The sedimentology of some Transvaal hominid cave deposits and its environmental and chronological implications

Abstract of paper presented at 5th SASQUA Conference, July 1979The sedimentology of cave deposits is principally influenced by two sets of factors: (1) those relating to the morphology of the depository and its evolution through time; and (2) those resulting from external influences, including the production of sediments and their introduction into the cave under varying conditions of climate and vegetation cover. The interaction of these two sets of factors often poses unique sedimentological problems which differ markedly from those encountered in other sedimentary environments. In particular, the imprint of intracavernous conditions on specific sedimentary facies frequently complicates interpretations relative to extracavernous environmental influences. Inferences from sedimentological studies should, therefore, be supplemented as far as possible with other evidence - for example from isotope analyses, palynology and faunal studies - in any meaningful attempt to reconstruct ancient environments from these deposits. The sequence of intracavernous events which occurred during the accumulation of the Makapansgat and Sterkfontein Formations will be outlined in relation to the probable imprint of external changes. When viewed in conjunction with the evidence of variations in the concentrations of 13C and 18O in the various stratigraphic units and with interpretations relative to the extent of the cover of woody vegetation near each site, a fairly consistent picture of climate fluctuations emerges. These early fluctuations may, in a general way, parallel those recorded by Shackleton and Opdyke in the northern hemisphere for the period between 3,2 My B.P. and the beginning of the Quaternary.Non

The stratigraphy of the Sterkfontein hominid deposit and its relationship to the underground cave system

A programme of orientated core drilling was carried out during 1989 to elucidate stratigraphic relationships within the Sterkfontein Formation and to obtain a representative suite of samples for palaeomagnetic analysis. The cores have revealed that the hominid-bearing cave deposits occur as a continuous succession comprising 6 Members and extending to a maximum depth of about 30 m below present surface. Of these Member I (comprising a sterile, residual fill) and Member 3 are the most extensive. This sequence has been displaced vertically downwards within a zone of decalcification coinciding with the central part of the deposit. This zone has been the focus of recent deep excavations at the site. The results of the drilling, in conjunction with recent surveys of the underground cave system, confirm that a dolomite floor existed at an average depth of about 20 m at the time offirst cave filling. Subsequent cavern development down to depths in excess of 50 m caused the local collapse of some lower units of the Sterkfontein Formation and, as new openings developed to the surface, permitted the ingress of younger fills below the base of the hominid-bearing succession

The nature and genesis of solution cavities (Makondos) in Transvaal Cave breccias

Main articleThe discovery of a large part of the cranium of a hominid, evidently closely related to Homo habilis (Hughes and Tobias 1977) in a solution cavity within the calcified Member 5 of the Sterkfontein Formation (Partridge 1978) has again drawn attention to the frequent occurrence of these features in the hominid-bearing breccias of the Transvaal. The authors first studied these features at Makapansgat (fig. 1) some fifteen years ago and have since then become aware of their very widespread occurrence in soluble rocks in many parts of the world. All subsequent information has served to confirm the origin of these features, but, since these were never published, it is worthwhile to place these findings on record. Solution cavities, or Makondos, in the Transvaal cave breccias are soil-filled pits shaped like an inverted cone. Their walls and intervening areas of the calcified cave deposit are usually rough, and the coalescing of adjacent cavities below the surface is common. They seldom exceed 2 m in diameter and 6 m in depth and occur at intervals of 2 to 3 m in the calcified cave deposit.Non

Bright soliton trains of trapped Bose-Einstein condensates

We variationally determine the dynamics of bright soliton trains composed of harmonically trapped Bose-Einstein condensates with attractive interatomic interactions. In particular, we obtain the interaction potential between two solitons. We also discuss the formation of soliton trains due to the quantum mechanical phase fluctuations of a one-dimensional condensate.Comment: 4 pages, 2 figures, submitted to PR

Deformation of a Trapped Fermi Gas with Unequal Spin Populations

The real-space densities of a polarized strongly-interacting two-component Fermi gas of $^6$Li atoms reveal two low temperature regimes, both with a fully-paired core. At the lowest temperatures, the unpolarized core deforms with increasing polarization. Sharp boundaries between the core and the excess unpaired atoms are consistent with a phase separation driven by a first-order phase transition. In contrast, at higher temperatures the core does not deform but remains unpolarized up to a critical polarization. The boundaries are not sharp in this case, indicating a partially-polarized shell between the core and the unpaired atoms. The temperature dependence is consistent with a tricritical point in the phase diagram.Comment: Accepted for publication in Physical Review Letter

The Bayesian Decision Tree Technique with a Sweeping Strategy

The uncertainty of classification outcomes is of crucial importance for many safety critical applications including, for example, medical diagnostics. In such applications the uncertainty of classification can be reliably estimated within a Bayesian model averaging technique that allows the use of prior information. Decision Tree (DT) classification models used within such a technique gives experts additional information by making this classification scheme observable. The use of the Markov Chain Monte Carlo (MCMC) methodology of stochastic sampling makes the Bayesian DT technique feasible to perform. However, in practice, the MCMC technique may become stuck in a particular DT which is far away from a region with a maximal posterior. Sampling such DTs causes bias in the posterior estimates, and as a result the evaluation of classification uncertainty may be incorrect. In a particular case, the negative effect of such sampling may be reduced by giving additional prior information on the shape of DTs. In this paper we describe a new approach based on sweeping the DTs without additional priors on the favorite shape of DTs. The performances of Bayesian DT techniques with the standard and sweeping strategies are compared on a synthetic data as well as on real datasets. Quantitatively evaluating the uncertainty in terms of entropy of class posterior probabilities, we found that the sweeping strategy is superior to the standard strategy

