Materials Engineering of Violin Soundboards by Stradivari and Guarneri.

We investigated the material properties of Cremonese soundboards using a wide range of spectroscopic, microscopic, and chemical techniques. We found similar types of spruce in Cremonese soundboards as in modern instruments, but Cremonese spruces exhibit unnatural elemental compositions and oxidation patterns that suggest artificial manipulation. Combining analytical data and historical information, we may deduce the minerals being added and their potential functions-borax and metal sulfates for fungal suppression, table salt for moisture control, alum for molecular crosslinking, and potash or quicklime for alkaline treatment. The overall purpose may have been wood preservation or acoustic tuning. Hemicellulose fragmentation and altered cellulose nanostructures are observed in heavily treated Stradivari specimens, which show diminished second-harmonic generation signals. Guarneri's practice of crosslinking wood fibers via aluminum coordination may also affect mechanical and acoustic properties. Our data suggest that old masters undertook materials engineering experiments to produce soundboards with unique properties.

Improving the High-Frequency Response of PEI-Based Earphone with Sodium Copper Chlorophyllin.

The polyetherimide diaphragm, sodium copper chlorophyllin (SCC), and copper ion coating composite used on earphones were observed to improve the high-frequency (10k-14k Hz) performance. This reinforcement phenomenon was expected to make the sound experience brighter and more diverse. By SEM observation, the mixed coating of SCC/Cu2+ on the polyethylenimine (PEI) diaphragm exhibited a planar blocky structure and was tightly bonded to the surface of the PEI polymer without the aid of colloids. The endothermic process of SCC and metal ion complexation was analyzed by isothermal titration calorimetry. The association ratios of SCC/Cu2+ and SCC/Ni2+ were 4/1 and 6/1, respectively, and the SCC/Cu2+ association yielded a stronger binding constant and more free energy. It was expected that the SCC/Cu2+(4/1) mixed liquid would be immobilized on the PEI polymer by multivalent interaction, including hydrogen-bonding networks between carboxyl groups of SCC and amine groups of PEI, and cross-linking of bridging copper ions. We used dimethylethylenediamine (DME) monomer instead of PEI polymer to analyze this multivalent interaction and observed a two-stage exothermic association of SCC/Cu2+(4/1) and DME with a total Gibbs free energy of 15.15 kcal/mol. We observed that the binding energy could be used to explain that the SCC/Cu2+ mixed formulation could be fixed on the surface of the PEI polymer and could enhance the strength of the PEI film. Compared with graphene films, which can continuously improve the performance of high and ultrasonic frequencies, this study was devoted to and was initiated for the purpose of applying porphyrin compounds to improve music performance.

Potent anti-HIV activities and mechanisms of action of a pine cone extract from Pinus yunnanensis.

The anti-HIV activities of a pine cone extract (YNS-PY-F) from Pinus yunnanensis have been evaluated, and its mechanisms of action were also explored. The pine cone extract, YNS-PY-F, potently inhibited HIV-1(IIIB), HIV-1(RF), HIV-1(A17), HIV-1(AO18) and HIV-2(ROD) and induced cytopathic effect in C8166 cells with EC50 values of 0.96 µg/mL, 1.53 µg/mL, 0.88 µg/mL, 7.20 µg/mL and 6.17 µg/mL, respectively. The quantification of a p24 production assay showed that YNS-PY-F significantly inhibited the acute replication of HIV-1(IIIB), HIV-1RF, HIV-1(A17) and HIV-1(AO18) in C8166 cells. An MTT assay showed that YNS-PY-F also significantly inhibited the HIV-1(IIIB) induced cytolysis in MT-4 cells with an EC50 value of 2.22 µg/mL. The mechanism assays showed that YNS-PY-F had potent inhibitory effects on the fusion between infected cells and uninfected cells, and the activity of HIV-1 reverse transcriptase, with EC50 values of 7.60 µg/mL and 4.60 µg/mL, respectively. Overall, these data suggest that the pine cone extract from Pinus yunnanensis has potent inhibitory activities against HIV-1(IIIB), HIV-1(RF), RT inhibitor-resistant strains HIV-1(A17) and HIV-1(AO18), and HIV-2(ROD), and its anti-HIV mechanisms include inhibition of HIV entry and inhibition of reverse transcriptase activity.

HPLC analyses and pharmacokinetic studies of baicalin and oxymatrine in rabbits.

In the present study two simple RP-HPLC methods were developed to determine baicalin and oxymatrine in rabbit serum. Separation was performed on a Diamonsil C18 column (200 mm x 4.6 mm I.D., 5 microm) with UV detector at 277 nm for baicalin and 220 nm for oxymatrine. The mobile phase was methanol-water-phosphoric acid 50:50:0.2 v/v for baicalin and acetonitrile-water (20:80, v/v, 5 mmol/L sodium octanesulfonate was contained and pH was adjusted to 3.2 with phosphoric acid for oxymatrine. p-Nitrobenzoic acid and phenacetin were used as internal standards for baicalin and oxymatrine, respectively. The standard curves were linear from 0.5 to 200.0 mg/L for baicalin and from 0.5 to 100.0 mg/L for oxymatrine with correlation coefficients of 0.9994 and 0.9965, respectively. The intra-day and inter-day RSD were less than 5.4% and 7.2% for baicalin and 6.6% and 13.8% for oxymatrine. The mean recoveries were 100.1% for baicalin and 99.1% for oxymatrine. The methods were applied to a pharmacokinetic study of baicalin and oxymatrine in rabbits. The pharmacokinetic parameters were determined after intravenous injections of baicalin and oxymatrine (40 mg/kg) separately and together to rabbits. They all fit to the two-compartment open model. Student's t test shows that there is no significant difference in the main pharmacokinetic parameters including AUC(0-infinity), when alpha and beta, when baicalin and oxymatrine were administered separately or together.