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Massive stars have strong stellar winds that direct their evolution through the upper Hertzsprung–Russell diagram and determine the black hole mass function. Furthermore, wind strength dictates the atmospheric structure that sets the ionizing flux. Finally, the wind directly intervenes with the stellar envelope structure, which is decisive for both single-star and binary evolution, affecting predictions for gravitational wave events. Key findings of current hot star research include: The traditional line-driven wind theory is being updated with Monte Carlo and comoving frame computations, revealing a rich multivariate behavior of the mass-loss rate in terms of M, L, Eddington Γ, Teff, and chemical composition Z. Concerning the latter, is shown to depend on the iron (Fe) opacity, making Wolf–Rayet populations, and gravitational wave events dependent on host galaxy Z. On top of smooth mass-loss behavior, there are several transitions in the Hertzsprung–Russell diagram, involving bistability jumps around Fe recombination temperatures, leading to quasi-stationary episodic, and not necessarily eruptive, luminous blue variable and pre-SN mass loss. Furthermore, there are kinks. At 100 a high Γ mass-loss transition implies that hydrogen-rich, very massive stars have higher mass-loss rates than commonly considered. At the other end of the mass spectrum, low-mass stripped helium stars no longer appear as Wolf–Rayet stars but as optically thin stars. These stripped stars, in addition to very massive stars, are two newly identified sources of ionizing radiation that could play a key role in local star formation as well as at high redshift. [ABSTRACT FROM AUTHOR]

This study was an investigation of the interaction of loamy sand and clay loam soils with a sweep under field conditions by studying the role of particle shape utilised in a discrete element method (DEM) model of soil-sweep interaction. Beside the soil modelling a validated DEM model of roots present in the soil was developed which highlighted the role of roots in the soil reinforcement. Using the results of field and laboratory tests, layered DEM model of soil structure was improved. In the DEM soil model developed, Young's modulus in the contacts of particles was selected based on oedometric test as 5 MPa in clay loam and 10 MPa in loamy sand soil. A combined calibration process was performed in three different assemblies composed of clumps or spheres, where a DEM model of cone penetration tests' and a soil-sweep DEM model were applied together to confirm the adequate utilisation of layers with different cohesive and frictional parameters. Clumps were utilised for modelling clay loam soil, while for loamy sand spheres were utilised. The geometry of the utilised particles corresponds to the particle assembly coordination number of 9.4 in clay loam and 4.6 in loamy sand which effected comparable quality change in the DEM, based on field test. The model of root for soil–sweep–root interaction was validated by a laboratory shear cut test. The simulation with the developed model showed that breakable roots have a notable influence on draught force, while the number of roots utilised was also an important parameter. • Young's modulus of 5 MPa was utilised for clay loam and 10 MPa for loamy sand soil. • Higher bond strengths on the lower layer with lower friction angle is increase CPR. • CPT to be calibrated with clumps for clay loam and spheres for loamy sand soil. • The DEM model of plant roots was improved and root breaking was implemented. • The soil–sweep–root interaction DEM model has been improved. [ABSTRACT FROM AUTHOR]

A multitude of phenomena—such as the chemical enrichment of the Universe, the mass spectrum of planetary nebulae, white dwarfs and gravitational wave progenitors, the frequency distribution of supernovae, the fate of exoplanets, etc.—are highly regulated by the amounts of mass that stars expel through a powerful wind. For more than half a century, these winds of cool aging stars have been interpreted within the common interpretive framework of 1D models. I here discuss how that framework now appears to be highly problematic. Current 1D mass-loss rate formulae differ by orders of magnitude, rendering contemporary stellar evolution predictions highly uncertain. These stellar winds harbor 3D complexities that bridge 23 orders of magnitude in scale, ranging from the nanometer up to thousands of astronomical units. We need to embrace and understand these 3D spatial realities if we aim to quantify mass loss and assess its effect on stellar evolution. We therefore need to gauge the following: The 3D life of molecules and solid-state aggregates: The gas-phase clusters that form the first dust seeds are not yet identified. This limits our ability to predict mass-loss rates using a self-consistent approach. The emergence of 3D clumps: They contribute in a nonnegligible way to the mass loss, although they seem of limited importance for the wind-driving mechanism. The 3D lasting impact of a (hidden) companion: Unrecognized binary interaction has biased previous mass-loss rate estimates toward values that are too large. Only then will it be possible to drastically improve our predictive power of the evolutionary path in 4D (classical) spacetime of any star. [ABSTRACT FROM AUTHOR]

