To send content items to your account,
please confirm that you agree to abide by our usage policies.
If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account.
Find out more about sending content to .
To send content items to your Kindle, first ensure email@example.com
is added to your Approved Personal Document E-mail List under your Personal Document Settings
on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part
of your Kindle email address below.
Find out more about sending to your Kindle.
Note you can select to send to either the @free.kindle.com or @kindle.com variations.
‘@free.kindle.com’ emails are free but can only be sent to your device when it is connected to wi-fi.
‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
During the detection of industrial hazardous gases, like formaldehyde (HCHO), the selectivity is still a challenging issue. Herein, an alternative HCHO chemosensor that based on the tin oxide nanoparticles is proposed, which was obtained through a facile hydrothermal method. Gas sensing performances showed that the optimal working temperature located at only 180 °C, the response value of 79 via 50 ppm HCHO was much higher than that of 35 at 230 °C. However, the compromised test temperature was selected as 230 °C, taking into account the faster response/recovery speeds than 180 °C, named 20/23versus 53/60 s, respectively. The response (35) of the SnO2 nanoparticles-based sensor to 50 ppm of HCHO is about 400% higher than that of bulk SnO2 sensor (9), especially when the gas concentration is 1 ppm, SnO2 nanoparticles also has a higher sensitivity which may possibly result from more exposed active sites and small size effect for nanoparticles than for bulk ones. The gas sensor based on SnO2 nanoparticles can be utilized as a promising candidate for practical low-temperature detectors of HCHO due to its higher gas response, excellent response–recovery properties, and perfect selectivity.
The purpose of this study was to construct a glycyrrhetinic acid (GA)-mediated, breakable, intracellular, nanoscale drug-delivery carrier via amide and esterification reactions. The structures were identified by Fourier-transformed infrared (FTIR) and 1H-nuclear magnetic resonance (1H-NMR) spectrophotometry. The compatibility and safety of the carrier were evaluated using hemolysis and cytotoxicity tests. The GA-copolymer micelle was prepared using the solvent evaporation method. FTIR and 1H-NMR detection demonstrated the successful construction of the polymer. No hemolysis occurred in any concentration of polymer within 3 h, and the hemolysis rate was less than 5%. 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) experimental results showed that the novel polymer reduced the cell survival rate and had significant cytotoxic effects. The blank nanoparticles were liquid with light blue opalescence. Transmission electron microscopy revealed that the empty micelles were uniform spheres, with an average size of 62 nm and a zeta potential of −13 mV. The novel GA-mediated polymeric carrier material developed here has the potential to effectively kill human SMMC-7721 cancer cells within 3 days when the dose is above 500 ug/mL.
Only 30% or fewer of individuals at clinical high risk (CHR) convert to full psychosis within 2 years. Efforts are thus underway to refine risk identification strategies to increase their predictive power. Our objective was to develop and validate the predictive accuracy and individualized risk components of a mobile app-based psychosis risk calculator (RC) in a CHR sample from the SHARP (ShangHai At Risk for Psychosis) program.
In total, 400 CHR individuals were identified by the Chinese version of the Structured Interview for Prodromal Syndromes. In the first phase of 300 CHR individuals, 196 subjects (65.3%) who completed neurocognitive assessments and had at least a 2-year follow-up assessment were included in the construction of an RC for psychosis. In the second phase of the SHARP sample of 100 subjects, 93 with data integrity were included to validate the performance of the SHARP-RC.
The SHARP-RC showed good discrimination of subsequent transition to psychosis with an AUC of 0.78 (p < 0.001). The individualized risk generated by the SHARP-RC provided a solid estimation of conversion in the independent validation sample, with an AUC of 0.80 (p = 0.003). A risk estimate of 20% or higher had excellent sensitivity (84%) and moderate specificity (63%) for the prediction of psychosis. The relative contribution of individual risk components can be simultaneously generated. The mobile app-based SHARP-RC was developed as a convenient tool for individualized psychosis risk appraisal.
The SHARP-RC provides a practical tool not only for assessing the probability that an individual at CHR will develop full psychosis, but also personal risk components that might be targeted in early intervention.
