Miracle-dz/UniFAR-FTUs huggingface dataset:
Structure-property relationship of blocked diisocyanates : synthesis of polyimides using imidazole-blocked isocyanates

Imidazole, 2-methylimidazole and benzimidazole-blocked aromatic and aliphatic diisocyanates have been prepared and polymerized with pyromellitic dianhydride in the presence of a basic catalyst. The polymers are characterized with FTIR, 1H NMR and 13C NMR spectroscopy and GPC, DSC and TGA. The structure–property relationship of blocked diisocyanates are discussed in terms of molecular weight of the polyimides obtained. Considering the blocking agent, GPC results show that the benzimidazole blocked adduct yields higher molecular weight polymer than the 2-methylimidazole-blocked adduct which, in turn, yields higher molecular weight polymer than the imidazole-blocked adduct. Considering the structure of the isocyanate, the molecular weight of polymer increases from isophorone diisocyanate to hexamethylene diisocyanate and to toluene diisocyanate (TDI). DSC traces of the polymers derived from TDI show glass transitions (Tg) in the temperature range 152–180 °C and the values increase from the polymer based on imidazole-blocked TDI to 2-methylimidazole-blocked TDI and to benzimidazole-blocked TDI. © 2000 Society of Chemical Industry
The correlation of total and extractable heavy metals from soil and domestic sewage sludge and their transfer to maize ( Zea mays L.) plants

A study to understand the mobility and transport of heavy metals (HMs) from soil and soil amended with sewage sludge to maize plants was carried out. The total and ethylenediaminetetraaceticacid (EDTA)-extractable HMs in agricultural soil and untreated domestic sewage sludge samples, and the correlation between the total and extractable metals in soil and sewage sludge were carried out. Pot experiments were performed to study the transfer of HMs to maize grains, grown in soil (control) and in soil amended with sewage sludge (test samples). The total and extractable HMs in soil, sewage sludge, and maize grains were analysed by FAAS/ETAAS (flame atomic absorption spectrometer/electrothermal atomic absorption spectrometer) after digestion in microwave oven. Statistically significant correlations were obtained between the total contents of Cu, Cd, As and their respective extractable fractions in soil, while in domestic wastewater sludge (DWS) the better correlation was observed only for Ni and Cd. The edible part of maize plants (grains) from test samples presented high concentration of Zn, Pb, Ni, Cd, Cu, As, and Cr concentrations (80.7–85.6, 3.8–3.95, 2.35–2.5, 0.75–0.82, 3.21–3.29, 0.23–0.27, and 0.22–0.29 mg kg−1, respectively). Good correlations were found between metals in exchangeable fractions of both soil and DWS and total metals in control and test samples of maize grains. The transfer factor of all HMs from DWS to maize grains was also determined.
Study of Structural and Optoelectronic Properties of ZnO Codoped with Ca and Mg

ZnO codoped with Ca and Mg in various proportions was prepared by a chemical method and annealed at 600 C. The structural and optical properties of these oxide samples were systematically studied by XRD, SEM, EDS, and PL spectrometer. XRD pattern shows a hexagonal wurtzite structure. The size of particle as shown by XRD machine and calculated by Scherer’s formula is found in the nano range. The formation of particles showed that they were polycrystalline. Due to larger ionic and covalent radii of Ca than those of Zinc, a lattice deformation occurs with the development of strain field. New phases were observed in XRD pattern of few samples ZnO-2.2 and ZnO-2.4. SEM micrograph shows the formation of nanoparticles. EDS study confirms the codoping of ZnO with Ca and Mg. Optical properties like photoluminescence emission showed a blue shift in peak wavelength. General conductivity and photoconductivity were found high in samples containing certain proportion of Ca and Mg in comparison with pure ZnO.
Adsorption of Zn2+ and Cd2+ Ions on Vermiculite in Buffered and Unbuffered Aqueous Solutions

