We show that demand pressure from retail investors makes options on low-price stocks relatively expensive-delta-hedged options on low-price stocks underperform those on high-price stocks by 0.63% per week for calls and 0.36% for puts. Natural experiments corroborate this finding: options become more expensive following stock splits, options on mini indices are more expensive than those on main indices, and mini contract options are more expensive than standard options. We attribute our findings to retail investors' preference for skewness and divergence of opinion. Limits to arbitrage and strategic quote setting by market makers contribute to, but do not fully explain, this effect. (JEL G13, G14)

In the last decade, the self-field critical current density Jc(s.f.) in Type-II superconductors has been considered fundamentally limited by a Silsbee-like criterion of Jc(s.f.) = Hc1/λ. We show that this universal limit to self-field critical current density Jc(s.f.) is not universally valid. We present several examples for this in YBa2Cu3O7-δ-type and REBa2Cu3O7-δ thin films and one for Nb thin films and show that calculated Jc(s.f.) using the Silsbee-like criterion using thermodynamic parameters has been substantially exceeded experimentally. We also show that Jc(s.f.) can be significantly improved by incorporation of artificial pinning centers (APCs), further implying that no such universal limit to Jc(s.f.) can exist because such an upper bound, Jc(s.f.) would have to be independent of APCs. These findings call for a revision of the accepted understanding of current-carrying limits in Type-II superconductors and reveal substantial potential for improving Jc in REBCO-based coated conductors through optimization of APCs for large-scale applications, including commercial nuclear fusion.

Cerium oxide (CeO2) is often used as a lattice-match cap layer for heteroepitaxial growth of REBa2Cu3O7-x (RE: rare earth) superconductors. In this work, we investigated how the nanostructure and grain size of CeO2 heteroepitaxial films on biaxially-textured, coated conductor substrates can be modified via annealing in humid, mixed N2/4%-H2 gas mixtures. X-Ray diffraction (XRD) analysis shows annealing at higher temperatures shifts the lattice constant to lower values. The full-width-half-maximum (FWHM) of omega and phi scans show that the in-plane and the out-of-plane crystallographic texture is relatively unchanged with post-annealing. Surface reconstruction, roughness and grain sizes were characterized using Atomic Force Microscopy (AFM).

This study analyzes the calculation of the critical current density Jc,mag by means of Bean’s critical state model, using the equation formulated by Gyorgy et al. and other similar equations derived from it reported in the literature. While estimations of Jc,mag using Bean’s model are widely performed, improper use of different equations with different magnetic units and pre-factors leads to confusion and to significant errors in the reported values of Jc,mag. In this work, a SINGLE general equation is proposed for the calculation of Jc,mag for a rectangular parallelepiped sample in perpendicular field using Bean’s critical state model, underlying how the simple conversion of magnetic units can lead to a Jc,mag in the desired units, without the need to introduce any other correction or use other specific equations depending on the units of Jc,mag. In this equation, the numerical pre-factor is dimensionless, independent of the unit system used. A comparison between the expression reported in the literature is done, showing how they can lead to different results depending on the used units, and that these results can be at least one order of magnitude different from the correct results obtained with the general equation proposed in this work. This resolves all ambiguities and aligns with the correct dimensional analysis, eliminates discrepancies in the calculated Jc,mag, and will avoid further propagation of errors in the literature.

We document that implied volatility (IV) curves extracted from short-term equity options frequently become concave prior to the earnings announcement day (EAD) reflecting a bimodal risk-neutral distribution for the underlying stock price. Firms with concave IV curves exhibit significantly higher absolute stock returns on EAD and higher realized volatility after the announcement, as compared to firms with non-concave IV curves. Hence, concavity in the IV curve constitutes an ex-ante option-based signal for event risk in the underlying stock. Returns on delta-neutral straddles around EADs are significantly lower in the presence of concave IV curves, showing that investors pay a high premium to hedge against this event risk.

To realize the potential of superconducting devices, carefully optimized fabrication processes are essential. In this paper, we report on microfabrication via a wet chemical etching process for superconducting films. The film comprised a superconducting EuBa2Cu3O7-δ with 3.4vol% of insulating BaHfO3 nanocolumns at nanoscale intercolumn spacings within the film. The superconducting properties were measured with patterned bridges of varying bridge widths of 25μm, 50μm, 75μm, 100μm, 150μm and 200μm. Electrical transport measurements show that onset of the superconducting transition for the etched bridges was unaffected by chemical etching and was within the experimental accuracy (Δ < 1 K). The critical currents Ic measured at 77K (1T - 7T) and 65 K (1T - 7T) show that the Ic results do not vary much for the same measurement temperature and magnetic field, for different bridge widths of the etched superconducting films, indicating that wet chemical etching microfabrication procedure adopted yields consistent results.

