bluuebunny/crossref_metadata_2025 huggingface dataset:
Some Properties of the Visual Imagery System Investigated through Backward Spelling
Authors: Hampson P. J. , Morris P. E.
Published: July 2007

Kosslyn (1973) and Kosslyn, Ball and Reiser (in press) have claimed that a quasi perceptual “scanning” process operates on visual images. Lea (1975) has suggested that this process should be redescribed in terms of iteration through an underlying list structure. It is known that images are subject to capacity limitations. This restriction of processing capacity suggests a model of imagery in which only information displayed in the image may be scanned, while iteration operates between such successive information displays. Three experiments on backward spelling from images support this view. Words of greater length involve more iteration problems. In Experiment I, backward spelling took longer than forward spelling for 8-letter but not for 4-letter words. Experiment II provides evidence for a directional scanning process, using a Brooksian interference technique. Experiment III demonstrates that the structure of the internal representation affects the manner in which it is iterated and that subjects can modify their iteration strategies.
The Relationship between Reaction Time and Intensity in Discrete Auditory Tasks
Authors: van der Molen M. W. , Keuss P. J. G.
Published: July 2007

The effect of signal intensity upon reaction time (RT) was studied in three auditory RT tasks in which the signal was a tone of high or low frequency. Experiment I showed the well-known negative gradient with intensity of simple RT when the subject was instructed to ignore the frequency and give the same response to both tones. But when the subject had to discriminate the frequency in a choice RT task, the RT/intensity relationship appeared to be U-shaped. Experiment II showed that when the subject was required to make a response to one signal but withhold it for the other, a task which requires discrimination of the frequency of the tone but removes the necessity to choose between overt responses, no increase in RT at high intensities was obtained. The results indicate that it is the response choice stage rather than the stimulus encoding stage which is retarded at higher energy levels. Experiment I also demonstrated that visual and auditory leading signals have similar facilitating effects without affecting the RT/intensity relationships.
Memory for Urban Geography
Authors: Byrne R. W.
Published: July 2007

Consistent patterns of errors are found in estimations of distances and angles along urban routes, even among subjects who know the areas well. These patterns can be used to discover the organization of the knowledge we use to find our way around in everyday life.

In the first experiment, 80 undergraduates estimated by ratio scaling the walking distances between pairs of locations in St. Andrews. Routes varied independently in their location, number of major bends, and length. Relative overestimation of length was found with routes in the town centre, with routes having several major bends, and (perhaps as an experimental artifact) with short routes. In the second experiment, 30 Cambridge residents estimated the angles between pairs of roads, by drawing the configuration of roads at their junctions. The real angles were either in the range 60–70° or 110–120°. All the estimates differed little from 90°, regardless of the true magnitude of the angle.

The implications of these findings for theories of mental representation of largescale space are discussed. A model is supported in which a spatial area is represented as a “network-map”, consisting of strings of locations forming a net of paths known to be traversable, but vector distance is not preserved.
Language Organization and Language Change in Bilinguals
Authors: Rees Olav A.
Published: July 2007

Two experimental studies with bilingual speakers examined the influence of (I) semantic organization across language, (2) input language change and (3) output language change on speech encoding during a sentence completion task. The first study used fluent Welsh-English bilinguals while the second used fluent French-English bilinguals; all subjects were at school in the U.K. A model proposed how subjects with different degree of overlap in bilingual semantic organization achieved functional separation of the two languages. Predictions derived from this were tested and were substantially confirmed for both groups of bilinguals. It was concluded that subjects have different degrees of overlap in semantic organization of their two languages and that this influences speech encoding where input or output language changes are present.
An Analysis of Illusion Components with ⌞ and ⊥ - Figures in Active Touch
Authors: von Collani Gernot
Published: July 2007

The influence of radial movement in haptically explored ⌞ and ⊥-figures is investigated by tilting them from the frontoparallel to the horizontal plane. Inclining an upright ⌞-figure towards the horizontal plane leads to an illusion that increases with the degree of inclination (Experiment I). The same curve, only shifted upwards, is found with a ⊥-figure (Experiment II), indicating an additive bisection effect. A theoretical function relating illusion magnitude and angle of inclination is presented. The results confirm an interpretation of the illusion in terms of radial and tangential components of arm movements. The implications of these results are discussed in relation to theoretical explanations of the haptic and visual form of the horizontal-vertical illusion.
Integration of Information in Visual Search
Authors: Prinz Wolfgang
Published: July 2007

Two experiments studied how information about the nontarget items in a visual search task is used for the control of the search. The first experiment used the detection of “hurdle” stimuli to demonstrate that efficient memory representations of the context items can be established within each particular trial. This finding is explained by a model for the short-term integration of context information. The second experiment which varied the complexity of the local but not the global context provided some information about the nature of the integration operations involved. In its final version the model postulates two stages of processing with independent mechanisms of integration. Spatial integration at the first stage deletes repetitions within small samples. Temporal integration at the second stage stores and primes the memory representations of the context items over larger intervals. It is assumed that transient temporal integration within trials is mediated by the same mechanism that underlies permanent temporal integration between trials.
The Relative Importance of Responses to S+ and S− in Simultaneous Discrimination Learning
Authors: Mullins G. P. , Winefield A. H.
Published: July 2007

Earlier research indicated that errors were more important in discrimination learning than correct responses (the Moss-Harlow effect). This conclusion was based on a variety of experimental designs each of which had basic methodological problems, usually involving novelty or order effects. A circular apparatus which allowed the simultaneous presentation of several different stimuli was used to study discrimination learning with S + and S − differentially weighted. It was found that variability in S − was more detrimental to discrimination learning than variability in S + although this finding depended on the presence of a constant stimulus. The results were interpreted as supporting the proposition that in discrimination learning rats learn more to avoid S− than to approach S+.
Left and Right Visual Field Superiority for Letter Classification
Authors: Jonides John
Published: July 2007

