Exploring the local solvation structure of redox molecules in a mixed solvent for increasing the Seebeck coefficient of thermocells.

A thermocell is an emerging alternative to thermoelectric devices and exhibits a high Seebeck coefficient (Se) due to the large change of solvation entropy associated with redox reactions. Here, the Se of p-chloranil radicals/dianions (CA˙-/2-) in acetonitrile was drastically increased from -1.3 to -2.6 mV K-1 by the addition of ethanol, and the increment surpassed the estimation of the classical Born model with continuum solvent media. UV-vis spectroscopy and electrochemical measurements at various mixing ratios of acetonitrile to ethanol revealed that the strong hydrogen bonding between ethanol and oxygen atoms of CA2- forms a 4 : 1 solvent-ion pair, while the ethanol molecules binding to CA2- dissociate upon its oxidation to CA˙-. The local solvation structures of CA2- are in good agreement with density functional theory. This order-disorder transition of the local solvation structure around the CA˙-/2- ions produces a large entropy change and results in a large Se value. The tailored solvation structure of redox ions by hydrogen bonding is a versatile method applicable to a variety of redox pairs and solvents, contributing to the development of electrolyte engineering for thermocells.

Localization of nuclear wave functions of lithium in [Li+@C60]PF6-: molecular insights into two-site disorder-order transition.

Lithium endohedral fullerene, Li+@C60, is a porous system ideal for studying the quantized translational motion of the Li+ nucleus under subnanoscale confinement. The quantized nuclear motion strongly depends on the anharmonic and polarizable adsorbent potential within the C60 cage, which can be perturbed by cage distortion and/or exterior ions. In our recent paper, H. Ando and Y. Nakao, Phys. Chem. Chem. Phys., 2021, 23, 9785-9803, we focused on a [Li+@C60]PF6- salt and theoretically investigated how the Li+ ion in each C60 cage is simultaneously localized at two equivalent disordered sites in 24 K < T ≪ 100 K. At 24 K, the salt exhibits a disorder-order transition, whereby every Li+ ion becomes mostly localized at one of the two disordered sites below that temperature. Herein we discuss the origin of this transition with special attention to the local structural distortion and intermolecular interactions. Using the Fourier grid Hamiltonian method and a model function that fits a post-Hartree-Fock potential energy surface, we obtained hundreds of low-energy nuclear wave functions of Li+ confined within the cage. The weak distortions of the C60 cage and the PF6- coordination sphere below 24 K and concurrent inversion-symmetry breaking affect intermolecular interactions, thus making the wave functions of the nuclear ground state and several low-energy excited states localized around the experimental high-occupancy disordered site. This demonstrates that the distortions correlate closely with the two-site disorder-order transition. Finally, we reveal that two absorption peaks in the terahertz frequency range show substantial blueshifts upon cooling below 24 K, which serve as fingerprints of the transition.

Effect of Static Jahn-Teller Distortion on the Li+ Transport in a Copper Hexacyanoferrate Framework.

Prussian blue (PB) and its analogues (PBAs) are potential cathode-active materials for rechargeable lithium-ion batteries. Although a body of research has assessed the performances of various PB/PBA cathodes with an eye to practical use, the underlying Li+-transport mechanism is still unclear. Focusing on copper hexacyanoferrate (CuHCF), a PBA that exhibits static Jahn-Teller (JT) distortion, we theoretically investigate how the framework's distortion affects the pathways and energetics of the Li+ transport. Density functional theory calculations of a local structure model of CuHCF reveal that the static JT distortion makes the favorable Li+-transport pathways quasi-two-dimensional, contrary to an intuitive picture of isotropic Li+ diffusion within the regular jungle-gym framework. The pathways are mutually interconnected, thereby creating an almost barrierless transport network. To better understand the distortion-induced transport anisotropy, we visually analyze the framework's electronic structure and noncovalent Li+-framework interactions. This study helps deepen the fundamental understanding of intrinsic Li+-transport properties of a distorted porous framework.

