Miracle-dz/UniFAR-FTUs huggingface dataset:
Magnesium Isotopes Constraints on the Origin of Refractory Olivines from the Allende Chondrite: Nebular Versus Planetary?

article i nfo High precision Mg isotope measurements by multi-collector ion microprobe show that refractory olivines from the Allende chondrite, either olivines isolated in the matrix (2 samples studied) or olivines in type I chondrules (6 samples studied), have variable δ 26 Mg* enrichments and deficits (calculated in permil as the 26 Mg deviation from the instrumental mass fractionation line) relative to the Earth. Most average δ 26 Mg* (noted δ 26 Mg*av) values (between 10 and 20 analyses per chondrule) are negative but the total range is from −0.029 (±0.010) ‰ (2 sigma errors) to +0.011 (±0.011) ‰ with an exception of one olivine at +0.043 (±0.023) ‰. These variations in δ 26 Mg*av reflect the formation of the olivines from reservoirs enriched in various amounts of 26 Mg by the decay of short-lived 26 Al (T1/2=0.73 Ma). Similarly, 30 analyses of olivines from the Eagle Station pallasite show a δ
Properties of Carbon-Supported Platinum Catalysts: Role of Carbon Surface Sites

The effect of oxidation treatments of the support on the properties of carbon-supported platinum catalysts has been analyzed. A set of activated carbon carriers has been prepared by oxidative treatments of a commercial carbon in liquid as well as in gas phase. The carbons obtained had largely identical pore structures but differed considerably in their surface chemistry as shown, for example, by their point of zero charge (PZC) values. The catalysts were prepared by equilibrium impregnation of the supports with an aqueous solution of hexachloroplatinic acid. N2 adsorption, TPD, XPS, TPR, and H2 chemisorption were used to characterize the supports and the catalysts. The Pt load of the catalysts was found to depend on the PZC of the supports. However, the Pt dispersion was found to depend on the total surface oxygen content of the supports. These results were rationalized by the assumption that the surface basic groups of the supports are anchoring sites for the strong adsorption of platinum.
Peer-Led Team Learning in General Chemistry: Implementation and Evaluation

Peer-led team-learning (PLTL) groups have been implemented in both semesters of the general chemistry series at Washington University. We have adapted the PLTL model to fit into a traditional university structure (classes are large; there are multiple sections with different instructors; and graduate students are teaching assistants in the course) by establishing an optional PLTL program outside the course structure. Using data from the fall semesters of 2003 and 2004, we found that students who participated in PLTL groups performed approximately one-third of a grade point (an average of B versus B-) higher in our first-semester General Chemistry course compared with students who opted not to participate, even after controlling for differences in the students' background characteristics. These results of PLTL's effect on students' performance and attitudes correspond to those found in PLTL programs elsewhere. This improved performance was obtained even though our PLTL-participating students were less prep.
Studies on amino acids and peptides. Part 6. Methods for introducing thioamide bonds into the peptide backbone: synthesis of the four monothio analogues of leucine enkephalin

A methodology for preparing peptide analogues in which a thioamide bond replaces the normal amide bond is described. Thus, the synthesis of the three leucine enkephalin analogues [Phet4]-, [Glyt2]-, and [Tyrt1]-leucine enkephalin and the attempted synthesis of [Glyt3]-leucine enkephalin is reported. The replacement of an amide group in position 4 is most conveniently achieved by thionation of Boc–Phe–Leu–OBzl using Lawesson's Reagent (LR), followed by deprotection of the Boc-group and segment coupling with Boc–Tyr(Bzl)–Gly–Gly–OH. Final deprotection is accomplished by using liquid HF–anisole. Single thioamino acid residues are introduced in positions 1, 2, and 3, respectively, by using protected amino acid dithio esters, which are prepared in high yields in a four-step reaction sequence starting from the N-protected amino acids.
Ionization, Energetics, and Geometry of the Phenol−S Complexes (S = H2O, CH3OH, and CH3OCH3)

The present study combines both experiment and molecular modeling to describe the photoionization behavior of the gas-phase hydrogen-bonded complexes of phenol with water, methanol, and dimethyl ether, in particular the occurrence of fragmentation following ionization. Using the two-color two-photon resonant ionization laser technique, the threshold for dissociative ionization of these species has been measured. For the first time, precise binding energies have been deduced for the neutral species: D0(phenol−H2O) = 243 ± 5 meV and D0(phenol−CH3OH) = 265 ± 8 meV. Using a semiempirical potential model, the minimum energy structures of both neutral and ionic species have been determined. This theoretical study has emphasized the role of the dispersive interactions in the geometry of these neutral complexes, in particular the interactions between the alkyl group of the solvent molecule (CH3 in the case of methanol or dimethyl ether) and the π-cloud of the aromatic molecule. In addition, the comparison between.
Soft Biodegradable Elastomers Based on Poly (Octanediol-Tartarate) for Drug Delivery and Tissue Engineering: Synthesis, Characterization and Biocompatibility Studies

