bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tectonic significance of carbonatite and ultrahigh-pressure rocks in the Pan-African Dahomeyide suture zone, southeastern Ghana
Authors: Attoh Kodjopa , Nude Prosper M. 
Published: May 2008

Abstract

The association of carbonatite and ultrahigh-pressure (UHP) metamorphic rocks in the Dahomeyide suture zone of southeastern Ghana is unique among the Neoproterozoic orogens that surround the West African craton (WAC). Carbonatite occurs in an alkaline complex that decorates the sole thrust of the suture zone and is characterized by high concentrations of incompatible trace elements such as light rare earth elements (LREE), Sr and Ba. Within the suture zone deformed alkaline rocks, including carbonatite, together with mafic granulites form an imbricate stack of thrust panels that involve 2.1 Ga rocks of the WAC basement. The dominant rock unit of the suture zone is composed of mafic granulites in which garnet megacrysts preserve a diagnostic microstructure of UHP metamorphism; it consists of a crystallographically controlled array of exsolved rutile rods in garnet. Metamorphic pressures estimated from Ti concentrations in the inferred precursor garnet indicate
P
>3 GPa, which requires subduction (and exhumation) of the suture zone rocks to and from mantle depths during collisional orogeny on the WAC margin. Available age constraints on carbonatite magmatism suggest that continental rifting, leading to the formation of the passive WAC margin
c
. 700 Ma, occurred
c
. 100 Ma before intrusion of carbonatite, which was preceded by HP and UHP metamorphism at 610±5 Ma.
Petrogenesis and geodynamic evolution of the Late Neoproterozoic post-collisional felsic magmatism in NE Afyon area, western central Turkey
Authors: Gürsu S. , Goncuoglu M. C. 
Published: May 2008

Abstract
In western Turkey, Late Neoproterozoic basement rocks are represented by variably deformed metasedimentary and meta-igneous rocks within different tectonostratigraphical units that make up the Alpine Tauride–Anatolide Platform. In the Kütahya–Bolkar Dagı unit to the NE of Afyon this basement mainly includes garnet-bearing mica schists intruded by metamorphic granitic rocks with relict porphyritic textures. The youngest zircon ages obtained from the granitic rocks by the single zircon evaporation method are 542±5.0 Ma on average, which correlate with the Late Pan-African–Cadomian granitic magmatism. The granitic rocks are rhyodacitic or dacitic and peraluminous in composition, and display geochemical characteristics of I-type (tonalite–trondhjemite–granodiorite (TTG) source) felsic intrusive rocks. Trace and rare earth element patterns with distinct depletion in Rb, K, Nb, Sr, P and Ti relative to the other trace elements correlate very well with a Proterozoic TTG source. The petrogenetic modelling also implies that they were developed by partial melting of a TTG source by 20% fractional melting plus 20% Rayleigh fractional crystallization. The emplacement temperatures estimated by using zircon (790–820 °C), apatite and monazite saturation thermometry are about 827–1035 °C; these are in accordance with I-type rather than S-type granite melts. A geochemical comparison of the NE Afyon granitic rocks with the coeval quartz-porphyries in the Sandikli area of the Geyik Dag tectonic unit suggests that the latter may represent the more evolved felsic part of the Cadomian magmatism. Hence, both basement complexes are parts of the same Gondwanan terrane and represent the eastern continuation of the North African–Southern European terrane assemblage.
The ‘Rich’ group of the Drâa Basin (Lower Devonian, Anti-Atlas, Morocco): an integrated sedimentary and tectonic approach
Authors: Ouanaimi Hassan , Lazreq Nezha 
Published: May 2008

