Miracle-dz/UniFAR-FTUs huggingface dataset:
Highly Efficient and Selective Deprotection Method for Prenyl, Geranyl, and Phytyl Ethers and Esters Using Borontrifluoride–Etherate

Abstract An efficient, simple, and practical method has been developed for the deprotection of prenyl, geranyl, and phytyl ethers and esters of aromatic and aliphatic compounds using borontrifluoride–etherate (BF3 · OEt2) at room temperature in good to excellent yields for the first time. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications® to view the free supplemental file. GRAPHICAL ABSTRACT
Bubble formation in 'simple' and complex liquids

In this paper we examine the formation of bubbles in a point to plane geometry in different liquids: a synthetic insulating oil-monobenzyltoluene (BT) and a liquefied atomic gas (argon), under a continuous negative voltage. It has already been shown that in highly purified aliphatic hydrocarbons (e.g. cyclohexane) a bubble is systematically produced following a current pulse, and that these pulses occur at a frequency of the order of kHz under similar conditions to those here. We compare phenomena in the three liquids and explain the observed differences and similarities. <<ETX>>
Thermoneutral zone of chickens as determined by measuring heat production, respiration rate, and electromyographic and electroencephalographic activity in light and dark environments and changing ambient temperatures

Summary Electromyographic (EMG) activity, electroencephalographic (EEG) activity, heat production (H), respiration rate (RR), and body temperature (TB) of unacclimatized chickens were measured during periods of light and darkness at ambient temperatures (Ta) between 7·7 and 37·7 °C. The difference between pectoral muscle and abdomen temperature was less than 0·1 °C over the entire temperature range. Body temperature increased (P ≤ O·l) when Ta was above 27·5 °C and was higher in the light than in the dark (P ≤ 0·05). Respiration rate decreased significantly with increasing Ta. The decrease, however, was not as great during the dark (P ≤ 0·05) as during the light period (P s£ 001). Heat production decreased (P ≤ 0·01) with increasing Ta up to Ta = 22·3 °C. There was no significant difference between heat production during the light period and that during the dark period. EMG amplitude declined (P ≤ 0·01) with increasing Ta up to 27·5 °C in the light and 22·3 °C in the dark and was higher (P ≤ 0·05) in the light than in the dark. Mean frequency of EMG activity was independent of light and Ta. The percentage of low-frequency EEG activity in the dark did not change significantly over the entire Ta range, but in the light it decreased as Ta increased above 25·7 °C (P ≤ 0·05). The percentage of high-frequency EEG activity appeared as a mirror image of low-frequency activity. Overall results indicated a thermoneutral zone between 32·2 and 37·7 °C in the light and between 27·5 and 37·7 °C in the dark.
Covalently Attached Monolayers of Oligo(dimethylsiloxane)s on Silica: A Siloxane Chemistry Approach for Surface Modification

This work describes the synthesis of oligo(dimethylsiloxane) [−Si(CH3)2O−]n monolayers supported on silica. The fundamental properties of siloxane (Si−O−Si) backbones, for example, high flexibility and high thermal stability, set siloxane monolayers apart from self-assembled monolayers derived from long-chain alkylsilanes, alkylthiols, and so forth and provide attractive features for using “siloxane chemistry” for the modification of surfaces. Oligo(dimethylsiloxane) surfaces were prepared by reaction of low molecular weight α,ω-dichloro-dimethylsilane/oligo(dimethylsiloxane)s [Cl[Si(CH3)2O]n−Si(CH3)2Cl, n = 0, 1, 2, 3, 4] with mesoporous precipitated silica (pore diameter 15 nm). Reactions with silicas of different degrees of hydration (dried at 200 °C in a vacuum, “as received”, and saturated with water vapors) were studied under two conditions: (1) in the vapor phase and (2) in solution. Reactions of Cl[Si(CH3)2O]n−Si(CH3)2Cl with dry silicas yield surfaces with bonding densities of 2.35 ± 0.15 [Si(CH.
A versatile method for the synthesis of diaryl and alkyl aryl ketones via palladium‐catalysed cross‐coupling reaction of arylboronic acids with acyl chlorides

An efficient catalytic system using 1-benzyl-4-aza-1-azoniabicyclo[2.2. 2]octane chloride and PdCl2 was developed for the cross-coupling reaction of arylboronic acids with acyl chlorides. The catalytic amount of this homogeneous catalytic system affords the corresponding diaryl and alkyl aryl ketones in good to excellent yields under mild reaction conditions. Copyright © 2015 John Wiley & Sons, Ltd.
Successful protein cryocooling for powder diffraction

