A model for water uptake by plant roots.

We present a model for water uptake by plant roots from unsaturated soil. The model includes the simultaneous flow of water inside the root network and in the soil. It is constructed by considering first the water uptake by a single root, and then using the parameterized results thereby obtained to build a model for water uptake by the developing root network. We focus our model on annual plants, in particular the model will be applicable to commercial monocultures like maize, wheat, etc. The model is solved numerically, and the results are compared with approximate analytic solutions. The model predicts that as a result of water uptake by plant roots, dry and wet zones will develop in the soil. The wet zone is located near the surface of the soil and the depth of it is determined by a balance between rainfall and the rate of water uptake. The dry zone develops directly beneath the wet zone because the influence of the rainfall at the soil surface does not reach this region, due to the nonlinear nature of the water flow in the partially saturated soil. We develop approximate analytic expressions for the depth of the wet zone and discuss briefly its ecological significance for the plant. Using this model we also address the question of where water uptake sites are concentrated in the root system. The model indicates that the regions near the base of the root system (i.e. close to the ground surface) and near the root tips will take up more water than the middle region of the root system, again due to the highly nonlinear nature of water flow in the soil

A mathematical model of plant nutrient uptake

The classical model of plant root nutrient uptake due to Nye. Tinker and Barber is developed and extended. We provide an explicit closed formula for the uptake by a single cylindrical root for all cases of practical interest by solving the absorption-diffusion equation for the soil nutrient concentration asymptotically in the limit of large time. We then use this single root model as a building block to construct a model which allows for root size distribution in a more realistic plant root system, and we include the effects of root branching and growth. The results are compared with previous theoretical and experimental studies

Adsorption and desorption dynamics of citric acid anions in soil

The functional role of organic acid anions (e.g. citrate, oxalate, malonate, etc) in soil has been intensively investigated with special focus either on (i) microbial respiration and soil carbon dynamics, (ii) nutrient solubilization, or (iii) metal detoxification. Considering the potential impact of sorption processes on the functional significance of these effects, comparatively little is known about the adsorption and desorption dynamics of organic acid anions in soils. The aim of this study therefore was to experimentally characterize the adsorption and desorption dynamics of organic acid anions in different soils using citrate as a model carboxylate. Results showed that both adsorption and desorption processes were fast, reaching a steady state equilibrium solution concentration within approximately 1 hour. However, for a given total soil citrate concentration(ctot) the steady state value obtained was critically dependent on the starting conditions of the experiment (i.e. whether most of the citrate was initially present in solution (cl) or held on the solid phase (cs)). Specifically, desorption-led processes resulted in significantly lower equilibrium solution concentrations than adsorption led processes indicating time-dependent sorption hysteresis. As it is not possible to experimentally distinguish between different sorption pools in soil (i.e. fast, slow, irreversible adsorption/desorption), a new dynamic hysteresis model was developed that relies only on measured soil solution concentrations. The model satisfactorily explained experimental data and was able to predict dynamic adsorption and desorption behaviour. To demonstrate its use we applied the model to two relevant scenarios (exudation and microbial degradation), where the dynamic sorption behaviour of citrate occurs. Overall, this study highlights the complex nature of citrate sorption in soil and concludes that existing models need to incorporate both a temporal and sorption hysteresis component to realistically describe the role and fate of organic acids in soil processes

Klassifizierung von pflanzlichen Produkten aus ökologischem und konventionellem Anbau durch Messung sekundärer Pflanzenstoffe

The content of secondary plant compounds in plants is influenced by various environmental factors. Cultivation and fertilization are factors which are characteristic for the farming system organic or conventional. Within a german governmental funded project (BÖL02OE170/F) carrot, maize and wheat samples from different farming systems (defined trials and farm pairs) are differentiated and classified using their polyphenolic and carotenoid contents and profiles, respectively. The samples from organic farming could be differentiated from samples which were conventionally grown as statistical significant for carrot and wheat samples in a two year repetition. The samples could be classified by both, polyphenolic as well as carotenoid profiles. The sum parameters only can not be applied for the differentiation and classification of the samples. Factors like cultivar and site have a strong influence on the classification. Therefore for the classification of the carrot samples according to the farming systems land site must be included

