bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Mechanism of Lewis Acid Catalyzed Glucose Transformations in Ionic Liquids
Authors: Pidko Evgeny A. , Degirmenci Volkan , Hensen Emiel J. M. 
Published: April 2012

AbstractA complementary computational and experimental study of the reactivity of Lewis acidic CrCl2, CuCl2 and FeCl2 catalysts towards glucose activation in dialkylimidazolium chloride ionic liquids is performed. The selective dehydration of glucose to 5‐hydroxymethylfurfural (HMF) proceeds through the intermediate formation of fructose. Although chromium(II) and copper(II) chlorides are able to dehydrate fructose with high HMF selectivity, reasonable HMF yields from glucose are only obtained with CrCl2 as the catalyst. Glucose conversion by CuCl2 is not selective, while FeCl2 catalyst does not activate sugar molecules. These differences in reactivity are rationalized on the basis of in situ X‐ray absorption spectroscopy measurements and the results of density functional theory calculations. The reactivity in glucose dehydration and HMF selectivity are determined by the behavior of the ionic liquid‐mediated Lewis acid catalysts towards the initial activation of the sugar molecules. The formation of a coordination complex between the Lewis acidic Cr2+ center and glucose directs glucose transformation into fructose. For Cu2+ the direct coordination of sugar to the copper(II) chloride complex is unfavorable. Glucose deprotonation by a mobile Cl− ligand in the CuCl42− complex initiates the nonselective conversion. In the course of the reaction the Cu2+ ions are reduced to Cu+. Both paths are prohibited for the FeCl2 catalyst.
Application of Laser‐Backscattering Instruments for In Situ Monitoring of Crystallization Processes – A Review
Authors: Heinrich J. , Ulrich J. 
Published: April 2012

AbstractLaser‐backscattering instruments, such as the focused beam reflectance measurement or threefold dynamical optical reflectance measurement, are promising tools to aid crystallization process development, allowing an in situ, real‐time, and nondestructive measurement of particle size distributions. Besides the instrument principles, in detail geometrical and optical models are discussed which deconvolute the recorded chord length distribution. Emphasis is thereby laid on the influence of the suspension density on instrument recordings. The application of laser‐backscattering devices for determination of kinetic constants is discussed and future directions and perspectives are given.
Analysis of Liquid Jet Breakup in One‐ and Two‐Phase Flows
Authors: Ochowiak M. , Broniarz‐Press L. , Rozanska S. 
Published: April 2012

AbstractThe phenomenon of breakup of a jet into drops has been applied mainly to separation technologies in the chemical, pharmaceutical, and metallurgical industries. The paper deals with the experimental analysis directed at the breakup of polymer solutions flowing through an orifice nozzle. The analysis of the breakup and atomization of a liquid jet by a high‐speed gas jet is presented. Additionally, non‐Newtonian effects on the breakup of the liquid jet into drops were studied using the microphotography method. In the experiments, various aqueous solutions of polyacrylamide were used. The polymer solutions studied were power‐law fluids. Analysis of the photographs of the jet breakup showed that the length of the jets depends on the liquid and gas flow rates and on the concentration of the polymer used. High‐molecular‐weight polymers added to a solvent lead to changes in the rheological properties of the liquid and the breakup length of the jet.
Nucleation Kinetics of the γ‐Polymorph of DL‐Methionine
Authors: Wantha L. , Flood A. E. 
Published: April 2012

