Lodz University of Technology
Recent publications
The aim of this article is to conduct an analysis leading to the optimization of industrial safety related to the use of a cotton fabric automatic screen printing press. The author’s multistage algorithm, i.e., the analysis-synthesis-minimization procedure, brings effective solutions to the issue in question. There are several risk factors at the printing press workstation and its environment, which are identified by employee surveys, scorecards and airborne samples testing. The risks are visualized by the fishbone/Ishikawa diagram. In accordance with the Fine–Kinney method, a set of 70 scorecards assessing occupational risk is applied to support the identification of critical hazards, which is next re-analyzed using the Analytic Hierarchy Process (AHP). Hierarchically assessed risk factors related to the use of a printing press are easy to be minimized by organizational and technical solutions which are intended to be implemented at the workplace.
In the manuscript, a novel method for the preparation of cyclopent-1-enecarbonitriles via tandem Giese/HWE reaction initiated by visible light in the presence of fac-Ir(ppy)3 as a photocatyst has been described. The cascade reactivity combining radical and polar processes has proven applicable for a wide range of N-(acyloxy)phthalimides (which serve as precursors of the corresponding radicals) as well as diethyl (E)-(1-cyano-2-arylvinyl)phosphonates. The key parameters responsible for the success of the described strategy are: visible light, 1 mol% of photoredox catalyst, base, anhydrous solvent and inert atmosphere. The reaction results in new sp3-sp3 and sp2-sp2 carbon-carbon bonds formation under mild conditions.
The stickiness effect is a fundamental feature of quasi-integrable Hamiltonian systems. We propose the use of an entropy-based measure of the recurrence plots (RPs), namely, the entropy of the distribution of the recurrence times (estimated from the RP), to characterize the dynamics of a typical quasi-integrable Hamiltonian system with coexisting regular and chaotic regions. We show that the recurrence time entropy (RTE) is positively correlated to the largest Lyapunov exponent, with a high correlation coefficient. We obtain a multi-modal distribution of the finite-time RTE and find that each mode corresponds to the motion around islands of different hierarchical levels.
By employing Clark’s theorem we prove the existence of infinitely many homoclinic solutions to the local and nonlocal discrete p-Laplacian equations on the integers. Our results extend and correct the reasoning of some recent findings expressed in the literature.
C5-substituted pyrimidine nucleosides are an important class of molecules that have practical use as biological probes and pharmaceuticals. Herein we report an operationally simple protocol for C5-functionalization of uridine and cytidine via transformation of underexploited 5-trifluoromethyluridine or 5-trifluoromethylcytidine, respectively. The unique reactivity of the CF3 group in the aromatic ring allowed the direct incorporation of several distinct C5-C "carbon substituents": carboxyl, nitrile, ester, amide, and amidine.
Compound-specific isotope analysis (CSIA) for natural isotope ratios has been recognized as a promising tool to elucidate biodegradation pathways of organic pollutants by microbial enzymes by relating reported kinetic isotope effects (KIEs) to apparent KIEs (AKIEs) derived from bulk isotope fractionations (εbulk). However, for many environmental reactions, neither are the reference KIE ranges sufficiently narrow nor are the mechanisms elucidated to the point that rate-determining steps have been identified unequivocally. In this work, besides providing reference KIEs and rationalizing AKIEs, good relationships have been explained by DFT computations for diverse biodegradation pathways with known enzymatic models between the theoretical isotope fractionations (εbulk') from intrinsic KIEs on the rate-determining steps and the observed εbulk. (1) To confirm the mechanistic details of previously reported pathway-dependent CSIA, it includes isotope changes in MTBE biodegradation between hydroxylation by CYP450 and SN2 reaction by cobalamin-dependent methyltransferase, the regioselectivity of toluene biodegradation by CYP450, and the rate-determining step in toluene biodegradation by benzylsuccinate synthase. (2) To yield new fundamental insights into some unclear biodegradation pathways, it consists of the oxidative function of toluene dioxygenase in biodegradation of TCE, the epoxidation mode in biodegradation of TCE by toluene 4-monooxygenase, and the weighted average mechanism in biodegradation of cDCE by CYP450.
