bluuebunny/crossref_metadata_2025 huggingface dataset:
Montecito debris flows of 9 January 2018: Physical processes and social implications
Authors: Keller Edward , Adamaitis Chandler , Alessio Paul , Goto Erica , Gray Summer
Published: May 2020

Montecito, California, has a complicated Quaternary history of debris flows, the most recent being the Montecito debris flows of 9 January 2018, which were wildfire-debris flow–linked events that took 23 lives and damaged or destroyed several hundred homes. Relative flow chronology, based on boulder weathering, incision rates, and soil dates with limited numerical (radiocarbon and exposure) dating, is used to identify paths of prehistoric debris flows. Topography of debris flow fans on the piedmont is significantly affected by the south-side-up reverse Mission Ridge fault system. Examination of weathering rinds from Pleistocene debris flows confirms that the Rattlesnake Creek–Mission ridge debris flows are folded over the ridge, and that lateral propagation linked to uplift of marine terraces (uplift rate of ~0.5–1 m/k.y.) significantly altered debris flow paths. As communities continue to rebuild and live in these hazard-prone areas, disaster risk reduction measures must take into account both spatial and temporal components of vulnerability.

This field guide includes four stops from Montecito to Santa Barbara. The first stop will be to observe debris flow stratigraphy over the past ~30 ka beneath an earthquake terrace and a prehistoric Chumash site on the beach near the Biltmore Hotel in Montecito. The second stop will be at San Ysidro Creek in San Ysidro Canyon, the site of the largest Montecito debris flow that occurred on 9 January 2018. We will discuss source area and processes of the debris flow, and take a short hike up the canyon to visit the debris flow basin and a ring net designed to reduce the future hazard. The final two stops will explore the debris flow chronology of Santa Barbara over the past ~100 ka. Figure 1 shows the location of the field-trip stops. There is no road log as field sites can be found with a search on a smartphone.
Structure, metamorphism, and geodynamic significance of the Catalina Schist terrane
Authors: Platt* John P. , Grove* Marty , Kimbrough* David L. , Jacobson* Carl E.
Published: May 2020

This guide begins with an overview of the internal structure and petrology of the Catalina Schist terrane as exposed on Santa Catalina Island, California, followed by a discussion of the tectonic setting and exhumational history of the terrane, and the Cenozoic tectonic and geological evolution of the Inner Borderland, within which it lies. The guide then presents an itinerary for a three-day field trip from 9–11 May 2020. Next, we present a tectonic model for the formation of the Catalina Schist, followed by a discussion of its relationship to the Pelona, Orocopia, Rand, and related schists in southern California.
Measuring functional recovery in somatic symptom and related disorders: a scoping review
Authors: Winarizal Afiah Salsabila , Horvath Anita , Sawyer Susan M
Published: May 2020

Objective

Somatic symptom and related disorders (SSRDs) are prevalent, heterogenous conditions that have the potential to profoundly affect normative function in children and adolescents. Yet there is little understanding of pathways to recovery. This study aimed to systematically scope how functional recovery has been measured in children and adolescents with SSRD .

Design

Scoping review of primary studies.

Method

Medline (Ovid) and PsychInfo were systematically searched for publications from January 1998 to April 2019. Primary studies in English that reported functional outcomes of children and adolescents with SSRD were included. Case reports and population studies were excluded. Within the tools and clinician notes, the core domains of functional outcome were identified.

Results

Sixteen studies were identified that used 11 different functional outcome tools. The domains assessed within these functional outcome tools, together with the domains noted by clinicians, included physical and mental health symptoms, as well as school attendance and academic outcomes, recreational participation, impact on family and service utilisation. There was no evidence of a preferred outcome measure as only two of the tools were used in more than one study.

Conclusions

The variability of tools and domains used to measure functional recovery in children and adolescents with SSRD suggests lack of conceptual agreement about what constitutes functional recovery. Continued focus on symptom measurement or mental health comorbidities risks limiting research to single types of disorder (eg, functional neurological disability) or interventions, which threatens a much needed wider research agenda around appropriate treatment, including of complex and persistent disorders.
Hepatocellular carcinoma tumour volume doubling time: a systematic review and meta-analysis
Authors: Nathani Piyush , Gopal Purva , Rich Nicole , Yopp Adam , Yokoo Takeshi , John Binu , Marrero Jorge , Parikh Neehar , Singal Amit G
Published: May 2020

Background

Tumour growth patterns have important implications for surveillance intervals, prognostication and treatment decisions but have not been well described for hepatocellular carcinoma (HCC). The aim of our study was to characterise HCC doubling time and identify correlates for indolent and rapid growth patterns.

Methods

We performed a systematic literature review of Medline and EMBASE databases from inception to December 2019 and national meeting abstracts from 2010 to 2018. We identified studies reporting HCC tumour growth or tumour volume doubling time (TVDT), without intervening treatment, and abstracted data to calculate TVDT and correlates of growth patterns (rapid defined as TVDT <3 months and indolent as TVDT >9 months). Pooled TVDT was calculated using a random-effects model.

