Planning District‐Wide Professional Development: Insights Gained From Teachers and Students Regarding Mathematics Teaching in a Large Urban District

This paper describes the mechanism used to gain insights into the state of the art of mathematics instruction in a large urban district in order to design meaningful professional development for the teachers in the district. Surveys of close to 2,000 elementary, middle school, and high school students were collected in order to assess the instructional practices used in mathematics classes across the district. Students were questioned about the frequency of use of various instructional practices that support the meaningful learning of mathematics. These included practices such as problem solving, use of calculators and computers, group work, homework, discussions, and projects, among others. Responses were analyzed and comparisons were drawn between elementary and middle school students' responses and between middle school and high school responses. Finally, fifth‐grade student responses were compared to those of their teachers. Student responses indicated that they had fewer inquiry‐based experiences, fewer student‐to‐student interactions, and fewer opportunities to defend their answers and justify their thinking as they moved from elementary to middle school to high school. In the elementary grades students reported an overemphasis on the use of memorization of facts and procedures and sparse use of calculators. Results were interpreted and specific directions for professional development, as reported in this paper, were drawn from these data. The paper illustrates how student surveys can inform the design of professional development experiences for the teachers in a district.     

Strukturelle Untersuchungen einiger neutraler Komplexe des zweiwertigen Molybdäns

Unit cell parameters have been calculated from x-ray powder diffraction data of Mo₂Br₄ Py ₄ (A), Mo₂I₄ Py ₄ (B), Mo₂I₄ Pic ₄ (C), Mo₂(SCN)₄ Py ₄ (D) and Mo₂(SCN)₄ Pic ₄ (E), A, B and C crystallize tetragonal. A witha=9,4₂,c=15,O₂ Å; B witha=9,4₆,c=14,9₈ Å and C witha=9,6₆ andc=15,7₂ Å D and E crystallize orthorhombic. D witha=10,0₉,b=9,1₄,c=15,0₈ Å; E witha=10,2₂,b=9,4₁ andc=15,1₅ Å.Py=pyridine,Pic=4-methylpyridine.

     

Progress,highlights and perspectives on NiO in perovskite photovoltaics

The power conversion efficiency (PCE) of NiO based perovskite solar cells has recently hit a record 22.1% with a hybrid organic–inorganic perovskite composition and a PCE above 15% in a fully inorganic configuration was achieved. Moreover, NiO processing is a mature technology, with different industrially attractive processes demonstrated in the last few years. These considerations, along with the excellent stabilities reported, clearly point towards NiO as the most efficient inorganic hole selective layer for lead halide perovskite photovoltaics, which is the topic of this review. NiO optoelectronics is discussed by analysing the different doping mechanisms, with a focus on the case of alkaline and transition metal cation dopants. Doping allows tuning the conductivity and the energy levels of NiO, improving the overall performance and adapting the material to a variety of perovskite compositions. Furthermore, we summarise the main investigations on the NiO/perovskite interface stability. In fact, the surface of NiO is commonly oxidised and reactive with perovskite, also under the effect of light, thermal and electrical stress. Interface engineering strategies should be considered aiming at long term stability and the highest efficiency. Finally, we present the main achievements in flexible, fully printed and lead-free perovskite photovoltaics which employ NiO as a layer and provide our perspective to accelerate the improvement of these technologies. Overall, we show that adequately doped and passivated NiO might be an ideal hole selective layer in every possible application of perovskite solar cells.

The power conversion efficiency of NiO based perovskite solar cells has recently hit a record 22.1%. Here, the main advances are reviewed and the role of NiO in the next breakthroughs is discussed.     

Novel heterocycle-based two-photon absorbing dyes

[structure: see text]. The synthesis and nonlinear optical characterization of two novel heteroaromatic-based chromophores is described. The new dyes present an A-pi-D-pi-A general framework, where A is a pi-deficient heteroaromatic ring (pyridine, quinoline, benzothiazole) and D a pi-excessive pyrrolyl moiety. Both systems exhibit large two-photon absorption (TPA) values in the femtoseconds regime (TPA cross section as high as 150 x 10(-50) cm(4) s photon(-1) molecule(-1) with 150 fs laser pulses). Their TPA-based optical limiting activity is also shown.     

