The community characteristics of natural secondary forests on the north slope of Changbai Mountain after selective cutting were investigated, and the dynamics of arborous species diversity during the restoration perio...The community characteristics of natural secondary forests on the north slope of Changbai Mountain after selective cutting were investigated, and the dynamics of arborous species diversity during the restoration period of 28 years were studied. The results showed that the arborous species richness (S) had little change and kept the range of 18-22 all along, the Simpson index (D) of the secondary layer and regeneration layer and whole stand had similar trends of change, but that of the canopy layer descended slowly in initial 15 years and had little change later, and the change of diversity index was not obvious and the Shannon-Wiener index (H? fluctuated in a very small scopes (H±10%).展开更多
For a long time,forestry primarily had industrial goals.Volume of wood production was the main criterion of forestry efficacy,and thus rapid-growing arboreal species were cultivated in natural forests.More recently,na...For a long time,forestry primarily had industrial goals.Volume of wood production was the main criterion of forestry efficacy,and thus rapid-growing arboreal species were cultivated in natural forests.More recently,nature protection has become one of forestry＇s goals.Unfortunately,some introduced,rapid-growing species became aggressive components of natural ecological systems during the interim.In this paper,we first describe a method that we developed to categorize aggressiveness of invasive arboreal plants in natural forest ecosystems of Kazakhstan.We then apply this new scheme to monitoring data of invasive arboreal plants to provide an insight into the invasion potential of different species in the fruit forests of Southeast Kazakhstan.展开更多
A linear forest is a forest whose components are paths. The linear arboricity la （G） of a graph G is the minimum number of linear forests which partition the edge set E（G） of G. The Cartesian product G□H of two g...A linear forest is a forest whose components are paths. The linear arboricity la （G） of a graph G is the minimum number of linear forests which partition the edge set E（G） of G. The Cartesian product G□H of two graphs G and H is defined as the graph with vertex set V（G□H） = {（u, v）｜ u ∈V（G）, v∈V（H） } and edge set E（G□H） = { （ u, x） （ v, Y）｜u=v and xy∈E（H）, or uv∈E（G） and x=y}. Let Pm and Cm,, respectively, denote the path and cycle on m vertices and K, denote the complete graph on n vertices. It is proved that （Km□Pm）=[n＋1/2]for m≥2,la（Km□Cm）=[n＋2/2],and la（Km□Km）=[n＋m-1/2]. The methods to decompose these graphs into linear forests are given in the proofs. Furthermore, the linear arboricity conjecture is true for these classes of graphs.展开更多
In this paper, secondary forest of Pinus massoniana , coniferous-broad-leaved mixed forest and broad-leaved evergreen forest were taken as research objects, to explore carbon reserve of arbor layer and its spatial dis...In this paper, secondary forest of Pinus massoniana , coniferous-broad-leaved mixed forest and broad-leaved evergreen forest were taken as research objects, to explore carbon reserve of arbor layer and its spatial distribution characteristics. At different succession stages, the sequence of organic carbon content in each organ was secondary forest of P. massoniana > coniferous-broad-leaved mixed forest> broad-leaved evergreen forest. Carbon reserve of arbor layer was the highest in broad-leaved evergreen forest, which was 129.34 t/hm 2, followed by coniferous-broad-leaved mixed forest (95.83 t/hm 2), and the minimum was 85.27 t/hm 2 in secondary forest of P. massoniana . In each stand type, the sequence of carbon reserve of each organ in arbor layer was trunk>root>branch>leaf>bark. Carbon reserve of arbor layer mainly concentrated in trunk, and the proportion to carbon reserve of arbor layer declined from secondary forest of P. massoniana to broad-leaved evergreen forest, while it had increasing relationship in root. In secondary forest of P. massoniana , coniferous-broad-leaved mixed forest and broad-leaved evergreen forest, individual with the diameter more than 20 cm accounted for the majority of carbon reserve in the arbor layer.展开更多
