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1.
Proc Natl Acad Sci U S A ; 109(21): 7982-7, 2012 May 22.
Artigo em Inglês | MEDLINE | ID: mdl-22566651

RESUMO

We present the results of a search for planetary companions orbiting near hot Jupiter planet candidates (Jupiter-size candidates with orbital periods near 3 d) identified in the Kepler data through its sixth quarter of science operations. Special emphasis is given to companions between the 21 interior and exterior mean-motion resonances. A photometric transit search excludes companions with sizes ranging from roughly two-thirds to five times the size of the Earth, depending upon the noise properties of the target star. A search for dynamically induced deviations from a constant period (transit timing variations) also shows no significant signals. In contrast, comparison studies of warm Jupiters (with slightly larger orbits) and hot Neptune-size candidates do exhibit signatures of additional companions with these same tests. These differences between hot Jupiters and other planetary systems denote a distinctly different formation or dynamical history.


Assuntos
Astronomia/métodos , Meio Ambiente Extraterreno , Júpiter , Modelos Teóricos , Planetas , Planeta Terra , Temperatura Alta , Netuno
2.
Proc Natl Acad Sci U S A ; 108(48): 19152-8, 2011 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-22106251

RESUMO

Through the laboratory study of ancient solar system materials such as meteorites and comet dust, we can recognize evidence for the same star-formation processes in our own solar system as those that we can observe now through telescopes in nearby star-forming regions. High temperature grains formed in the innermost region of the solar system ended up much farther out in the solar system, not only the asteroid belt but even in the comet accretion region, suggesting a huge and efficient process of mass transport. Bi-polar outflows, turbulent diffusion, and marginal gravitational instability are the likely mechanisms for this transport. The presence of short-lived radionuclides in the early solar system, especially (60)Fe, (26)Al, and (41)Ca, requires a nearby supernova shortly before our solar system was formed, suggesting that the Sun was formed in a massive star-forming region similar to Orion or Carina. Solar system formation may have been "triggered" by ionizing radiation originating from massive O and B stars at the center of an expanding HII bubble, one of which may have later provided the supernova source for the short-lived radionuclides. Alternatively, a supernova shock wave may have simultaneously triggered the collapse and injected the short-lived radionuclides. Because the Sun formed in a region where many other stars were forming more or less contemporaneously, the bi-polar outflows from all such stars enriched the local region in interstellar silicate and oxide dust. This may explain several observed anomalies in the meteorite record: a near absence of detectable (no extreme isotopic properties) presolar silicate grains and a dichotomy in the isotope record between (26)Al and nucleosynthetic (nonradiogenic) anomalies.


Assuntos
Fenômenos Astronômicos , Meio Ambiente Extraterreno/química , Sistema Solar/química , Astros Celestes/química , Radioisótopos/análise
3.
J Healthc Manag ; 55(6): 381-97; discussion 397-8, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21166322

RESUMO

In an era when healthcare organizations are beset by intense competition, lawsuits, and increased administrative costs, it is essential that employees perform their jobs efficiently and without distraction. Deviant workplace behavior among healthcare employees is especially threatening to organizational effectiveness, and healthcare managers must understand the antecedents of such behavior to minimize its prevalence. Deviant employee behavior has been categorized into two major types, individual and organizational, according to the intended target of the behavior. Behavior directed at the individual includes such acts as harassment and aggression, whereas behavior directed at the organization includes such acts as theft, sabotage, and voluntary absenteeism, to name a few (Robinson and Bennett 1995). Drawing on theory from organizational behavior, we examined two important features of supportive leadership, leader-member exchange (LMX) and perceived organizational support (POS), and two important features of job design, intrinsic motivation and depersonalization, as predictors of subsequent deviant behavior in a sample of over 1,900 employees within a large US healthcare organization. Employees who reported weaker perceptions of LMX and greater perceptions of depersonalization were more likely to engage in deviant behavior directed at the individual, whereas employees who reported weaker perceptions of POS and intrinsic motivation were more likely to engage in deviant behavior directed at the organization. These findings give rise to specific prescriptions for healthcare managers to prevent or minimize the frequency of deviant behavior in the workplace.