Two letter classification experiments examine the hypothesis that lateral asymmetries in perceptual processing are sensitive to subtle changes in task demands. The first experiment reports a right visual field superiority for an easy letter classification, but a left field superiority for a difficult classification using the same population of stimuli. Experiment II demonstrates that the right field superiority can be reversed if the easy classification trials are embedded among more difficult trials. The implications of these results for theories of hemispheric localization are discussed.
Feedback in Discriminative Avoidance Learning: Mechanistic versus Cognitive Views
Authors: Galvani Peter F.
Published: July 2007

Presentation of a feedback stimulus, a non-aversive event never paired with shock, following an avoidance response has been found to be an effective reinforcer in avoidance learning. Alternative formulations of the feedback effect, one a version of the traditional S-R mechanistic, two-factor theory and the other a cognitive (informational) theory, were evaluated with a view toward determining which type of formulation provides a more viable explanation of avoidance learning. The conclusion reached, however, was that both informational and fear-reduction positions operationalize their critical concepts in the same manner, and to date there are no empirical grounds for distinguishing these different views.
Accessing Ambiguous Words during Sentence Comprehension
Authors: Holmes V. M.
Published: July 2007

In five experiments visual processing of sentences containing either a more frequent or a less frequent usage of an ambiguous word was examined. When prior or subsequent context was pragmatically related to the relevant sense of the ambiguous word, sentences intending the more frequent sense produced longer ambiguity detection times and shorter immediate comprehension times than sentences intending the less frequent sense. This relative frequency effect was not obtained in comprehension of corresponding unambiguous sentences containing relatively high or low frequency unambiguous synonyms of the senses. These results suggest that access of ambiguous word-senses tends to occur in order of relative frequency, and that multiple access of senses tends only to occur for low frequency usages. When the preceding verb imposed selection constraints on which sense could follow, the frequency effect did not occur consistently; and it was virtually eliminated when biasing context took the form of a previous sentence containing an unambiguous synonym of the relevant sense. Implications for models of access of unambiguous words in sentences, as well as for models of processing ambiguous sentences, are considered.
Changes in Immediate Memory Strategy under Induced Muscle Tension and with Time of Day
Authors: Folkard Simon
Published: July 2007

It is suggested that the influence of arousal on immediate memory may, at least in part, be mediated by changes in strategy, such that subjects are less likely to rely on cumulative subvocal rehearsal of the items under high arousal. Experiment I found a detrimental effect of induced muscle tension on immediate memory, but only when subjects were free to engage in such rehearsal, and not under either enforced vocalisation or articulatory suppression. Experiment II manipulated strategy by instruction, and compared immediate memory at 10.30 (low arousal) with that at 19.30 (high arousal). A 10.30 superiority in immediate memory was found when no specific instructions as to how to either encode/store, or recall, the items were given. This superiority disappeared under four of the five alternative types of instruction where subjects were told to group and rehearse the items during presentation, or to recall the items in a specific order, or both. It is concluded that manipulations commonly held to affect arousal level may indeed influence the type of strategy that subjects spontaneously adopt. This may be responsible for some of the inconsistencies in the arousal and memory literature.
A Search for Perceptual Differentiation Produced by Nondifferential Reinforcement
Authors: Hall Geoffrey , Channell Stephen
Published: July 2007

In each of four experiments (three using pigeons as the subjects and one using rats) animals in an experimental condition were given exposure to a pair of stimuli that subsequently they were required to discriminate between. During the exposure phase response to either stimulus was consistently followed by reward. These subjects were uniformly found to be retarded in learning the discrimination when compared with control subjects that received equivalent pre-training in the absence of the critical stimuli. These results provide no support for the suggestion that stimuli may become “perceptually differentiated” during the pre-training phase but are consistent with the proposal that novel stimuli possess a high level of associability that declines as a result of experience.
Dichotic Pairing of Digits with Tones: High Performance Level and Lack of EAR Effect
Authors: Teng Evelyn Lee
Published: July 2007

Fifty-six subjects each listened to four types of dichotic input: digit-digit, tone-tone, digit (left ear)-tone (right ear), and tone (left ear)-digit (right ear). When digits were paired with tones, performance improved substantially over that with digit-digit and tone-tone input, and material-specific ear differences disappeared. The results indicate that both capacity limitation and an advantage of the contra-lateral over the ipsilateral input appear only when inputs from the two ears compete for the same kind of processing.
Adaptation to Visual Displacement with Active and Passive Limb Movements: Effect of Movement Frequency and Predictability of Movement
Authors: Mather Jennifer A. , Lackner James R.
Published: July 2007

Three experiments were performed to evaluate the influence of active and passive limb movements on adaptation to visual displacement. Over a wide frequency range (0·5-1·25 Hz) with constant amplitude, 30°, significant adaptation was achieved with active and passive movements. When arm movement frequency was constant at 1·0 Hz but amplitude of movement was varied, less adaptation was achieved for both active and passive movements than when amplitude was held constant. Even at a frequency above that of most naturally occurring limb movements, 1·67 Hz, and with variable amplitude motion, significant adaptation was achieved with active and passive limb movements. These findings emphasize the importance of visual-proprioceptive discordances for adaptation to visual displacement when only sight of the hand is permitted. Significant differences did not appear between the active and passive movement conditions in any of the experiments.
A Simultaneous Shift in Apparent Direction: Further Evidence for a “Distribution-Shift” Model of Direction Coding
Authors: Mather George , Moulden Bernard
Published: July 2007

