The adhesive revolution of restorative dentistry

In many countries, the incidence of dental decay in the young is decreasing, and Hong Kong is no exception. However, there remains in the region, a number of restorative dental problems of some significance. These are tooth discolouration, fracture, and root surface decay. This article discusses these problems and the way in which their treatment is increasingly being undertaken by means of minimalԸ?intervention adhesive techniques. The formulation of dental adhesive systems that are effective on a wet substrate has played a significant role in the development of modern dental practice. This development is briefly outlined, as are the principles underlying dental adhesion.published_or_final_versio

Towards a universal “baseline” characterisation of air masses for high- and low-altitude observing stations using Radon-222

We demonstrate the ability of atmospheric radon concentrations to reliably and unambiguously identify local and remote terrestrial influences on an air mass, and thereby the potential for alteration of trace gas composition by anthropogenic and biogenic processes. Based on high accuracy (lower limit of detection 10–40 mBq m–3), high temporal resolution (hourly) measurements of atmospheric radon concentration we describe, apply and evaluate a simple two-step method for identifying and characterising constituent mole fractions in baseline air. The technique involves selecting a radon-based threshold concentration to identify the “cleanest” (least terrestrially influenced) air masses, and then performing an outlier removal step based on the distribution of constituent mole fractions in the identified clean air masses. The efficacy of this baseline selection technique is tested at three contrasting WMO GAW stations: Cape Grim (a coastal low-altitude site), Mauna Loa (a remote high-altitude island site), and Jungfraujoch (a continental high-altitude site). At Cape Grim and Mauna Loa the two-step method is at least as effective as more complicated methods employed to characterise baseline conditions, some involving up to nine steps. While it is demonstrated that Jungfraujoch air masses rarely meet the baseline criteria of the more remote sites, a selection method based on a variable monthly radon threshold is shown to produce credible “near baseline” characteristics. The seasonal peak-to-peak amplitude of recent monthly baseline CO2 mole fraction deviations from the long-term trend at Cape Grim, Mauna Loa and Jungfraujoch are estimated to be 1.1, 6.0 and 8.1 ppm, respectively

Identification of a predominant isolate of Mycobacterium tuberculosis using molecular and clinical epidemiology tools and in vitro cytokine responses

BACKGROUND: Tuberculosis (TB) surveillance programs in Canada have established that TB in Canada is becoming a disease of geographically and demographically distinct groups. In 1995, treaty status aboriginals from the province of Manitoba accounted for 46% of the disease burden of this sub-group in Canada. The TB incidence rates are dramatically high in certain reserves of Manitoba and are equivalent to rates in African countries. The objective of our study was to identify prevalent isolates of Mycobacterium tuberculosis in the patient population of Manitoba using molecular epidemiology tools, studying the patient demographics associated with the prevalent strain and studying the in vitro cytokine profiles post-infection with the predominant strain. METHODS: Molecular typing was performed on all isolates available between 1992 to1997. A clinical database was generated using patient information from Manitoba. THP-1 cells were infected using strains of M. tuberculosis and cytokine profiles were determined using immunoassays for cytokines IL-1β, IL-10, IL-12, IFN-γ and TNF-α. RESULTS: In Manitoba, 24% of the disease burden is due to a particular M. tuberculosis strain (Type1). The strain is common in patients of aboriginal decent and is responsible for at least 87% of these cases. Cytokine assays indicate that the Type1 strain induces comparatively lower titers of IL-1β, IFN-γ and TNF-α in infected THP-1 cells as compared to H37Ra and H37Rv strains. CONCLUSION: In Manitoba, Type1 strain is predominant in TB patients. The majority of the cases infected with this particular strain are newly active with a high incidence of respiratory disease, positive chest radiographs and pulmonary cavities. In vitro secretion of IL-1β, IFN-γ and TNF-α is suppressed in Type1 infected culture samples when compared to H37Ra and H37Rv infected cells

Numerical simulation of blood flow and pressure drop in the pulmonary arterial and venous circulation

