Facile preparation of glycine-based mesoporous graphitic carbons with embedded cobalt nanoparticles

Journal of Materials Science - A simple route has been developed for the preparation of mesoporous graphitic carbons with embedded cobalt nanoparticles just using glycine as a nitrogen source,...     

Liquid-crystallization induced reactions. Microstructure and morphology of copolyesters synthesized by transesterification of PET with some LCP monomers

The transesterification of poly(ethylene terephthalate) (PET) with a mixture of sebacic acid (S), 4,4′-diacetoxybiphenyl (B) and 4-acetoxybenzoic acid (H), carried out under conditions expectedly favoring the formation of a p(ET-SBH) random copolyester, produces biphasic materials with an isotropic matrix and a highly fibrous, liquid-crystalline dispersed phase. Spectroscopic, calorimetric, microscopic and diffractometric characterization of the fractions separated by solvent extraction has shown that the two phases consist of practically random copolyesters having different average composition. Interestingly, the degree of aromaticity of the matrix is even lower than that of PET, whereas that of the minor phase is appreciably higher than that calculated for the SBH copolyester that would be produced from the monomer mixture in the absence of PET. This unexpected result is interpreted on the basis of an enthalpy-driven progressive diffusion of aromatic-rich material toward the mesophase which segregates at an early stage of the polycondensation within the isotropic mixture of low molar mass oligomers initially produced by the PET acidolysis. Thus, an increasing differentiation, rather than an equilibration, of the composition of the two phases takes place. It is noteworthy that, despite the strong compositional difference, the two phases of these products show fairly good compatibility and interfacial adhesion.     

Variational formulation for every nonlinear problem

It is shown that for every linear or nonlinear problem, whose solution exists and is unique, one may find many functionals whose minimum is the solution of the problem. They are obtained after a transformation of the given problem into another by the application of an “integrating operator”: this transforms a differential problem into an integro-differential one. The procedure used to obtain such functionals is straightforward and is described in detail. Examples are exhibited and the numerical effectiveness of the method is tested. The variational formulation so obtained contains the classical formulation as a particular case when it exists.     

MOS Technology Drivers

The semiconductor industry has entered a new revolution where connectivity, applications, and an overall pervasive market drives the need for increased circuit density, improved performance, and a decrease in power dissipation. These issues are the backbone for some of the latest silicon technology advancements, including the integration of stress-enabled transistors and advanced silicon-on-insulator substrates. Future advancements may include multiple gated devices, high- gate oxides, and band-gap-tailored devices. This paper will review some of the early complementary metal-oxide-semiconductor transistor reliability issues and solutions that have allowed this industry to flourish over the last 25 years. A discussion on how these past issues and new advances affect power versus performance is the framework and motivation of this paper.     

Visuo-Acoustic Stimulation’s Role in Synaptic Plasticity: A Review of the Literature

Brain plasticity is the capacity of cerebral neurons to change, structurally and functionally, in response to experiences. This is an essential property underlying the maturation of sensory functions, learning and memory processes, and brain repair in response to the occurrence of diseases and trauma. In this field, the visual system emerges as a paradigmatic research model, both for basic research studies and for translational investigations. The auditory system remains capable of reorganizing itself in response to different auditory stimulations or sensory organ modification. Acoustic biofeedback training can be an effective way to train patients with the central scotoma, who have poor fixation stability and poor visual acuity, in order to bring fixation on an eccentrical and healthy area of the retina: a pseudofovea. This review article is focused on the cellular and molecular mechanisms underlying retinal sensitivity changes and visual and auditory system plasticity.     

