bluuebunny/crossref_metadata_2025_split huggingface dataset:
Zwitterionic Aza‐Claisen Rearrangements Controlled by Pyrrolidine Auxiliaries – Useful Key Steps in Convergent Enantioselective Syntheses
Authors: Friedemann Nora M. , Härter Alice , Brandes Sebastian , Groß Steffen , Gerlach Dorothea , Münch Winfried , Schollmeyer Dieter , Nubbemeyer Udo 
Published: March 2012

AbstractChiral pyrrolidine substituents served as efficient auxiliaries in diastereoselective zwitterionic ketene aza‐Claisen rearrangements. Palladium‐catalysed N‐allylation starting from optically active proline and prolinol derivatives, as well as from (2S,5S)‐2,5‐dimethoxymethylpyrrolidine, gave various allylamines bearing trisubstituted olefin moieties. Treatment with complex carboxylic acid fluorides in the presence of trimethylaluminium induced activated ketene addition to the nitrogen and subsequent [3,3] sigmatropic rearrangement to give γ,δ‐unsaturated amides with excellent simple diastereoselectivities and up to 11:1 auxiliary‐induced diastereomeric ratios. Cleavage of the pyrrolidine amide was achieved through iodolactonization, with the option for recovery of the auxiliary pyrrolidine. The stereochemical outcomes of the rearrangements and the iodocyclizations were established by X‐ray and NOEDS analyses of suitable amides and lactones. Overall, both enantiomers were accessible selectively. The optically active amides and lactones of defined configurations formed in this way should be useful as key intermediates in convergent steroidal natural and pharmaceutically important product synthesis.
An efficient algorithm based on the differential quadrature method for solving Navier–Stokes equations
Authors: Hamed Meraji S. , Ghaheri Abbas , Malekzadeh Parviz 
Published: March 2012

SUMMARYIn this paper, an approach to improve the application of the differential quadrature method for the solution of Navier–Stokes equations is presented. In using the conventional differential quadrature method for solving Navier–Stokes equations, difficulties such as boundary conditions' implementation, generation of an ill conditioned set of linear equations, large memory storage requirement to store data, and matrix coefficients, are usually encountered. Also, the solution of the generated set of equations takes a long running time and needs high computational efforts. An approach based on the point pressure–velocity iteration method, which is a variant of the Newton–Raphson relaxation technique, is presented to overcome these problems without losing accuracy. To verify its performance, four cases of two‐dimensional flows in single and staggered double lid‐driven cavity and flows past backward facing step and square cylinder, which have been often solved by researchers as benchmark solution, are simulated for different Reynolds numbers. The results are compared with existing solutions in the open literature. Very good agreement with low computational efforts of the approach is shown. It has been concluded that the method can be applied easily and is very time efficient. Copyright © 2012 John Wiley & Sons, Ltd.
BMP‐2 immobilized on nanocrystalline diamond–coated titanium screws; demonstration of osteoinductive properties in irradiated bone
Authors: Kloss Frank R. , Singh Sarvpreet , Hächl Oliver , Rentenberger Julia , Auberger Thomas , Kraft Anna , Klima Guenther , Mitterlechner Thomas , Steinmüller‐Nethl Doris , Lethaus Bernd , Rasse Michael , Lepperdinger Guenter , Gassner Robert 
Published: March 2012

AbstractBackgroundIrradiation results in impaired bone healing. Thus, osteosynthesis procedures are afflicted with increased failure rates. To improve osseointegration bone morphogenetic protein‐2 (BMP‐2) immobilized on nanocrystalline diamond (NCD)–coated implant surfaces might be 1 solution.MethodsBy 4 weeks after irradiation of pig's mandible with a dose of 60 Gy a fracture was accomplished. Osteosynthesis was performed either with titanium osteosynthesis screws or NCD‐coated screws with immobilized BMP‐2. Nonirradiated animals served as control. After 1, 2, 4, and 8 weeks screws were evaluated histologically. Bone biopsies were gained to extract mesenchymal stem or precursor cells (MSCs).ResultsMSCs after irradiation demonstrated a behavior comparable to that of unirradiated cells. Consequently, immobilized BMP‐2 resulted in an initial increased bone contact ratio (p = .014) but demonstrated no sustainable effect compared with osseointegration in nonirradiated bone (p = .08).ConclusionImmobilized BMP‐2 demonstrates an osteoinductive effect in irradiated bone. MSCs as effector cells possess protective mechanisms to overcome the destructive effect of irradiation. © 2012 Wiley Periodicals, Inc. Head Neck, 2013
Phenotypic fidelity (or not?) of epithelial cells in the liver
Authors: Malato Y , Naqvi S , Schurmann N , Ng R , Wang B , Zape J 
Published: March 2012

