Miracle-dz/UniFAR-FTUs huggingface dataset:
Crystal-chemical study of wavellite from Zbirov, Czech Republic

Abstract The crystal chemistry of wavellite from Zbirov (Czech Republic), ideally Al3(PO4)2(OH,F)3·5H2O, was addressed by means of a multi-methodological approach based on electron microprobe analysis (EMPA) using wave-dispersive spectroscopy, single-crystal X-ray diffraction, powder and singlecrystal infrared spectroscopy and Raman spectroscopy. The EMPA data showed the presence of significant F replacing OH in the sample studied. The structure was solved in the Pcmn orthorhombic space group, with the following unit-cell constants: a = 9.6422(7), b = 17.4146(15), c = 7.0094(2) Å, V = 1176.98(10) Å3. Phosphorus atoms display tetrahedral (PO4) coordination, while Al cations display octahedral coordination. The mineral framework can be viewed as the repetition of cationic arrays made up of AlO6 polyhedra, bridged by PO4 groups and further joined by O-H…O hydrogen bonds. The single-crystal unpolarized Fourier transform infrared (FTIR) spectrum shows combination bands indicating the presence of both OH and H2O in the structure. Both FTIR and Raman spectra show a broad absorption extending from 3600 to 2800 cm-1 resulting from the overlapping of several components due to the water molecules and the OH group. The frequencies observed are comparable to those expected on the basis of the Libowitzky relationship for the range of D-H …A bond systems in the structure.
Liquid drops on homogeneous and chemically heterogeneous surfaces: A two-dimensional lattice Boltzmann study

A boundary condition of a two-phase lattice Boltzmann (LB) method is proposed to model smooth substrates of chemically heterogeneous surfaces. The present technique is applied to the LB simulations of liquid drops on homogeneous, regularly heterogeneous, and randomly heterogeneous surfaces. It is found (i) that the LB technique can mimic not only homogeneous substrates with arbitrary wettabilities but also chemically heterogeneous substrates with arbitrary heterogeneities and wettabilities and (ii) that, in the presence of surface heterogeneities, it also can capture the contact line pinning, the contact angle hysteresis, and the effects of size and distribution of the heterogeneities on them. The results indicate that the present LB method is useful for the simulation of wetting phenomena of chemically heterogeneous surfaces.
Molecular dynamics simulation of a bilayer of 200 lipids in the gel and in the liquid crystal phase

We have constructed and simulated a membrane-water system which consists of 200 molecules of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine forming a rectangular patch of a bilayer and of 5483 water molecules covering the head groups on each side of the bilayer. The total number of atoms is approximately 27 000. The lateral dimensions of the bilayer are 85 A×100 A, and the distance between the bilayer surfaces as given by the average phosphorus to phosphorus distance is 35 A. The thickness of each water layer is up to 15 A. In all, we simulated 263 ps of the dynamics of the system. To prevent system disintegration, atoms within 5 A from the surface were harmonically restrained and treated by Langevin dynamics, forming a stochastic boundary
Equilibrium Geometries and Electronic Structure of Iron−Porphyrin Complexes: A Density Functional Study

We have performed density functional theory (DFT) calculations of iron−porphyrin (FeP) and its complexes with O2, CO, NO, and imidazole (Im). Our fully optimized structures agree well with the available experimental data for synthetic heme models. Comparison with crystallographic data for proteins highlights interesting features of carbon monoxymyoglobin. The diatomic molecule induces a 0.3−0.4 A displacement of the Fe atom out of the porphyrin nitrogen (Np) plane and a doming of the overall porphyrin ring. The energy of the iron−diatomic bond increases in the order Fe−O2 (9 kcal/mol) < Fe−CO (26 kcal/mol) < Fe−NO (35 kcal/mol). The ground state of FeP(O2) is an open shell singlet. The bent Fe−O2 bond can be formally described as FeIII−O2-, and it is characterized by the anti-ferromagnetic coupling between one of the d electrons of Fe and one of the π* electrons of O2. FeP(CO) is a closed shell singlet, with a linear Fe−C−O bond. The complex with NO has a doublet ground state and a Fe−NO geometry intermed.
Solution-Processed Zinc Indium Oxide Transparent Nonvolatile Memory Thin-Film Transistors with Polymeric Ferroelectric Gate Insulator

