Littérature scientifique sur le sujet « Multilevel proximal methods »

In this paper, problems of bi-level convex minimization in a Hilbert space are considered. The bi-level convex minimization problem is to minimize the first convex function on the set of minima of the second convex function. This setting has many applications, but the implicit constraints generated by the internal problem make it difficult to obtain optimality conditions and construct algorithms. Multilevel optimization problems are formulated in a similar way, the source of which is the operation research problems (optimization according to sequentially specified criteria or lexicographic optimization). Attention is focused on problem solving using two proximal methods. The main theoretical results are theorems on the convergence of methods in various situations. The first of the methods is obtained by combining the penalty function method and the proximal method. Strong convergence is proved in the case of strong convexity of the function of the exterior problem. In the general case, only weak convergence has been proved. The second, the so-called proximal-gradient method, is a combination of one of the variants of the fast proximal-gradient algorithm with the method of penalty functions. The rates of convergence of the proximal-gradient method and its weak convergence are proved.

OBJECTIVE: To analyze how individual characteristics and the social context, together, are associated with self-perception of the oral health. METHODS: A multilevel cross-sectional study with data from the Brazilian National Health Survey 2013, the United Nations Development Program, and the National Registry of Health Establishments. The explanatory variables for the “oral health perception” outcome were grouped, according to the study framework, into biological characteristics (sex, color, age), proximal social determinants (literacy, household crowding, and socioeconomic stratification), and distal (years of schooling expectancy at age 18, GINI, Human Development Index, and per capita income). The described analysis was performed, along with bivariate Poisson analysis and multilevel Poisson analysis for the construction of the explanatory model of oral health perception. All analyzes considered the sample weights. RESULTS: Both the biological characteristics and the proximal and distal social determinants were associated with the perception of oral health in the bivariate analysis. A higher prevalence of bad oral health was associated to lower years of schooling expectancy (PR = 1.31), lower per capita income (PR = 1.45), higher income concentration (PR = 1.41), and worse human development (PR = 1.45). Inversely, oral health services in both primary and secondary care were negatively associated with oral health perception. All the biological and individual social characteristics, except reading and writing, made up the final explanatory model along with the distal social determinants of the Human Development Index and coverage of basic care in the multilevel analysis. CONCLUSIONS: Biological factors, individual and contextual social determinants were associate synergistically with the population’s perception of oral health. It is necessary to improve individual living conditions and the implementation of public social policies to improve the oral health of the population.

Introduction: Multilevel femur fracture is being encountered frequently than previously thought. The literature reports the incidence anywhere between 6-11%. Management of these fractures in isolation are technically demanding, and presence of other bone or organ involvement complicates the scenario in achieving the optimal functional results. The use of a single implant provides the technically better overlapping fixation. Methods: Our study represents a prospective cohort study in a 2-year period, between 2017 till 2019. Twenty-six patients with multilevel femur fractures being treated by a single step all in one interlocked cephalomedullary nail were included. Results: In our study 16 patients (88.8%) had been treated by Antegrade cephalomedullary reconstruction nail / proximal femoral nail. Healing of all the femoral fractures was without major complications or requirement of additional surgical procedures. In our study the femur fractures, on an average healed by 18 weeks. Conclusion: For multilevel segmental femur fracture in young adults, stabilization using All-in-one device such as the intramedullary nail is recommended. Closed reduction with PFNA?long / Reconstruction nail is an effective treatment for long?segment femoral fracture with good strength in fixation, high rate of fracture union, and low rate of complications.