ABSTRACT: Volunteer corn occurrence with soybean is favored by the glyphosate-resistant (GR) corn cultivation preceding soybean and no-tillage systems. Volunteer corn interference causes significant losses in soybean grain yield. The levels of crop losses change with the corn density, origin, and time of emergence. High levels of weed interference in crops can result in the production of reactive oxygen species and lead to the occurrence of oxidative stress. The objectives of this study were to evaluate the effects of interference of (1) different origins (individual plants and clumps) and times of emergence of volunteer corn on soybean growth, yield components, and grain yield loss; and (2) if the volunteer corn interference causes oxidative stress in soybean. Field experiment and laboratory analyses were performed. The evaluated variables were soybean yield components, grain yield, hydrogen peroxide - H2O2 content, and antioxidant enzyme superoxide dismutase - SOD, catalase - CAT, and ascorbate peroxidase - APX activities. Volunteer corn interference reduced the yield components and soybean yield. The highest yield losses were observed with volunteer corn clumps regarding individual plants. The interference of volunteer corn emerged 10 days before or on the same day as soybean caused the greater yield losses than those emerged 10 days after, independently of its origin. The content of H2O2 and enzyme SOD, CAT and APX activities changed in soybean leaves in response to the interference of volunteer corn plants and clumps. However, the results indicate that the volunteer corn interferences does not cause oxidative stress in soybean.

Here we present the study on chemical properties of massive star forming clumps using N2H+(1-0), H13CO+(1-0), HCN(1-0) and HN13C(1-0) data from the literature [Astron. Astrophys. 563, A97 (2014)]. We found that abundances of H13CO+ and HN13C are affected by H2 column densities. As the median values of these two abundances increase by nearly 10 times from stages A to B, H13CO+ and HN13C are suitable for tracing the evolution of massive star forming clumps. The order of rapidity in growth of abundances of all the four studied molecules from stages A to B, is H13CO+, HCN, HN13C, and N2H+, from the highest to the lowest. Our results suggest that the observing optically thin molecular lines with high angular resolution are necessary to study the chemical evolution of massive star forming clumps. [ABSTRACT FROM AUTHOR]

Here, we briefly review possible indirect effects of dark matter (DM) of the universe. It includes effects in cosmic rays (CR): first of all, the positron excess at ∼ 500 GeV and possible electron–positron excess at 1–1.5 TeV. We tell that the main and least model-dependent constraint on such possible interpretation of CR effects goes from gamma-ray background. Even ordinary e + e − mode of DM decay or annihilation produces prompt photons (FSR) so much that it leads to contradiction with data on cosmic gamma-rays. We present our attempts to possibly avoid gamma-ray constraint. They concern with peculiarities of both space distribution of DM and their physics. The latter involves complications of decay/annihilation modes of DM, modifications of Lagrangian of DM-ordinary matter interaction and inclusion of mode with identical fermions in final state. In this way, no possibilities to suppress were found except, possibly, the mode with identical fermions. While the case of spatial distribution variation allows achieving consistency between different data. Also, we consider stable form of DM which can interact with baryons. We show which constraint such DM candidate can get from the damping effect in plasma during large-scale structure (LSS) formation in comparison with other existing constraints. [ABSTRACT FROM AUTHOR]

