Electric field-induced magnetochiral dichroism in a ferroaxial crystal.

In a chiral medium, any mirror symmetries are broken, which induces unique physical properties represented by natural optical rotation. When electromagnetic waves propagate through a chiral medium placed in a magnetic field, the refractive index, or equivalently, the absorption encountered by the electromagnetic waves differs depending on whether it travels parallel or antiparallel to the magnetic field. Such a phenomenon is known as magnetochiral dichroism (MChD), which is the characteristic interplay between chirality and magnetism. Similar to chirality, the so-called ferroaxial order, an emergent ferroic state of crystalline materials, is also characterized by mirror symmetry breaking. In contrast to chiral materials, however, the mirror symmetry perpendicular to the crystalline principal axis is allowed in ferroaxial materials. In other words, chirality and thus phenomena unique to chirality can be induced by breaking the remaining mirror symmetry by applying an electric field. Here, we show electric control of chirality and resulting electric field-induced MChD (E-MChD) of the short-wavelength infrared region in a ferroaxial crystal, NiTiO3. We performed spectroscopy measurements of E-MChD by taking a difference of absorption coefficients obtained with and without electric and magnetic fields. As a result, E-MChD was observed around the excitation energy corresponding to Ni2+ d-d magnetic-dipole transitions. The result is nicely explained by adopting the theory of MChD concerning the pseudo-Stark splitting of the energy state. Ferroaxial materials therefore provide platforms to achieve electric control of chirality-related phenomena.

Nonvolatile Switching of Large Nonreciprocal Optical Absorption at Shortwave Infrared Wavelengths.

We report large nonreciprocal optical absorption at shortwave infrared (SWIR) wavelengths in the magnetoelectric (ME) antiferromagnet (AFM) LiNiPO_{4}. The difference in absorption coefficients for light propagating in opposite directions, divided by the sum, reaches up to ∼40% at 1450 nm. Moreover, the nonreciprocity is switched by a magnetic field in a nonvolatile manner. Using symmetry considerations, we reveal that the large nonreciprocal absorption is attributed to Ni^{2+} d-d transitions through the spin-orbit coupling. Furthermore, we propose that an even larger nonreciprocity can be achieved for a Ni-based ME AFM where electric dipoles of every NiO_{6} unit and Ni^{2+} spins are orthogonal and, respectively, form a collinear arrangement. This study provides a pathway toward nonvolatile switchable one-way transparency of SWIR light.

Imaging and Control of Magnetic Domains in a Quasi-One-Dimensional Quantum Antiferromagnet BaCu_{2}Si_{2}O_{7}.

We visualize antiferromagnetic domains in a representative quasi-one-dimensional S=1/2 quantum antiferromagnet, BaCu_{2}Si_{2}O_{7}, using nonreciprocal directional dichroism, which differentiates the optical absorption of a pair of antiferromagnetic domains. Opposite antiferromagnetic domains, each about submillimeter in size, are found to coexist in a single-crystal specimen, and the domain walls run predominantly along the spin chains. We also demonstrate that the domain walls can be moved by an applied electric field through a magnetoelectric coupling and that the direction of the domain walls is maintained during the motion. We explain the domain wall anisotropy by the quasi-one-dimensional nature of the exchange interactions. This Letter will contribute to the understanding of the domain physics of quasi-one-dimensional quantum antiferromagnets.

Revisiting the Transtheoretical Model for Physical Activity: A Large-Scale Cross-Sectional Study on Japanese-Speaking Adults.

BACKGROUND: The Transtheoretical Model (TTM) has been the basis of health promotion programs, which are, for example, used to tailor behavioral interventions according to the stages of change. Empirical studies have shown that the TTM effectively describes the processes of behavioral adaptation to acquire healthier lifestyles; however, it has been argued that TTM-based interventions are not superior to non-TTM-based interventions for promoting physical activity (PA). Evidence has also highlighted some inconsistencies with theoretical assumptions, especially regarding how each process-of-change strategy emerges across the stages. PURPOSE: Therefore, we investigated (a) how well the TTM describes the distributional characteristics of PA levels as well as other relevant variables (e.g., process of change, self-efficacy) across stages, and (b) how predictive the TTM variables are of PA levels within each stage. METHODS: We analyzed data from 20,573 Japanese-speaking adults who completed online questionnaires on PA and TTM variables. RESULTS: The results replicated previous findings that stage membership is associated with PA, the process of change, decisional balance, and self-efficacy, albeit with inconclusive evidence of temptations. Regression analyses revealed that some processes of change (self-reevaluation, reinforcement management, and self-liberation) were more predictive of PA in pre-active stages than in post-action stages; self-efficacy was predictive of PA only in the maintenance stage but not in the other stages. CONCLUSIONS: Overall, the data support the theoretical assumptions of the TTM, but the stage specificity of the active processes may not always be consistent with the theory.

