A fourth-order accurate, three-point compact approximation of the boundary gradient, for electrochemical kinetic simulations by the extended Numerov method

The fourth-order accurate, three-point compact (extended Numerov) finite-difference scheme of Chawla [J. Inst. Math. Appl. 22 (1978) 89] has been recently found superior (in terms of accuracy and efficiency) to the conventional second-order accurate spatial discretisation commonly used in electrochemical kinetic simulations. However, the two-point compact boundary gradient approximation, accompanying the scheme, is difficult to apply in the case of time-dependent kinetic partial differential equations, because it introduces unwanted second temporal derivatives into calculations. The conventional five-point gradient formula is free from this drawback, but it is also not very convenient, owing to the locally increased bandwidth of the matrix of linear equations arising from the spatio-temporal discretisation. A new three-point compact boundary gradient approximation derived in this work, avoids the above inconveniences and economically re-uses expressions utilised by the extended Numerov discretisation. The fourth-order accuracy of the new approximation is proven theoretically and verified in computational experiments performed for examples of kinetic models.     

MIR spectroscopy and partial least-squares regression for determination of phospholipids in rapeseed oils at various stages of technological process

Fourier transform-mid infrared spectroscopy (FT-MIR) and partial least-square (PLS) regression were used for determination of phospholipids (PL) in rapeseed oils at various stages of technological process. The standard error of calibration (SEC) and the standard error of prediction (SEP) were calculated for evaluation of the calibration models. The chemometric calibration model was prepared in spectral region 1760–860 cm⁻¹ for standard PL solutions (1.5–120 mg/mL). Obtained mean concentrations of PL in rapeseed oils at different stages of conventional technological operations varied from 22,710 to 224.6 mg/kg. Satisfactory values of precision (RSD = 0.23–0.73%) and accuracy (recovery – 96.1–101.9%), demonstrate the benefit of the proposed MIR-PLS method in the routine analysis of PL in vegetable oils.     

Lexicon randomization for near-duplicate detection with I-Match

Detection of near duplicate documents is an important problem in many data mining and information filtering applications. When faced with massive quantities of data, traditional techniques relying on direct inter-document similarity computation are often not feasible given the time and memory performance constraints. On the other hand, fingerprint-based methods, such as I-Match, while very attractive computationally, can be unstable even to small perturbations of document content, which causes signature fragmentation. We focus on I-Match and present a randomization-based technique of increasing its signature stability, with the proposed method consistently outperforming traditional I-Match by as high as 40–60% in terms of the relative improvement in near-duplicate recall. Importantly, the large gains in detection accuracy are offset by only small increases in computational requirements. We also address the complimentary problem of spurious matches, which is particularly important for I-Match when fingerprinting long documents. Our discussion is supported by experiments involving large web-page and email datasets.     

The Influence of Bisphenol A (BPA) on the Occurrence of Selected Active Substances in Neuregulin 1 (NRG1)-Positive Enteric Neurons in the Porcine Large Intestine

Bisphenol A (BPA) is a substance used in the manufacture of plastics which shows multidirectional adverse effects on living organisms. Since the main path of intoxication with BPA is via the gastrointestinal (GI) tract, the stomach and intestine are especially vulnerable to the impact of this substance. One of the main factors participating in the regulation of intestinal functions is the enteric nervous system (ENS), which is characterized by high neurochemical diversity. Neuregulin 1 (NRG1) is one of the lesser-known active substances in the ENS. During the present study (performed using the double immunofluorescence method), the co-localization of NRG1 with other neuronal substances in the ENS of the caecum and the ascending and descending colon has been investigated under physiological conditions and after the administration of BPA. The obtained results indicate that NRG1-positive neurons also contain substance P, vasoactive intestinal polypeptide, a neuronal isoform of nitric oxide synthase and galanin and the degree of each co-localization depend on the type of enteric plexus and the particular fragment of the intestine. Moreover, it has been shown that BPA generally increases the degree of co-localization of NRG1 with other substances.     