To investigate the hypothesis that folic acid supplementation and dietary folate intake before conception and during pregnancy reduce the risk of small for gestational age (SGA) and to examine the joint effect of folic acid supplementation and dietary folate intake on the risk of SGA.
Participants were interviewed by trained study interviewers using a standardized and structured questionnaire. Information on birth outcomes and maternal complications was abstracted from medical records and dietary information was collected via a semi-quantitative FFQ before conception and during pregnancy.
A birth cohort data analysis using the 2010–2012 Gansu Provincial Maternity and Child Care Hospital.
Women (n 8758) and their children enrolled in the study.
Folic acid supplementation was associated with a reduced risk of SGA (OR = 0·72, 95 % CI 0·60, 0·86), with the reduced risk seen mainly for SGA at ≥37 weeks of gestational age (OR = 0·70, 95 % CI 0·58, 0·85) and nulliparous SGA (OR = 0·67, 95 % CI 0·54, 0·84). There was no significant association between dietary folate intake and SGA risk.
Our study suggested that folic acid supplementation was associated with a reduced risk of SGA and the risk varied by preterm status and parity.
The present study explored the mechanism of Zn-methionine (Zn-Met) influencing eggshell quality of laying hens and investigated whether the mechanism was related to Ca deposition. Hyline grey layers (n 384, 38 weeks old) were divided into four groups: 0 mg Zn/kg, 40, 80 mg Zn/kg as Zn-Met, and 80 mg Zn/kg as zinc sulphate (ZnSO4). Eggshell quality, Zn contents, Zn-containing enzyme activities and expressions of shell matrix proteins in eggshell gland (ESG) were analysed. Zn-Met treatment at 80 mg/kg increased (P < 0·05) egg weight and eggshell strength throughout the experiments. The 80 mg/kg Zn-Met group (P < 0·05) had decreased mammillary knob width and larger relative atomic weight percentage of Ca, stronger signal intensity of Ca in linear distribution and the Ca was more evenly distributed in the transversal surface of eggshell. Zn contents (P < 0·001) in yolk and serum, Ca, albumin (Alb) levels in ESG as well as carbonic anhydrase (CA) activity in serum (P < 0·05) and mRNA levels of CA and Ca-binding protein-d28k (CaBP-D28k) (P < 0·001) in the 80 mg/kg Zn-Met group were the highest among all treatments. In conclusion, shell strength as one of eggshell qualities was mostly related to mammillary cone width in ultrastructure caused by the pattern of Ca deposition in eggshell formation. Also, the increase in Zn-Met-induced Ca deposition may be due to the increased Zn contents in serum and tissues, which were attributable to the increased CA concentrations in serum, Ca, Alb levels and up-regulated CA and CaBP-D28k mRNA levels in ESG.
Spray-painting equipments are important for the automatic spraying of long conical objects such as rocket fairing. This paper proposes a spray-painting equipment that consists of a feed worktable, a gantry frame and two serial–parallel mechanisms and investigates the optimal design of PRR–PRR parallel manipulator in serial–parallel mechanisms. Based on the kinematic model of the parallel manipulator, the conditioning performance, workspace and accuracy performance indices are defined. The dynamic model is derived using virtual work principle and dynamic evaluation index is defined. The conditioning performance, workspace, accuracy performance and dynamic performance are involved in multi-objective optimization design to determine the optimal geometrical parameters of the parallel manipulator. Furthermore, the geometrical parameters of the gantry frame are optimized. An example is given to show how to determine these parameters by taking a long object with conical surface as painted object.
