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A Sufficient Condition for Kernel Perfectness of a Digraph in Terms of Semikernels Modulo F

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Acta Mathematica Sinica,English Series 2012年第2期28卷 349-356页

作者： Camino BALBUENA Hortensia GALEANA-SNCHEZ Mucuy-kak GUEVARA departament de matematica Aplicada III Universitat Politècnica de Catalunya instituto de matemáticas Universidad Nacional Autónoma de México rea de la Investigación Científica Circuito Exterior Ciudad Universitaria Facultad de Ciencias Universidad Nacional Autónoma de México Universidad 3000 Circuito Exterior s/n Ciudad Universitaria

A kernel of a directed graph is a set of vertices which is both independent and absorbent. And a digraph is said to be kernel perfect if and only if any induced subdigraph has a kernel. Given a set of arcs F, a semikernel S modulo F is an independent set such that if some Sz-arc is not in F, then there exists a zS-arc. A sufficient condition on the digraph is given in terms of semikernel modulo F in order to guarantee that a digraph is kernel perfect. To do that we give a characterization of kernel perfectness which is a generalization of a previous result given by Neumann-Lara [Seminucleos de una digrafica. Anales del instituto de matematicas 2, Universidad Nacional AutSnoma de Mexico, 1971]. And moreover, we show by means of an example that our result is independent of previous known sufficient conditions.

关键词： Digraphs. kernel kernel-nerfect semikernel

Nightlife in the city: drivers of the occurrence and vocal activity of a tropical owl

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Avian Research 2020年第2期11卷 92-105页

作者： Oscar Humberto Marín‑Gómez Michelle García‑Arroyo Camilo ESánchez‑Sarria JRoberto Sosa‑López Diego Santiago‑Alarcon Ian MacGregor‑Fors Red de Ambiente y Sustentabilidad Instituto de Ecología A.C.Carretera antigua a Coatepec 351El Haya91073 XalapaVeracruzMexico departamento de Ciencias Naturales y matemáticas Pontificia Universidad Javeriana Cali760044 CaliColombia Centro Interdisciplinario de Investigación para el desarrollo Integral Regional Unidad Oaxaca(CIIDIR) Instituto Politécnico NacionalOaxacaMexico Dirección de Cátedras Consejo Nacional de Ciencia y Tecnología(CONACYT)Mexico CityMexico Red de Biología y Conservación de Vertebrados Instituto de Ecología A.C91073 XalapaVeracruzMexico

Background:Cities differ from non-urban environments by the intensity,scale,and extent of anthropogenic pres-sures,which can drive the occurrence,physiology,and behavior of the organisms thriving in these *** as green cover often predict the occurrence patterns of bird species in urban ***,anthropogenic noise and artificial light at night(ALAN)could also limit the presence and disrupt the behavior of ***,there is still a dearth of knowledge about the influence of urbanization through noise and light pollution on nocturnal bird species *** this study,we assessed the role of green cover,noise,and light pollution on the occurrence and vocal activity of the Mottled Owl(Ciccaba virgata)in the city of Xalapa(Mexico).Methods:We obtained soundscape recordings in 61 independent sites scattered across the city of Xalapa using autonomous recording *** performed a semi-automated acoustic analysis of the recordings,corroborating all Mottled Owl *** calculated two measures of anthropogenic noise at each study site:daily noise(during 24 h)and masking noise(mean noise amplitude at night per site that could mask the owl’s vocalizations).We further performed generalized linear models to relate green cover,ALAN,daily noise,and masking noise in relation to the owl’s occurrence(i.e.,detected,undetected).We also ran linear models to assess relationships among the beginning and ending of vocal activity with ALAN,and with the anthropogenic and masking noise levels at the moment of which vocalizations were ***,we explored variations of the vocal activity of the Mottled Owl measured as vocalization rate across ***:The presence of Mottled Owls increased with the size of green cover and decreased with increases in both artificial light at night and noise *** the temporal scale,green cover was positively related with the ending of the owl’s vocal activity,while daily noise and ALAN levels were not related to the tim

