Muons are particles with a spin of ½ that can be implanted into a wide range of condensed matter materials to act as a local probe of the surrounding atomic environment. Measurement of the muon’s precession and relaxation provides an insight into how it interacts with its local environment. From this, unique information is obtained about the static and dynamic properties of the material of interest. This has enabled muon spin spectroscopy, more commonly known as muon spin rotation/relaxation/resonance (μSR), to develop into a powerful tool to investigate material properties such as fundamental magnetism, superconductivity and functional materials. Alongside this, μSR may be used to study, for example, energy storage materials, ionic diffusion in potential batteries, the dynamics of soft matter, free radical chemistry, reaction kinetics, semiconductors, advanced manufacturing and cultural artefacts. This Primer is intended as an introductory article and introduces the μSR technique, the typical results obtained and some recent advances across various fields. Data reproducibility and limitations are also discussed, before highlighting promising future developments. Muon spin spectroscopy examines how muons interact with their local environment through measurement of the muon’s precession and relaxation. This provides unique information about the static and dynamic properties of a material. This Primer gives an introductory overview to muon spin spectroscopy, describing how muons are produced and used experimentally in various applications.
The ⁵⁷Fe Mössbauer spectrum obtained after ⁵⁷Mn (T1/2 = 1.45 min) implantation of solid hydrogen was measured at 7 K. The spectrum was analyzed as three components, and the chemical species of each component was assigned from the obtained Mössbauer parameters and the results of density functional theory (DFT) calculations. The formation process of chemical species and the oxidation states of Fe atoms produced by β– decay of ⁵⁷Mn are discussed considering the charge transfer process, in relation to previous emission Mössbauer spectroscopy experiments with ⁵⁷Co implantation of solid hydrogen at low temperature.
We demonstrate a measurement system for synchrotron-radiation-based Mössbauer absorption spectra with ¹⁶¹Dy using the 25.7 keV nuclear first excited state. Mössbauer spectra of DyF3, Dy metal and DyPc2 (Pc = phthalocyaninato) were obtained and the parameters for the hyperfine structure of ¹⁶¹Dy nuclei in them were evaluated to demonstrate the feasibility of this method. Isomer shifts showed that Dy atoms in all of them are in trivalent state although those in Dy metal was in the region of trivalent metal region. The magnetic hyperfine field of Dy metal of 569 ± 1 T agreed with the literature of the Mössbauer experiments. That of DyPc2 of 489 ± 1 T was reasonable because the ground state of DyPc2 were in the state of Jz = ±13/2. Considering the highly penetrative nature of the 25.7 keV incident radiation, it will be straightforward to apply this method for the study of materials under various conditions such as high pressure, high magnetic fields, and reactive atmospheres.
The quantum Cramér–Rao bound sets a fundamental limit on the accuracy of unbiased parameter estimation in quantum systems, relating the uncertainty in determining a parameter to the inverse of the quantum Fisher information. We experimentally demonstrate near saturation of the quantum Cramér–Rao bound in the phase estimation of a solid-state spin system, provided by a nitrogen-vacancy center in diamond. This is achieved by comparing the experimental uncertainty in phase estimation with an independent measurement of the related quantum Fisher information. The latter is independently extracted from coherent dynamical responses of the system under weak parametric modulations, without performing any quantum-state tomography. While optimal parameter estimation has already been observed for quantum devices involving a limited number of degrees of freedom, our method offers a versatile and powerful experimental tool to explore the Cramér–Rao bound and the quantum Fisher information in systems of higher complexity, as relevant for quantum technologies.
