The stress system in the brain plays a pivotal role in keeping humans and animals from harmful stimuli. However, excessive stress will cause maladaptive changes to the stress system and lead to ...depression. Despite the high prevalence of depression, the treatment remains limited. PKMζ, an atypical PKC isoform, has been demonstrated to play a crucial role in maintaining long-term potentiation and memory. Recent evidence shows that PKMζ is also involved in stress response and depressive-like behavior. In particular, it was demonstrated that stress that resulted in depressive-like behavior could decrease the expression of PKMζ in the prefrontal cortex, which could be reversed by antidepressants. Importantly, modulation of PKMζ expression could regulate depressive-like behaviors and the actions of antidepressants. These data suggested that PKMζ could be a molecular target for developing novel antidepressants. Here, I review the advance on the role of PKMζ in mediating stress response and its involvement in the development of depression.
To better understand the creep mechanical behavior of salt rock under very long-term tests and more accurately predict the long-term deformation of the salt caverns, a series of long-term uniaxial ...creep tests lasting for 21000 h (875 days) were carried out. The results show that the creep strain and creep rate of salt rock increase with the increase of axial stress. The initial creep stage under lower stresses lasted for 4.3–8.3 months, which was much higher than that under high stresses. Predicting the true creep rate of the salt cavern based on the test results of the creep rate in this paper is more accurate than the existing research results. A new nonlinear creep-damage constitutive model is proposed by introducing the nonlinear damage body and using the fractional derivative theory. Using the presented model and the classic creep constitutive models to fit the experimental data, it is found that the presented model best characterizes the creep evolution characteristics of salt rock. The fitting function obtained from the experimental data at different times predicts the final creep results, revealing that the longer the test duration, the more accurate the predicted results. The research in this paper provides the necessary basis for intensive investigation and prediction of the long-term creep mechanical behavior of salt storage caverns.
The mechanical characteristics and gas tightness of salt rock play a decisive role in the safety evaluation of salt caverns. Triaxial compression coupled permeability tests were performed on Chinese ...impure salt rocks under thermal-hydro-mechanical (THM) coupling condition. The results revealed that the peak strength decreased with the decrease of confining pressure and the increase of temperature. The permeability of salt rock decreased with the increase of confining pressure, while the increase of temperature led to an increase in permeability under lower effective confining pressure, and a decrease in permeability under higher effective confining pressure. Moreover, there is a critical effective confining pressure, which controls the evolution trend of salt rock permeability with temperature. The dilatancy boundary and failure strength envelope of impure salt rock at different temperatures were given, which can be expressed by exponential and hyperbolic functions respectively. An empirical formula for the evolution of the final permeability of the salt rock with the effective confining pressure at different temperatures was established. Considering the effects of effective confining pressure and inelastic volume strain, a new model was proposed to predict the permeability evolution of salt rock under THM coupling condition at different temperatures. The results of this paper can help understand the mechanical characteristics and permeability evolution of salt rock under THM coupling condition, and provide the necessary basis for the safety evaluation of salt caverns.
•The mechanical characteristics of salt rock under THM coupling was obtained.•The permeability evolution of salt rock under THM coupling was investigated.•The expansion boundary of salt rock under THM coupling was given.•A novel model for predicting permeability evolution of salt rock was proposed.
The mechanical properties and behavior of coal rock under both static and dynamic loading rates are of importance in the coal mining practices. In this study, both quasi-static and dynamic uniaxial ...compression tests are conducted on coal rock, considering the bedding directivity of coal rocks using a MTS hydraulic servo-control testing machine and split Hopkinson pressure bar (SHPB), respectively. The attained strain rates range from 10⁻⁵to 10⁻² s⁻¹for static tests and 20 to 100 s⁻¹for dynamic SHPB tests. For dynamic tests, pulse-shaping technique is utilized to achieve dynamic force balance and thus validate the quasi-static data reduction. A high-speed camera is used to capture the failure process in SHPB tests. The characteristics of failure mode, fracture strength, energy dissipation, and fractal dimension are investigated. A significant strain-rate-dependent behavior of coal rock is revealed, and the compressive strength, elasticity modulus and energy consumption increase with increasing strain rate. The bedding effect on the coal behavior at static strain rate is more prominent than that at dynamic strain rate. The measured strengths along different bedding directions exhibit distinct variations, featuring significant anisotropy. In addition, a sieving statistics analysis of the recovered fragments depicts obvious fractal; and the fracture dimension can be correlated to the fractal energy dissipation.
