bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Densely Organized Maltose Shells on the Biological Properties of Poly(propylene imine) Dendrimers: New Effects Dependent on Hydrogen Bonding
Authors: Klajnert Barbara , Appelhans Dietmar , Komber Hartmut , Morgner Nina , Schwarz Simona , Richter Sven , Brutschy Bernhard , Ionov Maksim , Tonkikh Anatoly K. , Bryszewska Maria , Voit Brigitte 
Published: June 2008

AbstractMaltose‐modified poly(propylene imine) (PPI) dendrimers were synthesized by reductive amination of unmodified second‐ to fifth‐generation PPI dendrimers in the presence of excess maltose. The dendrimers were characterized by using 1H NMR, 13C NMR, and IR spectroscopies; laser‐induced liquid beam ionization/desorption mass spectrometry; dynamic light scattering analyses; and polyelectrolyte titration. Their scaffolds have enhanced molecular rigidity and their outer spheres, at which two maltose units are bonded to the former primary amino groups on the surface, have hydrogen‐bond‐forming properties. Furthermore, the structural features reveal the presence of a dense shell. Experiments involving encapsulation (1‐anilinonaphthalene‐8‐sulfonic acid) and biological properties (hemolysis and interactions with human serum albumin (HSA) and prion peptide 185‐208) were performed to compare the modified with the unmodified dendrimers. These experiments gave the following results: 1) The modified dendrimers entrapped a low‐molecular‐weight fluorescent dye by means of a dendritic box effect, in contrast to the interfacial uptake characteristic of the unmodified PPI dendrimers. 2) Both low‐ and high‐generation dendrimers containing maltose units showed markedly reduced toxicity. 3) The desirable features of bio‐interactions depended on the generation of the dendrimer; they were retained after maltose substitution, but were now mainly governed by nonspecific hydrogen‐bonding interactions involving the maltose units. The modified dendrimers interacted with HSA as strongly as the parent compounds and appeared to have potential use as antiprion agents. These improvements will initiate the development of the next platform of glycodendrimers in which apparently contrary properties can be combined, and this will enable, for example, therapeutic products such as more efficient and less toxic antiamyloid agents to be synthesized.
Heterocycles as Key Substrates in Multicomponent Reactions: The Fast Lane towards Molecular Complexity
Authors: Isambert Nicolas , Lavilla Rodolfo 
Published: June 2008

AbstractHeterocycles display an intrinsic reactivity which enables rich, versatile and productive transformations. Taking into account their ubiquitous presence in natural products and drugs, the development of new, fast and efficient preparative protocols for these structures remains an urgent task in Organic Synthesis. Multicomponent reactions using heterocyclic chemistry offer new possibilities to exploit this exclusive reactivity. Recent results show relevant examples of such transformations. Several approaches which allow the construction of complex heterocyclic compounds from simple starting materials using this principle have been analyzed.
The effects of differences in explanations, employee attributions, type of infraction, and discipline severity on perceived fairness of employee discipline
Authors: Cole Nina D. 
Published: June 2008

AbstractParticipants reported perceptions of fairness after reading 1 of 72 scenarios describing a disciplinary discussion between a manager and an employee (crossing four different disciplinary infractions, with three types of explanations for each infraction, three different levels of discipline severity, and two types of employee attributions for their behaviour). Results indicate that type of attribution, type of infraction, and level of discipline severity all have significant effects on perceptions of distributive, procedural, interpersonal, and informational justice. Type of explanation also has significant effects on perceptions of justice other than informational justice. It appears that managing disciplinary fairness may require a contingency approach. Copyright © 2008 ASAC. Published by John Wiley & Sons, Ltd.
The business of blacklisting
Authors: Spector Bert 
Published: June 2008

AbstractThe omission of ideology from managerial discourse leaves unacknowledged the dominant influences that shape patterns of thinking and acting. The Cold War offers one such framework for analyzing the intersection of management and ideology. Specifically, the anti‐Communist blacklist in the United States offers a rich opportunity to explore the actions of business leaders and to test the assumptions on which those actions were based. Businessmen played a key role in creating and supporting the blacklist. This study suggests that enforcers of the blacklist distorted the nature of public response. The evidence suggests that businessmen were responding from an ideological rather than a pragmatic position and that, from a pragmatic perspective, they might have been well advised to ignore the blacklisters. Copyright © 2008 ASAC. Published by John Wiley & Sons, Ltd.
Taking a positive approach to organizational downsizing
Authors: Armstrong‐Stassen Marjorie , Schlosser Francine 
Published: June 2008

