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Post-disaster archaeological investigations at Jaffna Fort have revealed material demonstrating pre-colonial contact, shedding new light on the importance of the site in Indian Ocean trade and communications networks before European occupation.
One of the Indus Civilization's most striking features is its cultural uniformity evidenced by a common script, artefact forms and motifs, weights and measures, and the presence of proscribed urban plans. Early excavators and commentators utilized ideas of diffusion, and concepts of kingship and slavery remained prevalent within interpretations of the Indus. Whilst Childe questioned ideas of diffusion and hereditary rule he still identified a system of economic exploitation in which the vast majority of the population was subordinated. More recently scholars have begun to argue that small sections of the Indus population may have willingly subordinated themselves in order to secure positions of power. This article explores the dichotomy between traditional Eurocentric normative models of social organization and those derived from south Asian cultural traditions.
In recent years, several frameworks and systems have been proposed that extend Inductive Logic Programming (ILP) to the Answer Set Programming (ASP) paradigm. In ILP, examples must all be explained by a hypothesis together with a given background knowledge. In existing systems, the background knowledge is the same for all examples; however, examples may be context-dependent. This means that some examples should be explained in the context of some information, whereas others should be explained in different contexts. In this paper, we capture this notion and present a context-dependent extension of the Learning from Ordered Answer Sets framework. In this extension, contexts can be used to further structure the background knowledge. We then propose a new iterative algorithm, ILASP2i, which exploits this feature to scale up the existing ILASP2 system to learning tasks with large numbers of examples. We demonstrate the gain in scalability by applying both algorithms to various learning tasks. Our results show that, compared to ILASP2, the newly proposed ILASP2i system can be two orders of magnitude faster and use two orders of magnitude less memory, whilst preserving the same average accuracy.
The Son Ferrer archaeological site presents a series of successive occupations spanning a long period of time. At the beginning of the Iron Age (∼850 BC), a staggered turriform structure was built for a ritual purpose over an artificial hypogeum that had already been used as a collective necropolis during the Early Bronze Age (∼1800–1500 BC). Later, in the post-Talayotic phase (Second Iron Age, 550–123 BC), the hypogeum was again reused as a collective burial place. The present work is focused on the chronological and functional analysis of this last phase, which began ∼500 BC and ended ∼180 BC with the saturation and sealing of the hypogeum. The excavation process revealed that significant removal of archaeological material has occurred as a result of complex funerary space management practices, which generated a secondary archaeological context. Given this situation, and in order to establish the different use phases of the post-Talayotic necropolis, a dual strategy of excavation and research was implemented. First, an extensive series of radiocarbon dates on human remains (18 dates) was obtained, which were later analyzed following Bayesian strategies. Second, a detailed spatial analysis was carried out, georeferencing the location of all the archaeological finds. This strategy allowed the reconstruction of the space management processes and movement patterns that took place in the burial space. Despite some initial difficulties, the combination of these research strategies embedded in a contextual analysis provided both material and chronological references that have contributed to define the various use phases of the hypogeum.
To date, it is unclear whether chemical order (or disorder) is in any way connected to double exchange, electronic phase separation, or charge ordering (CO) in manganites. In this work, we carry out an atomic resolution study of the colossal magnetoresistant manganite La2−2xSr1+2xMn2O7 (LSMO). We combine aberration-corrected electron microscopy and spectroscopy with spectroscopic image simulations, to analyze cation ordering at the atomic scale in real space in a number of LSMO single crystals. We compare three different compositions within the phase diagram: a ferromagnetic metallic material (x=0.36), an insulating, antiferromagnetic charge ordered (AF-CO) compound (x=0.5), which also exhibits orbital ordering, and an additional AF sample (x=0.56). Detailed image simulations are essential to accurately quantify the degree of chemical ordering of these samples. We find a significant degree of long-range chemical ordering in all cases, which increases in the AF-CO range. However, the degree of ordering is never complete nor can it explain the strongly correlated underlying ordering phenomena. Our results show that chemical ordering over distinct crystallographic sites is not needed for electronic ordering phenomena to appear in manganites, and cannot by itself explain the complex electronic behavior of LSMO.
The domed stupas are among the most distinctive of South Asia's religious monuments and have been shown to be sensitive indicators for their society. Since arguments for economic and political change depend on accurate dating, and since the stupas are largely composed of brick, the authors here assess the potential for dating building sequences by applying optically stimulated luminescence to brick fabric. As so often, good scientific dates obtained from specimens must be tempered by their context: brick may be replaced or recycled during repair and embellishment. Nevertheless, the method promises important insights by distinguishing different episodes of building, and so writing ‘biographies’ for stupas with different functions.
The study of plant speciation on oceanic islands has improved enormously with the help of molecular systematics. Studies have targeted groups present on both the mainland and islands with the aim of understanding plant migration and evolution in isolation. In addition, relatively young volcanic islands give the opportunity to place the evolutionary process in a time frame, by dating molecular trees according to the age of the islands or by relying on the fossil record. Molecular phylogenetics can also be valuable in helping to reconstruct character evolution and understand the syndrome of characters diagnosing oceanic species.
A model based on the state-of-the-art, first-principles layer Korringa-Kohn-Rostoker (LKKR) method has proven to be very effective in describing the electronic and magnetic structure of metal/ceramic interfaces. We have performed self-consistent field computations incorporating spin polarization both for Fe/MgO superlattice (bulk technique) and for MgO/Fe/MgO sandwich (layer technique) systems. Muffin-tin potentials were employed for both materials in our computations. Iron layer was embedded in MgO, the host material, to have a (100)Fe / (100)MgO contact configuration. A large enhancement of magnetic moments has been found at the interface.
