bluuebunny/crossref_metadata_2025 huggingface dataset:
A synthesis and a practical approach to complex systems
Authors: Brodu Nicolas
Published: September 2008

This document is both a synthesis of current notions about complex systems and a practical approach description. A disambiguation is proposed and exposes possible reasons for controversies related to causation and emergence. Theoretical considerations about simulations are presented. A justification is then given for the development of practical tools and techniques for the investigation of complex systems. A methodology for the usage of these tools is finally suggested, illustrated by application examples. © 2008 Wiley Periodicals, Inc. Complexity, 2009.
Immunocytochemical study of urine cytological preparations from secondary prostatic adenocarcinoma involving the urinary bladder
Authors: Mai Kien T. , Ahmed Itrat , Robertson Susan J. , Belanger Eric C. , Veinot John P. , Islam Shahid
Published: September 2008

Involvement of the urinary bladder by prostatic adenocarcinoma (PCA) occasionally occurs. In this study, we analyzed urine cytological findings in patients with secondary involvement of the urinary bladder by PCA with the help of the immunocytochemistry. The cases were divided into two groups: (1) prospective study group: three cases; and (2) retrospective study group: 12 cases which were retrieved from our cytopathological files. The urine cytology specimens (cytospins) from all cases were submitted for prostatic specific antigen (PSA) immunocytochemistry. Additional immunostaining for high‐molecular‐weight cytokeratin (HMWCK) was performed if PSA immunoreactivity was negative. All cytospin smears showed atypical cells characterized by large, round and uniform nuclei with prominent nucleoli and dense cytoplasm. They were present as single cells or in cell groups simulating urothelial carcinoma. The diagnosis of PCA was made if the atypical cells were either immunoreactive for PSA or nonreactive for HMWCK. The urothelial cells were PSA− and HMWCK+. The immunostaining supported the PCA diagnosis in all three cases from the prospective group and two cases in the retrospective group. The remaining 10 cases in the retrospective group were diagnosed as negative: 3, atypia: 5 urothelial carcinoma: 2. The positive diagnosis for PCA was based on the PSA immunoreactivity or nonreactivity to HMWCK and the cytological atypia. In conclusions, immunostaining for PSA and HMWCK performed on cytospins of urine specimens from patients with a prior history of high‐grade and/or stage of PCA is helpful to make a positive diagnosis of secondary bladder involvement from PCA. Diagn. Cytopathol. 2008;36:715–720. © 2008 Wiley‐Liss, Inc.
Restoring satisfactory status in ThinPrep Pap test specimens with too few squamous cells and containing microscopic red blood cells
Authors: Pang Yijun , Smola Brian , Pu Robert T. , Michael Claire W.
Published: September 2008

Treatment of specimens that contain excessive blood can effectively reduce the unsatisfactory rate; however, a considerable number of unsatisfactory specimens remain. We evaluated the effectiveness of reprocessing unsatisfactory specimens that had too few squamous cells and contained microscopic red blood cells (TFSQRBC).

Out of the 688 unsatisfactory specimens at microscopic screening, 197 (28.63%) were TFSQRBC that were reprocessed by treatment of glacial acetic acid (GAA). Red blood cells were observed clogging the pores in the filter of the ThinPrep device. After reprocessing, 129 (68.48%) yielded a satisfactory diagnosis, which accounted for a reduction of the unsatisfactory rate by 18.25%. In the restored satisfactory specimens, abnormal diagnoses of 1 high‐grade squamous intraepithelial lesion (HSIL) (0.78%), 3 atypical glandular cells (AGC) (2.33%), and 13 atypical squamous cells of undetermined significance (ASCUS) (10.08%) were made. The abnormal diagnoses in this group of patients were significantly higher than that in the general population screened.

Reprocessing unsatisfactory ThinPrep® (TP) specimens of TFSQRBC can reduce the unsatisfactory rate of the TP Pap test significantly and is a cost‐effective measure. The initially unsatisfactory specimens are more likely to represent cases with an abnormal diagnosis, which also justifies the effort of reprocessing this group of specimens. Adjustment of the pore size on the ThinPrep filter device may reduce the interference of red blood cells. Diagn. Cytopathol. 2008;36:696–700. © 2008 Wiley‐Liss, Inc.
On‐line dynamic security assessment to mitigate the risk of blackout in the Italian power system
Authors: Cirio Diego , Lucarella Dario , Massucco Stefano
Published: September 2008

This paper provides a comprehensive survey of the major initiatives and research projects recently carried out by the Italian system operator, Cesi Ricerca, and Universities on power system monitoring, defense, and security assessment. The technological and methodological features of an advanced wide area measurement system (WAMS) are described and the main aspects of an adaptive system for event‐based automatic load shedding are presented. Then preventive and corrective security assessment, with particular emphasis to dynamic security assessment—DSA, is introduced. Results from an EU project, where the Italian power system served as a test site for on‐line experimentation, are reported. Considering the need for very fast assessment by stability indices, a complementary approach to the above “conventional” DSA, currently under way, is described in further detail. The methodology relies on a correlation model relating significant power system measurements with local loadability margins. Results of some tests on the Italian power system are presented and discussed. Copyright © 2008 John Wiley & Sons, Ltd.
The effects of PRGF on bone regeneration and on titanium implant osseointegration in goats: A histologic and histomorphometric study
Authors: Anitua Eduardo , Orive Gorka , Pla Rafael , Roman Pedro , Serrano Victoriano , Andía Isabel
Published: September 2008