The Transtheoretical Model has been the basis of many behavioral interventions for promoting physical activity. One of the key concepts of the model is the stage of change, which is a framework to help understand the readiness to begin physical activity and exercise. The model assumes five progressive stages of behavior change (e.g., the precontemplation stage, where people have no intention to change behavior; the maintenance stage, where people have continued physical activity for a long enough period), through which individuals acquire an active lifestyle. The model also assumes that different strategies for behavior change are appropriate at different stages and, confidence and attitudes toward physical activity vary dynamically across stages. The current study examined how valid these theoretical assumptions using data from 20,573 Japanese-speaking adults. The data overall supported the assumptions of the Transtheoretical Model, for example, highlighting the importance of enhancing awareness about the causes and (dis)advantages of being (in)active at earlier stages. Although some inconsistencies were identified (some strategies were not as useful as the model assumed), these findings may suggest that the Transtheoretical Model holds universal theoretical value as a descriptive model of behavioral change for active lifestyle across Western and East Asian populations.

Detecting Magnetoelectric Effect in a Metallic Antiferromagnet via Nonreciprocal Rotation of Reflected Light.

Certain types of media breaking both space-inversion (P) and time-reversal (T) symmetries but preserving their combination PT exhibit the polarization rotation of reflected light even when that of transmitted light is prohibited. Such an effect is termed nonreciprocal rotation of reflected light (NRR). Although NRR shows nearly the same phenomenon as the magnetooptical Kerr effect or, equivalently, the Hall effect at optical frequencies, its origin is distinct and ascribed to a magnetoelectric (ME) effect at optical frequencies, i.e., the optical ME effect. Here we show the observation of NRR in a metallic antiferromagnet TbB_{4}. The result demonstrates that the ME effect in a metallic system, which is considered to be ill defined, can be detected using reflected light. Furthermore, we spatially resolve antiferromagnetic domains in TbB_{4} by microscope observations of NRR. Our work offers a unique way to probe the ME effect in metallic systems.

Substrate complex structure, active site labeling and catalytic role of the zinc ion in cysteine glycosidase.

ß-l-Arabinofuranosidase HypBA1 from Bifidobacterium longum belongs to the glycoside hydrolase family 127. At the active site of HypBA1, a cysteine residue (Cys417) coordinates with a Zn2+ atom and functions as the catalytic nucleophile for the anomer-retaining hydrolytic reaction. In this study, the role of Zn2+ ion and cysteine in catalysis as well as the substrate-bound structure were studied based on biochemical and crystallographic approaches. The enzymatic activity of HypBA1 decreased after dialysis in the presence of EDTA and guanidine hydrochloride and was then recovered by the addition of Zn2+. The Michaelis complex structure was determined using a crystal of a mutant at the acid/base catalyst residue (E322Q) soaked in a solution containing the substrate p-nitrophenyl-ß-l-arabinofuranoside. To investigate the covalent thioglycosyl enzyme intermediate structure, synthetic inhibitors of l-arabinofuranosyl haloacetamide derivatives with different anomer configurations were used to target the nucleophilic cysteine. In the crystal structure of HypBA1, ß-configured l-arabinofuranosylamide formed a covalent link with Cys417, whereas α-configured l-arabinofuranosylamide was linked to a noncatalytic residue Cys415. Mass spectrometric analysis indicated that Cys415 was also reactive with the probe molecule. With the ß-configured inhibitor, the arabinofuranoside moiety was correctly positioned at the subsite and the active site integrity was retained to successfully mimic the covalent intermediate state.

Mechanism-based inhibition of GH127/146 cysteine glycosidases by stereospecifically functionalized l-arabinofuranosides.

To understand the precise mechanism of the glycoside hydrolase (GH) family 127, a cysteine ß-l-arabinofuranosidase (Arafase) - HypBA1 - has been isolated from Bifidobacterium longum in the human Gut microbiota, and the design and synthesis of the mechanism-based inhibitors such as l-Araf-haloacetamides have been carried out. The α-l-Araf-azide derivative was used as the monoglycosylamine equivalent to afford the l-Araf-chloroacetamides (α/ß-1-Cl) as well as bromoacetamides (α/ß-1-Br) in highly stereoselective manner through Staudinger reaction followed by amide formation with/without anomerization. Against HypBA1, the probes 1, especially in the case of α/ß-1-Br inhibited the hydrolysis. Conformational implications of these observations are discussed in this manuscript. Additional examinations using l-Araf-azides (α/ß-5) resulted in further mechanistic observations of the GH127/146 cysteine glycosidases, including the hydrolysis of ß-5 as the substrate and oxidative inhibition by α-5 using the GH127 homologue.

