The 3,4-Quinones of Estrone and Estradiol Are the Initiators of Cancer whereas Resveratrol and N-acetylcysteine Are the Preventers

This article reviews evidence suggesting that a common mechanism of initiation leads to the development of many prevalent types of cancer. Endogenous estrogens, in the form of catechol estrogen-3,4-quinones, play a central role in this pathway of cancer initiation. The catechol estrogen-3,4-quinones react with specific purine bases in DNA to form depurinating estrogen-DNA adducts that generate apurinic sites. The apurinic sites can then lead to cancer-causing mutations. The process of cancer initiation has been demonstrated using results from test tube reactions, cultured mammalian cells, and human subjects. Increased amounts of estrogen-DNA adducts are found not only in people with several different types of cancer but also in women at high risk for breast cancer, indicating that the formation of adducts is on the pathway to cancer initiation. Two compounds, resveratrol, and N-acetylcysteine, are particularly good at preventing the formation of estrogen-DNA adducts in humans and are, thus, potential cancer-prevention compounds.     

c-Myc or cyclin D1 mimics estrogen effects on cyclin E-Cdk2 activation and cell cycle reentry

Estrogen-induced progression through G1 phase of the cell cycle is preceded by increased expression of the G1-phase regulatory proteins c-Myc and cyclin D1. To investigate the potential contribution of these proteins to estrogen action, we derived clonal MCF-7 breast cancer cell lines in which c-Myc or cyclin D1 was expressed under the control of the metal-inducible metallothionein promoter. Inducible expression of either c-Myc or cyclin D1 was sufficient for S-phase entry in cells previously arrested in G1 phase by pretreatment with ICI 182780, a potent estrogen antagonist. c-Myc expression was not accompanied by increased cyclin D1 expression or Cdk4 activation, nor was cyclin D1 induction accompanied by increases in c-Myc. Expression of c-Myc or cyclin D1 was sufficient to activate cyclin E-Cdk2 by promoting the formation of high-molecular-weight complexes lacking the cyclin-dependent kinase inhibitor p21, as has been described, following estrogen treatment. Interestingly, this was accompanied by an association between active cyclin E-Cdk2 complexes and hyperphosphorylated p130, identifying a previously undefined role for p130 in estrogen action. These data provide evidence for distinct c-Myc and cyclin D1 pathways in estrogen-induced mitogenesis which converge on or prior to the formation of active cyclin E-Cdk2-p130 complexes and loss of inactive cyclin E-Cdk2-p21 complexes, indicating a physiologically relevant role for the cyclin E binding motifs shared by p130 and p21.     

Properties of an Infrared‐Transparent MgO:Y2O3 Nanocomposite

A 50:50 vol% MgO–Y₂O₃ nanocomposite with ~150 nm grain size was prepared in an attempt to make 3–5 μm infrared‐transmitting windows with increased durability and thermal shock resistance. Flexure strength of the composite at 21°C is 679 MPa for 0.88 cm² under load. Hardness is consistent with that of the constituents with similar grain size. For 3‐mm‐thick material at 4.85 μm, the total scatter loss is 1.5%, forward scatter is 0.2%, and absorptance is 1.8%. Optical scatter below 2 μm is 100%. Variable intensity OH absorption (~6% absorptance) is observed near 3 μm. The refractive index is ~0.4% below the volume‐fraction‐weighted average of those of the constituents. Thermal expansion is equal to the volume‐fraction‐weighted average of expansion of the constituents. Specific heat capacity is equal to the mass‐fraction‐weighted average of heat capacities of the constituents. Thermal conductivity lies between those of the constituents up to 1200 K. Elastic constants lie between those of the constituents. The Hasselman mild thermal shock resistance parameter for the composite is twice as great as that of common 3–5 μm window materials, but half as great as that of c‐plane sapphire.     

Carboxylic acids and polyethylene glycol assisted synthesis of nanocrystalline nickel ferrites

Different synthesis methods for the preparation of nanocrystalline nickel ferrites are reported: the thermal decomposition of precursors, made of: (i) metal-nitrate salts with carboxylic acids (citric, malonic and tartaric), and (ii) metal-nitrate salts and polyethylene glycol (PEG), in the presence of potassium chloride as a capping agent. The as-prepared gel precursors were characterized by TGA/DTA, while the samples obtained after annealing at 450 °C were investigated by FTIR, FESEM, XRD and Mössbauer spectroscopy. Regardless of the type of carboxylic acid used, nanocrystallites prepared by (i) method are similar in size (11–16 nm), while the method (ii) gives crystallites ∼33 nm in size with negligible microstrain. The differences in the lattice parameter, ranging from 8.3369(2) to 8.3574(2) Å, result from cation distribution, nonstoichiometry and structural imperfections in the nickel ferrite nanoparticles. The Mössbauer spectra analysis indicates existence of large distortions of tetrahedral and octahedral sites in these spinel compounds.     

A machine vision approach to the grading of crushed aggregate

The grading of crushed aggregate is carried out usually by sieving. We describe a new image-based approach to the automatic grading of such materials. The operational problem addressed is where the camera is located directly over a conveyor belt. Our approach characterizes the information content of each image, taking into account relative variation in the pixel data, and resolution scale. In feature space, we find very good class separation using a multidimensional linear classifier. The innovation in this work includes (i) introducing an effective image-based approach into this application area, and (ii) our supervised classification using wavelet entropy-based features.     

Direct measurement of triaxial strain fields around ferroelectric domains using X-ray microdiffraction

Ferroelectric materials, such as BaTiO(3), have piezoelectric properties that make them attractive for microelectronic and sensing applications. It is well known that the application of mechanical stress or electric field can alter the domain structure in ferroelectrics. Indeed, the constitutive behaviour of a ferroelectric is largely governed by the formation, movement and interaction of its domains. Therefore, it is crucial that the micromechanics of domains and their effect on internal stresses in ferroelectrics be understood. Here we show that the emerging technique of scanning X-ray microdiffraction can be used to measure directly, for the first time, the local triaxial strain fields around 90 degrees domains in single-crystal BaTiO(3). Specifically, residual strain maps in a region surrounding an isolated, approximately 40 microm wide, 90 degrees domain were obtained with 3 microm resolution, revealing significant residual strains. This information is critical for accurate micromechanical modelling of domain behaviour in ferroelectrics.     

Artificial intelligence techniques in simulation of viscoplasticity of polymeric composites

The viscoplastic behavior of a carbon fiber/polymer matrix composite is investigated via different modeling schemes. The first model is phenomenological in nature based on the overstress‐viscoplasticity. The second model utilizes neural networks paradigms. Genetic algorithm‐based strategies are used to prune the proposed neural network. Several optimization algorithms are implemented for training the network. In comparison, the neurocomputational model is found to outperform the phenomenological model. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers