1,222 research outputs found
Studies in the Hellenistic Sculpture of the Island of Rhodes
The study of Hellenistic sculpture is often based upon its division into local schools centering around Pergamon, Alexandria and Rhodes. The underlying premise of the present study is that if a distinctly Rhodian Hellenistic school of sculpture existed, it should be possible to define its characteristics by means of a study of the extant sculpture of known Rhodian provenance, supplemented by the preserved statue bases. If it is not possible to demonstrate recurring technical, iconographic and stylistic traits within the Rhodian material, it may be assumed that the theory of regional schools should not be applied to Rhodes.
One hundred and sixteen pieces of sculpture are catalogued and discussed. They consist of sculptures in the Rhodes Archaeological Museum, and the Lindos excavation sculpture now in Copenhagen and Istanbul. The statue bases from Lindos are analyzed for the information they yield about the now missing statues they once held and about the sculptors who signed them. An attempt is then made to correlate the evidence of the extant sculpture with that of the statue bases, and to correlate the entire body of the material evidence with the literary sources.
The preserved marble sculpture is characterized principally by the frequent use of non-Rhodian marble, probably of Cycladic
origin, the rather small size of many pieces, the extensive and skilful use of the piecing technique, the employment of sometimes drastic undercutting for stylistic effect, and a general technical competence. A wide variety of types, stylistic devices and eclectic tendencies can be found, but several types known in multiple replicas can be isolated as specifically Rhodian creations. Most of the marble sculpture can be dated, mainly on stylistic grounds, to the late Hellenistic period. The statue bases give evidence of a continuous pattern of bronze votive and honorary portrait statuary from the fourth century into the first century of the Christian era. There is clear evidence of local sculptural production in the bronze portraits, which must have been locally produced because of their very nature, in the occasional use of local Rhodian stone, in the presence of multiple replicas of individual types, in the repetition of small stylistic and technical traits which allows some of the marble sculptures to be grouped into workshops, and in the epigraphic evidence of families of sculptors resident in Rhodes for several generations.
It is concluded that the sculptors, both Rhodian and foreign, producing statuary in Rhodes were working within and reflecting general Hellenistic sculptural trends, but with a definite strain of local originality, and influenced by local technical limitations. The statuary is best understood not as a school in the artistic sense, reflecting great works mentioned in the literary sources, but as a highly competent substratum of sculpture produced for local votive, honorary and decorative needs and tastes
Studies in the Hellenistic Sculpture of the Island of Rhodes
The study of Hellenistic sculpture is often based upon its division into local schools centering around Pergamon, Alexandria and Rhodes. The underlying premise of the present study is that if a distinctly Rhodian Hellenistic school of sculpture existed, it should be possible to define its characteristics by means of a study of the extant sculpture of known Rhodian provenance, supplemented by the preserved statue bases. If it is not possible to demonstrate recurring technical, iconographic and stylistic traits within the Rhodian material, it may be assumed that the theory of regional schools should not be applied to Rhodes.
One hundred and sixteen pieces of sculpture are catalogued and discussed. They consist of sculptures in the Rhodes Archaeological Museum, and the Lindos excavation sculpture now in Copenhagen and Istanbul. The statue bases from Lindos are analyzed for the information they yield about the now missing statues they once held and about the sculptors who signed them. An attempt is then made to correlate the evidence of the extant sculpture with that of the statue bases, and to correlate the entire body of the material evidence with the literary sources.
The preserved marble sculpture is characterized principally by the frequent use of non-Rhodian marble, probably of Cycladic
origin, the rather small size of many pieces, the extensive and skilful use of the piecing technique, the employment of sometimes drastic undercutting for stylistic effect, and a general technical competence. A wide variety of types, stylistic devices and eclectic tendencies can be found, but several types known in multiple replicas can be isolated as specifically Rhodian creations. Most of the marble sculpture can be dated, mainly on stylistic grounds, to the late Hellenistic period. The statue bases give evidence of a continuous pattern of bronze votive and honorary portrait statuary from the fourth century into the first century of the Christian era. There is clear evidence of local sculptural production in the bronze portraits, which must have been locally produced because of their very nature, in the occasional use of local Rhodian stone, in the presence of multiple replicas of individual types, in the repetition of small stylistic and technical traits which allows some of the marble sculptures to be grouped into workshops, and in the epigraphic evidence of families of sculptors resident in Rhodes for several generations.
