Učinak Butadin-akrilnog umreživača na udarnu čvrstoću poli(metilmetakrilata)

A cross-linking agent, ethylene glycol dimethacrylate, which is added to poly (methyl methacrylate) (VMMA) denture base resins to improve crazing resistance, has little effect on the mechanical properties o f the resultant denture base. A poly functional cross-linking agent, butadiene acrylate (BDA), has been considered to have a greater cross-linking efficiency and thus altering the mechanical properties. The purpose o f this study was to investigate the effect o f BDA on the impact strength o f a PMMA specimens containing 0%, 1%, 4% and 12% BDA o f monomer volume which had been produced by a conventional dental dough-moulded technique as determined. Mean impact strengths were 1.789 KJ/m2 (SD 0.254), 1.720 KJ/m2 (SD 0.273); 1.715 KJ/m2 (SD 0.280) and 1.838 KJ/m2 (SD 0.244), respectively. These differences were not significant (p >0.05) as tested by the analysis o f variance. It was concluded that the cross-linking agent BDA did not affect the impact strength of the PMMA resin specimens.U svrhu povećanja otpornosti poli(metilmetakrilatnih) proteznih smola na lomove i stvaranje napuklina, monomer-kapljevini se tvornički dodaje tvar za umrežavanje, najčešće etilen-glikol-dimetakrilat (EGDMA), koji se u tome smislu nije pokazao učinkovitim. Ovo istraživanje je provedeno s pretpostavkom da bi polifunkcionalna tvar za umrežavanje, kao što je to butadin - akrilat (BDA), mogla imati veći učinak na umrežavanje i poboljšanje mehaničkih svojstava poli(metilmetakrilatnih) smola. Ispitivana je udarna čvrstoća Zwick-postupkom poli(metilmetakrilatnih) pripravaka, podijeljenih u četiri skupine s obzirom na količinu tvari za umreživanje (0%, 1%, 4% i 12%), te dobivenih uobičajenom kivetnom tehnikom oplopolimerizirajućeg postupka. Vrijednosti za udarnu čvrstoću pripravaka po skupinama iznosile su: 0% BDA - 1,789 KJ/m2 (SD 0,254); 1% BDA - 1,720 KJ/m2 (SD 0,273); 4% BDA - 1,715 KJ/m2 (SD 0,280) i 12% BDA - 1,838 KJ/m2 (SD 0,244), a razlike među skupinama nisu se pokazale statistički značajnim (p > 0,05). Zaključeno je da istraživana tvar za umrežavanje (BDA) nije doprinijela poboljšanju udarne čvrstoće poli(metilmetakrilatnih) pripravaka

Surface Modification of an Experimental Silicone Rubber Maxillofacial Material to Improve Wettability

OBJECTIVES: Good wettability of maxillofacial prosthetic materials is important so hat a lubricating layer is formed with supporting tissues thus reducing patient discomfort. The purpose of the study was to surface modify an experimental silicone rubber material in order to improve wettability. METHODS : Samples of experimental silicone rubber were surface modified by first argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes. These were compared with the same silicone rubber which had ethyleneoxy functional surfactants incorporated into the polymer matrix. In all cases contact angles, tear strength and water uptake were measured. RESULTS: Surface modified materials had comparable contact angles to surfactant modified silicone rubber, all being significantly lower than the unmodified material. Surface modified materials however had a significantly higher tear strength and lower water uptake in comparison to surfactant modified materials. CONCLUSION: Argon plasma treatment followed by chemisorption of ethyleneoxy functional silanes proved an effective way of improving the wettability of an experimental silicone rubber maxillofacial prosthetic material without altering bulk properties

Is late-life dependency increasing or not? A comparison of the Cognitive Function and Ageing Studies (CFAS)

