34,798 research outputs found
The Water Uptake of Experimental Soft Lining Materials
No full textPhDIn order to develop a successful soft lining material various factors have to be
considered; physical strength, adhesion to the denture base ( or prosthetic) and the
durability of the material's properties when in the mouth. It has been recognised that in
order to fulfil these criteria the material must be stable and have a low water uptake from
the aqueous environments of the mouth.
In the dental field comparatively little work has focused on how soft lining materials
behave in water where as water in polymers has received a considerable amount of
interest, with many different types of behaviour being observed and explained. It has
been realised by previous authors that the water uptake of elastomers is primarily driven
by soluble impurities, these form solution droplets within the material. The nature of the
growth is somewhat more debatable, with both Fickian and dual sorption kinetics being
reported.
Two basic types of materials were used in the study; silicone polymers and elastomer /
methacrylate materials. Silicone polymers are characterised by a low water uptake and
form the basis of perhaps the most successful soft lining material ('Molloplast B'). The
elastomer / methacrylate materials were based on those developed by Parker (1982),
Parker and Braden (1990) which showed considerable promise but suffered from an
extensive protracted uptake. Water uptake at 370C in conjunction with the tensile
strength were used to evaluate the materials produced as these simple tests enabled the
behaviour of the material in service to estimated.
Three different types of silicone polymers were used during the study classified by the
curing mechanism (condensation, peroxide and hydrosilanised), various fillers and
additives (such as calcium stearate) were incorporated into the materials and different
uptakes observed. The condensation silicones demonstrated large weight losses (up to
20 wt%) in water which is attributed to hydrolytic instability of the siloxane bridge in the
presence of an organo tin compound leading to a leaching of siloxane. The pure
peroxide and hydrosilanised materials both demonstrated a low water uptake but when
doped they form solution droplets in a similar way to that described in the literature.
Other additives showed different behaviour with the formation of cracks within the
silicone due to failure of the material around the droplets, the action of hydrophilic but
insoluble fillers also promotes the uptake. The hydrosilanised silicone polymers showed
considerable promise as soft lining materials with low water uptake and good tensile
strength.
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The elastomer / methacrylate materials were based initially on butadiene styrene
copolymer and a higher methacrylate monomer which formed a gel this was then free
radically cured. The water uptake of these materials was attributed to soluble separating
agent added to the butadiene styrene (to prevent particle agglomeration) during the
production of the powdered elastomer. The extent of the uptake could be controlled by
improving the strength of the material but the overall uptake remained too high. When
the material was placed in an osmotic solution (Na CI or glucose) the water uptake was
significantly reduced and the behaviour could be described by a modified (for small
strains) version of the Thomas and Muniandy (1987) theory for the growth of water
droplets in a elastomer.
In order to reduce the water uptake of the elastomer / methacrylate materials butadiene
styrene copolymers without separating agent was used. The emulsion polymerised
material contained soluble impurities from the polymerisation (i.e. soap)which acted to
drive the water uptake. Solution polymerised butadiene styrene also demonstrated a high
uptake but this is attributed to a clustering behaviour of carboxylic and hydroxyl groups
which formed post production. Similar behaviour is also seen for a solution polymerised
isoprene styrene elastomer. The role of crosslinking the material in restraining the
growth of the droplets is also investigated with dramatic reductions in the uptake being
observed as the crosslink density increased. The employment of a reinforcing silica filler
proved more effective than simply using a dimethacrylate. Oxidation is another problem
(characterised by an upturn in the absorption), although not observed in every case it was
a problem for all of the unsaturated elastomers and was found to be promoted by ions
present within saliva. Saturated butyl based (including chloro and bromo butyl)
elastomers were used instead and did not show any tendency for oxidation but they still
showed an uptake of approximately 3 to 4 wt%. Their stability however and reasonable
strength makes them suitable for further development as soft lining materials.
