Utilization by humans of a precise and adaptable internal model of the dynamics of the body in generating movements is a well-supported concept. The prevailing opinion is that such an internal model ...ceaselessly develops through long-term repetition and accumulation in the central nervous system (CNS). However, a long-term learning process would not be absolutely necessary for the formation of internal models. It is possible to estimate the dynamics of the system by using a motor command and its resulting output, instead of constructing a model of the dynamics with precise parameters. In this study, a computational model is proposed that uses a motor command and its corresponding output to estimate the dynamics of the system and it is examined whether the proposed model is capable of describing a series of empirical movements. The proposed model was found to be capable of describing humans' fast movements which require compensation for system dynamics as well as sensory delays. In addition, the proposed model shows equifinality under inertial perturbations as seen in several experimental studies. This satisfactory reproducibility of the proposed computation raises the possibility that humans make a movement by estimating the system dynamics with a copy of motor command and sensory output on a momentary basis, without the need to identify precise system parameters.
ABSTRACT We report the discovery of a new ultra-faint Milky Way satellite candidate, Horologium II (Hor II), detected in the Dark Energy Survey Y1A1 public data. Hor II features a half-light radius ...of pc and a total luminosity of that place it in the realm of ultra-faint dwarf galaxies on the size-luminosity plane. The stellar population of the new satellite is consistent with an old (∼13.5 Gyr) and metal-poor (Fe/H ) isochrone at a distance modulus of , or a heliocentric distance of 78 8 kpc, in the color-magnitude diagram. Hor II has a distance similar to the Sculptor dwarf spheroidal galaxy (∼82 kpc) and the recently reported ultra-faint satellites Eridanus III (87 8 kpc) and Horologium I (79 8 kpc). All four satellites are well aligned on the sky, which suggests a possible common origin. As Sculptor is moving on a retrograde orbit within the Vast Polar Structure when compared to the other classical MW satellite galaxies including the Magellanic Clouds, this hypothesis can be tested once proper motion measurements become available.
We report an analytical assessment of an iron oxide (Fe2O3)/graphene (G) nanocomposite electrode used in combination with in situ plated bismuth (Bi) working as an electrochemical sensor for the ...determination of trace Zn2+, Cd2+, and Pb2+. The as-synthesized nanocomposites were characterized by transmission electron microscopy, scanning electron microscopy, thermo-gravimetric analyzer, and X-ray diffraction. The electrochemical properties of the Fe2O3/G/Bi composite modified electrode were investigated. Differential pulse anodic stripping voltammetry was applied for the detection of metal ions. Due to the synergetic effect between graphene and the Fe2O3 nanoparticles, the modified electrode showed improved electrochemical catalytic activity high sensitivity toward trace heavy metal ions. Several parameters such as the preconcentration potential, bismuth concentration, preconcentration time, and pH were carefully optimized to determine the target metal ions. Under optimized conditions, the linear range of the electrode was 1–100μgL−1 for Zn2+, Cd2+, and Pb2+, and the detection limits were 0.11μgL−1, 0.08μgL−1, and 0.07μgL−1, respectively (S/N =3). Repeatability (% RSD) was found to be 1.68% for Zn2+, 0.92% for Cd2+, and 1.69% for Pb2+ for single sensor with 10 measurements and 0.89% for Zn2+, 1.15% for Cd2+, and 0.91% for Pb2+ for 5 different electrodes. The Fe2O3/G/Bi composite electrode was successfully applied to the analysis of trace metal ions in real samples. The solventless thermal decomposition method applied to the simple and easy synthesis of nanocomposite electrode materials can be extended to the synthesis of nanocomposites and promising electrode materials for the determination of heavy metal ions.
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•Fe2O3 nanoparticle/graphene nanocomposites were synthesize by solventless method.•A modified electrode for heavy metal ions detection is constructed using Fe2O3 nanoparticle/graphene composite.•The modified electrode was used for the selective and sensitive detection of Zn2+, Cd2+, and Pb2+.•The proposed sensor was successfully applied to the analysis of trace metals in real samples
In this study, we report the determination of dopamine (DA) and acetaminophen (AC) using activated graphene-Nafion modified glassy carbon electrode (AG-NA/GCE). The AG was prepared by simple and ...facile method of thermal activation of graphene oxide (GO) with potassium hydroxide (KOH) to enhance the pore volume and specific surface area. The surface morphology and pore structure of AG were characterized by field-emission scanning electron microscope, transmission electron microscopy, Raman spectroscopy and nitrogen isothermal adsorption-desorption technique. The electrochemical characterization of AG-NA/GCE was examined with cyclic voltammetry analysis of potassium ferricyanide. The electroanalytical performance of AG-NA/GCE toward the oxidation of DA and AC was analyzed via cyclic voltammetry and differential pulse voltammetry. The result showed excellent selectivity and sensitivity toward analysis of DA and AC with low detection limit values of 0.33 and 0.031μM (S/N=3) for DA and AC, respectively. As for the examination and evaluation of electrochemical activities in real samples, the determination of DA and AC was examined with AG-NA/GCE in diluted human urine samples.
