bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and thermal properties of hybrid nanocomposites of poly(methyl methacrylate)/octavinyl polyhedral oligomeric silsesquioxane blends
Authors: Feng Yan , Jia Yong , Xu Hongyao
Published: December 2008

A series of poly(methyl methacrylate) (PMMA)/octavinyl polyhedral oligomeric silsesquioxane (POSS) blends were prepared by the solution‐blending method and characterized with Fourier transform infrared, X‐ray diffraction, transmission electron microscopy, differential scanning calorimetry, and thermogravimetric analysis techniques. The glass‐transition temperature (Tg) of the PMMA–POSS blends showed a tendency of first increasing and then decreasing with an increase in the POSS content. The maximum Tg reached 137.2°C when 0.84 mol % POSS was blended into the hybrid system, which was 28.2°C higher than that of the mother PMMA. The X‐ray diffraction patterns, transmission electron microscopy micrographs, and Fourier transform infrared spectra were employed to investigate the structure–property relationship of these hybrid nanocomposites and the Tg enhancement mechanism. The results showed that at a relatively low POSS content, POSS as an inert diluent decreased the interaction between the dipolar carbonyl groups of the homopolymer molecular chains. However, a new stronger dipole–dipole interaction between the POSS and the carbonyl of PMMA species formed at the same time, and a hindrance effect of nanosize POSS on the motion of the PMMA molecular chain may have played the main role in the Tg increase of the hybrid nanocomposites. At relatively high POSS concentrations, the strong dipole–dipole interactions that formed between the POSS and carbonyl groups of the PMMA gradually decreased because of the strong aggregation of POSS. This may be the main reason for the resultant Tg decrease in these hybrid nanocomposites. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Poly(vinyl acetate)/polyacrylate semi‐interpenetrating polymer networks, part 1: Synthesis and polymerization kinetics
Authors: Martinelli A. , Tighzert L. , D'Ilario L. , Francolini I. , Piozzi A.
Published: December 2008

Bulk photopolymerization was used to synthesize a series of semi‐interpenetrating polymer network (s‐IPN) based on linear poly(vinyl acetate) and crosslinked N‐butyl acrylate/1,6‐hexandiol diacrylate (HDDA) copolymer. Different formulations were used by varying the monoacrylate/diacrylate molar ratio and the linear polymer concentration. The polymerization kinetics was studied as a function of the s‐IPN composition by FTIR spectroscopy. It was observed that the reaction rate increases by increasing the linear polymer amount. This effect is much more pronounced in the reaction mixtures with a higher diacrylate concentration, playing a key role the restricted mobility of the macroradicals involved in the bimolecular termination. The maximum conversion increases regularly with linear polymer concentration in the blend and resulted to be very high, ranging from 95 to 98%. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Preparation and properties of ethylene/POSS copolymer with rac‐Et(Ind)2ZrCl2 catalyst
Authors: Zhang He‐xin , Jung Myung‐sung , Shin Young‐jun , Yoon Keun‐byoung , Lee Dong‐ho
Published: December 2008

The various monovinyl‐functional polyhedral oligomeric silsesquioxane (POSS) monomers had been copolymerized with ethylene (E) using rac‐Et(Ind)2ZrCl2 and a modified methylaluminoxane (MMAO) cocatalyst. The unreacted POSS monomer could be removed completely by washing the copolymerization product with n‐hexane. And the copolymers were characterized with 1H NMR, TEM, DSC, TGA, and GPC to know the composition, thermal properties, molecular weight and its distribution, respectively. According to 1H NMR data, the monomer reactivity ratios of various POSS monomers were calculated by the Fineman‐Ross and Kelen‐Tudos methods. Thermogravimetric analysis of E/POSS copolymers exhibited an improved thermal stability with a higher degradation temperature and char yields, demonstrating that the inclusion of inorganic POSS nanoparticles made the organic polymer matrix more thermally robust. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Poly(vinyl acetate)/polyacrylate semi‐interpenetrating polymer networks. II. Thermal, mechanical, and morphological characterization
Authors: Martinelli A. , Tighzert L. , D'Ilario L. , Francolini I. , Piozzi A.
Published: December 2008

The thermal, dynamic mechanical, and mechanical properties and morphology of two series of semi‐interpenetrating polymer networks (s‐IPNs) based on linear poly(vinyl acetate) (PVAc) and a crosslinked n‐butyl acrylate/1,6‐hexanediol diacrylate copolymer were investigated. The s‐IPN composition was varied with different monoacrylate/diacrylate monomer ratios and PVAc concentrations. The crosslinking density deeply affected the thermal behavior. The results showed that a more densely crosslinked acrylate network promoted phase mixing and a more homogeneous structure. The variation in the linear polymer concentration influenced both the morphology and mechanical properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009
Asymmetry of Thyroid Lobe Volume in Normal Chinese Subjects: Association with Handedness and Position of Esophagus
Authors: Ying Michael , Yung Dennis M.C.
Published: December 2008

