A Dilatometric Study of Graphite Electrodes during Cycling with X-ray Computed Tomography

Graphite is the most commonly used anode material in commercial lithium-ion batteries (LiBs). Understanding the mechanisms driving the dimensional changes of graphite can pave the way to methods for inhibiting degradation pathways and possibly predict electrochemical performance loss. In this study, correlative microscopy tools were used alongside electrochemical dilatometry (ECD) to provide new insights into the dimensional changes during galvanostatic cycling. X-ray computed tomography (CT) provided a morphological perspective of the cycled electrode so that the effects of dilation and contraction on effective diffusivity and electrode pore phase volume fraction could be examined. During the first cycle, the graphite electrode underwent thickness changes close to 9% after lithiation and, moreover, it did not return to its initial thickness after subsequent delithiation. The irreversible dilation increased over subsequent cycles. It is suggested the primary reason for this dilation is electrode delamination. This is supported by the finding that the electrode porosity remained mostly unchanged during cycling, as revealed by X-ray CT

Modelling and experimental investigation of Nb2O5 as a high-rate battery anode material

Modelling and understanding the battery electrochemical performance at high rates is a great challenge. Known for its fast rate and good cyclability, niobium pentoxide (Nb2O5) is a promising anode material for lithium-ion batteries and is specifically modelled and investigated in this work. Commercially sourced Nb2O5 was characterised using scanning electron microscopy, X-ray diffraction, and micro-computed tomography. The Nb2O5 material was found to contain large rod- and ball-like polycrystalline particles of tens of microns in size and have mixed T-Nb2O5 and H-Nb2O5 phases. The electrochemical performance of the material after ball milling was tested via cyclic voltammetry and constant-current cycling at different C-rates up to 50C (10,000 mA g−1). The material achieved a similar charge capacity (143 mAh g−1) to T-Nb2O5 at 0.5C and this capacity could be retained by more than 55% when C-rate was increased to 10C. The experimental results were used to support the development of the Doyle-Fuller-Newman electrochemical model for Nb2O5. By model parameterization, the reference exchange-current density and solid-state diffusivity of the present Nb2O5 were estimated to be 9.6 × 10−4 A m−2 and 6.2 × 10−14 m2 s−1, respectively. The model achieved accurate prediction of the battery performance up to currents of 5C with the obtained constant properties. However, the properties of Nb2O5 were found to be rate-dependent at higher C-rates when good agreements between the model and experiment were maintained. The decrease of the two properties at 10−50C revealed that there was a change of dominant charge storage mechanism from diffusion-controlled lithium insertion to capacitive effects, which was experimentally observed in the cyclic voltammetry

Residual Stress, Mechanical Behavior and Electrical Properties of Cu/Nb Thin-Film Multilayers

Effect of compositional wavelength (modulation) on residual stress, electrical resistivities and mechanical properties of Cu/Nb thin-film multilayers sputtered onto single-crystal Si substrates, was evaluated. Electrical resistivities were measured down to 4 K using a standard 4-point probe. Differential specimen curvature was used to determine residual stress, and a microprobe was used to obtain hardness and elastic modulus. Profilometry, ion-beam analysis and TEM were used. Hardness of the Cu-Nb multilayers increased with decreasing compositional wavelength so that the layered structures had hardness values in excess of either constituent and the hardness predicted by the rule of mixtures. A peak in net residual compressive stress of the multilayers was observed at a compositional wavelength of 100 nm. No resistivity plateau was observed within the composition wavelength range studied

ICMSF Methods Studies. XV. Comparison of Four Media and Methods for Enumerating Staphylococcus aureus in Powdered Milk.

Four media were examined for their usefulness in enumerating Staphylococcus aureus inoculated (a) into milk that was then dried or (b) directly into dried milk powder. In all, seven strains of S. aureus were inoculated individually into each preparation and were enumerated after two periods of storage (18 to 19 d and 60 to 61 d). Fourteen laboratories from twelve countries participated in the comparison which found that direct plating on agar medium in 14-cm petri dishes may be as useful as enrichment followed by streaking. Plating on Baird-Parker medium or on Hauschild pork plasma fibrinogen medium and a MPN method using Giolitti and Cantoni's broth with Tween 80 were equally sensitive for enumerating S. aureus in dried milk powder. The use of Hauschild medium may eliminate the need for supplementary tests to confirm colonies as S. aureus , but in some cases was found to fail in some laboratories. Giolitti and Cantoni's broth without Tween 80 generally was less useful than the three other media for enumerating S. aureus . S. aureus inoculated into milk that was then dried survived longer than when inoculated into dried milk

Curved Tails in Polymerization-Based Bacterial Motility

The curved actin ``comet-tail'' of the bacterium Listeria monocytogenes is a visually striking signature of actin polymerization-based motility. Similar actin tails are associated with Shigella flexneri, spotted-fever Rickettsiae, the Vaccinia virus, and vesicles and microspheres in related in vitro systems. We show that the torque required to produce the curvature in the tail can arise from randomly placed actin filaments pushing the bacterium or particle. We find that the curvature magnitude determines the number of actively pushing filaments, independent of viscosity and of the molecular details of force generation. The variation of the curvature with time can be used to infer the dynamics of actin filaments at the bacterial surface.Comment: 8 pages, 2 figures, Latex2

Biochemical properties of Paracoccus denitrificans FnrP:Reactions with molecular oxygen and nitric oxide

