bluuebunny/crossref_metadata_2025 huggingface dataset:
On steady Stokes flow in a trihedral
rectangular corner
Authors: GOMILKO A. M. , MALYUGA V. S. , MELESHKO V. V.
Published: March 2003

Motivated by the recent paper of Hills & Moffatt (2000), we investigate the Stokes
flow in a trihedral corner formed by three mutually orthogonal planes, induced by a
non-zero velocity distribution over one of the walls of the corner. It is shown that the
local behaviour of the velocity field near the edges of the corner, where a discontinuity
of the boundary velocity is assumed, coincides with the Goodier–Taylor solution for
a two-dimensional wedge. Analysis of the streamline patterns confirms the existence
of eddies near the stationary edge in the flow, induced either by uniform translation
of one of the walls of the corner in the direction perpendicular to its bisectrix or
by uniform rotation of a side about the vertex of the corner. These flows are shown
to be quasi-two-dimensional. If the wall rotates about a centre displaced from the
vertex, the induced flow is essentially three-dimensional. In the antisymmetric velocity
field, a stagnation line appears composed of stagnation points of different types.
Otherwise the three-dimensionality manifests itself in a non-closed spiral shape of the
streamlines.
On the relation between viscoelastic and
magnetohydrodynamic flows and their
instabilities
Authors: OGILVIE GORDON I. , PROCTOR MICHAEL R. E.
Published: March 2003

We demonstrate a close analogy between a viscoelastic medium and an electrically
conducting fluid containing a magnetic field. Specifically, the dynamics of the
Oldroyd-B fluid in the limit of large Deborah number corresponds to that of a
magnetohydrodynamic (MHD) fluid in the limit of large magnetic Reynolds number.
As a definite example of this analogy, we compare the stability properties of differentially
rotating viscoelastic and MHD flows. We show that there is an instability
of the Oldroyd-B fluid that is physically distinct from both the inertial and elastic
instabilities described previously in the literature, but is directly equivalent to the
magnetorotational instability in MHD. It occurs even when the specific angular momentum
increases outwards, provided that the angular velocity decreases outwards;
it derives from the kinetic energy of the shear flow and does not depend on the curvature
of the streamlines. However, we argue that the elastic instability of viscoelastic
Couette flow has no direct equivalent in MHD.
On Euclidean invariance of algebraic Reynolds stress models in turbulence
Authors: WEIS J. , HUTTER K.
Published: March 2003

This article shows how Euclidean invariance can be preserved in the so-called algebraic Reynolds stress model (ARSM) approximation. This approximation is used to reduce the transport equation for the Reynolds stresses to an explicit algebraic relation. A number of known models, which make use of this approximation, are not form-invariant under transformations to rotating coordinate systems. A simple extension is presented to show how this artifact can be removed.
Scale-by-scale budget and similarity laws for shear turbulence
Authors: CASCIOLA C. M. , GUALTIERI P. , BENZI R. , PIVA R.
Published: March 2003

Turbulent shear flows, such as those occurring in the wall
region of turbulent boundary layers, show a substantial increase of intermittency in comparison
with isotropic conditions. This suggests a close link between anisotropy and intermittency.
However, a rigorous statistical description of anisotropic flows is, in most cases, hampered
by the inhomogeneity of the field. This difficulty is absent for homogeneous shear flow. For
this flow the scale-by-scale budget is discussed here by using the appropriate form of the
Kámán–Howarth equation, to determine the range of scales where the shear is dominant. The resulting generalization of the four-fifths law is then used to extend to shear-dominated flows the Kolmogorov–Oboukhov theory of intermittency. The procedure leads naturally to the formulation of generalized structure functions, and the description of intermittency thus obtained reduces to the K62 theory for vanishing shear. The intermittency corrections to the scaling exponents are related to the moments of the coarse-grained energy dissipation field. Numerical experiments give indications that the dissipation field is statistically unaffected by the shear, supporting the conjecture that the intermittency corrections are universal. This observation together with the present reformulation of the theory gives a reason for the increased intermittency observed in the classical longitudinal velocity increments.
How vortices mix
Authors: MEUNIER P. , VILLERMAUX E.
Published: March 2003

The advection of a passive scalar blob in the deformation field of an axisymmetric vortex is a simple mixing protocol for which the advection–diffusion problem is amenable to a near-exact description. The blob rolls up in a spiral which ultimately fades away in the diluting medium. The complete transient concentration field in the spiral is accessible from the Fourier equations in a properly chosen frame. The concentration histogram of the scalar wrapped in the spiral presents unexpected singular transient features and its long time properties are discussed in connection with real mixtures.
State and Coffee Capital in São Paulo's Export Economy (Brazil 1889–1930)
Authors: PERISSINOTTO RENATO MONSEFF
Published: March 2003

Some recent works on the relationship between coffee interests and the State during the Brazilian ‘First Republic’ (1899–1930) have shown that the relationship between the national State and ‘coffee bourgeoisie’ was not quite as simple as earlier studies had made it seem. However, these analyses seem to assume that, at the regional level, the federalism of the First Republic placed regional political structures under class control. The goal of this article is to show that the ‘instrumentalist’ thesis is not even valid for the State apparatus when considered at the regional level. The article focuses on São Paulo state, seat of the most powerful interests linked to the coffee economy.
Railroad, Oil and Other Foreign Interests in the Mexican Revolution, 1911–1914
Authors: SKIRIUS JOHN
Published: March 2003

