Return connectedness and multiscale spillovers across clean energy indices and grain commodity markets around COVID-19 crisis.

The aim of this paper is to examine the return connectedness and multiscale spillovers between the Clean Energy Index and the grain commodity market around COVID-19. Using daily data from January 4, 2017 to July 1, 2022, a time-varying parametric vector autoregressive (TVP-VAR) connectedness approach is first used to reveal connectedness patterns before and during COVID-19. We further used Baruník and Krehlík (2018)'s frequency domain spillover method to assess connectedness in different domain horizons. Our results show spillover effects over time and frequency, with COVID-19 significantly affecting the connectedness of the whole system. Dynamic connectedness peaks significantly after sudden bursts of COVID-19, validating the reported uncertainty. We also documented higher spillover levels in the short term than in the medium and long term. In addition, We find that (i) most clean energy indices are positively affected by the COVID-19 outbreak; (ii) the NASDAQ OMX Bio/Clean Fuels Index and NASDAQ OMX Geothermal Index send spillovers to all grain commodities throughout the sample period, while the WilderHill Clean Energy Index and NASDAQ OMX Wind Energy Index indices are the largest recipients of spillovers from other markets regardless of time horizon; (iii) the OMX Bio/Clean Fuels and OMX Geothermal Energy indices dominate spillover shocks to grain commodity markets. This is the first study to analyse the connectedness and time-frequency dynamics of returns in the green energy index and the grain commodity market. These results provide valuable insights to investors and key policymakers, especially at a time of more significant uncertainty.

Wilforol A inhibits human glioma cell proliferation and deactivates the PI3K/AKT signaling pathway.

OBJECTIVES: To study the anti-proliferation activity of wilforol A against glioma cells and its possible molecular mechanisms. METHODS: Human glioma cell lines U118 MG and A172, human tracheal epithelial cells (TECs) and astrocytes (HAs) were exposed to various concentrations of wilforol A and evaluated for viability, apoptosis, and levels of proteins using WST-8 assay, flow cytometry and Western blot analysis, respectively. RESULTS: Wilforol A inhibited the growth of U118 MG and A172 cells, but not TECs and HAs, in a concentration-dependent manner and the estimated IC50 were 6 to 11 µM after 4 h-exposure. Apoptosis was induced at an apoptotic rate of about 40% at 100 µM in U118 MG and A172 cells, but the rates were less than 3% in TECs and HAs. Co-exposure to caspase inhibitor Z-VAD-fmk significantly reduced wilforol A-induced apoptosis. Wilforol A treatment also reduced the colony formation ability of U118 MG cells and triggered a significant increase in ROS production. Elevated levels of pro-apoptotic proteins p53, Bax and cleaved caspase 3 and reduced level of the anti-apoptotic protein Bcl-2 were observed in glioma cells exposed to wilforol A. The expression of PI3K and p-Akt genes in the PI3K/AKT pathways were significantly downregulated in glioma cells treated with wilforol A. CONCLUSIONS: Wilforol A inhibits the growth of glioma cells, reduces the levels of proteins in the P13K/Akt signal transduction pathways and increases the levels of pro-apoptotic proteins.

Dependence and spillover among oil market, China's stock market and exchange rate: new evidence from the Vine-Copula-CoVaR and VAR-BEKK-GARCH frameworks.

We first employ the method of multivariate GARCH models and Vine-Copula-CoVaR to analyse relationships between dependence, systematic risk spillover, and volatility spillover between the USD/CNY exchange rate and the returns on WTI crude oil futures and the Chinese stock market since China's 2005 foreign exchange reform. We utilise daily data from 2005 to 2020. We find a more complex dependence of the USD/CNY exchange rate on stock markets and WTI crude oil prices. All have negative risk spillovers among paired markets, with WTI having the most substantial risk spillover. However, the strength of the systematic risk spillover varies across markets. Based on the results of the VAR(1)-BEKK-GARCH ( 1 , 1 ) and Wald tests confirm that there is a substantial mean spillover from the Chinese stock market and the USD/CNY exchange rate to the WTI crude oil price, whereas there is a more significant spillover from the WTI crude oil price to Chinese stock market volatility. The empirical findings extend the systematic understanding of the international crude oil price shocks to the dependence and transmission mechanism between the Chinese stock market and the USD/CNY exchange rate (USD/CNY). Our findings can help investors and policymakers to manage risk better and develop more sensible market rules.

