Microcrystals of Th-rich monazite (La) with a negative Ce anomaly in metadiorite and their role for documenting Cretaceous metamorphism in the Slavonian Mountains (Croatia)

Microcrystals (1–15 μm) of unusual monazite (La) with 41–47 mol% cheralite [ThCa(PO₄)₂] component and a strong negative Ce anomaly are described from a metadiorite from the SW Slavonian Mountains, Psunj, Croatia. The dioritic host rock still shows a relictic igneous fabric on macroscopic scale. However, metamorphic reaction textures can be recognized in thin section. These include partial recrystallization of igneous plagioclase to albite coupled with the formation of epidote. Furthermore, partial replacement of igneous hornblende by a fine-grained orthoamphibole-chamosite-epidote paragenesis can be observed and replacement of ilmenite by titanite. The compositions of the metamorphic minerals indicate upper greenschist facies conditions (460–500 °C according to two-feldspar geothermometry) under a high oxygen fugacity. Microstructures show that the monazite crystals belong to the metamorphic paragenesis and formed at the expense of magmatic allanite. Their negative Ce anomalies reflect the oxidizing conditions of metamorphism. Application of the xenotime in monazite solvus geothermometer provides unrealistically high temperatures of ~500–660 °C which disagree with the greenschist facies metamorphic paragenesis. We interpret that the presence of cheralite has a profound effect on the nature of the monazite-xenotime solvus curve and hence the existing calibrations of this geothermometer may be generally unsuitable for cheralite-rich monazite. An important geological result is that the Th-U-total Pb ages of the monazite grains are uniformingly Upper Cretaceous. Our data thus suggest that the imprint of the Alpine orogeny on the Slavonian Mountains was stronger than presumed until now.     

A Review of Coastal Fog Microphysics During C-FOG

Boundary-Layer Meteorology - Our goal is to provide an overview of the microphysical measurements made during the C-FOG (Toward Improving Coastal Fog Prediction) field project. In addition, we...     

Toxicity of the organophosphate pesticide diazinon to crayfish of differing age

Diazinon is a widely applied agricultural pesticide whose effect importantly on the environment and the possible contamination of surface waters has led to increased interest in toxicological studies. Crayfish, as an ecologically important benthic macroinvertebrate, seems to be an appropriate model organism for such assessments. Acute toxicity tests were carried out on three crayfish age groups: young-of-the-year (total length = 25.0 ± 4.9 mm), juvenile (total length = 56.5 ± 3.8 mm) and adult (total length = 83.5 ± 5.7 mm). Young-of-the-year crayfish were found to be the most sensitive to diazinon (96 h LC50 = 0.15 mg L^?1), followed by juvenile crayfish (96 h LC50 = 0.27 mg L^?1), and adults (96 h LC50 = 0.51 mg L^?1). Crayfish were highly sensitive to diazinon. A delayed effect of Diazinon 60EC on adults was detected (144 h LC50 = 0.44 mg L^?1) suggests functional damage from the use of sublethal concentrations.     

Initiation of Coronal Mass Ejections by Sunspot Rotation

We study a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in NOAA Active Region 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux-rope, using three-dimensional zero-β MHD simulations. We first consider a relatively simple and symmetric system, and then study a more complex and asymmetric magnetic configuration, whose photospheric-flux distribution and coronal structure are guided by the observations and a potential field extrapolation. In both cases, we find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux-rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux-rope enters an unstable regime characterised by a strong acceleration. Our simulations thus suggest a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots.     

A Small Pore Observed with a 1.6 m Telescope

A small pore was observed with the New Solar Telescope of 1.6 m aperture at Big Bear Solar Observatory. At a wavelength of 705.68 nm, a diffraction limit of 0.09″ was reached and approximately 700 small structures were analyzed. The achieved high resolution has revealed details about the dynamics of small structures in and around the pore. The small structures either reside in the pore, enter the pore from the vicinity, or dip in and out of the pore. Their sizes are similar, ≈?0.2″, but their observed oscillations do not show power peaks at the same periods. Horizontal plasma flows were suppressed in the pore by 38 % for average velocities, and 65 % for maximum velocities, compared to the quiet Sun.     

