911 resultados para Limits to growth


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Weed biotypes resistant and susceptible to herbicides may have differences in their adaptive values. The aims of this study were to compare, under controlled and non-competitive condition, the growth analysis, germination features and seed weight of Fimbristylis miliacea (FIMMI) biotypes resistant and susceptible to acetolactate synthase (ALS) inhibiting herbicides. Experiments were conducted in a greenhouse and in a laboratory from October 2008 to February 2010. Two resistant biotypes (FIMMI 10 and FIMMI 12) and one susceptible biotype (FIMMI 13) were used for the studies. For the study on growth analysis, the treatments were arranged in a completely randomized experimental design with four replications and sampled at 21, 28, 35, 42, 49, 56, 69 days after emergence (DAE) and at flowering stage. For the studies on germination speed, germination and seed weight, the indexes for germination speed, percentage of germination at different temperatures and seed weight of the biotypes were determined. The results showed that the resistant biotype FIMMI 12 shows differences in all variables compared to the resistant biotype FIMMI 10 and compared to the susceptible biotype FIMMI 13, only for the evaluation at flowering. The susceptible biotype FIMMI 13 showed a higher germination speed index and higher germination rate when compared with the resistant biotypes. On the other hand, the resistant biotypes FIMMI 10 and FIMMI 12 showed higher seed weight.

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Sorghum, pearl millet, and Brachiaria ruziziensis have similar characteristics which have led to their use for mulch formation in no-till systems. This study was carried out to evaluate the potential of these three species as straw suppliers to suppress weed emergence. Initial findings led to the conclusion that both pearl millet and Brachiaria ruziziensis have similar or superior potential as weed suppressors, compared to sorghum straw, a species with recognized allelopathic potential. Subsequently, new trials were conducted under greenhouse conditions by sowing weed species in pots, followed by covering of the soil with the straw under evaluation. Independent experiments were conducted for Euphorbia heterophylla and Bidens pilosa. In each experiment, the factors analyzed were type of straw (pearl millet and B. ruziziensis), amount of straw (equivalent to 4 and 8 t ha-1 dry mass) and irrigation method (surface and subsurface). Both pearl millet and B. ruziziensis have shown to be species that can be cultivated to produce straw with allelopathic potential. These effects were effective in suppressing the emergence or early growth of E. heterophylla and B. pilosa. There was no difference in the suppression of emergence of these species when the soil cover level was alternated between 4 and 8 t ha-1 dry mass.

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ABSTRACT Understanding the critical period of weed competition is indispensable in the development of an effective weed management program in field crops. Current experiment was planned to evaluate the critical growth period ofSetaria and level of yield losses associated with delay in weeding in rain-fed drip irrigated wheat production system of Saudi Arabia. Field experiment was conducted to evaluate the effect of weeding interval (07-21, 14-28, 21-35, 28-42 and 35-49 days after sowing) and drought stress (75% and 50% of field capacity) on Setaria growth, wheat yield and water use efficiency. Season long weedy check and wellwatered (100% FC) plots were also maintained for comparison. Weeding interval and drought stress significantly (p ≤ 0.05) affected the growth and yield of Setaria and wheat. Drought stress from 75% to 50% FC resulted in reductions of 29-40% in Setaria height, 14-27% in Setaria density and 11-26% in Setaria dry biomass. All weeding intervals except 35-49 DAS significantly suppressedSetaria growth as compared with control. Delay in weeding increased weed-crop competition interval and reduced wheat yield and yield contributors. Therefore, the lowest yield of 1836 kg ha-1 was attained for weeding interval of 35-49 DAS at 50% FC. Water use efficiency and harvest index increased with decreasing FC levels but reduced with delay in weeding. Correlation analysis predicted negative association ofSetariadensity with wheat yield and yield contributors and the highest negative association was for harvest index (-0.913) and water use efficiency (-0.614). Early management of Setaria is imperative for successful wheat production otherwise yield losses are beyond economical limits.

