bluuebunny/crossref_metadata_2025 huggingface dataset:
Cancer stem/progenitor cells are highly enriched in CD133+CD44+ population in hepatocellular carcinoma
Authors: Zhu Zheng , Hao Xiangfang , Yan Mingxia , Yao Ming , Ge Chao , Gu Jianren , Li Jinjun
Published: August 2009

Both our previous study and other reports have suggested that CD133, originally classified as a hematopoietic stem cell marker, could be used for enrichment of cancer stem cells (CSCs) in human hepatocellular carcinoma (HCC). It was also noted that not all of CD133+ cells were representative of CSCs. Further identification and characterization of CSCs or tumor‐initiating cells in HCC are necessary to better understand hepatocarcinogenesis. In present study, we demonstrated that CSC phenotype could be precisely defined by co‐expression of CD133 and CD44 cell surface markers. CD133+CD44+ HCC cells showed stem cell properties, including extensive proliferation, self‐renewal, and differentiation into the bulk of cancer cells. In vivo xenograft experiments revealed that, actually, the highly tumorigenic capacity of CD133+ cells as previously described was primarily attributed to CD133+CD44+ cell subpopulation, instead of their CD133+CD44− counterparts. Moreover, cells double‐positive for CD133 and CD44 exhibited preferential expression of some stem cell‐associated genes and were more resistant to chemotherapeutic agents due to the upregulation of ATP‐binding cassette (ABC) superfamily transporters, including ABCB1, ABCC1, and ABCG2, further supporting these cells as HCC cell origin. Our findings suggest that CD133+CD44+ cells might represent true cancer stem/progenitor cells in HCC, which could allow a better understanding of HCC initiation and progression, as well as establish a precise target for the development of more effective therapies.
A framework of view‐dependent planar scene active camouflage
Authors: Lin Huei‐Yung , Lie Wen‐Nung , Wang Min‐Liang
Published: August 2009

Active camouflage is a technique for occluding objects disappear from the observer. Current implementations make assumptions on the viewpoints of both the observer and the camouflaged target. In this work, we present a framework of view‐dependent planar scene camouflage. The cameras representing the observer and the occluding object are placed in general positions. The images captured by the object camera are transformed to the observer viewpoint to generate globally consistent visual data for transparent camouflage. Experimental results are presented for real scene images. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 167–174, 2009
EM algorithm‐based adaptive custom thresholding for image denoising in wavelet domain
Authors: Raja S. Selvakumar , John Mala
Published: August 2009

In this article, a novel denoising technique based on custom thresholding operating in the wavelet transform domain is proposed. The denoising process is spatially adaptive and also sub‐band adaptive. To render the denoising algorithm space adaptive, a Vector Quantization (VQ)‐based algorithm is used. The design of the VQ is based on Expectation Maximization (EM) algorithm. The results of the algorithm is demonstrated on SAR images corrupted by speckle noise. Experimental results show that Custom thresholding function outperforms the traditional soft, hard, and Bayes threshoding functions, improving the denoised results significantly in terms of Peak Signal to Noise Ratio (PSNR). © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 175–178, 2009
Texture‐based parametric active contour for target detection and tracking
Authors: Vard Ali Reza , Moallem Payman , Nilchi Ahmad Reza Naghsh
Published: August 2009

In recent years, active contour models (ACM) have been considered as powerful tools for image segmentation and object tracking in computer vision and image processing applications. This article presents a new tracking method based on parametric active contour models. In the proposed method, a new pressure energy called “texture pressure energy” is added to the energy function of the parametric active contour model to detect and track a texture target object in a texture background. In this scheme, the texture features of the contour are calculated by a moment‐based method. Then, by comparing these features with texture features of the target object, the contour curve is expanded or contracted to be adapted to the object boundaries. Experimental results show that the proposed method is more efficient and accurate in the tracking of objects compare to the traditional ones, when both object and background are textures in nature. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 187–198, 2009
Visual data association for real‐time video tracking using genetic and estimation of distribution algorithms
Authors: Patricio Miguel A. , García Jesús , Berlanga Antonio , Molina José M.
Published: August 2009

In this article, an efficient and novel approach for video data association is developed. This new method is formulated as a search across the hypotheses space defined by the possible association among tracks and detections, carried out for each frame of a video sequence. The full data association problem in visual tracking is formulated as a combinatorial hypotheses search with a heuristic evaluation function taking into account structural and specific information such as distance, shape, color, etc. To guarantee real‐time performance, a time limit is set for the search process explore alternative solutions. This time limit defines the upper bound of the number of evaluations depending on search algorithm efficiency. Estimation distribution algorithms are proposed as an efficient evolutionary computation technique to search in this hypothesis space. Finally, an exhaustive comparison of the performance of alternative algorithms is carried out considering complex representative situations in real video sets. © 2009 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 19, 208–220, 2009
An acidic extracellular pH disrupts adherens junctions in HepG2 cells by Src kinases‐dependent modification of E‐cadherin
Authors: Chen Ying , Chen Chia‐Huei , Tung Po‐Yuan , Huang Shih‐Horng , Wang Seu‐Mei
Published: August 2009

