bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigation of hydrodynamics of binary fluidized beds via radioactive particle tracking and dual‐source densitometry
Authors: Upadhyay Rajesh K. , Roy Shantanu
Published: June 2010

The mixing and hydrodynamic behaviour of binary fluidized beds of particles of same size and differing density has been investigated experimentally by using radiation based non‐invasive techniques, viz. radioactive particle tracking (RPT) and dual‐source densitometry. The effect of air inlet velocity and bed composition has been investigated. RPT experiments are performed individually for both the solids by tracking one particle at a time. Many interesting findings are discussed, for example, such as the heavier (jetsam) phase is seen to be fluidized by action of the lighter (flotsam) phase even below its minimum fluidization velocity. Further, it has been found that while with increase in air inlet velocity, the extent of mixing of solid phases increases; even at very high air velocities the jetsam phase is not completely mixed. The important role played by the particle–particle collisions in the fluidization of binary mixtures is quantitatively highlighted.

Le mélange et le comportement hydrodynamique des lits fluidisés binaires de particules de même taille et de différentes densités ont été étudiés expérimentalement en utilisant une technique non invasive à base de rayonnements par le suivi des particules radioactives et la densitométrie à double foyer. L'effet de la vitesse d'admission d'air et de la composition du lit a été étudié. Des expériences de suivi des particules radioactives sont exécutées individuellement pour chacun des deux solides par le suivi d'une particule à la fois. Plusieurs résultats intéressants sont discutés, comme par exemple, il est observé que la phase plus lourde (jetsam) est fluidisée par l'action de la phase plus légère (flotsam), même en dessous de sa vitesse minimum de fluidisation. De plus, il a été constaté que, tandis qu'avec l'accroissement de la vitesse d'admission d'air, l'ampleur du mélange des phases solides augmente, la phase jetsam n'est pas complètement mélangée même à des vitesses d'air très élevées. Le rôle important joué par les collisions particule‐particule dans la fluidisation des mélanges binaires est quantitativement mis en évidence.
Intensified operation of slurry bubble columns using structured gas injection
Authors: Hooshyar Nasim , Hamersma Peter J. , Mudde Robert F. , van Ommen J. Ruud
Published: June 2010

We investigate uniform gas injection using a needle sparger as a structuring methodology to reduce backmixing in slurry bubble columns. Using optical probes, we determined the gas fraction and the bubble behaviour in 2D and 3D slurry bubble columns with a uniform gas injection. Experimental results for air–water–glass beads (ds = 108 µm, Usg = 0–0.10 m/s) indicate that a strong reduction in the vortical structures has been achieved and the homogeneous flow regime can be extended beyond 30% gas fraction. Increasing the solids concentration decreases the gas fraction and widens the bubble velocity distribution. Furthermore, we show by modelling that the reduced backmixing leads to a major improvement of the conversion in case of Fischer–Tropsch synthesis.
Clustering behaviour in gas–liquid–solid circulating fluidized beds with low solid holdups of resin particles
Authors: Liu Jianhua , Liu Mingyan , Zongding Hu
Published: June 2010

The flow in a gas–liquid–solid circulating fluidized bed is self‐organised and manifests itself with clustering of particles and bubbles. The clustering behaviour in the fluidized bed at low solid holdups of resin particles was experimentally investigated with a high‐speed image measurement and treatment technique of complementary metal oxide semiconductor to enhance the fundamental understanding on such a flow. Several new physical quantities were suggested to characterise such ordered flow structures. The main findings are as follows. The clusters of solid particles largely exist as doublets and triplets, the mixed groups of particles and bubbles mostly exist as one bubble carrying two to four particles. Increasing superficial liquid velocity, particle diameter or density weakens the aggregation degrees of both particle and mixed clusters in the riser and downer, except that the increase of superficial liquid velocity enhances the mixed clustering behaviour in the riser. The climbing of the auxiliary liquid velocity or liquid phase viscosity intensifies the aggregation behaviour, except that the increase of liquid phase viscosity reduces the mixed clustering degree in the riser. The influences of superficial gas velocity and surface tension of liquid phase on the clustering behaviour seem to be a little complex and the trends are not simply increasing or decreasing. The life cycle of solid particle clusters in the GLS riser is not sensitive to the operation conditions, being around 0.07 s. The mixed clusters' life cycle is more sensitive to the conditions and physical properties of phases, changing from 0.02 to 0.07 s.
Dynamic adsorption of octanols at air/water interface
Authors: Phan Chi M.
Published: June 2010

The dynamic adsorptions of 1‐, 2‐ and 3‐octanols at air/water interface were monitored using pendant drop method. It has been found that 1‐octanol had strongest interfacial effects, yet slowest rate of adsorption. The experimental data were compared with diffusion‐controlled and diffusion‐kinetic‐mixed models. Excepting 3‐octanol at 1 mM, all systems required kinetic step. The effective kinetic constant was found varying with the concentration and the carbinol position. The results highlighted the influence of hydrophobic tails on the dynamic adsorption.
Simulation of hydrodesulfurization using artificial neural network
Authors: Wang Weizhi , Zhang Qikai , Ding Lianhui , Zheng Ying
Published: June 2010

