Onset Of Competition Research Articles

Cell-scale biophysical determinants of cell competition in epithelia.

How cells with different genetic makeups compete in tissues is an outstanding question in developmental biology and cancer research. Studies in recent years have revealed that cell competition can either be driven by short-range biochemical signalling or by long-range mechanical stresses in the tissue. To date, cell competition has generally been characterised at the population scale, leaving the single-cell-level mechanisms of competition elusive. Here, we use high time-resolution experimental data to construct a multi-scale agent-based model for epithelial cell competition and use it to gain a conceptual understanding of the cellular factors that governs competition in cell populations within tissues. We find that a key determinant of mechanical competition is the difference in homeostatic density between winners and losers, while differences in growth rates and tissue organisation do not affect competition end result. In contrast, the outcome and kinetics of biochemical competition is strongly influenced by local tissue organisation. Indeed, when loser cells are homogenously mixed with winners at the onset of competition, they are eradicated; however, when they are spatially separated, winner and loser cells coexist for long times. These findings suggest distinct biophysical origins for mechanical and biochemical modes of cell competition.

Film Dokumenter Budaya Betawi Ondel-Ondel di Negeri Silancang Kuning Berdasarkan Sinematografi Teknik Pengambilan Gambar

The Betawi culture is increasingly marginalized because Jakarta is experiencing rapid urbanization, excessive so that the onset of competition in the world of work and many people Were going to leave his hometown to which many have worked such as Batam city. Batam city is one of the cities with high economic growth rates so that Betawi people come to Batam for getting job. Based on an initial survey, it shows that Betawi culture is not really famous among the citizens in Batam. This research aims to make a documentary film to provide information that is more apparent in dissemination to the public of the Betawi and Batam City Community. The film is a cinematographic technique which provides information used in the filming of documentaries. The film is packed into a CD that will be submitted to the Chairman of the Betawi forum in Batam and society Betawi of Batam City Community. Based on the try out, this film is well received and successfully gives information about the culture of the Betawi non Betawi and Betawi that exist in Batam city.

The effect of pH, electrolytes and temperature on the rhizosphere geochemistry of phytosiderophores

Background and aimsGraminaceous plants are grown worldwide as staple crops under a variety of climatic and soil conditions. They release phytosiderophores for Fe acquisition (Strategy II). Aim of the present study was to uncover how the rhizosphere pH, background electrolyte and temperature affect the mobilization of Fe and other metals from soil by phytosiderophores.MethodsFor this purpose a series of kinetic batch interaction experiments with the phytosiderophore 2′-deoxymugineic acid (DMA), a calcareous clay soil and a mildly acidic sandy soil were performed. The temperature, electrolyte concentration and applied electrolyte cation were varied. The effect of pH was examined by applying two levels of lime and Cu to the acidic soil.ResultsFe mobilization by DMA increased by lime application, and was negatively affected by Cu amendment. Mobilization of Fe and other metals decreased with increasing ionic strength, and was lower for divalent than for monovalent electrolyte cations at equal ionic strength, due to higher adsorption of metal-DMA complexes to the soil. Metal mobilization rates increased with increasing temperature leading to a faster onset of competition; Fe was mobilized faster, but also became depleted faster at higher temperature. Temperature also affected biodegradation rates of metal-DMA complexes.ConclusionRhizosphere pH, electrolyte type and concentration and temperature can have a pronounced effect on Strategy II Fe acquisition by affecting the time and concentration ‘window of Fe uptake’ in which plants can benefit from phytosiderophore-mediated Fe uptake.

Muscle contraction velocity, strength and power output changes following different degrees of hypohydration in competitive olympic combat sports.