We have previously shown that culturing HepG2 cells in pH 6.6 culture medium increases the c‐Src‐dependent tyrosine phosphorylation of β‐catenin and induces disassembly of adherens junctions (AJs). Here, we investigated the upstream mechanism leading to this pH 6.6‐induced modification of E‐cadherin. In control cells cultured at pH 7.4, E‐cadherin staining was linear and continuous at cell–cell contact sites. Culturing cells at pH 6.6 was not cytotoxic, and resulted in weak and discontinuous junctional E‐cadherin staining, consistent with the decreased levels of E‐cadherin in membrane fractions. pH 6.6 treatment activated c‐Src and Fyn kinase and induced tyrosine phosphorylation of p120 catenin (p120ctn) and E‐cadherin. Inhibition of Src family kinases by PP2 attenuated the pH 6.6‐induced tyrosine phosphorylation of E‐cadherin and p120ctn, and prevented the loss of these proteins from AJs. In addition, E‐cadherin was bound to Hakai and ubiquitinated. Furthermore, pH 6.6‐induced detachment of E‐cadherin from AJs was blocked by pretreatment with MG132 or NH4Cl, indicating the involvement of ubiquitin‐proteasomal/lysosomal degradation of E‐cadherin. An early loss of p120ctn prior to E‐cadherin detachment from AJs was noted, concomitant with a decreased association between p120ctn and E‐cadherin at pH 6.6. PP2 pretreatment prevented the dissociation of these two proteins. In conclusion, pH 6.6 activated Src kinases, resulting in tyrosine phosphorylation of E‐cadherin and p120ctn and a weakening of the association of E‐cadherin with p120ctn and contributing to the instability of E‐cadherin at AJs. J. Cell. Biochem. 108: 851–859, 2009. © 2009 Wiley‐Liss, Inc.
Regenerative medicine in the treatment of peripheral arterial disease
Authors: Sneider Erica B. , Nowicki Philip T. , Messina Louis M.
Published: August 2009

The last decade has witnessed a dramatic increase in the mechanistic understanding of angiogenesis and arteriogenesis, the two processes by which the body responds to obstruction of large conduit arteries. This knowledge has been translated into novel therapeutic approaches to the treatment of peripheral arterial disease, a condition characterized by progressive narrowing of lower extremity arteries and heretofore solely amenable to surgical revascularization. Clinical trials of molecular, genetic, and cell‐based treatments for peripheral artery obstruction have generally provided encouraging results. J. Cell. Biochem. 108: 753–761, 2009. © 2009 Wiley‐Liss, Inc.
Transitive partitions in realizations of tournament score sequences
Authors: Busch Arthur H. , Chen Guantao , Jacobson Michael S.
Published: August 2009

A tournament is an oriented complete graph, and one containing no
directed cycles is called transitive. A tournament
T=(V, A) is called m‐partition
transitive if there is a partition
such that the subtournaments induced by each Xi are all transitive, and T is m‐partition k‐transitive if max|Xi|=k. Two tournaments are equivalent if they have the same out‐degree sequence. We show that for any m and k, T is equivalent to an m‐partition k‐transitive tournament T′ whenever T is equivalent to any tournament which contains a transitive subtournament of order at least k. This generalizes results of Guiduli et al. and Acosta et al., who proved the claim for m=2 and k=⌈n/2⌉, and m>2 and k⩽⌈n/2⌉, respectively. © 2009 Wiley Periodicals, Inc. J Graph Theory 64: 52–62, 2010
Effect of shot number on the calculated apparent diffusion coefficient in phantoms and in human liver in diffusion‐weighted echo‐planar imaging
Authors: Shiehmorteza Masoud , Sirlin Claude B. , Wolfson Tanya , Gamst Anthony , Soumekh Andre E. , Heaton Shay P. , Kohl Chad A. , Pinto Nicholas , Bydder Mark
Published: August 2009

Purpose

To show the signal intensity varies with shot number in diffusion‐weighted (DW) echo‐planar imaging (EPI) and affects apparent diffusion coefficient (ADC) calculation.

Materials and Methods

This prospective study was performed on 35 adult patients and 20 volunteers. Measurements were made on a 3T scanner using a breathhold DW spin‐echo EPI (SE EPI) sequence. Three protocols were used: A) eight consecutive shots at a fixed b‐value of 0 seconds/mm2 with TR = 1000 and 3000 msec; B) seven consecutive shots at b‐values = 0, 1000, 750, 500, 250, 100, 0 seconds/mm2 (in that order) with TR = 3500 msec; and C) seven consecutive shots (as in B) with TR = 1000, 1750, and 7000 msec.

Results

For protocol A, signal intensity decreased significantly from the first to second shot (P<0.0001) and thereafter remained constant. For protocol B, the ADC depended on which b = 0 seconds/mm2 image was used. Using the first b = 0 seconds/mm2, the mean ADC was 15% higher than using the second b = 0 seconds/mm2 (P<0.0001). For protocol C, the difference between ADC using the first b = 0 seconds/mm2 and the second b = 0 seconds/mm2 decreased as the TR increased.

Conclusion

The signal intensity can vary with shot number in SE EPI. For TR ≥ 3000 msec, steady‐state is attained after one shot. Using data acquired prior to steady‐state confounds the calculation of ADC values. J. Magn. Reson. Imaging 2009;30:547–553. © 2009 Wiley‐Liss, Inc.
Segmentation of human skull in MRI using statistical shape information from CT data
Authors: Wang Defeng , Shi Lin , Chu Winnie C.W. , Cheng Jack C.Y. , Heng Pheng Ann
Published: August 2009

Purpose

To automatically segment the skull from the MRI data using a model‐based three‐dimensional segmentation scheme.