When two superimposed moving dot fields are presented simultaneously, their axes of movement appear shifted away from each other. The shift only occurs when the two directions are within 90° of each other, and is directly comparable to that which results from adapting to one and testing on the other direction. This effect is taken as further evidence for a distribution-shift model in the direction domain. It is argued that the currently accepted model of movement detection, which restricts itself to comparisons only between oppositely-tuned direction detectors, should be elaborated to include comparisons across a very wide range of detectors.
Structure of the Visual Array and Saccadic Latency: Implications for Oculomotor Control
Authors: Heywood Simon , Churcher John
Published: July 2007

Subjects were required to look saccadically at single targets selected from one- or two-dimensional arrays of different numbers of possible alternative targets. Saccadic latencies varied with the direction but not the distance of the target, with practice and with individual subject. The effect of number of alternatives was complex, and it is suggested that an important factor influencing saccadic latency is not the number of targets per se but the number of possible directions in which a saccade may have to go.
Varieties of Residual Experience
Authors: Weiskrantz L.
Published: July 2007

The apparent discrepancy between the results of animal studies and clinical findings on the effects of occipital lobe damage became even greater with the results of animal experiments over the past 20 years in which subjects showed significant residual vision. But there is now evidence that the human subject can also show considerable residual capacity. It appears to be extremely helpful to use forced choice discrimination methods and specific training, as with animals, rather than to depend on verbal commentary by the human subject, who may be unaware of his discriminative capacity. Where man and monkey can be compared, it would appear that they are not qualitatively different, and that residual capacity is biased for detection and localisation rather than identification. Preliminary evidence is presented on the incidence of “blind-sight” and related aspects of residual function, including examination of different dimensions such as form, detection, movement, orientation, and spatial localisation within field defects. Some of these dimensions appear to be dissociable, but each also seems capable of disconnexion from the subject's own commentary and acknowledgement.
Behaviour of Rats During Selfinitiated Pauses in Feeding and Drinking, and during Periodic Response-Independent Delivery of Food and Water
Authors: Roper T. J.
Published: July 2007

In Experiment I rats deprived of either food or water were given free access to food or water respectively, and their behaviour was observed during self-imposed pauses in feeding or drinking. In Experiment II food or water were delivered according to fixed-time 30-s and fixed-time 60-s schedules, and the behaviour of the rats was observed during the interreinforcement intervals imposed by these schedules. In both experiments the temporal pattern of those activities that occurred during pauses in eating differed from the pattern of activities occurring during pauses in drinking; and with both food and water the temporal pattern of activities during self-imposed pauses in consummatory behaviour in Experiment I proved a good predictor of the pattern of activities during schedule-imposed interreinforcement intervals in Experiment II. This suggests that intermittent schedules permit the occurrence of those activities that are normally closely associated with the consummatory behaviour in question. In Experiment II certain activities that occurred towards the end of the interreinforcement interval were found to be enhanced relative to baseline level, but there was no enhancement of activities occurring near the beginning of the interval. This is contrary to Staddon's (1977) account of schedule-induced behaviour, and suggests that schedule-induction is not as common as has sometimes been supposed.
Spatial Memory and Response Strategies in Rats: Age, Sex and Rearing Differences in Performance
Authors: Einon Dorothy
Published: July 2007

Rats reared in social isolation made more errors on a spatial memory task and made errors earlier in each trial than socially reared rats. The difference in performance only occurred when rats were isolated prior to 50 days of age, and it survived IOO days of subsequent social housing. IOO days of isolation after 50 days of age did not influence performance on the spatial memory task. Subsequent experiments suggest that spatial abilities may not differ between groups but that isolates are slower to learn to make a particular response and to locate a particular arm when spatial and response cues are irrelevant. In contrast to previous experiments, clear response strategies were seen in the present experiments. These were prevalent in the young (54-days-old) rats, were less common at 90 days and had completely disappeared by 180 days. Response strategies were more common in male rats and in socially reared rats.
Short-Term Retention of “Surprising” Events by Pigeons
Authors: Colwill Ruth M. , Dickinson Anthony
Published: July 2007

Terry and Wagner (1975) have suggested that the short-term retention of information about an event is enhanced if the occurrence of the event is made unexpected or surprising. Three experiments tested this idea using delayed conditional position (Experiment I) and colour discriminations (Experiments II and III). The subjects were pigeons and the presentation of food was the target event to be remembered. Choice of one of two simultaneously presented stimuli was reinforced if the retention interval had been initiated by presentation of target food. Contrary to Terry and Wagner's claim, retention was superior on probe test trials in Experiments I and II if the presentation of the target food was preceded by a previously established signal for food (CS+) rather than by a stimulus which had not been paired with food (CS-). Experiment III systematically manipulated the signalling conditions used during initial discrimination training. Retention was better following a CS+ presentation if the target food had been signalled during initial discrimination training but worse if the food presentation had been unsignalled. These results do not favour the idea that retention of an event is directly affected by whether or not the target event is surprising.
Bilingualism and Lexical Representation
Authors: Kirsner Kim , Brown Heather L. , Abrol S. , Chadha N. K. , Sharma N. K.
Published: July 2007

