Combinatorial Formulae for Vassiliev Invariants from Chern-Simons Gauge Theory

We analyse the perturbative series expansion of the vacuum expectation value of a Wilson loop in Chern-Simons gauge theory in the temporal gauge. From the analysis emerges the notion of the kernel of a Vassiliev invariant. The kernel of a Vassiliev invariant of order n is not a knot invariant, since it depends on the regular knot projection chosen, but it differs from a Vassiliev invariant by terms that vanish on knots with n singular crossings. We conjecture that Vassiliev invariants can be reconstructed from their kernels. We present the general form of the kernel of a Vassiliev invariant and we describe the reconstruction of the full primitive Vassiliev invariants at orders two, three and four. At orders two and three we recover known combinatorial expressions for these invariants. At order four we present new combinatorial expressions for the two primitive Vassiliev invariants present at this order.Comment: 73 pages, latex, epsf, 18 figures, 2 table

The use of a 30-degree radiolucent triangle during surgery in distal avulsion fractures of the patella.

Avoiding patella baja or alta after the Krackow suture technique for distal avulsion fractures of the patella can be challenging. We aim to introduce a simple and reproducible technique using a 30-degree radiolucent triangle involving the contralateral knee to ensure the correct positioning of the patella intraoperatively. The radiolucent triangle is positioned under the contralateral knee before operating the injured knee. A strict lateral view is obtained using fluoroscopy as a reference before a Krackow technique is performed on the avulsion fracture of the patella. The triangle technique is straightforward and easily reproducible by surgeons of all levels. It allows the surgeon to correctly position the patella intraoperatively in avulsion fracture repair and modify tension on the patellar tendon. This method avoids millimetric mispositioning of the operated patella, thus improving the management intraoperatively and could decrease postoperative complications

Outcomes of combined hip procedure with dual mobility cup versus osteosynthesis for acetabular fractures in elderly patients: a retrospective observational cohort study of fifty one patients.

Acetabular fractures are more and more common in the elderly. Open reduction and internal fixation (ORIF) may lead to poor outcomes and high revision rates. Primary total hip arthroplasty (THA) combined with internal fixation, also known as the combined hip procedure (CHP), associated with dual mobility cup (DM-CHP) could be an efficient procedure in selected elderly patients. The aim of this study is to compare functional and radiological outcomes between ORIF and DM-CHP. Between 2007 and 2018, 51 patients older than 65 years were surgically treated for acetabular fractures. Twenty-six patients were treated by DM-CHP and 25 by ORIF. Each group was divided into two subgroups regarding a single or combined approach. Hospital stay, surgical time, intraoperative blood loss, and complications were documented. The Harris Hip Score (HHS) was used for measuring the functional outcome. Radiological analysis was used to assess the centre of rotation in the DM-CHP group. Median surgery time and intra-operative blood loss were higher in DM-CHP than those in ORIF. Early medical complication rate was higher for a combined approach as compared with a single posterior approach in DM-CHP (p = 0.003). Dislocation rate was 7.7% in DM-CHP. Revision rate was higher in ORIF (20% versus 7.7%). HHS was similar in both groups. DM-CHP leads to similar functional outcomes and less revision than ORIF. This study strengthens the practice of using only the posterior approach for primary THA in the elderly. Dual mobility is a valid therapeutic option for acetabular fractures in elderly patients

Clinical and radiological outcome of the Chimaera short nailing system in inter- and subtrochanteric fractures.

cephalomedullary devices are popular treatment for femoral intertrochanteric or subtrochanteric fractures. Various complications include post-surgical lateral thigh pain and cut-out. To prevent those complications, a new concept cephalomedullary device system was designed (Chimaera, Orthofix®). This study aimed to evaluate the clinical and radiological outcomes in patients with femoral intertrochanteric or subtrochanteric fractures treated with the proximal femoral cephalomedullary device system. A prospective cohort study involved consecutive patients with Arbeitsgemeinschaft für Osteosynthesefragen/ Orthopaedic Trauma Association type 31-A1, 2, 3 fractures treated with the Chimaera short cephalomedullary device system from October 2016 to September 2017 at our level 1 trauma center. The Parker and Palmer mobility score and Jensen social function scores and post-surgical lateral thigh pain were assessed at 3 months post-operatively and compared to before surgery. Radiologic assessment consisted of controlling the position of the cephalic screw by using the tip-apex distance (TAD) and Cleveland zone as well as union and cut-out rates. We included 99 patients (79 women; 100 hips; one bilateral fracture 3 months after a first trochanteric fracture) with a mean follow-up of 2 years. The Parker and Palmer mobility score decreased by 22% at 3 months post-operatively as compared with the pre-fracture score (42/99 patients showed a return to their pre-injury level). The Jensen social function score increased by 16.5% at 3 months post-operatively as compared with the pre-fracture score (68/99 patients showed a return to their pre-injury level). No major intra-operative complication was recorded. Nine TAD scores were > 25 mm. The mean TAD was 16.5 mm (range 5-36), and the lag screw position was well positioned in most (95%) hips according to Cleveland zones. Three patients required revision surgery (one for cut-out of the lag screw, one for hip osteoarthritis and one for gluteus medius insufficiency). All patients but the one with the cut-out showed fracture union. The Chimaera short cephalomedullary device exhibited good mid-term functional and radiological outcomes