The effect of local application of scaffold‐like preparation rich in growth factors (PRGF) on bone regeneration in artificial defects and the potential effect of humidifying titanium dental implants with liquid PRGF on their osseointegration were investigated. The PRGF formulations were obtained from venous blood of three goats and applied either as a 3D fibrin scaffold (scaffold‐like PRGF) in the regeneration of artificial defects or as liquid PRGF via humidifying the implants before their insertion. Initially, 12 defects were filled with scaffold‐like PRGF and another 12 were used as controls. The histological analysis at 8 weeks revealed mature bone trabeculae when PRGF was used, whereas the control samples showed mainly connective tissue with incipient signs of bone formation. For the second set of experiments, 26 implants (13 humidified with liquid PRGF) were placed in the tibiae of goats. Histological and histomorphometric results demonstrated that application of liquid PRGF increased the percentage of bone‐implant contact in 84.7%. The whole surface of the PRGF‐treated implants was covered by newly formed bone, whereas only the upper half was surrounded in control implants. In summary, PRGF can accelerate bone regeneration in artificial defects and improve the osseointegration of titanium dental implants. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
In vitro biodegradation of designed tubular scaffolds of electrospun protein/polyglyconate blend fibers
Authors: Zhang Xing , Thomas Vinoy , Vohra Yogesh K.
Published: September 2008

Electrospun polyglyconate (Maxon®) and its blends with proteins such as gelatin and elastin, with a spatially designed layer structure, were prepared as potential scaffolds for vascular tissue engineering. In vitro biodegradation of the electrospun tubular protein/Maxon scaffolds in phosphate buffered saline (pH = 7.3) was studied for the first time. The biodegradation is manifested by uptake of the PBS medium by the hydrophilic proteins and also by the mass loss due to the removal of degraded fragments and uncrosslinked proteins from the matrices. The effect of degradation on the structure–property relations was evaluated by IR, XRD, and DSC analyses of the aged scaffolds. The degradation of amorphous phase of Maxon in the early stages of aging has resulted in an increase in the crystallinity of the polymer. SEM analysis indicated a significant change in nanofiber morphology and fiber‐breaking. The mass loss and fiber breaking have negatively impacted the mechanical properties and the effect was maximum at 15–20 days of aging. The scaffold containing low molecular weight buffer soluble elastin revealed relatively better degradation properties compared to that containing high molecular weight buffer insoluble elastin. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009
Dual‐level direct dynamics studies for the reactions of OH radical with bromine‐substituted ethanes
Authors: Wang Li , Liu Jing‐yao , Gao Hong , Wan Su‐qin , Li Ze‐sheng
Published: September 2008

The dynamic properties of the multichannel hydrogen abstraction reactions of CH3CH2Br + OH → products and CH3CHBr2 + OH → products are studied by dual‐level direct dynamics method. For each reaction, three reaction channels, one for α‐hydrogen abstraction and two for β‐hydrogen abstractions, have been identified. The minimum energy paths (MEPs) of both the reactions are calculated at the Becke's half‐and‐half (BH&H)‐Lee‐Yang‐Parr (LYP)/6‐311G(d, p) level and the energy profiles along the MEPs are further refined with interpolated single‐point energies (ISPE) method at the G2M(RCC5)//BH&H‐LYP level. There are complexes with energies less than those of the reactants or products located at the entrance or exit channels, which indicates that the reactions may proceed via an indirect mechanism. By canonical variational transition‐state theory (CVT) the rate constants are calculated incorporating the small‐curvature tunneling (SCT) correction in the temperature range of 220–2000 K. The agreement of the rate constants with available experimental values for two reactions is good in the measured temperature range. The calculated results show that α‐hydrogen abstraction channel is the major reaction pathway in the lower temperature for two reactions, while the contribution of β‐hydrogen abstraction will increase with the increase in temperature. © 2008 Wiley Periodicals, Inc. J Comput Chem 2009
Comments on the molecular geometry of ferrocene: The dangers of using quantum chemistry programs as black boxes
Authors: Martin Jason , Baker Jon , Pulay Peter
Published: September 2008

The dangers of using standard quantum chemistry programs as black boxes is illustrated by analyzing some results in a recent paper published in this journal (Zhang et al., J Comput Chem 2007, 28, 2260). The main danger is that nonlinear optimizations of both the wavefunction and the molecular geometry may converge to higher local minima or to saddle points, producing misleading results. For instance, some of the calculated molecular geometries of ferrocene in the aforementioned paper correspond to an SCF solution that converged to an excited state. This is the cause of the apparent large variation in the calculated iron‐ring distance with the basis set. Another problem we noticed is that the source of the diffuse functions used in the earlier work in connection with the 6‐31G and 6‐311G basis sets for transition metals is not specified in the literature or the program manual. They are also a poor match for the 6‐31G basis set. We re‐emphasize that the 6‐31G basis set used in this paper lacks the necessary diffuse d‐type functions for the late first‐row transition metals, and ought to be replaced by the m6‐31G basis that offers a more balanced description of the atomic valence states. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Mesoscopic model for mechanical characterization of biological protein materials
Authors: Yoon Gwonchan , Park Hyeong‐Jin , Na Sungsoo , Eom Kilho
Published: September 2008