This study aimed to investigate the association of handedness and position of esophagus with thyroid size asymmetry. One hundred and five healthy subjects were included, and their occurrence of thyroid nodules and position of the esophagus were assessed with ultrasound. Three‐dimensional ultrasound was used to measure the volume of the thyroid lobes. The handedness of the subjects was also assessed. Thyroid nodules were found in 43 subjects who were excluded from the study, whereas 62 subjects showed normal thyroid. For normal thyroid, the right lobe (6.8 mL) was significantly larger than the left lobe (5.66 mL) (P < 0.05). Right‐handed subjects (mean, 7.11 mL) had a significantly larger right lobe than left‐handed subjects (mean, 5.82 mL) (P < 0.05). There was no significant difference in the left lobe volume between right‐handers (mean, 5.81 mL) and left‐handers (mean, 5.18 mL) (P > 0.05). Subjects with an esophagus deviated to the left (mean, 7.15 mL) had a significantly larger right lobe than those with a centrally located esophagus (mean, 5.7 mL) (P < 0.05). There was no significant difference in the left lobe volume between subjects with different esophageal positions (deviated to left: mean, 5.76 mL; centrally located: mean, 5.19 mL) (P > 0.05). Thyroid asymmetry is associated with the handedness of subjects and the position of the esophagus. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.
Effect of eda Loss of Function on Upper Jugal Tooth Morphology
Authors: Charles Cyril , Pantalacci Sophie , Peterkova Renata , Tafforeau Paul , Laudet Vincent , Viriot Laurent
Published: December 2008

The Tabby/eda mice, which bear a loss of function mutation for the eda (ectodysplasinA) gene, are known to display developmental anomalies in organs with an ectodermal origin. Although the lower jugal (cheek) teeth of Tabby/eda mice have been extensively studied, upper teeth have never been investigated in detail. However, this may help us to further understand the function of the eda gene in tooth development. In this work, the shape and size of both the crown and the radicular system were studied in the Tabby/eda mice upper jugal teeth. To deal with the high morphological variability, we defined several morphotypes based on cusp numbers and position. Statistical tests were then performed within and between the different morphotypes to test the correlation between tooth size and morphology. Our analysis reveals that, as in lower teeth, eda is necessary to segment the dental lamina into three teeth with the characteristic size and proportions of the mouse. Nevertheless, since strong effects are observed in heterozygous upper teeth while lower are only mildly affected, it seems that the upper jaw is more sensitive than the lower jaw to the loss of eda function. Modifications in cusp number and the abnormal crown size of the teeth are clearly linked, and our results indicate a role of eda in cusp patterning. Moreover, we found that the Tabby mutation induces variations in the dental root pattern, sometimes associated with hypercementosis, suggesting a newly uncovered role played by eda in root patterning and formation. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.
Diffusion Tensor Imaging of Ex Vivo Cervical Spinal Cord Specimens: The Immediate and Long‐Term Effects of Fixation on Diffusivity
Authors: Kim T.H. , Zollinger L. , Shi X.F. , Rose J. , Jeong E.‐K.
Published: December 2008

Diffusion tensor imaging (DTI) is an emerging noninvasive method for evaluating tissue microstructure, but is highly susceptible to in vivo motion artifact. Ex vivo experiments on fixed tissues are needed to improve DTI techniques, which require fixed tissue specimens. Several efforts have been made to study the effect of fixation on both human and mouse tissue, with varying results. Four human cervical cords and three segments of pig cervical spinal cord specimens were imaged both before and after tissue fixation using 3D multishot diffusion weighted imaging (ms‐DWEPI). Fixation caused a significant decrease in the longitudinal diffusivity whereas the relative anisotropy (RA) and radial diffusivity remained unaffected. Additionally, once adequately preserved, the diffusivity parameters of fixed tissue remain constant over time. Fixation has important effects on the diffusivity of tissue specimens. These findings have important implications for the determination of tissue microstructure and function using DTI technologies. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.
Area of Rests of Malassez in Young and Adult Rat Molars: Evidences in the Formation of Large Rests
Authors: Cerri Paulo Sérgio , Gonçalves Jakobe De Souza , Sasso‐cerri Estela
Published: December 2008

Recently, we have demonstrated that the reduction in the number of rests of Malassez (RM) according to age may be due to epithelial cell death by apoptosis. It is known that, under experimental or pathological conditions, the epithelial cells of RM can proliferate, resulting in the formation of odontogenic cysts and tumors. In this study, the area of RM profiles and the number of profiles of epithelial cell nuclei/RM were investigated in young and adult rats. Fragments containing upper molars of rats aged 29, 45, and 120 days were fixed, decalcified, and embedded for light microscopy. In the sections stained by hematoxylin and eosin, the numerical density of RM profiles/mm2 of periodontal ligament, the area of each RM profile and the number of epithelial cell nuclei profile/RM were obtained. Moreover, detection of cytokeratin by immunohistochemistry and ultrastructural analysis of RM were carried out. Smaller RM were found in all groups, but the very large RM were only observed in the 120‐day‐old rats. The presence of cells in close juxtaposition exhibiting cytokeratin filaments in their cytoplasm, including in the large RM, characterized their epithelial nature. The number of epithelial cells/RM varied proportionally to the area. Moreover, epithelial cells in mitosis were found in small and large RM, indicating that cellular proliferation can be responsible for the enlargement of RM, under physiological conditions. The results suggest that a possible disequilibrium between the proliferative and apoptotic processes can be related to the enlargement of some RM in the 120‐day‐old rats. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.
Intramural Purkinje Cell Network of Sheep Ventricles as the Terminal Pathway of Conduction System
Authors: Ryu Shonosuke , Yamamoto Shoji , Andersen Clark R. , Nakazawa Kiyoshi , Miyake Fumihiko , James Thomas N.
Published: December 2008

