General Experimental Method Research Articles

Initialization-free multistate memristor: Synergy of spin–orbit torque and magnetic fields

Spin–orbit torque (SOT)-based perpendicularly magnetized memory devices with multistate memory have garnered significant interest due to their applicability in low-power in-memory analog computing. However, current methods are hindered by initialization problems, such as prolonged writing duration, and limitations, on the number of magnetic states. Consequently, a universal method for achieving multistate in perpendicular magnetic anisotropy (PMA)-based stacks remains elusive. Here, we propose a general experimental method for achieving multistate without any initialization step in SOT-driven magnetization switching by integrating an external out-of-plane magnetic field. Motivated by macrospin calculations coupled with micromagnetic simulations, which demonstrate the plausibility of magnetization state changes due to out-of-plane field integration, we experimentally verify multistate behavior in Pt/Co/Pt and W/Pt/Co/AlOx stacks. The occurrence of multistate behavior is attributed to intermediate domain states with Néel domain walls. We achieve repeatable 18 multistate configurations with a minimal reduction in retentivity through energy barrier measurements, paving the way for efficient analog computing.

Mapping electronic decoherence pathways in molecules.

Establishing the fundamental chemical principles that govern molecular electronic quantum decoherence has remained an outstanding challenge. Fundamental questions such as how solvent and intramolecular vibrations or chemical functionalization contribute to the decoherence remain unanswered and are beyond the reach of state-of-the-art theoretical and experimental approaches. Here we address this challenge by developing a strategy to isolate electronic decoherence pathways for molecular chromophores immersed in condensed phase environments that enables elucidating how electronic quantum coherence is lost. For this, we first identify resonance Raman spectroscopy as a general experimental method to reconstruct molecular spectral densities with full chemical complexity at room temperature, in solvent, and for fluorescent and non-fluorescent molecules. We then show how to quantitatively capture the decoherence dynamics from the spectral density and identify decoherence pathways by decomposing the overall coherence loss into contributions due to individual molecular vibrations and solvent modes. We illustrate the utility of the strategy by analyzing the electronic decoherence pathways of the DNA base thymine in water. Its electronic coherences decay in [Formula: see text]30 fs. The early-time decoherence is determined by intramolecular vibrations while the overall decay by solvent. Chemical substitution of thymine modulates the decoherence with hydrogen-bond interactions of the thymine ring with water leading to the fastest decoherence. Increasing temperature leads to faster decoherence as it enhances the importance of solvent contributions but leaves the early-time decoherence dynamics intact. The developed strategy opens key opportunities to establish the connection between molecular structure and quantum decoherence as needed to develop chemical strategies to rationally modulate it.

Design and Testing of an Elastic Comb Reciprocating a Soybean Plant-to-Plant Seedling Avoidance and Weeding Device

Although there are existing interplant weed control devices for soybeans, they mostly rely on image recognition and intelligent navigation platforms. Simultaneously, automated weed control devices are not yet fully mature, resulting in issues such as high seedling injury rates and low weeding rates. This paper proposed a reciprocating interplant weed control device for soybeans based on the idea of intermittent reciprocating opening and closing of weeding execution components. The device consists of a laser ranging sensor, servo motor, Programmable Logic Controller (PLC), and weeding mechanism. Firstly, this paper explained the overall structure and working principle of the weed control device, and discussed the theoretical analysis and structural design of the critical component, elastic comb teeth. This paper also analyzed the working principle of the elastic comb teeth movement trajectory and seedling avoidance action according to soybean agronomic planting requirements. Then, field experiments were conducted, and the experiment was designed by the quadratic regression general rotation combination experimental method. The number of combs, the speed of the field management robot, and the stabbing depth were taken as the test factors to investigate their effects on the test indexes of weeding rate and seedling injury rate. The experiment utilized a response surface analysis method and designed a three-factor, three-level quadratic regression general rotation combination experimental method. The results demonstrate that the number of comb teeth has the most significant impact on the weeding rate, while the forward speed has the most significant impact on the seedling injury rate. The optimal combination of 29.06 mm stabbing depth, five comb teeth, and a forward speed of 0.31 m/s achieves an optimal operational weeding rate of 98.2% and a seedling injury rate of 1.69%. Under the optimal parameter combination conditions, the machine’s performance can meet the requirements of intra-row weeding operations in soybean fields, and the research results can provide a reference for the design and optimization of mechanical weed control devices for soybean fields.

