bluuebunny/crossref_metadata_2025_split huggingface dataset:
Syntheses, Reactivity and DFT Studies of Group 2 and Group 12 Metal Complexes of Tris(pyrazolyl)methanides Featuring “Free” Pyramidal Carbanions
Authors: Bigmore Helen R. , Meyer Jens , Krummenacher Ivo , Rüegger Heinz , Clot Eric , Mountford Philip , Breher Frank 
Published: May 2008

AbstractReactions of HC(Me2pz)3 with Grignard reagents, dialkyl magnesium compounds and dimethylzinc are reported, together with a DFT study on some of the aspects of this chemistry. Reactions of HC(Me2pz)3 with MeMgX (X=Cl or Br) gave the half‐sandwich zwitterionic compounds [Mg(MeTpmd)X] (X=Cl (2) or Br (3); MeTpmd−=[C(Me2pz)3]−). Addition of HCl to 2 gave the structurally characterised half‐sandwich compound [Mg{HC(Me2pz)3}Cl2(thf)] (4). The zwitterionic sandwich compound [Mg(MeTpmd)2] (5) formed in low yields in the reaction of MeMgX with HC(Me2pz)3 but was readily prepared from HC(Me2pz)3 and either MgnBu2 or MgPh2. The structurally characterised compound 5 contains two “naked” sp3‐hybridised carbanions fully separated from the dicationic metal centre. Only by using MgPh2 as starting material could the half‐sandwich compound [Mg(MeTpmd)Ph(thf)] (6) be isolated. The zwitterionic sandwich compound 5 reacted with HOTf (OTf−=[O3SCF3]−) to form the dication [Mg{HC(Me2pz)3}2]2+ (72+), which was structurally characterised. Pulsed field gradient spin‐echo (PGSE) diffusion NMR spectroscopy revealed both compounds to be intact in solution. In contrast to the magnesium counterparts, HC(Me2pz)3 reacted only slowly with ZnMe2 (and not at all with ZnPh2) to form the half‐sandwich zwitterion [Zn(MeTpmd)Me] (8), which contains a cationic methylzinc moiety separated from a single sp3‐hybridised carbanion. Density functional calculations on the zwitterions [M(MeTpmd)Me] and [M(MeTpmd)2] (M=Mg, Zn) revealed that the HOMO in each case is a MeTpmd‐based carbanion lone pair. The κ1C isomers of [M(MeTpmd)Me] were calculated to be considerably less stable than their κ3N‐bound counterparts, with the largest gain in energy for Mg due to the greater ease of electron transfer from metal to the MeTpmd apical carbon atom on formation of the zwitterion. Moreover, the computed MC bond dissociation enthalpies of the κ1C isomers of [M(MeTpmd)Me] are considerably higher than expected by simple extrapolation from the corresponding computed HC bond dissociation enthalpy.
Highly Effective and Reversible Control of the Rocking Rates of Rotaxanes by Changes to the Size of Stimulus‐Responsive Ring Components
Authors: Hirose Keiji , Ishibashi Kazuaki , Shiba Yoshinobu , Doi Yasuko , Tobe Yoshito 
Published: May 2008

AbstractWe have designed and synthesized rotaxanes whose rates of rocking motion (pendular motion) were switched reversibly through changes to the size of the ring component in response to external stimuli. The ring molecules of the rotaxanes incorporate a metaphenylene unit, which swings like a pendulum, and a dianthrylethane unit, which undergoes reversible isomerization in response to photo‐ and thermal stimuli and changes the size of the ring component. The rocking rates were estimated quantitatively by variable‐temperature (VT) NMR spectroscopy and saturation transfer experiments, which revealed substantial changes in the rates between the open and closed forms, particularly in the case of rotaxanes with an isopropoxy group attached to a phenylene unit.
The Elusive Structure of CrCl2—A Combined Computational and Gas‐Phase Electron‐Diffraction Study
Authors: Vest Brian , Varga Zoltán , Hargittai Magdolna , Hermann Andreas , Schwerdtfeger Peter 
Published: May 2008

