bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytic solutions of ∇
×
B=λB having separatrices for geometries with one ignorable coordinate
Authors: Turner Leaf
Published: March 2003

Analytic solutions of ∇×B=λB are presented for PS-1 and CTX types of spheromaks, and for the proposed Wisconsin reversed-field pinch. Inherent in the spheromak solutions is a separatrix that separates a region of closed magnetic field lines from a surrounding region of open ones. Such a structure enhances the plausibility of maintaining steady-state spheromak operation by driving a steady current along the open field lines.
Stochastic E
×
B particle transport
Authors: Kleva Robert G. , Drake J. F.
Published: March 2003

The E×B particle guiding center motion caused by two propagating electrostatic waves is investigated. Particle motion is stochastic if three criteria are met: (1) the phase velocities of the two waves are not equal, (2) the E×B drift velocities generated by each wave are nearly the same, and (3) the total E×B drift velocity is larger than the phase velocity of each wave. Particle transport in the stochastic regime is distinguished by three important characteristics: (1) the diffusion coefficient is virtually independent of the electric field fluctuation amplitude Ẽ at large Ẽ, (2) particle transport is generated only by waves which produce nearly commensurate E×B drifts, and (3) the velocity correlation time does not depend on Ẽ, but rather on the wave periods. The physical mechanism underlying stochastic particle transport is discussed. At large Ẽ the transport is dominated by a small group of particles which make long jumps along the separatrix of the potential contours of the waves.
Electron cyclotron emission in a rf current-driven tokamak plasma
Authors: Giruzzi G. , Fidone I. , Granata G. , Meyer R. L.
Published: March 2003

The general properties of electron cyclotron radiation emitted by the current-carrying superthermal tail in tokamak plasmas are investigated. Two situations are considered, namely, the case of an extended tail as it occurs in present-day experiments and that in which the velocity range of the tail is much less than its mean speed. For the former case, we show that most of the emitted radiation obeys Kirchhoff’s law. In the latter case, which is suited for reactor-like parameters, a simple relation is obtained between the tail momentum distribution and the radiation temperature.
Magnetic coordinates for equilibria with a continuous symmetry
Authors: Dewar R. L. , Monticello D. A. , Sy W. N.-C.
Published: March 2003

Magnetic coordinates for hydromagnetic equilibria are defined which treat toroidal and ‘‘straight’’ helical plasmas equivalently and yet exploit the existence of a continuous symmetry to derive relations between various geometrical and physical qualities. This allows the number of equilibrium quantities which must be known to be reduced to a minimal, or primitive, set. Practical formulas for various quantities required in hydromagnetic stability calculations (interchange, ballooning, and global) are given in terms of this primitive set.
Low mode number stability of a quadrupole tandem mirror
Authors: Phillips M. W. , Callen J. D.
Published: March 2003

The low mode number macroscopic stability of plasmas in the Phaedrus tandem mirror is studied. The stability analysis includes finite Larmor radius effects and takes into account the nonaxisymmetric nature of the equilibrium. A variational principle is formulated which is solved for the normal modes of the system by a Rayleigh–Ritz method. Despite the full 3-D representation of the modes and nonaxisymmetry of the equilibrium it is found that for values of ρi/Rp>0.05 the most unstable modes are to a large extent composed of a single poloidal Fourier (m) component. For the Phaedrus tandem mirror experiment the most unstable mode is an m=1 rigid displacement.
Equilibrium calculations for helical axis stellarators
Authors: Hender T. C. , Carreras B. A.
Published: March 2003

An average method based on a vacuum flux coordinate system is presented. This average method permits the study of helical axis stellarators with toroidally dominated shifts. An ordering is introduced, and to lowest order the toroidally averaged equilibrium equations are reduced to a Grad–Shafranov equation. Also, to lowest order, a Poisson-type equation is obtained for the toroidally varying corrections to the equilibrium. By including these corrections, systems that are toroidally dominated, but with significant helical distortion to the equilibrium, may be studied. Numerical solutions of the average method equations are shown to agree well with three-dimensional calculations.
Three-dimensional stellarator equilibria by iteration
Authors: Boozer Allen H.
Published: March 2003

The iterative method of evaluating plasma equilibria is especially simple in a magnetic coordinate representation. This method is particularly useful for clarifying the subtle constraints of three-dimensional equilibria and studying magnetic surface breakup at high plasma beta.
A plasma model with energy transport and dynamo for sustained reversed field pinches
Authors: Schaffer Michael J.
Published: March 2003

A method is presented to calculate the hypothesized dynamo mean electric field required to sustain reversed field pinch (RFP) plasmas in time-independent states such as have been observed in recent RFP experiments. It is also shown how to simultaneously calculate energy transport in terms of a phenomenological radial thermal conductivity κ. It was found that the dynamo extracts energy from the central plasma in order to drive the large azimuthal current needed by the RFP. The quantitative results are only weakly sensitive to the choice of parameters. The principal predictions are the distribution of the dynamo mean electric field in the plasma and the ratio between average and peak electrical conductivity. The theory is compared with experimental RFP data, and it is concluded that the mean plasma resistivity is not much different from the classical resistivity of Spitzer.
Multipole-field stabilization of the rotational instability in a theta pinch. I
Authors: Ishimura T.
Published: March 2003

