Clump Size Research Articles

Floral display influences male and female reproductive success of the deceptive orchid Phaius delavayi

The influence of floral display on male and female reproductive success is variable without consistent patterns. Few studies concentrate on the integrated influence of the different components of floral display on reproductive fitness at population level. We studied the impact of different components of floral display on reproductive success in the Chinese orchid Phaius delavayi. This deceptive orchid has flowers in which male and female success can be readily assessed in the field by observing rates of pollinarium removal and fruit initiation. The results showed that mean pollinarium removal (52.05 ± 2.08%) was higher than fruit set (36.78 ± 1.89%), and both male and female reproductive success decreased with increasing clump size in Phaius delavayi. Nevertheless, floral display expressed by clump size and flower position impacted both female and male reproductive success, whereas flowering initiation and duration, and inflorescence size had no effect.

Cellular Immune Response of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae) during Mycosis of the Entomopathogenic Fungus Beauveria bassiana (Balsamo) Vuillemin

Beauveria bassiana one of the most common and ubiquitous entomopathogens, is known to be a highly potential bioagent for the control of insects belonging to various orders. The cellular immune response was examined in Spodoptera litura larvae infected with B. bassiana . Third instar larvae were treated with a fungal suspension @ 2.03x10 8 spores ml -1 . Haemolymph of treated and untreated larvae were taken after 2, 12, 24,48,72, 96 and 120 hours after inoculation. Plasmatocytes and granulocytes swelled 2 hours after inoculation (HAI) followed by lysis of plasma membrane. Within 24 HAI, apposition was observed. The encapsulation process started after 48 hours and continued for up to 72 hours. After 96 hours of inoculation the granulocytes and plasmatocytes were observed to form nodules. With increasing inoculation time, the size of clump increased, forming multiple layers at 120 HAI. However, despite these insect defense responses, growth of fungal hyphae was observed after 120 hours of inoculation which ultimately resulted in the death of the host.

THE SINS SURVEY OFz∼ 2 GALAXY KINEMATICS: PROPERTIES OF THE GIANT STAR-FORMING CLUMPS

We have studied the properties of giant star-forming clumps in five z ∼ 2 star-forming disks with deep SINFONI AO spectroscopy at the ESO VLT. The clumps reside in disk regions where the Toomre Q-parameter is below unity, consistent with their being bound and having formed from gravitational instability. Broad Hα/[N ii] line wings demonstrate that the clumps are launching sites of powerful outflows. The inferred outflow rates are comparable to or exceed the star formation rates, in one case by a factor of eight. Typical clumps may lose a fraction of their original gas by feedback in a few hundred million years, allowing them to migrate into the center. The most active clumps may lose much of their mass and disrupt in the disk. The clumps leave a modest imprint on the gas kinematics. Velocity gradients across the clumps are 10–40 km s−1 kpc−1, similar to the galactic rotation gradients. Given beam smearing and clump sizes, these gradients may be consistent with significant rotational support in typical clumps. Extreme clumps may not be rotationally supported; either they are not virialized or they are predominantly pressure supported. The velocity dispersion is spatially rather constant and increases only weakly with star formation surface density. The large velocity dispersions may be driven by the release of gravitational energy, either at the outer disk/accreting streams interface, and/or by the clump migration within the disk. Spatial variations in the inferred gas phase oxygen abundance are broadly consistent with inside-out growing disks, and/or with inward migration of the clumps.