Diamond coated artificial cardiovascular devices.

Ultrananocrystalline diamond (UNCD), an extremely smooth, low cost diamond coating was successfully developed herein for antithrombogenic application which requires high biocompatibility, low wear, low friction, and chemical inertness. The substrate materials utilized in the Jarvik 2000 ventricular assist device (VAD), silicon carbide and titanium alloy, provide an excellent substrate match for UNCD integration. The paper addresses the development of medical-quality UNCD films to significantly improve the knowledge base regarding the defect mechanisms of UNCD films, to reduce or eliminate known wear-inducing imperfections in the film, and to thoroughly characterize and test the films as well as assembled UNCD-coated VADs. After the defect reduction and seeding experiments to improve film adhesion and coating quality, the best candidate deposition method has been down-selected for coating and assembly of VAD parts from Jarvik Heart. The coated and assembled devices have been tested with mechanical and blood-simulating fluid hydrodynamic testing at Jarvik Heart for full verification of the new coating technology. UNCD interface takes advantage of combining unmatched durability and antithrombogenicity.

Ultrananocrystalline Diamond Integration with Pyrolytic Carbon Components of Mechanical Heart Valves.

In this report, an idea of integrating ultrananocrystalline diamond (UNCD) with pyrolytic carbon (PyC) -based mechanical heart valves, has been demonstrated. The report addresses the strategies to avoid graphitization and film delamination during the diamond coating. Raman and scratch tests showed that a UNCD film with high purity could adhere to the PyC substrate strongly. A thrombin generation study demonstrated an excellent biocompatibility of UNCD towards fresh human platelets. These results suggest that UNCD could be a good candidate of surface material for next generation heart valves and other implantable devices.

Polyetherimide-grafted Fe3O4@SiO22 nanoparticles as theranostic agents for simultaneous VEGF siRNA delivery and magnetic resonance cell imaging.

Engineering a safe and high-efficiency delivery system for efficient RNA interference is critical for successful gene therapy. In this study, we designed a novel nanocarrier system of polyethyleneimine (PEI)-modified Fe3O4@SiO2, which allows high efficient loading of VEGF small hairpin (sh)RNA to form Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites for VEGF gene silencing as well as magnetic resonance (MR) imaging. The size, morphology, particle stability, magnetic properties, and gene-binding capacity and protection were determined. Low cytotoxicity and hemolyticity against human red blood cells showed the excellent biocompatibility of the multifunctional nanocomposites, and also no significant coagulation was observed. The nanocomposites maintain their superparamagnetic property at room temperature and no appreciable change in magnetism, even after PEI modification. The qualitative and quantitative analysis of cellular internalization into MCF-7 human breast cancer cells by Prussian blue staining and inductively coupled plasma atomic emission spectroscopy analysis, respectively, demonstrated that the Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites could be easily internalized by MCF-7 cells, and they exhibited significant inhibition of VEGF gene expression. Furthermore, the MR cellular images showed that the superparamagnetic iron oxide core of our Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites could also act as a T2-weighted contrast agent for cancer MR imaging. Our data highlight multifunctional Fe3O4@SiO2/PEI/VEGF shRNA nanocomposites as a potential platform for simultaneous gene delivery and MR cell imaging, which are promising as theranostic agents for cancer treatment and diagnosis in the future.

The effect of electrode size and surface heterogeneity on electrochemical properties of ultrananocrystalline diamond microelectrode.

We report here the effect of electrode size on electrochemical properties of boron-doped ultrananocrystalline diamond (UNCD) microelectrodes using electrochemical impedance spectroscopy (EIS). By reducing microelectrode size from 250-µm to 10-µm diameter (D), the shape of impedance spectra changes from linear line to two-arcs. The fitting of experimental data to electrochemical circuit model suggests that each arc likely corresponds to UNCD grains and grain boundary phases. The two phases become separable as a result of microelectrode size reduction. In addition, for D ≤ 100-µm, microstructural and morphological defects/heterogeneities of grain boundaries and the presence of surface oxygen are also revealed in the spectra. The microelectrode size reduction specifically affect the impedance of the grain boundaries, e.g. for ultramicroelectrodes, UMEs (D ≤ 25-µm), as the grain boundary impedance increases by ~30-fold. Thus, at UMEs, the grain-grain boundary properties are revealed more sensitively in the spectra. Atomic force microscopy, scanning electron microscopy, Raman spectroscopy and surface profilometry measurements were performed to study the influence of microfabrication on surface properties. A significant increase in surface roughness after microfabrication shows that heterogeneities as observed in the spectra are not only due to intrinsic UNCD properties but also arises from microfabrication.

