Determinants and characteristics of female migration: a case study of Salem City in Tamil Nadu,India

A random sample of 521 male and 481 female migrants surveyed in Salem city in Tamil Nadu, India, during 1980-1981 was analyzed on the basis of a classification related to reasons (association, marriage, distress, and voluntary) for migration. Women were found to outnumber males in associational migration, both in rural to urban and urban to urban streams. They also formed almost all the marriage migrants. They were more numerous in distress migration as well. There were, however, comparatively few women among voluntary migrants. The incidence of illiteracy among migrant women was generally high, except for voluntary migrants who had completed high school. The share of working women was not negligible, but in most cases present work status was achieved after migrating.     

A ‘mathematical’ spider living on gravel plains of the Namib Desert

In certain areas of the Namib gravel plains a new Ariadna sp. was discovered. It rims its vertical burrow with a stone circle, made on average of seven quartz stones. Some mathematical relationships between hole diameter, stone sizes and weight, and animal size were studied. A correlation was found, and stone selection by this spider postulated. Different hypotheses on the adaptive value of stone circle are suggested.     

Toroidal versus poloidal magnetic fields in Sun-like stars: a rotation threshold

From a set of stellar spectropolarimetric observations, we report the detection of surface magnetic fields in a sample of four solar-type stars, namely HD 73350, HD 76151, HD 146233 (18 Sco) and HD 190771. Assuming that the observed variability of polarimetric signal is controlled by stellar rotation, we establish the rotation periods of our targets, with values ranging from 8.8 d (for HD 190771) to 22.7 d (for HD 146233). Apart from rotation, fundamental parameters of the selected objects are very close to the Sun's, making this sample a practical basis to investigate the specific impact of rotation on magnetic properties of Sun-like stars.
We reconstruct the large-scale magnetic geometry of the targets as a low-order  (ℓ < 10)  spherical harmonic expansion of the surface magnetic field. From the set of magnetic maps, we draw two main conclusions. (i) The magnetic energy of the large-scale field increases with rotation rate. The increase in chromospheric emission with the mean magnetic field is flatter than observed in the Sun. Since the chromospheric flux is also sensitive to magnetic elements smaller than those contributing to the polarimetric signal, this observation suggests that a larger fraction of the surface magnetic energy is stored in large scales as rotation increases. (ii) Whereas the magnetic field is mostly poloidal for low rotation rates, more rapid rotators host a large-scale toroidal component in their surface field. From our observations, we infer that a rotation period lower than ≈12 d is necessary for the toroidal magnetic energy to dominate over the poloidal component.     

Some studies on the solar microwave bursts in relation to the slowly varying component

The occurrences of 5772 microwave bursts recorded by the Sagamore Hill and Manilla Solar Radio Observatories over the period January 1968 to July 1970, covering the maximum phase of the current solar cycle at frequencies 2695, 4995 and 8800 MHz and their energy excesses have been examined in relation to the S-component of solar radio emission. The average slowly varying component has been determined by the superposed epoch method commonly known as the Chree analysis. Similar treatment of the bursts, data, mentioned above has been made to examine any probable 27-day variation and the results obtained have been compared with that of the S-component. Further, spectra of the microwave bursts under the so-called spectral type - inverted U, particularly those having a peak at 4995 MHz, have also been examined and compared with the average spectrum of the S-component. Some of the important results obtained from the present analysis are: (1) the nature of variation of both the average number of occurrences and energy excesses of the microwave bursts follow in general the average 27-day variation of the S-component, (2) the number of occurrences and energy excesses of the microwave bursts are comparatively greater in the ascending phase of the 27-day cycle than those in the descending phase, (3) bursts at progressively higher frequencies originate at lower levels in the solar atmosphere than those of the associated S-component, and (4) the average spectrum of the microwave bursts of inverted U spectral type having a peak at 4995 MHz is quite identical in nature to that of the S-component.     