AbstractChromium dichloride poses a challenge to the structural chemist. Its different forms of aggregation and association display all well‐known structural distortions induced by vibronic interactions. The monomeric molecule has a Renner–Teller distorted bent geometry, the crystal exhibits strong Jahn–Teller distortion, and the oligomers have slightly distorted four‐membered‐ring structures due to the pseudo‐Jahn–Teller effect. In this paper we report on the low‐energy structures of the monomer and its clusters, Cr2Cl4, Cr3Cl6, and Cr4Cl8, from unrestricted Kohn–Sham (broken‐symmetry) density functional calculations. CrCl2 was also investigated at higher level, including coupled‐cluster and state‐average CASSCF computations. The global minima of the gas‐phase clusters consist of two‐dimensional, antiferromagnetically coupled chains of CrCl2 units forming four‐membered, doubly bridged Cr2Cl2 rings, closely resembling the solid‐state structure of α‐CrCl2. Each Cr atom in these chains has spin quantum number S=2. This suggests that the CrCl2 nucleation starts very early on the structural chain motif found in the solid. There is only a very small change in energy from the antiferromagnetically to the ferromagnetically coupled Cr atoms, which indicates little spin‐coupling between the metal centers. There is an approximately constant change in energy, about 50 kcal mol−1, with every new CrCl2 unit during cluster formation. Information about the structure of these clusters was used in the re‐analysis of high‐temperature electron‐diffraction data. The vapor at 1170 K contained about 77 % monomeric molecules, 19 % dimers, and a small amount of trimers. Monomeric CrCl2 was found to be bent with a bond angle of 149(10)°, in good agreement with our computations, which resulted in a Renner–Teller distortion of the lowest‐energy 5Πg electronic state into the bent 5B2 ground state. The vibrational spectrum of chromium dichloride is discussed and the thermodynamics of cluster formation from 1000–2000 K is examined.
Fossil Fuel Saving through a Direct Solar Energy Water Heating System
Authors: Michels Ademar , Dias Mayer Flávio , Gallon Roger , Hoffmann Ronaldo , Tiago Serafini Seimur 
Published: May 2008

AbstractThe global warming and energy crisis is motivating the search for sustainable power sources. The objective of this work is to analyze the economic return and quantify the reduction in the emission of pollutants, when low‐cost solar collectors are used as a partial substitute for a boiler that uses fuel oil as the energy source, in order to heat water for the swimming pools of the Physical Education Center, Federal University of Santa Maria. The collectors are made from PVC and other easily acquired materials. The estimations for energy saving are based on a collecting area of 182 m2. From knowledge of the collectors' efficiency, the mathematical demonstration shows a fuel oil saving of 13,174 kg, representing 24% of the total amount consumed per annum. The investment required for the construction and installation of the collectors is US$ 6,445 and the estimated useful live is five years. The internal rate of return is 30%. The emission of pollutants is reduced by a considerable amount of 41,213 kg CO2 equivalent/year. The use of direct sun energy as an alternative power source represents a significant economic interest as well as contributing to the mitigation of greenhouse gases.
Optimizing the Recovery of Surrogates for Bacterial Bioterrorism Agents from Ventilation Filters
Authors: Kim Seung Won , Raynor Peter C. , Kuehn Thomas H. , Goyal Sagar M. , Ramakrishnan M. A. , Anantharaman Senthilvelan , Farnsworth James E. 
Published: May 2008

AbstractHeating, ventilating, and air‐conditioning (HVAC) filters have the potential to serve as long‐term integrated samplers for biological particles that may be released intentionally or unintentionally into a public building. Methods for eluting bacteria that are surrogates for potential bioterrorism agents from HVAC filters were tested for their ability to recover as high a percentage of culturable bacteria as possible. A solution of 0.02% Tween‐80 in water was an effective eluent for Bacillus globigii (BG) spores whereas phosphate‐buffered saline was the most effective eluent for vegetative bacteria. Hand shaking was a more effective agitation method for high recovery rates than vortexing or mechanical shaking. The results indicate that BG spores can be eluted successfully while maintaining essentially 100% culturability. The recovery of the vegetative bacteria Mannheimia haemolytica and Yersinia ruckeri was 80% or higher under optimal conditions. The culturability of the vegetative bacteria eluted from HVAC filters declined substantially within as little as 2 h after the bacteria were loaded onto the filter. The culturability of the BG spores eluted from filters exhibited an exponential decay subsequent to loading with a half‐life of 8–9 days.
Renal cell cancer stage migration
Authors: Kane Christopher J. , Mallin Katherine , Ritchey Jamie , Cooperberg Matthew R. , Carroll Peter R. 
Published: May 2008