Materials and Methods

This study exploited the statistical anatomy extracted from the CT data of a group of subjects by means of constructing an active shape model of the skull surfaces. To construct a reliable shape model, a novel approach was proposed to optimize the automatic landmarking on the coupled surfaces (i.e., the skull vault) by minimizing the description length that incorporated local thickness information. This model was then used to locate the skull shape in MRI of a different group of patients.

Results

Compared with performing landmarking separately on the coupled surfaces, the proposed landmarking method constructed models that had better generalization ability and specificity. The segmentation accuracies were measured by the Dice coefficient and the set difference, and compared with the method based on mathematical morphology operations.

Conclusion

The proposed approach using the active shape model based on the statistical skull anatomy presented in the head CT data contributes to more reliable segmentation of the skull from MRI data. J. Magn. Reson. Imaging 2009;30:490–498. © 2009 Wiley‐Liss, Inc.
Computer‐aided detection of brain tumor invasion using multiparametric MRI
Authors: Jensen Todd R. , Schmainda Kathleen M.
Published: August 2009

Purpose

To determine the potential of using a computer‐aided detection method to intelligently distinguish peritumoral edema alone from peritumor edema consisting of tumor using a combination of high‐resolution morphological and physiological magnetic resonance imaging (MRI) techniques available on most clinical MRI scanners.

Materials and Methods

This retrospective study consisted of patients with two types of primary brain tumors: meningiomas (n = 7) and glioblastomas (n = 11). Meningiomas are typically benign and have a clear delineation of tumor and edema. Glioblastomas are known to invade outside the contrast‐enhancing area. Four classifiers of differing designs were trained using morphological, diffusion‐weighted, and perfusion‐weighted features derived from MRI to discriminate tumor and edema, tested on edematous regions surrounding tumors, and assessed for their ability to detect nonenhancing tumor invasion.

Results

The four classifiers provided similar measures of accuracy when applied to the training and testing data. Each classifier was able to identify areas of nonenhancing tumor invasion supported with adjunct images or follow‐up studies.

Conclusion

The combination of features derived from morphological and physiological imaging techniques contains the information necessary for computer‐aided detection of tumor invasion and allows for the identification of tumor invasion not previously visualized on morphological, diffusion‐weighted, and perfusion‐weighted images and maps. Further validation of this approach requires obtaining spatially coregistered tissue samples in a study with a larger sample size. J. Magn. Reson. Imaging 2009;30:481–489. © 2009 Wiley‐Liss, Inc.
MR imaging of endometrial carcinoma for preoperative staging at 3.0 T: Comparison with imaging at 1.5 T
Authors: Hori Masatoshi , Kim Tonsok , Murakami Takamichi , Imaoka Izumi , Onishi Hiromitsu , Nakamoto Atsushi , Nakaya Yasuhiro , Tomoda Kaname , Tsutsui Tateki , Enomoto Takayuki , Kimura Tadashi , Nakamura Hironobu
Published: August 2009

Purpose

To prospectively compare magnetic resonance imaging (MRI) at 3.0 T and 1.5 T in the same patients for preoperative evaluation of endometrial carcinoma.

Materials and Methods

Thirty consecutive patients with endometrial carcinoma underwent MRI at both 3.0 T and 1.5 T as well as surgery. Quantitative and qualitative analyses were performed. Two radiologists independently evaluated images. MR findings were compared with surgicopathologic findings.

Results

Image homogeneity of T2‐weighted images at 3.0 T was significantly inferior to that at 1.5 T (P = 0.007). The scores of image homogeneity and susceptibility artifacts were not significantly different between 3.0 T gadolinium‐enhanced imaging and 1.5 T imaging (P = 0.09 and 0.36). Kappa statistics showed good interobserver agreement between the two radiologists for local‐regional staging on T2‐weighted images (κ>0.6). The area under the receiver operating characteristic curve (Az) values for T2‐weighted imaging in terms of myometrial invasion, cervical invasion, and lymph node metastases were 0.88 (3.0 T) versus 0.91 (1.5 T), 0.84 versus 0.83, and 0.94 versus 0.95 for reader 1, respectively. There were no significant differences between imaging at 3.0 T and at 1.5 T in Az values for either reader (P > 0.35).

Conclusion

3.0 T MRI is an equivalent imaging modality to 1.5 T imaging for presurgical evaluation of endometrial carcinoma, although not significantly superior to 1.5 T imaging. J. Magn. Reson. Imaging 2009;30:621–630. © 2009 Wiley‐Liss, Inc.
Half‐fourier‐acquisition single‐shot turbo spin‐echo (HASTE) MRI of the lung at 3 Tesla using parallel imaging with 32‐receiver channel technology
Authors: Henzler Thomas , Dietrich Olaf , Krissak Radko , Wichmann Tobias , Lanz Titus , Reiser Maximilian F. , Schoenberg Stefan O. , Fink Christian
Published: August 2009

Purpose

To assess the feasibility of half‐Fourier‐acquisition single‐shot turbo spin‐echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32‐channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy.

Materials and Methods

Nine volunteers were examined on a 32‐channel 3T MRI system using a prototype 32‐channel‐torso‐array‐coil. HASTE‐MRI of the lung was acquired at both, end‐inspiratory and end‐expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal‐to‐noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements.

Results

Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans.

