bluuebunny/crossref_metadata_2025 huggingface dataset:
The succession and structure of the Borrowdale volcanic rocks Northwest of Ullswater
Authors: Moseley F.
Published: February 2007

The succession consists of Skiddaw Slates followed by Borrowdale Volcanic rocks (Ordovician) and is very similar to that previously described southeast of Ullswater (Moseley 1960). The Ullswater Group, more than 4000 ft thick forms the lowest part of the volcanic succession and consists of tuffs, basalts, basic andesites, and andesites. Above this about 1000 ft of the rocks of the Birk Fell Group, which are dominantly felsitic, are exposed.

Important structural elements are the Ullswater Anticline, the Ullswater Thrust and the high angle faults. The anticlinal axis follows Ullswater as far as Glencoynedale and can be demonstrated only in the Borrowdale Volcanic rocks. The anticline does not appear to continue downwards into the Skiddaw Slates which are not only of different tectonic facies to the volcanics, but are separated from them by the southeasterly dipping Ullswater Thrust. This thrust was induced by the disharmony between the competent volcanics and the incompetent Skiddaw Slates, and is thought to be an imbricate thrust complex rather than a single dislocation.

The high angle faults, the third important structural element, have northwest, northerly and westerly trends. It is probable that the northwesterly faults, at least, are wrench faults, although a strike slip component can be demonstrated in one instance only. The nature of the movement of the northerly and westerly faults cannot be ascertained.
Deformed acid intrusions in the Manx Slate Series, Isle of man
Authors: Simpson Alexander
Published: February 2007

Previous research by the present author has established the Caledonian polyphase tectonics (F1, F2, F3) of the Manx Slate Series. Emplaced along the bedding or the first axial‐plane cleavage (S1) in these strata, and confined to a relatively narrow belt following the middle of the island, is a swarm of acid sheets which dip steeply and strike to the northeastern quadrant. Associated with these minor intrusions in the northeast of the island is the small Dhoon granite. The latter appears to have the form of a thick, lenticular sheet emplaced along S1 and inclined steeply southward.

All these intrusions are post‐F1 in age. The field and textural evidence demonstrates their syn‐tectonic emplacement close to the hinge of the large‐scale F2 Manx synform near the beginning of the F2 episode. The strong deformation which they display was largely acquired during the F2 movement. This includes shearing parallel to the margins of the intrusions, penetration by the second axial‐plane cleavage (S2), flexuring by minor F2 folding and injection by syn‐tectonic F2 quartz‐veining. The F3 phase has also left a mild imprint upon the deformed intrusions.
The stratigraphy and composition of the Latterbarrow and Redmain sandstones, Lake District, England
Authors: Allen P. M. , Cooper D. C.
Published: February 2007

The Latterbarrow Formation, 400 m thick, has been mapped and subdivided informally into three members. These consist of quartz wacke sandstone and, in the upper member only, intercalated mudstones. The formation unconformably overlies the fossiliferous Skiddaw Group of late Tremadoc to middle Arenig age and is overlain disconformably by volcanic rocks that have been attributed to the Borrowdale Volcanic Group. Chemically, the sandstones are characterized by very low concentrations of CaO, Na2O, and K2O and unusually high total iron. MnO and MgO, such that iron, as Fe2O3, exceeds Al2O3. Mudstone in the upper member is illite rich, has a high K2O content and is compositionally similar to K‐bentonites derived from volcanic ash. Sedimentary structures and petrography suggest that the sediments were deposited in a sandy estuary and were derived from a similar source area to that of the Skiddaw Group. Throughout the succession there is evidence of distal volcanism, probably representing the earliest eruptions of the Borrowdale volcanic episode.

The Redmain Formation, 100 m thick, is unconformably overlain by Carboniferous rocks but its relationship to the underlying Skiddaw Group is unknown. Though this lithic arenite shows some petrographic and geochemical similarities with the Latterbarrow sandstone, differences are such that it is possible they are not equivalent in age. The Redmain sandstone may be derived from the erosion of Skiddaw Group rocks.
Petrology, structure and age of the Rough Point sill, Donegal
Authors: Elsdon R.
Published: February 2007

The Rough Point sill, which is one of the thickest of a large number of sills intruded into the Appin Group metasediments of the Dalradian sequence in north Donegal, contains a number of internal features including mafic:felsic banding, pegmatite bands and significant variations in grain size. There are also appreciable variations in mineralogy, particularly the proportions of plagioclase and amphibole, and in the major and trace element chemistry. Together these features indicate that the sill is, like the metasediments which it intrudes, inverted, and is therefore older than the Caledonian F2 structures which caused the inversion. Disruption of the sediments at the sill contact is also earlier than the F2 event. The timing of the basic magmatic episode together with the geochemistry of the sill invite comparison with the metadolerites of the southwest Highlands of Scotland.
Stratigraphic approaches to hydrocarbon exploration and exploitation
Authors: Mazzullo S. J.
Published: February 2007

The stratigraphic approach toward hydrocarbon exploration and exploitation is a fundamental aspect of the continued development and consequent future addition of new reserves from mature basins. This approach, albeit not novel, involves systematic attempts at locating subtle stratigraphic reservoirs and traps, as well as methods of enhancing hydrocarbon recoveries from existing fields, by coordinating petrophysical studies and conventional subsurface mapping techniques.
The formation of large diameter plant fossil moulds and the Walton theory of compaction
Authors: Thomas Barry A.
Published: February 2007

