Putative intermediates in the nerve cell differentiation pathway in hydra have properties of multipotent stem cells

We have investigated the properties of nerve cell precursors in hydra by analyzing the differentiation and proliferation capacity of interstitial cells in the peduncle of Hydra oligactis, which is a region of active nerve cell differentiation. Our results indicate that about 50% of the interstitial cells in the peduncle can grow rapidly and also give rise to nematocyte precursors when transplanted into a gastric environment. If these cells were committed nerve cell precursors, one would not expect them to differentiate into nematocytes nor to proliferate apparently without limit. Therefore we conclude that cycling interstitial cells in peduncles are not intermediates in the nerve cell differentiation pathway but are stem cells. The remaining interstitial cells in the peduncle are in G1 and have the properties of committed nerve cell precursors (Holstein and David, 1986). Thus, the interstitial cell population in the peduncle contains both stem cells and noncycling nerve precursors. The presence of stem cells in this region makes it likely that these cells are the immediate targets of signals which give rise to nerve cells

Politics of Language: The California Bilingual Education Initiative

This essay examines issues of power and multiculturalism in relation to the education of children through debate over monolingual versus bilingual education and how language is a source of power

Phonon Squeezing in a Superconducting Molecular Transistor

Josephson transport through a single molecule or carbon nanotube is considered in the presence of a local vibrational mode coupled to the electronic charge. The ground-state solution is obtained exactly in the limit of a large superconducting gap, and is extended to the general case by variational analysis. Coherent charge fluctuations are entangled with non-classical phonon states. The Josephson current induces squeezing of the phonon mode, which is controlled by the superconducting phase difference and by the junction asymmetry. Optical probes of non-classical phonon states are briefly discussed

Nucleon Polarizabilities

The subject of nucleon polarizabilities in real, virtual, and doubly virtual Compton scattering is discussed with respect to what is known and how such quantities can be extracted from data.Comment: 13 page Latex file; Talk given at Chiral Dynamics 2000 Workshop, Jefferson Lab, July 200

Allowed Eta Decay Modes and Chiral Symmetry

Recently, the development of chiral perturbation theory has allowed the generation of rigorous low energy theorems for various hadronic processes based only on the chiral invariance of the underlying QCD Lagrangian. Such techniques are highly developed and well tested in the domain of pionic and kaonic reactions. In this note we point out that with the addition of a few additional and reasonable assumptions similar predictive power is available for processes involving the eta meson.Comment: Contribution to Eta Physics Handbook, Workshop on Eta Physics, Uppsala 2001, 28 page latex file with 9 figure

Weak Hypernuclear Decay

Because of Pauli suppression effects the $N\pi$ decay of the free $\Lambda$ is not of importance in hypernuclei with $A\geq 10$. Rather the decay of such hypernuclei proceeds via the nucleon-stimulated mode $\Lambda N\rightarrow NN$, analysis of which presents a considerable theoretical challenge and about which there exists only a limited amount of experimental information. Herein we confront existing data wih various theoretical analyses which have been developed.Comment: 19 page standard Latex file; invited talk at 2nd DAFNE Workshop, April, 199

Hadronic Parity Violation: an Analytic Approach

Using a recent reformulation of the analysis of nuclear parity-violation (PV) within the framework of effective field theory (EFT), we show how predictions for parity-violating observables in low-energy light hadronic systems can be understood in an analytic fashion. It is hoped that such an analytic approach may encourage additional experimental work as well as add to the understanding of such parity-violation phenomena, which is all too often obscured by its description in terms of numerical results obtained from complex two-body potential codes.Comment: 49 pages, 4 figures, dedicated to the memory of Dubravko Tadi

Low Energy Tests of Chiral Symmetry

The present status of low energy test of chiral invariance via chiral perturbation theory is reviewed, both in the meson and baryon sectors, and future prospects are discussed.Comment: Invited talk given at PANIC 96, Standard 8 page Latex fil

Hyperon Physics-a Personal Overview

A range of issues in the field of hyperon physics is presented, together with an assessment of where important challenges remain.Comment: Introductory talk given at FNAL Hyperon99 Workshop--6pg latex fil