The synthesis, characterization and cytocompatibility of amorphous poly (octanediol-tartarate) thermoset biodegradable elastomeric polyesters are reported. The synthesis was achieved by preparing an aliphatic saturated polyester prepolymer via polycondensation reaction of L-tartaric acid with 1,8 Octanediol which was then thermally crosslinked with different ratios of the crosslinking agent, 2,2-bis(ϵ-caprolactone-yl)-propane to form an elastomer. The prepared prepolymers were characterized by means of FT-IR, 1H-NMR, GPC, and DSC. The thermal properties, mechanical characteristics, the sol content, in vitro degradation of the prepared elastomers and their cytocompatibility were also reported. The mechanical and degradation properties of this new elastomer can be controlled by manipulating the elastomer crosslinking density upon varying the ratio of prepolymers to the crosslinking agent. The controllable mechanical properties, homogenous degradability of the prepared elastomers, and their biocompatibility make them good candidates for use in controlled delivery of drugs and in other biomedical and tissue engineering applications.
The effect of orchard soil management on soil temperature and apple tree nutrition.

Soil temperature was measured from 1981 to 1985 at 0.2- and 1.0-m depths for four soil management treatments which included full ground cover, total vegetation control, shallow tillage and black plastic mulching in a high-density orchard planted to Bisbee Red Delicious (Malus domestica Borkh.) on Mailing 26 rootstock. Ground cover suppression treatments, especially black plastic mulching, increased degree day accumulations above 10 °C in all 5 yr at 0.2-m and in 3 yr at 1.0-m depths relative to full ground cover. However, these treatments also resulted in more extreme temperature fluctuations as characterized by higher summer maximum and lower winter minimum temperatures under black plastic mulching. Despite a potential for more extreme soil temperatures, apple yield was significantly higher under black plastic relative to full ground cover. For these two contrasting temperature treatments, leaf N and Mg concentrations were usually significantly higher under black plastic while leaf P and K were consisten.
Monte Carlo simulations of water solubility and structures in poly(difluoromethylene)

Poly(difluoromethylene), also known as polytetrafluoroethylene or Teflon®, is a polymer which is encountered in many applications. The information on influence of temperature, and perfluoroalkane chain length, on water content of this polymer was lacking in the literature. The Gibbs ensemble Monte Carlo method was used to simulate systems of perfluoroalkanes+water. The temperature ranged from 300 to 600 K, and the perfluoroalkane chain length ranged from 8 to 300 carbon atoms. The transferable potentials for phase equilibrium model was used for the perfluoroalkane molecules, and the simple point charge-extended model was used for the water molecules. The molar water content of perfluorodecane was exponentially dependent on temperature, whilst the mass water content of perfluoroalkanes converged to 60 g/kg polymer. No continuous water clustering trends were observed for perfluoroalkane chain lengths in the range of 8–50 carbon atoms, and there was little water clustering at a perfluoroalkane chain length of 300 carbon atoms. An irregularity was observed around a perfluoroalkane chain length of 12 carbon atoms, which may be related to the helicity of the perfluoroalkane molecules.
New Suberato-bridged Supramolecular Layers: Crystal Structure of [Cu2(phen)2(C8H12O4)2] · 3 H2O with phen = 1,10-phenanthroline