Improving Allocative Efficiency in Zimbabwe’s Health Sector: Results from the Health Interventions Prioritization Tool

The country of Zimbabwe has seen some important improvements in key health outcomes since 2009. However, despite progress in some areas of the health sector, the country did not meet its Millennium Development Goals (MDGs) and current progress falls short of the Sustainable Development Goals (SDGs) milestones. As is often the case, the poor and rural populations in Zimbabwe bear a disproportionate burden of disease and health risks. The situation is compounded by national economic challenges and health sector spending inefficiencies that have resulted in households bearing an increasing share of health sector financing, mainly through out-of-pocket expenditures. Households provide approximately 25 percent of health sector financing in Zimbabwe. Again, the poor and rural populations are hardest hit by this economic reality. Zimbabwe was one of the few countries in which HIPtool was piloted at the proof of concept stage. HIPtool enables the mathematical prioritization of interventions based on existing data and a set of criteria. It provides a technical foundation to further develop an essential health benefits package. However, HIPtool, at this stage in development, still has strong limitations, which are outlined along with results in this report

An analytical study of PPP-RTK corrections: precision, correlation and user-impact

PPP-RTK extends the PPP concept by providing single-receiver users, next to orbits and clocks, also information about the satellite phase and code biases, thus enabling single-receiver ambiguity resolution. It is the goal of the present contribution to provide an analytical study of the quality of the PPP-RTK corrections as well as of their impact on the user ambiguity resolution performance. We consider the geometry-free and the geometry-based network derived corrections, as well as the impact of network ambiguity resolution on these corrections. Next to the insight that is provided by the analytical solutions, the closed form expressions of the variance matrices also demonstrate how the corrections depend on network parameters such as number of epochs, number of stations, number of satellites, and number of frequencies. As a result we are able to describe in a qualitative sense how the user ambiguity resolution performance is driven by the data from the different network scenarios

Review and principles of PPP-RTK methods

PPP-RTK is integer ambiguity resolution-enabled precise point positioning. In this contribution, we present the principles of PPP-RTK, together with a review of different mechanizations that have been proposed in the literature. By application of S-system theory, the estimable parameters of the different methods are identified and compared. Their interpretation is essential for gaining a proper insight into PPP-RTK in general, and into the role of the PPP-RTK corrections in particular. We show that PPP-RTK is a relative technique for which the ‘single-receiver user’ integer ambiguities are in fact double-differenced ambiguities. We determine the transformational links between the different methods and their PPP-RTK corrections, thereby showing how different PPP-RTK methods can be mixed between network and users. We also present and discuss four different estimators of the PPP-RTK corrections. It is shown how they apply to the different PPP-RTK models, as well as why some of the proposed estimation methods cannot be accepted as PPP-RTK proper. We determine analytical expressions for the variance matrices of the ambiguity-fixed and ambiguity-float PPP-RTK corrections. This gives important insight into their precision, as well as allows us to discuss which parts of the PPP-RTK correction variance matrix are essential for the user and which are not

Seasonal variations in carbon, nitrogen and phosphorus concentrations and C:N:P stoichiometry in different organs of a Larix principis-rupprechtii Mayr. plantation in the Qinling Mountains, China

