Fabrication of ordered flower-like ZnO nanostructures by a microwave and ultrasonic combined technique and their enhanced photocatalytic activity

Ordered flower-like zinc oxide (ZnO) nanostructures were fabricated via a facile microwave and ultrasonic combined technique. The product was characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and selected area electron diffraction pattern (SAED). The flower-like ZnO nanostructures were assembled by a central petal and six symmetrical petals which grew radially from the center. The flower-like ZnO sample showed an enhanced photocatalytic performance compared with the ZnO microrods for the methylene blue (MB) degradation, which could be attributed to its special structure feature. Au/ZnO and Ag/ZnO nanocomposites were also synthesized and exhibited enhanced photocatalytic efficiency after decorating noble metal nanoparticles on the surface of flower-like ZnO nanostructures.     

Enhanced mechanical response of hybrid alloy AZ31/AZ91 based on the addition of Si3N4 nanoparticles

The main aim of this study was to simultaneously increase tensile strength and ductility of AZ31/AZ91 hybrid magnesium alloy with Si₃N₄ nanoparticles. AZ31/AZ91 hybrid alloy nanocomposite containing Si₃N₄ nanoparticle reinforcement was fabricated using solidification processing followed by hot extrusion. The nanocomposite exhibited similar grain size to the monolithic hybrid alloy, reasonable Si₃N₄ nanoparticle distribution, non-dominant (0 0 0 2) texture in the longitudinal direction, and 13% higher hardness than the monolithic hybrid alloy. Compared to the monolithic hybrid alloy (in tension), the nanocomposite simultaneously exhibited higher yield strength, ultimate strength, failure strain and work of fracture (+12%, +5%, +64% and +71%, respectively). Compared to the monolithic hybrid alloy (in compression), the nanocomposite exhibited higher yield strength and ultimate strength, lower failure strain and higher work of fracture (+35%, +4%, −6% and +6%, respectively). The beneficial effects of Si₃N₄ nanoparticle addition on the enhancement of tensile and compressive properties of AZ31/AZ91 hybrid alloy are investigated in this paper.     

A hierarchical Bayesian approach for risk assessment of melamine in infant formula based on cases of related nephrolithiasis in children

Although the 2008 outbreak of nephrolithiasis in children due to melamine-contaminated infant formula has subsided, it remains uncertain whether the present tolerable daily intake (TDI) of melamine provides sufficient protection for young children. To conduct a safety assessment for melamine in infant formula, we established a dose-response relationship based on 13 nephrolithiasis cases selected from 932 children, all of whom were under 5 years of age and had potentially been exposed to contaminated milk in China or Taiwan. According to the children's exposure history, distributions of individual daily melamine intake (mg/kg BW/day) were reconstructed using Monte Carlo simulations to account for uncertainties in exposure duration and melamine concentrations in the contaminated milk. Based on the simulated individual average daily intake (AVDI) of melamine, subjects were further classified into four separate AVDI groups: high, medium, low and a reference group. A statistical logistic model was then fitted for the dose-response relationship between nephrolithiasis incidence and daily melamine intakes using Markov chain Monte Carlo (MCMC) simulations. Based on the background exposure, spontaneous rate, and mode of action (MOA) of nephrolithiasis in children, the simulated lower bounds of the 95% CIs daily melamine intake ranged from 0.008 to 0.03 mg/kg BW/day corresponding to an additional risks of 0.1% is proposed as a plausible TDI, which is approximately an order lower than the current WHO-suggested TDI level of 0.2 mg/kg BW/day. More stringent regulations on melamine levels in infant formula should be considered to protect young children fully.     

Measurements of isoprene-derived organosulfates in ambient aerosols by aerosol time-of-flight mass spectrometry - part 1: single particle atmospheric observations in Atlanta

Organosulfate species have recently been identified as a potentially significant class of secondary organic aerosol (SOA) species, yet little is known about their behavior in the atmosphere. In this work, organosulfates were observed in individual ambient aerosols using single particle mass spectrometry in Atlanta, GA during the 2002 Aerosol Nucleation and Characterization Experiment (ANARChE) and the 2008 August Mini-Intensive Gas and Aerosol Study (AMIGAS). Organosulfates derived from biogenically produced isoprene were detected as deprotonated molecular ions in negative-ion spectra measured by aerosol time-of-flight mass spectrometry; comparison to high-resolution mass spectrometry data obtained from filter samples corroborated the peak assignments. The size-resolved chemical composition measurements revealed that organosulfate species were mostly detected in submicrometer aerosols and across a range of aerosols from different sources, consistent with secondary reaction products. Detection of organosulfates in a large fraction of negative-ion ambient spectra - ca. 90-95% during ANARChE and ~65% of submicrometer particles in AMIGAS - highlights the ubiquity of organosulfate species in the ambient aerosols of biogenically influenced urban environments.     

