The Olsen P method as an agronomic and environmental test for predicting phosphate release from acid soils

The role of soil phosphorus (P) in the eutrophication of fresh water systems is well established. It is crucial therefore to assess the potential loss of P from soil in the various scenarios where soil can come into contact with water. To date, such assessment has often been based on soil P tests that are used for agronomic purposes (e.g. fertilizer recommendations). The purpose of this work was to examine the usefulness of one such test (viz. the Olsen test, which is based on extraction with bicarbonate) for predicting not only the amount of soil P available to plants, but also that which can be desorbed to water in a group of 32 Portuguese soils, of which 29 were acid and 3 calcareous. To this end, we (i) assessed the total amount of phytoavailable P in soil by successively pot-cropping Chinese cabbage, buckwheat and rye; and (ii) measured the amount of phosphate-P desorbed to a dilute electrolyte mimicking fresh water over periods of up to 218 days at soil:solution ratios of 1:100, 1:1000 and 1:10000. Total phytoavailable P and Olsen P were found to bear a quadratic relationship, with Olsen’s extractant underestimating the content in phytoavailable P of soils with high Olsen P contents relatively to soils with low contents. The “change point” at which phytoavailable P began to increase rapidly per unit change in Olsen P was 53 mg Olsen P kg⁻¹ soil. For the acid soils, a significant quadratic relationship was found between the amount of P desorbed to water and Olsen P at the three soil:solution ratios studied. However, these relationships became less significant when only the soils with an Olsen P value of less than 50 mg kg⁻¹ were considered. For the acid soils, the change point at which P input to water began to increase rapidly per unit change in Olsen P was 20, 61 and 57 mg kg⁻¹ at the 1:100, 1:1000 and 1:10000 ratio, respectively. At comparable Olsen P values, the calcareous soils released more phosphate to water than the acid soils. On the basis of our results, we suggest the following environmental threshold values for Olsen P in acid soils: 20 mg kg⁻¹ for P desorption scenarios where the soil:solution ratio is high (e.g. drainage water) and 50 mg kg⁻¹ for desorption scenarios where the soil:solution ratio is low (e.g., runoff, water in reservoirs). Both values are higher than the agronomic threshold above which plants are well supplied with P.     

Bioactivity-based screening methods for antibiotics residues: a comparative study of commercial and in-house developed kits

Two bioactivity-based screening methods for antibiotic residue analysis (FAST Antimicrobial Screening Test and PremiTest) were compared, in terms of sensitivity, with a new in-house developed tube test assay using Escherichia coli. Tests were performed using antibiotic standards, spiked samples and real incurred samples. The minimum inhibitory concentration (MIC) for several antibiotics was established and compared with maximum residue levels (MRLs) in samples. The results of all evaluated tests are compared with liquid chromatography-tandem mass spectrometry multi-residue screening tests to compare parameters such as sample preparation, cost, time of analysis and confidence in results. For all tests, values of half the maximum residue limit (0.5 × MRL) were considered as a satisfactory target for a screening method. The potential and limitations of each method are discussed to indicate more rational and effective strategies for high-throughput residue monitoring and surveillance programmes. It was concluded that bioactivity-based screening methods are a useful tool, but the best compromise between minimum performance limits, cost and selectivity must be taken into account. For laboratories equipped with mass spectrometry, multi-class screening methods provide more specific responses with high sensitivity.     

Homophily in higher education research: a perspective based on co-authorships

Scientometrics - Research collaborations are the norm in science today, and are usually evaluated using co-authorships as the unit of analysis. Research collaborations have been typically analyzed...     

Hierarchical clustering analysis for the distribution of origanum-oil components in dense CO<Subscript>2</Subscript>

Hierarchical Clustering (HC) technique is demonstratively applied to analyze the distribution and classification of essential-oil components in oil and dense (subcritical/supercritical) CO₂ phases. For this purpose, relative-equilibrium-distribution data obtained for the 24 characteristic components of origanum-oil (Origanum Munituflorum) at 35, 45, 55 °C and 20–110 atm pressure range are used. With 24 components and 25 different pressure levels at three different temperatures, the total number of data points amounts to 600, which is large compared to other similar works, making the task of drawing of conclusions by visual inspection quite tedious. As demonstrated in this work, the use of HC technique facilitates the classification of the distribution of essential-oil components. HC-based classification analysis helps to reveal that the distributions of monoterpenes are the most sensitive to changes in temperature and pressure, and they are more soluble in CO₂ especially in the supercritical region. At 35 °C, at higher pressures, due to high solvent density/power, almost all components show similar distributions in the CO₂ and oil phases, indicating the loss of fractionation potential. Deterpenation by CO₂ is more favorable at higher temperatures. Cophnetic correlation shows the significance level of data clustering. HC analysis proved to be a useful tool in classification of the components and in determination of component clusters in the dense-gas and liquid phases.     

A computer tool to support in design of industrial Ethernet

This paper presents a computer tool to support in the project and development of an industrial Ethernet network, verifying the physical layer (cables-resistance and capacitance, scan time, network power supply-POE’s concept ”Power Over Ethernet” and wireless), and occupation rate (amount of information transmitted to the network versus the controller network scan time). These functions are accomplished without a single physical element installed in the network, using only simulation. The computer tool has a software that presents a detailed vision of the network to the user, besides showing some possible problems in the network, and having an extremely friendly environment.     

Reconfigurable multi-mode sigma-delta modulator for 4G mobile terminals

A reconfigurable sigma-delta modulator, which is able to support the predictable standards for the fourth generation (4G) of mobile communication systems, is presented in this paper. This modulator was designed to cope with six different communications standards relying on a flexible architecture. Furthermore, the proposed architecture introduces the ability to process concurrently two different signals. The major design issues are outlined and operation modes are detailed. The feasibility of the presented solution is demonstrated using high-level system-level simulations as well as device-level simulations of the modulator implemented with switched capacitor circuits.     

Computer Modeling Explains the Structural Reasons for the Difference in Reactivity of Amine Transaminases Regarding Prochiral Methylketones

Amine transaminases (ATAs) are pyridoxal-5′-phosphate (PLP)-dependent enzymes that catalyze the transfer of an amino group from an amino donor to an aldehyde and/or ketone. In the past decade, the enzymatic reductive amination of prochiral ketones catalyzed by ATAs has attracted the attention of researchers, and more traditional chemical routes were replaced by enzymatic ones in industrial manufacturing. In the present work, the influence of the presence of an α,β-unsaturated system in a methylketone model substrate was investigated, using a set of five wild-type ATAs, the (R)-selective from Aspergillus terreus (Atr-TA) and Mycobacterium vanbaalenii (Mva-TA), the (S)-selective from Chromobacterium violaceum (Cvi-TA), Ruegeria pomeroyi (Rpo-TA), V. fluvialis (Vfl-TA) and an engineered variant of V. fluvialis (ATA-256 from Codexis). The high conversion rate (80 to 99%) and optical purity (78 to 99% ee) of both (R)- and (S)-ATAs for the substrate 1-phenyl-3-butanone, using isopropylamine (IPA) as an amino donor, were observed. However, the double bond in the α,β-position of 4-phenylbut-3-en-2-one dramatically reduced wild-type ATA reactivity, leading to conversions of <10% (without affecting the enantioselectivity). In contrast, the commercially engineered V. fluvialis variant, ATA-256, still enabled an 87% conversion, yielding a corresponding amine with >99% ee. Computational docking simulations showed the differences in orientation and intermolecular interactions in the active sites, providing insights to rationalize the observed experimental results.