bluuebunny/crossref_metadata_2025 huggingface dataset:
Representational Accuracy of Stochastic Neural Populations
Authors: Wilke Stefan D. , Eurich Christian W.
Published: July 2002

Fisher information is used to analyze the accuracy with which a neural population encodes D stimulus features. It turns out that the form of response variability has a major impact on the encoding capacity and therefore plays an important role in the selection of an appropriate neural model. In particular, in the presence of baseline firing, the reconstruction error rapidly increases with D in the case of Poissonian noise but not for additive noise. The existence of limited-range correlations of the type found in cortical tissue yields a saturation of the Fisher information content as a function of the population size only for an additive noise model. We also show that random variability in the correlation coefficient within a neural population, as found empirically, considerably improves the average encoding quality. Finally, the representational accuracy of populations with inhomogeneous tuning properties, either with variability in the tuning widths or fragmented into specialized subpopulations, is superior to the case of identical and radially symmetric tuning curves usually considered in the literature.
Modeling the Surround of MT Cells and Their Selectivity for Surface Orientation in Depth Specified by Motion
Authors: Liu Lin , Hulle Marc M. Van
Published: July 2002

The projective transformation onto the retina loses the explicit 3D shape description of a moving object. Theoretical studies show that the reconstruction of 3D shape from 2D motion information (shape from motion, SFM) is feasible provided that the first- and second-order directional derivatives of the 2D velocity field are available. Experimental recordings have revealed that the receptive fields of the majority of the cells in macaque area middle temporal (MT) display an antagonistic (suppressive) surround and that a sizable portion of these surrounds are asymmetrical. This has led to the conjecture that these cells provide a local measure for the directional derivatives of the 2D velocity field. In this article, we adopt a nonparametric and biologically plausible approach to modeling the role played by the MT surrounds in the recovery of the orientation in depth (the slant and tilt) of a moving (translating) plane. A three-layered neural network is trained to represent the slant and tilt from the projected motion vectors. The hidden units of the network have speed-tuning characteristics and represent the MT model neurons with their surrounds. We conjecture that the MT surround results from lateral inhibitory connections with other MT cells and that populations of these cells, with different surround types, code linearly for slant and tilt of translating planes.
Feature Extraction Through LOCOCODE
Authors: Hochreiter Sepp , Schmidhuber Jürgen
Published: July 2002

Low-complexity coding and decoding (LOCOCODE) is a novel approach to sensory coding and unsupervised learning. Unlike previous methods, it explicitly takes into account the information-theoretic complexity of the code generator. It computes lococodes that convey information about the input data and can be computed and decoded by low-complexity mappings. We implement LOCOCODE by training autoassociators with flat minimum search, a recent, general method for discovering low-complexity neural nets. It turns out that this approach can unmix an unknown number of independent data sources by extracting a minimal number of low-complexity features necessary for representing the data. Experiments show that unlike codes obtained with standard autoencoders, lococodes are based on feature detectors, never unstructured, usually sparse, and sometimes factorial or local (depending on statistical properties of the data). Although LOCOCODE is not explicitly designed to enforce sparse or factorial codes, it extracts optimal codes for difficult versions of the “bars” benchmark problem, whereas independent component analysis (ICA) and principal component analysis (PCA) do not. It produces familiar, biologically plausible feature detectors when applied to real-world images and codes with fewer bits per pixel than ICA and PCA. Unlike ICA, it does not need to know the number of independent sources. As a preprocessor for a vowel recognition benchmark problem, it sets the stage for excellent classification performance. Our results reveal an interesting, previously ignored connection between two important fields: regularizer research and ICA-related research. They may represent a first step toward unification of regularization and unsupervised learning.
Design and Implementation of a Virtual Reality System and Its Application to Training Medical First Responders
Authors: Stansfield Sharon , Shawver Daniel , Sobel Annette , Prasad Monica , Tapia Lydia
Published: July 2002

This paper presents the design and implementation of a distributed virtual reality (VR) platform that was developed to support the training of multiple users who must perform complex tasks in which situation assessment and critical thinking are the primary components of success. The system is fully immersive and multimodal, and users are represented as tracked, full-body figures. The system supports the manipulation of virtual objects, allowing users to act upon the environment in a natural manner. The underlying intelligent simulation component creates an interactive, responsive world in which the consequences of such actions are presented within a realistic, time-critical scenario. The focus of this work has been on the training of medical emergency-response personnel. BioSimMER, an application of the system to training first responders to an act of bio-terrorism, has been implemented and is presented throughout the paper as a concrete example of how the underlying platform architecture supports complex training tasks. Finally, a preliminary field study was performed at the Texas Engineering Extension Service Fire Protection Training Division. The study focused on individual, rather than team, interaction with the system and was designed to gauge user acceptance of VR as a training tool. The results of this study are presented.
A Virtual Environment Testbed for Training Laparoscopic Surgical Skills
Authors: Tendick Frank , Downes Michael , Goktekin Tolga , Cavusoglu Murat Cenk , Feygin David , Wu Xunlei , Eyal Roy , Hegarty Mary , Way Lawrence W.
Published: July 2002

With the introduction of minimally invasive techniques, surgeons must learn skills and procedures that are radically different from traditional open surgery. Traditional methods of surgical training that were adequate when techniques and instrumentation changed relatively slowly may not be as efficient or effective in training substantially new procedures. Virtual environments are a promising new medium for training.

