Spin Caloritronics in Metallic Superlattices.

Spin caloritronics, a research field studying on the interconversion between a charge current (Jc) and a heat current (Jq) mediated by a spin current (Js) and/or magnetization (M), has attracted much attention not only for academic interest but also for practical applications. Newly discovered spin-caloritronic phenomena such as the spin Seebeck effect (SSE) have stimulated the renewed interest in the thermoelectric phenomena of a magnet, which have been known for a long time, e.g. the anomalous Nernst effect (ANE). These spin-caloritronic phenomena involving the SSE and the ANE have provided with a new direction for thermoelectric conversion exploitingJsand/orM. Importantly, the symmetry of ANE allows the thermoelectric conversion in the transverse configuration betweenJqandJc. Although the transverse configuration is totally different from the conventional longitudinal configuration based on the Seebeck effect and has many advantages, we are still facing several issues that need to be solved before developing practical applications. The primal issue is the improvement of conversion efficiency. In the case of ANE-based applications, a material with a large anomalous Nernst coefficient (SANE) is the key for solving the issue. This review article introduces the increase ofSANEcan be achieved by forming superlattice structures, which has been demonstrated for several kinds of materials combinations. The overall picture of studies on spin caloritronics is first surveyed. Then, we mention the pioneering work on the transverse thermoelectric conversion in superlattice structures, which was performed using Fe-based metallic superlattices, and show the recent studies for the Ni-based metallic superlattices and the ordered alloy-based metallic superlattices.

Direct-Contact Seebeck-Driven Transverse Magneto-Thermoelectric Generation in Magnetic/Thermoelectric Bilayers.

Transverse thermoelectric generation converts temperature gradient in one direction into an electric field perpendicular to that direction and is expected to be a promising alternative in creating simple-structured thermoelectric modules that can avoid the challenging problems facing traditional Seebeck-effect-based modules. Recently, large transverse thermopower has been observed in closed circuits consisting of magnetic and thermoelectric materials, called the Seebeck-driven transverse magneto-thermoelectric generation (STTG). However, the closed-circuit structure complicates its broad applications. Here, STTG is realized in the simplest way to combine magnetic and thermoelectric materials, namely, by stacking a magnetic layer and a thermoelectric layer together to form a bilayer. The transverse thermopower is predicted to vary with changing layer thicknesses and peaks at a much larger value under an optimal thickness ratio. This behavior is verified in the experiment, through a series of samples prepared by depositing Fe-Ga alloy thin films of various thicknesses onto n-type Si substrates. The measured transverse thermopower reaches 15.2 ± 0.4 µV K-1, which is a fivefold increase from that of Fe-Ga alloy and much larger than the current room temperature record observed in Weyl semimetal Co2MnGa. The findings highlight the potential of combining magnetic and thermoelectric materials for transverse thermoelectric applications.

Inhibition of Aflatoxin Production in Aspergillus flavus by a Klebsiella sp. and Its Metabolite Cyclo(l-Ala-Gly).

During an experiment where we were cultivating aflatoxigenic Aspergillus flavus on peanuts, we accidentally discovered that a bacterium adhering to the peanut strongly inhibited aflatoxin (AF) production by A. flavus. The bacterium, isolated and identified as Klebsiella aerogenes, was found to produce an AF production inhibitor. Cyclo(l-Ala-Gly), isolated from the bacterial culture supernatant, was the main active component. The aflatoxin production-inhibitory activity of cyclo(l-Ala-Gly) has not been reported. Cyclo(l-Ala-Gly) inhibited AF production in A. flavus without affecting its fungal growth in a liquid medium with stronger potency than cyclo(l-Ala-l-Pro). Cyclo(l-Ala-Gly) has the strongest AF production-inhibitory activity among known AF production-inhibitory diketopiperazines. Related compounds in which the methyl moiety in cyclo(l-Ala-Gly) is replaced by ethyl, propyl, or isopropyl have shown much stronger activity than cyclo(l-Ala-Gly). Cyclo(l-Ala-Gly) did not inhibit recombinant glutathione-S-transferase (GST) in A. flavus, unlike (l-Ala-l-Pro), which showed that the inhibition of GST was not responsible for the AF production-inhibition of cyclo(l-Ala-Gly). When A. flavus was cultured on peanuts dipped for a short period of time in a dilution series bacterial culture broth, AF production in the peanuts was strongly inhibited, even at a 1 × 104-fold dilution. This strong inhibitory activity suggests that the bacterium is a candidate for an effective biocontrol agent for AF control.