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•Activated graphene was prepared by thermal treatment of graphene mixed with KOH.•The activated graphene mixed with Nafion was used to modify the glassy carbon electrode surface.•The electrochemical determination of dopamine and acetaminophen using the modified electrode was studied.•The result showed excellent selectivity and sensitivity toward dopamine and acetaminophen with low detection limit.
Engineering cost‐effective catalysts with exceptional performance for the electrochemical oxygen evolution reaction (OER) remains crucial for the accelerated development of renewable energy ...techniques, and especially so, given the pivotal role of OER in water electrolysis. On the basis of the metal nodes (clusters) and organic linkers, metal‐organic frameworks (MOFs) and their derivatives are rapidly gaining ground in the fabrication of electrocatalysts, with promising catalytic activity and sound durability in OER, thanks to their controllable pore structures, abundant unsaturated active sites of metal ion, extensive specific surface area, as well as easily functionalized/modified surfaces. This review presents an in‐depth understanding of the established progress of MOFs‐derived materials for OER electrocatalysis. The material designing strategies of the pristine, monometallic, and multimetallic MOFs‐based catalysts are summarized to indicate the infinite possibilities of the morphology and the composition of MOF‐derived materials. While emphasis is laid on the essential features of MOF‐derived materials for the electrocatalysis of the corresponding reactions, insights about the applications in OER are discussed. Finally, this paper is concluded by presenting challenges and perspectives for MOF‐derived materials’ future applications in OER electrocatalysis.
This review presents an in‐depth understanding of the established progress of metal‐organic framework (MOFs)‐derived materials for oxygen evolution reaction (OER) electrocatalysis. The material designing strategies of the pristine, monometallic, and multimetallic MOFs‐based catalysts are summarized to indicate the infinite possibilities of the morphology and the composition of MOF‐derived materials.
Highlights
This study reviews metal‐organic frameworks (MOFs)‐derived novel nanostructured electrocatalysts for oxygen evolution reaction (OER), including the designing and synthesizing strategies of the pristine, monometallic, and multimetallic MOFs‐based catalysts. Moreover, the morphology, composition, and essential features of MOF‐derived materials for the electrocatalysis are discussed. Finally, several perspectives for the challenges and future application of MOF‐derived materials in OER electrocatalysis are presented.
Though both contraction of agonist muscles and co-contraction of antagonistic muscle pairs across the ankle joint are essential to postural stability, they are perceived to operate independently of ...each other, In an antagonistic setup, agonist muscles contract generating moment about the joint, while antagonist muscles contract generating stiffness across the joint. While both work together in maintaining robustness in the face of external perturbations, contractions of agonist muscles and co-contractions of antagonistic muscle pairs across the ankle joint play different roles in responding to and adapting to external perturbations. To determine their respective roles, we exposed participants to repeated perturbations in both large and small magnitudes. The center of pressure (COP) and a co-contraction index (CCI) were used to quantify the activation of agonist muscles and antagonistic muscle pairs across the ankle joint. Our results found that participants generated moment of a large magnitude across the ankle joint-a large deviation in the COP curve-in response to perturbations of a large magnitude (p <0.05), whereas the same participants generated higher stiffness about the ankle-a larger value in CCI-in response to perturbations of a small magnitude (p <0.05). These results indicate that participants use different postural strategies pertaining to circumstances. Further, the moment across the ankle decreased with repetitions of the same perturbation (p <0.05), and CCI tended to remain unchanged even in response to a different perturbation following repetition of the same perturbation (p <0.05). These findings suggest that ankle muscle contraction and co-contraction play different roles in regaining and maintaining postural stability. This study demonstrates that ankle moment and stiffness are not correlated in response to external perturbations.
