Search

Crop domestication for increasing growth rates and yields appears to have altered the features of adaxial and abaxial stomata, but its effect on leaf water use efficiency (WUE) have not been experimentally verified. In this study, we characterized stomatal anatomy and carbon isotope discrimination (δ13C) in 32 wild and 36 domesticated genotypes of cotton grown under agricultural field conditions. The results showed that domesticated genotypes possessed lower WUE, as indicated by low or more negative δ13C compared with wild genotypes. Higher theoretical maximum stomatal conductance (gsmax) after domestication was accounted for by more stomata rather than significantly enlarged stomata. Specifically, abaxial stomatal density was higher whilst there was no change in the adaxial density. The size of both adaxial and abaxial stomata was greater due to larger guard cells but without there being any increase in pore size. However, there was a negative relationship between δ13C and stomatal size across wild and domesticated genotypes, especially on the abaxial leaf surface, because bigger stomata resulted in a lower maximum stomatal response rate to fluctuating canopy light, resulting in increased water loss. Overall, our results indicate that cotton domestication has resulted in substantial variation in stomatal anatomy, and that WUE and drought tolerance can potentially be improved in future breeding by decreasing the size of abaxial stomata to produce a faster stomatal response and hence a reduction in unnecessary water loss.

Background and aims: Genipin, an iridoid derived from geniposide by β-glucosidase hydrolysis, has shown potential benefit in the treatment of heart function insufficiency despite its unclear therapeutic mechanism. This study aimed to investigate the primary cardioprotective mechanism of genipin. We hypothesized that genipin demonstrated the antiapoptosis and anti-inflammation for cardiac protection by inhibiting the cyclooxidase 2 (COX2)-prostaglandin D2 (PGD2) and murine double minute 2 (MDM2)-p53 pathways. Methods: The normal Sprague-Dawley rats were made into myocardial infarction models by conventional methods. Animals were treated with genipin for 5 weeks after myocardial infarction (MI). Morphometric and hemodynamic measurements were performed 5 weeks post-MI. Biological and molecular experiments were performed after the termination. Results: Both morphometry and hemodynamics in systole and diastole were significantly impaired in the model group but restored close to basal level after treatment with genipin. Genipin also restored the post-MI upregulated expressions of cytochrome c, p53, COX2, and PGD2 and downregulated expression of MDM2 to the approximate baseline. Genipin inhibited apoptotic and inflammatory pathways to prevent post-MI structure-function remodeling. Conclusions: This study showed the cardioprotective mechanism of genipin and implied its potential clinical application for the treatment of ischemic heart failure.

Tissue engineering is an alternative method for preparing small-caliber (6 mm) vascular grafts. Dynamic mechanical conditioning is being researched as a method to improve mechanical properties of tissue engineered blood vessels. This method attempts to induce unique reaction in implanted cells that regenerate the matrix around them, thereby improving the overall mechanical stability of the grafts. In this study, we used a bioreactor to seed endothelial cells and smooth muscle cells into the inner and outer layers of the electrospun spider silk protein scaffold respectively to construct vascular grafts. The cell proliferation, mechanical properties, blood compatibility and other indicators of the vascular grafts were characterized in vitro. Furthermore, the vascular grafts were implanted in Sprague Dawley rats, and the vascular grafts' patency, extracellular matrix formation, and inflammatory response were evaluated in vivo. We aimed to construct spider silk protein vascular grafts with the potential for in vivo implantation by using a pulsating flow bioreactor. The results showed that, when compared with the static culture condition, the dynamic culture condition improved cell proliferation on vascular scaffolds and enhanced mechanical function of vascular scaffolds. In vivo experiments also showed that the dynamic culture of vascular grafts was more beneficial for the extracellular matrix deposition and anti-thrombogenesis, as well as reducing the inflammatory response of vascular grafts. In conclusion, dynamic mechanical conditioning aid in the resolution of challenges impeding the application of electrospun scaffolds and have the potential to construct small-caliber blood vessels with regenerative function for cardiovascular tissue repair.

