Day-to-day regularity and diurnal switching of physical activity reduce depression-related behaviors: a time-series analysis of wearable device data

BACKGROUND

Wearable devices have been widely used in research to understand the relationship between habitual physical activity and mental health in the real world. However, little attention has been paid to the temporal variability in continuous physical activity patterns measured by these devices. Therefore, we analyzed time-series patterns of physical activity intensity measured by a wearable device and investigated the relationship between its model parameters and depression-related behaviors.

METHODS

Sixty-six individuals used the wearable device for one week and then answered a questionnaire on depression-related behaviors. A seasonal autoregressive integral moving average (SARIMA) model was fitted to the individual-level device data and the best individual model parameters were estimated via a grid search.

RESULTS

Out of 64 hyper-parameter combinations, 21 models were selected as optimal, and the models with a larger number of affiliations were found to have no seasonal autoregressive parameter. Conversely, about half of the optimal models indicated that physical activity on any given day fluctuated due to the previous day's activity. In addition, both irregular rhythms in day-to-day activity and low-level of diurnal variability could lead to avoidant behavior patterns.

CONCLUSION

Automatic and objective physical activity data from wearable devices showed that diurnal switching of physical activity, as well as day-to-day regularity rhythms, reduced depression-related behaviors. These time-series parameters may be useful for detecting behavioral issues that lie outside individuals' subjective awareness.

Real-Space Observation of Emergent Complexity of Phase Evolution in Micrometer-Sized IrTe_{2} Crystals

We report complex behaviors in the phase evolution of transition-metal dichalcogenide IrTe_{2} thin flakes, captured with real-space observations using scanning Raman microscopy. The phase transition progresses via growth of a small number of domains, which is unlikely in statistical models that assume a macroscopic number of nucleation events. Consequently, the degree of phase evolution in the thin flakes is quite variable for the selected specimen and for a repeated measurement sequence, representing the emergence of complexity in the phase evolution. In the ∼20-μm^{3}-volume specimen, the complex phase evolution results in the emergent coexistence of a superconducting phase that originally requires chemical doping to become thermodynamically stable. These findings indicate that the complexity involved in phase evolution considerably affects the physical properties of a small-sized specimen.

Propagation dynamics of spin excitations along skyrmion strings

Magnetic skyrmions, topological solitons characterized by a two-dimensional swirling spin texture, have recently attracted attention as stable particle-like objects. In a three-dimensional system, a skyrmion can extend in the third dimension forming a robust and flexible string structure, whose unique topology and symmetry are anticipated to host nontrivial functional responses. Here we experimentally demonstrate the coherent propagation of spin excitations along skyrmion strings for the chiral-lattice magnet Cu₂OSeO₃. We find that this propagation is directionally non-reciprocal and the degree of non-reciprocity, as well as group velocity and decay length, are strongly dependent on the character of the excitation modes. These spin excitations can propagate over a distance exceeding 50 μm, demonstrating the excellent long-range ordered nature of the skyrmion-string structure. Our combined experimental and theoretical analyses offer a comprehensive account of the propagation dynamics of skyrmion-string excitations and suggest the possibility of unidirectional information transfer along such topologically protected strings.

Magnetization-polarization cross-control near room temperature in hexaferrite single crystals

Mutual control of the electricity and magnetism in terms of magnetic (H) and electric (E) fields, the magnetoelectric (ME) effect, offers versatile low power consumption alternatives to current data storage, logic gate, and spintronic devices. Despite its importance, E-field control over magnetization (M) with significant magnitude was observed only at low temperatures. Here we have successfully stabilized a simultaneously ferrimagnetic and ferroelectric phase in a Y-type hexaferrite single crystal up to 450 K, and demonstrated the reversal of large non-volatile M by E field close to room temperature. Manipulation of the magnetic domains by E field is directly visualized at room temperature by using magnetic force microscopy. The present achievement provides an important step towards the application of ME multiferroics.

Mutual control of the electric polarization and magnetization promises for low power consumption spintronic devices but remains challenging. Here the authors show reversal of non-volatile magnetization by electric field as well as the polarization switching by magnetic field in a single-component material, close to room temperature.

