An evolutionary model explaining the Neolithic transition from egalitarianism to leadership and despotism.

The Neolithic was marked by a transition from small and relatively egalitarian groups to much larger groups with increased stratification. But, the dynamics of this remain poorly understood. It is hard to see how despotism can arise without coercion, yet coercion could not easily have occurred in an egalitarian setting. Using a quantitative model of evolution in a patch-structured population, we demonstrate that the interaction between demographic and ecological factors can overcome this conundrum. We model the coevolution of individual preferences for hierarchy alongside the degree of despotism of leaders, and the dispersal preferences of followers. We show that voluntary leadership without coercion can evolve in small groups, when leaders help to solve coordination problems related to resource production. An example is coordinating construction of an irrigation system. Our model predicts that the transition to larger despotic groups will then occur when: (i) surplus resources lead to demographic expansion of groups, removing the viability of an acephalous niche in the same area and so locking individuals into hierarchy; (ii) high dispersal costs limit followers' ability to escape a despot. Empirical evidence suggests that these conditions were probably met, for the first time, during the subsistence intensification of the Neolithic.

Open to closed system transition traced through the TDIC isotopic signature at the aquifer recharge stage, implications for groundwater 14C dating

14C dating models are limited when considering recent groundwater for which the carbon isotopic signature of the total dissolved inorganic carbon (TDIC) is mainly acquired in the unsaturated zone. Reducing the uncertainties of dating thus implies a better identification of the processes controlling the carbon isotopic composition of the TDIC during groundwater recharge. Geochemical interactions between gas, water and carbonates in the unsaturated zone were investigated for two aquifers (the carbonate-free Fontainebleau sands and carbonate-bearing Astian sands, France) in order to identify the respective roles of CO2 and carbonates on the carbon isotopic signatures of the TDIC; this analysis is usually approached using open or closed system terms. Under fully open system conditions, the seasonality of the 13C values in the soil CO2 can lead to important uncertainties regarding the so-called "initial 14C activity" used in 14C correction models. In a carbonate-bearing unsaturated zone such as in the Astian aquifer, we show that an approach based on fully open or closed system conditions is not appropriate. Although the chemical saturation between water and calcite occurs rapidly within the first metre of the unsaturated zone, the carbon isotopic contents (δ13C) of the CO2 and the TDIC evolve downward, impacted by the dissolution-precipitation of the carbonates. In this study, we propose a numerical approach to describe this evolution. The δ13C and the A 14C (radiocarbon activity) of the TDIC at the base of the carbonate-hearing unsaturated zone depends on (i) the δ13C and the A 14C of the TDIC in the soil determined by the soil CO2, (ii) the water's residence time in the unsaturated zone and (iii) the carbonate precipitation-dissolution fluxes. In this type of situation, the carbonate δ13C-A 14C evolutions indicate the presence of secondary calcite and permit the calculation of its accretion flux, equal to ~ 4.5 ± 0.5 x 10-9 mol grock-1 yr-1. More generally, for other sites under temperate climate and with similar properties to the Astian sands site, this approach allows for a reliable determination of the carbon isotopic composition at the base of the unsaturated zone as the indispensable "input function" data of the carbon cycle into the aquifer.

Effects of the transition time between muscle-tendon stretch and shortening on mechanical efficiency.

The net mechanical efficiency of positive work (eta(pos)) has been shown to increase if it is immediately preceded by negative work. This phenomenon is explained by the storage of elastic energy during the negative phase and its release during the subsequent positive phase. If a transition time (T) takes place, the elastic energy is dissipated into heat. The aim of the present study was to investigate the relationship between eta(pos) and T, and to determine the minimal T required so that eta(pos) reached its minimal value. Seven healthy male subjects were tested during four series of lowering-raising of the body mass. In the first series (S (0)), the negative and positive phases were executed without any transition time. In the three other series, T was varied by a timer (0.12, 0.24 and 0.56 s for series S (1), S (2) and S (3), respectively). These exercises were performed on a force platform sensitive to vertical forces to measure the mechanical work and a gas analyser was used to determine the energy expenditure. The results indicated that eta(pos) was the highest (31.1%) for the series without any transition time (S (0)). The efficiencies observed with transition times (S (1), S (2) and S (3)) were 27.7, 26.0 and 23.8%, respectively, demonstrating that T plays an important role for mechanical efficiency. The investigation of the relationship between eta(pos) and T revealed that the minimal T required so that eta(pos) reached its minimal value is 0.59 s.

How adult specialists deal with the principles of a successful transition.

