bluuebunny/crossref_metadata_2025 huggingface dataset:
Forward or backward, that is the question: phospholipid trafficking by the Mla system
Authors: Abellon-Ruiz Javier
Published: December 2022

The distinctive feature of Gram-negative bacteria is the presence of an asymmetric outer membrane (OM), which acts as a permeation barrier blocking the diffusion of noxious components such as antibiotics that could compromise cell survival. The outer membrane has an inner leaflet, mainly formed by phospholipids (PLs), and the outer leaflet, composed of molecules of lipopolysaccharide (LPS). Building this membrane is a very complex process as every OM element needs to be transported from the cytoplasm or the inner membrane and properly placed in the OM. In addition, the asymmetry needs to be maintained to guarantee the barrier function of the membrane. The presence of misplaced PLs in the outer leaflet of the OM causes increased permeability, endangering cell survival. The Mla system (maintenance of OM lipid asymmetry) has been linked to the removal of the misplaced PLs, restoring OM asymmetry. The Mla system has elements in all compartments of the cell envelope: the lipoprotein MlaA in complex with the trimeric porins OmpC/F in the OM, MlaC in the periplasmic space and an ABC transporter in the inner membrane called MlaFEDB. While genetic and structural work suggest that the Mla pathway is retrograde (PL movement from OM to IM), several groups have advocated that transport could happen in an anterograde fashion (from IM to OM). However, recent biochemical studies strongly support retrograde transport. This review provides an overview of the current knowledge of the Mla system from a structural point of view and addresses the latest biochemical findings and their impact in transport directionality.
Mitigating the impact of fast charging on distribution grids using vehicle‐to‐vehicle power transfer: A Paris city case study
Authors: Sehimi Yacine , Almaksour Khaled , Suomalainen Emilia , Robyns Benoit
Published: December 2022

The deployment of DC fast charging stations (DCFCSs) in cities requires costly reinforcement of low‐voltage (LV) distribution grids, due to the high power required. It results in high investments for the station operator as well as for the distribution system operator and limits the profitability of such projects. In this study, a novel concept of fast charging station which reduces the connection to the grid is presented. This station uses Vehicle‐to‐vehicle (V2V) power transfer from a fleet of carsharing electric vehicles to provide a high charging power while mitigating the power demand on the grid. Based on data from a carsharing operator in the city of Paris, a simulation model of a combined carsharing/V2V fast charging system is proposed, allowing to simulate carsharing trips and V2V transfers. The reduction of the grid connections required to provide fast charging is evaluated and the impact of the repeated discharges on the level of service of the carsharing system is discussed. Moreover, simulation of LV distribution grids allows to compare the grid losses of the V2V system with conventional DCFCSs.
Evaluation of the impact of the electric network's quality on the appliance's signatures
Authors: Sonfack Gisele Beatrice , Ravier Philippe
Published: December 2022

The continuous increase in the demand for electrical energy has led to the design of highly complex electrical systems, which can even extend to entire countries. In this context, active residential customer participation in the smart grid can benefit from having control over a number of data points related to the behaviour of the grid and the devices connected to it. The load signatures are the basis for practical energy's consumption monitoring technologies, which involve identifying an electrical device and determining their operating status. Although several load identification techniques are under development in research laboratories, it is important to note that studies on the impact of power system quality on the signatures underlying these developments are not yet clear. Knowing that load profiles depend on environmental factors, user habits, and other non‐deterministic factors, it is important to assess the impact that grid quality can have on load signatures in order to take it into account in the development of identification systems to be integrated into the smart grid. This research focuses on the two central components of these approaches: (1) Presenting an assessment of the different network faults that can impact the signatures of connected loads, (2) Analysing and quantifying the impact of each fault through load behavioural models and virtual simulation. The study considers the two types of loads generally encountered in homes (linear and non‐linear). It then analyses the characteristic quantities such as waveforms, effective current and voltage values, active and reactive power (harmonics) and non‐deforming power (fundamentals). The results of the simulations performed on Simulink/Simscape show that some network faults such as flicker have a significant and permanent impact on the signatures while others (Voltage Sag) have a temporary and sometimes insignificant effect.
Gas phase Photoemission studies in the hard X-ray domain
Authors: Simon Marc
Published: December 2022

Recent results obtained in gas phase photoemission studies are presented in this article with particular emphasis on recoil, Double Core Hole and Post Collision Interaction. These three important effects are not specific to the gas phase and could have more general applications in condensed matter studies.
Methodological developments to expose and analyse buried interfaces in lithium solid-state batteries using ex situ, in situ and operando cycling
Authors: Morey Julien , Ledeuil Jean-Bernard , Madec Lénaïc , Martinez Hervé
Published: December 2022