To identify the anatomical basis for cardiac electrical signal conduction, particularly seeking the intramural terminals of conduction pathway within the ventricles, sheep hearts were examined compared with human hearts utilizing the characteristic morphology of Purkinje cells as a histological marker. In 15 sheep and five human autopsies of noncardiac death, prevalence of Purkinje or Purkinje‐type cells were histologically examined in the atrioventricular node, its distal conduction pathway, the interventricular septum, and the right‐ and left‐ventricular free walls. Myocardial tissue cleavages were examined in the transmural sections (along cardiac base‐to‐apex axis) obtained from the septum and ventricular free walls. Serial histological sections through virtually the entirety of the septum in selected sheep were used as the basis of a three‐dimensional reconstruction of the conduction pathway, particularly of the intramural Purkinje cell network. Purkinje cells were found within the mural myocardium of sheep ventricles whereas no intramural Purkinje‐type cell was detected within the human ventricles. In the sheep septum, every intramural Purkinje cell composed a three‐dimensional network throughout the mural myocardium, which proximally connected to the subendocardial extension of the bundle branches and distally formed an occasional junction with ordinary working myocytes. The Purkinje‐cell network may participate in the ventricular excitation as the terminal conduction pathway. Individual connections among the Purkinje cells contain the links of through‐wall orientation which would benefit the signal conduction crossing the architectural barriers by cleavages in sheep hearts. The myocardial architectural changes found in diseased hearts could disrupt the network links including those with transmural orientation. Anat Rec, 2009. © 2008 Wiley‐Liss, Inc.
Redistribution of xylan in maize cell walls during dilute acid pretreatment
Authors: Brunecky Roman , Vinzant Todd B. , Porter Stephanie E. , Donohoe Bryon S. , Johnson David K. , Himmel Michael E.
Published: December 2008

Developing processes for the conversion of biomass for use in transportation fuels production is becoming a critically important economic and engineering challenge. Dilute acid pretreatment is a promising technology for increasing the enzymatic digestibility of lignocellulosic biomass. However, a deeper understanding of the pretreatability of biomass is needed so that the rate of formation and yields of sugars can be increased. Xylan is an important hemicellulosic component of the plant cell wall and acts as a barrier to cellulose, essentially blocking cellulase action. To better understand xylan hydrolysis in corn stover, we have studied changes in the distribution of xylan caused by dilute acid pretreatment using correlative microscopy. A dramatic loss of xylan antibody signal from the center of the cell wall and an increase or retention of xylan at the plasma membrane interface and middle lamella of the cell were observed by confocal laser scanning microscopy (CLSM). We also observed a reduction in xylan fluorescence signal by CLSM that is generally consistent with the decrease in xylan content measured experimentally in the bulk sample, however, the compartmentalization of this xylan retention was not anticipated. Biotechnol. Bioeng. 2009;102: 1537–1543. © 2008 Wiley Periodicals, Inc.
3D culture of osteoblast‐like cells by unidirectional or oscillatory flow for bone tissue engineering
Authors: Du Dajiang , Furukawa Katsuko S. , Ushida Takashi
Published: December 2008

A medium perfusion system is expected to be beneficial for three‐dimensional (3D) culture of engineered bone, not only by chemotransport enhancement but also by mechanical stimulation. In this study, perfusion systems with either unidirectional or oscillatory medium flow were developed, and the effects of the different flow profiles on 3D culturing of engineered bone were studied. Mouse osteoblast‐like MC 3T3‐E1 cells were 3D‐cultured with porous ceramic scaffolds in vitro for 6 days under static and hydrodynamic conditions with either a unidirectional or oscillatory flow. We found that, in the static culture, the cells proliferated only on the scaffold surfaces. In perfusion culture with the unidirectional flow, the proliferation was significantly higher than in the other groups but was very inhomogeneous, which made the construct unsuitable for transplantation. Only the oscillatory flow allowed osteogenic cells to proliferate uniformly throughout the scaffolds, and also increased the activity of alkaline phosphatase (ALP). These results suggested that oscillatory flow might be better than unidirectional flow for 3D construction of cell‐seeded artificial bone. The oscillatory perfusion system could be a compact, safe, and efficient bioreactor for bone tissue engineering. Biotechnol. Bioeng. 2009;102: 1670–1678. © 2008 Wiley Periodicals, Inc.
Modification of native collagen with cell‐adhesive peptide to promote RPE cell attachment on Bruch's membrane
Authors: Sistiabudi Rizaldi , Paderi John , Panitch Alyssa , Ivanisevic Albena
Published: December 2008

Current efforts to reverse loss of visual function due to Age‐related Macular Degeneration point to the restoration of the Retinal Pigment Epithelial (RPE) layer. Restoration of the RPE layer involves replacing lost RPE cells as well as addressing the degeneration of the underlying Bruch's membrane (BM). To advance the potential of using donor BM, we present a strategy to achieve specific and controllable modification of the inner collagenous layer (ICL) of the Bruch's membrane. In particular, interaction between a collagen binding peptide (CBP) sequence with exposed collagen fibers on the ICL surface is utilized to anchor bioactive molecules. Here, a cell‐adhesion sequence is added to the collagen binding sequence to promote attachment and survival of ARPE‐19. First, the binding specificity of the CBP sequence is verified with a fluorescent binding assay. Subsequently, the effect of modification using the peptide is studied qualitatively using confocal fluorescent imaging and quantitatively through a cell proliferation assay. Results of these experiments indicate that the peptide sequence binds specifically to collagen fibers. Additionally, modification using the peptide enhanced cell adhesion, allowing large uniform cell networks to be formed on the surface. Furthermore, modification with the peptide also delayed the onset of apoptosis on adherent cells. Biotechnol. Bioeng. 2009;102: 1723–1729. © 2008 Wiley Periodicals, Inc.
Development of mammalian production cell lines expressing CNTO736, a glucagon like peptide‐1‐MIMETIBODYTM: Factors that influence productivity and product quality
Authors: Dorai Haimanti , Nemeth Jennifer F. , Cammaart Erwin , Wang Yonghui , Tang Qing Mike , Magill Allen , Lewis Michael J. , Raju T. Shantha , Picha Kristen , O'Neil Karyn , Ganguly Subinay , Moore Gordon
Published: December 2008