Artificial neural network (ANN) is applied to investigate the hydrodesulfurization (HDS) process with light‐cycle oil as feed and NiMo/Al2O3 as catalyst. ANN models frequently work as a “black box” which makes the model invisible to users and always need significant data for training. In this work, a new ANN is proposed. The Langmuir–Hinshelwood kinetic mechanism is incorporated into the model so that the proposed ANN model is forced to follow the given reaction mechanisms. Both advantages of self‐learning ability of ANN and the existing knowledge of HDS were taken into account. Lengthy training process is minimised. Effects of operating temperature, pressure, and LHSV on the sulfur removal rate are studied. The inhibition of nitrogen compounds is also investigated. It is shown that the presence of nitrogen can significantly reduce the conversion rate of sulfur components, in particularly, hard sulfur such as 4,6‐DMDBT.
Bitumen content estimation of Athabasca oil sand from broad band infrared reflectance spectra
Authors: Rivard B. , Lyder D. , Feng J. , Gallie A. , Cloutis E. , Dougan P. , Gonzalez S. , Cox D. , Lipsett M.G.
Published: June 2010

Oil sand is a mixture of quartz grains, clay minerals, bitumen, water, and minor accessory minerals. There is a need in oil sands mining operations for a robust method to estimate total bitumen content in real time; and so modelling of the total bitumen content (TBC) in Athabasca oil sands of Western Canada was undertaken on the basis of hyperspectral reflectance spectra. A selection of different bitumen, water, and clay mineral spectral features (3.0–30.0 µm) was used to develop broad‐band TBC predictive models that have good accuracy, with less than 1.5% error with respect to laboratory methods of bitumen assay. These models are also robust, in that they are independent of mine location. Simple broad band models, based upon previously identified Gaussian features or wavelet features, provide an incremental improvement over the currently deployed industry two‐band ratio model. An improved two‐band model was also developed, which makes use of a combination of the same two bands but normalised to their mean. A wavelet‐based, broad‐band model comprised of indices and five bands, where the bands are normalised to the mean of the bands, adequately addresses the influence of water, clay, and textural variation on selected bitumen features. This five‐band model appears to produce the most robust estimator of TBC, with a dispersion of ∼1.1–1.5%, which can be applied to different sites within a mine and to different mines without additional tuning or calibration, as evidenced by regression slopes of 0.99–1.0 for modelling, validation, and blind data sets.
Conditional gene expression and lineage tracing of tuba1a expressing cells during zebrafish development and retina regeneration
Authors: Ramachandran Rajesh , Reifler Aaron , Parent Jack M. , Goldman Daniel
Published: June 2010

The tuba1a gene encodes a neural‐specific α‐tubulin isoform whose expression is restricted to the developing and regenerating nervous system. By using zebrafish as a model system for studying CNS regeneration, we recently showed that retinal injury induces tuba1a gene expression in Müller glia that reentered the cell cycle. However, because of the transient nature of tuba1a gene expression during development and regeneration, it was not possible to trace the lineage of the tuba1a‐expressing cells with a reporter directly under the control of the tuba1a promoter. To overcome this limitation, we generated tuba1a:CreERT2 and β‐actin2:loxP‐mCherrry‐loxP‐GFP double transgenic fish that allowed us to label tuba1a‐expressing cells conditionally and permanently via ligand‐induced recombination. During development, recombination revealed transient tuba1a expression in not only neural progenitors but also cells that contribute to skeletal muscle, heart, and intestine. In the adult, recombination revealed tuba1a expression in brain, olfactory neurons, and sensory cells of the lateral line, but not in the retina. After retinal injury, recombination showed tuba1a expression in Müller glia that had reentered the cell cycle, and lineage tracing indicated that these cells are responsible for regenerating retinal neurons and glia. These results suggest that tuba1a‐expressing progenitors contribute to multiple cell lineages during development and that tuba1a‐expressing Müller glia are retinal progenitors in the adult. J. Comp. Neurol. 518:4196–4212, 2010. © 2010 Wiley‐Liss, Inc.
Complete mapping of glomeruli based on sensory nerve branching pattern in the primary olfactory center of the cockroach Periplaneta americana
Authors: Watanabe Hidehiro , Nishino Hiroshi , Nishikawa Michiko , Mizunami Makoto , Yokohari Fumio
Published: June 2010

Glomeruli are structural and functional units in the primary olfactory center in vertebrates and insects. In the cockroach Periplaneta americana, axons of different types of sensory neurons housed in sensilla on antennae form dorsal and ventral antennal nerves and then project to a number of glomeruli. In this study, we identified all antennal lobe (AL) glomeruli based on detailed innervation patterns of sensory tracts in addition to the shape, size, and locations in the cockroach. The number of glomeruli is ∼205, and no sex‐specific difference is observed. Anterograde dye injections into the antennal nerves revealed that axons supplying the AL are divided into 10 sensory tracts (T1–T10). Each of T1–T3 innervates small, oval glomeruli in the anteroventral region of the AL, with sensory afferents invading each glomerulus from multiple directions, whereas each of T4–T10 innervates large glomeruli with various shapes in the posterodorsal region, with a bundle of sensory afferents invading each glomerulus from one direction. The topographic branching patterns of all these tracts are conserved among individuals. Sensory afferents in a sub‐tract of T10 had axon terminals in the dorsal margin of the AL and the protocerebrum, where they form numerous small glomerular structures. Sensory nerve branching pattern should reflect developmental processes to determine spatial arrangement of glomeruli, and thus the complete map of glomeruli based on sensory nerve branching pattern should provide a basis for studying the functional significance of spatial arrangement of glomeruli and its developmental basis. J. Comp. Neurol. 518:3907–3930, 2010. © 2010 Wiley‐Liss, Inc.
Computational modeling of passive myocardium
Authors: Göktepe S. , Acharya S. N. S. , Wong J. , Kuhl E.
Published: June 2010