Assuntos
Instalações de Saúde , Liderança , Má Conduta Profissional , Humanos , Relações Interprofissionais
4.
J Healthc Manag ; 54(2): 127-40; discussion 141, 2009.
Artigo em Inglês | MEDLINE | ID: mdl-19413167

RESUMO

Numerous challenges confront managers in the healthcare industry, making it increasingly difficult for healthcare organizations to gain and sustain a competitive advantage. Contemporary management challenges in the industry have many different origins (e.g., economic, financial, clinical, and legal), but there is growing recognition that some of management's greatest problems have organizational roots. Thus, healthcare organizations must examine their personnel management strategies to ensure that they are optimized for fostering a highly committed and productive workforce. Drawing on a sample of 2,522 employees spread across 312 departments within a large U.S. healthcare organization, this article examines the impact of a participative management climate on four employee-level outcomes that represent some of the greatest challenges in the healthcare industry: customer service, medical errors, burnout, and turnover intentions. This study provides clear evidence that employee perceptions of the extent to which their work climate is participative rather than authoritarian have important implications for critical work attitudes and behavior. Specifically, employees in highly participative work climates provided 14 percent better customer service, committed 26 percent fewer clinical errors, demonstrated 79 percent lower burnout, and felt 61 percent lower likelihood of leaving the organization than employees in more authoritarian work climates. These findings suggest that participative management initiatives have a significant impact on the commitment and productivity of individual employees, likely improving the patient care and effectiveness of healthcare organizations as a whole.


Assuntos
Atitude , Esgotamento Profissional , Administradores Hospitalares/psicologia , Erros Médicos , Reorganização de Recursos Humanos , Competição Econômica
5.
Biomolecules ; 9(10)2019 10 08.
Artigo em Inglês | MEDLINE | ID: mdl-31597350

RESUMO

Tannins are one of the most natural, non-toxic, and highly reactive aromatic biomolecules classified as polyphenols. The reactive phenolic compounds present in their chemical structure can be an alternative precursor for the preparation of several polymeric materials for applications in distinct industries: adhesives and coatings, leather tanning, wood protection, wine manufacture, animal feed industries, and recently also in the production of new porous materials (i.e., foams and gels). Among these new polymeric materials synthesized with tannins, organic and carbon gels have shown remarkable textural and physicochemical properties. Thus, this review presents and discusses the available studies on organic and carbon gels produced from tannin feedstock and how their properties are related to the different operating conditions, hence causing their cross-linking reaction mechanisms. Moreover, the steps during tannin gels preparation, such as the gelation and curing processes (under normal or hydrothermal conditions), solvent extraction, and gel drying approaches (i.e., supercritical, subcritical, and freeze-drying) as well as the methods available for their carbonization (i.e., pyrolysis and activation) are presented and discussed. Findings from organic and carbon tannin gels features demonstrate that their physicochemical and textural properties can vary greatly depending on the synthesis parameters, drying conditions, and carbonization methods. Research is still ongoing on the improvement of tannin gels synthesis and properties, but the review evaluates the application of these highly porous materials in multidisciplinary areas of science and engineering, including thermal insulation, contaminant sorption in drinking water and wastewater, and electrochemistry. Finally, the substitution of phenolic materials (i.e., phenol and resorcinol) by tannin in the production of gels could be beneficial to both the bioeconomy and the environment due to its low-cost, bio-based, non-toxic, and non-carcinogenic characteristics.


Assuntos
Carbono/química , Flavonoides/química , Taninos/química , Géis , Estrutura Molecular , Porosidade
6.
Nature ; 442(7104): 756, 2006 Aug 17.
Artigo em Inglês | MEDLINE | ID: mdl-16915277
7.
Astrobiology ; 7(1): 30-65, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17407403

RESUMO

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 M(Sun)), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid-surface-water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 M(Earth) orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchronous rotation within the narrow habitable zone does not necessarily lead to atmospheric collapse, and active stellar flaring may not be as much of an evolutionarily disadvantageous factor as has previously been supposed. We conclude that M dwarf stars may indeed be viable hosts for planets on which the origin and evolution of life can occur. A number of planetary processes such as cessation of geothermal activity or thermal and nonthermal atmospheric loss processes may limit the duration of planetary habitability to periods far shorter than the extreme lifetime of the M dwarf star. Nevertheless, it makes sense to include M dwarf stars in programs that seek to find habitable worlds and evidence of life. This paper presents the summary conclusions of an interdisciplinary workshop (http://mstars.seti.org) sponsored by the NASA Astrobiology Institute and convened at the SETI Institute.


