improved flexibility and robustness compared to traditional Gaussian-based models. Simulation experiments reveal that the skewness parameter significantly affect forecasting accuracy, with reductions in mean absolute error (MAE) and root mean square error (RMSE) observed across both positively and negatively skewed scenarios. Notably, in negative-skew contexts, the model achieved an MAE of 0.40 and RMSE of 0.49, outperforming its symmetric-error counterparts. The inclusion of zero-inflation probabilities further enhances model performance in sparse datasets, yielding superior values in goodness-of-fit criteria such as the Akaike Information Criterion (AIC) and Bayesian Information Criterion (BIC). To illustrate the practical value of the methodology, a real-world case study is presented involving the modeling of optical density (OD₆₀₀) data from Escherichia coli during stationary-phase growth. A SARIMAX(1,1,1) model with skew-normal errors was fitted to 200 time-stamped absorbance measurements, revealing significant positive skewness in the residuals. Bootstrap-derived confidence intervals confirmed the significance of the estimated skewness parameter ($\alpha =14.033$ with 95% CI [12.07, 15.99]). The model outperformed the classical ARIMA benchmark in capturing the asymmetry of the stochastic structure, underscoring its relevance for biological, environmental, and industrial applications in which non-Gaussian features are prevalent. Full article

The flight feather rachis is a lightweight, anisotropic structure that must withstand asymmetric aerodynamic loads generated during flapping flight—particularly under unidirectional compression during the wing downstroke. To accommodate this spatiotemporal loading regime, the rachis exhibits refined internal organization, especially along the dorsoventral axis. In this study, we used finite element modeling (FEM) to investigate how dorsoventral polarization in cortical keratin allocation modulates the mechanical performance of shaft-like structures under bending. All models were constructed with conserved second moments of area and identical material properties to isolate the effects of spatial material placement. We found that dorsal-biased reinforcement delays yield onset, enhances strain dispersion, and promotes elastic recovery, while ventral polarization leads to premature strain localization and plastic deformation. These outcomes align with the dorsally thickened rachises observed in flight-specialized birds and reflect their adaptation to asymmetric aerodynamic forces. In addition, we conducted a conceptual exploration of radial (cortex–medulla) redistribution, suggesting that even inner–outer asymmetry may contribute to directional stiffness tuning. Together, our findings highlight how the flight feather rachis integrates cortical material asymmetry to meet directional mechanical demands, offering a symmetry-informed framework for understanding biological shaft performance. Full article

Asymmetric deformation has been observed along the Altyn Tagh Fault (ATF), the northern boundary of the Tibetan Plateau. Several mechanisms have been proposed to explain this asymmetry, including contrasts in crustal strength, lower crust/upper mantle rheology, deep fault dislocation shifts, and dipping fault geometry; however, the real scenario remains debated. This study utilizes a time series Interferometric Synthetic Aperture Radar (InSAR) technique to investigate spatially variable asymmetries across the western section of the ATF (83–89°E). We generated a high-resolution three-dimensional (3D) crustal velocity field from Sentinel-1 data for the northwestern Tibetan Plateau (~82–92°E; 33–40°N). Our results confirm that pronounced greater deformations within the Tibetan Plateau occur only along the westernmost section of the ATF (83–85.5°E). We propose this asymmetry is primarily driven by a splay fault system within a transition zone, bounded by the ATF in the north and the Margai Caka Fault (MCF)–Kunlun Fault (KLF) in the south, which accommodates an east–west extension in the central Tibetan Plateau while transferring sinistral shear to the KLF. The concentrated strain observed along the ATF and MCF–KLF lends more support to a block-style eastward extrusion model, rather than a continuously deforming model, for Tibetan crustal kinematics. Full article

