997 resultados para Antipredator behavior
Resumo:
Mixture model techniques are applied to a daily index of monsoon convection from ERA‐40 reanalysis to show regime behavior. The result is the existence of two significant regimes showing preferred locations of convection within the Asia/Western‐North Pacific domain, with some resemblance to active‐break events over India. Simple trend analysis over 1958–2001 shows that the first regime has become less frequent while the second becomes much more dominant. Both undergo a change in structure contributing to the total OLR trend over the ERA‐40 period. Stratifying the data according to a large‐scale dynamical index of monsoon interannual variability, we show the regime occurrence to be strongly perturbed by the seasonal condition, in agreement with conceptual ideas. This technique could be used to further examine predictability issues relating the seasonal mean and intraseasonal monsoon variability or to explore changes in monsoon behavior in centennial‐scale model integrations.
Resumo:
This study addresses the extent to which insecure and disorganized attachments increase risk for externalizing problems using meta-analysis. From 69 samples (N = 5,947), the association between insecurity and externalizing problems was significant, d = 0.31 (95% CI: 0.23, 0.40). Larger effects were found for boys (d = 0.35), clinical samples (d = 0.49), and from observation-based outcome assessments (d = 0.58). Larger effects were found for attachment assessments other than the Strange Situation. Overall, disorganized children appeared at elevated risk (d = 0.34, 95% CI: 0.18, 0.50), with weaker effects for avoidance (d = 0.12, 95% CI: 0.03, 0.21) and resistance (d = 0.11, 95% CI: −0.04, 0.26). The results are discussed in terms of the potential significance of attachment for mental health.
Resumo:
Using the recently-developed mean–variance of logarithms (MVL) diagram, together with the TIGGE archive of medium-range ensemble forecasts from nine different centres, an analysis is presented of the spatiotemporal dynamics of their perturbations, showing how the differences between models and perturbation techniques can explain the shape of their characteristic MVL curves. In particular, a divide is seen between ensembles based on singular vectors or empirical orthogonal functions, and those based on bred vector, Ensemble Transform with Rescaling or Ensemble Kalman Filter techniques. Consideration is also given to the use of the MVL diagram to compare the growth of perturbations within the ensemble with the growth of the forecast error, showing that there is a much closer correspondence for some models than others. Finally, the use of the MVL technique to assist in selecting models for inclusion in a multi-model ensemble is discussed, and an experiment suggested to test its potential in this context.
Resumo:
The coordination behavior of pyridylmethylthioether type of organic moieties having N2S2 donor set [L-1=1,2-bis(2-pyridylmethylthio)ethane, L-2 = 1,3-bis(2-pyridylmethyl-thio)propane and L-3 = 1,4-bis(2-pyridylmethylthio)butane] with copper(II) chloride and copper(II) bromide have been studied in different chemical environments. Copper(II) chloride assisted C-S bond cleavage of the organic moieties leading to the formation of copper(II) picolinate derivatives, whereas, under similar experimental conditions, no C-S bond cleavage was observed in the reaction with copper(II) bromide. The resulted copper(II) complexes isolated from the different mediums have been characterized by spectroscopic and X-ray crystallographic tools.
Resumo:
The hypothesis of a low dimensional martian climate attractor is investigated by the application of the proper orthogonal decomposition (POD) to a simulation of martian atmospheric circulation using the UK Mars general circulation model (UK-MGCM). In this article we focus on a time series of the interval between autumn and winter in the northern hemisphere, when baroclinic activity is intense. The POD is a statistical technique that allows the attribution of total energy (TE) to particular structures embedded in the UK-MGCM time-evolving circulation. These structures are called empirical orthogonal functions (EOFs). Ordering the EOFs according to their associated energy content, we were able to determine the necessary number to account for a chosen amount of atmospheric TE. We show that for Mars a large fraction of TE is explained by just a few EOFs (with 90% TE in 23 EOFs), which apparently support the initial hypothesis. We also show that the resulting EOFs represent classical types of atmospheric motion, such as thermal tides and transient waves. Thus, POD is shown to be an efficient method for the identification of different classes of atmospheric modes. It also provides insight into the non-linear interaction of these modes.
