Oval Zone Research Articles

Weakly barred early-type ringed galaxies. II - The double-ringed S0(+) galaxy NGC 7187

This paper presents BVR CCD surface photometry of NGC 7187, a southern S0^+^ galaxy possessing a bright circular inner ring and a faint elongated outer ring. The rings both have a contrast comparable to those observed in typical (R)SB(r)-type galaxies, yet there is no obvious bar crossing the inner ring as in such galaxies. Instead, there are two nearly orthogonal, small oval zones in the bulge region, one of which may be a nuclear bar. The inner ring is a narrow zone of slightly enhanced blue colors and is therefore a place where star formation has been favored in the disk. An asymmetry in the outer ring region suggests that the galaxy has suffered some interaction, possibly associated with membership in a group whose mean redshift is 2500 km s^-1^. The origin of the two rings is uncertain. If they are resonance rings, then NGC 7187 would be a possible example of a galaxy which once had a stronger, more important bar than it has now. This bar could have evolved to a more axisymmetric state through an internal interaction, leaving the rings and an inner lens as signatures of its presence. However, the data do not exclude completely the possibility that both rings are a result of a collision or merger/accretion of one or more smaller galaxies with an S0, in which case NGC 7187 would more properly belong into the pure ring galaxy or Hoag-type ring galaxy classes. The main argument against this possibility is that NGC 7187 does not resemble the more prototypical members of those classes. Other considerations are discussed in some detail.

The Kupferschiefer Cu–Ag ore deposits in Poland: a re-appraisal of the evidence of their origin and presentation of a new genetic model

The Kupferschiefer stratiform copper deposits in central Europe have long been considered a classic example of syngenetic mineralization. However, metal zoning and host-rock relationships determined during exploration around the recently discovered Lubin district orebodies in southwest Poland suggest that the ore may instead be late diagenetic. The mineralization occurs as thin, extensive blankets of sulphides in the pyritic, organic-rich basal units of the Late Permian Zechstein restricted marine sequence and in the eolian Weissliegendes sandstone at the top of the Early Permian Rotliegendes continental rift sequence of bimodal volcanic rocks and redbeds. It is directly underlain and controlled by irregular, oval zones of Rote Fäule (RF), a barren oxidized and reddened portion of the normally dark grey, pyritic basal Zechstein rocks. In plan view, the metals occur as successive belts enriched in copper (+ silver), lead, and zinc, which developed laterally from and encircle the RF zones. The ore transgresses the depositional strike of the basal Zechstein and can occur in any sedimetary facies. In section, the ore cuts across sedimentary layering from the Zechstein limestone down through the Kupferschiefer shale (Ks) into the sand stone below. Framboidal, presumably very early diagenetic, pyrite is the dominant sulphide above and lateral to the ore zones; over most of the basin, the Ks is pyritic and not anomalously high in metals compared with similar shale elsewhere. In the ore bodies, Cu, Ag, Pb, and Zn are significantly above the typical background contents, implying that these metals have been introduced. Metal contents in the RF are within the range of background contents of the Ks, suggesting that the metal source is external to the Ks. The RF–copper zones are coincident with underlying buried basement highs and occur only above Rotliegendes sediments with underlying volcanic rocks, indicating a possible genetic connection. The metal zones generally dip away from the highs toward the basin centres, suggesting convective, rather than throughgoing, fluid flow. Sulphides, as disseminations and streaks, commonly replace earlier calcite cement and lenses, lithic fragments, and quartz grains. Horizon tal and vertical dilatant veinlets of calcite and copper sulphides appear to have formed after lithification and contemporaneously with the disseminations and streaks, but not by remobilization of existing sulphides. The veinlet orientations are believed to be Kimmerian age (mid-Triassic to Late Jurassic), and the orebodies are cut and displaced, but not remobilized, by fractures and dikes of inferred Alpine (Cretaceous) age. Published sulphur-isotope ratios indicate that the copper sulphides were not formed in isotopic equilibrium with the pyrite, but adequate sulphur- and lead-isotope information on the ore deposits is not available to support an early or late diagenetic timing. The paleomagnetic age of the stable chemical remanence of the RF is Middle Triassic, supporting a late diagenetic origin of the ore coincident with a second rifting event. On account of these asso ciations and controls, it is proposed that the RF–ore systems were formed by converting Na–Ca–CI Rotliegendes formational brines. The metals were leached from the Rotliegendes volcanic detritus and carried in solution as chloride complexes through the redbeds up the flanks of the buried basement highs to the reduced pyritic Ks above. The fluids oxidized the original Ks pyrite to form the Rote Fäule, and the ore sulphides were precipitated on the far side of this subhorizontal oxidation–reduction front. This late diagenetic mineralizing event likely occurred during the Triassic, when rapid burial and increased heat flow, associated with the opening of the Tethys ocean to the south, generated natural gases and vertical fractures in the Ks and increased convective fluid velocities in the Rotliegendes basins.