Spectral noise reduction and temporal coherence control using a phase unsynchronized wave synthesizing method.

Highly accurate spectrometry requires spectral noise reduction. In this paper, we propose a phase unsynchronized wave synthesizing (PuwS) method that provides different optical path lengths for different wave elements obtained from the division of a wavefront and synthesizes the respective wave elements to have the same propagation direction. PuwS achieves spectral noise reduction and contributes to temporal coherence control. To confirm these properties observed in experimental data, we propose a series of analytical models based on a traditional wave train model. According to the analytical model, PuwS generates an ensemble average effect that prevents spectral noise and decreases the visibility of the spectral fringe pattern. The experimental data show that the spectral noise is reduced when the total number of wave elements increases. PuwS is found to drastically change the measured spectral profile of a silk sample, achieving highly accurate spectrometry. The data also show that a combination of PuwS and an appropriate diffuser decreases the spectral visibility regarding the temporal coherence more effectively than a conventional method using one or more diffusers.

Quantum states of the endohedral fullerene Li+@C60 surrounded by anions: energy decomposition analysis of nuclear wave functions.

Lithium is the lightest metal element. To date, little is known about its quantized nuclear motion in nanoscale porous structures. Endohedral fullerene Li+@C60 is an ideal porous system for studying such a quantized motion. Recent studies suggest that the anions surrounding the C60 cage exterior and a slight cage distortion can alter the potential field in the cage interior and thus the nuclear wave function of Li+. It has yet to be clarified how the electronic state, particularly the flexible π electron cloud of the C60 cage, is associated with (de)localization of the Li+ wave function. Focusing on the [Li+@C60]PF6- crystal, we constructed a local structure model considering the PF6- coordination and the cage distortion. We developed model functions that fit the post-Hartree-Fock potential energy surface for the Li+ motion and its decomposed components, four interaction energy surfaces. The decomposition clarified the origins of the shell-like adsorbent potential and the potential wells therein. The Fourier grid Hamiltonian method allowed us to obtain low-energy Li+ wave functions. The ground state is nearly two-fold degenerate, and its wave functions are mostly localized underneath two C6 rings, near the disordered sites of Li+ in the X-ray crystal structure. By extending the energy decomposition analysis within the clamped-nuclei approximation to incorporate the delocalization of nuclear wave functions, we demonstrated that the ground state is stabilized by the polarization, dispersion, and electrostatic interactions. Beyond the common picture of Li+ moving in a classical electrostatic field, our approach will deepen the understanding of the flexible Li+ wave function confined in a polarizable porous structure by various intermolecular interactions.

Initial treatment of seizures in children in an emergency department in rural Japan.

OBJECTIVE: Although the initial treatment of childhood seizures is important, treatment within an appropriate time window is often difficult in resource-limited areas. This study examined childhood seizure treatment in a rural area in Japan. METHODS: We retrospectively investigated children presenting to Nakatsugawa Municipal General Hospital emergency department between 2015 and 2018. From the hospital database, we identified children who were diagnosed with seizures, epilepsy, or acute infectious encephalitis/encephalopathy or were given benzodiazepines. We considered etiology, seizure duration, and treatment according to the specialties of the doctors providing initial care. RESULTS: We extracted 236 seizure events: 40 initially treated by pediatricians, 16 by a mobile doctor team, and 180 by other doctors. Twenty patients had continuous seizures for longer than 5 min on admission. Two were treated by pediatricians at presentation; it took 4 and 7 min after arrival to stop the seizures. Four were treated by a mobile team, and 14 by other doctors; the median response times were 11.5 (range 3-47) and 19 (range 5-60) min, respectively. All patients treated by pediatricians or mobile doctor teams received intravenous or intramuscular diazepam, whereas 50% of those treated by other doctors initially received diazepam suppositories. In three of the 20 events, establishing intravenous access was difficult. SIGNIFICANCE: In rural Japan, many children with seizures are initially treated by doctors other than pediatricians or emergency physicians, and they require a longer time to achieve seizure cessation. Non-intravenous benzodiazepine formulas, which have not yet been approved in Japan, would be helpful.

