bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivation and Reuse of a Hydrotreating Spent Catalyst for Cyclohexene Conversion
Authors: Ahmed H. S. , Menoufy M. F. 
Published: May 2009

AbstractA comparative study has been made on the efficiency of leaching, using different concentrations of oxidized oxalic acid, and thermally treating techniques to reactivate a Ni‐Mo‐spent hydrotreating catalyst. The reactivation of the treated catalysts was performed in a pulse microcatalytic reactor under atmospheric pressure of hydrogen and reaction temperatures ranging from 250 °C to 450 °C using cyclohexene as model hydrocarbon. The studies revealed that a decoking spent catalyst after leaching using a low concentration (2 %) enhanced its physical characteristics (surface area and average pore diameter) and catalytic activity towards maximum cyclohexene hydrogenation and hydroisomerization reactions at 300 °C and 350 °C, respectively.
Magnetostructural Correlations in Tetrairon(III) Single‐Molecule Magnets
Authors: Gregoli Luisa , Danieli Chiara , Barra Anne‐Laure , Neugebauer Petr , Pellegrino Giovanna , Poneti Giordano , Sessoli Roberta , Cornia Andrea 
Published: May 2009

AbstractTunable single‐molecule magnets: The spin‐level landscape in a series of FeIII4 single‐molecule magnets with propeller‐like structure was analyzed by means of high‐frequency EPR spectroscopy. The zero‐field splitting parameter D of the ground S=5 spin state correlates strongly with the pitch of the propeller γ (see picture), and thus provides a simple link between molecular structure and magnetic behavior.magnified imageWe report three novel tetrairon(III) single‐molecule magnets with formula [Fe4(L)2(dpm)6] (Hdpm=2,2,6,6‐tetramethylheptane‐3,5‐dione), prepared by using pentaerythritol monoether ligands H3L=R′OCH2C(CH2OH)3 with R′=allyl (1), (R,S)‐2‐methyl‐1‐butyl (2), and (S)‐2‐methyl‐1‐butyl (3), along with a new crystal phase of the complex containing H3L=11‐(acetylthio)‐2,2‐bis(hydroxymethyl)‐ undecan‐1‐ol (4). High‐frequency EPR (HF‐EPR) spectra at low temperature were collected on powder samples in order to determine the zero‐field splitting (zfs) parameters in the ground S=5 spin state. In 1–4 and in other eight isostructural compounds previously reported, a remarkable correlation is found between the axial zfs parameter D and the pitch γ of the propeller‐like structure. The relationship is directly demonstrated by 1, which features both structurally and magnetically inequivalent molecules in the crystal. The dynamics of magnetization has been investigated by ac susceptometry, and the results analyzed by master‐matrix calculations. The large rhombicities of 2 and 3 were found to be responsible for the fast magnetic relaxation observed in the two compounds. However, complex 3 shows an additional faster relaxation mechanism which is unaccounted for by the set of spin Hamiltonian parameters determined by HF‐EPR.
Using the stereotype content model to examine group depictions in Fascism: An archival approach
Authors: Durante Federica , Volpato Chiara , Fiske Susan T. 
Published: May 2009

AbstractThe Stereotype Content Model (SCM) suggests potentially universal intergroup depictions. If universal, they should apply across history in archival data. Bridging this gap, we examined social groups descriptions during Italy's Fascist era. In Study 1, articles published in a Fascist magazine—La Difesa della Razza—were content analyzed, and results submitted to correspondence analysis. Admiration prejudice depicted ingroups; envious and contemptuous prejudices depicted specific outgroups, generally in line with SCM predictions. No paternalistic prejudice appeared; historical reasons might explain this finding. Results also fit the recently developed BIAS Map of behavioral consequences. In Study 2, ninety‐six undergraduates rated the content‐analysis traits on warmth and competence, without knowing their origin. They corroborated SCM's interpretations of the archival data. Copyright © 2009 John Wiley & Sons, Ltd.
The effect of essentialism in settings of historic intergroup atrocities
Authors: Zagefka Hanna , Pehrson Samuel , Mole Richard C. M. , Chan Eva 
Published: May 2009