AbstractThe heterogeneous nucleation kinetics of γ‐DL‐methionine (γ‐DL‐met) in aqueous solution was measured using direct determination of the rate of nucleation based on measurements of particle (crystal) counts appearing in a microdroplet as a function of nucleation time. The nucleation rates increase with increasing temperature when the supersaturation ratio is used as a measure of the driving force, but the dependence is less clear when the nucleation rates are plotted against the absolute supersaturation. The nucleation rates were found to exponentially increase with respect to the supersaturation ratio of DL‐met. The measured nucleation kinetics follow trends expected from the classical nucleation theory (CNT), allowing approximate interfacial energies to be estimated by fitting the measured data to the CNT. The predicted interfacial energies and nucleation rates are consistent with results of similar species given in the literature.
Electronic Structure Analysis of the Oxygen‐Activation Mechanism by FeII‐ and α‐Ketoglutarate (αKG)‐Dependent Dioxygenases
Authors: Ye Shengfa , Riplinger Christoph , Hansen Andreas , Krebs Carsten , Bollinger J. Martin , Neese Frank 
Published: April 2012

Abstractα‐Ketoglutarate (αKG)‐dependent nonheme iron enzymes utilize a high‐spin (HS) ferrous center to couple the activation of oxygen to the decarboxylation of the cosubstrate αKG to yield succinate and CO2, and to generate a high‐valent ferryl species that then acts as an oxidant to functionalize the target CH bond. Herein a detailed analysis of the electronic‐structure changes that occur in the oxygen activation by this enzyme was performed. The rate‐limiting step, which is identical on the septet and quintet surfaces, is the nucleophilic attack of the distal O atom of the O2 adduct on the carbonyl group in αKG through a bicyclic transition state (5, 7TS1). Due to the different electronic structures in 5, 7TS1, the decay of 7TS1 leads to a ferric oxyl species, which undergoes a rapid intersystem crossing to form the ferryl intermediate. By contrast, a HS ferrous center ligated by a peroxosuccinate is obtained on the quintet surface following 5TS1. Thus, additional two single‐electron transfer steps are required to afford the same FeIV–oxo species. However, the triplet reaction channel is catalytically irrelevant. The biological role of αKG played in the oxygen‐activation reaction is dual. The αKG LUMO (CO π*) serves as an electron acceptor for the nucleophilic attack of the superoxide monoanion. On the other hand, the αKG HOMO (C1C2 σ) provides the second and third electrons for the further reduction of the superoxide. In addition to density functional theory, high‐level ab initio calculations have been used to calculate the accurate energies of the critical points on the alternative potential‐energy surfaces. Overall, the results delivered by the ab initio calculations are largely parallel to those obtained with the B3LYP density functional, thus lending credence to our conclusions.
Unraveling the Mechanism of the Photodeprotection Reaction of 8‐Bromo‐ and 8‐Chloro‐7‐hydroxyquinoline Caged Acetates
Authors: Ma Jiani , Rea Adam C. , An Huiying , Ma Chensheng , Guan Xiangguo , Li Ming‐De , Su Tao , Yeung Chi Shun , Harris Kyle T. , Zhu Yue , Nganga Jameil L. , Fedoryak Olesya D. , Dore Timothy M. , Phillips David Lee 
Published: April 2012

AbstractPhotoremovable protecting groups (PPGs) when conjugated to biological effectors forming “caged compounds” are a powerful means to regulate the action of physiologically active messengers in vivo through 1‐photon excitation (1PE) and 2‐photon excitation (2PE). Understanding the photodeprotection mechanism is important for their physiological use. We compared the quantum efficiencies and product outcomes in different solvent and pH conditions for the photolysis reactions of (8‐chloro‐7‐hydroxyquinolin‐2‐yl)methyl acetate (CHQ‐OAc) and (8‐bromo‐7‐hydroxyquinolin‐2‐yl)methyl acetate (BHQ‐OAc), representatives of the quinoline class of phototriggers for biological use, and conducted nanosecond time‐resolved spectroscopic studies using transient emission (ns‐EM), transient absorption (ns‐TA), transient resonance Raman (ns‐TR2), and time‐resolved resonance Raman (ns‐TR3) spectroscopies. The results indicate differences in the photochemical mechanisms and product outcomes, and reveal that the triplet excited state is most likely on the pathway to the product and that dehalogenation competes with release of acetate from BHQ‐OAc, but not CHQ‐OAc. A high fluorescence quantum yield and a more efficient excited‐state proton transfer (ESPT) in CHQ‐OAc compared to BHQ‐OAc explain the lower quantum efficiency of CHQ‐OAc relative to BHQ‐OAc.
Mechanistic Origin of Antagonist Effects of Usual Anionic Bases (OH−, CO32−) as Modulated by their Countercations (Na+, Cs+, K+) in Palladium‐Catalyzed Suzuki–Miyaura Reactions
Authors: Amatore Christian , Jutand Anny , Le Duc Gaëtan 
Published: April 2012

