How Hard Are the Form Factors in Hadronic Vertices with Heavy Mesons?

The $ND\Lambda_c$ and $ND^*\Lambda_c$ form factors are evaluated in a full QCD sum rule calculation. We study the double Borel sum rule for the three point function of one meson one nucleon and one $\Lambda_c$ current up to order six in the operator product expansion. The double Borel transform is performed with respect to the nucleon and $\Lambda_c$ momenta, and the form factor is evaluated as a function of the momentum $Q^2$ of the heavy meson. These form factors are relevant to evaluate the charmonium absorption cross section by hadrons. Our results are compatible with constant form factors in these vertices.Comment: 12 pages, RevTeX including 5 figures in ps file

Progress in the determination of the J/ψ−πJ/\psi-\pi cross section

Improving previous calculations, we compute the $J/\psi \pi\to {charmed mesons}$ cross section using QCD sum rules. Our sum rules for the $J/\psi \pi\to \bar{D} D^*$, $D \bar{D}^*$, ${\bar D}^* D^*$ and ${\bar D} D$ hadronic matrix elements are constructed by using vaccum-pion correlation functions, and we work up to twist-4 in the soft-pion limit. Our results suggest that, using meson exchange models is perfectly acceptable, provided that they include form factors and that they respect chiral symmetry. After doing a thermal average we get $\sim 0.3$ mb at T=150\MeV.Comment: 22 pages, RevTeX4 including 7 figures in ps file

History of clinical transplantation

How transplantation came to be a clinical discipline can be pieced together by perusing two volumes of reminiscences collected by Paul I. Terasaki in 1991-1992 from many of the persons who were directly involved. One volume was devoted to the discovery of the major histocompatibility complex (MHC), with particular reference to the human leukocyte antigens (HLAs) that are widely used today for tissue matching.1 The other focused on milestones in the development of clinical transplantation.2 All the contributions described in both volumes can be traced back in one way or other to the demonstration in the mid-1940s by Peter Brian Medawar that the rejection of allografts is an immunological phenomenon.3,4 © 2008 Springer New York

The importance of mineralization based on sulfate reduction for nutrient regeneration in tropical seagrass sediments

Nutrient dynamics (nitrogen and phosphate), sediment organic matter mineralization (sulfate reduction rates) and stable carbon isotope composition in two tropical seagrass sediments were studied at a intertidal sandflat of Ban Pak Klok, Thailand. The seagrass beds were composed of meadows of Cymodocea rotundata (Ehrenb. and Hempr.) Aschers and Thalassia hemprichii (Ehrenb.) Aschers. The nutrient concentrations in porewaters were low (< 1 muM NO2- + NO3- 30-70 muM NH4+ and 2-5 muM PO43-) in the low-organic sediments (<0.6% DW POC and <0.03% DW PON). Sulfate reduction rates were significantly higher in the C. rotundata sediments (6.6 mmol m(-2) per day), whereas there was no difference between rates in the T. hemprichii and bare sediments (2.1 and 2.2 mmol m(-2) per day). The depth distribution of sulfate reduction rates in C. rotundata sediments was positively correlated with the below- ground biomass suggesting that the enhanced anaerobic activity was due to supply of microbial substrates from the seagrasses. The stable isotopic composition of the sediment bacteria resembled the seagrasses suggesting that the bacteria used organic matter derived from the seagrasses. A two-compartment experiment showed that both seagrasses released organic compounds from the roots (7.0 and 5.4% of photosynthetic rate for C. rotundata and T. hemprichii, respectively), and that the loss was sufficient to support the measured sulfate reduction rates. The contribution of sulfate reduction to nutrient availability was, however, low supporting only 6-22% of the nutrient demand, except for PO43- in C. rotundata sediments where 81% of the demand was covered by sulfate reduction. The relatively high nutrient content of the seagrasses (1.5-2.0% DW N and 0.18-0.20% DW P) suggested that their growth was not limited by nutrients. The low contribution of sulfate reduction to nutrient availability thus indicates that other mineralization processes or uptake of nutrients from the water column are important for plant growth. [KEYWORDS: Cymodocea rotundata; Thalassia hemprichii; sediments; sulfate reduction; nutrients Organic-carbon; mangrove forest; zostera-marina; phosphorus limitation; nitrogen-fixation; south sulawesi; danish estuary; growth; indonesia; beds]

The importance of mineralization based on sulfate reduction for nutrient regeneration in tropical seagrass sediments

Nutrient dynamics (nitrogen and phosphate), sediment organic matter mineralization (sulfate reduction rates) and stable carbon isotope composition in two tropical seagrass sediments were studied at a intertidal sandflat of Ban Pak Klok, Thailand. The seagrass beds were composed of meadows of Cymodocea rotundata (Ehrenb. and Hempr.) Aschers and Thalassia hemprichii (Ehrenb.) Aschers. The nutrient concentrations in porewaters were low (<1 muM NO2- + NO3- 30-70 muM NH4+ and 2-5 muM PO43-) in the low-organic sediments