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AbstractThis study employs a Granger non-causality test in quantiles to analyze the causal relationship between Bitcoin and representative stock indices. We further bifurcate our analysis into pre- and post-COVID-19 periods, providing a unique perspective on hedge evaluation in different market conditions. The empirical findings reveal several key insights. First, a traditional causal test conducted over the entire period, which only considers causality at the mean, leads us to reject the null hypothesis that Bitcoin does not Granger cause any of the nine stock indices. However, we find that Bitcoin is not Granger caused by five out of nine stock indices. Second, by extending the analysis to the overall quantile interval, we find significant results in 12 out of 18 cases. Third, we identify robust causal relationships between Bitcoin and stock indices across lower and higher quantile intervals. Lastly, in the post-COVID-19 period, characterized by heightened price volatility and increased uncertainty, we observe a near-universal reversal in the causal relationships between Bitcoin and stock indices. Furthermore, the number of cases exhibiting causality increased markedly compared with the pre-COVID-19 period, which was characterized by more moderate price volatility and uncertainty. [ABSTRACT FROM AUTHOR]

Covariance matrix estimation is of great importance in formulating a portfolio. The sample covariance matrix, the most frequently used estimator, is well known to be unstable due to the estimation error, when the sample size is small. A shrinkage approach is one of the popular methods for estimating a stable covariance matrix. This study compares and evaluates performance of the three different shrinkage type covariance matrix estimators for the optimal portfolio selection strategy. To evaluate the performance of the covariance matrix estimators, we consider both the in- and out-of-sample value at risk, conditional value at risk, Sharpe-ratio, adjusted Sharpe-ratio, and a beta of the portfolio selection strategies. Empirical results show that a portfolio using shrinkage covariance matrix estimator with the identity matrix or constant correlation matrix as the shrinkage target tends to have a lower risk. We also find that the random matrix approach has a relatively high out-of-sample return and Sharpe-ratio under the small sample size cases. [ABSTRACT FROM AUTHOR]

This study examines the dynamic conditional correlations between the US and Korean financial markets and identifies the determinants of those correlations using the VAR-DCC-MGARCH model. We find that the Global Financial Crisis (GFC) affects both countries. Although the shocks to the Korean market before the GFC are not shared by the US market, those to the US market after the GFC are shared by the Korean market. We also examine the determinants of the dynamic conditional relations between the US and Korean markets using domestic macroeconomic variables and US/Korean financial variables. The results indicate that the US financial variables are more significant than domestic macroeconomic variables and that they have become increasingly important over time. [ABSTRACT FROM AUTHOR]

The nonlinear unit root test of Kapetanios, Shin, and Snell (2003) (KSS) has attracted much recent attention. However, the KSS test relies on the ordinary least squares (OLS) estimator, which is not robust to a heavy-tailed distribution and, in practice, the test suffers from a large power loss. This study develops three kinds of quantile nonlinear unit root tests: the quantile t-ratio test; the quantile Kolmogorov-Smirnov test; and the quantile Cramer-von Mises test. A Monte Carlo simulation shows that these tests have significantly better power when an innovation follows a non-normal distribution. In addition, the quantile t-ratio test can reveal the heterogeneity of the asymmetric dynamics in a time series. In our empirical studies, we investigate the unit root properties of U.S. macroeconomic time series and the real effective exchange rates for 61 countries. The results show that our proposed tests reject the unit roots more often, indicating that the series are likely to be asymmetric nonlinear reverting processes. [ABSTRACT FROM AUTHOR]

Using the dynamic conditional correlation multivariate generalized autoregressive conditional heteroskedasticity (DCC-MGARCH) model, we empirically examine the dynamic relationship between stock market returns (KOSPI200 returns) and implied volatility (VKOSPI), as well as their statistical mechanics, in the Korean market, a representative and leading emerging market. We consider four macroeconomic variables (exchange rates, risk-free rates, term spreads, and credit spreads) as potential determinants of the dynamic conditional correlation between returns and volatility. Of these macroeconomic variables, the change in exchange rates has a significant impact on the dynamic correlation between KOSPI200 returns and the VKOSPI, especially during the recent financial crisis. We also find that the risk-free rate has a marginal effect on this dynamic conditional relationship. [ABSTRACT FROM AUTHOR]

