Parametric Estimation of Ordinary Differential Equations with Orthogonality Conditions

Differential equations are commonly used to model dynamical deterministic systems in applications. When statistical parameter estimation is required to calibrate theoretical models to data, classical statistical estimators are often confronted to complex and potentially ill-posed optimization problem. As a consequence, alternative estimators to classical parametric estimators are needed for obtaining reliable estimates. We propose a gradient matching approach for the estimation of parametric Ordinary Differential Equations observed with noise. Starting from a nonparametric proxy of a true solution of the ODE, we build a parametric estimator based on a variational characterization of the solution. As a Generalized Moment Estimator, our estimator must satisfy a set of orthogonal conditions that are solved in the least squares sense. Despite the use of a nonparametric estimator, we prove the root-$n$ consistency and asymptotic normality of the Orthogonal Conditions estimator. We can derive confidence sets thanks to a closed-form expression for the asymptotic variance. Finally, the OC estimator is compared to classical estimators in several (simulated and real) experiments and ODE models in order to show its versatility and relevance with respect to classical Gradient Matching and Nonlinear Least Squares estimators. In particular, we show on a real dataset of influenza infection that the approach gives reliable estimates. Moreover, we show that our approach can deal directly with more elaborated models such as Delay Differential Equation (DDE).Comment: 35 pages, 5 figure

Comparative effect of N-substituted dehydroamino acids and alpha-tocopherol on rat liver lipid peroxidation activities

Free radical damage has been associated with a growing number of diseases and conditions, such as autoimmune diseases, neurodegenerative disorders and multiple types of cancer. Some dehydroamino acids and corresponding peptides can function as radical scavengers. In this study the in vitro effects on rat liver lipid peroxidation levels of fourteen N-substituted dehydroamino acid derivatives and alpha-tocopherol were investigated. alpha-Tocopherol is a powerful antioxidant that is beneficial in the treatment of many free radical related diseases. The results indicated that all the compounds showed very good inhibitory effect on the lipid peroxidation compound with alpha-tocopherol at 1 mM concentrations and the inhibition rate was in the range of 70-79 % with the exception of compound 5. At 0.1 mM concentrations compounds 1, 2 and 9 were found more active than alpha-tocopherol. The results confirmed that molecules such as dehydroamino acids which have reactive double bonds can act as a guard in vitro against oxidants.- (undefined

Analysis of postural disorders using a stabilometric platform in patients with rheumatic diseases