A polarisation of foreign railroad, oil and other business interests in Mexico occurred during the early years of the Mexican Revolution. Some of the American interests resented Porfirio Díaz's favouritism towards Europe and supported Francisco Madero for a change, and later, Venustiano Carranza. There is evidence of limited logistical support by the US government in May 1911 for the Madero revolution, and of financial support by US railroad and oil magnate Henry Clay Pierce. The overthrow of President Madero at the instigation of General Victoriano Huerta and General Félix Díaz, with the tacit support of British railroad and oil magnate Weetman Pearson, had very strong repercussions through President Huerta's subsequent alliance with British interests in Mexico. The US military superpower intervention in Veracruz of April 1914 was the action involving US business lobbying which had the greatest impact on the outcome of the Mexican Revolution, in favour of Carranza.
The Vestey Cattle Enterprise and the Regime of Juan Vicente Gómez, 1908–1935
Authors: YARRINGTON DOUG
Published: March 2003

This article seeks to expand our understanding of the dynamics of the Gómez regime and of its treatment of foreign investment by examining its relationship with a large British enterprise engaged in ranching and frozen meat exports. The company and the regime established mutually beneficial relationships during the First World War, but when the tighter market conditions of the post-war period obliged the company to restrict its purchases of cattle from Gómez, he forced the company to end its exports. The regime's treatment of the Vestey enterprise thus offers a vivid contrast to its treatment of foreign oil companies.
The Venezuelan Caracazo of 1989: Popular Protest and Institutional Weakness
Authors: MAYA MARGARITA LÓPEZ
Published: March 2003

27 February 1989 saw a popular revolt, which was to escalate dramatically, break out in Venezuela. Both Caracas and most of the main and secondary cities of the country were the scene of barricades, road closures, the stoning of shops, shooting and widespread looting. This article describes the events occurring during the Caracazo or Sacudón, as the episode is known, in order to show the key role played by the weakness of a set of social and political institutions in the violent forms of collective action that prevailed. This data, on a comparative basis, may enrich our understanding of other similar uprisings in the region and worldwide.
The Contrasting Variants of the Populism of Hugo Chávez and Alberto Fujimori
Authors: ELLNER STEVE
Published: March 2003

During the 1990s Peru's Alberto Fujimori and Argentina's Carlos Menem were the two main political successes of Latin American populism. Both completed two successive presidential terms, a unique accomplishment in the continent, and overcame the political instability that previously beset their nations. Scholars who analysed these and other contemporary regimes concluded that Latin American populism was flexible and resilient enough to adapt to a radically different environment from that of the 1930s and 1940s, when it had emerged as a major force. Some political scientists labelled as ‘neopopulism’ the newer variant of populism in the context of globalisation and widespread acceptance of neoliberal policies. These scholars stressed two salient features of neopopulism that contrasted with ‘classical populism’ of the 1930s and 1940s: its social base consisting of members of the informal economy, as opposed to the organised working class; and its implementation of neoliberal policies, as against the model of import substitution and state interventionism.
Political parties and the transition from authoritarianism: the case of Algeria
Authors: Bouandel Youcef
Published: March 2003

Since the bloody events of October 1988, Algeria has experienced important transformations. That date marked the beginning of the transition from authoritarianism with the opening of political space to previously excluded groups. A number of reforms were introduced, partly because of pressure from the street, but mainly because the incumbent authorities needed them to legitimise themselves and hang on to power. In the aftermath of the October events, the regime fragmented and a hitherto hidden struggle for power among the various political clans rose to the surface. This paper looks at the Algerian transition and assesses the role of Algeria's political parties in this process, asking whether they played a traditional role, or whether they were just puppets of the regime which served only to legitimise the process of change.
The Bakassi Boys: fighting crime in Nigeria
Authors: Harnischfeger Johannes
Published: March 2003

Nigeria's police and judiciary have failed to protect its citizens and have therefore lost all credibility. European principles of justice have likewise become discredited. Militias like the Bakassi Boys offer a popular alternative, which includes public executions and the use of the occult in fighting evil. But the growing fear of crime is only one reason why ‘jungle justice’ may spread. Governors and influential politicians help finance armed vigilante groups, and may make use of young men with machetes and pump-action shotguns to intimidate political opponents. As an ethnic militia that is ready to defend the interests of the ‘Igbo nation’, the Bakassi Boys have also been used to kill members of other ethnic groups. In many parts of Nigeria, ethnic and religious communities are preparing for ‘self-defence’, because they have no trust in the ability of democratic institutions to settle their conflicts.
Gateway to international victory: the diplomacy of the African National Congress in Africa, 1960–1994
Authors: Pfister Roger
Published: March 2003