Observation of Ferrochiral Transition Induced by an Antiferroaxial Ordering of Antipolar Structural Units in Ba(TiO)Cu4(PO4)4.

Ferrochiral transition, i.e., a transition involving an emergence of chirality, provides an unique opportunity to achieve a nonvolatile reversible control of chirality with external fields. However, materials showing pure ferrochiral transitions, which are accompanied by no other types of ferroic transition, are exceedingly rare. In this study, we propose that a pure ferrochiral transition is achieved by a combination of antipolar and antiferroaxial orderings of structural units, and substantiate this proposal through a study of the chiral compound Ba(TiO)Cu4(PO4)4. Single crystal X-ray diffraction measurements have revealed that this material undergoes a second order ferrochiral transition whose order parameter is described by an antiferroaxial (staggered) rotation of antipolar structural units, thus demonstrating our proposal. Furthermore, by measuring spatial distributions of optical rotation, we successfully visualized a temperature evolution of ferrochiral domains across the transition temperature and demonstrated the relationship between chirality and optical rotation. This work provides a guide to find a pure ferrochiral transition, thus providing an opportunity to achieve a ferroic control of chirality.

Broad spectral tuning of ultra-low-loss polaritons in a van der Waals crystal by intercalation.

Phonon polaritons-light coupled to lattice vibrations-in polar van der Waals crystals are promising candidates for controlling the flow of energy on the nanoscale due to their strong field confinement, anisotropic propagation and ultra-long lifetime in the picosecond range1-5. However, the lack of tunability of their narrow and material-specific spectral range-the Reststrahlen band-severely limits their technological implementation. Here, we demonstrate that intercalation of Na atoms in the van der Waals semiconductor α-V2O5 enables a broad spectral shift of Reststrahlen bands, and that the phonon polaritons excited show ultra-low losses (lifetime of 4 ± 1 ps), similar to phonon polaritons in a non-intercalated crystal (lifetime of 6 ± 1 ps). We expect our intercalation method to be applicable to other van der Waals crystals, opening the door for the use of phonon polaritons in broad spectral bands in the mid-infrared domain.

Coexistence of Magnetoelectric and Antiferroelectric-like Orders in Mn3Ta2O8.

In materials showing a linear magnetoelectric (ME) effect, unconventional functionalities can be anticipated such as electric control of magnetism and nonreciprocal optical responses. Thus, the search for new linear ME materials is of interest in materials science. Here, using a recently proposed design principle of linear ME materials, which is based on the combination of local structural asymmetry and collinear antiferromagnetism, we demonstrate that an anion-deficient fluorite derivative, Mn3Ta2O8, is a new linear ME material. This is evidenced by the onset of magnetic-field-induced electric polarization in its collinear antiferromagnetic phase below TN = 24 K. Furthermore, we also find an antiferroelectric-like phase transition at TS = 55 K, which is attributable to an off-center displacement of magnetic Mn2+ ions. The present study shows that Mn3Ta2O8 is a rare material that exhibits both ME and antiferroelectric-like transitions. Thus, Mn3Ta2O8 may provide an opportunity to investigate the physics associated with complicated interactions between magnetic (spin) and electric dipole degrees of freedom.

Synthesis, Structure, and Anomalous Magnetic Ordering of the Spin-1/2 Coupled Square Tetramer System K(NbO)Cu4(PO4)4.

