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Notes: A cluster model for the binding of Cs atoms on the (110) surface of GaAs is examined for polarization, charge transfer, and dispersion interactions. Binding energies for two or three atom clusters on GaAs are calculated to be less than 0.1 eV per Cs atom indicating only small binding contributions from charge transfer and polarization. Orbital and total charge density plots reveal an alkali valence charge weakly bonded between the alkali atoms and polarized toward the Ga atom. A London analysis of the dispersion energy between quasilinear Cs clusters and GaAs clusters finds it is large compared to the difference in stability between polyhedral clusters and the quasilinear clusters that are experimentally observed on the GaAs surface. The large dispersion energy is due to the large polarizabilities for quasilinear chains of Cs atoms whose longitudinal component increases approximately with the square of the chain length.

Notes: Energy curves of Cs2 that correlate to the ground (SS) and first excited asymptote (SP) are calculated using compact effective potentials (CEP) and core polarization potentials (CPP) which reduce the alkali atom to a single valence electron. Dissociation energies and equilibrium internuclear separations are in good agreement with experimental values. The long-range properties of the energy curves are analyzed to determine the region where the chemical interactions begin. Analogous energy curves and spectroscopic constants are obtained for the Rb2 molecule. The ground state singlet and triplet energy curves are also determined for K2. For completeness, the ground state spectroscopic constants are also reported for the Li and Na neutral and cation homonuclear diatomic molecules to illustrate the accuracy of the CEP and CPP for all the alkali atoms. Both doublet and quartet energy curves of the homonuclear anions also were examined. The dissociation energies and electron detachment energies of the doublet ground state for Rb−2 and Cs−2 are in good agreement with experiment. An assignment of the photoelectron spectra of Cs−2 is possible from the electronic structure of the ground state and the excitation energies of the neutral states. Quartet excited states of Cs−2 are calculated to be bound relative to the 3Σ+u neutral state but are metastable with respect to the ground 1Σ+g state. The accuracy of the ionic energy curves shows that the CEP and CPP are transferrable to the ionic systems.

Notes: Eighteen children with perennial asthma and allergy to house-dust mite (HDM) underwent a bronchial challenge with HDM. Before and 24 h after the test, a venous blood sample was taken to determine levels of eosinophils, eosinophil cationic protein (ECP), soluble interleukin-2 receptor (IL-2R), and interleukin-6 (IL-6). A histamine challenge was performed before and 24 h after the HDM challenge. All subjects showed an immediate asthmatic reaction (IAR). A definite late asthmatic reaction (LAR) was observed in 15 children, a probable LAR in two, and no LAR in one. Because of persistent bronchial obstruction (FEV1〉70%), eight children were unable to perform a histamine challenge 24 h after the allergen challenge. These were the children with the lowest prechallenge provocation dose (PD20) of histamine. In the other 10 children, the mean PD20 histamine decreased after the HDM challenge (mean PD20 before was 0.56 mg/ml; after challenge it was 0.14 mg/ml; P= 0.007). After the HDM challenge, an increase was detected in the mean values of blood eosinophils (mean before was 446/mm3; mean after was 733/mm3; P= 0.002), ECP (mean before was 26.3 μg/1; mean after was 34.3 μg/1; P〈0.040), and IL-2R (mean before was 116.35 U/ml; mean after was 128.52 U/ml; P〈0.040). On the other hand, IL-6 remained unchanged after the HDM challenge (mean before was 9.47 pg/1; mean after was 9.70 pg/1; P= 0.360). Furthermore, as compared with a group of normal, age-matched children (n =18), asthmatic children were found to have higher prechallenge levels of ECP (mean: 10.3 μg/1 compared with 26.3 μg/1) (P〉0.001) and IL-2R (mean: 80.30 U/ml compared with 116.35 U/ml) (P =0.009), but not of IL-6 (mean: 11.34 pg/1 compared with 9.47 pg/1) (P = 0.436).A correlation was found between the duration of asthma and the severity of the LAR expressed as area under the curve (AUCLAR) (r = 0.50; P〈0.040). Furthermore, a correlation was detected between the level of total IgE and the level of ECP (r = 0.51; P〈0.030). The decrease in FEV1 during the LAR tended to correlate with the increase of IL-2R (r = 0.48; P = 0.050). This tendency was not found with the increase of eosinophils, nor with the increase of ECP. We conclude that both lymphocytes and eosinophils are activated by an allergen challenge, but that only the activation of lymphocytes tends to correlate with the LAR, suggesting that lymphocytes are also closely involved in the pathogenesis of the allergen-induced LAR.

Notes: With the conventional, discrete RAST various tests are required to detect IgE of different specificities in the same serum. To overcome this problem and to reduce the costs, a multiple RAST with seven different mixtures was compared with the individual mixture constituents and with the 12 individual allergens currently in use in our department. One grass pollen mixture (gx3), two weed pollen mixtures (wx3, wx4), two tree pollen mixtures (tx5, tx6), one mould mixture (mx1) and one epithelial mixture (ex1) were used. A mixture of mites was not evaluated as there is only one important pathogenic organism in our regions (Dermatophagoides pteronyssinus or House dust mite). For grasses the gx3 mixture offered no advantage over the discrete RAST. The weed mixture wx3 was more sensitive than the most common discrete RAST's but at the cost of specificity. The wx4 mixture should not be used because the specificity is too low. The tree mixtures were not significantly more sensitive than the most common individual tree allergens, and were less specific. Mould mixtures should not be used because there is little cross-reactivity between the individual allergens, thus using a mixture would necessitate the subsequent determination of individual allergens, and the number of tests and the cost would be even higher. Neither should a mixture be used for epithelia because one wants to detect allergies to individual allergens. Moreover, the sensitivity of the epithelial mixture was too low. In general, we suggest the use of a limited panel of discrete RAST's instead of mixtures.