3,696 research outputs found
1998 Sewall Wright Award: William Donald Hamilton
Journal ArticleThe Sewall Wright Award was established in 1991 to honor active investigators who have contributed in especially significant ways to the conceptual unification of the biological sciences. This year's recipient is William D. Hamilton of Oxford University. Beginning in the 1960s with his papers on the theory of inclusive fitness and the evolution of eusociality, Bill Hamilton's publications have permanently changed the landscape of ideas and interpretation surrounding a wide range of biological phenomena. His papers have clarified murky problems, generated new research agendas, and unified our understanding of many central concepts, on a truly revolutionary scale
Parasites and sex
Book ChapterParasites of many kinds have long been recognized as important regulators of population size (e.g., May, 1983b), but only during the last decade or two have they been widely viewed as the protagonists in fast-paced (and long-running) evolutionary thrillers involving subtle features of the biochemistry, anatomy, and behavior of their hosts. On this view, their power as agents of evolution derives from their ubiquity and from the great amounts of mortality they can cause (which are also the properties that make them effective agents of population regulation) and, just as importantly, from their imperfect (but improvable) abilities to defeat the imperfect (but improvable) defenses of their hosts. Thus each party is expected to experience the other as a changeable (and generally worsening) part of its environment
ERK1c regulates Golgi fragmentation during mitosis
Extracellular signal-regulated kinase 1c (ERK1c) is an alternatively spliced form of ERK1 that is regulated differently than other ERK isoforms. We studied the Golgi functions of ERK1c and found that it plays a role in MEK-induced mitotic Golgi fragmentation. Thus, in late G2 and mitosis of synchronized cells, the expression and activity of ERK1c was increased and it colocalized mainly with Golgi markers. Small interfering RNA of ERK1c significantly attenuated, whereas ERK1c overexpression facilitated, mitotic Golgi fragmentation. These effects were also reflected in mitotic progression, indicating that ERK1c is involved in cell cycle regulation via modulation of Golgi fragmentation. Although ERK1 was activated in mitosis as well, it could not replace ERK1c in regulating Golgi fragmentation. Therefore, MEKs regulate mitosis via all three ERK isoforms, where ERK1c acts specifically in the Golgi, whereas ERK1 and 2 regulate other mitosis-related processes. Thus, ERK1c extends the specificity of the Ras-MEK cascade by activating ERK1/2-independent processes
The formal verification of a pipelined double-precision IEEE floating-point multiplier
Floating-point circuits are notoriously difficult to design and verify. For verification, simulation barely offers adequate coverage, conventional model-checking techniques are infeasible, and theorem-proving based verification is not sufficiently mature. In this paper we present the formal verification of a radix-eight, pipelined, IEEE double-precision floating-point multiplier. The verification was carried out using a mixture of model-checking and theorem-proving techniques in the Voss hardware verification system. By combining model-checking and theorem-proving we were able to build on the strengths of both areas and achieve significant results with a reasonable amount of effort.
Two-phase model of hydrogen transport to optimize nanoparticle catalyst loading for hydrogen evolution reaction
With electrocatalysts it is important to be able to distinguish between the effects of mass transport and reaction kinetics on the performance of the catalyst. When the hydrogen evolution reaction (HER) is considered, an additional and often neglected detail of mass transport in liquid is the evolution and transport of gaseous H2, since HER leads to the continuous formation of H2 bubbles near the electrode. We present a numerical model that includes the transport of both gaseous and dissolved H2, as well as mass exchange between them, and combine it with a kinetic model of HER at platinum (Pt) nanoparticle electrodes. We study the effect of the diffusion layer thickness and H2 dissolution rate constant on the importance of gaseous transport, and the effect of equilibrium hydrogen coverage and Pt loading on the kinetic and mass transport overpotentials. Gaseous transport becomes significant when the gas volume fraction is sufficiently high to facilitate H2 transfer to bubbles within a distance shorter than the diffusion layer thickness. At current densities below about 40 mA/cm2 the model reduces to an analytical approximation that has characteristics similar to the diffusion of H2. At higher current densities the increase in the gas volume fraction makes the H2 surface concentration nonlinear with respect to the current density. Compared to the typical diffusion layer model, our model is an extension that allows more detailed studies of reaction kinetics and mass transport in the electrolyte and the effects of gas bubbles on them.Peer reviewe
Preparing for a Northwest Passage: A Workshop on the Role of New England in Navigating the New Arctic
Preparing for a Northwest Passage: A Workshop on the Role of New England in Navigating the New Arctic (March 25 - 27, 2018 -- The University of New Hampshire) paired two of NSF\u27s 10 Big Ideas: Navigating the New Arctic and Growing Convergence Research at NSF. During this event, participants assessed economic, environmental, and social impacts of Arctic change on New England and established convergence research initiatives to prepare for, adapt to, and respond to these effects. Shipping routes through an ice-free Northwest Passage in combination with modifications to ocean circulation and regional climate patterns linked to Arctic ice melt will affect trade, fisheries, tourism, coastal ecology, air and water quality, animal migration, and demographics not only in the Arctic but also in lower latitude coastal regions such as New England. With profound changes on the horizon, this is a critical opportunity for New England to prepare for uncertain yet inevitable economic and environmental impacts of Arctic change
A variational approach to the stochastic aspects of cellular signal transduction
Cellular signaling networks have evolved to cope with intrinsic fluctuations,
coming from the small numbers of constituents, and the environmental noise.
