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The surface topology of biomaterial has a definite effect on the growth behavior of nerve cells for peripheral nerve regeneration. In this study, the silk fibroin (SF) film with different anisotropic microgroove/ridge was constructed by micropatterning technology. The effects of topologies width on the directional growth of dorsal root ganglion (DRG) neurons were evaluated. The results showed that the topological structure of the SF film with higher SF concentration was more clear and complete. The microtopography of the SF film with a concentration of 15% and a groove width of around 30 μm could effectively guide the directional growth of the nerve fibers of DRG. And nerve fibers could obviously form nerve fiber bundles which may have a certain pavement effect on the recovery of nerve function. The study indicated that the SF film with a specific width of the topological structure may have potential applications in the field of directional nerve regeneration.
Recent studies have demonstrated that the nutritional properties of peanut meal (PM) can be improved after being fermented. The assessment of fermented PM has been reported to be limited to various physical and chemical evaluations in vitro. In the present study, PM was fermented by Bacillus natto to explore the effects of fermented PM extract (FE) on growth performance, learning and memory ability and intestinal microflora in mice. Ninety newly weaned male Kunming (KM) mice were randomly divided into seven groups: normal group (n 20), low-dose FE group (n 10), middle-dose FE group (MFE) (n 10), high-dose FE group (HFE) (n 20), unfermented extraction group (n 10), model group (10) and natural recovery group (10). Learning and memory skills were performed by the Morris water maze (MWM) test, and the variation in gut microbiota (GM) composition was assessed by 16S rDNA amplicon sequencing. The results show that HFE remarkably improved the growth performance in mice. In the MWM test, escape latency was shortened in both MFE and HFE groups, while the percentage of time, distance in target quadrant and the number crossing over the platform were significantly increased in the HFE group. Moreover, the FE played a preventive role in the dysbacteriosis of mice induced by antibiotic and increased the richness and species evenness of GM in mice.
The control problem for a ship steering system with speed loss is discussed in this paper. Two methods are proposed to deal with the unknown bounded disturbance for a sliding mode controller applied to a nonlinear surface vessel heading control system. The system uncertainties caused by speed changes are taken as internal disturbances, while the wave moments are considered as external disturbances. A feedback linearization method is adopted to simplify the nonlinear system. An adaptive method and a Nonlinear Disturbance Observer (NDO) are proposed for course keeping manoeuvres and speed keeping in vessel steering and provide robust performance for time varying wave disturbance and actuator dynamics. Furthermore, the overall stability conditions of the proposed controllers are analysed by Lyapunov's direct method. Finally, simulation results using the characteristics of a naval vessel illustrate the effectiveness of the presented control algorithms.
A series of titanium silicate glasses along the composition joins TiO2-SiO2, TiO2-Na2SiO3, TiO2-K2SiO3 and TiO2-CaSiO3, has been examined using oxygen K-edge X-ray absorption near edge structure spectroscopy (XANES) confined to the near-surface region. Sharp pre-edge features in the spectra can be used to determine the Ti coordination in the glasses. The presence of Ti is indicated by a pre-edge peak at ∼534 eV while Ti is indicated by a peak at ∼533 eV. Titanium exists in all these glasses as Ti and Ti with no Ti being present. For alkali-containing glasses the Ti site becomes more prevalent with increasing TiO2. TiO2-K2SiO3 compositions contain a greater proportion of Ti than comparable Na2O compositions. This is consistent with earlier Ti L-edge findings. The TEY spectra for the TiO2-CaSiO3 compositions indicate the presence of significant amounts of Ti at high TiO2 contents; however, comparison of TEY (near surface) and FY (bulk sample) XANES shows that the Ti is confined to the surface of the glass sample with the bulk of the glass containing Ti.