In an attempt to develop a high producing mammalian cell line expressing CNTO736, a Glucagon like peptide‐1‐antibody fusion protein (also known as a Glucagon like peptide‐1 MIMETIBODYTM), we have noted that the N‐terminal GLP‐1 portion of the MIMETIBODYTM was susceptible to proteolytic degradation during cell culture, which resulted in an inactive product. Therefore, a number of parameters that had an effect on productivity as well as product quality were examined. Results suggest that the choice of the host cell line had a significant effect on the overall product quality. Product expressed in mouse myeloma host cell lines had a lesser degree of proteolytic degradation and variability in O‐linked glycosylation as compared to that expressed in CHO host cell lines. The choice of a specific CHOK1SV derived clone also had an effect on the product quality. In general, molecules that exhibited minimal N‐terminal clipping had increased level of O‐linked glycosylation in the linker region, giving credence to the hypothesis that O‐linked glycosylation acts to protect against proteolytic degradation. Moreover, products with reduced potential for N‐terminal clipping had longer in vivo serum half‐life. These findings suggest that early monitoring of product quality should be an essential part of production cell line development and therefore, has been incorporated in our process of cell line development for this class of molecules. Biotechnol. Bioeng. 2009;103: 162–176. © 2008 Wiley Periodicals, Inc.
The state and evolution of information systems research in canada: a scientometric analysis
Authors: Serenko Alexander , Cocosila Mihail , Turel Ofir
Published: December 2008

This paper investigates the state and evolution of information systems (IS) research in Canada as reflected in publications of the proceedings of the annual conference of the Administrative Sciences Association of Canada from 1974 to 2007. We present a scientometric analysis of (a) individual and institutional research outputs; (b) differences in three productivity score calculation methods: straight count, equal credit, and author position; (c) study topics; (d) research methods; and (e) use of student samples. Copyright © 2008 ASAC. Published by John Wiley & Sons, Ltd.
Promoter methylation of the Wnt/β‐catenin signaling antagonist Dkk‐3 is associated with poor survival in gastric cancer
Authors: Yu Jun , Tao Qian , Cheng Yuen Y. , Lee Kwan Y. , Ng Simon S. M. , Cheung Kin F. , Tian Linwei , Rha Sun Y. , Neumann Ulf , Röcken Christoph , Ebert Matthias P. A. , Chan Francis K. L. , Sung Joseph J. Y.
Published: December 2008

BACKGROUND:

Abnormal activation of the Wnt/β‐catenin signaling pathway is common and critical in the pathogenesis of digestive cancers. In this study, the authors investigated the promoter methylation of the dickkopf homolog 3 gene Dkk‐3 in these cancers and its prognostic significance in gastric cancer.

METHODS:

Dkk‐3 methylation was assessed in 173 patients with gastric cancers (including 104 patients who were followed for up to 4090 days) and in 128 patients with colorectal cancer. Cell growth was evaluated by using a colony‐formation assay. For survival analyses, the authors used Kaplan‐Meier plots, the log‐rank test, and Cox proportional regression.

RESULTS:

Dkk‐3 was silenced or down‐regulated in 12 of 17 gastric cancer cell lines (70.6%) and in 3 of 9 colon cancer cell lines (33.3%). The loss of gene expression was associated with promoter methylation, which could be restored by demethylating agents. Ectopic expression of Dkk‐3 suppressed colony formation. Moreover, methylation of Dkk‐3 was detected in 117 of 173 primary gastric tumors (67.6%) and in 67 of 128 colorectal tumors (52.3%). The clinical significance and the prognostic value of Dkk‐3 methylation also were examined in 104 gastric cancers and in 84 colorectal cancers. Multivariate analysis indicated that Dkk‐3 methylation was associated significantly and independently with poor disease survival (relative risk, 2.534; 95% confidence interval, 1.54–4.17; P = .002) in gastric cancer, but not in colorectal cancer. Kaplan‐Meier survival curves revealed that patients who had Dkk‐3 methylated gastric cancers had a significantly shorter survival (median, 0.76 years) compared with patients who did not have Dkk‐3 methylation (median, 2.68 years; P < .0001; log‐rank test).

CONCLUSIONS:

Epigenetic silencing of the Dkk‐3 gene by promoter methylation was a common event in gastric cancer and was associated with a poor outcome in such patients. Cancer 2009. © 2008 American Cancer Society.
Murine bone marrow–derived mesenchymal stem cells as vehicles for interleukin‐12 gene delivery into Ewing sarcoma tumors
Authors: Duan Xiaoping , Guan Hui , Cao Ying , Kleinerman Eugenie S.
Published: December 2008

BACKGROUND:

This study evaluated the therapeutic efficacy of interleukin 12 (IL‐12) gene therapy in Ewing sarcoma and whether murine mesenchymal stem cells (MSCs) could serve as vehicles for IL‐12 gene delivery.

