bluuebunny/crossref_metadata_2025 huggingface dataset:
ChemInform Abstract: Three‐Membered Heterocycles: Structure and Reactivity
Authors: Murphree S. Shaun
Published: December 2011

Review: 833 refs.
ChemInform Abstract: Oxadiazoles
Authors: Romeo Giovanni , Chiacchio Ugo
Published: December 2011

Review: 757 refs.
ChemInform Abstract: Five‐Membered Heterocycles with 2 Heteroatoms: O and S Derivatives
Authors: Wilkins David J.
Published: December 2011

Review: 266 refs.
ChemInform Abstract: Five‐Membered Heterocycles: 1,2‐Azoles. Part 2. Isoxazoles and Isothiazoles
Authors: Silva Artur M. S. , Tome Augusto C. , Pinho e Melo Teresa M. V. D. , Elguero Jose
Published: December 2011

Review: 416 refs.
ChemInform Abstract: The Chemistry of Benzodiazepines
Authors: Valdes Carlos , Bayod Miguel
Published: December 2011

Review: 244 refs.
ChemInform Abstract: Synthetic and Application Perspectives of Azapodophyllotoxins. Alternative Scaffolds of Podophyllotoxin
Authors: Kumar A. , Kumar V. , Alegria A. E. , Malhotra S. V.
Published: December 2011

Review: 42 refs.
ChemInform Abstract: The Chemistry of 2‐Azetidinones (β‐Lactams)
Authors: Alcaide Benito , Almendros Pedro , Luna Amparo
Published: December 2011

Review: 419 refs.
ChemInform Abstract: Fabrication and Functionalization of Hydrogels Through “Click” Chemistry
Authors: Yigit Sezin , Sanyal Rana , Sanyal Amitav
Published: December 2011

Review: 40 refs.
ChemInform Abstract: Higher‐Dimensional and Functional Molecular Wires: Toward Molecular Circuits
Authors: Tanaka Yuya , Akita Munetaka
Published: December 2011

Review: ca. 50 refs.
Correlation of biomechanics to tissue reaction in aortic aneurysms assessed by finite elements and [18F]–fluorodeoxyglucose–PET/CT
Authors: Maier Andreas , Essler Markus , Gee Michael W. , Eckstein Hans‐Henning , Wall Wolfgang A. , Reeps Christian
Published: December 2011

Mechanobiological interactions are essential for the adaption of the cardiovascular system to altered environmental and internal conditions, but are poorly understood with regard to abdominal aortic aneurysm (AAA) pathogenesis, growth and rupture. In the present study, we therefore calculated mechanical AAA quantities using nonlinear finite element methods and correlated these to [18F]‐fluorodeoxyglucose (FDG)‐metabolic activity in the AAA wall detected by positron emission tomography/computed tomography (PET/CT). The interplay between mechanics and FDG‐metabolic activity was analyzed in terms of maximum values and the three‐dimensional spatial relationship, respectively.

Fluorodeoxyglucose‐positron emission tomography/computed tomography (FDG‐PET/CT) data sets of n = 18 AAA patients were studied. Maximum FDG‐uptake (SUV max) in the AAA wall varied from 1.32 to 4.60 (average SUV max 3.31 ±0.87). Maximum wall stresses and strains ranged from 10.0 to 64.0 N∕cm2 (38.2 ±13.8  N∕cm2) and from 0.190 to 0.260 (0.222 ±0.023), respectively. SUV max was significantly correlated to maximum wall stress and strain (SUV max to stress: r = 0.71,p = 0.0005; SUV max to strain: r = 0.66,p = 0.0013). To evaluate the three‐dimensional spatial interaction between FDG‐uptake and acting wall stress, element‐wise correlations were performed. In all but 2 AAAs, positive element‐wise correlation of FDG‐uptake to wall stress was obtained, with the Pearson's correlation coefficient ranging from −0.168 to 0.738 ( 0.372 ±0.263).

The results indicate that mechanical stresses are correlated quantitatively and spatially to FDG‐uptake in the AAA wall. It is hypothesized that unphysiologically increased loading in the AAA wall triggers biological tissue reaction, such as inflammation or regenerative processes, causing elevated FDG‐metabolic activity. These findings strongly support experimental hypotheses of mechanotransduction mechanisms in vivo. Copyright © 2011 John Wiley & Sons, Ltd.
Heterogeneous Fenton Catalysts Based on Activated Carbon and Related Materials
Authors: Navalon Sergio , Dhakshinamoorthy Amarajothi , Alvaro Mercedes , Garcia Hermenegildo
Published: December 2011

The Fenton reaction is widely used for remediation of waste water and for the degradation of organic pollutants in water. Currently, there is considerable interest to convert the classical Fenton reaction, which consumes stoichiometric amounts of iron(II) salts, into a catalytic process that is promoted by a solid. This review describes the work that has used carbonaceous materials either directly as catalysts or, more frequently, as a large‐area support for catalytically activated transition metals or metal‐oxide nanoparticles. The interest in this type of catalyst derives from the wide use of carbon in conventional water treatments and the wide applicability of the Fenton reaction. After two general sections that illustrate the scope and background of Fenton chemistry, the review describes the activity of activated carbon in the absence or presence of metal‐containing particles. The last sections of the review focus on different types of carbonaceous materials, such as carbon nanotubes and diamond nanoparticles. The review concludes with a section that anticipates future developments in this area, which are aimed at overcoming the current limitations of low activity and occurrence of metal leaching.
CO Oxidation at the Perimeters of an FeO/Pt(111) Interface and how Water Promotes the Activity: A First‐Principles Study
Authors: Gu Xiang‐Kui , Ouyang Runhai , Sun Dapeng , Su Hai‐Yan , Li Wei‐Xue
Published: December 2011

