Density Limitation Research Articles

Graphene oxide-based nanofluidic system for power generation from salinity difference

In converting a salinity difference to the electrical power by using an ion-selective membrane, achieving a high-power density necessitates both a high ion permeability and ion selectivity of the membrane. However, meeting these two requirements often leads to the conflicting tradeoff in the membrane properties. In this study, we introduce a new mechanistic approach to meeting both requirements by combining an ultra-thin (<100 nm thickness) graphene oxide-based membrane for a high permeability with an asymmetric access area for a high ion selectivity, forming a new type of ionic-diode nanofluidic system. With a graphene oxide/silk fibroin composite membrane, a large power density of 2kW/m2 is achieved with 32% conversion efficiency under a 1000-fold salt concentration ratio. This approach can be utilized to overcome the low power density limitation with any ultra-thin membranes, and thereby it will provide a new route to utilize blue energy in a reliable and efficient way.

Ultralong‐Term High‐Density Data Storage with Atomic Defects in SiC

AbstractThere is an urgent need to increase the global data storage capacity, as current approaches lag behind the exponential growth of data generation driven by the Internet, social media, and cloud technologies. In addition to increasing storage density, new solutions should provide long‐term data archiving that goes far beyond traditional magnetic memory, optical disks, and solid‐state drives. Here, a concept of energy‐efficient, ultralong, high‐density data archiving is proposed, based on optically active atomic‐size defects in a radiation resistance material, silicon carbide (SiC). The information is written in these defects by focused ion beams and read using photoluminescence or cathodoluminescence. The temperature‐dependent deactivation of these defects suggests a retention time minimum over a few generations under ambient conditions. With near‐infrared laser excitation, grayscale encoding and multi‐layer data storage, the areal density corresponds to that of Blu‐ray discs. Furthermore, it is demonstrated that the areal density limitation of conventional optical data storage media due to the light diffraction can be overcome by focused electron‐beam excitation.

Mathematical Modeling of the Evolutionary Dynamics of a Planktonic Community Using a Discrete-Time Model

This study proposes a discrete-time eco-genetic model of a planktonic community that includes zooplankton and two competing phytoplankton haplotypes with and without a toxicity trait. The Holling type II response function describes predator consumption. We use the Ricker model to consider density limitation and regulation. The model is analytically and numerically studied. The loss of stability of fixed points occurs via the Neimark–Sacker scenario and a cascade of period-doubling bifurcations. The model reveals bistability and multistability. Therefore, the initial conditions can determine which of the coexisting dynamic modes will be attracted. If the competition of haplotypes is weaker than their self-regulation, then the variation in the current densities of community components can shift the observed dynamics, while the evolution direction remains unchanged. The ratio of haplotype fitnesses and predator pressure generally determines the asymptotic genetic composition of phytoplankton. If competition of haplotypes is higher than their self-regulation, then the bistability of monomorphic fixed points occurs when the displacement of one haplotype by another depends on initial conditions. The presence of predators can maintain the genetic polymorphism of the prey. This system shows dynamic modes similar to experimental dynamics: oscillation with delay, long-period antiphase fluctuations, and cryptic cycles emerging due to rapid evolution.

A Review of Miscellaneous Spectrum Sensing Algorithms in 5G Ultra-dense Networks

The continual development of advanced networks within the Fifth Generation (5G) of wireless systems, and beyond, has seen the rise of multiple important research directions. These include cognitive radio (CR) and ultra-dense networks (UDNs), which are the focus of this article. The CR systems rely on an accurate assessment of the radio environment, which is provided by the spectrum sensing functionality. A review of such algorithms that are characterized by the detection of miscellaneous features of the received signal, together with their performance comparison, is presented. In addition, the application of a simple and adequate solution is assessed through its probability of detection, for a relevant UDN system model under the critical density limitation for the access point (AP) deployment

Ceria nanoflowers decorated Co3O4 nanosheets electrodes for highly efficient electrochemical supercapacitors