A theoretical analysis based on the magnetohydrodynamic approximation is carried out on the effect of multipole-field suppression of the rotational instabilities excited in a high-β plasma column. The multipole field is assumed not to penetrate into the plasma column but to exert magnetic pressure on its boundary surface in order to suppress the distortion of the plasma column. Analytical theory, which takes into account only the effects of the fundamental wave, gives the stability criterion for the n=2 mode as Bs≥Bs,c= 1/2 (m−1)−1/2rs‖Ω‖(μ0 ρ0)1/2, where rs, ρ0, and Ω are the radius, mass density, and rotational angular velocity of the plasma column, respectively, 2m the order of the multipole field, Bs the field strength at radius rs in the vacuum state, and μ0 the permeability of vacuum. Numerical calculations including the effects of the waves parasitic to the fundamental wave support the stability criterion for hexapole (m=3) and octopole (m=4) fields. For quadrupole (m=2) fields, it is shown that the stable range of Bs is limited between 0.841 Bs,c and 0.856 Bs,c, where Bs,c is the analytical threshold for m=2.
Evidence of parametric instabilities in second harmonic spectra from 1054 nm laser-produced plasmas
Authors: Tanaka K. , Seka W. , Goldman L. M. , Richardson M. C. , Short R. W. , Soures J. M. , Williams E. A.
Published: March 2003

Second harmonic spectra emitted from 1054 nm laser-produced plasmas have been observed in side- and backscattering and are shown to have angularly dependent, complex structures. Sidescattered spectra show regularly spaced (∼20 Å) Stokes components at intensities above 5×1013 W/cm2. The Stokes components are polarized and stronger in the plane of the polarization of the incident laser. These Stokes components are interpreted to be caused by a combination of electron plasma waves generated by the parametric decay instability and the subsequent electron decay instability. Backscattered spectra show additional finely spaced red-shifted satellites above 4×1014 W/cm2, indicative of the electron decay instability of plasmons generated from resonance absorption.
Time scales in turbulent channel flow
Authors: Alfredsson P. Henrik , Johansson Arne V.
Published: March 2003

Scaling laws for turbulent channel flow were studied, with emphasis on the near-wall region. The scaling behavior of power spectra and autocorrelations, as well as frequency of occurrence and duration of events detected with the variable-interval time-averaging (VITA) technique was investigated for Reynolds numbers ranging from 13 800 to 123 000 (based on centerline velocity and channel height). The governing time scale for the near wall region (of channel flow) was found to be a mixture (the geometric mean) of inner and outer time scales. This time scale collapsed data for different Reynolds numbers on, e.g., frequency of occurrence (cf. ‘‘bursting frequency’’) of VITA-events detected in the near-wall region. It is tentatively proposed that this behavior is due to interaction between the outer flow and the flow in the near-wall region.
Pseudosolitons formation in resonant absorption of electromagnetic waves
Authors: Serveniere-Heron A. Gourdin , Adam J. C.
Published: March 2003

The resonant absorption of electromagnetic waves in an inhomogeneous plasma is studied at low intensity. Both fluid and particle models confirm the formation of solitons predicted by the Zakharov equations. The effects on the absorption coefficient and hot electron production are considered.
Energy balance of the collisional tearing mode
Authors: Bondeson Anders , Sobel J. R.
Published: March 2003

The energy balance of the collisional tearing mode is examined within linear theory. It is found that in an asymmetric case the quadratic form given by Furth for the net release of magnetic energy must be completed with a term connected with the current gradient in the resistive layer. The growth-rate and the inner-layer solution are calculated in the limit where viscosity dominates over inertia. The amounts of energy going into Joule heating and either kinetic energy or viscous dissipation are calculated analytically. In the inertial regime 1/4 of the net decrease in magnetic energy goes into kinetic energy and (3)/(4) into Joule heating, while, in viscous regime, (1)/(6) goes into viscous dissipation and (5)/(6) into Joule heating. The analytical results, based on the constant-ψ approximation, are in good agreement with numerical simulations when the resistive layer is sufficiently narrow.
Nonlocal effects on the convective properties of the electrostatic current-driven ion-cyclotron instability
Authors: Ganguli G. , Bakshi P. , Palmadesso P.
Published: March 2003

Nonlocal effects due to magnetic shear and finite current channel width on the convective characteristics of the current-driven ion-cyclotron instability have been investigated. When the magnetic shear length (Ls) is smaller than the current channel width (Lc), the group velocity parallel to the external magnetic field at the origin (Vgz) vanishes, and there is a reduction in the group velocity perpendicular to the external magnetic field (Vgy). For Lc∼10−2 Ls the values of Vgz and Vgy as given by local theory are recovered. When Lc≲ρi, where ρi is the mean ion Larmor radius, both Vgz and Vgy change sign, indicating a reversal of the direction of propagation.
Stabilizing effects of a magnetic field gradient in a perpendicular shock wave on electron-cyclotron-drift instability
Authors: Zhou Y. M. , Li Y. Y. , Wu C. S.
Published: March 2003

