bluuebunny/crossref_metadata_2025_split huggingface dataset:
Iridium‐Catalyzed Asymmetric Hydrogenation of Unfunctionalized Enamines
Authors: Baeza Alejandro , Pfaltz Andreas 
Published: February 2009

AbstractOptically active tertiary amines are readily prepared by iridium‐catalyzed asymmetric hydrogenation of unfunctionalized enamines (see scheme). The best enantioselectivities with >90 % ee were obtained with N‐aryl‐ and N‐benzyl‐substituted enamines with a terminal double bond. The hydrogenation of enamines derived from cyclic ketones, which has not been reported yet with other catalysts, gave enantiomeric excesses of up to 87 %.magnified image
Cover Picture: A Chemical System that Mimics Decoding Operations (ChemPhysChem 3/2009)
Authors: Giansante Carlo , Ceroni Paola , Venturi Margherita , Sakamoto Junji , Schlüter A. Dieter 
Published: February 2009

AbstractThe cover picture illustrates the decoding operation that can be mimicked by a solution containing a shape‐persistent macrocycle bearing two 2,2'‐bipyridine units and two Coumarin 2 moieties upon chemical inputs (protons) and photophysical outputs (four protonation states of the macrocycle under UV illumination are represented in the picture). M. Venturi et al. show on p. 495 that equilibrium mixtures of protonated species of this macrocycle contain more chemical information than the sum of information carried by the individual molecules.magnified image
Mathematical learning disabilities in children with 22q11.2 deletion syndrome: A review
Authors: De Smedt Bert , Swillen Ann , Verschaffel Lieven , Ghesquière Pol 
Published: February 2009

AbstractMathematical learning disabilities (MLD) occur frequently in children with specific genetic disorders, like Turner syndrome, fragile X syndrome and neurofibromatosis. This review focuses on MLD in children with chromosome 22q11.2 deletion syndrome (22q11DS). This syndrome is the most common known microdeletion syndrome with a prevalence of at least 1:4000 to 1:6000 live births. Although the clinical presentation of 22q11DS is quite variable, its major characteristics include velopharyngeal abnormalities, congenital cardiac anomalies, mild facial dysmorphism and learning difficulties. Children with 22q11DS show considerable difficulties in mathematics, despite relatively normal reading performance. While fact retrieval seems to be preserved, impairments in procedural calculation and word problem solving are particularly prominent. Children with 22q11DS also have substantial difficulties in understanding and representing numerical quantities, possibly related to poor visuospatial attention, which all might stem from their underlying abnormalities in the inferior parietal cortex. This review ends with a discussion on how research on genetic disorders might aid our understanding of MLD in general. © 2009 Wiley‐Liss, Inc. Dev Disabil Res Rev 2009;15:4–10.
Mathematical skills in Williams syndrome: Insight into the importance of underlying representations
Authors: O'Hearn Kirsten , Luna Beatriz 
Published: February 2009

AbstractWilliams syndrome (WS) is a developmental disorder characterized by relatively spared verbal skills and severe visuospatial deficits. Serious impairments in mathematics have also been reported. This article reviews the evidence on mathematical ability in WS, focusing on the integrity and developmental path of two fundamental representations, namely those that support judgments of “how much” (i.e., magnitude) and “how many” (i.e., number of objects). Studies on magnitude or “number line” representation in WS suggest that this core aspect of mathematical ability, is atypical in WS throughout development, causing differences on some but not all aspects of math. Studies on the representation of small numbers of objects in WS are also reviewed, given the proposed links between this type of representation and early number skills such as counting. In WS, representation appears to be relatively typical in infancy but limitations become evident by maturity, suggesting a truncated developmental trajectory. The math deficits in WS are consistent with neurological data indicating decreased gray matter and hypoactivation in parietal areas in WS, as these areas are implicated in mathematical processing as well as visuospatial abilities and visual attention. In spite of their deficits in core mathematical representations, people with WS can learn many mathematical skills and show some strengths, such as reading numbers. Thus individuals with WS may be able to take advantage of their relatively strong verbal skills when learning some mathematical tasks. The uneven mathematical abilities found in persons with WS provide insight into not only appropriate remediation for this developmental disorder but also into the precursors of mathematical ability, their neural substrates, and their developmental importance. © 2009 Wiley‐Liss, Inc. Dev Disabil Res Rev 2009;15:11–20.
Mathematics deficiencies in children with very low birth weight or very preterm birth
Authors: Taylor H. Gerry , Espy Kimberly Andrews , Anderson Peter J. 
Published: February 2009

