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- Wang, Sheng-Jun, 1981-, et al.
(författare)
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Influence of synaptic interaction on firing synchronization and spike death in excitatory neuronal networks
- 2008
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - New York : American Physical Society through the American Institute of Physics. - 1063-651X .- 1095-3787. ; 78:6, s. 061906-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the influence of efficacy of synaptic interaction on firing synchronization in excitatoryneuronal networks. We find spike death phenomena: namely, the state of neurons transits from the limit cycleto a fixed point or transient state. The phenomena occur under the perturbation of an excitatory synapticinteraction, which has a high efficacy. We show that the decrease of synaptic current results in spike deaththrough depressing the feedback of the sodium ionic current. In the networks with the spike death property thedegree of synchronization is lower and insensitive to the heterogeneity of neurons. The mechanism of theinfluence is that the transition of the neuron state disrupts the adjustment of the rhythm of the neuronsoscillation and prevents a further increase of the firing synchronization.
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- Abdulghani, Saba, et al.
(författare)
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The influence of initial pressurization and cup introduction time on the depth of cement penetration in an acetabular model.
- 2007
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Ingår i: Acta Orthopaedica. - : Medical Journals Sweden AB. - 1745-3682 .- 1745-3674. ; 78:3, s. 333-339
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Tidskriftsartikel (refereegranskat)abstract
- Background Acetabular cementation during total hip arthroplasty is considered difficult mainly due to the appearance and anatomy of the acetabulum. Improved cementation technique has been shown to improve the longevity of acetabular components. Method We designed a ceramic model to investigate the effect of varying the initial cement pressurization and cup introduction times on the depth of cement penetration. 4 groups were prepared, 2 of which involved varying initial cement pressurization and cup introduction times. Group 3 involved initial cement pressurization with no cup introduction, while group 4 involved cup introduction with no prior cement pressurization. Results and interpretation Most cement penetration occurred in the early pressurization phase, and we conclude that a relatively early and longer cement pressurization time and late cup introduction are positive factors for increased cement penetration in the acetabulum model.
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| 4. |
- Camire, Christopher, et al.
(författare)
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Material characterization and in vivo behavior of silicon substituted alpha-tricalcium phosphate cement.
- 2006
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Ingår i: Journal of Biomedical Materials Research. Part B - Applied Biomaterials. - : Wiley. - 1552-4981 .- 1552-4973. ; 76B:2, s. 424-431
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Tidskriftsartikel (refereegranskat)abstract
- The possibility and biological effects of substituting silicon in a-tricalcium phosphate (alpha-TCP) by way of solid-state reaction have been evaluated. a-TCP powders with varying substitution amounts (1 and 5 mol % Ca2SiO4) were synthesized by reacting mixtures of CaCO3, Ca(2)P(2)O7, and SiO2, at a rate of 4 degrees C(min)(-1) to 1100 degrees C, left to dwell for 2 h and then heated to 1325 degrees C at 4 degrees C(min)(-1) and left to dwell for a period of 4 h. The powders were then rapidly quenched in air. Si incorporation could be verified by X-ray diffraction analysis, indicating an increase of the lattice volume with increasing Si content from 4284.1(8) to 4334(1) angstrom(3) for pure alpha-TCP and alpha-Si5%TCP, respectively. The hydrolysis of milled alpha-SiTCP powders was monitored by isothermal calorimetry, and the compressive strength of set cements was tested. The results showed changes in speed and amount of heat released during reactivity tests and a decrease in mechanical strength (60, 50, and 5 MPa) with increasing Si content. In vitro bioactivity of the set cements after soaking in simulated body fluid for 4 weeks was also tested. The formation of a bonelike apatite layer on the surface of the set cements could be observed and was thickest for 1% Si (20 mu m). These results were in good agreement with the in vivo studies performed, which showed strong evidence that the cement containing 1% silicon doped alpha-TCP enhanced mesenchymal cell differentiation and increased osteoblast activity compared with alpha-TCP. (c) 2005 Wiley Periodicals, Inc.
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| 5. |
- Löwemark, Ludvig, et al.