It is shown that the magnetic-field gradient in a shock wave can result in a stabilizing effect on the electron-cyclotron-drift instability and consequently tends to reduce the growth rate significantly. The present discussion generalizes the earlier work of Sanderson and Priest who also considered similar problems.
Calculation of the poloidal ambipolar field in a stellarator and its effect on transport
Authors: Mynick Harry E.
Published: March 2003

The portion Φ1 of the ambipolar potential Φ which produces an electric field in the flux surfaces of a stellarator is self-consistently calculated, and its effect on stellarator transport at low collisionality is considered. The effect is small in a parameter δh, which is proportional to the square root of the ripple amplitude, εh. However, since δh can be an appreciable fraction of 1 for realistic parameters, the effect of Φ1 on transport can also be appreciable. Whether the effect is harmful or beneficial to confinement depends on the degree of pressure anisotropy and on the sign of p⊥−p∥.
Rayleigh–Taylor growth rate scaling for laser ablated plasmas
Authors: Manheimer Wallace M. , Colombant Denis G.
Published: March 2003

An approximate scaling law for the linear growth rate of the Rayleigh–Taylor instability of a laser ablatively accelerated fluid slab is given based on two-dimensional fluid simulations. It is shown that this scaling agrees with one obtained from recent theoretical analyses. This scaling law allows one to substantially reduce the dimensionality of the parameter space.
Computer simulation of critical velocity ionization
Authors: Machida Shinobu , Abe Takashi , Terasawa Toshio
Published: March 2003

The mechanism of critical velocity ionization is studied through electrostatic particle simulations which include a neutral-particle ionization process. It is shown that the rapid ionization of neutral particles takes place when the flow velocity of the neutral particles across a magnetic field exceeds a certain threshold. The mechanism is explained in terms of lower-hybrid wave excitation by a plasma instability, resultant electron energization, and neutral-particle ionization. It is found that the phase space relationship between the most unstable wave and the particles remains appropriate for the operation of the above process.
Kinetic theory of shear Alfvén waves
Authors: Mahajan S. M.
Published: March 2003

The addition of electron parallel dynamics in the description of an inhomogeneous current-carrying cylindrical plasma is shown to replace the magnetohydrodynamic continuum, associated with Alfvén waves, by a discrete spectrum. The spectrum of the resulting discrete modes is determined analytically and numerically.
Azimuthal ambipolar potential variations and tandem mirror transport
Authors: Lee X. S. , Myra J. R. , Catto P. J.
Published: March 2003

Azimuthal ambipolar potential variations are induced by the magnetic drifts in a qlodrupole tandem mirror. Consequently, radial E×B drifts occur and contribute along with the magnetic drifts to the total radial flux in a collisional plasma. This effect is studied self-consistently in the resonant-plateau regime assuming Maxwell–Boltzmann electrons along the field lines. A general form exhibiting the contribution of the E×B drifts to the flux is obtained and shown, in general, to be significant. In the square-well limit a particularly transparent form results which illustrates the role of dielectric shielding. When the azimuthal E×B drift and the azimuthal electron diamagnetic drift are equal and in opposite directions, the shielding becomes small and a large induced ambipolar contribution to the flux can occur.
Stability of mirrors with inverted pressure profiles
Authors: D’Ippolito D. A. , Myra J. R.
Published: March 2003

The stability of an axisymmetric tandem mirror with an inverted (or hollow) pressure profile is treated within the framework of scalar-pressure, ideal magnetohydrodynamics. A two-surface sharp-boundary model is formulated to describe the low-m ballooning stability of the annular plasma in the paraxial limit. Included in the analysis are the stabilizing effects of an externally applied force, such as the rf-induced ponderomotive force, and of a perfectly conducting lateral wall. It is shown that there is a stability boundary associated with each of these effects. In critical ranges of the plasma’s annular thickness, the rf intensity and the wall position, the stability regions merge giving complete stability at all values of the plasma pressure.
Magnetic field errors in bumpy torus configurations
Authors: Hazeltine R. D. , Catto P. J.
Published: March 2003

The effects of magnetic field errors in a bumpy torus confinement devices are studied. The analysis relies on large-aspect-ratio and near-axis approximations, but includes toroidal effects and allows for any shape of the magnetic field bumps. The main features of the present results agree with those of previous numerical studies. However, the analysis of field line trajectories can be made surprisingly explicit and reveals some features which have not been anticipated.
Collisional transport of momentum in axisymmetric configurations
Authors: Hogan John T.
Published: March 2003

Calculations of the cross-field transport of toroidal momentum are presented for the collision-dominated regime in devices with an axisymmetric magnetic configuration. Intended as a point of reference for more complex calculations of transport in the low collision frequency regime, the development treats the case of pure toroidal flow and closely parallels previous calculations of collisional thermal conductivity in tokamaks. Certain counter-intuitive features of previous fluid-regime calculations of momentum diffusion are removed, and the contribution of viscous heating to the ion energy balance is discussed. A relation between internal disruptions (sawtooth oscillations) and momentum transport is proposed.
Stability of laminar electron layers
Authors: Chernin D. , Lau Y. Y.
Published: March 2003