This paper provides a critical analysis of the molecular mechanisms presently used to explain transcriptional strand asymmetries of single base substitution (SBS) signatures observed in cancer genomes curated at the Catalogue of Somatic Mutations in Cancer (COSMIC) database (Wellcome Trust Sanger Institute). The analysis is based on a deaminase-driven reverse transcriptase (DRT) mutagenesis model of cancer oncogenesis involving both the cytosine (AID/APOBEC) and adenosine (ADAR) mutagenic deaminases. In this analysis we apply what is known, or can reasonably be inferred, of the immunoglobulin somatic hypermutation (Ig SHM) mechanism to the analysis of the transcriptional stand asymmetries of the COSMIC SBS signatures that are observed in cancer genomes. The underlying assumption is that somatic mutations arising in cancer genomes are driven by dysregulated off-target Ig SHM-like mutagenic processes at non-Ig loci. It is reasoned that most SBS signatures whether of “unknown etiology” or assigned-molecular causation, can be readily understood in terms of the DRT-paradigm. These include the major age-related “clock-like” SBS5 signature observed in all cancer genomes sequenced and many other common subset signatures including SBS1, SBS3, SBS2/13, SBS6, SBS12, SBS16, SBS17a/17b, SBS19, SBS21, as well as signatures clearly arising from exogenous causation. We conclude that the DRT-model provides a plausible molecular framework that augments our current understanding of immunogenetic mechanisms driving oncogenesis. It accommodates both what is known about AID/APOBEC and ADAR somatic mutation strand asymmetries and provides a fully integrated understanding into the molecular origins of common COSMIC SBS signatures. The DRT-paradigm thus provides scientists and clinicians with additional molecular insights into the causal links between deaminase-associated genomic signatures and oncogenic processes. Full article

The data envelopment analysis is related to a non-parametric mathematical tool used to assess the relative efficiency of productive units. In different studies on productive efficiency, it is common to employ semi-parametric procedures in two stages to determine whether any exogenous factors of interest affect the performance of productive units. However, some of these procedures, particularly those based on conventional statistical inference, generate inconsistent estimates when dealing with incoherent data-generating processes. This inconsistency arises due to the efficiency scores being limited to the unit interval, and the estimated scores often exhibit serial correlation and have limited observations. To address such inconsistency, several strategies have been suggested, with the most well-known being an algorithm based on a parametric bootstrap procedure using the truncated normal distribution and its regression model. In this work, we present a modification of this algorithm that utilizes the beta distribution and its regression structure. The beta model allows for better accommodation of asymmetry in the data distribution. Our proposed algorithm introduces inferential characteristics that are superior to the original algorithm, resulting in a more statistically coherent data-generating process and improving the consistency property. We have conducted computational experiments that demonstrate the improved results achieved by our proposal. Full article

Network layer multicast is a powerful method for transmitting data from sources to multiple group members. When joining a multicast group, a group member first sends a request to a designated router (DR). Then, the DR selects a node in the existing multicast tree (known as a multicast joining node, or MJN) to establish a multicast distribution path from the MJN to itself. The MJN selection method runs on the DR and has a significant impact on the distribution of the multicast tree, that directly affects the load distribution in the network. However, the current MJN selection method cannot effectively detect the load status of the downlink multicast path in the case of asymmetric routing, leading to network congestion and limiting the number of multicast groups that the network can accommodate (multicast capacity). To solve this problem, we propose an MJN selection method based on the reverse shortest path tree (RSPT). RSPT can effectively detect the load status of downlink multicast paths in case of routing asymmetry. Based on the detection results of RSPT, DR can select the MJN with the lowest path load to join the multicast tree. Our experimental results indicate that compared to existing multicast methods, our method has a lower cost and delay, and can effectively balance the network load in the case of asymmetric routing, increasing multicast capacity by more than two times. Full article

A general review of the crystalline solutions of the generalized Skyrmemodel and their application to the study of cold nuclear matter at finite density and the Equation of State (EOS) of neutron stars is presented. For the relevant range of densities, the ground state of the Skyrmemodel on the three torus is shown to correspond to configurations with different symmetries, with a sequence of phase transitions between such configurations. The effects of nonzero finite isospin asymmetry are taken into account by the canonical quantization of isospin collective coordinates, and some thermodynamical and nuclear observables (such as the symmetry energy) are computed as a function of the density. We also explore the extension of the model to accommodate strange degrees of freedom, and find a first-order transition for the condensation of kaons in the Skyrme crystal background in a thermodynamically consistent, non-perturbative way. Finally, an approximate EOS of dense matter is constructed by fitting the free parameters of the model to some nuclear observables close to saturation density, which are particularly relevant for the description of nuclear matter. The resulting neutron star mass–radius curves already reasonably satisfy current astrophysical constraints. Full article

