bluuebunny/crossref_metadata_2025_split huggingface dataset:
Computational fluid dynamic (CFD) simulation of snowdrift in alpine environments, including a local weather model, for operational avalanche warning
Authors: Schneiderbauer Simon , Tschachler Thomas , Fischbacher Johann , Hinterberger Walter , Fischer Peter 
Published: June 2008

AbstractA new continuum approach to snowdrift modelling is introduced. In addition, numerical studies are carried out to identify the influence of time-varying wind conditions on snowdrift simulations. We compare the snowdrift patterns at Grimming mountain, Austria, derived using a time-averaged wind field and a time-varying wind field obtained from the numerical weather prediction model INCA. The results show significant differences in the deposition patterns and snow depth even after a 6 hour drift period. Using time-averaged boundary conditions leads to an underprediction of the resulting snow depth caused by averaging the wind speed, which lets gusts of wind disappear while snow transport is a non-linear function of the wind speed. Using numerical weather prediction models for snowdrift simulation therefore provides enhanced knowledge of the snow depth for local avalanche warning services.
Influence of precipitation seasonality on glacier mass balance and its sensitivity to climate change
Authors: Fujita Koji 
Published: June 2008

AbstractNumerical calculations are described, aimed at evaluating the influence of precipitation seasonality (summer and winter) on glacier mass balance. First, equilibrium-line altitudes (ELAs) are modeled using idealized meteorological variables. Modeled climatic conditions (summer mean temperature and annual precipitation) at the ELA of glaciers located within a winter accumulation pattern confirm the observational results of earlier studies. However, the ELA of glaciers located within a summer accumulation climate pattern locates in a colder environment than that of glaciers located within a winter accumulation climate pattern. This difference is mainly due to the annual snow accumulation and the surface albedo. A warming test (+1K) reveals higher sensitivities for the glaciers located within a summer accumulation pattern than for the glaciers located within a winter accumulation pattern. In a humid environment, a significant decrease in snow accumulation on the glaciers located within a summer accumulation pattern directly causes higher sensitivities. In an arid environment, on the other hand, the decreased summer snow induces accelerated melting by lowering the surface albedo and thus increasing absorption of solar radiation on the glaciers located within a summer accumulation pattern. Both influences are due to significant differences in summer precipitation. This study shows the importance of precipitation seasonality on the climatic sensitivity of glacier mass balance, which in previous studies has been linked only with annual precipitation.
Polymer Multilayer Microspheres Loaded with Semiconductor Quantum Dots
Authors: Petukhova Alla , Paton Andrew S. , Wei Zhixiang , Gourevich Ilya , Nair Selvakumar V. , Ruda Harry E. , Shik Alexander , Kumacheva Eugenia 
Published: June 2008

AbstractOptically active nanostructures comprised of polymer multilayer microspheres surrounding semiconductor quantum dots are studied. Comparative analysis of the optical properties of the microspheres with four alternating layers with different refractive indices is performed. Photoluminescence and extinction characteristics of the microspheres are determined by the dimensions, internal structure, and the average refractive index of the particles.
Lattice‐Registered Two‐Photon Polymerized Features within Colloidal Photonic Crystals and Their Optical Properties
Authors: Nelson Erik C. , García‐Santamaría Florencio , Braun Paul V. 
Published: June 2008

AbstractIn this work we demonstrate a significant advance in the introduction of embedded defects in 3D photonic crystals by means of two‐photon polymerization. We have developed the ability to precisely position embedded defects with respect to the lattice of 3D photonic crystals by imaging the structure concurrently with two‐photon writing. Defects are written with near‐perfect lattice registration and at specifically defined depths within the crystal. The effect of precise defect position on the optical response is investigated for embedded planar cavities written in a photonic crystal. The experimental data are compared to spectra calculated using the Scalar Wave Approximation (SWA).
Efficient Nonlinear Absorbing Platinum(II) Acetylide Chromophores in Solid PMMA Matrices
Authors: Westlund Robert , Malmström Eva , Lopes Cesar , Öhgren Johan , Rodgers Thomas , Saito Yuika , Kawata Satoshi , Glimsdal Eirik , Lindgren Mikael 
Published: June 2008

