Reconstruction of Copper Smelting Technology Based on 18–20th-Century Slag Remains from the Old Copper Basin, Poland

This research was conducted on historical copper slags from Leszczyna and Kondratów in Lower Silesia, Poland. The area, formerly known as the Old Copper Basin, was a mining and smelting centre between the 18th and 20th centuries, with a dominant period in the 19th century. Cu-carbonates and residual chalcocite dominate local strata-bound copper deposits. Ore bodies are restricted to carbonate strata. A geochemical and mineralogical study of slag samples from four research sites allowed us to establish that a low amount of sulphur in slags results from S-poor ores, and pyrite with gypsum was implemented as reducing agents. Arkose sandstones served as a flux. During smelting, oxygen availability was limited, and temperature exceeded 1200 °C (18th- and 19th-century smelting) and 1400 °C (20th-century smelting). Calculated viscosity indexes mark the low efficiency of metal separation between the silicate and metallic phases. The skeletal and dendritic form of the crystals proved that slag melt was relatively rapidly cooled after formation, usually in air conditions. We estimated that approx. 2000 m3 of slag was created during the leading smelter (Stilles Glück) activity. The research provided various details of the historical copper smelting technological process in Leszczyna and Kondratów.

Visual experience instructs dendrite orientation but is not required for asymmetric wiring of the retinal direction selective circuit

ABSTRACTChanges in dendritic morphology in response to activity have long been thought to be a critical component of how neural circuits develop to properly encode sensory information. Here we report the impact of dark-rearing on the dendritic morphology and function of a retinal ganglion cell type, a ventral-preferring direction-selective ganglion cell (vDSGC). vDSGCs have asymmetric dendrites oriented along their preferred direction. We found that, at eye opening, vDSGC dendrites are not yet ventrally oriented, and that, surprisingly, dark-rearing prevents ventral orientation of vDSGC dendrites. Despite their dramatic change in dendritic morphology, vDSGCs in dark-reared mice maintain ventral directional preference. Direction selective tuning in dark-reared mice is mediated by asymmetric inhibition, as observed in vDSGCs of normally reared animals. Hence, we postulate that dendritic form follows proper circuit function, where dendritic orientation is refined over the course of development and is dependent on structured visual experience following eye opening.

Eph and Ephrin function in dispersal and epithelial insertion of pigmented immunocytes in sea urchin embryos

The mechanisms that underlie directional cell migration are incompletely understood. Eph receptors usually guide migrations of cells by exclusion from regions expressing Ephrin. In sea urchin embryos, pigmented immunocytes are specified in vegetal epithelium, transition to mesenchyme, migrate, and re-enter ectoderm, distributing in dorsal ectoderm and ciliary band, but not ventral ectoderm. Immunocytes express Sp-Eph and Sp-Efn is expressed throughout dorsal and ciliary band ectoderm. Interfering with expression or function of Sp-Eph results in rounded immunocytes entering ectoderm but not adopting a dendritic form. Expressing Sp-Efn throughout embryos permits immunocyte insertion in ventral ectoderm. In mosaic embryos, immunocytes insert preferentially in ectoderm expressing Sp-Efn. We conclude that Sp-Eph signaling is necessary and sufficient for epithelial insertion. As well, we propose that immunocytes disperse when Sp-Eph enhances adhesion, causing haptotactic movement to regions of higher ligand abundance. This is a distinctive example of Eph/Ephrin signaling acting positively to pattern migrating cells.

Nutrient load concept-reservoir vs. bay impacts: a case study from a semi-arid watershed

Large flow-through reservoirs and lakes possess environmental gradients and monitoring programs are mostly adapted for cost and time effectiveness. Bay areas are often more isolated from the main water body and are likely to have unobserved different environmental processes and impacts. This study was performed at the Itaparica Reservoir, São Francisco River, located in semi-arid Northeast Brazil, with dendritic form. Water residence time in the Icó-Mandantes Bay was estimated by hydrodynamic flow and transport simulations. The P-chlorophyll a relationship was used to develop the P use efficiency coefficient for critical P load estimation of 25 μg P L−1. Phosphorus sources and input rates into a bay and the respective reservoir were calculated and compared regarding their different origins for the period after flooding (1988) and for 2013. After impoundment, the P load highly exceeded the carrying capacity because of leaching and mineralization processes. In 2013, P inputs were still above this threshold, whereas inflow and sub-basin P export during the rainy season were crucial. But eutrophication processes have increased in the bay relative to the main water body. Hence, water in hydraulic isolated parts is prone to eutrophication processes, thus, bays have to be specially considered in water resource management.

Structures and Undercooling Technology of Ag-28.1 wt.% Cu Eutectic Alloy

Effects of the technological parameters (superheat, cycle times and holding time) on undercooling and structure of Ag-28.1 wt.% Cu eutectic alloy were discussed by orthogonal experiment. It shows that the influence of the superheat on undercooling is biggest, followed by cycle times, and finally holding time. Then the optimum process parameters of getting different undercooling are given in this paper. In the Ag-28.1 wt.% Cu eutectic alloy melt, cellular growth of lamellar eutectics takes place because of the large difference in composition between the two eutectic phases and the very large thermal diffusion coefficient of the liquid, and when undercooling is equal to or higher than 76 K, lamellar eutectics grow in a dendritic form during rapid solidification.

MODEL OF RAMIFICATION IN ELECTRODEPOSITED FRACTALS

The macroscopic branching and shape of a metal, electrodeposited in quasi-two dimensions, can be represented by a Lindenmayer System of multiple iterated function systems. The motif of a central branch that continues and two side branches is shown to allow modeling of the observed shapes. The dilation (or contraction) in length, and the angle of a branch with respect to the central stem are the only parameters needed to create realistic simulations of such ramified deposits. Values for these quantities together with standard deviations measured from a number of electrodeposited copper fractals have been used to generate simulations. Measurement of the parameters of the motif, the average linear dilation factor from one generation to the next, and the angles between branches, show a 5% relative standard deviation of these factors across one growth. The values of these parameters can also indicate the transition from an open fractal form to the more directed dendritic form. The results are compared with other approaches to describing these systems.