Challenges in imaging and predictive modeling of rhizosphere processes

Background Plant-soil interaction is central to human food production and ecosystem function. Thus, it is essential to not only understand, but also to develop predictive mathematical models which can be used to assess how climate and soil management practices will affect these interactions. Scope In this paper we review the current developments in structural and chemical imaging of rhizosphere processes within the context of multiscale mathematical image based modeling. We outline areas that need more research and areas which would benefit from more detailed understanding. Conclusions We conclude that the combination of structural and chemical imaging with modeling is an incredibly powerful tool which is fundamental for understanding how plant roots interact with soil. We emphasize the need for more researchers to be attracted to this area that is so fertile for future discoveries. Finally, model building must go hand in hand with experiments. In particular, there is a real need to integrate rhizosphere structural and chemical imaging with modeling for better understanding of the rhizosphere processes leading to models which explicitly account for pore scale processes

Ультразвуковой контроль качества заготовок в условиях металлургического предприятия

Целью работы является изучение возможности использования неразрушающего контроля качества металлопродукции с помощью ультразвуковой установки в условиях современного металлургического предприятия. Использование эхо–импульсного метода для испытания заготовок сечением 150х150 мм позволяет достаточно хорошо выявлять дефекты типа шлаковых включений, усадочной раковины, внутренних трещин и разрывов, расслоений. Анализ результатов ультразвукового контроля позволяет оценить уровень технологии производства и качества проката, определить ряд технических и организационных мер, обеспечивающих конкурентоспособность продукции.Метою роботи є вивчення можливості використання неруйнівного контролю якості металопродукції за допомогою ультразвукової установки в умовах сучасного металургійного підприємства. Використано ехо–імпульсний метод для контролю якості заготовок перетином 150х150 мм, що дозволяє достатньо надійно виявляти дефекти типу шлакових включень, усадкової раковини, внутрішніх тріщин і розривів, розшарувань. Аналіз результатів ультразвукового контролю дозволяє оцінити рівень технології виробництва і якості прокату, визначити ряд технічних і організаційних заходів, що забезпечують конкурентоспроможність продукції.The work purpose of not destroying quality assurance application possibility studying of metal products by means of ultrasonic apparatus in the conditions of the modern metallurgical enterprise. Application of an echo-impulse method for test of billet with the section 150х150 mm allows to reveal well enough defects of slag inclusions type, a pipe, internal cracks and ruptures, stratifications. The analysis of results of the ultrasonic control allows to estimate a technological level of manufacture and quality of rolled metal, to define a number of the technical and organizational measures providing competitiveness of production

Major depression with ischemic heart disease: Effects of paroxetine and nortriptyline on long-term heart rate variability measures

Background: Studies have linked depression to sudden death and serious cardiovascular events in patients with preexisting cardiac illness. Recent studies have shown decreased vagal function in cardiac patients with depression and depressed patients without cardiac illness. Methods: We compared 20-hour, sleeping, and awake heart period variability measures using spectral analysis, fractal dimension, and symbolic dynamics in two patient groups with major depression and ischemic heart disease (mean age 59-60 years) before and after 6 weeks of paroxetine or nortriptyline treatment. Results: Spectral measures showed decreases in awake and sleeping total power (TP: 0.0-0.5 Hz), ultra low frequency power (ULF: 0-0.0033 Hz), very low frequency power (VLF: 0.0033-0.04 Hz), and low-frequency power (LF: 0.04-0.15 Hz) for nortriptyline condition and a decrease in high-frequency power (HF: 0.15-0.5 Hz) for the awake condition in patients who received nortriptyline. A measure of nonlinear complexity, WC-100, significantly increased after paroxetine during the awake condition. Conclusions: These findings suggest that nortriptyline has stronger vagolytic effects on cardiac autonomic function compared with paroxetine, which is in agreement with previous clinical and preclinical reports. Paroxetine may have some cardio-protective effects, especially in cardiac patients

Assessment of processing technologies which may improve the nutritional composition of dairy products – Overview of progress

Among consumers there is a growing demand for food products with a natural nutritional-physiological advantage over comparable conventional products. As part of an EU funded project, ALP is examining the possible impact of processing on nutritionally valuable milk components, using the example of conjugated linoleic acids (CLA). The extent to which processing influences the CLA content of the end product was determined by literature research and own investigations of organic and conventional butter. Furthermore, new chemical, sensory-based and bio crystallization methods were evaluated by ALP and the University of Kassel to determine the oxidation stability of butter. In a further step the storage stability of CLA enriched and conventional butter was examined and the different methods will be compared. As a third objective a process for low-input CLA enrichment of milk fat (with a focus on alpine butter) has been developed. Since the process selected for the work is a physical enrichment process, it is accepted by international organic farming and food groups. Among the many benefits ascribed to CLA, it is believed to be an effective agent against cancer. The demand for foods with properties that promote human health is growing. The dairy industry has the opportunity to meet this demand by developing new dairy products with a nutritional-physiological function for the functional food market