3,913 research outputs found
Melting of cognetic depleted and enriched reservoirs and the production of high Ti Mare basalts
Implicit in current understanding of the location of terrestrial enriched and depleted reservoirs is the notion that they are spatially separated. The depleted reservoir on Earth is situated in the upper mantle, and the complementary enriched reservoir is located in the crust. However, Earth reservoirs are continually being modified by recycling driven by mantle convection. The Moon is demonstrably different from Earth in that its evolution was arrested relatively early - effectively with 1.5 Ga of its formation. It is possible that crystallized trapped liquids (from the late stages of a magma ocean) have been preserved as LILE-enriched portions of the lunar mantle. This would lead to depleted (cumulate) and enriched (magma ocean residual liquid) reservoirs in the lunar upper mantle. There is no evidence for significant recycling from the highland crust back into the mantle. Therefore, reservoirs created at the Moon's inception may have remained intact for over 4.0 Ga. The topics discussed include the following: (1) radiogenic isotopes in high-Ti mare basalts; (2) formation of cogenetic depleted and enriched reservoirs; and (3) melting of the source to achieve high-Ti mare basalts
Area Law and Continuum Limit in "Induced QCD"
We investigate a class of operators with non-vanishing averages in a
D-dimensional matrix model recently proposed by Kazakov and Migdal. Among the
operators considered are ``filled Wilson loops" which are the most reasonable
counterparts of Wilson loops in the conventional Wilson formulation of lattice
QCD. The averages of interest are represented as partition functions of certain
2-dimensional statistical systems with nearest neighbor interactions. The
``string tension" , which is the exponent in the area law for the
``filled Wilson loop" is equal to the free energy density of the corresponding
statistical system. The continuum limit of the Kazakov--Migdal model
corresponds to the critical point of this statistical system. We argue that in
the large limit this critical point occurs at zero temperature. In this
case we express in terms of the distribution density of eigenvalues
of the matrix-valued master field. We show that the properties of the continuum
limit and the description of how this limit is approached is very unusual and
differs drastically from what occurs in both the Wilson theory () and in the ``adjoint'' theory (). Instead, the continuum limit of the model appears to be
intriguingly similar to a string theory.Comment: 38 page
On the use of low-cost computer peripherals for the assessment of motor dysfunction in Parkinson’s disease – Quantification of bradykinesia using target tracking tasks
The potential of computer games peripherals to measure the motor dysfunction in Parkinson’s diseases is assessed. Of particular interest is the quantification of bradykinesia. Previous studies used modified or custom haptic interfaces, here an unmodified force feedback joystick and steering wheel are used with a laptop. During testing an on screen cursor moves in response to movements of the peripheral, the user has to track a continuously moving target (pursuit tracking), or move to a predetermined target (step tracking). All tasks use movement in the horizontal axis, allowing use of joystick or steering wheel. Two pursuit tracking tasks are evaluated, pseudo random movement, and a swept frequency task. Two step tracking tasks are evaluated, movement between two or between two of five fixed targets. Thirteen patients and five controls took part on a weekly basis. Patients were assessed for bradykinesia at each session using standard clinical measures. A range of quantitative measures was developed to allow comparison between and within patients and controls using ANOVA. Both peripherals are capable of discriminating between controls and patients, and between patients with different levels of bradykinesia. Recommendations for test procedures and peripherals are given
Two Rb-Sr Whole Rock Isochrons from Plutons In the Cobequid Highlands, Nova Scotia, Canada
Two Rb-Sr Hhole rock isochrons have been obtained from plutons In the Cobequid Highlands of Nova Scotia: the Debert River and Hart Lake-Byers Lake Plutons. The undeformed, unfoilated Debert River Pluton yielded an age of 596± 70 Ma and an Initial 87Sr/88Sr ratio of 0.7059 ± 0.0007. This age places an upper age limit on the detonation recorded In the Folly River Schist (youngest unit of the Bass River Complex), the d I or I tic Frog Lake Pluton, and the sedimentary rocks immediately north and east of the Debert River Pluton.