INTRODUCTION: A common cause of neurosurgical malpractice cases is the misrepresentation of idiopathic brachial neuritis (incidence: 1/1000) as an iatrogenic neurological insult caused by a surgeon. METHODS: Confirmed postprocedural brachial neuritis patients from a single quaternary care institution were identified and analyzed. RESULTS: We identified 6 (3 female) postprocedural brachial neuritis patients with mean age 63.7 (range 50-75) years. Procedures included 5 cervical spine surgeries (3 multilevel ACDFs, 2 multilevel posterior fusions with laminectomies, 1 multilevel disc arthroplasty) and 1 intrajugular central venous catheter placement. Average time to symptom onset was 1 week post-procedure (range 1 day-2.5 weeks). Initial symptom was moderate-to-severe shoulder (5), arm (4), and/or neck (1) pain. Subsequently, all developed axillary/shoulder weakness; 3 distal arm/hand weakness, 2 winged scapula, and 2 dyspnea/orthopnea. For diagnosis, two patients had confirmatory EMG, 1 had MR neurography confirming plexus inflammation, and 3 had both (positive EMG findings and inflammation on MR Neurography). Average time to accurate diagnosis was 3.1 (range 1.5-5) months. Average number of clinicians seen prior to accurate diagnosis: 5. Treatments included opioids (5), steroids (1), and/or physical therapy (6). All experienced partial pain relief by 1-8 weeks; 2 had persistent pain requiring gabapentin past 6 months. All patients continued to experience motor deficits past 6 months: (4 patients had atrophy and 2-4/5 motor strength in proximal the proximal arm, 1 had distal arm 3/5 motor strength, and 1 had scapular winging). CONCLUSIONS: Postoperative idiopathic brachial plexitis mimics iatrogenic nerve damage following neurosurgical procedures. Recognition of this entity is difficult, and 6 patients at our institution saw on average 5 providers over 3 months prior to accurate diagnosis. Brachial plexitis has a prolonged course with typically only partial recovery at 6 months.

The extreme manifestation of atherosclerotic lesion of the arteries of the lower extremities is the critical ischemia of the lower extremities. The number of high amputations in such patients ranges from 120 to 500 per 1 million population in the general population annually. In order to achieve the best results in the patency of the arterial bed in the near and distant periods, revascularization of the arteries of the proximal and distal blood flow is necessary. The aim of the work was to evaluate the possibilities and effectiveness of endovascular, open and hybrid arterial interventions on the lower extremities, particularly in patients with multilevel arterial disease, by conducting a retrospective analysis of treatment of critical ischemia. The results of the preoperative ultrasound duplex scan (UDS) of the arteries of 212 patients with critical ischemia of the lower limbs (CILL) shoved, that in 78 (36.8%) were multilevel arterial lesions (MLAL). Patients were divided into two groups. The first (main group) consisted of 50 patients (64%), who have been restored to the open-end and endovascular methods of MLAL, or only endovascular. The second (control) group included 28 patients (36%) — with restoration of permeability of the proximal segment without intervention on the arteries of the distal. Installed, during the period of 16 months, postoperative observation of 78 patients with MLAL, the primary frontal area of the femoral reconstruction in the main group was 92%, and limb preservation - 96%. In the control group, the permeability of the reconstruction zone was 75%, limb preservation — 82%. Thus, it has been established that the most optimal method of recovery of inflow and outflow pathways is one-time hybrid surgical interventions performed in 88% of these patients, which allow to achieve more effectively the recurrence of ischemia and maintain limb.

Sports performance is the result of a complex interaction between individual and environmental factors. The purpose of this paper is to explain the methods used in the InTrack Project, a cross-sectional and cross-cultural project developed to investigate the variance in the performance of runners from different countries and to understand whether the differences in the performance can be explained by micro-level (athletes characteristics and proximal environment), meso-level (the distal environment that plays a relevant role on the relationships established at micro-level), and the macro-level (environmental features that shape countries characteristics). The sample will be comprised of runners, of both sexes, from four countries. Data collection will be performed in two steps: i) Individual information and ii) Country-level information. At the individual level, data will be obtained from an online survey. At the country level, characteristics data will be obtained from the secondary data available (demographic, social, and economic variables). Statistical procedures expected to be used include multilevel analysis, latent class analysis, addictive and multiplicative interaction in regression models. This wealth of information is of relevance to fill gaps regarding the existence of variables to connect different levels of information, and to provide scientific support about environmental characteristics important to predict runners’ performance within and between countries.

