Our previous studies have shown that hindbrain neural tube cells can regulate to form neural crest cells for a limited time after neural fold removal (Scherson, T., Serbedzija, G., Fraser, S. E. and Bronner-Fraser, M. (1993). Development 188, 1049-1061; Sechrist, J., Nieto, M. A., Zamanian, R. T. and Bronner-Fraser, M. (1995). Development 121, 4103-4115). In the present study, we ablated the do...

Endpoint estimates are proved for model cases of restricted X-ray transforms and singular fractional integral operators in R4.

BACKGROUND & OBJECTIVES The classification of group B streptococcal (GBS) isolates is based on the capsular polysaccharides (Ia-VIII), and antigenic characterization of clinical isolates is augmented by the detection of various surface-localized protein antigens. In our laboratory, all GBS isolates are routinely analysed for the alpha trypsin-resistant and the beta trypsin-sensitive c protein a...

BACKGROUND Cell patterning in the developing central nervous system seem to involve a coordinate system of positional information, in which specific fates are assigned to multipotent precursor cells by positional signals acting on the antero-posterior and dorso-ventral axes of the neural tube. Before neurons differentiate in the hindbrain, it becomes subdivided antero-posteriorly into a series ...

Dirac operators are important geometric operators on a manifold. The Dirac operator DA on the four dimensional Euclidean space M = R is the order one differential operator whose square DA ◦ DA is the Euclidean Laplacian − ∑4 i=1 ∂ψ ∂xi . However, this is not possible unless we allow coefficients for this linear operator to be matrix-valued. Let M = R be the four dimensional Euclidean space with...

We study the homotopy types of complements of arrangements of n transverse planes in R4, obtaining a complete classification for n ≤ 6, and lower bounds for the number of homotopy types in general. Furthermore, we show that the homotopy type of a 2-arrangement in R4 is not determined by the cohomology ring, thereby answering a question of Ziegler. The invariants that we use are derived from the...

Two new bounds for multicolor Ramsey numbers are proved: R(K3,K3, C4, C4) ≥ 27 and R4(C4) ≤ 19.

The model of a stationary universe and the notion of local times presented in [10] are reviewed with some alternative formulation of the consistent unification of the Riemannian and Euclidean geometries of general relativity and quantum mechanics. The method of unification adopted in the present paper is by constructing a vector bundle X ×R6 or X × R4 with X being the observer’s reference frame...