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Dynamic light scattering (DLS) has been used to quantify nanoscale heterogeneity in the industrially significant polyacrylonitrile (PAN) polymer solution. The heterogeneity in polymer solution, traced by the ratio of amplitudes of the slow to fast mode, is observed to be related to various parameters, such as molecular weight of the polymer, the type of co-monomer, processing time, concentration of the solution, and the choice of the solvents. It has been identified that low molecular weight PAN homopolymer have the least heterogeneity issues. Amongst the chosen co-polymers for this study, similar degree of heterogeneity was observed at concentration slightly above the critical concentration at which the polymer chains begin to overlap. Whereas, at higher concentration, PAN-methacrylic acid (4 wt%) copolymer showed the least heterogeneity issue. The aggregate diffusion coefficient of PAN-methacrylic acid (4 wt%) copolymer solution in dimethylformamide (DMF) and A/,A/-dimethylacetamide (DMAc) are respectively determined to be ~1.6 x [10.sup.-12] [cm.sup.2]/s and ~1.6 x [10.sup.-13] [cm.sup.2]/s, which results in an estimated aggregate size of 9 nm and 90 nm., INTRODUCTION Dynamic light scattering (DLS) has been extensively used to study the dynamics and relaxation behavior of polymer chains [1-9] and to measure the particle size of various colloids [10]. [...]

Unattended sensor networks are a cost-effective strategy to enhance the resolution of environmental datasets and are required to understand how large aquatic ecosystems respond to complex stressors (e.g., climate change). We made unattended and continuous measurements of the quantum yield of photosystem II ([φ.sub.PSII]) photochemistry in the surface mixed layer of Lake Erie during three lake-wide cruises to observe how phytoplankton physiology varied across nutrient and taxonomic gradients. Three prominent diel [φ.sub.PSII] patterns were noted. The diel maximum consistently occurred at sunrise or sunset, nocturnal measurements were consistently lower than diel maxima, and daytime values were strongly diminished by nonphotochemical quenching. The diurnal pattern was modeled as a function of irradiance to a mean accuracy of 0.03 to 0.04. Contrary to previously published reports in Lake Erie, [φ.sub.PSII] was largely insensitive to indices of nutrient deficiency through space and time. This finding was consistent with much recent literature about [φ.sub.PSII] and suggests that Lake Erie phytoplankton, like many others, can tune their photosynthetic machinery to maintain relatively high efficiency of photochemistry in photosystem II even when deficient in phosphorus or nitrogen. Les reseaux de capteurs surveilles a distance constituent une strategie economique pour ameliorer la resolution d'ensembles de donnees environnementales et sont necessaires a la comprehension de la reaction des grands ecosystemes aquatiques a des facteurs de stress complexes tels que les changements climatiques. Nous avons pris des mesures a distance et en continu du rendement quantique de la photochimie du photosysteme II ([φ.sub.PSII]) dans la couche de melange superficielle du lac Erie durant trois croisieres a la grandeur du lac afin d'observer les variations de la physiologie du phytoplancton le long de gradients taxinomiques et de nutriments. Trois grands motifs nycthemeraux du [φ.sub.PSII] ont ete notes. Le maximum nycthemeral se produisait uniformement au lever ou au coucher du soleil, les mesures nocturnes etaient uniformement inferieures au maximum nycthemeral et les valeurs diurnes etaient fortement reduites par l'extinction non photochimique. La modelisation du motif diurne en tant que fonction de l'eclairement energetique a donne une exactitude moyenne de 0,03 a 0,04. Contrairement a des publications anterieures concernant le lac Erie, le [φ.sub.PSII] etait en bonne partie insensible aux indices de deficit de nutriments dans l'espace et le temps. Ce resultat concorde avec de nombreuses etudes recentes concernant le φPSII et donne a penser que le phytoplancton du lac Erie, comme bien d'autres, peut ajuster ses mecanismes photosynthetiques de maniere a maintenir une efficacite relativement elevee de la photochimie dans le photosysteme II, meme en situation de deficit de phosphore ou d'azote. [Traduit par la Redaction], Introduction Phytoplankton production dictates the flow of energy and mass in large aquatic ecosystems, including the Laurentian Great Lakes. Accurate monitoring of phytoplankton health and productivity is critical to understand [...]

