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Objectives To report the outcomes and complications of a cohort of dogs with primary and recurrent anal sac adenocarcinoma managed with surgery as the first-line treatment. To report the use of lymph node cytology for identification of metastatic disease. Methods Retrospective review of case records of a single referral centre population of dogs diagnosed with anal sac adenocarcinoma. Results Fifty-two clinical cases were identified. Altered ultrasonographic appearance of lymph nodes was highly consistent with metastatic disease as assessed by cytology and histopathology. Seven of 58 (12%) perineal surgeries had reported minor complications and seven (12%) others required further surgical intervention. Minor controllable intraoperative bleeding was the only complication noted associated with lymph node extirpation in two of 39 (5%) metastectomy procedures. Six dogs (12%) suffered local recurrence and 22 (42%) developed subsequent or recurrent nodal metastatic disease. From the time of detection of disease recurrence, median additional survival associated with a second surgical intervention was 283 days. Clinical Significance Coeliotomy for lymph node metastatectomy in dogs with adenocarcinoma of the anal sac has low morbidity and should be considered in patients presenting with evidence of regional metastatic disease both at initial presentation and with recurrent disease.

Objectives To report the short- and long-term complications and clinical outcomes of a cohort of dogs managed for gastric dilatation-volvulus using a modified right-sided tube gastropexy technique. Materials and methods Retrospective case series. Results Of 31 dogs treated, 29 (93·5%) had an excellent short-term outcome, and gastric dilatation-volvulus did not recur in any dog. Twenty-six dogs (84%) were initially fed via the gastrostomy tube postoperatively; three (9·7%) suffered a major complication including septic peritonitis (n=1), and premature tube removal (n=2). Fourteen dogs (45·1%) had minor complications including mild, self-limiting discharge from the stoma site in 13. Clinical significance Modified tube gastropexy using a mushroom-tipped silicone catheter is an effective and safe surgical method for the management of gastric dilatation-volvulus. The gastrostomy tube allowed early enteral feeding and easy administration of medications, including gastroprotectants.

OBJECTIVES To report short-term radiographic and clinical outcome and complications following tibial plateau levelling osteotomy for the treatment of cranial cruciate ligament insufficiency in dogs less than 18·1 kg with tibial plateau angle greater than 35° using anatomically contoured six-hole locking compression plates. METHODS Retrospective data were collected on: preoperative, postoperative and follow-up tibial plateau angles, plateau segment rotation, tibial tuberosity width and length of the cranial aspect of tibial tuberosity segment from the patellar tendon insertion and rotation of the tibial plateau below the level of the insertion of the patellar ligament. RESULTS In 26 small dogs (29 stifles in total), mean preoperative, postoperative and follow-up tibial plateau angles were 38·2°, 4·8°, and 4·4°, respectively. Documented postoperative complications were limited to patellar tendinopathy in a single case (3·4%) and tibial tuberosity or fibula fracture were not observed. CLINICAL SIGNIFICANCE Short-term radiographic and clinical outcome of tibial plateau levelling osteotomy stabilised with anatomically contoured six-hole locking compression plates for the treatment of small dogs with large tibial plateau angle suggests a very low risk of complications. Rotation beyond the “safe point” is necessary to perform full rotation in some cases, but does not appear to incur an increased risk of tibial tuberosity fracture.

SummaryObjective: To compare complication rates and the outcomes of these complications after lateral plate fixation with figure-ofeight tension-band-wire and pin or lag screw fixation for arthrodesis of the calcaneoquartal joint, following non-traumatic disruption of the plantar tarsal ligament in dogs.Methods: Data were collected retrospectively from five UK referral centres. Diplomate specialists and their residents performed all procedures. Referring veterinarians were contacted for long-term follow-up.Results: Seventy-four procedures were undertaken in 61 dogs. There were 58 arthrodeses in the lateral plate group (Plate), nine in the pin and tension-band-wire group (Pin), and seven in the lag screw and tension-band wire-group (Screw). Compared to Plate (17%), further surgical intervention was required more frequently following Pin (56%, OR = 3.2) or Screw (43%, OR = 2.5) fixation. Clinical failure of arthrodesis occurred less frequently with Plate (5%) compared with Screw (43%, OR = 8.6) and Pin fixation (22%, OR = 4.4). Cases managed with external coaptation postoperatively were more likely to suffer from postoperative complications (OR = 2.2).Clinical significance: Lateral plating was associated with fewer postoperative complications than pin and tension-band-wire fixation for arthrodesis of the calcaneoquartal joint in dogs with non-traumatic disruption of the plantar tarsal ligament.

We describe the extension of the recent charge- and energy-conserving one-dimensional electrostatic particle-in-cell algorithm in Ref. [G. Chen, L. Chacon, D.C. Barnes, An energy- and charge-conserving, implicit electrostatic particle-in-cell algorithm, Journal of Computational Physics 230 (2011) 7018-7036] to mapped (body-fitted) computational meshes. The approach maintains exact charge and energy conservation properties. Key to the algorithm is a hybrid push, where particle positions are updated in logical space, while velocities are updated in physical space. The effectiveness of the approach is demonstrated with a challenging numerical test case, the ion acoustic shock wave. The generalization of the approach to multiple dimensions is outlined.

