Morphology, structure, optical, and electrical properties of AgSbO₃

The morphology of defect pyrochlore-type, AgSbO₃ microparticle/nanoparticles obtained via solid state reaction evolve from irregular to Fullerene-like polyhedra before finally decomposing into metal-organic framework-5 like particles with increase in sintering temperature. The defect pyrochlore-type AgSbO₃ particles are slightly Ag deficient while the valence of the antimony ion is shown to be +5 giving rise to a probable stoichiometry of Ag₁ˍₓ SbVO₃ˍₓ/₂, with x∼0.01–0.04. A highly structured diffuse intensity distribution observed via electron diffraction is interpreted in terms of correlated displacements of one-dimensional (1D) silver ion chains along ⟨110⟩ directions. A redshifting in the absorption edges in UV-visible absorption spectra is observed for samples prepared at sintering temperatures higher than 1000 °C and attributed to the surface plasma resonance effect associated with small amounts of excess metallic Ag on the Ag₁ˍₓ SbVO₃ˍₓ/₂ particles. An electrical properties investigation of the silver antimonate samples via dielectric, conductivity, and electric modulus spectroscopy shows a prominent dielectric relaxation associated with grain boundaries. The silver ion conductivity is associated with correlated displacements of 1D silver ion chains along ⟨110⟩ directions.Z.G.Y., Y.L., and R.L.W. acknowledge financial support from the Australian Research Council ARC in the form of ARC Discovery Grants

Tracing the tin-opacified yellow glazed ceramics in the western Islamic world: the findings at Madinat al-Zahra’

A small group of opaque yellow glazed sherds has recently been identified among the ceramics excavated at the Islamic city of Madinat al-Zahra’ near Cordoba, in al-Andalus (southern Spain), which was founded in 936 AD as the seat of the Umayyad Caliphate power. A small group of sherds from Madinat al-Zahra’, which can be dated to about 960–980 AD, has been examined in polished section in a SEM with EDS attached. These analyses have established that the Madinat al-Zahra’ sherds were opacified with lead stannate, and not lead antimonate, as was being used to opacify yellow glazed ceramics in Egypt and Tunisia in the ninth and tenth centuries AD. Islamic opaque yellow glazed ceramics, with lead stannate as the opacifier, were first produced (Beiträge Zur Islamischen Kunst Und Archäologie 4:125–144, 2014) in Egypt and Syria in seventh/eighth centuries AD, and from there, the technology spread eastwards into Iraq and Iran in the ninth century AD and continued in use in Iran and Central Asia into the tenth century AD and beyond. However, the question of where these opaque yellow glazed ceramics were produced has not been fully resolved. Because such ceramics are extremely rare in al-Andalus, it seems most likely that they were either imported from Iran or Central Asia or produced locally by potters arriving from these areas. The study adds one further, yet not fully understood chapter to the story of a persistent glaze technology which has been widely ignored.Peer ReviewedPostprint (published version

Alkali oxide-tantalum, niobium and antimony oxide ionic conductors

The phase equilibrium relations of four systems were investigated in detail. These consisted of sodium and potassium antimonates with antimony oxide and tantalum and niobium oxide with rubidium oxide as far as the ratio 4Rb2O:llB2O5 (B=Nb, Ta). The ternary system NaSbO3-Sb2O4-NaF was investigated extensively to determine the actual composition of the body centered cubic sodium antimonate. Various other binary and ternary oxide systems involving alkali oxides were examined in lesser detail. The phases synthesized were screened by ion exchange methods to determine mobility of the mobility of the alkali ion within the niobium, tantalum or antimony oxide (fluoride) structural framework. Five structure types warranted further investigation; these structure types are (1) hexagonal tungsten bronze (HTB), (2) pyrochlore, (3) the hybrid HTB-pyrochlore hexagonal ordered phases, (4) body centered cubic antimonates and (5) 2K2O:3Nb2O5. Although all of these phases exhibit good ion exchange properties only the pyrochlore was prepared with Na(+) ions as an equilibrium phase and as a low porosity ceramic. Sb(+3) in the channel interferes with ionic conductivity in this case, although relatively good ionic conductivity was found for the metastable Na(+) ion exchanged analogs of RbTa2O5F and KTaWO6 pyrochlore phases

Search for solid conductors of Na(+) and K(+) ions: Five new conductors

Five conductors of three structure types were discovered which, as solids, can transport Na(+) or K(+) ions with conductivities of approximately .00001/(omega cm) at 300 K. These compounds are: (1) the pyrochlores NaTaWO6 and NaTa2O5F, both with an activation energy for conduction delta E of 21 kJ/mole; (2) the bodycentered cubic form of NaSbO3, with delta E = 42 kJ/mole; and (3) the niobates 2Na2O with 3Nb2O5 and 2K2O with 3Nb2O5, with the alkali ions probably in open layers of the incompletely determined structure; delta E = 17 kJ/mole. On the basis of approximately 40 structure types, some generalizations were made regarding the relation between structure and ionic transport

Structures, targets and recent approaches in anti-leishmanial drug discovery and development.

