319 research outputs found
Project-Fair and Truthful Mechanisms for Budget Aggregation
We study the budget aggregation problem in which a set of strategic voters
must split a finite divisible resource (such as money or time) among a set of
competing projects. Our goal is twofold: We seek truthful mechanisms that
provide fairness guarantees to the projects. For the first objective, we focus
on the class of moving phantom mechanisms [Freeman et al., 2021], which are --
to this day -- essentially the only known truthful mechanisms in this setting.
For project fairness, we consider the mean division as a fair baseline, and
bound the maximum difference between the funding received by any project and
this baseline. We propose a novel and simple moving phantom mechanism that
provides optimal project fairness guarantees. As a corollary of our results, we
show that our new mechanism minimizes the distance to the mean (a
measure suggested by Caragiannis et al. [2022]) for three projects and gives
the first non-trivial bounds on this quantity for more than three projects
Freeze-in and freeze-out of sterile neutrino dark matter
A sterile neutrino with a keV-scale mass is a compelling dark matter
candidate. We propose a new production mechanism involving the decay and
annihilation of a complex scalar singlet with a Higgs portal coupling which
develops a vacuum expectation value. The interactions of the resulting pseudo
Nambu-Goldstone boson may thermalise the dark sector. We determine the region
of parameter space where dark sector thermalisation is reached and discuss the
most relevant cosmological observables. The scenario can be considered as the
combination of a freeze-in of the dark sector followed by relativistic
freeze-out.Comment: 37 pages, 9 figure
Administration of Tramadol or Buprenorphine via the drinking water for post-operative analgesia in a mouse-osteotomy model
Adequate analgesia is essential whenever pain might occur in animal experiments. Unfortunately, the selection of suitable analgesics for mice in bone-linked models is limited. Here, we evaluated two analgesics - Tramadol [0.1 mg/ml (Tlow) vs. 1 mg/ml (Thigh)] and Buprenorphine (Bup; 0.009 mg/ml) - after a pre-surgical injection of Buprenorphine, in a mouse-osteotomy model. The aim of this study was to verify the efficacy of these opioids in alleviating pain-related behaviors, to provide evidence for adequate dosages and to examine potential side effects. High concentrations of Tramadol affected water intake, drinking frequency, food intake and body weight negatively in the first 2-3 days post-osteotomy, while home cage activity was comparable between all groups. General wellbeing parameters were strongly influenced by anesthesia and analgesics. Model-specific pain parameters did not indicate more effective pain relief at high concentrations of Tramadol. In addition, ex vivo high-resolution micro computed tomography (µCT) analysis and histology analyzing bone healing outcomes showed no differences between analgesic groups with respect to newly formed mineralized bone, cartilage and vessels. Our results show that high concentrations of Tramadol do not improve pain relief compared to low dosage Tramadol and Buprenorphine, but rather negatively affect animal wellbeing
Hydrodynamic Simulation of the Cosmological X-ray Background
(Abridged) We use a hydrodynamic simulation of a LambdaCDM model to predict
the extragalactic X-ray background (XRB), focussing on emission from the
intergalactic medium (IGM). We also include X-rays from point sources
associated with galaxies in the simulation, and make maps of the angular
distribution of the emission. We find that filaments in the maps are not
evident, being diluted by projection. In the soft (0.5-2 keV) band, the mean
intensity of radiation from intergalactic and cluster gas is 2.3*10^-12
ergdeg^-2cm^-2s^-1, 35% of the total soft band emission. This is compatible at
the ~1 sigma level with estimates of the unresolved soft background from ROSAT
and {\it Chandra}. Only 4% of the hard (2-10 keV) emission is associated with
the IGM. Relative to AGN flux, the IGM component peaks at a lower redshift
(median z~0.45) so its clustering makes an important contribution to that of
the total XRB. The angular correlations on 0.1-10 arcmin scales are
significant, with an amplitude roughly consistent with an extrapolation of
recent ROSAT results to small scales. A cross-correlation of the XRB against
nearby galaxies taken from a simulated redshift survey also yields a strong
signal from the IGM. Although some recent papers have argued that the expected
soft band intensity from gas in galaxy, group, and cluster halos would exceed
XRB limits unless much of the gas is expelled by supernova feedback, we obtain