Overcoming a low energy density (1–50 Whkg−1) limitation is a challenge for supercapacitor electrode materials. To achieve higher performance (up to 100 Whkg−1), the transition metal-based pseudocapacitors (PCs) have been utilized owing to advantages viz. Faradaic reversible redox reaction significantly boosts the capacitance compared to that of the traditional electrical double layers capacitors (EDLCs). In this work, ceria nanoflowers decorated Co3O4 nanosheets structured active material deposited on nickel foam (denoted as CeO2@Co3O4/NF) by hydrothermal synthesis, demonstrates enhanced supercapacitor performance due to high conductivity, large surface area, and stable reversible oxidation states of Ce3+/Ce4+ and Co2+/Co3+ and greatly supported the Faradaic redox reaction of PCs. The CeO2@Co3O4/NF electrode showed a high areal-specific capacitance of 1598 mFcm−2 at 1 mAcm−2 for the 0–0.5 V potential windows and stability up to 96.6% after 6000 cycles. In an asymmetric supercapacitor (ASC) device, the CeO2@Co3O4/NF was used as a positive electrode which revealed an excellent energy density and power density viz. 92 Whkg−1 and 1580 Wkg−1, respectively. Overall, the present research findings signify the advantages of the novel combination of nanostructured ceria and cobalt oxide active materials for enhanced supercapacitor performance.

Overcharge‐Induced Phase Heterogeneity and Resultant Twin‐Like Layer Deformation in Lithium Cobalt Oxide Cathode for Lithium‐Ion Batteries

Overcharging is expected to be one of the solutions to overcome the current energy density limitation of lithium-ion battery cathodes, which will support the rapid growth of the battery market. However, high-voltage charging often poses a major safety threat including fatal incendiary incidents, limiting further application. Numerous researches are dedicated to the disadvantages of the overcharging process; nonetheless, the urgent demand for addressing failure mechanisms is still unfulfilled. Herein, it is revealed that overcharging induces phase heterogeneity into layered and cobalt oxide phases, and consequent "twin-like deformation" in lithium cobalt oxide. The interplay between the uncommon cobalt(III) oxide and the deformation is investigated by revealing the atomistic formation mechanism. Most importantly, abnormal cracking is discovered in the vicinity of the cobalt oxide where structural instability induces substantial contraction. In addition, surface degradation is widely observed in the crack boundary inside the particle. As unintentional overcharging can occur due to local imbalance in state-of-charge in severe operating conditions such as fast charging, the issues on overcharging should be emphasized to large extent and this study provides fundamental knowledge of overcharge by elucidating the crack development mechanism of layered cathodes, which is expected to broaden the horizon into high voltage operation.

Current density limitation during disruptions due to plasma-sheaths

The presented experimental study realized in the COMPASS tokamak demonstrates, for the first time, that the current density that flows from the plasma into the vacuum vessel during disruptions is limited by the ion particle flux. Such a limitation shows that, at least in COMPASS, the sheath that forms between the plasma and the first wall dominates the halo current flow. This observation is achieved by measuring simultaneously the ion saturation current with negatively biased Langmuir probes and the halo current with grounded probes to the vacuum vessel. These comparative measurements, which were never performed during disruptions in other machines, directly confirm that the halo current density remains below the ion particle flux in COMPASS. The study also shows, using Mirnov coils measurement, that the total electric current entering the wall grows with the plasma current while the current density obtained by Langmuir probes remains unaffected. This, together with the current density limitation, leads to a novel finding that the halo current width increases with the pre-disruptive plasma current, which limits the local forces. The new findings reported here could also provide potential constraints on the modeling of disruption-induced loads on future reactor scale tokamaks and motivation for further experiments on existing devices.