In Paracoccus denitrificans, three CRP/FNR family regulatory proteins, NarR, NnrR and FnrP, control the switch between aerobic and anaerobic (denitrification) respiration. FnrP is a [4Fe-4S] cluster containing homologue of the archetypal O2 sensor FNR from E. coli and accordingly regulates genes encoding aerobic and anaerobic respiratory enzymes in response to O2, and also NO, availability. Here we show that FnrP undergoes O2-driven [4Fe-4S] to [2Fe-2S] cluster conversion that involves up to 2 O2 per cluster, with significant oxidation of released cluster sulfide to sulfane observed at higher O2 concentrations. The rate of the cluster reaction was found to be ~6-fold lower than that of E. coli FNR, suggesting that FnrP can remain transcriptionally active under microaerobic conditions. This is consistent with a role for FnrP in activating expression of the high O2 affinity cytochrome c oxidase under microaerobic conditions. Cluster conversion resulted in dissociation of the transcriptionally active FnrP dimer into monomers. Therefore, along with E. coli FNR, FnrP belongs to the subset of FNR proteins in which cluster type is correlated with association state. Interestingly, two key charged residues, Arg140 and Asp154, that have been shown to play key roles in the monomer-dimer equilibrium in E. coli FNR are not conserved in FnrP, indicating that different protomer interactions are important for this equilibrium. Finally, the FnrP [4Fe-4S] cluster is shown to undergo reaction with multiple NO molecules, resulting in iron nitrosyl species and dissociation into monomers

Conventional radical versus focal treatment for localised prostate cancer: a propensity score weighted comparison of 6-year tumour control

Background: For localised prostate cancer, focal therapy offers an organ-sparing alternative to radical treatments (radiotherapy or prostatectomy). Currently, there is no randomised comparative effectiveness data evaluating cancer control of both strategies. Methods: Following the eligibility criteria PSA < 20 ng/mL, Gleason score ≤ 7 and T-stage ≤ T2c, we included 830 radical (440 radiotherapy, 390 prostatectomy) and 530 focal therapy (cryotherapy, high-intensity focused ultrasound or high-dose-rate brachytherapy) patients treated between 2005 and 2018 from multicentre registries in the Netherlands and the UK. A propensity score weighted (PSW) analysis was performed to compare failure-free survival (FFS), with failure defined as salvage treatment, metastatic disease, systemic treatment (androgen deprivation therapy or chemotherapy), or progression to watchful waiting. The secondary outcome was overall survival (OS). Median (IQR) follow-up in each cohort was 55 (28–83) and 62 (42–83) months, respectively. Results: At baseline, radical patients had higher PSA (10.3 versus 7.9) and higher-grade disease (31% ISUP 3 versus 11%) compared to focal patients. After PSW, all covariates were balanced (SMD < 0.1). 6-year weighted FFS was higher after radical therapy (80.3%, 95% CI 73.9–87.3) than after focal therapy (72.8%, 95% CI 66.8–79.8) although not statistically significant (p = 0.1). 6-year weighted OS was significantly lower after radical therapy (93.4%, 95% CI 90.1–95.2 versus 97.5%, 95% CI 94–99.9; p = 0.02). When compared in a three-way analysis, focal and LRP patients had a higher risk of treatment failure than EBRT patients (p < 0.001), but EBRT patients had a higher risk of mortality than focal patients (p = 0.008). Conclusions: Within the limitations of a cohort-based analysis in which residual confounders are likely to exist, we found no clinically relevant difference in cancer control conferred by focal therapy compared to radical therapy at 6 years

Analysing Change: Complex Rather than Dialectical?

The file attached to this record is the author's final peer reviewed version. The Publisher's final version can be found by following the DOI link.This article offers a discussion of dialectics from a complexity perspective. Dialectics is a term much utilized but infrequently defined. This article suggests that a spectrum of ideas exist concerning understandings of dialectics. We are particularly critical of Hegelian dialectics, which we see as anthropocentric and teleological. While Marxist approaches to dialectics, in the form of historical materialism, marked a break from the idealist elements of Hegelian dialectics, they retained traces of this approach. The article offers a partial discussion of essential elements of dialectics, which we consider to be the analysis of change, the centrality of contradiction, and the methodology of abstraction. Points of overlap with complexity thinking are highlighted, together with those points where complexity thinking and dialectical approaches diverge. We conclude with some suggestions as to how complexity thinking might contribute to a development of dialectical approaches

Public Governance. A Blueprint for Political Action and Better Government

This paper sets forth a comprehensive viewpoint about how Public Governance should be assessed and worked-out, by making three contributions to the subject matter. Firstly, it provides the semantics by which this field of learning and practice may become operational in Political Science. Next, a four-tiered framework of analysis is laid bare, which deals with architecture, covenants and safeguards, collective action, and deviant behavior. Afterwards, and focusing on conflict systems, we give heed to the underlying logic of Public Governance, which stems from a network built up around the mechanisms of participation, contest and safeguarding

Essential role of proteasomes in maintaining self-renewal in neural progenitor cells

Protein turnover and homeostasis are regulated by the proteasomal system, which is critical for cell function and viability. Pluripotency of stem cells also relies on normal proteasomal activity that mitigates senescent phenotypes induced by intensive cell replications, as previously demonstrated in human bone marrow stromal cells. In this study, we investigated the role of proteasomes in self-renewal of neural progenitor cells (NPCs). Through both in vivo and in vitro analyses, we found that the expression of proteasomes was progressively decreased during aging. Likewise, proliferation and self-renewal of NPCs were also impaired in aged mice, suggesting that the down-regulation of proteasomes might be responsible for this senescent phenotype. Lowering proteasomal activity by loss-of-function manipulations mimicked the senescence of NPCs both in vitro and in vivo; conversely, enhancing proteasomal activity restored and improved self-renewal in aged NPCs. These results collectively indicate that proteasomes work as a key regulator in promoting self-renewal of NPCs. This potentially provides a promising therapeutic target for age-dependent neurodegenerative diseases