Families of automata characterizing context-sensitive languages

In the hierarchy of infinite graph families, rational graphs are defined by rational transducers with labelled final states. This paper proves that their traces are precisely context-sensitive languages and that this result remains true for synchronized rational graphs.Received: 17 December 2003, Published online: 27 December 2004     

Bed-Shear Stress Characteristics of a Simple, Prismatic, Rectangular Channel

This paper examines the use of data obtained from large eddy simulations in exploring the instantaneous characteristics of boundary shear stress. The probability density functions (PDF) of the shear stress are shown to be non-Gaussian, whereas the PDF of the shear force per unit length is found to be approximately Gaussian. Conditional sampling is used in order to provide an insight into the average behavior of an extreme shear stress event. Finally, proper orthogonal decomposition illustrates that the behavior of the shear stress is complex and cannot necessarily be attributed to a single major flow event.     

Investigation of the action patterns of pectinmethylesterase isoforms through kinetic analyses and NMR spectroscopy. Implications In cell wall expansion

Well characterized pectin samples were incubated with cell wall-bound and -solubilized pure isoforms of pectinmethylesterase from mung bean hypocotyls (Vigna radiata). Both enzyme activity and average product structure were determined at intervals along the deesterification pathway at pH 5.6 and 7.6. The latter analyses were performed by 13C NMR spectroscopy, and the degree of esterification was probed by both 13C NMR and potentiometric measurements. A dichotomy was observed in the behavior of the alpha and gamma isoforms when compared with that of the beta isoenzyme. Ideal blockwise deesterification mechanisms reproduced the experimental average structures (methylester distribution) throughout the course of the reaction. In the case of the alpha and gamma isoforms, a single chain mechanism associated with a free carboxyl group at the second nearest neighbor position could be postulated at pH 5.6, whereas some multiple attack character was required to reproduce the data at pH 7.6. Several mechanisms that differed from the preceding ones were compatible with the data for the beta isoform at the two pH values. Both the nature of the polysaccharides produced in these reactions and the role of pectinmethylesterase in the cell wall-stiffening process along the growth gradient are discussed.     

On the properness condition for modal analysis of non-symmetric second-order systems

Non-symmetric second-order systems can be found in several engineering contexts, including vibroacoustics, rotordynamics, or active control. In this paper, the notion of properness for complex modes is extended to the case of non-self-adjoint problems. The properness condition is related to the ability of a set of complex modes to represent in an exact way the behavior of a physical second-order system, meaning that the modes are the solutions of a quadratic eigenvalue problem whose matrices are those of a physical system. This property can be used to identify the damping matrices which may be difficult to obtain with mathematical modeling techniques. The first part of the paper demonstrates the properness condition for non symmetric systems in general. In the second part, the authors propose a methodology to enforce that condition in order to perform an optimal reconstruction of the “closest” physical system starting from a given basis complex modes. The last part is dedicated to numerical and experimental illustrations of the proposed methodology. A simulated academic test case is first used to investigate the numerical aspects of the method. A physical application is then considered in the context of rotordynamics. Finally, an experimental test case is presented using a structure with an active control feedback. An extension of the LSCF identification technique is also introduced to identify both left and right complex mode shapes from measured frequency response functions.     

Determination of pre-impact occupant postures and analysis of consequences on injury outcome. Part I: a driving simulator study

This paper considers pre-impact vehicle maneuvers and analyzes the resulting driver motion from their comfort seating position. Part I of this work consists of analyzing the driver behavior during a crash. The study is conducted using the LAMIH driving simulator and involves 76 participants. The emergency situation is created by a truck emerging from behind a tractor on the opposite side of the road and tearing along the participant. The driver positioning throughout the simulation is recorded via five video cameras allowing view of the front scene, the driver face, feet and pedals, hands on the steering wheel and global lateral view. Data related to braking force, seat pressure, muscular activity for major groups of muscles and actions on the steering wheel are also collected.The typical response to this type of emergency event is to brace rearward into the seat and to straighten the arms against the steering wheel, or, to swerve to attempt to avoid the impacting vehicle. While turning the steering wheel, the forearm can be directly positioned on the airbag module at time of crash which represents a potential injurious situation.These positions are used in Part II to determine scenario of positions for numerical simulation of a frontal collision.     