This paper describes a testbed developed at the San Francisco, Berkeley, and Santa Barbara campuses of the University of California for research in understanding, assessing, and training surgical skills. The testbed includes virtual environments for training perceptual motor skills, spatial skills, and critical steps of surgical procedures. Novel technical elements of the testbed include a four-DOF haptic interface, a fast collision detection algorithm for detecting contact between rigid and deformable objects, and parallel processing of physical modeling and rendering. The major technical challenge in surgical simulation to be investigated using the testbed is the development of accurate, real-time methods for modeling deformable tissue behavior. Several simulations have been implemented in the testbed, including environments for assessing performance of basic perceptual motor skills, training the use of an angled laparoscope, and teaching critical steps of the cholecystectomy, a common laparoscopic procedure. The major challenges of extending and integrating these tools for training are discussed.
Fuzzy Posture Input for Virtual-Hand Models
Authors: Sun Hanqiu , Tsang Kwok-hang
Published: July 2002

Virtual-hand input realizes the natural and dexterous functionality in direct humancomputer interaction. The recognition of virtual-hand models is difficult due to two reasons: the complexity of hand structure and the lack of accurate measure, which may be caused by either mechanical noise or human factors. This paper presents a novel fuzzy-logic recognition system that can effectively deal with imprecise hand data. The system consists of three components: the classifier, identifier, and posture database. Fuzzy-logic processing is applied in both the classifier (to build class-indexing structure in the posture database) and in the identifier (to find the most likely match from the database in real-time VR applications). The posture database provides a GUI interface for the user to browse the posture images and interactively update the database by adding and deleting the sample postures, as well as adjusting the certainty threshold in recognition. Our experiments show that the fuzzy-logic method can keep nearly constant performance in recognition using tens of microseconds, even as the size of posture database increases. The recognition rate declines only slightly when the standard derivation of the noise distribution (Gaussian distribution) in the input parameters is below 15 deg. The bounded value in uniform distribution to achieve accurate recognition is below 20. The results show that the fuzzy-logic processing can improve the tolerance of noise or imprecise data in an efficient way. A free-hand modeler based on fuzzy-logic processing has been developed for creating virtual objects and Web-based 3-D VRML worlds.
Efficient Point-Based Rendering Techniques for Haptic Display of Virtual Objects
Authors: Ho Chih-Hao , Basdogan Cagatay , Srinivasan Mandayam A.
Published: July 2002

Computer haptics, an emerging field of research that is analogous to computer graphics, is concerned with the generation and rendering of haptic virtual objects. In this paper, we propose an efficient haptic rendering method for displaying the feel of 3-D polyhedral objects in virtual environments (VEs). Using this method and a haptic interface device, the users can manually explore and feel the shape and surface details of virtual objects. The main component of our rendering method is the “neighborhood watch” algorithm that takes advantage of precomputed connectivity information for detecting collisions between the end effector of a force-reflecting robot and polyhedral objects in VEs. We use a hierarchical database, multithreading techniques, and efficient search procedures to reduce the computational time such that the haptic servo rate after the first contact is essentially independent of the number of polygons that represent the object. We also propose efficient methods for displaying surface properties of objects such as haptic texture and friction. Our haptic-texturing techniques and friction model can add surface details onto convex or concave 3-D polygonal surfaces. These haptic-rendering techniques can be extended to display dynamics of rigid and deformable objects.
Teaching Industrial Ecology to Graduate Students: Experiences at the Norwegian University of Science and Technology
Authors: Marstrander Rolf , Brattebø Helge , Røine Kjetil , Støren Sigurd
Published: July 2002

We reflect on our experiences in developing and teaching industrial ecology to interdisciplinary classes of M.Sc. and Ph.D. students. During a three‐year period different ways of teaching a course in industrial ecology were tested. We conclude that an industrial ecology course has positive effects on the students' ability to acquire a holistic understanding of life‐cycle environmental performance, a skill much in demand by industry. Such a course should be based on problem‐oriented learning. We recommend the use of thematically‐focused seminars with time for both lectures and workshops. We found that substantial participation by teachers from different disciplines and partners from industry and government is very effective. Such a course also facilitates a broader process of change within the university. Implementing industrial ecology in the university requires a joint effort and collaboration among various faculties and departments, where research activities, student projects, as well as regular student teaching and tutoring, must be complementary elements of a major interdisciplinary strategy. Such a strategy has been employed at the Norwegian University of Science and Technology (NTNU) since the first initiatives in this area were taken in 1993, and this has led to our present more comprehensive Industrial Ecology Programme (IndEcol).
A Response to Andrew Moravcsik
Authors: Keeler John T. S.
Published: July 2002