AbstractWe drew from the literature on positive organizational behaviour (Luthans & Youssef, 2007) to test a process model relating generalized optimism (Carver & Scheier, 1999) to the cognitions, affect, and behaviour of 237 Canadian federal government managers during and following a major organizational downsizing. Our data supported a model in which generalized optimism measured 18 months prior to the downsizing (T1) associated positively with managers' cognitions, attitudes, job performance, and self‐reported coping effectiveness measured 12 months postdownsizing (T3). Analyses suggested that some of these associations were partially mediated by a positive thinking coping strategy and expectations for future career and job success reported during the downsizing (T2). We advocate for more research that draws from the positive organizational behaviour literature to study the effects of downsizing on survivors. Copyright © 2008 ASAC. Published by John Wiley & Sons, Ltd.
DFT and Experimental Studies of Perchlorate Ion Coordination incis/trans‐Copper(II) Complexes of Tetradentate Pyridyl Ligands
Authors: Pandiyan Thangarasu , Guadalupe Hernández J. , Cruz Julian , Bernès Sylvain , Ugalde‐Salvdivar Víctor M. , González Ignacio 
Published: June 2008

AbstractSpectral and structural studies ofN,N′‐dimethyl‐N,N′‐bis(pyridin‐2‐ylmethyl)‐1,2‐diaminoethane (L1),N,N′‐dimethyl‐N,N′‐bis(pyridin‐2‐ylmethyl)‐1,3‐diaminopropane (L2), and their copper(II) complexes were carried out by spectroscopic and DFT methods. The DFT results show that conventional and nonconventional H‐bonds present in L1and L2influence the NMR chemical shifts at different pH values, which thus suggests that the protonation sites at the pyridyl and tertiary nitrogen atoms of the ligands change the chemical environment of the adjacent carbon atoms; this observation is consistent with13C NMR spectra recorded at different pH values. Furthermore, for their copper complexes, two possible geometrical isomers (cisandtrans) are obtained; for example,cis‐[CuL1]2+, where both NCH3groups are oriented in the same plane, is in equilibrium with itstransisomer and, as a result, a small energy difference (0.9 kcal mol–1) appears. In contrast,trans‐[CuL2]2+does not equilibrate with thecisisomer, because there is a greater energy difference (ΔE= 3.9 kcal mol–1) between the two isomers. Indeed, when [CuL1]2+with two perchlorate ions was optimized, it was found that although onlycis‐[CuL1]2+was able to accommodate a perchlorate ion in the axial position of the square pyramidal geometry by stabilizing the structure with twocisNCH3groups through H‐bonds, thetransisomer was unable to retain the perchlorate ion in the coordination sphere, because the NCH3groups were in thetransposition; this disfavors the presence of the perchlorate ion in the sphere, because of the absence of H‐bonds. This is consistent with the X‐ray structure, in whichcis‐[CuL1(ClO4)]+is resolved, whereas thetransisomer is not. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Selective Cleavage by Acids of One Metal–Carbon σ‐Bond of a Bis(ortho‐platinated) Triarylphosphane: A 31P NMR trans‐Influence Series Based on the Unit Pt(κ2‐C6H3‐5‐Me‐2‐PPh2)(PPh2‐4‐tol)
Authors: Bennett Martin A. , Bhargava Suresh K. , Privér Steven H. , Willis Anthony C. 
Published: June 2008

