Effect of debris size on the tribological performance of thermally sprayed coatings

This research aims to assess the effect of the debris particle size on the tribological performance and lubrication regime parameters of a Ni-based alloy coating. This is a key industrial problem, and its resolution can contribute to better machine endurance and proper maintenance. The debris particles are simulated by hard Al2O3 particles of size ranging from nanometers to 45 μm and dispersed in an oil lubricant. The coating studied is NiCrBSi deposited by flame spraying technique followed by the Surface Flame Melting (SFM) process. The counterpart disk sample was fabricated from quenched and tempered F-5220 steel (in line with A681(O1) ASTM). This pair was tested under linear sliding contact. Our results show that the addition of alumina particles contributes to a significant increase in wear, particularly for the largest particles (micrometric size). In the case of micrometric particles, it is possible to observe the formation of higher surface roughness, numerous microgrooves, and plastic flow of NiCrBSi coating perpendicular to the sliding direction, resulting in higher loss of volume. It was found that the actual surface roughness (obtained as a function of the debris particle size) allows better identification and prediction of the lubrication regime for wear processes instead of the traditional approach that uses the initial surface roughness as a parameter

Diagonally Reinforced Concrete Coupling Beams with Grade 120 (830) High-Strength Steel Bars

Four large-scale coupling beams were tested under fully reversed cyclic loads to investigate the effects on behavior of diagonal bar grade (60 or 120 [420 or 830]), beam shear stress (9.5 or 14√fc′, psi [0.79 or 1.17√fc′, MPa]), and longitudinal bar detailing (either terminated near the beam-wall interface or developed into the walls). Coupling beam chord rotation capacity was 7.1% for the beam with Grade 60 (420) bars and between 5.1 and 5.6% for the beams with Grade 120 (830) bars, a difference likely due to having hoops spaced at 3.4db and 4db for Grade 60 and 120 (420 and 830) bars, where db is the diagonal bar diameter. Effective stiffness, energy dissipation, and residual chord rotations were approximately inversely proportional to bar grade. Developing the secondary longitudinal reinforcement reduced rotation demands at beam ends but did not improve deformation capacity. Beam shear stress did not affect beam chord rotation capacity

Diagonally-Reinforced Concrete Coupling Beams with High-Strength Steel Bars

The use of high-strength steel in diagonally reinforced coupling beams was investigated with the aims of minimizing reinforcement congestion and increasing the maximum permissible design shear stress without compromising behavior under large displacement reversals. Five large-scale diagonally reinforced concrete coupling beam specimens with clear span-to-depth ratios of 1.9 were tested under fully reversed cyclic loads. The primary variables were yield stress of the diagonal reinforcement (60 and 120 ksi [420 and 830 MPa]), target beam shear stress (1.0 and 1.5 times the ACI Building Code limit), length of the secondary (non-diagonal) longitudinal reinforcement, and axial restraint. All specimens had the same nominal concrete compressive strength and beam dimensions. Chord rotation capacities exhibited by the specimens with Grade 120 (830) reinforcement were between 5.1 and 5.6%, less than that of the control specimen with Grade 60 (420) diagonal reinforcement (7.1%). Neither development of secondary reinforcement nor increases in design shear stress affected specimen chord rotation capacity. The axially-restrained specimen with Grade 120 (830) diagonal reinforcement showed the same chord rotation capacity as a similar specimen without axial restraint, but 14% larger strength. In specimens with secondary longitudinal reinforcement extended into the wall (such that the embedment length exceeded the calculated development length), the localization of damage evident along the beam-wall interface in tests of specimens with bars terminating near the wall face was not observed. Although damage was more distributed throughout the beam span, deformation capacity was not increased. Among the specimens, it was shown that the initial stiffness, area of the shear force-chord rotation hysteresis cycles, and residual chord rotation at zero shear force changed in inverse proportion to the diagonal bar yield stress. A database of results from tests of diagonally reinforced coupling beams was compiled and used to evaluate the sensitivity of coupling beam chord rotation capacity to a range of variables. Variables included aspect ratio, reinforcement grade, transverse confinement reinforcement (type, spacing, and ratio), shear stress, and length of secondary (non-diagonal) reinforcement (whether terminated near the beam-wall interface or developed into the wall). An equation was proposed for calculating coupling beam chord rotation capacity as a function of beam clear span-to-height ratio and the ratio of hoop spacing to diagonal bar diameter. Chord rotation capacity was not correlated with other variables. Modifications are also proposed to the stiffness and deformation capacity modeling parameters recommended in ASCE 41-17 and ACI 369.1-17 for diagonally reinforced coupling beams to account for reinforcement grade

Diagonally Reinforced Concrete Coupling Beams: Effects of Axial Restraint

Two pairs of nominally identical large-scale coupling beam specimens were tested under reversed cyclic displacements. Within each pair, one specimen was free to elongate and the other had resistance to elongation during testing. The specimens had clear span-to-overall-depth ratios of 1.9, a nominal concrete compressive strength of 6000 psi (42 MPa), Grade 60 or 120 (420 or 830) diagonal bars, and nominal shear stresses near the ACI Building Code (ACI 318) limit of 10√fc′ psi (0.83√fc′ MPa). Passive axial restraint resulted in beam axial forces and was correlated with higher coupling beam strength, lower chord rotation capacity, earlier diagonal bar buckling, and greater damage. The importance of these effects increased with the magnitude of the induced axial force. The ACI equation for coupling beam nominal strength (based on the area, yield stress, and inclination of diagonal bars) underestimated beam strength by up to 80%, whereas estimates based on flexural strength were substantially more accurate and allowed consideration of axial force effects

