Miracle-dz/UniFAR-FTUs huggingface dataset:
Friedeland Triterpenoids from Peritassa compta: Complete 1H and 13C Assignments by 2D nmr Spectroscopy

An investigation of the stems and bark of Peritassa compta has led to the isolation of three new natural products, friedelane-3,15-dione [3], 15α-hydroxyfriedelin [4], and 15α-hydroxyfriedelane-1,3-dione [5], along with friedelin [1] and friedelane-1,3-dione [2]. Complete 1 H and 13 C assignments for all compounds were achieved by 2D spectroscopy
Smooth transitions between biaxial intermediate smectic phases

The possibility of smooth transitions between biaxial smectic subphases via defect propagation is considered on the basis of our theoretical approach reported previously [Emelyanenko et al., Phys. Rev. E, 2006, 74, 011705]. The extrapolation of our results suggests an infinite number of biaxial intermediate phases, each one existing stably only at a particular temperature, and not over a range. Three- and four-layer subphases are confirmed to be important due to the minor differences between them and their neighboring subphases. Some other subphases (including a six-layer subphase) are also found to be very similar to the neighboring subphases. Several sets of intermediate phases are recognized. Each set represents a combination of two typical fragments of the smectic structure in various proportions.
The Study of Structural Transition of ZnS Nanorods under High Pressure

The study of pressure behavior for ZnS nanorods by X-ray diffraction measurements up to 37.2 GPa is carried out. ZnS nanorods transform from the initial wurtzite phase to rock salt phase at 19.6 GPa without undergoing the transition to zinc blende structure, and this is the first report about the direct phase transition from wurtzite to rock salt phase for ZnS. The longitudinal c-axis of ZnS nanorods exhibits more compressible behavior than that of radial a-axis direction, which is caused by the special rod morphology, and this induces the special direct phase transition to rock salt phase without zinc blende phase in the transition process. The results show the morphology of ZnS nanorods plays a crucial role in the special pressure behavior and also suggests we could explore the various pressure behaviors applying particular shaped nanomaterials under high pressure.
Bond length relationships in diazo and diazonium compounds

Geometrical data for 52 instances of the C-N=N substructure have been retrieved from the Cambridge Structural Database. A scatterplot of the N=N bond length (range 1.078-1.146 A) versus the C-N bond length (range 1.278-1.450 A) shows a strong negative correlation (linear correlation coefficient= -0.846) : a decrease in N=N triple-bond character is directly correlated with increasing double-bond character of C-N. Three discrete chemical subgroups can be identified in the dataset : benzenediazonium compounds, diazoketones and diazoalkanes with mean N=N/C-N bond lengths of 1.093 (2)/1.394(6), 1.115(3)/1.328(5) and 1.133(3) /1.301(8)A, respectively.
Hydrogen Oxidation at the Ni/Yttria-Stabilized Zirconia Interface: A Study Based on Density Functional Theory

A new mechanism for hydrogen oxidation on the nickel/yttria-stabilized zirconia (Ni/YSZ) interface is proposed based on density functional theory. The new mechanism involves oxidation of hydrogen by the oxygen atoms that are bound to both nickel and zirconium (or yttrium) at the interface. The free energy change (ΔG) for this pathway is compared to ΔG for reaction steps of previously proposed oxidation mechanisms involving spillover of oxygen from YSZ to nickel or hydrogen spillover from nickel to YSZ. For all mechanisms, we consider both a stoichiometric (YSZ) surface as well as an oxygen enriched YSZ surface (YSZ+O) where in the latter case a vacant site is filled by an oxygen atom transferred from the YSZ bulk. The release of water as the final product in hydrogen oxidation is facilitated at high temperatures by entropy. The difference between the current and previous mechanisms is that for the hydrogen oxidation now we only consider the involvement of oxygen atoms that are bound to both nickel and zir.
Production patterns of perennial herbaceous biomass crops in the Great Lakes Region