A kinetic-free approach to the sensitivity analysis of axial flow continuous reactors: A general experimental method

The intensification of fast and exothermic reaction processes is an important development trend of the chemical industry, because of productivity, safety and product quality reasons. Whenever the reaction can be performed in tubular rather than in stirred tank reactors, a number of additional advantages can be achieved, in terms of a higher conversion as well as of an improved heat transfer efficiency per unit volume. In these cases, however, the reactor must be designed and operated so as to prevent its pseudo-adiabatic behavior, which makes the system sensitive to even normal fluctuations of the process variables as well as to the design parameters, with unpredictable effects on the process performances. In this work a general experimental procedure is presented, through which the sensitive behavior of a tubular reactor can be detected through local temperature and flowrate measurements, even in the absence of a detailed kinetic characterization of the system. The developed approach has a higher responsiveness compared with the existing criteria and can be easily adopted for finetuning the operating conditions of a running reactor as well as for the design of a new one. The proposed method has been validated through experimental data, both in the non-sensitive and sensitive regimes, of a well-known catalytic process of the chemical industry.

Customizing twisted Schell-model beams.

Since the celebrated twist phase was proposed by Simon and Mukunda, despite the tremendous progress made in theory over the past decades, developing a simple and flexible experimental method to customize this novel phase has long been a tricky challenge. In this Letter, we demonstrate a general experimental method for generating twisted Schell-model beams by implementing the continuous coherent beam integral function in a discrete form. Experimental results based on rigorous Laguerre-Gauss modes superposition are also demonstrated, indicating that our method is more convenient and of higher quality. The twist factor is also measured using the rotation characteristics during propagation, and the results agree well with the theoretical prediction. The method could serve as a general way for customizing bona fide twisted cross-spectral densities while facilitating certain applications.

Effects and interactions of the agricultural waste residues and binder type on physical properties and calorific values of carbonized briquettes

Multiple factors are responsible for the properties of developed briquettes. The effect of the agricultural residue type in determining resulting properties of developed briquettes is seldom elucidated. Agricultural residue biochars from groundnut shells, sugarcane bagasse, coffee husks, and rice husks were used in developing carbonized briquettes using the low-cost compression method. In this study, a general factorial multi-level categorical experimental design method was used to investigate the effects and interactions of the carbonized agricultural type, binder type, and binder amount on physical properties and calorific values of developed briquettes. Statistically significant models (p < 0.05) were obtained for physical property responses of fixed carbon, ash content, volatile matter, and moisture content as well as calorific values for the developed briquettes. In experiments where only cassava starch binder (30 g and 50 g) was used, carbonized agricultural residues played a significant role in the resulting physical property. Increasing the cassava starch binder from 30 to 50 g had a minimal impact on the resulting briquette physical property. In experiments where cassava starch binder and wheat starch binder were used, it was clear that the physical property of the developed briquette was affected significantly by the carbonized agricultural residue used and binder type. Calorific values of groundnut shell and bagasse briquettes were observed to be significantly affected by the agricultural residue type. The highest calorific values of 23.9 MJ/kg and 23.3 MJ/kg were obtained for groundnut shell and bagasse biochar briquettes, respectively, when only 30 g of cassava starch binder was used. Changes in cassava and wheat starch binder amounts did not significantly affect heating values of developed groundnut shell and bagasse briquettes.

General Experimental Method of Research of Anisotropy of Conductive Materials

The paper devotes a new general experimental method for studying the anisotropy of conducting materials of various functional purposes. The difference between the presented method and the previously known one is in the high rate of anisotropy assessment, ensuring the possibility of anisotropy assessment of the properties of materials by the volume of the sample or product under investigation during their manufacture or operation. The procedure for measuring the anisotropy of electrophysical properties and the results of the study of some samples are presented.

