University of Grenoble

About: University of Grenoble is a education organization based out in Saint-Martin-d'Hères, France. It is known for research contribution in the topics: Population & Context (language use). The organization has 25658 authors who have published 45143 publications receiving 909760 citations.

Conditional gradient algorithms for norm-regularized smooth convex optimization

Abstract: Motivated by some applications in signal processing and machine learning, we consider two convex optimization problems where, given a cone $$K$$K, a norm $$\Vert \cdot \Vert $$?·? and a smooth convex function $$f$$f, we want either (1) to minimize the norm over the intersection of the cone and a level set of $$f$$f, or (2) to minimize over the cone the sum of $$f$$f and a multiple of the norm. We focus on the case where (a) the dimension of the problem is too large to allow for interior point algorithms, (b) $$\Vert \cdot \Vert $$?·? is "too complicated" to allow for computationally cheap Bregman projections required in the first-order proximal gradient algorithms. On the other hand, we assume that it is relatively easy to minimize linear forms over the intersection of $$K$$K and the unit $$\Vert \cdot \Vert $$?·?-ball. Motivating examples are given by the nuclear norm with $$K$$K being the entire space of matrices, or the positive semidefinite cone in the space of symmetric matrices, and the Total Variation norm on the space of 2D images. We discuss versions of the Conditional Gradient algorithm capable to handle our problems of interest, provide the related theoretical efficiency estimates and outline some applications.

Increased lipid peroxidation in patients with pulmonary hypertension.

Abstract: Isoprostanes are chemically stable lipid peroxidation products of arachidonic acid, the quantification of which provides a novel approach to the assessment of oxidative stress in vivo. The main objective of this study was to quantify the urinary levels of isoprostaglandin F2 α type III (iPF2 α-III), an F2-isoprostane, in patients with pulmonary hypertension (PHT) in comparison with healthy controls. The secondary objective was to test whether baseline iPF2 α-III levels correlate to the reversibility of pulmonary hypertension in response to inhaled NO challenge. Urinary iPF2 α-III levels were measured by gas chromatography-mass spectrometry in 25 patients with PHT, 14 of whom were investigated for response to inhaled NO challenge. Urinary iPF2 α-III levels in PHT patients (225 ± 27 pmol/mmol creatinine) were 2.3 times as high as in controls (97 ± 7 pmol/mmol creatinine, p < 0.001). The mean pulmonary arterial pressure variation and the pulmonary vascular resistance variation in response to inhaled NO were ...

Deep brain stimulation for Parkinson's disease: Surgical issues

Abstract: Numerous factors need to be taken into account when implanting deep brain stimulation (DBS) systems into patients with Parkinson's disease. The surgical procedure itself can be divided into immediate preoperative, intraoperative, and immediate postoperative phases. Preoperative considerations include medication withdrawal issues, stereotactic equipment choices, imaging modalities, and targeting strategy. Intraoperative considerations focus on methods for physiological confirmation of a given target for DBS electrode deployment. Terms such as microelectrode recording, microstimulation, and macrostimulation will be defined to clarify inconsistencies in the literature. Advantages and disadvantages of each technique will be addressed. Furthermore, operative decisions such as staging, choice of electrode and implantable pulse generator, and methods of device fixation will be outlined. Postoperative issues include imaging considerations, including magnetic resonance safety, device-device interactions, and immediate surgical complications pertaining to the DBS procedure. This report outlines answers to a series of questions developed to address all aspects of the DBS surgical procedure and decision-making with a systematic overview of the literature (until mid-2004) and by the expert opinion of the authors. This is a report from the Consensus on Deep Brain Stimulation for Parkinson's Disease, a project commissioned by the Congress of Neurological Surgeons and the Movement Disorder Society. It outlines answers to a series of questions developed to address all surgical aspects of deep brain stimulation.