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Constraining the Hubble constant with scattering in host galaxies of fast radio bursts
No full textAims. Measuring the Hubble constant (H0) is one of the most important missions in astronomy. Nevertheless, recent studies exhibit differences between the employed methods. Methods. Fast radio bursts (FRBs) are coherent radio transients with large dispersion measures (DM) with a duration of milliseconds DMIGM, the free electron column density along a line of sight in the intergalactic medium (IGM), could open a new avenue for probing H0. However, it has been challenging to separate DM contributions from different components (i.e., the IGM and the host galaxy plasma), and this hampers the accurate measurements of DMIGM and hence H0. We adopted a method to overcome this problem by using the temporal scattering of the FRB pulses due to the propagation effect through the host galaxy plasma (scattering time). The scattering-inferred DM in a host galaxy improves the estimate of DMIGM, which in turn leads to a better constraint on H0. In previous studies, a certain value or distribution has conventionally been assumed of the dispersion measure in host galaxies (DMh). We compared this method with ours by generating 100 mock FRBs, and we found that our method reduces the systematic (statistical) error of H0 by 9.1% (1%) compared to the previous method. Results. We applied our method to 30 localized FRB sources with both scattering and spectroscopic redshift measurements to constrain H0. Our result is H0 = 74-7.2+7.5 km s-1 Mpc-1, where the central value prefers the value obtained from local measurements over the cosmic microwave background. We also measured DMh with a median value of 103-48+68 pc cm-3. Conclusions. The DMh had to be assumed in previous works to derive DMIGM. Scattering enables us to measure DMIGM without assuming DMh to constrain H0. The reduction in systematic error is comparable to the Hubble tension (∼10%). Combined with the fact that more localized FRBs will become available, our result indicates that our method can be used to address the Hubble tension using future FRB samples
Human-in-the-loop optimization of perceived realism of multi-modal haptic rendering under conflicting sensory cues
No full textDuring haptic rendering, a visual display and a haptic interface are commonly utilized together to elicit multi-sensory perception of a virtual object, through a combination and integration of force-related and movement-related cues. In this study, we explore visual-haptic cue integration during multi-modal haptic rendering under conflicting cues and propose a systematic means to determine the optimal visual scaling for haptic manipulation that maximizes the perceived realism of spring rendering for a given haptic interface. We show that the parameters affecting visual-haptic congruency can be effectively optimized through a qualitative feedback-based human-in-the-loop (HiL) optimization to ensure a consistently high rating of perceived realism. Accordingly, the multi-modal perception of users can be successfully enhanced by solely modulating the visual feedback without altering the haptic feedback, to make virtual environments feel stiffer or more compliant, significantly extending the range of perceived stiffness levels for a haptic interface. We extend our results to a group of individuals to capture the multi-dimensional psychometric field that characterizes the cumulative effect of feedback modalities utilized during sensory cue integration under conflicts. Our results not only provide reliable estimates of just noticeable difference thresholds for stiffness with and without visual scaling but also capture all the prominent features of sensory cue integration, indicating weights that are proportional to the congruency level of manipulated visual signals. Overall, preference-based HiL optimization excels as a systematic and efficient method of studying multi-modal perception under conflicts
Aggregate earnings and global equity returns
No full textThis paper compares the predictive power of aggregate earnings for equity returns in international markets. We rank 51 non-US countries based on the time-series averages of their price synchronicity and market concentration measures, calculated at the firm level using daily data. We find that aggregate earnings negatively predict one-quarter-ahead stock returns in country groups that contain less synchronous and concentrated markets, as opposed to country groups that contain more synchronous and concentrated markets. We attribute the negative predictive power of aggregate earnings to a business cycle effect because high (low) corporate earnings correspond to economic expansions (contractions) that tend to be associated with negative (positive) risk premia. However, this business cycle effect is offset by the positive relation between firm-level earnings and future stock returns that translates to the aggregate level in more synchronous and concentrated markets due to a lower degree of diversification. Our results remain robust after controlling for various macroeconomic variables and in alternative subsamples
On some classes of generalized numerical semigroups
No full textA generalized numerical semigroup is a submonoid of Nd with finite complement in it. In this work we study some properties of three different classes of generalized numerical semigroups defined starting from numerical semigroups. In particular, we prove that the class of the so called T-stripe generalized numerical semigroups satisfies a generalization of Wilf’s conjecture. Some partial results for the generalized Wilf’s conjecture, together with characterizations for the properties of quasi-irreducibility and quasi-symmetry, are obtained for the so called Tgraded semigroups and for the generalized numerical semigroups S ⊆ Nd such that elements of Nd \ S belong to the coordinate axes
Nanomaterial-based scaffolds for bone regeneration with piezoelectric properties
No full textFor proper cellular growth, to prepare tissue scaffold mimicking the tissue properties is a significant challenge. Bone is a vital organ supporting the whole human body for its function. The efficiencies in its structure for a variety of reasons should properly be remedied. Bone tissue engineering (BTE) is an emerging field addressing to develop or repair bone tissue for its proper function. The bone is naturally a piezoelectric material and generates electrical stimuli because of mechanical stress. Thus, the use of piezoelectric materials to build bone tissue is of great interest in BTE. Both piezoelectric polymers and nanomaterials (NMs) are investigated for this goal. In this review, we give an overview of the recent advances in piezoelectric NMs to construct piezoelectric scaffolds in BTE
Partially hydrolyzed poly(2-alkyl/aryl-2-oxazoline)s as thermal latent curing agents: effect of composition and pendant groups on curing behavior
