In recent years, interest has grown in modeling spatio-temporal data generated from monitoring networks, satellite imaging, and climate models. Under Gaussianity, the covariance function is core to spatio-temporal modeling, inference, and prediction. In this article, we review the various space-time covariance structures in which simplified assumptions, such as separability and full symmetry, are made to facilitate computation, and associated tests intended to validate these structures. We also review recent developments on constructing space-time covariance models, which can be separable or nonseparable, fully symmetric or asymmetric, stationary or nonstationary, univariate or multivariate, and in Euclidean spaces or on the sphere. We visualize some of the structures and models with visuanimations. Finally, we discuss inference for fitting space-time covariance models and describe a case study based on a new wind-speed data set. Expected final online publication date for the Annual Review of Statistics, Volume 8 is March 8, 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Saudi Arabia has a long tradition of relying on fossil fuels for satisfying its energy demand.With the rising energy needs due to population growth and societal development, the nation is seeking other sources of energy, which include its largely underused wind resources. In this paper, we analyze the wind power potential in Saudi Arabia based on the MENA CORDEX (Middle East North Africa Coordinated Regional Climate Downscaling Experiment) model output. We investigate which climate settings and MENA CORDEX runs best capture the spatiotemporal patterns of reanalysis products, as assessed by multiple statistical metrics. Although there is a systematic negative bias in wind speed magnitudes for the five analyzed MENA CORDEX simulations, all runs are able to reproduce the seasonality and annual cycle of wind speed shown in the reanalysis data. The MENA CORDEX run with the highest skills is used to quantify the wind energy potential in Saudi Arabia in both current and future climates. Our analysis shows that a high wind energy potential exists over a vast area of western Saudi Arabia, particularly in the region between Medina and the Red Sea coast and during summer months. Based on model projections, the energy potential in these areas is likely to persist at least until the middle of the 21st century and thus may provide a valuable renewable source of energy. Key Points:• Performance of five MENA CORDEX runs in simulating wind speed spatiotemporal variabilities is assessed against reanalysis data • MENA CORDEX runs with the highest skills are used to quantify the wind energy potential in Saudi Arabia for current and future climates • Regions and months or seasons with high wind energy potential for current and future climates are identified Supporting Information:• Supporting Information S1

Background/Aims: Periapical periodontitis is caused by bacterial infection and results in both one destruction and tooth loss. Osteopontin (OPN) is a secreted phosphorylated glycoprotein that participates in bone metabolism. Methods: Thirty-three patients with chronic periapical periodontitis and 10 patients who had undergone the orthodontic removal of healthy tooth tissue (control) at the periodontal ligament were investigated, and an animal model of mouse periapical periodontitis was established for an in vivo analysis. The relationship between OPN and bone destruction during periapical periodontitis was analyzed. Osteoblasts and osteoclasts were cultured in vitro and treated with lipopolysaccharide. An inhibitor of NF-κB was used to pretreat the transfected cells. Results: OPN increased osteoclast proliferation and differentiation, but reduced osteoblasts proliferation and differentiation. OPN activated the NF-κB pathway during periapical periodontitis and accelerated the transfer and phosphorylation of P65 from the cytoplasm to the nucleus. Conclusion: This study demonstrated that OPN played important roles in the progression of periapical periodontitis, and a dual role in bone metabolism during periapical periodontitis, linking osteoclasts and osteoblasts. The underlying mechanism may be related to the NF-κB pathway.

STUDY QUESTIONHow does aquaporin-3 (AQP3) affect endometrial receptivity?SUMMARY ANSWERAQP3, which is regulated by the combination and estrogen (E2) and progesterone (P4), induces epithelial–mesenchymal transition (EMT) of endometrial epithelial cells.WHAT IS KNOWN ALREADYEmbryo implantation is an extremely complex process, and endometrial receptivity is essential for successful embryo implantation. Estrogen and progesterone regulate endometrial receptivity. AQP3, which is regulated by estrogen (E2), increases cell migration and invasion ability by regulating the expression of EMT-related factors and influencing the reorganization of the actin cytoskeleton.STUDY DESIGN, SIZE, DURATIONThis study investigated the pathophysiological significance of AQP3 in human endometrial function during different phases of the menstrual cycle.PARTICIPANTS/MATERIALS, SETTING, METHODSAQP3 expression levels during different phases of the menstrual cycle were measured using immunohistochemical assays. In cells of different receptivity (high-receptive RL95-2 cells and low-receptive HEC-1A cells), the expression of AQP3 was measured using western blotting, qRT-PCR and immunofluorescence assays. Activities of AQP3, and its regulation by E2 and P4, were studied through in-vitro experiments using RL95-2 cells.MAIN RESULTS AND THE ROLE OF CHANCEAQP3 expression in the mid- and late-secretory phases of the human endometrium is significantly higher than in other phases. Since AQP3 expression levels were higher in RL95-2 cells than in HEC-1A cells, mechanisms of AQP3 regulation by E2 and P4 were studied using RL95-2 cells. We provided the first report that P4 up-regulates AQP3 by directly targeting the promoter of the AQP3 gene. The up-regulation of AQP3 expression by a combination of E2 and P4 is significantly higher than that caused by either E2 or P4 alone. Together E2 and P4 promote RL95-2 cell migration and invasion by inducing EMT through AQP3. We also found that AQP3 co-localizes with ezrin and affects the formation of filopodia and lamellipodia during the E2 and P4-induced EMT process but has no effect on the expression of ezrin and F-actin.LARGE SCALE DATAN/A.LIMITATIONS, REASONS FOR CAUTIONIt is still unclear whether AQP3 is a main regulator of endometrial receptivity or one of several factors influencing the process.WIDER IMPLICATIONS OF THE FINDINGSFurther investigation on AQP3 may contribute to a greater understanding of endometrial receptivity.STUDY FUNDING/COMPETING INTEREST(S)This work was supported by the National Natural Scientific Grants of China (No. 31570798), the Program for Liaoning Excellent Talents in University (LR2017042), the Doctoral Scientific Research Foundation of Liaoning province (201601236), and the Liaoning Provincial Program for Top Discipline of Basic Medical Sciences. There are no conflicts of interest.

We construct a flexible class of parametric models for both traditional and pseudo variogram matrix (valued functions), where the off-diagonal elements are the traditional cross variograms and pseudo cross variograms, respectively, and the diagonal elements are the direct variograms, based on the method of latent dimensions and the linear model of coregionalization. The entries in the parametric variogram matrix allow for a smooth transition between boundedness and unboundedness by changing the values of parameters, and thus between joint second-order and intrinsically stationary vector random fields, or between multivariate geometric Gaussian processes and multivariate Brown-Resnick processes in spatial extreme analysis. Keywords bounded and unbounded variogram • cross variogram • intrinsic stationarity • second-order stationarity • variogram matrix