To review a large series of dogs referred for treatment of traumatic impalement injuries to the thorax and/or abdomen and to report aetiologies, injury characteristics, management and long-term outcomes.Previously collected data on dogs that were surgically treated for impalement injuries to the trunk at six veterinary specialist referral institutions in the UK over an 11-year period were reviewed. Data included patient signalment, physiological variables, injury-specific variables, diagnostic imaging reports, surgical procedures undertaken, duration of hospitalisation, antibiotic use, complications and outcomes. Data were reported with summary statistics.Fifty-four dogs were included. Impalement occurred most frequently on wooden objects (n=34), and the thoracic cavity was most commonly penetrated (n=37). Computed tomography was sensitive and specific to identifying wooden material in 64% and 88% of cases (n=11), respectively. Thoracotomy was performed in 56%, coeliotomy in 20% and a foreign body or its fragments were retrieved during surgery in 37% of the cases. Complications occurred in 19 dogs (35%), and of these, 68% were minor and 32% major. The survival rate for thoracotomy cases was 93% (n=30). Overall long-term survival was 90%.Despite the often dramatic presentation of impalement injuries, the majority of patients treated in the specialist referral setting can achieve excellent outcomes. These injuries require thorough diagnostic imaging and interpretation before adequate surgical exploration and management, augmented by anaesthesia and critical care during the peri- and postoperative periods; therefore stable patients should be referred to centres able to provide this type of care.

To report the short- and long-term complications and clinical outcomes of a cohort of dogs managed for gastric dilatation-volvulus using a modified right-sided tube gastropexy technique.Retrospective case series.Of 31 dogs treated, 29 (93·5%) had an excellent short-term outcome, and gastric dilatation-volvulus did not recur in any dog. Twenty-six dogs (84%) were initially fed via the gastrostomy tube postoperatively; three (9·7%) suffered a major complication including septic peritonitis (n=1), and premature tube removal (n=2). Fourteen dogs (45·1%) had minor complications including mild, self-limiting discharge from the stoma site in 13.Modified tube gastropexy using a mushroom-tipped silicone catheter is an effective and safe surgical method for the management of gastric dilatation-volvulus. The gastrostomy tube allowed early enteral feeding and easy administration of medications, including gastroprotectants.

To report the outcomes and complications of a cohort of dogs with primary and recurrent anal sac adenocarcinoma managed with surgery as the first-line treatment. To report the use of lymph node cytology for identification of metastatic disease.Retrospective review of case records of a single referral centre population of dogs diagnosed with anal sac adenocarcinoma.Fifty-two clinical cases were identified. Altered ultrasonographic appearance of lymph nodes was highly consistent with metastatic disease as assessed by cytology and histopathology. Seven of 58 (12%) perineal surgeries had reported minor complications and seven (12%) others required further surgical intervention. Minor controllable intraoperative bleeding was the only complication noted associated with lymph node extirpation in two of 39 (5%) metastectomy procedures. Six dogs (12%) suffered local recurrence and 22 (42%) developed subsequent or recurrent nodal metastatic disease. From the time of detection of disease recurrence, median additional survival associated with a second surgical intervention was 283 days.Coeliotomy for lymph node metastatectomy in dogs with adenocarcinoma of the anal sac has low morbidity and should be considered in patients presenting with evidence of regional metastatic disease both at initial presentation and with recurrent disease.

To report short-term radiographic and clinical outcome and complications following tibial plateau levelling osteotomy for the treatment of cranial cruciate ligament insufficiency in dogs less than 18·1 kg with tibial plateau angle greater than 35° using anatomically contoured six-hole locking compression plates.Retrospective data were collected on: preoperative, postoperative and follow-up tibial plateau angles, plateau segment rotation, tibial tuberosity width and length of the cranial aspect of tibial tuberosity segment from the patellar tendon insertion and rotation of the tibial plateau below the level of the insertion of the patellar ligament.In 26 small dogs (29 stifles in total), mean preoperative, postoperative and follow-up tibial plateau angles were 38·2°, 4·8°, and 4·4°, respectively. Documented postoperative complications were limited to patellar tendinopathy in a single case (3·4%) and tibial tuberosity or fibula fracture were not observed.Short-term radiographic and clinical outcome of tibial plateau levelling osteotomy stabilised with anatomically contoured six-hole locking compression plates for the treatment of small dogs with large tibial plateau angle suggests a very low risk of complications. Rotation beyond the "safe point" is necessary to perform full rotation in some cases, but does not appear to incur an increased risk of tibial tuberosity fracture.