Lithium solid-state batteries (SSBs) are a promising technology for electrochemical energy storage systems. So far, the performance of SSBs are mainly governed by the electro-chemo-mechanical properties of the diverse solid/solid interfaces and their evolution upon cycling. However, as these interfaces are buried in the battery stack, their comprehensive understanding remains a challenge. Here, we thus provide some advances in methodological developments for ex situ, in situ and operando cycling/analysis of these buried interfaces. It is showed that noble gaz ion milling at liquid nitrogen temperature is a suitable and reproducible method to prepare cross-section without any chemical/physical change even for polymer-based SSBs. In addition, innovative operando cycling using Auger analysis was proposed for the first time on a model Li/Li6PS5Cl stack. The interest of this approach is to be able to proceed without a dedicated electrochemical cell and to use the fully adjustable electron beam of the auger to create a surface potential difference followed by lithium migration then SEI (Solid Electrolyte Interface) formation and Li plating. Overall, this work should greatly benefits to all researchers working on buried interfaces study in lithium solid-state batteries.
Core and safety design for France–Japan common concept on sodium-cooled fast reactor
Authors: Takano Kazuya , Ohki Shigeo , Ozawa Takayuki , Yamano Hidemasa , Kubo Shigenobu , Ogura Masashi , Yamada Yumi , Koyama Kazuya , Kurita Koichi , Costes Laurent , Venard Christophe , Carluec Bernard , Perrin Benoit , Verrier Denis
Published: December 2022

France (CEA and FRAMATOME) and Japan (JAEA, MFBR, and MHI) teams have carried out collaborative works to have common technical views regarding a sodium-cooled fast reactor (SFR) concept. This paper mainly describes the capabilities of ASTRID 600 to demonstrate SFR technologies of both countries. Japan has studied the feasibility of an enhanced high burnup low-void effect (CFV) core and fuel using oxide dispersion-strengthened steel cladding in ASTRID 600, considering Japan’s target for core performance. The neutronics design of the core has satisfied most required design targets and conditions. Regarding passive shutdown capabilities, Japan team has performed a preliminary numerical analysis for ASTRID 600 using a complementary safety device (CSD), called a self-actuated shutdown system (SASS), one of the safest approaches in Japan. Japan’s team used the SASS in place of the hydraulically suspended absorber rod, called RBH, one of the safest approaches of France, to investigate the potential of the SASS as a design measure common to the countries. The preliminary analysis has shown that the SASS can satisfy the countries’ main requirements. This study has also revealed that the mitigation measures of ASTRID 600 against a severe accident are promising to achieve in-vessel retention for both countries.
Mechanism of improving transverse corner cracks of peritectic steel slab based on control of inclusions and microstructures with magnesium treatment
Authors: Cai Wenjing , Yang Jian , Deng Liqin , Zuo Kanglin , Wu Xufeng
Published: December 2022

In this paper, in order to clarify the mechanism of improving the transverse corner crack of peritectic steel slab with Mg treatment, the inclusions and microstructure characteristics at the slab corner of Al deoxidized (S-Al), (Al+Ca) deoxidized (S-Ca) and (Al+Mg) deoxidized (S-Mg) peritectic steels were studied. The inclusions in S-Al sample are mainly Al2O3, Al2O3 · MnS and MnS inclusions. The S-Ca sample mainly contains Al2O3 inclusions and their complex inclusions. In the S-Mg sample, the number of Mg containing inclusions increase sharply. The S-Mg sample has the smallest average size of inclusions and the largest number of inclusions with the size smaller than 1 µm. The brittle structures are dominant in S-Al sample, which basically disappear in S-Ca sample and S-Mg sample. Mg treatment refines the size of grains at the slab corner, reduces the size of the proeutectoid ferrite films, and restrains the crack propagation along the grain boundary. More IAF microstructures are formed in S-Mg sample. IAFs take MgO · Al2O3 · MnS, MgO · Al2O3 · TiN · MnS and other complex inclusions as the nucleation cores, which diverge and grow outward from the inclusions. Thus, IAFs form a fine crack resistant microstructure, improving the microstructure at the slab corner to prevent the occurrence of transverse corner cracks.
Investigating the nanomechanical and thermal characteristics of Ti20-Al20-V20-Fe20-Ni20 HEA developed via SPS for high energy applications
Authors: Ujah Chika O. , Popoola Patricia A. , Popoola Olawale M. , Afolabi Ebenezer A. , Orji Uwa O.
Published: December 2022

Ti6Al4V is one of the most popular alloys used in the aerospace, biomedical and high temperature/strength applications due to its high strength, low weight, high oxidation resistance and low CTE. But its low shear strength undermines its performance in some critical engineering applications. This work was aimed at developing high entropy alloy of Ti-Al-V-Fe-Ni at equiatomic level using spark plasma sintering technique which would be able to address the above weakness of Ti64. The powders were blended, sintered at varying temperatures from 700 °C to 1100 °C and characterized. Results showed that HEA sintered at 1100 °C possessed the best nanomechanical, thermal and microstructural properties while that sintered at 700 °C had the weakest properties. The developed alloy had elastic modulus improvement of about 667% over Ti6Al4V and about 51% over Ti6Al4V-0.55B alloys. It had creep resistance of 1.5%, densification of 98.94%, porosity of 1.06% and very high resistance to oxidation. It was concluded that the developed alloy can perform much better than Ti64 in high temperature and high strength applications.
Update FDG-PET in der Demenzdiagnostik
Authors: Buchert Ralph , Förster Stefan
Published: December 2022

