A state-of-the-art review of curve squeal noise: Phenomena, mechanisms, modelling and mitigation

[EN] Curve squeal is an intense tonal noise occurring when a rail vehicle negotiates a sharp curve. The phenomenon can be considered to be chaotic, with a widely differing likelihood of occurrence on different days or even times of day. The term curve squeal may include several different phenomena with a wide range of dominant frequencies and potentially different excitation mechanisms. This review addresses the different squeal phenomena and the approaches used to model squeal noise; both time-domain and frequency-domain approaches are discussed and compared. Supporting measurements using test rigs and field tests are also summarised. A particular aspect that is addressed is the excitation mechanism. Two mechanisms have mainly been considered in previous publications. In many early papers the squeal was supposed to be generated by the so-called falling friction characteristic in which the friction coefficient reduces with increasing sliding velocity. More recently the mode coupling mechanism has been raised as an alternative. These two mechanisms are explained and compared and the evidence for each is discussed. Finally, a short review is given of mitigation measures and some suggestions are offered for why these are not always successful.Squicciarini, G.; Thompson, D.; Ding, B.; Baeza González, LM. (2018). A state-of-the-art review of curve squeal noise: Phenomena, mechanisms, modelling and mitigation. Notes on Numerical Fluid Mechanics and Multidisciplinary Design. 139:3-41. https://doi.org/10.1007/978-3-319-73411-8_1S341139Anderson, D., Wheatley, N., Fogarty, B., Jiang, J., Howie, A., Potter, W.: Mitigation of curve squeal noise in Queensland, New South Wales and South Australia. In: Conference on Railway Engineering. pp. 625–636, Perth, Australia (2008)Hanson, D., Jiang, J., Dowdell, B., Dwight, R.: Curve squeal: causes, treatments and results. In INTER-NOISE and NOISE-CON Congress and Conference Proceedings, vol. 249, pp. 6316–6323. Melbourne, Australia (2014)Rudd, M.J.: Wheel/rail noise—part II: wheel squeal. J. Sound Vib. 46(3), 381–394 (1976)Remington, P.J.: Wheel/rail squeal and impact noise: what do we know? What don’t we know? Where do we go from here? J. Sound Vib. 116(2), 339–353 (1987)Remington, P.J.: Wheel/rail rolling noise: what do we know? What don’t we know? Where do we go from here? J. Sound Vib. 120(2), 203–226 (1988)Wickens, A.H.: Fundamentals of Rail Vehicle Dynamics, Guidance and Stability. Swets & Zeitlinger, Lisse (2003)Thompson, D.J.: Railway Noise and Vibration: Mechanisms, Modelling and Mitigation. Elsevier, Oxford (2009)Kalker, J.J.: Three Dimensional Elastic Bodies in Rolling Contact. Kluwer academic publishers, Dordrecht (1990)Vermeulen, P.J., Johnson, K.L.: Contact of nonspherical elastic bodies transmitting tangential forces. J. Appl. Mech. 31(2), 338–340 (1964)Shen, Z.Y., Hedrick, J.K., Elkins, J.A.: A comparison of alternative creep-force models for rail vehicle dynamic analysis. In: Proceedings of 8th IAVSD Symposium, Cambridge MA, Swets and Zeitlinger, Lisse, pp. 591–605 (1983)Huang, Z.Y.: Theoretical Modelling of Railway Curve Squeal. Ph.D. thesis, University of Southampton, UK (2007)Hoffmann, N., Fischer, M., Allgaier, R., Gaul, L.: A minimal model for studying properties of the mode-coupling type instability in friction induced oscillations. Mech. Res. Commun. 29(4), 197–205 (2002)Hoffmann, N., Gaul, L.: Effects of damping on mode-coupling instability in friction induced oscillations. J. Appl. Math. Mech. 83(8), 524–534 (2003)Sinou, J.J., Jezequel, L.: Mode coupling instability in friction-induced vibrations and its dependency on system parameters including damping. Eur. J. Mech.