Insects respond to changes in microhabitat caused by canopy disturbance, and thus can be used to examine the ecological impacts of harvesting. Single-tree selection harvesting is the most common silvicultural system u...Insects respond to changes in microhabitat caused by canopy disturbance, and thus can be used to examine the ecological impacts of harvesting. Single-tree selection harvesting is the most common silvicultural system used to emulate local small-scale natural disturbance and maintain uneven-aged forest structure in temperate forests. Here, we test for differences in richness, abundance, and composition of hymenopteran and saproxylic insect assemblages at four different taxon levels （selected insect orders; and all hymenopteran families, and braconid subfamilies and morphospecies） between the canopy and understory of unharvested and single-tree selection harvested sites in a northern temperate forest from central Canada. Harvesting had no effect on insect assemblage richness, composition or abundance at the three highest taxon levels （order, family and subfamily）. Similarly, richness and abundance at the lowest-taxon level （braconid morphospecies） were similar, although composition differed slightly between unharvested and harvested stands. Insect assemblages were vertically stratified, with generally higher abundance （for Diptera, Hymenoptera, some hymenopteran families and braconid subfamilies） and richness （for braconid morphospecies） in the understory than the canopy. In particular, composition of the braconid morphospecies assemblage showed relatively low similarity between the understory and canopy. Single-tree selection harvesting appears to influence wood-associated insect taxa only subtly through small changes in community composition at the lowest taxon level, and thus is recommended as a conservative approach for managing these northern temperate forests.展开更多
Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodici...Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodicity analysis of the optical light curve also showsevidence for a shorter period. Here we discuss whether such a behavior can be explained by a binaryblack hole model where the accretion disk of one of the supermassive black holes is precessing dueto the tidal effects of the companion. We estimate the mass of the accreting hole and analyzeconstraints on the secondary mass and the orbital parameters of the system. It is possible toprovide a viable interpretation of the available multiwavelength data.展开更多
We study the statistical mechanics of small clusters (N ~ 10 - 100) for two-level systems and harmonic oscillators. Both Boltzmann’s and Gibbs’s definitions of entropy are used. The properties of the studied systems...We study the statistical mechanics of small clusters (N ~ 10 - 100) for two-level systems and harmonic oscillators. Both Boltzmann’s and Gibbs’s definitions of entropy are used. The properties of the studied systems are evaluated numerically but exactly;this means that Stirling’s approximation was not used in the calculation and that the discrete nature of energy was taken into account. Results show that, for the two-level system, using Gibbs entropy prevents temperatures from assuming negative values;however, they reach very high values that are not plausible in physical terms. In the case of harmonic oscillators, there are no significant differences when using either definition of entropy. Both systems show that for N = 100 the exact results evaluated with statistical mechanics coincide with those found in the thermodynamic limit. This suggests that thermodynamics can be applied to systems as small as these.展开更多
The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7....The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7.8 earthquake happened. This earthquake occurred at a margin characterized by moderately big to giant earthquakes such as the 1906 （Mw 8.8）. A heavily sedimented trench explains the abnormal lengths of the rupture zones in this system as inhibits the role of natural barriers on the propagation of rupture zones. High amount of sediment thickness is associated with tropical climates, high erosion rates and eastward Pacific dominant winds that provoke orographic rainfalls over the Pacific slope of the Ecuatorian Andes. Offshore sediment dispersion off the oceanic trench is controlled by a close arrangement of two aseismic ridges that hit the Costa Rico and South Ecuador margin respectively and a mid ocean ridge that separates the Cocos and Nazca plate trapping sediments. Gravity field and Ocean Circulation Explorer （GOCE） satellite data are used in this work to test the possible relationship between gravity signal and earthquake rupture structure as well as registered aftershock seismic activity. Reduced vertical gravity gradient shows a good correlation with rupture structure for certain degrees of the harmonic expansion and related depth of the causative mass; indicating, such as in other analyzed cases along the subduction margin, that fore-arc structure derived from density heterogeneities explains at a certain extent propagation of the rupture zones. In this analysis the rupture zone of the April 2016 Ecuador earthquake developed through a relatively low density zone of the fore-arc sliver. Finally, aftershock sequence nucleated around the area of maximum slips in the rupture zone, suggesting that heterogeneous density structure of the fore-arc determined from gravity data could be used in forecasting potential damaged zones associated with big ruptures along the subduction border.展开更多
