Search

In seismically active regions, high-filled embankment slopes on liquefiable soils tend to damage after strong earthquakes. Therefore, post-seismic damages should be estimated as soon as possible to mitigate potential losses. Fragility function is an efficient tool for assessing the seismic vulnerability conditions of structures, which links the probability of exceeding different limit states to seismic intensity. An embankment slope on liquefiable soils at Yading Airport in China was selected as the study object, and a series of numerical analyses of the embankment-foundation system utilizing the finite element method were conducted. Advanced dynamic constitutive models considering liquefaction and hysteresis characteristics were also adopted to simulate the nonlinear stress–strain behavior of soils under cyclic loadings. The post-seismic stability of embankment slopes was assessed using the strength reduction method (SRM) based on the stress–strain analysis. On this basis, the permanent ground deformation (PGD) at the ground-free field conditions was selected as the intensity measure (IM), while the factor of safety (FoS) of the slopes was selected as the damage measure (DM). Then, a procedure was presented for deriving seismic fragility functions with different damage states in light of incremental dynamic analysis (IDA). This paper aims to investigate the effects of different embankment typologies, such as the thickness of liquefiable soils and slope inclination, on the post-seismic vulnerability of embankment slopes. The fragility curves constructed in this study may soon be helpful for predicting the post-seismic damage of similar high-filled embankment slopes on liquefiable soils, which enables efficient traffic control and rapid disaster response.

Body-temperature and solvent-free polymerization and in situ fabrication of drug-loaded microparticles are reported for the first time. The key point is to simplify the cumbersome processes and avoid the harsh conditions in the traditional fabrication of biodegradable medical microparticles, reducing the energy consumption and fabricating cleaner biodegradable formulations with controlled size and drug release profiles. We have designed a surfactant P(CL–GA)–PFPE–P(CL–GA) which efficiently promotes the formation of narrowly distributed microparticles of minimum 5 μm at body temperature. The following drug loading investigation confirmed that PTX evenly distributes in the PPDO microparticles in amorphous state, giving a controlled release profile with the cumulative releasing rate reaching 50% in one month. Most importantly, all the processes are conducted at body temperature in one-pot, presenting promising possibilities of both energy and cost conservation.

Wellhead subsidence is one of the most severe engineering disasters during drilling operations in cold regions. Based on the characteristics of thaw-induced settlement of frozen soil, a th...

Daily average temperature data from 48 meteorological stations in Chinese oases that are within the distribution area of Populus euphratica were analyzed to determine the spatiotemporal responses of this tree to climate change. Specifically, the start and end date as well as the number of days that comprised the growing season were analyzed with a multi-year trend line and using the Mann-Kendall mutation test, inverse distance weighted interpolation (IDW) in the software ArcGIS, a Morlet wavelet power spectrum, and correlation analysis. The results of this study show that, over the last 56 years, the start date of the P. euphratica growing season has advanced, while the end date has been postponed, and the number of days that comprise the growing season have gradually increased. The changing trend rates recovered in this analysis for these three time slices are –1.34 d/10 a, 1.33 d/10a, and 2.66 d/10a (α ⩾ 0.001), respectively. Data show that while spatial disparity is extremely significant, it is nevertheless the case that along a southwest-to-northeast transect of Chinese oases, the later the start date of the P. euphratica season, the sooner the end data and the shorter the growing season. Mutations points in start and end date, as well as for the growing season overall were observed in 2001, 1989, and 1996, respectively, and the data presented in this paper show that, in particular, the date of this end of this period is most sensitive to climate warming. Growing season cycles for P. euphratica are between 3.56 years and 7.14 years, consistent with the periodicity of El Nino events, while a start date cycle between 3.56 years and 4.28 years is consistent with atmospheric circulation cyclicity. The causal analysis presented in this paper shows that the Asian polar vortex area index (APVAI), the Qinghai- Tibet Plateau index (TPI), the westerly circulation index (WCI), and carbon dioxide emissions (CDE) are the main factors influencing spatiotemporal changes in the growth of P. euphratica, the effect of latitude during the growing season is more significant than altitude, and the start date of the growing season is more significantly influenced by these factors than end date. In addition, data show that the start date, end date, and length of the growing season are all significantly correlated with their average corresponding monthly temperature (correlation coefficients are –0.875, 0.770, and 0.897; α⩾0.001). Thus, if the average temperature in March increases by 1°C, the start date of the growing season will advance by 2.21 days, while if the average temperature in October increases by the same margin then the seasonal end date will be delayed by 2.76 days. Similarly, if the average temperature between March and October increases by 1°C, the growing season will be extended by 7.78 days. The results of this study corroborate the fact that changes in the P. euphratica growing are sensitive to regional warming and are thus of considerable theoretical significance to our understanding of the responses of Chinese vegetation to climate change as well as to ecological restoration.