This work deals with the computational modeling of passive myocardial tissue within the framework of mixed, non‐linear finite element methods. We consider a recently proposed, convex, anisotropic hyperelastic model that accounts for the locally orthotropic micro‐structure of cardiac muscle. A coordinate‐free representation of anisotropy is incorporated through physically relevant invariants of the Cauchy–Green deformation tensors and structural tensors of the corresponding material symmetry group. This model, which has originally been designed for exactly incompressible deformations, is extended towards entirely three‐dimensional inhomogeneous deformations by additively decoupling the strain energy function into volumetric and isochoric parts along with the multiplicative split of the deformation gradient. This decoupled constitutive structure is then embedded in a mixed finite element formulation through a three‐field Hu–Washizu functional whose simultaneous variation with respect to the independent pressure, dilatation, and placement fields results in the associated Euler–Lagrange equations, thereby minimizing the potential energy. This weak form is then consistently linearized for uniform‐pressure elements within the framework of an implicit finite element method. To demonstrate the performance of the proposed approach, we present a three‐dimensional finite element analysis of a generic biventricular heart model, subjected to physiological ventricular pressure. The parameters employed in the numerical analysis are identified by solving an optimization problem based on six simple shear experiments on explanted cardiac tissue. Copyright © 2010 John Wiley & Sons, Ltd.
Reflectance factor measurement systematic errors due to near infrared fluorescence
Authors: Nadal Maria E. , Miller C. Cameron , Zarobila Clarence
Published: June 2010

Orange and red ceramic tiles that are widely used as measurement standards for reflectance factor unexpectedly exhibit near infrared fluorescence. Two measurement methods, illuminating the sample with broadband light and spectrally resolving the reflectance or illuminating the sample with monochromatic light and using a broadband detector, are commonly used to measure reflectance factor. The effect this fluorescence component has on the measured reflectance factor utilizing different measurement methods is analyzed. Published 2010 Wiley Periodicals, Inc. Col Res Appl, 2011
Predicting dispersion in porous media
Authors: Hunt A. G. , Skinner T. E.
Published: June 2010

We present a fundamental theory of solute dispersion in porous using (i) critical path analysis and cluster statistics of percolation theory far from the percolation threshold and (ii) the tortuosity and structure of large clusters near the percolation threshold. We use the simplest possible model of porous media, with a single length scale of heterogeneity in which the statistics of local conductances are uncorrelated. This combination of percolation‐based techniques allows comprehensive investigation and predictions concerning the process of dispersion. Our predictions, which ignore molecular diffusion and make minimal use of unknown parameters, account for results obtained in a comprehensive set of nearly 1100 experiments performed on systems ranging in size from centimeters to 100 km. The success of our simple treatment overturns many existing notions about transport in porous media, such as (1) multiscale heterogeneity must be accounted for in predictions (single scale is sufficient), (2) geologic correlations are of great importance (the randomness of percolation theory is more appropriate for prediction than the most complicated models in other frameworks), (3) geologic complexity is more important than statistical physics (exactly the reverse), (4) knowledge of the subsurface is more important than knowledge of the initial conditions of the plume (the latter is critical, the former may be virtually irrelevant), (5) diffusion is dominant over advection (diffusion appears seldom to be relevant at all), (6) fracture networks are fundamentally different, and more complex, than porous media (the two are mostly equivalent), (7) the fractal structure of the medium is relevant to power‐law behavior of the dispersion (in fact, at short times it is the heterogeneity of the medium, while at long times it is the fractal structure of the critical paths), and (8) there is a relation between an increase in dispersion with scale and a similar increase in the hydraulic conductivity (in fact the present model is consistent with both a diminishing hydraulic conductivity and a diminishing solute velocity with increasing spatial scale). © 2009 Wiley Periodicals, Inc. Complexity, 16,43–55, 2010
Detection of TiO2 nanoparticles in cells by flow cytometry
Authors: Zucker R. M. , Massaro E. J. , Sanders K. M. , Degn L. L. , Boyes W. K.
Published: June 2010