The analysis of space-time surface deformation during earthquakes reveals the variable state of stress that occurs at deep crustal levels, and this information can be used to better understand the seismic cycle. Under...The analysis of space-time surface deformation during earthquakes reveals the variable state of stress that occurs at deep crustal levels, and this information can be used to better understand the seismic cycle. Understanding the possible mechanisms that produce earthquake precursors is a key issue for earthquake prediction. In the last years, modern geodesy can map the degree of seismic coupling during the interseismic period, as well as the coseismic and postseismic slip for great earthquakes along subduction zones. Earthquakes usually occur due to mass transfer and consequent gravity variations, where these changes have been monitored for intraplate earthquakes by means of terrestrial gravity measurements. When stresses and correspondent rupture areas are large, affecting hundreds of thousands of square kilometres（as occurs in some segments along plate interface zones）, satellite gravimetry data become relevant. This is due to the higher spatial resolution of this type of data when compared to terrestrial data, and also due to their homogeneous precision and availability across the whole Earth.Satellite gravity missions as GOCE can map the Earth gravity field with unprecedented precision and resolution. We mapped geoid changes from two GOCE satellite models obtained by the direct approach,which combines data from other gravity missions as GRACE and LAGEOS regarding their best characteristics. The results show that the geoid height diminished from a year to five months before the main seismic event in the region where maximum slip occurred after the Pisagua Mw = 8.2 great megathrust earthquake. This diminution is interpreted as accelerated inland-directed interseismic mass transfer before the earthquake, coinciding with the intermediate degree of seismic coupling reported in the region. We highlight the advantage of satellite data for modelling surficial deformation related to preseismic displacements. This deformation, combined to geodetical and seismological data, could be useful for delimiting and monitoring areas of higher seismic hazard potential.展开更多
In this review we study the nuclear pastas as they are expected to be formed in neutron star crusts.We start with a study of the pastas formed in nuclear matter(composed of protons and neutrons),we follow with the rol...In this review we study the nuclear pastas as they are expected to be formed in neutron star crusts.We start with a study of the pastas formed in nuclear matter(composed of protons and neutrons),we follow with the role of the electron gas on the formation of pastas,and we then investigate the pastas in neutron star matter(nuclear matter embedded in an electron gas).Nuclear matter(NM)at intermediate temperatures(1 MeV≤T≤15.MeV),at saturation and and sub-saturation densities,and with proton content ranging from 30%to 50%was found to have liquid,gaseous and liquid-gas mixed phases.The isospin-dependent phase diagram was obtained along with the critical points,and the symmetry energy was calculated and compared to experimental data and other theories.At low temperatures(T≤1 MeV)NM produces crystal-like structures around satura-tion densities,and pasta-like structures at sub-saturation densities.Properties of the pasta structures were studied with cluster-recognition algorithms,caloric curve,the radial distribution function,the Lindemann coefficient,Kolmogorov statistics,Minkowski functionals;the symmetry energy of the pasta showed a connection with its morphology.Neutron star matter(NSM)is nuclear matter embedded in an electron gas.The electron gas is included in the calculation by the inclusion of an screened Coulomb potential.To connect the NM pastas with those in neutron star matter(NSM),the role the strength and screening length of the Coulomb interaction have on the formation of the pastas in NM was investigated.Pasta was found to exist even without the presence of the electron gas,but the effect of the Coulomb interaction is to form more defined pasta structures,among other effects.Likewise,it was determined that there is a minimal screening length for the developed structures to be independent of the cell size.Neutron star matter was found to have similar phases as NM,phase transitions,symmetry energy,structure function and thermal conductivity.Like in NM,pasta forms at around T≈1.5 MeV,and liquid-to-solid phase changes were detected at T≈0.5 MeV.The structure function and the symmetry energy were also found to depend on the pasta structures.展开更多
