The capacity to exercise control over the nature and quality of one's life is the essence of humanness. Human agency is characterized by a number of core features that operate through phenomenal and functional consciousness. These include the temporal extension of agency through intentionality and forethought, self-regulation by self-reactive influence, and self-reflectiveness about one's capabilities, quality of functioning, and the meaning and purpose of one's life pursuits. Personal agency operates within a broad network of sociostructural influences. In these agentic transactions, people are producers as well as products of social systems. Social cognitive theory distinguishes among three modes of agency: direct personal agency, proxy agency that relies on others to act on one's behest to secure desired outcomes, and collective agency exercised through socially coordinative and interdependent effort. Growing transnational embeddedness and interdependence are placing a premium on collective efficacy to exercise control over personal destinies and national life.
We previously found that a polymer conjugated to the anticancer protein neocarzinostatin, named smancs, accumulated more in tumor tissues than did neocarzinostatin. To determine the general mechanism of this tumoritropic accumulation of smancs and other proteins, we used radioactive (51Cr-labeled) proteins of various molecular sizes (Mr 12,000 to 160,000) and other properties. In addition, we used dye-complexed serum albumin to visualize the accumulation in tumors of tumor-bearing mice. Many proteins progressively accumulated in the tumor tissues of these mice, and a ratio of the protein concentration in the tumor to that in the blood of 5 was obtained within 19 to 72 h. A large protein like immunoglobulin G required a longer time to reach this value of 5. The protein concentration ratio in the tumor to that in the blood of neither 1 nor 5 was achieved with neocarzinostatin, a representative of a small protein (Mr 12,000) in all time. We speculate that the tumoritropic accumulation of these proteins resulted because of the hypervasculature, an enhanced permeability to even macromolecules, and little recovery through either blood vessels or lymphatic vessels. This accumulation of macromolecules in the tumor was also found after i.v. injection of an albumin-dye complex (Mr 69,000), as well as after injection into normal and tumor tissues. The complex was retained only by tumor tissue for prolonged periods. There was little lymphatic recovery of macromolecules from tumor tissue. The present finding is of potential value in macromolecular tumor therapeutics and diagnosis.
In this paper, we discuss consensus problems for networks of dynamic agents with fixed and switching topologies. We analyze three cases: 1) directed networks with fixed topology; 2) directed networks with switching topology; and 3) undirected networks with communication time-delays and fixed topology. We introduce two consensus protocols for networks with and without time-delays and provide a convergence analysis in all three cases. We establish a direct connection between the algebraic connectivity (or Fiedler eigenvalue) of the network and the performance (or negotiation speed) of a linear consensus protocol. This required the generalization of the notion of algebraic connectivity of undirected graphs to digraphs. It turns out that balanced digraphs play a key role in addressing average-consensus problems. We introduce disagreement functions for convergence analysis of consensus protocols. A disagreement function is a Lyapunov function for the disagreement network dynamics. We proposed a simple disagreement function that is a common Lyapunov function for the disagreement dynamics of a directed network with switching topology. A distinctive feature of this work is to address consensus problems for networks with directed information flow. We provide analytical tools that rely on algebraic graph theory, matrix theory, and control theory. Simulations are provided that demonstrate the effectiveness of our theoretical results.
An analogy with the way ant colonies function has suggested the definition of a new computational paradigm, which we call ant system (AS). We propose it as a viable new approach to stochastic combinatorial optimization. The main characteristics of this model are positive feedback, distributed computation, and the use of a constructive greedy heuristic. Positive feedback accounts for rapid discovery of good solutions, distributed computation avoids premature convergence, and the greedy heuristic helps find acceptable solutions in the early stages of the search process. We apply the proposed methodology to the classical traveling salesman problem (TSP), and report simulation results. We also discuss parameter selection and the early setups of the model, and compare it with tabu search and simulated annealing using TSP. To demonstrate the robustness of the approach, we show how the ant system (AS) can be applied to other optimization problems like the asymmetric traveling salesman, the quadratic assignment and the job-shop scheduling. Finally we discuss the salient characteristics-global data structure revision, distributed communication and probabilistic transitions of the AS.
