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This paper examines the information content of insider silence, periods of no insider trading. We hypothesize that, to avoid litigation risk, rational insiders do not sell own-company shares when they anticipate bad news; neither would they buy, given unfavorable prospects. Thus, they keep silent. By contrast, insiders sell shares when they do not anticipate significant bad news. Future stock returns are significantly lower following insider silence than following insider net selling, especially among firms with higher litigation risk. We examine two quasinatural experiments where new laws result in changes in shareholder litigation risks for insiders. In both cases, with higher shareholder litigation risks, stocks where insiders stay silent earn significantly lower returns than other stocks. This paper was accepted by Karl Diether, finance.

For nearly three years, humans have experienced multiple rounds of global transmission of SARS-CoV-2 and its variant strains. In addition, the widely used vaccines against SARS-CoV-2 involve multiple strategies of development and inoculation, globally. Thus, the acquired immunity established among humans is quite complicated, and there is still a lack of understanding within a panoramic vision. Here, we provide the special characteristics of the cellular and humoral immune responses in 2-year convalescents after the inoculation of inactivated vaccine, in parallel to vaccinated COVID-19 naïve persons and unvaccinated controls. The decreasing trends of the IgG, IgA, and neutralizing antibodies (NAb), but not IgM of the convalescents were reversed by the vaccination. Both cellular and humoral immunity to SARS-CoV-2 in convalescents after vaccination were higher than the vaccinated COVID-19 naïve persons. Notably, the inoculation of inactivated vaccine fueled the NAb to Omicron BA.1, BA.2, BA.4, and BA.5 in the 2-year convalescents, much higher than the NAb during 6 months and 1 year after symptoms onset. And no obvious T cell escaping to the S protein was observed after the inoculation in the 2-year convalescents. The study provides insight into the complicated features of acquired immunity of humans to SARS-CoV-2 and variants in the real world, and indicated that promoting vaccine inoculation is an essential way to achieve herd immunity against emerging viral variants for the ongoing COVID-19 pandemic, including the convalescents.

Emerging in December 2019, coronavirus disease 2019 (COVID-19) eventually became a pandemic and has posed a tremendous threat to global public health. However, the origins of SARS-CoV-2, the causative agent of COVID-19, remain to be determined. It has reported that a certain number of the early case clusters had a contact history with Huanan Seafood Market. Therefore, surveillance of SARS-CoV-2 within the market is of vital importance. Herein, we presented the SARS-CoV-2 detection results of 1380 samples collected from the environment and the animals within the market in early 2020. By SARS-CoV-2-specific RT-qPCR, 73 environmental samples tested positive for SARS-CoV-2 and three live viruses were successfully isolated. The viruses from the market shared nucleotide identity of 99.980% to 99.993% with the human isolate HCoV/Wuhan/IVDC-HB-01. In contrast, no virus was detected in the animal swabs covering 18 species of animals in the market. The SARS-COV-2 nucleic acids in the positive environmental samples showed significant correlation of abundance of Homo sapiens with SARS-CoV-2. In summary, this study provided convincing evidence of the prevalence of SARS-CoV-2 in the Huanan Seafood Market during the early stage of COVID-19 outbreak.

We compare the interventions conducted by the Federal Reserve in response to the subprime and COVID–19 crises with respect to their effectiveness in reducing disaster risk. Using model-free measures of disaster risk derived from daily options data, we document that interventions in response to both crises reduced tail risks in domestic equity markets. The spillover effects of the two crises have been markedly dissimilar. While subprime interventions are generally characterized by negative spillovers to international equity markets, policy responses to the COVID–19 crisis are generally associated with positive spillovers. We interpret these results as consistent with the different degrees of protagonism by central banks in the two episodes, emphasizing the importance of a broader participation of monetary authorities in expanding their balance sheets to counteract the effects of major crises.

We show that the beta with respect to an index of global ex ante tail risk concerns (𝔾ℝ𝕀𝕏), which we construct using out-of-the-money options on multiple global assets, negatively drives cross-sectional return variations across asset classes, including international equity indices, foreign currencies, and government bond futures. The pricing power of 𝔾ℝ𝕀𝕏 becomes stronger when more asset-class-level tail risk concerns are incorporated in the index construction. 𝔾ℝ𝕀𝕏 also dominates asset-class-level tail risk concerns in pricing assets within each asset class. These evidences imply that the pricing effect of tail risk concerns works predominantly as a global channel. The 𝔾ℝ𝕀𝕏 pricing effect is distinct from that of tail risk factors based on historical realizations, consistent with the interpretation that tail risk concerns likely reflect investors’ ex ante subjective belief about tail risk. This paper was accepted by Neng Wang, finance.

