Miracle-dz/UniFAR-FTUs huggingface dataset:
Computational Studies of the Reactivity, Regio-Selectivity and Stereo-Selectivity of Pericyclic Diels-Alder Reactions of Substituted

The power of the Diels-Alder reaction was expanded recently through the discovery by Li and Danishefsky that cyclobutenone is an unusually reactive dienophile and that the adducts formed can be converted to products that are formally the Diels-Alder adducts of unreactive dienophiles. However, the effects of substituents on the reactivity as well as the region - and stereo-selectivity of the Diels-Alder reactions of cyclobutenone have not been clearly elucidated yet. This paper reports the results of a computational study at the MP2/6-31G* level of theory into the effects of substituents on the reactivity, regio-selectivity and stereo-selectivity of the Diels-Alder reactions of some substituted cyclobutenones with cyclic and acyclic dienes. It was found that the Diels-Alder reaction of maleic anhydride is far more feasible kinetically than the reaction of cyclobutenone, the activation barrier of the former being more than thrice that of the latter, indicating that maleic anhydride is a far better dienophile than cyclobutenone, which in turn implies that for cyclic dienophiles ring strain is not the dominant factor controlling the kinetics of the Diels-Alder reaction as has been suggested elsewhere. The Diels - Alder reactions of cyclobutenones were all found to follow an asynchronous concerted reaction pathway. In the reactions of the parent (unsubstituted) cyclobutenone with 1,3-butadiene and cyclopentadiene, the endo pathway is the most preferred kinetically, by 2.24 and 1.64 kcal/mol respectively. However, in the reactions of the 4,4-disubstituted cyclobutenones the exo pathway becomes the most preferred in the reactions with both 1,3-buadiene and cyclopentadiene, except for the CN-substituted cyclobutenone where the endo pathway is still the most preferred pathway. In the reactions of the 4-monosubstituted cyclobutenone with 1,3-butadiene, the anti-positions are preferred over the syn positions. The endo-anti position gives the most reactive dienophile kinetically. In the reactions of trans-piperylene with substituted cyclobutenones, the meta-endo position is the most preferred kinetically. In the reactions of isoprene with substituted cyclobutenones, the para-endo substitution gives the lowest activation barriers and therefore the most favorable reaction kinetics. In all the reactions considered in this work, the CN-substituted species have the lowest activation barriers and the most stable products. In the reactions of 4,4-disubstituted cyclobutenones with 1,3-butadiene and cyclopentadiene, the order of activation barriers is CN OH>Cl>CH 3 .
Efficiency potential of organic bulk heterojunction solar cells

In order for organic bulk heterojunction solar cells to compete with the traditional inorganic cells, power conversion efficiencies of more than 10% are desirable. Nowadays, efficiencies up to 5% are reached and the question about the limits for the attainable efficiency of organic cells arises. In this paper, we study the efficiency potential of organic bulk heterojunction solar cells. We make realistic assumptions to predict efficiencies obtainable in the near future, and calculate the upper‐limit. We study the influence of the difference between the lowest unoccupied molecular orbital (LUMO)‐energy levels of donor and acceptor, and the absorption window on the efficiency. Ideal material characteristics are obtained from these calculations, giving an idea how the ideal organic solar cell should look like. The calculations show that nowadays an efficiency of 5·8% for the single junction bulk heterojunction solar cell should be possible. Considering parameters which are credible to be achieved in the future, an organic solar cell of 15·2% is in reach, with an optimal bandgap of 1·5 eV for the absorber. We also consider the situation where both the n‐ and p‐type materials are absorbers. All calculations are not only done for a single junction cell, but also for tandem solar cells. For a tandem structure of organic cells, we find in a realistic scenario a maximum attainable efficiency of 10·1% and an efficiency of 23·2% in an optimistic scenario with optimal bandgaps Eg1 = 1·7 eV and Eg2 = 1·1 eV. Copyright © 2007 John Wiley & Sons, Ltd.
Benzimidazole Derivatives: Active Class of Antioxidants