Evaluation of the potential hazard of man‐made nanomaterials has been hampered by a limited ability to observe and measure nanoparticles in cells. In this study, different concentrations of TiO2 nanoparticles were suspended in cell culture medium. The suspension was then sonicated and characterized by dynamic light scattering and microscopy. Cultured human‐derived retinal pigment epithelial cells (ARPE‐19) were incubated with TiO2 nanoparticles at 0, 0.1, 0.3, 1, 3, 10, and 30 μg/ml for 24 hours. Cellular reactions to nanoparticles were evaluated using flow cytometry and dark field microscopy. A FACSCalibur™ flow cytometer was used to measure changes in light scatter after nanoparticle incubation. Both the side scatter and forward scatter changed substantially in response to the TiO2. From 0.1 to 30 μg/ml TiO2, the side scatter increased sequentially while the forward scatter decreased, presumably due to substantial light reflection by the TiO2 particles. Based on the parameters of morphology and the calcein‐AM/propidium iodide viability assay, TiO2 concentrations below 30 μg/ml TiO2 caused minimal cytotoxicity. Microscopic analysis was done on the same cells using an E‐800 Nikon microscope containing a xenon light source and special dark field objectives. At the lowest concentrations of TiO2 (0.1–0.3 μg/ml), the flow cytometer could detect as few as 5–10 nanoparticles per cell due to intense light scattering by TiO2. Rings of concentrated nanoparticles were observed around the nuclei in the vicinity of the endoplasmic reticulum at higher concentrations. These data suggest that the uptake of nanoparticles within cells can be monitored with flow cytometry and confirmed by dark field microscopy. This approach may help fulfill a critical need for the scientific community to assess the relationship between nanoparticle dose and cellular toxicity Such experiments could potentially be performed more quickly and easily using the flow cytometer to measure both nanoparticle uptake and cellular health. Published 2010 Wiley‐Liss, Inc.
Weak Ferromagnetism Caused by a 2D Effect in Two New Cobalt(II)– and Nickel(II)–1,2‐Bis(4‐pyridyl)ethane (bpa) Polynuclear Compounds
Authors: de la Pinta Noelia , Madariaga Gotzon , Lezama Luis , Fidalgo M. Luz , Cortés Roberto
Published: June 2010

The combination of bpa [1,2‐bis(4‐pyridyl)ethane] with the pseudohalide cyanato (NCO–) ligand leads to the preparation of two new isomorphous compounds exhibiting the general formula [M(NCO)2(bpa)2]n [M = Co (1) and M = Ni (2)]. Both compounds consist of M–(gauche‐bpa)2–M chains linked by hydrogen bonds to give a global 2D network. CoII and NiII ions are octahedrally coordinated to four bpa ligands and two terminal NCO groups. The two compounds exhibit slight antiferromagnetic interactions through bpa groups and a 2D effect leading to a ferromagnetic component.
Oxidative Nucleophilic Substitution of Hydrogen in Nitroarenes with Carbanions of Protected Serine and Threonine Esters
Authors: Sulikowski Daniel , Mąkosza Mieczysław
Published: June 2010

The reactions of carbanions of protected serine and threonine esters with nitroarenes were studied. The main process involves the addition of the carbanions to the para position of the nitroarenes, which is occupied by a hydrogen atom, to form σH adducts that are subsequently oxidized by 2,3‐dichloro‐5,6‐dicyanobenzoquinone to give p‐nitroaryl derivatives of the protected serine and threonine. Oxidation of the σH adducts with dimethyldioxirane resulted in the formation of the corresponding p‐hydroxyaryl derivatives of these amino acids. Addition of the carbanions of the protected threonine ester is a highly stereoselective process controlled by the second chiral center of threonine.
Function of OPG as a traffic regulator for RANKL is crucial for controlled osteoclastogenesis
Authors: Aoki Shigeki , Honma Masashi , Kariya Yoshiaki , Nakamichi Yuko , Ninomiya Tadashi , Takahashi Naoyuki , Udagawa Nobuyuki , Suzuki Hiroshi
Published: June 2010

The amount of the receptor activator of NF-κB ligand (RANKL) on the osteoblastic cell surface is considered to determine the magnitude of the signal input to osteoclast precursors and the degree of osteoclastogenesis. Previously, we have shown that RANKL is localized predominantly in lysosomal organelles, but little is found on the osteoblastic cell surface, and consequently, the regulated subcellular trafficking of RANKL in osteoblastic cells is important for controlled osteoclastogenesis. Here we have examined the involvement of osteoprotegerin (OPG), which is currently recognized as a decoy receptor for RANKL, in the regulation of RANKL behavior. It was suggested that OPG already makes a complex with RANKL in the Golgi apparatus and that the complex formation is necessary for RANKL sorting to the secretory lysosomes. It was also shown that each structural domain of OPG is indispensable for exerting OPG function as a traffic regulator. In particular, the latter domains of OPG, whose physiologic functions have been unclear, were indicated to sort RANKL molecules to lysosomes from the Golgi apparatus. In addition, the overexpression of RANK-OPG chimeric protein, which retained OPG function as a decoy receptor but lost the function as a traffic regulator, inhibited endogenous OPG function as a traffic regulator selectively in osteoblastic cells and resulted in the upregulation of osteoclastogenic ability despite the increased number of decoy receptor molecules. Conclusively, OPG function as a traffic regulator for RANKL is crucial for regulating osteoclastogenesis at least as well as that as a decoy receptor. © 2010 American Society for Bone and Mineral Research.
Options for determination of 2‐D distribution of collagen fibrils in transmission electron micrographs—Application to the mammalian corneal stroma
Authors: Doughty Michael J.
Published: June 2010