Abstract Optimal management strategies for herbaceous biomass production depend on the interaction of crop and environmental resources and the resulting yield patterns through time. The objectives of this study were to determine the production potential of different perennial herbaceous biomass crops under several management regimes and to test regression analysis as a method for determining the effect of stand age on the production potential of these species on representative soils of the Eastern Great Lakes Region of the United States. Eastern gamagrass, flatpea, reed canarygrass, switchgrass, and mixtures of alfalfa-smooth bromegrass, timothy-redtop-red clover, and naturalized meadows were grown at three fertility levels under two cutting-management regimes for up to 5 years at various locations in New York State. Annual yields ranged from about 4 to more than 12 Mg ha−1, depending on species, soil, and crop management. Regression analyses revealed four patterns of change with time and provide a conven.
Structures of the Ordered Water Monolayer on MgO(001)

Global ab initio structure optimizations combined with statistical thermodynamics and experimental studies reveal atomic structures of the ordered water monolayer on the MgO(001) surface. Calculations based on density functional theory predict the existence of two stable surface structures: a c(4×2) structure containing ten water molecules per unit cell stable at low temperature and a p(3×2) structure containing six water molecules per unit cell stable at high temperature. Both structures feature four surface hydroxyl groups resulting from the dissociation of two water molecules per surface cell. The calculated properties of the two structures are in agreement with a multitude of experimental data, including infrared reflection absorption, sum frequency generation and X-ray photoelectron spectroscopy. Comparison of calculated and experimental vibrational spectra allows for assignment of the observed vibrational modes.
Solution Properties of Poly(Methyl Methacrylate) in Dimethylsulfoxide

Abstract The solution properties of polymethylmethacrylate in dimethylsulfoxide were studied using multi-angle light scattering and an online viscometer coupled to size exclusion chromatography. The data demonstrate that DMSO is a suitable eluent for the determination of the molecular weight of PMMA by SEC. The Mark-Houwink coefficients K and α were determined as a function of temperature. At 35°C, DMSO is a theta solvent for PMMA, and it becomes a good solvent as the temperature increases. The unperturbed dimension Kθ was calculated using three different procedures. The data do not show evidence of a conformational transition controlled by the temperature such as the one reported in benzene and confirm the existence of a general relationship between the ratio K/Kθ and α. In the case of PMMA, the comparison of the dipole moment of the side group to that of the solvent can be used to predict the existence of a conformational transition.
Pressure dependence of energetic (⩽160 keV) focused electron beams arising from heated or cooled (LiNbO3) pyroelectric crystals

An interesting effect, “gas amplification of electron energy” is reported here; namely when a cylindrical pyroelectric crystal such as (LiNbO3) is contained in a concentric cylindrical chamber and is heated and then allowed to cool in a dilute gas the maximum energy of the resultant focused electron beam more than doubles as the pressure increases from 0.05 to 4 mTorr for seven different gases.
Displacements at the nitrogen of lithioalkoxylamides by organometallic reagents

The conversions of N-(o-bromobenzyl)methoxylamine to N-acetylbenzoazetine (1), of N-(3-(o-bromophenyl)-n-propyl)methoxylamine to N-acetyltetrahydroquinoline (2), and of N-(4-(o-bromophenyl)-n-butyl)-methoxylamine to N-acetylbenzazapine (3) illustrate the use of this displacement reaction to form nitrogen-containing rings in an exocyclic reaction mode. An x-ray structural determination is reported for 1. The formations of anilides by amination of aromatic organolithium reagents with lithium methoxylamide is also reported. Lithium reagents are found to be more effective than Grignard, copper, or zinc reagents in these displacements, and the yields decrease as the size of the substituents around nitrogen increases. The endocyclic restriction test is used to show that this displacement on nitrogen cannot occur within the endocyclic confines of a seven-membered ring. A S{sub N}2 reaction pathway in a lithium complex is considered to be supported by these results.
Enhancing the stability of immobilized catalase on activated carbon with gelatin encapsulation