In this study, we prepared some new benzimidazole derivatives and investigated their antioxidant properties by determination of DPPH Radical scavenging, Superoxide Scavenging, Iron Chelating assays methods. Benzimidazoles are an important class of compounds with a wide spectrum of biological activity. The five membered heterocyclic moieties also confer for various biological activities. Hence a series of benzimidazole derivatives have been synthesized characterized by UV, IR and 1 H NMR spectral data and evaluated for their in vitro and antioxidant activity. The synthesized benzimidazole derivatives showed remarkable antioxidant activity Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships.
Selective alkali-metal cation complexation by chemically modified calixarenes. Part 4. Effect of substituent variation on the Na+/K+ selectivity in the ester series and X-ray crystal structure of the trifluoroethyl ester

The cation complexing abilities of a series of p-tert-butylcalix[4]arenes bearing ligating ester groups in the cone conformation have been assessed by stability constant measurements in methanol and extraction studies from water into dichloromethane. The cations studied were Na+ and K+ and variations in the ester function (CO2R) included R = methyl, ethyl, n-butyl, tert-butyl, benzyl, phenyl, phenacyl, methoxyethyl, trifluoroethyl, methylthioethyl and prop-2-ynyl. The effect of replacing one or two ester functions in the tetraethyl ester by methyl ester, carboxylic acid, ketone and amide functions was also studied. Selectivities for Na+ relative to K+ in stability constants range from 2 to 2500, the phenacyl derivative having the highest selectivity. X-Ray diffraction analysis was used to probe the conformation of the trifluoroethyl ester 11. Crystals of 11 are monoclinic, space group P21/n, in a cell of dimensions a= 13.987(2), b= 16.194(3), c= 27.630(5)A; β= 98.70(1)°; R= 0.077 for 3172 observed data. The compound possesses a distorted cone conformation.
Particle Size Characterization of an Extra Fine Milled Product

The present research aims to characterize the particle size distribution of sub micron particles suspended in a liquid. The particles milled are an organic poorly water soluble crystalline product. To characterize the size of these particles, different techniques have been tested: imaging techniques (SEM, CryoTEM), static light scattering techniques, dynamic light scattering techniques, centrifugation and flow field flow fractionation.
Nitrate leaching from reseeded pasture

Abstract. Nitrate leaching and soil mineral N status under grassland were measured on three contrasting soils, spanning winters 1995/96, 1996/97 and 1997/98, in Western England. The soils investigated were a freely draining silty clay loam (Rosemaund), a well drained loam (IGER 1) and a poorly drained clay loam (IGER 2). The effects of reseeding (ploughing and resowing grass) at IGER 1 and IGER 2 in autumn 1995 or 1996 were compared with undisturbed pasture. Reseeding at Rosemaund, in autumns 1995 or 1996, or spring 1996 was compared with undisturbed pasture of 3 sward ages (2, 5, >50 years).
Chemical vapor deposition of polycrystalline Fe3O4 thin films by using the cyclohexadiene iron tricarbonyl liquid precursor

Magnetite (Fe3O4) thin films are synthesized by chemical vapor deposition (CVD) with the cyclohexadiene iron tricarbonyl Fe(C6H8)(CO)3 liquid precursor. The growth of pure, polycrystalline, and stoichiometric Fe3O4 films is confirmed by X-ray diffraction, Raman spectroscopy, time-of-flight secondary ion mass spectrometry, and conversion electron Mossbauer spectroscopy. At 297 K, the resistivity for 24.8 nm (100 nm) Fe3O4 thin film is 17 × 10−3 Ω cm (4.2 × 10−3 Ωcm), indicating the good electrical quality of the as-deposited layers. Magnetoresistance (MR) up to −2.2% is measured at 297 K at 1.1 T, corresponding to 15% electron spin polarization. A gradual increase of MR is observed at low temperature. In particular, the observed MR = −4.4% at 120 K (at 0.8 T) is attributed to an intrinsic enhancement of the electrons spin polarization up to 21.5%.
Effect of ensiling pumpkin Cucurbita maxima with the addition of inoculant or without it on chemical composition and quality of silages

