Effect of Tapered Interference Fit between Impeller and Shaft in Turbo Machines

In Turbo machines, there are many components which are provided with interference to transmit torque and to maintain contact between them. There are transient scenarios where impeller and shaft lose interference and limits the speed of the impeller. In this paper, a case study on centrifugal compressor has been presented to see the effect of taper pairing of shaft with impeller. When the centrifugal compressor starts then a transient condition is dominant wherein the impeller of the centrifugal compressor gains higher temperature quickly compared to shaft. Since the thermal expansion of the impeller will be much more than the shaft, interference between impeller and shaft is likely to reduce. With reduced interference, the impeller should retain minimum required contact pressure with the shaft and the torque transmitting capability. For conventional fitted impeller, stress built up is a major concern especially at higher speeds. This paper gives a proposal about the importance of tapered interference fit method compared to cylindrical fitted impeller assembly. An effective analysis between the conventional straight fitted impeller and impeller having tapered bore is presented for the same torque transfer capability. The analysis reveals that for the impeller with tapered bore, the stress for impeller reduces and a healthy contact pressure exists.

Presence of Acanthamoeba in the ocular surface in a Spanish population of contact lens wearers

Pathogenic strains of Acanthamoeba are causative agents of a sight-threatening infection of the cornea known as Acanthamoeba keratitis (AK) which mainly affects contact lens wearers and it is commonly related to poor hygiene of contact lenses and their cases. Moreover, treatment of AK is complex due to the existence of a highly resistant cyst stage and if not diagnosed early has poor prognosis, leading to blindness and/or keratoplasty. Even though AK is increasing worldwide as well as awareness among patients and clinicians, it is still a poorly studied pathogen. Additionally, a remaining question to be answered is whether these opportunistic pathogens are present in the ocular surface of healthy contact lens wearers since they are the main group at risk.In order to carry out this study, sterile Schirmer strip tests were collected from a group of individuals all of them contact lens wearers who were attending a local ophthalmology clinic in Tenerife, Canary Islands, Spain. The collected samples (100 eyes of 50 patients) were cultured in 2% Non-Nutrient Agar (NNA) plates and positive plates (16) were then cultured in axenic conditions for further analyses. Molecular analysis classified all isolated strains belonged to Acanthamoeba genotype T4 and osmotolerance and thermotolerance assays revealed that all strains were potentially pathogenic. In conclusion, the ocular surface of contact lens wearers included in this study was colonized by potentially pathogenic strains of Acanthamoeba and should be considered as a risk for AK infection in this region and worldwide.

Molecular Characterization of Enteroviruses Isolated from Acute Flaccid Paralysis Cases in Poland, 1999–2014

Enteroviruses (EVs) are among viral pathogens that can cause acute flaccid paralysis (AFP). This study represents an overview of EVs isolated through AFP surveillance in Poland between 1999 and 2014. The presence of enteroviruses was studied in stool samples that were collected from 747 AFP cases and their asymptomatic contacts. Fifty five (6.12%) cases of AFP were associated with enterovirus isolation. Out of the 55 positive cases, 40 were associated with detection of enterovirus in patient, and 15 with detection of EV in healthy contact, without positive detection in paralytic patient. Polioviruses were isolated from 35 AFP cases. The results of this study showed that about 43.6% of positive AFP cases were found in association with the isolation of non-polio enteroviruses (NPEV). A total of 12 different types of the species B were detected (CVA9, CVB1, CVB3, CVB4, CVB5, E3, E4, E9, E11, E13, E30), and one additional isolate represented the species enterovirus A (EV71). Among the 12 serotypes of species B, CVB3 and CVB5 were more frequently detected than others, representing 40% of the characterized isolates, followed by CVB4 (16%), E4 (8%), and E11(8%). Phylogenetic analysis revealed that strains from Poland had the closest genetic relationship with isolates previously identified in Europe (France, Finland, Denmark, Moldova) but also in other parts of the world (Tunisia, China, USA), suggesting wide distribution of these lineages. The paper provides information about NPEV circulation in Poland in the past 16 years, about its association with the AFP and it indicates the need for monitoring NPEV circulation even after the eradication of poliomyelitis.

The secretory immunoglobulin A response to Mycobacterium tuberculosis in a childhood population

We report on the measurement of saliva anti-Purified Protein Derivative sIgA and 38kDa antibodies from 127 children, of whom 31 were strong tuberculosis suspects and 96 were healthy contact children. The results concerning the percentage of children with antibody reactivity to PPD and 38kDa antigens showed that, of these 2 antigens, 38kDa induced higher reactivity in patients positive and negative for the Tuberculin Skin Test (28% and 16.6%, respectively) in comparison to controls positive and negative for the TST (11.7% and 7.1%, respectively). There was a statistically significant difference between patients positive and controls negative for the TST. In relation to the Purified Protein Derivative antigen, while 14.2% of patients positive for the TST showed antibody reactivity to the PPD antigen, no patients negative for the TST had reactivity to this antigen. The findings suggest that these two antigens seem be associated with a different development of the mucosal defence mechanisms mediated by sIgA against Mycobacterium tuberculosis.

Circulation of Type 1 Vaccine-Derived Poliovirus in the Philippines in 2001

ABSTRACT In 2001, highly evolved type 1 circulating vaccine-derived poliovirus (cVDPV) was isolated from three acute flaccid paralysis patients and one contact from three separate communities in the Philippines. Complete genomic sequencing of these four cVDPV isolates revealed that the capsid region was derived from the Sabin 1 vaccine strain but most of the noncapsid region was derived from an unidentified enterovirus unrelated to the oral poliovirus vaccine (OPV) strains. The sequences of the cVDPV isolates were closely related to each other, and the isolates had a common recombination site. Most of the genetic and biological properties of the cVDPV isolates were indistinguishable from those of wild polioviruses. However, the most recently identified cVDPV isolate from a healthy contact retained the temperature sensitivity and partial attenuation phenotypes. The sequence relationships among the isolates and Sabin 1 suggested that cVDPV originated from an OPV dose given in 1998 to 1999 and that cVDPV circulated along a narrow chain of transmission. Type 1 cVDPV was last detected in the Philippines in September 2001, and population immunity to polio was raised by extensive OPV campaigns in late 2001 and early 2002.