Characterization of ultrananocrystalline diamond microsensors for in vivo dopamine detection.

We show the technical feasibility of coating and micro patterning boron-doped ultrananocrystalline diamond (UNCD®) on metal microwires and of applying them as microsensors for the detection of dopamine in vivo using fast-scan cyclic voltammetry. UNCD electrode surface consistently generated electrochemical signals with high signal-to-noise ratio of >800 using potassium ferrocyanide-ferricyanide redox couple. Parylene patterned UNCD microelectrodes were effectively applied to detect dopamine reliably in vitro using flow injection analysis with a detection limit of 27 nM and in the striatum of the anesthetized rat during electrical stimulation of dopamine neurons.

A quantitative study of detection mechanism of a label-free impedance biosensor using ultrananocrystalline diamond microelectrode array.

It is well recognized that label-free biosensors are the only class of sensors that can rapidly detect antigens in real-time and provide remote environmental monitoring and point-of-care diagnosis that is low-cost, specific, and sensitive. Electrical impedance spectroscopy (EIS) based label-free biosensors have been used to detect a wide variety of antigens including bacteria, viruses, DNA, and proteins due to the simplicity of their detection technique. However, their commercial development has been hindered due to difficulty in interpreting the change in impedance upon antigen binding and poor signal reproducibility as a result of surface fouling and non-specific binding. In this study, we develop a circuit model to adequately describe the physical changes at bio functionalized surface and provide an understanding of the detection mechanism based on electron exchange between electrolyte and surface through pores surrounding antibody-antigen. The model was successfully applied to extract quantitative information about the bio surface at different stages of surface functionalization. Further, we demonstrate boron-doped ultrananocrystalline diamond (UNCD) microelectrode array (3 × 3 format, 200 µm diameter) improves signal reproducibility significantly and increases sensitivity by four orders of magnitude. This study marks the first demonstration of UNCD array based biosensor that can reliably detect a model Escherichia coli K12 bacterium using EIS, positioning this technology for rapid adoption in point-of-use applications.

Control of Nanoscale Environment to Improve Stability of Immobilized Proteins on Diamond Surfaces.

Immunoassays for detection of bacterial pathogens rely on the selectivity and stability of bio-recognition elements such as antibodies tethered to sensor surfaces. The search for novel surfaces that improve the stability of biomolecules and assay performance has been pursued for a long time. However, the anticipated improvements in stability have not been realized in practice under physiological conditions because the surface functionalization layers on commonly used substrates, silica and gold, are themselves unstable on time scales of days. In this paper, we show that covalent linking of antibodies to diamond surfaces leads to substantial improvements in biological activity of proteins as measured by the ability to selectively capture cells of the pathogenic bacterium Escherichia coli O157:H7 even after exposure to buffer solutions at 37 °C for extended periods of time, approaching 2 weeks. Our results from ELISA, XPS, fluorescence microscopy, and MD simulations suggest that by using highly stable surface chemistry and controlling the nanoscale organization of the antibodies on the surface, it is possible to achieve significant improvements in biological activity and stability. Our findings can be easily extended to functionalization of micro and nanodimensional sensors and structures of biomedical diagnostic and therapeutic interest.

[Effect of phosphor on accumulation and chemical forms of cadmium, and physiological characterization in different varieties of Capsicum annuum L].