Aims: To assess methods for both measurement of and comparison between fibril spacing arrangement in transmission electron micrograph (TEM) images of collagen fibrils. Methods: Rabbit corneas were glutaraldhyde fixed, treated with osmium tetroxide and then thin sections stained with aqueous phosphotungstic acid. TEM images, at 28,000 magnification, of collagen fibrils in cross section were projected at a final magnification close to 250,000 to obtain overlays. Fibril centers were marked and the relative position of all fibrils measured either from a cluster of fibrils within a fixed region of interest (ROI) or by using a variable sequential ROI across the micrograph. The 2‐D organization of the interfibril distance (IFD) data were analyzed using a radial distribution analysis and the difference in outcome statistically compared. Results: Repeated measures of IFDs provides data on the nearest neighbor distance within a fixed or sequential ROI of close to 48 nm and provides a numerical descriptor of the radial positions of all other fibril centers. From the set of radial positions (IFD) data, simple statistical comparisons can be made to both assess location‐to‐location and sample‐to‐sample variability. The sequential use of an ROI of fibril arrays however provide a more complete and accurate numerical descriptor. Conclusions: Methods are presented that will allow for assessment of the nearest neighbors distances and the overall 2‐D pattern of collagen fibrils in electron micrographs. The sets of IFDs and their pattern can be compared using simple statistical analyses. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.
Enameloid microstructure of some Cretaceous Hexanchiformes and Synechodontiformes (Chondrichthyes, Neoselachii): New structures and systematic implications
Authors: Guinot Guillaume , Cappetta Henri
Published: June 2010

Modern neoselachian sharks may be separated from more basal relatives by the presence of tooth enameloid comprising three layers. Although enameloid microstructure studies were mostly used in the aim of differentiating supposed basal neoselachians from hybodonts, differences in the enameloid organization among neoselachians have been recognized suggesting the potential for use of enameloid microstructure as a phylogenetic tool within the neoselachian sharks. The enameloid microstructure of five taxa of neoselachian sharks belonging to two orders, the Hexanchiformes and Synechodontiformes, has been studied. The Hexanchiformes are a monophyletic order with extant representatives, whereas the extinct Synechodontiformes have been considered as monophyletic, paraphyletic, or polyphyletic by different authors. This study has revealed numerous new enameloid microstructures such as amalgamated crystallites in the internal units [parallel‐bundled enameloid (PBE) and tangled‐bundled enameloid], cavities at the shiny‐layered enameloid (SLE)/PBE boundary, radial furrows in the PBE, as well as different original organizations at the base of the crown and in the PBE at the level of the cutting edges.Pachyhexanchus pockrandti(Hexanchiforme) andWelcommia bodeurihave the most of the features in common and they share more characters with those ofParaorthacodussp. andSphenodussp. than withSynechodussp. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.
The effect of exercise training on the metabolic interaction between feeding and locomotion in the juvenile southern catfish (Silurus meridionalis Chen)
Authors: Li Xiu‐Ming , Cao Zhen‐Dong , Fu Shi‐Jian
Published: June 2010

The southern catfish exhibits the largest decrease in critical swimming speeds (Ucrit) during digestion among the fish species that have been investigated. To test whether the maximum metabolic capacity of the southern catfish was improved after exercise training to alleviate the competitive interaction between digestion and swimming, we measured postprandial metabolic responses, Ucrit and oxygen consumption rates (MO2) during swimming in both fasting and digesting fish. Twenty‐one days of training (50 min swimming at 60% Ucrit followed by 10 min chasing) did not produce significant differences in resting MO2 (MO2rest) or postprandial peak MO2 (MO2peak). However, it did result in a significant decrease in energy expenditure during digestion. Feeding caused a significant decrease in Ucrit and an increase in active MO2 (MO2active), whereas training caused a significant increase in Ucrit but no significant change in MO2active. Neither digestion nor training had a significant effect on metabolic scope (MO2active−MO2rest). Training had no interactive effect on postprandial changes in any measured variable, so we conclude that training did not alleviate the competitive interaction between digestion and swimming. Our results suggest that: (1) the metabolic capacity of nontrained fish cannot support the metabolic demands of both digestion and locomotion simultaneously, and swimming metabolism, therefore, is sacrificed to sustain digestion when feeding and locomotion are combined (digestion‐prioritization mode); (2) the metabolic capacity and metabolic mode of competition did not change after training, but trained fish did exhibit improved swimming performance, possibly due to their increased rate of O2 extraction. J. Exp. Zool. 313A:557–563, 2010. © 2010 Wiley‐Liss, Inc.
Dissociation mechanisms and implication for the presence of multiple conformations for peptide ions with arginine at the C‐terminus: time‐resolved photodissociation study
Authors: Yoon So Hee , Moon Jeong Hee , Kim Myung Soo
Published: June 2010

Time‐resolved photodissociation (PD) patterns of singly protonated peptides with arginine at the C‐terminus (C‐arg peptide ions) have been used to classify the dissociation channels into two categories, i.e. high‐energy channels generating v, w and x and low‐energy ones generating b, y and z. x + 1 formed by CαCO cleavage seems to be the intermediate ion in high‐energy channels just as a + 1 is for N‐arg peptide ions. Difference in time‐resolved pattern indicates that the two sets of channels, high‐ and low‐energy ones, are not in direct competition. Noncompetitive dissociation is also indicated by the observation of anomalous effect of matrix used in matrix‐assisted laser desorption ionization, a cooler matrix generating more high‐energy product ions both in spontaneous dissociation and in PD. Results from detailed investigation suggest that the two sets of channels start from two (or more) different conformations. Copyright © 2010 John Wiley & Sons, Ltd.
Gallic acid induces G2/M phase cell cycle arrest via regulating 14‐3‐3β release from Cdc25C and Chk2 activation in human bladder transitional carcinoma cells
Authors: Ou Ting‐Tsz , Wang Chau‐Jong , Lee Yung‐Shu , Wu Cheng‐Hsun , Lee Huei‐Jane
Published: June 2010