It is shown that samples of microcrystalline tetragonal chicken egg white lysozyme can be effectively cryoprotected for high-resolution synchrotron X-ray powder diffraction studies at 100 K. The survival of the powder in the beam is increased by a factor of around 30. Thus, a high-quality powder diffraction pattern could be collected at 100 K, which attains a resolution of dmin ≃ 2.6 A, significantly better than the previous limit of ∼3.27 A at room temperature, despite a smaller volume of sample. Systematic variations of the concentration and type of cryoprotectant agent show that the lattice microstrains that accompany cooling, and degrade the quality of the powder diffraction data by broadening the diffraction peaks, are caused by a collapse in the volume of the crystalline unit cell.
Polymerization kinetics under confinement

The kinetics of polymerization under confinement is considered. Experimental results show that the polymerization kinetics inside a core–shell electrospun nanofiber differs from that in the bulk (inside a thick film). The observed phenomena can be described in the framework of polychromatic kinetics. In order to explain the chemical reaction mechanism, the spatial features of the process in question, namely the cluster structure forming during the system polymerization, are to be taken into account. The key point of the proposed mechanism is as follows: when the mean size of the clusters becomes comparable with the internal fiber diameter, the rate of reaction will decrease. This decrease is due to two reasons. Firstly, the presence of a boundary obstructs the cluster growth due to steric restrictions; and secondly, the formed clusters separate the reacting area into several isolated regions, in which fluctuations in catalyst concentration are observed without their diffusive dissipation. As a result the polymerization reaction becomes a polychromatic one, where the rate of reaction is decreasing with time.
Identification of Coniferous Forests with Incipient Nitrogen Saturation through Analysis of Arginine and Nitrogen‐15 Abundance of Trees

Stands of Norway spruce [ficea abies (L.) Karst. ] differing in throughfall N deposition and NO 3 - leaching were investigated to determine if arginine concentrations and δ 15 N abundances of needles could be used to predict NO 3 - leaching from stands. Twenty-three stands, all located in southern Sweden, were sampled and five of these had average NO 3 - concentrations > 0.1 mg NO 3 - -N L -1 in soil water at a 50-cm depth. Arginine concentrations and δ 15 N abundances of needles were significantly higher for sites that exhibited NO 3 - leaching. The δ 15 N enrichment (e), i.e., difference between foliage and soil organic matter in δ 15 N, showed less variation than δ 15 N of needles alone in regressions against NO 3 - leaching and was, thus, a better predictor of leaching. All sites that exhibited N leaching had arginine concentrations > 5 μmol g dw -1 and e > -0.5 (‰) and thus, there was a strong correlation between arginine and e values. To test if arginine accumulation, as such, can affect the δ 15 N of needles, arginine and δ 15 N were determined for Scots pine (Pinus sylvestris L.) trees given different amounts of N fertilizer. Although fertilization caused a dramatic increase in arginine concentrations of needles, no immediate change in δ 15 N was observed. A hypothesis is proposed to explain the causal linkage between elevated arginine and δ 15 N of needles and leaching of N. Thus, arginine accumulation in trees corresponds to decreased uptake rates of NH 4 + leaving NH 4 + ions available for nitrification. During nitrification, discrimination against the heavier 15 N takes place resulting in a depleted NO 3 - pool and enriched NH 4 + pool. Preferential uptake of NH 4 + by conifer trees will then lead to elevated 15 N abundance of needles. It is concluded that N leaching coniferous forests can be identified through analysis of arginine and δ 15 N of needles.
Determination, prediction, and understanding of structures, using the energy landscapes of chemical systems – Part II

Abstract In the past decade, new theoretical approaches have been developed to determine, predict and understand the struc-ture of chemical compounds. The central element of these methods has been the investigation of the energy landscape of chemical systems. Applications range from extended crystalline and amorphous compounds over clusters and molecular crystals to proteins. In this review, we are going to give an introduction to energy landscapes and methods for their investigation, together with a number of examples. These include structure prediction of extended and mo-lecular crystals, structure prediction and folding of proteins, structure analysis of zeolites, and structure determination of crystals from powder diffraction data.
Asymmmetric Diamino Functionalization of Nanotubes Assisted by BOC Protection and Their Epoxy Nanocomposites

