Wrocław University of Technology

About: Wrocław University of Technology is a education organization based out in Wrocław, Poland. It is known for research contribution in the topics: Laser & Fuzzy logic. The organization has 13115 authors who have published 31279 publications receiving 338694 citations.

Photonic crystal fibers for sensing applications

Abstract: This paper discusses the sensing capabilities of the highly birefringent index-guided photonic crystal fibers (PCFs) such as dispersion characteristics of phase and group modal birefringence, polarization characteristics, sensitivity to hydrostatic pressures, temperature, and strain. Different types of applications including interferometric and polarimetric sensors of different physical parameters as well as evanescent field sensors for monitoring specific chemical compounds in gases and liquids are reported.

Inconsistency of knowledge and collective intelligence

Abstract: Is the intelligence of a collective larger than the intelligence of its members? How does one determine the knowledge of a collective on the basis of the knowledge of its members? In this paper, we try to answer these questions. Many examples show that the knowledge of a collective is not a usual union of the knowledge of its members. If we assume that the members of a collective possess their knowledge states about some common real world, and these states reflect to some degree the proper (real) state of the knowledge about the real world, then a question arises: How does one determine the knowledge of the collective, and what is its quality? In this paper, we use Consensus Theory to solve this problem and to show that, in many cases, the collective knowledge state is more proper than the knowledge states of the collective intelligence.

Transition state stabilization and substrate strain in enzyme catalysis: ab initio QM/MM modelling of the chorismate mutase reaction.

Abstract: To investigate fundamental features of enzyme catalysis, there is a need for high-level calculations capable of modelling crucial, unstable species such as transition states as they are formed within enzymes. We have modelled an important model enzyme reaction, the Claisen rearrangement of chorismate to prephenate in chorismate mutase, by combined ab initio quantum mechanics/molecular mechanics (QM/MM) methods. The best estimates of the potential energy barrier in the enzyme are 7.4–11.0 kcal mol−1 (MP2/6-31+G(d)//6-31G(d)/CHARMM22) and 12.7–16.1 kcal mol−1 (B3LYP/6-311+G(2d,p)//6-31G(d)/CHARMM22), comparable to the experimental estimate of ΔH‡ = 12.7 ± 0.4 kcal mol−1. The results provide unequivocal evidence of transition state (TS) stabilization by the enzyme, with contributions from residues Arg90, Arg7, and Arg63. Glu78 stabilizes the prephenate product (relative to substrate), and can also stabilize the TS. Examination of the same pathway in solution (with a variety of continuum models), at the same ab initio levels, allows comparison of the catalyzed and uncatalyzed reactions. Calculated barriers in solution are 28.0 kcal mol−1 (MP2/6-31+G(d)/PCM) and 24.6 kcal mol−1 (B3LYP/6-311+G(2d,p)/PCM), comparable to the experimental finding of ΔG‡ = 25.4 kcal mol−1 and consistent with the experimentally-deduced 106-fold rate acceleration by the enzyme. The substrate is found to be significantly distorted in the enzyme, adopting a structure closer to the transition state, although the degree of compression is less than predicted by lower-level calculations. This apparent substrate strain, or compression, is potentially also catalytically relevant. Solution calculations, however, suggest that the catalytic contribution of this compression may be relatively small. Consideration of the same reaction pathway in solution and in the enzyme, involving reaction from a ‘near-attack conformer’ of the substrate, indicates that adoption of this conformation is not in itself a major contribution to catalysis. Transition state stabilization (by electrostatic interactions, including hydrogen bonds) is found to be central to catalysis by the enzyme. Several hydrogen bonds are observed to shorten at the TS. The active site is clearly complementary to the transition state for the reaction, stabilizing it more than the substrate, so reducing the barrier to reaction.