Objective: To investigate the feasibility of exponential apparent diffusion coefficient (eADC) derived from diffusion-weighted imaging (DWI) in evaluating prostate cancers at 3 T. Methods: 74 consecutive patients with surgically confirmed single peripheral zone (PZ) prostate cancer ≥0.5 cm³ who underwent pre-operative DWI at 3 T were retrospectively selected. Based on radiological-pathological correlation, eADC and apparent diffusion coefficient (ADC) (×10-3 mm² s-1) for the cancers and benign PZ were measured by two independent readers. Tumour eADC or ADC was correlated with Gleason score. Receiver operating characteristic curve analysis was performed to differentiate between Gleason score 6 and 7 or higher, by eADC and ADC. Lesion-to-background contrast ratio was compared between eADC and ADC. Results: Mean tumour eADC (0.48-0.50) and ADC (0.72-0.75) were significantly different from those of benign PZ (eADC, 0.20-0.27; ADC, 1.34-1.66), respectively (p < 0.001). A moderate correlation between tumour eADC or ADC and Gleason score was seen. For differentiating between Gleason score 6 and 7 or higher, eADC (0.818-0.883) showed a similar area under the curve with ADC (0.840-0.889) (p > 0.05). Lesion-to-background contrast ratio of eADC (Reader 1, 2.43; Reader 2, 2.23) was significantly greater than that of ADC (Reader 1, 2.21; Reader 2, 2.12) (p < 0.001). Conclusion: The eADC may offer similar diagnostic utility with ADC in the differentiation of the cancer from benign prostate tissue. Moreover, the eADC appears to allow improved tissue contrast. Advances in knowledge: The eADC may be a comparable alternative to ADC for evaluating prostate cancer, with removing T2 shine-through effects from DWI. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the antioxidant activities of pepsin-digested water-soluble protein (WSP) and salt-soluble protein (SSP) extracted from pork ham. WSP and SSP were hydrolysed by pepsin for 2-10 h with 2-h increments. The protein hydrolysates by pepsin were analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, and reducing power of the hydrolysates was measured. In addition, antioxidant activity of the hydrolysates was determined using linoleic acid emulsion system. Protein bands with molecular weight higher than 7 kDa in WSP and SSP were completely hydrolysed by pepsin after 2 h of digestion time. WSP hydrolysates (WSPH) and SSP hydrolysates (SSPH) had higher ferric reducing power than controls (WSP and SSP without pepsin digestion). Reducing powers of WSPH were higher than those of SSPH, regardless of digestion time. The oxidative activity of linoleic acid was predominantly inhibited by the addition of WSPH and SSPH, especially 0.5% protein hydrolysate. These results indicate that several functional peptides of pork protein digested by pepsin might have antioxidant activity, and thus they may be used as an antioxidant agent in muscle food system. [ABSTRACT FROM AUTHOR]

Onions with or without heating (100 °C, 30 min) were extracted with water or methanol, and antioxidant and antimicrobial activities of onion extracts were evaluated. Product characteristics of fresh pork patties containing various onion extracts were measured during refrigerated storage. Water extracts of onions showed higher extraction yield and iron chelating ability than methanol extracts ( P < 0.05), whereas, the latter was more effective than the former in phenolic compounds and reducing power ( P < 0.05). The addition of onion extracts [water extract from fresh onion (WEFO), methanol extract from heated onion (MEHO) and their combinations (WEFMEHO)] to pork patties decreased redness, increased yellowness, and inhibited lipid peroxidation ( P < 0.05). One per cent of WEFMEHO in pork patties had antioxidant activities as effective as butylated hydroxyl toluene (BHT, 0.01%). Redness and yellowness decreased and increased with the addition of onion extract, respectively ( P < 0.05). [ABSTRACT FROM AUTHOR]

The objectives of this study were to screen the optimum conditions for antioxidant and antimicrobial activities of garlic as affected by pre-heating and different extraction solvents, and to evaluate the antioxidant and antimicrobial effects of these extracts in ground meat during refrigerated storage. Methanol extracted garlic had a greater total phenolic content, 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical scavenging activity and reducing power than water extracted one ( P < 0.05), whereas the latter had a greater yield and iron chelating ability than the former ( P < 0.05). Moreover, water extract from fresh garlic (WEFG) and methanol extract from heated garlic (MEHG) produced an inhibition zone against Escherichia coli O157:H7 and Listeria monocytogenes. The addition of garlic extracts (WEFG, MEHG and their combinations WEFMEHG)) to pork patties decreased the pH, hunter a values (redness), thiobarbituric acid substances values and the number of total plate count and Enterobacteriaceae ( P < 0.05), while the hunter b values (yellowness) increased ( P < 0.05). Results of this study indicated that the use of the garlic extracts was able to control lipid oxidation and microbial growth in pork patties. [ABSTRACT FROM AUTHOR]

