bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural correlates of the interaction between transient and sustained processes: A mixed blocked/event‐related fMRI study
Authors: Scheibe Christina , Wartenburger Isabell , Wüstenberg Torsten , Kathmann Norbert , Villringer Arno , Heekeren Hauke R.
Published: September 2005

Complete understanding of the neural correlates of cognitive processes requires investigation of both event‐ and state‐related correlates of cognitive performance as well as their interaction. Neuroimaging studies using blocked designs confound these two types of processes and studies using event‐related designs focus exclusively on the detection of transient effects. Recent fMRI studies used mixed blocked/event‐related designs and found that transient and sustained activity can be dissociated, but it is not yet known how event‐related and state‐related processing interact. Here we used a phonological categorization paradigm in a mixed blocked/event‐related design to investigate where in the brain transient activity interacts with sustained activity. Task difficulty was parametrically manipulated based on individually determined categorization thresholds. We found an interaction effect of transient and sustained activity in the left precuneus. In this cortical structure transient activity increased with increasing task difficulty, while sustained neural activity decreased with increasing task difficulty. Our data suggest that sustained activity is enhanced during processing of an easy task, presumably because of ongoing internally cued endogenous processing, still allowing effortless processing of transient stimuli. During performance of a difficult task, sustained activity in the precuneus is reduced to provide resources for processing incoming stimuli. Processing of stimuli that are expected to be difficult elicits increased transient responses independent of the actual physical properties of the stimuli. In showing an interaction between transient and sustained activity in the precuneus, the present results accommodate seemingly diverging results from previous studies using event‐related or blocked designs and expand the knowledge emerging from previous studies using mixed blocked/event‐related designs. Hum Brain Mapp, 2005. © 2005 Wiley‐Liss, Inc.
Optimal segmentation of microcomputed tomographic images of porous tissue‐engineering scaffolds
Authors: Rajagopalan Srinivasan , Lu Lichun , Yaszemski Michael J. , Robb Richard A.
Published: September 2005

The morphometric properties of the porous tissue‐engineering scaffolds play a dominant role in the initial cell attachment and subsequent tissue regeneration. These properties can be derived nondestructively with the use of quantitative analysis of high‐resolution microcomputed tomography (μCT) imaging of scaffolds. Accurate segmentation of these acquired images into solid and porous subspaces is critical to the integrity of morphometric analysis. The absence of a single image‐processing technique to provide such accurate separability immune to all the intricacies of the acquired data makes this seemingly simple task significantly error prone. Consequently, an optimal segmentation has to be selected by ranking the segmentations produced by a multiplicity of methods. This article proposes a robust, easy‐to‐implement, unambiguous, signal‐processing‐based, ground‐truth‐free, segmentation rating metric that correlates with visual acuity. With the use of this metric it is possible, for the first time, to threshold the data with a wide range of techniques and select automatically the technique that best delineates the acquired image. The proposed solution has been extensively tested on μCT images of scaffolds fabricated with biodegradable poly (propylene fumarate) (PPF) with the use of a solvent casting particulate leaching process. The approaches proposed and the results obtained may have profound implications for accurate image‐based characterization of tissue‐engineering scaffolds. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2005
Positive in vivo heterologous gene regulation by electric pulses delivery with metallothionein I gene promoter
Authors: Rubenstrunk Anne , Trollet Capucine , Orsini Cécile , Scherman Daniel
Published: September 2005

Background

In vivo electrotransfer is a physical method of gene delivery in various tissues and organs. It is a promising strategy for the systemic secretion of therapeutic proteins and for DNA vaccination. Nevertheless, for the success of gene therapy in clinics, it is essential to develop gene regulation systems. The existing systems described in the literature all rely on the creation of an artificial transcription factor and/or an inducer drug. New strategies based on endogenous regulatable elements are being developed. We have previously identified the murine metallothionein promoter as an endogenous promoter inducible by controlled electric stimuli applied for electrotransfer experiments. We report here a regulation strategy based on this murine metallothionein promoter in a plasmid context using electric pulses delivery as an inducer.

Methods

Plasmids containing different constructions of the murine metallothionein I (mMT‐I) promoter were transfected in mice tibialis‐cranalis muscles using the simple skeletal muscle electrotransfer method. The regulation system was studied with the murine secreted alkaline phosphatase (MUSEAP) reporter gene.

Results

The mMT‐I promoter can be transiently induced in vivo by application of electric fields. Its inducibility was analyzed in a plasmid context. We demonstrated that the mechanism of this transcriptional induction is not mediated by the cellular entry of metal ions. The ARE (antioxidant‐responsive element) sequence was identified as the element responsive to the electric field stimulation.

Conclusions

This time‐control of the expression of a therapeutic gene by physical stimuli could be of value in the context of gene regulation for gene therapy. Copyright © 2005 John Wiley & Sons, Ltd.
DNA damage responses after exposure to DNA‐based products
Authors: Smith Catherine C. , Aylott Michael C. , Fisher Krishna J. , Lynch Anthony M. , Gooderham Nigel J.
Published: September 2005

Background

The development of DNA‐based therapies holds great promise for the treatment of diseases that remain difficult to manage using conventional pharmaceuticals. Whilst there are considerable data regarding chemical‐induced DNA damage, there are limited reports published studying the potential of exogenous DNA to damage genomic DNA.