Mechanical characterization of protein molecules has played a role on gaining insight into the biological functions of proteins, because some proteins perform the mechanical function. Here, we present the mesoscopic model of biological protein materials composed of protein crystals prescribed by Go potential for characterization of elastic behavior of protein materials. Specifically, we consider the representative volume element (RVE) containing the protein crystals represented by Cα atoms, prescribed by Go potential, with application of constant normal strain to RVE. The stress–strain relationship computed from virial stress theory provides the nonlinear elastic behavior of protein materials and their mechanical properties such as Young's modulus, quantitatively and/or qualitatively comparable with mechanical properties of biological protein materials obtained from experiments and/or atomistic simulations. Further, we discuss the role of native topology on the mechanical properties of protein crystals. It is shown that parallel strands (hydrogen bonds in parallel) enhance the mechanical resilience of protein materials. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009
Discoidin domain receptor 1 activation suppresses α2β1 integrin‐dependent cell spreading through inhibition of Cdc42 activity
Authors: Yeh Yi‐Chun , Wang Chau‐Zen , Tang Ming‐Jer
Published: September 2008

Upregulation and overexpression of discoidin domain receptor 1 (DDR1) have been implied in the regulation of kidney development and progression of cancers. Our previous studies with Mardin–Darby canine kidney (MDCK) cells showed that overexpression of DDR1 inhibited cell spreading, whereas dominant negative DDR1 promoted cell spreading on collagen‐coated dish. Cell spreading is an important characteristic for cell differentiation and survival. However, little is known about the molecular mechanisms underlying the role of DDR1 in cell spreading. We have found here a novel signaling pathway of DDR1 consisting of Cdc42 that regulates the assembly and disassembly of cytoskeleton and cell spreading in MDCK cells. Cell spreading involves the organization of cytoskeleton that is mainly regulated by Rho‐family GTPases. We assessed the activity of Rho‐family GTPases and transfected MDCK cells with constitutively active or dominant negative GTPases, and quantified the extent of cell spreading. These results showed that DDR1 decreased the filamentous actin ratio and Rac1/Cdc42 activities, but had no effects on RhoA activity. Neither constitutively active nor dominant negative Rac1 altered DDR1‐inhibited cell spreading. Constitutively active Cdc42 could rescue the DDR1‐inhibited cell spreading, whereas dominant negative Cdc42 inhibited cell spreading, indicating that DDR1‐inhibited cell spreading is Cdc42 dependent. With the use of α2β1 integrin blocking antibody, we showed that collagen‐induced Cdc42 activation was mediated by α2β1 integrin. Moreover, ectopic FAK expression enhanced the Cdc42 activity. Reducing FAK activity by dominant negative FAK (FRNK) markedly abolished the Cdc42 activity. These findings show that DDR1a/b activation inhibits cell spreading through suppressing α2β1 integrin‐mediated Cdc42 activation. J. Cell. Physiol. 218: 146–156, 2009. © 2008 Wiley‐Liss, Inc.
Breast filariasis: Real‐time sonographic imaging of the filarial dance
Authors: Surendrababu Narayanam R.S. , Thomas Elsa , Rajinikanth Janakiraman , Keshava Shyamkumar N.
Published: September 2008

A 50‐year‐old woman presented with a palpable tender nodule in the upper quadrant of the breast that was clinically thought to be a fibroadenoma, with mammographic findings of a well‐defined lobulated density. Sonographic examination revealed a “filarial dance sign” within the cystic lesion, which is diagnostic of lymphatic breast filariasis. In endemic areas, sonographic examination is recommended to search for this pathognomonic real‐time diagnostic feature and, if present, to initiate treatment without delay. © 2008 Wiley Periodicals, Inc. J Clin Ultrasound, 2008
Parallel imaging enhanced MR colonography using a phantom model
Authors: Morrin Martina M. , Pedrosa Ivan , McKenzie Charles A. , Farrell Richard J. , Bloch Nicolas , Solazzo Stephanie , Ngo Long , Goldberg Shraga N. , Rofsky Neil M.
Published: September 2008

Purpose

To compare various Array Spatial and Sensitivity Encoding Technique (ASSET)‐enhanced T2W SSFSE (single shot fast spin echo) and T1‐weighted (T1W) 3D SPGR (spoiled gradient recalled echo) sequences for polyp detection and image quality at MR colonography (MRC) in a phantom model. Limitations of MRC using standard 3D SPGR T1W imaging include the long breath‐hold required to cover the entire colon within one acquisition and the relatively low spatial resolution due to the long acquisition time. Parallel imaging using ASSET‐enhanced T2W SSFSE and 3D T1W SPGR imaging results in much shorter imaging times, which allows for increased spatial resolution.

Materials and Methods

Using two porcine colon phantoms each with eight simulated 3–10‐mm “polyps,” baseline reference sequences acquired without ASSET (6‐mm slices and readout bandwidth [BW] 62 kHz) were compared with 11 SSFSE and 8 SPGR sequences acquired with 2‐fold ASSET acceleration. ASSET‐enhanced SSFSE and SPGR sequences comprised BW/matrix combinations ranging from 20–62 kHz / 256–352 × 256, respectively, with slice thicknesses adjusted from 3.0 to 4.5 mm to maintain a 23–26‐second acquisition time and 30 cm slab thickness. Two experienced radiologists viewed the datasets in a randomized, blinded fashion.

Results

Compared to reference sequences, ASSET‐enhanced SSFSE and SPGR sequences facilitated better polyp detection and had similar overall image quality and per‐phantom specificity. The two best ASSET‐enhanced SSFSE (3 and 4.5 mm slices, each with BW of 62.5 kHz and 352 × 256 matrices) and three best ASSET‐enhanced SPGR BW / slice thickness / matrix combinations of 31 kHz / 4.4 msec / 192 × 256; 62 / 3.4 / 192 × 256; and 62 / 4.0 / 192 × 256, respectively, permitted detection of all polyps ≥5 mm.