Monitoring conical intersections in the ring opening of furan by attosecond stimulated X-ray Raman spectroscopy.

Attosecond X-ray pulses are short enough to capture snapshots of molecules undergoing nonadiabatic electron and nuclear dynamics at conical intersections (CoIns). We show that a stimulated Raman probe induced by a combination of an attosecond and a femtosecond pulse has a unique temporal and spectral resolution for probing the nonadiabatic dynamics and detecting the ultrafast (∼4.5 fs) passage through a CoIn. This is demonstrated by a multiconfigurational self-consistent-field study of the dynamics and spectroscopy of the furan ring-opening reaction. Trajectories generated by surface hopping simulations were used to predict Attosecond Stimulated X-ray Raman Spectroscopy signals at reactant and product structures as well as representative snapshots along the conical intersection seam. The signals are highly sensitive to the changes in nonadiabatically coupled electronic structure and geometry.

Stochastic Liouville equations for femtosecond stimulated Raman spectroscopy.

Electron and vibrational dynamics of molecules are commonly studied by subjecting them to two interactions with a fast actinic pulse that prepares them in a nonstationary state and after a variable delay period T, probing them with a Raman process induced by a combination of a broadband and a narrowband pulse. This technique, known as femtosecond stimulated Raman spectroscopy (FSRS), can effectively probe time resolved vibrational resonances. We show how FSRS signals can be modeled and interpreted using the stochastic Liouville equations (SLE), originally developed for NMR lineshapes. The SLE provide a convenient simulation protocol that can describe complex dynamics caused by coupling to collective bath coordinates at much lower cost than a full dynamical simulation. The origin of the dispersive features that appear when there is no separation of timescales between vibrational variations and the dephasing time is clarified.

Femtosecond stimulated Raman spectroscopy of the cyclobutane thymine dimer repair mechanism: a computational study.

Cyclobutane thymine dimer, one of the major lesions in DNA formed by exposure to UV sunlight, is repaired in a photoreactivation process, which is essential to maintain life. The molecular mechanism of the central step, i.e., intradimer C-C bond splitting, still remains an open question. In a simulation study, we demonstrate how the time evolution of characteristic marker bands (C═O and C═C/C-C stretch vibrations) of cyclobutane thymine dimer and thymine dinucleotide radical anion, thymidylyl(3'→5')thymidine, can be directly probed with femtosecond stimulated Raman spectroscopy (FSRS). We construct a DFT(M05-2X) potential energy surface with two minor barriers for the intradimer C5-C5' splitting and a main barrier for the C6-C6' splitting, and identify the appearance of two C5═C6 stretch vibrations due to the C6-C6' splitting as a spectroscopic signature of the underlying bond splitting mechanism. The sequential mechanism shows only absorptive features in the simulated FSRS signals, whereas the fast concerted mechanism shows characteristic dispersive line shapes.

A switchable molecular rotator: neutron spectroscopy study on a polymeric spin-crossover compound.

A quasielastic neutron scattering and solid-state (2)H NMR spectroscopy study of the polymeric spin-crossover compound {Fe(pyrazine)[Pt(CN)(4)]} shows that the switching of the rotation of a molecular fragment--the pyrazine ligand--occurs in association with the change of spin state. The rotation switching was examined on a wide time scale (10(-13)-10(-3) s) by both techniques, which clearly demonstrated the combination between molecular rotation and spin-crossover transition under external stimuli (temperature and chemical). The pyrazine rings are seen to perform a 4-fold jump motion about the coordinating nitrogen axis in the high-spin state. In the low-spin state, however, the motion is suppressed, while when the system incorporates benzene guest molecules, the movements of the system are even more restricted.

Comparison of electronic structures and light-induced excited spin state trapping between [Fe(2-picolylamine)(3)](2+) and its iron(III) analogue.

