New Insights into the Charge-Transfer-to-Solvent Spectrum of Aqueous Iodide: Surface versus Bulk.

Liquid phase charge-transfer-to-solvent (CTTS) transitions are important, as they serve as photochemical routes to solvated electrons. In this work, broadband deep-ultraviolet electronic sum frequency generation (DUV-ESFG) and two-photon absorption (2PA) spectroscopic techniques were used to assign and compare the nature of the aqueous iodide CTTS excitations at the air/water interface and in bulk solution. In the one-photon absorption (1PA) spectrum, excitation to the 6s Rydberg-like orbital (5p → 6s) gives rise to a pair of spin-orbit split iodine states, 2P3/2 and 2P1/2. In the 2PA spectra, the lower-energy 2P3/2 peak is absent and the observed 2PA peak, which is ∼0.14 eV blue-shifted relative to the upper 2P1/2 CTTS peak seen in 1PA, arises from 5p → 6p electronic promotion. The band observed in the ESFG spectrum is attributed to mixing of excited states involving 5p → 6p and 5p → 6s promotions caused by both vibronic coupling and the external electric field generated by asymmetric interfacial solvation

Faktor kritičnog intenziteta naprezanja (I. mod) MDF ploča dobiven testom savijanja

The Mode I critical stress intensity factor (KIc) obtained by single-edge-notched bending (SENB) tests of medium-density fiberboard (MDF) was experimentally analyzed. In the SENB test, the critical load for crack propagation (Pc) was determined from the relationship between load/loading-line displacement and load/crack opening displacement (COD). A double cantilever beam (DCB) test was also conducted and the results were compared with those of SENB tests. The value of Mode I critical stress intensity factor was obtained by introducing an additional crack length, when the crack length ranged from 0.5 to 0.7 times the depth of the specimen. This range coincided well with that used to derive the appropriate KIc value in the single-edge-notched tension (SENT) test, which was conducted using the specimens with a similar confi guration cut from the MDF panel used in this study.U radu se eksperimentalno analizira faktor kritičnog intenziteta naprezanja (I. mod) (KIc ) dobiven testom savijanja s jednim rubnim urezom (SENB) za ploče vlaknatice srednje gustoće (MDF ploče). U SENB testu kritično opterećenje za širenje pukotine (Pc ) određeno je iz odnosa opterećenja i linije pomaka te iz odnosa opterećenja i širenja pukotine (COD). Proveden je i dvostruki konzolni test (DCB), a rezultati su uspoređeni s rezultatima SENB testova. Vrijednost faktora kritičnog intenziteta naprezanja (I. mod) dobiven je uvođenjem dodatne duljine pukotine kada je duljina pukotine u rasponu od 0,5 do 0,7 debljine uzorka. Taj se raspon podudario s rasponom koji se koristi za dobivanje odgovarajuće KIC vrijednosti u tenzijskom testu s jednim rubnim urezom (SENT), a proveden je na uzorcima slične konfi guracije izrađenima od MDF ploče koja je upotrijebljena i u ovom istraživanju

Saturable Absorption of Free-Electron Laser Radiation by Graphite near the Carbon K-Edge

The interaction of intense light with matter gives rise to competing nonlinear responses that can dynamically change material properties. Prominent examples are saturable absorption (SA) and two-photon absorption (TPA), which dynamically increase and decrease the transmission of a sample depending on pulse intensity, respectively. The availability of intense soft X-ray pulses from free-electron lasers (FELs) has led to observations of SA and TPA in separate experiments, leaving open questions about the possible interplay between and relative strength of the two phenomena. Here, we systematically study both phenomena in one experiment by exposing graphite films to soft X-ray FEL pulses of varying intensity. By applying real-time electronic structure calculations, we find that for lower intensities the nonlinear contribution to the absorption is dominated by SA attributed to ground-state depletion; our model suggests that TPA becomes more dominant for larger intensities (\u3e1014 W/cm2). Our results demonstrate an approach of general utility for interpreting FEL spectroscopies

Demonstration of a Light-Driven SO42- Transporter and Its Spectroscopic Characteristics.

