In interconnection networks, matching preclusion is a measure of robustness in the event of link failure. Let G be a graph of even order. The matching preclusion number mp(G) is defined as the ...minimum number of edges whose deletion results in a graph without perfect matchings. Many interconnection networks are super matched, that is, their optimal matching preclusion sets are precisely those induced by a single vertex. In this paper, we obtain general results of vertex-transitive graphs including many known networks. A k-regular connected vertex-transitive graph of even order has matching preclusion number k and is super matched except for six classes of graphs. From this many results already known can be directly obtained and matching preclusion for some other networks, such as folded k-cube graphs, Hamming graphs and halved k-cube graphs, are derived.
Similar to the well-known Wiener index, Eu et al. Int. J. Quantum Chem. 106 (2006) 423–435 introduced three families of topological indices including Schultz index and modified Schultz index, called ...generalized Wiener indices, and gave the similar formulae of generalized Wiener indices of hexagonal chains. They also mentioned three families of graph polynomials in
x
, called generalized Hosoya polynomials in contrast to the (standard) Hosoya polynomial, such that their first derivatives at
x
= 1 are equal to generalized Wiener indices. In this note we gave explicit analytical expressions for generalized Hosoya polynomials of hexagonal chains.
In this study, a novel metabolomics technique based on ultra-performance liquid chromatography-quadrupole-time of flight mass spectrometry in the MSE mode was used to investigate the milk ...metabolomics of healthy, subclinical, and clinical mastitis cows, which were classified based on somatic cell count and presentation of clinical symptoms. Meanwhile, univariate and multivariate statistical analyses were performed to identify the significant differences across the 3 groups. Compared with healthy milk samples, less glucose, d-glycerol-1-phosphate, 4-hydroxyphenyllactate, l-carnitine, sn-glycero-3-phosphocholine, citrate, and hippurate were detected in the clinical mastitic milk samples, whereas less d-glycerol-1-phosphate, benzoic acid, l-carnitine, and cis-aconitate were found in the subclinical mastitic milk samples. Meanwhile, the milk concentration of arginine and Leu-Leu increased in both the clinical and subclinical mastitis groups. Besides, less 4-hydroxyphenyllactate, cis-aconitate, lactose, and oxoglutarate were detected in the clinical than the subclinical mastitic milk samples, whereas the abundance of some oligopeptides (Leu-Ala, Phe-Pro-Ile, Asn-Arg-Ala-Ile, and Val-Phe-Val-Tyr) increased by over 7.95-fold. Our results suggest that significant variations exist across healthy and mastitis cows. The current metabolomics approach will help in better understanding the pathobiology of mastitis, although clinical validation will be required before field application.
Let G be a graph and A(G) the adjacency matrix of G. The permanental polynomial of G is defined as π(G,x)≜per(xI-A(G)). If two graphs G and H have the same permanental polynomial, then G is called a ...per-cospectral mate of H. A graph G is said to be characterized by its permanental polynomial if all the per-cospectral mates of G are isomorphic to G. It is shown that complete graphs, stars, regular complete bipartite graphs, and odd cycles are characterized by their permanental polynomials. We prove that in general the permanental polynomial cannot characterize the paths and even cycles. In particular, for each l⩾1 and m⩾2, we can find non-isomorphic per-cospectral mates of P4l+3 and C4m, respectively. When we restrict our consideration to connected graphs, both the paths and even cycles C4l+2 are characterized by their permanental polynomials.
Interest has been growing in the co-fermentation of starter cultures with probiotic bacteria in milk. However, the representative metabolites and metabolic changes at different key time points during ...milk fermentation and storage in starter cultures and probiotic bacteria are still unclear. In this study, we used gas chromatography/mass spectrometry–based metabolomics to identify volatile metabolites and discriminate between 6 different time points fermentation initiation (FI), fermentation curd (FC), fermentation termination (FT), storage 1 d (S1d), storage 7 d (S7d), and storage 14 d (S14d) during the fermentation and storage of starter cultures and Lactobacillus casei Zhang milk. Of the 52 volatile metabolites identified, 15 contributed to discrimination of the 6 time points. Then, using the profile from the different time points, we analyzed pairwise comparisons (FI vs. FC; FC vs. FT; FT vs. S1d; S1d vs. S7d; S7d vs. S14d); these time-lapse comparisons showed metabolic progressions from one fermentation stage to the next. We found representative and exclusive metabolites at specific fermentation and storage time points. The greatest difference in metabolites occurred between FC and FT, and the metabolic profiles between S7d and S14d were most similar. Interestingly, decanoic acid, octanoic acid, and hexanoic acid reached their highest level at storage 14 d, indicating that the post-fermentation storage of fermented milk with L. casei Zhang may add more probiotic functions. This work provides detailed insight into the time-specific profiles of volatile metabolites and their dynamic changes; these data may be used for understanding and eventually predicting metabolic changes in milk fermentation and storage, where probiotic strains may be used.
