Proof complexity of propositional default logic

Default logic is one of the most popular and successful formalisms for non-monotonic reasoning. In 2002, Bonatti and Olivetti introduced several sequent calculi for credulous and skeptical reasoning in propositional default logic. In this paper we examine these calculi from a proof-complexity perspective. In particular, we show that the calculus for credulous reasoning obeys almost the same bounds on the proof size as Gentzen??s system LK. Hence proving lower bounds for credulous reasoning will be as hard as proving lower bounds for LK. On the other hand, we show an exponential lower bound to the proof size in Bonatti and Olivetti??s enhanced calculus for skeptical default reasoning.     

The Equilibrium Partial Pressure of HgI2 over and Thermodynamic Properties of Hg3Te2I2 1)

The high temperature vaporization pattern of Hg₃Te₂I₂(s,l) shows four distinctly different regimes, similar to those of the HgTe vaporization. The most predominant species in the vapor phase in all four regimes is HgI₂(g), followed by Hg(g) and, possibly, Te₂I₂(g). The width of the “homogeneity range” of Hg₃Te₂I₂(s) was determined to be less than about 0.17 mole‐% HgI₂. Applying the second‐law method to the vaporization of HgTe‐saturated Hg₃Te₂I₂(s) at higher temperatures yields the heat and entropy of vaporization of 20.9 ± 2.3 (kcal/mole) and of 27.5 ± 2.8 (cal/mole K), respectively, with estimated total uncertainties of less than ± 5.8 (kcal/mole) and ± 7.6 (cal/mole K), at an average temperature of 722 K. With an estimated heat capacity function of Hg₃Te₂I₂(s) and estimated thermodynamic values for HgI₂‐saturated HgTe(s), the heat of formation and absolute entropy of Hg₃Te₂I₂(s) are computed to be = ?49.7 ± 1.1 (kcal/mole) and = 97.3 ± 1.4 (cal/mole K), with estimated total uncertainties of ± 8.3 (kcal/mole) and ± 14.0 (cal/mole K). The combined results of this investigation provide valuable information for the crystal growth of this material from the vapor and molten phase.     

Monoclinic AlPO4 tridymite at 473 and 463 K from X‐ray powder data

Upon cooling from its hexagonal high‐temperature modification, AlPO₄ (aluminium phosphate) tridymite successively transforms to several displacively distorted forms, including a normal structure–incommensurate–lock‐in phase transition sequence. The space‐group symmetries in this series are P112₁, P112₁(αβ0) and P2₁2₁2₁, respectively. The distortion pattern of the intermediate P112₁ phase can be described as alternate shifts of adjacent layers of tetrahedra coupled with tilting of the tetrahedra. The symmetry and direction of the shifts are different from the analogous SiO₂ tridymite modification. The atomic displacement parameters of the O atoms are strongly anisotropic due to thermal motions of the rigid tetrahedra. Condensation of a lattice vibration mode results in the formation of an incommensurate structural modulation below 473 K. The 3+1 superspace‐group symmetry of the modulated phase is P112₁(αβ0).     

Electroluminescence from a current-emitting nanostructured silicon device

A three-dimensional silicon based nanodevice mainly consisting of two conductive silicon cantilevers was fabricated out of silicon-on-insulator material by electron beam lithography, reactive ion etching, and fluoride based wet chemical etching. One of the cantilevers is bent and sticks to the silicon substrate while the other one is freely suspended. We observed electroluminescence in the visible range when a voltage of any polarity is dropped across both levers. The measured spectra covered the range 400–950 nm peaking at about 650 nm. The current applied to the device could tune the intensity of the electroluminescence spectrum. Light powers ranging from 160 fW to some pW were measured at frequencies up to 17 kHz. The origin of the electroluminescence is discussed in comparison to porous silicon and spark-processed silicon.     

Zur Titration des Mangans mit amperometrischer Endpunktsanzeige

Analytical and Bioanalytical Chemistry -     

Competition between lipases and monoglycerides at interfaces

Tensiometry (the pendant drop technique), interfacial shear rheology, and ellipsometry have been used to study the effect of polar lipids that are generated during fat digestion on the behavior of lipases at the oil-water interface. Both Sn-1,3 regiospecific and nonregiospecific lipases have been used, and a noncatalytically active protein, beta-lacloglobulin, has been used as reference in the interfacial shear rheology experiments. The results from the pendant drop measurements and the interfacial rheology studies were in agreement with each other and demonstrated that the Sn-2 monoglyceride, which is one of the lipolysis products generated when a Sn-1,3 regiospecific lipase catalyzes triglyceride hydrolysis, is very interfacially active and efficiently expels the enzyme from the interface. Ellipsometry conducted at the liquid-liquid interface showed that the lipase forms a sublayer in the aqueous phase, just beneath the monoglyceride-covered interface. Sn-1/3 monoglycerides do not behave this way because they are rapidly degraded to fatty acid and glycerol and the fatty acid (or the fatty acid salt) does not have enough interfacial activity to expel the lipase from the interface. Since the lipases present in the gastrointestinal tract are highly Sn-1,3 regiospecific, we believe that the results obtained can be transferred to the in vivo situation. The formation of stable and amphiphilic Sn-2 monoglycerides can be seen as a self-regulatory process for fat digestion.