Spatial Graphs with Local Knots

It is shown that for any locally knotted edge of a 3-connected graph in $S^3$, there is a ball that contains all of the local knots of that edge and is unique up to an isotopy setwise fixing the graph. This result is applied to the study of topological symmetry groups of graphs embedded in $S^3$.Comment: 20 pages, 3 figures; in v. 2 the proof of Theorem 1 has been clarified, and other minor revisions have been mad

Q-Value and Half-Lives for the Double-Beta-Decay Nuclide 110Pd

The 110Pd double-beta decay Q-value was measured with the Penning-trap mass spectrometer ISOLTRAP to be Q = 2017.85(64) keV. This value shifted by 14 keV compared to the literature value and is 17 times more precise, resulting in new phase-space factors for the two-neutrino and neutrinoless decay modes. In addition a new set of the relevant matrix elements has been calculated. The expected half-life of the two-neutrino mode was reevaluated as 1.5(6) E20 yr. With its high natural abundance, the new results reveal 110Pd to be an excellent candidate for double-beta decay studies

On the validity of the Wigner-Seitz approximation in neutron star crust

The inner crust of neutron stars formed of nuclear clusters immersed in a neutron sea has been widely studied in the framework of the Wigner-Seitz approximation since the seminal work of Negele and Vautherin. In this article, the validity of this approximation is discussed in the framework of the band theory of solids. For a typical cell of $^{200}$Zr, present in the external layers of the inner crust, it is shown that the ground state properties of the neutron gas are rather well reproduced by the Wigner-Seitz approximation, while its dynamical properties depend on the energy scale of the process of interest or on the temperature. It is concluded that the Wigner-Seitz approximation is well suited for describing the inner crust of young neutron stars and the collapsing core of massive stars during supernovae explosions. However the band theory is required for low temperature fluid dynamics.Comment: 7 pages, with figures - PTH, version

Counterfactual Theory in Social Epidemiology: Reconciling Analysis and Action for the Social Determinants of Health

Abstract There is a strong and growing interest in applying formal methods for causal inference with observational data in social epidemiology. A number of challenges in defining, identifying, and estimating counterfactual-based causal effects have been especially problematic in social epidemiology, particularly for commonly used exposures such as race, education, occupation, or socioeconomic position. The purpose of this article is to revisit these challenges in light of the conceptual and analytic advancements in causal inference over the last two decades. We focus on a central assumption for causal inference known as the stable unit treatment value assumption, which can be divided into two component assumptions: counterfactual consistency and the absence of interference. We give simple hypothetical examples to illustrate how and why these assumptions are often violated in research on the social determinants of health (e.g., education, race/ethnicity, socioeconomic position) and provide strategies that can be used to sidestep these assumptions. In particular, we note that a recently proposed mediation analysis strategy can be used to explore questions about health disparities in a more formal causal inference framework. We emphasize that a central obstacle to estimating causal effects variables such as race, education (e.g., high school versus no high school), or occupation is the need to identify an intervention (possibly hypothetical) that will lead to changes in the exposure of interest

Les aménagements agricoles de l’Anti-Atlas: De l’abandon aux risques de dégradation des sols et du patrimoine paysager

The Western Anti Atlas Mountains, located at the South-west of Morocco, have been prone to intense rural migration for several decades. As a consequence, the agricultural terraces built for several centuries on valley walls have been abandoned and degraded. The risks of runoff and erosion are becoming significant both at the upstream and the downstream (flash floods, dam silting). The objective of this work is to introduce this issue. The state of the art was described in the terroirs of Tizerkine and Timzemzit, commune of M’Zal, province of Chtouka-Ait Baha.Following the characterization of soil surface conditions of the terraces, the status of erosion and the risk of runoff were appraised according to the age of terrace abandonment. Erosion was appreciated by estimating the "soil surface factor, SSF” of PAP/CAR method and the infiltration rate was measured using double rings method. The results showed that the abandonment of terraces has led to the reduction of surface vegetation cover, the decrease of surface openings (soil sealing) and to soil compaction. The differences are significant as of the first year and the risk of runoff was high. A year of abandonment caused the soil surface to lose 40% of its infiltration capacity. At the end of 5 years abandonment, the infiltration rate has been reduced to 1/3. The retaining walls of terraces deteriorated gradually with the age of abandonment. More than half (57 %) of the surface of valley walls terraces experienced moderate to high water erosion, and severe forms of erosion have already been present. More than 11% of the surface has been strongly degraded after 20 years of abandonment. Therefore watershed upstream risks to lose its soils and its scenery, and the downstream are likely to suffer devastating floods. Landscape inheritance made up of these arranged valley walls are being lost. Thus a meticulous attention must be given to these landscapes to better understand their socio-economic and agro-ecological functioning and to better rehabilitate and preserve them. For instance, the introduction of payment for environmental services (PES) could help to rehabilitate the agricultural terraces of the Anti-Atlas. Key words: Terraces, Abandonment, Degradation, Infiltration capacity, Water erosion, Anti-Atlas, MoroccoL’Anti Atlas occidental, montagne du Sud-Ouest marocain, est sujet à un exode rural intense depuis plusieurs décennies. Ainsi les terrasses agricoles aménagées depuis plusieurs siècles sur les versants des vallées sont abandonnées et dégradées. Les risques de ruissellement et d’érosion deviennent importants aussi bien à l’amont qu’à l’aval (crues éclaires, inondations, envasement des barrages). L’objectif de ce travail est d’introduire cette problématique. Les états des lieux ont été décrits dans les terroirs de Tizerkine et Timzemzit, commune M’Zal, province Chtouka-Ait Baha. Après caractérisation des états de surface des sols des terrasses, l’importance de l’érosion et le risque de ruissellement ont été évalués en fonction de l’âge d’abandon. L’érosion a été appréciée par l’estimation du « facteur de surface du sol, FSS » de la méthode PAP/CAR et le taux d’infiltration a été mesuré par la méthode des doubles anneaux. Les résultats ont montré que l’abandon des terrasses a conduit à la réduction de la couverture végétale à la surface du sol, à la diminution de son ouverture (croûte de battance) et à la compaction du sol. Les différences sont significatives dès la première année et le risque de ruissellement a été élevé. Une année d’abandon fait perdre à la surface du sol 40% de sa capacité d’infiltration. Au bout de 5 ans, l’infiltration a été réduite au 1/3. Les murs de soutènement des terrasses se sont détériorés progressivement avec l’âge de l’abandon. Plus de la moitié (57 %) de la surface des versants aménagés en terrasses a subi une érosion hydrique modérée à élevée, et des formes d’érosion sévères ont déjà été présentes. Plus de 11% des surfaces ont été fortement dégradées après 20 ans d’abandon. Par conséquent l’amont des bassins versants risque de perde ses terres et ses paysages et l’aval risque de connaître des crues et des inondations dévastatrices. Le patrimoine paysager constitué par ces versants aménagés est en train de se perdre. Donc une attention particulière doit être accordée à ces paysages pour mieux comprendre leurs fonctionnements socio-économique et agro-écologique et pour mieux les réhabiliter et les conserver. L’introduction par exemple, du payement pour services environnementaux (PSE) pourrait aider à réhabiliter les terrasses agricoles de l’Anti Atlas. Mots clés: Terrasses, Abandon, Dégradation, Capacité d’infiltration, Erosion, Anti Atlas, Maro