Effect of ensiling pumpkin Cucurbita maxima with the addition of inoculant or without it on chemical composition and quality of silages. The aim of the studies was to determine the effect of ensiling the pumpkin on chemical composition and quality of silages. The silages were produced from pumpkin of Justynka variety. Before ensiling, the disintegrated pumpkin fruits were mixed with the dried beet pulp in ratio equals 80 : 20. Two variants of silages were prepared: with the inoculant and without it. In the silages, the following basic chemical composition was determined: the content of dry matter, crude ash, crude protein, crude fat, crude fi bre, NDF, ADF and ADL. The indicators, being an evidence of the run of ensiling process and the quality of the obtained silages, were also determined, i.e. pH, lactic, acetic and butyric acids, ammonia nitrogen, ethanol and aerobic stability. In the obtained silages, as compared to the material before ensiling, the lower content of crude fi bre and ADF was found whereas in the silage with inoculant, NDF level was also lowered. The silages with the inoculant were characterized by higher content of lactic and acetic acids and lower level of nitrogen, ammonia and ethanol. The silages with the inoculant had also higher aerobic stability. The conducted studies indicate that the application of inoculant has affected the improvement of the quality of the obtained
Ultrafast and Low Barrier Motions in the Photoreactions of the Green Fluorescent Protein*

Green fluorescent protein (GFP) fluoresces efficiently under blue excitation despite major electrostatic rearrangements resulting from photoionization of the chromophore and neutralization of Glu-222. A competing phototransformation process, which ionizes the chromophore and decarboxylates Glu-222, mimics the electrostatic and structural changes in the fluorescence photocycle. Structural and spectroscopic analysis of the cryogenically stabilized photoproduct at 100 K and a structurally annealed intermediate of the phototransformed protein at 170 K reveals distinct structural relaxations involving protein, chromophore, solvent, and photogenerated CO2. Strong structural changes of the 100 K photoproduct after decarboxylation appear exclusively within 15 Å of the chromophore and include the electrostatically driven perturbations of Gln-69, Cys-70, and water molecules in an H-bonding network connecting the chromophore. X-ray crystallography to 1.85 Å resolution and static and picosecond time-resolved IR spectroscopy identify structural mechanisms common to phototransformation and to the fluorescence photocycle. In particular, the appearance of a 1697 cm-1 (+) difference band in both photocycle and phototransformation intermediates is a spectroscopic signature for the structural perturbation of Gln-69. This is taken as evidence for an electrostatically driven dynamic response that is common to both photoreaction pathways. The interactions between the chromophore and the perturbed residues and solvent are decreased or removed in the T203H single and T203H/Q69L double mutants, resulting in a strong reduction of the fluorescence quantum yield. This suggests that the electrostatic response to the transient formation of a buried charge in the wild type is important for the bright fluorescence.
Online-Publication of the German Food Composition Table “Souci–Fachmann–Kraut“ on the Internet

Abstract The German Food Composition Table, founded in the 1960s by S. W. Souci, W. Fachmann and H. Kraut has been published since 1968 as a regular printed version via a scientific publisher. Analogous to the development of this media, an electronic version of the database, corresponding to the fifth edition of the table, was available for the first time in 1995. However, contemporaneously with the publishing of the sixth edition an online-version of the database has been developed and transferred into the World Wide Web, providing detailed food composition data of about 800 food items and 260 food constituents ( http://www.sfk-online.net ). The documentation includes the average values and variations of the nutrient concentrations, as well as energy- and waste values of the specific food items. The concept of the database enables the user to search for specific food items, defined constituent concentrations and energy values, as well as to export data tables of single food items. Additionally the calculation of the composition of raw food mixtures based on the data included in the database is realized by this electronic version.
Effects of Treatments on the Total Tannins in Black Gram Husk (Vigna mungo)

ABSTRACT Black gram (Vigna mungo) husk is one such agro industrial by products available in substantial quantity in Tamil Nadu. The use of tropical legume seeds and its by-products can be limited due to the presence of one or other toxic factors including tannins. Black gram husk samples were analyzed for total tannin. The total tannin content of black gram husk ranges from 2.70 to 4.55 per cent with a mean of 3.67 ± 0.31. per cent The ground samples of black gram husk were subjected to water soaking or calcium hydroxide [Ca (OH)2] treatment to reduce the total tannins. When overnight water soaking or calcium hydroxide treatments were carried out the total tannins content in the husk was significantly (P0.01) reduced to 1.14 or 1.77 per cent respectively. Water soaking was more effective in reducing the total tannins than the calcium hydroxide treatment and it was cost effective and easily adopted by farming community to utilize the nutrient content in Black gram husk.
Dystrophy effects on the LIZA RAMADA (Risso, 1826) (Pisces, Mugilidae) population in the Cabras lagoon (Central-Western Sardinia)

