We develop nonsmooth optimization techniques to solve H ∞ synthesis problems under additional structural constraints on the controller. Our approach avoids the use of Lyapunov variables and therefore ...leads to moderate size optimization programs even for very large systems. The proposed framework is versatile and can accommodate a number of challenging design problems including static, fixed-order, fixed-structure, decentralized control, design of PID controllers and simultaneous design and stabilization problems. Our algorithmic strategy uses generalized gradients and bundling techniques suited for the H ∞ norm and other nonsmooth performance criteria. We compute descent directions by solving quadratic programs and generate steps via line search. Convergence to a critical point from an arbitrary starting point is proved and numerical tests are included to validate our methods. The proposed approach proves to be efficient even for systems with several hundreds of states.
The acquisition of new motor skills is dependent on task practice. In the case of motor transfer, learning can be facilitated by prior practice of a similar skill. Although a multitude of studies ...have investigated the brain regions contributing to skill acquisition, the neural bases associated with the savings seen at transfer have yet to be determined. In the current study, we used functional MRI to examine how brain activation differs during acquisition and transfer of a visuomotor adaptation task. Two groups of participants adapted manual aiming movements to three different rotations of the feedback display in a sequential fashion, with a return to baseline display conditions between each rotation. Subjects showed a savings in the rate of adaptation when they had prior adaptive experiences (i.e., positive transfer of learning). This savings was associated with a reduction in activity of brain regions typically recruited early in the adaptation process, including the right inferior frontal gyrus, primary motor cortex, inferior temporal gyrus, and the cerebellum (medial HIII). Moreover, although these regions exhibit activation that is correlated across subjects with the rate of acquisition, the degree of savings at transfer was correlated with activity in the right cingulate gyrus, left superior parietal lobule, right inferior parietal lobule, left middle occipital gyrus, and bilaterally in the cerebellum (HV/VI). The cerebellar activation was in the regions surrounding the posterior superior fissure, which is thought to be the site of storage for acquired internal models. Thus we found that motor transfer is associated with brain activation that typically characterizes late learning and storage. Transfer seems to involve retrieval of a previously formed motor memory, allowing the learner to move more quickly through the early stage of learning.
Research suggests that the basal ganglia complex is a major component of the neural circuitry that mediates reward-related processing. However, human studies have not yet characterized the response ...of the basal ganglia to an isolated reward, as has been done in animals. We developed an event-related functional magnetic resonance imaging paradigm to identify brain areas that are activated after presentation of a reward. Subjects guessed whether the value of a card was higher or lower than the number 5, with monetary rewards as an incentive for correct guesses. They received reward, punishment, or neutral feedback on different trials. Regions in the dorsal and ventral striatum were activated by the paradigm, showing differential responses to reward and punishment. Activation was sustained following a reward feedback, but decreased below baseline following a punishment feedback.
When used in addition to environmentally friendly cultural practices, buffer zones can limit the water transfer of pollutants, in particular pesticides, towards water resources. The choice of the ...buffer zones' type and positioning, considering water pathways and flow components, is crucial. When this choice has been performed, buffer zones dimensions must still be optimized, according to the environment characteristics, which strongly influence their effectiveness. This article presents a method and its associated tools, including VFSMOD model, which aim at optimizing vegetative buffer zones (VFS) sizes, by simulating their transfer mitigation effectiveness. A first application of this methodology is illustrated on a small agricultural watershed in Brittany. A second application, based on the simulation of a large number of scenarios, leads to the elaboration of nomograms. They allow optimizing VFS size in a simpler way from the user's point of view.
