A Toy Model of Flying Snake's Glide

We have developed a toy model of flying snake's glide [J.J. Socha, Nature vol. 418 (2002) 603.] by modifying a model for a falling paper. We have found that asymmetric oscillation is a key about why snake can glide. Further investigation for snake's glide will provide us details about how it can glide without a wing.Comment: 6 pages, to be submitted to J. Phys. Soc. Jpn. Revised Version submitted to the abov

Determination of solidus and liquidus temperatures for S34MnV steel grade by thermal analysis and calculations

The paper is devoted to the comparison of the results in the frame of solidus and liquidus temperatures obtained by thermo analytical methods with the generally used empirically based formulas and thermo dynamical Computherm software. The series of thermal analysis measurements of high temperature phase transformations of real steel grade (S34MnV) under conditions of two analytical devices (Netzsch STA 449 F3 Jupiter; Setaram Multi High Temperature Calorimeter (MHTC)) were carried out. Two thermo analytical methods were used (DSC and Direct Thermal Analysis). The different weight of samples was used (2,6 g; 23 g). The liquidus and solidus temperatures for close to equilibrium conditions during heating (DSC: 1 °C/min; 2 °C/min) and during cooling (Direct Thermal Analysis: 1 °C/min) were determined and compared. Then, the discussion on the different values obtained by experiments and empirically based calculation is realised

Orthogonal methods based ant colony search for solving continuous optimization problems

Research into ant colony algorithms for solving continuous optimization problems forms one of the most significant and promising areas in swarm computation. Although traditional ant algorithms are designed for combinatorial optimization, they have shown great potential in solving a wide range of optimization problems, including continuous optimization. Aimed at solving continuous problems effectively, this paper develops a novel ant algorithm termed "continuous orthogonal ant colony" (COAC), whose pheromone deposit mechanisms would enable ants to search for solutions collaboratively and effectively. By using the orthogonal design method, ants in the feasible domain can explore their chosen regions rapidly and e±ciently. By implementing an "adaptive regional radius" method, the proposed algorithm can reduce the probability of being trapped in local optima and therefore enhance the global search capability and accuracy. An elitist strategy is also employed to reserve the most valuable points. The performance of the COAC is compared with two other ant algorithms for continuous optimization of API and CACO by testing seventeen functions in the continuous domain. The results demonstrate that the proposed COAC algorithm outperforms the others

PMF the front end electronic for the ALFA detector

International audienceThe PMF (Photo Multiplier Front end) is the front end electronics designed for the ATLAS luminometer ALFA (Absolute Luminosity For ATLAS) made of 20 staggered U-V scintillating fiber layers inserted in Roman Pots (eight in total). Each of these plans is made of 64 fibers. The PMF consists of a 64 channels photomultiplier (MAPMT) and a very compact stack of three different PCBs (3x3 cm2), mounted directly on the back and in the shadow of the MAPMT: a board which brings the high voltage to the MAPMT, an intermediate board used to send the signals to connectors located on the edge and, finally, a board with the readout chip MAROC (Multi Anode Read Out Chip), directly bonded on the PCB, on one side and a FPGA on the other. The 64 inputs MAROC ASIC allows correcting for the gain spread of MAPMT channels thanks to a 6 bits variable gain preamplifier. For each channel the signal is shaped (fast shaper, 15ns) and discriminated to produce a trigger output. A multiplexed charge output is also produced both in analog and digital thanks to a Wilkinson ADC. The main requirements are the following: 100 % trigger efficiency for a signal greater than 1/3 of a photoelectron, a charge measurement up to 30 photoelectrons with a linearity of 2 % or better and a cross talk of 1 % or less. The performances of the second version of MAROC were checked successfully during the year 2007 at LAL-Orsay. A nice dispersion of the trigger output (± 5 fC) was, in particular, observed. A sample of PMFs was produced during autumn 2007 as a prototype. Laboratory tests were performed both at LAL and CERN respectively on the third PCB (the one with MAROC) and on a full PMF equipped with a MAPMT illuminated by a LED. They were carried out using dedicated test board and acquisition software and have allowed the approval of the design and the green light for the final production and integration with the detector. Beam tests of a complete Roman Pot, equipped with 23 PMFs, will take place during summer 2008 for two periods and will conclude the test phase and mark the beginning of the final production

Mycobacterium tuberculosis ClpP Proteases Are Co-transcribed but Exhibit Different Substrate Specificities

PMCID: PMC3613350This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

A mathematical framework for critical transitions: normal forms, variance and applications

Critical transitions occur in a wide variety of applications including mathematical biology, climate change, human physiology and economics. Therefore it is highly desirable to find early-warning signs. We show that it is possible to classify critical transitions by using bifurcation theory and normal forms in the singular limit. Based on this elementary classification, we analyze stochastic fluctuations and calculate scaling laws of the variance of stochastic sample paths near critical transitions for fast subsystem bifurcations up to codimension two. The theory is applied to several models: the Stommel-Cessi box model for the thermohaline circulation from geoscience, an epidemic-spreading model on an adaptive network, an activator-inhibitor switch from systems biology, a predator-prey system from ecology and to the Euler buckling problem from classical mechanics. For the Stommel-Cessi model we compare different detrending techniques to calculate early-warning signs. In the epidemics model we show that link densities could be better variables for prediction than population densities. The activator-inhibitor switch demonstrates effects in three time-scale systems and points out that excitable cells and molecular units have information for subthreshold prediction. In the predator-prey model explosive population growth near a codimension two bifurcation is investigated and we show that early-warnings from normal forms can be misleading in this context. In the biomechanical model we demonstrate that early-warning signs for buckling depend crucially on the control strategy near the instability which illustrates the effect of multiplicative noise.Comment: minor corrections to previous versio