Miracle-dz/UniFAR-FTUs huggingface dataset:
Stereoselective aldol reactions catalyzed by acyclic amino acids in aqueous micelles

The catalytic properties of all proteinogenic, acyclic amino acids for direct aldol reaction in H2O, assisted by various surfactants, were investigated. The basic and neutral amino acids were shown to be efficient catalysts, giving rise to good-to-excellent yields of adducts (up to 95%), with moderate-to-good diastereoselectivities (up to 86%), L-arginine being the most-effective catalyst. The syn/anti diastereoisomer ratio could be readily tuned by proper choice of the amino acid used. Also, the range of substrates that underwent the reaction was extended to less-reactive aldehydes carrying electron-donating Br substituents.
Effect of artesunate on the dissolution profile and antimicrobial activity of ciprofloxacin hydrochloride

This study evaluated the in vitro physico-chemical implication of co-presentation of ciprofloxacin with artesunate. Thin layer chromatography (TLC) and ultraviolet (UV) analysis was used to monitor the co-presentation of the two drugs. The in vitro dissolution profile of ciprofloxacin hydrochloride tablet in the presence of artesunate tablet was evaluated in buffer with pH 1.2 and water at 37± 0.5°C as well as the effect artesunate on the antibacterial activity of ciprofloxacin. Physico-chemical interaction was not observed between ciprofloxacin and artesunate. However, a significant reduction in the dissolution rate of ciprofloxacin was observed in buffer pH 1.2 solution when compared with water as the medium (p 0.05). The results obtained in this study suggest that care should be taken during the co-administration of ciprofloxacin with the starting dose of artesunate. Key words: Ciprofloxacin, artesunate, physico-chemical interaction, dissolution rate,Staphylococcus aureus and Escherichia coli.
Dynamics of flow–soot interaction in wrinkled non-premixed ethylene–air flames

A two-dimensional simulation of a non-premixed ethylene–air flame was conducted by employing a detailed gas-phase reaction mechanism considering polycyclic aromatic hydrocarbons, an aerosol-dynamics-based soot model using a method of moments with interpolative closure, and a grey gas and soot radiation model using the discrete transfer method. Interaction of the sooting flame with a prescribed decaying random velocity field was investigated, with a primary interest in the effects of velocity fluctuations on the flame structure and the associated soot formation process for a fuel-strip configuration and a composition with mature soot growth. The temporally evolving simulation revealed a multi-layered soot formation process within the flame, at a level of detail not properly described by previous studies based on simplified soot models utilizing acetylene or naphthalene precursors for initial soot inception. The overall effect of the flame topology on the soot formation was found to be consistent with previous experimental studies, while a unique behaviour of localised strong oxidation was also noted. The imposed velocity fluctuations led to an increase of the scalar dissipation rate in the sooting zone, causing a net suppression in the soot production rate. Considering the complex structure of the soot formation layer, the effects of the imposed fluctuations vary depending on the individual soot reactions. For the conditions under study, the soot oxidation reaction was identified as the most sensitive to the fluctuations and was mainly responsible for the local suppression of the net soot production.
Curvy steps for density matrix-based energy minimization: Application to large-scale self-consistent-field calculations

A unitary transformation approach to avoiding the diagonalization step in density functional theory calculations is developed into an algorithm that can scale linearly with molecular size. For target accuracy of 10−5 in the rms rotation gradient, the average number of matrix multiples required per self-consistent field iteration is between about 35 (STO-3G) and 50 (6-31G**). This compares favorably to the existing canonical purification method. Crossovers with direct diagonalization are demonstrated for 1D alkane chains and 2D water clusters.
Vibrational Energy Relaxation and Spectral Diffusion in Water and Deuterated Water