Studies of Zn2+ and Cd2+ ion adsorption onto vermiculite from buffered and unbuffered aqueous solutions were conducted in order to compare their ion adsorption behaviours in different systems. The use of buffer reagents had a strong and negative effect on the adsorption of the metal ions under study. The experimental data obtained from both the buffered and unbuffered solutions could not be described by a single traditional adsorption isotherm due to the effect of the adsorbent concentration (W). The equilibrium ion concentration in bulk solution (Z) and the equilibrium ion adsorption density (X/W ratio) decreased with increasing W in both buffered and unbuffered systems, indicating that the use of a buffer solution is not an effective measure for eliminating the effect of the adsorbent concentration. The addition of competitive ions (H+, Cd2+ and Zn2+) greatly reduced the adsorption of the target metal ion. Within the pH range tested (initial pH < 7), the competitive effect of H+ ions was equivalent to that of Zn2+ and Cd2+ ions. In unitary, binary and ternary systems, highly significant linear correlations were obtained between the change in the ionic strength (ΔI) and the quantity of ion adsorption. The results obtained suggest that it is not necessary to control the ionic strength in ion adsorption experiments because ΔI is a function of ion adsorption, and the use of buffer reagents has a negative effect on ion adsorption.
Highly P-Typed Mg-Doped GaN Films Grown with GaN Buffer Layers

Mg-doped GaN films were grown with GaN buffer layers on a sapphire substrate. Hall-effect measurement of as-grown GaN films showed that the hole concentration was 2×1015/cm3, the hole mobility was 9 cm2/V·s and the resistivity was 320 Ω·cm at room temperature. After the low-energy electron-beam irradiation (LEEBI) treatment, each value became 3×1018/cm3, 9 cm2/V·s and 0.2 Ω·cm at room temperature, respectively. This value of the hole concentration is the highest ever reported for the p-type GaN films and that of the resistivity is the lowest.
In Situ Characterization of Lifetime and Morphology in Operating Bulk Heterojunction Organic Photovoltaic Devices by Impedance Spectroscopy

Time‐dependent charge transport in operating poly(3‐hexylthiophene):[6,6]‐phenyl‐C61‐butyric acid methyl ester (P3HT:PCBM) bulk heterojunction organic photovoltaic (OPV) devices has been characterized with impedance spectroscopy. Devices with varied composition and morphology were measured over a range of illumination intensities ranging from dark conditions to 1 sun and applied bias voltages ranging from 0.0 V to 0.75 V. Using an equivalent circuit model, materials properties such as dielectric constant and conductivity were determined and found to be in agreement with values measured by other methods. Average carrier lifetimes were also extracted from the model and found to correlate with measured power conversion efficiencies. At the short circuit condition and ∼1 sun illumination, the average electron lifetime was found to vary from 7.8 to 22 μs for devices with power conversion efficiencies ranging from 2.0 to 2.5%. These results suggest that impedance spectroscopy is an effective tool for predicting how processing parameters can impact device performance in organic bulk heterojunction photovoltaic devices.
COMPORTAMENTO REOLÓGICO DO MEL DE Apis mellifera DO MUNICÍPIO DE TABULEIRO DO NORTE-CE

O objetivo do trabalho foi estudar as caracteristicas de viscosidade dos meis do Municipio de Tabuleiro do Norte-CE nas temperaturas de 20, 25, 30, 35 e 40oC em funcao do tempo de armazenamento de 0, 45 e 90 dias. Os meis utilizados foram obtidos a partir de coletas realizadas por apicultores de Tabuleiro do Norte-CE e conduzidos ao Laboratorio de Processamento e Armazenamento de Produtos Agricolas da UFCG, onde o estudo foi conduzido. Para determinacao das viscosidades foi utilizado um viscosimetro da marca Brookfield, modelo RVT. Verificou-se que o armazenamento nao provocou aumentos ou reducoes consequentes de viscosidade, no entanto o aumento de temperatura resultou em diminuicoes de viscosidade, com diferencas significativas entre todas as amostras. Diante dos resultados conclui-se que com o aumento da temperatura, ocorre uma reducao na viscosidade dos meis, sendo mais acentuada com o inicio do aquecimento, entre 20 e 30oC.
Preparation and Investigation of Thermolysis of l-Aspartic Acid-Intercalated Layered Double Hydroxide

l-Aspartic acid (l-Asp) has been intercalated into magnesium−aluminum layered double hydroxides by coprecipitation. The structure and composition of the intercalated material have been studied by X-ray diffraction, inductively coupled plasma emission spectroscopy, and elemental analysis. A schematic model of the intercalated structure has been proposed. Furthermore, the thermal decomposition of the hybrid material has been characterized by in situ powder X-ray diffraction, in situ Fourier transform infrared spectroscopy, thermogravimetry, differential thermal analysis, 13C solid-state magic-angle spinning nuclear magnetic resonance, temperature-programmed decomposition, and gas chromatography−mass spectrometry. The thermolysis of l-Asp LDH is quite different from that of the pristine l-Asp studied as a reference sample and is characterized by three steps: the first from room temperature to 150 °C is attributed to the loss of both adsorbed and interlayer water, accompanied by the destruction of the hydrog.
Study on key step of 1,3-butadiene formation from ethanol on MgO/SiO2

