No abstract

Reaction of the previously reported Cp*Ti(N t Bu)Cl(py) (1) with bulky ortho-substituted anilines ArNH 2 afforded the corresponding aryl imido derivatives Cp*Ti(NAr)Cl(py) (Ar ) 2,6-C 6 H 3 i Pr 2 (2), 2,6-C 6 H 3 -Br 2 (3), 2-C 6 H 4 t Bu (4), and 2-C 6 H 4 i Pr ( 5)). Reaction of 2 with B(C 6 F 5 ) 3 in C 6 D 6 or heating in vacuo at 200 °C afforded the imido-bridged dimer Cp* 2 Ti 2 (µ-N-2,6-C 6 H 3 i Pr 2 ) 2 Cl 2 (8). Activation of 1-5 with MAO gave moderately active catalyst systems for the polymerization of ethylene in contrast to the previously reported, highly active titanium imido systems Ti(Me 3 [9]aneN 3 )(NR)Cl 2 /MAO and Ti{HC(Me 2pz) 3 }(NR)Cl 2 /MAO, which are isolobal and isoelectronic with 1-5. The Cp*-supported precatalyst productivities were sensitive to both the imido N-substituents and initial precatalyst/cocatalyst concentrations. Depending upon the imido N-substituents and initial precatalyst/cocatalyst concentrations, polyethylene with unimodal (either rather low or very high molecular weight) or bimodal molecular weight distributions can be obtained. Excess AlMe 3 suppresses catalyst productivity but does not affect the overall molecular weight distribution in the system evaluated (1/MAO). Both chain transfer to aluminum and β-hydrogen transfer appear to be active pathways for formation of the low molecular weight fractions of the polymers formed with 1-5/MAO. Under otherwise identical polymerization conditions the catalyst systems 2/MAO and 8/MAO had comparable productivities and gave polyethylene with very similar molecular weight and molecular weight distributions, suggesting a potential role for binuclear species in the catalyst systems 1-5/MAO.

1. The muskrat, Ondatra zibethicus, is a predator known to affect species composition, population size and age structure of freshwater unionid mussel communities. Muskrats leave large piles of dead shells (middens) on the edges of rivers, lakes and streams. We compared the species composition and size structure of shells collected from muskrat middens to the nearby live unionid community in the lower Licking River (Kentucky, USA). 2. Like previous studies, our results suggest that muskrats are both size-selective and species-specific predators; however, our results indicate that mussel shape is also an important factor. 3. We generated a shape metric ('cubocity') sensitive to the overall shape of the mussel. Species with relatively lower cubocity values (around 0.85) are plate-like or spike-like, while mussels with more cuboidal shells have higher cubocity values (near 1.0). 4. Our results suggest muskrats prefer cuboidal mussels and generally avoid spike-shaped mussels. The endangered fanshell, Cyprogenia stegaria, was the most favoured prey; the fanshell's relative size and shape appear to make it particularly vulnerable to muskrats. 5. We believe the predictive capabilities of this shape metric will be of benefit to those who monitor and manage threatened mussel populations.

In vitro metamorphosis of freshwater mussel glochidia allows researchers to acquire juvenile mussels in the absence of a fish host. One major impediment to the success of in vitro mussel culture is the lack of control over fungal contamination brought in from the larvae and/or parent mussel. Eight antimycotics were investigated for controlling fungal contamination during in vitro culture with a unionid bivalve: amphotericin B, hygromycin B, nystatin, benomyl, dichloran, econazole, ketoconazole and thiabendazole. While all performed well on unionid fungal isolates on agar testing, no antimycotics were successful at controlling fungal growth at a concentration not cytotoxic to glochidia under culture conditions. The imidazole class antimycotics (econazole and ketoconazole) best controlled fungi commonly associated with mussels, but depressed larval development. Modifications to the culture protocol, including reduced concentrations of amphotericin B combined with daily media changes, closure of larvae before extraction, elimination of dead and contaminated larvae and the use of fish serum tested were also investigated. The resultant modified protocol was the best method for reducing fungal growth and increasing the efficacy of in vitro mussel culture.

Intoxication and withdrawal syndromes are common presentations in acute medicine. A comprehensive history, including a collateral one, and thorough examination looking for patterns of signs and symptoms, backed by appropriate investigations, forms the basis of good management. A collaborative, empathic and non-judgemental approach that recognizes the patient's distress, explains the goals of management and sets clear boundaries significantly reduces potential complications and improves outcomes. An understanding of the pharmacology and clinical effects of alcohol, benzodiazepines, opioids and stimulants is essential to accurately diagnose and manage patients who may not be able to give an accurate history.