In this paper, the Pinus massoniana forest in the early stage of succession, the coniferous broad-leaved mixed forest in the middle stage of succession, and the evergreen broad-leaved forest in the late stage of succe...In this paper, the Pinus massoniana forest in the early stage of succession, the coniferous broad-leaved mixed forest in the middle stage of succession, and the evergreen broad-leaved forest in the late stage of succession were studied, and the biomass and its spatial distribution characteristics of the tree layer in different succession stages of the ecosystem were discussed. The results showed that the biomass of the arbor layer was the highest in the evergreen broad-leaved forest, which was 292.51 t/ hm2, followed by the coniferous and broad-leaved mixed forest, which was 206.87 t/hm2, and the Pinus massoniana forest, which was 171.76 t/hm2. The biomass of trunks accounted for the largest proportion in the total biomass of the arbor layer, which reduced from the Pinus massoniana forest to the evergreen broad-leaved forest. The proportion of the biomass of roots in the total biomass of the arbor layer increased from the Pinus massoniana forest to the evergreen broad-leaved forest. The biomass of the diameter class above 20 cm in the Pinus massoniana forest, the coniferous and broad-leaved mixed forest and the evergreen broad-leaved forest accounted for a large proportion of total biomass.展开更多
Pine wilt disease caused by pine wood nema-todes is a deadly disease of the genus Pinus requiring strong quarantine measures.Since its discovery,it has been widely distributed throughout the world.China is one of the ...Pine wilt disease caused by pine wood nema-todes is a deadly disease of the genus Pinus requiring strong quarantine measures.Since its discovery,it has been widely distributed throughout the world.China is one of the coun-tries with a severe rate of infections due to its abundant pine resources.In this study,nematode-trapping fungi were collected from pine trees in Ninghai City,Zhejiang Prov-ince,which is the key area of pine wilt control in Febru-ary,May,September,October and November.The results showed that nematode-trapping fungi of pine are abundant,especially the number and species detected in each month and are quite different;species of fungi in July,Septem-ber and November were more numerous and had higher separation rates.The dominant species in November was Arthrobotrys oligospora followed by Arthrobotrys cladodes;July and September it was A.cladodes.In each part of the tree,A.cladodes was the most widely distributed with a high separation rate.Therefore,it is the dominant fungal species in the area.Arboreal Bursaphelenchus xylophilus-trapping fungi are dependent on pine wood nematodes,and none were isolated from healthy pine trees.More arboreal B.xylophilus-trapping fungi were found under the bark than in the xylem.There is a close relationship between arboreal B.xylophilus-trapping fungi and pine wood nematodes.How to make use of these resources to reduce the damage of pine wood nematode fusarium is the focus of future research.展开更多
Purpose The purpose of this work is to develop a novel pattern tracking algorithm to be used on the detectors of the future electron-positron colliders.Method ArborTracking,a light-weighted tracking algorithm,has been...Purpose The purpose of this work is to develop a novel pattern tracking algorithm to be used on the detectors of the future electron-positron colliders.Method ArborTracking,a light-weighted tracking algorithm,has been developed based on the tree topology of track clusters and applied to the baseline detector of the circular electron-positron collider(CEPC).The algorithm collects all the hits in the tracker as a tree(forest),splits the tree branches to form the track segments,and merges the track segments to form the tracks.Results Compared with the general track following method,the algorithm has the advantages of low coding complicity and low CPU cost.The performances at different benchmarks are studied.The results are exhaustively listed showing that the method is approaching the limit of the detector.The tracking efficiencies on single muon sample and three-prong sample are both higher than 99%.The transverse momentum resolution reaches 0.1%level and the boson mass resolution reaches 4.7 GeV/c.Conclusions The performances are similar with those of the baseline tracking algorithm of CEPC,and the physics requirement of CEPC is satisfied.The new tree pattern recognition algorithm is a necessary part in the CEPC software.And it is also a competitive algorithm on the market,which can be chosen by the future experiments.展开更多
