HAL-HCL

    Hyperquaternions and Physics: Historical Outlook

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    International audienceHyperquaternions being defined as a tensor product of quaternion algebras (or a subalgebra thereof), it follows that they constitute Clifford algebras due to a theorem by Clifford (1845−1879). Examples of hyperquaternions are quaternions H(e1=i, e2=j), biquaternions H⊗C(e1=iI, e2=jI, e3=kI), tetraquaternions H⊗H(e0=j, e1=kI, e2=kJ, e3=kK), and so on H⊗H⊗C,H⊗H⊗H.... Quaternions were discovered in 1843 by Hamilton (1805−1865) after a long vain search of triplets and satisfy the multiplication rule i2=j2=k2=ijk=−1. Containing R and C as particular cases, quaternions were immediately perceived as a major discovery and were to lead to the 3D vector calculus still in use today. Hamilton also introduced complex quaternions which he named biquaternions. Independently of Clifford, Lipschitz (1832−1903) discovered in 1880, as an extension of quaternions, what is called today the even subalgebra as well as the formula of ndimensional rotations in euclidean spaces y=axa−1(a∈C+n). Moore(1876−1931), working on a canonical decomposition of rotations was to call the elements of Lipschitz’s algebra hyperquaternions which justifies the terminology adopted above. Hyperquaternions constitute a new mathematical formalism which seems to be particularly well adapted to physics. Since H⊗H'M4(R), [H⊗H]⊗C'M4(C),[H⊗H]⊗H'M4(H) it follows that hyperquaternions yield all real matrices aswell as the complex and quaternionic ones. Introducing a hyperconjugation, one obtains a simple expression of major symmetry groups of physics. Prof. Dr Girard who has a Ph.D. in History of Science (UW-Madison) retraces historically the uses (and frequent misuses) of hyperquaternions up to the present day in physics.References:[1] Girard, Patrick R. et al., Differential Geometry Revisited by Biquaternion Clifford Algebra. In J.-D. Boissonat et al (Eds.): Curves and Surfaces (Springer, 2015).[2] Girard, Patrick R., Quaternions, Clifford Algebras and Relativistic Physics (Birkhauser, Basel, 2007).[3] Clifford, W. K., Applications of Grassmann’s extensive algebra, Amer. J. Math., 1 (1878), pp. 350-358.[4] Lipschitz R., Principes d’un calcul algébrique qui contient comme espèces particulières le calcul des quantités imaginaires et des quaternions, C. R. Acad. Sci. Paris, 91 (1880), pp. 619-621, 660-664.[5] Moore, C. J. E., Hyperquaternions, Journal of Mathematical Physics, 1 (1922), pp. 63-77.[6] Hankins, Thomas L., Sir William Rowan Hamilton (The Johns Hopkins University Press, Baltimore, 1980)

    Contribution of Clinical Neuroimaging to the Understanding of the Pharmacology of Methylphenidate

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    International audienceMethylphenidate (MPH) is currently the most widely used molecule in the pharmacologic treatment of attention-deficit hyperactivity disorder (ADHD). Although experience of its application now extends over several decades, its psychotropic nature, prolonged use in children, and chemical relation to amphetamines still raise doubts in the minds of prescribers and the families of the patients. Brain imaging has shed considerable light on the neuropharmacology of MPH. The two main in vivo neuroimaging techniques are positron-emission tomography (PET) and magnetic resonance imaging (MRI), and these can be applied in both animal models and humans. The present review seeks to show how human molecular and functional imaging has contributed to determining not only the molecular targets of MPH, and the action kinetics of the various pharmaceutical forms available, but also the connectivity and brain networks activated by treatment. We also discuss the perspectives opened up by new hybrid PET–MRI techniques that enable multimodal tracking of the impact of methylphenidate on neurotransmission.TrendsOne of the main pharmacologic treatments for ADHD is MPH.Although MPH is a psychostimulant studied in many clinical trials, many issues have remained unresolved regarding pharmacologic mechanisms, brain bioavailability, pharmacokinetic/pharmacodynamic relations, impacts on brain neurochemistry and connectivity, and positive and negative long-term effects.The development of anatomic, isotopic, molecular, and functional brain imaging has made a considerable contribution to our knowledge of MPH.In humans, PET imaging explores MPH brain bioavailability and molecular targeting of dopamine and norepinephrine transporters; MRI explores the neuroanatomic and functional effects of MPH.New hybrid PET–MRI cameras enable multimodal exploration protocols generating simultaneous pharmacokinetic/pharmacodynamic modeling data for MPH