Background: Little is known about how the proportions of dependency states have changed between generational cohorts of older people. We aimed to estimate years lived in different dependency states at age 65 years in 1991 and 2011, and new projections of future demand for care. Methods: In this population-based study, we compared two Cognitive Function and Ageing Studies (CFAS I and CFAS II) of older people (aged ≥65 years) who were permanently registered with a general practice in three defined geographical areas (Cambridgeshire, Newcastle, and Nottingham; UK). These studies were done two decades apart (1991 and 2011). General practices provided lists of individuals to be contacted and were asked to exclude those who had died or might die over the next month. Baseline interviews were done in the community and care homes. Participants were stratified by age, and interviews occurred only after written informed consent was obtained. Information collected included basic sociodemographics, cognitive status, urinary incontinence, and self-reported ability to do activities of daily living. CFAS I was assigned as the 1991 cohort and CFAS II as the 2011 cohort, and both studies provided prevalence estimates of dependency in four states: high dependency (24-h care), medium dependency (daily care), low dependency (less than daily), and independent. Years in each dependency state were calculated by Sullivan's method. To project future demands for social care, the proportions in each dependency state (by age group and sex) were applied to the 2014 England population projections. Findings: Between 1991 and 2011, there were significant increases in years lived from age 65 years with low dependency (1·7 years [95% CI 1·0-2·4] for men and 2·4 years [1·8-3·1] for women) and increases with high dependency (0·9 years [0·2-1·7] for men and 1·3 years [0·5-2·1] for women). The majority of men's extra years of life were spent independent (36·3%) or with low dependency (36·3%) whereas for women the majority were spent with low dependency (58·0%), and only 4·8% were independent. There were substantial reductions in the proportions with medium and high dependency who lived in care homes, although, if these dependency and care home proportions remain constant in the future, further population ageing will require an extra 71 215 care home places by 2025. Interpretation: On average older men now spend 2·4 years and women 3·0 years with substantial care needs, and most will live in the community. These findings have considerable implications for families of older people who provide the majority of unpaid care, but the findings also provide valuable new information for governments and care providers planning the resources and funding required for the care of their future ageing populations. Funding: Medical Research Council (G9901400) and (G06010220), with support from the National Institute for Health Research Comprehensive Local research networks in West Anglia and Trent, UK, and Neurodegenerative Disease Research Network in Newcastle, UK

Functional P2X7 receptors in the auditory nerve of hearing rodents localize exclusively to peripheral glia

P2X7 receptors (P2X7Rs) are associated with numerous pathophysiological mechanisms, and this promotes them as therapeutic targets for certain neurodegenerative conditions. However, the identity of P2X7R-expressing cells in the nervous system remains contentious. Here we examined P2X7R functionality in auditory nerve cells from rodents of either sex, and determined their functional and anatomical expression pattern. In whole-cell recordings from rat spiral ganglion cultures, the purinergic agonist 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP) activated desensitizing currents in spiral ganglion neurons (SGNs), but non-desensitizing currents in glia that were blocked by P2X7R-specific antagonists. In imaging experiments, BzATP gated sustained Ca2+ entry into glial cells. BzATP-gated uptake of the fluorescent dye YO-PRO-1 was reduced and slowed by P2X7R-specific antagonists. In rats, P2X7Rs were immuno-localized predominantly within satellite glial cells (SGCs) and Schwann cells (SCs). P2X7R expression was not detected in the portion of the auditory nerve within the central nervous system. Mouse models allowed further exploration of the distribution of cochlear P2X7Rs. In GENSAT reporter mice, EGFP expression driven via the P2rx7 promoter was evident in SGCs and SCs but was undetectable in SGNs. A second transgenic model showed a comparable cellular distribution of EGFP-tagged P2X7Rs. In wild-type mice the discrete glial expression was confirmed using a P2X7-specific nanobody construct. Our study shows that P2X7Rs are expressed by peripheral glial cells, rather than by afferent neurons. Description of functional signatures and cellular distributions of these enigmatic proteins in the peripheral nervous system will help our understanding of ATP-dependent effects contributing to hearing loss and other sensory neuropathies.Significance statementP2X7 receptors have been the subject of much scrutiny in recent years. They have been promoted as therapeutic targets in a number of diseases of the nervous system, yet the specific cellular location of these receptors remains the subject of intense debate. In the auditory nerve, connecting the inner ear to the brainstem, we show these multi-modal ATP-gated channels localize exclusively to peripheral glial cells rather than the sensory neurons, and are not evident in central glia. Physiological responses in the peripheral glia display classical hallmarks of P2X7 receptor activation, including the formation of ion-permeable and also macromolecule-permeable pores. These qualities suggest these proteins could contribute to glial-mediated inflammatory processes in the auditory periphery under pathological disease states

Is late-life dependency increasing or not? A comparison of the Cognitive Function and Ageing Studies (CFAS)

