Photoactivated Nitrene Chemistry to Prepare Gold Nanoparticle Hybrids with Carbonaceous Materials

Photolysis of organic solvent soluble aryl azide‐modified gold nanoparticles (N₃‐AuNPs) with a core size of 4.6±1.6 nm results in the generation of interfacial reactive nitrene intermediates. The high reactivity of the nitrenes is utilized to tether the AuNP to the native surface of carbon nanotubes, and reduce graphene oxide and micro‐diamond powder, likely via addition to π‐conjugated carbon skeleton or insertion into the functionalities at the surface, to yield the desired hybrid material without the need for pretreatment of the surface. The AuNP‐covalent hybrid materials are robust in that they survive vigorous washing and sonication. In the absence of photolysis no attachment occurs with the same N₃‐AuNP. The nanohybrid AuNP‐nanohybrid materials are characterized using a combination of TEM, powder XRD, XPS and UV/Vis and IR spectroscopies. All of the characterization studies confirm the uniform incorporation of the AuNP on the irradiated substrates.     

Nonlocal boundary value problems for discrete systems

Our goal in this paper is to provide sufficient conditions for the existence of solutions to discrete, nonlinear systems subject to multipoint boundary conditions. The criteria we present depends on the size of the nonlinearity and the set of solutions to the corresponding linear, homogeneous boundary value problems. Our analysis is based on the Lyapunov–Schmidt Procedure and Brouwer?s Fixed Point Theorem. The results presented extend the previous work of D. Etheridge and J. Rodríguez (1996, 1998) [5], [6] and J. Rodríguez and P. Taylor (2007) [18], [19].     

Magnetic structure variation in manganese-oxide clusters

Negative-ion photoelectron spectroscopy and ab initio simulations are used to study the variation in magnetic structure in Mn(x)O(y) (x = 3, 4[semicolon] y = 1, 2) clusters. The ferrimagnetic and antiferromagnetic ground-state structures of Mn(x)O(y) are 0.16-1.20 eV lower in energy than their ferromagnetic isomers. The presence of oxygen thus stabilizes low-spin isomers relative to the preferred high-spin ordering of bare Mn(3) and Mn(4). Each cluster has a preferred overall magnetic moment, and no evidence is seen of competing states with different spin multiplicities. However, non-degenerate isomags, which possess the same spin multiplicity but different arrangements of local moments, do contribute additional features and peak broadening in the photoelectron spectra. Proper accounting for all possible isomags is shown to be critical for accurate computational prediction of the spectra.     

Quantitative Estimation: One, Two, or Three Abilities?

The mathematics education literature refers to 3 types of quantitative estimation skill: numerosity, measurement, and computational estimation. The psychometric literature includes a confusing array of tests intended to define quantitative estimation. This study examined relations among tests for numerosity, measurement, and computational estimation, and recognized tests for numerical facility and quantitative reasoning using principal components analysis. 2 components were identified. The first component aligned computational estimation with numerical facility and general quantitative reasoning. The second component included the tests of numerosity and measurement estimation. It was suggested that this second component might be related to spatial ability. Implications for mathematics education and assessment are discussed.     

Isotopic metrology of carbon dioxide. I. Interlaboratory comparison and empirical modeling of inlet equilibration time,inlet pressure,and ion source conductance

We report a pilot study of high-precision differential isotope ratio measurements made on replicate samples of pure carbon dioxide using three instruments of identical manufacture. Measurement protocols were designed to explore the effects of sample size, ion source conductance, and inlet changeover equilibration time on the raw measurements. Our goal was better understanding of factors that influence these measurements in order to establish procedures for highly reproducible and accurate determinations of Reference Material (RM) isotopic compositions. Evaluation and modeling of reported data illuminated effects consistent with two instrumental memory sources--one short-lived (t((1/2)) approximately 10 s) and the other long-lived (t((1/2)) approximately 6-10 min), uncompensated by normal background measurements--that can significantly influence measurements made by the dual inlet method. These biases, proportional to the difference in isotopic compositions between the measured sample and reference gases, decrease in magnitude with increasing sample size, source conductance, and equilibration time. We observed biases as high as 0.1 per thousand per 10 per thousand difference between sample and reference gases. These memory sources may be responsible for measured delta(13)C values of RMs generally being highly reproducible within any single laboratory but less reproducible among independent laboratories. The magnitude of the bias is consistent with the ranges of delta(13)C values reported in prior laboratory intercomparisons. Uncertainties are most likely due to high and variable long-lived memory among the instruments tested.     