    Sofosbuvir-based antiviral therapy in hepatitis C virus patients with severe renal failure

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    IF 4.470International audienceBackgroundChronic hepatitis C virus (HCV) infection is the most common chronic liver disease in patients with end-stage renal disease (ESRD). Over the last few years, second-generation direct-acting antivirals have been revolutionary in the treatment of hepatitis C, and sofosbuvir (SOF) is the backbone of most modern treatment strategies. Since SOF is eliminated through the kidney, the aim of this multicentre retrospective study was to assess its antiviral efficacy and safety in HCV-infected patients with severe renal failure [including haemodialysis (HD) patients].MethodsFifty patients (36 males, mean age ± standard deviation 60.5 ± 7.5 years) with chronic HCV infection (G1: 28/56%, cirrhosis: 27/54%) and severe renal failure [i.e. MDRD estimated glomerular filtration rate (eGFR) <35 mL/min], including 35 on HD, were enrolled. Antiviral treatment consisted of SOF/ribavirin (RBV) (n = 7), SOF/RBV/pegylated interferon (n = 2), SOF/daclatasvir ± RBV (n = 30) or SOF/simeprevir ± RBV (n = 11) for 12 or 24 weeks. A reduced dose of SOF (400 mg three times a week or 400 mg every other day) was given to all HD patients. Initial dose of RBV (n = 12) ranged from 400 to 4200 mg/week.ResultsOn an intent-to-treat-based analysis, sustained virological response rate was 86% at 12 weeks. During therapy, haemoglobin levels were not significantly modified, but recombinant erythropoietin (rEPO) dose significantly increased in patients treated with RBV. Two patients (4%) required blood transfusion. No patient had treatment discontinuation due to side effects. Dose of RBV was reduced in two patients (16.7%) during antiviral therapy. Dose of SOF was reduced in two non-HD patients because of side effects. In non-HD patients, median eGFR was not significantly modified during treatment.ConclusionsOur results strongly suggest that SOF-based antiviral therapy, with a reduced dose of SOF, is safe and effective for the treatment of HCV patients with ESRD, including HD patients

    Application of fluence field modulation to proton computed tomography for proton therapy imaging

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    International audienceThis simulation study presents the application of fluence field modulated computed tomography, initially developed for x-ray CT, to proton computed tomography (pCT). By using pencil beam (PB) scanning, fluence modulated pCT (FMpCT) may achieve variable image quality in a pCT image and imaging dose reduction.Three virtual phantoms, a uniform cylinder and two patients, were studied using Monte Carlo simulations of an ideal list-mode pCT scanner. Regions of interest (ROI) were selected for high image quality and only PBs intercepting them preserved full fluence (FF). Image quality was investigated in terms of accuracy (mean) and noise (standard deviation) of the reconstructed proton relative stopping power compared to reference values. Dose calculation accuracy on FMpCT images was evaluated in terms of dose volume histograms (DVH), range difference (RD) for beam-eye-view (BEV) dose profiles and gamma evaluation. Pseudo FMpCT scans were created from broad beam experimental data acquired with a list-mode pCT prototype.FMpCT noise in ROIs was equivalent to FF images and accuracy better than  −1.3%(−0.7%) by using 1% of FF for the cylinder (patients). Integral imaging dose reduction of 37% and 56% was achieved for the two patients for that level of modulation. Corresponding DVHs from proton dose calculation on FMpCT images agreed to those from reference images and 96% of BEV profiles had RD below 2 mm, compared to only 1% for uniform 1% of FF. Gamma pass rates (2%, 2 mm) were 98% for FMpCT while for uniform 1% of FF they were as low as 59%. Applying FMpCT to preliminary experimental data showed that low noise levels and accuracy could be preserved in a ROI, down to 30% modulation.We have shown, using both virtual and experimental pCT scans, that FMpCT is potentially feasible and may allow a means of imaging dose reduction for a pCT scanner operating in PB scanning mode. This may be of particular importance to proton therapy given the low integral dose found outside the target

    The evolution of outcomes and indications for the dual-mobility cup: a systematic review