Metabolism, especially by CYP450 enzymes, is the main reason for mediating the toxification and detoxification of xenobiotics in humans, while some uncommon metabolic pathways, especially for emerging pollutants, probably causing idiosyncratic toxicity are easily overlooked. The pollution of sulfonamide antibiotics in aqueous system has attracted increasing public attention. Hydroxylation of the central amine group can trigger a series of metabolic processes of sulfonamide antibiotics in humans; however, this work parallelly reported the coupling and fragmenting initiated by amino H-abstraction of sulfamethoxazole (SMX) catalyzed by human CYP450 enzymes. Elucidation of the emerging metabolic profiles was mapped via a multistep synergy between computations and experiments, involving preliminary DFT computations and in vitro and in vivo assays, profiling adverse effects, and rationalizing the fundamental factors via targeted computations. Especially, the confirmed SMX dimer was shown to potentially act as a metabolism disruptor in humans, while spin aromatic delocalization resulting in the low electron donor ability of amino radicals was revealed as the fundamental factor to enable coupling of sulfonamide antibiotics by CYP450 through the nonconventional nonrebound pathway. This work may further strengthen the synergistic use of computations prior to experiments to avoid wasteful experimental screening efforts in environmental chemistry and toxicology.
Understanding and controlling the nucleation and crystallization in solution‐processed perovskite thin films are critical to achieving high in‐plane charge carrier transport in field‐effect transistors (FETs). This work demonstrates a simple and effective additive engineering strategy using pentanoic acid (PA). Here, PA is introduced to both modulate the crystallization process and improve the charge carrier transport in 2D 2‐thiopheneethylammonium tin iodide ((TEA)2SnI4) perovskite FETs. It is revealed that the carboxylic group of PA is strongly coordinated to the spacer cation TEAI and [SnI6]4− framework in the perovskite precursor solution, inducing heterogeneous nucleation and lowering undesired oxidation of Sn2+ during the film formation. These factors contribute to a reduced defect density and improved film morphology, including lower surface roughness and larger grain size, resulting in overall enhanced transistor performance. The reduced defect density and decreased ion migration lead to a higher p‐channel charge carrier mobility of 0.7 cm2 V−1 s−1, which is more than a threefold increase compared with the control device. Temperature‐dependent charge transport studies demonstrate a mobility of 2.3 cm2 V−1 s−1 at 100 K due to the diminished ion mobility at low temperatures. This result illustrates that the additive strategy bears great potential to realize high‐performance Sn‐based perovskite FETs. Overall improved performance of 2D Sn‐based perovskite field‐effect transistors is prepared by incorporating pentanoic acid as an additive to inhibit the Sn oxidation and fine‐tune the crystallization process. Benefiting from the passivated defects and increased grain size, a high field‐effect mobility of 0.7 cm2 V−1 s−1 at room temperature is achieved.
This contribution is devoted to the study of the collective behavior of two HR neurons followed by a network of HR neurons. The collective behavior of the two coupled neuron was obtained from the connection between the traditional 3D HR and a memristive 2D HR neuron via a gap junction. The dynamical properties of this rst topology revealed that it is dissipative therefore can support complex phenomena. From numerical simulations, it is found that the coupled neurons display a variety of behaviors just by varying the control parameter. Amongst these behaviors found, we have periodic bursting or spiking, quasi-periodic bursting or spiking, and chaotic bursting or spiking. Non-synchronized motion is observed when the electrical coupling strength is weak. However, synchronized cluster states are observed when the coupling strength is increased. Also varied of cross ring networks made of combination of N = 100 these different HR neurons in the network are also investigated. It is discovered that the spatiotemporal patterns are affected by the network topology. The cluster states are represented in the non- homogenous network's ring and star structures. The ring and ring-star structures contain single and double-well chimera states. Finally, in the PSIM simulation environment, a comparable electronic circuit for the two coupled heterogeneous neurons is designed and investigated. The results obtained from the designed analog circuit and the mathematical model of the two coupled neurons match perfectly.
The aim of this study was to determine the effect of temperature and time of convective drying on the content of fructooligosaccharides (FOS) in apples, plums and strawberries to which FOS had been introduced by osmoconcentration. The share of oligosaccharides in total sugars was analyzed. In apple tissue, fructooligosaccharides were stable in the temperature range 40–80°C during drying for up to 8 h. Convective drying of osmotically dehydrated strawberries caused FOS losses; the FOS retention after 8 hours at 80°C was 40%. In the case of plums, 40% retention was recorded after just two hours at 80°C. Therefore, in the case of some fruits, obtaining a satisfactory level of fructooligosaccharides in the dried material with the assumed level of dry substance requires the determination of appropriate process parameters.