Forty-eight Hindi-English bilinguals completed two blocks of trials where each trial involved presentation of a letter string requiring a lexical decision. In the first block subjects were exposed to 22 words and 11 non-words in either English or Hindi. In the second block the original words were repeated in either the same language or in the alternative language. In this block the old (repeated) words were mixed with 22 new words, and 22 non-words. Twelve subjects were included in each of the four groups given by the factorial combination of blocks and languages. Reaction time in the lexical decision task was facilitated when words were repeated in the same language (109 and 125 ms in the English-English and Hindi-Hindi groups respectively), but little or no facilitation was observed in the inter-lingual conditions (-22 and 23 ms in the Hindi-English and English-Hindi conditions respectively). The results support the view that lexical representation in bilinguals is language-specific.
Internet Adoption and Use
Authors: Madden Gary , Savage Scott J. , Coble-Neal Grant
Published: July 2007

Network economics suggests that Internet growth may be explained by an externality. This study empirically tests for the presence of such an externality, and analyses a cross-section of Internet subscribers to identify adopter characteristics, and applications fuelling early subscription. The results confirm that the establishment of a secure base of commercial users generates endogenous growth. Further, the analysis of Internet subscribers suggests that access pricing and the availability of valued applications are important factors for inducing subscription.
Towards a Knowledge Economy? Changes in New Zealand's Information Work Force 1976‐1996
Authors: Engelbrecht Hans-Jürgen
Published: July 2007

The New Zealand economy has undergone tremendous change since 1984, being transformed from one of the most regulated OECD economies to one of the most deregulated. Recently, the concept of a 'knowledge economy' has received attention in New Zealand, and policies are now aimed at creating such an economy. This study contributes to the debate by exploring the changes in the country's information work force in recent decades, and by attempting to relate them to some of the major features of the economy which have to be addressed in the search for an appropriate knowledge economy model.
On Poetic Reason of State: Benjamin, Baudelaire, and the Multitudes
Authors: McLaughlin Kevin
Published: July 2007

The paper starts from Walter Benjamin's interpretation of the phrase "reason of state" that Paul Valéry applies to Charles Baudelaire's poetry. After exploring how this phrase points to the interconnections between poetry and politics in Benjamin's writings on lyric, from the early essay on Hölderlin to the later commentaries on Baudelaire, it goes on to explicate Baudelaire's reading of a book on the concept of reason of state by the Italian philosopher and historian Giuseppe Ferrari. The connections between Baudelaire's aesthetic theory of la modernité and Ferrari's politico-historical theory of reason of state are analyzed as a basis for reading a set of prose poems composed by Baudelaire during the period when he read Ferrari. Special attention is given to the poem from the Petits poëmes en prose entitled "Les Veuves" ("The Widows").
The Other Face of Gershon Shaked
Authors: Schwarz Igal
Published: July 2007

An obituary for Gershon Shaked (1929–2006), a major authority in Israeli Literary studies, the author of the master-narrative of secular Hebrew literature. The article points to a disparity between Shaked's recognized status in the country and his view of himself as a subversive, balloon-puncturing eiron, critical of the exalted Apollonian stance in literature as well as in criticism.
Adaptive multivariable optimal predictive control
Authors: McDermott Patrick E.
Published: July 2007

A multivariable control strategy that incorporates long‐term prediction is presented. The future control policy is calculated so as to minimize a weighted sum of squared input and output deviations from reference values. Constraints on inputs are explicitly incorporated in the minimization to allow optimum operation of the process. The control approach is developed to allow either adaptive operation or operation using a constant model that has been identified on‐ or off‐line. Several simulation examples are presented to demonstrate the robustness of the controller to unknown load dusturbances, process‐model mismatch, time‐varying dynamics and non‐minimum phase characteristics.
Ein Beitrag zur Epitaxie von Alkalihalogeniden auf Calcium‐ und Bariumfluorid
Authors: Kleber W. , Ickert L. , Ahrens E.
Published: July 2007

Alkalihalogenide (LiF, NaF, NaCl, NaBr, KCl, KBr, KJ) wurden im Hochvakuum auf (111)‐Flächen von Calcium‐ und Bariumfluorid aufgedampft. Vor dem Bedampfen wurden die Trägerkristalle an der Luft gespalten. Die orientierte Kristallisation der isotypen Alkalihalogenide auf den beiden isotypen Substraten wird auf Grund zahlreicher elektronenmikroskopischer Aufnahmen beschrieben und diskutiert.

Außer der (111)‐Orientierung treten noch (100)‐Orientierungen und bei den Fluoriden die (110)‐Orientierung auf. Als Grundtendenz wird bei den Verwachsungsgesetzen der Einfluß übereinstimmender Symmetrie der simultanen Netzebenen deutlich. Bei Variation von Trägertemperatur und Übersättigung kommt die Wirkung von Oberflächenstufen und Adsorptionsschichten auf die Epitaxie zum Ausdruck. Die Keimdichte zeigt einen Zusammenhang mit der Gitterenergie der Depositkristalle. Es wird der Versuch unternommen, einige Fragen vom Standpunkt der kinetischen Theorie der Epitaxie zu deuten.
Hochtemperaturdiffraktometrie von Pulvermaterialien auf ZrO2‐Basis
Authors: Filatov S. K. , Frank‐Kamenetzkij V. A.
Published: July 2007

Es wird eine Methode zur Hochtemperaturdiffraktometrie (bis 1300 °C) monokliner Pulvermaterialien auf ZrO2‐Basis beschrieben. Beispiele werden angeführt. Besondere Aufmerksamkeit gilt der Genauigkeit der Indizierung der Debye–Scherrer‐Aufnahmen und der Abschätzung der Fehler bei der Bestimmung der Parameter nach einer vereinfachten Methode. Die Bedingungen für die Hochtemperaturdiffraktometrie tetragonaler und kubischer Materialien auf ZrO2‐Basis werden erörtert.
Experimentelle Verfolgung des BaSO4‐ und BaCrO4‐Fällungsvorganges
Authors: Kleber W. , Wagner G. , Hähnert M.
Published: July 2007