Physical Phenomena and Length Scales Governing the Behaviour of Wildfires: A Case for Physical Modelling

This paper is an overview of the physical mechanisms and length scales governing the propagation of wildfires. One of the objectives is to identify the physical and mathematical constraints in the modelling of wildfires when using a ??fully?? physical approach. The literature highlights two regimes in the propagation of surface fires, i.e. wind-driven fires and plume-dominated fires, which are governed by radiation and convective heat transfer, respectively. This division leads to the identification of two governing length scales: the extinction length characterising the absorption of radiation by vegetation, and the integral turbulent length scale characterising the interaction between wind and canopy. Some numerical results published during the last decade using a fully physical approach are presented and discussed with a focus on the models FIRESTAR, FIRELES, FIRETEC and WFDS. Numerical simulations were compared with experimental data obtained at various scales, from laboratory to field fires in grassland and in Mediterranean shrubland. Some perspectives are presented concerning the potential coupling between physical fire models with mesoscale atmospheric models to study the impacts of wildfires at larger scale. Some of the topics on wildfire physical modelling that need further research are identified in the conclusions.     

Study of an argon–hydrogen RF inductive thermal plasma torch used for silicon deposition by optical emission spectroscopy

The hydrogenation of silicon deposited on a substrate for photovoltaic applications has been obtained by a plasma torch. This method shows a great advantage and leads to the improvement of the electronic properties of the material. The hydrogenation of silicon allows the crystallographic defects elimination (dislocations, dangling bonds) which leads to an increase of the diffusion length.In order to understand silicon hydrogenation by RF inductive thermal plasma spraying, a study of the discharge by optical emission spectroscopy (OES) has been undertaken. This study has been compared with the hydrogen content measured by the exodiffusion technique.The detection of highly excited species of atomic and molecular hydrogen proves the specificity of the inductive plasma. Hydrogen emission lines have been used to calculate the electronic density on the plasma axis. Furthermore, the ArI lines were used to calculate the electronic temperature in the plasma. With this information, the deviation from the local thermodynamic equilibrium (LTE) of the plasma has also been estimated.     

Efficacy and tolerance of vinorelbine and fluorouracil combination as first-line chemotherapy of advanced breast cancer: results of a phase II study using a sequential group method

PURPOSE: To assess the antitumor efficacy and safety profile of the combination of Fluorouracil (5FU) and vinorelbine given as first-line therapy to patients with advanced breast cancer. PATIENTS AND METHODS: As defined in the seven consecutive steps of a phase II group sequential design, 63 patients received 5FU 750 mg/m2/d for 5 consecutive days as a continuous infusion and vinorelbine 30 mg/ m2 on days 1 and 5 as a short intravenous (I/V) infusion every 3 weeks. RESULTS: Forty-one of 63 patients achieved an objective response, which allowed us to discontinue the study and reject a response rate less than 50% with a statistical power of 90%. The unbiased estimate of the response rate was 61.6%. Response rate did not differ significantly according to the following: (1) type of prior adjuvant therapy (none, n = 23; without anthracycline, n = 6; with anthracyline, n = 34); (2) site of metastatic disease; and (3) number of metastatic sites. The median time to progression was 8.4 months. The median response duration was 12.3 months, and the median duration of complete response (CR), from the first assessment of CR, was 7.3 months. The median overall survival time was 23 months (28.1 months for patients with a CR). The main toxicities (grades 3 and 4) were neutropenia (90% of patients), infection (12.7%), mucositis (37%), and constipation (9.5%). Nevertheless, treatment could be given on an outpatient basis to the majority of patients, and the median relative dose-intensity was 86%. CONCLUSION: This phase II study, which used a group-sequential design, shows that the combination of 5FU and vinorelbine is an active and tolerable regimen for the treatment of first metastatic progression of breast cancer. It provides an alternative regimen for patients who have previously received anthracycline-based adjuvant chemotherapy or in whom anthracyclines cannot be used.