BackgroundIt is habitual for combat sports athletes to lose weight rapidly to get into a lower weight class. Fluid restriction, dehydration by sweating (sauna or exercise) and the use of diuretics are among the most recurrent means of weight cutting. Although it is difficult to dissuade athletes from this practice due to the possible negative effect of severe dehydration on their health, athletes may be receptive to avoid weight cutting if there is evidence that it could affect their muscle performance. Therefore, the purpose of the present study was to investigate if hypohydration, to reach a weight category, affects neuromuscular performance and combat sports competition results.MethodsWe tested 163 (124 men and 39 woman) combat sports athletes during the 2013 senior Spanish National Championships. Body mass and urine osmolality (UOSM) were measured at the official weigh-in (PRE) and 13–18 h later, right before competing (POST). Athletes were divided according to their USOM at PRE in euhydrated (EUH; UOSM 250–700 mOsm · kgH2O−1), hypohydrated (HYP; UOSM 701–1080 mOsm · kgH2O−1) and severely hypohydrated (S-HYP; UOSM 1081–1500 mOsm · kgH2O−1). Athletes’ muscle strength, power output and contraction velocity were measured in upper (bench press and grip) and lower body (countermovement jump - CMJ) muscle actions at PRE and POST time-points.ResultsAt weigh-in 84 % of the participants were hypohydrated. Before competition (POST) UOSM in S-HYP and HYP decreased but did not reach euhydration levels. However, this partial rehydration increased bench press contraction velocity (2.8-7.3 %; p < 0.05) and CMJ power (2.8 %; p < 0.05) in S-HYP. Sixty-three percent of the participants competed with a body mass above their previous day’s weight category and 70 of them (69 % of that sample) obtained a medal.ConclusionsHypohydration is highly prevalent among combat sports athletes at weigh-in and not fully reversed in the 13–18 h from weigh-in to competition. Nonetheless, partial rehydration recovers upper and lower body neuromuscular performance in the severely hypohydrated participants. Our data suggest that the advantage of competing in a lower weight category could compensate the declines in neuromuscular performance at the onset of competition, since 69 % of medal winners underwent marked hypohydration.

Effect of Spacing Regimes on Growth, Yield, and Wood Properties ofTectona grandisat Longuza Forest Plantation, Tanzania

This study examined the effects of planting spacing on growth, yield, and wood properties of teak planted at square spacing regimes of 2 m, 3 m, and 4 m at Longuza Forest Plantation, Tanzania. To achieve this, tree, stand, and wood properties were studied at age of 14 years. Results showed that diameter at breast height and total height increased with increasing spacing. Mean annual increment increased significantly with increasing spacing while spacing did not have significant effect on total volume production and basal area. Basic density is also not affected by spacing while heartwood proportion increases as planting spacing increases. All studied wood properties (modulus of rupture, modulus of elasticity, compression strength tangential to grain, and shear tangential to the grain) except cleavage tangential to grain were not significantly affected by increasing spacing. It is recommended to use the spacing of 3 × 3 m, but if thinning can be done before onset of competition at 5 years, the currently used spacing of 2.5 × 2.5 m can still be used. However, the use of a spacing of 4 × 4 m can give at least 50% heartwood at shorter rotation age of 30 years.

FRUIT DRY WEIGHT AND QUALITY OF 'BING' SWEET CHERRIES GROWN WITHOUT SOURCE LIMITATIONS

Understanding the seasonal pattern of potential fruit growth is important for identification and timing of possible management operations, and quantification of this pattern is an important prerequisite to serve as input for crop growth models. `Bing? sweet cherry trees were heavily thinned at 63 degree-days (DD) (=8 days) after full bloom so weight and quality of the remaining fruit could be monitored under conditions of limiting and non-limiting carbohydrate supply. The effect of fruit thinning on mean shoot growth and trunk cross-sectional area also was analysed to detect possible translocation from reproductive to vegetative growth. Mean Fruit Dry Weight (MFDW) of tagged fruit was estimated weekly, based on fruit diameter, to identify the moment of the onset of competition between fruit within trees. At harvest, Fruit Number to Leaf Area Ratio (FNLAR, fruits m-2 LA) was 52% lower in heavily-thinned trees than in non-thinned trees. Yield per tree was higher (P

Comparison of 17-year realized plot volume gains with selection for early traits for loblolly pine ( Pinus taeda L.)

