bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preparative Purification of Solanesol from Tobacco Leaf Extracts by Macroporous Resins
Authors: Du X. L. , Yuan Q. P. , Li Y. , Zhou H. H. 
Published: December 2007

AbstractIn the present study, the preparative purification of solanesol by macroporous resins was studied. The adsorption and desorption properties of solanesol on macroporous resins including SP207, SP700, SP825, SP850 and HP20 were compared. SP850 resin offered the best adsorption and desorption capacities based on the research results. Both Langmuir and Freundlich isotherms were used to describe the interactions between the solutes and resin at different temperatures, and the experimental data fits best to the Freundlich isotherms. Adsorption and desorption kinetic curves were obtained for solanesol adsorption on SP850 resin in the temperature range of 298–303 K. The results showed that the mobility of solanesol adsorption increased and the proportion of adsorbed solanesol decreased with increasing temperature. The adsorption kinetic curve can be classified into three portions, i.e., instantaneous adsorption stage, intraparticle diffusion stage and the final equilibrium stage. Dynamic adsorption and desorption experiments were carried out with the column packed by SP850 resin to optimize the separation process. The isocratic and stepwise operations were designed for the separation of solanesol. The use of stepwise elution allowed a reduction in the process time and solvent consumption, but also led to some loss in purity. The corresponding optimal parameters for adsorption and desorption were determined. According to the research results, it can be concluded that SP850 resin possesses a good ability to separate solanesol and the results in this study may provide scientific references for large‐scale solanesol production from tobacco leaf extracts.
Heterogeneous Catalysis in Supercritical Media: 1. Carbon Dioxide
Authors: Kruse A. , Vogel H. 
Published: December 2007

AbstractOver the past few years, supercritical fluids have received considerable interest as reaction media. Supercritical fluids combine properties of gases and liquids. Densities are lower than in the liquid phase, but significantly higher than in the gas phase. This makes supercritical fluids excellent solvents for a variety of substances. The good dissolution capacity exists only in or near the supercritical range. Reaction products can be separated, for instance, simply by decreasing temperature and pressure. This may be used to intensify the process as complex separation processes, like distillation, are avoided.
Extension of a Method for the Design of Divided Wall Columns
Authors: Sotudeh N. , Shahraki B. H. 
Published: December 2007

AbstractFor most separations, a fully thermally coupled distillation column or divided wall columns are thermodynamically more efficient than conventional columns. This paper develops a method for the design of divided wall columns consisting of multi‐component mixtures (more than three components) with constant relative volatilities and a relatively sharp separation between the key components.
Degradation of Pentoses and Hexouronic Acids in Subcritical Water
Authors: Usuki C. , Kimura Y. , Adachi S. 
Published: December 2007

AbstractThe degradation of arabinose, xylose, ribose and lyxose in subcritical water was measured at 200, 220 and 240 °C. Ribose was the most rapidly degraded among the pentoses tested. The degradation of the glucuronic and galacturonic acids proceeded at lower temperatures than that of the pentoses, and was measured at 140, 150 and 160 °C. The degradation processes of the pentoses and hexouronic acids could be expressed by the Weibull model, and the kinetic parameters were then estimated. The activation energy and frequency factor for the degradation of each substrate were estimated from the temperature dependence of the rate constant. The enthalpy‐entropy compensation held for the degradation of the pentoses as well as the hexoses, which suggests that the degradation of the hexouronic acids proceeded through a mechanism different from that for the pentoses and hexoses. The molar yield of a pentose to furfural was ca. 0.3 at any temperature, irrespective of the pentose type. Acidic compounds were also formed from the pentoses in proportion to the amount of consumed substrates. The formation of acidic compounds resulted in a rapid decrease in pH.
Folding Control in Cyclic Peptides through N‐Methylation Pattern Selection: Formation of Antiparallel β‐Sheet Dimers, Double Reverse Turns and Supramolecular Helices by 3α,γ Cyclic Peptides
Authors: Amorín Manuel , Castedo Luis , Granja Juan R. 
Published: December 2007