-A/Solids 26(1), 106–122 (2007)Johnson, K.L.: Contact Mechanics. Cambridge University Press, Cambridge (1985)Kinkaid, N.M., O’Reilly, O.M., Papadopoulos, P.: Automotive disc brake squeal. J. Sound Vib. 267(1), 105–166 (2003)Ghazaly, N.M., El-Sharkawy, M., Ahmed, I.: A review of automotive brake squeal mechanisms. J. Mech. Des. Vibr. 1(1), 5–9 (2013)Ouyang, H., Nack, W., Yuan, Y., Chen, F.: Numerical analysis of automotive disc brake squeal: a review. Int. J. Veh. Noise Vib. 1(3–4), 207–231 (2005)Dorf, R.C., Bishop, R.H.: Modern Control Systems, 11th edn. Prentice Hall. (2008)De Beer, F.G., Janssens, M.H.A., Kooijman, P.P., van Vliet, W.J.: Curve squeal of railbound vehicles (part 1): frequency domain calculation model. In: Proceedings of Internoise, vol. 3, pp. 1560–1563. Nice, France (2000)Von Stappenbeck, H.: Das Kurvengeräusch der Straßenbahn. Möglichkeiten zu seiner Unterdrückung. Z. VDI 96(6), 171–175 (1954)Van Ruiten, C.J.M.: Mechanism of squeal noise generated by trams. J. Sound Vib. 120(2), 245–253 (1988)Nakai, M., Chiba, Y., Yokoi, M.: Railway wheel squeal: 1st report, on frequency of squeal. Bull. Jpn. Soc. Mech. Eng. 25, 1127–1134 (1982)Nakai, M., Chiba, Y., Yokoi, M.: Railway wheel squeal: 2nd report, mechanism of specific squeal frequency. Bull. Jpn. Soc. Mech. Eng. 27, 301–308 (1984)Nakai, M., Chiba, Y., Yokoi, M.: Railway wheel squeal: 3rd report, squeal of a disk simulating a wheel in internal resonances. Bull. Jpn. Soc. Mech. Eng. 28, 500–507 (1985)Schneider, E., Popp, K., Irretier, H.: Noise generation in railway wheels due to rail-wheel contact forces. J. Sound Vib. 120(2), 227–244 (1988)Kraft, K.: Der Einfluß der Fahrgeschwindigkeit auf den Haftwert zwischen Rad und Schiene. Arch. für Eisenbahntechnik 22, 58–78 (1967)Fingberg, U.: A model of wheel-rail squealing noise. J. Sound Vib. 143(3), 365–377 (1990)Périard, F.: Wheel-Rail Noise Generation: Curve Squealing by Trams. Ph.D. thesis, Technische Universiteit Delft (1998)Heckl, M.A., Abrahams, I.D.: Curve squeal of train wheels, part 1: mathematical model for its generation. J. Sound Vib. 229(3), 669–693 (2000)Heckl, M.A.: Curve squeal of train wheels, part 2: which wheel modes are prone to squeal? J. Sound Vib. 229(3), 695–707 (2000)Heckl, M.A.: Curve squeal of train wheels: unstable modes and limit cycles. Proc. R. Soc. Lond. A: Math. Phys. Eng. Sci. 458, 1949–1965 (2002)Liu, X., Meehan, P.A.: Wheel squeal noise: a simplified model to simulate the effect of rolling speed and angle of attack. J. Sound Vib. 338, 184–198 (2015)Meehan, P.A., Liu, X.: Analytical prediction and investigation of wheel squeal amplitude. In: Anderson, D., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 139, pp 69–80. Springer, Heidelberg (2018)Kooijman, P.P., Van Vliet, W.J., Janssens, M.H.A., De Beer, F.G.: Curve squeal of railbound vehicles (part 2): set-up for measurement of creepage dependent friction coefficient. In: Proceedings of Internoise, vol. 3, pp. 1564–1567. Nice, France (2000)De Beer, F.G., Janssens, M.H.A., Kooijman, P.P.: Squeal noise of rail-bound vehicles influenced by lateral contact position. J. Sound Vib. 267(3), 497–507 (2003)Thompson, D.J., Hemsworth, B., Vincent, N.: Experimental validation of the TWINS prediction program for rolling noise, part 1: description of the model and method. J. Sound Vib. 193(1), 123–135 (1996)Monk-Steel, A., Thompson, D.J.: Models for railway curve squeal noise. In: VIII International Conference on Recent Advances in Structural Dynamics, Southampton, UK (2003)Barman, J.F., Katzenelson, J.: A generalized Nyquist-type stability criterion for multivariable feedback systems. Int. J. Control 20(4), 593–622 (1974)Huang, Z.Y., Thompson, D.J., Jones, C.J.C.: Squeal prediction for a bogied vehicle in a curve. In Schulte-Werning, B., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM vol. 99, pp. 313–319. Springer, Heidelberg (2008)Hsu, S.S., Huang, Z., Iwnicki, S.D., Thompson, D.J., Jones, C.J., Xie, G., Allen, P.D.: Experimental and theoretical investigation of railway wheel squeal. Proc. Inst. Mech. Eng. Part F: J. Rail Rapid Transit 221(1), 59–73 (2007)Squicciarini, G., Usberti, S., Thompson, D.J., Corradi, R., Barbera, A.: Curve squeal in the presence of two wheel/rail contact points. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 603–610. Springer, Heidelberg (2015)Xie, G., Allen, P.D., Iwnicki, S.D., Alonso, A., Thompson, D.J., Jones, C.J., Huang, Z.Y.: Introduction of falling friction coefficients into curving calculations for studying curve squeal noise. Veh. Syst. Dyn. 44(sup1), 261–271 (2006)Giménez, J.G., Alonso, A., Gómez, E.: Introduction of a friction coefficient dependent on the slip in the FastSim algorithm. Veh. Syst. Dyn. 43(4), 233–244 (2005)Chiello, O., Ayasse, J.B., Vincent, N., Koch, J.R.: Curve squeal of urban rolling stock—part 3: theoretical model. J. Sound Vib. 293(3), 710–727 (2006)Collette, C.: Importance of the wheel vertical dynamics in the squeal noise mechanism on a scaled test bench. Shock Vibr. 19(2), 145–153 (2012)Brunel, J.F., Dufrénoy, P., Naït, M., Muñoz, J.L., Demilly, F.: Transient models for curve squeal noise. J. Sound Vib. 293(3), 758–765 (2006)Glocker, C., Cataldi-Spinola, E., Leine, R.I.: Curve squealing of trains: measurement, modelling and simulation. J. Sound Vib. 324(1), 365–386 (2009)Pieringer, A.: A numerical investigation of curve squeal in the case of constant wheel/rail friction. J. Sound Vib. 333(18), 4295–4313 (2014)Pieringer, A., Kropp, W.: A time-domain model for coupled vertical and tangential wheel/rail interaction—a contribution to the modelling of curve squeal. In: Maeda, T., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 118, pp. 221–229. Springer, Heidelberg (2012)Pieringer, A., Baeza, L., Kropp. W.: Modelling of railway curve squeal including effects of wheel rotation. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 417–424. Springer, Heidelberg (2015)Zenzerovic, I., Pieringer, A., Kropp. W.: Towards an engineering model for curve squeal. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 433–440. Springer, Heidelberg (2015)Zenzerovic, I., Kropp, W., Pieringer, A.: An engineering time-domain model for curve squeal: tangential point-contact model and Green’s functions approach. J. Sound Vib. 376, 149–165 (2016)Pieringer, A., Torstensson, P.T., Giner, J., Baeza, L.: Investigation of railway curve squeal using a combination of frequency- and time-domain models. In: Anderson, D., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 139, pp 81–93. Springer, Heidelberg (2018)Chen, G.X., Xiao, J.B., Liu, Q.Y., Zhou. Z.R.: Complex eigenvalue analysis of railway curve squeal. In: Schulte-Werning, B., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 99, pp. 433–439. Springer, Heidelberg (2008)Fourie, D.J., Gräbe, P.J., Heyns, P.S., Fröhling, R.D.: Analysis of wheel squeal due to unsteady longitudinal creepage using the complex eigenvalue method. In: Anderson, D., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 139, pp 55–67. Springer, Heidelberg (2018)Wang, C., Dwight, R., Li, W., Jiang, J.: Prediction on curve squeal in the case of constant wheel rail friction coefficient. In: Anderson, D., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 139, pp XXX–XXX. Springer, Heidelberg (2018)Ding, B., Squicciarini, G., Thompson, D.J.: Effects of rail dynamics and friction characteristics on curve squeal. In: XIII International Conference on Motion and Vibration Control and XII International Conference on Recent Advances in Structural Dynamics (MoViC/RASD), Southampton (2016)Bleedorn, T.G., Johnstone. B.: Steerable steel wheel systems and wheel noise suppression. In: Conference Rec IAS 12th Annual Meeting, Los Angeles, California (1977)Koch, J.R., Vincent, N., Chollet, H., Chiello, O.: Curve squeal of urban rolling stock—part 2: parametric study on a 1/4 scale test rig. J. Sound Vib. 293(3), 701–709 (2006)Logston, C.F., Itami, G.S.: Locomotive friction-creep studies. ASME J. Eng. Ind. 102(3), 275–281 (1980)Ertz, M.: Creep force laws for wheel/rail contact with temperature-dependent coefficient of friction. In: 8th Mini Conference on Vehicle System Dynamics, Identification and Anomalies, Budapest (2002)Lang, W., Roth, R.: Optimale Kraftschlussausnutzung bei Hochleistungs-Schienenfahrzeugen. Eisenbahntechnische Rundsch. 