Creation of flexible spin-caloritronic material with giant transverse thermoelectric conversion by nanostructure engineering.

Functional materials such as magnetic, thermoelectric, and battery materials have been revolutionized through nanostructure engineering. However, spin caloritronics, an advancing field based on spintronics and thermoelectrics with fundamental physics studies, has focused only on uniform materials without complex microstructures. Here, we show how nanostructure engineering enables transforming simple magnetic alloys into spin-caloritronic materials displaying significantly large transverse thermoelectric conversion properties. The anomalous Nernst effect, a promising transverse thermoelectric phenomenon for energy harvesting and heat sensing, has been challenging to utilize due to the scarcity of materials with large anomalous Nernst coefficients. We demonstrate a remarkable ~ 70% improvement in the anomalous Nernst coefficients (reaching ~ 3.7 µVK-1) and a significant ~ 200% enhancement in the power factor (reaching ~ 7.7 µWm-1K-2) in flexible Fe-based amorphous materials by nanostructure engineering without changing their composition. This surpasses all reported amorphous alloys and is comparable to single crystals showing large anomalous Nernst effect. The enhancement is attributed to Cu nano-clustering, facilitating efficient transverse thermoelectric conversion. This discovery advances the materials science of spin caloritronics, opening new avenues for designing high-performance transverse thermoelectric devices for practical applications.

Predicting the Extent of Damage in the Humphrey Field Analyzer 24-2 Visual Fields Using 10-2 Test Results in Patients With Advanced Glaucoma.

Purpose: To predict Humphrey Field Analyzer 24-2 test (HFA 24-2) results using 10-2 results. Methods: A total of 175 advanced glaucoma eyes (175 patients) with HFA 24-2 mean deviation (MD24-2) of < -20 dB were prospectively followed up for five years using HFA 10-2 and 24-2 (twice and once in a year, respectively). Using all the HFA 24-2 and 10-2 test result pairs measured within three months (350 pairs from 85 eyes, training dataset), a formula to predict HFA 24-2 result using HFA 10-2 results was constructed using least absolute shrinkage and selection operator regression (LASSO). Using 90 different eyes (testing dataset), the absolute differences between the actual and LASSO-predicted MD24-2 and that between the slopes calculated using five actual and LASSO-predicted MD24-2 values, were adopted as the prediction error. Similar analyses were performed for the mean total deviation values (mTD) of the superior (or inferior) hemifield [hemi-mTDsup.24-2(-hemi-mTDinf.24-2)]. Results: The prediction error for the LASSO-predicted MD24-2 and its slope were 2.98 (standard deviation [SD] = 1.90) dB and 0.32 (0.33) dB/yr, respectively. The LASSO-predicted hemi-mTDsup.24-2 (hemi-mTDinf.24-2), and its slope were 3.02 (2.89) and 3.76 (2.72) dB, and 0.37 (0.41) and 0.44 (0.38) dB/year, respectively. These prediction errors were within two times SD of repeatability of the simulated stable HFA 24-2 VF parameter series. Conclusions: HFA 24-2 results could be predicted using the paired HFA 10-2 results with reasonable accuracy using LASSO in patients with advanced glaucoma. Translational Relevance: It is useful to predict HFA24-2 test from HFA10-2 test, when the former is not available, in advanced glaucoma.

Observation of the Anisotropic Magneto-Thomson Effect.

We report the observation of the anisotropic magneto-Thomson effect (AMTE), which is one of the higher-order thermoelectric effects in a ferromagnet. Using lock-in thermography, we demonstrated that in a ferromagnetic NiPt alloy, the cooling or heating induced by the Thomson effect depends on the angle between the magnetization direction and the temperature gradient or charge current applied to the alloy. AMTE observed here is the missing ferromagnetic analog of the magneto-Thomson effect in a nonmagnetic conductor, providing the basis for nonlinear spin caloritronics and thermoelectrics.

