Linear Unidimensional Scaling in the L 2 -Norm: Basic Optimization Methods Using MATLAB

L₂ -norm: (1) dynamic programming; (2) an iterative quadratic assignment improvement heuristic; (3) the Guttman update strategy as modified by Pliner's technique of smoothing; (4) a nonlinear programming reformulation by Lau, Leung, and Tse. The methods are all implemented through (freely downloadable) MATLAB m-files; their use is illustrated by a common data set carried throughout. For the computationally intensive dynamic programming formulation that can a globally optimal solution, several possible computational improvements are discussed and evaluated using (a) a transformation of a given m-function with the MATLAB Compiler into C code and compiling the latter; (b) rewriting an m-function and a mandatory MATLAB gateway directly in Fortran and compiling into a MATLAB callable file; (c) comparisons of the acceleration of raw m-files implemented under the most recent release of MATLAB Version 6.5 (and compared to the absence of such acceleration under the previous MATLAB Version 6.1). Finally, and in contrast to the combinatorial optimization task of identifying a best unidimensional scaling for a given proximity matrix, an approach is given for the confirmatory fitting of a given unidimensional scaling based only on a fixed object ordering, and to nonmetric unidensional scaling that incorporates an additional optimal monotonic transformation of the proximities.     

Zur Austestung von Wachstumsinhibitoren für Tuberkelbazillenin vitro

Summary The addition of serum or Tween 80 to a synthetic culture medium for tubercle bacilli considerably reduces the inhibitory effect of various substances with the exception of streptomycin and promin, whose effect is less weakened, and which retain their tuberculostatic action to a considerable degree. The antagonistic effect of Tween 80 is still recognizable in small dilutions where its diffusion effect can no longer be observed.

---

---

Die Arbeit wurde durch einen Arbeitsbeschaffungskredit des Bundes ermöglicht, für dessen Gewährung wir auch an dieser Stelle danken.     

Inhibition by transmembrane peptides of chimeric insulin receptors

Receptor tyrosine kinases play essential roles in cell proliferation and differentiation. We have recently shown that peptides corresponding to the transmembrane domains of the epidermal growth factor (EGF) and ErbB2 receptors inhibit their corresponding receptor activation in cancer cell lines. We extend this observation to cells transfected with chimeric insulin receptors where the transmembrane domain has been replaced by that of the EGF receptor or a mutated Erb2 domain. Peptides corresponding to the transmembrane domains of the EGF receptor and ErbB2 are able to inhibit specifically the autophosphorylation of insulin receptors with the corresponding domain. This inhibitory effect is correlated with the propensity of the different transmembrane domains to self-associate in a genetic reporter assay. Thus, our data strengthen the notion that transmembrane domains are involved in erbB receptor activation, and that these receptors can be modulated by inhibiting proteinprotein interactions within the membrane.Received 25 May 2005; received after revision 13 July 2005; accepted 22 July 2005     

Phénomènes chromatiques et rythme nycthéméral chezHippolyte varians Leach (crustacé décapode)

Summary Hippolyte varians passes through a daily colour-cycle, but a given pigment shows an opposite behaviour according to the chromatophore pattern. A significant variation in the state of concentration of pigments is observed in males and females.     

Stability of atmospheric CO2 levels across the Triassic/Jurassic boundary

The Triassic/Jurassic boundary, 208 million years ago, is associated with widespread extinctions in both the marine and terrestrial biota. The cause of these extinctions has been widely attributed to the eruption of flood basalts of the Central Atlantic Magmatic Province. This volcanic event is thought to have released significant amounts of CO2 into the atmosphere, which could have led to catastrophic greenhouse warming, but the evidence for CO2-induced extinction remains equivocal. Here we present the carbon isotope compositions of pedogenic calcite from palaeosol formations, spanning a 20-Myr period across the Triassic/Jurassic boundary. Using a standard diffusion model, we interpret these isotopic data to represent a rise in atmospheric CO2 concentrations of about 250 p.p.m. across the boundary, as compared with previous estimates of a 2,000-4,000 p.p.m. increase. The relative stability of atmospheric CO2 across this boundary suggests that environmental degradation and extinctions during the Early Jurassic were not caused by volcanic outgassing of CO2. Other volcanic effects-such as the release of atmospheric aerosols or tectonically driven sea-level change-may have been responsible for this event.