Introduction L’HbA1c mesurée en laboratoire est le marqueur de référence pour l’équilibre glycémique dans le DT1 et DT2, mais elle n’est réalisée qu’épisodiquement. L’ASG offre la possibilité ...d’estimer l’HbA1c en temps réel (eA1C) et augmenter la motivation des patients. Nous présentons ici un modèle dynamique d’évaluation de l’eA1C, à partir de données de l’ASG. Matériels et méthodes Un nouvel algorithme à 2-étapes a été développé avec un modèle compartimental comprenant 1) le suivi de la glycémie à jeun (GAJ) moyenne pour calculer l’eA1C de base et 2) la calibration de l’eA1C par un profil glycémique 7 points chaque mois environ, qui utilise un model factoriel mesurant les principaux facteurs de variation glycémique. Une première base de données est utilisée pour paramétrer le modèle (379 patients insulinonaifs, 17 863 glycémies, 1 599 HbA1c de références, soit en moyenne 47 J de données individuelles). Le modèle est ensuite évalué sur une base de données indépendante : 375 patients, 17 925 glycémies, 1 628 HbA1c de référence, 48 j de données individuelles en moyenne). La précision est estimée par calcul des déviations moyennes absolue et relative (DMA/DMR) entre l’eA1c et l’HbA1c de référence, ainsi que leur corrélation (R). Résultats DMA = 0,51, DMR = 6,8 %, R = 0,76 comparée aux résultats obtenues par la formule de l’ADA : DMA = 0,98, DMR = 13,1 % (R = 0,73). Plus précisément, 80 % des estimations d’eA1c dévient de moins de 10 % des valeurs de référence, et 99 % de moins de 20 % ; la formule de l’ADA donnant respectivement 55 % et 87 %. Conclusion Ce modèle dynamique, même avec des mesures ASG peu fréquentes (ex DT2), permet un suivi précis des variations de la glycémie moyenne (DMR < 7 %) et offre un nouvel outil aux patients pour suivre l’évolution de l’HbA1c en temps réel avec une précision comparable à celle des mesures de l’ASG.
Introduction L’HbA1c mesurée en laboratoire est le marqueur de référence pour l’équilibre glycémique dans le DT1 et DT2, mais elle n’est réalisée qu’épisodiquement. Dans une présentation associée, ...nous démontrons l’utilité de l’ASG pour estimer l’HbA1c en temps réel (eA1c) nous évaluons ici la robustesse de cette nouvelle méthode. Matériels et méthodes Une première base de données est utilisée pour paramétrer le modèle (379 patients insulinonaifs, 17 863 mesures glycémiques, 1 599 HbA1c de références, soit en moyenne 47 j de données individuelles). Le modèle est ensuite évalué sur une base de données indépendante : 375 patients, 17 925 mesures glycémiques, 1 628 HbA1c de référence, 48 j de données individuelles en moyenne). Sont ensuite calculées les performance d’estimation stratifiée (référence et estimation), les performances lors de l’initialisation, et enfin la sensibilité aux données manquants de GAJ (ASG) et aux erreurs d’étiquetage du profile d’ASG (i.e. confusion entre valeurs pré- et postprandiales). Résultats La méthode est optimale dans la fourchette de 7 à 8 % d’HbA1c, sans biais et avec une DMR (déviation moyenne relative) de 4,5 %. Dans la fourchette de 6 à 10 % d’HbA1c, l’erreur est toujours < 1 % et la DMR < 10 %. La stratification des données par eA1c démontre la stabilité de l’algorithme (biais : − 0,23 % 0,19 % ; DMR : 6,74 % 7,24 %. La performance initiale chez chaque patient est semblable à la performance globale (DMR 7 % vs 6,8 %). Ni les données manquantes de GAJ (DMR 6,9 % vs 6,8 %) ni l’étiquetage erroné (DMR 7,0 % vs 6,8 %) n’ont altéré significativement les performances de la méthode. Conclusion Ce modèle dynamique permet une estimation précise et fiable de l’HbA1c, avec un DMR toujours < 10 %. Les effets limités de valeurs manquantes ou mal étiquetées autorisent son utilisation sur le terrain. La simplicité de calcul du modèle permet son implémentation dans des glucomètres courants.