AbstractThree studies tested the effects of essentialist beliefs regarding the national ingroup in situations where a perpetrator group has inflicted harm on a victim group. For members of the perpetrator group, it was hypothesised that ‘essentialism’ has a direct positive association with ‘collective guilt’ felt as a result of misdeeds conducted by other ingroup members in the past. Simultaneously, it was hypothesised to have an indirect negative association with collective guilt, mediated by perceived threat to the ingroup. Considering these indirect and direct effects jointly, it was hypothesised that the negative indirect effect suppresses the direct positive effect, and that the latter would only emerge if perceived ‘ingroup threat’ was controlled for. This was tested in a survey conducted in Latvia among Russians (N = 70) and their feelings toward how Russians had treated ethnic Latvians during the Soviet occupation; and in a survey in Germany among Germans (N = 84), focussing on their feelings toward the Holocaust. For members of the victim group, it was hypothesised that essentialism would be associated with more anger and reluctance to forgive past events inflicted on other ingroup members. It was proposed that this effect would be mediated by feeling connected to the ingroup victims. This was tested in a survey conducted among Hong Kong Chinese and their feelings toward the Japanese and the Nanjing massacre (N = 56). Results from all three studies supported the hypotheses. Copyright © 2009 John Wiley & Sons, Ltd.
Model of twelve properties of a set of organic solvents with graph‐theoretical and/or experimental parameters
Authors: Pogliani Lionello 
Published: May 2009

AbstractTwelve properties of a highly heterogeneous class of organic solvents have been modeled with a graph‐theoretical molecular connectivity modified (MC) method, which allows to encode the core electrons and the hydrogen atoms. The graph‐theoretical method uses the concepts of simple, general, and complete graphs, where these last types of graphs are used to encode the core electrons. The hydrogen atoms have been encoded by the aid of a graph‐theoretical perturbation parameter, which contributes to the definition of the valence delta, δv, a key parameter in molecular connectivity studies. The model of the twelve properties done with a stepwise search algorithm is always satisfactory, and it allows to check the influence of the hydrogen content of the solvent molecules on the choice of the type of descriptor. A similar argument holds for the influence of the halogen atoms on the type of core electron representation. In some cases the molar mass, and in a minor way, special “ad hoc” parameters have been used to improve the model. A very good model of the surface tension could be obtained by the aid of five experimental parameters. A mixed model method based on experimental parameters plus molecular connectivity indices achieved, instead, to consistently improve the model quality of five properties. To underline is the importance of the boiling point temperatures as descriptors in these last two model methodologies. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
Egg sac silk of Theridiosoma gemmosum (Araneae: Theridiosomatidae)
Authors: Hajer Jaromír , Malý Jan , Hrubá Lenka , Řeháková Dana 
Published: May 2009

AbstractCocoons of Theridiosoma gemmosum consist of two main parts, the egg sac case and the stalk. The inner space of the egg sac case is filled with nonsticky flocculent silk. Measuring 600–800 nm in diameter, the flocculent threads are never made up of bundles of longitudinally oriented nanofibrils. The egg case wall consists of a lower layer of highly ordered threads and an upper layer of cover silk. The lower, permanently white layer consists of threads in a mesh‐like arrangement, the thicker threads being 4–6 μm and the thinner threads being 2–3 μm in diameter. Each thread is a bundle of parallel nanofibrils, with a diameter between 150 and 300 nm. The silk secretions of these fibers, emitted from spigots, are processed by legs. The upper layer of the egg case is applied to the threads of the lower layer by direct rubbing against its surface, i.e. without the use of legs. In the lower and middle part of the egg case, the accumulated secretion forms a virtually compact encrustation, whereas in the upper, conically shaped, part of the egg case where it becomes the stalk, this secretion becomes substantially scarcer. The stalk is a continuation of the egg case, its proximal part made of fibers similar to those forming the inner layer of the egg case wall. The distal part of the stalk continues towards the suspension area either as a compact bundle of parallel fibers, or the stalk forks into two bundles of roughly the same thickness, which continue towards the suspension area separately. On the surface of objects onto which cocoons are attached, the secretion of the piriform glands acts as an adhesive sheet. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.
Histological and ultrastructural aspects of the nasal complex in the harbour porpoise, Phocoena phocoena
Authors: Prahl Susanne , Huggenberger Stefan , Schliemann Harald 
Published: May 2009