The reaction of CuCl2 · 2 H2O, 1,10-phenanthroline (phen), suberic acid and Na2CO3 in a CH3CN–H2O solution yielded blue needle-like crystals of [Cu2(phen)2(C8H12O4)2] · 3 H2O. The crystal structure (monoclinic, P21/n, a = 10.756(2) A, b = 9.790(2) A, c = 18.593(4) A, β = 91.15(3)°, Z = 2, R = 0.043, wR2 = 0.1238) consists of suberato-bridged [Cu2(phen)2(C8H12O4)4/2] layers and hydrogen bonded H2O molecules. The Cu atoms are coordinated by two N atoms from one bidentate chelating phen ligand and three carboxyl O atoms from different suberato ligands to form distorted [CuN2O3] square-pyramids with one carboxyl O atom at the apical position (d(Cu–N) = 2.017(2), 2.043(3) A, basal d(Cu–O) = 1.936(2), 1.951(2) A and axial d(Cu–O) = 2.389(2) A). Two [CuN2O3] square-pyramids are condensed via a common O–O edge to a centrosymmetric [Cu2N4O4] dimer with the Cu…Cu distance of 3.406(1) A indicating no interaction between Cu atoms. The resultant [Cu2N4O4] dimers are interlinked by the tridentate suberato ligands to form [Cu2(phen)2(C8H12O4)4/2] layers parallel to (101). These are assembled via π-π stacking interactions into 3D network with H2O molecules in the tunnels extending in the [010] direction. Neue suberat-verbruckte supramolekulare Schichten. Kristallstruktur von [Cu2(phen)2(C8H12O4)2] · 3 H2O mit phen = 1,10-Phenanthrolin Die Reaktion von CuCl2 · 2 H2O, 1,10-Phenanthrolin (phen), Korksaure und Na2CO3 fuhrt in einer Acetonitril/Wasser-Losung zu blauen, nadelformigen Kristallen von [Cu2(phen)2(C8H12O4)2] · 3 H2O. Die Kristallstruktur (monoklin, P21/n, a = 10.756(2) A, b = 9.790(2) A, c = 18.593(4) A, β = 91.15(3)°, Z = 2, R = 0.043, wR2 = 0.1238) besteht aus suberato-verbruckten Schichten [Cu2(phen)2(C8H12O4)4/2] und wasserstoff-verbruckten Wassermolekulen. Die Kupferatome werden durch zwei Stickstoffatome eines zweizahnig-chelatisierenden phenLiganden und drei Carboxyl-Sauerstoffatomen unterschiedlicher Suberat-Liganden in Form einer verzerrten quadratischen Pyramide [CuN2O3] koordiniert, wobei ein Carboxyl-Sauerstoffatom die apikale Position einnimmt (d(Cu–N) = 2.017(2), 2.043(3) A, basal d(Cu–O) = 1.936(2), 1.951(2) A und axial d(Cu–O) = 2.389(2) A). Zwei quadratische Pyramiden [CuN2O3] werden uber eine O–O-Kante zu einem zentrosymmetrischen Dimer [Cu2N4O4] verknupft, mit einem Cu…Cu-Abstand von 3,406(1) A. Die Dimeren werden durch dreizahnige Suberat-Liganden zu Schichten [Cu2(phen)2(C8H12O4)4/2] verknupft, die parallel (101) verlaufen. π-π-Wechselwirkungen fuhren zu einem dreidimensionalen Netzwerk; Wassermolekule sind in Tunnels, die in Richtung [010] verlaufen, eingelagert.
Linear Rheology of Guar Gum Solutions

We have investigated the linear viscoelastic behavior of guar gum solutions as a function of frequency, temperature, polymer concentration, and molecular weight. This was done to sort out the importance of different relaxation mechanisms like reptation or the breakup of physical bonds. In the kilohertz regime, Rouse behavior is observed. At lower frequencies, two storage modulus plateau zones were found, indicating two additional relaxations. One is operative between 1 and 100 Hz and gives rise to a very broad relaxation spectrum, even for monodisperse guar. Describing the dependencies of the relaxation time and low-shear viscosity on concentration and molecular weight with power laws resulted in unusually high coefficients. The second relaxation becomes manifest below 0.01 Hz and has not been earlier reported. Here the temperature dependence is very strong whereas all other dependencies are weak. Analyzing the experiments with existing models for transient polymer networks revealed that at best a partial decription of the experimental dependencies can be obtained. It was concluded that at least two different relaxation mechanisms must play a role, classical reptation not being one of these. Best overall predictions were obtained with a model assuming two types of associations. However, also the picture of star polymer-like structures held together via bonds with a long lifetime could give comparable predictions. For a further distinction between these mechanisms, more information about the mesoscopic structure is needed.
Bioavailability and uptake of arsenic by wetland vegetation : Effects on plant growth and nutrition

Abstract This study reports on the uptake, potential bioavailability and phytotoxicity of arsenic (As) to an important wetland plant species growing in the vicinity of produced water discharge. The effects caused by As chemical form and concentration on growth, tissue concentrations and distribution of As and nutrient elements were studied in Spartina patens, growing in hydroponic conditions. A 4 × 3 factorial experiment was conducted with treatments consisting of four As chemical forms [arsenite, As(III); arsenate, As(V); monomethyl arsonic acid, MMAA; and dimethyl arsinic acid, DMAA] and four As concentrations (0, 0.2, 0.8, and 2.0 mg As.L‐1). Arsenic phytoavailability and phytotoxicity were primarily determined by the As chemical form present in the nutrient solution. DMAA was the most phytotoxic species to this marsh grass. As(V) and MMAA significantly increased total dry biomass production at low As rates of application. Arsenic availability followed the trend DMAA << MMAA ? As(V) < As(III). The As c.
Temperature Effects on Structural Properties of Pluronic P104 and F108 PEO-PPO-PEO Block Copolymer Solutions