AbstractTreatment of the bis(chelate) complex cis‐[Pt(κ2‐C6H3‐5‐Me‐2‐PPh2)2] (1) with strong acids causes selective cleavage of one of the metal–aryl bonds to give cis‐[PtX(κ2‐C6H3‐5‐Me‐2‐PPh2)(PPh2‐4‐tol)] [X = Cl (2), Br (3), I (4), ONO2 (5) and OCOCF3 (6)], from which a series of neutral and cationic derivatives can be derived by metathetical reactions. The complexes 2 and 6 rearrange spontaneously to the corresponding trans isomers, this reaction being promoted by CO. The J(Pt‐P) values for the phosphorus atom of the four‐membered ring can be ordered to establish a trans‐influence series of anionic ligands X and neutral ligands L, which correlates well with, but is more extensive than, that based earlier on PtMe(dppe) complexes. Single‐crystal X‐ray structural analysis of trans‐[Pt(κ1‐OCOCF3)(κ2‐C6H3‐5‐Me‐2‐PPh2)(PPh2‐4‐tol)] (trans‐6), cis‐[PtX(κ2‐C6H3‐5‐Me‐2‐PPh2)(PPh2‐4‐tol)] [X = Cl (2), CN (11), Me (43) and C6F5 (45)], and [Pt(κ2‐C6H3‐5‐Me‐2‐PPh2)(PPh2‐4‐tol)2]BF4 (34) show these complexes to have distorted square‐planar geometry. The Pt–P distances to the phosphorus atom of the four‐membered ring in 2, 11, 43 and 45 broadly follow the trend of J(Pt–P) values, Cl– being placed near the bottom and Me– near the top of the trans‐influence series, but the corresponding Pt–P distance in 34 is out of line. The Pt–P distances to PPh2‐4‐tol cis to X or L tend to decrease with increasing trans‐influence of X or L, in agreement with previous indications of a ligand cis‐influence that runs opposite to the trans‐influence. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Quantitative confirmation of testosterone and epitestosterone in human urine by LC/Q‐ToF mass spectrometry for doping control
Authors: Danaceau Jonathan P. , Scott Morrison M. , Slawson Matthew H. 
Published: June 2008

AbstractTestosterone (T) is the primary male sex hormone. In addition to the development of secondary sex characteristics, testosterone has anabolic effects including increases in muscle size and strength and increases in lean body mass, making it an attractive candidate to enhance athletic performance. In the case of exogenous administration of testosterone, the ratio of testosterone to its isomer, epitestosterone (E), is elevated. WADA has set a standard for T/E ratios of 4.0 as indicative of possible exogenous testosterone administration. Typically, a sample that screens for a T/E ratio above that threshold is then subjected to quantitative confirmation by GC/MS. This methodology, however, can limited due to sensitivity issues as well as a limited number of qualifying ions that can be used for unambiguous identification. We have developed a confirmation method which uses liquid/liquid extraction, followed by room temperature Girard P derivatization, and analysis using LC/MS‐ToF. We observe a number of advantages over conventional GC/MS analysis. Analysis time is decreased. Sensitivity is increased, resulting in limits of detection of 2 and 0.5 ng/ml for testosterone and epitestosterone, respectively. The number of diagnostic qualifier ions is also increased allowing more confident identification of the analytes. Finally, while this method has been developed on a QToF instrument, it should be easily transferable to any tandem LC/MS/MS system. Copyright © 2008 John Wiley & Sons, Ltd.
MALDI‐TOF MS Coupled with Collision‐Induced Dissociation (CID) Measurements of Poly(methyl methacrylate)
Authors: Baumgaertel Anja , Becer C. Remzi , Gottschaldt Michael , Schubert Ulrich S. 
Published: June 2008

AbstractMatrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) was chosen for an in‐detail analysis of poly(methyl methacrylate) (PMMA) in order to determine the possible fragmentation mechanism with the help of collision‐induced dissociation (CID). All experiments were performed on a well‐defined PMMA standard and were optimized for sample preparation and measurement conditions of both MS and MS/MS. In order to investigate the fragmentation pathways, two parent peaks—both charged with sodium (m/z = 1 625.9 and 2 226.2 Da, respectively)—were selected, thus permitting the examination of possible cleavages, and reaction pathways. For both chosen peaks, the MALDI‐TOF MS/MS spectra revealed four fragmentation series that could be explained by single or multiple main chain scissions and secondary reactions of the PMMA side groups. According to the molar mass of the fragments, a loss or migration of the side group to the end of the free radical, followed by a β‐scission, was favored. These insights are the first steps toward the construction of a library with fragments and fragmentation pathways, complementary to proteomics libraries, in order to obtain fast and automated identification of substances.magnified image
The Maximum Likelihood Ensemble Filter as a non‐differentiable minimization algorithm
Authors: Zupanski Milija , Navon I. Michael , Zupanski Dusanka 
Published: June 2008

