R Symmetry Breaking Versus Supersymmetry Breaking

We point out a connection between R symmetry and \susy\ breaking. We show that the existence of an R symmetry is a necessary condition for \susy\ breaking and a spontaneously broken R symmetry is a sufficient condition provided two conditions are satisfied. These conditions are: {\it genericity}, \ie\ the effective Lagrangian is a generic Lagrangian consistent with the symmetries of the theory (no fine tuning), and {\it calculability}, \ie\ the low energy theory can be described by a supersymmetric Wess-Zumino effective Lagrangian without gauge fields. All known models of dynamical supersymmetry breaking possess such a spontaneously broken R symmetry and therefore contain a potentially troublesome axion. However, we use the fact that genericity is {\it not} a feature of supersymmetric theories, even when nonperturbative renormalization is included, to show that the R symmetry can in many cases be explicitly broken without restoring supersymmetry and so the axion can be given an acceptably large mass.Comment: 20 pages, UCSD/PTH 93-27, RU-93-4

Blind test of density-functional-based methods on intermolecular interaction energies

In the past decade, a number of approaches have been developed to fix the failure of (semi) local density-functional theory (DFT) in describing intermolecular interactions. The performance of several such approaches with respect to highly accurate benchmarks is compared here on a set of separation-dependent interaction energies for ten dimers. Since the benchmarks were unknown before the DFT-based results were collected, this comparison constitutes a blind test of these methods

Surface Binding of Organophosphates on Silica: Comparing Experiment and Theory

A consistent embedding hierarchy is applied to the calculation of binding enthalpies for organophosphate molecules to a silica surface and compared to experiment. The interaction of four probe molecules, dimethyl methylphosphonate (DMMP), diisopropyl methylphosphonate (DIMP), diisopropyl fluorophosphate (DFP), and sarin, with the silica surface is examined. Quantum chemical methods are employed to compute binding enthalpies and vibrational spectra for all interactions between probe molecules and silanol sites on the silica surface. Comparison with experimentally measured infrared shifts indicates that the theoretically modeled adsorption sites are similar to those found in experiment. The calculated binding enthalpies agree well with experiment for sarin, Δ<i>H</i>_ads,443K = −22.0 kcal/mol (calculated) vs −18.8 ± 5.5 kcal/mol (measured, 433 K < <i>T</i>_expt < 453 K), and DIMP, Δ<i>H</i>_ads,463K = −26.9 kcal/mol (calculated) vs −29.3 ± 0.9 kcal/mol (measured, 453 K < <i>T</i>_expt < 473 K). Agreement with experiment is less good for DMMP, Δ<i>H</i>_ads,463K = −19.7 kcal/mol (calculated) vs −26.1 ± 1.5 kcal/mol (measured, 453 K < <i>T</i>_expt < 473 K), and DFP, Δ<i>H</i>_ads,423K = −20.4 kcal/mol (calculated) vs −27.5 ± 3.1 kcal/mol (measured, 413 K < <i>T</i>_expt < 433 K)

Crescimento e composição mineral do porta-enxerto tangerineira cleópatra cultivado em substrato acrescido de polímero hidrorretentor Growth and mineral composition of the cleópatra mandarin rootstock growing on substratum added with hidroretentive polymers

Os efeitos de polímero hidrorretentor acrescido ao substrato foi avaliado na fase inicial de produção do porta-enxerto tangerineira 'Cleópatra' cultivado em tubetes plásticos com substrato comercial à base de casca de Pinus compostada e parcialmente fertilizado. Foi utilizado o delineamento experimental de blocos casualizados com três repetições, sendo os tratamentos seis doses do hidrorretentor (0, 4, 8, 12, 16 e 32 mg.dm-3) incorporado ao substrato, com 60 plantas úteis por parcela. Avaliaram-se o Índice de Velocidade de Emergência (IVE), altura de planta, peso da matéria seca total e seus teores de N, P, K, Ca, Mg, S, B, Cu, Mn, Zn e Fe, e valores de pH do substrato ao final do período experimental. A incorporação do hidrorretentor ao substrato de cultivo promoveu elevação nos valores do pH do substrato, decréscimos no IVE, no crescimento e no peso da matéria seca total, não havendo alteração expressiva no estado nutricional dos porta-enxertos aos 150 dias pós-semeadura.<br>The effects of hidroretentive polymers added to the substratum was evaluated in the initial phase of production of 'Cleópatra' mandarin rootstock. They were cultivated in container seedlings with commercial pine bark substratum composted and partially fertilized. The randomized blocks experimental design was used with three replications, being the treatments six doses of the hydroretentive polymer (0, 4, 8, 12, 16 and 32 mg.dm-3) incorporated to the substratum. The Index of Emergency Speed (IVE), plant height, weight of the matter total drought and their tenors of N, P, K, Ca, Mg, S, B, Cu, Mn, Zn and Fe, and values of pH substratum were evaluated. The use of incorporated hydroretentive polymer to the cultivation substratum increased the values of pH of the substratum, decreases in IVE, the growth and the weight of the total dry matter, not having expressive alteration in the nutritional state of the rootstocks