•We proposed an efficient and effective data-mining procedure that models the travel patterns of transit riders using the transit smart card data.•Transit riders’ trip chains are identified based on ...the temporal and spatial characteristics of smart card transaction data.•A Density-based Spatial Clustering of Applications with Noise (DBSCAN) algorithm is used to detect each transit rider’s historical travel patterns.•The K-Means++ clustering algorithm and the rough-set theory are jointly applied to clustering and classifying the travel pattern regularities.
To mitigate the congestion caused by the ever increasing number of privately owned automobiles, public transit is highly promoted by transportation agencies worldwide. A better understanding of travel patterns and regularity at the “magnitude” level will enable transit authorities to evaluate the services they offer, adjust marketing strategies, retain loyal customers and improve overall transit performance. However, it is fairly challenging to identify travel patterns for individual transit riders in a large dataset. This paper proposes an efficient and effective data-mining procedure that models the travel patterns of transit riders in Beijing, China. Transit riders’ trip chains are identified based on the temporal and spatial characteristics of their smart card transaction data. The Density-based Spatial Clustering of Applications with Noise (DBSCAN) algorithm then analyzes the identified trip chains to detect transit riders’ historical travel patterns and the K-Means++ clustering algorithm and the rough-set theory are jointly applied to cluster and classify travel pattern regularities. The performance of the rough-set-based algorithm is compared with those of other prevailing classification algorithms. The results indicate that the proposed rough-set-based algorithm outperforms other commonly used data-mining algorithms in terms of accuracy and efficiency.
The key to successful positioning of autonomous mobile robots in complicated indoor environments lies in the strong anti-interference of the positioning system and accurate measurements from sensors. ...Inertial navigation systems (INS) are widely used for indoor mobile robots because they are not susceptible to external interferences and work properly, but the positioning errors may be accumulated over time. Thus ultra wideband (UWB) is usually adopted to compensate the accumulated errors due to its high ranging precision. Unfortunately, UWB is easily affected by the multipath effects and non-line-of-sight (NLOS) factor in complex indoor environments, which may degrade the positioning performance. To solve above problems, this paper proposes an effective system framework of INS/UWB integrated positioning for autonomous indoor mobile robots, in which our modeling approach is simple to implement and a Sage⁻Husa fuzzy adaptive filter (SHFAF) is proposed. Due to the favorable property (i.e., self-adaptive adjustment) of SHFAF, the difficult problem of time-varying noise in complex indoor environments is considered and solved explicitly. Moreover, outliers can be detected and corrected by the proposed sliding window estimation with fading coefficients. This facilitates the positioning performance improvement for indoor mobile robots. The benefits of what we propose are illustrated by not only simulations but more importantly experimental results.
In this work, chitin microspheres (NCM) having a nanofibrous architecture were constructed using a “bottom‐up” fabrication pathway. The chitin chains rapidly self‐assembled into nanofibers in ...NaOH/urea aqueous solution by a thermally induced method and subsequently formed weaved microspheres. The diameter of the chitin nanofibers and the size of the NCM were tunable by controlling the temperature and the processing parameters to be in the range from 26 to 55 nm and 3 to 130 μm, respectively. As a result of the nanofibrous surface and the inherent biocompatibility of chitin, cells could adhere to the chitin microspheres and showed a high attachment efficiency, indicating the great potential of the NCM for 3D cell microcarriers.