reasonable compatibility with current observations in a simulation that
incorporates cooling, star formation, and only modest feedback. A prediction of
our model is that the unresolved portion of the soft XRB will remain mostly
unresolved.Comment: Improved referencing of related papers. Submitted to ApJ, 19 pages,
17 postscript figures, most reduced in resolution, emulateapj.sty, for full
resolution version, see http://cfa-www.harvard.edu/~rcroft/xray.ps.g
Stress and Radiation-Induced Activation of Multiple Intracellular Signaling Pathways
Exposure of cells to a variety of stresses induces compensatory activations of multiple intracellular signaling pathways. These activations can play critical roles in controlling cell survival and repopulation effects in a stress-specific and cell type-dependent manner. Some stress-induced signaling pathways are those normally activated by mitogens such as the EGFR/RAS/PI3K-MAPK pathway. Other pathways activated by stresses such as ionizing radiation include those downstream of death receptors, including pro-caspases and the transcription factor NFKB. This review will attempt to describe some of the complex network of signals induced by ionizing radiation and other cellular stresses in animal cells, with particular attention to signaling by growth factor and death receptors. This includes radiation-induced signaling via the EGFR and IGFI-R to the PI3K, MAPK, JNK, and p38 pathways as well as FAS-R and TNF-R signaling to pro-caspases and NFKB. The roles of autocrine ligands in the responses of cells and bystander cells to radiation and cellular stresses will also be discussed. Based on the data currently available, it appears that radiation can simultaneously activate multiple signaling pathways in cells. Reactive oxygen and nitrogen species may play an important role in this process by inhibiting protein tyrosine phosphatase activity. The ability of radiation to activate signaling pathways may depend on the expression of growth factor receptors, autocrine factors, RAS mutation, and PTEN expression. In other words, just because pathway X is activated by radiation in one cell type does not mean that pathway X will be activated in a different cell type. Radiation-induced signaling through growth factor receptors such as the EGFR may provide radioprotective signals through multiple downstream pathways. In some cell types, enhanced basal signaling by proto-oncogenes such as RAS may provide a radioprotective signal. In many cell types, this may be through PI3K, in others potentially by NFKB or MAPK. Receptor signaling is often dependent on autocrine factors, and synthesis of autocrine factors will have an impact on the amount of radiation-induced pathway activity. For example, cells expressing TGFalpha and HB-EGF will generate protection primarily through EGFR. Heregulin and neuregulins will generate protective signals through ERBB4/ERBB3. The impact on radiation-induced signaling of other autocrine and paracrine ligands such as TGFbeta and interleukin 6 is likely to be as complicated as described above for the ERBB receptors.Fil: Dent, Paul. Virginia Commonwealth University; Estados UnidosFil: Yacoub, Adly. Virginia Commonwealth University; Estados UnidosFil: Contessa, Joseph. Virginia Commonwealth University; Estados UnidosFil: Caron, Ruben Walter. Virginia Commonwealth University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Medicina y Biología Experimental de Cuyo; ArgentinaFil: Amorino, Geroge. Virginia Commonwealth University; Estados UnidosFil: Valerie, Kristoffer. Virginia Commonwealth University; Estados UnidosFil: Hagan, Michael P.. Virginia Commonwealth University; Estados UnidosFil: Grant, Steven. Virginia Commonwealth University; Estados UnidosFil: Schmidt Ullrich, Rupert. Virginia Commonwealth University; Estados Unido
Soft x-ray spectroscopy experiments on the near K-edge of B in MB2 (M=Mg, Al, Ta, and Nb)
Soft X-ray absorption and emission measurements are performed for the K- edge
of B in MB (M=Mg, Al, Ta and Nb). Unique feature of MgB with a high
density of B 2-state below and above the Fermi edge, which
extends to 1 eV above the edge, is confirmed. In contrast, the B 2 density
of states in AlB and TaB, both of occupied and unoccupied states,
decreased linearly towards the Fermi energy and showed a dip at the Fermi
energy. Furthermore, there is a broadening of the peaks with
-character in XES and XAS of AlB, which is due to the increase of
three dimensionality in the -band in AlB. The DOS of NbB has a
dip just below the Fermi energy. The present results indicate that the large
DOS of B-2 states near the Fermi energy are crucial for the
superconductivity of MgB.Comment: 3 pages text and 4 pages figures. accepted for publication to Phys.
Rev.
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