We find hedge funds that have higher return covariation with a disaster concern index, which we develop through out-of-the-money puts on various economic sector indices, earn significantly higher returns in the cross section. We provide substantial evidence that these funds have better skills in exploiting the market's ex ante rare disaster concerns (SED), which may not realize as disaster shocks ex post. In particular, high-SED funds on average outperform low-SED funds by 0.96% per month, but have less exposure to disaster risk. They continue to deliver superior future performance when SED is estimated using the disaster concern index purged of disaster risk premium, and have leverage-managing and extreme-market-timing abilities. We also provide strong evidence against alternative interpretations.

Purpose The purpose of this paper is to empirically examine whether corporate insiders extract information from activity of outsiders, specifically the short sellers. Design/methodology/approach Using portfolio approach and Fama-MacBeth regressions, this study examines the relation between short interest and subsequent insider trading activities. Findings The following results are reported. First, there is a strong inverse relation between short selling and subsequent insider trading, which is partially due to common private information and same target firm characteristics. Second, insiders extract information from shorts. This information extraction effect is more pronounced for firms whose insiders have stronger incentives to extract shorts information (insider purchases, higher short sale constraints, and better information environments). Third, during the September 2008 shorting ban, the information extraction affect disappeared among the large banned firms, whose shorting activities were distorted. Research limitations/implications The findings contradict the of-cited accusations corporate executives hold against short sellers. Instead, corporate insiders appear to trade in the same direction as suggested by shorting activities. Practical implications Among the vocal critics of short sellers are corporate insiders, who allege that short sellers beat down their stock prices. Many corporations even engage in stock repurchases to show confidence that the stock will perform well going forward despite the short sellers’ actions. This paper’s analysis on their personal portfolios suggests the other way around. Originality/value By focusing on how corporate insider trading is related to shorts information, this paper sheds new light on whether corporate decisions convey the true information the corporate insiders possess.

We document strong weekly lead-lag return predictability across stocks from different industries with no customer-supplier linkages (economically unrelated stocks). Between 1980 and 2010, the industry-neutral long-short hedge portfolio earns an average of over 19 basis points per week. This predictability is distinct from previously documented lead-lag effects coming from weekly reversals, momentum, nonsynchronous trading, or other known factors. Common institutional ownership is a complementary rather than a substitute explanation for return predictability. Information linkages are enough to induce return predictability among stocks in the same industry, but economically unrelated stocks exhibit return predictability only when they have common institutional owners. We find that return predictability among economically unrelated stocks is significantly higher during Russell index reconstitution weeks, the last week of each quarter, and the last week of each month, consistent with higher predictability being driven by more intense institutional portfolio readjustments. Our findings suggest that institutional portfolio reallocations can induce return predictability among otherwise unrelated stocks.

We address the problem of how to extract counterexamples for the transitive-closure-based model checking (TCMC) technique. TCMC is a representation of the CTLFC (CTL with fairness constraints) model checking problem in first-order logic with transitive closure (FOLTC) and has been implemented in the Alloy Analyzer. It is a declarative, symbolic model checking method. As a CTL model checking method, TCMC is defined over transition systems and states (rather than paths) and therefore, returns a transition system with a bug as a counterexample. Our contribution is to isolate a counterexample path/subgraph in a declarative manner by adding constraints that do not depend on the property. Our method does not require extensions to Alloy.

We find that inventory productivity strongly predicts future stock returns among a sample of publicly listed U.S. retailers during the period from 1985 to 2010. A zero-cost portfolio investment strategy, which consists of buying from the two highest and selling from the two lowest quintiles formed on inventory turnover, earns more than 1% average monthly abnormal return benchmarked to the Fama–French–Carhart four-factor model. Our results are robust to different measures of inventory productivity, distinct from the well-known firm characteristics known to generate abnormal returns, and not driven by a particular subsample period. A longitudinal analysis of portfolio returns over longer holding periods shows that although inventory productivity is predictive of stock returns, its information dissipates about one to two years after release. This paper was accepted by Serguei Netessine, operations management.

Among the vocal critics of short sellers are corporate insiders, who allege that short sellers beat down their stock prices. Many corporations even engage in stock repurchases to show confidence that the stock will perform well going forward despite the short sellers’ actions. In this paper, we analyze insiders’ trading actions in their personal portfolios. We document a strong inverse relation between short selling and subsequent insider trading, which is partially due to common private information and same target firm characteristics. Additionally, we find that insiders extract information from shorts. This information extraction effect is more pronounced for firms whose insiders have stronger incentives to extract shorts information (insider purchases, higher short-sale constraints, and better information environments). During the September 2008 shorting ban, the information extraction effect disappeared among the large banned firms, whose shorting activities were distorted. Our empirical evidence contradicts the oft-cited accusations corporate executives hold against short sellers.

