Mathematical Modeling of Two-Stage Extraction Kinetics using the Single Drop Technique

This paper focuses on the mathematical modeling of the two-stage extraction using the single drop technique. Two stages of extraction are being considered: the drop formation step, where dimensions of the drop are highly dependent on time, and the drop travel step, during which the drops size and dimensions are assumed constant. Models for both extraction steps are derived and the combined model is proposed. Two-stage and one-stage models of extraction are compared. Errors occuring when considering only the travel stage of the single drop extraction have been calculated and their dependencies on various extraction parameters have been determined. The analysis of the combined two-stage model has proven that the travel-stage-only model generates significant errors during the determination of reaction rate constants when the drop formation time is significant in relation to the whole extraction time. Thus, the two-stage model should be used to reduce originating errors.     

Molecular and Circulating Biomarkers of Brain Tumors

Brain tumors are the most common malignant primary intracranial tumors of the central nervous system. They are often recognized too late for successful therapy. Minimally invasive methods are needed to establish a diagnosis or monitor the response to treatment of CNS tumors. Brain tumors release molecular information into the circulation. Liquid biopsies collect and analyze tumor components in body fluids, and there is an increasing interest in the investigation of liquid biopsies as a substitute for tumor tissue. Tumor-derived biomarkers include nucleic acids, proteins, and tumor-derived extracellular vesicles that accumulate in blood or cerebrospinal fluid. In recent years, circulating tumor cells have also been identified in the blood of glioblastoma patients. In this review of the literature, the authors highlight the significance, regulation, and prevalence of molecular biomarkers such as O₆-methylguanine-DNA methyltransferase, epidermal growth factor receptor, and isocitrate dehydrogenase. Herein, we critically review the available literature on plasma circulating tumor cells (CTCs), cell-free tumors (ctDNAs), circulating cell-free microRNAs (cfmiRNAs), and circulating extracellular vesicles (EVs) for the diagnosis and monitoring of brain tumor. Currently available markers have significant limitations. While much research has been conductedon these markers, there is still a significant amount that we do not yet understand, which may account for some conflicting reports in the literature.     

Identification of Novel miRNAs and Their Target Genes in the Response to Abscisic Acid in Arabidopsis

miRNAs are involved in various biological processes, including adaptive responses to abiotic stress. To understand the role of miRNAs in the response to ABA, ABA-responsive miRNAs were identified by small RNA sequencing in wild-type Arabidopsis, as well as in abi1td, mkkk17, and mkkk18 mutants. We identified 10 novel miRNAs in WT after ABA treatment, while in abi1td, mkkk17, and mkkk18 mutants, three, seven, and nine known miRNAs, respectively, were differentially expressed after ABA treatment. One novel miRNA (miRn-8) was differentially expressed in the mkkk17 mutant. Potential target genes of the miRNA panel were identified using psRNATarget. Sequencing results were validated by quantitative RT-PCR of several known and novel miRNAs in all genotypes. Of the predicted targets of novel miRNAs, seven target genes of six novel miRNAs were further validated by 5′ RLM-RACE. Gene ontology analyses showed the potential target genes of ABA-responsive known and novel miRNAs to be involved in diverse cellular processes in plants, including development and stomatal movement. These outcomes suggest that a number of the identified miRNAs have crucial roles in plant responses to environmental stress, as well as in plant development, and might have common regulatory roles in the core ABA signaling pathway.     

Analytical estimation of coordinate measurement uncertainty

The paper presents the assumptions and theoretical background of analytical method of estimation the coordinate measurement uncertainty. The uncertainty for each characteristic is estimated separately. Mathematical model for each characteristic uses the minimal number of so-called “characteristic points” of the measured workpiece. Each characteristic is defined by a formula presented in a form where it is a function of coordinates’ differences’ of characteristic points. The uncertainty budget for the coordinates’ differences includes influences of particular geometrical errors of CMM, probing system errors, as well as temperature errors. The applied algorithms of uncertainty estimation use the type B method according to the rules of GUM.     

Load capacity and deflection of fire-resistant steel beams

The methodology of defining safety of constructions in fire has not yet been sufficiently verified and agreed upon. This paper includes calculation results for steel beams, which prove that the ultimate load-bearing capacity predicted by plastic design theory, which is valid in engineering calculations, is not sufficient for determining the critical temperature. The reason is that this temperature tends to be limited in some cases by large deflections of beams in fire.     

Behavior of composite beams prestressed with external tendons: Experimental study

The paper deals with the failure mechanisms and behavior of composite steel-concrete beams prestressed with external tendons and subjected to positive bending. Experimental tests were carried out on beams with straight and draped tendons as well as on a non-prestressed beam. Six simply supported beams subjected to a positive static bending moment were tested up to failure. The influence of shear connection flexibility was taken into account and slip was measured along the beam axis. Concurrently, push-out specimens were made and tested to determine shear force vs. slip curves. It was found that at the same eccentricity of tendons (draped or straight without saddle points) the tendon shape has no significant effect on the behavior and ultimate resistance of composite steel-concrete beams. It is also shown that steel-concrete bond cohesion can significantly influence the behavior of the shear connection in composite beams. This influence is comparable with the design shear resistance of a single stud connector.     

The structure of mineral fillers and their stiffening properties in filler-bitumen mastics

The subject of the study was limestone filler samples of various structures, which were obtained through planned laboratory processing. The aim of the paper was to improve knowledge on the subject of the structure of limestone fillers (grain-size distribution, specific surface area, void content, shape ‘sphericity’ and texture of grain surfaces ‘roundness’), as well as investigating the numerical quantity relationship between the structures of fillers and their stiffening properties. Analysis of the results showed considerable differences in the structure of the tested fillers regarding Rigden void (RV), specific surface area S _sp, average grain diameter and grain morphology. It also proved, for 95% confidence interval that there is a considerable influence of RV, S _sp, as well as the roundness of the grains of the fillers on their stiffening properties.