AbstractThe mechanism of the reaction of trans‐ArPdBrL2 (Ar=p‐Z‐C6H4, Z=CN, H; L=PPh3) with Ar′B(OH)2 (Ar′=p‐Z′‐C6H4, Z′=H, CN, MeO), which is a key step in the Suzuki–Miyaura process, has been established in N,N‐dimethylformamide (DMF) with two bases, acetate (nBu4NOAc) or carbonate (Cs2CO3) and compared with that of hydroxide (nBu4NOH), reported in our previous work. As anionic bases are inevitably introduced with a countercation M+ (e.g., M+OH−), the role of cations in the transmetalation/reductive elimination has been first investigated. Cations M+ (Na+, Cs+, K+) are not innocent since they induce an unexpected decelerating effect in the transmetalation via their complexation to the OH ligand in the reactive ArPd(OH)L2, partly inhibiting its transmetalation with Ar′B(OH)2. A decreasing reactivity order is observed when M+ is associated with OH−: nBu4N+> K+> Cs+> Na+. Acetates lead to the formation of trans‐ArPd(OAc)L2, which does not undergo transmetalation with Ar′B(OH)2. This explains why acetates are not used as bases in Suzuki–Miyaura reactions that involve Ar′B(OH)2. Carbonates (Cs2CO3) give rise to slower reactions than those performed from nBu4NOH at the same concentration, even if the reactions are accelerated in the presence of water due to the generation of OH−. The mechanism of the reaction with carbonates is then similar to that established for nBu4NOH, involving ArPd(OH)L2 in the transmetalation with Ar′B(OH)2. Due to the low concentration of OH− generated from CO32− in water, both transmetalation and reductive elimination result slower than those performed from nBu4NOH at equal concentrations as Cs2CO3. Therefore, the overall reactivity is finely tuned by the concentration of the common base OH− and the ratio [OH−]/[Ar′B(OH)2]. Hence, the anionic base (pure OH− or OH− generated from CO32−) associated with its countercation (Na+, Cs+, K+) plays four antagonist kinetic roles: acceleration of the transmetalation by formation of the reactive ArPd(OH)L2, acceleration of the reductive elimination, deceleration of the transmetalation by formation of unreactive Ar′B(OH)3− and by complexation of ArPd(OH)L2 by M+.
Factors Controlling the Diffusion of Ions in Ionic Liquids
Authors: Tsuzuki Seiji 
Published: April 2012

AbstractThe development of ionic liquids with low viscosity and high ionic conductivity is important for many applications of ionic liquids, such as their use as electrolytes for electronic devices. The transport properties depend on the motion of ions in ionic liquids. The viscosity becomes low and the ionic conductivity becomes high as the diffusion of ions becomes fast. Therefore the elucidation of the factors controlling the diffusion of ions is needed for developing new ionic liquids. In this Minireview we discuss the factors controlling the diffusion of ions in ionic liquids (size of ion; shape of ion; magnitude of interaction between cation and anion; conformational flexibility; molecular mass of ion; mixture of solute; and the effects of nanostructures in ionic liquids). We emphasize the importance of the use of computational methods (molecular dynamic simulations and quantum mechanical calculations) combined with experimental measurements for elucidating the factors controlling the diffusion of ions in ionic liquids.
Spectroscopy and Structure of LnIII Complexes with Sulfonylamidophosphate‐Type Ligands as Sensitizers of Visible and Near‐Infrared Luminescence
Authors: Gawryszewska Paula , Moroz Olesia V. , Trush Victor A. , Amirkhanov Vladimir M. , Lis Tadeusz , Sobczyk Marcin , Siczek Miłosz 
Published: April 2012