Diameter, height, survival, and per-hectare volume of loblolly pine ( Pinus taeda L.) at 9 years of age were evaluated as traits for indirect selection to improve per-hectare volume at age 17. Competition-induced mortality begins between these two ages, and the concern is that early selection may not account for family differences in competitive ability and thereby not maximize gains in stand volume after the onset of competition. Eight half-sib North Carolina families and one Mississippi–Alabama commercial check were grown in replicated single-family blocks at three spacings (1.5 m × 1.5 m, 2.4 m × 2.4 m, and 3.0 m × 3.0 m), and actual per-hectare volumes were determined at age 17. Family selections based on age 9 measurements were compared with the average for all families and the check to determine “realized” gains in age 17 stand volume. Early selection on age 9 diameter or volume per planted tree yielded the greatest realized gain in volume per hectare at age 17. The lack of family diameter and survival differences at age 9, before the onset of competition, reduced the effectiveness of early selection. Results suggest planting progeny tests at closer spacings may allow earlier observation of family differences in competitive ability and thereby improve genetic gains in stand productivity from early selection.

Alternative final states when Daphnia magna invades a system with Keratella cochlearis

The effect of Daphnia magna invasion on a system with Keratella cochlearis was studied with respect to the competition outcomes between these two planktonic species in cultures lasting for 75 days. Four Daphnia invasion events were carried out at different moments of Keratella population growth curve. We found that D. magna always displaced to + K. cochlearis when it was inoculated during the first period of growth curve (minimum rate was 1 individual of D. magna invading 1000 individuals of K. cochlearis). The ratio of competitors was decisive on the competition outcomes, because when Keratella could develop a large population before the onset of competition, this fact could tip the balance in favour of its persistence. Thus, when D. magna was inoculated during K. cochlearis stationary period (minimum rate in the invasion moment was 1 D: 6000 K in all these treatments) different alternative competitive results were observed: D. magna was excluded or K. cochlearis was excluded or they co-existed, reaching a ratio of 1 D: 300 K. Keratella exhibited two distinct models of growth dynamics and, depending on these dynamics, the competition result varied. We did not find statistically significant differences between population features (growth rate, fecundity, etc.) when comparing them among the different trajectories which promoted different competition outcomes. Although the implied competition mechanisms were known, their effect on competitors, and therefore on the competition outcomes, depended on population history (self-dynamics).

Differing selection in alternative competitive environments: shade-avoidance responses and germination timing.

Under competitive conditions, stem elongation in plants is thought to enhance fitness by increasing light interception. However, the onset of competition should vary with the species of competitor due to interspecific differences in timing of emergence and plant growth form. The fitness benefits of elongation may therefore depend on the timing of this plastic response. Phenotypic selection analyses and path analysis were used to evaluate selection acting on stem elongation at early and late life-history stages and the combination of germination timing and elongation in an annual plant. Velvetleaf (Abutilon theophrasti) were raised in one of three environments experienced by natural populations (cornfields; soybean fields; and disturbed, weedy sites). Due to the rapid growth rate and high density of plants in disturbed areas, selection to increase seedling-stage elongation was expected in weedy sites. Due to the wide spacing of crop plants, competition for light is initially low in cultivated fields, but intensifies as the season progresses. Selection for increased elongation at later nodes was expected in soybean fields because velvetleaf can often overtop soy and thereby increase leaf exposure. In contrast, selection against late elongation was expected in cornfields because velvetleaf are incapable of overtopping corn. Individuals that elongate would experience the carbon cost of allocating to structural tissue, but fail to experience a carbon return through increased light interception. The phenotypic selection analyses were consistent with these predictions and therefore support the role of stem elongation as an adaptation to interspecific competition. Selection also acted on the combination of germination timing and elongation. In the weedy environment, early emergence in conjunction with enhanced stem elongation conveyed the highest fitness. Reduced elongation was favored among individuals that emerged late, potentially because these individuals were unable to overtop neighbors. The results of this study demonstrate that the timing of stem elongation strongly affects competitive success. Environments that differ in the timing of competition for light select for elongation at different life-history stages, and this selection depends on the timing of emergence.

