Communication: a density functional with accurate fractional-charge and fractional-spin behaviour for s-electrons

We develop a new density-functional approach combining physical insight from chemical structure with treatment of multi-reference character by real-space modeling of the exchange-correlation hole. We are able to recover, for the first time, correct fractional-charge and fractional-spin behaviour for atoms of groups 1 and 2. Based on Becke's non-dynamical correlation functional [A. D. Becke, J. Chem. Phys. 119, 2972 (2003)] and explicitly accounting for core-valence separation and pairing effects, this method is able to accurately describe dissociation and strong correlation in s-shell many-electron systems.     

High resolution slit-jet infrared spectroscopy of ethynyl radical: 2Π-2Σ+ vibronic bands with sub-Doppler resolution

High resolution infrared spectra for four (2)Π-(2)Σ(+) bands of jet-cooled ethynyl radical (i.e., C(2)H) in the gas phase are reported. The combination of (i) slit-jet cooling (T(rot) ≈ 12 K) and (ii) sub-Doppler resolution (≈ 60 MHz) permits satellite branches in each (2)Π-(2)Σ(+) band to be observed and resolved for the first time as well as help clarify a systematic parity misassignment from previous studies. The observed lines in each band are least squares fit to a Hamiltonian model containing rotational, spin-rotational, spin-orbit, and lambda-doubling contributions for the (2)Π state, from which we report revised excited state constants and band origins for the observed bands. Three of the four bands fit extremely well within a conventional (2)Π model (i.e., σ < 20 MHz), while one band exhibits a local perturbation due to an avoided crossing with a near resonant dark state. Vibronic assignments are given for the observed bands, with the dark state clearly identified as a highly excited stretch and bending overtone level X? (1,2(2),0) by comparison with high level ab initio efforts.     

Synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones utilizing pyrrole Weinreb amides

A regiocontrolled synthesis of unsymmetrical 3,4-diaryl-3-pyrrolin-2-ones has been achieved in three steps from 1,2-diaryl-1-nitroethenes with pyrrole-2-carboxamides (pyrrole Weinreb amides) serving as the key linchpin intermediates. Two different methods for the preparation of the requisite nitroalkenes were investigated: (1) modified Henry reaction between arylnitromethanes and arylimines; and (2) Suzuki-Miyaura cross-coupling reaction of 2-aryl-1-bromo-1-nitroethenes with arylboronic acids. Some difficulty was encountered in the preparation of arylnitromethanes, thus leading to the exploration of a cross-coupling strategy that proved more useful. A Barton-Zard pyrrole cyclocondensation reaction between 1,2-diaryl-1-nitroethenes and N-methoxy-N-methyl-2-isocyanoacetamide gave the corresponding pyrrole Weinreb amides, which were then converted into the desired 3-pyrrolin-2-ones in two steps. Overall, this method allowed for the construction of 3,4-diaryl-3-pyrrolin-2-ones with complete regiocontrol of the substituents with respect to the lactam carbonyl. The utility of this synthetic methodology was demonstrated by the preparation of eight unsymmetrical and symmetrical 3,4-diaryl-3-pyrrolin-2-ones including the N-H lactam analogue of the selective COX-II inhibitor, rofecoxib.     

Formation of hydroxyl and water layers on MgO films studied with ambient pressure XPS

To understand the interaction of water with MgO(100), a detailed quantitative assessment of the interfacial chemistry is necessary. We have used ambient pressure X-ray photoelectron spectroscopy (XPS) to measure molecular (H₂O) and dissociative (OH) water adsorption on a 4 monolayer (ML) thick MgO(100)/Ag(100) film under ambient conditions. Since the entire 4 ML metal oxide (Ox) film is probed by XPS, the reaction of the MgO film with water can be quantitatively studied. Using a multilayer model (Model 1) that measures changes in Ox thickness from O 1s (film) and Ag 3d (substrate) spectra, it is shown that the oxide portion of the MgO film becomes thinner upon hydroxylation. A reaction mechanism is postulated in which the top-most layer of MgO converts to Mg(OH)₂ upon dissociation of water. Based on this mechanism a second model (Model 2) is developed to calculate Ox and OH thickness changes based on OH/Ox intensity ratios from O 1s spectra measured in situ, with the known initial Ox thickness prior to hydroxylation. Models 1 and 2 are applied to a 0.15 Torr isobar experiment, yielding similar results for H₂O, OH and Ox thickness changes as a function of relative humidity.     

Phosphonic acid functionalized asymmetric phthalocyanines: synthesis, modification of indium tin oxide, and charge transfer

Metalated and free-base A(3)B-type asymmetric phthalocyanines (Pcs) bearing, in the asymmetric quadrant, a flexible alkyl linker of varying chain lengths terminating in a phosphonic acid (PA) group have been synthesized. Two parallel series of asymmetric Pc derivatives bearing aryloxy and arylthio substituents are reported, and their synthesis and characterization through NMR, combustion analysis, and MALDI-MS are described. We also demonstrate the modification of indium tin oxide (ITO) substrates using the PA functionalized asymmetric Pc derivatives and monitoring their electrochemistry. The PA functionalized asymmetric Pcs were anchored to the ITO surface through chemisorption and their electrochemical properties characterized using cyclic voltammetry to investigate the effects of PA structure on the thermodynamics and kinetics of charge transfer. Ionization energies of the modified ITO surfaces were measured using ultraviolet photoemission spectroscopy.     

