Sonolysis of chlorobenzene in Fenton-type aqueous systems

The influence of ultrasounds (200 kHz frequency) on the decomposition of chlorobenzene (CB) in a water solution (around 100 ppm concentration) containing iron or palladium sulfates was investigated. The intermediates of the sonolysis were identified, thus allowing a deeper insight into the degradation mechanism. It was established that CB degradation starts by pyrolysis inside the cavitation bubbles. The initial sonolysis product is benzene, formed in a reaction occurring outside the cavitation from phenyl radicals and the hydrogen atoms sonolytically generated from the water. Polyphenols as products of the CB sonochemical degradation are reported for the first time. The palladium salt was found to be a useful and sensitive indicator for differentiating the sites and mechanisms of the product formation. An alternative mechanism for the CB sonolysis is advanced, explaining the formation of phenols, polyphenols, chlorophenols and benzene.     

Synthesis of caeliferins, elicitors of plant immune responses: accessing lipophilic natural products via cross metathesis

A cross metathesis (CM)-based synthesis of the caeliferins, a family of sulfooxy fatty acids that elicit plant immune responses, is reported. Unexpectedly, detailed NMR spectroscopic and mass spectrometric analyses of CM reaction mixtures revealed extensive isomerization and homologation of starting materials and products. It is shown that the degree of isomerization and homologation in CM strongly correlates with substrate chain length and lipophilicity. Side-product suppression requires appropriate catalyst selection and use of 1,4-benzoquinone as a hydride scavenger.     

Assessment of metabolic changes in the striatum of a MPTP-intoxicated canine model: in vivo ¹H-MRS study of an animal model for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the progressive loss of the dopaminergic neurons in the substantia nigra pars compacta, which projects to the striatum. We induced a selective loss of nigrostriatal dopamine neurons, by infusing the mitochondrial complex 1 inhibitor 1-methyl 4-phenyl 1,2,3,6-tetrahydropyridine (MPTP) into adult beagle dogs (N=5). Single voxel ¹H water suppressed magnetic resonance spectroscopy (¹H-MRS) at 3 T was used to assess the metabolic changes in the striatum of canine before and after MPTP intoxication. The metabolite spectra obtained from the striatum (voxel size: 2 cm³) showed a lower N-acetyl aspartate to total creatine (creatine+phosphocreatine) ratio after MPTP intoxication. There were no significant differences in other metabolite ratios such as glutamate+glutamine, choline-containing compounds (glycerophosphocholine+phophorylcholine and myo-inositol). Our findings indicated that ¹H-MRS is a sensitive, noninvasive measure of neural toxicity and biochemical alterations of the striatum in a canine model of PD, and further studies are needed to confirm brain metabolic changes in association with progression of MPTP-intoxication.     

Dielectric electrorheological fluids: Theory and experiment

Electrorheological (ER) fluids are a class of materials whose rheological properties are controllable by the application of an electric field. A dielectric electrorheological (DER) fluid is the simplest type of ER fluid, in which the material components follow a linear electrostatic response. We review and discuss the progress of the studies on physics of this type of material. A first-principles theory of DER fluids, along with relevant experimental verifications, are presented in some detail. In particular, the properties presented include static equilibrium structure, shear modulus, static yield stress and its variation with applied electric field frequency, and structure-induced dielectric nonlinearity.     

Comparative metabolomics reveals biogenesis of ascarosides, a modular library of small-molecule signals in C. elegans

In the model organism Caenorhabditis elegans, a family of endogenous small molecules, the ascarosides function as key regulators of developmental timing and behavior that act upstream of conserved signaling pathways. The ascarosides are based on the dideoxysugar ascarylose, which is linked to fatty-acid-like side chains of varying lengths derived from peroxisomal β-oxidation. Despite the importance of ascarosides for many aspects of C. elegans biology, knowledge of their structures, biosynthesis, and homeostasis remains incomplete. We used an MS/MS-based screen to profile ascarosides in C. elegans wild-type and mutant metabolomes, which revealed a much greater structural diversity of ascaroside derivatives than previously reported. Comparison of the metabolomes from wild-type and a series of peroxisomal β-oxidation mutants showed that the enoyl CoA-hydratase MAOC-1 serves an important role in ascaroside biosynthesis and clarified the functions of two other enzymes, ACOX-1 and DHS-28. We show that, following peroxisomal β-oxidation, the ascarosides are selectively derivatized with moieties of varied biogenetic origin and that such modifications can dramatically affect biological activity, producing signaling molecules active at low femtomolar concentrations. Based on these results, the ascarosides appear as a modular library of small-molecule signals, integrating building blocks from three major metabolic pathways: carbohydrate metabolism, peroxisomal β-oxidation of fatty acids, and amino acid catabolism. Our screen further demonstrates that ascaroside biosynthesis is directly affected by nutritional status and that excretion of the final products is highly selective.     

