Severe Limiting Factor Research Articles

EFFECT OF DROUGHT ON MORPHOPHYSIOLOGICAL TRAITS OF RICE: A REVIEW

Drought is the condition of prolonged paucity in the water supply, whether atmospheric, surface water, or groundwater. This significant abiotic stress is a severe limiting factor of plant growth and rice productivity, adversely affecting the economic rice production globally. Drought stress has a considerable effect on the rice plant’s morphological and physiological traits preventing it from reaching the maximum yield. Morphological alteration in rice includes inhibition of seed germination, reduced tillers, early maturity, reduced biomass while physiological changes involve restricted cell division and elongation, stomatal closure, loss of turgor adjustment, lower photosynthesis, slower growth rate, yield reduction, etc. The stress further brings about a biochemical change by accumulating stress metabolites, increasing Reactive Oxygen Species (ROS) accumulations, increasing antioxidative enzymes and, Abscisic acid (ABA) accumulation. Various mitigation measures are applied to adhere to the effect of drought on rice plants by selecting drought-tolerant cultivars, planting early varieties, sufficient moisture maintenance, conventional breeding, molecular maintenance, and development of varieties with high yielding attributes. Thus, this review aims to assess the complex responses of rice plants to drought in morpho-physiological characters of rice along with its mitigation strategies in adoption to drought stress.

Effect of phytochrome-mediated red light signaling on phosphorus uptake and accumulation in rice

ABSTRACT Phosphorus (P) is a macronutrient essential for plant growth and productivity. Plants uptake P as inorganic phosphate (Pi); however, in the natural ecosystem, Pi availability is frequently a severe limiting factor for plant growth. Thus, plants have evolved several mechanisms, such as the expression of Pi starvation-responsive genes, to adapt to Pi deficient conditions. Although we recently reported that phytochrome (Phy)-mediated red light signaling promotes Pi uptake by increasing expression levels of such genes in the model plant Arabidopsis, it remains elusive whether a similar mechanism exists in agricultural crops. In the present study, we analyzed the effects of red light signaling on Pi uptake in rice (Oryza sativa L.) using osphyA and osphyB single mutants, and the osphyA osphyB double mutant. Unlike osphyA seedlings, osphyB seedlings showed a reduction in Pi uptake and Pi content. Furthermore, illumination of wild-type seedlings with red light significantly promoted Pi uptake, whereas illumination with blue or far-red light did not. The osphyB mutant showed reduced expression levels of several Pi starvation-responsive genes including Pi transporter genes. Additionally, these phenotypes of osphyB knockout mutants were much more evident under Pi deficient conditions than under Pi sufficient conditions. Moreover, red light promoted Pi uptake in seedlings of other plant species including broccoli (Brassica oleracea L. var. italica) and lettuce (Latuca sativa L.). These results suggest that OsPhyB-mediated red light signaling promotes Pi uptake in rice by up-regulating the expression of Pi starvation response-associated genes, and this phenomenon may be conserved in a wide range of plant species.

Polarity Control in Ge Nanowires by Electronic Surface Doping.

The performance of nanoscale electronic and photonic devices critically depends on the size and geometry and may significantly differ from those of their bulk counterparts. Along with confinement effects, the inherently high surface-to-volume ratio of nanostructures causes their properties to strongly depend on the surface. With a high and almost symmetric electron and hole mobility, Ge is considered to be a key material extending device performances beyond the limits imposed by miniaturization. Nevertheless, the deleterious effects of charge trapping are still a severe limiting factor for applications of Ge-based nanoscale devices. In this work, we show exemplarily for Ge nanowires that controlling the surface trap population by electrostatic gating can be utilized for effective surface doping. The reproducible transition from hole- to electron-dominated transport is clearly demonstrated by the observation of electron-driven negative differential resistance and provides a significant step towards a better understanding of charge-trapping-induced transport in Ge nanostructures.

