Phototoxicity and cytotoxicity of chlorophyll a/cyclodextrins complexes on Jurkat cells

The aggregation status of chlorophyll a (Chl a) and the ability of four cyclodextrins, hydroxypropyl-beta-cyclodextrin (HP-beta-CD), hydroxypropyl-gamma-cyclodextrin (HP-gamma-CD), heptakis(2,6-di-O-methyl)-beta-cyclodextrin (DIMEB), and heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TRIMEB), to solubilize the pigment in the complete cellular medium RPMI 1640 was estimated by means of UV-Vis absorption and static resonance light scattering (RLS) measurements. The results indicate that the pigment interacts with cyclodextrins in the cellular medium differently to that observed in water. The cytotoxic and phototoxic activity of these complexes towards human leukemia T-lymphocytes (Jurkat cells) was tested by means of experiments aimed to discriminate between the intrinsic toxicity and the toxicity induced by light. The overall data indicate that the HP-beta-CD is the cyclodextrins having the best characteristics to form with Chl a a potential supramolecular system for the photodynamic therapy.     

Calibration of NaI(TI) spectrometer for radiocesium volume-samples. Some results from Transylvania region

A four-channel NP-424 type gamma analyzer coupled with a large NaI(Tl) scintillator was calibrated using a¹³⁷Cs point source. The volume-samples were plexiglas cylindrical boxes (D=76mm, H=40mm) directly placed on the NaI(Tl) detector. Measurements for 64 indoor positions at full-662 keV-peak were made. Sample selfabsorbtion was determined considering a linear attenuation for gamma rays and measuring the absorption factor for maximum thickness of the volume sample (h0=40mm). The obtained results for two types of environmental samples (soil and milk-powder) are compared with the data acquired from other Romanian laboratories, in the frame of the Environmental Radioactivity Action (ERA) which standardized such types of measurements. The same samples were measured with a calibrated GeLi detector (INAN-Louvain la Neuve) and the results were in good agreement with our measurements. Using this NaI(Tl) calibrated spectrometer some radiocesium deposits (56 localities) from Transylvanian region were measured. The results show that a large deposit exists in the direction NE-SW in connection with the radioactive cloud passing. For Alba region were measured more than 40 kBq/m² of cesium deposit.     

Computational Mechanics: Pattern and Prediction, Structure and Simplicity

Computational mechanics, an approach to structural complexity, defines a process's causal states and gives a procedure for finding them. We show that the causal-state representation—an -machine—is the minimal one consistent with accurate prediction. We establish several results on -machine optimality and uniqueness and on how -machines compare to alternative representations. Further results relate measures of randomness and structural complexity obtained from -machines to those from ergodic and information theories.     

Gamma-ray spectrometric analysis of neutron irradiated golden sands

A nondestructive method has been used for the qualitative and quantitative determination of elements such as Au, Cu, Ag in minerals and especially in golden sand. The induced radioactivity has been analyzed with a high resolution gamma spectrometer containing a Ge(Li) semiconductor detector type and a multichannel analyzer. The samples have been collected from the alluvia of the Mure? and Some?ul Mic river basins, proving the presence of gold and copper in small concentrations. These results have been correlated to previous data showing the existence of some gold mines in these zones. This nondestructive, rapid and highly sensitive method can be used for industrial processes [1] control and prospections. The use of a NaI(Tl) scintillation crystal for routine measurements of the ¹⁹⁸Au radioisotope type and the interferences by copper, silver and indium in the irradiated samples are discussed.     

13C separation by IRMPD of CF2HCL molecules with a powerful CO2-TEA laser

The single pulse separation parameters in IRMPD of CF₂HCL molecules have been obtained in relation with the laser fluence, the number of laser pulses, and the gas pressure. The measurements have been carried out using a fixed laser line (9P22) and an ordinary shape of the laser pulses.     

