Coulomb dissociation of N 20,21

Neutron-rich light nuclei and their reactions play an important role in the creation of chemical elements. Here, data from a Coulomb dissociation experiment on N20,21 are reported. Relativistic N20,21 ions impinged on a lead target and the Coulomb dissociation cross section was determined in a kinematically complete experiment. Using the detailed balance theorem, the N19(n,γ)N20 and N20(n,γ)N21 excitation functions and thermonuclear reaction rates have been determined. The N19(n,γ)N20 rate is up to a factor of 5 higher at

Field Experiments in the Global South: Assessing Risks, Localizing Benefits, and Addressing Positionality

Randomized controlled trials (RCTs) have emerged as a leading methodological tool to strengthen causal inference in the social sciences. Yet RCTs carry significant risks for ev- eryone involved, from participants to researchers themselves, especially in the Global South. In this article, we explore how researchers’ identities and power influence the conduct of research and their positionality within the research contexts—especially when conducting RCTs in the Global South. Our goal is to center local contexts and demands at each stage of the research process. Overall, we argue that centering local contexts, stakeholders, and de- mands at each stage of the research process is key to ensuring that RCTs in the Global South are ethically sound and generate insights that can serve the communities they investigate

Characterization and developmental expression of the amphioxus homolog of Notch (AmphiNotch): Evolutionary conservation of multiple expression domains in amphioxus and vertebrates

See http://dx.doi.org/10.1006/dbio.2001.0271 for erratum correcting omission of Robert Kortschak from original author identificationNotch encodes a transmembrane protein that functions in intercellular signaling. Although there is one Notch gene in Drosophila, vertebrates have three or more with overlapping patterns of embryonic expression. We cloned the entire 7575-bp coding region of an amphioxus Notch gene (AmphiNotch), encoding 2524 amino acids, and obtained the exon/intron organization from a genomic cosmid clone. Southern blot and PCR data indicate that AmphiNotch is the only Notch gene in amphioxus. AmphiNotch, like Drosophila Notch and vertebrate Notch1 and Notch2, has 36 EGF repeats, 3 Notch/lin-12 repeats, a transmembrane region, and 6 ankyrin repeats. Phylogenetic analysis places it at the base of all the vertebrate genes, suggesting it is similar to the ancestral gene from which the vertebrate Notch family genes evolved. AmphiNotch is expressed in all three embryonic germ layers in spatiotemporal patterns strikingly similar to those of all the vertebrate homologs combined. In the developing nerve cord, AmphiNotch is first expressed in the posteriormost part of the neural plate, then it becomes more broadly expressed and later is localized dorsally in the anteriormost part of the nerve cord corresponding to the diencephalon. In late embryos and larvae, AmphiNotch is also expressed in parts of the pharyngeal endoderm, in the anterior gut diverticulum, and, like AmphiPax2/5/8, in the rudiment of Hatschek’s kidney. A comparison with Notch1 and Pax5 and Pax8 expression in the embryonic mouse kidney helps support homology of the amphioxus and vertebrate kidneys. AmphiNotch is also an early marker for presumptive mesoderm, transcripts first being detectable at the gastrula stage in a ring of mesendoderm just inside the blastopore and subsequently in the posterior mesoderm, notochord, and somites. As in sea urchins and vertebrates, these domains of AmphiNotch expression overlap with those of several Wnt genes and brachyury. These relationships suggest that amphioxus shares with other deuterostomes a common mechanism for patterning along the anterior/posterior axis involving a posterior signaling center in which the Notch and Wnt pathways and brachyury interact.Linda Z. Holland, Laurent Abi Rached, Richard Tamme, Nicholas D. Holland, Hidetoshi Inoko, Takashi Shiina, Carola Burgtorf, and Michael Lardellihttp://www.sciencedirect.com/science/journal/0012160