Evolutionary dynamics of structured populations with density-dependent limitation of juvenile survival

The paper considers evolutionary dynamics of a structured population with density-dependent regulation of juvenile survival. Such a type of density limitation is not unusual for natural populations. It occurs as either competition for food resources or sibling aggression, and, moreover, cannibalism or infanticide. Birth rate is assumed to change during the process of microevolution. The stability loss of non-trivial fixed points was shown to realize according to both the Neimark–Sacker​ scenario and the Feigenbaum one. The stability loss scenario is shown to be determined by both the mature individuals’ contribution to limiting juvenile survival and birth rate level. The bifurcations, dynamic modes and a possibility of their shifting are studied for the model proposed. The model reveals bistability and multistability both the population number and gene frequencies dynamics. There are bifurcations leading to fluctuations of gene frequencies in the proposed model. Thus, both monomorphic equilibriums and oscillation modes of the population genetic composition are simultaneously possible in the system. With the same values of population parameters in the case of variations in its current stage and/or genetic composition, such multistability can lead not only to a change in the dynamic mode due to an evolutionary growth of individual fitness, but also to a change in the evolution direction. As a result, different mechanisms of fluctuation emergence can be realized in a population at the same values of demographic parameters.

Commercialization-Driven Electrodes Design for Lithium Batteries: Basic Guidance, Opportunities, and Perspectives.

Current lithium-ion battery technology is approaching the theoretical energy density limitation, which is challenged by the increasing requirements of ever-growing energy storage market of electric vehicles, hybrid electric vehicles, and portable electronic devices. Although great progresses are made on tailoring the electrode materials from methodology to mechanism to meet the practical demands, sluggish mass transport, and charge transfer dynamics are the main bottlenecks when increasing the areal/volumetric loading multiple times to commercial level. Thus, this review presents the state-of-the-art developments on rational design of the commercialization-driven electrodes for lithium batteries. First, the basic guidance and challenges (such as electrode mechanical instability, sluggish charge diffusion, deteriorated performance, and safety concerns) on constructing the industry-required high mass loading electrodes toward commercialization are discussed. Second, the corresponding design strategies on cathode/anode electrode materials with high mass loading are proposed to overcome these challenges without compromising energy density and cycling durability, including electrode architecture, integrated configuration, interface engineering, mechanical compression, and Li metal protection. Finally, the future trends and perspectives on commercialization-driven electrodes are offered. These design principles and potential strategies are also promising to be applied in other energy storage and conversion systems, such as supercapacitors, and other metal-ion batteries.

Internal Illumination to Overcome the Cell Density Limitation in the Scale-up of Whole-Cell Photobiocatalysis.

Cyanobacteria have the capacity to use photosynthesis to fuel their metabolism, which makes them highly promising production systems for the sustainable production of chemicals. Yet, their dependency on visible light limits the cell‐density, which is a challenge for the scale‐up. Here, it was shown with the example of a light‐dependent biotransformation that internal illumination in a bubble column reactor equipped with wireless light emitters (WLEs) could overcome this limitation. Cells of the cyanobacterium Synechocystis sp. PCC 6803 expressing the gene of the ene‐reductase YqjM were used for the reduction of 2‐methylmaleimide to (R)‐2‐methylsuccinimide with high optical purity (>99 % ee). Compared to external source of light, illumination by floating wireless light emitters allowed a more than two‐fold rate increase. Under optimized conditions, product formation rates up to 3.7 mm h−1 and specific activities of up to 65.5 U gDCW −1 were obtained, allowing the reduction of 40 mm 2‐methylmaleimide with 650 mg isolated enantiopure product (73 % yield). The results demonstrate the principle of internal illumination as a means to overcome the intrinsic cell density limitation of cyanobacterial biotransformations, obtaining high reaction rates in a scalable photobioreactor.