(författare)
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Glacio-eustatic influence on deep water circulation in the South China Sea over the past 500 kyrs – implications for global biogeochemical cycling
- 2008
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Ingår i: Western Pacific Geophysics Meeting, American Geophysical Union, Cairns, Australia, July/August 2008.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- We provide new evidence for the development of a stable estuarinecirculation characterized by stagnating water bodies, nutrient recycling and increased primary productivity in the South China Seaduring glacial intervals caused by the closure of the shallow andnarrow straits connecting the South China Sea in the south and west. Our main evidence comes from records of Mn concentrations and Mn/Al ratios in two sedimentary cores from the northern and southeastern South China Sea covering the last 500 ky. Concentrations and Mn/Al ratios of the redox sensitive element Mn show clear glacial-interglacial cycles with maxima during interglacial periods and minima during glacial periods. These cycles indicate ventilation cycles of the bottom water connected to the glacial-interglacial changes in sea level. In contrast, total organic carbon (TOC) concentrations display an opposite pattern with pronounced maxima during glacial times, especially in the southern part of the basin. The variations in TOC can be ascribed to two factors. Firstly to variations in primary productivity controlled by variations in theintensity of the winter monsoon. Secondly to the degree of preservation of TOC controlled by variations in ventilation, ultimately controlled by sea level. Variations in TOC consequentlyrepresent a superimposition of sea level influenced preservationcontrol and primarily winter monsoon driven variations in primaryproductivity intensity. The decrease in Mn correspond to times when sea level dropped below 40-50 m. Larger amplitude of the variations in TOC and Mn in the southern part of the basin compared to the northern sites suggest that oxygen depletion and nutrient recycling was stronger in the parts of the basin situated the furthest from the only remaining opening to the open Pacific, the Luzon strait.
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| 7. |
- Smith, Pete, et al.
(författare)
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Sectoral approaches to improve regional carbon budgets
- 2008
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Ingår i: Climatic Change. - : Springer Science and Business Media LLC. - 0165-0009 .- 1573-1480. ; 88:3-4, s. 209-249
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Forskningsöversikt (refereegranskat)abstract
- Humans utilise about 40% of the earth's net primary production (NPP) but the products of this NPP are often managed by different sectors, with timber and forest products managed by the forestry sector and food and fibre products from croplands and grasslands managed by the agricultural sector. Other significant anthropogenic impacts on the global carbon cycle include human utilization of fossil fuels and impacts on less intensively managed systems such as peatlands, wetlands and permafrost. A great deal of knowledge, expertise and data is available within each sector. We describe the contribution of sectoral carbon budgets to our understanding of the global carbon cycle. Whilst many sectors exhibit similarities for carbon budgeting, some key differences arise due to differences in goods and services provided, ecology, management practices used, land-management personnel responsible, policies affecting land management, data types and availability, and the drivers of change. We review the methods and data sources available for assessing sectoral carbon budgets, and describe some of key data limitations and uncertainties for each sector in different regions of the world. We identify the main gaps in our knowledge/data, show that coverage is better for the developed world for most sectors, and suggest how sectoral carbon budgets could be improved in the future. Research priorities include the development of shared protocols through site networks, a move to full carbon accounting within sectors, and the assessment of full greenhouse gas budgets.
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| 8. |
- Wang, Jian-Sheng, et al.
(författare)
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Indentation testing of a bone defect filled with two different injectable bone substitutes
- 2005
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Ingår i: Key Engineering Materials. - 1013-9826. ; 284-286, s. 89-92
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Konferensbidrag (refereegranskat)abstract
- Injectable bone substitutes (IBS) based on calcium phosphate (CaP) and/or calcium sulphate (CaS) are used as fillers in bone defects to stimulate bone integration and allow mechanical loading. Two types of IBS, IBS-1 is CaP+20%CaS and IBS-2 is CaS+40% hydroxyapatite, were investigated. The materials were injected into holes in the femur and tibia in rabbits. After 10 weeks the femora were subjected to indentation testing and tibiae were prepared for histology evaluation. IBS-1 lead to a higher indentation load compared to control, that is no material inserted, while IBS-2 showed no significant difference between material and control. Histology showed that with IBS-1, the bone penetrated into and integrated with the material in the defect. With IBS-2, new bone grew into the outer 0.5-1.0 mm. The materials could be used for different indications, such as to support fracture healing or in contained cavities
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