Quantized chiral edge conduction on domain walls of a magnetic topological insulator

Electronic ordering in magnetic and dielectric materials forms domains with different signs of order parameters. The control of configuration and motion of the domain walls (DWs) enables nonvolatile responses against minute external fields. Here, we realize chiral edge states (CESs) on the magnetic DWs of a magnetic topological insulator. We design and fabricate the magnetic domains in the quantum anomalous Hall state with the tip of a magnetic force microscope and prove the existence of the chiral one-dimensional edge conduction along the prescribed DWs through transport measurements. The proof-of-concept devices based on reconfigurable CESs and Landauer-Büttiker formalism are realized for multiple-domain configurations with well-defined DW channels. Our results may lead to the realization of low-power-consumption spintronic devices.

Effects of behavioral activation program without psychotropic medication treatment for depression in late adolescence: case report

BACKGROUND

A Japanese study revealed that 20.7% of first-year undergraduate students had a major depressive episode during the previous 12 months: first-year undergraduate students with depression need early support. Reportedly, antidepressant medication use during adolescence is associated with modestly increased risk of suicidality. This case study of a late-adolescent woman with depression illustrates the effects of behavioral activation without psychotropic medication.

CASE PRESENTATION

A first-year undergraduate student was diagnosed as having major depressive disorder. From earlier studies, we developed a behavioral activation program for late-adolescent people with major depressive disorder. Behavioral activation administered in 10 weekly 60-minute sessions decreased depressive symptoms, avoidant behaviors, and rumination. Moreover, the Beck Depression Inventory, second version score was 1 at 1-year follow-up.

CONCLUSION

Results of this case study show that behavioral activation is effective without psychotropic medication. Future studies of large samples must be conducted to assess the effectiveness of behavioral activation without psychotropic medication for depression in late adolescence.

Electrical magnetochiral effect induced by chiral spin fluctuations

Chirality of matter can produce unique responses in optics, electricity and magnetism. In particular, magnetic crystals transmit their handedness to the magnetism via antisymmetric exchange interaction of relativistic origin, producing helical spin orders as well as their fluctuations. Here we report for a chiral magnet MnSi that chiral spin fluctuations manifest themselves in the electrical magnetochiral effect, i.e. the nonreciprocal and nonlinear response characterized by the electrical resistance depending on inner product of current and magnetic field. Prominent electrical magnetochiral signals emerge at specific temperature-magnetic field-pressure regions: in the paramagnetic phase just above the helical ordering temperature and in the partially-ordered topological spin state at low temperatures and high pressures, where thermal and quantum spin fluctuations are conspicuous in proximity of classical and quantum phase transitions, respectively. The finding of the asymmetric electron scattering by chiral spin fluctuations may explore new electromagnetic functionality in chiral magnets.

The magnetism-induced chirality in electron transportation is of fundamental importantance in condensed matter physics but the origin is still unclear. Here the authors demonstrate that the asymmetric electron scattering by chiral spin fluctuations can be the key to the electrical magnetochiral effect in MnSi.

Shift current photovoltaic effect in a ferroelectric charge-transfer complex

Shift current is a steady-state photocurrent generated in non-centrosymmetric single crystals and has been considered to be one of the major origins of the bulk photovoltaic effect. The mechanism of this effect is the transfer of photogenerated charges by the shift of the wave functions, and its amplitude is closely related to the polarization of the electronic origin. Here, we report the photovoltaic effect in an organic molecular crystal tetrathiafulvalene-p-chloranil with a large ferroelectric polarization mostly induced by the intermolecular charge transfer. We observe a fairly large zero-bias photocurrent with visible-light irradiation and switching of the current direction by the reversal of the polarization. Furthermore, we reveal that the travel distance of photocarriers exceeds 200 μm. These results unveil distinct features of the shift current and the potential application of ferroelectric organic molecular compounds for novel optoelectric devices.The bulk photovoltaics refers to an effect whereby electrons move directionally in non-centrosymmetric crystals upon light radiation. Here, Nakamura et al. observe this effect in a ferroelectric organic charge-transfer complex, which shows large diffusion distance of photogenerated electrons over 200 µm.