A procedure is developed for the selective photometric redox determination of bromate ions in drinking waters of different types. Methylene Blue (MB), Variamine Blue (VB) and Safranin T (SAF) are studied as irreversibly oxidized redox indicators. The limits of detection for bromate ions are 0.4 and 1 [micro]g/L for MB (VB) and SAF, respectively. Using MB as an indicator at the concentration of bromate ions 1 [micro]g/L, the acceptable mass ratios of concomitant ions are as follows: I[O.sup.-.sub.3], N[O.sup.-.sub.2] (1 : 60); Cl[O.sup.- ], Cl[O.sup.-.sub.2] (1 : 100); Cl[O.sup.-.sub.3], Cl[O.sup.-.sub.4], I[O.sup.-.sub.4], [Br.sup.-], [I.sup.-] (1 : 200). In the concentration range of bromate ions 1-10 [micro]g/L, the total determination error is 5-7%. Keywords: bromate ions, determination, redox indicators, photometry, drinking water DOI: 10.1134/S1061934815020136, Ozone is widely used for the disinfection of drinking water from superficial and underground sources both in Russia [1] and abroad [2]. The treatment of natural waters with ozone or [...]

1. Introduction The photodegradation of fluorophores is an important process that determines the accuracy of many biological assays (1), the efficacy of photodynamic therapy (2), and the phototoxicity of drugs. […]

Observations of the Io plasma torus and neutral clouds indicate that the extended ionian atmosphere must contain sodium, potassium, and chlorine in, atomic and/or molecular form. Models that consider sublimation of pure sulfur dioxide frost as the sole mechanism for generating an atmosphere on Io cannot explain the presence of alkali and halogen species in the atmosphere--active volcanoes or surface sputtering must also be considered, or the alkali and halide species must be discharged along with the S[O.sub.2] as the frost sublimates. To determine how volcanic outgassing can affect the chemistry of Io's atmosphere, we have developed a one-dimensional photochemical model in which active volcanoes release a rich suite of S-, O-, Na-, K-, and Cl-bearing vapor and in which photolysis, chemical reactions, condensation, and vertical eddy and molecular diffusion affect the subsequent evolution of the volcanic gases. Observations of Pele plume constituents, along with thermochemical equilibrium calculations of the composition of volcanic gases exsolved from high-temperature silicate magmas on Io, are used to constrain the composition of the volcanic vapor. We find that NaCl, Na, Cl, KCl, and K will be the dominant alkali and chlorine gases in atmospheres generated from Pele-like plume eruptions on Io. Although the relative abundances of these species will depend on uncertain model parameters and initial conditions, these five species remain dominant for a wide variety of realistic conditions. Other sodium and chlorine molecules such as NaS, NaO, [Na.sub.2], NA[S.sub.2], Na[O.sub.2], NaOS, NaS[O.sub.2], SCl, ClO, [Cl.sub.2], [S.sub.2]Cl, and S[O.sub.2][Cl.sub.2] will be only minor constituents in the ionian atmosphere because of their low volcanic emission rates and their efficient photochemical destruction mechanisms. Our modeling has implications for the general appearance, properties, and variability of the neutral sodium clouds and jets observed near Io. The neutral NaCl molecules present at high altitudes in atmospheres generated by active volcanoes might provide the Na[X.sup.+] ion needed to help explain the morphology of the high-velocity sodium 'stream' feature observed near Io. Key Words: Io; photochemistry; atmospheres, composition; volcanism; geochemistry; alkalis; halogens.

To determine how active volcanism might affect the standard picture of sulfur dioxide photochemistry on Io, we have developed a one-dimensional atmospheric model in which a variety of sulfur-, oxygen-, sodium-, potassium-, and chlorine-bearing volatiles are volcanically outgassed at Io's surface and then evolve due to photolysis, chemical kinetics, and diffusion. Thermochemical equilibrium calculations in combination with recent observations of gases in the Pele plume are used to help constrain the composition and physical properties of the exsolved volcanic vapors. Both thermochemical equilibrium calculations (Zolotov and Fegley 1999, Icarus 141, 40-52) and the Pele plume observations of Spencer et al. (2000; Science 288, 1208-1210) suggest that [S.sub.2] may be a common gas emitted in volcanic eruptions on Io. If so, our photochemical models indicate that the composition of Io's atmosphere could differ significantly from the case of an atmosphere in equilibrium with S[O.sub.2] frost. The major differences as they relate to oxygen and sulfur species are an increased abundance of S, [S.sub.2], [S.sub.3], [S.sub.4], SO, and [S.sub.2]O and a decreased abundance of O and [O.sub.2] in the Pele-type volcanic models as compared with frost sublimation models. The high observed SO/S[O.sub.2] ratio on Io might reflect the importance of a contribution from volcanic SO rather than indicate low eddy diffusion coefficients in Io's atmosphere or low SO 'sticking' probabilities at Io's surface; in that case, the SO/S[O.sub.2] ratio could be temporally and/or spatially variable as volcanic activity fluctuates. Many of the interesting volcanic species (e.g., [S.sub.2], [S.sub.3], [S.sub.4], and [S.sub.2]O) are short lived and will be rapidly destroyed once the volcanic plumes shut off; condensation of these species near the source vent is also likely. The diffuse red deposits associated with active volcanic centers on Io may be caused by [S.sub.4] radicals that are created and temporarily preserved when sulfur vapor (predominantly [S.sub.2]) condenses around the volcanic vent. Condensation of SO across the surface and, in particular, in the polar regions might also affect the surface spectral properties. We predict that the S/O ratio in the torus and neutral clouds might be correlated with volcanic activity--during periods when volcanic outgassing of [S.sub.2] (or other molecular sulfur vapors) is prevalent, we would expect the escape of sulfur to be enhanced relative to that of oxygen, and the S/O ratio in the torus and neutral clouds could be correspondingly increased. Key Words: Io; photochemistry; atmospheres, composition; volcanism; geochemistry.