A new methodology for the provision of reserve in an isolated power system

New operating and planning policies are emerging in power utilities throughout the world with the onset of competition and deregulation. These new policies fundamentally differ from those previously implemented. In particular, the approach adopted to power system security is significantly different. Previously, power systems were operated to ensure a certain level of security was maintained at all times. In the new competitive markets, the balance between cost and security is a dominant factor. To illustrate this, a new economic dispatch methodology is proposed for a small isolated power system. This methodology enables the cost of providing sufficient reserves to just avoid load shedding following the loss of any given unit to be calculated and assessed against the risk and cost of load shedding. An illustrative test case is examined in this paper which considers the loss of the three largest units. The dispatch costs are calculated and compared to the cost and probability of load shedding to create a schedule consistent with the new utility policies.

Should Energy Users Pay for Their Utilities' Stranded Costs?

High-cost electric utilities face the same problem as did other high-cost equated industries at the onset of competition. Once, energy users, who are their customers, can choose their suppliers, utilities won`t be able to charge more for electricity than the competitive market price. The high-cost utilities will argue that they incurred their costs at the behest of regulators who ordered them to buy overpriced power from favored generators, who prevented them from marketing their product, and who demanded support of costly social and environmental programs. Changing the rules of the game now and leaving the utilities hanging seems unfair because, after all, they argue, they were only acting as good citizens. Can utilities somehow recover the difference between their total costs and market prices, now called ``stranded costs`` or, even better, ``stranded revenues?`` The author concludes that business acumen and technology--not regulation--will ultimately determine recovery of stranded costs.

Estimation of Critical Period of Weed Control

An estimation of the critical period of weed control is helpful in formulating appropriate weed-control strategies. A regression approach is presented to estimate the thresholds of critical period of weed control and time of equal interference (or time of onset of competition). In this approach, yields were either a linear or logistic function of the duration of weed-free and weed-infested periods. Confidence intervals of the thresholds of critical period and time of equal interference were determined for the linear model. An approximation to the standard error of critical period and associated confidence interval were given for any general form of the model. The method was applied to estimate the critical period of weed control in rainfed lentil using data from four field experiments conducted in Jordan. The relationship of yield with the duration of weed-free period was described by a linear function, whereas the relationship with the duration of weed-infested period showed a better fit with a logistic function. To maintain 90% of maximum seed yield, the maximum time allowed to let weeds grow after the crop emergence varied over locations from 4.8 to 5.8 wk. The same level could be achieved if the crop is kept free of weeds from its emergence until 12.1 to 14.1 wk; while the time when the same amount of yield would be achieved under both approaches varied from 7.7 to 9.3 wk after crop emergence. For straw yield, the time to get 90% of the maximum yield could vary over location from a maximum of 4.5 to 8.0 wk under weed-infestation and from at least 11.5 to 13.5 wk when weed-free. The time to achieve the same amount of straw under two systems of competition varied from 6.5 to 9.9 wk after crop emergence. One of the four experiments showed a longer critical period than the others for seed and straw yields.

