Efficient bifunctional gallium-68 chelators for positron emission tomography: tris(hydroxypyridinone) ligands

A new tripodal tris(hydroxypyridinone) bifunctional chelator for gallium allows easy production of (68)Ga-labelled proteins rapidly under mild conditions in high yields at exceptionally high specific activity and low concentration.     

The liquid state of large clusters with pairwise atomic interactions

Formation of the liquid state for clusters with a pair interaction between atoms is examined within the framework of the void model, in which configurational excitation of atoms results from formation of voids. Void parameters are found from computer simulation by molecular dynamics methods for Lennard-Jones clusters and from real thermodynamic parameters of the liquid states of condensed inert gases. Phase transitions are analyzed in terms of two aggregate states. This information allows us to divide the entropy jump during the solid-liquid phase transitions in two parts, so that one corresponds to configuration excitation at zero temperature, and the other is a contribution from thermal vibrations of atoms. The latter part contributes from approximately 40% for Lennard-Jones clusters consisting of 13 and 55 atoms up to 56% for bulk inert gases. These magnitudes explain the validity of melting criteria based on thermal motion of atoms, even though this phase transition results from configurational excitation of ensembles of bound atoms. It is shown that the void concept allows us to analyze various aspects of the liquid state of clusters including the existence of the freezing temperature below which no metastable liquid state exists, and the properties of glassy states which may exist below the freezing point.     

Phase transitions in simple clusters

Formation of the liquid state of clusters with pairwise interactions between atoms is examined within the framework of the void model, in which configurational excitation of atoms results from formation of voids. Void parameters are found from computer simulation by molecular dynamics methods for Lennard-Jones clusters. From that standpoint, phase transitions are analyzed in terms of two aggregate states. This information allows us to divide the entropy jump during a solid-liquid phase transition into two parts: one corresponds to configurational excitation at zero temperature and the other arises from thermal vibrations of atoms. The latter part contributes approximately 40% for Lennard-Jones clusters consisting of 13 and 55 atoms, increasing to 56% for bulk inert gases. These magnitudes explain the validity of melting criteria based on thermal motion of atoms, even though the distinctive mechanism of this phase transition results from configurational excitations. It is shown that the void concept allows analyzing various aspects of the liquid state of clusters including the existence of a limiting freezing temperature below which no metastable liquid state exists, as well as the existence and properties of glassy states that may exist below the freezing limit.     

Dilute solution studies of pyrrone prepolymers

Data on dilute solutions of a pyrrone “prepolymer” are presented and the tendency of this polymer to aggregate in certain solvents commonly used in dilute solution studies is discussed. It is concluded that reliable molecular weights can be determined if solvents that interact with the prepolymer through hydrogen bonding are used.     

Unequal freezing and melting temperatures for clusters

Using a previously introduced quantum statistical model, analyze necessary and sufficient conditions on the density of states for coexistence of liquid and solid clusters. We conclude that clusters of N particles have sharp freezing and melting temperatures limiting the ranges of phase stability and that these temperatures are unequal.     

High power,single frequency operation of a Q-switched TEM00 Mode NdYAG laser

An actively Q-switched NdYAG laser, using a telescopic resonator configuration has produced single longitudinal mode, TEM₀₀ outputs of 100 mJ with output pulses free from any observable mode-beating.     

Cryoscopy on sulfuric acid solutions of a heterocyclic polymer (BBB) and related compounds

Cryoscopic measurements have been carried out on solutions in sulfuric acid of a heterocyclic polymer, its monomers, and certain of its oligomers. The polymer, BBB, is prepared by the polycondensation of 1,4,5,8-naphthalenetetracarboxylic acid (NTC) with 3,3′-diaminobenzidine (DAB). The results show that the polymer, its oligomers and one of its monomers, DAB, are all extensively protonated in sulfuric acid, whereas its other monomer is not. The degree of protonation appears to be greater for the polymer than for its low molecular weight oligomers.