The African National Congress (ANC) of South Africa extended the struggle against apartheid into the international arena when it was banned in 1960. This aspect of its policy became crucial and remained paramount until South Africa's first democratic elections were held in 1994. This paper focuses on the ANC's attempts to secure the support of the community of African states, and singles out three themes that were dominant in the period under review, namely acceptance by the African states; the modus operandi of their assistance; and their role in the negotiation process. The findings are based partly on new archival documentation, drawing two main conclusions. First, the ANC only won exclusive backing from African states after a lengthy struggle. Second, their diplomatic support proved to be a pivotal factor during the negotiations in South Africa after 1990, significantly contributing to the ANC's eventual victory in 1994.
‘They Stole Our Land’: debating the expropriation of white farms in Zimbabwe
Authors: Shaw William H.
Published: March 2003

In Zimbabwe today, Robert Mugabe and his ZANU-PF colleagues are busy expropriating white-owned farms, and claiming the moral high ground while they do so. Indeed, many observers, inside Zimbabwe and elsewhere, take it for granted that, whatever Mugabe's excesses, there is justice in his cause. But is there? This paper examines three moral arguments that Mugabe and his supporters advance to justify their land policies: that the peasants need the land, that the war of liberation was fought for the land, and that Zimbabweans are only taking back land that was originally stolen from them. The last of these arguments, which rests on an implicit entitlement theory of justice, is the strongest, and this essay therefore scrutinises it closely. It argues, however, that despite their emotive appeal, all three arguments are flawed beyond repair. Debunking them should help pave the way for a more sensible and more viable approach to the land question in Zimbabwe.
Integration or exclusion of Fulbe pastoralists in West Africa: a comparative analysis of interethnic relations, state and local policies in Ghana and Côte d'Ivoire
Authors: Tonah Steve
Published: March 2003

This paper undertakes a comparative analysis of the situation of the pastoral Fulbe in the two neighbouring West African countries of Ghana and Côte d'Ivoire. The migration of the Fulbe into the northern parts of both countries is quite a recent phenomenon. In spite of the similar social, economic and environmental conditions in both countries, the two governments responded differently to Fulbe migrations. Generally, the Ivorian government was more receptive of the Fulbe while the Ghanaian authorities have been hostile to them. The paper also discusses interethnic relations between the Fulbe and the indigenous farming groups. Finally, responses of both governments to farmer–herder conflicts are examined and some general reflections on how West African states are dealing with the issue of pastoral migration are provided.
Politics, ethno-religious conflicts and democratic consolidation in Nigeria
Authors: Ukiwo Ukoha
Published: March 2003

This article examines the explosion of violent ethno-religious and communal conflicts in Nigeria, contrary to the widespread expectation that the inauguration of the civilian administration would usher in democratic stability. The nature of the politics of the transition programme and the reluctance of the post-military regime to address the national question have led to the resurgence of social groups that make demands for incorporation and empowerment. The central argument is that unbridled competition for power, and the failure of government to deliver democratic dividends, have resulted in violent conflicts, especially between ethnic and religious groups, endangering the country's nascent democracy. Good governance, especially accountability, transparency and equity, would restore governmental legitimacy, inter-ethnic and religious harmony and promote democratic consolidation.
Sapphire anniversary reflections on the study of United States foreign policy towards Africa
Authors: Schraeder Peter
Published: March 2003

The creation in 1958 of a separate Bureau of African Affairs within the United States State Department served as a turning point in US foreign policy towards Africa, in that it signalled Africa's growing significance within the US policymaking establishment. This historical event has served as a point of reference for Africanists, as demonstrated by Crawford Young's (1984) ‘silver’ (25-year) anniversary reflections on the state of US Africa policies as president of the African Studies Association. The primary purpose of this essay is to provide ‘sapphire’ (45-year) anniversary reflections on US foreign policy towards Africa, by offering a select review of forty books that have been published on this topic during the last decade (1993–2002). It is important to note, however, that this essay does not provide a comprehensive review of all the books published since 1993, nor does it offer a comprehensive review of the literature published prior to that date. The intention is rather to illuminate trends in scholarship.
Ionization equilibrium and thermodynamic
and transport properties of a non-ideal
hydrogen plasma
Authors: RAMAZANOV T. S. , DZHUMAGULOVA K. N.
Published: March 2003

The composition of a non-ideal plasma and the thermodynamic functions
and conductivity of the system are calculated using the minimum Gibbs free energy
method. Interactions of charged particles are described by a pseudopotential model
that takes into account collective phenomena (high-order correlation effects) in the
plasma.
Does neutral dynamics suppress instabilities in partially ionized plasma?
Authors: SHAIKH A. A. , DAS A. C.
Published: March 2003

We present two findings: (i) in the absence of compressibility of (cold) neutrals, the instability triggered by neutral drift due to gradients in plasma density and magnetic field and (ii) the equilibrium pressure-gradient- (PG-) driven instabilities with and without neutral dynamics. The results of detailed analysis suggest that on account of neutral dynamics the growth of these instabilities is suppressed by a neutral perturbational effect. Suppression of PG-driven instabilities is highlighted and the critical wavelength for sustainable growth is found. The physics involved in the mechanism of instabilities is discussed. The endeavour in these investigations is justifiable in its usefulness for understanding the phenomena pertinent to partially ionized plasma (PIP). The stability analysis presented here may be useful for understanding the plasma processes in ‘deep’ coma (very near to the nucleus of coma), at the edges of a plasma column, near a divertor region and in the case of sublimating gas from a cloud.
Relations between interstellar density and magnetic field fluctuations I. Kinetic theory of fluctuations
Authors: SCHLICKEISER R. , LERCHE I.
Published: March 2003