Robust metastable skyrmions and their triangular-square lattice structural transition in a high-temperature chiral magnet

Skyrmions, topologically protected nanometric spin vortices, are being investigated extensively in various magnets. Among them, many structurally chiral cubic magnets host the triangular-lattice skyrmion crystal (SkX) as the thermodynamic equilibrium state. However, this state exists only in a narrow temperature and magnetic-field region just below the magnetic transition temperature T_c, while a helical or conical magnetic state prevails at lower temperatures. Here we describe that for a room-temperature skyrmion material, β-Mn-type Co ₈Zn ₈Mn ₄, a field-cooling via the equilibrium SkX state can suppress the transition to the helical or conical state, instead realizing robust metastable SkX states that survive over a very wide temperature and magnetic-field region. Furthermore, the lattice form of the metastable SkX is found to undergo reversible transitions between a conventional triangular lattice and a novel square lattice upon varying the temperature and magnetic field. These findings exemplify the topological robustness of the once-created skyrmions, and establish metastable skyrmion phases as a fertile ground for technological applications.

Critical phenomena of emergent magnetic monopoles in a chiral magnet

Second-order continuous phase transitions are characterized by symmetry breaking with order parameters. Topological orders of electrons, characterized by the topological index defined in momentum space, provide a distinct perspective for phase transitions, which are categorized as quantum phase transitions not being accompanied by symmetry breaking. However, there are still limited observations of counterparts in real space. Here we show a real-space topological phase transition in a chiral magnet MnGe, hosting a periodic array of hedgehog and antihedgehog topological spin singularities. This transition is driven by the pair annihilation of the hedgehogs and antihedgehogs acting as monopoles and antimonopoles of the emergent electromagnetic field. Observed anomalies in the magnetoresistivity and phonon softening are consistent with the theoretical prediction of critical phenomena associated with enhanced fluctuations of emergent field near the transition. This finding reveals a vital role of topology of the spins in strongly correlated systems.

Phase transitions in topologically non-trivial systems are characterized by changes of topological invariants, rather than conventional order parameters. Here, the authors propose a real-space topological phase transition upon pair annihilation of emergent monopoles inherent in chiral magnet MnGe.

Spontaneous Polarization and Bulk Photovoltaic Effect Driven by Polar Discontinuity in LaFeO_{3}/SrTiO_{3} Heterojunctions

Structurally coherent and chemically abrupt interfaces formed between polar and nonpolar perovskite oxides provide an ideal platform for examining the purely electronic reconstruction known as the polar catastrophe and the emergence of mobile or bound charges at the interface. The appearance of mobile charges induced by the polar catastrophe is already established in the LaAlO_{3}/SrTiO_{3} heterojunctions. Although not experimentally verified, the polar catastrophe can also lead to the emergence of spontaneous polarization. We report that thin films of originally nonpolar LaFeO_{3} grown on SrTiO_{3} are converted to polar as a consequence of the polar catastrophe. The induced spontaneous polarization evokes photovoltaic properties distinct from conventional p-n junctions, such as a switching of the photocurrent direction by changing the interfacial atomic sequence. The control of the bulk polarization by engineering the interface demonstrated here will expand the possibilities for designing and realizing new polar materials with photovoltaic functions.

Microwave Magnetochiral Dichroism in the Chiral-Lattice Magnet Cu_{2}OSeO_{3}

Through broadband microwave spectroscopy in Faraday geometry, we observe distinct absorption spectra accompanying magnetoelectric (ME) resonance for oppositely propagating microwaves, i.e., directional dichroism, in the multiferroic chiral-lattice magnet Cu_{2}OSeO_{3}. The magnitude of the directional dichroism critically depends on the magnetic-field direction. Such behavior is well accounted for by considering the relative direction of the oscillating electric polarizations induced via the ME effect with respect to microwave electric fields. Directional dichroism in a system with an arbitrary form of ME coupling can be also discussed in the same manner.

Robust formation of Skyrmions and topological Hall effect anomaly in epitaxial thin films of MnSi

Magnetotransport properties have been investigated for epitaxial thin films of B20-type MnSi grown on Si(111) substrates. Lorentz transmission electron microscopy images clearly point to the robust formation of Skyrmions over a wide temperature-magnetic field region. New features distinct from those reported previously for MnSi are observed for epitaxial films: a shorter (nearly half) period of the spin helix and Skyrmions, and a topological Hall effect anomaly consisting in ∼2.2 times enhancement of the amplitude and in the opposite sign with respect to bulk samples.

