ObjectivePatients with renal failure suffer from symptoms caused by uraemic toxins, possibly of gut microbial origin, as deduced from studies in animals. The aim of the study is to characterise relationships between the intestinal microbiome composition, uraemic toxins and renal failure symptoms in human end-stage renal disease (ESRD).DesignCharacterisation of gut microbiome, serum and faecal metabolome and human phenotypes in a cohort of 223 patients with ESRD and 69 healthy controls. Multidimensional data integration to reveal links between these datasets and the use of chronic kidney disease (CKD) rodent models to test the effects of intestinal microbiome on toxin accumulation and disease severity.ResultsA group of microbial species enriched in ESRD correlates tightly to patient clinical variables and encode functions involved in toxin and secondary bile acids synthesis; the relative abundance of the microbial functions correlates with the serum or faecal concentrations of these metabolites. Microbiota from patients transplanted to renal injured germ-free mice or antibiotic-treated rats induce higher production of serum uraemic toxins and aggravated renal fibrosis and oxidative stress more than microbiota from controls. Two of the species, Eggerthella lenta and Fusobacterium nucleatum, increase uraemic toxins production and promote renal disease development in a CKD rat model. A probiotic Bifidobacterium animalis decreases abundance of these species, reduces levels of toxins and the severity of the disease in rats.ConclusionAberrant gut microbiota in patients with ESRD sculpts a detrimental metabolome aggravating clinical outcomes, suggesting that the gut microbiota will be a promising target for diminishing uraemic toxicity in those patients.Trial registration numberThis study was registered at ClinicalTrials.gov (NCT03010696).

Precise control of the electronic surface states of two-dimensional (2D) materials could improve their versatility and widen their applicability in electronics and sensing. To this end, chemical surface functionalization has been used to adjust the electronic properties of 2D materials. So far, however, chemical functionalization has relied on lattice defects and physisorption methods that inevitably modify the topological characteristics of the atomic layers. Here we make use of the lone pair electrons found in most of 2D metal chalcogenides and report a functionalization method via a Lewis acid-base reaction that does not alter the host structure. Atomic layers of n-type InSe react with Ti(4+) to form planar p-type [Ti(4+)n(InSe)] coordination complexes. Using this strategy, we fabricate planar p-n junctions on 2D InSe with improved rectification and photovoltaic properties, without requiring heterostructure growth procedures or device fabrication processes. We also show that this functionalization approach works with other Lewis acids (such as B(3+), Al(3+) and Sn(4+)) and can be applied to other 2D materials (for example MoS2, MoSe2). Finally, we show that it is possible to use Lewis acid-base chemistry as a bridge to connect molecules to 2D atomic layers and fabricate a proof-of-principle dye-sensitized photosensing device.

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Small-signal stability analysis is about power system stability when subject to small disturbances. If power system oscillations caused by small disturbances can be suppressed, such that the deviations of system state variables remain small for a long time, the power system is stable. On the contrary, if the magnitude of oscillations continues to increase or sustain indefinitely, the power system is unstable. Power system small-signal stability is affected by many factors, including initial operation conditions, strength of electrical connections among components in the power system, characteristics of various control devices, etc. Since it is inevitable that power system operation is subject to small disturbances, any power system that is unstable in terms of small-signal stability cannot operate in practice. In other words, a power system that is able to operate normally must first be stable in terms of small-signal stability. Hence, one of the principal tasks in power system analysis is to carry out small-signal stability analysis to assess the power system under the specified operating conditions.The dynamic response of a power system subject to small disturbances can be studied by using the method introduced in Chap. 7 to determine system stability. However, when we use the method for power system small-signal stability analysis, in addition to slow computational speed, the weakness is that after a conclusion of instability is drawn, we cannot carry out any deeper investigation into the phenomenon and cause of system instability. The Lyapunov linearized method has provided a very useful tool for power system small-signal stability analysis. Based on the fruitful results of eigensolution analysis of linear systems, the Lyapunov linearized method has been widely used in power system small-signal stability analysis. In the following, we shall first introduce the basic mathematics of power system small-signal stability analysis.The Lyapunov linearized method is closely related to the local stability of nonlinear systems. Intuitively speaking, movement of a nonlinear system over a small range should have similar properties to its linearized approximation. To study the stability of the nonlinear system at point x e(1) If the linearized system is asymptotically stable, i.e., all eigenvalues of A have negative real parts, the actual nonlinear system is asymptotically stable at the equilibrium point. (2) If the linearized system is unstable, i.e., at least one of eigenvalues of A has a positive real part, the actual nonlinear system is unstable at the equilibrium point. (3) If the linearized system is critically stable, i.e., real parts of all eigenvalues of A are nonpositive but the real part of at least one of them is zero, no conclusion can be drawn about the stability of the nonlinear system from its linearized approximation.The basic principle of the Lyapunov linearized method is to draw conclusions about the local stability of the nonlinear system around the equilibrium point from the stability of its linear ap...

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