We aim to tackle the longstanding debate on whether stock liquidity enhances or impedes firm innovation. This topic is of interest because innovation is crucial for firm- and national-level ...competitiveness and stock liquidity can be altered by financial market regulations. Using a difference-in-differences approach that relies on the exogenous variation in liquidity generated by regulatory changes, we find that an increase in liquidity causes a reduction in future innovation. We identify two possible mechanisms through which liquidity impedes innovation: increased exposure to hostile takeovers and higher presence of institutional investors who do not actively gather information or monitor.
During 2005 to 2007, the SEC ordered a pilot program in which one-third of the Russell 3000 index were arbitrarily chosen as pilot stocks and exempted from shortsale price tests. Pilot firms' ...discretionary accruals and likelihood of marginally beating earnings targets decrease during this period, and revert to pre-experiment levels when the program ends. After the program starts, pilot firms are more likely to be caught for fraud initiated before the program, and their stock returns better incorporate earnings information. These results indicate that short selling, or its prospect, curbs earnings management, helps detect fraud, and improves price efficiency.
The epithelial-mesenchymal transition (EMT) is crucial to cancer progression and metastasis. Although multiple cellular miRNAs have been identified to regulate the EMT and metastasis in cancers, the ...role of viral miRNAs in cancer progression remains largely unknown. Nasopharyngeal carcinoma (NPC) is an Epstein-Barr virus (EBV)-associated malignancy typically characterized by its early metastasis. In the present study, we have discovered the involvement of a viral miRNA, EBV-miR-BART7-3p, in the EMT and metastasis of NPC cells. Initially, we observed that EBV-miR-BART7-3p was highly expressed in NPC and positively correlated with lymph node metastasis and clinical stage of NPC. Subsequently, we demonstrated that EBV-miR-BART7-3p enhanced cell migration/invasion in vitro, cancer metastasis in vivo, and particularly the EMT characterized by loss of epithelial markers and gain of mesenchymal features in NPC cells. Furthermore, mechanistic studies disclosed that EBV-miR-BART7-3p targeted a major human tumor suppressor PTEN, modulating PI3K/Akt/GSK-3β signaling and eventually leading to the high expression and nuclear accumulation of Snail and β-catenin, which favor EMT. Knockdown of PTEN could phenocopy the effect of EBV-miR-BART7-3p, whereas re-expression of PTEN resulted in a phenotypic reversion. Moreover, these findings were supported by an observation of an EBV-positive cell model in which silencing of endogenous EBV-miR-BART7-3p partially attenuated cell migration/invasion and altered EMT protein expression pattern via reverting PI3K/Akt, Snail and β-catenin expression. Thus, this study suggests a novel mechanism by which EBV-miR-BART7-3p modulates the EMT and metastasis of NPC cells, and a clinical implication of EBV-miR-BART7-3p as a potential biomarker or therapeutic target.
We explore the dependence of the incidence of moderate-luminosity (L0.5−8 keV = 1041.9−43.7 erg s-1) active galactic nuclei (AGNs) and the distribution of their accretion rates on host color at 0.5 ...<z < 2.5. Based on the deepest X-ray and UV-to-far-infrared data in the two The Great Observatories Origins Deep Survey (GOODS) fields, we identify 221 AGNs within a mass-complete parent galaxy sample down to M∗ > 1010 M⊙. We use extinction-corrected rest-frame U−V colors to divide both AGN hosts and non-AGN galaxies into red sequence (red), green valley (green), and blue cloud (blue) populations. We find that the fraction of galaxies hosting an AGN at fixed X-ray luminosity increases with stellar mass and redshift for all the three galaxy populations, independent of their colors. However, both the AGN fraction at fixed stellar mass and its evolution with redshift are clearly dependent on host colors. Most notably, red galaxies have the lowest AGN fraction (~5%) at z ~ 1 yet with most rapid evolution with redshift, increasing by a factor of ~5 (24%) at z ~ 2. Green galaxies exhibit the highest AGN fraction across all redshifts, which is most pronounced at z ~ 2 with more than half of them hosting an AGN at M∗ > 1010.6 M⊙. Together with the high AGN fraction in red galaxies at z ~ 2, this indicates that (X-ray) AGNs could be important in both transforming (quenching) star-forming galaxies into quiescent ones and subsequently maintaining their quiescence at high redshift. Furthermore, consistent with previous studies at lower redshifts, we show that the probability of hosting an AGN for the total galaxy population can be characterized by a universal Eddington ratio (as approximated by LX/M∗) distribution (p(λEdd) ~ λEdd-0.4), which is independent on host mass. Yet consistent with their different AGN fractions, galaxies with different colors appear to also have different p(λEdd) with red galaxies exhibiting more rapid redshift evolution compared with that for green and blue galaxies. Evidence for a steeper power-law distribution of p(λEdd) in red galaxies (p(λEdd) ~ λEdd-0.6) is also presented, though larger samples are needed to confirm. These results suggest that the AGN accretion or the growth of supermassive black holes is related to their host properties, and may also influence their hosts in a different mode dependent on the host color.