THE EFFECT OF DIFFERENTIATION ON PHOTOSENSITIZER UPTAKE BY HL60 CELLS

The capability of human promyelocytic leukemia cells HL60 to be induced to differentiate to various stages along the monocytic or myelocytic pathway was exploited for investigation of the uptake of selected photo-sensitizers by diverse types of cells of the same origin. The results showed that there was no substantial difference in photofrin uptake between noninduced HL60 cells, immature monocytes, immature neutrophils and cells differentiated along the eosinophilic pathway. In contrast, HL60 cells differentiated into macrophages (HL609) exhibited markedly increased photofrin uptake, which was further enhanced by their pretreatment with bacterial lipopolysaccharide. Similar results were obtained with other photosensitizers tested: di-and tetrasulfonated aluminum phthalocyanines (AIPcS₂ and AIPcS₄), tetrasulfonated zinc phthalocyanine (ZnPcS₄), tetraphenylporphine tetrasulfonate (TPPS₄) and benzoporphyrin derivative monoacid (BPD). Despite marked differences in the state of self-aggregation and other chemical properties of these compounds, the degree of their preferential uptake by HL60 PH cells showed very little variation. In a typical experiment, the uptake of these photosensitizers by HL60 PH cells was four to five times higher than the uptake by noninduced HL60 cells. In addition to the fluorometric assay employed in most of the experiments, cellular concentration of AlPcS₄ was determined by measurement of elementary aluminum using atomic absorption spectroscopy.     

Investigation of the Montmorillonite clay-catalyzed [1,3] shift reaction of 3-methyl-2-butenyl phenyl ether

The [1,3] shift reaction of 3-methyl-2-butenyl phenyl ether was catalyzed more effectively by Montmorillonite K10 clay than Montmorillonite KSF clay, and proceeded with greatest ortho-selectivity in carbon tetrachloride at room temperature.     

Intramolekulare Basenkoordination je nach Bedarf: Der 1-(Dimethylaminoethyl)-2,3,4,5-tetramethylcyclopentadienyl-Ligand in der Komplexchemie von s-, p-, d- und f-Block-Elementen

The synthesis of cyclopentadienyl complexes containing the polydentate C₅Me₄(CH₂CH₂NMe₂) ligand is described. The compounds (C₅Me₄CH₂CH₂NMe₂)₂M (M = Ca, Sm), (C₅Me₄CH₂CH₂ NMe₂)AIEt₂, [(C₅Me₄CH₂CH₂NMe₂)M(CO)₂]₂ (M = Mo, Fe) and [(C₅Me₄CH₂CH₂NMe₂)Fe(CO)₂]⁺BF₄^± are obtained by standard procedures. Except for the dimeric metal carbonyls, all cyclopentadienyl compounds are characterized by an additional intramolecular coordination of the nitrogen atom in the side chain.     

A theoretical study of the staggered and eclipsed forms of the dinuclear complex Mn Re(CO)10

Two possible conformers of the dinuclear complex Mn Re(CO)10, each of C(4v) symmetry, with eclipsed and staggered conformations, have been analyzed theoretically. Using both the B3LYP and BP86 density functionals we find that the staggered form is lower in energy. A determination of the B3LYP potential energy surface as a function of the Mn-Re distance is presented for both conformers. The computed bond lengths, bond angles, and rotational constant for the staggered conformation compare favorably with the results from microwave experiments. The harmonic frequencies for the staggered structure have been determined using several basis sets, with both analytical and finite difference methods. These unscaled vibrational frequencies, together with their intensities for both infrared and Raman activity, are used to assign the three most intense experimental IR and Raman bands, and in particular, the nu(CO) region. The lowest A(2) vibration was calculated to occur at 41 cm(-1) in the staggered conformer; this frequency becomes imaginary in the (saddle point) eclipsed form. Several fundamentals remain to be observed experimentally.     

A first-principles study of oxygen adsorption and interaction with Al adatoms on Al(110)

We use first-principles density-functional theory to identify several stable binding sites for adsorbed O₂ and O on Al(110). Our calculations indicate that it is energetically favorable for O₂ to dissociate to two atoms on Al(110). When O₂ dissociates, it is energetically favorable for the resulting O atoms to exist as dimers. We identify several possible configurations for O dimers on this surface, and quantify atomic interactions between an Al adatom and these dimers. Our work provides insight into the initial stages of oxidation of Al(110), as well as the role of oxygen impurities in Al thin-film epitaxy.