Zhi-Zhong Chen

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Soil salinity is a major abiotic stress that decreases plant growth and productivity. Recently, it was reported that plants overexpressing AtNHX1 or SOS1 have significantly increased salt tolerance. To test whether overexpression of multiple genes can improve plant salt tolerance even more, we produced six different transgenic Arabidopsis plants that(More)
Given a set of species and their similarity data, an important problem in evolutionary biology is how to reconstruct a phylogeny (also called evolutionary tree) so that species are close in the phylogeny if and only if they have high similarity. Assume that the similarity data are represented as a graph G = (V,E) where each vertex represents a species and(More)
We present an O(n)-time approximation algorithm for the maximum traveling salesman problem whose approximation ratio is asymptotically 61 81 , where n is the number of vertices in the input complete edge-weighted (undirected) graph. We also present an O(n)-time approximation algorithm for the metric case of the problem whose approximation ratio is(More)
We propose a general methodology for testing whether a polynomial with integer coefficients is identically zero. The methodology is to evaluate the polynomial at suitable approximations of easily computable irrational points. An innovative feature of the methodology is that the error probability of the testing algorithm can be decreased by increasing the(More)
The problem of computing a matching of maximum weight in a given edge-weighted graph is not known to be P-hard or in RNC. This paper presents four parallel approximation algorithms for this problem. The first is an RNC-approximation scheme, i.e., an RNC algorithm that computes a matching of weight at least 1 − times the maximum for any given constant > 0.(More)