Many Body Problems with "Spin"-Related Contact Interactions

We study quantum mechanical systems with "spin"-related contact interactions in one dimension. The boundary conditions describing the contact interactions are dependent on the spin states of the particles. In particular we investigate the integrability of $N$-body systems with $\delta$-interactions and point spin couplings. Bethe ansatz solutions, bound states and scattering matrices are explicitly given. The cases of generalized separated boundary condition and some Hamiltonian operators corresponding to special spin related boundary conditions are also discussed.Comment: 13 pages, Late

Improving women's and children's nutrition in sub-Saharan Africa : an issues paper

The main sources of malnutrition in Africa, as elsewhere, are inadequate food intake, excessive disease, maternal malnutrition, and deleterious food and health behavior. The authors review several successful innovative approaches to addressing nutrition problems in Africa: the Iringa Nutrition Program in Tanzania, the Zimbabwe Children's Supplementary Feeding Program, the Zaire Weaning Foods Processing Program, and the Senegal Growth Promotion Program. They identify the lessons from these programs, including the need: (a) to involve the community actively in program development; (b) for training in nutrition at all levels, from doctor to village health worker; (c) for strong growth monitoring and nutrition education components; (d) for close supervision, including regular supervisory visits to villages and health huts, discussions with clients, and observations; and (e) for a variety of institutional and financing mechanisms. Africa's nutrition problems require many of the same services as problems elsewhere - growth monitoring, nutrition education, targeted feeding, and food fortification. Africa shares the universal need for good training, management, communications, and information systems. But new and innovative institutional mechanisms are needed to address Africa's nutrition problems. Each country must look for its own institutional strengths and weaknesses in developing nutrition programs.Early Child and Children's Health,Nutrition,Agricultural Knowledge&Information Systems,Primary Education,Health Monitoring&Evaluation

A trapped mercury 199 ion frequency standard

Mercury 199 ions confined in an RF quadrupole trap and optically pumped by mercury 202 ion resonance light are investigated as the basis for a high performance frequency standard with commercial possibilities. Results achieved and estimates of the potential performance of such a standard are given

Crystallographic investigation into the self-assembly, guest binding, and flexibility of urea functionalised metal-organic frameworks

Introduction of hydrogen bond functionality into metal-organic frameworks can enhance guest binding and activation, but a combination of linker flexibility and interligand hydrogen bonding often results in the generation of unwanted structures where the functionality is masked. Herein, we describe the self-assembly of three materials, where Cd2+, Ca2+, and Zn2+ are linked by N,Nʹ-bis(4-carboxyphenyl)urea, and examine the effect of the urea units on structure formation, the generation of unusual secondary building units, structural flexibility, and guest binding. The flexibility of the Zn MOF is probed through single-crystal to single-crystal transformations upon exchange of DMF guests for CS2, showing that the lability of the [Zn4O(RCO2)6] cluster towards solvation enables the urea linkers to adopt distorted conformations as the MOF breathes, even facilitating rotation from the trans/trans to the trans/cis conformation without compromising the overall topology. The results have significant implications in the mechanistic understanding of the hydrolytic stability of MOFs, and in preparing heterogeneous organocatalysts