bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrochemical sensors for biofilm and biocorrosion
Authors: Tribollet B.
Published: July 2003

The presence of biofilm modifies the electrochemical properties of the interface and the mass transport near the interface. Two biofilm effects are damageable: the reduction of heat and/or mass transfer and the biocorrosion or microbiologically influenced corrosion (MIC).

Two kinds of electrochemical sensors were developed: the first kind for the biofilm detection and the second one to evaluate the MIC risk. The biofilm detection is obtained by considering either the potential modification of the interface or the mass transport modification. The mass transport modification is analysed by considering the limiting diffusion current measured on a gold electrode where the biofilm development occurs.

The MIC risk is evaluated with a sensor composed of two concentric electrodes in the material under investigation (e.g. carbon steel): a small disk electrode in the centre and a large ring. In a first step, a pit is artificially initiated by applying a current through these electrodes. In a second step, the risk factors of MIC are investigated by analysing the free coupling current circulating between these two short‐circuited electrodes.
Biofouling on austenitic stainless steels in spent nuclear fuel pools
Authors: Sarró M. I. , Moreno D. A. , Chicote E. , Lorenzo P. I. , García A. M. , Montero F.
Published: July 2003

The objective of this study was to investigate the biofilm formation on three different types of austenitic stainless steel (UNS S30400, S30466 and S31600) submerged in a spent nuclear fuel pool. The presence of microorganisms in coupons was characterised using standard culture microbiological methods, microscopic techniques (epifluorescence microscopy and scanning electron microscopy), and molecular biology techniques (denaturing gradient gel electrophoresis and sequencing fragments of 16S rDNA). The microscopy techniques showed signs of colonisation of stainless steels in spite of these extreme conditions. Based on sequencing of cultured microorganisms, different bacteria belonging to α, β, γ‐Proteobacteria, Bacilli, and Actinobacteria classes have been identified. The biofilm radioactivity was measured using gamma‐ray spectrometry and, according to the data gathered, the radionuclides present in the water pool were entrapped in the biofilm increasing the amount of radiation at the surface of the different materials.
Chain Connectivity and Conformational Variability of Polymers: Clues to an Adequate Thermodynamic Description of Their Solutions, 1
Authors: Bercea Maria , Cazacu Maria , Wolf Bernhard A.
Published: July 2003

This is the first of two parts investigating the Flory‐Huggins interaction parameter, χ, as a function of composition and chain length. Part 1 encompasses experimental and theoretical work. The former comprises the synthesis of poly(dimethylsiloxane)s with different molar mass and the measurements of their second osmotic virial coefficients, A2, in solvents of diverse quality as a function of M via light scattering and osmotic pressures. The theoretical analysis is performed by subdividing the dilution process into two clearly separable steps. It yields the following expression for χo, the χ value in range of pair interaction: χo = α − ζ λ. The parameter α measures the effect of contact formation between solvent molecules and polymer segments at fixed chain conformation, whereas the parameter ζ quantifies the contributions of the conformational changes taking place in response to dilution; ζ becomes zero for theta conditions. The influences of M are exclusively contained in the parameter λ The new relation is capable of describing hitherto incomprehensible experimental findings, like a diminution of χo with rising M. The evaluation of experimental information for different systems according to the established equation displays the existence of a linear interrelation between ζ and α. Part 2 of this investigation presents the generalization of the present approach to solutions of arbitrary composition and discusses the physical meaning of the parameters in more detail.

Conformational response, ζ, as a function of α, the interaction parameter for fixed conformation.

magnified image

Conformational response, ζ, as a function of α, the interaction parameter for fixed conformation.
Preparation of Inclusion Complexes between Amylose and Ester‐Containing Polymers by Means of Vine‐Twining Polymerization
Authors: Kadokawa Jun‐ichi , Nakaya Atsushi , Kaneko Yoshiro , Tagaya Hideyuki
Published: July 2003

This paper reports the preparation of inclusion complexes of amylose with synthetic polymers by means of enzymatic polymerization of α‐D‐glucose 1‐phosphate monomer (Glc‐1‐P). The synthetic polymers, employed as the guests, are poly(ε‐caprolactone), poly(δ‐valerolactone), and poly(ester‐ether), containing ester groups in the main chains. The formation of the inclusion complexes was carried out by the enzymatic polymerization of Glc‐1‐P catalyzed by phosphorylase in the presence of the guest polymers.

magnified image
Homologous Series of 2,5‐Diheptyloxy‐p‐Phenylene Vinylene (DHepO‐PV) Oligomers with Vinyl or 1‐Butenyl End Groups: Synthesis, Isolation, and Microstructure
Authors: Peetz Ralf , Strachota Adam , Thorn‐Csányi Emma
Published: July 2003

In this paper we report the synthesis, isolation, and microstructure characterization of 2,5‐diheptyloxy‐p‐phenylene vinylene (PV) oligomers. Two homologous series with their chain length dependent NMR and IR spectra are presented and discussed in detail. To obtain the products, first, oligomer mixtures were synthesized by acyclic diene metathesis (ADMET) polycondensation of 2,5‐diheptyloxy‐1,4‐divinylbenzene. The Schrock‐type alkylidene complex Mo(NPhMe2)(CHCMe2Ph) [OCMe(CF3)2]2 served as a catalyst. The polycondensation mixture was used either for the isolation of the oligomers with vinyl end groups or as a feed component for a cross metathesis reaction with 3‐hexene yielding thermally stable derivatives (investigated up to 250 °C) with 1‐butenyl end groups. From the oligomer mixtures, single oligomers up to the octamer (n = 2 … 8) were isolated by means of column chromatography. The monodispersity was determined by means of MALDI‐TOF mass spectrometry. The colors within the homologous series span widely from colorless (monomer) to yellow (trimer) to red (hexamer and upwards). The chain‐length dependence of the NMR spectra is resolved in detail. The presented data could also be used for valuable reference compounds for analogue polymer systems.

