Fault-tolerant analysis of augmented cubes

The augmented cube $AQ_n$, proposed by Choudum and Sunitha [S. A. Choudum, V. Sunitha, Augmented cubes, Networks 40 (2) (2002) 71-84], is a $(2n-1)$-regular $(2n-1)$-connected graph $(n\ge 4)$. This paper determines that the 2-extra connectivity of $AQ_n$ is $6n-17$ for $n\geq 9$ and the 2-extra edge-connectivity is $6n-9$ for $n\geq 4$. That is, for $n\geq 9$ (respectively, $n\geq 4$), at least $6n-17$ vertices (respectively, $6n-9$ edges) of $AQ_n$ have to be removed to get a disconnected graph that contains no isolated vertices and isolated edges. When the augmented cube is used to model the topological structure of a large-scale parallel processing system, these results can provide more accurate measurements for reliability and fault tolerance of the system

Molecular Epidemiology of Multi-Drug Resistant Acinetobacter baumannii Isolated in Shandong, China

Acinetobacter baumannii is an emerging nosocomial pathogen prevalent in hospitals worldwide. In order to understand the molecular epidemiology of multi-drug resistant (MDR) A. baumannii, we investigated the genotypes of A. baumannii isolated from ten hospitals in Shandong, China, from August 2013 to December 2013, by pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Antimicrobial resistance genes were analyzed by PCR and DNA sequencing. By PFGE analysis, we discovered 11 PFGE types in these ten hospitals. By MLST, we assigned these isolates to 12 sequence types (STs), 10 of which belong to the cloning complex CC92, including the prevalent ST369, ST208, ST195, and ST368. Two new STs, namely ST794 and ST809, were detected only in one hospital. All isolates of the MDR A. baumannii were resistant to carbapenem, except 2 isolates, which did not express the blaOXA-23 carbapenemase gene, indicating blaOXA-23 is the major player for carbapenem resistance. We also discovered armA is likely to be responsible for amikacin resistance, and may play a role in gentamicin and tobramycin resistance. aac(3)-I is another gene responsible for gentamicin and tobramycin resistance. In summary, we discovered that the majority of the isolates in Shandong, China, were the STs belonging to the CC92. Besides, two new STs were detected in one hospital. These new STs should be further investigated for prevention of outbreaks caused by A. baumannii

Cycles in folded hypercubes

This work investigates important properties related to cycles of embedding into the folded hypercube FQ n for n ≥ 2. The authors observe that FQ n is bipartite if and only if n is odd, and show that the minimum length of odd cycles is n + 1ifn is even. The authors further show that every edge of FQ n lies on a cycle of every even length from 4 to 2 n;ifn is even, every edge of FQ n also lies on a cycle of every odd length from n + 1to2 n − 1

Panconnectivity of locally twisted cubes

www.elsevier.com/locate/aml The locally twisted cube LTQ n which is a newly introduced interconnection network for parallel computing is a variant of the hypercube Qn. Yang et al. [X. Yang, G.M. Megson, D.J. Evans, Locally twisted cubes are 4-pancyclic, Applied Mathematics Letters 17 (2004) 919–925] proved that LTQ n is Hamiltonian connected and contains a cycle of length from 4 to 2 n for n ≥ 3. In this work, we improve this result by showing that for any two different vertices u and v in LTQ n (n ≥ 3), there exists a uv-path of length l with d(u,v)+ 2 ≤ l ≤ 2 n − 1 except for a shortest uv-path. c ○ 2005 Elsevier Ltd. All rights reserved