AbstractLanthanide complexes with sulfonylamidophosphate‐type ligands: dibenzyl(phenylsulfonyl)amidophosphate (HSB) and di(4‐methylphenyl)‐phenylsulfonyl‐amidophosphate (HSK) have been synthesized and show promise as new sensitizers of visible and near‐infrared luminescence. They constitute a new part of coordination chemistry for this type of ligand, creating simultaneously a new class of lanthanide complexes with π‐conjugated ligands possessing the structural fragment SO2NHP(O). Two series of stable lanthanide complexes Na[Ln(SB)4] (1Ln) and Na[Ln(SK)4] (2Ln), where Ln=NdIII, EuIII, GdIII, TbIII, ErIII, YbIII, were characterized by X‐ray structure analysis. The IR, absorption, emission, and excitation spectra at 293, 77, and 4 K, as well as luminescence decay times and emission quantum yields were used to characterize the complexes in the solid state. The relation between the crystal structure and its spectroscopic properties is also discussed. The influence of the π–π stacking interactions and a ligand‐to‐metal charge transfer state on ligand‐to‐metal energy transfer efficiency was demonstrated and discussed. Crystal‐field lines determined from absorption and fluorescence spectra of 2Nd were used in computational analysis employing free‐ion operators, one‐electron crystal‐field operators, and two‐particle correlation crystal‐field operators. The performed analysis enabled the determination of the Hamiltonian parameters and an unambiguous assignment of 85 crystal‐field levels of NdIII ion with a mean error of 12.0 cm−1.
Comparison between power line communication multipath model and coaxial cable interferometer theory
Authors: Vitor Ulysses R. C. , de Melo M. T. 
Published: April 2012

SUMMARYThe authors have studied a new method to find parameters of broadband power line communication channel model. Lossless power line communication channel model is compared with classical interferometers approach to develop this model. The authors also used coaxial cables to simulate a multipath channel, because it can behave like a lossless power line communication channel. Thus, measurements were carried out with a network analyzer to findSparameters. The modeling parameters, for the multipath model were found after using MATLAB software and classical interferometers approach. Then, theoretical and experimental results are presented and compared. Copyright © 2012 John Wiley & Sons, Ltd.
Electrochemiluminescence of Dendritic Magnetic Quantum Dots Nanostructure and Its Quenching by Gold Nanoparticles for Cancer Cells Assay
Authors: Jie Guifen , Yuan Jinxin , Huang Tingyu , Zhao Yanbin 
Published: April 2012

AbstractA novel dendritic CdS‐ZnS‐Quantum Dots (QDs) nanocomposite with intense electrochemiluminescence (ECL) and excellent magnetism was prepared, which was applied to the cancer cells assay based on ECL quenching of QDs by gold nanoparticles (NPs). DNA conjugation, gold NPs linking and sensing target cells can be directly performed on the magnetic nanocomposites, which is more rapid, convenient, and has better reproducibility than the conventional methods. So far, this is the first report on magnetic electrochemiluminescent QDs nanocomposites for cell detection based on ECL quenching, which opens a new approach for developing multifunctional QDs nanocomposite for ECL assays of cancer cells.
Dioctylamine‐Sulfonamide‐Modified Carbon Nanoparticles as High Surface Area Substrates for Coenzyme Q10Lipid Electrochemistry
Authors: Lawrence Katherine , Watkins John D. , James Tony D. , Taylor James E. , Bull Steven D. , Nelson Geoffrey W. , Foord John S. , Long Yi‐Tao , Marken Frank 
Published: April 2012

