Standards of selecting short stories for use in secondary schools in America

Thesis (M.A.)--Boston Universit

The Humoral Theory of Transplantation: Epitope Analysis and the Pathogenicity of HLA Antibodies.

Central to the humoral theory of transplantation is production of antibodies by the recipient against mismatched HLA antigens in the donor organ. Not all mismatches result in antibody production, however, and not all antibodies are pathogenic. Serologic HLA matching has been the standard for solid organ allocation algorithms in current use. Antibodies do not recognize whole HLA molecules but rather polymorphic residues on the surface, called epitopes, which may be shared by multiple serologic HLA antigens. Data are accumulating that epitope analysis may be a better way to determine organ compatibility as well as the potential immunogenicity of given HLA mismatches. Determination of the pathogenicity of alloantibodies is evolving. Potential features include antibody strength (as assessed by antibody titer or, more commonly and inappropriately, mean fluorescence intensity) and ability to fix complement (in vitro by C1q or C3d assay or by IgG subclass analysis). Technical issues with the use of solid phase assays are also of prime importance, such as denaturation of HLA antigens and manufacturing and laboratory variability. Questions and controversies remain, and here we review new relevant data

Anomaly Analysis of Brane-Antibrane Systems

String theories with branes can often be generalized by adding brane-antibrane pairs. We explore the cancellation of anomalies in this more general context, extending the familiar anomaly-cancelling mechanisms, both for ten-dimensional string theories with D-branes and for certain supersymmetric compactifications.Comment: 28 pages; v2: references adde

Retrofitted Natural Supersymmetry from a U(1)

We propose that a single, spontaneously broken, U(1) gauge symmetry may be responsible for suppressing both the first two generation Yukawa couplings, and also, in a correlated manner, parameters in the dynamical supersymmetry (SUSY) breaking sector by the mechanism of retrofitting. In the dynamical SUSY breaking sector, these small parameters are typically required in order to introduce R-symmetry breaking in a controlled manner and obtain phenomenologically viable meta-stable vacua. The heavy U(1) multiplet mediates a dominant contribution to the first two generation MSSM sfermion soft masses, while gauge mediation provides a parametrically suppressed soft term contribution to the stop and most other states, so realising a natural SUSY spectrum in a fashion consistent with SUSY unification. In explicit models the spectra obtained can be such that current LHC limits are evaded, and predictions of flavour changing processes are consistent with observation. We examine both implementations with low scale mediation, and string-motivated examples where the U(1) is anomalous before the inclusion of a generalised Green-Schwarz mechanism.Comment: V2: References adde

Oxygen isotope ratios in olivine from the Hawaii Scientific Drilling Project

Oxygen isotope ratios of olivine in 23 tholeiites from the Hawaii Scientific Drilling Project (HSDP) core (15 from Mauna Kea, 8 from Mauna Loa) and three samples of outcropping subaerial or dredged submarine Mauna Kea lavas have been measured by laser fluorination. The δ^(18)O values are 4.6–5.4 ‰, confirming previous observations that some Hawaiian lavas are derived from sources with δ^(18)O values lower than typical upper mantle (δ^(18)Oolivine ≈ 5.2±0.2 ‰). The Mauna Kea-Mauna Loa transition marks a shift from δ^(18)O values lower than the mantle average in Mauna Kea olivines (∼4.8) to more typical mantle values in Mauna Loa olivines. Lavas containing olivines with δ^(18)O values similar to the typical upper mantle are associated with more “primitive” or less depleted radiogenic isotope characteristics; i.e., with higher ^3He/^4He (>13 Ra), higher ^(87)Sr/^(86)Sr (>0.7036) and lower є_(Nd) (<6.5), and with ^(206)Pb/^(204)Pb ratios less than -18.3. These relationships indicate that the δ^(18)O values of the relatively enriched source components of the Hawaiian plume sampled by Mauna Loa lavas are comparable to (or greater than) the mantle average. This conclusion is supported by δ^(18)O values of olivine from other high ^3He/^4He islands, which are also comparable to the upper mantle average. The low δ^(18)O values in Hawaiian lavas are derived from a source having more MORB-like, or depleted, He, Nd, and Sr isotope ratios, but more radiogenic Pb than is seen in the Mauna Loa lavas Assimilation of ^(18)O-depleted lower oceanic crust from the underlying Pacific crust by hot, MgO-rich parental magmas or melting of older, recycled oceanic crust entrained in the Hawaiian plume are both possible sources of this ^(18)O-depleted, MORB-like component in Hawaiian magmas