Elaboration Conditions Research Articles

Three-dimensional simulation of CVD diamond film growth

As often reported in the case of CVD diamond synthesis, the elaboration conditions strongly affect the quality of the deposit interms of roughness, grain boundary quantity, structural defect density or non diamond phase insertion. It is recognised that this quality mainly depends of the texture evolution. To our knowledge, numerical simulations of this growth model that allow the diamond film quality to be predicted do not exist. In this way, we have developed a three-dimensional computer simulation of diamond growth. This numerical model is based on the homothetic growth of single diamond crystals in an Euclidean space and the selection of the enveloping surface obtained after the crystal interpenetration. By this way and in the limit of the exposed hypotheses, it is possible to build the topographies and to simulate its theoretical evolutions in the case of textured films synthesised on scratched silicon wafers according to the growth conditions such as the nucleation density, the growth rate ratio α = √3(V100/V111) or the synthesis time. We have particularly studied the ratio R{hkl} = (S{100}/S{100} + S{111}) of the topography according to the synthesis time, in order to follow the evolution of surface morphology.

Nanocrystallized thin films of transition metal obtained by low energy cluster beam deposition

Nanocrystallized thin films of iron obtained from low energy cluster beam deposition (LECBD) have been produced by adjusting different source parameters and elaboration conditions in an attempt to control the size distribution of supported clusters, In all cases, the films exhibit a nanostructure characteristic of the LECBD technique (mean 5 nm-diameter of the particles) and only the percentage of oxide in the form of a thin skin surrounding the particles changes. The specific magnetic behavior of these weakly correlated entities is described by ferromagnetic resonance and magnetization measurements. We showed that the magnetic properties of these cluster assembled materials can be interpreted using the random anisotropy model with a scale law related to grain size. The increasing interest of the scientific community in the magnetism of “small particles” 1 is mainly driven by their potential application as high density storage devices 2,3. From the Stoner criterion, the size and the first-neighbor number reduction would be favourable to ferromagnetism in transition metals. In this context, metallic clusters are interesting for their large surface volume ratio but they are very oxygen reactive. By varying the elaboration conditions (vacuum quality, substrate temperature, size distribution of the incident clusters…) we obtained nanostructured iron-films by Low Energy Cluster Beam Deposition (LECBD). This paper is mainly concerned with the structural and magnetic properties of these original cluster assembled materials. The laser vaporization source operating in the laboratory of Lyon 4 allows the production of an intense cluster beam in a wide range of size (from few to a thousand atoms per cluster), to synthetize thin films of any kind of materials even the most refractory. Roughly, the plasma created at the laser impact on the iron rod, is thermalized by a synchronized high pressure (5 bars) helium pulse. The nascent clusters are then rapidly quenched during the following isentropic expansion into the vacuum (10 −4 torr) chamber containing the source. The size distributions of clusters are checked by time-of-flight mass spectrometry before deposition. The deposit of neutral clusters at low energy on various substrates are subsequently realized after the retraction of the time-of-flight acceleration grids. This type of source produces cold clusters and we succeeded previously in the stabilisation of very low size fullerenes 4. In particular we deposited C 20-clusters without fragmentation on the substrate in order to produce original diamondlike structures 4.

Primacy and Recency in Recognition of Odours and Recall of Odour Names

This study examined the serial position curve for recognition of odours and recall of odour names, both with and without instructions for verbal elaboration. Participants were allocated to one of two experimental conditions, either with instructions to rehearse verbally the stimuli or with no elaboration instructions. After presentation of 17 odours, either recognition or free recall of the odours was tested immediately after presentation of the last target odour. Recognition showed evidence of primacy for the verbal elaboration condition and recency for both instruction conditions. Recall of odour names showed evidence of primacy for the verbal elaboration conditions and recency for both conditions. Instructions to verbalize did not significantly affect over-all performance for either test condition.