Results

We identified 20 studies, including 1374 HCC lesions in 1334 patients. The pooled TVDT was 4.6 months (95% CI 3.9 to 5.3 months I2=94%), with 35% classified as rapid, 27.4% intermediate and 37.6% indolent growth. In subgroup analysis, studies from Asia reported shorter TVDT than studies elsewhere (4.1 vs 5.8 months). The most consistent correlates of rapid tumour growth included hepatitis B aetiology, smaller tumour size (continuous), alpha fetoprotein doubling time and poor tumour differentiation. Studies were limited by small sample sizes, measurement bias and selection bias.

Conclusion

TVDT of HCC is approximately 4–5 months; however, there is heterogeneity in tumour growth patterns, including more aggressive patterns in Asian hepatitis B-predominant populations. Identifying correlates of tumour growth patterns is important to better individualise HCC prognostication and treatment decisions.
Tobacco smoking among chrysotile asbestos workers in Asbest in the Russian Federation
Authors: Olsson Ann , Kovalevskiy Evgeny V , Talibov Madar , Moissonnier Monika , Byrnes Graham , Bouaoun Liacine , Schonfeld Sara J , Feletto Eleonora , Kashanskiy Sergey V , Ostroumova Evgenia , Kromhout Hans , Bukhtiyarov Igor V , Schüz Joachim
Published: May 2020

Objectives

A historical cohort study of cancer mortality is being conducted among workers in a chrysotile mine and its enrichment factories in the town of Asbest, Russian Federation. Because individual-level information on tobacco use is not available for Asbest Chrysotile Cohort members, a cross-sectional survey of smoking behaviours was conducted among active and retired workers.

Methods

Self-administered questionnaires were completed by active workers during meetings organised by occupational safety personnel. Retired workers completed questionnaires during meetings of the Veterans Council or were interviewed via telephone or in person. Of the respondents, 46% could be linked to the Asbest Chrysotile Cohort. Among those, logistic regression models were used to assess associations between smoking and cumulative dust exposure.

Results

Among men, smoking prevalence was high and relatively consistent across birth decades (average, 66%), and was similar in workers across all levels of cumulative dust exposure (p trend, 0.44). Among women, the prevalence increased from <10% in those born before 1960 to 30% in those born after 1980, and smoking was associated with exposure to dust versus not exposed to dust (p value, 0.006), but did not vary appreciably across workers in different cumulative dust exposure categories (p trend, 0.29).

Conclusions

Our study suggests that cross-sectional surveys may be a useful tool for understanding the potential health impact from smoking in occupational cohorts, including possible confounding by smoking. This survey showed that adjustment at the age group level among women is needed to reduce residual confounding and account for smoking patterns, which have changed substantially over time.
Long‐term outcome of a surgically resected intracranial vascular hamartoma in a dog
Authors: Vicens Zanoguera Lucia , Pumarola Marti , Ruhi Paula , Fernandez Rodriguez Pablo , Luján Feliu‐Pascual Alejandro
Published: May 2020

A 13‐year‐old, 6.25‐kg (13.8‐lb) female mongrel was referred to the authors’ hospital with an acute‐onset left pleurothotonus and intermittent opisthotonus. Neurological examination showed clinical signs consistent with a multifocal brain lesion, and neoplastic, vascular, inflammatory and infectious conditions were considered. Precontrast and postcontrast CT images of the brain were obtained and revealed a precontrast hyperattenuating lesion with ring enhancement affecting the left frontoparietal junction. There was severe perilesional oedema, moderate midline shift, and left caudal transtentorial and foramen magnum herniations. A neoplastic lesion with a recent haemorrhagic component was therefore suspected. Following medical treatment with a mannitol bolus and prednisone for eight days, the neurological examination was considered normal. A dark‐grey capsulated mass was removed during a left frontoparietal craniectomy. Immediate postsurgical CT confirmed complete excision. Biopsy results were consistent with a cerebral vascular hamartoma. At 27‐month follow‐up, the dog was clinically normal.
Multiphoton signals of a (96 GeV?) stealth boson
Authors: Aguilar-Saavedra J. A. , Joaquim F. R.
Published: May 2020

Cascade decays of new scalars into final states with multiple photons and possibly quarks may lead to distinctive experimental signatures at high-energy colliders. Such signals are even more striking if the scalars are highly boosted, as when produced from the decay of a much heavier resonance. We study this type of events within the framework of the minimal stealth boson model, an anomaly-free $$\text {U}(1)_{Y'}$$

U

(
1
)

Y
′

extension of the Standard Model with two complex scalar singlets. It is shown that, while those signals may have cross sections that might render them observable with LHC Run 2 data, they have little experimental coverage. We also establish a connection with a CMS excess observed in searches for new scalars decaying into diphoton final states near 96 GeV. In particular, we conclude that the predicted multiphoton signatures are compatible with such excess.
Conformally invariant proper time with general non-metricity
Authors: Delhom Adrià , Lobo Iarley P. , Olmo Gonzalo J. , Romero Carlos
Published: May 2020