Die Bariumsulfat‐ und Bariumchromatabscheidung wird durch kombinierten Einsatz elektrischer und elektronenmikroskopischer Messungen verfolgt. Die Übereinstimmung der durch den Leitfähigkeitsverlauf registrierten Teilvorgänge der Fällung mit den aus elektronenmikroskopisch abgeleiteten Kristallisationsstadien (Keimbildung, Kristallwachstum, Ostwald‐Reifung) ist gut.
Die dreidimensionale Orientierungsverteilungsfunktion und Methoden zu ihrer Bestimmung
Authors: Bunge H.‐J.
Published: July 2007

Um die Orientierung eines Kristalles in einer vielkristallinen Probe vollständig beschreiben zu können, benötigt man mindestens drei Parameter. Zwei Parameter beschreiben die Orientierung einer bestimmten Kristallrichtung im Raum, der dritte legt eine Drehung um diese Richtung herum fest. Die Orientierungsverteilung der Kristallite wird daher durch eine Verteilungsfunktion von drei Variablen beschrieben. Diese Funktion ist nicht direkt meßbar, sie kann jedoch aus Einzelorientierungsmessungen oder aus Polfiguren berechnet werden. Diese beiden Methoden wurden zur Bestimmung der Orientierungsverteilung der Kristallite in kaltgewalzten Kupfer‐ und Stahlblechen verwendet. In beiden Fällen ergaben sich hohe Orientierungsdichtewerte nur innerhalb eines gewissen Schlauches im Orientierungsraum. Die Textur kann am besten durch das von Wassermann und Grewen eingeführte Modell der Fasertexturkomponenten beschrieben werden. Es wurden quantitative Kriterien zur Abschätzung des experimentellen Fehlers von Polfiguren entwickelt. Sie zeigen, daß mit Neutronenbeugung gemessene Polfiguren besonders geringe experimentelle Fehler aufweisen. Die aus der Textur berechneten Werte des Elastizitätsmoduls stimmen gut mit den experimentell ermittelten überein.
Feldelektronenmikroskopische Untersuchung der heterogenen Silberkeimbildung
Authors: Paunov M. , Michailov E.
Published: July 2007

Die heterogene Silberkeimbildung auf W‐Spitzenunterlage wird untersucht. Es wird eine Silberdampfquelle benutzt, die gleichmäßige Bedampfung der Spitze erlaubt. Die kritischen Adatomkonzentrationen für die 111‐ und 110‐Gebiete werden zu 2,3 · 1014 At cm−2 bzw. 1013 At cm−2 bestimmt. Mit dem von Gretz für die 100‐Gebiete bestimmten Wert wird die Reihenfolge der kritischen Adatomkonzentrationen mit n n > n aufgestellt. Auf Grund der Temperaturabhängigkeit der τkr werden die Aktivierungsenergien zur Desorption berechnet – Q = 25,700 cal mol−1 und Q = 27,000 cal mol−1. Es wird bei niedrigen Temperaturen eine Erhöhung des τkr‐Wertes festgestellt. Das wird als eine Abnahme der Wachstumsgeschwindigkeit interpretiert.
Crystal Structure of K2Cr2O7, and a Structural Aspect of its Morphology
Authors: Kuz'Min E. A. , Iljukhin V. V. , Kharitonov Yu. A. , Belov N. V.
Published: July 2007

The structure of triclinic crystals of K‐bichromate is fully determined. The structure was separated from the three‐dimensional P(uvw) Patterson function by using the strong (multiple) peaks of the latter. The carefully worked out algorythm allowed the separation of 16 points of the fundamental set from the vector set (eight K atoms and eight Cr atoms). The remaining (light) atoms of the structure were localized at the second stage by reference to these latter. For the structure with 66 independent coordination parameters the divergence factor R over the entire volume of the sphere of 2500 non‐zero reflections hk0‐hk7 and 0kl‐3kl is equal to 0138.
X‐ray diffraction topography study of defects in potassium dihydrogen phosphate (KDP) and ammonium dihydrogen phosphate (ADP) single crystals
Authors: Lutsau V. G. , Fishman Ju. M. , Res I. S.
Published: July 2007

The direct observation of dislocations in KH2PO4(KDP) and NH4H2PO4 (ADP) single crystals has been performed by X‐ray diffraction topography methods. Crystals were grown by slow cooling of stirred solutions on different types of seed crystals. It is demonstrated that the main sources of dislocation generation are the seed surface, inclusions of mother liquor and foreign particles. Space orientation of dislocations and their Burgers vector directions are found. In regions far from the seed the dislocation density did not exceed 103 cm−2 and a number of specimens with cross‐sectional areas up to several cm2 were free from dislocations. Dynamical phenomena characteristic of the diffraction in a weakly deformed lattice have been observed over a wide range of μ t at the boundaries between the {101} and {100} growth sectors having different impurity contents. Several crystals show also nonuniform impurity distribution in the form ot the layers parallel to growing face (growth layers).
Über den Zusammenhang zwischen Kompressibilität und Härte von Mineralen und nichtmetallischen kristallinen Substanzen
Authors: Beckmann G.
Published: July 2007