关键词： Anthropogenic noise Acoustic monitoring Nighttime ecology Urban ecology Urbanization Vocal activity

Numerical Simulation of Bed Load and Suspended Load Sediment Transport Using Well-Balanced Numerical Schemes

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Communications on Applied Mathematics and Computation 2023年第2期5卷 885-922页

作者： J.C.González-Aguirre J.A.González-Vázquez J.Alavez-Ramírez R.Silva M.E.Vázquez-Cendón División Acádemica de Ciencias Básicas Universidad Juárez Autónoma de TabascoCarr.Cunduacán-Jalpa de Mendéz KM.1CP 86690CunduacánTabascoMexico Universidad Autónoma Metropolitana-Unidad Iztapalapa Av.San Rafael Atlixco no.186Mexico CityMexico instituto de Ingeniería Universidad Nacional Autónoma de México04510 Mexico CityMexico departamento de matemática Aplicada Universidade de Santiago de Compostela15706 Santiago de CompostelaSpain

Sediment transport can be modelled using hydrodynamic models based on shallow water equations coupled with the sediment concentration conservation equation and the bed con-servation *** complete system of equations is made up of the energy balance law and the Exner *** numerical solution for this complete system is done in a seg-regated ***,the hyperbolic part of the system of balance laws is solved using a finite volume *** ways to compute the numerical flux have been considered,the Q-scheme of van Leer,the HLLCS approximate Riemann solver,and the last one takes into account the presence of non-conservative products in the *** discretisation of the source terms is carried out according to the numerical flux *** the second stage,the bed conservation equation is solved by using the approximation computed for the system of balance *** numerical schemes have been validated making comparisons between the obtained numerical results and the experimental data for some physical *** numerical results show a good agreement with the experimental data.

关键词： Sediment transport Suspended load Bed load Finite volume method Numerical simulation Well-balanced schemes

Convex Mean Curvature Flow with a Forcing Term in Direction of the Position Vector

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Acta Mathematica Sinica,English Series 2012年第2期28卷 313-332页

作者： Guang Han LI Jing MAO Chuan Xi WU School of Mathematics and Computer Science Key Laboratory of Applied Mathematics of Hubei ProvinceHubei UniversityWuhan 430062P.R.China departamento de matemática Instituto Superior TecnicoTechnical University of LisbonEdifício CiênciaPiso 3Av.Rovisco Pais1049-001 LisboaPortugal Institute of Mathematics Hubei UniversityWuhan 430062P.R.China

A smooth, compact and strictly convex hypersurface evolving in R^n＋1 along its mean curvature vector plus a forcing term in the direction of its position vector is studied in this paper. We show that the convexity is preserving as the case of mean curvature flow, and the evolving convex hypersurfaces may shrink to a point in finite time if the forcing term is small, or exist for all time and expand to infinity if it is large enough. The flow can converge to a round sphere if the forcing term satisfies suitable conditions which will be given in the paper. Long-time existence and convergence of normalization of the flow are also investigated.

关键词： Evolution equation mean curvature flow forcing term normalization

Near shore seismic movements induced by seaquakes using the boundary element method

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Earthquake Engineering and Engineering Vibration 2017年第3期16卷 571-585页

作者： Alejandro Rodríguez-Castellanos Manuel Carbajal-Romero Norberto Flores-Guzmán J.Efraín Rodríguez-Sánchez Andriy Kryvko instituto mexicano del petróleo eje central lázaro cárdenas 152Gustavo A.MaderoDistrito FederalMéxico escuela superior de ingeniería mecánicay eléctrica instituto politécnico nacionalupalmEdif.5Av.Instituto Politécnico Nacional S/NCol.LindavistaGustavo A.MaderoDistrito FederalMéxico escuela superior de ingeniería mecánicay eléctrica instituto politécnico nacionalunidad profesional azcapotzalcoDistrito FederalMéxico centro de investigación en matemáticas jalisco s/nmineral de valencianaguanajuatoMéxico

