Parent-child relationships as systems of support or risk for adolescent suicidality.

This study examined a process model of predicting adolescent suicidality. Adolescent emotional distress was hypothesized to mediate the relationship between parental behaviors and subsequent adolescent suicidality. The parental behaviors studied included parental warmth and parental hostility. A sample of 451 families from rural Iowa participated in this longitudinal study, which included both observational and self-report data. Models were tested with structural equation modeling. Adolescent emotional distress was found to be a mediating variable between paternal warmth and adolescent suicidality. Results indicated that maternal warmth predicted adolescent suicidality but not emotional distress. Parental hostility did not predict either latent variable. Clinical implications are provided. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Learning mathematics from procedural instruction: Externally imposed goals influence what is learned.

Do externally imposed achievement goals influence what children learn from procedural instruction? Third- and 4th-grade children's goals were manipulated toward either learning or performance. All children were then taught a procedure for solving mathematical equivalence problems (e.g., a?+?b?+?c?=?a?+?_). Children who were given learning goals were initially more likely to gain conceptual knowledge from the procedural lesson than were children who were given performance goals. After a 2-week period, however, children who were given performance goals exhibited the same conceptual gains as children who were given learning goals. Both initially and after the 2-week period, children who were given either goal were more likely to extend their knowledge beyond the taught procedure than were children who were not given goals. External sources such as teachers and parents may have the potential to foster children's learning by shaping children's goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

MMPI performance, response set, and the "self-concept hypothesis."

The MMPI can be viewed as communicating information about the self to a tester or institution. It is suggested that self-information is organized by self-concepts and that these more abstract self-concepts mediate specific responses to inventory items. This self-concept hypothesis provides an alternative to explanations emphasizing acquiescence response set, social desirability response set, or deviation set. In Study 1, replicated self-concept scales were constructed to index varied content dimensions of the MMPI. These scales, as well as the MMPI and the Marlowe-Crowne Social Desirability Scale, were administered to 83 neuropsychiatric (NP) patients and the results factor analyzed. Inclusion of self-concept markers produced an unusually differentiated factor solution, with self-concept dimensions accounting for two-thirds of the explained MMPI variance. In Study 2 these procedures were replicated with a larger (201 Ss) and more heterogeneous group of respondents (NP patients, participants in alcoholism programs, and college students) and additional self-concept measures. Results support the conclusions that no evidence exists for additional and important self-concept dimensions within the MMPI item pool and that the MMPI acts mainly as a medium for the transmission of self-concept information and that self-concepts mediate and organize specific item responses. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thermomechanical Responses of Microcracks in a Honeycomb Particulate Filter

Manufacturing honeycomb-structured catalysts require a careful understanding of the microstructure of the solid substrate and its dependence on thermal-processing conditions. Herein, it is the thermal responses of microcracks in an uncoated microcracked aluminum titanate honeycomb catalyst is investigated by analyzing the material's resonance frequency using the high-temperature impulse excitation technique. The resonance frequencies are presented as Young's modulus values to avoid sample size effects. Dynamic Young's modulus measurements show closed-loop hysteresis due to microcracks healing and reopening, causing a reversible response. The hysteresis is further used to understand microcracks’ dependence on critical thermal-processing conditions used in a catalyst manufacturing plant, including peak operating temperature (800–1000 °C), dwell period (1–3 h), and heating rates (1–5 °C min⁻¹). Microcracks are observed to have two healing responses: instantaneous and delayed healing. Both responses significantly influence the design of catalyst manufacturing. Complete reopening of microcracks from their healing temperature (1150 °C) is a very time-consuming process (50–60 h). However, it is shown in the analysis that microcrack relaxation is a critical phenomenon that must be considered in quality-controlled environments.     

Improvement of Poly(lactide) Ductile Properties by Plasticization with Biobased Tartaric Acid Ester

Diethyl l -tartrate (DET) is used as a biobased plasticizer for poly(lactide) (PLA) formulations with improved ductile properties without compromising biodegradation. Different weight percentages (wt.%) of DET in the 0–50 wt.% range are added to PLA by melt compounding and subsequently processed by injection molding. The effect of wt.% DET on mechanical, thermal, thermo-mechanical, morphology, biodegradation, and crystallinity is studied. Addition of 20 wt.% DET leads to a noticeable increase in elongation at break up to values of 567%, which is quite an interesting result considering the extreme brittleness of PLA. These results are verified by field emission scanning electron microscopy (FESEM) images, where filament-like structures are observed, indicative of an effective plasticization. Differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA) show that the glass transition temperature of PLA is drastically decreased down to values of 23 °C for the sample with the highest amount of DET (50 wt.%), thus increasing its ductility and processability. Fourier-transformed infrared spectroscopy (FTIR) spectra show that there exists chemical interactions between PLA and DET. Finally, the biodegradability analysis proves that the developed blends are fully biodegradable, achieving complete disintegration after 49 days. It is observed that DET enhanced the disintegration rate of PLA.     

Study of the flow behavior of polymer-natural fiber suspensions in the power law validity range

The melt flow properties of PVC suspensions with henequen, coconut and bovine leather, in their raw condition, and after extraction of all their low molecular weight substances were studied. The experimental results show that, at the strain rates employed, the behavior of the suspensions is described by a power law (η = mγ^n–1). It is important to mention that in the present work we do not restrict our analysis to the evolution of the suspension Newtonian viscosity with the fiber concentration (as commonly is reported in the literature), but a more complete analysis is performed by describing the evolution of the consistency (m) and the power law (n) indices with the fiber concentration. Both indices were evaluated using a technique previously developed. The flow index (n) presents an anomalous behavior, it increases when the fibers are incorporated into the melted matrix at low fiber concentrations. This unexpected behavior is very different from that commonly reported in the literature and is apparently due to the flexibility of fibers. Moreover, the influence of the fiber extractable materials on the behavior of these suspensions was also evaluated. It was found that these latter materials apparently influence the value of the consistency index (m) of suspensions, at fiber concentrations above the critical pigment volume fraction; however, they do not have a significant effect on the power law index (n). Concerning the mechanical behavior of composites molded from the previous suspensions, it was found that when the fiber content augments, their elastic modulus increases, but their tensile strength falls. This behavior, however, could be improved by increasing the adhesion between the fibers and matrix.     

Lactose recovery from Panela cheese whey: Effect of whey acidification on spontaneous and stirring-induced crystallisation

This work aimed to investigate the kinetics, yield, size and composition changes in lactose crystals when Panela cheese whey was acidified (pH 3.80) or slightly alkalinised (pH 6.89) before being subjected to spontaneous or stirring-induced crystallisation. At pH 3.8, the crystallisation was accelerated, and the incorporation of salts and proteins in lactose crystals decreased. Nevertheless, these conditions induced the formation of amorphous lactose. In contrast, at pH 6.89 and under stirring conditions, the amorphous lactose was not formed and gave a high crystallisation yield (∼25 g of lactose per Kg of whey) with ∼80% of lactose recovery.