11,026 research outputs found
Will the United States continue to allocate a growing proportion of its GDP to health care?
What policy options would improve the access, efficiency, and quality shortcomings found in the current U.S. health care system? This session will address the efficacy of the available policy alternatives and their likely interactions. What, for instance, are the cost implications of providing better insurance coverage and encouraging ongoing scientific progress? How should these desirable objectives be financed? Can better measures of quality and outcomes and more effective management systems help to balance our health care goals?Health care reform
Nutritional disturbances in white children as seen in private paediatric practice
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Mechanism of T-Cell Lymphomagenesis: Transformation of Growth-Factor-Dependent T-Lymphoblastoma Cells to Growth-Factor-Independent T-Lymphoma Cells
In a previous paper we described the induction by x-irradiation or radiation-induced leukemia virus-in-oculation of two classes of lymphoid T-cell neoplasms: The first class, designated T-cell lymphoblastoma (TCLB), consists of growth-factor-dependent eudiploid cells that home to the spleen and give rise to splenic tumors on injection into syngeneic mice; the second class, designated T-cell lymphoma (TCL), consists of growth-factor-independent aneuploid or pseudodiploid cells that give rise to local tumors at the site of subcutaneous injection. This paper describes the generation of a family of growth-factor-independent aneuploid or pseudodiploid TCL cells after the injection into the thymus of growth-factor-dependent diploid TCLB cells. In contrast to the donor TCLB cells, the resulting TCL cells could be cloned in semisolid medium, produced local tumors at the site of subcutaneous injection, and proliferated in a growth-factor-independent fashion in vitro. The induced growth-factor-independent TCL cells were chromosomally and phenotypically unstable and continued to evolve both in vivo and in vitro. After propagation in the thymus, the cells often showed stable translocations in addition to the evolving aneuploidy. We propose that the chromosome abnormalities induced during the proliferation of growth-factor-dependent TCLB cells in the thymus constitute a general mechanism by which neoplastic cells progress from growth-factor dependency to independency
Phase transition of one dimensional bosons with strong disorder
We study one dimensional disordered bosons at large commensurate filling.
Using a real space renormalization group approach we find a new random fixed
point which controls a phase transition from a superfluid to an incompressible
Mott-glass. The transition can be tuned by changing the disorder distribution
even with vanishing interactions. We derive the properties of the transition,
which suggest that it is in the Kosterlitz-Thouless universality class.Comment: 4 pages 3 embedded eps figure
Microscopic thickness determination of thin graphite films formed on SiC from quantized oscillation in reflectivity of low-energy electrons
Low-energy electron microscopy (LEEM) was used to measure the reflectivity of
low-energy electrons from graphitized SiC(0001). The reflectivity shows
distinct quantized oscillations as a function of the electron energy and
graphite thickness. Conduction bands in thin graphite films form discrete
energy levels whose wave vectors are normal to the surface. Resonance of the
incident electrons with these quantized conduction band states enhances
electrons to transmit through the film into the SiC substrate, resulting in
dips in the reflectivity. The dip positions are well explained using
tight-binding and first-principles calculations. The graphite thickness
distribution can be determined microscopically from LEEM reflectivity
measurements.Comment: 7 pages, 3 figure
From an insulating to a superfluid pair-bond liquid
We study an exchange coupled system of itinerant electrons and localized
fermion pairs resulting in a resonant pairing formation. This system inherently
contains resonating fermion pairs on bonds which lead to a superconducting
phase provided that long range phase coherence between their constituents can
be established. The prerequisite is that the resonating fermion pairs can
become itinerant. This is rendered possible through the emergence of two kinds
of bond-fermions: individual and composite fermions made of one individual
electron attached to a bound pair on a bond. If the strength of the exchange
coupling exceeds a certain value, the superconducting ground state undergoes a
quantum phase transition into an insulating pair-bond liquid state. The gap of
the superfluid phase thereby goes over continuously into a charge gap of the
insulator. The change-over from the superconducting to the insulating phase is
accompanied by a corresponding qualitative modification of the dispersion of
the two kinds of fermionic excitations. Using a bond operator formalism, we
derive the phase diagram of such a scenario together with the elementary
excitations characterizing the various phases as a function of the exchange
coupling and the temperature.Comment: 10 pages, 5 figure
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