bluuebunny/crossref_metadata_2025 huggingface dataset:
Retention of Attended and Unattended Auditorily and Visually Presented Material
Authors: Martin Maryanne
Published: July 2007

In the first of two experiments investigating focussed attention, sets of four pairs of digits were dichotically presented to subjects who were instructed to attend to digits arriving in either the left or the right ear. Following presentation, two different report orders were used: attended followed by unattended, and unattended followed by attended. It was found that unattended items did not suffer from being recalled second rather than first. The serial position curve for unattended items was U-shaped. These results were interpreted as evidence that unattended items are not retained in a limited-capacity auditory buffer with a fast rate of loss. The experiment was repeated using visually presented pairs of letters. A similar pattern of results was obtained, consistent with the hypothesis that unattended items are recalled from a store with a large capacity and a very slow rate of loss.
The Basis and Implications of the Restoration of a Recency Effect in Immediate Serial Recall
Authors: Routh David A. , Frosdick Richard M.
Published: July 2007

When a spoken presentation of a supra-span sequence of to-be-remembered (TBR) items is followed immediately by a similarly-spoken non-TBR item (stimulus suffix) the typical salience of the terminal item in recall is almost destroyed. However, Salter (1975) observed restoration of salience when pre-terminal and terminal TBR items differed in category membership. Five experiments are reported which aimed to clarify the basis and locus of Salter's effect. Survival of salience for the heterogeneous item was found under the following conditions: with the occurrence of the item unpredictable from trial-to-trial (Experiment I); with enforced processing of the suffix (Experiment II); with performance of a secondary task during list presentation (Experiment III); with the requirement to retain both the location and identity of the item (Experiment IV); and with the item as the terminal member of a non-suffixed visual list (Experiment V). It is argued that the effect has a postcategorical locus, and that its origin is not in better registration (mediated by selective attention), but, rather, in the enhancement of retrieval (mediated by access to distinctive information encoded during presentation). It is suggested that the latter hypothesis may have wide application in accounting for many kinds of salience.
The Effects of Subsidiary Tasks on Memory Retrieval from Long and Short Lists
Authors: Okada Ronald , Burrows David
Published: July 2007

Burrows and Okada (1975) found that reaction time in an item recognition task was a monotonic but non-linear function of memory set size when set size varied from two to 20. A bilinear function with a steep slope for short lists and a shallow slope for long lists provided a good description of the data. Two experiments were conducted to determine whether the difference in slope between long and short lists arises from the extra attention devoted to, or rehearsal of, items within the span of immediate memory. Rehearsal of a prememorized list was discouraged by including a counting backwards task (Experiment I) or by presenting a second list of items that required processing (Experiment II). In neither experiment did the subsidiary task reduce the slope difference. It would appear that the slope difference is not a result of rehearsal of subspan lists.
Suffix Effects in Lists of Temporally Grouped Words
Authors: Penney Catherine G.
Published: July 2007

Two groups of university students were presented with auditory lists of temporally grouped words for recall. The lists were immediately followed by either a redundant suffix, a nonredundant suffix or no suffix. One group of subjects was instructed to recall the items in strict serial order; the second group was required to write the last items first, indicating the position of all items in the list. According to Kahneman's (1973) account of the suffix effect, the interfering effect of the suffix should be eliminated when the suffix is segregated in a different group or perceptual unit from the memory items. The results did not support the prediction from Kahneman's hypothesis. An alternative account of the suffix effect was presented.
Perception of Movement Patterns. Recognition from Visual Arrays of Distorted Patterns
Authors: Bairstow Phillip J. , Laszlo Judith I.
Published: July 2007

A review of literature indicates that the perception and memory of movement patterns with kinaesthesis might be expected to differ depending on whether a movement pattern is actively commanded or passively induced. In addition, it has been suggested that kinaesthesis is a gross sense in the absence of vision. An attempt was made to demonstrate differences between the perception and memory of actively commanded movement patterns, passively induced movement patterns, and visual patterns formed by a moving light. A visual recognition test was employed. While it was apparent that the recognition task was a sensitive one for testing the accuracy of pattern perception, no significant difference was demonstrated between the three movement conditions.
Phonemic Dyslexia: Errors of Meaning and the Meaning of Errors
Authors: Patterson K. E.
Published: July 2007

Most paralexic errors made by phonemic dyslexic patients in reading single words aloud are classifiable as derivational (marriage → “married”), semantic (projector → “camera”), or visual (pivot → “pilot”) errors. A study of two such patients’ assessment of their own reading showed differences as a function of error type, with the patients generally identifying semantic paralexias as errors but classifying derivational and visual paralexias as correct readings. This pattern was confirmed in a test of the patients’ ability to select one of three spoken words to match a printed word. The results are discussed in terms of a theoretical account of the processing of written words by normal readers and by phonemic dyslexics.
The Effects of Context and Content on Immediate Processing in Reading
Authors: Mitchell D. C. , Green D. W.
Published: July 2007

Four experiments were conducted to examine the processes by which fluent readers comprehend prose. In each study the material was presented a few words at a time on an on-line visual display and the subject pressed a button to move on from one display to the next. The inter-reponse time was used as an index of local processing difficulty. The results of Experiment I indicated that readers pause considerably at the ends of clauses and sentences, and that they show no tendency to speed up across sentences. This pattern of results questions the role of prediction in reading. In Experiments II and III immediate processing was found to be unaffected by two types of syntactically-predictive clue and the effect of a third (semantic) clue was equivocal. Experiment IV replicated the results of Experiment I and showed, in addition, that pausing at the ends of clauses and sentences is a function of the difficulty of the content of the text. More detailed analyses showed that reading rate is modulated by the frequency of the words and by the number of characters in the display. Taken together the results suggest that reading rate is largely determined by the speed with which a reader can access the meanings of words and construct a representation of the text rather than by the speed with which they can formulate and test successive predictions about it.
The Effects of Uncontrollable and Unpredictable Events on Anagram Solving
Authors: Winefield A. H. , Tiggemann Marika
Published: July 2007