Abstract

Recent evidence has contradicted the prevailing view that homeostasis and regeneration of the adult liver are mediated by self duplication of lineage-restricted hepatocytes and biliary epithelial cells. These new data suggest that liver progenitor cells do not function solely as a backup system in chronic liver injury; rather, they also produce hepatocytes after acute injury and are in fact the main source of new hepatocytes during normal hepatocyte turnover. In addition, other evidence suggests that hepatocytes are capable of lineage conversion, acting as precursors of biliary epithelial cells during biliary injury. To test these concepts, we generated a hepatocyte fate-tracing model based on timed and specific Cre recombinase expression and marker gene activation in all hepatocytes of adult Rosa26 reporter mice with an adenoassociated viral (AAV) vector. We found that newly formed hepatocytes derived from preexisting hepatocytes in the normal liver and that liver progenitor cells contributed minimally to acute hepatocyte regeneration. Further, we found no evidence that biliary injury induced conversion of hepatocytes into biliary epithelial cells. These results therefore restore the previously prevailing paradigms of liver homeostasis and regeneration. In addition, our new vector system will be a valuable tool for timed, efficient, and specific loop out of floxed sequences in hepatocytes.
Development and validation of a simple assay for the determination of cholinesterase activity in whole blood of laboratory animals
Authors: Naik Ramachandra S. , Liu Weiyi , Saxena Ashima 
Published: March 2012

ABSTRACTCurrent methods for measuring acetylcholinesterase (AChE) activities in whole blood use butyrylcholinesterase (BChE)‐selective inhibitors. However, the poor selectivity of these inhibitors results in the inhibition of AChE activity to some degree, leading to errors in reported values. The goal of this study was to develop and validate a simple assay for measuring AChE and BChE activities in whole blood from humans as well as experimental animals. Blood was fractionated into plasma and erythrocytes, and cholinesterase activities were titrated against ethopropazine and (−)‐huperzine A to determine the lowest concentration of ethopropazine that inhibited BChE completely without affecting AChE activity and the lowest concentration of (−)‐huperzine A that inhibited AChE completely without interfering with BChE activity. Results indicate that 20 µm ethopropazine can be successfully used for the accurate measurement of AChE activity in blood from humans as well as animals. Use of (−)‐huperzine A is not required for measuring BChE activity in normal or ‘exposed’ blood samples. The method was validated for blood from several animal species, including mice, rats, guinea pigs, dogs, minipigs, and African green, cynomolgus and rhesus monkeys. This method is superior to all reported methods, does not require the separation of erythrocyte and plasma fractions, and is suitable for measuring cholinesterase activities in fresh or frozen blood from animals that were exposed to nerve agents or those that were administered high doses of BChE. The method is simple, direct, reproducible, and reliable and can easily be adapted for high‐throughput screening of blood samples. Published 2012. This article is a US Government work and is in the public domain in the USA.
Efficient gene therapy based targeting system for the treatment of inoperable tumors
Authors: Wirth Thomas , Pikkarainen Jere Tuomas , Samaranayake Haritha Dhammika , Lehtolainen‐Dalkilic Pauliina , Lesch Hanna Pirita , Airenne Kari Juhani , Marjomäki Varpu , Ylä‐Herttuala Seppo Pasi Antero 
Published: March 2012