No full textPoly(2-alkyl/aryl-2-oxazoline)-polyethylenimine (POZ-PEI) copolymers resulting from the partial hydrolysis of poly(2-alkyl/aryl-2-oxazoline)s (POZs) offer highly tunable properties. The amine groups on the PEI units are suitable for a range of postpolymerization modifications such as ring-opening of epoxides, acylation, and coupling. The reactivity of these amines can be controlled by altering the available structural variables of the copolymer. This makes these copolymers promising candidates as thermal latent curing agents (TLCs) for cross-linking of epoxides. In this paper, a range of POZ homopolymers with different alkyl/aryl pendant groups (ethyl/propyl/pentyl/phenyl) and molar masses (1000, 2000, and 5000 g/mol) were hydrolyzed at different hydrolysis ratios (25%, 50%, and 75%) to synthesize POZ-PEI copolymers. The effects of these parameters on the thermal and structural properties of the copolymers were analyzed using 1H NMR, FTIR, DSC, and TGA. The POZ-PEI copolymers exhibited lower glass transition temperature (Tg) and decomposition temperature (Td) values in contrast to their precursor homopolymers. TLCs based on the obtained POZ-PEI copolymers were prepared and mixed with bisphenol A diglycidyl ether (DGEBA) to obtain one-component epoxy resins (OCERs). The effect of the mentioned variables on the curing behavior of the prepared OCERs was studied in terms of the enthalpy of curing, left limit temperature, and conversion. POZ-PEI-based TLCs with more hydrophobic side chains, at low hydrolysis ratios and with low molar masses, showed the best latency. PPhOZ-PEI-1 copolymer, with a Tg of 52 °C was chosen as the optimal TLC providing mainly chemical latency though steric effects and physical latency by remaining solid at room temperature. Isothermal DSC tests were performed at different temperatures to examine the stability of the resulting OCER. The results showed that this sample was stable at 40 °C for 3 h and partially cured at 60 °C. Also, the viscoelastic properties of the chosen OCER were investigated by rheology studies, namely, amplitude, frequency, and temperature sweeps. The linear viscoelastic region of the PPhOZ-PEI-1-DGEBA OCER extended up to 10% shear strain. The lowest viscosity for this OCER was observed at 104 °C, and a crossover point was seen at 118 °C. Lastly, the thermomechanical properties of the cured sample were analyzed using DMA, which showed a tan δ peak at 87.6 °C
A central limit theorem associated with a sequence of positive line bundles
No full textWe prove a central limit theorem for smooth linear statistics associated with zero divisors of standard Gaussian holomorphic sections in a sequence of holomorphic line bundles with Hermitian metrics of class C3 over a compact Kähler manifold. In the course of our analysis, we derive first-order asymptotics and upper decay estimates for near and off-diagonal Bergman kernels, respectively. These results are essential for determining the statistical properties of the zeros of random holomorphic sections
Investigating middle school students' eye movements on the mathematical representations: an eye-tracking study
No full textIn mathematics education, representations are used in place of mathematical structures, ideas, or relationships to concretize, transform, and represent them. When students interact with these representations, they engage in various cognitive activities such as thinking, reasoning, understanding, remembering, problem-solving, attention, and decision-making, which are difficult to observe. Therefore, uncovering these cognitive activities is very significant for mathematics education. However, they are not easy to uncover as they cannot be directly observed. Eye tracking is an important approach that can be used to reveal cognitive activities that cannot be directly observed. This study investigated how middle school students examine representations by examining their eye movements. Eighty-five (40 girls and 45 boys) 7th-grade middle school students participated in the study. In the study, gaze durations, fixation count, and fixation duration on four different representation types: verbal representation, symbolic representation, number line representation, and counters representation were compared. The findings showed that students fixated more on the verbal representation and gazed at it for longer. However, fixation durations on the verbal representation were quite short compared to the other representations. In contrast, when examining the counters, there were fewer fixations and shorter gaze durations, but fixation durations were longer. Gazes on the number line and symbolic representation did not differ across all three variables. The findings indicated that gaze on verbal and non-verbal representations differed to some extent, but not entirely. Finally, the findings are discussed in the context of mathematical representation and eye-tracking literature
Rigorous perturbation bounds for the QX decomposition for centrosymmetric matrices
No full textKonrad Burnik suggests a structure-preserving (Formula presented.) factorization for centrosymmetric matrices, known as (Formula presented.) factorization. In this article, we obtain the explicit expressions for rigorous perturbation bounds of the (Formula presented.) factorization when the original matrix is perturbed, either norm-wise or component-wise. First, using the matrix-equation approach, weak rigorous perturbation bounds are derived. Then, strong rigorous perturbation bounds are obtained by combining the modified matrix-vector equation approach with the strategy for the Lyapunov majorant function and the Banach fixed-point theorem. The mixed and component-wise condition numbers and their upper bounds are also explicitly expressed. Numerical tests illustrate the validity of the obtained results
From single-chain polymeric nanoparticles to interpenetrating polymer network organogels: a one-pot fabrication approach
No full textIn this study, we developed a novel one-pot synthesis method to fabricate well-defined single-chain polymeric nanoparticles (SCNPs) integrated with interpenetrating polymer network (IPN) systems. The synthesis process involved an initial intramolecular crosslinking of poly(methyl methacrylate-co-glycidyl methacrylate) to form SCNP followed by intermolecular crosslinking to produce single-chain nanogel (SCNG) structures. In addition, the achieved single-chain polymeric nanoparticle was subsequently incorporated into an IPN structure through urethane bond formation and a Diels–Alder click reaction involving furfuryl methacrylate (FMA) and bismaleimide (BMI). The thermal properties, swelling behaviors, and morphologies of the resulting SCNP-IPN systems were investigated. This work presents a novel strategy that integrates the single-chain folding concept with IPN systems, providing a promising platform for the development of robust and functional polymeric materials with potential applications in advanced materials science