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Experimental
Kinds of Experimental Terms modified by Experimental Selected AbstractsEXPERIMENTAL AND NEURAL NETWORK PREDICTION OF THE PERFORMANCE OF A SOLAR TUNNEL DRIER FOR DRYING JACKFRUIT BULBS AND LEATHERJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2005B.K. BALA ABSTRACT This article presents the field performance of a solar tunnel drier for drying jackfruit bulbs and leather. The drier consists of a transparent plastic-covered flat-plate collector and a drying tunnel connected in series to supply hot air directly into the drying tunnel using two direct-current fans operated by a photovoltaic module. The drier has a loading capacity of 120,150 kg of fruits. Sixteen experimental runs were conducted for drying jackfruit bulbs and leather (eight runs each). The use of a solar tunnel drier led to a considerable reduction in drying time and dried products of better quality in comparison to products dried under the sun. A multilayered neural network approach was used to predict the performance of the solar tunnel drier. Using solar drying data of jackfruit bulbs and leather, the model has been trained using backpropagation algorithm. The prediction of the performance of the drier was found to be excellent after it was adequately trained. It can be used to predict the potential of the drier for different locations, and can also be used in a predictive optimal control algorithm. [source] SAND FOR ROMAN GLASS PRODUCTION: AN EXPERIMENTAL AND PHILOLOGICAL STUDY ON SOURCE OF SUPPLY*ARCHAEOMETRY, Issue 3 2006A. SILVESTRI This paper reports the results of an experimental study performed on Campanian littoral sand, together with a careful philological analysis of Pliny's text concerning the production of glass using the above sand in order to verify its suitability. Accurate chemical and mineralogical characterization of sand samples and experimental glasses was carried out, proving the unsuitability of sand for glass production in its original state. Taking into account both the results of the philological analysis of Pliny's text and the mineralogical assemblage of the sand, a new hypothesis regarding Roman glass-making technology is proposed and tested here. The technology implies the production of ,quartz-enriched' sand by means of selective grindings according to the different degrees of hardness and cleavage of the mineralogical phases. Melting experiments, carried out on treated sand and in the temperature range compatible with Roman technology, yielded a glass with composition similar to those of typical Roman glasses. Therefore, new perspectives on the sources of supply of raw materials, hitherto debated, are opened up. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 2 2010Article first published online: 20 APR 2010 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2010Article first published online: 22 FEB 2010 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 1 2008Article first published online: 11 MAR 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 6 2006Article first published online: 8 DEC 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Current Awareness in Contrast Media and Molecular ImagingCONTRAST MEDIA & MOLECULAR IMAGING, Issue 5 2006Article first published online: 10 OCT 200 In order to keep subscribers up-to-date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of Contrast Media and Molecular Imaging. Each bibliography is divided into 15 sections: 1 Reviews; 2 General; Contrast Agents: 3 Chemistry; 4 Technique; 5 Experimental; 6 Applications; Molecular Imaging: 7 Carbon; 8 Fluorine; 9 Gallium; 10 Hydrogen; 11 Indium; 12 Iodine; 13 Phosphorus; 14 Technetium; 15 Others. Within each section, articles are listed in alphabetical order with respect to author. If, in the preceding period, no publications are located relevant to any one of these headings, that section will be omitted. [source] Experimental and theoretical study of recovery mechanism of impurity effect by the addition of EDTACRYSTAL RESEARCH AND TECHNOLOGY, Issue 5 2007Y. Asakuma Abstract The impurity effect by trivalent metal ion such as Al3+, Fe3+ and Cr3+ during crystal growth of KDP is reasonably well documented. If a metal ion is adsorbed onto the crystal surface, it prevents the step propagation relevant to the crystal growth rate. However, this impurity adsorption mechanism is still not well understood. Recently, in our work on the addition of chelate agents, a recovery effect of the metal ion adsorption was discovered. However, its recovery mechanism is not clearly understood both theoretically and phenomenally. In this research, ethylene-diamine-tetra-acetic acid, EDTA, which is the most common chelate agent, was used as a recovery agent. The recovery mechanism was considered from the correlation of experimental data and the interfacial distribution model that we proposed in our former study. Furthermore, quantum calculation of EDTA metal complex can explain the relaxation of impurity adsorption by the addition of EDTA. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Forest age, wood and nutrient dynamics in headwater streams of the Hubbard Brook Experimental Forest, NHEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2007Dana R. Warren Abstract Instream processing may substantially alter nutrient export from forested watersheds. This study tested how instream uptake of N and P were affected by successional differences in the accumulation of large wood and debris dams in a 66-year chronosequence formed by five watersheds within the Hubbard Brook Experimental Forest (HBEF), NH. Nutrient enrichment releases in summer 1998 were used to measure the uptake velocities of phosphate, nitrate and ammonium for five streams within HBEF, and results indicated that uptake of PO43, was closely associated with forest age. In 2004, we quantified volume and abundance of large wood in each stream to test whether large wood abundance could be linked to nitrate uptake as well as phosphate. The volume of instream wood increased with forest age, at an apparent rate of 0·03 m3 (100 m),1 per year for these early to mid-successional forests (r2 = 0.95); however, debris dam frequency did not. Instead, debris dam frequency, when controlled for stream size, followed a U-shaped distribution, with high dam frequency in very young forests, low frequency in forests around 20,30 years of age and increasing dam frequency again as forests matured. Phosphate uptake velocity increased strongly with both forest age and large wood volume (r2 = 0·99; p < 0·001 in both cases); however, nitrate and ammonium uptake were not related to either factor. We attribute the positive relationship between phosphate uptake velocity and forest age/large wood volume to increased abiotic adsorption of phosphate by the inorganic sediments retained by wood. Nitrogen uptake in these streams is primarily biologically driven and did not vary predictably with these structural features of channels. We expect wood abundance to increase in HBEF streams as the forest matures, with a subsequent increase in stream phosphate uptake capacity. Copyright © 2007 John Wiley & Sons, Ltd. [source] Experimental study of rill bank collapseEARTH SURFACE PROCESSES AND LANDFORMS, Issue 2 2007Jovan R. Stefanovic Abstract Rill bank collapse is an important component in the adjustment of channel morphology to changes in discharge and sediment flux. Sediment inputs from bank collapse cause abrupt changes in flow resistance, flow patterns and downstream sediment concentrations. Generally, bank retreat involves gradual lateral erosion, caused by flow shear stress, and sudden bank collapse, triggered by complex interactions between channel flow and bank and soil water conditions. Collapse occurs when bank height exceeds the critical height where gravitational forces overcome soil shear strength. An experimental study examined conditions for collapse in eroding rill channels. Experiments with and without a deep water table were carried out on a meandering rill channel in a loamy sand and sandy loam in a laboratory flume under simulated rainfall and controlled runon. Different discharges were used to initiate knickpoint and rill incision. Soil water dynamics were monitored using microstandpipes, tensiometers and time domain reflectometer probes (TDR probes). Bank collapse occurred with newly developed or rising pre-existing water tables near rill banks, associated with knickpoint migration. Knickpoint scour increased effective bank height, caused positive pore water pressure in the bank toe and reduced negative pore pressures in the unsaturated zone to near zero. Matric tension in unsaturated parts of the bank and a surface seal on the ,interrill' zone behind the bank enhanced stability, while increased effective bank height and positive pore water pressure at the bank toe caused instability. With soil water contents >35 per cent (sandy loam) and >23 per cent (loamy sand), critical bank heights were 0·11,0·12 m and 0·06,0·07 m, respectively. Bank toe undercutting at the outside of the rill bends also triggered instability. Bank displacement was quite different on the two soils. On the loamy sand, the failed block slid to the channel bed, revealing only the upper half of the failure plane, while on the sandy loam the failed block toppled forwards, exposing the failure plane for the complete bank height. This study has shown that it is possible to predict location, frequency and magnitude of the rill bank collapse, providing a basis for incorporation into predictive models for hillslope soil loss or rill network development. Copyright © 2006 John Wiley & Sons, Ltd. [source] Experimental frost weathering of sandstone by various combinations of saltsEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2001R. B. G. Williams Abstract Weathering experiments are reported combining frost and a range of salts that occur naturally on rock faces in western and central Europe. Potassium and ammonium alums enhanced frost