Solution-Processed Zinc Indium Oxide Transparent Nonvolatile Memory Thin-Film Transistors with Polymeric Ferroelectric Gate Insulator Sung-Min Yoon, Shin-Hyuk Yang, Soon-Won Jung, Chun-Won Byun, Sang-Hee Ko Park, Chi-Sun Hwang, and Hiroshi Ishiwara* Tokyo Institute of Technology, Yokohama 226-8502, Japan Convergence Components and Material Research Laboratory, Electronics and Telecommunications Research Institute, Daejeon 305-700, Korea
Nitrogen miscible displacement of light crude oil : a laboratory study

A comprehensive laboratory study of N{sub 2} miscible flooding for enhanced recovery of light crude oil was performed. The minimum miscibility pressure (MMP) of N{sub 2} is a major constraint to its EOR application, so an empirical correlation for MMP estimation was developed and found to be reliable. Supporting work included many in-house slim-tube displacement determinations of MMP and the compilation and analysis of previously published data. The reservoir fluid composition, especially the amounts of the methane and ethane-through-pentane fractions, was found to be the major determining factor for miscibility. High-pressure coreflooding tests with sandstone cores were performed to evaluate the effects of gravity stability and injection mode on the N{sub 2} miscible process. N{sub 2}-gas miscible flooding successfully recovered most of the oil from laboratory cores. Gravity-stable and gravity-unstable displacements gave different oil recoveries, as did secondary and tertiary N{sub 2} displacements.
Natural Dewatering of Marine Dredged Sediments

The aim of this study is to explore the water content decrease in dredged sediment by natural evaporation and/or drainage. This operation constitutes, in several fields, a preliminary operation to insure a reliable beneficial use of this material. Firstly, a methodology is proposed to assess the relative efficiency of drainage and evaporation in the process of water content reduction in the dredged sediment. Secondly, comparisons of measured evaporation rates are compared to predictions of an available model in the literature. Thirdly, the observed stages during drying are explained in the light of standard parameters measured on the sediment. Finally, a relationship between water content decrease and increase of shear strength of the sediment is discussed. These results will allow a better management of beneficial use of the sediment and enhance scheduling of the drying operation and its transport.
Investigation of excess 1/f noise in CdTe single crystals

Experimental studies of noise characteristics of CdTe crystals, prepared using the travelling heater method, have been carried out. Three types of basic material were used: low-ohmic n-type with n = 5 × 1015 cm−3, semi-insulating n-type with n = 1.5 × 109 cm−3 and low-ohmic p-type with holes concentration p = 7 × 1014 cm−3. The noise measurements show that the dominant noise is 1/fn noise with parameter n in range from 0.9 to 1.5 and often very close to 1. The experimental value of 1/f noise is always much higher than the theoretical value which corresponds to the total value of free carriers in the sample. The voltage noise spectral density of 1/f noise depends on the quantity of free carriers in the sample. Free carriers are distributed uniformly throughout the homogenous part of the sample. But within the depleted region there is very low concentration of free carriers which increases exponentially in the direction from the contact area to the homogenous part of the sample. Analysis shows that the excess 1/f noise is caused by the low carrier concentration within the depleted region at the metal–semiconductor junction.
Acetyl Group Distribution in Acetylated Wood Investigated by Microautoradiography

Summary Sapwood of Scots pine (Pinus silvestris L.) was acetylated with 14C- and 3H-labelled acetic anhydride. The distribution of acetyl groups was investigated with microautoradiography and microautoradiographs were evaluated with ESEM, Environmental Scanning Electron Microscopy. The investigation showed that the impregnation of wood with radioisotope-labelled substances provides a good opportunity to investigate the location of substances covalently bonded to the wood material. Introduced 14C-labelled acetyl groups show an even distribution in the wood cell wall, with no discernible concentration gradients at acetylation levels of about 5, 15 and 20% weight gain. 3H-labelled acetyl groups show an even distribution in the wood cell wall at 15 and 20% weight gain, with no discernible concentration gradients. At the 5% weight gain level, however, an uneven distribution of 3H-labelled acetyl groups over the cell wall is observed. Nevertheless, the unevenness is random and no concentration gradient is discernible at this level. 3H with a relatively high resolution, 0.5–1 μm, compared to 14C with a resolution of 2–5 μm, gives more accurate information about where exactly the acetyl groups are situated in the wood cell wall. Acetic anhydride was evenly distributed when a full impregnation procedure was used. The chemical and physical properties of acetic anhydride allow a uniform penetration into the pine cell wall and a complete acetylation takes place when the specimens are heated.
Adsorption of mercury(II) by kaolinite