Survival, Growth, and Fecundity of the Invasive Swallowworts (Vincetoxicum rossicum and V. nigrum) in New York State

AbstractBlack and pale swallowwort (BSW and PSW, respectively) are perennial, herbaceous vines in the Apocynaceae that are native to Europe. The species are becoming increasingly abundant in the northeastern United States and southeastern Canada and are difficult to manage. However, we know little about the demographic parameters of these species. We determined the survival, annual rate of vegetative growth, and fecundity of mature clumps of these swallowwort species. We selected four PSW sites (three of which comprised both old-field and forest habitats) in central New York and three BSW old fields in southeastern New York. BSW is largely restricted to higher light habitats in its introduced range. In each habitat, we followed the growth of 30 to 32 randomly selected clumps of similar size (2 to 5 stems clump−1 in the initial year) for 3 to 4 yr. Yearly survival was 99.6 ± 0.3% [mean ± standard error] for PSW and 100 ± 0% for BSW. In old fields, vegetative expansion varied from −0.01 ± 0.1 to 4.6 ± 0.4 stems clump−1 yr−1 for BSW and −0.02 ± 0.2 to 2.1 ± 0.5 stems clump−1 yr−1 for PSW. In forests, PSW growth was lower with vegetative expansion ranging from −0.01 ± 0.1 to 0.8 ± 0.2 stems clump−1 yr−1. Fecundity of PSW in 2007 and 2008 (130 ± 10 viable seeds stem−1 yr−1) was similar to BSW (100 ± 10 viable seeds stem−1 yr−1). Fecundity of PSW in forests was generally lower than PSW in old fields, but it varied greatly among sites (0 to 170 viable seeds stem−1 yr−1). We found that stem growth and fecundity did not vary with clump size (stems per clump). Since vegetative expansion and fecundity rates were high in old-field habitats, but were generally low or nonexistent in forest habitats, we suggest that management of these two invasive vines be focused in higher light environments to reduce overall seed production and its subsequent spread to surrounding areas.

Impacts of tree canopy structure on wind flows and fire propagation simulated with FIRETEC

Forest fuel management in the context of fire prevention generally induces heterogeneous spatial patterns of vegetation. However, the impact of the canopy structure on both wind flows and fire behavior is not well understood. Here, a coupled atmosphere wildfire behavior model, HIGRAD/FIRETEC, was used to investigate the effects of canopy treatment on wind field and fire behavior in a typical Mediterranean pine ecosystem. First, the treatment-induced winds were simulated with the model. We observed that with decreasing cover fraction the wind velocity increased within the treated zone. The wind spatial variability increased when the vegetation was aggregated into larger clumps. Fire simulations indicated that a decrease of fire intensity occurred after several meters of propagation in the treated zone. This intensity decrease was significant with a cover fraction below 25%, but negligible with a cover fraction greater than 50%. The treatment also induced a more significant inclination of the plume away from vertical. The size of the tree clumps did not show significant effects on fire behavior. This study was a preliminary investigation of wind/fire interaction over various canopy treatments, by using a physically based model. It gives some practical considerations for discerning the appropriate cover fraction and open perspectives for further investigations.

Structure Formation and Characterization in Supernova Explosions

AbstractObservations of supernova remnants show that large- and small scale structures form at various points in the explosion. We present a case study of structure formation in 3D in a 15 M⊙ supernova for different parameters. We investigate the structure formation and morphology of the Rayleigh-Taylor unstable region. We also propose a method of characterizing the sizes of overdense clumps that can be compared directly with observations. The RT instabilities result in clumps that are overdense by 1-2 orders of magnitude with respect to the ambient gas, have size scales on the level of a few% of the remnant diameter, and are not diffused after the first ~30 yrs of the remnant evolution, in the absence of a surrounding medium.

Controlling an Invasive Shrub, Japanese Barberry (Berberis thunbergiiDC), using Directed Heating with Propane Torches

ABSTRACT: Japanese barberry (Berberis thunbergii DC) is a non-native shrub currently found in 31 states and four Canadian provinces. We examined the effectiveness of directed heating using 400,000 BTU backpack propane torches to control Japanese barberry infestations at two study areas in southern Connecticut. Each study area had eight 50-m × 50-m plots. Treatment combinations included a pre-leafout or post-leafout initial treatment with propane torches to reduce the size of established clumps and an early (late June), mid (early July), or late (late July) follow-up treatment to kill sprouts that developed from surviving root crowns. All treatment combinations were equally effective and reduced barberry abundance (a surrogate for cover) from 31% prior to treatment to only 0.5% the following autumn (i.e., a 98% reduction). All treatment combinations were also equally effective in reducing the size of surviving barberry to an average of only 11 cm compared with 74 cm for untreated clumps. Estimated labor co...