AbstractChildren with very low birth weight (VLBW, <1500 g) or very preterm birth (VPTB, <32 weeks gestational age or GA) have more mathematics disabilities or deficiencies (MD) and higher rates of mathematics learning disabilities (MLD) than normal birth weight term‐born children (NBW, >2500 g and >36 weeks GA). MD are found even in children without global disorders in cognition or neurosensory status and when IQ is controlled, and they are associated with other learning problems and weaknesses in perceptual motor abilities and executive function. Factors related to poorer mathematics outcomes include lower birth weight and GA, neonatal complications, and possible abnormalities in brain structure. While little is known about the nature of MD in these children, studies of MLD in other neurodevelopmental disorders and in children with learning disabilities provide useful models for further investigation. Further investigation of the neuropsychological and neuropathological correlates of distinct types of mathematics difficulties is also needed. Studies along these lines will yield information about the unique features of MD in children with VLBW/VPTB and about the nature and origins of poor mathematics achievement more generally. © 2009 Wiley‐Liss, Inc. Dev Disabil Res Rev 2009;15:52–59.
Potential influences on mathematical difficulties in children and adolescents with neurofibromatosis, type 1
Authors: Moore Bartlett D. 
Published: February 2009

AbstractNeurofibromatosis, type 1 (NF‐1) is a common genetic disorder affecting 1 in 3,500–4,000 individuals in the world. Mutations of the NF‐1 gene produce a myriad of physical, medical, and psychological manifestations. Although there is a very high degree of variability in the manifestations between individuals with NF‐1, the majority of children and adolescents with NF‐1 encounter difficulties that negatively impact their educational attainment. NF‐1 is associated with a very high incidence of cognitive deficits and learning disability, sometimes including mathematical learning disabilities (MLD). A number of possible inter‐related etiologies for MLD specific to children and adolescents with NF‐1 are discussed, including the high incidence of attention deficit hyperactivity disorder, visual spatial impairment, morphological and functional brain abnormalities. Thus NF‐1 exemplifies the wide ranging sources of potential influences on mathematical learning and MLD. © 2009 Wiley‐Liss, Inc. Dev Disabil Res Rev 2009;15:45–51.
Statistics and biomedical informatics in forensic sciences
Authors: Zvárová Jana 
Published: February 2009

AbstractStatistics and biomedical informatics play a very important role in forensic sciences. Statistics can be regarded as the science of uncertainty. It is therefore natural that statistics should be applied to evidence used for legal purposes or the individual's identification as uncertainty is a feature of any legal or identification processes where decisions are based on upon the basis of evidence. Biomedical informatics is bringing new approaches how to handle genetic and other data supporting decision‐making processes. We will show the simultaneous application of statistical and biomedical informatics approaches in the field of forensic dentistry and for calculating weight‐of‐evidence for forensic DNA profiles. Copyright © 2009 John Wiley & Sons, Ltd.
Ex vivo analysis of rotational stiffness of different osteosynthesis techniques in mouse femur fracture
Authors: Histing Tina , Holstein Joerg H. , Garcia Patric , Matthys Romano , Kristen Alexander , Claes Lutz , Menger Michael D. , Pohlemann Tim 
Published: February 2009