Graphene quantum dots (GQDs) are promising materials in a variety of optical applications, such as bioimaging and photovoltaics, but such applications are hindered by the poor understanding of their optical properties, in particular under the influence of functional groups. By theoretically studying the effects of the surface functionalization of oxygen-containing groups (–COC–, –OH, –OCH3, –COOH, and –COCH3) on the optical properties of a GQD, we found that the absorption and emission properties of the systems vary significantly depending on the chemisorption sites of the functional group. Remarkably, given that the optical gap of the GQD is just 2.68 eV, the optical gap difference between two GQD oxide isomers can be as large as 2.39 eV. The notably small optical gaps (

Many of the relevant compounds for anticancer therapy are metal-based compounds (metallodrugs), being platinum-based drugs such as cisplatin, carboplatin (Paraplatin®), and oxaliplatin (Eloxatin®) the most widely used. Despite this, their application is limited by issues such as cell-acquired platinum resistance and manifold side effects following systemic delivery. Thus, the development of new metal-based compounds is highly needed. The catalytic properties of a variety of metal-based compounds are nowadays very well known, which opens new opportunities to take advantage of them inside living cells or organisms. However, many of these compounds are hydrophobic and thus not soluble in aqueous solution, as they lack stability against water or oxygen presence. Thus, versatile platforms capable of enhancing the features of these compounds in aqueous solutions are of importance in the development of new drugs. Surface engineered nanoparticles may render metallodrugs with good colloidal stability in water and in complex media containing high salt concentration and/or proteins. Herein, polymer coated nanoparticles are proposed as a platform to link insoluble and water/oxygen sensitive drugs. The linkage of insoluble and oxygen sensitive tin clusters to nanoparticles is presented, aiming to enhance both, the solubility and the stability of these compounds in water, which may be an alternative approach in the development of metal-based drugs. The formation of the cluster-nanoparticle system was confirmed via inductively coupled plasma mass spectrometry experiments. The catalytic activity and the stability of the cluster in water were studied through the reduction of methylene blue. Results demonstrate that in fact the tin clusters could be transferred into aqueous solution and retained their catalytic activity.

Currently, there is a large interest in the labeling of neural stem cells (NSCs) with iron oxide nanoparticles (IONPs) to allow MRI-guided detection after transplantation in regenerative medicine. For such biomedical applications, excluding nanotoxicity is key. Nanosafety is primarily evaluated in vitro where an immortalized or cancer cell line of murine origin is often applied, which is not necessarily an ideal cell model. Previous work revealed clear neurotoxic effects of PMA-coated IONPs in distinct cell types that could potentially be applied for nanosafety studies regarding neural cell labeling. Here, we aimed to assess if DMSA-coated IONPs could be regarded as a safer alternative for this purpose and how the cell model impacted our nanosafety optimization study. Hereto, we evaluated cytotoxicity, ROS production, calcium levels, mitochondrial homeostasis and cell morphology in six related neural cell types, namely neural stem cells, an immortalized cell line and a cancer cell line from human and murine origin. The cell lines mostly showed similar responses to both IONPs, which were frequently more pronounced for the PMA-IONPs. Of note, ROS and calcium levels showed opposite trends in the human and murine NSCs, indicating the importance of the species. Indeed, the human cell models were overall more sensitive than their murine counterpart. Despite the clear cell type-specific nanotoxicity profiles, our multiparametric approach revealed that the DMSA-IONPs outperformed the PMA-IONPs in terms of biocompatibility in each cell type. However, major cell type-dependent variations in the observed effects additionally warrant the use of relevant human cell models. Statement of Significance Inorganic nanoparticle (NP) optimization is chiefly performed in vitro. For the optimization of iron oxide (IO)NPs for neural stem cell labeling in the context of regenerative medicine human or rodent neural stem cells, immortalized or cancer cell lines are applied. However, the use of certain cell models can be questioned as they phenotypically differ from the target cell. The impact of the neural cell model on nanosafety remains relatively unexplored. Here we evaluated cell homeostasis upon exposure to PMA- and DMSA-coated IONPs. Of note, the DMSA-IONPs outperformed the PMA-IONPs in each cell type. However, distinct cell type-specific effects were witnessed, indicating that nanosafety should be evaluated in a human cell model that represents the target cell as closely as possible.