Gelatin (Gel) encapsulation onto activated carbon (AC) with catalase (CAT) was developed as an alternative method for CAT immobilization in this study. The immobilized CAT with AC encapsulated by Gel as the supporter accounted for 65.69% of the native enzyme activity. Furthermore, the properties of the immobilized CATs were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. Among free CAT and the two immobilized CATs, the immobilized CAT with AC encapsulated by Gel as the supporter showed the highest relative enzymatic activity and a high stability in a broad range of pH values and temperatures, and its residual activity was 80% after 15 uses, whereas the immobilized CAT with AC as the supporter was retained at a level of only 50% under the same conditions. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1498–1502, 2013
Chemical characteristics of soil fulvic acids fractionated using polyvinylpyrrolidone (PVP)

Abstract Elementary composition, IR spectra, 13C-NMR spectra and molecular size distribution were determined for fulvic acids (FAs), polyvinylpyrrolidone (PVP)-adsorbed and non-adsorbed fractions of FAs and humic acids (HAs). The analytical data showed that the properties were distinctly different between the PVP-adsorbed and the non-adsorbed fractions. Atomic ratio, IR spectra and 13C-NMR spectra indicated that the PVP-adsorbed fractions contained a larger number of aromatic rings and carboxyl groups including ester than the non-adsorbed fractions. On the other hand, carbohydrates and N-containing compounds such as peptides or amino acids were concentrated in the PVP-non-adsorbed fractions. Weight average molecular weights (Mw ) of the adsorbed fractions were lower and the range of molecular size distribution was narrower than those of the non-adsorbed fractions. Chemical characteristics of HAs varied depending on the types of soils, while the characteristics of the PVP-adsorbed and non-adsorbed fraction.
Effect of ionic strength solution on the stability of chitosan–DNA nanoparticles

Chitosan–DNA nanoparticles employed in gene therapy protocols consist of a neutralised, stoichiometric core and a shell of the excess of chitosan which stabilises the particles against further coagulation. At low ionic strength, these nanoparticles possess a high stability; however, as the ionic strength increases, it weakens the electrostatic repulsion which can play a decisive part in the formation of highly aggregated particles. In this study, new results about the effect of ionic strength on the colloidal stability of chitosan–DNA nanoparticles were obtained by studying the interaction between chitosans of increasing molecular weights (5, 10, 16, 29, 57 and 150 kDa) and calf thymus DNA. The physicochemical properties of polyplexes were investigated by means of dynamic light scattering, static fluorescence spectroscopy, optic microscopy, transmission electronic microscopy and gel electrophoresis. After subsequent addition of salt to the nanoparticles solution, secondary aggregation increased the size of the polyplexes. The nanoparticles stability decreased drastically at the ionic strengths 150 and 500 mM, which caused the corresponding decrease in the thickness of the stabilising shell. The morphologies of chitosan/DNA nanoparticles at those ionic strengths were a mixture of large spherical aggregates, toroids and rods. The results indicated that to obtain stable chitosan–DNA nanoparticles, besides molecular weight and N/P ratio, it is quite important to control the ionic strength of the solution.
Sequential optimization and kinetic modeling of L-asparaginase production by Pectobacterium carotovorum in submerged fermentation

L-Asparaginase is a therapeutic enzyme widely used as an antitumor agent for the treatment of acute lymphoblastic leukemia and lymphosarcoma. Its potential applications as a therapeutic agent and food additive require production at high yields in a low-cost medium with high purity and stability. Statistical experimental designs were applied to identify and optimize the significant parameters for the fermentative production of L-asparaginase by Pectobacterium carotovorum Microbial Type Culture Collection (MTCC) 1428. Screening of different carbon sources identified galactose as the best carbon source for the production of L-asparaginase. Twelve medium components were selected and sixteen experiments were carried out based on the Plackett–Burman (PB) design for identifying the most significant medium components. Yeast extract, galactose, monosodium glutamate, MgSO4.7H2O and CaCl2.2H2O were found to be the most significant components that affected the production of L-asparaginase, and they were optimized by response surface methodology (RSM) using central composite design. This optimized medium showed maximum production rates of periplasmic and extracellular L-asparaginase of 3.25 and 0.83 U ml−1, respectively. The periplasmic L-asparaginase production in the optimized medium was twofold higher than in the basal medium. Unstructured kinetic models were applied and satisfactorily described the cell growth, product formation and substrate utilization profile, thus providing a better understanding and prediction of the fermentation profile. This paper details the application of PB experimental design and RSM for the optimization of L-asparaginase production from Pe. carotovorum MTCC 1428 in submerged fermentation. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.
Composted MSW Effects on Soil Properties and Native Vegetation in a Degraded Semiarid Shrubland

