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An analysis of the external pressure coefficient on the surface of a ruin in different flow directions is presented. The ruin has almost cube-like proportions with an open roof plane and a destroyed corner. Flow simulations were performed using 3D Time Steady RANS and compared with experimental results from the boundary layer wind tunnel at the Slovak University of Technology in Bratislava. The optimal turbulence model and internal mesh settings were selected based on their statistical evaluation. For an evaluation of the critical directions of the wind flow around the ruin, the values of the external wind pressure coefficient were obtained from the selected calculation model and settings.

The characteristics of aerodynamic forces acting on an elliptic cylinder with an aspect ratio of 0.5 with a wind attack angle from 0 to 90° and subjected to the boundary layer wind tunnel were investigated. The model was initially calibrated and compared with the existing work. The aspect ratio of the investigated model was 0.5, and the model was emerging in a turbulent flow. The mean and fluctuating drag and lift coefficients were investigated. The minimum drag coefficient occurred in the wind direction of 0° and the maximum at 90°. The lift coefficient was the largest in the 30° wind direction and the smallest at 0°. Fluctuating coefficients were similar profiles as the mean coefficients. Around the 30° wind direction, an inappropriate phenomenon occurred, caused by the generation of asymmetrical vortices structures and wake instabilities.

The value of the total aerodynamic resistance of the structure is depended on the values of the highly variable coefficients of external pressure, the quantification of which is a typical task of aerodynamics of structures solved on a rigid model in a wind tunnel. The aim of the paper is to analyze the distribution of wind pressure on a 150 m high chimney of a nuclear power plant. Due to today’s changing climate and the emergence of unwanted windstorms, it is necessary to pay increased attention to tall and slender structures, where the effects of wind play an important role. The effect of wind, the influence of the terrain and surrounding structures has a significant impact on the safety of the chimney, which is a part of the nuclear power plant, where increased safety is required not only for the chimney itself but also for buildings in its immediate vicinity. Surrounding structures can modify wind flow and cause increased chimney load. Experimental measurements were performed in the STU BLWT wind tunnel in Bratislava, where the influence of the changing terrain, as well as the influence of the surrounding objects on the external wind pressure coefficients at different altitude levels were monitored.

The article presents the aerodynamic study of solar panel assemblies and determination of wind load. In the first part, the task is solved by computer simulation of the wind flow around the proposed rectangular assembly in the scale of 1:1 using the FLUENT ANSYS program; realization of experimental measurements in the wind tunnel with a boundary layer (BLWT) in Bratislava is presented subsequently. The aim of the solution was to determine the maximum pressure and suction wind load on top and bottom surfaces of panels. The resulting net pressure coefficient represents the maximum local pressure in each panel row as maximum values from all wind directions. The experimentally obtained net pressure coefficient values were compared with computer simulation and the procedures mentioned in standard STN EN 1991-1-4. It can be seen that the inner panels are loaded considerably less than the standard defines. The panels placed on the side of the assembly or on the edge of the aisle are loaded significantly more than the standard defines. Frontal panels are also less wind stressed than in the standard defines.

The wind flow around the elliptical object was investigated experimentally in the BLWT wind tunnel in Bratislava and subsequently solved by computer wind flow simulation. On a high-rise building model, the external wind pressure coefficients were evaluated for different wind directions and then compared with the numerical CFD simulation in ANSYS, where different models of turbulence and mesh types were used. The aim of the article was to evaluate and compare the obtained values and after analysing the results to choose the most suitable model of turbulence and mesh types, which showed the smallest deviations from the experimental values.

The article deals with aerodynamic study of solar panel assemblies. Experimental measurements were realized in BLWT wind tunnel. The aim of the solution was to determine the maximum pressure and suction wind load on top and bottom surfaces of panels. The resulting net pressure coefficient represents the maximum local pressure in each panel row as maximum values from all wind directions. The experimentally obtained cp,net values were compared with the conservative values in EN 1991-1-4 for open monopitch canopies. A lower wind load in the inner regions of the triangular assemblies should be used in the design of fixing supports.