Fish samples were collected between 1999 and 2002 in the Cabras lagoon, the largest brackish area in Sardinia and one of the most important areas for the artisanal lagoon fishery in the Mediterranean area. Because of its natural connection with both the Oristano Gulf and the ‘Mare e Foghe’ river, in which pollution problems are frequent, this area suffers from dystrophic crises linked to phytoplanktonic or macrophytes blooms. The effect of the 1999 dystrophy on the fish population was studied by analysing the commercial landings variations and the modification of the demographic structure of the most important species, Liza ramada. Because of the dystrophy, the yields have decreased by about 90% since 1998. These effects are most likely attributable to the reduction in recruitment as the VPA analysis on L. ramada suggests. The calculated growth parameters of Thinlip mullet, which are the first reported for a Sardinia lagoon, are useful for fishery management of these areas. The study leads us to conclude that the trophic conditions probably changed, causing the reduction in the natural lagoon's ‘call-effect’ of recruits from the sea.
Structural refinements of the individual grains within polycrystals and powders

A method is presented for simultaneous structural refinement of up to several hundred grains inside powders or polycrystals. The method is based on the use of hard X-rays and the indexing program GRAINDEX, where grain orientations are found by scanning in Euler space. Conventional experimental setups and refinement programs for single-crystal work can be applied. The method is validated by a study of a sintered plate of α-Al 2 O 3 , containing of the order of 1500 grains in the gauge volume. 57 of the largest grains were refined with respect to the Alz and Ox positions as well as the isotropic atomic displacement parameters. The R1 values were 3.4% and 3.8% for the grain average and the best grain, respectively. A discussion of the potential of the method is presented, as well as the main limitation: grain size and overlap of diffraction spots.
Simultaneous Synchronous Fluorescence Determination of Carbaryl, Propoxur, and Carbofuran with Multivariate Calibration Methods

Abstract A synchronous fluorescence method for the determination of carbaryl (CAB), propoxur (PRO), and carbofuran (CAF) with the aid of multivariate calibration methods, such as classical least squares (CLS), principal component regression (PCR), and partial least squares (PLS), was proposed. Because the synchronous fluorescence spectra (SFS) of these three compounds are seriously overlapped, it is difficult to determine these compounds individually from their mixtures. In this work, the experimental conditions were investigated and optimized to obtain the high sensitivities and well‐defined waves for each analyte. Furthermore, chemometrics models were established from a set of known samples and were then applied to the prediction of these three pesticides in a set of validation samples with a relative prediction error (RPET) of around 4% and limits of detection of 0.50, 5.5, and 23 ng L−1 for carbaryl, propoxur, and carbofuran, respectively. The proposed method was also successfully applied to determine the contents of these three compounds in spiked fruit and vegetable samples.
Shedding the hydrophilic mantle of polymersomes

Block copolymers of polybutadiene-b-poly(ethylene glycol) were prepared in which both segments were coupled via an acid sensitive hydrazone moiety. Polymersomes that were subsequently formed showed a strong pH-dependent colloidal stability as a result of the pH sensitive removal of the PEG block. By mixing this stimulus responsive block polymer with an inert analogue it was possible to systematically remove percentages of PEG from the polymersome mantle. The minimum amount of surface PEGylation needed to retain stable polymersomes was found to be as low as five percent.
A New Polymer-Supported Reagent for the Synthesis of β-Lactams in Solution

A modified Mukaiyama reagent was prepared on a PS-DVB resin. This reagent was used for the preparation of β-lactams, using the Staudinger reaction. The products were obtained by generating the ketene from a carboxylic acid under sonication with the resin followed by reaction with the imine. Excess of the imine was removed by reduction followed by acid scavenging.
EXCITED AND IONIZED STATES OF FREE BASE PORPHIN STUDIED BY THE SYMMETRY ADAPTED CLUSTER-CONFIGURATION INTERACTION (SAC-CI) METHOD

