Asymptotic results on the spectral radius and the diameter of graphs

Cioaba, S.M.,van Dam, E.R.,Koolen, J.H.,Lee, J.H. North Holland [etc.] 2010 Linear Algebra and its Applications Vol. No.

We study graphs with spectral radius at most 322 and refine results by Woo and Neumaier [R. Woo, A. Neumaier, On graphs whose spectral radius is bounded by 322, Graphs Combinatorics 23 (2007) 713-726]. We study the limit points of the spectral radii of certain families of graphs, and apply the results to the problem of minimizing the spectral radius among the graphs with a given number of vertices and diameter. In particular, we consider the cases when the diameter is about half the number of vertices, and when the diameter is near the number of vertices. We prove certain instances of a conjecture posed by Van Dam and Kooij [E. R. Van Dam, R. E. Kooij, The minimal spectral radius of graphs with a given diameter, Linear Algebra Appl. 423 (2007) 408-419] and show that the conjecture is false for the other instances.

Cospectral graphs and the generalized adjacency matrix

van Dam, E.R.,Haemers, W.H.,Koolen, J.H. Elsevier 2007 Linear algebra and its applications Vol.423 No.1

<P><B>Abstract</B></P><P>Let <I>J</I> be the all-ones matrix, and let <I>A</I> denote the adjacency matrix of a graph. An old result of Johnson and Newman states that if two graphs are cospectral with respect to <I>yJ</I>−<I>A</I> for two distinct values of <I>y</I>, then they are cospectral for all <I>y</I>. Here we will focus on graphs cospectral with respect to <I>yJ</I>−<I>A</I> for exactly one value yˆ of <I>y</I>. We call such graphs yˆ-cospectral. It follows that yˆ is a rational number, and we prove existence of a pair of yˆ-cospectral graphs for every rational yˆ. In addition, we generate by computer all yˆ-cospectral pairs on at most nine vertices. Recently, Chesnokov and the second author constructed pairs of yˆ-cospectral graphs for all rational yˆ∈(0,1), where one graph is regular and the other one is not. This phenomenon is only possible for the mentioned values of yˆ, and by computer we find all such pairs of yˆ-cospectral graphs on at most eleven vertices.</P>

Inheritance of the Cracking Characteristics of Abscission Layer and its Relation with the Degree of Grain Shedding

Dam Xuan Van,진일두 한국작물학회 2009 Journal of crop science and biotechnology Vol.12 No.4

Seed shattering is an undesirable characteristic of rice cultivars affecting field loss of grain yield before and during harvesting. This research was designed to clarify the inheritance of the cracking characteristics of abscission layers formed between the rice grains and its pedicel using F2 populations derived from the crossing of Milyang 23 and Ashahi. The results indicated that the cracking characteristic of Milyang 23 was dominant to absence of cracking in Ashahi, and controlled by a single dominant gene. The degrees of grain shedding were somewhat related with the cracking characteristics of the abscission layer. The breaking tensile strengths closely correlated with the diameter of the supporting zone, the thickness of sclerenchyma tissue between the inner side of abscission layer and the central vascular tissues in the lemma side, and in the palea side, respectively. Some negative correlations were observed between the breaking tensile strengths and some agronomic traits such as plant height, culm length, panicle length, number of matured grains, and the ratio of fertility.

Inheritance of Grain Shedding and Abscission Layers in the Cross Combination between Rice Varieties

Dam Xuan Van,진일두 한국작물학회 2010 Journal of crop science and biotechnology Vol.13 No.2

Seed shattering is an undesirable characteristic of rice cultivars affecting the loss of grain yield before and during harvesting. These grain losses are influenced by varietal characteristics. The histological peculiarities of the abscission region obtained were different among rice varieties, and had a close relationship with grain shedding. In order to obtain information for the breeding of new persistent shedding varieties, this study was designed to clarify the inheritance of grain shedding habits in relation to the abscission layer. In the cross combination of two easily shedding varieties, Milyang 23, a japonica-indica hybrid rice with cracked abscission layers and Ashahi, a japonica-type rice with uncracked abscission layers, the cracking of parenchymatous cells in the abscission layer was controlled by a single dominant gene. The breaking tensile strength coincided well with cracked and uncracked abscission layers. In four crosses between a persistent shedding variety without abscission layers and two easily shedding varieties with cracked abscission layers, and two medium shedding varieties with uncracked abscission layers, respectively, the formation of the abscission layer was controlled by a single dominant gene. The easily shedding and persistent shedding habits coincided well when the abscission layers were both present and absent. The easily shedding characteristics were dominant in cross combination. The close negative correlations were recognized between degrees of grain shedding and breaking tensile strengths.

Relationship between Esterase Isozymes and Some Agronomic Traits in $F_2$ Populations Derived from the Crossing of Milyang 23 and Ashahi

Van, Dam Xuan,Jin, Il-Doo 한국작물학회 2011 Journal of crop science and biotechnology Vol.14 No.1

Esterase isozymes in the leaf blade were observed in the $F_2$ populations derived from the cross combination between a japonicaindica hybrid rice variety with EIZ 1 ($EST_1,\;EST^S_2,\;EST^F_3$) and a japonica rice variety with EIZ 6 ($EST_1,\;EST^O_2,\;EST^S_3$). The esterase isozyme of the 6A ($EST^S_2$) band was controlled by a dominant allele, while the esterase isozymes of 12A ($EST^S_3$) and 13A ($EST^F_3$) bands were controlled by codominant alleles. No linkage relation was indicated while between $EST_2$, and $EST_3$. The presence of esterase isozyme of 13A ($EST^F_3$) band is related to the grain shedding habit and esterase isozyme of 13A ($EST^F_3$) band itself is somewhat related to the cracking characteristics of the abscission layer. The presence of esterase isozyme of 6A ($EST^S_2$) band is related the days to heading and it might due to the panicle length and ratio of fertility. There was no difference in the plant height, culm length, and number of tillers per hill between EIZ in the $F_2$ population. Therefore, there were the relationships between esterase isozymes and some agronomic traits in rice plants.

