Search

A NaOH/urea (or thiourea) solvent system capable of dissolving cellulose at lower temperatures is a breakthrough in cellulose chemistry, and it was reported that cellulose rapidly dissolved when it was added to a precooled aqueous solution of sodium hydroxide (NaOH) and additives. In fact, upon initiating this work, we plan to fabricate pulp fibers based cushioning packaging material based on part dissolution of dissolving pulp in aqueous NaOH/additives solutions, and found certain dissolving pulp added to a precooled aqueous solution did not show better dissolution. Therefore, this work compared the effectiveness of the direct dissolution method and freezing-thaw method in dissolving pulp fiber and pure cellulose. Three aqueous solutions were examined: 7% NaOH/12% urea, 9.5% NaOH/4.5% thiourea, and 8% NaOH/8% urea/6.5% thiourea. The dissolving capacity of three NaOH/additives aqueous solutions was analyzed by polarized optical microscopy and the dissolved cellulose proportion was determined. The results showed that the never-dried softwood dissolving pulp and bamboo dissolving pulp achieved better dissolution using freezing-thaw method than using direct dissolution method in the three aqueous solutions. The dissolving method had a negligible effect on the dissolution of each dissolving pulp in the 8% NaOH/8% urea/6.5% thiourea solution. It seems that the direct dissolution method was more suitable for oven-dried microcrystalline cellulose with a low degree of polymerization (DP) and the freezing-thaw method was more suitable for never-dried pulp cellulose fibers with a higher DP.

The present research investigated the quasi-causal relationship between foreign language classroom anxiety (FLCA) and English performance in relation to gender and discipline via cross-lagged regression analyses. A total of 934 freshmen from a well-known state-owned university in Beijing answered the Foreign Language Classroom Anxiety Scale and a background questionnaire at the beginning and the end of a term. Their English test scores in both phases were also collected. Results demonstrated that FLCA was significantly negatively correlated with English test performance for all students. Another major finding was that the overall FLCA, low self-confidence in speaking English, and worry about English classroom performance impacted the students’ test performance differently, depending on gender and discipline, so did test performance impact different aspects of FLCA. These findings show that FLCA is a primary cause for test performance, while the latter is not necessarily an important cause for the former.

The aim of this study was to investigate the mechanisms by which nitrogen (N) and phosphorous (P) additions affect plant C:N:P stoichiometry via changes in AMF communities in a Chinese fir plantation. Experimental plots in a 10-year-old Chinese fir plantation were treated with N addition (LN, 30 kg•ha−1•yr−1, and HN, 60 kg•ha−1•yr−1) and P addition (LP, 20 mg•kg−1, and HP, 40 mg•kg−1) for 2 years starting from 2017. Soil properties, leaf C:N:P stoichiometry, and changes in AMF community composition and diversity were measured. N or P addition increased soil N availability, decreased P availability, and increased N:P in the leaves and soil. Changes in soil pH induced by N and P additions affected the colonization rate and spore density of AMF. AMF colonization rate was increased by N or P addition, and AMF diversity was increased by LN addition. N and P additions altered AMF species composition, and the dominant genus of the AMF in the soil was Glomus in all treatments. The interaction of N and P treatments had no significant effect on AMF diversity. AMF colonization rate and diversity, rather than its composition, affected leaf C:N:P stoichiometry. N and P additions affected colonization rate and diversity of AMF though changes in soil pH, which drove leaf C:N:P stoichiometry, and potentially affected forest productivity via the fungi-soil-plant system.

Since the photocatalytic effect of a single conventional photocatalyst is often not ideal, it is particularly important to design and construct an efficient and stable photocatalyst in a compound way. In this study, we exploited the sol–gel method to combine BiOCl and TiO2 and gave full play to their respective advantages to prepare BiOCl/TiO2 composite materials. Then, X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) characterization techniques were utilized to study important indicators of composites—composition, morphology, and structure. In the photodegradation experiment of methyl orange (MO), it was found that the photocatalytic performance of 10BTO (the molar ratio of TiO2 to BiOCl is 10:1) was the best among all the composite photocatalysts, and almost complete degradation of MO was realized. Besides, repeated experiments and recyclability tests on composite materials display favorable stability. Through ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), photoluminescence (PL), transient photocurrent response, electrochemical impedance spectroscopy (EIS), and electron spin resonance (ESR), a possible degradation mechanism is proposed. Given that there are serious environmental pollution problems in our country, we sincerely hope this research will do its best to degrade organic pollutants in wastewater.