Parameters Affecting the Success of Protected Shoals Spider Lily,Hymenocallis Coronaria, in the Savannah River Basin, Georgia

ABSTRACT: Populations of state protected Augusta Shoals spider lily (Hymenocallis coronaria) are declining throughout its southeastern range in Alabama, Georgia, and South Carolina. Artificial flow rates and deer herbivory appear to be the major detriments to the three remaining populations of this species in the Augusta Shoals of the Savannah River, Georgia, where it was first discovered in 1773 by William Bartram. High and fluctuating flow rates in the Savannah River during the May–October portion of the growing season adversely affect flowering and seedling establishment compared to a tributary population in Stevens Creek east of Plum Branch, South Carolina. Water quality parameters and non-deer herbivory were similar in both populations as were asexual ramet formation and general clump size. Seed production and seedling establishment were examined in H. coronaria to determine how these were affected by flow rates. Cooperation between state and federal agencies regulating stream flow rates and deer her...

Orbital parameters of supergiant fast X-ray transients

Supergiant fast X-ray transient (SFXT) is a new class of the high mass X-ray binary that shows short X-ray flares. The physical mechanism of SFXT short flares is still open for discussion. The accretion process of dense clumps in stellar wind onto neutron star (NS) has been proposed as the origin of such short flares. In order to examine the applicability of the clumpy wind scenario, we focus on the accretion mode that depends on orbital parameters. Our goal is to impose restrictions on the orbital parameters of SFXT. Assuming a simple analytic model of clumpy wind, we investigate the condition where the size of accretion cylinder overcomes the clump size. The allowed parameter region for SFXT is restricted in a relatively narrow window in $P_{\rm{orb}} - e$ diagram. Binary systems with large eccentricities ($e \ga 0.4$) and moderate orbital periods ($P_{\rm{orb}} \sim 10$ d) are prone to show periodic X-ray outbursts which are characteristic for SFXT. We confirm that systems with a long orbital period of more than 100 days cannot produce bright X-ray flares in the simple clumpy wind scenario.

Density segregation in a vertically vibrated granular bed

The dominant mechanism affecting the flow behavior of granular materials is the random motions of particles that results from the interactive collisions between particles. The velocity fluctuations induce the segregation in granular flows. The different densities of granular materials with different filling layers and packing ratios were used to investigate the segregation mechanisms in a vibrated granular bed in this study. The image processing techniques were employed to track the motion of granular materials. The fluctuating velocities of granular materials were measured under segregation in a vibrated granular bed. The segregation phenomena depend on the packing ratio and the filling layer of the stainless steel–glass mixtures. At the fewer filling layers, the heavier stainless steel beads migrate to the bottom regions with the lower granular temperature, so the granular temperature plays a significant role on density segregation. For the higher filling layers, the bulk convection motion is the main mechanism affecting segregation, so the heavier beads clump to the convection center and the clump size enlarges with the increasing packing ratio of heavier beads due to the bulk convection motion.

SPECTROPOLARIMETRIC SIGNATURES OF CLUMPY SUPERNOVA EJECTA

Polarization has been detected at early times for all types of supernova, indicating that such systems result from or quickly develop some form of asymmetry. In addition, the detection of strong line polarization in supernovae is suggestive of chemical inhomogeneities ("clumps") in the layers above the photosphere, which may reflect hydrodynamical instabilities during the explosion. We have developed a fast, flexible, approximate semi-analytic code for modeling polarized line radiative transfer within 3-D inhomogeneous rapidly-expanding atmospheres. Given a range of model parameters, the code generates random sets of clumps in the expanding ejecta and calculates the emergent line profile and Stokes parameters for each configuration. The ensemble of these configurations represents both the effects of various host geometries and of different viewing angles. We present results for the first part of our survey of model geometries, specifically the effects of the number and size of clumps (and the related effect of filling factor) on the emergent spectrum and Stokes parameters. Our simulations show that random clumpiness can produce line polarization in the range observed in SNe Ia (~1-2%), as well as the Q-U loops that are frequently seen in all SNe. We have also developed a method to connect the results of our simulations to robust observational parameters such as maximum polarization and polarized equivalent width in the line. Our models, in connection with spectropolarimetric observations, can constrain the 3-D structure of supernova ejecta and offer important insight into the SN explosion physics and the nature of their progenitor systems.