Aim. To assess results of Meshalkin National Research Medical Center and Tomsk National Research Medical Center in surgical treatment of DeBakey type I aortic dissection using hybrid technologies (“frozen elephant trunk”) compared with classical standard interventions.Material and methods. The study included patients operated on successively in the 2002­2010 timeframe with a diagnosis of acute and subacute DeBakey type I aortic dissection. A retrospective observational comparison of the surgical treatment results of patients (two groups) was performed: using standard surgical approaches (beveled anastomosis or aortic arch replacement using multi­branched prosthesis) and frozen elephant trunk (FET) intervention. The groups included 70 and 31 patients, respectively. Mortality and morbidity were evaluated in the postoperative period, the frequency of aorto­related events — during the observation period.Results. Mortality and the frequency of complications between the groups in the early and late postoperative periods did not differ. Aorto­related events of the groups in the long­term period differed statistically significantly in favor of hybrid interventions (p=0,005).Conclusion. The hybrid technology of thoracic aorta reconstruction using “frozen elephant trunk” type allows to make one­step reconstruction of the aorta during its multilevel lesion. Observation of patients in the long­term period allows us to announce of a longtime, stable result of surgical treatment in the absence of additional perioperative risks.

We aimed to evaluate whether children’s caries experience exerts an influence on the performance of visual and radiographic methods in detecting nonevident proximal caries lesions in primary molars. Eighty children (3–6 years old) were selected and classified as having a lower (≤3 decayed, missing, or filled surfaces; dmf-s) or higher (> 3 dmf-s) caries experience. Two calibrated examiners then assessed 526 proximal surfaces for caries lesions using visual and radiographic methods. As a reference standard, 2 other examiners checked the surfaces after temporary separation. Noncavitated and cavitated lesion thresholds were considered and Poisson multilevel regression analyses were conducted to evaluate the influence of caries experience on the performance of diagnostic strategies. Accuracy parameters stratified by caries experience were also derived. A statistically significant influence of caries experience was observed only for visual inspection, with more false-positive results in children with a higher caries experience at the noncavitated lesion threshold, and more false results at the cavitated threshold. The detection of noncavitated caries lesions in children with a higher caries experience was overestimated (specificity = 0.696), compared to children with a lower caries experience (specificity = 0.918), probably due to confirmation bias. However, the examiners underestimated the detection of cavitated lesions in children with a higher caries experience (sensitivity = 0.143) compared to lower-caries-experience children (sensitivity = 0.222), possibly because of representativeness bias. The radiographic method was not influenced by children’s caries experience. In conclusion, children’s caries experience influences the performance of visual inspection in detecting proximal caries lesions in primary teeth, evidencing the occurrence of cognitive biases.

Background. Australia has made significant progress towards universal access to primary health care (PHC) services. However, disparities in the utilisation of health services and health status remain challenges in achieving the global target of universal health coverage (UHC). This scoping review aimed at synthesizing the drivers of PHC services towards UHC in Australia. Methods. We conducted a scoping review of the literature published from 1 January 2010 to 30 July 2021 in three databases: PubMed, Scopus, and Embase. Search terms were identified under four themes: health services, Australia, UHC, and successes or challenges. Data were analysed using an inductive thematic analysis approach. Drivers (facilitators and barriers) of PHC services were explained by employing a multilevel framework that included the proximal level (at the level of users and providers), intermediate level (organisational and community level), and distal level (macrosystem or distal/structural level). Results. A total of 114 studies were included in the review. Australia has recorded several successes in increased utilisation of PHC services, resulting in an overall improvement in health status. However, challenges remain in poor access and high unmet needs of health services among disadvantaged/priority populations (e.g., immigrants and Indigenous groups), those with chronic illnesses (multiple chronic conditions), and those living in rural and remote areas. Several drivers have contributed in access to and utilisation of health services (especially among priority populations)operating at multilevel health systems, such as proximal level drivers (health literacy, users’ language, access to health facilities, providers’ behaviours, quantity and competency of health workforce, and service provision at health facilities), intermediate drivers (community engagement, health programs, planning and monitoring, and funding), and distal (structural) drivers (socioeconomic disparities and discriminations). Conclusion. Australia has had several successes towards UHC. However, access to health services poses significant challenges among specific priority populations and rural residents. To achieve universality and equity of health services, health system efforts (supply- and demand-side policies, programs and service interventions) are required to be implemented in multilevel health systems. Implementation of targeted health policy and program approaches are needed to provide comprehensive PHC and address the effects of structural disparities.

