How can Qualitative Comparative Analysis contribute to causal knowledge? The article's answer builds on the shift from design to models that the Structural Causal Model framework has compelled in the probabilistic analysis of causation. From this viewpoint, models refine the claim that a ‘treatment’ has causal relevance as they specify the ‘covariates’ that make some units responsive. The article shows how QCA can establish configurational models of plausible ‘covariates’. It explicates the rationale, operations, and criteria that confer explanatory import to configurational models, then illustrates how the basic structures of the SCM can widen the interpretability of configurational solutions and deepen the dialogue among techniques.

Benchmarking function modeling and representation approaches requires a direct comparison, including the inferencing support by the different approaches. To this end, this paper explores the value of a representation by comparing the ability of a representation to support reasoning based on varying amounts of information stored in the representational components of a function structure: vocabulary, grammar, and topology. This is done by classifying the previously developed functional pruning rules into vocabulary, grammatical, and topological classes and applying them to function structures available from an external design repository. The original and pruned function structures of electromechanical devices are then evaluated for how accurately market values can be predicted using the graph complexity connectivity method. The accuracy is found to be inversely related to the amount of information and level of detail. Applying the topological rule does not significantly impact the predictive power of the models, while applying the vocabulary rules and the grammar rules reduces the accuracy of the predictions. Finally, the least predictive model set is that which had all rules applied. In this manner, the value of a representation to predict or answer questions is quantified.

Considering a random binary tree with n labelled leaves, we use a pruning procedure on this tree in order to construct a β(3/2,1/2)-coalescent process. We also use the continuous analogue of this construction, i.e. a pruning procedure on Aldous's continuum random tree, to construct a continuous state space process that has the same structure as the β-coalescent process up to some time change. These two constructions enable us to obtain results on the coalescent process, such as the asymptotics on the number of coalescent events or the law of the blocks involved in the last coalescent event.

Introduction In Morocco the olive growers rely totally on pesticides to control the black scale Saissetia oleae, although this technique has adverse effects on natural enemies, on product quality and on the environment. However, the pesticides are not used efficiently because of ignorance of the developmental cycle of the insect, and of the periods of vulnerable instar presence. We studied these two parameters. Next, we tested the efficacy of the pesticide and we studied the effect of pruning on the scales as an alternative to chemicals. Materials and methods The seasonal trend of the black scale was studied in two olive orchards near Essaouira, in the west of Morocco, during 2005 and 2006. One of these orchards was subject to chemical treatment in 2007, while two new orchards were selected to study the effect of pruning on the scales. The evolution of crawler and nymph density on different olive tree organs was followed in order to discover their preferences for these different organs. Results and discussion The seasonal trend study showed the presence of one generation of S. oleae per year and the tendency to colonise young organs rather than old ones. The optimum of mobile instar population coincided with the beginning and the end of July. On the organs of the chemically-treated samples, numbers of crawlers and nymphs were highly reduced. The results showed a small-scale infestation in pruned trees compared with the unpruned trees (control). Conclusion. Though the chemical control has good results, pruning remains very efficient and can help improve the control of the black scale populations without harming the environment

Microglia are enigmatic non-neuronal cells that infiltrate and take up residence in the brain during development and are thought to perform a surveillance function. An established literature has documented how microglia are activated by pathogenic stimuli and how they contribute to and resolve injuries to the brain. However, much less work has been aimed at understanding their function in the uninjured brain. A series of recent in vivo imaging studies shows that microglia in their resting state are highly motile and actively survey their neuronal surroundings. Furthermore, new data suggest that microglia in their resting state are able to phagocytose unwanted synapses and in this way contribute to synaptic pruning and maturation during development. Coupled with their exquisite sensitivity to pathogenic stimuli, these data suggest that microglia form a link that couples changes in brain environment to changes in brain wiring. Here we discuss this hypothesis and propose a model for the role of microglia during development in sculpting brain connectivity.

Introduction. High–density orchards of ‘Amrapali’ mango trees become overcrowded and show progressive decline in yield after 14–15 years of planting; hence, trees require pruning for sustainable production. Reduction in yield in such orchards is due to poor light interception and a low photosynthetic rate, which influence vegetative growth, flower initiation, fruit set and, thereby, the fruit yield. Hence, to help design a tree canopy for optimum plant growth and yield, we studied the effect of pruning on light interception and on different leaf physiological parameters of ‘Amrapali’ mango trees under high density. Materials and methods. Sixteen-year-old trees of an ‘Amrapali’ mango high-density orchard were subjected to tipping and light, moderate and heavy pruning; un-pruned trees were used as control. The available photosynthetic photon flux (PPF) and leaf physiological parameters such as rate of photosynthesis, specific leaf weight (SLW) and leaf chlorophyll (Chl) content were measured in pruned and un-pruned tree canopies, following standard procedures. Results and discussion. The percent available PPF was greater in all pruned tree canopies than in un-pruned tree canopies; this could be due to tree openness caused by pruning. The light interception was lower at the lowest height of the tree canopy, probably because the center of the tree canopy was partially blocked by new growth or criss-cross branches. The rate of photosynthesis was greater in leaves that developed in pruned tree canopies than in those developed in un-pruned tree canopies, although there was no difference in SLW; this could be due to better light interception in pruned trees. In contrast, total leaf chlorophyll content was the highest in leaves that developed in un-pruned and tipped tree canopies; this may be due to increased shade owing to overlapping or crowding of tree canopies in these trees, indicating that mango leaves that developed in shade appeared to be more physiologically efficient at synthesizing chlorophyll than leaves that grew in the sun or on the sunny side. Conclusions. The studies indicated that pruning ‘Amrapali’ mango trees by removing about 10–15 cm of the top from old branches improves light penetration, which influences the leaf physiology considerably. Hence, it would be useful for designing high-density ‘Amrapali’ mango orchards to maximize productivity, although it requires additional studies to recommend a particular pruning intensity.