Es wird versucht, die Kompressibilität χ feindispers verteilter, nichtmetallischer Einschlußsubstanzen mit Hilfe von Mikrohärtebestimmungen (nach Vickers) abzuschätzen. Unter Beachtung von thermoelastischen Beziehungen, namentlich aus der Bindungstheorie der Kristalle und der Diamantstruktur, führt eine logarithmische Darstellung χ (log HV) zu einem Büschel linearer χ‐Funktionen. Daneben läßt sich (zur Anwendung im technischen Bereich) eine Umrechnungsbeziehung zwischen Mohshärte und Vickershärte und umgekehrt angeben.
Die Bestimmung der intrakristallinen Magnesium‐Eisen‐Verteilung in Orthopyroxenen mit röntgenstrukturanalytischen Mitteln
Authors: Schubert G.
Published: July 2007

Von metamorphen und vulkanischen Orthopyroxenen wurden die Intensitätsdaten (hk0) und (h0l) aus integrierten Weißenbergaufnahmen mit MoK‐Strahlung gewonnen. Die Gitterkonstanten wurden aus geeichten Weißenbergaufnahmen mit CuK‐Strahlung ermittelt. Der Chemismus für die metamorphen Proben ergab sich aus Elektronenstrahlmikroanalysen. Mit Hilfe von Elektronendichteprojektionen ϱ(xy) und ϱ(xz) konnten die Literaturangaben der Atomkoordinaten bestätigt, bzw. zum Teil neue bestimmt werden. Die intrakristalline MgFe‐Verteilung zwischen den Kationenlagen M1 und M2 ist einmal aus Elektronendichteprojektionen und zum anderen aus Strukturfaktorrechnungen gewonnen werden. Allgemein ist eine Preferenz des Eisens gegenüber der verzerrten M2‐Lage festzustellen. Die metamorphen Orthopyroxene weisen einen hohen Ordnungsgrad der MgFe‐Verteilung auf. Der vulkanische Orthopyroxen zeigt dagegen eine weniger geordnete Verteilung. Die Gründe für die Unterschiede werden diskutiert.
Stable Layer Systems with Diffusion Barrier Arrangements in Thin Film Technology
Authors: Langer H.‐D. , Schneider H. G.
Published: July 2007

The physical and chemical interaction processes in thin film arrangements are followed by different ageing phenomena which influence the stability of their physical parameters. These determine the reliability of the electronic components existing of thin films.

On the base of own experimental investigations on tantalum and its oxides, beryllium oxide and tantalum‐rhenium alloys technological aspects and the application of new materials for lowering the ageing intensity are considered.
Point defects in barium‐sodium niobate (Ba2NaNb5O15) crystals
Authors: Arsenev P. A. , Linda J. G. , Sarafanova M. N. , Tikhonov V. E. , Farshtendiker V. L.
Published: July 2007

The paper deals with studies of the nature and the kinetics of point defect formation and dissociation in barium‐sodium niobate single crystals as a result of vacuum heat treatement and ionizing Co60 γ‐radiation.
Kristallstruktur und katalytische Wirksamkeit
Authors: Engels S.
Published: July 2007

Es werden Zusammenhänge zwischen Strukturaspekten und katalytischer Wirksamkeit für Aluminiumoxide, röntgenamorphe Alumosilicate, Zeolithe, Aktivkohlen und Metalle diskutiert.
Über das elektrolytische Wachstum und die Auflösung von Silbereinkristallen unter potentiostatischen Bedingungen. Einfluß der Zwillingsgrenzen
Authors: Kristev I. , Velinov V.
Published: July 2007

Die Wachstums‐ und Auflösungsgeschwindigkeit von Silbereinkristallen wurden bei potentiostatischen Bedingungen untersucht. Es wurde festgestellt, daß die Auflösung bedeutend schneller als das Wachstum verläft, was mit der Wirkung solcher zusätzlicher aktiver Stellen bei der Auflösung erklärt wird, die keinen bedeutenden Einfluß auf die Wachstumsgeschwindigkeit des Einkristalls haben.

Es wird gezeigt, daß die Zwillingsgrenzen einen starken Einfluß auf die Wachstumsgeschwindigkeit haben. Bei der Auflösung ist ihre Wirkung viel schwächer und kann nicht registriert werden.

Der asymmetrische Verlauf der Wachstums‐ und Auflösungsvorgänge ist am stärksten bei niedrigen Potentialen und wird besonders in Abhängigkeit von der Morphologie bei den Normalkristallen ausgedrückt.

Mit Erhöhung der Überspannung wird der Einfluß der Zwillingsgrenzen auf die Wachstumsgeschwindigkeit verstärkt.
The Precipitation of Sparingly‐Soluble Alkaline‐Earth Metal and Lead Salts with Slow Development of Supersaturation (Slow Anion and Hydroxyl Ion Addition): Kinetics of Nucleation and Induction Periods
Authors: Packter A. , Sahay S.
Published: July 2007

Barium and lead sulphate and chromate precipitations were studied at 20° to 95°C at precipitation rates varying from 10−3to 10−7ionl−1sec−1: the supersaturation was developed by slow direct addition of anion to metal nitrate solution and by neutralisation of equivalent metal salt in excess acid solution. Slow heterogeneous nucleation occurred onto particles dispersed within the aqueous solution. The nucleation rate at any time wasequation imageWhereknis the rate constant for heterogeneous nucleation,N∞is the maximum number of potential nuclei,ntis the number of nuclei after timet,I.Ptis the ionic product (Cmt)(Cmt) and 2π is the number of metal salt ions in the critical nucleus, generally eight.

Crystal growth started after induction periods (t̄) at times just after the times for maximum rate of formation of nuclei. The induction periods (t̄) for precipitations from solutions of initial cation concentrationcM0varied with precipitation rate (R) according to the relation, where γ = π/(π + 1) andk1(the unit reciprocal induction period) =.