Homogenous dispersion and strong interfacial bonding are prerequisites for taking full advantage of the mechanical properties of nanotubes in a composite. In order to simultaneously achieve both conditions, a highly efficient and mechanically non‐destructive functionalization of nanotubes is developed. With fluoronanotubes as the precursor, asymmetric diamine molecules, N‐BOC‐1,6‐diaminohexane, are used to replace fluorines on the wall of fluoronanotubes and construct covalent bonding to the surface of the nanotubes. A BOC de‐protection reaction is conducted and the resulting exposed amino groups create strong covalent bonds with the matrix in the course of epoxy ring‐opening etherification and curing chemical reactions. In comparison with the conventional functionalization based on symmetric diamine molecules, the functionalized nanotubes derived from the BOC‐protected diamine molecule are more dispersed within the epoxy matrix. Dynamic mechanical analysis shows that the functionalized nanotubes have better crosslinking with the matrix. The composites reinforced by the nanotubes demonstrate improvement in various mechanical properties. The Young’s Modulus, ultimate tensile strength, and storage modulus of composites loaded with 0.5 wt% functionalized nanotubes are enhanced by 30%, 25%, and 10%, respectively, compared with the neat epoxy. The increase of the glass transition temperature, as much as 10 °C, makes the composites suited for engineering applications under higher temperatures. The new functionalization method allows for an competitive enhancement in the composite performance in use of relatively low cost raw nanotubes at a small loading level. The reinforcement mechanism of the functionalized nanotubes in the epoxy resin is discussed.
MODELING OF RING VORTICES AND THEIR INTERACTION WITH TURBULENT PREMIXED FLAMES

Depending on amplitude and frequency of self-excited flame/pressure oscillations in technical combustion systems, the formation of large-scale turbulent ring vortices can be observed which interact with the flame. The phenomenon was investigated with numerical simulations using unsteady Reynolds-averaged Navier–Stokes methods. The results were validated against experimental data. The calculation of the forced isothermal flow field yields that the prediction of the transient vortex positions works very well. In contrast, the turbulent diffusion is underestimated. The flame frequency response of a forced premixed turbulent axial methane jet flame (P therm = 40 kW) was calculated using a simplistic turbulent reaction model. The measured flame frequency response was derived via detection of the global radiation of OH radicals and the calculated flame response via analysis of the global heat release rate. Despite the fact that a quantitative comparison of these properties is not possible, a qualitative comparison shows good agreement regarding the representation of amplitude response and phase-angle function.
Polydisperse hard sphere mixtures: equations of state and the melting transition

Three-component mixtures of hard spheres have been investigated by Monte Carlo (MC) simulations and semi-empirical equations of state (EOS). Symmetric and dissymmetric size distributions have been studied. The polydispersity is limited to values below 10%. The pressure of the fluid phase is found to be quite accurately described by the analytical EOS of Mansoori et al. As for the solid phase, MC simulations show that the substitutionally disordered fcc structure is mechanically stable up to a polydispersity of the order of 8%. An EOS based on a free volume-type approximation is proposed. Its expression is found to be independent of the shape of the size distribution function. Using these two EOS, the cloud–shadow points for the melting transition have been computed. The phase coexistence is found to terminate at a polydispersity of about 4%.
Particle statistics in quantitative X-ray diffractometry

Particle statistics in quantitative X-ray diffractometry relates to the number of particles (crystallites) contributing to the diffracted intensity for a given line. Variations in line intensity between replicate preparations of the same sample arise from statistical variations in the number of diffracting particles. The uncertainty in line intensity, and hence in quantitative estimates of analyte concentration, is termed the particle statistics error. A theoretical estimate of the error for stationary samples qives σPS=ξ[μ*〈v〉/c]1/2, where μ* is the mass absorption coefficient of the mixture, and 〈v〉 and c are the mean particle volume and mass concentration respectively of the analyte. The factor ξ is a function mainly of diffractometer geometry, but also contains contributions from rocking angle and reflection multiplicity. For measurements of the (112) quartz line with a Philips PW1050 vertical goniometer with 2o divergence slit and 0.3 mm receiving slit, ξ was calculated to be 116 g1/2 cm−5/2 for stationary samples. Three close-cut size fractions of quartz were prepared at various concentrations in a calcium carbonate matrix. Replicate preparations were measured and the standard deviation obtained as a function of particle volume and concentration. After correction for other contributing errors, including counting statistics and thermal fluctuations, the experimental value ξ=122±10 g1/2 cm−5/2 was obtained. The effect of sample spinning is considered briefly and predicted to reduce σPS by a factor of about 5. Experimentally, a reduction in σPS of about this order is observed, but the effect is rather variable.
Nanometer‐scale structure for the study of flux‐line lattice shearing in superconducting double layers of a‐Nb3Ge and NbN