METHODS:

MSCs were isolated from murine bone marrow cells. Cells were phenotyped using flow cytometry. Cultured MSCs differentiated into osteocytes and adipocytes using the appropriate media. Freshly isolated MSCs were transfected with adenoviral vectors containing either the β‐galactosidase (Ad:β‐gal) or the IL‐12 (Ad:IL‐12) gene. Expression of IL‐12 was confirmed using reverse transcription polymerase chain reaction. Mice with TC71 Ewing sarcoma tumors were then treated intravenously with MSCs transfected with Ad:β‐gal or Ad:IL‐12. Tumors were measured and analyzed by immunohistochemical analysis for expression of IL‐12 protein.

RESULTS:

Expression of both p35 and p40 IL‐12 subunits was demonstrated in MSCs transfected in vitro with Ad:IL‐12. IL‐12 expression was seen in tumors from mice treated with MSCs transfected with Ad:IL‐12. Tumor growth was also significantly inhibited compared with that in mice treated with MSCs transfected with Ad:β‐gal.

CONCLUSIONS:

MSCs can be transfected with the IL‐12 gene. These transfected cells localize to tumors after intravenous injection and induce local IL‐12 protein production and the regression of established tumors. Cancer 2009. © 2008 American Cancer Society.
Analysis of early ventral telencephalic defects in mice lacking functional Gli3 protein
Authors: Yu Tian , Fotaki Vassiliki , Mason John O. , Price David J.
Published: December 2008

The transcription factor Gli3 is expressed throughout developing telencephalon. Previous studies have focused on Gli3's role in dorsal telencephalon, which is greatly reduced in size inGli3Xt/Xtmutants. We examined the effects of loss of Gli3 on early development of ventral telencephalon. Ventral telencephalon was defined in both wildtypes andGli3Xt/Xtmutants on the basis of its expression of Olig2, Nkx2.1, Mash1, and Foxg1 and its lack of expression of Pax6. We found that at embryonic day (E)10.5 the volume of the ventral telencephalon is about 50% greater inGli3Xt/Xtmutants than in wildtypes. By E12.5, however, the volume of the ventral telencephalon is about 20% lower inGli3Xt/Xtmutants than in wildtypes. We observed a significant increase in the number of both apoptotic cells and newly differentiated neurons in the E10.5Gli3Xt/Xtventral telencephalon, suggesting that increased cell death and withdrawal of cells from the cell cycle might account for the failure of theGli3Xt/Xtventral telencephalon to grow normally by E12.5. We found no changes in the lengths of the cell cycles of proliferating ventral telencephalic cells at E10.5. We used marker analysis and optical projection tomography to assess theGli3Xt/Xtforebrain in three dimensions and found that theGli3Xt/Xtdiencephalon is shifted relatively rostrally. We conclude that in the absence of Gli3 an abnormally large portion of the newly formed telencephalon is specified to a ventral fate but this then suffers impaired growth, due to defects of cell differentiation and death, contributing to severe distortion of the forebrain. J. Comp. Neurol. 512:613–627, 2009. © 2008 Wiley‐Liss, Inc.
Central projections of octavolateralis nerves in the brain of a soniferous damselfish (Abudefduf abdominalis)
Authors: Maruska Karen P. , Tricas Timothy C.
Published: December 2008

Sounds and hydrodynamic stimuli are important cues detected by the octavolateralis system in fishes. The central organization of auditory, mechanosensory, and vestibular projections is known for only a few phylogenetically diverse fishes, and less is known about projections in derived perciforms that use sounds for acoustic communication. We used neuronal labeling to provide a detailed analysis of octavolateralis endorgan projections in a soniferous perciform that does not have accessory morphological structures to enhance hearing. Octavolateralis nerves terminate ipsilaterally within seven medullary octaval nuclei: caudal (CON) and medial (MON) octavolateralis, anterior (AON), descending (DON), magnocellular (MgON), tangential (TON), and posterior (PON) octaval nuclei, and the eminentia granularis (EG). Anterior and posterior lateral line nerves project to the CON and MON, with dense projections to the EG. Semicircular canal nerves project primarily to ventral regions including the TON, ventral DON, intermediate DON (DONi), and MgON. Otolithic, semicircular canal, and anterior lateral line nerves all project to the MgON, which may serve a sensorimotor integration function. The DONi receives primarily segregated projections from all otolithic and semicircular canal nerves, whereas the ventral DON and TON receive principally utricular and semicircular canal afferents. The AON receives dense lateral and ventral projections from the saccule and utricle, and medial and dorsal projections from the lagena. These projection patterns are similar to those reported for non‐sonic perciforms, and indicate the absence of neuroanatomical modifications in first‐order octavolateralis nuclei in species that use acoustic communication. Thus patterns of central projections may be conserved among vocal and non‐vocal perciforms. J. Comp. Neurol. 512:628–650, 2009. © 2008 Wiley‐Liss, Inc.
Application of the homotopy perturbation method for the Fokker–Planck equation
Authors: Yıldırım Ahmet
Published: December 2008

In this paper, we will discuss the solution of an initial value problem of parabolic type. The main objective is to propose an alternative method of solution, one not based on finite difference or finite element or spectral methods. The aim of the present paper is to investigate the application of the Homotopy perturbation method (HPM) for solving the Fokker–Planck equation and some similar equations. This method is a powerful tool for solving various kinds of problems. Employing this technique, it is possible to find the exact solution or an approximate solution of the problem. The results show applicability, accuracy and efficiency of HPM in solving nonlinear differential equations. It is predicted that HPM can be widely applied in science and engineering problems. Copyright © 2008 John Wiley & Sons, Ltd.
A new numerical method for BLT forward problem based on high‐order finite elements
Authors: Hou Yanbin , Tian Jie , Wu Yan , Liang Jimin , He Xiaowei
Published: December 2008