Conclusion

Parallel imaging using ASSET‐enhanced T2W SSFSE and T1W 3D SPGR improves the ability to detect significant colon polyps in an MRC phantom model. J. Magn. Reson. Imaging 2008;28:664–672. © 2008 Wiley‐Liss, Inc.
MRI diagnosis of brown tumor based on magnetic susceptibility
Authors: Knowles Negar G. , Smith Deven L. , Outwater Eric K.
Published: September 2008

A 56‐year‐old male with chronic renal failure was incidentally found to have lytic bone lesions in the pubic symphysis, left femoral head, left acetabulum, left iliac bone, and L1 vertebra on computed tomography (CT). Subsequent magnetic resonance imaging (MRI) of the abdomen was performed (for evaluation of a renal lesion) which demonstrated marked loss of signal intensity in the L1 bone lesion on increasing TE gradient echo images, consistent with magnetic susceptibility effect due to hemosiderin. Brown tumor was confirmed at biopsy. The susceptibility imaging probes one particular histological characteristic of tissues and allows a restricted differential of lytic tumors that contain significant hemosiderin, including brown tumor. J. Magn. Reson. Imaging 2008;28:759–761. © 2008 Wiley‐Liss, Inc.
T1ρ‐prepared balanced gradient echo for rapid 3D T1ρ MRI
Authors: Witschey Walter R.T. , Borthakur Arijitt , Elliott Mark A. , Fenty Matthew , Sochor Matthew A. , Wang Chenyang , Reddy Ravinder
Published: September 2008

Purpose

To develop a T1ρ‐prepared, balanced gradient echo (b‐GRE) pulse sequence for rapid three‐dimensional (3D) T1ρ relaxation mapping within the time constraints of a clinical exam (<10 minutes), examine the effect of acquisition on the measured T1ρ relaxation time and optimize 3D T1ρ pulse sequences for the knee joint and spine.

Materials and Methods

A pulse sequence consisting of inversion recovery–prepared, fat saturation, T1ρ‐preparation, and b‐GRE image acquisition was used to obtain 3D volume coverage of the patellofemoral and tibiofemoral cartilage and lower lumbar spine. Multiple T1ρ‐weighted images at various contrast times (spin‐lock pulse duration [TSL]) were used to construct a T1ρ relaxation map in both phantoms and in the knee joint and spine in vivo. The transient signal decay during b‐GRE image acquisition was corrected using a k‐space filter. The T1ρ‐prepared b‐GRE sequence was compared to a standard T1ρ‐prepared spin echo (SE) sequence and pulse sequence parameters were optimized numerically using the Bloch equations.

Results

The b‐GRE transient signal decay was found to depend on the initial T1ρ‐preparation and the corresponding T1ρ map was altered by variations in the point spread function with TSL. In a two compartment phantom, the steady state response was found to elevate T1ρ from 91.4 ± 6.5 to 293.8 ± 31 and 66.9 ± 3.5 to 661 ± 207 with no change in the goodness‐of‐fit parameter R2. Phase encoding along the longest cartilage dimension and a transient signal decay k‐space filter retained T1ρ contrast. Measurement of T1ρ using the T1ρ‐prepared b‐GRE sequence matches standard T1ρ‐prepared SE in the medial patellar and lateral patellar cartilage compartments. T1ρ‐preparedb‐GRE T1ρ was found to have low interscan variability between four separate scans. Mean patellar cartilage T1ρ was elevated compared to femoral and tibial cartilage T1ρ.

Conclusion

The T1ρ‐prepared b‐GRE acquisition rapidly and reliably accelerates T1ρ quantification of tissues offset partially by a TSL‐dependent point spread function. J. Magn. Reson. Imaging 2008;28:744–754. © 2008 Wiley‐Liss, Inc.
Mapping of vertebral artery perfusion territories using arterial spin labeling MRI
Authors: Kansagra Akash P. , Wong Eric C.
Published: September 2008

Purpose

To demonstrate the use of a noninvasive arterial spin labeling (ASL) MRI technique and evaluate vertebral artery (VA) territories in the brain.

Materials and Methods

Vessel‐encoded ASL was used to determine the territories of the left and right VAs in five healthy subjects. Territory maps were analyzed quantitatively by comparing the fractional contributions of the left and right VAs in selected regions of interest within the brain.

Results

VA territory maps demonstrated a complicated pattern of perfusion to the posterior aspect of the brain, but were consistent with the posterior cerebral and cerebellar artery distributions. Cerebellar perfusion was predominantly ipsilateral (P < 0.01). The total left and right VA contributions were unequal (P < 0.01), and there was relatively little mixing in the vertebrobasilar system.

Conclusion

Vessel‐encoded ASL can reveal individual VA territories in the brain. In a small sample of healthy volunteers the VAs appeared to contribute unequally, provide predominantly ipsilateral supply to the cerebellum, and undergo minimal mixing in the basilar artery. J. Magn. Reson. Imaging 2008;28:762–766. © 2008 Wiley‐Liss, Inc.
Fast projective carotid MR angiography using arterial spin‐labeled balanced SSFP
Authors: Koktzoglou Ioannis , Edelman Robert R.
Published: September 2008

Purpose

To determine whether pulsed arterial spin‐labeled (pulsed ASL) balanced steady‐state free precession (bSSFP) imaging allows for rapid projective depiction of the carotid arteries without electrocardiographic (ECG) gating.