High-temperature superconducting wires have many large-scale, niche applications such as commercial nuclear fusion as well as numerous other large-scale applications in the electric power industry and in the defense, medical and transportation industries. However, the price/performance metric of these coated conductor wires is not yet favorable to enable and realize most large-scale applications. Here we report on probing the limits of Jc (H, T) possible via defect engineering in heteroepitaxially deposited high-temperature superconducting thin-films on coated conductor substrates used for long-length wire fabrication. We report record values of Jc (H, T) and pinning force, Fp (H, T) in (RE)BCO films with self-assembled BaZrO3 nanocolumns deposited on a coated conductor substrate. A Jc of ~190 MA/cm2 at 4.2 K, self-field and ~90 MA/cm2, at 4.2 K, 7 T was measured. At 20 K, Jc of over 150 MA/cm2 at self-field and over 60 MA/cm2 at 7 T was observed. A very high pinning force, Fp, of ~6.4 TN/m3 and ~4.2 TN/m3 were observed at 7 T, 4.2 K and 7 T, 20 K respectively. We report on the highest values of Jc and Fp obtained to date for all fields and operating temperatures from 4.2 K to 77 K. These results demonstrate that significant performance enhancements and hence far more favorable price/performance metrics are possible in commercial high-temperature superconducting wires.

We discuss issues related to calculation of critical current density, Jc,mag, reported by Goyal et al [1] using the Bean's model [2,3] via the expression developed by Gyorgy et al. [4] for calculating Jc,mag. When used with the correct formalism with respect to magnetic units, this expression yields to errors in the reported values of Jc,mag, in A/cm2. The authors emphasize the need for self-consistent magnetic unit applications when employing the formula from Gyorgy et al., proposing an expression that eliminates ambiguities and aligns with the correct dimensional analysis. This note emphasizes the importance of using appropriate magnetic units and urges researchers to reconsider the established methodologies in the literature, fostering improved accuracy in future studies of (RE)BCO-based coated conductors.

We provide comments on article "Fundamental nature of the self-field critical current in superconductors" by Talantsev and Tallon, arXiv:2409.16758 and https://papers.ssrn.com/sol3/papers.cfm?abstract_id=4978589 related to the predictions of the key equation proposed in article "Universal self-field critical current for thin-film superconductors," by Talantsev and Tallon, Nat. Commun. 6 (2015) 7820. We respond to claims and assertions made in these articles and also show that the so-called "Universal self-field critical current" and the "fundamental limit" for self-field Jc suggested by Talantsev and Tallon, has been proven incorrect experimentally and this invalidates the key claims and findings stated in both these articles.

We provide comments on article titled "Procedures for proper validation of record critical current density claims" by Chiara Tarantini and David C. Larbalestier, https://arxiv.org/abs/2410.22195. We respond to claims and assertions that the expressions for calculation of Jc,mag from magnetic moments proposed in Polichetti et al. 2024, https://arxiv.org/abs/2410.09197, are incorrect. We show that the analysis presented in Tarantini and Larbalestier is wrong. We also re-emphasize the expression presented in Polichetti et al. for calculation of Jc,mag from magnetic moments in which the pre-factor is dimensionless and has NO units. We make the case for establishment of national user facilities for measurement of transport Jc (H,T,theta) that are easily accessible in an equitable and rapid manner to enable much needed advances in the field.

Recent advances in semiconductor based electronic devices can be attributed to the technological demands of ever increasing, application specific markets. These rapidly evolving markets for devices such as displays, wireless communication, photovoltaics, medical devices, etc. are demanding electronic devices that are increasingly thinner, smaller, lighter and flexible. High-quality, III-V epitaxial thin-films deposited on single-crystal substrates have yielded extremely high-performance, but are extremely expensive and rigid. Here we demonstrate heteroepitaxial deposition of GaAs thin-films on large-grained, single-crystal-like, biaxially-aligned, flexible, metallic substrates. We use molecular beam epitaxy (MBE) for the controlled growth of high quality GaAs layers on lattice matched Ge capped, flexible metal substrates. The structural, optical, interfacial and electrical characteristics and properties of the heteroepitaxial GaAs layers are analyzed and discussed. The results show that heteroepitaxial GaAs layers with good crystalline and optoelectronic properties can be realized for flexible, III-V based semiconductor devices. III-V materials integrated on large-grained, single-crystal-like, flexible, metallic substrates offer a potential route towards fabrication of large-area, high-performance electronic devices.

Illiquidity measures appear to be related to monthly realized returns but do they impact long-run costs of capital (CoC) for firms? Using U.S. data, we find cross-sectional evidence that, controlling for market capitalization, the Amihud (2002, Journal of Financial Markets, 5, 31) measure of illiquidity is negatively related to CoC estimates. A difference-in-differences analysis around exogenous brokerage closures reveals that Amihud illiquidity increases without an impact on CoC. Nonetheless, other illiquidity measures, such as those based on serial covariances, zero returns, and price impact, do show a strong positive relation with CoC. However, we do not find evidence that liquidity risk and the probability of informed trade influence CoC. Overall, our results advance our understanding of precisely which illiquidity measures influence required firm returns.