An experiment is reported which investigated the effects of uncontrollability and unpredictability in an anagram solving task. It was found that performance was disrupted following experience of outcomes which were uncontrollable or unpredictable or both. It was concluded that the effects of uncontrollability cannot be explained solely in terms of unpredictability.
Situation Similarity and the Generalization of Learned Helplessness
Authors: Tiggemann Marika , Winefield A. H.
Published: July 2007

An experiment is reported which investigated the effects of situation similarity on learned helplessness. After initial pretreatment strong helplessness effects were found on a similar, but not on a dissimilar, test task. It was concluded that situation similarity is an important determinant of the generalization of the learned helplessness phenomenon.
Effect of Effort and Latent Extinction on Resistance to Extinction
Authors: Viney Wayne , Johnson Neil , Jacobson Larry
Published: July 2007

Sixty-four male Wistar rats were given acquisition training in an enclosed straight-alley runway which could be adjusted for angles of inclination. The 2×2×2 design involved two angles of inclination in acquisition (0° and 40°) and two angles of inclination in extinction (0° and 40°). Between acquisition and extinction, half the subjects were exposed to a latent extinction procedure and half served as controls. Number of responses in a 30-min extinction session was an inverse function of effort required in extinction. Additionally, latent extinction procedures resulted in reduced resistance to extinction, but only when the effort conditions of acquisition and extinction were constant. When the effort conditions of acquisition and extinction were dissimilar, latent extinction procedures resulted in increased resistance to extinction. The results raise questions about the nature of the learning which occurs during latent extinction training.
Development of Visual Stimulus-Seeking in Kittens
Authors: Timney Brian N. , Emerson Victor F. , Dodwell P. C.
Published: July 2007

Three studies of the development of stimulus-seeking kittens are reported. In Experiment I kittens were housed, from before eye-opening, in total darkness or in a normal laboratory environment. They were given the opportunity, for one hour each day, to press a panel to illuminate a pattern in an otherwise dark experimental chamber. The normally-reared kittens scarcely availed themselves of this opportunity throughout the experiment. In contrast, the dark-reared kittens showed a sudden onset of visual stimulus-seeking around the end of the second month and thereafter pressed the panel for extended periods. This behaviour was maintained for as long as the cats were kept in the dark. In Experiment II, kittens were given varying periods of normal visual experience before being housed in the dark. The results showed that onset of stimulus-seeking was age-dependent and required only that the animals be housed in darkness at or after the end of the second month. Experiment III showed that stimulus-seeking did not extend to auditory stimuli and also that moving and stationary visual stimuli were equally effective in promoting the phenomenon. It is suggested that visual stimulus-seeking is one aspect of the maturation of a system underlying visual approach and exploratory behaviour. Evidence bearing on this point is discussed.
The Sensory Basis of Target Location
Authors: Buck Leslie
Published: July 2007

Overshoot rate in a target alignment task depends on the location of the target with reference to the operational boundary of the task. Subjects performed a step tracking task under four conditions combining pursuit and compensatory display modes with joystick and crank control devices. The boundary effect was found when the joystick was used but not the crank, while the display mode had no effect, indicating that subjects moved with respect to a frame of reference based on proprioceptive information. Movements were made according to the postures adopted, irrespective of the concomitant visual consequences.
Instructions, Illusory Self-Tilt and the Rod-and-Frame Test
Authors: Sigman Eric , Goodenough Donald R. , Flannagan Michael
Published: July 2007

If an illusion of self-tilt is involved in rod-and-frame test performance, then instructions to adjust the rod to the body midline (egocentric instructions) should result in less rod adjustment error than the standard instructions for the rod-and-frame test to adjust the rod to the gravitational vertical. Two experiments were designed to examine this possibility. The results of the first experiment indicate that the tilted rod-and-frame display induces an illusion of self-tilt in the opposite direction. Significant differences between instructional conditions were found in the second experiment as expected. Other rod-and-frame studies are discussed in view of these findings.
Phonological Encoding in the Lexical Decision Task
Authors: Coltheart Max , Besner Derek , Jonasson Jon Torfi , Davelaar Eileen
Published: July 2007

In lexical decision experiments, subjects have difficulty in responding NO to non-words which are pronounced exactly like English words (e.g. BRANE). This does not necessarily imply that access to a lexical entry ever occurs via a phonological recoding of a visually-presented word. The phonological recoding procedure might be so slow that when the letter string presented is a word, access to its lexical entry via a visual representation is always achieved before phonological recoding is completed. If prelexical phonological recodings are produced by using grapheme-phoneme correspondence rules, such recodings can only occur for words which conform to these rules (regular words), since applications of the rules to words which do not conform to the rules (exception words) produce incorrect phonological representations. In two experiments, it was found that time to achieve lexical access (as measured by YES latency in a lexical decision task) was equivalent for regular words and exception words. It was concluded that access to lexical entries in lexical decision experiments of this sort does not proceed by sometimes or always phonologically recoding visually-presented words.
Behaviour of Humans in Concurrent Schedules Programmed on Spatially Separated Operanda
Authors: Ruddle H. , Bradshaw C. M. , Szabadi E. , Bevan P.
Published: July 2007

