The relative importance of immediate allelopathy and allelopathic legacy in invasive plant species

Abstract Some introduced invasive species may be competitively superior to natives because they release allelochemicals, which negatively affect native species. Allelochemicals can be immediately effective after being released but can also persist in soils, resulting in a legacy effect. However, to our knowledge there are no studies which distinguish between allelopathic legacy and immediate allelopathy of invasive species and also test for their relative importance and possible interdependence. We used eleven invasive species and tested whether they show immediate allelopathy and allelopathic legacy effects in a factorial pairwise competition experiment using field-collected soil (invaded/non-invaded) and activated carbon to neutralize allelochemicals. We grew two native and the invasive species in both monocultures and pairwise mixtures. In monocultures, the native species did not experience an allelopathic legacy effect of the invasives, suggesting that invaders generally lack persistent allelochemicals. However, the effects of invader allelochemicals were modulated by competitive interactions. In competition, immediate allelopathy decreased competitive ability of natives, while allelopathic legacy positively affected the natives. Moreover, immediate allelopathic and allelopathic legacy effects were strongly negatively correlated. Our results suggest that both immediately released allelochemicals and the allelochemical legacy of invasive species are important for plant performance under natural conditions, and that natives should be able to recover once the invaders are removed. To test whether immediate allelopathy is responsible for plant invasion success, further studies should compare allelopathic effects between invasive and closely related native species.

Leader–member exchange (LMX), job autonomy, and creative work involvement

Researchers have claimed that high quality of supervisor–employee relationships (i.e., leader– member exchange; LMX) fosters creativity at work. Moreover, researchers have acknowledged that this relationship is not clear-cut but rather complex. The present study focused on the moderating role of job autonomy in the LMX-creative work involvement relationship. Longitu-dinal field survey data (N = 144) collected in a high-technology firm revealed a positive asso-ciation between LMX and creative work involvement and confirmed our assumptions on the moderating role of job autonomy. The positive relationship between LMX and creative work involvement was stronger when employees experienced greater job autonomy. Our findings point to the importance of considering the interplay of both, the leader–member relationship and job design issues for increasing employees' creative work involvement.

Sur une inscription hébrai͏̈que relative à la synagogue de Tàdif : extrait

M. Euting

The trouble with quality filtering based on relative Cramér-Rao lower bounds.

Cramér Rao Lower Bounds (CRLB) have become the standard for expression of uncertainties in quantitative MR spectroscopy. If properly interpreted as a lower threshold of the error associated with model fitting, and if the limits of its estimation are respected, CRLB are certainly a very valuable tool to give an idea of minimal uncertainties in magnetic resonance spectroscopy (MRS), although other sources of error may be larger. Unfortunately, it has also become standard practice to use relative CRLB expressed as a percentage of the presently estimated area or concentration value as unsupervised exclusion criterion for bad quality spectra. It is shown that such quality filtering with widely used threshold levels of 20% to 50% CRLB readily causes bias in the estimated mean concentrations of cohort data, leading to wrong or missed statistical findings-and if applied rigorously-to the failure of using MRS as a clinical instrument to diagnose disease characterized by low levels of metabolites. Instead, absolute CRLB in comparison to those of the normal group or CRLB in relation to normal metabolite levels may be more useful as quality criteria. Magn Reson Med, 2015. © 2015 Wiley Periodicals, Inc.

Partiality, Agent-Relative Reasons, and the Individuals View

The paper offers a critical discussion of Simon Keller’s individuals view concerning the grounds of special obligations. It is argued that the view offers a misleading account of agent-relative reasons, which leads to problems with the arguments Keller offers for his view – the Kantian, consequentialist, particularistic argument. Furthermore, it argues that Keller’s argument from phenomenology suffers from not distinguishing between reasons for partiality and reasons from partiality. At best, it can be applied to reasons from partiality – reasons that agents have in virtue of standing in a relationship of partiality with some other person. Thus, the argument does not support the individuals view, as it is compatible with the other approaches Keller discusses. The paper suggests a modified relationship view to ground reasons of partiality.

Autonomy as a protective factor against the detrimental effects of ego depletion on tennis serve accuracy under pressure

It has been repeatedly demonstrated that athletes in a state of ego depletion do not perform up to their capabilities. We assume that autonomous self-control exertion, in contrast to forced self-control exertion, can serve as a buffer against ego depletion effects and can help individuals to show superior performance. In the present study, we applied a between-subjects design to test the assumption that autonomously exerted self-control is less detrimental for subsequent self-control performance in sports than is forced self-control exertion. In a primary self-control task, the level of autonomy was manipulated through specific instructions, resulting in three experimental conditions (autonomy-supportive: n = 19; neutral: n = 19; controlling: n = 19). As a secondary self-control task, participants executed a series of tennis serves under high-pressure conditions, and performance accuracy served as our dependent variable. As expected, a one-way between-groups ANOVA revealed that participants from the autonomy-supportive condition performed significantly better under pressure than did participants from the controlling condition. These results further highlight the importance of autonomy-supportive instructions in order to enable athletes to show superior achievements in high-pressure situations. Practical implications for the coach–athlete relationship are discussed.