In the broad water stretching band (2900−3700 cm-1), frequency-dependent vibrational energy relaxation (VER), and spectral diffusion both occur on the time scale of a few picoseconds. Ultrafast IR−Raman spectroscopy of water is used to study both processes. VER is also studied in solutions of HDO in D2O (HDO/D2O). The OH stretch (νOH) lifetime for water and HDO is ∼1 ps. The OD stretch (νOD) lifetime for D2O is ∼2 ps. Stretch decay generates substantial excitation of the bending modes. The lifetimes of bending vibrations (δ) in H2O, HDO, and D2O can be estimated to be in the 0.6 ps ≤ T1 ≤ 1.2 ps range. νOH decay in water produces δH2O with a quantum yield 1.0 ≤ φ ≤ 2.0. In HDO/D2O solutions, νOH(HDO) decay generates νOD(D2O), δHDO, and δD2O. The quantum yield for generating νOD(D2O) is φ ≈ 0.1. The quantum yield for generating both δHDO and δD2O is φ ≥ 0.6. Thus, each νOH(HDO) decay generates at minimum 1.2 quanta of bending excitation. After narrow-band pumping, the distribution of excitations within the.
Focused ion beam deposition of Pt containing films

Focused ion beam induced deposition of platinum films from a gas of methylcyclopentadienyl trimethyl platinum is reported. Deposition was carried out with a 25 kV beam of Ga+ with current densities of 2–7 A/cm2 that was controlled by a digital scan generator. Film yields and resistivity were measured as a function of beam current density, gas flux, scan dwell, and loop time. Relatively high yields of 1.4 μm3/nC and resistivities as low as 400 μΩ cm were measured for deposition carried out in 1×10−6 Torr background pressure of residual gas. Auger studies revealed that the films were surprisingly free of oxygen, but contained significant amounts of carbon. A figure‐of‐merit, Fm=ρ/Y, is defined which enables comparison of films used for interconnects. Fm for the Pt films is superior to that of W(CO)6 deposited W films.
Hot Air Assisted Infrared Drying of Vegetables and Its Quality

Hot air assisted infrared (IR) drying of potato and carrot is carried out and product quality is compared with hot air dried samples. The synergistic effect of hot air and IR during combined mode (hot air assisted IR) drying reduced the processing time by nearly 48% as compared to hot air drying alone, besides improving the quality of products. Higher rehydration ratio and lower browning index values are observed for combined mode dried products. Photomicrographs of dehydrated carrot and potato showed superiority of product structure for combined mode dried products. The IR dried carrot had higher (by 17%) retention of carotenoid than hot air dried sample. The processing conditions such as velocity and temperature of air affected the drying characteristics during combined mode drying. Higher values of effective diffusivity of water are observed with combined mode drying.
The Influence of Inorganic Filler Particle Size on Composite Ion-Exchange Membranes for Desalination

In this work, we report a new class of organic–inorganic nanocomposite ion-exchange membranes containing a sulfonated functionalized polymer (sulfonated polyethersulfone) and sulfonated mesoporous silica (SS). The effect of SS filler size (20 and 100 nm) on membrane structures and properties has been investigated. The results revealed the significant impact of filler sizes on macroscopic properties, such as morphologies, physico-electrochemical performance, and mechanical and thermal stabilities of the resultant composite membranes. The appropriate amount of smaller-sized SS fillers (20 nm diameter) led to better overall properties of the composite membranes with a conductivity up to 2.7 mS cm–1, a permselectivity of 98% (around 640% and 16% improvement of conductivity and permselectivity compared with the pristine membranes, respectively), and high thermal and mechanical stability due to intimate polymer–inorganic filler interaction. The performance of the composite membranes in the desalination of a NaC.
All‐atom empirical force field for nucleic acids: II. Application to molecular dynamics simulations of DNA and RNA in solution

Molecular dynamics simulations based on empirical force fields can greatly enhance knowledge of DNA and RNA structure and dynamics in solution. Presented are results on simulations of three DNA sequences and one RNA sequence using the new all‐atom CHARMM27 force field for nucleic acids presented in the accompanying manuscript (Foloppe, MacKerell, J Comput Chem, this issue). Data are reported on structural, dynamic, and hydration properties including dihedral angle, sugar puckering, and helicoidal parameter probability distributions. Also presented are calculations of a DNA hexamer in 0 and 75% ethanol starting from both the canonical A and B forms. Analysis of RMS differences with respect to the canonical A and B forms of DNA show a highly anticorrelated behavior indicating that the force field samples the equilibrium between the A and B forms of DNA. Proper stabilization of B form DNA in aqueous solution and A form DNA in 75% ethanol show that this equilibrium can be perturbed by environmental contributions. Success of the force field in reproducing a variety of experimental data for duplex DNA and RNA indicates that it is of general use for computational investigations of nucleic acids as well as nucleic acids in complexes with proteins and lipids. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 105–120, 2000
Computational investigation of noble gas adsorption and separation by nanoporous materials.

