Small-scale Laboratory Research Articles

Benefits of derivatization in GC–MS-based identification of new psychoactive substances

Drug isomer identification is a significant problem in forensic laboratories due to the rise of New Psychoactive Substances (NPS). Correct identification of the precise isomeric form is of crucial importance as legal controls can vary among individual isomers. Currently, GC–MS is the method of choice in routine drug identification. This technique, however, falls short for isomeric differentiations due to i) very similar chromatographic behavior, ii) almost identical mass spectra, and iii) limited availability of reference standards. Unambiguous NPS identification often requires additional analysis on advanced analytical instrumentation unavailable in small-scale routine laboratories. This work demonstrates the advantages of an easy and robust derivatization step for GC–MS-based NPS identification. Derivatized extracts yield shelf lives of multiple years, eliminating the need to frequently re-prepare reference standards. After derivatization, chromatographic selectivity and peak shapes are improved enabling identification on retention time. For fluoroamphetamine ring-isomers the mass spectra of their derivates differ more significantly allowing robust assignment through a simple ion abundance-ratio check. Mass spectra of the derivatized mephedrone ring-isomers were visually still very similar. However, isomers could be identified by using Linear Discriminant Analysis (LDA). In a retrospective analysis of 132 mass spectra recorded between 2015 and 2020, a 100% correct classification was achieved using external training data from 2020. Finally, derivatization aids structural elucidation of NPS by the inability to form derivates for tertiary amine isomers as shown for a dimethylated cathinone. This study shows that in specific cases NPS can robustly be identified using conventional GC–MS instrumentation in combination with active ingredient derivatization.

An experimental study of mitigating coastal sand dune erosion by microbial- and enzymatic-induced carbonate precipitation

Due to more extreme weather events and accelerating sea-level rise, coastal sand dunes are subjected to more frequent storm wave inundation and surge impacts, which contribute to widespread coastal erosion problems. In this study, two novel bio-mediated methods, microbial-induced carbonate precipitation (MICP) and enzymatic-induced carbonate precipitation (EICP), were investigated and compared for their effectiveness in mitigating sand dune erosion under wave attack. Small-scale laboratory model tests were performed on MICP-treated, EICP-treated, and untreated sand dunes at dune slope angles and two wave intensities for up to 2 h. The cross-shore profile was captured continuously during the course of the erosion test. The erosion volume above the still water level (SWL) and landward retreat distance at the SWL were calculated based on the captured bed profiles. The results show that both EICP and MICP could substantially reduce sand dune erosion at mild-to-moderate wave and dune slope conditions. However, the effectiveness of MICP treatment deteriorated at steeper dune slopes with longer period of wave attack. Under the most adverse condition (i.e., steepest dune slope, biggest wave, and longest period of wave attack), neither EICP nor MICP could effectively mitigate erosion. Fundamentally, the variable effectiveness of MICP and EICP treatment for sand dune erosion control was attributed to the spatial distribution pattern of formed calcite precipitation, which was determined by the way how EICP and MICP were applied. The calcite precipitation was relatively uniform in EICP-treated sand dunes. In MICP-treated ones, however, substantial calcite precipitation concentrated in the shallow surface layer as confirmed by the surface penetration test and SEM observation.

Paraffin wax as self-sealing insulation material of seasonal sensible heat storage systems-A laboratory study.