Synthesis of diheptyloxy‐PV oligomers by olefin metathesis.

magnified image

Synthesis of diheptyloxy‐PV oligomers by olefin metathesis.
Complexation of Bisphenol A with Calix[6]arene‐Polymer Conjugates
Authors: Kitano Hiromi , Hirabayashi Tadashi , Ide Makoto , Kyogoku Mayumi
Published: July 2003

Sodium calix[6]arenehexasulfonic acid (SCX6) was introduced into polymer molecules by the cross‐linking of SCX6 with epichlorohydrin (PolySCX6) or by the covalent binding of carboxymethylated SCX6 to an amino group‐carrying vinyl polymer (Poly(SCX6HMA‐co‐AAm)). The complexation of bisphenol A (BPA) with the SCX6 group in the polymers was examined fluorimetrically using acridine red (AR) as a probe. From the inhibitory effect of BPA on the complexation of AR with the SCX6 group in the polymers, the association constant (Kassoc) of BPA with the SCX6 group was evaluated and the value for BPA with the SCX6 group in Poly(SCX6HMA‐co‐AAm) was much larger than that with the non‐conjugated SCX6, probably because of the support of hydrophobic interactions between the guest and the hydrocarbon moieties in the polymer (polymer main chain and hexamethylene groups introduced for the conjugation of SCX6). The Kassoc value for bisphenol B (BPB) with a non‐conjugated SCX6 was larger than those for bisphenol A and bisphenol F, because of the higher hydrophobicity of BPB among the bisphenols examined. Thermodynamic parameters indicated that the inclusion of BPA into the cavity of sodium propyloxycalix[6]arenehexasulfonic acid (SPCX6) was enthalpy driven, and the entropy change was largely negative (−92 J · mol−1 · K−1). This is probably because of a tight fit of guest molecules in the SPCX6 cavity, resulting in the loss of freedom of both the SPCX6 and the guest molecules. The entropy change for the complexation of BPA with the SCX6 group in the polymer was less negative, probably because of a partial release of water molecules around the SCX6 group upon the complexation. The effect of the structure of guest and host molecules on the complexation was also examined.

Chemical structure of various calix[6]arenes: R = H, sodium calix[6]arenehexasulfonic acid; R = C3H7, sodium propyloxycalix[6]arenehexasulfonic acid; R = C4H9, sodium butyloxycalix[6]arenehexasulfonic acid; R = C6H13, sodium hexyloxycalix[6]arenehexasulfonic acid.

magnified image

Chemical structure of various calix[6]arenes: R = H, sodium calix[6]arenehexasulfonic acid; R = C3H7, sodium propyloxycalix[6]arenehexasulfonic acid; R = C4H9, sodium butyloxycalix[6]arenehexasulfonic acid; R = C6H13, sodium hexyloxycalix[6]arenehexasulfonic acid.
Exponential stability for a mirror–symmetric three phase boundary motion by surface diffusion
Authors: Escher Joachim , Garcke Harald , Ito Kazuo
Published: July 2003

We apply the principle of linearized stability to prove that a stationary state is exponentially stable under a mirror–symmetric three phase boundary motion by surface diffusion. A main difficulty in the application of the linearized stability principle arises from the inhomogeneous nonlinear boundary conditions.
An elliptic boundary problem in a half–space
Authors: Faierman Melvin , Möller Manfred
Published: July 2003

The spectral theory for general non–selfadjoint elliptic boundary problems involving a discontinuous weight function has been well developed under certain restrictions concerning the weight function. In the course of extending the results so far established to a more general weight function, there arises the problem of establishing, in an Lp Sobolev space setting, the existence of and a priori estimates for solutions for a boundary problem for the half–space ℝn+ involving a weight function which vanishes at the boundary xn = 0. In this paper we resolve this problem.
The theory of trying and goal‐directed behavior: The effect of moving up the hierarchy of goals
Authors: Bay Darlene , Daniel Harold
Published: July 2003

This article extends the literature regarding goal‐directed behavior as modeled by the theory of trying by incorporating the concept of the hierarchy of goals. Individuals develop “programs” intended to implement their principles and life goals. Within these programs, goals are arranged in a hierarchical order depending on how close they are to the overall goal of the program. Lower‐level goals are intended to set the stage for the achievement of higher‐level goals. Although most tests of the theory of trying have been implemented with the use of fairly low‐level goals (losing weight or learning a new piece of software), in this article, the model is applied in the context of a higher‐level goal: achieving a college education. There are important differences in the results compared to those in prior tests of the theory of trying. Most importantly, attitude toward failure is highly significant and attitude toward process is not. © 2003 Wiley Periodicals, Inc.
Musical tempo and waiting perceptions
Authors: Oakes Steve
Published: July 2003

Digital technology was used to isolate musical tempo from other musical variables, and experimental results in an undergraduate registration queue context confirmed the existence of a significant, positive relationship between background musical tempo variation and temporal perception (perceived minus actual wait duration). Findings also revealed how slow‐tempo music produced significantly enhanced affective response (satisfaction, positive disconfirmation of expectations, and relaxation) compared to fast‐tempo music. © 2003 Wiley Periodicals, Inc.
Face consciousness and risk aversion: Do they affect consumer decision‐making?
Authors: Bao Yeqing , Zhou Kevin Zheng , Su Chenting
Published: July 2003