Molecular simulations are used to assess the ability of metal-organic framework (MOF) materials to store and separate noble gases. Specifically, grand canonical Monte Carlo simulation techniques are used to predict noble gas adsorption isotherms at room temperature. Experimental trends of noble gas inflation curves of a Zn-based material (IRMOF-1) are matched by the simulation results. The simulations also predict that IRMOF-1 selectively adsorbs Xe atoms in Xe/Kr and Xe/Ar mixtures at total feed gas pressures of 1 bar (14.7 psia) and 10 bar (147 psia). Finally, simulations of a copper-based MOF (Cu-BTC) predict this material's ability to selectively adsorb Xe and Kr atoms when present in trace amounts in atmospheric air samples. These preliminary results suggest that Cu-BTC may be an ideal candidate for the pre-concentration of noble gases from air samples. Additional simulations and experiments are needed to determine the saturation limit of Cu-BTC for xenon, and whether any krypton atoms would remain in the Cu-BTC pores upon saturation.
CORRELATION BETWEEN CLEARED CHANNELS AND SURFACE SLIP STEPS IN NEUTRON IRRADIATED COPPER CRYSTALS.

Abstract A technique utilizing electroplating is described for the preparation of specimens for transmission electron microscopy, which show the relation between surface detail and internal structure. The cleared channels in deformed neutron irradiated copper crystals have been correlated with surface slip steps indicating that the surface slip bands are a true representation of the bulk deformation behaviour. The slip steps show a uniform distribution of shear within the central region of the cleared channel, with a decreasing shear strain near the edges. The channel is, however, cleared of irradiation produced defects for approximately the full width of the slip step, indicating that the removal mechanism is relatively efficient. This and other features of the slip process are discussed in terms of the observations.
Morphology and Photophysical Properties of Light-Emitting Electrospun Nanofibers Prepared from Poly(fluorene) Derivative/PMMA Blends

Light-emitting electrospun (ES) nanofibers with diameters of 250−750 nm were successfully prepared through the binary blends of polyfluorene derivative/poly(methyl methacrylate) (PMMA) using a single-capillary spinneret. The studied poly(fluorene)s included poly(9,9-dioctylfluoreny-2,7-diyl) (PFO), poly[2,7-(9,9-dihexylfluorene)-alt-5,8-quinoxaline] (PFQ), poly[2,7-(9,9-dihexylfluorene)-alt-4,7-(2,1,3-benzothiadiazole)] (PFBT), and poly[2,7-(9,9-dihexylfluorene)-alt-5,7-(thieno[3,4-b]pyrazine)] (PFTP). The transmission electron microscopy (TEM) studies showed that uncontinuous fiberlike structure was obtained at the low PFO/PMMA blend ratio but became a core−shell structure at a high PFO blend ratio. The poorer solubility of PFO in chloroform than that of PMMA probably forced it to be solidified first as the fiber core. Besides, a porous surface structure on the PFO/PMMA blend fibers was observed due to the rapid evaporation of the chloroform solvent. The PFO aggregation domain in the ES fibers was much s.
Total and dissociative photoionization cross sections of N2 from threshold to 107 eV

The absolute cross sections for the production of N+ and N+2 have been measured from the dissociative ionization threshold to 115 A. In addition, the absolute photoabsorption and photoionization cross sections are tabulated between 114 and 796 A. The ionization efficiencies are also given at several discrete wavelengths between 660 and 790 A. The production of N+ fragment ions are discussed in terms of the doubly excited N+2 states with binding energies in the range 24 to 44 eV.
Dual-shape properties of triple-shape polymer networks with crystallizable network segments and grafted side chains