Recently, we introduced an epoxy group to mebendazole by a reaction with epichlorohydrin and obtained two isoforms, mebendazole C1 (M-C1) and mebendazole C2 (M-C2). The in vitro effects of mebendazole derivatives at different concentrations on Echinococcus multilocularis protoscoleces and metacestodes as well as cytotoxicity in rat hepatoma (RH) cells were examined. The results demonstrated that the solubility of the two derivatives was greatly improved compared to mebendazole. The mortality of protoscoleces in vitro reached to 70–80% after 7 days of exposure to mebendazole or M-C2, and M-C2 showed higher parasiticidal effects than mebendazole (P > 0.05). The parasiticidal effect of M-C1 was low, even at a concentration of 30 µm. The percentage of damaged metacestodes that were treated with mebendazole and M-C2 in vitro at different concentrations were similar, and M-C1 exhibited insignificant effects on metacestodes. Significant morphological changes on protoscoleces and metacestodes were observed after treatment with mebendazole and M-C2. In addition, the introduction of an epoxy group to mebendazole also reduced its cytotoxicity in RH cells. Our results demonstrate that the introduction of an epoxy group not only improved the solubility of mebendazole, but also increased its parasiticidal effects on E. multilocularis and reduced its cytotoxicity in RH cells.
This paper reports on an atomic-scale investigation into the β′ precipitates and the long-period stacking ordered phase (LPSO) in Mg–5Y–2.5Ni–0.5Zr (at.%) alloy, using Cs-corrected high angle annular dark field-scanning transmission electron microscopy (HAADF-STEM). The results displayed that the 18R-type and 14H-type LPSO phases coexisted in the as-cast and the solid solution states, and the 18R-type and 14H-type LPSO structures were thermal stable. After aging treatment, the aging peak hardness reached 138 HV at 225 °C for 48 h. The significant increase in hardness was attributed to the formation of the metastable β′ phase. The lattice parameters of a and b axes for β′ phases are a = 0.65 nm, b = 2.20 nm, and c = 0.52 nm by HAADF-STEM. The interaction between the LPSO phase and the β′ can be found. The atomic-scale interactions between the LPSO and β′ phases are divided into two parts: under-aging and peak-aging conditions between the building blocks.
This article reports on the growth kinetics of cerium oxide (CeO2) nanoparticles prepared via a sintering method. By varying the sintering temperatures and periods of time, particle size of CeO2 nanoparticles was tuned from 11 to 100 nm. Ostwald ripening mechanism prevails in the growth process, and the growth kinetics is determined to follow an equation, D5 = 16.25 + 3.6 × 1020 exp(−344.20/RT) in the temperature range of 700 to 1000°C. After dispersing Pt on CeO2 nanoparticles, the size effect for the catalytic performance of the CO oxidation reaction was researched. When temperature and period of time are set at 700 °C and 2 h, respectively, dispersion of Pt onto CeO2 nanoparticles led to the largest quantity of chemisorbed oxygen species on the surface and the best catalytic performance. The findings reported here would provide a feasible path for the preparation of advanced catalysts in the future and moreover to discover novel size-dependent supports for many catalytic applications.
The novel visible-light-responsive direct solid-state Z-scheme g-C3N4/BiOI heterojunction has been synthesized successfully by means of a solid phase calcination method and used for the degradation of microcystin-LR (MC-LR). The layered g-C3N4 disperses on the surface of BiOI microspheres. The samples are characterized by FESEM, HRTEM, XRD, FT-IR, UV-vis spectroscopy, XPS, BET, PL, and Mott–Sckottky. The photocatalytic activity and photodegradation mechanism of the as-prepared g-C3N4/BiOI microsphere photocatalysts are conducted under visible light irradiation using MC-LR as the target pollutant. The g-C3N4/BiOI material exhibits superior photocatalytic performance when compared with pure BiOI, the possible reason is the efficient separation of photogenerated carriers at the interface between g-C3N4 and BiOI. The heterostructure is responsible for the improved separation efficiency of photogenerated electron–hole pairs and thus the higher photocatalytic activity. The possible photocatalytic mechanism is proposed based on relative band positions of these two semiconductors.
Methods for efficient variance-based global sensitivity analysis of complex high-dimensional problems are presented and compared. Variance decomposition methods rank inputs according to Sobol indices that can be computationally expensive to evaluate. Main and interaction effect Sobol indices can be computed analytically in the Kennedy and O'Hagan framework with Gaussian processes. These methods use the high-dimensional model representation concept for variance decomposition that presents a unique model representation when inputs are uncorrelated. However, when the inputs are correlated, multiple model representations may be possible leading to ambiguous sensitivity ranking with Sobol indices. In this work, we present the effect of input correlation on sensitivity analysis and discuss the methods presented by Li and Rabitz in the context of Kennedy and O'Hagan's framework with Gaussian processes. Results are demonstrated on simulated and real problems for correlated and uncorrelated inputs and demonstrate the utility of variance decomposition methods for sensitivity analysis.
