bluuebunny/crossref_metadata_2025 huggingface dataset:
Brain Activation During Mental Transformation of Size
Authors: Larsen Axel , Bundesen Claus , Kyllingsbæk Søren , Paulson Olaf B. , Law Ian
Published: July 2002

Visual comparison between different-sized objects with respect to shape can be done by encoding one of the objects as a mental image, transforming the image to the size format of the other object, and then testing for a match (Bundesen, C., & Larsen, A. [1975]. Visual transformation of size. Journal of Experimental Psychology: Human Perception and Performance, 1, 214-220). To identify the brain structures implicated in mental transformation of size, we measured the distribution of regional cerebral blood flow (rCBF) by positron emission tomography (PET) in 12 normal subjects who compared random stimulus patterns with respect to shape regardless of variations in size in a one-back match-to-sample paradigm. Each subject was PET-scanned 12 times during repetitive injections of H2 15O. In one condition (three scans), all stimulus patterns were small. In a second condition (three scans), all stimuli were large. In the third condition (six scans), the stimuli alternated between small and large. Mental transformation of size should occur in the alternating-size condition but not in the fixed-size conditions. As expected, behavioral measures (reaction time [RT], d', β) were nearly the same for the two fixed-size conditions but mean RT was longer and d' smaller in the alternating-size condition. Changes in rCBF specific to mental transformation of size were estimated by contrasting the alternating-size with the fixed-size conditions by use of statistical parametric mapping (SPM96) at a threshold of p < .05 corrected for multiple comparisons. The detected brain structures implicated in mental transformation of size were primarily located in the dorsal pathways, comprising structures in the occipital, parietal, and temporal transition zone (predominantly in the left hemisphere), posterior parietal cortex (bilaterally), area MT/V5 (left), and vermis (bilaterally). Contrasts between the two fixed-size conditions showed significant effects in only the occipital cortex.
Asymmetry of Neuronal Activity During Extracellular Microelectrode Recording from Left and Right Human Temporal Lobe Neocortex During Rhyming and Line-Matching
Authors: Schwartz Theodore H. , Haglund Michael M. , Lettich Ettore , Ojemann George A.
Published: July 2002

Recordings of neuronal activity in humans have identified few correlates of the known hemispheric asymmetries of functional lateralization. Here, we examine single-unit activity recorded from both hemispheres during two delayed match-to-sample tasks that show strong hemispheric lateralization based on lesion effects; a line-matching (LM) task related to the right hemisphere, and a rhyming (RHY) task related to the left. Nineteen neuronal populations were recorded with extracellular microelectrodes from the left temporal neocortex of 11 awake patients, and 18 from the right in 9 patients during anterior temporal lobectomy for complex partial seizures under local anesthesia. All subjects were left hemisphere dominant for language. Twelve (32%) populations exhibited statistically significant changes in activity at p < .05. Although changes in firing frequency were recorded from both hemispheres during both tasks, the RHY task elicited changes in activity several hundred milliseconds earlier on the left side than on the right. The LM task, on the other hand, induced changes earlier on the right side than on the left. Both hemispheres contained units active during verbal responses regardless of which behavior elicited the response. Our results indicate that cerebral dominance is reflected in earlier neuronal activity in the anterior temporal lobe during tasks lateralized to that hemisphere.
A Functional Neuroimaging Description of Two Deep Dyslexic Patients
Authors: Price C. J. , Howard D. , Patterson K. , Warburton E. A. , Friston K. J. , Frackowiak R. S. J.
Published: July 2002

Deep dyslexia is a striking reading disorder that results from left-hemisphere brain damage and is characterized by semantic errors in reading single words aloud (e.g., reading spirit as whisky). Two types of explanation for this syndrome have been advanced. One is that deep dyslexia results from a residual left-hemisphere reading system that has lost the ability to pronounce a printed word without reference to meaning. The second is that deep dyslexia reflects right-hemisphere word processing. Although previous attempts to adjudicate between these hypotheses have been inconclusive, the controversy can now be addressed by mapping functional anatomy. In this study, we demonstrate that reading by two deep dyslexic patients (CJ and JG) involves normal or enhanced activity in spared left-hemisphere regions associated with naming (Broca's area and the left posterior inferior temporal cortex) and with the meanings of words (the left posterior temporo-parietal cortex and the left anterior temporal cortex). In the right-hemisphere homologues of these regions, there was inconsistent activation within the normal group and between the deep dyslexic patients. One (CJ) showed enhanced activity (relative to the normals) in the right anterior inferior temporal cortex, the other (JG) in the right Broca's area, and both in the right frontal operculum. Although these differential right-hemisphere activations may have influenced the reading behavior of the patients, their activation patterns primarily reflect semantic and phonological systems in spared regions of the left hemisphere. These results preclude an explanation of deep dyslexia in terms of purely right-hemisphere word processing.
The Minimal Local-Asperity Hypothesis of Early Retinal Lateral Inhibition
Authors: Balboa Rosario M. , Grzywacz Norberto M.
Published: July 2002

Recently we found that the theories related to information theory existent in the literature cannot explain the behavior of the extent of the lateral inhibition mediated by retinal horizontal cells as a function of background light intensity. These theories can explain the fall of the extent from intermediate to high intensities, but not its rise from dim to intermediate intensities. We propose an alternate hypothesis that accounts for the extent's bell-shape behavior. This hypothesis proposes that the lateral-inhibition adaptation in the early retina is part of a system to extract several image attributes, such as occlusion borders and contrast. To do so, this system would use prior probabilistic knowledge about the biological processing and relevant statistics in natural images. A key novel statistic used here is the probability of the presence of an occlusion border as a function of local contrast. Using this probabilistic knowledge, the retina would optimize the spatial profile of lateral inhibition to minimize attribute-extraction error. The two significant errors that this minimization process must reduce are due to the quantal noise in photoreceptors and the straddling of occlusion borders by lateral inhibition.
Dynamics of Encoding in Neuron Populations: Some General Mathematical Features
Authors: Knight Bruce W.
Published: July 2002