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A field experiment was conducted for two consecutive years to study the effect of fertilizer application methods and inter and intra-row weed-crop competition durations on density and biomass of different weeds and growth, grain yield and yield components of maize. The experimental treatments comprised of two fertilizer application methods (side placement and below seed placement) and inter and intra-row weed-crop competition durations each for 15, 30, 45, and 60 days after emergence, as well as through the crop growing period. Fertilizer application method didn't affect weed density, biomass, and grain yield of maize. Below seed fertilizer placement generally resulted in less mean weed dry weight and more crop leaf area index, growth rate, grain weight per cob and 1000 grain weight. Minimum number of weeds and dry weight were recorded in inter-row or intra-row weed-crop competition for 15 DAE. Number of cobs per plant, grain weight per cob, 1000 grain weight and grain yield decreased with an increase in both inter-row and intra-row weed-crop competition durations. Maximum mean grain yield of 6.35 and 6.33 tha-1 were recorded in inter-row and intra-row weed competition for 15 DAE, respectively.

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The objective of this work was to evaluate the initial growth and the physiological characteristics of eucalypt submitted to different managements of signalgrass. The experiment was conducted in a protected environment, using a randomized blocks design with five repetitions. The treatments were arranged in a (5 x 2) + 1 factorial design, and the first factor corresponded to the types of weed management (no control; chemical control keeping the signalgrass shoot on the soil; chemical control with removal of the signalgrass shoot; mechanical control keeping the signalgrass shoot on the soil, and mechanical control with removal of the signalgrass shoot); the second factor corresponded to the two weeds species (U. brizantha and U. decumbens) and a control relative to the eucalypt in monoculture. The eucalypt growth was not affected by the presence of the Urochloa species until 50 days after treatments (DAT). However, the coexistence of these species with eucalypt for 107 DAT reduced the collar diameter, total dry matter, and the leaf area, but did not alter the characteristics related to photosynthesis and transpiration. The control method adopted, with removal or maintenance of the signalgrass shoot, regardless of species, did not change the initial eucalypt growth. It can be concluded that the coexistence of eucalypt with Urochloa decumbens or Urochloa brizantha for 105 days reduces the eucalypt growth. However, the use of chemical or mechanical control, with or without removal of signalgrass residue, were effective methods to prevent interference of these weeds.

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The Tradescantia micronucleus test is a sensitive bioassay for mutagenesis that may be employed both under field and laboratory conditions. This test has been standardized mostly on the basis of the results obtained with clone 4430. However, this clone is not well adapted to tropical weather, frequently showing problems with growth and flowering. In addition, it is attacked by parasites and insects, a fact that limits its use in field studies aiming at the biomonitoring of air pollution. In the city of São Paulo, Tradescantia pallida (Rose) Hunt. var. purpurea Boom is widely distributed as an ornamental plant in gardens and along roadsides and streets, mostly because of its natural resistance and its easy propagation. In this report, we present dose-response curves indicating that the sensitivity of T. pallida and clone 4430 to X-radiation (1, 10, 25 and 50 cGy) is similar. The results confirm our previous suggestion that T. pallida represents a good alternative for in situ mutagenesis testing in tropical regions, especially biomonitoring studies in which the exposure conditions may not be fully controllable.

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Changes in glutathione levels were determined in tissues of 11- to 12-week-old Swiss albino mice at different stages of Dalton's lymphoma tumor growth and following cisplatin (8 mg/kg body weight, ip) treatment for 24-96 h, keeping 4-5 animals in each experimental group. Glutathione levels increased in spleen of tumor-bearing compared to normal mice (9.95 ± 0.14 vs 7.86 ± 1.64 µmol/g wet weight, P<=0.05) but decreased in blood (0.64 ± 0.10 vs 0.85 ± 0.09 mg/ml) and testes (9.28 ± 0.15 vs 10.16 ± 0.28 µmol/g wet weight, P<=0.05). Dalton's lymphoma cells showed an increase in glutathione concentration (4.43 ± 0.26 µmol/g wet weight) as compared to splenocytes, their normal counterpart (3.62 ± 0.41 µmol/g wet weight). With the progression of tumor in mice, glutathione levels decreased significantly in testes (~10%) and bone marrow cells (~13%) while they increased in Dalton's lymphoma cells (28-46%) and spleen (15-27%). Glutathione levels in kidney, Dalton's lymphoma cells and bone marrow cells (8.50 ± 1.22, 4.43 ± 0.26 and 3.28 ± 0.17 µmol/g wet weight, respectively) decreased significantly (6.04 ± 0.42, 3.51 ± 0.32 and 2.17 ± 0.14 µmol/g wet weight, P<=0.05) after in vivo cisplatin treatment for 24 h. Along with a decrease in glutathione level, the glutathione-S-transferase (GST) activity also decreased by 60% in tumor cells after cisplatin treatment. The elevated drug uptake by the tumor cells under the conditions of reduced glutathione concentration and GST activity after treatment could be an important contributory factor to cisplatin's anticancer activity leading to tumor regression. Furthermore, lower doses of cisplatin in combination with buthionine sulfoximine (an inhibitor of glutathione synthesis) may be useful in cancer chemotherapy with decreased toxicity in the host.

