Comparison of the acute toxicity of tributyltin and copper to veliger larvae of Nassarius reticulatus (L.)

The ban on the use of tributyltin (TBT) is promoting an increasing use of copper as an active biocide in antifouling paints, with consequent rising levels of this metal in the environment. This study assesses the acute toxicity of copper and tributyltin to the larvae of the mollusc gastropod Nassarius reticulatus. Recently hatched veligers were exposed to nominal TBT‐Sn concentrations of 0.9, 1.4, 1.9, 2.8, 3.8, 4.7 and 5.6 µg l^?1 and nominal copper concentrations of 9.4, 23.4, 46.9, 70.3, 93.8, 117.2, 140.6 and 164.1 µg l^?1 for up to 96 h, under static conditions (17 ± 1 °C and 33 ± 1 psu). The percentage of larval mortality was determined for each organometal/metal concentration and exposure time (1, 24, 48, 72 and 96 h). Both TBT and copper had a highly significant effect on larvae survival (p < 0.001) for all times of exposure, except for the first hour in the particular case of TBT. The lowest observed effect concentration for TBT‐Sn decreased over time from 3.8 µg l^?1 at 24 h to 1.9 µg l^?1 at 96 h, whereas for copper it remained constant over time (46.9 µg l^?1). The median lethal concentration (LC₅₀) for TBT‐Sn decreased from 4.87 µg l^?1 at 24 h to 1.78 µg l^?1 at 96 h, and the LC₅₀ for copper decreased from 83.08 µg l^?1 at 24 h to 58.84 µg l^?1 at 96 h. TBT is far more toxic to N. reticulatus larvae than copper. However, owing to the higher copper environmental concentrations, the risk factors of the two biocides may approach each other. This stresses the need to find adequate substitutes for organotin biocides in future antifouling paints. Copyright © 2005 John Wiley & Sons, Ltd.     

Effects of Tributyltin(IV) Chloride Exposure on Larvae of Ciona intestinalis (Urochordata): An Ultrastructural Study

The effects of tributyltin(IV) chloride (TBT chloride) have been tested on embryos of the ascidian Ciona intestinalis , at two different stages of development: (1) before hatching (coiled larval stage) and (2) 2 h after hatching (swimming larval stage). In vivo observations carried out with a light microscope showed that embryos at the coiled larval stage did not hatch following exposure to TBT chloride. Severe anomalies in the swimming larva, mainly concerning the morphology of the tail, which appeared twisted and squatter than in the controls, were observed. Such anomalies were also found at a functional level, i.e. contractile movements were poor so that the larvae appeared motionless. Ultrastructural investigations carried out using a transmission electron microscope (TEM) evidenced that the muscle cells were damaged. Modifications mainly occurred in mitochondria and myofibrils, i.e. the energetic and enzymic centres. This fact is probably the main cause of the loss of mobility of the larvae.     

Electrospray ionization mass spectrometry of tributyltin(IV) complexes and their larvicidal activity on mosquito larvae: crystal and molecular structure of polymeric (Bu3Sn[O2CC6H4{NN(C6H3‐4‐OH(C(H)NC6H4OCH3‐4))}‐o])n

A series of tributyltin(IV) complexes of 2‐[(E)‐2‐(3‐formyl‐4‐hydroxyphenyl)‐1‐diazenyl]benzoic acid and 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls have been investigated by electrospray mass spectrometry (ESI‐MS) and tandem mass spectrometry (MSⁿ) techniques. The assignments are facilitated by agreement between observed and calculated isotopic patterns and MSⁿ studies. Single‐crystal X‐ray crystallography of (Bu₃Sn[O₂CC₆H₄{N?N(C₆H₃‐4‐OH(C(H)?NC₆H₄OCH₃‐4))}‐o])_n reveals a polymeric structure. Toxicity studies of the tributyltin(IV) complexes of the 4‐[((E)‐1‐{2‐hydroxy‐5‐[(E)‐2‐(2‐carboxyphenyl)‐1‐diazenyl]phenyl}methylidene)amino]aryls on the second larval instar of the Aedes aegypti and Anopheles stephensi mosquito larvae are also reported. The LC₅₀ values indicate that the complexes are effective larvicides, which range from a low of 0.36 ppm to a high of 0.69 ppm against the Ae. aegypti larvae and between 0.82 and 1.17 ppm against the An. stephensi larvae. Copyright © 2005 John Wiley & Sons, Ltd.     