AbstractPeptide foldamers constitute a growing class of nanomaterials with potential applications in a wide variety of chemical, medical and technological fields. Here we describe the preparation and structural characteristics of a new class of cyclic peptide foldamers (3α,γ‐CPs) that, depending on their backbone N‐methylation patterns and the medium, can either remain as flat rings that dimerize through arrays of hydrogen bonds of antiparallel β‐sheet type, or can fold into twisted double reverse turns that, in the case of double γ‐turns, associate in nonpolar solvents to form helical supramolecular structures. A 3α,γ‐CP consists of a number of multiples of a repeat unit made up of four amino acid residues of alternating chirality: three corresponding to α‐amino acids and one to a γ‐amino acid (acis‐3‐aminocycloalkanecarboxylic acid).
Towards a Fully Conjugated, Double‐Stranded Cycle: A Mass Spectrometric and Theoretical Study
Authors: Denekamp Chagit , Etinger Alexander , Amrein Walter , Stanger Amnon , Stuparu Mihaiela , Schlüter A. Dieter 
Published: December 2007

AbstractThe two compounds, 1 and 5, are investigated by means of collision‐induced dissociation experiments by using ion cyclotron resonance mass spectrometry and other mass spectrometric techniques as to their ability to act as precursors for the fully unsaturated double‐stranded target compound 2. These experiments are complemented by flask‐type pyrolyses of 5, the products of which are analyzed by mass spectrometry. For 1, no conditions were found under which the expected molecular ion of 2 at m/z 932 appeared, however, for its derivative 5 this was possible. This interesting finding is not in contradiction with the chemical structure of the long sought for compound 2 but calculations suggest that this compound may have isomerized into one where the conjugation is interrupted by hydrogen shift from the solubilizing alkyl chains into the cycle's perimeter. The key driving force for such an isomerization would be the considerable relief of strain energy.
Delicate Crystal Structure Changes Govern the Magnetic Properties of 1D Coordination Polymers Based on 3d Metal Carboxylates
Authors: Gavrilenko Konstantin S. , Cador Olivier , Bernot Kevin , Rosa Patrick , Sessoli Roberta , Golhen Stéphane , Pavlishchuk Vitaly V. , Ouahab Lahcène 
Published: December 2007

AbstractHomo‐ and heterometallic 1D coordination polymers of transition metals (CoII, MnII, ZnII) have been synthesized by an in‐situ ligand generation route. Carboxylato‐based complexes [Co(PhCOO)2]n (1 a, 1 b), [Co(p‐MePhCOO)2]n (2), [ZnMn(PhCOO)4]n (3), and [CoZn(PhCOO)4]n (4) (PhCOOH=benzoic acid, p‐MePhCOOH=p‐methylbenzoic acid) have been characterized by chemical analysis, single‐crystal X‐ray diffraction, and magnetization measurements. The new complexes 2 and 3 crystallize in orthorhombic space groups Pnab and Pcab respectively. Their crystal structures consist of zigzag chains, with alternating MII centers in octahedral and tetrahedral positions, which are similar to those of 1 a and 1 b. Compound 4 crystallizes in monoclinic space group P21/c and comprises zigzag chains of MII ions in a tetrahedral coordination environment. Magnetic investigations reveal the existence of antiferromagnetic interactions between magnetic centers in the heterometallic complexes 3 and 4, while ferromagnetic interactions operate in homometallic compounds (1 a, 1 b, and 2). Compound 1 b orders ferromagnetically at TC=3.7 K whereas 1 a does not show any magnetic ordering down to 330 mK and displays typical single‐chain magnet (SCM) behavior with slowing down of magnetization relaxation below 0.6 K. Single‐crystal measurements reveal that the system is easily magnetized in the chain direction for 1 a whereas the chain direction coincides with the hard magnetic axis in 1 b. Despite important similarities, small differences in the molecular and crystal structures of these two compounds lead to this dramatic change in properties.
(Me3Si)3SiH: Twenty Years After Its Discovery as a Radical‐Based Reducing Agent
Authors: Chatgilialoglu Chryssostomos 
Published: December 2007

AbstractThis Concept shows the flexibility and applicability of (Me3Si)3SiH in several synthetic transformations, such as radical reductions, consecutive radical reactions and hydrosilylation. The reactivity of (Me3Si)3SiH combines the multidisciplinary aspects of physical organic chemistry and organic synthesis, extending to polymers and materials science, as in the functionalization of flat silicon surfaces.
The Total Synthesis of (+)‐Tedanolide—A Macrocyclic Polyketide from Marine Sponge Tedania ignis
Authors: Ehrlich Gunnar , Hassfeld Jorma , Eggert Ulrike , Kalesse Markus 
Published: December 2007

