High accuracy determination of copper in copper concentrate with double genetic algorithm and partial least square in laser-induced breakdown spectroscopy.

There are many challenges in the determination of elements in complex matrix such as soil, coal and minerals by laser induced breakdown spectroscopy (LIBS) method. Due to the influence of matrix effect, instability of laser plasma and fluctuation of laser parameters, the repeatability and accuracy of quantitative results are always not satisfactory. In order to improve the accuracy, high-energy laser (30mJ-100mJ) with precise control was utilized in many laboratories. In this paper, quantitative analysis of copper in copper concentrate by low-energy (10µJ) LIBS is studied. In order to reduce the influence of matrix effect and other factors, a partial least square regression method based on double genetic algorithm (DGA-PLS) is proposed. The detail operations are as follow: the reference spectral lines are automatically selected by GA as the optimal internal standard for spectral normalization. Then the GA is used to select variables from the normalized spectra for PLS. The results showed that, for univariate model, the coefficient of determination (R2) was improved from 0.6 to 0.97 by the optimal internal standard normalization. Compared with tradition PLS, the root mean square error of cross validation (RMSECV) and root mean square error of prediction (RMSEP) of PLS trained by the normalized spectral data decreased from 1.4% and 0.42% to 0.9% and 0.29% respectively. Compared with the normalized PLS, the RMSECV and RMSEP of the DGA-PLS trained by the normalized and feature selected spectral data decreased from 0.9% and 0.29% to 0.26% and 0.21% respectively. The results show that DGA-PLS can significantly reduce matrix effect, improve prediction accuracy and reduce the risk of overfitting in determination of copper in copper concentrate.

A medicated shape memory composite of grafting tannin/poly(l-lactide).

Establishing drug release from shape memory polymers (SMPs) for biomedical applications will broaden the horizon of SMP applications from commercial medical device to scientific drug delivery system. Therefore, a strategy combining degradable SMP with drug release is put forward. However, there are few reports about the relevance between them so far. In the work, incorporations of three grafting tannins (TA) as switching phase into poly (l-lactide)(PLLA) construct different thermoresponsive SM composites. TA-PCL-COOH/PLLA exhibites good shape fixation (Rf) and recovery rate (Rr) at 55 °C, and its recovery time is 75 s. After loading lipophilic drug, SM capability of medicated TA-PCL-COOH/PLLA enhances, the Rf and Rr are 97.8% and 97.2%, in particular, its recovery time decreases to 32 s. The effect of SM on drug release is explored. After the first round of SM, the drug release accelerates obviously at body temperature; for example, the release amount of drug increases from 46.5% to 66.1% at initial 12 h due to change of microstructure and improvement of wettability. The drug release rate climbs only slightly as the SM round increases.

A drug-loaded amphiphilic polymer/poly(l-lactide) shape-memory system.

Biodegradable shape-memory polymers (SMPs) which are functional materials with applicability for medicine devices are designed to acquire their therapeutically relevant shape and drug release after implantation. In the work, an amphiphilic polymer (PVAD) is synthesized by using polytetrahydrofuran (PTMG), vinyl acetate (VAc), acrylic acid (AA), tetramethyltetravinylcyclotetrasiloxane (D4vi) as raw materials. PVAD encapsulating hydrophilic drug as switching phase and poly(l-lactide) (PLLA) as fixing matrix construct an SM system with the characteristic of "reservoir-matrix" drug release. The shape recovery ratio (Rr) of medicated PVAD/PLLA reaches 99 % by heat-water stimulation. The effects of release temperature and SM on drug release are investigated. With the release temperature increasing, the medicated PVAD/PLLA accelerates drug release and shows burst release initially, while the drug release for the medicated PLLA changes slightly. The drug release rate goes up after 3 rounds of SM. The mechanism of SM system controlling drug release is put forward based on structural changes. The yield strength and elongation at break of medicated PVAD/PLLA are 29.8 MPa and 44.6 %, respectively. It opens up new perspectives for drug carrier matrices in Pharmaceutical Sciences.