Conclusion

Using optimized multi‐element coil geometry HASTE‐MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541–546. © 2009 Wiley‐Liss, Inc.
Initial experience on utility of gadobenate dimeglumine (Gd‐BOPTA) enhanced T1‐weighted MR cholangiography in diagnosis of acute cholecystitis
Authors: Akpinar Erhan , Turkbey Baris , Karcaaltincaba Musturay , Balli Omur , Akkapulu Nezih , Balas Sener , Tirnaksiz Bulent , Akata Deniz , Akhan Okan
Published: August 2009

Purpose

To investigate the feasibility of the use of gadobenate dimeglumine (also known as Gd‐BOPTA) ‐enhanced T1‐weighted MR cholangiography in diagnosis of acute cholecystitis.

Materials and Methods

This prospectively designed institutional review board‐approved HIPAA‐compliant study was done between January and November 2007. We included 11 consecutive patients (7 male, mean age 59 years) who presented to the emergency room with acute right upper quadrant pain and with equivocal physical examination and/or ultrasound findings. The control group included 15 patients who underwent liver MRI with Gd‐BOPTA. All patients underwent contrast‐enhanced (CE) MR cholangiography examinations. CE‐MR cholangiography was performed on a 1.5 Tesla magnet using 3D T1‐weighted high resolution isotrophic volume examination (THRIVE) obtained at the 90th min after intravenous injection of Gd‐BOPTA. Imaging features detected on CE‐MR cholangiography were correlated with operative and histopathologic findings.

Results

In the control group, GD‐BOPTA was visualized within the gallbladder in all subjects. For the study group, gallstones were present in nine patients (n = 7 both in gallbladder and cystic duct, n = 1 only in gallbladder, n = 1 only in cystic duct) on MRCP. Hydropic gallbladder was detected in seven patients, significant wall thickening in seven patients, and pericholecystic free fluid in 6 patients. On delayed phase CE cholangiography, significant enhancement of gallbladder wall was seen in 10 patients, and contrast agent excretion into gallbladder was absent in all patients. Surgery was performed in 10 patients, and cholecystostomy was done in 1 patient. Surgery and histopathology findings were consistent with cholecystitis in all patients.

Conclusion

In addition to anatomical assessment, Gd‐BOPTA‐enhanced MR cholangiography can provide functional evaluation similar to HIDA scintigraphy in diagnosing acute cholecystitis in patients with acute right upper quadrant pain and equivocal findings. J. Magn. Reson. Imaging 2009;30:578–585. © 2009 Wiley‐Liss, Inc.
Use of cardiac output to improve measurement of input function in quantitative dynamic contrast‐enhanced MRI
Authors: Zhang Jeff L. , Rusinek Henry , Bokacheva Louisa , Chen Qun , Storey Pippa , Lee Vivian S.
Published: August 2009

Purpose

To validate a new method for converting MR arterial signal intensity versus time curves to arterial input functions (AIFs).

Materials and Methods

The method constrains AIF with patient's cardiac output (Q). Monte Carlo simulations of MR renography and tumor perfusion protocols were carried out for comparison with two alternative methods: direct measurement and population‐averaged input function. MR renography was performed to assess the method's inter‐ and intraday reproducibility for renal parameters.

Results

In simulations of tumor perfusion, the precision of the parameters (Ktrans and ve) computed using the proposed method was improved by at least a factor of three compared to direct measurement. Similar improvements were obtained in simulations of MR renography. Volunteer study for testing interday reproducibility confirmed the improvement of precision in renal parameters when using the proposed method compared to conventional methods. In another patient study (two injections within one session), the proposed method significantly increased the correlation coefficient (R) between GFR of the two exams (0.92 vs. 0.83) compared to direct measurement.

Conclusion

A new method significantly improves the precision of dynamic contrast‐enhanced (DCE) parameters. The method may be especially useful for analyzing repeated DCE examinations, such as monitoring tumor therapy or angiotensin converting enzyme‐inhibitor renography. J. Magn. Reson. Imaging 2009;30:656–665. © 2009 Wiley‐Liss, Inc.
Quantitation of the main constituents of vanilla by reverse phase HPLC and ultra‐high‐pressure‐liquid‐chromatography with UV detection: Method validation and performance comparison
Authors: Cicchetti Esmeralda , Chaintreau Alain
Published: August 2009

Vanilla's main constituents, i. e., vanillin, para‐hydroxybenzaldehyde, and their corresponding acids, can be easily quantified by RP LC with UV detection and external calibration. This paper describes two methods that were developed using HPLC and ultra‐high‐pressure LC (UHPLC), respectively, and validated according to the International Conference on Harmonisation of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) [1]. Both methods were highly specific, exhibited good linearities with high precision, and achieved good accuracies of quantitative results. The UHPLC method was more sensitive, five times shorter, and gave better peak resolutions than the HPLC alternative.
A data base for polymer chromatography: Temperature dependence of interaction parameters in liquid adsorption chromatography
Authors: Trathnigg Bernd , Viet Cuong Nguyen , Ahmed Hasnat
Published: August 2009

The temperature dependence of retention behaviour of polyethylene glycol (PEG) and its mono‐ and dimethyl ethers was studied on various RP columns in different mobile phases. The accessible volumes and the interaction parameters were determined from slope and intercept in a plot of the elution volumes of the oligomers of a polymer homologous series as a function of the difference of the elution volumes of consecutive oligomers. A quite different dependence of the interaction parameters was observed in the different mobile phases. While in methanol–water the interaction parameter decreases with increasing temperature, the opposite effect is observed in acetonitrile (ACN)–water. In acetone–water, the temperature dependence is almost negligible.
Potential application of antioxidant capacity assays to assess the quality of edible vegetable oils
Authors: Castelo‐Branco Vanessa N. , Torres Alexandre G.
Published: August 2009