AbstractThe various molecular mechanisms of cell regeneration and tissue healing can best be studied in mouse models with the availability of a wide range of monoclonal antibodies and gene‐targeted animals. The influence of the mechanical stability of individual stabilization techniques on the molecular mechanisms of fracture healing has not been completely elucidated yet. Although during recent years several osteosynthesis techniques have been introduced in mouse fracture models, no comparative study on fracture stabilization is available yet. We therefore analyzed herein in a standardized ex vivo setup the rotational stiffness of seven different osteosynthesis techniques using osteotomized right cadaver femora of CD‐1 mice. Uninjured femora without osteotomy served as controls. Femur stabilization with a locking plate or an external fixator resulted in a rotational stiffness almost similar to the intact femur. The use of a “pin‐clip” device, a “locking nail,” a “mouse nail,” or an “intramedullary screw” produced a lower torsional stiffness, which, however, was still significantly higher than that achieved with the widely applied conventional pin. By the use of the presented data a more specific choice of stabilization technique will be possible according to the various questions concerning molecular aspects in fracture healing. © 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 27: 1152–1156, 2009
Comparative analysis of essential oils from eight herbal medicines with pungent flavor and cool nature by GC–MS and chemometric resolution methods
Authors: Zhao Chenxi , Zeng Yingxu , Wan Mingzhu , Li Rongxi , Liang Yizeng , Li Chengyong , Zeng Zhongda , Chau Foo‐Tim 
Published: February 2009

AbstractSystematic comparative research was conducted on essential oils from eight traditional Chinese medicines (TCM) of pungent flavor and cool nature because the essential oils are the main active ingredients of herbs of this kind. The work was based on their component analysis by gas chromatography–mass spectrometry (GC–MS), on their retention indices, as well as on chemometric resolution methods. A total of 144 compounds were tentatively identified, accounting for 69.0% to 91.8% of the total essential oils. It is worth noting that there are 67 compounds in at least three of these eight essential oils. Moreover, many biologically active compounds, such as hexanal, α‐pinene, camphene, β‐pinene, p‐cymene, limonene, eucalyptol, (Z)‐ocimene, γ‐terpinene, camphor, p‐menthone, 4‐terpineol, α‐terpineol, carvone, eugenol, caryophyllene, β‐farnesene, α‐curcumene, β‐selinene, δ‐cadinene, caryophyllene oxide, cedrol, n‐hexadecanoic acid, benzaldehyde, benzeneacetaldehyde, phthalic acid diisobutyl ester, linoleic acid, tetradecanoic acid, (Z,Z,Z)‐9,12,15‐octadecatrienoic acid, eucalyptol, pentadecanoic acid, hexadecanoic acid methyl ester, linoleic acid methyl ester, exist in at least four of the eight essential oils. These results might help us to understand why the eight herbs are all of pungent flavor and cool nature according to the theory of TCM, and may provide a useful chemical basis for future research on herbs of this kind.
Moving reaction boundary and isoelectric focusing: IV. Systemic study on Hjertén's pH gradient mobilization
Authors: Xu Yan‐Jie , Li Si , Zhang Wei , Fan Liu‐Yin , Shao Jing , Cao Cheng‐Xi 
Published: February 2009

AbstractIn this paper, Hjertén's mobilization of pH gradient in IEF was systemically and quantitatively analyzed with the Rr value of judgment expression comparing the fluxes of hydrogen and hydroxyl ions. The theoretical results show that (i) there is Rr = 0, viz., quasi‐equal fluxes of proton and hydroxyl ion, in a classic IEF with sulfuric acid and sodium hydroxide used as the anolyte and catholyte, respectively, this is the main reason why pH gradient is quite stable in IEF; (ii) but if the salt of sodium sulfate is added into the sodium hydroxide, there is Rr > 0, viz., the flux of proton being higher than that of hydroxyl ion, the Rr value implies a cathodic mobilization of pH gradient, and the higher the Rr value is the faster the cathodic mobilization becomes; (iii) if the salt is added into the sulfuric acid, there is Rr < 0, the Rr value indicates an anodic mobilization, and the smaller the Rr value is the faster the anodic mobilization turns. To test these theoretical results above, a novel procedure was developed for the run of classic IEF followed by Hjertén's mobilization of pH gradient. The strict experiments were in well coincidence with the theoretical results. The results have obvious significances for the mechanism and development of Hjertén's mobilization.
Multifunctional Block Copolymers Based on Styrene Derivatives
Authors: Stadermann Jan , Fleischmann Sven , Messerschmidt Martin , Komber Hartmut , Voit Brigitte 
Published: February 2009