Molecular imaging possesses the ability to characterize and measure biological processes at the cellular and molecular level in vivo. As one of the new molecular imaging modalities, bioluminescence tomography (BLT) is to reconstruct the light distribution inside a small animal from the photon flux measured on its surface. To obtain accurate and robust reconstruction, it needs a good understanding of the propagation of photons in biological tissues, which is referred to as the forward problem in BLT. Because the turbid media is high scattering and low absorption, the propagation process can be described by the steady diffusion equation. In this paper, an hp‐adaptivity method for BLT forward problem is presented based on finite elements of high orders and moderate meshes by finite element method (FEM). Both numerical simulation and physical experiment are performed to evaluate the accuracy of solution and the efficiency of computation. The relevant results show that element order is more critical than mesh size to produce an accurate FEM solution efficiently. Copyright © 2008 John Wiley & Sons, Ltd.
Low power switched‐current circuits with low sensitivity to the rise/fall time of the clock
Authors: Rudnicki Radek , Kropidłowski Marek , Handkiewicz Andrzej
Published: December 2008

The switched‐current (SI) technique permits realizing analog discrete‐time circuits in standard digital CMOS technology. A very important property of the analog part of a system on a chip is the possibility it offers for realizing some functions of a digital circuit, but with reduced power consumption. In this paper, a low power SI integrator is presented. It is shown that an integrator consuming a fraction of a milliwatt can be designed in 0.35µm CMOS technology with the use of narrow transistor channels, and with the channel length as a design parameter. The impact of the rise/fall time of the clock signal on the integrator operation is observed. It is shown that this effect can be reduced when the proper switch dimensions are taken for the integrator. Analysis and measurements of the integrator noise are presented. The integrator was built with equal size transistors, yielding less sensitivity to variations in production parameters. An experimental chip in 0.35µm CMOS technology was fabricated, and measurements are compared with results obtained during analysis and simulations. In order to verify the properties of the designed integrator experimentally, a first‐order filter is built with the use of elementary cells on the chip. Copyright © 2008 John Wiley & Sons, Ltd.
Insight into the microbial multicellular lifestyle via flow‐cell technology and confocal microscopy
Authors: Pamp Sünje Johanna , Sternberg Claus , Tolker‐Nielsen Tim
Published: December 2008

Biofilms are agglomerates of microorganisms surrounded by a self‐produced extracellular matrix. During the last 10 years, there has been an increasing recognition of biofilms as a highly significant topic in microbiology with relevance for a variety of areas in our society including the environment, industry, and human health. Accordingly a number of biofilm model systems, molecular tools, microscopic techniques, and image analysis programs have been employed for the study of biofilms under controlled and reproducible conditions. Studies using confocal laser scanning microscopy (CLSM) of biofilms formed in flow‐chamber experimental systems by genetically color‐coded bacteria have provided detailed knowledge about biofilm developmental processes, cell differentiations, spatial organization, and function of laboratory‐grown biofilms, in some cases down to the single cell level. In addition, the molecular mechanisms underlying the increased tolerance that biofilm cells often display towards antibiotic treatment are beginning to be unravelled. © 2008 International Society for Advancement of Cytometry
Die hard: Are cancer stem cells the Bruce Willises of tumor biology?
Authors: Fábián Ákos , Barok Márk , Vereb György , Szöllősi János
Published: December 2008

In recent years, an exponentially growing number of studies have focused on identifying cancer stem cells (CSC) in human malignancies. The rare CSCs could be crucial in controlling and curing cancer: through asymmetric division CSCs supposedly drive tumor growth and evade therapy with the help of traits shared with normal stem cells such as quiescence, self‐renewal ability, and multidrug resistance pump activity. Here, we give a brief overview of techniques used to confirm the stem cell‐like behavior of putative CSCs and discuss markers and methods for identifying, isolating, and culturing them. We touch on the limitations of each marker and why the combined use of CSC markers, in vitro and in vivo assays may still fail to identify all relevant CSC populations. Finally, the various experimental findings supporting and contradicting the CSC hypothesis are summarized. The large number of tumor types thus far with a subpopulation of uniquely tumorigenic and therapy resistant cells suggests that despite the unanswered questions and inconsistencies, the CSC hypothesis has a legitimate role to play in tumor biology. At the same time, experimental evidence supporting the established alternative theory of clonal evolution can be found as well. Therefore, a model that describes cancer initiation and progression should combine elements of clonal evolution and CSC theory. © 2008 International Society for Advancement of Cytometry
Toward an Allosteric Metallated Container
Authors: Szelke Helga , Wadepohl Hubert , Abu‐Youssef Morsy , Krämer Roland
Published: December 2008

