10,227 research outputs found
More on heavy tetraquarks in lattice QCD at almost physical pion mass
We report on our progress in studying exotic, heavy tetraquark states,
. Using publicly available dynamical
Wilson-Clover gauge configurations, generated by the PACS-CS collaboration,
with pion masses 164, 299 and 415 MeV, we extend our previous analysis
to heavy quark components containing heavier than physical bottom quarks or , charm and bottom quarks and also only charm quarks
. Throughout we employ NRQCD and relativistic heavy quarks for
the heavier than bottom, bottom and charm quarks. Using our previously
established diquark-antidiquark and meson-meson operator basis we comment in
particular on the dependence of the binding energy on the mass of the heavy
quark component , with heavy quarks ranging from . In the heavy flavor non-degenerate case, ,
and especially for the tetraquark channel , we extend our work
to utilize a GEVP to study the ground and threshold states thereby
enabling a clear identification of possible binding. Finally, we present
initial work on the system where a much
larger operator basis is available in comparison to flavor combinations with
NRQCD quarks.Comment: 8 pages, 5 figures, proceedings contribution to "Lattice 2017. 35th
International Symposium on Lattice Field Theory", 18th-24th June 2017,
Granada, Spai
Evidence for charm-bottom tetraquarks and the mass dependence of heavy-light tetraquark states from lattice QCD
We continue our study of heavy-light four-quark states and find evidence from
lattice QCD for the existence of a strong-interaction-stable
tetraquark with mass in the range of 15 to 61 MeV below
threshold. Since this range includes the electromagnetic
decay threshold, current uncertainties do not allow us to
determine whether such a state would decay electromagnetically, or only weakly.
We also perform a study at fixed pion mass, with NRQCD for the heavy quarks,
simulating and tetraquarks with or
and variable, unphysical in order to investigate the heavy
mass-dependence of such tetraquark states. We find that the dependence of the
binding energy follows a phenomenologically-expected form and that, though
NRQCD breaks down before is reached, the results at higher
clearly identify the channel as the
most likely to support a strong-interaction-stable tetraquark state at
. This observation serves to motivate the direct
simulation. Throughout we use dynamical ensembles
with pion masses 415, 299, and 164 MeV reaching down almost to the
physical point, a relativistic heavy quark prescription for the charm quark,
and NRQCD for the bottom quark(s).Comment: 24 pages, 4 figure
Exploring New Chemotherapeutic Strategies Against Brain Cancer
Approximately 4,000 children in the United States are diagnosed each year with a brain tumor. Brain cancers are the deadliest of all pediatric cancers as they have survival rates of less than 20%. Typical treatments include surgery and radiation therapy. However, chemotherapy is the primary therapeutic option for children, especially against aggressive brain tumors. An important chemotherapeutic agent is temozolomide, an alkylating agent that causes cell death by damaging DNA. In this project, we tested the ability of non-natural nucleosides developed in our lab in order to increase the ability of temozolomide to kill brain cancer cells. Our results show that combining low doses of our nucleoside with temozolomide kills more cells compared to treatment with either compound individually. The increase in efficacy is specific for temozolomide as similar effects are not observed in cells treated with other chemotherapeutic agents such as cisplatin, 5-fluorouracil, and taxol. High-field microscopy techniques demonstrate that the combination of our nucleoside and temozolomide causes cell death via apoptosis as opposed to necrosis. A model is provided describing how our novel nucleoside analog increases the cell-killing effects of temozolomide by inhibiting the misreplication of damaged DNA created by this agent. Collectively, these studies provide pharmacological evidence for a new treatment strategy to more effectively treat patients with brain cancers.https://engagedscholarship.csuohio.edu/u_poster_2013/1007/thumbnail.jp
An Unusual Case of Colon Perforation Complicating Acute Pancreatitis
Colonic complications of severe acute pancreatitis occur rarely. Although there have been several theories on how pancreatic pseudocysts rupture into the colon, the exact pathogenesis remains unknown. We report an unusual case of pseudocysts complicating severe acute pancreatitis presenting with colonic perforation in a 71-year-old man with a history of chronic mesenteric ischemia. Pressure effects from a giant pseudocyst and intravascular volume depletion with acute insult on chronic mesenteric ischemia are highlighted as possible etiologic factors
Dimensionality of social networks using motifs and eigenvalues
We consider the dimensionality of social networks, and develop experiments
aimed at predicting that dimension. We find that a social network model with
nodes and links sampled from an -dimensional metric space with power-law
distributed influence regions best fits samples from real-world networks when
scales logarithmically with the number of nodes of the network. This
supports a logarithmic dimension hypothesis, and we provide evidence with two
different social networks, Facebook and LinkedIn. Further, we employ two
different methods for confirming the hypothesis: the first uses the
distribution of motif counts, and the second exploits the eigenvalue
distribution.Comment: 26 page
Forming Early-type Galaxies in Groups Prior to Cluster Assembly
We study a unique proto-cluster of galaxies, the supergroup SG1120-1202. We
quantify the degree to which morphological transformation of cluster galaxies
occurs prior to cluster assembly in order to explain the observed early-type
fractions in galaxy clusters at z=0. SG1120-1202 at z~0.37 is comprised of four
gravitationally bound groups that are expected to coalesce into a single
cluster by z=0. Using HST ACS observations, we compare the morphological
fractions of the supergroup galaxies to those found in a range of environments.
We find that the morphological fractions of early-type galaxies (~60 %) and the
ratio of S0 to elliptical galaxies (0.5) in SG1120-1202 are very similar to
clusters at comparable redshift, consistent with pre-processing in the group
environment playing the dominant role in establishing the observed early-type
fraction in galaxy clusters.Comment: 5 pages, 2 figures, 2 tables. Accepted for publication in ApJ Letter
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