Hearers of the Word : Luke\u27s Gospel as Sacramental Formation for a Liturgical Community

(Excerpt) It is privilege to return to the Institute of Liturgical Studies after a long absence, especially on a subject that has consumed me in one way or another over the last fifteen years. I am very grateful to the advisory council for assigning me a topic that develops the biblical foundations of the catechumenate. My doctoral work on Emmaus, my vocation as professor of exegesis and pastoral theology, my participation in the ELCA and LCMS working groups on the catechumenate, as well as my participation in the Missouri Synod\u27s efforts to develop its own catechumenal process, have all contributed to my remarks this afternoon. But it is through conversations with colleagues about the New Testament as a catechetical document, and particularly my work on Luke\u27s gospel, that has been seminal to my own thinking about the biblical foundations for the catechumenate

Roche volume filling and the dissolution of open star clusters

From direct N-body simulations we find that the dynamical evolution of star clusters is strongly influenced by the Roche volume filling factor. We present a parameter study of the dissolution of open star clusters with different Roche volume filling factors and different particle numbers. We study both Roche volume underfilling and overfilling models and compare with the Roche volume filling case. We find that in the Roche volume overfilling limit of our simulations two-body relaxation is no longer the dominant dissolution mechanism but the changing cluster potential. We call this mechnism "mass-loss driven dissolution" in contrast to "two-body relaxation driven dissolution" which occurs in the Roche volume underfilling regime. We have measured scaling exponents of the dissolution time with the two-body relaxation time. In this experimental study we find a decreasing scaling exponent with increasing Roche volume filling factor. The evolution of the escaper number in the Roche volume overfilling limit can be described by a log-logistic differential equation. We report the finding of a resonance condition which may play a role for the evolution of star clusters and may be calibrated by the main periodic orbit in the large island of retrograde quasiperiodic orbits in the Poincar\'e surfaces of section. We also report on the existence of a stability curve which may be of relevance with respect to the structure of star clusters.Comment: 14 pages, 10+1 figures, accepted by Astronomische Nachrichte

Pests and Agricultural Production under Climate Change

Although the effect of climate change on agricultural pests has been studied by biologists, thus far, large-scale assessments of climate change and agriculture have not included the impact of pests. We develop a simple theoretical model of farmer-pest interaction under climate change and explore the potential impacts on land values.Environmental Economics and Policy,

Why farmers sometimes love risks: evidence from India

Using a unique data set collected among farmers in India’s semiarid tropics, we document the surprising prevalence of risk-taking behavior in the face of realistically framed high-stakes gambles. We hypothesize that this apparently anomalous behavior is due to a combination of credit constraints and nonconvexities in production. In particular, the high-stakes nature of the gambles creates the potential for a farmer to undertake a productive investment that would normally be unaffordable and thereby move to a permanently higher level of income. We show that the degree to which farmers are willing to accept risk in return for this opportunity appears to relate in an intuitive way to their current agricultural production technology as well as the demographic composition of their household

The star cluster survivability after gas expulsion is independent of the impact of the Galactic tidal field

We study the impact of the tidal field on the survivability of star clusters following instantaneous gas expulsion. Our model clusters are formed with a centrally-peaked star-formation efficiency profile as a result of star-formation taking place with a constant efficiency per free-fall time. We define the impact of the tidal field as the ratio of the cluster half-mass radius to its Jacobi radius immediately after gas expulsion, $\lambda = r_{h}/R_{J}$. We vary $\lambda$ by varying either the Galactocentric distance, or the size (hence volume density) of star clusters. We propose a new method to measure the violent relaxation duration, in which we compare the total mass-loss rate of star clusters with their stellar evolutionary mass-loss rate. That way, we can robustly estimate the bound mass fraction of our model clusters at the end of violent relaxation. The duration of violent relaxation correlates linearly with the Jacobi radius, when considering identical clusters at different Galactocentric distances. In contrast, it is nearly constant for the solar neighbourhood clusters, slightly decreasing with $\lambda$. The violent relaxation does not last longer than 50 Myr in our simulations. Identical model clusters placed at different Galactocentric distances have the same final bound fraction, despite experiencing different impacts of the tidal field. The solar neighbourhood clusters with different densities experience only limited variations of their final bound fraction. In general, we conclude that the cluster survivability after instantaneous gas expulsion, as measured by their bound mass fraction at the end of violent relaxation, $F_{bound}$, is independent of the impact of the tidal field, $\lambda$.Comment: accepted for publication in MNRAS, 8 pages, 5 figures,3 table

Coexisting patterns of population oscillations: the degenerate Neimark Sacker bifurcation as a generic mechanism

We investigate a population dynamics model that exhibits a Neimark Sacker bifurcation with a period that is naturally close to 4. Beyond the bifurcation, the period becomes soon locked at 4 due to a strong resonance, and a second attractor of period 2 emerges, which coexists with the first attractor over a considerable parameter range. A linear stability analysis and a numerical investigation of the second attractor reveal that the bifurcations producing the second attractor occur naturally in this type of system.Comment: 8 pages, 3 figure

Effects of anisotropy in a nonlinear crystal for squeezed vacuum generation

Squeezed vacuum (SV) can be obtained by an optical parametric amplifier (OPA) with the quantum vacuum state at the input. We are interested in a degenerate type-I OPA based on parametric down-conversion (PDC) where due to phase matching requirements, an extraordinary polarized pump must impinge onto a birefringent crystal with a large \chi(2) nonlinearity. As a consequence of the optical anisotropy of the medium, the direction of propagation of the pump wavevector does not coincide with the direction of propagation of its energy, an effect known as transverse walk-off. For certain pump sizes and crystal lengths, the transverse walk-off has a strong influence on the spatial spectrum of the generated radiation, which in turn affects the outcome of any experiment in which this radiation is employed. In this work we propose a method that reduces the distortions of the two-photon amplitude (TPA) of the states considered, by using at least two consecutive crystals instead of one. We show that after anisotropy compensation the TPA becomes symmetric, allowing for a simple Schmidt expansion, a procedure that in practice requires states that come from experimental systems free of anisotropy effects