Reconstruction of the lost Muisca Siecha raft pouring process by reverse engineering methodology

ABSTRACT

This work presents a study of a pre-Hispanic artifact based on a reverse engineering methodology, by which an object is reconstructed by computer-aided design to obtain information. The object of the study is the Siecha raft–a Muisca goldwork piece that disappeared in the nineteenth century and was reconstructed based on historical sources. The pouring process of the raft was studied by characterizing the metal flow within a mold, by using the analytical, experimental, and computational fluidity length parameter. After this, the flow was studied, by using estimated parameters from the previous three methods, in the reconstructed geometry of the raft. Pouring temperature, materials, and temperature of the mold, entrance velocity, and other parameters of the fabrication process were calculated. The results showed that the geometry of the raft could have been cast by gravity casting pouring process, with the calculated parameters.     

Let the light be a guide: Chromophore communication in metal-organic frameworks

The photonic characteristics of chromophore-containing metal-organic frameworks(MOFs)have led to extensive photophysical studies in an effort to capitalize on the potency of precisely controlled chromophore ensembles.Several examples have laid the foundation that demonstrates how photophysical properties of chromophores can be manipulated by tuning their communications(interactions)through integration within a MOF matrix.The main focus of this review is on harnessing the versatile MOF platform to accentuate the photophysical properties of integrated chromophores.In particular,this review will highlight chromophore dynamics that enhance,alter,or tune the photoluminescence response of single-and multi-chromophore-containing scaffolds,as well as alignment-guided anisotropic fluorescence.Building upon this groundwork,utilization of a hybrid crystalline motif can induce preferential orientation of chromophores resulting in enhanced communication and tailored behavior compared to randomly oriented emissive molecules.Moreover,frameworks that produce upconverted emission via sensitized triplet-triplet annihilation(sTTA),excited-state absorption(ESA),energy transfer upconversion(ETU),multi-photon absorption(MPA),or second-harmonic generation(SHG)can invoke dynamic control of material properties using photochromic linkers and will be discussed herein with a focus on the effects of chromophore alignment.Integration within a framework is a vehicle tofuse chromophores into solid-state platforms,opening an avenue for chromophore utilization in applications such as portable electronics that require solids or thin films.For those reasons,the design of chromophore-containing MOFs with desirable properties that rely on the alignment and communication of hundreds of chromophores within a single platform is a pressing demand for the development of futuristic technologies.     

Ultrafast method of fullerenes extraction from carbon condensate

The Soxhlet extraction method (SE) only used in the extraction of fullerenes from carbon condensate (CC) obtained in the fullerene production facility, which in the literature is often referred to as carbon black, does not provide complete extraction. Fullerenes can also be extracted from the CC suspension and the solvent by the mechanical extraction method (ME) and show higher degree of extraction efficiency. This method combined with filtration process takes only a few minutes and allows a significant reduction in solvent consumption. Extraction via the ME method application makes it possible to carry out extraction of fullerenes twenty times faster than by the SE method. It can be used as an independent method, bypassing the extraction by the SE method, and also as an additional one. Application of the ME method allows additional extraction of fullerenes weight percentage from the CC, after extracting fullerenes from it applying the SE method. In this instance the higher fullerenes prevail in the essences extracted by the ME method with their content reaching as high as 39.50?wt%. The obtained samples of fullerene mixtures (FM) are characterized by the methods of high-performance liquid chromatography and mass spectrometry. Analysis of the results shows that the composition of the FM, isolated by the ME method, differs from the compositions extracted via the SE method.     

Chitosan impregnation with biologically active tryaryl imidazoles in supercritical carbon dioxide

The presented paper is focused on impregnation of chitosan and its derivatives with a biologically active triaryl imidazole model compound ((2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole) in the supercritical carbon dioxide medium. Since initial chitosan represents a polycation-exchange resin and does not swell in supercritical carbon dioxide, the impregnation was carried out in the presence of water (0.15–3.0 vol%). The maximum 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole concentration in a chitosan film was achieved at the ~5?×?10^?3?g/cm³ water content in the reactor. We also used hydroxy carboxylic acid derivatives of chitosan and its copolymer with polylactide as matrices for introduction of hydrophobic 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole. We have shown that unmodified chitosan contains the greatest amount of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole, as compared with its hydrophobic derivatives. The kinetics of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole diffusion from a chitosan matrix was studied in acidified water with pH 1.6. We found that the complete release of 2-2-hydroxyphenyl)-4.5-diphenyl-1H-imidazole into the aqueous phase from unmodified chitosan films occurred in 48?h, while its complete release from chitosan modified with hydroxy carboxylic acids occurred in 5?min or less.     