AbstractSeveral functionalized block copolymers based on polystyrene with considerably different block polarities have been prepared using controlled radical polymerization techniques (NMRP, RAFT). The target polymers, having hydroxy, alkyne or amine functionalities in at least one block were characterized by techniques like NMR, GPC and DSC to verify structure, molar masses, molecular weight distributions and thermal properties. With the example of partly protected hydroxystyrene based block copolymers, regular structured film surfaces could be created and were shown to be converted into homogeneous polymer surfaces by applying heat as external trigger. With alkyne functionalized block copolymers, modifications with objects of varying sizes were carried out, employing the 1,3‐dipolar cycloaddition of alkynes with azides. Once again, the “click approach” proved its high efficiency as the reactions proceeded completely even with objects of high steric demand. Studying the influence on the macromolecular architecture, we found a strong alteration of glass transition temperatures for the compared polymer materials, indicating a bracing of the chains due to steric hindrance between the bulky side objects.
Synthesis of Polypeptide Based Rod‐Coil Block Copolymers by Using TEMPO Based Bifunctional Initiator
Authors: Stern Maria , Jurjevic Simone , Heise Andreas , Menzel Henning 
Published: February 2009

AbstractA bifunctional initiator was synthesized having two functional groups for the initiation of the nickel mediated ring‐opening polymerization of γ‐benzyl‐l‐glutamate‐N‐carboxyanhydride and for the controlled radical polymerization of styrene via NMP. Molecular weights and molecular weight distributions of the polypeptides and block copolymers (PBLG‐b‐PS) were measured by SEC/MALLS. The controlled character of the NMP of styrene was examined by investigation of monomer consumption by gas chromatography.
Electrodeposition of Amino‐Functionalized Particles in a pH Gradient: Quantitative Investigations Employing an Electrochemical Quartz Crystal Microbalance
Authors: Bünsow Johanna , Grabs Ilka‐Marina , Schmidt‐Naake Gudrun , Johannsmann Diethelm 
Published: February 2009

AbstractThe electrodeposition of amino‐functionalized polystyrene and polybutylacrylate particles onto a gold electrode was investigated by an electrochemical quartz crystal microbalance (EQCM) and by AFM imaging. Particles with diameters in the range of 100 nm were prepared by miniemulsion polymerization. An electrochemical pH modulation in front of the electrode induced the neutralization of the amino groups and the particles readily precipitated onto the surface. The efficiency of the deposition was a function of the applied voltage, of the particles' softness, and of the amino content of the particles. Depending on the polymer composition, the coatings consisted of a dense array of individual miniemulsion particles or of a smooth polymer surface produced by coalescence.
Control of the Molecular Weight Distribution in Continuous Emulsion Polymerization in a Pulsed Sieve Plate Column
Authors: Smeets Niels M.B. , Dautzenberg Bart A.J. , Heuts Johan P.A. , Meuldijk Jan , van Herk Alex M. 
Published: February 2009

AbstractControl of the molecular weight distribution in continuous emulsion polymerization in a pulsed sieve plate column (PSPC) is experimentally studied. A global model, based on the Mayo equation, incoporating catalyst partitioning and deactivation was used to quantitatively illustrate the effect of the COBF addition on the instantaneous degree of polymerization in a batch reactor and the PSPC. Operating conditions have a strong influence on the cumulative molecular weight distribution of the latex product produced in the PSPC.
Characterization of Z‐RAFT Star Polymerization of Butyl acrylate by Size‐Exclusion Chromatography
Authors: Boschmann Daniel , Edam Rob , Schoenmakers Peter J. , Vana Philipp 
Published: February 2009

AbstractZ‐RAFT star polymerization of butyl acrylate using multifunctional trithiocarbonate‐type RAFT agents carrying methyl propionate as the leaving group were used to form star polymers having 3, 4, and 6 arms. The polymerizations showed well controlled behavior up to high monomer conversions. By using a mixture of mono‐ and multifunctional RAFT agents, arm and star polymer were obtained simultaneously within a single RAFT polymerization, which enabled the evaluation of the apparent arm numbers. The desired topology of the star polymers was found being present already from the early phase of polymerization on. The apparent arm number slightly increases at very high monomer conversions in accordance to earlier reported star coupling reactions. Correction factors for conventionally calibrated SEC showed excellent agreement with data for polystyrene stars, indicating that the contraction of the hydrodynamic volume in comparison to linear polymer is only dependent on the polymer topology. The evaluation of absolute molar masses of star polymers was however limited by the accuracy of the conventional calibration.
Free Radical Polymerization in Ionic Liquids – Solvent Influence of New Dimension
Authors: Schmidt‐Naake G. , Woecht I. , Schmalfuß A. , Glück T. 
Published: February 2009

