Grating of single Lu@C(82) molecules using supramolecular network

A supramolecular grating of single Lu@C(82) molecules was obtained by depositing Lu@C(82) molecules onto a room temperature PTCDI-melamine network.     

Authentication of Radix Aucklandiae and its substitutes by GC-MS and hierarchical clustering analysis

Radix Aucklandiae (Muxiang in Chinese), the dried root of Aucklandia lappa, is used as a medicinal material for digestive system disorders in traditional Chinese medicine for centuries. Owing to the similarity of morphologies and trade names, Radix Vladimiriae (Chuan-Muxiang), the roots of Vladimiria souliei and V. souliei var. cinerea, and Radix Inulae (Tu-Muxiang), the roots of Inula helenium and Inula racemosa, as well as the renal toxic aristolochic acid containing Radix Aristolochiae (Qing-Muxiang), the roots of Aristolochia debilis and Aristolochia contorta, are often used confusedly as the substitutes of Radix Aucklandiae. In order to ensure the effective and safe utility of Radix Aucklandiae, a GC-MS method was developed to generate the chemical profiles of essential oils of Radix Aucklandiae and its substitutes. In addition, hierarchical clustering analysis was used to compare the similarities of these chemical profiles. It was found that all the samples of A. lappa have similar chemical profiles and were clustered into one group, while the samples of Radix Vladimiriae, Radix Inulae, and Radix Aristolochiae were clustered into their own independent groups, respectively, suggesting that together with hierarchical clustering analysis, chemical profiles of essential oils generated by GC-MS could objectively discriminate Radix Aucklandiae from its common substitutes.     

The effect of word learning on the perception of non-native consonant sequences

Previous research in cross-language perception has shown that non-native listeners often assimilate both single phonemes and phonotactic sequences to native language categories. This study examined whether associating meaning with words containing non-native phonotactics assists listeners in distinguishing the non-native sequences from native ones. In the first experiment, American English listeners learned word-picture pairings including words that contained a phonological contrast between CC and CVC sequences, but which were not minimal pairs (e.g., [ftake], [ftalu]). In the second experiment, the word-picture pairings specifically consisted of minimal pairs (e.g., [ftake], [ftake]). Results showed that the ability to learn non-native CC was significantly improved when listeners learned minimal pairs as opposed to phonological contrast alone. Subsequent investigation of individual listeners revealed that there are both high and low performing participants, where the high performers were much more capable of learning the contrast between native and non-native words. Implications of these findings for second language lexical representations and loanword adaptation are discussed.     

The <Emphasis Type="Italic">ψ</Emphasis>-associate <Emphasis Type="Italic">X</Emphasis><Superscript>#</Superscript> of a flat <Emphasis Type="Italic">X</Emphasis> in PG(<Emphasis Type="Italic">n</Emphasis>, 2)

For a given hypersurface ψ in PG(n, 2), with equation Q(x) = 0, where Q is a polynomial of (reduced) degree d > 1, a definition is given of the ψ-associate X ^# of a flat X in PG(n, 2). The definition involves the fully polarized form of the polynomial Q; in the cubic case d = 3 it reads: X ^# = {z ∈ PG(n, 2) | T(x, y, z) = 0 for all x, y ∈ X}, where T(x, y, z) denotes the alternating trilinear form obtained by completely polarizing Q. Some general results, valid for any degree d and projective dimension n, are first expounded. Thereafter several choices of ψ are visited, but for each choice just a few aspects are highlighted. Despite the partial nature of the survey quite a variety of behaviours of the ψ-associate are uncovered. Many of the choices of ψ which are considered are of cubic hypersurfaces in PG(5, 2). If ψ is the Segre variety it is shown that the 48 planes external to fall into eight pairs of ordered triplets {(P ₁, R ₁, S ₁), (P ₂, R ₂, S ₂)} such that and . Further those lines L of PG(5, 2) which are singular, satisfying that is L ^# = PG(5.2), are in this case shown to form a complete spread of 21 lines. Another result of note arises in the case where ψ is the underlying 35-set of a non-maximal partial spread Σ₅ of five planes in PG(5, 2), where it is shown that one plane is singled out by the property that every line is singular.      

Changing dynamical complexity with time delay in coupled fiber laser oscillators

We investigate the complexity of the dynamics of two mutually coupled systems with internal delays and vary the coupling delay over 4 orders of magnitude. Karhunen-Loève decomposition of spatiotemporal representations of fiber laser intensity data is performed to examine the eigenvalue spectrum and significant orthogonal modes. We compute the Shannon information from the eigenvalue spectra to quantify the dynamical complexity. A reduction in complexity occurs for short coupling delays while a logarithmic growth is observed as the coupling delay is increased.     

Flexible statistical modelling detects clinical functional magnetic resonance imaging activation in partially compliant subjects

Clinical functional magnetic resonance imaging (fMRI) occasionally fails to detect significant activation, often due to variability in task performance. The present study seeks to test whether a more flexible statistical analysis can better detect activation, by accounting for variance associated with variable compliance to the task over time. Experimental results and simulated data both confirm that even at 80% compliance to the task, such a flexible model outperforms standard statistical analysis when assessed using the extent of activation (experimental data), goodness of fit (experimental data), and area under the operator characteristic curve (simulated data). Furthermore, retrospective examination of 14 clinical fMRI examinations reveals that in patients where the standard statistical approach yields activation, there is a measurable gain in model performance in adopting the flexible statistical model, with little or no penalty in lost sensitivity. This indicates that a flexible model should be considered, particularly for clinical patients who may have difficulty complying fully with the study task.     