<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> This paper provides a theoretical framework for analysis of consensus algorithms for multi-agent networked systems with an emphasis on the role of directed information flow, robustness to changes in network topology due to link/node failures, time-delays, and performance guarantees. An overview of basic concepts of information consensus in networks and methods of convergence and performance analysis for the algorithms are provided. Our analysis framework is based on tools from matrix theory, algebraic graph theory, and control theory. We discuss the connections between consensus problems in networked dynamic systems and diverse applications including synchronization of coupled oscillators, flocking, formation control, fast consensus in small-world networks, Markov processes and gossip-based algorithms, load balancing in networks, rendezvous in space, distributed sensor fusion in sensor networks, and belief propagation. We establish direct connections between spectral and structural properties of complex networks and the speed of information diffusion of consensus algorithms. A brief introduction is provided on networked systems with nonlocal information flow that are considerably faster than distributed systems with lattice-type nearest neighbor interactions. Simulation results are presented that demonstrate the role of small-world effects on the speed of consensus algorithms and cooperative control of multivehicle formations. </para>
In a recent Physical Review Letters article, Vicsek et al. propose a simple but compelling discrete-time model of n autonomous agents (i.e., points or particles) all moving in the plane with the same speed but with different headings. Each agent's heading is updated using a local rule based on the average of its own heading plus the headings of its "neighbors." In their paper, Vicsek et al. provide simulation results which demonstrate that the nearest neighbor rule they are studying can cause all agents to eventually move in the same direction despite the absence of centralized coordination and despite the fact that each agent's set of nearest neighbors change with time as the system evolves. This paper provides a theoretical explanation for this observed behavior. In addition, convergence results are derived for several other similarly inspired models. The Vicsek model proves to be a graphic example of a switched linear system which is stable, but for which there does not exist a common quadratic Lyapunov function.
Abstract The concept of an agent has become important in both artificial intelligence (AT) and mainstream computer science. Our aim in this paper is to point the reader at what we perceive to be the most important theoretical and practical issues associated with the design and construction of intelligent agents. For convenience, we divide these issues into three areas (though as the reader will see, the divisions are at times somewhat arbitrary). Agent theory is concerned with the question of what an agent is, and the use of mathematical formalisms for representing and reasoning about the properties of agents. Agent architectures can be thought of as software engineering models of agents; researchers in this area are primarily concerned with the problem of designing software or hardware systems that will satisfy the properties specified by agent theorists. Finally, agent languages are software systems for programming and experimenting with agents; these languages may embody principles proposed by theorists. The paper is not intended to serve as a tutorial introduction to all the issues mentioned; we hope instead simply to identify the most important issues, and point to work that elaborates on them. The article includes a short review of current and potential applications of agent technology.
Journal Article Multitask Principal–Agent Analyses: Incentive Contracts, Asset Ownership, and Job Design Get access Bengt Holmstrom, Bengt Holmstrom Yale University Search for other works by this author on: Oxford Academic Google Scholar Paul Milgrom Paul Milgrom Stanford University Search for other works by this author on: Oxford Academic Google Scholar The Journal of Law, Economics, and Organization, Volume 7, Issue special_issue, January 1991, Pages 24–52, https://doi.org/10.1093/jleo/7.special_issue.24 Published: 01 January 1991
