Understanding person acquisition using an interactive activation and competition network

Face perception is one of the most developed visual skills that humans display, and recent work has attempted to examine the mechanisms involved in face perception through noting how neural networks achieve the same performance. The purpose of the present paper is to extend this approach to look not just at human face recognition, but also at human face acquisition. Experiment 1 presents empirical data to describe the acquisition over time of appropriate representations for newly encountered faces. These results are compared with those of Simulation 1, in which a modified IAC network capable of modelling the acquisition process is generated. Experiment 2 and Simulation 2 explore the mechanisms of learning further, and it is demonstrated that the acquisition of a set of associated new facts is easier than the acquisition of individual facts in isolation of one another. This is explained in terms of the advantage gained from additional inputs and mutual reinforcement of developing links within an interactive neural network system. <br/

Minimum effective area for high resolution crater counting of martian terrains

The acquisition of high-resolution imagery for the surface of Mars has enabled mapping of spatially limited (order of 200 m) on four type terrains using Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) imagery that span the Noachian, Hesperian, and Amazonian epochs. The counts from each location include a region covering 10,000 km2, ten 1000 km2 subsets of that larger area, and approximately one hundred 100 km2 samples. The data demonstrate significant variation in the crater size frequency and derived model ages across a single terrain type for the 100 km2 samples. The crater size frequency at this area scale varies across a single, uniform geologic unit by up to a factor of 2–3 on the four different terrains. At 1000 km2, the local pattern variations that are relevant at the 100 km2 scale become less important and the age variations are tighter. In all four terrain cases, the 10,000 km2 and 1000 km2 samples capture distinct crater populations (km-sized craters) that formed before and after resurfacing event(s). However, due to the relatively high mean distance between km-sized craters, the 100 km2 size area samples more commonly than not exclude a statistically significant sample at the kilometer size range, masking important information about the pre-resurfacing history of the terrain. We therefore suggest that due to the effect of pattern variability in cratering over 100 km2 and the susceptibility of smaller craters to resurfacing, crater counts derived from small area samples are suspect to major uncertainties

Capacity for epithelial differentiation in synovial sarcoma: analysis of a new human cell line

Aim—To analyse the capacity for epithelial differentiation in synovial sarcoma using a new human cell line. Methods—A new human cell line, KU-SS-1, was established from a monophasic, spindle cell type of synovial sarcoma by grafting those cells on to severe combined immunodeficient (SCID) mice and then transferring them to in vitro culture systems. The KU-SS-1 cells were characterised by light and electron microscopy, and by immunohistochemical, flow cytometric, and cytogenetic analysis. Results—Primary tumour and cultured cells at passage 20 showed a positive reaction for vimentin, which is a mesenchymal marker. After 40 passages, subcultured cells were injected into SCID mice to induce further tumours. These advanced subcultured cells and the tumour cells that they induced were positive for cytokeratin, an epithelial marker, and exhibited epithelial ultrastructural features such as intermediate junctions. Furthermore, two colour immunofluorescent analysis for proliferating nuclear cell antigen (PCNA) and intermediate filaments showed that a large number of PCNA expressing cells were positive for vimentin, and that part of this fraction also expressed cytokeratin. The existence of cells with reactivity for these three markers indicated that, in this cell line, a fraction with high proliferating capacity had both mesenchymal and epithelial markers. In addition, cytogenetically, this cell line expressed the SYT–SSX chimaeric transcript as a result of the t(X;18)(p11;q11) translocation. Conclusions—A human synovial sarcoma cell line was established and stably maintained in cell culture for more than 70 passages. In addition, this cell line showed epithelial differentiation, which supports the hypothesis that synovial sarcoma is a carcinosarcoma like tumour with true epithelial differentiation. This cell line will be a useful tool for investigating the nature of this tumour and will contribute to clinical studies. Key Words: synovial sarcoma • cell line • carcinosarcoma • differentiatio