Population Dynamic Consequences of Competitive Symmetry in Annual Plants

Asymmetric competition is a form of resource division among plants, in which large plants greatly suppress the growth of smaller neighbors. In annual plants, small size differences between seedlings at the onset of competition are magnified into large differences in seed-set by asymmetric competition. We formulate a novel neighborhood model, which reflects this seedling size effect as modified by the type of competitive symmetry. In the model, competition type is represented by a single, biologically meaningful parameter. We implement the model in a population growth model for two species, one at low density (the invader), and one at high density (the resident). The species are the same, except for their seedling biomass distributions. Under these conditions, we find that asymmetric competition always favors invasion by the species with lager average seedling size, but impairs invasion by the other species. Based on this invasibility criterion, we conclude that asymmetric competition always favors competitive exclusion in our model. However, by modifying some of the model assumptions, we suggest scenarios in which asymmetric competition may promote coexistence

Beyond liberalization III: Reforming universal service

At present, transfer within a telecommunications monopoly from some users to others support universal service. With the onset of competition in the USA, a complex system of contributory access charges, revenue pools and other devices has been added. Yet these arrangements are not suitable in a competitive environment. This article therefore develops an alternative system for the financing of universal service that is compatible with a multi-provider world. The proposal is for an accounting system that would debit a carrier's added value and credit its transfers to universal service schemes. It creates a fund to support portable vouchers for the benefited users and credits for low-density areas. It operates on the premise of competitive neutrality - equal rights and equal burdens to all carriers, and customer choice.

Agronomic modification of resource use and intercrop productivity

Suitable land areas for food production remain fixed or are diminishing, yet farmers and agronomists are faced with the task of increasing production. Raising productivity, through a more effective use of natural (e.g. light) and added (e.g. fertilizer) resources, is possible through intercropping, provided component crop demands for resources are well understood. Management of intercrops to maximize their complementarity and synergism, and to minimize competition between them follows simple natural principles, and its practice is limited only by the imagination of farmers and agronomists. Successful crop mixtures extend the sharing of available resources, over time and space, exploiting variation between component crops in such characteristics as rates of canopy development, final canopy width and height, photosynthetic adaptation of canopies to irradiance conditions and rooting depth. Occasionally, commensalism is effected. Loosely defined as one organism gaining benefits from another without damaging or benefiting it, it is exemplified when one crop modifies the microenvironment to suit another. Prime examples are the benefits of shading during crop, particularly transplanted crop, establishment under hot or dry conditions, the supply of nitrogen and solubilization of phosphorus by legumes for companion crops, and the suppression of weeds through direct competition or allelopathic effects. The onset of competition between intercrops can be delayed by judicious choice of relative planting dates. The differential influence of weather (in particular temperature) on component crop growth and development can be modified through reasoned planting dates, and relative proportions of crop component yields can be targeted. In general, to ensure its high yield the main crop should be planted first. Choice of plant population density and crop geometry, including row orientation, permits a planned sharing of natural resources and manipulation of competitiveness to suit targeted yields. Increases in rectangularity in the crop geometry of the main crop tends to enhance transmission of light to shorter crops for longer periods before canopy closure. Crops harvested for their vegetative yield appear less sensitive to supra-optimum population densities within mixtures than do seed crops. The period over which intercrops compete for resources can be shortened by the supply of external inputs, in as much as they permit greater exploitation of the finite supply of light. Supplementary irrigation has been shown to raise total productivity in various intercrop systems, but little research effort has been turned towards mineral nutrients. Addition of N fertilizer to legume intercrops reduces the relative over-yielding, i.e. compared to mixtures without N fertilizer, but not without overall improvement in total yield. Benefits of residual N on succeeding crops following legume intercrops are also not unsubstantial, and deserve attention when evaluating the merits of intercropping. In order to sustain enhanced productivity from intercrops, it will become increasingly more important to substitute natural resources where feasible for purchased inputs. Since the major focus of intercrop research has been on small-scale resource-poor systems, a serious gap in our knowledge on high input intercrop systems will hinder their rapid spread.