Nimbly weaved: Chitin chains rapidly self‐assembled into nanofibers in aqueous NaOH/urea solution by a thermally induced method. Subsequently, the nanofibers formed weaved chitin microspheres (NCM) having a uniform architecture throughout. Cells could adhere to the nanofibrous NCM, which indicates the great potential of the NCM for cell microcarriers.
The application of PEG-b-PCL micelles was dampened by their inherent low drug-loading capability and relatively poor cell uptake efficiency. In this study, a series of novel PEG-b-PCL copolymers ...methoxy poly(ethylene glycol)-b-poly(ε-caprolactone-co-γ-dimethyl maleamidic acid -ε-caprolactone) (mPEG-b-P(CL-co-DCL)) bearing different amounts of acid-labile β-carboxylic amides on the polyester moiety were synthesized. The chain structure and chemical composition of copolymers were characterized by 1H NMR, Fourier transform infrared spectroscopy (FT-IR), and gel permeation chromatography (GPC). mPEG-b-P(CL-co-DCL) with critical micellar concentrations (CMCs) of 3.2–6.3 μg/mL could self-assemble into stable micelles in water with diameters of 100 to 150 nm. Doxorubicin (DOX), a cationic hydrophobic drug, was successfully encapsulated into the polymer micelles, achieving a very high loading content due to electrostatic interaction. Then the stability, charge-conversional behavior, loading and release profiles, cellular uptake and in vitro cytotoxicity of free drug and drug-loaded micelles were evaluated. The β-carboxylic amides functionalized polymer micelles are negatively charged and stable in neutral solution but quickly become positively charged at pH 6.0, due to the hydrolysis of β-carboxylic amides in acidic conditions. The pH-triggered negative-to-positive charge reversal not only resulted in a very fast drug release in acidic conditions, but also effectively enhanced the cellular uptake by electrostatic absorptive endocytosis. The MTT assay demonstrated that mPEG-b-P(CL-co-DCL) micelles were biocompatible to HepG2 cells while DOX-loaded micelles showed significant cytotoxicity. In sum, the introduction of acid-labile β-carboxylic amides on the polyester block in mPEG-b-P(CL-co-DCL) exhibited great potentials for the modifications in the stability in blood circulation, drug solubilization, and release properties, as well as cell internalization and intracellular drug release.
•Nonlinear responses of water quality to landscape pattern were modeled.•Three types of landscape thresholds were defined and identified based on nonlinear relations.•The landscape thresholds can act ...as targets of landscape pattern management.
Investigating the relationship between landscape pattern and water quality is essential for making sustainable landscape development policies. A clear understanding of such relationship remains elusive partly due to ubiquitous nonlinearity, behind which the landscape threshold can potentially act as quantifiable target of landscape conservation. In the upper Huai River Basin in China, six landscape metrics were quantified for forested, agricultural, and residential land use categories at broad sub-basin and finer riparian buffer scales. Five water quality indicators were collected from 24 monitoring stations during the period of 2006–2012. On the basis of nonlinear regression models, including power, exponential, quadratic, and segmented regressions, one-to-one relations between landscape metrics and water quality variables were fitted with R2 generally varying between 0.32 and 0.74. Meanwhile, three types of defined landscape thresholds were also identified on the basis of the fitted nonlinear relations. From the perspective of spatial scale dependence, the percentage of landscape area and largest patch index could well explain water quality variables at a broad sub-basin scale; the opposite could be said for patch density. The type-1 and type-2 landscape thresholds can act as the long-term targets where landscape pattern management strategy should be timely adjusted. By contrast, the type-3 landscape threshold can be set as a short-term target of landscape conservation to ensure water quality up to a certain management requirement. This study suggests that considering nonlinearity and threshold effect could provide insights into the complicated landscape pattern–water quality relations and thus provide a scientific basis for balancing the coupled socioecological system of landscape development and water quality protection.
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