The seasonality and relative abundance of arboreal ant species were studied in the oil palm plantations of CSIR-OPRI at Kusi in order to identify the different arboreal ant species in the oil palm canopy and their pos...The seasonality and relative abundance of arboreal ant species were studied in the oil palm plantations of CSIR-OPRI at Kusi in order to identify the different arboreal ant species in the oil palm canopy and their possible interaction with other fauna and flora. Chemical knockdown and field observation and were used in the data collection. Chemical knockdown study was used to collect data on the relative abundance of the ants with application of a synthetic pyrethroid. Field observation was used to study the nesting behaviour, types of nests and where they were built as well as the interaction between the ant species. The fields which were of ages of 8, 11 and 14 years were one hectare containing 143 palms. Chemical knockdown and ant colony studies revealed higher abundance of arboreal ant species on the I 1 years followed by the 8 years and 14 years fields in that order. Oecophylla longinoda was abundant on the I 1-and 14-year-old fields while Crematogaster sp. was the most abundant species on the 8-year old fields. Relatively high numbers of the ant species were encountered in the dry months of study. Positive interaction indicated coexistence between O. longinoda and Crematogaster sp. Interaction between Crematogaster sp. and Tetramorium sp. was antagonistic. Similarly, O. longinoda and Tetramorium sp. were antagonistic to each other. The high abundance and diversity hold promise for the potential use of these ant species as biocontrol agents in an integrated pest management system for the management of the oil palm leaf miner.展开更多
Trees belong to humanity’s heritage,but they are more than that.Their loss,through catastrophic fires or under business-as-usual,is devastating to many forms of life.Moved by this fact,we begin with an assertion that...Trees belong to humanity’s heritage,but they are more than that.Their loss,through catastrophic fires or under business-as-usual,is devastating to many forms of life.Moved by this fact,we begin with an assertion that heritage can have an active role in the design of future places.Written from within the field of architecture,this article focuses on structures that house life.Habitat features of trees and artificial replacement habitats for arboreal wildlife serve as concrete examples.Designs of such habitats need to reflect behaviours,traditions and cultures of birds,bats,and other animals.Our narrative highlights the nonhuman aspect of heritage,seeking to understand how nonhuman stakeholders can act as users and consumers of heritage and not only as its constituents.Our working definition states that more-than-human heritage encompasses tangible and intangible outcomes of historical processes that are of value to human as well as nonhuman stakeholders.From this basis,the article asks how the established notions of heritage can extend to include nonhuman concerns,artefacts,behaviours and cultures.As a possible answer to this question,the hypothesis tested here is that digital information can(1)contribute to the preservation of more-than-human heritage;and(2)illuminate its characteristics for future study and use.This article assesses the potential of three imaging technologies and considers the resulting data within the conceptual framework of more-than-human heritage,illuminating some of its concrete aspects and challenges.展开更多
A star forest is a forest whose components are stars. The star arboricity of a graph G,denoted by sa（ G）,is the minimum number of star forests needed to decompose G. Let k be a positive integer. A k-star forest is a...A star forest is a forest whose components are stars. The star arboricity of a graph G,denoted by sa（ G）,is the minimum number of star forests needed to decompose G. Let k be a positive integer. A k-star forest is a forest whose components are stars of order at most k ＋ 1. The k-star arboricity of a graph G,denoted by sak（ G）,is the minimum number of k-star forests needed to decompose G. In this paper,it is proved that if any two vertices of degree 3 are nonadjacent in a subcubic graph G then sa2（ G） ≤2.For general subcubic graphs G, a polynomial-time algorithm is described to decompose G into three 2-star forests. For a tree T and[Δ k, T）/k]t≤ sak（ T） ≤[Δ（ T）- 1/K]＋1,where Δ（ T） is the maximum degree of T.kMoreover,a linear-time algorithm is designed to determine whether sak（ T） ≤m for any tree T and any positive integers m and k.展开更多