The stability of a finite thickness, laminar cylindrical shell of electrons rotating azimuthally and enclosed in a coaxial waveguide is considered. The equilibrium rotation of the electrons is supported either by a radial electric field, an axial magnetic field, or a combination of both. The stability problem is formulated exactly as an eigenvalue problem, including all relativistic and electromagnetic effects as well as all effects of self and applied equilibrium fields. An approximate dispersion relation, valid for thin beams, is obtained analytically and the classical results for the ‘‘longitudinal’’ modes, i.e., the negative mass, cyclotron maser, and diocotron instabilities and for the ‘‘transverse’’ mode are recovered in appropriate limits. The dispersion relation is relatively simple and is valid for arbitrary values of the equilibrium electric and magnetic fields and for arbitrary beam energy. It therefore provides a ready comparison of the small signal properties of such devices as the Astron, gyrotron, orbitron, heliotron and the various cross field devices. It may also be of interest in accelerator and space physics applications. Some heretofore unnoticed effects on beam stability of equilibrium fields are reported; one such effect in particular leads to formulation of a simple, effective method either to maximize or eliminate altogether the longitudinal mode growth. Results from the dispersion relation compare favorably to results obtained from a numerical solution of the eigenvalue problem.
Macroscopic extraordinary-mode stability properties of relativistic non-neutral electron flow in a planar diode with applied magnetic field
Authors: Davidson Ronald C. , Tsang Kang , Swegle John A.
Published: March 2003

Extraordinary-mode stability properties of relativistic non-neutral electron flow in a planar diode with applied magnetic field are investigated within the framework of the macroscopic cold-fluid-Maxwell equations. The eigenvalue equation is derived for flute perturbations (kz=0) about the general class of relativistic planar equilibria characterized by electron density profile n0b(x), sheared velocity profile V0y(x) =−cE0x(x)/B0z(x), and relativistic mass factor γ0b(x) =[1−E02x(x)/B02z(s)]−1/2. The full influence of equilibrium self-electric and self-magnetic fields is retained in the analysis, and the cathode is located at x=0 and the anode at x=d. The exact eigenvalue equation is simplified for low-frequency perturbations in the guiding-center limit of strongly magnetized electrons with m→0. In this regime, it is shown that (∂/∂x)[n0b(x)/γ0b(x)]≤0 over the interval 0≤x≤d is a sufficient condition for stability of the relativistic electron flow to extraordinary-mode perturbations. A specific example of stable oscillations [rectangular profile for n0b(x)/γ0b(x)] is analyzed in detail. Finally, the exact eigenvalue equation is solved numerically for a wide range of electron density corresponding to weak and strong instability driven by velocity shear with ∂V0y/∂x≠0.
Harmonic generation and parametric decay in the ion-cyclotron frequency range
Authors: Skiff F. , Wong K. L. , Ono M.
Published: March 2003

Harmonic generation and parametric decay are examined in a toroidal ACT-1 plasma using electrostatic plate antennas. The harmonic generation, which is consistent with sheath rectification, is sufficiently strong that the nonlinearly generated harmonic modes themselves decay parametrically. Resonant and nonresonant parametric decay of the second harmonic are observed and compared with uniform pump theory. Resonant decay of lower-hybrid waves into lower-hybrid waves and slow ion-cyclotron waves is seen for the first time. Surprisingly, the decay processes are nonlinearly saturated, indicating absolute instability.
A bumpy-torus betatron
Authors: Chernin D. , Mondelli A. , Roberson C.
Published: March 2003

The combination of a bumpy-torus field and a conventional betatron field leads to an interesting strongly focused, high-current accelerator configuration. The question of orbital stability of a test particle in such a device is discussed and it is shown that the alternating gradient focusing in this accelerator can easily lead to greater than 20% bandwidth in allowed mismatch between the vertical magnetic field and the average beam particle energy.
The boundary layer on an impulsively started rotating and translating cylinder
Authors: Ece M. C. , Walker J. D. A. , Doligalski T. L.
Published: March 2003

The time-dependent boundary-layer flow past an impulsively started translating and rotating circular cylinder is investigated. Two different solution methods are used to calculate the initial flow development; these are an expansion of the solution in a power series in time after the impulsive start and a fully numerical integration of the governing equations. Both solution methods are in excellent agreement during the initial stages of the motion. Calculations are carried out for various rotational speeds of the cylinder and in the boundary-layer limit of infinitely large Reynolds number. The results show a wide variety of unusual and complex boundary layer separation flow patterns; it is demonstrated how separation is affected by increasing rotation rates and further how it is ultimately completely suppressed by the rotation. This problem involves both an upstream and downstream moving wall for the boundary layer flow and consequently is of interest in connection with the Moore–Rott–Sears criterion for unsteady separation; the present results suggest the criterion for both the upstream moving wall and the downstream moving wall will be achieved in these flows.
Role ofMannheimia haemolyticaleukotoxin in the pathogenesis of bovine pneumonic pasteurellosis
Authors: Jeyaseelan Samithamby , Sreevatsan Srinand , Maheswaran Samuel K.
Published: March 2003

