Associative Retrieval Processes in Episodic Memory

Association and context constitute two of the central ideas in the history of episodic memory research. Following a brief discussion of the history of these ideas, we review data that demonstrate the complementary roles of temporal contiguity and semantic relatedness in determining the order in which subjects recall lists of items and the timing of their successive recalls. These analyses reveal that temporal contiguity effects persist over very long time scales, a result that challenges traditional psychological and neuroscientific models of association. The form of the temporal contiguity effect is conserved across all of the major recall tasks and even appears in item recognition when subjects respond with high confidence. The nearuniversal form of the contiguity effect and its appearance at diverse time scales is shown to place tight constraints on the major theories of association

Trends in neutron single-particle energies below N=82

Two separate investigations are described, linked by their common interest in single-particle structure around the N=82 shell closure. A systematic study of single-particle strength below the N=82 shell closure is reported. States in 137Ba, 139Ce, 141Nd and 143Sm were populated using the single-neutron removal reactions (p,d) and (3He,α) at beam energies of 23 MeV and 34 MeV, respectively. Absolute cross sections are presented for all observed states. Relative spectroscopic factors have been determined through a dwba analysis. The observed g 7/2 strength is consistently lower than that of h11/2 across all four isotones. It is postulated that as much as 50% of the g7/2 strength is fragmented into unresolved states which form part of the reaction background below 3.5 MeV. A speculative analysis based upon the observed strength reveals a relative behaviour of the g7/2 and h11/2 centroid energies that is in qualitative agreement with the predicted action of the tensor force.Details are presented also from an exploratory study of the 132Sn region using the 136Xe + 238U reaction at 926 MeV. The time-of-flight spectrometer prisma was used to identify the beam-like reaction products, and a mass resolution > 1/200 and Z-resolution of ~ 1/60 is reported. The total production yields at the focal plane are compared to calculations using the multi-nucleon transfer code grazing and rather poor agreement found for transfer of more then a few nucleons. The prospects for future studies in the region, particularly lifetime measurements, are discussed.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Main steps in DNA double-strand break repair: An introduction to homologous recombination and related processes

DNA double-strand breaks arise accidentally upon exposure of DNA to radiation, chemicals or result from faulty DNA metabolic processes. DNA breaks can also be introduced in a programmed manner, such as during the maturation of the immune system, meiosis or cancer chemo- or radiotherapy. Cells have developed a variety of repair pathways, which are fine-tuned to the specific needs of a cell. Accordingly, vegetative cells employ mechanisms that restore the integrity of broken DNA with the highest efficiency at the lowest cost of mutagenesis. In contrast, meiotic cells or developing lymphocytes exploit DNA breakage to generate diversity. Here, we review the main pathways of eukaryotic DNA double-strand break repair with the focus on homologous recombination and its various sub-pathways. We highlight the differences between homologous recombination and end-joining mechanisms including nonhomologous end-joining and microhomology-mediated end-joining, and offer insights into how these pathways are regulated. Finally, we introduce non-canonical functions of the recombination proteins, in particular during DNA replication stress

Far-Infrared Hydrogen Lasers in the Peculiar Star MWC 349A

Far-infrared hydrogen recombination lines H15(alpha)(169.4 micrometers), H12(alpha)(88.8 micrometers), and H10(alpha)(52.5 micrometers) were detected in the peculiar luminous star MWC 349A from the Kuiper Airborne Observatory. Here it is shown that at least H15(alpha) is strongly amplified, with the probable amplification factor being greater than or about equal to 10(exp 3) and a brightness temperature that is greater than or about equal to 10(exp 7) kelvin. The other two lines also show signs of amplification, although to a lesser degree. Beyond H10(alpha) the amplification apparently vanishes. The newly detected amplified lines fall into the laser wavelength domain. These lasers, as well as the previously detected hydrogen masers may originate in the photoionized circumstellar disk of MWC 349A and constrain the disk's physics and structure

