Most of our knowledge of the electronic structure of atoms and molecules is derived from excitation energies and transition probabilities. These observable quantities are related to the electronic wave functions by integrals over unmeasured variables. Another observable more directly related to the wave function than energy or transition probability is the single-electron momentum density, the probability that an electron in a well-defined orbital has a given value of momentum. Over the last twenty years a technique has been developed for measuring momentum densities in atoms and molecules. The technique, (e,2e) spectroscopy, is based on electron-impact ionization with complete determination of the momentum of both incoming and outgoing electrons. The conditions necessary to extract momentum-density information from the ionization experiments are examined and related to general theories of electron scattering. Different experimental arrangements are reviewed and momentum-density results from selected examples are discussed.

Electron transmission spectra and mass spectra of negative ions from dissociative electron attachment have been obtained for four series of halogenated alkenes: vinyl halides, chloroethylenes, halobenzenes, para-dihalobenzenes. The stabilizing effect of halogen substituents upon anion state energies is obvious. Systematic observations permit assignment ofã nd n anion states. Dissociative attachment usually proceeds through the n anion state. An enormous enhancement of the cross section for dissociative attachment of threshold electrons is observed in some cases.

Unrivalled in its coverage and unique in its hands-on approach, this guide to the design and construction of scientific apparatus is essential reading for every scientist and student of engineering, and physical, chemical, and biological sciences. Covering the physical principles governing the operation of the mechanical, optical and electronic parts of an instrument, new sections on detectors, low-temperature measurements, high-pressure apparatus, and updated engineering specifications, as well as 400 figures and tables, have been added to this edition. Data on the properties of materials and components used by manufacturers are included. Mechanical, optical, and electronic construction techniques carried out in the lab, as well as those let out to specialized shops, are also described. Step-by-step instruction supported by many detailed figures, is given for laboratory skills such as soldering electrical components, glassblowing, brazing, and polishing.

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Enteroaggregative Escherichia coli (EAEC) is increasingly recognized as a major cause of diarrheal disease globally. In the current study, we investigated the impact of zinc deficiency on the host and pathogenesis of EAEC. Several outcomes of EAEC infection were investigated including weight loss, EAEC shedding and tissue burden, leukocyte recruitment, intestinal cytokine expression, and virulence expression of the pathogen in vivo. Mice fed a protein source defined zinc deficient diet (dZD) had an 80% reduction of serum zinc and a 50% reduction of zinc in luminal contents of the bowel compared to mice fed a protein source defined control diet (dC). When challenged with EAEC, dZD mice had significantly greater weight loss, stool shedding, mucus production, and, most notably, diarrhea compared to dC mice. Zinc deficient mice had reduced infiltration of leukocytes into the ileum in response to infection suggesting an impaired immune response. Interestingly, expression of several EAEC virulence factors were increased in luminal contents of dZD mice. These data show a dual effect of dietary zinc in benefitting the host while impairing virulence of the pathogen. The study demonstrates the critical importance of zinc and may help elucidate the benefits of zinc supplementation in cases of childhood diarrhea and malnutrition.