Implicit memory for textual materials

As a word moves from isolation in a list to being contextually bound in meaningful discourse, its probability of priming in tests of implicit memory decreases. The present experiments explore whether considerable priming effects can be revealed with conceptual tests of implicit memory as compared to perceptual tests. In the study phase, meaningful actions were described within a coherent text. In Experiment 1 subjects elaborated half of the actions by visual imagery. In Experiment 2, subjects elaborated the actions by enacting them symbolically. In both experiments, subjects in a control condition were simply required to read the same activities. In Experiment 2, a further group of subjects had to detect orthographic errors. The results demonstrated reliable effects of implicit memory in terms of associations with verbs repeated from the studied text. This form of repetition priming for textual materials in a conceptual test of implicit memory was enhanced by both types of elaboration. A word-stem completion task for the same targets revealed a less pronounced and inconsistent priming effect, uninfluenced by both types of elaboration. But the latter form of perceptual priming was found to be more pronounced within the error-detection condition. Measures of explicit memory showed similar effects of elaborative encoding conditions but there were some dissimilarities to measures of implicit memory, too. In general and in accordance with a transfer-appropriate processing view, conceptual tests rather than perceptual tests may be more suitable for detecting effects of implicit memory within the domain of text processing.

Using elaborative interrogation to facilitate acquisition of factual information in cooperative learning settings: One good strategy deserves another

AbstractThe primary purpose of this study was to determine whether providing 6th‐grade students with cooperative elaborative interrogation instruction would facilitate learning relative to providing them with cooperative learning, elaborative interrogation or reading‐for‐under‐standing instructions. All students were presented with 36 factual statements about six animals. Cooperative elaborative interrogation students were instructed to work collaboratively and use their prior knowledge to state why each fact is true. Cooperative learning students were told to work collaboratively to learn target materials, while elaborative interrogation students were instructed to generate answers to the why questions on their own. Reading‐control students were also on their own and instructed to read the animal facts for understanding. For immediate free recall and immediate associative matching tests, students in the experimental conditions outperformed those in the control condition. Cooperative elaborative interrogation and elaborative interrogation students maintained this advantage on a 30‐day follow‐up associative matching test, with elaborative interrogation students maintaining a significant advantage relative to reading controls on a 60‐day associative matching follow‐up. (There was also a strong trend favouring the cooperative elaborative interrogation condition on this 60‐day measure.) The quality of the ‘why’ answer affected learning: Generating and listening to scientifically correct answers that used relevant prior knowledge to clarify target information was associated with better memory for facts than were other types of study responses. Students in this study learned the most when they were explicitly directed to activate relevant prior knowledge that supports and clarifies new information–processing that occurs following either small‐group or individual elaborative interrogation instruction.

Electrochemical intercalation of sodium ions into fullerene

Electrochemical intercalation of sodium ions into C 60 or C 60 C 70 mixtures has been obtained in solid state cells working with a ionic conducting polymeric electrolyte. Low speed cyclic voltammetry and low intensity galvanostatic charge experiments give evidence for five successive redox states, as previously noticed for lithium ion intercalation. Reduction potentials of fullerene are strongly dependent on the experimental elaboration conditions of the composite working electrode (fullerene associated with a binding material) and on the open circuit voltage of the cell before intercalation. Preliminary X-ray and electron diffraction studies have allowed the identification of different Na xC 60 phases.

Effects of mood on high elaboration attitude change: The mediating role of likelihood judgments

AbstractTwo experiments examined the processes by which positive and negative mood states produce attitude change under high elaboration conditions. We hypothesized that under high elaboration conditions, mood would influence attitudes by affecting the perceived likelihood of occurrence for consequences presented in message arguments. In Experiment I, arguments were framed positively, and positive mood led to greater perceived likelihood of the consequences and more favourable attitudes than negative mood for subjects high in need for cognition (NC). In Experiment 2, arguments were framed either positively or negatively, and a mood × frame interaction was obtained on attitude and likelihood judgments for high‐NC subjects. That is, positive mood led to marginally greater perceived likelihood of positive consequences but to lower likelihood of negative consequences as compared to negative mood. As a result, positive mood tended to lead to more persuasion than negative mood when the message was framed positively, but to less persuasion when the message was framed negatively In both experiments, path analyses supported the prediction that likelihood judgments mediated the impact of mood on attitudes for high‐NC individuals.