Displacement-type ferroelectricity with off-center magnetic ions in perovskite Sr(1-x)Ba(x)MnO3

We report a ferroelectric transition driven by the off-centering of magnetic Mn(4+) ions in antiferromagnetic Mott insulators Sr(1-x)Ba(x)MnO(3) with a perovskite structure. As x increases, the perovskite lattice shows the typical soft-mode dynamics, as revealed by the momentum-resolved inelastic x-ray scattering and far-infrared spectroscopy, and the ferroelectricity shows up for x ≥ 0.45. The observed polarization is comparable to that for a prototypical ferroelectric BaTiO(3). We further demonstrate that the magnetic order suppresses the ferroelectric lattice dilation by ∼70% and increases the soft-phonon energy by ∼50%, indicating the largest magnetoelectric effects yet attained.

Electric-field control of solitons in a ferroelectric organic charge-transfer salt

The role of solitons in transport, dielectric, and magnetic properties has been revealed for the quasi-one-dimensional organic charge-transfer salt, TTF-QBrCl3 [tetrathiafulvalene (TTF)-2-bromo-3,5,6-trichloro-p-benzoquinone (QBrCl3)]. The material was found to be ferroelectric and hence the solitons should be located at the boundary of the segments with opposite electric polarization. This feature enabled the electric-field control of soliton density and hence the clear-cut detection of soliton contributions. The gigantic dielectric response in the ferroelectric phase is ascribed to the dynamical bound and creeping motions of spinless solitons.

Dynamical disorder of pi-molecular structures induced by proton dynamics in an organic ferroelectric compound

We have investigated the optical response resulting from the proton-pi-electron-molecular-skeleton coupled dynamics in an organic ferroelectric 55DMBP-Hia. Upon the ferroelectric-to-paraelectric transition, almost all of the vibrational modes below 500 cm;{-1} are anomalously blurred and amalgamated into the high-frequency tail of the polarization-relaxation mode. This indicates that the constituent molecular shape is no more well defined around T_{C} due to the dynamical disorder of the pi-conjugated structure originating from proton delocalization on the intermolecular bifurcated hydrogen bond.

Dynamics of multiferroic domain wall in spin-cycloidal ferroelectric DyMnO3

We report the dielectric dispersion of the giant magnetocapacitance (GMC) in multiferroic DyMnO3 over a wide frequency range. The GMC is found to be attributable not to the softened electromagnon but to the electric-field-driven motion of multiferroic domain wall (DW). In contrast to conventional ferroelectric DWs, the present multiferroic DW motion holds an extremely high relaxation rate of approximately 10;{7} s;{-1} even at low temperatures. This mobile nature as well as the model simulation suggests that the multiferroic DW is not atomically thin as in ferroelectrics but thick, reflecting its magnetic origin.

Health, climate change and energy vulnerability: a retrospective assessment of strategic health authority policy and practice in England

BACKGROUND

A number of policy documents suggest that health services should be taking climate change and sustainability seriously and recommendations have been made to mitigate and adapt to the challenges health care providers will face. Actions include, for example, moving towards locally sourced food supplies, reducing waste, energy consumption and travel, and including sustainability in policies and strategies. A Strategic Health Authority (SHA) is part of the National Health Service (NHS) in England. They are responsible for developing strategies for the local health services and ensuring high-quality performance. They manage the NHS locally and are a key link between the U.K. Department of Health and the NHS. They also ensure that national priorities are integrated into local plans. Thus they are in a key position to influence policies and practices to mitigate and adapt to the impact of climate change and promote sustainability.

AIM

The aim of this study was to review publicly available documents produced by Strategic Health Authorities (SHA) to assess the extent to which current activity and planning locally takes into consideration climate change and energy vulnerability.

METHODS

A retrospective thematic content analysis of publicly available materials was undertaken by two researchers over a six month period in 2008. These materials were obtained from the websites of the 10 SHAs in England. Materials included annual reports, plans, policies and strategy documents.

RESULTS

Of the 10 SHAs searched, 4 were found to have an absence of content related to climate change and sustainability. Of the remaining 6 SHAs that did include content related to climate change and energy vulnerability on their websites consistent themes were seen to emerge. These included commitment to a regional sustainability framework in collaboration with other agencies in the pursuit and promotion of sustainable development. Results indicate that many SHAs in England have yet to embrace sustainability, or to integrate preparations for climate change and energy vulnerability within their organisational strategies. Evidence also suggests that SHAs that have recognised the importance of sustainability within their documentation and policies have yet to fully demonstrate this in practice through the implementation of these policies.