This study deals with an extensive evaluation focusing on phylogenetic and chemotaxonomic infrageneric relationships of the genus Annulohypoxylon(Xylariaceae,Ascomycota),whose species are ubiquitously associated with ...This study deals with an extensive evaluation focusing on phylogenetic and chemotaxonomic infrageneric relationships of the genus Annulohypoxylon(Xylariaceae,Ascomycota),whose species are ubiquitously associated with seed plants as endophytes and saprotrophs in all forested areas of the world.Using evidence from phylogenetic,chemotaxonomic and morphological data,various varieties within the genus are raised to species level,leading to the new combinations for A.areolatum(:A.bovei var.microsporum),A.macrosporum(:A.leptascum var.macrosporum),and A.microdiscum(:A.moriforme var.microdiscum).Annulohypoxylon substygium nom.nov.is applied for A.stygium var.annulatumand the four new tropical and subtropical species A.massivum,A.violaceopigmentum,A.viridistratum and A.yungensis are introduced.Furthermore,A.leucadendri is excluded from the genus as its morphological characters disagree with the generic concept,the recently erected A.palmicola is synonymized with A.leptascum and A.austrobahiense has been reassigned to the genus Hypoxylon.In addition,the key taxa A.annulatum and A.truncatum have been reinvestigated and epitypes have been defined.For the first time,a dichotomous key to the genus is provided.A phylogenetic b-tubulin tree in conjunction with stromatal HPLC profiles clearly shows that Annulohypoxylon comprises two distinct lineages.The A.cohaerens/multiforme group might eventually warrant segregation into a new genus as further molecular data become available.展开更多
Insect flight is a complex trait involved in different behaviors,from the search for sexual partners,food,or breeding sites.Many studies have postulated the adaptive advantages of certain morphological traits in relat...Insect flight is a complex trait involved in different behaviors,from the search for sexual partners,food,or breeding sites.Many studies have postulated the adaptive advantages of certain morphological traits in relation to increased flight capacity,such as low values of wing loading or high values of wing:thorax ratio and wing-aspect ratio.However,few studies have evaluated the relationship between variables related to flight and morphological traits in Drosophila.This work aimed to study morphological traits in males and females of two pairs of sibling species:Drosophila buzzati Patterson and Wheeler-Drosophila koeferae Fontdevila and Wasserman,and Drosophila melanogaster Meigen-Drosophila simulans Sturtevant,and to analyze its relationship with flight.We detected the highest proportion of flight time in D.koepferae and D.simulans compared to D.buzzati and D.melanogaster,respectively.Our results also revealed sexual dimorphism,with males exhibiting a higher proportion of flight time than females.Surprisingly,we did not find a general pattern to explain the relationship between morphology and the proportion of flight time because associations varied depending upon the analyses(considering all groups together or each sex-species combination separately).Moreover,these associations explained a low percentage of variation,suggesting that other nonmorphological components related to flight,such as physiological variables,should be taken into account.This work allowed us to show the variability and complexity of an aspect of flight,suggesting that the adaptive role of the morphological traits studied might have been overestimated.展开更多
基金funded by the Richard Ivey Foundationthe Haliburton ForestWild Life Reserve
文摘Insects respond to changes in microhabitat caused by canopy disturbance, and thus can be used to examine the ecological impacts of harvesting. Single-tree selection harvesting is the most common silvicultural system used to emulate local small-scale natural disturbance and maintain uneven-aged forest structure in temperate forests. Here, we test for differences in richness, abundance, and composition of hymenopteran and saproxylic insect assemblages at four different taxon levels （selected insect orders; and all hymenopteran families, and braconid subfamilies and morphospecies） between the canopy and understory of unharvested and single-tree selection harvested sites in a northern temperate forest from central Canada. Harvesting had no effect on insect assemblage richness, composition or abundance at the three highest taxon levels （order, family and subfamily）. Similarly, richness and abundance at the lowest-taxon level （braconid morphospecies） were similar, although composition differed slightly between unharvested and harvested stands. Insect assemblages were vertically stratified, with generally higher abundance （for Diptera, Hymenoptera, some hymenopteran families and braconid subfamilies） and richness （for braconid morphospecies） in the understory than the canopy. In particular, composition of the braconid morphospecies assemblage showed relatively low similarity between the understory and canopy. Single-tree selection harvesting appears to influence wood-associated insect taxa only subtly through small changes in community composition at the lowest taxon level, and thus is recommended as a conservative approach for managing these northern temperate forests.
基金Supported by the National Natural Science Foundation of China
文摘Recent analysis of the long term radio light curve of the extremely variableBL Lacertae object AO 0235+16 by Raiteri et al. have revealed the presence of recurrent outburstswith a period of ～ 5.7 +- 0.5 yr. Periodicity analysis of the optical light curve also showsevidence for a shorter period. Here we discuss whether such a behavior can be explained by a binaryblack hole model where the accretion disk of one of the supermassive black holes is precessing dueto the tidal effects of the companion. We estimate the mass of the accreting hole and analyzeconstraints on the secondary mass and the orbital parameters of the system. It is possible toprovide a viable interpretation of the available multiwavelength data.
