Confocal Raman microscopy reveals changes in chemical composition of wood surfaces exposed to artificial weathering.

Weathering leads to rapid depolymerization and modification of wood chemical components. The present study aims to assess the structural and distributional changes in the main wood polymers, such as lignin and polysaccharides, located in the surface layers during weathering exposure. A confocal Raman microscopic technique, which is useful for evaluating the structure of molecules with a high spatial resolution, was utilized to examine the effects of weathering on the chemical composition of wood surfaces at the cellular level. Raman spectra showed that lignin degradation during weathering proceeds with the formation of o- and p-quinones, carbonyl groups, and certain types of CC double bonds such as stilbene derivatives. Comparing the weathering conditions between light only and light plus water exposure, it was found that weathering in the presence of water significantly enhances the degradation of lignin. The Raman images exhibited that the degree of lignin degradation by light only exposure is according to the depth. However, in the case of light plus water exposure, lignin degradation in the outermost cell walls proceeded from both the exposed surface side and the lumen side of the cell walls. This study is expected to potentially promote development of more effective and efficient methods to protect wood surfaces against weathering.

An ab initio and DFT study of trifluoromethylation using Umemoto's reagent.

Trifluoromethylation using Umemoto's reagent is an important transformation that allows the preparation of compounds bearing trifluoromethyl groups. To investigate the mechanism of this reaction, ab initio and density functional theory (DFT) calculations were carried out using pyrrole, aniline, sodium acetylacetonate, and sodium methyl acetoacetate as nucleophiles. At the highest level of theory examined (i.e., CCSD(T)/6-311+G(d,p)//M06-2X/6-311+G(d,p)), the energy barriers for the forward process (ΔE‡1) of both the backside and frontside attack of pyrrole on a model Umemoto reagent (i.e., S-(trifluoromethyl)dimethylsulfonium, CF3DMS) were predicted to be 135.9 and 192.3 kJ mol-1, respectively, while values of 131.9 and 188.2 kJ mol-1 were obtained at the MP2/6-311+G(d,p)//M06-2X/6-31+G(d,p) level. These outcomes suggest that the reaction proceeds via the backside mechanism. Using the MP2 method, the investigation of the trifluoromethylation of pyrrole and sodium acetoacetate with the sulfonium moiety of Umemoto's reagent, S-(trifluoromethyl)dibenzothionium, revealed that this reaction would also occur through the backside mechanism, thereby indicating that this pathway remains feasible despite solvent effects. Finally, computational investigations revealed that the simple single-electron transfer mechanism, which should occur between Umemoto's reagent and nucleophiles, did not take place during this reaction.

Allodynia corresponding to the levels of cervical cord injury treated by surgical decompression: a report of 3 cases.

BACKGROUND: The role and timing of surgical decompression for SCI remains controversial, when the surgical outcomes are evaluated only by neurologic recovery. Other than neurologic deficits, severe pain after SCI is a significant problem, deteriorating the patient's activity of daily living. In the present report, allodynia of patients' upper limbs caused by cervical SCI was treated successfully by surgical decompression. CASE DESCRIPTIONS: Three male patients received cervical SCI through minor accidents. They complained of allodynia and motor dysfunction at the spinal level compressed by preexisting lower cervical spondylosis, but they lacked symptoms or neurologic abnormalities below that spinal level. Severe pain was induced by soft touch or exposure to water at room temperature preoperatively. Surgical decompressions of the spinal cord and nerve roots were performed between 20 and 83 days (mean, 48.7 days) after the SCI. Allodynia was reduced in all patients immediately after surgery. Pain induced by soft touch disappeared within 4 days of operations, whereas pain by water exposure diminished within months. Recurrence of allodynia has not been observed in patients at least until the last follow-up, within periods ranging from 15 to 39 months (average, 26 months). The mean preoperative VAS was 6.0, and this improved to 2.2 at 1 month and 0.8 at the final follow-up. CONCLUSION: We propose that patients with SCI with allodynia and motor dysfunction of the upper limbs related only to the compressed spinal levels are potentially treatable by surgical decompression.