We investigated mer- and fac-[Fe(II)(2-pic)(3)](2+) (pic = picolylamine) and Fe(iii) analogue, mer-[Fe(III)(2-pic)(3)](3+), by the DFT method to clarify the mechanism of light-induced excited spin state trapping (LIESST). In mer-[Fe(II)(2-pic)(3)](2+), the potential energy surface (PES) of the triplet state is the least stable but it is close to the PESs of the singlet and quintet states at the equilibrium geometry of the triplet state within 5 kcal mol(-1). This indicates that intersystem crossing occurs from the triplet state to either the singlet state or the quintet state around the equilibrium geometry of the triplet state. The quintet state is as stable as the singlet state in their equilibrium geometries. All Fe-N bonds of the quintet state are longer than those of the singlet state by about 0.19 A. These are consistent with the general understanding that the Fe-ligand distances are considerably different but the relative stability is little different between the low spin and high spin states in LIESST complexes. Actually, a large activation barrier is calculated for the conversion between the singlet and quintet states, which is enough to suppress thermal spin transition and tunneling between them. The d-d transition energies are calculated with the TD-DFT method to be 2.05, 2.07, and 2.09 eV in the singlet state and 1.46 and 1.64 eV in the quintet state. Because of the significantly large difference in excitation energy between the singlet and quintet states, irradiation of visible light with different wavelengths selectively induces the excitation to the singlet excited state or the quintet one. All these results are consistent with the fact that both LIESST and reverse-LIESST are observed in mer-[Fe(II)(2-pic)(3)](2+). The fac-isomer is also useful for the LIESST/reverse-LIESST, though the mer-isomer is better. In the Fe(iii) analogue, mer-[Fe(III)(2-pic)(3)](3+), the DFT-computational results indicate small activation barriers and a large overlap of absorption spectra between the doublet and sextet states. Also, the Fe(III)-N bond distances are less different between the low spin and high spin states than the Fe(II)-N ones, leading to the narrow potential wall between the doublet and sextet states. As a result, the LIESST and reverse-LIESST cannot be observed in this Fe(iii) complex.

Repetitive breath-hold diving causes serious brain injury.

We report on a Japanese male professional breath-hold diver (Ama) who developed neurological disorders during repetitive dives to 22 meters of sea water. Each diving duration and surface interval were 40-80 seconds and 20-30 seconds, respectively. He suffered from sensory numbness of the right cheek, hand and foot, and double vision after more than two hours of consecutive dives. Magnetic resonance images of his brain showed multiple cerebral infarcts, and one of the lesions was situated in the brainstem. There is a possibility that repetitive deep breath-hold dives with short surface intervals can induce fatal accidents for divers.

Bidirectional chemo-switching of spin state in a microporous framework.

The ins and outs of spin: Using the microporous coordination polymer {Fe(pz)[Pt(CN)(4)]} (1, pz=pyrazine), incorporating spin-crossover subunits, two-directional magnetic chemo-switching is achieved at room temperature. In situ magnetic measurements following guest vapor injection show that most guest molecules transform 1 from the low-spin (LS) state to the high-spin (HS) state, whereas CS(2) uniquely causes the reverse HS-to-LS transition.

Effect of short-term exposure to whole body vibration in humans: relationship between wakefulness level and vibration frequencies.

The purpose of this study was to clarify the influence of different vibration frequencies on wakefulness level. Subjects were 7 healthy male university students aged 21.9+/-1.6 years (mean). All students were non-smokers. Three exposure conditions were used (10 Hz vibration, 20 Hz vibration, and no vibration). Whole-body vertical vibration was applied to subjects sitting on a car passenger seat using a whole-body vibration shaker (CV-300, Akashi) at a single frequency (10 or 20 Hz) at an acceleration level of 0.3 ms(-2) r.m.s. for 24 min. The objective wakefulness level based on EEGs was evaluated in terms of the alpha attenuation coefficient (AAC) obtained by the Alpha Attenuation Test (AAT). As parameters of psychological stress, salivary 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were used. The subjective wakefulness level was evaluated using a questionnaire based on the Kwansei Gakuin Sleepiness Scale (KSS), which is a scale developed for the Japanese based on the Stanford Sleepiness Scale (SSS). The KSS score, representing the subjective wakefulness level, decreased after the exposure irrespective of the exposure condition, but the decrease was not significant. The AAC, representing the objective wakefulness level, significantly decreased only after vibration exposure (10 Hz/20 Hz) but did not differ between the two vibration frequencies. No significant changes were observed after exposure to whole-body vibration in MHPG or HVA as parameters of vibration-related stress. The AAC decreased after exposure to whole-body vibration (10 Hz/20 Hz), suggesting a decrease in the wakefulness level. However, no differences were observed in the influence of the two different vibration frequencies test.