The total antioxidant capacity of edible vegetable oils corresponds to the integrated action of the complex mixture of antioxidant components against oxidation reactions in these oils, and takes into account potential physical and chemical interactions between oil components. Consequently, the total antioxidant capacity might be an indicator of quality attributes of edible oils, such as bioactivity and oxidative stability. In this paper we present an overview of the antioxidant capacity assays currently applied to the analysis of edible oils, and we briefly review current evidence indicating associations of the total antioxidant capacity (TAC) with the bioactivity and the oxidative stability of vegetable oils. Based on these data, we discuss the potential application of TAC assays for integrated quality control of edible vegetable oils, which includes bioactivity and oxidative stability.
Poly(carbazole)‐Based Copolymers Containing Deep‐Blue Chromophore for Polymer Light‐Emitting Diode Applications
Authors: Park Jin Su , Song Myungkwan , Jin Sung‐Ho , Lee Jae Wook , Lee Chan Woo , Gal Yeong‐Soon
Published: August 2009

A new series of two poly(carbazole)‐based copolymers (poly(9‐hexyl‐carbazole‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PCVz) and poly(9,9‐dioctylfluorene‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PFCVz)) containing carbazoylphenylquinoline pendant groups were synthesized via the Suzuki coupling reaction for polymer light‐emitting diode applications. The electro‐optical properties of ITO/PEDOT/Polymer/PBD/LiF/Al devices based on these copolymers were investigated using UV‐visible, photoluminescence, and electroluminescence spectroscopy. The turn‐on voltages of the copolymer devices were found to be 6.0–8.0 V. The maximum brightness and luminescence efficiency of the copolymers device were found to be 230 cd · m−2 and 0.28 cd · A−1 at 11 V, respectively.

magnified image
Polymer‐Infiltrated Aligned Carbon Nanotube Fibers by in situ Polymerization
Authors: Zhang Shanju , Zhu Lingbo , Wong Ching‐Ping , Kumar Satish
Published: August 2009

Carbon nanotube–polymer composite fibers are obtained by infiltration of a monomer liquid into aligned carbon nanotube aerogel fibers with subsequent in situ polymerization. The monomer, methyl methacrylate (MMA), was infiltrated into the aerogel fibers of multi‐walled carbon nanotubes (MWNTs) at room temperature and subsequently polymerized at 50 °C into poly(methyl methacrylate) (PMMA). Cross‐sections of the PMMA/MWNT composite fibers showed that the PMMA filled the spaces of the nanotube fibers and bound the nanotubes together. PMMA in the composite fibers exhibited local order. The resultant composite fibers with 15 wt.‐% nanotube loading exhibited a 16‐fold and a 49‐fold increase in tensile strength and Young's modulus, respectively, compared to the control PMMA.

magnified image
Construction of Large‐Scale Highly Ordered Macroporous Monoliths of π‐Conjugated Polymers
Authors: Zuo Zicheng , Guo Yanbing , Li Yuliang , Lv Jing , Liu Huibiao , Xu Jialiang , Li Yongjun
Published: August 2009

Large scale of well‐ordered macroporous π‐conjugated polymer monoliths have been successfully prepared through a new approach using micrometer‐sized naphthalene crystals as templates. The macroporous monoliths of poly(p‐phenylenevinylene) (PPV) and poly(p‐phenyleneethynylene) (PPE) grew along the unidirectional freezing direction inside the template naphthalene crystals which lead to the formation of controlling morphologies and homogeneous diameters. The polymer monoliths show straight and lamella macroporous structures. The diameters of pores and the thickness of pore walls can be controlled by tuning the freezing temperature.

magnified image
Cyclopolymerization of Nonconjugated Dienes with a Tridentate Phenoxyamine Hafnium Complex Supported by an sp3‐C Donor: Isotactic Enchainment and Diastereoselective cis‐Ring Closure
Authors: Edson Joseph B. , Coates Geoffrey W.
Published: August 2009

Cyclopolymerization of nonconjugated dienes produces poly(methylene‐1,3‐cycloalkanes) and provides a pathway to a number of stereochemically complex polymers. Activation of a diastereomeric mixture of a six‐membered metallacycle complex (rac‐1) in the presence of 1,5‐hexadiene produced poly(methylene‐1,3‐cyclopentane) (PMCP) with >98% cyclization of the diene monomer. The catalyst was found to cyclopolymerize 1,5‐hexadiene with relatively high activity. The microstructure of the PMCP furnished by rac‐1 was found to contain a high proportion of cis‐cyclopentane rings (σ = 0.70–0.74) and a relatively high isotactic content (α = 0.93–0.96). These are the first cis‐enriched isotactic cyclopolymers of 1,5‐hexadiene. Cyclopolymerization of 1,6‐heptadiene with rac‐1/B(C6F5)3 produced poly(methylene‐1,3‐cyclohexane) containing 97% cis‐isotactic rings. This is the first report of this highly isotactic and diastereomerically‐pure microstructure.

magnified image
Electrochemical Polymerisation of N‐Arylated and N‐Alkylated EDOT‐Substituted Pyrrolo[3,4‐c]pyrrole‐1,4‐dione (DPP) Derivatives: Influence of Substitution Pattern on Optical and Electronic Properties
Authors: Zhang Kai , Tieke Bernd , Forgie John C. , Skabara Peter J.
Published: August 2009