Evaluation of displacement damage in solids induced by fast positrons: Modeling and effect on vacancy measurement

• The latest theoretical models of radiation damage in solid and numerical results of Mott differential cross section were used; • Displacement cross section by positrons for elements in most commonly used solids was calculated and the difference between positron and electron radiation was emphasized; • Displacement thresholds of kinetic energy for positrons in 30 elemental solids were presented; • Defects spatial distribution was obtained using Monte Carlo modeling. Positron Annihilation Technique is very sensitive to vacancy defects and small vacancy clusters and has been used as supplementary for TEM in radiation damage research. In this paper, we evaluated the displacement damage in solids induced by positrons and its effect on defects measurement, which has not been considered carefully in most PAT application. Displacement damage could only be produced when kinetic energy of positron exceeds a threshold determined by average displacement energy and the mass of atoms. Based on the latest models of displacement damage and numerical Mott elastic differential cross section of positrons interacting with atoms, displacement cross section for fast positron in solids was calculated and compared with that for electrons. In the energy range from 1 MeV to 100 MeV, electrons will produce more displacement defects than positrons do, especially in high-Z materials. Number of total defects depends on the primary displacement cross section and the size of damage cascades. To get distributions of defects and terminating position of positrons in materials, a Monte Carlo tool with full damage model was developed and validated. From the results of Monte Carlo modeling, the defects -generated by mono-energy positron beam have shallower distribution than the stopping position of positrons, indicating separation of defects and positrons and this fact benefits defects measurement because displacement damage produced by fast probing positron beam have little affection on the measurement. But for the positron beams from radioactive sources (such as 22 Na and 64 Cu) with continuous energy spectrum (from 0 to E max ), the depth profile of defects and terminated position of positrons overlap with each other and this fact indicated that defects measurement in materials will be affected by extra defects produced by positrons. The density of defects produced by positron beam is quite low with a typical value of about 0.01–0.1 cm −3 per positron in low-Z materials, which could be comparable with the defect density limitation if enough accumulated positrons are implanted into materials during measurement. For commonly used structural metals (such as Fe, Mn, Cu and metals with Z number higher than 40), using positron from 22 N and 64 Cu directly to measure defects density is quite safe because the energy is smaller than the displacement threshold.

Simulations of COMPASS vertical displacement events with a self-consistent model for halo currents including neutrals and sheath boundary conditions

The understanding of the halo current properties during disruptions is key to design and operate large scale tokamaks in view of the large thermal and electromagnetic loads that they entail. For the first time, we present a fully self-consistent model for halo current simulations including neutral particles and sheath boundary conditions. The model is used to simulate vertical displacement events (VDEs) occurring in the COMPASS tokamak. Recent COMPASS experiments have shown that the parallel halo current density at the plasma-wall interface is limited by the ion saturation current during VDE-induced disruptions. We show that usual magneto-hydrodynamic boundary conditions can lead to the violation of this physical limit and we implement this current density limitation through a boundary condition for the electrostatic potential. Sheath boundary conditions for the density, the heat flux, the parallel velocity and a realistic parameter choice (e.g. Spitzer’s resistivity and Spitzer–Härm parallel thermal conductivity) extend present VDE simulations beyond the state of the art. Experimental measurements of the current density, temperature and heat flux profiles at the COMPASS divertor are compared with the results obtained from axisymmetric simulations. Since the ion saturation current density () is shown to be essential to determine the halo current profile, parametric scans are performed to study its dependence on different quantities such as the plasma resistivity and the particle and heat diffusion coefficients. In this respect, the plasma resistivity in the halo region broadens significantly the profile, increasing the halo width at a similar total halo current.

Correlation between weight-bearing asymmetry and bone mineral density in patients with bilateral knee osteoarthritis