AbstractBACKGROUND.Evidence exists to suggest a pattern of increasing early diagnosis of renal cell carcinoma (RCC). The aim of the study was to analyze patterns of disease presentation and outcome of RCC by AJCC stage using data from the National Cancer Data Base (NCDB) over a 12‐year period.METHODS.The NCDB was queried for adults diagnosed between 1993 and 2004 presenting with ICD‐O‐2 of 3 renal cell tumors arising in the kidney. Cases were classified by demographics, 2002 AJCC stage (6th edition), and histology. The Cochran‐Armitage Test for Trend was used to determine statistical significance of trends over time. Cox regression multivariate analysis was used to evaluate the impact of stage and histology on relative survival. SPSS 14.0 was used for analyses.RESULTS.Between 1993 and 2004 a total of 205,963 patients from the NCDB fit our case definition of RCC. Comparisons between 1993 and 2004 data show an increase in stage I disease and decrease in stage II, III, and IV disease (P≤ .001). The size of stage I tumors also decreased from a mean of 4.1 cm in 1993 to 3.6 cm in 2003. In multivariate analysis, stage, but not histology, predicted relative survival. A 3.3% increase in survival was found for patients diagnosed in 1998 compared with patients diagnosed in 1993.CONCLUSIONS.A greater proportion of newly diagnosed patients with RCC currently present with stage I disease compared with earlier years. Stage predicts relative survival for patients with kidney cancer. More recently diagnosed patients have improved relative survival. Cancer 2008. © 2008 American Cancer Society.
Spatial Effect of CH Dipoles on the Electron Affinity of Diamond (100)‐2×1 Adsorbed with Organic Molecules
Authors: Hoh Hui Ying , Loh Kian Ping , Sullivan Michael B. , Wu Ping 
Published: May 2008

AbstractCycloaddition of allyl organics on the dimer rows of a clean C(100)‐2×1 diamond surface can be used for the controlled functionalization of such a surface. Sticking probability measurements confirm that appreciable uptake of acetylene and butadiene occur on the clean diamond surface at room temperature. The change in electron affinity of the surface as a function of the coverage of the organic molecules is investigated with periodic DFT calculations. The presence of CH dipoles on these adsorbates modify the surface charge density and gives rise to an induced dipolar layer that modifies the electrostatic potential outside the surface. There is a significant reduction of up to 2.5 eV in electron affinity following the chemisorption of ethylene. Therefore, the adsorbed molecules play the same role as surface hydrogen in inducing the NEA condition on the clean diamond. The change in electron affinity does not scale linearly with the coverage of the organic molecules, because the spatial profile of the CH dipoles as well as the orientation of the molecules on the surface have a predominant effect on the surface charge density.
Timing error estimation for baseband multicarrier modulation
Authors: López‐Fernández Jesús , Martos‐Naya Eduardo , Díez del Río Luís , Entrambasaguas Muñoz José Tomás 
Published: May 2008

AbstractIn this paper, the topic of timing error estimation for baseband discrete multitone modulation is addressed in the context of high‐speed digital subscriber line applications. To the authors' best knowledge, this problem is sparsely and not in depth treated in the literature. In this study the modified Cramer–Rao lower bound is derived, two conventional estimators are considered and a new one is proposed. Behavior of these estimators is evaluated in terms of bias, variance and computational complexity in a wide variety of scenarios, concluding that the proposed estimator appears to be superior in all instances. Copyright © 2008 John Wiley & Sons, Ltd.
Production technology and characteristics of Styrian pumpkin seed oil
Authors: Fruhwirth Gilbert O. , Hermetter Albin 
Published: May 2008

AbstractCucurbita pepo subsp. pepo var. Styriaca, the so‐called Styrian oil pumpkin, is a phylogenetically young member of the Cucurbita spp. A single mutation occurred only in the 19th century and led to dark green seeds with stunted outer hulls. This mutation facilitated the production of Styrian pumpkin seed oil that became a regional specialty oil in the south‐eastern part of Europe during the last few decades. We describe in this article the production and economic value of this edible specialty oil as well as the most important parameters relevant for its quality. Furthermore, we report on its molecular composition including fatty acids, vitamins, phytosterols, minerals, polyphenols, and those compounds that are responsible for its color, taste and flavor. Finally, information is provided on potential contaminants of Styrian pumpkin seed oil as well as its putative beneficial health effects.
Self‐Assembly of Shape‐Persistent Hexagonal Macrocycles with Trimeric Bis(terpyridine)–FeII Connectivity
Authors: Li Sinan , Moorefield Charles N. , Wang Pingshan , Shreiner Carol D. , Newkome George R. 
Published: May 2008