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The availability of an increasing number of antiretroviral agents and the rapid evolution of new information has introduced extraordinary complexity into the treatment of HIV-infected persons. In 1996, the Department of Health and Human Services and the Henry J. Kaiser Family Foundation convened the Panel on Clinical Practices for the Treatment of HIV to develop guidelines for the clinical management of HIV-infected adults and adolescents. This report recommends that care should be supervised by an expert, and it makes recommendations for laboratory monitoring with particular emphasis on measurement of plasma levels of HIV RNA.It also provides guidelines for antiretroviral therapy, including when to start treatment, what drugs to initiate, when to change therapy, and therapeutic options when changing therapy. Special consideration is given to adolescents and pregnant women. As with decisions about treatment of other chronic conditions, therapeutic decisions about HIV disease require a mutual understanding between the patient and the health care provider regarding the benefits and risks of treatment. Like treatment for most chronic diseases, antiretroviral regimens are complex, have major side effects, pose difficulty with compliance, and carry serious potential consequences with the risk for resistance from nonadherence to the drug regimen or suboptimal levels of antiretroviral agents. Patient education and involvement in therapeutic decisions is important for all medical conditions but is considered especially critical for HIV infection and its treatment. With regard to specific recommendations, treatment should be offered to all patients with the acute HIV syndrome, those within 6 months of seroconversion, and all patients with symptoms ascribed to HIV infection.Recommendations for offering antiretroviral therapy to asymptomatic patients depend on virologic and immunologic factors. In general, treatment should be offered to individuals with fewer than 500 CD4+ T cells/mm3 or plasma HIV RNA levels exceeding 10 000 copies/mL (branched DNA assay) or 20 000 copies/mL (reverse transcriptase polymerase chain reaction assay). The strength of the recommendation to treat asymptomatic patients should be based on the patient's willingness to accept therapy, the probability of adherence with the prescribed regimen, and the prognosis in terms of time to an AIDS-defining complication as predicted by plasma HIV RNA levels and CD4+ T-cell counts, which independently help predict prognosis. Once the decision has been made to initiate antiretroviral therapy, the goal is maximum viral suppression for as long as possible. Results of clinical trials to date indicate that this may currently be best achieved with a potent protease inhibitor in combination with two nucleoside analogue reverse transcriptase inhibitors (NRTIs). Another option is the combination of saquinavir plus ritonavir combined with one or two NRTIs. Other currently available regimens may be used in selected settings but are considered by many to be less likely to produce maximum viral suppression. Results of therapy are evaluated primarily with plasma HIV RNA levels; these are expected to show a one-log (10-fold) decrease at 8 weeks and no detectable virus (<500 copies/mL) at 4 to 6 months after initiation of treatment. Failure of therapy (i.e., plasma HIV RNA levels >500 copies/mL) at 4 to 6 months may be ascribed to nonadherence, inadequate potency of drugs or suboptimal levels of antiretroviral agents, resistance, and other factors that are poorly understood. Patients whose therapy fails should change to at least two new agents that are not likely to show cross-resistance with drugs given previously; ideally, the regimen should be changed to a completely new regimen that is devoid of anticipated cross-resistance and for which clinical trial data support a high probability of viral response. Rational changes in therapy may be especially difficult to achieve for patients for whom the preferred regimen has failed, because of limitations in the available alternative antiretroviral regimens that have documented efficacy; these decisions are further confounded by problems with adherence, toxicity, and resistance. In some settings, it may be preferable for a patient to participate in a clinical trial with or without access to new drugs or to use a regimen that may not achieve the optimal virologic goal. It is emphasized that concepts relevant to HIV management evolve rapidly.The Panel has a mechanism to update recommendations on a regular basis, and the most recent information is available on the AIDS Treatment Information Service World Wide Web site (http://www.hivatis.org). These Guidelines were developed by the Panel on Clinical Practices for Treatment of HIV Infection convened by the Department of Health and Human Services and the Henry J.Kaiser Family Foundation. Leadership of the Panel consists of Anthony S. Fauci, National Institutes of Health, Bethesda, MD (co-chair); John G. Bartlett, Johns Hopkins University, Baltimore, MD (co-chair); Eric P. Goosby, Department of Health and Human Services (convener); Mark D. Smith, California HealthCare Foundation, San Francisco, CA, formerly of the Henry J. Kaiser Foundation (convener), succeeded by Sophia W. Chang, Henry J. Kaiser Foundation. Members of the Panel who participated in the development of this document included Jean Anderson (Johns Hopkins University, Baltimore, MD), Rodney Armstead (Watts Health