Organometallic complexes in ascidian embryonic development: II. Effects on different stages and larvae

The effects of the organometallic compounds Bu₂Sn-D -(?;)sorbitol, Bu₂Sn-D -(+)glucose, Bu₂Sn-D -(?)fructose and Bu₂Sn-D -(+)glyceraldehyde were tested in vivo on different stages of Ascidian development, larval movement and metamorphosis. Organotin(IV) complexes are organometallic compounds widely used as industrial biocides, antifouling agents and agricultural fungicides and are toxic to a range of organisms. Two-cell stage embryos, if incubated for one hour in the organotin (IV) solutions, stopped the cleavage, which was restored when they were transferred into normal sea water. The gastrula stage was seriously affected in 10^?4mol dm^?3 solutions of the above-mentioned complexes: 85% of the embryos were anomalous neurulae with open neural folds, 5% were twisted larvae. The gastrulae, when incubated for 1 h in 10^?5mol dm^?3 solutions, developed twisted larvae in ovular envelopes and immobile larvae with twisted tails. Larvae treated with 10^?4mol dm^?3 and 10^?5 mol dm^?3 Bu₂Sn-D -(?)sorbitol, Bu₂Sn-D -(+)glucose and Bu₂Sn-D -(+)glyceraldehyde solutions stopped swimming, did not metamorphose and afterwards underwent cytolysis. An initial hyperactivity of circular movements, followed by immobility, was observed in the larvae incubated in Bu₂Sn-D -(?;)fructose.     

On‐line solid‐phase extraction coupled with liquid chromatography/electrospray ionization mass spectrometry for the determination of trace tributyltin and triphenyltin in water samples

On‐line solid‐phase extraction (SPE) for pre‐concentration and sample cleanup is one strategy to reduce matrix effects and to simultaneously improve detection sensitivity in liquid chromatography/mass spectrometry (LC/MS). This paper describes an on‐line SPE‐LC/MS method for the determination of tributyltin (TBT) and triphenyltin (TPhT) at trace levels in water samples. The direct coupling of an on‐line C₁₈ pre‐column to LC/MS was used to pre‐concentrate TBT and TPhT at trace levels from waters and to remove interfering matrix effects. Pre‐concentration was followed by separation of TBT and TPhT on a C₁₈ column using a mobile phase containing 0.1% (v/v) HCOOH/5 mM HCOONH₄ and methanol. While both electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) can be interfaced with MS for the detection of TBT and TPhT, ESI‐MS was preferred for this application. The calibration curve for the targets was linear in the concentration range 0.1–30 µg L^?1. The detection limit (signal‐to‐noise (S/N) ratio = 3) was 0.02 µg L^?1 when 3.0 mL of sample was enriched on the C₁₈ pre‐column. The recoveries of TBT and TPhT in spiked waters were from 81.0 to 101.9%. The reproducibilities for the analysis of the standard mixture (10 µg L^?1) for TBT and TPhT were 13.1 and 5.0%, respectively. The developed method was an easy and fast way to analyze TBT and TPhT in water samples. Copyright © 2009 John Wiley & Sons, Ltd.     

Emission to air of volatile organotins from tributyltin‐contaminated harbour sediments

