Bounding rare event probabilities in computer experiments

We are interested in bounding probabilities of rare events in the context of computer experiments. These rare events depend on the output of a physical model with random input variables. Since the model is only known through an expensive black box function, standard efficient Monte Carlo methods designed for rare events cannot be used. We then propose a strategy to deal with this difficulty based on importance sampling methods. This proposal relies on Kriging metamodeling and is able to achieve sharp upper confidence bounds on the rare event probabilities. The variability due to the Kriging metamodeling step is properly taken into account. The proposed methodology is applied to a toy example and compared to more standard Bayesian bounds. Finally, a challenging real case study is analyzed. It consists of finding an upper bound of the probability that the trajectory of an airborne load will collide with the aircraft that has released it.Comment: 21 pages, 6 figure

Maximin design on non hypercube domain and kernel interpolation

In the paradigm of computer experiments, the choice of an experimental design is an important issue. When no information is available about the black-box function to be approximated, an exploratory design have to be used. In this context, two dispersion criteria are usually considered: the minimax and the maximin ones. In the case of a hypercube domain, a standard strategy consists of taking the maximin design within the class of Latin hypercube designs. However, in a non hypercube context, it does not make sense to use the Latin hypercube strategy. Moreover, whatever the design is, the black-box function is typically approximated thanks to kernel interpolation. Here, we first provide a theoretical justification to the maximin criterion with respect to kernel interpolations. Then, we propose simulated annealing algorithms to determine maximin designs in any bounded connected domain. We prove the convergence of the different schemes.Comment: 3 figure

Influence of support on intra-abdominal pressure, hepatic kinetics of indocyanine green and extravascular lung water during prone positioning in patients with ARDS: a randomized crossover study

INTRODUCTION: Prone positioning (PP) on an air-cushioned mattress is associated with a limited increase in intra-abdominal pressure (IAP) and an absence of organ dysfunction. The respective influence of posture by itself and the type of mattress on these limited modifications during the PP procedure remains unclear. The aim of this study was to evaluate whether the type of support modifies IAP, extravascular lung water (EVLW) and the plasma disappearance rate of indocyanine green (PDR(ICG)) during PP. METHODS: A prospective, randomized, crossover study of 20 patients with acute respiratory distress syndrome (ARDS) was conducted in a medical intensive care unit in a teaching hospital. Measurements were made at baseline and repeated after 1 and 6 hours of two randomized periods of 6 hours of PP with one of two support types: conventional foam mattress or air-cushioned mattress. RESULTS: After logarithmic transformation of the data, an analysis of variance (ANOVA) showed that IAP and PDR(ICG )were significantly influenced by the type of support during PP with an increase in IAP (P < 0.05 by ANOVA) and a decrease in PDR(ICG )on the foam mattress (P < 0.05 by ANOVA). Conversely, the measurements of EVLW did not show significant modification between the two supports whatever the posture. The ratio of the arterial oxygen tension to the fraction of inspired oxygen significantly increased in PP (P < 0.0001 by ANOVA) without any influence of the support. CONCLUSION: In comparison with a conventional foam mattress, the use of an air-cushioned mattress limited the increase in IAP and prevented the decrease in PDR(ICG )related to PP in patients with ARDS. Conversely, the type of support did not influence EVLW or oxygenation

Medical kit for single-handed offshore yacht races

Background: The medical kit is the basis of medical support in maritime environment; it is defined by international or national regulations and guidelines. For offshore races, rules and recommendations are proposed by national or international sailing federations. Sailing and racing offshore alone presents specificities that sometimes make it difficult to apply the usual recommendations. The epidemiology of single-handed offshore race is dominated by traumatic risks. Medical events are relatively rare because competitors are high-level athletes, generally young and subject to complete medical assessments. The scarcity of available scientific data makes it necessary to choose appropriate methods for developing recommendations. The purpose of this work is to propose a medical kit adapted and applicable to these situations. Materials and methods: The method used was that of “Professional recommendations by formal consensus of experts” derived from the Rand/UCLA method. After a critical analysis of the literature, a panel of 19 experts having expertise in medicine in maritime environment was gathered from various medical specialties (cardiologist, internist, intensivist and emergency physician, ear-nose-throat physician and general practitioner) and from varied medical activities. They had not declared any direct conflict of interest. Results: A medical kit proposal has been developed. The choice of drugs was based on the analysis of the epidemiology of medical events observed during the last offshore races. The experts’ choice was to reduce the quantity of medication and medical devices in order to limit the risk of confusion of medicines and dosages. Drugs with significant side effects or requiring third party monitoring have been removed. Medical devices designed to do an intervention impossible to perform on oneself have also been eliminated. Conclusions: Solo sailing remains a marginal maritime activity with specific risks. The development of single-handed races requires an adaptation of medical support through the development of a specific medical kit and adapted training. The formalised consensus of experts seems to be an appropriate method for developing recommendations in the field of maritime medicine