weathering quite considerably, both singly and in combination, though they were less potent than halite, the destructiveness of which, at sub-zero temperatures, was again confirmed. By contrast, alunogen and gypsum had little or no effect on rates of frost weathering either singly or in combination. Combining halite and gypsum produced breakdown that was intermediate between that of the two salts individually, as did the combination of gypsum and potassium alum. Breakdown in solutions of ammonium alum and gypsum, and in a combination of potassium and ammonium alum with gypsum, caused greater breakdown over 25 cycles of freeze,thaw than was recorded with the salts singly. The results extend the range of salts known to enhance frost weathering, and show that it is difficult to predict the aggressiveness of combinations of salts by experimenting with each salt separately. Copyright © 2001 John Wiley & Sons, Ltd. [source] Experimental and analytical study on pounding reduction of base-isolated highway bridges using MR dampersEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 11 2009Anxin Guo Abstract Pounding between adjacent superstructures has been a major cause of highway bridge damage in the past several earthquakes. This paper presents an experimental and analytical study on pounding reduction of highway bridges subjected to earthquake ground motions by using magnetorheological (MR) dampers. An analytical model, which incorporates structural pounding and MR dampers, is developed. A series of shaking table tests on a 1:20 scaled base-isolated bridge model are performed to investigate the effects of pounding between adjacent superstructures on the dynamics of the structures. Based on the test results, the parameters of the linear and the nonlinear viscoelastic impact models are identified. Performance of the semiactive system for reducing structural pounding is also investigated experimentally, in which the MR dampers are used in conjunction with the proposed control strategy, to verify the effectiveness of the MR dampers. Structural responses are also simulated by using the established analytical model and compared with the shaking table test results. The results show that pounding between adjacent superstructures of the highway bridge significantly increases the structural acceleration responses. For the base-isolated bridge model considered here, the semiactive control system with MR dampers effectively precludes pounding. Copyright © 2009 John Wiley & Sons, Ltd. [source] HDR devices for the seismic protection of frame structures: Experimental results and numerical simulationsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2009Laura Ragni Abstract As part of a national research programme an experimental campaign was carried out on a real scale mock-up consisting of a steel,concrete composite frame equipped with dissipative bracings, based on high damping rubber (HDR) devices. Free vibration tests, followed by force-controlled and displacement-controlled cyclic tests were performed. The experimental tests were aimed at studying the dynamic response of the coupled system in order to demonstrate the effectiveness of HDR devices in increasing the stiffness and dissipation capacity of the frame and investigating the ability of the constitutive HDR model proposed by the authors to predict the dynamic response of the coupled system. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experimental study of dynamic damage of an arch damEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 3 2007Haibo Wang Abstract Seismic responses of a 292-m high arch dam were studied by experiment on a shaking table. The model system included the arch dam with contraction joints, a part of a reservoir, and a partial foundation with a topographic feature near the dam. Potential rock wedges on the abutments and the mechanical properties including uplift on the kinematic planes were carefully simulated. A damping boundary consisting of a viscous liquid was introduced to simulate the effect of dynamic energy emission to far field, which made the dynamic interaction between the dam and the foundation be adequately represented in the model test of an arch dam system. Dynamic responses of the arch dam system under a sequence of seismic loadings in increasing strength were examined. Eleven cracks or overstresses on the model dam due to the earthquake excitations were observed, and consequently, its natural frequency dropped by about 14%, but the model dam was stable under the hydrostatic load of the impounded water after the test. Copyright © 2006 John Wiley & Sons, Ltd. [source] Experimental study of the semi-active control of building structures using the shaking tableEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 15 2003Qing Sun Abstract A magnetorheological (MR) damper has been manufactured and tested and a non-linear model is discussed. The parameters for the model are identified from an identification set of experimental data; these parameters are then used