The effects of temperature on the micellization properties and the structure of the micelles for two poly(ethylene-oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (PEO-PPO-PEO) copolymers, having similar size hydrophobic (PPO) blocks and different size hydrophilic (PEO) blocks, are reported. Critical micellization concentration (CMC) and temperature (CMT) values for aqueous copolymer solutions were obtained from a dye solubilization method and corroborated with differential scanning calorimetry, surface tension, density, light scattering intensity, and fluorescence spectroscopy experiments; very good agreement among the different techniques is observed. The extraction of CMC and CMT values from the characteristic features of the data obtained from the various techniques is discussed. The hydrodynamic radii of the copolymer micelles, determined using dynamic light scattering, remained constant over the temperature range investigated; the polydispersity of the micelle size decreased with temperature. The micropolarity in aqueous copolymer solutions was probed as a function of temperature using the I{sub 1}/I{sub 3} intensity ratio of the pyrene vibrational fine structure recorded in fluorescence emission spectra. The decreasing values for the intensity ratio, following the formation of micelles, were considered to be a linear combination of the temperature effects on polarity observed in bulk PEO and PPO homopolymers, and in water. 59 refs., 10 figs., 2 tabs.
Dendrimer Templates for the Formation of Gold Nanoclusters

Charged poly(amidoamine) (PAMAM) dendrimers are used to create organic−inorganic hybrid colloids in aqueous solution. The formation of gold colloids upon reduction of a gold salt precursor serves as a model reaction to study the influence of reaction conditions and dendrimer generation on the resulting nanostructures. Characterization by transmission electron microscopy (TEM), small-angle neutron scattering (SANS), and small-angle X-ray scattering (SAXS) show that the gold particles are formed inside the dendrimer and located offset from the center. Although lower generation dendrimers aggregate when stabilizing the metal particles formed, dendrimers of generation 6−9 can template one gold colloid per dendrimer molecule, the size of which is well-controlled by the number of gold atoms added per dendrimer. For generation 10, multiple smaller gold particles per dendrimer are observed. The effectiveness of PAMAM dendrimers as templates in the host−guest nanoscale synthesis is confirmed for different chemical.
Quantitation of Nonextractable Anthropogenic Quantitation of Nonextractable Anthropogenic Sediments after Chemical Degradation

Four highly contaminated sediment samples obtained from three sampling locations of the Teltow Canal, Berlin, were investigated by quantitation of extractable and nonextractable organic contaminants. The selection of the anthropogenic contaminants (including chlorinated and brominated naphthalenes, 2, 4, 6-tribromoaniline, phthalates, tri-n-butylphosphate, 2, 2, 4-trimethyl-1, 3-pentanediol diisobutyrate, bisphenol A, butylated nitrophenols, 4-nitrobenzoic acid, galaxolide, and tonalide) based on the results of extended GC-MS screening analyses applied to the extracts of the sediment samples as well as to the extracts derived from selective chemical degradation procedures. In detail, alkaline hydrolyses, BBr3-treatment and RuO4-oxidation were applied to the pre-extracted sediment samples in both a separate and a sequential mode. Quantitative Bestimmung nichtextrahierbarer anthropogener Kontaminanten, freigesetzt aus Sedimenten des Teltow-Kanals nach chemischer Degradation Extrahierbare und nichtextrahierbare Kontaminanten von vier hochkontaminierten Sedimenten aus drei Probenahmelokalitaten des Teltow-Kanals, Berlin, wurden quantitativ erfasst. Die Auswahl der untersuchten Substanzen (chlorierte und bromierte Naphthaline, 2, 4, 6-Tribromanilin, Phthalate, Tri-n-butylphosphat, 2, 4, 4-Trimethyl-1, 3-pentandiol-diisobutyrat, Bisphenol A, butylierte Nitrophenole, 4-Nitrobenzoesaure, Galaxolit und Tonalit) basierte auf den Ergebnissen von detaillierten GC-MS-Screening-Analysen sowohl der extrahierbaren als auch der gebundenen Verbindungen, die durch Methoden der chemischen Degradation freigesetzt worden sind. Diese Methoden umfassten die alkalische Hydrolyse, die Bortribromid-Behandlung und die Rutheniumtetroxid-Oxidation und wurden sowohl parallel als auch sequentiell auf die vorextrahierten Sedimentruckstande angewendet.
The effect of long-term ambient aging on the mechanical properties of conducting polysiloxane-polypyrrole graft copolymers

