Efficient Magnon Injection and Detection via the Orbital Rashba-Edelstein Effect.

Orbital currents and accumulation provide a new avenue to boost spintronic effects in nanodevices. Here, we use interconversion effects between charge current and orbital angular momentum to demonstrate a dramatic increase in the magnon spin injection and detection efficiencies in nanodevices consisting of a magnetic insulator contacted by Pt/CuO_{x} electrodes. Moreover, we note distinct variations in efficiency for magnon spin injection and detection, indicating a disparity in the direct and inverse orbital Rashba-Edelstein effect efficiencies.

Measurement of the Spin Absorption Anisotropy in Lateral Spin Valves.

The spin absorption process in a ferromagnetic material depends on the spin orientation relative to the magnetization. Using a ferromagnet to absorb the pure spin current created within a lateral spin valve, we evidence and quantify a sizable orientation dependence of the spin absorption in Co, CoFe, and NiFe. These experiments allow us to determine the spin-mixing conductance, an elusive but fundamental parameter of the spin-dependent transport. We show that the obtained values cannot be understood within a model considering only the Larmor, transverse decoherence, and spin diffusion lengths, and rather suggest that the spin-mixing conductance is actually limited by the Sharvin conductance.

Optimal control of complex atomic quantum systems.

Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit - the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.

Atomic Hong-Ou-Mandel experiment.

Two-particle interference is a fundamental feature of quantum mechanics, and is even less intuitive than wave-particle duality for a single particle. In this duality, classical concepts--wave or particle--are still referred to, and interference happens in ordinary space-time. On the other hand, two-particle interference takes place in a mathematical space that has no classical counterpart. Entanglement lies at the heart of this interference, as it does in the fundamental tests of quantum mechanics involving the violation of Bell's inequalities. The Hong, Ou and Mandel experiment is a conceptually simpler situation, in which the interference between two-photon amplitudes also leads to behaviour impossible to describe using a simple classical model. Here we report the realization of the Hong, Ou and Mandel experiment using atoms instead of photons. We create a source that emits pairs of atoms, and cause one atom of each pair to enter one of the two input channels of a beam-splitter, and the other atom to enter the other input channel. When the atoms are spatially overlapped so that the two inputs are indistinguishable, the atoms always emerge together in one of the output channels. This result opens the way to testing Bell's inequalities involving mechanical observables of massive particles, such as momentum, using methods inspired by quantum optics, and to testing theories of the quantum-to-classical transition. Our work also demonstrates a new way to benchmark non-classical atom sources that may be of interest for quantum information processing and quantum simulation.

Crystallization in Ising quantum magnets.

Dominating finite-range interactions in many-body systems can lead to intriguing self-ordered phases of matter. For quantum magnets, Ising models with power-law interactions are among the most elementary systems that support such phases. These models can be implemented by laser coupling ensembles of ultracold atoms to Rydberg states. Here, we report on the experimental preparation of crystalline ground states of such spin systems. We observe a magnetization staircase as a function of the system size and show directly the emergence of crystalline states with vanishing susceptibility. Our results demonstrate the precise control of Rydberg many-body systems and may enable future studies of phase transitions and quantum correlations in interacting quantum magnets.

Observation of correlated particle-hole pairs and string order in low-dimensional Mott insulators.

Quantum phases of matter are characterized by the underlying correlations of the many-body system. Although this is typically captured by a local order parameter, it has been shown that a broad class of many-body systems possesses a hidden nonlocal order. In the case of bosonic Mott insulators, the ground state properties are governed by quantum fluctuations in the form of correlated particle-hole pairs that lead to the emergence of a nonlocal string order in one dimension. By using high-resolution imaging of low-dimensional quantum gases in an optical lattice, we directly detect these pairs with single-site and single-particle sensitivity and observe string order in the one-dimensional case.

MICA compatibility and immunization in third kidney transplantations.

