First measurement of the helicity dependence for the γp → pπreaction

The helicity dependence of the total cross-section and the invariant-mass distributions in the (pπ^±) and (π⁺π^-) final states for the γp → pπ⁺π^- reaction have been measured for the first time at incident photon energies from 400 to 800MeV. The measurement was performed with the large-acceptance detector DAPHNE at the tagged photon beam facility of the MAMI accelerator in Mainz. Although this channel is found to be predominantly excited by the intermediate production of a Δπ state, both the measured unpolarized and the helicity-dependent observables are generally not well described by the existing theoretical models.     

Alkanoylation of quinazoline by nucleophilic aromatic substitution: Combined experimental and computational study

A combined experimental and computational study on the key intermediates of NHC-catalyzed acylation reaction, Breslow intermediates (BIs), has been conducted in order to achieve a direct nucleophilic alkanoylation of N-heterocycles. Various BI precursors are alternatively prepared and used in the reaction with 4-chloroquinazoline. The present study reveals that the intermediates having benzimidazole moiety serve as acylating agents for the introduction of straight-chain alkanoyl groups. Natural bond orbital analysis indicates that the reactivity of intermediates partly correlates to the occupancy of the π_C-C bonds of the hydroxyl enamine moieties. The putative rate-determining step of the acylation reaction has been theoretically investigated. Several new 4-alkanoylquinazolines are synthesized using the BI precursors.     

Development of a micropulverized extraction method for rapid toxicological analysis of methamphetamine in hair

We developed a rapid sample preparation method for the toxicological analysis of methamphetamine and amphetamine (the major metabolite of methamphetamine) in human hair by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), to facilitate fast screening and quantitation. Two milligrams of hair were mechanically micropulverized for 5 min in a 2-ml plastic tube together with 100 microl of an aqueous solvent containing 10% acetonitrile, 100 mM trifluoroacetic acid and the corresponding deuterium analogues as internal standards. The pulverizing highly disintegrated the hair components, simultaneously allowing the extraction of any drugs present in the hair. After filtering the suspension with a membrane-filter unit, the clear filtrate was directly analyzed by HPLC-MS/MS. No evaporation processes were required for sample preparation. Method optimization and validation study were carried out using real-case specimens and fortified samples in which the drugs had been artificially absorbed, respectively. Concentration ranges for quantitation were 0.040-125 and 0.040-25 ng/mg for methamphetamine and amphetamine, respectively. Real-case specimens were analyzed by the method presented here and by conventional ones to verify the applicability of our method to real-world analysis. Our method took less than 30 min for a set of chromatograms to be obtained from a washed hair sample.     

Accurate LC-MS analyses for microcystins using per-15N-labeled microcystins

Per-¹⁵N-labeled microcystins were prepared for use as surrogates for accurate liquid chromatography–mass spectrometry analysis. Two strains of Microcystis aeruginosa were cultured in ¹⁵NO₃-containing TS-15 medium. To change from the incorporation of ¹⁴N to ¹⁵N into all cell components, cells of Microcystis aeruginosa were precultured in Na¹⁵NO₃-containing medium for more than 6 months. After mass cultivation of the strains, cells of each strain were harvested and lyophilized. Microcystin variants were extracted from the lyophilized cells and per-¹⁵N-labeled microcystin variants were purified using high-performance liquid chromatography and high-performance thin-layer chromatography. The structures of per-¹⁵N-labeled microcystin variants were confirmed by their mass spectrometry spectra and NMR spectra. When per-¹⁵N-labeled microcystins were used as surrogates for quantitative analysis of these toxins in cyanobacterial cells, excellent accuracy (98–106%) was obtained, with the m/z of M⁺, [M+1]⁺, and [M+2]⁺ of both microcystins and the per-¹⁵N-labeled microcystins as surrogates being completely separated. In conclusion, per-¹⁵N-labeled microcystins are excellent surrogates for microcystin analysis using liquid chromatography–mass spectrometry.     

