Les conditions du milieu et la morphologie de la plante en fin de croissance chez le haricot, Phaseolus vulgaris L.

Le nombre d'entre-noeuds est déterminé très tôt, à la levée germinative, par les facteurs du milieu. Il est limité au maximum à 7 pour toutes les variétés naines et, le plus souvent, à un nombre supérieur pour les variétés à rames. La notion de croissance illimitée a été expliquée. L'entre-noeud "moyen", le premier entre-noeud, à partir de la base, à présenter une longueur supérieure à la longueur moyenne de tous les entre-noeuds de la tige, admet un seuil (9 cm chez les variétés naines) au-dessous duquel la plante est érigée et au-dessus duquel elle est volubile. Lors de la pleine croissance de cet entre-noeud apparaît le port futur (érigé ou volubile) de la plante suivant que la longueur de celui-ci est inférieure ou supérieure au seuil. Il n'y a pas de relation de cause à effet entre la longueur et le port de la plante. (Résumé d'auteur

Comment on "Estimate of the vibrational frequencies of spherical virus particles"

This comment corrects some errors which appeared in the calculation of an elastic sphere eigenenergies. As a result, the symmetry of the mode having the lowest frequency is changed. Also a direction for calculating the damping of these modes for embedded elastic spheres is given.Comment: comment L. H. Ford Phys. Rev. E 67 (2003) 05192

High voltage measurements on a prototype PFN for the LHC injection kickers

Two LHC injection kicker magnet systems must produce a kick of 1.3 T.m each with a flattop duration of 4.25 mu s or 6.5 mu s, a rise time of 900 ns, and a fall time of 3 mu s. The ripple in the field must be less than +or-0.5The electrical circuit of the complete system has been simulated with PSpice. The model includes a 66 kV resonant charging power supply (RCPS), a 5 Omega pulse forming network (PFN), a terminated 5 Omega kicker magnet, and all known parasitic quantities. Component selection for the PEN was made on the basis of models in which a theoretical field ripple of less than +or-0.1as attained. A prototype 66 kV RCPS was built at TRIUMF and shipped to CERN. A prototype 5 Omega system including a PFN, thyratron switches, and terminating resistors, was built at CERN. The system (without a kicker magnet) was assembled as designed without trimming of any PFN component values. The PFN was charged to 60 kV via the RCPS operating at 0.1 Hz. The thyratron timing was adjusted to provide a 30 kV, 5.5 mu s duration pulse on a 5 Omega terminating resistor. Measurement data is presented for the prototype PFN, connected to resistive terminators. A procedure has been developed for compensating the probe and oscilloscope amplifier calibration errors. The top of the 30 kV pulse is flat to +or-0.3after an initial oscillation of 600 ns total duration. The post-pulse period is flat to within +or-0.1after approximately 600 ns from the bottom of the falling edge of the pulse. A calculation was performed in which a measured 27.5 kV pulse with a 5.5 mu s flattop was fed into a PSpice model of a kicker magnet with a 690 ns delay length. The resultant predicted kick rise time, from 0.2to 99.8, is 834 ns and the fall time 2.94 mu s, for a field pulse with a flattop of 4.69 mu s and a ripple of less than +or-0.2(12 refs)

Design of the injection kicker magnet system for CERN's 14 TeV proton collider LHC

Two counter-rotating proton beams will be injected into the LHC at an energy of 450 GeV by two kicker magnet systems, producing magnetic field pulses of approximately 750 ns rise time and 6.6 µs flat top duration. To avoid dilution of the beam emittance during injection, a stringent design requirement of the system is a flat top ripple of the magnetic field of less than ± 0.5%. Both injection systems are composed of 4 travelling wave kicker magnets of 2.17 m length each, powered by pulse forming networks (PFN's) and matched to their characteristic impedance. To achieve the high required kick strength of 1.2 Tm, for a compact and cost efficient design, a comparably low characteristic impedance of 5 has been chosen. The electrical circuit of the system is being designed with the help of PSpice computer modelling. Most known parasitic elements are included in the model to obtain a realistic pulse response prediction. The present paper reports on design and modeling results of the LHC injection kicker magnet system that has several novel and demanding design requirements

Kick Stability Analysis of the LHC Inflectors

Two sets of four LHC inflector magnet systems must produce a kick of 1.36 Tm each with a duration of 6.5 µs, a rise time of 750 ns, and an overall stability of ± 0.5%. The electrical circuit of the complete system, including all known stray quantities, has been simulated with PSpice. Many stray elements were determined from Opera2D simulations which included eddy-currents. 3D analyses have also been carried out for the kicker magnet using the electromagnetic analysis code Opera3D. Equivalent circuits which simulate the frequency dependence of inductance and resistance of the Pulse Forming Network (PFN) have been derived. The dimensions of the PFN coil have been selected to give the correct pulse response. The end cells of the PFN have also been optimised. The discharge stability of various PFN capacitors has been measured. This paper presents the results of both the analyses and measurements

Resonant Raman Scattering by quadrupolar vibrations of Ni-Ag Core-shell Nanoparticles

Low-frequency Raman scattering experiments have been performed on thin films consisting of nickel-silver composite nanoparticles embedded in alumina matrix. It is observed that the Raman scattering by the quadrupolar modes, strongly enhanced when the light excitation is resonant with the surface dipolar excitation, is mainly governed by the silver electron contribution to the plasmon excitation. The Raman results are in agreement with a core-shell structure of the nanoparticles, the silver shell being loosely bonded to the nickel core.Comment: 3 figures. To be published in Phys. Rev.

