307 research outputs found
Determination of the photodisintegration reaction rates involving charged particles: systematical calculations and proposed measurements based on Extreme Light Infrastructure - Nuclear Physics (ELI-NP)
Photodisintegration reaction rates involving charged particles are of
relevance to the p-process nucleosynthesis that aims at explaining the
production of the stable neutron-deficient nuclides heavier than iron. In this
study, the cross sections and astrophysical rates of (g,p) and (g,a) reactions
for about 3000 target nuclei with 10<Z<100 ranging from stable to proton
dripline nuclei are computed. To study the sensitivity of the calculations to
the optical model potentials (OMPs), both the phenomenological Woods-Saxon and
the microscopic folding OMPs are taken into account. The systematic comparisons
show that the reaction rates, especially for the (g,a) reaction, are
dramatically influenced by the OMPs. Thus the better determination of the OMP
is crucial to reduce the uncertainties of the photodisintegration reaction
rates involving charged particles. Meanwhile, a gamma-beam facility at ELI-NP
is being developed, which will open new opportunities to experimentally study
the photodisintegration reactions of astrophysics interest. Considering both
the important reactions identified by the nucleosynthesis studies and the
purpose of complementing the experimental results for the reactions involving
p-nuclei, the measurements of six (g,p) and eight (g,a) reactions based on the
gamma-beam facility at ELI-NP and the ELISSA detector for the charged particles
detection are proposed, and the GEANT4 simulations are correspondingly
performed. The minimum required energies of the gamma-beam to measure these
reactions are estimated. It is shown that the direct measurements of these
photonuclear reactions within the Gamow windows at T_9=2.5 for p-process are
fairly feasible and promising at ELI-NP. The expected experimental results will
be used to constrain the OMPs of the charged particles, which can eventually
reduce the uncertainties of the reaction rates for the p-process
nucleosynthesis.Comment: 14 pages, 8 figures, Phys. Rev. C accepte
Trojan Horse as an indirect technique in nuclear astrophysics. Resonance reactions
The Trojan Horse method is a powerful indirect technique that provides
information to determine astrophysical factors for binary rearrangement
processes at astrophysically relevant energies by measuring
the cross section for the Trojan Horse reaction in
quasi-free kinematics. We present the theory of the Trojan Horse method for
resonant binary subreactions based on the half-off-energy-shell R matrix
approach which takes into account the off-energy-shell effects and initial and
final state interactions.Comment: 6 pages and 1 figur
Molecular Structures in T=1 states of 10B
Multi-center (molecular) structures can play an important role in light
nuclei. The highly deformed rotational band in 10Be with band head at 6.179 MeV
has been observed recently and suggested to have an exotic alpha:2n:alpha
configuration. A search for states with alpha:pn:alpha two-center molecular
configurations in 10B that are analogous to the states with alpha:2n:alpha
structure in 10Be has been performed. The T=1 isobaric analog states in 10B
were studied in the excitation energy range of E=8.7-12.1 MeV using the
reaction 1H(9Be,alpha)6Li*(T=1, 0+, 3.56 MeV). An R-matrix analysis was used to
extract parameters for the states observed in the (p,alpha) excitation
function. Five T=1 states in 10B have been identified. The known 2+ and 3-
states at 8.9 MeV have been observed and their partial widths have been
measured. The spin-parities and partial widths for three higher lying states
were determined. Our data support theoretical predictions that the 2+ state at
8.9 MeV (isobaric analog of the 7.54 MeV state in 10Be) is a highly clustered
state and can be identified as a member of the alpha:np:alpha rotational band.