Red tide caused severe impacts on marine fisheries, ecology, economy and human life safety. The formation mechanism of the red tide is rather complicated; thus, red tide prediction and forecasting ...have long been a research hotspot around the globe. This study collected ocean monitoring data before and after the occurrence of red tides in Xiamen sea area from 2009 to 2017. The Pearson correlation coefficient method was used to obtain the associated factors of red tide occurrence, including water temperature, saturated dissolved oxygen, dissolved oxygen, chlorophyll-aand potential of hydrogen. Then, we built a short-time red tide prediction model based on the combination of multiple feature factors. chlorophyll-a, dissolved oxygen, saturated dissolved oxygen, potential of hydrogen, water temperature, salinity, turbidity, wind speed, wind direction and Air pressure were used as the input variables, building a short-time prediction model based on the combination of multiple feature factors to forecast red tide in the next 6 h by using the monitoring data. The accuracy of different forecast models with different feature combinations was compared. Results show that the distinguishing factors which have the most significant influence on red tide prediction in Xiamen are chlorophyll-a, dissolved oxygen, saturated dissolved oxygen, potential of hydrogen, and water temperature. the convergence speed of the Gated Recurrence Unit (GRU) prediction model based on the main feature factor proposed in this paper was faster and obtained the expected result, and the accuracy rates of the buoys are above 92%. The research shows the feasibility to use GRU network model to predict the occurrence of red tide with multi-feature factors as input parameters. the paper provides an effective method for the red tide early warning in Xiamen sea area.
•A strong correlation between different environmental monitoring factors.•The main feature factors are Temp, SDO, Do, CHl and PH value.•With the decrease of samples, the accuracy decreases.•The convergence speed of the GRU prediction model based on the main feature factor proposed in this paper is faster.•The relationship between environmental factors is analyzed by Pearson correlation coefficient.•Temp, SDO, Do, CHl and PH have the association with the red tide occurrence in Xiamen sea area.•The abundant experimental samples have the higher predicting accuracy.•Our proposed model achieved the state-of-the-art predicting performance.
Temporomandibular joint disorders are common diseases characterized by joint clicking, limited mouth opening and pain, which have a huge impact on the patients' daily life. Conservative methods ...include medicine, physiotherapy and occlusal application. With the advancement of medical technology, the arthroscopy is becoming popular for its minimally invasion and high efficiency. This review focuses on the common arthroscopic methods, and provides an outlook of the arthroscopic surgery.
Whole Atmosphere Community Climate Model (WACCM) simulations are used to investigate solar and lunar tide changes in the mesosphere and lower thermosphere (MLT) that occur in response to sudden ...stratosphere warmings (SSWs). The average tidal response is demonstrated based on 23 moderate to strong Northern Hemisphere SSWs. The migrating semidiurnal lunar tide is enhanced globally during SSWs, with the largest enhancements (∼60–70%) occurring at mid to high latitudes in the Northern Hemisphere. Enhancements in the migrating solar semidiurnal tide (SW2) also occur up to an altitude of 120 km. Above this altitude, the SW2 decreases in response to SSWs. The SW2 enhancements are 40–50%, making them smaller in a relative sense than the enhancements in the migrating semidiurnal lunar tide. Changes in nonmigrating solar tides are, on average, generally small and the only nonmigrating tides that exhibit changes greater than 20% are the diurnal tide with zonal wave number 0 (D0) and the westward propagating semidiurnal tide with zonal wave number 1 (SW1). D0 is decreased by ∼20–30% at low latitudes, while SW1 exhibits a similar magnitude enhancement at mid to high latitudes in both hemispheres. The tidal changes are attributed to a combination of changes in the zonal mean zonal winds, changes in ozone forcing of the SW2, and nonlinear planetary wave‐tide interactions. We further investigate the influence of the lunar tide enhancements on generating perturbations in the low latitude ionosphere during SSWs by using the WACCM‐X thermosphere to drive an ionosphere‐electrodynamics model. For both solar maximum and solar minimum simulations, the changes in the equatorial vertical plasma drift velocity are similar to observations when the lunar tide is included in the simulations. However, when the lunar tide is removed from the simulations, the low latitude ionosphere response to SSWs is unclear and the characteristic behavior of the low latitude ionosphere perturbations that is seen in observations is no longer apparent. Our results thus indicate the importance of variability in the lunar tide during SSWs, especially for the coupling between SSWs and perturbations in the low latitude ionosphere.