Hollow plant organs can react in different ways to the forces exerted during compaction of the surrounding sediments. Large infilled lycophyte stems, lying flat in the sediments, flatten and expand in width. The width of the mould that is ultimately formed will therefore approach half the original circumference of the stem rather than being equal to its original diameter.
The Pyroclastic deposits of Mount Etna volcano, Sicily
Authors: Chester D. K. , Duncan A. M. , Guest J. E.
Published: February 2007

Throughout most of its geological evolution Etna has been characterized by the eruption of lava flows of a predominantly hawaiitic composition, but within the stratigraphical record there are four major sequences of pyroclastic materials: the Acireale tephra and lahars (˜100000 B.P.); the ‘lower tephra’ and Milo lahars (both ˜26000 B.P.); the Biancavilla ignimbrites (15–15500 B.P.) and the ‘upper tephra’ (˜5000–6000 B.P.). This paper reports investigations carried out on these deposits in order to determine their stratigraphy, petrology, sedimentology, and likely origins. Whereas the Biancavilla ignimbrites were generated when a more evolved, gas‐charged magma (benmoreite) was being produced by the volcano, the other suites of pyroclastic deposits were erupted from hawaiitic magmas—similar to those that have characterized the volcano during historical times. These deposits resulted from two processes: violent strombolian activity producing lapilli‐rich. coarse, but well‐sorted sediments, and hydrovolcanism when the mixing of water and magma in the conduit, brought about more violently explosive activity, giving rise to highly fragmented, poorly sorted, airfall tephra and lahars. Conditions favouring hydrovolcanism occurred at times in the volcano's history when palaeoenvironment and palaeogeography were conducive to the retention of large amounts of surface and subsurface water. Although climates favouring the retention of water at high levels on the volcano have occurred on many occasions in the history of the volcano, at ˜26.000 and ˜5000‐6000 B.P. these occurred in conjunction with a construct of sufficient height and suitable configuration to allow storage of water and give rise to hydrovolcanic activity. The nature of the mechanisms responsible for the emplacement of these hydrovolcanic deposits is considered and it is concluded that airfall is the most probable process. Finally, the implications of this research for the assessment of hazard are reviewed.
The Structure and Stratigraphy of the Western External Sierras of the Pyrenees, Northern Spain
Authors: Nichols G. J.
Published: February 2007

The External Sierras of the southern Pyrenees represent the frontal thrust complex of a south Pyrenean thrust sheet which was active from the late Eocene to early Miocene. Triassic, Cretaceous and Eocene limestones, sandstones and mudstones involved in this thrusting can be divided into eight mappable units. Mapping and the construction of serial sections across the Western External Sierras show that the amount of southward translation of the thrust sheet increases eastwards from the thrust tip. There is an increased slip of at least 5km along 30km of the External Sierras. Structures show a progressive development from a “primitive” form in the west to a more complex thrust and fold geometry in the east. The general pattern is one of thrust and fold development in response to compression from the north. Backthrusting has occurred on the forward side of the frontal thrust complex. These backthrusts cut up section towards the north and form triangle zones where they intersect thrusts which cut up sections towards the south. The latest thrust movements deformed early Miocene fanglomerates and were out‐of‐sequence reactivations of earlier thrusts.
The age of the Oughterard Granite, Connemara, Ireland
Authors: Kennan P. S. , Feely M. , Mohr P.
Published: February 2007

Despite a wide latitude for interpretation of previous Rb–Sr isotopic data on the Oughterard Granite the age of this intrusion has been regarded as a critical time‐marker in resolving the Caledonian evolution of Connemara. New isotopic data suggest that the age of the intrusion be revised from c. 460 Ma to c. 400 Ma, thus making the Oughterard Granite one among the many Newer Caledonian Granites in Ireland. The preferred age is 407 ± 23 Ma, and the initial 87 Sr/86Sr ratio is 0·7076 ± 1. Heterogeneity within the granite is demonstrated, which explains the difficulty in obtaining reliable isotopic ages from this intrusion.
Metamorphic carbonate–mafic amphibolite interactions from Arinteiro, northwest Spain
Authors: Williams Patrick J.
Published: February 2007

Some contacts between interlayered marbles and amphibolites at the Arinteiro copper mine are associated with zoned metasomatic calc‐silicate assemblages. Textures indicate that formation of the calc‐silicate zones involved mass transfer over distances up to 15 cm and that pore fluid solution (infiltration) may have been a significant reaction mechanism. The sequence of minerals is very similar to previously described products of metasomatic interactions between marbles and pelites. Similar metasomatic processes involving primary concentrations of carbonates can be invoked to explain the common occurrence of zoned calc‐silicate patches and folia in metaigneous amphibolites both near Arinteiro and in other terrains.
Sr‐Nd isotope compositions of cenozoic granitoids along a traverse of the central Peruvian Andes
Authors: Soler Pierre , Rotach‐Toulhoat Nelly
Published: February 2007

Sr‐Nd isotopic compositions of late Eocene to Pliocene intrusive rocks from a traverse (⋍11° lat. S) of the central Peruvian Andes are presented. The data set suggests that the calc‐alkaline magmatism is mainly the end‐product of the evolution at deep crustal levels of magmas derived from a slightly depleted, but not MORB‐type, subcontinental mantle, which have assimilated crustal material and have mixed with new batches of primary magma. Assimilation of crustal material increased eastwards and with time. The evolution of Sr‐Nd isotope compositions in time and space along the traverse reflect both the lateral heterogeneities in the subcontinental mantle, the lower crust composition, and the progressive tectonic thickening of the crust during the Cenozoic. No granulitic basement akin to the early Proterozoic south Peruvian Arequipa massif has participated in the genesis of the central Peruvian calc‐alkaline and alkaline magmas.
A sulphur isotope study on selected Caledonian granites of Britain and Ireland
Authors: Laouar R. , Boyce A. J. , Fallick A. E. , Leake B. E.
Published: February 2007