Introduction. The chataigne or breadnut, Artocarpus camansi Blanco, has high nutritive value but it is an under-utilised food source. Yield losses due to tree height and limited information on productivity are constraints to commercial production. Our study was undertaken to determine fruit yield and seed yield, the relationship between fruit size and seed yield, and the response of yield to pruning. Materials and methods. Fruit and seed yield data were collected from 1996 to 2002 from three seedling trees established at the University of the West Indies in Trinidad and Tobago in 1993. The trees were pruned in December 1998. Results. The highest fruit mass per tree (139.7 kg), fruit number per tree (126) and seed mass per tree (59 kg) were obtained in 5-year-old trees. Fruit and seed yields were significantly (P < 0.001) lower in the years after pruning. Fruit mass per tree was positively correlated with fruit number (r = 0.99). Seed mass per fruit was positively correlated with seed number per fruit (r = 0.87) and both variables had strong, positive correlations with mean fruit mass (r = 0.83 and r = 0.77, respectively) and fruit volume (r = 0.63 and r = 0.67, respectively). Discussion and conclusions. Chataigne fruit and seed yield potential is greater than originally estimated. Both are strongly related and selection for high seed number per fruit with more effective pollination, disease control and proper tree height management may further increase productivity. In the field, estimated fruit volume is the most practical indicator of seed yield.

Introduction. The distribution of shoots and fruits in the tree is an important consideration to improve peach cropping. Therefore, the effects of intensity of pruning were investigated for two years in trees with the same fruit load and, the following year, in trees with different fruit loads. Materials and methods. In an early-maturing peach orchard (cv. Alexandra), three pruning intensities were applied for three years: light, medium and severe. The first two years, the same fruit load was applied for the different pruning treatments; in the last year, three fruit loads per tree were tested: low, intermediate and high. Results and discussion. Increasing severity of pruning stimulated average fruit weight and fruit diameter, limiting (2nd year) or not (3rd year) fruit yield. Severe pruning also tended to enhance young shoot growth on the shoot bearing fruit and on the scaffold branch. Fruit diameter improvement with severe pruning might be therefore explained by the increase in vegetative growth likely to enhance available assimilates for fruit growth. However, severe pruning could favor an alternation in flower setting, as observed in the 2nd year. Increasing fruit load stimulated fruit yield, but, with the highest fruit load, no significant fruit yield enhancement was detected compared with the intermediate fruit load. On the contrary, average fruit weight and fruit soluble solids always decreased with increasing fruit load. Conclusion. Intensity of pruning and fruit load must be well adapted to ensure an appropriate peach production; excessive pruning and fruit load of an early-maturing peach cultivar should be avoided in order not to limit fruit yield and quality, respectively.

Introduction. Vegetative and fruit growth in fruit trees are differentially sensitive to water deficit during the season depending on the stage of fruit growth. Attempts have been made to evaluate the possibilities of using regulated deficit irrigation to control vegetative growth and save water in the fruit industry. Materials and methods. Effects of water stress (WS) and crop load (CL) on fruit growth and carbon assimilation rates were evaluated in a 7-year-old ‘Elegant Lady’ peach orchard. A completely randomized block design with 2 × 3 factors [irrigation with two levels (control and WS) and CL with three levels (light, commercial and heavy)] was used. Results and discussion. Both WS and CL affected fruit growth during the last stages but not early on. CL did not affect trunk water potential which was, however, significantly reduced by WS throughout the day and the season. Trunk water potential of water-stressed trees was lower than that of control trees throughout the day and the season regardless of CL. The magnitude of WS increased as the season progressed. Stomatal conductance, transpiration rate and CO2 assimilation rate were not affected by CL but were reduced by WS. The trees responded (acclimated) to stress by progressively reducing their transpiration rate as the severity of stress increased. For each irrigation regime, assimilation rates were similar for all three crop levels. This indicated the existence of alternate sinks for assimilates when CL was low, which compensate for the reduction of fruit sink activity resulting from fruit thinning. Conclusion. Water deficit reduced trunk water potential, stomatal conductance, transpiration and photosynthesis in ‘Elegant Lady’ peach trees. However, CL had a limited effect on these functions. There were good correlations between trunk water potential and either stomatal conductance or assimilation rate in water-stressed trees but not in control trees. This indicates a poor coordination between leaf functions in peach trees under optimal conditions. However, these relationships were stronger under WS conditions. Thus, water use efficiency appeared to increase under water deficit conditions.

One of the most fascinating aspects of brain research is the subject of language. As in many other cases, the malfunctions that occur in different persons for various reasons give us insight on the mechanisms that support our ability to talk, read and listen. Following the work of Plaut and associates, we deal with the dyslexia disorder, which is the overall name for a large number of reading disorders. A Boltzmann machine neural network scheme was trained to implement the nonlinear mapping task of graphic representation into semantic representation, which may model the brain sections responsible for the translation of a written word into meanings and syllables. After training, various types of lesions were applied and the performance of the network was tested in order to measure the effect of each lesion on the error rate and type distribution that were detected. The system's errors were classified into several categories and the distribution of errors between the categories was studied. Using the simulations, it is demonstrated that a finite scheduling process in the Boltzmann machine causes the distribution of the network's errors to be unique and different from its expected error distribution. The phenomenon is given a mathematical explanation rooted in the statistical mechanics basics of the Boltzmann machine. Test results suggest the localization of certain reading functions within the network. Comparison is made to relevant types of dyslexia and shows resemblance in major symptoms as well as in certain known side effects. (JINS, 2000, 6, 620–626.)