The use of a population dynamics approach promises efficient simulation of large assemblages of neurons. Depending on the issues addressed and the degree of realism incorporated in the simulated neurons, a wide range of different population dynamics formulations can be appropriate. Here we present a common mathematical structure that these various formulations share and that implies dynamical behaviors that they have in common. This underlying structure serves as a guide toward efficient means of simulation. As an example, we derive the general population firing-rate frequency-response and show how it may be used effectively to address a broad range of interacting-population response and stability problems. A few specific cases will be worked out. A summary of this work appears at the end, before the appendix.
Learning Object Representations Using A Priori Constraints Within ORASSYLL
Authors: Krüger Norbert
Published: July 2002

In this article, a biologically plausible and efficient object recognition system (called ORASSYLL) is introduced, based on a set of a priori constraints motivated by findings of developmental psychology and neuro-physiology. These constraints are concerned with the organization of the input in local and corresponding entities, the interpretation of the input by its transformation in a highly structured feature space, and the evaluation of features extracted from an image sequence by statistical evaluation criteria. In the context of the bias-variance dilemma, the functional role of a priori knowledge within ORASSYLL is discussed. In contrast to systems in which object representations are defined manually, the introduced constraints allow an autonomous learning from complex scenes.
Efficient Learning in Boltzmann Machines Using Linear Response Theory
Authors: Kappen H. J. , Rodríguez F. B.
Published: July 2002

The learning process in Boltzmann machines is computationally very expensive. The computational complexity of the exact algorithm is exponential in the number of neurons. We present a new approximate learning algorithm for Boltzmann machines, based on mean-field theory and the linear response theorem. The computational complexity of the algorithm is cubic in the number of neurons.

In the absence of hidden units, we show how the weights can be directly computed from the fixed-point equation of the learning rules. Thus, in this case we do not need to use a gradient descent procedure for the learning process. We show that the solutions of this method are close to the optimal solutions and give a significant improvement when correlations play a significant role. Finally, we apply the method to a pattern completion task and show good performance for networks up to 100 neurons.
Predictive Neural Networks for Learning the Time Course of Blood Glucose Levels from the Complex Interaction of Counterregulatory Hormones
Authors: Prank Klaus , Jürgens Clemens , von zur Mühlen Alexander , Brabant Georg
Published: July 2002

Diabetes mellitus is a widespread disease associated with an impaired hormonal regulation of normal blood glucose levels. Patients with insulin-dependent diabetes mellitus (IDDM) who practice conventional insulin therapy are at risk of developing hypoglycemia (low levels of blood glucose), which can lead to severe dysfunction of the central nervous system. In large retrospective studies, up to approximately 4% of deaths of patients with IDDM have been attributed to hypoglycemia (Cryer, Fisher, & Shamoon, 1994; Tunbridge, 1981; Deckert, Poulson, & Larsen, 1978). Thus, a better understanding of the complex hormonal interaction preventing hypoglycemia is crucial for treatment. Experimental data from a study on insulin-induced hypoglycemia in healthy subjects are used to demonstrate that feedforward neural networks are capable of predicting the time course of blood glucose levels from the complex interaction of glucose counterregulatory (glucose-raising) hormones and insulin. By simulating the deficiency of single hormonal factors in this regulatory network, we found that the predictive impact of glucagon, epinephrine, and growth hormone secretion, but not of cortisol and norepinephrine, were dominant in restoring normal levels of blood glucose following hypoglycemia.
Computing with Self-Excitatory Cliques: A Model and an Application to Hyperacuity-Scale Computation in Visual Cortex
Authors: Miller Douglas A. , Zucker Steven W.
Published: July 2002

We present a model of visual computation based on tightly inter-connected cliques of pyramidal cells. It leads to a formal theory of cell assemblies, a specific relationship between correlated firing patterns and abstract functionality, and a direct calculation relating estimates of cortical cell counts to orientation hyperacuity. Our network architecture is unique in that (1) it supports a mode of computation that is both reliable and efficent; (2) the current-spike relations are modeled as an analog dynamical system in which the requisite computations can take place on the time scale required for an early stage of visual processing; and (3) the dynamics are triggered by the spatiotemporal response of cortical cells. This final point could explain why moving stimuli improve vernier sensitivity.
Visuomotor Adaptation to Virtual Hand Position in Interactive Virtual Environments
Authors: Groen Joris , Werkhoven Peter J.
Published: July 2002

In virtual environments the virtual hand may not always be exactly aligned with the real hand. Such misalignment may cause an adaptation of the users' eye-hand coordination. Further, misalignment may cause a decrease in manipulation performance compared to aligned conditions. This experimental study uses a prism-adaptation paradigm to explore visuomotor adaptation to misaligned virtual hand position. Participants were immersed in an interactive virtual environment with a deliberately misaligned virtual hand position (a lateral shift of 10 cm). We carried out pointing tests with a nonvisible hand in the real world before (pretest) and after (posttest) immersion in the virtual world. A comparison of preand post-tests revealed aftereffects of the adaptation of eye-hand coordination in the opposite direction of the lateral shift (negative aftereffects). The magnitude of the aftereffect was 20% under stereoscopic viewing conditions. However, decreased manipulation performance in VE (speed/accuracy) during the immersion with misaligned hand conditions was not found.
Fitness Landscapes, Memetic Algorithms, and Greedy Operators for Graph Bipartitioning
Authors: Merz Peter , Freisleben Bernd
Published: July 2002

