New systemic radial velocities of suspected RR Lyrae binary stars

Among the tens of thousands of known RR Lyrae stars there are only a handful that show indications of possible binarity. The question why this is the case is still unsolved, and has recently sparked several studies dedicated to the search for additional RR Lyraes in binary systems. Such systems are particularly valuable because they might allow to constrain the stellar mass. Most of the recent studies, however, are based on photometry by finding a light time effect in the timings of maximum light. This approach is a very promising and successful one, but it has a major drawback: by itself, it cannot serve as a definite proof of binarity, because other phenomena such as the Blazhko effect or intrinsic period changes could lead to similar results. Spectroscopic radial velocity measurements, on the other hand, can serve as definite proof of binarity. We have therefore started a project to study spectroscopically RR Lyrae stars that are suspected to be binaries. We have obtained radial velocity (RV) curves with the 2.1m telescope at McDonald observatory. From these we derive systemic RVs which we will compare to previous measurements in order to find changes induced by orbital motions. We also construct templates of the RV curves that can facilitate future studies. We also observed the most promising RR Lyrae binary candidate, TU UMa, as no recent spectroscopic measurements were available. We present a densely covered pulsational RV curve, which will be used to test the predictions of the orbit models that are based on the O-C variations.Comment: 4 pages, 1 figure, to appear in the No. 105 issue of the Communications from the Konkoly Observatory of the Hungarian Academy of Science

Incorporation of diverse catch crop mixtures in crop rotation cycles increase biodiversity and nutrient availability in soils

Catch cropping have positive impacts on plant nutrition, on biological, chemical, and physical soil properties and reduce the amount of fertilizers. Mixtures of diverse catch crops with varying rooting depth and microbial associations can have additional impact on the nutrient and water acquisition from the subsoil. The decay rate of the catch crop litter during the crop rotation controls the release of nutrients for the succeeding crop. This study investigates the release of nutrients and the microbial community in the cause of litter decomposition from catch crops of varying biodiversity. Therefore, litter-bags filled with litter of the previous catch crop rotation was buried in 15 cm soil depth beneath the main crop maize. The experiment used a fallow treatment as control, mustard as single catch crop, a mixture of crimson clover, oat, phacelia and mustard, and the commercial mixture TerraLife® (12 plant species). All treatments were applied in triplicates and straw from the previous main crop (winter wheat) was used as control. The litter decay was investigated at five time points, each every four weeks. At each time point 14 macro and micro-elements where measured. The temporal fluctuation within the decomposer community was investigated by phospholipid-fatty-acid and neutral-fatty-acid analysis (PLFA/NLFA) and quantitative-PCR techniques. Mustard litter showed the longest residence time in soil and decrease over the four mix and wheat straw towards the TerraLife mix. Significantly higher amounts of P, K, Fe and Al were found in the litter of the two catch crop mixtures compared to mustard and the control. Phosphorous and K from the mixed catch crops were released in the early stage of decomposition and meet the nutrient demand of those elements in young maize plants. The diversity index and total microbial biomass increasing in the order: fallow, mustard, four mix and TerraLife. Particularly the markers for saprophytic and arbuscular mycorrhiza fungi indicated doubling of their biomass in the mix treatments compared to mustard and the fallow. Application of high diverse catch crop mixtures support the nutrient demand of main crops and support higher microbial biomass and diversity. Crop rotation with high diverse catch crops leads to continuous soil health and is recommended as a sustainable form of farm land management

A cautionary tale of interpreting O-C diagrams: period instability in a classical RR Lyr Star Z CVn mimicking as a distant companion

We present a comprehensive study of Z CVn, an RR Lyrae star that shows long-term cyclic variations of its pulsation period. A possible explanation suggested from the shape of the O-C diagram is the light travel-time effect, which we thoroughly examine. We used original photometric and spectroscopic measurements and investigated the period evolution using available maximum times spanning more than one century. If the binary hypothesis is valid, Z CVn orbits around a black hole with minimal mass of $56.5$ $\mathfrak{M}_{\odot}$ on a very wide ($P_{\rm orbit}=78.3$ years) and eccentric orbit ($e=0.63$). We discuss the probability of a formation of a black hole-RR Lyrae pair and, although we found it possible, there is no observational evidence of the black hole in the direction to Z CVn. However, the main objection against the binary hypothesis is the comparison of the systemic radial velocity curve model and spectroscopic observations that clearly show that Z CVn cannot be bound in such a binary. Therefore, the variations of pulsation period are likely intrinsic to the star. This finding represents a discovery/confirmation of a new type of cyclic period changes in RR Lyrae stars. By the analysis of our photometric data, we found that the Blazhko modulation with period of 22.931 d is strongly dominant in amplitude. The strength of the phase modulation varies and is currently almost undetectable. We also estimated photometric physical parameters of Z CVn and investigated their variations during the Blazhko cycle using the Inverse Baade-Wesselink method.Comment: 15 pages, 8 tables, 9 figures, accepted for publication in MNRA