NiTiO3/Bi4NbO8Cl heterostructure photocatalysts were successfully synthesized by a mechanical mixing method. The crystal structure, morphology, optical properties and energy band structures of all samples were determined by X-ray powder diffraction, X-ray photoelectron spectroscopy, scanning electron microscope, transmission electron microscope, ultraviolet–visible diffuse reflection spectra (UV–Vis DRS), and Mott–Schottky tests. The NiTiO3/Bi4NbO8Cl composites were observed to possess an improved activity in the photocatalytic degradation of organic dye rhodamine B (RhB) under irradiation. In particular, Bi4NbO8Cl modified with NiTiO3 (10% in weight) exhibits the best photocatalytic performance. The enhanced photocatalytic performance can be ascribed to the formation of intimate interfacial contact and type-II band alignment between NiTiO3 and Bi4NbO8Cl. From the results of photoluminescence spectra (PL), time-resolved decay spectra (TR-PL), photocurrent and electrochemical impedance spectroscopy, the rapid separation and transportation of photoinduced charge carriers were proved. In addition, the proposed mechanism for the enhanced photocatalytic activities is proposed in this paper.

A new type of polyurethane and polyaniline foam-derived nickel oxide-incorporated porous carbon composite (PPFPC-NiO) was synthesized through a combination of in situ polymerization, chemical blowing and carbonization methods and was studied for the first time. By taking advantage of a polyaniline-introduced polyurethane foam as a porous carbon skeleton precursor, interconnected nickel oxide-incorporated nanowires provided hierarchical porous conductive network structures after carbonization treatment, forming stable three-dimensional coralline-like open nano-architectures, which not only enhance the electrical conductivity and accelerate the electron transport rate during the charge–discharge process but also provide myriads of open hierarchical porous channels for rapid ion diffusion, increasing the number of available reactive sites in the PPFPC-NiO. As an electrode in supercapacitors, the PPFPC-NiO exhibits a high specific capacitance of 1012.8 F g−1 at 1 A g−1, with a capacitance retention of 96.43% after 5000 cycles in a three-electrode test and with 6 M KOH as the electrolyte. Because of these properties, an asymmetric supercapacitor is assembled using the PPFPC-NiO as the positive electrode and a mixture of activated carbon and graphite as the negative electrode. In a potential window of 1.5 V, the capacitor exhibits a high energy density of 32.2 Wh kg−1 at a power density of 281.3 W kg−1, which remains at 22.5 Wh kg−1, even at a high-power density of 1472.7 W kg−1. More importantly, the capacitor also shows excellent cycling stability, with 92.71% capacitance retention after 5000 cycles.

As trust becomes increasingly important in software domain, software trustworthiness — as a complex high-composite concept, has developed into a big challenge people have to face, especially in the current open, dynamic and ever-changing Internet environment. Furthermore, how to recognize and define trust problem from its nature and how to measure software trustworthiness correctly and effectively play a key role in improving users’ trust in choosing software. Based on trust theory in the field of humanities and sociology, this paper proposes a measurable S2S (Social-to-Software) software trustworthiness framework, introduces a generalized indicator loss to unify three parts of trustworthiness result, and presents a whole metric solution for software trustworthiness, including the advanced J-M model based on power function and time-loss rate for ability trustworthiness measurement, the fuzzy comprehensive evaluation advanced-model considering effect of multiple short boards for basic standard trustworthiness, and the identity trustworthiness measurement method based on the code homology detecting tools. Finally, it provides a case study to verify that the solution is applicable and effective.