This article explores the effects of two cultural dimensions, face consciousness and risk aversion, on consumers' decision‐making styles. Data from China and the United States show that consumers in the United States differ from their counterparts in China in decision‐making styles. Face consciousness and risk aversion appear to contribute to such divergence. Implications for future research are discussed. © 2003 Wiley Periodicals, Inc.
New Millable Polyurethane/Organoclay Nanocomposite: Preparation, Characterization and Properties
Authors: Mishra Joy K. , Kim Il , Ha Chang‐Sik
Published: July 2003

The preparation, characterization and properties of novel millable polyurethane/organoclay nanocomposites are reported. Clay treated with methyl tallow bis(2‐hydroxyethyl) quaternary ammonium chloride was used as an organoclay for nanocomposite preparation. X‐ray diffraction indicated the intercalation of polymer chains inside the interlayer spacings of the clay. Dynamic mechanical analysis showed a significant increase in storage modulus, and tensile strength increases with increased organoclay loading.

X‐ray diffraction patterns of millable polyurethane/organoclay nanocomposites.

magnified image

X‐ray diffraction patterns of millable polyurethane/organoclay nanocomposites.
η3‐Benzyl‐Nickel‐Diimine Complex: Synthesis and Catalytic Properties in Ethylene Polymerization
Authors: Fassina Viviane , Ramminger Carolina , Seferin Marcus , Mauler Raquel S. , de Souza Roberto F. , Monteiro Adriano L.
Published: July 2003

The oxidative addition of benzyl chloride to Ni(cod)2 in the presence of 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine followed by chloride abstraction affords [(η3‐CH2C6H5)Ni(α‐diimine)][PF6] (α‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) in 70% yield. The complex is active in ethylene polymerization in the presence of methylaluminoxane and under mild reaction conditions. The polyethylenes obtained are highly branched, have very low densities, do not show Tm or measurable crystallinity and have molecular weights ranging from 80 × 103 to 290 × 103 g · mol−1.

magnified image
Inkjet Printing of Polymer Micro‐Arrays and Libraries: Instrumentation, Requirements, and Perspectives
Authors: de Gans Berend‐Jan , Schubert Ulrich S.
Published: July 2003

This article reviews commercially available instrumentation for inkjet printing of polymer micro‐arrays for combinatorial materials research, and requirements thereof. These include a print head positioning accuracy better than 10 μm and a minimum drop volume of 100 pL. Commercially available instruments that fulfill these requirements can be divided into two categories, depending on whether they receive ink from a reservoir (dispense mode) or through fluid aspiration (pipette mode). Instruments belonging to the first category are restricted to the preparation of polymer blend micro‐arrays. These consist of a few substances mixed in various ratios. The other instruments can be used for the preparation of both micro‐arrays of large numbers of different pure polymer compounds and polymer blend micro‐arrays. Moreover, ways to mix compounds are discussed.

magnified image
Polysilsesquioxane Nanosheets Synthesized in Confined Environment
Authors: Ma Jun , Su Wei , Zhang Yong‐Jun , Hu Teng‐Jiao , Liu Hai‐Yun , Li Bai‐Yu , Shi Liang‐He , Xu Jian , Mai Yiu‐Wing
Published: July 2003

Polysilsesquioxane nanosheets with a thickness of four nanometers and lateral dimensions of several hundreds of nanometers were synthesized by polymerization of a trifunctional monomer in the layer space of montmorillonite as the confined environment.

AFM image of a polymethylsilsesquioxane nanosheet.

magnified image

AFM image of a polymethylsilsesquioxane nanosheet.
Mild Synthesis of Amino‐Poly(ethylene glycol)s. Application to Steric Stabilization of Clays
Authors: Mongondry Philippe , Bonnans‐Plaisance Chantal , Jean Martine , Tassin Jean François
Published: July 2003

The hydroxyl end groups of poly(ethylene glycol) (PEG) have been transformed easily and quantitatively into amino groups via the Mitsunobu reaction. Phthalimide was alkylated with PEGs and the hydrazinolysis of the resulting phthalimido‐PEGs gave the amino compounds in high yields. Quaternization of the amino groups leads to hydrophilic polymer chains bearing a positive charge on one or two ends, depending on the chosen PEG. Such products can be used to protect sterically, negatively charged particles such as clays.

magnified image
Thermal Breakdown by the Retro Diels–Alder Reaction of Crosslinking in Poly[styrene‐co‐(furfuryl methacrylate)]
Authors: Goiti Eunate , Huglin Malcolm B. , Rego José M.
Published: July 2003

Crosslinked poly[styrene‐co‐(furfuryl methacrylate)] has been produced by the Diels–Alder (D‐A) reaction between the furan ring (within the copolymer) and the maleimide (MI) group (within the other reactant, bismaleimide). The retro D‐A reaction was followed by the analysis of MI groups produced at different times at five constant temperatures. The process was shown to follow first‐order kinetics, and the rate constants were determined. The findings are believed to be the first to provide quantitative information on the breakdown by a retro D‐A reaction of crosslinking in a polymer system. The D‐A and retro D‐A processes constitute a thermoreversible gelling system with respect to the formation and breakdown of crosslinks.