Methods

To investigate this problem, the differential gene expression (DGE) of DNA repair genes was examined to identify biomarkers, based on the hypothesis that DNA damage, including double‐strand breaks (DSBs) and insertional mutagenesis, would be expected to induce biological pathways associated with repair. Human HepG2 cells were exposed to the chemical genotoxins, etoposide (ETOP) and methylmethanesulphonate (MMS), as positive controls, or biological agents (i.e. exogenous DNA with and without the use of transfection complexes or via various viral vectors). Following transfection (6–72 h) the cells were harvested for RNA and DGE was determined by quantitative real‐time polymerase chain reaction (qRT‐PCR).

Results

The expression of genes involved in the repair of DSBs were significantly increased after treatment with ETOP (>4‐fold) or MMS (>5‐fold). Transfection using Effectene and ExGen 500 resulted in no significant changes; however, transfection with ExGen 500 resulted in an increase in the expression levels of GADD45 mRNA, consistent with global cellular stress. Viral vectors increased (3–6‐fold) expression of genes associated with DSBs and cellular stress responses and, as expected, the effect was the most marked with the retroviral vector.

Conclusions

The DGE profiles observed in HepG2 cells following transduction/transfection suggest that a subset of DNA repair genes may provide novel biomarkers to rapidly detect DNA damage induced by DNA products at the level of the genome, rather than at selected genes. Copyright © 2005 John Wiley & Sons, Ltd.
Physical incorporation of a single‐stranded oligodeoxynucleotide during targeted repair of a human chromosomal locus
Authors: Radecke Sarah , Radecke Frank , Peter Ingrid , Schwarz Klaus
Published: September 2005

Background

Targeted gene repair is an attractive method to correct point‐mutated genes at their natural chromosomal sites, but it is still rather inefficient. As revealed by earlier studies, successful gene correction requires a productive interaction of the repair molecule with the target locus. The work here set out to investigate whether DNA repair, e.g., mismatch repair, or a direct incorporation of the correction molecule follows as the step upon the initial interaction.

Methods

Single‐stranded 21mer oligodeoxynucleotides (ODNs) of sense orientation were directed towards point‐mutated enhanced green fluorescence protein transgene loci in HEK‐293‐derived cell clones. First gene repair assays compared ODNs carrying the canonical termini 5′‐phosphate and 3′‐OH with their respective variants harbouring non‐canonical termini (5′‐OH, 3′‐H). Second, a protocol was established to allow efficient recovery of integrated short biotin‐labelled ODNs from the genomes of gene‐corrected cells using streptavidin‐coated beads in order to test directly whether transfected ODNs become bona fide parts of the target locus DNA.

Results

Oligodeoxynucleotides with canonical termini were about 34‐fold more efficient than their counterparts carrying non‐canonical termini in a phosphorothioate‐modified backbone. Furthermore, biotinylated fragments were successfully recovered from genomic DNAs of gene‐corrected cells.

Conclusions

The experiment showed that ODNs are incorporated into a mammalian genome. This unravels one early repair step and also sets an unexpected example of genome dynamics possibly relevant to other ODN‐based cell techniques. Copyright © 2005 John Wiley & Sons, Ltd.
Strangulation signs: Initial correlation of MRI, MSCT, and forensic neck findings
Authors: Yen Kathrin , Thali Michael J. , Aghayev Emin , Jackowski Christian , Schweitzer Wolf , Boesch Chris , Vock Peter , Dirnhofer Richard , Sonnenschein Martin
Published: September 2005

Purpose

To evaluate multislice spiral computed tomography (MSCT) and magnetic resonance imaging (MRI) findings in hanging and manual strangulation cases and compare them with forensic autopsy results.

Materials and Methods

Postmortem MSCT and MRI of nine persons who died from hanging or manual strangulation were performed. The neck findings were compared with those discovered during forensic autopsy. In addition, two living patients underwent imaging and clinical examination following severe manual strangulation and near‐hanging, respectively. For evaluation, the findings were divided into “primary” (strangulation mark and subcutaneous desiccation (i.e., soft‐tissue thinning as a result of tissue fluids being driven out by mechanical compression) in hanging, and subcutaneous and intramuscular hemorrhage in manual strangulation) and “collateral” signs. The Wilcoxon two‐tailed test was used for statistical analysis of the lymph node and salivary gland findings.

Results

In hanging, the primary and most frequent collateral signs were revealed by imaging. In manual strangulation, the primary findings were accurately depicted, with the exception of one slight hemorrhage. Apart from a vocal cord hemorrhage, all frequent collateral signs could be diagnosed radiologically. Traumatic lymph node hemorrhage (P = 0.031) was found in all of the manual strangulation cases.

Conclusion

MSCT and MRI revealed strangulation signs concordantly with forensic pathology findings. Imaging offers a great potential for the forensic examination of lesions due to strangulation in both clinical and postmortem settings. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Correction for heart rate variability improves coronary magnetic resonance angiography
Authors: Leiner Tim , Katsimaglis George , Yeh Ernest N. , Kissinger Kraig V. , van Yperen Gert , Eggers Holger , Manning Warren J. , Botnar René M.
Published: September 2005

Purpose

To address degradation of coronary MR angiography (MRA) image quality due to heart rate variability (HRV)‐associated variations in coronary artery position and motion.