The incidence rate of cardiovascular diseases is increasing year by year. The demand for coronary artery bypass grafting has been very large. Acellular blood vessels have potential clinical application because of their natural vascular basis, but their biocompatibility and anticoagulant energy need to be improved. We decellularized the abdominal aorta of SD rats, and then modified with bivalirudin via polydopamine. The mechanical properties, blood compatibility, cytocompatibility, immune response, and anticoagulant properties were evaluated, and then the bivalirudin-modified acellular blood vessels were implanted into rats for remodeling evaluation in vivo. The results we got show that the bivalirudin-modified acellular blood vessels showed good cytocompatibility and blood compatibility, and its anti-inflammatory trend was dominant in the immune response. After 3 months of transplantation, the bivalirudin-modified acellular blood vessels did not easily form thrombus. It was not easy to form calcification and could make the host cells grow better. Through vascular stimulation and immunofluorescence test, we found that vascular smooth muscle cells and endothelial cells proliferated well in the bivalirudin group. Bivalirudin-modified acellular blood vessels provided new idea for small diameter tissue engineering blood vessels, and may become a potential clinical substitute for small-diameter vascular grafts.

The problem of target detection and localization in layered media can be solved by the mixed TR–RTM. The highlight of this paper is on multilayer media, where the target is harder to detect than in...

Gold as a vital hedging asset plays increasing critical roles in risk management during turmoil macroeconomic environments. For the massive and indistinct impactors of gold price volatility, this paper tries to investigate whether the short‐ and long‐term asymmetry, extreme observations, and jump components in past gold volatility help to obtain higher forecasting accuracy in future volatility from both in‐sample and out‐of‐sample perspectives. A variety of evaluation methods are utilized to compare the performances of GARCH‐MIDAS models incorporating these volatility components and the standard ones without them. The results of in‐sample estimation show first that all the short‐term and long‐term asymmetry, extreme observations, and jump components have significantly impact on gold volatility. The evaluation results of out‐of‐sample forecasts suggest that the forecasting accuracy of gold volatility can be significantly improved by most of the extended GARCH‐MIDAS models including asymmetry, extreme observations, and jump components. The model including short‐term jump intensity and the model with both long‐term asymmetry and long‐term leverage effects have better forecasting performances than other models for gold volatility, especially for regular volatility. Moreover, GARCH‐MIDAS models incorporating long‐term leverage and long‐term jump have better performances in forecasting accuracy of extreme gold volatility.

Crop domestication appears to alter the adaxial and abaxial stomatal features for increasing growth rate and yield. However, its effect on leaf water use efficiency (WUE) has not been experimentally verified under domestication. In this study, we characterized stomatal anatomy and carbon isotope (δ 13C) in 32 wild and 36 domesticated genotypes of cotton grown under agricultural field. The results showed that domesticated genotypes possessed lower WUE as indicated by low or more negative δ 13C compared with wild genotypes. Higher maximum theoretical stomatal conductance (gsmax) was underpinned by more stomata rather than significantly enlarged stomata after domestication. Specifically, abaxial stomatal density was higher but no change in adaxial stomatal density following domestication, while both adaxial and abaxial stomatal size were greater due to larger guard cell without the contribution to stomatal pore size. However, there was a negative relationship between δ 13C and SS, especially the abaxial SS across wild and domesticated genotypes, because enlarged stomata resulted in a lower stomatal response rate to fluctuating canopy light, consequently excessive water loss. In conclusion, cotton domestication has triggered substantial variation in stomatal anatomy. WUE and drought tolerance in cotton can be improved by decreasing abaxial stomatal size for faster stomatal response and reducing unnecessary water loss in future cotton breeding.

