Novel two‐stage phenol–formaldehyde resol resin synthesis

The synthesis of phenol–formaldehyde resol resins was carried out in two stages to facilitate the start of a conventional batch process. In the first stage, the starting material solution was preprocessed in a continuous‐flow stirred‐tank reactor with a 5‐min residence time. In the second stage, synthesis was continued in a batch reactor. Samples were analyzed by titrimetric methods, gas chromatography, nuclear magnetic resonance spectroscopy, and differential scanning calorimetry. Most of the starting materials were consumed in the preprocessing reactor, which allowed better control of the reactivity of the prepolymer solution in the second stage. The methylolation and condensation reactions proceeded steadily during the production process in the batch reactor. The results of the study indicated that dividing a conventional one‐stage batch process into two stages could facilitate the control of the initial stages of resol production. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103:371–379, 2007     

Properties and Stability of Mining-Induced Meromixis in Two Small Boreal Lakes in Eastern Finland

Mine waters are a significant point source stressor for aquatic environments, not only due to their acidity and high metal concentrations, but also because of their high electrolyte concentrations. Ion-rich mine waters can disturb the seasonal mixing of lake waters, even leading to permanent stratification, i.e. meromixis. In this study, we investigated two small natural lakes receiving waters from closed Ni-Cu mines. To characterize the present chemical and physical conditions of these two boreal lakes, we collected water samples and in-situ water column measurements seasonally in 2017 and 2018. We modelled the stability of meromixis in the lakes under varying physico-chemical and meteorological conditions with the MATLAB-based open-source model code, MyLake. Chemical analyses and water column measurements show that both lakes are currently meromictic with a chemocline separating the circulating, well-oxygenated upper water from the non-circulating, hypoxic bottom water. The main anion was SO₄ in both lakes, while the main cations were Ca, Mg, Na, and K. Elevated concentrations of conservative elements flowing from the mine areas are crucial in maintaining the meromixis. Modelling scenarios suggest that the meromixis would be sustained for several decades even if the external load ceased completely. Lake morphology and sheltered surroundings also seem to contribute to maintaining the meromixis in these lakes. Consequently, our results indicate that small headwaters are sensitive to persistent meromixis even when external loading is mild.

     

Miscibility,morphology and mechanical properties of rubber‐modified biodegradable poly(ester‐urethanes)

Biodegradable, lactic acid based amorphous poly(ester‐urethane)s (PEU) were modified with poly(L‐lactic acid‐co‐ϵ‐caprolactone‐urethane) elastomer (P[LA/CL]U) by melt blending. The phase separation of P(LA/CL)U elastomer with three different ϵ‐caprolactone (CL) compositions (CL content 30, 50, and 70 mol %) and the mechanical properties of the resulting impact‐modified linear and branched PEU were investigated. The amounts of P(LA/CL)U elastomer in the PEU blends were 10, 15, 20, and 30 wt %. Dynamic mechanical thermal analysis (DMTA) of the blends with P(LA50/CL50)U and P(LA30/CL70)U elastomers revealed separate glass transition temperatures for rubber and matrix, indicating phase separation. No phase separation was found for P(LA70/CL30)U elastomer. The effect of mixing rate and temperature during processing on composite properties was tested by blending P(LA30/CL70)U rubber with PEU under various processing conditions. Impact modification studies were also made with two P(LA30/CL70)U elastomers having different amounts of functional groups. The influence of end‐functionalization and cross‐linking on mechanical properties was investigated in blends containing PEU and 15 wt % of these elastomers. Scanning electron microscopy (SEM) showed the morphology to change dramatically with increase in the degree of cross‐linking in the rubber. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1074–1084, 2000     

Fatty Acid Fingerprints and Hyaluronic Acid in Extracellular Vesicles from Proliferating Human Fibroblast-like Synoviocytes

Extracellular vesicles (EVs) function as conveyors of fatty acids (FAs) and other bioactive lipids and can modulate the gene expression and behavior of target cells. EV lipid composition influences the fluidity and stability of EV membranes and reflects the availability of lipid mediator precursors. Fibroblast-like synoviocytes (FLSs) secrete EVs that transport hyaluronic acid (HA). FLSs play a central role in inflammation, pannus formation, and cartilage degradation in joint diseases, and EVs have recently emerged as potential mediators of these effects. The aim of the present study was to follow temporal changes in HA and EV secretion by normal FLSs, and to characterize the FA profiles of FLSs and EVs during proliferation. The methods used included nanoparticle tracking analysis, confocal laser scanning microscopy, sandwich-type enzyme-linked sorbent assay, quantitative PCR, and gas chromatography. The expression of hyaluronan synthases 1–3 in FLSs and HA concentrations in conditioned media decreased during cell proliferation. This was associated with elevated proportions of 20:4n-6 and total n-6 polyunsaturated FAs (PUFAs) in high-density cells, reductions in n-3/n-6 PUFA ratios, and up-regulation of cluster of differentiation 44, tumor necrosis factor α, peroxisome proliferator-activated receptor (PPAR)-α, and PPAR-γ. Compared to the parent FLSs, 16:0, 18:0, and 18:1n-9 were enriched in the EV fraction. EV counts decreased during cell growth, and 18:2n-6 in EVs correlated with the cell count. To conclude, FLS proliferation was featured by increased 20:4n-6 proportions and reduced n-3/n-6 PUFA ratios, and FAs with a low degree of unsaturation were selectively transferred from FLSs into EVs. These FA modifications have the potential to affect membrane fluidity, biosynthesis of lipid mediators, and inflammatory processes in joints, and could eventually provide tools for translational studies to counteract cartilage degradation in inflammatory joint diseases.     