Theoretical considerations were investigated by HI NMR imaging with the formation of
droplets being observed, the profiles seen indicating the absorption to be two stage
rather than Fickian. The role of creep or stress relaxation is also identified as a
mechanism for extending the uptake by reducing the restraining force. Further reasoning
on all the data presented here concluded the role of chemical potential change associated
with the water into the matrix or the droplets will determine the nature of the uptake
observed
Acuaria irhami Dewi & Zhang 2010
No full textAcuaria irhami Dewi & Zhang, 2010. Journal of Helminthology, 84, 245–252; Figs. 3–4 (Dewi & Zhang, 2010). MZBNa 419 (Holo. 1♂, Para. 1♂). Type locality: Kangean Island, Indonesia (06 o 52’41.6”S and 115 o 25’ 12.7”E); type host: Dicrurus hottentottus jentincki (under lining of gizzard).Published as part of Animalesto, Gloria, Dewi, Kartika & Apriyanti, Yuni, 2022, The helminth endoparasite type specimens of the Museum Zoologicum Bogoriense Indonesia, pp. 281-293 in Zootaxa 5159 (2) on page 284, DOI: 10.11646/zootaxa.5159.2.6, http://zenodo.org/record/677725
†Chuchinolepididae Zhang 1978
No full textFamily †Chuchinolepididae Zhang 1978, spelling in prevailing recent practice †Chuchinolepidae Zhang 1978a: 296 (family) † Chuchinolepis Zhang 1978 [family name also seen as †Chuchinolepididae; author also seen as Chang] †Qujinolepidae Zhang 1978b: 173 (family) † Qujinolepis Zhang 1978 [family name sometimes seen as † Qujinolepididae] †Procondylolepidae Zhang 1984: 82 (family) † Procondylolepis Zhang 1984Published as part of Laan, Richard Van Der, 2018, Family-group names of fossil fishes, pp. 1-167 in European Journal of Taxonomy 466 on page 27, DOI: 10.5852/ejt.2018.466, http://zenodo.org/record/555755
An enhanced author name dataset for PubMed/MEDLINE
No full text<p>The incompleteness of author names is a well-known issue in the MEDLINE database. It was since 2002, the full author name has been systematically indexed in MEDLINE. Although many full author names have been added to MEDLINE, we still found a significant number of abbreviated names in papers published after 2002.</p>
<p>Here we built an enhanced author name dataset for MEDLINE, called EAN, achieved by linking the whole PubMed to other large literature databases and conducting a large-scale name comparison and restoration with obtained multi-sources author names. Our evaluation shows that more than 90% of author names in EAN are complete as compared to the ratio of ~60% in MEDLINE.</p>
An enhanced author name dataset for PubMed/MEDLINE
No full text<p>The incompleteness of author names is a well-known issue in the MEDLINE database. It was since 2002, the full author name has been systematically indexed in MEDLINE. Although many full author names have been added to MEDLINE, we still found a significant number of abbreviated names in papers published after 2002.</p>
<p>Here we built an enhanced author name dataset for MEDLINE, called EAN, achieved by linking the whole PubMed to other large literature databases and conducting a large-scale name comparison and restoration with obtained multi-sources author names. Our evaluation shows that more than 90% of author names in EAN are complete as compared to the ratio of ~60% in MEDLINE.</p>
Study on Crack Development of Concrete Lining with Insufficient Lining Thickness Based on CZM Method
No full textThe most common structural defect of a tunnel in the operation period is the cracking of concrete lining. The insufficient thickness of tunnel lining is one of the main reasons for its cracking. This study studied the cracking behavior of standard concrete specimens and the failure behavior of tunnel structures caused by insufficient lining thickness using Cohesive Zone Model (CZM). Firstly, zero-thickness cohesive elements were globally inserted between solid elements of the standard concrete specimen model, and the crack development process of different concrete grades was compared. On this basis, a three-dimensional numerical model of the tunnel in the operation period was established. The mechanism and characteristics of crack propagation under different lining thicknesses were discussed. In addition, the statistics of cracks were made to discuss the development rules of lining cracks quantitatively. The results show that the CZM can reasonably simulate the fracture behavior of concrete. With the increase in concrete strength grade, the number of cohesive damaged elements and crack area increases. The insufficient lining thickness changes the lining stress distribution characteristics, reduces the lining structure’s overall safety, and leads to the cracking of the diseased area more easily. When surrounding rock does not contact the insufficient lining thickness, its influence on the structure is more evident than when surrounding rock fills the entire lining thickness. The number of cohesive damaged elements and the size of the crack area increases significantly
Astragalus wui M. Idrees & Z. Y. Zhang 2021, nom. nov.