We show that the definition of proper time for Weyl-invariant space-times given by Perlick naturally extends to spaces with arbitrary non-metricity. We then discuss the relation between this generalized proper time and the Ehlers–Pirani–Schild definition of time when there is arbitrary non-metricity. Then we show how this generalized proper time suffers from a second clock effect. Assuming that muons are a device to measure this proper time, we constrain the non-metricity tensor on Earth’s surface and then elaborate on the feasibility of such assumption.
Charged reflecting shells supporting non-minimally coupled massless scalar field configurations
Authors: Hod Shahar
Published: May 2020

We study analytically the physical and mathematical properties of spatially regular massless scalar field configurations which are non-minimally coupled to the electromagnetic field of a spherically symmetric charged reflecting shell. In particular, the Klein–Gordon wave equation for the composed charged-reflecting-shell-nonminimally-coupled-linearized-massless-scalar-field system is solved analytically. Interestingly, we explicitly prove that the discrete resonance spectrum $$\{R_{\text {s}}(Q,\alpha ,l;n)\}^{n=\infty }_{n=1}$${Rs(Q,α,l;n)}n=1n=∞ of charged shell radii that can support the non-minimally coupled massless scalar fields can be expressed in a remarkably compact form in terms of the characteristic zeros of the Bessel function (here Q, $$\alpha $$α, and l are respectively the electric charge of the central supporting shell, the dimensionless non-minimal coupling parameter of the Maxwell-scalar theory, and the angular harmonic index of the supported scalar configuration).
Scalar 1-loop Feynman integrals as meromorphic functions in space-time dimension d, II: special kinematics
Authors: Phan Khiem Hong
Published: May 2020

Based on the method developed in Phan and Riemann (Phys Lett B 791:257, 2019), detailed analytic results for scalar one-loop two-, three-, four-point integrals in general d-dimension are presented in this paper. The calculations are considered all external kinematic configurations and internal mass assignments. Analytic formulas are expressed in terms of generalized hypergeometric series such as Gauss $$_2F_1$$2F1, Appell $$F_1$$F1 and Lauricella $$F_S$$FS functions.
Cooperative mechanism of resonant behaviors in a fluctuating-mass generalized Langevin system with generalized Mittag–Leffler memory kernel
Authors: Lin Lifeng , Chen Cong , Wang Huiqi
Published: May 2020

In this study, we investigate the resonant behaviors in the fluctuating-mass generalized Langevin equation (GLE) with generalized Mittag–Leffler (M–L) memory kernel. By using the stochastic averaging method and Laplace transform, we obtain the exact expression of the first-order moment of system steady response, based on which we analyze the dynamical mechanism of the various non-monotonic phenomena. Based on tbe numerical results, we further discuss the dependence on various parameters systematically and study the interplay and cooperation between the generalized M–L memory kernel and trichotomous noise in terms of output amplitude amplification. The results reveal the coexistence of non-monotonic phenomena in the proposed system, such as bona fide stochastic resonance (SR), conventional SR and wide-sense SR. We even observe the stochastic multi-resonance (SMR) behaviors with five or six peaks in the evolution of output amplitude amplification varying with the driving frequency. It is worth emphasizing that quintuple-peak and sextuple-peak bona fide SR phenomena had never been observed in the previous literatures. Thus, these results will provide more extensive support for manipulating the resonant behaviors through system parameter control in the potential applications.
Enhanced room temperature ammonia sensing properties of polypyrrole–zinc tin oxide nanocomposite
Authors: Juybari Seyede Azadeh Hejazi , Moghaddam Hossain Milani
Published: May 2020

Polypyrrole (PPy)–Zn2SnO4 nanocomposites with different weight percentages (0–20%) of Zn2SnO4 were successfully prepared by chemical oxidative polymerization. The prepared nanocomposites were deposited on epoxy glass substrate using a spin coating technique and have been characterized using various techniques such as X-ray diffractometer, field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FTIR) spectrometer. The physicochemical characterization confirmed well-formed dodecylbenzene (DBSA)-doped PPy–Zn2SnO4 nanocomposites with granular morphology and high porosity. Among various nanocompositions, DBSA-doped PPy–Zn2SnO4 (10 wt.%) nanocomposite was found to be highly sensitive towards NH3 vapor at room temperature i.e. with a chemiresistive response of 5.44% at 27 ppm with a reasonably fast recovery time of 76 s. Additionally, it shows a linear response and appropriate recovery time at all concentrations of NH3 vapor. The DBSA-doped PPy–Zn2SnO4 nanocomposite response is four times better than pure PPy toward NH3 vapor at room temperature. Therefore, it is expected that such material with excellent gas sensing properties at room temperature can be used for high-performance NH3 sensors.
Open quantum systems and thermal non-equilibrium processes
Authors: Rahdar Z. , Lari B.
Published: May 2020

In this paper, we investigate the effects of convexity and concavity of states on entanglement of the system under thermal non-equilibrium condition. In this regard, we consider a system consisting of two spin 1/2 particles with Dzyaloshinskii–Moriya (DM) interaction that follows the Tsallis statistics.Also, according to the desired statistics, the effect of environment parameters and the convexity or concavity of the input states on the output behavior of the SWAP gate is obtained.
Analysis of chaotic characteristics of trigonometric function system
Authors: Yu Wanbo , Yu Ting
Published: May 2020