Understanding how concentrations of elements and their stoichiometry change with plant growth and age is critical for predicting plant community responses to environmental change. Weusedlong-term field experiments to explore how the leaf, stem and root carbon (C), nitrogen (N) and phosphorous (P) concentrations and their stoichiometry changed with growth and stand age in a L.principis-rupprechtii Mayr. plantation from 2012–2015 in the Qinling Mountains, China. Our results showed that the C, N and P concentrations and stoichiometric ratios in different tissues of larch stands were affected by stand age, organ type andsampling month and displayed multiple correlations with increased stand age in different growing seasons. Generally, leaf C and N concentrations were greatest in the fast-growing season, but leaf P concentrations were greatest in the early growing season. However, no clear seasonal tendencies in the stem and root C, N and P concentrations were observed with growth. In contrast to N and P, few differences were found in organ-specific C concentrations. Leaf N:P was greatest in the fast-growing season, while C:N and C:P were greatest in the late-growing season. No clear variations were observed in stem and root C:N, C:P andN:Pthroughout the entire growing season, but leaf N:P was less than 14, suggesting that the growth of larch stands was limited by N in our study region. Compared to global plant element concentrations and stoichiometry, the leaves of larch stands had higher C, P, C:NandC:PbutlowerNandN:P,andtherootshadgreater PandC:NbutlowerN,C:Pand N:P. Our study provides baseline information for describing the changes in nutritional elements with plant growth, which will facilitates plantation forest management and restoration, and makes avaluable contribution to the global data pool on leaf nutrition and stoichiometry

Microeconomic institutions and personnel economics for health care delivery: a formal exploration of what matters to health workers in Rwanda

Background: Most developing countries face important challenges regarding the quality of health care and there is a growing consensus that health workers play a key role in this process. Our understanding as to what are the key institutional challenges in human resources, and their underlying driving forces, is more limited. A conceptual framework that structures existing insights and provides concrete directions for policy making is also missing. Methods: To gain a bottom up perspective we gather qualitative data through semi-structured interviews with different levels of health workers and users of health services in rural and urban Rwanda. We conducted discussions with 48 health workers and 25 users of health services in nine different groups in 2005. We maximized within-group heterogeneity by selecting participants using specific criteria that affect health worker performance and career choice. The discussion were analysed electronically, to identify key themes and insights, and are documented with a descriptive quantitative analysis relating to the associations between quotations. The findings from this research are then revisited ten years later making use of detailed follow up studies that have been carried out since then. Findings: The original discussions identified both key challenges in human resources for health, and driving forces of these challenges, as well as possible solutions. Two sets of issues were highlighted: those related to the size and distribution of the workforce, and those related to health workers’ on-the-job performance. Among the latter, four categories were identified: health workers’ poor attitudes towards patients, absenteeism, corruption and embezzlement, and lack of medical skills among some categories of health workers. The discussion suggest that four components constitute the deeper causal factors, which are, ranked in order of ease of malleability: incentives, monitoring arrangements, professional and workplace norms and intrinsic motivation. Three institutional innovations are identified that aim at improving performance: performance pay, community health workers and increased attention to training of health workers. Revisiting the findings from this primary research making use of later in depth studies, the analysis demonstrates their continued relevance and usefulness. We discuss how the different factors affect the quality of care by impacting on health worker performance and labour market choices, making use of insights from economics and development studies on the role of institutions. Conclusion: The study results indicates that health care quality to an important degree depends on four institutional factors at the micro level that strongly impact on health workers performance and career choice, and which deserve more attention in applied research and policy reform. The analysis also helps to identify ways forwards, which fit well with the Ministry’s most recent strategic plan

From sleep spindles of natural sleep to spike and wave discharges of typical absence seizures: is the hypothesis still valid?

The temporal coincidence of sleep spindles and spike-and-wave discharges (SWDs) in patients with idiopathic generalized epilepsies, together with the transformation of spindles into SWDs following intramuscular injection of the weak GABAA receptor (GABAAR) antagonist, penicillin, in an experimental model, brought about the view that SWDs may represent ‘perverted’ sleep spindles. Over the last 20 years, this hypothesis has received considerable support, in particular by in vitro studies of thalamic oscillations following pharmacological/genetic manipulations of GABAARs. However, from a critical appraisal of the evidence in absence epilepsy patients and well-established models of absence epilepsy it emerges that SWDs can occur as frequently during wakefulness as during sleep, with their preferential occurrence in either one of these behavioural states often being patient dependent. Moreover, whereas the EEG expression of both SWDs and sleep spindles requires the integrity of the entire cortico-thalamo-cortical network, SWDs initiates in cortex while sleep spindles in thalamus. Furthermore, the hypothesis of a reduction in GABAAR function across the entire cortico-thalamo-cortical network as the basis for the transformation of sleep spindles into SWDs is no longer tenable. In fact, while a decreased GABAAR function may be present in some cortical layers and in the reticular thalamic nucleus, both phasic and tonic GABAAR inhibitions of thalamo-cortical neurons are either unchanged or increased in this epileptic phenotype. In summary, these differences between SWDs and sleep spindles question the view that the EEG hallmark of absence seizures results from a transformation of this EEG oscillation of natural sleep