ABSTRACT: Volunteer corn is extremely competitive with soybean and the degree of interference varies with the corn density, time of emergence and origin. The objectives of this work were to determine the economic threshold (ET) of volunteer corn GR® F2 in soybean as a function of the time of emergence (same day and nine days after soybean) and origin (individual plants or clumps). Each clump was manually adjusted to have seven corn plants. Four field experiments were conducted in randomized blocks design with four replicates in Passo Fundo, RS, Brazil. The soybean yield losses (%) were calculated and adjusted to the model of the rectangular hyperbola and generated the parameters for the determination of the ET, that was calculated based on the volunteer corn control costs (US$ ha-1), efficiency of control (%), price paid for soybean (US$ kg-1) and soybean yield (kg ha-1). The ET mean was 0.3 and 0.48 for individual corn plants m-2 emerged together and nine days after soybean, and 0.08 and 0.03 m-2 for individual plants and clumps, respectively. Increases in grain yield and price paid for soybean, greater control efficiency of corn and lower control cost promote reduction in the ET of volunteer corn in soybean. The control of volunteer corn is justified in a density less than 0.5 individual plant m-2 and is close to zero when corn originates from clumps. Volunteer corn is one of the most competitive weed in soybean crops.

ABSTRACT: Dry bean cultivation after corn favors the occurrence of volunteer corn plants which interfere with the crop and cause yield losses of dry bean. Yield losses resulting from interferences caused by corn may be related to oxidative stress, which, in turn, is caused by the higher production of reactive oxygen species (ROS), such as hydrogen peroxide (H2O2). This work aimed to quantify H2O2 contents, and the activity of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) in dry beans under interference with densities of volunteer corn F2 originated from individual plants and clumps (seven corn plants emerged at the same point). Two experiments were carried out in a randomized blocks design with three replicates in Passo Fundo - RS, Brazil. Enzyme analysis was performed in a laboratory at 21, 35 and 46 days after dry bean emergence (DAE). Corn densities were 0, 0.5, 1, 2, 4, 8 and 12 plants or clumps m-2. The results show changes in H2O2 levels and in the activity of SOD, CAT, and APX enzymes with the increase of corn densities, in which the highest activity occurred for SOD. The interference of volunteer corn with dry beans alters the stress metabolism of dry bean but does not cause oxidative stress. The yield of dry beans reduced under interference with volunteer corn F2, but it is higher when the corn was originated from clumps.

ABSTRACT: Volunteer corn has high competitive capacity with bean, and the degree of interference varies as a function of corn density and origin (individual plant or clump). This study aimed to quantify bean yield losses under interference with densities of individual plants and clumps (seven plants at the same point) of GR® F2 volunteer corn and calculate the economic threshold (ET). Two experiments were carried out in a randomized blocks design with three replicates in Passo Fundo, RS, Brazil. The studied volunteer corn densities were 0, 0.5, 1, 2, 4, 8, and 12 individual plants and clumps m-2. The bean yield was assessed and calculated the yield losses (%) in response to volunteer corn interference. The yield loss data were fitted to the rectangular hyperbola model to generate the parameters for ET determining. ET was calculated as a function of cost (US$ ha-1) and control efficiency (%) of volunteer corn, the price paid for bean (US$ kg-1), and bean yield (kg ha-1). Interferences caused by densities of volunteer corn of 0.5, 1, and 2 individual plants and clumps m-2 in bean resulted in yield losses of 9%, 17%, and 30%, and 33%, 51%, and 70%, respectively. The ET of volunteer corn on bean was, on average, 0.21 individual plants m-2 and 0.04 clumps m-2. Increases in yield and price paid for beans, higher efficiency of volunteer corn control, and a decrease in costs of control promote a reduction in ET. Interferences caused by clumps resulted in higher bean yield losses than individual plants.

