2,134 research outputs found
All-optical combiner-splitter and gating devices based on straight waveguides
A two-mode optical combiner-splitter device is designed based on all straight waveguides that maintains the integrity of the two modes during propagation and allows for an analytic analysis. The design analysis has the potential to improve the precision of the device fabrication. The design is used in an analytic optical gate based on a nonlinear Mach-Zehnder interferometer. The design reduces the size of a previously proposed device and simplifies its analysis
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
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
Ureteroscopic biopsy of upper tract urothelial carcinoma and role of urinary biomarkers
Ureteroscopic biopsy is an integral part of diagnosis of urothelial carcinoma of the upper urinary tract. It can be a technical challenge, but diagnostic rates have improved remarkably with refinements in surgical technique and specimen processing. Cytology aids with diagnosis and other urinary biomarkers continue to evolve, which may help further stratify patients for treatment. The current literature on the ureteroscopic biopsy and role of urinary biomarkers is reviewed and summarized below
The effect of RO3201195 and a pyrazolyl ketone P38 MAPK inhibitor library on the proliferation of Werner syndrome cells
No description supplie
Overview of the Tevatron Collider Complex: Goals, Operations and Performance
For more than two decades the Tevatron proton-antiproton collider was the
centerpiece of the world's high energy physics program. The collider was
arguably one of the most complex research instruments ever to reach the
operation stage and is widely recognized for numerous physics discoveries and
for many technological breakthroughs. In this article we outline the historical
background that led to the construction of the Tevatron Collider, the strategy
applied to evolution of performance goals over the Tevatron's operational
history, and briefly describe operations of each accelerator in the chain and
achieved performance.Comment: Includes modifications suggested by reviewer
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