An analytical method for determining the presence in air of volatile forms (e.g. chlorides) of tributyltin (TBT) and that of methylbutyltins Me _nBu_(4?n)Sn (n = 1–3) was developed and used to establish whether dredged harbour sediments contaminated with TBT served as sources of air pollution with respect to organotin compounds. The method was based on active sampling of the air being analysed and sorption of analytes onto Poropak‐N. Sorbed methylbutyltins were extracted with dichloromethane and analysed by gas chromatography using flame photometric detection. Other butyltins were converted into butyltin hydrides prior to analysis by gas chromatography. It was shown that TBT‐contaminated sediments from Marsamxett Harbour, Malta, placed in 0.5 l chambers through which air was displaced by continuous pumping for 11 days released mainly methylbutyltins, with concentrations (as tin) reaching maximum 48 h mean values of 8.7 (Me₃BuSn), 22.1 (Me₂Bu₂Sn) and 93.0 ng m^?3(MeBu₃Sn) being measured. Other volatile forms of TBT, dibutyltin and monobutyltin were detected in the headspace air, but very infrequently and at much lower tin concentrations (<2 ng m^?3). It was also shown that methylbutyltins dissolved in sea‐water ([Sn] = 0.2 to 400 ng l^?1) were very difficult to exsolve from this medium, even on prolonged evaporation of the solutions using mechanical agitation and active ventilation. The results suggest that emission of methylbutyltins from contaminated sediments probably occurs only from the surface of the material. The environmental implications of these findings in the management of TBT‐polluted harbour sediments are discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Effects of tri‐n‐butyltin (IV) chloride on neurulation of Ciona intestinalis (Tunicata,Ascidiacea): an ultrastructural study

This paper reports the cytotoxic effects of tri‐n‐butyltin (IV) chloride, TBTCl, on the neurulation process of the ascidian Ciona intestinalis. Exposure of the embryos at early neurula stage in 10^?5 and 10^?7 M TBT (IV) chloride solutions for 1–2 h provoked the irreversible arrest of their development. Morphological and ultrastructural observations suggested that most probably there are two principal causes determining the neurulation process block. The first is due to the TBT effects of inhibiting the polymerization and/or degradation of microfilaments and microtubules, proteins that constitute the cytoskeleton. The lack of orientation and extension of both microtubules and microfilaments of actin prevent the shape changes and mobility of neural plate blastomeres indispensable to the neurulation process. The second cause is certainly determined by the ultrastructural modification which mitochondria undergo. The ultrastructural anomalies showed by these organules are so serious as to impede their proper functionality with consequent inhibition of oxidative phosphorylation and ATP synthesis, remarkable metabolic processes that occur during ascidian neurulation. Copyright © 2005 John Wiley & Sons, Ltd.     

Modulation of the F1FO‐ATPase function by butyltin compounds

Among butyltin compounds, tributyltin (TBT), widely exploited in the past in antifouling paints for its biocidal properties, is long known as one of the most harmful sea contaminants. Among the ascertained and universal toxicity mechanisms, TBT targeting F₁F_O‐ATPase and thus impairing cell bioenergetics, is here reviewed. While TBT effects on F₁F_O‐ATPase have been investigated for decades, the possible impact of the derivatives dibutyltin (DBT) and monobutyltin (MBT), produced by abiotic and/or biotic dealkylation of TBT and usually considered far less toxic, have been poorly explored up until now. Butyltin effects on F₁F_O‐ATPase and their underlying action mechanism seem to be tightly structure dependent. Butyltins are membrane‐active toxicants. Owing to its more pronounced lipophilicity TBT targets the transmembrane F_O sector, blocks ionic translocation and causes a dose‐dependent loss of sensitivity to F_O inhibitors such as oligomycin and N,N′‐dicyclohexylcarbodiimide. DBT strongly inhibits F₁F_O‐ATPase activity by competing with the Mg⁺² cofactor in the F₁ catalytic site but is ineffective on the enzyme sensitivity to F_O inhibitors. MBT is apparently ineffective. The possible contribution of DBT to the overall butyltin toxicity on membrane systems may not be neglectable since usually TBT coexists with its derivatives in organotin‐exposed animal tissues. Copyright © 2013 John Wiley & Sons, Ltd.     