A novel multiscale mathematical and computational model of the pulmonary circulation is presented and used to analyse both arterial and venous pressure and flow. This work is a major advance over previous studies by Olufsen et al. (Ann Biomed Eng 28:1281–1299, 2012) which only considered the arterial circulation. For the first three generations of vessels within the pulmonary circulation, geometry is specified from patient-specific measurements obtained using magnetic resonance imaging (MRI). Blood flow and pressure in the larger arteries and veins are predicted using a nonlinear, cross-sectional-area-averaged system of equations for a Newtonian fluid in an elastic tube. Inflow into the main pulmonary artery is obtained from MRI measurements, while pressure entering the left atrium from the main pulmonary vein is kept constant at the normal mean value of 2 mmHg. Each terminal vessel in the network of ‘large’ arteries is connected to its corresponding terminal vein via a network of vessels representing the vascular bed of smaller arteries and veins. We develop and implement an algorithm to calculate the admittance of each vascular bed, using bifurcating structured trees and recursion. The structured-tree models take into account the geometry and material properties of the ‘smaller’ arteries and veins of radii ≥ 50 μ m. We study the effects on flow and pressure associated with three classes of pulmonary hypertension expressed via stiffening of larger and smaller vessels, and vascular rarefaction. The results of simulating these pathological conditions are in agreement with clinical observations, showing that the model has potential for assisting with diagnosis and treatment for circulatory diseases within the lung

Production of phi mesons at mid-rapidity in sqrt(s_NN) = 200 GeV Au+Au collisions at RHIC

We present the first results of meson production in the K^+K^- decay channel from Au+Au collisions at sqrt(s_NN) = 200 GeV as measured at mid-rapidity by the PHENIX detector at RHIC. Precision resonance centroid and width values are extracted as a function of collision centrality. No significant variation from the PDG accepted values is observed. The transverse mass spectra are fitted with a linear exponential function for which the derived inverse slope parameter is seen to be constant as a function of centrality. These data are also fitted by a hydrodynamic model with the result that the freeze-out temperature and the expansion velocity values are consistent with the values previously derived from fitting single hadron inclusive data. As a function of transverse momentum the collisions scaled peripheral.to.central yield ratio RCP for the is comparable to that of pions rather than that of protons. This result lends support to theoretical models which distinguish between baryons and mesons instead of particle mass for explaining the anomalous proton yield.Comment: 326 authors, 24 pages text, 23 figures, 6 tables, RevTeX 4. To be submitted to Physical Review C as a regular article. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm

Neuropsychological assessment of attention in children with spina bifida

<p>Abstract</p> <p>Background</p> <p>Children with the severe form of spina bifida (SBM: spina bifida with myelomeningocele with accompanying hydrocephalus) may manifest attention deficits, and have a similar psychological profile to children with hydrocephalus due to other etiologies. It is unclear to what extent tests to assess attention in SBM are confounded by the accompanying cognitive or visual-motor impairments. The aim of this study was to analyse attention functions by administering two different types of attention tests, one with high and the other with low cognitive and motor requirements. This enabled the possible interaction between attention and cognitive and motor impairment to be assessed.</p> <p>Methods</p> <p>The study group comprised 31 children with SBM with shunted hydrocephalus. Twenty children with SB-only formed a closely matched comparison group. Of these, 19 children with SBM and 18 with SB had a full-scale IQ (FSIQ) higher than 70. All had undergone spinal surgery and all children with SBM had been shunted within the first months of life. Between 6 and 15 years of age, the children were assessed on focused and sustained attention, encoding, and distractibility/impulsivity, using both traditional tests and computerized attention tests.</p> <p>Results</p> <p>Compared to the SB group, attention scores of children with SBM were lower on the traditional tests, but when interfering cognitive and visual-motor requirements were eliminated using the computerised tasks, most differences disappeared. Furthermore, in contrast to traditional attention tasks, computerized tests showed no significant correlations with IQ-scores and visual-motor skills.</p> <p>Conclusion</p> <p>Assessment of attention functions in children with SBM by traditional tests may be misleading, because this paediatric population with complex cerebral malformations has difficulty with the cognitive and visual-motor requirements. To control for these interactions, the use of both traditional and computerized attention tests is recommended.</p

The research on the immuno-modulatory defect of Mesenchymal Stem Cell from Chronic Myeloid Leukemia patients

