LaCl3-based catalysts for oxidative chlorination of CH4

LaCl₃ is an active, selective and stable catalyst for oxidative chlorination of methane to methyl chloride. Selective conversion to methyl chloride can be achieved by limiting methane conversion, for example, by using an excess of methane in the feed. Methylene chloride and carbon monoxide are the main side products at higher methane conversion levels. Transient OCl⁻ anion, formed by oxidation of Cl⁻ in LaOCl and LaCl₃ with molecular oxygen, is proposed to be the active site for the initial step of methane activation. CO _x formation is proposed to proceed through the formation of adsorbed multiply substituted chloromethanes.     

Spatial and movement-based heuristics for encoding pattern information through touch.

Seven experiments investigated the heuristics people use to encode spatial pattern information through touch. Observers traced a tangible pathway with 1 hand and then answered questions about either the Euclidean line between the pathway endpoints or the pathway itself. Parameters of the Euclidean line were held constant, while characteristics of the felt pathway were manipulated. Exps I–IV showed that 72 blindfolded university students and 30 blind 18–65 yr olds increasingly overestimated the length of the Euclidean line as the length of the explored pathway increased, which indicated a movement-based heuristic for encoding distance. Exps V–VII, with 40 normal undergraduates, showed that judgments of the position of the Euclidean line did not vary with the position of the felt pathway or the extent to which it deviated from that line. Instead, results indicated that Ss relied on implicit spatial axes, which were movement independent, to judge position. Implications for theories of haptic encoding of spatial pattern and for the construction of tangible graphics displays are discussed. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Resource allocation and the attentional demands of letter encoding.

Evaluated evidence provided by W. C. Ogden et al (see record 1981-11851-001) against encoding automaticity when the 1st letter is not terminated after a brief exposure. Seven studies were conducted using 105 undergraduates. Evidence of encoding interference was found in the 1st 2 studies when the interval between the 2 letters was varied (50–2,000 msec), but this interference disappeared when there was a constant 1,000-msec interval between letters. On the basis of these findings, it was hypothesized that any momentary reduction in the resources demanded by the primary task would result in a real allocation of resources to the secondary task, which in turn would reduce the sensitivity of the secondary task to the demands of the primary one. This was tested by reducing resource allocation to the probe task at the time of encoding by reducing the expectancy (i.e., the probability) of probes in the temporal proximity of the 1st letter. This manipulation produced a large and significant increase in encoding interference. When the intensity of the tone (probe) was decreased from 70 to 60 db, the magnitude of encoding interference was further increased. Findings suggest that the magnitude of secondary task interference depends on within-trial changes in resource allocation between primary and secondary tasks. This possibility has general implications for dual-task methodology and the measurement of attentional demands. (39 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recombinant tumor necrosis factor enhances the locomotion of memory and naive B lymphocytes from human tonsils through the selective engagement of the type II receptor

Recent studies performed in mice knocked out for the tumor necrosis factor (TNF ), the lymphotoxin-alpha, or the type I TNF receptor (R), genes have shown that these animals display gross defects in germinal center (GC) formation, suggesting that members of the TNF and TNFR superfamilies are involved in the control of B-cell migration. Based on these premises, we have here investigated the effects of human recombinant (r) TNF on the polarization and locomotion of tonsillar B cells. rTNF increased the spontaneous polarization and locomotion of unfractionated tonsillar B lymphocytes in a dose-dependent manner by inducing a true chemotactic response. Memory (IgD-, CD38(-)) and naive (IgD+, CD38(-)), but not GC (IgD-, CD38(+)) B cells purified from total tonsillar B lymphocytes, showed a significantly higher locomotion in the presence than in the absence of rTNF. Accordingly, type I and II TNF receptors (TNFRs) were detected by flow cytometry on the surface of memory and naive, but not GC, B lymphocytes. Blocking experiments with monoclonal antibodies to type I or II TNFR showed that rTNF enhanced the spontaneous chemotaxis of memory and naive B cells through the selective engagement of type II TNFR. Finally, the TNF gene was found to be expressed in memory, naive and GC B lymphocytes; the cytokine was released in culture supernatants from the three B-cell subsets after stimulation. These data may support the hypothesis that human TNF is involved in the paracrine and perhaps autocrine control of B-cell migration in secondary lymphoid tissues.     

How good is the evidence for a production deficiency among learning disabled students?

[Correction Notice: An erratum for this article was reported in Vol 77(6) of Journal of Educational Psychology (see record 2008-10974-001). Figures 1 and 2 (p. 557 and 559, respectively) are reversed. The captions are correct, but Figure 1 should be above the caption for Figure 2 and Figure 2 should be above the caption for Figure 1.] Investigated the spontaneous use of mnemonic strategies by learning disabled (LD) and non-LD children and adolescents to examine whether LD Ss can be distinguished from their non-LD peers on the basis of strategy use and recall. In Exp I, 105 LD and 105 non-LD 9–15 yr olds were administered a picture study/recall task, in which the strategies of interest were categorical organization during study and clustering during recall. In Exp II, 140 LD and 140 non-LD 11–17 yr olds were administered a paired-associate recall task, in which the strategy of interest was elaboration. In both studies, LD Ss earned lower mean recall scores than did the non-LD Ss. As a group, LD Ss did not differ from non-LD Ss in the use of categorical organization during study but showed less categorical clustering at recall. Fewer LD Ss used elaboration. Despite these differences, recall and strategy use were not useful predictors of classification as LD or non-LD and were only weak to moderate correlates of academic achievement. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Exception handling bug hazards in Android

Adequate handling of exceptions has proven difficult for many software engineers. Mobile app developers in particular, have to cope with compatibility, middleware, memory constraints, and battery restrictions. The goal of this paper is to obtain a thorough understanding of common exception handling bug hazards that app developers face. To that end, we first provide a detailed empirical study of over 6,000 Java exception stack traces we extracted from over 600 open source Android projects. Key insights from this study include common causes for system crashes, and common chains of wrappings between checked and unchecked exceptions. Furthermore, we provide a survey with 71 developers involved in at least one of the projects analyzed. The results corroborate the stack trace findings, and indicate that developers are unaware of frequently occurring undocumented exception handling behavior. Overall, the findings of our study call for tool support to help developers understand their own and third party exception handling and wrapping logic.     