Materials and Methods

The carotid arteries of six volunteers were scanned at 1.5 T using an ASL two‐dimensional bSSFP sequence. Three configurations were tested, with and without ECG gating: (a) full field‐of‐view (FOV) acquisition (scan time = 48 s), (b) full‐FOV acquisition with parallel acceleration of 2 (24 s), and sequence C (half‐FOV acquisition (24 s). Vessel‐to‐background contrast‐to‐noise ratios (CNRs) and vessel lengths were compared between sequence configurations. Vessel caliber measurements were compared with those obtained from three‐dimensional time‐of‐flight (TOF) angiography.

Results

The carotid arteries were seen over extensive lengths with ASL two‐dimensional bSSFP. Projected vessel length and vessel‐to‐background CNR did not differ with ECG gating (P = NS). Nonaccelerated full‐FOV and half‐FOV scans provided larger apparent vessel‐to‐background CNR and slightly longer vessel lengths than the parallel‐accelerated scans (P < 0.01). Carotid diameter measurements were in agreement with those obtained from three‐dimensional TOF (intraclass correlation coefficient = 0.810; P < 0.001).

Conclusion

pulsed ASL bSSFP is a fast technique for projective carotid angiography that may not require ECG gating. Acquisition time may be decreased with reduced FOV or parallel imaging strategies. J. Magn. Reson. Imaging 2008;28:778–782. © 2008 Wiley‐Liss, Inc.
Dixon techniques for water and fat imaging
Authors: Ma Jingfei
Published: September 2008

In 1984, Dixon published a first paper on a simple spectroscopic imaging technique for water and fat separation. The technique acquires two separate images with a modified spin echo pulse sequence. One is a conventional spin echo image with water and fat signals in‐phase and the other is acquired with the readout gradient slightly shifted so that the water and fat signals are 180° out‐of‐phase. Dixon showed that from these two images, a water‐only image and a fat‐only image can be generated. The water‐only image by the Dixon's technique can serve the purpose of fat suppression, an important and widely used imaging option for clinical MRI. Additionally, the availability of both the water‐only and fat‐only images allows direct image‐based water and fat quantitation. These applications, as well as the potential that the technique can be made highly insensitive to magnetic field inhomogeneity, have generated substantial research interests and efforts from many investigators. As a result, significant improvement to the original technique has been made in the last 2 decades. The following article reviews the underlying physical principles and describes some major technical aspects in the development of these Dixon techniques. J. Magn. Reson. Imaging 2008;28:543–558. © 2008 Wiley‐Liss, Inc.
Double‐reference cross‐correlation algorithm for separation of the arteries and veins from 3D MRA time series
Authors: Santini Francesco , Patil Sunil , Meckel Stephan , Scheffler Klaus , Wetzel Stephan G.
Published: September 2008

Purpose

To present a novel postprocessing technique for artery/vein separation and background suppression from contrast‐enhanced time‐resolved magnetic resonance angiography datasets in order to improve the diagnosis of vessel pathologies and arteriovenous fistulas.

Materials and Methods

Ten normal, two pathologic datasets of the brain, and one hand angiography dataset were postprocessed. Cross‐correlation maps between the signal time course of every voxel in the dataset and selected arterial and venous references regions of interest (ROIs) were obtained; these maps were subsequently nonlinearly transformed to obtain two indices representing the likelihood of a voxel belonging to a vessel category. Red‐green‐blue (RGB) color encoding was utilized to depict synthetic arteriogram and venogram images in a single diagnostically meaningful image.

Results

The technique enabled correct visual separation of vessels on various datasets, as evaluated by two expert neuroradiologists, and also highlighted characteristics of flow in arteriovenous fistulas. A quantitative comparison with existing techniques showed better separation performance on 3 out of 10 normal datasets and higher stability to acquisition characteristics and contrast agent bolus dispersion.

Conclusion

This method can be helpful in the diagnosis of vascular diseases in subjects where bolus dispersion makes it difficult to discriminate between arteries and veins with standard methods (subtraction or correlation analysis). J. Magn. Reson. Imaging 2008;28:646–654. © 2008 Wiley‐Liss, Inc.
Free‐breathing, nongated real‐time delayed enhancement MRI of myocardial infarcts: A comparison with conventional delayed enhancement
Authors: Detsky Jay S. , Graham John J. , Vijayaraghavan Ram , Biswas Labonny , Stainsby Jeffrey A. , Guttman Michael A. , Wright Graham A. , Dick Alexander J.
Published: September 2008

Purpose

To compare a free‐breathing, nongated, and black‐blood real‐time delayed enhancement (RT‐DE) sequence to the conventional inversion recovery gradient echo (IR‐GRE) sequence for delayed enhancement MRI.

Materials and Methods

Twenty‐three patients with suspected myocardial infarct (MI) were examined using both the IR‐GRE and RT‐DE imaging sequences. The sensitivity and specificity of RT‐DE for detecting MI, using IR‐GRE as the gold standard, was determined. The contrast‐to‐noise ratios (CNR) between the two techniques were also compared.

Results

RT‐DE had a high sensitivity and specificity (94% and 98%, respectively) for identifying MI. The total acquisition time to image the entire left ventricle was significantly shorter using RT‐DE than IR‐GRE (5.6 ± 0.9 versus 11.5 ± 1.9 min). RT‐DE had a slightly lower infarct‐myocardium CNR but a higher infarct‐blood CNR than IR‐GRE imaging. Compared with IR‐GRE, RT‐DE accurately measured total infarct sizes.

