bluuebunny/crossref_metadata_2025_split huggingface dataset:
Implant‐associated localized osteitis in murine femur fracture by biofilm forming Staphylococcus aureus: A novel experimental model
Authors: Windolf Ceylan D. , Meng Wei , Lögters Tim T. , MacKenzie Colin R. , Windolf Joachim , Flohé Sascha 
Published: July 2013

ABSTRACTStaphylococcus aureus (SA) is the most common causative agent for implant‐associated osteitis. The present study characterizes a novel model of a low grade acute SA osteitis with bone defect in the femur which is stabilized by a titanium locking plate. Wild‐type Balb/c mice were osteotomized, fixed by a locking plate and infected with SA. Mice underwent debridement 7 and 14 days later and were sacrificed at Day 28. At Days 7, 14, and 28 after inoculation local and systemic cell populations and IL‐6 were analyzed. Fracture healing was quantified by radiography. The control group underwent the same procedure without infection. The bacterial load of implant‐associated osteitis with biofilm formation was quantified by counting CFU and real‐time PCR. Fracture healing determined by radiography was delayed in infected compared to non‐infected mice. Throughout the investigation period CFU and leukocyte counts, as well as IL‐6 levels were found to be significantly elevated in infected mice at the infection site but not systemically. Our murine model allows the detailed investigation of implant associated localized osteitis with biofilm producing SA and its influence on fracture healing. The model provides a tool to analyze therapeutic or prophylactic approaches to the problem of biofilm‐associated osteitis. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:2013–2020, 2013
Connexin 43 is a potential regulator in fluid shear stress‐induced signal transduction in osteocytes
Authors: Li Xiaoting , Liu Chenglin , Li Ping , Li Shengnan , Zhao Zhihe , Chen Yangxi , Huo Bo , Zhang Ding 
Published: July 2013

ABSTRACTConnexin 43 (Cx43), a gap junctional protein, regulates osteocyte viability, and modulates mechanical stimulation‐induced bone remodeling. However, the underlying mechanisms of its action remain unclear. In the current study, osteocyte‐like MLO‐Y4 cells were exposed to fluid shear stress (FSS) of 16 (physiological) or 30 (high) dyne/cm2 for the indicated time points. Cx43 gene (Gja1) was silenced using siRNA or the protein was blocked chemically. The signaling molecules related to osteocyte apoptosis, osteogenesis, or osteoclastogenesis were detected at mRNA or protein levels. The results showed that physiological FSS significantly upregulated Cx43, which further inhibited apoptosis pathways (e.g., caspase‐3) and osteoclastogenesis signaling (e.g., RANKL), but activated osteogenesis signaling (Sost/sclerostin). Suppressing Cx43 gene (Gja1) by siRNA or chemically blocking gap junction communication enhanced caspase‐3, RANKL, and Sost/sclerostin, which could be restored with physiological FSS over 8 h. In addition, high FSS decreased Cx43 expression and adversely affected signaling molecules compared with physiological FSS. The findings indicate the involvement of Cx43 in mechanotransduction of FSS and in the modulation of mechanical loading‐related apoptosis, osteogenesis, and osteoclastogenesis of osteocytes. This may provide a cellular and molecular basis for interpreting the biomechanical mechanism of bone absorption and remodeling. © 2013 Orthopaedic Research Society Published by Wiley Periodicals, Inc. J Orthop Res 31:1959–1965, 2013
Determinants of resident competence in mastoidectomy: Role of interest and deliberate practice
Authors: Malik Mohammad U. , Diaz Voss Varela David A. , Park EunMi , Masood Hamid , Laeeq Kulsoom , Bhatti Nasir I. , Francis Howard W. 
Published: July 2013

