Recursive undecidability of the binding property for finitely presented equational classes

It is shown that there exists no algorithm which, given a finite presentation of an equational classC, decides whether the category of algebras inC is binding.     

Bredt Compounds and the Bredt Rule

The Bredt rule, which proved useful in earlier decades mainly as an exclusion criterion in the assignment of structures, has in recent years become the stimulus for efforts to synthesize strained bicyclic systems with a bridgehead double bond. On the basis of the ring-strain forces operating in such systems, an extended Bredt rule is discussed. The “Bredt comgounds” to which this rule applies, which include bicyclic systems not prevoously consodered from this point of view (e.g. bridged methylenecyclopropanes), form a clearly circumscribed, interesting field within the chemistry of highly-strained hydrocarbons with ring unsaturation.     

A phenomenological investigation of the shower particle pseudorapidity fluctuations in hadron-nucleus collisions

From the experimental matrix $\text{?(N}{}_{\mathrm{<mtext>g</mtext>}}\text{; n}{}_{\mathrm{<mtext>s</mtext>}}\text{, Δη}{}_{\mathrm{i}}\text{)}$ (the number of events with a given number N_g of particles with velocity 0.3c<v<0.7c, and n_s, the number of shower particles (v > 0.7c) in a pseudo-rapidity interval Δη_i) obtained from the Heidelberg-Igel hadron-nucleus experiment at CERN, we extract the shower particle multiplicity distributions as a function of ν, the number of nucleons that interacted with the projectile. We use a theoretically justified statistical correlation between ν and N_g (recoil protons) and the assumption that the correlation between n_s and N_g is given merely through ν. The data used are for incoming energies 50 and 150 GeV with a proton or pion as the projectile and Cu or Pb as the target. We find that the shower particle multiplicity distributions are of a Poissonian character in each η bin and for each value of ν. The average multiplicities $\text{〈n}{}_{\mathrm{<mtext>s</mtext>}}\text{〉(ν)}\text{Δη}{}_{\mathrm{i}}$ are approximately the same for the two targets and for the different projectile, possibly with a small excess for the pion projectile.The results are compared to a rather general theoretical model of the soft interaction type. The predictions from this model for the shower particle pseudorapidity distributions are very close to the derived values.     

Semiclassical calculation of energy transfer in polyatomic molecules. V. Differential cross sections for excitation of CO2 and N2O colliding with Li+ at E ≈ 4.72 eV

A semiclassical model has been used to calculate differential cross sections for vibrational excitation of CO₂ and N₂O at the center of mass collision energy E≈ 4.72 eV. Also the average rotational excitation as a function of the scattering angle is reported. Comparison is made with experimental data and previous more approximate theoretical calculations.