Abstract
We present chemical abundance measurements for seven stars with metallicities ranging from Fe/H = −3.3 to Fe/H = −2.4 in the Tucana II ultra-faint dwarf galaxy (UFD), based on ...high-resolution spectra obtained with the MIKE spectrograph on the 6.5 m Magellan-Clay Telescope. For three stars, we present detailed chemical abundances for the first time. Of those, two stars are newly discovered members of Tucana II and were selected as probable members from deep narrowband photometry of the Tucana II UFD taken with the SkyMapper telescope. This result demonstrates the potential for photometrically identifying members of dwarf galaxy systems based on chemical composition. One new star was selected from the membership catalog of Walker et al. The other four stars in our sample have been reanalyzed, following additional observations. Overall, six stars have chemical abundances that are characteristic of the UFD stellar population. The seventh star shows chemical abundances that are discrepant from the other Tucana II members and an atypical, higher strontium abundance than what is expected for typical UFD stars. While unlikely, its strontium abundance raises the possibility that it may be a foreground metal-poor halo star with the same systemic velocity as Tucana II. If we were to exclude this star, Tucana II would satisfy the criteria to be a surviving first galaxy. Otherwise, this star implies that Tucana II has likely experienced somewhat extended chemical evolution.
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•Activated carbon was prepared with a novel two-step activation process.•Kelp is used as source material for the biomass-derived activated carbon.•The modified electrode was used for ...the electrochemical determination of acetaminophen.•High sensitivity toward acetaminophen and a low detection limit were achieved.
The determination of the concentration of acetaminophen (AC) in the human body is of significant importance to carefully monitor and regular drug safety and public health. However, most conventional methods are insufficient due to their time-consuming, expensive and complicated nature. In this study, we report a novel two-step activation of biomass-derived carbon for the electrochemical determination of AC. The electrode material is prepared by a two-step activation process, which involves the initial activation of kelp powder with ZnCl2, followed by an activation step with KOH. The activation procedure greatly increased the overall pore volume and specific surface area. The characterizations of ZnCl2-KOH activated kelp carbon (ZKAKC) were conducted with scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Brunauer-Emmett-Teller (BET) surface area analysis, and electrochemical impedance spectroscopy (EIS). The electrochemical characterization of ZKAKC was performed with cyclic voltammetry (CV) analysis of potassium ferricyanide. The sensing ability of ZKAKC/GCE toward acetaminophen was conducted using CV analysis and differential pulse voltammetry (DPV). The modified electrode showed high sensitivity, selectivity and a good detection limit for the determination acetaminophen with the detection limit of 0.004 μM. Also, the modified electrode showed good result toward acetaminophen even in the presence of ascorbic acid and dopamine with the detection limit of 0.007 μM. For the evaluation of sensing ability as an actual electrochemical sensor, a real sample test was conducted. The electrochemical performance was enhanced due to the increased physical and electrochemical surface area, which occurred during the two-step activation process. This approach for producing activated carbon is crucial for future development and can be applied to different carbon source materials.
In this study, we consider an online monitoring procedure to detect a parameter change for integer-valued generalized autoregressive heteroscedastic (INGARCH) models whose conditional density of ...present observations over past information follows one parameter exponential family distributions. For this purpose, we use the cumulative sum (CUSUM) of score functions deduced from the objective functions, constructed for the minimum power divergence estimator (MDPDE) that includes the maximum likelihood estimator (MLE), to diminish the influence of outliers. It is well-known that compared to the MLE, the MDPDE is robust against outliers with little loss of efficiency. This robustness property is properly inherited by the proposed monitoring procedure. A simulation study and real data analysis are conducted to affirm the validity of our method.
Steel double-beam floor systems reinforced with concrete panels can improve the structural and environmental performance of buildings by reducing moment demands and embodied CO2 emissions. However, ...for steel double-beam floor systems, a time-consuming iterative analysis is required to derive an optimal design proposal owing to the rotational constraints in the composite joints between the concrete panel and steel beams. In this study, a non-iterative optimal design method using the LM index is proposed to minimize the embodied CO2 emissions of steel double-beam floor systems. The LM index is a measure that can be used to select the optimal cross-section of the steel beams considering the decreased moment capacity according to the unbraced length. The structural feasibility of the proposed design method was verified by investigating whether safety-related constraints were satisfied by the LM index with respect to the design variables under various gravity loads. The applicability of the proposed optimal design method is verified by comparing the embodied CO2 emissions derived from the proposed and code-based design methods. Applicable design conditions were presented based on the LM index to aid engineers. The proposed design method can provide environmentally-optimized design proposals to ensure structural safety by directly selecting the LM index of steel beams.
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