Materials and Methods

Free‐breathing navigator‐gated and ‐corrected coronary MRA using subject‐specific trigger delays and acquisition windows was combined with a real‐time HRV correction algorithm, such as commonly used in left ventricular wall motion studies. Ten healthy adults underwent free‐breathing navigator‐gated and ‐corrected coronary MRA with and without HRV correction. Signal‐to‐noise (SNR), contrast‐to‐noise (CNR), vessel length, diameter, sharpness, and subjective image quality (on a five‐point scale) were compared in a blinded fashion.

Results

Vessel sharpness improved significantly for both the left (LCA) and right (RCA) coronary artery systems (P = 0.016 and P = 0.015, respectively) with the use of HRV correction. Subjective image quality also improved significantly when HRV correction was used (P = 0.003). There were no significant differences with regard to SNR and CNR (P > 0.1).

Conclusions

Preliminary results suggest that HRV correction improves objective and subjective image quality in coronary MRA. Continued studies in patients with known or suspected coronary artery disease are warranted to investigate the clinical impact of this technique. J. Magn. Reson. Imaging 2005. © 2005 Wiley‐Liss, Inc.
Effects of harvest stage and re‐growth on yield, composition, ensilage and in vitro digestibility of new forage sorghum varieties
Authors: Miron Joshua , Solomon Ran , Adin Gabriel , Nir Uri , Nikbachat Moses , Yosef Edith , Carmi Avner , Weinberg Zwi G. , Kipnis Tal , Zuckerman Ephraim , Ben‐Ghedalia Daniel
Published: September 2005

The effect of growth stage and re‐growth on the nutritional and ensilage characteristics of two new sorghum hybrids, BMR‐101 and Silobuster, and one commercial variety, FS‐5, was examined in this study. Varieties were sampled during the summer at the early heading (EH) stage and were harvested at the soft dough (SD) stage. Additional irrigation enabled autumn re‐growth and a second harvest. Plants of FS‐5 and BMR‐101 were resistant to lodging at EH. However, BMR‐101 and Silobuster suffered from high lodging at the SD stage of the summer harvest. Dry matter (DM) content of FS‐5 and BMR‐101 at EH was below 250 g kg−1. DM yields of the varieties were similar at the summer harvest and higher than their respective re‐growth cuts. Ensilage DM losses were moderate and similar across varieties. Hemicellulose of SD plants was partly solubilised and most of the water‐soluble carbohydrate fermented, yielding lactic acid, ethanol and volatile fatty acids (VFA), and a pH < 4. In vitro DM digestibility of varieties was similar in summer silages, but lower in the respective re‐growth silages of FS‐5 and BMR‐101, reflecting the higher content of neutral detergent fibre and lignin in the re‐growth silages. The summer plus re‐growth cumulative yields of digestible DM of the respective FS‐5, Silobuster and BMR‐101 silages were 14.7, 16.6 and 14.5 t ha−1. The commercial variety, FS‐5, may have some advantage over BMR‐101 and Silobuster owing to its relative resistance to lodging in addition to its high yield and good ensilage properties. Copyright © 2005 Society of Chemical Industry
Clarification and sterilization of raw depectinized apple juice by ceramic ultrafiltration membranes
Authors: Li Jun , Wang Zhengfu , Ge Yiqiang , Sun Qingfu , Hu Xiaosong
Published: September 2005

Raw depectinized apple juice was clarified and sterilized in a cross‐flow pilot scale ultrafiltration system using ceramic tubular membranes (MEMBRALOX®, Pall) with mean pore size of 100 nm. The permeate flux significantly decreased with time until a steady‐state was established. An increase in filtration pressure increased the permeate flux while there is an optimum pressure (about 0.85 bar) above which the increase of pressure does not increase the flux significantly. The higher the cross‐flow velocity was, the higher was the transmembrane flux. When the operating temperature increased, the permeation rate increased subsequently. Analytical measurement showed that suspended solids and turbidity could almost be removed by the ceramic ultrafiltration membrane, but pH, acidity, sugar and soluble solid content of the juices showed no significant change. The bacteria challenge tests with Micrococcus flavus showed that the logarithm value of the bacteria reduction rate came up to above 9 in the cross‐flow tubular ceramic system. When the permeate was collected in sterile bottles in a laminar flow shell and kept at 4 °C, 8 °C, 25 °C and 35 °C, for 28 days, the apple juice experienced minimal changes in physicochemical properties at lower temperatures of 4 °C, or 8 °C. Copyright © 2005 Society of Chemical Industry
Injector‐internal thermal desorption from edible oils. Part 2: Chromatographic optimization for the analysis of migrants from food packaging material
Authors: Fiselier Katell , Biedermann Maurus , Grob Koni
Published: September 2005

Injector‐internal thermal desorption from edible oil or fat is a convenient sample preparation technique for the analysis of solutes in lipids or extracts from fatty foods. The injector temperature is selected to vaporize the solutes of interest while minimizing evaporation of the bulk material of the oil. This technique has been in routine use for pesticides for some time. Now its potential is explored for migrants from food contact materials, such as packaging, into simulant D (olive oil) or fatty/oily food, which means extending the range of application towards less volatile compounds. The performance for high boiling components was investigated for diisodecyl phthalate (DIDP) and diundecyl phthalate (DUP). Since the injector temperature needs to be as high as 260°C, some bulk material of the oil enters the column and must be removed after every analysis. This is achieved by a coated precolumn backflushed towards the end of each analysis. Desorption of the solutes is particularly efficient in the initial phase, when a thin sample film is spread on the liner wall, and is largely determined by the diffusion speed in the oil after the latter has contracted to droplets. An increased carrier gas flow rate during the splitless period supports the transfer into the column. It is concluded that the technique is attractive for migrant analysis, with DUP being at the upper limit of the boiling point.
Growth of Large Polymer Extended‐Chain Single Crystals in a Poly(ethylene terephthalate)/Bisphenol A Polycarbonate Blend under High Pressure
Authors: Lu Jun , Huang Rui , Li Liangbin , Luo Jianbin
Published: September 2005