AbstractPlatinum(II) acetylides were incorporated into poly(methyl methacrylate) (PMMA) glasses to obtain solid‐state nonlinear optical devices. We report on device fabrication, structural, chemical, and mechanical properties, as well as the optical limiting capabilities of the final solids. Two different guest‐host systems are presented: 1) Dye molecules functionalized to be readily dispersed in methyl methacrylate (MMA) and subsequent in situ polymerization of the MMA yielding solid PMMA host matrices. 2) Dye molecules functionalized to copolymerize with MMA forming covalent bonds between the guest and the PMMA host matrix. A range of doped organic solids were prepared, reaching concentrations up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices indicate that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photophysical properties observed for the same solute molecules in THF are maintained also in the solid state. Optical power limiting (OPL) characterization reveal clamping levels for the dyes nonbonded to the solid host being less than 4 µJ at pulse energies up to 110 µJ at 532 nm (f/5 arrangement and 5 ns pulses), which is comparable to the performance of similar dyes in THF solutions. In contrast, the highly crosslinked solid possesses a higher clamping level (8 µJ) at the same nominal concentration.
Fully Enzymatic Resolution of Chiral Amines: Acylation and Deacylation in the Presence of Candida antarctica Lipase B
Authors: Ismail Hilda , Lau Rute Madeira , van Rantwijk Fred , Sheldon Roger A. 
Published: June 2008

AbstractA fully enzymatic methodology for the resolution of chiral amines has been demonstrated. Candida antarctica lipase B (CaLB)‐catalyzed acylation with N‐methyl‐ and N‐phenylglycine, as well as analogues having the general formula R1XCH2CO2R2 (R1=Me, Ph; X=O, S) afforded the corresponding enantioenriched amides, which were subsequently enzymatically hydrolyzed. Surprisingly, CaLB also proved to be the catalyst of choice for this latter step. The heteroatom in the acyl donor profoundly influences both the enzymatic acylation and deacylation; the O‐substituted reagents performed best with regard to enantioselectivity as well as reaction rate in synthesis and hydrolysis.
A New Aspect of Magnesium Bromide‐Promoted Enantioselective Aryl Additions of Triaryl(tetrahydrofuran)aluminum to Ketones Catalyzed by a Titanium(IV) Catalyst of trans‐1,2‐Bis(hydroxycamphorsulfonylamino)cyclohexane
Authors: Chen Chien‐An , Wu Kuo‐Hui , Gau Han‐Mou 
Published: June 2008

AbstractA novel aspect of MgBr2‐promoted asymmetric triarylaluminum‐tetrahydrofuran [AlAr3(THF)] additions to ketones catalyzed by a titanium catalyst of 20 mol% trans‐1,2‐bis(hydroxycamphorsulfonylamino)cyclohexane (2) is reported. The catalytic system works excellently for aromatic ketones with either an electron‐withdrawing or an electron‐donating substituent on the aromatic ring at the 2′‐, 3′‐, or 4′‐positions, affording tertiary alcohols in excellent enantioselectivities of ≥90% ee, except for the cases of phenyl addition to 2′‐methoxyacetophenone and 4‐trimethylsilylphenyl (4‐TMSC6H4) addition to acetopheneone.
Zeolite NaY‐Promoted Monocyclization of Epoxy Polyene Terpenes: A Unique Route for the Direct Synthesis of Incompletely Cyclized Naturally Occurring Terpenols
Authors: Tsangarakis Constantinos , Raptis Christos , Arkoudis Elias , Stratakis Manolis 
Published: June 2008

AbstractA variety of epoxy polyene terpenes cyclize readily by confinement within zeolite NaY to form primarily products of monocyclization. The monocyclization pathway is highly predominant, irrespectively of the side chain of the epoxy terpene, while the monocyclic products possess regioselectively an exomethylenic double bond. The selective monocyclization in the case of epoxyfarnesyl acetate, epoxyfarnesylacetone or 2,3‐epoxysqualene, provides a direct route to the synthesis of a variety of natural products, such as elengasidiol, farnesiferols B–D, achilleol A, camelliol C and to four farnesylacetone‐derived metabolites isolated from the brown algae Cystophora monoliformis. The optical rotation of achilleol A derived from the cyclization of (S)‐2,3‐epoxysqualene matches with that of the natural product, thus the absolute configuration of achilleol A was established as 1S,3R. From the mechanistic point of view, the NaY‐promoted cyclization of 9,10‐epoxygeranylacetone, selectively deuterium labelled at the C‐10 methyl group, is >97% stereoselective with respect to the topicity of the gem‐dimethyl group. This result is in agreement with a concerted mechanism. Finally, we have proved through labelling experiments, for the first time, that the biomimetic transformation of epoxy polyene terpenes to 2,3,4‐trimethylcyclohexanones upon acid catalysis is a highly stereoselective process. Thus, the less hindered gem‐methyl group on the epoxide functionality becomes α‐ to the carbonyl in the final isomerized product.
Impact of Carbon Dioxide Pressurization on Liquid Phase Organic Reactions: A Case Study on Heck and Diels–Alder Reactions
Authors: Fujita S. , Tanaka T. , Akiyama Y. , Asai K. , Hao J. , Zhao F. , Arai M. 
Published: June 2008