The modules of parallel tool heads with 2R1T degrees of freedom (DOFs), i.e., two rotational DOFs and one translational DOF, have become so important in the field of machine tools that corresponding research studies have attracted extensive attention from both academia and industry. A 3-PUU (P represents a prismatic joint, U represents a universal joint) parallel mechanism with 2R1T DOFs is proposed in this paper, and a detailed discussion about its architecture, geometrical constraints, and mobility characteristics is presented. Furthermore, on the basis of its special geometrical constraint, we derive and explicitly express the parasitic motion of the 3-PUU mechanism. Then, the inverse kinematics problem, the Jacobian matrix calculation and the forward kinematics problem are also investigated. Finally, with a simplified dynamics model, the inverse dynamics analysis for the mechanism is carried out with the Principle of Virtual Work, and corresponding results are compared with that of the 3-PRS mechanism. The above analyses illustrate that the 3-PUU parallel mechanism has good dynamics features, which validates the feasibility of applying this mechanism as a tool head module.
To find the optimal Quenching and Partitioning (Q&P) process parameters of low-alloy wear resistant steel, various Q&P processes including quenching temperature, partitioning temperature and partitioning time were designed and tested by using orthogonal experiment method. Through analysis of orthogonal experiment, quenching temperature was the most important influential factor on the impact toughness and hardness, and partitioning time played a critical role on tensile strength. The optimal Q&P heat treatment parameters of low alloy wear resistant steel were partitioning at 350 °C for 10 min immediately after quenching at 100 °C. The microstructure of samples was composed of martensite laths and retained austenite. The relative volume fraction of retained austenite increased with the increase of quenching temperature and decreased gradually with the lengthening of partitioning time. Combining the results of Energy dispersive spectrometer, the reason for decrease of retained austenite was the existence of carbide precipitation and the carbide was (Fe, Cr)3C7. Compared to the traditional heat treatment of quenching and low temperature tempering, the samples under Q&P treatment displayed higher toughness and maintained relatively high tensile strength and wear resistance.
This paper presents a new numerical approach using a Genetic algorithm (GA) to search for the singularity-free cylindrical space of a 4-RRR planar redundant parallel manipulator and investigates the effects of the joint position (namely the length ratios of two links) of each leg on the singularity-free cylindrical space. A previous method investigated the maximal singularity-free zone in a 3-dimensional (3-D) space within a given workspace. The method in this paper is improved by optimizing the maximal singularity-free zone in a 2-dimensional (2-D) plane while considering the whole workspace. This improvement can be helpful for reducing the searching time and for finding a larger singularity-free zone. Furthermore, the effect of the joint position of each leg on the maximal singularity-free zone is studied in this paper, which reveals a larger singularity-free zone than before. This result shows that changing the joint positions of one or two legs may be more practical than changing the joint positions of more legs. The approach in this paper can be used to analyze the maximal singularity-free zone of any other three-degree-of-freedom (3-DOF) planar parallel mechanisms and will be useful for the optimal design of redundant parallel manipulators.
Inertia strongly influences the dynamic performance of parallel manipulators, and ignorance of inertia is apt to result in negative phenomena such as vibrations, overshoot, and slow response. This study analyzes the inertia-decoupling characteristic of Stewart platform. Because the inertia matrix of the Stewart platform is usually non-diagonal, inertia coupling occurs between its legs. Herein, decoupling to inertia is implemented, and independent control channels are determined. The influence of decoupled inertia on the control system is analyzed using the Adams simulation software, and the inertia index of the Stewart platform is proposed. Experiments are conducted on a prototype of the Stewart platform to verify the eigenvalue characteristic of decoupled inertia. The distribution of inertia index in the operational workspace is provided, and the influence of dimensional parameters on inertia index is discussed. Finally, dimensional optimization is realized with a set of optimized dimensions for good dynamic performance.