Summary: High‐quality synthetic polymer extended‐chain single crystals with c‐axis thickness exceeding 100 µm are obtained in a polyethylene terephthalate/polycarbonate (PET/PC) blend rapidly. Some crystals comprise of PET, while others are made up by the copolymers with PET and PC blocks. The fast growth of large crystals is attributed to the mechanisms including transesterification, segment nucleation, and chain‐sliding diffusion, which is a self‐assembling process induced by chemical reactions in multiphase polymer system at high pressure. Similar to the role of enzyme in biosystem, the PC plays as a macromolecular catalyst. This process provides a new direction to grow large polymer single crystals and suggests that self‐assembly under high pressure is a promising method to create materials with new structures and properties.

SEI for a wedge‐shaped extended‐chain single crystal grown in a PET/PC blend at 200 MPa, 623 K for 6 h.

magnified image

SEI for a wedge‐shaped extended‐chain single crystal grown in a PET/PC blend at 200 MPa, 623 K for 6 h.
Tegaserod (Zelnorm) for the treatment of constipation in Parkinson's disease
Authors: Sullivan Kelly L. , Staffetti Joseph F. , Hauser Robert A. , Dunne Peter B. , Zesiewicz Theresa A.
Published: September 2005

We performed a double‐blind randomized placebo‐controlled pilot study to determine the efficacy of tegaserod (Zelnorm) in treating constipation in 15 patients with Parkinson's disease (PD). There was a trend for improvement in the Subject's Global Assessment (SGA) of satisfaction with bowel habits (NS) and the total SGA (including abdominal discomfort, bothersome constipation, and satisfaction; NS). © 2005 Movement Disorder Society
The generalized Thomas–Fermi singular boundary value problems for neutral atoms
Authors: Agarwal Ravi P. , O'Regan Donal , Palamides Panos K.
Published: September 2005

This paper presents an upper and lower solution theory for singular boundary value problems modelling the Thomas–Fermi equation, subject to a boundary condition corresponding to the neutral atom with Bohr radius equal to its existence interval. Furthermore, we derive sufficient conditions for the existence–construction of the above‐mentioned upper–lower solutions. Copyright © 2005 John Wiley & Sons, Ltd.
W2, p estimates of the heat equation in Ω⊂ℝn and the restrictions on ∂Ω
Authors: Waters Gavin , Wang Lihe
Published: September 2005

This is an alternative approach of finding the W2, p estimates of the heat equation in a domain, Ω⊂ℝn. Methods used in (Acta Math. Sin. 2003; 19(2):381–396) are expanded to the case of a bounded domain. As a result, milder restrictions are applied to ∂Ω than previously required by using the classical singular integral approach. Copyright © 2005 John Wiley & Sons, Ltd.
A ratio‐dependent eco‐epidemiological model of the Salton Sea
Authors: Kundu Kusumika , Chattopadhyay J.
Published: September 2005

Ratio‐dependent models set up a challenging issue for their rich dynamics incomparison to prey‐dependent models. Little attention has been paid so far to describe the importance of transmissible disease in ecological situation by considering ratio‐dependent models. In this paper, by assuming the predator response function as ratio‐dependent, we consider a model of a system of three non‐linear differential equations describing the time evolution of susceptible and infected Tilapia fish population and their predator, the Pelican. Existence and stability analysis of different equilibria of the system lead to different realistic thresholds in terms of system parameters. The condition for extinction of the species is also worked out. Our analytical and numerical studies may be helpful to chalk out suitable control strategies for minimizing the extinction of the Pelicans. We also suggest that supply of alternative food source for predator population may be used as a possible solution to save the predator from their extinction. Copyright © 2005 John Wiley & Sons, Ltd.
1H and 13C chemical shifts for 2‐aryl and 2‐N‐arylamino benzothiazole derivatives
Authors: Billeau S. , Chatel F. , Robin M. , Faure R. , Galy J.‐P.
Published: September 2005

The 1H and 13C NMR resonances for forty‐three 2‐aryl and 2‐N‐arylamino benzothiazole derivatives were completely assigned using a concerted application of one‐ and two‐dimensional experiments (DEPT, gs‐COSY, gs‐HMQC and gs‐HMBC). Copyright © 2005 John Wiley & Sons, Ltd.
Flow compensation in balanced SSFP sequences
Authors: Bieri O. , Scheffler K.
Published: September 2005