Chaos, as an important subject of nonlinear science, plays an important role in solving problems in both natural sciences and social sciences such as the fields of secure communications, fluid motion, particle motion and so on. Aiming at this problem, this paper proposes a nonlinear dynamic system composed of product trigonometric functions and studies its chaotic characteristics. Through the mathematical derivation of the system’s period, the analysis of the necessary conditions at the fixed point, the experimental drawing of the Lyapunov exponential graph and the branch graph of the system, it is proved that the system has larger chaotic interval and stronger chaotic characteristics. The parameters of the proposed dynamic system are generated randomly, and then the chaotic sequence can be generated. The chaotic sequence is used to encrypt the digital image, a good encryption effect is obtained, and there is a large key space. At the same time, the motion of the particles in the space magnetic field is simulated, which further proves that the trigonometric system has strong chaotic characteristics.
Split Lie–Rinehart algebras
Authors: Albuquerque Helena , Barreiro Elisabete , Calderón A. J. , Sánchez José M.
Published: May 2020

We introduce the class of split Lie–Rinehart algebras as the natural extension of the one of split Lie algebras. We show that if [Formula: see text] is a tight split Lie–Rinehart algebra over an associative and commutative algebra [Formula: see text] then [Formula: see text] and [Formula: see text] decompose as the orthogonal direct sums [Formula: see text] and [Formula: see text], where any [Formula: see text] is a nonzero ideal of [Formula: see text], any [Formula: see text] is a nonzero ideal of [Formula: see text], and both decompositions satisfy that for any [Formula: see text], there exists a unique [Formula: see text] such that [Formula: see text]. Furthermore, any [Formula: see text] is a split Lie–Rinehart algebra over [Formula: see text]. Also, under mild conditions, it is shown that the above decompositions of [Formula: see text] and [Formula: see text] are by means of the family of their, respective, simple ideals.
Mahler coefficients of uniformly differentiable functions modulo p
Authors: Memić Nacima
Published: May 2020

In this work, we provide a complete description of Mahler coefficients of uniformly differentiable functions modulo [Formula: see text]. The main techniques are related to properties of van der Put coefficients of specific classes of functions, such as [Formula: see text]-Lipschitz measure-preserving functions and uniformly differentiable functions modulo [Formula: see text]. The relation tying Mahler coefficients and van der Put coefficients is also an important tool in the proof of the main results.
Multi-UAV Specification and Control with a Single Pilot-in-the-Loop
Authors: Moreno Patricio , Esteva Santiago , Mas Ignacio , Giribet Juan I.
Published: May 2020

This work presents a multi-unmanned aerial vehicle formation implementing a trajectory-following controller based on the cluster-space robot coordination method. The controller is augmented with a feed-forward input from a control station operator. This teleoperation input is generated by means of a remote control, as a simple way of modifying the trajectory or taking over control of the formation during flight. The cluster-space formulation presents a simple specification of the system’s motion and, in this work, the operator benefits from this capability to easily evade obstacles by means of controlling the cluster parameters in real time. The proposed augmented controller is tested in a simulated environment first, and then deployed for outdoor field experiments. Results are shown in different scenarios using a cluster of three autonomous unmanned aerial vehicles.
Hybrid Thermoelectrics
Authors: Liang Jia , Yin Shujia , Wan Chunlei
Published: May 2020

Constructing hybrid composites with organic and inorganic materials at different length scales provides unconventional opportunities in the field of thermoelectric materials, which are classified as hybrid crystal, superlattice, and nanocomposite. A variety of new techniques have been proposed to fabricate hybrid thermoelectric materials with homogeneous microstructures and intimate interfaces, which are critical for good thermoelectric performance. The combination of organic and inorganic materials at the nano or atomic scale can cause strong perturbation in the structural, electron, and phonon characteristics, providing new mechanisms to decouple electrical and thermal transport properties that are not attainable in the pure organic or inorganic counterparts. Because of their increasing thermoelectric performance, compositional diversity, mechanical flexibility, and ease of fabrication, hybrid materials have become the most promising candidates for flexible energy harvesting and solid-state cooling.
2D Molybdenum Disulfide Nanosheets As Functional Electroactive Materials and Additives for Lithium and Lithium Sulfur Based Batteries
Authors: Marschilok Amy C. , Takeuchi Esther S , Takeuchi Kenneth J
Published: May 2020

