Search

Landslides are highly destructive geological disasters, often preceded by changes in surface displacement. This study explores the effectiveness of real aperture radar (RAR) in landslide monitoring and early warning. Using the three-stage creep theory, the short-term simple moving average velocity (SMA) and long-term simple moving average velocity (LMA) were used to determine the end point of the constant displacement stage, while the hypothesis test method was used to confirm its starting point. Based on these points, the average velocity was calculated. A five-level warning model and criteria were established by integrating acceleration, velocity change, and tangent angle. Three landslide cases in Northeast China were analyzed to evaluate the dynamic application of this model. The results indicate that: (1) RAR effectively identifies abnormal displacement region; (2) Successful warnings in the three cases validate the effectiveness of the warning model and criteria; (3) The five-level warning model and criteria of RAR demonstrate strong application potential in the dynamic monitoring and early warning of landslide disasters. [ABSTRACT FROM AUTHOR]

A functional hybrid nano-hydroxyapatite (carboxymethyl cellulose-phytic acid-n-HA, CMC-PA-n-HA) was prepared by adding CMC and PA. The results of Fourier transformation infrared spectra, X-ray diffraction, thermal gravimetric analysis and dispersion experiments indicated that the addition of CMC and PA affected the morphology, crystallinity and crystal size of hybrid n-HA, and CMC endowed hybrid n-HA with excellent dispersion. Scanning electron microscope results showed that CMC-PA-n-HA nanoparticle could be uniformly dispersed in chitosan (CS) matrix to obtain composite membrane by casting technology, so that the highest tensile strength of CMC-PA-n-HA/CS composite membrane was 69.64% and 144.45% higher than that of CS membrane and n-HA/CS composite membrane, respectively. Contact angle test showed that CMC-PA-n-HA effectively improved hydrophilicity of the CS membrane. The simulated body fluid immersion results indicated that the CMC-PA-n-HA/CS composite membrane not only exhibited good degradability but also promoted bone-like apatite deposition. The cell proliferation experiments proved that the introduction of PA made the composite membrane have better cell adhesion and proliferation ability. Antibacterial tests demonstrated that PA could effectively improve the antibacterial properties of the composite membrane, which is expected to be applied as guide bone tissue regeneration membrane. [ABSTRACT FROM AUTHOR]

Irreversible eye lesions, such as glaucoma and traumatic optic neuropathy, can cause blindness; however, no effective treatments exist. The optic nerve, in particular, lacks the capacity to spontaneously regenerate, requiring the development of an effective approach for optic nerve repair, which has proven challenging. Here, we demonstrate that a combination of the small molecules 3BDO and trichostatin A (TSA)—which regulate mTOR and HDAC, respectively—packaged in thermosensitive hydrogel for 4-week-sustained release after intravitreal injection, effectively induced optic nerve regeneration in a mouse model of optic nerve crush injury. Moreover, this combination of 3BDO and TSA also protected axon projections and improved visual responses in an old mouse model (11 months old) of glaucoma. Taken together, our data provide a new, local small molecule-based treatment for the effective induction of optic nerve repair, which may represent a foundation for the development of pharmacological methods to treat irreversible eye diseases. [ABSTRACT FROM AUTHOR]

To obtain a high-performance poly(lactide-co-glycolide) (PLGA)-based composite, a novel functionalized hybrid nanohyoxyapatite (n-HA) was proposed by introducing carboxymethyl-β-cyclodextrin (CMCD) and zoledronic acid (ZA). IR, XRD, TGA, dispersion experiments for hybrid n-HA and universal testing machine, SEM, DSC, POM for the hybrid n-HA/PLGA composite were carried out. The results showed that initial adjusted pH = 11 was more favor for the grafting rate of CMCD, and ZA was preferentially grafted on n-HA surface due to stronger binding ability to Ca2+. The high content of CMCD and ZA of 40%CMCD-10%ZA-n-HA could be well dispersed in organic solvents, which could effectively promote crystallization, so that CMCD-ZA-n-HA displayed the best reinforce effect for PLGA, whose tensile strength and elongation at break were 16.20 and 41.99% higher than PLGA, respectively. In vitro soaking in simulated body fluid (SBF) and cell proliferation results demonstrated that CMCD-ZA-n-HA endowed PLGA with faster degradation, better bone-like apatite deposition and cells adhesion and proliferation ability. The study would provide a new simply method to obtain a functionalized hybrid n-HA, which had a great potential to obtain ideal n-HA/PLGA composite used in the bone materials field. [ABSTRACT FROM AUTHOR]

