823 research outputs found
Generalized measures for physical properties of nonperiodic chains
No full textPT: J; CR: AVISHAI Y, 1990, PHYS REV B, V41, P5492 BORN M, 1965, PRINCIPLES OPTICS BURROWS BL, 1991, J PHYS A-MATH GEN, V24, P3979 DAVISON SG, 1992, BASIC THEORY SURFACE GUMBS G, 1989, J PHYS A-MATH GEN, V22, P951 KIANG D, 1990, AM J PHYS, V58, P1200 KOHMOTO M, 1987, PHYS REV LETT, V58, P2436 KOLAR M, 1991, PHYS REV B, V43, P1034 PATTNAIK RK, 1992, J PHYS A-MATH GEN, V25, P577 THAKUR PK, 1992, J PHYS-CONDENS MAT, V4, P6095; NR: 10; TC: 5; J9: PHYS REV B; PG: 7; GA: QL717Source type: Electronic(1
Spatial oxygen heterogeneity in a Hediste diversicolor irrigated burrow
No full textThe heterogeneity of oxygen distribution in a Hediste diversicolor burrow environment was investigated in a laboratory experiment using a 6-mm thick tank equipped with oxygen planar optodes. The twodimensional oxygen distribution in a complete burrow was monitored every 2 min for 4 h. Oxygen concentrations fluctuated over a scale of minutes in the burrow lumen and wall (up to 2 mm) reflecting the balance between worm ventilation activity and oxygen consumption. The magnitude of the three surrounding micro-horizons (oxic, oscillating and anoxic) induced by the intermittent worm ventilation was spatially and temporally variable within the structure. Oxygen variations appeared to be controlled by distance from the sediment–water interface and the direction of water circulation. Moreover, there was an apparent ‘buffer effect’, induced by the proximity to the overlyingwater, which reduced the variations of lumen and wall oxygen in the upper part of the structure. These results highlight the heterogeneous distribution and dynamics of oxygen associated with H. diversicolor burrows and ventilation activity. They also highlight the necessity of integrating this complexity into the current burrow-base models in order to estimate the ecological importance of burrowing species in coastal ecosystems
Facial musculature in the rhesus macaque (Macaca mulatta): evolutionary and functional contexts with comparisons to chimpanzees and humans
No full textFacial expression is a common mode of visual communication in mammals but especially so in primates. Rhesus macaques (Macaca mulatta) have a well‐documented facial expression repertoire that is controlled by the facial/mimetic musculature as in all mammals. However, little is known about the musculature itself and how it compares with those of other primates. Here we present a detailed description of the facial musculature in rhesus macaques in behavioral, evolutionary and comparative contexts. Formalin‐fixed faces from six adult male specimens were dissected using a novel technique. The morphology, attachments, three‐dimensional relationships and variability of muscles were noted and compared with chimpanzees (Pan troglodytes) and with humans. The results showed that there was a greater number of facial muscles in rhesus macaques than previously described (24 muscles), including variably present (and previously unmentioned) zygomaticus minor, levator labii superioris alaeque nasi, depressor septi, anterior auricularis, inferior auricularis and depressor supercilii muscles. The facial muscles of the rhesus macaque were very similar to those in chimpanzees and humans but M. mulatta did not possess a risorius muscle. These results support previous studies that describe a highly graded and intricate facial expression repertoire in rhesus macaques. Furthermore, these results indicate that phylogenetic position is not the primary factor governing the structure of primate facial musculature and that other factors such as social behavior are probably more important. The results from the present study may provide valuable input to both biomedical studies that use rhesus macaques as a model for human disease and disorder that includes assessment of facial movement and studies into the evolution of primate societies and communication
Measurement of disorder in non-periodic sequences