OBJECTIVES: To evaluate whether adult specialists comply with the basic principles for a successful transition of adolescents with chronic disorders, and to determine whether the characteristics of the adult specialists have an influence on applying these principles. METHODS: Out of 299 adult specialists in four French-speaking Swiss cantons, 209 (70%) answered a paper-and-pencil mailed questionnaire between May and July 2007. Only those having received the transfer of at least one adolescent in the previous 2 years (N=102) were included in the analysis. We analyzed four dependent variables: discussing common concerns of adolescent patients, seeing the patient alone, having a transition protocol, and having a previous contact with the pediatric specialist. A logistic regression was performed for each dependent variable controlling for the physicians' characteristics (number of transfers, age, gender, workplace, and perceived experience). RESULTS: Fifty-four percent of the physicians did not spend time alone with their patients, and sensitive issues such as sexuality or substance use were not widely discussed with their young patients. Most respondents (59%) did not have an established protocol, and 54% did not have any contact with the pediatric specialist. In the multivariate analyses, the adult specialists' characteristics had little impact. CONCLUSIONS: For many adolescents with chronic disorders the transition from pediatric to adult healthcare seems to be limited to a simple transfer, often lacking adequate communication between physicians. Applying simple but basic principles such as a good coordination between providers would probably improve the quality of healthcare of adolescents with chronic illness.

K-T transition in Deccan Traps of central India marks major marine Seaway across India

Deccan intertrappean sediments in central India are generally considered as terrestrial deposits of Maastrichtian age, but the Cretaceous-Tertiary (K-T) position is still unknown. Here we report the discovery of the K-T transition, a marine incursion and environmental changes preserved within the intertrappean sediments at Jhilmili, Chhindwara District, Madhya Pradesh. Integrative biostratigraphic, sedimentologic, mineralogic and chemostratigraphic analyses reveal the basal Danian in the intertrappean sediments between lower and upper trap basalts that regionally correspond to C29r and the C29R/C29N transition, respectively. Intertrappean deposition occurred in predominantly terrestrial semi-humid to and environments. But a short aquatic interval of fresh water ponds and lakes followed by shallow coastal marine conditions with brackish marine ostracods and early Danian zone P1a planktic foraminifera mark this interval very close to the K-T boundary. This marine incursion marks the existence of a nearby seaway, probably extending inland from the west through the Narmada and Tapti rift valleys. The Jhilmili results thus identify the K-T boundary near the end of the main phase of Deccan eruptions and indicate that a major seaway extended at least 800 km across India. (C) 2009 Elsevier B.V. All rights reserved.

Couple conjugal et couple co-parental: quelle articulation lors de la transition à la parentalité ?

La venue d'un premier enfant implique d'importants remaniements. Le couple conjugal est mis à rude épreuve et la littérature anglo-saxonne fait état d'une baisse de la satisfaction conjugale durant la période de transition à la parentalité. De plus, au couple conjugal s'ajoutent le couple co-parental (relations entre les parents à propos de leur enfant) et les dyades parentales (parent/enfant). L'articulation entre les sous-systèmes conjugal, co-parental et parental va varier d'une famille à l'autre : prépondérance du parental ou du conjugal, présence d'un co-parentage soutenant ou non, etc. La baisse de la satisfaction conjugale lors de la transition à la parentalité est confirmée dans une étude réalisée en Suisse et présentée dans cet article. Des vignettes cliniques de jeux familiaux illustrent ensuite les différentes articulations possibles du conjugal, du co-parental et du familial. The birth of a first child implies important reorganizations. The marital relationship is under stress and Anglo-Saxon literature shows that there is a decrease of the marital satisfaction during the transition to parenthood. Moreover, when partners become parents, coparenting (relationship between the parents regarding their child) and parental dyads (parent-infant) are added to the marital relationship. The articulation between the conjugal, coparental and parental sub-systems varies from one family to the other : preponderance of the parental or the conjugal subsystem, presence of a supportive co-parenting or not, etc. The decrease of the marital satisfaction during the transition to parenthood is confirmed in a Swiss study and described in this article. Descriptions of family games illustrate then the different possible articulations of the conjugal, coparental and parental subsystems.

Transition et rétablissement

Cet article présente les risques liés aux transitians de soins et en particulier hospitalo-ambulatoires, qui, sans mesure d'accompagnement proactive, menacent le processus de rétablissement des personnes souffrant de troubles psychiatriques. En effet, les risques de rupture des soins et de réadmission sont davantage liés aux caractéristiques du système sociosanitaire qu'à celles du patient ou de la maladie. Des mesures d'accompagnement simples ne sont pas systématiques dans le domaine de la psychiatrie, alors même que ces patients sont particulièrement vulnérables dans les périodes de post-hospitalisation souvent synonymes de barrières au traitement. Le modèle de case management de transition développé à Lausanne est brièvement présenté et illustré au moyen d'une vignette clinique. Ses particularités sont notamment le recours systématique à certains outils soutenant le rétablissement et l'implication active du patient et de son entourage depuis l'hospitalisation jusqu'au retour dans la communauté.