AbstractHeck coupling reactions of methyl acrylate with various aryl bromides have been investigated using a Pd/TPP catalyst in toluene under pressurized CO2 conditions up to 13 MPa. Although CO2 is not a reactant, the pressurization of the reaction liquid phase with CO2 has positive and negative impacts on the rate of Heck coupling depending on the structures of the substrates examined. In the case of either 2‐bromoacetophenone or 2‐bromocinnamate, the conversion has a maximum at a CO2 pressure of about 3 MPa; for the former, it is much larger by a factor of 3 compared with that under ambient pressure. For 2‐bromobenzene, in contrast, the conversion is minimized at a similar CO2 pressure, being half compared with that at ambient pressure. In the other substrates, including the other isomers of these three aryl bromides, the conversion simply decreases or does not change so much with the CO2 pressure. To examine the factors responsible for the effects of CO2 pressurization, the phase behavior and the molecular interactions with dense phase CO2 have also been studied by visual observation and in situ high pressure FT‐IR spectroscopy. In addition, impact of CO2 pressurization was also studied for the Diels–Alder reactions of isoprene with a few dienophiles like methyl acrylate, methyl vinyl ketone, and acrolein in the same solvent, toluene, but a heterogeneous silica‐alumina catalyst was used (the reaction system was liquid‐solid biphasic). When the CO2 pressure is raised, the conversion monotonously decreases for the three dienophiles; however, the product selectivity changes with the pressure, in particular for acrolein. The FT‐IR spectroscopic measurements suggest that its reactivity is altered by interactions with CO2 molecules under pressurized conditions.
Chiral Brønsted Acid‐Mediated Enantioselective Organocatalytic Three‐Component Reaction for the Construction of Trifluoromethyl‐Containing Molecules
Authors: Zhang Guang‐Wu , Wang Lian , Nie Jing , Ma Jun‐An 
Published: June 2008

AbstractIn combination with the advantages of organocatalysis, we have developed a highly enantioselective Friedel–Crafts aminoalkylation of indoles with imines generated in situ from trifluoroacetaldehyde methyl hemiacetal and aniline. Novel chiral trifluoromethyl‐containing compounds were obtained in high yields with excellent enantioselectivities. This methodology was further extended to difluoroacetaldehyde methyl hemiacetal to demonstrate the broad scope of substrates.
An Efficient Approach for Immobilizing the Oxo‐Vanadium Schiff Base onto Polymer Supports using Staudinger Ligation
Authors: Jain Suman L. , Sain Bir 
Published: June 2008

AbstractThe present paper describes the use of Staudinger ligation as an efficient and high‐yielding approach for the immobilization of oxo‐vanadium Schiff base on polymeric supports via covalent attachment under mild conditions. The described strategy is simple in use, versatile, highly efficient with respect to better catalyst loading and proceeds under mild, metal‐free conditions. The catalytic potential of the prepared polymer immobilized oxo‐vanadium Schiff bases was tested for the oxidation of sulfides using aqueous tert‐butyl hydroperoxide (TBHP) as oxidant. The polymer‐supported catalysts could easily be recovered from the reaction mixture and reused for four runs without loss in activity and no metal leaching was observed during this course.
One‐Pot Oxidative Heteroannulations of N‐Sulfonylanilines with Styrenes for the Construction of 5‐Aminocoumaran Derivatives
Authors: Fan Renhua , Li Weixun , Ye Yang , Wang Linfei 
Published: June 2008

AbstractAn efficient one‐pot oxidative heteroannulation of N‐sulfonylaniline derivatives with styrene derivatives for the rapid construction of 5‐aminocoumaran derivatives is reported. Copper trifluoromethanesulfonate was found to be an excellent catalyst for the oxidative heteroannulation reactions with low reactive styrenes.
Chemisches Design von leistungsfähigen Nanosonden für die Kernspintomographie
Authors: Jun Young‐wook , Lee Jae‐Hyun , Cheon Jinwoo 
Published: June 2008

