Corrosion resistance and lifetime of polyimide-b-polyurea novel copolymer coatings

A novel class of polyurea-b-polyimide (PUI) block copolymer coating containing environmentally friendly aromatic polyurea has been successfully synthesized for corrosion protection of aluminum alloy 2024-T3 (Al 2024-T3). The PUI copolymer is able to self-assemble into a supramacromolecule by means of intra and inter-hydrogen bonds (H-bonds). The formation of H-bonds and effect of the later on the crystallinity of the copolymer was studied by using Fourier transform infrared spectroscopy (FTIR) and wide angle X-ray diffraction (WAXD). It was shown that increasing polyurea mole fraction up to 50 mol%, enhanced occurrence of H-bonding induced self-assembly, and resulted in remarkable enhancement in the degree of crystallinity, and corrosion resistance. Corrosion resistance and diffusivity of the copolymer coatings were investigated by electrochemical impedance spectroscopy (EIS), in a 3.5 wt% NaCl solution. The coating lifetime determined by using time-based corrosion resistance, was shown to be about 8 years for the optimized PUI copolymer coating. PUI coating synthesized by using 50 mol% of polyurea has a high contact angle (110°) and remarkably low surface energy of about 25.5 mJ/m².     

Effect of isothermal aging on the imidization of PMR-15

The imidization of polymerizable reactive mixtures, PMR-15 has been performed in a vacuum oven at isothermal aging temperatures ranging from 65 to 200°C for aging periods of 0.5 to 2.5 h. The weight loss of the resin and chemical changes that occurred as a result of aging were monitored gravimetrically and by FT-IR spectroscopy. Differential scanning calorimetry was used to determine the temperature at which imidization took place. Imidization was observed to commence at 65°C after long aging times, t ≥ 2.5 h and at ∼95°C at a shorter time, t ∼0.5 h. At higher aging temperatures of 135 to 165°C, extensive imidization occurred. This was shown by the dramatic increase in imide absorption bands at 1780 and 1380 cm⁻¹. Beyond 165°C, there were no significant changes in the imide absorption bands, suggesting that imidization was nearly complete. The activation energy for isothermal aging was determined from the slope of the log of the rate of weight loss vs 1/T curve to be ∼4.5 kJ/mol and is lower than the average activation energy for imidization ∼43 kJ/mol obtained from the plot of the log of the rate of increase of the imide carbonyl peak absorption at 1780 cm⁻¹ vs 1/T.     

Histamine H4 Receptor Agonism Induces Antitumor Effects in Human T-Cell Lymphoma

The discovery of the human histamine H4 receptor (H4R) has contributed to our understanding of the role of histamine in numerous physiological and pathological conditions, including tumor development and progression. The lymph nodes of patients with malignant lymphomas have shown to contain high levels of histamine, however, less is known regarding the expression and function of the H4R in T-cell lymphoma (TCL). In this work we demonstrate the expression of H4R isoforms (mRNA and protein) in three human aggressive TCL (OCI-Ly12, Karpas 299, and HuT78). Histamine and specific H4R agonists (VUF8430 and JNJ28610244) significantly reduced cell viability in a dose-dependent manner (p < 0.05). The combined treatment with the H4R antagonist (JNJ7777120, 10 µM) reversed the effects of the H4R ligands. Importantly, we screened a drug repurposing library of 433 FDA-approved compounds (1 μM) in combination with histamine (10 μM) in Hut78 cells. Histamine produced a favorable antitumor effect with 18 of these compounds, including the histone deacetylase inhibitor panobinostat. Apoptosis, proliferation, and oxidative stress studies confirmed the antitumoral effects of the combination. We conclude that the H4R is expressed in TCL, and it is involved in histamine-mediated responses.     

Energy consumption and economic growth revisited in African countries

The aim of this paper is to provide new empirical evidence on the relationship between energy consumption and economic growth for 21 African countries over the period from 1970 to 2006, using recently developed panel cointegration and causality tests. The countries are divided into two groups: net energy importers and net energy exporters. It is found that there exists a long-run equilibrium relationship between energy consumption, real GDP, prices, labor and capital for each group of countries as well as for the whole set of countries. This result is robust to possible cross-country dependence and still holds when allowing for multiple endogenous structural breaks, which can differ among countries. Furthermore, we find that decreasing energy consumption decreases growth and vice versa, and that increasing energy consumption increases growth, and vice versa, and that this applies for both energy exporters and importers. Finally, there is a marked difference in the cointegration relationship when country groups are considered.     