Significantly lower graft survival has been observed among recipients of a third (G3) compared with a first or second kidney transplantation. Because patients awaiting G3 are largely HLA immunized, they are usually transplanted with a high HLA match. Moreover, their rate of acute rejection episodes is similar to a first or second transplantation. Since major histocompatibility complex class I related chain A (MICA) molecules have been proposed as new targets for antibody recognition, we were interested to type donors and recipients for MICA alleles and to study MICA immunization of these patients. Forty-three pairs of donors and recipients were typed for MICA alleles using Luminex technology (LABtype RSSO). MICA alleles showed strong linkage disequilibrium with the B locus: some 4-digit alleles were preferentially associated with a given MICA allele. A greater frequency of patients with 2 MICA mismatches (MM) was observed among patients with rejection (40%), whereas all the graft losses were observed in patients with 0 or 1 MICA MM. MICA immunization was studied using sera from 52 patients collected on day 0 and after transplantation using a Luminex assay (LABScreen). MICA immunization was less frequent than HLA immunization, and MICA donor-specific antibody (DSA) was equally present in functional and failed grafts. These observations confirmed the potential role of MICA immunization in rejection, whereas the poor graft survival among third transplantations could not be explained by MICA incompatibility or immunization.

Identification of a new HLA-DRB1 allele, DRB1*0321.

This communication reports the identification of a new HLA-DRB1*03 allele identified in three members of a Caucasian French family. This new allele has been officially named HLA-DRB1*0321 by the World Health Organization Nomenclature Committee. The complete exon 2 sequence of DRB1*0321 is identical to that of DRB1*0307 except for the first and second nucleotides of codon 37 (TT replacing AA), which lead to the substitution of a tyrosine for a phenylalanine (AAC-->TTC at position 37). The family study showed that this new allele was transmitted into the HLA-A*0101/09, -B*0801/14, -Cw*0701, -DRB1*0321, -DRB3*0101, -DQB1*0503 and -DPB1*0401 haplotype. The complete exon 2 sequence of this new allele has been previously deposited in the EMBL Sequence Database under accession number AF297266.

Lack of evidence for a role of HLA-DP in unexplained recurrent spontaneous abortion.

Using the "Polymerase Chain Reaction-Sequence Specific Oligoprobes" (PCR-SSOp) technique, we studied the HLA-DPB locus in both partners of 59 couples with a history of three spontaneous abortions, and of 38 control couples in order to determine the role of this centromeric region of the major histocompatibility complex (MHC) in the immune reaction needed for a favorable course of pregnancy. As no particular phenotypes were noted, and also neither excessive HLA-DP homozygosity in sterile women nor excessive HLA-DP allele sharing between sterile partners, this MHC class II sub-region would seem to play no role either directly or by linkage disequilibrium, in the development of normal pregnancy.

[Kidney transplantation and HLA-DR compatibility evaluated by genomic analysis: one center study]. / Transplantation rénale et compatibilité HLA-DR évaluée par analyse génomique: étude unicentre.

The actual effect of HLA-DR matching in renal transplantation remains controversial. Since DNA analysis has been shown to be more reliable than serological typing, a re-evaluation of the impact of DR-matching on graft prognosis is required. In this study, 224 cadaver kidney transplantations performed in our center were retrospectively matched according to Restriction Fragment Length Polymorphism DR incompatibilities and compared to prospective serological DR-matching. Transplant outcome was evaluated using graft survival, first rejection onset and rejection frequency. In 18.8% individuals, a discrepancy between serology and DNA typing for at least one antigen was noted. Serology particularly failed to type recipients (21.7%) and 43.2% of the total missed antigens were serologically "blank" or unidentified ("X") alleles. A graft survival rate of 100% after one year was observed for transplantations with no DNA DR mismatch (n = 31). Furthermore, there was a definite correlation between DNA matching and (i), the percentage of individuals with one or more than one acute rejection episode (18% and 41.8% at one year for O incompatibility and pooled 1 and 2 incompatibilities respectively, p < 0.05); (ii), the mean of acute rejection per individual (p < 0.001); and (iii), the rejection onset time (p < 0.01). No correlation between serological matching and the acute rejection episodes parameters was noted. Since HLA typing could be performed in less than 2 hrs using new molecular biology techniques, we conclude that prospective DNA typing should improve kidney transplantation outcome in the near future.

Functional properties of HLA-DR-BON alleles associated with DQw5(w1) and with DQw7(w3): a family study.