In this work, carboxylated bamboo fiber (BF) was first incorporated into nano-hydroxyapatite/chitosan (n-HA/CS) system to obtain a novel porous composite by freeze-drying method for bone tissue engineering scaffold. The results of infrared spectrometer analysis, scanning electron microscope observation, porosity and compressive strength test revealed that the ionic-crosslinking of carboxylated BF and CS played an important role in the formation of the composite scaffold with a highly orientation groove porous structure. Especially, when 30 wt% carboxylated BF was added, the compressive strength of n-HA/CS composite scaffold was enhanced up to over three times, and the porosity was still higher than 80%. Moreover, simulated body fluids soaking demonstrated that the introduction of carboxylated BF not only slowed down the degradation of n-HA/CS composite scaffold by the ionic-crosslinking, but also induced more apatite to deposit owing to the exposure of excessive carboxyl of carboxylated BF. Additionally, in vitro cell culture results indicated that the introduction of BF were helpful for cell compatibility. Conclusively, carboxylated BF endowed the scaffold with a highly interconnected orientation porous structure, excellent compressive strength, appropriate degradation and good biocompatibility, which would provide a new way for realizing high value-added applications of BF as a low-cost biomass resource. In this manuscript, carboxylated bamboo (BF) was introduced to n-HA/chitosan (n-HA/CS) system, and the effect of carboxylated BF on the n-HA/CS composite scaffold was investigated. The results revealed that the carboxylated BF/n-HA/CS composite scaffold with high orientation groove porous structure could be obtained by freeze drying method, owing to the strong ionic cross-linking between carboxylated BF and CS, which endowed the novel modified BF/n-HA/CS composite scaffold with high mechanical properties, more suitable degradation and better bioactivity and biocompatibility. The study would offer a way of exploring the new application of natural BF in bone tissue engineering scaffold. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) has been an attractive bio-based material for biomedical applications due to its biocompatibility, non-toxicity, ultrafine nanofibril network, robust mechanical properties, and high water-holding capacity. However, native BC does not possess antimicrobial properties to prevent infection that significantly limit its biomedical applications. In the present study, we have demonstrated an easy-to-functionalize biohybrid system consisting of BC and metal-phenolic network (MPN). Specifically, plant-derived tannic acid (TA) and various metal ions were complexed and embedded into a highly intertwined BC nanofibrillar network followed by cationic functionalization to confer antimicrobial properties. The existence of MPN was successfully observed by scanning electron microscope, Fourier transform infrared spectroscopy (FT–IR) and energy-dispersive X-ray spectroscopy. Because of the synergetic antibacterial effect of TA and quaternary ammonium salts, the cationic BC@MPN composites showed good inhibitory effects on the growth of Escherichia coli and Staphylococcus aureus. This biohybrid antimicrobial BC/MPN material may have many potential applications in the food packaging and biomedical industries. [ABSTRACT FROM AUTHOR]

To obtain nano-hydroxyapatite/poly(lactide-co-glycolide) (n-HA/PLGA) nanocomposite with superior mechanical properties, here, lignin was chosen to surface-modify for n-HA through co-precipitation method. The different reaction conditions of reaction time, phosphorus source, and the lignin addition amount were studied by fourier transformation infrared spectra, X-ray diffraction, the intuitionistic dispersion experiment, transmission electron microscope and thermal gravimetric analysis. The reaction mechanism and the best appropriate reaction condition were obtained. More importantly, the results of electromechanical universal tester, scanning electron microscope, differential scanning calorimetric analyzer, polarized optical microscopy and dynamic mechanical analysis confirmed that the obtained n-HA could greatly increase the mechanical strength of PLGA, owing to the excellent dispersion and promotion crystallization effect. Moreover, in vitro cell culture experimental results indicated that the n-HA surface-modified by lignin was favorable to improve the cell biocompatibility of PLGA. The study suggested that the introduction of lignin was a novel method to acquire a highly dispersed n-HA, which would provide a new idea to achieve the n-HA/PLGA nanocomposite as bone materials in future, and it would pave the way towards a new application of lignin in biomedical field. [ABSTRACT FROM AUTHOR]

