Involvement of titanocene and related species in the reduction of dinitrogen and olefins

Journal ArticleSummary Four sequential products have been spectrally detected in the reduction by sodium of dicyclopentadienyltitanium(iv) dichloride: [(77-Cp)2TiCl]2, [(77-Cp)2-Ti]1-2, [(77-Cp)(C5H4)TiH]x, and (77-Cp)(C5H4)TiH2Ti- (C5H4)(77-Cp) ("stable titanocene"); the second of these reacts rapidly and reversibly with N2 to give a dark blue complex reducible to ammonia and appears to catalyse the cyclopentadienyltitanium-promoted rapid, room temperature-atmospheric pressure hydrogenation of olefins

Identifying customer requirements and designing for modularity in developing specialized, low production volume products

Field biologists are in need of more specialized and technical equipment than they are able to produce on their own in order to collect data more efficiently or gather data that is not currently available. This presents a challenge for design engineers because these products are typically highly specialized and are only needed in limited numbers. Thus, identifying customer requirements and minimizing design and production costs for low production devices are critical components of the design process. When identifying customer needs at the early design stage, many of the needs may be unspoken, especially when the design problem spans multiple disciplines. I compared the ability of a written survey and focus group to discover unspoken requirements for specialized products. Customer requirements for a new larval collector were generated in collaboration with biologists using both methods. The basic methodology includes: 1) select questions, 2) select subjects, 3) interview techniques, 4) extract useful information from the survey, 5) analysis, and 6) verification and validation. With extensive biological experience, I evaluated the requirements gathered and determined if there were any unspoken ones that were missed. Compared to focus groups, written surveys identified basic requirements better but were not as good at identifying attractive requirements. Both methods performed equally in identifying performance requirements. However, both methods failed to identify all the basic or attractive requirements even if the results for both methods were combined. Thus, having a deep customer understanding is critical in identifying unspoken customer requirements. Field biologists desire specialized, low production volume products at moderate to low cost. For high production volume products, modularity has been shown to increase diversity, flexibility, and customer satisfaction and decrease assembly, repair, subsequent product design time, but modularity may also limit performance and innovation and requires more initial design time. There is little information regarding the implementation of modularity for specialized, low production volume products. This thesis presents a method for incorporating modularity into the design of specialized products with low production volume. I tested this method by designing a device to collect marine larvae as they arrive on the shore. My first-generation prototype performed much better than other existing devices, decreasing sample processing time by more than half, but it was expensive. To reduce the production costs, I utilized the modularity of the new design, identified the functional modules where off-the-shelf components could be used to fulfill each module's functional requirements, yielding a more economic second-generation prototype, the design project is on-going, without compromising the performances. Another benefit from this modularity-based design is that several variations of the larvae collectors can be easily evolved from this collector because of the flexibility offered by introducing the modularity into the new design. This experience has led us to conjecture that modularity-based design may offer a promising approach for producing high-quality products with affordable price in the design of specialized, low production volume products

Algal community structure and organization in high intertidal rockpools

Gradients of physical disturbance are central to theories of community organization yet rarely are studies performed in which physical factors are experimentally manipulated. Pothole tidepool algal communities exhibit distinct zonation patterns from top to bottom that result from scouring by rocks and other debris in the pools. Scouring is easily manipulated by removing or adding rocks to tidepools. Thus, the gradient of physical disturbance potentially causing community patterns can be manipulated to test theories of community organization. I documented the distribution pattern of algae inhabiting pothole tidepools and measured a number of physical factors which were hypothesized to be responsible for the observed zonation patterns. Then, I experimentally evaluated the roles of physical disturbance, herbivory, and competition in these tidepool communities. I found that scouring by rocks was primarily responsible for the observed zonation patterns in pothole tidepools. However, not all pools are potholes. Evaluation of the physical properties effecting the cobble-retaining ability of tidepools enabled prediction over a broad geographic range of pools likely to have cobbles and thus show typical pothole algal zonation patterns. Coralline algae (Rhodophyta, Corallinaceae) are a dominant feature of tidepools as well as many low intertidal and subtidal habitats. I evaluated the relative resistance of coralline algae (both articulated and crustose forms) and other common tidepool algae to scouring by rocks. Coralline crusts were highly resistant to scouring while articulated coralline algae are very susceptible to scouring. Erect fleshy algal species showed intermediate resistance to scouring. This corresponds well to observed algal zonation patterns in intertidal potholes. Based on this information, I proposed that wave-induced scouring may have been the selective force for the initial incorporation of calcium carbonate into algal thalli

Two Antimycin A Analogues from Marine-Derived Actinomycete Streptomyces lusitanus

Two new antimycin A analogues, antimycin B1 and B2 (1–2), were isolated from a spent broth of a marine-derived bacterium, Streptomyces lusitanus. The structures of 1 and 2 were established on the basis of spectroscopic analyses and chemical methods. The isolated compounds were tested for their anti-bacterial potency. Compound 1 was found to be inactive against the bacteria Bacillus subtilis, Staphyloccocus aureus, and Loktanella hongkongensis. Compound 2 showed antibacterial activities against S. aureus and L. hongkongensis with MIC values of 32.0 and 8.0 μg/mL, respectively

Gram-Scale Synthesis of the (-)-Sparteine Surrogate and (-)-Sparteine

An 8-step, gram-scale synthesis of the (-)-sparteine surrogate (22% yield, with just 3 chromatographic purifications) and a 10-step, gram-scale synthesis of (-)-sparteine (31% yield) are reported. Both syntheses proceed with complete diastereocontrol and allow access to either antipode. Since the syntheses do not rely on natural product extraction, our work addresses long-term supply issues relating to these widely used chiral ligands

Alkylwanderungen bei Sextettumlagerungen

Die Wanderungstendenzen von Alkylgruppen bei der Beckmann- Criegee- und Isonitril-Nitril-Umlagerung werden untersucht. Aus den relativen Reaktionsgeschwindigkeiten der substituierten Benzylreste werden Rückschlüsse auf die Ladungsverteilung im Übergangszustand dieser Reaktionen gezogen und aus dem Verhältnis der Wanderungstendenzen des exo und endo- 2- Norbornylrestes auf die Geometrie der wandernden Gruppe im Übergangszustand. Der in verschiedenen Sextettumlagerungen unterschiedliche Einfluß der -Methylverzweigung in der wandernden Gruppe wird interpretiert