Influences of Coal Ash Leachates and Emergent Macrophytes on Water Quality in Wetland Microcosms.

The storage of coal combustion residue (CCR) in surface water impoundments may have an impact on nearby water quality and aquatic ecosystems. CCR contains leachable trace elements that can enter nearby waters through spills and monitored discharge. It is important, therefore, to understand their environmental fate in affected systems. This experiment examined trace element leachability into freshwater from fly ash (FA), the most common form of CCR. The effects on water quality of FA derived from both high and low sulfur coal sources as well as the influences of two different emergent macrophytes, Juncus effusus and Eleocharis quadrangulata, were evaluated in wetland microcosms. FA leachate dosings increased water electric conductivity (EC), altered pH, and, most notably, elevated the concentrations of boron (B), molybdenum (Mo), and manganese (Mn). The presence of either macrophyte species helped reduce elevated EC, and B, Mo, and Mn concentrations over time, relative to microcosms containing no plants. B and Mo appeared to bioaccumulate in the plant tissue from the water when elevated by FA dosing, while Mn was not higher in plants dosed with FA leachates. The results of this study indicate that emergent macrophytes could help ameliorate downstream water contamination from CCR storage facilities and could potentially be utilized in wetland filtration systems to treat CCR wastewater before discharge. Additionally, measuring elevated B and Mo in aquatic plants may have potential as a monitoring tool for downstream CCR contamination.

Anger Expression Style Predicts the Domain of the First Smoking Relapse After a Quit Attempt.

BACKGROUND: Risk for smoking relapse may be associated with context-dependent social and behavioral cues. However, lack of research examining the role of trait negative mood such as anger in this relationship and assessment of objective indices related to smoking status (e.g., biochemical measures) may limit existing findings. We examined the roles of trait anger, habitual anger expression behavior, and the situation in which the first incident of smoking lapse following a quit attempt occurs. METHODS: One-hundred and five smokers interested in cessation (mean age, SD: 34.7 ± 11.8) set a quit day and attended multiple post-quit assessments where they were asked to provide biochemical measures including exhaled carbon monoxide (CO) and self-report measurements, including smoking status. RESULTS: Eighty-eight participants (40 women) returned to smoking over the 12-month study period. Self-reported smoking status was verified by exhaled CO measurements. Thirty-one percent of participants who relapsed reported the first lapse occurring at home, 15% at work, 14% at a restaurant or a bar, and 8% in a car. Multinomial logistic regression models found that high levels of anger-out were associated with smoking relapse in situations other than work or home (p <.05). CONCLUSIONS: These results expand prior work suggesting habitual anger expression style may moderate associations between situational factors and risk for smoking relapse, highlighting the need to incorporate findings in treatment methods. Absence of gender differences suggests the situational factors explored here affect relapse independent of gender.

Life adversity is associated with smoking relapse after a quit attempt.

Multiple cross-sectional studies have linked adverse childhood events and adult adversities to current smoking, lifetime smoking, and former smoking. To date, however, there have been no direct observational studies assessing the influence of adversities on smoking relapse. We prospectively followed 123 participants, 86 of whom were habitual smokers, from pre-quit ad libitum smoking to four weeks post-quit. Thirty-seven non-smokers were also tested in parallel as a comparison group. Subjects provided biological samples for confirmation of abstinence status and self-report history of adversities such as abuse, neglect, family dysfunction, incarceration, and child-parent separation. They also completed mood and smoking withdrawal symptom measures. The results indicated that within non-smokers and smokers who relapsed within the first month of a quit attempt, but not abstainers, females had significantly higher adversity scores than males. Cigarette craving, which was independent from depressive affect, increased for low adversity participants, but not those with no adversity nor high adversity. These results demonstrate that sex and relapse status interact to predict adversity and that craving for nicotine may be an important additional mediator of relapse. These results add further support to the previous cross-sectional evidence of an adversity and smoking relationship. Further studies to clarify how adversity complicates smoking cessation and impacts smoking behaviors are warranted.

Mitochondrial biotransformation of omega-(phenoxy)alkanoic acids, 3-(phenoxy)acrylic acids, and omega-(1-methyl-1H-imidazol-2-ylthio)alkanoic acids: a prodrug strategy for targeting cytoprotective antioxidants to mitochondria.

