Order of Magnitude Effects of Thiazole Regioisomerism on the Near‐IR Two‐Photon Cross‐Sections of Dipolar Chromophores

We have investigated computationally the two‐photon absorption (2PA) properties of donor‐acceptor dipolar chromophores, the conjugated backbones of which contain two five‐membered heterocyclic groups which may be electron‐rich (thiophene‐2,5‐diyl) and/or electron‐deficient (thiazole‐2,5‐diyl). Quantum‐chemical calculations (INDO/MRDCI/S‐tensor and Sum‐Over‐States calculations based on DFT‐optimized geometries) indicate that the two‐photon cross‐sections into the lowest two excited states S₁ and S₂ can be tuned by more than an order of magnitude by varying the nature, order, and, in the case of thiazole, orientation of the heterocycles. Going from one thiazole regioisomer to the other has the strongest impact on the 2PA spectra and can even invert the ratio between the 2PA cross‐sections of S₁ and S₂. An essential‐state analysis reveals that different channels dominate 2PA into S₁ and S₂. The sensitivity of 2PA into S₁ towards the orientation of the thiazole ring stems from a local modulation on the thiazole ring of the change in state dipole moment upon excitation to S₁, Δµ₀₁, whereas the dominant essential parameter through which the thiazole orientation affects 2PA into S₂ is the transition dipole moment between S₁ and S₂, µ₁₂.     

Extraneous inclusions in Al/Si alloy pistons: their effect on single crystal and polycrystalline diamond turning tool edges

Polycrystalline diamond tools are shown to have a greater resistance to cutting edge fracture than do single crystal diamond tools when they encounter extraneous inclusions while turning Al/Si alloy pistons.     

Synthesis, electron mobility, and electroluminescence of a polynorbornene-supported silole

A solution-processable polynorbornene with pendant fluorescent and electron-transport silole groups was synthesized using ruthenium-complex-initiated ring-opening metathesis polymerization. A weight-average molecular weight around 59,300 and a low polydispersity index of 1.4 were estimated for the polymer using gel permeation chromatography. The thermal, electronic, photo- and electroluminescence properties of the polymer were investigated and compared with those of a small-molecule reference compound. The polymer exhibits better thermal stability than the small molecule and exhibits a glass transition temperature of 91 °C, while retaining the optical and electronic properties of the corresponding small-molecule silole. The room temperature electron mobility was measured using the time-of-flight technique to be 3.5 × 10⁻⁵ cm²/V/s at an applied electric field of 7.5 × 10⁵ V/cm. Organic light-emitting diodes fabricated using the polymer as the electron transport and emissive layer have low efficiencies; introduction of an additional tris(8-hydroxyquinolinato)aluminum (Alq₃) electron-transport layer leads not only to increased efficiency, but also to increased contributions to the electroluminescence from the Alq₃.     

Polycarbazole modified electrode; nitric oxide sensor

Summary A sensitive and quick measurement of Nitric Oxide (NO) in real time is described using differential pulse voltammetry in aqueous solution. NO is estimated over electrochemically deposited polycarbazole conducting polymer modified platinum minielectrode of 0.0078 cm² geometrical area in deoxygenated 0.1 M phosphate buffer (pH 7.4) at 25°C. NO oxidation peak is observed during anodic scan at 0.65 V vs. Ag/AgCl. A linear dependency between NO concentration and anodic peak current is obtained in the standard addition of NO from 10 nM to mM range. The interference with ascorbic acid and dopamine are found to be negligible over polycarbazole modified electrode. Received: 26 February 2001/Revised version: 25 June 2001/Accepted: 25 June 2001     

Activating knowledge through electronic collaboration: vanquishing the knowledge paradox

Electronic collaboration has become a driver for productivity as organizations develop linkages for the planning, sourcing, and execution of goods and services. These organizations require mechanisms to harness the diverse and personalized intellectual resources that are distributed across the world. While electronic collaboration technologies have made it possible to harness intellectual resources across space and time, knowledge management is locked in a paradox of perception-the more valuable a knowledge resource is seen to be, the less it is shared. This paper develops a framework for the activation of knowledge that relies on a view of knowledge-as-identity. The analysis of a case study reveals "activation conditions" that delineate processes in which electronic collaboration technologies can be most effective. This has implications for the creation of collaborative work environments that enhance knowledge activation in organizations.     

Choroidal tuberculosis diagnosed by polymerase chain reaction. A clinicopathologic case report

PURPOSE: To show the use of the polymerase chain reaction (PCR) in a granulomatous choroidal lesion to support a diagnosis of tuberculosis. DESIGN: Observational case report. TESTING: Nucleic acid target amplification of a choroidal specimen using PCR for detection of Mycobacterium tuberculosis was tested. MAIN OUTCOME MEASURES: Positive nucleic acid target amplification for M. tuberculosis in the ocular sample was measured. RESULTS: PCR was positive for M. tuberculosis with appropriate negative controls. CONCLUSIONS: PCR was thought to be a useful supportive technique in the diagnosis of choroidal tuberculosis.     

Substrate‐free cholesteric liquid‐crystal displays

Abstract— This paper demonstrates the first substrate‐free cholesteric liquid‐crystal displays. The encapsulated cholesteric displays are ultra‐thin (with a total thickness around 20 μm) and ultra‐lightweight (0.002 g/cm²). The displays exhibit unprecedented conformability, flexibility, and drapability while maintaining electro‐optical performance and mechanical integrity. All functional display layers are sequentially coated on a preparation substrate and then lifted‐off from the preparation substrate to form a free‐standing display. The display fabrication process, electro‐optical performance, and display flexibility are discussed.     

Using Simulation to Teach Negotiation Processes to Environmental Engineers

This paper reports on a simulation exercise used to teach engineers about negotiation in the context of hazardous waste site cleanups. In contrast to traditional approaches, which emphasize technical aspects of hazardous waste management, our simulation approach emphasizes the influence that personality characteristics and negotiating styles have on outcomes in the site cleanup process. In addition to describing the site cleanup process and the simulation exercise, the paper discusses results of running the simulation in classes at Stanford University and the effectiveness of the simulation approach.     

Development of a hybrid process and system model for the assessment of wellbore leakage at a geologic CO2 sequestration site

Sequestration of CO2 in geologic reservoirs is one of the promising technologies currently being explored to mitigate anthropogenic CO2 emissions. Large-scale deployment of geologic sequestration will require seals with a cumulative area amounting to hundreds of square kilometers per year and will require a large number of sequestration sites. We are developing a system-level model, CO2-PENS, that will predict the overall performance of sequestration systems while taking into account various processes associated with different parts of a sequestration operation, from the power plant to sequestration reservoirs to the accessible environment. The adaptability of CO2-PENS promotes application to a wide variety of sites, and its level of complexity can be increased as detailed site information becomes available. The model CO2-PENS utilizes a science-based-prediction approach by integrating information from process-level laboratory experiments, field experiments/observations, and process-level numerical modeling. The use of coupled process models in the system model of CO2-PENS provides insights into the emergent behavior of aggregate processes that could not be obtained by using individual process models. We illustrate the utility of the concept by incorporating geologic and wellbore data into a synthetic, depleted oil reservoir. In this sequestration scenario, we assess the fate of CO2 via wellbore release and resulting impacts of CO2 to a shallow aquifer and release to the atmosphere.