The structure and surface properties of the MgO/SiO2 catalyst were studied by both experimental characterization and the simulation method. The adsorption properties of ethanol on different MgO/SiO2 surfaces were researched by the density functional theory method and the result is that ethanol mainly adsorbed on MgO surface. The role of SiO2 in increasing the MgO crystal defects in the MgO/SiO2 has been obtained and the electronic properties of ethanol molecule before and after adsorption on the catalyst surfaces were compared. The initial step of ethanol dehydrogenation and the dehydration to 1,3-butadiene process, which is the dehydrogenation of ethanol to acetaldehyde reaction, on the flat sites, stepped sites and kinked sites was examined through the molecular simulation method. We investigated the preferable surface for the reaction of ethanol dissociation to an ethoxy group and the more active surface for the reaction of dehydrogenation of ethanol to acetaldehyde. The research results suggested that the stepped MgO surface is more active for the reaction of dehydrogenation of ethanol to acetaldehyde.
Metal-Nanocluster-Filled Carbon Nanotubes: Catalytic Properties and Possible Applications in Electrochemical Energy Storage and Production

Ensembles of highly aligned and monodisperse graphitic carbon nanotubules have been prepared via the template method using chemical vapor deposition of carbon within the pores of alumina membranes. Tubules with diameters of 200 nm have been prepared, and smaller diameters are possible. Free-standing aligned carbon-tubule membranes are formed by this template method. These novel carbon tubule membranes can be filled with nanoparticles of electrocatalytic materials (i.e., Pt, Ru, Pt/Ru), which can then be used to electrocatalyze O2 reduction and methanol oxidation as well as the gas-phase catalysis of hydrocarbons. Hence, these membranes have potential applications in fuel cell development. Smaller, highly ordered graphitic-carbon tubules can also be prepared within the template-synthesized carbon tubules, using Fe nanoparticles as catalysts. In these novel tube-in-tube structures, both the outer and the inner tubules are electrochemically active for Li+ intercalation, suggesting possible applications such .
Soil‐Test Methods for Florida Sands Treated with an Aluminum–Water Treatment Residual and Various Phosphorus Sources

Use of aluminum (Al)–rich water treatment residuals (Al‐WTR) has been suggested as a practice to immobilize excessive phosphorus (P) in Florida soils that could represent an environmental hazard. Fertilizer P requirements can differ in WTR‐amended and unamended soil, so careful selection of soil‐testing methodology is necessary. Acidic extractants can dissolve WTR sorbed P and overestimate plant‐available P. We evaluated the suitability of the Mehlich 1 P (M‐1P) and other agronomic soil‐test procedures in an Al‐WTR‐treated Florida soil. Bahiagrass (paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a Florida topsoil amended with four sources of P at 44 kg P ha−1 (P‐based rates) and 179 kg PAN ha−1 [nitrogen (N)–based rates] and three WTR rates (0, 10, and 25 g kg−1 oven‐dry basis). Both water‐extractable P (WEP) and iron (Fe) strip P (ISP), but not M‐1P, values of soil sampled at planting of each grass were greater in the absence than in the presence of WTR. Total plant P uptake correlated with WEP (r2 = 0.82***) and ISP (r2 = 0.75***), but not M‐1P (r2 = 0.34***). Correlations of the dry‐matter yield, P concentration, and P uptake of the first bahiagrass were also better with WEP and ISP than with M‐1P values. However, regression of plant responses with M‐1P improved after the first crop of bahiagrass. Both WEP and ISP values were better predictors of available soil P than M‐1P in a field study with same four P sources surface applied to established bahiagrass at the same two P rates, with and without WTR. Both WEP and ISP are recommended as predictors of P adequacy in soils treated with WTR, especially for soils recently (< 5 months) treated with Al‐WTR.
Pyridinium and imidazolium 1,3,4-oxadiazole ionic liquid crystals: a thermal and photophysical systematic investigation

