Defoliation Impact on the Above and Belowground Productivity of \u3cem\u3eFestuca arundinaceae\u3c/em\u3e Schreb

The main objective of pasture management is to maximize plant productivity and ensure sustainable animal performance, without inducing pasture deterioration. Many researchers indicated that plant survival and sustainable production is a function of seedbed preparation, irrigation and defoliation, with defoliation having the largest impact on plant persistence (Fulkerson and Donaghy, 2001). The net effect of defoliation (degree of intensity and frequency) can therefore either be beneficial or detrimental to survival and productivity of a pasture. The aim of this study was to quantify the impact of different intensities and frequencies of defoliation on above- and belowground phytomass production of the cultivated pasture Festuca arundinaceae Schreb. under irrigation

Soil Seed Bank Study on Abandoned Fields and Semi-Arid Grassland, South Africa

Up to the 1980’s marginal soils in the central grasslands of South Africa were successfully ploughed for crop production, but unfortunately those soils soon proved to be uneconomical. Due to high input costs, low maize prices, and unreliable rainfall, the Department of Agriculture soon implemented the “soil conversion scheme” to promote the conversion of those ploughed marginal soils to permanent pastures. Regardless of the implementation the soil conversion scheme, many farmers unfortunately just abandoned some of these marginal fields, not establishing permanent pastures. This led to many hectares of unproductive previously cultivated fields, referred to as abandoned fields. It was noted that such abandoned fields do not recover to the same potential as the natural grassland of those areas. Therefore, it was decided to investigate a few such fields at a single location in a semi-arid climate of the Free State province, South Africa. The aim was to gain some knowledge on the dynamics of such disturbed ecosystems and identify the restoration potential of such situations. Amongst others, the soil seed bank was investigated to quantify the soil seed bank potential of abandoned fields, and why climax grass species do not establish voluntarily on these disturbed areas. The main aim was to quantify the differences in the soil seed bank between abandoned fields and natural grasslands, by investigating the research question: are there any climax grass species in the soil seed bank of abandoned fields available for grassland restoration

Bias-free Parameter Identification of a Fractional Order Model

This paper deals with the parameter identification of a fractional system considering a noisy observation of the output signal. The novelty is that the instrumental variable method is applied to the modulating function method applied to a fractional system. A simulated output signal which is not correlated to noise is required as the instrumental variable. Because all known simulation algorithms only consider zero initial conditions, the simulated output signal converges against the true output signal in an undefined time if the zero initial conditions are penalized. Therefore, an algorithm is extended with the short-memory principle. The benefit is that after a fixed time the error between the simulated and true output signal is small and can be used as the instrumental variable. Considering this extension of the simulation algorithms, it is shown that a consistent estimation is yield with the instrumental variable method

Interaction between a South African population of xiphinema index and different grapevine rootstocks

CITATION: Malan, A. P. & Meyer, A. J. 1993. Interaction between a South African population of xiphinema index and different grapevine rootstocks. South African Journal of Enology & Viticulture, 14(1):11-15, doi:10.21548/14-1-2169.The original publication is available at http://www.journals.ac.za/index.php/sajevThirty-one grapevine rootstocks were used to test for reproduction, root feeding symptoms and transmission of grapevine fanleaf virus by a South African population of Xiphinema index. Grapevine fanleaf virus was transmitted within four months to the roots and systemically spread within six months to the leaves of all the rootstocks tested. No root damage and a low reproduction rate of X. index were found on the rootstocks Harmony, Freedom and 1613 C, all which have V. Longii and Othello in their parentage.http://www.journals.ac.za/index.php/sajev/article/view/2169Publisher's versio

Port-Hamiltonian Modeling of Hydraulics in 4th Generation District Heating Networks

In this paper, we use elements of graph theory and port-Hamiltonian systems to develop a modular dynamic model describing the hydraulic behavior of 4th generation district heating networks. In contrast with earlier generation networks with a single or few heat sources and pumps, newer installations will prominently feature distributed heat generation units, bringing about a number of challenges for the control and stable operation of these systems, e.g., flow reversals and interactions among pumps controllers, which may lead to severe oscillations. We focus thus on flexible system setups with an arbitrary number of distributed heat sources and end-users interconnected through a meshed, multi-layer distribution network of pipes. Moreover, differently from related works on the topic, we incorporate dynamic models for the pumps in the system and explicitly account for the presence of pressure holding units. By inferring suitable (power-preserving) interconnection ports, we provide a number of claims about the passivity properties of the overall, interconnected system, which proves to be highly beneficial in the design of decentralized control schemes and stability analyses

Search Engine Advertising: Channel Substitution when Pricing Ads to Context

We explore substitution patterns across advertising platforms. Using data on the advertising prices paid by lawyers for 139 Google search terms in 195 locations, we exploit a natural experiment in “ambulance-chaser” regulations across states. When lawyers cannot contact clients by mail, advertising prices per click for search engine advertisements are 5%–7% higher. Therefore, online advertising substitutes for offline advertising. This substitution toward online advertising is strongest in markets with fewer customers, suggesting that the relationship between the online and offline media is mediated by the marketers' need to target their communications.NET Institut

Complementâ induced activation of the cardiac NLRP3 inflammasome in sepsis

Cardiac dysfunction develops during sepsis in humans and rodents. In the model of polymicrobial sepsis induced by cecal ligation and puncture (CLP), we investigated the role of the NLRP3 inflammasome in the heart. Mouse heart homogenates from shamâ procedure mice contained high mRNA levels of NLRP3 and ILâ 1β. Usingthe inflamm a some protocol, exposure of cardiomyocytes (CMs) to LPS followed by ATP or nigericin caused release of mature ILâ 1β. Immuno staining of left ventricular frozen sections before and 8 h after CLP revealed the presence of NLRP3 and ILâ 1β proteins inCMs. CLP caused substantial increases in mRNAs for ILâ 1β and NLRP3 in CMs which are reduced in the absence of either C5aR1 or C5aR2. After CLP, NLRP32/2 mice showed reduced plasma levels of ILâ 1βand ILâ 6. In vitro exposure of wildâ type CMs to recombinant C5a (rC5a) cause delevations in both cytosolic and nuclear/mitochondrial reactive oxygen species (ROS), which were C5aâ receptor dependent. Use of a selective NOX2 inhibitor prevented increased cytosolic and nuclear/mitochondrial ROS levels and release of ILâ 1β. Finally, NLRP32/2 mice had reduced defects in echo/Doppler parameters in heart afterCLP. These studies establish that the NLRP3 inflammasome contributes to the cardiomyopathy of polymicrobial sepsis.â Kalbitz, M., Fattahi, F., Grailer, J. J., Jajou, L., Malan, E. A., Zetoune, F. S., Huberâ Lang, M., Russell, M. W., Ward, P. A. Complementâ induced activation of the cardiac NLRP3 inflammasome in sepsis. FASEB J. 30, 3997â 4006 (2016). www.fasebj.orgPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154362/1/fsb2fasebj30120728r.pd