The SAC(symmetry adapted cluster)/SAC‐CI method is applied to the calculations of the ground, excited, and ionized states of the free base porphin. The electronic spectrum of porphin is well reproduced and new assignments for the B (Soret), N, L, and M bands are proposed. The present result shows that the four‐orbital model is strongly perturbed for the B and N bands by the excitations from the lower 4b1u MO and that the σ electron correlations are important for the description of the excited states. The absorption peaks in the ionization spectrum are assigned and the reorganization effect is found to be large especially for the n and σ electron ionizations.
AN ASTROBIOLOGICAL EXPLORATION OF MASS DEPENDENT AND MASS INDEPENDENT SULFUR ISOTOPE FRACTIONATION

In this thesis, I examined multiple sulfur isotopes in two different systems: mass dependent fractionation and mass independent fractionation. Mass dependent sulfur isotopes elucidate low-temperature oxidative processes from pyrite nodules within Miocene lake sediments found in the Haughton impact structure on Devon Island, Nunuvat. Mass independent samples are investigated for lithological and geographical controls on the pattern of 33S and 36S anomalies in Mesoarchaean samples from Northwestern Ontario. In mass dependent systems, the distribution of isotopes can be predicted based on the differences in mass of the various isotopes. Published studies of abiotic and biotic sulfur oxidation show negligible fractionation between starting sulfide and resulting sulfates. Pyrite nodules are being oxidized in a polar desert environment to a variety of sulfates including gypsum, jarosite, schwertmannite, and goethite. Within individual nodules, fractionation between sulfate and sulfide range from -10.1 to +17.9 ‰. In addition, a two-component mixing between pyrite and bedrock sulfates divides the nodules into three types. The first two are explained by conventional oxidation and mixing; however, most samples cannot be described solely through mixing or oxidation. Measuring large fractionations in sulfide oxidation has implications for the study of ‘biosignatures’ such that an oxidizing environment, for example the surface of Mars, would be incompatible with the preservation of ‘biosignatures’. In samples older than approximately 2.45 billion years, mass independent fractionation is observed in rock samples. These anomalous enrichments or depletions in 33S cannot be predicted solely on mass differences; rather they are attributed to photochemical reactions of SO2 in an oxygen poor atmosphere. Within the Mesoarchaean the magnitude of these anomalous 33S measurements are considerably diminished compared to contiguous time periods. Previous work has focused on changes in atmospheric chemistry to explain these minimum values. By looking at samples from Northwestern Ontario, the effect of lithology and geography are tested. In addition, a sulfur isotope database compiles the literature data. The range of multiple sulfur isotope data is extended as compared to the data from South Africa and Australia; however, the magnitude remains small when compared to adjacent time periods. Nevertheless, the isotope systematics of the Mesoarchaean, with this added dataset, follow the Archaean reference array which has previously not been used for the Mesoarchaean samples. Regarding lithology, chemically and biologically precipitated samples show large variation in anomalous 33S whereas clastic rocks remain close to zero.
TLC Analysis of a Corrinoid Compound from Dark Muscle of the Yellowfin Tuna (Thunnus albacares)

Abstract A significant amount of vitamin B12 (52.9±8.9 µg/100 g) was found in the dark muscle of the yellowfin tuna (Thunnus albacares), in comparison to that of the light muscle. A corrinoid compound was purified to homogeneity from the dark muscle and partially characterized. TLC and HPLC patterns of the purified corrinoid compound were identical to those of authentic vitamin B12. These results indicate that dark muscle of the yellowfin tuna would be an excellent source of vitamin B12 for humans and aminals.
Stripping voltammetry at chemically modified graphenes

Several chemically modified graphene (CMG) materials were used to modify bare glassy carbon (GC) electrodes for the square wave anodic stripping voltammetry detection of cadmium ion concentration in aqueous solution, without the use of additives to amplify the detection signal. These CMGs included graphene oxide, graphite oxide, thermally reduced graphene oxide, chemically reduced graphene oxide and electrochemically reduced graphene oxide. The electrochemical performances of these modified electrodes were compared and the recently claimed advantages of using graphene materials to modify electrodes for the ASV detection of trace metal ions was thus challenged. Two CMG materials were proposed as suitable candidates for further investigations in their application towards real world sample analysis.