Foundation, Inc., Inglewood, CA), A. Cornelius Baker (National Association of People with AIDS, Washington, DC), David Barr (Forum for Collaborative HIV Research, Washington, DC), Samuel Bozzette (San Diego Veterans Affairs Medical Center, San Diego, CA), Spencer Cox (Treatment Action Group, New York, NY), Martin Delaney (Project Inform, San Francisco, CA), Fred Gordin (Veterans Administration Medical Center, Washington, DC), Wayne Greaves (Howard University, Washington, DC), Mark Harrington (Treatment Action Group, New York, NY), John J. Henning (American Medical Association, Chicago, IL), Martin S. Hirsch (Massachusetts General Hospital, Boston, MA), Jeffrey Jacobs (AIDS Action Council), Richard Marlink (Harvard AIDS Institute, Cambridge, MA), Celia Maxwell (AIDS Education and Training Center, Washington, DC), John W. Mellors (University of Pittsburgh, Pittsburgh, PA), David B. Nash (Thomas Jefferson University, Philadelphia, PA), Sallie Perryman (New York State Department of Health, New York, NY), Robert T. Schooley (University of Colorado, Denver, CO), Renslow Sherer (Cook County HIV Primary Care Center, Chicago, IL), Stephen A. Spector (University of California San Diego, La Jolla, CA), Gabriel Torres (St. Vincent's Hospital, New York, NY), Paul Volberding (University of California, San Francisco, CA); participants from the Department of Health and Human Services: Barbara A. Brady (Office of HIV/AIDS Policy), Oren Cohen (National Institutes of Health), Elaine M. Daniels (Office of HIV/AIDS Policy), David Feigal (Food and Drug Administration), Mark Feinberg (National Institutes of Health), Helene D. Gayle (Centers for Disease Control and Prevention), T. Randolph Graydon (Health Care Financing Administration), Jonathan Kaplan (Centers for Disease Control and Prevention), Abe Macher (Health Resources and Services Administration), R. Frank Martin (Indian Health Service), Henry Masur (National Institutes of Health), Lynne Mofenson (National Institutes of Health), Jeffrey Murray (Food and Drug Administration), Joseph O'Neill (Health Resources and Services Administration), Lucille C. Perez (Substance Abuse and Mental Health Services Administration), Richard Riseberg (Office of the Secretary), Samuel Shekar (Health Care Financing Administration), Sharilyn K. Stanley (National Institutes of Health), Jack Whitescarver (Office of AIDS Research). The Panel would like to extend special appreciation to Charles Carpenter (Brown University School of Medicine, Providence, RI) for his advice in the development of this document and Gerry Bally (Health Canada) and Anita Rachlis (Sunnybrook Health Science Centre, University of Toronto, Toronto, Canada) for their participation. The Panel would also like to acknowledge the special contributions of Sharilyn K. Stanley, Barbara A. Brady, and Elaine M. Daniels in the preparation of this document.
In this paper, we present a theoretical framework for design and analysis of distributed flocking algorithms. Two cases of flocking in free-space and presence of multiple obstacles are considered. We present three flocking algorithms: two for free-flocking and one for constrained flocking. A comprehensive analysis of the first two algorithms is provided. We demonstrate the first algorithm embodies all three rules of Reynolds. This is a formal approach to extraction of interaction rules that lead to the emergence of collective behavior. We show that the first algorithm generically leads to regular fragmentation, whereas the second and third algorithms both lead to flocking. A systematic method is provided for construction of cost functions (or collective potentials) for flocking. These collective potentials penalize deviation from a class of lattice-shape objects called /spl alpha/-lattices. We use a multi-species framework for construction of collective potentials that consist of flock-members, or /spl alpha/-agents, and virtual agents associated with /spl alpha/-agents called /spl beta/- and /spl gamma/-agents. We show that migration of flocks can be performed using a peer-to-peer network of agents, i.e., "flocks need no leaders." A "universal" definition of flocking for particle systems with similarities to Lyapunov stability is given. Several simulation results are provided that demonstrate performing 2-D and 3-D flocking, split/rejoin maneuver, and squeezing maneuver for hundreds of agents using the proposed algorithms.
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Agent-based modeling is a powerful simulation modeling technique that has seen a number of applications in the last few years, including applications to real-world business problems. After the basic principles of agent-based simulation are briefly introduced, its four areas of application are discussed by using real-world applications: flow simulation, organizational simulation, market simulation, and diffusion simulation. For each category, one or several business applications are described and analyzed.