No full textAn information theoretic measure is introduced to compare the disorder in non-periodic sequences. It is shown that the measure correctly distinguishes quasiperiodic and aperiodic sequences which have been deduced from earlier studies using diffraction patterns, although it is often necessary to use a set of measures, depending on the order of the source used. The particular sequences studied are the Thue-Morse sequence and the generalizations of the golden mean sequence commonly studied in connection with quasicrystals.PT: J; CR: ALI MK, 1988, PHYS REV B, V38, P7091 BOMBIERI E, 1986, J PHYS-PARIS, V47, P19 BOMBIERI E, 1987, CONT MATH, V64, P241 BURROWS BL, 1989, INT J MATH ED SCI TE, V20, P913 CHENG Z, 1988, PHYS REV B, V37, P4375 GUMBS G, 1988, J PHYS A, V21, L517 GUMBS G, 1988, PHYS REV LETT, V60, P1081 GUMBS G, 1989, J PHYS A-MATH GEN, V22, P951 HAMMING RW, 1980, CODING INFORMATION T HOLZER M, 1988, PHYS REV B, V38, P1709 HOLZER M, 1988, PHYS REV B, V38, P5756 KOLAR M, 1990, PHYS REV B, V41, P7108 KOLAR M, 1991, PHYS REV B, V43, P1034 MA HR, 1988, J PHYS C SOLID STATE, V21, P4311 MERLIN R, 1985, PHYS REV LETT, V55, P1768 MORSE M, 1921, AM J MATH, V43, P35 MORSE M, 1921, T AM MATH SOC, V22, P84 NIU Q, 1986, PHYS REV LETT, V57, P2057 PENROSE R, 1974, B I MATH APPL, V10, P266 QIN MG, 1990, J PHYS-CONDENS MAT, V2, P1059 RIKLUND R, 1987, INT J MOD PHYS B, V1, P121 SHANNON CE, 1949, MATH THEORY COMMUNIC SHECHTMAN D, 1984, PHYS REV LETT, V53, P1951 THUE A, 1906, NORSKE VID SELSK IMN, V7, P1 THUE A, 1912, NORSKE VID SELSK IMN, V1, P1; NR: 25; TC: 13; J9: J PHYS-A-MATH GEN; PG: 9; GA: GC466Source type: Electronic(1
Spatial distribution patterns of plague hosts: point pattern analysis of the burrows of great gerbils in Kazakhstan
No full textAIM: The spatial structure of a population can strongly influence the dynamics of infectious diseases, yet rarely is the underlying structure quantified. A case in point is plague, an infectious zoonotic disease caused by the bacterium Yersinia pestis. Plague dynamics within the Central Asian desert plague focus have been extensively modelled in recent years, but always with strong uniformity assumptions about the distribution of its primary reservoir host, the great gerbil (Rhombomys opimus). Yet, while clustering of this species' burrows due to social or ecological processes could have potentially significant effects on model outcomes, there is currently nothing known about the spatial distribution of inhabited burrows. Here, we address this knowledge gap by describing key aspects of the spatial patterns of great gerbil burrows in Kazakhstan. LOCATION: Kazakhstan. METHODS: Burrows were classified as either occupied or empty in 98 squares of four different sizes: 200 m (side length), 250 m, 500 m and 590-1020 m. We used Ripley's K statistic to determine whether and at what scale there was clustering of occupied burrows, and semi-variograms to quantify spatial patterns in occupied burrows at scales of 250 m to 9 km. RESULTS: Significant spatial clustering of occupied burrows occurred in 25% and 75% of squares of 500 m and 590-1020 m, respectively, but not in smaller squares. In clustered squares, the clustering criterion peaked around 250 m. Semi-variograms showed that burrow density was auto-correlated up to a distance of 7 km and occupied density up to 2.5 km. MAIN CONCLUSIONS: These results demonstrate that there is statistically significant spatial clustering of occupied burrows and that the uniformity assumptions of previous plague models should be reconsidered to assess its significance for plague transmission. This field evidence will allow for more realistic approaches to disease ecology models for both this system and for other structured host populations
Characterizing the Taphonomically Active Zone in Subtropical Peat from Barnes Sound in Key Largo, Florida
No full textSurficial mangrove peat from Barnes Sound in Key Largo, Florida preserves very thick leaf mats (19-37 stacked leaves). The incoherent leaf mat occurred below the coherent leaf mat to a depth of approximately 5 cm, and consisted of degraded and fragmented leaves intruded by living horizontal and vertical rootlets. Short cores (13 cm deep) indicated that the peat below the coherent and incoherent leaf mat consists primarily of living and dead roots and rootlets, large pieces of wood, and fecal pellets.