The responses to Andrew Moravcsik's article discuss the main substantive and methodological points raised in it. Although most of the respondents agree that Moravcsik has properly highlighted the importance of commercial concerns for de Gaulle's policy on European integration, they question the validity of his sharp separation between de Gaulle's political and economic goals for France. Several commentators argue that political and commercial concerns (including agricultural concerns) were closely intertwined in de Gaulle'bs vision of French grandeur. John Keeler brings up another crucial question: Was French agriculture really an obstacle to France's position in Europe? He argues that de Gaulle successfully supported and modernized French agriculture because he was convinced that this would contribute to France's geopolitical position in Europe and the Western world. In two longer commentaries, Jeffrey Vanke and Marc Trachtenberg raise questions about Moravcsik's methodology and use of sources. Both agree that Moravcsik draws on an impressive array of available materials concerning de Gaulle. But they both wonder whether a definitive account of de Gaulle's policies can be written when the documentary record is still incomplete, a point raised by the
The Pakistan Federal Shariat Court, Section 4 of the Muslim Family Laws Ordinance, and the Orphaned Grandchild
Authors: Carroll Lucy
Published: July 2002

Section 4 of the Pakistan Muslim Family Laws Ordinance, 1961, dramatically altered the law of succession applicable to Muslims by granting to the orphaned grandchild(ren) the share that their deceased parent would have taken had s/he survived the propositus. The principle of representation incorporated in the Pakistani solution contrasts with the compulsory bequest relied upon by several Middle Eastern countries to deal with the same problem, although arguably representation more closely reflects the experience and expectations of the people of Pakistan. Nearly two decades later, the Federal Shariat Court was established and endowed with jurisdiction to declare a law contrary to "the Injunctions of Islam" and thus void. Some laws, however, were specifically exempted from the Court's jurisdiction; falling within this category is "Muslim Personal Law." A 1981 decision of the appellate Court (the Shariat Bench of the Supreme Court) held that the provisions of the Muslim Family Laws Ordinance were included within the phrase "Muslim Personal Law," and were thus outside the jurisdiction of the Federal Shariat Court. This position was reversed by another decision of the appellate Court in 1993, and the provisions of the Ordinance were immediately challenged on the basis of their alleged divergence from the "Injunctions of Islam." This essay reviews the provisions of section 4 of the Ordinance and examines the decision of the Shariat Court as regards this particular provision.
KRSNA'S INITIATION AT SĀNDĪPANI'S HERMITAGE
Authors: Couture André
Published: July 2002

In the Harivamśa 79 [HV], the Visnu-Purāna 5.21 [ViP], the Brahma-Purāna 86 [BrP], and the Bhāgavata-Purāna 10.45 [BhP], immediately after the young Krsna kills Kamsa, Krsna's initiation at Sāndīpani's hermitage takes place. To date, this strange episode has not been studied in its own right. Occasionally mentioned in scholarly works, no attempt has been made to understand the importance or significance of this event within the Krsna tradition. This paper begins with a summary of HV 79, and then moves on to examine the character of Sāndīpani, his connection with Garga/Gārgya, the initiation process and the underlying father/son relationships, as well as variations on these themes. The episode provides a narrative link between Samkarsana and Krsna's childhood and the rest of the story which deals with their adult life as ksatriyas, and as such, helps to clarify the overall structure of the HV. Emphasizing Sāndīpani's role as a guru, this paper uncovers, little by little, his connections with (1) the whole trimūrti comprised of Brahmā, Visnu and Śiva-Rudra, (2) the sacrificial logic which involves one who sacrifices, a deity and an officiant, and (3) the variations on the theme of filiation implied in the narration.
PSALM LX UND PSALM CVIII
Authors: Knauf Ernst Axel
Published: July 2002

This historical allusions in Ps lx are sufficiently specific to date this psalm to the years 599 or 598 B.C.E.; the psalm may thus be understood as the work of a single author. The repetition of Ps lx 7-12 in Ps cviii 7-14, with due regard for the whole composition of Pss cviii-cx, leads further proof to the dating of Ps cx (and cviii) to the reign of John Hyrcan. Within the (proto-) canonical psalter, Ps lx and cviii read related to each other as promise (Ps lx) and fulfillment (Ps cviii).
Spermiogenesis and testicular cycle of the lizard Tropidurus torquatus (Squamata, Tropiduridae) in the Cerrado of central Brazil
Authors: Colli Guarino , Vieira Gustavo H.C. , Báo Sônia , Wiederhecker Helga
Published: July 2002

We studied the spermiogenesis and testicular cycle of the lizard Tropidurus torquatus, using light and electron microscopy. Males bearing spermatozoa were present practically year-round and spermatogenic activity showed a regenerative phase from late dry season to the end of the rainy season (July to March), with low frequency of initial stages of the spermatogenic cycle, and a brief degenerative phase from April to June, lacking the total regression of seminiferous tubules. These characteristics resemble those from species with continuous reproductive cycles, contrasting with the strongly seasonal reproductive cycle of females. Spermiogenesis includes nuclear elongation, chromatin condensation, acrosomal and flagellar development, and elimination of excessive cytoplasm. We describe some new aspects in the spermiogenesis of T. torquatus, including the interaction between spermatid and Sertoli cell, acrosomal granule, subacrosomal granule, and the fibrous sheath formation. The testicular cycle of T. torquatus is very similar to that of other lizards that inhabit seasonal environments, and its spermiogenesis and ultrastructure of mature sperm display a number of conservative features.
CHANGES IN PREY SIZE PREFERENCES DURING SUCCESSIVE STAGES OF FORAGING IN THE MEDITERRANEAN WATER SHREW NEOMYS ANOMALUS
Authors: Rychlik Leszek
Published: July 2002