The catalytic role of the PtFe cation ensemble presented at the perimeters of the FeO film supported on Pt(111) for low‐temperature CO oxidation and the promotion of water on activity were studied by using DFT calculations. We found that the perimeter sites along the edge of the FeO islands on Pt provided a favorable ensemble that consisted of coordinatively unsaturated ferrous species and nearby Pt atoms for O2 and H2O activation free from CO poison. A dissociative oxygen atom at the PtFe cation ensemble reacts easily with CO adsorbed on nearby Pt. The OH group from water dissociation not only facilitates activation of the oxygen molecule, more importantly it opens a facile reaction channel for CO oxidation through the formation of the carboxyl intermediate. The presence of the OH group on the FeO film strengthens interfacial interactions between FeO and Pt(111), which would make the FeO film more resistant to further oxidation. The importance of the PtFe cation ensemble and the role of water as a cocatalyst for low‐temperature CO oxidation is highlighted.
Cationic Group 4 Metallocene–(o‐Phosphanylaryl)oxido Complexes: Synthetic Routes to Transition‐Metal Frustrated Lewis Pairs
Authors: Chapman Andy M. , Haddow Mairi F. , Wass Duncan F.
Published: December 2011

Synthetic routes to cationic group 4 metallocene–(o‐phosphanylaryl)oxido compounds of the type [CpR2M(OPR2)][WCA] (M = Ti, Zr, Hf; WCA = weakly coordinating anion) are described. The neutral mono‐methyl complexes [CpR2ZrMe(OPR2)] 1–6 [CpR = Cp (1–3) or Cp* (4); OPR2 = o‐OC6H4(PtBu)2 (1 and 4), OCMe2CH2(PtBu)2 (2) or OC(CF3)2CH2(PtBu)2 (3)] are prepared by protonolysis of [CpR2ZrMe2] by the parent alcohol. The remaining methyl group in such complexes is best removed by protonolysis with [DTBP][B(C6F5)4] (DTBP = 2,6‐di‐tert‐butylpyridinium) to yield the desired cationic complexes 7 and 8 in the case of 1 and 4. In the case of 2 and 3, this method leads to side reactions. Treatment with B(C6F5)3 yields the desired cations in all cases; however, side reactions with the generated [MeB(C6F5)3] anion in subsequent reactions leads to problems. Hafnium analogues may be synthesised by similar routes. In the case of titanium, a different method must be adopted: chloride abstraction using [Et3Si][B(C6F5)4] from the parent complex [Cp2TiCl(OPR2)]. Such cationic group 4 metallocene–(o‐phosphanylaryl)oxido compounds exhibit reactivity that is best described by the frustrated Lewis pair concept.
Asymmetric Methods for the Synthesis of Flavanones, Chromanones, and Azaflavanones
Authors: Nibbs Antoinette E. , Scheidt Karl A.
Published: December 2011

Flavanones, chromanones, and related structures are privileged natural products that display a wide variety of biological activities. Although flavanoids are abundant in nature, there are a limited number of available general and efficient synthetic methods for accessing molecules of this class in a stereoselective manner. Their structurally simple architectures belie the difficulties involved in installation and maintenance of the stereogenic configuration at the C2 position, which can be sensitive and can undergo epimerization under mildly acidic, basic, and thermal reaction conditions. This review presents the methods currently used to access these related structures. The synthetic methods include manipulation of the flavone/flavanone core, carbon‐carbon bond formation, and carbon–heteroatom bond formation.
Phagocytosis of neuronal debris by microglia is associated with neuronal damage in multiple sclerosis
Authors: Huizinga Ruth , van der Star Baukje J. , Kipp Markus , Jong Rosa , Gerritsen Wouter , Clarner Tim , Puentes Fabiola , Dijkstra Christine D. , van der Valk Paul , Amor Sandra
Published: December 2011

Neuroaxonal degeneration is a pathological hallmark of multiple sclerosis (MS) contributing to irreversible neurological disability. Pathological mechanisms leading to axonal damage include autoimmunity to neuronal antigens. In actively demyelinating lesions, myelin is phagocytosed by microglia and blood‐borne macrophages, whereas the fate of degenerating or damaged axons is unclear. Phagocytosis is essential for clearing neuronal debris to allow repair and regeneration. However, phagocytosis may lead to antigen presentation and autoimmunity, as has been described for neuroaxonal antigens. Despite this notion, it is unknown whether phagocytosis of neuronal antigens occurs in MS. Here, we show using novel, well‐characterized antibodies to axonal antigens, that axonal damage is associated with HLA‐DR expressing microglia/macrophages engulfing axonal bulbs, indicative of axonal damage. Neuronal proteins were frequently observed inside HLA‐DR+ cells in areas of axonal damage. In vitro, phagocytosis of neurofilament light (NF‐L), present in white and gray matter, was observed in human microglia. The number of NF‐L or myelin basic protein (MBP) positive cells was quantified using the mouse macrophage cell line J774.2. Intracellular colocalization of NF‐L with the lysosomal membrane protein LAMP1 was observed using confocal microscopy confirming that NF‐L is taken up and degraded by the cell. In vivo, NF‐L and MBP was observed in cerebrospinal fluid cells from patients with MS, suggesting neuronal debris is drained by this route after axonal damage. In summary, neuroaxonal debris is engulfed, phagocytosed, and degraded by HLA‐DR+ cells. Although uptake is essential for clearing neuronal debris, phagocytic cells could also play a role in augmenting autoimmunity to neuronal antigens. © 2011 Wiley Periodicals, Inc.
Mechanism of DNA depurination by carcinogens in relation to cancer initiation
Authors: Cavalieri Ercole , Saeed Muhammad , Zahid Muhammad , Cassada David , Snow Daniel , Miljkovic Momcilo , Rogan Eleanor
Published: December 2011

