scholarly journals Controlled transitions between phyllotactic states of repulsive particles confined on the surface of a cylinder

Author(s):  
Austin Alexander Tomlinson ◽  
Nicola Wilkin

Abstract Phyllotaxis is a botanical classification scheme that can describe regular lattice-like structures on cylinders, often as a set of helical chains. In this letter, we study the general properties of repulsive particles on cylindrical geometries and demonstrate that this leads to a model which allows one to predict the minimum energy configuration for any given combination of system parameters. We are able to predict a sequence of transitions between phyllotactic ground states at zero temperature. Our results are understood in terms of a newly identified global scale invariant, \(\alpha\), dependent on circumference and density, which \emph{alone} determines the ground state structure. This representation provides a framework within which to understand and create lattice structures on more complex curved surfaces, which occur in both biological and nanoscale experimental settings.

Food Security ◽  
2021 ◽  
Author(s):  
Thomas Pircher ◽  
Conny J. M. Almekinders

AbstractA demand-driven approach is becoming increasingly central in the efforts to improve agricultural research and development. However, the question of how exactly demand is studied usually remains unstated and is rarely discussed. We therefore carried out a systematic review in order to better understand how farmers’ demand for seed in root, tuber and banana seed systems is studied. The review is based on data from a consultation with an expert panel and a structured literature search in the SCOPUS database. Screening the gathered articles resulted in 46 studies on a global scale, fitting the scope of our investigation. Through qualitative analysis and categorization of these studies, we developed a classification scheme according to the types of approaches applied in the retained studies. One group of studies explicitly articulates farmers’ preferences and choices through surveys or engagements in trials, auctions, choice experiments and interviews. Other studies implicitly articulate farmers’ demand by characterising their current use of varieties and seed. We discuss opportunities and limitations in the use of each type of study and we reflect on the body of available literature as a whole. Our conclusion is that a framework is necessary that purposefully combines the existing different methods and that it is necessary to involve stakeholders in a process where demand is articulated. Together, these two steps would characterise existing demands in a more effective and precise way, thus providing better guidance to decision-makers in their reactions pertaining to seed systems.


2013 ◽  
Vol 117 (38) ◽  
pp. 11015-11021 ◽  
Author(s):  
Maria M. Mendes-Pinto ◽  
Elodie Sansiaume ◽  
Hideki Hashimoto ◽  
Andrew A. Pascal ◽  
Andrew Gall ◽  
...  

2002 ◽  
Vol 17 (25) ◽  
pp. 3681-3688 ◽  
Author(s):  
LISA FREYHULT

We compute the effective potential of SU(2) Yang–Mills theory using the background field method and the Faddeev–Niemi decomposition of the gauge fields. In particular, we find that the potential will depend on the values of two scalar fields in the decomposition and that its structure will give rise to a symmetry breaking.


2012 ◽  
Vol 116 (47) ◽  
pp. 11651-11655 ◽  
Author(s):  
Xin Liu ◽  
Lin Li ◽  
Bo Liu ◽  
Dongqi Wang ◽  
Yuliang Zhao ◽  
...  

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