Time-delayed feedback control is one of the most successful methods to discover dynamically unstable features of a dynamical system in an experiment. This approach feeds back only terms that depend ...on the difference between the current output and the output from a fixed time T ago. Thus, any periodic orbit of period T in the feedback-controlled system is also a periodic orbit of the uncontrolled system, independent of any modelling assumptions. It has been an open problem whether this approach can be successful in general, that is, under genericity conditions similar to those in linear control theory (controllability), or if there are fundamental restrictions to time-delayed feedback control. We show that, in principle, there are no restrictions. This paper proves the following: for every periodic orbit satisfying a genericity condition slightly stronger than classical linear controllability, one can find control gains that stabilize this orbit with extended time-delayed feedback control. While the paper’s techniques are based on linear stability analysis, they exploit the specific properties of linearizations near autonomous periodic orbits in nonlinear systems, and are, thus, mostly relevant for the analysis of nonlinear experiments.
The fermentation of dietary fiber to various organic acids is a beneficial function provided by the microbiota in the human large intestine. In particular, butyric acid contributes to host health by ...facilitating maintenance of epithelial integrity, regulating inflammation, and influencing gene expression in colonocytes. We sought to increase the concentration of butyrate in 20 healthy young adults through dietary supplementation with resistant starch (unmodified potato starch-resistant starch (RS) type 2).
Fecal samples were collected from individuals to characterize butyrate concentration via liquid chromatography and composition of the microbiota via surveys of 16S rRNA-encoding gene sequences from the Illumina MiSeq platform. Random Forest and LEfSe analyses were used to associate responses in butyrate production to features of the microbiota.
RS supplementation increased fecal butyrate concentrations in this cohort from 8 to 12 mmol/kg wet feces, but responses varied widely between individuals. Individuals could be categorized into three groups based upon butyrate concentrations before and during RS: enhanced, high, and low (n = 11, 3, and 6, respectively). Fecal butyrate increased by 67 % in the enhanced group (from 9 to 15 mmol/kg), while it remained ≥11 mmol/kg in the high group and ≤8 mmol/kg in the low group. Microbiota analyses revealed that the relative abundance of RS-degrading organisms-Bifidobacterium adolescentis or Ruminococcus bromii-increased from ~2 to 9 % in the enhanced and high groups, but remained at ~1.5 % in the low group. The lack of increase in RS-degrading bacteria in the low group may explain why there was no increase in fecal butyrate in response to RS. The microbiota of individuals in the high group were characterized by an elevated abundance of the butyrogenic microbe Eubacterium rectale (~6 % in high vs. 3 % in enhanced and low groups) throughout the study.
We document the heterogeneous responses in butyrate concentrations upon RS supplementation and identify characteristic of the microbiota that appear to underlie this variation. This study complements and extends other studies that call for personalized approaches to manage beneficial functions provided by gut microbiomes.
Devolatilization of subducting lithologies liberates COH-fluids. These may become partially sequestered in peridotites in the slab and the overlying forearc mantle, affecting the cycling of volatiles ...and fluid mobile elements in subduction zones. Here we assess the magnitudes, timescales and mechanism of channelized injection of COH-fluids doped with
Ca
aq
2
+
,
Sr
aq
2
+
and
Ba
aq
2
+
into the dry forearc mantle by performing piston cylinder experiments between 1–2.5 GPa and 600–700 °C. Cylindrical cores of natural spinel-bearing harzburgites were used as starting materials. Based on mineral assemblage and composition three reaction zones are distinguishable from the rim towards the core of primary olivine and orthopyroxene grains. Zone 1 contains carbonates + quartz ± kyanite and zone 2 contains carbonates + talc ± chlorite. Olivine is further replaced in zone 3 by either antigorite + magnesite or magnesite + talc within or above antigorite stability, respectively. Orthopyroxene is replaced in zone 3 by talc + chlorite. Mineral assemblages and the compositions of secondary minerals depend on fluid composition and the replaced primary silicate. The extent of alteration depends on fluid CO
2
content and fluid/rock-ratio, and is further promoted by fluid permeable reaction zones and reaction driven cracking. Our results show that COH-fluid induced metasomatism of the forearc mantle is self-perpetuating and efficient at sequestering
Ca
aq
2
+
,
Sr
aq
2
+
,
Ba
aq
2
+
and CO
2aq
into newly formed carbonates. This process is fast with 90% of the available C sequestered and nearly 50% of the initial minerals altered at 650 °C, 2 GPa within 55 h. The dissolution of primary silicates under high COH-fluid/rock-ratios, as in channelized fluid flow, enriches SiO
2aq
in the fluid, while CO
2aq
is sequestered into carbonates. In an open system, the remaining CO
2
-depleted, Si-enriched aqueous fluid may cause Si-metasomatism in the forearc further away from the injection of the COH-fluid into peridotite.