The study was performed to evaluate the flavour profiles of low-fat comminuted sausage (LFS) as affected by the addition of various concentrations of glucose, fructose and sucrose combined with 0.1 m lysine. Among thirty-five volatile compounds, the concentrations of furfural, 2-furan methanol, 2-methoxy phenol, 2-methoxy-4-methyl phenol, myristicine and pentadecanal occupied approximately 60% of the total concentration of volatile compounds identified in full- and low-fat smoked sausages. Phenols and hetero-compounds derived mainly from the smoking process were the predominant chemical groups. Nine volatile compounds were affected by fat content and the reduction of fat predominantly increased the headspace concentration of myristicin and pentadecanal. The headspace concentration of total volatile compounds detected in LFS control was significantly higher than those of LFS treatments with the various sugars and lysine. The headspace concentration of most volatile compounds decreased with the addition of various sugars. The results indicate that the addition of glucose, fructose and sucrose at the concentrations higher than 0.05 m in combination with 0.1 m lysine delays the release of some flavour compounds in LFS. [ABSTRACT FROM AUTHOR]

Objectives To assess the correlation of the resected and ischaemic volume ( RAIV), which is a preoperatively calculated volume of nephron loss, with the amount of postoperative renal function ( PRF) decline after minimally invasive partial nephrectomy ( PN) in a multi-institutional dataset. Patients and Methods We identified 348 patients from March 2005 to December 2013 at six institutions. Data on all cases of laparoscopic ( n = 85) and robot-assisted PN ( n = 263) performed were retrospectively gathered. Univariable and multivariable linear regression analyses were used to identify the associations between various time points of PRF and the RAIV, as a continuous variable. Results The mean ( sd) RAIV was 24.2 (29.2) cm3. The mean preoperative estimated glomerular filtration rate ( eGFR) and the eGFRs at postoperative day 1, 6 and 36 months after PN were 91.0 and 76.8, 80.2 and 87.7 mL/min/1.73 m2, respectively. In multivariable linear regression analysis, the amount of decline in PRF at follow-up was significantly correlated with the RAIV (β 0.261, 0.165, 0.260 at postoperative day 1, 6 and 36 months after PN, respectively). This study has the limitation of its retrospective nature. Conclusion Preoperatively calculated RAIV significantly correlates with the amount of decline in PRF during long-term follow-up. The RAIV could lead our research to the level of prediction of the amount of PRF decline after PN and thus would be appropriate for assessing the technical advantages of emerging techniques. [ABSTRACT FROM AUTHOR]

This paper demonstrates the development of pH and thermo-responsive fluorescent nanoparticles, which are composed of graphene oxide (GO) with BODIPY conjugated PEG, to trigger the detection of cancer cells through imaging based on intracellular accommodation. Responsiveness to pH is studied using atomic force microscopy and apparent thickness differences are seen with changes in pH. Confocal images of the nanoparticles (NPs) exhibit remarkably bright fluorescence at lysosomal pH, while no fluorescence is observed under a physiological environment, making the NPs a novel fluorescent probe. The NPs are able to accumulate the hydrophobic anticancer drug DOX due to the hydrophobic surface of GO and show excellent drug release behavior. Therefore, the NPs developed are novel candidates for a fluorescent probe to identify cancer cells and a drug carrier for cancer therapy. [ABSTRACT FROM AUTHOR]

Physicochemical and textural properties, and volatile compounds of comminuted sausages with various added fat levels and fat replacers were evaluated. Sausages without added fat had higher expressible moisture and texture values, but their lightness and yellowness values were lower, as compared with sausages with 5%, 10%, or 15% fat. Increased fat levels with constant amounts of lean meat and added water increased the lightness and yellowness values, but tended the redness values tended to be similar. Low-fat sausages (LFSs, <3%) containing non-meat proteins, except egg white protein, had reduced texture values similar to those of regular-fat counterparts (RFC). The addition of non-meat proteins, except egg white protein, as components of fat replacers in LFS improved the textural characteristics, making them similar to those of RFC. LFSs containing sodium caseinate had reduced concentrations of pentadecanal and octadecanal, resulting in similar volatile compositions to those of RFC. Thus, sodium caseinate was the best non-meat protein for the improvement of both texture and flavour of LFSs. [ABSTRACT FROM AUTHOR]

This paper studies the connections among the asymmetric Laplace probability density (ALPD), maximum likelihood, maximum entropy and quantile regression. We show that the maximum likelihood problem is equivalent to the solution of a maximum entropy problem where we impose moment constraints given by the joint consideration of the mean and median. The ALPD score functions lead to joint estimating equations that delivers estimates for the slope parameters together with a representative quantile. Asymptotic properties of the estimator are derived under the framework of the quasi maximum likelihood estimation. With a limited simulation experiment we evaluate the finite sample properties of our estimator. Finally, we illustrate the use of the estimator with an application to the US wage data to evaluate the effect of training on wages. [ABSTRACT FROM AUTHOR]