The recently formed Plasma Science and Innovation Center (PSI-Center) is refining the NIMROD code to simulate field-reversed configurations (FRCs). The NIMROD code can resolve highly anisotropic heat conduction and viscosity. This, combined with its ability to include two-fluid effects, allows us to capture more detailed physics than previous calculations. Some initial simulations are focused on 2D (n = 0 only) non-linear two-fluid simulations. We present initial validations of a translating FRC and note good conservation of density and magnetic flux. As a validation of the effects of anisotropic thermal conduction, we present a comparison of an FRC with standard thermal transport to one with anisotropic conduction. Two-fluid simulations are shown which produce significant spin-up due to the end-shorting boundary condition. Finally, simulations of the tilt instability are presented, which show that Hall physics significantly retards, but does not eliminate the growth rate.

Peak performance for magnetically confined fusion plasmas occurs near thresholds of instability for macroscopic modes that distort and possibly disrupt equilibrium conditions. In some cases, however, the best approach is to exceed stability thresholds and rely upon nonlinear saturation effects. Understanding this behaviour is essential for achieving ignition in future burning plasma experiments, and advances in large-scale numerical simulation have an important role. High-order finite elements permit accurate representation of extreme anisotropies associated with the magnetic field, and a new implicit algorithm has been developed for advancing the two-fluid model. Implementation of parallel direct methods for solving the sparse matrices makes the approach practical. The resulting performance improvements are presently being applied to investigate the evolution of 'edge localized modes' including important drift effects.

The bounce-kinetic model is developed and applied to driven nonlinear Langmuir waves. The waves are described in terms of an eikonal with slow envelope variation. It is assumed that the bounce frequency of trapped electrons is large. A kinetic equation involving only slowly varying quantities is derived and it is shown that the characteristic equations form a Hamiltonian system. Conservation of particles, momentum, and energy are shown to depend on first-order corrections to this kinetic equation. The low order correction moments are derived exactly from these conservation laws, eliminating the need for a complicated boundary layer treatment of the separatrix. Previous results for nonlinear Langmuir waves are reproduced by a simplified version of this theory which neglects variations of the amplitude envelope and phase velocity. A particle-in-cell method is proposed for solution of the nonlinear kinetic problem. Extensions of this method required to correctly describe small amplitude waves are suggested. Such an extended model may be useful for the modeling of laser-plasma interaction in the trapping regime.

This paper describes the study of a force-free plasma with an initial sheet-pinch configuration ∇×B=−αB, where α is a scalar constant, using both linear theory and 2-1/2 dimensional particle-in-cell simulations with doubly periodic boundary conditions. Previous studies have shown that this configuration is unstable to the collisionless tearing instability. In this work, the linear growth rate in the long wavelength limit is found to have an upper bound at 1/τA, where τA is the Alfven traversal time through the region with sheared magnetic fields. The simulations show that the initial force-free state evolves by seeking a more “relaxed,” lower energy state within the constraints of the simulation geometry. Under the periodic boundary conditions, the amount of magnetic energy available for dissipation is determined mostly by the geometry. The reconnection region shows a multiscale structure, separated by ion and electron inertial lengths. Particle and flow dynamics at the reconnection regions have been anal...

The stability of a long field-reversed configuration is considered within the two-fluid model. A symmetric quadratic form is obtained with all Hall and finite Larmor radius (FLR) terms included. Assuming slow axial variation, this form is used to derive a leading-order stability formulation. As previously found for single fluid magnetohydrodynamics (MHD) analysis of this problem, the stability problem is posed as a field-line ordinary differential equation for the axial electron displacement alone. All stability results depend only on the ratio G=S*/E where E is the separatrix elongation and S* is the separatrix radius relative to the collisionless ion skin depth. Results are obtained for Hall MHD and also with FLR effects included (as large B gyroviscosity) and show stability for G

The stability of very elongated field-reversed configurations is solved by an expansion in the small parameter e (inverse elongation). It is first shown that all possible unstable modes have small growth rates (γ ∼e). The internal tilt mode is considered in detail. An explicit form for δW in leading order is derived, and leads to a quadratic form including Hall terms. A sufficient condition for stability is obtained by minimizing δW, leading to a field-line ordinary differential equation. Sufficient stability conditions are obtained from this formulation, and indicate stability for S*/E

A prospective, randomised, non-blinded, clinical study to assess the effect of peritoneal lavage using warmed fluid on body temperature in anesthetised cats and dogs of less than 10 kg body mass undergoing coeliotomy. A standardised anaesthetic protocol was used. Oesophageal and rectal temperatures were measured at various time points. At the end of surgery, group 1 patients (n=10) were lavaged with 200 ml/kg sterile isotonic saline at 34±1°C and group 2 (n=10) at 40±1°C. Groups were similar with respect to age, mass, body condition and surgical incision length. Duration of anaesthesia, surgical procedures and peritoneal lavage was similar between groups. Linear regression showed no significant change in oesophageal temperature during the lavage period for group 1 (P=0.64), but a significant increase for group 2 patients (P

An asymptotic theory of field-reversed configuration (FRC) equilibrium is developed, where the small expansion parameter is the square of the inverse elongation of the separatrix. It is shown that equilibrium alone completely determines the closed-field pressure profile of an elongated FRC in terms of the open-field profile. Examples show that the closed profile is insensitive to details of the open profile. A surprising result is that the open outflow plasma (axially beyond closed region) is always totally diamagnetic on the axis (β=1, where β is measured in the θ-pinch sense). The separatrix shape (axial variation) depends uniquely on the first-order pressure profile, and any separatrix shape may be realized within the limitations of the asymptotic theory. This sensitive dependence of shape on pressure profile explains extreme stiffness of the FRC equilibrium problem which was reported earlier. These results are compared favorably with experimental observations.