Seasonal heat storage is considered as one of the key elements on the path to a low-emission economy. Embedded in local district heating networks, they raise the share of renewable energies and balance out highly fluctuating supplies of e.g. solar systems or windmills. The technology of seasonal heat storage can be described as almost technically mature, with well-established concepts and some systems being in operation for a considerable time. Nevertheless, the operating experience gained to date also revealed two critical problems. On the one hand, even smallest leakages in sealing foils led to irreparable breakdowns. On the other hand, heat loss in the marginal areas was revealed as a key deficiency, preventing the technology from advancing towards global marketability. This study presents an experimental approach to address these two key issues in the field of seasonal energy storage. Two small-scale laboratory tests were carried out to test paraffin wax as a completely novel component in the marginal area of seasonal storages. This is based on two material properties: As hydrophobic and mobile medium, the warmed and molten paraffin should actively seal the fissures and holes in the event of leakage. Additionally, the latent heat storage properties of the paraffin wax should increase the systems’ total storage capacity and reduce lateral heat losses via its low thermal conductivity. With retardation periods from 2.5 to 4 hours, the results show an effective phase change effect of the paraffin wax, which reduces energy losses and allows to buffer short-term, intensive loading and unloading processes. By storing up to 138 kJ/kg energy in the paraffin wax, increased capacities of application-scale pit storages by up to 40.70 MWh are to be expected. Additionally, the self-healing features could be successfully demonstrated: With only small losses of between 1.5 and 17%, the paraffin wax effectively sealed artificially incised leaks. Thereby, the mechanism was most effective for local defects. Following these positive demonstrations of feasibility, technical design questions still remain, which concern prevention of deformation of the paraffin wax. Once solved, this new component can then provide a path for further optimization of seasonal heat storage technologies.

Estimation of surface depression storage capacity from random roughness and slope

Depression storage capacity (DSC) models found in the literature were developed using statistical regression for relatively large soil surface roughness and slope values resulting in several fitting parameters. In this research, we developed and tested a conceptual model to estimate surface depression storage having small roughness values usually encountered in rainwater harvesting micro-catchments and bare soil in arid regions with only one fitting parameter. Laboratory impermeable surfaces of 30 x 30 cm2 were constructed with 4 sizes of gravel and mortar resulting in random roughness values ranging from 0.9 to 6.3 mm. A series of laboratory experiments were conducted under 9 slope values using simulated rain. Depression storage for each combination of relative roughness and slope was estimated by the mass balance approach. Analysis of experimental results indicated that the developed linear model between DSC and the square root of the ratio of random roughness (RR) to slope was significant at p < 0.001 and coefficient of determination R2 = 0.90. The developed model predicted depression storage of small relief at higher accuracy compared to other models found in the literature. However, the model is based on small-scale laboratory plots and further testing in the field will provide more insight for practical applications.

Comparative Study on Bearing Capacity of Bottom Ash–Stabilized Soil Mixed with Natural and Synthetic Fibers

Abstract This article assesses the strength behavior of bottom ash (BA)–stabilized soil mixed with different fibers through a series of laboratory tests. Optimum BA and fiber percentage were obtained by small scale lab tests like compaction tests and unconfined compressive strength (UCS) tests. From compaction tests with varying proportions of BA (10, 20, 30, and 40 %), the optimum BA content was found to be 30 %. With this optimum BA content, UCS tests were conducted on soil-BA mix with different fibers (coir, areca, sisal, and polyvinyl alcohol) at various percentages (0.5, 1, 1.5, and 2 %) to find the optimum fiber content. A set of model footing tests were done to check the credibility of using fibers as a strengthening material beneath footing to upgrade the engineering properties of soil to make a reasonable subsoil for the foundation. A total of six model footing tests were performed on raw soil, on soil with optimum BA content, and on BA–stabilized soil mixed with different fibers in their optimum percentage (1.5 %). The bearing capacity of unstabilized unreinforced soil was found to increase significantly with the inclusion of fibers.

Analysis of Cascaded Buck–Boost Inverter for PMLG-Based Ocean Wave Energy Converter

The direct-drive Permanent Magnet Linear Generator (PMLG)-based Ocean Wave Energy Converter (OWEC) generates variable AC voltage, which cannot be directly utilized by the load. This paper presents a two-stage methodology to convert variable AC voltage to a constant amplitude AC voltage. First, a standard rectifier is used to convert variable AC voltage into variable DC voltage. After that, a cascaded buck–boost inverter is employed to achieve the constant frequency AC voltage. Systematic design and circuit analysis, along with working principle and voltage control strategy, are presented. A small scale laboratory prototype of PMLG associated with buck–boost inverter is developed to validate the proposed concept.

