Spontaneous plaquette dimerization in the J1−J2J_1-J_2 Heisenberg model

We investigate the non magnetic phase of the spin-half frustrated Heisenberg antiferromagnet on the square lattice using exact diagonalization (up to 36 sites) and quantum Monte Carlo techniques (up to 144 sites). The spin gap and the susceptibilities for the most important crystal symmetry breaking operators are computed. A genuine and somehow unexpected `plaquette RVB', with spontaneously broken translation symmetry and no broken rotation symmetry, comes out from our numerical simulations as the most plausible ground state for $J_2/J_1 \simeq 0.5$.Comment: 4 pages, 5 postscript figure

The Yin and Yang of How N-Terminal Acyl Caps Affect Collagen Triple Helices

N-terminal acylation is a common tool for the installationof functionalmoieties (e.g., sensors or bioactive molecules) on collagen modelpeptides (CMPs). The N-acyl group and its lengthare generally assumed to have little or no influence on the propertiesof the collagen triple helix formed by the CMP. Here, we show thatthe length of short (C-1-C-4) acyl cappinggroups has different effects on the thermal stability of collagentriple helices in POG, OGP, and GPO frames. While the effect of differentcapping groups on the stability of triple helices in the GPO frameis negligible, longer acyl chains stabilize OGP triple helices butdestabilize POG analogues. The observed trends arise from a combinationof steric repulsion, the hydrophobic effect, and n -> pi* interactions. Our study provides a basis for thedesign of N-terminally functionalized CMPs with predictable effectson triple helix stability.ISSN:1525-7797ISSN:1526-460

RISE- Response-inducing sustainability evaluation

RISE is a computer-supported indicator-based method for assessing the economic, social and environmental sustainability performance of agricultural production at the farm level. The purpose of RISE is to contribute to enhancing the sustainability of agricultural production, by supporting knowledge-based processes that are founded on voluntary participation, confidentiality and capacity building. The evaluation is based on ten indicators that reflect environmental, economic and social aspects. The most important data source is a questionnaire-based interview with the farmer. The evaluated data are visualized as a sustainability polygon and serve as a basis to a feedback dialogue in which the farmer and the trained RISE consultant jointly identify potentials for improving farm sustainability performance. Training in the RISE method for professionals in the agriculture and related industries are regularly carried out. On completion of the course, participants are able to use the RISE method independently to evaluate the sustainability of agricultural operations. RISE is aimed at agricultural consultants, for use in education, in development projects and in raw material sourcing. The tool is internationally relevant for all farms, organic and conventional. The software has been tested around the world, is available in seven languages and can be used both on- and off-line

Competing pathways for photoremovable protecting groups: the effects of solvent, oxygen and encapsulation

Extending the applications of Photoremovable Protecting Groups (PPGs) to "cage" phenols has generally met with unusually complex PPG byproducts. In this study, we demonstrate that thep-hydroxyphenacyl (pHP) cage for both simple and complex phenolics, including tyrosine, dispenses free phenols. With the simpler unsubstituted phenols, the reaction is governed by their Bronsted Leaving Group ability. On the other hand, the byproducts of the cage vary with these phenols. For the more acidic phenols the cage byproduct follows the Favorskii rearrangement to formp-hydroxyphenylacetic acid whereas for the weaker phenols other reactions such as reduction and hydrolysis begin to emerge. When the photolysis is conducted in octa acid (OA) containers, non-Favorskii, unrearranged fragments of the cage and other byproducts arise.Kansas University Endowment AssociationNational Institutes of HealthUnited States Department of Health & Human ServicesNational Institutes of Health (NIH) - USANational Science FoundationNational Science Foundation (NSF) [CHE-1807729]FCT - Foundation for Science and TechnologyPortuguese Foundation for Science and Technology [UID/Multi/04326/2019]operational program COMPETE 2020 [EMBRC.PT ALG-01-0145-FEDER-022121]info:eu-repo/semantics/publishedVersio