Example of a buffer sizing nomogram, depending on the contributing area length, for 70% retention efficiency. Each color stands for a climatic scenario (defined by rainfall event and soil initial humidity status). Each curve shows the result for a contributive area slope of 5%, the shallow zone corresponding to a slope varying from 2 to 10%. For example, for a contributive area 175m long, the VFS should be 13m wide to infiltrate 70% of the incoming water during the summer rainfall occurring on a wet contributive area. Display omitted
•A method and its associated tools for sizing VFS using process-based modeling.•Method which relies on the local agro-pedo-climatical VFS context, relevant for a wide range of pesticides•First time that a sizing method explicitly takes into account a shallow water table presence•Application on a small agricultural watershed, which gives relevant results•Elaboration of nomograms, easier to use even in the field
Sjögren's syndrome (SS) is a chronic autoimmune disease affecting exocrine glands leading to mouth and eyes dryness. The extent to which epigenetic DNA methylation changes are responsible for an ...X‐chromosome dose effect has yet to be determined. Our objectives were to (i) describe how epigenetic DNA methylation changes could explain an X‐chromosome dose effect in SS for women with normal 46,XX genotype and (ii) determine the relevant relationships to this dose effect, between X‐linked genes, genes controlling X‐chromosome inactivation (XCI) and genes encoding associated transcription factors, all of which are differentially expressed and/or differentially methylated in the salivary glands of patients with SS. We identified 58 upregulated X‐chromosome genes, including 22 genes previously shown to escape XCI, based on the analysis of SS patient salivary gland GEO2R gene expression datasets. Moreover, we found XIST and its cis regulators RLIM, FTX, and CHIC1, and polycomb repressor genes of the PRC1/2 complexes to be upregulated. Many of the X‐chromosome genes implicated in SS pathogenesis can be regulated by transcription factors which we found to be overexpressed and/or differentially methylated in patients with SS. Determination of the mechanisms underlying methylation‐dependent gene expression and impaired XCI is needed to further elucidate the etiopathogenesis of SS.
In this study, we utilized functional magnetic resonance imaging (fMRI) to examine which brain regions contribute to feedback and feedforward motor control processes. Several studies have ...investigated the contributions of cortical and subcortical brain regions to motor performance by independently varying factors such as movement rate, force, and speed, and observing the neural responses. Such studies have contributed greatly to our understanding of neural coding of movement variables. Under natural movement conditions, however, these factors interact in a complex manner to produce differing performance levels. In the current investigation, we induced performance changes in a less constrained way, by having subjects move a joystick to hit targets of differing sizes on an LCD screen. These parametric changes in target size resulted in the well-known speed–accuracy tradeoff effect, allowing us to examine the brain regions responsive to global shifts in motor performance levels. That is, movements made to larger targets relied more on feedforward control whereas movements made to smaller targets relied more on feedback control. Using functional MRI, we identified two sets of brain regions in which activation was modulated with task difficulty. Areas exhibiting activation that was positively correlated with increasing target size included primary motor cortex, premotor cortex, and the basal ganglia, regions that are typically classified as playing a role in force control and movement planning. Brain regions whose activation was negatively correlated with increasing target size included the ipsilateral sensorimotor cortex, multiple cerebellar regions, and the thalamus. These areas contributed to motor performance under higher levels of task difficulty. The results elucidate cortical and subcortical brain regions that are responsive to global shifts in motor performance, reflecting changes along the continuum of feedforward and feedback motor control.
Although mitochondrial DNA has been widely used in phylogeography, evidence has emerged that factors such as climate, food availability, and environmental pressures that produce high levels of stress ...can exert a strong influence on mitochondrial genomes, to the point of promoting the persistence of certain genotypes in order to compensate for the metabolic requirements of the local environment. As recently discovered, the gentoo penguins (Pygoscelis papua) comprise four highly divergent lineages across their distribution spanning the Antarctic and sub-Antarctic regions. Gentoo penguins therefore represent a suitable animal model to study adaptive processes across divergent environments. Based on 62 mitogenomes that we obtained from nine locations spanning all four gentoo penguin lineages, we demonstrated lineage-specific nucleotide substitutions for various genes, but only lineage-specific amino acid replacements for the ND1 and ND5 protein-coding genes. Purifying selection (dN/dS < 1) is the main driving force in the protein-coding genes that shape the diversity of mitogenomes in gentoo penguins. Positive selection (dN/dS > 1) was mostly present in codons of the Complex I (NADH genes), supported by two different codon-based methods at the ND1 and ND4 in the most divergent lineages, the eastern gentoo penguin from Crozet and Marion Islands and the southern gentoo penguin from Antarctica respectively. Additionally, ND5 and ATP6 were under selection in the branches of the phylogeny involving all gentoo penguins except the eastern lineage. Our study suggests that local adaptation of gentoo penguins has emerged as a response to environmental variability promoting the fixation of mitochondrial haplotypes in a non-random manner. Mitogenome adaptation is thus likely to have been associated with gentoo penguin diversification across the Southern Ocean and to have promoted their survival in extreme environments such as Antarctica. Such selective processes on the mitochondrial genome may also be responsible for the discordance detected between nuclear- and mitochondrial-based phylogenies of gentoo penguin lineages.