Thermal Expansion Coefficient of Monolayer Molybdenum Disulfide Using Micro-Raman Spectroscopy

Atomically thin two-dimensional (2D) materials have shown great potential for applications in nanoscale electronic and optical devices. A fundamental property of these 2D flakes that needs to be well-characterized is the thermal expansion coefficient (TEC), which is instrumental to the dry transfer process and thermal management of 2D material-based devices. However, most of the current studies of 2D materials' TEC extensively rely on simulations due to the difficulty of performing experimental measurements on an atomically thin, micron-sized, and optically transparent 2D flake. In this work, we present a three-substrate approach to characterize the TEC of monolayer molybdenum disulfide (MoS2) using micro-Raman spectroscopy. The temperature dependence of the Raman peak shift was characterized with three different substrate conditions, from which the in-plane TEC of monolayer MoS2 was extracted on the basis of lattice symmetries. Independently from two different phonon modes of MoS2, we measured the in-plane TECs as (7.6 ± 0.9) × 10-6 K-1 and (7.4± 0.5) × 10-6 K-1, respectively, which are in good agreement with previously reported values based on first-principle calculations. Our work is not only useful for thermal mismatch reduction during material transfer or device operation but also provides a general experimental method that does not rely on simulations to study key properties of 2D materials.

Experimental Analysis of Subscribers’ Privacy Exposure by LTE Paging

Over the last years, considerable attention has been given to the privacy of individuals in wireless environments. Although significantly improved over the previous generations of mobile networks, LTE still exposes vulnerabilities that attackers can exploit. This might be the case of paging messages, wake-up notifications that target specific subscribers, and that are broadcasted in clear over the radio interface. If they are not properly implemented, paging messages can expose the identity of subscribers and furthermore provide information about their location. It is therefore important that mobile network operators comply with the recommendations and implement the appropriate mechanisms to mitigate attacks. In this paper, we verify by experiment that paging messages can be captured and decoded by using minimal technical skills and publicly available tools. Moreover, we present a general experimental method to test privacy exposure by LTE paging messages, and we conduct a case study on three different LTE mobile operators.

Determination of the stiffness matrix of flat springs for modeling of the boundary condition at a pipeline support

Abstract Elastic mounting elements are often used in mechanical systems for reduction of undesired loads. In many engineering applications one-dimensional (1D) approximation of absorber reaction is an acceptable approach however in general, a six order stiffness matrix of an elastic element should be known. This can also be the case of water hammer with fluid-structure interaction in a pipeline fixed with elastic supports. For the standard model of this phenomenon the general boundary condition (BC) at the support should take into account all degrees of freedom of the pipe element. In this paper various methods of flexibility matrix determination of actual, self manufactured flat springs (FS) used as supports at a laboratory pipeline are discussed. Analytical calculations are based on modeling of elastic strain energy of a bar under external loads and formulas being developed for the FS flexibility coefficients are presented. Experimental verification of selected coefficients was performed and the results were consistent with theoretical findings. A general experimental method and a data processing scheme based on linear least squares (LS) method is also proposed and shortly discussed. Numerical investigations are based on FEM modeling of the FS structure and computations of their load-displacement characteristics with the ANSYS software. Flexibility matrix was determined with that same LS data processing scheme. Analytical, experimental and numerical results are compared and discussed. For non-singular flexibility matrix the stiffness matrix used in the BC can be easily determined as its reverse. Otherwise, for a singular case, a special treatment is required. A solution to this problem is developed and presented in the paper. It has been evidenced that singularity results in dimension reduction of the BC.