The article deals with the numerical analysis of the wind pressure distribution on a group of two high-rise buildings of different shape for different wind directions. The first building has the shape of a circular cylinder and the second was created by a combination of semicircles and a longitudinal member. The floor plan of the second building was similar to the letter S. The simulations were realized as 3D steady RANS. CFD results were compared with experimental measurements in the wind tunnel of the Slovak University of Technology in Bratislava. The results were processed using statistical methods such as correlation coefficient, fractional bias and fraction of data within a factor of 1.3, which determined the most suitable CFD model. The purpose of the present article was to verify the distribution of the external pressure coefficient on scale models at a scale of 1:350, which are located in the Atmospheric Surface Layer (ASL). In numerical modeling, the most important thing was to ensure similarity with the flow in the experimental Atmospheric Boundary Layer (ABL) and with the flow around the models. SST k–ω was evaluated as the most suitable turbulent model for the given type of problem. Turbulent models had a decisive influence on the overall distribution of external wind pressures on objects. The results showed that the most suitable orientation of the objects in terms of the external wind pressure coefficient is 0°, when the cylinder produced a shielding effect, with min mean cpe = −0.786. The most unfavorable wind effects were shown by the wind direction of 90° and 135° with the value min mean cpe = −1.361.

The interference effects on the distribution of external wind pressure coefficient between two high-rise buildings with an elliptical cross section were studied experimentally at the Boundary Layer Wind Tunnel (BLWT) at the Faculty of Civil Engineering STU in Bratislava, Slovakia. Various arrangements of models, which were derived from the breadth ratio, were investigated. The peak value of the external wind pressure coefficient for a stand-alone model was measured and compared with the peak value in the case of interference. The measurements showed that the wind loads on buildings in a close vicinity are considerably different from those on a stand-alone building. The interference effects significantly affect negative pressure zones. The optimal and critical arrangements of buildings were evaluated. The elimination of peak negative external wind pressure coefficients can be reduced by half. On the other hand, the interference effects had a strong impact on increasing the peak value of the negative external wind pressure coefficient, which can be more than roughly double compared to an isolated building.

Brassinosteroids (BRs) are plant-specific steroid hormones that play essential roles in the regulation of many important physiological processes in plant life. Their extremely low concentrations (~pmoles/g FW) in plant tissue and huge differences in polarity of individual members within the BR family hamper their detection and quantification. To address this problem, an immunoaffinity sorbent with broad specificity and high capacity for different BR metabolites containing a monoclonal antibody (mAb) against a BR spacer (20S)-2α,3α-dihydroxy-7-oxa-7α-homo-5α-pregnane-6-one-20 carboxylic acid (BR4812) was used for the rapid and highly selective isolation of endogenous BRs containing a 2α,3α-diol in ring A from minute plant samples. This enrichment procedure was successfully applied as a sample preparation method prior to quantitative analysis of BRs in real plant tissues by ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). Use of immunoaffinity chromatography (IAC) increased the sensitivity of the UHPLC-MS/MS analysis owing to improvements in the BR signal-to-noise ratio (S/N) and matrix factor (MF). Although MF values of BRs analyzed in classical samples ranged from 8.9% to 47.4%, MF values for the IAC purified samples reached 44.5-96.6%. Thus, the developed IAC-UHPLC-MS/MS approach was shown to be a simple, robust, effective and extremely fast procedure requiring minute amounts of plant samples suitable for the quantitative profiling of many BR metabolites, helping to overcome the major problems associated with their determination in very complex plant matrices., (Copyright © 2017 Elsevier B.V. All rights reserved.)