A sulphur isotope study was carried out to assess the value of such isotopic data in constraining the contributions of igneous and sedimentary protoliths for British and Irish Caledonian granites. Conventional separation techniques yielded sulphides from only 19 of the 50 selected granites, including both Newer and Older intrusions. These sulphides are dominated by pyrite, with lesser pyrrhotite, and rare chalcopyrite.

Two groups emerge from consideration of δ34S in conjunction with δ18O, initial 87Sr/86Sr (ISr) and age; Group I have δ18O generally < + 10·5‰, ISr in the range 0·703 to 0·708, and are younger than 435 Ma. δ34S of this group ranges from −4·5‰ to +4·4‰ x̄ = +0·7 ± 2·6‰ (n=40:1σ). Group II have δ18O generally > + 10·5‰, are generally older, ISr between 0·710 and 0·7208, with δ34S in the range +6·2‰ to +16‰: x̄ = +9·5 ± 3·3% (n = 13:1σ). The source region for group II granites contained a significant sedimentary component.

Since sulphides in Lower and Middle Dalradian metasediments are characterized by unusually high δ34S values, between +11‰ and +17‰. we suggest that group II granites contain a significant proportion of sulphur derived from these rocks.
Desilication of Caledonian granites in the Barnesmore complex, Co. Donegal: The origin and significance of metasomatic syenite bodies
Authors: Dempsey C. S. , Meighan I. G. , Fallick A. E.
Published: February 2007

The ca. 400 Ma Caledonian Barnesmore complex, Donegal, includes a 1·5 km2 area in the Main Granite (G2) in which pristine biotite monzogranite has undergone in situ alteration to brick‐red, two feldspar, chloritic syenite which is virtually quartz‐free. The principal chemical changes involve major elements (Si, Al, Ca, Na, K) rather than trace elements. Stable isotope mineral data (O, H) show essentially magmatic values. It is proposed that a silica‐under‐saturated, volatile (halogen?) — and alkali (+Al)‐enriched, late‐stage, aqueous magmatic fluid was channelled into vertical conduits, dissolving quartz, precipitating feldspar(s) and disrupting the fabric of the host granite. The resulting syenitic bodies and vents exposed elsewhere in the complex are believed to represent different levels in such pipes. The mineralogical and chemical modification recorded here has important implications for the study of granitic rocks elsewhere in the world in that more subtle degrees of alteration may have escaped recognition and other equally drastic examples may have associated mineralization potential.
Microgranular enclaves as indicators of hybridization processes in granitoid rocks, Hercynian Belt, Spain
Authors: Castro A. , Moreno‐Ventas I. , de la Rosa J. D.
Published: February 2007

Many Hercynian granitoids of calc‐alkaline composition are characterized by the presence of microgranular enclaves of tonalite to diorite composition. Though some differences in size, shape, and relative abundance of the enclaves are observed between deep‐seated, high‐level, and subvolcanic plutons, there are considerable similarities in texture, grain size, and composition. In magma interaction zones where basic and silicic magmas mingled, enclaves were generated from the disruption, by convective flow, of synplutonic dykes of basic, fractionated, perhaps hybrid, magmas. Many enclaves can be interpreted as non‐consolidated portions of basic magma in thermal equilibrium with the host granitoid. Under such condition, enclaves are easily disaggregated and mixed with the host granitoid, contributing to the hybridization of the latter. The process implies the development of special textures in both enclave and host granitoid, and may be tested by chemical variations and correlations, suggesting that the presence of enclaves, with these particular textures and compositions, may imply that a form of hybridization was involved in the genesis of the host granitoids.
The devonian and carboniferous volcanism of the peloritan mountains (sicily) and the evolution of palaeozoic basins in the calabrian‐peloritan arc
Authors: Acquafredda P. , Lorenzonis S. , Lorenzoni E. Zanettin
Published: February 2007

Volcanic rocks from three Palaeozoic low‐grade metamorphic sequences of different age from the Peloritan Mountains, Sicily, have been analysed for major and trace elements. On the basis of the relative abundances of certain comparatively immobile elements (especially Zr, Ti, Nb, and Y) the petrogenetic affinities of the volcanic rocks in each area have been established. The Fiumara Fitalia sequence contains Lower Devonian within‐plate alkaline basalts, the Ogliastrello sequence contains Upper Devonian continental within‐plate calc‐alkaline basalts and the Randazzo‐Floresta road sequence contains Lower Carboniferous calc‐alkaline basalts probably of island arc affinity.

