Long term stability of organic selenium species in aqueous solutions

Long term stability of organic selenium compounds (selenocystine, selenomethionine, trimethylselenonium ion) has been studied over a one year period for 2 analyte concentrations: 25 and 150 μg/L Se, at pH 4.5 in the dark, under different storage conditions: temperature of –20°C, 4°C, 20°C, 40°C; in Pyrex, Teflon, or polyethylene containers; in an aqueous matrix or in the presence of a chromatographic counter ion (pentyl sulfonate at 10^–4 mol/L concentration). Light effects have also been tested. The stability of the selenium species was monitored by HPLC-ICP/MS. Storage conditions can drastically alter the stability of organic selenium species. Organoselenium compounds were shown to be stable in the dark over a one year period in an aqueous matrix at pH 4.5 in Pyrex containers at both 4°C and 20°C. Pyrex vials exposed to natural sunlight at room temperature resulted in a steady decrease of the selenoamino acid concentration. Teflon containers caused losses of less than 25% at both 4° C and 20° C in the dark. However, polyethylene vials presented, at all temperatures tested, a rapid decrease of the TMSe⁺ concentration. The stability of the Se species studied did not show significant differences between 4° C and 20° C in any container material used. Storage of solutions at 40° C led to slight differences between the Pyrex and Teflon containers. However, polyethylene presented a drastic decrease of the three species over time at this higher temperature. Solutions frozen at –20° C in polyethylene vials did not stabilize the TMSe⁺ signal. Finally, concentrations and matrices of the samples did not significantly affect the stability of the species. Received: 15 July 1996 / Revised: 14 July 1997 / Accepted: 18 July 1997     

Solid State Nuclear Magnetic Resonance Studies of the Thermochromic Phase Transition of the Polydiacetylene from the Bis-n-Propylurethane of 5,7-Dodecadiyne-1,12-diol

The polydiacetylene (PDA) from the bis-n-propylurethane of 5,7-dodecadiyne-1,12-diol (PUDO) undergoes a first order phase transition near 135°C that is associated with a color change from blue at temperatures below the transition to red at temperatures above the transition. We have studied PDA-PUDO by solid state ¹³C nuclear magnetic resonance (NMR) spectra using cross polarization and magic angle spinning (CP-MAS) techniques at temperatures between 25° and 140°C. As observed previously, the acetylene carbon shift moves up field as the temperature is raised above the transition temperature. In addition, near 130°C, the oxymethylene carbon shows 3 resonances, indicating multiple side chain conformations as the PDA undergoes the phase transition.     

Temperature and Solar Radiation Interactions on 3H-leucine Incorporation by Bacterioplankton in a Subtropical Estuary

Although the effects of UV radiation are thought to be temperature independent, the photoinhibition of aquatic bacteria may be temperature dependent owing to enzymatic repair kinetics, an important consideration for climate change analyses. We examined the interactions between temperature and solar radiation in water samples collected from the Blackwater River, Pensacola Bay, and the coastal Gulf of Mexico (Florida) in July 2008. Subsamples were incubated in the dark for 20 h at either the in situ temperature, +5°C from in situ or −5°C from in situ after which they were amended with ³H-leucine and irradiated in full sunlight at their respective temperatures and compared to samples incubated simultaneously in the dark. Temperature and light significantly affected ³H-leucine incorporation at all locations and interactive effects between temperature and sunlight were found for Pensacola Bay and the Gulf. Generally, warmer waters reduced photoinhibition. The −5°C treatment was always significantly more inhibited than the +5°C treatment, but the in situ temperature and +5°C and −5°C treatments were not always significantly different. Photoinhibition reduction at warmer temperatures suggests specific effects on photobiology not observed in general cellular activity may be important in determining interactive ecosystem effects of climate change.     