AbstractBackgroundA considerable percentage of tumors are not amenable to surgery. We have designed a simple and powerful targeting system that offers an alternative option for the multi‐component pre‐targeting strategies used clinically. This targeting system can be used for any type of solid tumors independent of the tumor type, thereby omitting the need to engineer unique antibodies for each specific application or tumour type. In the present study, we show the expression of a chimeric fusion protein, which contains the low‐density lipoprotein receptor transmembrane domains and avidin, after local gene transfer and its ability to bind biotinylated compounds in vivo.MethodsSemliki Forest virus and lentivirus vectors were used to express the fusion protein with a high affinity binding site for biotinylated compounds in the tumor. Three different animal models and imaging modalities were used for the demonstration of the functionality and efficacy of the targeting system in vitro and in vivo.ResultsWe demonstrate targeting of biotinylated compounds after local gene transfer in vivo using two different gene transfer vectors. The findings were confirmed by immunohistochemistry, single‐photon emission computed tomography and magnetic resonance imaging. The therapeutic efficacy was tested in a syngeneic rat glioma model by injecting biotinylated‐90Yttrium into the tail vein of glioma bearing rats. The study demonstrates that animals, which were treated by using the gene therapy based targeting system, lived significantly longer than control animals.ConclusionsOur gene therapy based targeting system is a promising tool for the treatment of inoperable tumors and other disease conditions, as well as diagnostic imaging. Copyright © 2012 John Wiley & Sons, Ltd.
Use of continuously MR tagged imaging for automated motion assessment in the abdomen: A feasibility study
Authors: Sprengers Andre M.J. , van der Paardt Marije P. , Zijta Frank M. , Caan Matthan W.A. , Lamerichs Rolf M. , Nederveen Aart J. , Stoker Jaap 
Published: March 2012

AbstractPurpose:To investigate the feasibility of measuring motion in the abdomen using a continuously tagged magnetic resonance imaging sequence.Materials and Methods:To assess (nonperiodic) motion in the abdomen, a nontriggered, continuously tagged transient field echo (TFE) sequence was implemented that acquires one complete 3D dataset per prepulse after a fixed delay. In postprocessing, a frequency analysis approach was developed for compact reviewing of the data and noise suppression. For proof of principle, a simulation was made and one free‐breathing dynamic in vivo scan was acquired in a healthy volunteer. During the dynamic scan the volunteer received glucagon intravenously.Results:The simulation showed that this frequency analysis enables the extraction of motion at low signal‐to‐noise ratio levels. Motion information was successfully gathered from the in vivo scan. The decline in bowel motion caused by the administration of glucagon could be quantitatively measured using the continuously tagged sequence.Conclusion:Continuously tagged imaging in the abdomen for the purpose of automated gathering of motion information is feasible and could aid the study of bowel motion. J. Magn. Reson. Imaging 2012;36:492–497. © 2012 Wiley Periodicals, Inc.
Nucleation and growth kinetics of silver nanoparticles prepared by glutamic acid in micellar media
Authors: Zaheer Zoya , Rafiuddin  
Published: March 2012

AbstractThe title reaction in the presence of cetyltrimethylammonium bromide (CTAB) has been followed spectrophotometrically at 325 nm. In the process of reduction, characteristic surface resonance plasmon absorption peaks appear for the silver nanoparticles (NP) and the intensities increase with reaction time. UV–visible spectra suggest that [CTAB] and glutamic acid influence the morphology of the silver NP and act as shape‐directing agents, whereas [Ag+] has no effect. The effects of the total [glutamic acid], [CTAB], and [Ag+] on the apparent rate constants of silver NP formation are determined. The sigmoidal curve of absorbance versus reaction time indicates an autocatalytic path involved in the growth process. The α‐amino and COOH groups undergo chemical transformation (oxidative deamination and decarboxylation). The particles are spherical in shape with average diameters ranging between 12 and 25 nm, and their size distribution is wide. A plausible mechanism has been proposed with the following rate law: (d[silver sol])/dt = k[Ag+][Glutamic acid]T. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 680–691, 2012
Impact of topical nasal steroid therapy on symptoms of nasal polyposis
Authors: Rudmik Luke , Schlosser Rodney J. , Smith Timothy L. , Soler Zachary M. 
Published: March 2012

AbstractObjectives/Hypothesis:Topical steroid therapy is an important strategy in the management of chronic rhinosinusitis (CRS) with nasal polyposis. The objective of this study was to determine the impact of topical steroid therapy on nasal symptoms in patients with nasal polyposis.Study Design:Systematic review with meta‐analysis using standardized methodology.Methods:Study inclusion criteria included: randomized, placebo controlled trials, nasal polyposis, and topical steroid therapy. Exclusion criteria included: failure to report at least one symptom‐based outcome measure, concurrent use of systemic steroids, or mixed CRS cohorts (polyp and nonpolyp patients). Quantitative analysis was performed using a random effect model. The PRISMA guidelines for meta‐analysis reporting were followed.Results:A total of 19 studies fulfilled eligibility. Seven studies were excluded from the meta‐analysis due to significant heterogeneity in outcome reporting. A total of 12 studies were combined for quantitative analysis and demonstrated a pooled risk ratio of 1.72 (95% confidence interval, 1.41–2.09), indicating a significant improvement in nasal symptoms. All three topical steroid preparations (fluticasone, mometasone, and budesonide) resulted in symptom improvement. All seven studies excluded from the meta‐analysis qualitatively confirmed the overall findings.Conclusions:Topical nasal steroid therapy improves nasal symptoms in CRS patients with nasal polyposis. Future studies will need to evaluate the impact on quality of life, preferably using validated disease‐specific instruments.
Address Practices and Social Relationships in European Languages
Authors: Norrby Catrin , Warren Jane 
Published: March 2012

