7,867 research outputs found
Dual Confinement of Grand Unified Monopoles?
A simple formal computation, and a variation on an old thought experiment,
both indicate that QCD with light quarks may confine fundamental color magnetic
charges, giving an explicit as well as elegant resolution to the `global color'
paradox, strengthening Vachaspati's SU(5) electric-magnetic duality, opening
new lines of inquiry for monopoles in cosmology, and suggesting a class of
geometrically large QCD excitations -- loops of Z(3) color magnetic flux
entwined with light-quark current. The proposal may be directly testable in
lattice gauge theory or supersymmetric Yang-Mills theory. Recent results in
deeply-inelastic electron scattering, and future experiments both there and in
high-energy collisions of nuclei, could give evidence on the existence of Z(3)
loops. If confirmed, they would represent a consistent realization of the bold
concept underlying the Slansky-Goldman-Shaw `glow' model -- phenomena besides
standard meson-baryon physics manifest at long distance scales -- but without
that model's isolable fractional electric charges.Comment: 17 pages, standard LaTex, to appear in Physics Reports commemorating
Richard Slansk
Sulfur diagenesis in marine sediments
Bacterial sulfate reduction occurs in all marine sediments that contain organic matter. Aqueous sulfide (HS-, H2S), one of the initial products of bacterial sulfide reduction, is extremely reactive with iron bearing minerals: sulfur is fixed into sediments as iron sulfide (first FeS and then Fe2S2). A working definition is given of sulfur diagenesis in marine sediments. Controls and consequences of sulfate reduction rates in marine sediments are examined
Assessing the Determinants and Implications of Teacher Layoffs
Analyzes the factors that predict which teachers are likely to be laid off in Washington state in the current seniority-based system and which would likely be laid off in an effectiveness-based system. Considers implications for student achievement
National Board Certification and Teacher Effectiveness: Evidence from Washington
We study the effectiveness of teachers certified by the National Board for Professional Teaching Standards (NBPTS) in Washington State, which has one of the largest populations of National Board Certified Teachers (NBCTs) in the nation. Based on value-added models in math and reading, we find that NBPTS certified teachers are about 0.01-0.05 student standard deviations more effective than non-NBCTS with similar levels of experience. Certification effects vary by subject, grade level, and certification type, with greater effects for middle school math certificates. We find mixed evidence that teachers who pass the assessment are more effective than those who fail, but that the underlying NBPTS assessment score predicts student achievement. Finally, we use the individual assessment exercise scores to estimate optimal weights for value-added prediction
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