In this study we present the synthesis and complete structural characterization of twenty five 1,3,4-oxadiazole molecules (ionic and non-ionic) with some systematic structural variations, such as number of counterions, number of alkoxy chains, alkyl chain size, type of counterion and its position on the molecule. The thermal and photophysical properties for all compounds were investigated allowing a complete and interesting simultaneous study of the effect of structural changes on these properties. We show that every parameter studied affected both the thermal and photophysical properties. For these bent core molecules, the liquid crystalline behavior was observed only for compounds containing one counterion, SmA (monolayer or bilayer) being the predominant phase. The neutral (non-ionic) compounds and the imidazolium derivatives showed emission at around 360 nm and a high quantum yield, while most of the pyridinium derivatives showed emission at around 530 nm, a low quantum yield and a complex photophysical behavior. In all cases, the quantum yield for the different counterions follows the sequence ClO4− > BF4− > DS− > NO3− > Br−(I−).
Optimization of metal dispersion in doped graphitic materials for hydrogen storage

The noncovalent hydrogen binding on transition-metal atoms dispersed on carbon clusters and graphene is studied with the use of the pseudopotential density-functional method. It is found that the presence of acceptorlike states in the absorbents is essential for enhancing the metal adsorption strength and for increasing the number of hydrogen molecules attached to the metal atoms. Particular configurations of boron substitutional doping are found to be very efficient for providing such states and thus enhancing storage capacity. Optimal doping conditions are suggested based on our calculations for the binding energy and ratio between metal and hydrogen molecules.
Origin and distribution of the polyatomic molecules in the atmosphere

Of those gases which occur in the upper atmosphere and have strong absorption bands in the infra-red part of the spectrum and which must, therefore, be considered when calculating the absorption and radiation of heat in the atmosphere, only carbon dioxide is uniformly mixed with the air at all heights which we are likely to be dealing with; it will not be considered further here. The vertical distributions of water vapour and ozone are of great interest, particularly when considered together. Water vapour, originating at ground level, usually decreases rather rapidly with increasing height, particularly in the lower stratosphere. This leads to extremely low concentrations at a height of about 15 km. On the other hand, ozone, being formed by the action of solar ultra-violet radiation at a height of 30 km or more, decreases in concentration downwards. We find, therefore, ozone diffusing downwards and water vapour diffusing upwards through the same region of the atmosphere, but, as we shall see, with very different lapse rates. Water vapour The standard hygrometers which are used to measure the humidity from free balloons are only satisfactory at temperatures above about 235°K, and our knowledge of the humidity at high levels in the atmosphere is almost entirely dependent on measurements made with frost-point hygrometers carried on aircraft. The work of the Meteorological Research Flight of the British Meteorological Office is notable for the very large number of measurements made from Mosquito aircraft to a height of about 12 km and more recently from Canberra aircraft to 15 km. Most unfortunately, hardly any measurements having similar accuracy have been made in other parts of the world. However, at the present time Dr A. W. Brewer is in north Norway making such measurements with the kind co-operation of the Norwegian Air Force and I had hoped that some results might have been available in time to report them at this Discussion (see note at end of paper).
Sonochemical Synthesis and Characterization of Ni(C4H6N2)6(PF6)2, Fe(C4H6N2)6(BF4)2, and Ni(C4H6N2)6(BF4)2 in 1‐Butyl‐3‐methylimidazole with Hexafluorophosphate and Tetrafluoroborate

This paper reports on the inorganic sonochemical synthesis of crystalline Ni(C 4 H 6 N 2 ) 6 (PF 6 ) 2 , Fe(C 4 H 6 N 2 ) 6 (BF 4 ) 2 , and Ni(C 4 H 6 N 2 ) 6 (BF 4 ) 2 in the ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate(BMI) + (PF 6 ) - and 1-butyl-3-methylimidazolium tetrafluoroborate (BMI) + (BF 4 ) - . The structures of the compounds were determined and refined by using powder X-ray diffraction methods. The salts crystallize in the trigonal P3 space group. IR, Raman and 1 9 F NMR spectroscopic studies confirm that the PF 6 - and BF 4 - anions are not bonded to the metal cations. Magnetic measurements reveal the paramagnetic nature of the complexes. Mossbauer investigations show that the iron atom in Fe(C 4 H 6 N 2 ) 6 (BF 4 ) 2 is in the oxidation +2 state. The broad EPR signals, which reflect the octahedral symmetry of the nickel complexes, were measured for Ni(C 4 H 6 N 2 ) 6 (PF 6 ) 2 and Ni(C 4 H 6 N 2 ) 6 -(BF 4 ) 2 .
Protein and solvent engineering of subtilisin BPN' in nearly anhydrous organic media