Six human subjects responded on either of two levers for monetary reinforcement in a continuous choice situation. Responses on one lever (lever A) were reinforced at different frequencies specified by five variable-interval schedules. Reinforcements for responding on the other lever (lever B) were delivered according to a variable-interval schedule of standard reinforcement frequency. Results indicated that absolute response rate on lever A increased, while absolute response rate on lever B decreased as a function of reinforcement frequency for lever A. In terms of preference, the data conformed closely to Baum's (1974) generalized matching equation. Performances departing from perfect matching were obtained in four cases, but these deviations were not systematic either in the direction of overmatching or undermatching.
Discrimination of Response-Contingent and Response-Independent Shock by Rats: Effects of Chlordiazepoxide HCL and Sodium Amylobarbitone
Authors: Rawlins J. N. P. , Feldon J. , Gray Jeffrey A.
Published: July 2007

Rats, trained to press a lever for sucrose reward on a random interval (RI) schedule, were presented while lever-pressing with two stimuli, each associated with a different schedule of shock delivery: in the presence of one stimulus (Se), shock occurred on an RI schedule irrespective of the rat's behaviour; in the presence of the other (Sp) shocks were programmed by the same schedule but delivered only when the rat pressed the lever. Both stimuli suppressed lever-pressing. In addition, the rats developed significantly different response rates in the two stimuli, thus demonstrating a discrimination between response-contingent and response-independent shock. Group data showed faster responding in Se than in Sp, supporting the view that response-contingent shock produces greater suppression than response-independent shock. Individual animal analyses, however, demonstrated that this was the case in the majority of animals, but not in all. Response suppression was alleviated by amylobarbitone sodium (15 mg/kg) or chlordiazepoxide HCI (5 mg/kg); the latter drug alleviated suppression significantly more in Sp than Se and eliminated the difference between the response rates controlled by the two stimuli.
Transfer Effects in a Problem Solving Context
Authors: Sweller J.
Published: July 2007

In recent years hypothesis theory has been applied to transfer between problems and thus used to explain a variety of transfer phenomena. A version of the theory is presented which leads to the prediction that identical variations in identical problems can lead to opposite trends in speed of solution of a critical problem depending on the nature of that problem. Using numerical tasks it was demonstrated that identical variations in preliminary problems either can transform a normally simple problem into an insoluble one or alternatively an insoluble problem into a simple one with the only alteration being in the degree of similarity between the hypotheses required for the initial problems and the critical problem. Implications for Einstellung, the sequence effect and general problem solving are discussed.
Comprehension of Pronouns
Authors: Ehrlich Kate
Published: July 2007

An experiment is reported in which subjects had to choose referents for pronouns in sentences such as: John blamed Bill because he spilt the coffee. To examine whether the choice of referent is influenced by features of the main verb or by the events described in the sentence, the relation between the events was altered by changing the conjunction. A significant effect of conjunction was obtained, but only when both antecedents matched the gender of the pronoun. When only one antecedent matched the pronoun, referents were chosen faster. From these results it is argued that readers use general knowledge to select referents for pronouns when gender does not identify a unique referent. A further effect of sentence structure on the time taken to select a referent was interpreted as showing that subjects analysed the sentences clause by clause.
Tactual and Visual Alphanumeric Suffix Effects
Authors: Manning Susan Karp
Published: July 2007

Two experiments tested the effects of suffixes on the recall of tactual and visual sequences of alphabetic characters presented at 19 letters per min. Scoring techniques allowed for the differentiation of losses of item and order information. In Experiment I performance decrements were found for both modalities, which were mainly caused by item loss at the more recent part of the serial position curve in the suffix conditions. In Experiment II, these effects were replicated and a non-alphabetic suffix led to greater decrements for both modalities than an alphabetical suffix. While a suffix effect based on the loss of item information is consistent with a sensory trace interpretation of the suffix effect, the presence of a visual suffix effect with slow stimulus presentation is not. Additionally, the greater effect of the non-alphanumeric suffix challenges attentional interpretations. Some possible explanations are proposed.
Target Duration Effects on Iconic Memory: The Confounding Role of Changing Stimulus Dimensions
Authors: Long Gerald M. , Sakitt Barbara
Published: July 2007

Observers’ accuracy in detecting a narrow spatial gap between two brief, luminous rectangles presented successively was determined within a two-alternative, forced-choice procedure. This successive-field task requires iconic memory, because the information (rectangle position) in the two presentations must be combined for successful gap detection. On this task, the effect of varying the duration of the first rectangle was systematically investigated over several target luminance levels and for several ISI conditions between rectangles. At the long ISI conditions (100 and 300 ms), the effects of increasing stimulus duration was to improve performance. However, at the brief ISI condition (20 ms), increasing stimulus duration initially depressed task performance. It was found that, with practice, this initial performance drop largely disappeared, and the beneficial influence of increasing target duration was again obtained. These results are discussed in terms of (a) a proposed retinal locus for the iconic memory involved and (b), at a more general level, the potentially distracting role of changing stimulus dimensions on a task employing transient stimuli as in the present study.
Dichotic and Bisensory Grouping Effects
Authors: Hede Andrew J.
Published: July 2007

The relationship between the Gray and Wedderburn effect, the channel alternation effect and the class alternation effect was studied in dichotic and bisensory experiments using physically and semantically distinguishable word classes. With dichotic presentation all three effects were found to occur, but with bisensory presentation neither the Gray and Wedderburn effect nor the class alternation effect was detected. There were no significant differences between physically and semantically based grouping. The present investigation provides support for Broadbent's claim that the Gray and Wedderburn effect depends on the occurrence of the class alternation effect. The various dichotic and bisensory grouping effects are explicable in terms of selection by modality-specific processing systems.
Visual Tracking of Active and Passive Movements of the Hand
Authors: Mather Jennifer A. , Lackner James R.
Published: July 2007