Purpose ²¹¹ At, a promising alpha-particle-emitting radionuclide, can easily volatilize and contaminate the environment. To safely manage this unique alpha-particle-emitting radionuclide, we investigated the permeability of four types of plastic films and two types of rubber gloves against ²¹¹ At and identified suitable materials that prevent contamination by ²¹¹ At. Methods Four types of plastic films, polyethylene, polyvinylidene chloride, polyvinyl chloride, and a laminated film, and two types of rubber gloves, latex and nitrile, were examined. Small pieces of filter paper were covered with these materials, and a drop containing 100 kBq of ²¹¹ At was placed on them. The radioactivity of the pieces of filter paper under the materials was evaluated by measuring counts using a gamma counter and obtaining autoradiograms 3.5 h later. These experiments were also performed using ²²⁵ Ac, ¹²⁵ I, ¹¹¹ In, ²⁰¹ Tl, and 99m Tc. Results ²¹¹ At solution easily penetrated polyethylene, polyvinyl chloride, and latex rubber. Similar results were obtained for ¹²⁵ I, while other radionuclides did not penetrate films or gloves. These results suggest that halogenic radionuclides under anionic conditions are likely to penetrate plastic films and rubber gloves. Conclusion Our evaluation revealed that, when ²¹¹ At solution is used, the protection by polyvinylidene chloride, a laminated film, or nitrile rubber would be more effective than that by polyethylene, polyvinyl chloride, or latex rubber.
Previous psychological studies have shown that people detect emotional facial expressions more rapidly and accurately than neutral facial expressions. However, the cognitive mechanisms underlying the efficient detection of emotional facial expressions remain unclear. To investigate this issue, we used diffusion model analyses to estimate the cognitive parameters of a visual search task in which participants detected faces with normal expressions of anger and happiness and their anti-expressions within a crowd of neutral faces. The anti-expressions were artificially created to control the visual changes of facial features but were usually recognized as emotionally neutral. We tested the hypothesis that the emotional significance of the target’s facial expressions modulated the non-decisional time and the drift rate. We also conducted an exploratory investigation of the effect of facial expressions on threshold separation. The results showed that the non-decisional time was shorter, and the drift rate was larger for targets with normal expressions than with anti-expressions. Subjective emotional arousal ratings of facial targets were negatively related to the non-decisional time and positively associated with the drift rate. In addition, the threshold separation was larger for normal expressions than for anti-expressions and positively associated with arousal ratings for facial targets. These results suggest that the efficient detection of emotional facial expressions is accomplished via the faster and more cautious accumulation of emotional information of facial expressions which is initiated more rapidly by enhanced attentional allocation.
Single-cell RNA sequencing (scRNA-seq) can determine gene expression in numerous individual cells simultaneously, promoting progress in the biomedical sciences. However, scRNA-seq data are high-dimensional with substantial technical noise, including dropouts. During analysis of scRNA-seq data, such noise engenders a statistical problem known as the curse of dimensionality (COD). Based on high-dimensional statistics, we herein formulate a noise reduction method, RECODE (resolution of the curse of dimensionality), for high-dimensional data with random sampling noise. We show that RECODE consistently resolves COD in relevant scRNA-seq data with unique molecular identifiers. RECODE does not involve dimension reduction and recovers expression values for all genes, including lowly expressed genes, realizing precise delineation of cell fate transitions and identification of rare cells with all gene information. Compared with representative imputation methods, RECODE employs different principles and exhibits superior overall performance in cell-clustering, expression value recovery, and single-cell–level analysis. The RECODE algorithm is parameter-free, data-driven, deterministic, and high-speed, and its applicability can be predicted based on the variance normalization performance. We propose RECODE as a powerful strategy for preprocessing noisy high-dimensional data.
Rechargeable all-solid-state Li batteries with solid electrolytes (SE) are a prospective solution for safe and high-capacity energy storage systems. In recent decades, several types of SE with high ionic conductivity have been developed and tested with different techniques. In this study, we employed a non-destructive nuclear analytical method, Neutron Depth Profiling (NDP), to investigate the response of one of the promising electrolytes, Lithium Conductive Glass Ceramic (LICGC), to the applied voltage +2.8 V. The in-situ NDP measurements made it possible to directly monitor the migration of lithium ions in the electrolyte and to observe and quantify the formation of a space charge layer with depleted Li atoms, which depends on the biasing time.
