Investigating the role of c-Jun N-terminal kinases in the proliferation of Werner syndrome fibroblasts using diaminopyridine inhibitors

To develop more potent small molecules with enhanced free radical scavenger properties, a series of N-substituted isatin derivatives was synthesized, and the cytoprotective effect on the apoptosis of PC12 cells induced by H₂O₂ was screened. All these compounds were found to be active, and N-ethyl isatin was found with the most potent activity of 69.7% protective effect on PC12 cells. Structure-activity relationship analyses showed the bioactivity of N-alkyl isatins decline as the increasing of the chain of the alkyl group, furthermore odd-even effect was found in the activity, which is interesting for further investigation.     

New substantially fluorinated ionomers for electrochemical applications

Novel, substantially fluorinated ionomers based on vinylidene fluoride copolymers deliver attractive properties for lithium ion battery applications. This ionomer family exhibits excellent compatibility with electrode components, high affinity for carbonate solvents, flexibility in fabrication methods, and good ionic conductivity of solvent-swollen gel films. Controlled feed of microfluidized liquid sulfonyl fluoride comonomer allows for the production of random and compositionally tapered copolymers exhibiting features of block or graft-block structures. Post-polymerization functional group transformations include sulfonate salt and sulfonyl dicyanomethide salt formation as key processes for making ionomers having high ionic conductivity. Single-crystal X-ray structure analyses of model systems CF₃SO₃Li and LiPF₆, in the form of discrete solvates, provide a unifying view of lithium ion coordination in these systems.     

H-transfer rates in ion-neutral complexes versus those in intact aliphatic ions

The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd.     

Contributions of spin-spin interactions to the magnetic field dependence of the triplet quantum yield in photosynthetic reaction centers

Calculations are presented which show that dipolar coupling in the primary radical ion pair of quinone-depleted photosynthetic reaction centers substanually affects the magnetic field dependence of the triplet quantum yield, as does exchange coupling to the semiquinone-Fe(II) complex, when quinone is present. Inclusion of these interactions resolves significant discrepancies between theory and experiment.     

Effect of pH waves on capacitive charging in microfluidic flow channels

Novel energy-efficient desalination techniques, such as capacitive deionization (CDI), are a key element for the future of the fresh water supply, which is increasingly under stress due to the ever-growing world population and ongoing climate changes. CDI is a desalination technique where salt ions are removed from a flow channel by the application of an electrical potential difference across this channel and are stored in electrical double layers. The aim of this work is to visualize and explain the charging process of CDI using a new microfluidic approach. Namely, we implement the geometry of CDI on a chip and visualize the ion distributions in the channel using fluorescence microscopy. In contrast to normal CDI, our system was operated in the absence of flow, using non-porous electrodes. By using two pH-sensitive fluorescence dyes, we found the formation of pH waves across the channel, even though the system is operated at low potential differences in order to suppress Faradaic reactions, such as water splitting. From simulations of the transport process, we found that a small current density in the order of 0.1 A m^?2 can trigger the formation of such pH waves. CDI generally benefits from large electrode areas relative to the channel cross section. However, this large area ratio will also increase the magnitude of these waves, which might lead to a reduction in desalination efficiency.     

Disentangling the effects of phonation and articulation: Hemispheric asymmetries in the auditory N1m response of the human brain

Background  

The cortical activity underlying the perception of vowel identity has typically been addressed by manipulating the first and second formant frequency (F1 & F2) of the speech stimuli. These two values, originating from articulation, are already sufficient for the phonetic characterization of vowel category. In the present study, we investigated how the spectral cues caused by articulation are reflected in cortical speech processing when combined with phonation, the other major part of speech production manifested as the fundamental frequency (F0) and its harmonic integer multiples. To study the combined effects of articulation and phonation we presented vowels with either high (/a/) or low (/u/) formant frequencies which were driven by three different types of excitation: a natural periodic pulseform reflecting the vibration of the vocal folds, an aperiodic noise excitation, or a tonal waveform. The auditory N1m response was recorded with whole-head magnetoencephalography (MEG) from ten human subjects in order to resolve whether brain events reflecting articulation and phonation are specific to the left or right hemisphere of the human brain.     

Structural phase transition on W and Mo surfaces

The microscopic driving mechanisms for the structural phase transition on W(001) and Mo(001) surfaces are discussed. It is argued that the coherence length is short for these systems and an effective lattice dynamic Hamiltonian is appropriate for the study of these transitions. The Migdal renormalization scheme is applied to a simple model Hamiltonian and the overall phase diagram in the temperature-anisotropy field plane is obtained.