Period studies of classical Algol-type binaries II: UX Leo,RW Mon,EQ Ori,XZ UMa and AX Vul

This study presents an investigation of the orbital period variations of five Algol type binaries, UX Leo, RW Mon, EQ Ori, XZ UMa and AX Vul based on all available minima times. The O–C diagrams of all systems exhibit a periodic variation superimposed on a downward parabolic segment. The mass loss due to magnetic braking effect in the cooler components is assumed to account for the parabolic variation with a downward shape, while it is suggested that the light-time effect (LITE) due to an unseen component around the eclipsing binaries explains the tilted sinusoidal changes in their O–C diagrams. The orbital period decrease rates for the systems are estimated as approximately between about 0.7 and 2.5 s per century. It is clearly seen that mass loss effect is more dominant than the expected mass transfer for classical Algols in this study. The minimum mass of the probable third bodies around the eclipsing pairs was calculated to be ?0.5 M_⊙ except for UX Leo, in which it was estimated to be approximately 0.9 M_⊙. In order to search for third lights in the light curves of five systems, the V-light curves of the systems were analyzed and their physical and photometric parameters were determined. For UX Leo, a significant third light contribution was determined. We found a very small third light that can be tested using multi-color light curves, for RW Mon, EQ Ori and XZ UMa, while a third light for AX Vul could not be exposed.     

Binary asteroid population. 2. Anisotropic distribution of orbit poles of small,inner main-belt binaries

Our photometric observations of 18 main-belt binary systems in more than one apparition revealed a strikingly high number of 15 having positively re-observed mutual events in the return apparitions. Our simulations of the survey showed that it cannot be due to an observational selection effect and that the data strongly suggest that poles of mutual orbits between components of binary asteroids in the primary size range 3–8 km are not distributed randomly: The null hypothesis of an isotropic distribution of the orbit poles is rejected at a confidence level greater than 99.99%. Binary orbit poles concentrate at high ecliptic latitudes, within 30° of the poles of the ecliptic. We propose that the binary orbit poles oriented preferentially up/down-right are due to either of the two processes: (i) the YORP tilt of spin axes of their parent bodies toward the asymptotic states near obliquities 0° and 180° (pre-formation mechanism) or (ii) the YORP tilt of spin axes of the primary components of already formed binary systems toward the asymptotic states near obliquities 0° and 180° (post-formation mechanism). The alternative process of elimination of binaries with poles closer to the ecliptic by dynamical instability, such as the Kozai effect due to gravitational perturbations from the Sun, does not explain the observed orbit pole concentration. This is because for close binary asteroid systems, the gravitational effects of primary’s irregular shape dominate the solar-tide effect.     

Modelling long-term water yield effects of forest management in a Norway spruce forest

Abstract

Intensive forest management is one of the main land cover changes over the last century in Central Europe, resulting in forest monoculture. It has been proposed that these monoculture stands impact hydrological processes, water yield, water quality and ecosystem services. At the Lysina Critical Zone Observatory, a forest catchment in the western Czech Republic, a distributed physics-based hydrologic model, Penn State Integrated Hydrologic Model (PIHM), was used to simulate long-term hydrological change under different forest management practices, and to evaluate the comparative scenarios of the hydrological consequences of changing land cover. Stand-age-adjusted LAI (leaf area index) curves were generated from an empirical relationship to represent changes in seasonal tree growth. By consideration of age-adjusted LAI, the spatially-distributed model was able to successfully simulate the integrated hydrological response from snowmelt, recharge, evapotranspiration, groundwater levels, soil moisture and streamflow, as well as spatial patterns of each state and flux. Simulation scenarios of forest management (historical management, unmanaged, clear cutting to cropland) were compared. One of the critical findings of the study indicates that selective (patch) forest cutting results in a modest increase in runoff (water yield) as compared to the simulated unmanaged (no cutting) scenario over a 29-year period at Lysina, suggesting the model is sensitive to selective cutting practices. A simulation scenario of cropland or complete forest cutting leads to extreme increases in annual water yield and peak flow. The model sensitivity to forest management practices examined here suggests the utility of models and scenario development to future management strategies for assessing sustainable water resources and ecosystem services.

Editor D. Koutsoyiannis     

Multiple linear regression,multi-layer perceptron network and adaptive neuro-fuzzy inference system for forecasting precipitation based on large-scale climate signals

ABSTRACT

Nowadays, mathematical models are widely used to predict climate processes, but little has been done to compare the models. In this study, multiple linear regression (MLR), multi-layer perceptron (MLP) network and adaptive neuro-fuzzy inference system (ANFIS) models were compared for precipitation forecasting. The large-scale climate signals were considered as inputs to the applied models. After selecting the most effective climate indices, the effects of large-scale climate signals on the seasonal standardized precipitation index (SPI) of the Maharlu-Bakhtaran catchment, Iran, simultaneously and with a delay, was analysed using a cross-correlation function. Hence, the SPI time series was forecasted up to four time intervals using MLR, MLP and ANFIS. The results showed that most of the indices were significant with SPI of different lag times. Comparison of the SPI forecast results by MLR, MLP and ANFIS models showed better performance for the MLP network than the other two models (RMSE = 0.86, MAE = 0.74 for the first step ahead of SPI forecasting).

Editor D. Koutsoyiannis; Associate editor F. Pappenberger