Backbone NMR reveals allosteric signal transduction networks in the β1-adrenergic receptor

G protein-coupled receptors (GPCRs) are physiologically important transmembrane signalling proteins that trigger intracellular responses upon binding of extracellular ligands. Despite recent breakthroughs in GPCR crystallography, the details of ligand-induced signal transduction are not well understood owing to missing dynamical information. In principle, such information can be provided by NMR, but so far only limited data of functional relevance on few side-chain sites of eukaryotic GPCRs have been obtained. Here we show that receptor motions can be followed at virtually any backbone site in a thermostabilized mutant of the turkey β1-adrenergic receptor (β1AR). Labelling with [(15)N]valine in a eukaryotic expression system provides over twenty resolved resonances that report on structure and dynamics in six ligand complexes and the apo form. The response to the various ligands is heterogeneous in the vicinity of the binding pocket, but gets transformed into a homogeneous readout at the intracellular side of helix 5 (TM5), which correlates linearly with ligand efficacy for the G protein pathway. The effect of several pertinent, thermostabilizing point mutations was assessed by reverting them to the native sequence. Whereas the response to ligands remains largely unchanged, binding of the G protein mimetic nanobody NB80 and G protein activation are only observed when two conserved tyrosines (Y227 and Y343) are restored. Binding of NB80 leads to very strong spectral changes throughout the receptor, including the extracellular ligand entrance pocket. This indicates that even the fully thermostabilized receptor undergoes activating motions in TM5, but that the fully active state is only reached in presence of Y227 and Y343 by stabilization with a G protein-like partner. The combined analysis of chemical shift changes from the point mutations and ligand responses identifies crucial connections in the allosteric activation pathway, and presents a general experimental method to delineate signal transmission networks at high resolution in GPCRs.

ChemInform Abstract: X‐Ray Crystallography in Open‐Framework Materials

AbstractReview: [32 refs.

X-ray Crystallography in Open-Framework Materials.

Open-framework materials, such as metal-organic frameworks (MOFs) and coordination polymers have been widely investigated for their gas adsorption and separation properties. However, recent studies have demonstrated that their highly crystalline structures can be used to periodically organize guest molecules and non-structural metal compounds either within their pore voids or by anchoring to their framework architecture. Accordingly, the open framework can act as a matrix for isolating and elucidating the structures of these moieties by X-ray diffraction. This concept has broad scope for development as an analytical tool where obtaining single crystals of a target molecule presents a significant challenge and it additionally offers potential for obtaining insights into chemically reactive species that can be stabilized within the pore network. However, the technique does have limitations and as yet a general experimental method has not been realized. Herein we focus on recent examples in which framework materials have been utilized as a scaffold for ordering molecules for analysis by diffraction methods and canvass areas for future exploration.

Method for estimating ionicities of oxides using O1s photoelectron spectra

The average valence, ValO, of the oxygen anions in the perovskite oxide BaTiO3, was found using O1s photoelectron spectra to be −1.55. This experimental result is close to the theoretical value for BaTiO3 (−1.63) calculated by Cohen [Nature 358, 136 (1992)] using density functional theory. Using the same approach, we obtained values of ValO for several monoxides, and investigated the dependence of ValO and the ionicity on the second ionization energy, V(M2+), of the metal cation. We found that the dependence of the ionicity on V(M2+) in this work is close to that reported by Phillips [Rev. Mod. Phys. 42, 317 (1970)]. We therefore suggest that O1s photoelectron spectrum measurements should be accepted as a general experimental method for estimating the ionicity and average valence of oxygen anions.

The general experimental method in investigation of the spatial inhomogeneity of radiofrequency electromagnetic fields

The general experimental method in investigation of the spatial inhomogeneity of radiofrequency electromagnetic fields

The Energy of Charge‐Transfer States in Electron Donor–Acceptor Blends: Insight into the Energy Losses in Organic Solar Cells