AbstractTedanolide, which was isolated by Schmitz in 1984 from the marine sponge Tedania ignis, is a highly cytotoxic macrolide leading to strong growth inhibition of P338 tumor cells in bioassays. A unique structural feature of the known tedanolides is the primary hydroxyl group incorporated in the macrolactone. This unusual motif for macrolactones originated from PKS biosynthesis might arise through lactonizations others than those derived by the thioesterase reaction. First experimental data that support this hypothesis and reflect the inherent preference of PKS‐induced macrolactonization were obtained during this synthesis. The inherent preference for the formation of a 14‐membered macrocyclization is discussed together with the pivotal steps in the synthesis.
Synthesis, Characterization, Molecular Structure and Theoretical Studies of Axially Fluoro‐Substituted Subazaporphyrins
Authors: Rodríguez‐Morgade M. Salomé , Claessens Christian G. , Medina Anaïs , González‐Rodríguez David , Gutiérrez‐Puebla Enrique , Monge Angeles , Alkorta Ibon , Elguero José , Torres Tomás 
Published: December 2007

AbstractA new and general synthetic method for the preparation of fluoro‐substituted subazaporphyrins is reported that involves the treatment of the corresponding chloro‐ or aryloxy‐substituted subazaporphyrins (SubAPs) with BF3⋅OEt2. The strategy has been applied to both subphthalocyanines (SubPcs) and subporphyrazines (SubPzs). The yields were high for the latter, although low yields were obtained for the benzo derivatives. In contrast to the corresponding chloro derivatives, fluorosubazaporphyrins are quite robust towards hydrolysis. All of the new compounds were characterized by several spectroscopic techniques, which included1H,13C,19F,15N, and11B NMR spectroscopy, IR spectroscopy, UV/Vis spectrophotometry, and mass spectrometry (both high and low resolution). In addition, DFT calculations provided theoretical NMR spectroscopy values that are in good agreement with the experimental ones. The high dipole moments exhibited by the fluorosubazaporphyrins as a result of the presence of a fluorine atom in an axial position are responsible for the spontaneous and singular supramolecular aggregation of the macrocycles in the crystalline state. The molecular and crystal structures of two one‐dimensional fluorine SubAPs, namely, a SubPc and a SubPz, are discussed. Molecules of the same class stack in alternating configurations along thecaxis, which gives rise to columns that contain large numbers of monomers. SubPz3 cforms aggregates with the macrocycles arranged in a parallel fashion with the BF bonds perfectly aligned within a column, whereas with SubPc3 bthe neighboring columns cause a commensurate sinusoidal distortion along the columns in thecdirection, which prevents the alignment of the BF bonds. However, the most remarkable feature, common to both crystalline architectures, is the extremely short and unusual intermolecular F⋅⋅⋅N distances of the contiguous molecules, which are shorter than the sum of the corresponding van der Waals radii. Theoretical calculations have shown that these short distances can be explained by the existence of a cooperativity effect as the number of monomers included in the cluster increases.
Templated Growth of Hybrid Structures at the Peptide–Peptide Interface
Authors: Ghosh Surajit , Verma Sandeep 
Published: December 2007

AbstractThis study describes the use of peptide vesicular platforms for the templated growth of fibrillar structures to craft hybrids that retain the gross morphological features of two discreet self‐assembled peptides. A synthetic triskelion peptide, which results in the rapid emergence of self‐assembled spherical structures, was employed as a template. Addition of either one of two different peptides, both of which form long filamentous structures when co‐incubated with the triskelion solution, affords hybrids that retain the gross morphology of both the spherical and filamentous structures. It is surmised that this process is aided by hydrogen bonding and the interdigitation of aromatic residues, which leads to the growth of hybrid structures. We believe that observations concerning the surface‐assisted growth of peptide fibrils and tubular structures from vesicular platforms may have ramifications for the design and development of peptide‐based hybrid materials with controlled hierarchical structures.
Tunable scheduling in a GridRPC framework
Authors: Amar A. , Bolze R. , Caniou Y. , Caron E. , Chis A. , Desprez F. , Depardon B. , Gay J.‐S. , Le Mahec G. , Loureiro D. 
Published: December 2007