In organisms, ion transporters play essential roles in the generation and dissipation of ion gradients across cell membranes. Microbial rhodopsins selectively transport cognate ions using solar energy, in which the substrate ions identified to date have been confined to monovalent ions such as H+, Na+, and Cl-. Here we report a novel rhodopsin from the cyanobacterium Synechocystis sp. PCC 7509, which inwardly transports a polyatomic divalent sulfate ion, SO42-, with changes of its spectroscopic properties in both unphotolyzed and photolyzed states. Upon illumination, cells expressing the novel rhodopsin, named Synechocystis halorhodopsin (SyHR), showed alkalization of the medium only in the presence of Cl- or SO42-. That alkalization signal was enhanced by addition of a protonophore, indicating an inward transport of Cl- and SO42- with a subsequent secondary inward H+ movement across the membrane. The anion binding to SyHR was suggested by absorption spectral shifts from 542 to 536 nm for Cl- and from 542 to 556 nm for SO42-, and the affinities of Cl- and SO42- were estimated as 0.112 and 5.81 mM, respectively. We then performed time-resolved spectroscopic measurements ranging from femtosecond to millisecond time domains to elucidate the structure and structural changes of SyHR during the photoreaction. Based on the results, we propose a photocycle model for SyHR in the absence or presence of substrate ions with the timing of their uptake and release. Thus, we demonstrate SyHR as the first light-driven polyatomic divalent anion (SO42-) transporter and report its spectroscopic characteristics

EGUIDE project and treatment guidelines

Aim: Although treatment guidelines for pharmacological therapy for schizophrenia and major depressive disorder have been issued by the Japanese Societies of Neuropsychopharmacology and Mood Disorders, these guidelines have not been well applied by psychiatrists throughout the nation. To address this issue, we developed the ‘Effectiveness of Guidelines for Dissemination and Education in Psychiatric Treatment (EGUIDE)’ integrated education programs for psychiatrists to disseminate the clinical guidelines. Additionally, we conducted a systematic efficacy evaluation of the programs. Methods: Four hundred thirteen out of 461 psychiatrists attended two 1‐day educational programs based on the treatment guidelines for schizophrenia and major depressive disorder from October 2016 to March 2018. We measured the participants’ clinical knowledge of the treatment guidelines using self‐completed questionnaires administered before and after the program to assess the effectiveness of the programs for improving knowledge. We also examined the relation between the participants’ demographics and their clinical knowledge scores. Results: The clinical knowledge scores for both guidelines were significantly improved after the program. There was no correlation between clinical knowledge and participant demographics for the program on schizophrenia; however, a weak positive correlation was found between clinical knowledge and the years of professional experience for the program on major depressive disorder. Conclusion: Our results provide evidence that educational programs on the clinical practices recommended in guidelines for schizophrenia and major depressive disorder might effectively improve participants’ clinical knowledge of the guidelines. These data are encouraging to facilitate the standardization of clinical practices for psychiatric disorders

New Advances in Spectroscopy: Applications to Aqueous Interfaces and Liquid Carbon