Theoretical study of low-spin, high-spin, and intermediate-spin states of [Fe(III)(pap)2](+) (pap = N-2-pyridylmethylidene-2-hydroxyphenylaminato). Mechanism of light-induced excited spin state trapping.

The mechanism of light-induced excited spin state trapping (LIESST) of [FeIII(pap)2]+ (pap = N-2-pyridylmethylidene-2-hydroxyphenylaminato) was discussed on the basis of potential energy surfaces (PESs) of several important spin states, where the PESs were evaluated with the DFT(B3LYP) method. The PES of the quartet spin state crosses those of the doublet and sextet spin states around its minimum. This means that the spin transition occurs from the quartet spin state to either the doublet spin state or the sextet spin state around the PES minimum of the quartet spin state. The PES minimum of the sextet spin state is slightly less stable than that of the doublet spin state by 0.18 eV (4.2 kcal/mol). This small energy difference is favorable for the LIESST. The doublet-sextet spin crossover point is 0.41 eV (9.6 kcal/mol) above the PES minimum of the sextet spin state. Because of this considerably large activation barrier, the thermal spin transition and the tunneling process do not occur easily. In the doublet spin state, the ligand to ligand charge transfer (LLCT) transition is calculated to be 2.16 eV with the TD-DFT(B3LYP) method, in which the pi orbital of the phenoxy moiety and the pi* orbital of the imine moiety in the pap ligand participate. This transition energy is moderately smaller than the visible light of 550 nm used experimentally. In the sextet spin state, the ligand to metal charge transfer (LMCT) transition is calculated to be at 2.36 eV, which is moderately higher than the visible light (550 nm). These results indicate that the irradiation of the visible light induces the LIESST to generate the sextet spin state but the reverse-LIESST is also somewhat induced by the visible light, indicating that the complete spin conversion from the doublet spin state to the sextet one does not occur, as reported experimentally.

Effects of short-term exposure to whole-body vibration on wakefulness level.

To investigate the relationships between whole-body vibration and changes in wakefulness, We measured the change of a subjective wakefulness level and electroencephalogram (EEG). Subjects are ten healthy male university students. The subjects were exposed to whole-body vibration with frequency (10 Hz) and acceleration level (0.6 ms(-2) r.m.s.) for 12 min in the seated position. Subjective wakefulness level was evaluated using the questionnaire of VASS (Visual Analog Sleepiness Scale) and KSS (The Kwansei Gakuin Sleepiness Scale). For the electroencephalogram (EEG) measurement, AAT (Alpha Attenuation Test) which repeats three times each opened and closed eye for 1 min was conducted. Wakefulness levels were defined as the ratio of mean alpha-wave power during eyes closed versus eyes opened. VASS and KSS increased and subjective level of wakefulness decreased from pre- to post exposure in all subjects, regardless of vibration exposure. The objective wakefulness levels of AAT were reduced at the post-exposure test in all subjects. In the case with exposure to whole-body vibration was a significant difference from the case without exposure to whole-body vibration. It is suggested that a short-term exposure to whole-body vibration may cause a reduction of wakefulness level.

Effect of impulse vibration on red blood cells in vitro.

