The 1:1 adduct of arginine with 2,5-dihydroxybenzoic acid (DHB) has been studied in the gas phase and in the solid state. Experimentally, the ionization energy (IE) of the 1:1 cluster was determined by wavelength-dependent laser ionization of clusters formed by seeding DHB and arginine into a supersonic jet expansion. Ionization laser power studies performed at several discrete wavelengths established the upper and lower limits for the 1:1 cluster IE and dissociation energy. Subsequent one-color scanned-wavelength laser ionization studies allowed an experimental establishment of the 1:1 cluster IE of 7.193 eV. A combination of molecular dynamics/simulated annealing calculations on the 1:1 cluster followed by density functional theory geometry optimizations using reasonably large basis sets yielded 15 distinct minima on the potential energy surface, all within 5.2 kcal/mol in energy at the B3LYP/6-311++G(2df,2p)//B3LYP/6-31+G** level. The Boltzmann-averaged IE at the same level is 7.11−7.14 eV, in excellent agreement with experiment. Cocrystals of arginine and DHB have been grown, and the crystal structure has been solved. The dominant intermolecular interaction in the cocrystal is a double hydrogen bond (salt bridge) between the guanidinium group of arginine and the (deprotonated) carboxylate group of DHB. This is exactly the same interaction that is found in the lowest-energy structure of the gas-phase 1:1 adduct. The electronic structure of the solid-state cocrystal has been modeled using a cluster approach.
The California Current System (CCS) is one of the best sampled ocean regions, yet it remains obscurely understood and inadequately sampled.Technological advances in ocean modeling and observational techniques can now change this situation. Enhanced understanding of the features and dynamics of the CCS can aid fisheries and wildlife management, prediction and abatement of pollution and toxic phytoplankton blooms, atmospheric and climate change forecasts, and shipping and military operations.
The effects of baroclinicity on the air and ocean boundary layers under conditions for strong dynamical (compared to thermodynamic) forcing are studied by use of a numerical model of air-sea interaction, which consists of a closed system of equations including equations of motion, turbulent kinetic energy, turbulent exchange coefficient, local turbulent length scale, and assumptions of fixed stratification and baro½linicity in both the atmosphere and ocean. Baro½linicity is incorporated into the equations of motion by specifying horizontal gradients of air temperature in the atmosphere and seawater density in the ocean. Experiments were conducted to determine the effects of different magnitudes and directions of baroclinicity and of atmospheric stratification on the dynamical and turbulent structure of the interacting boundary layers. The results of the simulations demonstrate that certain levels of baroclinicity produce double maxima in the K profiles in the atmosphere and ocean. Baro½linic effects change the dominant components of the turbulent kinetic energy in both air and sea boundary layers from shear production and dissipation for dimensionless heights and depths of less than 0.1 (about 20% of the height or depth of the boundary layer at zero surface heat flux) to shear production and buoyant destruction for dimensionless heights and depths greater than 0.1. The results show that the most significant effects of baroclinicity in the air and sea boundary layers are the increases in turbulent exchange coefficient, turbulent kinetic energy budget, shear stresses, and dimensionless wind and windinduced current in the regions of the boundary layers far from the interface. The results of the simulations also show that for fixed stratification and baroclinicity, surface quantities (e.g., friction velocity, drag coefficient, and geostrophic drag coefficient) are affected more by surface heat flux than by barodinicity, whereas the opposite is true for characteristics of the whole boundary layer (e.g., boundary layer height and angle between the geostrophic wind and surface stress). Our results show good agreement with the few observations that have been taken where baroclinicity has been reported. INTRODUCTIONA more complete knowledge of air-sea interaction is necessary for advancing our understanding of phenomena ranging from small-scale turbulence in both the atmospheric and oceanic boundary layers to global-scale weather and climate. The ocean is a global-scale reservoir of heat and moisture whose temperature changes locally only very slowly compared with the diurnal cycle, thereby allowing for examination by use of stationary models. The ocean and atmosphere are dynamically and thermodynamically coupled through turbulent exchange processes at the interface. where u,• is the friction velocity of the corresponding boundary layer. We have taken the factor a, which may be a function of the ratio of boundary layer densities, to be an empiri- Baroclinicity is introduced into the governing equations by letting terms...
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