First‐order rate plot for the retro D‐A breakdown of crosslinked poly(ST‐co‐FM).

magnified image

First‐order rate plot for the retro D‐A breakdown of crosslinked poly(ST‐co‐FM).
Soluble Polyimides from a New Dianhydride: 5′‐tert‐Butyl‐m‐terphenyl‐3,4,3″,4″‐tetracarboxylic Acid Dianhydride
Authors: García Carolina , Lozano Angel E. , de la Campa José G. , de Abajo Javier
Published: July 2003

A novel tert‐butyl‐containing dianhydride was prepared from readily available reagents. It was reacted with various aromatic diamines to prepare a set of polyimides containing tert‐butyl pendent groups. The resulting polyimides exhibit high molecular weights (high inherent viscosity), and a combination of desirable properties, such as good solubility in aprotic amide solvents and cresols, high glass transition temperatures (up to 320 °C), high thermal resistance, film‐forming capability and good mechanical properties.

magnified image
Well‐posedness and asymptotic behaviour of a non‐dissipative beam equation with a quotient space method
Authors: O'Dowd G.
Published: July 2003

A beam equation model is studied, for which no suitable dissipative norm can be associated but only a semi‐norm, vanishing on some subspace. Considering a quotient by that subspace creates dissipativity which guarantees well posedness of this problem. Asymptotic behaviour is also obtained by using the quotient. The linear problem, involving high‐order multiplier is studied and then the non‐linear problem, thanks to the artificial problem method. Copyright © 2003 John Wiley & Sons, Ltd.
Blow‐up estimates for a quasi‐linear reaction–diffusion system
Authors: Zuodong Yang , Qishao Lu
Published: July 2003

In this paper, some sufficient conditions under which the quasilinear elliptic system ‐div(∣∇u∣p‐2∇u) = uv, ‐div(∣∇u∣q‐2∇u) = uv in ℝN(N≥3) has no radially symmetric positive solution is derived. Then by using this non‐existence result, blow‐up estimates for a class of quasilinear reaction–diffusion systems ut = div (∣∇u∣p‐2∇u)+uv,vt = div(∣∇v∣q‐2∇v) +uv with the homogeneous Dirichlet boundary value conditions are obtained. Copyright © 2003 John Wiley & Sons, Ltd.
A time‐marching finite element method for an electromagnetic scattering problem
Authors: Van Tri , Wood Aihua
Published: July 2003

In this paper, Newmark time‐stepping scheme and edge elements are used to numerically solve the time‐dependent scattering problem in a three‐dimensional polyhedral cavity. Finite element methods based on the variational formulation derived in Van and Wood (Adv. Comput. Math., to appear) are considered. Existence and uniqueness of the discrete problem is proved by using Babuska–Brezzi theory. Finite element error estimate and stability of the Newmark scheme are also established. Copyright © 2003 John Wiley & Sons, Ltd.
Initial boundary value problem for a class of non‐linear strongly damped wave equations
Authors: Zhijian Yang
Published: July 2003

The paper studies the existence, asymptotic behaviour and stability of global solutions to the initial boundary value problem for a class of strongly damped non‐linear wave equations. By a H00.5ptk‐Galerkin approximation scheme, it proves that the above‐mentioned problem admits a unique classical solution depending continuously on initial data and decaying to zero as t→+∞as long as the non‐linear terms are sufficiently smooth; they, as well as their derivatives or partial derivatives, are of polynomial growth order and the initial energy is properly small. Copyright © 2003 John Wiley & Sons, Ltd.
Higher order non‐resonance for differential equations with singularities
Authors: Yan Ping , Zhang Meirong
Published: July 2003

In this paper we prove an existence result of positive periodic solutions to second order differential equations with certain strong repulsive singularities near the origin and with some semilinear growth near infinity. Different from the nonsingular case, the result in this paper shows that both of the periodic and the antiperiodic eigenvalues play the same role in such an existence result. Copyright © 2003 John Wiley & Sons, Ltd.
Abnormal spermatogenesis at low temperatures in the Japanese red‐bellied newt, Cynops pyrrhogaster: Possible biological significance of the cessation of spermatocytogenesis
Authors: Yazawa Takashi , Nakayama Yuki , Fujimoto Kenta , Matsuda Yoshiko , Abe Keisuke , Kitano Takeshi , Abé Shin‐Ichi , Yamamoto Takashi
Published: July 2003

In newt testis, spermatocytes never appear during winter, because secondary spermatogonia die by apoptosis just before meiosis. In the current study, we examined the effect of low temperatures on spermatogenesis. Incubation of newts at low temperatures (8, 12, 15°C) induced defects in spermatogenesis in a temperature‐dependent manner. At 8°C, multinucleated giant cells (MGCs) were observed in spermatocytes and spermatogenesis never proceeded beyond meiosis. Although spermatocytes completed meiotic divisions at 12°C, severe cell death was observed in the spermatids. At 15°C both normal and abnormal spermiogenesis were observed. Under these conditions, impaired meiotic synapsis/recombination and down‐regulation of the expression of the DMC1 protein, which play pivotal roles in meiotic pairing in eukaryotes, were also observed. Furthermore, to examine the quality of the sperm produced at low temperature for supporting development, artificial insemination was performed. The eggs inseminated with spermatozoa derived from newts kept at 15°C demonstrated a restricted developmental capacity, even though these spermatozoa had an equal capacity for carrying out fertilization to those kept at 22°C. These results suggest that meiosis at low temperatures cause the production of abnormal spermatozoa. Conservation and the significance of this phenomenon in poikilothermic vertebrates living in the temperate zones are also discussed. Mol. Reprod. Dev. 66: 60–66, 2003. © 2003 Wiley‐Liss, Inc.
Bioactive aldehydes from diatoms block the fertilization current in ascidian oocytes
Authors: Tosti Elisabetta , Romano Giovanna , Buttino Isabella , Cuomo Annunziata , Ianora Adrianna , Miralto Antonio
Published: July 2003

