Search Results (588)

This paper investigates the constrained particle dynamics on rotational surfaces within the 4-dimensional pseudo-Euclidean space $E_2^4$, characterized by its second-order metric signature of index 2. A comprehensive Lagrangian and Hamiltonian formulation is developed to construct the specific energy and specific angular momentum as conserved Noetherian charges along timelike geodesics. By integrating Clairaut’s theorem into the geodesic flow equations, explicit analytical expressions for these fundamental physical invariants are obtained. This work explores the structural relationship between the surface’s continuous rotational symmetries and the mechanical stability of the geodesic flow. A mathematical resolution for the signature transitions manifested via the appearance of the imaginary unit i on elliptic surfaces is provided through analytic continuation and distinct coordinate charts. Furthermore, by reducing the second-order geodesic flow to a one-dimensional energy balance equation, the exact effective potentials ($V_{eff}$) are derived, and the local orbital stability zones are analytically verified via second-order radial derivatives (${\partial }_s^2{V}_{eff}>0$). These embedded geometric configurations are shown to share qualitative features with the equatorial slices of rotating relativistic spacetimes. Consequently, they can serve as potential geometric toy-models for studying the dynamics of photon spheres, ergosphere oscillations, and innermost stable circular orbits in extreme gravitational fields. Full article

Accurate interpretation of radiation sensor decay data is important for environmental monitoring, site remediation, radiation metrology, detector quality assurance, and nuclear data evaluation. When the original gamma spectrometry records are unavailable, a published decay plot may be the only source that can be reanalyzed independently. This study presents a reproducible reduced-data workflow for testing half-life estimates from a digitized ¹⁹⁸Au decay dataset. A weighted exponential fit to the digitized data points reproduces the published room-temperature half-life, indicating that the main decay scale is retained in the figure-level dataset. The analysis then tests how the fitted result changes under plausible figure-level effects, including baseline-like offsets, time-axis reconstruction, finite-window leverage, and ratio-based robustness checks using pairwise summaries and Steiner’s most frequent value statistics. The no-offset fit is locally well constrained, but small constant offsets can shift the fitted half-life because the normalization, decay constant, and residual baseline are partly degenerate over the limited time window. Toy Monte Carlo diagnostics show that some estimator shifts are expected for finite-window exponential data. This study does not revise recommended nuclear data or replace the original experiment. Instead, it shows how published radiation sensor decay data can be tested for reproducibility, identifiability, and sensitivity to analysis choices when only reduced or figure-level information is available. Full article

Recommender systems are widely used in e-commerce to model user preferences and deliver personalized services. However, conventional interaction-based recommendation approaches fail to fully capture users’ underlying motivations and emotional tendencies. User-generated reviews offer complementary sentiment information, yet integrating sentiment semantics with interaction modeling remains challenging due to feature heterogeneity and sparsity. This paper proposes a hybrid recommendation framework (HAIRec) that jointly models review sentiment and interaction information within a unified architecture. The model extracts sentiment representations, latent rating factors, user preference features, and item attributes through multi-source feature learning. To address the semantic heterogeneity between review sentiment and interaction behavior, a hierarchical heterogeneous feature fusion architecture is proposed. Specifically, a dual-level attention mechanism is designed to jointly model global feature importance and fine-grained semantic interactions, designed to facilitate multi-granularity preference learning across heterogeneous domains. In addition, a Deep & Cross Network V2 (DCN-V2) is adopted to explicitly and implicitly model high-order feature interactions. Extensive experiments are conducted on five real-world subcategories of the Amazon Product Dataset (including Movies and TV, Digital Music, Musical Instruments, Toys and Games, and Home and Kitchen). The experimental results demonstrate that the proposed HAIRec framework consistently outperforms several representative baselines (such as DeepCoNN, NARRE, and LightGCN). Notably, compared with the strong LightGCN benchmark, HAIRec achieves significant rating prediction improvements, reducing the Mean Squared Error (MSE) to 0.884 on Movies and TV, 0.882 on Digital Music, and 0.863 on Toys and Games, which corresponds to maximum performance gains of up to 7.14% in MSE reduction. Full article

