Visualization of lithium-ion transport and phase evolution within and between manganese oxide nanorods.

Multiple lithium-ion transport pathways and local phase changes upon lithiation in silver hollandite are revealed via in situ microscopy including electron diffraction, imaging and spectroscopy, coupled with density functional theory and phase field calculations. We report unexpected inter-nanorod lithium-ion transport, where the reaction fronts and kinetics are maintained within the neighbouring nanorod. Notably, this is the first time-resolved visualization of lithium-ion transport within and between individual nanorods, where the impact of oxygen deficiencies is delineated. Initially, fast lithium-ion transport is observed along the long axis with small net volume change, resulting in two lithiated silver hollandite phases distinguishable by orthorhombic distortion. Subsequently, a slower reaction front is observed, with formation of polyphase lithiated silver hollandite and face-centred-cubic silver metal with substantial volume expansion. These results indicate lithium-ion transport is not confined within a single nanorod and may provide a paradigm shift for one-dimensional tunnelled materials, particularly towards achieving high-rate capability

Research Progress on Preparation and Functions of Alginate Oligosaccharides with Different Structures

Alginate is one of the most abundant marine polysaccharides, which can be degraded into alginate oligosaccharides (AOS) by chemical, physical and biological methods. AOS, linear oligosaccharide composed of guluronic acid and mannuronic acid, have a variety of biological activities such as antimicrobial, anti-inflammatory, and immunoregulatory activities, and these biological activities are closely related to their structural diversity. AOS prepared by different degradation methods have different uronic acid compositions, polymerization degrees and special structures. Therefore, exploring the structure-function relationship of AOS will help to fully understand the activity of AOS and improve its application value. In this paper, the reaction mechanisms of the various methods to prepare AOS, the structures of the resulting products, and the structure-function relationship of AOS are reviewed in order to provide a reference for further research and application of AOS

Statistical Analysis of High-Resolution Coherent Monopulse Radar Sea Clutter

A statistical analysis that properly characterizes sea clutter processes is indispensable both for optimum detection algorithm design and for performance prediction problems in maritime surveillance applications. In this paper, we present the statistical analysis of experimental sea clutter data collected by a high-resolution coherent monopulse radar. First, we present the amplitude statistical analyses for these clutter data. The results show that the K, Pareto, and CIG distributions can each provide good fits to the clutter data for three channels of monopulse radar. The analyses on the variations of the K distribution parameters with range suggest that the scale parameter is closely associated with the clutter powers and that the shape parameter is influenced by the sea state. Then, we focus on the correlation properties. The averaged results suggest that the temporal and spatial correlation properties are similar for the clutter of all three channels. Moreover, the clutter between the sum and difference channels is almost completely correlated in elevation and is lowly correlated in azimuth. Finally, we perform a spectral analysis, highlighting the temporal and spatial variabilities of Doppler spectra. It is found that the individual Doppler spectra in all three channels can be represented by Gaussian-shaped power spectral densities, and their centroid and width can be modeled as two separate stage linear functions of spectrum intensity

Mitogen-activated protein kinase phosphatase-1 inhibits myocardial TNF-α expression and improves cardiac function during endotoxemia