The herbicide 2,4-D exhibits an auxinic activity and therefore can be used as a synthetic and traceable analog to study auxin-related responses. Here we identified that not only exogenous 2,4-D but also its amide-linked metabolite 2,4-D-Glu displayed an inhibitory effect on plant growth via the TIR1/AFB auxin-mediated signaling pathway. To further investigate 2,4-D metabolite conversion, identity and activity, we have developed a novel purification procedure based on the combination of ion exchange and immuno-specific sorbents combined with a sensitive liquid chromatography-mass spectrometry method. In 2,4-D treated samples, 2,4-D-Glu and 2,4-D-Asp were detected at 100-fold lower concentrations compared to 2,4-D levels, showing that 2,4-D can be metabolized in the plant. Moreover, 2,4-D-Asp and 2,4-D-Glu were identified as reversible forms of 2,4-D homeostasis that can be converted to free 2,4-D. This work paves the way to new studies of auxin action in plant development.

Sulfonamide antibiotics coming from both human and veterinary medicine are among the most common emerging pollutants in freshwater. The present paper shows the successful application of passive sampling using POCIS in combination with an immunochemical ELISA technique and HPLC/MS/MS analysis to study the distribution of sulfonamides in streams around small towns in the Czech Republic, as well as around a major agglomeration of the city of Brno, including its waste water treatment plant (WWTP). Results indicated the presence of sulfonamides at most studied sites with concentrations ranging from <20 up to 736 ng of sulfamethoxazole equivalents per POCIS. Very high levels were detected in both the influent and effluent of the Brno WWTP with maxima > 8000 ng SMX per POCIS. All samplers collected down-stream of the studied towns and WWTPs clearly showed an increase in sulfonamide drug residues. Higher concentrations were determined in rivers at the city of Brno agglomeration. In agreement with other available studies, these findings indicate low efficiency of conventional WWTPs to eliminate polar pharmaceuticals such as sulfonamides. Good performance and correlation with the LC/MS results, as well as ease of use, indicate good potential for the immunochemical ELISA technique to become the screening tool for sulfonamide determination in surface waters including passive samplers.

Polar organic compound integrative samplers (POCIS) in combination with instrumental techniques such as LC-MS-MS were previously used to monitor environmental pollutants but the performance of alternative immunochemical methods such as ELISA (enzyme-linked immunosorbent assay) has been explored less. In the present study, POCIS technology was applied to surface water sampling in the Czech Republic, and ELISA was used as a detection technique for the herbicide atrazine. In the first study, 28 samples from streams around small municipal waste water treatment plants (WWTPs) were collected using two different devices (POCISpest and POCISpharm) over the course of 21 days. Elevated atrazine concentrations (up to 25 ng per POCIS) were found in samples down-stream of WWTPs. This observation was also confirmed in another two year study (4 sampling periods) investigating 7 river sites around a major city of Brno as well as the inlet and outlet of the city's WWTP. High atrazine levels were systematically determined at the outlet from the WWTPs (120-605 ng per POCIS). A decreasing trend in the atrazine concentrations in rivers around the city of Brno has been observed, with the highest levels observed within the first sampling period in spring 2007 (100-600 ng per POCIS, with an extreme value of 2760 ng per POCIS). Results of the atrazine ELISA were closely correlated with LC-MS/MS, which confirmed good applicability of ELISA as a cost-effective screening tool.

The sensitivity of antibody/hapten-based labeling systems is limited by the natural affinity ceiling of immunoglobulins. Breaking this limit by antibody engineering is difficult. We thus attempted a different approach and investigated if the so-called bridge effect, a corecognition of the linker present between hapten and carrier protein during antibody generation, can be utilized to improve the affinity of such labeling systems. The well-known haptens 2,4-dinitrophenol (2,4-DNP) and 2,4-dichlorophenoxyacetic acid (2,4-D) were equipped with various linkers, and the resulting affinity change of their cognate antibodies was analyzed by ELISA. Anti-2,4-DNP antibodies exhibited the best affinity to their hapten when it was combined with aminobutanoic acid or aminohexanoic acid. The affinity of anti-2,4-D antibodies could be enhanced even further with longer aliphatic spacers connected to the hapten. The affinity toward aminoundecanoic acid-2,4-D derivatives, for instance, was improved about 100-fold compared to 2,4-D alone and yielded detection limits as low as 100 amoles of analyte. As the effect occurred for all antibodies and haptens tested, it may be sensible to implement the bridge effect in future antibody/hapten-labeling systems in order to achieve the highest sensitivity possible.