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Repowering existing power plants by replacing coal with biomass might offer an interesting option to ease the transition from fossil fuels to renewable energy sources and promote a fur-ther expansion of bioenergy in Europe, on account of the potential to decrease greenhouse gas emissions, as well as other pollutants (SOx, NOx, etcetera). In addition, a great part of the appeal of repowering projects comes from the opportunity to reuse the vast existing invest-ment and infrastructure associated with coal-based power generation. Even so, only a limited number of experiences with repowering are found. Therefore, efforts are required to produce technical and scientific evidence to determine whether said technology might be considered feasible for its adoption within European conditions. A detailed evaluation of the technical and economic aspects of this technology constitutes a powerful tool for decision makers to define the energy future for Europe. To better illustrate this concept, a case study is analyzed. A Slovakian pulverized coal plant was used as the basis for determining the effects on perfor-mance, operation, maintenance and cost when fuel is shifted to biomass. It was found that biomass fuel properties play a crucial role in plant repowering. Furthermore, results demon-strate that this technology offers renewable energy with low pollutant emissions at the cost of reduced capacity, relatively high levelized cost of electricity and sometimes, a maintenance-intensive operation. Lastly, regardless of the fact that existing equipment can be reutilized for the most part, extensive additions/modifications may be required to ensure a safe operation and an acceptable performance.

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Children with chronic renal failure in general present growth retardation that is aggravated by corticosteroids. We describe here the effects of methylprednisolone (MP) and recombinant human growth hormone (rhGH) on the growth plate (GP) of uremic rats. Uremia was induced by subtotal nephrectomy in 30-day-old rats, followed by 20 IU kg-1 day-1 rhGH (N = 7) or 3 mg kg-1 day-1 MP (N = 7) or 20 IU kg-1 day-1 rhGH + 3 mg kg-1 day-1 MP (N = 7) treatment for 10 days. Control rats with intact renal function were sham-operated and treated with 3 mg kg-1 day-1 MP (N = 7) or vehicle (N = 7). Uremic rats (N = 7) were used as untreated control animals. Structural alterations in the GP and the expression of anti-proliferating cell nuclear antigen (PCNA) and anti-insulin-like growth factor I (IGF-I) by epiphyseal chondrocytes were evaluated. Uremic MP rats displayed a reduction in the proliferative zone height (59.08 ± 4.54 vs 68.07 ± 7.5 µm, P < 0.05) and modifications in the microarchitecture of the GP. MP and uremia had an additive inhibitory effect on the proliferative activity of GP chondrocytes, lowering the expression of PCNA (19.48 ± 11.13 vs 68.64 ± 7.9% in control, P < 0.0005) and IGF-I (58.53 ± 0.96 vs 84.78 ± 2.93% in control, P < 0.0001), that was counteracted by rhGH. These findings suggest that in uremic rats rhGH therapy improves longitudinal growth by increasing IGF-I synthesis in the GP and by stimulating chondrocyte proliferation.