Effectiveness of Two-Stage Control Strategies for Japanese Barberry (Berberis thunbergii) Varies by Initial Clump Size

AbstractJapanese barberry is listed as an invasive shrub in 20 states and four Canadian provinces. Control of Japanese barberry was evaluated using several two-step processes over 16 mo using a total of 1,100 clumps at six study areas. Initial treatments in spring (prescribed burning, mechanical mowing with a brush saw or rotary wood shredder) reduced the size of established barberry clumps. Follow-up treatments in midsummer to kill new ramets that developed from surviving root crowns were foliar applications of triclopyr or glyphosate, directed heating with a propane torch, and untreated controls. Mortality was defined as the absence of ramets from a root crown and not the mortality of individual ramets of a given clump. Clump mortality and size of new ramets did not differ among initial treatments. However, larger clumps had higher survival and larger sprouts than smaller clumps 16 mo after initial treatment. Effectiveness of follow-up treatments varied by clump size. Two follow-up treatments of directed heating using propane torches were as effective as herbicides for clumps that were initially smaller than 120 cm. For clumps with pretreatment sizes of 120 cm and larger, clump mortality following herbicide treatments (90%) and directed heating (65%) was greater than for clumps that had no follow-up treatments (35%). Although clump sizes did not differ between follow-up methods 1 yr after treatment, both follow-up treatments resulted in smaller clumps than untreated controls. Effective control of Japanese barberry can be achieved in a single growing season by integrating an early-season initial treatment (prescribed fire or mechanical) that kills the aboveground tissues with a midseason follow-up treatment such as directed heating or targeted herbicide application.

Theory of Cluster Formation: Effects of Magnetic Fields

AbstractStars form predominantly in clusters inside dense clumps of molecular clouds that are both turbulent and magnetized. The typical size and mass of the cluster-forming clumps are ~1 pc and ~102 – 103 M⊙, respectively. Here, we discuss some recent progress on numerical simulations of clustered star formation in such parsec-scale dense clumps with emphasis on the role of magnetic fields. The simulations have shown that magnetic fields tend to slow down global gravitational collapse and thus star formation, especially in the presence of protostellar outflow feedback. Even a relatively weak magnetic field can retard star formation significantly, because the field is amplified by supersonic turbulence to an equipartition strength. However, in such a case, the distorted field component dominates the uniform one. In contrast, if the field is moderately-strong, the uniform component remains dominant. Such a difference in the magnetic structure is observed in simulated polarization maps of dust thermal emission. Recent polarization measurements show that the field lines in nearby cluster-forming clumps are spatially well-ordered, indicative of a rather strong field. In such strongly-magnetized clumps, star formation should proceed relatively slowly; it continues for at least several global free-fall times of the parent dense clump (tff ~ a few × 105 yr).