AbstractThe Maximum Likelihood Ensemble Filter (MLEF) equations are derived without the differentiability requirement for the prediction model and for the observation operators. The derivation reveals that a new non‐differentiable minimization method can be defined as a generalization of the gradient‐based unconstrained methods, such as the preconditioned conjugate‐gradient and quasi‐Newton methods. In the new minimization algorithm the vector of first‐order increments of the cost function is defined as a generalized gradient, while the symmetric matrix of second‐order increments of the cost function is defined as a generalized Hessian matrix. In the case of differentiable observation operators, the minimization algorithm reduces to the standard gradient‐based form.The non‐differentiable aspect of the MLEF algorithm is illustrated in an example with one‐dimensional Burgers model and simulated observations. The MLEF algorithm has a robust performance, producing satisfactory results for tested non‐differentiable observation operators. Copyright © 2008 Royal Meteorological Society
A wavelet‐coefficient score for comparison of two‐dimensional climatic‐data fields
Authors: Livina V. N. , Edwards N. R. , Goswami S. , Lenton T. M. 
Published: June 2008

AbstractA single‐valued wavelet‐coefficient score is proposed for assessing the similarity of two‐dimensional climate‐data fields (matrices). It is based on the comparison of wavelet‐decomposition coefficients by means of a mean‐squared‐error skill score. Two applications of the score are illustrated: comparison of real and model maps; and comparison of two model maps. The issue of missing data is addressed, and the evaluation is performed both when data are available over continents or oceans only, and when they are available globally, over the whole domain.The score is tested against the conventional two‐dimensional correlation coefficient, which is widely used in evaluating forecast performance. We show that the score eliminates random correlations, which the correlation coefficient incorrectly detects as similarity of fields that are actually dissimilar. The technique is first applied to the case of non‐square matrices (spatial fields) of the same dimensions (spatial grids), and then to the most general case of matrices of different dimensions, by applying some necessary interpolations. The technique is tested on data from several runs of different GENIE models. It is then applied to the comparison of climate data (global fields of temperature and specific humidity) from the NCEP and ECMWF reanalyses and from the HadCM3 and GENIE models. To study the time evolution of a given 2D field, we analyse a plot of the score values for consecutive time slices, thus visualizing the temporal dynamics. The technique is particularly useful for automated comparison of large sets of 2D data, where direct visualization is best avoided. The score may be generalized for comparison of data of higher dimensions, in particular 3D ocean fields. Copyright © 2008 Royal Meteorological Society
Turbulence energetics in stably stratified geophysical flows: Strong and weak mixing regimes
Authors: Zilitinkevich S. S. , Elperin T. , Kleeorin N. , Rogachevskii I. , Esau I. , Mauritsen T. , Miles M. W. 
Published: June 2008

AbstractTraditionally, turbulence energetics is characterised by turbulent kinetic energy (TKE) and modelled using solely the TKE budget equation. In stable stratification, TKE is generated by the velocity shear and expended through viscous dissipation and work against buoyancy forces. The effect of stratification is characterised by the ratio of the buoyancy gradient to squared shear, called the Richardson number, Ri. It is widely believed that at Ri exceeding a critical value, Ric, local shear cannot maintain turbulence, and the flow becomes laminar. We revise this concept by extending the energy analysis to turbulent potential and total energies (TPE, and TTE = TKE + TPE), consider their budget equations, and conclude that TTE is a conservative parameter maintained by shear in any stratification. Hence there is no ‘energetics Ric’, in contrast to the hydrodynamic‐instability threshold, Ric−instability, whose typical values vary from 0.25 to 1. We demonstrate that this interval, 0.25 < Ri < 1, separates two different turbulent regimes: strong mixing and weak mixing rather than the turbulent and the laminar regimes, as the classical concept states. This explains persistent occurrence of turbulence in the free atmosphere and deep ocean at Ri ≫ 1, clarifies the principal difference between turbulent boundary layers and free flows, and provides the basis for improving operational turbulence closure models. Copyright © 2008 Royal Meteorological Society
Impact of observational error on the validation of ensemble prediction systems
Authors: Candille G. , Talagrand O. 
Published: June 2008