Objectives/HypothesisThis study explores the influence of selected factors on achievement of competency in mastoid surgery.Study DesignA prospective study of surgical performance and a retrospective survey of learner and training factors.MethodsThe longitudinal performance of 15 residents was evaluated using the mastoidectomy task‐based checklist (TBC). The influence of surgical experience, resident interest, and training factors (course attendance, voluntary use of simulation laboratory) was also examined and compared for the acquisition of distinct levels of technical skill difficulty (cortical mastoidectomy vs. facial recess).ResultsNinety‐six observations made during the first otology rotation were analyzed. Cortical mastoidectomy tasks showed positive associations with cumulated case numbers (OR 1.13, CI 1.04–1.23,P = .003) and interest in otology (OR 3.86, CI 1.21–12.27,P = .022). Facial recess tasks showed a larger positive association with interest in otology (OR 10.38, CI 2.25–47.94,P = .003), and negative association with extra time spent in laboratory practice (OR .05, CI 0.011–0.23,P = .000).ConclusionsLearning trajectory for cortical mastoidectomy and facial recess may be influenced by different factors. Interest in otology, in particular, may have a moderating effect on the acquisition of more complex skills in mastoid surgery. A negative association between self‐directed laboratory simulation and performance may reflect the impact of assessment‐guided feedback in promoting deliberate practice. Further investigations are suggested to explore the interactions between individual trainee differences, educational models, and learning outcomes.Level of EvidenceN/A.Laryngoscope, 123:3162–3167, 2013
Chemical Composition Separation of EP Copolymers by CEF and HT‐SGIC: Crystallization versus Adsorption
Authors: Cheruthazhekatt Sadiqali , Mayo Nuria , Monrabal Benjamin , Pasch Harald 
Published: July 2013

Preparative temperature rising elution fractionation (prep TREF) suffers from co‐crystallization effects and, therefore, cannot provide reliable chemical composition distribution (CCD) information. This limitation can be overcome when prep TREF is combined with further fractionation methods such as crystallization elution fractionation (CEF) or high‐temperature solvent‐gradient‐interaction chromatography (HT‐SGIC) as a new approach. By CEF, significant amounts of (co‐crystallizing) amorphous ethylene‐propylene (EP) copolymer are identified in semicrystalline TREF fractions of a heterophasic ethylene/propylene copolymer (HEPC). Complete compositional fractionation with no influence of crystallization effects is accomplished by HT‐SGIC. Prep TREF–HT‐SGIC is found to be the most selective and suitable method for the fast and complete CCD analysis of such complex EP copolymers with CEF providing complementary information.
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Quantitative 31P HR‐MAS MR spectroscopy for detection of response to PI3K/mTOR inhibition in breast cancer xenografts
Authors: Esmaeili Morteza , Bathen Tone F. , Engebråten Olav , Mælandsmo Gunhild M. , Gribbestad Ingrid S. , Moestue Siver A. 
Published: July 2013

PurposePhospholipid metabolites are of importance in cancer studies, and have been suggested as candidate metabolic biomarkers for response to targeted anticancer drugs. The purpose of this study was to develop a phosphorus (31P) high resolution magic angle spinning magnetic resonance spectroscopy protocol for quantification of phosphorylated metabolites in intact cancer tissue.Methods31P spectra were acquired on a 14.1 T spectrometer with a triplet 1H/13C/31P MAS probe. Quantification of metabolites was performed using the PULCON principle. Basal‐like and luminal‐like breast cancer xenografts were treated with the dual PI3K/mTOR inhibitor BEZ235, and the impact of treatment on the concentration of phosphocholine, glycerophosphocholine, phosphoethanolamine and glycerophosphoethanolamine was evaluated.ResultsIn basal‐like xenografts, BEZ235 treatment induced a significant decrease in phosphoethanolamine (−25.6%, P = 0.01) whilst phosphocholine (16.5%, P = 0.02) and glycerophosphocholine (37.3%, P < 0.001) were significantly increased. The metabolic changes could partially be explained by increased levels of phospholipase A2 group 4A (PLA2G4A).Conclusion31P high resolution magic angle spinning magnetic resonance spectroscopy is a useful method for quantitative assessment of metabolic responses to PI3K inhibition. Using the PULCON principle for quantification, the levels of phosphocholine, glycerophosphocholine, phosphoethanolamine, and glycerophosphoethanolamine could be evaluated with high precision and accuracy. Magn Reson Med 71:1973–1981, 2014. © 2013 Wiley Periodicals, Inc.
Dynamic metabolic imaging of hyperpolarized [2‐13C]pyruvate using spiral chemical shift imaging with alternating spectral band excitation
Authors: Josan Sonal , Hurd Ralph , Park Jae Mo , Yen Yi‐Fen , Watkins Ron , Pfefferbaum Adolf , Spielman Daniel , Mayer Dirk 
Published: July 2013