AbstractSynthetische magnetische Nanopartikel (MNP) werden in der Biomedizin immer häufiger als Sonden eingesetzt. Dies gilt besonders für die Anwendung in der Kernspintomographie (Magnetic Resonance Imaging, MRI). Diese Nanopartikel sind von ähnlicher Größe wie biologische Funktionseinheiten. Deshalb und wegen ihrer einzigartigen magnetischen Eigenschaften eignen sie sich zur molekularen Bildgebung. Dieser Aufsatz gibt einen Überblick zu neuartigen MNP‐Sonden, mit denen biologische Ereignisse auf molekularer und zellulärer Ebene empfindlich und spezifisch nachgewiesen werden können.
Synthesis and Antimicrobial Study of Novel 1‐Aryl‐2‐oxo‐indano[3,2‐d]pyrido/pyrimido[1,2‐b]pyrimidines
Authors: Sarvesh Pandey K. , Nizamuddin Khan 
Published: June 2008

AbstractA series of 2‐(arylidene)‐indan‐1, 3‐diones1were prepared by Knoevenagel reaction between indane‐1,3‐dione and the appropriate araldehydes. The α,β‐enones1have been used as a component of Michael addition with equimolar amounts of 2‐aminopyridine/2‐aminopyrimidine to give novel heterocyclic systems4and5, respectively. They are reported here for the first time. The structures of the newly synthesized compounds were confirmed by IR,1H‐NMR,13C‐NMR, and elemental analysis. All compounds were screened for their antibacterial and antifungal activities. Some of them showed promising activities.
The Discovery of Taranabant, a Selective Cannabinoid‐1 Receptor Inverse Agonist for the Treatment of Obesity
Authors: Hagmann William K. 
Published: June 2008

AbstractThe cannabinoid‐1 receptor (CB1R) has emerged as one of the most important targets for the treatment of obesity. Pioneering studies with rimonabant helped to validate animal models of food intake reduction and weight loss and made the connection to weight loss in the clinic. A novel, acyclic amide was identified from a high throughput screen (HTS) of the Merck sample collection and found to be a potent and selective CB1R inhibitor. Further optimization led to more potent compounds that were orally active in reducing food intake and weight loss in diet‐induced obese (DIO) rats. However, many of these analogues exhibited a high potential for bioactivation and the formation of reactive intermediates and covalent protein binding. Identification of the products of oxidative metabolism guided medicinal chemistry efforts to minimize the formation of these unwanted products. These efforts resulted in the identification of the CB1R inverse agonist, taranabant, which is currently in Phase‐III clinical studies for the treatment of obesity. This mini‐review will describe some of the medicinal chemistry strategies that were followed from the original high throughput screen hit to the discovery of taranabant.
Induction of interferon‐α by scleroderma sera containing autoantibodies to topoisomerase I: Association of higher interferon‐α activity with lung fibrosis
Authors: Kim Daniel , Peck Anders , Santer Deanna , Patole Prashant , Schwartz Stephen M. , Molitor Jerry A. , Arnett Frank C. , Elkon Keith B. 
Published: June 2008

AbstractObjectivePeripheral blood cells (PBMCs) from some patients with systemic sclerosis (SSc) express an interferon‐α (IFNα) signature. The aim of this study was to determine whether SSc patient sera could induce IFNα and whether IFNα induction was associated with specific autoantibodies and/or clinical features of the disease.MethodsSSc sera containing autoantibodies against either topoisomerase I (anti–topo I; n = 12), nucleolar protein (ANoA; n = 12), or centromeric protein (ACA; n = 13) were cultured with a HeLa nuclear extract and normal PBMCs. In some experiments, different cell extracts or inhibitors of plasmacytoid dendritic cell (DC) activation, Fcγ receptor II (FcγRII), endocytosis, or nucleases were used. IFNα was measured by enzyme‐linked immunosorbent assay.ResultsTopo I–containing sera induced significantly higher levels of IFNα as compared with all other groups. IFNα induction was inhibited by anti–blood dendritic cell antigen 2 (90%), anti‐CD32 (76%), bafilomycin (99%), and RNase (82%). In contrast, ACAs induced low levels of IFNα even when necrotic, apoptotic, or demethylated extracts were used, despite the fact that CENP‐B–binding oligonucleotide containing 2 CpG motifs effectively stimulated IFNα. IFNα production was significantly higher in patients with diffuse SSc (mean ± SEM 641 ± 174 pg/ml) than in those with limited SSc (215 ± 66 pg/ml) as well as in patients with lung fibrosis than in those without.ConclusionAutoantibody subsets in SSc sera differentially induce IFNα and may explain the IFNα signature observed in SSc. IFNα is induced by plasmacytoid DCs and required uptake of immune complexes through FcγRII, endosomal transport, and the presence of RNA, presumably for interaction with Toll‐like receptor 7. The higher IFNα induction in sera from patients with diffuse SSc than in those with limited SSc as well as in sera from patients with lung fibrosis suggests that IFNα may contribute to tissue injury.
Elucidating bone marrow edema and myelopoiesis in murine arthritis using contrast‐enhanced magnetic resonance imaging
Authors: Proulx Steven T. , Kwok Edmund , You Zhigang , Papuga M. Owen , Beck Christopher A. , Shealy David J. , Calvi Laura M. , Ritchlin Christopher T. , Awad Hani A. , Boyce Brendan F. , Xing Lianping , Schwarz Edward M. 
Published: June 2008