Our goal was to investigate the effects of epidermal growth factor (EGF) and interferons (IFNs) on signal transducer and activator of transcription STAT1 and STAT4 mRNA and active phosphorylated ...protein expression in Sjögren's syndrome cell culture models. iSGECs (immortalized salivary gland epithelial cells) and A253 cells were treated with EGF, IFN-alpha, -beta, -gamma, or mitogen-activated protein kinase p38 alpha (p38-MAPK) inhibitor for 0-24-48-72 h. STAT1 and STAT4 mRNA expression was quantified by qRT-PCR. Untreated and treated cells were compared using the delta-delta-CT method based on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) normalized relative fold changes. phospho-tyrosine-701-STAT1 and phospho-serine-721-STAT4 were detected by Western blot analysis. STAT4 mRNA expression decreased 48 h after EGF treatment in A253 cells, immortalized salivary gland epithelial cells iSGECs nSS2 (
patient origin), and iSGECs pSS1 (anti-SSA negative Sjögren's Syndrome patient origin). EGF and p38-MAPK inhibitor decreased A253 STAT4 mRNA levels. EGF combined with IFN-gamma increased phospho-STAT4 and phospho-STAT1 after 72 h in all cell lines, suggesting additive effects for phospho-STAT4 and a major effect from IFN-gamma for phospho-STAT1. pSS1 and nSS2 cells responded differently to type I and type II interferons, confirming unique functional characteristics between iSGEC cell lines. EGF/Interferon related pathways might be targeted to regulate STAT1 and STAT4 expression in salivary gland epithelial cells. Further investigation is required learn how to better target the Janus kinases/signal transducer and activator of transcription proteins (JAK/STAT) pathway-mediated inflammatory response in Sjögren's syndrome.
We discuss the Douglas–Rachford algorithm to solve the feasibility problem for two closed sets
A
,
B
in
R
d
. We prove its local convergence to a fixed point when
A
,
B
are finite unions of convex ...sets. We also show that for more general nonconvex sets the scheme may fail to converge and start to cycle, and may then even fail to solve the feasibility problem.
Sensorimotor adaptation tasks can be classified into two types. When subjects adapt movements to visual feedback perturbations such as in prism lens adaptation, they perform kinematic adaptations. ...When subjects adapt movements to force field perturbations such as with robotic manipulanda, they perform kinetic adaptations. Neuroimaging studies have shown basal ganglia involvement in kinetic adaptations, but have found little evidence of basal ganglia involvement in kinematic adaptations, despite reports of deficits in patients with diseases of the basal ganglia, such as Parkinson's and Huntington's disease, in these. In an effort to resolve such apparent discrepancy, we used FMRI to focus on the first few minutes of practice during kinematic adaptation. Human subjects adapted to visuomotor rotations in the context of a joystick aiming task while lying supine in a 3.0 T MRI scanner. As demonstrated previously, early adaptive processes were associated with BOLD activation in the cerebellum and the sensory and motor cortical regions. A novel finding of this study was bilateral basal ganglia activation. This suggests that, at least for early learning, the neural correlates of kinematic adaptation parallel those of other types of skill learning. We observed activation in the right globus pallidus and putamen, along with the right prefrontal, premotor and parietal cortex, which may support spatial cognitive processes of adaptation. We also observed activation in the left globus pallidus and caudate nucleus, along with the left premotor and supplementary motor cortex, which may support the sensorimotor processes of adaptation. These results are the first to demonstrate a clear involvement of basal ganglia activation in this type of kinematic motor adaptation.
PDF