Scope: Cell cycle regulation is a critical issue in cancer treatment. Previously, gallic acid (GA) has been reported to possess anticancer ability. Here, we have evaluated the molecular mechanism of GA on cell cycle modulation in a human bladder transitional carcinoma cell line (TSGH‐8301 cell). Methods and results: Using flow cytometer analysis, exposure of the cells to 40 μM GA resulted in a statistically significant increase in G2/M phase cells, which was accompanied by a decrease in G0/G1 phase cells. GA‐treated cells resulted in significant growth inhibition in a dose‐dependent manner accompanied by a decrease in cyclin‐dependent kinases (Cdk1), Cyclin B1, and Cdc25C, but significant increases in p‐cdc2 (Tyr‐15) and Cip1/p21 by western blotting. Additional mechanistic studies showed that GA induces phosphorylation of Cdc25C at Ser‐216. This mechanism leads to its translocation from the nucleus to the cytoplasm resulting in an increased binding with 14‐3‐3β. When treated with GA, phosphorylated Cdc25C can be activated by ataxia telangiectasia‐mutated checkpoint kinase 2 (Chk2). This might be a DNA damage response as indicated by Ser‐139 phosphorylation of histine H2A.X. Furthermore, treatment of the cells with a Chk2 inhibitor significantly attenuated GA‐induced G2/M phase arrest. Conclusion: These results indicate that GA can induce cell cycle arrest at G2/M phase via Chk2‐mediated phosphorylation of Cdc25C in a bladder transitional carcinoma cell line.
Compressed sensing MRI with multichannel data using multicore processors
Authors: Chang Ching‐Hua , Ji Jim
Published: June 2010

Compressed sensing (CS) is a promising method to speed up MRI. Because most clinical MRI scanners are equipped with multichannel receive systems, integrating CS with multichannel systems may not only shorten the scan time but also provide improved image quality. However, significant computation time is required to perform CS reconstruction, whose complexity is scaled by the number of channels. In this article, we propose a reconstruction procedure that uses ubiquitously available multicore central processing unit to accelerate CS reconstruction from multiple channel data. The experimental results show that the reconstruction efficiency benefits significantly from parallelizing the CS reconstructions and pipelining multichannel data into multicore processors. In our experiments, an additional speedup factor of 1.6–2.0 was achieved using the proposed method on a quad‐core central processing unit. The proposed method provides a straightforward way to accelerate CS reconstruction with multichannel data for parallel computation. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Application of k‐space energy spectrum analysis for inherent and dynamic B0 mapping and deblurring in spiral imaging
Authors: Truong Trong‐Kha , Chen Nan‐kuei , Song Allen W.
Published: June 2010

Spiral imaging is vulnerable to spatial and temporal variations of the amplitude of the static magnetic field (B0) caused by susceptibility effects, eddy currents, chemical shifts, subject motion, physiological noise, and system instabilities, resulting in image blurring. Here, a novel off‐resonance correction method is proposed to address these issues. A k‐space energy spectrum analysis algorithm is first applied to inherently and dynamically generate a B0 map from the k‐space data at each time point, without requiring any additional data acquisition, pulse sequence modification, or phase unwrapping. A simulated phase evolution rewinding algorithm and an automatic residual deblurring algorithm are then used to correct for the blurring caused by both spatial and temporal B0 variations, resulting in a high spatial and temporal fidelity. This method is validated against conventional B0 mapping and deblurring methods, and its advantages for dynamic MRI applications are demonstrated in functional MRI studies. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Diffusion‐weighted spectroscopy: A novel approach to determine macromolecule resonances in short‐echo time 1H‐MRS
Authors: Kunz N. , Cudalbu C. , Mlynarik V. , Hüppi P. S. , Sizonenko S. V. , Gruetter R.
Published: June 2010

Quantification of short‐echo time proton magnetic resonance spectroscopy results in >18 metabolite concentrations (neurochemical profile). Their quantification accuracy depends on the assessment of the contribution of macromolecule (MM) resonances, previously experimentally achieved by exploiting the several fold difference in T1. To minimize effects of heterogeneities in metabolites T1, the aim of the study was to assess MM signal contributions by combining inversion recovery (IR) and diffusion‐weighted proton spectroscopy at high‐magnetic field (14.1 T) and short echo time (=8 msec) in the rat brain. IR combined with diffusion weighting experiments (with δ/Δ = 1.5/200 msec and b‐value = 11.8 msec/μm2) showed that the metabolite nulled spectrum (inversion time = 740 msec) was affected by residuals attributed to creatine, inositol, taurine, choline, N‐acetylaspartate as well as glutamine and glutamate. While the metabolite residuals were significantly attenuated by 50%, the MM signals were almost not affected (<8%). The combination of metabolite‐nulled IR spectra with diffusion weighting allows a specific characterization of MM resonances with minimal metabolite signal contributions and is expected to lead to a more precise quantification of the neurochemical profile. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Clinical prostate T2 quantification using magnetization‐prepared spiral imaging
Authors: Foltz Warren D. , Chopra Supriya , Chung Peter , Bayley Andrew , Catton Charles , Jaffray David , Wright Graham A. , Haider Masoom A. , Ménard Cynthia
Published: June 2010