A graph is NIC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share at most one common end vertex. It is proved that every NIC-planar graph with...A graph is NIC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share at most one common end vertex. It is proved that every NIC-planar graph with minimum degree at least 2(resp. 3) contains either an edge with degree sum at most 23(resp. 17) or a 2-alternating cycle(resp. 3-alternating quadrilateral). By applying those structural theorems, we confirm the Linear Arboricity Conjecture for NIC-planar graphs with maximum degree at least 14 and determine the linear arboricity of NIC-planar graphs with maximum degree at least 21.展开更多
The arboricity of graph G=(V,E), denoted by a(G), is defined as a(G)=min{n | E can be partitioned into n subsets E1,E2,...,En, such that each subset spans a subgraph of G so as to be a forest}.In this paper the follow...The arboricity of graph G=(V,E), denoted by a(G), is defined as a(G)=min{n | E can be partitioned into n subsets E1,E2,...,En, such that each subset spans a subgraph of G so as to be a forest}.In this paper the following results have been obtained. For any graph G of order p,and the bounds are sharp; especially as an integer function, 5p+7 could not be decreased. Furthermore, Nordhaus-Gaddum Theorem for arboricity has also been got.展开更多
The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(tran...The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.展开更多
基金This research was supported by Institute of Shenyang Applied Ecology CAS (SCXMS0101),National Key Technologies R&D Program (NKTRDP. 2002BA516A20) and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education
文摘The community characteristics of natural secondary forests on the north slope of Changbai Mountain after selective cutting were investigated, and the dynamics of arborous species diversity during the restoration period of 28 years were studied. The results showed that the arborous species richness (S) had little change and kept the range of 18-22 all along, the Simpson index (D) of the secondary layer and regeneration layer and whole stand had similar trends of change, but that of the canopy layer descended slowly in initial 15 years and had little change later, and the change of diversity index was not obvious and the Shannon-Wiener index (H? fluctuated in a very small scopes (H±10%).
文摘For a long time,forestry primarily had industrial goals.Volume of wood production was the main criterion of forestry efficacy,and thus rapid-growing arboreal species were cultivated in natural forests.More recently,nature protection has become one of forestry＇s goals.Unfortunately,some introduced,rapid-growing species became aggressive components of natural ecological systems during the interim.In this paper,we first describe a method that we developed to categorize aggressiveness of invasive arboreal plants in natural forest ecosystems of Kazakhstan.We then apply this new scheme to monitoring data of invasive arboreal plants to provide an insight into the invasion potential of different species in the fruit forests of Southeast Kazakhstan.
基金The National Natural Science Foundation of China(No.10971025)
文摘A linear forest is a forest whose components are paths. The linear arboricity la （G） of a graph G is the minimum number of linear forests which partition the edge set E（G） of G. The Cartesian product G□H of two graphs G and H is defined as the graph with vertex set V（G□H） = {（u, v）｜ u ∈V（G）, v∈V（H） } and edge set E（G□H） = { （ u, x） （ v, Y）｜u=v and xy∈E（H）, or uv∈E（G） and x=y}. Let Pm and Cm,, respectively, denote the path and cycle on m vertices and K, denote the complete graph on n vertices. It is proved that （Km□Pm）=[n＋1/2]for m≥2,la（Km□Cm）=[n＋2/2],and la（Km□Km）=[n＋m-1/2]. The methods to decompose these graphs into linear forests are given in the proofs. Furthermore, the linear arboricity conjecture is true for these classes of graphs.