Dieser Artikel soll ein Update zu unserem Übersichtsartikel „FDG-PET in der
Differenzialdiagnostik neurodegenerativer Demenzerkrankungen“ aus 2016 geben. Seitdem wurden
zahlreiche neue, technisch hochwertige Studien mit großen Patientenkollektiven sowie
systematische Übersichtsarbeiten internationaler Expertengruppen veröffentlicht. Außer den
aktualisierten Best-Practice-Empfehlungen dieser Expertengruppen sollen in diesem Update
einige ausgewählte neue Entwicklungen vorgestellt und diskutiert werden, die aus unserer Sicht
für den Einsatz der FDG-PET des Gehirns in der klinischen Routineversorgung von Patienten mit
kognitiven Einschränkungen besonders relevant sind, oder in naher Zukunft besonders relevant
werden könnten. Dazu gehören neue diagnostische Optionen durch die verbesserte räumliche
Auflösung der klinischen Hirn-PET mit „extraschnellen“ Time-of-Flight
Ganzkörper-PET/CT-Systemen und der Einsatz Künstlicher Intelligenz zur automatischen
Klassifikation der FDG-PET des Gehirns basierend auf konventionellen Kovarianzanalysen oder
Deep Learning mit künstlichen neuronalen Netzen.
Zum Abschied von Claus-Werner Wallesch und Max Schmauß als
Herausgeber der „Fortschritte der Neurologie ·
Psychiatrie“
Authors: Wallesch Claus-WWerner , Schmauß Max , Klosterkötter Joachim
Published: December 2022

Zum Jahresende 2022 treten gleich zwei langjährige Mitglieder des
Herausgebergremiums in den ehrenvollen Status eines „Editor
Emeritus“ der traditionsreichen „Fortschritte“ ein, die
schon jeder für sich, erst recht aber beide zusammen einige Worte der
besonderen Würdigung an dieser Stelle verdienen.
Trial of Labor after Three or More Previous Cesarean Sections:
Systematic Review and Meta-Analysis of Observational Studies
Authors: Fruscalzo Arrigo , Rossetti Emma , Londero Ambrogio P.
Published: December 2022

Aims To assess the success rate and prevalence of maternal or neonatal
complications in women undergoing a trial of labor after three or more
(≥3) previous cesarean sections (CSs).

Methods A systematic literature review and meta-analysis was conducted
from inception to May 2022 in Medline, Scopus, ENBASE, ClinicalTrials.gov, and
the Cochrane Central Register of Controlled Trials and Reviews. Items detailing
success rate and complications in women with a history of≥3 previous CSs
were considered. Selected articles were evaluated for quality, heterogeneity,
and publication bias. A pooled prevalence or odds ratio was calculated.

Findings Twelve articles were included for a total of 540 women with a
history of≥3 CSs, accounting for the 2% (CI 95%
1–4%) of the whole cohort of trial of labor. Our findings show a
0.67 (CI 95% 0.53–0.78) rate of successful vaginal delivery. A
higher success rate was observed in women having a history of a prior vaginal
delivery (0.90, CI 95% 0.77–0.96) and when prostaglandins,
peridural anesthesia or oxytocin were allowed (respectively 0.73, CI 95%
0.62–0.83, 0,73, CI 95% 0.57–0.85 and 0.73, CI
95% 0.64–0.81). Uterine rupture rate was 0.01 (CI 95%
0.00–0.01). No cases of fetal asphyxia or maternal or neonatal death
were registered.

Conclusions The success rate and low frequency of severe complications
observed seem to support a trial of labor in selected patients desiring a
natural birth. However, a potential underestimation of serious maternal and
neonatal complications should be considered in the decision-making process.
A Cytogenetic Study of Turkish Children with Global Developmental Delay
Authors: Demirhan Osman , Hergüner Özlem , Tunç Erdal
Published: December 2022

Global developmental delay (GDD)/intellectual disability (ID) is common in children and its etiology is unknown in many cases. Chromosomal abnormalities are predominant genetic causes of GDD/ID. The aim of this study is to determine the genetic risk factors that may be involved in the etiology of GDD/ID. In this study, 810 children with moderate to severe, clinically unexplained GDD/ID for whom cytogenetic analysis were performed were retrospectively rescreened. The results showed that GDD/ID affected more females than males (2 girls:1 boy). A total of 54 children (6.7%) with GDD showed chromosomal aberrations (CAs): 59.3% of these CAs were structural aberrations, and the rest were numerical aberrations (40.7%). Specifically, inversions, deletions, and reciprocal and robertsonian translocations, which were detected in 1, 0.7, 0.8, and 0.4% of the children, respectively, constituted important categories of structural CAs. Among numerical CAs, classic Turner and mosaics were detected in 1.2% of all children. Trisomy 21 and mosaic trisomy 21 were detected in 1% of the children. Marker chromosomes and 47,XXY karyotypes were found in two children each. Our results suggest that female sex is more affected by CAs among GDD/ID cases, and cytogenetic analysis is useful in the etiological diagnosis of GDD/ID.
Iatrogenic Withdrawal Syndrome in Critically Ill Neonates: A Review of Mechanisms, Assessment, Management, and Prevention
Authors: dos Santos Isaque Nilton , Peano Carolina Teixeira Goulart , Soares Ericks Sousa , Cimarosti Helena Iturvides
Published: December 2022