AbstractAddress practices – the way people use second‐person pronouns, first names, last names and titles, and other terms to address one another – are fundamental to expressing social relationships. They reflect cultural values and can tell us a great deal about social structures and change. This article gives an overview of recent research on address practices, focusing on three European languages – French, German and Swedish. It follows theoretical developments in the study of address from the 1960s onwards, and examines how address practices have evolved in French, German and Swedish since the socio‐political upheavals of that decade. It is argued that the notions of social distance and common ground are central to an understanding of address choice in these languages.
Materials and Corrosion 3/2012
Authors: Schönberger A. , Virtanen S. , Giese V. , Schröttner H. , Spießberger C. 
Published: March 2012

Cover: Grinding surface pattern of steel, coated with thick‐film E‐coat (40 μm) after a stone chipping defect exposed in an accelerated corrosion test (BMW AA‐0224) showing blistering and a corrosion progress. The small image represents a cross section of the sample which was carried out on the FEI Nanolab Nova200 dual‐beam focused ion beam (DB‐FIB – FEI company, Eindhoven, The Netherlands). For the single wide cut (1350 μm by 30 μm) a beam current of 20nA at an acceleration voltage of 20kV was used. Afterwards the part in front of the cross section was removed manually with a scalpel blade. Additional ion beam cross section cleaning with 7nA at 20kV was performed and images were taken with the electron beam using the Everhart‐Thornley detector at 52° tilt angle and an acceleration voltage of 5kV.Grinding surface pattern and analyzes were investigated at the Austrian Centre for Electron Microscopy and Nanoanalysis (ZFE‐Graz), Graz‐Austria, by Dr. J. Wagner.More detailed information can be found in: A. Schönberger, S. Virtanen, V. Giese, H. Schröttner, C. Spießberger, Non‐destructive detection of corrosion applied to steel and galvanized steel coated with organic paints by the pulsed phase thermography, Materials and Corrosion 2012, 63, 195.
Entorhinal cortex atrophy differentiates Parkinson's disease patients with and without dementia
Authors: Goldman Jennifer G. , Stebbins Glenn T. , Bernard Bryan , Stoub Travis R. , Goetz Christopher G. , deToledo‐Morrell Leyla 
Published: March 2012

AbstractVolumetric measures of mesial temporal lobe structures on MRI scans recently have been explored as potential biomarkers of dementia in patients with PD, with investigations primarily focused on hippocampal volume. Both in vivo MRI and postmortem tissue studies in Alzheimer's disease, however, demonstrate that the entorhinal cortex (ERC) is involved earlier in disease‐related pathology than the hippocampus. The ERC, a region integral in declarative memory function, projects multimodal sensory information to the hippocampus through the perforant path. In PD, ERC atrophy, as measured on MRI, however, has received less attention, compared to hippocampal atrophy. We compared ERC and hippocampal atrophy in 12 subjects with PD dementia including memory impairment, 14 PD subjects with normal cognition, and 14 healthy controls with normal cognition using manual segmentation methods on MRI scans. Though hippocampal volumes were similar in the two PD cognitive groups, ERC volumes were substantially smaller in the demented PD subjects, compared to cognitively normal PD subjects (P < 0.05). In addition, normalized ERC and hippocampal volumes for right and left hemispheres were significantly lower in the demented PD group, compared to healthy controls. Our findings suggest that ERC atrophy differentiates demented and cognitively normal PD subjects, in contrast to hippocampal atrophy. Thus, ERC atrophy on MRI may be a potential biomarker for dementia in PD, particularly in the setting of memory impairment. © 2012 Movement Disorder Society
Acquired neurosyphilis presenting as movement disorders
Authors: Shah Binit B. , Lang Anthony E. 
Published: March 2012