AbstractA novel family of bis(terpyridinyl) ligands was designed and constructed by facile Pd‐catalyzed coupling reactions. Subsequent terpyridine–transition‐metal complexation facilitated self‐assembly resulting in a hexagonal, trimeric series of metallomacrocycles. An enhanced solubility of a macrocycle and its bis(terpyridine) precursor possessing elongated, alkyl‐branched phenylacetylene spacers was achieved by the incorporation of dodecyloxy moieties. The characterization of the metallomacrocycles included 1H, 13C NMR, and UV spectroscopy and mass spectrometry, as well as electrochemistry.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Ring Expansion of 2‐(α‐Hydroxyalkyl)azetidines: A Synthetic Route to Functionalized Pyrrolidines
Authors: Durrat François , Sanchez Monica Vargas , Couty François , Evano Gwilherm , Marrot Jérôme 
Published: May 2008

AbstractA series of 2‐(α‐hydroxyalkyl)azetidines synthesized from enantiomerically pure β‐amino alcohols and presenting various patterns both on the four‐membered ring and on the adjacent hydroxy group were treated with either thionyl chloride or methanesulfonyl chloride in the presence of triethylamine. The thus‐prepared 2‐(α‐chloro‐ or α‐methanesulfonyloxyalkyl)azetidines were shown to rearrange stereospecifically into 3‐(chloro‐ or methanesulfonyloxy)pyrrolidines. When this rearrangement is conducted in the presence of an added nucleophile (NaN3, KCN, KOH, or NaOAc), the produced pyrrolidine incorporates the added nucleophile at C‐3 stereospecifically. The relative configuration of the substituents in the formed pyrrolidines is consistent with a mechanism involving the formation of an intermediate bicyclic aziridinium ion, which is opened regioselectively at the bridgehead carbon atom. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Amperometric Determination of Sugars at Activated Barrel Plating Nickel Electrodes
Authors: Sue Jun‐Wei , Hung Chi‐Jr , Chen Wei‐Chung , Zen Jyh‐Myng 
Published: May 2008

AbstractWe report amperometric determination of sugars by using a disposable barrel plating nickel electrode (Ni‐BPE) in this study. The activated Ni‐BPE possesses good reproducibility in flow injection analysis of sugars with a relative standard deviation of 3.16% for 10 consecutive injections of glucose. The electrocatalytic mechanism for the detection of sugars as well as the use as a detector in high‐performance liquid chromatography (HPLC) is investigated. We achieve a good separation of four sugars (glucose, fructose, sucrose, and maltose) in HPLC with favorable sensitivity at a detection potential of +0.55 V vs. Ag/AgCl. The results of wide linear calibration ranges and detection limits in the μM range meet the need of real sample analysis. This detection method is successfully used for quantitative determination of sugars in honey to identify its authentication.
Comparison of simulated wet bench fires with small‐ and intermediate‐scale fire tests
Authors: Wu Peter K. , Bill Robert G. 
Published: May 2008

AbstractFire hazard studies of clean room facilities indicated that significant losses due to fire may occur in the semiconductor industry. The present study reports the results of full‐scale wet bench fire tests conducted (1) to assess the fire hazards of existing wet bench materials not meeting the listing requirement of NFPA 318, (2) to assess the impact on wet bench fires of engineered materials with improved flammability characteristics, and (3) to compare the observed fire behavior with the results of simpler small‐ and intermediate‐scale fire tests using the same materials. The full‐scale wet bench fires were observed to be consistent in terms of chemical heat release rate, fire propagation, and smoke generation with the results of the small‐ and intermediate‐scale test results. The simpler fire tests are incorporated in FM Approvals 4910 certification for materials to be used in semiconductor fabrication facilities. The small‐scale test protocol is also standardized in NFPA 287. Copyright © 2008 John Wiley & Sons, Ltd.
Co‐occurrence of neuropsychiatric syndromes in demented and psychotic institutionalized elderly
Authors: Dechamps Arnaud , Jutand Marthe Aline , Onifade Chérifa , Richard‐Harston Sandrine , Bourdel‐Marchasson Isabelle 
Published: May 2008