Novel alkoxyanthracene donor and benzothiadiazole acceptor for organic thin film transistor and bulk heterojunction organic photovoltaic cells

Novel alkoxy anthracene (ODA)‐based polymeric semiconductors were designed for polymer solar cell applications. Alkoxyanthracene, which contains many π electrons and electron donating group, was easily synthesized. The copolymers, poly(alkoxy anthracene‐alt‐thiophene benzothiadiazole thiophene) poly(ODA‐TBT) and poly(alkoxy anthracene‐alt‐benzothiadiazole) poly(ODA‐BT), have been obtained by Suzuki coupling polymerization. Both polymers have ODA unit as a donor and benzothiadiazole as an acceptor. ODA‐TBT has thiophene linkages between ODA and benzothiadiazole. The optical, thermal, and electrochemical properties have been investigated by UV–visible absorption, thermal gravimetric analysis, differential scanning calorimetry, and CV. Organic thin‐film transistor using polymers showed that the hole mobility of poly(ODA‐alt‐TBT) was around 3.6 × 10^?3 cm²/Vs with on/off ratio of 9.91 × 10⁵ while that of poly(ODA‐alt‐BT) was around 1.21 × 10^?2 cm²/Vs with on/off ratio of 2.64 × 10⁶. Organic photovoltaic performance based on polymers were evaluated with a configuration of ITO/PEDOT:PSS/active layer/LiF/Al. Poly(ODA‐TBT) exhibits a short circuit current (J_sc) of 3.9 mA/cm² and power conversion efficiency (PCE) of 1.4%, and poly(ODA‐BT) exhibits the J_sc of 6.4 mA/cm² and PCE of 2.2%. The better device performance of poly(ODA‐BT) is attributed to its charge transfer ability and enhanced mobility and crystallinity although poly(ODA‐BT) does not have extended π‐conjugation due to twisted structure compared with poly(ODA‐TBT). © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 1306–1314     

Aromaticity Effects on the Profiles of the Lowest Triplet‐State Potential‐Energy Surfaces for Rotation about the CC Bonds of Olefins with Five‐Membered Ring Substituents: An Example of the Impact of Baird’s Rule

A density functional theory study on olefins with five‐membered monocyclic 4n and 4n+2 π‐electron substituents (C₄H₃X; X=CH⁺, SiH⁺, BH, AlH, CH₂, SiH₂, O, S, NH, and CH^?) was performed to assess the connection between the degree of substituent (anti)aromaticity and the profile of the lowest triplet‐state (T₁) potential‐energy surface (PES) for twisting about olefinic C?C bonds. It exploited both Hückel’s rule on aromaticity in the closed‐shell singlet ground state (S₀) and Baird’s rule on aromaticity in the lowest ππ* excited triplet state. The compounds CH₂?CH(C₄H₃X) were categorized as set A and set B olefins depending on which carbon atom (C2 or C3) of the C₄H₃X ring is bonded to the olefin. The degree of substituent (anti)aromaticity goes from strongly S₀‐antiaromatic/T₁‐aromatic (C₅H₄⁺) to strongly S₀‐aromatic/T₁‐ antiaromatic (C₅H₄^?). Our hypothesis is that the shapes of the T₁ PESs, as given by the energy differences between planar and perpendicularly twisted olefin structures in T₁ [ΔE(T₁)], smoothly follow the changes in substituent (anti)aromaticity. Indeed, correlations between ΔE(T₁) and the (anti)aromaticity changes of the C₄H₃X groups, as measured by the zz‐tensor component of the nucleus‐independent chemical shift ΔNICS(T₁;1)_zz, are found both for sets A and B separately (linear fits; r²=0.949 and 0.851, respectively) and for the two sets combined (linear fit; r²=0.851). For sets A and B combined, strong correlations are also found between ΔE(T₁) and the degree of S₀ (anti)aromaticity as determined by NICS(S₀,1)_zz (sigmoidal fit; r²=0.963), as well as between the T₁ energies of the planar olefins and NICS(S₀,1)_zz (linear fit; r²=0.939). Thus, careful tuning of substituent (anti)aromaticity allows for design of small olefins with T₁ PESs suitable for adiabatic Z/E photoisomerization.     