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    PURPOSE: Instability following total hip arthroplasty remains a common and disabling complication. The dual mobility cup (DMC) allows a reduction in the dislocation rate. An increasing number of studies have been undertaken to better understand DMC long term outcomes and complications. The goal of this systematic review was to clarify its different uses and outcomes according to the indications. METHODS: A comprehensive literature review was performed using the keywords 'dual mobility' and 'tripolar cup' with no limit regarding the year of publication. One hundred seventy six publications were identified. RESULTS: Current literature shows that "contemporary" dual mobility cup are a significant indication to manage instability following primary and revision hip arthroplasty. Survivorship at midterm is comparable to other articulations for primary THA, but is more difficult to evaluate in revision. Intra-prosthetic dislocation, wear, and loosening are now uncommon with new generations of DMC. CONCLUSIONS: Compared to previous generations of DMC, the current "contemporary" DMC presents a significant improvement. Current literature reveals a tendency to increase the indications but further studies with long term follow up remain important to consolidate these findings

    Can ICT improve the quality of life of elderly adults living in residential home care units ? From actual impacts to hidden artefacts

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    International audienceIn a context of progressive loss of intellectual and interactional capacities for the elderly, the goal of this article is to examine to what extent a new technological environment can improve their quality of life. In this study, we examine the very elderly (mean age 87) who have experienced a loss in functional capacities and are dependent on managed care such as residential home care units. Using qualitative methods amongst a group of 17 residents (semi-structured interviews and longitudinal observations), we examine whether new social practices form and whether subjects feel more socially recognised. Our study shows that information and communications technologies may, to some extent, play an instrumental role in interconnectedness and social stimulation, and can also be seen as a ‘boundary object’ that communicates between the residents’ world (who are rather isolated) and their families’ world (including grandchildren)

    Circulating tumor DNA and circulating tumor cells as predictor of outcome in the PRODIGE14-ACCORD21-METHEP2 phase II trial

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    IF 9.269International audienceBackground: We prospectively detected circulating tumor DNA (ctDNA) and circulating tumor cells (CTC) levels in patients (pts) included in the PRODIGE14-ACCORD21-METHEP2 randomized phase II trial.Methods: The trial enrolled colorectal cancer pts with potentially resectable liver metastases & no prior treatment; the primary endpoint was the rate of R0/R1 liver metastases resection achieved by 1st line regimen (targeted therapies & bi- vs tri-chemotherapy; Ychou, ASCO 2016). Blood samples were collected at inclusion, after 1 month of therapy and before any liver metastases surgery. CTCs (CellSearch) & ctDNA (ddPCR, BioRad) were detected in an experienced laboratory (Inst. Curie).Results: 153 pts had at least one blood analysis. High CTC count (≥3 CTC/7.5ml) was detected in 25/132 pts (19%) at baseline and associated with synchronous..

    Equivalent results of medial and lateral parapatellar approach for total knee arthroplasty in mild valgus deformities

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    PURPOSE: When performing total knee arthroplasty (TKA) in valgus knee deformities, a medial or lateral parapatellar approach can be performed, but the lateral approach is often considered technically more difficult. The purpose of this study was to compare intra-operative, early clinical and radiological outcomes of medial and lateral parapatellar approaches for TKA in the setting of moderate knee valgus

    Autosomal-Recessive Mutations in AP3B2, Adaptor-Related Protein Complex 3 Beta 2 Subunit, Cause an Early-Onset Epileptic Encephalopathy with Optic Atrophy

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    International audienceEarly-onset epileptic encephalopathy (EOEE) represents a heterogeneous group of severe disorders characterized by seizures, interictal epileptiform activity with a disorganized electroencephalography background, developmental regression or retardation, and onset before 1 year of age. Among a cohort of 57 individuals with epileptic encephalopathy, we ascertained two unrelated affected individuals with EOEE associated with developmental impairment and autosomal-recessive variants in AP3B2 by means of whole-exome sequencing. The targeted sequencing of AP3B2 in 86 unrelated individuals with EOEE led to the identification of an additional family. We gathered five additional families with eight affected individuals through the Matchmaker Exchange initiative by matching autosomal- recessive mutations in AP3B2. Reverse phenotyping of 12 affected individuals from eight families revealed a homogeneous EOEE phenotype characterized by severe developmental delay, poor visual contact with optic atrophy, and postnatal microcephaly. No spasticity, albinism, or hematological symptoms were reported. AP3B2 encodes the neuron-specific subunit of the AP-3 complex. Autosomal-recessive variations of AP3B1, the ubiquitous isoform, cause Hermansky-Pudlak syndrome type 2. The only isoform for the delta subunit of the AP-3 complex is encoded by AP3D1. Autosomal-recessive mutations in AP3D1 cause a severe disorder cumulating the symptoms of the AP3B1 and AP3B2 defects
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