A new 3-D finite-element model based on thin-film approximation for microelectrode array recording of extracellular action potential.

A transient finite-element model has been developed to simulate an extracellular action potential recording in a tissue slice by a planar microelectrode array. The thin-film approximation of the active neuron membrane allows the simulation within single finite-element software of the intracellular and extracellular potential fields. In comparison with a compartmental neuron model, it is shown that the thin-film approximation-based model is able to properly represent the neuron bioelectrical behavior in terms of transmembrane current and potential. Moreover, the model is able to simulate extracellular action potential recordings with properties similar to those observed in biological experiments. It is demonstrated that an ideal measurement system model can be used to represent the recording microelectrode, provided that the electronic recording system adapts to the electrode-tissue interface impedance. By comparing it with a point source approximated neuron, it is also shown that the neuron three-dimensional volume should be taken into account to simulate the extracellular action potential recording. Finally, the influence of the electrode size on the signal amplitude is evaluated. This parameter, together with the microelectrode noise, should be taken into account in order to optimize future microelectrode designs in terms of the signal-to-noise ratio.     

空间句法在城市规划中应用的局限性及改善和扩展途径

空间句法是一种在建筑领域认可度比较高的定量研究方法。近来得到城市规划领域关注,并广泛应用于城市规划理论和实践的探索。然而国外地理学空间分析领域对空间句法理论方法在城市规划中的应用一直存在争议。但随着近年来理论自身的不断修正和其他学科的不断扩展,增强了空间句法理论方法在城市规划应用的适应性。现着重从地理空间分析的视角讨论空间句法在城市规划中应用的局限性,同时回顾空间句法方法自身的近期发展,以及地理空间分析领域对其方法的扩充和发展。     

西九文化区

正OMA发展西九文化区,必须面对一项挑战:将一个盛载政府极大抱负,以及持分者多元利益的超大型多用途项目,转化成一个既有趣又严肃、既有规划又允许即兴、既中国化又国际化的文化区。这个文化区规模庞大,但不失亲密融洽的感觉;富地标性,但十分谦和;容易理解,却能带来惊喜。为避免造成过分冲击,OMA采纳了一种每个香港市民都熟悉的建筑类型作为方案的发展     

Good pharmaceutical manufacturing practices

In order to assure the quality of medicines and to encourage the implementation of the international system for the certification of the quality of pharmaceuticals, it was deemed necessary to specify the conditions under which pharmaceutical establishments should operate to provide full assurance that their products are safe for public health.

The French Government Order of 1. October. 1985 therefore provides for the establishement of new recommendations on good pharmaceutical manufacturing practices: “Bonnes Pratiques de Fabrication et de Production Pharmaceutiques: BPF 1985”.

Within the system of quality assurance, good pharmaceutical manufacturing practices represent that part which is concerned with manufacture.

Their implementation requires that the specification of the raw materials and packaging materials, the manufacturing and packaging processes and the control methods be defined and written beforehand, that the premises and equipment be adapted to the intended uses and that the staff have received appropriate training.

Good pharmaceutical manufacturing practices directly concern production departments and packing area, control laboratories, storage areas, purchasing departments, departments receiving raw materials and dispatching finished products. They also concern departments issuing instructions and written or computerised documents intended for the departments previously mentioned.

Although the collection of recommendations thus published constitutes a detailed document, the possibility of there being different methods for attaining the same objective is recognised.     

PWR steam generator R&D in France: thermal-hydraulic and vibratory aspects

Concomitant with the launching of the French pressurized water reactor (PWR) nuclear power program, a large research and development (R&D) effort was initiated, devoted to the steam generators (SGs). This program, managed cooperatively by Framatome, the SG designer and manufacturer; Electricité de France (EDF), the French electrical utility; and the Commissariat à l'Energie Atomique (CEA), the French Atomic Energy Commission, primarily responsible for nuclear research; was focused on four main objectives:

1. (1) To obtain a better understanding of the physical phenomena existing in these steam generators and leading to SG performance alterations or operating life reductions.

2. (2) To test and validate improved design solutions for the model 51 Framatome steam generator, which was the first one designed under Westinghouse license.