Depurinating DNA adducts formed by aromatic hydrocarbons and catechol estrogen quinones play a major role in cancer initiation. Most of these adducts depurinate instantaneously, but some guanine adducts depurinate from DNA with half‐lives of hours. We report here, that after 10 h at 37 °C, reaction of estradiol‐3,4‐quinone (E2‐3,4‐Q) with ds‐DNA to yield N7Gua and N3Ade adducts was complete and more efficient than with ss‐DNA. When E2‐3,4‐Q reacted with t‐RNA, no adducts were detected after 10 h, and the level of N3Ade and N7Gua adducts after 10 days was less than half that with ss‐DNA after 10 h. Reaction of E2‐3,4‐Q and dG yielded 4‐OHE2‐1‐N7dG, which spontaneously depurinated to yield 4‐OHE2‐1‐N7Gua. To investigate the mechanism of depurination, E2‐3,4‐Q was reacted with carbocyclicdeoxyguanosine, in which the ring oxygen of the deoxyribose moiety is substituted with CH2, and depurination was observed. The results from this experiment demonstrate that the oxocarbenium ion mechanism plays the major role in depurination and provides the first experimental evidence for this mechanism. A newly discovered β‐elimination mechanism also plays a minor role in depurination. Understanding why the depurinating estrogen‐DNA adducts come from DNA, and not from RNA, underscores the critical role that these adducts play in initiating cancer. © 2011 IUBMB IUBMB Life, 2011.
Pacific coral oxygen isotope and the tropospheric temperature gradient over the Asian monsoon region: a tool to reconstruct past Indian summer monsoon rainfall
Authors: Chakraborty Supriyo , Goswami Bhupendra N. , Dutta Koushik
Published: December 2011

Having recognized that it is the tropospheric temperature (TT) gradient rather than the land–ocean surface temperature gradient that drives the Indian monsoon, a new mechanism of El Niño/Southern Oscillation (ENSO) monsoon teleconnection has been unveiled in which the ENSO influences the Indian monsoon by modifying the TT gradient over the region. Here we show that equatorial Pacific coralline oxygen isotopes reflect TT gradient variability over the Indian monsoon region and are strongly correlated to monsoon precipitation as well as to the length of the rainy season. Using these relationships we have been able to reconstruct past Indian monsoon rainfall variability of the first half of the 20th century in agreement with the instrumental record. Additionally, an older coral oxygen isotope record has been used to reconstruct seasonally resolved summer monsoon rainfall variability of the latter half of the 17th century, indicating that the average annual rainfall during this period was similar to that during the 20th century. Copyright © 2011 John Wiley & Sons, Ltd.
Tropical cyclone activity and western North Atlantic stratification over the last millennium: a comparative review with viable connections
Authors: Woodruff Jonathan D. , Sriver Ryan L. , Lund David C.
Published: December 2011

Tropical cyclones (TC) are recognized to modify the thermal structure of the upper ocean through the process of vertical mixing. Assessing the role this mixing plays in the overall stratification of the upper ocean is difficult, due to the relatively short and incomplete instrumental record. Proxy records for both TC landfalls and oceanographic stratification are preserved within the geological record and provide insight for how past changes in TC‐induced mixing have potentially affected water column structure prior to the instrumental record. Here we provide the first comparison between previously published paleo‐reconstructions of vertical ocean density and tropical cyclone activity from the western North Atlantic. A prominent lull in TC activity has been observed prior to approximately 1700 CE that extends back several centuries. This interval of low TC activity is shown to be concurrent with the timing of increased ocean stratification near Great Bahama Bank, potentially due in part to reduced TC‐induced mixing. To test whether this relationship is feasible, we present numerical results from a coarse‐resolution ocean general circulation model experiment isolating the effect of TC surface wind forcing on the upper ocean. An anomaly of roughly 0.12 kg m−3 in vertical stratification occurs above and below the mixed layer for model runs with and without TC mixing. This anomaly is roughly 25% of the entire paleo‐density signal observed just prior to 1700 CE. These results suggest that TC mixing alone cannot completely explain the density anomaly observed prior to 1700 CE, but support TC variability as an important contributor to enhancing oceanic stratification during this interval. Copyright © 2011 John Wiley & Sons, Ltd.
An assessment of the utility of regional diatom‐based tidal‐level transfer functions
Authors: Wilson Graham P. , Lamb Angela L.
Published: December 2011

