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Quantum defect theory is applied to (time-dependent) density-functional calculations of Rydberg series for closed shell atoms: He, Be, and Ne. The performance and behavior of such calculations are much better quantified and understood in terms of the quantum defect rather than transition energies. 相似文献
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Meta M. Bloksma Renzo M. Paulus Huub P. C. van Kuringen Friso van der Woerdt Hanneke M. L. Lambermont‐Thijs Ulrich S. Schubert Richard Hoogenboom 《Macromolecular rapid communications》2012,33(1):92-96
The monomers 2‐methyl‐2‐oxazine (MeOZI), 2‐ethyl‐2‐oxazine (EtOZI), and 2‐n‐propyl‐2‐oxazine (nPropOZI) were synthesized and polymerized via the living cationic ring‐opening polymerization (CROP) under microwave‐assisted conditions. pEtOZI and pnPropOZI were found to be thermoresponsive, exhibiting LCST behavior in water and their cloud point temperatures (TCP) are lower than for poly(2‐oxazoline)s with similar side chains. However, comparison of poly(2‐oxazine) and poly(2‐oxazoline)s isomers reveals that poly(2‐oxazine)s are more water soluble, indicating that the side chain has a stronger impact on polymer solubility than the main chain. In conclusion, variations of both the side chains and the main chains of the poly(cyclic imino ether)s resulted in a series of distinct homopolymers with tunable TCP. 相似文献
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N.J. Martinez Meta 《Journal of solid state chemistry》2006,179(5):1486-1489
The dark green powder of Zr50Sc12O43N50 was produced from Zr50Sc12O118 under a constant flow of ammonia. Zr50Sc12O43N50 crystallizes cubic with space group and in the C-M2O3 structure (bixbyite structure). The reaction path was followed by in situ X-ray diffraction and showed that the substitution of 3O2− by 2N3− generates additional vacancies on the anion sites in the fluorite basis structure. On the way to the bixbyite structure time- and temperature-controlled X-ray diffractograms revealed the known fluorite-related superstructures (i.e. the vacancy distribution) for the compositions M14X26 and M7X12. The reverse process, i.e. the oxidation of the oxide nitride was followed in DTA/TG experiments exhibiting the different vacancy orderings at 420, 500 and . 相似文献
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Meta M. Bloksma Sarah Rogers Ulrich S. Schubert Richard Hoogenboom 《Journal of polymer science. Part A, Polymer chemistry》2011,49(13):2790-2801
The synthesis and microwave‐assisted polymerization of a series of chiral 2‐oxazolines with varying alkyl pendant groups, namely R‐2‐ethyl‐4‐ethyl‐2‐oxazoline (R‐EtEtOx), R‐2‐butyl‐4‐ethyl‐2‐oxazoline (R‐BuEtOx), R‐2‐octyl‐4‐ethyl‐2‐oxazoline, 2‐nonyl‐4‐ethyl‐2‐oxazoline, and R‐2‐undecyl‐4‐ethyl‐2‐oxazoline (R‐UndeEtOx), are reported. A kinetic investigation of the polymerization of R‐EtEtOx revealed a living polymerization mechanism. The poly(2‐oxazoline)s containing an ethyl, butyl, and octyl pendant group form similar chiral structures according to circular dichroism measurements. When the pendant group is further elongated, the chiral structure becomes more flexible in trifluoroethanol and the thermal response in hexafluoroisopropanol (HFIP) significantly changes. The short‐range structure of poly‐R‐BuEtOx dissolved in HFIP is thermoresponsive in a complex way, due to HFIP hydrogen bonding to the polymeric amide groups, whereas the long‐range structure determined from small angle neutron scattering is insensitive to temperature demonstrating that only the local secondary structure changes with temperature. In addition, the chiral structure of poly‐R‐UndeEtOx depends on the polarity of the solvent. The short‐range structure becomes more flexible in polar solvents, most likely due to interactions with the amide groups disturbing the secondary structure. In contrast, the long‐range structural transition from an ellipsoid in the apolar n‐hexane to a rod structure in the polar n‐butanol is ascribed to better solvation of the long aliphatic side chains. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011 相似文献
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The authors propose a novel approach to the problem of polarizabilities and dissociation in electric fields from the static limit of the Vignale-Kohn (VK) functional. The response to the purely scalar part of the VK response potential is considered. This potential has ground-state properties that notably improve over the full VK response density and over usual (semi-)local functionals. The correct qualitative behavior of our potentials means that it is expected to work well for polarizabilities in cases such as the H(2) chain, and it will also correctly dissociate open-shell fragments in a field. 相似文献