The effects of bioactive aldehydes from diatoms, unicellular algae at the base of the marine food web, were studied on fertilization and early development processes of the ascidian Ciona intestinalis. Using whole‐cell voltage clamp techniques, we show that 2‐trans‐4‐trans‐decadienal (DD) and 2‐trans‐4‐cis‐7‐cis‐decatrienal (DT) inhibited the fertilization current which is generated in oocytes upon interaction with the spermatozoon. This inhibition was dose‐dependent and was accompanied by inhibition of the voltage‐gated calcium current activity of the plasma membrane. DD and DT did not inhibit the subsequent contraction of the cortex. Moreover, DD specifically acted as a fertilization channel inhibitor since it did not affect the steady state conductance of the plasma membrane or gap junctional (GJ) communication within blastomeres of the embryo. On the other hand, DD did affect actin reorganization even though the mechanism of action on actin filaments differed from that of other actin blockers. Possibly this effect on actin reorganization was responsible for the subsequent teratogenic action on larval development. The effect of DD was reversible if oocytes were washed soon after fertilization indicating that DD may specifically target certain fertilization mechanisms. Thus, diatom reactive aldehydes such as DD may have a dual effect on reproductive processes, influencing primary fertilization events such as gating of fertilization channels and secondary processes such as actin reorganization which is responsible for the segregation of cell lineages. These findings add to a growing body of evidence on the antiproliferative effects of diatom‐derived aldehydes. Our results also report, for the first time, on the action of a fertilization channel blocker in marine invertebrates. Mol. Reprod. Dev. 66: 72–80, 2003. © 2003 Wiley‐Liss, Inc.
Comparison of developmental capacity for intra‐ and interspecies cloned cat (Felis catus) embryos
Authors: Wen Duan‐Cheng , Yang Cai‐Xia , Cheng Yong , Li Jin‐Song , Liu Zhong‐Hua , Sun Qing‐Yuan , Zhang Jia‐Xin , Lei Lei , Wu Yu‐Qi , Kou Zhao‐Hui , Chen Da‐Yuan
Published: July 2003

Interspecies nuclear transfer is an invaluable tool for studying nucleus–cytoplasm interactions; and at the same time, it provides a possible alternative to clone animals whose oocytes are difficult to obtain. In the present study, we investigated the possibility of cloning cat embryos using rabbit oocytes, and compared the developmental capacity; the timing of embryogenesis of the cat–rabbit cloned embryos with that of the cat–cat or the rabbit–rabbit cloned embryos. When cultured in M199, the rate of blastocyst formation of the cat–rabbit embryos was 6.9%, which was not significantly different than that of the cat–cat embryos (10.5%). However, the rate of blastocyst formation of rabbit–rabbit embryos (22.9%) was significantly greater than that of both the cat–rabbit and the cat–cat embryos (P < 0.05). The timing of the first three cleavages for the cat–rabbit embryos was similar to that of the rabbit–rabbit embryos, but significantly faster than that of the cat–cat embryos (P < 0.05), while the time to form blastocysts was similar to that of cat–cat embryos, but significantly slower than that of the rabbit–rabbit embryos (P < 0.05). Both M199 and SOF medium were evaluated for culturing cat–rabbit embryos; the rate of blastocyst formation in SOF (14.5%) was significantly greater than that in M199 (6.9%) (P < 0.05). These results demonstrate that: (1) the cat–rabbit embryos possess equal developmental capacity as cat–cat embryos; (2) the timing of the first three cleavages for the cat–rabbit embryos is recipient‐specific, while the time to form blastocysts is donor nucleus‐specific; and (3) SOF medium may be beneficial to overcome the morula‐to‐blastocyst block for cat–rabbit cloned embryos. Mol. Reprod. Dev. 66: 38–45, 2003. © 2003 Wiley‐Liss, Inc.
Rainbow trout follicular maturational competence acquisition is associated with an increased expression of follicle stimulating hormone receptor and insulin‐like growth factor 2 messenger RNAs
Authors: Bobe Julien , Maugars Gersende , Nguyen Thaovi , Rime Hélène , Jalabert Bernard
Published: July 2003

Post‐vitellogenic female rainbow trout (Oncorhynchus mykiss) were assayed in vitro for follicular maturational competence (FMC). Ovarian follicles were stimulated with a range of concentrations of partially purified gonadotropin. The efficient concentration for 50% germinal vesicle breakdown (GVBD) was calculated and used as an indicator of FMC. Before in vitro assay, ovarian tissue was sampled in order to quantify mRNA abundance of specific genes in the ovarian follicle by real‐time PCR. In addition, maturation‐inducing steroid (MIS, 17, 20beta‐dihydroxy‐4‐pregnen‐3‐one) and estradiol (E2) plasma levels were measured by radioimmunoassay. The mRNA expression of several genes such as luteinizing hormone receptor (LH‐r), follicular stimulating hormone receptor (FSH‐r), insulin‐like growth factor 1 (IGF1), insulin‐like growth factor 2 (IGF2), insulin‐like growth factor receptor 1a (IGF‐r1a), and 20beta‐hydroxysteroid dehydrogenase (20beta‐HSD) that are putatively expressed in the preovulatory ovary, was studied in females of varying FMC using real‐time PCR. FMC acquisition is characterized by an increase of MIS circulating levels and a concomitant drop of E2 levels. At the ovarian level, no significant variation of LH‐r, 20beta‐HSD, IGF1, and IGF‐r1a mRNA abundance was observed among females of varying FMC. In contrast, FSH‐r and IGF2 mRNA levels were significantly higher in females exhibiting high FMC. In addition, correlation analyses showed that IGF2 and FSH‐r, mRNA levels were positively correlated with FMC. These results indicate that FMC acquisition is associated with an increased expression of these gene products that may be useful markers of FMC. Mol. Reprod. Dev. 66: 46–53, 2003. © 2003 Wiley‐Liss, Inc.
Real‐time accelerated interactive MRI with adaptive TSENSE and UNFOLD
Authors: Guttman Michael A. , Kellman Peter , Dick Alexander J. , Lederman Robert J. , McVeigh Elliot R.
Published: July 2003

