The Influence of Abiotic Factors on the Uptake and Elimination of 3-Trifluoromethyl-4-Nitrophenol by Larval Sea Lamprey (Petromyzon marinus)

The backbone of sea lamprey (Petromyzon marinus) control in the Great Lakes is the use of the piscicide, 3-trifluoromethyl-4-nitrophenol (TFM), which is applied to streams containing larval sea lampreys. However, TFM effectiveness can be influenced by abiotic factors such as pH and temperature, which fluctuate daily and seasonally. The objectives of this thesis were to evaluate the influence of pH, temperature, and season on the toxicity, uptake, and elimination of TFM by larval sea lamprey. Radio-labeled TFM (14C-TFM) was used to determine how TFM uptake rates varied at different water pHs or temperatures during exposure to TFM at the 12 h LC50 (4.6 mg L-1) or 12 h LC99(7.6 mg L-1)of larval lamprey. These experiments indicated that TFM uptake rates were 4-5.5 fold greater at pH 6.5 compared to pH 9.0 and whole body TFM accumulation was also greater at pH 6.5. These differences were likely because a greater proportion of the total TFM (sum of ionized plus un-ionized TFM) concentration was in its more lipophilic, un-ionized (phenolic) form at pH 6.5 compared to pH 9.0. Uptake was also greater at 22 °C compared to 6 °C, which was likely caused by increased gill ventilation due to greater metabolic rates at warm temperatures. The effects of pH and temperature on TFM excretion were then tested by injecting lamprey with 100 nmol g-1 14C-TFM and measuring its appearance in TFM-free water over 24 h. In contrast to uptake, elimination rates were 1.3-1.9 fold greater at pH 9.0 than at pH 6.5 during 2-4 h of depuration in TFM-free water. Yet, temperature had no effect on the elimination rates. Season affected the sensitivity of lamprey to TFM, where the 12 h LC50 for lamprey was 2.5 fold greater in summer than in spring. Yet, season did not influence whole body TFM concentrations in lamprey that experienced mortality during TFM exposure, averaging between 40-50 nmol g-1 wet weight. However, the internal TFM burden was approximately 2.5 fold greater in these fish compared to those that survived. Differences in TFM detoxification capacity may have explained these findings, but whole body concentrations of the metabolite, TFM-glucuronide, were below detection. Neither was mRNA abundance of the enzyme UDP-glucuronosyltransferase (UGT) influenced by season or temperature. TFM applications during spring and fall could increase TFM efficiency when larval sea lampreys are less tolerant to TFM. Applying TFM to large streams in spring or fall should also be considered because it would result in reduced concentrations of TFM needed to control larval sea lamprey populations, resulting in more economical treatments, while still protecting Great Lakes fisheries from sea lamprey parasitism/predation

Metal-Metal Bonding in Uranium-Group 10 Complexes

Heterobimetallic complexes containing short uranium–group 10 metal bonds have been prepared from monometallic IU^IV(OAr^P-κ²<i>O</i>,<i>P</i>)₃ (<b>2</b>) {[Ar^PO]⁻ = 2-<i>tert</i>-butyl-4-methyl-6-(diphenylphosphino)­phenolate}. The U–M bond in IU^IV(μ-OAr^P-1κ¹<i>O</i>,2κ¹<i>P</i>)₃M⁰, M = Ni (<b>3–Ni</b>), Pd (<b>3–Pd</b>), and Pt (<b>3–Pt</b>), has been investigated by experimental and DFT computational methods. Comparisons of <b>3–Ni</b> with two further U–Ni complexes XU^IV(μ-OAr^P-1κ¹<i>O</i>,2κ¹<i>P</i>)₃Ni⁰, X = Me₃SiO (<b>4</b>) and F (<b>5</b>), was also possible via iodide substitution. All complexes were characterized by variable-temperature NMR spectroscopy, electrochemistry, and single crystal X-ray diffraction. The U–M bonds are significantly shorter than any other crystallographically characterized d–f-block bimetallic, even though the ligand flexes to allow a variable U–M separation. Excellent agreement is found between the experimental and computed structures for <b>3–Ni</b> and <b>3–Pd</b>. Natural population analysis and natural localized molecular orbital (NLMO) compositions indicate that U employs both 5f and 6d orbitals in covalent bonding to a significant extent. Quantum theory of atoms-in-molecules analysis reveals U–M bond critical point properties typical of metallic bonding and a larger delocalization index (bond order) for the less polar U–Ni bond than U–Pd. Electrochemical studies agree with the computational analyses and the X-ray structural data for the U–X adducts <b>3–Ni</b>, <b>4</b>, and <b>5</b>. The data show a trend in uranium–metal bond strength that decreases from <b>3–Ni</b> down to <b>3–Pt</b> and suggest that exchanging the iodide for a fluoride strengthens the metal–metal bond. Despite short U–TM (transition metal) distances, four other computational approaches also suggest low U–TM bond orders, reflecting highly transition metal localized valence NLMOs. These are more so for <b>3–Pd</b> than <b>3–Ni</b>, consistent with slightly larger U–TM bond orders in the latter. Computational studies of the model systems (PH₃)₃MU­(OH)₃I (M = Ni, Pd) reveal longer and weaker unsupported U–TM bonds vs <b>3</b>