Prey size preferences in successive stages of foraging of Mediterranean water shrews Neomys anomalus Cabrera, 1907 were investigated in a terrarium. Seven shrews were tested individually in five experimental variants (simulating different habitat conditions) totally for 504 hours. Water shrews displayed partial preferences for prey size but they were selective from the very beginning of the foraging period. When searching for food, N. anomalus preferred big food portions, abandoning significantly more small than big portions. This tendency was especially strong when few food portions were available on land and there were no natural structures in the terrarium. Selection of big portions was intensified probably by their easier detection. Shrews hoarded proportionally more big than small portions in the scattered hiding-places. This tendency was intensified by the presence of natural structures, dispersion of food and reduction of food quantity placed on land. Later, however, more small than big food portions were eaten, apparently because small portions were easier to manipulate. Scattered food hoarding and preference of large prey are proposed to be the strategy of N. anomalus to maximise the energy net gain and minimise the predation risk and competition for food.
Clay mineral authigenesis along a mid-continental scale fluid conduit in Palaeozoic sedimentary rocks from southern Ontario, Canada
Authors: Ziegler K. , Longstaffe F. J.
Published: July 2002

Rocks above and below the Precambrian-Palaeozoic unconformity at the base of many Palaeozoic sedimentary basins of mid-continental North America are distinguished by secondary K-feldspar, chlorite and illite. Thrusting of the Appalachian foreland is generally considered responsible for the fluid migrations which caused this alteration. We have examined secondary chlorite and illite from Cambro-Ordovician rocks which overlie the unconformity in southern Ontario, Canada. This area is situated along the interface between the Michigan and Appalachian basins. Water involved in chloritic alteration at ~150°C has an O isotope composition compatible with a basinal brine evolved from seawater. Brine migration was probably triggered by the Taconic Orogeny to the east. In comparison, the secondary illite (365–321 Ma) largely postdates the Acadian Orogeny, and the illite-forming fluids have stable isotopic compositions typical of tepid (~40–55°C) meteoric water. We suggest that basement arches beneath southern Ontario were reactivated by this orogeny, which facilitated introduction of meteoric water. Similar alteration in underlying Precambrian rocks shows that fluid flow was focused along the unconformity during the regional Ordovician brine migration, as well as during the localized Mississippian introduction of fresh water.
Influence of exchange cation and layer charge on the isomerization of α-pinene over SWy-2, SAz-1 and Sap-Ca
Authors: Breen C. , Moronta A. J.
Published: July 2002

SWy-2 (Wyoming), Sap-Ca saponite (California) and SAz-1 (Cheto, Arizona) were exchanged with different cations (Al, Ni, Mg, Ca and Na). The catalytic activity of these ionexchanged clays was measured directly using the isomerization of α-pinene at 80°C for 2 h to yield camphene, limonene and other minor products. The order of activity for the different cationexchanged forms was Al > Ni > Mg > Ca > Na, which correlated well with the known polarizing power of these cations and the resulting interlayer acidity. Catalysts derived from Sap-Ca were the most active followed by SWy-2, with SAz-1 the least active by a considerable margin. The greater activity of Sap-Ca over SWy-2 was attributed to the high tetrahedral charge in the former. Reduction of the layer charge of SAz-1 using Li fixation caused a significant improvement in the catalytic activity of the Al-exchanged reduced-charge SAz-1.
A far infrared study of K+ ions during K+ ⇋ Ca2+ exchange in vermiculite
Authors: Badreddine R. , Le Dred R. , Prost R.
Published: July 2002

K+ ⇋ Ca2+ exchange was performed on a mixed-layer (phlogopite-vermiculite) sample from Palabora, Republic of South Africa. Exchange isotherms, X-ray diffraction patterns and far infrared (FIR) spectra of the mineral were obtained. Different mineralogical phases were identified during the exchange process: K-vermiculite, Ca-vermiculite and a regular mixed-layer (VK–VCa) phase. Two types of exchange sites for K+ were identified by FIR during the exchange process. The first type, dominant in the K-vermiculite, gives an absorption band at 76 cm–1. The other, which was the most pronounced site in the mixed-layer phase, gives an absorption band at 72 cm–1. The mixed-layer phase was formed only when oxidation of Fe2+ resulted in the internal compensation of part of the negative charge of vermiculite. This study shows that the high selectivity displayed by vermiculite for K+ is enhanced by the formation of the mixed-layer phase.
Reduction of nitrate to ammonium by sulphate green rust: activation energy and reaction mechanism
Authors: Hansen H. C. B. , Bender Koch C.
Published: July 2002