Electric field-dependent phonon spectrum and heat conduction in ferroelectrics.

This article shows experimentally that an external electric field affects the velocity of the longitudinal acoustic phonons (vLA), thermal conductivity (κ), and diffusivity (D) in a bulk lead zirconium titanate-based ferroelectric. Phonon conduction dominates κ, and the observations are due to changes in the phonon dispersion, not in the phonon scattering. This gives insight into the nature of the thermal fluctuations in ferroelectrics, namely, phonons labeled ferrons that carry heat and polarization. It also opens the way for phonon-based electrically driven all-solid-state heat switches, an enabling technology for solid-state heat engines. A quantitative theoretical model combining piezoelectric strain and phonon anharmonicity explains the field dependence of vLA, κ, and D without any adjustable parameters, thus connecting thermodynamic equilibrium properties with transport properties. The effect is four times larger than previously reported effects, which were ascribed to field-dependent scattering of phonons.

Genome Editing Reveals Both the Crucial Role of OsCOI2 in Jasmonate Signaling and the Functional Diversity of COI1 Homologs in Rice.

Jasmonic acid (JA) regulates plant growth, development and stress responses. Coronatine insensitive 1 (COI1) and jasmonate zinc-finger inflorescence meristem-domain (JAZ) proteins form a receptor complex for jasmonoyl-l-isoleucine, a biologically active form of JA. Three COIs (OsCOI1a, OsCOI1b and OsCOI2) are encoded in the rice genome. In the present study, we generated mutants for each rice COI gene using genome editing to reveal the physiological functions of the three rice COIs. The oscoi2 mutants, but not the oscoi1a and oscoi1b mutants, exhibited severely low fertility, indicating the crucial role of OsCOI2 in rice fertility. Transcriptomic analysis revealed that the transcriptional changes after methyl jasmonate (MeJA) treatment were moderate in the leaves of oscoi2 mutants compared to those in the wild type or oscoi1a and oscoi1b mutants. MeJA-induced chlorophyll degradation and accumulation of antimicrobial secondary metabolites were suppressed in oscoi2 mutants. These results indicate that OsCOI2 plays a central role in JA response in rice leaves. In contrast, the assessment of growth inhibition upon exogenous application of JA to seedlings of each mutant revealed that rice COIs are redundantly involved in shoot growth, whereas OsCOI2 plays a primary role in root growth. In addition, a co-immunoprecipitation assay showed that OsJAZ2 and OsJAZ5 containing divergent Jas motifs physically interacted only with OsCOI2, whereas OsJAZ4 with a canonical Jas motif interacts with all three rice COIs. The present study demonstrated the functional diversity of rice COIs, thereby providing clues to the mechanisms regulating the various physiological functions of JA.

Identifying central 10° visual subfield associated with future worsening of visual acuity in eyes with advanced glaucoma.

BACKGROUND/AIMS: To determine a cluster of test points: visual subfield (VSF) of Humphrey Field Analyzer 10-2 test (HFA 10-2) of which baseline sensitivities were associated with future worsening of visual acuity (VA) in eyes with advanced glaucoma. METHODS: A total of 175 advanced glaucoma eyes of 175 advanced glaucoma patients with well controlled intraocular pressure (IOP), a mean deviation of the Humphrey Field Analyzer 24-2 (HFA 24-2) test ≤ -20 decibels and best corrected VA ≥20/40, were included. At baseline, HFA 24-2 and HFA 10-2 tests were performed along with VA measurements. All patients underwent prospective follow-up of 5 years, and VA was measured every 6 months. The Cox proportional hazards model was used to identify visual field sensitivities associated with deterioration of VA and also blindness. RESULTS: Deterioration of VA and blindness were observed in 15.4% and 3.4% of the eyes, respectively. More negative total deviation (TD) values in the temporal papillomacular bundle VSF were significantly associated with deterioration in VA. Averages of the TD values in this area of the HFA 10-2 test had the most predictive power of future VA deterioration (OR: 0.92, p<0.001). A very similar tendency was observed for blindness. CONCLUSION: In advanced glaucoma eyes with well-controlled IOP, careful attention is needed when the mean TD values in the temporal papillomacular bundle VSF, measured with a HFA 10-2 test is deteriorated. TD values of this VSF indicate higher risks for future deterioration of VA and also blindness.

