Optical Shielding of Destructive Chemical Reactions between Ultracold Ground-State NaRb Molecules.

We propose a method to suppress the chemical reactions between ultracold bosonic ground-state ^{23}Na^{87}Rb molecules based on optical shielding. By applying a laser with a frequency blue-detuned from the transition between the lowest rovibrational level of the electronic ground state X^{1}Σ^{+}(v_{X}=0,j_{X}=0), and the long-lived excited level b^{3}Π_{0}(v_{b}=0,j_{b}=1), the long-range dipole-dipole interaction between the colliding molecules can be engineered, leading to a dramatic suppression of reactive and photoinduced inelastic collisions, for both linear and circular laser polarizations. We demonstrate that the spontaneous emission from b^{3}Π_{0}(v_{b}=0,j_{b}=1) does not deteriorate the shielding process. This opens the possibility for a strong increase of the lifetime of cold molecule traps and for an efficient evaporative cooling. We also anticipate that the proposed mechanism is valid for alkali-metal diatomics with sufficiently large dipole-dipole interactions.

Ultracold Dipolar Molecules Composed of Strongly Magnetic Atoms.

In a combined experimental and theoretical effort, we demonstrate a novel type of dipolar system made of ultracold bosonic dipolar molecules with large magnetic dipole moments. Our dipolar molecules are formed in weakly bound Feshbach molecular states from a sample of strongly magnetic bosonic erbium atoms. We show that the ultracold magnetic molecules can carry very large dipole moments and we demonstrate how to create and characterize them, and how to change their orientation. Finally, we confirm that the relaxation rates of molecules in a quasi-two-dimensional geometry can be reduced by using the anisotropy of the dipole-dipole interaction and that this reduction follows a universal dipolar behavior.

Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels.

We have calculated the isotropic C6 coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X(1)Σ(+). We consider the ten species made up of (7)Li, (23)Na, (39)K, (87)Rb, and (133)Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.

Proposal for a laser control of vibrational cooling in Na(2) using resonance coalescence.

With a specific choice of laser parameters resulting in a so-called exceptional point (EP) in the wavelength-intensity parameter plane, it is possible to produce the coalescence of two Floquet resonances describing the photodissociation of the Na(2) molecule, which is one of the candidates for the formation of samples of translationally cold molecules. By appropriately tuning laser parameters along a contour encircling the exceptional point, the resonances exchange their quantum nature. Thus a laser-controlled transfer of the probability density from one field-free vibrational level to another is achieved through adiabatic transport involving these resonances. We propose an efficient scenario for vibrational cooling of Na(2) referring to cascade transfers involving multiple EPs and predicted to be robust up to a 78% rate against laser-induced dissociation.

Effect of surrounding tissue on propagation of axisymmetric waves in arteries.

A model of an artery consisting of a thin-walled flexible tube filled with a Newtonian incompressible liquid and surrounded by an external viscoelastic tissue is studied. The dispersion relations and attenuation lengths are determined for the lowest axially symmetric propagation modes: the Young, Lamb, and torsional modes. The numerical calculations confirm a low attenuation of the Young mode and a relatively weak dependence of its phase velocity on the elastic parameters of the surrounding medium. The Lamb and torsional modes show a nonzero frequency (a gap) at zero wave vector except for the limiting case of the absence of surroundings. The attenuation of the Lamb mode at zero frequency and the gap frequency turns out to be particularly sensitive to the elastic parameters of the surroundings. However, the spatial attenuation of the Lamb mode extends over a length of the order of 10cm at the viscoelastic parameters corresponding to human tissues. Such lengths are comparable to the size of human organs. Three kinds of local axially symmetric perturbations have been studied, and the corresponding amplitude ratios of the Lamb to the Young mode calculated. The amplitude of the Lamb mode turns out to exceed that of the Young mode by a factor of ten at some frequencies with perturbations involving axial motions. Physiological consequences of this effect are discussed.

Comparison of hematopoietic and immune recovery after autologous bone marrow or blood stem cell transplants.

We studied hematopoietic and immune recovery in 40 subjects receiving autologous bone marrow (ABMT) or blood stem cell transplants (ABSCT). Supportive care, transplant-related morbidity, duration of hospitalization and cost were also considered. ABSCT was associated with more rapid recovery of all hematopoietic lineages than was ABMT. However, kinetics of immune recovery were similar between the groups. In the ABSCT group, there was a correlation between numbers of blood progenitor cells infused and the rate of hematopoietic recovery. The accelerated hematopoietic recovery following ABSCT correlated with less morbidity, fewer transfusions, briefer hospitalization and lower cost than ABMT.

Collection of circulating stem cells and their use for autograft in adults with acute lymphoblastic leukaemia.

The level of peripheral blood granulocyte-monocytic precursors (PB CFU-GM) was studied serially in 10 adult patients with acute lymphoblastic leukaemia (ALL) in early complete remission after induction chemotherapy. The patients were distributed into 2 main groups according to the morphological French-American-British classification: ALL2 and ALL3. Collection of circulating stem cells (CSC) by cytapheresis was performed in 7 of these 10 patients with satisfactory results, except in 2 ALL2 patients, both of whom had chromosome translocation, which could have been a contributing factor. It appears, moreover, that even with 2 or 3 inductions courses, the more intensive the chemotherapy regimen in previously non-treated patients, the higher the peak of PB CFU-GM and the better the collection of CSC. The measurement of CFU-GM is certainly a less effective indicator of pluripotent stem cells in blood than in bone marrow, and it is probably necessary, but sufficient, to inject 5 times more CFU-GM than normally injected in marrow transplants to allow prompt and stable engraftment. The feasibility of this new graft technique seems for the moment undeniable, the main problem in ALL is the risk of relapse.

[Collection of circulating stem cells during remission after chemotherapy in acute leukemia]. / Collection de cellules souches circulantes en sortie d'aplasie post-chimiothérapique dans les leucémies aiguës.

The level of circulating myeloid progenitor cells (CFU-G), considered to be a good index of the quantity of circulating hemopoietic stem cells, was measured in the peripheral blood of 5 patients with acute leukemia as they entered first remission. High levels of circulating CFU-G were found in 4 of these 5 patients, depending on the intensity and the number of courses of induction chemotherapy. Repeated cytaphereses were done on 3 of these patients in order to collect and to cryopreserve circulating stem cells, to be used later for autologous transplantation. We propose a model which calculates the number of cytaphereses sufficient to obtain a level of 10(5) CFU-G/kg of weight, considered necessary to achieve a good hemopoietic reconstitution after transplantation.