Geochemical changes at the Permian-Triassic transition in Southern Alps and adjacent area: a review

Compilation of the recent literature from the Southern Alps and adjacent area confirms the geochemical variations of unusual amplitudes during the Permian-Triassic boundary interval (PTBI). A great attention has been given to the negative δ13C anomaly within the Tesero Member close to the Permian-Triassic boundary. Very detailed geochemical works have been done on the scientific Gartnerkofel core (Gk-1) and on the Slovenian sections. Major minor and rare earth elements (REE) data are reported and show a marked enrichment in alkaline metals and REE of some levels of the boundary interval. But recent studies show that the low Iridium anomalies and the Osmium and Helium isotopes anomalies lack the characteristics of a large extraterrestrial impact.

Transition to parenthood: The role of social interaction and endogenous networks

Empirical studies indicate that the transition to parenthood is influenced by an individual's peer group. To study the mechanisms creating interdepen- dencies across individuals' transition to parenthood and its timing we apply an agent-based simulation model. We build a one-sex model and provide agents with three different characteristics regarding age, intended education and parity. Agents endogenously form their network based on social closeness. Network members then may influence the agents' transition to higher parity levels. Our numerical simulations indicate that accounting for social inter- actions can explain the shift of first-birth probabilities in Austria over the period 1984 to 2004. Moreover, we apply our model to forecast age-specific fertility rates up to 2016.

Transition écologique, plutôt que développement durable. Entretien

Entretien

Lifetime of an ocean island volcano feeder zone: constraints from U-Pb dating on coexisting zircon and baddeleyite, and 40Ar/39Ar age determinations, Fuerteventura, Canary Islands

High-precision isotope dilution - thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon and baddeleyite ages from the PX1 vertically layered mafic intrusion Fuerteventura, Canary Islands, indicate initiation of magma crystallization at 22.10 +/- 0.07 Ma. The magmatic activity lasted a minimum of 0.52 Ma. Ar-40/Ar-39 amphibole dating yielded ages from 21.9 +/- 0.6 to 21.8 +/- 0.3, identical within errors to the U-Pb ages, despite the expected 1% theoretical bias between Ar-40/Ar-39 and U-Pb dates. This overlap could result from (i) rapid cooling of the intrusion (i. e., less than the 0.3 to 0.6 Ma 40Ar/39Ar age uncertainties) from closure temperatures (T-c) of zircon (699-988 degrees C) to amphibole (500-600 degrees C); (ii) lead loss affecting the youngest zircons; or (iii) excess argon shifting the plateau ages towards older values. The combination of the Ar-40/Ar-39 and U/Pb datasets implies that the maximum amount of time PX1 intrusion took to cool below amphibole T-c is 0.8 Ma, suggesting PX1 lifetime of 520 000 to 800 000 Ma. Age disparities among coexisting baddeleyite and zircon (22.10 +/- 0.07/0.08/0.15 Ma and 21.58 +/- 0.15/0.16/0.31 Ma) in a gabbro sample from the pluton margin suggest complex genetic relationships between phases. Baddeleyite is found preserved in plagioclase cores and crystallized early from low silica activity magma. Zircon crystallized later in a higher silica activity environment and is found in secondary scapolite and is found close to calcite veins, in secondary scapolite that recrystallised from plagioclase. close to calcite veins. Oxygen isotope delta O-18 values of altered plagioclase are high (+7.7), indicating interaction with fluids derived from host-rock carbonatites. The coexistence of baddeleyite and zircon is ascribed to interaction of the PX1 gabbro with CO2-rich carbonatite-derived fluids released during contact metamorphism.

Metabolic syndrome according to different definitions in a rapidly developing country of the African region

AIMS: We examined, in a country of the African region, i) the prevalence of the metabolic syndrome (MetS) according to three definitions (ATP, WHO and IDF); ii) the distribution of the MetS criteria; iii) the level of agreement between these three definitions and iv) we also examined these issues upon exclusion of people with diabetes. METHODS: We conducted an examination survey on a sample representative of the general population aged 25-64 years in the Seychelles (Indian Ocean, African region), attended by 1255 participants (participation rate of 80.3%). RESULTS: The prevalence of MetS increased markedly with age. According to the ATP, WHO and IDF definitions, the prevalence of MetS was, respectively, 24.0%, 25.0%, 25.1% in men and 32.2%, 24.6%, 35.4% in women. Approximately 80% of participants with diabetes also had MetS and the prevalence of MetS was approximately 7% lower upon exclusion of diabetic individuals. High blood pressure and adiposity were the criteria found most frequently among MetS holders irrespective of the MetS definitions. Among people with MetS based on any of the three definitions, 78% met both ATP and IDF criteria, 67% both WHO and IDF criteria, 54% both WHO and ATP criteria and only 37% met all three definitions. CONCLUSION: We identified a high prevalence of MetS in this population in epidemiological transition. The prevalence of MetS decreased by approximately 32% upon exclusion of persons with diabetes. Because of limited agreement between the MetS definitions, the fairly similar proportions of MetS based on any of the three MetS definitions classified, to a substantial extent, different subjects as having MetS.