When account is taken of their stratigraphic positions, geochemical characteristics of the volcanic rocks indicate Devonian extensional conditions and Lower Carboniferous compressional conditions. Evidence for Lower Devonian extension is present in several circum‐Mediterranean basins (i.e. Calabria, Sardinia, Carnic Alps). In the Peloritan Mountains, as well as in Calabria and Sardinia, extensional conditions were already present in the Cambro‐Ordovician. The compression in the Calabrian‐Peloritan Arc was probably related to a period of subduction during the Hercynian orogeny and resulted in the closure of the basins in the Carboniferous.
Genesis of lithium pegmatites from the leinster granite margin, southeast ireland: Geochemical constraints
Authors: O'Connor P. J. , Gallagher V. , Kennan P. S.
Published: February 2007

Extensive and economically‐important lithium pegmatites have been described from the eastern flank of the large S‐type peraluminous Leinster Granite batholith in southeast Ireland. This flank area is also the locus of a major dip‐slip ductile shear zone which was active during emplacement of the Tullow Lowlands pluton of the batholith. All the known bedrock occurrences of lithium pegmatite are contained within this marginal deformation zone.

Most previous studies have suggested derivation of the lithium pegmatites by fractionation from the Leinster Granite itself, though none are conclusive. More recently, an anatectic model has been proposed whereby the pegmatites were derived by melting of Li‐rich sediments adjacent to the batholithic contact. Our investigation has been concerned with a detailed study of the Rb‐Sr isotope systematics and trace element geochemistry of the pegmatites and their host granitoids in an attempt to resolve the problem of pegmatite genesis.

The results suggest a strong geochemical and temporal coherence between the Leinster Granite and the lithium pegmatites. A model is proposed in which Li enrichment in residual magmas may be linked to the development of muscovite instead of biotite in the Leinster Granite itself. The Li excluded from entry to biotite then accumulates in highly mobile, low‐viscosity pegmatitic fluids which migrate into the marginal shear zone of the Tullow Lowlands pluton where they crystallize at considerably lower temperatures.
Depositional and tectonic relationships of upper ordovician and lower silurian strata around dinas mawddwy, mid‐wales
Authors: James D. M. D.
Published: February 2007

The field evidence for the lateral impersistence of the Garnedd‐wen Formation (Hirnantian) and Derwen Formation (Aeronian) immediately northeast of Dinas Mawddwy is reviewed and the evidence for strike faulting as inferred by W. J. Pugh (1928) is reassessed. It is concluded that little if any strata are missing and that surfaces of non‐deposition, rather than fault cut‐out, better explain any strata that are locally abnormally thinned. However strike faulting is newly proven west of Dinas Mawddwy and accounts for much of the rapid apparent thickness variation in the Broad Vein (Rawtheyan) there. The newly constrained thickness estimates strongly imply that sedimentation was influenced by a basement fracture at Dinas Mawddwy. Structural reasoning and palaeocurrent evidence from the Garnedd‐wen Formation suggest that this fracture probably parallels the Corris‐Llangranog fracture to the southwest.
Reversals in the polarity of structural facing across an early ductile thrust; the Central Donegal Slide, northwest Ireland
Authors: Alsop G. I.
Published: February 2007

The Dalradian succession of central Donegal represents a tectono‐stratigraphic sequence everywhere separated into two distinct successions by the Central Donegal Slide. Each stratigraphic package consistently youngs away from this major D1structure which originated during lower greenschist facies metamorphism and corresponds with the development of locally preserved penetrative S1fabrics. The tectonic slide and associated reversal in the direction of structural facing are commonly marked by mylonites and tectonic schists, which have been subsequently folded and reactivated by kilometric‐scale sheath folds and the Ballybofey Nappe.

Structural correlations with northwest Donegal suggest that the Central Donegal Slide relates to the Knockateen Slide, and represents an early thrust with top to the northwest sense of shear. The Central Donegal Slide cuts up‐section through the Middle Dalradian sub‐basin centred on southern Donegal, emplacing younger, anoxic basinal sediments and turbidites over an older, inverted, shelf succession. The location of the Central Donegal Slide adjacent to the margin of this sub‐basin suggests that the siting and form of ductile thrusts may be strongly influenced by the geometry of the pre‐existing sedimentary basin.
Stable isotope constraints on the origin of the Cabo de Creus garnet‐tourmaline pegmatites, Massif des Alberes, Eastern Pyrenees, Spain
Authors: Damm Klaus‐Werner , Harmon Russell S. , Heppner Peter‐Michael , Dornsiepen Ulrich
Published: February 2007

Pegmatite dyke swarms are exposed within the easternmost Pyrenees at Cabo de Creus. These dykes were emplaced into high‐grade metamorphosed sedimentary strata of Cambro‐Ordovician age, but lack obvious field relationship to Hercynian intrusive rocks. Together with structural and geochemical data, equilibrium oxygen isotope fractionations at temperatures of ≈ 600°C, the lack of obvious subsolidus exchange, and the H‐ and O‐isotopic signatures of water in equilibrium with pegmatite mica and quartz are interpreted to indicate a derivation from anatexis of a metapelitic source at shallow crustal levels.
Biostratigraphy of Dinantian limestones and associated volcanic rocks in the Limerick Syncline, Ireland
Authors: Somerville Ian D. , Strogen Peter , Jones Gareth Li.
Published: February 2007