Cavity magnonics deals with the interaction of magnons — elementary excitations in magnetic materials — and confined electromagnetic fields. We introduce the basic physics and review the experimental and theoretical progress of this young field that is gearing up for integration in future quantum technologies. Much of its appeal is derived from the strong magnon–photon coupling and the easily-reached nonlinear regime in microwave cavities. The interaction of magnons with light as detected by Brillouin light scattering is enhanced in magnetic optical resonators, which can be employed to cool and heat magnons. The microwave cavity photon-mediated coupling of a magnon mode to a superconducting qubit enables measurements in the single magnon limit.
During the AD 68/9 Civil Wars, Galba, Otho, Vitellius and then Vespasian fought for — and gained — control of the Roman Empire. Our textual sources suggest that this was a period of serious and sustained disruption. However, existing analyses of gold coinages produced in AD 68/9 show only a minor reduction in the purity of the gold coinage. Using X-ray fluorescence, we identify a number of heavily debased gold coins issued during the AD 68/9 Civil Wars, and many slightly debased coins issued in their immediate aftermath. We then confirm the interior composition of these coins totally non-destructively using muonic X-ray emission spectroscopy, thus eliminating hypothetical problems of ‘surface enrichment’ or compositional differences between ‘surface’ and ‘core’. Here we show that heavily debased Civil War gold coinages were indeed produced; that copper was used to debase Roman gold coins during this time, c. 185 years earlier than first shown; and that slightly debased gold coins were regularly issued in the years immediately after the Civil Wars. The metallurgical evidence from the gold coinage now allows us to show that the AD 68/9 Civil Wars caused significant and sustained disruption to the Roman economic system. More broadly, we have shown that muonic X-ray emission spectroscopy is a powerful tool for generating important archaeological conclusions from high-value cultural heritage objects that simply cannot be destructively analysed, but need to have their interior compositions sampled.
Aquaculture in coastal environments has an increasingly important role in the world’s food supply; however, the accumulation of organic compounds on seafloors due to overfeeding adversely affects benthic ecosystems. To assess the ecological resilience of aquafarms to nutrient influx, we investigated the redox homeostasis of benthic ecosystems using a marine oligochaete as a model benthic organism in aquaculture fields. Real-time monitoring of the redox potential of a model benthic ecosystem constructed in an electrochemical reactor allowed evaluation of the homeostatic response of the system to nutrient addition. Although the detrimental effects of overfeeding were confirmed by irreversible potential changes in the sediment, redox homeostasis was reinforced through a cooperative relationship between oligochaetes and sediment microorganisms. Specifically, the oligochaetes exhibited reversible changes in metabolism and body position in response to dynamic changes in the sediment potential between −300 and 500 mV, thereby promoting the decomposition of organic compounds. The potential-dependent changes in metabolism and body position were reproduced by artificially manipulating the sediment potential in electrochemical reactors. Given the importance of benthic animals in sustaining coastal ecosystems, the electrochemical monitoring and physiologic regulation of marine oligochaetes could offer an intriguing approach toward sustainable aquaculture.
We measured single crystal elasticity of Ta under high pressures up to 54 GPa at room temperature using inelastic x-ray scattering at room temperature. Simultaneously, we measured the density of Ta using x-ray diffraction. Combining the bulk modulus and density, we obtain an equation of state of Ta as a primary scale. The Vinet equation was fitted to the pressure–volume data and we found consistency with previous work including experimental static and shock compressions and theoretical calculation. We proposed a parameter set for the Vinet equation [ K 0 = 191.1(3) GPa, K′ 0 = 4.006(2)] which is consistent with the pressure based on extrapolated velocities within 2% up to ∼80 GPa. Furthermore, we found the present scale to be consistent with a recent ruby scale (Ruby2020) up to ∼50 GPa.