Stream-scale flow experiment reveals large influence of understory growth on vegetation roughness

Vegetation is a key source of flow resistance in natural channels and floodplains. It is therefore important to accurately model the flow resistance to inform decision makers and managers. However, it is challenging to predict the resistance of real vegetation, because vegetation models are based on relatively small-scale lab experiments with mostly artificial vegetation. Experimental tests of real vegetation under field conditions are scarce. The purpose of this study is to measure the flow resistance of a submerged willow patch, where small herbaceous vegetation was allowed to grow in between the willow stems to simulate field conditions. Detailed flow velocity measurements were performed during an full scale experiment of flow around a submerged patch of willows. The parameter values of the willow vegetation model, as well as the friction coefficients of the vegetated banks and unvegetated channel bed, were computed simultaneously using Bayesian inference using a 2D hydrodynamic model.Results show that the presence of understory growth greatly affects flow patterns and the value of the effective vegetation density parameter. Measured flow velocities in the patch with understory growth were very low, and the patch has relatively high deflection. After removal of this undergrowth, flow velocities in the patch increased and deflection of the vegetation canopy decreased. We show that estimating vegetation density using an often-used rigid cylinder estimator based on vegetation sampling, underestimated the effective value by more than an order of magnitude. We argue that proposed extensions to existing vegetation models, which can take into account understory growth and reconfiguration, could be tested under field conditions using the approach followed in this paper.

Design Architecture for Continuous-Time Control of Dual Active Bridge Converter

The dual active bridge (DAB) is one of the useful interfaces for the bidirectional power exchange between two buses with galvanic isolation. In this article, a design framework is given in the analog domain that completely fulfills the operational features of a DAB under phase angle modulation. This is a cost-effective solution with configurable control parameters and easy to implement using well-established semiconductor integrated circuit (IC). Moreover, it provides an efficient way to study the behavior of power converters. A closed-loop control for bidirectional power exchange is established. For that, a control-to-output current transfer function is derived analytically considering the dc and first-order harmonic terms and verified experimentally. A small scale laboratory prototype of DAB is set up for the validation of the concept. It is shown that the design architecture has the facility for supervisory control that is useful for battery charging/discharging, microgrid application, etc.

Evaluation of the effects of sugarcane processing on the presence of GM DNA and protein in sugar

ABSTRACT The Brazilian Sucro-energy Sector produces both energy, in the form of ethanol fuel, industrial steam and electricity, and sugar. Centro de Tecnologia Canavieira (CTC), the leading Brazilian sugarcane breeding company, has developed a pipeline of insect-protected sugarcane varieties to control sugarcane borer damage. The goal of this manuscript is to present the results of studies with three genetically modified (GM) sugarcane varieties and to evaluate the published literature regarding the possible presence of GM sugarcane DNA or protein in raw or refined sugar. Specifically, two varieties of approved GM sugarcane, CTC91087-6 and CTC175-A, and an experimental CTC variety, were grown in four individual plots to produce four batches each of processed raw sugar using standard smaller-scale laboratory processing methods resulting in a total of 12 independent batches of raw sugar. Herein, we report the development of event-specific probes and DNA detection methods, designed to detect the junction of sugarcane genomic DNA and the inserted DNA of the two approved GM varieties. An identical approach was used for the testing of sugar made from the experimental CTC variety. The methodology used TaqMan® real-time PCR and ELISA assays validated for the four GM proteins expressed by these three events (Cry1Ab, Cry1Ac, NPTII, and PAT (bar)). The developed assays had very low limits of detection (LODs) for the various event-specific DNA probes (7.2–25 ng/g sugar) and insecticidal and selectable marker proteins (2.9–10.9 ng/g sugar). No event-specific DNA and no GM proteins were detectable in the 12 independent batches of raw sugar produced from these three GM sugarcane events. The results of this study, using very sensitive methods and testing several sugar batches, extend the conclusions of previous studies, reviewed herein, that showed the extensive degradation and removal of DNA and protein during sugarcane processing. Overall, these results indicate that there are no distinguishable differences between the highly purified, chemically defined sugar produced from conventional or GM varieties.