Rocks of Courceyan to Brigantian age are exposed in the Limerick Syncline. However, a complete Courceyan succession is known only from two boreholes which correlate closely, both faunally and lithologically, with a standard Limerick Province succession in the Pallaskenry Borehole on the Shannon estuary. This is followed by a thick Waulsortian sequence (the newly defined Limerick Limestone Formation) of late Courceyan to early Chadian age and overlying cherty micrites (the newly defined Lough Gur Formation) of early to late Chadian age, whose top is younger to the east. The Lough Gur Formation is succeeded by lavas and tuffs of the Knockroe Volcanic Formation whose upper part is interbedded with and overlain by shallow water oolites and algal‐rich bioclastic limestones of the Herbertstown Limestone Formation. The higher part of the latter is in turn interbedded with lavas and tuffs of the Knockseefin Volcanic Formation. The Herbertstown Limestone has rich and diverse coral/brachiopod and foraminiferal assemblages of late Chadian to Asbian age. Its base is markedly diachronous: late Chadian in the west of the syncline and Holkerian in the east. Both the base and top of the Knockroe Volcanic Formation are thus shown to be markedly diachronous and volcanism extends from the Chadian to early Asbian. The Knockseefin Volcanic Formation is entirely of Asbian age. The highest limestones (Dromkeen Limestone Formation) have a diagnostic late Asbian–early Brigantian fauna and are overstepped by mid‐Namurian shales.
Nautiloid cephalopods of the Kildare Limestone (Ashgill), Ireland
Authors: Holland C. H.
Published: February 2007

The nautiloid cephalopod fauna of the Kildare Limestone (Ordovician, Ashgill), County Kildare, eastern Ireland is described as a whole for the first time. It consists of four orthoconic taxa, newly assigned taxonomically, and one coiled form. There are other orthocones, doubtfully determined or undetermined.
Source of the Bicester magnetic anomaly
Authors: Kearey P. , Rabae A. M.
Published: February 2007

The Bicester magnetic anomaly is one of several high wavenumber features superimposed on the magnetic anomaly associated with the London Platform. Seismic reflection data suggest that the source of the Bicester anomaly is a body of basaltic rocks of Carboniferous age that can be traced from the Steeple Aston borehole. Three‐dimensional interpretational techniques indicate that the magnetic source has a total magnetization vector dipping at 60°, azimuth 170°, with an intensity of 1.39 A m−1 and this has been used to derive a three‐dimensional model of the source. The nature of the magnetic remanence contributing to this vector is discussed. A detailed two‐dimensional magnetic model has been constructed using the seismic control.
Pre‐Middle Silurian granitic magmatism and associated metamorphism in northern Japan: SHRIMP U‐Pb zircon chronology
Authors: Watanabe Teruo , Fanning C. Mark , Uruno Katsutoshi , Kano Hiroshi
Published: February 2007

The results of SHRIMP U‐Pb zircon dating are presented for igneous and metamorphic rocks of enigmatic age in northern Japan. The SHRIMP analyses for the Tsubonosawa metamorphic rocks included in the Hikami Granite reveals (1) Ordovician sedimentation of the original rocks, including Archaean‐Proterozoic detrital zircons, and (2) thermal metamorphism with partial melting or assimilation followed by intrusion of the Hikami Granite at ca. 440 Ma (end of Ordovician). This study allows the reconstruction of Siluro‐Ordovician palaeogeography and magmatism‐associated metamorphism in East Asia. The SHRIMP results are compared with those of CHIME (chemical U‐Pb total Th isochron method) chronology, which is evaluated as providing significant reconnaissance ages in some instances.
Dental health, nutritional status and recent‐onset dementia in a Korean community population
Authors: Kim Jae‐Min , Stewart Robert , Prince Martin , Kim Sung‐Wan , Yang Su‐Jin , Shin Il‐Seon , Yoon Jin‐Sang
Published: February 2007

Background

Dental health is an important determinant of nutritional status, but has not been investigated as a risk factor for dementia. This study aimed to investigate the association between number of teeth, use of dentures and recent‐onset dementia.

Methods

This was a cross‐sectional analysis nested within a prospective study of community dwelling elderly residents in two areas of Kwangju, South Korea. In a study of 686 community residents aged 65 or over without dementia followed over 2.4 years, measures of dental health were compared between those with and without dementia at follow‐up.

Results

Fewer teeth were significantly associated with dementia and Alzheimer's disease. This association was strongest in participants without dentures. Strong associations were found between fewer teeth and indices of poor nutrition in this group, but these did not account for the association with dementia.

Conclusions

Having fewer teeth may be a marker of risk for dementia. This might be explained by specific nutritional deficits, or by other side effects of periodontal disease. Further prospective research is indicated. Copyright © 2007 John Wiley & Sons, Ltd.
Parieto‐occipital sources account for the increase in alpha activity with working memory load
Authors: Tuladhar Anil M. , Huurne Niels ter , Schoffelen Jan‐Mathijs , Maris Eric , Oostenveld Robert , Jensen Ole
Published: February 2007

The role of oscillatory alpha activity (8–13 Hz) in cognitive processing remains an open question. It has been debated whether alpha activity plays a direct role in the neuronal processing required for a given task or whether it reflects idling and/or functional inhibition. Recent electroencephalography (EEG) studies have demonstrated that alpha activity increases parametrically with load during retention in working memory paradigms. While it is known that the parieto‐occipital cortex is involved in the generation of the spontaneous alpha oscillations, it remains unknown where the sources of the memory‐dependent alpha activity are located. We recorded brain activity using magnetoencephalography (MEG) from human subjects performing a Sternberg memory task where faces were used as stimuli. Spectral analysis revealed a parametric increase in alpha activity with memory load over posterior brain areas. We then applied a source reconstruction technique that allowed us to map the parametric increase in alpha activity to the anatomical magnetic resonance (MR) images of the subject. The primary sources of the memory‐dependent alpha activity were in the vicinity of the parieto‐occipital sulcus. This region is not directly involved in working memory maintenance of faces. Our findings are consistent with the notion that alpha activity reflects disengagement or inhibition of the visual dorsal stream. We propose that the disengagement reflected in alpha power serves to suppress visual input in order to devote resources to structures responsible for working memory maintenance. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
The bootstrap and cross‐validation in neuroimaging applications: Estimation of the distribution of extrema of random fields for single volume tests, with an application to ADC maps
Authors: Viviani Roberto , Beschoner Petra , Jaeckle Tina , Hipp Peter , Kassubek Jan , Schmitz Bernd
Published: February 2007