PurposeIn contrast to [1‐13C]pyruvate, hyperpolarized [2‐13C]pyruvate permits the ability to follow the 13C label beyond flux through pyruvate dehydrogenase complex and investigate the incorporation of acetyl‐coenzyme A into different metabolic pathways. However, chemical shift imaging (CSI) with [2‐13C]pyruvate is challenging owing to the large spectral dispersion of the resonances, which also leads to severe chemical shift displacement artifacts for slice‐selective acquisitions.MethodsThis study introduces a sequence for three‐dimensional CSI of [2‐13C]pyruvate using spectrally selective excitation of limited frequency bands containing a subset of metabolites. Dynamic CSI data were acquired alternately from multiple frequency bands in phantoms for sequence testing and in vivo in rat heart.ResultsPhantom experiments verified the radiofrequency pulse design and demonstrated that the signal behavior of each group of resonances was unaffected by excitation of the other frequency bands. Dynamic three‐dimensional 13C CSI data demonstrated the sequence capability to image pyruvate, lactate, acetylcarnitine, glutamate, and acetoacetate, enabling the analysis of organ‐specific spectra and metabolite time courses.ConclusionsThe presented method allows CSI of widely separated resonances without chemical shift displacement artifact, acquiring multiple frequency bands alternately to obtain dynamic time‐course information. This approach enables robust imaging of downstream metabolic products of acetyl‐coenzyme A with hyperpolarized [2‐13C]pyruvate. Magn Reson Med 71:2051–2058, 2014. © 2013 Wiley Periodicals, Inc.
Validation of planning‐free vessel‐encoded pseudo‐continuous arterial spin labeling MR imaging as territorial‐ASL strategy by comparison to super‐selective p‐CASL MRI
Authors: Hartkamp Nolan S. , Helle Michael , Chappell Michael A. , Okell Thomas W. , Hendrikse Jeroen , Bokkers Reinoud P. H. , van Osch Matthias J. P. 
Published: July 2013

PurposeVessel‐encoded (VE) pseudo‐continuous arterial spin labeling (p‐CASL) is a territorial ASL (T‐ASL) technique to identify the perfusion territories of cerebral arteries. The aim of this study was to validate the output of three Vessel‐encoded p‐CASL image processing methods, k‐means clustering with and without subsequent linear analysis and a Bayesian framework, by comparison with the perfusion maps acquired with super‐selective p‐CASL.MethodsThe comparison was done quantitatively using the Hausdorff distance and Dice similarity coefficient in the territories of the right and left internal carotid arteries, the basilar artery, and the right and left vertebral arteries. A qualitative comparison was done in the areas of the anterior and posterior circulation, and the deep gray matter.ResultsThe overall agreement between the Vessel‐encoded p‐CASL image processing methods and super‐selective p‐CASL was good; with the difference that the linear analysis and the Bayesian framework were able to detect mixed perfusion.ConclusionPlanning‐free Vessel‐encoded p‐CASL with k‐means clustering appears suitable as a general purpose T‐ASL strategy, but to determine mixed perfusion a combination with linear analysis, or the Bayesian framework is preferable, which are superior in this regard. To accurately determine the perfusion territory of a single vessel, super‐selective p‐CASL is still recommended. Magn Reson Med 71:2059–2070, 2014. © 2013 Wiley Periodicals, Inc.
Dynamic contrast enhanced MRI parameters and tumor cellularity in a rat model of cerebral glioma at 7 T
Authors: Aryal Madhava P. , Nagaraja Tavarekere N. , Keenan Kelly A. , Bagher‐Ebadian Hassan , Panda Swayamprava , Brown Stephen L. , Cabral Glauber , Fenstermacher Joseph D. , Ewing James R. 
Published: July 2013

PurposeTo test the hypothesis that a noninvasive dynamic contrast enhanced MRI (DCE‐MRI) derived interstitial volume fraction (ve) and/or distribution volume (VD) were correlated with tumor cellularity in cerebral tumor.MethodsT1‐weighted DCE‐MRI studies were performed in 18 athymic rats implanted with U251 xenografts. After DCE‐MRI, sectioned brain tissues were stained with Hematoxylin and Eosin for cell counting. Using a Standard Model analysis and Logan graphical plot, DCE‐MRI image sets during and after the injection of a gadolinium contrast agent were used to estimate the parameters plasma volume (vp), forward transfer constant (Ktrans), ve, and VD.ResultsParameter values in regions where the standard model was selected as the best model were: (mean ± S.D.): vp = (0.81 ± 0.40)%, Ktrans = (2.09 ± 0.65) × 10−2 min−1, ve = (6.65 ± 1.86)%, and VD = (7.21 ± 1.98)%. The Logan‐estimated VD was strongly correlated with the standard model's vp + ve (r = 0.91, P < 0.001). The parameters, ve and/or VD, were significantly correlated with tumor cellularity (r ≥ −0.75, P < 0.001 for both).ConclusionThese data suggest that tumor cellularity can be estimated noninvasively by DCE‐MRI, thus supporting its utility in assessing tumor pathophysiology. Magn Reson Med 71:2206–2214, 2014. © 2013 Wiley Periodicals, Inc.
Accurate T1 mapping for oxygen‐enhanced MRI in the mouse lung using a segmented inversion‐recovery ultrashort echo‐time sequence
Authors: Zurek M. , Johansson E. , Risse F. , Alamidi D. , Olsson L. E. , Hockings P. D. 
Published: July 2013