Turmeric nanofiber-encapsulated natural product formulation act as a phytogenic feed additive—A study in broilers on growth performance,biochemical indices of blood,and E. coli in cecum

A phytogenic feed additive (PFA) formulation was prepared with bioactive molecules—curcuminoids, gingerol, and carvacrol by encapsulating in nanofiber isolated from turmeric spent (turmeric nanofiber, TNF). This formulation was completely characterized by scanning electron microscope, ultra performance liquid chromatography, and gas chromatography and evaluated for its efficacy. PFA-encapsulated TNF (PFA@TNF) considerably increased mean body weight, decreased cholesterol level, mortality rate, and reduced Escherichia coli content of broilers than antibiotic growth promoter (AGP). The depth of crypts in the ileum of broilers was considerably reduced by the inclusion of PFA@TNF in diets compared with the AGP.     

Modulation of gramicidin channel structure and function by the aliphatic "spacer" residues 10, 12, and 14 between the tryptophans

In the linear gramicidins, the four aromatic residues at positions 9, 11, 13, and 15 are well-known to be important for the structure and function of membrane-spanning gramicidin channels. To investigate whether the "spacer" residues between the tryptophans in gramicidin A (gA) are important for channel structure and function, D-Leu-10, -12. and -14 of gA were replaced by Ala, Val, or Ile. (For practical reasons, the Ile substitutions were introduced into the enantiomeric gramicidin A-, gA-.) Circular dichroism spectra of [D-Ala10,12,14]gA, [D-Val10,12,14]gA, or [Ile10,12,14]gA- incorporated into sodium dodecyl sulfate micelles or 1, 2-dimyristoyl-sn-glycero-3-phosphocholine vesicles differ from the spectrum of the native [D-Leu10,12,14]gA. All the analogue spectra display reduced ellipticity at both 218 and 235 nm, indicating the presence of double-stranded conformers with the Ala analogue spectra showing the largest departure from the native gA spectra. Size-exclusion chromatograms of the Val and Ile analogues show both monomer and dimer peaks, accompanied by peak broadening; the chromatograms for the Ala analogue show broad, overlapping peaks and suggest the presence of higher oligomers and/or (rapidly) interconverting conformations. All three analogues form membrane-spanning channels, with the channel-forming potency of the Ala analogue being much less than that of gA or the other analogues. In 1.0 M CsCl, the conductance of each analogue channel is approximately 25% less than that of [D-Leu10,12,14]gA channels. The lifetimes of the analogue channels also are less than of [D-Leu10,12, 14]gA channels, with the largest (8-fold) reduction being for [D-Ala10,12,14]gA channels. Hybrid channel experiments show that the beta6.3-helical backbone folding pattern is retained in the channel-forming subunits and that the substitutions primarily influence ion entry. Both the bulk and the stereochemistry of the aliphatic residues between the tryptophans of gA are important for channel structure and function.     

Analysis of time-series MODIS 250 m vegetation index data for crop classification in the U.S. Central Great Plains

The global environmental change research community requires improved and up-to-date land use/land cover (LULC) datasets at regional to global scales to support a variety of science and policy applications. Considerable strides have been made to improve large-area LULC datasets, but little emphasis has been placed on thematically detailed crop mapping, despite the considerable influence of management activities in the cropland sector on various environmental processes and the economy. Time-series MODIS 250 m Vegetation Index (VI) datasets hold considerable promise for large-area crop mapping in an agriculturally intensive region such as the U.S. Central Great Plains, given their global coverage, intermediate spatial resolution, high temporal resolution (16-day composite period), and cost-free status. However, the specific spectral-temporal information contained in these data has yet to be thoroughly explored and their applicability for large-area crop-related LULC classification is relatively unknown. The objective of this research was to investigate the general applicability of the time-series MODIS 250 m Enhanced Vegetation Index (EVI) and Normalized Difference Vegetation Index (NDVI) datasets for crop-related LULC classification in this region. A combination of graphical and statistical analyses were performed on a 12-month time-series of MODIS EVI and NDVI data from more than 2000 cropped field sites across the U.S. state of Kansas. Both MODIS VI datasets were found to have sufficient spatial, spectral, and temporal resolutions to detect unique multi-temporal signatures for each of the region's major crop types (alfalfa, corn, sorghum, soybeans, and winter wheat) and management practices (double crop, fallow, and irrigation). Each crop's multi-temporal VI signature was consistent with its general phenological characteristics and most crop classes were spectrally separable at some point during the growing season. Regional intra-class VI signature variations were found for some crops across Kansas that reflected the state's climate and planting time differences. The multi-temporal EVI and NDVI data tracked similar seasonal responses for all crops and were highly correlated across the growing season. However, differences between EVI and NDVI responses were most pronounced during the senescence phase of the growing season.     