Purpose The development of tissue-engineered blood vessels provides a new source of donors for coronary artery bypass grafting and peripheral blood vessel transplantation. Fibrin fiber has good biocompatibility and is an ideal tissue engineering vascular scaffold, but its mechanical property needs improvement. Methods We mixed polyurethane (PU) and fibrin to prepare the PU/fibrin vascular scaffolds by using electrospinning technology in order to enhance the mechanical properties of fibrin scaffold. We investigated the morphological, mechanical strength, hydrophilicity, degradation, blood and cell compatibility of PU/fibrin (0:100), PU/fibrin (5:95), PU/fibrin (15:85) and PU/fibrin (25:75) vascular scaffolds. Based on the results in vitro, PU/fibrin (15:85) was selected for transplantation in vivo to repair vascular defects, and the extracellular matrix formation, vascular remodeling, and immune response were evaluated. Results The results indicated that the fiber diameter of the PU/fibrin (15:85) scaffold was about 712nm. With the increase of PU content, the mechanical strength of the composite scaffolds increased, however, the degradation rate decreased gradually. The PU/fibrin scaffold showed good hydrophilicity and hemocompatibility. PU/fibrin (15:85) vascular scaffold could promote the adhesion and proliferation of mesenchymal stromal cells (MSCs). Quantitative RT-PCR experimental results showed that the expression of collagen, survivin and vimentin genes in PU/fibrin (15:85) was higher than that in PU/fibrin (25:75). The results in vivo indicated the mechanical properties and compliance of PU/fibrin grafts could meet clinical requirements and the proportion of thrombosis or occlusion was significantly lower. The graft showed strong vasomotor response, and the smooth muscle cells, endothelial cells, and ECM deposition of the neoartery were comparable to that of native artery after 3 months. At 3 months, the amount of macrophages in PU/fibrin grafts was significantly lower, and the secretion of pro-inflammatory and anti-inflammatory cytokines decreased. Conclusion PU/fibrin (15:85) vascular scaffolds had great potential to be used as small-diameter tissue engineering blood vessels.

This paper explores the effectiveness of predictors, including nine economic policy uncertainty indicators, four market sentiment indicators and two financial stress indices, in predicting the realized volatility of the SP 500 index. We employ the MIDAS-RV framework and construct the MIDAS-LASSO model and its regime switching extension (namely, MS-MIDAS-LASSO). First, among all considered predictors, the economic policy uncertainty indices (especially the equity market volatility index) and the CBOE volatility index are the most noteworthy predictors. Although the CBOE volatility index has the best predictive ability for stock market volatility, its predictive ability has weakened during the COVID-19 epidemic, and the equity market volatility index is best during this period. Second, the MS-MIDAS-LASSO model has the best predictive performance compared to other competing models. The superior forecasting performance of this model is robust, even when distinguishing between high- and low-volatility periods. Finally, the prediction accuracy of the MS-MIDAS-LASSO model even outperforms the traditional LASSO strategy and its regime switching extension. Furthermore, the superior predictive performance of this model has not changed with the outbreak of the COVID-19 epidemic.

Previous studies have proved that fibrin is an excellent scaffold material for tissue engineered blood vessel. However, the mechanical properties of fibrin are not enough. One way to solve the problem is to combine polymer materials with fibrin to enhance its biomechanical properties. In this study, a novel polycaprolactone (PCL)/fibrin composite scaffold was prepared by electrospinning technology. The morphological, physicochemical analysis, blood compatibility, biomechanical properties, biocompatibility and biodegradability of this vascular scaffold were evaluated. The results showed that electrospun PCL/fibrin scaffold possessed smaller aperture and larger fiber diameter than that of fibrin scaffold. The swelling ratio of the vascular PCL/fibrin scaffold at (0:100), (10:90), (20:80) and (30:70) was 112 ± 5.3, 103 ± 6.9, 94 ± 5.9 and 89 ± 3.4%, respectively. Mechanical properties of fibrin scaffolds were enhanced significantly by the addition of PCL. Furthermore, the time of plasma re-calcification, activated partial thromboplastin time and thromboplastin time in four different proportions of PCL/fibrin scaffolds were similar to that of the control group. Degradation experiments

The main goal of this paper is to investigate the predictability of five economic uncertainty indices for oil price volatility in a changing world. We employ the standard predictive regression fram...

