Une structure active de type tensegrité

A tensegrity is a lightweight space reticulated structure consisting of compression members — struts — surrounded by a network of tension members — cables — that provide rigidity and stability. They can be easily dismantled and therefore, they provide innovative possibilities for reusable and modular structures. To date, tensegrity construction has been limited to sculptures. The number of full-scale prototypes built is increasing though few have been tested experimentally statically. Tensegrities are flexible structures and are thus often governed by serviceability criteria. They are able to adapt their shape by changing their selfstress, and when equipped with sensors and actuators, they can actively adapt to changing environments. In this way, they have the potential to become a part of an exhibition rather than merely provide shelter for one. Until now, most structural control research in civil engineering has focused on active control of structures in order to enhance safety under extreme loading. While maintaining serviceability was mentioned in early work as a goal of structural control, there has been little investigation in this area. Improving tensegrity performance througth active control needs to meet the following challenges: construction and design, structural analysis, finding and applying control commands. Full-scale prototypes of three-module, five-module and unique active fivemodule, modular and reusable tensegrity structures have been built and successfully tested. Shape is adapted through changing the length of a limited number of bars. Each module contains six struts and twenty-four cables of three different lengths. Good joint design is a priority for this type of structure. The thesis gives a detailed description of an assembly process, pin-joint design, elements and control set-up. Polyester reinforced fiber glass bars lighten the structure. Tensegrities are non-linear, highly coupled structures, that are sensitive to asymmetric loads and small environmental changes. Numerical and experimental tests show that active control satisfy serviceability criteria with a limited number of actuators. Tests show that the structure behaves linearly when subjected to vertical loads applied to a single joint. Non-linearities are detected for small displacements for loads applied to several joints and for adjusting combinations of telescoping compression members. Therefore, simplifications such as load superposition are not possible. Simulation of the nonlinear behavior using dynamic relaxation, an explicit analysis method, proved successful for predicting the response. Behavior and the control objectives, such as maintaining a constant roof slope, do not have closed loop form solutions. Therefore, stochastic search algorithms are required to find control commands. Simulated annealing search and PGSL proved successful for determining control commands. Storing good control commands improves control efficiency. Quasi-static control, through elongating active struts one by one, is effective and safe for maintaining the slope. The present work contributes to developing structures that, through computational control and recording previous good adjustments, improve their performance during service life. Finally, an extended active control concept is suggested for self repair

Combining dynamic relaxation method with artificial neural networks to enhance simulation of tensegrity structures

Abstract: Structural analyses of tensegrity structures must account for geometrical nonlinearity. The dynamic relaxation method correctly models static behavior in most situations. However, the requirements for precision increase when these structures are actively controlled. This paper describes the use of neural networks to improve the accuracy of the dynamic relaxation method in order to correspond more closely to data measured from a full-scale laboratory structure. An additional investigation evaluates training the network during the service life for further increases in accuracy. Tests showed that artificial neural networks increased model accuracy when used with the dynamic relaxation method. Replacing the dynamic relaxation method completely by a neural network did not provide satisfactory results. First tests involving training the neural network online showed potential to adapt the model to changes during the service life of the structure. DOI: 10.1061/�ASCE�0733-9445�2003�129:5�672

Strut assembly node for reticular space frame structure

The node assembly has a central unit (7) with surface portions rounded at a center of merged curve. Each unit (6) e.g. bar has an end inserted to the central unit by a compression on a point of each unit to form a ball and socket joint. A security device is arranged around the central unit for permitting a passage of the unit and for preventing the end to release from the central unit

Functional characterization of PD1+TIM3+ tumor-infiltrating T cells in DLBCL and effects of PD1 or TIM3 blockade

International audienceIn diffuse large B-cell lymphoma (DLBCL), tumor-infiltrating T lymphocytes (TILs) are involved in therapeutic responses. However, tumor-specific TILs can be dysfunctional, with impaired effector functions. Various mechanisms are involved in this exhaustion, and the increased expression of programmed cell death receptor 1 (PD1) and TIM3 on dysfunctional cells suggests their involvement. However, conflicting data have been published regarding their expression or coexpression in DLBCL. We evaluated the presence and phenotype of CD4+ and CD8+ TILs in freshly collected tumor tissues in DLBCL and compared the results with those in follicular lymphoma, classical Hodgkin lymphoma, and nonmalignant reactive lymphadenopathy. We found that TILs expressing both PD1 and TIM3 were expanded in DLBCL, particularly in the activated B cell-like subgroup. Isolated PD1+TIM3+ TILs exhibited a transcriptomic signature related to T-cell exhaustion associated with a reduction in cytokine production, both compromising the antitumor immune response. However, these cells expressed high levels of cytotoxic molecules. In line with this, stimulated PD1+TIM3+ TILs from DLBCL patients exhibited reduced proliferation and impaired secretion of interferon-γ, but these functions were restored by the blockade of PD1 or TIM3. In summary, the PD1+TIM3+ TIL population is expanded and exhausted in DLBCL but can be reinvigorated with appropriate therapies

