452 research outputs found
Population of bound excited states in intermediate-energy fragmentation reactions
Fragmentation reactions with intermediate-energy heavy-ion beams exhibit a
wide range of reaction mechanisms, ranging from direct reactions to statistical
processes. We examine this transition by measuring the relative population of
excited states in several sd-shell nuclei produced by fragmentation with the
number of removed nucleons ranging from two to sixteen. The two-nucleon removal
is consistent with a non-dissipative process whereas the removal of more than
five nucleons appears to be mainly statistical.Comment: 5 pages, 6 figure
DNA methylation plays a crucial role during early <i>Nasonia</i> development
Although the role of DNA methylation in insect development is still poorly understood, the number and role of DNA methyltransferases in insects vary strongly between species. DNA methylation appears to be widely present among the social hymenoptera and functional studies in Apis have suggested a crucial role for de novo methylation in a wide variety of developmental processes. The sequencing of three parasitoid Nasonia genomes revealed the presence of three Dnmt1 (Dnmt1a, Dnmt1b and Dnmt1c) genes and one Dnmt2 and Dnmt3 gene, suggesting a role of DNA methylation in Nasonia development. In the present study we show that in Nasonia vitripennis all Dnmt1 messenger RNAs (mRNAs) and Dnmt3 mRNA are maternally provided to the embryo and, of these, Dnmt1a is essential during early embryogenesis. Lowering of maternal Dnmt1a mRNA results in embryonic lethality during the onset of gastrulation. This dependence on maternal Dnmt1a during embryogenesis in an organismal group outside the vertebrates, suggests evolutionary conservation of the function of Dnmt1 during embryogenesis.</p
XHIP-II: Clusters and associations
Context. In the absence of complete kinematic data it has not previously been
possible to furnish accurate lists of member stars for all moving groups. There
has been an unresolved dispute concerning the apparent inconsistency of the
Hipparcos parallax distance to the Pleiades.
Aims. To find improved candidate lists for clusters and associations
represented among Hipparcos stars, to establish distances, and to cast light on
the Pleiades distance anomaly.
Methods. We use a six dimensional fitting procedure to identify candidates,
and plot CMDs for 20 of the nearest groups. We calculate the mean parallax
distance for all groups.
Results. We identify lists of candidates and calculated parallax distances
for 42 clusters and 45 associations represented within the Hipparcos catalogue.
We find agreement between parallax distance and photometric distances for the
most important clusters. For single stars in the Pleiades we find mean parallax
distance 125.6 \pm 4.2 pc and photometric distance 132 \pm 3 pc calibrated to
nearby groups of similar in age and composition. This gives no reason to doubt
either the Hipparcos database or stellar evolutionary theory.Comment: Accepted for publication in Astronomy Letters, 10 pages, 2 fig
Validation and discussion of clinical practicability of the 2022 graded prognostic assessment for NSCLC adenocarcinoma patients with brain metastases in a routine clinical cohort
IntroductionThe goal of this analysis is to validate the 2022 graded prognostic assessment (GPA) for patients with brain metastases from adenocarcinoma of the lung and to discuss its clinical practicability.Methods/material137 patients with adenocarcinoma of the lung were included in this analysis. The disease specific GPA for NSCLC, Lung-molGPA and the GPA for NSCLC adenocarcinoma were calculated. Overall survival was calculated for each GPA group. Additionally, expected and actual OS in the prognostic groups of the GPA available at the time of the patients’ diagnosis was compared.ResultsMedian overall survival (OS) from diagnosis of brain metastases was 15 months (95% confidence interval (CI) 9.7–20.3 months). The median OS in the three individual prognostic groups was 7 months for GPA 0-1, 16 months for GPA 1.5-2, 33 months for GPA 2.5-3 and not reached for GPA 3.5-4 (p<0.001). Median survival times for the individual groups were similar to those published in the original GPA publication. Regarding the expected and actual OS when using the available GPA at the time of diagnosis there was an underestimation of survival of more than 3 months for all except the worst prognosis group.ConclusionWe were able to validate the 2022 GPA for NSCLC adenocarcinoma patients with brain metastases in a similar cohort from a non-academic center. However, the practical applicability regarding the expected median OS might be limited due to the constantly evolving treatment landscape and the consecutive improvement in overall survival