Bovine pneumonic pasteurellosis continues to be a major respiratory disease in feedlot cattle despite the recent advances in our understanding of the underlying complexities of causation. The etiological agent,Mannheimia haemolytica, possesses several virulence factors, including capsule, outer membrane proteins, adhesins, neuraminidase, endotoxin and exotoxic leukotoxin. Accumulating scientific evidence implicates leukotoxin as the primary factor contributing to clinical presentation and lung injury associated with this disease. Unlike other virulence factors, leukotoxin shows cell-type- and species-specific effects on bovine leukocytes. Recent investigations have delineated the mechanisms underlying the target-cell-specificity of leukotoxin and how this contributes to the pathogenesis of lung damage. This review summarizes current understanding of the secretion, regulation, mechanisms of action and evolutionary diversity of leukotoxin ofM. haemolytica. Understanding the precise molecular mechanisms of leukotoxin is critical for the development of more effective prophylactic and therapeutic strategies to control this complex disease.
Characterization of avian metapneumoviruses isolated in the USA
Authors: Lwamba Humphrey C. M. , Bennett Richard S. , Lauer Dale C. , Halvorson David A. , Kariuki Njenga M.
Published: March 2003

Avian pneumovirus (APV; officially known as turkey rhinotracheitis virus) is an emergent pathogen of birds in the USA that results in upper respiratory tract disease in turkeys. Six years after the first outbreak in the USA, the disease continues to ravage turkey flocks, primarily in the state of Minnesota. From 1997 to 2000, the industry recorded losses estimated at US$15 million per annum. Researchers have developed sensitive diagnostic techniques, including the enzyme-linked immunosorbent assay and the reverse transcriptase–polymerase chain reaction, which, when used together, are highly sensitive in detecting APV outbreaks in commercial turkey flocks. Phylogenetic analysis of the nucleotide and predicted amino acid sequence of 15 US viruses isolated between 1996 and 2000 demonstrated that the US viruses are relatively homogenous but different from the European APV subgroups A and B, resulting in the classification of US isolates into subgroup C. Infectious APV was isolated from sentinel waterfowls placed close to an infected commercial turkey farm and from wild Canada geese captured in Minnesota, suggesting that free-ranging birds may be involved in the spread of APV. Current efforts to prevent and control the infection include improving management and biosecurity practices and developing attenuated live and deletion mutant vaccines capable of conferring protection.
EnterohemorrhagicEscherichia coliO157: epidemiology and ecology in bovine production environments
Authors: Renter David G. , Sargeant Jan M.
Published: March 2003

EnterohemorrhagicEscherichia coli, particularly the O157(:H7) serogroup, has become a worldwide public health concern. Since cattle feces are often implicated as the source ofE. coliO157 in human infections, considerable resources have been devoted to defining the epidemiology and ecology ofE. coliO157 in cattle environments so that control might begin at the farm level. Diagnostic limitations and the complexity of often interrelated microbial, animal, herd, environmental and production factors have hindered the determination of the epidemiology, ecology and subsequent farm-level control ofE. coliO157. The widespread distribution ofE. coliO157, the transitory nature of fecal shedding, multiple potential environmental sources, lack of species specificity, and age-, feed- and time-related differences in cattle prevalence are documented. However, the significance and/or role of these factors in the epidemiology and ecology ofE. coliO157 is still unclear. Cattle are a major source ofE. coliO157, but it may be simplistic to believe that most herds are relatively closed systems with small percentages of cattle serving as true reservoirs. Practical on-farm control may require explicit definitions of the seemingly complex system(s) and the microbial, animal, herd, environmental and production factors involved in the multiplication, maintenance and transmission ofE. coliO157.
Optimized simulation of the control of tsetse flies Glossina pallidipes and G. m. morsitans (Diptera: Glossinidae) using odour-baited targets in Zimbabwe
Authors: Hargrove J.W.
Published: March 2003

In 1984–1985 insecticide-treated targets were deployed in the 600-km2 Rifa Triangle, Zambezi Valley, Zimbabwe. Trap catches of Glossina pallidipes Austen were modelled using a function combining logistic growth with diffusive movement. A simulation routine was linked to a non-linear least-squares optimization programme and fits optimized with respect to population carrying capacities, rates of growth and movement, and to levels of imposed mortality. In March–September 1984, the overall additional mortality was 2% per day of adult female G. pallidipes, increasing thereafter to 8% per day, due to the deployment of more targets, the onset of the hot, dry season and the ground-spraying of the adjoining Zambezi escarpment with DDT. For G. m. morsitans Westwood the corresponding estimates were 1 and 2% per day. For both species, the deployment of four targets km−2 in a closed population will ensure eradication. For G. m. morsitans a halving of target efficacy would reduce the killing rate to the point where eradication would be unlikely. Estimated daily displacements were c. 200 m for G. m. morsitans and 660 m for G. pallidipes. The lower rate for G. m. morsitans means that, while targets kill this species less effectively, re-invasion of cleared areas is slower. Targets do not markedly affect robust populations outside the deployment area. The Zambian tsetse population adjacent to the Rifa Triangle declined markedly during the experiment, however, suggesting that it is largely maintained by immigration. The methods developed here will be applied to data from other campaigns with the aim of improving the efficiency of tsetse control programmes.
Biological characteristics of the mirids Macrolophus costalis and Macrolophus pygmaeus preying on the tobacco form of Myzus persicae (Hemiptera: Aphididae)
Authors: Margaritopoulos J.T. , Tsitsipis J.A. , Perdikis D.C.
Published: March 2003

