A study of serum-ionized calcium in neonates with unconjugated hyperbilirubinemia on phototherapy

Objectives: The objective is to study the occurrence of phototherapy-induced hypocalcemia in neonates with unconjugated hyperbilirubinemia and to compare the occurrence between pre-term and full-term neonates. Materials and Methods: The study was conducted in the Neonatology Unit of Department of Pediatrics, at a tertiary care teaching hospital for 12 months. A total of 230 full-term and pre-term neonates with jaundice were recruited. Of 230 neonates, 150 were given phototherapy (cases), while 80 did not receive phototherapy and were used as control. Serum-ionized calcium levels were measured at initiation, after 24 h and after 48 h, or at the end of phototherapy in the case duration of phototherapy was <48 h. Serum-ionized calcium was repeated at 24 h after the completion of phototherapy. In the control group, ionized calcium levels were measured at the time of development of jaundice and 24 h after the initial measurement. Results: Of 150 cases who received phototherapy, 105 were term and 45 were preterm. 69 babies (46%) developed hypocalcemia after 24 h of phototherapy. Of these, 28 (40.5%) were preterm and 41 were term (59.5%). 4 patients developed symptoms, which included jitteriness and seizures. 62.2% of the total pre-term and 39% of term neonates developed hypocalcemia after phototherapy. Conclusion: This study suggests that neonates exposed to phototherapy are at the risk of developing hypocalcemia. There is a significant decline in the ionized calcium levels after exposure to phototherapy, and this level can even fall to hypocalcemic levels. As the duration of phototherapy increases, the serum levels of calcium may decline further. The risk of developing hypocalcemia is higher in pre-term neonates

The influence of lubrication on two body abrasive wear of sealing elastomers

Elastomeric seals are prone to failure caused by abrasion during sliding against rough surfaces. In this research, the two body abrasive wear of sealing elastomers in dry and lubricated conditions has been studied. A two body abrasive wear tester has been used to investigate the abrasive wear of the elastomers under varying test parameters. This test aparatus reciprocates a rectangular elastomeric sample against an abrasive paper wrapped around the circumferential surface of a wheel. The samples were weighed using an accurate scale before and after the tests to quantify the abrasive wear. The experiments have been carried out at varying normal load and abrasive size in dry and lubricated conditions. The influence of two different lubricants, including a synthetic ester and a mineral oil, together with the test parameters on the abrasive wear has been studied. The results show that, depending on the material, lubricant, abrasive size, normal load and test duration, the abrasive wear of elastomers may increase or decrease in the presence of lubricants, however, in most cases, the abrasive wear in the lubricated condition is higher than that in the dry condition. The influence of lubricant on the increase in abrasive wear is more significant when a fine abrasive is used. Increase in the abrasive wear in presence of the synthetic ester is more pronounced than in presence of the mineral oil.Godkänd; 2008; 20080615 (brap

Friction and wear of some selected polymeric materials for conformal tribopairs under boundary lubrication conditions

Godkänd; 2012; 20121010 (brap

Frictional behaviour of some sealing elastomers in lubricated sliding

Frictional behaviour of four sealing elastomers, including an acrylonitrile butadienerubber (NBR), a hydrogenated acrylonitrile butadiene rubber (HNBR), an acrylate rubber(ACM) and a fluoroelastomer (FKM), sliding against a steel surface under unidirectionallubricated conditions have been studied. The lubricant used in this study was paraffinic oilwith no additive and the experiments were conducted under a block-on-ring testconfiguration. The friction coefficients of the elastomers have been measured at differentsliding velocities in boundary and fluid film lubrication regimes. In the first part of each test,the sliding velocity varied from low to high values and then, in the second part, the slidingvelocity varied from high to low values repeating the same conditions in reverse order. Theresults show that the friction coefficients at low speeds are different for the two parts whichcan be due to the oil absorption or possibly dissolution of some elastomer constituents in theoil. The NBR and the ACM were the least and the most affected elastomer by the lubricantrespectively. The friction coefficients of NBR and ACM at low speeds decreased in thesecond part of the tests (in which the interaction of oil and elastomer was for longerdurations) but the friction coefficient of HNBR and FKM increased in the second part of thetests.Godkänd; 2012; 20120830 (andbra

Influence of surface modification technologies on friction of conformal tribopair in boundary and full film lubrication regimes