We find that option expensiveness, as measured by implied volatility, is higher for low-ESG stocks, showing that investors pay a premium in the option market to hedge ESG-related uncertainty. Using delta-hedged option returns, we estimate this ESG premium to be about 0.3% per month. All three components of ESG contribute to option pricing. The effect of ESG performance heightens after the announcement of Paris Agreement, after speeches of Greta Thunberg, and in the aftermath of Me-Too movement. We find that investors pay ESG premium to hedge volatility, jump, and other higher moment risks. The influence of ESG on option premia is stronger for firms that are closer to end-consumers, facing severer product competition, with higher investors’ ESG awareness, and without corporate hedging activity.

Current R&D expenditures forecast cash-based operating profitability up to three years in the future and sometimes as much as ten years, but do not forecast asset growth. High R&D firms have positive loadings on a cash-based operating profitability factor, and zero alphas. Capitalizing R&D to augment book values with intangible assets is unnecessary for asset pricing, so long as expected profitability is explicitly recognized as a determinant of expected returns.

The closing auction has experienced significant growth over the last decade, and it has become increasingly important to traders. We find that the price impact in closing auctions in the US is significantly smaller than that in continuous markets. The opening auctions are relatively less active and less liquid. The price impact is significantly correlated with stock characteristics such as exchange, price, and volatility in all three trading avenues. We also examine the trading costs of several common trading strategies and find that the trading costs in closing auctions are smaller than that in the continuous market for all strategies.

Combinatorial synthesis via a continuous composition spread is an excellent route to develop thin-film libraries as it is both time- and cost-efficient. Creating libraries of functional, multicomponent, complex oxide films requires excellent control over the synthesis parameters combined with high-throughput analytical feedback. A reliable, high-throughput, in-situ characterization analysis method is required to meet the crucial need to rapidly screen materials libraries. Here, we report on the combination of two in-situ techniques-(a) Reflection high-energy electron diffraction (RHEED) for heteroepitaxial characterization and a newly developed compositional analysis technique, low-angle x-ray spectroscopy (LAXS), to map the chemical composition profile of combinatorial heteroepitaxial complex oxide films deposited using a continuous composition spread method via pulsed laser deposition. This is accomplished using a unique state-of-the-art combinatorial growth system with a fully synchronized four-axis mechanical substrate stage without shadow masks, alternating acquisition of chemical compositional data using LAXS at various different positions on the [Formula: see text] 41 mm [Formula: see text] 41 mm range and sequential deposition of multilayers of SrTiO[Formula: see text] and [Formula: see text] on a 2-inch (50.8 mm) [Formula: see text] wafer in a single growth run. Rutherford backscattering spectrometry (RBS) is used to calibrate and validate the compositions determined by LAXS. This study shows the feasibility of combinatorial synthesis of heteroepitaxial, functional complex oxide films at wafer-scale via two essential in-situ characterization tools-RHEED for structural analysis or heteroepitaxy and LAXS for compositional characterization. This is a powerful technique for development of new films with optimized heteroepitaxy and composition.

There is yet no consensus on why equity markets permit momentum although the literature proposes several rationales that have been empirically tested with US data. We use out-of-sample international data to assess the robustness of these rationales. We find that the frog-in-the-pan (FIP) hypothesis, which posits that investors underreact to information that arrives gradually rather than in concentrated doses, consistently wins. Also, internationally, momentum is stronger in less volatile markets and in up-markets. Information flows more gradually during these market states, implying additional support for FIP.

Intravenous immunoglobulin (IVIg) is used in the treatment of patients with generalized myasthenia gravis (gMG), a rare autoimmune disorder. The objective of this study was to assess real-world IVIg usage patterns and its implications on costs over 1 year post-initiation in adults with gMG in the United States. Adults (≥18 years) with gMG who initiated IVIg were identified from Symphony Health’s Integrated Dataverse (IDV)®, January 1, 2014 – December 31, 2019, unprojected de-identified patient prescription and medical claims, January 2020 dataset. IVIg courses were defined as ≥1 IVIg claims filed consecutively with ≤5 days between claims. Patients who received ≥6 IVIg courses over 1 year post-initiation were defined as chronic users (CU), while those who received ≤5 were defined as intermittent users (IU). Mean all-cause medical costs included medical service and pharmacy costs, and were assessed over 1 year post-IVIg initiation. Among 1627 patients with gMG who initiated IVIg during the study period, 928 (57.0%) were IU and 699 (43.0%) were CU during the first year. 41.9% (389/928) of IU and 46.6% (326/699) of CU had at least one exacerbation or crisis event (E/C) during the year preceding IVIg initiation. Mean annual medical costs per patient for CU were 2.2- to 2.9-fold greater compared with IU (Had prior E/C: IU $73,970, CU $164,223; No prior E/C: IU $53,766, CU $156,356). Although 43.9% of patients initiated IVIg after at least 1 E/C during the preceding year, 53.6% (IU, 491; CU, 381) still experienced at least 1 E/C during the year post-IVIg initiation. CU comprised 43.0% of IVIg initiators, and costs incurred for CU were significantly greater than that for IU. Regardless of the frequency of IVIg treatment, myasthenic exacerbations were still common.