BackgroundAlthough unloading of the joint is related to reduction of the local bone mineral density (BMD), little attention had been paid to the relationship between loading asymmetry and side-to-side difference of BMD in patients with bilateral knee osteoarthritis (OA). The aim of the present study was to evaluate and clarify the relationship between gait parameters and bone mineral density in those patients.MethodsA total of 36 knees in eighteen patients (mean age = 73.7 ± 6.3 years, mean body mass index = 26.7 ± 3.8 kg/m2) with bilateral medial knee OA were enrolled in the present study. All subjects performed relaxed standing and level walking at our gait laboratory after informed consent was obtained. First, ground reaction force was calculated on bilateral knees during standing. The knees in each patient were divided into higher and lower force side for the definition of dominant side limb. Second, gait parameters in each subject were obtained. To analyze the factors that affect the weight-bearing distribution in both limbs, clinical data and biomechanical parameters were compared between knees. Clinical data included radiographic OA grade, femorotibial angle, and BMD at the bilateral femoral neck.ResultsKnees on higher force side were significantly more extended than on lower force side in standing (P = 0.012) and knee excursion during weight acceptance phase in gait was significantly larger in higher side than in lower side (P = 0.006), while the other parameters were not significantly different. As to the clinical data, higher force side had greater BMD, compared to lower force side. In terms of Kellgren–Lawrence scale and femorotibial angle on plain radiographs, there were no significant differences between higher and lower force side.ConclusionsBased on loading asymmetry in the present study, lower BMD was observed on Lower force side in patients with knee OA. Therefore, it is helpful for orthopedic surgeons to examine side-to-side differences of bone mineral density or extension limitation during standing for evaluation of the loading condition in patients with bilateral knee OA.

Electrochemical Deposition of 3D Interconnects

3D integration is an emerging semiconductor technology that is used to form highly integrated small-factor electronic systems by vertically stacking two or more thin electronic chips in a single package. In metallization of 3D through-substrate vias (TSuV) such as through-silicon (TSV), through-glass (TGV), through-ceramic (TCV) interconnects et al, TSuV having a very small diameter (down to several microns) and long length (hundreds of microns) are filled with plated metal in order to create massive networks of uniform interconnects with high aspect ratio (length/diameter) > 20. Existing conventional industry processes are based on expensive physical-vapor-deposition (PVD) technology, which has serious limitations on via fill uniformity and metal quality (poor step coverage, voids and other defects) as well as is limited to aspect ratios < 10.Electrochemical deposition processes have been extensively studied for 3D interconnects. These processes are appealing due to superior performance as compared to conventional PVD processes at a substantially lower cost. NANO3D’s processes are based on novel electrochemical nanomaterials (plating solutions with self-assembled suppression-based organic additives to achieve bottom up fill and conformal electroless nickel alloys/copper barrier/seed) that provide defect-free TSuV fill with Cu or other metals for aspect ratios up to >20 [1-5]. Electrochemical deposition techniques have no limitations on chips design rules (down below 20 nm) and can be applied to all types of 3D applications from logic and memory to MEMS, wireless and power electronics. Electrochemical TSuV metallization is fully compatible with all process steps in various 3D TSuV manufacturing schemes currently under evaluation and can be easily incorporated into any finally standardized “process flow of reference”. The low cost electrochemical TSuV technology addresses the major threats for adoption of 3D TSuV that is the scalability to high aspect ratio and the cost. Another threat for adoption of 3D TSuV technology, that is related to power density limitation and thermal dissipation from thinned dies are expected to be solved by controlled expansion metal alloys (INVAR et al.) where electrochemical deposition offers high flexibility for designers with various aspect ratios and via sizes.In this work, copper and INVAR electroplating as well as nickel alloys and copper electroless deposition processes have been developed and characterized to achieve bottom up fill in trenches & vias of high aspect ratio and wide range of features sizes with superior interconnect properties including low electrical resistivity, CTE and internal stress. Plated films with low-thermal expansion (of about 0.4±0.1 (x10-6, (K-1)) and ultralow internal stress (of about 30 MPa) have been deposited on patterned substrates such as TSuV on various substrates, redistribution layers (RDL), pillars and bumps for 3D Interconnects. The plated patterned substrates are flat, smooth, uniform, defect free and possess with complete fill of TSuV and well controlled thickness non-uniformity of about 5 % @ 3 σ for Cu & INVAR & Ni alloys films (Figure). Thermal shock testing of plated TSuV substrates showed promising reliability & adhesion results after 500 cycles of thermal shock with no cracking and delamination. References V.M. Dubin, A.L. Gindilis, B.L. Walton, K. Norelli, A.U. Liyanage, S.R. Bauers and D.C. Johnson. ECS Transactions, 2017, 75 (34), 27.S. Taushanoff and V. M. Dubin. ECS Transactions, 2017, 77 (11), 877.V.M. Dubin, K. Norelli, and P.N. Plassmeyer. ECS Transactions, 2017, 77 (11), 887.V.M. Dubin, M.O. Lisunova, and B.L. Walton. Journal of The Electrochemical Society, 2017, 164, D321.S. Taushanoff, V.M. Dubin, A. Wallace and H. A. Mantooth. ECS Transactions, 2018, 85 (13) 803. Figure 1