During the last three decades, the impact of chemical pollution has focused almost exclusively on the conventional "priority" pollutants, especially those acutely toxic/carcinogenic pesticides and industrial intermediates displaying persistence in the environment. This spectrum of chemicals, however, is only one piece of the larger puzzle in "holistic" risk assessment. Another diverse group of bioactive chemicals receiving comparatively little attention as potential environmental pollutants includes the pharmaceuticals and active ingredients in personal care products (in this review collectively termed PPCPs), both human and veterinary, including not just prescription drugs and biologics, but also diagnostic agents, "nutraceuticals," fragrances, sun-screen agents, and numerous others. These compounds and their bioactive metabolites can be continually introduced to the aquatic environment as complex mixtures via a number of routes but primarily by both untreated and treated sewage. Aquatic pollution is particularly troublesome because aquatic organisms are captive to continual life-cycle, multigenerational exposure. The possibility for continual but undetectable or unnoticed effects on aquatic organisms is particularly worrisome because effects could accumulate so slowly that major change goes undetected until the cumulative level of these effects finally cascades to irreversible change--change that would otherwise be attributed to natural adaptation or ecologic succession. As opposed to the conventional, persistent priority pollutants, PPCPs need not be persistent if they are continually introduced to surface waters, even at low parts-per-trillion/parts-per-billion concentrations (ng-microg/L). Even though some PPCPs are extremely persistent and introduced to the environment in very high quantities and perhaps have already gained ubiquity worldwide, others could act as if they were persistent, simply because their continual infusion into the aquatic environment serves to sustain perpetual life-cycle exposures for aquatic organisms. This review attempts to synthesize the literature on environmental origin, distribution/occurrence, and effects and to catalyze a more focused discussion in the environmental science community.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTGadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and ApplicationsPeter Caravan, Jeffrey J. Ellison, Thomas J. McMurry, and Randall B. LaufferView Author Information EPIX Medical, Inc., 71 Rogers Street, Cambridge, Massachusetts 02142 Cite this: Chem. Rev. 1999, 99, 9, 2293–2352Publication Date (Web):August 20, 1999Publication History Received22 February 1999Revised24 June 1999Published online20 August 1999Published inissue 8 September 1999https://pubs.acs.org/doi/10.1021/cr980440xhttps://doi.org/10.1021/cr980440xresearch-articleACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views27447Altmetric-Citations3831LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Coordination compounds,Ions,Ligands,Molecular structure,Molecules Get e-Alerts
The volatile oils of black pepper [Piper nigrum L. (Piperaceae)], clove [Syzygium aromaticum (L.) Merr. & Perry (Myrtaceae)], geranium [Pelargonium graveolens L'Herit (Geraniaceae)], nutmeg [Myristica fragrans Houtt. (Myristicaceae), oregano [Origanum vulgare ssp. hirtum (Link) Letsw. (Lamiaceae)] and thyme [Thymus vulgaris L. (Lamiaceae)] were assessed for antibacterial activity against 25 different genera of bacteria. These included animal and plant pathogens, food poisoning and spoilage bacteria. The volatile oils exhibited considerable inhibitory effects against all the organisms under test while their major components demonstrated various degrees of growth inhibition.
ADVERTISEMENT RETURN TO ISSUEPREVArticleChemical Redox Agents for Organometallic ChemistryNeil G. Connelly and William E. GeigerView Author Information School of Chemistry, University of Bristol, U.K., and Department of Chemistry, University of Vermont, Burlington, Vermont 05405-0125 Cite this: Chem. Rev. 1996, 96, 2, 877–910Publication Date (Web):March 28, 1996Publication History Received3 October 1995Revised9 January 1996Published online28 March 1996Published inissue 1 January 1996https://pubs.acs.org/doi/10.1021/cr940053xhttps://doi.org/10.1021/cr940053xresearch-articleACS PublicationsRequest reuse permissionsArticle Views89729Altmetric-Citations3552LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose SUBJECTS:Oxidation,Reagents,Redox reactions,Salts,Solvents Get e-Alerts
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPlant antitumor agents. VI. Isolation and structure of taxol, a novel antileukemic and antitumor agent from Taxus brevifoliaMansukhlal C. Wani, Harold Lawrence Taylor, Monroe E. Wall, Philip Coggon, and Andrew T. McPhailCite this: J. Am. Chem. Soc. 1971, 93, 9, 2325–2327Publication Date (Print):May 1, 1971Publication History Published online1 May 2002Published inissue 1 May 1971https://pubs.acs.org/doi/10.1021/ja00738a045https://doi.org/10.1021/ja00738a045research-articleACS PublicationsRequest reuse permissionsArticle Views11293Altmetric-Citations3049LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
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