Preparation and medical follow-up for a single-handed transatlantic rowing race

Background: A single-handed transatlantic rowing race was organised between Senegal and French Guyana (2600 nautical miles). During the race, rowers adjust their lifestyle to maintain an optimal level of performance. Nutrition, circadian rhythm disturbance, psychological state, pain and other medical problems impact on physical abilities and increase the occurrence of accidents. We surveyed the prevalence of medical complications during this race and the preparation that we could suggest for this kind of activity. Materials and methods: This is a descriptive, retrospective case series study. Follow-up consisted of sending out a questionnaire and performing individual interviews. Results: A total of 23 participants including 1 woman and 22 men; mean age of 46.5 years (range: 35–59) entered the race. The race lasted for 39 to 52 days with participants rowing between 10 and 12 h/day. Nine participants dropped out. Energy intake was 4500 to 6000 kcal/day and fluid intake was 4 to 5.5 L/day. Mean weight loss was 13.3 kg. The resting period was 6 ± 1 h/24 h divided into 1.5 to 2 h periods essentially during darkness. A total of 92% of the racers required medical care for dermatological problems; other conditions requiring medical care were: tendinitis in 10 cases, diarrhoea in 4, moderate to severe seasickness in 4, hallucinations in 3, panic attacks in 2, burns in 2, and disembarkation syndrome (“land sickness”) lasting from 45 min to 6 h in 13. Conclusions: Physiological and psychological impact of this type of event is still unclear. The most common medical problems are dermatological, rheumatological complications and minor trauma. Medical and psychological preparation should be offered to candidates for these competitions.

A Medical Support in Offshore Racing — Workshop on Medical Kit Inventory in Offshore Yacht Racing, 12–13 May 2017, Lorient, France

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Medical treatment of seafarers in the Southern Indian Ocean — interaction between the French Telemedical Maritime Assistance Service (TMAS) and the medical bases of the French Southern and Antarctic Lands (TAAF)

Background: The waters surrounding the French Southern Lands are a fishing zone, accessible only bysailing for several days in a region where weather conditions are often difficult. The scientific bases of theregion have medical staff whose services can be called upon if seafarers require assessment and rapidmedical treatment. We conducted an epidemiological study of the maritime teleconsultations carried outby the French Telemedical Maritime Assistance Service (TMAS), where patients navigating in the SouthernIndian Ocean zone were advised to disembark on the medical bases in the French Southern Lands, between2015 and 2020, to receive medical treatment.Materials and methods: We extracted data from all of the maritime records from 1 January 2015 to31 December 2020 relating to patients who attended a maritime teleconsultation with a French TMASdoctor in the Southern Indian Ocean zone and who had been redirected to the medical bases in the FrenchSouthern Lands. Data were collected on the patients’ age, gender, nationality, rank, type of vessel, teleconsultationdiagnosis, patient management on board and in the French Southern Lands medical bases,as well as the medical outcome. We carried out a descriptive data analysis.Results: French TMAS doctors managed 11,908 cases including 76 in the Southern Indian Ocean zone(0.6%). Nineteen (25%) patients were redirected to the French Southern Lands over the study period.Eighteen patients were men with an average age of 45 ± 10 years. Eighteen patients were on boarda trawler and 11 of them were sailors. Nine patients were treated for a trauma-related condition, 8 fora medical condition and 2 for a surgical disease. Eleven (58%) patients were evacuated to Reunion Islandand 8 (42%) patients received medical treatment and were able to re-embark aboard their vessel.Conclusions: Relatively few patients are redirected to the French Southern Lands for medical assistance,but referrals occur on a regular basis. The presence of these medical bases is unusual in a maritime setting,but they can be a valuable asset when maritime medical assistance is required in this region. The type of condition encountered, and the patient profile, were typical of the fishing community. The presence of these bases and communication between the various stakeholders delivering maritime medical assistance provided these patients with optimal care despite their isolated location

Mimivirus in Pneumonia Patients

Mimivirus, the largest virus known to date, is an amebal pathogen like Legionella spp. When mimivirus was used as an antigen in a migration inhibition factor assay, seroconversion was found in patients with both community- and hospital-acquired pneumonia. Mimivirus DNA was found in respiratory samples of patients with hospital-acquired pneumonia

Langerhans cell (LC) proliferation mediates neonatal development, homeostasis, and inflammation-associated expansion of the epidermal LC network

Most tissues develop from stem cells and precursors that undergo differentiation as their proliferative potential decreases. Mature differentiated cells rarely proliferate and are replaced at the end of their life by new cells derived from precursors. Langerhans cells (LCs) of the epidermis, although of myeloid origin, were shown to renew in tissues independently from the bone marrow, suggesting the existence of a dermal or epidermal progenitor. We investigated the mechanisms involved in LC development and homeostasis. We observed that a single wave of LC precursors was recruited in the epidermis of mice around embryonic day 18 and acquired a dendritic morphology, major histocompatibility complex II, CD11c, and langerin expression immediately after birth. Langerin+ cells then undergo a massive burst of proliferation between postnatal day 2 (P2) and P7, expanding their numbers by 10–20-fold. After the first week of life, we observed low-level proliferation of langerin+ cells within the epidermis. However, in a mouse model of atopic dermatitis (AD), a keratinocyte signal triggered increased epidermal LC proliferation. Similar findings were observed in epidermis from human patients with AD. Therefore, proliferation of differentiated resident cells represents an alternative pathway for development in the newborn, homeostasis, and expansion in adults of selected myeloid cell populations such as LCs. This mechanism may be relevant in locations where leukocyte trafficking is limited