NODAL Secures Pluripotency upon Embryonic Stem Cell Progression from the Ground State

Naive mouse embryonic stem cells (ESCs) can develop multiple fates, but the cellular and molecular processes that enable lineage competence are poorly characterized. Here, we investigated progression from the ESC ground state in defined culture. We utilized downregulation of Rex1::GFPd2 to track the loss of ESC identity. We found that cells that have newly downregulated this reporter have acquired capacity for germline induction. They can also be efficiently specified for different somatic lineages, responding more rapidly than naive cells to inductive cues. Inhibition of autocrine NODAL signaling did not alter kinetics of exit from the ESC state but compromised both germline and somatic lineage specification. Transient inhibition prior to loss of ESC identity was sufficient for this effect. Genetic ablation of Nodal reduced viability during early differentiation, consistent with defective lineage specification. These results suggest that NODAL promotes acquisition of multi-lineage competence in cells departing naive pluripotency.This research was funded by the Wellcome Trust (091484/Z/10/Z). The Cambridge Stem Cell Institute receives core support from the Wellcome Trust and the Medical Research Council (G1100526). C.M. was funded by a BBSRC studentship (961424). A.S. is a Medical Research Council Professor

Anomalous resistance overshoot in the integer quantum Hall effect

In this work we report experiments on defined by shallow etching narrow Hall bars. The magneto-transport properties of intermediate mobility two-dimensional electron systems are investigated and analyzed within the screening theory of the integer quantized Hall effect. We observe a non-monotonic increase of Hall resistance at the low magnetic field ends of the quantized plateaus, known as the overshoot effect. Unexpectedly, for Hall bars that are defined by shallow chemical etching the overshoot effect becomes more pronounced at elevated temperatures. We observe the overshoot effect at odd and even integer plateaus, which favor a spin independent explanation, in contrast to discussion in the literature. In a second set of the experiments, we investigate the overshoot effect in gate defined Hall bar and explicitly show that the amplitude of the overshoot effect can be directly controlled by gate voltages. We offer a comprehensive explanation based on scattering between evanescent incompressible channels.Comment: 7 pages and 5 figure

Quantification of Plasma and Urine Thymidine and 2'-Deoxyuridine by LC-MS/MS for the Pharmacodynamic Evaluation of Erythrocyte Encapsulated Thymidine Phosphorylase in Patients with Mitochondrial Neurogastrointestinal Encephalomyopathy.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is an ultra-rare disorder caused by mutations in TYMP, leading to a deficiency in thymidine phosphorylase and a subsequent systemic accumulation of thymidine and 2'-deoxyuridine. Erythrocyte-encapsulated thymidine phosphorylase (EE-TP) is under clinical development as an enzyme replacement therapy for MNGIE. Bioanalytical methods were developed according to regulatory guidelines for the quantification of thymidine and 2'-deoxyuridine in plasma and urine using liquid chromatography-tandem mass spectrometry (LC-MS/MS) for supporting the pharmacodynamic evaluation of EE-TP. Samples were deproteinized with 5% perchloric acid (v/v) and the supernatants analyzed using a Hypercarb column (30 × 2.1 mm, 3 µm), with mobile phases of 0.1% formic acid in methanol and 0.1% formic acid in deionized water. Detection was conducted using an ion-spray interface running in positive mode. Isotopically labelled thymidine and 2'-deoxyuridine were used as internal standards. Calibration curves for both metabolites showed linearity (r > 0.99) in the concentration ranges of 10-10,000 ng/mL for plasma, and 1-50 µg/mL for urine, with method analytical performances within the acceptable criteria for quality control samples. The plasma method was successfully applied to the diagnosis of two patients with MNGIE and the quantification of plasma metabolites in three patients treated with EE-TP

A Numerical Study of the Flexural Behavior of Concrete Beams Reinforced with AFRP Bars