Assuntos
Exobiologia , Planetas , Fenômenos Astronômicos , Astronomia , Ecossistema , Meio Ambiente Extraterreno , Origem da Vida
8.
Nature ; 432(7020): 957-8, 2004 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-15616539
9.
Astrobiology ; 3(2): 219-35, 2003.
Artigo em Inglês | MEDLINE | ID: mdl-14577870

RESUMO

The NASA Astrobiology Roadmap provides guidance for research and technology development across the NASA enterprises that encompass the space, Earth, and biological sciences. The ongoing development of astrobiology roadmaps embodies the contributions of diverse scientists and technologists from government, universities, and private institutions. The Roadmap addresses three basic questions: How does life begin and evolve, does life exist elsewhere in the universe, and what is the future of life on Earth and beyond? Seven Science Goals outline the following key domains of investigation: understanding the nature and distribution of habitable environments in the universe, exploring for habitable environments and life in our own solar system, understanding the emergence of life, determining how early life on Earth interacted and evolved with its changing environment, understanding the evolutionary mechanisms and environmental limits of life, determining the principles that will shape life in the future, and recognizing signatures of life on other worlds and on early Earth. For each of these goals, Science Objectives outline more specific high-priority efforts for the next 3-5 years. These 18 objectives are being integrated with NASA strategic planning.


Assuntos
Exobiologia/métodos , Exobiologia/tendências , United States National Aeronautics and Space Administration , Planeta Terra , Meio Ambiente Extraterreno , Planetas , Estados Unidos
10.
Science ; 340(6132): 587-90, 2013 May 03.
Artigo em Inglês | MEDLINE | ID: mdl-23599262

RESUMO

We present the detection of five planets--Kepler-62b, c, d, e, and f--of size 1.31, 0.54, 1.95, 1.61 and 1.41 Earth radii (R⊕), orbiting a K2V star at periods of 5.7, 12.4, 18.2, 122.4, and 267.3 days, respectively. The outermost planets, Kepler-62e and -62f, are super-Earth-size (1.25 R⊕ < planet radius ≤ 2.0 R⊕) planets in the habitable zone of their host star, respectively receiving 1.2 ± 0.2 times and 0.41 ± 0.05 times the solar flux at Earth's orbit. Theoretical models of Kepler-62e and -62f for a stellar age of ~7 billion years suggest that both planets could be solid, either with a rocky composition or composed of mostly solid water in their bulk.


Assuntos
Planetas , Água , Exobiologia , Meio Ambiente Extraterreno , Modelos Teóricos , Astros Celestes
11.
J Appl Psychol ; 97(3): 637-50, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22309410

RESUMO

Despite decades of theory and empirical research on employee burnout, its temporal and developmental aspects are still not fully understood. This lack of understanding is problematic because burnout is a dynamic phenomenon and burnout interventions may be improved by a greater understanding of who is likely to experience changes in burnout and when these changes occur. In this article, we advance existing burnout theory by articulating how the 3 burnout dimensions should differ in their pattern of change over time as a result of career transition type: organizational newcomers, internal job changers (e.g., promotions or lateral moves), and organizational insiders (i.e., job incumbents). We tested our model in a broad sample of 2,089 health care employees, with 5 measurement points over 2 years. Using random coefficient modeling, we found that burnout was relatively stable for organizational insiders but slightly dynamic for organizational newcomers and internal job changers. We also found that the dimensions of emotional exhaustion and depersonalization were more sensitive to career transition type than reduced personal accomplishment. Finding some differences among different types of employees as well as the dimensions of burnout may begin to explain longstanding inconsistencies between theory and research regarding the dynamics of burnout, offering directions for future research that address both dynamism and stability.


