18 research outputs found
Time- and Angle-Resolved Photoemission Spectroscopy of Hydrated Electrons Near a Liquid Water Surface
世界で初めて、溶液反応の超高速時間・角度分解光電子分光に成功 --溶液化学反応の機構解明に前進--. 京都大学プレスリリース. 2014-04-22.We present time- and angle-resolved photoemission spectroscopy of trapped electrons near liquid surfaces. Photoemission from the ground state of a hydrated electron at 260 nm is found to be isotropic, while anisotropic photoemission is observed for the excited states of 1, 4-diazabicyclo[2, 2, 2]octane and I− in aqueous solutions. Our results indicate that surface and subsurface species create hydrated electrons in the bulk side. No signature of a surface-bound electron has been observed
Cultivable fungal endophytes in roots, rhizomes and leaves of Posidonia oceanica (L.) Delile along the Coast of Sicily, Italy
The presence of endophytic fungi in the roots, rhizomes, and leaves of Posidonia oceanica was evaluated in different localities of the Sicilian coast. Samples of roots, rhizomes, and leaves were
submitted to isolation techniques, and the obtained fungal colonies were identified by morphological and molecular (rRNA sequencing) analysis. Fungal endophytes occurred mainly in roots and
occasionally in rhizomes and leaves. Lulwoana sp. was the most frequent of the isolated taxa, suggesting a strong interaction with the host. In addition, eight other fungal taxa were isolated.
In particular, fungi of the genus Ochroconis and family Xylariaceae were identified as endophytes in healthy plants at all sampling stations, whereas Penicillium glabrum was isolated at only one
sampling station. Thus, several organs, especially roots of Posidonia oceanica, harbor endophytic fungi, potentially involved in supporting the living host as ascertained for terrestrial plants
Diazonium-based anchoring of PEDOT on Pt/Ir electrodes via diazonium chemistry
Conducting polymers, specifically poly (3,4-ethylenedioxythiophene) (PEDOT), have recently been coated onto Pt/Ir electrodes intended for neural applications, such as deep brain stimulation (DBS). This modification reduces impedance, increases biocompatibility, and increases electrochemically active surface area. However, direct electropolymerization of PEDOT onto a metallic surface results in physically adsorbed films that suffer from poor adhesion, precluding their use in applications requiring in vivo functionality (i.e. DBS treatment). In this work, we propose a new attachment strategy, whereby PEDOT is covalently attached to an electrode surface through an intermediate phenylthiophene layer, deposited by electrochemical reduction of a diazonium salt. Our electrodes retain their electrochemical performance after more than 1000 redox cycles, whereas physically adsorbed films begin to delaminate after only 40 cycles. Additionally, covalently attached PEDOT maintained strong adhesion even after 10 minutes of ultrasonication
(vs. 10 s for physically adsorbed films), confirming its suitability for long-term implantation in the brain. The simple two-step covalent attachment strategy proposed here is particularly useful for neural applications and could also be adapted to introduce other functionalities on the conducting surface
Tracking the stilbene photoisomerization in the S1 state using RASSCF
International audienc
Ab initio Investigation to Model Stilbene Photo-Physical Properties by Combining CC2 Topological Investigation and CASPT2 Energy Corrections
Stilbene photoexcitation and consequent decay to the ground state has been investigated by mapping the Minimum Energy Path (MEP) from S1 spectroscopic state triggering an almost barrierless reaction pathway to an S1/S0 degenerate region. The particular influence of the σ‐π excitation on the S1 wave function, dominated by a π→π* character, reveals how the non‐dynamical correlation energy was important to correctly describe the excited state behaviour and the topological aspect of its potential energy surface. Several strategies of calculations, by using CASSCF//CASPT2 methods, were performed trying to improve the photochemical description nowadays known. Both symmetry and non symmetry preserving computations were performed; systematically was concluded that, because of the limit of CASSCF description enables only to introduce the correlation effect such as the ones due to σ‐π excitations, CASSCF and CASPT2 topologies are probably often not in agreement. Thus CC2 methodology was adopted o optimize the S1 geometries and obtain reasonable structures for the minima. Two S1/S0 accessible conical intersections featured by pyramidalized carbons were located on the first excited state explaining the ultrafast radiationless decay to the ground state and the photoproducts observed within the timescale of ps
What do Diana monkeys know about the focus of attention of a conspecific?