The activation of oxygen for selective oxidation of organic molecules, such as hydrocarbons and alcohols, remains a major catalytic challenge. We have developed a catalytic system combining N-hydroxyphthalimide (NHPI) with cobalt tetraamide phthalocyanine [CoPc(CONH2)4] for the oxidation of hydrocarbons and alcohols at 75 °C under an oxygen atmosphere. CoPc(CONH2)4 was synthesized by trimellitic anhydride-urea method, and its structure was confirmed by FT-IR, UV–Vis and XRD. This catalyst, in synergy with NHPI/O2 system, exhibited excellent catalytic ability and high selectivity in the oxidation of hydrocarbons and alcohols. Based on the experimental results, a reasonable reaction mechanism was proposed for the oxidation of alkanes and alcohols, respectively. Cobalt tetraamide phthalocyanine (CoPc(CONH2)4) was synthesized by a simple solid-thermal method, and the synergistic catalysis oxidation of NHPI and CoPc(CONH2)4 was studied. A synergistic catalysis system for the aerobic oxidation of hydrocarbons and alcohols by N-hydroxyphthalimide combined with cobalt tetraamide phthalocyanine has been developed. [ABSTRACT FROM AUTHOR]

The space-based gravitational wave detectors at low frequencies has received great attention recently. Due to lack of considering the relative motion between spacecrafts, the accuracy of current sensitivity models is inadequate for space-based gravitational wave detectors. In this paper, an accurate sensitivity model of the space-based gravitational wave detector is established by taking into account the relative motion between two spacecrafts. The accurate sensitivity model is derived by employing a gravitational wave perturbed metric tensor. Then, to minimize the sensitivity loss due to the solar radiation, an enhancement strategy is proposed. Finally, simulation studies are presented with two drag-free spacecrafts in Earth's orbit. Simulation results validate the effectiveness of the proposed strategy. [ABSTRACT FROM AUTHOR]

We study the heavy-light mesons within basis light-front quantization. The resulting mass spectra of D, D s , B, and B s agree reasonably well with experiments. We also predict states which could be measured in the near future. In the light-front formalism, we calculate the light-front wave functions and additional experimental observables, such as parton distribution functions, distribution amplitudes, and decay constants by means of integrations over light-front wave functions. We also provide ratios of decay constants for selected pseudoscalar meson decays ( D s to D and B s to B) as they may prove to be theoretically more robust and more reliably determined in experiments. We find that our ratios are systematically smaller than existing experiments and other approaches by 5–18%. [ABSTRACT FROM AUTHOR]