Fibronectin Molecular Status in Plasma of Women with Endometriosis and Fertility Disorders

The diagnosis of endometriosis and fertility disorders is difficult; therefore, it is necessary to look for reliable biomarkers. Analysis of the molecular status of fibronectin as a key player in repair and wound healing processes, as well as in coagulation and fibrinolysis pathways, is justified. ELISA and SDS-agarose immunoblotting were applied to determine the fibronectin concentration and presence and occurrence of soluble FN-fibrin complexes in the blood plasma of women with endometriosis (n = 38), fertility disorders (n = 28) and the healthy group (n = 25). The concentration of fibronectin in the blood plasma of women with endometriosis (292.61 ± 96.17 mg/L) and fertility disorders (287.53 ± 122.68 mg/L) was significantly higher than in the normal group (226.55 ± 91.98 mg/L). The presence of FN-fibrin complexes of 750, 1000, 1300, 1600 and 1900 kDa in the plasma of women with endometriosis and fertility disorders was shown. The presence of FN-fibrin complexes with a molecular mass of more than 1300 kDa in women with endometriosis and infertility and the complete absence of these complexes in healthy women may indicate an increased and chronic activation of coagulation mechanisms in these patients. The presence of complexes of high molecular mass may be one of the biomarkers of fertility disorders in women.     

Toward integrated detection and graphene-based removal of contaminants in a lab-on-a-chip platform

A novel miniaturized microfluidic platform was developed for the simultaneous detection and removal of polybrominated diphenyl ethers (PBDEs).The platform consists of a polydimethylsiloxane (PDMS) microfluidic chip for an immunoreaction step,a PDMS chip with an integrated screen-printed electrode (SPCE) for detection,and a PDMS-reduced graphene oxide (rGO) chip for physical adsorption and subsequent removal of PBDE residues.The detection was based on competitive immunoassay-linked binding between PBDE and PBDE modified with horseradish peroxidase (HRP-PBDE) followed by the monitoring of enzymatic oxidation of o-aminophenol (o-AP) using square wave anodic stripping voltammetry (SW-ASV).PBDE was detected with good sensitivity and a limit of detection similar to that obtained with a commercial colorimetric test (0.018 ppb),but with the advantage of using lower reagent volumes and a reduced analysis time.The use of microfluidic chips also provides improved linearity and a better reproducibility in comparison to those obtained with batch-based measurements using screen-printed electrodes.In order to design a detection system suitable for toxic compounds such as PBDEs,a reduced graphene oxide-PDMS composite was developed and optimized to obtain increased adsorption (based on both the hydrophobicity and π-π stacking between rGO and PBDE molecules) compared to those of non-modified PDMS.To the best of our knowledge,this is the first demonstration of electrochemical detection of flame retardants and a novel application of the rGO-PDMS composite in a biosensing system.This system can be easily applied to detect any analyte using the appropriate immunoassay and it supports operation in complex matrices such as seawater.     

Heme Oxygenase-1 Has a Greater Effect on Melanoma Stem Cell Properties Than the Expression of Melanoma-Initiating Cell Markers

Melanoma-initiating cells (MICs) contribute to the tumorigenicity and heterogeneity of melanoma. MICs are identified by surface and functional markers and have been shown to display cancer stem cell (CSC) properties. However, the existence of MICs that follow the hierarchical CSC model has been questioned by studies showing that single unselected melanoma cells are highly tumorigenic in xenotransplantation assays. Herein, we characterize cells expressing MIC markers (CD20, CD24, CD133, Sca-1, ABCB1, ABCB5, ALDH^high) in the B16-F10 murine melanoma cell line. We use flow cytometric phenotyping, single-cell sorting followed by in vitro clonogenic assays, and syngeneic in vivo serial transplantation assays to demonstrate that the expression of MIC markers does not select CSC-like cells in this cell line. Previously, our group showed that heme-degrading enzyme heme oxygenase-1 (HO-1) can be upregulated in melanoma and increase its aggressiveness. Here, we show that HO-1 activity is important for non-adherent growth of melanoma and HO-1 overexpression enhances the vasculogenic mimicry potential, which can be considered protumorigenic activity. However, HO-1 overexpression decreases clone formation in vitro and serial tumor initiation in vivo. Thus, HO-1 plays a dual role in melanoma, improving the progression of growing tumors but reducing the risk of melanoma initiation.