197 research outputs found
Approximation of excitonic absorption in disordered systems using a compositional component weighted CPA
Employing a recently developed technique of component weighted two particle
Green's functions in the CPA of a binary substitutional alloy we
extend the existing theory of excitons in such media using a contact potential
model for the interaction between electrons and holes to an approximation which
interpolates correctly between the limits of weak and strong disorder. With our
approach we are also able to treat the case where the contact interaction
between carriers varies between sites of different types, thus introducing
further disorder into the system. Based on this approach we study numerically
how the formation of exciton bound states changes as the strengths of the
contact potentials associated with either of the two site types are varied
through a large range of parameter values.Comment: 27 pages RevTeX (preprint format), 13 Postscript figure file
Free induction signal from biexcitons and bound excitons
A theory of the free induction signal from biexcitons and bound excitons is
presented. The simultaneous existence of the exciton continuum and a bound
state is shown to result in a new type of time dependence of the free
induction. The optically detected signal increases in time and oscillates with
increasing amplitude until damped by radiative or dephasing processes.
Radiative decay is anomalously fast and can result in strong picosecond pulses.
The expanding area of a coherent exciton polarization (inflating antenna),
produced by the exciting pulse, is the underlying physical mechanism. The
developed formalism can be applied to different biexciton transients.Comment: RevTeX, 20 p. + 2 ps fig. To appear in Phys. Rev. B1
Identifying Cancers Impacted by CDK8/19
CDK8 and CDK19 Mediator kinases are transcriptional co-regulators implicated in several types of cancer. Small-molecule CDK8/19 inhibitors have recently entered or are entering clinical trials, starting with breast cancer and acute myeloid leukemia (AML). To identify other cancers where these novel drugs may provide benefit, we queried genomic and transcriptomic databases for potential impact of CDK8, CDK19, or their binding partner CCNC. sgRNA analysis of a panel of tumor cell lines showed that most tumor types represented in the panel, except for some central nervous system tumors, were not dependent on these genes. In contrast, analysis of clinical samples for alterations in these genes revealed a high frequency of gene amplification in two highly aggressive subtypes of prostate cancer and in some cancers of the GI tract, breast, bladder, and sarcomas. Analysis of survival correlations identified a group of cancers where CDK8 expression correlated with shorter survival (notably breast, prostate, cervical cancers, and esophageal adenocarcinoma). In some cancers (AML, melanoma, ovarian, and others), such correlations were limited to samples with a below-median tumor mutation burden. These results suggest that Mediator kinases are especially important in cancers that are driven primarily by transcriptional rather than mutational changes and warrant an investigation of their role in additional cancer types
Level structure of 32P from 31P(d, p)32P reactions
States up to an excitation energy of 6.8 MeV of the nucleus 32P are investigated by studying the angular distribution of protons in the reaction 31P(d, p)32P. One new state is found at 1.51 MeV. A state previously reported at 6.56 MeV is found to be a doublet with excitation energies 6.58 MeV and 6.53 MeV. The angular distributions for 28 of the stronger levels are fitted with Butler curves, and probable ln values are given for these levels. Relative reduced widths are given for the same levels. The results are discussed in terms of the Nilsson rotational model and the shell model.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32295/1/0000362.pd
Continuous symmetry of C60 fullerene and its derivatives
Conventionally, the Ih symmetry of fullerene C60 is accepted which is
supported by numerous calculations. However, this conclusion results from the
consideration of the molecule electron system, of its odd electrons in
particular, in a close-shell approximation without taking the electron spin
into account. Passing to the open-shell approximation has lead to both the
energy and the symmetry lowering up to Ci. Seemingly contradicting to a
high-symmetry pattern of experimental recording, particularly concerning the
molecule electronic spectra, the finding is considered in the current paper
from the continuous symmetry viewpoint. Exploiting both continuous symmetry
measure and continuous symmetry content, was shown that formal Ci symmetry of
the molecule is by 99.99% Ih. A similar continuous symmetry analysis of the
fullerene monoderivatives gives a reasonable explanation of a large variety of
their optical spectra patterns within the framework of the same C1 formal
symmetry exhibiting a strong stability of the C60 skeleton.Comment: 11 pages. 5 figures. 6 table
First direct measurements of g factors of the three superdeformed bands of 194Hg
The average g factors of the high-energy states of the three superdeformed bands in 194Hg were determined
directly in a transient field experiment. The reaction 150Nd(48Ca,4n)194Hg at a beam energy of 203 MeV was
used to provide recoiling reaction product nuclei with sufficient velocity to traverse a gadolinium ferromagnetic
layer. The resulting g factors g(SD1)50.36(10), g(SD2)50.41(20), and g(SD3)50.71(26) are in
agreement with cranked Hartree-Fock calculations as well as with the picture of a rigid rotation for which g
5Z/A
Single particle signatures in high-spin, quasi continuum states in 193,194 Hg from g-factor measurements
The average g factors of high spin, high-excitation energy, quasi continuum structures in 194,193Hg were measured by observing the precessions of the angular distributions of γ-ray transitions in several normal-deformation bands that coalesce in the decay of the entry distribution of states. The average g factors of the states leading to the three main bands in the 193,194Hg isoles were: 〈g(193Hg)〉 = +0.19(1) and 〈g(194Hg)〉 = +0.26(1), respectively. These average g factors are smaller than the average of the g factors of the high energy states in the three superdeformed bands of 194Hg, 〈g(SD;194Hg)〉 = +0.41(8). While the nucleus in the superdeformed well behaves like a rigid rotor, the present results demonstrate the important role played by multiple, quasi particle neutron configurations in the structure of normal-deformation, highly-excited nuclear states
An Aqueous Extract of Fagonia cretica Induces DNA Damage, Cell Cycle Arrest and Apoptosis in Breast Cancer Cells via FOXO3a and p53 Expression
Background - Plants have proved to be an important source of anti-cancer drugs. Here we have investigated the cytotoxic action of an aqueous extract of Fagonia cretica, used widely as a herbal tea-based treatment for breast cancer. Methodology/Principal Findings - Using flow cytometric analysis of cells labeled with cyclin A, annexin V and propidium iodide, we describe a time and dose-dependent arrest of the cell cycle in G0/G1 phase of the cell cycle and apoptosis following extract treatment in MCF-7 (WT-p53) and MDA-MB-231 (mutant-p53) human breast cancer cell lines with a markedly reduced effect on primary human mammary epithelial cells. Analysis of p53 protein expression and of its downstream transcription targets, p21 and BAX, revealed a p53 associated growth arrest within 5 hours of extract treatment and apoptosis within 24 hours. DNA double strand breaks measured as ?-H2AX were detected early in both MCF-7 and MDA-MB-231 cells. However, loss of cell viability was only partly due to a p53-driven response; as MDA-MB-231 and p53-knockdown MCF-7 cells both underwent cell cycle arrest and death following extract treatment. p53-independent growth arrest and cytotoxicity following DNA damage has been previously ascribed to FOXO3a expression. Here, in MCF-7 and MDA-MB-231 cells, FOXO3a expression was increased significantly within 3 hours of extract treatment and FOXO3 siRNA reduced the extract-induced loss of cell viability in both cell lines. Conclusions/Significance - Our results demonstrate for the first time that an aqueous extract of Fagonia cretica can induce cell cycle arrest and apoptosis via p53-dependent and independent mechanisms, with activation of the DNA damage response. We also show that FOXO3a is required for activity in the absence of p53. Our findings indicate that Fagonia cretica aqueous extract contains potential anti-cancer agents acting either singly or in combination against breast cancer cell proliferation via DNA damage-induced FOXO3a and p53 expression
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