Assuntos
Esgotamento Profissional/psicologia , Mobilidade Ocupacional , Adulto , Atenção à Saúde , Despersonalização/psicologia , Seguimentos , Humanos , Cultura Organizacional , Socialização , Inquéritos e Questionários , Fatores de Tempo , Recursos Humanos
12.
Science ; 337(6101): 1511-4, 2012 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-22933522

RESUMO

We report the detection of Kepler-47, a system consisting of two planets orbiting around an eclipsing pair of stars. The inner and outer planets have radii 3.0 and 4.6 times that of Earth, respectively. The binary star consists of a Sun-like star and a companion roughly one-third its size, orbiting each other every 7.45 days. With an orbital period of 49.5 days, 18 transits of the inner planet have been observed, allowing a detailed characterization of its orbit and those of the stars. The outer planet's orbital period is 303.2 days, and although the planet is not Earth-like, it resides within the classical "habitable zone," where liquid water could exist on an Earth-like planet. With its two known planets, Kepler-47 establishes that close binary stars can host complete planetary systems.

13.
J Appl Psychol ; 96(2): 412-22, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-21133529

RESUMO

Using Hollander's (1958) idiosyncrasy credit theory of leadership as the theoretical backdrop, we examined when and why organizational leaders escape punitive evaluation for their organizational transgressions. In a sample of 162 full-time employees, we found that leaders who were perceived to be more able and inspirationally motivating were less punitively evaluated by employees for leader transgressions. These effects were mediated by the leaders' LMX (leader-member exchange) with their employees. Moreover, the tendency of leaders with higher LMX to escape punitive evaluations for their transgressions was stronger when those leaders were more valued within the organization. Finally, employees who punitively evaluated their leaders were more likely to have turnover intentions and to psychologically withdraw from their organization. Theoretical and practical implications associated with relatively understudied leader-transgression dynamics are discussed.


Assuntos
Pesquisa Empírica , Relações Interpessoais , Julgamento/fisiologia , Liderança , Punição/psicologia , Adulto , Feminino , Humanos , Satisfação no Emprego , Masculino , Cultura Organizacional , Reorganização de Recursos Humanos , Inquéritos e Questionários
14.
Science ; 333(6049): 1602-6, 2011 Sep 16.
Artigo em Inglês | MEDLINE | ID: mdl-21921192

RESUMO

We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.

15.
Science ; 327(5968): 977-80, 2010 Feb 19.
Artigo em Inglês | MEDLINE | ID: mdl-20056856

RESUMO

The Kepler mission was designed to determine the frequency of Earth-sized planets in and near the habitable zone of Sun-like stars. The habitable zone is the region where planetary temperatures are suitable for water to exist on a planet's surface. During the first 6 weeks of observations, Kepler monitored 156,000 stars, and five new exoplanets with sizes between 0.37 and 1.6 Jupiter radii and orbital periods from 3.2 to 4.9 days were discovered. The density of the Neptune-sized Kepler-4b is similar to that of Neptune and GJ 436b, even though the irradiation level is 800,000 times higher. Kepler-7b is one of the lowest-density planets (approximately 0.17 gram per cubic centimeter) yet detected. Kepler-5b, -6b, and -8b confirm the existence of planets with densities lower than those predicted for gas giant planets.

16.
Astrobiology ; 8(4): 715-30, 2008 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-18793098

RESUMO

The NASA Astrobiology Roadmap provides guidance for research and technology development across the NASA enterprises that encompass the space, Earth, and biological sciences. The ongoing development of astrobiology roadmaps embodies the contributions of diverse scientists and technologists from government, universities, and private institutions. The Roadmap addresses three basic questions: how does life begin and evolve, does life exist elsewhere in the universe, and what is the future of life on Earth and beyond? Seven Science Goals outline the following key domains of investigation: understanding the nature and distribution of habitable environments in the universe, exploring for habitable environments and life in our own Solar System, understanding the emergence of life, determining how early life on Earth interacted and evolved with its changing environment, understanding the evolutionary mechanisms and environmental limits of life, determining the principles that will shape life in the future, and recognizing signatures of life on other worlds and on early Earth. For each of these goals, Science Objectives outline more specific high priority efforts for the next three to five years. These eighteen objectives are being integrated with NASA strategic planning.


Assuntos
Exobiologia/tendências , Planeta Terra , Meio Ambiente Extraterreno , Marte , Origem da Vida , Planetas , Sistema Solar , Estados Unidos , United States National Aeronautics and Space Administration
17.
Science ; 334(6059): 1057, 2011 Nov 25.
Artigo em Inglês | MEDLINE | ID: mdl-22116861
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