Reduced field‐of‐view (FOV) acceleration using time‐adaptive sensitivity encoding (TSENSE) or unaliasing by Fourier encoding the overlaps using the temporal dimension (UNFOLD) can improve the depiction of motion in real‐time MRI. However, increased computational resources are required to maintain a high frame rate and low latency in image reconstruction and display. A high‐performance software system has been implemented to perform TSENSE and UNFOLD reconstructions for real‐time MRI with interactive, on‐line display. Images were displayed in the scanner room to investigate image‐guided procedures. Examples are shown for normal volunteers and cardiac interventional experiments in animals using a steady‐state free precession (SSFP) sequence. In order to maintain adequate image quality for interventional procedures, the imaging rate was limited to seven frames per second after an acceleration factor of 2 with a voxel size of 1.8 × 3.5 × 8 mm. Initial experiences suggest that TSENSE and UNFOLD can each improve the compromise between spatial and temporal resolution in real‐time imaging, and can function well in interactive imaging. UNFOLD places no additional constraints on receiver coils, and is therefore more flexible than SENSE methods; however, the temporal image filtering can blur motion and reduce the effective acceleration. Methods are proposed to overcome the challenges presented by the use of TSENSE in interactive imaging. TSENSE may be temporarily disabled after changing the imaging plane to avoid transient artifacts as the sensitivity coefficients adapt. For imaging with a combination of surface and interventional coils, a hybrid reconstruction approach is proposed whereby UNFOLD is used for the interventional coils, and TSENSE with or without UNFOLD is used for the surface coils. Magn Reson Med 50:315–321, 2003. Published 2003 Wiley‐Liss, Inc.
On the artifact of a subvoxel susceptibility deviation in spoiled gradient‐echo imaging
Authors: Bos Clemens , Viergever Max A. , Bakker Chris J.G.
Published: July 2003

In MRI, susceptibility‐based negative contrast amplifies the effect of objects that are too small to be detected by water displacement or intrinsic contrast properties. In this work, a simplified description of the susceptibility artifact of a subvoxel object in spoiled gradient‐echo imaging is presented that focuses on the elimination of signal in its vicinity: the dephased‐volume. The size and position of the dephased‐volume are investigated using 3D time‐domain simulations and in vitro experiments in which scan parameters and object magnetic moment are systematically varied. Overall signal loss is found to be linearly related to a dephasing parameter that contains the susceptibility difference with tissue, object volume, and echo time (TE), and thus allows the magnetic moment of the object to be assessed. Gradient strength, in‐plane resolution, fractional echo, and slice orientation have limited influence. For the settings used, the center of mass of the artifact was always within 0.5 mm of the object's in‐plane position. Magn Reson Med 50:400–404, 2003. © 2003 Wiley‐Liss, Inc.
Intravascular extended sensitivity (IVES) MRI antennas
Authors: Susil Robert C. , Yeung Christopher J. , Atalar Ergin
Published: July 2003

The design and application of an intravascular extended sensitivity (IVES) MRI antenna is described. The device is a loopless antenna design that incorporates both an insulating, dielectric coating and a winding of the antenna whip into a helical shape. Because this antenna produces a broad region of high SNR and also allows for imaging near the tip of the device, it is useful for imaging long, luminal structures. To elucidate the design and function of this device, the effects of both insulation and antenna winding were characterized by theoretical and experimental studies. Insulation broadens the longitudinal region over which images can be collected (i.e., along the lumen of a vessel) by increasing the resonant pole length. Antenna winding, conversely, allows for imaging closer to the tip of the antenna by decreasing the resonant pole length. Over a longitudinal region of 20 cm, the IVES imaging antenna described here produces a system SNR of approximately 40,000/r (mL–1Hz1/2), where r is the radial distance from the antenna axis in centimeters. As opposed to microcoil antenna designs, these antennas do not require exact positioning and allow for imaging over broad tissue regions. While focusing on the design of the IVES antenna, this work also serves to enhance our overall understanding of the properties and behavior of the loopless antenna design. Magn Reson Med 50:383–390, 2003. © 2003 Wiley‐Liss, Inc.
Novel interleaved spiral imaging motion correction technique using orbital navigators
Authors: Moriguchi Hisamoto , Lewin Jonathan S. , Duerk Jeffrey L.
Published: July 2003

Although spiral imaging seldom produces apparent artifacts related to flow, it remains sensitive to rapid object motion. In this article, a new correction method is presented for rapid rigid body motion in interleaved spiral imaging. With this technique, an identical circular navigator k‐space trajectory is linked to each spiral trajectory. Data inconsistency due to both rotation and translation among spiral interleaves can be corrected by evaluating the magnitudes and phases of the data contained in the navigator “ring.” Further, it is difficult to create a frequency field map for off‐resonance correction when an object moves during a scan, because there is motion‐dependent misregistration between the two images acquired with different TEs. However, this difficulty can be overcome by combining the motion‐correction method with a recently proposed technique (off‐resonance correction using variable‐density spirals (ORC‐VDS)), thereby enabling both motion compensation and off‐resonance correction with no additional scanning. Magn Reson Med 50:423–428, 2003. © 2003 Wiley‐Liss, Inc.
Determinants of intramyocellular lipid concentrations in rat hindleg muscle
Authors: Neumann‐Haefelin Claudia , Kuhlmann Johanna , Belz Ulrich , Kalisch Juergen , Quint Manfred , Gerl Martin , Juretschke Hans‐Paul , Herling Andreas W.
Published: July 2003