Terahertz studies of carrier localization in spontaneously forming polar lateral heterostructures

We employ near‐bandgap terahertz emission spectroscopy to study lateral heterostructures resulting from basal plane stacking faults in m ‐plane GaN. The predominant stacking faults have I₁ character and behave as an array of spontaneously forming layers comprised of a single cubic stacking sequence within the wurtzite matrix that terminate the spontaneous polarization along the in‐plane c‐axis, leading to strong lateral electric fields. Spectral tuning of femtosecond excitation pulses enables observation of the transition from carrier transport in the continuum to formation of instantaneous dipoles and nonlinear susceptibility associated with both the quantum‐well‐like regions of the cubic layers and polarization‐induced triangular‐like potentials. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Developing a measure of risk adjusted revenue (RAR) in credit cards market: Implications for customer relationship management

Current models of customer lifetime value (CLV) consider the discounted value of profits that a customer generates over an expected lifetime of relationship with the firm. This practice can be misleading in the financial services markets because it ignores the risk posed by the customer (such as delinquency and default). Specifically, in the credit card market, the correlation between revenue and risk is positive. Therefore, firms need to adjust a customer’s profits for the associated risk before developing a measure of customer lifetime value. We propose a new measure, risk adjusted revenue (RAR), that can incorporate multiple sources of risk and demonstrate the usefulness of the proposed measure in correctly assessing the value of a customer in the credit card market. The model can be extended to compute risk adjusted lifetime value (RALTV). We use the RAR metric to understand the effectiveness of different modes of acquisition, and of retention strategies such as affinity cards and reward cards. We find that both reward- and affinity-cardholders generate higher RAR than non-reward and non-affinity cardholders respectively. The ordering of different modes of acquisition with respect to RAR (in decreasing order) is as follows: Internet, direct mail, telesales, and direct selling.     

Gradient ambient obstruction solitons on homogeneous manifolds

Annals of Global Analysis and Geometry - We examine homogeneous solitons of the ambient obstruction flow and, in particular, prove that any compact ambient obstruction soliton with constant scalar...     

Powdered rock versus solid rock comparisons in particle-induced X-ray emission measurements for planetary geochemical exploration

Grain size is an important consideration in the determination of the bulk chemistry of Martian rocks and unconsolidated materials in situ by the alpha particle X-ray spectrometer (APXS), deployed on the NASA-led Mars Science Laboratory mission. We used 2.5 MeV protons to emulate the particle-induced X-ray emission (PIXE) branch (5 MeV alphas) of the APXS. Seven polished rock slabs (igneous and sedimentary), ranging from fine- to coarse-grained, were analyzed by PIXE in their original form, then milled to powders and pressed into pellets for further analysis. The summed area (160 mm²) over 10 interrogated regions on each slab is comparable to the area interrogated on the APXS; analysis of two pellets per rock, each using a 16 mm² region, was found to be appropriate. The mean pellet/slab concentration ratio for Na, Mg, Al, Si, K, Ca, and Fe was close to 1.0 for fine-grained samples, but changed by ±10% for the coarser cases. The variability among PIXE concentration values across the 10 rock regions increased monotonically with coarseness in the rock slabs. Comparison of overall PIXE concentrations with values measured by borate-fusion WDXRF provides further quantitative support to the direct comparison of pellet and slab PIXE concentrations. This work affirms the use of the APXS on fine-grained Martian materials but recommends larger interrogation areas (including rastering) when analyzing coarser-grained materials. It also demonstrates that the presence of relatively large mineral grains (phenocrysts) or rock/mineral fragments within fine-grained materials can contribute to greater error for specific elements associated with those phenocrysts/fragments.     

Evaluation of ForenSeq™ Signature Prep Kit B on predicting eye and hair coloration as well as biogeographical ancestry by using Universal Analysis Software (UAS) and available web‐tools

This study examined 266 individuals from various populations including African American, East Asian, South Asian, European, and mixed populations to evaluate the ForenSeq? Signature Prep Kit Primer Mix B. Focus was placed on phenotypic and biogeographical ancestry predictions by Illumina's Universal Analysis Software (UAS). These outcomes were compared to those obtained through web‐tools developed at the Erasmus Medical Center (EMC) and available from the Forensic Resource/Reference on Genetics‐knowledge base (FROG‐kb), as well as to eye color predictions by the 8‐plex system. Due to drop‐outs, predictions for eye and hair color by UAS failed for various samples in each run. By including reads below thresholds, predictions could be obtained for all samples through the web‐tools. Eye and hair color predictions for African Americans, East Asians, and South Asians showed no errors. Difficulties however, were noted in intermediate (neither blue nor brown) eye color predictions. These were mitigated by the 8‐plex system through exclusion of one eye color (e.g. “not brown”). Additionally, notable discrepancies were observed in hair color predictions, where some black/dark‐brown haired individuals were predicted to have blond hair. Overall, ancestry predictions were more accurate by FROG‐kb compared to UAS, which did not predict South Asian ancestry, particularly Indian individuals.