In order to understand natural sea‐level variability, and to enhance future predictions, accurate and precise estimates of Holocene tidal levels are required. Although the application of diatom‐based transfer functions can yield such data, these work best when underpinned by local training sets. Urbanized estuaries offer little prospect of obtaining local training sets and, instead, the reliability of regional transfer functions has to be assessed. The performance of a published regional (UK) diatom‐based tidal‐level transfer function applied to fossil assemblages from two contrasting core sites in the Mersey Estuary, UK, is assessed using modern analogue techniques and sediment isotope data. We find that, although estimated tidal levels coincide with changes in organic matter source, the frequent lack of modern analogues mean that palaeotide estimates are without basis. This is likely a consequence of the site‐specific nature of diatom assemblages in higher intertidal and supratidal areas in particular, where local factors are expected to exert a greater control on their ecology. This situation may be partly resolved by constructing and applying much larger regional training sets from multiple higher intertidal and supratidal sites (where intact). Otherwise the application of alternative techniques, such as regional foraminiferal tidal‐level transfer functions, may be more appropriate. Copyright © 2011 John Wiley & Sons, Ltd.
Selective separation of magnolol using molecularly imprinted membranes
Authors: Zhu Xing‐Yi , Zheng Zhang‐Juan , Xie Jie , Wang Ping
Published: December 2011

Molecularly imprinted membranes (MIMs) for selective separation of magnolol were prepared by thermal polymerization using magnolol as the template, ethylene glycol dimethacrylate (EGDMA) as the cross‐linker, 2,2‐azobisisobutyronitrile (AIBN) as the initiator, organic solvent as the porogen, methacrylamide (MAM) and acrylic acid (AA) as the functional monomers and cellulose acetate as the agglutinant. Commercial filter paper was used as the supporting material. The effects of different porogens and the ratio of functional monomers on the binding and recognition capacity of MIMs were investigated, and the morphology of the membranes was examined by scanning electron microscopy (SEM). The results showed that the MIMs have the highest selectivity to magnolol when the ratio of MAM/AA was 1:4 and tetrahydrofuran (THF) with dimethyl sulfoxide (DMSO) was used as the porogen. The morphology of the imprinted membranes after template extracting is much rougher with big cavities than that of the non‐imprinted membranes (NIMs) and the imprinted membranes before template extracting. The MIMs can selectively separate the magnolol.
Perampanel, an AMPA antagonist, found to have no benefit in reducing “off” time in Parkinson's disease
Authors: Lees Andrew , Fahn Stanley , Eggert Karla M. , Jankovic Joseph , Lang Anthony , Micheli Federico , Maral Mouradian M. , Oertel Wolfgang H. , Olanow C. Warren , Poewe Werner , Rascol Olivier , Tolosa Eduardo , Squillacote David , Kumar Dinesh
Published: December 2011

Background:

Perampanel is a selective, noncompetitive α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazole‐propionic acid receptor antagonist. Two multicenter randomized, double‐blind, placebo‐controlled, parallel‐group phase III studies assessed the efficacy and safety of adjunctive perampanel in patients with Parkinson's disease and motor fluctuations.

Methods:

In both phase III studies (301 and 302), levodopa‐treated patients were randomized and treated with once‐daily oral placebo (n = 504), perampanel 2 mg (n = 509), or perampanel 4 mg (n = 501). The primary end point was change in daily “off” time from baseline. The treatment period was 30 weeks in study 301 and 20 weeks in study 302.

Results:

For any efficacy end point, perampanel 2 or 4 mg was not superior to placebo. Perampanel was well tolerated up to 4 mg/day.

Conclusions:

Perampanel failed to significantly improve motor symptoms versus placebo. There was also no effect on the duration or disability of levodopa‐induced dyskinesia. © 2011 Movement Disorder Society
Clinical validation of movement disorder society–recommended diagnostic criteria for Parkinson's disease with dementia
Authors: Barton Brandon , Grabli David , Bernard Bryan , Czernecki Virginie , Goldman Jennifer G. , Stebbins Glenn , Dubois Bruno , Goetz Christopher G.
Published: December 2011

The objective of this work was to evaluate the Movement Disorders Society (MDS) Task Force–proposed screening checklist for detecting Parkinson's disease dementia (PD‐D) in relation to full neuropsychological testing. An MDS Task Force has proposed diagnostic procedures for PD‐D, which have not been fully validated against more extensive neuropsychological testing. PD subjects were recruited from 2 specialty centers. A neuropsychologist evaluated them for dementia as part of routine clinical care. Independent clinical neurologists administered the MDS PD‐D screening checklist. Diagnosis of PD‐D by the 2 methods was compared. Ninety‐one PD subjects had a mean age of 66.3 (SD = 9.7) years and a mean PD duration of 8.8 (SD = 6.1) years. Seven subjects (7.7%) met all 8 screening checklist criteria from the MDS PD‐D screening tool and were classified as probable PD‐D. Fifteen (16.5%) subjects were classified as PD‐D by full neuropsychological assessment. The screening checklist showed 100% specificity, but only 46.7% sensitivity, for diagnosing PD‐D compared to the full neuropsychological assessment. PD‐D cases missed by the PD‐D screening tool were largely due to 2 checklist items that were not endorsed (absence of depression and Mini‐Mental State Examination [MMSE] scores <26). There was moderate agreement between these 2 methods for determination of PD‐D (kappa = 0.59, P < .001). The MDS‐PD‐D screening checklist is highly accurate for detecting PD‐D if all items are endorsed. However, for cases that do not meet these criteria, full neuropsychological testing is needed to differentiate PD‐D from milder cognitive impairment. Revision of the checklist by altering or eliminating the 2 problematic checklist items may improve sensitivity. © 2011 Movement Disorder Society
The postprandial inflammatory response after ingestion of heated oils in obese persons is reduced by the presence of phenol compounds
Authors: Perez‐Herrera A. , Delgado‐Lista J. , Torres‐Sanchez L. A. , Rangel‐Zuñiga O. A. , Camargo A. , Moreno‐Navarrete J. M. , Garcia‐Olid B. , Quintana‐Navarro G. M. , Alcala‐Diaz J. F. , Muñoz‐Lopez C. , Lopez‐Segura F. , Fernandez‐Real J. M. , Luque de Castro M. D. , Lopez‐Miranda J. , Perez‐Jimenez F.
Published: December 2011

