Evaluation of the ACR and SLICC classification criteria in juvenile-onset systemic lupus erythematosus: a longitudinal analysis.

Objectives The Systemic Lupus International Collaborating Clinics (SLICC) group proposed revised classification criteria for systemic lupus erythematosus (SLICC-2012 criteria). This study aimed to compare these criteria with the well-established American College of Rheumatology classification criteria (ACR-1997 criteria) in a national cohort of juvenile-onset systemic lupus erythematosus (JSLE) patients and evaluate how patients' classification criteria evolved over time. Methods Data from patients in the UK JSLE Cohort Study with a senior clinician diagnosis of probable evolving, or definite JSLE, were analyzed. Patients were assessed using both classification criteria within 1 year of diagnosis and at latest follow up (following a minimum 12-month follow-up period). Results A total of 226 patients were included. The SLICC-2012 was more sensitive than ACR-1997 at diagnosis (92.9% versus 84.1% p < 0.001) and after follow up (100% versus 92.0% p < 0.001). Most patients meeting the SLICC-2012 criteria and not the ACR-1997 met more than one additional criterion on the SLICC-2012. Conclusions The SLICC-2012 was better able to classify patients with JSLE than the ACR-1997 and did so at an earlier stage in their disease course. SLICC-2012 should be considered for classification of JSLE patients in observational studies and clinical trial eligibility.

Asynchronous partial contact motion due to internal resonance in multiple degree-of-freedom rotordynamics.

Sudden onset of violent chattering or whirling rotor-stator contact motion in rotational machines can cause significant damage in many industrial applications. It is shown that internal resonance can lead to the onset of bouncing-type partial contact motion away from primary resonances. These partial contact limit cycles can involve any two modes of an arbitrarily high degree-of-freedom system, and can be seen as an extension of a synchronization condition previously reported for a single disc system. The synchronization formula predicts multiple drivespeeds, corresponding to different forms of mode-locked bouncing orbits. These results are backed up by a brute-force bifurcation analysis which reveals numerical existence of the corresponding family of bouncing orbits at supercritical drivespeeds, provided the damping is sufficiently low. The numerics reveal many overlapping families of solutions, which leads to significant multi-stability of the response at given drive speeds. Further, secondary bifurcations can also occur within each family, altering the nature of the response and ultimately leading to chaos. It is illustrated how stiffness and damping of the stator have a large effect on the number and nature of the partial contact solutions, illustrating the extreme sensitivity that would be observed in practice.

Turn costs change the value of animal search paths.

The tortuosity of the track taken by an animal searching for food profoundly affects search efficiency, which should be optimised to maximise net energy gain. Models examining this generally describe movement as a series of straight steps interspaced by turns, and implicitly assume no turn costs. We used both empirical- and modelling-based approaches to show that the energetic costs for turns in both terrestrial and aerial locomotion are substantial, which calls into question the value of conventional movement models such as correlated random walk or Lévy walk for assessing optimum path types. We show how, because straight-line travel is energetically most efficient, search strategies should favour constrained turn angles, with uninformed foragers continuing in straight lines unless the potential benefits of turning offset the cost.

A practical technique for quantifying the performance of acoustic emission systems on plate-like structures.

A model for quantifying the performance of acoustic emission (AE) systems on plate-like structures is presented. Employing a linear transfer function approach the model is applicable to both isotropic and anisotropic materials. The model requires several inputs including source waveforms, phase velocity and attenuation. It is recognised that these variables may not be readily available, thus efficient measurement techniques are presented for obtaining phase velocity and attenuation in a form that can be exploited directly in the model. Inspired by previously documented methods, the application of these techniques is examined and some important implications for propagation characterisation in plates are discussed. Example measurements are made on isotropic and anisotropic plates and, where possible, comparisons with numerical solutions are made. By inputting experimentally obtained data into the model, quantitative system metrics are examined for different threshold values and sensor locations. By producing plots describing areas of hit success and source location error, the ability to measure the performance of different AE system configurations is demonstrated. This quantitative approach will help to place AE testing on a more solid foundation, underpinning its use in industrial AE applications.

Investigation of a multi-ball, automatic dynamic balancing mechanism for eccentric rotors.