T2 quantification may augment diagnostic T2‐weighted imaging; to improve cancer detection via auto‐segmentation of multi‐parametric acquisitions and to potentiate longitudinal studies of prostate cancer. However, robust quantitative techniques are not generally accessible or refined for clinical translation. This research describes the adaptation of a magnetization‐prepared spiral imaging technique, termed T2prep for prostate application, providing whole gland coverage within a 5‐min interval with considerable insensitivity to radio‐frequency (RF) inhomogeneities. Clinical piloting in two cohorts with distinct clinical histories demonstrated the anticipated differences in zonal and tumor T2, including tumor T2 shortening compared to peripheral zone, and post‐radiotherapy shortening of peripheral zone T2. SNR calculations were performed for data acquired with or without an endo‐rectal coil in tandem with a torso phased array, to judge the potential for voxel‐based T2 mapping and thereby support focal biological characterization of cancer, hypoxia, and response to therapy within regions of dense cancer burden. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
A robust methodology for in vivo T1 mapping
Authors: Barral Joëlle K. , Gudmundson Erik , Stikov Nikola , Etezadi‐Amoli Maryam , Stoica Petre , Nishimura Dwight G.
Published: June 2010

In this article, a robust methodology for in vivo T1 mapping is presented. The approach combines a gold standard scanning procedure with a novel fitting procedure. Fitting complex data to a five‐parameter model ensures accuracy and precision of the T1 estimation. A reduced‐dimension nonlinear least squares method is proposed. This method turns the complicated multi‐parameter minimization into a straightforward one‐dimensional search. As the range of possible T1 values is known, a global grid search can be used, ensuring that a global optimal solution is found. When only magnitude data are available, the algorithm is adapted to concurrently restore polarity. The performance of the new algorithm is demonstrated in simulations and phantom experiments. The new algorithm is as accurate and precise as the conventionally used Levenberg‐Marquardt algorithm but much faster. This gain in speed makes the use of the five‐parameter model viable. In addition, the new algorithm does not require initialization of the search parameters. Finally, the methodology is applied in vivo to conventional brain imaging and to skin imaging. T1 values are estimated for white matter and gray matter at 1.5 T and for dermis, hypodermis, and muscle at 1.5 T, 3 T, and 7 T. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Reweighted ℓ1 referenceless PRF shift thermometry
Authors: Grissom William A. , Lustig Michael , Holbrook Andrew B. , Rieke Viola , Pauly John M. , Butts‐Pauly Kim
Published: June 2010

Temperature estimation in proton resonance frequency (PRF) shift MR thermometry requires a reference, or pretreatment, phase image that is subtracted from image phase during thermal treatment to yield a phase difference image proportional to temperature change. Referenceless thermometry methods derive a reference phase image from the treatment image itself by assuming that in the absence of a hot spot, the image phase can be accurately represented in a smooth (usually low order polynomial) basis. By masking the hot spot out of a least squares (ℓ2) regression, the reference phase image's coefficients on the polynomial basis are estimated and a reference image is derived by evaluating the polynomial inside the hot spot area. Referenceless methods are therefore insensitive to motion and bulk main field shifts, however, currently these methods require user interaction or sophisticated tracking to ensure that the hot spot is masked out of the polynomial regression. This article introduces an approach to reference PRF shift thermometry that uses reweighted ℓ1 regression, a form of robust regression, to obtain background phase coefficients without hot spot tracking and masking. The method is compared to conventional referenceless thermometry, and demonstrated experimentally in monitoring HIFU heating in a phantom and canine prostate, as well as in a healthy human liver. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Calculation of strict error bounds for finite element approximations of non‐linear pointwise quantities of interest
Authors: Ladevèze P. , Chamoin L.
Published: June 2010

This paper deals with the verification of simulations performed using the finite element method. More specifically, it addresses the calculation of strict bounds on the discretization errors affecting pointwise outputs of interest which may be non‐linear with respect to the displacement field. The method is based on classical tools, such as the constitutive relation error and extraction techniques associated with the solution of an adjoint problem. However, it uses two specific and innovative techniques: the enrichment of the adjoint solution using a partition of unity method, which enables one to consider truly pointwise quantities of interest, and the decomposition of the non‐linear quantities of interest by means of projection properties in order to take into account higher‐order terms in establishing the bounds. Thus, no linearization is performed and the property that the local error bounds are guaranteed is preserved. The effectiveness of the approach and the quality of the bounds are illustrated with two‐dimensional applications in the context of elastic fatigue problems. Copyright © 2010 John Wiley & Sons, Ltd.
Prognostic significance of XIAP expression in DLBCL and effect of its inhibition on AKT signalling
Authors: Hussain Azhar R , Uddin Shahab , Ahmed Maqbool , Bu Rong , Ahmed Saeeda O , Abubaker Jehad , Sultana Mehar , Ajarim Dahish , Al‐Dayel Fouad , Bavi Prashant P , Al‐Kuraya Khawla S
Published: June 2010

