Variational Principle Involving the Stress Tensor in Elastodynamics

The decomposition of the stress tensor proposed in this article (1986) for a hyperelastic medium is now widely used in the literature. 16 pages.International audienceIn the mechanics of inviscid conservative fluids, it is classical to generate the equations of dynamics by formulating with adequate variables, that the pressure integral calculated in the time-space domain corresponding to the motion of the continuous medium is stationary. The present study extends this principle to the dynamics of large deformations for isentropic motions in thermo-elastic bodies: we use a new way of writing the equations of motion in terms of potentials and we substitute the trace of the stress tensor for the pressure term

Accuracy of Patient-Specific Instrumentation for Bone Tumor Resection within the pelvis: 1st study of 11 patients

Introduction Pelvic bone tumor resection is challenging due to complex geometry, limited visibility and restricted working space of the pelvis. Accurate resection in safe margin is required to reduce the risk of local recurrence. Computer-assisted preoperative planning and intraoperative navigation technologies have been developed for pelvic bone tumor surgeries, and clinical studies have already demonstrated the feasibility of achieving clinically adequate (tumor-free) resection margins [1]. Patient-specific instrumentation (PSI) technology has been developed and adapted to bone tumor surgery as a cheaper and less time-consuming alternative to intraoperative navigation. A recent experimental study has assessed an equivalent value-added of both PSI and navigation technologies in terms of the achieved surgical margins during simulated bone tumor resections of the pelvis [2]. The present study reports a series of 11 clinical cases of PSI-assisted bone tumor surgery within the pelvis, and assesses how accurately a preoperative resection strategy can be replicated intraoperatively with the PSI. Materials and methods The patient series consisted in 11 patients eligible for curative surgical resection of primary bone tumor of the pelvis. Eight patients had a bone sarcoma of iliac bone involving the acetabulum, two patients had a sacral tumor, and one patient had a chondrosarcoma of proximal femur with intra-articular hip extension. For all cases, magnetic resonance imaging (MRI) and computerized tomography (CT) were acquired preoperatively for diagnosis. The tumor volume was first delineated on the MRI. The set of MRI and CT images were fused to produce 3D models of bone and tumor volume (Figure (a)). Resection planning consisted in desired cut planes positioned close to the boundary of the tumor (from 1 up to 6 planes) defining the desired bone cutting with a safe margin defined by the surgeon from 3 up to 15 mm. PSI were designed in computer-aided design software according to the desired resection strategy and produced by additive manufacturing technology. PSI were designed to have bone-specific surfaces to fit in unique position on the bony structure of the patient. PSI were equipped with cylindric guides for 2-mm diameter Kirschner wires to be pinned on the bony structure and flat surfaces to materialize the desired cut planes. Intraoperatively, PSI were positioned freehand by the surgeon and fixed on the bone surface using the K-wires. Once the resection was achieved, both K-wires and PSI were taken off. The standard surgical approach has been used for each patient. Dissection of soft tissue for bone exposure was in accordance with the routine technique. There was no additional bone exposure to position the PSI. Histopathological analysis of the resected tumor specimens was performed to evaluate the safety of the achieved resection margins. Postoperative CT were acquired to assess the local control of the tumor. 3D bone models were reconstructed from the postoperative CT of the patient and registered with the corresponding preoperative bone model (Figure (b)). Two parameters were measured: achieved resection margin (RM) and location accuracy (L). RM was defined as the minimum distance (mm) between the achieved cut plane and the boundary of the tumor. Consequently, the error in the desired safe margin (ESM) was defined as the difference (mm) between RM and the desired safe margin. L was used in accordance with the ISO1101 standard [2] to evaluate accuracy between achieved and desired cut planes. L was defined as the maximum distance (mm) between the achieved cut plane and the desired cut plane. Results PSI were quick and easy to use with a positioning onto the bone surface in less than 5 minutes for all cases. The positioning of the PSI was considered unambiguous for all patients. Histopathological analysis classified all achieved resection margins as R0 (tumor-free), except for two patients. Patient #8 had an urgent morcelize

Studies on hemostasis in COVID-19 deserve careful reporting of the laboratory methods, their significance and their limitations

We read with much interest the recent observational study of Nougier et al., which aimed at studying thrombin generation (TG) and fibrinolysis profiles of COVID-19 patients admitted to an intensive care unit (ICU) or to an internal medicine ward and receiving various schemes of prophylactic heparin.[1] They reported that thrombin potential remained within normal range despite heparin and that fibrinolysis was decreased in relation with increased plasminogen activator inhibitor 1 (PAI-1) and thrombin-activatable fibrinolysis inhibitor (TAFI) antigen plasma levels. Using the rotational thromboelastometry (ROTEM) delta device with EXTEM reagents and the addition of 0.625µg/mL tPA (referred to as 'TEM-tPA'), they reported decreased clot lysis in COVID-19 patients, which was more pronounced in patients who presented a thrombotic event, compared to event-free patients

Recent advances in cancer treatment by Iron Chelators

International audienceThe development of new therapeutic alternatives for cancers is a major public health priority. Among the more promising approaches, the iron depletion strategy based on metal chelation in the tumoral environment has been particularly studied in recent decades. After a short description of the importance of iron for cancer cell proliferation, we will review the different iron chelators developed as potential chemotherapeutics. Finally, the recent efforts to vectorize the chelating agents specifically in the microtumoral environment will be discussed in detai