An asymptotic theory of field-reversed configuration equilibrium, where the small expansion parameter is the square of the inverse elongation of the separatrix, was previously developed [D. C. Barnes, Phys. Plasmas 8, 4856 (2001)]. This theory is used to compute consistent pressure profiles which are then used to obtain two-dimensional solutions of the Grad–Shafranov equation. Solutions are obtained for a range of normalized separatrix radii, elongations, and shapes. These solutions confirm the predictions of the asymptotic theory. Elongations up to 25:1 are obtained, and the shape is shown to assume any previously specified value.

In the Penning fusion device, a spherical cloud of electrons, confined in a Penning-type trap, creates the ion-confining electrostatic well. Calculations performed with a bounce-averaged Fokker–Planck model have suggested that highest fusion energy gains in Penning fusion systems occur when the ion population is predominantly Maxwellian. However, the question arises about the stability of the electron cloud in the presence of thermal ions. Here, a stability analysis of rigid-rotor electrons confining thermal ions is performed. The results indicate that such configuration is absolutely stable to electrostatic perturbations for arbitrary rigid-rotor electron distributions.

An equilibrium electron distribution is exhibited which forms a uniform electron density focus within a spherical system. Such a focus may be used to form a spherical, harmonic well for ion focusing as previously discussed. A self-consistent density and space-charge potential are calculated and the optimum focus radius is determined. Nonideal effects on electron and ion motion in the resulting electrostatic well are briefly discussed and strategies for their minimization are derived.

The problem of large-amplitude spherical oscillations of an ion cloud in an Inertial Electrostatic Confinement (IEC) device is examined. It is shown that ion fluctuations of a Gaussian profile in a spherical, harmonic well are stable to all hydrodynamic modes, and stable oscillations about the oscillating equilibrium state may be damped by continuum damping. It is also shown that the ion state forms a thermal equilibrium, in spite of the orders of magnitude, density, and temperature changes during the oscillation cycle. Finally, a brief discussion of how to experimentally realize the required electron distributions for these oscillations is presented.

An invention [US Patent and Trademark Office App. Nos. 60/596567 (2005) and 60/766791 (2006)] combines centrifugal and dipole confinement, with recent oscillating plasma theory. The plasma undergoes compression/expansion (C/E), parallel to B by centrifugal force and perpendicular to B by B variation, providing a thermal cycle which recovers most (>95%) of heating as mechanical energy. This gives a “Q-amplifier” for beam-target systems. Centrifugally confined Boron plasma undergoes C/E by slow, cross-B interchange activity. Parallel and perpendicular C/E are matched by the rotation profile which arises naturally. Hot plasma is heated and cold plasma is cooled. Beam-target fusion reactions occur in the hot plasma region and expansion returns most of the heat energy as rotation energy. Rotation energy, in turn, produces waves which drive protons to an energy near the fusion peak cross section. A possible machine, including the arrangement of magnets and HV, is described.

A simple modification to the heliac coil configuration [A. H. Boozer et al., Plasma Physics and Controlled Nuclear Fusion (International Atomic Energy Agency, Vienna, 1966), Vol. 1, p. 103] is described that reduces the toroidal perturbation to the magnetic field structure and significantly restores the helical symmetry. This is accomplished by shifting the internal current‐carrying conductor (hardcore) of the heliac radially inward from its normal position at the geometric center of the external l=1 coils. It is shown by computations that a large‐aspect‐ratio toroidal heliac is similar to a helically symmetric linear heliac in which the hardcore has been shifted. This similarity is seen in the analytic form of the magnetic potential, the flux surface shape, and in the harmonic spectra of the field lines. It is then shown that the toroidicity perturbations can be reduced in a toroidal heliac by combining these effects—using a radially inward hardcore shift in the toroidal configuration. In the experiments reported here the toroidal‐like effects are created in the linear High Beta Q Machine (HBQM) heliac [C. M. Greenfield et al., Phys. Fluids B 2, 133 (1990)] by shifting the hardcore off the geometric center of the l=1 coils. The induced toroidal‐like effects are seen from an asymmetry in the axial excluded flux; however, no decrease in global beta is seen as compared to the unshifted symmetric case (G. G. Spanjers, Ph.D. dissertation, University of Washington, 1992) indicating the absence of large‐scale magnetohydrodynamic instabilities at high beta.