Improving Reasoning and Recall: The Differential Effects of Elaborative Interrogation and Mnemonic Elaboration

This investigation sought to determine whether elaborative interrogation techniques would facilitate recall of information relevant to, but not included in, mnemonic and representational pictures. Fifty-three adolescents with learning disabilities or mild mental retardation were taught information about nine reasons for dinosaur extinction, ranked in order of plausibility. In the direct teaching condition, students were provided with each ordered reason and an explanation for why that reason may have resulted in dinosaur extinction. In the elaborative interrogation condition, students were provided with each ordered reason and prompted and questioned to provide an explanation for each. In the mnemonic elaborative interrogation condition, students were provided with mnemonic peg-words to facilitate recall of the ordered reasons for dinosaur extinction and also coached and prompted to provide explanations. Students' recall of ordered reasons was higher in the mnemonic elaborative interrogation condition, and students in the two elaborative interrogation conditions recalled more explanations than did students in the direct teaching condition. Further, students in both elaborative interrogation conditions more accurately linked reasons with explanations for those reasons. Findings are discussed with respect to previous findings of mnemonic instruction. Implications for teaching students with mild cognitive disabilities are provided.

In situ resistance measurements of YBaCuO thin films during the oxygenation process for various elaboration conditions

For YBaCuO films sputtered on polycrystalline YSZ, resistance monitoring during various oxygenation processes is reported. Ex situ rapid thermal annealing is considered first and compared with regular long annealing. A common feature is a temporary liquid phase state from which the superconducting material nucleates. In situ elaboration is then commented, while stressing upon possible parasitic superionic conductivity of the substrate.

Does Stimulus Elaboration Potentiate Exposure in vivo Treatment? Two Forms of One-Session Treatment of Spider Phobia

The hypothesis that elaboration of the phobic stimulus potentiates exposure in vivo treatment was put to the test in a clinical experiment. Forty-one female spider phobics, who applied for treatment, were randomly allocated to one of two conditions. In both conditions a 2.5 hour therapist-directed exposure treatment was given. In the elaboration condition Ss were required to attend to and describe the objective features of the spider constantly. In the non-elaboration condition the therapist tried to prevent this. A manipulation check suggested that Ss in the elaboration condition had indeed elaborated more extensively on the objective features of the spiders during exposure than Ss in the non-elaboration condition. However, Ss in the elaboration condition practised with somewhat fewer spiders than Ss in the non-elaboration condition, probably because of the time the elaboration took. Contrary to the hypothesis, elaboration did not potentiate either short-term or long-term effects of the exposure treatment. It seems superfluous to let patients elaborate on the phobic stimulus during exposure in vivo treatment: the processing of phobic stimulus information which is needed for an effective treatment seems to occur spontaneously when the patient engages in exposure in vivo exercises.

Nonstoichiometry in Ternary Oxides and Materials Science

The phenomenon of nonstoichiometry has been extensively studied in binary and ternary oxides. It includes many different aspects strongly connected with order-disorder phenomena. The models developed for oxides have been successfully applied to other nonstoichiometric compounds. Besides its basic interest in crystal chemistry, the nonstoicbiometry is of outstanding significance in materials science. Some examples are described: high temperature superconductors, superionic conductors, lasers and non linear optical materials. Not only the properties but also the conditions of elaboration and crystal growth are strongly dependent on the nonstoichiometry.

