"Nonlinear" covariance matrix and portfolio theory for non-Gaussian multivariate distributions

This paper offers a precise analytical characterization of the distribution of returns for a portfolio constituted of assets whose returns are described by an arbitrary joint multivariate distribution. In this goal, we introduce a non-linear transformation that maps the returns onto gaussian variables whose covariance matrix provides a new measure of dependence between the non-normal returns, generalizing the covariance matrix into a non-linear fractional covariance matrix. This nonlinear covariance matrix is chiseled to the specific fat tail structure of the underlying marginal distributions, thus ensuring stability and good-conditionning. The portfolio distribution is obtained as the solution of a mapping to a so-called phi-q field theory in particle physics, of which we offer an extensive treatment using Feynman diagrammatic techniques and large deviation theory, that we illustrate in details for multivariate Weibull distributions. The main result of our theory is that minimizing the portfolio variance (i.e. the relatively ``small'' risks) may often increase the large risks, as measured by higher normalized cumulants. Extensive empirical tests are presented on the foreign exchange market that validate satisfactorily the theory. For ``fat tail'' distributions, we show that an adequete prediction of the risks of a portfolio relies much more on the correct description of the tail structure rather than on their correlations.Comment: Latex, 76 page

Peripheral Facial Nerve Palsy in Severe Systemic Hypertension: A Systematic Review

BACKGROUND Signs of nervous system dysfunction such as headache or convulsions often occur in severe systemic hypertension. Less recognized is the association between severe hypertension and peripheral facial nerve palsy. The aim of this study was to systematically review the literature on the association of peripheral facial palsy with severe hypertension. METHODS Systematic review of Medline, Embase, Web of Science, and Google Scholar from 1960 through December 2011 and report of two cases. RESULTS The literature review revealed 24 cases to which we add two cases with severe hypertension and peripheral facial palsy. Twenty-three patients were children. Palsy was unilateral in 25 cases, bilateral in one case, and recurred in nine. The time between the first facial symptoms and diagnosis of hypertension was a median of 45 days (range, 0 days-2 years). In five case series addressing the complications of severe hypertension in children, 41 further cases of peripheral facial palsy were listed out of 860 patients (4.8%). CONCLUSIONS The association between severe hypertension and peripheral facial palsy is mainly described in children. Arterial hypertension is diagnosed with a substantial delay. Outcome is favorable with adequate antihypertensive treatment. The pathophysiology is still debate

Nervous system dysfunction in Henoch-Schönlein syndrome: systematic review of the literature

Objective. CNS or peripheral nervous system dysfunction sometimes occurs in Henoch-Schönlein patients. Methods. We review all Henoch-Schönlein cases published after 1969 with CNS dysfunction without severe hypertension and neuroimaging studies (n = 35), cranial or peripheral neuropathy (n = 15), both CNS and peripheral nervous system dysfunction without severe hypertension (n = 2) or nervous system dysfunction with severe hypertension (n = 2). Forty-four of the 54 patients were <20 years of age. Results. In patients with CNS dysfunction without or with severe hypertension the following presentations were observed in decreasing order of frequency: altered level of consciousness, convulsions, focal neurological deficits, visual abnormalities and verbal disability. Imaging studies disclosed the following lesions: vascular lesions almost always involving two or more vessels, intracerebral haemorrhage, posterior subcortical oedema, diffuse brain oedema and thrombosis of the superior sagittal sinus. Following lesions were noted in the subjects with cranial or peripheral neuropathy without severe hypertension: peroneal neuropathy, peripheral facial palsy, Guillain-Barré syndrome, brachial plexopathy, posterior tibial nerve neuropathy, femoral neuropathy, ulnar neuropathy and mononeuritis multiplex. Persisting signs of either CNS (n = 9) or peripheral (n = 1) nervous system dysfunction were sometimes reported. Conclusions. In Henoch-Schönlein syndrome, signs of nervous system dysfunction are uncommon but clinically relevant. This review helps clinicians managing Henoch-Schönlein syndrome with nervous system dysfunctio

A complex interprofessional intervention to improve the management of painful procedures in neonates