Using linear kinetic plasma theory the relation between electron density and magnetic field fluctuations for low-frequency plasma waves for Maxwellian background distribution functions of arbitrary temperatures in a uniform magnetic field is derived. By taking the non-relativistic temperature limit this ratio is calculated for the diffuse intercloud medium in our Galaxy. The diffuse intercloud medium is the dominant phase of the interstellar medium with respect to radio wave propagation, dispersion and rotation measure studies. The differences between the relation of electron density and magnetic field fluctuations from the linear kinetic theory compared with the classical magnetohydrodynamics theory are established and discussed.
Helicity resonant influence on the local Alfvén resonance structure in straight stellarators
Authors: GIRKA I. O. , LAPSHIN V. I.
Published: March 2003

Distribution of antenna-driven electromagnetic wave fields within the local Alfvén resonance is studied under resonant conditions such that the axial period of the fundamental harmonic of the magnetohydrodynamic oscillations in the axial direction is twice as large as the pitch length, and the poloidal number of the fundamental harmonic is twice as small as the polarity of the helical coils. It is shown that taking account of the helical inhomogeneity of the steady magnetic field can remove the infinite discontinuity of the wave fields that takes place in a straight magnetic field rather than with electron inertia or a finite ion Larmor radius.
Particle acceleration by lower-hybrid turbulence
Authors: BINGHAM R. , DAWSON J. M. , SHAPIRO V. D.
Published: March 2003

We investigate particle acceleration by strong lower-hybrid turbulence produced by the relaxation of an energetic perpendicular ion ring distribution. Ion ring distributions are associated with counterstreaming plasma flows in a magnetic field, and are found at perpendicular shocks as a result of ion reflection from the shock surface. Using a 2½D particle-in-cell (PIC) code that is fully electromagnetic and relativistic, we show that the ion ring is unstable to the generation of strong plasma turbulence at the lower-hybrid resonant frequency. The lower-hybrid wave turbulence collapses in configuration space, producing density cavities. The collapse of the cavities is halted by particle acceleration, producing energetic electron and ion tails. For solar flare plasmas with temperatures of 1 keV and a ratio of the plasma frequency to the electron cyclotron frequency of ½, we demonstrate electron acceleration to energies up to MeV, while the ions are accelerated to energies in the region of several MeV.
Energy gain by an electron in the fundamental mode of a rectangular waveguide by microwave radiation
Authors: MALIK HITENDRA K.
Published: March 2003

Energy gain by an electron during its motion in the fields of the fundamental TE10 mode excited by microwave radiation in a rectangular waveguide is analysed. Expressions have been obtained for the fields of the mode, the angle of deflection and the acceleration gradient of the electron when it is injected along the direction of mode propagation. An electron of energy 25 keV gains 120.44 keV when a microwave of intensity 1010 Wm−2 at frequency 6 GHz is employed to excite the mode in a waveguide of width 0.03 m and height 0.02 m. The effects of the microwave frequency and the width of the waveguide are to decrease the electron energy gain for fixed microwave intensity. However, higher acceleration gradients are obtained when the electron is injected with greater initial energy.
Generation of extra and very low-frequency (ELF/VLF) radiation by ionospheric electrojet modulation using high-frequency (HF) heating waves
Authors: KUO S. P.
Published: March 2003

Extra and very low-frequency (ELF/VLF) wave generation by modulated polar electrojet currents is studied numerically. Through Ohmic heating by the amplitude-modulated high-frequency heating wave, the conductivity and thus the current of the electrojet are modulated accordingly to set up the ionospheric antenna current. Stimulated thermal instability, which can further enhance the electrojet current modulation, is studied. It is first analysed analytically to determine the threshold heating power for its excitation. The nonlinear evolutions of the generated ELF/VLF waves enhanced by the instability are then studied numerically. Their spectra are also evaluated. The field intensity of the emission at the fundamental modulation frequency is found to increase with the modulation frequency in agreement with the Tromso observations. The efficiency enhancement by the stimulated thermal instability is hampered by inelastic collisions of electrons with neutral particles (mainly due to vibration excitation of N2), which cause this instability to saturate at low levels. However, the electron inelastic collision loss rate drops rapidly to a low value in the energy regime from 3.5 to 6 eV. As the heating power exceeds a threshold level, significant electron heating enhanced by the instability is shown, which indeed causes a steep drop in the electron inelastic collision loss rate. Consequently, this instability saturates at a much higher level, resulting to a near step increase (of about 10–13 dB depending on the modulation wave form) in the spectral intensity of ELF radiation. The dependence of the threshold power of the HF heating wave on the modulation frequency is determined.
Ion transport in electrode sheath with non-uniform dusts
Authors: SUN A. P. , QIU X. M. , TONG H. H. , CHEN Q. C.
Published: March 2003