In balanced steady‐state free precession (b‐SSFP) sequences, uncompensated first‐order moments of encoding gradients induce a nonconstant phase evolution for moving spins within the excitation train, resulting in signal loss and image artifacts. To restore these flow‐related phase perturbations, “pairing” of consecutive phase‐encoding (PE) steps is compared with a fully flow‐compensated sequence using compensating gradient waveforms along all three encoding directions. In volunteer studies, the quality of images acquired with the “pairing” technique was comparable to that of images obtained with the fully flow‐compensated technique, regardless of the selected view‐ordering scheme used for data acquisition. Nevertheless, the results of phantom experiments indicate that the pairing technique becomes ineffective at flow velocities exceeding roughly 0.5–1 m/s. Consequently, the additional scan time required to null the first gradient moments in a flow‐compensated b‐SSFP sequence makes the “pairing” technique preferable for applications in which slow to moderate flow velocities can be expected. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Murine orthostatic response during prolonged vertical studies: Effect on cerebral blood flow measured by arterial spin‐labeled MRI
Authors: Foley Lesley M. , Hitchens T. Kevin , Kochanek Patrick M. , Melick John A. , Jackson Edwin K. , Ho Chien
Published: September 2005

High‐field MRI scanners are, in principle, well suited for mouse studies; however, many high‐field magnets employ a vertical design that may influence the physiological state of the rodent. The purpose of this study was to investigate the orthostatic response of cerebral blood flow (CBF) in mice during a prolonged MR experiment in the vertical position. Arterial spin‐labeled (ASL) MRI was performed at 4.7‐Tesla with a 15‐cm gradient insert that allowed horizontal and vertical CBF measurements to be obtained with the same scanner. For mice in the head‐up (HU) vertical position, CBF decreased by approximately 40% compared to the horizontal position, although blood pressure did not differ. Furthermore, CBF values for vertically positioned mice treated with phenylephrine remained constant while blood pressure increased. These results support the conclusion that cerebral autoregulation was intact, albeit at a lower level. Since CBF recovers to near horizontal values by volume loading with saline, it appears that a decrease in central venous pressure (CVP) leading to an increase in sympathetic tone may be a contributing mechanism for lowered CBF. This suggests that using an HU vertical position for MRI in mice may have broader implications, especially for studies that rely on CBF (such as BOLD and fMRI). Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Acute blood–brain barrier opening in experimentally induced focal cerebral ischemia is preferentially identified by quantitative magnetization transfer imaging
Authors: Knight Robert A. , Nagesh Vijaya , Nagaraja Tavarekere N. , Ewing James R. , Whitton Polly A. , Bershad Eric , Fagan Susan C. , Fenstermacher Joseph D.
Published: September 2005

Pathologic changes in brain tissue during and after stroke may lead to injury of the blood–brain barrier (BBB) and subsequent hemorrhagic transformation (HT). In a rat model of HT, the apparent diffusion coefficient of water, cerebral blood flow, relaxation times, T1 and T2, and magnetization transfer (MT) related parameters (T1sat, Kfor and the MT ratio) were repetitively measured during 3 h of focal ischemia and 2 h of reperfusion (n = 8). Areas of BBB opening were identified by sequential assay of the transcapillary influx of Gd‐diethylenetriaminepentaacetic acid (Gd‐DTPA) by MRI and 14C‐α‐aminoisobutyric acid (AIB) by quantitative autoradiography. Ischemia‐injured regions of interest were identified from the MRI data and divided into those with and without BBB opening. Of the several MRI parameters measured, the T1sat in the caudate‐putamen and preoptic area during ischemia and the first 2 h of reperfusion correlated best with the regional pattern of BBB opening observed thereafter. These data suggest that an ipsilateral/contralateral T1sat ratio > 1.6 demarcates leakage of small molecules such as Gd‐DTPA and AIB across the BBB. As to clinical relevance, the quantitation of MT parameters in acute stroke may enable the early detection of areas of BBB opening and potential HT. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Simultaneous monitoring of temperature and T1: Methods and preliminary results of application to drug delivery using thermosensitive liposomes
Authors: Bos Clemens , Lepetit‐Coiffé Matthieu , Quesson Bruno , Moonen Chrit T. W.
Published: September 2005

A method is presented to obtain temperature and longitudinal relaxivity measurements simultaneously and in near real‐time. Quantitative relaxivity values are obtained from the signal magnitude from fast Look‐Locker EPI data, whereas phase information from all signal samples on the recovery curve is combined to provide temperature values using the proton resonance frequency method. The utility of this technique is illustrated in an in vitro experiment with thermosensitive liposomes, which are studied as potential micro vehicles for local drug delivery. The method allowed measuring the evolution of relaxivity during RF‐heating of liposomes containing a paramagnetic contrast agent, demonstrating increase of liposome permeability near the phase transition temperature. Potential applications are monitoring of local drug delivery using thermosensitive liposomes, and confirmation of reaching the liposomes' threshold temperature during thermal therapy. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Field map estimation with a region growing scheme for iterative 3‐point water‐fat decomposition
Authors: Yu Huanzhou , Reeder Scott B. , Shimakawa Ann , Brittain Jean H. , Pelc Norbert J.
Published: September 2005

Robust fat suppression techniques are required for many clinical applications. Multi‐echo water‐fat separation methods are relatively insensitive to B0 field inhomogeneity compared to the fat saturation method. Estimation of this field inhomogeneity, or field map, is an essential and important step, which is well known to have ambiguity. For an iterative water‐fat decomposition method recently proposed, ambiguities still exist, but are more complex in nature. They were studied by analytical expressions and simulations. To avoid convergence to incorrect field map solutions, an initial guess closer to the true field map is necessary. This can be achieved using a region growing process, which correlates the estimation among neighboring pixels. Further improvement in stability is achieved using a low‐resolution reconstruction to guide the selection of the starting pixels for the region growing. The proposed method was implemented and shown to significantly improve the algorithm's immunity to field inhomogeneity. Magn Reson Med, 2005. © 2005 Wiley‐Liss, Inc.
Numerical simulations of simple shear with non‐coaxial soil models
Authors: Yang Yunming , Yu H. S.
Published: September 2005