Three rates of dried composted MSW (40, 80 and 120 Mg ha−1) were surface applied to a degraded semiarid shrubland site near Madrid in central Spain. Various soil and plant parameters were determined one year after its application. MSW amendment had an effect on soil chemistry and nutrient levels. Available P and K, concentration of N-NO3 and EC. increased significantly after the MSW application. The concentration of total soil heavy metals, Zn, Pb, Cd, Ni, Cr and Cu rose with the application of MSW as compared with the control plot, but these increases were only significant in total Zn, Pb and Cu. Zn and Cu amounts of DTPA-extractable soil were also significantly higher in the amended soil. Total plant cover increased significantly in the plots treated with low and intermediate MSW rates. Total biomass production increased as compost rates were added but this rise is not proportional to the amount of MSW added. The degraded soil used in this study may require MSW rates up to 80 Mg ha−1 to improve soil chemical properties as well as to produce minimal changes in the native vegetation.
Crude Protein, Phosphorus, Common Salt, and Mineral Composition of Range Plants and their Nutritive Value for Grazing Ruminants in Southern Iran

Abstract The present study was conducted in a dry region to evaluate 1) the crude protein, phosphorus, common salt, and mineral composition of different range plants and 2) their value for grazing ruminants such as cattle, sheep, and goats. The research region was divided into five separate sites with vegetation cover of the range plants Atriplex lentiformis, A. nummularia, and A. halimus (all newly introduced species) and A. leucoclada and Salsola rigida (both native species). Six separate samples of the aerial parts were taken at random and analyzed for determination of their total nitrogen (N), phosphorus (P), sodium (Na), chloride (Cl), and mineral composition. The crude protein content ranged from 8.23% for S. rigida to 14.57% for A. nummularia. Except for P content, Na and Cl of the all tested plants were well more than the critical levels and may be considered adequate for grazing ruminants. However, all of the tested plants contained P levels below the critical concentration, and thus supplementation of P seems to be necessary in the research region. The results suggest that Ca, K, and Na levels may be considered adequate for grazing ruminants; however, supplementation of Mg would seem to be necessary in the research region in Dadin area, especially when A. leucoclada, A. nummularia, and S. rigida species are the main sources of animal food. Because iron (Fe), manganese (Mn), and copper (Cu) concentrations of the tested plants are greater than the critical levels, they may be considered to be adequate for grazing ruminants; however, supplementaion of zinc (Zn), especially for A. leucoclada, S. rigida, and A. lentiformis, would seem to be necessary in the research region. The total of mineral concentrations of the tested plants suggested that, from a nutritional point of view, the three new introduced species are richer than the two native species.
Micromodeling of Functionally Graded SOFC Cathodes

One approach to improve the performances of a solid oxide fuel cell (SOFC) cathodes is to use a composite electrode that typically consists of a two-phase porous mixture of a solid electrolyte (yttria-stabilized zirconia) and an electrocatalytic material. The best electrochemical performances with such a type of cathode are obtained when the composition varies within the composite cathode called graded electrode. The present modeling has been performed in order to give a complete description of the electrode microstructure, as well as the process occurring therein. A one-dimensional, homogeneous model and a discrete element method was used. The present study proposes a one-dimensional dc and ac model that takes into account mass and charge conservation, transport of species, and reaction kinetics. The influence of transport parameters and microstructure on the shape of both polarization curves and impedance diagrams is discussed.
Impact of Guided-Inquiry-Based Instruction with a Writing and Reflection Emphasis on Chemistry Students' Critical Thinking Abilities.