The notorious degradation susceptibility of peptides is a major obstacle to their use as medicinal drugs. Assays with which the stability of peptides in complex proteolytic environments can be determined are thus indispensable for peptide drug development. Herein, we describe a new peptide proteolysis assay that meets that demand. It unites the high-throughput capacity of heterogeneous with the well-defined kinetic characteristics of homogeneous assay formats and operates on the cleavage-caused loss of a detection handle. We have confirmed the assay's accuracy with well-defined model interactions and proved its high versatility and robustness with a representative application where we determined the half-lives of 375 different peptides in a crude intestinal protease preparation. With this reliable, reproducible, and efficient assay the enzyme kinetics of any peptide-protease interaction is accessible even for complex protease solutions.

Development of direct competitive enzyme-linked immunoadsorbent assays (ELISAs) based on polyclonal and monoclonal antibodies raised against 4-n-alkylphenol hapten mimics is described. A strong tendency to recognize 4-nonylphenol (NP) and 4-octylphenol (OP) as a total analyte amount was indicated by cross-reactivity pattern established for two polyclonal antibodies. These antibodies were employed for development of class-selective assays exhibiting IC(50) values around 40 microg.L(-1) for technical 4-NP. Specificity of the monoclonal antibody 4H6 and additional two polyclonal antibodies allowed sensitive detection of linear long-chain forms of 4-n-alkylphenols (4-n-AP). The assays incorporating these antibodies offer a potential for detecting the minor fraction of NP/OP isomer spectrum having IC(50) = 11.5 microg.L(-1) for 4-n-NP. No cross-reactivity interference was indicated for linear alkylbenzene sulfonates and phenolic compounds. To interpret the measured data in terms of analytical equivalents, a reliable relationship between the assay responses and AP content of contaminated samples should be verified and validated.

Seven hybridoma clones, E2/G2, E2/B5, E4/C2, G5/E10, F6/C10, B5/C3, and B7, produced within one fusion experiment in 1991 and the clone E4/C2 originated from 1995 were characterized by sequencing of genes coding for variable domains of the antibodies against 2,4-D herbicide. Amino acid sequences of selected antibodies, deduced from DNA analysis, were confirmed by mass spectrometry. Surprisingly, nucleotide sequence analysis of the clones E2/G2 and E2/B5, producing the most sensitive antibodies, proved to have sequence homology of their variable domains, although the IC(50) values determined for these antibodies 9 years prior to the DNA analysis were 2.0 and 8.2 ng/mL, respectively. The same findings arose from the comparison of the immunochemical to DNA data established for G5/E10, F6/C10, and B5/C3 clones producing antibodies with IC(50) values in the range of 26.3-43.1 ng /mL. The clone E4/C2, originating from the later fusion experiment, did not share nucleotide homology with any of the examined clones. Data obtained by ELISA, immunosensor, and DNA analysis within a 9 year period are discussed with respect to hybridoma stability, methodic artifacts, measurement reliability, and other possible factors influencing the result interpretation.

In this work, a disposable electrochemical immunosensor, based on a competitive assay scheme, was applied to detect polychlorinated biphenyls (PCBs) in food. For this purpose, antibodies against PCBs were directly immobilized onto the carbon surface of a disposable screen-printed electrode. A competition between the PCBs present in the sample and a fixed concentration of an enzyme-labeled PCB was realized and evaluated by electrochemical detection. Alkaline phosphatase was used as the enzyme label, coupled with differential pulse voltammetry (DPV) as the electrochemical technique. The immunosensor was tested on aroclor mixture detection (1242 and 1248) and then on some typologies of food samples to evaluate the possible application for real sample analysis. Samples analyzed were from different matrixes, such as sheep milk, bovine adipose tissue, and bovine muscle. Results obtained were compared with the accredited results according to ISO 17025 methods for PCB detection (HRGC-LRMS) as a confirmatory analysis. Preliminary results show the possibility to use this device as a screening method in food sample analysis. The negligible matrix effect observed may lead to a simplified extraction procedure, and considerable time and consumable savings are the immediate benefits given by the proposed method.