DIURNAL MODULATION OF PHOTOTROPIC RESPONSE BY TEMPERATURE AND LIGHT IN Chenopodium rubrum L. AS RELATED TO STEM EXTENSION RATE ANDARGININE DECARBOXYLASE ACTIVITY*

Abstract— Seedlings of Chenopodium rubrum were grown under 12: 12 h light-dark cycles with the light period at 32.5°C and darkness at 10°C (“normal” conditions) or with light at 10°C and darkness at 32.5^CC (“inverse” conditions). When grown under unilateral white light with the photo-thermoperiodic conditions described above, inverse seedlings did not show phototropic curvature while normal seedlings did. Regardless of temperature regime used, plants irradiated with unilateral blue light (456 nm) at 10°C failed to curve on subsequent incubation at 32.5°C. If the phototropic stimulus was given at 32.5°C followed again by 32.5°C in darkness, phototropic curvature was observed. The results with monochromatic blue light thus explain the lack of phototropic response of “inverse” seedlings with the unilateral light period given at 10°C. “Inverse “seedlings showed a sharp rhythm in their capacity to respond to phototropic stimulation at 32.5°C. The greatest capacity to respond came when the stem extension rate was actually zero. The differential growth accompanying phototropic curvature thus seems to be different from the growth responsible for uniform stem elongation. The curvature may result from differential turgor changes as in the case of sun tracking of leaves. “Inverse seedlings” showed clear signs of stress and displayed a rhythm in arginine decarboxylase, an enzyme thought to be stress-related, with maxima during the low temperature light periods. It is concluded that the phototropic perception transduction chain is modified by the inverse conditions somewhere before the final growth-turgor steps, since they exhibit geotropic sensitivity.     

TEMPERATURE AND MYCOCHROME SYSTEM IN NEAR-UV LIGHT INDUCIBLE AND BLUE LIGHT REVERSIBLE PHOTOINDUCTION OF CONIDIATION IN Alternaria tomato*

Abstract— When dark-grown colonies were exposed to near-UV light, conidiophore formation was induced, and conidia developed during a subsequent dark period. Simultaneous exposure to near-UV and blue light inhibited induction of conidiation. The inductive effect of near-UV light irradiation was greatly enhanced by treating colonies with low temperatures for 4 h during the 2nd-6th hour of incubation in the dark following inductive irradiation: the enhancement was greatest at 21^°C. The extent of inhibition by blue light increased with the temperature between 10 and 28^°C. This diminution by low temperature was greatest when colonies previously kept at a low temperature were exposed to inductive irradiation: the longer the duration between inductive irradiation and temperature treatment, the lower the diminution. Higher fluences of blue light were required to suppress conidial induction at lower temperature. Thus, it is evident that the inductive effect of near-UV light irradiation on conidiation and the suppressive effect of blue light irradiation are each responsive to different temperatures applied at different times.     

UVB Radiation Affects Growth,Reproduction and Tissue Structure of Daphnia magna Across Several Temperatures

We examined the effects of daily exposure to UVB on growth, reproduction and histological characteristics of Daphnia magna over two generations at 20, 22, 25 and 30°C. Animals were exposed to 16 h of UVA and photosynthetically active radiation daily. Treated animals received 6 h of UVB during the light phase. Parental (P) generation growth and reproduction was impaired by exposure to UVB at all temperatures, with the poorest production at 30°C. First brood size decreased with UVB exposure; it was lowest at 30°C. Although F1 length at birth increased with P generation age, F1 produced by UVB‐exposed mothers were smaller at all temperatures. The F1 generation was followed at 20 and 25°C; at both temperatures UVB exposure reduced F1 growth and reproduction. F1 growth and F2 production were lowest when both P and F1 generations were exposed to UVB. UVB exposure damaged ovarian and gut tissue at both 25 and 30°C; the consequences of this exposure were more severe at 30°C. The observed tissue damage may relate directly to the UVB‐induced impairment of growth and reproduction. This study provides new insights into the effects of UVB on an important component of the pelagic zooplankton.     