Evaluation of high-density tank cultivation of the live-feed cyclopoid copepod Apocyclops royi (Lindberg 1940)

Copepods are considered relevant live feed for fish larval marine aquaculture. They promote fish larval survival and growth rate and reduce deformities when used as food source. The cyclopoid copepod Apocyplops royi are among others used in extensive Taiwanese aquaculture. However, knowledge on its performance in intensive cultures is limited. This study investigates parameters that are relevant prerequisites before initiating intensive tank cultures with A. royi. We found that the biochemical profile of A. royi is promising and relevant when used as live feed with a C:N ratio of 4.7 and a fatty acid ratio (DHA/EPA 3.2 ± 0.7) that fulfil the minimum quantitatively dietary requirement of essential FAs for marine fish larvae and early juveniles. The size range of nauplii (78 - 245 μm) is evaluated to be a feasible size for small mouthed first feeding marine fish larvae. The copepod exhibits similar specific growth rates as other cyclopoids (10% DW d−1). Further, we tested A. royi populations relative composition (nauplii, copepodites, males, females and ovigerous females) as an effect of culture densities and found no change within the test range (300 to 3800 ind. L−1). To evaluate the recruitment into the population we conducted an experiment with densities from a few hundred to 10,000 ind. L−1. We observed no density limitation on the female ovigerous rate = ((ovigerous females) / copepodites + adults) x 100) ~6%) even at very high densities. We demonstrated, that A. royi is a promising candidate for intensive copepod cultures and a relevant live feed for marine larval fish culture.

Function and Application of Defect Chemistry in High‐Capacity Electrode Materials for Li‐Based Batteries

Current commercial Li-based batteries are approaching their energy density limitation, yet still cannot satisfy the energy density demand of the high-end devices. Hence, it is critical to developing advanced electrode materials with high specific capacity. However, these electrode materials are facing challenges of severe structural degradation and fast capacity fading. Among various strategies, constructing defects in electrode materials holds great promise in addressing these issues. Herein, we summarize a series of significant defect engineering in the high-capacity electrode materials for Li-based batteries. The detailed retrospective on defects specification, function mechanism, and corresponding application achievements on these electrodes are discussed from the view of point, line, planar, volume defects. Defect engineering can not only stabilize the structure and enhance electric/ionic conductivity, but also act as active sites to improve the ionic storage and bonding ability of electrode materials to Li metal. We hope this review can spark more perspectives on evaluating high-energy-density Li-based batteries.

Transfer of development rights for the effectiveness of the conservation plans: A case from Historic Kemeraltı, Izmir

The “Cultural and Natural Asset Protection” law implemented the transfer of development rights as a new tool for land use planning and management incorporated in the heritage conservation of Turkey in 2004, but no substantive implementation has yet been developed. There is no question that the inclusion of the transfer right is a significant advantage by statute, but the design and execution of TDR needs a guideline, a model proposal. The objective of the study is therefore twofold: 1) to explore the potential and pitfalls of incorporating TDR to conserve heritage sites with a set of factors derived from existing literature and 2) to propose a model for creating and calculating TDR to achieve density limitation in built-up heritage sites.Based on empirical evidence and actual implementation of TDRs, some generic factors in the literature affect the success of TDR programs, particularly in the United States. We, therefore, decided to use a set of fundamental factors to fully evaluate the efficacy of TDR in the Turkish planning system. On the other hand, there is also a lack of research for a successful framework that uses TDR for heritage conservation in general in literature. This study aims to overcome all these shortcomings by making a general evaluation of the integration of TDR into to the planning systems, to show the intrinsic quality of heritage conservation and TDR potentials, and finally to provide a straightforward guide to a TDR model. Evidence indicates that while TDR provides the potential to preserve Kemeraltı’s cultural heritage as a new market-based instrument, its use should be carefully designed and regulated by public authorities, Izmir's municipality, and the community at all.

