The technological development of stonepaste ceramics from the Islamic Middle East
Abstract The microstructures and chemical compositions of stonepaste bodies from the Islamic Middle East, typically produced from a mixture of ten parts crushed quartz, one part crushed glass and one part white clay, are investigated using analytical scanning electron microscopy. For comparison, replicate stonepaste bodies are produced in the laboratory at firing temperatures in the range 900–1200 °C, and are similarly examined. The stonepaste bodies are divided into four primary microstructural groups that reflect the increasing reaction during firing of the glass fragments with the clay and quartz particles. The observed microstructures are then used to assess the geographical and chronological variations in the production technology of stonepaste ceramics from Egypt, Syria, Iran, Uzbekistan and Turkey, spanning the period from 11th to 17th centuries AD.
Glazed ware from here and there: Petrographic analysis of the technological transfer of glazing knowledge
Abstract The typical method employed to analyze glaze surfaces has been chemical analysis often by means of scanning electron microscopy, which provides visual information as well. However, glazes can also be examined petrographically and their features related directly to the paste of the ceramic body. The link between raw materials used for producing the pottery and glaze features can inform on the technological transfer of glazing knowledge. Two case studies, one from Medieval Egypt and the other from pre-Hispanic and early Colonial New Mexico, provided an opportunity to explore the adoption and adaptation of glaze technology by potters working in different areas. In the case of Medieval Egypt, the industrial setting of pottery production and the extensive exchange networks resulted in the accurate reproduction of various types of glazes on locally made pottery. On the other hand, glaze ware production at the household level in New Mexico shows a change in glaze paint appearance that probably relates to the use of different glazing raw materials and/or a lack of knowledge of the recipe by potters located outside the original area of manufacture. Thus, petrography can provide valuable information on the ways technological knowledge of glazing was acquired and modified as the idea spread.
Climatology of the cusp-related thermospheric mass density anomaly, as derived from CHAMP observations
We report on the thermospheric mass density anomaly in the vicinity of the ionospheric cusp. A systematic survey of the anomalies is presented, based on a statistical analysis of 4 years of data (2002–2005) obtained by the accelerometer onboard CHAMP. The anomalies are detected during all years and seasons in both hemispheres but with stronger signatures in the Northern Hemisphere. For the same geophysical conditions, solar flux and geomagnetic activity the anomalies in the north are larger by a factor of about 1.35. Over the course of the survey period the amplitude decreases by more than a factor of 5 while the level of solar flux reduces by a factor of 2. The anomaly strength also depends on the solar wind input. The merging electric field, E merg , is generally enhanced for about an hour before the anomaly detection. There is a quadratic response of the anomaly amplitude to E merg . For geophysical conditions of P10.7 E merg E merg , where the weight of E merg , in mV/m, is by about 50 times higher than that of the solar flux level. The solar zenith angle and the influence of particle precipitation are found to play a minor role as a controlling parameter of seasonal variation. The well-known annual variation of the thermospheric density with a minimum around June also influences the formation of the cusp anomalies. This leads to a clear hemispheric asymmetry with very weak anomalies in the south during June solstice, which is supposed to be a combined effect of the minimum in annual variation and the seasonal decrease of solar insolation in this region.