Scope Heating during the process of cooking alters the chemical properties of foods and may affect subsequent postprandial inflammation. We tested the effects of four meals rich in different oils subjected to heating on the postprandial inflammatory metabolism of peripheral blood mononuclear cells (PBMCs).

Methods and results Twenty obese participants received four breakfasts following a randomized crossover design, consisting of milk and muffins made with different oils (virgin olive oil (VOO), sunflower oil (SFO), and a mixture of seeds oil (SFO/canola oil) with added either dimethylpolysiloxane (SOD), or natural antioxidants from olive mill wastewater alperujo (phenols; SOP)), previously subjected to 20 heating cycles. Postprandial inflammatory status in PBMCs was assessed by the activation of nuclear NF‐κB, the concentration in cytoplasm of the NF‐κB inhibitor (IκB‐α), the mRNA levels of NF‐κB subunits and activators (p65, IKKβ, and IKKα) and other inflammatory molecules (TNF‐α, IL‐1β, IL‐6, MIF, and JNK), and lipopolysaccharide (LPS) levels. VOO and SOP breakfasts reduced NF‐κB activation, increased IκB‐α, and decreased LPS plasma concentration. SFO increased IKKα, IKKβ, p65, IL‐1b, IL‐6, MIF, and JNK mRNA levels, and plasma LPS

Conclusion Oils rich in phenols, whether natural (VOO) or artificially added (SOP), reduce postprandial inflammation, compared with seed oil (sunflower).
A Kinetic Model for Non‐Oxidative Thermal Degradation of Nylon 66
Authors: Karimi Hadiseh , Schaffer Mark A. , McAuley Kim B.
Published: December 2011

A model is developed to predict rates of undesirable reactions in the low‐moisture, high‐temperature finishing stage of nylon 66 production. The model contains 56 unknown parameters and initial conditions, which are ranked based on their influence on model predictions, correlation with other parameters and uncertainty in their initial guesses. A mean‐square‐error criterion is used to determine that 43 of 56 parameters should be estimated. The proposed model, which describes the effect of melt‐phase water concentration on degradation, matches the data well with typical errors of 6.1 and 2.9%, respectively, for amine ends (A) and carboxyl ends (C) and 4.3, 27.2, and 29.4%, respectively, for evolution rates of CO2, NH3, and cyclopentanone (CPK).

magnified image
Shared velocity encoding: A method to improve the temporal resolution of phase‐contrast velocity measurements
Authors: Lin Hung‐Yu , Bender Jacob A. , Ding Yu , Chung Yiu‐Cho , Hinton Alice M. , Pennell Michael L. , Whitehead Kevin K. , Raman Subha V. , Simonetti Orlando P.
Published: December 2011

Phase‐contrast magnetic resonance imaging (PC‐MRI) is used routinely to measure fluid and tissue velocity with a variety of clinical applications. Phase‐contrast magnetic resonance imaging methods require acquisition of additional data to enable phase difference reconstruction, making real‐time imaging problematic. Shared Velocity Encoding (SVE), a method devised to improve the effective temporal resolution of phase‐contrast magnetic resonance imaging, was implemented in a real‐time pulse sequence with segmented echo planar readout. The effect of SVE on peak velocity measurement was investigated in computer simulation, and peak velocities and total flow were measured in a flow phantom and in volunteers and compared with a conventional ECG‐triggered, segmented k‐space phase‐contrast sequence as a reference standard. Computer simulation showed a 36% reduction in peak velocity error from 8.8 to 5.6% with SVE. A similar reduction of 40% in peak velocity error was shown in a pulsatile flow phantom. In the phantom and volunteers, volume flow did not differ significantly when measured with or without SVE. Peak velocity measurements made in the volunteers using SVE showed a higher concordance correlation (0.96) with the reference standard than non‐SVE (0.87). The improvement in effective temporal resolution with SVE reconstruction has a positive impact on the precision and accuracy of real‐time phase‐contrast magnetic resonance imaging peak velocity measurements. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.
Preserving the accuracy and resolution of the sodium bioscale from quantitative sodium MRI during intrasubject alignment across longitudinal studies
Authors: Atkinson Ian C. , Lu Aiming , Thulborn Keith R.
Published: December 2011