Sur quelques concentrations plombo-zinciferes du devonien inferieur du massif schisteux rhenan

Zusammenfassung The Lower Devonian of the Rhine Schist Massif is characterized by a fine detrital sedimentation which reflects a coastal plain environment located between the Old Red Sandstone continent in the N and the marine Bohemian Facies in the SE. Mineralisations are located within these coastal-plain sediments, especially in fractured horizons topped by pelitic and floored by sandy sediments of Sieg Emsian age. The mineralised localities occur in three zones: the districts of Bensberg, Eitorf and Mayen. The Lüderich locality (Bensberg) is the most important having approximately one million tons of Zn and Pb metal. It is localised within a zone having marked sedimentary characteristics since the Siegenian. Mineralisation occurs as penecontemporaneous lenses, fracture fillings etc, formed at abnormal contacts between lithological units having different competance during Siegenian and Lower Emsian deformation. However, locally there is lateral transition between the upper units of the sandy channel series and the lower units of the pelitic swamp facies. Vertical extension of mineralisations is strictly limited to the tectonic contact zone between the Odenspiel Sandstone and the Bensberg pelites. Study of mineralisations at various levels (mapping, morphology, structure, paragenetic and geochemical) leads to the formulation of a genetic model requiring complex fracturation at the contact between contrasting lithologies and preferential drainage through these fractured zones; metals are trapped on the sandstone floor, the pelitic roof trapping the vadose hydrothermal solutions. These basic controls seem to apply throughout the Bensberg, Eitorf and Mayen districts. On a more regional scale the age variations of the gangue sediments reflects a lateral displacement of red/grey facies limits due to coastal evolution. Thus one may demonstrate a type of mineral occurrence whose model may be that of epigenetic reconcentration within fractures affecting syngenetic geochemical anomalies.Zusammenfassung Das Unterdevon des Rheinischen Schiefergebirges wird durch eine feinkörnige detritische Sedimentation gekennzeichnet. Die Verteilung dieser detritischen Sedimente widerspiegelt eine flache Küstenlandschaft zwischen dem Kontinent des Unterrotliegenden im Norden und des Meeres mit der Böhmischen Fazies im Südosten. In diesen Schichten befinden sich gangförmige Vererzungen, die in Bruchzonen auftreten, die ein pelitisches Hangendes und ein sandsteinreiches Liegendes vom Siegen-Ems Alter haben. Die Lagerstätten kommen in drei Bezirken vor: Der Bensberger Bezirk, der Bezirk Eitorf und der Bezirk Mayen. Die Lagerstätte Lüderich (Bensberger Revier) ist die größte (ungefähr eine Million Tonnen Metall Zink+Blei). Sie befindet sich in einer Zone, in der schon in der Siegen-Stufe bemerkenswerte sedimentäre Strukturen auftreten. Die Vererzung tritt als penekonkordante Linsen, Gänge, Stockwerke in tektonischen Kontaktzonen auf. Diese Kontaktzonen befinden sich zwischen 2 verschiedenen sedimentären Einheiten, deren Gesteinseigenschaften sehr verschieden sind. Es handelt sich um Pelite mit Sandstein-Einschaltungen einerseits, die zur unteren Emsstufe gehören sollen und um fluviatile Sandsteine andererseits, die zur oberen Siegenstufe gehören sollen. Lokal ist ein lateraler Übergang durch Faziesänderung von den oberen Sandsteinen in die unteren Pelitschichten jedoch nicht unmöglich. Die Sandsteine vertreten einen fluviatilen Sedimentationsbereich, die Pelite einen sumpfigen Sedimentationsbereich. Die Vererzung (mit einer vertikalen Ausdehnung ungefähr von 300 m) tritt nur im Bereich der Kontaktzone zwischen den Odenspieler Sandsteinen und den Peliten der Unteren Bensberger Schichten auf. Die Resultate der Kartographie, der morphologischen Studie der Erzkörper, der Struktur und der Paragenese führen zu einem genetischen Modell. Dabei spielt die Anwesenheit einer Bruchstruktur an der Grenze zwischen 2 Bereichen mit verschiedenen lithologischen Eigenschaften eine Hauptrolle für die Konzentration der im Hangenden fein verteilten Metalle. Die hydrothermalen Lösungen kommen demnach nicht von der Teufe, sondern aus dem Nebengestein. Im ganzen Bensberger Erzrevier wie in der Gegend von Eitorf und in der Gegend von Mayen finden wir dieselben Leitfäden für die Vererzung in den Lagerstätten und Vorkommen. Beobachtet man die ganze Provinz, dann merkt man, daß die Altersverschiedenheiten in den Nebengesteinen der verschiedenen Lagerstätten eine geographische Wanderung der Faziesgrenze zwischen rot und grau in dieser küstennahen Ebene Widerspiegeln. Die verschiedenen Vorkommen und Lagerstätten treten immer in unmittelbarer Nähe dieser Grenze auf. Die Eigenschaften dieser Lagerstätten weisen auf eine Bildung durch eine epigenetische Umlagerung in eine gangförmige Bruchstruktur hin.     

