Visualizing the Structure of Large Trees

This study introduces a new method of visualizing complex tree structured objects. The usefulness of this method is illustrated in the context of detecting unexpected features in a data set of very large trees. The major contribution is a novel two-dimensional graphical representation of each tree, with a covariate coded by color. The motivating data set contains three dimensional representations of brain artery systems of 105 subjects. Due to inaccuracies inherent in the medical imaging techniques, issues with the reconstruction algo- rithms and inconsistencies introduced by manual adjustment, various discrepancies are present in the data. The proposed representation enables quick visual detection of the most common discrepancies. For our driving example, this tool led to the modification of 10% of the artery trees and deletion of 6.7%. The benefits of our cleaning method are demonstrated through a statistical hypothesis test on the effects of aging on vessel structure. The data cleaning resulted in improved significance levels.Comment: 17 pages, 8 figure

Parameter estimation validity and relationship robustness: A comparison of telephone and internet survey techniques

With the expansion of telecommunication and online technologies for the purpose of survey administration, the issue of measurement validity has come to the fore. The proliferation of automated audio services and computer-based survey techniques has been matched by a corresponding denigration of the quality of traditional phone survey data, most notably as an outcome of falling response rates. This trend, combined with the introduction of screening technologies and answering machines, represents a barrier to the proper execution of survey research. Whereas the question was once, “can technology-assisted surveys achieve the same level of validity as traditional phone surveys?”, the question now becomes, “what are the relative advantages and disadvantages of technology-assisted and phone surveys?” Each has its own challenges and opportunities, and this paper begins to explore these. The present study provides further insight into the validity of telephone and Internet survey data, and explores whether or not the robustness of relationships between variables varies by survey mode. Study data were provided by two surveys, the first of which was conducted in a metropolitan area of the Midwestern US, with interviews of 505 adults using a computer-aided telephone-interviewing (CATI) system. The second was a national survey of 2172 respondents conducted over the Internet by a commercial research firm that sends requests to a diverse set of potential respondents, who logged onto the survey site to participate. Results suggest that weighting in an attempt to achieve parametric matching does seem to increase robustness of relationships and, in this age of poor response rates, this seems to demand an increased use of parametric weightings. Implications of study findings for telematic survey practitioners are discussed

A Nonparametric Regression Model With Tree-Structured Response

Highly developed science and technology from the last two decades motivated the study of complex data objects. In this paper, we consider the topological properties of a population of tree-structured objects. Our interest centers on modeling the relationship between a tree-structured response and other covariates. For tree objects, this poses serious challenges since most regression methods rely on linear operations in Euclidean space. We generalize the notion of nonparametric regression to the case of a tree-structured response variable. In addition, a fast algorithm with theoretical justification is developed. We implement the proposed method to analyze a data set of human brain artery trees. An important lesson is that smoothing in the full tree space can reveal much deeper scientific insights than the simple smoothing of summary statistics

A comparative study of morphological characteristics in diploid and tetraploid (auto and allotetraploids) Citrullus genotypes

In this study, ploidy levels were determined by stomatal observations and flow cytometry analysis of plants polyploidised by the application of 0.05% colchicine to seedlings at the first true leaf stage. In the study of developing polyploid watermelon rootstocks, the survival rate of the plants was 77%, and the polyploidisation rates were 11% and 3% according to stomatal observations and flow cytometry analysis, respectively. According to the results of flow cytometry, 22 polyploid genotypes were determined. Auto- (12) and allotetraploids (10) of Citrullus genotypes were developed, and their plant growth performance was determined in hydroponic culture in comparison with diploids, commercial rootstocks (RS841, ‘Argentario’) and watermelon cultivar (‘Crimson Tide’). Putative tetraploids and their diploid controls were grown in hydroponic culture for 21 days, and their vegetative growth performances were determined. The results showed that the increases in plant biomass depending on polyploidisation were 100% in autotetraploids and 156% in allotetraploids as compared to diploid controls

SCREENING OF SOME GOURD SPECIES TO OBTAIN TOLERANT ROOTSTOCKS FOR SUSTAINABLE WATERMELON PRODUCTION UNDER CONTRASTING pH LEVELS

This study was conducted to screen hydroponically grown various gourd genotypes to obtain tolerant rootstocks for sustainable watermelon production under contrasting pH levels in relation to physiological and root morphological characters under greenhouse conditions. Two commercial watermelon cultivars (Crimson Tide and Crisby) and 20 different gourd genotypes includes Lagenaria siceraria and Cucurbita maxima and C. moschata interspecific hybrids were screened in nutrient solution under three different pH (High: 8.5, Neutral (control): 6.5 and Low: 4.5) levels. Shoot and root dry matter, leaf area, total root length and leaf mineral element compositions were significantly (P<0.001) affected by different levels of pH, genotype and pH x genotype interaction. Plants usually showed significantly lowest performances in shoot and root growth under both low and high pH conditions. However, some of the interspecific hybrids C. maxima x C. moschata (Nun9075, Ferro, Ercole and Jumbo) responded significantly positive by enhancing the shoot and root growth under both low and high pH conditions. Therefore, these genotypes are characterized by 'acid-tolerant' and 'alkaline-tolerant' which are highly appropriate to be used as rootstocks for the watermelon under both contrasting pH conditions. Because, two watermelon cultivars (Crisby and Crimson Tide) exhibited significantly lowest performance in all measured parameters under three pH levels as compared to twenty gourd genotypes. The tolerance mechanism of the determined gourd genotypes was closely associated with vigorous root system and large leaf area formation. These traits could be useful characters for the selection and/or breeding of 'pH-tolerant' gourd rootstocks for sustainable watermelon production in the future. However, this should be examined by grafting watermelon cultivars onto the 'acid-tolerant' and `alkaline-tolerant' characterized gourd genotypes in further study

EFFECT OF VERMICOMPOST ON SEEDLING QUALITY AND GROWTH IN WATERMELON (Citrullus lanatus L.)

In this study carried out under greenhouse conditions in summer period, a mixture of field soil, soil and farmmanure (1:1 v:v) was used as growth medium. 0 (control), %2.5, %5 and %10 vermicompost were added toeach soil. In the study using one liter pots, the amount of vermicompost was adjusted according to weight. Atotal of 8*9*2 = 144 seeds were used. In this study, the effects of watermelon (Citrillus lanatus L.) onseedling growth were investigated. The parameters measured in plants were measured plant height, stem andleaf fresh and dry weights and leaf area. According to the results obtained in the study, plant growth wasobserved in the highest soil and farm manure mixture and 5% vermicompost application, while the lowestplant seedling growth was observed in unmixed field soil. In both soil mix, after 10% vermicompostapplication, plant seedling growth decreased. As a result, it is seen that vermicompost application increasesplant growth but has a negative effect on plant growth after a certain place. For this, the mixture should beprepared for each plant species and according to the content of the vermicompost used.</p