We propose an empirical framework of disaster concerns to explain cross-sectional return variation both within and across asset classes. Using a large set of out-of-the-money options on international equity indices, foreign currencies, and global government bonds, we measure the global …nancial market’s rare disaster concerns under only no-arbitrage conditions. Assets that have low return covariations with such concerns earn high excess returns in the future. The return predictability driven by rare disaster concerns is distinct from that driven by exposures to realized disaster shocks such as macroeconomic downturns and liquidity crunches, and is not

A feasibility study has been performed for stator concept design and manufacturing of an 8 MW 11 RPM direct drive high temperature superconducting (HTS) generator. The new developments and studies have proven that the stator design concepts can be applied to multi-mega-watts rated direct drive wind turbine generators. The novel skewed stator design almost eliminates the cogging torque and minimizes the rotor HTS requirements. Electromagnetic, mechanical, thermal and insulation developments performed for the concept design are described in the paper. A wound stator section called statorette has been manufactured to prove the feasibility of a very large diameter stator for a production wind turbine generator. A multi-stress test facility has been developed to validate the developed design concepts.

Because of the increasing global demands for more energy productions, several green energy sources (such as wind, solar, biomass, etc.) have attracted great interest from many governments and industries. Among them, wind energy showed one of the highest levels of advancement for the last several years. Still, many challenges remain ahead, including harsh operation environments for most wind generators. Another obstacle is that very few qualification procedures for wind generator applications have been established by the industry so manufacturers use their own methods. In this paper, we will share some of our test methods and results regarding the development of a new and robust insulation system for these intended wind generation applications.

This paper examines the information content of insider silence, periods of no insider trading. We hypothesize that, to avoid litigation risk, rational insiders do not sell own-company shares when they anticipate bad news; neither would they buy, given unfavorable prospects; thus they keep silent. By contrast, insiders sell shares when they do not anticipate significant bad news. Consistent with this hypothesis, we find insiders are more likely to stay silent prior to shareholder litigations or large stock price drops. We also show future stock returns are significantly lower following insider silence than following insider net selling, and insider silence predicts more negative returns among firms at higher litigation risk. In sum, insider silence is bad news.

In order to better understand insulation performance under real-life operation conditions, a new test set-up was installed to apply multiple stresses (electrical, mechanical, and thermal) simultaneously on test coils in the formette. This is a continued effort from our previous study that focused mainly on the differences in dielectric performance of insulation systems between 60 Hz and high-frequency only. By adding additional thermal and mechanical stresses, this new set-up proved to be a more effective tool to evaluate stator insulation systems in service, especially under adjustable speed drive conditions where voltage spikes of fast rise time and high magnitude generated by some of these drives have put much greater stress on the insulation. Tests were performed on multiple insulation systems under both 60 Hz and high frequency conditions. Information gathered by this project enables us to better understand the different impacts service conditions have had on the insulation system. It also helps us verify the insulation integrity and improve the overall insulation performance and their service lives.

I suggest a characteristic-based covariance model that directly links the predetermined fi rm characteristics to time-varying covariance risk. Using a large cross section of individual stock-level data, I parsimoniously estimate both conditional expected returns and conditional covariances as functions of fi rm characteristics. I fi nd a strong and positive intertemporal risk-return relation on individual stocks. In comparison to the Fama-French three-factor model, the characteristic-based covariance model substantially reduces the pricing errors of characteristic-sorted portfolios on size, book-to-market, accruals, asset growth, investment-to-assets, return-on-assets, net stock issues, financial distress, and momentum. Portfolio tests similar to Daniel and Titman (1997) suggest that firm characteristics, mainly through the characteristic-based covariance structure of returns, appear to explain the cross section of average stock returns.

We find that inventory productivity strongly predicts future stock returns among a sample of publicly listed U.S. retailers during the period from 1985 to 2010. A zero-cost portfolio investment strategy, which consists of buying from the two highest and selling from the two lowest quintiles formed on inventory turnover, earns more than 1% average monthly abnormal return benchmarked to the Fama-French-Carhart four-factor model. Our results are robust to different measures of inventory productivity, distinct from the well-known firm characteristics known to generate abnormal returns, and not driven by a particular sub-sample period. A longitudinal analysis of portfolio returns over longer holding periods shows that, while inventory productivity is predictive of stock returns, its information dissipates about 1-2 years after release.