Spectral and chemical analysis of tropical forests: Scaling from leaf to canopy levels

Variation in the foliar chemistry of humid tropical forests is poorly understood, and airborne imaging spectroscopy could provide useful information at leaf and canopy scales. However, variation in canopy structure affects our ability to estimate foliar properties from airborne spectrometer data, yet these structural affects remain poorly quantified. Using leaf spectral (400–2500 nm) and chemical data collected from 162 Australian tropical forest species, along with partial least squares (PLS) analysis and canopy radiative transfer modeling, we determined the strength of the relationship between canopy reflectance and foliar properties under conditions of varying canopy structure.At the leaf level, chlorophylls, carotenoids and specific leaf area (SLA) were highly correlated with leaf spectral reflectance (r = 0.90–0.91). Foliar nutrients and water were also well represented by the leaf spectra (r = 0.79–0.85). When the leaf spectra were incorporated into the canopy radiative transfer simulations with an idealistic leaf area index (LAI) = 5.0, correlations between canopy reflectance spectra and leaf properties increased in strength by 4–18%. The effects of random LAI (= 3.0–6.5) variation on the retrieval of leaf properties remained minimal, particularly for pigments and SLA (r = 0.92–0.93). In contrast, correlations between leaf nitrogen (N) and canopy reflectance estimates decreased from r = 0.87 at constant LAI = 5 to r = 0.65 with randomly varying LAI = 3.0–6.5. Progressive increases in the structural variability among simulated tree crowns had relatively little effect on pigment, SLA and water predictions. However, N and phosphorus (P) were more sensitive to canopy structural variability. Our modeling results suggest that multiple leaf chemicals and SLA can be estimated from leaf and canopy reflectance spectroscopy, and that the high-LAI canopies found in tropical forests enhance the signal via multiple scattering. Finally, the two factors we found to most negatively impact leaf chemical predictions from canopy reflectance were variation in LAI and viewing geometry, which can be managed with new airborne technologies and analytical methods.     

Effects of dietary linolenate on the fatty acid composition of brain lipids in rats

Weanling male rats were fed hydrogenated coconut oil to induce essential fatty acid (EFA) deficiency. After 15 weeks, the rats were divided into six groups. Five groups were fed graded amounts of purified linolenate (18∶3ω3) with a constant amount of linoleate (18∶2ω6) for six weeks. Fatty acid composition was determined in brain lipids. Increasing dietary 18∶3ω3 resulted in a decrease in arachidonic acid (20∶4ω6), docosatetraenoic acid (22∶4ω6) and docosapentaenoic acid (22∶5ω6), whereas 18∶2ω6 and eicosatrienoic acid (20∶3ω6) were increased both in total lipids and phospholipids. These results suggest that dietary 18∶3ω3 exerts its inhibitory effect mainly on the desaturation of 20∶ω6 to 20∶4ω6 in brain lipids. Linolenate was undetectable in brain lipids from any dietary treatments. The levels of eicosapentaenoic acid (20∶5ω3) in groups receiving dietary 18∶3ω3 were not different from that of the group receiving no 18∶3ω3. These results indicate that, in the brain, 18∶3ω3 is rapidly converted mainly to 22∶6ω3 without being accumulated and imply that dietary 18∶3ω3 can modulate the level of precursor of diene prostaglandins (PG) but not that of triene PG in the rat brain.     

Fluorinated Hyperbranched Polymers as Additives in Cationic Photopolymerization

Summary: Different fluorinated hyperbranched polymers (HBP) were synthesized starting from fluorinated oxetanes and employed as additives in cationic photopolymerization of epoxy monomers. As previously observed for other hydroxyl containing HBP, they interact with the polymeric carbocation through a chain transfer mechanism inducing an increase in the final epoxy conversion. High gel content values (>96%) for the photocured films confirm that the HBP additive is tightly crosslinked to the polymeric network. In the presence of this fluorine‐containing HBP it is possible to influence the bulk properties, as well as, the surface properties. The fluorinated HBP tends to migrate to the surface inducing an increase of hydrophobicity.

The hyperbranched polymer used in this work.     

Safety assessment of a lithium target

This paper addresses the safety assessment of the lithium target of the International Fusion Materials Irradiation Facility (IFMIF) through evaluating the most important risk factors related to system operation and verifying the fulfillment of the safety criteria. The hazard assessment is based on using a well-structured Failure Mode and Effect Analysis (FMEA) procedure by detailing on a component-by-component basis all the possible failure modes and identifying their effects on the plant. Additionally, a systems analysis, applying the fault tree technique, is performed in order to evaluate, from a probabilistic standpoint, all the relevant and possible failures of each component required for safe system operation and assessing the unavailability of the lithium target system. The last task includes the thermal–hydraulic transient analysis of the target lithium loop, including operational and accident transients. A lithium target loop model is developed, using the RELAP5/Mod3.2 thermal–hydraulic code, which has been modified to include specific features of IFMIF itself. The main conclusions are that target safety is fulfilled, the hazards associated with lithium operation are confined within the IFMIF security boundaries, the environmental impact is negligible, and the plant responds to the simulated transients by being able to reach steady conditions in a safety situation.