New pyrrolo[3,4‐c]pyrrole‐1,4‐dione (DPP) derivatives carrying 3,4‐ethylenedioxy‐thiophenylphenyl (EDOT‐phenyl) substituent groups in the 3‐ and 6‐position, or in the 2‐ and 5‐position of the DPP chromophore were synthesised and electrochemically polymerised. The properties of the polymers were investigated using cyclic voltammetry and UV/Vis absorption spectroscopy. It was found that the optical and electronic properties differ greatly between the two polymers. Materials with EDOT‐phenyl groups in the 3‐ and 6‐positions represent conjugated polymers with a low oxidation potential and reversible electrochromic properties, whereas the polymer with EDOT‐phenyl groups in the 2‐ and 5‐positions is non‐conjugated and possesses a high oxidation potential and irreversible redox behaviour.

magnified image
De novo germline TP53 mutation presenting with synchronous malignancies of the central nervous system
Authors: Schniederjan Matthew J. , Shehata Bahig , Brat Daniel J. , Esiashvili Natia , Janss Anna J.
Published: August 2009

We present a case of a 14‐year‐old male with a germline TP53 mutation who presented with synchronous primitive neuroectodermal tumor and choroid plexus carcinoma. Identification of synchronous brain tumors prompted genetic testing for predisposition to malignancy. Within 5 months of presentation, the child developed widely metastatic alveolar rhabdomyosarcoma. Patient DNA sequencing showed a TP53 allele with a premature stop codon in the oligomerization/nuclear export signal (NES) domain (R342ter). The child's parents, younger brother, paternal grandparents, and maternal grandmother, are without history of malignancy. The patient's brother tested negative for TP53 mutations. This case identifies a rare, de novo, germline TP53 mutation presenting with synchronous CNS malignancies and exhibiting a more fulminant course than typical cases of Li–Fraumeni syndrome. Pediatr Blood Cancer 2009; 53:1352–1354. © 2009 Wiley‐Liss, Inc.
Hereditary hemochromatosis gene (HFE) variants are associated with birth weight and childhood leukemia risk
Authors: Dorak M. Tevfik , Mackay Rachel K. , Relton Caroline L. , Worwood Mark , Parker Louise , Hall Andrew G.
Published: August 2009

Background

Our original studies reported an association between the iron‐metabolism gene HFE and risk of childhood acute lymphoblastic leukemia (ALL), and a birth weight association in ALL. Through its effect on cell proliferation, iron is involved in both fetal development and cancer. We hypothesize that HFE links higher infant birth weight with leukemia risk and that maternal HFE genotype modifies this association.

Procedure

Nine hundred ninety‐five infants and their mothers from the North Cumbria Community Genetics Project, and 163 incident childhood ALL cases from the Newcastle Haematology Biobank were genotyped for HFE, HAMP, TFRC variants and 21 genomic control loci. Cord blood iron levels were measured in 217 control infants.

Results

Three HFE variants showed correlations with birth weight with a gene–dosage relationship in males (gender effect). The association was stronger in homozygotes for TFRC S142G and when the mother was positive for any HFE variant (maternal effect). The genotypes expected to increase fetal iron levels correlated with birth weight in males and their association with ALL was stronger in females who, we postulate, could not offset iron excess by increasing their weight.

Conclusions

Certain materno‐fetal genotype combinations that increase fetal iron exposure showed associations with higher birth weight in males and somewhat higher ALL risk in females. Gender‐specific use of iron during fetal growth may lead to this dichotomy in birth weight change. Only the materno‐fetal genotype combinations that increase iron levels most extremely correlated with birth weight and ALL risk in males. Pediatr Blood Cancer 2009; 53:1242–1248. © 2009 Wiley‐Liss, Inc.
Flow cytometric detection of Ewing sarcoma cells in peripheral blood and bone marrow
Authors: DuBois Steven G. , Epling C. Lorrie , Teague Juli , Matthay Katherine K. , Sinclair Elizabeth
Published: August 2009

Background

A new method for detecting circulating Ewing sarcoma cells using flow cytometry is described. This strategy exploits the nearly universal expression of CD99 and the lack of expression of CD45 by Ewing sarcoma cells.

Procedure

Ewing sarcoma cell line A673, peripheral blood mononuclear cells (PBMCs), and bone marrow mononuclear cells (BMMCs) were stained for CD99 and CD45 in order to detect CD99+CD45− cells by flow cytometry. Known quantities of A673 Ewing sarcoma cells were spiked into control PBMCs to test the accuracy of this method. Control PBMCs were evaluated to assess the level of background staining.

Results

Flow cytometry was accurate at frequencies as low as one A673 cell per 500,000 PBMCs. The background rate of CD99+CD45− cell detection was low in PBMCs from nine healthy volunteers (median 0.0001% of total cells; range 0–0.00046%) and was further reduced by incorporating stains to exclude dead cells, progenitor cells, and monocytes. In one subject with newly diagnosed localized Ewing sarcoma, CD99+CD45− cells were detected in both blood (0.0021%) and bone marrow (0.048%).