Abstract Introduction: Nonunions (NUs) of the fractured proximal third of the tibia are challenging to manage owing to a capacious canal and scarce anterior soft-tissue cover. Infection further complicates the use of internal fixators in such patients. We present a study of 25 cases of infected NU of the proximal third of the tibia that we treated using the Ilizarov ring fixator over 10 years. Materials and Methods: Twenty-three men and two women with infected NU of the proximal tibial meta-diaphyseal junction were studied. The mean age of the patients was 39.2 years. Treatment involved thorough debridement of the NU site with freshening of the bone ends followed by the application of a 3-ring hybrid Ilizarov construct. The patients were followed at regular intervals to assess the infection control, union, limb function, and complications. Results: Successful union and eradication of infection were achieved in 21 patients. Union was not satisfactory in four cases. The average fixator time was 7.12 months. Average knee flexion of 99.2° was observed. The Association for the Study and Application of the Methods of Ilizarov score was excellent in 56% of cases and good in 28%. Six patients required soft-tissue reconstruction. One patient suffered a fracture at the distal pin site while one had a refracture 4 months after treatment completion. Three patients developed a discharging sinus which required debridement and oral antibiotics. Conclusion: The Ilizarov construct provides multilevel, multidirectional, and multiplanar stability, aiding early mobility. Appropriate case selection, sound soft-tissue reconstruction, robust infection control, and good patient compliance are important for the success of the treatment.

La taille des problèmes de restauration d'images ne fait qu'augmenter. Cette croissance pose un problème majeur de passage à l'échelle pour les algorithmes d'optimisation, qui peinent à fournir des solutions satisfaisantes en un temps raisonnable. Parmi les méthodes proposées pour surmonter ce défi, les méthodes multi-niveaux semblent être un candidat idéal. En réduisant de manière systématique la dimension du problème, le coût computationnel nécessaire à sa résolution peut diminuer drastiquement. Ce type d'approche est classique pour la résolution numérique des équations aux dérivées partielles (EDP), avec des garanties théoriques et des démonstrations pratiques pour expliquer leur succès. Cependant, les méthodes actuelles d'optimisation multi-niveaux n'ont pas les mêmes garanties, ni les mêmes performances. Dans cette thèse, nous proposons de combler une partie de cet écart en introduisant un nouvel algorithme multi-niveaux, IML FISTA, possédant les garanties de convergence théoriques optimales pour les problèmes d'optimisation convexes non-lisses, i.e., convergence vers un minimiseur et taux de convergence de la fonction objectif vers une valeur minimale. IML FISTA est aussi en mesure de traiter les régularisations de l'état-de-l'art en restauration d'images. En comparant IML FISTA aux algorithmes standard sur un grand nombre de problèmes de restauration d'images: défloutage, débruitage, reconstruction de pixels manquants pour des images en couleur et des images hyperspectrales, ainsi qu'en reconstruction d'images radio-interférométriques, nous montrons qu'IML FISTA est capable d'accélérer la résolution de ces problèmes de manière significative. Le cadre d'IML FISTA est suffisamment général pour s'adapter à de nombreux autres problèmes de restauration d'images. Nous concluons cette thèse en proposant un nouveau point de vue sur les algorithmes multi-niveaux, en démontrant leur équivalence, dans certains cas, avec les algorithmes de descente par coordonnées qui sont nettement plus étudiés dans la littérature de l'optimisation non-lisse. Ce nouveau cadre théorique nous permet d'analyser les algorithmes multi-niveaux de manière plus rigoureuse, et notamment d'étendre leurs garanties de convergence à des problèmes non-lisses et non-convexes. Ce cadre est moins général que celui d'IML FISTA, mais il ouvre la voie à une conception plus solide sur le plan théorique des algorithmes multi-niveaux
The size of image restoration problems is constantly increasing. This growth poses a major scaling problem for optimisation algorithms, which struggle to provide satisfactory solutions in a reasonable amount of time. Among the methods proposed to overcome this challenge, multilevel methods seem to be an ideal candidate. By systematically reducing the size of the problem, the computational cost of solving it can be drastically reduced. This type of approach is standard in the numerical solution of partial differential equations (PDEs), with theoretical guarantees and practical demonstrations to explain their success. However, current multilevel optimisation methods do not have the same guarantees nor the same performance. In this thesis, we propose to bridge part of this gap by introducing a new multilevel algorithm, IML FISTA, which has the optimal theoretical convergence guarantees for convex non-smooth optimisation problems, i.e. convergence to a minimiser and convergence rate of the objective function to a minimum value. IML FISTA is also able to handle state-of-the-art regularisations in image restoration. By comparing IML FISTA with standard algorithms on many image restoration problems: deblurring, denoising, reconstruction of missing pixels for colour and hyperspectral images, and reconstruction of radio-interferometric images, we show that IML FISTA is capable of significantly speeding up the resolution of these problems. As IML FISTA's framework is sufficiently general, it can be adapted to many other image restoration problems. We conclude this thesis by proposing a new point of view on multilevel algorithms, by demonstrating their equivalence, in certain cases, with coordinate descent algorithms, which are much more widely studied in the non-smooth optimisation literature. This new theoretical framework allows us to analyse multi-level algorithms more rigorously, and in particular to extend their convergence guarantees to non-smooth and non-convex problems. This framework is less general than that of IML FISTA, but it paves the way for a more theoretically robust design of multilevel algorithms