To overcome the brittleness issue of SiCO aerogels, the polyacrylonitrile-based (PAN) carbon fiber was impregnated with SiCO sol to obtain carbon fiber-reinforced SiCO aerogel composites (C/SiCO). SiCO sol was prepared through an acid-alkaline two-step catalysis by using methyltrimethoxysilane (MTMS) and dimethyldiethoxysilane (DMDES) as precursors. C/SiCO-1, C/SiCO-2 and C/SiCO-3 were obtained after repeated impregnation of the SiCO sol and gelating, aging, supercritical drying and pyrolyzing one to three times. SEM images show that the SiCO aerogel fills the pores between the carbon fibers, and the nanoporous structure of the SiCO aerogel can effectively improve the thermal insulation of the composites. As the times of impregnation of the SiCO sol increased, the mechanical properties and oxidation resistance of C/SiCO have been improved significantly. The bending strength of C/SiCO-3 was 32.52 MPa, and the compressive strength (25%e) was 51.98 MPa. After heating at 1600 °C, the linear shrinkage in the thickness direction of C/SiCO-1 was 20.72%, while that of C/SiCO-3 was only 1.85%. A dense SiO2 molten oxide film formed on the surface of C/SiCO at high temperature, and its extremely low oxygen permeability effectively protected the inside of the composites.

In this paper we investigate the long-term connections between crude oil futures price and China stock market across the recent financial crisis by using a nonlinear threshold cointegration method within a multivariate framework. Three key macroeconomic fundamentals, i.e., foreign exchange market, domestic economic development and total foreign trade volume in China are used to detect their functions as transmission channels between oil futures market and China stock market. Different from extant literature, our empirical results show that firstly oil futures market has significant impacts on China stock market through both a direct way and an indirect way by the macroeconomic channels. Secondly, there are significant long-term cointegration relationships between crude oil futures price and China stock market even if two structural breaks in this relationship are observed in March 2008 and December 2012, respectively. The long-term connections between them vary dramatically at different market regimes, and are enhanced greatly in recent years with the adjustments in refined oil pricing mechanism and exchange rate regime in China. Finally, we find that, among the three macroeconomic fundamentals, exchange rate market plays the most significant role in transforming the impacts of oil prices on China stock market particularly after the financial crisis.

To improve the oxidative-resistant ability of carbon fibre-reinforced carbon aerogel composites (C/CAs), C/CAs were impregnated with a silicon oxycarbide (SiCO) precursor sol several times. After gelating, aging, solvent exchanging, ambient drying, and pyrolyzing, the SiCO precursor sol infiltrated the nanoporous C/CA, and anti-oxidation carbon aerogel composites with a SiCO ceramic inner coating (C/CA-SiCO) were prepared. It was found that the density of the material increases with the number of times that impregnation and pyrolysis were carried out. The mechanical properties and the anti-oxidant performance were significantly improved after the deposition with different numbers of the SiCO coating cycles. The bending strength increased from 2.2 MPa to 10.8–32.3 MPa and the compressive strength (10%e) increased from 0.4 MPa to 3.6–44.4 MPa. The weight loss for the as-prepared composites after heating at 1600 °C for 60 min in air was only 7.6%, and the in-plane shrinkage was less than 2%. Additionally, after the oxidation resistance test, the surface of the C/CA-SiCO had abundant β-SiO2 crystalline, whereas its inner region of the composite remained amorphous.

A TaSi2-MoSi2-ZrO2-borosilicate glass (TMZG) coating was prepared by a slurry method on a carbon fibre-reinforced porous silicon oxycarbide (SiCO) ceramic composite for thermal protection. The coating was well adhered to the substrate and showed a uniform thickness of approximately 375 µm. After thermal cycling from 1873 K to room temperature six times (total oxidation time of 180 min), the shape and dimension of the TMZG remain almost unchanged with no cracking or peeling of the coating surface. The TMZG-coated sample exhibits good oxidation resistance because of a molten SiO2 film with ZrSiO4 particles distributed on the outer layer of the coating. After ablation testing under an oxyacetylene flame at 1927 K for 90 s, the linear ablation rate of the TMZG coated sample are 8.33 × 10−4 mm/s. The whole coating retains integrity, preventing substrate ablation during the test. The TMZG coating with excellent temperature resistance shows broad applicability in thermal insulation materials.