The investigation of intramyocellular lipids (IMCLs) with proton MR spectroscopy (1H‐MRS) in humans has recently received increasing attention. IMCL levels correlate with insulin resistance and are affected by diet and exercise, making IMCL an interesting marker for metabolic investigations. In the present in vivo study, the feasibility of using 1H MRS for the detection of IMCL in rats is demonstrated, and the influence of various factors, such as age, gender, muscle type, and rat strain, on IMCL levels is systematically analyzed. In healthy Wistar and Sprague Dawley (SD) rats, the highest ratios of IMCL/tCr were found in young rats, and IMCL/tCr decreased with increasing age. In addition, IMCL concentration was clearly influenced by gender and muscle type. Insulin‐resistant, male, obese, Zucker diabetic fatty (ZDF) rats showed significantly higher IMCL levels than Wistar or SD rats. In conclusion, although IMCL levels are clearly influenced by insulin resistance, several other factors influence IMCL levels, such as age, gender, muscle type, and rat strain. Therefore, when using IMCL as a surrogate marker for insulin resistance, it is necessary to carefully compare results with age‐ and gender‐matched controls, and to use identical conditions. Magn Reson Med 50:242–248, 2003. © 2003 Wiley‐Liss, Inc.
Functional magnetic resonance imaging based on changes in vascular space occupancy
Authors: Lu Hanzhang , Golay Xavier , Pekar James J. , van Zijl Peter C.M.
Published: July 2003

During brain activation, local control of oxygen delivery is facilitated through microvascular dilatation and constriction. A new functional MRI (fMRI) methodology is reported that is sensitive to these microvascular adjustments. This contrast is accomplished by eliminating the blood signal in a manner that is independent of blood oxygenation and flow. As a consequence, changes in cerebral blood volume (CBV) can be assessed through changes in the remaining extravascular water signal (i.e., that of parenchymal tissue) without need for exogenous contrast agents or any other invasive procedures. The feasibility of this vascular space occupancy (VASO)‐dependent functional MRI (fMRI) approach is demonstrated for visual stimulation, breath‐hold (hypercapnia), and hyperventilation (hypocapnia). During visual stimulation and breath‐hold, the VASO signal shows an inverse correlation with the stimulus paradigm, consistent with local vasodilatation. This effect is reversed during hyperventilation. Comparison of the hemodynamic responses of VASO‐fMRI, cerebral blood flow (CBF)‐based fMRI, and blood oxygenation level‐dependent (BOLD) fMRI indicates both arteriolar and venular temporal characteristics in VASO. The effect of changes in water exchange rate and partial volume contamination with CSF were calculated to be negligible. At the commonly‐used fMRI resolution of 3.75 × 3.75 × 5 mm3, the contrast‐to‐noise‐ratio (CNR) of VASO‐fMRI was comparable to that of CBF‐based fMRI, but a factor of 3 lower than for BOLD‐fMRI. Arguments supporting a better gray matter localization for the VASO‐fMRI approach compared to BOLD are provided. Magn Reson Med 50:263–274, 2003. © 2003 Wiley‐Liss, Inc.
Using the vector potential in evaluating the likelihood of peripheral nerve stimulation due to switched magnetic field gradients
Authors: Bencsik Martin , Bowtell Richard , Bowley Roger M.
Published: July 2003

The time‐varying magnetic field gradients used in MRI can cause peripheral nerve stimulation (PNS) in human subjects, as a result of the electric fields induced in tissue. The local electric field, E, is given by E = −∂A/∂t − ∇ϕ where A, is the vector potential and ϕ is the scalar electric potential generated by charges accumulated at boundaries between regions of different conductivity. Difficulties in calculating ϕ have led some investigators to use −∂A/∂t alone as a predictor of the induced field. Here the spatial variation of −∂A/∂t and E is investigated for the case of a simple spherical conductor exposed to time‐varying gradients produced by two different gradient coils that generate identical internal magnetic fields, but very different vector potentials. The results indicate that the temporal derivative of A bears little relation to the induced electric field, and that consequently neglecting the effect of the scalar potential introduces significant errors in estimating the likelihood of PNS. Magn Reson Med 50:405–410, 2003. © 2003 Wiley‐Liss, Inc.
Real‐time MR temperature mapping of rabbit liver in vivo during thermal ablation
Authors: Weidensteiner Claudia , Quesson Bruno , Caire‐Gana Bénédicte , Kerioui Noureddine , Rullier Anne , Trillaud Hervé , Moonen Chrit T.W.
Published: July 2003

It has been shown that quantitative MRI thermometry using the proton resonance frequency (PRF) method can be used to noninvasively monitor the evolution of tissue temperature, and to guide minimally‐invasive tumor ablation based on local hyperthermia. Although hepatic tumors are among the main targets for thermal ablation, PRF‐based temperature MRI of the liver is difficult to perform because of motion artifacts, fat content, and low T. In this study the stability of real‐time thermometry was tested on a clinical 1.5 T scanner for rabbit liver in vivo. The fast segmented EPI principle was used together with respiratory gating to limit respiratory motion artifacts. Lipid signal suppression was achieved with a binomial excitation pulse. Saturation slabs were applied to suppress artifacts due to flowing blood. The respiratory‐gated MR thermometry in the rabbit liver in vivo showed a standard deviation (SD) of 1–3°C with a temporal resolution of 3 s per slice and 1.4 mm × 1.9 mm spatial resolution in plane (slice thickness = 5 mm). The method was used to guide thermal ablation experiments with a clinical infrared laser. The estimated size of the necrotic area, based on the thermal dose calculated from MR temperature maps, corresponded well with the actual lesion size determined by histology and conventional MR images obtained 5 days posttreatment. These results show that quantitative MR temperature mapping can be obtained in the liver in vivo, and can be used for real‐time control of thermal ablation and for lesion size prediction. Magn Reson Med 50:322–330, 2003. © 2003 Wiley‐Liss, Inc.
Magnitude image CSPAMM reconstruction (MICSR)
Authors: NessAiver Moriel , Prince Jerry L.
Published: July 2003