Emerging applications of sodium bioscales derived from quantitative sodium magnetic resonance imaging assess temporal changes in regional sodium concentration over intervals that vary from hours (monitoring tissue viability in stroke) to weeks (monitoring brain tumor treatment during radiation therapy) or even years (monitoring progression of neurodegenerative disease). Accurate interpretation of such quantitative data requires precise registration between magnetic resonance imaging sessions to avoid session‐to‐session changes in partial volume effects between normal tissue (∼38 mM sodium concentration), lesions (variable sodium concentration), and cerebrospinal fluid (∼144 mM sodium concentration). The existing Automated Image Registration algorithm is shown to be suitable for rapid, accurate, and precise determination of the transform that aligns sodium magnetic resonance images. Implementation of this transform during image reconstruction from thek‐space data is shown to produce smaller errors than conventional image‐domain interpolation. Experimental results at 9.4 T and 3.0 T demonstrating this registration approach to sodium data illustrate preservation of quantification accuracy during alignment of sodium magnetic resonance images acquired from the same subject during different imaging sessions. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Biexponential diffusion decay in formalin‐fixed prostate tissue: Preliminary findings
Authors: Bourne Roger M. , Kurniawan Nyoman , Cowin Gary , Stait‐Gardner Timothy , Sved Paul , Watson Geoffrey , Chowdhury Supriya , Price William S.
Published: December 2011

Magnetic resonance microimaging was used to measure diffusion decay over an extended b‐factor range in a formalin‐fixed normal prostate sample and a Gleason pattern 3+4 cancer tissue sample. The coefficients of biexponential fits to diffusion decay data from 1600 voxels of dimension 160 × 160 × 160 μm3 in each sample were correlated with underlying epithelial and stromal compartment partial volumes estimated from high‐resolution apparent diffusion coefficient (ADC) data (40 × 40 × 40 μm3 voxels) from the same tissue. In the normal tissue sample, the signal fractions of the low and high ADC components of the biexponential fits correlated linearly with partial volumes of epithelial tissue (R2 = 0.6) and stromal tissue (R2 = 0.5), respectively. Similar but weaker correlations were observed in the cancer sample. Epithelium‐containing high spatial resolution voxels appeared to be composed of ∼60% low ADC and ∼40% high ADC component. Stromal voxels appeared to be composed of ∼20% low ADC and ∼80% high ADC component. This preliminary report suggests that distinctly different diffusion properties in microscopically adjacent cell types contribute to the multiexponential diffusion decay phenomenon in prostate tissue. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Somatotopic arrangement of thermal sensory regions in the healthy human spinal cord determined by means of spinal cord functional MRI
Authors: Stroman Patrick W. , Bosma Rachael L. , Tsyben Anastasia
Published: December 2011

Previous functional MRI studies of normal sensory function in the human spinal cord, including right‐to‐left symmetry of activity, have been influenced by order effects between repeated studies. In this study, we apply thermal sensory stimulation to four dermatomes within each functional MRI time‐series acquisition. Each of the four dermatomes receives a unique stimulation paradigm, such that the four paradigms form a linearly independent set, enabling detection of each individual stimulus response. Functional MRI data are shown spanning the cervical spinal cord and brainstem in 10 healthy volunteers. Results of general linear model analysis demonstrate consistent patterns of activity within the spinal cord segments corresponding to each dermatome, and a high degree of symmetry between right‐side and left‐side stimulation. Connectivity analyses also demonstrate consistent areas of activity and connectivity between spinal cord and brainstem regions corresponding to known anatomy. However, right‐side and left‐side responses are not at precisely the same rostral–caudal positions, but are offset by several millimeters, with left‐side responses consistently more caudal than right‐side responses. The results confirm that distinct responses to multiple interleaved sensory stimuli can be distinguished, enabling studies of sensory responses within the spinal cord without the confounding effects of comparing sequential studies. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Prospective self‐gating for swallowing motion: A feasibility study in carotid artery wall MRI using three‐dimensional variable‐flip‐angle turbo spin‐echo
Authors: Fan Zhaoyang , Zuehlsdorff Sven , Liu Xin , Li Debiao
Published: December 2011

Three‐dimensional black‐blood MRI is a promising noninvasive imaging technique for the assessment of atherosclerotic carotid artery disease. However, this technique is inherently susceptible to motion. In particular, swallowing can result in considerable wall motion at the carotid bifurcations, which may induce drastic image degradation or substantial overestimation of wall thickness. Self‐gating techniques have previously been shown to be capable of resolving and compensating for cardiac or respiratory motion during MRI. This work presents a self‐gating‐based prospective motion gating scheme that is combined with a three‐dimensional variable‐flip‐angle turbo spin‐echo sequence (SPACE) for detecting swallowing motion. Self‐gating signal readouts along the superior–inferior direction during each repetition time period are used to derive the projection profiles of the imaging volume. Based on cross‐correlation analysis between the projection profiles and the corresponding reference profiles, swallowing motion can be detected and the motion‐contaminated data will subsequently be discarded and reacquired in the next repetition time. The self‐gated SPACE sequence was validated on eight healthy volunteers and two patients and, when compared with the conventional SPACE sequence, proved to be more resistant to swallowing motion and significantly improved image quality as well as the sharpness of carotid artery wall boundaries. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Influence of dense‐array EEG cap on fMRI signal
Authors: Luo Qingfei , Glover Gary H.
Published: December 2011