ABSTRACT: The cultivation of GR® maize prior to soybean, mainly in the no-tillage system favors the higher occurrence of GR® volunteer corn interfering in soybean crops. Volunteer corn originate from seeds that were lost during harvest or from non-harvested seeds from the field; these are individual seeds, originating individual plants, or several seeds adhered to segments of the rachis, which originate clumps. Volunteer corn in the form of clumps predominates in soybean crops, but little information about its effect on soybean is available in the literature. During two years, three experiments were carried out with the objective of evaluate the impact of the interference of GR® F2 generation volunteer corn populations coming from individual and clump seeds (seven corn plants emerged at the same point) over soybean yield components and grain yield. The results show that losses in soybean yield components and grain yield are influenced by the population and origin of volunteer corn. Clumps cause losses over 90% for populations above four clumps m-2, while the mean maximum loss observed for individual plants was 83% in the largest studied populations. Soybean yield decreased significantly when competing with populations below one plant or clump m-2, being 16% and 46% in the population of 0.5 individual plant and clump m-2, respectively.

A new methodology was developed to perform computer simulations of crushable rockfill particles using the discrete element method. Rockfill was modelled using a clump logic, responsible for providing a statistical and spatial variability in the strength and shape of the particles. Clumps have a major advantage of severely decreasing the number of contact equations to be solved in the model, resulting in less computer time. A series of single-particle crushing tests and an oedometer test were simulated using crushable particles and were in agreement with experimental data. A comprehensive study of the brittle failure of single-particle crushing tests is presented. [ABSTRACT FROM AUTHOR]

The article gives a quantitative assessment of the process of atoms diffusion activity by means of increasing the temperature based on the method of molecular dynamics simulation. The assessment is based on the formation of voids (dilatons) and condensations educed during the simulation process. As a result, the cooperative mechanism of diffusion will occur in defect-free crystal, whereas a combination of vacancy and cooperative mechanisms will be brought about in the crystal with vacancies. [ABSTRACT FROM AUTHOR]

This paper presents a new procedure to create numerical models considering grain shape and size as well as pore size in an explicit and stochastic equivalent manner. Four shape factors are introduced to reproduce shape and size of grains and pores. Thin sections are used to analyze grain shape and pore size of rock specimen. First, a particle-based numerical model is set up by best fitted clumps from a shape library according to thin sections. Finally, an equivalent Voronoi-based discrete element model is set up based on the superimposed particle model. Uniaxial compression and tensile tests are simulated for validation. Both tests indicate that grain boundaries and pores provide preferred paths of weakness for crack propagation, but they also reveal significant differences in terms of intra- and inter-granular fracturing. [ABSTRACT FROM AUTHOR]

Mycobacterium abscessus is a reemerging pathogen that causes pulmonary diseases similar to tuberculosis, which is caused by Mycobacterium tuberculosis. When grown in agar medium, M. abscessus strains generate rough (R) or smooth colonies (S). R morphotypes are more virulent than S morphotypes. In searching for the virulence factors responsible for this difference, R morphotypes have been found to form large aggregates (clumps) that, after being phagocytozed, result in macrophage death. Furthermore, the aggregates released to the extracellular space by damaged macrophages grow, forming unphagocytosable structures that resemble cords. In contrast, bacilli of the S morphotype, which do not form aggregates, do not damage macrophages after phagocytosis and do not form cords. Cording has also been related to the virulence of M. tuberculosis. In this species, the presence of mycolic acids and surface-exposed cell wall lipids has been correlated with the formation of cords. The objective of this work was to study the roles of the surface-exposed cell wall lipids and mycolic acids in the formation of cords in M. abscessus. A comparative study of the pattern and structure of mycolic acids was performed on R (cording) and S (non-cording) morphotypes derived from the same parent strains, and no differences were observed between morphotypes. Furthermore, cords formed by R morphotypes were disrupted with petroleum ether (PE), and the extracted lipids were analyzed by thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. Substantial amounts of trehalose polyphleates (TPP) were recovered as major lipids from PE extracts, and images obtained by transmission electron microscopy suggested that these lipids are localized to the external surfaces of cords and R bacilli. The structure of M. abscessus TPP was revealed to be similar to those previously described in Mycobacterium smegmatis. Although the exact role of TPP is unknown, our results demonstrated that TPP are not toxic by themselves and have a function in the formation of clumps and cords in M. abscessus, thus playing an important role in the pathogenesis of this species.