Arterial Filter Bypass Loop: What Occurs in this Area during Cardiopulmonary Bypass and Are There Potential Patient Implications

The arterial filter is an integral part of bypass circuitry. When introduced, manufacturers suggested a bypass loop for retrograde priming and de-airing, and for uninterrupted blood flow in case of malfunction. Practice has shown antegrade priming and de-airing is possible. This questions the necessity of the loop and presents the question—what occurs in the loop during bypass? After obtaining Human Research Ethics Board approval, eight consecutive patients (n = 8) were chosen for this study. Exclusive exclusion criterion was receiving any transfusions during cardiopulmonary bypass, as this could possibly influence results. The choice of patient numbers was based simply on proof of concept. Investigation involved isolation and collection of loop contents after cardiopulmonary bypass was completed. Testing included complete blood count, prothrombin time, international normalized ratio, partial thromboplastin time, activated clotting time, plasma free hemoglobin, slide photography with analysis for platelet clumping, and debris detection. One perfusionist collected samples, providing uniform collection and isolation technique. Regular blood samples were collected from the bypass circuitry, and from patients’ pre-operative blood work. Analysis of data revealed that platelet counts in the bypass loops were statistically lower than control. Evidence of platelet clumping was present in 3 of 8 bypass loop samples, representing 37.5% of the study population. There was no clumping detected in any of the controls. In patients where platelet clumping was present, a positive correlation was noted between mean bypass time and size of platelet clumps. Prothrombin time and international normalized ratio results were immeasurable. Hemoglobin levels were higher in the loop samples. There was no evidence of debris or fibrin monomer present in any of the samples analyzed. The study results indicate that during “normal” cardiopulmonary bypass with an arterial filter bypass loop, platelet aggregates can accumulate in the loop, therefore opening the arterial bypass loop in any case may subject the patient to micro/macro emboli.

Predator inadvertent social information use favours reduced clumping of its prey

When animals forage socially, individuals can obtain prey from their own searching (producer tactic) or by using the behaviour of others (scrounger tactic) when it provides inadvertent social information (ISI) that food has been located. This ISI may either indicate the location of food (social information, SI), or it may indicate the quality of the resource (public information, PI). To date, few studies have explored the selective consequences for prey of being exploited by predators that use ISI. Prey exploited by such predators should evolve traits that favour high levels of ISI use (scrounging) because this would result in lower predator search efficiency given that fewer predators would be searching directly for the prey. Our simulations confirm that ISI‐using predators should increase their use of ISI when their prey form larger clumps resulting in higher prey survival. Our objective therefore is to explore whether prey will evolve towards higher clumpiness when their predators use ISI, using genetic algorithm simulation. The prey were subjected to one of three types of predators for over 500 prey generations. The predators either used: (1) no social information (NS), (2) SI only, or (3) PI. Surprisingly, the prey evolved the highest clumpiness for NS predators. Prey evolved towards smaller clump sizes with SI predators and the clumps were marginally larger when predators used PI. The result is due to the prey evolving the minimum clumpiness required to cause maximal ISI use by their predators. We discuss how this response by prey may favour the use of PI over SI in their ISI‐using predators.

Quantitative assessment of shrub–grass mosaic development in grazed shrublands: An example in the Patagonian Monte (Argentina)

Grazing alters the spatial structure of shrubs and perennial grasses in desert shrub communities. The resulting spatial distribution of shrub–grass patches constitutes a sensitive indicator of the integrated result of grazing impacts on them. While several procedures were developed to estimate the size of shrub clumps, metrics of the geometry of the interacting grass matrix received less attention. In this study, we conceptualised the spatial structure of shrub–grass patches as consisting of two components: a grass crown of ill-defined outer borders (the ‘grass component’) encircling a shrub clump (the ‘shrub component’). We fitted exponential functions to autocorrelograms of spatially explicit shrub–grass cover data surveyed at different locations of the Patagonian Monte (Argentina) differing in livestock grazing pressure. After that, we derived two metrics from the function parameters that quantitatively estimate the size of both the shrub and the grass components of shrub–grass patches. The patterns of variation of these metrics are consistent with field measurements and observations previously reported for the studied areas, indicating that they are sensitive indicators of the state of development of the shrub–grass mosaic under different grazing pressures. These results suggest that its applicability to similar semi-arid shrublands deserves further attention.

