Inclusive production of D-mesons in e+e− annihilation at 7 GeV

Inclusive momentum and energy spectra of neutral and charged D-mesons produced in e⁺e^? annihilation at energies near 7 GeV are presented. The slope of the energy spectrum is similar to the charged pion spectrum at the same energy. The inclusive cross section σ(e⁺e^?→ D or $\text{D}$ + anything) at 7 GeV is 4.8±1.3 nb.     

A phenomenological analysis on γp → π+n, πOp below 1.2 GeV

A phenomenological partial-wave analysis on γp → π⁺n and π^Op reactions has been performed in the energy range 0.25–1.2 GeV with available data, laying special emphasis on the polarization and asymmetry data. A good fit has been obtained.     

A possible relativistic contribution to the singlet-triplet separation in methylene

The work of Desclaux et al. indicates that the Fock-Dirac relativistic correction to the s²p³-sp³ energy separation in carbon is of the same order of magnitude as the difference between experimental and theoretical estimates of the singlet-triplet separation in CH₂.     

Maintaining a high degree of research productivity at a predominately undergraduate institution as your career advances

In this perspective, two experienced academic administrators who are computational chemists discuss strategies for how to maintain an active research program at a predominately undergraduate institution as your career progresses. More responsibility equates to less time for research, so planning for research to remain a priority is essential. We all have the same amount of time, so figuring out how to use yours better is the key to remaining active. Professional organizations such as Council on Undergraduate Research, consortia of computational chemists such as Molecular Education and Research Consortium in computational chemistRY and Midwest Undergraduate Computational Chemistry Consortium, and attendance at professional conferences can help sustain your research program. Collaborations with faculty at other institutions provide a particularly effective accountability mechanism as well. Perhaps the best way to improve your productivity is to become a better mentor to your undergraduate students. Building a research group that is fun and exciting develops a culture that sustains itself and provides the momentum necessary to maintain progress toward scientific goals.     

High stability silver nanoparticles–graphene/poly(ionic liquid)-based chemoresistive sensors for volatile organic compounds’ detection

Hybrids of silver nanoparticle-decorated reduced graphene oxide (Ag-RGO) have been prepared with the use of poly(ionic liquid) (PIL) as a versatile capping agent to develop volatile organic compound (VOC) sensors. The hybrid materials of Ag-RGO/PIL were assembled into three-dimensional-laminated nanostructures, where spherical Ag nanoparticles with diameters between 50 and 300 nm were homogeneously distributed on the graphene sheets and interspaced between them. Ag-RGO/PIL sensors were fabricated by spray layer-by-layer technique and used to detect a set of polar (methanol, ethanol, methyl acetate, acetone and water) and non-polar (chloroform, dichlorobenzene, toluene and styrene) organic vapours. Much higher sensitivity and discriminability were obtained for polar vapours although non-polar ones could also be detected. In comparison with either simple reduced graphene oxide or carbon nanotubes (CNT) functionalised by PIL, the hybrid Ag-RGO/PIL-based sensors showed superior performances in terms of sensitivity, selectivity, stability and high reliability. For example, a signal-to-noise ratio up to 168 was obtained for 1 ppm of methanol and signals drift between two experiments spaced out in the time of 3 months was less than 3 %. It is expected that by extrapolation, a limit of detection at the parts per billion level can be reached. These results are promising to design e-noses based on high stability chemoresistive sensors for emerging applications such as anticipated diagnostic of food degradation or diseases by the analysis of VOC, some of them being in this case considered as biomarkers.     

On the effectiveness of CCSD(T) complete basis set extrapolations for atomization energies

The leading cause of error in standard coupled cluster theory calculations of thermodynamic properties such as atomization energies and heats of formation originates with the truncation of the one-particle basis set expansion. Unfortunately, the use of finite basis sets is currently a computational necessity. Even with basis sets of quadruple zeta quality, errors can easily exceed 8 kcal/mol in small molecules, rendering the results of little practical use. Attempts to address this serious problem have led to a wide variety of proposals for simple complete basis set extrapolation formulas that exploit the regularity in the correlation consistent sequence of basis sets. This study explores the effectiveness of six formulas for reproducing the complete basis set limit. The W4 approach was also examined, although in lesser detail. Reference atomization energies were obtained from standard coupled-cluster singles, doubles, and perturbative triples (CCSD(T)) calculations involving basis sets of 6ζ or better quality for a collection of 141 molecules. In addition, a subset of 51 atomization energies was treated with explicitly correlated CCSD(T)-F12b calculations and very large basis sets. Of the formulas considered, all proved reliable at reducing the one-particle expansion error. Even the least effective formulas cut the error in the raw values by more than half, a feat requiring a much larger basis set without the aid of extrapolation. The most effective formulas cut the mean absolute deviation by a further factor of two. Careful examination of the complete body of statistics failed to reveal a single choice that out performed the others for all basis set combinations and all classes of molecules.     

Eco‐friendly conductive polymer nanocomposites (CPC) for solar absorbers design

To reduce both the cost and the environmental impact of copper‐based thermal solar absorbers, we have investigated their possible substitution by bio‐based conductive polymer nanocomposite (CPC) elements. Our results show that carbon nanotubes (CNT) have no significant influence on polymers’ calorimetric properties such as T_m and T_g but lead to a strong increase in crystallinity of poly(lactic acid) (PLA) and to a lesser extent of poly(amide 12) poly(amide 12) (PA12) for 2 and 3 CNT wt % respectively. Percolation thresholds as low as 0.5 and 0.58 were obtained for PA12 and PLA, respectively, and visco‐elastic properties such as η*, G’ and G” were found to increase exponentially with CNT content confirming the formation of a CNT network within the matrix. All CPC are absorbing more energy in the visible and infrared than in the ultraviolet wavelength ranges. Finally, the thermal conductivity k of PLA–CNT and PA12–CNT were increased, respectively, of 85% and 24%, to reach 0.28 W.m^?1.K^?1 and 0.26 W.m^?1.K^?1, for only 5 wt% CNT. The figure of merit suggests that PA12 is the polymer which satisfies at best all criteria, particularly combining a lower viscosity at almost equivalent thermal conductivity and absorptivity. Copyright © 2013 John Wiley & Sons, Ltd.     

Supply of harmonic functions of an infinite number of variables. II

There are exceptionally many harmonic functions of an infinite number of variables. Using for the estimate of the infinite-dimensional Laplacian introduced by P. Levy, estimates of the germ of sums of orthogonal random variables, there are obtained optimal (in a certain sense) conditions of the harmonicity of the functions in a Hilbert space. Along with harmonicity conditions obtained earlier based on estimates of the germ of sums of dependent random variables, they allow one to encompass the manifold of harmonic functions of an infinite number of variables.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 42, No. 12, pp. 1687–1693, December, 1990.