Simple Solution for Single Final Vial Filling of Ga-68 Radiopharmaceuticals in One Hot Cell Isolator at Small-Scale Radiopharmacy Laboratories under Aseptic Conditions

A simple solution for fulfilling biosafety and national drug agency demands of radiation and biosafety during Ga-68 radionuclide containing radiopharmaceutical production (RP) by small scale laboratories has been demonstrated based on a novel sterile seal concept of multi-layer bag system prototype. These mid-and inner enclosures of the prototype with vial inside were sterilized by 50 kGy of gamma radiation. The microbial safety validation based on two-week testing confirmed successful sterilization of the sealing bags with vails. The analysis of physicochemical properties, namely mechanical properties, gel fraction studies revealed that sterilization did not cause any undesired changes in developed materials, compared to non-irradiated control samples.

Study of fin shape on the behaviour of finned piles under combined loading conditions

Several types of structures, such as bridge abutments, retaining walls, transmission line towers and other structures exposed to wind and earthquake loads, supported by pile foundation are being subjected to large lateral loads. Finned pile is an emerging form of pile foundation that is capable of resisting large lateral displacements. Here, it is attempted to assess the effect of the shape of fins on the lateral carrying capacity of a pile with fins subjected to combined loading conditions. Small-scale laboratory model tests were performed on normal piles (without fins) and also with finned piles. These piles were embedded in sand. The studies were carried out by varying the geometric factors such as length, width and shape of the fins. Results show that there is a substantial increase in lateral resistance capacity of the piles after fitting the fins close to the pile head. The increase in lateral resistance capacity gained by placing fins on a pile varies with dimension of the fins. On the basis of the laboratory model test results, optimum dimension of the fin for maximum improvement are recommended for combined loading conditions. The trend showed in the results were comparable with those reported in the literature as on studies with lateral load alone.

Numerical and experimental investigation of saturated granular column collapse in air

Many hazardous natural phenomena like debris flows, avalanches and submerged landslides are governed by the interactions between solid grains and interstitial fluid. They display a complex interplay of physical mechanisms, which are still very challenging to simulate with numerical methods. Different methods have been proposed in the literature to achieve this goal. This paper compares the results of two different numerical approaches: (i) a macromechanical continuum approach with the two-phase double-point Material Point Method (MPM) and (ii) a micromechanical approach with Discrete Element Method coupled with the Lattice Boltzmann Method (DEM-LBM). With the objective of highlighting potentialities and critical points of the two approaches, we conduct saturated granular column collapses in a small-scale laboratory experiment, subsequently reproduced by the numerical codes. Unlike previous experiments of collapse under gravity in dry or completely submerged conditions, in this paper the saturated material is released in air. These conditions better reproduce real natural onshore landslides and allows a discussion on the solid–fluid interaction.

Thermal activation of persulfates for wastewater depollution on pilot scale solar equipment

Thermal activation of new oxidant chemicals like Persulfate (PS) has recently gained attention in driving advanced oxidation processes (AOP) for a number of applications. On the other hand, addressing energy demand with carbon free and sustainable energy solutions represents an asset for new technologies in the modern society. This paper then investigates on the removal of pharmaceuticals residues in wastewater (WW), conducted with PS advanced oxidation reactions on a solar thermal pilot equipment. Indoor preliminary investigations on small scale laboratory experimentations show how increasing temperature has a direct positive impact on pollutants degradations rate (kapp value ranging from 0.4·10−3s−1 at ambient to 10.4·10−3 s−1 at 75 °C). However, after an experimental screening methodology, 65 °C and 200 µM appear as the appropriate target temperature and PS oxidant dosage to cope with both activation of PS oxidant and degradation of ten target micropollutants typically found in WW stream. Outdoor experimentations on the solar pilot equipment were conducted according to a batch running mode at a treatment capacity scale of a cubic meter. 95% pollutant removal rate is achieved within 2 h once the temperature has raised up to the target value (65 °C) in the bulk treated WW effluent. Series of treatment cycles under the natural day/night period demonstrate the reproducibility of the performance. As an early step result of the process optimization approach, heat recovery demonstration on the pilot equipment improves significantly the energetic balance over the now innovative thermal solar water treatment.