Design of a high-sensitivity negative ion source time-of-flight mass analyzer assembly created by cylindrical electrodes with a common axis

The new design incorporates the negative ion source and the mass analyzer, both constructed from cylindrical electrodes. The ion source is formed by three gridded cylindrical electrodes: a pulsed grid, the intermediate grid and the final accelerating grid. During a first time lapse, the electrons penetrate through the pulsed grid into the retarding field between this grid and the intermediate grid. The electrons are turning at some depth inside this intergrid space, where the attachment to neutral molecules most probably occurs. Next, the pulsed grid becoming strongly negative and ions are extracted towards the final acceleration grid. The ions from the cylindrical surface where they were created concentrate on the common axis of the electrodes (lateral focusing). The source lateral and time focus are coincident. A cylindrical electrostatic mirror is fitted to the source. The design, with a single stage, ensures also lateral focusing of the ions diverging from the common axis of the electrodes. The mirror electric and geometric parameters were selected to ensure both lateral and time focusing on the final detector with subsequent high luminosity. The basic parameters of the specific negative ion source time-of-flight mass analyzer design proposed here, are ion source final acceleration, intermediate, pulsed cylindrical grid radii 10, 20 and 30 mm, respectively, electrostatic mirror earthed grid and ion turning points surface radii 0.6 and 0.8 m, respectively. Ion packet smearing by the ion energy spread (resulting from the initial electron energy spread as electrons are turning at different depths inside the ionization region, from the moment when ions were created, being accelerated towards the pulsed grid during ionization) and by the turnaround time inside the cylindrical field was accounted for. Maintaining very high sensitivity, a resolution of the order of 100 is expected.     

The suzuki–heck polymerization as a tool for the straightforward obtainment of poly(fluorenylene‐vinylene) sensitizers for dye‐sensitized solar cells

This article describes the synthesis and properties of the first poly(arylene‐vinylene)‐based sensitizers for application in dye‐sensitized solar cells (DSSC). The polymers were prepared by the Suzuki–Heck copolymerization of potassium vinyltrifluoroborate (PVTB) with a mixture of dibromoaryl comonomers designed to obtain macromolecules able to bind onto the photoelectrode by means of carboxyphenylene units. The copolymerization reactions were carried out in the presence of an excess of PVTB to lower the molecular weights of the polymers, which were obtained as soluble materials. The polymers poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene] ( P1 ), poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐(4,7‐benzothiadiazolylene)‐vinylene] ( P2 ), and poly[(9,9‐didodecyl‐2,7‐fluorenylene)‐vinylene‐co‐(carboxy‐2,5‐phenylene)‐vinylene‐co‐2,5‐thienylene‐vinylene] ( P3 ) were used in DSSC devices, obtaining conversion efficiencies up to 0.88% ( P3 ). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Investigations into the reliability of SAR-OSL equivalent doses obtained for quartz samples displaying dose response curves with more than one component

Fast component dominated quartz single aliquot regenerative dose optically stimulated luminescence (SAR-OSL) dose response curves that display continuing growth at high doses are increasingly reported in literature. This behaviour would result in higher equivalent doses being obtained. Here we document the characteristics of OSL signals from fine (4–11 μm) and coarse (63–90 μm) quartz extracted from Romanian loess that display such behaviour. For very high doses (>1 kGy up to 5–15 kGy) the data could be closely fitted to a double saturating exponential regression model. Nonetheless, the saturation charcteristics of these fine and coarse quartz grains are very different, with average saturation chracteristic doses of D₀₁ ≈ 175 Gy and D₀₂ ≈ 1800 Gy in the case of the fine material, while in the case of the coarse material values of D₀₁ ≈ 55 Gy and D₀₂ ≈ 600 Gy have been obtained. Our results imply a hitherto unexplained mechanism in OSL production at high doses and question the reliability of obtaining SAR-OSL equivalent doses in the high dose region when a second function is needed to describe the dose response.     

Parametric study of the IRMPD of CF2HCl molecules with the 9P22 CO2 laser line

The separation of ¹³C by infrared multiple photon decomposition (IRMPD) of CF₂HCl has been parametrically studied in relation with some key parameters such as the laser fluence, the number of laser pulses, and the gas pressure. The process selectivity, the depletion of the ¹³C isotope in the residual gas, the relative amount of ¹³C separated per pulse, and the energy expenditure were determined as a function of the above mentioned parameters, and conclusions were drawn concerning the efficiency of the separation process. An isotopic selectivity of about 40 was obtained in the investigated range of pressure. At 10 Torr of pure CF₂HCl, the ¹³C depletion in the residual gas was 45% when only 300 laser pulses were used. A maximum amount of 4.6×10^–10 kg ¹³C separated per pulse was obtained.