Iron(II)-containing minerals are potential inorganic nitrate reductants in soils and sediments. Specifically, synthetic green rust (Fe4IIFeIII2(OH)12SO4.yH2O, GR) reduces nitrate to ammonium. The reaction of GR with two different nitrate salts, NaNO3and Ba(NO3)2, has been compared. The reaction stoichiometry and the reaction order with respect to Fe(II) in GR does not change in the examined temperature range (15-50°C) irrespective of the nitrate salt used. Activation energies of 83.9±7.6 kJ mol-1and 90.5±6.9 kJ mol-1have been determined for the reaction of GR with NaNO3and Ba(NO3)2, respectively. However, for the latter reaction the rate of reaction is increased 40 times. Based on X-ray and M6ssbauer investigations, this acceleration of the reaction rates is attributed to the forced exchange of sulphate with nitrate in GR interlayers caused by precipitation of BaSO4outside the GR particles, a reaction which does not occur in the presence of NaNO3. This difference in anion exchange behaviour is confirmed by anion exchange experiments with the redox-inactive GR-analogue, pyroaurite. A reaction model initiated by nitrate electrostatically bound at positively charged sites of GR is proposed.
Ga/Al substitutions in synthetic kaolinites and smectites
Authors: Martin F. , Petit S. , Decarreau A. , Ildefonse Ph. , Grauby O. , Beziat D. , de Parseval Ph. , Noack Y.
Published: July 2002

The Ga for A1 substitution in kaolinites and smectites was studied using clay synthesis from initial gels having an (Al + Ga)/Si ratio of kaolinites andMGa = Ga/(Ga + A1) ratio ranging from 0 to 1. Only kaolinite was obtained for MGa in the range 0-0.10. For higher MGa, synthesized clays were both kaolinite and beidellite, or pure beidellites. The evolution of b cell parameters, and the appearance of avAI-OH-Ga absorption band at 3600 cm-1in FFIR spectra, proves the progressive substitution of AI by Ga in kaolinite. The low substitution of AI by Ga in kaolinite can be correlated with the large difference in ionic radii between Al3+and Ga3+which causes a large increase in cell dimensions. By contrast, the incorporation of Ga in smectites is easy and can be complete.
Extracting K-Ar ages from shales: a theoretical test
Authors: Środoń J.
Published: July 2002

Diagenetic evolution of illite-smectite in shales corresponds more closely than in other rocks to the thermal history of a sedimentary basin. In bentonites, illitization can be significantly retarded by the diffusion of K+ (Altaner et al., 1984; Clauer et al., 1997), and in sandstones it can be related to a localized hot fluid flow (e.g. Whitney & Northrop, 1987). Thus, extracting the diagenetic ages of illite-smectite from shales remains an important opportunity for the verification of basin history models.
Mineralogy and chemistry of ochre sediments from an acid mine drainage near a disused mine in Cornwall, UK
Authors: Singh Balwant , Wilson M. J. , McHardy W. J. , Fraser A. R. , Merrington G.
Published: July 2002

Ochre sediments from acid mine drainage in Cornwall have been investigated using X-ray diffraction, thermal methods, infrared spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy and chemical methods in order to determine their mineralogical and chemical composition. Fresh sediments consist of ferrihydrite and goethite. Large fractions of these minerals are dissolved by the ammonium oxalate treatment reflecting their poorly crystalline structure. Fresh sediments contain large amounts of surface-adsorbed SO4 (up to 9.3%) which is readily desorbed by the PO4 treatment. Goethite is the only mineral present in relatively older sediments and the mineral is well crystallized with rod-shaped morphology. Environmental conditions, such as pH and SO4 content, are not favourable for the presence of schwertmannite at the site. Iron minerals appear to be precipitating around filamentous algae and the shape of algae is preserved in the Fe oxide matrix. The ubiquitous presence of algae in close association with Fe minerals indicate their possible role in the crystallization of Fe oxides.
An infrared reflectance study of Si–O vibrations in thermally treated alkali-saturated montmorillonites
Authors: Karakassides M. A. , Gournis D. , Petridis D.
Published: July 2002

Infrared reflectance spectra of Li-, Na-, K-, Rb- and Cs-saturated samples of montmorillonite Zenith-N (Milos, Greece) have been measured in the 400–1300 cm-1 region in an attempt to elucidate the behaviour and migration properties of alkali cations after heating the montmorillonites at 300°C for 24 h. Deconvolution of the complex Si–O stretching band reveals that the component band that arises from the asymmetric stretching vibrations of the silicon-apical oxygen units exhibits the biggest change upon heating the montmorillonites. The normalized absorption area of this band has been correlated with the decrease in the layer charge due to the cation migration. Analysis of the IR data for each alkali-saturated montmorillonite has shown that only Li+ migrates near, or to, vacant octahedral sites.
Amorphous silica from the Rigid Unit Mode approach
Authors: Dove M. T. , Hammonds K. D. , Harris M. J. , Heine V. , Keen D. A. , Pryde A. K. A. , Trachenko K. , Warren M. C.
Published: July 2002

We apply the Rigid Unit Mode model, which was initially developed for crystalline silicates, to the study of the flexibility of silica glass. Using a density-of-states approach we show that silica glass has the same flexibility against infinitesimal displacements of crystalline phases. Molecular dynamics simulations also show that parts of the silica structure are able to undergo large spontaneous changes through reorientations of the SiO4 tetrahedra with no energy cost.
The crystal structure of brunogeierite, Fe2GeO4 spinel
Authors: Welch M. D. , Cooper M. A. , Hawthorne F. C.
Published: July 2002