A magnetosphere model based on two zones of precipitating energetic particles

Contrary to widely held ideas on the oval zone of precipitation of energetic particles into the earth's atmosphere, the existence of two quasi-circular zones of precipitation was established several years ago on the basis of geomagnetic activity data. The two zones were found to be of quite a different nature. One of these zones, the higher-latitude one, has its maximum on the day side (latitude ∼77°); the other zone, the lower-latitude one, has a considerably longer latitudinal extension and has its maximum on the night side (latitude ∼67°). The concept of the oval zone as a single unified zone is not a necessary conclusion and could be a result of insufficient data or of incorrect data reduction. The same conclusion can also be reached on the basis of the analysis performed by Feldstein himself and on the basis of other direct and indirect data. In this paper the main features of two quasi-circular zones are presented on the basis of the instantaneous patterns of the distribution of geomagnetic activity as well as on the basis of the dynamics of these patterns. A magnetosphere model reflecting these features is presented. The suggested model links the lower-latitude zone with processes occurring in the magnetospheric tail, whereas the higher-latitude zone is connected with particle injection through the neutral points.

Gout: Clinical, Pathologic and Roentgenographs Observations

While it is true that gout often goes undiagnosed and much needs to be done toward educating American physicians to recognize this disease, nevertheless progress has been made. This progress has had a distinct bearing on roentgenology, for important developments in the clinical and pathological fields have greatly improved our ability to interpret roentgenographic findings in patients with this disease. In this paper, we shall outline briefly some historical features regarding roentgenography in gout. We shall also describe some significant developments concerning clinical and pathologic aspects of gout and relate these to the principles of roentgenology which are pertinent to the diagnosis of this condition. Historical The use of the roentgen rays as an aid in the diagnosis of gout was first reported by Huber (1). That writer, in 1896, published a reproduction of a roentgenogram which illustrated the lesions produced by gout in one case. Circular zones of translucency in the subchondral bone were demonstrated and their probable relationship to the deposition of urates in the affected tissues was discussed. Hypertrophic spurs, partial or complete destruction of some joints, and subluxations were described A very large number of publications have, since that time, referred to the roentgenographic phenomena associated with gout. This literature is not reviewed here in detail. It seems appropriate, however, to mention the contributions of a few outstanding writers. Points of distinction between the roentgen changes which are to be seen in gout and those encountered in patients with rheumatoid arthritis were described in 1905 by Strangeways and Burt (2). Their observations were based upon a comparison of roentgenograms from a hundred gouty and a hundred rheumatoid patients. Findings which were described as characteristic of gout included increased density of bone, bony additions about joints, nodes on the shafts of phalanges, spurs about the heads of the long bones, loss of cartilage, erosion of bone, transparent areas, and dislocations. There were some instances of complete disorganization of bones and even of bony ankylosis. Strangeways and Burt conducted this study with great thoroughness but unfortunately omitted a correlation of roentgenographic findings with the clinical aspects of the cases. As a result, roentgenographic changes which they encountered in advanced stages of gout were subsequently considered characteristic of all gouty joints. It remained for Jacobsohn (3) to point out, in 1913, that roentgenograms should not be relied upon to distinguish gout from other forms of arthritis in every instance. In some cases of gout he found changes which closely resembled those encountered in other diseases of joints, but in certain instances lesions which are not to be seen in any other form of joint disease, notably semicircular or oval zones of destruction irregularly disposed about affected joints, were present.