The Monte Carlo method is used to simulate ion transport in an Ar plasma electrode sheath with a non-uniform dust. Charge exchange and elastic collisions between ions and neutral atoms and also the collection and Coulomb scattering of ions on the dust particles are examined during the motion of ions in the sheath. In order to study the effect of the non-uniform dust density and size on ion transport, we choose an exponent dust density distribution with a uniform dust size and a normal dust radius distribution with a uniform density and compare the simulation results with those for a uniform dust. It is found that both a non-uniform and a uniform dust density affect the ion density arriving at the electrode significantly and to the same degree. At the same time, it is also found that a non-uniform and uniform dust size influence the ion density arriving at the electrode greatly, but with a slight difference. Therefore, although the dust content is very low in most processing plasmas, its influence becomes evident whether its content is uniform or non-uniform in content and size. So, we can come to the conclusion that the key factors affecting the influence of dust particles on plasma behaviour are the linear density and the average radius of dust particles rather than their distribution.
Simulation of the effect of random noise on Gaussian and Lorentzian widths in a Voigt profile
Authors: LUQUE J. M. , CALZADA M. D. , SÁEZ M.
Published: March 2003

Experimental line profiles can be altered by so-called spectral interference that appears due to different causes. One of the most commonly appearing sources of interference is random noise due to the detector used for measuring the spectra in the laboratory. In this work, the noise is studied using a simulation procedure. This study helps to pinpoint the changes that the noise produces in the parameters of the experimental profiles and, consequently, in the information provided by them.
Linear collapse of spatially linear, two-dimensional null points
Authors: MELLOR C. , TITOV V. S. , PRIEST E. R.
Published: March 2003

A technique is developed for analysing the linear collapse properties of spatially linear two-dimensional null points with open boundary conditions. A treatment is given of the collapse of nulls which have current and flow so that they are initially in a steady-state balance between a magnetic force, a pressure force and a centrifugal force. This extends the previous results for initially current-free X-type nulls with no flow. It is found that all X-points, regardless of the current and flow tend to collapse. Also, O-points collapse in the absence of a plasma flow, but O-points with a large current and possessing a highly super-Alfvénic plasma flow can be stable against linear collapse.
Plasma–wall interaction inside a Hall thruster
Authors: ROY SUBRATA , PANDEY B. P.
Published: March 2003

The dynamics of a Hall thruster is investigated numerically in the presence of a plasma–wall interaction. The plasma–wall interaction is a function of the wall potential, which in turn is determined by the secondary electron emission and sputtering yield. In the present work, the effect of secondary electron emission and sputter yield have been considered simultaneously. Owing to disparate temporal scales, ions and neutrals have been described by a set of time-dependent equations while electrons are considered in a steady state. Based on the experimental observations, a third-order polynomial in electron temperature is used to calculate the ionization rate. The changes in the plasma density, potential and azimuthal electron velocity due to the sputter yield are significant in the acceleration region. The change in ion and electron velocity and temperature is small. The neutral velocity, which decreases initially, starts increasing towards the exit consistent with the computed neutral density profile. The results are qualitatively compared with the experiments.
Activation of host constitutive immune defence by an intestinal trypanosome parasite of bumble bees
Authors: BROWN M. J. F. , MORET Y. , SCHMID-HEMPEL P.
Published: March 2003

Many parasites, including important species that affect humans and livestock, must survive the harsh environment of insect guts to complete their life-cycle. Hence, understanding how insects protect themselves against such parasites has immediate practical implications. Previously, such protection has been thought to consist mainly of mechanical structures and the action of lectins. However, recently it has become apparent that gut infections may interact with the host immune system in more complex ways. Here, using bumble bees, Bombus terrestris and their non-invasive gut trypanosome, Crithidia bombi, as a model system we investigated the effects of parasitic infection, host resources and the duration of infections on the host immune system. We found that infection doubled standing levels of immune defence in the haemolymph (the constitutive pro-phenoloxidase system), which is used as a first, general defence against parasites. However, physical separation of the parasite from the haemolymph suggests the presence of a messenger system between the gut and the genes that control the pro-phenoloxidase system. Surprisingly, we found no direct effect of host resource-stress or duration of the infection on the immune system. Our results suggest a novel and tactical response of insects to gut infections, demonstrating the complexity of such host–parasite systems.
Membrane-bound acid phosphatase (MAP) from Entamoeba histolytica has phosphotyrosine phosphatase activity and disrupts the actin cytoskeleton of host cells
Authors: AGUIRRE-GARCÍA M. M. , ANAYA-RUIZ M. , TALAMÁS-ROHANA P.
Published: March 2003

Protein tyrosine phosphatases (PTPases) have been described as virulence factors in different pathogenic microorganisms. The pathogenic process by Entamoeba histolytica is a multifactorial phenomenon that occurs in 3 steps: adhesion, cytolytic and cytotoxic effect, and phagocytosis. Lytic enzymes may participate during the second part of this process. In this work, we determined that purified membrane-bound acid phosphatase (MAP) from E. histolytica trophozoites has PTPase activity. The enzyme specifically dephosphorylated O-phospho-L-tyrosine at optimum pH of 5·0, with little activity towards O-phospho-L-serine, O-phospho-L-threonine, and ATP. It was inhibited by ammonium molybdate and sodium tungstate, and trifluoperazine did not show any effect. A monoclonal antibody against the catalytic domain of the human placental PTPase 1B, cross-reacted with a 55 kDa molecule present in the solubilized fraction. The interaction of the amoebic PTPase with HeLa cells resulted in the alteration of the cell actin cytoskeleton by disruption of the actin stress fibres.
Infection with Leishmania major stimulates haematopoiesis in susceptible BALB/c mice and suppresses haematopoiesis in resistant CBA mice
Authors: GUILPIN V. O. , NOSBISCH L. , TITUS R. G. , SWARDSON-OLVER C. J.
Published: March 2003