The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact that Mycobacterium tuberculosis presents a stable rough morphotype. Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear. Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes of Mycobacterium abscessus containing clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least 5 rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 hours post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 hours post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 hours post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors.

Mycobacterium abscessus is a reemerging pathogen that causes pulmonary diseases similar to tuberculosis, which is caused by Mycobacterium tuberculosis. When grown in agar medium, M. abscessus strains generate rough (R) or smooth colonies (S). R morphotypes are more virulent than S morphotypes. In searching for the virulence factors responsible for this difference, R morphotypes have been found to form large aggregates (clumps) that, after being phagocytozed, result in macrophage death. Furthermore, the aggregates released to the extracellular space by damaged macrophages grow, forming unphagocytosable structures that resemble cords. In contrast, bacilli of the S morphotype, which do not form aggregates, do not damage macrophages after phagocytosis and do not form cords. Cording has also been related to the virulence of M. tuberculosis. In this species, the presence of mycolic acids and surface-exposed cell wall lipids has been correlated with the formation of cords. The objective of this work was to study the roles of the surface-exposed cell wall lipids and mycolic acids in the formation of cords in M. abscessus. A comparative study of the pattern and structure of mycolic acids was performed on R (cording) and S (noncording) morphotypes derived from the same parent strains, and no differences were observed between morphotypes. Furthermore, cords formed by R morphotypes were disrupted with petroleum ether (PE), and the extracted lipids were analyzed by thin layer chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. Substantial amounts of trehalose polyphleates (TPP) were recovered as major lipids from PE extracts, and images obtained by transmission electron microscopy suggested that these lipids are localized to the external surfaces of cords and R bacilli. The structure of M. abscessus TPP was revealed to be similar to those previously described in Mycobacterium smegmatis. Although the exact role of TPP is unknown, our results demonstrated that TPP are not toxic by themselves and have a function in the formation of clumps and cords in M. abscessus, thus playing an important role in the pathogenesis of this species. [ABSTRACT FROM AUTHOR]

The study concerns the mechanics and water relationships of clumps of a species of endohydric moss, Polytrichastrum formosum., Anatomical and morphological studies were done using optical and scanning electron microscopy. Experiments on waterdrop capture and their distribution to adjacent shoots within a moss clump were performed with the experimental set-up for the droplet collision phenomena and ultra-high speed camera. The mechanical strength of the moss clump was tested on an electromechanical testing machine., During the process of moss clump wetting, the falling water drops were captured by the apical stem part or leaves, then flowed down while adhering to the gametophore and never lost their surface continuity. In places of contact with another leaf, the water drop stops there and joins the leaves, enabling their hydration. Mathematical analysis of anatomical images showed that moss stems have different zones with varying cell lumen and cell wall/cell radius ratios, suggesting the occurrence of a periodic component structure. Our study provides evidence that the reaction of mosses to mechanical forces depends on the size of the clump, and that small groups are clearly stronger than larger groups., The clump structure of mosses acts as a net for falling rain droplets. Clumps of Polytrichastrum having overlapping leaves, at the time of loading formed a structure similar to a lattice. The observed reaction of mosses to mechanical forces indicates that this phenomenon appears to be analogous to the 'size effect on structural strength' that is of great importance for various fields of engineering. [ABSTRACT FROM AUTHOR]