PurposeA segmented inversion‐recovery module combined with the 2D ultrashort echo time radial technique is proposed that allows accurate pixel level T1 mapping of mouse lung in vivo.MethodsNumerical simulations were performed to estimate T1 measurement accuracy and precision versus flip angle and signal‐to‐noise ratio. Phantom measurements were used for protocol validation, where the segmented inversion‐recovery ultrashort echo‐time sequence was compared with the reference technique (inversion‐recovery rapid acquisition with refocused echoes). The in vivo experiments were carried out on free‐breathing C57 mice (n = 10), breathing first air and then oxygen.ResultsThe simulations demonstrated the high potential of the technique for accurate and precise T1 assessment. Phantom experiments showed good agreement for T1 values measured with segmented inversion‐recovery ultrashort echo‐time and the reference technique. The in vivo experiment demonstrated the utility of the technique in oxygen‐enhanced assessment, where small T1 changes were detected with high precision.ConclusionSegmented inversion‐recovery ultrashort echo‐time provides accurate, high resolution T1 mapping of the lung parenchyma. Magn Reson Med 71:2180–2185, 2014. © 2013 Wiley Periodicals, Inc.
Whole brain perfusion measurements using arterial spin labeling with multiband acquisition
Authors: Kim Tae , Shin Wanyong , Zhao Tiejun , Beall Erik B. , Lowe Mark J. , Bae Kyongtae T. 
Published: July 2013

PurposeThe multiband (MB) excitation and reconstruction technique was both developed and evaluated for accelerated data acquisition of arterial spin labeling (ASL) to cover whole brain perfusion maps.Theory and MethodsMB excitation was incorporated into a pulsed ASL (PASL) technique and compared with conventional single‐band excitation PASL from healthy subjects, using a 32‐channel head receiver coil at 3 T. The MB de‐aliasing performance and effectiveness in perfusion measurement were measured with varying MB acceleration factors and gaps between MB excitations.ResultsThe MB PASL perfusion maps were in good agreement with the conventional single‐band PASL maps at matched slices. The imaging coverage could be effectively extended with the MB technique by a factor up to 5. A gap as small as 3 cm between MB excitations resulted in a comparable ASL signal loss and temporal‐signal‐to‐noise ratio with single‐band PASL.ConclusionThe MB ASL technique is an effective method to evaluate whole brain perfusion because it minimizes the temporal spread of labeled spins across slices, resulting in more accurate perfusion measurements. Magn Reson Med 70:1653–1661, 2013. © 2013 Wiley Periodicals, Inc.
Three‐dimensional heart locator for whole‐heart coronary magnetic resonance angiography
Authors: Moghari Mehdi H. , Roujol Sébastien , Henningsson Markus , Kissinger Kraig V. , Annese David , Nezafat Reza , Manning Warren J. , Geva Tal , Powell Andrew J. 
Published: July 2013

PurposeCoronary magnetic resonance angiography (MRA) is commonly performed with diaphragmatic navigator (NAV) gating to compensate for respiratory motion, but this approach is inefficient as data must be reacquired when it is outside the acceptance window. We therefore developed and validated a motion compensation technique based on three‐dimensional (3D) spatial registration in which data are accepted throughout the respiratory cycle.MethodsA novel respiratory motion compensation method was implemented that acquires a low‐resolution 3D‐image of the heart (3D‐LOC) just prior to coronary MRA data acquisition. 3D‐LOC volumes were registered to the first 3D‐LOC to estimate the respiratory‐induced heart motion and to modify the coronary MRA data and reconstruct motion‐corrected images. Whole‐heart coronary MRA datasets were acquired from nine healthy subjects using a diaphragmatic NAV and using 3D‐LOC.ResultsThere was no significant difference between the subjective image score of NAV and 3D‐LOC in three main coronary branches. The vessel sharpness of 3D‐LOC was higher than NAV in the right (0.44 ± 0.08 vs. 0.49 ± 0.08; P = 0.055) and left circumflex arteries (0.49 ± 0.05 vs. 0.52 ± 0.04; P = 0.039). Scan time for 3D‐LOC was significantly shorter than NAV (4.3 ± 0.6 vs. 8.3 ± 2.3 min; P = 0.004).ConclusionCompared to NAV gating, 3D‐LOC for coronary MRA reduces scan time by nearly 50% without compromising image quality. Magn Reson Med 71:2118–2126, 2014. © 2013 Wiley Periodicals, Inc.
SPEED: SPectral Elements in Elastodynamics with Discontinuous Galerkin: a non‐conforming approach for 3D multi‐scale problems
Authors: Mazzieri I. , Stupazzini M. , Guidotti R. , Smerzini C. 
Published: July 2013