Characterization of CO2 fixation on algal biofilms with an infrared gas analyzer and importance of a space-rich structure on the surface

An attached microalgal culture system, or a biofilm system, which can reduce the cost of biomass recovery, is an attractive approach to solve the CO2 problem. In this study, we developed a method for precisely measuring CO2 fixation on algal biofilms, and optimized the photosynthetic capacity of a unicellular microalga, Chlorella. The CO2 concentration in the sample gas, measured with an infrared gas analyzer, was corrected by considering the difference in H2O concentration between the sample gas and the reference gas. The corrected CO2 concentration coincided with that of the reference gas, for which there were no cells. Using the established method, the photosynthetic capacity of Chlorella attached to a glass fiber membrane filter was characterized. Interestingly, the CO2 fixation rate per chlorophyll was almost the same as in liquid, at cell densities of up to 120 mg chlorophyll m−2. The light-dependency on the filter was very similar to that in liquid, while the photosynthetic rate was more markedly limited under low CO2 conditions than in liquid, suggesting that CO2 is a more severe limiting factor than light on the filter. The cell concentration-dependency of photosynthesis and microscopic observations suggest that photosynthesis is only performed by cells in a few top layers on the filter. To improve the CO2 supply, the solid surface was changed to a towel, which increased the photosynthetic rate in spite of its low optical transparency. The maximum rate of CO2 capture per area was estimated to be over 110 tons ha−1 year−1. These findings suggest that the Chlorella solid-surface culture system is a promising system for carbon capture, and that it can be further improved if the solid surface is converted into a steric structure with a high optical transparency.

Light Management: A Key Concept in High-Efficiency Perovskite/Silicon Tandem Photovoltaics.

The remarkable recent progress in perovskite photovoltaics affords a novel opportunity to advance the power conversion efficiency of market-dominating crystalline silicon (c-Si) solar cells. A severe limiting factor in the development of perovskite/c-Si tandems to date has been their inferior light-harvesting ability compared to single-junction c-Si solar cells, but recent innovations have made impressive headway on this front. Here, we provide a quantitative perspective on future steps to advance perovskite/c-Si tandem photovoltaics from a light-management point of view, addressing key challenges and available strategies relevant to both the 2-terminal and 4-terminal perovskite/c-Si tandem architectures. In particular, we discuss the challenge of achieving low optical reflection in 2-terminal cells, optical shortcomings in state-of-the-art devices, the impact of transparent electrode performance, and a variety of factors which influence the optimal bandgap for perovskite top-cells. Focused attention in each of these areas will be required to make the most of the tandem opportunity.

Health Concerns of Various Nanoparticles: A Review of Their in Vitro and in Vivo Toxicity.

Nanoparticles (NPs) are currently used in diagnosis and treatment of many human diseases, including autoimmune diseases and cancer. However, cytotoxic effects of NPs on normal cells and living organs is a severe limiting factor that hinders their use in clinic. In addition, diversity of NPs and their physico-chemical properties, including particle size, shape, surface area, dispersity and protein corona effects are considered as key factors that have a crucial impact on their safe or toxicological behaviors. Current studies on toxic effects of NPs are aimed to identify the targets and mechanisms of their side effects, with a focus on elucidating the patterns of NP transport, accumulation, degradation, and elimination, in both in vitro and in vitro models. NPs can enter the body through inhalation, skin and digestive routes. Consequently, there is a need for reliable information about effects of NPs on various organs in order to reveal their efficacy and impact on health. This review covers the existing knowledge base on the subject that hopefully prepares us better to address these challenges.