Objectif La précision des glucomètres dépend de l’absorption d’un volume d’échantillon suffisant. Les dispositifs de mesure sont censés afficher un message d’erreur en cas d’absorption incomplète. ...Cette étude de laboratoire a été réalisée afin de tester les performances de 31 glucomètres en cas de remplissage incomplet. Matériels et méthodes Des échantillons avec 2 niveaux de glycémie (60-90 et 300-350 mg/dL) ont été utilisés dans trois volumes différents : 0,20 μl (volume en dessous du volume seuil demandé), 0,32 μl (volume limite), 1,20 μl (volume suffisant). Suite à une mesure de référence (StatStrip, NovaBiomedical), les bandelettes ont été remplies (6×) avec le volume respectif et la réponse des lecteurs (2 de chaque lecteur testé) a été documentée (72 déterminations par lecteur). Une réponse était considérée comme correcte si la valeur était proche de la mesure de référence (± 20 %) ou si un message d’erreur apparaissait, indiquant un remplissage incomplet. » Résultats Seuls 5 glucomètres ont donné des réponses toujours correctes : AccuChek Compact+ et Mobile (Roche), OneTouch Verio (Lifescan), BGStar et iBGStar (Sanofi). La plupart des lecteurs (17) ont donné jusqu’à 10 % de réponses erronées : Precision Xceed, Xtra, FreeStyle lite et Freedom lite (tous d’Abbott) ; GlucoCard+, GlucoMen GM (Menarini) ; Contour, Contour USB, Breeze2 (Bayer) ; OneTouch Easy, Ultra2 et UltraSmart (Lifescan) ; Wellion Dialoget Premium (MedTrust) ; FineTouch (Terumo), AccuCheck Aviva (Roche), et GlucoTalk (Axis-Shield)). 10–20 % de fausses réponses ont été observées avec : OneTouch Vita (Lifescan) ; AccuChek Aviva Nano (Roche) ; OmniTest+ (BBraun) ; et AlphaChek (Progen). Plus de 20 % de fausses réponses ont été obtenues avec : Pura (Ypsomed), GlucoCardX et GlucoMen LX (Menarini), Elite (Bayer), et MediTouch (Medisana). Conclusion La majorité des glucomètres et bandelettes disponibles dans le commerce peuvent parfois afficher une lecture erronée en cas de remplissage incomplet de la bandelette. Ces résultats soulignent l’importance de l’éducation du patient sur cet aspect de l’auto-surveillance glycémique.
Abstract
High-pressure experiments were performed to investigate the effectiveness, rate and mechanism of carbonation of serpentinites by a carbon-saturated COH fluid at 1·5–2·5 GPa and 375–700 °C. ...This allows a better understanding of the fate and redistribution of slab-derived carbonic fluids when they react with the partially hydrated mantle within and above the subducting slab under pressure and temperature conditions corresponding to the forearc mantle. Interactions between carbon-saturated CO2–H2O–CH4 fluids and serpentinite were investigated using natural serpentinite cylinders with natural grain sizes and shapes in piston-cylinder experiments. The volatile composition of post-run fluids was quantified by gas chromatography. Solid phases were examined by Raman spectroscopy, electron microscopy and laser ablation inductively coupled plasma mass spectrometry. Textures, porosity and phase abundances of recovered rock cores were visualized and quantified by three-dimensional, high-resolution computed tomography. We find that carbonation of serpentinites is efficient at sequestering CO2 from the interacting fluid into newly formed magnesite. Time-series experiments demonstrate that carbonation is completed within ∼96 h at 2 GPa and 600 °C. With decreasing CO2,aq antigorite is replaced first by magnesite + quartz followed by magnesite + talc + chlorite in distinct, metasomatic fronts. Above antigorite stability magnesite + enstatite + talc + chlorite occur additionally. The formation of fluid-permeable reaction zones enhances the reaction rate and efficiency of carbonation. Carbonation probably occurs via an interface-coupled replacement process, whereby interconnected porosity is present within reaction zones after the experiment. Consequently, carbonation of serpentinites is self-promoting and efficient even if fluid flow is channelized into veins. We conclude that significant amounts of carbonates may accumulate, over time, in the hydrated forearc mantle.