Mitochondrial reactive oxygen species (ROS) generation and the attendant mitochondrial dysfunction are implicated in a range of disease states. The objective of the present studies was to test the hypothesis that the mitochondrial beta-oxidation pathway could be exploited to deliver and biotransform the prodrugs omega-(phenoxy)alkanoic acids, 3-(phenoxy)acrylic acids, and omega-(1-methyl-1H-imidazol-2-ylthio)alkanoic acids to the corresponding phenolic antioxidants or methimazole. 3- and 5-(Phenoxy)alkanoic acids and methyl-substituted analogs were biotransformed to phenols; rates of biotransformation decreased markedly with methyl-group substitution on the phenoxy moiety. 2,6-Dimethylphenol formation from the analogs 3-([2,6-dimethylphenoxy]methylthio)propanoic acid and 3-(2,6-dimethylphenoxy)acrylic acid was greater than that observed with omega-(2,6-dimethylphenoxy)alkanoic acids. 3- and 5-(1-Methyl-1H-imidazol-2-ylthio)alkanoic acids were rapidly biotransformed to the antioxidant methimazole and conferred significant cytoprotection against hypoxia-reoxygenation injury in isolated cardiomyocytes. Both 3-(2,6-dimethylphenoxy)propanoic acid and 3-(2,6-dimethylphenoxy)acrylic acid also afforded cytoprotection against hypoxia-reoxygenation injury in isolated cardiomyocytes. These results demonstrate that mitochondrial beta-oxidation is a potentially useful delivery system for targeting antioxidants to mitochondria.

Ring currents in tangentially p-p bonded sigma-aromatic systems.

We report a theoretical study of ring systems that delocalize electrons in a cyclic array of p orbitals arranged tangentially in sigma-bonding fashion. Sigma-bonded arrays are compared to conventional pi-bonded analogues with respect to orbital symmetry and aromatic/antiaromatic behavior. In a one-to-one correspondence between pi and tangential molecular orbitals of a cycle, local rotation turns each pi to a tangential basis function, changing bonding interactions to antibonding and inverting the order of filling of molecular orbitals. The ipsocentric ring-current mapping approach is used to evaluate aromaticity on the magnetic criterion. As for conventional pi-ring currents, the sigma-ring current in tangential p-p bonded systems is dominated by the HOMO-LUMO transition, corresponding to circulation of four electrons in diatropic (4n + 2)-electron cycles but two in paratropic (4n)-electron cycles. The systems examined here utilize either C 2p or Si 3p orbitals for delocalization. Although interchangeable with C with respect to the fundamental orbital symmetry and ring-current rules, Si bonds at greater internuclear distances, a feature that allows easier design of potentially stable sigma-aromatic structures. Calculations show the wheel-like Si10C50H70 structure 6 as a stable, neutral aromatic molecule with a diatropic ring current following the sigma-bond path formed by Si 3p orbitals.

Theoretical studies of quantum amplified isomerizations for imaging systems involving hexamethyl Dewar benzene and related systems.

The ring-opening reactions of the radical cations of hexamethyl Dewar benzene (1) and Dewar benzene have been studied using density functional theory (DFT) and complete active-space self-consistent field (CASSCF) calculations. Compound 1 is known to undergo photoinitiated ring opening by a radical cation chain mechanism, termed "quantum amplified isomerization" (QAI), which is due to the high quantum yield. Why QAI is efficient for 1 but not other reactions is explained computationally. Two radical cation minima of 1 and transition states located near avoided crossings are identified. The state crossings are characterized by conical intersections corresponding to degeneracy between doublet surfaces. Ring opening occurs by formation of the radical cation followed by a decrease in the flap dihedral angle. A rate-limiting Cs transition state leads to a second stable radical cation with an elongated transannular C-C bond and an increased flap dihedral. This structure proceeds through a conrotatory-like pathway of Cs symmetry to give the benzene radical cation. The role of electron transfer was investigated by evaluating oxidation of various systems using adiabatic ionization energies and electron affinities calculated from neutral and cation geometries. Electron-transfer theory was applied to 1 to investigate the limiting effects of back-electron transfer as it is related to the unusual stability of the two radical cations. Expected changes in optical properties between reactants and products of Dewar benzene compounds and other systems known to undergo QAI were characterized by computing frequency-dependent indices of refraction from isotropic polarizabilities. In particular, the reaction of 1 shows greater contrast in index of refraction than that of the Dewar benzene parent system.

Peroxynitrate and peroxynitrite: a complete basis set investigation of similarities and differences between these NOx species.