A CNN-Based Fusion Method for Feature Extraction from Sentinel Data

Sensitivity to weather conditions, and specially to clouds, is a severe limiting factor to the use of optical remote sensing for Earth monitoring applications. A possible alternative is to benefit from weather-insensitive synthetic aperture radar (SAR) images. In many real-world applications, critical decisions are made based on some informative optical or radar features related to items such as water, vegetation or soil. Under cloudy conditions, however, optical-based features are not available, and they are commonly reconstructed through linear interpolation between data available at temporally-close time instants. In this work, we propose to estimate missing optical features through data fusion and deep-learning. Several sources of information are taken into account—optical sequences, SAR sequences, digital elevation model—so as to exploit both temporal and cross-sensor dependencies. Based on these data and a tiny cloud-free fraction of the target image, a compact convolutional neural network (CNN) is trained to perform the desired estimation. To validate the proposed approach, we focus on the estimation of the normalized difference vegetation index (NDVI), using coupled Sentinel-1 and Sentinel-2 time-series acquired over an agricultural region of Burkina Faso from May–November 2016. Several fusion schemes are considered, causal and non-causal, single-sensor or joint-sensor, corresponding to different operating conditions. Experimental results are very promising, showing a significant gain over baseline methods according to all performance indicators.

Personality type of homicide offenders based on psychiatrist expert reviews

Despite the relatively prudent regulations and dissuasive punishments worldwide, the number of homicide offenses are not decreasing. In my study those psychiatrist expert opinions were reviewed, which were created in closed homicide cases in the institute of forensic medicine of Debrecen over five years from 2007.The subject of my study was that what kinds of personalities these crime offenders have, and whether they were in a pathological mental state while committing the crime. The majority of the offenders were from the most active age group between 20 and 40, for the victims, however, the opposite can be said, as the most common homicide acts were committed against the older age group, because due to their age they are less able to defend themselves than the truly active age group. Out of 25 committers, 9 had psychiatric treatment in its antecedents – mostly suicidal intentions or attempts, alcohol dependence or depressive episode. Among the cases examined, antisocial personality disorder was only made probable in 42% of the perpetrators; however, it was not qualified as restrictive factor in neither case.43.5% of the offenders were under the influence of alcohol at the time of committing the act, and 58.3% had no criminal record before.The public believes about the homicide offenders that only people with abnormal mental condition can commit them – however, based on the reviewed psychiatrist expert opinions, the limitation of imputation ability can rarely be established professionally. Milder or more severe limiting factor were established in only 12% of the offenders.Disclosure of interestThe author has not supplied his declaration of competing interest.

EVALUASI KESESUAIAN LAHAN TANAMAN KAYU PUTIH KABUPATEN BURU, PROVINSI MALUKU

Maluku province is also famous as a producer of cajeput oil in Indonesia’s number one, but its potential until now have not been optimally utilized in accordance with the carrying capacity of land for public welfare. Melaleuca Cajeputi Roxb have not managed intensively as industrial plants, consequently low production. Based on the results of land suitability assessment, pewilayahan eucalyptus trees on the island of Buru include areas that are not so large, that is 188,743 ha or 20.60% of the total area of the island of Buru, with the details:Land is very suitable (S1) covering 54,832 hectares, or 6 percent of the total land area,mainly scattered in the northern part of Buru District, the floodplain physiography. Enough suitable land class (S2) on Buru Island reached a total area of 45,404 hectares of territory, with the main limiting factor is the rainfall and slope. Class marginal land suitable (S3) with severe limiting factor on regional conditions and slope roots reach a total area of 88,507 hectares.Class of land not available for this moment (N1) reached 513,937 hectares with a very heavy barrier so that if the current efforts will be made to harm the environment or very costly. Spread primarily on physiography tectonics with sloping hills more than 25 percent and its height more than 400 m above sea level. Land Not Available forever (N2) are lands that have very severe limiting factor, so for good both physically and economically impossible to be undertaken.Keywords: capability, suitability, land, cajuput oil

Illumina sequencing reveals a rhizosphere bacterial community associated with foxtail millet smut disease suppression

