Dynamic digital photorefractive memory for optoelectronic neural network learning modules

Neural network modules based on page-oriented dynamic digital photorefractive memory are described. The modules can implement two different interconnection organizations, fan-out and fan-in, depending on their target network applications. Neural network learning is realized by the real-time memory update of dynamic digital photorefractive memory. Physical separation of subvolumes in the page-oriented photorefractive memory architecture contributes to the low cross talk and high diffraction efficiency of the stored interconnection weights. Digitally encoded interconnection weights ensure high accuracy, providing superior neural network system scalability. Module scalability and feedforward throughput have been investigated based on photorefractive memory geometry and the photodetector power requirements. The following four approaches to extend module scalability are discussed: partial optical summation, semiparallel feedforward operation, time partitioning, and interconnection matrix partitioning. Learning capabilities of the system are investigated in terms of required interconnection primitives for implementing learning processes and three memory-update schemes. The experimental results of Perceptron learning network implementation with 900 input neurons with digital 6-bit accuracy are reported.     

Copper‐Catalyzed Asymmetric Conjugate Addition of Dimethylzinc to Acyl‐N‐methylimidazole Michael Acceptors: Scope,Limitations and Iterative Reactions

An efficient copper‐catalyzed enantioselective conjugate addition of dimethylzinc to unsaturated 2‐acyl‐N‐methylimidazoles has been achieved using a chiral bidentate hydroxyalkyl‐NHC ligand. The reactions proceed with excellent regioselectivity (1,4 vs. 1,6 and 1,8) in extended conjugated systems to afford the 1,4‐adducts in high enantioselectivities. This regioselectivity could be ascertained by DFT studies highlighting the crucial role of the imidazole ring. Thanks to the development of efficient protocols to regenerate the unsaturated 2‐acyl‐N‐methylimidazole moiety, an iterative process has been developed ultimately leading to 3,5,7 all‐syn or anti‐anti polydeoxypropionate stereodiads.

     

Characterization of extended defects in SiGe alloys formed by high dose Ge implantation into Si

The synthesis of SiGe/Si heterostructures by Ge⁺ ion implantation is reported. 400 keV Ge⁺ ions were implanted at doses ranging from 3 × 10¹⁶ to 10 × 10¹⁶ ions/cm² into (001) Si wafers, followed by Si⁺ amorphisation and low temperature Solid Phase Epitaxial Regrowth (SPER). TEM investigations show that strained alloys can be fabricated if the elastic strain energy (E_el) of the SiGe layer does not exceed a critical value (E′_el) of about 300 mJ/m², which is independent of the implantation energy. Our analysis also suggests that “hairpin” dislocations are formed as strain relieving defects in relaxed structures. A “strain relaxation” model is proposed to explain their formation.     

Immunolocalization of myoepithelial cells in isolated acini of rat exorbital lacrimal gland: cellular distribution of muscarinic receptors

The secretion of proteins and fluids from the exorbital lacrymal gland of rat is mainly controlled by muscarinic receptors. In a recent pharmacological study. Mauduit et al (Am J Physiol (1993) 264, C1550-C1560) identified a homogeneous population of M3 muscarinic receptors in preparations of acini from these tissues. In order to define the cellular composition of these acini and localize the muscarinic receptors, we have performed an immunofluorescent labelling study combined with confocal scanning microscopy. Antibodies raised against components of the different cytoskeletal networks (alpha-smooth muscle actin, cytokeratin peptide 14 and alpha-tubulin) revealed the presence of two different cell types. Cells with a stellate form are identified as myoepithelial cells, whereas rounded cells are secretory acinar cells. Both cell types are reactive with an antibody specifically directed against the muscarinic receptor. However, myoepithelial cells appear more intensely labelled than acinar cells. The roles of myoepithelial cells and secretory cells in the physiological function of the gland are discussed in terms of the distribution of muscarinic receptors.     

The influence of neutron and gamma irradiation in bubble garnet films

The behaviour of garnet films, containing 3 micronsbubbles, exposed to neutron irradiation and gamma rays is reported. The implanted and non implanted (YSmLuCa)3(FeGe)5O12epitaxial garnet films were irradiated with fast neutrons (10¹⁵n/cm²) and 10⁸rad (Si) gamma rays with 1 MeV energy. In these harsh conditions, the variations of physical characteristic parameters were analysed. In ion implanted films, the coercive field increased from 0.3 to 0.4 oe after neutron irradiation. The gamma rays irradiation brought the strip width back to the value it had before the ion implant. The anisotropy field increased slightly (3%) under both irradiations. The decrease in operating margins of 64 K bit memory chips is presented and a good correlation is made with the previous results. These effects are explained by general phenomena describing the interaction between the irradiation and the material. These experiments show that bubble memories will only fail at a high level of neutron and gamma ray exposure.     

Complexity of the hydrolytic degradation of aliphatic polyesters

Aliphatic polyesters are more or less hydrolytically degradable, depending on their chemical, configurational and morphological structures. Hydrolysis can be either homogeneous or heterogeneous, depending on many structural and environmental factors. The present understanding of this hydrolytic degradation is recalled. The importance of diffusion-reaction phenomena is discussed on the basis of the behaviors of polyesters derived from α-hydroxy acids, namely lactic and glycolic acids and attempts are made to extend the understanding to other members of the aliphatic polyester family. The main results of some recent investigations of the effects on poly(lactic acid) polymers of basic additives and of initiators such as stannous octoate and zinc metal, which are now industrially used, are presented.     

Synthesis Optimization and Catalytic Activity Screening of Industrially Relevant Ruthenium-Based Metathesis Catalysts

Olefin metathesis is a powerful catalytic reaction that has a huge potential in the pharmaceutical, polymer and specialty chemicals industries. Cost-effective industrial applications require large-scale availability of catalyst precursors which combine high activity, high selectivity and long life-time. Among the known numerous families of olefin metathesis catalysts, the Umicore M7-catalyst family represents a novel class of Hoveyda-type complexes showing excellent chemical stabilities and modular activity profiles. Relevant aspects related to their industrial synthesis as well as their catalytic performance in valuable olefin metathesis transformations are overviewed here.

     

Peroxy bleaches Part 2. Determination of the thermodynamic and kinetic chemistry of some peroxy compounds

The thermodynamic and kinetic properties of a series of inorganic and organic peroxy bleaches were determined using adiabatic rate calorimetry and isothermal microcalorimetry. Results are compared to calculated oxygen balance values. The decomposition of the majority of the compounds is complex. Data indicate the need for cooling during the storage and transport for some materials evaluated. Although no overall structure/activity relationship could be established because of the diversity of molecular architectures studied, a combination of decomposition and activation energy data provides a means for hazard and risk classification.     

Multivariate multifractal texture DCGAN synthesis: How well does it work ? How does one know ?

Journal of Signal Processing Systems - In a recent past, Deep Learning emerged as a standard tool in Image Processing, commonly involved in numerous and various tasks. Notably, Deep Learning has...