A“Proteoglycan Targeting Strategy” for the Scintigraphic Imaging and Monitoring of the Swarm Rat Chondrosarcoma Orthotopic Model

Our lab developed 99mTc-NTP 15-5 radiotracer as targeting proteoglycans (PGs) for the scintigraphic imaging of joint. This paper reports preclinical results of 99mTc-NTP 15-5 imaging of an orthotopic model of Swarm rat chondrosarcoma (SRC). 99mTc-NTP 15-5 imaging of SRC-bearing and sham-operated animals was performed and quantified at regular intervals after surgery and compared to bone scintigraphy and tumoural volume. Tumours were characterized by histology and PG assay. SRC exhibited a significant 99mTc-NTP 15-5 uptake at very early stage after implant (with tumour/muscle ratio of 1.61 ± 0.14), whereas no measurable tumour was evidenced. As tumour grew, mean tumour/muscle ratio was increased by 2.4, between the early and late stage of pathology. Bone scintigraphy failed to image chondrosarcoma, even at the later stage of study. 99mTc-NTP 15-5 imaging provided a suitable set of quantitative criteria for the in vivo characterization of chondrosarcoma behaviour in bone environment, useful for achieving a greater understanding of the pathology

Scientific shallow saturation dive expedition using diving rebreathers and a specific dry habitat: medical management of the “Capsule” programme

Background: Scientific underwater exploration could benefit from professional diving facilities. This could allow marine research for durations far exceeding anything currently possible. The closed-circuit rebreather expansion provides new perspectives by unleashing divers and their diving bell. “Under the Pole Expeditions” developed an innovative compact underwater habitat for this purpose. Materials and methods: The habitat’s depth was fixed at 20 m. Saturation lasted 3 days and was followed by a 245 min long decompression procedure with mandatory in-water phase. Isolation and environmental constraints will require specific medical and safety procedures. “In situ” medical concerns were considered, and a specific evacuation plan was established. This report describes the medical management of this atypical project and the systematic clinical follow-up mostly targeted on the cardiovascular system, fatigue and psychological tolerance. Results: Seventeen individual saturation exposures were performed. All selected divers were professional. Neither severe illness nor decompression sickness was observed. These short-term saturation exposures appeared to be well tolerated. There was a relatively low bubble grade after decompression. Psychological tolerance appeared good. However, a transient moderate orthostatic hypotension suggested cardiovascular deconditioning after dive. Conclusions: This first experiment demonstrates the interest and feasibility of a shallow revisited saturation dive with rebreather use. This isolation requires medical accompaniment and rigorous preparation. Medical and physiological risks assessment is essential in this context and must be consolidated by new experiences

Pharmaceuticals and personal care products in the environment: What are the big questions?

Background: Over the past 10-15 years, a substantial amount of work has been done by the scientific, regulatory, and business communities to elucidate the effects and risks of pharmaceuticals and personal care products (PPCPs) in the environment. Objective: This review was undertaken to identify key outstanding issues regarding the effects of PPCPs on human and ecological health in order to ensure that future resources will be focused on the most important areas. Data sources: To better understand and manage the risks of PPCPs in the environment, we used the "key question" approach to identify the principle issues that need to be addressed. Initially, questions were solicited from academic, government, and business communities around the world. A list of 101 questions was then discussed at an international expert workshop, and a top-20 list was developed. Following the workshop, workshop attendees ranked the 20 questions by importance. Data synthesis: The top 20 priority questions fell into seven categories: a) prioritization of substances for assessment, b) pathways of exposure, c) bioavailability and uptake, d) effects characterization, e) risk and relative risk, f) antibiotic resistance, and g) risk management. Conclusions: A large body of information is now available on PPCPs in the environment. This exercise prioritized the most critical questions to aid in development of future research programs on the topic.Centro de Investigaciones del Medioambient

Origin : a 60 GHz radio-over-fiber home area network project

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Characterization of Macrophages and Osteoclasts in the Osteosarcoma Tumor Microenvironment at Diagnosis: New Perspective for Osteosarcoma Treatment?

Biological and histopathological techniques identified osteoclasts and macrophages as targets of zoledronic acid (ZA), a therapeutic agent that was detrimental for patients in the French OS2006 trial. Conventional and multiplex immunohistochemistry of microenvironmental and OS cells were performed on biopsies of 124 OS2006 patients and 17 surgical (“OSNew”) biopsies respectively. CSF-1R (common osteoclast/macrophage progenitor) and TRAP (osteoclast activity) levels in serum of 108 patients were correlated to response to chemotherapy and to prognosis. TRAP levels at surgery and at the end of the protocol were significantly lower in ZA+ than ZA− patients (padj = 0.0011; 0.0132). For ZA+-patients, an increase in the CSF-1R level between diagnosis and surgery and a high TRAP level in the serum at biopsy were associated with a better response to chemotherapy (p = 0.0091; p = 0.0251). At diagnosis, high CD163+ was associated with good prognosis, while low TRAP activity was associated with better overall survival in ZA− patients only. Multiplex immunohistochemistry demonstrated remarkable bipotent CD68+/CD163+ macrophages, homogeneously distributed throughout OS regions, aside osteoclasts (CD68+/CD163−) mostly residing in osteolytic territories and osteoid-matrix-associated CD68−/CD163+ macrophages. We demonstrate that ZA not only acts on harmful osteoclasts but also on protective macrophages, and hypothesize that the bipotent CD68+/CD163+ macrophages might present novel therapeutic targets