Adsorption of Pb on iron oxide colloids as a function of DOM concentration

Soil contamination with lead (Pb) is of particular concern for human health, especially with respect to potential transport to the groundwater. Pb can be co-transported with both organic and inorganic colloidal particles in soils. The aim of this study is to determine the interactions between Pb and typical soil colloids such as dissolved organic matter (DOM), goethite colloids, and organic matter coated goethite (OMCG) colloids as well as to investigate the influence of these colloidal particles on the mobility of Pb in soils. For that, experiments were conducted with DOM derived from Fagus sylvatica litter and goethite colloids with mean particle size of 500 nm. The effects of DOM concentration on goethite colloid zeta potentials and aggregation behavior were investigated to determine potential mobility in soil materials. Furthermore, the adsorption of Pb2+ onto iron oxides and DOM was determined at pH 6 in three variants: (i) goethite colloids + Pb2+, (ii) DOM + Pb2+, and (iii) OMCG colloids + Pb2+. In the absence of DOM, the zeta potential of goethite colloids was positive. With rising DOC concentration, the zeta potential turned increasingly negative. The zeta potential affected goethite colloid aggregation behavior. While colloids repel each other both in the absence of DOM and at DOC concentrations above 1.0 mg/l, the more neutral zeta potential at 0.1 mg/l DOC caused aggregation of OMCG colloids. Furthermore, the adsorption of Pb2+ onto goethite colloids at different DOC concentrations is likewise related to zeta potentials. Only small amounts of Pb2+ were adsorbed on pure goethite surfaces in the absence of DOM. In contrast, Pb2+ was readily adsorbed onto OMCG colloids at 1.0 mg/l DOC. Notably, the largest amount of Pb2+ adsorption was found for pure DOM in the absence of goethite colloids. This can be explained by the fact that pure DOM has more potential sorption sites left for Pb2+ than DOM coatings on goethite colloids have. We conclude that DOM-induced changes in goethite colloid zeta potentials affected both the colloid aggregation behavior and the sorption capacity for Pb2+.These results serve as the base for transport experiments, in which the mobility of (i) Pb2+, (ii) Pb2+ + DOM, and (iii) Pb2+ + OMCG colloids will be determined in different soil materials ranging from HCl-cleaned quartz sand to goethite coated sand to undisturbed natural soil

Class I Gap-formation in Highly-viscous Glass-ionomer Restorations: Delayed vs Immediate Polishing

This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000× magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80–100 gaps were found. In the latter case, only 9–21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.</p

Fractional Brownian Motion in a Finite Interval: Correlations Effect Depletion or Accretion Zones of Particles Near Boundaries

Fractional Brownian motion (FBM) is a Gaussian stochastic process with stationary, long-time correlated increments and is frequently used to model anomalous diffusion processes. We study numerically FBM confined to a finite interval with reflecting boundary conditions. The probability density function of this reflected FBM at long times converges to a stationary distribution showing distinct deviations from the fully flat distribution of amplitude 1/L in an interval of length L found for reflected normal Brownian motion. While for superdiffusion, corresponding to a mean squared displacement (MSD) ⟨X2(t)⟩ ≃ tα with 1 \u3c α \u3c 2, the probability density function is lowered in the centre of the interval and rises towards the boundaries, for subdiffusion (0 \u3c α \u3c 1) this behaviour is reversed and the particle density is depleted close to the boundaries. The MSD in these cases at long times converges to a stationary value, which is, remarkably, monotonically increasing with the anomalous diffusion exponent α. Our a priori surprising results may have interesting consequences for the application of FBM for processes such as molecule or tracer diffusion in the confines of living biological cells or organelles, or other viscoelastic environments such as dense liquids in microfluidic chambers

Class I Gap-formation in Highly-viscous Glass-ionomer Restorations: Delayed vs Immediate Polishing