This paper investigates the effects of a non‐coaxial model on simulated stress–strain behaviour of granular materials subject to simple shearing under various initial conditions. In most cases, a significant difference of predictions between coaxial and non‐coaxial modelling is found during the early stage in shearing. With the increase in shearing, non‐coaxial simulations approach and tend to coincide with coaxial simulations. It is also found that the roles of non‐coaxial modelling in simulating simple shear behaviour are considerably influenced by hardening rules, flow rules, initial static lateral pressure coefficients. In some cases, the non‐coaxial modelling gives a similar simulation as the coaxial modelling. In other cases, the non‐coaxial modelling decreases the hardening response or softening response of materials, compared with the coaxial modelling. Under certain conditions, the predicted peak strength of materials with non‐coaxial modelling is larger than that for coaxial modelling. Some of these observations can be attributed to the amount of principal stress rotation in various cases analysed. Others can be attributed to the difference between the directions of the non‐coaxial plastic flow and those for coaxial plastic flow. Copyright © 2005 John Wiley & Sons, Ltd.
Cross‐linking emulsion copolymerization of butyl acrylate with diallyl maleate
Authors: Bouvier‐Fontes Ludivine , Pirri Rosangela , Asua José M. , Leiza Jose R.
Published: September 2005

The emulsion copolymerization of butyl acrylate (BA) with a trifunctional cross‐linker, diallyl maleate (DAM), was investigated. The effect of the monomer feeding time and the amount of cross‐linker on the microstructural properties (branching, cross‐linking, gel formation, and sol MWD) of the seeded semicontinuous emulsion copolymerization of BA with DAM was investigated. It was found that the gel content was not significantly affected by increasing feeding time, but the level of quaternary carbons (an indication of the branching density) increased. On the other hand, increasing the amount of DAM in the feed composition caused gel content, level of quaternary carbons, and the cross‐linking density to increase. Interestingly, the level of quaternary carbons and the cross‐linking density sharply increased during the cooking period. The molecular weight of the sol decreased as DAM increased in the feed. In addition, the effect of process type, batch versus semibatch, was also considered and important differences in the level of quaternary carbons, cross‐linking, and gel content were found. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4684–4694, 2005
Hyperbranched fluorocopolymers by atom transfer radical self‐condensing vinyl copolymerization
Authors: Cheng Chong , Wooley Karen L. , Khoshdel Ezat
Published: September 2005

Hyperbranched fluorocopolymers were synthesized by the atom transfer radical self‐condensing vinyl copolymerization (ATR–SCVCP) of an inimer, either p‐chloromethylstyrene (CMS) or p‐bromomethylstyrene (BMS), with 2,3,4,5,6‐pentafluorostyrene (PFS), with 2,2′‐bipyridine together with CuCl or CuBr as the ligand/catalyst system. The reaction conditions were studied to provide for control over the copolymer compositions, molecular weights, degrees of branching, and properties, as characterized by 1H, 13C, and 19F NMR spectroscopy, gel permeation chromatography, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and solubility tests. Copolymers having number‐average molecular weights from 2.9 to 260 kDa and polydispersities (weight‐average molecular weight/number‐average molecular weight) from 1.8 to 4.8 were obtained. The molar fractions of PFS units increased with increases in the feed ratio of PFS to the inimer. The degrees of branching were typically about 30% with the feed of 1.0 or 2.0 equiv of PFS with respect to the inimer, although slight variations could be achieved through the variation of the inimer composition. Under similar reaction conditions with CuCl as the catalyst, ATR–SCVCP of BMS with PFS led to higher degrees of branching than ATR–SCVCP of CMS with PFS. Solubility tests indicated that the polymers prepared under conditions that avoided extensive biradical coupling were soluble in a broad range of organic solvents. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4754–4770, 2005
Tacticity of poly‐α‐olefins from poly‐1‐hexene to poly‐1‐octadecene
Authors: Galland Griselda Barrera , Da Silva Luciano Forgiarini , Nicolini Adriana
Published: September 2005

A systematic study of the influence of the α‐olefin size, the catalyst stereospecificity and the reaction temperature was done on the catalytic activity and tacticity of poly‐α‐olefins from 1‐hexene to 1‐octadecene. The metallocenes used were rac‐Et[Ind2]ZrCl2 (1) and Me2C[Cp(9‐Flu)]ZrCl2 (2) to obtain isotactic and syndiotactic polyolefins. Some catalysts giving atactic polymers were also used in order to study all the possible 13C NMR pentades. Catalytic activities increased and isotacticity and syndiotacticity decreased with temperature, but no real trend was found with the α‐olefin size. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4744–4753, 2005
Control of thermal cross‐linking reactions and the degree of crystallinity of syndiotactic 1,2‐polybutadiene
Authors: Cai Jiali , Yu Qing , Zhang Xuequan , Lin Jiaping , Jiang Liansheng
Published: September 2005