Taphonomic analysis of 100 leaves from the coherent leaf mat at Barnes Sound indicated that fallen leaves record canopy herbivory and parasitism, as well as the decomposition pathways occurring on the mire surface: microbial decomposition and detritivory by snails. Canopy herbivory and parasitism by micro-arthropods, insects and the mangrove crab was most prominent. Abundant fecal pellets (106 ��m ��� 2 mm), edge feeding, and skeletonization in the coherent and incoherent leaf mats indicated the importance micro-detritivores. Shells belonging to the detritivorous neogastropod Melampus coffeus occurred in the core, but leaf deterioration by M. coffeus was hard to distinguish. Leaves showing attack patterns characteristic of detritivorous mangrove crabs appeared in the coherent leaf mat, but no crab burrows appeared on the mire surface.
Macro-detritivores (specifically crabs) play an important role in the decomposition pathways in many modern mangrove mires. Mangrove peat at Barnes Sound preserved an exceptionally thick leaf mat, possibly due to the scarcity of detritivorous mangrove crabs at this locality. If crabs are reduced or absent, thick leaf mats can accumulate in saltwater mires. Our results indicate that in the absence of these and similar macro-detritivores, thick leaf mats could have accumulated in ancient saltwater mires. Low shoot-to-root ratios and the presence of thick leaf mats cannot confidently be used as taphonomic indicators of freshwater peat
Long and short term residence in refuge burrows by endangered pygmy bluetongue lizards
No full textAuthor version made available in accordance with the publisher's policyThe pygmy bluetongue lizard (Tiliqua adelaidensis) is an endangered species which is restricted to native grassland remnants in South Australia. Individuals live in vertical burrows with a single entrance from which they ambush invertebrate prey. We monitored marked burrows over two entire spring-summer seasons, the period when the lizards are active, and found that the population contained a mixture of dispersers that remained in a burrow briefly, and residents that occupy a burrow for the entire study period. There were more females than males among the residents and most of the burrow abandonment happened in the early spring, the time when male lizards probably move around to seek matings. Our study described burrow occupancy dynamics, and will assist the conservation management of this endangered species. Key words: Scincid lizards; burrows; long-term residency; conservatio
Figure 5 in Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water
No full textFigure 5. Typical distribution of Neohela monstrosa burrows in a densely populated area. The photo from a video transect at station 301 at 1935 m depth shows ~15 burrows made by small (white arrows) and large (black arrows) individuals. Scale is indicated by two laser spots that are 10 cm apart.Published as part of Buhl-Mortensen, Lene, Tandberg, Anne Helene S., Buhl-Mortensen, Pål & Gates, Andrew R., 2015, Behaviour and habitat of Neohela monstrosa (Boeck, 1861) (Amphipoda: Corophiida) in Norwegian Sea deep water, pp. 323-337 in Journal of Natural History 50 on page 331, DOI: 10.1080/00222933.2015.1062152, http://zenodo.org/record/398335
Consequences of climate-driven biodiversity changes for ecosystem functioning of North European rocky shores
No full textWe review how intertidal biodiversity is responding to globally driven climate change,
focusing on long-term data from rocky shores in the British Isles. Physical evidence of warming
around the British Isles is presented and, whilst there has been considerable fluctuation, sea surface
temperatures are at the highest levels recorded, surpassing previous warm periods (i.e. late 1950s).
Examples are given of species that have been advancing or retreating polewards over the last 50 to
100 yr. On rocky shores, the extent of poleward movement is idiosyncratic and dependent upon life
history characteristics, dispersal capabilities and habitat requirements. More southern, warm water
species have been recorded advancing than northern, cold water species retreating. Models have
been developed to predict likely assemblage composition based on future environmental scenarios.
We present qualitative and quantitative forecasts to explore the functional consequences of changes
in the identity, abundance and species richness of gastropod grazers and foundation species such as
barnacles and canopy-forming algae. We forecast that the balance of primary producers and secondary
consumers is likely to change along wave exposure gradients matching changes occurring
with latitude, thereby shifting the balance between export and import of primary production.
Increases in grazer and sessile invertebrate diversity are likely to be accompanied by decreasing
primary production by large canopy-forming fucoids. The reasons for such changes are discussed in
the context of emerging theory on the relationship between biodiversity and ecosystem functioning.
KEY WORDS: Climate change · Intertidal · Range shifts · Biodiversity · Ecosystem functioning ·
Northeast Atlanti
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