ERK signaling mediates CaSR-promoted axon growth

The extracellular calcium-sensing receptor (CaSR) is a G-protein coupled receptor that monitors the systemic extracellular free ionized calcium level ([Ca2+]o) in organs involved in systemic [Ca2+]o homeostasis. CaSR is widely expressed in the nervous system and its activation promotes axon and dendrite growth during development, but the mechanism by which it does this is not known. Here we show that enhanced axon growth and branching from cultured embryonic sympathetic neurons by activation of the endogenous CaSR depends on the presence of nerve growth factor (NGF). Our observation that activation of overexpressed CaSR promotes axon growth in NGF-free medium has enabled us to investigate CaSR downstream signaling contributing to axon growth in the absence of NGF signaling. We show that activation of overexpressed CaSR leads to activation of ERK1 and ERK2, and pharmacological inhibition of CaSR-dependent ERK1/ERK2 activation prevents CaSR-dependent axon growth. Analysis of axon growth from cultured neurons expressing deletion mutants of the CaSR cytoplasmic tail revealed that the region between alanine 877 and glycine 907 is required for promoting axon growth that is distinct from the high-affinity filamin-A binding site that has previously been implicated in ERK1/ERK2 activation

Unification of favourable intermediate‐, unfavourable intermediate‐, and very high‐risk stratification criteria for prostate cancer

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/139069/1/bju13903.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/139069/2/bju13903_am.pd

NBS1 promotes the endonuclease of the MRE11-RAD50 complex by sensing CtIP phosphorylation

DNA end resection initiates DNA break repair by homologous recombination. MRE11-RAD50-NBS1 and phosphorylated CtIP perform the first resection step by MRE11-catalyzed endonucleolytic DNA cleavage. Human NBS1, more than its Xrs2 homologue from Saccharomyces cerevisiae, is crucial for this process, highlighting complex mechanisms that regulate the MRE11 nuclease in high eukaryotes. Using a reconstituted system, we show here that NBS1, through its FHA and BRCT domains, functions as a sensor of CtIP phosphorylation. NBS1 then activates the MRE11-RAD50 nuclease through direct physical interactions with MRE11. In absence of NBS1, MRE11-RAD50 exhibits a weaker nuclease activity, which requires CtIP but not strictly its phosphorylation. This identifies at least two mechanisms by which CtIP promotes MRE11: a phosphorylation-dependent mode through NBS1, and a phosphorylation-independent mode without NBS1. In support, we show that limited DNA end resection in absence of the FHA and BRCT domains of NBS1 occurs in vivo. Collectively, our data suggest that NBS1 restricts the MRE11- RAD50 nuclease to S-G2 phase when CtIP is extensively phosphorylated. This defines mechanisms that regulate the MRE11 nuclease in DNA metabolism

K2-19b and c are in a 3:2 Commensurability but out of Resonance: A Challenge to Planet Assembly by Convergent Migration

K2-19b and c were among the first planets discovered by NASA's K2 mission and together stand in stark contrast with the physical and orbital properties of the solar system planets. The planets are between the size of Uranus and Saturn at 7.0 ± 0.2 R⊕ and 4.1 ± 0.2 R⊕, respectively, and reside a mere 0.1% outside the nominal 3:2 mean-motion resonance. They represent a different outcome of the planet formation process than the solar system, as well as the vast majority of known exoplanets. We measured the physical and orbital properties of these planets using photometry from K2, Spitzer, and ground-based telescopes, along with radial velocities from Keck/HIRES. Through a joint photodynamical model, we found that the planets have moderate eccentricities of e ≈ 0.20 and well-aligned apsides Δϖ ≈ 0°. The planets occupy a strictly nonresonant configuration: the resonant angles circulate rather than librate. This defies the predictions of standard formation pathways that invoke convergent or divergent migration, both of which predict Δ ≈ 180° and eccentricities of a few percent or less. We measured masses of M_(p,b) = 32.4 ± 1.7 M⊕ and M_(p,c) = 10.8 ± 0.6 M⊕. Our measurements, with 5% fractional uncertainties, are among the most precise of any sub-Jovian exoplanet. Mass and size reflect a planet's core/envelope structure. Despite having a relatively massive core of M_(core) ≈ 15 M⊕, K2-19b is envelope-rich, with an envelope mass fraction of roughly 50%. This planet poses a challenge to standard models of core-nucleated accretion, which predict that cores ≳10 M⊕ will quickly accrete gas and trigger runaway accretion when the envelope mass exceeds that of the core