Considering that neonatal pain is a relevant matter given its implications and consequences, many neonates, particularly those undergoing critical care, are subjected to analgo-sedation therapies, which commonly includes treatment with opioids and benzodiazepines. These drugs, however, can induce tolerance and dependency, leading to the development of the so-called iatrogenic withdrawal syndrome (IWS) which is observed following discontinuation of these therapeutic agents particularly when utilized for a prolonged period of time (≥5 days). IWS consists of signs and symptoms manifested especially in young children, such as term and premature newborns in the neonatal intensive care unit, who are less capable of metabolizing and eliminating these drugs, compared with older patients. In this study, we review assessment tools that were developed to identify, evaluate, and manage children affected by IWS. The studies reviewed demonstrate that optimal management of IWS includes consideration of alternate routes of drug administration, the need for adequate time for drug tapering, and also the presence of planned rescue therapy when encountering cases refractory to ongoing management. Equally important is prevention of IWS which can be accomplished with the implementation of drug rotation protocols and, adherence to evidenced-based guidelines which facilitate an overall decline in the use and duration of opioids and benzodiazepines. Finally, our review strongly supports the need for more research on IWS in neonates given their increased susceptibility and sparse published data for this age group.
Investigation of the Antimicrobial Effect of Different Disinfectants on Alginate Measurement Materials
Authors: Güntekin Neslihan , Arslan Gökçe Kader , Özdemir Mehmet , Tunçdemir Ali Rıza
Published: December 2022

Objective The impression materials are contaminated with pathogenic microorganisms carried by saliva and blood in the mouth. The aim of this study is to evaluate the antimicrobial activity of 1 and 5.25% sodium hypochlorite (NaClO) and zeta 7 solution, a commercial disinfectant, on alginate and to compare it washing with distilled water.

Methods Samples obtained from alginate impressions taken from eight pediatric patients selected in accordance with the inclusion criteria with a size of 1 × 1 cm were subjected to five different disinfection protocols. After samples were vortexed in 3-mL physiological saline, 1-mL volume were inoculated onto brain heart infusion agar and cultured at 37°C for 72 hours to determine the number of colony-forming units/mL. Streptococcus mutans, Staphylococcus aureus, Escherichia coli, Candida albicans were used as control strains. The data obtained were statistically evaluated by using analysis of variance and post-hoc tests. The differences were considered statistically significant when p < 0.05.

Results All of the disinfectant solutions tested were effective in the disinfection of the impression materials examined. The control group with no treatment and the water and flushing group had a significantly higher bacterial load compared to the other disinfectant-treated groups in terms of bacterial load, and no significant difference has been observed between the disinfectant solutions (p < 0.05). Simple rinsing of the impressions in sterile water reduced the number of microorganisms but did not decontaminate the impressions.

Conclusion Washing with water alone is insufficient for measured disinfection. Although NaClO is an effective disinfectant even at low concentrations, microorganism growth was not observed at 5.25% concentration. It is appropriate to use NaClO at 1 and 5.25% concentrations for impression disinfection.
A simple system for measuring the transmittance curve of x-ray filters at low x-ray energies
Authors: Cao Jiewei , Chen Tianxiang , He Huilin , Xu Yupeng , Cui Xingzhu , Gao Na , Xu Xiongwei
Published: December 2022

To prevent the x-ray detectors from the interference of optical photons, x-ray filters are widely used in x-ray space missions. As the flux of low energy x-rays would be significantly attenuated by the filters, it is important to derive the transmittance of the filters below 10 keV. In this paper, we present a simple experimental apparatus and data processing method to measure the transmittance curve of x-ray filters in the energy range from 1.6 to 10 keV. The measured spectra were further processed with Geant4 Monte Carlo simulation results and a direct demodulation algorithm. The obtained transmittance is in good accordance with the theoretical calculation and the synchrotron radiation test result, which proves that the proposed system with the algorithm is a reasonable way to characterize the x-ray transmittance performance of filters above 1.6 keV.
Elastocaloric effect characterization of a NiTi tube to be applied in a compressive cooler
Authors: Cheng Siyuan , Xiao Yinan , Li Xueshi , Lin Hongyang , Hua Peng , Sheng Liyuan , Sun Qingping
Published: December 2022

In this article, the elastocaloric effect of a commercial superelastic NiTi shape memory alloy (SMA) tube (with an outer diameter of 5 mm and wall thickness of 1 mm) to be applied in a compressive cooler was measured and analyzed. The elastocaloric effect of the tube was measured vs the applied strain and strain rate. The largest temperature changes of 21 K during loading and 16 K during unloading were measured at an applied strain of 3.30% and strain rate of 0.33 s−1. In the fatigue testing of the sample, only 0.20% of the residual strain accumulated after a runout of 1 × 106 sinusoidal force-controlled loading–unloading cycles at a maximum compressive stress of 1100 MPa and frequency of 20 Hz. Numerical results of the cooling characteristics of a compressive device using a single NiTi tube with the above-mentioned cross section and an aspect ratio of 60:1 as the refrigerant showed that the device could produce a total cooling power of up to 20 W and a coefficient of performance of up to 6.5. The results of this article demonstrate that superelastic NiTi SMA tubes of suitable wall thickness and aspect ratios are good candidates to be applied in a compressive elastocaloric cooler.
Using Raman spectroscopy and x-ray diffraction for phase determination in ferroelectric mixed Hf1−xZrxO2-based layers
Authors: Schroeder Uwe , Sachdeva Ridham , Lomenzo Patrick D. , Xu Bohan , Materano Monica , Mikolajick Thomas , Kersch Alfred
Published: December 2022