Relationships between Holocene sea-level variations,trophic development,and climatic change in Negra Lagoon,Southern Uruguay

Paleolimnological data are presented on trophic development, climatic change and sea level variations in Negra Lagoon, a 142 km² coastal lagoon in southern Uruguay. Using a sediment core that extended to the early Holocene, analyses of organic matter, carbonate, diatoms and opal phytoliths allowed us to track changes in trophic state and paleosalinity levels, which were closely related to Holocene sea level variation, temperature and humidity. Diatom Association Zones (DAZ) corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and organic matter. Opal Phytoliths Association Zones (OPAZ) also were identified, temperature and humidity indices were calculated, and climatic trends were inferred. During the middle Holocene (i.e., ~5000–4000 yr BP), cool–dry climatic conditions were established. After ~4000 yr BP, a transition from cool to warm–humid conditions was observed, but fully warm humid conditions established only after ~1700 yr BP. Such climatic amelioration led to increases in trophic state.     

Proper motion surveys in the infrared

Current and future wide field surveys in infrared passbands present opportunities for ultra low‐mass stellar sample selection via proper motions, as well as or instead of purely photometric techniques. Furthermore, proper motion measurements yield additional clues as to candidate membership of cluster or field (kinematic) populations. In this paper we review some recent results and speculate as to the possibilities afforded by the next generation of wide‐field infrared surveys. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Strontium and oxygen isotope evidence relating to the petrogenesis of the Kangerdlugssuaq alkaline instrusion,East Greenland

The Kangerdlugssuaq intrusion, East Greenland, consists of quartzsyenites, syenites, pulaskites and foyaites. The age and petrogenesis of the intrusion has been investigated by strontium and oxygen isotope analyses of the major rock types (and some separated minerals) and the surrounding country rocks. Crystallization and rapid cooling of the intrusion close to 50 m.y. ago is indicated by concordance of an Rb-Sr mineral isochron (49.9±1.0 m.y.) and an Rb-Sr whole-rock isochron (50.0±1.9 m.y.) with previously published mineral dates. The feldspathoid-bearing rocks of the intrusion, which were the last to crystallize, have uniformly depleted oxygen (¹⁸O = +3.9, SMOW) and homogeneous initial ⁸⁷Sr/⁸⁶Sr ratios (0.70450±7). This is ascribed to equilibration of the magma prior to the crystallization of these rocks with about 10% by weight of meteoric ground water. The concommittant increase of to about 1 Kb (the lithostatic load pressure) would depress the liquidus surfaces in the system Ne-Ks-Qz by about 200 ° C, allowing the magma to evolve continuously down temperature from oversatuated to undersaturated compositions. The chemical mechanism responsible for this trend has not been uniquely identified, but probably involved reduction of SiO₂ content in an open system. The outer, quartz-normative, rocks of the intrusion have ¹⁸O values ranging up to +5.5 and initial ⁸⁷Sr/⁸⁶Sr ratios ranging up to 0.7095. This is due to interaction of the solid rocks, down to temperatures approaching 500 ° C, with ground water which had been enriched in ¹⁸O and ⁸⁷Sr by previous exchange with the Precambrian country rocks. Minimum water/rock ratios are lower than in certain other known cases of interaction in the North Atlantic Tertiary Igneous Province.