This study quantifies seismic amplifications in near-shore arising from seaquakes. Within the Boundary Element Method, boundary elements are used to irradiate waves and force densities obtained for each element. Huygens′ Principle is implemented since the diffracted waves are constructed at the boundary from which they are radiated, which is equivalent to Somigliana′s theorem. Application of boundary conditions leads to a system of integral equations of the Fredholm type of second kind and zero order. Several numerical configurations are analyzed： The first is used to verify the present formulation with ideal sea floor configurations to estimate seismic amplifications. With the formulation verified, simple slope configurations are studied to estimate spectra of seismic motions. It is found that P-waves can produce seismic amplifications from 1.2 to 3.9 times the amplitude of the incident wave. SV-waves can generate seismic amplifications up to 4.5 times the incident wave. Another relevant finding is that the highest amplifications are at the shore compared to the ones at the sea floor.

关键词： seismic amplifications seaquake earthquake elastic waves boundary element method near shore cities

The 2.7 K black-body radiation background reference frame

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Chinese Physics B 2010年第4期19卷 16-20页

作者： López-Carrera Benjamín Rosales Marco Antonio Ares de Parga Gonzalo departamento de Física Escuela Superior de Física y MatemticasInstituto Politécnico NacionalU.P.A.López MateosZacatenco 07738México DFMéxico departamento de Física Universidad de las AméricasSanta Catarina MrtirC.P.72820CholulaPuebla.México

This paper reports that the directional temperature is used to present a scheme for deducing the velocity of the reference frame where the black-body which produces the 2.7 K radiation background is at rest. The new r... 详细信息

关键词： relativistic transformations thermodynamics covariance black-body radiation

Genetic testing vs microforceps biopsy in pancreatic cysts:Systematic review and meta-analysis

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World Journal of Gastroenterology 2019年第26期25卷 3450-3467页

作者： Sandra Faias Luisa Pereira Angelo Luis Paula Chaves Marilia Cravo department of Gastroenterology Instituto Portugues de Oncologia de Lisboa de Francisco GentilEPELisboa 1099-023Portugal Faculdade de Ciencias da Seude Universidade da Beira InteriorCovilha 200-506Portugal GRUBI-Grupo de Revisoes Sistematicas Universidade da Beira InteriorCovilha 6200-506Portugal Centro de matemática e Aplicacoes(CMA-UBI) Universidade da Beira InteriorCovilha 6200-506Portugal Centro de Investigacao em Ciencias da Saude(CICS-UBI) Universidade da Beira InteriorCovilha 6200-506Portugal department of Pathology Instituto Portugues de Oncologia de Lisboa de Francisco GentilEPELisboa 1099-023Portugal department of Gastroenterology Hospital Beatriz AngeloLoures 2674-514Portugal Faculdade de Medicina Universidade de LisboaLisboa 1099-023Portugal

