Publications

Analytical and numerical results are presented for the intersection of electronic energies of the same space symmetry for electrons in the field of two Coulomb centers in D-dimensions. We discuss why such crossings are allowed and may be less ``exceptional'' than one could think because even for a diatomic molecule there is more than one parameter in the electronic Hamiltonian. For a one electron diatomic molecule at the large-D limit, the electronic energies are shown analytically to diverge quadratically from the point of their intersection. The one electron two Coulomb centers problem allows a separation of variables even when the charges on the two centers are not equal. The case of two electrons, where their Coulombic repulsion precludes an exact symmetry, is therefore treated in the large-D limit. It is then found that, in addition to the quadratic intersection, there is also a curve crossing where the energies diverge linearly. (C) 2001 American Institute of Physics.

A new approach for designing a voltammetric selective electrode is presented. The approach is based on the formation of a disorganised inert self-assembled monolayer (SAM), in which an amphiphilic molecule is incorporated. The latter serves as the selectivity factor, which extracts the analyte. The purpose of these experiments is to study the parameters that affect the capability of a monolayer to host amphiphiles. As model systems we focused on the incorporation of simple amphiphilic molecules (quaternary alkyl ammonium salts), electroactive amphiphiles (dialkylviologens) and a macrocycle ligand (tetramethylcyclam) into octadecyl silane monolayers formed on indium tin oxide (ITO) and purposely made disorganised alkanethiols on gold. We find that basically, the incorporation of amphiphiles into a hydrophobic inert SAM resembles a reversed stationary phase in liquid chromatography and this configuration can be used for designing selective electrodes.[on SciFinder (R)]

A new approach for designing a voltammetric selective electrode is presented. The approach is based on the formation of a disorganized inert self-assembled monolayer (SAM), in which an amphiphilic mol. is incorporated. The latter serves as the selectivity factor, which exts. the analyte. The purpose of these expts. is to study the parameters that affect the capability of a monolayer to host amphiphiles. As model systems the authors focused on the incorporation of simple amphiphilic mols. (quaternary alkyl ammonium salts), electroactive amphiphiles (dialkylviologens) and a macrocycle ligand (tetramethylcyclam) into octadecyl silane monolayers formed on In Sn oxide (ITO) and purposely made disorganized alkanethiols on Au. Basically, the incorporation of amphiphiles into a hydrophobic inert SAM resembles a reversed stationary phase in liq. chromatog. and this configuration can be used for designing selective electrodes. [on SciFinder(R)]

A disposable heating unit for use for heating the contents of a container, includes a first region contg. a combination of at least two solid substances which undergo an exothermic chem. reaction which is not spontaneous at room temp. Adjacent to the first region is a second region contg. at least a first reagent. A storage cell is configured for releasing the liq. contg. a second reagent into the second region. The first and second reagents undergo a spontaneous exothermic chem. reaction when brought into contact, thereby initiating the exothermic chem. reaction of the solid substances. [on SciFinder(R)]

We are witnessing the continuation of an accelerated, unprecedented explosion of scientific information that might make the life of a serious investigator unbearably complicated. Unlike our pioneering investigators, however, we are fortunate to have access to modern information-retrieving pools such as Medline, Biological Abstracts, and more recently selected electronic journals. These allow us, at the press of a key, to choose desired scientific citations. A search for articles in the medical

We present symmetry-breaking and electronic-structure phase diagrams for two-center molecules with one and two electrons in the limit of a space of large dimensions. For one electron, the phase diagram in the internuclear distance-nuclear charge (R-Z) plane has two different stable phases. One corresponds to the electron equidistant from the two nuclei; the other where the electron is localized on one of the nuclei. The phase diagram for two electrons with two equally charged centers shows three different stable phases corresponding to different electronic-structure configurations. This phase diagram is characterized by a bicritical point. When the charges are unequal, the phase diagram shows only two stable phases, covalent and ionic. This phase diagram is characterized by a tricritical point, where the first-order transition line meets with the second-order transition line. The role of the inter-electron Coulombic repulsion in giving rise to different electronic structures and the distinction between a continuous deformation of one structure into another versus a discontinuous, so-called first-order, transition, where two isomers can coexist, are emphasized. The connection to the spectroscopic notion of intersecting potential energy curves is discussed.

The use of a classical limit for the electronic degrees of freedom avoids the need to keep the nuclei clamped while solving for the dynamics of the electrons. The Hamiltonian for the electrons will then depend on the nuclear coordinates as dynamical variables. The resulting (classical) electron-nuclear coupled equations of motion exhibit dynamical symmetry and are shown to depend only on the ratio, kappa (-4), of the electron to nuclear mass, We explore the coupled electron-nuclear dynamics as a function of kappa for the special case of a single electron moving between two centers. Ln the dynamical regime where the nuclei are heavy and the Born-Oppenheimer separation should work, the full dynamical procedure is in excellent agreement with the nuclear dynamics as computed using the Born-Oppenheimer separation. In the opposite regime where the period of the electronic motion is long, a case that can be physically realized for very high Rydberg states, one reaches an `inverse' behavior where the nuclei adiabatically adjust to the slow electronic motion. The failure of the Born-Oppenheimer separation, as judged by the electronic coupling not being governed solely by the instantaneous position of the nuclei, is more severe when the initial electronic state is not stationary.

BACKGROUND: Human mesenchymal stem cells (hMSCs) are pluripotent cells that can differentiate to various mesenchymal cell types. Recently, a method to isolate hMSCs from bone marrow and expand them in culture was described. Here we report on the use of hMSCs as a platform for gene therapy aimed at bone lesions. METHODS: Bone marrow derived hMSCs were expanded in culture and infected with recombinant adenoviral vector encoding the osteogenic factor, human BMP-2. The osteogenic potential of genetically engineered hMSCs was assessed in vitro and in vivo. RESULTS: Genetically engineered hMSCs displayed enhanced proliferation and osteogenic differentiation in culture. In vivo, transplanted genetically engineered hMSCs were able to engraft and form bone and cartilage in ectopic sites, and regenerate bone defects (non-union fractures) in mice radius bone. Importantly, the same results were obtained with hMSCs isolated from a patient suffering from osteoporosis. CONCLUSIONS: hMSCs represent a novel platform for skeletal gene therapy and the present results suggest that they can be genetically engineered to express desired therapeutic proteins inducing specific differentiation pathways. Moreover, hMSCs obtained from osteoporotic patients can restore their osteogenic activity following human BMP-2 gene transduction, an important finding in the future planning of gene therapy treatment for osteoporosis.

When psychologists test a commonsense (CS) hypothesis and obtain no support, they tend to erroneously conclude that the CS belief is wrong, In many such cases it appears, after many years, that the CS hypothesis was valid after all. It is argued that this error of accepting the "theoretical" null hypothesis reflects confusion between the operationalized hypothesis and the theory or generalization that it is designed to test. That is, on the basis of reliable null data one can accept the operationalized null hypothesis (e.g., "A measure of attitude x is not correlated with a measure of behavior y"). In contrast, one cannot generalize from the findings and accept the abstract or theoretical null (e.g., "We know that attitudes do not predict behavior"). The practice of accepting the theoretical null hypothesis hampers research and reduces the trust of the public in psychological research.