Sm-Co-based amorphous alloy films for zero-field operation of transverse thermoelectric generation.

Transverse thermoelectric generation using magnetic materials is essential to develop active thermal engineering technologies, for which the improvements of not only the thermoelectric output but also applicability and versatility are required. In this study, using combinatorial material science and lock-in thermography technique, we have systematically investigated the transverse thermoelectric performance of Sm-Co-based alloy films. The high-throughput material investigation revealed the best Sm-Co-based alloys with the large anomalous Nernst effect (ANE) as well as the anomalous Ettingshausen effect (AEE). In addition to ANE/AEE, we discovered unique and superior material properties in these alloys: the amorphous structure, low thermal conductivity, and large in-plane coercivity and remanent magnetization. These properties make it advantageous over conventional materials to realize heat flux sensing applications based on ANE, as our Sm-Co-based films can generate thermoelectric output without an external magnetic field. Importantly, the amorphous nature enables the fabrication of these films on various substrates including flexible sheets, making the large-scale and low-cost manufacturing easier. Our demonstration will provide a pathway to develop flexible transverse thermoelectric devices for smart thermal management.

An ancestral function of strigolactones as symbiotic rhizosphere signals.

In flowering plants, strigolactones (SLs) have dual functions as hormones that regulate growth and development, and as rhizosphere signaling molecules that induce symbiosis with arbuscular mycorrhizal (AM) fungi. Here, we report the identification of bryosymbiol (BSB), an SL from the bryophyte Marchantia paleacea. BSB is also found in vascular plants, indicating its origin in the common ancestor of land plants. BSB synthesis is enhanced at AM symbiosis permissive conditions and BSB deficient mutants are impaired in AM symbiosis. In contrast, the absence of BSB synthesis has little effect on the growth and gene expression. We show that the introduction of the SL receptor of Arabidopsis renders M. paleacea cells BSB-responsive. These results suggest that BSB is not perceived by M. paleacea cells due to the lack of cognate SL receptors. We propose that SLs originated as AM symbiosis-inducing rhizosphere signaling molecules and were later recruited as plant hormone.

Thermoelectric Polarization Transport in Ferroelectric Ballistic Point Contacts.

We formulate a scattering theory of polarization and heat transport through a ballistic ferroelectric point contact. We predict a polarization current under either an electric field or a temperature difference that depends strongly on the direction of the ferroelectric order and can be detected by its magnetic stray field and associated thermovoltage and Peltier effect.

A new metabolite, mannogeranylnerol, specifically produced at body temperature by Schizophyllum commune, a causative fungus of human mycosis.

Schizophyllum commune is a causative fungus of human mycosis. Its metabolites produced at 27 °C were compared with those produced at 37 °C, to obtain a candidate low-molecular-weight virulence factor related to the pathogenicity of this fungus. We found that S. commune specifically produces two acyclic terpene mannosides at 37 °C. They were identified as nerolidol ß-D-mannoside (1) and geranylnerol ß-D-mannoside (2) by NMR, MS, and CD analyses. Compound 2, a new compound named mannogeranylnerol, showed weak antibiotic activity that was slightly stronger than that of compound 1.

Chitooligosaccharide elicitor and oxylipins synergistically elevate phytoalexin production in rice.