The fitness landscape of the graph bipartitioning problem is investigated by performing a search space analysis for several types of graphs. The analysis shows that the structure of the search space is significantly different for the types of instances studied. Moreover, with increasing epistasis, the amount of gene interactions in the representation of a solution in an evolutionary algorithm, the number of local minima for one type of instance decreases and, thus, the search becomes easier. We suggest that other characteristics besides high epistasis might have greater influence on the hardness of a problem. To understand these characteristics, the notion of a dependency graph describing gene interactions is introduced. In particular, the local structure and the regularity of the dependency graph seems to be important for the performance of an algorithm, and in fact, algorithms that exploit these properties perform significantly better than others which do not. It will be shown that a simple hybrid multi-start local search exploiting locality in the structure of the graphs is able to find optimum or near optimum solutions very quickly. However, if the problem size increases or the graphs become unstructured, a memetic algorithm (a genetic algorithm incorporating local search) is shown to be much more effective.
Optical Coating Designs Using the Family Competition Evolutionary Algorithm
Authors: Yang Jinn-Moon , Horng Jorng-Tzong , Lin Chih-Jen , Kao Cheng-Yan
Published: July 2002

A robust evolutionary approach, called the Family Competition Evolutionary Algorithm (FCEA), is described for the synthesis of optical thin-film designs. Based on family competition and adaptive rules, the proposed approach consists of global and local strategies by integrating decreasing mutations and self-adaptive mutations. The method is applied to three different optical coating designs with complex spectral quantities. Numerical results indicate that the proposed approach performs very robustly and is very competitive with other approaches.
The Road to the Austrian State Treaty
Authors: Williams Warren W.
Published: July 2002

The path that led to Austrian independence in 1955 has often been ignored in Cold War scholarship. Although Austria was a battleground for East-West conflict in Europe from 1945 to 1955, it often gets short shrift compared to the detailed analysis of Germany's role in the Cold War. This essay seeks to redress that imbalance, taking as a starting point the valuable new book by Günter Bischof, Austria and the First Cold War, 1945–1955. Bischof's analysis is not uniformly convincing, but he makes a valuable contribution to our understanding of a neglected part of Cold War history. Although the book provides some helpful speculation about why the Soviet Union decided to sign the Austrian State Treaty after years of stalling, far more research on this particular issue is needed.
"AUF DER MAUER – AUF DEM ALTAR" NOCH EINMAL DIE VISIONEN DES AMOS
Authors: Bergler Siegfried
Published: July 2002

Nach Würdigung der bisherigen Bewertung der fünf sog. Amos-Visionen (Am vii 1-3; vii 4f.; vii 7f.; viii 1f.; ix 1-4) erfolgt eine Neubetrachtung aufgrund festzustellender formaler, sprachlicher und inhaltlicher Parallelen zwischen der 3. und 5. Vision. Es wird die These vertreten, dass – falls die letzte eine spätere Hinzufügung sein sollte – zwingend auch die dritte eine zeitgleiche Sekundärbildung darstellen muss. Zudem interpretieren beide Strophen einander, was besonders der Erhellung des Begriffes "an k und des Textverständnisses von ix 1a dient. Andererseits wird aufgezeigt, warum das erste Visionenpaar zusammen mit der abschließenden (vierten!) Gerichtsvision über das Nordreich eine ursprüngliche Einheit, wahrscheinlich noch aus Amos' Feder, bildete. Vor allem die postulierte Abhängigkeit von der Berufungsvision Jes vi legt es nahe, Vision 3 und 5 frühestens ins ausgehende 7. Jh. v. Chr. zu datieren und als Ansage des Untergangs Jerusalems und des Südreiches zu werten.
CRUSTACEAN BIODIVERSITY IN ANCIENT LAKES: A REVIEW
Authors: Martens Koen , Schon Isa
Published: July 2002

Several crustacean groups have produced extensive species flocks in ancient lakes. However, except for the Amphipoda in Lake Baikal, crustacean diversity per se is not significantly higher in ancient lakes than in non-marine aquatic habitats in general. Yet the degree of endemicity in such long-lived habitats is certainly higher in these crustacean groups than in the average of noncrustacean groups. Causality must thus be sought in the evolutionary biology, rather than in the ecology of the groups at issue. Several potential, intrinsic factors, possibly promoting speciation, have been cited, but thus far no singular cause for high crustacean endemicity in ancient lakes could be demonstrated. Plusieurs groupes de crustaces ont produit de vastes ensembles d'especes dans les lacs anciens. Cependant, excepte pour les amphipodes du lac Baikal, la diversite des crustaces en elle-meme n'est pas significativement plus grande dans les lacs anciens que dans les habitats aquatiques nonmarins en general. Pourtant, le degre d'endemisme dans des habitats habites de si longue date est certainement plus eleve dans les groupes de crustaces que dans la moyenne des groupes non crustaces. La cause doit alors etre recherchee dans la biologie evolutive, plutot que dans l'ecologie des groupes concernes. Plusieurs facteurs potentiels, intrinseques, pouvant induire la speciation, ont ete cites, mais pour l'instant, aucune cause particuliere n'a pu etre etablie pour expliquer l'endemisme crustaceen superieur dans les lacs anciens.
Analysis of chemosensory responses of second stage juveniles of Globodera rostochiensis using electrophysiological techniques
Authors: Rolfe Richard , Barrett John , Perry Roland
Published: July 2002