Two experiments were performed to evaluate the influence of movement frequency and predictability on visual tracking of the actively and the passively moved hand. Four measures of tracking precision were employed: (a) saccades/cycle, (b) percent of pursuit movement, (c) eye amplitude/arm amplitude, (d) asynchrony of eye and hand at reversal. Active and passive limb movements were tracked with nearly identical accuracy and were always vastly superior to tracking an external visual target undergoing comparable motion. Proprioceptive information about target position appears to provide velocity and position information about target location. Its presence permits the development of central eye-movement programmes that move the eyes in patterns that approximate but do not exactly match, temporally or spatially, the motion of the hand.
Non-Informative Effects of Stimuli Functioning as Cues
Authors: Harvey Nigel
Published: July 2007

The category of a first stimulus (S1) serving as a cue may allow a subject to predict the category of a second stimulus (S2). However, a cue may have effects on RT to S2 that are independent of those derived from its intended role as a predictor. These non-informative effects of a cue may add to or subtract from the benefits associated with its predictive function. Two experiments demonstrate that when S1 is in the same category as S2 (as is frequently the case for valid cues in cueing experiments) but provides no information about S2, RT is slower than when S1 is in a different category from S2. It is suggested that this category relation effect arises because inhibition of a response to S1 is still present when S2 arrives and that, in some cueing experiments, it may subtract from the RT benefits derived from the cue as a predictor of S2. Also, RT to a visual but not to an auditory S2 was faster after an auditory S1 than after a visual S1. It is argued that this modality combination effect is consistent with the view that auditory signals are more alerting than visual ones and that this is another factor to be taken into account in the design of cueing and other experiments.
Short-Term Visual Recognition Memory in Pigeons
Authors: Macphail Euan M.
Published: July 2007

Recognition memory for lists of items was investigated in pigeons using a YES-NO recognition technique. Experiment I showed that increasing the exposure duration of the first item of a two-item list improved recognition for that item without impairing recognition of the second item. Experiment II showed that decreasing the inter-trial interval had no effect on correct YES responses but significantly increased the number of false YES responses. Experiment III showed that recognition for the last two items of a three-item list was no poorer than that for lists of only two items. Experiment IV showed that increasing the delay between presentation and test of a two-item list (from 0·25-1 s) had a more disruptive effect on recognition for the second than for the first item. The data from these four experiments support a model proposed by Roberts and Grant, according to which memory traces are independent, and decay as a negatively accelerated function of time. Experiments V, VI, and VII investigated recognition for lists of three, four, and five items, and found no evidence for a primacy effect, performance being a linear function of time since sample offset.
Letter Interactions in Brief Visual Displays
Authors: Gilmore Grover C.
Published: July 2007

Three experiments were conducted to examine the influence of non-target letters on target detection performance. It was hypothesised that letters which are similar would exert a stronger masking influence on each other than letters which have a low level of feature similarity. The results indicate, however, that every letter has the same inhibitory potential regardless of its similarity rating to other letters. The highly significant letter interactions which did occur in the study were interpreted as evidence for an additive, rather than a subtractive, influence by the non-targets. It is proposed that when a target has an ambiguous identity, due to an impoverished representation, it may be disambiguated by the addition of feature information from the immediate letter context. The effect of filling in the target representation with a feature value from a non-target letter will be to weight the final representation towards the target which has the value most similar to the one substituted. In a sense, then, non-targets which are similar to a target can actually enhance target detection scores.
Housing Prices and Housing Preferences in Israel
Authors: Borukhov Eli , Ginsberg Yona , Werczberger Elia
Published: July 2007

Israel's housing market differs from other countries in that most of the urban population lives in owner-occupied apartments in multi-family buildings. This paper is concerned with the implications of this situation for housing preferences. The study is based on the prices of a sample of apartments offered for sale in the Tel Aviv metropolitan area. Using multiple regression analysis hedonic price indexes were obtained for a large number of characteristics of the apartment, the building, adjacent properties, the neighbourhood and the location in the metropolitan area. It was found that a premium is paid for characteristics which facilitate maintenance and for features which serve as indicators for the social composition of the neighbours and their attitudes.
Reading Against All Odds: A Pilot Study of Two Deaf Students With Dyslexia
Authors: Enns Charlotte , Lafond Lori Dustan
Published: July 2007

Learning to read and write is a challenge for most deaf children due to their limited experiences with, and access to, spoken language. In the case of deaf students who have difficulty processing visual print, literacy becomes an even greater challenge. The study piloted an intervention procedure that incorporated the principles of automaticity, repetition, functional vocabulary, and a positive teacher-student relationship as recommended in programs for struggling readers and adapted them to the needs of two deaf high school students with dyslexia in an American Sign Language–English bilingual program. The findings reveal gains in reading ability on the formal measures, though not more than would be expected over a 6-month period simply due to development. The real improvements were noted in the students' attitudes toward literacy, improved social interaction, and increased self-confidence.
On adaptive estimation and pole assignment of overparametrized systems
Authors: Xia Liga , Moore J. B. , Gevers M.
Published: July 2007

In this paper a first step is taken to avoid ill‐conditioning in adaptive estimation and pole assignment schemes for the case when there is a signal model overparametrization. Such a situation can occur in practice when an unknown model order is guessed too high so as to be on the ‘safe’ side. The methods proposed in the paper are relatively simple compared with on‐line order determination, being based on introducing suitable excitation in the ‘regression’ vectors of the parameter estimation algorithms to ensure parameter convergence. For the case when the models are non‐unique in that pole‐zero cancellations can occur, the algorithms seek to estimate the unique model where the cancellations occur at the origin. Applying estimates of this (unique) model turns out to avoid ill‐conditioning in central tendency adaptive pole assignment. For the case of one pole‐zero cancellation the convergence theory of the algorithm is complete. For the more general case algorithms are readily devised which appear to work well but for which a complete theory is not available.
Ein Beitrag zur Bildung von Adsorptionsmischkristallen (KCL‐MeCl2 · XH2O)
Authors: Steinike Ursula
Published: July 2007

In den Systemen KCl‐MeCl2‐H2O (CuCl2 · 2 H2O, CoCl2 ·6 H2O, NiCl2 · 6 H2O) wird die Verteilung der Mikrokomponente zwischen Lösung und Kristallisat untersucht. Für die Verteilung wird eine Potenzfunktion Ck=A · C gefunden. Von einer bestimmten Ausgangskonzentration an Metallchloriden tritt ein Sättigungseffekt in den Kristallen auf.