Brunogeierite, Fe2GeO4, a = 8.4127(7) Å, V = 595.4(1) Å3, is a rare germanate spinel from Tsumeb, Namibia. Its structure has been refined to an R index of 2.2%. The oxygen parameter, u, is 0.2466(1), indicating nearly ideal cubic close-packing of oxygen atoms. There is exact agreement between the observed a unit-cell dimension and that calculated from the observed Ge–O and Fe–O bond lengths. The cations Ge and Fe are fully ordered at tetrahedral (A) and octahedral (B) sites, respectively, in keeping with synthetic germanate spinels, all of which are fully-ordered normal spinels.
Crustal anatexis and its relation to the exhumation of collisional orogenic belts, with particular reference to the Himalaya
Authors: Whittington A. G. , Treloar P. J.
Published: July 2002

We review the causes, mechanisms and consequences of crustal anatexis during the exhumation of metamorphic terranes, from a petrological perspective. During both prograde and retrograde metamorphism, limited influx of free hydrous fluids may result in small volumes of very hydrous melts, which cannot ascend far (if at all) before reaching their solidus. If thermal conditions for dehydration melting are attained in fertile micaceous crustal layers, much larger volumes of water-undersaturated granitic magmas may result, especially where limited external fluid influx raises water activities above those that may be buffered by dehydrating hydrous phases. Magmas have specific trace element characteristics depending on the reaction which formed them which, combined with accessory phase thermometry, may enable the (P-T) conditions of melting to be ascertained. Small volume-fraction magmas will typically remain as in situ migmatites unless their extraction is assisted by deformation. In turn, deformation will be focused in weaker partially molten zones, so that water-undersaturated magmas may often be mobilized. Once segregated, their ascent is limited by the rate of dyke propagation, and they may reach shallow levels (<2 kbar) before crystallizing. The complex interplay between deformation and melting is exemplified by the Miocene evolution of the central Himalaya, where thrust and normal faulting, melting and exhumation were all simultaneously active processes which were linked by feedback relations. In the Nanga Parbat Massif of the western Himalaya, rapid post-Miocene denudation and vigorous fluid flux enabled rocks to experience more than one episode of melting simultaneously, at different levels of the same exhuming crustal section.
Optical properties and crystal structure of triclinic growth sectors in vesuvianite
Authors: Tanaka T. , Akizuki M. , Kudoh Y.
Published: July 2002

Sectored vesuvianite showing optically triclinic properties was studied by X-ray and P-FTIR analyses, and the origins of the internal optical texture are discussed. A monoclinic refinement (space groupP2/n) suggests that site occupancies are slightly different among the Al(2) series, though the OH–dipole is randomly oriented in all sectors. A relationship between the surface and internal texture suggests that these sectoral structures were produced during crystal growth, not by phase transitions.
Palladseite and its oxidation: evidence from Au-Pd vein-type mineralization (jacutinga), Cauê iron-ore mine, Quadrilátero Ferrífero, Minas Gerais, Brazil
Authors: Cabral A. R. , Lehmann B. , Kwitko R. , Galbiatti H. F. , Pereira M. C.
Published: July 2002

Palladseite (palladium selenide) and palladian gold occur as euhedral inclusions in specularite and as infill of microfractures and interstices in magnetite aggregates (host rock fragments) within specularite-rich auriferous veins (jacutinga). Palladseite has minor amounts of Pt (0.6–3.5 wt.%), Cu (2.9–3.5 wt.%), Hg (0.9–1.9 wt.%), and Ag (0.3–0.5 wt.%). The palladian gold contains up to 6 wt.% Pd, and minor Cu and Ag. Isomertieite (Pd11Sb2As2) and sudovikovite (PtSe2) are also recorded. The veins cross-cut the main tectonic foliation of the wallrock (itabirite). The feature of fracture infill and the Se-Sb-As-Hg-Cu-Ag geochemical/mineralogical signature of the Au-Pd mineralization point to a post-ductile deformation and possibly low-temperature (epithermal) origin of the jacutinga mineralization style.

Palladseite is replaced locally by a Pd-rich oxidation phase. Electron microprobe analysis of alteration halos around palladseite yields 76–80 wt.% Pd. Oxygen calculated by stoichiometry accords with a monoxide compound of the type PdO. However, the measured oxygen content is lower than expected for the PdO stoichiometry, suggesting loss of volatile species, and a more ‘hydrated’ compound, such as an oxyhydroxide.
A computer simulation study of point defects in diopside and the self-diffusion of Mg and Ca by a vacancy mechanism
Authors: Azough Feridoon , Freer Robert , Wright Kate , Jackson Robert
Published: July 2002

Computer simulation techniques have been used to investigate defect formation and the diffusion of Ca and Mg in diopside. It was found that isolated, non-interacting CaO and MgO Schottky defects had the lowest formation energies (3.66 and 3.97 eV respectively); oxygen Frenkel defects are the most favourable oxygen defects (formation energies 3.93 eV). Magnesium and calcium self-diffusion in the c-direction of diopside is easiest by a vacancy mechanism involving either direct jumps along the c-direction, or double jumps in the b-c plane. In the extrinsic regime, diffusion activation energies for Mg are predicted to be 9.82 eV (direct route) and 1.97 eV (double jump route); for Ca diffusion, activation energies are predicted to be 6.62 eV (direct route) and 5.63 eV (double jump route). If additional vacancies (oxygen or magnesium) are present in the vicinity of the diffusion path, Ca migration energies fall to 1.97–2.59 eV. At elevated temperatures in the intrinsic regime, diffusion activation energies of ⩾ 5.95 eV are predicted for Mg self-diffusion and 9.29–10.28 eV for Ca self-diffusion. The values for Ca diffusion are comparable with published experimental data. It is inferred that a divacancy mechanism may operate in diopside crystals.
Concentric zoning patterns in crystallizing (Cd,Ca)CO3solid solutions from aqueous solutions
Authors: Fernández-González Á. , Prieto M. , Putnis A. , López-Andrés S.
Published: July 2002