Diagnostics of Hybrid Water/Argon Thermal Plasma Jet with Water, Ethanol and Their Mixture Injection to Plasma

A plasma torch with the water/argon stabilization of an arc is characterized by extremely hot and high velocity plasma together with the relatively low flow rate of plasma, therefore, the torch might be properly used for plasma suspension spraying. Enthalpy probe and emission spectroscopy measurements were carried out at constant arc power with the combination of the injection of water, ethanol or their mixture to the plasma jet to diagnose the changes in temperature, heat flux and other characteristics

Differential uranyl(v) oxo-group bonding between the uranium and metal cations from groups 1, 2, 4, and 12; a high energy resolution X-ray absorption, computational, and synthetic study

The uranyl(VI) ‘Pacman’ complex [(UO₂)(py)(H₂L)] A (L = polypyrrolic Schiff-base macrocycle) is reduced by Cp₂Ti(η²-Me₃SiC[triple bond, length as m-dash]CSiMe₃) and [Cp₂TiCl]₂ to oxo-titanated uranyl(V) complexes [(py)(Cp₂$Ti^{III}$OUO)(py)(H₂L)] 1 and [(ClCp₂$Ti^{IV}$OUO)(py)(H₂L)] 2. Combination of $Zr^{II}$ and $Zr^{IV}$ synthons with A yields the first $Zr^{IV}$–uranyl(V) complex, [(ClCp₂ZrOUO)(py)(H₂L)] 3. Similarly, combinations of $Ae^{0}$ and $Ae^{II}$ synthons (Ae = alkaline earth) afford the mono-oxo metalated uranyl(V) complexes [(py)₂(ClMgOUO)(py)(H₂L)] 4, [(py)₂(thf)₂(ICaOUO)(py) (H₂L)] 5; the zinc complexes [(py)₂(XZnOUO)(py)(H₂L)] (X = Cl 6, I 7) are formed in a similar manner. In contrast, the direct reactions of Rb or Cs metal with A generate the first mono-rubidiated and mono-caesiated uranyl(V) complexes; monomeric [(py)₃(RbOUO)(py)(H₂L)] 8 and hexameric [(MOUO)(py)(H₂L)]₆ (M = Rb 8b or Cs 9). In these uranyl(V) complexes, the pyrrole N–H atoms show strengthened hydrogen-bonding interactions with the endo-oxos, classified computationally as moderate-strength hydrogen bonds. Computational DFT MO (density functional theory molecular orbital) and EDA (energy decomposition analysis), uranium M₄ edge HR-XANES (High Energy Resolution X-ray Absorption Near Edge Structure) and 3d4f RIXS (Resonant Inelastic X-ray Scattering) have been used (the latter two for the first time for uranyl(V) in 7 (ZnI)) to compare the covalent character in the $U^{V}$–O and O–M bonds and show the 5f orbitals in uranyl(VI) complex A are unexpectedly more delocalised than in the uranyl(V) 7 (ZnI) complex. The $O_{exo}$–Zn bonds have a larger covalent contribution compared to the Mg–$O_{exo}$/Ca–$O_{exo}$ bonds, and more covalency is found in the U–$O_{exo}$ bond in 7 (ZnI), in agreement with the calculations

Self-seeded growth of germanium nanowires: coalescence and ostwald ripening

We report the controlled self-seeded growth of highly crystalline Ge nanowires, in the absence of conventional metal seed catalysts, using a variety of oligosilylgermane precursors and mixtures of germane and silane compounds (Ge:Si ratios between 1:4 and 1:1). The nanowires produced were encased in an amorphous shell of material derived from the precursors, which acted to isolate the Ge seed particles from which the nanowires were nucleated. The mode diameter and size distribution of the nanowires were found to increase as the growth temperature and Ge content in the precursors increased. Specifically, a model was developed to describe the main stages of self-seeded Ge nanowire growth (nucleation, coalescence, and Ostwald ripening) from the oligosilylgermane precursors and, in conjunction with TEM analysis, a mechanism of growth was proposed

Molecular oligogermanes and related compounds: Structure, optical and semiconductor properties

The optical (UV/Vis absorbance, fluorescence in the solid state and in solution) and semiconducting properties of a number of di- and trigermanes as well as related silicon- and tin-containing germanes, 1–6 ((p-Tol)3GeGeMe3 (1), Ph3SnGe(SiMe3)3 (2), (C6F5)3GeGePh3 (3), (p-Tol)3GeSiMe2SiMe3 (4), (p-Tol)3GeGeMe2Ge(p-Tol)3 (5), (p-Tol)3GeSiMe2SiMe2Ge(p-Tol)3 (6)) were investigated. Molecular structures of 5 and 6 were studied by X-ray diffraction analysis. All compounds displayed luminescence properties. In addition, a band gap (of about 3.3 eV) was measured for compounds 1–6 showing that those molecules display semiconductor properties