Understanding the dependence and risk spillover among hedging assets is crucial for portfolio allocation and regulatory decision making. Using various copula and conditional Value-at-Risk (CoVaR) measures, this paper quantifies the dependence and risk spillover effects between three traditional and emerging hedging assets: Bitcoin, gold, and USD. Furthermore, we investigate these effects at various short- and long-term horizons using a variational model decomposition (VMD) method. The empirical results show that there is strong negative dependence between gold and USD, but Bitcoin and gold are weakly and positively connected. Secondly, risk spillovers exist only between Bitcoin and gold and between gold and USD. The risk spillover effect between Bitcoin and gold are not stable, that is, if Bitcoin or gold faces the downward or upward risk, both the downward and upward risk of another asset have the chance to increase. The negative risk spillover between gold and USD is stable, especially in long-term horizons. Finally, the risk spillover between Bitcoin and gold as well as between gold and USD are asymmetric at downward and upward market environment.

We examine whether the high cash ratio and the secular increase in cash holdings of U.S. firms are driven by healthcare and technology industries. We find that these two industries have significantly increased their cash holdings from 1980 to 2015. It is only in these two industries that firms with riskier cash flow, financially constrained firms, R&D firms, low-efficiency firms, and firms with low institutional ownership and high board size dramatically increase their cash holdings. Similar firms in other industries do not substantially accumulate cash reserves. The explanatory powers of firm characteristics, industry characteristics, and industry competition on cash holdings in healthcare and technology industries are stronger than in other industries. Moreover, we find a causal effect of the 2008 financial crisis on the difference in cash holdings between healthcare and technology industries, and other industries.

The success of artificial vascular graft in the host to obtain functional tissue regeneration and remodeling is a great challenge in the field of small diameter tissue engineering blood vessels. In our previous work, poly(ε-caprolactone) (PCL)/fibrin vascular grafts were fabricated by electrospinning. It was proved that the PCL/fibrin vascular graft was a suitable small diameter tissue engineering vascular scaffold with good biomechanical properties and cell compatibility. Here we mainly examined the performance of PCL/fibrin vascular graft in vivo. The graft showed randomly arranged nanofiber structure, excellent mechanical strength, higher compliance and degradation properties. At 9 months after implantation in the rat abdominal aorta, the graft induced the regeneration of neoarteries, and promoted ECM deposition and rapid endothelialization. More importantly, the PCL/fibrin vascular graft showed more microvessels density and fewer calcification areas at 3 months, which was beneficial to improve cell infiltration and proliferation. Moreover, the ratio of M2/M1macrophage in PCL/fibrin graft had a higher expression level and the secretion amount of pro-inflammatory cytokines started to increase, and then decreased to similar to the native artery. Thus, the electrospun PCL/fibrin tubular vascular graft had great potential to become a new type of artificial blood vessel scaffold that can be implanted in vivo for long term., Highlights • In this manuscript, we successfully prepared the PCL/fibrin vascular scaffold through electrospinning technology. • We further explore its role as a substitute for artificial blood vessels in vivo. • Mechanical properties, cell formation, extracellular matrix, immune response and calcification of grafts were assessed. • PCL/fibrin tubular vascular graft had great potential to become a new type of artificial blood vessel scaffold. • This research will bring significance to treatment of cardiovascular diseases, and promote development of vascular grafts.

Megaselia spiracularis Schmitz, 1938 (Diptera: Phoridae) is a pest that often appears in human living areas where it can spread pathogens. Besides, the species is of forensic value. Currently, studies focusing on the development of this species are limited. Understanding the developmental patterns of M. spiracularis, therefore, is important for controlling populations of this pest and for estimating the minimum postmortem interval (PMImin). Here, we studied the development of M. spiracularis exposed to seven constant temperatures ranging from 16 to 34 °C. The developmental durations, accumulated degree hours and larval body length changes were measured. Three kinds of development models that can be used to estimate the PMImin were established, including isomorphen diagram, isomegalen diagram and thermal summation model. The duration of M. spiracularis development at 16, 19, 22, 25, 28, 31 and 34 °C from egg to adult stage were 1131.1 ± 34.5, 807.3 ± 9.3, 529.6 ± 1.8, 367.0 ± 8.8, 302.4 ± 7.0, 250.0 ± 2.1 and 232.6 ± 1.9 h, respectively. The developmental threshold temperature and the thermal summation constant were estimated as 12.0 ± 0.5 °C and 4989.7 ± 308.9° hours, respectively. A general model represented by a logistic equation describing how larval body length will change with the time after hatching was fit to data. The present study provides basic developmental data of M. spiracularis, which can be used for achieving better control of this noxious insect as well as for estimation of its PMImin at different temperatures.