The discovery of ferroelectric properties in the doped HfO2 and mixed Hf1−xZrxO2 systems made precise phase determination very important. However, due to the similarities of the diffraction peaks between the tetragonal and the orthorhombic phases, the discrimination of these two critical phases by x-ray diffraction remains challenging. This work introduces Raman spectroscopy as a structural characterization method to unambiguously identify phases by comparing experimental data with density functional simulation results for the mixed hafnia–zirconia system in the complete composition range. Raman modes for the non-polar monoclinic and tetragonal phases are presented in comparison to those of the polar orthorhombic phase. Changes in phonon mode frequencies in the hafnia–zirconia system with Hf/Zr composition are related to the appearance of ferroelectric properties.
Robust finite-time adaptive control for high performance voice coil motor-actuated fast steering mirror
Authors: Wang Lina , Wang Zhongshi , Wang Fuchao , Shi Guangfeng , Xu Rui
Published: December 2022

Fast steering mirror (FSM) is an efficient and reliable mechanical device in aerial optical image systems for controlling the beam direction with high precision. With the advantages of compact size, high speed, simple structure, and long linear stroke, voice coil motors are ideal actuators for FSM systems. However, model uncertainty can lead to poor performance or even system divergence, especially in environments with temperature variations, electromagnetic environment changes, etc. This paper proposes a novel finite-time adaptive control (FAC) algorithm for an FSM system to obtain high performance, i.e., positioning accuracy, dynamic performance, and robustness. In addition, the finite-time convergence of the controller is analyzed. In the experiments, the controller is implemented in a DSP-based microprocessor. The step response results show that the proposed algorithm has a shorter setting time, smaller overshoot, and smaller steady-state error compared to classical sliding mode control (SMC). The sinusoidal signal tracking accuracy of FAC + SMC has been improved by 19.8%. In addition, as the model uncertainty increases 10%, the root mean square errors (RMSEs) are 1.73″ and 1.18″ for SMC and FAC + SMC, respectively. With 20% model uncertainty, the RMSEs increase to 2.56″ and 1.85″, respectively. Extensive experiments demonstrate the general effectiveness of the proposed algorithm.
Resolving turbulent boundary layer on coarse grid using function enrichment based on variational reconstructions
Authors: Xu Xiaorui , Ren Yu-Xin
Published: December 2022

An improved finite volume scheme based on variational reconstruction and function enrichment has been proposed in this paper. By incorporating the law-of-the-wall into the variational reconstruction, the proposed method can resolve turbulent flow accurately on grids much coarser than those needed by traditional methods. The usual reconstruction in a finite volume scheme assumes that the solution is belonging to a polynomial function space, which is inaccurate to resolve the velocity profile within the turbulent boundary layer unless the grid in wall-normal direction is fine enough. In the present paper, this function space is “enriched” by adding a basis function that is derived from the logarithmic law of the turbulent boundary layer. Then variational reconstruction procedure is applied to find the “best” solution belonging to the expanded function space. The advantage of the present method over the traditional wall function model is that the turbulent flow within the boundary layer is resolved rather than modeled. The algorithms and the implementations are discussed in detail. The proposed method is applied to the turbulent flow over a flat plate at a Reynolds number of 5×106 and the turbulent flow over a plate with a bump at a Reynolds number of 3×106. The results of second- and third-order schemes are presented for the turbulent velocity profile and the skin friction coefficients. The numerical results suggest that this approach not only resolves the near wall turbulent accurately on very coarse grids but also reduces the computational time significantly.
Collaborative behavior of intruders moving amid grains
Authors: Carvalho Douglas D. , Franklin Erick M.
Published: December 2022

We investigate the motion of groups of intruders in a two-dimensional granular system by using discrete numerical simulations. By imposing either a constant velocity or a thrusting force on larger disks (intruders) that move within smaller ones (grains), we obtained instantaneous positions and components of forces for each intruder and grain. We found that (i) intruders cooperate even when at relatively large distances from each other; (ii) the cooperative dynamics is the result of contact chains linking the intruders as well as compaction and expansion of the granular medium in front and behind, respectively, each intruder; (iii) the collaborative behavior depends on the initial arrangement of intruders; and (iv) for some initial arrangements, the same spatial configuration is eventually reached. Finally, we show the existence of an optimal distance for minimum drag for a given set of intruders, which can prove useful for devices stirring the ground or other granular surfaces.
Effect of interfacial nitrogen defects on tunnel magnetoresistance in an Fe/MgO/Fe magnetic tunnel junction
Authors: Ogawa Yutaro , Araidai Masaaki , Endoh Tetsuo , Shiraishi Kenji
Published: December 2022

We investigated the effect of interfacial nitrogen (N) defects on tunnel magnetoresistance (TMR) in Fe/MgO/Fe magnetic tunnel junctions (MTJs) which are the basic building block of magnetoresistive random access memory. The N atoms are predicted to originate from the SiN covering for antioxidation. It was found from first-principles quantum-transport calculations that the N defects significantly worsen the TMR. This is particularly evident in the MTJ models with an additional N atom at the MgO/Fe interface, because a conduction channel appears in the antiparallel magnetization configuration due to the N defects. The TMR is directly related to the read error rate of data and the scaling of the memory cell. Therefore, the prevention of nitrogen contamination during the manufacturing processes is a prerequisite for maintaining high performance.
Simulations of electric field gradient fluctuations and dynamics around sodium ions in ionic liquids
Authors: Gimbal-Zofka Yann , Karg Beatrice , Dziubinska-Kühn Katarzyna , Kowalska Magdalena , Wesolowski Tomasz A. , Rumble Christopher A.
Published: December 2022

