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22452. Upper bound for the non-maximal eigenvalues of irreducible nonnegative matrices
- Creator:
- Zhang, Xiao-Dong and Luo, Rong
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- eigenvalue, irreducible nonnegative matrix, and averaged minimal cut
- Language:
- English
- Description:
- We present a lower and an upper bound for the second smallest eigenvalue of Laplacian matrices in terms of the averaged minimal cut of weighted graphs. This is used to obtain an upper bound for the real parts of the non-maximal eigenvalues of irreducible nonnegative matrices. The result can be applied to Markov chains.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22453. Upper bounds for the domination subdivision and bondage numbers of graphs on topological surfaces
- Creator:
- Samodivkin, Vladimir
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- domination subdivision number, graph property, bondage number, Roman bondage number, induced-hereditary property, orientable genus, and non-orientable genus
- Language:
- English
- Description:
- For a graph property $\mathcal {P}$ and a graph $G$, we define the domination subdivision number with respect to the property $\mathcal {P}$ to be the minimum number of edges that must be subdivided (where each edge in $G$ can be subdivided at most once) in order to change the domination number with respect to the property $\mathcal {P}$. In this paper we obtain upper bounds in terms of maximum degree and orientable/non-orientable genus for the domination subdivision number with respect to an induced-hereditary property, total domination subdivision number, bondage number with respect to an induced-hereditary property, and Roman bondage number of a graph on topological surfaces.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22454. Upper bounds on the node numbers of hidden layers in MLPs
- Creator:
- Liu, Jiang, Ni, Feng, Du, Mingjun, Zhang, Xuyang, Que, Zhongli, and Song, Shihang
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- feedforward neural network, hidden node, multilayer perceptron (MLP), and upper bound
- Language:
- English
- Description:
- It is one of the fundamental and challenging problems to determine the node numbers of hidden layers in neural networks. Various efforts have been made to study the relations between the approximation ability and the number of hidden nodes of some specific neural networks, such as single-hidden-layer and two-hiddenlayer feedforward neural networks with specific or conditional activation functions. However, for arbitrary feedforward neural networks, there are few theoretical results on such issues. This paper gives an upper bound on the node number of each hidden layer for the most general feedforward neural networks called multilayer perceptrons (MLP), from an algebraic point of view. First, we put forward the method of expansion linear spaces to investigate the algebraic structure and properties of the outputs of MLPs. Then it is proved that given k distinct training samples, for any MLP with k nodes in each hidden layer, if a certain optimization problem has solutions, the approximation error keeps invariant with adding nodes to hidden layers. Furthermore, it is shown that for any MLP whose activation function for the output layer is bounded on R, at most k hidden nodes in each hidden layer are needed to learn k training samples.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22455. Upper quasi continuous maps and quasi continuous selections
- Creator:
- Matejdes, Milan
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- selection, quasi continuity, minimal usco multifunction, cluster point, and generalized quasi continuity
- Language:
- English
- Description:
- The paper deals with the existence of a quasi continuous selection of a multifunction for which upper inverse image of any open set with compact complement contains a set of the form $(G\setminus I)\cup J$, where $G$ is open and $I$, $J$ are from a given ideal. The methods are based on the properties of a minimal multifunction which is generated by a cluster process with respect to a system of subsets of the form $(G\setminus I)\cup J$.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22456. Uppers to zero in $R[x]$ and almost principal ideals
- Creator:
- Borna, Keivan and Mohajer-Naser, Abolfazl
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Subject:
- almost principal ideal, divisorial ideal, greatest common divisor domain, Schreier domain, and uppers to zero
- Language:
- English
- Description:
- Let $R$ be an integral domain with quotient field $K$ and $f(x)$ a polynomial of positive degree in $K[x]$. In this paper we develop a method for studying almost principal uppers to zero ideals. More precisely, we prove that uppers to zero divisorial ideals of the form $I = f(x)K[x] \cap R[x]$ are almost principal in the following two cases: – $J$, the ideal generated by the leading coefficients of $I$, satisfies $J^{-1} = R$. – $I^{-1}$ as the $R[x]$-submodule of $K(x)$ is of finite type. Furthermore we prove that for $I = f(x)K[x] \cap R[x]$ we have: – $I^{-1}\cap K[x]=(I:_{K(x)}I)$. – If there exists $p/q \in I^{-1}-K[x]$, then $(q,f)\neq 1$ in $K[x]$. If in addition $q$ is irreducible and $I$ is almost principal, then $I' = q(x)K[x] \cap R[x]$ is an almost principal upper to zero. Finally we show that a Schreier domain $R$ is a greatest common divisor domain if and only if every upper to zero in $R[x]$ contains a primitive polynomial.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22457. Upregulation of gastric norepinephrine with beta-adrenoceptors and gastric dysmotility in a rat model of functional dyspepsia
- Creator:
- Song, Jin, Wang, Tianyuan, Zhang, Xiaoli, Li, Bo, Zhu, Chunyang, and Zhang, Shengsheng
- Format:
- počítač and online zdroj
- Type:
- model:article and TEXT
- Subject:
- functional dyspepsia, disordered gastric motility, norepinephrine, and β-adrenoceptors
- Language:
- English
- Description:
- Disordered motility is one of the most important pathogenic characteristics of functional dyspepsia (FD), although the underlying mechanisms remain unclear. Since the sympathetic system is important to the regulation of gastrointestinal motility, the present study aimed to investigate the role of norepinephrine (NE) and adrenoceptors in disordered gastric motility in a rat model with FD. The effect of exogenous NE on gastric motility in control and FD rats was measured through an organ bath study. The expression and distribution of β-adrenoceptors were examined by real-time PCR, Western blotting and immunofluorescence. The results showed that endogenous gastric NE was elevated in FD rats, and hyperreactivity of gastric smooth muscle to NE and delayed gastric emptying were observed in the rat model of FD. The mRNA levels of β1-adrenoceptor and norepinephrine transporter (NET) and the protein levels of β2-adrenoceptor and NET were increased significantly in the gastric corpus of FD rats. All three subtypes of β-adrenoceptors were abundantly distributed in the gastric corpus of rats. In conclusion, the enhanced NE and β-adrenoceptors and NETs may be contributed to the disordered gastric motility in FD rats.