A facile and sensitive detection of pathogenic bacteria using magnetic nanoparticles and optical nanocrystal probes

We report a facile and sensitive analytical method for the detection of pathogenic bacteria. Salmonella bacteria in milk were captured by antibody-conjugated magnetic nanoparticles (MNPs) and separated from analyte samples by applying an external magnetic field. The MNP-Salmonella complexes were re-dispersed in a buffer solution then exposed to antibody-immobilized TiO(2) nanocrystals (TNs), which absorb UV light. After magnetically separating the MNP-Salmonella-TN complexes from solution, the UV-Vis absorption spectrum of the unbound TN solution was obtained. Because the light absorption intensity was reversely proportional to the Salmonella concentration, the assay exhibited high sensitivity toward low concentrations of Salmonella bacteria. The detection limit of Salmonella in milk was found to be more than 100 cfu mL(-1).     

Size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots

We investigate size-dependent carrier dynamics in self-assembled CdTe/ZnTe quantum dots (QDs) grown using molecular beam epitaxy and atomic layer epitaxy. Photoluminescence (PL) spectra show that the excitonic peak corresponding to transitions from the ground electronic subband to ground heavy-hole band in CdTe/ZnTe QDs shifts to a lower energy with increasing ZnTe buffer thicknesses. This shift of the PL peak can be attributed to size variation of the CdTe QDs. In particular, carrier dynamics in CdTe QDs grown on various ZnTe buffer layer thicknesses is studied using time-resolved PL measurements. As a result, the decay time of CdTe QDs is shown to increase with increasing ZnTe buffer layer thicknesses due to the reduction of the exciton oscillator strength in the larger QDs.     

Amide-Functionalized Porous Carbonaceous Anode Materials for Lithium-Ion Batteries

Porous carbonaceous anode materials have received considerable attention as an alternative anode material, however, there is a critical bottleneck as it suffers from a large irreversible specific capacity loss over several initial cycles owing to undesired surface reactions. In order to suppress undesired surface reactions of porous carbonaceous anode material, here, we suggest a simple and convenient two-step surface modification approach that allows the embedding of an amide functional group on the surface of a porous carbonaceous anode, which effectively improves the surface stability. In this approach, the porous carbonaceous anode material is firstly activated by means of strong acid treatment comprising a combination of H₂SO₄ and HNO₃, and it is subjected to further modification by means of an amide coupling reaction. Our additional systematic analyses confirm that the acid functional group effectively transforms into the amide functional group. The resulting amide-functionalized porous carbon exhibits an improved electrochemical performance: the initial discharge specific capacity is greatly reduced to less than 2,620 mA h g⁻¹ and charge specific capacity is well still remained, indicating stabling cycling performance of the cell.     

Effects of fingerprint development reagents on subsequent DNA analysis

A variety of evidences are found at crime scenes. Fingerprint and DNA evidences are especially important in the process of identifying personal sources. Among evidences found at crime scenes, cigarette butts are important because they might contain both fingerprints and DNA. In this study, latent fingerprints were detected in cigarette butts using 1,8‐diazafluoren‐9‐one (DFO) and 1,2‐Indanedione/zinc chloride (1,2‐IND/Zn). Next, DNA extraction and real‐time qPCR were performed to quantify and identify the DNA present. Short tandem repeat (STR) profiling was also performed. The results showed that the quantity of DNA recovered was decreased by 16% in DFO‐treated cigarettes and by 27% in 1,2‐IND/Zn‐treated cigarettes when compared to untreated controls. When the STR profiling results were compared with those of the control sample, DFO, and 1,2‐IND/Zn reagent‐treated DNA samples showed individualized genotyping at several loci. Results of this study showed that when cigarette butts were found, DFO and 1,2‐IND/Zn reagents could be used for DNA profiling after fingerprint identification. However, the effect of DFO on STR profiling was less than that of 1,2‐IND/Zn. Therefore, we recommend the use of DFO for fingerprinting cigarette butts if further DNA processing is planned.     

Pore‐Surface Engineering by Decorating Metal‐Oxo Nodes with Phenylsilane to Give Versatile Super‐Hydrophobic Metal–Organic Frameworks (MOFs)

Hydrophobization of metal‐organic frameworks (MOFs) is important to push forward their practical use and thus has attracted increasing interest. In contrast to the previous reports, which mainly focused on the modification of organic ligands in MOFs, herein, we reported a novel strategy to decorate the metal‐oxo nodes of MOFs with phenylsilane to afford super‐hydrophobic NH₂‐UiO‐66(Zr), which shows highly improved base resistance and holds great promise in versatile applications, such as organic/water separation, self‐cleaning, and liquid‐marble fabrication. This work demonstrates the first attempt at metal‐oxo node modification for super‐hydrophobic MOFs, advancing a new concept in the design of MOFs with controlled wettability for practical applications.