Inheritance of Grain Shedding and Abscission Layers in the Cross Combination between Rice Varieties

Van, Dam Xuan,Jin, Il-Doo 한국작물학회 2010 Journal of crop science and biotechnology Vol.13 No.2

Seed shattering is an undesirable characteristic of rice cultivars affecting the loss of grain yield before and during harvesting. These grain losses are influenced by varietal characteristics. The histological peculiarities of the abscission region obtained were different among rice varieties, and had a close relationship with grain shedding. In order to obtain information for the breeding of new persistent shedding varieties, this study was designed to clarify the inheritance of grain shedding habits in relation to the abscission layer. In the cross combination of two easily shedding varieties, Milyang 23, a japonica-indica hybrid rice with cracked abscission layers and Ashahi, a japonica-type rice with uncracked abscission layers, the cracking of parenchymatous cells in the abscission layer was controlled by a single dominant gene. The breaking tensile strength coincided well with cracked and uncracked abscission layers. In four crosses between a persistent shedding variety without abscission layers and two easily shedding varieties with cracked abscission layers, and two medium shedding varieties with uncracked abscission layers, respectively, the formation of the abscission layer was controlled by a single dominant gene. The easily shedding and persistent shedding habits coincided well when the abscission layers were both present and absent. The easily shedding characteristics were dominant in cross combination. The close negative correlations were recognized between degrees of grain shedding and breaking tensile strengths.

Multilocus Sequence Typing of Pasteurella multocida Isolates from Acute Fowl Cholera Outbreak in Layer

Van Dam Lai,Jong-Seung Kim,In-Pil Mo 한국가금학회 2020 韓國家禽學會誌 Vol.47 No.2

Fowl cholera is an infectious disease caused by Pasteurella multocida that contributes to high economic loss in the commercial chicken industry. Three Pasteurella multocida strains were isolated from outbreaks of acute fowl cholera in the Korean layer farms from 2018 to 2019. One strain was identified and serotyped using capsular PCR typing. This strain was also genotyped by lipopolysaccharide (LPS) PCR typing as A: L3, whereas other strains were non-typable. The multilocus sequence typing (MLST) result showed that the A: L3 strain is sequence type (ST) 134; the non-typable strains were recorded as the following new STs: ST 366 and ST 374. Using phylogenetic tree analysis based on MLST sequences, we determined that ST 366 and ST 374 are closely related to the reference strains that were previously isolated from duck and chicken in Korea, and they were highly prevalent within the Korean cluster. In conclusion, Pasteurella multocida strains were identified and isolated in this study. Furthermore, this is the first report of using MLST to determine the prevalence of fowl cholera in Korea.

Inheritance of the Cracking Characteristics of Abscission Layer and its Relation with the Degree of Grain Shedding

Van, Dam Xuan,Jin, Il-Doo 한국작물학회 2009 Journal of crop science and biotechnology Vol.12 No.4

Seed shattering is an undesirable characteristic of rice cultivars affecting field loss of grain yield before and during harvesting. This research was designed to clarify the inheritance of the cracking characteristics of abscission layers formed between the rice grains and its pedicel using $F_2$ populations derived from the crossing of Milyang 23 and Ashahi. The results indicated that the cracking characteristic of Milyang 23 was dominant to absence of cracking in Ashahi, and controlled by a single dominant gene. The degrees of grain shedding were somewhat related with the cracking characteristics of the abscission layer. The breaking tensile strengths closely correlated with the diameter of the supporting zone, the thickness of sclerenchyma tissue between the inner side of abscission layer and the central vascular tissues in the lemma side, and in the palea side, respectively. Some negative correlations were observed between the breaking tensile strengths and some agronomic traits such as plant height, culm length, panicle length, number of matured grains, and the ratio of fertility.

Relationship between Esterase Isozymes and Some Agronomic Traits in F₂Populations Derived from the Crossing of Milyang 23 and Ashahi

Dam Xuan Van,Il-Doo Jin 한국작물학회 2011 Journal of crop science and biotechnology Vol.14 No.1

Esterase isozymes in the leaf blade were observed in the F₂populations derived from the cross combination between a japonicaindica hybrid rice variety with EIZ 1 (EST₁, EST₂ S, EST₃ F) and a japonica rice variety with EIZ 6 (EST₁, EST₂O, EST₃S). The esterase isozyme of the 6A (EST₂S) band was controlled by a dominant allele, while the esterase isozymes of 12A ( EST₃S) and 13A ( EST₃F) bands were controlled by codominant alleles. No linkage relation was indicated while between EST₂and EST₃. The presence of esterase isozyme of 13A ( EST₃F) band is related to the grain shedding habit and esterase isozyme of 13A ( EST₃F) band itself is somewhat related to the cracking characteristics of the abscission layer. The presence of esterase isozyme of 6A (EST₂S) band is related the days to heading and it might due to the panicle length and ratio of fertility. There was no difference in the plant height, culm length,and number of tillers per hill between EIZ in the F₂ population. Therefore, there were the relationships between esterase isozymes and some agronomic traits in rice plants.

Expression of partial capsid related immuno-proteins of fowl adenovirus serotype 4 as vaccine candidate by utilizing yeast vector

Van Dam Lai,Tae-Sik Kim,Joo-Seong Son,Kang-San Kim,Kang-Il Lee,In-Pil Mo 한국가금학회 2017 한국가금학회 정기총회 및 학술발표회 Vol.2017 No.11