KEY MESSAGE: We show that in rice, the amino acid-conjugates of JA precursor, OPDA, may function as a non-canonical signal for the production of phytoalexins in coordination with the innate chitin signaling. The core oxylipins, jasmonic acid (JA) and JA-Ile, are well-known as potent regulators of plant defense against necrotrophic pathogens and/or herbivores. However, recent studies also suggest that other oxylipins, including 12-oxo-phytodienoic acid (OPDA), may contribute to plant defense. Here, we used a previously characterized metabolic defense marker, p-coumaroylputrescine (CoP), and fungal elicitor, chitooligosaccharide, to specifically test defense role of various oxylipins in rice (Oryza sativa). While fungal elicitor triggered a rapid production of JA, JA-Ile, and their precursor OPDA, rice cells exogenously treated with the compounds revealed that OPDA, rather than JA-Ile, can stimulate the CoP production. Next, reverse genetic approach and oxylipin-deficient rice mutant (hebiba) were used to uncouple oxylipins from other elicitor-triggered signals. It appeared that, without oxylipins, residual elicitor signaling had only a minimal effect but, in synergy with OPDA, exerted a strong stimulatory activity towards CoP production. Furthermore, as CoP levels were compromised in the OPDA-treated Osjar1 mutant cells impaired in the oxylipin-amino acid conjugation, putative OPDA-amino acid conjugates emerged as hypothetical regulators of CoP biosynthesis. Accordingly, we found several OPDA-amino acid conjugates in rice cells treated with exogenous OPDA, and OPDA-Asp was detected, although in small amounts, in the chitooligosaccharide-treated rice. However, as synthetic OPDA-Asp and OPDA-Ile, so far, failed to induce CoP in cells, it suggests that yet another presumed OPDA-amino acid form(s) could be acting as novel regulator(s) of phytoalexins in rice.

Factors Threatening Central Visual Function of Patients with Advanced Glaucoma: A Prospective Longitudinal Observational Study.

PURPOSE: To identify risk factors for further deterioration of central visual function in advanced glaucoma eyes. DESIGN: Prospective, observational 5-year study. PARTICIPANTS: Advanced glaucoma patients with well-controlled intraocular pressure (IOP), mean deviation (MD) of the Humphrey Field Analyzer (HFA) 24-2 program ≤-20 dB and best-corrected visual acuity (BCVA) of 20/40. METHODS: The HFA 10-2 test and BCVA examination were performed every 6 months, and the HFA 24-2 test was performed every 12 months for 5 years. The Cox proportional hazards model was used to identify risk factors for deterioration of HFA 10-2 and 24-2 results and BCVA. MAIN OUTCOME MEASURES: Deterioration of HFA 10-2 results was defined by the presence of the same ≥3 points with negative total deviation slope ≤-1 dB/year at P < 0.01 on ≥3 consecutive tests, deterioration of HFA 24-2 results by an increase ≥2 in the Advanced Glaucoma Intervention Study score on ≥2 consecutive tests, and deterioration of BCVA by an increase of ≥0.2 logarithm of the minimum angle of resolution (logMAR) on ≥2 consecutive tests. RESULTS: A total of 175 eyes of 175 patients (mean age, 64.1 years; mean baseline IOP, 13.2 mmHg; mean BCVA, 0.02 logMAR; mean HFA 24-2 and 10-2 MD, -25.9 and -22.9 dB, respectively) were included. The probabilities of deterioration in HFA 10-2 and 24-2 results and BCVA were 0.269 ± 0.043 (standard error), 0.173 ± 0.031, and 0.194 ± 0.033, respectively, at 5 years. Lower BCVA at baseline (P = 0.012) was associated significantly with further deterioration of HFA 10-2 results. Better HFA 24-2 MD (P < 0.001) and use of systemic antihypertensive agents (P = 0.009) were associated significantly with further deterioration of HFA 24-2 results, and a greater ß-peripapillary atrophy area-to-disc area ratio (P < 0.001), use of systemic antihypertensive agents (P = 0.025), and lower BCVA (P = 0.042) were associated significantly with further deterioration of BCVA, respectively. CONCLUSIONS: In advanced glaucoma eyes with well-controlled IOP, BCVA, ß-peripapillary atrophy area-to-disc area ratio, and use of systemic antihypertensive agents were significant prognostic factors for further deterioration of central visual function.

Preparation and characterization of silver orthophosphate photocatalytic coating on glass substrate.

