Characterization of Photodegradation of Meta-tetra (Hydroxyphenyl)chlorin (mTHPC) in Solution: Biological Consequences in Human Tumor Cells

The photobleaching of meta -tetra(hydroxyphenyl)chlorin m THPC) (irradiation wavelength 413 nm) in protein-containing solution was evaluated by decay in absorbance in Soret band and in fluorescence (λ_exc= 423 nm, λ_em= 655 nm). Light exposure resulted in a decrease in absorption throughout the spectrum and simultaneous appearance of new absorption bands in the spectral region 325–450 nm. The rate of m THPC photodegradation, followed by decay in absorbance, was 15-fold lower than that observed in fluorescence. This fact reflects the photobleaching of presumably monomeric, fluorescing species of m THPC. In order to determine the consequences of photobleaching of fluorescing m THPC material on cellular uptake and photocytotoxicity, human HT29 colon adenocarcinoma cells were incubated with photobleached m THPC during 5 h with or without following irradiation with the fixed fluence. Surprisingly, but up to the time when the fluorescence decreased by 50%, only a slight decrease in photocytotoxicity was detected. Either aggregated forms that have been taken up undergo intracellular monomerization (but we did not observe increase in fluorescence in living cells) or the photodynamic activity is mostly due to aggregates. The discrepancy of m -THPC-photodynamic therapy (PDT) effect and fluorescence measurements may suggest that aggregated m -THPC plays an important role in m THPC-PDT.     

Active damping control for an underactuated multibody system

Light-weight robots and manipulators stand out due to their very good weight-to-load ratio and a low energy consumption. Unfortunately, the light-weight design yields a lower stiffness, which results in undesired elastic deformations, especially during high-speed working motion. One way to limit these unwanted oscillations can be implemented with modifications of the command signals, e.g. by input shaping or pre-computed feed-forward control. However, a feedback control-concept has the ability to provide a fast compensation of elastic deformations due to high-speed working motions or in case of unwanted environment contact as well as in the presence of other external disturbances. In this contribution, an active damping control (ADC) for fast moving manipulators with significant structural elasticities is presented. This approach does not require additional actuators and it is suitable for a large variety of manipulators that exhibit structural vibrations. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Gerrymander-proof representative democracies

International Journal of Game Theory - This article is devoted to the analysis of electoral systems involving two step procedures. It appears that designers are able to manipulate the result of...     

Study of the polymerization of acrylic resins by photocalorimetry

Due to their advantages from an environmental point of view (i.e. reduction of volatile organic compounds (VOC)), photocurable finishes should be extensively used for industrial wood joinery in the near future. However, several problems are reported, particularly the poor durability of the finishing system. In the present work, the curing reaction of acrylic resins containing some improved photoinitiators was studied by means of photocalorimetry under monochromatic irradiation from 366 to 450 nm. The results show that finishes can be cured even under daylight so that they could be directly applied on site in case of restoration.     

Electric field effects on intersubband transitions in quantum well structures

We report on a Raman scattering study of the electric-field dependence of c₀ → c₁ intersubband transitions of electrons in a 264 Å GaAs- Al_0.3Ga_0.7As quantum-well structure. The measured Stark shifts are in very good agreement with theoretical predictions. The intensity of the intersubband peak increases rapidly with applied field due to parity-mixing. In contrast to the enhanced broadening shown by excitation resonances, the width of c₀ → c₁ is nearly independent of the field. This feature is attributed to effects of structural disorder.     

Mo(CO)3(NCMe)(PPh3)2: Synthesis, X-ray structure and evaluation of its catalytic activity for the homogeneous hydrogenation of olefins and their mixtures

The complex Mo(CO)₃(NCMe)(PPh₃)₂, was synthesized by the reaction of Mo(NCMe)₃(CO)₃ with two equivalents of PPh₃ and characterized by UV–Vis, IR, NMR and X-ray diffraction. This complex was used as a catalyst precursor for the hydrogenation of 1-hexene, styrene, cyclohexene and 2,3-dimethyl-1-butene and their mixtures under moderate conditions in homogeneous media. Under mild reaction conditions (T = 373 K, P = 60 atm), the substrates showed the following reactivity order: styrene > 1-hexene > cyclohexene > 2,3-dimethyl-1-butene. A quaternary equimolar mixture showed a different hydrogenation order: 1-hexene > cyclohexene > styrene > 2,3-dimethyl-1-butene; the presence of dibenzothiophene or mercury does not interfere with the activity of the catalyst.     

Observation of surface-avoiding waves: a new class of extended states in periodic media

Coherent time-domain optical experiments on GaAs-AlAs superlattices reveal the existence of an unusually long-lived acoustic mode at approximately 0.6 THz which couples weakly to the environment by evading the sample boundaries. Classical as well as quantum states that steer clear of surfaces are generally shown to occur in the spectrum of periodic structures, for most boundary conditions. These surface-avoiding waves are associated with frequencies outside forbidden gaps and wave vectors in the vicinity of the center and edge of the Brillouin zone. Possible consequences for surface science and resonant-cavity applications are discussed.     

Kinetics and mechanisms of homogeneous catalytic reactions. Part 4. Hydrogenation of cyclohexanone and 2-cyclohexen-1-one catalysed by the complexes [MH(CO)(NCMe)2(PPh3)2]BF4 (M = Ru,Os)

Kinetic and mechanistic studies of the homogeneous hydrogenation of cyclohexanone were carried out using the cationic complexes [MH(CO)(NCMe)₂(PPh₃)₂]BF₄ (M = Ru, Os) as the catalyst precursors, which were very efficient under mild reaction conditions in 2-methoxyethanol solution. For both complexes, the catalytic hydrogenation of cyclohexanone proceeds according to the rate law r = k[M][H₂]. The activation parameters were also calculated, the activation energy for the osmium catalyst being higher than for the ruthenium(I). All experimental data are consistent with a mechanism involving the oxidative addition of hydrogen as the rate-determining step of the catalytic cycle. Finally, the [MH(CO)(NCMe)₂(PPh₃)₂]BF₄ complexes were efficient precatalysts for the selective reduction of 2-cyclohexen-1-one to cyclohexanone; the reduction of the CO group of cyclohexanone only begins to take place when the ,-unsaturated ketone has been consumed.     

Magnon squeezing in an antiferromagnet: reducing the spin noise below the standard quantum limit

We report the first experimental demonstration of quantum squeezing of a collective spin-wave excitation (magnon) using femtosecond optical pulses to generate correlations involving pairs of spins in an antiferromagnetic insulator MnF2. In the squeezed state, the fluctuations of the magnetization of a crystallographic unit cell vary periodically in time and are reduced below that of the ground-state quantum noise.     

Transient strain driven by a dense electron-hole plasma

We measure transient strain in ultrafast laser-excited Ge by time-resolved x-ray anomalous transmission. The development of the coherent strain pulse is dominated by rapid ambipolar diffusion. This pulse extends considerably longer than the laser penetration depth because the plasma initially propagates faster than the acoustic modes. X-ray diffraction simulations are in agreement with the observed dynamics.