Abstract
In this study, based on a sedimentary analysis, an interpretation in terms of sequence stratigraphy is proposed for the ‘Rich’ group of the Early Devonian Drâa Basin (of Pragian to late Eifelian age). This group is composed of four depositional sequences (third order) containing a transgressive systems tract and a highstand systems tract, both deposited on a storm- and tide-dominated shelf. The depositional sequences are related to global sea-level changes but their geometric architecture is controlled by tectonic subsidence and by sediment supply. The basin forms an ENE–WSW channel with two internal high blocks acting on the depocentre shifts. The channel is surrounded by high points and by marine distal condensed series, and bordered by inherited various regional faulted axes. The regional setting corresponds to an extensional passive margin on the northern edge of the West African craton.
Two Mesoarchaean terranes in the Reguibat shield of NW Mauritania
Authors: Key R. M. , Loughlin S. C. , Gillespie M. , Del Rio M. , Horstwood M. S. A. , Crowley Q. G. , Darbyshire D. P. F. , Pitfield P. E. J. , Henney P. J. 
Published: May 2008

Abstract

Two domains have previously been recognized in the Archaean Reguibat shield of NW Mauritania, based primarily on their gross lithological differences. New fieldwork has identified a major ductile shear zone (Tâçarât–Inemmaûdene Shear Zone) separating these domains and new geochronological studies show that the two domains record different Mesoarchaean histories. As such, the two domains are redefined as the Choum–Rag el Abiod Terrane and Tasiast–Tijirit Terrane. Previous isotopic studies of metamorphic lithologies of the eastern Choum–Rag el Abiod Terrane indicate a succession of crustal growth from about 3.5–3.45 Ga to between about 3.2 and 2.99 Ga. Isotopic data presented in this contribution from the Tasiast–Tijirit Terrane indicate that emplacement of major calc-alkaline plutons occurred at
c
. 2.93 Ga after volcanism (preserved as greenstone belts) that included late felsic eruptive centres dated at
c
. 2965 Ma. This Mesoarchaean intrusive and extrusive magmatism was confined to the Tasiast–Tijirit Terrane, where it was emplaced through migmatitic orthogneisses that are the oldest lithodemic unit of the Tasiast–Tijirit Terrane. Widespread bimodal, post-tectonic magmatism in both terranes included major granitic magmatism dated at
c
. 2730 Ma. The north–south- to NNE–SSW-trending curvilinear Tâçarât–Inemmaûdene Shear Zone that separates the two terranes records late intense transpressive ductile shearing. It has a flower structure over a horizontal distance of about 70 km across its southern portion with unquantifiable sinistral horizontal offset, and east-directed thrusting on its eastern side where it cuts into the Choum–Rag el Abiod Terrane. A new U–Pb zircon age of 2954±111 Ma is presented for a deformed granite confined within the central part of this shear zone. A minimum age for the shearing is provided by a previously determined
c
. 2.73 Ga age for a post-tectonic granite that cuts across the easternmost part of the shear zone in the Choum–Rag el Abiod Terrane.
Geological setting of the Guelb Moghrein Fe oxide-Cu-Au-Co mineralization, Akjoujt area, Mauritania
Authors: Kolb Jochen , Meyer F. Michael , Vennemann Torsten , Hoffbauer Radegund , Gerdes Axel , Sakellaris Gregori A. 
Published: May 2008

Abstract

The Guelb Moghrein Fe oxide–Cu–Au–Co deposit is located at the western boundary of the West African craton in NW Mauritania. The wall rocks to the mineralization represent a meta-volcanosedimentary succession typical of Archaean greenstone belts. Two types of meta-volcanic rocks are distinguished: (1) volcanoclastic rocks of rhyodacite–dacite composition (Sainte Barbe volcanic unit), which form the stratigraphic base; (2) tholeiitic andesites–basalts (Akjoujt meta-basalt unit). The trace element signature of both types is characteristic of a volcanic arc setting. A small meta-pelitic division belongs to the Sainte Barbe volcanic unit. A meta-carbonate body, which contains the mineralization, forms a tectonic lens in the Akjoujt meta-basalt unit. It can be defined by the high
X
Mg
(=36) of Fe–Mg carbonate, the REE pattern and the δ
13
C values of −18 to −17‰ as a marine precipitate similar to Archaean banded iron formation (BIF). Additionally, small slices of Fe–Mg clinoamphibole–chlorite schist in the meta-carbonate show characteristics of marine shale. This assemblage, therefore, does not represent an alteration product, but represents an iron formation unit deposited on a continental shelf, which probably belongs to the Lembeitih Formation. The hydrothermal mineralization at 2492 Ma was contemporaneous with regional D
2
thrusting of the Sainte Barbe volcanic unit and imbrications of the meta-carbonate in the upper greenschist facies. This resulted in the formation of an ore breccia in the meta-carbonate, which is enriched in Fe, Ni, Co, Cu, Bi, Mo, As and Au. Massive sulphide ore breccia contains up to 20 wt% Cu. The ore fluid was aqueous–carbonic in nature and either changed its composition from a Mg-rich oxidizing to an Fe-rich reducing fluid or the two fluid types mixed at the trap site. All lithologies at Guelb Moghrein were deformed by D
3
thrusting to the east in the lower greenschist facies. The mobility of REE in the retrogressed rocks explains the formation of a second generation of hydrothermal monazite, which was dated at
c
. 1742 Ma. Archaean rocks of the West African craton extend to the west to Guelb Moghrein. The active continental margin was deformed and mineralized in the Late Archaean–Early Proterozoic and again reactivated in the Mid-Proterozoic and Westphalian, showing that the western boundary of the craton was reactivated several times.
Alternate Task Inhibits Single-neuron Category-selective Responses in the Human Hippocampus while Preserving Selectivity in the Amygdala
Authors: Steinmetz Peter N. 
Published: May 2008