A new type of polyurethane (PU) foam derived nitrogen-enriched porous carbon/reduced graphene oxide (PU/rGO) composite was synthesized and studied for the first time. By taking advantages of PU foam as carbon skeleton precursor, GO nanosheets wrapped onto the skeleton’s surface through hydrothermal process, then the stable porous sandwich-like nanoarchitectures built after carbonization process. Moreover, the wrapped GO can be transformed into rGO due to thermal reduction during the carbonization process. When being applied as supercapacitor electrodes, the prepared PU/rGO composite could achieve an extremely high specific capacitance of 490 and 341.7 F g−1 at a current density of 1 and 20 A g−1, respectively. After 5000 cycles, the specific retention yielded to 97.3% at 1 A g−1. Resulting from these merits, the as-assembled symmetric supercapacitor device with a wide operating voltage window of 1.5 V exhibit an excellent energy density of 21.66 Wh kg−1 at a power density of 825 W kg−1 and remain 7.5 Wh kg−1 even at a high power density of 2250 W kg−1. Most importantly, this work may offer a strategy for converting the PU foam wastes into carbon material with excellent electrochemical performance applied on energy storage.

In this study, TiO2 photoanodes doped with samarium ions via a method of hydrothermal treatment were used to fabricate dye-sensitized solar cells (DSSCs). Different doping concentrations were investigated on the effects of the cell’s performance. Some techniques including XRD, scanning electron microscopy, HRTEM, XPS, UV-Vis, photoluminescence were used to characterize the morphology, structure, and optic properties of the prepared photoanodes. The photovoltaic performance of the fabricated cells was further evaluated by measuring the current density–voltage (J–V) curves. It was found that: (1) The down-conversion luminescence effect derived from samarium doping could enhance the light-harvesting ability. (2) Compared with the undoped sample, the samarium-doped cells exhibited enhanced photovoltaic performance. Among the cells with different doping concentrations, the cell TiO2:0.015 Sm showed the best power conversion efficiency of 6.08% with a high open-circuit voltage (Voc) and a short-circuit current density (Jsc).

Long glass fiber-reinforced polyamide 6 (LGF–PA6) composites were prepared by using self-designed impregnation device. Polypropylene grafted with maleic anhydride (PP-g-MAH) and polyolefin elastomer grafted with maleic anhydride (POE-g-MAH) were chosen as compatibilizers. Dynamic mechanical properties of LGF–PA6 composites were investigated by using dynamic mechanical analysis (DMA). The DMA measurement results showed that test frequency, long glass fiber content and compatibilizers had an influence on dynamic mechanical properties and glass transition temperature (T g) of LGF–PA6 composites. The frequency had a complex influence on storage modulus (E′), loss modulus (E″) and loss tangent (tan δ). The T g of the composites is shifted to high temperature with the increasing of test frequency and was affected insignificantly by the glass fiber content. Storage modulus and loss modulus (E″) increased with the increasing fiber content, while the tan δ decreased. The effect of the addition of PP-g-MAH and POE-g-MAH on the dynamic mechanical properties of LGF–PA6 composites was complex. Scanning electron microscopy (SEM) was used to investigate the morphology of the fractured composites surface. The SEM results suggested that the PP-g-MAH and POE-g-MAH both improved the fiber/matrix interface adhesion, which was consistent with the DMA measurement results.

The present research examined the associations between foreign language listening anxiety (FLLA) and strategy use (FLLSU) and their predicting effects on test performance of high- and low-proficient Chinese university English as a foreign language learners. 1160 first-year undergraduate non-English majors answered the battery of questionnaires and took the listening test, among whom 227 low- and 243 high-proficient students were included in the final analyses of the collected data. The findings were as follows: (1) the low-proficient group was significantly more anxious about English listening and less confident in their English listening proficiency, and employed word-oriented and less active listener strategies significantly more often than their high-proficient peers, (2) FLLA was generally significantly correlated with FLLSU for both high- and low-proficient groups, and (3) FLLSU was a good predictor for English listening test performance for both low- and high-proficient students. It is thus concluded that FLLA and FLLSU are two closely interrelated and important factors in second/foreign language (SL/FL) learning, that FLLSU is a more influential factor for SL/FL listening learning, and that proficiency greatly mediates students’ FLLA levels and FLLSU frequencies.