to reconstruct the force vs. displacement and the force vs. velocity hysteresis cycles of the MR damper for the hysteretic model. Then experiments are conducted on a three-storey frame model using impact excitation, which identifies dynamic parameters of the model equipped with and without the MR damper. Natural frequencies, damping ratios and mode shapes, as well as structural properties, such as the mass, stiffness and damping matrices, are obtained. A semi-active control method such as a variable structure controller is studied. Based on the ,reaching law' method, a feedback controller is presented. In order to evaluate the efficiency of the control system and the effect of earthquake ground motions, both numerical analysis and shaking table tests of the model, with and without the MR damper, have been carried out under three different ground motions: El Centro 1940, Taft 1952, and Ninghe 1976 (Tangshan Earthquake in Chinese). It is found from both the numerical analysis and the shaking table tests that the maximum accelerations and relative displacements for all floors are significantly reduced with the MR damper. A reasonable agreement between the results obtained from the numerical analysis and those from the shaking table tests is also observed. On the other hand, tests conducted at different earthquake excitations and various excitation levels demonstrate the ability of the MR damper to surpass the performance of a comparable passive system in a variety of situations. Copyright © 2003 John Wiley & Sons, Ltd. [source] Experimental and theoretical simulations of seismic poundings between two adjacent structuresEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 4 2003K. T. Chau Abstract Shaking table tests have been carried out to investigate the pounding phenomenon between two steel towers of different natural frequencies and damping ratios, subject to different combinations of stand-off distance and seismic excitations. Both harmonic waves and ground motions of the 1940 El Centro earthquake are used as input. Subjected to sinusoidal excitations, poundings between the two towers could appear as either periodic or chaotic. For periodic poundings, impact normally occurs once within each excitation cycle or within every other excitation cycle. A type of periodic group poundings was also observed for the first time (i.e. a group of non-periodic poundings repeating themselves periodically). Chaotic motions develop when the difference of the natural frequency of the two towers become larger. Under sinusoidal excitations, the maximum relative impact velocity always develops at an excitation frequency between the natural frequencies of the two towers. Both analytical and numerical predictions of the relative impact velocity, the maximum stand-off distance, and the excitation frequency range for pounding occurrences were made and found to be comparable with the experimental observations in most of the cases. The stand-off distance attains a maximum when the excitation frequency is close to that of the more flexible tower. Pounding appears to amplify the response of the stiffer structure but suppress that of the more flexible structure; and this agrees qualitatively with previous shaking table tests and theoretical studies. Copyright © 2003 John Wiley & Sons, Ltd. [source] Experimental and modeling investigation of metal release from metal-spiked sedimentsENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Richard F. Carbonaro Abstract In sediments that contain iron monosulfide, cadmium, nickel, lead, zinc, and silver(I) form insoluble metal sulfides that lower the metal ion activity in the sediment,pore water system, thereby reducing toxicity. However, metal sulfides are susceptible to oxidation by molecular oxygen resulting in metal solubilization. To better understand the sources and sinks of metal sulfides in sediments, iron monsulfide,rich freshwater sediments were spiked with cadmium, nickel, lead, zinc, or silver(I) and placed into cylindrical cores with an overlying layer of oxygen-saturated water. Measurements of the dissolved metal concentration in the overlying water were made as a function of time and the vertical profiles of acid-volatile sulfide (AVS) and simultaneously extracted metal (SEM) were measured after 150 d. A one-dimensional reactive and transport model has been employed to help elucidate processes controlling the fate of metals in sediments. The model incorporates metal-sulfide formation, metal-sulfide oxidation, and metal partitioning onto sediment organic carbon and iron oxyhydroxide to simulate the vertical transport of metals throughout the sediment core. [source] Experimental and Clinical Evidence for Loss of Effect (Tolerance) during Prolonged Treatment with Antiepileptic DrugsEPILEPSIA, Issue 8 2006Wolfgang Löscher Summary:, Development of tolerance (i.e., the reduction in response to a drug after repeated administration) is an adaptive response of the body to prolonged exposure to the drug, and tolerance to antiepileptic