AbstractAfter a significant decline in the second half of the 20th century, rates of infection with syphilis are again on the rise. Long known as the “great mimicker,” syphilitic infection can be difficult to recognize clinically and this particularly holds true for neurologic manifestations of the disease. Gait dysfunction and sensory ataxia have been historically well described in neurosyphilis literature; however, other movement disorders have been reported to a lesser extent. Here we review reports of movement disorders in acquired neurosyphilis. Given its increasing incidence, it is important to be cognizant of its diverse presentation and retain a high index of suspicion for syphilis, particularly as it is completely curable in the early stages. © 2012 Movement Disorder Society
Reconstruction of divergence‐free velocity fields from cine 3D phase‐contrast flow measurements
Authors: Busch Julia , Giese Daniel , Wissmann Lukas , Kozerke Sebastian 
Published: March 2012

AbstractThree‐dimensional phase‐contrast velocity vector field mapping shows great potential for clinical applications; however measurement inaccuracies may limit the utility and robustness of the technique. While parts of the error in the measured velocity fields can be minimized by background phase estimation in static tissue and magnetic field monitoring, considerable inaccuracies remain. The present work introduces divergence‐reduction processing of 3D phase‐contrast flow data based on a synergistic combination of normalized convolution and divergence‐free radial basis functions. It is demonstrated that this approach effectively addresses erroneous flow for image reconstructions from both fully sampled and undersampled data. Using computer simulations and in vivo data acquired in the aorta of healthy subjects and a stenotic valve patient it is shown that divergence arising from measurement imperfections can be reduced by up to 87% resulting in improved vector field representations. Based on the results obtained it is concluded that integration of the divergence‐free condition into postprocessing of vector fields presents an efficient approach to addressing flow field inaccuracies. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Single‐shot echo‐planar imaging with Nyquist ghost compensation: Interleaved dual echo with acceleration (IDEA) echo‐planar imaging (EPI)
Authors: Poser Benedikt A. , Barth Markus , Goa Pål‐Erik , Deng Weiran , Stenger V. Andrew 
Published: March 2012

AbstractEcho planar imaging (EPI) is most commonly used for blood oxygen level‐dependent fMRI, owing to its sensitivity and acquisition speed. A major problem with EPI is Nyquist (N/2) ghosting, most notably at high field. EPI data are acquired under an oscillating readout gradient and hence vulnerable to gradient imperfections such as eddy current delays and off‐resonance effects, as these cause inconsistencies between odd and even k‐space lines after time reversal. We propose a straightforward and pragmatic method herein termed “interleaved dual echo with acceleration (IDEA) EPI”: two k‐spaces (echoes) are acquired under the positive and negative readout lobes, respectively, by performing phase encoding blips only before alternate readout gradients. From these two k‐spaces, two almost entirely ghost free images per shot can be constructed, without need for phase correction. The doubled echo train length can be compensated by parallel imaging and/or partial Fourier acquisition. The two k‐spaces can either be complex averaged during reconstruction, which results in near‐perfect cancellation of residual phase errors, or reconstructed into separate images. We demonstrate the efficacy of IDEA EPI and show phantom and in vivo images at both 3 T and 7 T. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.
Super‐resolution for multislice diffusion tensor imaging
Authors: Poot Dirk H. J. , Jeurissen Ben , Bastiaensen Yannick , Veraart Jelle , Van Hecke Wim , Parizel Paul M. , Sijbers Jan 
Published: March 2012

AbstractDiffusion weighted magnetic resonance images are often acquired with single shot multislice imaging sequences, because of their short scanning times and robustness to motion. To minimize noise and acquisition time, images are generally acquired with either anisotropic or isotropic low resolution voxels, which impedes subsequent posterior image processing and visualization. In this article, we propose a super‐resolution method for diffusion weighted imaging that combines anisotropic multislice images to enhance the spatial resolution of diffusion tensor data. Each diffusion weighted image is reconstructed from a set of arbitrarily oriented images with a low through‐plane resolution. The quality of the reconstructed diffusion weighted images was evaluated by diffusion tensor metrics and tractography. Experiments with simulated data, a hardware DTI phantom, as well as in vivo human brain data were conducted. Our results show a significant increase in spatial resolution of the diffusion tensor data while preserving high signal to noise ratio. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.