Peroxynitric acid/peroxynitrate (PNA) rivals peroxynitrous acid/peroxynitrite (PNI) in importance as a reactive oxygen species. These species possess similar two-electron oxidative behavior. On the other hand, stark differences exist in the stability of these molecules as a function of pH and in the presence of CO(2), and also in the types of bond homolysis reactions that PNA and PNI may undergo. Using CBS-QB3 theory, we examine these similarities and differences. The activation barriers for two-electron oxidation of NH(3), H(2)S, and H(2)C=CH(2) by PNA and PNI are found to be generally similar. The O-O BDE of O(2)NOOCO(2-) is predicted to be 26 kcal/mol greater than that of ONOOCO(2-). This accounts for the insensitivity of PNA to the presence of CO(2). Likewise, the O-O BDE of O(2)NOOH is predicted to be 19 kcal/mol greater than that of ONOOH, in excellent agreement with experiment. The fundamental principle underlying the large differences in O-O BDEs between PNA and PNI species is that the NO(2) that is formed from PNI can relax from the (2)B(2) excited state to the (2)A(1) ground state, whereas no such comparable state change occurs with NO(3) from PNA. Decomposition of the anions O(x)NOO(-) is more complex, with the energetics influenced by solvation. ONOO(-) can homolyze to yield NO/O(2-); however, this pathway represents a thermodynamic "dead end" since the radical pairs generated by homolysis should mostly revert to starting material. However, decomposition of O(2)NOO(-) yields the stable products NO(2-)/(3)O(2), a couple that is more stable than starting material. This may occur either by initial formation of NO(2)/O(2-) or NO(2-)/(1)O(2), with the latter intermediates thermodynamically favored both in the gas phase and in solution. Given the extremely fast back-reaction of the homolysis products, heterolysis probably dominates the observed O(2)NOO(-) decomposition kinetics. This is in agreement with the first of two "kinetically indistinguishable" mechanistic possibilities proposed for O(2)NOO(-) decomposition (Goldstein, S.; Czapski, G.; Lind, J.; Merényi, G. Inorg. Chem. 1998, 37, 3943-3947).

Conformation-dependent state selectivity in O-O cleavage of ONOONO: an "inorganic cope rearrangement" helps explain the observed negative activation energy in the oxidation of nitric oxide by dioxygen.

ONOONO has been proposed as an intermediate in the oxidation of nitric oxide by dioxygen to yield nitrogen dioxide. The O-O bond breaking reactions of this unusual peroxide, and subsequent rearrangements, were evaluated using CBS-QB3 and B3LYP/6-311G hybrid density functional theory. The three stable conformers (cis,cis-, cis,trans-, and trans,trans-ONOONO, based on the O-N-O-O dihedral angles of either approximately 0 degrees or approximately 180 degrees ) are predicted to have very different O-O cleavage barriers: 2.4, 13.0, and 29.8 kcal/mol, respectively. These large differences arise because bond breaking leads to correlation of the nascent NO(2) fragments with either the ground (2)A(1) state or the excited (2)B(2) state of NO(2), depending on the starting ONOONO conformation. A cis-oriented NO(2) fragment correlates with the (2)A(1) state, whereas a trans-oriented NO(2) fragment correlates with the (2)B(2) state. Each NO(2) fragment that correlates with (2)A(1) lowers the O-O homolysis energy by approximately 15 kcal/mol, similar to the approximately 17-25 kcal/mol (2)A(1) --> (2)B(2) energy difference in NO(2). Hence, this provides an unusual example of conformation-dependent electronic state selectivity. The O-O bond homolysis of cis,cis-ONOONO is particularly interesting because it has a very low barrier and arises from the most stable ONOONO conformer, and also due to obvious similarities to the well-known [3,3]-sigmatropic shift of 1,5-hexadiene, i.e., the Cope rearrangement. As an additional proof of our state selectivity postulate, a comparison is also made to breakage of the O-O bond of cis,cis-formyl peroxide, where no significant stabilization of the transition state is available because the (2)A(1) and (2)B(2) states of formyloxy radical are near-degenerate in energy. In the case of trans,trans-ONOONO, the O-O bond breaking transition state is a concerted rearrangement yielding O(2)NNO(2), whereas for cis,cis- and cis,trans-ONOONO, the initially formed NO(2) radical pairs can undergo further rearrangement to yield ONONO(2). It is proposed that previous spectroscopic observations of certain N=O stretching frequencies in argon-matrix-isolated products from the reaction of NO with O(2) (or (18)O(2)) are likely from ONONO(2), not the OONO radical as reported.