Plain Blocks Research Articles

Between private and public: The use of marble in Late Antique Caesarea Maritima

Late Antique Caesarea was a city of marble. Marble cargoes continued to arrive at the port after the 4th century AD as plain blocks, half-finished or finished products; these constituted a significant addition to the available Roman marble products, which were used as-is or recycled in streets, as well as private, public, and semi-public constructions. Large-scale sawing, cutting and carving took place in Late Antique Caesarea. Craftsmen were employed in producing opus sectile panels, in paving, veneering, and carving architectural members, champlevé reliefs and lattice screen panels, and in mounting all marble products comprising the exterior and interior decoration of each complex. In all structures marble was used for similar purposes, although each was unique in terms of quantity, quality, and diversity of the material. The examples discussed show that at every stage of the city’s existence the Caesareans were familiar with the most up-to-date fashions and were no less innovative than their counterparts in the region and beyond. The aesthetic principle of varietas, which became fashionable in Late Antiquity and was adopted by the Caesareans, found its way from the public to the private and semi-public spheres, and is manifested in most, if not all, of the complexes discussed in this paper.

A Genenral Feistal Structure Based Color Image Encryption Algorithm

A General Feistal Structure based color image encryption and authentication algorithm is designed in this paper. The plain image is first permuted, then divided into groups of size pixels and encrypted by block encryption algorithm; finally the cipher image is obtained by performing inverse permutation on the image. In which, block encryption function is the kernel part of the encryption algorithm, and is designed with general feistel structure. To provide integrality authentication function, the last cipher block is the cipher of the sum of all plain blocks. It’s from experiments and analysis that the algorithm is secure and valid.

The Hellenistic and Byzantine Defences of Tocra (Taucheira)

AbstractThe fortifications of the Hellenistic and Roman city of Tocra are over 2 km long (including the sea-wall) and comprise a curtain wall up to 2 m wide flanked by 31 rectangular towers. Three main structural phases were noted in the survey carried out in 1966 by David Smith: (1) Hellenistic walls of isodomic ashlar, (2) later Hellenistic work of isodomic ashlar with bevelled edges, associated with the indented trace along the south rampart, and (3) an extensive rebuild of plain ashlar blocks including the towers and reconstruction to the East and West Gates, dateable, on the basis of Procopius, to the reign of Justinian. The general significance of the fortifications at Tocra is considered in the second part: these include the Hellenistic indented trace along the south side, later reinforced by towers in the sixth century AD. Also of wider importance was the use of an outer wall orproteichisma, and the pentagonal, pointed towers at the two main gates. Both these elements were unusual in Byzantine North Africa and they are discussed as part of the more general repertory of Byzantine fortifications. The unusual tower adjacent to the West Church is considered in the context of literary accounts. The article concludes by considering how the architecture and magnitude of the fortifications can allow a reassessment of the wider role of the city in the sixth and seventh century defences of Cyrenaica.

Effect of Intertunnel Distance and Nest-Surface Aspect on Progeny Production Rate and Sex Ratio in the Alfalfa Leafcutting Bee (Hymenoptera: Megachilidae)

Populations of the alfalfa pollinator, Megachile rotundata (F.), nest in dense aggregations in artificial shelters in alfalfa fields. The closeness of the nest tunnels in these shelters (5–10 mm apart) fosters what appear to be numerous counterproductive interactions among females. By increasing the distance between nest tunnels and patterning the nest-block surface to help orient bees returning from foraging trips, we sought to reduce interactions and to increase both the number of progeny produced and the proportion of female progeny. Only the nest-block surface aspect affected progeny production rate; progeny were produced at a Significantly faster rate in patterned blocks than in plain blocks. Intertunnel distance did not affect progeny production rate. Nest blocks with tunnels 5 mm apart contained a significantly greater proportion of female progeny than did nest blocks with tunnels spaced farther apart. Sex ratio of progeny was unaffected by surface patterning of blocks. Females strongly preferred patterned to plain blocks and preferred 5-mm and 2-cm intertunnel distances to those of 4 cm. Beekeepers and alfalfa growers can increase bee productivity by supplying patterned nest blocks with intertunnel distances between 5 and 10 mm.

A Study of Pressure Homogeneity in the Hexahedral Anvil High-Pressure Apparatus

A study of operational characteristics and stress distribution in a large volume hexahedral apparatus has been made. Pyrophyllite containers with integral preformed gaskets were found to be superior to plain blocks. Pregasketing reduced material flow and sample deformation, increased by over 100 percent the central region of the container over which little or no deformation occurs, and greatly increased anvil life. Even so, large pressure gradients still existed within the container. These gradients become more severe the higher the pressure. Pressure efficiency and distribution were appreciably changed by varying the length and thickness of preformed gaskets. Built-in metal intensifiers increased pressure efficiency by up to 30 percent. The inclusion of a metal heater tube had no measurable influence on pressure gradients. Cycling decreased the applied load required to reach a given pressure only if the load was not allowed to fall below a certain minimum. This is attributed to the ability of pyrophyllite to remain static while supporting large stress gradients.