Molecular characterisation of benign and malignant thyroid dysfunction

Nodular thyroid disease is common (prevalence 2-6%) and is a significant risk factor for the development of thyroid cancer. My aim was to apply genome-wide- linkage-analysis to identify the defect in a large kindred with multi-nodular goitre (MNG) of adolescent onset progressing to papillary thyroid cancer (PTC). Genomic DNA from 18 individuals (8 affected) was hybridized to Affymetrix GeneChip® Human Mapping 10K 2.0 Arrays. Results were analysed with Affymetrix GTYPE software to produce a call rate of ~92%. Extensive quality control steps were performed (PLINK, GRR) prior to linkage analysis using Merlin software in multipoint non-parametric and parametric (dominant) model. A non-parametric LOD score of 3.01 was obtained on chromosome 20 across 20cM, the same region produced a dominant LOD score of 2.03. Haplotype analysis reduced the region of interest to 3.7 Mbp, (encodes 10 genes). Analysis of copy number variation in an affected individual (Illumina Human 660W-Quad) revealed an intronic deletion of ~1000 bp in one copy of Phospholipase-C β1 (PLCβ1), (the first in the 10 gene list), which is present in all affected family members and carriers. The deletion contained ‘ATAA’ at the junction site and this InDel was found in 1 of 105 healthy unrelated people, a similar variant was reported in the database of genomic variants in ~1% of Europeans . The deletion was not present in 70 unrelated PTC patients but was found in 4/81 with MNG (all European); the deletion frequency in the general population vs. MNG gives a X2 value of 5.076 (p=0.024). PLCβ1 expression was measured in thyroid tissues from affected family members and subjects free of the InDel and were significantly higher in the former (p< 0.02). In conclusion, the InDel identified in familial MNG occurs in a proportion of sporadic MNG. It predisposes to goitre formation, possibly by increasing PLCβ1 transcription and activating the diacyl-glycerol, PKC and MAPK pathways

Plasmid DNA Analysis of Pasteurella multocida Serotype B isolated from Haemorrhagic Septicaemia outbreaks in Malaysia

A total of 150 purified isolates of Pasteurella multocida serotype B were used (Salmah, 2004) for plasmid DNA curing experiment to determine hyaluronidase activity, antibiotic resistance pattern (ARP) and mice lethality test (LD50) for their role of pathogenicity. A plasmid curing experiment was carried out by using the intercalating agent; ethidium bromide and rifampicin, where it was found all the plasmids had been cured (plasmidless) from Pasteurella multocida. All of these plasmidless isolates maintained their phenotypic characteristics. They showed the same antibiotic resistancepattern as before curing, produced hyaluronidase and possessed lethality activity in mice when injected intraperitoneally(i.p). Based on this observation, the antibiotic resistance, hyaluronidase activity and mice virulence could probably be chromosomal-mediated. Plasmids were detected 100% in all P. multocida isolates with identical profile of 2 plasmids size 3.0 and 5.5 kb. No large plasmids could be detected in all isolates. Since all the isolates appeared to have identicalplasmid profiles, they were subjected to restriction enzyme(RE) analysis. From RE analysis results obtained, it can be concluded that the plasmid DNA in serotype B isolates are identical. Only 4 of 32 REs were found to cleave these plasmids with identical restriction fingerprints; BglII, HaeIII, RsaI and SspI. From RE analysis results, it can be concluded that the plasmid DNA isolates are identical. This plasmid might not played any role in pathogenicity of Pasteurella multocida serotype B, however this information is important for the construction of shuttle vectors in genetic studies of the pathogenicity of haemorrhagic septicaemia(HS)

Risk Exposure to Hepatitis B infection among Senior Secondary School Students in a Metropolitan City of North-central Nigeria

Background: Hepatitis B is the most prevalent chronic infectious liver disease worldwide with serious sequelae. Reduction of hepatitis B infection is a national public health priority. Despite international efforts to prevent the infection through global vaccination programs, new cases are still being reported throughout the world.Objectives: This study aims to determine the risk exposure factors for hepatitis B infection among senior secondary school students in Ilorin East Local Government Area of Kwara state, Nigeria.Methods: Multistage sampling technique was used to recruit 424 adolescents into the study. Pretested interviewer administered semi-structured questionnaires were used for the study. Data were analyzed using STATA version 10.1 software. A p-value of less than 0.05 was considered as statistically significant.Results: The major risk exposure factors in the study population were contact with blood or body fluids (33.7%), family history of previous infection of HBV (30.4%) of the respondents; one sexual partner (16.5%), multiple sexual partners (15.3%) and ear or body piercing (14.9%). Majority (78.1%) of the respondents had low risk exposure, while 8.0% had medium risk exposure, only 59 (13.9%) of the respondents had high risk exposure for Hepatitis B virus infection. Significant relationships were found between risk exposure score and school type, gender, family history of the disease mothers’ and fathers’ educational background of the respondents (p&lt;0.05).Conclusion: Risk exposure was low among the respondents. There is a need for a community wide campaign on health risk awareness and perception of HBV. [Ethiop. J. Health Dev. 2016;30(2):96-102]Keywords: Hepatitis B surface antigen (HBsAg), Hepatitis B virus (HBV), Risk Exposur