AbstractAmong existing grid middleware approaches, one simple, powerful, and flexible approach consists of using servers available in different administrative domains through the classic client–server or remote procedure call paradigm. Network Enabled Servers (NES) implement this model, also called GridRPC. Clients submit computation requests to a scheduler, whose goal is to find a server available on the grid using some performance metric. The aim of this paper is to give an overview of a NES middleware developed in the GRAAL team called distributed interactive engineering toolbox (DIET) and to describe recent developments around plug‐in schedulers, workflow management, and tools. DIET is a hierarchical set of components used for the development of applications based on computational servers on the grid. Copyright © 2007 John Wiley & Sons, Ltd.
CFAR detection of weak target in clutter using chaos synchronization
Authors: He Di , Leung Henry 
Published: December 2007

AbstractIn this paper, a novel constant false alarm rate (CFAR) approach for detecting weak targets in sea clutter spectrum based on chaos synchronization is proposed. The weak target signal is detected when the synchronization between two identical chaotic systems is realized, even if the target spectrum lies inside the clutter spectrum. The threshold for the proposed CFAR detection is derived theoretically. The proposed chaos‐synchronization‐based CFAR technique is shown to be able to enhance the detectability of the target when the signal‐to‐clutter ratio and signal‐to‐noise ratio are low. Numerical experiments based on real radar sea clutter data confirm the effectiveness of the proposed chaos‐synchronization‐based CFAR detection method. The performance is superior to those of the standard autoregressive estimation‐based and the cell‐averaging CFAR detectors. Copyright © 2007 John Wiley & Sons, Ltd.
Losses of 3p14 and 9p21 as shown by fluorescence in situ hybridization are early events in tumorigenesis of oral squamous cell carcinoma and already occur in simple keratosis
Authors: Schwarz Stephan , Bier Johannes , Driemel Oliver , Reichert Torsten E. , Hauke Sven , Hartmann Arndt , Brockhoff Gero 
Published: December 2007

AbstractTumorigenesis of oral squamous cell carcinoma (OSCC) has been postulated to represent a multistep process driven by the accumulation of carcinogen‐induced genetic changes. Alterations of the 3p14 fragile site containing the fragile histidine triade gene and of the 9p21 tumor suppressor locus containing methylthioadenosine phosphorylase, p16 and p15 characteristically occur in oral leukoplakia, a known precursor of OSCC, and are at present considered to indicate the transition from simple keratosis (hyperplasia) to dysplasia. The aim of the study was to evaluate the occurrence of losses of 3p14 and 9p21 and to evaluate polysomies 3 and 9 in leukoplakias using highly sensitive fluorescence in situ hybridization (FISH) probes. Examining 67 leukoplakias (24 hyperplasias, 33 dysplasias, 10 in situ carcinomas), control tissues of oral mucosa from infants and adults as well as invasive carcinomas and normal epithelia of tumor patients with locus specific FISH probes targeting 3p14 and 9p21, and centromeric probes for chromosomes 3 and 9 we could demonstrate that losses of these sites appeared very early in the tumorigenesis of OSCC and were already present in the great majority of simple keratoses. Polysomy 3 occurring more frequently than polysomy 9 was characteristic of dysplasia and in situ carcinomas and thus seems to follow losses of 3p14 and 9p21 during oral squamous cell carcinogenesis. © 2007 International Society for Analytical Cytology.
Toward quantitative fluorescence measurements with multicolor flow cytometry
Authors: Wang Lili , Gaigalas Adolfas K. , Marti Gerald , Abbasi Fatima , Hoffman Robert A. 
Published: December 2007