Biological and population parameters of the predatory bugs Macrolophus costalis Fieber and Macrolophus pygmaeus Rambur preying on the tobacco aphid Myzus persicae (Sulzer) were examined. Tobacco was used as host plant and all experiments were carried out at 23°C and L16:D8. In M. costalis, the developmental time for eggs and the total duration of nymphal instars was 13.1 and 22.2 days and in M. pygmaeus 13.0 and 20.2 days, respectively. Both species completed their nymphal development feeding only on plant juices although they required significantly more time to attain adulthood than when feeding on prey. The longevity of M. costalis females and the preoviposition period were 49.9 and 5.6 days and those of M. pygmaeus were 50.3 and 6.3 days, respectively. Adult males showed a higher longevity than females in both species. The intrinsic rate of increase and the mean total number of eggs laid were 0.0644 and 121 in M. costalis and 0.0615 and 104 in M. pygmaeus, respectively. Mean total aphid consumption by nymphs of M. costalis was 61 aphids, about twice that of M. pygmaeus (37 aphids). Total aphid consumption by a male and female pair of M. costalis and M. pygmaeus until the death of the female was 244 and 285 aphids, respectively. The results of the study are discussed in relation to the impact of the two predatory bugs on tobacco aphid populations.
Differential parasitism of Plutella xylostella (Lepidoptera: Plutellidae) larvae by the parasitoid Cotesia plutellae (Hymenoptera: Braconidae) on two host plant species
Authors: Liu Shu-sheng , Jiang Li-hui
Published: March 2003

Laboratory experiments were conducted to examine host selection by Cotesia plutellae Kurdjumov when larvae of its host, Plutella xylostella (Linnaeus), fed on Chinese cabbage, Brassica campestris L. ssp. pekinensis and those fed on common cabbage, Brassica oleracea L. var. capitata were provided simultaneously, and to investigate the roles of plant and host volatiles in mediating host selection. When C. plutellae were provided with equal numbers of host larvae on plants of the two species in one arena, the parasitoid parasitized 4- to 15-fold more host larvae on Chinese cabbage than on common cabbage. This preference changed little with host density. However, an experience of searching coupled with an oviposition in a host larva on a leaf of the less-preferred plant, common cabbage, significantly increased the preference for parasitizing host larvae on this plant and resulted in twice as many host larvae parasitized on this plant than on Chinese cabbage. Dual choice tests with a Y-tube olfactometer showed that plant volatiles from Chinese cabbage were more attractive to female C. plutellae than those from common cabbage when plants of both species were either intact or infested. In parallel to the increased parasitism on common cabbage following experience, oviposition in a host larva on this less-preferred plant significantly increased the response to volatiles emanating from that plant. These results indicate that host plants may strongly influence the foraging behaviour of C. plutellae, but their differential attractiveness to the parasitoid may be altered by experience of the parasitoid.
Techniques for dissecting adult aleocharine beetles (Coleoptera: Staphylinidae)
Authors: Hanley R.S. , Ashe J.S.
Published: March 2003

Methodology for detailed dissections of the phylogenetically most informative structures from adult aleocharine staphylinid beetles is provided. These methods include specimen preparation, relaxation, clearing, bleaching, dehydration and full dissection. A detailed summary of mouthpart and male and female genitalic dissections is provided. Recently described character systems, including those of the mouthparts and the thoracic regions, have been successfully used in phylogenetic studies of aleocharine staphylinids. This paper provides the first thorough description of the techniques necessary to reveal these character systems.
European monitoring of resistance to insecticides in Myzus persicae and Aphis gossypii (Hemiptera: Aphididae) with special reference to imidacloprid
Authors: Nauen R. , Elbert A.
Published: March 2003

