Microfluidic mixers: from microfabricated to self-assembling devices

This paper begins with a survey of both passive and active microfluidic mixers that have been implemented in recent years. It then describes a micromixing device based on dynamic self-assembly. This device is easy to fabricate and has excellent working characteristics in the continuous-flow mode. The paper concludes with a brief discussion of possible applications of self-assembly in microfluidics.     

Fixed point method for autonomous on-line neural network training

This paper considers on-line training of feedforward neural networks. Training examples are only available through sampling from a certain, possibly infinite, distribution. In order to make the learning process autonomous, one can employ Extended Kalman Filter or stochastic steepest descent with adaptively adjusted step-sizes. Here the latter is considered. A scheme of determining step-sizes is introduced that satisfies the following requirements: (i) it does not need any auxiliary problem-dependent parameters, (ii) it does not assume any particular loss function that the training process is intended to minimize, (iii) it makes the learning process stable and efficient. An experimental study with several approximation problems is presented. Within this study the presented approach is compared with Extended Kalman Filter and LFI, with satisfactory results.     

Quantitative Control of Early Flowering in White Lupin (Lupinus albus L.)

White lupin (Lupinus albus L.) is a pulse annual plant cultivated from the tropics to temperate regions for its high-protein grain as well as a cover crop or green manure. Wild populations are typically late flowering and have high vernalization requirements. Nevertheless, some early flowering and thermoneutral accessions were found in the Mediterranean basin. Recently, quantitative trait loci (QTLs) explaining flowering time variance were identified in bi-parental population mapping, however, phenotypic and genotypic diversity in the world collection has not been addressed yet. In this study, a diverse set of white lupin accessions (n = 160) was phenotyped for time to flowering in a controlled environment and genotyped with PCR-based markers (n = 50) tagging major QTLs and selected homologs of photoperiod and vernalization pathway genes. This survey highlighted quantitative control of flowering time in white lupin, providing statistically significant associations for all major QTLs and numerous regulatory genes, including white lupin homologs of CONSTANS, FLOWERING LOCUS T, FY, MOTHER OF FT AND TFL1, PHYTOCHROME INTERACTING FACTOR 4, SKI-INTERACTING PROTEIN 1, and VERNALIZATION INDEPENDENCE 3. This revealed the complexity of flowering control in white lupin, dispersed among numerous loci localized on several chromosomes, provided economic justification for future genome-wide association studies or genomic selection rather than relying on simple marker-assisted selection.     

Assessing the effectiveness of colloidal microcrystalline cellulose as a suspending agent for black and white liquid dyes

This study aimed to determine the effect of the concentration (1, 5, or 8 wt%) of colloidal microcrystalline cellulose (MCCS) as suspending agent on the long-term stability and rheology of the vegetable carbon (C) and calcium carbonate (CC) suspended in water–glycerine mixture. These suspensions as ready-to-use black and white liquid dyes containing 10 wt% C or CC were assessed for particle size, Turbiscan stability index (TSI), steady shear, thixotropy and dynamic viscoelasticity. After 370 days, the black dyes showed excellent stability (TSI ≪ 0.5) at 4 °C and 25 °C already at 1 wt% MCCS, while the white dyes showed reasonable stability (TSI 1–3) only at 5 and 8 wt% MCCS. Dye formulations exhibited a relatively liquid-like viscoelastic behaviour, while they showed extremely shear-thinning behaviour with a network structure dependent on the concentration of the MCCS as exhibited by the increase in thixotropy and the existence of the measurable yield stress.     

Hydrogen production by direct injection of ethanol microdroplets into nitrogen microwave plasma flame

Liquid ethanol introduced as microdroplets into the tip of microwave nitrogen plasma, operating at 2.45 GHz under atmospheric pressure, has been investigated. Injection of ethanol outside the region of plasma generation eliminated a problem of soot formation at that region, which was responsible for short reactor lifetime. Using liquid ethanol allows to save energy needed for vaporization. Hydrogen, carbon monoxide and solid carbon were the main outlet products. Other products detected with gas chromatography were CH₄, C₂H₄ and C₂H₂. The best results concerning hydrogen production were as follows: concentration in the outlet gas up to 28%, production rate up to 1043 L/h, energy yield up to 209 L per kWh of microwave power, and were obtained for liquid C₂H₅OH flow rate of 3.7 L/h. A numerical 0D model was used to determine contributions of chemical reactions in formation of measured gaseous products. Simplified model involving only radical reactions without any ions and electrons predicts final concentrations of main compounds quite well for microwave power up to 4 kW.     

