Cuiyun Yang

The Pd-catalyzed hydrodechlorination of chlorophenols in aqueous solutions under mild conditions: A promising approach to practical use in wastewater

Catalytic hydrotreating of chlorophenols was carried out in water with Pd/C at 25 degrees C under atmospheric pressure. 1.0% (w/w) monocholophenols was completely dechlorinated within 60 min. Phenol, cyclohexanone and cyclohexanol were formed. In contrast to the dechlorination of monochlorophenols, the hydrogenation reaction of polychlorinated phenols became difficult and reaction rates were strongly dependent upon the number of the chlorine atoms. The solvent property had a considerably important influence on the dechlorination reaction. Water as a solvent showed more advantages than organic solvents. It was much easier to be hydrodechlorinated for chlorophenols in aqueous solutions. However, the presence of THF, dioxane, DMSO or DMF in water was disadvantageous to the reaction and easily to cause Pd/C deactivation. Additionally, when different halogenated organic compounds were present in aqueous solution, the dehalogenation reaction was the competitive hydrogenation process.

Growth and Antioxidant System of Escherichia coli in Response to Microcystin-RR

Microcystins are a kind of cyclic hepatoxins produced by many species of cyanobacteria. The toxic effects of microcystins on animals and plants have been well studied. However, the reports about the effects of microcystins on microbial cells are very limited. In present paper, Escherichia coli was undertaken to determine the effect of microcystin-RR. These results suggested that microcystin-RR could prolong the growth of E. coli when exposed to high concentrations of microcystin-RR and cause the accumulation of ROS and induce the oxidant stress for a short time. The antioxidant system protects E. coli from oxidative damage.

Magnetically driven negative thermal expansion in antiperovskite Ga1-xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3)

Negative thermal expansion (NTE) was investigated for Ga1−xMnxN0.8Mn3 (0.1 ≤ x ≤ 0.3). As x increases, the temperature range where lattice contracts upon heating becomes broad and shifts to lower temperatures. The coefficient of linear thermal expansion beyond −40 ppm/K with a temperature interval of ∼50 K was obtained around room temperature in x = 0.2 and 0.25. Local lattice distortion which was thought to be intimately related to NTE is invisible in the X-ray pair distribution function of x = 0.3. Furthermore, a zero-field-cooling exchange bias was observed as a result of competing ferromagnetic (FM) and antiferromagnetic (AFM) orders. The concomitant FM order serves as an impediment to the growth of the AFM order, and thus broadens the temperature range of NTE. Our result suggests that NTE can be achieved in antiperovskite manganese nitrides by manipulating the magnetic orders without distorting the local structure.

Combination of hydrodechlorination and biodegradation for the abatement of chlorophenols

A method for abatement for chlorophenols (CPs) in contaminated water based on successive steps of catalytic hydrodechlorination (HDC) over Pd/C at ambient temperature and pressure, followed by aerobic biodegradation using yeast Candida tropicalis (C. tropicalis) was studied. The results showed that 4-chlorophenol (4-CP) and 2,4-dichlorophenol (2,4-DCP) could be easily and completely dechlorinated under mild conditions, ultimately yielding phenol as product. Subsequently, phenol (0-900 mg L(-1)) could be completely degraded by C. tropicalis within 30 h. Moreover, during the biodegradation of phenol, definite mass of ethanol (≤0.5%) caused a modest increase in the duration of the lag phase, but led to a great increase in the maximum degradation rates. This means that CPs with higher concentration could be efficiently detoxified under mild conditions by a combination of HDC and biodegradation in water or water-ethanol systems.

The possible role of bacterial signal molecules N-acyl homoserine lactones in the formation of diatom-biofilm (Cylindrotheca sp.)

Bacterial quorum sensing signal molecules N-acyl homoserine lactones (AHLs) (C10-HSL, 3-OXO-C10-HSL and 3-OH-C10-HSL) as possible chemical cues were employed to investigate the role in the formation of fouling diatom-biofilm (Cylindrotheca sp.). Results showed that AHLs promoted Chlorophyll a (Chl.a) and extracellular polymeric substance (EPS) contents in the diatom-biofilm. In the presence of AHLs-inhibitor 3, 4-Dibromo-2(5)H-furanone, which was used to avoid the possible interference of AHLs from bacteria, AHLs also increased the Chl.a and EPS contents. Scanning electron microscope and confocal laser scanning microscope analysis further demonstrated that AHLs promoted the formation of the diatom-biofilm. Non-invasive micro-test technique showed that AHLs promoted Ca(2+) efflux in Cylindrotheca sp., which implied that Ca(2+) might be correlated with AHLs-induced positive effect on the formation of diatom-biofilm. This study provides direct evidences that AHLs play an important role in developing the diatom-biofilm and AHLs-inhibitors might be promising active agents in marine antifouling.

Size effects on negative thermal expansion in cubic ScF3

Scandium trifluoride (ScF3), adopting a cubic ReO3-type structure at ambient pressure, undergoes a pronounced negative thermal expansion (NTE) over a wide range of temperatures (10 K–1100 K). Here, we report the size effects on the NTE properties of ScF3. The magnitude of NTE is reduced with diminishing the crystal size. As revealed by the specific heat measurement, the low-energy phonon vibrations which account for the NTE behavior are stiffened as the crystal size decreases. With decreasing the crystal size, the peaks in high-energy X-ray pair distribution function (PDF) become broad, which cannot be illuminated by local symmetry breaking. Instead, the broadened PDF peaks are strongly indicative of enhanced atomic displacements which are suggested to be responsible for the stiffening of NTE-related lattice vibrations. The present study suggests that the NTE properties of ReO3-type and other open-framework materials can be effectively adjusted by controlling the crystal size.