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, temperature etc. The overall frictional losses in machines are thus dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a conformal tribopair both in boundary and full film lubrication regimes. The conformal pair chosen is a hydrodynamic bearing with some hydrostatic lift.A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range so as to enable studies in all lubrication regimes i.e., in boundary, mixed and full-film lubrication.The influence of application of different surface modification technologies on friction has been studied. In all, rollers with five coatings (four hard DLC coatings and one self-lubricating coating) and two rollers without coating having different surface finish. Friction measurements were made on the new as well as the previously run-in components. The different coatings exhibit different levels of boundary friction, with the self-lubricating coating having lowest boundary friction, closely followed by those with hard DLC coatings. The softer amongst the hard DLC coatings showed similar boundary friction compared to that with uncoated rollers. The lift-off speed, i.e., the transition between full-film to mixed and boundary lubrication mainly governed by the surface topography characteristics. A smooth surface finish can be achieved either by polishing before the test or by effective running in of the new surface. The effectiveness of running-in of surfaces was influenced by the surface roughness and hardness of the interacting surfaces.Godkänd; 2010; Bibliografisk uppgift: CD-ROM; 20100628 (ysko

The influence of lubrication on two body abrasive wear of sealing elastomers

Elastomeric seals are prone to failure caused by abrasion during sliding against rough surfaces. In this research, the two body abrasive wear of sealing elastomers in dry and lubricated conditions has been studied. A two body abrasive wear tester has been used to investigate the abrasive wear of the elastomers under varying test parameters. This test aparatus reciprocates a rectangular elastomeric sample against an abrasive paper wrapped around the circumferential surface of a wheel. The samples were weighed using an accurate scale before and after the tests to quantify the abrasive wear. The experiments have been carried out at varying normal load and abrasive size in dry and lubricated conditions. The influence of two different lubricants, including a synthetic ester and a mineral oil, together with the test parameters on the abrasive wear has been studied. The results show that, depending on the material, lubricant, abrasive size, normal load and test duration, the abrasive wear of elastomers may increase or decrease in the presence of lubricants, however, in most cases, the abrasive wear in the lubricated condition is higher than that in the dry condition. The influence of lubricant on the increase in abrasive wear is more significant when a fine abrasive is used. Increase in the abrasive wear in presence of the synthetic ester is more pronounced than in presence of the mineral oil.Godkänd; 2008; 20080615 (brap

Tribological performance evaluation of cold pilgering lubricants

Godkänd; 2010; 20100920 (jenhar

Tribological performance evaluation of cold pilgering lubricants

Godkänd; 2010; 20100920 (jenhar

Influence of surface modification technologies on friction of conformal tribopair in boundary and full film lubrication regimes

Moving machine assemblies are generally designed to operate in full film lubrication regime to ensure high efficiency and durability of components. However, it is not always possible to ensure this owing to changes in operating conditions such as load, speed, temperature etc. The overall frictional losses in machines are thus dependent on the operating lubrication regimes (boundary, mixed or full-film). The present work is thus aimed at investigating the role of different surface modification technologies on friction of a conformal tribopair both in boundary and full film lubrication regimes. The conformal pair chosen is a hydrodynamic bearing with some hydrostatic lift.A special test rig comprising of two bearings was built for the experimental studies. Tribological tests were conducted in a wide speed range so as to enable studies in all lubrication regimes i.e., in boundary, mixed and full-film lubrication.The influence of application of different surface modification technologies on friction has been studied. In all, rollers with five coatings (four hard DLC coatings and one self-lubricating coating) and two rollers without coating having different surface finish. Friction measurements were made on the new as well as the previously run-in components. The different coatings exhibit different levels of boundary friction, with the self-lubricating coating having lowest boundary friction, closely followed by those with hard DLC coatings. The softer amongst the hard DLC coatings showed similar boundary friction compared to that with uncoated rollers. The lift-off speed, i.e., the transition between full-film to mixed and boundary lubrication mainly governed by the surface topography characteristics. A smooth surface finish can be achieved either by polishing before the test or by effective running in of the new surface. The effectiveness of running-in of surfaces was influenced by the surface roughness and hardness of the interacting surfaces.Godkänd; 2010; Bibliografisk uppgift: CD-ROM; 20100628 (ysko

Contact pressure dependency in frictional behaviour of burnished molybdenum disulphide coatings

The drop of coefficient of friction of MoS2 coatings with increase in contact pressure has been reported by various earlier researchers. Different hypothesis have been put forward to explain this phenomenon. This paper covers details of experiments carried out to investigate this further. Experiments have been carried out on reciprocating sliding wear and friction machine to bring out the influence of different parameters on the tribological behavior of MoS2 films. Role of frictional heating in this behavior has also been brought out. It is concluded that frictional properties of MoS2 are dependent on prevalent humidity as well as contact pressure and the drop of μ with contact pressure is independent of frictional heating.Upprättat; 2000; 20071119 (brap)</p