We present evidence of a predictable drift in stock prices before the earnings announcements of firms that announce their earnings later than other firms in their industry. We form portfolios based on the returns of later announcers that are implied by the abnormal returns of earlier announcers and the historical pair-wise covariance of the abnormal earnings announcement date returns of earlier and later announcers. A long-short trading strategy based on these implied returns generates monthly returns of more than 100 basis points. The drift is neither due to the well-known momentum effect nor a manifestation of post-earnings announcement drift; it is evident both between the earlier announcers’ earnings announcement dates and the later announcers’ earnings announcement dates and at the later announcers’ earnings announcement dates. The continued under-reaction after later announcers’ earnings announcements is shown to be an under-reaction to the later announcers’ own earnings announcements (i.e., post-earnings announcement drift) rather than a continued under-reaction to the earnings news of earlier announcers (i.e., pre-earnings announcement drift). We show that transaction costs explain the predictability of later announcers’ returns.

Partial Discharge (PD) off- line and on-line measurements are required to prevent early failures on low voltage induction motors fed by inverter drives. Conventional methods use commercial Digital Scopes to visualize simultaneously the waveform of the applied impulsive voltage and the acquired PD pulses, as well as appropriate solutions to attenuate power electronic voltage impulses. A new approach is proposed in this paper, relying upon a Phase-Resolved PD (PRPD) pattern, which constitutes a simple and efficient tool for PD activity detection in adjustable speed drives. Off-line PD measurements were done on low voltage induction motors fed by a voltage impulse generator and detecting PD Inception Voltage (PDIV) on each phase. Then, PD on line measurements were carried out using a commercial PWM inverter and showing interesting correlation between off-line and on-line tests. All the measurements were performed using antenna sensors, achieving excellent sensitivity.

This paper presents technical design and evaluation experience on wind turbine generator insulation under conditions of the turbine operation conditions. Today, roughly 99% of wind turbine generators are connected with power converters. Since over 70% of the installed turbines utilize wound rotor induction machines (referred to as double-fed induction generators DFIG), this paper will use the DFIG type generator as an example to present the design challenges for wind power generating applications as compared to traditional ones. Several special considerations and evaluation methods will be presented.

In the last decade, industries have refined motor insulation systems to be more suitable for low voltage (LV) adjustable speed drive (ASD) applications. Furthermore, recent advances in power electronics and control systems have significantly increased the use of medium voltage (MV) ASD on motors. However, the challenge for reliability and service life has become more critical since many MV ASD fed motor systems are often associated with much larger and more critical process controls as compared with LV ASD fed motor systems. Thus far, only limited research has been conducted to evaluate and further develop medium voltage ASD fed motor insulation systems. IEC TC 2 WG 27 experts have spent nearly 5 years developing guidelines for qualifying insulation systems that are used for ASD fed motors (IEC TC 60034-18-42). To support the frame work of this technical guideline development, a series of research studies have been conducted. In this report, partial results of these studies will be presented. The focus of this research was to evaluate the impacts of MV ASD on all insulation components in motor stator windings. Information gathered by this project provides a better understanding of the aging processes generated from MV drives on the insulation system, and helps with the improvement of insulation system designs.

A novel technique incorporating fiber optic strain gages has been successfully used to measure the mechanical stresses on large motor stator winding end turns at different operating conditions. The testing was conducted both on high voltage, large horsepower and medium voltage, medium horsepower motors with form wound coils. The goals for this project were to: (1) accurately measure the mechanical stress on the winding end turns and to determine the reliability of bracing system designs with consideration for reduced insulation allowances, and (2) compare the test data with theoretical calculated values obtained from FEA models. In this paper, the new test method is described and certain test results are discussed.

Investigations were conducted on the insulation life of adjustable speed drive-fed motors (also called inverter duty motors) from different manufacturers containing a variety of commercially available magnet wire and varnish insulation types. Test samples included wires, stators and motors. The goal for this project is to develop an accelerated aging test method for evaluating new materials and manufacturing processes used on ASD-fed motors, and for establishing factory quality assurance criteria. The test methods will be described and certain test results methods will be described and certain test results will be discussed in this paper.

Nectin and nectin-like proteins are cell adhesion molecules that mediate the formation of cell adherens junctions by forming homo- or hetero-dimers. Some members of this protein family can also be used by immune receptors to mediate immune recognition. For instance, nectin-like 2 (Necl-2) is used as a ligand for the immune system by interaction with the immune receptor CRTAM (class-I MHC restricted T-cell associated molecule), which is mainly expressed on the surface of cytotoxic lymphocyte cells. However, the Necl-2/CRTAM binding mode and its relationship to cell adhesion are not known. Here, we report a Necl-2/CRTAM complex structure, demonstrating that Necl-2 binding to CRTAM competes with the dimerization of CRTAM and possibly Necl-2. Necl-2 occupies the CRTAM homodimer interface, making homodimerization impossible. Mutational and functional analyses identified key amino acids (double "lock-and-key") responsible for the binding. Our work illustrates how the cell adhesion molecule Necl-2 competitively binds the immune receptor CRTAM. Otherwise, the nectin proteins can also be employed as the virus receptors, such as herpes simplex virus and measles virus.