Smut disease is a severe limiting factor in foxtail millet production, caused by the Ustilago crameri fungus. The aim of this study is to characterize specific bacterial populations that might contribute to smut disease suppression. Rhizosphere bacterial community compositions of three foxtail millet cultivars differing in smut disease resistance were compared using high throughput Illumina sequencing. As a disease-resistant cultivar, Jigu20 showed the lowest disease incidence (0.7 %) after Ustilago crameri inoculation, compared with 14.8 % and 62.5 % for Jingu21 and Changnong35, respectively. Under the Ustilago crameri-inoculation condition, higher bacterial diversity was present in the rhizosphere of Jigu20 (I.Ji20) than in other two soil samples (I.Jin21 and I.Chang35). The same trend was observed in enzyme activities of phosphatase, catalase, and polyphenol oxidase. Compared to I.Jin21 and I.Chang35, I.Ji20 harbored higher abundance of Actinobacteria, while lower abundance of Bacteroidetes and Firmicutes. At the genus level, the hierarchical cluster of I.Ji20 was clearly separated from I.Jin21 and I.Chang35. Pearson’s correlation analysis showed that the abundance of Bradyrhizobium and Streptomyces was negatively correlated with smut disease incidence (P < 0.05). Different smut resistant cultivars occupied different rhizosphere bacterial communities, and smut disease suppression might be correlated with high bacterial diversity.

Demography, breeding success and effects of nest type in artificial colonies of Red-footed Falcons and allies

Abstract Shortage of breeding sites is an important limiting factor of bird populations. Artificial breeding platforms, nest-boxes or man-made twig nests often present solutions with remarkable results, however long-term sustainability of these populations remains to be resolved. Furthermore, the question whether the inference of results of studies conducted on birds breeding in artificial breeding sites can be generalized to other populations, still remains open. Here we present the history, and the results of a 20 year old (1995-2015) nest-box programme initiated to increase potential breeding possibilities of Red-footed Falcons in an area, where nest-site shortage was a severe limiting factor. We show how various other species (Jackdaws, Kestrels and Long-eared Owls) have utilized these resources, and present descriptive statistics on their reproductive performance. Analysing the data of a total of 1432 breeding attempts, we show that Red-footed Falcons have similar clutch sizes, and nesting success (i.e. ratio of nests with at least on fledgling), however fledging success (ratio of the number of eggs/fledged nestlings) was different in artificial nest-boxes. When we excluded closed box types from artificial nests, this difference was not apparent. In case of Kestrels (n=1626 breeding attempts) clutch size was significantly higher in artificial nests, while we found no difference in fledging or nesting success. When only comparing open boxes to natural nests, the difference in clutch size was no longer significant. We also analysed the effect of nest box design on reproductive parameters of the two species using regression trees. Inter annual effects were the most important in shaping clutch size and fledging rate of both falcon species, however we also found nest-box design effects, but only in Red-footed Falcons. In years when mean clutch size was high, these birds had lower clutch size in an older, darker nest-box type compared to an alternative design, and to open boxes. However, fledging rate in the same years was lower for both open boxes and older nest-boxes. We conclude that artificial colonies are an important and successful tool in Red-footed Falcon conservation, and that the breeding parameters measured in artificial colonies depend on nest-box design. We present correlative evidence that closed boxes have a significant positive species specific effect on reproduction, probably due to their protection against weather. We also show that birds may have a preference for a certain nest-box design, and that the breeding success in the less favoured box type may be similar to that in open nests. We recommend that future studies incorporate nest-type and nest-box design effects in all comparisons made on reproductive performance in case of Red-footed Falcons and Kestrels.