Distance metric-based time-efficient fuzzy algorithm for abnormal magnetic resonance brain image segmentation

Image segmentation is one of the significant computational applications of the biomedical field. Automated computational methodologies are highly preferred for medical image segmentation since these techniques are immune to human perception error. Artificial intelligence (AI)-based techniques are often used for this process since they are superior to other automated techniques in terms of accuracy and convergence time period. Fuzzy systems hold a significant position among the AI techniques because of their high accuracy. Even though these systems are exceptionally accurate, the time period required for convergence is exceedingly high. In this work, a novel distance metric-based fuzzy C-means (FCM) algorithm is proposed to tackle the low-convergence-rate problem of the conventional fuzzy systems. This modified approach involves the concept of distance-based dimensionality reduction of the input vector space that substantially reduces the iterative time period of the conventional FCM algorithm. The effectiveness of the modified FCM algorithm is explored in the context of magnetic resonance brain tumor image segmentation. Experimental results show promising results for the proposed approach in terms of convergence time period and segmentation efficiency. Thus, this algorithm proves to be highly feasible for time-oriented real-time applications.     

Evaluation of spatio-temporal variations in chlorophyll-a in Lake Naivasha,Kenya: remote-sensing approach

Restoration of the ecosystem services and functions of lakes requires an understanding of the turbidity dynamics in order to arrive at informed environmental management decisions. The understanding of the spatio-temporal dynamics of turbidity requires frequent monitoring of the turbidity components such as chlorophyll-a concentration. In this study, we explored the use of Moderate Resolution Imaging Spectroradiometer Aqua (MODIS-Aqua) satellite data in studying the spatio-temporal changes in chlorophyll-a concentration in Lake Naivasha, a turbid tropical system. The temporal trend of chlorophyll-a concentration over the study period in the lake was also evaluated. The temporal trend assessment was achieved through the removal of periodic seasonal interference using Seasonal-Trend decomposition based on the LOESS (Local Regression) procedure. The resultant chlorophyll-a concentration maps derived from MODIS-Aqua satellite data give an indication of the monthly spatial variation in chlorophyll-a concentration from 2002 to 2012. The results of regression analyses between satellite-derived chlorophyll-a and in situ measurements reveal a high level of precision, but with a measureable bias with the satellite underestimating actual in situ measurements (R² = 0.65, P < 0.001). Although the actual values of the chlorophyll-a concentrations are underestimated, the significant relationship between satellite-derived chlorophyll-a and in situ measurements provides reliable information for studying spatial variations and temporal trends. In 2009 and 2010, it was difficult to detect chlorophyll-a from the MODIS-Aqua imagery, and this coincided with a period of the lowest water levels in Lake Naivasha. An inverse relationship between de-seasoned water level and chlorophyll-a concentration was evident. This study shows that MODIS-Aqua satellite data provide useful information on the spatio-temporal variations in Lake Naivasha, which is useful in establishing general trends that are more difficult to determine through routine ground measurements.     

Effect of MnO2 on the dielectric and piezoelectric properties of alkaline niobate based lead free piezoelectric ceramics

Lead free ferroelectric ceramics of the KNN–LiTaO₃–LiSbO₃ system were prepared using the mixed oxide route. This work reports the effect of doping (K_0.44Na_0.52Li_0.04)(Nb_0.86Ta_0.1Sb_0.04)O₃ produced through the conventional solid state sintering method with different amounts of MnO₂. With 1 mol% of the dopant, ～96.5% of the theoretical density of the ceramics was achieved while grain growth inhibition was attained through pinning of the grain boundary movement. A polymorphic phase transition (PPT) was induced in the ceramic from the orthorhombic crystal structure to the tetragonal structure with increasing dopant amount. At lower temperatures, the doped samples had higher epsilon values but there was a decrease in both T_c (from 333 °C to 249 °C) and epsilon value at T_c (from ≈9500 to <6000). At temperatures below 300 °C however, the loss tangent in the doped samples (≈2.5 mol%) was much lower and steady when compared to the undoped one. The ferroelectric properties were slightly lowered with the addition of MnO₂. The remnant polarisation (P_r) was lowered from ～18 μC/cm² to ～9 μC/cm², the coercive field (E_c) from ～8.5 kV/cm to ～6.2 kV/cm and the piezoelectric charge coefficient (d₃₃) decreased as well.