Pot experiments were carried out to investigate the influence of different Phosphor (P) levels (0, 0.3% and 0.5%) on the plant growth, activities of antioxidant enzymes, accumulation and chemical forms of cadmium (Cd) in Capsicum annuum L. when exposed to Cd (10 mg x kg(-1)). The results showed that dry weights of leaf, fruit, roots and total dry weights of plant, and concentration and accumulation of Cd significantly differed between two varieties of Capsicum annuum L. Dry weights of fruit and total plant of Chaotianjiao increased by P (0.3% and 0.5%), while that of Yanjiao425 was inhibited. Activities of catalase (CAT) were increased at first, and then reduced in the presence of P; Activities of superoxide dismutase (SOD) and peroxidase (POD) of Chaotianjiao increased with increasing levels of P, but activities of SOD and POD of Yanjiao425 decreased with increasing levels of P. Chemical forms of Cd in fruit of Capsicum annuum L. were in order of F(NaCl) > F(HAC) > F(E) > Fr > F(HC) > F(W). The total extractable Cd, ethanol-extractable Cd, hydrochloric acid-extractable Cd and residual Cd in fruit of Ynajiao425 obviously decreased in the presence of P compared to the control, while the total extractable Cd, water-extractable Cd, acetic acid-extractable Cd and residual Cd in fruit of Chaotianjiao increased. Cadmium accumulations of Capsicum annuum L. were in order of roots > stew > leaf > fruit. Cadmium accumulations in fruit and plant of Yanjiao425 were decreased by 47.7% and 58.5% , 5.5% and 13. 1% in the presence of 0.3% and 0.5% P when exposed to Cd, and Cd accumulations in fruit and plant of Chaotianjiao were decreased by 23.6% in the presence of 0.3% P.

Surface functionalization of thin-film diamond for highly stable and selective biological interfaces.

Carbon is an extremely versatile family of materials with a wide range of mechanical, optical, and mechanical properties, but many similarities in surface chemistry. As one of the most chemically stable materials known, carbon provides an outstanding platform for the development of highly tunable molecular and biomolecular interfaces. Photochemical grafting of alkenes has emerged as an attractive method for functionalizing surfaces of diamond, but many aspects of the surface chemistry and impact on biological recognition processes remain unexplored. Here we report investigations of the interaction of functionalized diamond surfaces with proteins and biological cells using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, and fluorescence methods. XPS data show that functionalization of diamond with short ethylene glycol oligomers reduces the nonspecific binding of fibrinogen below the detection limit of XPS, estimated as > 97% reduction over H-terminated diamond. Measurements of different forms of diamond with different roughness are used to explore the influence of roughness on nonspecific binding onto H-terminated and ethylene glycol (EG)-terminated surfaces. Finally, we use XPS to characterize the chemical stability of Escherichia coli K12 antibodies on the surfaces of diamond and amine-functionalized glass. Our results show that antibody-modified diamond surfaces exhibit increased stability in XPS and that this is accompanied by retention of biological activity in cell-capture measurements. Our results demonstrate that surface chemistry on diamond and other carbon-based materials provides an excellent platform for biomolecular interfaces with high stability and high selectivity.

[Effect of different zinc levels on accumulation and chemical forms of cadmium, and physiological characterization in Capsicum annuum L].

Pot experiments were carried out to investigate the influence of different zinc (Zn) levels (0, 100, 200, 400 and 600 micromol x L(-1)) on the plant growth,activities of antioxidant enzymes, contents of chlorophyll a and b, accumulation and chemical forms of cadmium (Cd) in Capsicum annuum L. when exposed to Cd (20 mg x kg(-1)). The results showed that dry weights of leaf, stem, fruit and root, and contents of chlorophyll a and b in Capsicum annuum L. were increased by Zn ( < or = 400 micromol x L(-1)), while inhibited by high Zn (600 micromol x L(-1)). Activities of superoxide dismutase (SOD) and catalase (CAT) were reduced by Zn ( < or =400 micromol x L(-1)), the lowest activities of SOD and CAT were recorded in 400 micromol x L(-1) Zn, but activities of SOD and CAT were increased when Zn >400 micromol x L(-1). Cadmium concentrations in stem, fruit and root of Capsicum annuum L. were decreased by 2.7%-5.4%, 7.5%-28.1% and 7.6%-21.8% in the presence of Zn when exposed to Cd. The total extractable Cd, NaCl- extractable Cd, water-extractable Cd and ethanol-extractable Cd in fruit were reduced by 7.7%-21.8%, 4.11%-23.6%, 54.5%-66.8% and 4.8%-86.7% in the presence of Zn,while acetic acid- extractable Cd and residual Cd were increased by 28.0%-68.0% and 12.6%-25.0%.