Poly(p-dioxanone)–poly(ethylene glycol)–poly(p-dioxanone) triblock copolymers (PPDO–PEG–PPDO) were first synthesized by suspension ring-opening polymerization (ROP) of p-dioxanone (PDO) in supercritical carbon dioxide (scCO2) using different molecular weights (2–10 K) of poly(ethylene glycol) (PEG) as macroinitiators. White and fine flow powders were successfully obtained when the molecular weight of PEG was below 6 K and its feed content below 20 wt.%. The 1H nuclear magnetic resonance (NMR) result indicated the formation of PPDO–PEG–PPDO block structure even in a confined polymerized environment of particles. All the powderous samples contained irregular shaped particles that were observed by scanning electron microscope (SEM). Except for the copolymer with 10 wt.% PEG10K feed content, the mean particle sizes of other powderous samples showed identical values close to 15 μm. This fact was in agreement with the crystallinity of PPDO in the copolymers measured by differential scanning calorimetry (DSC). The water absorption of these copolymers was also measured, and as compared with PPDO homopolymer, the introduction of PEG increased the water absorption of the copolymers. The green and environmentally friendly method disclosed in this work is attractive to directly synthesize biodegradable polymeric particles with potential biomedical applications.

Ammonia oxidation is the rate-limiting step in nitrification process and dominated by ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA). In the present study, a highly enriched culture of AOA was obtained from urban polluted water in Shahe River, Shenzhen, China. The optimum growth conditions were identified by orthogonal analysis as 37 °C, with pH 7.0 and initial ammonia concentration of 1.0 mM. Under these conditions, the highest abundance of AOA was obtained as 4.6 × 107 copies/ng DNA. Growth of AOA in polluted river water showed significant reduction in ammonia concentration in AOA-enriched cultures without antibiotics after 10 days of incubation, while synchronous increase in nitrate concentration was up to 12.7 mg/L. However, AOA-enriched by antibiotic showed insignificant changes in ammonia or nitrite concentration. This study showed that AOB play an important role in ammonia oxidation of polluted river water, and AOA alone showed insignificant changes in ammonia or nitrite concentrations. Therefore, the ammonia oxidation performance of natural water could not be improved by adding high concentration AOA bacterial liquid.

With the aim to develop novel biodegradable materials with good flexibility and fast degradation rate, random copolymers of ɛ-caprolactone (CL) and p-dioxanone (PDO) with a full range of compositions were synthesized in bulk using stannous octoate as the ring-opening catalyst. The chemical composition and number average sequence lengths of CL and PDO units determined by 1H-NMR were used to correlate with various properties of the copolymers. Although both CL and PDO are crystalline components, only one crystalline phase could be present for each copolymer. The low limit of average block length for the copolymers that could crystallize is 3.22 for LCL and 3.43 for LPDO, respectively. The crystallinity and crystalline morphology of the copolymers are dependent on the crystalline component as well as its number average sequence length. Irrespective of composition, all the copolymers have good solubility in chloroform with glass transition temperature much below room temperature, implying good flexibility of the materials. The incorporation of PDO component could significantly increase the water wettability of the copolymer surfaces and thereby accelerate the degradation rate of the materials. In conclusion, flexible biodegradable polymers with adjustable degradation and crystalline properties were acquired by random copolymerization of CL and PDO, which are expected to use in tissue engineering and drug delivery fields. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2978–2986, 2013