No full textAstragalus wui M. Idrees & Z.Y. Zhang, nom. nov. Replaced name:— Astragalus sylvaticus Y.H. Wu (2015: 718), nom. illeg., non A. sylvaticus (Pall.) Willd. (1802: 1300). Type:— CHINA. Xinjiang: Yecheng Country, Sukepiya, in border forest, alt. 3000 m, 15 Aug. 1987, Exped. Qinghai-Tibet Wu Yuhu 1067 (holotype: QTPMB, not seen). Etymology:—The specific epithet honours Prof. Dr. Wu Yuhu (Northwest Institute of Plateau Biology, Chinese Academy of Science, Xining, China), author of the replaced name, who first described this new species.Published as part of Idrees, Muhammad & Zhang, Zhiyong, 2021, Astragalus wui, a new replacement name for A. sylvaticus Y. H. Wu (Galegeae, Papilionoideae, Fabaceae), pp. 210-211 in Phytotaxa 524 (3) on page 210, DOI: 10.11646/phytotaxa.524.3.6, http://zenodo.org/record/564936
sj-docx-1-jis-10.1177_01655515221074323 – Supplemental material for Collaboration of issuing agencies and topic evolution of health informatisation policies in China
No full textSupplemental material, sj-docx-1-jis-10.1177_01655515221074323 for Collaboration of issuing agencies and topic evolution of health informatisation policies in China by Wenli Zhang, Rui Yao, Richard Evans, Wenjing Huang, Guang Cao and Lining Shen in Journal of Information Science</p
Professor Zhang Weihua's Clinical Experience in the Application of Yongquan Acupoint
No full textSummarizing Professor Zhang Weihua's understanding of the bidirectional regulation function of Yongquan Point and his clinical application experience, the author believes that Yongquan is a meeting place of Yin and Yang qi, and both Yin and Yang qi are rooted here, which can be used to balance Yin and Yang, and proposes that Yongquan is the key point of bidirectional regulation, which has the functions of bidirectional regulation, bidirectional lifting, bidirectional replenishing. At the same time, Professor Zhang believes that Yongquan point should be combined with the corresponding stimulation method in the treatment of different diseases, which provides a new idea for the clinical treatment of some difficult diseases
Study of contact pressure between primary lining and secondary lining for tunnels of passenger dedicated lines
No full textTo systematically study the mechanical properties of the secondary lining for tunnels of the passenger dedicated lines(PDL), in-site monitoring is used to measure the contact pressures between the primary lining and the secondary lining for some typical tunnels of different Lines, such as Guiguang Line, Lanyu Line and Jinghu Line. According to the research, the contact pressure reaches its maximum value at the moment when the tunnel lining trolley is removed. The load acting on secondary lining is the actual deformation pressure, which is totally different from the loose pressure prescribed in Chinese tunnel criteria. The safety factor for secondary lining under the measured load is higher than that under the criteria load and satisfies the safety requirements. It is therefore possible for the primary lining to sustain the entire surrounding rock pressure with the help of necessary auxiliary method and suitable installation time. The result given in this research enhances our understanding towards the mechanical characteristics of secondary lining for the PDL tunnel and it will be helpful for secondary lining design.link_to_subscribed_fulltex
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