Improved numerical approach for time-independent Gross-Pitaevskii nonlinear Schroedinger equation

In the present work, we improve a numerical method, developed to solve the Gross-Pitaevkii nonlinear Schroedinger equation. A particular scaling is used in the equation, which permits to evaluate the wave-function normalization after the numerical solution. We have a two point boundary value problem, where the second point is taken at infinity. The differential equation is solved using the shooting method and Runge-Kutta integration method, requiring that the asymptotic constants, for the function and its derivative, are equal for large distances. In order to obtain fast convergence, the secant method is used.Comment: 2 figure

Biodiversity-rich European grasslands : ancient, forgotten ecosystems

Worldwide reforestation has been recommended as a landscape restoration strategy to mitigate climate change in areas where the climate can sustain forest. This approach may threaten grassland ecosystems of unique biodiversity as such policies are based on the false assumption that most grasslands are man-made. Here, we use multiple lines of evidence (palaeoecological, pedological, phylogenetic, palaeontological) from Central Eastern Europe and show that various types of grasslands have persisted in this area throughout the postglacial i.e., the past 11,700 years. A warm and dry climate, frequent fires, herbivore pressure and early Neolithic settlements kept forests open until widespread forest clearance beginning 4000 to 3000 years ago. Closed forest cover has been the exception for the last two million years. This long-term persistence has likely contributed to the high biodiversity of these grasslands. Consequently, we call for a more cautious prioritisation of the protection of what may be erroneously considered natural, i.e. forests, by many environmental specialists and managers. Instead we provide a new framework for a better understanding of the evolution and persistence of different grassland types and their biodiversity, so that grasslands can be better understood, valued and conserved

Single Particle Tracking for Simultaneous Long and Short Electron Bunches in the BESSY II Storage Ring

A scheme where 1.5 ps and 15 ps long bunches rms can be stored simultaneously in the BESSY II storage ring has recently been proposed BESSYVSR . This paper presents simulations of single particle beam dynamics influenced by superconducting cavities used for the strong longitudinal beam focusing. The effect of RF jitter on very short bunches is investigated and results are discussed. Furthermore, possible effects on beam dynamics during ramp up and ramp down of the high gradient fields in the cavities are studied. The primary goal is to reveal preliminary design specifications for RF jitter on the basis of single particle dynamic

Enhancement of the Deuteron-Fusion Reactions in Metals and its Experimental Implications

Recent measurements of the reaction d(d,p)t in metallic environments at very low energies performed by different experimental groups point to an enhanced electron screening effect. However, the resulting screening energies differ strongly for divers host metals and different experiments. Here, we present new experimental results and investigations of interfering processes in the irradiated targets. These measurements inside metals set special challenges and pitfalls which make them and the data analysis particularly error-prone. There are multi-parameter collateral effects which are crucial for the correct interpretation of the observed experimental yields. They mainly originate from target surface contaminations due to residual gases in the vacuum as well as from inhomogeneities and instabilities in the deuteron density distribution in the targets. In order to address these problems an improved differential analysis method beyond the standard procedures has been implemented. Profound scrutiny of the other experiments demonstrates that the observed unusual changes in the reaction yields are mainly due to deuteron density dynamics simulating the alleged screening energy values. The experimental results are compared with different theoretical models of the electron screening in metals. The Debye-H\"{u}ckel model that has been previously proposed to explain the influence of the electron screening on both nuclear reactions and radioactive decays could be clearly excluded.Comment: 22 pages, 12 figures, REVTeX4, 2-column format. Submitted to Phys. Rev. C; accepte

Influence of Transient Beam Loading on the Longitudinal Beam Dynamics at BESSY VSR

BESSY VSR, a scheme where 1.7 ps and 15 ps long bunches rms can be stored simultaneously in the BESSY II storage ring has recently been proposed [1]. The strong longitudinal bunch focusing is achieved by superconducting high gradient RF cavities. If the bunch fill pattern exhibits a significant inhomogeneity, e.g. due to gaps, transient beam loading causes a distortion of the longitudinal phase space which is different for each bunch. The result are variations along the fill pattern in synchronous phase, synchrotron fre quency and bunch shape. This paper presents investigations of transient beam loading and depicts the consequences on bunch length, phase stability and longitudinal multi bunch oscillations for the projected setup of BESSY VS

Magma decompression rates during explosive eruptions of Kīlauea volcano, Hawai'i, recorded by melt embayments

The decompression rate of magma as it ascends during volcanic eruptions is an important but poorly constrained parameter that controls many of the processes that influence eruptive behaviour. In this study we quantify decompression rates for basaltic magmas using volatile diffusion in olivine-hosted melt tubes (embayments) for three contrasting eruptions of Kīlauea volcano, Hawai'i. Incomplete exsolution of H₂O, CO₂ and S from the embayment melts during eruptive ascent creates diffusion profiles that can be measured using microanalytical techniques, and then modelled to infer the average decompression rate. We obtain average rates of ~0.05-0.45 MPa s-1 for eruptions ranging from Hawaiian style fountains to basaltic subplinian, with the more intense eruptions having higher rates. The ascent timescales for these magmas vary from around ~5 to ~36 minutes from depths of ~2 to ~4 km respectively. Decompression-exsolution models based on the embayment data also allow for an estimate of the mass fraction of pre-existing exsolved volatiles within the magma body. In the eruptions studied this varies from 0.1-3.2 wt%, but does not appear to be the key control on eruptive intensity. Our results do not support a direct link between the concentration of pre-eruptive volatiles and eruptive intensity; rather they suggest that for these eruptions decompression rates are proportional to independent estimates of mass discharge rate. Although the intensity of eruptions is defined by the discharge rate, based on the currently available dataset of embayment analyses it does not appear to scale linearly with average decompression rate. This study demonstrates the utility of the embayment method for providing quantitative constraints on magma ascent during explosive basaltic eruptions

Stability analysis of the D-dimensional nonlinear Schroedinger equation with trap and two- and three-body interactions

Considering the static solutions of the D-dimensional nonlinear Schroedinger equation with trap and attractive two-body interactions, the existence of stable solutions is limited to a maximum critical number of particles, when D is greater or equal 2. In case D=2, we compare the variational approach with the exact numerical calculations. We show that, the addition of a positive three-body interaction allows stable solutions beyond the critical number. In this case, we also introduce a dynamical analysis of the conditions for the collapse.Comment: 6 pages, 7 figure

The 198Au beta-half-life in the metal Au revisited

The half-life of the beta-decay of 198Au has been measured for room temperature and 12 K. The resulting values of T(RT) = 2.684 +- 0.004 d and T(12 K) = 2.687 +- 0.005 d agree well within statistical uncertainties. An evidence for a temperature dependence of the half-life was not observed.Comment: accepted for publication in Eur. Phys. J.