The rough morphotypes of non-tuberculous mycobacteria have been associated with the most severe illnesses in humans. This idea is consistent with the fact that Mycobacterium tuberculosis presents a stable rough morphotype. Unlike smooth morphotypes, the bacilli of rough morphotypes grow close together, leaving no spaces among them and forming large aggregates (clumps). Currently, the initial interaction of macrophages with clumps remains unclear . Thus, we infected J774 macrophages with bacterial suspensions of rough morphotypes of M. abscessus containing clumps and suspensions of smooth morphotypes, primarily containing isolated bacilli. Using confocal laser scanning microscopy and electron microscopy, we observed clumps of at least five rough-morphotype bacilli inside the phagocytic vesicles of macrophages at 3 h post-infection. These clumps grew within the phagocytic vesicles, killing 100% of the macrophages at 72 h post-infection, whereas the proliferation of macrophages infected with smooth morphotypes remained unaltered at 96 h post-infection. Thus, macrophages phagocytose large clumps, exceeding the bactericidal capacities of these cells. Furthermore, proinflammatory cytokines and granuloma-like structures were only produced by macrophages infected with rough morphotypes. Thus, the present study provides a foundation for further studies that consider mycobacterial clumps as virulence factors. [ABSTRACT FROM AUTHOR]

• Developed a numerical DEM framework that simulates flexural strength of PC. • Validated numerical simulations with lab experiments on various PC mix designs. • Assessed merits of using DEM to reduce experimentation and conserve materials. • Developed a promising DEM approach to simulate flexural responses of PC. Pervious concrete (PC) is a sustainable pavement material that has been widely used for low volume roads, walkways, and bicycle paths. Past literature studies have proposed several mix design methods to prepare PC with desired properties. However, the current mix design procedure involves substantial consumption of materials and is labor-intensive iterative process. Several numerical simulation studies used discrete element method (DEM) in simulating PC as a granular material (aggregates) coated with cement paste. Even though several researchers investigated mechanical properties such as compressive, flexural, and tensile strengths in the laboratory, and simulated the behavior of PC under compression and tensile loads, no known study has attempted simulating flexural response of PC. Given the significance of flexural strength in the pavement design process, it is essential to simulate the flexural behavior of PC. Therefore, the objective of this study was to develop a DEM framework to simulate PC mixtures and predict their flexural behavior by simulating the flexural strength test in a DEM based software YADE. A laboratory experimental program was conducted to obtain the experimental data required for calibration and validation of the proposed PC simulation model. In addition, a DEM program was developed to simulate the PC mixtures with the desired gradation and porosity levels, as achieved in the laboratory. A flexural strength test similar to ASTM C78 (1 MPa/s loading rate) was devised to simulate the flexural behavior of the prepared numerical PC specimens. The cohesive particle model in YADE was calibrated using experimental data and then used as the constituent model to simulate the interaction between cement coated aggregates in these flexural strength simulations. Overall, the proposed DEM approach could simulate the PC specimens with specified porosities and was able to predict the flexural response of the PC mixtures at 97% accuracy. It is envisioned that the proposed model could be further used to design PC mixtures with desired porosity and flexural strength properties instead of preparing trial mixtures, which would substantially reduce wastage of materials and human effort. [ABSTRACT FROM AUTHOR]

Abstract: Recently there has been renewed interest in understanding vortex patterns in superconductors and Bose–Einstein condensates, where the repulsive vortex–vortex interactions have an additional intermediate or long range attractive component. These states can arise in low-κ materials and may occur in multi-band superconductors. A combination of repulsive and attractive pairwise interactions can also occur in certain types of Bose–Einstein condensates and in magnetic superconductors. We show that when the pairwise interaction includes a long range attractive term, the ground state consists of a single vortex cluster. In the presence of pinning there is a well defined transition to a fragmented state as a function of pinning strength and density. We also demonstrate that in systems with intermediate range attraction and long range repulsion, ordered stripe and bubble phases occur. [Copyright &y& Elsevier]