CONCLUSIONS

Further research is required to investigate means by which SHAs (U.K.) and agencies responsible for health service policy in other countries may be enabled to include a greater consideration of sustainability and climate change within their policies, and to find effective ways of implementing these policies within daily working practice.

Rotation of an electric polarization vector by rotating magnetic field in cycloidal magnet Eu0.55Y0.45MnO3

To clarify the microscopic origin of the gigantic magnetoelectric effect in multiferroics, we have investigated the variation of an electric polarization (P) vector under a rotating magnetic field (H) for a cycloidal helimagnet Eu0.55Y0.45MnO3 as a canonical example. P rotates smoothly by rotating H around the magnetic propagation wave vector k, which can be well understood by the rotation of the conical spin structure around k. We also show that the rotation process of the conical spin structure under H is crucial for the retention or reversal of the spin helicity or equivalently of the direction of P.

Unconventional critical behaviour in a quasi-two-dimensional organic conductor

Changing the interactions between particles in an ensemble--by varying the temperature or pressure, for example--can lead to phase transitions whose critical behaviour depends on the collective nature of the many-body system. Despite the diversity of ingredients, which include atoms, molecules, electrons and their spins, the collective behaviour can be grouped into several families (called 'universality classes') represented by canonical spin models. One kind of transition, the Mott transition, occurs when the repulsive Coulomb interaction between electrons is increased, causing wave-like electrons to behave as particles. In two dimensions, the attractive behaviour responsible for the superconductivity in high-transition temperature copper oxide and organic compounds appears near the Mott transition, but the universality class to which two-dimensional, repulsive electronic systems belongs remains unknown. Here we present an observation of the critical phenomena at the pressure-induced Mott transition in a quasi-two-dimensional organic conductor using conductance measurements as a probe. We find that the Mott transition in two dimensions is not consistent with known universality classes, as the observed collective behaviour has previously not been seen. This peculiarity must be involved in any emergent behaviour near the Mott transition in two dimensions.

Magnetic-field-induced Mott transition in a quasi-two-dimensional organic conductor

We investigated the effect of magnetic field on the highly correlated metal near the Mott transition in the quasi-two-dimensional layered organic conductor, kappa-(BEDT-TTF)(2)Cu[N(CN)(2)]Cl, by the resistance measurements under control of temperature, pressure, and magnetic field. It was demonstrated that the marginal metallic phase near the Mott transition is susceptible to the field-induced localization transition of the first order, as was predicted theoretically. The thermodynamic consideration of the present results gives a conceptual pressure-field phase diagram of the Mott transition at low temperatures.

CT findings of descending necrotising mediastinitis via the carotid space ('Lincoln Highway')

A 3-year-old girl with fever and neck swelling showed widening of the superior mediastinum on chest radiographs. Contrast-enhanced CT of the neck revealed ill-defined low-attenuation areas with a thick, enhanced rim adjacent to the hypertrophied palatine tonsil. The abscess extended inferiorly within the carotid sheath between the carotid artery and the internal jugular vein into the anterior mediastinum. The carotid space is considered an important conduit of descending necrotising mediastinitis and is called the 'Lincoln Highway' as previously suggested.

Plasma fibronectin response to Escherichia coli and hemoglobin

Low levels of plasma fibronectin (PFN), an adhesive glycoprotein postulated to augment reticuloendothelial function, can predispose animals to a poor clinical outcome following sepsis. In the present study, the PFN levels of adult male rats were measured prior to injection of intraperitoneal Escherichia coli and/or stroma-free hemoglobin (SFH) and subsequently at 4, 24, and 48 hours. Intraperitoneal E coli alone elicited insignificant PFN level depression at four hours, with significantly elevated levels only in the high-dose group at 24 (P less than .05) and 48 hours (P less than .01). Intraperitoneal SFH alone did not alter PFN levels from baseline values; when combined with E coli significant four-hour level depression is noted (P less than .05). Elevation of PFN levels by 24 hours occurs in a dose-dependent fashion, returning to baseline values 48 hours postinoculation. Significant mortality was observed only with high doses of E coli combined with SFH. The PFN levels are elevated 24 to 48 hours following high-dose E coli injection. Stroma-free hemoglobin alone has no effect, but when combined with E coli results in PFN level depression four hours postinoculation, contributing to impairment of systemic host defenses and possibly predisposing to greater mortality.