Detecting discontinuities in GNSS coordinate time series with STARS: case study, the Bologna and Medicina GPS sites

Global navigation satellite systems (GNSS) data are a fundamental source of information for achieving a better understanding of geophysical and climate-related phenomena. However, discontinuities in the coordinate time series might be a severe limiting factor for the reliable estimate of long-term trends. A methodological approach has been adapted from Rodionov (Geophys Res Lett 31:L09204, 2004; Geophys Res Lett 31:L12707, 2006) and from Rodionov and Overland (J Marine Sci 62:328–332, 2005) to identify both the epoch of occurrence and the magnitude of jumps corrupting GNSS data sets without any a priori information on these quantities. The procedure is based on the Sequential t test Analysis of Regime Shifts (STARS) (Rodionov in Geophys Res Lett 31:L09204, 2004). The method has been tested against a synthetic data set characterized by typical features exhibited by real GNSS time series, such as linear trend, seasonal cycle, jumps, missing epochs and a combination of white and flicker noise. The results show that the offsets identified by the algorithm are split into 48 % of true-positive, 28 % of false-positive and 24 % of false-negative events. The procedure has then been applied to GPS coordinate time series of stations located in the southeastern Po Plain, in Italy. The series span more than 15 years and are affected by offsets of different nature. The methodology proves to be effective, as confirmed by the comparison between the corrected GPS time series and those obtained by other observation techniques.

EVALUASI KESESUAIAN LAHAN TANAMAN TOMAT DI NAGARI AIA DINGIN KECAMATAN LEMBAH GUMANTI KABUPATEN SOLOK

This study aims to evaluate land suitability of tomato plants and create maps of land suitability of tomato plants in the Valley of the Nagari Aia Cold Gumanti Solok District. Soil at the sites is soil that develops Andisol of volcanic rocks. The unit of analysis in this study is the suitability of tomato crop land in Nagari Aia Cold Valley Gumanti Solok District. Corresponding map of the location of the study Nagari cold Aia Valley Gumanti Solok District 1: 50,000 scale in order to get the five points that the samples Jorong Data, Jorong Koto, Jorong Aia Sonsang (dryland) and Jorong Aia Sonsang and Jorong Data (wetland / paddy). The data analysis conducted in the field and in the laboratory by means of matching between the quality or characteristics of the land on condition of growing tomato plants. To calculate the indices of climate and land use methods Storie and Square Root. Land suitability assessment in the five study sites representing the Valley of the Nagari Aia Cold Gumanti Solok district to Jorong Data and Jorong Koto land suitability classes N1, there is a severe limiting factor in the availability of water is rainfall and potential of mechanization the slopes as well as nutrient retention is pH, but This can be enhanced S3 (marginally suitable) for tomato plants is by liming and terracing, guludan / beds and mulching. In the area of fitness classes land Jorong Aia Sonsang the N2, the limiting factor on the slopes there are very heavy so it can not be repaired. Jorong Aia Sonsang and Jorong Data, (wetland / paddy) land suitability class S3m classified, there are severe limiting factor in the availability of water is rainfall, but this can be upgraded to S2 (moderately suitable) for tomato plants, by taking into account the condition of the lowest rainfall based on agricultural climate zones.

Influence of Mode Loss on the Feasibility of Grating-Assisted Optical Fiber Surface Plasmon Resonance Refractive Index Sensors

In this paper, the influence of mode loss on the feasibility of grating-assisted optical fiber surface plasmon resonance (SPR) refractive index (RI) sensors is investigated. The loss of surface plasmon polarition (SPP) mode plays a key role in the design and implementation of such sensors. It is demonstrated through simulation that the grating length should be smaller than or comparable with the propagation length of SPP mode in order to achieve effective coupling. The loss of SPP mode is the severe limiting factor for the implementation of the grating-assisted SPR-RI sensors. More generally, in order to achieve effective mode coupling with the help of waveguide grating, the grating length is bounded by the shortest propagation length of the modes in lossy waveguides.