This in vitro study evaluated the effects of delayed versus immediate polishing to permit maturation of interfacial gap-formation around highly viscous conventional glass-ionomer cement (HV-GIC) in Class I restorations, together with determining the associated mechanical properties. Cavity preparations were made on the occlusal surfaces of premolars. Three HV-GICs (Fuji IX GP, GlasIonomer FX-II and Ketac Molar) and one conventional glass-ionomer cement (C-GIC, Fuji II, as a control) were studied, with specimen subgroups (n=10) for each property measured. After polishing, either immediately (six minutes) after setting or after 24 hours storage, the restored teeth were sectioned in a mesiodistal direction through the center of the model Class I restorations. The presence or absence of interfacial-gaps was measured at 1000× magnification at 14 points (each 0.5-mm apart) along the cavity restoration interface (n=10; total points measured per group = 140). Marginal gaps were similarly measured in Teflon molds as swelling data, together with shear-bond-strength to enamel and dentin, flexural strength and moduli. For three HV-GICs and one C-GIC, significant differences (p<0.05) in gap-incidence were observed between polishing immediately and after one-day storage. In the former case, 80–100 gaps were found. In the latter case, only 9–21 gaps were observed. For all materials, their shear-bond-strengths, flexural strength and moduli increased significantly after 24-hour storage.</p

Fractional Brownian Motion in a Finite Interval: Correlations Effect Depletion or Accretion Zones of Particles Near Boundaries

Fractional Brownian motion (FBM) is a Gaussian stochastic process with stationary, long-time correlated increments and is frequently used to model anomalous diffusion processes. We study numerically FBM confined to a finite interval with reflecting boundary conditions. The probability density function of this reflected FBM at long times converges to a stationary distribution showing distinct deviations from the fully flat distribution of amplitude 1/L in an interval of length L found for reflected normal Brownian motion. While for superdiffusion, corresponding to a mean squared displacement (MSD) ⟨X2(t)⟩ ≃ tα with 1 \u3c α \u3c 2, the probability density function is lowered in the centre of the interval and rises towards the boundaries, for subdiffusion (0 \u3c α \u3c 1) this behaviour is reversed and the particle density is depleted close to the boundaries. The MSD in these cases at long times converges to a stationary value, which is, remarkably, monotonically increasing with the anomalous diffusion exponent α. Our a priori surprising results may have interesting consequences for the application of FBM for processes such as molecule or tracer diffusion in the confines of living biological cells or organelles, or other viscoelastic environments such as dense liquids in microfluidic chambers

Particle size as controlling factor of soil microaggregate formation

Aggregates are formed when soil particles connect to larger secondary units. Stable microaggregates in soils are supposed to consist of close associations of Fe-oxides and clay minerals with both components being attracted by electrostatic forces between the oppositely charged particles. However, the geometric preconditions for the formation of stable associations between Fe oxides and clay minerals are poorly known. Therefore, our goal was to determine geometrical constraints resulting from particle size and morphology likely impeding optimum arrangement of particles for shielding of charges during aggregate formation. Aggregation kinetics was determined for nine combinations of each three particle size fractions of goethite and mica in a Zetasizer at pH 6. Experiments were conducted using needle-shape goethites synthesized at 4, 20, and 60°C (lengths of 0.42, 0.46 and 0.84 µm, specific surface areas (SSA) of 87, 75, and 60 m²/g, respectively) and ground platy muscovite separated in fine, medium and coarse clay (diameters of 0.16, 0.80, and 2.9 µm, SSA of 182, 100, and 27 m²/g, respectively). For five combinations even smallest additions of goethite to muscovite facilitated aggregation. By further additions of goethite maximum aggregate sizes up to 5.6 µm were obtained, the respective mixing ratio strongly depending on the type of combination. After that sizes declined. For medium and coarse-sized muscovite, goethite amendments &gt;18% did not facilitate aggregation, indicating the dominance of repulsive forces. In contrast, for fine-sized muscovite aggregation was facilitated up to an addition of 63% fine-sized goethite and of 90% coarse-sized goethite. Here also biggest aggregate sizes were obtained. Based on all examined size fraction combinations, our results suggest a strong impact of particle size on aggregation. Whereas all combinations with fine-sized muscovite facilitated aggregation at very different mixing ratios, the amendment of the finest fraction of goethite to medium- and coarse-sized muscovite facilitated aggregation at small additions only. Aggregation was favored for evenly sized combinations. The quantification of surface charge density of minerals and calculation of charge balances of the combinations is in progress and will help interpreting the observed aggregation patterns. For soils it is likely that aggregation by electrostatic interactions occurs only at certain mineral mixing ratios highly depending on particle morphology