In this study, analytical and numerical investigations were extensively conducted to evaluate the flexural behavior of concrete beams reinforced with aramid fiber-reinforced polymer (AFRP) rebars. The AFRP-reinforced concrete beams were analyzed using the separated finite element method containing different elements for concrete and reinforcement. In addition, this study used two different effective moment of inertia expressions to estimate the load-deflection responses and the service-load deflections of the beams. The service-load deflections of the AFRP-reinforced concrete beams obtained from the finite element analysis were in close agreement with those from the effective moment of inertia expressions. The numerical ultimate moments also correlated well with the analytical values of concrete stress-strain models. Numerical analyses, which hardly predict the sudden reduction in the flexural rigidity of FRPreinforced concrete beams due to the crushing of cover concrete, were shown to provide somewhat conservative deflection estimates.Представлены результаты аналитических и численных исследований, целью которых является определение изгибных характеристик железобетонных балок, упрочненных полимерными стержнями из армированных волокон. С помощью специального метода конечных элементов, включающего различные элементы для процессов бетонирования и армирования, провели анализ железобетонных балок, армированных полимерными стержнями. Для оценки характеристик прогиба под действием нагрузки и прогиба балки под действием рабочей нагрузки использовали два различных уравнения эффективного момента инерции. Значения прогиба железобетонных балок с полимерными стержнями под действием рабочей нагрузки, полученные конечноэлементным методом, хорошо сопоставляются со значениями из уравнений момента инерции. Численные значения разрушающего момента также хорошо согласуются с аналитическими значениями, полученными в результате применения модели зависимости деформации от напряжения для бетона. Для консервативной оценки прогиба представлены результаты численного анализа, которые почти не спрогнозировали внезапное уменьшение показателя жесткости при изгибе железобетонных балок с полимерными стержнями вследствие разрушения защитного слоя бетона.Представлено результати аналітичних і чисельних досліджень, метою яких є визначення згинальних характеристик залізобетонних балок, зміцнених полімерними стрижнями з армованих волокон. За допомогою спеціального методу скінченних елементів, що включає різні елементи для процесів бетонування й армування, проаналізовано залізобетонні балки, армовані полімерними стрижнямі. Для оцінки характеристик прогину під дією навантаження і прогину балки під дією робочого навантаження використовували два різних рівняння ефективного моменту інерції. Значення прогину залізобетонних балок із полімерними стрижнями під дією робочого навантаження, отримані скінченно-елементним методом, добре зіставляються зі значеннями з рівнянь моменту інерції. Числові значення руйнівного моменту також добре узгоджуються з аналітичними значеннями, отриманими по моделі залежності деформації від напруження для бетону. Для консервативної оцінки прогину представлено дані чисельного аналізу, які майже не спрогнозували раптове зменшення показника жорсткості при згині залізобетонних балок із полімерними стрижнями внаслідок руйнування захисного шару бетону

Quantification of Thermal Oxidation in Metallic Glass Powder using Ultra-small Angle X-ray Scattering

In this paper, the composition, structure, morphology and kinetics of evolution during isothermal oxidation of Fe 48Cr 15Mo 14Y 2C 15B 6 metallic glass powder in the supercooled region are investigated by an integrated ex-situ and in-situ characterization and modelling approach. Raman and X-ray diffraction spectra established that oxidation yielded a hierarchical structure across decreasing length scales. At larger scale, Fe 2O 3 grows as a uniform shell over the powder core. This shell, at smaller scale, consists of multiple grains. Ultra-small angle X-ray scattering intensity acquired during isothermal oxidation of the powder over a wide Q-range delineated direct quantification of oxidation behavior. The hierarchical structure was employed to construct a scattering model that was fitted to the measured intensity distributions to estimate the thickness of the oxide shell. The relative gain in mass during oxidation, computed theoretically from this model, relatively underestimated that measured in practice by a thermogravimetric analyzer due to the distribution in sizes of the particles. As a whole, this paper introduces the first direct quantification of oxidation in metallic glass powder by ultra-small angle X-ray scattering. It establishes novel experimental environments that can potentially unfold new paradigms of research into a wide spectrum of interfacial reactions in powder materials at elevated temperatures