Recent years have seen a significant improvement in available treatment options for leishmaniasis. Two new drugs, miltefosine and paromomycin, have been registered for the treatment of visceral leishmaniasis (VL) in India since 2002. Combination therapy is now explored in clinical trials as a new treatment approach for VL to reduce the length of treatment and potentially prevent selection of resistant parasites. However there is still a need for new drugs due to safety, resistance, stability and cost issues with existing therapies. The search for topical treatments for cutaneous leishmaniasis (CL) is ongoing. This review gives a brief overview of recent developments and approaches in anti-leishmanial drug discovery and development

The Glass Mosaic of S. Agnese fuori le mura: New Tesserae in the Puzzle of Early Medieval Rome

The present study, which is part of a wider inter-disciplinary research project on Medieval Rome funded by the Swiss National Science Foundation, focuses on the archaeometric characterisation of glass tesserae from the apse mosaic of the church of S. Agnese fuori le mura, dated to the 7th century AD and never analysed until now. The main aims of the study are the identification of chemical compositions of glassy matrices and colouring/opacifying techniques by means of the combination of micro-textural, chemical, and mineralogical data. In S. Agnese tesserae, the results show the presence of glassy matrices and opacifiers/pigments, typical of both Roman and Late Antique/Early Medieval periods. The technological features identified (in particular, glassy matrices and opacifiers/pigments) allow us to discriminate not only new-production tesserae, i.e., those probably produced in the 7th century for the realisation of the S. Agnese mosaic, but also those obtained from recycling or re-using previous glass. This testifies to a quite complex “puzzle”, unusual in other glass mosaics from the same city and coeval with S. Agnese, supporting further the potentiality of archaeometric studies on glass to uncover the technical and socio-cultural knowledge that underpins its manufacturing, use, re-use, and recycling in the Early Medieval Rome

A Mosaic of Colors: Investigating Production Technologies of Roman Glass Tesserae from Northeastern Italy

In the current study, a set of 60 glass tesserae from two disrupted Roman mosaics located in Pordenone and Trento (northeastern Italy) are analyzed, with the aim of investigating the coloring and opacification techniques, with a focus on the causes of specific textural features. All the available colors and textures were selected for archaeometric analyses, in order to guarantee the full characterization of both assemblages and comparisons between the two sites. The applied analytical protocol comprises micro-textural and preliminary chemical characterizations of the tesserae by means of OM and SEM-EDS, mineralogical analysis of the opacifiers by XRD and chemical analysis of the glassy matrices by EPMA; in addition, on specific tesserae, micro Raman spectroscopy, FORS, and EPR were also performed to clarify the type of opacifer, coloring ion and oxidation state, respectively. Results show that both the base-glass and the coloring/opacification techniques identified are consistent with the presumed Roman dating of the mosaics. All the tesserae are natron-based and chemically comparable with major Roman compositional groups, except for red samples. Antimony-based opacifiers are identified in most of the blue, turquoise, white, yellow and green tesserae, and copper-based opacifiers in the red ones; cobalt and copper are the most frequent ionic colorants used to obtain various shades of blue, turquoise and green colors. Despite the general comparability of both assemblages with the published data on glass tesserae coeval in age, the present study shows differences in the technological solutions used for obtaining the same color, and less common coloring and opacification techniques in three samples from Pordenone. The banded textures of some tesserae were also carefully investigated, and multiple factors influencing the changes in color (different distribution or relative abundance of opacifiers, crystal size, micro-texture, chemical composition of glassy matrix) are identified

Comparison of the Calcium Distribution Pattern Among Several Kinds of Hard Tissue Forming Cells of Some Living Vertebrates

We investigated the ultrastructural distribution of calcium in several kinds of hard tissue forming cells (secretory and maturation ameloblasts, odontoblasts osteoblasts, chondrocytes, and osteodentine forming cells) of mammals, amphibians, and fish by use of the potassium pyroantimonate technique. The calcium distribution pattern is compared among these cells, and its biological significance is discussed. Except for mammalian odontoblasts, all types of the hard tissue forming cells exhibited fundamentally the same distribution pattern of calcium; the antimonate reaction product was mainly localized on the inner face of the plasmalemma and inside mitochondria. On the other hand, in mammalian odontoblasts, the reaction product was found within secretory granules and in the intercellular spaces. Thus, the calcium distribution pattern in odontoblasts of lower vertebrates differed from that of mammalian odontoblasts and was similar to that of the osteoblasts or chondrocytes of the vertebrates examined. The differences in calcium distribution pattern among these hard tissue forming cells were not related to their origin, ectodermal or mesodermal (ectomesenchymal). We suggest on the basis of previous studies cited in this paper and of the present data that they are closely associated with the phylogeny and physiological system of Ca-ATPase