文摘We study the statistical mechanics of small clusters (N ~ 10 - 100) for two-level systems and harmonic oscillators. Both Boltzmann’s and Gibbs’s definitions of entropy are used. The properties of the studied systems are evaluated numerically but exactly;this means that Stirling’s approximation was not used in the calculation and that the discrete nature of energy was taken into account. Results show that, for the two-level system, using Gibbs entropy prevents temperatures from assuming negative values;however, they reach very high values that are not plausible in physical terms. In the case of harmonic oscillators, there are no significant differences when using either definition of entropy. Both systems show that for N = 100 the exact results evaluated with statistical mechanics coincide with those found in the thermodynamic limit. This suggests that thermodynamics can be applied to systems as small as these.
文摘The Ecuador Mw - 7.8 earthquake on April 16, 2016, ruptured a nearly 200 km long zone along the plate interface between Nazca and South American plates which is coincident with a seismic gap since 1942, when a Mw - 7.8 earthquake happened. This earthquake occurred at a margin characterized by moderately big to giant earthquakes such as the 1906 （Mw 8.8）. A heavily sedimented trench explains the abnormal lengths of the rupture zones in this system as inhibits the role of natural barriers on the propagation of rupture zones. High amount of sediment thickness is associated with tropical climates, high erosion rates and eastward Pacific dominant winds that provoke orographic rainfalls over the Pacific slope of the Ecuatorian Andes. Offshore sediment dispersion off the oceanic trench is controlled by a close arrangement of two aseismic ridges that hit the Costa Rico and South Ecuador margin respectively and a mid ocean ridge that separates the Cocos and Nazca plate trapping sediments. Gravity field and Ocean Circulation Explorer （GOCE） satellite data are used in this work to test the possible relationship between gravity signal and earthquake rupture structure as well as registered aftershock seismic activity. Reduced vertical gravity gradient shows a good correlation with rupture structure for certain degrees of the harmonic expansion and related depth of the causative mass; indicating, such as in other analyzed cases along the subduction margin, that fore-arc structure derived from density heterogeneities explains at a certain extent propagation of the rupture zones. In this analysis the rupture zone of the April 2016 Ecuador earthquake developed through a relatively low density zone of the fore-arc sliver. Finally, aftershock sequence nucleated around the area of maximum slips in the rupture zone, suggesting that heterogeneous density structure of the fore-arc determined from gravity data could be used in forecasting potential damaged zones associated with big ruptures along the subduction border.
文摘The analysis of space-time surface deformation during earthquakes reveals the variable state of stress that occurs at deep crustal levels, and this information can be used to better understand the seismic cycle. Understanding the possible mechanisms that produce earthquake precursors is a key issue for earthquake prediction. In the last years, modern geodesy can map the degree of seismic coupling during the interseismic period, as well as the coseismic and postseismic slip for great earthquakes along subduction zones. Earthquakes usually occur due to mass transfer and consequent gravity variations, where these changes have been monitored for intraplate earthquakes by means of terrestrial gravity measurements. When stresses and correspondent rupture areas are large, affecting hundreds of thousands of square kilometres（as occurs in some segments along plate interface zones）, satellite gravimetry data become relevant. This is due to the higher spatial resolution of this type of data when compared to terrestrial data, and also due to their homogeneous precision and availability across the whole Earth.Satellite gravity missions as GOCE can map the Earth gravity field with unprecedented precision and resolution. We mapped geoid changes from two GOCE satellite models obtained by the direct approach,which combines data from other gravity missions as GRACE and LAGEOS regarding their best characteristics. The results show that the geoid height diminished from a year to five months before the main seismic event in the region where maximum slip occurred after the Pisagua Mw = 8.2 great megathrust earthquake. This diminution is interpreted as accelerated inland-directed interseismic mass transfer before the earthquake, coinciding with the intermediate degree of seismic coupling reported in the region. We highlight the advantage of satellite data for modelling surficial deformation related to preseismic displacements. This deformation, combined to geodetical and seismological data, could be useful for delimiting and monitoring areas of higher seismic hazard potential.
基金The participation of J.A.L.was partly financed by the National Science Foundation grant NSF-PHY 1066031USA DOE's Visiting Faculty Program,and by the China-US Theory Institute for Physics with Exotic Nuclei(CUSTIPEN).C.O.D.received support from the Carrera de Investigador CON-ICET,by CONICET grants PIP0871,PIP 2015-2017 GI,founding D4247(12-22-2016)Inter-American Development Bank(IDB),Grant Number PICT 1692.