The Hubble tension is usually formulated as a disagreement between two determinations of a single scalar parameter, $H_0$, within an exactly isotropic FLRW model. We develop a quantitative framework in which the tension is instead treated as a consistency test of the scalar FLRW compression of cosmological data in a homogeneous but anisotropically expanding Bianchi type I background. Beyond synthesizing established results on Bianchi I kinematics, null geodesics and optical propagation, the original contribution is a worked weak-shear, axisymmetric calculation that maps a specified shear history into a low-redshift luminosity-distance quadrupole. The calculation explicitly separates the direction-dependent redshift–affine-parameter mapping from the Jacobi-focusing contribution and then propagates the resulting distance quadrupole through an analytic polar-cap toy window. For freely decaying shear we obtain $A_D\left(z\right)=-B_{H0}+(2q_0-1)B_{H0}z/2+(5-q_0-18q_0^2+6j_0)B_{H0}{z}^2/12+\mathcal{O}(z^3,B_{H0}^2)$, where $B_{H0}=(H_{\Vert 0}-H_{\perp 0})/H_0$ and $j_0$ is the mean jerk parameter. A representative BBN limit, ${\mathrm{\Omega }}_{\sigma 0}\lesssim {10}^{-23}$, implies $|B_{H0}|\lesssim 9.5\times {10}^{-12}$ and a distance-modulus quadrupole below approximately $2.4\times {10}^{-11}$ mag at $z=0.15$. The early-Universe bound used in this comparison is adopted from previous work and is not itself a new result of the present analysis; the novelty is its propagation through the derived direction-dependent redshift and Sachs–Jacobi mapping into quantitative limits on the luminosity-distance quadrupole and on the catalog-window bias of an isotropic $H_0$ fit. By contrast, even a maximally aligned one-percent directional shift requires ${\mathrm{\Omega }}_{\sigma 0}\simeq 2.5\times {10}^{-5}$, while a shift comparable with the Planck 2018–SH0ES 2022 benchmark separation requires ${\mathrm{\Omega }}_{\sigma 0}\simeq 1.8\times {10}^{-3}$. Thus the minimal shear-only model cannot resolve the tension, although the framework supplies a falsifiable program for testing sustained late-time anisotropy with supernovae, BAO, distance-ladder measurements and future standard sirens. Full article

Biological research relies on the use of taxa, with species expressed in the form of a Latin binomial. Although taxa are commonly regarded as established entities, they actually represent hypotheses on the distribution of natural biological variation and may change their status as new systematic knowledge becomes available. A long-standing problem affecting systematics and taxonomy, with important consequences for other biological disciplines, is that a binomial itself conveys no information about the strength of the taxonomic hypothesis it represents. Here, we introduce the concept of a standardized heuristic index, named Turrill’s Omega Index (TOI), to estimate the degree of support for a taxonomic hypothesis. Turrill’s Omega Index is a single numerical value calculated by integrating four macro-categories of comparative data: Phenotype, Genealogy, Isolation, and Geography-Ecology. Turrill’s Omega Index provides a practical and reliable framework for quantifying the support for a taxonomic hypothesis, without requiring resolution of the long-standing debate surrounding species delimitation and species concepts. Accordingly, it has the potential to represent a valuable and transformative advance in systematics and taxonomy. In addition, TOI can support conservation decision-making by helping prioritize funding allocation among equally threatened taxa according to their degree of support. Full article

Free-energy-based variational principles provide a powerful framework for describing perception, inference, and decision making. The Free Energy Principle (FEP) is one prominent realization of this idea, but its standard formulation is usually expressed in terms of classical probabilistic generative models. Here, we propose an FEP-inspired, quantum-like variational approach by integrating Quantum State Over Time (QSOT), Schrödinger-bridge (SB) theory, and quantum logic into a unified framework. Cognitive evolution is formulated as the optimization of temporally extended quantum-like states under a composite action consisting of an SB-inspired path divergence, a cognitive free-energy functional, and context-dependent quantum-logical constraints with terminal target propositions. Contextual updating is modeled by time-dependent non-selective Lüders projections, while endogenous cognitive steering is represented by an internal control field. A minimal two-state toy model illustrates how these components jointly shape temporal quantum-like cognitive trajectories. The proposed framework provides a temporally extended quantum-like analogue of the variational structure underlying the FEP and suggests a general mathematical basis for modeling context-dependent cognitive dynamics. Full article

