The symmetry energy describes how the energy of nuclear matter rises as one goes away from equal numbers of neutrons and protons. This is very important to describe neutron rich matter in ...astrophysics. This article reviews our knowledge of the symmetry energy from theoretical calculations, nuclear structure measurements, heavy-ion collisions, and astronomical observations. We then present a roadmap to make progress in areas of relevance to the symmetry energy that promotes collaboration between the astrophysics and the nuclear physics communities.
The proton is one of the main building blocks of all visible matter in the Universe
. Among its intrinsic properties are its electric charge, mass and spin
. These properties emerge from the complex ...dynamics of its fundamental constituents-quarks and gluons-described by the theory of quantum chromodynamics
. The electric charge and spin of protons, which are shared among the quarks, have been investigated previously using electron scattering
. An example is the highly precise measurement of the electric charge radius of the proton
. By contrast, little is known about the inner mass density of the proton, which is dominated by the energy carried by gluons. Gluons are hard to access using electron scattering because they do not carry an electromagnetic charge. Here we investigated the gravitational density of gluons using a small colour dipole, through the threshold photoproduction of the J/ψ particle. We determined the gluonic gravitational form factors of the proton
from our measurement. We used a variety of models
and determined, in all cases, a mass radius that is notably smaller than the electric charge radius. In some, but not all cases, depending on the model, the determined radius agrees well with first-principle predictions from lattice quantum chromodynamics
. This work paves the way for a deeper understanding of the salient role of gluons in providing gravitational mass to visible matter.
We present a search at the Jefferson Laboratory for new forces mediated by sub-GeV vector bosons with weak coupling α' to electrons. Such a particle A' can be produced in electron-nucleus ...fixed-target scattering and then decay to an e + e- pair, producing a narrow resonance in the QED trident spectrum. Using APEX test run data, we searched in the mass range 175-250 MeV, found no evidence for an A'→ e+ e- reaction, and set an upper limit of α'/α ~/= 10(-6). Our findings demonstrate that fixed-target searches can explore a new, wide, and important range of masses and couplings for sub-GeV forces.
Measurement of the parity-violating electron scattering asymmetry is an established technique at Jefferson Lab and provides a new opportunity to measure the weak charge distribution and hence pin ...down the neutron radius in nuclei in a relatively clean and model-independent way. This is because the
Z
boson of the weak interaction couples primarily to neutrons. We will describe the PREX and CREX experiments on
208
Pb and
48
Ca , respectively; these are both doubly magic nuclei whose first excited state can be discriminated by the high-resolution spectrometers at JLab. The heavier lead nucleus, with a neutron excess, provides an interpretation of the neutron skin thickness in terms of properties of bulk neutron matter. For the lighter
48
Ca nucleus, which is also rich in neutrons, microscopic nuclear theory calculations are feasible and are sensitive to poorly constrained 3-neutron forces.
Prediction of protein function from protein interaction networks has received attention in the post-genomic era. A popular strategy has been to cluster the network into functionally coherent groups ...of proteins and assign the entire cluster with a function based on functions of its annotated members. Traditionally, network research has focused on clustering of nodes. However, clustering of edges may be preferred: nodes belong to multiple functional groups, but clustering of nodes typically cannot capture the group overlap, while clustering of edges can. Clustering of adjacent edges that share many neighbors was proposed recently, outperforming different node clustering methods. However, since some biological processes can have characteristic 'signatures' throughout the network, not just locally, it may be of interest to consider edges that are not necessarily adjacent.
We design a sensitive measure of the 'topological similarity' of edges that can deal with edges that are not necessarily adjacent. We cluster edges that are similar according to our measure in different baker's yeast protein interaction networks, outperforming existing node and edge clustering approaches. We apply our approach to the human network to predict new pathogen-interacting proteins. This is important, since these proteins represent drug target candidates.
Software executables are freely available upon request.
tmilenko@nd.edu
Supplementary data are available at Bioinformatics online.
Blastomycosis is a systemic mycotic infection caused by dimorphic fungi. The disease is rare in cats, and reports on imaging findings with central nervous system (CNS) involvement are limited. ...Magnetic resonance imaging (MRI) was performed antemortem in three feline patients. Imaging findings that may allow prioritization of intracranial blastomycosis over other differential diagnoses included focal or multifocal intra-axial mass lesions with dural contact, lesion hypointensity on T2-weighted images and diffusion-weighted imaging/apparent diffusion coefficient map (DWI/ADC), strong and homogeneous contrast enhancement of the lesion(s), concurrent meningeal enhancement, marked perilesional edema and mass-effect, and ocular abnormalities. One cat was managed successfully and had a recurrence of CNS blastomycosis more than 4.5 years after the initial diagnosis. Repeat MRI at that point revealed both new and persistent (chronic) abnormalities.
Parity violating electron scattering allows model-independent measurements of neutron densities that are free from most strong interaction uncertainties. In this paper, we present statistical error ...estimates for a variety of experiments. The neutron radius Rn can be measured in several nuclei, as long as the nuclear excited states are not too low in energy. We present error estimates for Rn measurements in 40Ca, 48Ca, 112Sn, 120Sn, 124Sn and 208Pb. In general, we find that the smaller the nucleus, the easier the measurement. This is because smaller nuclei can be measured at higher momentum transfers where the parity violating asymmetry Apv is larger. Also in general, the more neutron rich the isotope, the easier the measurement, because neutron-rich isotopes have larger weak charges and larger Apv. Measuring Rn in 48Ca appears very promising because it has a higher figure of merit than 208Pb. In addition, Rn(48Ca) may be more easily related to two-nucleon and three-nucleon interactions, including very interesting three-neutron forces, than Rn(208Pb). After measuring Rn, one can constrain the surface thickness of the neutron density an with a second measurement at somewhat higher momentum transfers. We present statistical error estimates for measuring an in 48Ca, 120Sn and 208Pb. Again, we find that an is easier to measure in smaller nuclei.
The (2)H(e,e'p)n cross section at a momentum transfer of 3.5 (GeV/c)(2) was measured over a kinematical range that made it possible to study this reaction for a set of fixed missing momenta as a ...function of the neutron recoil angle θ(nq) and to extract missing momentum distributions for fixed values of θ(nq) up to 0.55 GeV/c. In the region of 35°≤θ(nq)≤45° recent calculations, which predict that final-state interactions are small, agree reasonably well with the experimental data. Therefore, these experimental reduced cross sections provide direct access to the high momentum component of the deuteron momentum distribution in exclusive deuteron electrodisintegration.
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► SHG spectra reveal unusually strong surface adsorption. ► Spectra fit best to concerted ion pair adsorption model. ► Nitrite and nitrate behave very differently. ► Resembles ...‘Jones–Ray Effect.’
We describe the first detailed experimental characterization of surface adsorption of an aqueous ion pair and quantify the unusual surface behavior of sodium nitrite, a ubiquitous component of natural waters. The onset of unusually strong adsorption at concentrations as low as ca. 0.1
M resembles the controversial ‘Jones–Ray Effect,’ wherein 13 salts exhibited surface tension minima in the millimolar region before resuming the normal linear increase with bulk concentrations. Given the compelling analogy recently found between adsorption of ions to the air–water interface, and the Hofmeister Effects of biochemistry, these results have important implications for the mechanism underlying these phenomena.
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