Introducció a la mecànica celeste

Treballs Finals de Grau de Matemàtiques, Facultat de Matemàtiques, Universitat de Barcelona, Any: 2024, Director: Àngel Jorba i Monte[en] This Bachelor’s Thesis provides a rigorous introduction to the fundamental concepts of celestial mechanics from a mathematical standpoint. The text explores the foundational principles governing the motion of particles due to their gravitational interactions in space. Key concepts such as Kepler’s laws, conservation of energy, and the n-body problem are addressed. Special emphasis is placed on the latter, as well as its particular cases of two and three bodies, with an analysis of the inherent challenges in accurately predicting the trajectories of these systems

Maladie de Crohn fistulisante ano-périnéale (que peut-on attendre aujourd'hui de l'IRM?)

OBJECTIFS : Evaluer la reproductibilité des signes IRM caractérisant les lésions fistulisantes de maladie de Crohn ano-périnéale et leur évoluton sous traitement combiné, puis bâtir un score d'activité inflammatoire IRM des trajets fistuleux. MATERIEL ET METHODE : Etude prospective de 29 patients consécutifs, atteints de maladie de Crohn périnéale fistulisante, ayant bénéficié d'un traitement combiné médico-chirurgical. Ces patients ont été explorés par IRM pelvienne aux différentes étapes du traitement. Les IRM ont été relues par 3 radiologues : 1 junior et 2 seniors. Pour chaque IRM ont été analysés les éléments séméiologiques caractérisant les trajets fistuleux et un score inflammatoire analogique a été renseigné. La concordance intra et inter-observateur a été calculée. L'évolution au cours du traitement des signes d'inflammation et du score inflammatoire analogique a été étudiée. RESULTATS : La reproductibilité inter-ibservateur des signes inflammatoires est excellente pour la présence de collection. Elle est bonne pour la prise de contraste, l'inflammation de la graisse et la topographie des collections. Elle est moyenne pour le signal T2. Le score inflammatoire analogique présente une reproductibilité inter et intra-observateur excellentes. CONCLUSION : L'évaluation par IRM des patients atteints de MCFAP bénéficiant d'un traitement combiné, devrait bien différencier les éléments descriptifs anatomiques indispensables à la prise en charge chirurgicale initiale et l'évaluation de l'activité inflammatoire des trajets sous traitement médical. Le rôle de l'IRM dans la description anatomique des trajets et collections est reconnu. La reproductibilité moyenne à bonne des signes inflammatoires classiques en IRM ne permet pas, à l'heure actuelle, une évaluation objective l'activité inflammatoire des trajets. Un score analogique présente cependant une excellente reproductibilité. Un compte rendu IRM standardisé, tenant compte de ces objectifs est proposé.BORDEAUX2-BU Santé (330632101) / SudocSudocFranceF

Dinocyst-derived sea-surface characteristics, palynomorph abundances, ice-rafted debris, and planktonic foraminifera abundances and δ¹⁸O of the 35-41 ka BP interval of core MD99-2285

The last glacial millennial climatic events (i.e. Dansgaard-Oeschger and Heinrich events) constitute outstanding case studies of coupled atmosphere-ocean-cryosphere interactions. Here, we investigate the evolution of sea-surface and subsurface conditions, in terms of temperature, salinity and sea ice cover, at very high-resolution (mean resolution between 55 and 155 years depending on proxies) during the 35-41 ka cal BP interval covering three Dansgaard-Oeschger cycles and including Heinrich event 4, in a new unpublished marine record, i.e. the MD99-2285 core (62.69°N; -3.57°E). We use a large panel of complementary tools, which notably includes dinocyst-derived sea-ice cover duration quantifications. The high temporal resolution and multiproxy approach of this work allows us to identify the sequence of processes and to assess ocean-cryosphere interactions occurring during these periodic ice-sheet collapse events. Our results evidence a paradoxical hydrological scheme where (i) Greenland interstadials are marked by a homogeneous and cold upper water column, with intensive winter sea ice formation and summer sea ice melting, and (ii) Greenland and Heinrich stadials are characterized by a very warm and low saline surface layer with iceberg calving and reduced sea ice formation, separated by a strong halocline from a less warm and saltier subsurface layer. Our work also suggests that this stadial surface/subsurface warming started before massive iceberg release, in relation with warm Atlantic water advection. These findings thus support the theory that upper ocean warming might have triggered European ice-sheet destabilization. Besides, previous paleoceanographic studies conducted along the Atlantic inflow pathways close to the edge of European ice-sheets suggest that such a feature might have occurred in this whole area. Nonetheless, additional high resolution paleoreconstructions are required to confirm such a regional scheme

Comparison of MRI-based response criteria and radiomics for the prediction of early response to transarterial radioembolization in patients with hepatocellular carcinoma

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Intraductal papillary mucinous neoplasms of the pancreas and European guidelines: importance of the surgery type in the decision-making process