Since the discovery of submarine hot vents in the late 1970s, it has been postulated that submarine hydrothermal environments would be suitable for emergence of life on Earth. To simulate warm spring conditions, we designed a series of microwave-assisted amino acid synthesis involving direct reactions between succinic acid and ammonia in the presence of the magnetite catalyst. These reactions which generated aspartic acid and glycine were carried out under mild temperatures and pressures (90–180 °C, 4–19 bar). We studied this specific reaction inasmuch as succinic acid and ammonia were traditionally identified as prebiotic compounds in primitive deep-sea hydrothermal systems on Earth. The experimental results were discussed in both biochemical and geochemical context to offer a possible route for abiotic amino acid synthesis. With extremely diluted starting materials (0.002 M carboxylic acid and 0.002 M ammonia) and catalyst loading, an obvious temperature dependency was observed in both cases [neither product was detected at 90 °C in comparison with 21.08 μmol L−1 (aspartic acid) and 70.25 umol L−1 (glycine) in 180 °C]. However, an opposite trend presented for reaction time factor, namely a positive correlation for glycine, but a negative one for aspartic acid.
How prebiotic metabolic pathways could have formed is an essential question for the origins of life on early Earth. From the abiogenetic point of view, the emergence of primordial metabolism may be postulated as a continuum from Earth's geochemical processes to chemoautotrophic biochemical procedures on mineral surfaces. In the present study, we examined in detail the reversible amination of α-ketoglutarate on UV-irradiated ZnS particles under variable reaction conditions such as pH, temperature, hole scavenger species and concentrations, and different amino acids. It was observed that the reductive amination of α-ketoglutarate and the oxidative amination of glutamate were both effectively performed on ZnS surfaces in the presence and absence of a hole scavenger, respectively. Accordingly, a photocatalytic mechanism was proposed. The reversible photochemical reaction was more efficient under basic conditions but independent of temperature in the range of 30–60 °C. SO32− was more effective than S2− as the hole scavenger. Finally, we extended the glutamate dehydrogenase-like chemistry to a set of other α-amino acids and their corresponding α-oxo acids and found that hydrophobic amino acid side chains were more conducive to the reversible redox reactions. Since the experimental conditions are believed to have been prevalent in shallow water hydrothermal vent systems of early Earth, the results of this work not only suggest that the ZnS-assisted photochemical reaction can regulate the redox equilibrium between α-amino acids and α-oxo acids, but also provide a model of how prebiotic metabolic homoeostasis could have been developed and regulated. These findings can advance our understanding of the establishment of archaic non-enzymatic metabolic systems and the origins of autotrophy.
Diffusion of interstitial hydrogen atoms in α-iron was investigated using molecular dynamic simulation. In particular, hydrogen diffusivities in bulk, on (001) surface and within a Σ5 /(013) symmetric tilt grain boundary (STGB) were estimated in a temperature range of 400 and 700 K. Furthermore, hydrogen diffusivities in a series of Σ5  tilt grain boundaries with different inclinations were also determined as a function of temperature. The inclination dependence of activation energy for diffusion exhibits two local maxima, which correspond to two STGBs. Additional calculation of inclination dependence of boundary energy and boundary specific excess volume shows two local minima at the same STGBs. This suggests hydrogen diffusion into and within a grain boundary might be assisted by grain boundary excess volume and stress. Simulation of effects of hydrostatic pressure on diffusion shows tensile stress can promote hydrogen diffusion in lattice into grain boundary or surface traps, while compressive stress leads to a decrease in diffusivity, and a slower rate of filling these traps.
Nitrogen-doped multiwalled carbon nanotubes (N-doped MWNTs) were synthesized in a large quantity by the pyrolysis of pyridine at various temperatures in the range of 750–950 °C. The influence of temperature on the morphology, composition, thermal stability, and bonding nature of N-doped MWNTs was investigated. It is found that the yield of N-doped MWNTs increases linearly with the increase of the growth temperature. The maximum N content (4.6 at%) in MWNTs was obtained from a sample grown at 900 °C. N-doped MWNTs synthesized at 950 °C possess a unique drumlike morphology with the highest oxidizing temperature (535 °C). It is evidenced that N atoms are incorporated into the graphitic network in three different bonding forms and their relative content is affected by the growth temperature, which shows a clear influence on the morphology of N-doped MWNTs.
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