Estimation of Critical Temperature of Thermal Explosion for Nitrosubstituted Azetidines Using Non-isothermal DSC

Based on reasonable hypothesis, two general expressions and their six derived formulae for estimating the critical temperature (T_b) of thermal explosion for energetic materials (EM) were derived from the Semenov's thermal explosion theory and eight non‐isothermal kinetic equations. We can easily obtain the values of the initial temperature (T_0i) at which DSC curve deviates from the baseline of the non‐isothermal DSC curve of EM, the onset temperature (T_ei), the exothermic decomposition reaction kinetic parameters and the values of T₀₀ and T_e0 from the equation T_{0i or ei}=T_{00 or e0}+a₁β_i+a₂β_i²+···+a_L?2β_i^L?2, i=1, 2, ;···, L and then calculate the values of T_b by the six derived formulae. The T_b values for seven nitrosubstituted azetidines, 3,3‐dinitroazetidinium nitrate ( 1 ), 3,3‐dinitroazetidinium picrate ( 2 ), 3,3‐dinitroazetidinium‐3‐nitro‐1,2,4‐triazol‐5‐onate ( 3 ), 1,3‐bis(3′,3′‐dinitroazetidine group)‐2,2‐dinitropropane ( 4 ), 1‐(2′,2′,2′‐trinitroethyl)‐3,3‐dinitroazetidine ( 5 ), 3,3‐dinitroazetidinium perchlorate ( 6 ) and 1‐(3′,3′‐dinitroazetidineyl)‐2,2‐dinitropropane ( 7 ), obtained with the six derived formulae are agreeable to each other, whose differences are within 1.5%. The results indicate that the heat‐resistance stability of the seven nitrosubstituted azetidines decreases in the order 6 > 7 > 5 > 4 > 3 > 2 > 1 .     

Theoretical Studies of the Reactions CFxH3−xCOOR+Cl and CF3COOCH3+OH

The mechanism and kinetics of the reactions of CF₃COOCH₂CH₃, CF₂HCOOCH₃, and CF₃COOCH₃ with Cl and OH radicals are studied using the B3LYP, MP2, BHandHLYP, and M06‐2X methods with the 6‐311G(d,p) basis set. The study is further refined by using the CCSD(T) and QCISD(T)/6‐311++G(d,p) methods. Seven hydrogen‐abstraction channels are found. All the rate constants, computed by a dual‐level direct method with a small‐curvature tunneling correction, are in good agreement with the experimental data. The tunneling effect is found to be important for the calculated rate constants in the low‐temperature range. For the reaction of CF₃COOCH₂CH₃+Cl, H‐abstraction from the CH₂ group is found to be the dominant reaction channel. The standard enthalpies of formation for the species are also calculated. The Arrhenius expressions are fitted within 200–1000 K as k_T(1)=8.4×10^?20T ^2.63exp(381.28/T), k_T(2)=2.95×10^?21T ^3.13exp(?103.21/T), k_T(3)=1.25×10^?23T ^3.37exp(791.98/T), and k_T(4)=4.53×10^?22T ^3.07exp(465.00/T).     

Preliminary evidence for in vitro methylation of tributyltin in a marine sediment

Recent reports from our laboratory on the occurrence of methylbutyltins in marine sediments and seawater suggest that these compounds are formed in the environment by the methylation of both tributyltin (TBT) and that­of its degradation products, i.e. dibutyltin and monobutyltin, to give Me_nBu_(4?n)Sn for which n = 1, 2 and 3 respectively. We investigated the possibility of inducing methylation of TBT in seawater–sediment mixtures in experiments carried out in vitro using environmental materials collected from a yacht marina in Msida, Malta. Three water–sediment mixtures, which were shown to contain TBT, dibutyltin and monobutyltin but no other organotins, were spiked with tributyltin chloride (90 mg in 100 ml sea‐water/100 ml sediment); to one mixture was added sodium acetate and to another methanol, to act as possible additional carbon sources, and all mixtures were allowed to stand at 25 °C in stoppered clear‐glass bottles in diffused light for a maximum of 315 days. Speciation and quantification of organotins was performed using aqueous phase boroethylation with simultaneous solvent extraction followed by gas chromatography with flame photometric detection. The atmosphere inside the bottles quickly became reducing with abundant presence of H₂S, and after an induction period of about 112 days, and only in the reaction mixture containing methanol, methyltributyltin (MeBu₃Sn) was observed in both sediment (maximum concentration 0.87 µg_Sn g^?1) and overlying water (maximum concentration 6.0 µg_Sn l^?1). The minimum conversion yield of TBT into MeBu₃Sn was estimated to be 0.3%. MeBu₃Sn has a significantly lower affinity for sediment than TBT and, therefore, is more mobile in the marine environment, possibly also migrating into the atmosphere to generate a hitherto unsuspected flux of organotin into that phase. Copyright © 2001 John Wiley & Sons, Ltd.     

