Influence of Using High Volume Fraction of Silica Fume on Mechanical and Durability Properties of Cement Mortar

The high pollution caused by CO2 emission and the high level of energy consumed during cement manufacturing led the researchers to look for alternative techniques to reduce these environmental effects. One of these techniques includes reducing the content of cement in the mix by replacing it with supplementary cementitious materials such as fly ash, slag, silica fume, and so on. Many previous studies dealt with the utilizing of the high volume of supplementary cementitious materials, such as fly ash and slag. However, limited studies investigated the impact of silica fume on mortar or concrete properties in percentages of more than 30%. Thus, to produce environmentally friendly concrete, this study was performed to investigate the effect of the high replacement level of cement with silica fume on the properties of cement mortar. Six replacement proportions of silica fume (0%, 30%, 40%, 50%, 60% and 70%) were used in this paper. This paper used the flow rate, compressive strength, water absorption, bulk density and volume of permeable voids tests to test the effect of silica fume on different mortar characteristics. The results indicated that the best mixture among all other mixes was found by 50% substitution of silica fume. At this percentage, an enhancement in compressive strength of nearly 83%, 74% and 75% at 7, 28 and 56 days, respectively and an improvement in water absorption resistance by 8% compared to the control mixture were achieved

Mechanical behaviour of biodegradable AZ31 magnesium alloy after long term in vitro degradation

Biodegradable magnesium alloys including AZ31 are exciting candidates for temporary implants as they eliminate the requirement for surgical removal, yet have higher mechanical properties than degradable polymers. However, the very long term mechanical properties and degradation of these alloys have not been fully characterized. The tensile, bending and corrosion behaviour of biodegradable AZ31 Mg alloy specimens have been investigated for up to 9 months in vitro in phosphate buffered saline (PBS). Small AZ31 Mg specimens showed a significant drop in bend yield strength and modulus after 3 months in vitro degradation and an average mass loss of 6.1%. Larger dumbbell specimens showed significant drops in tensile strength from 251.96 ± 3.53 MPa to 73.5 ± 20.2 MPa and to 6.43 ± 0.9 MPa and in modulus from 47.8 ± 5.6GPa to 25.01 ± 3.4GPa and 2.36 ± 0.89GPa after 3 and 9 months respectively. These reductions were accompanied by an average mass loss of 18.3% in 9 months. Degradation rate for the small and large specimens followed similar profiles with immersion time, with peak degradation rates of 0.1747 g m− 2 h−1 and 0.0881 g m− 2 h−1, and average rates of 0.1038 g m− 2 h−1 and 0.0397 g m− 2 h−1 respectively. SEM fractography and polished specimen cross-sections revealed corrosion pits, cracks and corrosion induced defects. These data indicate the potential of AZ31 Mg for use in implants that require medium term degradation with load bearing mechanical properties

Topical use of MMC in the upper aerodigestive tract: a review on the side effects

Not much is known about the side effects of mitomycin C (MMC), an anti-fibrogenetic agent, in the upper aerodigestive tract. However, its use in ophthalmology is widely known and without quantitatively important side effects. A literature review was performed for side effects of MMC in the upper aerodigestive tract. Forty-six articles, describing the use of MMC to prevent scarring, were retracted from PubMed. Thirty-two are human studies. MMC is used in different concentrations (0.1–10 mg/ml) with different application times (2–5 min) and frequencies (up to 4 times). Five hundred and thirty-eight patients were included in those publications, of whom 19 developed side effects (3.53%). No side effects developed in studies, where post-application irrigation with saline was reported. The longest mean follow-up period is 75.5 months. Direct relations between the reported side effects and MMC seem absent in most studies. Serious complications seem to occur when MMC is used in high concentrations. Unfortunately, sometimes crucial information is lacking. One patient was described who supposedly developed laryngeal carcinoma after repeated treatment of hyperkeratosis and anterior commissure webbing. Animal studies show that excessive fibrin production can lead to acute airway obstruction. In conclusion, topical application of MMC on a wound with consecutive irrigation with saline can be performed safely to prevent scar formation in circular structures of the upper aerodigestive tract. Long-term yearly control of the application site seems advisable

Evaluation of 15 Functional Candidate Genes for Association with Chronic Otitis Media with Effusion and/or Recurrent Otitis Media (COME/ROM)

DNA sequence variants in genes involved in the innate immune response and secondary response to infection may confer susceptibility to chronic otitis media with effusion and/or recurrent otitis media (COME/ROM). We evaluated single nucleotide polymorphisms (SNPs) in 15 functional candidate genes. A total of 99 SNPs were successfully genotyped on the Sequenom platform in 142 families (618 subjects) from the Minnesota COME/ROM Family Study. Data were analyzed for association with COME/ROM using the Generalized Disequilibrium Test (GDT). Sex and age at exam were adjusted as covariates, relatedness was accounted for, and genotype differences from all phenotypically discordant relative pairs were utilized to measure the evidence of association between COME/ROM and each SNP. SNP rs2735733 in the region of the mucin 5, subtypes A/C gene (MUC5AC) exhibited nominal evidence for association with COME/ROM (P = 0.002). Two additional SNPs from this region had P values<0.05. Other variants exhibiting associations with COME/ROM at P<0.05 included the SCN1B SNP rs8100085 (P = 0.013), SFTPD SNP rs1051246 (P = 0.039) and TLR4 SNP rs2770146 (P = 0.038). However, none of these associations replicated in an independent sample of COME/ROM families. The candidate gene variants examined do not appear to make a major contribution to COME/ROM susceptibility, despite a priori evidence from functional or animal model studies for a role in COME/ROM pathology

A methodology to estimate the potential to move inpatient to one day surgery

BACKGROUND: The proportion of surgery performed as a day case varies greatly between countries. Low rates suggest a large growth potential in many countries. Measuring the potential development of one day surgery should be grounded on a comprehensive list of eligible procedures, based on a priori criteria, independent of local practices. We propose an algorithmic method, using only routinely available hospital data to identify surgical hospitalizations that could have been performed as one day treatment. METHODS: Moving inpatient surgery to one day surgery was considered feasible if at least one surgical intervention was eligible for one day surgery and if none of the following criteria were present: intervention or affection requiring an inpatient stay, patient transferred or died, and length of stay greater than four days. The eligibility of a procedure to be treated as a day case was mainly established on three a priori criteria: surgical access (endoscopic or not), the invasiveness of the procedure and the size of the operated organ. Few overrides of these criteria occurred when procedures were associated with risk of immediate complications, slow physiological recovery or pain treatment requiring hospital infrastructure. The algorithm was applied to a random sample of one million inpatient US stays and more than 600 thousand Swiss inpatient stays, in the year 2002. RESULTS: The validity of our method was demonstrated by the few discrepancies between the a priori criteria based list of eligible procedures, and a state list used for reimbursement purposes, the low proportion of hospitalizations eligible for one day care found in the US sample (4.9 versus 19.4% in the Swiss sample), and the distribution of the elective procedures found eligible in Swiss hospitals, well supported by the literature. There were large variations of the proportion of candidates for one day surgery among elective surgical hospitalizations between Swiss hospitals (3 to 45.3%). CONCLUSION: The proposed approach allows the monitoring of the proportion of inpatient stay candidates for one day surgery. It could be used for infrastructure planning, resources negotiation and the surveillance of appropriate resource utilization

A retrospective case series of 318 tracheostomy-related adverse events over 6 years – a Scottish context

No abstract available