5,940 research outputs found
Comments on SUSY inflation models on the brane
In this paper we consider a class of inflation models on the brane where the
dominant part of the inflaton scalar potential does not depend on the inflaton
field value during inflation. In particular, we consider supernatural
inflation, its hilltop version, A-term inflation, and supersymmetric (SUSY) D-
and F-term hybrid inflation on the brane. We show that the parameter space can
be broadened, the inflation scale generally can be lowered, and still possible
to have the spectral index .Comment: 7 page
Knowledge-Grounded Reinforcement Learning
Receiving knowledge, abiding by laws, and being aware of regulations are
common behaviors in human society. Bearing in mind that reinforcement learning
(RL) algorithms benefit from mimicking humanity, in this work, we propose that
an RL agent can act on external guidance in both its learning process and model
deployment, making the agent more socially acceptable. We introduce the
concept, Knowledge-Grounded RL (KGRL), with a formal definition that an agent
learns to follow external guidelines and develop its own policy. Moving towards
the goal of KGRL, we propose a novel actor model with an embedding-based
attention mechanism that can attend to either a learnable internal policy or
external knowledge. The proposed method is orthogonal to training algorithms,
and the external knowledge can be flexibly recomposed, rearranged, and reused
in both training and inference stages. Through experiments on tasks with
discrete and continuous action space, our KGRL agent is shown to be more sample
efficient and generalizable, and it has flexibly rearrangeable knowledge
embeddings and interpretable behaviors
Nedd4-2-dependent ubiquitination potentiates the inhibition of human NHE3 by cholera toxin and enteropathogenic Escherichia coli
BACKGROUND & AIMS: Diarrhea is one of the most common illnesses and is often caused by bacterial infection. Recently, we have shown that human Naþ/Hþ exchanger NHE3 (hNHE3), but not non-human NHE3s, interacts with the E3 ubiquitin ligase Nedd4-2. We hypothesize that this property of hNHE3 contributes to the increased severity of diarrhea in humans. METHODS: We used humanized mice expressing hNHE3 in the intestine (hNHE3int) to compare the contribution of hNHE3 and mouse NHE3 to diarrhea induced by cholera toxin (CTX) and enteropathogenic Escherichia coli (EPEC). We measured Naþ/ Hþ exchange activity and fluid absorption. The role of Nedd4-2 on hNHE3 activity and ubiquitination was determined by knockdown in Caco-2bbe cells. The effects of protein kinase A (PKA), the primary mediator of CTX-induced diarrhea, on Nedd4-2 and hNHE3 phosphorylation and their interaction were determined. RESULTS: The effects of CTX and EPEC were greater in hNHE3int mice than in control wild-type (WT) mice, resulting in greater inhibition of NHE3 activity and increased fluid accumulation in the intestine, the hallmark of diarrhea. Activation of PKA increased ubiquitination of hNHE3 and enhanced interaction of Nedd4-2 with hNHE3 via phosphorylation of Nedd4-2 at S342. S342A mutation mitigated the Nedd4-2–hNHE3 interaction and blocked PKA-induced inhibition of hNHE3. Unlike non-human NHE3s, inhibition of hNHE3 by PKA is independent of NHE3 phosphorylation, suggesting a distinct mechanism of hNHE3 regulation. CONCLUSIONS: The effects of CTX and EPEC on hNHE3 are amplified, and the unique properties of hNHE3 may contribute to diarrheal symptoms occurring in humans
On The Assembly History of Dark Matter Haloes
(abridged) We study the mass assembly history (MAH) of dark matter haloes. We
compare MAHs obtained using (i) merger trees constructed with the extended
Press-Schechter (EPS) formalism, (ii) numerical simulations, and (iii) the
Lagrangian perturbation code PINOCCHIO. We show that the PINOCCHIO MAHs are in
excellent agreement with those obtained using numerical simulations. Using a
suite of 55 PINOCCHIO simulations, with 256^3 particles each, we study the MAHs
of 12,924 cold dark matter haloes in a \LambdaCDM concordance cosmology. We
show that haloes less massive than the characteristic non-linear mass scale
establish their potential wells much before they acquire most of their mass.
The time when a halo reaches its maximum virial velocity roughly divides its
mass assembly into two phases, a fast accretion phase which is dominated by
major mergers, and a slow accretion phase dominated by minor mergers. Each halo
experiences about 3 \pm 2 major mergers since its main progenitor had a mass
equal to one percent of the final halo mass. This major merger statistic is
found to be virtually independent of halo mass. However, the average redshift
at which these major mergers occur, is strongly mass dependent, with more
massive haloes experiencing their major mergers later.Comment: 15 pages, 13 figures (with 2 new), accepted by MNRA
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