Quasi-zero-dimensional antiferromagnets with weakly coupled clusters of multiple spins can provide an excellent platform for exploring exotic quantum states of matter. Here, we report the synthesis and the characterization of a copper-based insulating antiferromagnet, K(NbO)Cu4(PO4)4. Single-crystal X-ray diffraction measurements reveal that the crystal structure belongs to the tetragonal space group P4/nmm, in which Cu2+ ions align to form a quasi-two-dimensional layer of spin-1/2 coupled square tetramers. The structure is quasi-isostructural to recently reported magnetoelectric antiferromagnets, A(TiO)Cu4(PO4)4 (A = Ba, Sr, and Pb) with the P4212 space group. Despite their structural similarities, whereas the antiferromagnetic transition in A(TiO)Cu4(PO4)4 produces conventional anomalies in magnetization and heat capacity, that in K(NbO)Cu4(PO4)4 has several unusual features such as an upturn in magnetic susceptibility and a very weak specific heat anomaly that corresponds to a spin entropy release as small as 3%. These results indicate that the magnetism of K(NbO)Cu4(PO4)4 is far different from that of A(TiO)Cu4(PO4)4 and suggest that the ground state is very close to a quantum nonmagnetic singlet state. The origin of the distinct magnetism in K(NbO)Cu4(PO4)4 is discussed in terms of structural modifications of a Cu4O12 unit forming a square tetramer. Our study demonstrates that the present material family, represented by an extended chemical formula A(BO)Cu4(PO4)4 (AB = KNb, BaTi, SrTi, and PbTi), has broad chemical controllability of their magnetism. This makes this system an attractive material platform to study the physics of quantum spin-1/2 coupled square tetramers.

Imbalance Between Salivary Cortisol and DHEA Responses Is Associated with Social Cost and Self-perception to Social Evaluative Threat in Japanese Healthy Young Adults.

BACKGROUND: Social evaluative threat activates the HPA-axis system, namely cortisol and dehydroepiandrosterone (DHEA) responses. Additionally, cognitive and behavioral models in social anxiety, which is aroused anxiety symptoms in social situations, indicate that negative cognitions have a role in the maintenance of symptoms. Thus, the present study examined the relationship between HPA-axis activity and cognitive features in social situations. METHOD: We conducted the Trier Social Stress Test (TSST) with 44 male participants and assessed HPA-axis responses, fear of negative evaluation, the estimated social cost, and self-perceptions of their speech performance, which are core negative cognitions in social situations. RESULTS: Results revealed that the cortisol-DHEA ratio significantly correlated with self-perceptions of participants' speech performance (r = .30, p = .044) and the discrepancy between self-ratings and others' ratings of the speech (r = .44, p = .003). After controlling for depressive symptoms, significant correlations remained (r = .39, p = .01 and r = .50, p = .001, respectively). In addition, the estimated social cost, assessed before the speech task, significantly correlated with both the AUCg cortisol (r = .38, p = .011) and cortisol-DHEA ratios (r = .40, p = .007). CONCLUSION: These results suggest that estimating social costs in social situations, as well as distorted self-perceptions of that stressor, is related to dysfunctional endocrine regulation.

Absence of Jahn-Teller transition in the hexagonal Ba3CuSb2O9 single crystal.

With decreasing temperature, liquids generally freeze into a solid state, losing entropy in the process. However, exceptions to this trend exist, such as quantum liquids, which may remain unfrozen down to absolute zero owing to strong quantum entanglement effects that stabilize a disordered state with zero entropy. Examples of such liquids include Bose-Einstein condensation of cold atoms, superconductivity, quantum Hall state of electron systems, and quantum spin liquid state in the frustrated magnets. Moreover, recent studies have clarified the possibility of another exotic quantum liquid state based on the spin-orbital entanglement in FeSc2S4. To confirm this exotic ground state, experiments based on single-crystalline samples are essential. However, no such single-crystal study has been reported to date. Here, we report, to our knowledge, the first single-crystal study on the spin-orbital liquid candidate, 6H-Ba3CuSb2O9, and we have confirmed the absence of an orbital frozen state. In strongly correlated electron systems, orbital ordering usually appears at high temperatures in a process accompanied by a lattice deformation, called a static Jahn-Teller distortion. By combining synchrotron X-ray diffraction, electron spin resonance, Raman spectroscopy, and ultrasound measurements, we find that the static Jahn-Teller distortion is absent in the present material, which indicates that orbital ordering is suppressed down to the lowest temperatures measured. We discuss how such an unusual feature is realized with the help of spin degree of freedom, leading to a spin-orbital entangled quantum liquid state.

Magnetoelectric Behavior from S=1/2 Asymmetric Square Cupolas.

Magnetoelectric properties are studied by a combined experimental and theoretical study of a quasi-two-dimensional material composed of square cupolas, Ba(TiO)Cu_{4}(PO_{4})_{4}. The magnetization is measured up to the field above the saturation, and several anomalies are observed depending on the field directions. We propose a S=1/2 spin model with Dzyaloshinskii-Moriya interactions, which reproduces the full magnetization curves well. Elaborating the phase diagram of the model, we show that the anomalies are explained by magnetoelectric phase transitions. Our theory also accounts for the scaling of the dielectric anomaly observed in the experiments. The results elucidate the crucial role of the in-plane component of Dzyaloshinskii-Moriya interactions, which is induced by the noncoplanar buckling of a square cupola. We also predict a "hidden" phase and another magnetoelectric response, both of which appear in a nonzero magnetic field.