BACKGROUND Carcinoembryonic antigen(CEA)and cytology in pancreatic cystic fluid are suboptimal for evaluation of pancreatic cystic *** testing and microforceps biopsy are promising tools for pre-operative diagnostic improvement but comparative performance of both methods is *** To compare the accuracy of genetic testing and microforceps biopsy in pancreatic cysts referred for *** We performed a literature search in Medline,Scopus,and Web of Science for studies evaluating genetic testing of cystic fluid and microforceps biopsy of pancreatic cysts,with endoscopic ultrasound with fine-needle aspiration(EUSFNA)prior to surgery and surgical pathology as reference standard for *** evaluated the diagnostic accuracy for:1-benign cysts;2-mucinous low-risk cysts;3-high-risk cysts,and the diagnostic yield and rate of correctly identified cysts with microforceps biopsy and molecular *** also assessed publication bias,heterogeneity,and study *** Eight studies,including 1206 patients,of which 203(17%)referred for surgery who met the inclusion criteria were analyzed in the systematic review,and seven studies were included in the *** testing and microforceps biopsies were identical for diagnosis of benign *** analysis was superior for diagnosis of both low and high-risk mucinous cysts,with sensitivities of 0.89(95%CI:0.79-0.95)and 0.57(95%CI:0.42-0.71),specificities of 0.88(95%CI:0.75-0.95)and 0.88(95%CI:0.80-0.93)and AUC of 0.9555 and 0.92,*** diagnostic yield was higher in microforceps biopsies than in genetic analysis(0.73 vs 0.54,respectively)but the rates of correctly identified cysts were identical(0.73 with 95%CI:0.62-0.82 vs 0.71 with 95%CI:0.49-0.86,respectively).CONCLUSION Genetic testing and microforceps biopsies are useful second tests,with identical results in benign pancreatic *** analysis performs better for low-and high-risk cysts but has lower diagnos

关键词： Pancreatic cysts Endoscopic ultrasound Endoscopic ultrasound with fineneedle aspiration Genetic testing Microforceps biopsy Molecular analysis KRAS Carcinoembryonic antigen Cytology

Morse Potential in the Momentum Representation

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Communications in Theoretical Physics 2012年第12期58卷 815-818页

作者：孙国华董世海 Centro Universitario Valle de Chalco Universidad Autónoma del Estado de México Valle de Chalco SolidaridadEstado de México 56615 Mexico departamento de Física Escuela Superior de Física y Matemáticas Instituto Politécnico Nacional Edificio 9 Unidad Profesional Adolfo López MateosMexico D.F. 07738 Mexico

The momentum representation of the Morse potential is presented analytically by hypergeometric function. The properties with respect to the momentum p and potential parameter β are studied. Note that [q2（p）l is a nodeless function and the mutual orthogonality of functions is ensured by the phase functions arg[（p）], It is interesting to see that the [~ （p）[ is symmetric with respect to the axis p = 0 and the number of wave crest of [ （p）[ is equal to n ＋ 1. We also study the variation of ]k（p）l with respect to . The arnplitude of ｜ψ（p）] first increases with the quantum number n and then deceases. Finally, we notice that the discontinuity in phase occurs at some points of the momentum p and the position and momentum probability densities are symmetric with respect to their arguments.

关键词： morse potential momentum representation phase discontinuity

Almost sure, L1-and L2-growth behavior of supercritical multi-type continuous state and continuous time branching processes with immigration

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Science China Mathematics 2020年第10期63卷 2089-2116页

作者： Mátyás Barczy Sandra Palau Gyula Pap MTA-SZTE Analysis and Stochastics Research Group Bolyai InstituteUniversity of SzegedSzeged H-6720Hungary department of Statistics and Probability Instituto de Investigaciones en Matemáticas Aplicadas y en SistemasUniversidad Nacional Autònoma de MéxicoCiudad de México 04510México Bolyai Institute University of SzegedSzeged H-6720Hungary

Under a first order moment condition on the immigration mechanism,we show that an appropriately scaled supercritical and irreducible multi-type continuous state and continuous time branching process with immigration(CBI process)converges almost *** an x log(x)moment condition on the branching mechanism does not hold,then the limit is *** this x log(x)moment condition holds,then we prove L1 convergence as *** projection of the limit on any left non-Perron eigenvector of the branching mean matrix is ***,in addition,a suitable extra power moment condition on the branching mechanism holds,then we provide the correct scaling for the projection of a CBI process on certain left non-Perron eigenvectors of the branching mean matrix in order to have almost sure and L1 ***,under a second order moment condition on the branching and immigration mechanisms,we prove L2 convergence of an appropriately scaled process and the above-mentioned projections as well.A representation of the limits is also provided under the same moment conditions.

关键词： multi-type continuous state and continuous time branching processes with immigration almost sure L1-and L2-growth behaviour