This study presents a model for the organization of educational content customized for environments of individual studies. For many students the availability of content in general form can not be efficient. It proposed a multilevel structure of concepts to provide the development of different combinations to show the same content. The work shows that it is possible to customize the content in order to encourage other students with the use of proximal learning standards. These patterns are obtained from the analysis of the action of students with positive results in the individual organization of the content. The formal representation establishes the definition of the student profile, multi-level content, the distribution plan of correction of concepts and teaching career. The structure of the trajectory of student teaching is formally established by the method of finite differences. The system uses artificial intelligence techniques to organize and personalize content reactively. Customization is provided by an artificial neural network that enables the classification of the student profile and assign that profile to a standard proximal learning. To mediate and adjust the contents of a reactive system was inserted into a set of rules from experts in teaching. The experiment showed the applicability and appropriateness of the proposed model. The results indicated the suitability of the approach by automating the organization\'s custom content so adaptive and reactive. The intelligent system to establish the structure of the custom content to be presented was considered efficient, giving the student a better use of the content, with higher and lower final average study time and content presented.
Este trabalho apresenta uma modelagem para a organização personalizada de conteúdos didáticos para ambientes de estudos individuais. Para muitos estudantes a disponibilização do conteúdo em formato generalizado pode não ser eficiente. É proposta uma estrutura multinível de conceitos para proporcionar o desenvolvimento de diferentes combinações para a apresentação do mesmo conteúdo. O trabalho mostra que é possível personalizar o conteúdo de forma a favorecer outros estudantes com o uso de padrões proximais de aprendizagem. Estes padrões são obtidos da análise da ação de estudantes, com resultados positivos na organização individual do conteúdo. A representação formal estabelece a definição do perfil do estudante, o conteúdo multinível, o plano de distribuição dos conceitos e a correção da trajetória didática. A estruturação da trajetória didática do estudante é formalmente estabelecida pelo método das diferenças finitas. O sistema utiliza técnicas de inteligência artificial para organizar e personalizar reativamente o conteúdo. A personalização é proporcionada por uma rede neural artificial que possibilita a classificação do perfil do estudante e associa esse perfil a um padrão proximal de aprendizagem. Para mediar e ajustar o conteúdo de forma reativa foi inserido no sistema um conjunto de regras de especialistas em docência. O experimento realizado mostrou a aplicabilidade e a adequação da modelagem proposta. Os resultados indicaram a adequação da abordagem, automatizando a organização personalizada do conteúdo de forma adaptativa e reativa. O sistema inteligente ao estabelecer a estruturação personalizada do conteúdo a ser apresentado foi considerado eficiente, proporcionando ao estudante um melhor aproveitamento do conteúdo, com maior média final e menor tempo de estudo e conteúdo apresentado.
Doutor em Ciências