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22458. Upregulation of genes involved in cardiac metabolism enhances myocardial resistance to ischemia / reperfusion in the rat heart
- Creator:
- Ravingerová, T., Slávka Čarnická, Ledvényiová, V., Barlaka, E., Galatou, E., Chytilová, A., Mandíková, P., Nemčeková, M., Adriana Adameová, František Kolář, and Lazou, A.
- Format:
- Type:
- article, články, model:article, and TEXT
- Subject:
- Fyziologie člověka a srovnávací fyziologie, apoptóza, apoptosis, myocardial ischemia, delayed preconditioning, RRAR activation, metabolic genes, WY-14643, 14, and 612
- Language:
- English
- Description:
- Genes encoding enzymes involved in fatty acids (FA) and glucose oxidation are transcriptionally regulated by peroxisome proliferator-activated receptors (PPAR), members of the nuclear receptor superfamily. Under conditions associated with O 2 deficiency, PPAR-α modulates substrate switch (between FA and glucose) aimed at the adequate energy production to maintain basic cardiac function. Both, positive and negative effects of PPAR-α activation on myoc ardial ischemia/reperfusion (I/R) injury have been reported. Moreover, the role of PPAR-mediated metabolic shifts in cardioprotective mechanisms of preconditioning (PC) is relatively less investigated. We explored the effects of PPAR-α upregulation mimicking a delayed “second window” of PC on I/R injury in the rat heart and potential downstream mechanisms involved. Pretreatment of rats with PPAR-α agonist WY-14643 (WY, 1 mg/kg, i.p.) 24 h prior to I/R reduced post-ischemic stunning, arrhythmias and the extent of lethal injury (infarct size) and ap optosis (caspase-3 expression) in isolated hearts exposed to 30-min global ischemia and 2-h reperfusion. Protection was associated with remarkably increased expression of PPAR- α target genes promoting FA utilization (medium-chain acyl-CoA de hydrogenase, pyruvate dehydrogenase kinase-4 and carnitine palmitoyltransferase I) and reduced expression of glucose transporter GLUT-4 responsible for glucose transport and metabolism. In addition, enhanced Akt phosphorylation and protein levels of eNOS, in conjunction with blunting of cardioprotection by NOS inhibitor L-NAME, were observed in the WY-treated hearts. Conclusions: upregulation of PPAR-α target metabolic genes involved in FA oxidation may underlie a delayed phase PC-like protection in the rat heart. Potential non-genomic effects of PPAR-α-mediated cardioprotection may involve activation of prosurvival PI3K/Akt pathway and its downstream targets such as eNOS and subsequently reduced apoptosis., T. Ravingerová ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public
22459. Ups and downs of Ugaritic myth and ritual studies
- Creator:
- Čech, Pavel
- Format:
- bez média and svazek
- Type:
- model:article and TEXT
- Language:
- English
- Rights:
- http://creativecommons.org/publicdomain/mark/1.0/ and policy:public
22460. Uptake, reflux, and excretion of bromosulfophthalein in ischaemia-reperfusion injury of rat liver
- Creator:
- Kukan, M., Bezek, Š., and Trnovec, T.
- Type:
- article, model:article, and TEXT
- Subject:
- ischaemia, reperfusion, liver, and bromosulfophthalein uptake, reflux, excretion
- Language:
- English
- Description:
- The uptake, reflux and excretion of bromosulfophthalein (BSP) were studied on a model of total warm ischaemia for 30 min (group 1) or 60 min (group 2) followed by reperfusion for 45 min in the isolated perfused rat liver of unfasting rats. In group 1, the BSP hepatic uptake was comparable to control livers (30 s ischaemia plus 45 min reperfusion), but was significantly reduced in group 2. The reflux of BSP from liver to perfusate in group 1 and group 2 resulted in the appearance of secondary concentration time peaks of BSP in the reservoir perfusate. This result suggests that ischaemia-reperfusion induced a qualitative change in BSP pharmacokinetics. Excretion of the dye into bile was significantly impaired in group 2 only. The leakage of lactate dehydrogenase into the perfusate was increased moderately in both group 1 and group 2 in comparison to the controls, suggesting a low degree of liver parenchymal injury. In conclusion, the results of this investigation showed that BSP pharmacokinetics were not only undergoing quantitative changes but also a qualitative change in the model of ischaemia-reperfusion injury of the liver obtained from fed rats and may thus serve as a highly sensitive indicator of liver viability.
- Rights:
- http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public