The fabrication of a nanometer‐scale device structure for the study of flux‐line lattice shearing in a superconducting double layer of 500‐nm amorphous Nb3Ge (bottom) and 50‐nm polycrystalline NbN (top) is reported. The device, serving as a model system for technical type‐II superconductors, consists of an array of channels in the NbN top layer, each about 100 nm wide and 500 μm long. The preliminary measurements show unique features of flux line shear in a well‐defined channel structure.
Effects of Bivalent Cations on Corrosion Inhibition of Steel by 1‐Hydroxyethane‐1,1‐diphosphonic Acid

The influence of calcium and zinc ions on the corrosion inhibition effect of 1-hydroxyethane-1,1-diphosphonic acid (HEDP) on carbon steel has been investigated by electrochemical techniques, X-ray photoelectron spectroscopy, and atomic force microscopy. Addition of calcium or zinc ions greatly increased the inhibition efficiency of HEDP in a synergistic manner. The highest inhibition effect was obtained for molar ratios of Ca/HEDP = 0.5 and Zn/HEDP = 3 for 3 X 10 -4 mol dm -3 HEDP. The corrosion inhibition mechanism in the presence of these additives proved to be different from that with HEDP alone and was related to the formation of different complex species between HEDP and cation additives. The frequency response of the studied system was described by a transfer function containing two relaxation time constants corresponding to the charge-transfer process and the porous oxide layer. Higher zinc and phosphorous content in the inhibitor layer and a continuous change in the O-Fe and HO-Fe ratio were achieved by increasing zinc concentration in the solution (in the range Zn/HEDP = 0.5-3) as supported by XPS measurements. Changes in the chemical structure were established in the oxide-hydroxide layer developed spontaneously on the steel surface. The synergistic effect of inhibitor compounds appeared also in surface morphology, leading to the development of smooth, i.e., dense, protective layers as revealed by atomic force microscopy.
The unusual electronic structure of ambipolar dicyanovinyl-substituted diketopyrrolopyrrole derivatives

We have synthesized two novel dicyanovinylene-substituted DPP–oligothiophene semiconductors, DPP-4T-2DCV and 2DPP-6T-2DCV. In these materials, the combination of an extended oligothiophene conjugated skeleton with the strong electron-withdrawing DPP–dicyanovinylene groups results in semiconductors exhibiting ambipolar TFT response with reasonably balanced electron and hole mobilities of up to 0.16 cm2 V−1 s−1 and 0.02 cm2 V−1 s−1, respectively. Furthermore, no thermal annealing of the semiconductors is necessary to afford high mobility, making them ideal candidates for low cost fabrication of devices on inexpensive plastic foils. Analysis of the molecular and electronic structures by means of electronic and vibrational spectroscopy techniques, electrochemistry and DFT calculations highlights a unique electronic scenario in these semiconductors, where the external cyano groups are isolated from the π-conjugated core. The appearance of these unusual π-systems explains the similar electron mobilities recorded for both DPP-4T-2DCV and 2DPP-6T-2DCV, despite their different skeletal dimensions. Furthermore, it also supports the appearance of moderately balanced hole and electron mobilities in semiconductors with such large accumulation of acceptor units. Transient spectroscopy measurements indicate the appearance of triplet excited state species, which may be related to the semiconductors' low performances in OPVs, due to the intrusion of triplets in the carrier formation process.
PdII Complexes of Tridentate PCP N‐Heterocyclic Carbene Ligands: Structural Aspects and Application in Asymmetric Hydroamination of Cyano Olefins