Adsorption of Hg(II) by kaolinite was investigated as a function of solution pH, ionic strength, and the competitive or complexation effects of ligands (Cl, SO 4 , PO 4 ) and metals (Ni and Pb). Mercury(II) adsorption from a 0.6 μM Hg(II) solution was primarily influenced by pH. The Hg(II) adsorption edge was described by a pH 50 (pH where 50% adsorption occurs) of 3.4 and a pH max (pH where maximum adsorption occurs) of 4.4. At pH values above the pH max , Hg(II) retention decreased with increasing pH. Chloride and Ni shifted pH 50 from 3.4 to 7 and 4.1, respectively. Nickel and Pb reduced the amount of Hg(II) adsorbed throughout the pH range examined. Ionic strength and the presence of SO 4 and PO 4 had relatively little impact on the Hg(II) adsorption envelope. The adsorption of Hg(II) was predicted through the application of the triple layer model (TLM) by assuming that the kaolinite surface was composed of equal proportions of silanol and aluminol groups. The TLM model suggests that the silanol group was responsible for retaining the bulk of the adsorbed Hg(II), through the formation of the =SiO - -HgOH + outer-sphere, and the ≡SiOHg (OH) 2 - and ≡SiOHgCl 0 or ≡SiOHgOHCl - (Cl system) inner-sphere species. The ≡AlO - -HgOH + outer-sphere complex accounted for a small percentage (<15-35%) of the adsorbed Hg(II). The TLM results suggested that Hg(II) adsorption by both ≡SiOH and ≡AIOH sites on kaolinite should be considered to predict adequately Hg(II) retention.
Study of the Fixed‐Bed Adsorption Behavior of Phenylalanine on Solvent Impregnated Resins, Part III

Abstract The implementation of the SIR technique for the amino acid separation from diluted aqueous solutions in a fixed‐bed column is presented and a mathematical model for the prediction of the adosrption behavior is developed. Independently determined equilibrium and kinetic parameters are used for the calculation of the breakthrough curves. Fixed‐bed parameters, such as axial dispersion and bed porosity, are determined experimently and compared with correlations. Analysis of the Biot and Bodenstein number reveal that the mass transfer through the film liquid around the particles, as well as the axial dispersion in the column, could be neglected at the studied experimental conditions. A simplified mathematical model was found to give the best prediction to the experimental breakthrough curves over a wide range of feed concentrations and flow rates.
Measuring unsaturated sorptivity and hydraulic conductivity using multiple disc permeameters

A new field method of obtaining, with minimal disturbance, the unsaturated hydraulic conductivity (K0) and sorptivity (S0) from unconfined disc permeameter measurements is introduced. Conventionally, the sorptivity is obtained from the initial square‐root‐of‐time behaviour of discharge from the disc permeameter. In some cases this can be difficult to measure, in part because multi‐dimensional flows approach quasi‐steady state very rapidly. As an alternative we extend the ponded twin‐ring method to unsaturated discs of several radii. This method has the advantage that only long‐time, quasi‐steady discharges are needed to obtain K0 and S0. In the present study, the two methods are tested using data obtained for a fine sandy loam at a supply potential (Ψ0) of – 35 mm and agreement is good.
Structure Analysis of A-Type Carbonate Apatite by a Single-Crystal X-Ray Diffraction Method

Abstract The crystal structure of carbonate apatite was determined by X-ray diffraction analysis with Rw=0.027 using a single crystal grown by a CaCO3 flux method. The chemical formula of the crystal was Ca9.75[(PO4)5.5(CO3)0.5]CO3, in which all the A sites corresponding to OH sites in hydroxyapatite were substituted by CO3 ions. The space group was P 6 (hexagonal) with lattice parameters of a=0.9480(3) nm and c=0.6898(1) nm. The triangular plane of the CO3 ion substituting the A site randomly occupied one of six equivalent sites around the 6 axis parallel to the c-axis; one of three C–O bonds of CO3 lay on the 6 axis. The quantitative relation between CO3 ions in the A (OH) site and B (PO4) site of the present crystal was accounted for via Ca deficiency.
Brain voltage-sensitive calcium channel subtypes differentiated by ω-conotoxin fraction GVIA