A direct competitive ELISA for determination of polychlorinated biphenyls (PCB) in soil samples was described. The standard calibration curve based on Delor 103 (Aroclor 1242) was constructed in the dynamic range of 10-1000 micro g L(-1) and a detection limit of 5.0-12.9 micro g L(-1) (or 0.5-1.29 micro g g(-1) soil) was achieved. When spiked soil samples were extracted with methanol recoveries were 90.6-106.3 %. The effect of methanol and DMSO on assay signal and sensitivity was established. Eight PCB-contaminated soil samples were analyzed by ELISA and gas chromatography (GC). The ELISA results from Soxhlet extraction were in a good agreement with those of GC (correlation coefficient 0.9866; n=8). Except for one soil sample the results from ELISA with methanol extraction were not significantly different from those from GC.

Piezoelectric quartz crystals (resonance frequency 10 MHz) were used for an investigation of the immunochemical reaction between 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide and several monoclonal antibodies prepared against 2,4-D. The herbicide was immobilized on the gold electrodes of the crystals silanized with 3-aminopropyltriethoxysilane. The activated carboxylic group of 2,4-D was linked either directly to the silanized surface or through hexamethylenediamine or albumin as a macromolecule. The interaction of the immobilized antigen with monoclonal antibody in solution was followed as a change in the resonant frequency of the crystals. The best results were achieved using 2,4-D attached to albumin. The affinity binding of five monoclonal antibodies was characterized by association (ka) and dissociation (kd) kinetic rate constants and by equilibrium association constants (KA) which were obtained from the experimental frequency vs. time curves.

Directly iodinated oestradiol-2(4)-iodo-[125I] and oestradiol-6-O-(CMO)-[125I]iodohistamine were prepared and used in conjunction with anti-oestradiol-2(4)-azo and anti-oestradiol-6-O-(CMO) sera for the development of various radioimmunoassay (RIA) systems which showed marked differences in sensitivity and relatively small differences in specificity. Whereas the heterologous combination of oestradiol-6-O-(CMO)-[125I]iodohistamine and anti-oestradiol-2(4)-azo-serum showed a sensitivity expressed in femtograms, the homologous combination using oestradiol-6-O-(CMO)-[125I]iodohistamine radioligand exhibited a sensitivity two orders lower. The specificity of both the heterologous and homologous system did not differ significantly from the RIA system using tritiated radioligand. The combination of directly iodinated oestradiol and anti-oestradiol-2(4)-azo-serum showed a higher sensitivity and a lower specificity as compared with tritiated radioligand.

The paper gives a review of the immunogens most frequently used for preparing antibodies against steroid haptens. The structural concepts of immunological specificity and complementarity are applied to a description of the formation of antibodies in immunized animals and the binding mechanisms of steroid-antibody interactions in systems in vitro. Recent experimental findings show that Ehrlich's lock and key principle is too static for many steroid-antibody complexes and that a more important factor in the binding events is the overall flexibility of these complexes. In this connection a discussion is undertaken of the properties of unsaturated steroid skeletons, the multispecificity of binding sites and further critical factors involved in the formation of the final specificity. Special attention is paid to considerations of the size of steroid determinants in connection with the question of the so-called bridge effect. The relevant expositions of this phenomenon are based in this article more on conformation changes of the steroid ligands than on direct binding interaction of the bridge substituent with the antibody. This interpretation makes it possible to interpret more broadly the experimental facts and gives new stimuli for an improvement of the present strategies of steroid immunoanalysis.