Synthesis and properties of wholly aromatic polymers bearing cardo fluorene moieties

Three series of aromatic polyamides, polyesters, and poly(1,3,4‐oxadiazole)s containing bulky fluorene structures were prepared from 9,9‐bis(4‐carboxyphenyl) fluorene. All of the polymers were readily soluble in many organic solvents and showed useful thermal stability associated with high glass‐transition temperatures in the range of 220–366 °C. These wholly aromatic polymer films were colorless, with high optical transparency, and exhibited UV‐vis absorption bands at 266–348 nm and photoluminescence maximum bands at 368–457 nm within the purple to green region in N,N‐dimethylacetamide (DMAc) solutions. The poly(amine‐amide) Ic exhibited excellent electrochromic contrast and coloration efficiency, changing color from the colorless neutral form to green and then to the dark blue oxidized forms with good stability of electrochromic characteristics. Almost all of these wholly aromatic polymer films were colorless and showed high optical transparency. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4352–4363, 2007     

Preparation of neutrally colorless,transparent polynorbornenes with multiple redox‐active chromophores via ring‐opening metathesis polymerization toward electrochromic applications

A new electrochromic norbornene derivative containing triphenylamine groups (NBDTPAC8) was synthesized using norbornene amine and bromotriphenylamine. NBDTPAC8 was used in ring‐opening metathesis polymerization to obtain poly(NBDTPAC8) using different Grubbs' catalysts and followed by hydrogen reduction to obtain poly(HNBDTPAC8). The glass transition temperatures (T_g) of poly(NBDTPAC8) and hydrogenated poly(HNBDTPAC8) were 132 and 89 °C, respectively. Poly(HNBDTPAC8) film exhibited a fluorescence maximum around 416 nm with a quantum yield of up to 60%. Hydrogenated poly(HNBDTPAC8) film showed excellent transparency (up to 93%). Poly(HNBDTPAC8) showed cyclic voltammetric and electrochromic behaviors similar to those of poly(NBDTPAC8). The cyclic voltammogram of a poly(HNBDTPAC8) film cast onto an indium tin oxide (ITO)‐coated glass substrate exhibited three reversible oxidation redox couples at 0.69, 0.94 and 1.38 V versus Ag/Ag⁺ in an acetonitrile solution. The electrochromic characteristics of poly(HNBDTPAC8) showed excellent stability and reversibility, with multi‐staged color changes from its colorless neutral form to green, light blue and dark blue upon the application of potentials ranging from 0 to 1.60 V. The color switching time and bleaching time of the poly(HNBDTPAC8) film were 6.2 s and 4.3 s at 1175 nm and 6.6 s and 4.4 s at 970 nm, respectively. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Synthesis and properties of new aromatic polyamides with redox‐active 2,4‐dimethoxytriphenylamine moieties

A new triphenylamine‐based diamine monomer, 4,4′‐diamino‐2″,4″‐dimethoxytriphenylamine ( 2 ), was synthesized from readily available reagents and was reacted with various aromatic dicarboxylic acids to produce a series of aromatic polyamides ( 4a–h ) containing the redox‐active 2,4‐dimethoxy‐substituted triphenylamine (dimethoxyTPA) unit. All the resulting polyamides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers exhibited good thermal stability with glass transition temperatures of 243–289 °C and softening temperatures of 238–280 °C, 10% weight loss temperatures in excess of 470 °C in nitrogen, and char yields higher than 60% at 800 °C in nitrogen. The redox behaviors of the polymers were examined using cyclic voltammetry (CV). All these polyamides showed two reversible oxidation processes in the first CV scan. The polymers also displayed low ionization potentials as a result of their dimethoxyTPA moieties. In addition, the polymers displayed excellent stability of electrochromic characteristics with coloration change from a colorless neutral state to green and blue‐purple oxidized states. These anodically coloring polyamides showed high green coloration efficiency (CE = 329 cm²/C), high contrast of optical transmittance change (ΔT% = 84% at 829 nm), and long‐term redox reversibility. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3392–3401, 2010     

Calcination temperature-dependent morphology of photocatalytic ZnO nanoparticles prepared by an electrochemical–thermal method