AbstractDuring the evolution of odontocetes, the nasal complex was modified into a complicated system of passages and diverticulae. It is generally accepted that these are essential structures for nasal sound production. However, the mechanism of sound generation and the functional significance of the epicranial nasal complex are not fully understood. We have studied the epicranial structures of harbor porpoises (Phocoena phocoena) using light and electron microscopy with special consideration of the nasal diverticulae, the phonic lips and dorsal bursae, the proposed center of nasal sound generation. The lining of the epicranial respiratory tract with associated diverticulae is consistently composed of a stratified squamous epithelium with incomplete keratinization and irregular pigmentation. It consists of a stratum basale and a stratum spinosum that transforms apically into a stratum externum. The epithelium of the phonic lips comprises 70–80 layers of extremely flattened cells, i.e., four times more layers than in the remaining epicranial air spaces. This alignment and the increased number of desmosomes surrounding each cell indicate a conspicuous rigid quality of the epithelium. The area surrounding the phonic lips and adjacent fat bodies exhibits a high density of mechanoreceptors, possibly perceiving pressure differentials and vibrations. Mechanoreceptors with few layers and with perineural capsules directly subepithelial of the phonic lips can be distinguished from larger, multi‐layered mechanoreceptors without perineural capsules in the periphery of the dorsal bursae. A blade‐like elastin body at the caudal wall of the epicranial respiratory tract may act as antagonist of the musculature that moves the blowhole ligament. Bursal cartilages exist in the developmental stages from fetus through juvenile and could not be verified in adults. These histological results support the hypothesis of nasal sound generation for the harbor porpoise and display specific adaptations of the echolocating system in this species. J. Morphol. 2009. © 2009 Wiley‐Liss, Inc.
Fragmentation of deprotonated cyclic dipeptides by electrospray ionization mass spectrometry
Authors: Guo Yanchun , Cao Shuxia , Wei Donghui , Zong Xiangkun , Yuan Xingbo , Tang Mingsheng , Zhao Yufen 
Published: May 2009

AbstractThe fragmentation pathways of deprotonated cyclic dipeptides have been studied by electrospray ionization multi‐stage mass spectrometry (ESI‐MSn) in negative mode. The results showed that the fragmentation pathways of deprotonated cyclic dipeptides depended significantly on the different substituents, the side chains of amino acid residues at the diketopiperazine ring. In the spectra of deprotonated cyclic dipeptides, the ion [MHsubstituent radical]− was firstly observed in the ESI mode. The characteristic fragment ions [MHsubstituent radical]− and [MH(substituentH)]− could be used as the symbols of particular cyclic dipeptides. The hydrogen/deuterium (H/D) exchange experiment, the high‐resolution mass spectrometry (Q‐TOF) and theoretical calculations were used to rationalize the proposed fragmentation pathways and to verify the differences between the fragmentation pathways. The relative Gibbs free energies (ΔG) of the product ions and possible fragmentation pathways were estimated using the B3LYP/6–31++G(d, p) model. The results have some potential applications in the structural elucidation and interpretation of the mass spectra of homologous compounds and will enrich the gas‐phase ESI‐MS ion chemistry of cyclic dipeptides. Copyright © 2009 John Wiley & Sons, Ltd.
Magnetic resonance elastography in the liver at 3 Tesla using a second harmonic approach
Authors: Herzka D.A. , Kotys M.S. , Sinkus R. , Pettigrew R.I. , Gharib A.M. 
Published: May 2009

AbstractMagnetic resonance elastography (MRE) using mechanical stimulation has demonstrated diagnostic value and clinical promise in breast, liver, and kidney at 1.5 Tesla (T). However, MRE at 1.5T suffers from long imaging times and would benefit from greater signal‐to‐noise for more robust postprocessing. We present an MRE sequence modified for liver imaging at 3.0T. To avoid artifacts in the phase images, the sequence maintains a short TE by using a second harmonic approach, including stronger motion encoding gradients, shorter radio frequency pulses and an echo‐planar readout. Scan time was decreased by a factor of ∼2 relative to 1.5T by using an EPI readout and a higher density sampling of the phase waveform was used to calculate shear stiffness and viscosity. Localized (small region of interest) and global (whole‐liver region of interest) measurements in normal healthy subjects compared very favorably with previously published results at 1.5T. There was no significant difference between global and localized measures. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Self‐refocused spatial‐spectral pulse for positive contrast imaging of cells labeled with SPIO nanoparticles
Authors: Balchandani Priti , Yamada Mayumi , Pauly John , Yang Phillip , Spielman Daniel 
Published: May 2009