Background: Digital behavioral phenotyping of autism spectrum disorder (ASD) offers a promising approach for developing more scalable diagnostic frameworks across diverse global contexts. Machine learning (ML) models show promise for ASD diagnosis using behavioral videos, but critical questions remain regarding whether models trained on data from one country work in another, and how the background of the raters affects the accuracy. Our work addresses these questions by testing whether ML models can accurately diagnose ASD across different populations and rater groups. Methods: This work evaluates the performance of a supervised ML framework for binary classification of ASD versus non-ASD [speech, language and communication disorders (SLC) + neurotypical (NT)] in a cohort of 227 children in Bangladesh. We first assessed the cross-domain model transferability of a clinical-instrument-trained logistic regression model (LR-9) on behavioral ratings that were based on videos of Bangladeshi children interacting with caregivers and toys at two major child development centers in Dhaka, Bangladesh. We then trained five diverse classifiers (Logistic Regression, Random Forest, XGBoost, SVM, and RuleFit) on the full annotated Bangladeshi dataset. Using SHAP-based consensus elbow feature selection, we identified a compact set of features that maintained the performance. Finally, we developed ensemble models to improve predictive stability. Results: The LR-9 model, originally trained on U.S. clinical instrument data, was evaluated on video-based behavioral ratings from 214 Bangladeshi children. When tested on Bangladeshi clinician ratings, the LR-9 model achieved a sensitivity of 86.1% (95% CI: [0.78–0.93]) and AUC of 0.79 (95% CI: [0.73–0.86]). The distinction across rater groups was between trained raters (clinicians and students) and crowd workers, who showed lower sensitivity 28.5% (95% CI: [0.21, 0.39]). When tested on the aggregated ratings from all groups, the model achieved an AUC of 0.78 (95% CI: [0.72–0.84]). Inter-rater reliability followed the same pattern: individual agreement was fair (Krippendorff’s α = 0.26), but the multi-rater consensus was reliable (ICC(1,k) = 0.84), with Bangladeshi clinicians showing the highest agreement (α = 0.34) and crowd workers the lowest (α = 0.20). We then trained new models directly on the Bangladeshi ratings. All model types achieved similar AUC values (0.86–0.89), with overlapping confidence intervals. Using just 8–11 key behaviors kept the similar performance while cutting the features by 66–75%. Combining ensembles gave similar results (e.g., Bayesian averaging: AUC 0.88 [0.78, 0.95]) but with more stable predictions. Conclusion: This study provides evidence that mobile video-based ASD diagnosis can achieve comparable performance (AUC: 0.89 [0.76, 0.96]) to models trained on clinical instrument data. This work contributes to the development of broader adaptable autism detection tools, bypassing the dependence on traditional clinical instrument data. Full article

Existing evaluations of sandstone-hosted uranium deposits commonly describe ore-controlling troughs and faults qualitatively, which limits the quantitative characterization of structural ore-controlling elements and the prediction of favorable mineralization areas. This study proposes a relative geological time (RGT)-constrained method for quantitatively computing intra-stratal trough attributes and a 3D seismic-based workflow for trough–fault coupled structural favorability prediction in sandstone-hosted uranium exploration and applies this framework to the Qianjiadian uranium mining area. An interpreted-horizon-constrained RGT volume was constructed to extract stratal two-way travel time (TWT) slices, and multi-scale trough attributes were calculated from local TWT relief differences. Fault attributes were constructed from laterally smoothed fault-scan results to improve fault-response continuity. Known mineralized wells were used to calibrate trough and fault responses and to construct trough ore-controlling index (TOI) and fault ore-controlling index (FOI) volumes. The calibrated TOI and FOI volumes were then integrated to generate a coupled favorability index (CFI) volume for structural favorability prediction. High CFI values occur mainly near major fault zones and in areas with moderate trough responses, indicating favorable trough–fault coupled structural conditions for uranium mineralization. Blind-well validation shows that 15 of 20 blind wells agree with the CFI prediction, yielding an overall accuracy of 75.0% and an AUC of 0.85. The proposed method converts qualitative trough and fault ore-control knowledge into computable, mineralization-calibrated, and blind-well-validated 3D structural favorability results, supporting favorable-area selection and drilling deployment in sandstone-hosted uranium exploration. Full article