The susceptibility to several insecticides of 16 and 8 strains of Myzus persicae Sulzer and Aphis gossypii Glover, respectively, received from different European countries in 2001 was investigated. Most of the strains were derived from places known for their aphid resistance problems to conventional insecticides before imidacloprid was introduced. In many regions and agronomic cropping systems imidacloprid has been an essential part of aphid control strategies for a decade, and therefore the susceptibility of aphid populations to imidacloprid using FAO-dip tests and diagnostic concentrations in a leaf-dip bioassay was checked. Additional insecticides tested were cyfluthrin (chemical class: pyrethroid), pirimicarb (carbamate), methamidophos and oxydemeton-methyl (organophosphates). Diagnostic concentrations (LC99-values of reference strains) for each insecticide were established by dose response analysis using a new leaf-disc dip bioassay format in 6-well tissue culture plates. Virtually no resistance to imidacloprid in any of the field-derived populations of M. persicae and A. gossypii was detected. In contrast, strong resistance was found to pirimicarb and oxydemeton-methyl, and to a lesser extent also to cyfluthrin. Two strains of A. gossypii exhibited reduced susceptibility to imidacloprid when tested directly after collection. However, after maintaining them for six weeks in the laboratory, the aphids were as susceptible as the reference strain. The diagnostic concentration of methamidophos did not reveal any resistance in M. persicae, but did so in four strains of A. gossypii.
Enrichment of a single clone from a high diversity library of phage-displayed antibodies by panning with Anopheles gambiae (Diptera: Culicidae) midgut homogenate
Authors: Killeen G.F. , Foy B.D. , Frohn R.H. , Impoinvil D. , Williams A. , Beier J.C.
Published: March 2003

A high diversity library of recombinant human antibodies was selected on complex antigen mixtures from midguts of female Anopheles gambiae Giles. The library of phage-displayed single chain variable region fragment constructs, derived from β-lymphocyte mRNA of naïve human donors, was repeatedly selected and reamplified on the insoluble fraction of midgut homogenates. Five rounds of panning yielded only one midgut-specific clone, which predominated the resulting antibody panel. In A. gambiae, the epitope was found throughout the tissues of females but was absent from the midgut of males. The cognate antigen proved to be detergent soluble but very sensitive to denaturation and could not be isolated or identified by Western blot of native electrophoresis gels or by immunoprecipitation. Nevertheless, immunohistology revealed that this sex-specific epitope is associated with the lumenal side of the midgut. Severe bottlenecking may limit the utility of phage display selection from naïve libraries for generating diverse panels of antibodies against complex mixtures of antigens from insect tissues. These results suggest that the selection of sufficiently diverse antibody panels, from which mosquitocidal or malaria transmission-blocking antibodies can be isolated, may require improved selection methods or specifically enriched pre-immunized libraries.
The stable core and dynamic periphery in top management teams
Authors: Roberto Michael A.
Published: March 2003

This study explores how top management teams make strategic decisions. The findings indicate that the top management team performs a variety of monitoring and control functions within most firms, but that a single team with stable composition does not make strategic choices in most organizations. Instead, different groups, with members from multiple organizational levels, form to make various strategic decisions. A stable subset of the top team forms the core of each of these multiple decision‐making bodies. The findings offer a possible explanation for inconsistent findings in the top management team literature, and suggest several new directions for future senior team research.
Pre‐alliance planning: development of an information system infrastructure to support strategic alliance activities
Authors: Mandal Purnendu , Love Peter E.D. , Irani Zahir
Published: March 2003

Traditional business models are undergoing a process of redefinition following the drive to develop new business structures that support competition. The result of this has led to the development of virtual organizations, which are founded on alliance structures. In this paper a case study is used to describe the way in which a telecommunications organization and other retail electricity organizations initiated a strategic alliance, so that they could improve their market position, financial stability and customer base. A case study is used to describe the way in which a telecommunications organization explored how a strategic alliance with retail electricity organizations would be structured. Pre‐alliance activities and its impact on alliance formation, such as the design of an information systems framework, are presented and discussed. The experiences identified from the case study provide a learning opportunity for those organizations that are seeking to seize new business opportunities through strategic alliances.
First mover advantages in emerging economies: a discussion
Authors: Rahman Zillur , Bhattacharyya S.K.
Published: March 2003

It is essential for a firm to create and capture value to justify its existence in competitive settings. In this context, first mover advantages in an emerging economy constitute an important topic of research in management because the order of entry of a firm to a new market influences its ability to create and capture value. Performances of the firms in an emerging economy like India suggest that a first moving firm enjoys several differential advantages. However there are certain market imperatives that the firm must address to derive sustainable competitive advantage.
P/OM and societal development: a historical perspective
Authors: Mansour Ali H.
Published: March 2003

This research paper delineates and analyzes the relationship between production and operations management and the development of society. An attempt is made to take the reader into a historical journey whereby events and contributions to the field are not only listed and described but also analyzed with regard to their impact on societal development through time.
Customer satisfaction: the historical perspective
Authors: Reis Dayr , Pena Leticia , Lopes Paulo A.
Published: March 2003

Successful firms are making a concerted effort to develop closer ties to their customers. However, the customer has not always been king. By describing the dialectic character of customer service and tracing it back in history, this paper provides some of the knowledge necessary to explain its present status and predict its future course.
Leadership development for learning organizations
Authors: Prewitt Vana
Published: March 2003

While discussions of the learning organization (LO) often center on nuances of its definition and application, little attention has been given to the role that organizational leaders play in fostering goals of becoming an LO. Varied research indicates that leaders may play the single most important role in determining the success or failure of LO efforts, with trust, modeled behaviors, and positive reinforcement critical to gaining worker acceptance and support. This paper recommends that, to improve chances of success, organizations should first attend to developing learning leaders before implementing any LO efforts.
Linking organisational learning to organisational performance and success: Singapore case studies
Authors: Yeo Roland
Published: March 2003

