Ni-rich LiNi x Co y Mn1–x–y O2 cathodes (x = 0.6, 0.8, 0.9, and 0.95) were tested to characterize the capacity fading mechanism of extremely rich Ni compositions. Increasing the Ni fraction in the ...cathode delivered a higher discharge capacity (192.9 mA h g–1 for LiNi0.6Co0.2Mn0.2O2 versus 235.0 mA h g–1 for LiNi0.95Co0.025Mn0.025O2); however, the cycling stability was substantially reduced. LiNi0.6Co0.2Mn0.2O2 and LiNi0.8Co0.1Mn0.1O2 retained more than 95% of their respective initial capacities after 100 cycles, while the capacity retention of LiNi0.9Co0.05Mn0.05O2 and LiNi0.95Co0.025Mn0.025O2 was limited to 85% during the same cycling period. The relatively inferior cycling stability of LiNi x Co y Mn1–x–y O2 with x > 0.8 is attributed to the phase transition near the charge-end, causing an abrupt anisotropic shrinkage (or expansion during discharge), which was suppressed for compositions of x < 0.8. Residual stress stemming from the phase transition destabilized the internal microcracks and allowed the microcracks to propagate to the surface, providing channels for electrolyte penetration and subsequent degradation of the exposed internal surfaces formed by the microcracks. Further developments in particle morphology are required to dissipate the intrinsic lattice strain, stabilize the surface, and modify the composition to attain a satisfactory long-term cycling stability, and hence battery life.
Recent adjustments to the histological diagnosis and the introduction of molecular classification are providing renewed support for the paradigm that antibody‐mediated rejection (ABMR) is an ...important clinical problem for which there is an urgent need for better therapies. Acute ABMR is observed when the graft is exposed to rapid increases in high‐titer donor‐specific antibodies (DSA) that are most often generated as anamnestic responses in sensitized recipients or de novo responses in nonsensitized patients who are nonadherent. Chronic ABMR is associated with slower increases in DSA, which may be high or low titer and transient or persistent. These DSA elicit cycles of injury and repair that manifest as multilamination of the peritubular capillary basement membrane or arteriopathy manifesting as intimal fibrosis. Mitigating the problem of AMBR requires the anamnestic and de novo DSA responses to be prevented and established DSA responses to be reversed. To this end, a better understanding of the immunobiology of DSA production is necessary and also the development of assays capable of detecting early humoral immune responses.Recent advances in understanding the immunobiology of B cells and areas requiring further investigation that might lead to new therapies or better diagnosis are discussed in this review.
This review focusses on recent advances in understanding the immunobiology of B cells and highlights areas requiring further investigation that might lead to new therapies or better diagnosis of antibody‐mediated rejection.
The transcription factor IRF4 regulates immunoglobulin class switch recombination and plasma cell differentiation. Its differing concentrations appear to regulate mutually antagonistic programs of B ...and plasma cell gene expression. We show IRF4 to be also required for generation of germinal center (GC) B cells. Its transient expression in vivo induced the expression of key GC genes including Bcl6 and Aicda. In contrast, sustained and higher concentrations of IRF4 promoted the generation of plasma cells while antagonizing the GC fate. IRF4 cobound with the transcription factors PU.1 or BATF to Ets or AP-1 composite motifs, associated with genes involved in B cell activation and the GC response. At higher concentrations, IRF4 binding shifted to interferon sequence response motifs; these enriched for genes involved in plasma cell differentiation. Our results support a model of “kinetic control” in which signaling-induced dynamics of IRF4 in activated B cells control their cell-fate outcomes.
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•IRF4 regulates GC B cell differentiation by directly activating Bcl6 and Obf1•IRF4 cellular concentrations orchestrate antigen-induced B cell fates•Occupancy of ISRE motif correlates with high cellular concentrations of IRF4•ISRE motifs are enriched in plasma cell genes
Careful reassessment of new and pre-existing data shows that recorded scatter in the hot-wire-measured near-wall peak in viscous-scaled streamwise turbulence intensity is due in large part to the ...simultaneous competing effects of the Reynolds number and viscous-scaled wire length l+. An empirical expression is given to account for these effects. These competing factors can explain much of the disparity in existing literature, in particular explaining how previous studies have incorrectly concluded that the inner-scaled near-wall peak is independent of the Reynolds number. We also investigate the appearance of the so-called outer peak in the broadband streamwise intensity, found by some researchers to occur within the log region of high-Reynolds-number boundary layers. We show that the ‘outer peak’ is consistent with the attenuation of small scales due to large l+. For turbulent boundary layers, in the absence of spatial resolution problems, there is no outer peak up to the Reynolds numbers investigated here (Reτ = 18830). Beyond these Reynolds numbers – and for internal geometries – the existence of such peaks remains open to debate. Fully mapped energy spectra, obtained with a range of l+, are used to demonstrate this phenomenon. We also establish the basis for a ‘maximum flow frequency’, a minimum time scale that the full experimental system must be capable of resolving, in order to ensure that the energetic scales are not attenuated. It is shown that where this criterion is not met (in this instance due to insufficient anemometer/probe response), an outer peak can be reproduced in the streamwise intensity even in the absence of spatial resolution problems. It is also shown that attenuation due to wire length can erode the region of the streamwise energy spectra in which we would normally expect to see kx−1 scaling. In doing so, we are able to rationalize much of the disparity in pre-existing literature over the kx−1 region of self-similarity. Not surprisingly, the attenuated spectra also indicate that Kolmogorov-scaled spectra are subject to substantial errors due to wire spatial resolution issues. These errors persist to wavelengths far beyond those which we might otherwise assume from simple isotropic assumptions of small-scale motions. The effects of hot-wire length-to-diameter ratio (l/d) are also briefly investigated. For the moderate wire Reynolds numbers investigated here, reducing l/d from 200 to 100 has a detrimental effect on measured turbulent fluctuations at a wide range of energetic scales, affecting both the broadband intensity and the energy spectra.