Triple-shape materials have recently been introduced as a promising class of active polymers, that can change on demand from a first shape (A) to a second shape (B) and from there to a third shape (C). Here, the dual-shape capability of such a triple-shape polymer network system having two distinct melting transitions is investigated by cyclic, thermomechanical experiments. These multiphase polymer networks are synthesized by photopolymerization from poly(ethylene glycol) monomethyl ether monomethacrylate and poly(e-caprolactone) dimethacrylate as crosslinker. While their permanent shape is determined by the chemical crosslinks formed during network preparation, the two different crystallizable phases can be used to fix other temporary shapes. When programmed appropriately in a two-step thermomechanical process these materials can exhibit a triple-shape effect. Here, one-step programming methods for dual-shape effects are applied to these polymer networks under variation of process parameters, especially thermal conditions. In this way, crystalline phases formed by both segments can be used either individually or simultaneously to fix a temporary second shape. The permanent shape can be recovered by heating, exceeding a specific switching temperature. This switching temperature correlates with the melting transition of the related domain, if one domain is used for fixation. If both domains are used, the switching temperature correlates with the higher melting temperature.
Assessing the reliability of paleochemical tracers: barium uptake in the shells of planktonic foraminifera

The trace metal composition of foraminiferal shells preserved in deep-sea sediments is a critical source of data used in reconstructing the physical and chemical characteristics of ancient oceans. However, paleoceanographic information derived from these tracers is limited by the accuracy with which calcite shells record ambient seawater chemistry and the question of whether changing environmental conditions or interspecific differences affect shell chemistry. Experiments with living foraminifera are one of the most direct ways to quantitatively evaluate the relationship between shell and seawater chemistry and the influence, if any, of environmental variables. Here we present results from laboratory experiments on the living planktonic foraminifers Globigerina sacculifer and Orbulina universa that demonstrate that precipitated shells provide an accurate record of seawater barium, a tracer used in reconstructing nutrient and alkalinity distributions in past oceans. On the basis of culturing data at 29°C, 36.7‰ salinity, the best estimate of the partition coefficient D relating foraminifera shell Ba/Ca to seawater Ba/Ca is 0.147 ± 0.004. Data show that when environmental conditions are held constant, there is no significant variability in Ba uptake between individual shells of one or both species. Results also demonstrate that temperature varying over a 7°C range and salinity varying over a 3‰ range do not appreciably influence Ba uptake.
Flocculation Properties and Antimicrobial Activities of Quaternized Celluloses Synthesized in NaOH/Urea Aqueous Solution

Three water-soluble quaternized cellulose derivatives (QCs) with degree of substitution (DS) values of 0.38, 0.50, and 0.74 were synthesized in NaOH/urea aqueous solutions. The flocculation characteristics of QCs have been evaluated in montmorillonite (MMT) suspensions and simulated dye (Reactive Red) aqueous solutions by spectrophotometry. The results showed that QCs were effective flocculating agents for MMT over a wide range of pH values, and the flocculation efficiency of MMT was up to nearly 100%. Decolorization efficiency of Reactive Red dye reached 93% under optimum conditions. In vitro antimicrobial activity of QC was evaluated by determining minimum inhibition concentration (MIC) values against Gram-positive bacteria (S. aureus) and Gram-negative bacteria (E. coli), respectively. The results showed that QC could strongly inhibit the growth of E. coli and S. aureus. Therefore, quaternized cellulose is applicable as a novel wastewater treatment agent with high flocculation efficiency as well as eff.
Influence of Deposition Temperature on the Structure of Si3N4 Thin Film Prepared by MWECR-PECVD

The Si3N4 thin film is prepared by MWECR-PECVD at different deposition temperature and the structure of the Si3N4 thin film is investigated. The results indicate that the structure of the Si3N4 thin film prepared at low deposition temperature is in the amorphous phase. However, when the deposition temperature increases to 280°C, the Si3N4 thin film changes to crystalline α-Si3N4. With a further increase of the deposition temperature, the grain of the Si3N4 thin film becomes more fine, uniform and flat. XRD analysis shows that the structure of the Si3N4 thin film prepared at 280°C is of a crystalline structure.
An improved potential for krypton

An improved potential for krypton is presented. It has the simple but realistic form used by Aziz and Chen for argon based on the HFD potential suggested by Ahlrichs et al. The potential, with known long-range behaviour, was fitted to second virial, viscosity and thermal conductivity data. The potential appears to have the best overall predictive ability for dilute gas, bulk and micro-scopic data.
Iron Coordination Chemistry of N2Py2 Ligands Substituted by Carboxylic Moieties and Their Impact on Alkene Oxidation Catalysis