The T1 relaxation time measured in nuclear magnetic resonance experiments contains information about electric field gradient (EFG) fluctuations around a nucleus, but computer simulations are typically required to interpret the underlying dynamics. This study uses classical molecular dynamics (MD) simulations and quantum chemical calculations, to investigate EFG fluctuations around a Na+ ion dissolved in the ionic liquid 1-ethyl 3-methylimidazolium tetrafluoroborate, [Im21][BF4], to provide a framework for future interpretation of NMR experiments. Our calculations demonstrate that the Sternheimer approximation holds for Na+ in [Im21][BF4], and the anti-shielding coefficient is comparable to its value in water. EFG correlation functions, CEFG(t), calculated using quantum mechanical methods or from force field charges are roughly equivalent after 200 fs, supporting the use of classical MD for estimating T1 times of monatomic ions in this ionic liquid. The EFG dynamics are strongly bi-modal, with 75%–90% of the de-correlation attributable to inertial solvent motion and the remainder to a highly distributed diffusional processes. Integral relaxation times, ⟨τEFG⟩, were found to deviate from hydrodynamic predictions and were non-linearly coupled to solvent viscosity. Further investigation showed that Na+ is solvated by four tetrahedrally arranged [BF4]− anions and directly coordinated by ∼6 fluorine atoms. Exchange of [BF4]− anions is rare on the 25–50 ns timescale and suggests that motion of solvent-shell [BF4]− is the primary mechanism for the EFG fluctuations. Different couplings of [BF4]− translational and rotational diffusion to viscosity are shown to be the source of the non-hydrodynamic scaling of ⟨τEFG⟩.
Simulation and theoretical study of AlGaN-based deep-ultraviolet light-emitting diodes with a stepped electron barrier layer
Authors: Zhao Fengyi , Jia Wei , Dong Hailiang , Jia Zhigang , Li Tianbao , Yu Chunyan , Zhang Zhuxia , Xu Bingshe
Published: December 2022

Owing to the COVID-19 outbreak, sterilization of deep-ultraviolet light-emitting diodes (DUV LEDs) has attracted increasing attention. Effectively improving the radiative recombination efficiency and mitigating the efficiency degradation, mainly caused by electron leakage and nonradiative recombination, have also emerged as two of the main issues to be addressed. In this study, a DUV LED epitaxial structure with a novel electron-blocking layer (EBL) is proposed. The DUV LED with a luminescence wavelength of ∼297 nm was formed by the stepwise variation of the Al component. Through the simulation and analysis of its performance parameters, we found that, compared to the conventional EBL structure, this new EBL structure not only reduces the electron leakage to the p-region effectively but also increases the hole injection into the active region, resulting in an increase in carrier concentration in the active region, a two-to-three-fold increase in the radiative recombination rate, and a 58% increase in the internal quantum efficiency, thus alleviating the efficiency droop and achieving a more efficient operation at high current densities.
Origins of observational errors in field sweep DC measurements for unidirectional magnetoresistance
Authors: Fan Yihong , Saha Renata , Yang Yifei , Wang Jian-Ping
Published: December 2022

Understanding the mechanisms of unidirectional magnetoresistance (UMR) has become an important topic for its potential application of a two-terminal spin–orbit torque device. Field sweep DC measurements have been proposed and adopted to measure the value of UMR instead of second harmonic measurements. In this paper, potential measurement errors in conventional DC measurements are investigated. Oersted field and field-like torque usually do not influence the measurement, but a large field-like torque was found to lead to an anisotropic magnetoresistance difference when the sample is not perfectly aligned with the external field. The existence of ordinary magnetoresistance was also found to contribute to a large background. In this paper, an alternative measurement method for UMR was proposed and demonstrated to address those issues related to previous DC measurements. Our work may broaden the understanding of the error sources of UMR measurements and provide a reliable DC measurement method for the characterization of UMR.
Characterization of correlations of fast-ion H-alpha measurement volumes in Wendelstein 7-X by particle tracking
Authors: Mencke Jacob Emil , Moseev Dmitry , Salewski Mirko , Larsen Mads Rud , Schmidt Bo Simmendefeldt , Järleblad Henrik , Lazerson Samuel , Poloskei Peter Zsolt , Ford Oliver ,   Wendelstein 7-X Team
Published: December 2022

This paper characterizes the correlation of simultaneous measurements with different fast-ion H-alpha (FIDA) spectroscopy sightlines on Wendelstein 7-X. Using a collisionless guiding-center code, it is shown that, for two investigated volumes in the bulk of the plasma, some regions of phase space are correlated and the magnetic configuration has little influence on this correlation. For the sightlines of the FIDA system, the correlation between these is explained well by the magnetic configuration. Sightlines with measurement volumes at the same spatial locations have the highest correlation, and sightlines with measurement volumes near the same flux surface but on different sides of the magnetic axis have a high correlation. The correlation between the blueshifted signal in the starting sightline and redshifted signal in the detection sightline is investigated, demonstrating that it is possible to investigate any finite interval of detection wavelengths. Due to the different shapes of the weight functions for the toroidal and oblique sightlines, the blue–redshift correlation is very different from the total–spectrum correlation. The correlation between the toroidal and oblique sightline fans is relatively much larger than the internal correlation in the oblique sightlines, which is however, much larger than the internal correlation in the toroidal sightlines. This is a result of the dependence of the weight functions on the angle between the sightline and magnetic field, illustrating how important it is for the FIDA sightlines to cover different angles with the magnetic field.
Quantum dynamics reveal different ligand effects by vibrational excitation in the dissociative chemisorption of HCl on the Au/Ag(111) surface
Authors: Liu Tianhui , Shi Huixia , Fu Bina , Zhang Dong H.
Published: December 2022