The G-Protein-Coupled Membrane Estrogen Receptor Is Present in Horse Cryptorchid Testes and Mediates Downstream Pathways

Cryptorchidism in horses is a commonly occurring malformation. The molecular basis of this pathology is not fully known. In addition, the origins of high intratesticular estrogen levels in horses remain obscure. In order to investigate the role of the G-protein-coupled membrane estrogen receptor (GPER) and establish histological and biochemical cryptorchid testis status, healthy and cryptorchid horse testes were subjected to scanning electron microscopy analysis, histochemical staining for total protein (with naphthol blue black; NBB), acid content (with toluidine blue O; TBO), and polysaccharide content (with periodic acid–Schiff; PAS). The expression of GPER was analyzed by immunohistochemistry and Western blot. GPER-mediated intracellular cAMP and calcium (Ca2+) signaling were measured immunoenzymatically or colorimetrically. Our data revealed changes in the distribution of polysaccharide content but not the protein and acid content in the cryptorchid testis. Polysaccharides seemed to be partially translocated from the interstitial compartment to the seminiferous tubule compartment. Moreover, the markedly decreased expression of GPER and GPER downstream molecules, cAMP and Ca2+, suggests their potential role in testis pathology. Increased estrogen levels in cryptorchid conditions may be linked to disturbed GPER signaling. We postulate that GPER is a prominent key player in testis development and function and may be used as a new biomarker of horse testis in health and disease.     

Sensitivity of antioxidant-deficient yeast to hypochlorite and chlorite

Sodium hypochlorite and sodium chlorite are commonly used as disinfectants, and understanding the mechanisms of microbial resistance to these compounds is of considerable importance. In this study, the role of oxidative stress and antioxidant enzymes in the sensitivity of the yeast Saccharomyces cerevisiae to hypochlorite and chlorite was studied. Yeast mutants lacking Cu-Zn superoxide dismutase, but not mutants deficient in cytoplasmic and peroxisomal catalase, were hypersensitive to the action of both hypochlorite and chlorite. Both compounds depleted cellular glutathione, induced the production of reactive oxygen species and decreased the viability of the cells. The toxicity of hypochlorite and chlorite was abolished by hypoxic and anoxic conditions and ameliorated by thiol antioxidants and ascorbate. The results demonstrated that the action of hypochlorite and chlorite involves the formation of superoxide and peroxide and that SOD1 is protective, probably by limiting the formation of hydroxyl radicals and damage to proteins.     

Electrical conductivity and reaction with lithium of LiFe1−yMnyPO4 olivine-type cathode materials

Structural, electrical and electrochemical properties of Mn-substituted phospho-olivines LiFe_1−yMn_yPO₄ were investigated and compared to those of LiFePO₄. Rietvield refined XRD patterns taken in the course of delithiation process showed apparent difference between phase compositions of these cathode materials upon lithium extraction. Contrary to the LiFePO₄ and LiMnPO₄ compositions for which a two-phase mechanism of electrochemical lithium extraction/insertion is observed, in case of Mn-substituted LiFe_1−yMn_yPO₄ samples a single-phase mechanism of deintercalation was observed in the studied range of lithium concentration. Electrochemical characterization of the cathode materials were performed in Li/Li⁺/Li_xFe_1−yMn_yPO₄-type cells for y = 0.0, 0.25, 0.55, 0.75 and 1.0 compositions. Voltammery studies showed low reversibility of the lithium extraction process in the high-voltage “manganese” range, while in the “iron” range the reversibility of lithium extraction is high. Impedance measurements of the LiFe_1−yMn_yPO₄ cathode materials, which enabled separation of the ionic and electronic components of their entire electrical conductivity, showed distinct influence of Mn content on the electronic part of conductivity. EIS measurements performed at different states of cell charge revealed that the charge-transfer impedance in Li_xFe_1−yMn_yPO₄ is much lower than that of Li_xFePO₄.     

Interactions between carbon coatings and tissue

The unique properties of thin diamond layers make them perspective candidates for producing advanced micro-electronic devices, coatings for cutting tools and optics. However, due to the highest biocompatibility of carbon resulting from the presence of this element in the human body, it appears to be a potential biomaterial.Carbon, especially in the form of the nanocrystalline diamond film, have found industrial applications in the area of medical implants.The studies of carbon films as coatings for implants in surgery were aimed at the investigations of biological resistance of implants, histopathological investigations on laboratory animals, tests of corrosion resistance, measurements of mechanical properties and a breakdown test in Tyrode's solution.Different medical implants are covered by Nanocrystalline Diamond Coatings (NCD). NCD forms the barrier diffusion between implant and human environment. The research on NCD proved that diamond layers are biocompatible with living organisms.Diamond Powder Particles (DPP) is an extended surface of NCD. Biological research with diamond powder can answer the basic question: what is the influence of DPP on cells, tissues and organs in human organism?