A LiLi0.19Ni0.16Co0.08Mn0.57O2 cathode was coated with AlF3 on the surface. The AlF3‐coating enhanced the overall electrochemical characteristics of the electrode while overcoming the typical ...shortcomings of lithium‐enriched cathodes. This improvement was attributed to the transformation of the initial electrode layer to a spinel phase, induced by the Li chemical leaching effect of the AlF3 coating layer.
Programmable protein circuits in living cells Gao, Xiaojing J; Chong, Lucy S; Kim, Matthew S ...
Science (American Association for the Advancement of Science),
09/2018, Letnik:
361, Številka:
6408
Journal Article
Recenzirano
Odprti dostop
Synthetic protein-level circuits could enable engineering of powerful new cellular behaviors. Rational protein circuit design would be facilitated by a composable protein-protein regulation system in ...which individual protein components can regulate one another to create a variety of different circuit architectures. In this study, we show that engineered viral proteases can function as composable protein components, which can together implement a broad variety of circuit-level functions in mammalian cells. In this system, termed CHOMP (circuits of hacked orthogonal modular proteases), input proteases dock with and cleave target proteases to inhibit their function. These components can be connected to generate regulatory cascades, binary logic gates, and dynamic analog signal-processing functions. To demonstrate the utility of this system, we rationally designed a circuit that induces cell death in response to upstream activators of the Ras oncogene. Because CHOMP circuits can perform complex functions yet be encoded as single transcripts and delivered without genomic integration, they offer a scalable platform to facilitate protein circuit engineering for biotechnological applications.
Abstract
Doping is a well-known strategy to enhance the electrochemical energy storage performance of layered cathode materials. Many studies on various dopants have been reported; however, a general ...relationship between the dopants and their effect on the stability of the positive electrode upon prolonged cell cycling has yet to be established. Here, we explore the impact of the oxidation states of various dopants (i.e., Mg
2+
, Al
3+
, Ti
4+
, Ta
5+
, and Mo
6+
) on the electrochemical, morphological, and structural properties of a Ni-rich cathode material (i.e., LiNi
0.91
Co
0.09
O
2
). Galvanostatic cycling measurements in pouch-type Li-ion full cells show that cathodes featuring dopants with high oxidation states significantly outperform their undoped counterparts and the dopants with low oxidation states. In particular, Li-ion pouch cells with Ta
5+
- and Mo
6+
-doped LiNi
0.91
Co
0.09
O
2
cathodes retain about 81.5% of their initial specific capacity after 3000 cycles at 200 mA g
−1
. Furthermore, physicochemical measurements and analyses suggest substantial differences in the grain geometries and crystal lattice structures of the various cathode materials, which contribute to their widely different battery performances and correlate with the oxidation states of their dopants.
Ordered occupation of Ni ions in the Li ion layer (and vice versa) was observed in 0.4 mol % Zr-doped LiNiO2 with R3̅m structure. Although cation mixing is prevalent in LiNiO2 and in other Ni-rich ...layered cathodes, cation ordering (Li and Ni) has not been previously reported in the as-prepared or fully discharged states. First-principles calculations verified that low-level doping of LiNiO2 with Zr can energetically promote the observed cation ordering. Contrary to previous beliefs, antisite defects (or cation mixing), whose presence is unequivocally justified by the cation ordering, had hardly any negative effect on the electrochemical performance of LiNiO2; both pristine and Zr-doped LiNiO2 delivered 247.5 and 246.5 mAh g–1, respectively, with a Coulombic efficiency of 97%. The capacity retention after 100 cycles was improved by increasing Zr doping to 81% from 74%. The improved cycling stability was attributed to the particle morphology being conducive to Li migration and relieving the deeply charged Li x NiO2 of its inherent structural instability.
Adaptable Peptide-Based Porous Material Rabone, J; Yue, Y.-F; Chong, S.Y ...
Science (American Association for the Advancement of Science),
08/2010, Letnik:
329, Številka:
5995
Journal Article
Recenzirano
Porous materials find widespread application in storage, separation, and catalytic technologies. We report a crystalline porous solid with adaptable porosity, in which a simple dipeptide linker is ...arranged in a regular array by coordination to metal centers. Experiments reinforced by molecular dynamics simulations showed that low-energy torsions and displacements of the peptides enabled the available pore volume to evolve smoothly from zero as the guest loading increased. The observed cooperative feedback in sorption isotherms resembled the response of proteins undergoing conformational selection, suggesting an energy landscape similar to that required for protein folding. The flexible peptide linker was shown to play the pivotal role in changing the pore conformation.
Current methods for studying central nervous system myelination necessitate permissive axonal substrates conducive to myelin wrapping by oligodendrocytes. We have developed a neuron-free culture ...system in which electron-spun nanofibers of varying sizes substitute for axons as a substrate for oligodendrocyte myelination, thereby allowing manipulation of the biophysical elements of axonal-oligodendroglial interactions. To investigate axonal regulation of myelination, this system effectively uncouples the role of molecular (inductive) cues from that of biophysical properties of the axon. We use this method to uncover the causation and sufficiency of fiber diameter in the initiation of concentric wrapping by rat oligodendrocytes. We also show that oligodendrocyte precursor cells display sensitivity to the biophysical properties of fiber diameter and initiate membrane ensheathment before differentiation. The use of nanofiber scaffolds will enable screening for potential therapeutic agents that promote oligodendrocyte differentiation and myelination and will also provide valuable insight into the processes involved in remyelination.
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