Electrophysiological techniques were developed to obtain recordings of
electrical activity from the anterior end of live, second stage juveniles
(J2) of Globodera rostochiensis. Sequential exposure of individual J2 to
test semiochemicals was also possible using a modified perfusion system.
Concentration-dependent responses were obtained from J2 during exposure to
0.1, 1, 10 and 100 mM acetylcholine. The delay before any response was not
concentration-dependent. The responses to 10 mM concentrations of several
chemicals known to elicit a feeding response in insects were assessed. There
was a significant increase in spike activity when J2 were exposed to
D-tryptophan but glycine and citric acid elicited no responses. Exposure to
D-glutamic acid resulted in a significant increase in spike activity but
exposure to the L-isomer gave no response. This was confirmed by sequential
exposure of J2 to the L- then to the D-isomer. Exposure to potato root
diffusate elicited a response, whereas a non-host root diffusate from sugar
beet and female secretory-excretory (S-E) product caused no change in
activity. Die Analyse chemosensorischer Reaktionen von Juvenilen des zweiten
Stadiums von Globodera rostochiensis mit elektrophysiologischen Techniken -
Zur Gewinnung von Informationen über die elektrische Aktivität des
Vorderendes von Juvenilen des zweiten Stadiums (J2) von Globodera
rostochiensis wurden elektrophysiologische Untersuchungsmethoden entwickelt.
Aufeinander folgende Behandlungen einzelner J2 zur Prüfung von
Semiochemikalien wurden auch durch ein verändertes Perfusionssystem
erreicht. Bei der Behandlung von J2 mit 0.1, 1, 10 und 100 mM Acetylcholin
wurden konzentrationsabhängige Reaktionen erzielt. Die Verzögerung vor dem
Sichtbarwerden einer Reaktion war dagegen nicht konzentrationsabhängig. Es
wurden auch die Reaktionen auf 10 mM Konzentrationen mehrerer Substanzen
geprüft, die bei Insekten eine Nahrungsaufnahme auslösen. Bei D-Tryptophan
trat eine deutliche Erhöhung der Spitzenaktivität ein, bei Glycin und
Zitronensäure erfolgte keine Reaktion. Eine Behandlung mit DGlutaminsäure
erhöhte die Spitzenaktivität deutlich, nicht jedoch das L-Isomer. Diese
Beobachtung wurde bestätigt, wenn man die J2 erst dem L- und anschließend
dem D-Isomer aussetzte. Die Behandlung mit Kartoffelwurzel-Ablaufwasser rief
eine Reaktion hervor, nicht aber Wurzelextrakte des Nichtwirtes Zuckerrübe
und Produkte des sekretorisch-exkretorischen Systems von Weibchen.
Quartz cementation inhibited by crestal oil charge: Miller deep water sandstone, UK North Sea
Authors: Marchand A. M. E. , Haszeldine R. S. , Macaulay C. I. , Swennen R. , Fallick A. E.
Published: July 2002

In the Miller Field, diagenetic quartz abundance, isotopic compositions and salinities of quartz-cementing fluids display a distinct pattern which is related to the structural depth of the reservoir sandstones. Quartz cement volumes increase from the crest of the field (average 6.0±1.5%) towards the flanks of the field (average 13.2±2.1%) and directly reduce reservoir porosity. By integrating petrographic observations with results of fluid inclusion measurements and O isotope analyses of diagenetic quartz, the pattern of quartz cementation is seen to be related to the reservoir filling history. Oil filled the crest of the reservoir first and prevented extensive quartz cementation. At greater depth in the reservoir oil zone, quartz overgrowths continued to precipitate until inhibited by the developing oil column. Oxygen isotope compositions of diagenetic quartz imply that quartz cement continued to precipitate in the water zone of the reservoir up to the present day.
Methods of laser-based stable isotope measurement applied to diagenetic cements and hydrocarbon reservoir quality
Authors: Macaulay C. I. , Fallick A. E. , Haszeldine R. S. , Graham C. M.
Published: July 2002

The stable isotopic compositions of diagenetic minerals can provide valuable constraints on the sources, precipitation temperatures and relative timing of cements in reservoir rocks. This type of information is essential when trying to understand and predict the distribution of cements in the subsurface, and their impact on reservoir quality. Conventional isotope methods contribute to answers to many diagenetic problems, but where core or time are scarce, or where good mineral separation is unobtainable, laser-based stable isotope methods offer several advantages. These include the ability to analyse carbonates, sulphides and anhydritein situwith 50–100 μm resolution, simple and clear sample and analysis viewing optics, savings on sample preparation time and greatly reduced sample size requirements.