OBJECTIVES: This study was carried out to evaluate the damage induced in red blood cells by exposure to impulse vibration. METHODS: The peak accelerations of impulse vibration included 50, 100, 200, 250 and 300 x 10(3) km/s2. A blood sample was put in a container filled with heparin so that there was no space inside. For each peak acceleration the exposure durations of 10, 20, and 30 minutes were used. The repetition rate of the impulses was 1 cycle per second (1 cycle/s). After the vibration exposure, the percentage of damaged red blood cells was calculated. Then the red blood cells were studied microscopically. RESULTS: Each vibration caused damage to red blood cells with all durations. The higher the peak acceleration and the longer the exposure duration, the more the damage to the red blood cells. Of the five impulse vibration levels with the three exposure durations, the largest damage was done by the vibration exposure with a peak acceleration of 300 km/s2 for 30 minutes with a mean value of 76.7% for the damaged cells, followed by the exposure with a peak acceleration of 300 km/s2 for 20 minutes with 55.5% of the cells being damaged. For exposure for 20 and 30 minutes, the vibration with peak accelerations of higher than 200 km/s2 provoked damage to red blood cells out of proportion to those with peak accelerations lower than 200 km/s2. CONCLUSIONS: Impulse vibration was shown in vitro to cause damage to red blood cells. It is suggested that the damage of red blood cells depends on both the peak acceleration and exposure duration of impulse vibration.

Significance of finger coldness in hand-arm vibration syndrome.

OBJECTIVES: To evaluate the relationship between subjective symptoms of coldness in fingers and peripheral circulation in patients with hand-arm vibration syndrome (HAVS). METHODS: Thirty-five male patients confirmed to have HAVS as an occupational disease took part in this study. Their mean age was 62 years (SD 5) and all were chain-saw operators exposed to vibration for an average of 25 years. Their annual health examination included the history of their daily habits (smoking, drinking, and therapeutic exercise), report of subjective symptoms such as coldness, numbness and tingling in the fingers, and a physical examination; laboratory tests consisted of skin temperature measurement, and pain and vibration perception under conditions of cold provocation. A frequently used method of cold provocation, immersion of the left hand up to the wrist in water of 10°C for 10 min, was used. RESULTS: Finger coldness was classified into 3 groups according to its severity: mild group (n=8), moderate group (n=17) and severe group (n=10). There was no significant difference in age or occupational background between the groups. A significant association was found between finger coldness and prevalence of Raynaud's pheno menon (p<001, χ(2)). The mean skin temperature was significantly lower with the severity of finger coldness (ANOVA, p<0.05). In the cold provocation test, there was no significant difference between skin temperature and coldness at 5 min and 10 min after immersion, though a difference was observed immediately after immersion. No significant difference was observed in the relationship between finger coldness and vibrotactile threshold before, during or after the cold provocation test. CONCLUSIONS: The severity of coldness in the fingers is significantly related to skin temperature. The severity of finger coldness reflects the extent of peripheral circulatory vasoconstriction. Coldness in the fingers may be a good warning of potential problems in peripheral, circulatory function.

Dependence of palmar sweating response and central nervous system activity on the frequency of whole-body vibration.

OBJECTIVES: This study was carried out to determine the effects of the frequency of whole-body vibration on palmar sweating response and the activity of the central sympathetic nervous system. METHODS: Palmar sweating volume was measured on the right palm of six healthy men before and during 3 minutes of exposure to sinusoidal whole-body vibration at three different frequencies (16, 31.5, and 63 Hz). The whole-body vibration had a frequency-weighted, root mean square (rms) acceleration magnitude of 2.0 m/s2. As the index of the activated central sympathetic nervous system, saliva level of 3-methoxy-4-hydroxyphenylglycol (MHPG) was analyzed before and immediately after each vibration exposure. RESULTS: Each vibration frequency induced a palmar sweating response, that of 31.5 Hz being the largest. However, no significant difference was found between the three vibration conditions. Saliva MHPG increased in all the vibration exposures, and the largest change was observed at 31.5 Hz, the difference being significant. CONCLUSIONS: Acute exposure to whole-body vibration induced a palmar sweating response and activated the central sympathetic nervous system. The effects on the central nervous system were found to be dependent on the frequency of the vibration.