Conclusion

RT‐DE can be used for delayed enhancement imaging during free‐breathing and without cardiac gating. J. Magn. Reson. Imaging 2008;28:621–625. © 2008 Wiley‐Liss, Inc.
Gadobenate dimeglumine–enhanced magnetic resonance imaging of primary leiomyoma of the liver
Authors: Marin Daniele , Catalano Carlo , Rossi Massimo , Guerrisi Antonino , Di Martino Michele , Berloco Pasquale , Passariello Roberto
Published: September 2008

We report a case of histologically proven primary leiomyoma of the liver that was evaluated with multiphasic 64‐section computed tomography (CT) and gadobenate dimeglumine–enhanced magnetic resonance (MR) imaging. This lesion showed vivid enhancement during the arterial phase with sustained enhancement during the hepatic venous and equilibrium phases. During the liver‐specific MR imaging phase (150 minutes after contrast injection), the same lesion demonstrated lack of contrast retention, thus appearing hypointense compared with the background liver. Because of this latter finding, the patient underwent partial resection of the liver. In primary hepatic leiomyoma, the absence of contrast uptake during the liver‐specific phase of gadobenate dimeglumine–enhanced MR imaging may be inappropriately interpreted as a sign of malignancy, thus leading to unnecessary, aggressive management of such lesions. J. Magn. Reson. Imaging 2008;28:755–758. © 2008 Wiley‐Liss, Inc.
Modifications of the DC Raytheon–Statz model for SiC MESFETs
Authors: Zarębski Janusz , Bisewski Damian
Published: September 2008

In the paper the problem of modelling DC characteristics of SiC MESFETs is presented. Some modifications of the popular Raytheon–Statz model built‐in in SPICE are proposed. The original and the modified models are verified experimentally by comparison of the measured and simulated device characteristics. One of the two available today on the market SiC MESFETs–the transistor CRF24010 offered by Cree, Inc. is chosen for investigations. Copyright © 2008 John Wiley & Sons, Ltd.
Concentration‐ and temperature‐dependent conformation change of cyclohexyl isocyanide on gold nanoparticle surfaces
Authors: Joo Sang‐Woo , Kang Weekyung , Oh Jeong Jin
Published: September 2008

The conformational changes of cyclohexyl isocyanide (CHNC) on gold nanoparticle surfaces were investigated by means of concentration‐ and temperature‐dependent surface‐enhanced Raman scattering (SERS). The equatorial chair conformer appeared to be dominant at high‐bulk concentrations or low temperatures, whereas both the equatorial and axial chair conformers of CHNC were found to exist at low‐bulk concentrations or high temperatures as in the previous reports of cyclohexanethiol (CHT). Depending on concentrations and temperatures, the spectral changes of the NC stretching vibration on gold nanoparticles appeared to be more conspicuous than those of the cyclohexyl ring modes. A density functional theory (DFT) calculation was performed at the level of B3LYP/6‐31G + + (d,p) to compare the energetic stability of the various conformers of CHT and CHNC. The energy differences between the equatorial and axial chair conformers were predicted to be smaller for CHNC than for CHT by ∼3 kJ mol−1 from the DFT calculation. Copyright © 2008 John Wiley & Sons, Ltd.
Development and validation of gas chromatography and real‐time quantitative PCR for the quantification of landscape‐scale gene flow from varieties of high erucic acid (HEAR) oilseed rape
Authors: Cullen Danny W , Squire Geoffrey R , McNicol Jim W , Jacobs Jennifer H , Osborne Juliet L , Ford Linda , Ramsay Gavin , Scrimgeour Charlie , Young Mark W
Published: September 2008

BACKGROUND: High erucic acid oilseed rape (HEAR) was tested as a source crop for estimates of regional geneflow. Two methods to detect HEAR in low erucic acid oilseed rape (LEAR) were compared: real‐time quantitative PCR (qPCR) and gas chromatography (GC).

RESULTS: Fields (2.5 ha) of a LEAR variety (0.028% EA) in Tayside and Hertfordshire were juxtaposed adjacent to and 1 km distant from a HEAR (44% EA) field. The LEAR variety was a varietal association to ensure high cross‐pollination (CP). The methods were highly correlated, measuring between 30% and 0.5% CP. However, the qPCR method became unreliable below 0.5% CP, whereas GC was robust enough to detect raised EA equivalent to one F1 seed in 500 (0.2%). A statistical mixture model was fitted to the distributions of EA in samples in order to assign a CP value to each 500‐seed sample. Declines of CP from 30% to < 1%, and EA from 5% to 0.2%, with distance up to 150 m in the near fields was best fitted with a power function. The combined mean EA for both far fields was 0.11%, well above the background LEAR value of 0.028%, and mean CP was 0.36%.