Seasonal variations in fouling diatom communities on the Yantai coast

Fouling diatoms are a main component of biofilm, and play an important role in marine biofouling formation. We investigated seasonal variations in fouling diatom communities that developed on glass slides immersed in seawater, on the Yantai coast, northern Yellow Sea, China, using microscopy and molecular techniques. Studies were conducted during 2012 and 2013 over 3, 7, 14, and 21 days in each season. The abundance of attached diatoms and extracellular polymeric substances increased with exposure time of the slides to seawater. The lowest diatom density appeared in winter and the highest species richness and diversity were found in summer and autumn. Seasonal variation was observed in the structure of fouling diatom communities. Pennate diatoms Cylindrotheca, Nitzschia, Navicula, Amphora, Gomphonema, and Licmophora were the main fouling groups. Cylindrotheca sp. dominated in the spring. Under laboratory culture conditions, we found that Cylindrotheca grew very fast, which might account for the highest density of this diatom in spring. The lower densities in summer and autumn might result from the emergence of fouling animals and environmental factors. The Cylindrotheca sp. was identified as Cylindrotheca closterium using18S rDNA sequencing. The colonization process of fouling diatoms and significant seasonal variation in this study depended on environmental and biological factors. Understanding the basis of fouling diatoms is essential and important for developing new antifouling techniques.

Indole derivatives inhibited the formation of bacterial biofilm and modulated Ca2+ efflux in diatom

Marine biofouling is a serious environmental problem worldwide. As an effort to find environmental friendly antifoulants, indole derivatives were determined for their activities to inhibit the growth of bacteria and diatom. The minimum inhibitory concentrations (MICs) of indole derivatives against bacteria were very low, especially for 6-chloroindole. It was proved that 6-chloroindole obviously inhibited the growth of bacteria, interfered with the formation of bacterial biofilm, destroyed bacterial cell morphology and also inhibited the growth of diatom Cylindrotheca sp. as well. By using noninvasive micro-test technique (NMT), 6-chloroindole triggered algal cellular Ca(2+) efflux. The highest value was 72.03 pmol cm(-2)s(-1), 10.6 times of the control group. The present studies indicated that indole derivatives might have the potential to be new antifouling agents because of their excellent antibacterial and anti-algal activities. At the same time, Ca(2+) efflux might be one of the mechanisms that indole derivatives inhibited the growth of diatom.

Toxic effects of environment‐friendly antifoulant nonivamide on Phaeodactylum tricornutum

Nonivamide, a synthetic derivate of natural capsaicin, has an effective antifouling activity. However, the poor understanding of the toxicity mechanism limits the application of nonivamide in antifouling paints. The present study investigated the inhibitory effects and toxicity mechanism of nonivamide on Phaeodactylum tricornutum. Under a 1.5 × 10(5) cells/ml of initial algal density (IAD), the effective concentration causing 50% inhibition at 4- d (4 d-EC50) value of nonivamide was 5.1 mg/L. Reactive oxygen species (ROS) level was significantly increased in nonivamide-treated algae. Algal antioxidants, including catalases (CAT), peroxidases (POD), superoxide dismutases (SOD), and glutathione (GSH), were all stimulated by the ROS burst. The excessive ROS substances led to the loss of algal photosynthetic pigments and also damage to the integrity of the lipid membrane. Furthermore, ROS-related genes, including psbA, psbD, psaB, rbcL, nad1, and cob, were found to be suppressed in the chloroplasts and mitochondria of nonivamide-treated algae, and the concentration of cytoplasmic Ca(2+) , an important regulator of chloroplast and mitochondrion, was elevated. The present study demonstrates that nonivamide could cause peroxidative damages to P. tricornutum by inducing ROS overproduction, which may be initiated by the suppression of ROS-related genes in algal chloroplasts and mitochondria.

Magnetic evolution of spinel Mn1−xZnxCr2O4 single crystals

Mn1−xZnxCr2O4 (0 ≤ x ≤ 1) single crystals have been grown using the chemical vapor transport (CVT) method. The crystallographic, magnetic, and thermal transport properties of the single crystals were investigated by room-temperature X-ray diffraction, magnetization M(T) and specific heat CP(T) measurements. Mn1−xZnxCr2O4 crystals show a cubic structure, the lattice constant a decreases with the increasing content x of the doped Zn2+ ions and follows the Vegard law. Based on the magnetization and heat capacity measurements, the magnetic evolution of Mn1−xZnxCr2O4 crystals has been discussed. For 0 ≤ x ≤ 0.3, the magnetic ground state is the coexistence of the long-range ferrimagnetic order (LFIM) and the spiral ferrimagnetic one (SFIM), which is similar to that of the parent MnCr2O4. When x changes from 0.3 to 0.8, the SFIM is progressively suppressed and spin glass-like behavior is observed. When x is above 0.8, an antiferromagnetic (AFM) order presents. At the same time, the magnetic specific heat (Cmag.) was also investigated and the results are coincident with the magnetic measurements. The possible reasons based on the disorder effect and the reduced molecular field effect induced by the substitution of Mn2+ ions by nonmagnetic Zn2+ ones in Mn1−xZnxCr2O4 crystals have been discussed.