Wstęp W przebiegu reumatoidalnego zapalenia stawów (RZS) ważnym problemem wpływającym na stabilność oraz symetrię obciążenia kończyn dolnych jest globalne upośledzenie motoryki stopy spowodowane jej płasko-koślawą deformacją, a także występowanie licznych zmian w obrębie stawów stóp. W zesztywniającym zapaleniu stawów kręgosłupa (ZZSK) dochodzi ostatecznie do trwałego ograniczenia ruchomości kręgosłupa co prowadzi do zaburzeń prawidłowego obciążania kończyn dolnych i równowagi ciała. W twardzinie układowej (TU) ból i przykurcze stawowe negatywnie oddziałują na prawidłową postawę i stabilność ciała oraz prawidłowe obciążenie kończyn dolnych. Metodyka Badanie balansu ciała oraz stabilności i symetrii obciążenia kończyn dolnych wykonano na komputerowej dwupłytowej platformie stabilometrycznej. Badanie składało się z dwóch prób – pierwszej z otwartymi i drugiej z zamkniętymi oczami. Wyniki Ogółem przebadano 50 chorych z ZZSK, 68 chorych z RZS oraz 53 chorych z TU. Nie wykazano istotnych statystycznie różnic między badanymi grupami z uwzględnieniem badania z oczami otwartymi jak i zamkniętymi. W każdej grupie badanej wykazano istotnie statystycznie wyższe wartości całkowitej drogi, którą przebył środek nacisku stóp chorego w ciągu badania, ocenianego przy zamkniętych oczach względem ocenianego przy otwartych oczach. Dyskusja Analizowane w pracy grupy stanowią trzy odrębne funkcjonalnie choroby tkanki łącznej, charakteryzujące się zajęciem innych składowych elementu ruchu. Twardzina układowa jawi się jako choroba o zupełnie odmiennym wzorcu ruchu charakteryzującego się zmniejszeniem wychylenia środka nacisku stóp zarówno w badaniu z zamkniętymi jak i otwartymi oczami. Wnioski W chorobach reumatycznych powszechnie występują zaburzenia postawy i prawidłowego utrzymania równowagi, a wzorzec zaburzeń ruchowych jest zależny od danej choroby.Background: In the course of rheumatoid arthritis (RA), an important problem that affects the stability and symmetry of lower limb loading is the global motor impairment of the foot due to its planovalgus deformity, as well as the occurrence of numerous lesions in the foot joints. In ankylosing spondylitis (AS), there is eventually a permanent limitation of spinal mobility, which results in impaired lower limb loading and body balance. In systemic sclerosis (SSc), pain and joint contractures negatively affect the proper posture and stability of the body and the normal lower limb loading. Material and methods:Tests of body balance, stability and symmetry of lower limb loading were performed on a computerised two-plate stabilometric platform. The testing consisted of two trials — the first performed with eyes open (open-eye test) and the second performed with eyes closed (closed-eye test). Results: There were a total of 50 AS patients, 68 RA patients and 53 SSc patients examined. There were no statistically significant differences between the study groups including the open-eye test and the closed-eye test. Each study group revealed statistically significant higher values for the total distance travelled by the patient's centre of pressure of the feet over the course of testing as assessed using the closed-eye test compared to the open-eye test. Discussion: The groups analysed in this paper represent three functionally distinct connective tissue diseases that are marked by involvement of different constituents of the motor system component. Systemic sclerosis (SSc) presents itself as a disease with a completely different movement pattern that is marked by a reduction in the amplitudes of the centre of pressure (CoP) in both the closed-eye test and the open-eye test. Conclusions: Postural and balance disorders are common in rheumatic diseases, and the pattern of movement disorders is disease-specific.

Gut microbiota-derived propionate reduces cancer cell proliferation in the liver

Peer reviewedPublisher PD

Modes of Foreign Entry under Asymmetric Information about Potential Technology Spillovers

This paper studies the effect of technology spillovers on the entry decision of a multinational enterprise into a foreign market. Two alternative entry modes for a foreign direct investment are considered: Greenfield investment versus acquisition. We find that with quantity competition a spillover makes acquisitions less attractive, while with price competition acquisitions become more attractive. Asymmetric information about potential spillovers always reduces the number of acquisitions independently of whether the host country or the entrant has private information. Interestingly, we find that asymmetric information always hurts the entrant, while it sometimes is in favor of the host country

The relationship between redox enzyme activity and electrochemical potential—cellular and mechanistic implications from protein film electrochemistry

In protein film electrochemistry a redox protein of interest is studied as an electroactive film adsorbed on an electrode surface. For redox enzymes this configuration allows quantification of the relationship between catalytic activity and electrochemical potential. Considered as a function of enzyme environment, i.e., pH, substrate concentration etc., the activity–potential relationship provides a fingerprint of activity unique to a given enzyme. Here we consider the nature of the activity–potential relationship in terms of both its cellular impact and its origin in the structure and catalytic mechanism of the enzyme. We propose that the activity–potential relationship of a redox enzyme is tuned to facilitate cellular function and highlight opportunities to test this hypothesis through computational, structural, biochemical and cellular studies