Based on fracture mechanics theory, a finite element method was used to determine the stress intensity factors of the inclined crack on the inner surface of the pipe under axial compression load and external pressure. The effects of different influencing factors on the stress intensity factor along the crack front considering crack closure were systematically explored, which were different to those under internal pressure. The effects of high aspect ratio on K_II, the crack inclination asymmetry caused by curvature and the effects of the friction coefficient on the stress intensity factors of the pipe with an inclined inner surface crack under axial compression load and external pressure were explored in this paper. To be fit for defect assessment, the solutions for stress intensity factors K_II and K_III were derived, and new correction factors f_θ and f_μ were proposed in the empirical solutions to accommodate the crack inclination asymmetry and the friction coefficient, respectively. Full article

This paper presents an important theorem, which shows that, heading from the moments of the standard normal distribution, one can generate density functions originating a family of models. Additionally, we discussed that different random variable domains are achieved with transformations. For instance, we adopted the moment of order two, from the proposed theorem, and transformed it, which enabled us to exemplify this class as a unit distribution. We named it as Alpha-Unit (AU) distribution, which contains a single positive parameter $\alpha$ ($\mathrm{AU}\left(\alpha \right)\in [0,1]$). We presented its properties and demonstrated two estimation methods for the $\alpha$ parameter, the maximum likelihood estimator (MLE) and uniformly minimum-variance unbiased estimator (UMVUE) methods. In order to analyze the statistical consistency of the estimators, a Monte Carlo simulation study was carried out, in which the robustness was demonstrated. As a real-world application, we adopted two sets of unit data, the first regarding the dynamics of Chilean inflation in the post-military period, and the other one regarding the daily maximum relative humidity of the air in the Atacama Desert. In both cases presented, the AU model is competitive, whenever the data present a range greater than 0.4 and extremely heavy asymmetric tail. We compared our model with other commonly used unit models, such as the beta, Kumaraswamy, logit-normal, simplex, unit-half-normal, and unit-Lindley distributions. Full article

Magnetic Resonance Imaging (MRI) is a noninvasive technique used in medical imaging to diagnose a variety of disorders. The majority of previous systems performed well on MRI datasets with a small number of images, but their performance deteriorated when applied to large MRI datasets. Therefore, the objective is to develop a quick and trustworthy classification system that can sustain the best performance over a comprehensive MRI dataset. This paper presents a robust approach that has the ability to analyze and classify different types of brain diseases using MRI images. In this paper, global histogram equalization is utilized to remove unwanted details from the MRI images. After the picture has been enhanced, a symlet wavelet transform-based technique has been suggested that can extract the best features from the MRI images for feature extraction. On gray scale images, the suggested feature extraction approach is a compactly supported wavelet with the lowest asymmetry and the most vanishing moments for a given support width. Because the symlet wavelet can accommodate the orthogonal, biorthogonal, and reverse biorthogonal features of gray scale images, it delivers higher classification results. Following the extraction of the best feature, the linear discriminant analysis (LDA) is employed to minimize the feature space’s dimensions. The model was trained and evaluated using logistic regression, and it correctly classified several types of brain illnesses based on MRI pictures. To illustrate the importance of the proposed strategy, a standard dataset from Harvard Medical School and the Open Access Series of Imaging Studies (OASIS), which encompasses 24 different brain disorders (including normal), is used. The proposed technique achieved the best classification accuracy of 96.6% when measured against current cutting-edge systems. Full article

Compartmentalization, together with transbilayer and lateral asymmetries, provide the structural foundation for functional specializations at the cell surface, including the active role of the lipid microenvironment in the modulation of membrane-bound proteins. The chemical synapse, the site where neurotransmitter-coded signals are decoded by neurotransmitter receptors, adds another layer of complexity to the plasma membrane architectural intricacy, mainly due to the need to accommodate a sizeable number of molecules in a minute subcellular compartment with dimensions barely reaching the micrometer. In this review, we discuss how nature has developed suitable adjustments to accommodate different types of membrane-bound receptors and scaffolding proteins via membrane microdomains, and how this “effort-sharing” mechanism has evolved to optimize crosstalk, separation, or coupling, where/when appropriate. We focus on a fast ligand-gated neurotransmitter receptor, the nicotinic acetylcholine receptor, and a second-messenger G-protein coupled receptor, the cannabinoid receptor, as a paradigmatic example. Full article