Semantic Transformation of Web Services

Web services have become the predominant paradigm for the development of distributed software systems. Web services provide the means to modularize software in a way that functionality can be described, discovered and deployed in a platform independent manner over a network (e.g., intranets, extranets and the Internet). The representation of web services by current industrial practice is predominantly syntactic in nature lacking the fundamental semantic underpinnings required to fulfill the goals of the emerging Semantic Web. This paper proposes a framework aimed at (1) modeling the semantics of syntactically defined web services through a process of interpretation, (2) scop-ing the derived concepts within domain ontologies, and (3) harmonizing the semantic web services with the domain ontologies. The framework was vali-dated through its application to web services developed for a large financial system. The worked example presented in this paper is extracted from the se-mantic modeling of these financial web services

Planck Observations of M33

We have performed a comprehensive investigation of the global integrated flux density of M33 from radio to ultraviolet wavelengths, finding that the data between $\sim$100 GHz and 3 THz are accurately described by a single modified blackbody curve with a dust temperature of $T_\mathrm{dust}$ = 21.67$\pm$0.30 K and an effective dust emissivity index of $\beta_\mathrm{eff}$ = 1.35$\pm$0.10, with no indication of an excess of emission at millimeter/sub-millimeter wavelengths. However, sub-dividing M33 into three radial annuli, we found that the global emission curve is highly degenerate with the constituent curves representing the sub-regions of M33. We also found gradients in $T_\mathrm{dust}$ and $\beta_\mathrm{eff}$ across the disk of M33, with both quantities decreasing with increasing radius. Comparing the M33 dust emissivity with that of other Local Group members, we find that M33 resembles the Magellanic Clouds rather than the larger galaxies, i.e., the Milky Way and M31. In the Local Group sample, we find a clear correlation between global dust emissivity and metallicity, with dust emissivity increasing with metallicity. A major aspect of this analysis is the investigation into the impact of fluctuations in the Cosmic Microwave Background (CMB) on the integrated flux density spectrum of M33. We found that failing to account for these CMB fluctuations would result in a significant over-estimate of $T_\mathrm{dust}$ by $\sim$5 K and an under-estimate of $\beta_\mathrm{eff}$ by $\sim$0.4.Comment: Accepted for publication in MNRA

Post-Den Emergence Behavior of Polar Bears (Ursus maritimus) in Northern Alaska

We observed polar bear (Ursus maritimus) maternity den sites on Alaska’s North Slope in March 2002 and 2003 in an effort to describe bears’ post-den emergence behavior. During 40 sessions spanning 459 h, we observed 8 adults and 14 dependent cubs outside dens for 37.5 h (8.2% of total observation time). There was no significant difference between den emergence dates in 2002 (mean = 15 Mar ± 4.1 d) and 2003 (mean = 21 Mar ± 2.1 d). Following initial den breakout, polar bears remained at their den sites for 1.5 to 14 days (mean = 8.1 ± 5.1 d). The average length of stay in dens between emergent periods was significantly shorter in 2002 (1.79 h) than in 2003 (4.82 h). While outside, adult bears were inactive 49.5% of the time, whereas cubs were inactive 13.4% of the time. We found no significant relationships between den emergence activity and weather. Adult polar bears at den sites subjected to industrial activity exhibited significantly fewer bouts of vigilance than denned bears in undisturbed areas (t = -5.5164, df = 4, p = 0.00). However, the duration of vigilance behaviors at sites near industrial activity was not significantly shorter than at the other sites studied (t = -1.8902, df = 4, p = 0.07). Results for these bears were within the range of findings in other studies of denned polar bears.Nous avons observé des tanières de maternité d’ours polaires (Ursus maritimus) sur le versant nord de l’Alaska aux mois de mars 2002 et 2003 dans le but de décrire le comportement de sortie des ours après leur séjour dans la tanière. Dans le cadre de 40 séances d’observation ayant duré 459 heures, nous avons observé 8 ours adultes et 14 oursons à charge en dehors des tanières pendant 37,5 heures (soit 8,2 % de la durée d’observation totale). Il n’y avait pas de différence importante entre les dates de sortie des tanières en 2002 (moyenne = 15 mars ± 4,1 j) et 2003 (moyenne = 21 mars ± 2,1 j). Après la première sortie de la tanière, les ours polaires restaient à l’emplacement de leur tanière pendant 1,5 à 14 jours (moyenne = 8,1 ± 5.1 j). La longueur moyenne du séjour en tanière entre les périodes de sortie était beaucoup plus courte en 2002 (1,79 h) qu’en 2003 (4,82 h). Une fois sortis, les ours adultes étaient inactifs pendant 49,5 % du temps, tandis que les oursons étaient inactifs pendant 13,4 % du temps. Nous n’avons pas trouvé de lien important entre l’activité une fois sorti de la tanière et le temps qu’il faisait. Les ours polaires adultes à l’emplacement de tanières assujetties à des activités industrielles affichaient beaucoup moins de séquences de vigilance que les ours en tanière des régions tranquilles (t = -5,5164, dl = 4, p = 0,00). Cependant, la durée des comportements de vigilance aux emplacements situés près d’activités industrielles n’était pas beaucoup plus courte qu’aux autres emplacements étudiés (t = - 1,8902, dl = 4, p = 0,07). Les résultats enregistrés pour ces ours tombaient dans l’étendue des constatations découlant d’autres études d’ours polaires en tanière