Improving metabolic stability of cancer chemoprotective polyphenols

Dietary flavonoids and other polyphenols have the potential to be developed as effective food supplements as well as drugs for the prevention, as well as treatment of, cancer and other disease conditions. However, their very poor oral bioavailability, mainly due to extensive conjugation by glucuronidation and sulfation, is a severe limiting factor. First, this review shows the use of a simple, commercially available model system, the human hepatic S9 fraction, by which metabolic stability can be assessed effectively and accurately. Second, permethylation of the polyphenols effectively blocks the metabolic conjugation reactions, thereby dramatically increasing both metabolic stability and intestinal absorption, while maintaining or even increasing the biologic activities. Thus, permethylated polyphenols may have a future as chemoprotective agents.

Universal spin-polarization fluctuations in one-dimensional wires with magnetic impurities

We study conductance and spin-polarization fluctuations in one-dimensional wires with spin-5/2 magnetic impurities (Mn). Our tight-binding Green function approach goes beyond mean field thus including s-d exchange-induced spin-flip scattering. In a certain parameter range, we find that spin flip suppresses conductance fluctuations while enhancing spin-polarization fluctuations. More importantly, spin-polarization fluctuations attain a universal value 1/3 for large enough spin flip strengths. This intrinsic spin-polarization fluctuation may pose a severe limiting factor to the realization of steady spin-polarized currents in Mn-based 1D wires.

Nonlinear theory of short-wavelength free-electron lasers.

The nonlinear evolution of free-electron laser (FEL) amplifiers is studied for infrared and shorter wavelengths. The configuration of interest consists in the propagation of an energetic electron beam through a drift tube in the presence of a periodic wiggler magnetic field with planar symmetry. A three-dimensional formulation is derived in which the electromagnetic field is represented as an expansion of Gaussian optical modes. Since the wiggler model is characterized by planar symmetry, the Gauss-Hermite modes are used for this purpose. A set of nonlinear differential equations is derived for the evolution of the amplitude and phase of each mode, and they are solved simultaneously in conjunction with the three-dimensional Lorentz force equations for an ensemble of electrons in the presence of the magneto-static wiggler, self-electric and self-magnetic fields due to the charge and current distributions of the beam, and the electromagnetic fields. It is important to note that no wiggler average is used in the integration of the electron trajectories. This permits the self-consistent modeling of effects associated with (1) the injection of the beam into the wiggler, (2) emittance growth due to inhomogeneities in the wiggler and radiation fields as well as due to the self-fields, (3) the effect of wiggler imperfections, and (4) betatron oscillations. The optical guiding of the radiation field is implicitly included in the formulation. This approach has important practical advantages in analyzing FELs, since it is necessary only to characterize the beam upon injection into the wiggler, and the subsequent evolution is treated self-consistently.Numerical simulations are performed for two examples corresponding to an infrared FEL at wavelengths near 3.5 \ensuremath{\mu}m, and an x-ray FEL operating in the neighborhood of 1.4 \AA{} wavelengths corresponding to the proposed linear coherent light source (LCLS) at the Stanford Linear Accelerator Center. Results for both cases indicate that the more severe limiting factor on the performance of the FEL is the beam emittance. For the infrared example, the transition to the thermal regime occurs for an axial energy spread of \ensuremath{\Delta}${\ensuremath{\gamma}}_{\mathit{z}}$/${\ensuremath{\gamma}}_{0}$\ensuremath{\approxeq}0.19%, and optimal performance is obtained for \ensuremath{\Delta}${\ensuremath{\gamma}}_{\mathit{z}}$/${\ensuremath{\gamma}}_{0}$0.1% and \ensuremath{\gamma} is the relativistic factor. This restriction is more severe for the LCLS parameters, for which the thermal transition is found for \ensuremath{\Delta}${\ensuremath{\gamma}}_{\mathit{z}}$/${\ensuremath{\gamma}}_{0}$\ensuremath{\approxeq}0.05% and optimal performance requires \ensuremath{\Delta}${\ensuremath{\gamma}}_{\mathit{z}}$/${\ensuremath{\gamma}}_{0}$\ensuremath{\le}0.01%. Wiggler imperfections are found to be a much less important constraint on FEL design. Simulations indicate that there is no coherent ``walkoff'' of the beam from the symmetry axis due to wiggler imperfections, and that the radiation field is sufficiently guided by the interaction that no severe degradation is found in the extraction efficiency or growth rate for moderate levels of wiggler fluctuations.