Tree cover and height estimation in the Fennoscandian tundra-taiga transition zone using multiangular MISR data

The tundra-taiga transition zone stretches around the northern hemisphere separating boreal forest to the south from treeless tundra to the north. Tree cover and height are important variables to characterize this vegetation transition. Accurate continuous fields of tree cover and height would enable the delineation of the forest extent according to different criterion and provide useful data for change detection of this climatically sensitive ecotone. This study examined if multiangular remote sensing data has potential to improve the accuracy of the tree cover and height estimates in relation to nadir-view data. The satellite data consisted of Multi-angle Imaging SpectroRadiometer (MISR) data at 275 m and 1.1 km resolutions. The study area was located in the Fennoscandian tundra-taiga transition zone, in northernmost Finland. The continuous fields of tree cover and height were estimated using neural networks, which were trained and assessed by high-resolution biotope inventory data. The spectral-angular data together produced lower estimation errors than single band nadir, multispectral nadir or single band multiangular data alone. RMSE of the tree cover estimates reduced from 7.8% (relative RMSE 67.4%) to 6.5% (56.1%) at 275 m resolution, and from 5.4% (49.2%) to 4.1% (36.9%) at 1.1 km resolution, when multispectral nadir data were used together with multiangular data. RMSE of the tree height estimates reduced from 2.3 m (44.3%) to 2.0 m (37.6%) and from 1.8 m (35.4%) to 1.3 m (25.4%), respectively. The largest estimation errors occurred in mires and in areas of dense shrub cover, but the use of multiangular data also reduced estimation errors in these areas. The results suggest that directional information has potential to improve the tree cover and height estimates, and hence the accuracy of the land cover change detection in the tundra-taiga transition zone.     

Carbon nanotube micropillars trigger guided growth of complex human neural stem cells networks

Nano Research - New strategies for spatially controlled growth of human neurons may provide viable solutions to treat and recover peripheral or spinal cord injuries. While topography cues are known...     

Magnetotransport study on as-grown and annealed n- and p-type modulation-doped GaInNAs/GaAs strained quantum well structures

We report the observation of thermal annealing- and nitrogen-induced effects on electronic transport properties of as-grown and annealed n- and p-type modulation-doped Ga_{1 - x}In_xN_yAs_{1 - y} (x = 0.32, y = 0, 0.009, and 0.012) strained quantum well (QW) structures using magnetotransport measurements. Strong and well-resolved Shubnikov de Haas (SdH) oscillations are observed at magnetic fields as low as 3 T and persist to temperatures as high as 20 K, which are used to determine effective mass, 2D carrier density, and Fermi energy. The analysis of temperature dependence of SdH oscillations revealed that the electron mass enhances with increasing nitrogen content. Furthermore, even the current theory of dilute nitrides does not predict a change in hole effective mass; nitrogen dependency of hole effective mass is found and attributed to both strain- and confinement-induced effects on the valence band. Both electron and hole effective masses are changed after thermal annealing process. Although all samples were doped with the same density, the presence of nitrogen in n-type material gives rise to an enhancement in the 2D electron density compared to the 2D hole density as a result of enhanced effective mass due to the effect of nitrogen on conduction band. Our results reveal that effective mass and 2D carrier density can be tailored by nitrogen composition and thermal annealing-induced effects.

PACS

72.00.00; 72.15.Gd; 72.80.Ey     

States on semi-divisible residuated lattices

Given a residuated lattice L, we prove that the subset MV(L) of complement elements x ^* of L generates an MV-algebra if, and only if L is semi-divisible. Riečan states on a semi-divisible residuated lattice L, and Riečan states on MV(L) are essentially the very same thing. The same holds for Bosbach states as far as L is divisible. There are semi-divisible residuated lattices that do not have Bosbach states. These results were obtained when the authors visited Academy of Science, Czech Republic, Institute of Comp. Sciences in Autumn 2006.     

Specification-based data reduction in dimensional data warehouses

Many data warehouses contain massive amounts of data, accumulated over long periods of time. In some cases, it is necessary or desirable to either delete “old” data or to maintain the data at an aggregate level. This may be due to privacy concerns, in which case the data are aggregated to levels that ensure anonymity. Another reason is the desire to maintain a balance between the uses of data that change as the data age and the size of the data, thus avoiding overly large data warehouses. This paper presents effective techniques for data reduction that enable the gradual aggregation of detailed data as the data ages. With these techniques, data may be aggregated to higher levels as they age, enabling the maintenance of more compact, consolidated data and the compliance with privacy requirements. Special care is taken to avoid semantic problems in the aggregation process. The paper also describes the querying of the resulting data warehouses and an implementation strategy based on current database technology.