MÖSSBAUER SPECTROSCOPY OF DIFFERENT INTERSTITIAL COMPOUNDS AND SOLID SOLUTIONS CONTAINING 57Fe

Les variations des paramètres hyperfins du fer sont discutées dans les solutions solides interstitielles , les carbures et les nitrures .The hyperfine parameters of iron are discussed in interstitial solid solutions, carbides and nitrides

DEFECTS IN Fe7C3 TYPE CARBIDE FORMED DURING THE CRYSTALLIZATION OF AMORPHOUS HIGH CARBON ALLOYS AND THEIR RELATION WITH THE AMORPHOUS STATE

Les carbures de type M7C3 ont une structure orthorhombique (R. FRUCHART et al.). Cette structure peut être masquée par des défauts qui sont propres au mode de préparation. Dans le cas du carbure Fe7C3 formé lors de la recristallisation d'un alliage amorphe Fe75C25 préparé par sputtering, la taille des défauts (inférieure à 100 Å) est du même ordre de grandeur que celle des domaines allongés suivant certaines directions. Pour les carbures primaires présents dans les fontes blanches et les aciers au carbone, les domaines sont environ cent fois plus grands. Ces résultats suggèrent que la croissance des domaines est bloquée pendant la cristallisation de l'amorphe. Un très grand nombre de germes peut déjà exister dans l'état amorphe ou se former très rapidement. L'apparition de Fe7C3 est discutée dans le cadre du modèle de GASKELL.M7C3 type carbides have an orthorhombic structure, as proposed by R. FRUCHART et al. This structure may be hidden by defects which are typical of the preparation method. In Fe7C3 formed by crystallization of sputter-deposited amorphous Fe75C25 alloys, the defects are only consistent with elongated domains whose size is less than [MATH] 100 Å, the order of the defect size. In primary M7C3 carbides, present in white cast-iron and chromium steels, domains are about 100 times larger than in the latter case. Both results suggest that domain growth is impeded during the crystallization of amorphous Fe75C25. Nuclei may thus already exist in or be easily formed with a large density from the amorphous state. The formation of Fe7C3 is discussed within the frame of the GASKELL model

BiCMOS amplifier–discriminator integrated circuit for gas-filled detector readout

The paper presents a 16-channel amplifier-discriminator designed in BiCMOS technology. It will be used for the binary parallel readout of gas-filled detectors being designed at the European Synchrotron Radiation Facility. The circuit (named AMS211) has been manufactured. The measured transimpedance gain (400 KΩ), bandwidth (25 MHz) and noise (1570 e−+95 e−/pF ENC) well match the simulated results. The discriminator thresholds are individually controlled by built-in Digital to Analogue Converter. The experience gained with a first prototype of readout electronics indicates that the AMS211 should meet our requirements

Arginine 260 of the amino-terminal domain of NR1 subunit is critical for tissue-type plasminogen activator-mediated enhancement of N-methyl-D-aspartate receptor signaling.

International audienceTissue-type plasminogen activator (tPA) has been involved in both physiological and pathological glutamatergic-dependent processes, such as synaptic plasticity, seizure, trauma, and stroke. In a previous study, we have shown that the proteolytic activity of tPA enhances the N-methyl-D-aspartate (NMDA) receptor-mediated signaling in neurons (Nicole, O., Docagne, F., Ali, C., Margaill, I., Carmeliet, P., MacKenzie, E. T., Vivien, D., and Buisson, A. (2001) Nat. Med. 7, 59-64). Here, we show that tPA forms a direct complex with the amino-terminal domain (ATD) of the NR1 subunit of the NMDA receptor and cleaves this subunit at the arginine 260. Furthermore, point mutation analyses show that arginine 260 is necessary for both tPA-induced cleavage of the ATD of NR1 and tPA-induced potentiation of NMDA receptor signaling. Thus, tPA is the first binding protein described so far to interact with the ATD of NR1 and to modulate the NMDA receptor function