CXCR5 and ICOS expression identifies a CD8 T-cell subset with T features in Hodgkin lymphomas

International audienceA better characterization of T-cell subsets in the microenvironment of classical Hodgkin lymphoma (cHL) would help to develop immunotherapies. Using multicolor flow cytometry, we identified in 6 of 43 cHL tissue samples a previously unrecognized subset of CD8 T cells coexpressing CXCR5 and inducible T-cell costimulator (ICOS) molecules (CD8). These cells shared phenotypic features with follicular helper T (T) cells including low CCR7 expression together with high expression of B-cell lymphoma-6, programmed cell death 1, B and T lymphocyte attenuator, CD200, and OX40. They had deficient cytotoxicity, low interferon-γ secretion, and common functional properties with intratumoral CD4 T cells, such as production of interleukin-4 (IL-4), IL-21, CXCL13, and capacity to sustain B cells. Gene profiling analysis showed a significant similarity between the signatures of CD8 T cells and CD4 T cells. Benign lymphadenitis tissues (n = 8) were devoid of CD8 cells. Among the 35 B-cell lymphoma tissues analyzed, including follicular lymphomas (n = 13), diffuse large cell lymphomas (n = 12), marginal zone lymphomas (MZLs; n = 3), mantle cell lymphomas (n = 3), and chronic lymphocytic leukemias (n = 4), only 1 MZL sample contained CD8 cells. Lymphoma tumors with CD8 cells shared common histopathological features including residual germinal centers, and contained high amounts of activated CD8 cells. These data demonstrate a CD8 T-cell differentiation pathway leading to the acquisition of some T similarities. They suggest a particular immunoediting process with global CD8 activation acting mainly, but not exclusively, in HL tumors

Human anti-smallpox long-lived memory B cells are defined by dynamic interactions in the splenic niche and long-lasting germinal center imprinting

International audienceMemory B cells (MBCs) can persist for a lifetime, but the mechanisms that allow their long-term survival remain poorly understood. Here, we isolated and analyzed human splenic smallpox/vaccinia protein B5-specific MBCs in individuals who were vaccinated more than 40 years ago. Only a handful of clones persisted over such an extended period, and they displayed limited intra-clonal diversity with signs of extensive affinity-based selection. These long-lived MBCs appeared enriched in a CD21hiCD20hi IgG+ splenic B cell subset displaying a marginal-zone-like NOTCH/MYC-driven signature, but they did not harbor a unique longevity-associated transcriptional or metabolic profile. Finally, the telomeres of B5-specific, long-lived MBCs were longer than those in patient-paired naive B cells in all the samples analyzed. Overall, these results imply that separate mechanisms such as early telomere elongation, affinity selection during the contraction phase, and access to a specific niche contribute to ensuring the functional longevity of MBCs

How should we diagnose and treat blastic plasmacytoid dendritic cell neoplasm patients?

Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is a rare and aggressive leukemia for which we developed a nationwide network to collect data from new cases diagnosed in France. In a retrospective, observational study of 86 patients (2000-2013), we described clinical and biological data focusing on morphologies and immunophenotype. We found expression of markers associated with plasmacytoid dendritic cell origin (HLA-DRhigh, CD303+, CD304+, and cTCL1+) plus CD4 and CD56 and frequent expression of isolated markers from the myeloid, B-, and T-lymphoid lineages, whereas specific markers (myeloperoxidase, CD14, cCD3, CD19, and cCD22) were not expressed. Fifty-one percent of cytogenetic abnormalities impact chromosomes 13, 12, 9, and 15. Myelemia was associated with an adverse prognosis. We categorized chemotherapeutic regimens into 5 groups: acute myeloid leukemia (AML)-like, acute lymphoid leukemia (ALL)-like, lymphoma (cyclophosphamide, doxorubicin, vincristine, and prednisone [CHOP])-like, high-dose methotrexate with asparaginase (Aspa-MTX) chemotherapies, and not otherwise specified (NOS) treatments. Thirty patients received allogeneic hematopoietic cell transplantation (allo-HCT), and 4 patients received autologous hematopoietic cell transplantation. There was no difference in survival between patients receiving AML-like, ALL-like, or Aspa-MTX regimens; survival was longer in patients who received AML-like, ALL-like, or Aspa-MTX regimens than in those who received CHOP-like regimens or NOS. Eleven patients are in persistent complete remission after allo-HCT with a median survival of 49 months vs 8 for other patients. Our series confirms a high response rate with a lower toxicity profile with the Aspa-MTX regimen, offering the best chance of access to hematopoietic cell transplantation and a possible cure