We discuss the assessment of signal change in single magnetic resonance images (MRI) based on quantifying significant departure from a reference distribution estimated from a large sample of normal subjects. The parametric approach is to build a test based on the expected distribution of extrema in random fields. However, in conditions where the variance is not uniform across the volume and the smoothness of the images is moderate to low, this test may be rather conservative. Furthermore, parametric tests are limited to datasets for which distributional assumptions hold. This paper investigates resampling methods that improve statistical tests for signal changes in single images in such adverse conditions, and that can be used for the assessment of images taken for clinical purposes. Two methods, the bootstrap and cross‐validation, are compared. It is shown that the bootstrap may fail to provide a good estimate of the distribution of extrema of parametric maps. In contrast, calibration of the significance threshold by means of cross‐validation (or related sampling without replacement techniques) address three issues at once: improved power, better voxel‐by‐voxel estimate of variance by local pooling, and adaptation to departures from ideal distributional assumptions on the signal. We apply the cross‐validated tests to apparent diffusion coefficient maps, a type of MRI capable of detecting changes in the microstructural organization of brain parenchyma. We show that deviations from parametric assumptions are strong enough to cast doubt on the correctness of parametric tests for these images. As case studies, we present parametric maps of lesions in patients suffering from stroke and glioblastoma at different stages of evolution. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
Neural mechanisms of evoked oscillations: Stability and interaction with transient events
Authors: Moratti Stephan , Clementz Brett A. , Gao Yuan , Ortiz Tomás , Keil Andreas
Published: February 2007

There is increasing evidence that early event‐related potentials are a result of phase alignment of ongoing background oscillations of the electroencephalogram rather than additive amplitude modulation. Steady state visual‐evoked potentials (ssVEPs) can be recorded using an intensity modulated stimulus, resulting in an evoked brain response at a known frequency, i.e. the stimulation frequency. Given this property, the ssVEP is ideally suited for examining the relationship between single‐trial fluctuations in phase/amplitude and the evoked brain potential resulting from averaging across trials. To address this issue, the current study investigated the contribution of single trial power and intertrial phase locking to ssVEP generation by presenting a peripheral flicker. Further, transient stimuli were presented during flicker and at three increasing latency lags following flicker offset to examine (1) to what extent a stimulus can disturb the ssVEP oscillation and (2) how phase alignment during P1‐N1‐P2 time windows is affected during presence of evoked oscillations. The former assessment evaluates the stability of ssVEPs and the latter the phase alignment processes to transient stimuli under experimentally induced background oscillations. We observed that ssVEPs are a result of phase alignment rather than single trial amplitude modulation. In addition, ssVEP oscillations were not disturbed by transient stimuli. Finally, phase alignment in P1‐N1‐P2 time windows was distorted during and shortly after steady state stimulation. We conclude that ssVEPs represent strongly phase locked oscillations sharing the same generation mechanisms as early evoked potentials. Hum Brain Mapp, 2007. © 2007 Wiley‐Liss, Inc.
Bias between MNI and Talairach coordinates analyzed using the ICBM‐152 brain template
Authors: Lancaster Jack L. , Tordesillas‐Gutiérrez Diana , Martinez Michael , Salinas Felipe , Evans Alan , Zilles Karl , Mazziotta John C. , Fox Peter T.
Published: February 2007

MNI coordinates determined using SPM2 and FSL/FLIRTwith the ICBM‐152 template were compared to Talairach coordinates determined using a landmark‐based Talairach registration method (TAL). Analysis revealed a clear‐cut bias in reference frames (origin, orientation) and scaling (brain size). Accordingly, ICBM‐152 fitted brains were consistently larger, oriented more nose down, and translated slightly down relative to TAL fitted brains. Whole brain analysis of MNI/Talairach coordinate disparity revealed an ellipsoidal pattern with disparity ranging from zero at a point deep within the left hemisphere to greater than 1‐cm for some anterior brain areas. MNI/Talairach coordinate disparity was generally less for brains fitted using FSL. The mni2tal transform generally reduced MNI/Talairach coordinate disparity for inferior brain areas but increased disparity for anterior, posterior, and superior areas. Coordinate disparity patterns differed for brain templates (MNI‐305, ICBM‐152) using the same fitting method (FSL/FLIRT) and for different fitting methods (SPM2, FSL/FLIRT) using the same template (ICBM‐152). An MNI‐to‐Talairach (MTT) transform to correct for bias between MNI and Talairach coordinates was formulated using a best‐fit analysis in one hundred high‐resolution 3‐D MR brain images. MTT transforms optimized for SPM2 and FSL were shown to reduced group mean MNI/Talairach coordinate disparity from a 5‐13 mm to 1‐2 mm for both deep and superficial brain sites. MTT transforms provide a validated means to convert MNI coordinates to Talairach compatible coordinates for studies using either SPM2 or FSL/FLIRTwith the ICBM‐152 template. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
Phase lag index: Assessment of functional connectivity from multi channel EEG and MEG with diminished bias from common sources
Authors: Stam Cornelis J. , Nolte Guido , Daffertshofer Andreas
Published: February 2007

Objective:

To address the problem of volume conduction and active reference electrodes in the assessment of functional connectivity, we propose a novel measure to quantify phase synchronization, the phase lag index (PLI), and compare its performance to the well‐known phase coherence (PC), and to the imaginary component of coherency (IC).