Stochastic chemical kinetics equations govern the way biochemical networks
process noisy signals. The essential difficulty associated with the master
equation approach to solving the stochastic chemical kinetics problem is the
enormous number of ordinary differential equations involved. In this work, we
show how to achieve tremendous reduction in the dimensionality of specific
reaction cascade dynamics by solving variationally an equivalent quantum field
theoretic formulation of stochastic chemical kinetics. The present formulation
avoids cumbersome commutator computations in the derivation of evolution
equations, making more transparent the physical significance of the variational
method. We propose novel time-dependent basis functions which work well over a
wide range of rate parameters. We apply the new basis functions to describe
stochastic signaling in several enzymatic cascades and compare the results so
obtained with those from alternative solution techniques. The variational
ansatz gives probability distributions that agree well with the exact ones,
even when fluctuations are large and discreteness and nonlinearity are
important. A numerical implementation of our technique is many orders of
magnitude more efficient computationally compared with the traditional Monte
Carlo simulation algorithms or the Langevin simulations.Comment: 15 pages, 11 figure
Hubungan antara Servant Leadership dengan Efektifitas Tim ditinjau dari Persepsi Anggota Tim PHKI-Jurusan di Institut Teknologi Sepuluh Nopember Surabaya
The purpose of this study was to know the correlation between Servant Leadership and Team Effectiveness. The research was conducted on 46 members of PHKI (Program of grant competition for institution) team in eight department at Institute Technology of Sepuluh November Surabaya. Data collection tools used two questionnaires: 1) Servant Leadership scale consisiting 38 items, and 2) team effectiveness scale. Servant Leadership scale consists of 38 items developed by John E. Barbuto, JR. and Daniel W. Wheeler (2006). Servant leadership has 5 characteristics: altruistic calling, emotional healing, wisdom, persuasive maping and organizational stewardship. The second is Team Effectiveness scale consisting of 20 items developed by Larson and La Fasto. There are 8 characteristics of team effectiveness scale: clear - elevating goal, results – driven structure, competent team members, unified commitment among members, collaborative climate, standards of excellence, external support and recognition, principled leadership. This research used Alpha Cronbach for reliability test. Reliability coefficient scale Servant Leadership variable is 0,95, while the reliability coefficient of Team Effectiveness variable is 0,92. Data was analyzed using Spearman's Rank Order by SPPS 15.0 for windows. The correlation between the Servant Leadership and the Team Effectiveness is 0,574 with p value is 0,000. It indicates that there is significant positive correlations between Servant Leadership and Team Effectiveness in PHKI departments at Institute Technology of Sepuluh November Surabay
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Impact of Hypothyroidism and Heart Failure on Hospitalization Risk.
BackgroundPrior studies suggest that the relationship between hypothyroidism and mortality is dependent on underlying cardiovascular risk. Little is known about the association of hypothyroidism with hospitalization risk, and how these associations are modified by cardiovascular status.MethodsThis study examined the association of thyroid status, defined by serum thyrotropin (TSH), with hospitalization risk among patients who received care at a large university-based tertiary care center between 1990 and 2015. Thyroid status was categorized as hypothyroidism versus euthyroidism (TSH >4.7 vs. 0.3-4.7 mIU/L, respectively). The relationship between thyroid status and hospitalization risk stratified by cardiovascular status was examined using multivariable Cox models.ResultsAmong 52,856 patients who met eligibility criteria, 49,791 (94.2%) had euthyroidism and 3065 (5.8%) had hypothyroidism. In analyses stratified by congestive heart failure (CHF) status, compared to euthyroidism, hypothyroidism was associated with higher risk of hospitalization in those with CHF but slightly lower risk in those without CHF (adjusted hazard ratio [aHRs] = 1.86 [confidence interval (CI) 1.17-2.94] and HR = 0.95 [CI 0.92-0.99], respectively; p = 0.006). In sensitivity analyses accounting for death as a competing event, underlying coronary artery disease modified the hypothyroidism-hospitalization relationship, such that stronger associations were observed among those with versus without coronary artery disease. In competing risk analyses, hypothyroidism was associated with higher versus lower risk of hospitalization among those with versus without cerebrovascular disease, respectively.ConclusionsHypothyroidism is associated with higher hospitalization risk among patients with underlying cardiovascular disease. Future studies are needed to determine whether correction of thyroid status with replacement therapy ameliorates hospitalization risk in this population
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