The Hart Lake-Byers Lake Pluton yielded anageof348±5Maandan Initial 87Sr/88Sr ratio of 0.7046 ± 0.0008. The similarity of this age to that of the adjacent felsic volcanics of the Byers Brook For nation suggests that they are comagmatic and confine that a Carboniferous igneous event forms an Important part of the geological history of the Cobequid Highlands. The Initial 87Sr/88Sr ratio and the blotite-hornblende content of the two granites suggest a mafic Igneous loner crustal source or possible untie component for the magma.
RÉSUMÉ
Les plutons de Debert River et Hart Lake-Byers Lake dans les monts Cobequld en Nouvel le-Écosse ont livre deux isochrones Rb-Sr de roche globale. Il déformé ni fellé, le pluton de Debert River a donné un âge de 596± 70 Ma et un rapport 87Sr/88Sr initial de 0.7059 ± 0.0007. Ceci place une limite supérieure sur l’âge de la déformation enregistrée dans le schiste de Folly River (L’unité la plus jeune du complexe de Bass River), le pluton diorltique de Frog Lake et dans les roches sédimentaires Jouxtant le pluton de Debert River au nord et à l’est.
Le pluton de Hart Lake-Byers Lake à produit un âge de 348 ± 5 Ma et un rapport isotopique 87Sr/88Sr initial de 0.7046 ± 0.008. Cet âge, similaire à ceux des volcanites felslques adjacentes de la formation de Byers Brook, suggére qu'lis sent comagnatiques, signe evident qu'un épisode igné carbonifère forme l’un des faits majeurs de L’histoire géologique des monts Cobequid. Le rapport 87Sr/88Sr initial et la teneur en blotite et hornbIende de ces deux granites suggérent une genèse crustale profonde du magma avec une possible contribution mantellique.
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Open challenges in the management of autoimmune hepatitis
Autoimmune Hepatitis (AIH) is a rare autoimmune disease of the liver with many open questions as regards its aetiopathogenesis, natural history and clinical management. The classical picture of AIH is chronic hepatitis with fluctuating elevation of serum transaminases and Immunoglobulin G levels, the presence of circulating autoantibodies and typical histological features. However, atypical presentations do occur and are not well captured by current diagnostic scores, with important consequences in terms of missed diagnoses and delayed treatments. AIH is treated with corticosteroids and immunosuppressive drugs but up to 40% of patients do not achieve full biochemical response and are at risk of progressing to cirrhosis and liver failure. Moreover, standard therapies are associated by significant side-effects which may impair the quality of life of patients living with AIH. However, advances in the understanding of the underlying immunology of AIH is raising the prospect of novel therapies and optimisation of existing therapeutic approaches to reduce side-effect burdens and potentially restore immunological tolerance. In this review we outline the clinical characteristics, aetiopathogenesis and management of AIH and current challenges in the diagnosis and management of AIH and provide evidence underlying the evolution of diagnostic and clinical management protocols
First impressions and perceived roles: Palestinian perceptions on foreign aid
This paper summarizes some results of a wider research on foreign aid that was conducted in the West Bank and Gaza Strip in 2010. It seeks to describe the impressions and feelings of Palestinian aid beneficiaries as well as the roles and functions they attached to foreign aid. To capture and measure local perceptions on Western assistance a series of individual in depth interviews and few focus group interviews were conducted in the Palestinian territories. The interview transcripts were processed by content analysis. As research results show — from the perspective of aid beneficiaries — foreign aid is more related to human dignity than to any economic development. All this implies that frustration with the ongoing Israeli-Palestinian conflict inevitably embraces the donor policies and practices too
Collaborative Epistemic Discourse in Classroom Information Seeking Tasks
We discuss the relationship between information seeking, and epistemic beliefs – beliefs about the source, structure, complexity, and stability of knowledge – in the context of collaborative information seeking discourses. We further suggest that both information seeking, and epistemic cognition research agendas have suffered from a lack of attention to how information seeking as a collaborative activity is mediated by talk between partners – an area we seek to address in this paper. A small-scale observational study using sociocultural discourse analysis was conducted with eight eleven year old pupils who carried out search engine tasks in small groups. Qualitative and quantitative analysis were performed on their discussions using sociocultural discourse analytic techniques. Extracts of the dialogue are reported, informed by concordance analysis and quantitative coding of dialogue duration. We find that 1) discourse which could be characterised as ‘epistemic’ is identifiable in student talk, 2) that it is possible to identify talk which is more or less productive, and 3) that epistemic talk is associated with positive learning outcomes
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