Wear-resistant diamond nanoprobe tips with integrated silicon heater for tip-based nanomanufacturing.

We report exceptional nanoscale wear and fouling resistance of ultrananocrystalline diamond (UNCD) tips integrated with doped silicon atomic force microscope (AFM) cantilevers. The resistively heated probe can reach temperatures above 600 degrees C. The batch fabrication process produces UNCD tips with radii as small as 15 nm, with average radius 50 nm across the entire wafer. Wear tests were performed on substrates of quartz, silicon carbide, silicon, or UNCD. Tips were scanned for more than 1 m at a scan speed of 25 mum s(-1) at temperatures ranging from 25 to 400 degrees C under loads up to 200 nN. Under these conditions, silicon tips are partially or completely destroyed, while the UNCD tips exhibit little or no wear, no signs of delamination, and exceptional fouling resistance. We demonstrate nanomanufacturing of more than 5000 polymer nanostructures with no deterioration in the tip.

Rapid thermal lysis of cells using silicon-diamond microcantilever heaters.

This paper presents the design and application of microcantilever heaters for biochemical applications. Thermal lysis of biological cells was demonstrated as a specific example. The microcantilever heaters, fabricated from selectively doped single crystal silicon, provide local resistive heating with highly uniform temperature distribution across the cantilevers. Very importantly, the microcantilever heaters were coated with a layer of 100 nm thick electrically insulating ultrananocrystalline diamond (UNCD) layer used for cell immobilization on the cantilever surface. Fibroblast cells or bacterial cells were immobilized on the UNCD/cantilever surfaces and thermal lysis was demonstrated via optical fluorescence microscopy. Upon electrical heating of the cantilever structures to 93 degrees C for 30 seconds, fibroblast cell and nuclear membrane were compromised and the cells were lysed. Over 90% of viable bacteria were also lysed after 15 seconds of heating at 93 degrees C. This work demonstrates the utility of silicon-UNCD heated microcantilevers for rapid cell lysis and forms the basis for other rapid and localized temperature-regulated microbiological experiments in cantilever-based lab on chip applications.

Nanofabrication in cellulose acetate.

We have demonstrated nanofabrication with commercialized cellulose acetate. Cellulose acetate is used for bulk nanofabrication and surface nanofabrication. In bulk nanofabrication, cellulose acetate reacts with an e-beam and permanent patterns are formed in it instead of being transferred to other substrates. We have studied the nano relief modulation performance of cellulose acetate before and after development. The depth of the nanopatterns is magnified after development, and is varied by exposing dosage and line width of the pattern. The thinnest 65 nm wide line is achieved in the bulk fabrication. We also demonstrate a binary phase Fresnel lens array which is directly patterned in a cellulose acetate sheet. Because of its unique mechanical and optical properties, cellulose is a good candidate for a template material for soft imprinting lithography. In the surface nanofabrication, cellulose acetate thin film spin-coated on silicon wafers is employed as a new resist for e-beam lithography. We achieved 50 nm lines with 100 nm pitches, dots 50 nm in diameter, and single lines with the smallest width of 20 nm. As a new resist of e-beam lithography, cellulose acetate has high resolution comparable with conventional resists, while having several advantages such as low cost, long stock time and less harmfulness to human health.

Micro/nanosized refractive lens arrays formed by means of conformal thin film deposition.

We provide a 'growing' method for fabricating a microlens array with lateral size of a few microns or less. Instead of using complicated etching techniques, the method forms a spherical profile of the lens using conformal chemical vapor deposition. We have fabricated two lens arrays. One has a pitch of 1200 nm, a circular aperture 1000 nm in diameter and a sag height of 130 nm. The other array has a pitch of 600 nm, and a square aperture of 600 nm × 600 nm, with a fill factor close to 100%. The maximum profile deviation between the fabricated lens and an ideal sphere is about 11% and 14% respectively. The calculation indicates that the curvature difference of the profile of the square lens in the orthogonal and diagonal direction is 5.5%. The roughness of the lens is measured as approximately 6 nm.