This paper examines the dependence structure between crude oil market and China stock market over different investment horizons, before and after the recent financial crisis, by combining the variational mode decomposition (VMD) method with various static and time-varying copulas. Based on the decomposed time series and the copula dependence, the Value-at-Risk (VaR), conditional VaR (CoVaR) and delta CoVaR (ΔCoVaR) are quantified to analyze the upside and downside risk spillovers from oil market to China stock market in raw, short- and long-run investment horizons before and after the financial crisis. The empirical results show that, first, the recent financial crisis enhances the dependences between the crude oil market and China stock market, and the long-run dependence increases more significantly than that of short-run. For the raw return series, there are symmetric upper and lower tail dependencies in full sample and pre-crisis subsample periods, but an average dependence in post-crisis subsample period. Second, the VaR of China stock market increases heavily around the financial crisis, but the average VaR after the crisis deceases compared to the risk before the crisis. Third, the risk spillovers from crude oil price to China stock market are found in each sample periods. Before the crisis, however, it mainly exists in long-run horizon, while after the crisis, it happens in both short- and long-run horizons. Finally, the risk spillovers from oil price to China stock market display strong asymmetric features, with larger long-term, downside risk spillovers in post-crisis subsample.

This paper examines stock liquidity in explaining the mixed relations between financial constraints and stock returns and the pricing of stock liquidity across financially constrained and unconstrained firms. We find a negative relation in liquid portfolios and a positive relation in illiquid portfolios. Financially constrained firms have higher liquidity risk and earn a higher illiquidity premium than unconstrained firms. Financial constraints cannot be independently priced in stock returns and can only be priced in conjunction with stock liquidity in bad economic times. Stock liquidity is independently priced for financially constrained firms or in good times, but not for unconstrained firms.

In order to improve the thermal oxidation resistance of carbon fiber-reinforced porous silicon oxycarbide (SiCO) ceramic composites, an Al2O3-containing TaSi2–MoSi2–borosilicate glass coating was formed on the surface of the composites via brushing and sintering. The anti-oxidation property of the coated composites at 1873 K was investigated. Microstructures and chemical compositions of the sample before and after anti-oxidation test were determined using XRD, SEM and EDS. After heating in air at 1873 K for 20 min, the Al2O3-containing TaSi2–MoSi2–borosilicate glass coating effectively protects the SiCO ceramic composites and the coated sample kept its appearance well without obvious defects on the surface. The cross-sectional SEM images show that the coating is covered by a film of oxidation products with a thickness of about 40 μm, which is dense and crack free. Inside the A-TMG coating, irregular-shaped silicides are surrounded by continuous borosilicate glass and no penetrating holes or visible cracks are found. Al2O3 increases the viscosity of the borosilicate glass, which improves oxidation resistance of the coated sample by enhancing gas-penetration resistance of the glass. In contrast, the sample without Al2O3 in the coating slurry is severely oxidized and exhibits lots of open pores on the surface after oxidation test.

In this study, we focus on the role of jumps and leverage in predicting the realized volatility (RV) of China's crude oil futures. We employ a standard mixed data sampling (MIDAS) modeling framework. First, the in-sample results indicate that the jump and leverage effects are useful in predicting the RV of Chinese crude oil futures. Second, the out-of-sample results suggest that jump has very significant predictive power at the one-day-ahead horizon while the leverage effect contains more useful information for long-term predictions. Moreover, our results are supported by a number of robustness checks. Finally, we find new evidence that the prediction model that considers the leverage effect has the best predictive power during the COVID-19 pandemic.