A comparative study of Young's modulus of single-walled carbon nanotube by CPMD, MD, and first principle simulations

Carbon nanotubes (CNTs), due to their exceptional magnetic, electrical and mechanical properties, are promising candidates for several technical applications ranging from nanoelectronic devices to composites. Young's modulus holds the special status in material properties and micro/nano-electromechanical systems (MEMS/NEMS) design. The excellently regular structures of CNTs facilitate accurate simulation of CNTs' behavior by applying a variety of theoretical methods. Here, three representative numerical methods, i.e., Car-Parrinello molecular dynamics (CPMD), density functional theory (DFT) and molecular dynamics (MD), were applied to calculate Young's modulus of single-walled carbon nanotube (SWCNT) with chirality (3,3). The comparative studies showed that the most accurate result is offered by time consuming DFT simulation. MID simulation produced a less accurate result due to neglecting electronic motions. Compared to the two preceding methods the best performance, with a balance between efficiency and precision, was deduced by CPMD.

Differentiate performance of eight filter media in vertical flow constructed wetland: Removal of organic matter, nitrogen and phosphorus

A comparative study was conducted to reveal the differentiate effects of eight different filter media including gravel, zeolites, anthracite, shale, vermiculite, ceramic filter media, blast furnace steel slag and round ceramsite. The study mainly related to the eight different filter media's removal performances of organic matter, nitrogen and phosphorus in the vertical flow constructed wetland simulated system, which treating wastewater at hydraulic loading rate of 1000-2500 mm/d. The results indicated that the removal effects were closely related to the physical and chemical properties of medium materials. Anthracite-filled system had the highest removal rate for the total organic carbon (TOC), up to 70%, and the removal rates of other systems ranged from 20% to 30%. As for the five-day biochemical oxygen demand (BOD5), anthracite-filled and steel slag-filled systems had the highest removal rates, also up to 70%, as well as other systems all exceeded 50%. At the same time, for the total nitrogen (TN) and NH4(+)-N, the zeolites-filled and ceramic-filled systems had the best performances with the removal rates of more than 70%, the other way round, the removal rates of other systems were only about 20%. The distinguishable effects were also observed in removal performances of total phosphorus (TP) and total dissoluble phosphorus (TDP). The removal rates of TP and TDP in steel slag-filled systems were more than 90%, a much higher value, followed by that of the anthracite-filled system, more than 60%, but those of other systems being the less. Our study provided a potential mechanism to optimize the filter media design for the vertical flow constructed wetlands.

Comparative study on the effect of dietary lipid level on growth and feed utilization for gibel carp (Carassius auratus gibelio) and Chinese longsnout catfish (Leiocassis longirostris Gunther)

An 8-week growth trial investigated the effect of dietary lipid level on growth performance of a carnivorous fish, Chinese longsnout catfish (Leiocassis longirostris Gunther) and an omnivorous fish, gibel carp (Carassius auratus gibelio). For each species, seven isonitrogenous semi-purified diets (455 g kg(-1) crude protein for Chinese longsnout catfish and 385 g kg(-1) crude protein for gibel carp) were formulated to contain 30, 60, 90, 120, 150, 180 or 210 g kg(-1) lipid. For Chinese longsnout catfish, feed intake (FI) decreased with increasing dietary lipid and there was no significant difference in feed intake from 90 to 210 g kg(-1) lipid. Specific growth rate (SGR) increased with dietary lipid level (P < 0.05) and the 150 and 180 g kg(-1) groups were the best. Feed conversion efficiency (FCE), protein retention efficiency (PRE) and energy retention efficiency (ERE) were higher at 180 g kg(-1) lipid. For gibel carp, FI decreased with increased dietary lipid and 180 and 210 g kg(-1) lipid groups showed lower values. SGR increased with dietary lipid level and the 150 and 180 g kg(-1) were the best. FCE was higher at 180 g kg(-1) lipid level. PRE increased with dietary lipid level and there was no significant difference in groups from 120 to 210 g kg(-1) dietary lipid. ERE increased with increasing dietary lipid level, and groups fed 120, 150 and 180 g kg(-1) lipid showed the highest values. In Chinese longsnout catfish, increase in dietary lipid level, resulted in increased carcass dry matter, crude protein, crude lipid and gross energy. In gibel carp, dry matter, crude protein, and crude lipid increased with dietary lipid level. Based on regression between SGR and dietary lipid, dietary lipid requirements for Chinese longsnout catfish and gibel carp were 142.6 and 140.5 g kg(-1), respectively.

