Growth states of catalytic reaction networks exhibiting energy metabolism

All cells derive nutrition by absorbing some chemical and energy resources from the environment; these resources are used by the cells to reproduce the chemicals within them, which in turn leads to an increase in their volume. In this study, we introduce a protocell model exhibiting catalytic reaction dynamics, energy metabolism, and cell growth. Results of extensive simulations of this model show the existence of four phases with regard to the rates of both the influx of resources and the cell growth. These phases include an active phase with high influx and high growth rates, an inefficient phase with high influx but low growth rates, a quasi-static phase with low influx and low growth rates, and a death phase with negative growth rate. A mean field model well explains the transition among these phases as bifurcations. The statistical distribution of the active phase is characterized by a power law and that of the inefficient phase is characterized by a nearly equilibrium distribution. We also discuss the relevance of the results of this study to distinct states in the existing cells.Comment: 21 pages, 5 figure

Bedded Pack Management System Case Study

Agribusiness, Agricultural Finance, Farm Management,

Use of swivel desks and aisle space to promote interaction in mid-sized college classrooms

Traditional designs for most mid-sized college classrooms discourage 1) face-to-face interaction among students, 2) instructor movement in the classroom, and 3) efficient transitions between different kinds of learning activities. An experimental classroom piloted during Spring Semester 2011 at the University of North Carolina at Chapel Hill uses clusters of stationary desks that swivel 360-degrees and aisle space to address these challenges. The findings from a study involving ten courses taught in the room suggest that there is a need for designs that not only promote quality interactions but also facilitate movement between small group work, class discussion, and lecture

Application of Electronic Analog Computer to Solution of Hydrologic and River Basin Planning Problems: Utah Simulation Model II

As demands upon available water supplies increase, there is an accompanying increase in the need to assess the downstream hydrologic system. At Utah State University this problem is being approached by electronic analog simulation of the hydrologic system. Modeling concepts are based upon the development of basic relationships which describe the various hydrologic processes. Within a system, these relationships are linked by the continuity -of-mass principle which requires a hydrologic balance at all points. Once established, the model is applied to any particular geographic unit by determining the appropriate constants of the hydrologic equations. The analog computer is ideally suited to the solution of the many time-dependent differential equations which are encountered in the hydrologic systems. The complexity of a hydrologic model depends to a large extent upon the magnitude of the time and spatial increments utilized in the model. In this study the mathematical development was based on the concepts of relatively small increments of space and large time increments. The model is, therefore, applicable to in-basin probelms involving a time increment of, for example, one month. To test individual equations and to verify the model, the Circle Valley subbasin of the Servier River system in Utah was simulated. Close agreement between computed and observed outflows was achieved on both a monthly and a total annual basis

A protein conformational change associated with the photoreduction of the primary and secondary quinones in the bacterial reaction center

AbstractA comparison is made between the PQA → P+Q−A and PQAQB → P+QAQ−B transitions in Rps. viridis and Rb. sphaeroides reaction centers (RCs) by the use of light-induced Fourier transform infrared (FTIR) difference spectroscopy. In Rb. sphaeroides RCs, we identify a signal at 1650 cm−1 which is present in the P+QA-minus-PQA spectrum and not in the P+QAQ−B-minus-PQAQB spectrum. In contrast, this signal is present in both P+Q−A-minus-PQ−A and P+QAQ−B-minus-PQAQB spectra of Rps. viridis RCs. These data are interpreted in terms of a conformational change of the protein backbone near QA (possible at the peptide CO of a conserved alanine residue in the QA pocket) and of the different bonding interactions of QB with the protein in the RC of the two species

Retarding Sub- and Accelerating Super-Diffusion Governed by Distributed Order Fractional Diffusion Equations

We propose diffusion-like equations with time and space fractional derivatives of the distributed order for the kinetic description of anomalous diffusion and relaxation phenomena, whose diffusion exponent varies with time and which, correspondingly, can not be viewed as self-affine random processes possessing a unique Hurst exponent. We prove the positivity of the solutions of the proposed equations and establish the relation to the Continuous Time Random Walk theory. We show that the distributed order time fractional diffusion equation describes the sub-diffusion random process which is subordinated to the Wiener process and whose diffusion exponent diminishes in time (retarding sub-diffusion) leading to superslow diffusion, for which the square displacement grows logarithmically in time. We also demonstrate that the distributed order space fractional diffusion equation describes super-diffusion phenomena when the diffusion exponent grows in time (accelerating super-diffusion).Comment: 11 pages, LaTe