ABSTRACT
This study introduces a new BEKK-CARR model to explore the volatility spillover effects among mainland China, Hong Kong, and Taiwan stock markets during the COVID-19 pandemic. We also extend the approach of Diebold and Yilmaz (2009, 2012) to infer a brand-new volatility spillover index to discuss the bi-directional volatility transmission. Our results show that the trading information flow among these three markets has changed significantly as a result of the COVID-19 pandemic. The strength of volatility spillover is increasing during this momentous period. The Hong Kong stock market plays a pivotal role in volatility transmission. The values for half-lives by exogenous shocks keep relatively low during the pandemic period. A reasonable explanation is that the trading information transmissions among stock markets are quicker than in the non-pandemic period. © 2023 The Authors. Asia-Pacific Journal of Financial Studies published by John Wiley & Sons Australia, Ltd on behalf of Korean Securities Association.
ABSTRACT
Turkey coronaviral enteritis caused by turkey coronavirus (TCoV) continues to infect turkey flocks, resulting in significant economic loss. Determining and understanding genetic relationships among different TCoV isolates or strains is important for controlling the disease. Using two-step RT-PCR assays that amplify the full length of TCoV spike (S) gene, TCoV isolates can be sequenced, analyzed, and genotyped. Described in this chapter is the protocol on PCR amplification and sequencing analysis of full-length TCoV S gene. Such protocol is useful in molecular epidemiology for establishing an effective strategy to control the transmission of TCoV among turkey flocks. Copyright © Springer Science+Business Media New York 2016
ABSTRACT
Turkey coronavirus (TCoV) infection causes acute atrophic enteritis in turkey poults, leading to significant economic loss in the turkey industry. Rapid detection, differentiation, and quantitation of TCoV are critical to the diagnosis and control of the disease. A specific one-step real-time reverse transcription-polymerase chain reaction (RT-PCR) assay using TCoV-specific primers and dual-labeled fluorescent probe for detection and quantitation of TCoV in feces and intestine tissues is described in this chapter. The fluorogenic probe labeled with a reporter dye (FAM, 6-carboxytetramethylrhodamine) and a quencher dye (Absolute QuencherTM) was designed to bind to a 186 base-pair fragment flanked by the two PCR primers targeting the 3' end of spike gene (S2) of TCoV. The assay is highly specific and sensitive and can quantitate between 102 and 1010 copies/mL of viral genome. It is useful in monitoring the progression of TCoV-induced atrophic enteritis in the turkey flocks. Copyright © 2016 Springer Science+Business Media New York.
ABSTRACT
A multiplex polymerase chain reaction (PCR) method for differential detection of turkey coronavirus (TCoV), infectious bronchitis virus (IBV), and bovine coronavirus (BCoV) is presented in this chapter. Primers are designed from the conserved or variable regions of nucleocapsid (N) or spike (S) protein genes of TCoV, IBV, and BCoV and used in the same PCR reaction. Reverse transcription followed by PCR reaction is used to amplify a portion of N or S gene of the corresponding coronaviruses. Two PCR products, a 356-bp band corresponding to N gene and a 727-bp band corresponding to S gene, are obtained for TCoV. In contrast, one PCR product of 356 bp corresponding to a fragment of N gene is obtained for IBV strains and one PCR product of 568 bp corresponding to a fragment of S gene is obtained for BCoV. Copyright © Springer Science+Business Media New York 2016.
ABSTRACT
Turkey coronavirus (TCoV) infection continues to threaten turkey industry. Because specific treatment and effective vaccination program are not available, rapid and cost-effective detection of antibodies to TCoV infection is an important control measure to monitor the disease status in the fields. Two antibody-capture enzyme-linked immunosorbent assay (ELISA) procedures for detection of antibodies to TCoV are outlined in this chapter. One ELISA method uses chicken infectious bronchitis coronavirus (IBV) as the coating antigen based on antigenic cross-reactivity between TCoV and IBV. The other method relies on a recombinant TCoV nucleocapsid protein. Both methods are useful for serological diagnosis of TCoV infection in the turkey flocks. Copyright © Springer Science+Business Media New York 2016.
ABSTRACT
Expression and purification of turkey coronavirus (TCoV) nucleocapsid (N) protein from a prokaryotic expression system as histidine-tagged fusion protein are presented in this chapter. Expression of histidine-tagged fusion N protein with a molecular mass of 57 kDa is induced with isopropyl beta-D-1-thiogalactopyranoside (IPTG). The expressed N protein inclusion body is extracted and purified by chromatography on nickel-agarose column to near homogeneity. The protein recovery can be 10 mg from 100 ml of bacterial culture. The purified N protein is a superior source of TCoV antigen for antibody-capture ELISA for detection of antibodies to TCoV. Copyright © Springer Science+Business Media New York 2016.
ABSTRACT
Turkey coronavirus (TCoV) infection induces the production of protective antibodies against the sequent exposure of TCoV. Serological tests to determine TCoV-specific antibodies are critical to evaluate previous exposure to TCoV in the turkey flocks and differentiate serotypes from different isolates or strains. A specific virus neutralization assay using embryonated turkey eggs and immunofluorescent antibody assay for determining TCoV-specific neutralizing antibodies is described in this chapter. Virus neutralization titer of turkey serum from turkeys infected with TCoV is the dilution of serum that can inhibit TCoV infection in 50 % of embryonated turkey eggs. Virus neutralization assay for TCoV is useful to monitor the immune status of turkey flocks infected with TCoV for the control of the disease. Copyright © Springer Science+Business Media New York 2016.
ABSTRACT
Disease detection and monitoring play a critical role in the ongoing COVID-19 pandemic. A comprehensive detection platform that enables early virus detection can effectively stem the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). In this study, a polycrystalline silicon nanowire field-effect transistor (NWFET) was developed to detect the spike protein of SARS-CoV-2. The NWFET were fabricated through the application of sidewall spacer etching to maintain a nanowire diameter of less than 100 nm. The on-off current ratio of the transistor reached 10(6), and its subthreshold swing was 125 mV/decade, indicating the transistor's strong attributes and stability. The biosensor based on this transistor reached a sensitivity of 59 mV pH(-1) when used to test solutions with a pH value ranging between 6 and 9. We employed the biosensor in the detection of the SARS-CoV-2 spike protein, and the results revealed that the characteristic curve gradually shifted toward the left as the antigen of spike protein progressively increased in concentration. The limit of detection was estimated to be 0.51 ag ml(-1). The results of the real-time testing of the spike protein were also successful, verifying the performance and applicability of the biosensor as a rapid screening tool for SARS-CoV-2.