Compressible viscoelastodynamics of a spherical body at long timescales and its isostatic equilibrium

Cyanophage abundance has been shown to fluctuate over long timescales and with depth, but little is known about how it varies over short timescales. Previous short-term studies have relied on counting total virus numbers and therefore the phages which infect cyanobacteria cannot be distinguished from the total count.In this study, an isolation-based approach was used to determine cyanophage abundance from water samples collected over a depth profile for a 24 h period from the Indian Ocean. Samples were used to infect Synechococcus sp. WH7803 and the number of plaque forming units (pfu) at each time point and depth were counted. At 10 m phage numbers were similar for most time-points, but there was a distinct peak in abundance at 0100 hours. Phage numbers were lower at 25 m and 50 m and did not show such strong temporal variation. No phages were found below this depth. Therefore, we conclude that only the abundance of phages in surface waters showed a clear temporal pattern over a short timescale. Fifty phages from a range of depths and time points were isolated and purified. The molecular diversity of these phages was estimated using a section of the phage-encoded psbD gene and the results from a phylogenetic analysis do not suggest that phages from the deeper waters form a distinct subgroup.

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A Transient Formulation of Newton's Cooling Law for Spherical Bodies

Journal of Heat Transfer ◽

10.1115/1.1337650 ◽

2000 ◽

Vol 123 (1) ◽

pp. 63-64 ◽

Cited By ~ 17

Author(s):

S. S. Sazhin ◽

V. A. Gol'dshtein ◽

M. R. Heikal

Keyword(s):

Thermal Conductivity ◽

Heat Flux ◽

Diesel Engine ◽

Effective Thermal Conductivity ◽

Spherical Body ◽

Fuel Droplet ◽

Transient Effects ◽

Newton's Law ◽

Initial Stage ◽

Newton’S Law

Newton's law of cooling is shown to underestimate the heat flux between a spherical body (droplet) and a homogeneous gas after this body is suddenly immersed into the gas. This problem is rectified by replacing the gas thermal conductivity by the effective thermal conductivity. The latter reduces to the gas thermal conductivity in the limit of t→∞, but can be substantially higher in the limit of t→0. In the case of fuel droplet heating in a medium duty truck Diesel engine the gas thermal conductivity may need to be increased by more than 100 percent at the initial stage of calculations to account for transient effects during the process of droplet heating.

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Intensities and travel times of seismic rays in a sphere with a linear velocity function

Bulletin of the Seismological Society of America ◽

10.1785/bssa0670010033 ◽

1977 ◽

Vol 67 (1) ◽

pp. 33-42

Author(s):

Mark E. Odegard ◽

Gerard J. Fryer

Keyword(s):

Velocity Profile ◽

Travel Time ◽

Upper Mantle ◽

Intensity Ratio ◽

Computation Time ◽

Spherical Body ◽

Travel Times ◽

Velocity Function ◽

Intensity Ratios ◽

Distance Travel

Abstract Equations are presented which permit the calculation of distances, travel times and intensity ratios of seismic rays propagating through a spherical body with concentric layers having velocities which vary linearly with radius. In addition, a method is described which removes the infinite singularities in amplitude generated by second-order discontinuities in the velocity profile. Numerical calculations involving a reasonable upper mantle model show that the standard deviations of the errors for distance, travel time and intensity ratio are 0.0046°, 0.057 sec, and 0.04 dB, respectively. Computation time is short.

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Contact force analysis on two-fingered robot grasping

Proceedings of the Institution of Mechanical Engineers Part K Journal of Multi-body Dynamics ◽

10.1177/1464419320964022 ◽

2020 ◽

pp. 146441932096402

Author(s):

Jiun-Ru Chen ◽

Wei-En Chen ◽

CH Liu ◽

Yin-Tien Wang ◽

CB Lin ◽

...