Conclusions

Multicolor flow cytometry for CD99+CD45− cells provides a new strategy for detecting circulating Ewing sarcoma cells. Clinical evaluation and validation of this method is ongoing. Pediatr Blood Cancer 2010; 54:13–18. © 2009 Wiley‐Liss, Inc.
Alginate‐nanofibers fabricated by an electrohydrodynamic process
Authors: Kim GeunHyung , Park Ko‐eun
Published: August 2009

Alginate, a natural polymer, is potentially useful in biomedical applications, because it is very similar to macromolecular substances, unlike synthetic polymers that may cause problems due to toxicity and lack of recognition by cells. Alginate's processability characteristics, however, are a potential drawback to its use as a biomedical nanofiber scaffold. To improve electrospinnability, alginate has been processed with various synthetic polymers and surfactants. Although this has enhanced the processability of the polymer, a new approach is required to obtain a sufficient production rate over a short period of time. We used a multiple‐nozzle electrospinning system complemented with auxiliary cylindrical electrodes. The nanofibers of alginate/poly(ethylene oxide) supplemented with lecithin as a surfactant were electrospun using a multiple nozzle system. We measured the production rate and size uniformity of the spun fibers with and without auxiliary electrodes. We observed that a multiple nozzle system with auxiliary electrodes provided much better and more stable processability, as well as higher mass productivity of alginate nanofibers compared with a normal multiple nozzle system. The resulting nanofiber mat showed potential for use as a biomedical scaffold based on our tests with cell‐cultured human dermal fibroblasts. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Effect of rubber types on synthesis, morphology, and properties of ABS resins
Authors: Yu Zhisheng , Li Yang , Zhao Zhongfu , Wang Chaoxian , Yang Juan , Zhang Chunqing , Li Zhansheng , Wang Yurong
Published: August 2009

A series of acrylonitrile–butadiene–styrene (ABS) copolymers were prepared using lithium‐catalyzed low‐cis rubber (PB700A), nickel‐catalyzed high‐cis rubber (BR9004), and their compounded rubber (PB700A/BR9004 = 50:50) as toughening agents through bulk polymerization. The effects of molecular structures of rubbers on the dissolving and grafting process of them were investigated. The structure and properties of ABS resins were characterized with FTIR, TEM, and performance measurements. It is shown that the characteristics of rubbers affect their dissolving state and grafting reaction and consequently influence the morphology and properties of ABS materials. BR9004 promotes the formation of irregular microsized rubber particles with special “salami”‐like structure and, therefore, presents better mechanical properties. PB700A has much higher 1,2‐isomers, which benefits its dispersion and grafting reaction; its toughening effect, however, is unsatisfactory and can be improved by the incorporation of BR9004. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Polyurethane dispersions derived from polycarbonatediols and m‐di(2‐isocyanatopropyl)benzene
Authors: Lee Da‐Kong , Yang Zong‐Da , Tsai Hong‐Bing , Tsai Ruey‐Shi
Published: August 2009

Aqueous polyurethane dispersions derived from various polycarbonatediols, m‐di(2‐isocyanatopropyl)benzene(TMXDI), and various carboxylic diols including dimethylol propionic acid (DMPA), dimethylol butyric acid (DMBA), and a carboxylic polycaprolactonediol (Placcel 205BA) were prepared by a method in which the dispersing procedure was modified to enhance the molecular weight. The NH2/NCO ratio during chain extension affected the molecular weight of the polyurethanes, significantly, and an optimum ratio of 0.67:1.0 was used. The molecular weight, particle size, tensile properties, and thermal properties of the polyurethane dispersions were investigated. The effect chemical structure of the polycarbonatediols on the properties shows no obvious trend, but the polyurethane dispersions derived from the carboxylic polycaprolactonediol exhibit smaller particle size and softer tensile properties when compared with those derived from DMPA and DMBA. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Study on the melt‐spinnability of poly(L‐lactic acid)
Authors: Zhang Huihui , Yang Gesheng , Wang Xiangbing , Shao Huili , Hu Xuechao
Published: August 2009

In this work, three kinds of different poly(L‐lactic acid) (PLLA) materials for melt‐spinning were investigated with respect to the molecular weight (MW) and molecular weight distribution (MWD), racemization, optical purity, thermal properties, and melt‐spinnability. It was found that the high MW was not the only factor to affect the melt spinnability of PLLA, the racemization and the amount of residual monomer would also affect the thermal properties and melt‐spinnability of PLLA. The results showed that it could be melt‐spun and hot‐drawn by using the general melt‐spinning device for PLLA pellet with good stereoregularity and comparatively high MW. For PLLA pellet with high MW and moderate stereoregularity, it must be treated at an appropriate temperature to increase the crystallinity before dry and extrusion, which could make the pellet be spun without agglomeration, whereas the draw ability of such as‐spun fiber was still poor. However, if the stereoregularity of PLLA pellet was poor, it could not be spun even it had very high MW. Only when MW, racemization, and the amount of residual monomer of the PLLA pellets all meet the requirements, PLLA fibers could be prepared by melt‐spinning. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Minimum “safe cycle time”: Selecting the frozen layer thickness
Authors: Chang Keh‐Chyou , Hioe Yunior , Villarreal Maria G. , Castro Jose M.
Published: August 2009

Predicting the minimum safe cycle time in injection molding is complicated by the cyclic nature of the process. The mold thermal state changes with continuous molding until a quasi steady state is achieved. In the first part of these series, we presented and experimentally tested a simple approach to predict part and mold surface temperature during continuous molding. In this work, we evaluate the minimum frozen layer thickness required before the part can be demolded and how the growth of this frozen layer is affected as the mold thermal state changes with continuous molding cycles. Experiments are used to relate the minimum frozen layer thickness to dimensional stability. Based on these experiments, statistical tools are used to select an ejection criterion to obtain a minimum safe cooling time. We show that the ejection criteria should be adjusted depending on the precision required from the molded parts. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Nonisothermal crystallization kinetics of high‐density polyethylene/barium sulfate nanocomposites
Authors: Chen Xiaolei , Wang Lumin , Liu Yongli , Shi Jiangao , Shi Hang
Published: August 2009

