Towards curricular coherence in integers and fractions: a study of the efficacy of a lesson sequence that uses the number line as the principal representational context

This paper reports a study of the efficacy of Learning Mathematics through Representations (LMR), an innovative curriculum unit designed to support upper elementary students’ understandings of integers and fractions. The unit supports an integrated treatment of integers and fractions through (a) the use of the number line as a cross-domain representational context, and (b) the building of mathematical definitions in classroom communities that become resources to support student argumentation, generalization, and problem solving. In the efficacy study, fourth and fifth grade teachers employing the same district curriculum (Everyday Mathematics) were matched on background indicators and then assigned to either the LMR experimental classrooms (n = 11) or the comparison group (n = 8 with 10 classrooms). During the fall semester, LMR teachers implemented the LMR unit on 19 days and district curriculum on other days of mathematics instruction. HLM analyses documented greater achievement for LMR students than Comparison students on both the end-of-unit and the end-of year assessments of integers and fractions knowledge; the growth rates of LMR students were similar regardless of entering ability level, and gains for LMR students occurred on item types that included number line representations and those that did not. The findings point to the efficacy of the LMR sequence in supporting teaching and learning in the domains of integers and fractions.     

Electrochemical transduction on self-assembled monolayers: are covalent links essential?

Electrochemical transduction without covalent links between redox and complexant units in a complexing self-assembled monolayer has been established. The results demonstrate that transduction depends on the crown ether/ferrocene ratio and appears to be tunable.     

Evaluation of a new matrix-free laser desorption/ionization method through statistic studies: comparison of the DIAMS (desorption/ionization on self-assembled monolayer surface) method with the MALDI and TGFA-LDI techniques

This work demonstrates that the desorption/ionization on self-assembled monolayer surface (DIAMS) mass spectrometry, a recent matrix-free laser desorption/ionization (LDI) method based on an organic target plate, is as statistically repeatable and reproducible as matrix assisted laser desorption ionization (MALDI) and thin gold film-assisted laser desorption/ionization (TGFA-LDI) mass spectrometries. On lipophilic DIAMS of target plates with a mixture of glycerides, repeatability/reproducibility has been estimated at 15 and 30% and the relative detection limit has been evaluated at 0.3 and 3 pmol, with and without NaI respectively. Salicylic acid and its d(6)-isomer analysis confirm the applicability of the DIAMS method in the detection of compounds of low molecular weight.     

Separation of amino acid enantiomers VIA chiral derivatization and non-chiral gas chromatography

Two GC-MS methods for the enantioselective separation of the 20 proteinogenic amino acids are compared. Ethyl chloroformate and 2-chloropropanol were used to derivatize amino acid enantiomers. The diastereomers formed were separated on a non-chiral column by capillary gas chromatography. The separation performances were compared to those obtained when using non-chiral derivatization on a chiral column.     

Synthesis and electrochemical and photophysical studies of tetrathiafulvalene-annulated phthalocyanines

The synthesis of tetrakis(tetrathiafulvalene)-annulated metal-free and metallophthalocyanines 5-8 via the tetramerization of the phthalonitrile derivative 4 is reported. All of them have been fully characterized by electronic absorption spectroscopy, thin-layer cyclic voltammetry, mass spectrometry, and elemental analysis. Their solution electrochemical data show two reversible four-electron oxidation waves, indicating that these fused systems are strong pi-electron donors, which give rise to tetra- or octaradical cation species. For the metal-free phthalocyanine 5, additionally a reversible one-electron wave was found in the negative direction arising from the reduction of the macrocycle. Moreover, the tetrathiafulvalene unit acts as an efficient reductive electron-transfer quencher for the phthalocyanine emission, but upon its oxidation, an intense luminescence is switched on.     

镜像配基筛选:克服“酶屏障”的多肽、寡核苷酸药物研发技术

生物体内存在的酶屏障是功能性多肽和寡核苷酸成药的重要瓶颈.以镜像噬菌体展示技术(mirror-image phage display)和镜像适配体筛选技术(Spiegelmer technology)为代表的镜像配基筛选技术能有效地克服这一屏障,获得对靶点具有特异识别能力且在生理条件下高度稳定的D型多肽和L型寡核苷酸配基,有望成为多肽或寡核苷酸类特异性药物研发的有利工具.本文主要综述镜像配基筛选技术的原理及其在药学领域的研究进展.     

Submicrometer digital in-line holographic microscopy at 32 nm with high-order harmonics

Soft-x-ray digital in-line microscopic holography is achieved using a fully coherent high-order harmonic source emitting at 32 nm. Combination of commercial-grade soft-x-ray optics and a back-illuminated CCD detector allows a compact and versatile holographic setup. Different experimental geometries have been tested by imaging calibrated 50 nm tips and 1 microm wires. Spatial resolution of 800 nm is measured with magnifications ranging from 30 to 110 and a numerical aperture around 0.01. Finally, the potentiality of three-dimensional numerical reconstruction from a single hologram acquisition is shown experimentally.