The paper deals with numerical modeling of electrothermal phenomena in 3D GaN core-shell light-emitting diode (LED) structures that were developed in the frame of GECCO project. 1 The simulations investigate the influence of pillar dimensions on the LED work conditions. The inherent feature of such a design is the discrepancy between the internal contact footprint current density J FP and the current density on the junction active area J AA , which, at the same contact current, decreases when the pillar is taller. The simulations indicate that the decrease of J AA results in significant changes in the LED parameters. At the same diode current, i.e., constant light emission, it leads to the voltage decrease leading to the reduction of power delivered to the diode and, consequently, to the increase of its efficiency.
The transport of liquid sweat in clothing worn close to human skin is very important from the point of view of the thermo-physiological comfort of clothing users. It ensures the drainage of sweat secreted by the human body and condensed on the human skin. In the presented work, knitted fabrics made of cotton and cotton blends with other fibers (elastane, viscose, polyester) were measured in the range of liquid moisture transport using the Moisture Management Tester MMT M290. The fabrics were measured in unstretched form and stretched to 15%. Stretching of the fabrics was performed using the MMT Stretch Fabric Fixture. Obtained results confirmed that stretching significantly changed the values of parameters characterizing the liquid moisture transport in the fabrics. Before stretching, the best liquid sweat transport performance was stated for the KF5 knitted fabric made of 54% cotton and 46% polyester. For this, the greatest value (10 mm) of maximum wetted radius for the bottom surface was obtained. The Overall Moisture Management Capacity (OMMC) of the KF5 fabric was 0.76. This was the highest value among all values obtained for the unstretched fabrics. The lowest value of the OMMC parameter (0.18) was stated for the KF3 knitted fabric. After stretching, the KF4 fabric variant was assessed as the best one. Its OMMC improved from 0.71 before stretching to 0.80 after stretching. The value of the OMMC for the KF5 fabric remained after stretching at the same level (0.77) than before stretching. The most significant improvement was observed for the KF2 fabric. Before stretching, the value of the OMMC parameter for the KF2 fabric was 0.27. After stretching, the OMMC value increased to 0.72. It was also stated that the changes in the liquid moisture transport performance of the investigated knitted fabrics were different for the particular fabrics being investigated. Generally, in all cases, the ability of the investigated knitted fabrics to transfer liquid sweat was improved after stretching.
This paper proposes a simple mathematical model based on the variable fractional-order difference equation of a robot arm. The model of the described arm does not consider the impact of the movement of the mobile platform, it was assumed that all degrees of freedom would be taken away from it. The implementation of the task was divided into two stages. First, a mechanical model was developed. In order to estimate the torques of nodal propulsion motors, a description of the components of the Lagrange equation for the considered system, i.e., energy, power, and external interactions, and derivation of the equations of motion of the tested manipulator based on the Lagrange equation was made. An additional criterion was also considered in the selection of drives in the kinematic nodes of the links, which was to set the manipulator in a vertical position at a specific time. Processing the measured data of a robot arm, model parameters were selected, and the order function was chosen. The second stage was a simulation, whose results were compared with the collected data.
The paper describes a new approach to the issue of controlling an indirect elevator with a bidirectional variable-speed pump and a simple controller based on the position sensor. The aim of this paper is to present a method of controlling the speed of the elevator to ensure smooth movement and proper positioning of the car on the floor, regardless of its load and ropes rigidity. The main feature of the proposed solution is the use of a frequency inverter in vector mode to control the speed of the car in both directions. The control function is based on virtual cams comparing actual measurements from the car position sensor. The proposed control strategy has been experimentally verified on the existing indirect elevator drive, and the obtained results indicate a very high accuracy in maintaining and shaping the speed and positioning of the car. The conducted research confirms the possibility of using a new method of controlling hydraulic and indirect elevators. The benefits of this method include a less complex hydraulic system, the control of overloads in the car and vibrations in the rope system, and the possibility of energy recovery.
Polyurea coatings as a possible structural reinforcement system” is a research project aimed at exploring possible applications of polyurea coatings for improving structural performance (including steel, concrete, wooden and other structures used in the construction industry). As part of the project, this paper focuses on evaluating the performance of bent reinforced concrete (RC) beams covered with a polyurea coating system. Easy polyurea application and its numerous advantages can prove very useful when existing RC structural elements are repaired or retrofitted. Laboratory tests of three types of RC beams with three different longitudinal reinforcement ratios were performed for the purposes of this paper. The tests were designed to determine the bending strength, performance and cracking patterns of the coated RC beams. In addition, a theoretical model was developed to predict the impact of the polyurea coating on the bending strength of the RC beams. On this basis, the effect of the coating on the bending strength and the performance of the coated beams at the ultimate limit state (ULS) was examined and analyzed. The results showed that the use of the polyurea coating has a positive impact on the cracking state of the RC beams subject to bending and little effect on their bending strength.