Image reconstruction of tagged cardiac MR images using complementary spatial modulation of magnetization (CSPAMM) requires the subtraction of two complex datasets to remove the untagged signal. Although the resultant images typically have sharper and more persistent tags than images formed without complementary tagging pulses, handling the complex data is problematic and tag contrast still degrades significantly during diastole. This article presents a magnitude image CSPAMM reconstruction (MICSR) method that is simple to implement and produces images with improved contrast and tag persistence. The MICSR method uses only magnitude images — i.e., no complex data — but yields tags with zero mean, sinusoidal profiles. A trinary display of MICSR images emphasizes their long tag persistence and demonstrates a novel way to visualize myocardial deformation. MICSR contrast and contrast‐to‐noise ratios (CNR) were evaluated using simulations, a phantom, and two normal volunteers. Tag contrast 1000 msec after the R wave trigger was 3.0 times better with MICSR than with traditional CSPAMM reconstruction techniques, while CNRs were 2.0 times better. Magn Reson Med 50:331–342, 2003. © 2003 Wiley‐Liss, Inc.
Patlak plots of Gd‐DTPA MRI data yield blood–brain transfer constants concordant with those of 14C‐sucrose in areas of blood–brain opening
Authors: Ewing James R. , Knight Robert A. , Nagaraja Tavarekere N. , Yee John S. , Nagesh Vijaya , Whitton Polly A. , Li Lian , Fenstermacher Joseph D.
Published: July 2003

The blood‐to‐brain transfer rate constant (Ki) of Gd‐DTPA was determined in MRI studies of a rat model of transient cerebral ischemia. The longitudinal relaxation rate, R1, was estimated using repeated Look‐Locker measurements. A model‐independent analysis of ΔR1, the Patlak plot, produced maps of Ki for Gd‐DTPA and the distribution volume of the mobile protons (Vp) with intravascular‐Gd changed R1's. The Ki's of Gd‐DTPA were estimated in regions of interest with blood–brain barrier (BBB) opening (regions of interest, ROIs) and compared to those of 14C‐sucrose determined shortly thereafter by quantitative autoradiography. The Ki's for both Gd‐DTPA and sucrose were much higher than normal within the ROIs (n = 7); linear regression of Ki for Gd‐DTPA vs. Ki for sucrose yielded a slope of 0.43 ± 0.11 and r2 = 0.72 (P = 0.01). Thus, Ki for Gd‐DTPA varied in parallel with, but was less than, Ki for sucrose. In the ROIs, mean Vp was 0.071 ml g−1 and much higher than mean vascular volume estimated by dynamic‐contrast‐enhancement (0.013 ml g−1) or mean Vp in contralateral brain (0.015 ml g−1). This elevated Vp may reflect increased capillary permeability to water. In conclusion, Ki can be reliably calculated from Gd‐DTPA‐MRI data by Patlak plots. Magn Reson Med 50:283–292, 2003. © 2003 Wiley‐Liss, Inc.
Measurements of cerebral perfusion and arterial hemodynamics during visual stimulation using TURBO‐TILT
Authors: Hendrikse Jeroen , Lu Hanzhang , van der Grond Jeroen , van Zijl Peter C.M. , Golay Xavier
Published: July 2003

Estimation of cerebral blood flow (CBF) in functional perfusion imaging could benefit from a method capable of separating effects of arterial arrival time and trailing edge. To accomplish this, the transfer insensitive labeling technique (TILT) was combined with a train of 13 consecutive acquisitions, called TURBO‐TILT. Visual activation maps obtained at 13 postlabeling delay times (TI) showed a spatial shift from regions surrounding the arterial vasculature at short TI to brain parenchyma at longer delay times. High baseline CBF and short arrival times were found for the voxels with maximum activation at short TI (<1200 ms), while CBF values (43 ml / 100 g tissue/min) and its increase upon activation (55%) at longer TI were in agreement with literature data on regional cerebral perfusion. Magn Reson Med 50:429–433, 2003. © 2003 Wiley‐Liss, Inc.
Geometrical optimization of a phased array coil for high‐resolution MR imaging of the carotid arteries
Authors: Liffers A. , Quick H.H. , Herborn C.U. , Ermert H. , Ladd M.E.
Published: July 2003

The geometry of an RF phased‐array receiving coil for high‐resolution MRI of the carotid artery, particularly the bifurcation, was optimized with respect to signal‐to‐noise ratio (SNR). A simulation tool was developed to determine homogeneity, sensitivity, and SNR for a given imaging situation. The algorithm takes into account the coil geometry, the parameters of the measured object, and the imaging parameters of the pulse sequence. The coil with the optimum geometry was implemented as a receive‐only coil for 1.5 T and comparative SNR measurements with different coils were performed. The experimental SNR measurements verified the simulations. The optimized carotid artery phased array offered the best SNR over the desired field of view. In vivo high‐resolution MRI of the carotid arteries of healthy volunteers and patients with known stenosis was conducted with the optimized phased array coil. The capability of the phased array coil for resolving components within the carotid artery walls is demonstrated. Magn Reson Med 50:439–443, 2003. © 2003 Wiley‐Liss, Inc.