Measurement of excited states in 40Si and evidence for weakening of the N=28 shell gap
Excited states in 40Si have been established by detecting gamma-rays
coincident with inelastic scattering and nucleon removal reactions on a liquid
hydrogen target. The low excitation energy, 986(5) keV, of the 2+[1] state
provides evidence of a weakening in the N=28 shell closure in a neutron-rich
nucleus devoid of deformation-driving proton collectivity.Comment: accepted for publication in PR
Enhanced collectivity in 74Ni
The neutron-rich nucleus 74Ni was studied with inverse-kinematics inelastic
proton scattering using a 74Ni radioactive beam incident on a liquid hydrogen
targetat a center-of-mass energy of 80 MeV. From the measured de-excitation
gamma-rays, the population of the first 2+ state was quantified. The
angle-integrated excitation cross section was determined to be 14(4) mb. A
deformation length of delta = 1.04(16) fm was extracted in comparison with
distorted wave theory, which suggests that the enhancement of collectivity
established for 70Ni continues up to 74Ni. A comparison with results of shell
model and quasi-particle random phase approximation calculations indicates that
the magic character of Z = 28 or N = 50 is weakened in 74Ni
Evolution of the energy spacing in odd-mass K, Cl and P isotopes for
The energy of the first excited state in the neutron-rich N=28 nucleus 45Cl
has been established via in-beam gamma-ray spectroscopy following proton
removal. This energy value completes the systematics of the
E(1/2^+_1)-E(3/2^+_1) level spacing in odd-mass K, Cl and P isotopes for
N=20-28. The results are discussed in the framework of shell-model calculations
in the sd-fp model space. The contribution of the central, spin-orbit and
tensor components is discussed from a calculation based on a proton single-hole
spectrum from G-matrix and pi + rho meson exchange potentials. A composite
model for the proton 0d_{3/2}-1s_{1/2} single-particle energy shift is
presented.Comment: Phys. Rev. C, in pres
Shell structure at N=28 near the dripline: spectroscopy of Si, P and S
Measurements of the N=28 isotones 42Si, 43P and 44S using one- and two-proton
knockout reactions from the radioactive beam nuclei 44S and 46Ar are reported.
The knockout reaction cross sections for populating 42Si and 43P and a 184 keV
gamma-ray observed in 43P establish that the d_{3/2} and s_{1/2} proton orbits
are nearly degenerate in these nuclei and that there is a substantial Z=14
subshell closure separating these two orbits from the d_{5/2} orbit. The
increase in the inclusive two-proton knockout cross section from 42Si to 44S
demonstrates the importance of the availability of valence protons for
determining the cross section. New calculations of the two-proton knockout
reactions that include diffractive effects are presented. In addition, it is
proposed that a search for the d_{5/2} proton strength in 43P via a higher
statistics one-proton knockout experiment could help determine the size of the
Z=14 closure.Comment: Phys. Rev. C, in pres
Z=50 shell gap near Sn from intermediate-energy Coulomb excitations in even-mass Sn isotopes
Rare isotope beams of neutron-deficient Sn nuclei from the
fragmentation of Xe were employed in an intermediate-energy Coulomb
excitation experiment yielding transition strengths.
The results indicate that these values are much larger
than predicted by current state-of-the-art shell model calculations. This
discrepancy can be explained if protons from within the Z = 50 shell are
contributing to the structure of low-energy excited states in this region. Such
contributions imply a breaking of the doubly-magic Sn core in the light
Sn isotopes.Comment: 4 pages, 4 figure
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