AbstractMRI has been used extensively to noninvasively track the location of cells labeled with superparamagnetic iron‐oxide nanoparticles (SPIOs) in vivo. Typically, SPIOs are employed as a negative contrast agent which makes it difficult to differentiate labeled cells from extraneous sources of inhomogeneity and actual voids in the image. As a result, several novel approaches have been put forth to obtain positive contrast from SPIOs. One technique proposed by Cunningham et al. utilizes spectrally selective pulses to excite and refocus spins in the vicinity of the SPIOs. Although the frequency selectivity of this technique provides effective positive contrast, the lack of slice selectivity results in interfering signal from sources of off‐resonance outside the slice of interest. We have developed a self‐refocused spatial‐spectral (SR‐SPSP) pulse to achieve slice‐selective spin‐echo imaging of off‐resonant spins. Using a self‐refocused pulse affords flexibility in echo‐time selection since the spin echo may be placed at any time after the end of the pulse. The spatial selectivity achieved by the SR‐SPSP RF pulse eliminates background signal from out‐of‐slice regions and reduces the on‐resonant water suppression requirements. Phantom and in vivo data demonstrate that positive contrast and slice‐selectivity are achieved using this novel RF pulse. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Cortical hypoperfusion in the B6.PS2APP mouse model for Alzheimer's disease: Comprehensive phenotyping of vascular and tissular parameters by MRI
Authors: Weidensteiner Claudia , Metzger Friedrich , Bohrmann Andreas Bruns Bernd , Kuennecke Basil , von Kienlin Markus 
Published: May 2009

AbstractFunction and morphology of the cerebral vasculature were studied in the amyloid (Aβ) plaque‐containing double‐transgenic (TG) B6.PS2APP Alzheimer's disease (AD) mouse model with MRI at an age range of 10 to 17 months. Perfusion, blood volume, and average vessel geometry were assessed in the brain and compared to age‐matched controls (wild‐type [WT] C57Bl/6). Additionally, the MR relaxation times T1, T2, and T were measured to detect potential pathological changes that might be associated with Aβ plaque depositions. Both decreased perfusion and decreased blood volume were observed in the occipital cortex in B6.PS2APP mice as compared to controls. A significant decrease in T1 and T2 was found in the frontal cortex and in the subiculum/parasubiculum. Immunohistochemistry confirmed plaque depositions in the cortex and in the subiculum/parasubiculum. In summary, our data indicate a reduced blood supply of B6.PS2APP mice in the occipital cortex that parallels the findings in cortical regions of patients with AD. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Multiple repetition time balanced steady‐state free precession imaging
Authors: Çukur Tolga , Nishimura Dwight G. 
Published: May 2009

AbstractAlthough balanced steady‐state free precession (bSSFP) imaging yields high signal‐to‐noise ratio (SNR) efficiency, the bright lipid signal is often undesirable. The bSSFP spectrum can be shaped to suppress the fat signal with scan‐efficient alternating repetition time (ATR) bSSFP. However, the level of suppression is limited, and the pass‐band is narrow due to its nonuniform shape. A multiple repetition time (TR) bSSFP scheme is proposed that creates a broad stop‐band with a scan efficiency comparable with ATR‐SSFP. Furthermore, the pass‐band signal uniformity is improved, resulting in fewer shading/banding artifacts. When data acquisition occurs in more than a single TR within the multiple‐TR period, the echoes can be combined to significantly improve the level of suppression. The signal characteristics of the proposed technique were compared with bSSFP and ATR‐SSFP. The multiple‐TR method generates identical contrast to bSSFP, and achieves up to an order of magnitude higher stop‐band suppression than ATR‐SSFP. In vivo studies at 1.5 T and 3 T demonstrate the superior fat‐suppression performance of multiple‐TR bSSFP. Magn Reson Med 62:193–204, 2009. © 2009 Wiley‐Liss, Inc.
A new approach to analysis of the impulse response function (IRF) in dynamic contrast‐enhanced MRI (DCEMRI): A simulation study
Authors: Fan Xiaobing , Karczmar Gregory S. 
Published: May 2009