Enhancing the Performance of the Organic Light-emitting Device (OLED) by Thermal Treatment

A comparative study on the annealing of the ITO substrates and the organic layers were conducted on Organic light-emitting device (OLED). We fabricated four devices with the structure of Al/Alq(3)/TPD: PVK/NiO/ITO/Glass, and investigated the effect of heat on device performance by selectively annealing. When the TPD: PVK layers were annealed at 90 degrees C with 30 min annealing time and the ITO substrates were annealed at 300 degrees C with a constant annealing time (100 min). We find the OLED shows obvious performance improvement in brightness and current efficiency, which is attributable to the fact that annealing reduces defects and improves the interface structures of the organics and the organic/ITO interfaces. On the other hand, an appropriate annealing would slow the transportation of the hole, thus finally leads to more balanced electron and hole.

Comparative study of paclitaxel physically encapsulated in and chemically conjugated with PEG-PLA

Paclitaxel-loaded poly(ethylene glycol)-b-poly(L-lactide (LA)) (PEG-PLA) micelles were prepared by two methods. One is physical encapsulation of paclitaxel in micelles composed of a PEG-PLA block copolymer and the other is based on a PEG-PLA-paclitaxel conjugate, abbreviated as "conjugate micelles" Their physicochemical characteristics, e.g. critical micelle concentration (CMC), morphology, and micelle size distribution were then evaluated by means of fluorescence spectroscopy, scanning electron microscopy (SEM), and dynamic light scattering (DLS). The results show that the CMC of PEG-PLA-paclitaxel and PEG-PLA are 6.31 x 10(4) and 1.78 x 10(-3) g L-1, respectively. Both micelles assume a spherical shape with comparable diameters and have unimodal size distribution. Moreover, in vitro drug delivery behavior was studied by high performance liquid chromatography (HPLC). The antitumor activity of the paclitaxel-loaded micelles against human liver cancer H7402 cells was evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) method.

COMPARATIVE-STUDY OF KALMAN FILTERING, SYNCHRONOUS EXCITATION AND NUMERICAL DERIVATIVE TECHNIQUES IN FLUOROMETRY

The performance of Kalman filtering, synchronous excitation and numerical derivative techniques for the resolution of overlapping emission spectra in spectrofluorimetry was studied. The extent of spectrum overlap was quantitatively described by the separation degree D(s), defined as the ratio of the peak separation to the full width at half-maximum of the emission spectrum of the interferent. For the system of Rhodamine B and Rhodamine 6G with a large D(s) of about 0.4, both Kalman filtering and synchronous techniques are able to resolve the overlapping spectra well and to give satisfactory results while the derivative spectra are still overlapped with each other. Moreover, the sensitivities are greatly decreased in derivative techniques. For more closely spaced spectra emitted by the complexes of Al and Zn with 7-iodo-8-hydroxyquinoline-5-sulphonic acid (Ferron)-hexadecyltrimethylammonium bromide, the synchronous excitation technique cannot completely separate the overlapping peaks, although it increases the separation degree from 0.25 in the conventional spectra to 0.37 in the synchronous spectra. On the other hand, Kalman filtering is capable of resolving this system. When the Al/Zn intensity ratio at the central wavelength of Al was > 1, however, the accuracy and precision of the estimates for Zn concentration produced by the Kalman filter became worse. In this event, the combination of synchronous excitation and Kalman filtering can much improve the analytical results.

Comparative analysis of astaxanthin and its esters in the mutant E1 of Haematococcus pluvialis and other green algae by HPLC with a C30 column

A gradient reversed-phase high-performance liquid chromatography (HPLC) method using a C30 column was developed for the simultaneous determination of astaxanthin, astaxanthin monoesters and astaxanthin diesters in the green algae Chlorococcum sp., Chlorella zofingiensis, Haematococcus pluvialis and the mutant E1, which was obtained from the mutagenesis of H. pluvialis by exposure to UV-irradiation and ethyl methanesulphonate (EMS) with subsequent screening using nicotine. The results showed that the contents of total astaxanthins including free astaxanthin and astaxanthin esters ranged from 1.4 to 30.9 mg/g dry biomass in these green algae. The lower total astaxanthin levels (< 2 mg/g dry biomass) were detected in the green algae Chlorococcum sp. and C. zofingiensis. The higher total astaxanthin levels (> 16 mg/g dry biomass) were found in the green alga H. pluvialis and its mutant E1. It is notable that the mutant E1 is found to have considerably higher amounts of total astaxanthin (30.9 mg/g) as compared to the wild strain of H. pluvialis (16.1 mg/g). This indicates that UV-irradiation and EMS compound mutagenesis with subsequent screening using nicotine is an effective method for breeding of a high-producing astaxanthin strain of H. pluvialis. In addition, the green alga C. zofingiensis had a remarkably higher percentage of astaxanthin diesters (76.3% of total astaxanthins) and a remarkably lower percentage of astaxanthin monoesters (18.0% of total astaxanthins) in comparison with H. pluvialis (35.5% for diesters and 60.9% for monoesters), the mutant E1 (49.1% and 48.1%) and Chlorococcum sp. (18.0% and 58.6%).

