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Editorial

Effect of three natural pozzolans in portland cement hydration

Natural pozzolans have been used since ancient times and continues to be used today. The chemistry and morphological composition of natural pozzolans and their particle size distribution allows classifying them as more or less reactive pozzolan. In this research several techniques have been used to study the influence…

Extraction and characterization of collagen with or without telopeptides from chicken skin

Poultry by-products are not often processed into high-value products. Rather than being transformed into meal for animal feed, a large quantity of chicken skin could be used to produce collagen, which is valued for its unique functional properties. The purpose of this research project was to extract and characterize c…

Petrophysical characteristics of the sandstones used in the construction of the Monumental Heritage of Ciudad Rodrigo, Salamanca. Spain

Knowledge of the petrophysical characteristics of stones used in construction is evidently advantageous in the sense that it can help avoid wasting time and future disappointments when attempting to assess the results both in restoration work and in actual construction work. However, if the material used is sandstone,…

Effective conductivity in a lattice model for binary disordered media with complex distributions of grain sizes

Using numerical simulations and analytical approximations we study a modified version of the two-dimensional lattice model [R. Piasecki,phys. stat. sol. (b) 209, 403 (1998)] for random pH:(1-p)L systems consisting of grains of high (low) conductivity for H-(L-)phase, respectively. The modification reduces a spectrum o…

X-ray Study of Freezing and Melting of Water Confined within SBA-15

To examine the freezing and melting behavior of water in partially filled pores of porous silica, we performed X-ray diffraction measurements of water confined inside the cylindrical pores of SBA-15 with a pore radius of 3.9 nm as a function of temperature and pore filling. The freezing temperature increased continuou…

Spinning and Characterization of Conducting Microfibers

Abstract Conducting microfibers of poly(3,4‐ethylenedioxythiophene) doped with poly(4‐styrene sulfonate), having a diameter ranging between 4.6 and 16 μm, were fabricated by a wet‐spinning technique. The as‐spun microfiber had no notable orientation of polymer chains with poor crystallinity, and electrical conductivit…

Theory of Composites. Cambridge Monographs on Applied and Computational Mathematics

3R27. Theory of Composites. Cambridge Monographs on Applied and Computational Mathematics. - GW Milton (Dept of Math, Univ of Utah, Salt Lake City UT). Cambridge UP, Cambridge, UK. 2002. 719 pp. ISBN 0-521-78125-6. $80.00. AT Sawicki (Inst of Hydro-Eng, Koscierska 7, Gdansk-Oliwa, 80-953, Poland).This is a book about…

Defect structures in MgB2 wires introduced by hot isostatic pressing

The microstructures of MgB2 wires prepared by the powder-in-tube technique and subsequent hot isostatic pressing were investigated using transmission electron microscopy. Large amount of crystalline defects including small angle twisting, tilting, and bending boundaries, in which high densities of dislocations reside,…

Electron Spin-Relaxation Times of Phosphorus Donors in Silicon

Pulsed electron paramagnetic resonance measurements of donor electron spins in natural phosphorus-doped silicon (Si:P) and isotopically-purified 28Si:P show a strongly temperature-dependent longitudinal relaxation time, T1, due to an Orbach process with DeltaE = 126 K. The 2-pulse echo decay is exponential in 28Si:P,…

Condensation and Slow Dynamics of Polar Nanoregions in Lead Relaxors

It is now well established that the unique properties of relaxor ferroelectrics are due to the presence of polar nanoregions (PNR's). We present recent results from Neutron and Raman scattering of single crystals of PZN, PZN-xPT, and PMN. Both sets of measurements provide information on the condensation of the PNR's a…

Novel Inorganic−Organic-Layered Structures: Crystallographic Understanding of Both Phase and Morphology Formations of One-Dimensional CdE (E = S, Se, Te) Nanorods in Ethylenediamine

A novel class of inorganic-organic-layered structures, CdE.0.5en (E = S, Se, Te; en = ethylenediamine), were obtained through reactions between elemental S, Se, or Te and Cd(2+) at appropriate solvothermal temperatures. These compounds contain atomic sheets of inorganic CdE frameworks spaced by ethylenediamine molecul…

A new approach to the diagnosis of solid insulation systems based on PD signal inference

The authors have developed digital instrumentation that can measure the amplitude, shape, phase, and number of pulses per cycle. Examples are given of results obtained from an induction motor, a hydrogenerator, a polymeric cable system with a defective joint, and a high-voltage current transformer.

Control of Biodegradability of Polylactide via Nanocomposite Technology

Abstract Polymer/layered silicate nanocomposite technology is not only suitable for the significant improvement of mechanical and various other materials properties of virgin polymers, it is also suitable to enhance the rate of biodegradation of biodegradable polymers such as polylactide. The biodegradability of polyl…

Electrospinning of Collagen Type II: A Feasibility Study

Collagen is the natural scaffolding found in all tissues and has been explored extensively for use as a tissue engineering scaffold with limited success. In this feasibility study, the electrospinning of collagen type II and subsequent chondrocyte seeding was investigated for potential use in cartilage tissue engineer…

Relaxor ferromagnetic behavior below the antiferromagnetic transition in La0.5Ca0.5MnO3

A detailed reinvestigation of magnetization in La0.5Ca0.5MnO3 reveals that although a field of H = 7 T applied at T = 5 K after zero field cooling is insufficient to convert the low temperature charge ordered antiferromagnetic phase into ferromagnetic, annealing in a magnetic field as small as H = 1 T induces ferromag…

Synthesis of Highly Porous Yttria‐Stabilized Zirconia by Tape‐Casting Methods

Porous ceramics of Y 2 O 3 ‐stabilized ZrO 2 (YSZ) were prepared by tape‐casting methods using both pyrolyzable pore formers and NiO followed by acid leaching. The porosity of YSZ wafers increased in a regular manner with the mass of graphite or polymethyl methacrylate (PMMA) to between 60% and 75% porosity. SEM indic…

Chemically modified smectites

Abstract This paper summarizes recent results obtained on chemical modifications of smectites. These include replacement of exchangeable cations with protons, a process connected with smectite autotransformation – attack of protons on the layers and liberation of central atoms from the octahedral and tetrahedral sheet…

Leucine Biosynthesis in Fungi: Entering Metabolism through the Back Door

After exploring evolutionary aspects of branched-chain amino acid biosynthesis, the review focuses on the extended leucine biosynthetic pathway as it operates in Saccharomyces cerevisiae. First, the genes and enzymes specific for the leucine pathway are considered: LEU4 and LEU9 (encoding the alpha-isopropylmalate syn…

Nanomechanics of carbon nanotubes and composites

Computer simulation and modeling results for the nanomechanics of carbon nanotubes and carbon nanotube-polyethylene composite materials are described and compared with experimental observations. Young’s modulus of individual single-wall nanotubes is found to be in the range of 1 TPa within the elastic limit. At room t…