Thermal stability, crystallization, morphological development, subsequently melting, and crystallinity control of a syndiotactic 1,2‐polybutadiene sample were carefully carried out by thermogravimetry (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), temperature‐modulated differential scanning calorimetry (TMDSC), and wide‐angle X‐ray diffraction (WAXD), respectively. The experiments indicate that thermal cross‐linking reaction rates under nitrogen protection and in air are different for this polymer at temperature above 155 °C. Under nitrogen protection, the thermal cross‐linking reaction rate is delayed and the mechanism of melt crystallization obtained from the DSC results is in good accordance with that from POM observation. TMDSC results indicate that melting–recrystallization–melting model is more proper to explain the double melting events of this sample. At the same time, the evolution of the degree of crystallinity as the function of the time was investigated by WAXD profiles for the samples firstly crystallized at 145 °C for 1 h and then kept at 163 °C mediated between the temperatures of the double peaks. It shows that as prolonging the annealing time at 163 °C thermal cross‐linking reactions possibly occur, leading to gradual reduction of the apparent crystallite sizes, evaluated by Scherrer equation and the degree of crystallinity. The changing sequence of the relative intensity of the stronger four diffraction peaks with time due to thermal cross‐linking reactions is (111)/(201) > (210) > (010) > (200)/(110). © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2885–2897, 2005
Multiscale dewetting of triblock copolymer thin film induced by solvent vapor
Authors: Zhu Jintao , Zhao Junchai , Liao Yonggui , Jiang Wei
Published: September 2005

Multiscale dewetting of poly(styrene‐b‐ethylene/butylenes‐b‐styrene) (SEBS) triblock copolymer thin films induced by volatile solvent vapor treatment were observed in this study. Film rupture occurred at first and produced macroscopic holes. Near‐regular droplets (which represented a compromise between complete disorder and perfect order) could be formed at the last stage. The mechanism of solvent‐driven dewetting was discussed by comparing with that of thermal‐induced dewetting. Similar to thermal‐induced dewetting, the block copolymer thin films initially break up through the nucleation of holes that perforated the films. The rapid growing holes became unstable and formed nonequilibrium fingering patterns. The films exhibit autophobic or autodewetting phenomena. The velocity of the holes growth was nearly a constant (3.3 μm/min). The stages of the dewetting were quite similar to that found for homopolymer and block copolymer thin films dewetting on solid or liquid substrates under thermal treatment. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2874–2884, 2005
New synthesis of cis 5‐tert‐butyl‐L‐proline via cuprate. Evaluation as a cis proline mimetic in a biological active octapeptide
Authors: Aubry Carine , Oulyadi Hassan , Dutheuil Guillaume , Leprince Jerome , Vaudry Hubert , Pannecoucke Xavier , Quirion Jean‐Charles
Published: September 2005

cis 5‐tert‐butyl‐L‐proline (Cbp) was prepared rapidly and efficiently by the addition of low‐valent tert‐butyl cuprate to an aminal derived from proline. [Cbp2, D‐Leu5]‐OP was then synthesized, showing a predominant cis peptide bond conformation, as confirmed by NMR. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd.
Current strategies for the development of peptide‐based anti‐cancer therapeutics
Authors: Borghouts Corina , Kunz Christian , Groner Bernd
Published: September 2005

The completion of the human genome sequence and the development of new techniques, which allow the visualisation of comprehensive gene expression patterns, has led to the identification of a large number of gene products differentially expressed in tumours and corresponding normal tissues. The task at hand is the sorting of these genes into correlative and causative ones. Correlative genes are merely changed as a consequence of transformation and have no decisive effects upon transformation. In contrast, causative genes play a direct role in the process of cellular transformation and the maintenance of the transformed state, which can be exploited for therapeutic purposes. Oncogenes and tumour suppressor genes are prime targets for the development of new inhibitors and gene therapeutic strategies. However, many target oncogene products do not exhibit enzymatic activity that can be inhibited by conventional small molecular weight compounds. They exert their functions through regulated protein–protein or protein–DNA interactions and might require other compounds for efficient interference with such functions. Peptides are emerging as a novel class of drugs for cancer therapy, which could fulfil these tasks. Peptide therapy aims at the specific inhibition of inappropriately activated oncogenes. This review will focus on the selection procedures, which can be employed to identify useful peptides for the treatment of cancer. Before peptide‐based therapeutics can become useful, it will be necessary to increase their stability by modifications or the use of scaffolds. Additionally, various delivery methods including liposomes and particularly the use of protein transduction domains (PTDs) have to be explored. These strategies will yield highly specific and more effective peptides and improve the potential of peptide‐based anti‐cancer therapeutics. Copyright © 2005 European Peptide Society and John Wiley & Sons, Ltd.
Comparison of Bi2Sr2CaCu2O8 surfaces cleaved at low temperature and at room temperature from secondary ion mass spectrometry and work function measurements
Authors: Saito S. , Uhara Y. , Kogushi Y. , Yoshida H. , Isono S. , Yamasaki H. , Murakami H. , Sutou T. , Soumura T. , Kioka T.
Published: September 2005