42, 61–66 (1993)Polach, O.: Creep forces in simulations of traction vehicles running on adhesion limit. Wear 258(7), 992–1000 (2005)Zhang, W., Chen, J., Wu, X., Jin, X.: Wheel/rail adhesion and analysis by using full scale roller rig. Wear 253(1), 82–88 (2002)Harrison, H., McCanney, T., Cotter, J.: Recent developments in coefficient of friction measurements at the rail/wheel interface. Wear 253(1), 114–123 (2002)Gallardo-Hernandez, E.A., Lewis, R.: Twin disc assessment of wheel/rail adhesion. Wear 265(9), 1309–1316 (2008)Fletcher, D.I., Lewis, S.: Creep curve measurement to support wear and adhesion modelling, using a continuously variable creep twin disc machine. Wear 298–299, 57–65 (2013)Fletcher, D.I.: A new two-dimensional model of rolling–sliding contact creep curves for a range of lubrication types. Proc. Inst. Mech. Eng. Part J: J. Eng. Tribol. 227(6), 529–537 (2013)Matsumoto, A., Sato, Y., Ono, H., Wang, Y., Yamamoto, M., Tanimoto, M., Oka, Y.: Creep force characteristics between rail and wheel on scaled model. Wear 253(1), 199–203 (2002)Janssens, M.H.A., van Vliet, W.J., Kooijman, P.P., De Beer, F.G.: Curve squeal of railbound vehicles (part 3): measurement method and results. In: Proceedings of Internoise, vol. 3, pp. 1568–1571, Nice, France (2000)Monk-Steel, A.D., Thompson, D.J., De Beer, F.G., Janssens, M.H.A.: An investigation into the influence of longitudinal creepage on railway squeal noise due to lateral creepage. J. Sound Vib. 293(3), 766–776 (2006)Liu, X., Meehan, P.A.: Investigation of the effect of lateral adhesion and rolling speed on wheel squeal noise. Proc. Inst. Mech. Eng. Part F: J. Rail Rapid Transit 227(5), 469–480 (2013)Liu, X., Meehan, P.A.: Investigation of the effect of relative humidity on lateral force in rolling contact and curve squeal. Wear 310(1), 12–19 (2014)Liu, X., Meehan, P.A.: Investigation of squeal noise under positive friction characteristics condition provided by friction modifiers. J. Sound Vib. 371, 393–405 (2016)Jie, E., Kim, J.Y., Hwang, D.H., Lee, J.H., Kim, K.J., Kim, J.C.: An experimental study of squeal noise characteristics for railways using a scale model test rig. In: J. Pombo (ed.) Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance, Cagliari, Sardinia, Italy (2016)Eadie, D.T., Santoro, M., Kalousek, J.: Railway noise and the effect of top of rail liquid friction modifiers: changes in sound and vibration spectral distributions in curves. Wear 258(7), 1148–1155 (2005)Bullen, R., Jiang, J.: Algorithms for detection of rail wheel squeal. In: 20th International Congress on Acoustics 2010, ICA 2010—Incorporating Proceedings of the 2010 Annual Conference of the Australian Acoustical Society. pp. 2212–2216 (2010)Stefanelli, R., Dual, J., Cataldi-Spinola, E.: Acoustic modelling of railway wheels and acoustic measurements to determine involved eigenmodes in the curve squealing phenomenon. Veh. Syst. Dyn. 44(sup1), 286–295 (2006)Vincent, N., Koch, J.R., Chollet, H., Guerder, J.Y.: Curve squeal of urban rolling stock—part 1: state of the art and field measurements. J. Sound Vib. 293(3), 691–700 (2006)Anderson, D., Wheatley, N.: Mitigation of wheel squeal and flanging noise on the Australian network. In: Schulte-Werning, B., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 99, pp. 399–405. Springer, Heidelberg (2008)Curley, D., Anderson, D.C., Jiang, J., Hanson, D.: Field trials of gauge face lubrication and top-of-rail friction modification for curve noise mitigation. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 449–456. Springer, Heidelberg (2015)Jiang, J., Hanson, D., Dowdell, B.: Wheel squeal—insights from wayside condition monitoring measurements and field trials. In: Anderson, D., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 139, pp 41–53. Springer, Heidelberg (2018)Jiang, J., Dwight, R., Anderson, D.: Field verification of curving noise mechanisms. In: Maeda, T., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 118, pp. 349–356. Springer, Heidelberg (2012)Jiang, J., Anderson, D.C., Dwight, R.: The mechanisms of curve squeal. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 587–594. Springer, Heidelberg (2015)Fourie, D.J., Gräbe, P.J., Heyns, P.S., Fröhling, R.D.: Experimental characterisation of railway wheel squeal occurring in large-radius curves. Proc. Inst. Mech. Eng. Part F: J. Rail Rapid Transit 230(6), 1561–1574 (2016)Corradi, R., Crosio, P., Manzoni, S., Squicciarini, G.: Experimental investigation on squeal noise in tramway sharp curves. In: Proceedings of the 8th International Conference on Structural Dynamics, EURODYN 2011, Leuven (2011)Merideno, I., Nieto, J., Gil-Negrete, N., Landaberea, A., Iartza, J.: Constrained layer damper modelling and performance evaluation for eliminating squeal noise in trams. Shock and Vibration (2014)Nelson J.T.: Wheel/rail noise control manual, TCRP Report 23 (1997)Krüger, F.: Schall- und Erschütterungsschutz im Schienenverkehr. Expert Verlag, Renningen (2001)Elbers, F., Verheijen, E.: Railway noise technical measures catalogue, UIC report UIC003-01-04fe (2013)Oertli, J.: Combatting curve squeal, phase II, final report, UIC (2005)Eadie, D.T., Santoro, M., Powell, W.: Local control of noise and vibration with KELTRACK™ friction modifier and protector® trackside application: an integrated solution. J. Sound Vib. 267(3), 761–772 (2003)Eadie, D.T., Santoro, M.: Top-of-rail friction control for curve noise mitigation and corrugation rate reduction. J. Sound Vib. 293(3), 747–757 (2006)Suda, Y., Iwasa, T., Komine, H., Tomeoka, M., Nakazawa, H., Matsumoto, K., Nakai, T., Tanimoto, M., Kishimoto, Y.: Development of onboard friction control. Wear 258(7), 1109–1114 (2005)Bühler, S., Thallemer, B.: How to avoid squeal noise on railways: state of the art and practical experience. In: Schulte-Werning, B., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 99, pp. 406–411. Springer, Heidelberg (2008)Jones, C.J.C., Thompson, D.J.: Rolling noise generated by railway wheels with visco-elastic layers. J. Sound Vib. 231(3), 779–790 (2000)Wetta, P., Demilly, F.: Reduction of wheel squeal noise generated on curves or during braking. In 11th International of Wheelset Congress, Paris (1995)Brunel, J.F., Dufrénoy, P., Demilly, F.: Modelling of squeal noise attenuation of ring damped wheels. Appl. Acoust. 65(5), 457–471 (2004)Marjani, S.R., Younesian, D.: Suppression of train wheel squeal noise by shunted piezoelectric elements. Int. J. Struct. Stab. Dyn. (2016)Heckl, M.A., Huang, X.Y.: Curve squeal of train wheels, part 3: active control. J. Sound Vib. 229(3), 709–735 (2000)Thompson, D.J., Jones, C.J.C., Waters, T.P., Farrington, D.: A tuned damping device for reducing noise from railway track. Appl. Acoust. 