The stabilization of the internal tilt mode of a field‐reversed configuration by injecting a minority energetic ion component has been investigated numerically. Calculations that follow ion orbits in a specified three‐dimensional magnetic field configuration, corresponding to a partially tilted field‐reversed configuration, demonstrate how a beam can provide a restoring force to the n=1 tilt instability. A fully self‐consistent three‐dimensional numerical model, which treats the background plasma as a Hall fluid and the energetic ions as a collisionless Vlasov species, has also been developed. Calculations have been made for a variety of beam injection parameters, and indicate that the tilt mode can be stabilized with a beam energy of about 40% of the total, beam plus plasma, energy.

The application of supercomputers and advanced numerical techniques to problems of coronal structure and dynamics is described. Numerical methods appropriate for the long time scale simulation of nonlinear magnetohydrodynamic systems are discussed. Three specific examples of the application of these techniques to the solar corona are given. These are magnetic energy storage and conversion, a model for steady coronal heating, and calculation of stable force-free equilibria from given boundary data, such as that obtained with a vector magnetograph. It is suggested that the continued application of these methods will result in substantial advances in the understanding of coronal dynamics and structure.

To assess reliability of the mechanical axes stifle angle in dogs positioned for radiography with a neutral stifle (neutral stifle angle (nSA)). To investigate radiographic landmarks for assessment of nSA from a collimated radiographic view. One hundred radiographs were taken of normal stifles belonging to 55 skeletally mature medium and large breed dogs, positioned using a repeatable protocol. Radiographs were widely collimated to include the femoral head and the talus. The angle of Blumensaat's line through the intercondylar fossa relative to the Mechanical Axis of the femur (intercondylar fossa angle, IFA), the angle of inclination of a tibial crest tangent line relative to the Mechanical Axis of the tibia (tibial crest angle, TCA) and the tibial plateau angle (TPA) were recorded. Mean nSA was 133.5°. Mean IFA was 155.5°. TCA had a mean of 6.7°. Estimates for nSA were calculated using mean IFA combined with mean TCA (enSA1), mean TPA (enSA2) and the mechanical axis of the tibia (enSA3). Mean percentage error relative was 2.99 per cent for enSA1, 2.82 per cent for enSA2, 1.67 per cent for enSA3. Blumensaat's line provides a consistent radiological feature for assessment of nSA. Assessment of nSA and correction for values varying from 135° may allow more consistent and accurate measurement of patellar tendon angle for presurgical planning.

Summary form only given. Virtual cathode machines (usually called Penning Fusion or PF machines) have achieved the required physics goals of maintaining required nonthermal electron distributions, spherical focussing, and excellent electron energy confinement, and are poised to study ion physics. PF systems attempt to tailor the electron cloud to produce a spherical ion well, while maintaining desired electron confinement. In addition to the steady ion convergent mode of IEC machines (Spherically Convergent Ion Focus or SCIF), PF systems potentially may access a recently discovered oscillating ion mode (Periodically Oscillating Plasma Sphere or POPS), if a uniform density electron cloud is formed with appropriate electrostatic boundary conditions. The Penning Fusion eXperiment-Ions (PFX-I), part of the Innovative Concepts Initiative of the Office of Fusion Energy (OFE) is a unique magnetic confinement concept based upon the traditional nonneutral-plasma Penning trap. It is an electron/ion trap comprised of a small magnetic flux-shaper, an electron emitter, and gas supply. The trap itself has an ID of less than 40 mm, with access to the center restricted through ports less than 15 mm in diameter.

Inertial electrostatic confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P.T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams. Gridded IEC systems have demonstrated neutron yields as high as 2*10 neutrons/sec in steady state. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application. This paper discusses the IEC concept and how it can be adapted to a steady-state assaying source and an intense pulsed neutron source. Theoretical modeling and experimental results are presented.

Conservative, multidimensional, Lagrangian, staggered-grid hydrodynamics algorithms are well known[l]. Here, these principles are extended to include magnetic fields in the discretized momentum and energy equations. A magnetic vector potential, A, formulation is centered on edges so that the divergence law, ▽ · B = 0 is maintained to round-off error. The magnetic field is cell-centered. Magnetic forces from Maxwell's stress tensor are expressed in terms of the field and geometric quantities. This assures momentum and energy conservation. The method is expressed in 3D, but is generalizable to 1 or 2D. Resistive diffusion of the madoes not serve to straighten the azimuthal magnetic field lines [2]. gnetic field is handled by implicit time differencing and is solved by preconditioned, conjugate gradient methods. Multi-material, Z-pinch, test-problems are shown.

Drugs that are currently used for therapeutic purposes can also be used in diagnostic tests. This paper will review the use of such pharmacological interventions in cardiac assessment in Nuclear Medicine. To fully comprehend the effect of these drugs, a small review of diagnostic nuclear medicine as currently used to assess cardiac perfusion is included. This will allow pharmacists to understand the rationale behind the single administration of either vasodilator or inotropic agents and to review which drugs and food may interact with the test.