To obtain an ideal guided bone tissue regeneration (GBR) membrane, carboxylated bamboo fiber (BF) was designed to be introduced into the chitosan/nano-hydroxyapatite (CS/n-HA) system by ionic crosslinking to fabricate a novel BF/CS/n-HA composite membranes with different weight ratios. The formation mechanism of the BF/CS/n-HA ternary composite membrane and the effect of BF different contents on the BF/CS/n-HA composite membranes were studied by Fourier Transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), electromechanical universal tester, in vitro soaking in simulated body fluid (SBF). Results demonstrated that CS and modified BF would be ionic crosslinked by electrostatic interaction to form a three dimensional polyelectrolyte structure, meanwhile, n-HA was loaded in the polyelectrolyte structure by hydrogen bonding, which ensured the modified BF/CS/n-HA composite membranes to possess excellent tensile strength, compared to the CS/n-HA and untreated BF/CS/n-HA composite membrane. Moreover, the weight ratio of the modified BF/CS/n-HA of 2:6:2 displayed the highest tensile strength, whose tensile strength was improved by over two folds than that of CS/n-HA composite membrane owing to the most suitable proportion. In addition, in vitro simulated body fluids soaking results indicated that the modified BF/CS/n-HA composite membranes presented different degradation rates and could promote the apatite to deposit by investigating the weight loss, water absorption rate, SEM morphology observation and tensile strength reduce. All results revealed that the ionic crosslinking of carboxylated BF and CS was conducive to fabricate BF/CS/n-HA composite membrane with higher mechanical property, more suitable degradation and better bioactivity, in contrast with the CS/n-HA and untreated BF/CS/n-HA composite membranes, which had a great promising to obtain more satisfactory GBR membrane, moreover, the study would provide a new application for natural BF in the biomedical membrane field. In this manuscript, carboxylated bamboo fiber (BF) was designed to be introduced into the chitosan/nano-hydroxyapatite (CS/n-HA) system to fabricate a novel BF/CS/n-HA composite membranes with different weight ratios. The formation mechanism of the BF/CS/n-HA ternary composite membrane and the effect of modified BF different contents on the BF/CS/n-HA composite membranes were studied, and the main purpose of the study was to explore the feasibility of preparing the new BF/CS/n-HA composite membrane by ionic crosslinking. Results revealed that the ionic crosslinking of carboxylated BF and CS played an essential role in fabricating BF/CS/n-HA composite membrane with higher mechanical properties, more suitable degradation and better bioactivity. The study proved that the carboxylated BF/CS/n-HA composite membrane fabricated by ionic crosslinking had a great potential in obtaining more satisfactory GBR membrane in contrast with the CS/n-HA and untreated BF/CS/n-HA composite membranes, which would open up a new application for natural BF in the biomedical membrane field. [ABSTRACT FROM AUTHOR]

The realization of picosecond level laser time transfer between satellites plays a key role in microgravity scientific missions, such as gravitational wave detection, next generation GNSS (Global Navigation Satellite System), deep space exploration, testing general relativity and searching for dark matter. In picosecond or higher level, a deep insight of relativistic error of laser time transfer between satellites induced by orbit perturbations and attitude jitters is urgently needed, which contributes to the compensation of relativistic error. Firstly, this paper points out the problem of orbit perturbations and attitude jitters. Then, the relativistic evaluation models of one-way laser time transfer and two-way laser time transfer resulting from orbit perturbations and attitude jitters are investigated. The relativistic evaluation models are proposed with incorporation of attitude dynamics and orbit dynamics of satellites, as well as relativistic models of one-way laser time transfer and two-way laser time transfer. Simulation studies are carried out to analyze the effect of orbit perturbations and attitude jitters on the relativistic error. Simulation results show that the relativistic error induced by orbit perturbations increases with time and the relativistic error induced by attitude jitters displays periodic variation. Furthermore, the relativistic error of two-way laser time transfer is less than one-way laser time transfer. [ABSTRACT FROM AUTHOR]

Biomass fiber is currently one of the most attractive research pursuits in the biomaterials field. In this study, bamboo fiber (BF) was firstly chosen to replace other polymers to prepare nano-hydroxyapatite (n-HA)-based nanocomposite, and the effects of different states, treatments methods, the addition amounts and addition methods of BF on the formation of n-HA on BF fiber and the corresponding n-HA/BF composites were investigated by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, electromechanical universal tester, in vitro soaking in simulated body fluid and in vitro cell culture experiment. Results demonstrated that n-HA with the irregular morphology was attached on BF fibers, and it could be hybridized with BF to form n-HA/BF composite, however, there was subtle difference of the crystallinity, size and formed amount of n-HA attached on the different BF fibers, which brought about different surface properties of the n-HA/BF composites. And 30 wt% BF endowed the n-HA/BF composite with the best mechanical properties, whose was by far higher than that of pure n-HA. In addition, in vitro simulated body fluids soaking results indicated that n-HA/BF composites displayed different water absorption rates, and all n-HA/BF composites could promote the apatite deposit. Meanwhile, the n-HA/BF composites exhibited good cytocompatibility, including attachment and proliferation. All results proved that single BF polymer could be used to act as the organic matrix to prepare n-HA-based nanocomposite by replacing collagen component of natural bone, and the alkali treated and undissolved BF with 30 wt% addition amount by precipitated method was the best appropriate condition to prepare the ideal n-HA/BF composite. Consequently, the study would open up a new application of natural BF in the biomedical field. In this manuscript, bamboo fiber (BF) was firstly chosen to replace other polymers to prepare nano-hydroxyapatite (n-HA)-based nanocomposite, and the effects of different states, treatments methods, the addition amounts and addition methods of BF on the formation of n-HA were investigated. Results demonstrated that n-HA with the irregular morphology was attached onto BF and hybridized with BF, and n-HA possessed different crystallinity and size, which brought about different properties of the n-HA/BF composites. Overall, the alkali treated and undissolved BF with 30 wt% addition amount by co-precipitated method was the best appropriate condition to prepare the ideal n-HA/BF composite, which had a great potential to be used as bone materials. The study proved that single BF could replace other polymers to develop n-HA-based nanocomposite used as bone materials, which would open up a new idea to utilize BF in biomedical field. SEM micrographs of samples. (a) Pure n-HA, (b) alkali/undissolved/precipitated, (c) unalkali/undissolved/precipitated, (d) alkali/dissolved/co-precipitated, (e) alkali/undissolved/blended, (f) acid/undissolved/precipitated, (A) 20%BF/n-HA, (B) 30%BF/n-HA, (C) 40%BF/n-HA [ABSTRACT FROM AUTHOR]