SUMMARYThis work presents a new high performance open‐source numerical code, namely SPectral Elements in Elastodynamics with Discontinuous Galerkin, to approach seismic wave propagation analysis in visco‐elastic heterogeneous three‐dimensional media on both local and regional scale. Based on non‐conforming high‐order techniques, such as the discontinuous Galerkin spectral approximation, along with efficient and scalable algorithms, the code allows one to deal with a non‐uniform polynomial degree distribution as well as a locally varying mesh size. Validation benchmarks are illustrated to check the accuracy, stability, and performance features of the parallel kernel, whereas illustrative examples are discussed to highlight the engineering applications of the method. The proposed method turns out to be particularly useful for a variety of earthquake engineering problems, such as modeling of dynamic soil structure and site‐city interaction effects, where accounting for multiscale wave propagation phenomena as well as sharp discontinuities in mechanical properties of the media is crucial. Copyright © 2013 John Wiley & Sons, Ltd.
Port reduction in parametrized component static condensation: approximation and a posteriori error estimation
Authors: Eftang Jens L. , Patera Anthony T. 
Published: July 2013

SUMMARYWe introduce a port (interface) approximation and a posteriori error bound framework for a general component‐based static condensation method in the context of parameter‐dependent linear elliptic partial differential equations. The key ingredients are as follows: (i) efficient empirical port approximation spaces—the dimensions of these spaces may be chosen small to reduce the computational cost associated with formation and solution of the static condensation system; and (ii) a computationally tractable a posteriori error bound realized through a non‐conforming approximation and associated conditioner—the error in the global system approximation, or in a scalar output quantity, may be bounded relatively sharply with respect to the underlying finite element discretization.Our approximation and a posteriori error bound framework is of particular computational relevance for the static condensation reduced basis element (SCRBE) method. We provide several numerical examples within the SCRBE context, which serve to demonstrate the convergence rate of our port approximation procedure as well as the efficacy of our port reduction error bounds. Copyright © 2013 John Wiley & Sons, Ltd.
Coupling finite element and reliability analysis through proper generalized decomposition model reduction
Authors: Gallimard L. , Vidal P. , Polit O. 
Published: July 2013

SUMMARYThe FEM is the main tool used for structural analysis. When the design of the mechanical system involves uncertain parameters, a coupling of the FEM with reliability analysis algorithms allows to compute the failure probability of the system. However, this coupling leads to successive finite element analysis of parametric models involving high computational effort. Over the past years, model reduction techniques have been developed in order to reduce the computational requirements in the numerical simulation of complex models. The objective of this work is to propose an efficient methodology to compute the failure probability for a multi‐material elastic structure, where the Young moduli are considered as uncertain variables. A proper generalized decomposition algorithm is developed to compute the solution of parametric multi‐material model. This parametrized solution is used in conjunction with a first‐order reliability method to compute the failure probability of the structure. Applications to multilayered structures in two‐dimensional plane elasticity are presented.Copyright © 2013 John Wiley & Sons, Ltd.
Coupling of polynomial approximations with application to a boundary meshless method
Authors: Tampango Yendoubouam , Potier‐Ferry Michel , Koutsawa Yao , Tiem Sonnou 
Published: July 2013

SUMMARYNew bridging techniques are introduced to match high degree polynomials. This permits piecewise resolutions of elliptic partial differential equations (PDEs) in the framework of a boundary meshless method introduced recently. This new meshless method relies on the computation of Taylor series approximations deduced from the PDE, the shape functions being high degree polynomials. In this way, the PDE is solved quasi‐exactly inside the subdomains so that only discretization of the boundary and the interfaces are needed, which leads to small size matricial problems. The bridging techniques are based on the introduction of Lagrange multipliers and a set of collocation points on the boundary and the interfaces. Several numerical applications establish that the method is robust and permits an exponential convergence with the degree. Copyright © 2013 John Wiley & Sons, Ltd.