The 2D structured dichalcogenide molybdenum(IV) sulfide (MoS2) has generated significant interest for Li ion batteries due to its high theoretical capacity, good rate capability, and minimal volume changes during cycling. To enable full realization of MoS2 as an electroactive material, an important and continuing challenge is to understand the many polymorphs of MoS2 that can be (de)stabilized by electrochemical lithiation and nanosizing. Characteriation of bulk MoS2 and nanosheet-type MoS2 as solids, both structurally (X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS)) and compositionally (X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-optical emission spectroscopy (ICP-OES)) will be described to rationalize observed differences in capacity and efficiency in lithium based cells. X-ray analysis compatible lithium cells (in situ XRD and ex situ XAS) measurements of the specific phase changes to rationalize the significant difference in electrochemistry between the nanosheet and bulk materials upon (de)lithiation will also be discussed. The application of 2D MoS2 nanosheets for lithium sulfur batteries (Li−S) will also be described. Significantly improved Li−S electrochemistry in an environmentally friendly electrolyte solvent is demonstrated through implementation of MoS2 nanosheet materials as cathode additives, leading to improved capacity retention upon extended cycling in lithium sulfur cells. The findings will be discussed in light of the unique attributes of the MoS2 atomic level (2D) and mesoscale (3D) heterostructure.
Rapid Proton Transmission through Nafion | Graphene | ALD Alumina | Nafion Membranes
Authors: Bukola Saheed , Martinson Alex B. F. , Cao Duyen , Creager Stephen E
Published: May 2020

Recent reports from several laboratories indicate that proton transmission through graphene and other 2D materials in contact with proton-conducting electrolytes can occur rapidly with a much lower activation energy than expected from a wide range of computational studies on the proton / graphene interaction energy, and a much higher selectivity relative to transmission of other ions than would be expected based only on ion size. It would be desirable to be able to control transport through the graphene, and many approaches have been tried to rationally control transport rates through graphene via chemical treatments applied to the graphene. One such approach involves use of atomic layer deposition (ALD), in which single layers of inorganic materials, often oxides, are coated in a self-limiting way onto a surface by a series of pulsed reaction steps delivered in series. A common ALD implementation involves coatings of aluminum oxide, or alumina, created by sequential dosing of a surface with trimethyl aluminum and water vapor. We report here on use of the ALD method to coat single-layer CVD graphene supported on copper foil or on Nafion membranes with layers of alumina. Coatings resulting from 50 ALD cycles are found to be thick enough and homogeneous enough to block photoelectron emission from the underlying substrates (copper or Nafion) when the coatings are analyzed by X-ray photoelectron spectroscopy. Electrochemical hydrogen pump experiments were then performed to assess the degree to which ALD treatment of the graphene on Nafion, delivered prior to preparing Nafion | graphene | Nafion sandwich membranes, could change the rate of proton transmission through the graphene that is embedded within the Nafion. As little as two ALD treatment cycles are sufficient to reduce proton transmission currents through graphene by approximately half relative to graphene that is not treated by ALD. Surprisingly, fifty ALD cycles has almost the same effect as two cycles. This finding indicates that that ALD alumina coating is a relatively good proton conductor which is thought to reflect the action of transport pathways on the hydrated surface of the porous ALD alumina layer. The insensitivity of proton transmission to the number of ALD cycles applied suggests that the function of the ALD is to change the transport rates at interfaces, perhaps by creating a new ALD alumina / Nafion interface that protons must traverse in order to pass through the membrane.
(Invited) Chemical Functionalization and Transformation of 2D Layered Chalcogenide Materials
Authors: Wang Qing Hua
Published: May 2020

Layered chalcogenide materials are a diverse class of crystalline materials that consist of covalently bound building blocks held together by van der Waals forces. Among these materials are the transition metal dichalcogenides (TMDCs) which can be exfoliated into two-dimensional (2D) nanosheets, and the pnictogen chalcogenides (PCs) which can be exfoliated into one-dimensional (1D) nanoribbons and 2D nanosheets. Controlling the electronic and optical properties of these materials, as well as forming interfaces with other materials structures, is important for a wide range of potential applications, and can be achieved using a set of strategies for chemical modification that has been pursued in our laboratory. This talk will highlight our recent work on covalent chemical functionalization, structural and geometric conversion, and self-assembly of organic van der Waals heterostructures.

In the first strategy, semiconducting MoS2 is covalently functionalized using aryl diazonium salts that form out-of-plane bonds on the basal plane. Detailed imaging studies of the reaction under a range of parameters combined with density functional theory (DFT) calculations show that the functionalization initiates at point defects but then propagates in a chain-like morphology across the MoS2 surface. The reaction is also shown to be well-described by Freundlich and Temkin isotherm models, and to have pseudo-second-order kinetics. The diazonium salts can also be modified to enable tethering of proteins to the MoS2 surface. The same reaction scheme is also extended across the TMDC and PC layered chalcogenides including MoSe2, WS2, WSe2, Bi2S3, and Sb2S3. In the second strategy, MoO3 and WO3 nanoscrolls are formed by transformation from 2D MoS2 and WS2 nanosheets, respectively, via atmospheric plasma treatment. The combination of different radicals in the plasma simultaneously oxidize the layered disulfides and initiate delamination from the substrate, so that the strain of the altered crystal structure is relieved by rolling into nanoscroll geometries. In the final strategy, we form a self-assembled monolayer of fullerene molecules on WSe2, and use atomic resolution scanning tunneling microscopy to show that the molecules exhibit a 2x2 rotational superstructure due to the interplay of molecule-molecule, molecule-substrate, van der Waals, and Coulomb interactions. The system forms a charge redistribution network with long-range ordering.
(Invited) Optimizing 2D Material-Based Electrodes for Electrochemical Energy and Conversion Devices
Authors: Worsley Marcus A.
Published: May 2020