AbstractDioctylaminesulfonamide‐modified carbon nanoparticles are characterised and employed as high surface area substrate for (i) coenzyme Q10 and (ii) 1,2‐dimyristoyl‐sn‐glycero‐3‐phosphocholine (or DMPC) ‐ Q10 redox processes. The carbon nanoparticles provide a highly hydrophobic substrate with ca. 25 Fg−1 capacitance when bare. Q10 or DMPC‐Q10 immobilised onto the carbon nanoparticles lower the capacitance, but give rise to well‐defined pH‐dependent voltammetric responses. The DMPC‐Q10 deposit shows similar characteristics to those of Q10, but with better reproducibility and higher sensitivity. Both redox systems, Q10 and DMPC‐Q10, are sensitive to the Na+ concentration in the electrolyte and mechanistic implications are discussed.
Petrogenesis and geotectonic setting of early Svecofennian arc cumulates in the Roslagen area, east‐central Sweden
Authors: Johansson Åke , Andersson ULF B. , Hålenius Ulf 
Published: April 2012

Several intrusions of ultrabasic to basic composition occur in the Roslagen area of east‐central Sweden in close spatial and temporal association with the surrounding 1.90–1.87 Ga old early orogenic Svecofennian granitoids. An imprecise Sm‐Nd WR errorchron yields an age of 1895 ± 71 Ma. In spite of the penetrative deformation in the granitoids, the basic–ultrabasic rocks mostly appear undeformed and largely preserve magmatic textures with plagioclase, olivine (in some rock types), orthopyroxene and clinopyroxene, and amphibole as major constituents. The plagioclase is typically very anorthitic (ca. An90).The Roslagen intrusions range in composition from primitive to evolved (Mg# 80 to 49) but contain only 40–50 wt% SiO2. Many samples are highly elevated in Al2O3 (up to 30 wt%), CaO (up to 16 wt%) and Sr (up to 800 ppm), with strongly positive Eu and Sr anomalies, in line with being plagioclase cumulates. Although masked by cumulus effects, the relative trace element contents indicate a volcanic arc signature. The initial Nd isotope composition is homogeneously ‘mildly depleted’, with εNd of +0.3 to +1.1, and the initial Sr isotope composition ‘mildly enriched’, with εSr of +8 to +15.Non‐cumulus rocks with small Eu and Sr anomalies can be used to deduce the composition of the parental magma. This LILE‐ and LREE‐enriched and HFSE‐depleted high‐alumina basalt magma, with Mg# of ca. 50–60 and Ca# of ca. 80, most likely formed by partial melting of mantle material, enriched by fluids in a subduction environment, at 1.9 Ga. The cumulate rocks apparently crystallized from a somewhat more evolved water‐rich magma with Mg# of ca. 40. Crystallization was followed by the development of late‐magmatic to post‐magmatic coronas between olivine and plagioclase in the presence of H2O‐rich fluids. The subduction‐related setting would make these intrusions Palaeoproterozoic counterparts of Alaskan‐type ultramafic intrusions, but they differ from those in being plagioclase enriched, possibly reflecting different levels of exposure. Copyright © 2012 John Wiley & Sons, Ltd.
Hematological malignancies and pregnancy: Treat or no treat during first trimester
Authors: Avilés Agustin , Neri Natividad , Nambo María‐Jesús 
Published: April 2012