3. (3) To test and validate new Framatome SG designs.

4. (4) To test and validate new, high-performance design tools.

This vast R&D program covers the following theses:

• - SG thermal-hydraulics,

• - SG tube vibration and wear,

• - SG materials (production, corrosion, etc.),

• - Primary and secondary fluid chemistry,

• - SG technology (manufacturing processes, NDT, etc.),

• - SG in-service inspection, and

• - SG maintenance.

These themes are too numerous to be dealt with in a single article. Consequently, the present article will focus on only the first two themes.     

Critères généraux de conception des réseaux de diodes lasers à rubans couplés par champs évanescents

The aim of this article is to define the general criteria for design of phase-locked diode laser arrays. A general method for designing these devices is presented using the effective index method and the coupled mode theory. The confinement required for the individual diodes is defined, and the allowed structure geometries are determined.     

Ancient Analogues of Modern Cement: Calcium Hydrosilicates in Mortars and Concretes from Gallo–Roman Thermal Baths of Western France

The long-term durability of cementbased materials over periods of time not directly accessible to laboratory experiments has to be thoroughly assessed to guarantee the safety of a radioactive waste repository. In this work, archaeological mortars and concretes have been studied to check whether their use as analogues of actual technological cements used for waste disposal is possible. Samples of mortar and concrete have been collected from several Gallo-Roman thermae of western France; they were examined as petrographically thin sections with optical microscopy and were analyzed by X-ray diffraction of microsamples (10⁻³ mg) and by electron probe microanalysis. The masonry cement appears to be entirely carbonated with large voids and fissures. In contrast, the use of lime with additional crushed brick or tile for the bath structure concrete and coating mortar induced pozzuolanic reactions. Despite the fact that the matrices are essentially composed of calcium carbonate, calcium aluminosilicates with compositions close to those of hydrogrossular, hydrated calcium silicates with composition and a structure comparable with those of calcium hydrosilicate formed in modern cement, and ettringite deposits in voids of concretes could also be identified. It is suggestea that these ancient artifacts can help identify very slow processes that rule cement alteration over long periods of time. The artifacts may be considered as possible analogues of present-day materials whenever sufficient care is taken in interpreting and extrapolating data.     

Combination of multi-model predictive control and the wave theory for the control of simulated moving bed plants

In this work a new approach to the control of simulated moving bed (SMB) chromatographic separation processes is presented. This approach is based on the combination of the wave theory and Multi-Model Predictive Control (MMPC). The wave theory provides the theoretical framework in which the control law is formulated whereas receding-horizon MPC is used for determining the appropriate controller parameters. As SMB plants are distributed parameter systems (DPS) with nonlinearity arising from the expression of the adsorption isotherms, classical numerical methods for the solution of DPS are computationally demanding for MPC purposes. Reduced-order models are therefore derived using the proper orthogonal decomposition (POD) technique. To ensure stability, the POD model is updated on-line, resulting in MMPC.     

Ultrastrong Anchoring Yet Barrier‐Free Adsorption of Composite Microgels at Liquid Interfaces

Microgel particles display an interesting duality with properties attributed typically both to polymeric and colloidal systems. When adsorbed at a liquid‐liquid interface, this duality becomes particularly apparent as the various phenomena at play are governed by different aspects of these soft and responsive particles. The introduction of a solid, fluorescently labeled, polystyrene core into the microgels allows direct and accurate visualization without the necessity of potential perturbing sample preparation techniques. By combining in‐situ imaging and tensiometry, we determine that composite microgels at a wide variety of oil‐water interfaces anchor strongly, with adsorption energies of approximately 10⁶ k_BT, typical for particle adsorption, yet accumulate at the interface spontaneously without any energy barrier, which is more typical for polymers. The high adsorption energies allow the particle to spontaneously form very dense crystalline packings at the liquid interface in which the microgels are significantly compressed with respect to their swollen state in bulk solutions. Finally, we demonstrate the unique nature of these particles by producing highly stable and monodisperse microgel‐stabilized droplets using microfluidics.