Decarbonization has been set as the ultimate target of the European energy policy, and, under this frame, Greece has substantially reformed its electricity mix over the last two decades. Yet, the rapid transition of the country’s electricity production system towards a model that strongly relies on non-controllable renewables, without improving its energy storage means, has caused several adverse impacts that reasonably raise serious concerns about its sustainability. Further questions arise when accounting for the projections and underlying assumptions reported in the National Energy and Climate Plan. In this vein, key policy, societal, technical, sustainability and science issues are discussed, involving the challenges, perspectives and potential drawbacks of Greece’s long-term energy planning. To reveal the critical role of storage, a toy simulation-optimization model is applied at the national scale to evaluate several scenarios of wind and solar P/V development under the premise of a theoretically fully decarbonized mix. This allows the exploration of trade-offs between energy storage and power capacity needs against key performance metrics (frequency and quantity of deficits and percentage of rejected renewable energy). Preliminary feasibility issues are also highlighted by considering alternative configurations of pumped hydropower storage units and associating their approximative investment costs with scale and geometry. Full article

Symbolic execution of embedded systems faces path explosion, Satisfiability Modulo Theories (SMT) solver bottlenecks, interrupt nondeterminism, and environment modeling complexity. Recent artificial intelligence (AI)-guided approaches using reinforcement learning, graph neural networks, and large language models improve exploration efficiency, yet all reason over raw symbolic states and ignore structural equivalences that arise from symmetry in embedded software. This paper presents S³E, a formal framework that organizes symbolic execution around equivalence classes of states under symmetry transformations. Symmetry groups partition the state space into orbits, and exploration proceeds over canonical representatives within quotient transition systems. Symmetry-aware AI components operate on orbit representatives rather than raw states. Four theoretical results support the framework: orbit preservation, quotient soundness, canonicalization correctness, and constraint reuse correctness. An illustrative case study based on a FreeRTOS-like scheduling environment shows how symmetry reduction collapses equivalent states into orbits, with the potential for reductions that scale factorially with symmetric components. S³E is a theoretical framework; a toy-model prototype validates the core quotient-exploration and constraint-caching mechanis, while empirical evaluation on production firmware remains future work. Full article

Spurious correlations between time series are a persistent problem: simple, low-complexity patterns are abundant, so unrelated series can easily exhibit high Pearson correlation. We argue that Kolmogorov complexity—a series’ resistance to compression—provides a principled diagnostic for flagging such cases. We prove an algorithmic trilemma: a pair of binary sequences cannot simultaneously be algorithmically independent, highly correlated, and highly complex. This gives a deterministic complexity ceiling for independent correlated pairs and a probabilistic bound under which spurious correlations among independent high-complexity pairs are exponentially rare; we further bridge these results to an effective Hausdorff dimension obstruction. These guarantees hold for binary sequences under Hamming correlation; their extension to real-valued series via serialisation and LZ compression is empirically validated rather than proved, so the joint indicator $J_{\mathrm{LZ}}=\min \{{\tilde{C}}_{\mathrm{LZ}}\left(x\right),{\tilde{C}}_{\mathrm{LZ}}\left(y\right)\}$ is a calibrated diagnostic, not a causal test. On two toy models—coupled logistic maps and multivariate fractional Brownian motion (${\dim }_H=2-H$)—false positives are far more common among low-complexity series. Because noise inflates complexity and non-stationary processes can be both complex and spuriously correlated, we recommend a two-stage workflow: establish stationarity, then report $J_{\mathrm{LZ}}$ alongside $\rho$. Full article

