[Ulcerative colitis diagnosed with facial pyoderma gangrenosum: a case report].

Pyoderma gangrenosum (PG) is a sterile inflammatory skin condition that is frequently associated with immune-related diseases, including inflammatory bowel disease (IBD). PG causes noninfectious ulcers. Facial PG is uncommon while PG usually occurs on the trunk and lower limbs. Herein, we report a case of a male teenager with fever, pustules, ulcers, and necrosis on both cheeks. He was initially diagnosed with complicated acne with bacterial infection, but the condition progressed to subcutaneous ulcers despite treatment. Biopsy revealed inflammatory lesions in dermal and subcutaneous tissue with neutrophil infiltration, consistent with PG. Although lacking typical IBD symptoms, blood tests revealed anemia and positive fecal occult blood. Sigmoidoscopy revealed inflammation, ulcers, and pseudopolyps in the colon and rectum, thereby diagnosing ulcerative colitis (UC). After treating PG and UC with prednisolone and skin grafts, golimumab was prescribed. The patient is now in remission. Necrotic tissue buildup can complicate closure in PG cases;this emphasizes the need for effective IBD treatment to facilitate procedures such as skin grafts.

Impact of the Solid Interface on Proton Conductivity in Nafion Thin Films.

Proton conductivity of polyelectrolytes in the interfacial region with a solid is key to the performance of polyelectrolyte-based fuel cells. The proton conductivity of Nafion thin films was examined as a function of the thickness along both directions, normal and parallel to the interface. Neutron reflectivity measurements revealed that a water-containing multilamellar structure was formed at the substrate interface. The presence of the interfacial layer, or the two-dimensional proton-conductive pathway, suppressed and enhanced the out-of-plane and in-plane proton conductivities, respectively. The method of proton conductivity in the interfacial region differed from that in the bulk, namely, the Grotthuss mechanism. Using laminated films, we conclude by showing that the proton conductivity in the Nafion thin film changes on the basis of the interface-to-volume ratio. This knowledge will be helpful for the design of devices containing polyelectrolytes with solid materials.

Solvent Dependence of Double Proton Transfer in the Formic Acid-Formamidine Complex: Path Integral Molecular Dynamics Investigation.

Solvent dependence of double proton transfer in the formic acid-formamidine (FA-FN) complex at room temperature was investigated by means of ab initio path integral molecular dynamics (AIPIMD) simulation with taking nuclear quantum and thermal effects into account. The conductor-like screening model (COSMO) was applied for solvent effect. In comparison with gas phase, double proton delocalization between two heavy atoms (O and N) in FA-FN were observed with reduced proton transfer barrier height in low dielectric constant medium (<4.8). For dielectric constant medium at 4.8, the chance of finding these two protons are more pronounced due to the solvent effect which completely washes out the proton transfer barrier. In the case of higher dielectric constant medium (>4.8), the ionic species becomes more stable than the neutral ones and the formate anion and formamidium cation are thermodynamically stable. For ab initio molecular dynamics simulation, in low dielectric constant medium (<4.8) a reduction of proton transfer barrier with solvent effect is found to be less pronounced than the AIPIMD due to the absence of nuclear quantum effect. Moreover, the motions of FA-FN complex are significantly different with increasing dielectric constant medium. Such a difference is revealed in detail by the principal component analysis.

Substituent-dependent backward reaction in mechanofluorochromism of dibenzoylmethanatoboron difluoride derivatives.

The thermally backward reaction involved in the mechanofluorochromism of dibenzoylmethanatoboron difluoride (BF2DBM) derivatives, accompanied by an amorphous-crystalline phase transition, was quantitatively evaluated based on kinetics and thermodynamics. The kinetics was discussed by evaluation of the effect of temperature on the time-dependent changes of the fluorescence intensity for amorphous samples obtained by mechanical grinding. The thermodynamics was discussed based on data for the amorphous-crystalline phase transition obtained by differential scanning calorimetry. The enthalpy of activation (ΔH(‡)) of BF2DBM derivatives with MeO groups (2aBF2) was larger than that of derivatives with alkyl groups (2b-dBF2), whereas the entropy of activation (ΔS(‡)) was smaller than that of the derivatives with alkyl groups. It is proposed that the reaction dynamics of 2aBF2 will be governed by rotational motion around the C(methyl)-O bond. Interestingly, the Gibbs energies of activation (ΔG(‡)) were comparable for the reactions of all members of the BF2DBM series, though ΔH(‡) and ΔS(‡) were strongly dependent on the identity of the substituent. It is proposed that the substituent-dependent ΔS(‡) term is one of the key parameters for understanding the mechanofluorochromism of BF2DBM derivatives associated with the amorphous-crystalline phase transition. These findings will also provide important insights into the process of formation of crystal nuclei in moving from the melted to the crystalline state.