Otavite-calcite solid solutions have been synthesized to investigate the factors which control the patterns of compositional zoning. The equilibrium partitioning of otavite between the aqueous and the solid phase can be described by means of a functionXCdCO3(XCd,aq)eq, which relates the solid mole fraction and the aqueous activity fraction of Cd. According to this function, there is a strong preferential partitioning of Cd towards the solid. A set of experiments starting with parent solutions with different Cd2+/Ca2+ratios was carried out. In these experiments nucleation takes place at high supersaturations and the Cd2+and Ca2+ions tend to be laid down in a ratio which deviates from the equilibrium distribution. Experimental nucleation data can be fitted to a curveXCdCO3(XCd,aq)efof the same functionality as that for equilibrium.

After nucleation, supersaturation decreases as the crystals grow. During this process, substituting ions are not incorporated into the solid in the same stoichiometric proportion as in the aqueous solution. Therefore, crystal and fluid compositions tend to vary as growth proceeds and this evolution is registered as a compositional zoning. The curvesXCdCO3(XCd,aq)eqandXCdCO3(XCd,aq)efconfine the reaction path corresponding to the growth process. Here, these curves are used to account for the observed zoning patterns.
Molecular mechanism for ganciclovir resistance in human T lymphocytes transduced with retroviral vectors carrying the herpes simplex virus thymidine kinase gene
Authors: Garin Marina I. , Garrett Elaine , Tiberghien Pierre , Apperley Jane F. , Chalmers David , Melo Junia V. , Ferrand Christophe
Published: July 2002

The herpes simplex virus thymidine kinase gene type 1 (HSV-Tk) ganciclovir (GCV) system is a novel therapeutic strategy for the modulation of graft-versus-host disease (GVHD), a major complication of allogeneic stem cell transplantation (allo-SCT). Retroviral-mediated gene transfer of the HSV-Tk gene into donor T lymphocytes before allo-SCT may allow their in vivo selective depletion after treatment with GCV. The expression of theHSV-Tk gene was analyzed in vitro in CEM cells, a human lymphoblastoid cell line, transduced with 2 different vectors, each containing the HSV-Tk gene and a selectable marker gene. GCV-resistant clones were identified within the clones expressing the marker gene. Characterization of the molecular events leading to this resistance revealed a 227-bp deletion in the HSV-Tk gene due to the presence of cryptic splice donor and acceptor sites within the HSV-Tk gene sequence. Furthermore, it was confirmed that this deletion was present in human primary T cells transduced with either vector and in 12 patients who received transduced donor T cells, together with a T-cell–depleted allo-SCT. In vivo circulating transduced T cells containing the truncated HSV-Tk gene were identified in all patients immediately after infusion and up to 800 days after transplantation. In patients who received GCV as treatment for GVHD, a progressive increase in the proportion of transduced donor T cells carrying the deleted HSV-Tkgene was observed. These results suggest that the limitations within the HSV-Tk/GCV system can be improved by developing optimized retroviral vectors to ensure maximal killing ofHSV-Tk–transduced cells.
Recombinant human granulocyte colony-stimulating factor therapy for patients with neutropenia and/or neutrophil dysfunction secondary to glycogen storage disease type 1b
Authors: Calderwood Stanley , Kilpatrick Laurie , Douglas Steven D. , Freedman Melvin , Smith-Whitley Kim , Rolland Martha , Kurtzberg Joanne
Published: July 2002

The purpose of this study was to evaluate the efficacy and toxicity of recombinant human granulocyte colony-stimulating factor (rhG-CSF) therapy in patients with neutropenia and/or neutrophil dysfunction secondary to glycogen storage disease (GSD) type 1b. Thirteen patients with neutropenia and/or neutrophil dysfunction secondary to GSD type 1b were treated with rhG-CSF. The effects of therapy on neutrophil numbers and in vitro neutrophil function and on bone marrow cellularity and morphology were studied. The clinical status of the patients and the occurrence of adverse events associated with rhG-CSF use were monitored. Use of rhG-CSF therapy was associated with a significant increase in circulating neutrophil numbers (P < .01) and an improvement in neutrophil function as assessed in vitro. In addition, rhG-CSF therapy produced a significant increase in marrow cellularity and an increase in myeloid:erythroid (M:E) ratio, indicating stimulation of granulopoeisis. No adverse effects on marrow function were noted; in particular, no myelodysplasia or marrow exhaustion was seen. Use of rhG-CSF therapy was associated with objective and subjective improvements in infection-related morbidity. The therapy was well tolerated, although all patients developed splenomegaly, and 5 patients developed mild hypersplenism that did not require any specific treatment. rhG-CSF therapy is efficacious in the management of neutropenia and neutrophil dysfunction associated with GSD type 1b. Patients on this therapy need to be monitored for hypersplenism. Continued follow-up will be necessary to confirm long-term safety; however, no significant short-term toxicity was noted.
Potent and specific antitumor effects of an anti-CD22–targeted cytotoxic ribonuclease: potential for the treatment of non-Hodgkin lymphoma
Authors: Newton Dianne L. , Hansen Hans J. , Mikulski Stanislaw M. , Goldenberg David M. , Rybak Susanna M.
Published: July 2002