ZnO nanoparticles (NPs) with tunable morphologies were synthesized by a hybrid electrochemical–thermal method at different calcination temperatures without the use of any surfactant or template. The NPs were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction, dynamic light scattering, thermogravimetry–differential thermal analysis, scanning electron microscope and N₂ gas adsorption–desorption studies. The FT-IR spectra of ZnO NPs showed a band at 450 cm^?1, a characteristic of ZnO, which remained fairly unchanged at calcination temperatures even above 300 °C, indicating complete conversion of the precursor to ZnO. The products were thermally stable above 300 °C. The ZnO NPs were present in a hexagonal wurtzite phase and the crystallinity of ZnO increased with an increasing calcination temperature. The ZnO NPs calcined at lower temperature were mesoporous in nature. The surface areas of ZnO NPs calcined at 300 and 400 °C were 51.10 and 40.60 m² g^?1, respectively, which are significantly larger than commercial ZnO nanopowder. Surface diffusion has been found to be the key mechanism of sintering during heating from 300 to 700 °C with the activation energy of sintering as 8.33 kJ mol^?1. The photocatalytic activity of ZnO NPs calcined at different temperatures evaluated by photocatalytic degradation of methylene blue under sunlight showed strong dependence on the surface area of ZnO NPs. The ZnO NPs with high surface area showed enhanced photocatalytic activity.     

Characterization of aqueous rose bengal dye solution for the measurement of low doses of gamma radiation

Aqueous solution of rose bengal dye has been studied spectrophotometrically as a gamma-ray dosimeter for the measurement of low doses of radiation. The useful dose range was found to be from 50 to 1000 Gy when the measurements were made at 549 nm. The effects of temperature and light conditions on the stability of response during post-irradiation storage were also investigated. When stored in dark at room temperature, the dosimetric solutions showed a stable response up to 22 days. The storage of irradiated solutions in diffused sunlight showed a stable response only up to 6 days. When exposed to direct sunlight, very prominent and fast bleaching of dye solution occurred. At low storage temperature (ca. 11 °C), dosimetric response was found to be stable up to 22 days while at higher temperature (ca. 30 °C), the response of dosimetric solution was stable only up to 6 days. The rose bengal aqueous solution showed promising characteristics as a low dose radiation dosimeter when stored at lower temperatures (<25 °C) in dark.     

Non-equilibrium thermodynamic studies of electrokinetic effects: VII. Methanol + acetonitrile mixtures

Experimental results for the measurement of electro-osmosis and electro-osmotic pressure differences for methanol + acetonitrile (MeOHMeCN) mixtures (25% and 75% by volume) and a Pyrex sintered disc at temperatures 20 to 40°C and at voltages upto 320 V are reported. The data are analysed in the light of the theory of non-equilibrium thermodynamics. Attempts have been made to explore the domain of validity of linear phenomenological relations in the case of non-aqueous mixtures. The second order coefficients for these systems have been estimated from the measurements of electro-osmosis and electro-osmotic pressure differences.     

Achieving Pure Deep‐Blue Electroluminescence with CIE y≤0.06 via a Rational Design Approach for Highly Efficient Non‐Doped Solution‐Processed Organic Light‐Emitting Diodes

Deep‐blue fluorescent emitters with Commission Internationale de l'Eclairage (CIE) y≤0.06 are urgently needed for high‐density storage, full‐color displays and solid‐state lighting. However, developing such emitters with high color purity and efficiency in solution‐processable non‐doped organic light‐emitting diodes (OLEDs) remains an important challenge. Here, we present the synthesis of two new deep‐blue fluorescent emitters ( AFpTPI and AFmTPI ) based on 10‐(9,9‐diethyl‐9H‐fluoren‐2‐yl)‐9,9‐dimethyl‐9,10‐dihydroacridine as a core and 1,3‐ and/or 1,4‐phenylene‐linked triphenylimidazole (TPI) analogues for non‐doped solution‐processable OLEDs. Their thermal, photophysical, electrochemical, and device characteristics are explored, and also strongly supported by density functional theory (DFT) study. AFpTPI and AFmTPI exhibit excellent thermal stability (≈450 °C) with high glass transition temperatures (T_g; 141–152 °C) and deep‐blue emission with high quantum yields. Specifically, the solution‐processed non‐doped device with AFpTPI as an emitter exhibits a maximum external quantum efficiency (EQE) of 4.56 % with CIE coordinates of (0.15, 0.06), which exactly matches the European Broadcasting Union (EBU) blue standard. In addition, AFmTPI also displays good efficiency and better color purity (EQE: 3.37 %; CIE (0.15, 0.05)). To the best of our knowledge, the present work is the first report on non‐doped solution‐processable OLEDs with efficiency close to 5 % and CIE y≤0.06.     