Dieser Effekt läßt sich durch die Annahme der Bildung von Adsorptionsmischkristallen erklären. Die Bildung der Adsorptionsmischkristalle in den Systemen KCl‐CuCl2 · 2 H2O, KCl‐CoCl2 · 6 H2O und KCl‐NiCl2 · 6 H2O wird diskutiert.
Der Einfluß von Zusätzen auf die Verschiebungsgeschwindigkeit von KCl‐{100}‐Flächen (K4[Fe(CN)6] · 3 H2O, PbCl2, CoCl2 · 6 H2O, CuCl2 · 2H2O)
Authors: Steinike U.
Published: July 2007

Der Einfluß von anorganischen Zusätzen (K4[Fe(CN)6] · 3 H2O, PbCl2, CoCl2 · 6 H2O und CuCl2 · 2H2O) auf die Verschiebungsgeschwindigkeit von KCl‐{100}‐Flächen wurde untersucht. Die genannten Zusätze erniedrigen die VG, wobei die von Bliznakov angegebene Formel erfüllt wird. Der wachstumshemmende Charakter der Zusätze nimmt in der Reihenfolge K4[Fe (CN)6] · 3 H2O — PbCl2 — CoCl2 · 6 H2O und CuCl2 · 2 H2O ab. In der gleichen Reihenfolge nimmt auch die Strukturaffinität gegenüber KCl ab. Der stärker blockierende Charakter des CoCl2 · 6 H2O im Vergleich zum CuCl2 · 2 H2O ist auch auf Grund der größeren Adsorptionswärme des Kobaltsalzes an den KCl‐{100}‐Flächen zu verstehen.

Die Adsorptionswärmen von CoCl2 · 6 H2O und CuCl2 2 H2O an KCl wurden berechnet (β=7,1 ± 1 kcal, β=5,5 ± 1,2 kcal).

Bei hohen KCl‐Übersättigungen (1,5%) tritt in Gegenwart von CuCl2 · 2 H2O‐Zusätzen in einem ganz bestimmten Konzentrationsbereich eine Erhöhung der VG auf.
Grenzflächenstruktur und Orientierung bei der Epitaxie
Authors: Ickert Lars
Published: July 2007

Es wird eine Übersicht über die bisher bekannten Behandlungen des Problems gegeben, ihre Aussagen und Gültigkeitsbereiche. Ein kurzer Abriß der Vorstellungen zur Grenzflächenstruktur bildet in Verbindung mit der Keimbildungstheorie die Ausgangsposition; die Orientierung wird damit als Keimbildungs‐Phänomen ausgelegt. Wie eine Überschlagsrechnung zeigt, muß diese Vorstellung für die Epitaxie in dünnen Schichten erweitert werden. Die Zusätze können durch neuere Angaben aus der Literatur gestützt werden, wobei einige Widersprüche verständlich werden.
Wachstum und Verzwillingung von Tridymit
Authors: Flörke O. W.
Published: July 2007

Tridymit verzwillingt nach (3034) und (1016). Die ungewöhnlichen Indizes der Zwillingsebenen lassen sich darauf zurückführen, daß Tridymitkristalle aus Cristobalitkeimen orientiert herauswachsen, und daß sich die Zwillinge schon bei diesem paramorphen Übergang von Cristobalit in Tridymit bilden. Auf diese Weise läßt sich das (3034)‐Gesetz erklären. Das (1016)‐Gesetz findet seine Erklärung im Wachstum von Tridymitkristallen aus nach (111) verzwillingten Cristobalitkeimen. Im Röntgeneinkristalldiagramm zeigt sich die Verzwillingung auch bei makroskopisch ideal gewachsenen Kristallen. Durch polysynthetische Zwillingsbildung wird zwar nicht der Anteil, wohl aber die Verteilung der Si2O7‐Gruppen mit ungünstiger Sauerstoffanordnung in der Tridymitstruktur geändert.
Autoklaven zur Hydrothermalsynthese von Quarz für Drucke von 2000 at
Authors: Bibr B. , Matêcha J. , Placák B. , Tajovský M.
Published: July 2007

Es wurde eine modifizierte Methode der Festigkeitsberechnung von Betriebshochdruckautoklaven beschrieben und auf die hydrothermale Synthese von Quarzkristallen beim Betriebsdruck 2000 at und bei einer Arbeitstemperatur von 400 °C angewendet. Ein veränderlicher Bruchsicherheitsfaktor wurde anstatt eines konstanten Faktors eingeführt und als Funktion des Verhältnisses des Außen‐ und Innendurchmessers der Zylinderwand des Druckgefäßes behandelt. Auf diese Weise ist es möglich, die Vorteile des Hochdruckes für die Erniedrigung der Betriebs‐ und Bezugskosten auszunutzen.
Zur Realstruktur zonengeschmolzener Siliziumeinkristalle
Authors: Peibst Herbert
Published: July 2007

Es wird die auftretende Versetzungsstruktur beim Dünnziehen und Stauchen von Siliziumeinkristallen diskutiert. Im Zusammenhang damit lassen sich einige Aussagen über die Entstehungsursachen dieser Baufehler und deren Auswirkung auf die elektrischen Eigenschaften machen.
Über die Kristallisation von NaCl aus bleichloridhaltigen Lösungen und über den Einbaumechanismus der Fremdkomponente
Authors: Kleber Will , Schiemann Sigrid
Published: July 2007

Aus gesättigten wässerigen NaCl‐Lösungen mit PbCl2‐Zusätzen wurden NaCl‐Mischkristalle mit Pb‐Einbau in Abhängigkeit von Sättigungstemperatur, Übersättigung und Fremdstoffgehalt der Lösung gezüchtet. Die Kristalle bilden unter dem Einfluß des Pb‐Zusatzes neben (100)‐ auch (111)‐Flächen aus. Bei geringen Bleigehalten in der Lösung nehmen die linearen Verschiebungsgeschwindigkeiten der Kristallflächen stark ab, steigen dann aber mit wachsender Temperatur, Übersättigung und Fremdstoff‐Konzentration an.