The mechanical behavior of conducting polysiloxane-polypyrrole graft copolymers has been investigated as a function of ambient oxidative aging period. Graft copolymers of N-pyrrolyl-terminated polydimethylsiloxane (SPPy) with pyrrole were synthesized electrochemically at constant potential by using p -toluene sulfonic acid as the supporting electrolyte. Mechanical tests were performed on both unwashed and dichloromethane -washed copolymers after aging. An initial decrease followed by an increase in the tensile strength and strain values was observed with aging. The conductivities and mechanical properties of the films were determined to remain almost unchanged after 6 months of aging at about 46 S/cm.
Kinetics of the Dushman reaction at low I− concentrations

We have reinvestigated the kinetics of the Dushman reaction, IO3−+5 I−+6 H+→3 I2+3 H2O, under the conditions of the oscillating Bray–Liebhafsky reaction, perchloric acid solutions and low iodide concentrations, using a CSTR (continuous flow stirred tank reactor) and an iodide ion selective electrode. We show that it is possible to get meaningful results with this electrode at iodide concentrations in the range [I−]=5×10−8 to 5×10−6 M. The experimental rate law is r=[IO3−][H+]2 {k′[I−]+k″[I−]2} with k′=(1200±150) M−3 s−1 and k″=(4.2±0.8)×108 M−4 s−1 at 25°C and 0.2 M ionic strength. It is the first time that the two terms, first and second order in [I−], are observed simultaneously.
Effects of Temperature on the Formation of Lignin-Derived Oligomers during the Fast Pyrolysis of Mallee Woody Biomass

This paper reports the evolution of the composition of bio-oil obtained from the fast pyrolysis of Mallee woody biomass as a function of temperature between 350 and 580 °C. Several analytical techniques were used to quantify bio-oil composition. For the volatile components, the results obtained by gas chromatography−mass spectrometry and Karl Fischer titration agree very well with those obtained by thermogravimetric analyses. However, for the heavy components, especially lignin-derived oligomers, synchronous UV-fluorescence spectroscopy and thermogravimetric analysis give more reliable results than the precipitation in cold water. Our results indicate that the accuracy of the precipitation methods to quantify lignin-derived oligomer in bio-oil is limited by the relatively large amounts of small oligomers remaining soluble in a metastable form in cold water. A maximum in the yield of lignin-derived oligomers was observed between 450 and 500 °C. In fact, most of the increases in the yield of bio-oil with in.
From molecules to solids with the DMol3 approach

Recent extensions of the DMol3 local orbital density functional method for band structure calculations of insulating and metallic solids are described. Furthermore the method for calculating semilocal pseudopotential matrix elements and basis functions are detailed together with other unpublished parts of the methodology pertaining to gradient functionals and local orbital basis sets. The method is applied to calculations of the enthalpy of formation of a set of molecules and solids. We find that the present numerical localized basis sets yield improved results as compared to previous results for the same functionals. Enthalpies for the formation of H, N, O, F, Cl, and C, Si, S atoms from the thermodynamic reference states are calculated at the same level of theory. It is found that the performance in predicting molecular enthalpies of formation is markedly improved for the Perdew–Burke–Ernzerhof [Phys. Rev. Lett. 77, 3865 (1996)] functional.
COMPARISONS OF CLASSIFICATION ALGORITHMS ON SEEDS DATASET USING MACHINE LEARNING ALGORITHM

In history, agriculture has been the backbone of the economy. These agricultural activities remain undeveloped due to different factors. The current seed classification analysis is inefficient and has no validation mechanism. In this research, we have made an effort to present a predictive model to predict seed classes using machine learning algorithms. For this development, machine learning algorithm is used to learn from data which can be used to make predictions, to make real-world simulations. The developed model is experimented using seed dataset and then seed classes are predicted using the developed model. The main machine learning methods used in this research is Logistic Regression (LR), Linear Discriminant Analysis (LDA), K Neighbors Classifier (KNN), Decision Tree Classifier (CART), Gaussian NB (NB), and Support Vector Machine (SVM). This is a good combination of simple linear (LR and LDA), nonlinear (KNN, CART, NB and SVM) algorithm. In this research we are trying to present distinctive machine learning approaches, for classification of various seeds which provide opportunity to individuals or agriculturist to identify various seeds.