Temperature-Controlled Conversion of Boc-Protected Methylene Blue: Advancing Solid-State Time-Temperature Indicators

Cold-chain management is of high importance in preserving perishable products and in retaining quality. A visible marker on packages indicating complete maintenance of the cold chain assures safe consumption of products by end-users and assists in reducing waste. Time-temperature indicators (TTIs) are integrated markers that provide information about exposure of packages to adverse temperature and have been gaining increased attention by consumers. Here we present a methylene-blue-based derivative, N,N,N′,N′-tetramethyl-N¹⁰-Boc-phenothiazine-3,7-diamine (BocPTDA), that can be used as a solid-state organic TTI dye, exhibiting an irreversible change from colorless to blue green upon heating. The conversion properties, studied using a silicagel-coated plate, confirmed that BocPTDA undergoes a color change above 20 °C. At temperatures of 4 °C and below, no visible changes are exhibited, making BocPTDA a well-suited marker for monitoring abrupt temperature deviations indicating improper cold-chain management. Thus, application of BocPTDA-based TTI systems on packages could inform consumers about the cold-chain maintenance, assuring quality and safe consumption.     

Kinetic and equilibrium phenomena in the system: Acetone vapor and polycarbonate film

Amorphous films of Lexan polycarbonate have been exposed to acetone vapor at controlled temperatures and partial pressures in order to study sorption kinetics and thermodynamics and polymer crystallization behavior. Sorption isotherms show a discontinuity is slope at or near the depressed glass transition, which itself was identified by torsion pendulum measurements. Crystallization abruptly begins to occur at partial pressures equal to or slightly above that of the solubility transition and is manifested by delayed desorption and whitening phenomena. In this process 20% crystallinity is usually developed, as measured by calorimetry which, however, produces a 40% drop in acetone solubility. Although the depressed glass temperature is near 0°C. in saturated atmospheres—a drop of 145°C.—the melting point is only depressed 60 or 70°C. Such disparity probably accounts for the enhanced polycarbonate crystallization rate in acetone over that in the dry bulk polymer above the normal T_g.     

Synthesis of photosensitive and thermosetting poly(phenylene ether) based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol‐co‐2,6‐dimethyl‐phenol] and a photoacid generator

A chemically amplified photosensitive and thermosetting polymer based on poly[2,6‐di(3‐methyl‐2‐butenyl)phenol (15 mol %)‐co‐2,6‐dimethylphenol (85 mol %)] ( 3c ) and a photoacid generator [(5‐propylsulfonyloxyimino‐5H‐thiophen‐2‐ylidene)‐(2‐methylphenyl)acetonitrile] was developed. Poly[2,6‐bis(3‐methyl‐2‐butenyl)phenol]‐co‐2,6‐dimethylphenol)] ( 3 ) with high molecular weights (number‐average molecular weight ～ 24,000) was prepared by the oxidative coupling copolymerization of 2,6‐di(3‐methyl‐2‐butenyl)phenol with 2,6‐dimethylphenol in the presence of copper(I) chloride and pyridine as the catalyst under a stream of oxygen. The structures of 3 were characterized with IR, ¹H NMR, and ¹³C NMR spectroscopy. 3 was crosslinked by a thermal treatment at 300 °C for 1 h under N₂. The 5% weight loss temperatures and glass‐transition temperatures of the cured copolymers reached around 420 °C in nitrogen and 300 °C, respectively. The average refractive index of the cured copolymer ( 3c ) film was 1.5452, from which the dielectric constant at 1 MHz was estimated to be 2.6. The resist showed a sensitivity of 35 mJ cm^?2 and a contrast of 1.6 when it was exposed to 436‐nm light, postexposure‐baked at 145 °C for 5 min, and developed with toluene at 25 °C. A fine negative image featuring 8‐μm line‐and‐space patterns was obtained on a film exposed to 100 mJ cm^?2 with 436‐nm light in the contact‐printed mode. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 149–156, 2005     