Polymer-dispersed liquid-crystal polymers (PDLCPs). Morphology of the LCP droplets

“Synthetic blends” of a flexible polymer forming the matrix and a liquid-crystalline polymer (LCP) forming the dispersed phase have been prepared by transesterification of PET with a mixture of sebacic acid (S), 4,4′-diacetoxybiphenyl (B) and 4-acetoxybenzoic acid (H) in the mole ratio 1:1:2. A change of the synthesis conditions causes marked variations of the chemical composition and the morphology of the phases. The SEM investigation of the inner morphology of the LCP droplets of blends consisting of two phases with fairly different aromatic content has shown that the LCP macromolecules are aligned tangentially at the matrix surface boundary, and that the nematic director configuration is toroidal. When the two phases have closer chemical composition, and are therefore supposed to possess improved mutual compatibility, a perpendicular anchoring of the LCP fibrils to the matrix cavity surface, and an axial configuration of the nematic director, are observed. The expected effect of the nematic configuration of the LCP droplets on their ability to deform into fibrils under appropriate flow conditions is preliminarily discussed.     

Phase behavior of blends of poly(ethylene terephthalate) with liquid-crystalline polymers

Poly(ethylene terephthalate) (PET) was melt blended with several liquid-crystalline polymers (LCPs), both with and without Ti(OBu)₄ catalyst. The LCPs, referred to as VA, LC5, LC3, and SBH, respectively, were Vectra-A950, Rodrun LC-5000, Rodrun LC-3000, and a laboratory copolyester of sebacic acid (S), 4,4′-diacetoxybiphenyl (B), and 4-acetoxybenzoic acid (H). Their degree of aromaticity decreases in that order. The phase behavior and the morphology of the blends were studied by differential scanning calorimetry and scanning electron microscopy. All the LCPs retard the dynamic crystallization of PET. The lower the LCPs degree of aromaticity, the more pronounced was the effect. It was not possible to obtain any evidence of ester exchange reactions by the reactive blending of PET with VA. On the contrary, appreciable changes of phase behavior and morphology were observed under comparable conditions for the other blends. With LC5 and LC3, the transesterification process predominantly involved the ET-rich phase of those polymers. Extensive transesterification occurred between PET and SBH, as proven by the gradual formation of a quasi homogeneous material, with lowered temperatures and enthalpies of fusion and crystallization. For blends with more than 25% SBH, homogenization is followed by the segregation of a new, highly aromatic phase.     

Long-term bias temperature reliability of P+ polysilicongated FET devices

An instability was found to be associated with +BT stress for P ⁺ poly-gated NMOSFETs (PNMOS) and PMOSFETs (PPMOS), but not with the N⁺ poly-gated devices (NNMOS and NPMOS). The instability with the P⁺ poly-gated devices, which is a decrease in threshold voltage (V_t) and an increase in interface state density (D_it), was significantly reduced following N₂ annealing at 400°C. It is shown that adequate reliability for P⁺ poly-gated devices can be achieved for VLSI technologies     

Large-scale monitoring of coppice forest clearcuts by multitemporal very high resolution satellite imagery. A case study from central Italy

Reliable assessment of forest resource stock, productivity and harvesting is a commonly agreed objective of environmental monitoring programs. Distinctively, the assessment of wood harvesting has become even more relevant to evaluate the sustainability of forest management and to quantify forest carbon budget. This paper presents the development and testing of procedures for assessing forest harvesting in coppice forests by very high resolution (VHR) satellite imagery. The study area is located in central Italy over approximately 34,000 km². A set of SPOT5 HRG multispectral images was acquired for the study years (2002-2007). Official administrative statistics of coppice clearcuts were also acquired. More than 9500 clearcuts were mapped and dated by on-screen interpretation of the SPOT5 images. In a subset of the study area various methods for semi-automatic clearcut mapping were tested by pixel- and object-oriented approaches. The following results are presented: (i) clearcut map developed by visual interpretation of the SPOT5 images resulted in high thematic (overall accuracy of 0.99) and geometric (root mean square error of clearcut boundary delineation of 5.3 m) reliability; (ii) object-oriented approach achieved significantly better accuracy than pixel-based methods for semi-automatic classification of the coppice clearcuts; (iii) comparison between mapped clearcut area and official forest harvesting statistics proved a significant underestimation by the latter (65% of the total mapped clearcut area). A sample-based procedure exploiting VHR satellite imagery is finally proposed to correct the official statistics of coppice clearcuts.