Die Adsorption des Lösungsgenossen erfolgt auf den (111)‐Flächen wesentlich intensiver als auf den Würfelflächen. Ein Maximum des Pb‐Einbaus in die Kristalle wurde bei niedrigen Züchtungstemperaturen, bei geringer Übersättigung und geringen Pb‐Gehalten in der Lösung erreicht.

Die beobachtete Trachtänderung ist auf die unterschiedliche „Blockierung”︁ der verschiedenen Flächenarten zurückzuführen. Bei kleinen Fremdstoff‐Konzentrationen wird das Wachstum der (111)‐Flächen stärker gehemmt als das der Würfelflächen. Mit steigendem Pb‐Gehalt ist ein steilerer Anstieg der Verschiebungsgeschwindigkeit für (100) zu registrieren, so daß schließlich Kristalle mit oktaedrischem Habitus entstehen. Die gleiche Tendenz zeigt sich bei Erhöhung der Übersättigung.

Die sprunghafte Verringerung der Verschiebungsgeschwindigkeiten bei Pb‐Zusatz ist auf Adsorption von Blei bzw. eines Pb‐haltigen Komplexes zurückzuführen. Jedoch ist die Fremdstoff‐Adsorption nicht unmittelbar für die Trachtänderung verantwortlich.

Es wird angenommen, daß es sich bei den gezüchteten Kristallen um Adsorptionsmischkristalle handelt.
Über die Bildung künstlicher Ag‐Kristalle unter hydrothermalen Bedingungen
Authors: Christoph Arthur , Görlich H. C. Paul , Lüdkeveb Werner
Published: July 2007

Es wird über das hydrothermale Wachstum von Silberkristallen bei unterschiedlichen Wachstumsbedingungen berichtet. Während in silikathaltigen Lösungen nadelartige Silberkristalle bis 13 mm Länge entstehen, findet man in CaCl2‐haltigen Lösungen neben Silber‐Nadeln auch farnartige Dendrite auf Kalksteinunterlage, wie sie auch in der Natur vorkommen.

Aus den Beobachtungen werden Möglichkeiten des Wachstumsmechanismus aufgestellt.
Zur Möglichkeit der physikalischen Modellierung industrieller Kristallisatoren für den Fall des diffusionsgesteuerten Kristallwachstums
Authors: Todes O. M. , Litunovskij N. I.
Published: July 2007

Die Kinetik der Kristallisation in Industrieapparaten wird oft durch die Geschwindigkeit der Molekulardiffusion begrenzt. Bei der Analyse der linearen Geschwindigkeit des Kristallwachstums sind unter diesen Voraussetzungen die Grenzbedingungen für das Nusselt‐Kriterium formuliert worden. Zwei Beispiele werden diskutiert: die Kristallisation von Zuckerlösung durch Verdampfung und die Kristallisation von Kaliumbichromat aus einer in einem Trommelkristallisator abkühlenden Lösung. Es wird gezeigt, wie und unter welchen Voraussetzungen dieser Prozeß modelliert werden kann; die Bedingungen hierfür werden formuliert. Im wesentlichen kommt es darauf an, in der Laboratoriumsanlage dieselbe Dauer der Wärmerelaxation und dieselbe Kurve der zeitlichen Temperaturveränderung zu erhalten wie im Industrieapparat.
Entstehung, Phasenbestand und Reaktionen von Brennstoffschlacken in Hochdruckdampfkraftwerken
Authors: Kirsch H. , Pollmann S.
Published: July 2007

Es wird die Entstehung von Schlacken, Aschen und Flugstäuben aus den Mineralen und anorganischen Substanzen der Brennstoffe, wie sie in Kraftwerken verfeuert werden, dargestellt. Die in den Schlacken auskristallisierenden Substanzen werden gekennzeichnet, und ferner wird auf die Reaktionen der Schlacken mit den feuerfesten Stampfmassen der Feuerräume eingegangen. Getrennte Behandlung finden Schlacken aus Kohle—Öl‐Gemisch‐Feuerungen und Versuche zur Kristallisation von glasigem Steinkohlenschlackegranulat.
Interpolation in der Funktionstafel zum Meßkompensator 0…130 λ mit Kombinationsplatte aus Kalkspat (Drehkompensator nach Ehringhaus)
Authors: Schultz Johannes
Published: July 2007

Es wird eine Formel zur Berechnung des Gangunterschiedes doppelbrechender Objekte für beliebige Wellenlängen aus den für F‐ und C‐Linie gegebenen Gangunterschiedswerten abgeleitet. Nach dieser Formel erfolgt die Berechnung schneller als nach der alten von A. Ehringhaus angegebenen Beziehung.
Goniomètre a deux cercles pour monocristaux aux neutrons
Authors: Guillen M. , Roudaut E.
Published: July 2007

Un diffractomètre à deux cercles permettant de mesurer les intensités des réflexions en zone a été réalisé au Centre d'Etudes Nucléaires de Grenoble. Les données sont fournies à l'appareil, soit par un calculateur, soit par bandes perforées. Les positions angulaires sont lues par des codeurs digitaux et les résultats sont imprimés, perforés et peuvent être aussi dirigés vers le calculateur fonctionnant en boucle fermée.