AbstractHere, a general experimental method to determine the energy ECT of intermolecular charge‐transfer (CT) states in electron donor–acceptor (D–A) blends from ground state absorption and electrochemical measurements is proposed. This CT energy is calibrated against the photon energy of maximum CT luminescence from selected D–A blends to correct for a constant Coulombic term. It is shown that ECT correlates linearly with the open‐circuit voltage (Voc) of photovoltaic devices in D–A blends via eVoc = ECT − 0.5 eV. Using the CT energy, it is found that photoinduced electron transfer (PET) from the lowest singlet excited state (S1 with energy Eg) in the blend to the CT state (S1 → CT) occurs when Eg − ECT &gt; 0.1 eV. Additionally, it is shown that subsequent charge recombination from the CT state to the lowest triplet excited state (ET) of D or A (CT → T1) can occur when ECT − ET &gt; 0.1 eV. From these relations, it is concluded that in D–A blends optimized for photovoltaic action: i) the maximum attainable Voc is ultimately set by the optical band gap (eVoc = Eg − 0.6 eV) and ii) the singlet–triplet energy gap should be ΔEST &lt; 0.2 eV to prevent recombination to the triplet state. These favorable conditions have not yet been met in conjugated materials and set the stage for further developments in this area.

Rapid assessment of anisotropic surface processes: experiments on the corrosion of Inconel 600

We present a general experimental method for rapid characterization of surface processes on crystals of many orientations. By correlating maps of crystallographic orientation (obtained by electron backscatter diffraction methods) with those of surface topography (obtained by atomic force microscopy), we illustrate how a surface property can be elucidated on many off-principle crystal surfaces from a single polycrystalline specimen. For the corrosion of Inconel 600 in a dilute aqueous solution of HCl, we find that corrosion rates scale with the deviation angle of the surface normal from an ideal 〈1 1 1〉 direction. The use of atomic force microscopy can also provide mechanistic details about the surface process in question. For Inconel 600, we correlate the surface oxide morphology directly to the orientation of the underlying crystal.

Experimental constructions of self-dual codes

We give a general experimental method generalizing the codes of Carlach and Vervoux (Proceedings of the 13th Applicable Algebra in Engineering Communication and Computing (AAECC 13), Hawaii, USA, 14–19 November 1999, p. 15) to construct self-dual codes. We consider the particular fields GF(2), GF(3), GF(4) (both Euclidean and Hermitian cases), GF(5) and GF(7). We give numerical tables of the best known self-dual codes over these alphabets up to lengths where minimum distances are computable. These tables regularly fill gaps between known codes with good parameters such as the quadratic residue codes, the Pless symmetry codes (J. Combin. Theory Ser. A A12 (1972) 119) or the quadratic double circulant codes (J. Combin. Theory Ser. A 97 (2002) 85). Many new codes with better parameters are constructed: in particular the first extremal ternary self-dual [52,26,15] and [78,39,18] codes and the first binary self-dual [114,57,18] and [116,58,18] codes are constructed. We also give the minimum weight of the Pless symmetry codes of length 84. We also update tables for quadratic residue codes over GF(4), GF(5) and GF(7) and we obtain in particular a [62,31,20] code over GF(5).

Van't Hoff-Le Bel Stranger: Formation of a Phosphonium Cation with a Planar Tetracoordinate Phosphorus Atom

A novel intriguing type of coordination mode in phosphorus chemistry has been established that is of fundamental interest in the understanding of chemical bonding. Besides the synthesis of the first planar phosphonium cation PR(4)(+) 1 by a surprisingly simple metathesis reaction, a potentially general experimental method that reaches the seemingly impossible high-energy region of basic molecular and isoelectronic ER(4) systems (E=B(-), C, N(+), Al(-), Si, P(+)) is provided.

Van't Hoff–Le Bel Stranger: Formation of a Phosphonium Cation with a Planar Tetracoordinate Phosphorus Atom

A novel intriguing type of coordination mode in phosphorus chemistry has been established that is of fundamental interest in the understanding of chemical bonding. Besides the synthesis of the first planar phosphonium cation PR4+ 1 by a surprisingly simple metathesis reaction, a potentially general experimental method that reaches the seemingly impossible high-energy region of basic molecular and isoelectronic ER4 systems (E=B−, C, N+, Al−, Si, P+) is provided.