The reactivity and selectivity of bimetallic surfaces are of fundamental importance in industrial applications. Here, we report the first six-dimensional (6D) quantum dynamics study for the role of surface strain and ligand effects on the reactivity of HCl on a strained pseudomorphic monolayer of Au deposited onto a Ag(111) substrate, with the aid of accurate machine learning-based potential energy surfaces. The substitute of Au into Ag changes the location of the transition state; however, the static barrier height remains roughly the same as pure Au(111). The 6D quantum dynamics calculations reveal that the surface strain due to lattice expansion slightly enhances the reactivity. The ligand effect due to electronic structure interactions between Au and Ag substantially suppresses the reactivity of HCl in the ground vibrational state but promotes the reactivity via vibrational excitation at high kinetic energies. This finding can be attributed to more close interaction with Ag atoms at the transition state close to the fcc site, as well as the tight transition-state region, making the vibrational excitation highly efficient in enhancing the reactivity. Our study quantitatively unravels the dynamical origin of reactivity control by two metals, which will ultimately provide valuable insight into the selectivity of the catalyst.
Introduction to the Materials Science of Rechargeable Batteries
Authors: Reeves-McLaren Nik
Published: December 2022

A keyword search for “lithium-ion batteries” in a leading publication search engine returns almost 12 000 unique results for the 2021 calendar year alone, with significant year-on-year growth for well over a decade. It is fair to say that there is a high likelihood the majority of those research articles, review papers, book chapters, and so on all start with a similar broad message: that since their first development over 30 years ago, lithium-ion battery (LIB) technology has enabled a revolution in societies across the world, enabling significant advances in portable electronics, electric vehicles, and many other applications. The research that led to Sony's commercialization of LIBs eventually resulted in the award of the 2019 Nobel Prize in Chemistry to the scientists who led key parts of the work: John B. Goodenough, M. Stanley Whittingham, and Akira Yoshino.
Instrument Design
Authors: Reeves-McLaren Nik
Published: December 2022

Understanding the basic principles of how x-ray and neutron diffractometers operate is essential if one is to avoid common pitfalls and collect reliable and useful data. In this chapter, the most common instrumental options are described for standard laboratory x-ray diffractometers, with additional discussion on the complementary options available at many of the synchrotron facilities around the world. Neutron diffraction is then considered as an alternative, with information on both constant wavelength and time-of-flight facilities presented. By the end of the chapter, researchers should feel well equipped to understand how to select the best setup for the experiments they need to conduct.
X-ray Absorption Spectroscopy
Authors: Reeves-McLaren Nik
Published: December 2022

X-ray absorption spectroscopic techniques have emerged over the past 50 years to offer important insights into the coordination environments, valence, and spin states in a wide variety of materials. They are particularly relevant to research on energy storage materials where even the most subtle changes in metal oxidation state and local atomic coordination can play a significant role in determining key parameters of electrochemical performance, and understanding these structure–property relationships is often critical in optimization. Drawing upon real examples from the wider literature, this chapter seeks to inform on common experimental and analytical approaches for x-ray absorption spectroscopic techniques to help new researchers understand the potential applications offered.
Operando and In Situ Electrochemical Cell Designs
Authors: Reeves-McLaren Nik
Published: December 2022

A battery might seem a relatively simple device, but it can be hard to understand what is occurring within the casing during use and relate parameters of electrochemical performance to real physical processes. In this chapter, a range of prototype and commercially relevant electrochemical cell designs are presented and discussed for in situ and operando x-ray and neutron experiments, with common adaptations outlined for windows and current collectors.
Non-Ambient Experiments for Energy Storage Materials
Authors: Reeves-McLaren Nik
Published: December 2022

This chapter focuses on non-ambient experiments, looking at what variable temperature, atmosphere and pressure experiments can tell us about energy storage materials. From tracking the progress of synthetic reactions, to looking at thermal expansion and phase transformations, high temperature experiments help to expand our understanding of structure-property relations while allowing for the use of different atmospheres to offer new routes for improved processing. This chapter also looks at how variable temperature diffraction experiments can be used to identify ionic diffusion pathways in crystalline materials, and how pressure-induced amorphization has opened a new pathway towards improved conductivity in Li4Ti5O12 spinel anodes.
Trabecular bone ontogeny tracks neural development and life history among humans and non-human primates
Authors: Saers Jaap P. P. , Gordon Adam D. , Ryan Timothy M. , Stock Jay T.
Published: December 2022

