view Abstract Citations (37) References (33) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Early-Time Spectra of Type IC Supernovae: Further Evidence for the Presence of Hydrogen Filippenko, Alexei V. Abstract Comparison of the early-time optical spectra of the Type II SN 1985L and the Type Ic SN 1987M confirms the previously suspected presence of Hα in SN 1987M. The Hα line has a P Cygni profile in both objects, but it is not as prominent as in the Type II SN 1987K, whose spectrum at late times became indistinguishable from that of SNs Ic. A spectrum of the Type Ic SN 1991A reveals a weak but nearly unmistakable Hα emission line; faint Hα emission may also be present in the Type Ic SN 1990aa. These observations support the hypothesis that SNs Ic and SNs II are physically related, with the main variable being the amount of hydrogen in the outer envelope. The fact that O I λ7774 absorption is strong in the early-time spectra of SNs Ic, but absent in the corresponding spectra of SNs II, may be consistent with this hypothesis. However, the data do not yet conclusively eliminate white dwarf models for SNs Ic. Publication: The Astrophysical Journal Pub Date: January 1992 DOI: 10.1086/186257 Bibcode: 1992ApJ...384L..37F Keywords: H Alpha Line; Stellar Spectra; Supernovae; Visible Spectrum; White Dwarf Stars; Emission Spectra; Line Spectra; Astrophysics; STARS: SUPERNOVAE: INDIVIDUAL ALPHANUMERIC: SN 1985L; STARS: SUPERNOVAE: INDIVIDUAL ALPHANUMERIC: SN 1987M; STARS: WHITE DWARFS full text sources ADS | data products NED (10) SIMBAD (5)
This stimulating research review analyses how the theory of the firm evolved from several core concepts and building blocks that underpin this important area of economics. It discusses a variety of perspectives from leading scholars in the field, including the basic elements of: risk and uncertainty; information and knowledge; bounded rationality and decision making; motives and incentives; resources and capabilities; and transactions. The review goes on to examine how the various elements are integrated into the modern Theory of the Firm with the notion of organization coming increasingly to the fore. It focuses on norms; rules and routines; the entrepreneur; governance; hierarchies; co-operation, teams and networks; innovation and appropriability. This comprehensive review will be an invaluable reference tool for all researchers and students with an interest in the modern theory of the firm, highlighting how it needs to evolve further to address the important management and policy issues of our time.
The concepts of asset co-specialization and dynamic capabilities have been instrumental in furthering the organization and strategy scholarship agenda, but have so far had limited impact on the theory of the multinational enterprise (MNE) and foreign direct investment (FDI). In addition, the role of entrepreneurial management in orchestrating system-wide value creation through market and eco-system creation and co-creation, in order to advance private appropriation, has been all but ignored. We claim that these ideas can help explicate the nature of the MNE in the knowledge-based, semi-globalized economy. The nature of the MNE in its turn should not be seen as separable from either the objectives of the agents (entrepreneurs) who set them up or its essence--the employment of strategy to capture co-created value. Copyright 2010 The Author 2010. Published by Oxford University Press on behalf of Associazione ICC. All rights reserved., Oxford University Press.
The current congestion control paradigm assumes that end users will use a single mandated algorithm. While the work done in this area has proven to be of great value, we need to recognize as a community that this paradigm is clearly inappropriate for future public networks. The reformulation of congestion control for best-effort service is discussed. We are not attempting to design specific new congestion control algorithms. Instead, we are merely trying to articulate the design principles. Many of these principles have been discussed before; however, with ATM currently designing a best-effort service under the name available bit rate (ABR) and the increasing commercialization of the Internet, these issues warrant revisiting. We outline the service model for best-effort service, describe the set of mechanisms available to implement this service model and contrast their various roles. The implications of our findings for future network design are discussed including some well-known examples of congestion control mechanisms.
Community interventions and service programs for grandparents raising grandchildren are being identified and tracked through the Brookdale Grandparent Caregiver Information Project. Based on the first year's examination of 124 such programs, an overview of community intervention effort is provided, with special attention to support groups and comprehensive multi-service programs for grandparent caregivers. Lack of funding and institutional support, and the consequent inability to provide child care, were among key obstacles faced, while sponsorship by health and social service agencies often played a vital role in providing in-kind support and part-time professional staff.