Biodegradable copolymers of l-lactide(l-LA) and p-dioxanone(PDO) were synthesized in supercritical carbon dioxide (scCO2) with stannous octoate as the ring-opening catalyst and a fluorocarbon polymer surfactant as an stabilizer. Fine powderous products were achieved when more than 90% (w/w) l-LA was fed. Scanning electron micrographic images and laser diffraction particle size analysis of the products showed the mean diameter of particles greatly increased as the content of PDO increased. The obtained polymers had the number-average molecular weights ranging from 15,000 to 26,000 g mol−1 (polydispersity index ranging from 1.3 to 2.1) according to the gel permeation chromatography measurements. The polymer structure was characterized by NMR spectroscopy, indicating the formation of copolymers. Thermal properties of the obtained polymers investigated using differential scanning calorimetry showed that the morphology of products was directly relevant to the crystallinity of the copolymers. The polymerization of l-LA and PDO copolymers in scCO2 is also proposed as a novel production technique for high-purity, biodegradable polymers.

A highly branched hybrid copolymer based on polyhedral oligomeric silsesquioxane (POSS) was designed to improve the brittleness of poly(d,l-lactide) (PDLLA). The toughening material was synthesized using POSS-OH as the core, which initiated the ring-opening polymerization of e-caprolactone and d,l-lactide sequentially to form the highly branched POSS-g-poly (e-caprolactone)-b-poly(d,l-lactide) (POSS-g-PCL-b-PLA) copolymer with eight PCL-b-PLA arms. The POSS-g-PCL-b-PLA copolymer had a very good dispersion in the PDLLA matrix with the size of microdomains smaller than 1 µm when added at a low content below 10 wt %. In related to the nano-scale size of microdomains in the blends, the crystallinity of PCL blocks was significantly suppressed. Thus, the addition of POSS-g-PCL-b-PLA is very effective to improve the roughness of the matrix polymer when added at a low content. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40776.

We use the Markov ChainMonte Carlo method to investigate global constraints on the generalized holographic (GH) dark energy with flat and non-flat universe from the current observed data: the Union2 dataset of type supernovae Ia (SNIa), high-redshift Gamma-Ray Bursts (GRBs), the observational Hubble data (OHD), the cluster X-ray gas mass fraction, the baryon acoustic oscillation (BAO), and the cosmic microwave background (CMB) data. The most stringent constraints on the GH model parameter are obtained. In addition, it is found that the equation of state for this generalized holographic dark energy can cross over the phantom boundary wde =-1., 14 pages, 5 figures. arXiv admin note: significant text overlap with arXiv:1105.1868

Biodegradable particles of poly(glycolide-co-p-dioxanone) (PGDO) were directly synthesized by suspension copolymerization of glycolide (GA) and p-dioxanone (PDO) in supercritical carbon dioxide (scCO2) using stannous octoate as the ring-opening catalyst and a fluorocarbon polymer surfactant as a stabilizer. Fine powdered products were achieved when more than 60% (w/w) GA was fed. Interestingly, some spherical particles formed when the feed content of GA was intermediate (70–90%), while other compositions resulted in irregular particles. The particle size and degree of aggregation was also affected significantly by copolymer composition. The mechanism for three cases of particle formation were discussed, and the crystallization behavior within the polymerizing droplets played a critical role in determining the final morphology of particles. Well-defined particles with spherical morphology could be achieved if a delicate balance between the two opposing effects of crystallization and plasticization was reached inside the droplets. The possibility that spherical particles for biodegradable polyesters could be fabricated directly by suspension polymerization in scCO2 implies the potential use of this clean technique in biomedical fields.