DNA photoreactivating enzyme from human tissues

Photoreactivating enzyme activity has been quantitated in human fetal skin, kidney, lung, liver, brain and intestine, and in neonatal human foreskin. In all the tissues examined there were at least two activities: one nominally greater than 10,000 Da, and one nominally less than 10,000 Da. Both can photolyze pyrimidine dimers in DNA using only light of wavelengths greater than 320 nm, thus excluding tryptophan-mediated dimer splitting as an important mechanism for these activities. The activities are inactivated by digestion with trypsin or pronase, and decreased partially or totally by heating to 65 degrees C. The activities from all six tissues, as well as that from neonatal foreskin, act catalytically in dimer photolysis. The properties of macromolecular size, heat lability, protease sensitivity and catalytic pyrimidine dimer photolysis by a non-tryptophan-mediated mechanism correspond to those of a true photoreactivating enzyme.     

QUANTITATION OF PYRIMIDINE DIMERS BY IMMUNOSLOT BLOT FOLLOWING SUBLETHAL UV-IRRADIATION OF HUMAN CELLS

An immunoslot blot assay was developed to detect pyrimidine dimers induced in DNA by sublethal doses of UV (254 nm) radiation. Using this assay, one dimer could be detected in 10 megabase DNA using 200 ng or 0.5 megabase DNA using 20 ng irradiated DNA. The level of detection, as measured by dimer specific antibody binding, was proportional to the dose of UV and amount of irradiated DNA used. The repair of pyrimidine dimers was measured in human skin fibroblastic cells in culture following exposure to 0.5 to 5 J m^-2 of 254 nm UV radiation. The half-life of repair was approximately 24, 7 and 6 h in cells exposed to 0.5, 2 and 5 J m^-2 UV radiation, respectively. This immunological approach utilizing irradiated DNA immobilized to nitrocellulose should allow the direct quantitation of dimers following very low levels of irradiation in small biological samples and isolated gene fragments.     

Environmental effects on a prion's helix II domain: copper(II) and membrane interactions with PrP180-193 and its analogues

An abnormal interaction between copper and the prion protein is believed to play a pivotal role in the pathogenesis of prion diseases. Copper binding has been mainly attributed to the N-terminal domain of the prion protein, but this hypothesis has recently been challenged in some papers which suggest that the C-terminal domain might also compete for metal anchoring. In particular, the segment corresponding to the helix II region of the prion protein, namely PrP180-193, has been shown both to bind copper and to exhibit a copper-enhanced cytotoxicity, as well as to interact with artificial membranes. The present work is aimed at extending these results by choosing the most representative model of this domain and by determining its copper affinity. With this aim, the different role played by the electrostatic properties of the C- and N-termini of PrP180-193 (VNITIKQHTVTTTT) in determining its conformational behaviour, copper coordination and ability to perturb model membranes was investigated. Owing to the low solubility of PrP180-193, its copper affinity was evaluated by using the shorter PrPAc184-188NH2 (IKQHT) analogue as a model. ESI-MS, ESR, UV/Vis, and CD measurements were carried out on the copper(II)/PrPAc184-188NH2 and copper(II)/PrP180-193NH2 systems, and showed that PrPAc184-188NH2 is a reliable model for the metal interaction with the helix II domain. The affinity of copper(II) for the helix II fragment is higher than that for the octarepeat and PrP106-126 peptides. Finally, the different ability of PrP180-193 analogues to perturb the DPPC model membrane was assessed by DSC measurements. The possible biological consequences of these findings are also discussed briefly.     

Novel heteroaromatic-based multi-branched dyes with enhanced two-photon absorption activity

The first examples of heterocycle-based multi-branched dyes with efficient two-photon absorption (TPA) activity are reported; the novel chromophores exhibit large TPA cross sections (as high as 1600 x 10(-50) cm4 s photon(-1) molecule(-1), measured with 150 fs laser pulses at 800 nm); a strong cooperative enhancement in the branched systems with respect to the one-dimensional sub-units is found.