C
6
F
12
O (perfluoro-2-methyl-3-pentanone) is a high-potential environmentally friendly substitute agent applied in fire protection, the power industry and refrigeration. Herein, a series of ...reactive force field molecular dynamics (ReaxFF MD) simulations is performed to investigate C
6
F
12
O pyrolysis. Six initial pyrolysis reaction pathways are determined mainly through fission of the C-C bond of C
6
F
12
O. The terminal C-C bond dissociation forming the CF
3
radical occurs prior to that of those at the other positions. High-energy C-F and C=O bonds are broken at high temperatures and CF
3
and F radical chain reactions. CF
4
, C
2
F
2
and COF
2
are the main pyrolysis products, while other products including C
2
F
6
, C
3
F
8
, F
2
and C
2
OF
6
are also observed in the simulations. The environmental impacts, toxicity and corrosiveness of these products need to be further evaluated. The whole C
6
F
12
O pyrolysis process is endothermic except for certain bonding reactions. COF
2
is largely generated through a combination of the F and COF radicals and COF
3
defluorination. First-order kinetic analysis of C
6
F
12
O pyrolysis is also performed and the pre-exponential factor and apparent activation energy of C
6
F
12
O are calculated.
To identify the psychosocial and clinical correlates of attention-deficit hyperactivity disorder (ADHD) in a community sample of children and to examine the validity of a subclinical form of ADHD.
...The sample of 449 children (mean age 9.2 years, SD 1.78; 53.6% boys) participated in the second stage of a community survey. Of these, 359 (80%) screened positive at stage 1. On the basis of a structured diagnostic interview with a parent, children were classified into 1 of 3 mutually exclusive groups: ADHD (n = 89), subthreshold ADHD (n = 100), and non-ADHD (n = 260).
As measured by the Children's Global Assessment Scale, the ADHD group was more impaired than the subthreshold group, which was more impaired than the non-ADHD group (p < .05 for each test). Children in the ADHD group were more likely to be male, to have mothers with a history of psychiatric treatment, to have fathers with a history of excessive alcohol use, and to live in low-income families with higher levels of family dysfunction (p < .05 for all variables). A model containing male gender, family dysfunction, and low income was most predictive of ADHD status (p < .01). ADHD was also associated with psychiatric comorbidity, especially disruptive behavior disorders.
These results support a dimensional approach to ADHD. More severe forms of ADHD are associated with psychosocial adversity and psychiatric comorbidity.
The human gut hosts complex microbial communities, which are linked to health and disease. The gut microbiota is continuously reshaped by multiple environmental factors, especially diet. Gut ...dysbiosis may promote various metabolic, neurological, intestinal, and cardiovascular diseases, and even tumor development. Probiotics have shown promising prophylactic, mitigating, or even curative effects when use as nutrient supplements or adjunctive therapy. These beneficial and/or symptom alleviation effects are often accompanied by gut microbiome and metabolome changes.
Differing from other published review articles, here we summarized the latest knowledge of evidence-based health-promoting effects of probiotics by scouring literature of recent animal and human probiotic intervention studies.
To elucidate the beneficial mechanisms of probiotics in enhancing intestinal homeostasis, intestinal barrier function, host immunity, and through modulating the gut microbiome and its metabolites. Meanwhile, we also discussed challenges in data analysis in clinical research of probiotics and data comparison between laboratories, and provides an outlook for future perspectives in the applications of probiotics.
The beneficial mechanisms of probiotics are achieved through enhancing intestinal homeostasis, intestinal barrier function, host immunity, and gut microbiome and metabolome modulation. Current challenges in data analysis and comparison in clinical research of probiotics are discussed. Finally, an outlook for future perspectives in the applications of probiotics is provided.
•Summarizes the regulatory effects of probiotics on gut microbes and metabolites.•Outlines probiotic mechanisms of improving host health and disease.•Recapitulates clinical efficacy of probiotics in clinical trials.•Discusses current challenges in clinical research of probiotics.•Recommends improvement strategies.
Display omitted
•Utra-elastic SiC aerogel were obtained based on the coaxial precursor strategy.•The SiC aerogel has excellent thermal insulation and good adsorption capacity.•The sintering time with ...this strategy is reduced to10 minutes.
Silicon Carbide (SiC) aerogel is a material with 3D network structure, low density, and high-temperature resistance, showing a broad application potential in various areas. It is currently challenging for SiC aerogels to balance the mechanical and high-temperature insulation properties. Here, a novel strategy was implemented for the first time, by constructing coaxial precursors. This structure can achieve in-situ Si-C binding and maximization the reaction sites to achieve fibers growth uniformly. The sintering time is reduced by over 90%. The fatigue resistance and elastic properties of the SiC aerogel were significantly improved. In addition, the uniform nanowire fiber and pore structure enable an ultra-low thermal conductivity of 0.018 W/(m K) at room temperature, 0.082 W/(m K) even at 900 °C, and superior structural stability at 1400 °C. Our strategy provides a feasible approach for the structural design of thermally insulated SiC aerogels with high elastic resilience and good adsorbability.
Pacific Biosciences’ (Menlo Park, CA) single molecule, real-time sequencing technology was reported to have some advantages in generating finished genomes and characterizing the epigenome of ...bacteria. In the present study, this technology was used to sequence 2 Lactobacillus strains, Lactobacillus casei Zhang and Lactobacillus plantarum P-8. Previously, the former bacterium was sequenced by an Applied Biosystems 3730 DNA analyzer (Grand Island, NY), whereas the latter one was analyzed with Roche 454 (Indianapolis, IN) and Illumina sequencing technologies (San Diego, CA). The results showed that single molecule, real-time sequencing resulted in high-quality, finished genomes for both strains. Interestingly, epigenome analysis indicates the presence of 1 active N6-methyladenine methyltransferase in L. casei Zhang, but none in L. plantarum P-8. Our study revealed for the first time a completely different methylation pattern in 2 Lactobacillus strains.
PDF