Lactose and heparin were covalently coupled to poly(chloromethyl styrene) and the modified polymer was used as a substrate for rat hepatocyte culture. Lactose and heparin are recognized by rat hepatocytes and can be used to mediate cell attachment to the substrate. Rat hepatocytes cultured in serum-free media on these substrates were able to maintain enzymes and peptides important in the detoxification functions of hepatocytes, without the addition of hormones such as dexamethasone, media additives such as DMSO, or complex biological extracellular factors.
The growing interest in large-scale cell culture and in tissue engineering requires substrates of different geometries. Therefore, we have fabricated the derivatized polymers into microcarriers and, most recently, foams. These three-dimensional structures, combined with the chemistries of the polymers, provided the hepatocytes with more cell-cell interactions and in vivo-like geometries than conventional flat-dish culture.
Screening and detecting virus by receptor-ligand interactions presents an important challenge in medical and environmental diagnostics, and in drug development. We have developed a direct colorimetric detection method based on a polymeric bilayer assembly. The bilayer is composed of a self-assembled monolayer of octadecyl siloxane and a Langmuir-Blodgett layer of polydiacetylene. The polydiacetylene layer is functionalized with receptor-specific ligands such as analogs of sialic acid. The ligand serves as a molecular recognition element, while the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. The color transition can be inhibited by the presence of soluble inhibitors. Raman spectroscopic analysis shows that the color transition may arise from binding induced strain on the material resulting in bond elongation and conjugation length reduction.
A biomimetic approach utilizing biomolecular self-assembly was used to tailor quantum-dot composites for use as nonlinear optical media. Yeast tRNA was utilized as an ion-exchange/nucleation site within a polymeric matrix (polyacrylamide). Cadmium ion-exchange and subsequent sulfide precipitation resulted in quantum-dot formation. Illumination of samples with an Argon laser (514 nm) utilizing the Z-scan measurement method resulted in χ3 values of +3.7 ×10−6 esu.
In recent experiments we have patterned smooth HOPG surfaces with periodic arrays of nanometer dimension holes on a 20nm lattice using two-dimensional (2-D) protein crystals as templates. The bacterial cell wall crystals were deposited on HOPG substrate and overcoated at oblique incidence with an ultrathin (3.5 nmn) TiO2 film. Fast atom beam (FAB) milling patterns the TiO2 film into a screen having the protein lattice periodicity and the screen then acts as a mask for the pattern transfer to the HOPG substrate. This method provides an inexpensive, “benchtop,” intrinsically parallel technique for the periodic nanostructuring of surfaces. Here we extend it to the patterning of silicon single crystal surfaces. We will describe the use of silane coupling agents to enable protein adhesion with the cytoplasmic side up, as is preferable for the patterning. We will show AFM images of the T1O2 -protein-silicon composite surface at various stages of the fabrication process.
The failure processes of the bessbeetle cuticle were studied through the use of scanning electron microscopy, light microscopy, and image analysis techniques. Specimens of elytra and pronotum were failed in tension under the light microscope. The failure process was documented in real time through the use of image analysis equipment and a video camera. Failure occurs primarily in a mixed-mode fashion due to the inherent curvature of the cuticle specimens and their complex hierarchical microstructure. A variety of energy-absorbing mechanisms were observed including remote microcracking, fiber pullout, and crack bridging. Damage accumulation around the failed region is extensive consisting of a significant amount of delamination, fiber-matrix disbonds, microcracking, and intra-fiber failure. The experimental methods and results will be discussed.
A material having the characteristics of very low density and high mechanical stability has been developed. This material is prepared by crosslinking the biopolymer alginic acid. Bulk densities as low as 0.15 g/cc have been obtained, while still possessing useful strength, 10% deformation at 347 psi. The physical properties can be varied by controlling the processing conditions, which affect pore volume, pore diameter, bulk density and surface area. Preparation of this material involves solvent exchange and subsequent crosslinking. The resin's minimum compressibility and physical strength allow this material to be considered for a number of applications including adsorbents, insulation and as a polymeric carrier for time release.
Hemoglobin (Hb) and myoglobin (Mb) were encapsulated in transparent silica glasses prepared by the sol-gel method. The preparation of the silica glasses was tailored so that when proteins were entrapped in the pores of the inorganic matrix, they retained their biochemical activity, i.e. they could bind ligands reversibly. Using optical spectroscopy to monitor ligand binding, we studied the binding of O2, CO, and NO with these two heme proteins encapsulated in silica glasses and compared them to heme proteins in aqueous buffer. Both Hb and Mb in the sol-gel glass bound O2, CO, and NO, producing the same spectroscopic properties as those in aqueous buffer. In addition, silica encapsulated Mb was used to evaluate the rate of ligand (O2) transport through the pores of the glass. When varying oxygen concentration and measuring the time required for full conversion of deoxyMb to MbO2 in the silica gel, the time vs. concentration data followed an exponential trend, as expected for diffusion controlled processes.
This contribution summarizes some strategies that we followed for the optimization of supramolecular architectures aiming at controlling the binding and organization of biopolymers at solid/solution-interfaces in a membrane-mimetic approach. The examples given concern mostly self-assembly processes and the biorecognition between biotin and streptavidin.
A total of 20 biogenic carboxylic acids, which contain one to three negatively charged -COO− group(s), were investigated as dispersion additives in the processing of ceramic particles. Only carboxylic acids containing one or more hydroxyl groups were able to disperse α-A12O3 particles in aqueous suspensions. Detailed studies of two carboxylic acids, citric acid and tricarballylic acid were undertaken: measurements of zeta potential, particle packing, and dispersant adsorption characeristics indicated that carboxylic acid groups and hydroxyl groups are both important for dispersion of the ceramic particles. Hydroxyl groups increased the adsorption of the molecules to the particles.