The photocatalytic activity of silver orthophosphate Ag3PO4 has been studied and shown to have a high photo-oxidation capability. However, there is few reported example of a simple method to prepare Ag3PO4 coatings on various substrates. In this study a novel and simple method to immobilize Ag3PO4 on the surface of glass substrates has been developed. A silver phosphate paste based on a polyelectrolyte solution was applied to a smooth glass surface. The resulting dried material was calcined to obtain a coating that remained on the glass substrate. The coating layer was characterized by X-ray diffraction and energy dispersive X-ray spectrometry, and the optical band gap of the material was determined. The results indicated that an Ag3PO4 coating responsive to visible light was successfully prepared. The coating, under visible light irradiation, has the ability to decompose methylene blue. Although the coating contained some elemental silver, this did not adversely affect the optical band gap or the photocatalytic ability.

Simultaneous harvesting of radiative cooling and solar heating for transverse thermoelectric generation.

For any thermoelectric effects to be achieved, a thermoelectric material must have hot and cold sides. Typically, the hot side can be easily obtained by excess heat. However, the passive cooling method is often limited to convective heat transfer to the surroundings. Since thermoelectric voltage is proportional to the temperature difference between the hot and cold sides, efficient passive cooling to increase the temperature gradient is of critical importance. Here, we report simultaneous harvesting of radiative cooling at the top and solar heating at the bottom to enhance the temperature gradient for a transverse thermoelectric effect which generates thermoelectric voltage perpendicular to the temperature gradient. We demonstrate this concept by using the spin Seebeck effect and confirm that the spin Seebeck device shows the highest thermoelectric voltage when both radiative cooling and solar heating are utilized. Furthermore, the device generates thermoelectric voltage even at night through radiative cooling which enables continuous energy harvesting throughout a day. Planar geometry and scalable fabrication process are advantageous for energy harvesting applications.

Deciphering OPDA Signaling Components in the Momilactone-Producing Moss Calohypnum plumiforme.

Jasmonic acid (JA) and its biologically active form jasmonoyl-L-isoleucine (JA-Ile) regulate defense responses to various environmental stresses and developmental processes in plants. JA and JA-Ile are synthesized from α-linolenic acids derived from membrane lipids via 12-oxo-phytodienoic acid (OPDA). In the presence of JA-Ile, the COI1 receptor physically interacts with JAZ repressors, leading to their degradation, resulting in the transcription of JA-responsive genes by MYC transcription factors. Although the biosynthesis of JA-Ile is conserved in vascular plants, it is not recognized by COI1 in bryophytes and is not biologically active. In the liverwort Marchantia polymorpha, dinor-OPDA (dn-OPDA), a homolog of OPDA with two fewer carbons, and its isomer dn-iso-OPDA accumulate after wounding and are recognized by COI1 to activate downstream signaling. The moss Calohypnum plumiforme produces the antimicrobial-specialized metabolites, momilactones. It has been reported that JA and JA-Ile are not detected in C. plumiforme and that OPDA, but not JA, can induce momilactone accumulation and the expression of these biosynthetic genes, suggesting that OPDA or its derivative is a biologically active molecule in C. plumiforme that induces chemical defense. In the present study, we investigated the biological functions of OPDA and its derivatives in C. plumiforme. Searching for the components potentially involving oxylipin signaling from transcriptomic and genomic data revealed that two COI1, three JAZ, and two MYC genes were present. Quantification analyses revealed that OPDA and its isomer iso-OPDA accumulated in larger amounts than dn-OPDA and dn-iso-OPDA after wounding. Moreover, exogenously applied OPDA, dn-OPDA, or dn-iso-OPDA induced the transcription of JAZ genes. These results imply that OPDA, dn-OPDA, and/or their isomers potentially act as biologically active molecules to induce the signaling downstream of COI1-JAZ. Furthermore, co-immunoprecipitation analysis showed the physical interaction between JAZs and MYCs, indicating the functional conservation of JAZs in C. plumiforme with other plants. These results suggest that COI1-JAZ-MYC mediated signaling is conserved and functional in C. plumiforme.