A(2+) Cation Control of Chiral Domain Formation in A(TiO)Cu4(PO4)4 (A = Ba, Sr).

Single crystals of two novel tetragonal chiral materials, A(TiO)Cu4(PO4)4 (A = Ba, Sr), were grown from Na2Mo2O7 flux, and their crystal and chiral domain structures were characterized. Polarized-light microscopy studies of the chiral domain structures in the crystals show that Ba(TiO)Cu4(PO4)4 mostly hosts a multidomain state, while a monodomain state predominantly appears in Sr(TiO)Cu4(PO4)4. To explain this striking difference, we quantified the chirality strength of these materials by comparing atomic positions in the chiral and nearest-achiral crystal structures, revealing larger chirality strength in Sr(TiO)Cu4(PO4)4 than in Ba(TiO)Cu4(PO4)4. Our proposed mechanisms linking the chirality strength and domain formation can account for the different occurrence frequency of chiral domains in this system.

Exploring individual, social and environmental factors related to physical activity: a network analysis.

Objectives: Insufficient physical activity (PA) has long been a global health issue, and a number of studies have explored correlates of PA to identify the mechanisms underlying inactive lifestyles. In the literature, dozens of correlates have been identified at different (eg, individual, environmental) levels, but there is little or no direct evidence for the mutual associations of these correlates. This study analysed 44 variables identified as theoretically and empirically relevant for PA to clarify the factors directly and indirectly associated with PA. Methods: A cross-sectional survey dataset of 19 005 Japanese-speaking adults (mean age=53.50 years, SD=17.40; 9706 women) was analysed. The data encompassed demographic and anthropometric variables; self-reported PA levels; perceived social support and environments (eg, awareness of urban facilities for PA); psychological traits and health-behaviour characteristics (eg, personality, motivation, self-efficacy, decisional balance, process of change strategies); and technology use (eg, mobile health apps). Results: Network analyses were performed to select meaningful associations (partial correlations) among variables, which identified nine variables directly positively associated with PA: job/employment status, self-efficacy, perceived social support, intrinsic motivation, stage of change, counter conditioning, self-reevaluation, environment and technology use. Indirect associations (two-step neighbourhood) were identified for 40 (out of 44) variables, implying that most of the known PA-correlates are associated with PA-at least indirectly. Conclusion: These identified associations echo the importance of the multilevel perspective in understanding how people maintain (in)active lifestyles. Interventions for PA could have mixed-level targets, including intraindividual characteristics, social support and physical and digital environments.

Deconstructing Fitbit to Specify the Effective Features in Promoting Physical Activity Among Inactive Adults: Pilot Randomized Controlled Trial.

BACKGROUND: Wearable activity trackers have become key players in mobile health practice as they offer various behavior change techniques (BCTs) to help improve physical activity (PA). Typically, multiple BCTs are implemented simultaneously in a device, making it difficult to identify which BCTs specifically improve PA. OBJECTIVE: We investigated the effects of BCTs implemented on a smartwatch, the Fitbit, to determine how each technique promoted PA. METHODS: This study was a single-blind, pilot randomized controlled trial, in which 70 adults (n=44, 63% women; mean age 40.5, SD 12.56 years; closed user group) were allocated to 1 of 3 BCT conditions: self-monitoring (feedback on participants' own steps), goal setting (providing daily step goals), and social comparison (displaying daily steps achieved by peers). Each intervention lasted for 4 weeks (fully automated), during which participants wore a Fitbit and responded to day-to-day questionnaires regarding motivation. At pre- and postintervention time points (in-person sessions), levels and readiness for PA as well as different aspects of motivation were assessed. RESULTS: Participants showed excellent adherence (mean valid-wear time of Fitbit=26.43/28 days, 94%), and no dropout was recorded. No significant changes were found in self-reported total PA (dz<0.28, P=.40 for the self-monitoring group, P=.58 for the goal setting group, and P=.19 for the social comparison group). Fitbit-assessed step count during the intervention period was slightly higher in the goal setting and social comparison groups than in the self-monitoring group, although the effects did not reach statistical significance (P=.052 and P=.06). However, more than half (27/46, 59%) of the participants in the precontemplation stage reported progress to a higher stage across the 3 conditions. Additionally, significant increases were detected for several aspects of motivation (ie, integrated and external regulation), and significant group differences were identified for the day-to-day changes in external regulation; that is, the self-monitoring group showed a significantly larger increase in the sense of pressure and tension (as part of external regulation) than the goal setting group (P=.04). CONCLUSIONS: Fitbit-implemented BCTs promote readiness and motivation for PA, although their effects on PA levels are marginal. The BCT-specific effects were unclear, but preliminary evidence showed that self-monitoring alone may be perceived demanding. Combining self-monitoring with another BCT (or goal setting, at least) may be important for enhancing continuous engagement in PA. TRIAL REGISTRATION: Open Science Framework; https://osf.io/87qnb/?view_only=f7b72d48bb5044eca4b8ce729f6b403b.