Cet appareil nous a permis de définir la structure cristallographique du Titanate de Lanthane et en particulier de positionner les atomes d'oxygène.
Über die spontane Keimbildung bei der Herstellung von Einkristallen durch Rekristallisation
Authors: Ibe G. , Lücke K.
Published: July 2007

Bei der Herstellung von Einkristallen nach der bekannten Rekristallisationstechnik tritt häufig trotz Anwendung einer Durchlaufglühung in einem Ofen mit großem Temperaturgradienten eine unerwünschte, über die ganze Probenlänge verteilte spontane Keimbildung auf. Ihre Abhängigkeit von den Versuchsparametern wurde hier am Beispiel drahtförmiger Proben aus 3%igem Silizium‐Eisen quantitativ untersucht. Es zeigte sich, daß die Keimdichte mit höherem Temperaturgradienten und kleinerer Vorschubgeschwindigkeit in guter quantitativer Übereinstimmung mit der Theorie von WILLIAMSON und SMALLMAN abnahm. Außerdem steigt die Keimdichte stark mit zunehmender Verformung der Probe an und wird durch Oberflächenabtragung verringert. Einen besonders starken Einfluß übte eine vorherige Alterungsbehandlung der Proben aus, die eine Abnahme der Keimdichte um einen Faktor 10 bewirkte.
Zum Nachweis von Orientierungszusammenhängen makroskopischer Substrukturen durch Drahtschattenabbildung mittels Berg‐Barrett‐Technik
Authors: Wadewitz H.
Published: July 2007

An Berg–Barrett‐Aufnahmen mit einem Einzeldraht oder Paralleldrahtgitter im primären Röntgenstrahlbündel werden charakteristische Schattenstrukturen, die Aussagen über Orientierungs‐Zusammenhänge von makroskopischen Substrukturen gestatten, diskutiert. Als ausgewählte Beispiele werden je ein durch Elektronenzonenschmelze hergestellter Molybdän‐Einkristall und ein nach dem Verneuil‐Verfahren hergestellter Rubin‐Kristall benutzt.
Über Wachstum und Epitaxie von CdSe durch Sublimation und chemische Transportreaktionen
Authors: Kleber W. , Mietz I. , Elsasser U.
Published: July 2007

Mit Hilfe chemischer Transportreaktionen und durch Kristallisation aus der Dampfphase wurden unter verschiedenen Bedingungen CdSe‐Kristalle gezüchtet. Morphologische und röntgenographische Untersuchungen ergaben, daß es sich ausschließlich um die hexagonale Modifikation (Wurtzitstruktur) handelt. Polytype Strukturvarianten konnten nicht festgestellt werden.

Mit Hilfe chemischer Transportreaktionen konnten ferner auf (111)‐Flächen von CaF2 (Fluorit), BaF2, Si und auf (001) von NaF orientierte Aufwachsungen von CdSe erzielt werden. Eine orientierte Kristallisation durch Sublimation von CdSe konnte nur auf BaF2 — nicht dagegen auf CaF2 — erhalten werden.

Auch bei allen Epitaxieversuchen bildeten sich ausschließlich Kristalle der hexagonalen Modifikation.
Ein Beitrag zu den Eigenschaften von Wolframaten und Molybdaten
Authors: Barta Č. , Žemlička J. , Srb I.
Published: July 2007

Der Vergleich der Abhängigkeit des Ionenradius A2+ von dem Einheitsvolumen, von der Lage der Absorptionskante und des Maximums der Emission sowie von der Stokes‐Verschiebung bei tetragonalen und monoklinen Wolframaten und Molybdaten führt die Autoren zu der tetragonalen Überzeugung, daß die Symmetrie bzw. die Deformation der Anionengruppe beim CdMoO4 entgegen der bisherigen Meinung den monoklinen Wolframaten und Molybdaten näher legt als den tetragonalen. Diese Ansicht wurde auch mit Hilfe von Schwingungsspektren der Anionengruppen im Bereich von 400 bis 1200 cm−1 bestätigt.
The Effect of Direction of Floating Zone Travel on the Shape of Solidified Rod and on the Distribution of Solutes
Authors: Kadečková S. , Šesták B.
Published: July 2007

The effect of direction of vertical molten zone travel on the shape of solidified rod and distribution of silicon in preparation of Fe‐3% Si alloy single crystals by means of a floating zone method with induction heating is studied. With upward direction of zone travel, from circular rods, single crystals with periodical changes of the cross section and of silicon content were obtained. Using the same conditions of growth, but the downward direction of zone travel, single crystals with constant cross section and silicon content were produced. This fact is explained by the influence of variations in zone shape on inductive coupling between the coil and the molten zone, occurring during the melting.
Synthese und Züchtung von Vielkomponenten‐Halbleiterkristallen durch chemische Transportreaktion
Authors: Averkieva G. K. , Gorjunova N. A. , Nazarov A. , Pročuchan V. D.
Published: July 2007

In der vorliegenden Arbeit wurden diamantartige Mischkristalle von Galliumarsenid mit den ternären Verbindungen ZnSiAs2, ZnGeAs2 und Cu2GeSe3 untersucht, deren Homogenitätsbereiche bestimmt wurden.

Durch chemische Transportreaktionen wurden Kristalle von Vielkomponentenphasen verschiedener Zusammensetzungen in den Schnitten magnified image erhalten. Verschiedene Faktoren, die die Stofftransportprozesse beeinflussen, wurden variiert, und die optimalen Bedingungen für die Kristallzüchtung wurden festgelegt.