International audienceBACKGROUND:The European Consensus 2018 established a new algorithm with absolute and relative criteria for intraductal papillary mucinous neoplasms of the pancreas (IPMN) management. The aim of this study was to validate these criteria and analyse the outcomes in function of the surgical procedure and IPMN subtype.METHODS:Clinical, radiological and surgical data (procedure, morbidity/mortality rates) of patients who underwent surgery for IPMN between 2007 and 2017. The predictive value of the different criteria was analysed.RESULTS:124 patients (men 67%; mean age 65 years) underwent surgery for IPMN (n = 62 malignant tumours; 50%). Jaundice, cyst ≥4 cm and Wirsung duct size 5-9.9 mm or ≥ 10 mm were significantly associated with malignancy (4.77 < OR < 11.85 p < 0.0001). The positive predictive value of any isolated criterion ranged from 71 to 87%, whereas that of three relative criteria together reached 100%. The mortality and morbidity (grade III-IV complications according to the Dindo-Clavien classification) rates were 3 and 8%, respectively. Morbidity/mortality after duodenopancreatectomy and total pancreatectomy were significantly higher for benign IPMN (p = 0.01).CONCLUSION:Considering the morbidity associated with extended surgery, particularly for benign IPMN, the results of the present study suggest that high-risk surgery should be considered only in the presence of three relative criteria and including the surgery type in the decision-making algorithm

Study protocol of the HYPER-LIV01 trial: a multicenter phase II, prospective and randomized study comparing simultaneous portal and hepatic vein embolization to portal vein embolization for hypertrophy of the future liver remnant before major hepatectomy for colo-rectal liver metastases

International audienceIn patients undergoing major liver resection, portal vein embolization (PVE) has been widely used to induce hypertrophy of the non-embolized liver in order to prevent post-hepatectomy liver failure. PVE is a safe and effective procedure, but does not always lead to sufficient hypertrophy of the future liver remnant (FLR). Hepatic vein(s) embolization has been proposed to improve FLR regeneration when insufficient after PVE. The sequential right hepatic vein embolization (HVE) after right PVE demonstrated an incremental effect on the FLR but it implies two different procedures with no time gain as compared to PVE alone. We have developed the so-called liver venous deprivation (LVD), a combination of PVE and HVE during the same intervention, to optimize the phase of liver preparation before surgery. The main objective of this randomized phase II trial is to compare the percentage of change in FLR volume at 3 weeks after LVD or PVE. Methods Patients eligible to this multicenter prospective randomized phase II study are subjects aged from 18 years old suffering from colo-rectal liver metastases considered as resectable and with non-cirrhotic liver parenchyma. The primary objective is the percentage of change in FLR volume at 3 weeks after LVD or PVE using MRI or CT-Scan. Secondary objectives are assessment of tolerance, post-operative morbidity and mortality, post-hepatectomy liver failure, rate of non-respectability due to insufficient FLR or tumor progression, per-operative difficulties, blood loss, R0 resection rate, post-operative liver volume and overall survival. Objectives of translational research studies are evaluation of pre- and post-operative liver function and determination of biomarkers predictive of liver hypertrophy . Sixty-four patients will be included (randomization ratio 1:1) to detect a difference of 12% at 21 days in FLR volumes between PVE and LVD. Discussion Adding HVE to PVE during the same procedure is an innovative and promising approach that may lead to a rapid and major increase in volume and function of the FLR, thereby increasing the rate of resectable patients and limiting the risk of patient’s drop-out. Trial registration This study was registered on clinicaltrials.gov on 15th February 2019 ( NCT03841305 )

Preoperative Predictors of Neoplasia in Patients Undergoing Small Bowel Resection for Complicated Crohn’s Disease: A Multicentre Case-Control Study

Crohn’s disease (CD) is associated with an increased risk of small bowel neoplasia (SBN). We aimed to assess preoperative predictors of SBN in CD patients. We conducted a retrospective case-control study including CD patients who underwent surgery: cases were diagnosed with SBN on histopathological analysis and controls had no neoplasia. Preoperative cross-sectional imaging was reviewed by a panel of blinded expert radiologists. Fifty cases were matched to one hundred and fifty consecutive controls. In multivariable analysis, predictors of SBN were age ≥ 50 years (OR = 28, 95% CI = 5.05–206), median CD duration ≥ 17.5 years (OR = 4.25, 95% CI = 1.33–14.3), and surgery for stricture (OR = 5.84, 95% CI = 1.27–35.4). The predictors of small bowel adenocarcinoma were age ≥ 50 years (OR = 5.14, 95% CI = 2.12–12.7), CD duration ≥ 15 years (OR = 5.65, 95% CI = 2.33–14.3), and digestive wall thickening > 8 mm (OR = 3.79, 95% CI = 1.45–11.3). A predictive score based on the aforementioned factors was constructed. Almost 73.7% of patients with a high score had SBA. Old age, long small bowel CD duration, and stricture predicted the presence of SBN, particularly adenocarcinoma when patients have digestive wall thickening > 8 mm on preoperative imaging