Evaluating the impact of competition using relative growth rate in red pine ( Pinus resinosa Ait.) stands

The development of red pine ( Pinus resinosa Ait.) stands originating in different spacings was analyzed using absolute growth rate (AGR) and relative growth rate (RGR) in diameter at breast height for several ages. The objectives were to determine whether RGR better reflected the effect of competition than AGR, and to interpret the relationship between RGR and tree size. While AGR was always positively related to tree size, RGR decreased with an increase in tree size before the onset of competition and when competition was not severe, and increased with tree size under severe competitive stress. This implied that small trees were more efficient than large trees at producing new biomass before the onset of competition. The effect of competition was to reduce the efficiency of small trees relative to large trees. It was concluded that RGR expressed the competitive status of stands better than AGR.

Competition and Allometry in Three Species of Annual Plants

Comparisons between competing and noncompeting populations of three annual plant species demonstrate that plant allometry is altered by competition. When plants are grown in isolation, relationships between stem diameter, height, and plant mass generally show simple allometry (i.e., the relationships are linear on log—log scale). When plants are competing, however, these relationships are curvilinear or discontinuous. We attempt to clarify the relationship between interindividual allometry (the usual source of allometric data) and allometric growth. When plants are not competing, the allometric relationships among individuals of different sizes at one point in time and the allometry of individual plants as they grow appear to be similar, but these two classes of allometric relationships are very different for competing plants. We present a simple model that explains both static and dynamic patterns of plant allometry in terms of (a) the allometric responses of individual plants to competition, and (b) the size dependence of growth after the onset of competition. Our results illustrate the importance of reciprocal interactions between competition and allometry, and emphasize the difficulty in making inferences from one size measure to another. We conclude that the commonly held assumption that plant size is a single entity, which can be reflected by any of several measures, may not be justified.

Competition of Spurred Anoda (Anoda cristata) and Velvetleaf (Abutilon theophrasti) with Cotton (Gossypium hirsutum) During Simulated Drought and Recovery

Cotton was grown alone (one plant/pot), in intraspecific competition (two plants/pot), and in interspecific competition with spurred anoda and velvetleaf in controlled-environment chambers, subjected to water stress by withholding water, and allowed to recover before the final harvest. Minimum leaf water potential reached during the drought period ranged from −1.87 MPa in cotton grown alone to −2.63 MPa in velvetleaf grown in intraspecific competition. Water stress reduced plant height, total dry weight, and leaf area in all species, compared to well-watered controls. Reductions in cotton growth due to intra- or interspecific competition were evident by 11 days following the onset of competition. The competitive impact of both weeds tended to increase with time. Growth reductions in cotton due to competition were associated primarily with reductions in leaf area duration; during drought the net assimilation rate also was reduced. Relative yields of cotton confirmed that interspecific competition from the weeds was more severe than intraspecific competition. Imposed drought did not affect the relative competitive abilities of the three species or the impact of the weeds on cotton.

WEED COMPETITION IN TRANSPLANTED SPRING CABBAGE

Summary. The presence of weeds during autumn and winter had no effect on the growth of transplanted spring cabbage provided they were removed before rapid growth of crop and weeds began in early spring. Weeds left beyond this time competed with the crop, resulting in smaller marketable heads. Increasingly severe competition affected internal head quality, reduced the numbers of plants producing heads and resulted in the death of a proportion of the crop plants. The main weed species responsible for crop loss was Stellaria media, which survived winter frosts and grew rapidly in early spring to fill all available ground space, dominating the weed flora and shading the crop foliage.Application of propachlor at planting time failed to give sufficient control of S. media to avoid crop loss, although the onset of competition was delayed. Trifluralin gave excellent control of S. media and resistant species were kept in check by the crop.Comparison of cropped and uncropped plots showed that the crop exerted considerable competitive pressure on the growth and development of weeds particularly where this had been reduced or delayed by herbicide treatment. The presence or absence of the crop did not, however, affect the relative proportions of the weed species, except on plots treated with trifluralin, where the crop suppressed Capsella bursa‐pastoris. Compétition des mauvaises herbes dans les choux de printemps repiqués