AbstractFor the free radical polymerization of polar monomers which are soluble in ionic liquids (ILs) an extraordinary strong solvent effect can be observed. The solvent influence of the ILs leads to a strong enhancement of the polymerization rate and extremely high, mostly broadly distributed molecular weights. The experimentally determined very high propagation rate coefficient kp and the reduction of the activation energy of propagation EA can be explained by H‐bonds between both the monomer molecules and the growing radical chains and the cations and anions of the ILs. The high viscosity of the ILs themselves as well as the increase of the viscosity during the polymerization process are responsible for the high molecular weights and the mostly high polydispersities. The systematic variation of the rate constants of propagation kp and termination kt using microwave reactor, IL/conventional organic solvent mixtures and increased reaction temperatures is studied.
Modification of the Solvent Influence on the Free Radical Polymerization in Ionic Liquids by Microwave Irradiation
Authors: Glück T. , Woecht I. , Schmalfuß A. , Schmidt‐Naake G. 
Published: February 2009

AbstractMicrowave irradiation is supposed to disturb the polar interactions between the ionic liquid and the monomer molecules or the polymer radicals which probably leads to a decrease in kp compared to conventional heating. This work deals with the comparison of the influence of microwave heating and conventional heating on polymerizations in the ionic liquids [EMIM]EtSO4 and [BMIM]BF4. Different monomers were homo‐ and copolymerized at 60 and 80 °C in DMF or methanol and [EMIM]EtSO4 or [BMIM]BF4 as solvent. Lower conversions were observed under microwave irradiation when polymerizing in the ionic liquid (IL), but not when polymerizing in DMF or methanol. Nevertheless there were no systematical differences in the molecular weights and in the copolymer compositions between microwave heating and conventional heating.
Aspects of Free Radical Polymerization of Styrene and n‐Butylmethacrylate in Imidazolium Tosylates
Authors: Strehmel Veronika , Reynaud Eric , Wetzel Hendrik , Görnitz Eckhard , Laschewsky André 
Published: February 2009

AbstractSummery: A series of 1‐alkyl‐3‐methylimidazolium tosylates was explored as new solvents for the free radical polymerization of n‐butylmethacrylate and styrene. The use of these ionic liquids results in high yields and high molecular weights of the polymers, often even exceeding the molecular weights achieved in bulk polymerization. The obtained molecular weights and their distributions are sensitive to the structure of the ionic liquids, namely to substituents of the imidazolium ring. The broad and bimodal molecular weight distributions of the polystyrene made in the 1‐alkyl‐3‐methylimidazolium tosylates is caused by a heterophase polymerization.
Three‐compartment T1 relaxation model for intracellular paramagnetic contrast agents
Authors: Strijkers Gustav J. , Hak Sjoerd , Kok Maarten B. , Springer Charles S. , Nicolay Klaas 
Published: February 2009

AbstractThe goal of this work was to elaborate a model describing the effective longitudinal relaxation rate constant R1 for 1H2O in three cellular compartments experiencing possible equilibrium water exchange, and to apply this model to explain the effective R1 dependence on the overall concentration of a cell‐internalized Gd3+‐based contrast agent (CA). The model voxel comprises three compartments representing extracellular, cytoplasmic, and vesicular (e.g., endosomal, lysosomal) subcellular spaces. Relaxation parameters were simulated using a modified Bloch–McConnell equation including magnetization exchange between the three compartments. With the model, several possible scenarios for internalized CA distribution were evaluated. Relaxation parameters were calculated for contrast agent restricted to the cytoplasmic or vesicular compartments. The size or the number of CA‐loaded vesicles was varied. The simulated data were then separately fitted with empirical mono‐ and biexponential inversion recovery expressions. The voxel CA‐concentration dependencies of R1 can be used to qualitatively and quantitatively understand a number of different experimental observations reported in the literature. Most important, the simulations reproduced the relaxivity “quenching” for cell‐internalized contrast agent that has been observed. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.