Aims: Myocardial tumour necrosis factor-α (TNF-α) expression induces cardiac dysfunction in endotoxemia. The aim of this study was to investigate the role of mitogen-activated protein kinase phosphatase-1 (MKP1) pathway in myocardial TNF-α expression and cardiac function during endotoxemia. Methods and results: Lipopolysaccharide (LPS) increased MKP1 expression in the myocardium in vivo and in cultured neonatal cardiomyocytes in vitro. LPS-induced extracellular signal-regulated kinase (ERK) 1/2 and p38 phosphorylation in the myocardium was prolonged in MKP1 -/- mice. Myocardial TNF-α mRNA and protein levels were enhanced in MKP1 -/- compared with wild-type (WT) mice in endotoxemia, leading to a further decrease in cardiac function. To study if Rac1/p21-activated kinase 1 (PAK1) signalling regulates MKP1 expression, cardiomyocytes were treated with LPS. Inhibition of Rac1 and PAK1 by a dominant negative Rac1 adenovirus (Ad-Rac1N17) and PAK1 siRNA, respectively, blocked LPS-induced MKP1 expression in cardiomyocytes. PAK1 siRNA also decreased p38 and c-Jun N-terminal kinase (JNK) activation, and TNF-α expression induced by LPS. Furthermore, deficiency in either Rac1 or JNK1 decreased myocardial MKP1 expression in endotoxemic mice. Conclusion: LPS activates the Rac1/PAK1 pathway, which increases myocardial MKP1 expression via JNK1. MKP1 attenuates ERK1/2 and p38 activation, inhibits myocardial TNF-α expression, and improves cardiac function in endotoxemia. Thus, MKP1 represents an important negative feedback mechanism limiting pro-inflammatory response in the heart during sepsis. © The Author 2011

7-Ketocholesterol Induces Cell Apoptosis by Activation of Nuclear Factor kappa B in Mouse Macrophages

We investigated the molecular mechanisms responsible for the induction of apoptosis in mouse monocytic macrophage cell line J774A.1 stimulated by 7-ketocholesterol (7-KC). Cell apoptosis was detected by Annexin V-propidium iodide (PI) staining. The DNA-binding activity of nuclear factor kappa B (NF-kappaB) was assessed by electrophoretic mobility shift assay (EMSA). Results showed that 7-KC-stimulation in J774A.1 cells activated NF-kappaB, which is involved in cell apoptosis, in a time- and dose-dependent manners. 7-KC was also found to increase the binding activity of NF-kappaB to specific DNA binding sites, a possible mechanism for the induction of the cell apoptosis. Moreover, these effects were partially inhibited by pyrrolidine dithiocarbamate (PDTC), an NF-kappaB inhibitor. Taken together, 7-KC may be an important factor in atherosclerosis due to the ability of 7-KC to induce cell apoptosis, which is at least partially mediated through the activation of NF-kappaB.</p

Dynamic evolution of ceftazidime–avibactam resistance due to interchanges between blaKPC-2 and blaKPC-145 during treatment of Klebsiella pneumoniae infection

BackgroundThe emergence of ceftazidime–avibactam (CZA) resistance among carbapenem-resistant Klebsiella pneumoniae (CRKP) is of major concern due to limited therapeutic options.MethodsIn this study, 10 CRKP strains were isolated from different samples of a patient with CRKP infection receiving CZA treatment. Whole-genome sequencing (WGS) and conjugation experiments were performed to determine the transferability of the carbapenem resistance gene.ResultsThis infection began with a KPC-2-producing K. pneumoniae (CZA MIC = 2 μg/mL, imipenem MIC ≥ 16 μg/mL). After 20 days of CZA treatment, the strains switched to the amino acid substitution of T263A caused by a novel KPC-producing gene, blaKPC-145, which restored carbapenem susceptibility but showed CZA resistance (CZA MIC ≥ 256 μg/mL, imipenem MIC = 1 μg/mL). The blaKPC-145 gene was located on a 148,185-bp untransformable IncFII-type plasmid. The subsequent use of carbapenem against KPC-145-producing K. pneumoniae infection led to a reversion of KPC-2 production (CZA MIC = 2 μg/mL, imipenem MIC ≥ 16 μg/mL). WGS analysis showed that all isolates belonged to ST11-KL47, and the number of SNPs was 14. This implied that these blaKPC-positive K. pneumoniae isolates might originate from a single clone and have been colonized for a long time during the 120-day treatment period.ConclusionThis is the first report of CZA resistance caused by blaKPC-145, which emerged during the treatment with CZA against blaKPC-2-positive K. pneumoniae-associated infection in China. These findings indicated that routine testing for antibiotic susceptibility and carbapenemase genotype is essential during CZA treatment