We discuss an analogy between magnetically confined nonneutral plasmas and geophysical fluid dynamics. The analogy has its roots in the modified drift Poisson model, a recently proposed model that takes into account the plasma compression due to the variations of the plasma length [1]. The conservation of the line integrated density in the new model is analogous to the conservation of potential vorticity in the shallow water equations, and the variation of the plasma length is isomorphic to variations in the Coriolis parameter with latitude or to topography variations in the quasigeostrophic dynamics. We discuss a new class of linear and nonlinear waves that owe their existence to the variations of the plasma length. These modes are the analog of Rossby waves in geophysical flows.

Combining spherical convergence with electrostatic or electro-magnetostatic confinement of a nonneutral plasma offers the possibility of high fusion gain in a centimeter-sized system. The physics principles, scaling laws, and experimental embodiments of this approach are presented. Steps to development of this approach from its present proof-of-principle experiments to a useful fusion power reactor are outlined. This development path is much less expensive and simpler, compared to that for conventional magnetic confinement and leads to different and useful products at each stage. Reactor projections show both high mass power density and low to moderate wall loading. This approach is being tested experimentally in PFX-I (Penning Fusion eXperiment-Ions), which is based on the following recent advances: 1) Demonstration, in PFX (our former experiment), that it is possible to combine nonneutral electron plasma confinement with nonthermal, spherical focussing; 2) Theoretical development of the POPS (Periodically Oscillating Plasma Sphere) concept, which allows spherical compression of thermal-equilibrium ions; 3) The concept of a massively-modular approach to fusion power, and associated elimination of the critical problem of extremely high first wall loading. PFX-I is described. PFX-I is being designed as a small (

According to conventional theory based on the drift-Poisson equations, the m=1 diocotron mode is stable, even for hollow density profiles. However, experiments [C. F. Driscoll, Phys. Rev. Lett. 64, 645 (1990)] show instability for this mode. These results have remained unexplained since 1990. We have found two effects, related to compression parallel to the magnetic field, which lead to instability with growth rates and other properties in good agreement with the experiments. The first is due to curvature of the sheaths at the ends of the trap. The second is the free boundary effect due to the linearized perturbation of the plasma length. These effects are described in terms of the modified drift-Poisson model, which states the conservation of the line integrated density. The modified drift-Poisson equations derived are analogous to the shallow water equations of geophysical fluid dynamics (GFD), with the line integrated density corresponding to the potential vorticity. This is explained in more detail in...

The Penning fusion experiment (PFX) studies the feasibility of using a Penning trap as a fusion confinement device. Such use would require spatial and/or temporal compression of the plasma to overcome the Brillouin density limit imposed by the nonneutrality of Penning trap plasmas. In an earlier experiment, we achieved enhanced plasma density at the center of a pure, electron plasma confined in a hyperbolic, Penning trap by inducing spherically convergent flow in a nonthermal plasma(1,2,3). The goal of this work is to induce similar flow in a positive ion plasma confined in the virtual cathode provided by a spherical, uniform density electron plasma. This approach promises the greatest flexibility in operating with multi-species plasmas (e.g. D+/T+) or implementing temporal compression schemes such as the Periodically Oscillating Plasma Sphere of Nebel and Barnes(4,5). Here, we report on our work to produce and diagnose the necessary electron plasma.

Rotationally driven modes of long systems with dominantly axial magnetic field are considered. We apply the incompressible model and order axial wavenumber small. A recently developed gyro-viscous model is incorporated. A one-dimensional equilibrium is assumed, but radial profiles are arbitrary. The dominant toroidal (azimuthal) mode numbers l=1 and l=2 modes are examined for a variety of non-reversed (B) and reversed profiles. Previous results for both systems with rigid rotor equilibria are reproduced. New results are obtained by incorporation of finite axial wavenumber and by relaxing the assumption of rigid electron and ion rotation. It is shown that the frequently troublesome l=2 field reversed configuration (FRC) mode is not strongly affected by ion kinetic effects (in contrast to non-reversed cases) and is likely stabilized experimentally only by finite length effects. It is also shown that the l=1 wobble mode has a complicated behavior and is affected by a variety of configuration and profile effe...

We perform linear stability studies of the ion temperature gradient (ITG) instability in unsheared slab geometry using kinetic and extended magnetohydrodynamics (MHD) models, in the regime k∥/k⊥≪1. The ITG is a parallel (to B) sound wave that may be destabilized by finite ion Larmor radius (FLR) effects in the presence of a gradient in the equilibrium ion temperature. The ITG is stable in both ideal and resistive MHD; for a given temperature scale length LTi0, instability requires that either k⊥ρi or ρi/LTi0 be sufficiently large. Kinetic models capture FLR effects to all orders in either parameter. In the extended MHD model, these effects are captured only to lowest order by means of the Braginskii ion gyro-viscous stress tensor and the ion diamagnetic heat flux. We present the linear electrostatic dispersion relations for the ITG for both kinetic Vlasov and extended MHD (two-fluid) models in the local approximation. In the low frequency fluid regime, these reduce to the same cubic equation for the compl...