Simultaneous quantification of T4, T3, rT3, 3,5‐T2 and 3,3′‐T2 in larval zebrafish (Danio rerio) as a model to study exposure to polychlorinated biphenyls

Environmental toxicants that interfere with thyroid hormone (TH) signaling can impact growth and development in animals and humans. Zebrafish represent a model to study chemically induced TH disruption, prompting the need for sensitive detection of THs. Simultaneous quantification of 3,3′,5‐triiodo‐l ‐thyronine (T3), thyroxine (T4), 3,3′,5′‐triiodo‐l ‐thyronine (rT3), 3,5‐diiodo‐l ‐thyronine (3,5‐T2) and 3,3′‐diiodo‐l ‐thyronine (3,3′‐T2) in zebrafish larvae was achieved by ultra‐performance liquid chromatography–tandem mass spectrometry in positive ion mode. Solid‐phase extraction with SampliQ cartridges and derivatization with 3 m hydrochloric acid in n‐butanol reduced matrix effects. Derivatized compounds were separated on an Acquity UPLC BEH C₁₈ column with mobile phases consisting of 0.1% acetic acid in deionized water and 0.1% acetic acid in methanol. The limits of detection ranged from 0.5 to 0.6 pg injected on column. The method was validated by evaluating recovery (77.1–117.2%), accuracy (87.3–123.9%) and precision (0.5–12.4%) using diluted homogenized zebrafish embryos spiked with all target compounds. This method was then applied to zebrafish larvae collected after 114 h of exposure to polychlorinated biphenyls (PCBs), including PCB 28, PCB 66 and PCB 95, or the technical mixture Aroclor 1254. Exposure to PCB 28 and PCB 95 increased the T4:T3 ratio and decreased the T3:rT3 ratio, demonstrating that this method can effectively detect PCB‐induced alterations in THs.     

Photoexcited Singlet and Triplet States of a UV Absorber Ethylhexyl Methoxycrylene

The excited states of UV absorber, ethylhexyl methoxycrylene (EHMCR) have been studied through measurements of UV absorption, fluorescence, phosphorescence and electron paramagnetic resonance (EPR) spectra in ethanol. The energy levels of the lowest excited singlet (S₁) and triplet (T₁) states of EHMCR were determined. The energy levels of the S₁ and T₁ states of EHMCR are much lower than those of photolabile 4‐tert‐butyl‐4′‐methoxydibenzoylmethane. The energy levels of the S₁ and T₁ states of EHMCR are lower than those of octyl methoxycinnamate. The weak phosphorescence and EPR B_min signals were observed and the lifetime was estimated to be 93 ms. These facts suggest that the significant proportion of the S₁ molecules undergoes intersystem crossing to the T₁ state, and the deactivation process from the T₁ state is predominantly radiationless. The photostability of EHMCR arises from the ³ππ* character in the T₁ state. The zero‐field splitting (ZFS) parameter in the T₁ state is D** = 0.113 cm^?1.     

Nanocrystals of Co2+‐Doped MgGa2O4: Preparation by a Low‐Temperature Combustion Method and Optical Properties

Co²⁺‐doped MgGa₂O₄ nanocrystals were prepared at 500°C by a low‐temperature combustion method without any further calcination. Powder X‐ray diffraction (XRD) indicated that the only crystalline phase in the product was MgGa₂O₄ with a grain size of 33–36 nm. Scanning electron microscopy (SEM) showed that the products contained pores formed by the gases evolved during the combustion reaction. The excitation and emission spectra of the nanocrystalline powders in the visible and near infrared regions were characteristic of tetrahedral Co²⁺ ions, suggesting that Co²⁺ ions replaced tetrahedral Mg²⁺ ions in the MgGa₂O₄ crystals. We assigned the visible and near infrared luminescent bands to the spin‐allowed ⁴T₁(⁴P) → and ⁴A₂(⁴F) and ⁴T₁(⁴P) → ⁴T₂(⁴F) transitions.     