The synthesis of the ligand precursor 1,3-bis{(R)-1-[(S)-2-(diphenylphosphanyl)ferrocenyl]ethyl}imidazolium iodide ([PCPH]I, 1) was extended to the electronically and sterically modified ligand precursors 1,3-bis{(R)-1-[(S)-2-{[3,5-bis(trifluoromethyl)phenyl]phosphanyl}ferrocenyl]ethyl}imidazolium iodide ([3,5-CF3-PCPH]I, 6), and 1,3-bis[(R)-1-{(S)-2-[bis(3,5-dimethylphenyl)phosphanyl]ferrocenyl}ethyl]imidazolium iodide ([3,5-Me-PCPH]I, 7). Palladium complexes were prepared starting from [Pd(OAc)2]3 in THF to afford [PdI(PCP)]OAc (8), [Pd(OAc)(3,5-CF3-PCP)]I (9), and [PdI(3,5-Me-PCP)]OAc (10), in excellent yields. The crystal structures of the ligand precursor [3,5-CF3-PCPH]I (6), the complex [PdI(3,5-CF3-PCP)]PF6 (14), as well as the dicationic complex [Pd(NCCH3)(PCP)](PF6)2 (11), were determined by X-ray diffraction. Complex 11 and its derivative [Pd(NCCH3)(3,5-Me-PCP)](PF6)2 (13) have been tested as catalysts in the asymmetric addition of, for example, thiomorpholine tomethacrylonitrile giving selectivities up to 63 and 75 % ee, respectively, at –80 °C. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Correction factor based on the ratio of the magnesium atom to ion background signals used for evaluating robustness in inductively coupled plasma optical emission spectrometry

ABSTRACT The ratio of the magnesium ion to atom signals with wavelengths of 280.270 and 285.213 nm, respectively, is frequently employed to estimate plasma robustness in inductively coupled plasma optical emission spectrometry. To guarantee a rigorous and accurate calculation of this indicator of the plasma condition, a correction for the difference in the response of the instrument at the two wavelengths of magnesium has been frequently applied. However, the literature reviewed shows inconsistencies in the values of the correction factor used. Also it is notable the lack of information concerning the procedures to calculate such correction factor. In this paper, we propose a simple method for the best estimate of the correction factor from an appropriate measurement of the magnesium atomic and ion background signals, when a blank solution, contaminated by magnesium, is nebulized. We proved that a bad selection of the wavelengths used for background signal estimation can underestimate the correction factor up to a 56%.
Anthocyanin Distribution in `Delicious' Apples and the Relationship between Anthocyanin Concentration and Chromaticity Values

Fruit of 10 'Delicious' apple (Malus domestica Borkh.) strains were harvested 149 days after full bloom in 1988. Fruit color was measured at four locations on each fruit at the midpoint between the stem and calyx end with a Minolta CR-200b portable tristimulus calorimeter. Anthocyanin content of corresponding skin disks was determined spectrophotometrically. Significant differences existed among strains in both the amount and distribution of antho- cyanin around the fruit. High-coloring strains had a significantly higher anthocyanin concentration at both the blushed and the nonblushed surface when compared to low-coloring strains. A linear regression of anthocyanin content on the ratio of (a*/b*) 2 provided an R 2
Characterization of air plasma‐treated polymer surfaces by ESCA and contact angle measurements for optimization of surface stability and cell growth

A radiofrequency air plasma has been used to incorporate new functionalities at the surface of cycloolefin polymers (Zeonex® and Topas®), polymethyl methacrylate (PMMA), styrene–acrylonitrile copolymer (SAN), and polystyrene (PS). The main goals with the plasma treatment of the different plastics were to hydrophilize the surfaces and to provide good cell culture properties. Surfaces treated at high RF power/gas flow ratios (50 to 100 W/sccm) became highly hydrophilic (water contact angles of about 5 degrees) and stable towards washing in 70% (v/v) ethanol. Those treated at lower power/gas flow ratios (3 to 10 W/sccm) were less hydrophilic and not wash-stable. Cell growth properties of HeLa cervix carcinoma cells as good as on commercial tissue-culture polystyrene could be obtained for Zeonex, SAN, and PS, treated at relatively low RF power/gas flow ratios. However, no untreated plastics were suitable for culturing these cells. XPS spectra features show that ester, ether/alcohol, and ester/carboxyl groups are formed during the plasma treatments of the different plastics. Measurable amounts of carboxylic acid carbon after plasma treatment were only observed for PS and Topas. Furthermore, at high RF power/gas flow ratios fluorine, aluminium and silicon were incorporated in all investigated plastics surfaces due to ablation–deposition processes in the reaction chamber. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2618–2625, 2002