AbstractThe purpose of this research was to develop a novel numerical procedure to deconvolute the arterial input function (AIF) from contrast concentration vs. time curves and to obtain the impulse response functions (IRFs) from dynamic contrast‐enhanced MRI (DCEMRI) data. Numerical simulations were performed to study variations of contrast concentration vs. time curves and the corresponding IRFs. The simulated contrast media concentration curves were generated by varying the parameters of an empirical mathematical model (EMM) within reasonable ranges based on a previous experimental study. The AIF was calculated from plots of contrast media concentration vs. time in muscle under assumption that they are well approximated by the “two‐compartment model” (TCM). A general simple mathematical model of the IRF was developed, and the physiological meaning of the model parameters was determined by comparing them with the widely accepted TCM. The results demonstrate that the deconvolution procedure developed in this research is a simple, robust, and useful technique. In addition, “impulse response analysis” leads to the derivation of novel parameters relating to tumor vascular architecture, and these new parameters may have clinical utility. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
A transmit/receive system for magnetic field monitoring of in vivo MRI
Authors: Barmet Christoph , De Zanche Nicola , Wilm Bertram J. , Pruessmann Klaas P. 
Published: May 2009

AbstractMagnetic field monitoring with NMR probes has recently been introduced as a means of measuring the actual spatiotemporal magnetic field evolution during individual MR scans. Receive‐only NMR probes as used thus far for this purpose impose significant practical limitations due to radiofrequency (RF) interference with the actual MR experiment. In this work these limitations are overcome with a transmit/receive (T/R) monitoring system based on RF‐shielded NMR probes. The proposed system is largely autonomous and protected against RF contamination. As a consequence the field probes can be positioned freely and permit monitoring imaging procedures of arbitrary geometry and angulation. The T/R approach is also exploited to simplify probe manufacturing and remove constraints on material choices. Probe miniaturization permits monitoring imaging scans with nominal resolutions on the order of 400 μm. The added capabilities of the new probes and system are demonstrated by first in vivo results, obtained with monitored gradient‐echo and spin‐echo echo‐planar imaging (EPI) scans. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.
Quantification of cerebral blood flow, cerebral blood volume, and blood–brain‐barrier leakage with DCE‐MRI
Authors: Sourbron Steven , Ingrisch Michael , Siefert Axel , Reiser Maximilian , Herrmann Karin 
Published: May 2009

AbstractDynamic susceptibility contrast MRI (DSC‐MRI) is the current standard for the measurement of Cerebral Blood Flow (CBF) and Cerebral Blood Volume (CBV), but it is not suitable for the measurement of Extraction Flow (EF) and may not allow for absolute quantification. The objective of this study was to develop and evaluate a methodology to measure CBF, CBV, and EF from T1‐weighted dynamic contrast‐enhanced MRI (DCE‐MRI). A two‐compartment modeling approach was developed, which applies both to tissues with an intact and with a broken Blood‐Brain‐Barrier (BBB). The approach was evaluated using measurements in normal grey matter (GM) and white matter (WM) and in tumors of 15 patients. Accuracy and precision were estimated with simulations of normal brain tissue. All tumor and normal tissue curves were accurately fitted by the model. CBF (mL/100 mL/min) was 82 ± 21 in GM and 23 ± 14 in WM, CBV (mL/100 mL) was 2.6 ± 0.8 in GM and 1.3 ± 0.4 in WM. EF (mL/100 mL/min) was close to zero in GM (−0.009 ± 0.05) and WM (−0.03 ± 0.08). Simulations show an overlap between CBF values of WM and GM, which is eliminated when Contrast‐to‐Noise (CNR) is improved. The model provides a consistent description of tracer kinetics in all brain tissues, and an accurate assessment of perfusion and permeability in reference tissues. The measurement sequence requires optimization to improve CNR and the precision in the perfusion parameters. With this approach, DCE‐MRI presents a promising alternative to DSC‐MRI for quantitative bolus‐tracking in the brain. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.