During hospitalization, neonates are exposed to a stressful environment and a high number of painful procedures. If pain is not treated adequately, short- and long-term complications may develop. Despite evidence about neonatal pain and available guidelines, procedural pain remains undertreated. This gap between research and practice is mostly due to limited implementation of evidence-based knowledge and time constraints. This study describes in detail the development process of a complex interprofessional intervention to improve the management of procedural pain in neonates called NEODOL© (NEOnato DOLore). The framework of the Medical Research Council (MRC) for the development and evaluation of complex interventions was used as a methodological guide for the design of the NEODOL© intervention. The development of the intervention is based on several steps and multiple methods. To report this process, we used the Criteria for Reporting the Development of Complex Interventions in Healthcare (CReDECI 2). Additionally, we evaluated the content of the intervention using a Delphi method to obtain consensus from experts, stakeholders, and parents. The complex interprofessional intervention, NEODOL©, is developed and designed for three groups: healthcare professionals, parents, and neonates for a level IIb neonatal unit at a regional hospital in southern Switzerland. A total of 16 panelists participated in the Delphi process. At the end of the Delphi process, the panelists endorsed the NEODOL© intervention as important and feasible. Following the MRC guidelines, a multimethod process was used to develop a complex interprofessional intervention to improve the management of painful procedures in newborns. Complex interprofessional interventions need theoretical bases, careful development, and integration of stakeholders to provide a comprehensive approach. The NEODOL intervention consists of promising components and has the potential to improve the management of painful procedures and should facilitate the knowledge translation into practice. KEYWORDS bundle of care, complex interventions, interprofessional relations, knowledge translation, neonate, procedural pai

Kidney tubular injury induced by valproic acid: systematic literature review.

BACKGROUND Valproic acid is prescribed for epilepsy and as prophylaxis for bipolar disorder and migraine headaches. It has also been implicated as a cause of a kidney tubular injury. METHODS We undertook a review of the literature to characterize the biochemical and histopathological features of the overt kidney tubular injury and to evaluate the possible existence of a pauci-symptomatic injury. The pre-registered review (CRD42022360357) was performed following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology. Searches were conducted in Excerpta Medica, the National Library of Medicine, and Web of Science. The gray literature was also considered. RESULTS For the final analysis, we retained 36 articles: 28 case reports documented 48 individuals with epilepsy on valproic acid for 7 months or more and presenting with features consistent with an overt kidney tubular injury. The following disturbances were noted: hypophosphatemia (N = 46), normoglycemic glycosuria (N = 46), total proteinuria (N = 45), metabolic acidosis (N = 36), hypouricemia (N = 27), tubular proteinuria (N = 27), hypokalemia (N = 23), and hypocalcemia (N = 8). A biopsy, obtained in six cases, disclosed altered proximal tubular cells with giant and dysmorphic mitochondria. Eight case series addressed the existence of a pauci- or even asymptomatic kidney injury. In the reported 285 subjects on valproic acid for 7 months or more, an isolated tubular proteinuria, mostly N-acetyl-β-glucosaminidase, was often noted. CONCLUSIONS Valproic acid may induce an overt kidney tubular injury, which is associated with a proximal tubular mitochondrial toxicity. Treatment for 7 months or more is often associated with a pauci- or oligosymptomatic kidney tubular injury. A higher resolution version of the Graphical abstract is available as Supplementary information

Synthetic bone grafting in aseptic loosening of acetabular cup: Good clinical and radiological outcomes in contained bone defects at mediumterm follow up

Restoring bone loss is one of the major challenges when facing hip revision surgery. To eliminate the risk of disease transmission and antigenicity of allografts and donor-morbidity of autografts, the use of synthetic bioceramics has become popular in the last decade. Our study investigated the effectiveness of impaction bone grafting (IBG) of contained acetabular defects (Paprosky 2 and 3a) using a porous ceramic-based hydroxyapatite bone substitute (Engipore, provided by Finceramica Faenza S.p.A., Faenza, Italy) mixed with a low percentage of autologous bone (obtained from reaming when available). We retrospectively assessed 36 patients who underwent acetabular revision using IBG using a porous ceramic-based hydroxyapatite bone substitute with cementless implants with a mean follow-up of 4.4 years. We evaluated, at regular intervals, patients clinically (using the Hip Harris Score and Oxford Score) and radiologically to evaluate the rate of incorporation of the graft, the presence of radiolucent lines or migrations of the cup. Clinical scores significantly improved (WOMAC improved from 49.7–67.30, and the HSS from 56–89). The rate of implants’ survival was 100% at our medium follow-up (4.4 years). We reported five cases of minor migration of the cup, and radiolucent lines were visible in seven patients at the last-follow up. The graft was well-incorporated in all patients. The results presented in this study suggest the HA bone substitute is an effective and safe bone graft when facing hip revision surgery; thus, longer follow-up studies are required