Antioxidant therapy as a potential approach to severe influenza-associated complications

With the appearance of the novel influenza A (H1N1) virus 2009 strain we have experienced a new influenza pandemic and many patients have died from severe complications associated with this pandemic despite receiving intensive care. This suggests that a definitive medical treatment for severe influenza-associated complications has not yet been established. Many studies have shown that superoxide anion produced by macrophages infiltrated into the virus-infected organs is implicated in the development of severe influenza-associated complications. Selected antioxidants, such as pyrrolidine dithiocabamate, N-acetyl-L-cysteine, glutathione, nordihydroguaiaretic acid, thujaplicin, resveratrol, (+)-vitisin A, ambroxol, ascorbic acid, 5,7,4-trihydroxy-8-methoxyflavone, catechins, quercetin 3-rhamnoside, iso- quercetin and oligonol, inhibit the proliferation of influenza virus and scavenge superoxide anion. The combination of antioxidants with antiviral drugs synergistically reduces the lethal effects of influenza virus infections. These results suggest that an agent with antiviral and antioxidant activities could be a drug of choice for the treatment of patients with severe influenza-associated complications. This review article updates knowledge of antioxidant therapy as a potential approach to severe influenza-associated complications.     

A method for enlarging the Kerr constant of polymer-stabilised blue phases

Polymer-stabilised blue phase (PSBP) is one of the most promising materials for display devices because of its superior electro-optical properties compared with conventional nematics. However, the application of the PSBP has a serious practical issue in that the driving voltage required is too high to drive with thin film transitors, that is, the magnitude of the Kerr constant of PSBPs is insufficient. We present a useful method for increasing the Kerr constant based on the control of polymer aggregation structure using a cross-linker with a chiral structure. The director distortion arising from polymer networks in the PSBP seems to be responsible for the resulting improvement.     

Fifty-Two Membered Macromonocyclic Polyamine Possessing Twelve Nitrogen Atoms in the Ring: Cyclic Spermine Tetramer

By the reaction of 1, 4-dibromobutane with forty-eight membered acyclic polyamine in the presence of cesium carbonate in DMF, cyclic spermine (or thermospermine) tetramer was prepared in 72% yield.     

Bimodal colloidal mixtures: from fast to slow aggregation regions

A Brownian dynamics simulation has been used to investigate the aggregation kinetics of bimodal colloidal mixtures with similar surface chemistries but different sizes, driven by the DLVO interaction potential. The time evolution of structural formation is examined by the mean number of neighbors under fast and slow aggregation regions. It was found that the electrolyte ionic strength affects the kinetic pattern of colloidal aggregation. Under the high electrolyte ionic strength conditions (fast aggregation), the selective aggregation of the least stable single component can take place in the early stage, while the other component is enriched in this least stable component in the later stage. With the ionic strength decreasing (towards the slow aggregation), the hybrid aggregation (selective aggregation and heteroaggregation) gradually dominates the aggregation kinetics. Also in the early stage, this evolves to the heteroaggregation of different components under lower ionic strength conditions. The volume fraction has no obvious influence on this kinetic pattern in the early stage.     

Effect of pre-acid-hydrolysis treatment on morphology and properties of cellulose nanowhiskers from coconut husk

Three different pre-acid-hydrolysis treatments were used to treat coconut husk fibers for preparing cellulose nanowhiskers by sulfuric acid hydrolysis. The effects of those treatments on the morphology and properties of the nanowhiskers were investigated. FTIR was employed to evaluate the change of chemical composition due to different pre-acid-hydrolysis treatments. AFM images showed that there was no significant difference of size of nanowhiskers obtained by different pre-acid-hydrolysis treatment, 2–3 nm of average thickness. The thermal decomposition of nanowhiskers shifted to higher temperatures with removal of hemicellulose and lignin.