The flight dynamics model of air-breathing hypersonic vehicles (AHVs) is highly nonlinear and multivariable coupling, and includes inertial uncertainties and external disturbances that require strong, robust, and high-accuracy controllers. In this paper, we propose a linear-quadratic regulator (LQR) design method based on stochastic robustness analysis for the longitudinal dynamics of AHVs. First, input/output feedback linearization is used to design LQRs. Second, subject to various system parameter uncertainties, system robustness is characterized by the probability of stability and desired performance. Then, the mapping relationship between system robustness and LQR parameters is established. Particularly, to maximize system robustness, a novel hybrid particle swarm optimization algorithm is proposed to search for the optimal LQR parameters. During the search iteration, a Chernoff bound algorithm is applied to determine the finite sample size of Monte Carlo evaluation with the given probability levels. Finally, simulation results show that the optimization algorithm can effectively find the optimal solution to the LQR parameters. [ABSTRACT FROM AUTHOR]

This paper proposes a new terminal homing guidance law with line-of-sight angle constraint for a missile to intercept a noncooperative maneuvering target by integrating prescribed performance control with sliding mode control. The newly proposed guidance law is derived analytically with a prescribed performance controller in combination with the continuous nonsingular terminal sliding mode manifold and the disturbance observer. The prescribed performance controller is designed with a new prescribed performance function to avoid undesired abrupt change in the derivative of prescribed performance variable. In addition to its robustness and preciseness, this new homing guidance law is able to attenuate a largely abrupt change in guidance commands due to driving the sliding mode variable whose initial derivative is close to zero to a desired residual set at the beginning of the terminal homing phase. Furthermore, the time-varying control gain of the new guidance law is analytically determined by terminal tolerance. Theoretical analysis and numerical simulations are conducted to demonstrate the effectiveness of this new guidance law. [ABSTRACT FROM AUTHOR]

To investigate the osteoinductive and ectopicly osteogenic effects of a novel peptide P24 derived from bone morphogenetic protein 2 (BMP2), biodegradable collagen scaffolds (CS) were used to load BMP-2-derived peptide solutions with different concentrations (0.4 mg peptide/CS, 0.1 mg peptide/CS and pure CS, respectively), and the implants were implanted into muscular pockets on the back of Wistar rats. Radiographs and histological analysis were performed to evaluate the ectopic bone effects. Active ectopic bone formation was seen in both groups containing the peptide at different concentration (0.4 mg and 0.1 mg), whereas no bone formation and only fibrous tissue was seen in the pure CS group. The new bone formation induced by the peptide P24 displayed a dose-dependent and time-dependent efficiency. The new bone formation in the 0.4 mg peptide/CS group significantly increased than that of the 0.1 mg peptide/CS group. This novel BMP-2-derived peptide had excellent osteoinductive and ectopicly osteogenic properties which were similar to those of BMP2. [ABSTRACT FROM AUTHOR]