On Eisenbud's and Wigner's R-matrix: A general approach

The main objective of this paper is to give a rigorous treatment of Wigner's and Eisenbud's R-matrix method for scattering matrices of scattering systems consisting of two selfadjoint extensions of the same symmetric operator with finite deficiency indices. In the framework of boundary triplets and associated Weyl functions an abstract generalization of the R-matrix method is developed and the results are applied to Schrödinger operators on the real axis.     

Nonlinear modeling of hysteretic systems with double hysteretic loops using position and acceleration information

This paper presents two new dynamic hysteresis models obtained from the Bouc–Wen model by incorporating position and acceleration information. On the one hand, the model employing position information is rate-independent and it is able to reproduce some kind of double hysteretic loops unable to be reproduced with the original Bouc–Wen model. On the other hand, the model employing acceleration information is insensitive to linear time-scale variations. Moreover, a classification of the BIBO-stable models has been derived for both position and acceleration cases. Double hysteretic loops have been experimentally reported in shape-memory alloys, reinforced concrete structures, wood structures and lightweight steel shear wall structures. The proposed hysteretic models represent a prominent use in the field of structural dynamics and earthquake engineering because they can capture the nonlinear dynamics of the materials and structures presented earlier when they are subjected to dynamic loads as earthquake excitations.     

Simulated Molecular Evolution for Anticancer Peptide Design

A computational technique based on a simulated molecular evolution protocol was employed for anticancer peptide (ACP) design. Starting from known ACPs, innovative bioactive peptides were automatically generated in computer‐assisted design–synthesize–test cycles. This design algorithm offers a viable strategy for the generation of novel peptide sequences, without requiring a priori structure–activity knowledge. Sequence morphing and activity improvement were achieved through iterative amino acid variation and selection. Results show that not only the interaction of ACPs with the target membrane is important for their anticancer activity, but also the degree of peptide dimerization, which was corroborated by temperature profiling and electrospray mass spectrometry.     

Systematic Experimental Study on Quantum Sieving of Hydrogen Isotopes in Metal-Amide-Imidazolate Frameworks with narrow 1-D Channels

Quantum sieving of hydrogen isotopes is experimentally studied in isostructural hexagonal metal-organic frameworks having 1-D channels, named IFP-1, −3, −4 and −7. Inside the channels, different molecules or atoms restrict the channel diameter periodically with apertures larger (4.2 Å for IFP-1, 3.1 Å for IFP-3) and smaller (2.1 Å for IFP-7, 1.7 Å for IFP-4) than the kinetic diameter of hydrogen isotopes. From a geometrical point of view, no gas should penetrate into IFP-7 and IFP-4, but due to the thermally induced flexibility, so-called gate-opening effect of the apertures, penetration becomes possible with increasing temperature. Thermal desorption spectroscopy (TDS) measurements with pure H₂ or D₂ have been applied to study isotope adsorption. Further TDS experiments after exposure to an equimolar H₂/D₂ mixture allow to determine directly the selectivity of isotope separation by quantum sieving. IFP-7 shows a very low selectivity not higher than S=2. The selectivity of the materials with the smallest pore aperture IFP-4 has a constant value of S≈2 for different exposure times and pressures, which can be explained by the 1-D channel structure. Due to the relatively small cavities between the apertures of IFP-4 and IFP-7, molecules in the channels cannot pass each other, which leads to a single-file filling. Therefore, no time dependence is observed, since the quantum sieving effect occurs only at the outermost pore aperture, resulting in a low separation selectivity.     

New efficient catalyst for ammonia synthesis: barium-promoted cobalt on carbon

Barium-promoted cobalt catalysts supported on carbon exhibit higher ammonia activities at synthesis temperatures than the commercial, multipromoted iron catalyst and also a lower ammonia inhibition.     

Deconfinement transition in three-dimensional compact U(1) gauge theories coupled to matter fields

It is shown that permanent confinement in three-dimensional compact U(1) gauge theory can be destroyed by matter fields in a deconfinement transition. This follows from a nontrivial infrared fixed point caused by matter, and an anomalous scaling dimension of the gauge field. This leads to a logarithmic interaction between the defects of the gauge fields, which form a gas of magnetic monopoles. For logarithmic interactions, the original electric charges are unconfined. The confined phase, which is permanent in the absence of matter fields, is reached at a critical electric charge, where the interaction between magnetic charges is screened by a pair-unbinding in a Kosterlitz-Thouless-like phase transition.     

Smaller and faster: the 20-residue Trp-cage protein folds in 4 micros

We have used laser temperature jump spectroscopy to measure the folding speed of the 20-residue Trp-cage, the smallest polypeptide known to exhibit truly cooperative folding behavior. The observed folding time (4 mus at room temperature) makes this not only the smallest foldable protein, but also the fastest, with a folding speed that exceeds contact-order predictions and approaches anticipated diffusional "speed limits" for protein folding.     

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