The coronavirus membrane protein (M) is the most abundant viral structural protein and plays a central role in virus assembly and morphogenesis. However, the process of M protein-driven virus assembly are largely unknown. Here, we report the cryo-electron microscopy structure of the SARS-CoV-2 M protein in two different conformations. M protein forms a mushroom-shaped dimer, composed of two transmembrane domain-swapped three-helix bundles and two intravirion domains. M protein further assembles into higher-order oligomers. A highly conserved hinge region is key for conformational changes. The M protein dimer is unexpectedly similar to SARS-CoV-2 ORF3a, a viral ion channel. Moreover, the interaction analyses of M protein with nucleocapsid protein (N) and RNA suggest that the M protein mediates the concerted recruitment of these components through the positively charged intravirion domain. Our data shed light on the M protein-driven virus assembly mechanism and provide a structural basis for therapeutic intervention targeting M protein. M protein plays essential roles in virus assembly and morphogenesis. Here, authors reveal two cryo-EM structures of M protein from SARS-CoV-2 that suggest conformational dynamics of M protein and its role in virus assembly.
Plant cells exhibit remarkable plasticity of their differentiation states, enabling regeneration of whole plants from differentiated somatic cells. How they revert cell fate and express pluripotency, however, remains unclear. In this study we demonstrate that transcriptional activation of auxin biosynthesis is crucial for reprogramming differentiated Arabidopsis (Arabidopsis thaliana) leaf cells. Our data show that interfering with the activity of histone acetyltransferases dramatically reduces callus formation from leaf mesophyll protoplasts. Histone acetylation permits transcriptional activation of PLETHORAs (PLTs), leading to the induction of their downstream YUCCA1 (YUC1) gene encoding an enzyme for auxin biosynthesis. Auxin biosynthesis is in turn required to accomplish initial cell division through the activation of G2/M phase genes mediated by MYB DOMAIN PROTEIN 3-RELATED (MYB3Rs). We further show that the AUXIN RESPONSE FACTOR 7 (ARF7)/ARF19 and INDOLE-3-ACETIC ACID INDUCIBLE 3 (IAA3)/IAA18-mediated auxin signaling pathway is responsible for cell cycle reactivation by transcriptionally upregulating MYB3R4. These findings provide a mechanistic model of how differentiated plant cells revert their fate and reinitiate the cell cycle to become pluripotent.
Aim: Mutations in the SARS-CoV-2 spike (S) protein have dramatically changed the transmissibility and pathogenicity of the virus. Therefore, we studied the binding affinity of Omicron spike-receptor binding domain (S-RBD) with human ACE2 receptor. Materials & methods: We used pyDockWEB and HADDOCK 2.4 docking for our study. Results: Computational docking indicated higher binding affinity of Omicron S-RBD as compared with wild-type SARS-CoV-2 and Delta S-RBD with ACE2. Interface analysis suggested four mutated residues of Omicron S-RBD for its enhanced binding. We also showed decreased binding affinity of Omicron and Delta S-RBDs with monoclonal antibodies. Conclusion: Compared with wild-type SARS-CoV-2, Omicron S-RBD exhibit higher binding with ACE2 and lower affinity against monoclonal antibodies.
Development of speech rate is often reported as children exhibiting reduced speech rates until they reach adolescence. Previous studies have investigated the developmental process of speech rate using global measures (syllables per second, syllables per minute, or words per minute) and revealed that development continues up to around 13 years of age in several languages. However, the global measures fail to capture language-specific characteristics of phonological/prosodic structure within a word. The current study attempted to examine the developmental process of speech rate and language-specific rhythm in an elicited production task. We recorded the speech of Japanese-speaking monolingual participants (18 participants each in child [5-, 7-, 9-, 11-, and 13-year-old] and adult groups), who pronounced three types of target words: two-mora, two-syllable words (CV.CV); three-mora, two-syllable words (CVV.CV); and three-mora, three-syllable words (CV.CV.CV), where C is consonant and V is vowel. We analyzed total word duration and differences in two pairs of word types: a pair of three-mora words (to show the effect of syllables) and a pair of two-syllable words (to show the effect of moras). The results revealed that Japanese-speaking children have acquired adult-like word duration before 11 years of age, whereas the development of rhythmical timing control continues until approximately 13 years of age. The results also suggest that the effect of syllables for Japanese-speaking children aged 9 years or under was stronger than that of moras, whereas the effect of moras was stronger after 9 years of age, indicating that the default unit for children in speech rhythm may be the syllable even when the language is mora-based.
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