A biomimetic approach based on Rieske dioxygenase mimics has been undertaken, which uses the tetradentate N2Py2 ligand platform that contains two pyridine moieties linked to a 1,2-diaminoethane or a trans-1,2-diaminocyclohexane backbone. Here we report the impact of the incorporation of carboxylic functionalities with the N2Py2 ligand on the catalytic efficiency of its FeII complexes during epoxidation with H2O2 as the oxidant. Five complexes have been characterized in the solid state and solution. The X-ray structure of a ferrous complex with a ligand that contains two carboxylic acid moieties shows an unexpected N4O3-type iron coordination sphere. Moreover, the two carboxylic groups of the ligand remain protonated and bound by its sp2 oxygen atom. Two substitutions of the ligand with carboxylic moieties was found to be deleterious to the reactivity of the complex during alkene oxidation, whereas monosubstitution led to a slight change in the reactivity. Moreover, the catalyst built from the optically active trans-1,2-diaminocyclohexane backbone, L3, catalyzes the asymmetric epoxidation of trans-2-heptene with up to 17 % yield. The addition of acetic acid leads to better selectivity, enantioselectivity (38 %), and yield of the epoxidation of nonaromatic alkenes.
Recursive Maximum Entropy Algorithm and its Application to the Luminescence Lifetime Distribution Recovery

A simple algorithm, based on recursive quadratic optimization, is suggested for the numerical inversion of integral transforms. The algorithm was found particularly useful for “small scale” problems, with the number of independent parameters ranging between 100 and 200. The programming, parameterization, and performance of the algorithm are discussed, as well its application to the analysis of time-resolved luminescence data.
Complexation of Cd, Ni, and Zn by DOC in Polluted Groundwater: A Comparison of Approaches Using Resin Exchange, Aquifer Material Sorption, and Computer Speciation Models (WHAM and MINTEQA2)

Complexation of cadmium (Cd), nickel (Ni), and zinc (Zn) by dissolved organic carbon (DOC) in leachate-polluted groundwater was measured using a resin equilibrium method and an aquifer material sorption technique. The first method is commonly used in complexation studies, while the second method better represents aquifer conditions. The two approaches gave similar results. Metal−DOC complexation was measured over a range of DOC concentrations using the resin equilibrium method, and the results were compared to simulations made by two speciation models containing default databases on metal−DOC complexes (WHAM and MINTEQA2). The WHAM model gave reasonable estimates of Cd and Ni complexation by DOC for both leachate-polluted groundwater samples. The estimated effect of complexation differed less than 50% from the experimental values corresponding to a deviation on the activity of the free metal ion of a factor of 2.5. The effect of DOC complexation for Zn was largely overestimated by the WHAM model, and it w.
A numerical study of the effects of boost pressure and exhaust gas recirculation ratio on the combustion process and exhaust emissions in a diesel engine

Abstract Experimental studies carried out at the New ACE Institute revealed that a combination of high-pressure fuel injection, high-pressure supercharging, and high exhaust gas recirculation (EGR) ratio was very effective in reducing both emissions of NO x and soot in a heavy-duty diesel engine. However, it is difficult to clarify the mechanisms of emission reduction under such operating conditions by experiments alone because the mixture formation and combustion processes are very complicated. The main purpose of this study was to investigate the effects of boost pressure and EGR ratio on the combustion process and exhaust emissions in a direct injection diesel engine by means of a three-dimensional numerical analysis. The combustion processes under various conditions of boost pressure and EGR ratio in a research diesel engine have been numerically simulated using the authors' engine computational fluid dynamics code (GTT code). By comparing the calculated results with the experimental ones, it has been confirmed that the cylinder gas pressure, the rate of heat release, and the NO emission can be predicted reasonably well and the soot emission tendency can be predicted qualitatively. Furthermore, soot and NO formation characteristics have been examined under various EGR ratio and boost pressure conditions on the basis of φ-T (equivalence ratio-temperature) maps where the calculated local gas states in the combustion regions and the soot and NO peninsulas obtained by zero-dimensional numerical simulation have been plotted.