Keyword(s):

Kinetic Analysis ◽

Contact Force ◽

Numerical Procedure ◽

Spherical Body ◽

Solution Procedure ◽

The Body ◽

Contact Forces ◽

Grasping Forces ◽

Robot Grasping ◽

Force Displacement

A procedure for inverse kinetic analysis on two hard fingers grasping a hard sphere is proposed in this study. Contact forces may be found for given linear and angular accelerations of a spherical body. Elastic force-displacement relations predicted by Hertz contact theory are used to remove the indeterminancy produced by rigid body modelling. Two types of inverse kinetic analysis may be dealt with. Firstly, as the fingers impose a given tightening displacement on the body, and carry it to move with known accelerations, corresponding grasping forces may be determined by a numerical procedure. In this procedure one contact force may be chosen as the principal unknown, and all other contact forces are expressed in terms of this force. The numerical procedure is hence very efficient since it deals with a problem with only one unknown. The solution procedure eliminates slipping thus only nonslip solutions, if they exist, are found. Secondly, when the body is moving with known accelerations, if the grasping direction of the two fingers is also known, then the minimum tightening displacement required for non-sliding grasping may be obtained in closed form. In short, the proposed technique deals with a grasping system that has accelerations, and in this study the authors show that indeterminancy may be used to reduce the complexity of the problem.

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Hippocampal Place Fields Maintain a Coherent and Flexible Map across Long Timescales

Current Biology ◽

10.1016/j.cub.2018.09.037 ◽

2018 ◽

Vol 28 (22) ◽

pp. 3578-3588.e6 ◽

Cited By ~ 27

Author(s):

Nathaniel R. Kinsky ◽

David W. Sullivan ◽

William Mau ◽

Michael E. Hasselmo ◽

Howard B. Eichenbaum

Keyword(s):

Place Fields ◽

Long Timescales

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Developing predictive insight into changing water systems: use-inspired hydrologic science for the Anthropocene

Hydrology and Earth System Sciences ◽

10.5194/hess-17-5013-2013 ◽

2013 ◽

Vol 17 (12) ◽

pp. 5013-5039 ◽

Cited By ~ 90

Author(s):

S. E. Thompson ◽

M. Sivapalan ◽

C. J. Harman ◽

V. Srinivasan ◽

M. R. Hipsey ◽

...

Keyword(s):

Decision Making ◽

Water Resources ◽

Water Resources Management ◽

Research Agenda ◽

Water Systems ◽

Coupled Systems ◽

Model Data ◽

Resources Management ◽

Long Timescales ◽

Insight Into

Abstract. Globally, many different kinds of water resources management issues call for policy- and infrastructure-based responses. Yet responsible decision-making about water resources management raises a fundamental challenge for hydrologists: making predictions about water resources on decadal- to century-long timescales. Obtaining insight into hydrologic futures over 100 yr timescales forces researchers to address internal and exogenous changes in the properties of hydrologic systems. To do this, new hydrologic research must identify, describe and model feedbacks between water and other changing, coupled environmental subsystems. These models must be constrained to yield useful insights, despite the many likely sources of uncertainty in their predictions. Chief among these uncertainties are the impacts of the increasing role of human intervention in the global water cycle – a defining challenge for hydrology in the Anthropocene. Here we present a research agenda that proposes a suite of strategies to address these challenges from the perspectives of hydrologic science research. The research agenda focuses on the development of co-evolutionary hydrologic modeling to explore coupling across systems, and to address the implications of this coupling on the long-time behavior of the coupled systems. Three research directions support the development of these models: hydrologic reconstruction, comparative hydrology and model-data learning. These strategies focus on understanding hydrologic processes and feedbacks over long timescales, across many locations, and through strategic coupling of observational and model data in specific systems. We highlight the value of use-inspired and team-based science that is motivated by real-world hydrologic problems but targets improvements in fundamental understanding to support decision-making and management. Fully realizing the potential of this approach will ultimately require detailed integration of social science and physical science understanding of water systems, and is a priority for the developing field of sociohydrology.

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