Predicting oak tree mortality caused by the ambrosia beetle Platypus quercivorus in a cool‐temperate forest

AbstractMass mortality of fagaceous trees due to wilt disease, which has been spreading throughout Japan since the 1980s, is caused by the ambrosia beetle Platypus quercivorus. Quercus crispula is one of the species most susceptible to the disease. Previous studies have examined this disease in secondary forests, where fagaceous trees are dominant and are considered to be distributed uniformly. We examined whether the uneven distribution of Q. crispula in a natural forest affects the spread of this disease. We determined its distribution using Morisita’s index of dispersion (Iδ), and then predicted the probability of mortality using a generalized linear model with topographic variables (altitude and index of convexity), tree size (diameter at breast height, DBH), and basal areas of Q. crispula and Cryptomeria japonica (the dominant species at the study site) per 0.01, 0.09, and 0.25 ha as explanatory variables. The site included 310 Q. crispula within a 14 ha plot in a cool‐temperate forest of Japan with no signs of beetle infestation in 2003. The calculated index of dispersion showed a clumped distribution of Q. crispula with an estimated clump size of 0.08 ha. At the end of 2007, 36 Q. crispula in the study site were dead, and DBH and basal area of Q. crispula per 0.09 ha had significant positive effects on the probability of mortality. The basal area of C. japonica, a non‐host conifer species for P. quercivorus, per 0.09 ha also had a positive effect on the probability of mortality. These results suggest that P. quercivorus first flew to a cluster of Q. crispula aggregated in about a 0.1 ha area where the density of C. japonica is high, and then DBH played a role in determining the target trees.

Pollen clumping and wind dispersal in an invasive angiosperm

Pollen dispersal is a fundamental aspect of plant reproductive biology that maintains connectivity between spatially separated populations. Pollen clumping, a characteristic feature of insect-pollinated plants, is generally assumed to be a detriment to wind pollination because clumps disperse shorter distances than do solitary pollen grains. Yet pollen clumps have been observed in dispersion studies of some widely distributed wind-pollinated species. We used Ambrosia artemisiifolia (common ragweed; Asteraceae), a successful invasive angiosperm, to investigate the effect of clumping on wind dispersal of pollen under natural conditions in a large field. Results of simultaneous measurements of clump size both in pollen shedding from male flowers and airborne pollen being dispersed in the atmosphere are combined with a transport model to show that rather than being detrimental, clumps may actually be advantageous for wind pollination. Initial clumps can pollinate the parent population, while smaller clumps that arise from breakup of larger clumps can cross-pollinate distant populations.

Compound processes as models for clumped parasite data

Compound processes are proposed as models for the acquisition of hydatid cysts in sheep, caused by the parasite Echinococcus granulosus. The hypothesis of a clumped infection process against single ingestions is tested and it is shown that the clump-based approach provides a more accurate description of the two data sets investigated. Models with simple and mixed Poisson incidence processes and different clump size distributions are compared. A mixed Poisson incidence process with a zero-truncated negative binomial distribution for the clump sizes is shown to give an adequate description, suggesting that the acquisition of hydatid cysts in the sheep population is heterogeneous, and that the clump sizes are aggregated. The estimates of the parameters derived from the data take plausible values. The average infection rate and the clump size distribution are comparable in both data sets. Goodness-of-fit measures indicate that the model fits the data reasonably well.

Probing star formation at intermediate z

AbstractWe summarize the latest results of an ongoing project aimed at connecting starburst galaxies in the local Universe and Lyman-break galaxies (LBGs) in the distant Universe using rest-frame ultraviolet (UV) images. We are quantifying star formation in the local Universe using GALEX data of interacting galaxies and we are using Hubble Space TelescopeU-band and optical images of the Ultra Deep Field to quantify star formation at intermediate (z ~ 1) and high (z > 2) redshifts, respectively. We are measuring sizes of star-forming clumps in all redshift ranges and searching for evolutionary effects. We chose the rest-frame UV to do this work because young and massive stars radiate most their energy in the UV and also because LBGs are selected to be UV-bright. We discuss whether all galaxies go through an LBG phase and whether disks show any sign of size of evolution at z < 1.