Cytokine responses to Leishmania infection begin very early in infection, and differ between susceptible and resistant mice. Susceptibility to chronic Leishmania infection has been associated with increased haematopoiesis. To analyse the effect that acute infection with L. major has on bone-marrow haematopoiesis in susceptible (BALB/c) and resistant (CBA) mice, we enumerated erythroid progenitors and granulocyte-monocyte progenitors 3 days after infection. We found that haematopoiesis was stimulated in BALB/c mice infected with L. major, while haematopoiesis was inhibited in CBA mice. We found that this effect could be partially explained by cytokine production: interleukin-4 was involved in stimulation of BALB/c haematopoiesis and tumour necrosis factor-α was involved in inhibition of CBA haematopoiesis. Our conclusions are that haematopoietic changes occur shortly after L. major infection, and may be related to disease outcome.
Gross anatomy of the muscle systems and associated innervation of Apatemon cobitidis proterorhini metacercaria (Trematoda: Strigeidea), as visualized by confocal microscopy
Authors: STEWART M. T. , MOUSLEY A. , KOUBKOVÁ B. , šEBELOVÁ š. , MARKS N. J. , HALTON D. W.
Published: March 2003

The major muscle systems of the metacercaria of the strigeid trematode, Apatemon cobitidis proterorhini have been examined using phalloidin as a site-specific probe for filamentous actin. Regional differences were evident in the organization of the body wall musculature of the forebody and hindbody, the former comprising outer circular, intermediate longitudinal and inner diagonal fibres, the latter having the inner diagonal fibres replaced with an extra layer of more widely spaced circular muscle. Three orientations of muscle fibres (equatorial, meridional, radial) were discernible in the oral sucker, acetabulum and paired lappets. Large longitudinal extensor and flexor muscles project into the hindbody where they connect to the body wall or end blindly. Innervation to the muscle systems of Apatemon was examined by immunocytochemistry, using antibodies to known myoactive substances: the flatworm FMRFamide-related neuropeptide (FaRP), GYIRFamide, and the biogenic amine, 5-hydroxytryptamine (5-HT). Strong immunostaining for both peptidergic and serotoninergic components was found in the central nervous system and confocal microscopic mapping of the distribution of these neuroactive substances revealed they occupied separate neuronal pathways. In the peripheral nervous system, GYIRFamide-immunoreactivity was extensive and, in particular, associated with the innervation of all attachment structures; serotoninergic fibres, on the other hand, were localized to the oral sucker and pharynx and to regions along the anterior margins of the forebody.
The phylogeny of the Schistosomatidae based on three genes with emphasis on the interrelationships of Schistosoma Weinland, 1858
Authors: LOCKYER A. E. , OLSON P. D. , ØSTERGAARD P. , ROLLINSON D. , JOHNSTON D. A. , ATTWOOD S. W. , SOUTHGATE V. R. , HORAK P. , SNYDER S. D. , LE T. H. , AGATSUMA T. , MCMANUS D. P. , CARMICHAEL A. C. , NAEM S. , LITTLEWOOD D. T. J.
Published: March 2003

Schistosomes are digenean flukes, parasitic of birds, mammals and crocodiles. The family Schistosomatidae contains species of considerable medical and veterinary importance, which cause the disease schistosomiasis. Previous studies, both morphological and molecular, which have provided a good deal of information on the phylogenetics of this group, have been limited in the number of species investigated or the type or extent of molecular data used. This paper presents the most comprehensive phylogeny to date, based on the sequences of 3 genes, complete ribosomal small subunit rRNA and large ribosomal subunit rRNA, and mitochondrial cytochrome oxidase 1, sequenced from 30 taxa including at least 1 representative from 10 of the 13 known genera of the Schistosomatidae and 17 of the 20 recognized Schistosoma species. The phylogeny is examined using morphological characters, intermediate and definitive host associations and biogeography. Theories as to the origins and spread of Schistosoma are also explored. The principal findings are that Ornithobilharzia and Austrobilharzia form a sister group to the Schistosoma; mammalian schistosomes appear paraphyletic and 2 Trichobilharzia species, T. ocellata and T. szidati, seem to be synonymous. The position of Orientobilharzia within the Schistosoma is confirmed, as is an Asian origin for the Schistosoma, followed by subsequent dispersal through India and Africa.
Identification of a fibrinolytic enzyme in Schistosoma mansoni eggs and modulated blood fibrinogen metabolism in S. mansoni-infected mice
Authors: DOENHOFF M. J. , STANLEY R. G. , PRYCE D. , CURTIS R. C. H. , PARRY H. , GRIFFITHS K. , JACKSON C. L.
Published: March 2003