Abstract
One fifth of neurons in the medial-temporal lobe of human epilepsy patients respond selectively to categories of images, such as faces or cars. Here we show that responses of hippocampal neurons are rapidly modified as subjects alternate (over 60 sec) between two tasks (1) identifying images from a category, or (2) playing a simple video game superimposed on the same images. Category-selective responses, present when a subject identifies categories, are eliminated when the subject shifts to playing the game for 87% of category-selective hippocampal neurons. By contrast, responses in the amygdala are present during both tasks for 72% of category-selective amygdalar neurons. These results suggest that attention to images is required to evoke selective responses from single neurons in the hippocampus, but is not required by neurons in the amygdala.
Oscillatory Activity and Phase–Amplitude Coupling in the Human Medial Frontal Cortex during Decision Making
Authors: Cohen Michael X , Elger Christian E. , Fell Juergen 
Published: May 2008

Abstract
Electroencephalogram oscillations recorded both within and over the medial frontal cortex have been linked to a range of cognitive functions, including positive and negative feedback processing. Medial frontal oscillatory characteristics during decision making remain largely unknown. Here, we examined oscillatory activity of the human medial frontal cortex recorded while subjects played a competitive decision-making game. Distinct patterns of power and cross-trial phase coherence in multiple frequency bands were observed during different decision-related processes (e.g., feedback anticipation vs. feedback processing). Decision and feedback processing were accompanied by a broadband increase in cross-trial phase coherence at around 220 msec, and dynamic fluctuations in power. Feedback anticipation was accompanied by a shift in the power spectrum from relatively lower (delta and theta) to higher (alpha and beta) power. Power and cross-trial phase coherence were greater following losses compared to wins in theta, alpha, and beta frequency bands, but were greater following wins compared to losses in the delta band. Finally, we found that oscillation power in alpha and beta frequency bands were synchronized with the phase of delta and theta oscillations (“phase–amplitude coupling”). This synchronization differed between losses and wins, suggesting that phase–amplitude coupling might reflect a mechanism of feedback valence coding in the medial frontal cortex. Our findings link medial frontal oscillations to decision making, with relations among activity in different frequency bands suggesting a phase-utilizing coding of feedback valence information.
Are Vowels and Consonants Processed Differently? Event-related Potential Evidence with a Delayed Letter Paradigm
Authors: Carreiras Manuel , Gillon-Dowens Margaret , Vergara Marta , Perea Manuel 
Published: May 2008