This paper concerns an analytical and experimental investigation into the dynamics of an automatic dynamic balancer (ADB) designed to quench vibration in eccentric rotors. This fundamentally nonlinear device incorporates several balancing masses that are free to rotate in a circumferentially mounted ball race. An earlier study into the steady state and transient response of the device with two balls is extended to the case of an arbitrary number of balls. Using bifurcation analysis allied to numerical simulation of a fully nonlinear model, the question is addressed of whether increasing the number of balls is advantageous. It is found that it is never possible to perfectly balance the device at rotation speeds comparable with or below the first natural, bending frequency of the rotor. When considering practical implementation of the device, a modification is suggested where individual balls are contained in separate arcs of the ball race, with rigid partitions separating each arc. Simulation results for a partitioned ADB are compared with those from an experimental rig. Close qualitative and quantitative match is found between the theory and the experiment, confirming that for sub-resonant rotation speeds, the ADB at best makes no difference to the imbalance, and can make things substantially worse. Further related configurations worthy of experimental and numerical investigation are proposed.

Delay in access to appropriate care for children presenting with musculoskeletal symptoms and ultimately diagnosed with juvenile idiopathic arthritis.

OBJECTIVE: To document pathways of care, management, and interval from onset of symptoms to first pediatric rheumatology multidisciplinary team (PRhMDT) assessment for children with incident juvenile idiopathic arthritis (JIA). METHODS: We conducted a retrospective observational study of children with incident JIA over a 3-year period. RESULTS: The study included 152 patients with JIA (87 females). The median interval from symptom onset to first PRhMDT assessment was 20 weeks (range 0-416), with significant variation between JIA subtypes (P = 0.0097); children with extended oligoarticular JIA had the longest interval (median 60 weeks, range 12-320). Prior to pediatric rheumatology assessment, many children had referrals to multiple secondary care specialties and had been subjected to multiple and often invasive procedures including arthroscopy/synovial biopsy (18 [11.8%] of 152), but none were referred for ophthalmologic screening, physical therapy, or nursing input and a diagnosis of JIA was rarely made (98%). At first PRhMDT assessment, most patients had untreated active disease with active joint count >or=1 (135 [89%] of 152), restricted joint count >or=1 (135 [89%] of 152), and functional disability by Child Health Assessment Questionnaire score >0 (53 [68%] of 118); 1 child had undetected uveitis. Following PRhMDT assessment, interventions were invariably indicated, including joint injections (69 [45%] of 152), methotrexate (49 [32%] of 152), and physical therapy programs (all patients). CONCLUSION: Delay in access to pediatric rheumatology assessment is common with complex pathways of referral. Many children were subjected to inappropriate invasive investigations and many had prolonged untreated active disease at the initial PRhMDT assessment. This delay is likely to affect long-term outcome and warrants further exploration.

Musculoskeletal screening examination (pGALS) for school-age children based on the adult GALS screen.

OBJECTIVE: To develop and validate a musculoskeletal screening examination applicable to school-age children based on the adult Gait, Arms, Legs, Spine (GALS) screen. METHODS: Adult GALS was tested in consecutive school-age children attending pediatric rheumatology clinics and was compared with an examination conducted, on the same day, by a pediatric rheumatologist who classified children as having abnormal or normal joints. Adult GALS was tested for validity compared with the pediatric rheumatologist's assessment and deficiencies in adult GALS were identified. Experts proposed amendments to adult GALS, achieving consensus by modified Delphi techniques. The resultant pediatric screening tool (pGALS) was tested (methodology identical to the testing of adult GALS) in an additional group of children. RESULTS: Adult GALS was tested in 50 children (median age 11 years, range 4-16), of whom 37 (74%) had juvenile idiopathic arthritis. Adult GALS missed important abnormalities in 18% of children, mostly at the ankle, foot, and temporomandibular joints. The pGALS was tested in 65 children (median age 13 years, range 5-17 years) and demonstrated excellent sensitivity (97-100%) and specificity (98-100%) at all joints, with high acceptability scored by child and parent/guardian. The median time to perform pGALS was 2 minutes (range 1.5-3 minutes). CONCLUSION: The pGALS musculoskeletal screening tool has excellent validity, is quick to perform, and is acceptable to school-age children and parents/guardians. We propose that pGALS be incorporated into undergraduate and postgraduate medical training to improve pediatric musculoskeletal clinical skills and facilitate diagnosis and referral to specialists.