Diagenetic silicates such as quartz and clay cements cannot be analysedin situby laser but, wherein situanalysis of quartz δ18O is demanded, ion microprobe analysis can provide very high resolution (20–30 μm) capability with a precision of ±1%.
Climate, tectonics and meteoritic impact expressed by clay mineral sedimentation across the Cretaceous–Tertiary boundary at Blake Nose, Northwestern Atlantic
Authors: Martínez–Ruiz F. , Ortega-Huertas M. , Palomo I.
Published: July 2002

The ODP Leg 171B drilled a transect of four sites at Blake Nose in the NW Atlantic providing an excellent record of the K-T boundary. At the deepest, Site 1049, the boundary is marked by a 9–17 cm thick layer formed mostly of green spherules composed of Fe-rich smectite resulting from the diagenetic alteration of tektites and impact glasses. Minor amounts of authigenic zeolites and palygorskite also occur. This association represents a notable break in the clay mineral composition of Cretaceous and Tertiary sequences. The clay mineral assemblages of the Cretaceous and Tertiary sediments are dominated by inherited clays. Aluminium-rich smectite of pedogenic origin is abundant in both Cretaceous and Tertiary sediments, indicating a relatively warm and hydrolysing climate across the K-T boundary. At Hole 1049A, where the oldest sediments of the interval were analysed, an increase in kaolinite and smectite down core suggests tectonic rejuvenation and distal transport of illite and kaolinite, probably accompanied by more hydrolysing conditions during the late Maastrichtian.
Aluminium solubility characteristics of spodic B horizons containing imogolite-type materials
Authors: Gustafsson J. P. , Lumsdon D. G. , Simonsson M.
Published: July 2002

Fifteen Swedish and Finnish soil samples from spodic B horizons containing imogolite-type materials were equilibrated with dilute NaCl and HC1 at 8°C. For the NaCl extracts, apparent equilibrium with respect to an AI(OH)3 phase was reached in one to two weeks. Equilibrium with respect to an imogolite-type phase was slower, especially at large soil:solution ratios. The results show that log *Ks (gibbsite), i.e. the logarithm of the solubility constant for reactive AI(OH)3 at 8°C was ~9.40 (8.29 at 25°C) while log *Ks (imogolite) was variable; for the soil studied in most detail it was 7.66 (6.64 at 25°C) As well-ordered gibbsite rarely forms in spodic B horizons, it is suggested that Al(OH)3 and poorly-ordered allophanic materials may be slowly converted to less soluble and less reactive imogolite-type materials.
Leonite [K2Mg(SO4)2·4H2O], konyaite [Na2Mg(SO4)2·5H2O] and syngenite [K2Ca(SO4)2·H2O] fromTausoare Cave, Rodnei Mts, Romania
Authors: Onac B. P. , White W. B. , Viehmann I.
Published: July 2002

Tausoare Cave is renowned in Romania for its gypsum and mirabilite speleothems. Of interest are the white crystalline speleothems formed on the floor of the ‘Sala de Mese’ (Dining Room) that were previously described as consisting of mirabilite. The samples we collected reveal crystals of two different habits. One shows the characteristic mirabilite fibrous crystals (cotton-like speleothem) while the other formed bladed and short prismatic crystals which comprise the delicate ‘cave flowers’. The mineral association was characterized by means of X-ray analysis, scanning electron microscopy and electron microprobe. Beside thenardite (dehydration product of mirabilite) we also identified three sulphate minerals: leonite [K2Mg(SO4)2·4H2O], syngenite [K2Ca(SO4)2·H2O] and konyaite [Na2Mg(SO4)2·5H2O]. Of these, leonite and konyaite have never been reported in a cave environment. This paper describes the mineralogy of this particular sulphate deposit and offers some viewpoints on the crystallogenesis.
Nucleation environment of diamonds from Yakutian kimberlites
Authors: Bulanova G. P. , Griffin W. L. , Ryan C. G.
Published: July 2002

The micro-inclusions located in the genetic centre of Yakutian diamond monocrystals have been studied using optical (anomalous birefringence, photoluminescence, cathodoluminescence) and microanalytical (electron-microprobe, proton-microprobe, scanning electron microscope) methods. Most diamonds nucleated heterogeneously on mineral seeds, that lowered the energy barrier to nucleation. Nucleation of peridotitic diamonds occurred on a matrix of graphite+iron+wüstite, in an environment dominated by forsteritic olivine and Fe-Ni sulfide. Nucleation of eclogitic diamonds occurred on a matrix of sulfide ± iron in an environment dominated by Fe-sulfide and omphacite (±-K-Na-Al-Si-melt). The mineral assemblages recorded in the central inclusions of Yakutian diamonds indicate that they grew in a reduced environment, with oxygen fugacity controlled by the iron-wüstite equilibrium. Nucleation of diamond occurred in the presence of a fluid, possibly a volatile-rich silicate melt, highly enriched in LIL (K, Ba, Rb, Sr) and HFSE (Nb, Ti, Zr) elements. This fluid also carried immiscible Fe-Ni-sulfide melts, and possibly a carbonatitic component; the introduction of this fluid into a reduced refractory environment may have been accompanied by a thermal pulse, and may have created the conditions necessary for the nucleation and growth of diamond.
Stability of F-Ti-phlogopite in the system phlogopite–sillimanite–quartz: an experimental study of dehydration melting in H2O-saturated and undersaturated conditions
Authors: Tareen J. A. K. , Keshava Prasad A. V. , Basavalingu B. , Ganesha A. V.
Published: July 2002

Melt generation during granulite-grade metamorphism is believed to be controlled by the stability temperatures of biotite, whose breakdown provides H2O and controls fluid-absent melting in the lower crust. In a simple KMASH system, the restite minerals crystallising due to incongruent melting of phlogopite depend upon the bulk composition. In an alumina-poor and silica-rich portion of the system (Phl + Qtz), enstatite appears with the melt, while in an alumina-rich system (Phl + Sil + Qtz) cordierite appears first instead of enstatite. Since the temperature of biotite stability is believed to be strongly controlled by its F and Ti content, it will have significant effect on the fluid-absent melting reactions during granulite-grade metamorphism of mica-containing granites as well as pelitic rocks in the deeper crust.