Among the DR specificities undefined by serology, DR-BON is peculiar because RFLP cannot distinguish it from the well-defined allele DR1 even if the two specificities are very different functionally. The occurrence of two DR-BON-like alleles in the same family, one associated to the DQw5 split of DQw1 and the other associated to the DQw7 split of DQw3, enabled us to compare the properties of these alleles. The RFLP analysis showed a typical DR1-like picture for both alleles when probed with DR beta, but for one of the alleles the DQ beta probe gave a DQw7 pattern. Primary mixed lymphocyte cultures showed weak to moderate stimulation between cells from individuals identical for one haplotype and differing for the DR-blank haplotypes, but by test with cloned reagents we were not able to define differences between the two DR-blank molecules. Two-dimensional gel electrophoresis and spot-test with a probe covering the third hypervariable region of the DRB1 gene showed no difference between the two alleles. We thus think that the two DR alleles are identical and that the stimulation observed in primary cultures probably is caused by incompatibility for DQ and DP or class I.

HLA-DRw52a is involved in alloimmunization against PL-A1 antigen.

The alloimmunization against the platelet PL-A1 antigen is strongly associated with a HLA class II structure in mothers of thrombocytopenic neonates. Most of the immunized women have first been shown to possess the DR3 specificity and subsequently the DRw52 allele. The 18 immunized mothers studied here by restriction fragment length polymorphism analysis had the DRw52a specificity at the DRB3 locus whatever their HLA-DRB1 gene product. This finding strongly suggests that the DRB3 chain is directly involved in the presentation of the PL-A1 antigen to the specific T cell. In addition, the similarities between DR3 and DRw52 structures due to a hypothetical gene conversion event should be considered in order to understand the high frequency of DR3 among the DRw52a-responding women. Alternatively, the high frequency of DR3 among the DRw52-responding mothers might be due to the high responder status associated with the former specificity.

HLA class II genes polymorphism in DR4 giant cell arteritis patients.

We have previously reported a significant increase of HLA-DR4 antigen frequency in giant cell arteritis (GCA). This finding suggested an important role of immunogenetic factors in this syndrome. Recent data suggest that inherited susceptibility to several autoimmune diseases was associated with specific DR4 associated DQ beta alleles. DNAs from 27 DR4 positive patients with GCA were digested with Taq I and Bam HI, analysed on 0.7% agarose gel and hybridized with DR beta, DQ alpha and DQ beta probes. DR beta hybridization produced no variant detectable within DR4. DQ beta probe confirmed two clusters among DR4 associated DQW3 alleles: DQW 3.1 (Bam HI 360 Kb) and DQw 3.2 (Taq I 1.9 Kb and Bam HI 11 Kb). Among our 27 DR4 positive patients, 34% were DQW 3.1 and 66% were DQW 3.2. These frequencies are the same as those observed in healthy controls.

Definition of DRw10 specificity by restriction fragment length polymorphism.

The purpose of this study was the RFLP characterization of the DRw10 specificity. Twenty-two DRw10 cells were tested: the DNAs were digested by seven restriction enzymes and hybridized with DR beta, DQ beta and DQ alpha probes. Hybridization with DR beta revealed a pattern particular to the DRw10 specificity, with a specific TaqI 12.5Kb fragment. Hybridization with both DQ-specific probes showed that DRw10 is always associated with a special DQw1 subtype: DQw5. Furthermore, at DR and DQ levels, the 22 DRw10 cells behaved homogeneously.

[Populations of circulating T lymphocytes in patients with alcoholic cirrhosis]. / Populations de lymphocytes T circulants chez les patients atteints de cirrhose alcoolique.

The characteristics, the origin and the role in the determinism and/or in the course of hepatocellular necrosis of immune disorders in patients with alcoholic liver cirrhosis still remain unclear. In this study, the T-lymphocyte population was determined by sheep-rosette formation and labelling with OKT3-monoclonal antibodies. T-cell subsets were investigated using OKT4 and OKT8 monoclonal antibodies in the peripheral blood of 40 alcoholic patients with cirrhosis (CA) and of 23 non-cirrhotic alcoholic (ANC) patients. The results were compared to those in 34 healthy volunteers. A decrease in the percentage of T-lymphocytes in the two groups of alcoholic subjects was noted. However, this decrease was significant only in the CA group and only when OKT3 antibodies were used as markers. The lymphocyte-subset identified by OKT4 antibodies was decreased as well in the CA and ANC groups; however the OKT8+ subset was significantly decreased in the CA group only (p less than 0.001). No correlation was found between this decrease in OKT8+ subpopulation or between the increased OKT4/OKT8 ratio and all biochemical parameters of hepatic function measured in this study. The significance of this T-cell imbalance in CA has still to be elucidated, concerning both the functional activity of the reduced pool of OKT8+ cells (suppressor or cytotoxic?) and the mechanism of this decrease.