Converging experimental and observational evidence suggests that some non-human primates are able to co-orient with shifts in visual attention, both of conspecifics and humans. However, the underlying cognitive mechanisms involved are unclear. To investigate attention-following in Diana monkeys (Cercopithecus diana diana), we used photographs of familiar conspecifics orienting towards one of two locations. A subject monkey was shown a photograph, and shortly afterwards a toy appeared at one location or the other. The toy’s position therefore either matched the location signalled by the head and body orientation of the photographed monkey (compatible), or was opposite to that location (incompatible). Overall, monkeys’ first inspections, total duration of looking, and number of looks were more likely to be directed to the compatible location, i.e. towards the direction of attention shown in the photograph. Furthermore, when a photograph of an adult monkey signalled attention to one location, but the toy appeared at the opposite (incompatible) location, subjects re-inspected the monkey photographs more often than when the toy appeared at the compatible location, suggesting a violation of expectancy. This effect was not the case if the photograph was of an immature animal. Our results show that attention-following was not limited to simple reflexive orienting by the monkeys, and that monkeys perceived a relationship existing between agent and object of attention.Postprin
Photodynamics of Free and Solvated Tyrosine
We present a theoretical simulation of the ultrafast
nonadiabatic
photodynamics of tyrosine in the gas phase and in water. For this
purpose, we combine our TDDFT/MM nonadiabatic dynamics (Wohlgemuth
et al. <i>J. Chem. Phys.</i> <b>2011</b>, <i>135</i>, 054105) with the field-induced surface hopping method
(Mitrić et al. <i>Phys. Rev. A</i> <b>2009</b>, <i>79</i>, 053416) allowing us to explicitly include
the nonadiabatic effects as well as femtosecond laser excitation into
the simulation. Our results reveal an ultrafast deactivation of the
initially excited bright ππ* state by internal conversion
to a dark <i>n</i>π* state. We observe deactivation
channels along the O–H stretching coordinate as well as involving
the N–H bond cleavage of the amino group followed by proton
transfer to the phenol ring, which is in agreement with previous static
energy path calculations. However, since in the gas phase the canonical
form of tyrosine is the most stable one, the proton transfer proceeds
in two steps, starting from the carboxyl group that first passes its
proton to the amino group, from where it finally moves to the phenol
ring. Furthermore, we also investigate the influence of water on the
relaxation processes. For the system of tyrosine with three explicit
water molecules solvating the amino group, embedded in a classical
water sphere, we also observe a relaxation channel involving proton
transfer to the phenol ring. However, in aqueous environment, a water
molecule near the protonated amino group of tyrosine acts as a mediator
for the proton transfer, underlining the importance of the solvent
in nonradiative relaxation processes of amino acids
Retinal Photoisomerization in Rhodopsin: Electrostatic and Steric Catalysis
Excited state QM(CASPT2//CASSCF)/MM(GAFF) calculations, by our recently developed code COBRAMM (Computations at Bologna Relating Ab\u2010initio and Molecular Mechanic Methods), were carried out in rhodopsin to investigate on the steric and electrostatic effects in retinal photoisomerization catalysis due to the \u3b2\u2010ionone ring and glutammate 181 (GLU 181), respectively. The excited state photoisomerization channel has been mapped and a new christallographyc structure (2.2 \uc5 resolution) has been used for this purpose. Two different set\u2010ups have been used to evaluate the electrostatic effects of GLU 181 (which is very close to the central double bond of the chromophore): the first with a neutral GLU 181 (as commonly accepted), the second with a negatively charged (i.e. deprotonated) GLU 181 (as very recent experimental findings seem to suggest). On the other hand, \u3b2\u2010ionone ring steric effects were evaluated by calculating the photoisomerization path of a modified chromophore, where the ring double bond has been saturated. Spectroscopic properties were calculated and compared with the available experimental data