GABAA, NMDA and AMPA receptors: a developmentally regulated 'ménage à trois'

The main ionotropic receptors (GABAA, NMDA and AMPA) display a sequential participation in neuronal excitation in the neonatal hippocampus. GABA, the principal inhibitory transmitter in the adult CNS, acts as an excitatory transmitter in early postnatal stage. Glutamatergic synaptic transmission is first purely NMDA-receptor based and lacks functional AMPA receptors. Therefore, initially glutamatergic synapses are 'silent' at resting membrane potential, NMDA channels being blocked by Mg2+. However, when GABA and glutamatergic synapses are coactivated during the physiological patterns of activity, GABAA receptors can facilitate the activation of NMDA receptors, playing the role conferred to AMPA receptors later on in development. Determining the mechanisms underlying the development of this 'ménage à trois' will shed light not only on the wide range of trophic roles of glutamate and GABA in the developing brain, but also on the significance of the transition from neonatal to adult forms of plasticity.     

Effects of the amount of fillers and of the crosslink density on the mechanical behavior of carbon‐black filled styrene butadiene rubbers

Several carbon‐black filled styrene‐butadiene rubbers are subjected to monotonic uniaxial tension tests in order to investigate the effects of the amount of fillers and of the crosslink density on their mechanical properties. The Young modulus, the volume changes associated with material damage and the stretch to failure are extracted and discussed. Results compare well to the literature results when exist and quantitative analysis are proposed when possible. Results show that filled rubbers are not incompressible when submitted to uniaxial tension tests and their volume changes are strongly dependent of the amount of fillers but are unaffected by the crosslink density. The latter shows strong impact on the filled rubbers stretch to failure but more interestingly this impact is comparable to what is encountered in unfilled rubbers. The stretch to failure is improved by the addition of fillers with an optimum for material filled around 30 phr. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Dislocation mobility and electronic effects in semiconductor compounds

In situ transmission electron microscopy experiments provide a unique way to investigate in real time the dislocation behaviour at a microscopic scale and to decide which elementary process controls the dislocation glide in semiconductors. In this review the experimental results obtained on different semiconductors are presented and discussed. Particular attention is devoted to the radiation-enhanced glide process.     

SMIG model: A new geometrical model to quantify grain boundary-based plasticity

Stress-assisted grain boundary migration is a mechanism that has proven active in polycrystals but that relies on a limited number of models. Those models do not apply to general grain boundaries and often fail to reproduce the intensity of the coupling between the migration distance and the produced shear strain. Recently a new geometrical model, entitled the shear migration geometrical (SMIG) model, that is valid for all tilt boundaries has been introduced to account for the low coupling factors observed experimentally. In the present work we propose, on the basis of this model, (i) to determine, for a given tilt grain boundary, the number of possible coupling modes and (ii) to evaluate the shuffling needed to rearrange atoms as the grain boundary migrates. We will show that, for a given grain boundary defined by a misorientation angle and a grain boundary plane, it is almost always possible to find a coupling mode implying the shuffling of up to 20 atoms, supposedly without long-range diffusion. This characteristic is of prime importance in polycrystals where collective grain boundary motions are required to accommodate strain.     

A TEM in situ study of alloying effects in iron. II—Solid solution hardening caused by high concentrations of Si and Cr

The hardening effect of a high concentration of substitutional solute atoms in iron has been investigated by means of in situ straining experiments in FeSi and FeCr alloys, between 100 and 300 K. The results show that both screw and edge dislocations interact with solute atoms. This interaction is, however, strongest on screw dislocations, as a result of the formation of superjogs in the vicinity of solute atoms. Under such conditions, hardening takes place above a transition temperature for which the local pinning at superjogs becomes stronger than the Peierls friction stress.     

Comparison between hypo- and hyperglucidic diets on protein sparing in major visceral surgery (author's transl)

The authors compare the protein sparing effect of two diets, exclusively intravenous, including the same protein intake, but a different caloric intake, 21 calories/gm nitrogen for diet "A" (20 cases); 138 calories/gm nitrogen for diet "B" (20 cases). This has been observed during the six post-operative days of major visceral surgery: oesophagectomy, total gastrectomy, colic or rectocolic exeresis, sequestrectomy for acute pancreatitis, lots having been drawn for the diets. Daily nitrogen balances have been made and plasmatic and urinary levels of amino-acids have been measured before surgery and on the third and fifth post-operative days. Statistical exploitation is done by variance analysis (linear model of three factors) with a 99% confidence ratio: 1) Patient factor has no influence whatsoever on cumulative nitrogen balance. 2) Time factor arises only on the fourth post-operative day and only in the hypocaloric diet, leading to catabolism. 3) Metabolic condition is determinant. On no cancerous disease, superiority of hypercaloric diet is well demonstrated. On cancerous disease, nitrogen loss is only significantly different on 4th and 5th post-operative day: hypercaloric diet gives a better nitrogen balance.     

Carbon/platinum nanotextured films produced by plasma sputtering

Platinum loaded carbon layers were synthesized by a two-step plasma sputtering process. Two hundred nanometers thick columnar (columns with an average diameter of 20 nm) carbon films having a large open porosity were formed in the first step. Using the same plasma system, the films were subsequently loaded with platinum. SEM, TEM and Rutherford backscattering spectrometry analysis show that platinum diffuses into the carbon layer and forms nano-sized particles (mean diameter ca. 3 nm) along and around the carbon nanocolumns and down to the film/support interface. Optimized catalytic layers were formed at low plasma pressure operation (<1 Pa) and had an upper platinum loading limit of about 0.1 mg cm⁻².     

A new multi-finger SCR-based structure for efficient on-chip ESD protection

This paper introduces a new SCR-based (silicon controlled rectifier) structure for on-chip ESD protection. The STMSCR (smart triggered multi-finger SCR) relies on the bimodal operation of a LSCR (lateral SCR) using an external triggering circuitry that permits switching from a transparency mode to a protection mode as soon as an ESD event is detected. The trigger voltage can be adjusted by design without any impact on the ESD performance. The STMSCR is multi-finger compliant, thus allowing area-efficient design of pad-located ESD protection. The STMSCR is demonstrated in a 0.18 μm CMOS technology without any process customization; an HBM failure threshold over 115 V/μm is reached while always ensuring current uniformity in multi-finger structures.     

Grain boundary shear–migration coupling—I. In situ TEM straining experiments in Al polycrystals

Grain boundary (GB) migration was dynamically observed and characterized by means of in situ transmission electron microscopy straining experiments at moderate temperature in ultrafine grain aluminium. This motion is a response to the applied external stress, which leads to faceted fast growth of some grains at the expense of smaller ones. The combined use of fiducial markers and image correlation made possible a measure of strain associated with GB migration. The crystallographic orientation of both sides of moving GB was simultaneously recorded. The shear produced by the observed migration was thus estimated, leading to a coupling factor close to 20%. These results are discussed and compared with existing models describing the coupling between shear stress and GB migration.