The gyroviscous stress is computed for a weakly magnetized plasma, i.e., one in which the thermal ion gyroradius may exceed the equilibrium gradient scale length. A simple and useful formula is derived and shown to reduce to the previous strongly magnetized result. Applicability is illustrated with a typical field-reversed configuration equilibrium solution. This form is the most useful to date for the study of kinetic ion phenomena in weakly magnetized plasmas within a fluid model.

Inertial Electrostatic Confinement (IEC) is one of the earliest plasma confinement concepts, having first been suggested by P. T. Farnsworth in the 1950s. The concept involves a simple apparatus of concentric spherical electrostatic grids or a combination of grids and magnetic fields. An electrostatic structure is formed from the confluence of electron or ion beams.Gridded IEC systems have demonstrated neutron yields as high as 2*1010 neutron/sec. These systems have considerable potential as small, inexpensive, portable neutron sources for assaying applications. Neutron tomography is also a potential application.Atomic physics effects strongly influence the performance of all of these systems. Important atomic effects include elastic scattering, ionization, excitation, and charge exchange. This paper discusses how an IEC system is influenced by these effects and how to design around them. Theoretical modeling and experimental results are presented.

An experiment is being constructed at Los Alamos to investigate the possibility of using a Penning trap as a fusion confinement device. The goal is to demonstrate electron densities greater than the Brillouin density at the center of the trap by filling it with particles occupying a very restricted region of phase space. The trap under construction has a containment region diameter of 6 mm, standoff lengths of 25 mm, and gaps between electrodes of 1.5 mm. High voltage tests have demonstrated standoff breakdown voltages of ≳100 kV, and established that titanium electrodes offer better performance than stainless steel or copper ones. The main diagnostic of the degree of density focusing will be transmitted beam deflection measurements. The electron source will be biased to inject a probe beam through the trap center, and this will then be imaged on a phosphor screen outside the trap.

The authors reviewed planar, SPECT and other contemporaneous radiologic images of the spine and the medical records of 33 patients with back pain after lumbar fusion surgery in order to determine the value of SPECT in the assessment of painful late effects of spinal fusion surgery.Twenty-one patients had lateral fusion, nine patients had posterior fusion only and three patients had anterior and posterior fusions. There were 24 patients who had surgery more than 4 yr ago (late group, mean 11.8 yr) and 9 patients who had surgery less than 4 yr ago (early group, mean 17.8 mo).The most common SPECT abnormality in patients in the late group were lesions in the vertebral bodies and apophyseal joints in the free motion segments adjacent to the fused segments (62.5% of patients). Such lesions occurred in 46% of patients after lateral fusion, in 87.5% of patients after posterior fusion and in 67% of patients after posterior and anterior fusions. No SPECT abnormalities were detected in the fused segments in patients in the late group with solid lateral fusion but were detected in three patients with solid posterior fusion. These results correlate with biomechanical studies that have shown posterior fusion to produce the largest amount and lateral fusion to produce the least amount of stress in the free segments adjacent to the fusion. Lateral fusion was found to have a more stabilizing effect than posterior fusion.In addition to the already established value of SPECT in detecting painful pseudoarthrosis, our results indicate that SPECT is of value in the assessment of painful late effects of fusion.

Indium-111-white blood cell (111In-WBC) images of 17 Crohn's patients with fistulae and sinus tracts were reviewed and correlated with radiographic results (n = 16 patients) and surgery (n = 16 patients), to characterize the scintigraphic appearance of fistulization and to determine the role of 111In-WBC scintigraphy in this clinical setting. These were compared to 50 consecutive abnormal 111In-WBC studies obtained in Crohn's patients with suspected active disease but no known fistulae or sinus tracts.Scintigraphic findings which suggested the presence of fistulae were: (1) the presence of concomitant intestinal and extraintestinal lesions and (2) the absence of luminal activity on delayed images when early images detected bowel activity. The extraintestinal lesions were the drainage site of the fistula (n = 7) or an accompanying abscess (n = 6). Absence of luminal activity occurred in seven patients with fistulae and in two without fistulae; two patients had a proximal colostomy, two patients had bowel obstruction and five patients had fistulae to the skin (n = 3) or between the ileum and distal colon (n = 2). The distribution of active bowel disease as assessed scintigraphically was in complete agreement with surgery in 14 of 17 cases (82%) compared to 9 of 15 cases (60%) when correlating radiographic assessment with surgery. All surgically proven abscesses were detected on 111In-WBC images.These results indicate that 111In-WBC scintigraphy adds useful information to radiographic studies that is essential for appropriate management of Crohn's patients with fistulae and sinus tracts.