To understand such effects in an aluminous portion of the KMASH system, experiments were performed (between 850 and 1100°C and at 7, 10 and 12 kbar) with bulk composition containing 2Phl-6Sil- 9Qtz, where natural phlogopite with F/(F+OH) = 0.39 and Mg/(Mg+Fe) = 0.96 was used. In runs with this charge and containing 5 wt.% of excess water, cordierite appeared around 920°C at 7 kbar and 990°C at 12 kbar, and it disappeared at about 1080°C with the appearance of 221 sapphirine. In fluid-absent runs, these boundaries marginally shift to higher temperatures (30-50°C). The enstatite which was distinctly absent in H2O-saturated runs, crystallises in the high-temperature sapphirine field with up to 12 wt.% Al2O3 in H2O-undersaturated runs. The enstatite formation with cordierite is perhaps inhibited due to the Al consumption by cordierite and instability of Al-free enstatite at temperatures of cordierite stability. Re-equilibrated phlogopite persists in both the cordierite and sapphirine fields. The temperatures of the beginning of phlogopite breakdown are about 100-140°C above those reported for reaction Phl + Qtz → En + Sa + L (Vielzeuf and Clemens, 1992) with F and Ti-free phlogopite, but are ≈50–100°C lower than the temperatures reported (Tareen et al., 1995; Dooley and Patino Douce, 1996) for the same reaction containing F- and Ti- bearing phlogopite. The combined effect of the F and Ti content in phlogopite on its stability temperatures in the KMASH system has been found to be additive in relation to those containing only F or Ti. H2O-saturated runs produced per-aluminous melts with ≈27 wt.% Al2O3 in the cordierite field and ≈23% Al2O3 in the sapphirine field. The H2O-undersaturated runs produced melts rich in K2O (≈10 wt.%), SiO2 (72.5 wt.%) and relatively poor Al2O3 (12 wt.%).
Zussmanite in ferruginous metasediments from Southern Central Chile
Authors: Massonne H.-J. , Hervé F. , Medenbach O. , Muñoz V. , Willner A. P.
Published: July 2002

Zussmanite KFe13[AlSi17O42](OH)14, a modulated 2:1 layer silicate, has so far been found only in iron-rich metasediments from Laytonville, California (Agrell et al.), 1965). A new occurrence is reported here from Punta Nihue north of Valdivia, Chile, in banded stilpnomelane-schists. These are intercalated in the ‘Western Series’, a complex of low-grade metamorphic rocks with local high-pressure, low-temperature overprint (e.g. blueschists).

The rock contains conspicuous porphyroblasts of zussmanite of mm size and is composed of chemically distinct bands with the subsequent assemblages: (1) zussmanite-stilpnomelane-quartz, (2) siderite-quartz±stilpnomelane (3) apatite-stilpnomelane-quartz±siderite. The chemical composition of zussmanite, (K0.80Na0.05Ba0.01)(Fe11.292+Mg1.11Mn0.25Fe0.143+Cr0.01Al0.19Ti0.01)[Al1.23Si16.77O42](OH)14, its optical properties and X-ray data correlate well with the Californian occurrence. Additionally, we present new IR data. In type (2) bands of fine-grained crystals of a K,Al poor mineral formed from siderite and quartz. Its chemical composition is close to that of zussmanite. A similar phase was also reported from Laytonville, California (Muir Wood, 1980).

The rarity of rock-forming zussmanite can be explained by its occurrence in strongly Fe-rich and reduced rocks, as well as, by a possibly narrow P-T stability field.
Recent examples of cathodoluminescence as a probe of surface structure and composition
Authors: Townsend P. D. , Karali T. , Rowlands A. P. , Smith V. A. , Vazquez G.
Published: July 2002

Cathodoluminescence (CL) provides a sensitive analytical probe of the near-surface region of insulating materials, and some new examples of the strengths of the technique are presented using recent data from the University of Sussex. Analysis of float glass shows that by spectral and lifetime resolved data it is possible to separate the emission bands from excitonic, intrinsic imperfections, and impurities in various valence states, as a function of their depth beneath the surface. Correlation of the CL data with those from Mössbauer, ion beam and other analyses then provides the basis for models of the defect sites. CL from a second glass, ZBLAN, reveals the presence of microcrystallites and growth defects, and the work underpins confidence in the high purity gas levitation method of ZBLAN production. New results on CL of wavelength shifts with crystal field of Mn in carbonates are presented, and of Nd emission from Nd:YAG. The effects are directly linked to surface damage and dislocations caused by sample preparation steps of cutting and polishing. Methods to minimise the damage, by furnace or pulsed laser annealing, and chemical routes, are mentioned. Such surface preparation damage has a profound effect on all CL monitoring, whether for fundamental studies or mineralogical applications. Finally, a route to eliminate such problems is demonstrated, with consequent improvements in luminescence, transmission and laser performance of surface waveguides. The implications of improved surface quality range widely from mineralogical CL imaging through improved photonic materials and epitaxial growth to elimination of surface damage, and additional information.
Red blood cells inhibit activation-induced cell death and oxidative stress in human peripheral blood T lymphocytes
Authors: Fonseca Ana Mafalda , Porto Graça , Uchida Koji , Arosa Fernando A.
Published: July 2002

