1,902 research outputs found
Insights on Ceramics as Dental Materials. Part I: Ceramic Material Types in Dentistry
Ceramics are widely used biomaterials in prosthetic dentistry due to their attractive clinical properties. They are aesthetically pleasing with their color, shade and luster, and they are chemically stable. The main constituents of dental ceramic are Si-based inorganic materials, such as feldspar, quartz, and silica. Traditional feldspar-based ceramics are also referred to as "Porcelain". The crucial difference between a regular ceramic and a dental ceramic is the proportion of feldspar, quartz, and silica contained in the ceramic. A dental ceramic is a multiphase system, i. e. it contains a dispersed crystalline phase surrounded by a continuous amorphous phase (a glassy phase). Modern dental ceramics contain a higher proportion of the crystalline phase that significantly improves the biomechanical properties of ceramics. Examples of these high crystalline ceramics include lithium disilicate and zirconia. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 21 Feb 201
The effect of increased microporosity on bone formation within silicate-substituted scaffolds in an ovine posterolateral spinal fusion model
This study compared the bone forming capacity of the same formulation of silicate-substituted bone graft substitute materials with different microporosity in an instrumented posterolateral spinal fusion ovine model. Materials with a strut porosity of (i) 22.5% (SiCaP) or (ii) 36.0% (SiCaP(+)) were packed along either side of the spine. Bone apposition rates, % new bone formation, % bone-implant contact, and % graft resorption were quantified at 8, 12, and 24 weeks post surgery. Computed Tomography (CT) was used to grade the formation of fusion bridges between vertebrae. Results showed no significant difference in bone apposition rates, % new bone formation, and % bone-implant contact when the two materials were compared. However, at 8 weeks, a significantly higher CT score was obtained in the SiCaP(+) group (0.83±0.17) when compared with the SiCaP group (0.17±0.17; p=0.027). Significantly less scaffold remained in the SiCaP(+) group at 12 weeks (p=0.018). Both SiCaP and SiCaP(+) formulations augmented bone formation. Increasing the strut porosity did not significantly increase bone formation however, at 8 weeks it promoted the formation of more highly mineralized bone resulting in a significantly higher CT score, suggesting the bone tissue formed was more mature
Downregulation of the Gli Transcription Factors Regulator Kif7 Facilitates Cell Survival and Migration of Choriocarcinoma Cells
published_or_final_versio
The prognosis of allocentric and egocentric neglect : evidence from clinical scans
We contrasted the neuroanatomical substrates of sub-acute and chronic visuospatial deficits associated with different aspects of unilateral neglect using computed tomography scans acquired as part of routine clinical diagnosis. Voxel-wise statistical analyses were conducted on a group of 160 stroke patients scanned at a sub-acute stage. Lesion-deficit relationships were assessed across the whole brain, separately for grey and white matter. We assessed lesions that were associated with behavioural performance (i) at a sub-acute stage (within 3 months of the stroke) and (ii) at a chronic stage (after 9 months post stroke). Allocentric and egocentric neglect symptoms at the sub-acute stage were associated with lesions to dissociated regions within the frontal lobe, amongst other regions. However the frontal lesions were not associated with neglect at the chronic stage. On the other hand, lesions in the angular gyrus were associated with persistent allocentric neglect. In contrast, lesions within the superior temporal gyrus extending into the supramarginal gyrus, as well as lesions within the basal ganglia and insula, were associated with persistent egocentric neglect. Damage within the temporo-parietal junction was associated with both types of neglect at the sub-acute stage and 9 months later. Furthermore, white matter disconnections resulting from damage along the superior longitudinal fasciculus were associated with both types of neglect and critically related to both sub-acute and chronic deficits. Finally, there was a significant difference in the lesion volume between patients who recovered from neglect and patients with chronic deficits. The findings presented provide evidence that (i) the lesion location and lesion size can be used to successfully predict the outcome of neglect based on clinical CT scans, (ii) lesion location alone can serve as a critical predictor for persistent neglect symptoms, (iii) wide spread lesions are associated with neglect symptoms at the sub-acute stage but only some of these are critical for predicting whether neglect will become a chronic disorder and (iv) the severity of behavioural symptoms can be a useful predictor of recovery in the absence of neuroimaging findings on clinical scans. We discuss the implications for understanding the symptoms of the neglect syndrome, the recovery of function and the use of clinical scans to predict outcome
Comparison of Genome-Wide Association Scans for Quantitative and Observational Measures of Human Hair Curvature.