An den gezüchteten Kristallen wurden einige physikalisch‐chemische und elektro‐physikalische Untersuchungen durchgeführt.
Zur Kristallperfektion von Halbleiterepitaxieschichten (I) Nachweis und Identifizierung von Epitaxiebaufehlern
Authors: Schulz M.
Published: July 2007

Mit der Beschreibung der typischen Epitaxiebaufehler werden die Nachweis‐ und Registrierbedingungen diskutiert. Es wird gezeigt, daß die spezifischen Eigenschaften der Halbleiterepitaxieschichten gegenüber kompakten Materialien abweichende Untersuchungsmethoden erfordern. Die erzielten Ergebnisse bilden die Grundlage für die in den folgenden Teilen noch darzustellenden Untersuchungen.
The crystallisation of metal oxides from alkali halide melts
Authors: Packter A.
Published: July 2007

The crystallisation of metal oxides from sodium chloride melts has been studied. The effects of variation of range and rate of cooling and of solute‐solvent interaction on the crystal size have been investigated and the mechanism of crystallisation discussed.
Zum Ätzen von Versetzungen in MgZn2
Authors: Paufler P. , Schulze G. E. R.
Published: July 2007

Es werden Verfahren für das Ätzen von Versetzungen sowie die Form der Ätzgruben auf verschiedenen Ebenen der intermetallischen Verbindung MgZn2 angegeben.

Aus der Untersuchung der Reproduzierbarkeit der Ätzgruben nach wiederholtem Ätzen, der Korrespondenz auf Spaltflächen, der Anordnung der Ätzgruben nach plastischer Verformung und der Verzweigung und Richtungsänderung von Kleinwinkelkorngrenzen wird geschlossen, daß jede Ätzgrube den Durchstoßpunkt (mindestens) einer Versetzung durch die Kristalloberfläche markiert.
Über die orientierte Kristallisation von Arsenolith auf Glasunterlagen
Authors: Bliznakov G. , Delineschew S.
Published: July 2007

Die in einer früheren Arbeit erzielten theoretischen Ergebnisse bezüglich der orientierten Ausscheidung von Kristallen mit Diamantgitter auf strukturloser Unterlage (Bliznakov, Delineschew) wurden experimentell überprüft. Es wurde die orientierte Ausscheidung von Arsenolith auf Glasunterlagen untersucht.

Bei niedrigen Übersättigungen scheiden sich die Arsenolithkristalle auf der Glasunterlage vorzugsweise parallel der (111)‐Fläche aus, während die Ausscheidung parallel der (310)‐Fläche nur in geringem Umfang erfolgt. Mit steigender Übersättigung nehmen die Verwachsungen mit der (111)‐Fläche ab und die mit der (310)‐Fläche zu. Die relative Anzahl der Verwachsungen parallel den Flächen (110), (311) und (100), die bei niedrigen Übersättigungen klein ist, durchläuft Maxima in bestimmten Übersättigungsintervallen. Die erhaltenen Ergebnisse stimmen im allgemeinen mit den theoretischen Resultaten überein.
Über das Wachstum gerundeter Zink‐Einkristalle aus der Dampfphase unmittelbar unterhalb des Schmelzpunktes
Authors: Heyer H. , Nietruch F. , Stranski I. N.
Published: July 2007

Beim Wachstum gerundeter Zink‐Einkristalle aus übersättigtem Dampf dich unterhalb des Schmelzpunktes erscheint zunächst die Basisfläche {0001}, dann die Pyramide II.‐Stellung {1122}. Erst später treten die Flächen {1010} und {1011} auf, die sich beim weiteren Wachstum vergrößern und die Flächen II.‐Stellung von der Wachstumsform verdrängen. An der Endform verbleiben nur {0001}, {1010} und {1011}.

Das intermediäre Auftreten der Pyramiden II.‐Stellung und das anfängliche Ausbleiben der Flächen {1010} und {1011} läßt sich dadurch deuten, daß die gerundete Form auch unterhalb des Schmelzpunktes zunächst so wächst, als wäre sie noch von ihrer eigenen Schmelze umgeben.
Über den Einfluß der Kristallisationswärme und der Teilchengröße auf die Wachstumsgeschwindigkeit von Keimen
Authors: Skřivánek J. , Rychlý R.
Published: July 2007

Durch einen Vergleich der Beziehung zwischen der Masse, die in der Zeiteinheit der Teilchenoberfläche zugeführt wird, und der Wärmemenge, die in der Zeiteinheit von der Teilchenoberfläche im stationären Zustand abgeführt wird sowie nach einer mathematischen Umformung und Abschätzung von Korrekturfaktoren – (Kristallisationswärme, Diffusionskoeffizient, Wärmeleitfähigkeit) ergibt sich, daß man bei den theoretischen Überlegungen den Einfluß der Kristallisationswärme auf die Wachstumskinetik der Teilchen vernachlässigen kann.

Im zweiten Teil wird der Versuch unternommen, ein mathematisches Modell für die experimentell nachgewiesene Erscheinung aufzustellen, nach der es am Beginn des Keimwachstums zu einem steilen Anstieg der Wachstumsgeschwindigkeit und nach einer gewissen Zeit wieder zu einer Verringerung der Wachstumsgeschwindigkeit kommt.
A Study of the Effect of Sulfate Ions on the Growth of Sodium Chlorate Crystals
Authors: Bliznakov G. , Kirkova E.
Published: July 2007

The effect of sulfate ions on the growth of NaClO3 faces (100) and (111) has been investigated. The heat of adsorption on the active centers of growth for both types of faces has been derived from kinetic experimental data. Direct adsorption measurements have been performed which gave the heat of adsorption on the whole surface of each type of faces. A possible explanation of the experimental results is given.