Methods:

The PLI is a measure of the asymmetry of the distribution of phase differences between two signals. The performance of PLI, PC, and IC was examined in (i) a model of 64 globally coupled oscillators, (ii) an EEG with an absence seizure, (iii) an EEG data set of 15 Alzheimer patients and 13 control subjects, and (iv) two MEG data sets.

Results:

PLI and PC were more sensitive than IC to increasing levels of true synchronization in the model. PC and IC were influenced stronger than PLI by spurious correlations because of common sources. All measures detected changes in synchronization during the absence seizure. In contrast to PC, PLI and IC were barely changed by the choice of different montages. PLI and IC were superior to PC in detecting changes in beta band connectivity in AD patients. Finally, PLI and IC revealed a different spatial pattern of functional connectivity in MEG data than PC.

Conclusion:

The PLI performed at least as well as the PC in detecting true changes in synchronization in model and real data but, at the same token and like‐wise the IC, it was much less affected by the influence of common sources and active reference electrodes. Hum Brain Mapp 2007. © 2007 Wiley‐Liss, Inc.
Estimating the number of independent components for functional magnetic resonance imaging data
Authors: Li Yi‐Ou , Adalı Tülay , Calhoun Vince D.
Published: February 2007

Multivariate analysis methods such as independent component analysis (ICA) have been applied to the analysis of functional magnetic resonance imaging (fMRI) data to study brain function. Because of the high dimensionality and high noise level of the fMRI data, order selection, i.e., estimation of the number of informative components, is critical to reduce over/underfitting in such methods. Dependence among fMRI data samples in the spatial and temporal domain limits the usefulness of the practical formulations of information‐theoretic criteria (ITC) for order selection, since they are based on likelihood of independent and identically distributed (i.i.d.) data samples. To address this issue, we propose a subsampling scheme to obtain a set of effectively i.i.d. samples from the dependent data samples and apply the ITC formulas to the effectively i.i.d. sample set for order selection. We apply the proposed method on the simulated data and show that it significantly improves the accuracy of order selection from dependent data. We also perform order selection on fMRI data from a visuomotor task and show that the proposed method alleviates the over‐estimation on the number of brain sources due to the intrinsic smoothness and the smooth preprocessing of fMRI data. We use the software package ICASSO (Himberg et al. [ 2004]: Neuroimage 22:1214–1222) to analyze the independent component (IC) estimates at different orders and show that, when ICA is performed at overestimated orders, the stability of the IC estimates decreases and the estimation of task related brain activations show degradation. Hum Brain Mapp, 2007. © 2007 Wiley‐Liss, Inc.
An empirical investigation of the social market for cigarettes
Authors: Katzman Brett , Markowitz Sara , McGeary Kerry Anne
Published: February 2007

A major characteristic of teenage smoking is the ability to ‘bum’ cigarettes from peers. To date, research into the determinants of teenage smoking has largely ignored the effects of this social market on the smoking decisions of teenagers. In this paper, we estimate the demand for cigarettes using data from the Youth Risk Behavior Survey which distinguishes teens who primarily buy cigarettes from those who primarily borrow cigarettes. Our results demonstrate the ways in which higher cigarette prices and restrictions on smoking influence not only a teen's decision to smoke and the quantity of cigarettes smoked, but also the manner in which cigarettes are acquired. We show that current cigarette regulations are ineffective in reaching the group of light smokers who primarily obtain cigarettes through the social market, thus indicating that alternative measures should be explored in an effort to reduce the number of smokers in the future. Copyright © 2007 John Wiley & Sons, Ltd.
Salivary glutathione and uric acid levels in patients with head and neck squamous cell carcinoma
Authors: Almadori Giovanni , Bussu Francesco , Galli Jacopo , Limongelli Attilio , Persichilli Silvia , Zappacosta Bruno , Minucci Angelo , Paludetti Gaetano , Giardina Bruno
Published: February 2007

Background.

We evaluated the concentrations of glutathione and uric acid, low molecular weight antioxidants, in saliva of patients with head and neck squamous cell carcinoma (HNSCC), in order to identify differences with normal subjects and to obtain information about biochemical alterations of human saliva during carcinogenesis.

Methods.

We compared 50 HNSCC patients, divided in 2 subsets on the basis of tumor site, with a control group of 77 subjects, without a previous diagnosis of HNSCC, matched for age, sex, alcohol consumption, and smoking status.

Results.

At tests for equality of means by Welch and Brown‐Forsythe, differences between groups resulted probable for salivary levels of glutathione (p = .004 and p < .001 respectively) but not for salivary levels of uric acid (p = .228 and p = .122 respectively). Comparing groups by Tamhane test, the patients with oral or pharyngeal cancer had significantly higher salivary levels of glutathione than both controls and patients with laryngeal cancer.

Conclusions.

