Memory effects in vibrated granular systems

Granular materials present memory effects when submitted to tapping processes. These effects have been observed experimentally and are discussed here in the context of a general kind of model systems for compaction formulated at a mesoscopic level. The theoretical predictions qualitatively agree with the experimental results. As an example, a particular simple model is used for detailed calculations.Comment: 12 pages, 5 figures; to appear in Journal of Physics: Condensed Matter (Special Issue: Proceedings of ESF SPHINX Workshop on ``Glassy behaviour of kinetically constrained models.''

Generalized Sagnac Effect

Experiments were conducted to study light propagation in a light waveguide loop consisting of linearly and circularly moving segments. We found that any segment of the loop contributes to the total phase difference between two counterpropagating light beams in the loop. The contribution is proportional to a product of the moving velocity v and the projection of the segment length Deltal on the moving direction, Deltaphi=4pivDeltal/clambda. It is independent of the type of motion and the refractive index of waveguides. The finding includes the Sagnac effect of rotation as a special case and suggests a new fiber optic sensor for measuring linear motion with nanoscale sensitivity.Comment: 3 pages (including 3 figures

The Level 0 Trigger Decision Unit for the LHCb experiment

The Level 0 Decision Unit (L0DU) is one of the main components of the first trigger level (named level 0) of the LHCb experiment. This 16 layers custom board receives data from the calorimeter, muon and pile-up sub-triggers and computes the level 0 decision, reducing the rate from 40MHz to 1MHz. The processing is implemented in FPGA using a 40MHz synchronous pipelined architecture. The L0DU algorithm is fully configured via the Experiment Control System without any firmware reprogramming. An overall L0DU latency of less than 450ns has been achieved. The board was installed in the experimental area in April 2007 and since then has played a major role in the commissioning of the experiment

Decreased Sialidase Activity in Alveolar Macrophages of Guinea Pigs Exposed to Coal Mine Dust

International audienceThe origin of immune dysfunctions that are observed in pneumoconiotic miners still remains unknown. There is evidence that the carbohydrate moiety of membrane glycoconjugates is of primary importance in many functions of immunocompetent cells. The glycosylation, and especially the sialylation level of membrane components of various lymphocyte and macrophage subsets, vary depending on the state of cellular differentiation and activation. Sialidases, which may regulate the amount of sialic acids exposed on the cell membrane, can thus be considered as immunoregulatory enzymes. In this report, the sialidase activity has been measured in alveolar macrophages (AM) and in cell-free bronchoalveolar lavage fluid (BALF) from guinea pigs exposed for 4 months to coal mine dust at a concentration of 300 mg/m3. The samples were collected by bronchoalveolar lavage 2 months after cessation of exposure. The sialidase activity in the cell-free fluid and in the purified alveolar macrophages showed a 10-fold decrease (p < 0.001). Kinetic parameters of the enzyme such as K(m) and optimum pH did not change. This changed activity was specific for sialidase, as two other lysosomal glycosidases, beta-galactosidase and N-acetylglucosaminidase, showed unchanged activities. These results suggest the possibility that, by inducing a decreased sialidase activity, exposure to coal mine dust may lead to a modified expression of AM membrane-associated sialic acids giving rise to altered immune functions (i. e., phagocytosis, antigen processing response to cytokines, etc.)