Information is lacking on habitat and diversity of ectomycorrhizal (ECM) fungi of African humid forests. For three years, mushroom excursions were carried out in four sites with contrasted soil and altitude characteristics of South Cameroon, during wet seasons. Collected fungi were described in fresh state and dried exsiccates examined for microscopic description before morpho-anatomical identification. ECM fungi abundantly fruited exclusively in mixed caesalp, monodominant Gilbertiodendron and Uapaca forest clumps, independently of elevation, rainfall, topography and soil texture. 21 ECM tree species in 11 genera belonging to two families, Ceasalpiniaceae and Phyllanthaceae, dominated ECM forest clumps. More than 100 putative ECM fungal species in 27 genera were identified and assigned to seven families and one super family group. Members of Russulaceae and Amanitaceae recruited the highest number of ECM taxa, followed by species of Boletoids and Cantharellaceae. Paxillus, Clavulina, Coltricia, Scleroderma, Cortinarius and Inocybe genera contained limited species. 12 ECM fungal species were locally edible, including Lactarius gymnocarpus and all chanterelles. Though, species richness was very large in a mountainous area, all four sites shared a substantial large number of ECM mushroom species. Low plant diversity but high fungal richness recommends ECM forest clumps for biodiversity sanctuaries. [ABSTRACT FROM AUTHOR]

When plant populations are reduced to 5.0 to 7.0 plants m-2to conserve soil water, sorghum (Sorghum bicolorL. Moench) forms two to three tillers, but these often produce little grain. We hypothesized that under dryland conditions manipulating planting geometry into clumps spaced 0.75 m apart might result in greater yield by reducing the number of tillers and increasing the percentage of tillers that produce panicles compared with uniform spacing. A field study was conducted during 2007 at Bushland, Texas, with two planting geometries (clump vs. equidistant), two irrigation methods (LEPA vs. LESA) at three irrigation levels (dryland, 50 mm and 100 mm). Clump plants had only 0.6 tillers compared with 1.5 tillers per plant for rows. Tillers accounted for 33% of stover for the equidistant plants but only 23% of the grain under dryland. Our results suggest that growing sorghum in clumps may be a useful strategy in semiarid dryland areas. [ABSTRACT FROM AUTHOR]

Under dryland conditions of the Texas High Plains, increased tiller production in grain sorghum (Sorghum bicolor L. Moench) during early vegetative growth stages depletes stored soil water and potentially leads to severe water stress during the reproductive and grain-filling stages. The objective of this study was to understand how altered plant geometry and density affect light capture and determine tiller production in dryland grain sorghum clumps compared with uniformly spaced plants. Our data suggest that clump-planting geometry produced fewer tillers because of perception of lower red:far-red (R:FR) light ratio. In the Texas High Plains, planting sorghum seeds ≤2.5 cm apart in clumps of four plants seems to be a viable option to minimize tiller production, conserve water, and reduce plant water stress during later growth stages. [ABSTRACT FROM AUTHOR]

This paper briefly summarizes some of the practices being used in the semiarid U.S. Great Plains to grow crops without irrigation. Fallow periods are commonly used to increase the amount of plant-available water in the soil profile at the time of seeding a crop because growing-season precipitation is nearly always insufficient to produce economic grain yields. Maintaining plant residues on the surface as mulch has been very beneficial for this purpose. The most successful practices depend mostly on herbicides for controlling weeds during the fallow period and eliminating as much tillage as feasible. Reduced plant populations and, more recently, seeding plants in clumps rather than uniformly spacing plants in rows show some promise as useful strategies for reducing early vegetative growth so that more soil water is available during the grain-filling period late in the season. While these practices may not be applicable to other semiarid regions because of differences in soil, climatic, social, and economic conditions, some of the principles may apply and useful technologies can be developed. [ABSTRACT FROM AUTHOR]

Culm recruitment by semelparous bamboos has been reported to be severely depressed in the year prior to flowering, providing forewarning of flowering and subsequent die-off. However, supporting data are scant. We monitored productivity in 30 clumps in a wild stand of the riparian bamboo Bambusa arnhemica for four years, following which the clumps flowered and died. Stand-level productivity in the year prior to flowering was a minimum of 78% lower than previous years. However, the rate of depression was unevenly distributed, being close to 100% among clumps lower on the river bank and no more than 50% higher on the bank. This may be due to the impact of early and prolonged flooding in that year. Clumps high on the bank may have benefited from favourable conditions associated with above-average wet season rainfall, raising the possibility that resource allocation to vegetative growth and sexual reproduction in semelparous bamboos is flexible. [ABSTRACT FROM AUTHOR]