AbstractEnsemble prediction systems (EPSs) are usually validated under the assumption that the verifying observations are exact. In this paper, two methods are considered for taking observation errors into account. In the ‘perturbed‐ensemble’ method, which has already been studied by other authors, the predicted ensemble elements are randomly perturbed in a way that is consistent with the assumed observation error. In the ‘observational‐probability’ method, which is new, a verifying observation is considered as defining, together with the assumed associated error, a probability distribution. All standard scores for evaluation of EPSs (reliability diagram, Brier score, ranked probability score (RPS), continuous RPS (CRPS), relative‐operating‐characteristics (ROC) curve area), with the exception of the rank histogram, remain defined in this second method. In particular, the classical reliability–resolution decomposition of the Brier score, and of its extension to the RPS and CRPS, remain defined.Numerical simulations, partially supported by theoretical considerations, show that, with respect to the case when observation errors are ignored, the perturbed‐ensemble method improves reliability, as well as the ROC score, while it has no significant impact on resolution, as measured by the Brier score. The observational‐probability method, on the other hand, degrades reliability and the ROC score, but improves resolution.With respect to the ‘real’ performance of the system (i.e. the one that would be diagnosed if no error were present), reliability is unchanged in the perturbed‐ensemble method, while resolution and the ROC score are degraded. The observational‐probability method degrades reliability and the ROC score. As for resolution, an optimum value of the observational error is found, below which resolution is improved.Diagnostics performed on the operational EPS of the Canadian Meteorological Centre confirm the results of the simulations as to the consequences of ignoring observation errors, or on the contrary of taking them into account through either of the two methods. The significance of those various results is discussed. This article replaces a previously published version (Q. J. R. Meteorol. Soc. 134(631): 509–521, DOI: 10.1002/qj.221). Copyright © 2008 Royal Meteorological Society
Polymer‐Wrapped Peptide Nanotubes: Peptide‐Grafted Polymer Mass Impacts Length and Diameter
Authors: Couet Julien , Biesalski Markus 
Published: June 2008

AbstractThe external structure of polymer‐wrapped nanotubes resembles that of small nanorods with a core/shell morphology, where the core consists of a self‐assembled peptide nanotube surrounded by a soft polymeric coat. The length and the diameter of the nanorods are investigated as a function of the molar mass of the peptide‐grafted macromolecules by statistical atomic force microscopy cross‐section analysis of dry nanorods adsorbed to a solid substrate. With increasing molar mass of the grafted polymers, the height increases from less than 2 nm up to more than 10 nm, and the length of the objects decreases from about 120 nm to about 30 nm. Additional analysis suggests excluded volume interactions between the highly grafted polymer chains on the surface of the peptide nanotube to be the major driving force for the shortening of the nanotubes. The present findings may provide a base for fine tuning the dimensions of such novel bioinspired nanomaterials.
Leptin receptor deficiency is associated with upregulation of cannabinoid 1 receptors in limbic brain regions
Authors: Thanos Panayotis K. , Ramalhete Roberto C. , Michaelides Michael , Piyis Yianni K. , Wang Gene‐Jack , Volkow Nora D. 
Published: June 2008

AbstractLeptin receptor dysfunction results in overeating and obesity. Leptin regulates hypothalamic signaling that underlies the motivation to hyperphagia, but the interaction between leptin and cannabinoid signaling is poorly understood. We evaluated the role of cannabinoid 1 receptors (CB1R) in overeating and the effects of food deprivation on CB1R in the brain. One‐month‐old Zucker rats were divided into unrestricted and restricted (fed 70% of unrestricted rats) diet groups and maintained until adulthood (4 months). Levels of relative binding sites of CB1R (CB1R binding levels) were assessed using [3H] SR141716A in vitro autoradiography. These levels were higher (except cerebellum and hypothalamus) at 4 months than at 1 month of age. One month CB1R binding levels for most brain regions did not differ between Ob and Lean (Le) rats (except in frontal and cingulate cortices in Le and in the hypothalamus in Ob). Four month Ob rats had higher CB1R binding levels than Le in most brain regions and food restriction was associated with higher CB1R levels in all brain regions in Ob, but not in Le rats. CB1R binding levels increased between adolescence and young adulthood which we believe was influenced by leptin and food availability. The high levels of CB1R in Ob rats suggest that leptin's inhibition of food‐intake is in part mediated by downregulation of CB1R and that leptin interferes with CB1R upregulation under food‐deprivation conditions. These results are consistent with prior findings showing increased levels of endogenous cannabinoids in the Ob rats corroborating the regulation of cannabinoid signaling by leptin. Synapse 62:637–642, 2008. Published 2008 Wiley‐Liss, Inc.