POLYAMINOACIDS AS BIOMATERIALS

This paper surveys the author's, investigations on block-, random-, and oligo-polyaminoacids as materials with potential towards their biomedical applications. Theoretical considerations are made on the formation of novel microheterophase structures as revealed by peptide-elastomer-peptide type block copolymers, and their mechanical and dynamic mechanical behaviors of the mem-     

Time resolved ESR study on energy difference of quartet and doublet states in radical-triplet encounter pairs

The energy difference J of quartet and doublet states in a radical-triplet pair (RTP) has been studied in pairs of triplet naphthalene (Np) derivative/galvinoxyl(Galv) and triplet biphenyl (Biph) derivative/Galv systems by time resolved ESR spectroscopy. Most of the systems studied show an unusual positive sign for J that corresponds to the relative location of the quartet state being below the doublet state. In order to explain this unusual sign of J in RTPs, the effects of intermolecular charge transfer (CT) states were examined. The observation was explained by introducing configuration interaction between zero-order RTP (RTP⁰) and CT (CT⁰) states in the encounter pair, where the RTP⁰ state is located above the CT⁰ state. Among the RTP systems examined, triplet 1-chloro-Np/Galv, triplet 1-bromo-Np/Galv and triplet 4-cyano-Biph/Galv systems show a normal negative value of J. On the basis of the estimated energy gap between the RTP⁰ and CT⁰ states, it was concluded that configuration interaction is not significant in these three RTP systems. The value of J in these RTP systems is dominated by exchange interaction, giving a negative sign. The solvent effect on the sign of J in a triplet Np/Galv system is also reported, as evidence that the sign of J is controlled by the CT⁰ state.     

Rational-slice Knots via Strongly Negative-amphicheiral Knots

We show that certain satellite knots of every strongly negative-amphicheiral rational knot are rational-slice knots. This proof also shows that the O-surgery manifold of a certain strongly negative amphicheiral knot such as the figure-eight knot bounds a compact oriented smooth 4-manifold homotopy equivalent to the 2-sphere such that a second homology class of the 4-manifold is represented by a smoothly embedded 2-sphere if and only if the modulo two reduction of it is zero.     

Effect of a Combined Exercise and Cognitive Activity Intervention on Cognitive Function in Community-dwelling Older Adults: A Pilot Randomized Controlled Trial

Objective: The purpose of this study is to investigate the effect of an intervention combining exercise and cognitive activity on cognitive function in healthy older adults. Methods: This pilot randomized controlled trial recruited 33 eligible, healthy communitydwelling older adults (mean age, 77.1 years old; women, 51.5%), who were divided into intervention and waitlist control groups. The intervention group was engaged weekly in a group activity comprising exercise and discussions of homework, which included reading aloud, simple arithmetic, and simple activities, like spotting differences, for cognitive stimulation. They were also required to complete cognitive activity homework twice a week. The waitlist control group received no intervention. The main outcomes were cognitive function assessed using the Mini-Mental State Examination, delayed recall score on the Logical Memory IIA of the Wechsler Memory Scale Revised, Trail Making Test, and digit symbol substitution test. Results: According to the results, Mini-Mental State Examination scores were maintained in the intervention group but declined in the control group [Mean change in outcomes in control group (95% confidence interval): -1.68 (-2.89 to -0.48)]. Additional mean change in outcomes in intervention group were found [1.68 (0.02 to 3.35)]. Conclusions: Interventions combining exercise and cognitive activity can be helpful for preserving cognitive function in healthy older adults.     

Magnetic field dependence of the deactivation rates of triplet azocumene in solution

The triplet sensitized photo-decomposition of azocumene into nitrogen and cumyl radicals is investigated by time resolved EPR and optical absorption spectroscopy. It is found that the cumyl radicals carry an initial spin polarization and are formed with a yield that depends on both the solution viscosity and the strength of an external magnetic field. The phenomenon is interpreted in terms of a depopulation-type triplet mechanism, i.e. a competition between decay into radicals and fast, triplet sublevel selective intersystem crossing (ISC) back to the azocumene ground state. Analysis of the data yields relative rate constants for the ISC processes and the cleavage reaction of triplet azocumene. The energetically lower zero field triplet substate is depopulated by ISC about seven times faster than the upper one and about two orders of magnitude faster than depopulation by cleavage occurs. Cleavage probably takes place on the nanosecond time scale, while the ISC must proceed on the picosecond scale, as at elevated viscosity it becomes faster than the rotational Brownian motion of the molecule.     

Hysteresis and ferroelectric liquid crystal displays

One cause of the hysteresis in the voltage-transmittance curve is polarization in the alignment layers brought about by the spontaneous polarization of FLC molecules. The hysteresis was reduced by increasing the conductivity of the alignment layers. The structural changes on switching were examined by measuring time-resolved shifts of FT-IR peaks of selected groups. The shifts of selected groups in the IR peak can be attributed to changes in the local dielectric constants of the ambient environment during switching by molecular orbital calculations. The orientation on switching in the SmC* phase was found to be similar to that in the N* phase.     

Solvent effects on the intrinsic enhancement factors of the triplet exciplex generated by photoinduced electron transfer reaction between eosin Y and duroquinone

The spin dynamics of the duroquinone anion radical (DQ^?-) generated by photoinduced electron transfer reactions from triplet eosin Y (³EY^2-) to DQ have been studied by using transient absorption and pulsed EPR spectroscopy. Unusual net-absorptive electron spin polarization plus net-emissive polarization were observed, suggesting the production of the triplet exciplex or contact radical pair as the reaction intermediate. The kinetic parameters and intrinsic enhancement factors of the electron spin polarization were determined in various alcoholic solvents. The net-absorptive electron spin polarization was also observed in ethanol-water mixed solvents. The solvent effects on the radical yield are analysed on the basis of a stochastic Liouville equation established for the magnetic field effects on the radical yield. The zero-field splitting constants of the triplet exciplex are estimated from the solvent viscosity dependence of the enhancement factors due to spin-orbit coupling induced depopulation of the reaction intermediate.     

Polymerization of Methyl Methacrylate with Samarocene Complex Supported on Mesoporous Silica

Synthesis of polymers with controlled molecular weight and narrow polydispersity is of both fundamental interest and practical importance. In recent years, high molecular weight poly (methyl methacrylate) (PMMA) having an unusually narrow polydispersity has been synthesized by using the unique initiating property of (C5Me5)2LnⅢR (R=H, Me, Ln=Sm, Yb) complexes1,2. Herein we report the results of the first example of the polymerization of methyl methacrylate (MMA) with samarocene complex …     

QUENCHING OF EXCITED TRIPLET LUMIFLAVIN BY LUMIFLAVIN RADICALS FORMED IN ITS T-T REACTION

Abstract— Reactions of the triplet state of lumiflavin (³LF) in water adjusted at pH 7.2 were reexamined by means of a Xe-flash photolysis and a laser photolysis. Measurements of the decay of ³LF were made on solutions of LF ranging in the concentration from 4 to 61 times 10^-6 mol/dm³. A one-electron reduced and a one-electron oxidized species of lumiflavin (LF^- and LF⁺) were produced in the first decay stage of ³LF with a high efficiency (0.6 ± 0.1) in a bimolecular triplet-triplet reaction. The product radicals (LFH^- and LF⁺) quench ³LF very efficiently (3 ± 0.8 × 10⁹ mol^-1dm³ s^-1) compared with LF in the ground state (> 2 × 10⁷ dm³ mol^-1).