A novel damage model for concrete has been developed, which can reflect the complex hysteresis phenomena of concrete under cyclic loading, as well as other nonlinear behaviors such as stress softening, stiffness degradation, and irreversible deformation. The model cleverly transforms the complex multiaxial stress state into a uniaxial state by equivalent strain, with few computational parameters and simple mathematical expression. The uniaxial tensile and compressive stress–strain curves matching the actual characteristics are used to accommodate the high asymmetry of concrete in tension and compression, respectively. Meanwhile, an unloading path and a reloading path that can reflect the hysteresis effect under cyclic loading of concrete are established, in which the adopted expressions for the loading and unloading characteristic points do not depend on the shape of the curve. The proposed model has a concise form that can be easily implemented and also shows strong generality and flexibility. Finally, the reliability and correctness of the model are verified by comparing the numerical results with the three-point bending beam test, cyclic loading test, and a seismic damage simulation of the Koyna gravity dam. Full article

The clinical importance of peripheral refraction as a function of accommodation has become increasingly evident in the last years with special attention given to myopia control. Low order ocular aberrations were measured with a Hartmann–Shack aberrometer in a sample of 28 young emmetropic subjects. A stationary Maltese cross was presented at 2.5 D and 5.0 D of accommodative demand and at 0°, 10° and 20° of eccentricity in the horizontal visual field under two different illumination conditions (white and red light). Wavefront data for a 3 mm pupil diameter were analyzed in terms of the vector components of refraction (M, J0 and J45) and the relative peripheral refractive error (RPRE) was calculated. M was myopic at both accommodative demands and showed a statistically significant myopic increase with red illumination. No significant change in J0 and J45 was found with accommodation nor between illumination conditions. However, J0 increased significantly with eccentricity, exhibiting a nasal-temporal asymmetry. The RPRE was myopic at both accommodation demands and showed a statistically significant hyperopic shift at 20° in the nasal retina. The use of red light introduced statistically and clinically significant changes in M, explained by the variation of the ocular focal length under a higher wavelength illumination, increasing the experimental accommodative demand. These findings may be of relevance for research exploring peripheral refraction under accommodation, as the choice of target illumination is not trivial. Full article

Compared with the conventional hotel providing a standardized service, individual supply on an accommodation-sharing platform makes consumers uncertain about service quality, which is mainly caused by information asymmetry between the consumers and individual hosts. In this paper, we develop a game-theoretic model to study the accommodation-sharing platform’s optimal quality information disclosure and its determining factors with consideration of consumer uncertainty. We find that it is optimal to provide either opaque, i.e., completely uninformative, or transparent, i.e., fully informative, quality information. We also examine the impacts of the incumbent hotel and market heterogeneity on the platform’s quality disclosure. The results show that market heterogeneity and the hotel’s service cost jointly affect the platform’s information disclosure strategy. In general, the sharing platform provides opaque information when market heterogeneity is relatively low but provides transparent information when market heterogeneity is relatively high. However, when market heterogeneity is medium, the hotel’s service cost plays a key role in affecting its pricing strategy, hence the information disclosure strategy of the platform. Specifically, a sufficiently high price of the hotel prompts the platform to disclose transparent information. These findings provide guidance for sharing platforms to design their information disclosure systems. Full article

Rural areas and peripheral borderland territories are experiencing socio-economic marginalization featuring depopulation, population aging, and an increasing inequality gap in the quality of life compared to cities. Integrated rural tourism is argued to be ideal for supporting the well-being of rural communities, providing an additional income, decreasing unemployment, offering new and appealing jobs out of traditional rural activities, while preserving the conventional lifestyle. In this study, we discovered the tourism capacity of rural borderland territories affected by cross-border tourism using the data on the geography of cross-border movements, the distribution of tourist sights, and the density of tourist accommodation facilities. The geographical scope of the study covered two cross-border coastal regions—the Russian–Polish region on the Baltic Sea and the Russian–Kazakh region on the Caspian Sea. The statistical and geoinformation analysis were used to allocate areas of prospecting rural tourism integrated with cross-border movement. The research results on the development and distribution of tourist infrastructure suggest that: the rural territories of these regions feature tourist attractions and accommodation facilities at a different level of density and remoteness from the border crossing; each cross-border region is featuring different types of travel restrictions for tourists; and both border-land territories show asymmetry by the more active Russian tourists traveling abroad. Each of the regions under consideration is attractive for cross-border tourism while having different degrees of penetration of tourist flows into the interior territories and coverage of rural areas. The study resulted in a tourist flow model that allows integrating rural areas. Full article