Comparative growth and viability of hybrids between two populations of Chinese shrimp (Fennropenaeus chinensis)

Fenneropenaeus chinensis is confined to the Yellow Sea and Bohai Sea in China and the West Coast of the Korean Peninsula. Intra- and intercross populations were produced between Rushany (YP) and Korean (KN) populations. Seven traits were recorded. The heterosis of hybrids was computed and comparison between treatments was performed by ANOVA. At the fourth month after post-larvae, six indexes of growth trait and viability showed a range of heterosis, ranging from 0.514% to 14.950%. At the fifth month after post-larvae, six indexes of growth trait and viability ranged from -9.000% to 19.090%. The negative heterosis was observed in CL, HST and viability. The heterosis of KN female xYP male tended generally to increase as the age of the Chinese shrimp increased while the heterosis of YP female xKN male tended to decrease. The results indicated that the viability of reciprocal hybrids were not significantly different (P > 0.05) from their parents during the experiment. The result of ANOVA indicated that the F1 hybrids were significantly different (P < 0.05) in WST and TW at the fourth month. The multiple comparisons of LSD test indicated that the hybrids of YP female xKN male were significantly different (P < 0.05) from their parents in TW. The hybrids of YP female xKN male were significantly different (P < 0.05) from the other three combinations in WST. At the fifth months, the F1 hybrids had significant difference (P < 0.05) in body weight while other traits showed no significant differences (P > 0.05) from their parents. The multiple comparisons of LSD test indicated that the hybrids of KN female xYP male were significantly different (P < 0.05) from the KN parents in TW. The results indicate that in experimental conditions, the F-1 hybrids created from two populations of Chinese shrimp showed a certain level of heterosis for growth performance and viability. The crossing scheme may improve growth performance and viability in Chinese shrimp, but the improvement may be limited because effective crossbreeding requires the maintenance of pure, preferably inbred, lines and possibly involves specialized sire and dam lines. Therefore, the exploitation of heterosis through single crossbreeding in Chinese shrimp is of limited utility in practical commercial shrimp aquaculture in spite of the potential of significant heterosis. The crossbreeding of different populations can be applied in the establishment of base populations.

Anticorrosion performance of polyaniline nanostructures on mild steel

Different one-dimensional nanostructured polyanilines were synthesized in sulfuric acid solutions by conventional polymerization, interfacial polymerization and direct mixed reaction, respectively. The products were characterized with SEM, UV-vis and FTIR and the anticorrosion performance of products on mild steel were studied using electrochemical measurement in 3.5% NaCl aqueous solution. Results showed that the polyaniline nanofibers synthesized by direct mixed reaction have uniform morphology with diameters of 60-100 nm and more excellent protective properties than conventional aggregated polyaniline. Comparative studies revealed that the nanostructure and morphology of polyaniline could influence its anticorrosion performance. (C) 2010 Elsevier B.V. All rights reserved.

Comparative analysis of allantoin quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid in Nitraria tangutorum Bobr. Seed by HPLC-APCI-MS and CE

This paper describes the simultaneous determination of allantoin, quercetin, and 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid (MTCCA) in Nitraria tangutorum Bobr seed by HPLC-APCI-MS and CE (capillary electrophoresis) methods. The final optimized chromatographic conditions were investigated in a reversed-phase Eclipse XDB-C8 column (150 x 4.6 mm, 5 mu m). A seventeen-minute gradient elution, (A: aqueous acetonitrile 20% (v/v); B: aqueous acetonitrile 60% (v/v); C: pure acetonitrile 100%) at a flow rate of 1.0 mL/min was selected for the separation of three natural products with diode array detection (DAD) at 220 nm. A CE experiment was carried out in a fused silica capillary with 32 mmol/L boric acid (pH 10), 32 mmol/L SDS and acetonitrile (10.0%, v/v). The applied potential and temperature was, respectively, set at 19 kV and 25 degrees C. After development, the validation was performed in parallel for HPLC and CE, with the same standards and sample to avoid differences due to the manipulation. The validation parameters of both techniques were adequate for the intended purpose.