Synthesis,spectra and conductivity of 1‐D polymers of nickel(I)‐and copper(II )‐porphyrazine with sulfur bridges

The title polymers PNIPzS₄ and PCuPzS₄ were synthesized by reaction of phthalonitrile and 2,3,5,6‐tetracyano‐1,4‐dithiin with corresponding metal salt. Their structures and properties were characterized by associating the experimental results with MO and Cl calculations of the dimer molecule as model polymer in the ZINDO method. It has been found that the PNiPzS₄ (or PCuPzS₄) shows the semiconductivity at T < 253 K (or 260 K) and T > 278 K (or 286 K) and the conductivity increase with a hoist of temperature at 253 K (or 260 K) < T < 278 K (or 286 K). The conductivity σ of the PNiPzS₄ and PCuPzS₄ under pressure 13.73 MPa is 1.56×10^?4 and 9.33×10^?5 S/cm, respectively.     

Organometallic complexes with biological molecules. XV. Effects of tributyltin(IV)chloride on enzyme activity,Ca2+, and biomolecule and synthesis in Ciona intestinalis (Urochordata) ovary

Considerable attention has been given in recent years to the possibility that xenobiotics in the environment may affect reproduction in animals. In this study, the relative impact of tributyltin(IV) (TBT) chloride, one of the most toxic environmental pollutants, was investigated using Ciona intestinalis ovary as a model system. The pleiotropic effects of TBT exposure are concentration dependent and include a decrease of ATP levels, lipid content and nucleic acid content and synthesis. In contrast, a marked increase in calcium (Ca²⁺) and glucose content is observed. Furthermore, TBT alters enzymatic activity, inhibiting creatine kinase and stimulating alkaline phosphatase and cholinesterase (at concentrations higher than 10^?5M in sterile sea water solution). The implications of these effects on reproduction and embryonal development are discussed, along with the possibility that they reflect an extreme cellular defence mechanism triggered to avoid deleterious consequences for the survival of the species.Copyright © 2001 John Wiley & Sons, Ltd.     

Solid‐State NMR Study on Relationships between Miscibility and Chain Mobility in Poly(4‐Methylstyrene)/Poly(Cyclohexyl Methacrylate) Blend

The phase behavior and motional mobility in binary blends of poly(4‐methylstyrene) (P4MS) and poly(cyclohexyl methacrylate) (PCHMA) have been examined by ¹³C solid state NMR techniques. The blend miscibility was studied by measuring the ¹H spin‐relaxation times in the laboratory frame (T₁^H) and in the rotating frame (T_1ρ^H), respectively. Although intermolecular spin diffusion contributes to the proton relaxations in accordance with homogeneity, T_1ρ^H data shows signs of in complete averaging. The T_1ρ^H relaxation behavior indicates the existence of heterogeneous do mains with shortest dimensions in the nanometer range, which is also sup ported by the intermolecular cross polarization experiments with variable contact times. In addition, according to the resuits of carbon T_1ρ relaxation time measurements, it is concluded that mixing is intimate some what enough to cause a reduction in local chain mobility for P4MS and vice versa for PCHMA.     

Researches on Thermal Decomposition Kinetics of Composite Modified Double-base Propellants

The thermal decomposition kinetics of composite modified double‐base (CMDB) propellants with a series of contents of hexogeon (RDX) was investigated by using parameters of T_eo, T_i, T_p, T_f, T_b, T_a, E, lg A and ΔH, which were obtained from using a CDR‐4P differential scanning calorimeter (DSC) and Perkin‐Elmer Pyris 1 thermogravimetric analyzer (TG) analyses with heating rates of 5, 10, 15 and 20 K/min. Reliable activation energy was calculated using Flynn‐Wall‐Ozawa method before analyzing the thermal decomposition mechanism. TG‐DTG curves were treated with Malek method in order to obtain the reaction mechanisms. The obtained results show that the thermal decomposition mechanisms with the conversion from 0.2 to 0.4 was f(α)?1/2α, and with the conversion from 0.5 to 0.7 was f(α)?(1/4)(1?α)[?ln(1?α)]^?3.