Electrochemical energy storage (EES) and conversion devices (e.g. batteries, supercapacitors, and reactors) are emerging as primary methods for global efforts to shift energy dependence from limited fossil fuels towards sustainable and renewable resources. These electric-based devices, while showing great potential for meeting some key metrics set by conventional technologies still face significant limitations. For example, an EES device tends to exhibit large energy density (e.g. lithium-ion battery) or power density (e.g. supercapacitor), but not both. This inability of a single device to simultaneously achieve both metrics represents a major obstacle to widespread adoption of EES devices. Improvements in materials, such as the integration of 2D materials (e.g. graphene, dichalcogenides, MXene, etc.) into electrochemical devices has yielded some exciting results towards tackling this issue, but significant improvements are still needed. Our approach to simultaneously achieving high energy and power density is to focus on one of the fundamental processes that occur in these systems: mass (or charge) transport. The efficient transport of ions within EES devices is critical to realizing both large power and energy densities. The pore structure of the electrode is a key factor in determining this transport phenomena, but in many cases, engineering the pore structure in a highly deterministic fashion is not pursued or even possible for many electrode materials. In this work, we explore a number of additive manufacturing methods (e.g. direct ink write, projection microstereolithography, etc.) to engineer the pore structure of device electrodes. We also determine effective electrode geometries using both simple theory and topology optimization techniques. The topology optimization couples the solution of the forward electrochemical problem over the full electrode domain with gradient-based optimization. The output of our code is a three-dimensional CAD representation which optimizes over specific performance metrics and which can be used to print functional electrodes. This work provides a systematic path toward automatic design and fabrication of engineered electrodes with precise control over the fluid and species distribution.

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
(Keynote) The Rise of MXenes
Authors: Gogotsi Yury
Published: May 2020

Numerous compounds, ranging from clays to boron nitride (BN) and transition metal dichalcogenides, have been produced as 2D sheets. Although many of these materials remain subjects of purely academic interest, others have jumped into the limelight due to their attractive properties, which have led to practical applications. Among the latter are carbides and nitrides of transition metals known as MXenes (pronounced “maxenes”), a fast-growing family of 2D materials. The family of 2D transition metal carbides and nitrides (MXenes) has been expanding rapidly since the discovery of Ti3C2 at Drexel University in 2011 [1]. More than 30 different MXenes have been reported, and the structure and properties of numerous other MXenes have been predicted using density functional theory (DFT) calculations [2,3]. Moreover, the availability of solid solutions on M and X sites, control of surface terminations, and the discovery of ordered double-M MXenes (e.g., Mo2TiC2), i-MAX phases and their MXenes offer the potential for producing dozens of new distinct structures.

This presentation will describe the state of the art in the field. The manufacturing of MXenes, their delamination into single-layer 2D flakes and assembly into films, fibers and 3D structures will be briefly covered. Synthesis-structure-properties relations of MXenes will be addressed on the example of Ti3C2. The use of MXenes in ceramic- metal- and polymer-matrix composites, smart fibers and textiles will also be discussed. The versatile chemistry of the MXene family renders their properties tunable for a large variety of applications [3-5]. Oxygen or hydroxyl-terminated MXenes, such as Ti3C2O2, have been shown to have redox capable transition metals layers on the surface and offer a combination of high electronic conductivity with hydrophilicity, as well as fast ionic transport [4]. This, among many other advantageous properties, makes the material family promising candidates for energy storage and related electrochemical applications [4], but applications in plasmonics, electrocatalysis, biosensors, water purification/ desalination and other fields are equally exciting.

References

1. M. Naguib, M. Kurtoglu, V. Presser, J. Lu, J.-J. Niu, M. Heon, L. Hultman, Y. Gogotsi, M. W. Barsoum, Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2, Advanced Materials, 23 (37), 4248-4253 (2011)

2. M. Naguib, O. Mashtalir, J. Carle, V. Presser, J. Lu, L. Hultman, Y. Gogotsi, M.W. Barsoum, Two-Dimensional Transition Metal Carbides, ACS
Nano
6 (2) 1322–1331 (2012)

3. B. Anasori, Y. Gogotsi (Ed.) 2D Metal Carbides and Nitrides (MXenes): Structure, Properties and Applications (Springer), 2019

4. B. Anasori, M. Lukatskaya, Y. Gogotsi, 2D Metal Carbides and Nitrides (MXenes) for Energy Storage, Nature Reviews Materials, 2, 16098 (2017)

K. Hantanasirisakul, Y. Gogotsi, Electronic and Optical Properties of 2D Transition Metal Carbides and Nitrides (MXenes), Advanced Materials, 30 (5
(Invited) Utilizing the Properties of Transition Metal Dichalcogenides and Black Phosphorus for Novel Device and Circuit Applications
Authors: Appenzeller Joerg
Published: May 2020