CONCLUSIONS: The GC method of detection raised %EA should be a reliable and high‐throughput means of estimating %CP between fields, provided the %EA of single F1 seed in receptor fields is measured to confirm the presence of F1 seed. Copyright © 2008 Society of Chemical Industry
On realization of the Kreĭn–Langer class Nκ of matrix‐valued functions in Pontryagin spaces
Authors: Arlinskiĭ Yury , Belyi Sergey , Derkach Vladimir , Tsekanovskii Eduard
Published: September 2008

In this paper the realization problems for the Kreĭn–Langer class Nκ of matrix‐valued functions are being considered. We found the criterion when a given matrix‐valued function from the class Nκ can be realized as linear‐fractional transformation of the transfer function of canonical conservative system of the M. Livsic type (Brodskii–Livsic rigged operator colligation) with the main operator acting on a rigged Pontryagin space Πκ with indefinite metric. We specify three subclasses of the class Nκ (R) of all realizable matrix‐valued functions that correspond to different properties of a realizing system, in particular, when the domains of the main operator of a system and its conjugate coincide, when the domain of the hermitian part of a main operator is dense in Πκ . Alternatively we show that the class Nκ (R) can be realized as transfer matrix‐functions of some canonical impedance systems with self‐adjoint main operators in rigged spaces Πκ . The case of scalar functions of the class Nκ (R) is considered in details and some examples are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Atomic decompositions of function spaces with Muckenhoupt weights, and some relation to fractal analysis
Authors: Haroske Dorothee D. , Piotrowska Iwona
Published: September 2008

This paper deals with atomic decompositions in spaces of type Bsp,q (ℝn , w), Fsp,q (ℝn , w), 0 < p < ∞, 0 < q ≤ ∞, s ∈ ℝ, where the weight function w belongs to some Muckenhoupt class Ar. In particular, we consider the weight function wΓκ (x) = dist(x, Γ)κ, where Γ is some d ‐set, 0 < d < n, and κ > –(n – d). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On the existence of a solution for a model of stem cell differentiation
Authors: Witterstein Gabriele
Published: September 2008

In two dimensions we consider a model describing the biological material change in the process of stem cell differentiation. The arising system consists in the Navier–Stokes equations for viscous, compressible, isothermal flow and models a creep movement mainly caused by a mass production and affected by the changeover in the stem cell culture. These equations are coupled with an Allen–Cahn equation modeling the solidification of a liquid. As the main result, we show the existence of a weak, spherically symmetric solution in a plain domain. Copyright © 2008 John Wiley & Sons, Ltd.
Diffusion tensor imaging of left ventricular remodeling in response to myocardial infarction in the mouse
Authors: Strijkers Gustav J. , Bouts Annemiek , Blankesteijn W. Matthijs , Peeters Tim H. J. M. , Vilanova Anna , van Prooijen Mischa C. , Sanders Honorius M. H. F. , Heijman Edwin , Nicolay Klaas
Published: September 2008

The cardiac muscle architecture lies at the basis of the mechanical and electrical properties of the heart, and dynamic alterations in fiber structure are known to be of prime importance in healing and remodeling after myocardial infarction. In this study, left ventricular remodeling was characterized using diffusion tensor imaging (DTI) in a mouse model of myocardial infarction. Myocardial infarction was induced in mice by permanent ligation of the left anterior descending coronary artery. Serial ex vivo DTI measurements were performed 7, 14, 28, and 60 days after ligation. Apparent diffusion coefficient, fractional anisotropy, the three eigenvalues of the diffusion tensor, and the myofiber disarray served as readout parameters. After myocardial infarction, the mouse hearts displayed extreme wall thinning in the infarcted area, which covered large parts of the apex and extended into the free wall up to the equator. Average heart mass increased by 70% 7–60 days after infarction. Histological analysis showed that the infarct at 7 days consisted of unstructured tissue with residual necrosis and infiltration of macrophages and myofibroblasts. At 14 days after infarction, the necrotic tissue had disappeared and collagen fibers were starting to appear. From 28 to 60 days, the infarct had fully developed into a mature scar. DTI parameters showed dynamic changes as a function of time after infarction. The apparent diffusion coefficient in the infarcted region was lower than in remote regions and increased as a function of time after infarction. The fractional anisotropy was higher in the infarcted region and was maximum at 28 days, which was attributed to the development of structured collagen fibers. Myofiber disarray, which was analyzed by considering the alignment of fibers in neighboring voxels, was significantly higher in infarcted regions. DTI provides a valuable non‐destructive tool for characterizing structural remodeling in diseased myocardium. Copyright © 2008 John Wiley & Sons, Ltd.
The stability of stars of triangular equilibrium plate elements
Authors: Maunder E. A. W. , Moitinho de Almeida J. P.
Published: September 2008

Equilibrium models for finite element analyses are becoming increasingly important in complementary roles to those from conventional conforming models, but when formulating equilibrium models questions of stability, or admissibility of loads, are of major concern. This paper addresses these questions in the context of flat plates modelled with triangular hybrid elements involving membrane and/or flexural actions. Patches of elements that share a common vertex are considered, and such patches are termed stars. Stars may be used in global analyses as assemblies of elements forming macro‐elements, or in local analyses. The conditions for stability, or the existence and number of spurious kinematic modes, are determined in a general algebraic procedure for any degree of the interpolation polynomials and for any geometric configuration. The procedure involves the determination of the rank of a compatibility matrix by its transformation to row echelon form. Examples are presented to illustrate some of the characteristics of spurious kinematic modes when they exist in stars with open or closed links. Copyright © 2008 John Wiley & Sons, Ltd.
A three‐dimensional C1 finite element for gradient elasticity
Authors: Papanicolopulos S.‐A. , Zervos A. , Vardoulakis I.
Published: September 2008

In gradient elasticity strain gradient terms appear in the expression of virtual work, leading to the need for C1 continuous interpolation in finite element discretizations of the displacement field only. Employing such interpolation is generally avoided in favour of the alternative methods that interpolate other quantities as well as displacement, due to the scarcity of C1 finite elements and their perceived computational cost. In this context, the lack of three‐dimensional C1 elements is of particular concern. In this paper we present a new C1 hexahedral element which, to the best of our knowledge, is the first three‐dimensional C1 element ever constructed. It is shown to pass the single element and patch tests, and to give excellent rates of convergence in benchmark boundary value problems of gradient elasticity. It is further shown that C1 elements are not necessarily more computationally expensive than alternative approaches, and it is argued that they may be more efficient in providing good‐quality solutions. Copyright © 2008 John Wiley & Sons, Ltd.
Polyconvex energy densities with applications to anisotropic thin shells
Authors: Balzani D. , Schröder J. , Gruttmann F.
Published: September 2008