Abstract We have studied the voltage-activated influx of Ca2+ into synaptosomes. Rapid 45Ca2+ influx into synaptosomes, measured at 1 sec, was blocked by predepolarization and by low concentrations of cadmium (IC50, 1 microM), as anticipated for voltage-sensitive calcium channels (VSCCs). However, fluxes were insensitive to dihydropyridine drugs that block or activate VSCCs, including nitrendipine, Bay K 8644, and (+)- and (-)-PN202-791. Phenylalkylamine calcium antagonists, including verapamil and desmethoxyverapamil, blocked 45Ca2+ uptake in a nonspecific fashion. The peptide omega-conotoxin fraction GVIA (omega-CgTx GVIA) blocked 45Ca2+ uptake in a biphasic fashion, with a 30% reduction at 50 pM toxin and a further decrease at concentrations greater than 5 nM. The toxin inhibited neurotransmitter release from synaptosomes in nanomolar concentrations, corresponding to its low-affinity effects on 45Ca2+ influx. omega-CgTx GVIA also inhibited depolarization-induced increases in intracellular Ca2+ concentration in single hippocampal and striatal neurons. These findings indicate that omega-CgTx GVIA blocks VSCCs in both cell bodies and nerve terminals and that the predominant form of VSCC in nerve terminals is the dihydropyridine-insensitive N type.
Deep-fat Frying of Plantain (Musa paradisiacaL.). I. Characterization of Control Parameters

Abstract A frying process to make plantain ( Musa paradisiaca L.) chips in palm oil was investigated. The effects of the main control parameters (initial temperature of oil in frying bath, processing time and stirring velocity) on the response variables (plantain water loss and fat gain, relative variations in oil temperature, and energy consumption) were studied. Frying kinetics at the centre point of the experimental design were established at 120, 240, 360 and 600 s. The Munsell colour scale was used to assess the colour of chips for kinetics at the centre point. According to the experimental design validation results, an initial oil bath temperature of 165 °C should be used to obtain plantain chips with a final water content of less than 5 g/100 g of fried product and a fat gain of less than 16 g/100 g of fried product, with a processing time of 200 s, thus allowing minimal energy consumption/kg evaporated water ( En 0 ).
Factors affecting radionuclide availability to vegetables grown at Los Alamos

A field study was conducted in 1977 on /sup 238/ /sup 239/Pu and /sup 137/Cs availability to zucchini squash (Curcurbita melopepo, hybrid seneca) and green bush beans (Phaseolus vulgaris, Landreths stringless) grown under home-garden conditions in an area at Los Alamos National Laboratory used for treated radioactive liquid waste disposal. Radionuclide concentrations were measured as a function of tissue type, height above the soil, fertilization regime, and for the squash, food-cleansing procedures. Analysis of variance procedures was used to analyze the data. Ratios of the concentration of a radionuclide in oven-dried vegetation to dry soil ranged from 0.0004 to 0.116 for the Pu isotopes, and from 0.051 to 0.255 for /sup 137/Cs. Fertilization with cattle manure reduced the Pu concentration ratios by 30% and /sup 137/Cs by 50%. Vegetative parts sampled within 20 cm of the ground surface were contaminated about four times as much as those parts growing further from the ground surface. About 65% of the contamination was removed by washing, indicating the presence of surficial contamination. The 50-year radiation dose commitment to humans consuming vegetables from the garden plot would be less than 0.05 mrem and would be due almost entirely to /sup 137/Cs.
Role of Acid in Precursor Conversion During InP Quantum Dot Synthesis