68(1), 43–57 (2007)Jiang, J., Ying, I., Hanson, D., Anderson, D.C.: An investigation of the influence of track dynamics on curve noise. In: Nielsen, J.C.O., et al. (eds.) Noise and Vibration Mitigation for Rail Transportation Systems. NNFM, vol. 126, pp. 441–448. Springer, Heidelberg (2015)Toward, M., Squicciarini, G., Thompson, D.J.: Reducing freight wagon noise at source. Int. Railway J. March, 47–49 (2015)Illingworth, R., Pollard, M.G.: The use of steering axle suspensions to reduce wheel and rail wear in curves. Proc. Inst. Mech. Eng. 196(1), 379–385 (1982)Garcia, J.F., Olaizola, X., Martin, L.M., Gimenez, J.G.: Theoretical comparison between different configurations of radial and conventional bogies. Veh. Syst. Dyn. 33(4), 233–259 (2000)Bruni, S., Goodall, R., Mei, T.X., Tsunashima, H.: Control and monitoring for railway vehicle dynamics. Veh. Syst. Dyn. 45(7–8), 743–779 (2007)Hiensch, M., Larsson, P.O., Nilsson, O., Levy, D., Kapoor, A., Franklin, F., Nielsen, J., Ringsberg, J., Josefson, L.: Two-material rail development: field test results regarding rolling contact fatigue and squeal noise behaviour. Wear 258(7), 964–972 (2005)Kopp, E.: Fünf Jahre Erfahrungen mit asymmetrisch geschliffenen Schienenprofilen. Eisenbahn Techn. Rundsch. 40, 665 (1991

The development of novel LTA4H modulators to selectively target LTB4 generation

The pro-inflammatory mediator leukotriene B4 (LTB4) is implicated in the pathologies of an array of diseases and thus represents an attractive therapeutic target. The enzyme leukotriene A4 hydrolase (LTA4H) catalyses the distal step in LTB4 synthesis and hence inhibitors of this enzyme have been actively pursued. Despite potent LTA4H inhibitors entering clinical trials all have failed to show efficacy. We recently identified a secondary anti-inflammatory role for LTA4H in degrading the neutrophil chemoattractant Pro-Gly-Pro (PGP) and rationalized that the failure of conventional LTA4H inhibitors may be that they inadvertently prevented PGP degradation. We demonstrate that these inhibitors do indeed fail to discriminate between the dual activities of LTA4H, and enable PGP accumulation in mice. Accordingly, we have developed novel compounds that potently inhibit LTB4 generation whilst leaving PGP degradation unperturbed. These novel compounds could represent a safer and superior class of LTA4H inhibitors for translation into the clinic

Recent advances in understanding hypertension development in sub-Saharan Africa

Consistent reports indicate that hypertension is a particularly common finding in black populations. Hypertension occurs at younger ages and is often more severe in terms of blood pressure levels and organ damage than in whites, resulting in a higher incidence of cardiovascular disease and mortality. This review provides an outline of recent advances in the pathophysiological understanding of blood pressure elevation and the consequences thereof in black populations in Africa. This is set against the backdrop of populations undergoing demanding and rapid demographic transition, where infection with the Human Immunodeficiency Virus predominates, and where under and over-nutrition coexist. Collectively, recent findings from Africa illustrate an increased lifetime risk to hypertension from foetal life onwards. From young ages black populations display early endothelial dysfunction, increased vascular tone and reactivity, microvascular structural adaptions, as well as increased aortic stiffness resulting in elevated central and brachial blood pressures during the day and night, when compared to whites. Together with knowledge on the contributions of sympathetic activation and abnormal renal sodium handling, these pathophysiological adaptations result in subclinical and clinical organ damage at younger ages. This overall enhanced understanding on the determinants of blood pressure elevation in blacks encourages (a) novel approaches to assess and manage hypertension in Africa better, (b) further scientific discovery to develop more effective prevention and treatment strategies, and (c) policymakers and health advocates to collectively contribute in creating health-promoting environments in Africa

Stable carbon and nitrogen isotope enrichment in primate tissues