This work shows the capability to simulate anisotropic thin shells using polyconvex energy densities by analyzing numerical examples. The variational framework is based on the enhanced assumed strain formulation. The iterative enforcement of the zero normal stress condition at the integration points allows consideration of arbitrary three–dimensional constitutive equations. We consider an additive structure of the energy decoupled in an isotropic part for a matrix material and the superposition of transversely isotropic parts for embedded fiber families and focus on polyconvex strain energy functions. In two representative examples we document anisotropy effects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Entropy behaviour of evolution PDEs
Authors: Broadbridge P.
Published: September 2008

A second order nonlinear conservation equation displays entropy irreversibility if and only if the heat flux is in the direction of decreasing temperature. Unlike linear 4th order diffusion equations, some classes of nonlinear 4th order equations do in fact display entropy irreversibility. In known cases, this is associated with positivity. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
An alternating direction Galerkin method for elliptic problems with gradient nonlinearity
Authors: Chow S.‐S.
Published: September 2008

Several problems in many applications involve the solution of partial differential equations with gradient dependent nonlinearity. The numerical solution of the resulting nonlinear system is rather expensive. We present an alternating direction Galerkin method that allows much faster solution of the nonlinear system. The alternating direction formulation help reduce the problem into a sequence of nonlinear systems that may be solved very efficiently. Theoretical study of the convergence of the method will also be presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Matching shape graphs
Authors: Demirci M. Fatih , van Leuken Reinier , Veltkamp Remco
Published: September 2008

Graphs are important structures to model complex relationships such as chemical compounds, proteins, geometric or hierarchical parts, and XML documents. Given a query graph, indexing has become a necessity to retrieve similar graphs quickly from large databases. We propose a novel technique for indexing databases, whose entries can be represented as graph structures. Our method starts by representing the topological structure of a graph as well as that of its subgraphs as vectors in which the components correspond to the sorted laplacian eigenvalues of the graph or subgraphs. By doing a nearest neighbor search around the query spectra, similar but not necessarily isomorphic graphs are retrieved. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlocal‐means single‐frame image zooming
Authors: Ebrahimi Mehran , Vrscay Edward R.
Published: September 2008

In this paper we present a novel single‐frame image zooming technique which is inspired by fractal‐based image zooming, example‐based zooming, and nonlocal‐means image denoising and combines these techniques in a consistent and improved framework. In Bayesian terms, this example‐based zooming technique targets the minimum mean square error (MMSE) estimate by learning the posterior directly from examples taken from the image itself at a different scale, similar to fractalbased techniques. The examples are weighted according to a scheme introduced by Buades et al. to perform nonlocal‐means image denoising. Finally, various computational issues are addressed and some results of this image zooming method applied to natural images are presented. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Asymptotic analysis and relaxation of Mumford‐Shah type energies with obstacles
Authors: Focardi M.
Published: September 2008

We discuss in a model case some results concerning the homogenization and relaxation of free‐discontinuity energies subjected to (unilateral) obstacle conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Capillary hydrodynamics of the deposition of thin films and droplets on heterogeneous, porous substrates
Authors: Gerlach D. , Alleborn N. , Raszillier H. , Delgado A.
Published: September 2008

The work presented here deals with recent research on capillary hydrodynamics of thin viscous liquid films and droplets. The process engineering background comes from the industrial process to deposit thin films or droplets on substrates such as polymer foils or paper [1, 2, 3]. During the production of paper, for example, layers of coating color have to be applied onto the raw paper in order to ensure its usability. Ink–jet paper consists of several different functional layers to optimize the paper with regard to printing quality or paper handling. For the printing process by the ink–jet technique, a controlled application of droplets onto the paper and subsequent penetration of the fluid into the paper are crucial for the final quality of the print. The work summarized here considers the application of films or droplets on substrates as well as the flow of liquids inside porous media. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Smoothed aggregation multigrid for incompressible flows
Authors: Janka Aleš
Published: September 2008

We discuss the advantages of using algebraic multigrid based on smoothed aggregation for solving indefinite linear problems. The ingredients of smoothed aggregation are used to construct a black‐box monolithic multigrid method with indefinite coarse problems. Although we discuss some techniques for enforcing the uniform inf‐sup stability on all coarse levels, numerical experiments suggest that it is not strictly necessary. The proposed multigrid preconditioner shows robust behaviour for different time‐step parameters and even for very elongated geometries, where other techniques based on h ‐independent preconditioners of the pressure Schur complement lose their efficiency. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Synthesis of artificial turbulent fields with prescribed second‐order statistics using the random‐spot method
Authors: Kornev Nikolai , Kröger Hannes , Turnow Johann , Hassel Egon
Published: September 2008

The paper presents a short description of the mathematical procedure proposed in [1]–[4] for the generation of turbulent velocity fields with prescribed second‐order statistics. The velocity field is represented as the sum of velocities induced by a set of randomly distributed spots. Velocity distribution inside of each spot is found in such a way that the fluctuations possess prescribed statistical properties. The procedure is applied for the generation of LES inlet conditions for the decaying turbulence convecting downstream in a box. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)