Release of arsenic from soil by a novel dissimilatory arsenate-reducing bacterium, Anaeromyxobacter sp. strain PSR-1.

A novel arsenate-reducing bacterium, designated strain PSR-1, was isolated from arsenic-contaminated soil. Strain PSR-1 was phylogenetically closely related to Anaeromyxobacter dehalogenans 2CP-1(T) with 16S rRNA gene similarity of 99.7% and coupled the oxidation of acetate with the reduction of arsenate. Arsenate reduction was inhibited almost completely by respiratory inhibitors such as dicumarol and 2-heptyl-4-hydroxyquinoline N-oxide. Strain PSR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, oxygen, and fumarate as electron acceptors. Strain PSR-1 catalyzed the release of arsenic from arsenate-adsorbed ferrihydrite. In addition, inoculation of washed cells of strain PSR-1 into sterilized soil successfully reproduced arsenic release. Arsenic K-edge X-ray absorption near-edge structure (XANES) analysis revealed that the proportion of arsenite in the soil solid phase actually increased from 20% to 50% during incubation with washed cells of strain PSR-1. These results suggest that strain PSR-1 is capable of reducing not only dissolved arsenate but also arsenate adsorbed on the soil mineral phase. Arsenate reduction by strain PSR-1 expands the metabolic versatility of Anaeromyxobacter dehalogenans. Considering its distribution throughout diverse soils and anoxic sediments, Anaeromyxobacter dehalogenans may play a role in arsenic release from these environments.

Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1.

Dissimilatory As(V) (arsenate)-reducing bacteria may play an important role in arsenic release from anoxic sediments in the form of As(III) (arsenite). Although respiratory arsenate reductase genes (arrA) closely related to Geobacter species have been frequently detected in arsenic-rich sediments, it is still unclear whether they directly participate in arsenic release, mainly due to lack of pure cultures capable of arsenate reduction. In this study, we isolated a novel dissimilatory arsenate-reducing bacterium, strain OR-1, from Japanese paddy soil, and found that it was phylogenetically closely related to Geobacter pelophilus. OR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, and fumarate as electron acceptors. OR-1 catalyzed dissolution of arsenic from arsenate-adsorbed ferrihydrite, while Geobacter metallireducens GS-15 did not. Furthermore, inoculation of washed cells of OR-1 into sterilized paddy soil successfully restored arsenic release. Arsenic K-edge X-ray absorption near-edge structure analysis revealed that strain OR-1 reduced arsenate directly on the soil solid phase. Analysis of putative ArrA sequences from paddy soils suggested that Geobacter-related bacteria, including those closely related to OR-1, play an important role in arsenic release from paddy soils. Our results provide direct evidence for arsenic dissolution by Geobacter species and support the hypothesis that Geobacter species play a significant role in reduction and mobilization of arsenic in flooded soils and anoxic sediments.

Cardiac cycle affects risky decision-making.

This study investigates whether decision-making under uncertainty is influenced by the cardiac cycle. To test this hypothesis, we examined the influence of the cardiac cycle on an individual's decision-making process in a gambling experiment. Participants were asked to choose one option with a sure payout or uncertain option with varying degrees of winning probability, ambiguity, and monetary amounts. The onset of presentation of the options is timed to coincide with either cardiac ventricular systole or diastole. The results show that, for most participants, the risk aversion score was lower in the systole trial than in the diastole trial. Model-based exploratory analysis revealed that the higher propensity to take risks in the systole trial compared with that in the diastole trial could be captured better by the change in the gambling bias against the utility of the risky options, rather than by a change in risk attitude. The results provide evidence that the natural fluctuation of cardiac afferent signals can affect risky decision-making.