A study on population density, structure, distribution and early growth characteristics of Tarchonanthus camphoratus was carried out on a Tarchonanthus-dominated woodland. A line plot transect 4 km in length was laid out in a woodland along the altitudinal gradient capturing most of the observed vegetation variation. In total 34, 20 × 20 m plots were evaluated for their horizontal population structure and species composition. In addition, six more plots dominated by Tarchonanthus were monitored for coppice and shoot development for a period of 8 months. Understanding of growth and population characteristics of the dominant species in woodland is necessary for its effective management. Results indicate that the woodland can be delineated into three distinct stands by using cluster analysis based on location and composition. The diameter size class distribution of the woodland follows a reverse J curve, which indicate a normal uneven-aged forest. Tarchonanthus camphoratus has a high regenerative power after cutting or burning, which indicates its high potential for sustainable management. It was concluded that the woodland could be stratified into distinct stands for management. Permanent sample plots should be established to determine the sustained yield, as size-class distribution alone is insufficient. A management and utilization schedule based on distinct stands is recommended. [ABSTRACT FROM AUTHOR]

A pedagogical review of the historical development and current status (as of early 2000) of systematic statistical theories of plasma turbulence is undertaken. Emphasis is on conceptual foundations and methodology, not practical applications. Particular attention is paid to equations and formalism appropriate to strongly magnetized, fully ionized plasmas. Extensive reference to the literature on neutral-fluid turbulence is made, but the unique properties and problems of plasmas are emphasized throughout. Discussions are given of quasilinear theory, weak-turbulence theory, resonance-broadening theory, and the clump algorithm. The direct-interaction approximation (DIA) is developed as a central focus of the article, and its relationship to the earlier plasma theories is explained. Various methods of renormalized perturbation theory are described, then unified with the aid of the generating-functional formalism of Martin, Siggia, and Rose. A general expression for the renormalized dielectric function is deduced and discussed in detail. Modern approaches such as decimation and PDF methods are described. Derivations of DIA-based Markovian closures are discussed. The eddy-damped quasinormal Markovian (EDQNM) closure is shown to be nonrealizable in the presence of waves, and a new realizable Markovian closure is presented. The test-field model and a realizable modification thereof are also summarized. Numerical solutions of various closures for some plasma-physics paradigms are reviewed. The variational approach to bounds on transport is developed. Miscellaneous topics include Onsager symmetries for turbulence, the interpretation of entropy balances for both kinetic and fluid descriptions, self-organized criticality, statistical interactions between disparate scales, and the roles of both mean and random shear. Appendices are provided on Fourier transform conventions, dimensional and scaling analysis, the derivations of nonlinear gyrokinetic and gyrofluid equations, stochasticity criteria for quasilinear theory, formal aspects of resonance-broadening theory, Novikov''s theorem, the treatment of weak inhomogeneity, the derivation of the Vlasov and gyrokinetic weak-turbulence wave kinetic equation from a fully renormalized description, some features of a code for solving the DIA and related Markovian closures, the details of the solution of the EDQNM closure for a solvable three-wave model, and the notation used in the article. [Copyright &y& Elsevier]

This paper introduces the design and implementation of BCL-3, a high performance low-level communication software running on a cluster of SMPs (CLUMPS) called DAWNING-3000. BCL-3 provides flexible and sufficient functionality to fulfiil the communication requirements of fundamental system software developed for DAWNING-3000 while guaranteeing security, scalability, and reliability. Important features of BCL-3 are presented in the paper, including special support for SMP and heterogeneous network environment, semiuser-level communication, reliable and ordered data transfer and scalable flow control. The performance evaluation of BCL-3 over Myrinet is also given. [ABSTRACT FROM AUTHOR]