Abstract
To investigate the neural bases of consonant and vowel processing, event-related potentials (ERPs) were recorded while participants read words and pseudowords in a lexical decision task. The stimuli were displayed in three different conditions: (i) simultaneous presentation of all letters (baseline condition); (ii) presentation of all letters, except that two internal consonants were delayed for 50 msec (consonants-delayed condition); and (iii) presentation of all letters, except that two internal vowels were delayed for 50 msec (vowels-delayed condition). The behavioral results showed that, for words, response times in the consonants-delayed condition were longer than in the vowels-delayed condition, which, in turn, were longer than in the baseline condition. The ERPs showed that, starting as early as 150 msec, words in the consonants-delayed condition produced a larger negativity than words in vowels-delayed condition. In addition, there were peak latency differences and amplitude differences in the P150, N250, P325, and N400 components between the baseline and the two letter-delayed conditions. We examine the implications of these findings for models of visual-word recognition and reading.
Mobility beyond the clinic: the effect of environment on gait and its measurement in community-ambulant stroke survivors
Authors: Donovan Kimberley , Lord Susan E , McNaughton Harry K , Weatherall Mark 
Published: May 2008

Objective: To explore the impact of a complex community environment on gait parameters (speed, step length and cadence) for community-dwelling participants with a previous stroke, and compare outcome measures commonly used in a clinical environment. Design: Repeated measurement of participants in different environments. Setting: One clinic and two community environments (suburban street and shopping mall). Subjects: Thirty community-dwelling stroke participants with chronic stroke who were classified according to gait speed (20—50 m/min on 10-metre timed walk) as marginal community walkers. Outcome measures: During a six-minute walk test (6MWT) a step activity monitor (SAM) and odometer were used to calculate gait speed, step length and cadence. The 10-metre timed walk (10MTW) was measured in a clinic environment. Analysis: A mixed linear model examined differences in gait measurements in the different environments. Bland—Altman analysis illustrated agreement between gait speed measures (6MWT and 10MTW). Results: A statistically significant, but not a clinically significant difference in gait speed between some environments was found. Gait speed was slowest in the mall and fastest in the street with a difference of only 2.1 m/min between these environments (95% confidence interval (CI) -3.8 to -0.5, P<0.01). Comparison of clinic 10MTW and street 6MWT showed wide limits of agreement (-18.5 to 16.9 m/min) which improved for clinic 6MWT and street 6MWT comparisons (-5.7 to 8.9 m/min). Conclusion: Despite residual gait deficit, the gait parameters of these chronic stroke survivors did not deteriorate markedly under challenging conditions. The 6MWT is recommended as a clinical measure for community ambulation.
Handle size as a task constraint in spoon-use movement in patients with Parkinson's disease
Authors: Ma Hui-Ing , Hwang Wen-Juh , Chen-Sea Mei-Jin , Sheu Ching-Fan 
Published: May 2008

Objective: To examine the effect of spoon-handle size on kinematic performance in people with Parkinson's disease. Design: A counterbalanced repeated-measures design. Setting: A motor control laboratory in a university setting. Subjects: Eighteen individuals with Parkinson's disease and 18 age-matched controls. Experimental conditions: Each participant was instructed to scoop water (simulated soup) using spoons with three different-sized handles. Main measures: Kinematic variables (movement time, peak velocity and number of movement units) of arm movement, size of hand aperture and number of fingers to grasp the spoon. Results: The movement of the participants with Parkinson's disease was faster (shorter movement time) and smoother (fewer movement units) when they used spoons with a small- or medium-sized handle than when using a spoon with a large-sized handle. In contrast, the healthy controls showed no significant differences in movement kinematics between handle sizes. Moreover, the participants with Parkinson's disease had a significantly smaller hand aperture and used more fingers to hold the spoons than the controls did. Conclusions: These results suggest that, for people with Parkinson's disease, a small-to-medium-sized handle is more suitable than a large-sized built-up handle.
Sick leave reductions from a comprehensive manual therapy programme for low back pain: the Gotland Low Back Pain Study
Authors: Bogefeldt J. , Grunnesjö Marie I , Svärdsudd K. , Blomberg S. 
Published: May 2008