Piperidine induced polarity conversion in single-walled carbon nanotube field effect transistors

Piperidine is found to be an efficient electron doping agent that converts as-prepared p-type single-walled carbon nanotube (SWCNT) field effect transistors (FETs) into n-type SWCNT-FETs. Electron transfer from the amine group in piperidine to the SWCNTs is suggested to be the origin of the p- to n-type conversion. The effect of electron doping is further supported by the Raman tangential G(+) and G(-)-peak downshift up to 3 cm(-1) without the peak broadening. No detectable change in the Raman D-peak suggests non-covalent attachment of piperidine to the SWCNTs. A low temperature (110?°C) Si(3)N(4) passivation layer is used to maintain the long term air stability of the converted n-type devices. A complementary SWCNT inverter is demonstrated through integrating the n- and p-type SWCNT-FETs.     

A smart multifunctional nanocomposite for intracellular targeted drug delivery and self-release

A multifunctional 'all-in-one' nanocomposite is fabricated using a colloid, template and surface-modification method. This material encompasses magnetic induced target delivery, cell uptake promotion and controlled drug release in one system. The nanocomposite is characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, N(2) adsorption and vibrating sample magnetometry. The prepared material has a diameter of 350-400 nm, a high surface area of 420.29 m(2) g(-1), a pore size of 1.91 nm and a saturation magnetization of 32 emu g(-1). Doxorubicin (DOX) is loaded in mesopores and acid-sensitive blockers are introduced onto the orifices of the mesopores by a Schiff base linker to implement pH-dependent self-release. Folate was also introduced to improve DOX targeted delivery and endocytosis. The linkers remained intact to block pores with ferrocene valves and inhibit the diffusion of DOX at neutral pH. However, in lysosomes of cancer cells, which have a weak acidic pH, hydrolysis of the Schiff base group removes the nanovalves and allows the trapped DOX to be released. These processes are demonstrated by UV-visible absorption spectra, confocal fluorescence microscopy images and methyl thiazolyl tetrazolium assays in vitro, which suggest that the smart nanocomposite successfully integrates targeted drug delivery with internal stimulus induced self-release and is a potentially useful material for nanobiomedicine.     

Bio-inspired strategy for on-surface synthesis of silver nanoparticles for metal/organic hybrid nanomaterials and LDI-MS substrates

A strategy for the on-surface synthesis of silver nanoparticles (AgNPs) on a variety of two-?to three-dimensional material surfaces, utilizing polydopamine, an emerging surface modifying agent, is reported in this paper. This material-independent platform for AgNP synthesis is useful for fabricating organic/inorganic hybrid nanomaterials and for preparing substrates for laser desorption-ionization time-of-flight mass spectrometry (LDI-ToF MS).     

水热温度对二氧化钛结构及光催化活性的影响

以四氯化钛、环氧丙烷和乙醇为原料,采用水热法在不同温度下分别合成了金红石相纳米二氧化钛及板钛矿相与金红石相混晶结构的纳米二氧化钛,并利用X射线衍射(XRD)、透射电镜(TEM)和N2吸附-脱附对其进行了表征。以甲基橙为探针研究了不同水热温度对二氧化钛光催化活性的影响。     

End Effect on the Twin—Wire Depth Probe

The end effect on the output voltage of a twin-wire depth probe was investigated both theoretically and ex-perimentally.It was found that the contribution of the end of the probe to the output voltage depends uponthe distance between the boundary and the end of the probe and the geometrical configuration of the probe.By mounting a piece of plate to the end of the electrodes,the end effect can be reduced.However,the size ofthe plate required to eliminate completely this effect is much larger than that usually mounted on commerciallyavailable probes.Comparison between theoretical and experimental results was made.Reasonable agreementwas obtained.