Dense‐array (>64 channel) electroencephalography (EEG) systems are increasingly being used in simultaneous EEG–functional magnetic resonance imaging (fMRI) studies. However, with increasing channel count, dense‐array EEG caps can induce more severe signal dropout in the MRI images than conventional systems due to the radiofrequency shielding effect of the denser wire bundle. This study investigates the influence of a 256‐channel EEG cap on MRI image quality and detection sensitivity of blood oxygen level dependent fMRI signal. A theoretical model is first established to describe the impact of the EEG cap on anatomic signal, noise, signal‐to‐noise ratio, and contrast‐to‐noise ratio of blood oxygen level dependent signal. Seven subjects were scanned to measure and compare the T2*‐weighted image quality and fMRI detection sensitivity with and without the EEG cap using an auditory/visual/sensorimotor task. The results show that the dense‐array EEG cap can substantially reduce the anatomic signal in the brain areas (visual cortex) near the conducting wires (average percent decrease ≈ 38%). However, the image signal‐to‐noise ratio with and without the EEG cap was comparable (percent decrease < 8%, not statistically significant), and there was no statistically significant difference in the extent of blood oxygen level dependent activation. This suggests that the ability to detect fMRI signal is nearly unaffected by dense‐array EEG caps in simultaneous EEG–fMRI experiments. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Numerical simulation of SAR induced around Co‐Cr‐Mo hip prostheses in situ exposed to RF fields associated with 1.5 and 3 T MRI body coils
Authors: Powell John , Papadaki Annie , Hand Jeff , Hart Alister , McRobbie Donald
Published: December 2011

When patients with metallic prosthetic implants undergo an MR procedure, the interaction between the RF field and the prosthetic device may lead to an increase in specific absorption rate (SAR) in tissues surrounding the prosthesis. In this work, the distribution of SAR10g around bilateral CoCrMo alloy hip prostheses in situ in anatomically realistic voxel models of an adult male and female due to RF fields from a generic birdcage coil driven at 64 or 128 MHz are predicted using a time‐domain finite integration technique. Results indicate that the spatial distribution and maximum values of SAR10g are dependent on body model, frequency, and the position of the coil relative to the body. Enhancement of SAR10g close to the extremities of a prosthesis is predicted. Values of SAR10g close to the prostheses are compliant with recommended limits if the prostheses are located outside the coil. However, caution is required when the prostheses are within the coil since the predicted SAR10g close to an extremity of a prosthesis exceeds recommended limits when the whole body averaged SAR is 2 W kg−1. Compliance with recommended limits is likely to require a reduction in the time averaged input power. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Free‐breathing inner‐volume black‐blood imaging of the human heart using two‐dimensionally selective local excitation at 3 T
Authors: Abd‐Elmoniem Khaled Z. , Barmet Christoph , Stuber Matthias
Published: December 2011

Black‐blood fast spin‐echo imaging is a powerful technique for the evaluation of cardiac anatomy. To avoid fold‐over artifacts, using a sufficiently large field of view in phase‐encoding direction is mandatory. The related oversampling affects scanning time and respiratory chest motion artifacts are commonly observed. The excitation of a volume that exclusively includes the heart without its surrounding structures may help to improve scan efficiency and minimize motion artifacts. Therefore, and by building on previously reported inner‐volume approach, the combination of a black‐blood fast spin‐echo sequence with a two‐dimensionally selective radiofrequency pulse is proposed for selective “local excitation” small field of view imaging of the heart. This local excitation technique has been developed, implemented, and tested in phantoms and in vivo. With this method, small field of view imaging of a user‐specified region in the human thorax is feasible, scanning becomes more time efficient, motion artifacts can be minimized, and additional flexibility in the choice of imaging parameters can be exploited. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Overcoming the low relaxivity of gadofosveset at high field with spin locking
Authors: Richardson O. C. , Scott M. L. J. , Tanner S. F. , Waterton J. C. , Buckley D. L.
Published: December 2011

The contrast agent gadofosveset, which binds reversibly to serum albumin, has a high longitudinal relaxivity at lower magnetic fields (≤3.0 T) but a much lower relaxivity at high fields. Spin locking is sensitive to macromolecular content; it is hypothesized that combining this technique with the albumin‐binding properties of gadofosveset may enable increased relaxivity at high fields. In vitro measurements at 4.7 T found significantly higher spin‐lock relaxation rates, R1ρ (1/T1ρ), when gadofosveset was serum albumin‐bound than when unbound. R1ρ values for a nonbinding contrast agent (gadopentetate dimeglumine) in serum albumin were similar to those for unbound gadofosveset. R2 (1/T2) values were also significantly higher at 4.7 T for serum albumin‐bound gadofosveset than for unbound. Spin locking at high field generates significantly higher relaxation rates for gadofosveset than conventional contrast agents and may provide a method for differentiating free and bound molecules at these field strengths. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Fast cardiac T1 mapping in mice using a model‐based compressed sensing method
Authors: Li Wen , Griswold Mark , Yu Xin
Published: December 2011

Direct measurement of the longitudinal relaxation time T1 provides objective and quantitative diagnostic information. However, current T1 mapping methods are generally time consuming without the aid of fast imaging. This study used a model‐based compressed sensing method for fast cardiac T1 mapping in small animals. Based on the physics of magnetization recovery, the aliasing artifact associated with under‐sampling was removed by exploiting the sparsity of the signals in the T1 recovery direction. Simulation study was performed to evaluate the reconstruction accuracy under various experimental conditions. Several approaches that accounted for phase variations were compared for optimized reconstruction in the phantom study. In vivo validation was performed on a cardiac manganese‐enhanced MRI study using mice. Accurate reconstruction of the under‐sampled images and the resulting T1 maps were achieved in both simulation and MRI studies on phantom and in vivo mice. These results suggest that the current compressed sensing method allows fast (<80 s) T1 mapping of the mouse heart at high spatial resolution (234 × 469 μm2). Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.
Challenging Evidence‐based Decision‐making: A Hypothetical Case Study about Return to Work
Authors: Aas Randi W. , Alexanderson Kristina
Published: December 2011