Previous genetic studies on hair morphology focused on the overall morphology of the hair using data collected by self-report or researcher observation. Here, we present the first genome-wide association study (GWAS) of a micro-level quantitative measure of hair curvature. We compare these results to GWAS results obtained using a macro-level classification of observable hair curvature performed in the same sample of twins and siblings of European descent. Observational data were collected by trained observers, while quantitative data were acquired using an Optical Fibre Diameter Analyser (OFDA). The GWAS for both the observational and quantitative measures of hair curvature resulted in genome-wide significant signals at chromosome 1q21.3 close to the trichohyalin (TCHH) gene, previously shown to harbor variants associated with straight hair morphology in Europeans. All genetic variants reaching genome-wide significance for both GWAS (quantitative measure lead single-nucleotide polymorphism [SNP] rs12130862, p = 9.5 × 10-09; observational measure lead SNP rs11803731, p = 2.1 × 10-17) were in moderate to very high linkage disequilibrium (LD) with each other (minimum r2 = .45), indicating they represent the same genetic locus. Conditional analyses confirmed the presence of only one signal associated with each measure at this locus. Results from the quantitative measures reconfirmed the accuracy of observational measures
Worldvolume Superalgebra Of BLG Theory With Nambu-Poisson Structure
Recently it was proposed that the Bagger-Lambert-Gustavsson theory with
Nambu-Poisson structure describes an M5-brane in a three-form flux background.
In this paper we investigate the superalgebra associated with this theory. We
derive the central charges corresponding to M5-brane solitons in 3-form
backgrounds. We also show that double dimensional reduction of the superalgebra
gives rise to the Poisson bracket terms of a non-commutative D4-brane
superalgebra. We provide interpretations of the D4-brane charges in terms of
spacetime intersections.Comment: 23 pages; references added, section 4 clarification
More on the Nambu-Poisson M5-brane Theory: Scaling limit, background independence and an all order solution to the Seiberg-Witten map
We continue our investigation on the Nambu-Poisson description of M5-brane in
a large constant C-field background (NP M5-brane theory) constructed in
Refs.[1, 2]. In this paper, the low energy limit where the NP M5-brane theory
is applicable is clarified. The background independence of the NP M5-brane
theory is made manifest using the variables in the BLG model of multiple
M2-branes. An all order solution to the Seiberg-Witten map is also constructed.Comment: expanded explanations, minor corrections and typos correcte
Comets, historical records and vedic literature
A verse in book I of Rigveda mentions a cosmic tree with rope-like aerial
roots held up in the sky. Such an imagery might have ensued from the appearance
of a comet having `tree stem' like tail, with branched out portions resembling
aerial roots. Interestingly enough, a comet referred to as `heavenly tree' was
seen in 162 BC, as reported by old Chinese records. Because of weak surface
gravity, cometary appendages may possibly assume strange shapes depending on
factors like rotation, structure and composition of the comet as well as solar
wind pattern. Varahamihira and Ballala Sena listed several comets having
strange forms as reported originally by ancient seers such as Parashara,
Vriddha Garga, Narada and Garga.
Mahabharata speaks of a mortal king Nahusha who ruled the heavens when Indra,
king of gods, went into hiding. Nahusha became luminous and egoistic after
absorbing radiance from gods and seers. When he kicked Agastya (southern star
Canopus), the latter cursed him to become a serpent and fall from the sky. We
posit arguments to surmise that this Mahabharata lore is a mythical recounting
of a cometary event wherein a comet crossed Ursa Major, moved southwards with
an elongated tail in the direction of Canopus and eventually went out of sight.
In order to check whether such a conjecture is feasible, a preliminary list of
comets (that could have or did come close to Canopus) drawn from various
historical records is presented and discussed.Comment: This work was presented in the International Conference on Oriental
Astronomy held at IISER, Pune (India) during November, 201
Non-abelian Action for Multiple Five-Branes with Self-Dual Tensors
We construct an action for non-abelian 2-form in 6-dimensions. Our action
consists of a non-abelian generalization of the abelian action of Perry and
Schwarz for a single five-brane. It admits a self-duality equation on the field
strength as the equation of motion. It has a modified 6d Lorentz symmetry. On
dimensional reduction on a circle, our action gives the standard 5d Yang-Mills
action plus higher order corrections. Based on these properties, we propose
that our theory describes the gauge sector of multiple M5-branes in flat space.Comment: LaTeX, 26 pages. v2: improved discussion of Lorentz symmetry. ref
added. v3: add comments in the discussion section on the inclusion of scalar
fields and supersymmetry; title changed to a more suitable one; version
published in JHE
Boundary Conditions for Interacting Membranes
We investigate supersymmetric boundary conditions in both the Bagger-Lambert
and the ABJM theories of interacting membranes. We find boundary conditions
associated to the fivebrane, the ninebrane and the M-theory wave. For the ABJM
theory we are able to understand the enhancement of supersymmetry to produce
the (4,4) supersymmetry of the self-dual string. We also include supersymmetric
boundary conditions on the gauge fields that cancel the classical gauge anomaly
of the Chern-Simons terms.Comment: 36 pages, latex, v2 minor typos correcte
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