基金Sponsored by Forestry Science and Technology Plan of Hunan Province(XLK201806,XLK201925)National Forestry Science and Technology Development Project(KJZXSA2018011,KJZXSA2019009)Operational Subsidy Project of National Forestry Science and Technology Innovation Platform(2019132068)
文摘In this paper, secondary forest of Pinus massoniana , coniferous-broad-leaved mixed forest and broad-leaved evergreen forest were taken as research objects, to explore carbon reserve of arbor layer and its spatial distribution characteristics. At different succession stages, the sequence of organic carbon content in each organ was secondary forest of P. massoniana > coniferous-broad-leaved mixed forest> broad-leaved evergreen forest. Carbon reserve of arbor layer was the highest in broad-leaved evergreen forest, which was 129.34 t/hm 2, followed by coniferous-broad-leaved mixed forest (95.83 t/hm 2), and the minimum was 85.27 t/hm 2 in secondary forest of P. massoniana . In each stand type, the sequence of carbon reserve of each organ in arbor layer was trunk>root>branch>leaf>bark. Carbon reserve of arbor layer mainly concentrated in trunk, and the proportion to carbon reserve of arbor layer declined from secondary forest of P. massoniana to broad-leaved evergreen forest, while it had increasing relationship in root. In secondary forest of P. massoniana , coniferous-broad-leaved mixed forest and broad-leaved evergreen forest, individual with the diameter more than 20 cm accounted for the majority of carbon reserve in the arbor layer.
基金Sponsored by Forestry Science and Technology Plan of Hunan Province(XLK201925,XLK201806)National Forestry Science and Technology Development Project(KJZXSA2018011)Operational Subsidy Project of National Forestry Science and Technology Innovation Platform(2018-LYPT-DW-064)
文摘In this paper, the Pinus massoniana forest in the early stage of succession, the coniferous broad-leaved mixed forest in the middle stage of succession, and the evergreen broad-leaved forest in the late stage of succession were studied, and the biomass and its spatial distribution characteristics of the tree layer in different succession stages of the ecosystem were discussed. The results showed that the biomass of the arbor layer was the highest in the evergreen broad-leaved forest, which was 292.51 t/ hm2, followed by the coniferous and broad-leaved mixed forest, which was 206.87 t/hm2, and the Pinus massoniana forest, which was 171.76 t/hm2. The biomass of trunks accounted for the largest proportion in the total biomass of the arbor layer, which reduced from the Pinus massoniana forest to the evergreen broad-leaved forest. The proportion of the biomass of roots in the total biomass of the arbor layer increased from the Pinus massoniana forest to the evergreen broad-leaved forest. The biomass of the diameter class above 20 cm in the Pinus massoniana forest, the coniferous and broad-leaved mixed forest and the evergreen broad-leaved forest accounted for a large proportion of total biomass.
基金The work was supported by the Fundamental Research Funds for the Central University(No.2572020DY11).
文摘Pine wilt disease caused by pine wood nema-todes is a deadly disease of the genus Pinus requiring strong quarantine measures.Since its discovery,it has been widely distributed throughout the world.China is one of the coun-tries with a severe rate of infections due to its abundant pine resources.In this study,nematode-trapping fungi were collected from pine trees in Ninghai City,Zhejiang Prov-ince,which is the key area of pine wilt control in Febru-ary,May,September,October and November.The results showed that nematode-trapping fungi of pine are abundant,especially the number and species detected in each month and are quite different;species of fungi in July,Septem-ber and November were more numerous and had higher separation rates.The dominant species in November was Arthrobotrys oligospora followed by Arthrobotrys cladodes;July and September it was A.cladodes.In each part of the tree,A.cladodes was the most widely distributed with a high separation rate.Therefore,it is the dominant fungal species in the area.Arboreal Bursaphelenchus xylophilus-trapping fungi are dependent on pine wood nematodes,and none were isolated from healthy pine trees.More arboreal B.xylophilus-trapping fungi were found under the bark than in the xylem.There is a close relationship between arboreal B.xylophilus-trapping fungi and pine wood nematodes.How to make use of these resources to reduce the damage of pine wood nematode fusarium is the focus of future research.
