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Search Results: 1 - 10 of 2728 matches for " Ha Phan "
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The structure of Chip Firing Games and related models
Eric Goles,Michel Morvan,Ha Duong Phan
Mathematics , 2000,
Abstract: In this paper, we study the dynamics of sand grains falling in sand piles. Usually sand piles are characterized by a decreasing integer partition and grain moves are described in terms of transitions between such partitions. We study here four main transition rules. The more classical one, introduced by Brylawski (1973) induces a lattice structure $L_B (n)$ (called dominance ordering) between decreasing partitions of a given integer n. We prove that a more restrictive transition rule, called SPM rule, induces a natural partition of L_B (n) in suborders, each one associated to a fixed point for SPM rule. In the second part, we extend the SPM rule in a natural way and obtain a model called Chip Firing Game (Goles and Kiwi, 1993). We prove that this new model has interesting properties: the induced order is a lattice, a natural greedoid can be associated to the model and it also defines a strongly convergent game. In the last section, we generalize the SPM rule in another way and obtain other lattice structure parametrized by some t: L(n,t), which form for -n+2 <= t <= n a decreasing sequence of lattices. For each t, we characterize the fixed point of L(n,t) and give the value of its maximal sized chain's lenght. We also note that L(n,-n+2) is the lattice of all compositions of n.
Characterisation of lattices induced by (extended) Chip Firing Games
Clemence Magnien,Ha Duong Phan,Laurent Vuillon
Mathematics , 2001,
Abstract: The Chip Firing Game (CFG) is a discrete dynamical model used in physics, computer science and economics. It is known that the set of configurations reachable from an initial configuration (this set is called the configuration space) can be ordered as a lattice. We first present a structural result about this model, which allows us to introduce some useful tools for describing those lattices. Then we establish that the class of lattices that are the configuration space of a CFG is strictly between the class of distributive lattices and the class of upper locally distributive (or ULD) lattices. Finally we propose an extension of the model, the coloured Chip Firing Game, which generates exactly the class of ULD lattices.
Lattice of Triangulations: the proof and an algorithm
Thinh Duc Nguyen,Ha Duong Phan
Mathematics , 2008,
Abstract: This paper has been withdrawn by authors to be refined and to complete some important results. Whener it is completed, authors will contribute it to the mathematical community.
Lattices generated by Chip Firing Game models: criteria and recognition algorithm
Trung Van Pham,Thi Ha Duong Phan
Computer Science , 2012,
Abstract: It is well-known that the class of lattices generated by Chip Firing games (CFGs) is strictly included in the class of upper locally distributive lattices (ULD). However a necessary and sufficient criterion for this class is still an open question. In this paper we settle this problem by giving such a criterion. This criterion provides a polynomial-time algorithm for constructing a CFG which generates a given lattice if such a CFG exists. Going further we solve the same problem on two other classes of lattices which are generated by CFGs on the classes of undirected graphs and directed acyclic graphs.
Lattice Structure and Convergence of a Game of Cards
Eric Goles,Michel Morvan,Ha Duong Phan
Computer Science , 2000,
Abstract: This paper is devoted to the study of the dynamics of a discrete system related to some self stabilizing protocol on a ring of processors.
The impact of social franchising on the use of reproductive health and family planning services at public commune health stations in Vietnam
Anh D Ngo, Dana L Alden, Van Pham, Ha Phan
BMC Health Services Research , 2010, DOI: 10.1186/1472-6963-10-54
Abstract: The project involved networking and branding 36 commune health station (CHS) clinics in two central provinces of Da Nang and Khanh Hoa, Vietnam. A quasi-experimental design with 36 control CHSs assessed GSF model effects on client use as measured by: 1) clinic-reported client volume; 2) the proportion of self-reported RHFP service users at participating CHS clinics over the total sample of respondents; and 3) self-reported RHFP service use frequency. Monthly clinic records were analyzed. In addition, household surveys of 1,181 CHS users and potential users were conducted prior to launch and then 6 and 12 months after implementing the GSF network. Regression analyses controlled for baseline differences between intervention and control groups.CHS franchise membership was significantly associated with a 40% plus increase in clinic-reported client volumes for both reproductive and general health services. A 45% increase in clinic-reported family planning service clients related to GSF membership was marginally significant (p = 0.05). Self-reported frequency of RHFP service use increased by 20% from the baseline survey to the 12 month post-launch survey (p < 0.05). However, changes in self-reported usage rate were not significantly associated with franchise membership (p = 0.15).This study provides preliminary evidence regarding the ability of the Government Social Franchise model to increase use of reproductive health and family planning service in smaller public sector clinics. Further investigations, including assessment of health outcomes associated with increased use of GSF services and cost-effectiveness of the model, are required to better delineate the effectiveness and limitations of franchising RHFP services in the public health system in Vietnam and other developing countries.Franchising of health facilities has improved provision and increased use of RHFP services in several low- and middle-income countries [1-5]. Social franchising employs a high quality, cl
Bacterial and Yeast Endophytes from Poplar and Willow Promote Growth in Crop Plants and Grasses
Zareen Khan,Grant Guelich,Ha Phan,Regina Redman
ISRN Agronomy , 2012, DOI: 10.5402/2012/890280