Numerical Analysis of Stone Columns for the Reduction of the Risk of Soil Liquefaction

Although stone columns have been frequently used for the prevention of soil liquefaction in the last few years, their mechanical performance is still not fully understood. Both numerical calculations with conventional constitutive models and small-scale laboratory experiments do not explain the improving mechanisms satisfactorily. Under seismic effects, the interaction between the soil and the columns, especially between the pore water and the soil skeleton, makes the understanding of this method even more difficult. In this paper, an application of stone columns for the prevention of soil liquefaction is numerically investigated by means of 2D and 3D simulations. A hypoplastic model was used for the soil description. The drainage effect of the columns and their contribution to the stiffening of the ground were considered separately. Furthermore, the impact of the columns installation method was investigated by increasing soil density and stress ratio. Finally, the role of the intensity of the dynamic load was studied.

Heat generation by ultrasound wave propagation in porous media with low permeability: Theoretical framework and coupled numerical modeling

Abstract Ultrasound wave propagation through a porous medium results in a temperature increase due to mechanical dissipation. This temperature increase has different applications in medical science, food industry, and engineering. A fully coupled dynamic thermo-hydro-mechanical (THM) model is presented for numerical modelling of this phenomenon in deforming porous media. The temperature increase due to wave propagation is taken into account in the energy conservation equation by using a viscous drag force and considering solid-fluid interaction. The solid and fluid displacements ( U → s and U → w ) and the temperature ( T ) are taken as primary unknowns in the model known in literature as uUT model. The finite element method is used for the discrete approximation of the governing partial differential equations. Based on the numerical examples carried out in this study, it is shown that the scale of the simulated sample may have a very pronounced effect on the results, and that results from small scale laboratory samples should not be extrapolated to the actual field condition. Furthermore, the results of ultrasound application in porous media indicate a significant increase in temperature in the vicinity of the source boundary.

Scale-up of electrokinetic process for dredged sediments remediation

Most of electrokinetic remediation (EKR) reported researchs were performed on small-scale laboratory devices and less field-scale studies are available in literature. Understanding the scaling-up process is essential for the application of the EKR at field scale. This paper presents the results of laboratory experiments performed at two scales (involving 0.4 kg and 40 kg of dredged sediment) to evaluate the potential of EKR process on both organic and inorganic contaminants, and the scaling-up effect. Mixtures of eco-friendly enhancing additives were used: a biodegradable chelating agent (citric acid) combined with a nonionic surfactant (Tween 20) were promising candidates for the simultaneous EK remediation of a multi-contaminated harbor sediment. The values of energy consumption from the large scale tests showed that efficient decrease of pollutant concentrations and sustainable remediation could be achieved with moderate energy costs. Obtained results also indicated that better removals of Cr, PAHs and PCBs were achieved with the large-scale device using less energy and additives. However, the distribution of the pollutants in the specimen after the EK remediation indicated that the electric field did not totally control the migration process and that the interaction with likely heterogeneity and inertial effects reduced the EK effectiveness at the large scale. This scaling-up investigation allows considering EK tests at a larger scale (field installation) with adjusted parameters from a small-scale investigation.