NEW PHOTO-CONVERTIBLE REACTIONS OF BLUE-FLUORESCENT CALF α-CRYSTALLIN

Abstract— Both native blue fluorescent α-crystallin from calf lenses and UV (300 nm)-irradiated blue-fluorescent α-crystallin, when further irradiated with 365 nm-UV light, produce photo-products capable of emitting a new fluorescence at 455 nm. Illumination of the photo-products with 420 nm visible light regenerates the original fluorescence at 420–425 nm. In addition, another fluorescence at 400 nm has also been found in UV (300 nm)-irradiated blue-fluorescent α-crystallin, when exposed to 365 nm-UV light.     

THE RELATIONSHIP BETWEEN CAROTENOID PIGMENTS AND RESISTANCE TO RADIATION IN NON-PHOTOSYNTHETIC BACTERIA

Abstract— A radiation-resistant Micrococcus sp. and a colorless mutant subject to gamma radiation were found to have identical killing curves. Similar results were obtained with ultraviolet light. However when exposed to visible light in the presence of the photosensitizer, toluidine blue, the pigmented wild-type was unaffected whereas the colorless mutant was killed. Sarcina lutea and a colorless mutant were killed at similar rates following exposure to x-rays and U.V. light, whereas previous studies have demonstrated that the pigmented wild-type is protected against lethal photosensitizations by visible light. It is concluded that the effect of carotenoid pigments in radiation damage is limited to protecting cells against the lethal effects of visible light and is without effect at shorter wavelengths.     

Thermal transition of a wholly aromatic thermotropic liquid crystalline copolyester

A copolyester was prepared from p-hydroxybenzoic acid (HBA), 2,6-naphthalene dicaboxylic acid (NDA), and hydroquinone (HQ). Thermal transition behavior and the crystal structure of this copolyester were investigated by using polarized light microscopy (PLM), differential scanning calorimetry (DSC), and wide-angle X-ray diffraction (WAXD) after annealing at solid-phase polymerization conditions. A glass transition or newly ordered structure in the 270–290°C range was observed on annealing at 260°C, which increased with annealing time, attributed to mobility and reactive rearrangement in amorphous regions. Broad and unclear WAXD profiles and multimelting behaviors were found on annealing at 280°C, and explained by hexagonal and orthorhombic lattice formation and transformation. A large increase in melting temperature was observed only on annealing at a temperature (320°C) near the crystal–nematic transition, suggesting annealing temperatures near the melting point are required for sufficient mobility to afford crystalline rearrangement via transesterification. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3763–3769, 1999     

Thermal stability of recombinant green fluorescent protein (GFPuv) at various pH values

The thermal stability of the recombinant green fluorescent protein (GFPuv) expressed by Escherichia coli cells and isolated by three-phase partitioning extraction with hydrophobic interaction chromatography was studied. The GFPuv (3.5–9.0 μg of GFPuv/mL) was exposed to various pH conditions (4.91–9.03) and temperatures (75–95°C) in the 10 mM buffers: acetate (pH 5.0–7.0), phosphate (pH 5.5–8.0), and Tris-HCl (pH 7.0–9.0). The extent of protein denaturation (loss of fluorescence intensity) was expressed in decimal reduction time (D-value), the time exposure required to reduce 90% of the initial fluorescence intensity of GFPuv. For pH 7.0 to 8.0, the thermostability of GFPuv was slightly greater in phosphate buffer than in Tris-HCl. At 85°C, the D-values (pH 7.1–7.5) ranged from 7.24 (Tris-HCl) to 13.88 min (phosphate) The stability of GFPuv in Tris-HCl (pH>8.0) was constant at 90 and 95°C, and the D-values were 7.93 (pH 8.38–8.92) and 6.0 min (pH 8.05–8.97), respectively. The thermostability of GFPuv provides the basis for its potential utility as a fluorescent biologic indicator to assay the efficacy of moist-heat treatments at temperatures lower than 100°C.