It is concluded that the sculptors, both Rhodian and foreign, producing statuary in Rhodes were working within and reflecting general Hellenistic sculptural trends, but with a definite strain of local originality, and influenced by local technical limitations. The statuary is best understood not as a school in the artistic sense, reflecting great works mentioned in the literary sources, but as a highly competent substratum of sculpture produced for local votive, honorary and decorative needs and tastes
Preferential utilization of NADPH as the endogenous electron donor for NAD(P)H:quinone oxidoreductase 1 (NQO1) in intact pulmonary arterial endothelial cells
The goal was to determine whether endogenous cytosolic NAD(P)H:quinone oxidoreductase 1 (NQO1) preferentially uses NADPH or NADH in intact pulmonary arterial endothelial cells in culture. The approach was to manipulate the redox status of the NADH/NAD+ and NADPH/NADP+ redox pairs in the cytosolic compartment using treatment conditions targeting glycolysis and the pentose phosphate pathway alone or with lactate, and to evaluate the impact on the intact cell NQO1 activity. Cells were treated with 2-deoxyglucose, iodoacetate, or epiandrosterone in the absence or presence of lactate, NQO1 activity was measured in intact cells using duroquinone as the electron acceptor, and pyridine nucleotide redox status was measured in total cell KOH extracts by high-performance liquid chromatography. 2-Deoxyglucose decreased NADH/NAD+ and NADPH/NADP+ ratios by 59 and 50%, respectively, and intact cell NQO1 activity by 74%; lactate restored NADH/NAD+, but not NADPH/NADP+ or NQO1 activity. Iodoacetate decreased NADH/NAD+ but had no detectable effect on NADPH/NADP+ or NQO1 activity. Epiandrosterone decreased NQO1 activity by 67%, and although epiandrosterone alone did not alter the NADPH/NADP+ or NADH/NAD+ ratio, when the NQO1 electron acceptor duroquinone was also present, NADPH/NADP+ decreased by 84% with no impact on NADH/NAD+. Duroquinone alone also decreased NADPH/NADP+ but not NADH/NAD+. The results suggest that NQO1 activity is more tightly coupled to the redox status of the NADPH/NADP+ than NADH/NAD+ redox pair, and that NADPH is the endogenous NQO1 electron donor. Parallel studies of pulmonary endothelial transplasma membrane electron transport (TPMET), another redox process that draws reducing equivalents from the cytosol, confirmed previous observations of a correlation with the NADH/NAD+ ratio
Accelerator measurement of the energy spectra of neutrons emitted in the interaction of 3-GeV protons with several elements
The application of time of flight techniques for determining the shapes of the energy spectra of neutrons between 20 and 400 MeV is discussed. The neutrons are emitted at 20, 34, and 90 degrees in the bombardment of targets by 3 GeV protons. The targets used are carbon, aluminum, cobalt, and platinum with cylindrical cross section. Targets being bombarded are located in the internal circulating beam of a particle accelerator
Mesoderm formation in response to Brachyury requires FGF signalling
AbstractBackground: The Brachyury (T) gene is required for the formation of posterior mesoderm and for axial development in both mouse and zebrafish embryos. In these species, and in Xenopus, the gene is expressed transiently throughout the presumptive mesoderm, and transcripts then persist in notochord and posterior tissues. In Xenopus embryos, expression of the Xenopus homologue of Brachyury, Xbra, can be induced in presumptive ectoderm by basic fibroblast growth factor (FGF) and activin; in the absence of functional FGF or activin signalling pathways, expression of the gene is severely reduced. Ectopic expression of Xbra in presumptive ectoderm causes mesoderm to be formed. As Brachyury and its homologues encode sequence-specific DNA-binding proteins, it is likely that each functions by directly activating downstream mesoderm-specific genes.Results We show that expression in Xenopus embryos of RNA encoding a dominant-negative FGF receptor inhibits the mesoderm-inducing activity of Xbra. We demonstrate that ectopic expression of Xbra activates transcription of the embryonic FGF gene, and that embryonic FGF can induce expression of Xbra. This suggests that the two genes are components of a regulatory loop. Consistent with this idea, dissociation of Xbra-expressing cells causes a dramatic and rapid reduction in levels of Xbra, but the reduction can be inhibited by addition of FGF.Conclusion Formation of mesoderm tissue requires an intact FGF signalling pathway downstream of Brachyury. This requirement is due to a regulatory loop, in which Brachyury activates expression of a member of the FGF family, and FGF maintains expression of Brachyury. The existence of this loop explains why embryos lacking an FGF signalling pathway appear similar to those mutant for Brachyury, and why over-expression of truncated FGF receptors seems to inhibit induction of Brachyury expression by activin
Atmospheric neutrons
Contributions to fast neutron measurements in the atmosphere are outlined. The results of a calculation to determine the production, distribution and final disappearance of atmospheric neutrons over the entire spectrum are presented. An attempt is made to answer questions that relate to processes such as neutron escape from the atmosphere and C-14 production. In addition, since variations of secondary neutrons can be related to variations in the primary radiation, comment on the modulation of both radiation components is made
Characterization of theThreshold for NAD(P)H:quinone Oxidoreductase Activity in Intact Sulforaphane-treated Pulmonary Arterial Endothelial Cells
Treatment of bovine pulmonary arterial endothelial cells in culture with the phase II enzyme inducer sulforaphane (5 μM, 24 h; sulf-treated) increased cell-lysate NAD(P)H:quinone oxidoreductase (NQO1) activity by 5.7 ± 0.6 (mean ± SEM)-fold, but intact-cell NQO1 activity by only 2.8 ± 0.1-fold compared to control cells. To evaluate the hypothesis that the threshold for sulforaphane-induced intact-cell NQO1 activity reflects a limitation in the capacity to supply NADPH at a sufficient rate to drive all the induced NQO1 to its maximum activity, total KOH-extractable pyridine nucleotides were measured in cells treated with duroquinone to stimulate maximal NQO1 activity. NQO1 activation increased NADP+ in control and sulf-treated cells, with the effect more pronounced in the sulf-treated cells, in which the NADPH was also decreased. Glucose-6-phosphate dehydrogenase (G-6-PDH) inhibition partially blocked NQO1 activity in control and sulf-treated cells, but G-6-PDH overexpression via transient transfection with the human cDNA alleviated neither the restriction on intact sulf-treated cell NQO1 activity nor the impact on the NADPH/NADP+ ratios. Intracellular ATP levels were not affected by NQO1 activation in control or sulf-treated cells. An increased dependence on extracellular glucose and a rightward shift in the Km for extracellular glucose were observed in NQO1-stimulated sulf-treated vs control cells. The data suggest that glucose transport in the sulf-treated cells may be insufficient to support the increased metabolic demand for pentose phosphate pathway-generated NADPH as an explanation for the NQO1 threshold
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