AbstractObjectiveWhile bone marrow edema (BME) detected by magnetic resonance imaging (MRI) is a biomarker of arthritis, its nature remains poorly understood due to the limitations of clinical studies. In this study, MRI of murine arthritis was used to elucidate its cellular composition and vascular involvement.MethodsBME was quantified using normalized bone marrow intensity (NBMI) from precontrast MRI and normalized marrow contrast enhancement (NMCE) following intravenous administration of gadopentate dimeglumine. Wild‐type (WT) and tumor necrosis factor (TNF)–transgenic mice were scanned from 2 to 5 months of age, followed by histologic or fluorescence‐activated cell sorting (FACS) analysis of marrow. In efficacy studies, TNF‐transgenic mice were treated with anti‐TNF or placebo for 8 weeks, and then were studied using bimonthly MRI and histologic analysis.ResultsNBMI values were similar in WT and TNF‐transgenic mice at 2 months. The values in WT mice steadily decreased thereafter, with mean values becoming significantly different from those of TNF‐transgenic mice at 3.5 months (mean ± SD 0.29 ± 0.08 versus 0.46 ± 0.13; P < 0.05). Red to yellow marrow transformation occurred in WT but not TNF‐transgenic mice, as observed histologically at 5 months. The marrow of TNF‐transgenic mice that received anti‐TNF therapy converted to yellow marrow, with lower NBMI values versus placebo at 6 weeks (mean ± SD 0.26 ± 0.07 versus 0.61 ± 0.22; P < 0.05). FACS analysis of bone marrow revealed a significant correlation between NBMI values and CD11b+ monocytes (R2 = 0.91, P = 0.0028). Thresholds for “normal” red marrow versus pathologic BME were established, and it was also found that inflammatory marrow is highly permeable to contrast agent.ConclusionBME signals in TNF‐transgenic mice are caused by yellow to red marrow conversion, with increased myelopoiesis and increased marrow permeability. The factors that mediate these changes warrant further investigation.
Biomechanics of cartilage articulation: Effects of lubrication and degeneration on shear deformation
Authors: Wong Benjamin L. , Bae Won C. , Chun June , Gratz Kenneth R. , Lotz Martin , Robert L. Sah  
Published: June 2008

AbstractObjectiveTo characterize cartilage shear strain during articulation, and the effects of lubrication and degeneration.MethodsHuman osteochondral cores from lateral femoral condyles, characterized as normal or mildly degenerated based on surface structure, were selected. Under video microscopy, pairs of osteochondral blocks from each core were apposed, compressed 15%, and subjected to relative lateral motion with synovial fluid (SF) or phosphate buffered saline (PBS) as lubricant. When cartilage surfaces began to slide steadily, shear strain (Exz) and modulus (G) overall in the full tissue thickness and also as a function of depth from the surface were determined.ResultsIn normal tissue with SF as lubricant, Exz was highest (0.056) near the articular surface and diminished monotonically with depth, with an overall average Exz of 0.028. In degenerated cartilage with SF as lubricant, Exz near the surface (0.28) was 5‐fold that of normal cartilage and localized there, with an overall Exz of 0.041. With PBS as lubricant, Exz values near the articular surface were ∼50% higher than those observed with SF, and overall Exz was 0.045 and 0.062 in normal and degenerated tissue, respectively. Near the articular surface, G was lower with degeneration (0.06 MPa, versus 0.18 MPa in normal cartilage). In both normal and degenerated cartilage, G increased with tissue depth to 3–4 MPa, with an overall G of 0.26–0.32 MPa.ConclusionDuring articulation, peak cartilage shear is highest near the articular surface and decreases markedly with depth. With degeneration and diminished lubrication, the markedly increased cartilage shear near the articular surface may contribute to progressive cartilage deterioration and osteoarthritis.