The cost of drug discovery and development is increasing, while the rate of new drug approvals is declining. In contrast to major technological advances with in silico and in vitro screening tools, there have been almost no advances in the tools available for establishing the actions of agents in the complex biochemical networks characteristic of fully assembled living systems. The resulting poor capacity to predict clinical response underlies the high attrition rate of leads at every step of drug development. A potential solution would be provided by kinetic biomarkers (in vivo measurement of fluxes though the key pathways that drive disease processes and therapeutic response). Novel approaches using stable isotope labeling with mass spectrometric analysis have recently emerged for measuring molecular kinetics relevant to drug targets with some applications to drug development. This review discusses the general principles of kinetic biomarkers, providing examples where kinetics have generated meaningful insights into drug activity and highlighting areas where the application of kinetic biomarkers may be particularly useful for future drug discovery and development. Stable isotope mass spectrometric technologies may provide a parallel efficiency for converting molecules into approved drugs with sufficient throughput and reproducibility to maintain pace with the modern engine for generating leads.
Small organic molecules with strong intermolecular interactions have a wide range of desirable optical and electronic properties and rich phase behaviors. Incorporating them into block copolymer (BCP)-based supramolecules opens new routes to generate functional responsive materials. Using oligothiophene- containing supramolecules, we present systematic studies of critical thermodynamic parameters and kinetic pathway that govern the coassemblies of BCP and strongly interacting small molecules. A number of potentially useful morphologies for optoelectronic materials, including a nanoscopic network of oligothiophene and nanoscopic crystalline lamellae, were obtained by varying the assembly pathway. Hierarchical coassemblies of oligothiophene and BCP, rather than macrophase separation, can be obtained. Crystallization of the oligothiophene not only induces chain stretching of the BCP block the oligothiophene is hydrogen bonded to but also changes the conformation of the other BCP coil block. This leads to an over 70% change in the BCP periodicity (e.g., from 31 to 53 nm) as the oligothiophene changes from a melt to a crystalline state, which provides access to a large BCP periodicity using fairly low molecular weight BCP. The present studies have demonstrated the experimental feasibility of generating thermoresponsive materials that convert heat into mechanical energy. Incorporating strongly interacting small molecules into BCP supramolecules effectively increases the BCP periodicity and may also open new opportunities to tailor their optical properties without the need for high molecular weight BCP. © 2012 American Chemical Society.
Submicroscopic, needle-shaped titanomagnetite inclusions exsolved in silicate minerals commonly occur in mafic intrusive rocks and are protected from alteration by their silicate hosts, making them excellent candidates for paleomagnetic studies. A suite of samples containing clinopyroxene- and plagioclase-hosted magnetite inclusions from five geologically diverse sites was examined using magnetic force microscopy to image the inclusions' magnetic domain state. Alternating field demagnetization experiments indicate that some inclusions are more stable recorders than others. The two factors controlling the remanence behavior of the inclusions are internal microstructures and inclusion dimensions. Magnetite-ulvöspinel unmixing within an inclusion subdivides the original titanomagnetite solid solution into a boxwork structure composed of 103–105 magnetite prisms separated by thin ulvöspinel lamellae. The conversion of multidomain-sized needles into assemblages of interacting single domains increases the coercivity (and hence relaxation time) of the inclusions, and results in a thermochemical magnetic remanence. In samples without this exsolution microstructure, the inclusions' diameters determine coercivity and their magnetization is thermoremanent. Both styles of high-coercivity inclusions successfully record paleomagnetic directions in Mesozoic rocks, and their ubiquity within silicate minerals (clinopyroxene and plagioclase) of mafic intrusive rocks indicates their value as chemically and magnetically stable tools for elucidating the ancient magnetic field, marine magnetic anomalies, and crustal kinematics.
The behavior in the vicinity of a point where excitable, Hopf and Turing modes coexisting is analyzed within the framework of a simplified version of Chua's nonlinear circuits. The different factors (e.g., initial and boundary conditions and small changes in circuit parameters) which determine the final state of the system are numerically studied.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">></ETX>