A study was conducted relating to research on model systems for the mimicking of the process of photosynthesis, in particular, models involving the use of supramolecular assemblies of metal complexes and organic chromophores. The study reports the assemblies of metal complexes intercalated in the galleries of an inorganic phosphate, namely, n-butylammonium salt of alpha-zirconium phosphate. The experiment and its results are discussed.

A one-dimensional photochemical steady state model is used to study the vertical distribution of different gas species in the neutral atmosphere of Pluto. The major species is supposed to be [N.sub.2] with C[H.sub.4] as the leading minor species with a mixing ratio between 3.7 x [10.sup.-3] and 7.4 x [10.sup.-3], depending on the pressure and temperature on the surface. As a result of photolytic reactions, a number of hydrocarbons and nitriles are mainly produced in the 50-300 km region. Because of the uncertainty in the atmospheric thermal structure of Pluto, photochemical models with three different T(p) models have been developed. The turbulent processes have been parameterized, as in previous atmospheric models, with an eddy diffusion coefficient K = [K.sub.o][([n.sub.o]/n).sup.0.5] placing the homopause at an assumed altitude of [approximately]150 km. For the case we call nominal ([T.sub.surf] = 37 K and [p.sub.surf] = 10 [Mu]bar) parent molecules such as [N.sub.2], C[H.sub.4], and CO must be supplied from the surface with rates of 1.85 x [10.sup.7], 2.87 x [10.sup.8], and 6.83 x [10.sup.3] [cm.sup.-2] [sec.sup.-1], respectively. As a consequence of photolysis, H and [H.sub.2] escaping fluxes, scaled to the surface, are 3.50 x [10.sup.8] and 2.12 x [10.sup.8] [cm.sup.-2] [sec.sup.-1], respectively. Condensation of light hydrocarbons and nitriles occur between 3 and 5 km, depending on the compound and the surface temperature. Scaling the downward flux of these compounds to the amount of ice that would be deposited on the surface, we have deduced that the most abundant surface ices would be [C.sub.2] [H.sub.6], [C.sub.2] [H.sub.2], HCN, and [C.sub.2] [H.sub.4], in that order.

The photoreaction process of photoactive yellow protein (PYP) from Ectothiorhodopsin halophila was investigated by low-temperature spectroscopy. PYP formed intermediates after irradiation at -190 degrees centigrade. The intermediates consisted of a combination of bathochromic and hypsochromic photoproducts which converted into blue-shifted and then red-shifted intermediates upon warming. A diagram of the photocycle of PYP at low temperature is presented.

The effects of metal complexes on the environment are determined by their structure. The effects of metal-complex stoichiometry are different from the effects of ligand structure. The differences are identified thru experimental procedures that determine the molar absorptivities and quantum yields of individual components of given metal complexes. Procedures and mathematical models to determine molar absorptivities and quantum yields for complexes of a labile metal in solution are presented.

The application of an updated CIT photochemical airshed model to a Southern California Air Quality Study intensive monitoring period is discussed. Ozone concentrations were predicted using measured meteorological parameters, measured initial and boundary conditions and the government-prepared official emission imventory. Results indicate that in recent years, the estimation of organic gas emissions in Los Angeles have been understated.

Photosynthetic model systems using nematic liquid crystals are able to mimic most of the electronic states of photosynthetic reaction center's primary photochemistry. The model's abilities were confirmed using time-resolved electron paramagnetic resonance spectroscopy. The model does not contain the natural pigments but mimics the spin dynamics of triplet state formation in photosynthetic reaction center.