Many novel low-dimensional materials have been explored over the course of the past two decades, and it has widely been acknowledged that one-dimensional (1D) materials like nanotubes and nanowires and two-dimensional (2D) materials like transition metal dichalcogenides (TMDs) and black phosphorus (BP) offer unique opportunities and challenges when it comes to electronic applications. One aspect of 1D and 2D materials that makes them unique is the opportunity to build three-terminal transistor devices from them that show excellent response to the gate terminal due to the ultra-thin body of these materials. This tight gate control allows in particular achieving so-called ambipolar device characteristics that enable electron or hole currents to flow through the channel, depending on the chosen gate voltage polarity. However, in general, having both current polarities being present in the same device is not desirable for complementary metal-oxide semiconductor (CMOS) type circuits. In my presentation I will discuss how a properly designed device structure enables suppression of one type of carrier without losing the ability of generating n-type or p-type field-effect transistors (FETs) at will from the same channel material in the same gate geometry. Moreover, I will discuss how this concept translates into an opportunity to camouflage the circuit performance through the formation of devices that are only revealing their n-type or p-type nature through application of the correct gate and drain voltage polarity. Moreover, I will discuss in the context of the device performance the importance of gated contacts and will elucidate how in the past wrong mobility values were extracted by ignoring a particular feature of contacts to ultra-thin body FETs.
(Invited) Thickness-Modulated MoS2 for Electronic Applications
Authors: Adachi Michael M
Published: May 2020

Two dimensional transition metal dichalcogenides (TMDs) (e.g. MoS2) are atomically thin semiconductors that have remarkable properties such as a sizable electronic bandgap, relatively high carrier mobility, and flexibility. The atomically thin profile also facilitates the tuning of the electronic structure via surface effects such as charge traps and surface states. Two dimensional TMDs having two different thicknesses also have different electronic structures, forming heterojunctions. Here, we discuss the excellent rectification behavior of fabricated thickness-modulated (few layer - many layer) MoS2 diodes, including a large reverse breakdown voltage exceeding 10 V. The IV characteristics of the diodes can be strongly tuned by application of a gate voltage facilitating the demonstration of gate-voltage controlled tuning of simple electronic circuits including a voltage clipper and voltage regulator. The application of thickness-modulated diodes in high-frequency electronics is also discussed.
Capacitive Charging Mechanisms at the Molybdenum Disulfide/Ionic Liquid Interface
Authors: Pope Michael A , Lashkari Sima
Published: May 2020

Molybdenum disulfide (MoS2) is a 2D material of the transition metal dichalcogenide family which has recently gained significant attention for use in supercapacitors. MoS2 can exist as several polymorphs such as the 2H and 1T which are semiconducting and semi-metallic, respectively. The 2H phase, found in nature, is the most stable form of MoS2. The 1T phase is metastable and can be obtained by chemical methods such as via lithium intercalation. It shows a much higher conductivity (100 S/m). Furthermore, restacked single layers of 1T-MoS2 can be intercalated by smaller ions such as Na+, Li+, H+ and K+, in aqueous electrolyte, allowing the electrolyte to access their interlayer spacing and therefore providing impressively high volumetric capacitance of between 400 – 700 F/cm3. Hence, molybdenum disulfide is a promising material for supercapacitor application.

While these high values are achieved in aqueous electrolyte, few studies have examined their capacitive behavior in room temperature ionic liquid (IL) electrolytes which exhibit much higher electrochemical stability windows > 3-4 V. The potential of coupling high capacitance materials with high voltage operation has the potential to lead to high energy densities due to a supercapacitor’s square dependence of the energy density on cell voltage. However, it is currently unknown whether these electrolytes can intercalate between restacked 1T-MoS2. Furthermore, the intrinsic capacitance of the 1T-MoS2/IL electrolyte remains largely unexplored along with the impact that defects and oxidation may have. To investigate the charging behavior in IL electrolytes, we examined the electrochemical behaviour of monolayer MoS2 deposited on highly oriented pyrolytic graphite (HOPG), using cyclic voltammetry and electrochemical impedance spectroscopy. The monolayer MoS2 is deposited using a Langmuir Blodgett (LB) deposition method. Multilayers are deposited by sequential layer-by-layer deposition. The negligible roughness and surface coverage of the monolayers are confirmed and estimated by atomic force and scanning electron microscopies. Highly purified 1-ethyl, 3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) is used as the electrolyte and the monolayers are electrochemically probed in custom-made O-ring sealed electrochemical cell. Using these analyses, we probe the frequency and potential-dependence of the intrinsic capacitance of the MoS2/IL interface and provide design criteria for building improved IL-based supercapacitors.
Disorder-Features in Exfoliated Graphene from Variable Intercalation Times and Intercalant-Mix
Authors: Momodu Damilola , Sharif Farbod , Karan Kunal , Roberts Edward P.L.
Published: May 2020

Efficient exfoliation of relatively good-quality graphene with high-yield from graphite is critical for its extensive application in different emerging technologies. The cost-implication when undertaken via electrochemical exfoliation makes upscaling even more likely. In addition, the ability to constructively tune the final graphene properties (in terms of the defect metrics in the graphitic lattice) to fit a specific required application could be achieved by controlling operational parameters adopted during the intercalation and exfoliation steps.