Background: Little is known about how dependency levels have changed between generational cohorts of older people. We estimated years lived in different care states at age 65 in 1991 and 2011 and new projections of future demand for care. Methods: Two population-based studies of older people in defined geographical areas conducted two decades apart (the Cognitive Function and Ageing Studies) provided prevalence estimates of dependency in four states: high (24-hour care); medium (daily care); low (less than daily); independent. Years in each dependency state were calculated by Sullivan’s method. To project future demand, the proportions in each dependency state (by age group and sex) were applied to the 2014 England population projections. Findings: Between 1991 and 2011 there were significant increases in years lived from age 65 with low (men:1·7 years, 95%CI 1·0-2·4; women:2·4 years, 95%CI 1·8-3·1) and high dependency (men:0·9 years, 95%CI 0·2-1·7; women:1·3 years, 95%CI 0·5-2·1). The majority of men’s extra years of life were independent (36%) or with low dependency (36%) whilst for women the majority were spent with low dependency (58%), only 5% being independent. There were substantial reductions in the proportions with medium and high dependency who lived in care homes, although, if these dependency and care home proportions remain constant in the future, further population ageing will require an extra 71,000 care home places by 2025. Interpretation: On average older men now spend 2.4 years and women 3.0 years with substantial care needs (medium or high dependency), and most will live in the community. These findings have considerable implications for older people’s families who provide the majority of unpaid care, but the findings also supply valuable new information for governments and care providers planning the resources and funding required for the care of their future ageing populations

Gamma-ray bursts and terrestrial planetary atmospheres

We describe results of modeling the effects on Earth-like planets of long-duration gamma-ray bursts (GRBs) within a few kiloparsecs. A primary effect is generation of nitrogen oxide compounds which deplete ozone. Ozone depletion leads to an increase in solar UVB radiation at the surface, enhancing DNA damage, particularly in marine microorganisms such as phytoplankton. In addition, we expect increased atmospheric opacity due to buildup of nitrogen dioxide produced by the burst and enhanced precipitation of nitric acid. We review here previous work on this subject and discuss recent developments, including further discussion of our estimates of the rates of impacting GRBs and the possible role of short-duration bursts.Comment: 12 pages including 5 figures (4 in color). Added discussion of GRB rates and biological effects. Accepted for publication in New Journal of Physics, for special issue "Focus on Gamma-Ray Bursts

The Uneven Reach of Decentralization: A Case Study among Indigenous Peoples in the Bolivian Amazon

Decentralization reforms aim at strengthening democracy by promoting political participation among citizens. Research shows (1) that information is a prerequisite for political participation and (2) that people face different private costs in acquiring information. Here we combine the two lines of research and ask: what private costs hamper the acquisition of information on decentralization? For the analysis, we use data from an indigenous population of lowland Bolivia. We surveyed 319 Tsimane’ adults in 12 villages. We found that nine years after the passage of the decentralization laws, knowledge about those reforms had only partially reached the Tsimane’. People who live closer to municipal towns, had more schooling, and participated in the market economy were more aware of decentralization. Political authorities trying to spread the potential benefits of decentralization should address the structural limitations of the dissemination of political knowledge

What are the current and projected future cost and health-related quality of life implications of scaling up cognitive stimulation therapy?

Objectives: Cognitive stimulation therapy (CST) is one of the few non-pharmacological interventions for people living with dementia shown to be effective and cost-effective. What are the current and future cost and health-related quality of life implications of scaling-up CST to eligible new cases of dementia in England? // Methods/design: Data from trials were combined with microsimulation and macrosimulation modelling to project future prevalence, needs and costs. Health and social costs, unpaid care costs and quality-adjusted life years (QALYs) were compared with and without scaling-up of CST and follow-on maintenance CST (MCST). // Results: Scaling-up group CST requires year-on-year increases in expenditure (mainly on staff), but these would be partially offset by reductions in health and care costs. Unpaid care costs would increase. Scaling-up MCST would also require additional expenditure, but without generating savings elsewhere. There would be improvements in general cognitive functioning and health-related quality of life, summarised in terms of QALY gains. Cost per QALY for CST alone would increase from £12,596 in 2015 to £19,573 by 2040, which is below the threshold for cost-effectiveness used by the National Institute for Health and Care Excellence (NICE). Cost per QALY for CST and MCST combined would grow from £19,883 in 2015 to £30,906 by 2040, making it less likely to be recommended by NICE on cost-effectiveness grounds. // Conclusions: Scaling-up CST England for people with incident dementia can improve lives in an affordable, cost-effective manner. Adding MCST also improves health-related quality of life, but the economic evidence is less compelling