Red blood cells (RBCs) are known to perform one prominent function: to carry and deliver oxygen to the tissues. Earlier studies, however, suggested a role for RBCs in potentiating T-cell proliferation in vitro. Here it is shown that the presence of RBCs in cultures of stimulated human peripheral blood lymphocytes strengthens T-cell proliferation and survival. Analysis of phosphatidylserine externalization and DNA fragmentation showed that RBCs inhibit T-cell apoptosis. This inhibition correlated with a reduction in CD71 but not CD95 expression. RBCs enhanced T-cell proliferation and survival upon activation with phytohemagglutinin and with OKT3 antibodies. Studies aimed at characterizing the cellular and molecular basis of the protection afforded to T cells by RBCs showed that (1) optimal protection required intact RBCs and red cell/T-cell contact but not monocytes; (2) RBCs markedly reduced the level of intracellular reactive oxygen species; and (3) RBCs inhibited the formation of protein-bound acrolein, a peroxidation adduct in biologic systems. Overall, these data indicate that human RBCs protect T cells from activation-induced cell death, at least in part by reducing the pro-oxidant state, and suggest a role for RBCs as conceivable modulators of T-cell homeostasis.
Arrest of human dendritic cells at the CD34−/CD4+/HLA-DR+ stage in the bone marrow of NOD/SCID-human chimeric mice
Authors: Nobuyoshi Masaharu , Kusunoki Yoichiro , Seyama Toshio , Kodama Kazunori , Kimura Akiro , Kyoizumi Seishi
Published: July 2002

Human dendritic cell (DC) precursors were engrafted and maintained in NOD/SCID- human chimeric mice (NOD/SCID-hu mice) implanted with human cord blood mononuclear cells, although no mature human DCs were detected in lymphoid organs of the mice. Two months after implantation, bone marrow (BM) cells of NOD/SCID-hu mice formed colonies showing DC morphology and expressing CD1a in methylcellulose culture with granulocyte-macrophage colony-stimulating factor (GM-CSF) and tumor necrosis factor α (TNF-α). The CD34−/CD4+/HLA-DR+ cell fraction in NOD/SCID-hu mouse BM generated CD1a+ cells that were highly stimulatory in mixed leukocyte reactions in culture with GM-CSF and TNF-α. These results suggest a strong potential for NOD/SCID-hu BM to generate human DCs, although DC differentiation may be blocked at the CD34−/CD4+/HLA-DR+ stage.
Live attenuated measles virus induces regression of human lymphoma xenografts in immunodeficient mice
Authors: Grote Deanna , Russell Stephen J. , Cornu Tatjana I. , Cattaneo Roberto , Vile Richard , Poland Gregory A. , Fielding Adele K.
Published: July 2002

Derivatives of the Edmonston-B strain of measles virus (MV-Ed) are safe, live attenuated measles virus (MV) vaccines that have been used worldwide for more than 30 years. The cytoreductive potential of MV-Ed has been investigated in murine models of both aggressive and indolent B-cell lymphoma in severe combined immunodeficient (SCID) mice. The rationale for these studies was generated by experience with viral fusogenic membrane glycoproteins as cytotoxic genes and the recognition of the potential of replicating viruses in the treatment of human malignancy. Intratumoral injection of both unmodified MV-Ed and a strain of MV-Ed genetically modified by the addition of a β-galactosidase reporter gene (MVlacZ) induced regression of large established human lymphoma xenografts, in contrast to control therapy with UV-inactivated virus, in which all tumors progressed. The antitumor effect still occurred in the presence of passively transferred anti-MV antibody. Intravenous administration of MV also resulted in considerable slowing of tumor progression. Analysis of sections of residual tumor confirmed replication of MV within the tumors. Thus, the vaccine strain of MV mediates regression of large, established human B-cell lymphoma xenografts in SCID mice, and proof of principle is established that MV is oncolytic for lymphomas in vivo. Attenuated MVs may have value as a novel replicating-virus therapy for this group of disorders.
Mechanisms of granulocytosis in the absence of CD18
Authors: Horwitz Bruce H. , Mizgerd Joseph P. , Scott Martin L. , Doerschuk Claire M.
Published: July 2002

Genetic deficiency in CD18 leads to disease characterized by myeloid hyperplasia, including profound granulocytosis and splenomegaly. Myeloid hyperplasia could directly result from the disruption of CD18 functions essential to granulopoiesis or basal leukocyte trafficking. Alternatively, myeloid hyperplasia could be reactive in nature, due to disruption of essential roles of CD18 in leukocyte responses to microbial challenge. To distinguish between these mechanisms, the hematopoietic systems of lethally irradiated wild-type (WT) mice were reconstituted with either WT fetal liver cells or CD18-deficient fetal liver cells, or an equal mixture of both types of cells. Granulocytosis and splenomegaly developed in mice that received CD18-deficient fetal liver cells. Splenomegaly was prevented and granulocytosis was inhibited by more than 95% in mice that had received both CD18-deficient and WT fetal liver cells, suggesting that myeloid hyperplasia was largely reactive in nature. Consistent with this postulate, the circulating life spans in the blood and the fraction of neutrophils that incorporated BrdU in the bone marrow were not increased for CD18-deficient neutrophils compared with the WT. However, these animals did develop mild granulocytosis compared with mice reconstituted with WT cells alone, and a higher percentage of CD18-deficient leukocytes were neutrophils compared with the WT leukocytes. These observations suggest that the granulocytosis observed in the absence of CD18 occurs through at least 2 mechanisms: one that is dramatically improved by the presence of WT cells, likely reactive in nature, and a second that is independent of the WT hematopoietic cells, involving an alteration in the lineage distribution of blood leukocytes.
Defective development of NK1.1+ T-cell antigen receptor αβ+ cells in zeta-associated protein 70 null mice with an accumulation of NK1.1+CD3− NK-like cells in the thymus
Authors: Iwabuchi Kazuya , Iwabuchi Chikako , Tone Saori , Itoh Daisuke , Tosa Noriko , Negishi Izumi , Ogasawara Kazumasa , Uede Toshimitsu , Onoé Kazunori
Published: July 2002