Resumo:
Two series of zinc(II) complexes of two Schiff bases (H2L1 and H2L2) formulated as [Zn(HL1/HL2)]ClO4 (1a and 1b) and [Zn(L1/L2)] (2a and 2b), where H2L1 = 1,8-bis(salicylideneamino)-3,6-dithiaoctane and H2L2 = 1,9-bis(salicylideneamino)-3,7-dithianonane, have been prepared and isolated in pure form by changing the chemical environment. Elemental, spectral, and other physicochemical results characterize the complexes. A single crystal X-ray diffraction study confirms the structure of [Zn(HL1)]ClO4 (1a). In 1a, zinc(II) has a distorted octahedral environment with a ZnO2N2S2 chromophore.
Resumo:
The thermal properties, crystallization, and morphology of amphiphilic poly(D-lactide)-b-poly(N,N-dimethylamino- 2-ethyl methacrylate) (PDLA-b-PDMAEMA) and poly (L-lactide)-b-poly(N,N-dimethylamino-2-ethyl methacrylate) (PLLA-b-PDMAEMA) copolymers were studied and compared to those of the corresponding poly(lactide) homopolymers. Additionally, stereocomplexation of these copolymers was studied. The crystallization kinetics of the PLA blocks was retarded by the presence of the PDMAEMA block. The studied copolymers were found to be miscible in the melt and the glassy state. The Avrami theory was able to predict the entire crystallization range of the PLA isothermal overall crystallization. The melting points of PLDA/PLLA and PLA/PLA-b-PDMAEMA stereocomplexes were higher than those formed by copolymer mixtures. This indicates that the PDMAEMA block is influencing the stability of the stereocomplex structures. For the low molecular weight samples, the stereocomplexes particles exhibited a conventional disk-shape structure and, for high molecular weight samples, the particles displayed unusual star-like shape morphology.
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2-[Methyl(2-methylphenyl)amino]ethanol undergoes an ortho-alkyllithiation reaction with n-butyllithium to lead to a new mixed benzyllithium−lithium alkoxide. This organolithium species reacts with PPh2Cl, with selective P−C bond formation, to afford the ligand 2-[methyl(2-((diphenylphosphino)methyl)phenyl)amino]ethanol L1. The coordination of the ligand L1 to copper(I) leads to the complex [Cu(L1)2](BF4), whose structure has been determined by an X-ray diffraction study. In the solid state, one of the ligands acts as a monodentate phosphine while the other adopts a tridentate P,N,O coordination mode. A variable-temperature 31P NMR study demonstrated the existence of an equilibrium between the two modes in solution, with a coalescence temperature of ca. 0 °C, indicating a double-hemilabile behavior for the nitrogen and the oxygen functions. L1 reacts with [Pd(Me)(Cl)(COD)] to give a dinuclear complex in which the ligand appears to behave as a bridging anionic P,O ligand. Such a complex could serve as a model for a key intermediate in the proposed mechanism for the homogeneous catalysis of the methoxycarbonylation of propyne by certain palladium(II) complexes containing P,N ligands. L1 can undergo a second ortho-alkylmetalation reaction with n-butyllithium which, after addition of PPh2Cl, provides the new ligand 2-{methyl[2-(bis(diphenylphosphino)methyl)phenyl]amino}ethanol (L2) in high yield.
Resumo:
Models used in neoclassical economics assume human behaviour to be purely rational. On the other hand, models adopted in social and behavioural psychology are founded on the ‘black box’ of human cognition. In view of these observations, this paper aims at bridging this gap by introducing psychological constructs in the well established microeconomic framework of choice behaviour based on random utility theory. In particular, it combines constructs developed employing Ajzen’s theory of planned behaviour with Lancaster’s theory of consumer demand for product characteristics to explain stated preferences over certified animal-friendly foods. To reach this objective a web survey was administered in the largest five EU-25 countries: France, Germany, Italy, Spain and the UK. Findings identify some salient cross-cultural differences between northern and southern Europe and suggest that psychological constructs developed using the Ajzen model are useful in explaining heterogeneity of preferences. Implications for policy makers and marketers involved with certified animal-friendly foods are discussed.
Resumo:
As in any technology systems, analysis and design issues are among the fundamental challenges in persuasive technology. Currently, the Persuasive Systems Development (PSD) framework is considered to be the most comprehensive framework for designing and evaluation of persuasive systems. However, the framework is limited in terms of providing detailed information which can lead to selection of appropriate techniques depending on the variable nature of users or use over time. In light of this, we propose a model which is intended for analysing and implementing behavioural change in persuasive technology called the 3D-RAB model. The 3D-RAB model represents the three dimensional relationships between attitude towards behaviour, attitude towards change or maintaining a change, and current behaviour, and distinguishes variable levels in a user’s cognitive state. As such it provides a framework which could be used to select appropriate techniques for persuasive technology.