Inappropriate Detrending and Spurious Cointegration

The empirical literature is abundant with detrended cointegration, where cointegration relationships are tested and estimated with deterministic trend terms. Cointegration is, however, critically dependent on whether time series is detrended or not. A series of Monte Carlo experiments show that inappropriately detrended time series tend to exhibit a spurious cointegration. Although true time series are known not to be cointegrated, inappropriately detrended series tend to be cointegrated. Foreign exchange rates are analyzed to demonstrate the relevance and importance of the inappropriate detrending in the cointegration analysis.Deterministic trend, Foreign exchange rates, Monte Carlo study, Stochastic trend

International Terrorism, International Trade, and Borders

This paper shows that terrorism reduces bilateral trade flows, in real terms, by raising trading costs and hardening borders. Countries sharing a common land border and suffering from terrorism trade much less than neighboring or distant countries that are free of terrorism. The impact of terrorism on bilateral trade declines as distance between trading partners increases. This result suggests that terrorism redirects some trade from close to more distant countries. Our findings are robust in the presence of a variety of other calamities such as natural disasters or financial crises.financial crisis, natural disaster, trade gravity model, transaction cost

International Trade Efficiency, the Gravity Equation, and the Stochastic Frontier

In the gravity equation of international trade, bilateral trade flows are regressed on trading partners’ income and the distance that separates them along with other variables. This widely used equation is traditionally estimated by the ordinary least squares method. We employ an alternative technique of stochastic frontier estimation to assess the potential bilateral trade flows from the same gravity equation. Countries are shown to have low efficiencies in their international trade as the predicted trade from frontier estimation is generally far greater than actual trade. Trade efficiencies are computed and ranked for individual countries, ten geographical regions, and eleven regional trade agreements.efficiency coefficients, OLS residuals, trade gravity, trade potentials

Pitfalls in the use of Time as an Explanatory Variable in Regression

Regression of a trendless random walk on time produces R-squared values around .44 regardless of sample length. The residuals from the regression exhibit only about 14 percent as much variation as the original series even though the underlying process has no functional dependence on time. The autocorrelation structure of these "detrended" random walks is pseudo-cyclical and purely artifactual. Conventional tests for trend are strongly biased towards finding a trend when none is present, and this effect is only partially mitigated by Cochrane-Orcutt correction for autocorrelation. The results are extended to show that pairs of detrended random walks exhibit spurious correlation.

BlindHarmony: "Blind" Harmonization for MR Images via Flow model

In MRI, images of the same contrast (e.g., T$_1$) from the same subject can exhibit noticeable differences when acquired using different hardware, sequences, or scan parameters. These differences in images create a domain gap that needs to be bridged by a step called image harmonization, to process the images successfully using conventional or deep learning-based image analysis (e.g., segmentation). Several methods, including deep learning-based approaches, have been proposed to achieve image harmonization. However, they often require datasets from multiple domains for deep learning training and may still be unsuccessful when applied to images from unseen domains. To address this limitation, we propose a novel concept called `Blind Harmonization', which utilizes only target domain data for training but still has the capability to harmonize images from unseen domains. For the implementation of blind harmonization, we developed BlindHarmony using an unconditional flow model trained on target domain data. The harmonized image is optimized to have a correlation with the input source domain image while ensuring that the latent vector of the flow model is close to the center of the Gaussian distribution. BlindHarmony was evaluated on both simulated and real datasets and compared to conventional methods. BlindHarmony demonstrated noticeable performance on both datasets, highlighting its potential for future use in clinical settings. The source code is available at: https://github.com/SNU-LIST/BlindHarmonyComment: ICCV 2023 accepted. 9 pages and 5 Figures for manuscipt, supplementary include

HTRgene: a computational method to perform the integrated analysis of multiple heterogeneous time-series data: case analysis of cold and heat stress response signaling genes in Arabidopsis

