Collapse of the N=28 shell closure in 42^{42}Si

The energies of the excited states in very neutron-rich $^{42}$Si and $^{41,43}$P have been measured using in-beam $\gamma$-ray spectroscopy from the fragmentation of secondary beams of $^{42,44}$S at 39 A.MeV. The low 2$^+$ energy of $^{42}$Si, 770(19) keV, together with the level schemes of $^{41,43}$P provide evidence for the disappearance of the Z=14 and N=28 spherical shell closures, which is ascribed mainly to the action of proton-neutron tensor forces. New shell model calculations indicate that $^{42}$Si is best described as a well deformed oblate rotor.Comment: 4 pages, 3 figures, accepted for publication in Phys. Rev. let

In-beam spectroscopic studies of 44^{44}S nucleus

The structure of the $^{44}$S nucleus has been studied at GANIL through the one proton knock-out reaction from a $^{45}$Cl secondary beam at 42 A$\cdot$MeV. The $\gamma$ rays following the de-excitation of $^{44}$S were detected in flight using the 70 BaF${_2}$ detectors of the Ch\^{a}teau de Cristal array. An exhaustive $\gamma\gamma$-coincidence analysis allowed an unambiguous construction of the level scheme up to an excitation energy of 3301 keV. The existence of the spherical 2$^+_2$ state is confirmed and three new $\gamma$-ray transitions connecting the prolate deformed 2$^+_1$ level were observed. Comparison of the experimental results to shell model calculations further supports a prolate and spherical shape coexistence with a large mixing of states built on the ground state band in $^{44}$S.Comment: 6 pages, 5 figures, accepted for publication in Physical Review

Study of 19^{19} Na at SPIRAL

NESTERInternational audienceThe excitation function for the elastic-scattering reaction p18Ne, p18Ne was measured with the first radioactive beam from the SPIRAL facility at the GANIL laboratory and with a solid cryogenic hydrogen target. Several broad resonances have been observed, corresponding to new excited states in the unbound nucleus 19Na. In addition, two-proton emission events have been identified and are discussed

Development of the therapeutic regimen based on the synergistic activity of cyclophosphamide and double-stranded DNA preparation which results in complete cure of mice engrafted with Krebs-2 ascites

Cumulative evidence obtained in this series of studies has guided the logic behind the development of a novel composite dsDNA-based preparation whose therapeutic application according to the specific regimen completely cures the mice engrafted with otherwise lethal Krebs-2 ascites. The likely mechanism involves elimination of TAMRA+ tumor-inducing stem cells (TISCs) from Krebs-2 tumors. We performed quantitative analysis of TISC dynamics in Krebs-2  ascites following treatment with the cytostatic drug cyclophosphamide (CP) and untreated control cells. In intact ascites, TISC percentage oscillates around a certain value. Following CP treatment and massive apoptosis of committed cancer cell subpopulation, we observed relative increase in TISC percentage, which is consistent with reduced susceptibility of TISCs to CP. Nonetheless, this treatment apparently synchronizes TISCs in a cell cycle phase when they become sensitive to further drug treatments. We describe the regimen of synergistic DNA + CP activity against Krebs-2 ascites. This protocol results in a complete cure of 50 % of Krebs-2 engrafted mice and involves three metronomic injections of CP exactly at the timepoints when repair cycles are about to finish combined with dsDNA injections 18 hours following each CP injection. The “final shot” uses CP + DNA treatment, which targets the surviving yet highly synchronized and therefore treatmentsensitive cells. The first three CP/DNA injections appear to arrest Krebs-2 cells in late S-G2-M phase and result in their simultaneous progression into G1-S phase. The timing of the “final shot” is crucial for the successful treatment, which eradicates tumorigenic cell subpopulation from Krebs-2 ascites. Additionally, we quantified the changes in several biochemical, cellular and morphopathological parameters in mice throughout different treatment stages

Analysis of different therapeutic schemes combining cyclophosphamide and doublestranded DNA preparation for eradication of Krebs-2 primary ascites in mice

In the present paper, we report on the series of experiments where multiple regimens of CP and dsDNA injections were tested for targeting the ascites form of murine Krebs-2 cancer in situ. We show that combining CP with cross-linked human and salmon dsDNA results in a synergistic toxicity for ascites-bearing mice, an observation supported by the histopathology analysis of organs and tissues of experimental animals. In contrast, using a composite mixture of native and cross-linked human and salmon DNA after CP injections leads to a significant increase in average lifespan of the treated mice. Further, we demonstrate that repeated rounds of CP+dsDNA injections result in dramatic anticancer effect. The timing of injections is chosen so that they target the cells that were insensitive to the previous treatments as they were in the G2/M phase. 3-4 rounds of injections are needed to eliminate the subpopulation of tumor-initiating cancer stem cells. Our experiments identified the regimen when complete resorption of the primary Krebs-2 ascites occurs in all of the treated animals, followed by a remarkable remission period lasting 7-9 days. Yet, this regimen does not prevent secondary site metastases (either solid or ascites form) from developing, which is likely caused by the migration of ascites cells into adjacent tissues or by incomplete eradication of cancer stem cells. To address these and other questions, we expanded the study and performed histopathology analysis, which indicated that secondary metastases is not the only cause of death. In fact, many animals displayed unfolding systemic inflammatory reaction which was culminated by multiple organ failure. Thus, we developed the concept for treating ascites form of Krebs-2 cancer, which allows elimination of the primary ascites

Reaction cross-section and reduced strong absorption radius measurements of neutron-rich nuclei in the vicinity of closed shells N=20 and N=28

The energy-integrated reaction cross-sections of several neutron-rich nuclei (N17-22, O19-24, F21-27, Ne23-30, Na26-33, Mg28-35, Al31-38, Si33-40, (36-42)p, S39-44, Cl42-45, Ar-45,Ar-46), measured at intermediate energy (30-65 A MeV), via direct method, are presented. Silicon detectors have been used as the active target as well as for particles identification. The reduced strong absorption radii r(0)(2) are extracted and compared to the data available from the literature. New measurements for 19 nuclei (F-27, Ne-27,Ne-30, Na-33, (28,34-35)mg, Al36-38, Si38-40, P41-42, S42-44, Cl-45) are revealed. From the study of the isospin dependence of the reduced strong absorption radius, a new quadratic parameterisation of the nuclear radii in the closed shell regions N = 8 and N = 28, is proposed. According to this parameterisation, the proton/neutron rich nuclei skin effect is well described and a new anomalous structure: halo-structure or large deformation is suggested for Mg-35 and S-44 nuclei. (c) 2006 Elsevier B.V. All rights reserved

Reaction cross-sections and reduced strong absorption radii of nuclei in the vicinity of closed shells N=20 and N=28

Energy integrated reaction cross-section measurements of around sixty neutron-rich nuclei covering the region of closed shells N = 20 and N = 28 were performed at intermediate energy (30-65 A.MeV) using direct method. In this experiment, silicon detectors were used as active targets. The reduced strong absorption radii, r02, for 19 new nuclei (27F, 27,30Ne, 33Na, 28,34-35Mg, 36-38Al, 38-40Si, 41-42P, 42-44S and 45Cl) are deduced for the first time. An additional 60 radii, also measured in this experiment, are compared to results from literature. A new quadratic parametrization is proposed for the nuclear radius as a function of the isospin in the region of closed shells N = 8 and N = 28. According to this parametrization, the skin effect is well reproduced and anomalous behaviour on the radii are observed in 23N, 29Ne, 33Na, 35Mg, 44S, 45Cl and 45Ar nuclei