Isotopic studies of wild primates have used a wide range of tissues to infer diet and model the foraging ecologies of extinct species. The use of mismatched tissues for such comparisons can be problematic because differences in amino acid compositions can lead to small isotopic differences between tissues. Additionally, physiological and dietary differences among primate species could lead to variable offsets between apatite carbonate and collagen. To improve our understanding of the isotopic chemistry of primates, we explored the apparent enrichment (ε*) between bone collagen and muscle, collagen and fur or hair keratin, muscle and keratin, and collagen and bone carbonate across the primate order. We found that the mean ε* values of proteinaceous tissues were small (≤1‰), and uncorrelated with body size or phylogenetic relatedness. Additionally, ε* values did not vary by habitat, sex, age, or manner of death. The mean ε* value between bone carbonate and collagen (5.6 ± 1.2‰) was consistent with values reported for omnivorous mammals consuming monoisotopic diets. These primate-specific apparent enrichment values will be a valuable tool for cross-species comparisons. Additionally, they will facilitate dietary comparisons between living and fossil primates

Heterozygous Yeast Deletion Collection Screens Reveal Essential Targets of Hsp90

Hsp90 is an essential eukaryotic chaperone with a role in folding specific “client” proteins such as kinases and hormone receptors. Previously performed homozygous diploid yeast deletion collection screens uncovered broad requirements for Hsp90 in cellular transport and cell cycle progression. These screens also revealed that the requisite cellular functions of Hsp90 change with growth temperature. We present here for the first time the results of heterozygous deletion collection screens conducted at the hypothermic stress temperature of 15°C. Extensive bioinformatic analyses were performed on the resulting data in combination with data from homozygous and heterozygous screens previously conducted at normal (30°C) and hyperthermic stress (37°C) growth temperatures. Our resulting meta-analysis uncovered extensive connections between Hsp90 and (1) general transcription, (2) ribosome biogenesis and (3) GTP binding proteins. Predictions from bioinformatic analyses were tested experimentally, supporting a role for Hsp90 in ribosome stability. Importantly, the integrated analysis of the 15°C heterozygous deletion pool screen with previously conducted 30°C and 37°C screens allows for essential genetic targets of Hsp90 to emerge. Altogether, these novel contributions enable a more complete picture of essential Hsp90 functions

Are institutional combinations, mergers or amalgamation the answer? An investigation into staff perceptions

Many higher and further education institutions in South Africa are struggling to survive in a context of financial stringency, declining student enrolments and increasing competition. For some of these institutions merging or amalgamation with other institutions in the near future is becoming a strong likelihood. The perceptions of staff who will be directly affected by these processes seem to be very important, as knowledge and understanding of those perceptions will empower decision-makers and ensure that effective management of the merging process can be accomplished. This investigation focused on staff perceptions of a possible merging of three institutions in the Free State Province, which had been identified for possible merging with other institutions. The results indicate that staff are not opposed to the idea of institutional combinations or merging, but that careful consideration needs to be given to particularly personal factors and that staff fears will have to be addressed in the process to ensure effective merging. South African Journal of Higher Education Vol.15(1) 2001: 100-10