On the Relaxation of the Energy Distribution Function of Light Particles in Heavy Gases

A stochastic approach to the thermalization problem of light particles in heavy gases is discussed which presents a number of advantages with respect to more conventional techniques. The procedure is used to study the relaxation of the distribution function in cold gases in two situations in which: i) only first order terms are retained and ii) second order terms are also included, with respect to the ratio m/M between light-particle mass m and atomic mass M.     

Analytic proof systems for λ-calculus: the elimination of transitivity, and why it matters

We introduce new proof systems G[β] and G _ext[β], which are equivalent to the standard equational calculi of λβ- and λβη- conversion, and which may be qualified as ‘analytic’ because it is possible to establish, by purely proof-theoretical methods, that in both of them the transitivity rule admits effective elimination. This key feature, besides its intrinsic conceptual significance, turns out to provide a common logical background to new and comparatively simple demonstrations—rooted in nice proof-theoretical properties of transitivity-free derivations—of a number of well-known and central results concerning β- and βη-reduction. The latter include the Church–Rosser theorem for both reductions, the Standardization theorem for β- reduction, as well as the Normalization (Leftmost reduction) theorem and the Postponement of η-reduction theorem for βη-reduction      

Scale Inhibitor and Dispersant Based on Poly(Acrylic Acid) Obtained by Redox‐Initiated Polymerization

Low molar mass poly(acrylic acid) (PAA) is generally obtained by free radical polymerization of acrylic acid (AA) in aqueous solution, using thermal initiators and some chain transfer agent. However, under such conditions it is rather difficult to efficiently produce molar masses as low as those required for obtaining an effective dispersant. In this work, the semibatch polymerization of AA at 45 °C is considered, using potassium persulfate (KPS) and sodium metabisulfite (KPS/NaMBS), or alternatively KPS and sodium hypophosphite (KPS/NaHP) as redox initiators to produce PAA of controlled low molar masses. These initiation systems allow the production of PAA with M_n as low as 2.0 kDa, relatively narrow molar mass distribution (1.5 < M_w/M_n < 3.0), and low branching degree. Most of the investigated polymerizations reach almost complete conversions (>95%); and it is verified that both reductants, NaMBS and NaHP, also behave as chain transfer agents. Finally, the investigated process with redox couples allowed the production of PAA with acceptable dispersant and antiscaling properties.     

Comparison of monte carlo and boltzmann two-term calculations of time-dependent velocity distribution functions of electrons in an electric field in a gas

Summary An extended comparison has been made between Boltzmann two-term and rigorous Monte Carlo calculations of time-dependent velocity distribution functions of electrons in a d.c. electric field in a gas to assess the limits of the conventional approximations. It is shown that under various conditions the two-term approximation is unable to represent the velocity distribution correctly even if the conventional quasi-stationary approximation of the velocity distribution anisotropy, usually adopted in this kind of calculations, is abandoned. The conditions which permit to use the two-term theory are discussed.     

Synthesis of fluorinated anti-fluorenacenedione and the structural, electronic, and field-effect properties

Fluorinated anti-fluorenacenedione 6 was newly synthesized by oxidation of a dehydro[12]annulene fused with tetrafluorobenzene 4. X-Ray crystallography of 6 demonstrated a totally planar structure and shorter intramolecular distances for F ... I, F ... O, and I ... O than the corresponding sums of van der Waals (vdW) radii. In the packing structure, molecules are arranged in a pi-stacked motif, and the intermolecular distances between heavy atoms (C ... I, C ... F, C ... O, F ... I, and F ... O) of the adjacent columns are also shorter than the corresponding sums of vdW radii, indicating highly dense packing for the crystal structure of 6. In the 19F NMR spectrum of 6, a signal for the fluorine atom adjacent to iodine exhibited downfield shift by 29-40 ppm as compared with the other three signals. This is attributed to the intramolecular short contact between F and I atoms, which is supposed to cause a donor-acceptor interaction. Cyclic voltammetry of 6 exhibited two reversible reduction waves at E1/2 = -0.91 and -1.45 V vs. Fc/Fc+. A thin film of 6 was prepared by vacuum deposition and was applied to a field-effect transistor (FET) device, which exhibited n-type transistor responses although the mobility was not very high.