The Science Writing Heuristic (SWH) laboratory instruction approach has been used successfully over a decade to engage students in laboratory activities. SWH-based instruction emphasizes knowledge construction through individual writing and reflection, and collaborative learning as a group. In the SWH approach, writing is a core component of learning. Previous studies on the SWH approach have reported effective implementation of the SWH approach leads to an improvement in overall student academic performance and content knowledge. Using a rubric developed by Maria Oliver-Hoyo, we compared the critical thinking (CT) skills of students across three groups, based on their written laboratory reports for various traits of CT, and the cognitive skills embedded in the rubric. Participants in this study were first-year general chemistry students who received traditional laboratory instruction, first-year general chemistry students who were instructed using the SWH approach, and fourth-year chemistry students who .
Conformations of diterpenoids: an X-ray determination of the molecular structure of 6α-bromo-13-hydroxy-14-isopropylpodocarpa-8,11,13-trien-7-one and of the structure and absolute configuration of methyl 6α-bromo-13-isopropyl-7-oxopodocarpa-8,11,13-trien-15-oate

The crystal and molecular structures of the title compounds have been determined by X-ray diffraction methods from photographic data by the heavy-atom method; the absolute configuration was established for the second named. Crystals of the former (II) are tetragonal, a= 12·54, c= 23·97, A, space group P41212; the structure was refined by least squares to R 0·088. The latter (III) is triclinic, a= 6·20, b= 7·73, c= 10·79 A, α= 97·0, β= 79·3, γ= 104·6°, space group P1; refined to R 0·064. In (II) ring A has a chair conformation with a trans A/B ring fusion; ring B has an approximate boat conformation and the bromine atom has the α-configuration. The bromine is in the same configuration in compound (III) and ring A also adopts the chair conformation. There is trans A/B ring fusion with ring B somewhat distorted but describable as a ‘half-boat’. The stereochemistries at asymmetric centres confirm earlier evidence. There is considerable variation in detailed conformation, however, and a comparison between these compounds and with the molecular structure of methyl 6α-bromo-12-methoxy-7-oxopodocarpa-8,11,13-trien-16-oate leads to the view that steric rather than electronic factors are largely responsible for the path of bromine attack.
Catalytic determination of vanadium using the perphenazine–bromate redox reaction and a citric acid activator

Citric acid was found to have a highly activating effect on the vanadium-catalysed oxidation of perphenazine (PP) with bromate. An extremely sensitive, selective and simple method was developed for the determination of vanadium based on this effect. The reaction rate was followed spectrophotometrically by monitoring the formation of the red oxidation product of PP at 526 nm within 1 min of mixing. Using the recommended procedure, vanadium can be determined up to 6.5 ng ml–1 with a linear calibration graph and a detection limit of 0.08 ng ml–1. A suggested mechanism of the reaction and the activating mechanism of citric acid is presented. The method surpassed the standard Fishman–Skougstad catalytic method in sensitivity, selectivity and speed and was successfully applied to the determination of vanadium in polluted river waters.
The conductivity of thin wires in a magnetic field

A thin film or wire of metal has a lower electrical conductivity than the bulk material if the thickness is comparable with or smaller than the electronic mean free path. Previous workers have obtained expressions for the magnitude of the effect by integrating the Boltzmann equation and imposing the appropriate boundary conditions. The problem is re-examined from a kinetic theory standpoint, and it is shown that the same expressions are obtained by this method, usually rather more simply, while the physical picture is considerably clarified. The method is applied to an evaluation of the conductivity of a thin wire with a magnetic field along the axis, and it is found that the resistivity should decrease as the magnetic field is increased; it should be possible to derive the mean free path and velocity of the conduction electrons by comparison of theory and experiment. The theory has been confirmed by experimental measurements on sodium; estimates of electronic velocity and mean free path are obtained which are in fair agreement with the values given by the free-electron theory.