The curing behavior and kinetics of epoxy resin (diglycidyl ether of bisphenol-A) with curing agent polyamidoamine and cyclohexene oxide as active diluents were investigated by differential scanning calorimetry. The apparent activation energy obtained by Kissinger method was 44.37 kJ mol−1. The result of model-fitting kinetic analysis showed that autocatalytic model (Sestak–Berggren model) was suitable to describe the curing mechanism. The thermal–mechanical properties were characterized with dynamic mechanical analysis, and the activation energies for α relaxation were calculated according to the Arrhenius law. Thermogravimetric analysis showed that the performance of the thermal decomposition almost stayed the same although reactive diluent (cyclohexene oxide) was added in curing system.

AISI 304 stainless steel plates were welded with activated flux tungsten inert gas (A-TIG) method by utilizing self-developed activated flux. It is indicated from the experimental results that for 8 mm-thick AISI 304 stainless steel plate, weld joint of full penetration and one-side welding with good weld appearance can be obtained in a single pass without groove preparation by utilizing A-TIG welding. Moreover, activated flux powders do not cause significant effect on the microstructure of TIG weld and the mechanical properties of A-TIG weld joints are also superior to those of C-TIG (conventional TIG) welding.

The novel graphene non-covalently functionalized with amino-terminated dendronized polyamide (DPA) was prepared, then reduced and filled into the PA6 to prepare a series of nanocomposites. The structures and thermal properties of products were investigated by FTIR, XPS, XRD, TEM, SEM, TG, thermal conductivity measurements. The results revealed that mediated by the DPA, the amino-terminated dendronized polyamide functionalized graphene nanosheets (DPA-GNs) show good solubility in the organic solvents and more compatible with organic polymer matrix, which results in a certain promotion in thermal stability and thermal conductivity of nanocomposites.

We design a packaged micro-optical–electromechanical system (MOEMS) – micro-grating accelerometer – that measures the interference of light resulting from its passage through a diffraction grating and reflection from the proof mass. In the present glass–silicon–glass embodiment, the diffraction optical element made of gold and the sensing proof mass supported by eight aluminum symmetrical cantilevers are fabricated on glass and silicon, respectively. Additional system components include a semiconductor laser, photodiodes, and the necessary electronics. First, we analyze the optical model to achieve high optical sensitivity. Then we optimize the structure parameters using the finite element method. Finally, we successfully fabricated the micro-grating accelerometer and packaged it in a small surface-mount package (12 × 12 × 3.6 mm). Our experiments show that the micro-grating accelerometer has a sensitivity of 5.6 V/G in the linear operating region, a bias stability of 0.94 μG, a resolution of 5.6 μG, and a dynamic range of 82.5 dB. Such a MOEMS accelerometer integrates the micro-grating with the proof mass through an anodic bonding procedure with the advantages of small size and high resolution.

In this paper, TiO2 particles (~30 nm) modified with Gd2O3-coating layer (~2 nm) for dye-sensitized solar cells (DSSCs) were fabricated via the hydrothermal method. Among the solar cells based on the Gd3+-doped TiO2 photoanodes, the optimal conversion efficiency was obtained from the 0.025Gd3+-modified TiO2-based cell, with a 17.7% improvement in the efficiency as compared to the unmodified one (7.18%). This enhancement was probably due to the improved UV radiation harvesting via a down-conversion luminescence process by Gd3+ ions, enhancement of visible light absorption and improved dye loading capacity. In addition, after Gd modification, a thin coating could be formed on the TiO2 nanoparticles, which worked as an energy barrier and resulted in a lower charge recombination.

Curing reactions of epoxy resin (diglycidyl ether of bisphenol-A) with curing agent polyamido-amine, using cyclohexanediol diglycidyl ether as active diluents, was investigated by non-isothermal differential scanning calorimetry at different heating rates. Activation energy was calculated based on Kissinger method, and the results showed that E a changed from 68.01 to 54.84 kJ mol−1 after the diluents was added, which reduced about 20 %. Malek method was used to deduce the probable mechanism function and the results indicated that Sestak–Berggren model is fairly coincident with the experimental data.