In a recent study, we demonstrated a one-step electrochemical exfoliation process carried out in an inorganic electrolyte containing ammonium phosphate [1]. Phosphate groups on the resulting graphene led to a thermally stable material. The present study evaluates the incorporation of phosphate functionalization during the intercalation step of a two-step electrochemical exfoliation process.

Here-in, a systematic evaluation of the nature of defects is elucidated with respect to varying intercalation times and intercalant mix using an acid-blend containing sulphuric acid (H2SO4) and phosphoric acid (H3PO4). The type and location (edge or grain boundary-type), and relative concentration (%) of available defects is discussed with respect to increasing the intercalation times slightly beyond the point it attains a threshold intercalation voltage. Thermal stability of the graphene has also been explored based on the quantity of phosphoric acid content in the intercalant-mix. The exfoliated graphene sheets were characterized using Scanning Electron Microscopy, X-ray Diffraction, Thermal Gravimetric Analysis, X-ray Photoelectron and Raman Spectroscopy in detail to quantify defects and phosphorus contents in the doped-graphene framework. A thermally stable graphene was obtained with a constant “boundary-layer type” defect signature retained for increasing phosphoric acid in the mix. A shorter time to achieve the threshold intercalation voltage was observed with increasing H3PO4-acid content.

This study provides a facile and energy efficient recipe for synthesizing graphene nanostructures with signature defects relevant for use in energy storage and water treatment applications.
Insight into the Superior Photoactive Electrochemical Performances of NiCo2S4 for Efficient Bifunctional Catalyst Towards Oer/ORR in Rechargeable Zn-Air Batteries
Authors: Sarawutanukul Sangchai , Tomon Chanikarn , Phattharasupakun Nutthaphon , Sawangphruk Montree
Published: May 2020

The oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) are considered to be a fundamental basis of many energy conversion and storage technologies. Many studies have been devoted to developing high active ORR and OER bifunctional electrocatalysts to improve the efficiency of Zinc-air batteries (ZABs)[1]. However, the possibility of using free solar energy in ORR/OER electrocatalysts to enhance the efficiency of ZABs has not yet been recognized. Herein, we report a photoactive bifunctional catalyst of spinel-type NiCo2S4 (NCS) urchin-like structure with rich mesopores and direct band gap energies of ca. 1.4 and 2.4 eV which is good agreement with computational calculation. The NCS catalyst exhibits high catalytic activities for both OER (ɳ=338 mV at 10 mA cm-2) and ORR (ɳ=475 mV at E1/2), comparable to that of the state-of-the-art counterparts (e.g., Pt/C for ORR, RuO2 for OER). Under light illumination, the p-type photoactive NCS catalyst can absorb visible light, generating photogenerated holes and photoelectrons via the photoelectric effect for direct conversion of photoenergy into electric energy with increasing kinetic charge transfer process and provides ca. 10% and 18.5% lower OER and ORR overpotential than those under the dark condition. In addition, the as-fabricated zinc-air battery with the photoactive NCS as cathode exhibits the decrease in voltage gap from 0.82 to 0.60 V with an increase in round-trip efficiency from 59.2% to 68.8% after exposed to visible light. The zinc-air battery with a reversible redox reaction for simultaneous conversion of chemical and photoenergy into electric energy could open a new pathway for the utilization of a single energy conversion and storage device.

Figure 1. The schematic of photocatalytic Zn-Air-Batteries with NiCo2S4 cathode.

Keywords: Zn-air batteries, photoactive catalyst, Nickel cobalt sulfide.

References

1. Liu, W., et al., Defect-Enriched Nitrogen Doped–Graphene Quantum Dots Engineered NiCo2S4 Nanoarray as High-Efficiency Bifunctional Catalyst for Flexible Zn-Air Battery. Small, 2019. 15(44): p. 1903610.

Figure 1
The Hybrid Energy Conversion and Storage of Photoactive Nickel Metal Hydride Batteries
Authors: Kongsawatvoragul Ketsuda , Kalasina Saran , Sawangphruk Montree
Published: May 2020

Nickel metal hydride (NiMH) batteries are one type of batteries which are widely used commercially for various applications. NiMH consists of nickel hydroxide (Ni(OH)2) as a cathode electrode and lanthanum (La) alloy as an anode electrode. Many recent studies focused on developing the storage capacity, the self-discharge, and the degradation of performance at high temperature since they are cheaper than that of lithium-ion batteries. In this work, we’ve integrated the sunlight conversion and the storage abilities of NiMH. Ni(OH)2 as a cathode is a semiconductor material that can generate photovoltaic effect under the light which could facilitate electron transportation for electrochemical processes. The NiMH battery was fabricated as a coin-cell type with a transparent window to allow light passing toward Ni(OH)2. The NiMH battery was investigated via cyclic voltammogram (CV) and galvanostatic charge/discharge (GCD). In situ X-ray absorption spectroscopy (XAS) was also measured to elucidate the charge storage mechanisms. The result suggests the storage capacity enhancement under light illumination that could be one of the approaches for the development of NiMH batteries.

Figure 1