Pseudospark Switch Development for the LHC Extraction Kicker Pulse Generator

CERN, the European Laboratory for Particle Physics, has started construction of the Large Hadron Collider (LHC), a superconducting accelerator that will collide protons at a center of mass energy of 14 TeV from the year 2005 onwards. The kicker magnet pulse generators of the LHC beam extraction system require fast high power switches. One possible type is the pseudospark switch (PSS) which has several advantages for this application. A PSS fulfilling most of the requirements has been developed in the past years. Two outstanding problems, prefiring at high operating voltages and sudden current interruptions (quenching) at low voltage could be solved recently. Prefiring can be avoided for this special application by conditioning the switch at two times the nominal voltage after each power pulse. Quenching can be suppressed by choosing an appropriate electrode geometry and by mixing Krypton to the D2 gas atmosphere. One remaining problem, related to the required large dynamic voltage range (1.7 kV to 30 kV) is under active investigation: steps in forward voltage during conduction, occurring at low operation voltage at irregular time instants and causing a pulse to pulse jitter of the peak current. This paper presents results of electrical measurements concerning prefiring and quenching and explains how these problems have been solved. Furthermore the plans to cure the forward voltage step problem will be discussed

Solid State Switch Application for the LHC Extraction Kicker Pulse Generator

A semiconductor solid state switch has been constructed and tested in the prototype extraction kicker pulse generator of CERN's Large Hadron Collider (LHC) [1]. The switch is made of 10 modified 4.5 kV, 66 mm symmetric GTO's (also called FHCT-Fast High Current Thyristor), connected in series. It holds off a d.c. voltage of 30 kV and conducts a 5 µs half-sine wave current of 20 kA with an initial di/dt of 10 kA/µs. Major advantages of the switch are the extremely low self-firing hazard, no power consumption during the ready-to-go status, instantaneous availability, simple condition control, very low noise emission during soft turn-on switching and easy maintenance. However, the inherent soft, relatively slow turn-on time is a non negligible part of the required rise time and this involves adaptation of generator components. A dynamic current range of 16 is achieved with variations in rise time, which stay within acceptable limits. Important generator improvements have been made with the series diodes and freewheel diodes. A more efficient droop compensation circuit is being studied. It is directly connected in series with the freewheel diode stack and maintains an acceptable flattop variation of 5% of the magnet current during 90 µs. This paper presents the complete generator, in particular the solid state switch and discusses related electrical measurements

Analysis of Reporting Adverse Drug Reactions in Paediatric Patients in a University Hospital in the Netherlands

AIMS: The risk to develop adverse drug reactions (ADRs) is high for paediatric patients. This is, amongst other reasons, due to the inevitable use of off-label and unlicensed medicines. Moreover, there is limited knowledge on ADRs in children. Thus, adequate recognition may be challenging. The lack of dedicated studies and the voluntary nature of pharmacovigilance systems used to gain insight into the characteristics of ADRs contribute to this problem. The goal of this study is to identify whether ADRs in paediatric patients are adequately documented by the medical team and whether they are subsequently reported to the national pharmacovigilance system. METHODS: All patients admitted to the paediatric medium care of the Radboudumc Amalia Children's hospital during 1 month, and using one or more drugs, were included. Two researchers analysed retrospectively and independently the number of possible ADRs in the medical records. The ADRs were listed per paediatric subspecialty, to evaluate any differences in documentation and reporting of the ADRs. Subsequently, the causality, severity, and seriousness of the ADRs were assessed. The ADRs were categorised by system organ class and drug class. The national pharmacovigilance centre was consulted to check if there were any reports coming from our hospital and to collect the total number of reports. RESULTS: The medical records of 301 patients were analysed, 81 patients were suffering from one or more ADRs. In total 132 suspected ADRs were found, divided among 19 different paediatric subspecialties. Numbers were too small to investigate the differences in ADR documentation. Of these found ADRs, 55% were not explicitly noted as such in the medical records by the treating physician. None of the ADRs were reported to the national pharmacovigilance centre. Most ADRs scored 'possible' in the causality assessment, were mild or moderate, and a small number were serious. The ADRs occurred in 25 different organ systems. In total 25 different drug classes were involved. CONCLUSIONS: The results of the present study show that a large number of ADRs are not registered in the medical records and are not reported to the national pharmacovigilance system. Furthermore, it is shown that the number of ADRs occurring at our centre is much higher than the number reported to the national pharmacovigilance centre. Only an average of 513 ADRs in paediatric patients are reported per year nationwide, suggesting that there is extensive underreporting