The role of bone scintigraphy in the evaluation of patients with inflammatory spondyloarthropathy is controversial and previous studies have reported a lack of sensitivity and specificity. The aim of our study was to determine whether single photon emission computed tomography (SPECT) scanning would enhance the clinical utility of bone scintigraphy in the detection of inflammatory axial disease, in particular sacroiliitis.Twenty patients with definite sacroiliitis (New York criteria1) on plain film radiographs and 20 age matched controls were studied. Bone scintigraphy and SPECT scanning were carried out 2 h after an intravenous injection of 99mTc imidodiphosphonate (IDP). A quantitative and qualitative assessment of radiopharmaceutical uptake in the sacroiliac (SI) joints was derived from planar films and a qualitative analysis of uptake in the SI joints was derived from SPECT scans. All films were read without knowledge of patient identification.Quantitative analysis of planar films did not identify any difference between study and control groups (p0.05). Qualitative assessment of planar films identified features of sacroiliitis more frequently in patients than in controls (p0.05) with a sensitivity of 25% and a specificity of 95%. SPECT scanning also revealed enhanced radiopharmaceutical uptake in the SI joints more frequently in patients than in controls (p0.001) with a sensitivity of 85% and a specificity of 90%. Increased uptake in the lumbar facet joints and costovertebral joints was identified in 3 patients. Similar abnormalities were not detected in the control group.Our results indicate that SPECT scanning is both sensitive and specific for the detection of established sacroiliitis and may also identify inflammatory disease at other sites in the spine.

Single-photon emission computed tomography has been proven to detect more abnormalities than planar bone scintigraphy in patients with low back pain (LBP). Both 180 degrees and 360 degrees acquisitions were performed in 24 patients with LBP to determine whether the shorter 180 degrees posterior SPECT is as accurate for abnormality detection as 360 degrees acquisition. The vertebral bodies and posterior elements of 193 vertebrae were scored on a five-point score (1 = normal, 5 = abnormal), independently by three experienced physicians, on three separate reconstructed image sets: standard, filtered, back projection 360 degrees acquisition, distance-weighted 360 degrees acquisition, and standard, filtered, back projection 180 degrees acquisition. With one exception, no statistically significant difference in score was found between 180 degrees and 360 degrees images. For one observer, the mean score of the posterior elements was higher on 180 degrees compared to 360 degrees standard images. These results indicate that 180 degrees acquisition SPECT may be used for abnormality detection in patients with LBP.

The value of magnetic resonance imaging (MRI) in establishing the diagnosis of sacroiliitis was studied in 20 patients with established or suspected disease on conventional radiographs and in 10 healthy subjects. Coronal T1 weighted, axial T2 weighted and proton density MRI images of the sacroiliac joints in addition to plain film radiographs were obtained. All films were graded from 0 to 4 according to the modified New York criteria and independently for changes in joint width, erosions, sclerosis and ankylosis. Using the modified New York criteria, more abnormalities were detected by MRI than by conventional radiography (p = 0.04). This was due to the detection of definite abnormalities (grades 2-4) by MRI in joints that were graded normal or suspicious (grades 0-1) on plain films (p = 0.01). MRI tended to be superior to plain films in visualizing erosions. Only MRI detected abnormalities of articular cartilage (19 patients) and in subchondral bone marrow (7 patients). The latter 2 types represented fatty infiltration and inflammatory change. Intraobserver and interobserver variation were similar for the interpretation of MRI scans and plain film radiographs. These results suggest that MRI detects changes of established sacroilitis. Due to its ability to directly image articular cartilage it may be particularly useful in patients with early disease.

Two new low-noise particle closure methods are developed and tested. Closure of a small set of moment equations is accomplished with first or second order moments computed from a delta-f particle in cell (δf PIC) distribution. Conservation laws are developed and in one case apply to the discrete system, showing that squared weights are part of the system energy and therefore bounded for all time. Implicit time differencing and orbit averaging techniques are developed and implemented. Low-order moment constraints are satisfied exactly by a new particle representation. Numerical tests for one dimension, k⊥=0, and two dimension, k∥=0 show the successful application of both methods to damped waves and of the second order closure method to unstable gravitational modes. The methods described here are a natural and efficient way to close extended magnetohydrodynamic (MHD) equations to obtain a full kinetic description.

Large-scale numerical computation is applied to fluid-based plasma modeling of edge localized modes (ELMs). The modes are magnetohydrodynamic-like instabilities that nonlinearly release bursts of particles and energy across the flow-induced transport barrier that lies near the separatrix of closed and open magnetic flux in tokamaks. Some of the first nonlinear computations of ELMs to model the separate drifts of ions and electrons, which linearly stabilize the highest wavenumber modes and avoid a nonlinear 'ultraviolet catastrophe' without the use of ad hoc dissipation, are presented. The two-fluid system supports high-frequency dispersive modes that are not present in magnetohydrodynamics, and a new implicit leapfrog algorithm has been implemented to run these computations. We briefly describe the algorithm and computational requirements, in addition to physical results on nonlinear structure formation.

The Reversed-Field Pinch (RFP) is presented as a driven nonlinear dynamical system that evolves on time scales long compared with the fastest normal modes of the system. Numerical methods for the simulation of these processes, and examples of their application to experimentally observable phenomena, are presented.

A short-pulsed intense laser is injected into an underdense plasma to sustain a self-trapped photon channel. With either high-enough intensity or strong-enough focusing the optical beam causes total electron evacuation on the beam axis. Under appropriate conditions this laser and plasma fiber system can provide a slow wave structure of the electromagnetic wave that is suitable for high-energy acceleration.