文摘In this review we study the nuclear pastas as they are expected to be formed in neutron star crusts.We start with a study of the pastas formed in nuclear matter(composed of protons and neutrons),we follow with the role of the electron gas on the formation of pastas,and we then investigate the pastas in neutron star matter(nuclear matter embedded in an electron gas).Nuclear matter(NM)at intermediate temperatures(1 MeV≤T≤15.MeV),at saturation and and sub-saturation densities,and with proton content ranging from 30%to 50%was found to have liquid,gaseous and liquid-gas mixed phases.The isospin-dependent phase diagram was obtained along with the critical points,and the symmetry energy was calculated and compared to experimental data and other theories.At low temperatures(T≤1 MeV)NM produces crystal-like structures around satura-tion densities,and pasta-like structures at sub-saturation densities.Properties of the pasta structures were studied with cluster-recognition algorithms,caloric curve,the radial distribution function,the Lindemann coefficient,Kolmogorov statistics,Minkowski functionals;the symmetry energy of the pasta showed a connection with its morphology.Neutron star matter(NSM)is nuclear matter embedded in an electron gas.The electron gas is included in the calculation by the inclusion of an screened Coulomb potential.To connect the NM pastas with those in neutron star matter(NSM),the role the strength and screening length of the Coulomb interaction have on the formation of the pastas in NM was investigated.Pasta was found to exist even without the presence of the electron gas,but the effect of the Coulomb interaction is to form more defined pasta structures,among other effects.Likewise,it was determined that there is a minimal screening length for the developed structures to be independent of the cell size.Neutron star matter was found to have similar phases as NM,phase transitions,symmetry energy,structure function and thermal conductivity.Like in NM,pasta forms at around T≈1.5 MeV,and liquid-to-solid phase changes were detected at T≈0.5 MeV.The structure function and the symmetry energy were also found to depend on the pasta structures.
文摘This study deals with an extensive evaluation focusing on phylogenetic and chemotaxonomic infrageneric relationships of the genus Annulohypoxylon(Xylariaceae,Ascomycota),whose species are ubiquitously associated with seed plants as endophytes and saprotrophs in all forested areas of the world.Using evidence from phylogenetic,chemotaxonomic and morphological data,various varieties within the genus are raised to species level,leading to the new combinations for A.areolatum(:A.bovei var.microsporum),A.macrosporum(:A.leptascum var.macrosporum),and A.microdiscum(:A.moriforme var.microdiscum).Annulohypoxylon substygium nom.nov.is applied for A.stygium var.annulatumand the four new tropical and subtropical species A.massivum,A.violaceopigmentum,A.viridistratum and A.yungensis are introduced.Furthermore,A.leucadendri is excluded from the genus as its morphological characters disagree with the generic concept,the recently erected A.palmicola is synonymized with A.leptascum and A.austrobahiense has been reassigned to the genus Hypoxylon.In addition,the key taxa A.annulatum and A.truncatum have been reinvestigated and epitypes have been defined.For the first time,a dichotomous key to the genus is provided.A phylogenetic b-tubulin tree in conjunction with stromatal HPLC profiles clearly shows that Annulohypoxylon comprises two distinct lineages.The A.cohaerens/multiforme group might eventually warrant segregation into a new genus as further molecular data become available.
基金supported by funding of Agencia Nacional de Promocion Cientifica y Tecnologica granted to V.PC.(PICT-2018-00753 and PICT-2015-0277)and to JJF(PICT-2016-2256).
文摘Insect flight is a complex trait involved in different behaviors,from the search for sexual partners,food,or breeding sites.Many studies have postulated the adaptive advantages of certain morphological traits in relation to increased flight capacity,such as low values of wing loading or high values of wing:thorax ratio and wing-aspect ratio.However,few studies have evaluated the relationship between variables related to flight and morphological traits in Drosophila.This work aimed to study morphological traits in males and females of two pairs of sibling species:Drosophila buzzati Patterson and Wheeler-Drosophila koeferae Fontdevila and Wasserman,and Drosophila melanogaster Meigen-Drosophila simulans Sturtevant,and to analyze its relationship with flight.We detected the highest proportion of flight time in D.koepferae and D.simulans compared to D.buzzati and D.melanogaster,respectively.Our results also revealed sexual dimorphism,with males exhibiting a higher proportion of flight time than females.Surprisingly,we did not find a general pattern to explain the relationship between morphology and the proportion of flight time because associations varied depending upon the analyses(considering all groups together or each sex-species combination separately).Moreover,these associations explained a low percentage of variation,suggesting that other nonmorphological components related to flight,such as physiological variables,should be taken into account.This work allowed us to show the variability and complexity of an aspect of flight,suggesting that the adaptive role of the morphological traits studied might have been overestimated.