DSTL

Shingled magnetic recording (SMR) is regarded as a promising technology for resolving the areal density limitation of conventional magnetic recording hard disk drives. Among different types of SMR drives, drive-managed SMR (DM-SMR) requires no changes on the host software and is widely used in today’s consumer market. DM-SMR employs a shingled translation layer (STL) to hide its inherent sequential-write constraint from the host software and emulate the SMR drive as a block device via maintaining logical to physical block address mapping entries. However, because most existing STL designs do not simultaneously consider the access pattern and the data update frequency of incoming workloads, those mapping entries maintained within the STL cannot be effectively managed, thus inducing unnecessary performance overhead. To resolve the inefficiency of existing STL designs, this article proposes a demand-based STL (DSTL) to simultaneously consider the access pattern and update frequency of incoming data streams to enhance the access performance of DM-SMR. The proposed design was evaluated by a series of experiments, and the results show that the proposed DSTL can outperform other SMR management approach by up to 86.69% in terms of read/write performance.

Leading‐edge disequilibrium in alder and spruce populations across the forest–tundra ecotone

AbstractThe distribution and composition of Arctic vegetation are expected to shift with ongoing climate change. Global models generally predict northward shifts in high‐latitude ecotones, and analysis of remote sensing data shows widespread greening and changes in vegetation structure across the circumpolar Arctic. However, there are still uncertainties related to the timing of these shifts and variation among different plant functional types. In this paper, we investigate disequilibrium dynamics of green alder and white spruce in the Tuktoyaktuk Coastal Plain, NWT. We used high‐resolution air photographs captured in the 1970s and 2000s to quantify changes in the distribution and abundance of alder and spruce near their northern limits. We found increases in alder and spruce stem density over time, but no change in their range limits, indicating that both species are affected by leading‐edge disequilibrium. Low stand density and temperature limitation of reproduction along the northern margin likely contributed to observed disequilibrium in both species. We also observed the greatest change in species occupancy within a burned area, suggesting that the increased frequency of fire will play a significant role in the timing and magnitude of near‐term vegetation change.

Stabilized High-Voltage Cathodes via an F-Rich and Si-Containing Electrolyte Additive.

High-voltage cathodes provide a promising solution to the energy density limitation of currently commercialized lithium-ion batteries, but they are unstable in electrolytes during the charge/discharge process. To address this issue, we propose a novel electrolyte additive, pentafluorophenyltriethoxysilane (TPS), which is rich in elemental F and contains elemental Si. The effectiveness of TPS has been demonstrated by cycling a representative high-voltage cathode, LiNi0.5Mn1.5O4 (LNMO), in 1.0 M LiPF6-diethyl carbonate/ethylene carbonate/ethyl methyl carbonate (2/3/5 in weight). LNMO presents an increased capacity retention from 28 to 85% after 400 cycles at 1 C by applying 1 wt % TPS. Further electrochemical measurements combined with spectroscopic characterization and theoretical calculations indicate that TPS can not only construct a robust protective cathode electrolyte interphase via its oxidation during initial lithium desertion but also scavenge the detrimental hydrogen fluoride (HF) present in the electrolyte via its strong combination with the species HF, F-, and H+, highly stabilizing LNMO during the charge/discharge process. These features of TPS provide a new solution to the obstacle in the practical application of high-voltage cathodes not limited to LNMO.