Polytopic ligands L1 and L2 in which three 2,2′‐bipyridine units are linked to a central tris(pyrid‐2‐yl)amine (L1) or tris(pyrid‐2‐yl)methanol (L2) moiety by alkyl spacers were prepared by multistep organic syntheses. The parent tris(pyrid‐2‐yl)‐type ligands were shown to be modest‐to‐good chelators for Zn2+ and Cu2+ ions in solution, and bi‐ and tridentate N‐coordination was confirmed by crystal structures of CuII and RuII complexes, respectively. FeII and RuII smoothly form stable, cage‐like 1:1 complexes with L1 and L2, in which the metal ion is coordinated to the tris(bpy) site of the ligands. The vacant tris(pyrid‐2‐yl) site of these complexes is, however, a poor donor site for Zn2+ and Cu2+ ions. In addition, FeII modulates the coordination behaviour of the tris(pyrid‐2‐yl) site toward Zn2+: Whereas tris(5‐methylpyrid‐2‐yl)amine forms a 2:1 complex with Zn2+ in CH2Cl2, [Fe(L1)]2+ forms a 1:1 Zn complex. Spectrophotometric titrations suggest that [Fe(L2)]2+ forms a polynuclear Zn2+ complex in CH2Cl2, possibly involving bridging coordination of the alcohol OH group, which contrasts the smooth formation of a 2:1 complex of the parent tris(pyrid‐2‐yl)‐type ligand with Zn. FeII might therefore be considered as an allosteric effector, which modulates the metal binding properties of the second tris(pyrid‐2‐yl) site of L1 and L2. Contrary to expectation, Zn2+ and Cu2+ appear to associate weakly with donor atoms directed toward the exterior of the cage‐like complexes [Fe(Ln)]2+ and [Ru(L1)]2+, rather than locating in the interior of the container by tripodal coordination to the tris(pyrid‐2‐yl) site.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Group 4 Metal Complexes That Contain a Thioether‐Functionalized Phenolato Ligand: Synthesis, Structure, and 1‐Hexene Polymerization
Authors: Lian Bing , Beckerle Klaus , Spaniol Thomas P. , Okuda Jun
Published: December 2008

Reaction of group 4 metal tetrabenzyl complexes [M(CH2Ph)4] (M = Ti, Zr, Hf) with 1 or 2 equiv. of a thioether‐functionalized phenol 2,4‐tBu2‐6‐(PhSCH2)C6H2OH afforded dibenzyl complexes [M(L)2(CH2Ph)2] (M = Ti, 1; M = Zr, 2; M = Hf, 3) and the tribenzyl zirconium complex [Zr(L)(CH2Ph)3] (4). Benzyl abstraction with a Lewis acid gave the zirconium monobenzyl cation [Zr(L)2CH2Ph]+[PhCH2B(C6F5)3]– (5) and the dibenzyl cation [Zr(L)(CH2Ph)2]+[PhCH2B(C6F5)3]– (6). The monobenzyl cation 5 oligomerized 1‐hexene to low molecular‐weight atactic oligo(1‐hexene) (Mn = 560–820), while the dibenzyl cation 6 polymerized 1‐hexene isospecifically ([mmmm] > 90 %). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Mechanism of Hydride Abstraction by Cyclopentadienone‐Ligated Carbonylmetal Complexes (M = Ru, Fe)
Authors: Thorson Megan K. , Klinkel Kortney L. , Wang Jianmei , Williams Travis J.
Published: December 2008

Cyclopentadienone‐ligated ruthenium complexes, such as Shvo's catalyst, are known to oxidize reversibly alcohols to the corresponding carbonyl compounds. The mechanism of this reaction has been the subject of some controversy, but it is generally believed to proceed through concerted transfer of proton and hydride, respectively, to the cyclopentadienone ligand and the ruthenium center. In this paper we further study the hydride transfer process as an example of a coordinatively directed hydride abstraction by adding quantitative understanding to some features of this mechanism that are not well understood. We find that an oxidant as weak as acetone can be used to re‐oxidize the intermediate ruthenium hydride without catalyst re‐oxidation becoming rate‐limiting. Furthermore, C–H cleavage is a significantly electrophilic event, as demonstrated by a Hammett reaction parameter of ρ = –0.89. We then describe how the application of our mechanistic insights obtained from the study have enabled us to extend the ligand‐directed hydride abstraction strategy to include a rare example of an iron(0) oxidation catalyst.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Enantioselective Synthesis of Functionalized 1‐Benzoxepines by Phenoxide Ion Mediated 7‐endo‐tet Carbocyclization of Cyclic Sulfates
Authors: Das Sajal Kumar , Dinda Subal Kumar , Panda Gautam
Published: December 2008

A new asymmetric synthesis of 2,3‐disubstituted 1‐benzoxepines is described. Key steps include Sharpless asymmetricdihydroxylation of trans‐α,β‐unsaturated esters and phenoxide ion mediated intramolecular 7‐endo‐tet carbocyclization of syn‐2,3‐dihydroxy ester derived cyclic sulfates. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Instabilities of Boussinesq models in non‐uniform depth
Authors: Løvholt F. , Pedersen G.
Published: December 2008

The von Neumann method for stability analysis of linear waves in a uniform medium is a widely applied procedure. However, the method does not apply to stability of linear waves in a variable medium. Herein we describe instabilities due to variable depth for different Boussinesq equations, including the standard model by Peregrine and the popular generalization by Nwogu. Eigenmodes are first found for bathymetric features on the grid scale. For certain combinations of Boussinesq formulations and bottom profiles stability limits are found in closed form, otherwise numerical techniques are used for the eigenvalue problems. Naturally, the unstable modes in such settings must be considered to be as much a result of the difference method as of the underlying differential (Boussinesq) equations. Hence, modes are also computed for smooth depth profiles that are well resolved. Generally, the instabilities do not vanish with refined resolution. In some cases convergence is observed and we thus have indications of unstable solutions of the differential equations themselves. The stability properties differ strongly. While the standard Boussinesq equations seem perfectly stable, all the other formulations do display unstable modes. In most cases the instabilities are linked to steep bottom gradients and small grid increments. However, while a certain formulation, based on velocity potentials, is very prone to instability, the Boussinesq equations of Nwogu become unstable only under quite demanding conditions. Still, for the formulation of Nwogu, instabilities are probably inherent in the differential equations and are not a result of the numerical model. Copyright © 2008 John Wiley & Sons, Ltd.
Variable selection and oversampling in the use of smooth support vector machines for predicting the default risk of companies
Authors: Härdle Wolfgang , Lee Yuh‐Jye , Schäfer Dorothea , Yeh Yi‐Ren
Published: December 2008