Experimental and numerical studies for applying hybrid solar chimney and photovoltaic system to the solar-assisted air cleaning system

Under the background of global energy shortage and environment deterioration, researchers of the world pay high attention to develop renewable energy. This paper proposes a hybrid solar chimney and photovoltaic system for the novel solar-assisted air cleaning system. Small-scale laboratory setups are designed and fabricated. Experimental results reveal that replacing 50.60% acrylic glass of the collector top with photovoltaic panels will reduce the thermal air flow rate only by 14%, but generate significant electric power output. A three-dimensional numerical simulation model is established and validated by experimental results (air flow rate, temperature distribution). The model includes solar ray tracing model, surface to surface radiation model, buoyancy-driven flow and heat transfer model and power generation model. Then, this model is used to predict a large-scale system based on the Manzanares pilot power plant in Spain. For the large-scale system, the electrical energy generated by the photovoltaic panels can be used to drive suction fans to increase air input. Covering the entire top surface of the collector by photovoltaic panels (113-meter-wide), the total air flow rate would increase to 2.21 times compared with the system without photovoltaic panels. And setting photovoltaic panels on the collector bottom with 113-meter-wide, the total air flow rate would increase to 2.42 times. Thus, adding photovoltaic panels for the collector can greatly improve the utilization of solar energy. It can increase the amount of air purification, or reduce land requirement for the same flow rate.

Fabrication of ribbon-like films of orientation-controlled carbon nanotube/polymer composite using a robotic dispenser

Alignment of carbon nanotubes (CNTs) in CNT/polymer composite films is an attractive technique to obtain improved electrical, mechanical, and thermal properties. However, their alignment method is still confined to small laboratory scale sample preparation. In this letter, a novel method to prepare a continuous drawing of ribbon-like films of CNT/polymer composite is proposed using a robotic dispenser. We prepared 400–2000 μm wide oriented ribbon of CNT/polymer films that can be used for roll-to-roll processing in length scale. CNTs were found to be aligned along the drawing direction as confirmed by polarized Raman mapping and scanning electron microscope images.

Modelling and compensation of dead time in three-phase dual-active bridge DC-DC converter

ABSTRACT With growing decentralized power generation, medium-voltage (MV) dc-dc converters are becoming increasingly important. A three-phase dual-active bridge (DAB3) is a promising topology for high-power MV applications. The semiconductor devices used in such converters at multi-megawatt level tend to be slow in switching. Hence, a considerable dead time between switching instants is required to avoid shoot-through in phase legs. This dead time forces the current to commutate to the freewheeling diodes and introduces a current dependence of the phase voltages. In this work, the effects of dead time on the operation of DAB3 are analysed in detail. The derived analytical expressions are used in the control development to compensate for the effects of dead time and hence achieve superior control performance. Measurements are carried out on a small-scale laboratory prototype to validate the derived operational modes and the effectiveness of the proposed dead time compensation.

Laboratory characterization of sandy soil water content during drying process using electrical resistivity/resistance method (ERM)

Drought-induced evaporation can reduce soil water content and significantly alter soil hydro-mechanical behavior. Understanding the temporal and spatial distribution characteristics of soil water content during evaporation is of great significance for evaluating the encountered geotechnical and geo-environmental problems in arid or semi-arid regions. In this study, an electrical resistivity/resistance method (ERM) with a high spatial resolution of centimeter-level was developed for a small-scale laboratory test and applied to quantitatively characterize the evaporation-induced water content variations along a depth gradient. A total of 8 groups of initially saturated sandy soil columns (84 mm in diameter and 290 mm in height) were prepared, and eight pairs of mini electrodes (3.5 mm in diameter) were installed in each soil sample with a vertical distance of 30 mm. The soil columns were subjected to continuous drying. The changes in soil electrical resistance at different depths were monitored by the electrode couples. The gravimetric water contents at different depths were also measured at the end of drying. It is found that soil water content decreases exponentially with increasing electrical resistance. Based on the obtained data, a calibration relationship between soil gravimetric water content and corrected electrical resistance was well established with consideration of temperature effect. This relationship was validated successfully by the experimental results, indicating the feasibility of the developed ERM to characterize the soil water content dynamics during the drying process. Besides, the drying process with the movement of the evaporation front was discussed. The results of this study demonstrate the good performance of ERM in the estimation of temporal and spatial variations of soil water content and its potential application in arid or semi-arid regions with frequent droughts.