σ-Phase Formation in Super Austenitic Stainless Steel During Directional Solidification and Subsequent Phase Transformations

Metallurgical and Materials Transactions A - The solidification path and the σ-phase precipitation mechanism in the S31254 (UNS designation) steel are investigated thanks to Quenching during...     

Direct spectral measurements with a Brewer spectroradiometer: absolute calibration and aerosol optical depth retrieval

We present three different methods for the absolute calibration of direct spectral irradiances measured with a Brewer spectroradiometer, which are shown to agree to within +/- 2%. Direct irradiance spectra derived by Brewer and Bentham spectroradiometers agree to within 4 +/- 3%. Good agreement was also found by a comparison of the aerosol optical depth and Angstrom exponent retrieved by the two instruments and a multifilter rotational shadowband radiometer. The spectral aerosol optical depth (300-365 nm) derived from six years of direct irradiance measurements at Thessaloniki shows a distinct seasonal variation, averaging to approximately 0.3 at 340 nm in winter and approximately 0.7 in summer.     

Acoustic properties of the film/plate layered structure

A new propagation medium-a layered structure composed of a film and a plate-is suggested and studied, using c-oriented ZnO and AlN films on (001), {100}-Si plate, as two opposite examples of slow-on-fast and fast-on-slow material combinations. For both structures, the modes belonging to Lamb, quasi-longitudinal (QL), and Anisimkin Jr.' (AN) families are found. For each family, the velocities v(n), displacement profiles, and electromechanical coupling coefficients K(n)2 for 4 electrode configurations are numerically calculated by the matrix method as a function of the mode order n = 0 to 8, plate thickness H/λ = 0 to 2.0, and film thickness h/λ = 0.02 to 0.04 (H and h are thicknesses; λ is the wavelength). Some high-order modes in the structure have K(n)2 = 0 for any H/λ, h/λ, and electrode configuration. Other modes possess variable K(n) 2 with a maximum value larger than the coupling coefficient for the Rayleigh SAWs in ZnO and AlN single crystals or layered structures using the same films and semi-infinite silicon substrate. There are also QL-modes having high velocity v(n), large K(n)2, and low propagation loss caused by liquid loading. These modes are well suited for liquid sensors.     

The effects of D1 or D2 dopamine receptor antagonism in the medial preoptic area, ventral pallidum, or nucleus accumbens on the maternal retrieval response and other aspects of maternal behavior in rats.

The medial preoptic area (MPOA), ventral pallidum (VP), and nucleus accumbens (NA) receive dopaminergic afferents and are involved in maternal behavior. Experiments investigated whether dopamine (DA) receptor antagonism in NA disrupts maternal behavior, determined the type of DA receptor involved, and investigated the involvement of drug spread to VP or MPOA. Injection of SCH 23390 (D1 DA receptor antagonist) into NA of postpartum rats disrupted retrieving at dosage levels that were ineffective when injected into MPOA or VP. Motor impairment was not the cause of the deficit. Injection of eticlopride (D2 DA receptor antagonist) into NA or VP was without effect. Results emphasize the importance of DA action on D1 receptors in NA for retrieval behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mature market segmentation: a comparison of artificial neural networks and traditional methods

The need for in-depth knowledge of mature market segments and the need to overcome the limitations of using traditional methods to segment them motivate this study. The research objectives are (1) to examine neural networks, specifically Kohonen’s self-organising maps (SOM), as an alternative to traditional statistical segmentation methods (hierarchical and non-hierarchical cluster analysis) and (2) to identify segments in the mature market which may direct its targeting. The results show the superiority of non-hierarchical clustering and SOM over hierarchical clustering, and demonstrate their complementary nature. In addition, significant segments with particular characteristics are found in the mature market.