The Impact of Polymer Dynamics on Photoinduced Carrier Formation in Films of Semiconducting Polymers.

A better understanding of the carrier formation process in photosemiconducting polymers is crucial to design and construct highly functionalized thin film organic photodevices. Almost all studies published focus on the effect of structure on the photoinduced carrier formation process. Here, we study the dynamics of polymer chain impacts on the carrier formation process for a series of poly(3-alkylthiophene)s (P3ATs) with different alkyl side-chain lengths. The formation of polarons (P) from polaron pairs (PP) was accelerated at a temperature at which the twisting motion of thiophene rings occurs. Among all P3ATs employed, in P3AT with hexyl groups, or poly(3-hexylthiophene) (P3HT), it was easiest to twist the thiophene rings and generate P from PP. The activation energy for P formation was proportional to that of thiophene ring motion. This makes it clear that chain dynamics, in addition to the crystalline structure, is a controlling factor for the carrier formation process in photosemiconducting polymers.

Theoretical vibrational spectra of OH(-)(H2O)2: the effect of quantum distribution and vibrational coupling.

We performed ab initio path integral molecular dynamics simulations for the hydroxide-water cluster, OH(-)(H2O)2, at 50 K, 100 K, and 150 K to investigate its flexible structure. From our simulations, we found that nuclear quantum effects enhance hydroxide hydrogen atom inversion and the conformational change between isomers occurs by simultaneous rotation of the free hydrogen atom. We propose the importance of including the transition state conformer with C2 symmetry, for the description of this system at temperatures realized in predissociation experiments. Temperature dependence of relative populations of each conformer along with multidimensional vibrational calculations were used to simulate the vibrational spectra and compare with the experimental spectra of Johnson and coworkers. We assign the doublet peaks seen in the experiment at 2500 to 3000 cm(-1), as the mixture of the ionic hydrogen bonded OH stretching overtone, ionic hydrogen bonded OH bending overtone, and the combination band of the ionic hydrogen bonded OH stretch and bend, which are modulated by the van der Waals OO vibrations. We concluded that for OH(-)(H2O)2, the vibrational couplings between the ionic hydrogen bonded motion and floppy modes contribute to the broadening of peaks observed in the 2500 to 3000 cm(-1) region.

An effect of molecular motion on carrier formation in a poly(3-hexylthiophene) film.

Free carriers, polarons (P), in conjugated polymers play a key role in the performance of optoelectronic devices. Here, we present solid evidence that P can be predominantly generated from polaron pairs (PP) in a poly(3-hexylthiophene) (P3HT) film under zero electric field. P formation from PP strongly depends on temperature. The temperature dependence of P starts to change around 300 K. P3HT exhibits a thermal molecular motion named the α1 relaxation process, in which the twisting motion of thiophene rings is released, in this temperature region. Thus, it can be claimed that the twisting motion of P3HT thiophene rings is one of the determining factors of the photodynamics of P in P3HT films. This finding holds true for poly(thiophene)s with different alkyl lengths and should be considered in the design and construction of highly-functionalized organic devices based on poly(thiophene)s.

Multistep Thickening of Nafion Thin Films in Water.

Water sorption kinetics in thin Nafion films prepared on silver and silicon oxide substrates was examined by surface plasmon resonance and neutron reflectivity measurements. It was found that the films thickened in three regimes. The asymptotic swelling ratios in regimes I, II, and III were 1.05, 1.26, and 1.41, respectively. These values were independent of the substrate species and were coincident with the transition points of different hydration states in the bulk Nafion; water binding to sulfonic acid groups, the formation of sphere-like ionic clusters, and bridge formation between clusters. The swelling was much slower in thin films than in the bulk due to the mobility restriction of Nafion near the substrate.