Entropy effects in the fragmentation of 1,1-dimethylhydrazine ions

The 1,1-dimethylhydrazine ion ((CH3)2NNH2+*) has two low-energy dissociation channels, the loss of a hydrogen atom to form the fragment ion m/z 59, (CH3)(CH2)NNH2+, and the loss of a methyl radical to form the fragment ion m/z 45, the methylhydrazyl cation, CH3NNH2+. The dissociation of the 1,1-dimethylhydrazine ion has been investigated using threshold photoelectron-photoion coincidence (TPEPICO) spectroscopy, in the photon energy range 8.25-31 eV, and tandem mass spectrometry. Theoretical breakdown curves have been obtained from a variational transition state theory (VTST) modeling of the two reaction channels and compared to those obtained from experiment. Seven transition states have been found at the B3-LYP/6-31+G(d) level of theory for the methyl radical loss channel in the internal energy range of 2.32-3.56 eV. The methyl loss channel transition states are found at R(N-C) = 4.265, 4.065, 3.965, 3.165, 2.765, 2.665, and 2.565 A over this internal energy range. Three transition states have been found for the hydrogen atom loss channel: R(H-C) = 2.298, 2.198, and 2.098 A. The DeltaS++(45) value, at an internal energy of 2.32 eV and a bond distance of R(N-C) = 4.265 A, is 65 J K-1 mol-1. As the internal energy increases to 3.56 eV the variational transition state moves to lower R value so that at R(N-C) = 2.565 A, the DeltaS++ decreases to 29 J K-1 mol-1. For the hydrogen atom loss channel the variation in DeltaS++ is less than that for the methyl loss channel. To obtain agreement with the experimental breakdown curves, DeltaS++(59) = 26-16 J K-1 mol-1 over the studied internal energy range. The 0 K enthalpies of formation (DeltafH0) for the two fragment ions m/z 45 and m/z 59 have been calculated from the 0 K activation energies (E0) obtained from the fitting procedure: DeltafH0[CH3NNH2+] = 906 +/- 6 kJ mol-1 and DeltafH0[(CH3)(CH2)NNH2+] = 822 +/- 7 kJ mol-1. The calculated G3 values are DeltafH0[CH3NNH2+] = 911 kJ mol-1 and DeltafH0[(CH3)(CH2)NNH2+] = 825 kJ mol-1. In addition to the two low-energy dissociation products, 21 other fragment ions have been observed in the dissociation of the 1,1-dimethylhydrazine ion as the photon energy was increased. Their appearance energies are reported.     

A high‐fidelity low‐cost aerodynamic model using proper orthogonal decomposition

In this paper a high‐fidelity aerodynamic model is presented for use in parametric studies of weapon aerodynamics. The method employs a reduced‐order model obtained from the proper orthogonal decomposition (POD) of an ensemble of computational fluid dynamics (CFD) solutions with varying parameters. This decomposition produces an optimal linear set of orthogonal basis functions that best describe the ensemble of numerical solutions. These solutions are then projected onto this set of basis functions to provide a finite set of scalar coefficients that represent the solutions. A pseudo‐continuous representation of these projection coefficients is constructed, which allows predictions to be made of parameter combinations not in the original set of observations. The paper explores the performance of a few design‐of‐experiment approaches for the generation of the initial ensemble of computational experiments. Response surface construction methods based on parametric and non‐parametric models for the pseudo‐continuous representation of the projection coefficients are also evaluated. The model has been applied to two‐flow problems related to high‐speed weapon aerodynamics, inviscid flow around a flare‐stabilized hypersonic projectile and supersonic turbulent flow around a fin‐stabilized projectile with drooping nose control. Comparisons of model predictions with high‐fidelity CFD simulations suggest that the POD provides a reliable and robust approach to the construction of reduced‐order models. The practicality of the model is shown to be sensitive to the technique used to generate the ensemble of observations from which the model is constructed, while the accuracy of the approach depends on the pseudo‐continuous representation of the projection coefficients. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of commercial polybutylenes

A series of copolymers and blends based on polybutylene were characterized using ¹³C NMR and thermal analysis. Optical microscopy techniques were used to measure crystallization rates and examine their morphology, and this behavior was related to their composition. As expected, the highest melting and crystallization temperatures, and the fastest crystallization rates were obtained for the polybutylene homopolymer. Copolymerized ethylene randomly distributed along the chain, even at a level of 1%, significantly reduced the melting temperature and crystallization rate. Increasing the ethylene content to 5% results in a polybutylene which crystallizes with difficulty to produce poorly defined spherulites. Four blends based on a polybutylene containing 1% ethylene were studied. A dispersed crystalline phase could be detected in all cases. Two of the blends contained 6-7% ethylene but differed in molar mass. Their melting and crystallization behavior was similar although the spherulite growth rate for the lower molar mass material was a little higher. A second pair of blends contained 5-6% polypropylene and included a “nucleated” and a “nonnucleated” grade. Results for these suggested that the polypropylene itself was acting as a nucleating agent.