The European Fibres Group (EFG) 1993–2002: "Understanding and improving the evidential value of fibres"

The paper outlines the history of the European Fibres Group (EFG) and includes its aims and achievements from the time of its formation in 1993 to the present day. The main emphasis is on the subject of "the evidential value of fibres", how the EFG have provided the data and where to locate it. Additionally the paper provides a look into what the group has accomplished in the recognition of the "lack of data" and the research being conducted to correct this problem. Finally it outlines other projects that are underway to improve its members' knowledge.This paper is dedicated to the memory of Mike Grieve, co-founder and General Secretary of the EFG who passed away on 5th September 2002. Mike was to co-author this paper and much of it reflects his work. He was a colleague, friend and mentor to all forensic fibre examiners and was acknowledged as a premier forensic fibre expert in the world.K.G. Wiggins is the Chairman of the European Fibres Group     

Switching of banana liquid crystal mesophases under field

Taking advantage of the great number of bent-core or “banana" compounds synthesized and studied in the laboratory, we describe their behaviour under the application of an external electric field. If the field were a static one, we would work within the frame of an equilibrium phase diagram in a (field E, temperature T) space where some phases would be simple dielectrics and others ferroelectric ones with a macroscopic polarization, either spontaneous or induced by the field. In this paper, we deal with the basic responses of “banana” liquid crystals under the application of a low frequency (1 to 100 Hz) AC field. Firstly square-wave voltages allow us to locate the phase boundary between dielectric (at lower field) and ferroelectric phases (higher field) at a given temperature and field threshold. Then we apply slowly varying AC voltages with shapes like triangle or “triple-plateau” to check out the stability of the induced ferroelectric phase versus field removal. Three behaviours are encountered, the unstable one (short lifetime of the high-field ferroelectric phase) where the macroscopic polarization is destroyed and then rebuilt in the opposite direction during each half period and usually called “antiferroelectric”; the stable one (long lifetime) with a polarization that rotates at constant modulus which is labeled as “ferroelectric” and a new one where the macroscopic polarization is proportional to the applied fied, we named this behaviour as “superparaelectric”. Let us stress that these observations apply to the ferroelectric phases of the (E, T) phase diagram not to the zero field (0,T) phases observed in the usual phase characterization experiments except for an eventual spontaneous ferroelectric phase. Received 18 April 2002 and Received in final form 17 January 2003 Published online: 16 April 2003 RID="a" ID="a"e-mail: marcerou@crpp.u-bordeaux.fr RID="b" ID="b"URL: http://www.crpp-bordeaux.cnrs.fr     

One-dimensional optical reflectors based on self-organization of polymeric comb-shaped supramolecules

We demonstrate that complexation of dodecylbenzenesulphonic acid, DBSA, to a diblock copolymer of polystyrene- block-poly(4-vinylpyridine), PS- block-P4VP, leads to polymeric supramolecules PS- block-P4VP(DBSA)y (y = 1.0, 1.5, and 2.0), which self-organize with a particularly large lamellar periodicity in excess of 1000 A. The structures consist of alternating PS and P4VP(DBSA)y layers, where the latter contains smaller internal structure, probably lamellar. The DBSA side chains are bonded to the pyridines by protonation and hydrogen bonding and they effectively plasticize the material. In this way relatively well-developed structures are obtained even without annealing or macroscopic alignment. Transmission and reflectance measurements show that a relatively narrow and incomplete bandgap exists for supramolecules of high molecular weight block copolymer at ca. 460 nm.     

基于纤维丛表述的李变换群延拓群算子

本文提出积流形李变换群延拓群的概念，并应用纤维丛方法解决延拓群算子中的系数问题，进而讨论其在黎曼流形中的一个应用．     

Note on transport processes in dense colloidal suspensions

A new approach to transport processes in dense charged as well as neutral colloidal suspensions is presented. It is based on a far-reaching analogy between dense colloidal suspensions and dense hard-sphere fluids, implying, in turn, an analogy with atomic liquids. As a result, new expressions valid for a number of colloidal transport coefficients are predicted.     

AC field induced two-dimensional aggregation of multilamellar vesicles

The aggregation of 2D colloidal crystals can be performed by applying an AC field to a colloidal dispersion. This technique is used in this work for assembling multilamellar vesicles in suspension. The dynamics of the aggregation is followed by real-time recording of the pictures of the microsphere assembly through a phase contrast microscope. The influence of both the frequency and the amplitude of the alternating field on the dynamical evolution of the concentration of layered particles is discussed with respect to their size. A phenomenological model of double layer induced trapping of the particles is proposed and an electroconvective instability of the fluid surrounding the particles is suggested from the observation of the local dynamics of the particles, in accordance with a very recent argument of Yeh et al. [#!Yeh:97!#]. Received: 4 December 1997 / Revised: 24 March 1998 / Accepted: 4 May 1998     

Structural and dynamical properties of aqueous suspensions of NaPSS (HPSS) at very low ionic strength

Results on the structural and dynamical properties of aqueous solutions of NaPSS (HPSS) are reported. Most samples of previous measurements, including our own, are contaminated by the presence of (temporal) aggregates. The emphasis of this paper lies on investigations of well purified samples at very low ionic strength where interacting effects are maximum. As previously reported, this can be achieved by pumping the suspension through ion exchange resin by means of a tube-pump, using filters of pore size. Information has been extracted from static and dynamic light scattering and viscosity measurements. A second maximum is observed in the scattering curves versus wavenumber for the first time. It is discussed on the basis of two current models describing the structure of charged macromolecules. The short time dynamics reflects the measured intensity. Detailed viscosity data in comparison of those of rodlike (TMV), slightly flexible so-called fd virus particles (length 880 nm) are used to confirm the interpretation of the light scattering results. The recently observed maximum in the reduced viscosity could be confirmed. Received: 5 May 1997 / Revised: 1 September 1997 / Accepted: 10 November 1997     

光敏感核不育水稻愈伤组织的超低温保存和冻后再生植株的形成

研究了光敏感核不育水稻的悬浮细胞及愈伤组织的低温贮藏方法．实验采用１０％ＤＭＳＯ＋０．５ｍｏｌ·Ｌ－１山梨醇作冰冻保护剂，降温速率采用１．０℃·ｍｉｎ－１或０．５℃·ｍｉｎ－１，ＴＴＣ法测试的细胞存活率最高可达８５．９％，冻后材料经１５ｄ左右即可在暗培养条件下观察恢复生长的情况．３０ｄ后把长势良好的愈伤组织块转移至分化培养基中，来源于悬浮细胞团的绿苗分化率为１０．０％，愈伤组织的则为６６．６％．     

Precession photography of fibres: Prediction of patterns

The Buerger precession method of recording x-ray diffraction patterns can also be used for fibres. This method has some advantages over the conventional flat plate method. Since the fibre has inherent cylindrical symmetry, the precession photograph of the fibre is equivalent to the ‘rotation-precession’ photograph of a single crystal. An analytical prediction of diffraction patterns of the rotation-precession photography is discussed. Also, experimental data are provided to confirm the validity of the equations derived.     

棱镜分光式光学环行器及其应用

本文介绍梭镜分光式光学环行器设计理论与制备工艺以及在光纤通信和光纤传感系统中的应用。所研制的光学环行器光纤-光纤(单模)插入损耗小于2.8dB,隔离比大于25dB,回波损耗优于40dB.器件性能与偏振无关。