LL2, an anti-CD22 monoclonal antibody against B-cell lymphoma, was covalently linked to the amphibian ribonuclease, onconase, a member of the pancreatic RNase A superfamily. LL2 increased in vitro potency (10 000-fold) and specificity against human Daudi Burkitt lymphoma cells while decreasing systemic toxicity of onconase. Monensin further increased potency of LL2-onconase on Daudi cells (IC50, 20 and 1.5 pM, absence and presence of monensin, respectively). A 1-hour exposure to LL2-onconase was sufficient to kill Daudi cells in culture. These favorable in vitro properties translated to significant antitumor activity against disseminated Daudi lymphoma in mice with severe combined immunodeficiency disease. In mice inoculated with tumor cells intraperitoneally (ip), LL2-onconase (100 μg 5 times ip every day) increased the life span of animals with minimal disease 200%. The life span of mice with advanced disseminated Daudi lymphoma (tumor cells inoculated intravenously) was increased 135%. Mice injected with LL2-onconase tolerated a dose as high as 300 mg/kg. Because both onconase and LL2 are in clinical trials as cancer therapeutics, the covalently linked agents should be considered for treatment of non-Hodgkin lymphoma.
Prevention of lethal acute graft-versus-host disease in mice by oral administration of T helper 1 inhibitor, TAK-603
Authors: Lu Yue , Sakamaki Sumio , Kuroda Hiroyuki , Kusakabe Toshiro , Konuma Yuichi , Akiyama Takehide , Fujimi Akihito , Takemoto Naofumi , Nishiie Kyokusen , Matsunaga Takuya , Hirayama Yasuo , Kato Junji , Kon Shinichiro , Kogawa Katsuhisa , Niitsu Yoshiro
Published: July 2002

Acute graft-versus-host diseases (GVHD) is a major cause of morbidity and mortality in patients undergoing allogeneic bone marrow transplantation (BMT). T helper 1 (Th1)-type cytokines such as interferon-γ or tumor necrosis factor-α have been implicated in the pathogenesis of acute GVHD. TAK-603 is a new quinoline derivative, which is now in clinical trials for use as a disease-modifying antirheumatic drug. In preclinical studies, it inhibited delayed-type hypersensitivity, but not Arthus-type reaction, in mice, and selectively suppressed Th1 cytokine production. Thus, the present study was designed to investigate whether the Th1 inhibitor (TAK-603) ameliorates lethal acute GVHD in a mouse model. Administration of TAK-603 into BALB/c mice given 10 Gy total body irradiation followed by transplantation of bone marrow and spleen cells from C57BL/6 mice markedly reduced the mortality in association with minimal signs of GVHD pathology in the liver, intestine, and skin. TAK-603 reduced not only the production of Th1-type cytokines, but also the proportion of Th1 cells in CD4+ helper T cells in this GVHD mouse model. These results suggest that TAK-603 could be a potent therapeutic agent for acute lethal GVHD.
An Epstein-Barr virus deletion mutant associated with fatal lymphoproliferative disease unresponsive to therapy with virus-specific CTLs
Authors: Gottschalk Stephen , Ng Catherine Y. C. , Perez Margot , Smith Colton A. , Sample Clare , Brenner Malcolm K. , Heslop Helen E. , Rooney Cliona M.
Published: July 2002

There is a growing interest in using antigen-specific T cells for the treatment of human malignancy. For example, adoptive transfer of Epstein-Barr virus (EBV)-specific cytotoxic T lymphocytes (CTLs) has been effective prophylaxis and treatment of EBV-associated lymphoproliferative disease in immunocompromised patients. For all immunotherapies, however, there has been a hypothetical concern that mutations in tumor-specific antigens may lead to tumor escape. We now demonstrate that such events may indeed occur, with lethal outcome. A patient who developed lymphoma after marrow transplantation received donor-derived, EBV-specific CTLs but died with progressive disease. The tumor cells proved substantially less sensitive to cytolysis than the EBV-transformed B-cell line used for CTL generation. The major cytolytic activity of the donor CTL was directed against 2 HLA-A11–restricted epitopes in the viral EBNA-3B antigen. Sequence analysis of this gene in the tumor virus revealed a 245–base pair deletion, which removed these 2 CTL epitopes. Hence, the viral antigen in the tumor had mutated in a way that allowed escape from CTLs. Analysis of EBV polymorphisms demonstrated that before CTL infusion, more than one virus was present, including a virus with wild-type EBNA-3B. After CTL infusion, only the virus with the EBNA-3B deletion could be detected, suggesting that the infused CTLs had selected a resistant strain in vivo. Such an occurrence, even when polyclonal CTL lines are used against genetically stable virus antigens, suggests that escape mutants may be a serious problem when CTL therapy is directed against more unstable tumor cell–derived targets.