Reconstruction of sea surface temperatures from the oxygen isotope composition of fossil planktic foraminifera.

Knowledge of the historic surface temperature of sea water is of importance for the calibration of climate models. The oxygen isotope composition of the shells of several species of planktic foraminifera can be used as a measure for this sea surface temperature. In this paper we investigate how mathematical models can contribute to the process of extracting information about the temperature at which the foraminifera lived from measurement of the oxygen isotope composition of their shells. A simple model is proposed which captures both the average and the variability of the temperature. Preliminary findings suggest that this model forms a solid basis for future research

Multi-Overlap Simulations for Transitions between Reference Configurations

We introduce a new procedure to construct weight factors, which flatten the probability density of the overlap with respect to some pre-defined reference configuration. This allows one to overcome free energy barriers in the overlap variable. Subsequently, we generalize the approach to deal with the overlaps with respect to two reference configurations so that transitions between them are induced. We illustrate our approach by simulations of the brainpeptide Met-enkephalin with the ECEPP/2 energy function using the global-energy-minimum and the second lowest-energy states as reference configurations. The free energy is obtained as functions of the dihedral and the root-mean-square distances from these two configurations. The latter allows one to identify the transition state and to estimate its associated free energy barrier.Comment: 12 pages, (RevTeX), 14 figures, Phys. Rev. E, submitte

Spin glass overlap barriers in three and four dimensions

For the Edwards-Anderson Ising spin-glass model in three and four dimensions (3d and 4d) we have performed high statistics Monte Carlo calculations of those free-energy barriers $F^q_B$ which are visible in the probability density $P_J(q)$ of the Parisi overlap parameter $q$. The calculations rely on the recently introduced multi-overlap algorithm. In both dimensions, within the limits of lattice sizes investigated, these barriers are found to be non-self-averaging and the same is true for the autocorrelation times of our algorithm. Further, we present evidence that barriers hidden in $q$ dominate the canonical autocorrelation times.Comment: 20 pages, Latex, 12 Postscript figures, revised version to appear in Phys. Rev.

Multicanonical Multigrid Monte Carlo

To further improve the performance of Monte Carlo simulations of first-order phase transitions we propose to combine the multicanonical approach with multigrid techniques. We report tests of this proposition for the $d$-dimensional $\Phi^4$ field theory in two different situations. First, we study quantum tunneling for $d = 1$ in the continuum limit, and second, we investigate first-order phase transitions for $d = 2$ in the infinite volume limit. Compared with standard multicanonical simulations we obtain improvement factors of several resp. of about one order of magnitude.Comment: 12 pages LaTex, 1 PS figure appended. FU-Berlin preprint FUB-HEP 9/9

Biologische bestrijding van spint en trips in anjer : selectieproef met 6 soorten roofmijten

In de anjerteelt zijn de anjerspintmijt (Tetranychus cinnabarinus) en de californische trips (Frankliniella occi-dentalis) de twee belangrijkste plagen. Vanwege de gewasopbouw van anjer en de levenswijze van spint en trips zijn deze plagen met een bespuiting moeilijk te bestrijden. De ervaring tot nu toe is dat natuurlijke vijanden onvoldoende effect hebben op de bestrijding van spint en trips. In een kasproef zijn 6 roofmijten ingezet voor de bestrijding van spint en trips. Het ging hier om de soorten: Euseius ovalis, Typhlodromips swirskii, Amblyseius andersoni, Amblyseius cucumeris, Ty-plodromalus limonicus en Phytoseiulus persimilis. De 7de soort, Amblyseius barkei, werd halverwege de proef ingezet. Bij het onderzoek werd gekeken naar welke roofmijten zich in het gewas konden vestigen zonder dat de plaag aanwezig was. Zo’n roofmijt zou lang een hongerperiode kunnen overbruggen of hij weet gebruik te maken van plantafscheidingen of nectar van de plant. Na 3 weken werden er bij tellingen in het gewas nau-welijks roofmijten teruggevonden. Bij deze proefopzet werd niet aangetoond dat één van de getoetste roofmijten in staat is geweest zich zonder prooi in het gewas te vestigen

Search for Fragmented M1 Strength in 48-Ca

This research was sponsored by the National Science Foundation Grant NSF PHY-931478

Postpartum depression and anxiety:a community-based study on risk factors before, during and after pregnancy

Background: Depression and anxiety occur frequently postpartum, calling for early detection and treatment. Evidence on risk factors may support early detection, but is inconclusive. Our aim was to identify risk factors for postpartum depression and anxiety, before, during and after pregnancy. Methods: We used data from 1406 mothers of the intervention arm of the Post-Up study. Risk factors were collected at 3 weeks and 12 months postpartum. Depression and anxiety symptoms were measured in the first month postpartum by the Edinburgh Postnatal Depression Scale (EPDS) and 6-item State-Trait Anxiety Inventory (STAI-6), respectively. We used stepwise logistic regression to identify relevant risk factors. Results: Of the mothers, 8.0% had EPDS-scores ≥9 and 14.7% STAI-6-scores ≥42. Factors associated with higher risk of depression were: foreign language spoken at home, history of depression, low maternal self-efficacy and poor current health of the mother. No initiation of breastfeeding was associated with lower risk of depression, no breastfeeding at 3 weeks postpartum increased the risk. Factors associated with higher risk of anxiety were: higher educational level, history of depression, preterm birth, negative experience of delivery and first week postpartum, excessive infant crying, low maternal self-efficacy, low partner support and poor current maternal health. Limitations: Use of a self-report instrument, potential bias by postpartum mood status, and no inclusion of emerging depression cases after one month postpartum. Conclusions: The shared and separate risk factors for postpartum depression and anxiety may help professionals in identifying mothers at increased risk and provide opportunities for preventive interventions and treatment

Lattice-switch Monte Carlo

We present a Monte Carlo method for the direct evaluation of the difference between the free energies of two crystal structures. The method is built on a lattice-switch transformation that maps a configuration of one structure onto a candidate configuration of the other by `switching' one set of lattice vectors for the other, while keeping the displacements with respect to the lattice sites constant. The sampling of the displacement configurations is biased, multicanonically, to favor paths leading to `gateway' arrangements for which the Monte Carlo switch to the candidate configuration will be accepted. The configurations of both structures can then be efficiently sampled in a single process, and the difference between their free energies evaluated from their measured probabilities. We explore and exploit the method in the context of extensive studies of systems of hard spheres. We show that the efficiency of the method is controlled by the extent to which the switch conserves correlated microstructure. We also show how, microscopically, the procedure works: the system finds gateway arrangements which fulfill the sampling bias intelligently. We establish, with high precision, the differences between the free energies of the two close packed structures (fcc and hcp) in both the constant density and the constant pressure ensembles.Comment: 34 pages, 9 figures, RevTeX. To appear in Phys. Rev.

Search for Fragmented M1 Strength in the 48-Ca(p,p') Reaction

This research was sponsored by the National Science Foundation Grant NSF PHY-931478