Bond Strength of Resin Composite to Dentin with Different Adhesive Systems: Influence of Relative Humidity and Application Time.

PURPOSE To investigate the influence of relative humidity and application time on bond strength to dentin of different classes of adhesive systems. MATERIALS AND METHODS A total of 360 extracted human molars were ground to mid-coronal dentin. The dentin specimens were treated with one of six adhesive systems (Syntac Classic, OptiBond FL, Clearfil SE Bond, AdheSE, Xeno Select, or Scotchbond Universal), and resin composite (Filtek Z250) was applied to the treated dentin surface under four experimental conditions (45% relative humidity/application time according to manufacturers' instructions; 45% relative humidity/reduced application time; 85% relative humidity/application time according to manufacturers' instructions; 85% relative humidity/reduced application time). After storage (37°C, 100% humidity, 24 h), shear bond strength (SBS) was measured and data analyzed with nonparametric ANOVA followed by Kruskal-Wallis tests and Mann-Whitney U-tests with Bonferroni-Holm correction for multiple testing (level of significance: α = 0.05). RESULTS Increased relative humidity and reduced application time had no effect on SBS for Clearfil SE Bond and Scotchbond Universal (p = 1.00). For Syntac Classic, OptiBond FL, AdheSE, and Xeno Select there was no effect on SBS of reduced application time of the adhesive system (p ≥ 0.403). However, increased relative humidity significantly reduced SBS for Syntac Classic, OptiBond FL, and Xeno Select irrespective of application time (p ≤ 0.003), whereas for AdheSE, increased relative humidity significantly reduced SBS at recommended application time only (p = 0.002). CONCLUSION Generally, increased relative humidity had a detrimental effect on SBS to dentin, but reduced application time had no effect.

Vapnikite Ca3UO6 – a new double-perovskite mineral from pyrometamorphic larnite rocks of the Jabel Harmun, Palestinian Autonomy, Israel

The new mineral species vapnikite, Ca3UO6, was found in larnite pyrometamorphic rocks of the Hatrurim Formation at Jabel Harmun in the Judean desert, Palestinian Autonomy, Israel. Vapnikite is an analogue of the synthetic ordered double-perovskite β-Ca3UO6 and is isostructural with the natural fluorperovskite – cryolite Na3AlF6. Vapnikite Ca3UO6 (P21/n,Z = 2, a = 5.739(1), b = 5.951(1), c = 8.312(1) Å, β = 90.4(1)°, V = 283.9(1) Å3) forms yellow-brown xenomorphic grains with a strong vitreous lustre. Small grains up to 20 – 30 m m in size are wedged between larnite, brownmillerite and ye'elimite. Vapnikite has irregular fracture, cleavage and parting were not observed. The calculated density is 5.322 g cm–3, the microhardness is VHN25 = 534 kg mm–2 (mean of seven measurements) corresponding to the hardness of ~5 on the Mohs scale. The crystal structure of vapnikite Ca3UO6 differs from that of its synthetic analogue β-Ca3UO6 by having a larger degree of Ca, U disorder. Vapnikite formed at the high-temperature retrograde stage of pyrometamorphism when larnite rocks were altered by fluids/melts of high alkalinity.

Relative estimate of accuracy in orbit determination from a short tracklet

The Astronomical Institute of the University of Bern (AIUB) is conducting several search campaigns for orbital debris. The debris objects are discovered during systematic survey observations. In general only a short observation arc, or tracklet, is available for most of these objects. From this discovery tracklet a first orbit determination is computed in order to be able to find the object again in subsequent follow-up observations. The additional observations are used in the orbit improvement process to obtain accurate orbits to be included in a catalogue. In this paper, the accuracy of the initial orbit determination is analyzed. This depends on a number of factors: tracklet length, number of observations, type of orbit, astrometric error, and observation geometry. The latter is characterized by both the position of the object along its orbit and the location of the observing station. Different positions involve different distances from the target object and a different observing angle with respect to its orbital plane and trajectory. The present analysis aims at optimizing the geometry of the discovery observation is depending on the considered orbit.