Negative Additive Manufacturing of Complex Shaped Boron Carbides.

Boron carbide (B4C) is one of the hardest materials in existence. However, this attractive property also limits its machineability into complex shapes for high wear, high hardness, and lightweight material applications such as armors. To overcome this challenge, negative additive manufacturing (AM) is employed to produce complex geometries of boron carbides at various length scales.

Charge and temperature dependence of biomolecule conformations: K+ tryptamine(H2O)(n=0-1)Ar(m=0-1) cluster ions.

The impact of temperature and charge on the conformation of tryptamine (Tryp) is examined in the gas phase by infrared laser-vibrational predissociation spectroscopy in the 2800-3800 cm(-1) region. Previous studies of neutral Tryp(H(2)O)(n) clusters showed preferential stabilization of specific tryptamine conformers through hydrogen bonding. When complexed with the biologically significant potassium ion, the only conformers found to form under these experimental conditions are built on hitherto unobserved neutral Tryp conformers.

Hydrated alkali-metal cations: infrared spectroscopy and ab initio calculations of M+(H2O)(x=2-5)Ar cluster ions for M = Li, Na, K, and Cs.

A delicate balance between competing and cooperating noncovalent interactions determines the three-dimensional structure of hydrated alkali-metal ion clusters. With a single water molecule hydrating an ion, the electrostatic ion..

Entropic effects on hydrated alkali-metal cations: infrared spectroscopy and ab initio calculations of M+(H2O)(x=2-5) cluster ions for M = Li, Na, K, and Cs.

A delicate balance between competing and cooperating noncovalent interactions determines the three-dimensional structure of hydrated alkali-metal ion clusters. A critical factor influencing the balance reached is the internal energy content (or effective temperature) of the ion cluster. Cold cluster ions (approximately 50-150 K) have little internal energy, and enthalpic contributions have a greater influence on the relative population of low-lying minima.

Modeling competitive interactions in proteins: vibrational spectroscopy of M+(n-methylacetamide)1(H2O)n=0-3, M=Na and K, in the 3 microm region.

To properly understand the preferred structures and biological properties of proteins, it is important to understand how they are influenced by their immediate environment. Competitive intrapeptide, peptide..

Structures, energetics, and spectra of aqua-cesium (I) complexes: an ab initio and experimental study.

The design of cesium-selective ionophores must include the nature of cesium-water interactions. The authors have carried out extensive ab initio and density functional theory calculations of hydrated cesium cations to obtain reasonably accurate energetics, thermodynamic quantities, and IR spectra. An extensive search was made to find the most stable structures.

Hydration of ion-biomolecule complexes: ab initio calculations and gas-phase vibrational spectroscopy of K+ (indole)m(H2O)n.

In recent years neutral indole(H2O)n clusters have been used to model the hydration of biomolecules containing an indole moiety. Both experimental and theoretical studies of the binary indole..

Mimicking solvent shells in the gas phase. II. Solvation of K+.

The observed gas-phase coordination number of K+ in K+(H2O)m clusters is smaller than that observed in bulk solution, where the coordination number has been reported to be between 6 and 8. Both theoretical and gas-phase studies of K+(H2O)m cluster ions point to a coordination number closer to 4. In the gas phase, the coordination number is determined by a variety of factors-the most critical being the magnitude of the K+.