Scenario of Accelerating Universe from the Phenomenological \Lambda- Models

Dark matter, the major component of the matter content of the Universe, played a significant role at early stages during structure formation. But at present the Universe is dark energy dominated as well as accelerating. Here, the presence of dark energy has been established by including a time-dependent $\Lambda$ term in the Einstein's field equations. This model is compatible with the idea of an accelerating Universe so far as the value of the deceleration parameter is concerned. Possibility of a change in sign of the deceleration parameter is also discussed. The impact of considering the speed of light as variable in the field equations has also been investigated by using a well known time-dependent $\Lambda$ model.Comment: Latex, 9 pages, Major change

PRIMA subretinal wireless photovoltaic microchip implantation in non-human primate and feline models

PURPOSE: To evaluate the surgical technique for subretinal implantation of two sizes of PRIMA photovoltaic wireless microchip in two animal models, and refine these surgical procedures for human trials. METHODS: Cats and Macaca fascicularis primates with healthy retina underwent vitrectomy surgery and were implanted with subretinal wireless photovoltaic microchip at the macula/central retina. The 1.5mm PRIMA chip was initially studied in feline eyes. PRIMA implant (2mm,1.5mm sizes) arrays were studied in primates. Feasibility of subretinal chip implantation was evaluated with a newly-developed surgical technique, with surgical complications and adverse events recorded. RESULTS: The 1.5mm implant was placed in the central retina of 11 feline eyes, with implantation duration 43-106 days. The 1.5mm implant was correctly positioned into central macula of 11 primate eyes, with follow-up periods of minimum 6 weeks (n = 11), 2 years (n = 2), and one eye for 3 years. One primate eye underwent multi-chip 1.5mm implantation using two 1.5mm chips. The 2mm implant was delivered to 4 primate eyes. Optical coherence tomography confirmed correct surgical placement of photovoltaic arrays in the subretinal space in all 26 eyes. Intraoperative complications in primate eyes included retinal tear, macular hole, retinal detachment, and vitreous hemorrhage that resolved spontaneously. Postoperatively, there was no case of significant ocular inflammation in the 1.5mm implant group. CONCLUSIONS: We report subretinal implantation of 1.5mm and 2mm photovoltaic arrays in the central retina of feline and central macula of primate eyes with a low rate of device-related complications. The in vivo PRIMA implantation technique has been developed and refined for use for a 2mm PRIMA implant in ongoing human trials

An objective comparison of methods for augmented reality in laparoscopic liver resection by preoperative-to-intraoperative image fusion

Augmented reality for laparoscopic liver resection is a visualisation mode that allows a surgeon to localise tumours and vessels embedded within the liver by projecting them on top of a laparoscopic image. Preoperative 3D models extracted from CT or MRI data are registered to the intraoperative laparoscopic images during this process. In terms of 3D-2D fusion, most of the algorithms make use of anatomical landmarks to guide registration. These landmarks include the liver's inferior ridge, the falciform ligament, and the occluding contours. They are usually marked by hand in both the laparoscopic image and the 3D model, which is time-consuming and may contain errors if done by a non-experienced user. Therefore, there is a need to automate this process so that augmented reality can be used effectively in the operating room. We present the Preoperative-to-Intraoperative Laparoscopic Fusion Challenge (P2ILF), held during the Medical Imaging and Computer Assisted Interventions (MICCAI 2022) conference, which investigates the possibilities of detecting these landmarks automatically and using them in registration. The challenge was divided into two tasks: 1) A 2D and 3D landmark detection task and 2) a 3D-2D registration task. The teams were provided with training data consisting of 167 laparoscopic images and 9 preoperative 3D models from 9 patients, with the corresponding 2D and 3D landmark annotations. A total of 6 teams from 4 countries participated, whose proposed methods were evaluated on 16 images and two preoperative 3D models from two patients. All the teams proposed deep learning-based methods for the 2D and 3D landmark segmentation tasks and differentiable rendering-based methods for the registration task. Based on the experimental outcomes, we propose three key hypotheses that determine current limitations and future directions for research in this domain.Comment: 24 page