Development of natural killer 1.1+ (NK1.1+) CD3+ (NK1.1+ T) cells was analyzed in zeta-associated protein 70 (ZAP-70) null (−/−) mice. Both NK1.1+ TCRαβ+ and NK1.1+TCRγδ+ cell populations were absent in the thymus and spleen. By contrast, the number of NK1.1+ CD3−cells was increased in these tissues. The NK1.1+CD3− thymocytes in ZAP-70−/− mice had surface phenotypes in common with NK or NK1.1+ T cells. However, some of them were discordant either with NK cells or with NK1.1+ T cells. The NK1.1+ CD3−cells produced interferon-γ upon stimulation with NK1.1 cross-linking in the presence of interleukin-2 and exhibited a substantial cytotoxicity against YAC-1 cells. Moreover, the generation of NK1.1+ T cells with invariant Vα14Jα281 chains was induced from the NK1.1+ CD3− thymocytes following stimulation with phorbol myristate acetate and ionomycin in a neonatal thymic organ culture. An introduction of TCRα and β transgenes to the ZAP-70−/− mice resulted in generation of an NK1.1+ TCRαβdim population, whereas no substantial CD4+ CD8− or CD4−CD8+ population that expressed the introduced TCRαβ was generated in the mainstream T lineage. These findings demonstrate that ZAP-70 kinase is indispensable for the development of NK1.1+ T cells and that the unique NK1.1+ CD3− thymocytes in ZAP-70−/− mice contain immediate precursors of NK1.1+ T cells.
The interleukin-13 receptor α2 chain: an essential component for binding and internalization but not for interleukin-13–induced signal transduction through the STAT6 pathway
Authors: Kawakami Koji , Taguchi Jun , Murata Takashi , Puri Raj K.
Published: July 2002

The interleukin-13 receptor (IL-13R) complex is composed of 2 different chains, IL-13Rα1 (also known as IL-13Rα′) and IL-13Rα2 (also known as IL-13Rα). For a functional IL-13 receptor, the IL-13Rα1 chain forms a productive complex with the primary IL-4 binding protein (IL-4Rα also known as IL-4Rβ). However, the function of the IL-13Rα2 chain is not clear even though this chain binds IL-13 with high affinity. This study demonstrates that IL-13Rα2 can undergo internalization after binding to ligand without causing activation of its signaling pathways. These conclusions were drawn on the basis of (1) internalization of 125I–IL-13 in Chinese hamster ovarian (CHO-K1) and T98G glioblastoma cells transiently transfected with the IL-13Rα2 chain; (2) a recombinant chimeric fusion protein comprising IL-13 and a mutated form ofPseudomonas exotoxin (termed IL13-PE38QQR or IL-13 toxin) is specifically cytotoxic to IL-13Rα2–transfected CHO-K1 cells in a gene dose-dependent manner, whereas cells transfected with vector alone were not sensitive; and (3) IL-13 did not cause activation of signal transduction and activation of transcription 6 (STAT6) in IL-13Rα2–transfected cells. IL-13 efficiently caused activation of STAT6 protein in cells transfected with the IL-13Rα1 and IL-4Rα chains, and IL-13Rα2 inhibited this activation. Taken together, these observations indicate that internalization of IL-13Rα2 is signal independent and that this property of IL-13Rα2 can be exploited for receptor-directed cancer therapy.
Rapamycin induces apoptosis in monocyte- and CD34-derived dendritic cells but not in monocytes and macrophages
Authors: Woltman Andrea M. , de Fijter Johan W. , Kamerling Sylvia W. A. , van der Kooij Sandra W. , Paul Leendert C. , Daha Mohamed R. , van Kooten Cees
Published: July 2002

Rapamycin (Rapa), a recently introduced immunosuppressive drug, seems to be effective in preventing acute allograft rejection. Although its antiproliferative effect on T lymphocytes has been investigated extensively, its effect on the initiators of the immune response, the dendritic cells (DCs), is not known. Therefore, the effect of Rapa on monocyte- (mo-DCs) and CD34+-derived DCs in vitro but also on other myeloid cell types, including monocytes and macrophages, was examined. The present study shows that Rapa does not affect phenotypic differentiation and CD40L-induced maturation of mo-DCs. However, Rapa dramatically reduced cell recovery (40%-50%). Relatively low concentrations of Rapa (10−9 M) induced apoptosis in both mo-DCs and CD34+-derived DCs, as visualized by phosphatidylserine exposure, nuclear condensation and fragmentation, and DNA degradation. In contrast, Rapa did not affect freshly isolated monocytes, macrophages, or myeloid cell lines. The sensitivity to Rapa-induced apoptosis was acquired from day 2 onward of mo-DC differentiation. Rapa exerts its apoptotic effect via a reversible binding to the cytosolic receptor protein FKBP-12, as demonstrated in competition experiments with FK506, which is structurally related to Rapa. Partial inhibition of Rapa-induced apoptosis was obtained by addition of ZVAD-fmk, which implies caspase-dependent and caspase-independent processes. The fact that Rapa exerts a specific effect on DCs but not on monocytes and macrophages might contribute to the unique actions of Rapa in the prevention of allograft rejection and other immune responses.