Synthesis and Stabilization of Hexagonal Boron Nitride Materials

AbstractBoron nitride presents many interesting properties for high temperature applications: high specific modulus, high electrical resistivity, electromagnetic transparency and strong chemical stability. However synthesis and densification by liquid or gas phase reactions (CVD, CVI or plasma processes) required for high technology applications (thermal shield, protective coating, microwave windows) are difficult to bring into play because material characteristics are strongly dependent on elaboration conditions. Boron nitride ultrafine powder synthesized by gas phase reaction in RF plasma (using NH3 and BCh3 at 800-1400°C) and composites obtained using a rapid densification process (vapor phase infiltration using trichloroborazole compound as precursor) have been studied. In both cases post synthesis heat treatment had to be performed in order to get stabilization of the material, and to avoid its hydrolysis. The stability has been related to the physical characteristics of the material. Thermodynamical studies using Gibbs energy minimization calculations were helpful to determine synthesis and heat treatment conditions.

Positive mood and persuasion: Different roles for affect under high- and low-elaboration conditions.

Two experiments examined the processes by which positive mood influences attitude change under high and low message elaboration conditions. To examine elaboration, Experiment 1 included individuals who differed in their need for cognition, and Experiment 2 manipulated the relevance of the message. In each study, Ss were exposed to a persuasive communication following a positive or neutral mood induction. In both studies, positive mood produced more positive attitudes toward the advocacy, but positive mood influenced the positivity of Ss' thoughts only under high-elaboration conditions. Path analyses showed that positive mood had a direct on attitudes in the low-elaboration conditions but influenced attitudes indirectly by modifying the positivity of thoughts in the high-elaboration conditions. Does a positive mood facilitate persuasion? Many of the initial studies addressing this question suggested that manipulations inducing a positive mood either just before or during a persuasive communication increased the likelihood of attitude change (e.g., Biggers & Pryor, 1982; Dribben & Brabender, 1979; Srull, 1983). These main effect findings were so consistent that in reviewing the work on positive affect and persuasion, McGuire (1985) concluded that Persuasive impact is greater if the person is in a happy, benevolent mood when the message comes, noshing on peanuts and soda (Janis, Kaye, and Kirschner, 1965), watching a good program (Krugman, 1983), and with pleasant musical background (Galizio and Hendrick, 1972), an appropriately scented other (Baron, 1983), a smile on one's face (Laird, 1974), nodding one's head (Wells and Petty, 1980), or relaxed in posture (Petty, Wells, Heesacker, Brock, and Cacioppo, 1983). (p. 285) Since 1985, however, the picture has become more complicated. In particular, recent studies have found that positive

Characterization of the EPR new generation polycrystalline silicon flat plates

Abstract Two years ago, the EPR photocells photovoltaic efficiency was 7% without antireflection coatings. The starting material consisted of 3N5 silicon powder and two crystallization steps were necessary to obtain multicrystalline ribbons. Actually, after increasing the material quality, this efficiency has reached 9.4%. This paper deals with the electrical and mechanical characterization of a new generation EPR flat plates obtained with only one step of crystallization. Three parameters are used to note the evolution of the plate quality as a function of the pulling conditions. The diffusion length which appears to be between 40 and 100 μm, the majority carrier mobility of the order of 25 cm 2 V −1 s −1 and the thermal residual stresses which are between 30 and 120 MPa. A computer aided driving of the electron beam is set up to establish the best thermal elaboration conditions and so eliminate defects and stresses: the goal is to obtain a photovoltaic efficiency up to 12%.

The Committee Assignment Process and the Conditional Nature of Committee Bias

The view that congressional committees tend to be biased subsets of their parent chambers provides the foundations for a substantial body of theoretical literature on distributive politics and legislative structure. More recent revisionist work suggests that committees composed of preference outliers are in fact rare. We reject the categorical account of preference outliers a priori and elaborate conditions under which committees should be unrepresentative of their parent chambers. We argue that the most widely available and frequently used data—floor roll call votes—are inappropriate to the task of assessing outlier predictions in any form. Finally, we conduct a differentiated set of hypothesis tests within one policy jurisdiction to illustrate the characteristics of evidence and analysis necessary to evaluate alternative theoretical accounts of legislative organization. The appearance of policy-relevant biases in congressional work groups, we conclude, is not so much rare as it is conditional, and we suggest several conditions on which future models of legislative organization should build.