The inhibitor of apoptosis protein (IAP) family member X‐linked inhibitor of apoptosis protein (XIAP) is essential for cell survival in lymphoma. However, the role of XIAP overexpression in diffuse large B‐cell lymphoma (DLBCL) is not fully elucidated. Therefore, we analysed the expression of XIAP protein and its clinicopathological correlation in a large cohort of DLBCLs by immunohistochemistry in a tissue micro‐array format. XIAP was found to be overexpressed in 55% of DLBCLs and significantly associated with poor clinical outcome (p = 0.0421). To further elucidate the role of XIAP in DLBCL and the inter‐relationship with PI3‐kinase/AKT signalling, we conducted several in vitro studies using a panel of DLBCL cell lines. We found that pharmacological inhibition of XIAP led to caspase‐dependent apoptosis in DLBCL cells. We also detected an inter‐relationship between XIAP expression and activated AKT in DLBCL cells that may explain cellular resistance to PI3‐kinase/AKT inhibition‐mediated apoptosis. Finally, this anti‐apoptotic effect was overcome by simultaneous pharmacological inhibition of XIAP and PI3‐kinase/AKT signalling leading to a more potent synergistically induced apoptosis. In summary, our data suggest that XIAP expression is a poor prognostic factor in DLBCL and the XIAP‐AKT relationship should be explored further as a potential therapeutic target in DLBCL. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
p53 mutation and loss have different effects on tumourigenesis in a novel mouse model of pleomorphic rhabdomyosarcoma
Authors: Doyle Brendan , Morton Jennifer P , Delaney David W , Ridgway Rachel A , Wilkins Julie A , Sansom Owen J
Published: June 2010

Pleomorphic rhabdomyosarcoma is the most common variant of this tumour in adults and has a very poor outcome. Two genes which are known to play a role in rhabdomyosarcoma development are KRas and p53. In the majority of human tumours, p53 abnormalities are point mutations that result in the expression of a mutant form of the protein. It is now hypothesized that these mutant forms of p53 may be playing an oncogenic role, over and above simple loss of the wild‐type function. In this study, we use Cre‐LoxP technology to develop a novel mouse model of rhabdomyosarcoma, crossing mice expressing a common KRas mutation (G12V) with mice that either lose p53 expression or express a mutant form of p53. We use this model to explore the different effects of p53 loss and mutation in the setting of an activating KRas mutation. We found that either complete loss of p53 (p53$^{\rm{fl/fl}}$) or the expression of one mutant p53 allele with concomitant loss of the second allele (p53$^{\rm{R172H/fl}}$) resulted in the rapid development of rhabdomyosarcoma in 15/16 and 19/19 mice, respectively. In contrast, there was a marked difference between mice which lose a single copy of p53 (p53$^{{\rm{fl}}/+}$) and mice expressing a single copy of mutant p53 (p53$^{{\rm {172H}}/+}$). Fourteen out of 16 p53$^{{\rm{R172H}}/+}$ mice developed rhabdomyosarcoma, compared with two out of 31 p53$^{{\rm{fl}}/+}$ mice. As a consequence of this, p53$^{{\rm{fl}}/+}$ mice had a median lifespan nearly double that of the p53$^{{\rm{R172H}}/+}$ mice. To underline the enhanced effect of p53 mutation in tumour progression, metastases were seen only in those mice which expressed the mutant form. These data demonstrate that mutant p53 can co‐operate with activated, mutant KRas to influence tumourigenesis and metastatic potential, over and above simple loss of normal protein function. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Glial‐derived neurotrophic factor regulates intestinal epithelial barrier function and inflammation and is therapeutic for murine colitis
Authors: Zhang Dei Kui , He Fu Qian , Li Tian Ke , Pang Xue Hua , Cui De Jun , Xie Qin , Huang Xiao Li , Gan Hua Tian
Published: June 2010

Although enteric glial cells (EGCs) have been demonstrated to play a key role in maintaining intestinal epithelial barrier integrity, it is not known how EGCs regulate this integrity. We therefore hypothesized that glial‐derived neurotrophic factor (GDNF) produced by EGCs might be involved in this regulation. Here we investigated the role of GDNF in regulating epithelial barrier function in vivo. Recombinant adenoviral vectors encoding GDNF (Ad‐GDNF) were administered intracolonically in experimental colitis induced by dextran sulphate sodium (DSS). The disease activity index (DAI) and histological score were measured. Epithelial permeability was assayed using Evans blue dye. The anti‐apoptotic potency of GDNF in vivo was evaluated. The expression of tumour necrosis factor‐α (TNF‐α), interleukin‐1β (IL‐1β), and myeloperoxidase (MPO) activity were measured by ELISA assay and/or RT‐PCR. The expression of ZO‐1, Akt, caspase‐3, and NF‐κB p65 was analysed by western blot assay. Our results showed that GDNF resulted in a significant reduction in enhanced permeability, inhibited MPO activity, IL‐1β and TNF‐α expression, and increased ZO‐1 and Akt expression. Moreover, GDNF strongly prevented apoptosis in vivo and significantly ameliorated experimental colitis. Our findings indicate that GDNF participates directly in restoring epithelial barrier function in vivo via reduction of increased epithelial permeability and inhibition of mucosal inflammatory response, and is efficacious in DSS‐induced colitis. These findings support the notion that EGCs are able to regulate intestinal epithelial barrier integrity indirectly via their release of GDNF in vivo. GDNF is namely an important mediator of the cross‐talk between EGCs and mucosal epithelial cells. GDNF may be a useful therapeutic approach to the treatment of inflammatory bowel disease. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.