Here we present for the first time a potential wound dressing material implementing aptamers as binding entities to remove pathogenic cells from newly contaminated surfaces of wound matrix-mimicking collagen gels. The model pathogen in this study was the Gram-negative opportunistic bacterium Pseudomonas aeruginosa, which represents a considerable health threat in hospital environments as a cause of severe infections of burn or post-surgery wounds. A two-layered hydrogel composite material was constructed based on an established eight-membered focused anti-P. aeruginosa polyclonal aptamer library, which was chemically crosslinked to the material surface to form a trapping zone for efficient binding of the pathogen. A drug-loaded zone of the composite released the C14R antimicrobial peptide to deliver it directly to the bound pathogenic cells. We demonstrate that this material combining aptamer-mediated affinity and peptide-dependent pathogen eradication can quantitatively remove bacterial cells from the “wound” surface, and we show that the surface-trapped bacteria are completely killed. The drug delivery function of the composite thus represents an extra safeguarding property and thus probably one of the most important additional advances of a next-generation or smart wound dressing ensuring the complete removal and/or eradication of the pathogen of a freshly infected wound.
In this paper, a massively parallel implementation of Boltzmann’s thermally activated molecular transport model is presented. This models allows taking into account potential energy barriers in molecular simulations and thus modeling thermally activated diffusion processes in liquids. The model is implemented as an extension to the basic Dynamic Lattice Liquid (DLL) algorithm on ARUZ, a massively parallel FPGA-based simulator located at BioNanoPark Lodz. The advantage of this approach is that it does not use any exponentiation operations, minimizing resource usage and allowing one to perform simulations containing up to 4,608,000 nodes.
The aim of this study is to investigate the influence of manufacturing on the buckling and post-buckling behaviour of thin-walled, columns made from CFRP. Static compression was performed on channel-section profiles with dimensions equal to 80 mm × 38 mm × 240 mm (web × flange × length of profile) composed of an eight-layered symmetric laminate [45/−45/45/−45] and a thickness of 0.92 mm. The samples were manufactured by two distinct methods: 1) conventional lamination of a channel, and 2) by manufacturing a square cross-section and cutting it into two channels. Buckling tests showed that the second method is 2.5 times more material efficient and provides 18 % higher buckling resistance. Moreover, three finite element models were implemented—a model that did not include any prestress (residual stresses), and simulations of the channel and square cross sections where residual stresses were included. The conventional channels matched the numerical results of the model which did not include any prestress (nominal error of 1.8%). Whereas the buckling response of the square cross section samples were substantially influenced by the residual stresses (18.1% increase in buckling load). These results have significant implications for the design/production of CFRP channels with enhanced buckling performance.
The degradation of bio-based plastic materials in field soil under natural conditions was investigated in this study. Three bio-based plastics materials, which contained polylactide (PLA) with polybutylene adipate terephthalate and additives (PLA_1), PLA-based polyester blend with mineral filler (PLA_2), and polybutylene succinate with mineral filler (PBS_1) in the form of the film, were subjected to soil burial biodegradation processes. The experiments were carried out in a climate with an average annual temperature of 9.4 °C, in winter and summer periods for one year. The degradation of the materials was evaluated by macro- and microscopic observations, weight loss, thermogravimetric analysis, and tensile test. Macroscopic observation indicated that changes in the color of film surface were visible for samples PBS_1 after 12 months of degradation. Using microscopic inspection the erosion of surface samples PLA_1 and PBS_1 after 12 months was observed. Mass loss of samples PLA_1 and PLA_2 after one year of degradation were below 0.6 %. Moreover, for PBS_1 sample, mass loss was equal to 4.3 %. Based on the obtained results of the mass loss, a description of the degradation kinetics was proposed, showing the changes in the thickness of the tested polymer over time. The thermal stability of the samples PLA_1 and PLA_2 decreased during the degradation process by 16.1 and 2.6 °C, respectively, and for PBS_1 increased by 1.7 °C. Tensile strength at break after 12 months of degradation decreased for sample PLA_1 and PLA_2 by 27.3 and 5.8 %, respectively, and increased for sample PBS_1 by 28.2 % compare to unexposed sample.
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4,588 members
Grzegorz Liśkiewicz
  • Institute of Turbomachinery
Dorota Bociaga
  • Institute of Materials Science and Engineering
Jolanta Prywer
  • Institute of Physics
Żeromskiego 116, 90-924, Łódź, Poland
Head of institution
Sławomir Wiak