基金supported by the Continuous Basic Scientific Research Project(No.WDJC-2019-16)National Key Research and Development Project(2018YFE0104800,2016YFE0100900,2016 YFA0400300)National Natural Science Foundation of China(11775313)
文摘Purpose The purpose of this work is to develop a novel pattern tracking algorithm to be used on the detectors of the future electron-positron colliders.Method ArborTracking,a light-weighted tracking algorithm,has been developed based on the tree topology of track clusters and applied to the baseline detector of the circular electron-positron collider(CEPC).The algorithm collects all the hits in the tracker as a tree(forest),splits the tree branches to form the track segments,and merges the track segments to form the tracks.Results Compared with the general track following method,the algorithm has the advantages of low coding complicity and low CPU cost.The performances at different benchmarks are studied.The results are exhaustively listed showing that the method is approaching the limit of the detector.The tracking efficiencies on single muon sample and three-prong sample are both higher than 99%.The transverse momentum resolution reaches 0.1%level and the boson mass resolution reaches 4.7 GeV/c.Conclusions The performances are similar with those of the baseline tracking algorithm of CEPC,and the physics requirement of CEPC is satisfied.The new tree pattern recognition algorithm is a necessary part in the CEPC software.And it is also a competitive algorithm on the market,which can be chosen by the future experiments.
文摘The seasonality and relative abundance of arboreal ant species were studied in the oil palm plantations of CSIR-OPRI at Kusi in order to identify the different arboreal ant species in the oil palm canopy and their possible interaction with other fauna and flora. Chemical knockdown and field observation and were used in the data collection. Chemical knockdown study was used to collect data on the relative abundance of the ants with application of a synthetic pyrethroid. Field observation was used to study the nesting behaviour, types of nests and where they were built as well as the interaction between the ant species. The fields which were of ages of 8, 11 and 14 years were one hectare containing 143 palms. Chemical knockdown and ant colony studies revealed higher abundance of arboreal ant species on the I 1 years followed by the 8 years and 14 years fields in that order. Oecophylla longinoda was abundant on the I 1-and 14-year-old fields while Crematogaster sp. was the most abundant species on the 8-year old fields. Relatively high numbers of the ant species were encountered in the dry months of study. Positive interaction indicated coexistence between O. longinoda and Crematogaster sp. Interaction between Crematogaster sp. and Tetramorium sp. was antagonistic. Similarly, O. longinoda and Tetramorium sp. were antagonistic to each other. The high abundance and diversity hold promise for the potential use of these ant species as biocontrol agents in an integrated pest management system for the management of the oil palm leaf miner.
基金The Australia Research Council’s Discovery Project grant DP170104010,Place and Parametricism:Provocations for the Rethinking of Design,supported the work on the project discussed in this article。
文摘Trees belong to humanity’s heritage,but they are more than that.Their loss,through catastrophic fires or under business-as-usual,is devastating to many forms of life.Moved by this fact,we begin with an assertion that heritage can have an active role in the design of future places.Written from within the field of architecture,this article focuses on structures that house life.Habitat features of trees and artificial replacement habitats for arboreal wildlife serve as concrete examples.Designs of such habitats need to reflect behaviours,traditions and cultures of birds,bats,and other animals.Our narrative highlights the nonhuman aspect of heritage,seeking to understand how nonhuman stakeholders can act as users and consumers of heritage and not only as its constituents.Our working definition states that more-than-human heritage encompasses tangible and intangible outcomes of historical processes that are of value to human as well as nonhuman stakeholders.From this basis,the article asks how the established notions of heritage can extend to include nonhuman concerns,artefacts,behaviours and cultures.As a possible answer to this question,the hypothesis tested here is that digital information can(1)contribute to the preservation of more-than-human heritage;and(2)illuminate its characteristics for future study and use.This article assesses the potential of three imaging technologies and considers the resulting data within the conceptual framework of more-than-human heritage,illuminating some of its concrete aspects and challenges.