The high‐density polyethylene (HDPE)/barium sulfate (BaSO4) nanocomposites had been successfully prepared by melt‐blending. Nonisothermal melt‐crystallization kinetics of neat HDPE and HDPE/BaSO4 nanocomposites was investigated with differential scanning calorimetry under different cooling rates. The nonisothermal crystallization behavior was analyzed by Ozawa, Avrami, and combined Ozawa–Avrami methods. It was found that the Ozawa method failed to describe the nonisothermal crystallization behavior of neat HDPE and HDPE/BaSO4 nanocomposites. The modified Avrami method by Jeziorny was only valid for describing the middle stage of crystallization but was not able to describe the later stage of neat HDPE and HDPE/BaSO4 nanocomposites crystallization. The value of Avrami exponent n for neat HDPE ranged from 3.3 to 5.7 and for HDPE/BaSO4 nanocomposites ranged from 1.8 to 2.5. It is postulated that the values of n close to 3 are caused by spherulitic crystal growth with heterogeneous nucleation, whereas simultaneous occurrence of spherulitic and lamellar crystal growth with heterogeneous nucleation account for lower values of n. The combined Ozawa–Avrami method by Mo and coworkers (Polym. Eng. Sci.,37(3), 568 (1997)) was able to satisfactorily describe the crystallization behavior of neat HDPE and HDPE/BaSO4 nanocomposites. In addition, the activation energy of nonisothermal crystallization was determined using the Kissinger (J. Res. Natl. Bur. Stand.,57(4), 217 (1956)) method, showing that the crystallization activation energy of HDPE/BaSO4 nanocomposites was lower than that of neat HDPE. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Birefringence in gas‐assisted tubular injection moldings: Simulation and experiment
Authors: Carrillo Antonio J. , Isayev A.I.
Published: August 2009

The influence of the processing variables on the birefringence and polymer/gas interface distribution is analyzed for polystyrene moldings obtained by gas‐assisted injection molding (GAIM) under various processing conditions. The processing variables studied were: melt and mold temperatures, shot size, gas pressure, injection speed, and gas‐delay time. Measurements and viscoelastic simulations of the radial distribution of birefringence components, Δn and nrr − nθθ, the variation of the average birefringence, 〈nzz − nθθ〉, along the molding and polymer/gas interface along the length of spiral‐shaped tubular moldings are presented. The polymer/gas interface distribution and flow stresses were simulated using a numerical scheme based on a hybrid finite element/finite difference/control volume method. The birefringence was calculated from the flow‐induced stresses using the stress‐optical rule. Simulations qualitatively agreed with measurements and correctly described theeffect of the processing variables on the birefringence andthe polymer/gas interface distribution in GAIM moldings. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
New concept of reducing a birefringence of poly(ethylene naphthalate) by a novel alloy with fluorene‐based polyester
Authors: Kawasaki Shinichi , Kato Mariko , Kobori Kana , Sakamoto Hiroki , Kondo Yoshikazu , Takata Toshikazu
Published: August 2009

This study proposes the new concept of reducing the birefringence of poly(ethylene naphthalate) (PEN) by a novel alloy with fluorene‐based polyester (FBP) involving the “cardo” structure in it. The alloys composed of PEN and FBP were prepared by simple melt blending method (process A) and reactive melt blending (process B). The resulting alloys were characterized by DSC, XRD, DMA, tensile testing, and polarized light microscopy. All PEN‐FBP alloys showed transparency and a single glass transition temperature (Tg), indicating that PEN‐FBP alloys were completely compatible. It was also demonstrated that Tg for PEN was shifted to the high‐temperature side by alloying with FBP. A large amount of the orientation‐induced birefringence was induced in drawn PEN sheets; however, in the cases of PEN‐FBP alloys, it was drastically decreased because of alloying with FBP. We could reveal the new concept for “low‐orientation‐induced birefringence material.” POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers
Multiscale modeling of structural dynamics underlying force generation and product release in actomyosin complex
Authors: Zheng Wenjun
Published: August 2009

To decrypt the mechanistic basis of myosin motor function, it is essential to probe the conformational changes in actomyosin with high spatial and temporal resolutions. In a computational effort to meet this challenge, we have performed a multiscale modeling of the allosteric couplings and transition pathway of actomyosin complex by combining coarse‐grained modeling of the entire complex with all‐atom molecular dynamics simulations of the active site. Our modeling of allosteric couplings at the pre‐powerstroke state has pinpointed key actin‐activated couplings to distant myosin parts which are critical to force generation and the sequential release of phosphate and ADP. At the post‐powerstroke state, we have identified isoform‐dependent couplings which underlie the reciprocal coupling between actin binding and nucleotide binding in fast Myosin II, and load‐dependent ADP release in Myosin V. Our modeling of transition pathway during powerstroke has outlined a clear sequence of structural events triggered by actin binding, which lead to subsequent force generation, twisting of central β‐sheet, and the sequential release of phosphate and ADP. Finally we have performed atomistic simulations of active‐site dynamics based on an on‐path “transition‐state” myosin conformation, which has revealed significantly weakened coordination of phosphate by Switch II, and a disrupted key salt bridge between Switch I and II. Meanwhile, the coordination of MgADP by Switch I and P loop is less perturbed. As a result, the phosphate can be released prior to MgADP. This study has shed new lights on the controversy over the structural mechanism of actin‐activated phosphate release and force generation in myosin motor. Proteins 2010. © 2009 Wiley‐Liss, Inc.