This paper addresses the development of organisational learning, which involves various groups of people and different stages. It further explores the link between organisational learning and performance outcomes, providing an insight into the various interpretations of organisational success associated with learning. The study was conducted through in‐depth interviews and data were collected from four Singapore organisations from the private and public sectors. Data were subsequently analysed using qualitative techniques of content analysis, particularly within‐case analysis, cross‐case analysis, matrix displays and pattern matching. Findings addressed most of these issues adequately but revealed that there were several aspects on the linkage between learning and performance that had not been mentioned in the literature. The main contribution of this theory‐building study is the development of an empirically confirmed, theoretical and practical model of the influences of organisational learning on organisational performance and success.
Surface and deep approaches to business ethics
Authors: Fisher Josie
Published: March 2003

Despite the attention being paid to business ethics, it seems the behaviour of business leaders and employees has not improved. This paper takes a different approach to understanding why this is the case. A distinction made in the higher education literature between surface and deep approaches to learning is adapted to provide an insight into the reason for the difference between the rhetoric concerning ethics and actual business practice. It is argued that a surface approach to ethics, which is associated with self‐interest, will not promote ethical behaviour, while a deep approach, motivated by the desire to do the right thing, does have the potential to do so. The difference between the rhetoric and business practice suggests that most businesses either intentionally or unintentionally adopt a surface approach to ethics.
Ghosts in the machine: people and organisation level issues in distributed digital libraries
Authors: Nicholson Dennis
Published: March 2003

This article deals with people and organisation level issues in distributed digital libraries, and in the process introduces the range of topics relevant to this new column and the involvement of the author in projects dealing with these topics. User issues are not covered.
Franz Reuleaux: Contributions to 19th century kinematics and theory of machines
Authors: Moon Francis C
Published: March 2003

This review surveys late 19th century kinematics and the theory of machines as seen through the contributions of the German engineering scientist, Franz Reuleaux (1829–1905), often called the “Father of Kinematics.” Extremely famous in his time and one of the first honorary members of ASME, Reuleaux was largely forgotten in much of modern mechanics literature in English until the recent rediscovery of some of his work. In addition to his contributions to kinematics, we review Reuleaux’s ideas about design synthesis, optimization and aesthetics in design, and in engineering education, as well as his early contributions to biomechanics. A unique aspect of this review has been the use of Reuleaux’s kinematic models at Cornell University and in the Deutsches Museum, in Munich, as a tool to rediscover lost engineering and kinematic knowledge of 19th century history of machines. This review article cites 108 references.
Nonlinear Numerical Analysis in Transient Cutting Tool Temperatures
Authors: Jen Tien-Chien , Eapen Sunil , Gutierrez Gustavo
Published: March 2003

In any cutting processes, the temperature distribution in the cutting tool is intrinsically three-dimensional and very steep temperature gradient can be generated in the vicinity of the tool-chip interface. In this region, where the maximum temperature occurs, the effect of temperature dependent thermal properties may become important. The full three-dimensional nonlinear transient heat conduction equation is solved numerically using a control volume approach to study these nonlinear effects on cutting tool temperatures. The extremely small size of the heat input zone (tool-chip interface), relative to the tool insert rake surface area, requires the mesh to be dense enough in order to obtain accurate solutions. This usually requires very intensive computational efforts. Due to the size of the discretized domain, an optimized algorithm is used in the solution of the problem to significantly reduce the required computing time. This numerical model can be used for process development in an industrial setting. The effect of two different heat flux input profiles, a spatially uniform plane heat flux and a spatially nonuniform parabolic heat flux at the tool-chip interface, on the tool temperatures are also investigated in the present study. Some recommendations are given regarding the condition when these nonlinear effects cannot be ignored.
Autonomously Generative CMM Part Programming for In-Process Inspection
Authors: Liu Jiancheng , Ng Hung , Yamazaki Kazuo , Nakanishi Kazuo
Published: March 2003

This paper presents an in-process inspection-oriented autonomously generative CMM (Coordinate Measuring Machine) part programming methodology with a simplified part programming process to decrease the time and skill for CMM part programming. The proposed method differs from the CAD-based CMM programming approach. Using this new method, machining features in a complex part can be efficiently inspected after any stage of machining operations or after machining these features. The concept of the proposed CMM part programming approach and its implementation are described in this paper. The results obtained from the feasibility study show the developed CMM part programming system can autonomously generate an inspection plan for a work-in-progress part model generated from NC programs to realize the in-process measurement.
Modeling and Closed-Loop Control of Stretch Bending of Aluminum Rectangular Tubes
Authors: Zhu Hong , Stelson Kim A.
Published: March 2003

During stretch bending, considerable springback will occur after a tube has been plastically bent. To predict the springback, a simplified two-flange model for stretch bending of a rectangular tube has been developed in which the strain history has been considered. A comparison has been made between the springback predicted by this model and experimental data, which shows rough agreement. Based on this model, a real time closed-loop control algorithm is developed.