Influence of elaboration on the microstructure and on the electrical and magnetical properties in YBaCuO ceramics

The microstructure of the high Tc superconductors is known to have a great effect on the electrical and magnetical properties. In order to correlate the elaboration conditions with the microstructure and physical properties, different YBaCuO ceramic superconductors have been prepared using various treatment conditions. The microstructure has been characterized by optical, scanning and transmission electron microscopy techniques (SEM, TEM, STEM). Chemical analyses have also been performed. The ceramics present various grain sizes. The 123 phase is sometimes associated with the 211 or with a phase presenting a barium deficiency and a copper excess. Different kinds of extended defects such as intergranular phases, stacking faults and dislocations have been observed. Room temperature resistivity, Tc, transition width, Hc 2 w, transport critical current density and magnetic shielding have been measured. Microstructures and superconducting properties appear to be strongly linked.

The effect of encoding task on memory for sentence pairs varying in causal relatedness

Subjects read pairs of sentences varying in degree of causal relatedness and then recalled one sentence of each pair given the other as cue. When subjects read for comprehension, recall was a quadratic function of causal relatedness. When subjects wrote an elaboration sentence for each pair, recall did not vary with causal relatedness. When subjects studied each pair for 30 s, recall again varied with causal relatedness. When recall was delayed, performance dropped more steeply in the comprehension and study conditions than in the elaboration condition. The results support a model in which elaborations are the critical factor influencing the shape of the recall function. Other models based on strength or quality of links or on reconstructive strategies are also discussed.

Influence of the elaboration and dehydration conditions of Fe(III) hydrous oxides on the characteristics of resulting α-Fe2O3 powders

Abstract Fine powders of α-Fe 2 O 3 were obtained from precipitation of Fe 3+ ions in aqueous solution, drying and calcination. After characterization of the intermediate and final products, it appeared that their properties depend strongly on the ageing of the initial precipitate in the solution. For example, all the powders obtained from fresh precipitates are constituted of agglomerated fine particles, whereas those obtained after ageing of the precipitates show large particle sizes, little agglomeration and microstrains. On sintering, the powders obtained from aged precipitates are those with the highest ability to densify. We believe that these differences in morphology and properties originate in the fixation of variable amounts of crystallization water on the hydrous oxides, followed by the formation of micropores, and a subsequent increase in the specific area, when this water is released upon calcination.

Elaborative interrogation effects on children's learning of factual content.

In 2 experiments children in Grades 4-8 learned facts under different instructional conditions. Control Ss were given base sentences containing facts and were permitted to study them as they wished. In some conditions fact sentences were accompanied by elaborations (e.g., an explanation of why a stated animal lived in a stated locale). Ss in the elaborative interrogation conditions attempted to construct their own reasons for why the facts held true. Ss in the imagery conditions constructed internal imaginal representations for each (e.g., an image of a stated animal living in the stated locale)

The Effect of Vivid Attributes on the Evaluation of Alternatives: The Role of Differential Attention and Cognitive Elaboration

The differential attention model and the cognitive elaboration model suggest vivid information has certain properties that exert greater influence on attitudinal judgments than does nonvivid information. To test these models, subjects evaluated alternatives described in terms of vivid and nonvivid attributes and elaborated on the material in high and low elaboration conditions. Our results demonstrate disproportionate influence for vivid versus nonvivid attributes included in the same description only in the high elaboration condition. Findings suggest that cognitive elaboration may be a necessary condition to produce an effect for vividness on attitudes.