Nucleation rate constants for different precipitations were estimated from thek1values and are tabulated. For slow precipitations by direct anion addition, the rate constants were lower for precipitation from solution of the salt of greater solubility. The rate constants for slow precipitation of metal chromates from acid solution were far lower than those for slow precipitation by direct chromate addition. Rate constants decreased somewhat with rise in precipitation temperature.
Verteilung von Aktivatoren in Laser‐Kristallen
Authors: Kvapil Jiří , Perner B. , Kvapil Josef
Published: July 2007

Es wird der Einfluß der Züchtungsbedingungen auf den Verteilungskoeffizienten und auf die radiale Verteilung von Aktivatoren in Rubinen und Yttrium‐Aluminium‐Granaten beschrieben. Der Verteilungskoeffizient von Chrom hängt von allem von der Zusammensetzung der Züchtungsatmosphäre ab, während von ihr der Verteilungskoeffizient von Neodym unabhängig ist. Der Gradient der Aktivatorkonzentration im Querschnitt der Kristalle ist der mit der Phasengrenze parallelen Komponente des Temperaturgradienten proportional. Die Form der Phasengrenze der nach der Czochralski‐Methode gezüchteten Kristalle paßt sich der Form der Isothermen in der Schmelze an und die mit der Phasengrenze parallele Komponente des Temperaturgradienten ist vernachlässigbar. Die Phasengrenze der nach der Verneuil‐Methode gezüchteten Kristalle ist gewöhnlich unabhängig von der Form der Isothermen.
Luminescence of (GaAl)As layers grown by temperature gradient liquid phase epitaxy
Authors: Kühn G. , Zehe A. , Sutter D. , Streubel P. , Neels H.
Published: July 2007

In this paper the growth of AlxGa1–xAs layers with nearly constant composition along their thickness is described. By means of electroluminescence and cathodoluminescence measurements recombination mechanisms connected with the presence of Si are discussed. The aging behaviour of the light emitting diodes is supposed to depend on the AlAs content of the layers and to be connected with the diffusion of acceptors in the p‐n junction region.
Zur Kristallographie der martensitischen ε → α‐Gitterumwandlung
Authors: Schumann H.
Published: July 2007

Manche Eisen‐ und Kobaltlegierungen wandeln nach der martensitischen Reaktion γ → ε → α um. Die hexagonalen ε‐Martensitplatten sind nur sehr dünn. Infolgedessen ist das Wachstum der α‐Martensitkristalle in Richtung [0001]ε eingeschränkt, und die ε → α‐Umwandlung kann als ebenes Problem behandelt werden. An Hand metallographischer Untersuchungen konnten Größe, Form und Lage der α‐Martensitkristalle nach Abkühlung ohne und mit äußerer Spannung ermittelt werden. Auf der Grundlage des Orientierungszusammenhanges werden Transformationsformeln für Kristallrichtungen angegeben sowie die Volumen‐ und Formänderungen bei der ε → α‐Umwandlung berechnet.
Zu Problemen des Innenboart‐Trennschleifens
Authors: Hofmann H. M. E. , Schulz H. O. F.
Published: July 2007

Es werden einige Ergebnisse vorgestellt, welche die Leistungsfähigkeit und Grenzen der bisher üblichen technologisch‐phänomenologischen Betrachtungsweise des Trennschleifens demonstrieren. Gleichzeitig ergibt sich eine Reihe von Ansatzpunkten für weitere, den Trennprozeß analysierende Untersuchungen.
Züchtung und optisches Verhalten von BiOCl‐Kristallen
Authors: Žemlička J. , Markov J. F.
Published: July 2007

Es werden die Wachstumsbedingungen für BiOCl‐Kristalle aus der Dampfphase ermittelt und deren Absorption und Raman‐Spektren gemessen.
Über die Zerfallsstruktur des Ni‐Katalysators und die Ni(C)‐Phase des Diamanten bei der Diamantsynthese
Authors: Vavrda J.
Published: July 2007

Es wird die Natur intermediärer Phasen im NiC‐System diskutiert und die Konzentrationsabhängigkeit des spezifischen Atomvolumens vom C‐Gehalt ermittelt. Die Zerfallstrukturen der hohen Drücken und Temperaturen unterworfenen NiC‐Proben werden metallographisch und röntgenographisch untersucht. Mit Hilfe der asymmetrischen Pulvermethode wird das spezifische Atomvolumen der Ni(C)‐Zerfallsphase und der Ni(C)‐Begleitphase des Diamanten und daraus die C‐Konzentration erhalten. Es wird festgestellt, daß die Ni(Cy)‐Begleitphase des Diamanten — die feste Lösung des Kohlenstoffs im Nickel am Prozeßende ≈︁ 3 At.% C enthält. Daraus wird geschlossen, daß diese Phase das Produkt des letzten Zerfallsstadiums des mit Kohlenstoff übersättigten Katalysators ist und sie keine besondere Rolle bei der Keimbildung des Diamanten spielt.
Grundlagen der Theorie des Parakristalls und ihre Anwendungsmöglichkeiten bei der Untersuchung der Realstruktur kristalliner Stoffe
Authors: Hosemann R.
Published: July 2007

Es wird ein kurzer Überblick über die Grundvorstellungen der Theorie des Parakristalls und ihre Anwendung in der Röntgen‐Feinstrukturanalyse gegeben. Weiterhin werden die Beziehungen erörtert, die zwischen der Theorie des Parakristalls und den Flüssigkeitstheorien von ORNSTEIN, ZERNIKE und ZERNIKE, PRINS sowie der von KRIVOGLAZ eingeführten Beschreibung gestörter Kristalle bestehen.
Eine Methode zur genauen Messung des Massenschwächungskoeffizienten für Röntgenstrahlung
Authors: Löschau W.
Published: July 2007