Trabecular bone—the spongy bone inside marrow cavities—adapts to its mechanical environment during growth and development. Trabecular structure can therefore be interpreted as a functional record of locomotor behavior in extinct vertebrates. In this paper, we expand upon traditional links between form and function by situating ontogenetic trajectories of trabecular bone in four primate species into the broader developmental context of neural development, locomotor control, and ultimately life history. Our aim is to show that trabecular bone structure provides insights into ontogenetic variation in locomotor loading conditions as the product of interactions between increases in body mass and neuromuscular maturation. Our results demonstrate that age-related changes in trabecular bone volume fraction (BV/TV) are strongly and linearly associated with ontogenetic changes in locomotor kinetics. Age-related variation in locomotor kinetics and BV/TV is in turn strongly associated with brain and body size growth in all species. These results imply that age-related variation in BV/TV is a strong proxy for both locomotor kinetics and neuromuscular maturation. Finally, we show that distinct changes in the slope of age-related variation in bone volume fraction correspond to the age of the onset of locomotion and the age of locomotor maturity. Our findings compliment previous studies linking bone development to locomotor mechanics by providing a fundamental link to brain development and life history. This implies that trabecular structure of fossil subadults can be a proxy for the rate of neuromuscular maturation and major life history events like locomotor onset and the achievement of adult-like locomotor repertoires.
Wide-field optical imaging of electrical charge and chemical reactions at the solid–liquid interface
Authors: Mahanta Sushanta , Vallejo-Ramirez Pedro , Karedla Narain , Puczkarski Paweł , Krishnan Madhavi
Published: December 2022

From molecules and particles to macroscopic surfaces immersed in fluids, chemical reactions often endow interfaces with electrical charge which in turn governs surface interactions and interfacial phenomena. The ability to measure the electrical properties of a material immersed in any solvent, as well as to monitor the spatial heterogeneity and temporal variation thereof, has been a long-standing challenge. Here, we describe an optical microscopy-based approach to probe the surface charge distribution of a range of materials, including inorganic oxide, polymer, and polyelectrolyte films, in contact with a fluid. The method relies on optical visualization of the electrical repulsion between diffusing charged probe molecules and the unknown surface to be characterized. Rapid image-based measurements enable us to further determine isoelectric points of the material as well as properties of its ionizable chemical groups. We further demonstrate the ability to optically monitor chemically triggered surface charge changes with millisecond time resolution. Finally, we present a scanning-surface probe technique capable of diffraction-limited imaging of spatial heterogeneities in chemical composition and charge over large areas. This technique will enable facile characterization of the solid–liquid interface with wide-ranging relevance across application areas from biology to engineering.
Topology, vorticity, and limit cycle in a stabilized Kuramoto–Sivashinsky equation
Authors: Chen Yong-Cong , Shi Chunxiao , Kosterlitz J. M. , Zhu Xiaomei , Ao Ping
Published: December 2022

A noisy stabilized Kuramoto–Sivashinsky equation is analyzed by stochastic decomposition. For values of the control parameter for which periodic stationary patterns exist, the dynamics can be decomposed into diffusive and transverse parts which act on a stochastic potential. The relative positions of stationary states in the stochastic global potential landscape can be obtained from the topology spanned by the low-lying eigenmodes which interconnect them. Numerical simulations confirm the predicted landscape. The transverse component also predicts a universal class of vortex-like circulations around fixed points. These drive nonlinear drifting and limit cycle motion of the underlying periodic structure in certain regions of parameter space. Our findings might be relevant in studies of other nonlinear systems such as deep learning neural networks.
Alanine synthesized by alanine dehydrogenase enables ammonium-tolerant nitrogen fixation in
Paenibacillus sabinae
T27
Authors: Li Qin , Zhang Haowei , Song Yi , Wang Minyang , Hua Chongchong , Li Yashi , Chen Sanfeng , Dixon Ray , Li Jilun
Published: December 2022

Most diazotrophs fix nitrogen only under nitrogen-limiting conditions, for example, in the presence of relatively low concentrations of NH
4
+
(0 to 2 mM). However,
Paenibacillus sabinae
T27 exhibits an unusual pattern of nitrogen regulation of nitrogen fixation, since although nitrogenase activities are high under nitrogen-limiting conditions (0 to 3 mM NH
4
+
) and are repressed under conditions of nitrogen sufficiency (4 to 30 mM NH
4
+
), nitrogenase activity is reestablished when very high levels of NH
4
+
(30 to 300 mM) are present in the medium. To further understand this pattern of nitrogen fixation regulation, we carried out transcriptome analyses of
P. sabinae
T27 in response to increasing ammonium concentrations. As anticipated, the
nif
genes were highly expressed, either in the absence of fixed nitrogen or in the presence of a high concentration of NH
4
+
(100 mM), but were subject to negative feedback regulation at an intermediate concentration of NH
4
+
(10 mM). Among the differentially expressed genes,
ald1
, encoding alanine dehydrogenase (ADH1), was highly expressed in the presence of a high level of NH
4
+
(100 mM). Mutation and complementation experiments revealed that
ald1
is required for nitrogen fixation at high ammonium concentrations. We demonstrate that alanine, synthesized by ADH1 from pyruvate and NH
4
+
, inhibits GS activity, leading to a low intracellular glutamine concentration that prevents feedback inhibition of GS and mimics nitrogen limitation, enabling activation of
nif
transcription by the nitrogen-responsive regulator GlnR in the presence of high levels of extracellular ammonium.