Distal radial and ulnar fractures in miniature- and toy-breed dogs are associated with high rates of delayed union, non-union, and refracture. This retrospective observational study evaluated the outcomes of simple distal radial and ulnar fractures treated by open reduction and internal fixation using a locking plate in a non-rigid configuration. Ten fractures in eight dogs weighing less than 5 kg were included. Cases were selected according to predefined biomechanical construct criteria, including a plate bridge ratio > 0.7, plate span ratio > 10, plate working length > 40% of the plate length, and screw density < 0.6. The median radiographic follow-up was 224 days (range, 46–408 days). Radiographic bone healing was achieved in all cases, with a mean time to union of 53 days (range, 28–113 days), and healing occurred faster in skeletally immature dogs. Indirect bone healing with callus formation was observed in 7 of 10 fractures. Minor postoperative complications occurred in three cases and resolved with local treatment. No implant failures or refractures associated with previous screw holes were observed. A reduction in ulnar thickness was identified in evaluable cases, although this finding remained stable during follow-up and did not appear clinically relevant. These findings suggest that locking plate fixation in a non-rigid configuration provides reliable bone healing with a low complication rate in simple distal radial and ulnar fractures of miniature- and toy-breed dogs. Full article

Between 2021 and 2023, the French market surveillance authority anonymously bought a sample of 50 toys containing a total of 103 individual LEDs from French retailers and had them tested by third-party laboratories accredited to perform tests in compliance with the international standard for electric toy safety IEC 62115, editions 2003 and 2017. Compliance with the harmonized EN IEC version of this standard is mandatory in the European Union under directive 2009/48/EC. The results revealed that 15 toys (30% of the tested toys) had at least one LED that did not comply with the eye safety requirements: 10 LEDs were non-compliant with respect to the retinal blue-light hazard, and 5 LEDs were non-compliant with respect to the retinal thermal hazard. A subsample of 10 toys with a total of 19 LEDs was assessed using the respective test methods corresponding to the 2003 and 2017 editions of the standard. The 2017 test method was found to be more permissive than the 2003 test method, a conclusion explained by the use of different risk assessment distances. Full article

The safety of non-food products is embedded in the United Nations 2030 Agenda for Sustainable Development and the European Union (EU) framework, supporting health protection, responsible production and consumption, and market surveillance. The EU Rapid Alert System for dangerous non-food products, known as Safety Gate (formerly RAPEX), was established in 2005 to facilitate the exchange of information on products posing risks within the internal market. The aim of this study was to present the interdependencies reported in the Safety Gate system/RAPEX in 2005–2025, considering: product category, type of risk, country of origin, notifying country and year, as well as measures taken. The VOSviewer 1.6.20 and Statistica 13.3 were used. The results highlighted the following problems: toys from China with chemical, choking and injury risks; electrical appliances also from China with electric shock hazards; motor vehicles from Germany with injury risks; cosmetics from Italy with chemical and microbiological risks; and clothing from Turkey with suffocation risks. Reporting is expected to continue under existing regulatory frameworks, although changing the name of the system from RAPEX to “Safety Gate” may reduce its recognition. The findings highlight the need for targeted enforcement, improved risk profiling by product category and origin, and ongoing monitoring of emerging safety risks. Full article

This study evaluated fracture risk associated with varying trochlear groove depth-to-patellar thickness (D/T) ratios in toy and small-breed dogs using finite element analysis and cadaveric mechanical testing. Finite element models derived from computed tomography data of a 4.5-kg toy poodle were adjusted to simulate D/T ratios ranging from 0.5 to 2.0 and analyzed for von Mises stress, principal strain, safety factor, and fatigue life under standing, trotting, and jumping conditions. Increasing D/T ratios led to progressive rises in stress and compressive strain, with the safety factor falling below 1.0 during jumping at ratios of 1.0 or higher. Fatigue life declined sharply beyond a ratio of 1.25 and reached zero-cycle failure at 2.0. Complementary mechanical testing of six distal femurs (6.42–8.7 kg), surgically modified to D/T ratios of 0.5, 1.0, or 1.5, revealed fracture patterns consistent with finite element predictions. These findings suggest that excessive trochlear deepening may compromise femoral integrity and elevate fracture risk, particularly under cyclic loading. Maintaining a D/T ratio between 0.75 and 1.0 may provide an optimal balance between effective patellar tracking and mechanical safety. Full article