Electronic trajectories in atomic physics: The chemical bond in the H2 + ion.

The H2 + ion is the simplest example in which a chemical bond exists, created by one electron between two protons. As all chemical bonds, it is usually considered inexplicable in a classical frame. Here, in view of the extremely large velocities attained by the electron near the protons, we consider a relativistic extension of the standard classical three-body model. This has a great impact since the reference unperturbed system (clamped protons) is no more integrable, and indeed by molecular dynamics simulations, we find that the modification entails the existence of a large region of strongly chaotic motions for the unperturbed system, which lead, for the full system, to a collapse of the molecule. For motions of generic type, with the electron bouncing between the protons, there exists an open region of motions regular enough for producing a bond. Such a region is characterized by the property that the electron's trajectories have an angular momentum pφ along the inter-nuclear axis of the order of the reduced Planck's constant ℏ. Moreover, special initial data exist for which the experimental bond length and oscillation frequency of the protons (but not the dissociation energy) are well reproduced. Also, well reproduced is the quantum potential, albeit only in an extended interval about the minimum.

Over 30% of patients with splenic marginal zone lymphoma express the same immunoglobulin heavy variable gene: ontogenetic implications.

We performed an immunogenetic analysis of 345 IGHV-IGHD-IGHJ rearrangements from 337 cases with primary splenic small B-cell lymphomas of marginal-zone origin. Three immunoglobulin (IG) heavy variable (IGHV) genes accounted for 45.8% of the cases (IGHV1-2, 24.9%; IGHV4-34, 12.8%; IGHV3-23, 8.1%). Particularly for the IGHV1-2 gene, strong biases were evident regarding utilization of different alleles, with 79/86 rearrangements (92%) using allele (*)04. Among cases more stringently classified as splenic marginal-zone lymphoma (SMZL) thanks to the availability of splenic histopathological specimens, the frequency of IGHV1-2(*)04 peaked at 31%. The IGHV1-2(*)04 rearrangements carried significantly longer complementarity-determining region-3 (CDR3) than all other cases and showed biased IGHD gene usage, leading to CDR3s with common motifs. The great majority of analyzed rearrangements (299/345, 86.7%) carried IGHV genes with some impact of somatic hypermutation, from minimal to pronounced. Noticeably, 75/79 (95%) IGHV1-2(*)04 rearrangements were mutated; however, they mostly (56/75 cases; 74.6%) carried few mutations (97-99.9% germline identity) of conservative nature and restricted distribution. These distinctive features of the IG receptors indicate selection by (super)antigenic element(s) in the pathogenesis of SMZL. Furthermore, they raise the possibility that certain SMZL subtypes could derive from progenitor populations adapted to particular antigenic challenges through selection of VH domain specificities, in particular the IGHV1-2(*)04 allele.

Coil-to-globule transition of poly(N-isopropylacrylamide) doped with chiral amino acidic comonomers.

By combined light scattering and circular dichroism measurements (CD), we have investigated the coil-to-globule transition of the thermosensitive polymer poly(N-isopropylacrylamide) (pNIPAAm) copolymerized with a 1/10 fraction of valine- or leucine-derived groups randomly positioned along the chains. The comonomers provide the pNIPAAm chains with chirality, electric charge, and increased hydrophobicity. For valine-derived copolymers, the coil-globule transition is basically unmodified with respect to pNIPAAm, whereas doping with leucine-derived groups significantly lowers the transition temperature and makes the transition discontinuous. We find the CD signal of the chiral comonomers to cleanly depend on the local chain density. We interpret this behavior as an effect of the whole chain conformation on the conformations accessible to the chiral groups.

Surface CD14 positivity in B-cell chronic lymphocytic leukaemia is related to clinical outcome.

The aberrant expression of the myelomonocytic antigen CD14 was investigated in 128 untreated patients diagnosed with B-cell chronic lymphocytic leukaemia (B-CLL). A cut-off value of 5 x 10(9)/l CD14-positive cells was chosen for statistical analysis because it showed the best discriminating power among patients with different clinical features. 56 cases had a CD14+ cell count >5 x 10(9)/l. A significant correlation was found between Rai and Binet stages and total tumour mass (TTM) score on one hand, and the absolute CD14+ cell cut-off, on the other. This relationship was more evident in Rai 0-II and Binet A-B stages, where a CD14+ cell count >5 x 10(9)/l was preferentially distributed among patients with a higher tumoral mass. In univariate analysis the survival probability at 5 and 10 years showed a significant correlation with Rai and Binet stages, TTM score, CD14+ absolute cell count and median age. The median overall survival (OS) was 63 months for patients with a CD14+ cell count >5 x 10(9)/l and 136 months for those with a CD14+ cell count < 5 x 10(9)/l. In the multivariate Cox regression model, Rai stage, age and CD14+ cell count were independent significant factors for the prediction of OS. Finally, when the same analysis was restricted to Rai stages 0-II, CD14+ cell count was the only significant independent parameter influencing OS, with a relative death risk of 3.8. In conclusion, these data reveal that CD14+ represents an important marker for predicting OS in B-CLL patients and, therefore, we suggest that it should be included in the immunological characterization of B-CLL.