Objective: To evaluate if a comprehensive manual therapy programme reduces sick leave due low back pain and facilitates return to work more than the conventional optimized activating care. Design: A randomized controlled trial over a 10-week period with a two-year follow-up. Setting: Primary health care and Visby Hospital, Municipality of Gotland, Sweden. Subjects: One hundred and sixty patients (70 women, 90 men, ages 20—55 years) with acute or subacute low back pain with or without pain radiation into the legs. Interventions: Standardized optimized activating care (n = 71) versus a comprehensive pragmatic manual therapy programme including specific corticosteroid injections (n = 89). Main measures: Sick leave measured as net sick leave volume, point prevalence and return to work. Results: After 10 weeks, significantly more manual therapy patients than reference patients had returned to work (hazards ratio 1.62, 95% confidence interval (CI) 1.006—2.60, P<0.05), and among those on sick leave at baseline, significantly fewer were still on sick leave (8/58 versus 13/40, ratio 0.35, 95% CI 0.13—0.97, P<0.05). For all other measures there were inconclusive differences in favour of the manual therapy group. No significant differences remained after two years. Conclusions: The manual therapy programme used in this study decreased sick leave and increased return to work more than the standardized optimized activating care only up to 10 weeks but not up to two years.
Measures for rating social participation in people with aphasia: a systematic review
Authors: Dalemans Ruth , de Witte Luc P , Lemmens Jessie , van den Heuvel Wim JA , Wade Derick T 
Published: May 2008

Background: Re-establishing participation in social life is an important aim of rehabilitation, but instruments to measure participation in people with aphasia are rare. Aims: To identify and describe measures of social participation that may be specifically useful when measuring participation in people with aphasia. Methods and procedures: A systematic review of the literature concerning participation instruments was conducted. Then six speech and language therapists evaluated the suitability of selected participation measures for use in people with aphasia and a systematic literature review concerning the feasibility, internal consistency, validity, reliability and responsiveness of the measures selected by the therapists was carried out. Results: In total 12 instruments measuring aspects of participation were found: seven measured actual performance and five measured actual performance combined with experienced problems. Two were considered unsuitable for people with aphasia, leaving 10. Six speech and language therapists working with people with aphasia scored the 10 selected instruments, and two instruments were judged as possibly suitable for use in people with aphasia: the Community Integration Questionnaire (CIQ) and the Nottingham Extended Activities of Daily Living (NEADL). However, the Community Integration Questionnaire is much closer to the concept of participation. The literature review concerning the psychometric properties of the Community Integration Questionnaire revealed that very little is known about the use of this instrument in people with aphasia. Conclusion: The Community Integration Questionnaire is possibly suitable for use in people with aphasia when measuring participation, but data on its psychometric properties in people with aphasia are absent.
Influence of combined exercise training on indices of obesity, diabetes and cardiovascular risk in type 2 diabetes patients
Authors: Lambers Sabine , Van Laethem Christophe , Van Acker Kristien , Calders Patrick 
Published: May 2008

Objective: To investigate the influence of combined exercise training on indices of obesity, diabetes and cardiovascular risk in type 2 diabetes patients. Design: A double-blind randomized controlled trial with patients receiving either combination (COM), endurance (END) or no training (C). Setting: Sint-Jozef hospital (Belgium), general practice (Holland). Subjects: Forty-six type 2 diabetes patients (17 female, 29 male). Interventions: COM versus END and C. Patients exercised for three months, three times a week for 1 hour. Main measures: Six-minute walk test (6MW T), peak Vo2, strength in upper and lower limbs, sit-to-stand, height, weight, body mass index, fat mass, glycosylated haemoglobin (HbA1c), glycaemia, triglycerides, high-density lipoprotein (HDL), total cholesterol and quality of life (General Health Survey Short Form (SF-36)). Results: COM had significant better results on sit-to-stand (P<0.05), 6MW T (P<0.01), strength in upper (P<0.001) and lower limbs (P<0.001) compared with C. A different evolution among COM and C was found for HbA1c (P<0.05) and cholesterol (P<0.01), both decreased in COM and increased in C. HDL increased in COM and decreased in C (P<0.01). END had significant higher results on the 6MW T (P<0.01) compared with C. Compared with END, COM had significantly higher results on strength in upper (P<0.01) and lower limbs (P<0.01). The evolution of SF-36 items was not significantly different between the three groups. Conclusion: In diabetes type 2 patients, COM had significant better effects on indices of physical condition, diabetes and cardiovascular risk compared with C. Compared with END, COM gave a tendency towards better results, however more research with a larger number of participants is needed.