We have studied the speciation of P(SiMe3)3 during the synthesis of colloidal InP quantum dots in the presence of proton sources. Using 31P NMR spectroscopy, we show H3-nP(SiMe3)n formation on exposure of P(SiMe3)3 to a variety of protic reagents including water, methanol, and carboxylic acid, corroborating observations of P(SiMe3)3 speciation during the hot injection synthesis of InP QDs. Quantitative UV–vis comparisons between InP growth from P(SiMe3)3 and HP(SiMe3)2 show unambiguously that when total H+-content is accounted for, particle size, size dispersity, and concentration are indistinguishable for these two reagents. The dual role of myristic acid in P–Si bond cleavage and as a source of the myristate anion, an essential component of the quantum dot surface, is interrogated using tetrabutylammonium myristate, confirming that it is the protons that are responsible for increased quantum dot polydispersity. Together these data support the existence of a competing acid-catalyzed pathway in the conver.
Fluorescent probe solubilised in cetyltrimethylammonium bromide micelles by molecular dynamics simulation

In this paper, the solubilisation process of pyrene molecule, as the fluorescence probe molecule, in cetyltrimethylammonium bromide (CTAB) surfactant micelle solution is studied by molecular dynamics (MD) method. When one pyrene molecule is in the micellar solution, it can be adsorbed into the micelle spontaneously and vertically. The probe molecule mainly locates in the interior cavity or the palisade layer of the micelle. When two pyrene molecules exist in the micellar solution, they transfer from the interior to the palisade layer. Although strong π–π interactions exist between the pyrene molecules, the pyrenes separate to each other in the palisade layer in two-third simulated time.
Classical Theory of Rotational Relaxation in Diatomic Gases

In his well‐known theory, Parker assumes that the rotational relaxation of diatomic gases may be described by a single relaxation time which is calculated for the special case of initially nonrotating molecules. In the present theory the evolution of the rotational distribution function is described by a diffusion‐equation approximation to the master equation. This equation is linearized and solved for the case of acoustic waves. The results indicate that the absorption and dispersion of acoustic waves cannot be described by a single relaxation time. However, the behavior at very low and very high frequencies can be described in terms of “apparent relaxation times” which differ by approximately 50%. The temperature dependence of the apparent relaxation times is similar to that predicted by Parker, but the magnitudes are larger by approximately a factor of 2.
THE INFLUENCE OF PEG MOLECULAR WEIGHT ON MORPHOLOGIES AND PROPERTIES OF PVDF ASYMMETRIC MEMBRANES

The preparation and properties of asymmetric poly(vinyldiene fluoride) (PVDF) membranes are described in this study. Membranes were prepared from a casting solution of PVDF, N, N-dimethylacetamide (DMAc) solvent and water-soluble poly(ethylene glycol) (PEG) additives by immersing them in water as coagulant medium. Experiments showed that when PEG molecular weight increased, the changes in the resultant membranes' morphologies and properties showed a transition point at PEG6000. This indicated that PEG with a relatively low molecular weight was used as a pore-forming agent to enhance pure water flux and reduce solute rejection of membranes, but PEG was used as a pore-reducing agent with a further increment of PEG molecular weight to result in pure water flux decreasing and solute rejection increasing. Finally, combined with the precipitation rates of different membrane-forming systems, the membrane formation mechanism describing PEG mobility was discussed extensively basing on the length changes of PEG molecular chains and the affinity between PEG and casting solution. The results offered a better understanding of effects of PEG additives on membrane structure and properties.
Textbook Questions in Context-Based and Traditional Chemistry Curricula Analysed from a Content Perspective and a Learning Activities Perspective

In this study, questions in context-based and traditional chemistry textbooks were analysed from two perspectives that are at the heart of chemistry curricula reforms: a content perspective and a learning activities perspective. To analyse these textbook questions, we developed an instrument for each perspective. In total, 971 textbook questions were analysed. Textbook questions in context-based and traditional curricula appeared to differ significantly in their orientation on content and in the activation to engage students in certain learning activities. Although traditional curricula included more questions that stress traditional chemistry content and included more reproductive chemistry questions than context-based curricula, they were not always as traditional as we had expected. Context-based chemistry curricula focused more on chemistry content relating to societal/technological issues and chemistry theory development and also more questions were included that activate students to regulate their own learning. However, context-based chemistry curricula still included a considerable amount of traditional chemistry content and did not focus as much on higher order learning as we had expected. The developed instruments might be helpful in chemistry curricula design to gain insights into the content which is stressed and how students are activated by textbook questions to engage in learning.