drugs (AEDs) is no exception. Tolerance develops to some drug effects much more rapidly than to others. The extent of tolerance depends on the drug and individual (genetic?) factors. Tolerance may lead to attenuation of side effects but also to loss of efficacy of AEDs and is reversible after discontinuation of drug treatment. Different experimental approaches are used to study tolerance in laboratory animals. Development of tolerance depends on the experimental model, drug, drug dosage, and duration of treatment, so that a battery of experimental protocols is needed to evaluate fully whether tolerance to effect occurs. Two major types of tolerance are known. Pharmacokinetic (metabolic) tolerance, due to induction of AED-metabolizing enzymes has been shown for most first-generation AEDs, and is easy to overcome by increasing dosage. Pharmacodynamic (functional) tolerance is due to "adaptation" of AED targets (e.g., by loss of receptor sensitivity) and has been shown experimentally for all AEDs that lose activity during prolonged treatment. Functional tolerance may lead to complete loss of AED activity and cross-tolerance to other AEDs. Convincing experimental evidence indicates that almost all first-, second-, and third-generation AEDs lose their antiepileptic activity during prolonged treatment, although to a different extent. Because of diverse confounding factors, detecting tolerance in patients with epilepsy is more difficult but can be done with careful assessment of decline during long-term individual patient response. After excluding confounding factors, tolerance to antiepileptic effect for most modern and old AEDs can be shown in small subgroups of responders by assessing individual or group response. Development of tolerance to the antiepileptic activity of an AED may be an important reason for failure of drug treatment. Knowledge of tolerance to AED effects as a mechanism of drug resistance in previous responders is important for patients, physicians, and scientists. [source] Ruthenium-to-Platinum Interactions in ,6,,1 NCN-Pincer Arene Heterobimetallic Complexes: An Experimental and Theoretical StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 29 2010Sylvestre Bonnet Abstract A series of ,6,,1 -heterobimetallic complexes have been prepared in which a [Ru(,6 -arene)(C5R5)]+ fragment (R = H or Me) and an ,1 -NCN-pincer platinum fragment are combined within the same molecule. In complexes [2]+ and [3]+, the ruthenium and platinum centers are ,6 and ,1 coordinated, respectively, to the same arene ring, whereas in [4A]+ and [5A]+ they are coordinated to two different arene rings that are linked with a covalent bond ([4A]+) or an ethyl bridge ([5A]+). Upon changing the organic manifold between both metal centers, very strong ([2]+) to very weak ([5A]+) ruthenium-to-platinum interactions are obtained. Experimentally, X-ray crystal structures show an increaing steric hindrance when the Ru,Pt distance diminishes, and electrochemical and 195Pt NMR spectroscopic studies show a decreasing electron density on platinum from [5A]+ to [2]+. Theoretical DFT calculations were undertaken, which show an increasing charge on platinum from [5A]+ to [2]+. Our theoretical analysis shows that the particularly strong ruthenium-to-platinum electronic interactions in [2]+ and [3]+ do not come from binding of ruthenium to platinum, but from the pincer Cipso sharing its electron density between both metal centers, which decreases the , donation to platinum, and from increased backdonation of the platinum d electrons into the , system of the arene ring. [source] "Tail,Tail Dimerization" of Ferrocene Amino Acid DerivativesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 25 2010Daniel Siebler Abstract Acid anhydrides of N-protected 1,-aminoferrocene-1-carboxylic acid (Fca) have been prepared and spectroscopically characterized (protection group Boc, Fmoc, Ac; 4a,4c). The structure of the Boc-derivative 4a has been determined by single-crystal X-ray crystallography. An intramolecular N,H···O hydrogen bond involving the carbamate units results in a ring structure containing the two ferrocene units, the anhydride moiety, and the hydrogen bond. In the crystal, the individual molecules are connected by intermolecular N,H···O hydrogen bonds of the carbamate unit. Experimental and theoretical studies suggest that the ring motif is also a dominant species in solution. Electronic communication across the anhydride moiety is found to be very weak as judged from electrochemical, spectroscopic, and theoretical experiments. [source] Experimental and Theoretical Evidence of ,-d Interactions in Supramolecular Assemblies Based on TTF-CH=CH-Py Ligands Tethered to Mo6Xi8 Octahedral Molybdenum Halide Cluster CoresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2009Ganesan Prabusankar Abstract Synthesis, characterization, and physical properties of [Mo6Xi8(TTF-CH=CH-Py)a6]4+ supramolecular assemblies [TTF = tetrathiafulvalene; Py = pyridine; X = Cl (1), Br (2),I (3)] resulting from the reaction between [Mo6Xi8(OSO2CF3)6]2, cluster precursor and TTF-CH=CH-Py ligands were investigated. They are based on the association of the strongly delocalized metallic electron [Mo6Xi8]4+ cluster cores with six redox-active ,-conjugated TTF-CH=CH-Py terminal ligands attached to the Mo clusters through the pyridinyl group. Synergetic ,-d interactions between the organic ligands and the cluster core were experimentally evidenced by electrochemistry and absorption measurements, and corroborated by DFT calculations.