In the era of Basel II a powerful tool for bankruptcy prognosis is vital for banks. The tool must be precise but also easily adaptable to the bank's objectives regarding the relation of false acceptances (Type I error) and false rejections (Type II error). We explore the suitability of smooth support vector machines (SSVM), and investigate how important factors such as the selection of appropriate accounting ratios (predictors), length of training period and structure of the training sample influence the precision of prediction. Moreover, we show that oversampling can be employed to control the trade‐off between error types, and we compare SSVM with both logistic and discriminant analysis. Finally, we illustrate graphically how different models can be used jointly to support the decision‐making process of loan officers. Copyright © 2008 John Wiley & Sons, Ltd.
Mortality forecasting using neural networks and an application to cause‐specific data for insurance purposes
Authors: Shah Paras , Guez Allon
Published: December 2008

Mortality forecasting is important for life insurance policies, as well as in other areas. Current techniques for forecasting mortality in the USA involve the use of the Lee–Carter model, which is primarily used without regard to cause. A method for forecasting morality is proposed which involves the use of neural networks. A comparative analysis is done between the Lee–Carter model, linear trend and the proposed method. The results confirm that the use of neural networks performs better than the Lee–Carter and linear trend model within 5% error. Furthermore, mortality rates and life expectancy were formulated for individuals with a specific cause based on prevalence data. The rates are broken down further into respective stages (cancer) based on the individual's diagnosis. Therefore, this approach allows life expectancy to be calculated based on an individual's state of health. Copyright © 2008 John Wiley & Sons, Ltd.
Distinctive expression and function of four GSDM family genes (GSDMA‐D) in normal and malignant upper gastrointestinal epithelium
Authors: Saeki Norihisa , Usui Takebumi , Aoyagi Kazuhiko , Kim Dal Ho , Sato Megumi , Mabuchi Tomoko , Yanagihara Kazuyoshi , Ogawa Kenji , Sakamoto Hiromi , Yoshida Teruhiko , Sasaki Hiroki
Published: December 2008

Gasdermin (GSDM or GSDMA), expressed in the upper gastrointestinal tract but frequently silenced in gastric cancers (GCs), regulates apoptosis of the gastric epithelium. It has three human homologs, GSDMB, GSDMC, and GSDMD (GSDM family) and they are considered to be involved in the regulation of epithelial apoptosis but not yet known. We investigated the expression pattern of the family genes in the upper gastrointestinal epithelium and cancers. Reverse transcriptase‐polymerase chain reaction revealed that, unlike GSDMA expressed in differentiated cells, GSDMB is expressed in proliferating cells and GSDMD in differentiating cells. GSDMC, meanwhile, is expressed in both differentiating and differentiated cells. Colony formation assay showed that GSDMB, closely related to GSDMA, has no cell‐growth inhibition activity in gastric cancer cells, and that GSDMC and GSDMD, respectively, exhibit the activity with different strengths from that of GSDMA. Expression analyses of the four family genes in esophageal and GCs suggested that GSDMC and GSDMD as well as GSDMA are tumor suppressors and that GSDMB, which was amplified and overexpressed in some GCs, could be an oncogene. The results of the expression analysis and colony formation assay suggest that each family gene may have a distinct function in the upper gastrointestinal epithelium. © 2008 Wiley‐Liss, Inc.
Promoter methylation blocks FES protein‐tyrosine kinase gene expression in colorectal cancer
Authors: Shaffer Jonathan M. , Smithgall Thomas E.
Published: December 2008

The FES locus encodes a unique nonreceptor protein‐tyrosine kinase (FES) traditionally viewed as a proto‐oncogene but more recently implicated as a tumor suppressor in colorectal cancer (CRC). Recent studies have demonstrated that while FES is expressed in normal colonic epithelium, expression is lost in tumor tissue and colorectal cancer cell lines, a finding common among tumor suppressors. Here we provide compelling evidence that promoter methylation is an important mechanism responsible for downregulation of FES gene expression in colorectal cancer cells. Treatment with the DNA methyltransferase inhibitor 5‐aza‐2′‐deoxycytidine resulted in the expression of functional FES transcripts in all CRC cell lines examined, including Caco‐2, COLO 320, DLD‐1, HCT 116, SNU‐1040, SW‐480, and HT‐29. Bisulfite sequencing of genomic DNA isolated from 5‐aza‐2′‐deoxycytidine‐treated HT‐29 cells identified methylated CpG dinucleotides immediately upstream from the FES transcription initiation sites. In contrast, this region of the FES promoter was hypomethylated in genomic DNA from normal colonic epithelium. In addition, methylation completely blocked the activity of the FES promoter in reporter gene assays. Promoter methylation is a previously unrecognized mechanism by which FES expression is suppressed in CRC cell lines, and is consistent with a tumor suppressor role for FES in this tumor site despite its tyrosine kinase activity. © 2008 Wiley‐Liss, Inc.