Noninvasive prenatal testing (NIPT) is increasingly used in the clinical prenatal screening of twin pregnancies, and its screening performance for chromosomal abnormalities requires further ...evaluation. For twin pregnancies with indications for prenatal diagnosis, there is a lack of clinical data to assess the prenatal diagnosis rate (PDR). The aim of this study was to evaluate the screening performance of NIPT for foetal chromosomal abnormalities in twin pregnancies and the PDR in the second and third trimesters.
Ultrasound scans were carried out for all twin pregnancies between 11 and 13
gestational weeks. For twin pregnancies with nuchal translucency thickness˂3.0 mm and no foetal structural malformations, NIPT was performed after blood sampling, followed by routine ultrasound monitoring. Women with twin pregnancies who underwent NIPT at the prenatal diagnostic centre of Xiangya Hospital from January 2018 to May 2022 were included in the study. Genetic counselling was offered to each pregnant woman when the NIPT result indicated a high risk of abnormalities or abnormal ultrasonographic (USG) findings were detected. We followed up twin pregnancies for NIPT results, USG findings, prenatal diagnosis results and pregnancy outcomes.
In 1754 twin pregnancies, the sensitivity, specificity and positive predictive value of NIPT for trisomy 21 were 100%, 99.9% and 75%, and the corresponding values for sex chromosome aneuploidy (SCA) were 100%, 99.9% and 50%, respectively. For the 14 twin pregnancies for which the NIPT results indicated a high risk of abnormalities, the PDR was 78.6% (11/14). For the 492 twin pregnancies for which the NIPT results indicated a low risk of abnormalities, the rate of USG findings in the second and third trimesters was 39.4% (194/492); of these pregnancies, prenatal diagnosis was recommended for 16.7% (82/492), but it was actually performed in only 8.3% (41/492), and the PDR was 50% (41/82). There was no significant difference in the PDR between the NIPT high-risk and low-risk groups.
The screening performance of NIPT for SCA in twin pregnancies needs to be further evaluated. When abnormal NIPT results or USG findings are used as the main prenatal diagnostic indicator in the second and third trimesters, the PDR is poor.
Let G˙ be an unbalanced signed graph. In this paper, we establish that e(G˙)⩽12(n2−n)−(n−3) and ρ(G˙)⩽n−2 if G˙ does not contain unbalanced K4 as a signed subgraph. Moreover, comprehensive ...characterizations of the extremal signed graphs have been obtained.
•The situation that the index of signed graph equals to the spectral radius of underlying graph has been characterized.•We determine the Turán number of K4− in unbalanced signed graph, and we characterize all the extremal signed graphs.•We solve the spectral Turán problem among all K4−-free unbalanced signed graphs.
Graph G is H-saturated if H is not a subgraph of G and H is a subgraph of G+e for any edge e not in G. The saturation number for a graph H is the minimal number of edges in any H-saturated graph of ...order n. In this paper, the saturation number for Kp∪(t−1)Kq (t⩾3 and 2⩽p<q) is determined, and the extremal graph for Kp∪2Kq is determined. Moreover, the saturation number and the extremal graph for Kp∪Kq∪Kr (r⩾p+q) are completely determined.
Let q(G) be the Q-index (the largest eigenvalue of the signless Laplacian) of G. Let Sn,k be the graph obtained by joining each vertex of a complete graph of order k to each vertex of an independent ...set of order n−k. The main result of this paper is the following theorem:
Let k≥3, n≥110k2, and G be a graph of order n. If G has no C2k+1, then q(G)<q(Sn,k), unless G=Sn,k.
This result proves the odd case of the conjecture in de Freitas et al. (2013) 7.
•Let G be a graph. For a subset X of V (G), the switching σ of G is the signed graph Gσ obtained from G by reversing the signs of all edges between X and V (G) ∖X. Let A(Gσ) be the adjacency matrix ...of Gσ. An eigenvalue of A(Gσ) is called a main eigenvalue if it has an eigenvector the sum of whose entries is not equal to zero. Two switching equivalent graphs share the same spectrum, while they may have different main eigenvalues. Akbari et al. (2021) conjectured that let G≠K2,K4∖{e}. Then there exists a switching σsuch that all eigenvalues of Gσ are main. Let Sn,k be the graph obtained from the complete graph Kn−r by attaching r pendent edges at some vertex of Kn−r. In this paper we prove that there exists a switching σ such that all eigenvalues of Gσ are main when G is a complete multipartite graph, or G is a harmonic tree, or G is a Sn,k. These results partly confirm a conjecture of Akbari et al.
Let G be a graph. For a subset X of V(G), the switching σ of G is the signed graph Gσ obtained from G by reversing the signs of all edges between X and V(G)∖X. Let A(Gσ) be the adjacency matrix of Gσ. An eigenvalue of A(Gσ) is called a main eigenvalue if it has an eigenvector the sum of whose entries is not equal to zero. Let Sn,k be the graph obtained from the complete graph Kn−r by attaching r pendent edges at some vertex of Kn−r. In this paper we prove that there exists a switching σ such that all eigenvalues of Gσ are main when G is a complete multipartite graph, or G is a harmonic tree, or G is a Sn,k. These results partly confirm a conjecture of Akbari et al.
The fractional matching number of a graph G, written as α′(G), is the maximum size of a fractional matching of G. The following sharp lower bounds for a graph G of order n are proved, and all ...extremal graphs are characterized in this paper.
(1) α′(G)+α′(G¯)≥n2 for n≥2.
(2) If G and G¯ are non-empty, then for n≥30, α′(G)+α′(G¯)≥n+12.
(3) If G and G¯ have no isolated vertices, then for n≥30, α′(G)+α′(G¯)≥n+42.
Let
be the set of graphs of order n with given matching number β. Let
be the diagonal matrix of the degrees of the graph G and
be the adjacency matrix of the graph G. The largest eigenvalue of the ...nonnegative matrix
is called the α-spectral radius of G. The graphs with maximal α-spectral radius in
are completely characterized in this paper. In this way, we provide a general framework to attack the problem of extremal spectral radius in
. More precisely, we generalize the known results on the maximal adjacency spectral radius in
and the signless Laplacian spectral radius.
It is acknowledged that low molecular weight chitosan (LMWC) is advantageous over high molecular weight chitosan (HMWC) in the biodegradability. In this report, the potential of LMWC in DNA vaccine ...delivery via mucosa was evaluated. Firstly, the effects of molecular weight of chitosan on the physicochemical properties and
in vitro transfection efficiency of chitosan/DNA polyplexes were investigated. Secondly, the capabilities of the polyplexes based on LMWC to elicit serum IgG antibodies and to attenuate the development of atherosclerosis after intranasal vaccination were compared with the polyplexes based on HMWC in the rabbit model. Finally, the intramucosal transport of the double-labeled polyplexes was observed by confocal microscopy. The results indicated that LMWC had lower binding affinity to DNA and mediated higher transfection efficiency. Intranasal vaccination with LMWC/DNA polyplexes could elicit significant systemic immune responses, modulate the plasma lipoprotein profile and attenuate the progression of atherosclerosis. Those aspects were comparable to those obtained by HMWC/DNA polyplexes. As revealed by confocal images, LMWC/DNA polyplexes remained stable during interaction with the nasal mucosa, and were internalized by nasal epithelial cells, which was similar to the case of HMWC/DNA polyplexes. In conclusion, LMWCs have potential applications in DNA vaccine delivery via mucosa.
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