Bacterial and Yeast Endophytes from Poplar and Willow Promote Growth in Crop Plants and Grasses
Zareen Khan,Grant Guelich,Ha Phan,Regina Redman,Sharon Doty
ISRN Agronomy , 2012, DOI: 10.5402/2012/890280
Abstract: Endophytic associations with plants have a beneficial effect for many different plant species with some of them being host specific. Several endophytes isolated from poplar and willow were screened for their effects on commercially important crops including corn, tomato, pepper, squash, sunflower, and grasses. Most of these endophytes produce growth hormones such as indoleacetic acid (IAA) and have the nitrogenase gene required for nitrogen fixation. The effects of these isolates on plant growth and yield were evaluated under greenhouse conditions. We found that inoculated plants not only had better viability and earlier flowering and fruiting, they also had increased plant growth and fruit yields when grown in nitrogen-limited soil. In a particular variety of perennial rye grass, the endophytes increased the total nitrogen content of the plants, indicative of nitrogen fixation, in addition to promoting plant growth. The use of specific endophytes may be preferable to the use of chemical fertilizers because of the monetary and environmental costs, contributing to more sustainable agricultural systems. 1. Introduction Agriculture has become increasingly dependent on chemical sources of nitrogen. Production of nitrogen fertilizers is a chemically expensive process and uses nonrenewable resources including petroleum. Synthetic fertilizers also are hazardous to the environment. Excessive use of fertilizer produces nitrous oxide (a potent greenhouse gas) through soil microbial activity on excess fertilizer or leaches into water systems causing anoxia and algal blooms. The use of nitrogen fertilizer is of great importance in production of crops, as nitrogen is the major factor limiting growth under most conditions. Despite nitrogen’s abundance in the atmosphere, it is not present in the form that can be utilized by plants to become an integral component of proteins, nucleic acids, and other biomolecules [1]. Since agriculture is expected to move toward environmentally sustainable methods [2], much attention has been recently paid to natural methods of biological nitrogen fixation. Biological nitrogen fixation has been well demonstrated in the legume-rhizobium symbiosis. It is a highly regulated system where these specific bacteria are able to biologically convert the atmospheric dinitrogen gas into ammonia by using the enzyme nitrogenase and high levels of ATP. More recently, it was found that certain microbes (termed endophytes) living inside sugarcane, a nonleguminous crop, provided fixed nitrogen to the plant. Since that discovery, endophytes have been
Immunolocalization of cation-chloride cotransporters in the developing and mature spinal cord of opossums, Monodelphis domestica
Ha-Loan Phan,Jean-Fran?ois Pflieger
Frontiers in Neuroanatomy , 2013, DOI: 10.3389/fnana.2013.00012
Abstract: Spinal inhibition is required to generate coordinated outputs between antagonistic muscles during locomotion. It relies on low neuronal chloride concentration set by two cation-chloride cotransporters, NKCC1 and KCC2 which, respectively, pumps Cl? in or out of neurons. It is generally accepted that NKCC1 is gradually inactivated during development, while KCC2 is upregulated and activated, resulting in low intracellular [Cl?]. Newborn opossums are very immature but perform rhythmic and alternate movements of the forelimbs to crawl on the mother's belly and attach to a teat. Their hindlimbs are immobile. The alternation of the forelimbs suggests that mechanisms allowing spinal inhibition are present at birth. We studied the anatomical basis of inhibition in the spinal enlargements of postnatal opossums by immunolocalizing NKCC1 and KCC2. In some specimens, motoneurons and sensory afferents were labeled with TRDA prior to immunolabeling. At birth, both NKCC1 and KCC2 are detected in the presumptive gray and white matter of the ventral and the intermediolateral cord of both enlargements, but are sparse in the dorsal horn, where KCC2 is mostly seen on a small bundle of dendrites along primary afferents. KCC2 labeling is bright and has a mesh-like appearance in the gray matter and a radial appearance in the white matter, whereas NKCC1 is pale and diffuse. The subsequent expression of the cotransporters follows general ventrodorsal and mediolateral gradients, with the lumbar segments slightly lagging the cervical segments, until the mature pattern is observed around the 5th week. At all ages studied, KCC2 labeling is strong in the periphery of neurons. NKCC1 labeling decreases and becomes more uniformly distributed in the cells with age. Despite the significant anatomical and motor differences between the forelimbs and the hindlimbs of neonatal opossums, the maturation of KCC2 and NKCC1 is quite similar in both enlargements.
On the set of Fixed Points of the Parallel Symmetric Sand Pile Model
Kevin Perrot,Thi Ha Duong Phan,Trung Van Pham
Computer Science , 2012,
Abstract: Sand Pile Models are discrete dynamical systems emphasizing the phenomenon of Self-Organized Criticality. From a configuration composed of a finite number of stacked grains, we apply on every possible positions (in parallel) two grain moving transition rules. The transition rules permit one grain to fall to its right or left (symmetric) neighboring column if the difference of height between those columns is larger than 2. The model is nondeterministic and grains always fall downward. We propose a study of the set of fixed points reachable in the Parallel Symmetric Sand Pile Model (PSSPM). Using a comparison with the Symmetric Sand Pile Model (SSPM) on which rules are applied once at each iteration, we get a continuity property. This property states that within PSSPM we can't reach every fixed points of SSPM, but a continuous subset according to the lexicographic order. Moreover we define a successor relation to browse exhaustively the sets of fixed points of those models.
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