On the kinetic equation approach to pair production by time-dependent electric field

We investigate the quantum kinetic approach to pair production from vacuum by time-dependent electric field. Equivalence between this approach and the more familiar S-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.Comment: 8 pages, 4 figure

Is head-shaft angle a valuable continuous risk factor for hip migration in cerebral palsy?

BACKGROUND: Reimer's migration percentage (MP) is the most established radiographic risk factor for hip migration in cerebral palsy (CP), and it assists surgical decision-making. The head-shaft angle (HSA) measures the valgus of the head and neck in relation to the shaft and may also be a useful predictor of hip migration at a young age. This study first defined normal values and investigated whether the head-shaft angle (HSA) is a continuous risk factor for hip migration in CP. METHODS: Three hundred and fifty AP pelvic radiographs of 100 consecutive children comprising the hip surveillance programme in our region were analysed for MP and HSA. Inclusion criteria were children with spastic CP and Gross Motor Function Classification System (GMFCS) levels of III-V, along with a minimum follow-up of 5 years. The mean age was 8.8 (range 3-18) years and the mean follow-up time was 7.5 (range 5-10) years. Radiographs of 103 typically developing children (TDC) were selected for the control group. The reliability of the measurements was determined. A random effects analysis was used to assess the relationship between MP and HSA for all data and for MP > 40 %. RESULTS: The TDC cohort had a mean HSA of 157.7° whilst that for the CP cohort was 161.7°. The value declined with age in both groups but remained consistently higher in the CP group. A random effects analysis considering the longitudinal data showed that there was no significant effect of HSA on MP. Similarly, when excluding CP patients with MP < 40 %, there was no significant effect of HSA on MP. CONCLUSIONS: This study found no correlation between HSA and hip migration in children with CP in this age group. Using the HSA as a routine radiographic measure in the management pathway across childhood does not offer any added value. Early enrolment onto the hip surveillance programme could offer a better prediction of hip migration using the HSA at a very young age. LEVEL OF EVIDENCE: II retrospective prognostic study

Does idiopathic congenital talipes equinovarus have an impact on attainment of developmental milestones? A multicentre international study.

Purpose: The Ponseti method is a well-established approach to treating clubfoot. Potentially, both the underlying pathology and adherence to post-correction bracing can affect lower limb function and age of independent standing and walking. This cohort study investigates the age at which infants with idiopathic clubfoot treated using the Ponseti method achieved three selected developmental milestones and whether or not this correlated with treatment compliance. Methods: A prospectively collected database from four centres was visited. Inclusion criteria were patients with idiopathic clubfoot with no comorbidities or prior treatment. Age at attainment of independent standing, walking, nocturnal continence was compared across three groups: I) congenital talipes equinovarus (CTEV) children compliant with treatment; II) CTEV children non-compliant with treatment; and III) typically-developed siblings. Minimum follow-up was five years. Results: In all, 130 patients (198 feet) fitted the inclusion criteria: 43:87 (F:M). Standing was achieved by a mean 12.0 months in group I (sd 2.50); 12.0 months (sd 2.0) in II and ten months (sd 3.0) in III. Walking was achieved by a mean 15 months (sd 4.0) in group I, 14 months (sd 1.75) in II and 12 months (sd 3) in III, respectively. Both the compliant and non-compliant CTEV children were significantly slower at achieving standing and walking compared to sibling controls (p < 0.0001). There was no significant difference between age of nocturnal continence between the three groups. Conclusion: Infants with idiopathic clubfoot treated according to the Ponseti method achieve independent standing and walking approximately two months later than their typically-developed siblings. The delay is not related to the use of the foot abduction brace. Level of evidence: III

On the kinetic equation approach to pair production by time-dependent electric field

We investigate the quantum kinetic approach to pair production from vacuum by time-dependent electric field. Equivalence between this approach and the more familiar S-matrix approach is explicitly established for both scalar and fermion cases. For the particular case of a constant electric field exact solution for kinetic equations is provided and the accuracy of low-density approximation is estimated.Comment: 8 pages, 4 figure

Overview of the contemporary management of supracondylar humeral fractures in children.

PURPOSE: Supracondylar fractures are common injuries accounting for approximately 15% of all fractures in children with a large body of literature on this subject. METHODS:  This article critically appraises the available evidence to provide an overview of the treatment options including the role and timing of surgery, the geometry of wire fixation and the management of nerve and arterial injury. CONCLUSION:  Management decisions are based on a number of considerations particularly fracture stability. Closed reduction and percutaneous K-wire stabilisation are commonly recommended for an unstable displaced fracture. These techniques are however associated with the potential for iatrogenic neurological injury. Vascular injury is also rare but must be recognised and treated promptly to avoid significant permanent morbidity

Processing of True and False Affirmative Sentencees By Aphasic Subjects

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Covariation Among Vowel Height Effects on Acoustic Measures

Covariation among vowel height effects on vowel intrinsic fundamental frequency (IF0), voice onset time (VOT), and voiceless interval duration (VID) is analyzed to assess the plausibility of a common physiological mechanism underlying variation in these measures. Phrases spoken by 20 young adults, containing words composed of initial voiceless stops or /s/ and high or low vowels, were produced in habitual and voluntarily increased F0 conditions. High vowels were associated with increased IF0 and longer VIDs. VOT and VID exhibited significant covariation with IF0 only for males at habitua

The clinical features, management options and complications of paediatric femoral fractures.

This article discusses the incidence, applied anatomy and classification of paediatric femoral fractures based on critical appraisal of the available evidence. The aim is to identify techniques that are relevant to contemporary practice whilst excluding the technical details of individual procedures that are beyond the scope of this review. Injuries of the proximal, diaphyseal and distal segments are considered individually as there are considerations that are specific to each anatomical site. Femoral neck fractures are rare injuries and require prompt anatomical reduction and stable fixation to minimise the potentially devastating consequences of avascular necrosis. Diaphyseal fractures are relatively common, and there is a spectrum of management options that depend on patient age and size. Distal femoral fractures often involve the physis, which contributes up to 70% of femoral length. Growth arrest is common consequence of fractures in this region, resulting in angular and length-related deformity. Long-term surveillance is recommended to identify deformity in evolution and provide an opportunity for early intervention. Deliberate injury should be considered in all fractures, particularly distal femoral physeal injuries and fractures in the non-walking child