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Mechanistic Insights into Acetophenone Transfer Hydrogenation Catalyzed by Half-Sandwich Ruthenium(II) Complexes Containing 2-(Diphenylphosphanyl)aniline , A Combined Experimental and Theoretical StudyEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 28 2008Alessia Bacchi Abstract Several new half-sandwich ruthenium(II) complexes containing 2-(diphenyphosphanyl)aniline (PNH2) of formula {Ru[(,2P,N)PNH2](p -cymene)Cl}Y [Y = Cl (1a), PF6 (1b), BF4 (1c), BPh4 (1d), TfO (1e)] were synthesized and fully characterized both in solution (1H NMR and 31P{1H} NMR spectroscopy) and in the solid state (FTIR, X-ray analysis on single crystal). Complexes 1a and 1b are active precatalysts in the hydrogen transfer reaction of acetophenone, leading to tof values up to 4440 h,1. In comparison, the {Ru[(,2P,N)PNMe2](p -cymene)Cl}Cl complex leads to a tof value of 100 h,1 under the same catalytic conditions. The mechanism through which the precatalysts operate was deeply explored by high-resolution MS (ESI) and DFT/PCM studies. The results reveal that the complexes containing PNH2 operate through a bifunctional mechanism analogous to that proposed for diamines and amino alcohol ligands. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Experimental and Theoretical Studies of Homoleptic Tellurium Cyanides Te(CN)x: Crystal Structure of Te(CN)2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2004Thomas M. Klapötke Abstract The labile tellurium cyanide species Te(CN)2 and Te(CN)4 have been prepared by treatment of tellurium(IV) tetrahalides with cyanide. Both are thermosensitive solids and, in addition, the tetracyanide was found to be pyrophoric. The crystal structure of Te(CN)2 has been determined. The structures of Te(CN)2, Te(CN)4, and Te(CN)6 have been calculated at various levels of theory. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Photochemistry of Salicylaldoxime in Solid Argon: An Experimental and Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 27 2010Joanna Grzegorzek Abstract The photochemistry of salicylaldoxime in solid argon has been investigated by FTIR spectroscopy and DFT calculations. The salicylaldoxime molecule trapped in the matrix from the vapor above the solid sample has the most stable syn1 conformation with an intramolecular hydrogen bond. Irradiation (, > 320 nm) leads to conversion of the syn1 conformer into the syn3 one, in which the C(H)NOH and (C)OH groups are rotated around the C,C and C,O bonds, respectively, and the intramolecular hydrogen bond is broken. The photochemistry of syn3 involves three possible routes: (i) conversion of syn3 into anti2 conformer, this process requires rearrangement of the NOH group with respect to the C=N bond; (ii) photodissociation of salicylaldoxime into 2-cyanophenol and water, which form a hydrogen-bonded complex; and (iii) regeneration of the syn1 conformer. The third route is a very small contribution to the overall process. The study performed with [D2]salicylaldoxime indicates that the dehydration reaction of salicylaldoxime involves cleavage of the N,O bond and formation of OH and Ph(OH)C(H)N radicals in the first step. Then, the OH radical abstracts a hydrogen atom from the CH group to form 2-cyanophenol and water molecules. When the sample is exposed to the full output of the mercury lamp the 2-cyanophenol complex with water becomes the dominating product. [source] Lewis Acid Activated Aza-Diels,Alder Reaction of N -(3-Pyridyl)aldimines: An Experimental and Computational StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 11 2010Francisco Palacios Abstract A combined theoretical and experimental study of a Povarov-type cycloaddition reaction suggests an asynchronous concerted process that is favored by double Lewis acid activation with BF3·Et2O; endo selectivity was observed in the reactions between N -(3-pyridyl)aldimines and styrene, cyclopentadiene, or indene, and substituted tetrahydro-1,5-naphthyridine derivatives were obtained in a regio- and stereoselective fashion. [source] Synthetic and Mechanistic Aspects of Acid-Catalyzed Disproportionation of Dialkyl Diarylmethyl Ethers: A Combined Experimental and Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2009Margherita Barbero Abstract The disproportionation reactions of various dialkyl diarylmethyl ethers have been carried out in the presence of a catalytic amount (10 mol-%) of o -benzenedisulfonimide as a Brønsted acid catalyst; the reaction conditions were mild, and the yields of the diarylmethane target products were good. The catalyst was easily recovered and purified, ready to be used in further reactions. The theoretical study confirmed that the reaction proceeds in two steps: The formation of a carbocation from the protonated ether followed by hydride transfer. Although the hydride transfer is the rate-determining step, it is the stability of the carbocation that determines the reaction rate and therefore the yields. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] A Combined Experimental and Theoretical Study of Anion,, Interactions in Bis(pyrimidine) SaltsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 35 2007Angel Garcia-Raso Abstract We report the synthesis and X-ray characterization of an N,N, -tetramethylenebis(2-aminopyrimidinium) tetrafluoroborate salt that exhibits anion,, interactions that are responsible for the crystal packing. The anion forms a sandwich complex with two pyrimidine rings. When the anion is nitrate, the crystal packing is governed by anion,, interactions and hydrogen bonds, and the sandwich complex is not formed. Finally, a theoretical study of the anion,, interactions in charged pyrimidine rings is in good agreement with the experimental findings. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] The Tautomerism of 5-Amino-3-oxo-1,2,4-thiadiazole: An Experimental and Theoretical StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 33 2007Arantxa Encinas Abstract The 1,2,4-thiadiazole system was the subject of our research as a consequence of the pharmacological activity of some derivatives as GSK3 inhibitors. Therefore, in order to explore the active form responsible for receptor interaction, a systematic study of the tautomerism in the 5-amino-3-oxo-1,2,4-thiadiazole system was performed by using experimental and theoretical methods. Thus, the relative stability of the possible tautomers was studied in the gas phase by density functional theory and local density functional methods. The theoretical study in solution was carried out by using severalcontinuum solvation models. Finally, experimental studies were carried out to unambiguously establish the tautomeric form.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Advanced Experimental and Simulation Approaches to Meet Reliability Challenges of New Electronics SystemsADVANCED ENGINEERING MATERIALS, Issue 4 2009Dietmar Vogel Abstract This paper focuses on some advanced aspects of physics of failure approaches. Tracing of failure modes under realistic loading is a key issue to separate relevant failure sites to be studied in more detail. In the past design of experiment (DoE) tools have been developed to handle this problem. They allow to optimize design and/or material selection with respect to different failure mechanisms and sites. The application of these methods is demonstrated by optimizations performed for fracture problems. Interface fracture has been chosen as one of the most important failure mechanisms. Finally, local stress and strain measurement tools developed over the past years are presented at the end of the paper. They are tools to validate simulation results and therefore the underlying mechanical modeling. Namely, local stress measurement tools under development are needed to make realistic assumptions of loading conditions and to provide residual stress data for FEA. [source] ADAPTATION TO EXPERIMENTAL ALTERATIONS OF THE OPERATIONAL SEX RATIO IN POPULATIONS OF DROSOPHILA MELANOGASTEREVOLUTION, Issue 2 2008Max Reuter Theory predicts that males adapt to sperm competition by increasing their investment in testis mass to transfer larger ejaculates. Experimental and comparative data support this prediction. Nevertheless, the relative importance of sperm competition in testis size evolution remains elusive, because experiments vary only sperm competition whereas comparative approaches confound it with other variables, in particular male mating rate. We addressed the relative importance of sperm competition and male mating rate by taking an experimental evolution approach. We subjected populations of Drosophila melanogaster to sex ratios of 1:1, 4:1, and 10:1 (female:male). Female bias decreased sperm competition but increased male mating rate and sperm depletion. After 28 generations of evolution, males from the 10:1 treatment had larger testes than males from other treatments. Thus, testis size evolved in response to mating rate and sperm depletion, not sperm competition. Furthermore, our experiment demonstrated that drift associated with sex ratio distortion limits adaptation; testis size only evolved in populations in which the effect of sex ratio bias on the effective population size had been compensated by increasing the numerical size. We discuss these results with respect to reproductive evolution, genetic drift in natural and experimental populations, and consequences of natural sex ratio distortion. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||