Das Verfahren besteht darin, daß die zu untersuchende Substanz (z. B. eine intermetallische Verbindung) mit Säure aufgeschlossen und anschließend mit Wasser so weit verdünnt wird, daß die Schwächung bei gut meßbarer Dicke der durchstrahlten Lösung in einem gut meßbaren Rahmen bleibt. Durch Herstellen einer Vergleichslösung ohne die Meßsubstanz, aber mit der gleichen Säuredichte, kann die Schwächung der Säure und des Wassers eliminiert werden. Analog ist das Verfahren bei wasserlöslichen Salzen. Aus dem hiernach erhaltenen (μ/ϱ)‐Wert kann mit der pyknometrisch bestimmten Dichte μ0 des kompakten Materials der Schwächungskoeffizient μ0 des kompakten Materials berechnet werden. Die praktische Meßanordnung mit einer Planküvette und das Auswerteverfahren werden beschrieben. Es wurden (μ/ϱ)‐Werte der intermetallischen Verbindung CaCu5 und von H2O auf diese Weise mit Maximalfehlern von ±1% bzw. ±0,5% bestimmt.
Das Dotieren aufgedampfter heteroepitaktischer Siliziumschichten
Authors: Ecke W. , Duda P.
Published: July 2007

Im Ultrahochvakuum aufgedampfte heteroepitaktische Siliziumschichten wurden auf ihr Dotierungsverhalten untersucht. Es wurde gefunden, daß beim Einsatz mehrerer Dotierungsverfahren ein großer Konzentrationsbereich der freien Ladungsträger eingestellt werden kann. Speziell wurden die gleichzeitige Aufdampfung von Silizium und der Dotierungsstoffe, Aluminium und Antimon, die Verdampfung von Silizium mit unterschiedlichem Borgehalt und die Diffusion von Phosphor und Lithium untersucht.
Surface tension of the molten stoichiometric InP
Authors: Popov A. S. , Demberel L.
Published: July 2007

The value of surface tension was determined to be 280 dyne/cm for stoichiometric InP at the melting point. The dependence of surface tension on phosphorus pressure was investigated too. The data permit to determine the optimum conditions for the floating zone process of InP.
Profile‐sapphire and its structural perfection
Authors: Dobrovinskaya E. R. , Litvinov L. A. , Pishchik V. V.
Published: July 2007

The paper is concerned with the growing of sapphire of various profiles and with the investigation of its structural perfection. It is shown that the kind of the crystallographic forms and the dislocation structure essentially depends on the degree of overheating of the melt. Near the surface of profiled crystals wide dislocation‐free zones (upto 200 μm) may be obtained. A dependence of the length of the mosaic block boundary on the rate of growing can be observed. A high ratio of the area of the radiating surface to the crystal volume gives the possibility of a rapid growing of profile crystals.
Growth of hollow Se–Te whisker crystals
Authors: Bhatt V. P. , Trivedi S. B.
Published: July 2007

On the basis of micro‐ and macro‐morphological studies the mechanism responsible for the growth of Se–Te whiskers has been suggested. It has been shown that Sc–Te whiskers grow by layer growth mechanism in which screw dislocation is not the source of step but the growth proceeds by two‐dimensional nucleation. This has been supported by the supersaturation data. The plausible mechanism for the growth of hollow whiskers has also been suggested.
Phillipsite‐type synthetic zeolite with high silica contents and accompanying phases
Authors: Cichocki A. , Grochowski J. , Lebioda Ł.
Published: July 2007

A zeolite of P type with a molar ratio SiO2 : Al2O3 of about 6 was obtained on laboratory and on enlarged scale, by synthesis carried out at 100°C in Na2OK2OSiO2Al2O3H2O system, without complexing agents. It was found that the products depend not only on the chemical composition of hydrogel but also on the kinetic factors such as: the material of the reactor wall, the amount of substrates taken for crystallization and stiring. It was found that the stability of zeolites increases in the order: L < T < Ch < P. The factors accelerating crystallization led to the more stable zeolites as products. The paper shows difficulties in implementing the laboratory results into an industrial production.
In‐situ investigations on the deformation, crack, and fracture behaviour of carbon materials in the scanning electron microscope
Authors: Irmer E. , Wetizig K. , Fischer G.
Published: July 2007

An attachment for scanning microscopes was developed in order to study the deformation, crack, and fracture behaviour of carbon materials during their electron optical observation. Thus the simultaneous registration of electron microscope images, stress‐strain‐curves and acoustic emission rates at different load regimes is possible. The combination of the mentioned methods allows a correlation between the macroscopic material behaviour and the microscopic processes taking place in the material under load. From the submitted experimental results it can be concluded that the fracture toughness of graphitic materials rises with a growing part of lamellar structure and with grain coarsening.
Covalent bonding effect on magnetic susceptibility in AIIIBV semiconductor compounds
Authors: Sirota N. N. , Vitkina Ts. Z.
Published: July 2007

On the basis of the expression for magnetic susceptibility of zinc blende semiconductors obtained earlier in the MOLKAO approximation (Sirota, Vitkina) the effect of the degree of covalency on the magnetic suceptibility is studied. The increase of covalency of bonding is shown to be accompanied by the shift of the center of gravity of the charge cloud to the center of bonding and by the increase of the Van Vleck paramagnetic term of the magnetic susceptibility.