AbstractObjectivesTo explore and determine the clinical figures of behavioral syndromes from the factor structure of the Neuropsychiatric Inventory‐Nursing Home version (NPI‐NH) in demented and psychotic patients.SettingTwo nursing homes and two long‐term care homes.DesignObservational, cross‐sectional.ParticipantsOne hundred and sixty‐three institutionalized elderly with dementia or psychosis (66.9% female), mean age 80.9 ± 9.1 years.MeasurementsThe NPI‐NH includes 12 neuropsychiatric symptoms and a distress scale. The product score of frequency (F) and severity (S) ratings provides an overall score for each of the 12 items. An exploratory principal component analysis with Varimax rotation was performed on the F × S scores according to patients' diagnosis.ResultsHigh internal consistency of the NPI‐NH was found (α = 0.8). In demented patients a 4‐factor solution was found that explained 63.9% of the variance, with the syndromes: (a) ‘hyperactivity’; (b) ‘affective’; (c) ‘psychosis’; and (d) ‘Hallucinations’. A four‐factor solution was also found in psychotic patients, explaining 61.3% of variance, with syndromes: (a) ‘affective’; (b) ‘frontal lobe symptoms’; (c) ‘sundowning’; and (d) ‘psychomotor agitation’. A syndrome was unlikely to appear alone but was most likely to occur with other syndromes. A specific pattern of syndrome co‐occurrence were found in demented (a + b + c in 30.5% of cases) and psychotic patients (a + b + c + d in 35.2% of cases).ConclusionThe syndrome taxonomies are consistent with the diagnostic criteria. The clinical use of syndrome co‐occurrence could help to further understand and evaluate behavioral changes in pharmacological and non‐pharmacological treatments. Copyright © 2008 John Wiley & Sons, Ltd.
Mechanical exposure and musculoskeletal disorder risk at the production system level: A framework and application
Authors: Pascual Silvia A. , Frazer Mardy B. , Wells Richard , Cole Donald 
Published: May 2008

AbstractIntervention research to reduce musculoskeletal disorders (MSDs) has usually been focused at the job level. However, to intervene in and monitor change at a production system level, an approach to assess mechanical exposure and risk at this level is needed. The first purpose of this article is to present an example of production system level risk estimates. The second purpose is to compare the impact of an intervention at the job system and the production system level. One product was tracked throughout an entire production system to quantify the “product cycle” exposure and risks experienced by the low back. The intervention described decreased the predicted production system exposures and predicted risk substantially, if adopted across all departments. © 2008 Wiley Periodicals, Inc.
Quality of working life and turnover intention in information technology work
Authors: Korunka Christian , Hoonakker Peter , Carayon Pascale 
Published: May 2008

AbstractHigh turnover has been a major issue in information technology (IT) organizations. A conceptual model to explain turnover was developed and tested in two national samples of IT and IT manufacturing work. The model postulates that quality of working life mediates the relations between job/organizational characteristics and turnover intention. The American sample consisted of 624 IT employees of five IT organizations. The Austrian sample consisted of 677 employees from an international IT production company (IT manufacturing work). A similar questionnaire was used in both studies. The model was tested with path analysis. A core model with main pathways between job demands and supervisory support to emotional exhaustion, and between emotional exhaustion and job satisfaction to turnover intention was confirmed in the national samples and in subsamples of demographics and job types. © 2008 Wiley Periodicals, Inc.
Evaluation of a digital camera image applied to PCB inspection
Authors: Jiang Bernard C. , Wang C. C. , Huang W. H. 
Published: May 2008

AbstractRapid advancement and widespread digital camera applications have made it possible to replace charge‐coupled device (CCD) cameras in automatic inspections for industrial applications. However, most digital camera applications using the automatic exposure mode may not be effective in some of the inspection environments. The reflection from a board surface in printed circuit board (PCB) inspections is one such problem area. The objective of this study is to develop a methodology to evaluate the effectiveness of using digital cameras for inspection. The indices used for evaluating digital camera image quality are the perceived image quality, the visual resolution, and the noise. An experiment was designed and conducted to determine the optimal camera parameter combination for attaining the best image quality. The desirability function was used to compare various digital camera parameter settings in considering three image quality indices for selecting the best camera‐operating conditions. Based on the developed model and the subjective image quality index, the overall image quality improved 9.4% and 13.86%, respectively. The developed methodology can be used to: (a) determine the digital camera image quality, (b) provide an improved model for determining the automatic exposure setting for digital camera designers, and (c) adjust the digital camera parameters for automatic inspection. © 2008 Wiley Periodicals, Inc.