Human recombinant granulocyte‐macrophage colony stimulating factor (hrGM‐CSF) improves double hemibody irradiation (DHBI) tolerance in patients with stage III multiple myeloma: A pilot study

Double hemibody irradiation (DHBI) is an alternative treatment of stage III multiple myeloma (MM) in patients aged over 55 years. Toxic side-effects such as myelosuppression are a severe limiting factor to its use. We performed DHBI associated with human recombinant granulocyte-macrophage colony stimulating factor (hrGM-CSF) as support therapy in 10 patients with stage III MM to improve the tolerance to this treatment. Ten patients received subcutaneously 5 micrograms/kg/d of hrGM-CSF during 2 weeks after each course of hemibody irradiation. All these patients had stage III MM: eight previously received chemotherapy, six of them were regarded as patients with refractory MM and two with relapse. Two patients received DHBI as first-line treatment. hrGM-CSF increased safety and tolerance of DHBI. GM-CSF support reduced the mean time between upper body irradiation (UBI) and lower body irradiation (LBI): 41 v 108 d in a cohort of 32 patients previously treated without growth factor support. Overall there was no lethal infection with hrGM-CSF or granulocytopenia (5.0 x 10(9)/l v 0.4 x 10(9)/l at day 15 in patients without growth factor). hrGM-CSF also reduced stomatitis grading and thrombocytopenia (90 x 10(9)/l v 45 x 10(9)/l at day 15). Furthermore, hrGM-CSF increased blood colony forming unit-granulocyte macrophage (CFU-GM) and was well tolerated in all but one patient. hrGM-CSF reduces toxic side-effects of DHBI, thus providing an effective treatment in patients with advanced and resistant MM.

FALL BROCCOLI PRODUCTION USING MICRONUTRIENTS IN A SUSTAINABLE SYSTEM

Arkansas soils can range in pH from the low 4's to 7 depending on the location and liming history. Deficiency of zinc, boron and molybdenum coupled with the soil acidity complex of manganese toxicity had been previously identified as a severe limiting factor in production of quality brassica crops on our farmer cooperator's land. Building on the results reported here in 1991, the fall 1991 broccoli study focused on the effect of including/not including micronutrients in the watering solution during the greenhouse growth phase coupled with/without micronutrients in the transplant water. Additional treatments looked at the contribution of individual micronutrients to the final yield. The final yields of the boron, zinc and magnesium treatments were found to contribute approximately 75-80% of the final yield of a full range micronutrient solution. Research supported by a LISA grant.

System identification for yield limits and hardening moduli in discrete elastic-plastic structures by nonlinear programming

The paper deals with the inverse (system identification) problem for discrete structures with elastic-plastic piece wise-linear behaviour. It is shown that elastic limits and hardening moduli can be identified on the basis of information on displacements, when a structure is subjected to a given set of proportional loads. The problem is solved through the minimization of a non-convex objective function under nonlinear inequality constraints. Simulated tests show that convergence towards local minima is likely and that different sets of parameters may lead to identical displacements; this difficulty can be circumvented by a fairly high number of measurements and/or by means of several load conditions; good results, generally, are provided by two load conditions. The numerical simulations, however, show that computing times tend to be very high (much more than for the corresponding analysis problem). As an alternative method, the iterative procedure known as the least-squares linear-Taylor differential-correction technique is envisaged and some numerical experience is briefly discussed. This method can be implemented by an easily programmable computer code with rather small storage requirements, but the performance and the efficiency of the first procedure are more promising. On the basis of the numerical results, it can be claimed that the present mathematical programming approach offers a general solution method for the problem discussed, but a severe limiting factor is represented by computation time.