Background Integrated analysis that uses multiple sample gene expression data measured under the same stress can detect stress response genes more accurately than analysis of individual sample data. However, the integrated analysis is challenging since experimental conditions (strength of stress and the number of time points) are heterogeneous across multiple samples. Results HTRgene is a computational method to perform the integrated analysis of multiple heterogeneous time-series data measured under the same stress condition. The goal of HTRgene is to identify response order preserving DEGs that are defined as genes not only which are differentially expressed but also whose response order is preserved across multiple samples. The utility of HTRgene was demonstrated using 28 and 24 time-series sample gene expression data measured under cold and heat stress in Arabidopsis. HTRgene analysis successfully reproduced known biological mechanisms of cold and heat stress in Arabidopsis. Also, HTRgene showed higher accuracy in detecting the documented stress response genes than existing tools. Conclusions HTRgene, a method to find the ordering of response time of genes that are commonly observed among multiple time-series samples, successfully integrated multiple heterogeneous time-series gene expression datasets. It can be applied to many research problems related to the integration of time series data analysis.This work, including publication costs, was supported by National Research Foundation of Korea(NRF) funded by the Ministry of Science, ICT (No.NRF-2017M3C4A7065887). This work was also supported by the Collaborative Genome Program for Fostering New Post-Genome Industry of the National Research Foundation (NRF) funded by the Ministry of Science and ICT (MSIT) (No. NRF-2014M3C9A3063541), and a grant of the Korea Health Technology R&D Project through the Korea Health Industry Development Institute (KHIDI), funded by the Ministry of Health & Welfare, Republic of Korea (grant number: HI15C3224). This work was supported for W.J. by the Agenda program (No.PJ012465032019), Rural Development of dministration of Republic of Korea

Insulin Sensitivity Is Retained in Mice with Endothelial Loss of Carcinoembryonic Antigen Cell Adhesion Molecule 1

CEACAM1 regulates endothelial barrier integrity. Because insulin signaling in extrahepatic target tissues is regulated by insulin transport through the endothelium, we aimed at investigating the metabolic role of endothelial CEACAM1. To this end, we generated endothelial cell-specific Ceacam1 null mice (VECadCre+Cc1(fl/fl)) and carried out their metabolic phenotyping and mechanistic analysis by comparison to littermate controls. Hyperinsulinemic-euglycemic clamp analysis showed intact insulin sensitivity in VECadCre+Cc1(fl/fl) mice. This was associated with the absence of visceral obesity and lipolysis and normal levels of circulating non-esterified fatty acids, leptin, and adiponectin. Whereas the loss of endothelial Ceacam1 did not affect insulin-stimulated receptor phosphorylation, it reduced IRS-1/Akt/eNOS activation to lower nitric oxide production resulting from limited SHP2 sequestration. It also reduced Shc sequestration to activate NF-kappaB and increase the transcription of matrix metalloproteases, ultimately inducing plasma IL-6 and TNFalpha levels. Loss of endothelial Ceacam1 also induced the expression of the anti-inflammatory CEACAM1-4L variant in M2 macrophages in white adipose tissue. Together, this could cause endothelial barrier dysfunction and facilitate insulin transport, sustaining normal glucose homeostasis and retaining fat accumulation in adipocytes. The data assign a significant role for endothelial cell CEACAM1 in maintaining insulin sensitivity in peripheral extrahepatic target tissues

The cointegration relationships among G-7 foreign exchange rates

A search method is applied to foreign exchange rates of G-7 countries, in terms of the US dollar, to estimate cointegration relationships. The method searches numerically, by strictly following the definition of the cointegration, a particular linear combination of nonstationary series in order to make it a stationary series. The list of those exchange rates which are cointegrated from the new method is very different from those derived from the conventional maximum likelihood estimation or ordinary least squares methods. The new method also provides confidence intervals for cointegration coefficients. From the confidence intervals, it is determined that certain G-7 currencies expressed in terms of the mark or the pound become stationary.