AbstractA procedure is presented for calibrating the output of a multicolor flow cytometer in units of antibodies bound per cell (ABC). The procedure involves two steps. First, each of the fluorescence channels of the flow cytometer is calibrated using Ultra Rainbow beads with assigned values of equivalent number of reference fluorophores (ERF). The objective of this step is to establish a linear relation between the fluorescence signal in a given fluorescence channel of multicolor flow cytometers and the value of ERF. The second step involves a biological standard such as a lymphocyte with a known number of antibody binding sites (e.g., CD4 binding sites). The biological standard is incubated with antibodies labeled with one type of fluorophores for a particular fluorescence channel and serves to translate the ERF scale to an ABC scale. A significant part of the two‐step calibration procedure involves the assignment of ERF values to the different populations of Ultra Rainbow beads. The assignment of ERF values quantifies the relative amount of embedded fluorophore mixture in each bead population. It is crucial to insure that the fluorescence signal in a given range of fluorescence emission wavelengths is related linearly to the assigned values of ERF. The biological standard has to posses a known number of binding sites for a given antibody. In addition, this antibody has to be amenable to labeling with different types of fluorophores associated with various fluorescence channels. The present work suggests that all of the requirements for a successful calibration of a multicolor flow cytometer in terms of ABC values can be fulfilled. The calibration procedure is based on firm scientific foundations so that it is easy to envision future improvements in accuracy and ease of implementation. Published 2007 Wiley‐Liss, Inc.
Modification to the Lampariello approach to evaluate reactive oxygen species production by flow cytometry
Authors: Brescia Francesca , Sarti Maurizio 
Published: December 2007

AbstractThe aim of this article is to perform a statistical analysis of reactive oxygen species (ROS) cytometric data. It is demonstrated that the classical parametric and nonparametric statistical tests are not suitable to examine these data; the Kolmogorov‐Smirnov test and the modification proposed by Lampariello are shown to be too sensitive with respect to the experimental bias (due to procedure or to the instrument) and variability in the ROS production within the repeated samples. Several approaches are examined and discussed. Modifications of the Lampariello's procedure are proposed to include the variability within samples. The validity of the proposed approach is verified by analyzing repeated measurements of ROS formation in cultured human lymphocytes untreated or treated with ferrous sulfate. The proposed approach is successful in considering the “intersample” variability in the ROS data analysis and keeps a good level of validity. Nevertheless, this procedure is not user‐friendly and needs to be handled by an expert operator. © 2007 International Society for Analytical Cytology
An analytical workflow for investigating cytokine profiles
Authors: Siebert Janet C. , Inokuma Margaret , Waid Dan M. , Pennock Nathan D. , Vaitaitis Gisela M. , Disis Mary L. , Dunne John F. , Wagner David H. , Maecker Holden T. 
Published: December 2007

AbstractUnderstanding cytokine profiles of disease states has provided researchers with great insight into immunologic signaling associated with disease onset and progression, affording opportunities for advancement in diagnostics and therapeutic intervention. Multiparameter flow cytometric assays support identification of specific cytokine secreting subpopulations. Bead‐based assays provide simultaneous measurement for the production of ever‐growing numbers of cytokines. These technologies demand appropriate analytical techniques to extract relevant information efficiently. We illustrate the power of an analytical workflow to reveal significant alterations in T‐cell cytokine expression patterns in type 1 diabetes (T1D) and breast cancer. This workflow consists of population‐level analysis, followed by donor‐level analysis, data transformation such as stratification or normalization, and a return to population‐level analysis. In the T1D study, T‐cell cytokine production was measured with a cytokine bead array. In the breast cancer study, intracellular cytokine staining measured T cell responses to stimulation with a variety of antigens. Summary statistics from each study were loaded into a relational database, together with associated experimental metadata and clinical parameters. Visual and statistical results were generated with custom Java software. In the T1D study, donor‐level analysis led to the stratification of donors based on unstimulated cytokine expression. The resulting cohorts showed statistically significant differences in poststimulation production of IL‐10, IL‐1β, IL‐8, and TNFβ. In the breast cancer study, the differing magnitude of cytokine responses required data normalization to support statistical comparisons. Once normalized, data showed a statistically significant decrease in the expression of IFNγ on CD4+ and CD8+ T cells when stimulated with tumor‐associated antigens (TAAs) when compared with an infectious disease antigen stimulus, and a statistically significant increase in expression of IL‐2 on CD8+ T cells. In conclusion, the analytical workflow described herein yielded statistically supported and biologically relevant findings that were otherwise unapparent. © 2007 International Society for Analytical Cytology