A hypothetical case study about return to work was used to explore the process of translating research into practice. The method involved constructing a case study derived from the characteristics of a typical, sick‐listed employee with non‐specific low back pain in Norway. Next, the five‐step evidence‐based process, including the Patient, Intervention, Co‐Interventions and Outcome framework (PICO), was applied to the case study. An inductive analysis produced 10 technical and more fundamental challenges to incorporate research into intervention decisions for an individual with comorbidity. A more dynamic, interactive approach to the evidence‐based practice process is proposed. It is recommended that this plus the 10 challenges are validated with real life cases, as the hypothetical case study may not be replicable. Copyright © 2011 John Wiley & Sons, Ltd.
Loss Coefficients in Laminar Flows: Essential for the Design of Micro Flow Systems
Authors: Schmandt Bastian , Herwig Heinz
Published: December 2011

The concept of head loss coefficients K for the determination of losses in conduit components is discussed in detail. While so far it has mainly been applied to fully turbulent flows it is extended here to also cover the laminar flow regime which is relevant for micro systems due to the low Reynolds numbers of these flows. Specific numbers of K can be determined by integration of the entropy generation field (second law analysis) obtained from a numerical simulation. It will be shown that a definition of K based on entropy generation is superior to a widely used definition that refers to a pressure drop caused by the conduit component. With the second law analysis details of the physics become available. For example it can be shown that often the main part of the entropy generation occurs downstream of the component. This aspect becomes important when several conduit components are combined in close proximity, like two 90 degree bends that are close to each other. Often in such situations the combination as a whole has to be looked upon as one new complex component. The general approach is discussed and illustrated for various conduit components and combinations of them. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Lightweight Robot ElRob: Interesting Aspects in Modeling and Control
Authors: Höbarth Wolfgang , Gattringer Hubert , Staufer Peter , Bremer Hartmut
Published: December 2011

The articulated robot ElRob, consisting of flexible links and joints, is considered in several publications. Recent developments are presented in this work.

The overall goal of the research is to decrease the effects of structural elasticities in lightweight robots. For this purpose model‐based control concepts are investigated and very accurate and efficient kinematic and dynamic models are necessary. The robot is split into groups of bodies, the so called subsystems, with separated describing velocities and coordinate systems. To obtain structured equations of motion the Projection Equation is used. The beams are modelled using the floating frame of reference formulation and a Ritz‐approach.

Because of its flexibility, the examined robot is an underactuated system leading to special difficulties. As an example is it not possible to compute the desired joint angles with respect to a reference path in task space for the flexible system (inverse kinematic problem).

Different methods to solve this drawback and other problems resulting from flexibility are discussed with special focus on feed forward control and different feedback control concepts. The resulting end point error, the necessary control input and other interesting results for the laboratory experiment are presented and compared. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal Control of Multibody Dynamics with Contact
Authors: Koch Michael W. , Leyendecker Sigrid
Published: December 2011

This work discusses two different structure preserving integrators in the framework of optimal control simulations with contact. The first one is a variational integrator, based on the constrained version of the Lagrange‐D'Alembert. The resulting scheme preserves the symplecticity and the momentum maps of the simulated multibody dynamics. The second integrator is an energy momentum scheme and it is based on the augmented Hamiltonian equations, which are discretised using the discrete derivative in [2]. Both integrators are applied to simulate the optimal control of compass gait, for which the contact between the foot and the ground is modelled as perfectly plastic contact. The second example represents a monopedal jumper and it is used to examine the dynamical behaviour of the perfectly elastic and perfectly plastic contact formulation. The resulting differential algebraic equations (DAEs) are solved by the aforementioned symplectic momentum method. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational multirate integration of constrained dynamics
Authors: Leyendecker Sigrid , Ober‐Blöbaum Sina
Published: December 2011

Mechanical systems with dynamics on varying time scales, in particular those including highly oscillatory motion, impose challenging questions for numerical integration schemes. Tiny step sizes are required to guarantee a stable integration of the fast frequencies. However, for the simulation of the slow dynamics, integration with a larger time step is accurate enough. Small time steps increase integration times unnecessarily, especially for costly function evaluations. For systems comprising fast and slow dynamics, multirate methods integrate the slow part of the system with a relatively large step size while the fast part is integrated with a small time step. Main challenges are the identification of fast and slow parts (e.g. by separating the energy or by distinguishing sets of variables), the synchronisation of their dynamics and in particular the treatment of mixed parts that often appear when fast and slow dynamics are coupled by constraints. In this contribution, a multirate integrator is derived in closed form via a discrete variational principle on a time grid consisting of macro and micro time nodes. Variational integrators (based on a discrete version of Hamilton's principle) lead to symplectic and momentum preserving integration schemes that also exhibit good energy behavior. The resulting multirate variational integrator has the same preservation properties. An example demonstrates the performance of the multirate integrator for constrained multibody dynamics. (© 2011 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)