The next member of this band, the 4+ state, has not been found. A very broad 0+
state at 11 MeV that corresponds to pure alpha+6Li(0+,T=1) configuration is
suggested and it might be related to similar structures found in 12C, 18O and
20Ne.Comment: 10 pages, 10 figures, accepted in Physical Review
High intensity X/ γ photon beams for nuclear physics and photonics
In this manuscript we review the challenges of Compton back-scattering sources in advancing photon beam performances in the1−20MeVenergy range, underlining the design criteria bringing tomaximum spectral luminosity and briefly describing the main achieve-ments in conceiving and developing new devices (multi-bunch RF cav-ities and Laser recirculators) for the case of ELI-NP Gamma BeamSystem (ELI-NP-GBS)
Recent Results for the Effects of Distortion in the Inter-Cluster Motion in Light Nuclei and Application to Nuclear Astrophysics
Deuteron induced quasi-free scattering and reactions have been extensively investigated in the past few decades. This was done not only for the study of the nuclear structure and processes but also for the important astrophysical implication (Trojan Horse Method, THM). In particular the width of the neutron momentum distribution in deuteron will be studied as a function of the transferred momentum. THM applications will also be discussed because the momentum distribution of the spectator particle inside the Trojan horse nucleus is a necessary input for this method. The impact of the width variation on the extraction of the astrophysical S(E)-factor is discussed as well as the relevance of the s and d wave component in the deuteron wave function
Measurement of the 20 and 90 keV resonances in the N reaction via THM
The reaction is of primary importance in
several astrophysical scenarios, including fluorine nucleosynthesis inside AGB
stars as well as oxygen and nitrogen isotopic ratios in meteorite grains. Thus
the indirect measurement of the low energy region of the reaction has been performed to reduce the nuclear
uncertainty on theoretical predictions. In particular the strength of the 20
and 90 keV resonances have been deduced and the change in the reaction rate
evaluated.Comment: 4 pages, 4 figures, submitted to PR
Clinical implications of discordant early molecular responses in CML patients treated with imatinib
A reduction in BCR-ABL1/ABL1IS transcript levels to <10% after 3 months or <1% after 6 months of tyrosine kinase inhibitor therapy are associated with superior clinical outcomes in chronic myeloid leukemia (CML) patients. In this study, we investigated the reliability of multiple BCR-ABL1 thresholds in predicting treatment outcomes for 184 subjects diagnosed with CML and treated with standard-dose imatinib mesylate (IM). With a median follow-up of 61 months, patients with concordant BCR-ABL1/ABL1IS transcripts below the defined thresholds (10% at 3 months and 1% at 6 months) displayed significantly superior rates of event-free survival (86.1% vs. 26.6%) and deep molecular response (≥ MR4; 71.5% vs. 16.1%) compared to individuals with BCR-ABL1/ABL1IS levels above these defined thresholds. We then analyzed the outcomes of subjects displaying discordant molecular transcripts at 3-and 6-month time points. Among these patients, those with BCR-ABL1/ABL1IS values >10% at 3 months but <1% at 6 months fared significantly better than individuals with BCR-ABL1/ABL1IS <10% at 3 months but >1% at 6 months (event-free survival 68.2% vs. 32.7%; p < 0.001). Likewise, subjects with BCR-ABL1/ABL1IS at 3 months >10% but <1% at 6 months showed a higher cumulative incidence of MR4 compared to patients with BCR-ABL1/ABL1IS <10% at 3 months but >1% at 6 months (75% vs. 18.2%; p < 0.001). Finally, lower BCR-ABL1/GUSIS transcripts at diagnosis were associated with BCR-ABL1/ABL1IS values <1% at 6 months (p < 0.001). Our data suggest that when assessing early molecular responses to therapy, the 6-month BCR-ABL1/ABL1IS level displays a superior prognostic value compared to the 3-month measurement in patients with discordant oncogenic transcripts at these two pivotal time points
Trojan Horse Particle Invariance: An Extensive Study
In the last decades, the Trojan Horse method (THM) has played a crucial role for the measurement of several particle (both neutron and charged one) induced cross sections for reactions of astrophysical interest. To better understand its cornerstones and its applications to physical cases, many tests were performed to verify all its properties and the possible future perspectives. The Trojan Horse nucleus invariance proves the relatively simple approach allowed by the pole approximation and sheds light in the involved reaction mechanisms. Here we shortly review the complete work for the binary 2H(d,p)3H, 6Li(d,α)4He, 6Li(p,α)3He, 7Li(p,α)4He reactions, by using the quasi free reactions after break-ups of different nuclides. Results are compared assuming the 6Li and 3He break-up in the case of the d(d,p)t, 6Li(d,α)4He reactions and considering the 2H and 3He break-up for 6Li(p,α)3He, 7Li(p,α)4He reactions. These results, regardless of the Trojan Horse particle or the break-up scheme, confirms the applicability of the standard description of the THM and suggests the independence of binary indirect cross section on the chosen Trojan Horse nuclei for a whole spectra of different cases. This gives a strong basis for the understanding of the quasi-free mechanism which is the foundation on which the THM lies
Resonance Strength Measurement at Astrophysical Energies: The 17O(p,α)14N Reaction Studied via THM
In recent years, the Trojan Horse Method (THM) has been used to investigate the low-energy cross sections of proton-induced reactions on 17 O nuclei, overcoming extrapolation procedures and enhancement effects due to electron screening. We will report on the indirect study of the 17 O(p, α ) 14 N reaction via the Trojan Horse Method by applying the approach developed for extracting the resonance strength of narrow resonance in the ultralow energy region. The mean value of the strengths obtained in the two measurements was calculated and compared with the direct data available in literature
Peripheral facial palsy following ventriculoperitoneal shunt. The lesson we have learned
The most frequent complications after shunt surgery are infective and obstructive. Other types are less common, and eventually occur due to technical errors during brain ventricular puncture, opening the intraperitoneal cavity or the tunnelling of the catheter between the two points. Although rare, there are well-reported complications related to the poor positioning of the distal catheter, with perforation of organs and tissues. We report a very rare case of a male patient with normal pressure hydrocephalus submitted to ventriculoperitoneal shunt. During tunnelling of the shunt stylet, a peripheral facial palsy due to injury to the extra cranial segment of the facial nerve occurred. To the best of our knowledge this is the second case described in Literature. The patient and the surgeon should be aware of this very rare but possible complication in shunt surgery being careful to the course of the facial nerve in the mastoid region
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