Economic and financial time series can feature locally explosive behavior when a bubble is formed. The economic or financial bubble, especially its dynamics, is an intriguing topic that has been attracting longstanding attention. To illustrate the dynamics of the local explosion itself, the paper presents a novel, simple, yet useful time series model, called the stochastic nonlinear autoregressive model, which is always strictly stationary and geometrically ergodic and can create long swings or persistence observed in many macroeconomic variables. When a nonlinear autoregressive coefficient is outside of a certain range, the model has periodically explosive behaviors and can then be used to portray the bubble dynamics. Further, the quasi-maximum likelihood estimation (QMLE) of our model is considered, and its strong consistency and asymptotic normality are established under minimal assumptions on innovation. A new model diagnostic checking statistic is developed for model fitting adequacy. In addition, two methods for bubble tagging are proposed, one from the residual perspective and the other from the null-state perspective. Monte Carlo simulation studies are conducted to assess the performances of the QMLE and the two bubble tagging methods in finite samples. Finally, the usefulness of the model is illustrated by an empirical application to the monthly Hang Seng Index.
In this article, convex optimization is introduced as a promising tool to study Eshelby based inverse micromechanics problems. The focus is on inverse micromechanics using the Mori–Tanaka model given the dielectric constants of the composite material and of all of its components. The model is exactly the same for the conductivity properties (thermal and electrical) as well. This choice of model is made since the model is fairly simple, has a closed form analytical solution, and is known to perform well for the case of spheroidal inclusions as well. The forward or direct micromechanics problem deals with the determination of effective properties of a composite material given the properties of its components and microstructural information. The focus is on isotropic composites, and the distribution of inclusions is assumed to be such that this holds. The inverse micromechanics problem considered in this paper deals with the determination of microstructural information given the properties of the composite material and all of its components. Since in this paper the isotropy of the composite and only spherical inclusions are considered, the goal is to determine only the volume fractions of the components of the composite material. The inverse problem is formulated as a Linear Programming problem and is solved. Before this, the inverse problem and certain important variants of it are examined through the lens of convex optimization. Lastly, promising results are presented on the relationship between dispersive materials, noise in measurements, and the quality of the obtained volumetric splits. The scope of the use of convex optimization in inverse micromechanics is discussed.
Cobalt is an essential trace element in biochemistry that plays a crucial role in the structure and function of several important biomolecules. In this review, vitamin B12 is discussed as one of the best-known examples in this area. Various forms of this vitamin, including methylcobalamin and adenosylcobalamin, play a crucial role in metabolic reactions in mammals and prokaryotes. It also discusses cobalt-containing enzymes that are essential for various biological processes. These enzymes are B12-dependent enzymes, which are well studied, and cobalt-containing enzymes, which are less well known, such as methionine aminopeptidase, nitrile hydratase, glucose isomerase, and prolidase. In addition to the significant role of cobalt complexes in biochemistry, these complexes are considered potent anticancer agents that can exert their antiproliferative effects through the production of ROS, cell cycle arrest, MMP breakdown, and induction of apoptosis in cancer cells. Cobalt complexes are also being explained here for their antimicrobial properties against a variety of pathogens, including bacteria, fungi, and viruses. Furthermore, examples of these complexes are presented as promising agents for the suppression of AD, which could be effective by binding to Aβ-peptides and preventing their aggregation, which is a central feature of the pathogenesis of AD, or by combating the oxidative damage associated with the disease, or even by interfering with the enzyme activities associated with this disease. Finally, the challenges related to the toxicity of cobalt and its compounds in medicine are discussed, and chelation therapy is considered an effective treatment for cobalt poisoning.
The endomembrane system is a complex and dynamic intracellular trafficking network. It is very challenging to track individual vesicles and their cargos in real time; however, affinity purification allows vesicles to be isolated in their natural state so that their constituent proteins can be identified. Pioneering this approach in plants, we isolated the SYP61 trans-Golgi network compartment and carried out a comprehensive proteomic analysis of its contents with only minimal interference from other organelles. The proteome of SYP61 revealed the association of proteins of unknown function that have previously not been ascribed to this compartment. We identified a complete SYP61 SNARE complex, including regulatory proteins and validated the proteome data by showing that several of these proteins associated with SYP61 in planta. We further identified the SYP121-complex and cellulose synthases, suggesting that SYP61 plays a role in the exocytic trafficking and the transport of cell wall components to the plasma membrane. The presence of proteins of unknown function in the SYP61 proteome including ECHIDNA offers the opportunity to identify novel trafficking components and cargos. The affinity purification of plant vesicles in their natural state provides a basis for further analysis and dissection of complex endomembrane networks. The approach is widely applicable and can afford the study of several vesicle populations in plants, which can be compared with the SYP61 vesicle proteome.
Glutathione is a ubiquitous antioxidant with critical roles in xenobiotic clearance and aerobic metabolism. Reduced glutathione (GSH) is converted to its oxidized counterpart, GSSG, in the process of neutralizing free radicals and maintaining biochemical homeostasis. An imbalance between free radical generation and antioxidant protection leads to oxidative stress and diminished GSH concentrations. Polymorphisms in GSH synthesis and metabolism genes have been associated with cardiovascular disease (CVD) development and progression, highlighting the critical need to explore the link between GSH system genetics and CVD. While those prior studies have focused on canonical GSH genes such as glutathione peroxidases (GPx), few studies to this date have investigated whether genes outside of traditional GSH pathways may be impacting the cardiac GSH redox system. Here, we performed high-precision genetic mapping using the Diversity Outbred (DO) mouse stock which revealed novel loci and genes underlying the cardiac GSH system. Mapping results indicated a locus on murine chromosome 14 at 54.240 Mbp associated with cardiac GSH concentrations, and bioinformatics analyses delineated five potential candidate genes: Slc7a7, Myh6, Myh7, MiR-208a, and Nfatc4. In addition, statistical analyses revealed notable variation in the cardiac GSH redox system under normal physiological conditions and correlations between cardiac and renal GSH phenotypes in the same cohort of mice. Overall, these findings expand our current knowledge of the vital GSH system, reveal novel genetic regulation of cardiac GSH status, and present candidate genes to be tested in future mechanistic studies.