AbstractTreatment of hematological malignancies (HM) during pregnancy remain unsolved, although the use of chemotherapy during second and third trimester has been accepted because of the low rate of toxicities, the use of cytotoxic drugs during first trimester is generally forbidden. Most of the concerns are related to congenital abnormalities and development, but long‐term follow‐up of these children are not available. From 1975 to 2008, we diagnosed and treated 15,750 cases of HM, and 143 female patients were pregnant during this time that were treated with combined chemotherapy. In our study, we present the long‐term follow‐up (the median follow‐up was 22.4 years with a range of 3.8–32.0 years) of 54 newborns, whose mothers received chemotherapy during the first trimester of pregnancy with an intent‐to‐cure HM. Physical and neurological development were carefully assessed, and cardiac and chromosomal studies were performed until the age of 20 years to evaluate late toxicities. The obstetrical development of pregnancy was normal, chemotherapy was used at doses and schedules used in normal patients. Low‐weight birth was the most frequent finding. No congenital abnormalities were detected. Physical, psychological and neurological developments were normal. Education and academic degree were according to the economical and social factors. Cardiac function and chromosomal examination were normal. No neoplasm or acute leukemia has been observed in these children. Forty‐three mothers are alive and disease‐free and can be considered cured. The use of cytotoxic drugs during the first trimester to treat HM seems to be beneficial to both the mother and fetus, and chemotherapy during the first trimester can be considered if the cure of the patient is the goal.
WHEN GROUNDWATER TAKES OVER: LINKING 40 YEARS OF AGRICULTURAL AND GROUNDWATER DYNAMICS IN A LARGE‐SCALE IRRIGATION SCHEME IN MOROCCO
Authors: Kuper Marcel , Hammani Ali , Chohin Anne , Garin Patrice , Saaf Mohamed 
Published: April 2012

ABSTRACTWhen large‐scale irrigation schemes were created, establishing viable, and closely supervised, medium‐sized family farms was considered essential to reap the benefits of state investments. This centralized development model was progressively dismantled, especially as farmers installed private tubewells relying less on surface water. Our aim is to analyse development pathways of family farms in the Tadla irrigation scheme (Morocco). Results showed that pathways were linked to groundwater access, but also to (informal) land markets, and off‐farm revenues. Groundwater enabled farmers to overcome reductions in surface water, and diversify crops. This concerned mainly the 36% large and medium‐sized farms. Such farmers also managed to increase their cropped area through land markets, as renting in land, and producing market crops, require capital. Groundwater showed limited redistributive capacities, as only 20% of small‐scale farmers obtained direct access. Farmers' off‐farm revenues sustained livelihoods, especially in dry years, but were generally not reinvested in agriculture. Over the past 40 years, groundwater has been mainly mobilized from phreatic aquifers, recharged by rainfall and surface irrigation. Their use seems sustainable, but farmers are exploring deeper aquifers while the administration encourages conversion to micro‐irrigation, thus reducing aquifer recharge and complicating the future of the groundwater economy. Copyright © 2012 John Wiley & Sons, Ltd.
Perioperative considerations in patients with adrenal tumors
Authors: Phitayakorn Roy , McHenry Christopher R. 
Published: April 2012

AbstractIn this article the pre‐operative, intraoperative, and post‐operative management of patients with pheochromocytoma, aldosterone‐producing adenoma, cortisol‐producing tumors, and adrenal cortical carcinoma are reviewed. A detailed plan for pre‐operative assessment and medical optimization is discussed. The potential intraoperative and post‐operative complications that occur in patients with an adrenal tumor are reviewed with emphasis on recognition, treatment and prevention. Recommendations for anesthetic management, intraoperative and post‐operative monitoring, blood pressure management, laboratory analysis and medication adjustments are presented. J. Surg. Oncol. 2012; 106:604–610. © 2012 Wiley Periodicals, Inc.
Sectorial Stieltjes functions and their realizations by L‐systems with a Schrödinger operator
Authors: Belyi Sergey 
Published: April 2012

AbstractWe consider classes of sectorial Stieltjes functions. It is shown that a function belonging to these classes can be realized as the impedance function of a singular L‐system with a sectorial state‐space operator. We provide an additional condition on a given function from this class so that the state‐space operator of the realizing L‐system is α‐sectorial with the exact angle of sectoriality α. Then these results are applied to L‐systems based upon a non‐self‐adjoint Schrödinger operator.