Overwhelming evidence from leukemia research has shown that the clonal population of neoplastic cells exhibits marked heterogeneity with respect to proliferation and differentiation. There are rare stem cells within the leukemic population that possess extensive proliferation and self-renewal capacity not found in the majority of the leukemic cells. These leukemic stem cells are necessary and sufficient to maintain the leukemia. While the hematopoietic stem cell (HSC) origin of CML was first suggested over 30 years ago, recently CML-initiating cells beyond HSCs are also being investigated. We have previously isolated fetal liver kinase-1-positive (Flk1+) cells carrying the BCR/ABL fusion gene from the bone marrow of Philadelphia chromosome-positive (Ph+) patients with hemangioblast property. Here, we showed that CML patient-derived Flk1+CD31-CD34-MSCs had normal morphology, phenotype and karyotype but appeared impaired in immuno-modulatory function. The capacity of patient Flk1+CD31-CD34- MSCs to inhibit T lymphocyte activation and proliferation was impaired in vitro. CML patient-derived MSCs have impaired immuno-modulatory functions, suggesting that the dysregulation of hematopoiesis and immune response may originate from MSCs rather than HSCs. MSCs might be a potential target for developing efficacious cures for CML

Differential Susceptibility of Interneurons Expressing Neuropeptide Y or Parvalbumin in the Aged Hippocampus to Acute Seizure Activity

Acute seizure (AS) activity in old age has an increased predisposition for evolving into temporal lobe epilepsy (TLE). Furthermore, spontaneous seizures and cognitive dysfunction after AS activity are often intense in the aged population than in young adults. This could be due to an increased vulnerability of inhibitory interneurons in the aged hippocampus to AS activity. We investigated this issue by comparing the survival of hippocampal GABA-ergic interneurons that contain the neuropeptide Y (NPY) or the calcium binding protein parvalbumin (PV) between young adult (5-months old) and aged (22-months old) F344 rats at 12 days after three-hours of AS activity. Graded intraperitoneal injections of the kainic acid (KA) induced AS activity and a diazepam injection at 3 hours after the onset terminated AS-activity. Measurement of interneuron numbers in different hippocampal subfields revealed that NPY+ interneurons were relatively resistant to AS activity in the aged hippocampus in comparison to the young adult hippocampus. Whereas, PV+ interneurons were highly susceptible to AS activity in both age groups. However, as aging alone substantially depleted these populations, the aged hippocampus after three-hours of AS activity exhibited 48% reductions in NPY+ interneurons and 70% reductions in PV+ interneurons, in comparison to the young hippocampus after similar AS activity. Thus, AS activity-induced TLE in old age is associated with far fewer hippocampal NPY+ and PV+ interneuron numbers than AS-induced TLE in the young adult age. This discrepancy likely underlies the severe spontaneous seizures and cognitive dysfunction observed in the aged people after AS activity

Birds use structural properties when selecting materials for different parts of their nests

Bird nests can have various roles but all act as the location for incubation, so at least have to serve to hold and support the incubating bird and its clutch of eggs. Nest construction is species specific and the use of materials varies between different parts of the nest. At present we know very little about the role that these materials play in the structural characteristics of the nest. This study examined materials from deconstructed nests from four species of thrush (Turdidae) and two species of finch (Fringillidae) that all constructed nests made of woody stems. It was hypothesised that structural properties would vary within the different regions of a nest, with thicker and stronger materials being found in parts of the nest needing the most support. Secondly, it was predicted that structural properties would vary little between nests of members of the same family, but would be quite different between nests of different families. Nests were deconstructed to quantify the materials used in the cup lining, and the upper and lower parts of the outer nest. The 20 thickest pieces of material were selected from each nest part and for each piece, and their diameter and mass quantified. Each piece was then subjected to a three-point bending test using an Instron universal testing machine to determine its rigidity and bending strength. Placement of materials in the nest was non-random in all species. The materials used in the outer part of the nest were thicker, stronger and stiffer than those materials found in the cup lining. The extent to which these structural properties varied between families depended on where the material was taken from the nest. Both strength and rigidity strongly positively correlated with the diameter of the piece of material. We hypothesise that birds are not directly aware of the structural properties of the material per se but rather assess diameter and mass of the material when they pick it up by the bill. Using this information they decide on whether the piece is suitable for that appropriate stage of nest construction