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Basic fibroblast growth factor (bFGF) regulates skin wound healing; however, the underlying mechanism remains to be defined. In the present study, we determined the effects of bFGF on the regulation of cell growth as well as collagen and fibronectin expression in fibroblasts from normal human skin and from hypertrophic scars. We then explored the involvement of mitochondria in mediating bFGF-inducedeffects on the fibroblasts. We isolated and cultivated normal and hypertrophic scar fibroblasts from tissue biopsies of patients who underwent plastic surgery for repairing hypertrophic scars. The fibroblasts were then treated with different concentrations of bFGF (ranging from 0.1 to 1000 ng/mL). The growth of hypertrophic scar fibroblasts became slower with selective inhibition of type I collagen production after exposure to bFGF. However, type III collagen expression was affected in both normal and hypertrophic scar fibroblasts. Moreover, fibronectin expression in the normal fibroblasts was up-regulated after bFGF treatment. bFGF (1000 ng/mL) also induced mitochondrial depolarization in hypertrophic scar fibroblasts (P < 0.01). The cellular ATP level decreased in hypertrophic scar fibroblasts (P < 0.05), while it increased in the normal fibroblasts following treatment with bFGF (P < 0.01). These data suggest that bFGF has differential effects and mechanisms on fibroblasts of the normal skin and hypertrophic scars, indicating that bFGF may play a role in the early phase of skin wound healing and post-burn scar formation.

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Doxorubicin (DOX) was conjugated to a single-chain variable fragment (scFv) against human midkine (MK), and the conjugate (scFv-DOX) was used to target the chemotherapeutic agent to a mouse solid tumor model in which the tumor cells expressed high levels of human MK. The His-tagged recombinant scFv was expressed in bacteria, purified by metal affinity chromatography, and then conjugated to DOX using oxidative dextran (Dex) as a linker. The molecular formula of this immunoconjugate was scFv(Dex)1.3(DOX)20. In vitro apoptosis assays showed that the scFv-DOX conjugate was more cytotoxic against MK-transfected human adenocarcinoma cells (BGC823-MK) than untransfected cells (55.3 ± 2.4 vs 22.4 ± 3.8%) for three independent experiments. Nude mice bearing BGC823-MK solid tumors received scFv-DOX or equivalent doses of scFv + DOX for 2 weeks and tumor growth was more effectively inhibited by the scFv-DOX conjugate than by scFv + DOX (51.83% inhibition vs 40.81%). Histological analysis of the tumor tissues revealed that the highest levels of DOX accumulated in tumors from mice treated with scFv-DOX and this resulted in more extensive tumor cell death than in animals treated with the equivalent dose of scFv + DOX. These results show that the scFv-DOX conjugate effectively inhibited tumor growth in vivo and suggest that antigen-specific scFv may be competent drug-carriers.

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A mathematical model previously developed to study microbial growth in food products under an isothermal environment was adapted to a time-varying temperature regime. The resulting model was applied to study the growth of Clostridium perfringens in meat products. This micro-organism is of particular relevance to public health and economy due to the loss of productivity caused by it. Results showed a similar performance of the model used compared to the Baranyi model under an isothermal situation and a slightly better performance under a non-isothermal temperature profile.

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Digitalization and technology megatrends such as Cloud services have provided SMEs with a suitable atmosphere and conditions to internationalize and seek for further business growth. There is a limited amount of research on Cloud services from the business perspective and the limitations and challenges SMEs encounter when pursuing international business growth. Thus, the main research question of this study was how Cloud services may enable Finnish SMEs to overcome international growth challenges. The research question was further divided into three sub-questions dealing with matters related to features and characteristics of Cloud services, limitations and challenges Finnish SMEs experience when pursuing international growth of business, and benefits and advantages of utilizing Cloud services to mitigate and suppress international growth challenges. First, the theoretical framework of this study was constructed based on the existing literature on Cloud services, SMEs, and international growth challenges. After this, qualitative research approach and methodology were applied for this study. The data was collected through six semi-structured expert interviews in person with representatives of IBM, Exidio, Big Data Solutions, and Comptel. After analyzing the collected data by applying thematic analysis method, the results were compared with the existing theory and the original framework was modified and complemented accordingly. Resource scarcity, customer base expansion and retention, and lack of courage to try new things and take risks turned out to be major international growth challenges of Finnish SMEs. Due to a number of benefits and advantages of utilizing Cloud services including service automation, consumption-based pricing model, lack of capital expenditures (capex) and huge upfront investments, lightened organization structure, cost savings, speed, accessibility, scalability, agility, geographical expansion potential, global reaching and covering, credibility, partners, enhanced CRM, freedom, and flexibility, it can be concluded that Cloud services can help directly and indirectly Finnish SMEs to mitigate and overcome international growth challenges and enable further business growth.