The combined effects of protein and solvent engineering have been studied using subtilisin BPN' as a model protease. The effects of site-specific mutations in the active site of subtilisin BPN' on the reactivity and substrate specificity of the enzyme are strongly dependent on the polarity of the substrate, active-site mutation, and solvent. In going from a polar solvent such as acetone to a nonpolar solvent such as hexane, subtilisin BPN' catalysis is activated dramatically (up to 178-fold) by employing a polar active-site mutation (Gly 166 →Asn). This activation is proposed to be due to significant transition-state stabilization afforded by the polar mutation on subtilisin catalysis
Composition of the Essential Oil from Leaves of Astronium graveolens Jacq Grown in Colombia

Abstract The composition of the essential oil from leaves of Astronium graveolens Jacq. was analyzed by GC and combined GC/MS. Eighty constituents were identified which constitute 98% of the total composition. Major compounds in the leaf oil were (E)-β-ocimene (40.1%) and myrcene (17.0%).
Diffusion of water adsorbed in hydrotalcite: neutron scattering Study

Layered double hydroxides (LDH) are a class of ionic lamellar solids with positively charged layers of two kinds of metallic cations and exchangeable hydrated anions. Quasi-elastic neutron scattering (QENS) measurements are performed in this type of LDH structured hydrated hydrotalcite sample to study the dynamical behaviour of the water in geometric confinement within the layers. Dynamical parameters correspond to the confined water molecules revealed that depending on the amount of excess water present, behaves differently and approaches bulk values at high concentration. Both translational and rotational dynamical parameters showed that at very low concentration of excess water, water molecules are attached to the surfaces and show the confinement effect.
Characterization of Al(III) complexes with hematein in artistic alum logwood inks

The complexes between Al(III) and hematein, the main coloring matter in alum logwood inks, were characterized by Raman and 27Al NMR (nuclear magnetic resonance) spectroscopies. Raman spectra of the crystallized complexes and of the compounds applied on a paper substrate are presented and assigned based on published data for the parent compounds. These Raman spectra show that the coordination of the hematein to the Al(III) ions takes place in both cases through the carbonyl and hydroxyl groups in the molecule, and that the aromatic rings are also involved in the interaction. The Raman spectra of the pure hematein–Al(III) complexes were found to be consistent with those recorded for a logwood ink prepared following a late 19th century recipe, using logwood chips instead of pure hematein, and applied on a paper substrate. These spectra can be used as references for the noninvasive identification of the compounds in works of art. 27Al solid-state NMR showed that the coordination of the Al(III) atoms in the crystallized powder is predominantly octahedral, while when applied on a paper substrate the colorant is present mainly as a tetrahedral complex, with an octahedral coordination also present in a smaller proportion. The fact that the predominant coordinations for the complexes in the crystallized material and for the ones present on the paper substrate are different is relevant for the study of the lightfastness and thermal stability of works of art bearing these media. Copyright © 2009 John Wiley & Sons, Ltd.
Batch and Tubular-Batch Crystallization of Paracetamol: Crystal Size Distribution and Polymorph Formation

The crystallization of paracetamol from ethanol and methanol solutions was used to examine the possibility of using rapid cooling in a tubular flow-through apparatus to manipulate crystal size distribution and morphology. Flow through the tubular portion of the apparatus was laminar, and hence, the device, including a receiving vessel, is referred to as a laminar-flow tubular crystallizer (LFTC). Undersaturated solution entered the tubular portion of the LFTC and was rapidly cooled to temperatures far below solubility conditions. Experimental results were also obtained using a typical batch configuration with the same solute and solvents, but with significantly lower cooling rates than in the LFTC. The crystals produced in the flow-through apparatus were of smaller mean size than those obtained from batch crystallizations, and evidence was found that using the rapid-cooling technique could lead to the generation of kinetically stable polymorphs. Moreover, the total run time required to relieve all of the .