The mechanical properties of poly(ethylene terephthalate)/high-density poly(ethylene) (PET/HDPE) blends were improved by γ-ray irradiation combined with using a cross-linking agent—trimethylol propane trimethacrylate (TMPTA). The effect of the weight ratio of PET/HDPE, the content of TMPTA and the absorbed dose on the phase morphology and the mechanical properties of the PET/HDPE blends were investigated through scanning electron microscopy (SEM), gel fraction, Fourier transform infrared spectroscopy (FTIR), tensile and impact tests. SEM images showed that the phase structure changed significantly as TMPTA coexistence. The results of tensile and impact tests indicated that their mechanical properties depended on their structures. FTIR spectra suggested that a new structure of HDPE-g-PET was generated. When the weight ratio of PET/HDPE blend was 80/20, the content of TMPTA was 1 wt% and the absorbed dose was 30 kGy, the tensile strength, elongation at break and impact strength of irradiated blends were improved greatly compared with non-irradiated blends.

Plasma membrane intrinsic proteins (PIPs) are a subfamily of aquaporins that enable fast and controlled translocation of water across the membrane. In this study, we systematically identified and cloned ten PIP genes from rice. Based on the similarity of the amino acid sequences they encoded, these rice PIP genes were classified into two groups and designated as OsPIP1-1 to OsPIP1-3 and OsPIP2-1 to OsPIP2-7 following the nomenclature of PIP genes in maize. Quantitative RT-PCR analysis identified three root-specific and one leaf-specific OsPIP genes. Furthermore, the expression profile of each OsPIP gene in response to salt, drought and ABA treatment was examined in detail. Analysis on transgenic plants over-expressing of either OsPIP1 (OsPIP1-1) or OsPIP2 (OsPIP2-2) in wild-type Arabidopsis, showed enhanced tolerance to salt (100 mM of NaCl) and drought (200 mM of mannitol), but not to salt treatment of higher concentration (150 mM of NaCl). Taken together, these data suggest a distinct role of each OsPIP gene in response to different stresses, and should add a new layer to the understanding of the physiological function of rice PIP genes.

It was shown in a previous analysis thatD5 gene from rice (Oryza sativa L.) was an anther-specific gene encoding a chalcone synthase-related protein. In this study,D5 gene was found specifically expressed in tapetum cells as well as in the peripheral cells of the vascular bundle of rice anthers by RNAin situ hybridization. In order to study its function,D5 was transformed into rice in both sense and antisense directions driven by a riceActin 1 promoter. It has been observed that the pollen grains from the antisenseD5 transgenic rice plants are abnormal, indicating thatD5 plays a critical role in rice pollen development.

The promoter fragments of wheatGstA1 and potatoGst1 have been amplified by PCR, cloned and fused respectively to the minimal promoter sequence of rice actin gene (Act1)) and its 5′ untranslated leader sequence together withGUS. The constructs with 2 chimeric promoters (WGA and PGA) have been transferred into rice in order to analyze their inducibility patterns in transgenic rice plants. The results show that: WGA and PGA are both inducible by elicitors ofPyricularia oryzae in transgenic rice cells; the intron I of riceAct1 gene is important for the heterogenic expression of monocot and dicot promoter elements in rice; and theAct1 minimal promoter and its 5′ untranslated leader sequence produced low level background expression in rice.

A cDNA clone, pS4, has been isolated from a cDNA library prepared from rice anthers of about 1.0 mm in length. DNA sequence analysis and database search show that the cDNA encodes a protein which is highly homologous to eukaryotic 80s ribosomal protein subunit 4 (S4). Northern hybridization indicates that this gene expresses in all tissues analyzed although the expression level varies and it cannot be induced by mechanical wounding in leaves. Southern blot analysis demonstrates that this riceS4 gene is from a multigene family.

The development of stamen is an important stage during the sexual reproduction in higher plants. Studying the genes that predominantly or even specifically expressed in stamens will aid in undestanding the molecular mechanism of stamen development. The structure of a rice CHS-like gene (D5) which predominantly expressed in anthers has been analysised, showing high structural similarity with two other anther-specific genes (A1 and BA42) fromBrassica napus. Northern analysis also reveals that the three genes share a similar expression pattern and that the expression of D5 may relate to the early development of pollens. It is concluded that D5, A1 and BA42 represent a group of diverged CHS-like genes which are related to stamen development.