Secondary ion mass spectrometry (SIMS) and work function measurements were made to examine the surface composition difference between Bi2Sr2CaCu2O8 surfaces that were cleaved at low temperature and at room temperature. SIMS measurements of the surfaces cleaved at room temperature indicated that the intensity of secondary ions Ca+, Sr+, and Cu+ increases and the intensity of O– decreases with time. More‐ over, the work function increased with time. On the other hand, SIMS of the surfaces cleaved at low temperature indicated comparatively much smaller changes in intensity of secondary ion spectra and work function. These findings are discussed in terms of the decrease in surface oxygen content, and the effectiveness of the cleavage at low temperature is clarified. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Electron radiation damage in Cu(In,Ga)Se2 analysed in‐situ by cathodoluminescence in a transmission electron microscope
Authors: Scheel Hanne , Frank Gerhard , Strunk Horst P.
Published: September 2005

This contribution describes the first results of a completely new approach to study in‐situ the radiation damage properties of semiconductors, particularly of Cu(In,Ga)Se2 thin solar films by cathodoluminescence in TEM. This method proved to be sensitive to the initial damage processes that occur on an atomic level and are thus inaccessible otherwise in the microscope. The in‐situ character of the investigation permits to analyze also the defect formation kinetics directly. We discuss the development of the cathodoluminescence spectra in dependence of electron dose and accelerating voltage for Cu(In1–xGax)Se2 with [Ga]/([Ga] + [In]) ratio x ranging from x = 0 to x = 1. The obtained results indicate that the films with equal Ga and In concentration are the least radiation sensitive ones. The voltage dependence of the damage rate indicates that the damage arises essentially due to displacement by electron knock‐on (in the voltage range 150–300 kV). The defect formation kinetics can be interpreted with a first model which is supported by annealing experiments. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A data‐driven approach for reduction of molecular simulations
Authors: Oguz Cihan , Gallivan Martha A.
Published: September 2005

Stochastic simulations based on non‐equilibrium statistical mechanics describe the interactions among many discrete atoms or molecules, and thus describe the dynamics of materials processing in applications ranging from inorganic crystalline films to amorphous polymer melts. In general, non‐equilibrium thermodynamics does not directly yield a closed, low‐dimensional dynamic equation, although such a model would be desirable to analyse the dynamics and to optimize and control the process. A practical approach is described here in which targeted simulations are combined with systematic tools to elucidate the dynamics. Copyright © 2005 John Wiley & Sons, Ltd.
Process aspects of electroless deposition for nickel–zinc–phosphorous alloys
Authors: Abdel Hamid Z. , Ghanem W. A. , Abo El Enin S. A.
Published: September 2005

Electroless deposition of Ni–Zn–P thin film was considered as a barrier film on a galvanic Zn or Ni–Zn sacrificial layer in a multicomponent corrosion protective coating on steel. The incorporation of zinc on the chemical composition of electroless Ni–Zn–P coating was studied. The effect of operating conditions such as temperature, pH value and concentration of zinc sulphate was investigated. Some physical characteristics such as morphology, structure, corrosion properties of Ni–Zn–P coatings were assessed in parallel with those of Ni–P. Inclusion of Zn to Ni–P is accompanied by the transformation of the coating structure from amorphous to crystalline. The effect of adding nonionic surfactant to the plating solution on the composition and surface morphologies was also investigated. The results indicate that nonionic surfactant has no effect on the Zn % in the deposit layer, but it affects the surface morphology and improves the corrosion resistance of Ni–Zn–P layers. Copyright © 2005 John Wiley & Sons, Ltd.
Development of B‐doped Si multiple delta‐layer reference materials for SIMS profiling
Authors: Kim K. J. , Moon D. W. , Chi P. , Simons D.
Published: September 2005

B‐doped Si multiple delta‐layers (MDL) were developed as certified reference materials (CRM) for secondary ion mass spectrometry (SIMS) depth profiling analysis. Two CRMs with different delta‐layer spacing were grown by ion beam sputter deposition (IBSD). The nominal spacing of the MDL for shallow junction analysis is 10 nm and that for high energy SIMS is 50 nm. The total thickness of the film was certified by high resolution transmission electron microscopy (HR‐TEM). The B‐doped Si MDLs can be used to evaluate SIMS depth resolution and to calibrate the depth scale. A consistency check of the calibration of stylus profilometers for measurement of sputter depth is another possible application. The crater depths measured by a stylus profilometer showed a good linear relationship with the thickness measured from SIMS profiling using the calibrated film thickness for depth scale calibration. The sputtering rate of the amorphous Si thin film grown by sputter deposition was found to be the same as that of the crystalline Si substrate, which means that the sputtering rate measured with these CRMs can be applied to a real analysis of crystalline Si. Copyright © 2005 John Wiley & Sons, Ltd.
Quantitative AES, XPS and RBS determination of intergranular bismuth coverage in copper bicrystals at 500 °C
Authors: Laporte V. , Berger P. , Wolski K.
Published: September 2005

We report on a comparative measurement of intergranular bismuth coverage on a copper substrate using Auger electron spectroscopy (AES), x‐ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). Bicrystalline copper samples were put in presence of bismuth vapour at 500 °C (consequently embrittled by the grain‐boundary penetration of Bi atoms), water‐quenched and subsequently fractured at room temperature. Each fracture surface was analysed by AES, XPS and RBS with the help of quantitative procedures developed for each of the three techniques. All possible sources of discrepancy were carefully examined. The combined quantitative approaches have led to excellent agreement. Such a good agreement constitutes a necessary condition to begin a critical discussion on the mechanisms potentially involved in the liquid metal embrittlement (LME) phenomenon. Copyright © 2005 John Wiley & Sons, Ltd.