Aqueous extracts of Schistosoma mansoni eggs have been shown to have fibrinolytic activity inhibitable by a serine protease inhibitor. Fibrinolytic activity was not present in extracts of either adult worms or cercariae. A 27 kDa enzyme that was proteolytically active on fibrinogen in zymography and that degraded fibrinogen in a pattern similar to that of plasmin, is presumed to be responsible for the schistosome egg fibrinolytic activity. Anti-human fibrinogen antisera were shown to have antibodies that cross-reacted with mouse fibrinogen in Western immunoblots. Electroblotted sera from S. mansoni-infected and control uninfected mice displayed different antigenic profiles when probed with the cross-reactive anti-human fibrinogen antibodies, suggesting an alteration in mouse host fibrinogen metabolism as a result of the parasitic infection. We discuss the possibility that modulation of fibrinogen metabolism is a factor in a recently discovered anti-atherogenic effect exerted by schistosomes.
Genetic and phenotypic analysis of Tunisian Theileria annulata clones
Authors: TAYLOR L. H. , KATZER F. , SHIELS B. R. , WELBURN S. C.
Published: March 2003

Many parasite species are known to show high levels of genetic diversity, yet the consequences of this diversity for host–parasite interactions are not well understood. Variation in phenotypic traits such as growth rates and the ability to form transmission stages are raw material for natural and artificial selection to act upon with consequences for the evolution of the parasite species and disease control. In order to study genetic and phenotypic diversity amongst Theileria annulata parasites, a collection of 52 parasite clones was generated from cattle isolates and tick material recently collected in Tunisia. Genetic diversity was assessed using PCR-RFLP and monoclonal antibody markers, and genetically distinct clones selected for further study. Clones varied significantly in their growth rates in culture at 37 °C, their viability after a period of culture at 41 °C and their differentiation rates into transmission stages after culturing at 41 °C. The viability of a clone after culturing at 41 °C could not be predicted from its growth rate at 37 °C, but across clones, differentiation rates were positively correlated with growth rates at 37 °C. All 3 in vitro measures are likely to have relevance to parasite–host interactions in animals with clinical theileriosis, and should be acted on by within-host and between-host selection.
An ultrastructural study of reproduction in the parthenogenetic metacercariae of Cercaria margaritensis Ching, 1982 (Digenea: Gymnophallidae)
Authors: IRWIN S. W. B. , GALAKTIONOV K. V. , MALKOVA I. I. , SAVILLE D. H. , FITZPATRICK S. M.
Published: March 2003

The parthenogenetic metacercarial stages of the gymnophallid trematode Cercaria margaritensis are found in the extrapallial cavity of the subtidal prosobranch mollusc Margarites helicinus. The primary metacercariae (M1) produce second-generation metacercariae (M2) which become independent and give rise to M3 metacercariae which are infective to the definitive host, the common eider (Somateria mollissima). This study used transmission electron microscopy to follow the development of M2 inside M1 organisms and M3 inside M2 organisms. The process is similar in both cases with embryos developing from individual cells from the parent body walls. In each case the brood sac was divided into brood chambers by multilaminated cells and both M2 and M3 embryos developed inside embryonic membranes that originated from specialized blastomeres. The tegument of M2 and M3 embryos developed in a similar manner underneath the embryonic membrane. Both the multilaminated cells and the embryonic membranes possessed features that indicated that they are involved in transport of nutrients. It is suggested that the continuous nature of M2 and M3 embryo development may well be similar to that postulated for ancestral digeneans.
A study of the effect of surface damage on the uptake of Texas Red–BSA by schistosomula of Schistosoma mansoni
Authors: TAN H. H. C. , THORNHILL J. A. , AL-ADHAMI B. H. , AKHKHA A. , KUSEL J. R.
Published: March 2003

In this paper we describe the effect of poly-L-lysines of different molecular weight on the schistosomula. In the control sample, the schistosomula of Schistosoma mansoni take up fluorescent Texas Red conjugated to bovine serum albumin (TxR–BSA) into the gut. Following slight damage by 24·0 kDa poly-L-lysine, a high proportion of schistosomula take up fluorescent TxR–BSA into the excretory system. Subsequently, the dye diffused into the bodies of the schistosomula. We suspected that this diffusion involved the process of endocytosis so we investigated this with the use of endocytosis inhibitor, Latrunculin A. Addition of the endocytosis inhibitor Latrunculin A following poly-L-lysine treatment inhibited gut uptake of TxR–BSA as well as the diffusion of excretory-ingested TxR–BSA molecules.
Immune-dependent thrombocytopaenia in mice infected with Schistosoma mansoni
Authors: STANLEY R. G. , NGAIZA J. R. , ATIENO E. , JELL G. , FRANCKLOW K. , JACKSON C. L. , PARRY H. , DOENHOFF M. J.
Published: March 2003