Salivary glutathione levels may be an index of oxidative stress at the level of the upper airways and in particular of oral cavity and pharynx. Therefore, high salivary glutathione may be an epidemiological marker to identify subjects with an increased risk of developing HNSCC, to submit to strict follow‐up and chemoprevention. Metabolic alterations of saliva could be both an epidemiological marker and a target for chemoprevention of oral and oropharyngeal carcinogenesis. © 2007 Wiley Periodicals, Inc. Head Neck 2007
Swallowing after major surgery of the oral cavity or oropharynx: A prospective and longitudinal assessment of patients treated by microvascular soft tissue reconstruction
Authors: Borggreven Pepijn A. , Leeuw Irma Verdonck‐de , Rinkel Rico N. , Langendijk Johannes A. , Roos Jan C. , David Eric F. L. , de Bree Remco , Leemans C. René
Published: February 2007

Background.

The aim of this study was to analyze swallowing outcome in advanced oral/oropharyngeal cancer patients treated with microvascular reconstructive surgery and adjuvant radiotherapy.

Methods.

Eighty patients were included. Patient, tumor, and treatment factors were assessed. Postoperative videofluoroscopic swallowing studies (VFSS) and scintigraphy tests were performed at 6 (n = 54 vs 44) and 12 (n = 32 vs 37) months. Swallowing parameters such as the oropharyngeal swallow efficiency and the Penetration/Aspiration Scale were analyzed.

Results.

Impaired swallowing status was found at 6 months, which remained stationary at 12 months. Comorbid condition, larger tumors (T3‐T4 vs T2), and resections of the base of tongue and soft palate combined (vs defects of other dynamic structures) were associated with most profound swallowing problems (p < .05).

Conclusions.

Swallowing difficulties are relatively frequent and can to a large extent be predicted. With the knowledge of this study, better counseling and vigilance as to swallowing difficulties may be possible. © 2007 Wiley Periodicals, Inc. Head Neck 2007
Lifetime physical activity and the risk of renal cell cancer
Authors: Tavani Alessandra , Zucchetto Antonella , Maso Luigino Dal , Montella Maurizio , Ramazzotti Valerio , Talamini Renato , Franceschi Silvia , La Vecchia Carlo
Published: February 2007

The relation between lifelong physical activity at work and during leisure‐time and the risk of renal cell cancer (RCC) was analyzed in a case‐control study conducted in Italy between 1992 and 2004. Cases were 767 subjects with incident, histologically confirmed RCC, and controls were 1,534 patients hospitalized for acute nonneoplastic conditions. Odds ratios (OR) and 95% confidence intervals (CI) for RCC were computed by multiple logistic regression models, conditioned on study center, sex and age, and adjusted for main covariates. Compared to the lowest level of occupational physical activity, the multivariate OR of RCC for the highest level were 0.65 (95% CI 0.49–0.87) at age 12 years, 0.67 (95% CI 0.53–0.84) at age 15–19, 0.74 (95% CI 0.59–0.93) at age 30–39 and 0.71 (95% CI 0.55–0.92) at age 50–59 years, with significant inverse trends in risk. The inverse association was consistent in strata of sex, age at diagnosis, body mass index, smoking habit and alcohol drinking. No significant association was found for leisure‐time physical activity. The inverse association between occupational physical activity and RCC risk, if real, may be related to the effects of insulin‐like growth factors, or lipid peroxidation and about 9% of cases of RCC in Italy could be avoided by increasing physical activity. However the inverse association might involve confounding by indirect mechanisms, such as body composition or other social class correlates. © 2006 Wiley‐Liss, Inc.
Increased expression of VEGF121/VEGF165–189 ratio results in a significant enhancement of human prostate tumor angiogenesis
Authors: Catena Raul , Muniz‐Medina Vanessa , Moralejo Beatriz , Javierre Biola , Best Carolyn J.M. , Emmert‐Buck Michael R. , Green Jeffrey E. , Baker Carl C. , Calvo Alfonso
Published: February 2007

Vascular endothelial growth factor (VEGF) is a proangiogenic factor upregulated in many tumors. The alternative splicing of VEGF mRNA renders 3 major isoforms of 121, 165 and 189 amino‐acids in humans (1 less amino‐acid for each mouse VEGF isoform). We have designed isoform specific real time QRT‐PCR assays to quantitate VEGF transcripts in mouse and human normal and malignant prostates. In the human normal prostate, VEGF165 was the predominant isoform (62.8% ± 5.2%), followed by VEGF121 (22.5% ± 6.3%) and VEGF189 (p < 0.001) (14.6% ± 2.1%). Prostate tumors showed a significant increase in the percentage of VEGF121 and decreases in VEGF165 (p < 0.01) and VEGF189 (p < 0.05). However, the amount of total VEGF mRNA was similar between normal and malignant prostates. VEGF164 was the transcript with the highest expression in the mouse normal prostate. Unlike human prostate cancer, tumors from TRAMP mice demonstrated a significant increase in total VEGF mRNA levels and in each of the VEGF isoforms, without changes in the relative isoform ratios. Morpholino phosphorodiamide antisense oligonucleotide technology was used to increase the relative amount of VEGF121 while proportionally decreasing VEGF165 and VEGF189 levels in human prostate cell lines, through the modification of alternative splicing, without changing transcription levels and total amount of VEGF. The increase in the VEGF121/VEGF165–189 ratio in PC3 cells resulted in a dramatic increase in prostate tumor angiogenesis in vivo. Our results underscore the importance of VEGF121 in human prostate carcinoma and demonstrate that the relative expression of the different VEGF isoforms has an impact on prostate carcinogenesis. © 2007 Wiley‐Liss, Inc.