925 resultados para Stability in organic solvents


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Objective: Healthy relationships between adolescents and their caregivers have been robustly associated with better youth outcomes in a variety of domains. Youth in contact with the child welfare system are at higher risk for worse outcomes including mental health problems and home placement instability. A growing body of literature points to youth mental health problems as both a predictor and a consequence of home placement instability in this population; the present study aimed to expand our understanding of these phenomena by examining the interplay among the caregiver-child relationship, youth mental health symptoms, and placement change over time. Method: The sample consisted of 1,179 youths aged 11-16, from the National Survey of Child and Adolescent Well-Being, a nationally representative sample of children in contact with the child welfare system. We used bivariate correlations and autoregressive cross-lagged path analysis to examine how youths’ reports of their externalizing and internalizing symptoms, their relationship with their caregivers, and placement changes reciprocally influenced one another over three time points. Results: In the overall models, early internalizing symptoms significantly negatively predicted the quality of the caregiver-child relationship at the next time point, and early externalizing symptoms predicted subsequent placement change. In addition, later externalizing symptoms negatively predicted subsequent reports of relationship quality, and later placement changes predicted subsequent externalizing problems; these relationships were significant only at the trend level (p < .10). The quality of the relationship was significantly negatively correlated with externalizing and internalizing problems at all time points, and all variables demonstrated autoregressive stability over time. Conclusions: Our findings support the importance of comprehensive interventions for youth in contact with the child welfare system, which target not only youth symptoms in isolation, but also the caregiver-child relationship, as a way to improve social-emotional outcomes in this high-risk population.

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Ramón's group has designed a simple, robust and inexpensive methodology for the impregnation of different transition metal oxides on the surface of magnetite and their use in catalysis.

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The coupling reaction between aryl bromides and boron reagents is efficiently catalyzed by an in situ generated palladium complex obtained from palladium(II) acetate (0.1 mol%) and 1,3-bis(carboxymethyl)imidazole (0.2 mol%). The catalytic system is very active in protic solvents, especially in methanol. Biaryl derivatives have been prepared in good isolated yields (up to >99%), and additionally styrene and stilbene derivatives have also been prepared by means of this protocol.

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Different Pt- and Ru-doped Ti/SnO2–Sb electrodes were synthesized by thermal decomposition. The effect of the gradual substitution of Sb by Ru in the nominal composition on the physicochemical and electrochemical properties were evaluated. The electrochemical stability of the electrodes was estimated from accelerated tests at 0.5 A cm–2 in 1 M NaOH. Both as-synthesized and deactivated electrodes were thoroughly characterized by scanning electron microscopy (SEM), energy-dispersive X-ray microanalysis (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction analysis (XRD). The incorporation of a small amount (about 3 at. %) of both Pt and Ru into the SnO2–Sb electrodes produced a 400-times increase in their service life in alkaline medium, with no remarkable change in the electrocatalysis of the oxygen evolution reaction (OER). It is concluded that the deactivation of the electrodes is promoted by alkaline dissolution of metal species and coating detachment at high potentials. The introduction of Pt has a coating compacting effect, and Ru(IV), at low amounts until 9.75 at. %, replaces the Sn(IV) cations in the rutile-like SnO2 structure to form a solid solution that strongly increases the stability of the electrodes. The observed Ru segregation and decreased stability for larger Ru contents (x > 9.75 at. %), together with the selective dissolution of Ru after deactivation, suggest that the formation of a homogeneous (RuδSn1−δ)O2 single-phase is crucial for the stabilization of these electrodes.

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This paper studies stability properties of linear optimization problems with finitely many variables and an arbitrary number of constraints, when only left hand side coefficients can be perturbed. The coefficients of the constraints are assumed to be continuous functions with respect to an index which ranges on certain compact Hausdorff topological space, and these properties are preserved by the admissible perturbations. More in detail, the paper analyzes the continuity properties of the feasible set, the optimal set and the optimal value, as well as the preservation of desirable properties (boundedness, uniqueness) of the feasible and of the optimal sets, under sufficiently small perturbations.

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Carbon and graphene-based materials often show some amount of pseudocapacitance due to their oxygen-functional groups. However, such pseudocapacitance is generally negligible in organic electrolytes and has not attracted much attention. In this work, we report a large pseudocapacitance of zeolite-templated carbon (ZTC) based on the oxygen-functional groups in 1 M tetraethylammonium tetrafluoroborate dissolved in propylene carbonate (Et4NBF4/PC). Due to its significant amount of active edge sites, a large amount of redox-active oxygen functional groups are introduced into ZTC, and ZTC shows a high specific capacitance (330 F g−1). Experimental results suggest that the pseudocapacitance could be based on the formation of anion and cation radicals of quinones and ethers, respectively. Moreover, ZTC shows pseudocapacitance also in 1 M lithium hexafluorophosphate dissolved with a mixture of ethylene carbonate and diethyl carbonate (LiPF6/EC+DEC) which is used for lithium-ion batteries and lithium-ion capacitors.

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This paper outlines guidelines for policymakers pursuing financial stability in developing Asia. It aims at supporting Asian policymakers’ judgment by providing policy views and recommendations that are based on the analysis of the recent sequence of events in the United States and Europe and of earlier crisis episodes, including those in Asia during the 1990s

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Emerging signs of economic difficulties have greatly compounded the tasks facing new Chinese leader Xi Jinping in the year of horse. After his government rolled out a surprisingly ambitious blueprint for systemic economic reform in November last year, Xi, the general secretary of the Chinese Communist Party (CCP), now finds his agenda complicated by the urgent need to stabilize the overleveraged financial sector while taking the first steps to implement enough of his promised reforms to gain credibility.

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"June 1979."

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"Prepared for the Air Force Ballistic Missile Division, Headquarters Air Research and Development Command, under contract AF 04 (647)-309, Thermonuclear Propulsion Research."

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"SFOSR 748."

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The behavior of [alpha]-monoglycerides.

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"U.S. Atomic Energy Commission Contract AT(29-1)-1106."

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"August 1980."