As has been shown previously, immunologically intact mice with patent Schistosoma mansoni infections has a significantly lower mean platelet number than intact uninfected mice (P<0·0001). However, platelet numbers in T-cell deprived mice with patent infections were not significantly different from those in uninfected T-cell deprived mice. Also, platelet counts in both the infected and uninfected T-cell deprived groups were not significantly different from those in intact uninfected mice. The S. mansoni-induced thrombocytopaenia in mice is thus seemingly immune dependent. Immunologically intact mice with chronic 12-week-old S. mansoni infections has IgG antibodies that were reactive in an ELISA-type assay wit whole fixed platelets of both mouse and human origin. In Western immunoblots the IgG antibodies from chronically-infected mice reacted in particular against mouse and human platelet antigens of 90, 37 and 30 kDa. Antisera raised from 2 rabbits, immunized respectively with mouse and human platelet antigens, cross-reacted with antigens of the larval, adult worm and egg stages of S. mansoni. These results support the hypothesis that an anti-platelet antibody response may be the cause of the thrombocytopaenia observed in mice with patent schistosome infections.
Taking it seriously: intertextuality and authenticity in two covers by the Pet Shop Boys
Authors: Butler Mark
Published: March 2003

When musicians ‘cover’ a previously recorded song, they provide an intertextual commentary on another musical work or style. This paper considers several ways in which such commentaries engage constructions of authenticity, focusing on two covers by the Pet Shop Boys: ‘Where the Streets Have No Name’, originally by U2, and ‘Go West’, first recorded by the Village People. I analyse the musical sound, performance style, and lyrical themes of each pair of songs, as well as the discourse surrounding their production and reception. I also consider how scholars have theorised authenticity in the interpretive traditions engaged by these songs. I argue that the Pet Shop Boys’ version of ‘Where the Streets Have No Name’ is subversive, poking fun at certain common ways of expressing authenticity in 1980s rock, while their cover of ‘Go West’ repositions disco - a genre that has widely been construed as inauthentic - as a type of ‘roots music’ for the gay community of the 1990s.
World music or Japanese - the gagaku of Tôgi Hideki
Authors: Lancashire Terence
Published: March 2003

The term ‘world music’ usually conjures up images of musics from ‘remote’ corners of the world. However, that remoteness is not always geographical and can, for example, be chronological. Tôgi Hideki, a former musician from the Imperial court in Japan, has sought to introduce court music - gagaku - to a wider audience through the reworking of traditional gagaku pieces and new compositions for gagaku instruments. Gagaku boasts a history of over 1,200 years and its esoteric nature inhibits popular interest. Tôgi Hideki’s popularised gagaku, on the other hand, has found a new audience for gagaku, and his music serves as a bridge introducing Japanese back to a remote part of Japanese musical culture.
Sampling the 1970s in hip-hop
Authors: Demers Joanna
Published: March 2003

Musical borrowings, or samples, have long been a means of creating lineage between hip-hop and older genres of African-American music such as funk, soul, and rhythm and blues. DJs who sample from this so-called ‘Old School’ attempt to link hip-hop to older, venerable traditions of black popular music. This article investigates the importance of 1970s pop and culture to hip-hop music. This era is depicted as a time in which African-American identity coalesced, and a new political consciousness was born. The primary source for images of the 1970s was and continues to be blaxploitation film, a genre of low-budget, black-oriented crime and suspense cinema. This article will detail how blaxploitation distilled certain societal concerns of the 1970s, and how in turn hip-hop feeds off blaxploitation both dramatically and musically, reusing its story lines and sampling its soundtracks.
For and against the record industry: an introduction to bootleg collectors and tape traders
Authors: Marshall Lee
Published: March 2003

This paper offers an introduction to a distinct group of musical consumers: bootleg collectors and tape traders. It begins by defining the types of recording under discussion before outlining some of the discourse surrounding the collection of unauthorised recordings. Bootleg collectors and tape traders exist in a relationship of mutual distrust with the legitimate music industry: collectors view the industry as a barrier to musical experience while the industry views these collectors as at best a nuisance and at worst as having a detrimental impact upon official sales. The paper argues, however, that the relationship is in fact more complex. It shows that through an intensification of discourses of authenticity, collectors of unauthorised recordings actually provide ideological support for the recording industry, helping valorise musical commodities and thus maintain a dialectical relationship between collectors and the legitimate industry.
Singing the pulse of the Egyptian-Arab street: Shaaban Abd al-Rahim and the geo-pop-politics of fast food
Authors: Gordon Joel
Published: March 2003

Veteran Egyptian shaabi singer Shaaban Abd al-Rahim recently attained superstar status as the ‘interpreter of the pulse of the Egyptian-Arab street’ due to a pop hit proclaiming his hatred for Israel. Shaaban’s notoriety has been further enhanced by his abortive sponsorship of an ‘indigenous’ sandwich marketed in Egypt by McDonald's. Contracted by the fast food giant precisely because of his popularity, the singer was soon after dismissed in the wake of political pressure outside Egypt regarding the song that had made him a star. The deliberate turn to a singer like Shaaban for product sponsorship, especially for a commercial to be broadcast by state-run media, underscores weakening boundaries between what is ‘classically’ approved and what is still considered to be ‘vulgar’ or ‘low-class’ music, however popular it is among wide sectors of the population. For the moment, at least, Shaaban has become a figure with whom even a scornful intelligentsia must contend.