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University−Urban High School Partnership: Math and Science Professional Learning Communities 下载免费PDF全文
mutindi ndunda Meta Van Sickle Lindsay Perry Alison Capelloni 《School science and mathematics》2017,117(3-4):137-145
This study focused on science and math professional learning communities (PLCs) that were implemented through a university‐urban high school partnership. These PLCs were part of mandated school‐wide, content‐based PLCs implemented as part of the reform efforts initiated in an urban school to address the school's failure to meet Adequate Yearly Progress (AYP) for four years consecutively and low graduation rate (less than 25%) for male students. The key issues were (a) students had continually earned low test scores; (b) there was continuous principal turnover; (c) faculty morale was at an all‐time low, and the quality of teaching was very poor; and (d) the students were not effectively disciplined. The study examined the impact that university faculty‐led mandated PLCs have on teachers' practices and students' learning and achievement. Analysis of data revealed practices that were effective in developing and implementing these successful math and science PLCs. Three themes emerged: ethics of care, teacher agency, and aesthetics of professional interactions. Each theme contained key features that appeared to contribute to the implementation of a successful PLC. 相似文献
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Phase shifts for single-channel elastic electron-atom scattering are derived from time-dependent density functional theory. The H- ion is placed in a spherical box, its discrete spectrum found, and phase shifts deduced. Exact exchange yields an excellent approximation to the ground-state Kohn-Sham potential, while the adiabatic local density approximation yields good singlet and triplet phase shifts. 相似文献
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Meta Kokalj Simona Strgulc Krajek Jasmina Omahen Bratua Samo Kreft 《Journal of Chemometrics》2010,24(10):611-616
Fourier transform infrared spectroscopy (FTIR) has been studied many times in the context of identification of plant, fungal and bacterial species. Infrared spectra are commonly analyzed using multivariate statistical methods such as cluster analysis (CA), principal component analysis (PCA), partial least squares analysis (PLS) and discriminant analysis (DA). In this study, a univariate statistical method for analysis of variance (ANOVA) was used to reduce the number of variables before applying the multivariate methods. Analyzing variables using ANOVA or a combination of ANOVA with CA produced better results. Here, experiments were carried out by performing ANOVA using the first derivative of the spectra instead of the original spectra or its second derivative because using the first‐derivative variables led to improved distinction between species. Different results were obtained by applying different validation methods. The leave‐one‐out validation method gave higher results than the validation‐with‐training and validation sample sets, thus indicating the non‐objectivity of the leave‐one‐out validation method. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Meta M. Bloksma Daniël J. Bakker Christine Weber Richard Hoogenboom Ulrich S. Schubert 《Macromolecular rapid communications》2010,31(8):724-728
The influence of Hofmeister salts was investigated on the cloud point of three poly(2‐oxazoline)s, namely poly(2‐ethyl‐2‐oxazoline) [PEtOx], poly(2‐n‐propyl‐2‐oxazoline) [PnPropOx], and poly(2‐isopropyl‐2‐oxazoline) [PiPropOx]. In addition, a comb polymer based on oligo‐2‐ethyl‐2‐oxazoline side chains and a methacrylate backbone (POEtOxMA) was included in this investigation. It was found that the ionic response of the poly(2‐oxazoline)s strongly depends on their hydrophilicity. The comb polymer POEtOxMA revealed a strikingly similar response to the salts as linear PEtOx even though the cloud points of the polymers in water differ. This indicates that the architecture does not significantly influence the effect of the Hofmeister ions, even though there is a difference in the absolute cloud point.