This dissertation comprises two major projects. The first is the study of ions and molecules at the air/water interface using second-order nonlinear spectroscopy to measure interfacial electronic |χ(2)|2-spectra. The second is the investigation of the liquid state of carbon using time-resolved soft X-ray free electron laser spectroscopy.The nature of ions and molecules at and near aqueous interfaces is central in many chemical systems including atmospheric chemistry, electrochemistry, and biochemistry, but remains incompletely understood. Contrary to widely held earlier views, recent studies have unambiguously shown that some ions adsorb strongly to the air/water interface, with compelling evidence for enhanced surface concentrations of larger, more polarizable, weakly solvated anions. While the mechanism of selective ion adsorption has been shown to correlate strongly with ionic radii and hydration properties, considerable debate remains. In this dissertation, I describe the development and application of femtosecond broadband deep ultraviolet electronic sum frequency generation (DUV-ESFG) spectroscopy which allows quantitative analysis of peak positions, linewidths, and relative intensities that can be directly compared with theoretical calculations to yield new insights into the nature of ions and molecules at aqueous interfaces. Under the electric dipole approximation, the second-order nonlinear susceptibility vanishes in centrosymmetric media, and SFG spectroscopy is a surface-sensitive probe with a probe depth of ca. 1 nm, corresponding to a few outermost monolayers. In Chapter 2, I present the interfacial charge-transfer-to-solvent spectrum of thiocyanate (SCN−), a prototypical chaotropic anion, and discuss selection rules and salient differences between interfacial and bulk solvation that contribute to the observed spectral differences. In Chapter 3, we investigate the lowest energy charge-transfer-to-solvent bands of aqueous iodide using broadband DUV-ESFG and two-photon absorption spectroscopy and assign the observed transitions using atomic selection rules within a Rydberg transition model based on the jj-coupling limit. We find that DUV-ESFG signal at the air/water interface arises from symmetry breaking and solute-solvent vibronic coupling effects that relax the selection rules. In Chapter 4, we revisit the π→π* transition of the nitrite ion at the air/water interface and, together with MD simulations and electronic structure calculations, find no evidence of a previously reported contact ion pair induced redshift and strongly favorable bimolecular adsorption mechanism. However, the presence of a distribution of local solvation environments at the interface, including solvent separated ion pairs, solvent shared ion pairs, contact ion pairs, and small ion clusters is not ruled out. In Chapter 5, I present the |χ(2)|2-spectra of phenol at the air/water interface in the deep UV (5.4-6.3 eV) and find an apparent redshift of the electronic transitions relative to the bulk aqueous spectrum. MD simulations and electronic structure calculations suggest stabilization of the excited states due to the highly specific hydration structure effected at the interface. Additional work is ongoing to elucidate the role of selection rules and solvent environment on the observed spectral differences. In Chapter 6, I discuss my efforts to attempt heterodyne-detected DUV-ESFG spectroscopy and future directions, including incorporating a flat-jet that would enable measurements at low concentrations and liquid/liquid interfaces. The liquid state of carbon is of fundamental chemical significance and has potential practical applications, but it remains very poorly characterized. For example, studies suggest that carbon nanotubes and Q-carbon are formed through liquid intermediates. Moreover, novel carbon materials and routes for synthesizing them are of great interest, as some proposed carbon allotropes may have exciting new properties for technological applications, and better understanding of the liquid properties may suggest new routes for synthesizing them. In this dissertation, I present our recent efforts to characterize liquid carbon using pump-probe soft X-ray free electron laser spectroscopy at the carbon K-edge. In Chapter 7, I detail time-resolved resonant inelastic X-ray scattering (tr-RIXS) and X-ray emission spectra (tr-XES) of non-thermally melted carbon films measured at the Pohang Accelerator Laboratory X-ray Free Electron Laser in South Korea. An initial decrease in tr-RIXS signal intensity at short delay times was observed, corresponding to a decrease in the absorption cross-section of sp2-hybridized carbon atoms as structural reorganization occurs to form liquid carbon. Additional theoretical work is ongoing to further elucidate the dynamics of the melting and ablation processes. In Chapter 8, I present and discuss our recent attempts to demonstrate optical & soft X-ray sum frequency generation spectroscopy at the carbon K-edge, building upon soft X-ray second harmonic generation spectroscopy demonstrated by our group at FERMI in Italy

Multidynamic Crystalline Molecular Rotors Comprising an N-Heterocyclic Carbene Binuclear Au(I) Complex Bearing Multiple Rotators

We report multidynamic molecular rotations in crystals using a concave-shape N-heterocyclic carbene (NHC) binuclear Au(I) complex rotor bearing pyrazine and tetrahydrofuran (THF) molecules as multicomponent rotators. Single-crystal X-ray diffraction (XRD) measurements revealed that two THF molecules are located near the central pyrazine encapsulated by two bulky NHC ligands. From H-2 solid-state NMR analysis, it was observed that the pyrazine rotated in a 2-fold site exchange with a 180 degrees rotational angle and a 31 kJ mol(-1) energy barrier, while the THF molecules showed a 23 degrees-38 degrees libration with a lower energy barrier (14 kJ mol(-1)). Interestingly, the pyrazine rotation was accelerated when the THF molecules rotated in fast site exchange with a large angle of libration, suggesting that the rotators exhibit multidynamics in a correlated manner

Charge-Transfer-to-Solvent Spectrum of Thiocyanate at the Air/Water Interface Measured by Broadband Deep Ultraviolet Electronic Sum Frequency Generation Spectroscopy.

Measurement of interfacial electronic spectra is a powerful tool for characterizing the properties of ions in physical, biological, environmental, and industrial systems. Here, we describe measurement of the complete charge-transfer-to-solvent (CTTS) spectrum of thiocyanate at the air/water interface using our recently developed femtosecond broadband deep ultraviolet electronic sum frequency generation technique. We find that the lower energy CTTS band characterized in bulk thiocyanate spectra is not observed in the | χ(2)|2-power spectrum of the air/water interface, likely reflecting the different solvation environments, altering of the charge distribution of the ion, and possible ion-ion effects, and that sodium and potassium salts yield identical spectra. Additional experiments and comparison with theoretical calculations are necessary to extract the interesting chemical details responsible for these salient spectral differences