Key Points
Investigate tidal variability due to SSWs based on WACCM simulations of 23 SSWs
Large changes in the migrating semidiurnal lunar and solar tides during SSWs
Changes in lunar tide are important for coupling between SSWs and ionosphere
Stock market liquidity and firm value Noe, Thomas H; Fang, Vivian W; Tice, Sheri
Journal of financial economics,
10/2009, Letnik:
94, Številka:
1
Journal Article
Recenzirano
This paper investigates the relation between stock liquidity and firm performance. The study shows that firms with liquid stocks have better performance as measured by the firm market-to-book ratio. ...This result is robust to the inclusion of industry or firm fixed effects, a control for idiosyncratic risk, a control for endogenous liquidity using two-stage least squares, and the use of alternative measures of liquidity. To identify the causal effect of liquidity on firm performance, we study an exogenous shock to liquidity--the decimalization of stock trading--and show that the increase in liquidity around decimalization improves firm performance. The causes of liquidity's beneficial effect are investigated: Liquidity increases the information content of market prices and of performance-sensitive managerial compensation. Finally, momentum trading, analyst coverage, investor overreaction, and the effect of liquidity on discount rates or expected returns do not appear to drive the results.
The Formosa Satellite‐7/Constellation Observing System for Meteorology, Ionosphere, and Climate‐2 (FORMOSAT‐7/COSMIC‐2) Global Navigation Satellite System radio occultation (RO) payload can provide ...global observations of slant total electron content (sTEC) with an unprecedentedly high spatial temporal resolution. Recently, a new ionospheric data assimilation system, the Community Gridpoint Statistical Interpolation (GSI) Ionosphere, is constructed with the National Oceanic and Atmospheric Administration GSI Ensemble Square Root Filter and the Global Ionosphere Plasmasphere and the Thermosphere Ionosphere Electrodynamic General Circulation Model. The paper demonstrates the capability of the GSI Ionosphere to improve the ionospheric specification and make a quantitative assessment of the impact of FORMOSAT‐7/COSMIC‐2 RO data on the ionospheric observing system simulation experiments conducted to calibrate key Ensemble Square Root Filter parameters that control detrimental effects of the sampling errors, particularly on the ensemble‐based estimation of the correlation between observations and model states, in order to yield high‐quality assimilation analysis. Results from the observing system simulation experiments show that (1) an ensemble size larger than 70 is recommended for assimilation of RO sTEC data with the GSI Ionosphere and (2) localizing the impact of observations around the tangent points in the horizontal direction with a length scale of 5,000 km is effective in improving assimilation analysis quality. Assimilation of sTEC data from FORMOSAT‐7/COSMIC‐2 can considerably improve the global ionospheric specification through the application of the GSI Ionosphere. The GSI Ionosphere can provide instantaneous global pictures of the ionosphere variability and help characterize day‐to‐day variability of the ionosphere and deepen our understanding of the observed day‐to‐day variability.
Key Points
Synthetic FORMOSAT‐7/COSMIC‐2 RO sTEC are assimilated into a coupled model of the thermosphere, ionosphere, and plasmasphere by the EnSRF
Observing system simulation experiments are used to examine the effects of key EnSRF parameters on the ionospheric specification in detail
The ensemble size larger than 70 and the horizontal covariance localization with a length scale of 5,000 km is required to improve the result
The importance of winds at different altitudes and latitudes for the electrodynamics of the low‐latitude evening ionosphere is examined with a model of the global coupled ionosphere‐thermosphere ...system. The model reproduces the main observed features of the evening equatorial plasma vortex and the prereversal enhancement (PRE) of the vertical drift. The electrodynamics is driven primarily by the zonal wind forced by the diurnally varying zonal pressure‐gradient force. The zonal wind lags the zonal pressure‐gradient force owing to inertia. When ion drag is important, the time lag of the wind behind the pressure gradient force is shortened, and the high‐altitude evening wind turns eastward earlier than the wind at lower altitudes, where ion drag is less important. Therefore, a vertical shear of the zonal wind tends to develop at altitudes around the transition between small and large ion drag at the bottom of the F region. This wind shear is closely associated with the vertical shear in the zonal convection velocity that is part of the evening plasma vortex. Unlike previous studies, we find that the winds driving the PRE lie mainly on field lines with apexes above the peak of the equatorial F layer, field lines that extend in magnetic latitude out to nearly 30° and encompass the entire evening equatorial ionization anomaly region. Contrary to previous suggestions, the westward convection in the bottomside of the evening plasma vortex is found to weaken, rather than strengthen, the PRE. Daytime winds have relatively little influence on the low‐latitude evening electrodynamics.
Key Points
Evening zonal wind shear occurs at the base of F region due to ion drag
Zonal winds at EIA latitudes drive prereversal enhancement of vertical drift
Westward drift in underside evening plasma vortex does not enhance PRE
PDF