基金National Natural Science Foundation of China(No.10971025)
文摘A star forest is a forest whose components are stars. The star arboricity of a graph G,denoted by sa（ G）,is the minimum number of star forests needed to decompose G. Let k be a positive integer. A k-star forest is a forest whose components are stars of order at most k ＋ 1. The k-star arboricity of a graph G,denoted by sak（ G）,is the minimum number of k-star forests needed to decompose G. In this paper,it is proved that if any two vertices of degree 3 are nonadjacent in a subcubic graph G then sa2（ G） ≤2.For general subcubic graphs G, a polynomial-time algorithm is described to decompose G into three 2-star forests. For a tree T and[Δ k, T）/k]t≤ sak（ T） ≤[Δ（ T）- 1/K]＋1,where Δ（ T） is the maximum degree of T.kMoreover,a linear-time algorithm is designed to determine whether sak（ T） ≤m for any tree T and any positive integers m and k.
基金Supported by the National Natural Science Foundation of China(Nos.11871055,11301410)the Natural Science Basic Research Plan in Shaanxi Province of China(No.2017JM1010)the Fundamental Research Funds for the Central Universities(Nos.JB170706)
文摘A graph is NIC-planar if it admits a drawing in the plane with at most one crossing per edge and such that two pairs of crossing edges share at most one common end vertex. It is proved that every NIC-planar graph with minimum degree at least 2(resp. 3) contains either an edge with degree sum at most 23(resp. 17) or a 2-alternating cycle(resp. 3-alternating quadrilateral). By applying those structural theorems, we confirm the Linear Arboricity Conjecture for NIC-planar graphs with maximum degree at least 14 and determine the linear arboricity of NIC-planar graphs with maximum degree at least 21.
文摘The arboricity of graph G=(V,E), denoted by a(G), is defined as a(G)=min{n | E can be partitioned into n subsets E1,E2,...,En, such that each subset spans a subgraph of G so as to be a forest}.In this paper the following results have been obtained. For any graph G of order p,and the bounds are sharp; especially as an integer function, 5p+7 could not be decreased. Furthermore, Nordhaus-Gaddum Theorem for arboricity has also been got.
基金approved by the Committee of Bio-ethics of the Lomonosov Moscow State University(research protocol no.2011-36)Video processing was performed with support of the Russian Science Foundation(project 14-50-00029“Scientific basis of the national biobank-depository of the living systems”)+1 种基金Acoustic analysis was supported by the Russian Science Foundation(project 14-14-00237)the Program of Basic Research of the Presidium of the Russian Academy of Sciences“Wildlife:Current Status and Problems of Development.”。
文摘The means of orientation is studied in the Vietnamese pygmy dormouse Typhlomys chapensis,a poorly known enigmatic semi-fossorial semi-arboreal rodent.Data on eye structure are presented,which prove that Typhlomys(translated as“the blind mouse”)is incapable of object vision:the retina is folded and retains no more than 2500 ganglion cells in the focal plane,and the optic nerve is subject to gliosis.Hence,Typhlomys has no other means for rapid long-range orientation among tree branches other than echolocation.Ultrasonic vocalization recordings at the frequency range of 50-100 kHz support this hypothesis.The vocalizations are represented by bouts of up to 7 more or less evenly-spaced and uniform frequency-modulated sweep-like pulses in rapid succession.Structurally,these sweeps are similar to frequency-modulated ultrasonic echolocation calls of some bat species,but they are too faint to be revealed with a common bat detector.When recording video simultaneously with the ultrasonic audio,a significantly greater pulse rate during locomotion compared to that of resting animals has been demonstrated.Our findings of locomotion-associated ultrasonic vocalization in a fast-climbing but weakly-sighted small mammal ecotype add support to the“echolocation-first theory”of pre-flight origin of echolocation in bats.