The presence of Ca-Mg-carbonates affects the melting and phase relations of peridotites and eclogites in the mantle, and (partial) melting of carbonates liberates carbon from the mantle to shallower ...depths. The onset and composition of incipient melting of carbonated peridotites and carbonated eclogites are influenced by the pure CaCO3-MgCO3-system making the understanding of the phase relations of Ca-Mg-carbonates fundamental in assessing carbon fluxes in the mantle. By performing high-pressure and high-temperature experiments, this study clarifies the suprasolidus phase relations of the nominally anhydrous CaCO3-MgCO3-system at 6 GPa showing that Ca-Mg-carbonates will (partially) melt for temperatures above ∼1300 °C. A comparison with data from thermodynamic modeling confirms the experimental results. Furthermore, partition coefficients for Li, Na, K, Sr, Ba, Nb, Y, and rare earth elements between calcite and dolomitic melt, Ca-magnesite and dolomitic melt, and magnesite and dolomitic melt are established. Experiments were performed at 6 GPa and between 1350 to 1600 °C utilizing a rotating multi-anvil press. Rotation of the multi-anvil press is indispensable to establish equilibrium between solids and carbonate liquid. Major and trace elements were quantified with EPMA and LA-ICP-MS, respectively. The melting temperature and phase relations of Ca-Mg-carbonates depend on the Mg/Ca-ratio. For instance, Ca-rich carbonates with a molar Mg/(Mg+Ca)-ratio (XMg) of 0.2 will transform into a dolomitic melt (XMg = 0.33-0.31) and calcite crystals (XMg = 0.19-0.14) at 1350-1440 °C. Partial melting of Mg-rich carbonates (XMg = 0.85) will produce a dolomitic melt (XMg = 0.5-0.8) and Ca-bearing magnesite (XMg = 0.89-0.96) at 1400-1600 °C. Trace element distribution into calcite and magnesite seems to follow lattice constraints for divalent cations. For instance, the compatibility of calcite (XMg = 0.14-0.19) for Sr and Ba decreases as the cation radii increases. Ca-Mg-carbonates are incompatible for rare earth elements (REEs), whereby the distribution between carbonates and dolomitic melt depends on the Mg/Ca ratio and temperature. For instance, at 1600 °C, partition coefficients between magnesite (XMg = 0.96) and dolomitic melt (XMg = 0.8) vary by two orders of magnitudes from 0.001 to 0.1 for light-REEs to heavy-REEs. In contrast, partition coefficients of REEs (and Sr, Ba, Nb, and Y) between magnesite (XMg = 0.89) and dolomitic melt (XMg = 0.5) are more uniform scattering marginal between ∼0.1-0.2 at 1400 °C.
In the plasma membrane, syntaxin 1 and syntaxin 4 clusters define sites at which secretory granules and caveolae fuse, respectively. It is widely believed that lipid phases are mandatory for cluster ...formation, as cluster integrity depends on cholesterol. Here we report that the native lipid environment is not sufficient for correct syntaxin 1 clustering and that additional cytoplasmic protein-protein interactions, primarily involving the SNARE motif, are required. Apparently no specific cofactors are needed because i), clusters form equally well in nonneuronal cells, and ii), as revealed by nanoscale subdiffraction resolution provided by STED microscopy, the number of clusters directly depends on the syntaxin 1 concentration. For syntaxin 4 clustering the N-terminal domain and the linker region are also dispensable. Moreover, clustering is specific because in both cluster types syntaxins mutually exclude one another at endogenous levels. We suggest that the SNARE motifs of syntaxin 1 and 4 mediate specific syntaxin clustering by homooligomerization, thereby spatially separating sites for different biological activities. Thus, syntaxin clustering represents a mechanism of membrane patterning that is based on protein-protein interactions.
Foreword to the special issue on new developments in structural stability Gerasimidis, S; Hutchinson, J W; Sieber, J ...
Philosophical transactions of the Royal Society of London. Series A: Mathematical, physical, and engineering sciences,
04/2023, Letnik:
381, Številka:
2244
Journal Article
PDF
