bluuebunny/crossref_metadata_2025 huggingface dataset:
Time course of 23Na signal intensity after myocardial infarction in humans
Authors: Sandstede Joern J.W. , Hillenbrand Hanns , Beer Meinrad , Pabst Thomas , Butter Felix , Machann Wolfram , Bauer Wolfgang , Hahn Dietbert , Neubauer Stefan
Published: August 2004

Experimental studies demonstrated persistently increased 23Na content in nonviable myocardium post‐myocardial infarction (MI). We hypothesized that nonviable myocardium in humans would show elevated 23Na content at all stages of infarct development, and therefore could be imaged with 23Na MRI. Ten patients were examined on days 4, 14, and 90 after infarction, and five of these patients participated in a 12‐month follow‐up. Double angulated short‐axis cardiac 23Na images were obtained with the use of a 23Na surface coil and an ECG‐triggered, 3D gradient‐echo sequence. 1H T2‐weighted imaging (N = 9) was performed on days 4, 14, and 90. Wall motion was assessed by cine MRI, and the infarct size was determined by late enhancement on day 90. The 23Na signal intensity (SI) of infarcted myocardium was expressed as the percentage increase over 23Na SI of noninfarcted myocardium. All of the patients showed an area of elevated SI on 23Na and 1H T2‐weighted images that correlated with wall motion abnormalities and late enhancement. 23Na SI was highest on day 4. It then decreased until day 90, but remained elevated (39% ± 18%, 31% ± 17%, 28% ± 13% on days 4, 14, and 90, respectively, P = 0.001). No further decrease was found 1 year after infarction (25% ± 7%, P = 0.89 vs. day 90). 1H T2‐weighted SI decreased between days 4 and 14, but on day 90 only six of nine patients had a residual elevated SI. Thus, 23Na SI is elevated in nonviable infarction at all time points following MI, and 23Na MRI may become a suitable technique for imaging nonviable myocardium in humans. Magn Reson Med 52:545–551, 2004. © 2004 Wiley‐Liss, Inc.
2D J‐resolved spiral spectroscopic imaging at 7 T: Application to mobile lipid mapping in a rat glioma
Authors: Hiba Bassem , Serduc Raphaël , Provent Peggy , Farion Régine , Rémy Chantal , Ziegler Anne
Published: August 2004

Lactate (Lac) and mobile lipids (Lip), which are present in rat gliomas, are difficult to map because their 1H resonances overlap in the 1.3 ppm region. 2D J‐resolved spectroscopy enables proper separation of the two resonance lines. To obtain high‐spatial‐resolution mapping of Lac and Lip resonances within a reasonable experiment time, we coupled 2D J‐resolved spectroscopy with a fast spectroscopic imaging (SI) method, based on an out‐and‐in spiral k‐space description. The method was applied to a rat glioma at 7 T, and Lac and Lip maps were reconstructed. The duration of SI (2D spatial, 2D spectral) was 64 min for a theoretical in‐plane resolution of 1 × 1 mm, and a slice thickness of 2 mm (voxel size 8.2 μl, taking into account the point‐spread function (PSF)). Magn Reson Med 52:658–662, 2004. © 2004 Wiley‐Liss, Inc.
Detection and volume determination of colonic tumors in Min mice by magnetic resonance micro‐imaging
Authors: Hensley Harvey H. , Chang Wen‐chi , Clapper Margie L.
Published: August 2004

We applied MRI to the in vivo detection of spontaneous colorectal tumors in a unique mouse model, the Fox Chase Cancer Center (FCCC) ApcMIN mouse. Unlike other Min (multiple intestinal neoplasia) strains, FCCC ApcMIN animals develop an appreciable number of tumors in the large intestine, which makes them an appropriate mouse model for colon cancer in humans. We describe a method for marking the colon on MRI data sets that involves a bowel‐cleansing procedure and the insertion of a polyurethane tube (filled with an MRI contrast agent) fully into the colon. We found that tumors as small as 1.5 mm in diameter can be consistently identified from MRI datasets with a voxel size of 0.1 mm × 0.133 mm × 0.133 mm. Tumor volumes were determined from the MRM data sets with the use of a novel approach to planimetry in 3D data sets. We observed a correlation between tumor volume (as measured from the MRI datasets) and tumor weight of 0.942, and a P‐value of 0.008, based on Spearman's test. These data show that MRI can be used to accurately monitor tumor growth in mouse models of colorectal carcinogenesis. Magn Reson Med 52:524–529, 2004. © 2004 Wiley‐Liss, Inc.
Determining the longitudinal relaxation time (T1) of blood at 3.0 Tesla
Authors: Lu Hanzhang , Clingman Chekesha , Golay Xavier , van Zijl Peter C.M.
Published: August 2004

It is important to determine the longitudinal relaxation time of blood for black blood imaging, as well as for quantifying blood flow by arterial spin labeling (ASL). In this study a circulation system was used to measure blood T1 under physiological conditions at the new clinical field strength of 3.0T. It was found that 1/T1 in s−1 was linearly dependent (P < 0.05) on hematocrit (Hct) within a normal range of 0.38–0.46. The relationships were 1/T1 = (0.52 ± 0.15) · Hct + (0.38 ± 0.06) and 1/T1 = (0.83 ± 0.07) · Hct + (0.28 ± 0.03) for arterial (oxygenation = 92% ± 7%) and venous blood (69% ± 8%), respectively, which led to estimated T1 values of 1664 ± 14 ms (arterial) and 1584 ± 5 ms (venous) at a typical human Hct of 0.42. The temperature dependencies of blood T1 were 22.3 ± 0.6 ms/°C and 19.8 ± 0.8 ms/°C for Hct values of 0.42 and 0.38, respectively. When a head coil transmit/receive setup was used, radiation damping caused a slight reduction (19 ms) of the measured T1 values. Magn Reson Med 52:679–682, 2004. © 2004 Wiley‐Liss, Inc.
In vivo study of microbubbles as an MR susceptibility contrast agent
Authors: Wong Kelvin K. , Huang Ingjye , Kim Young R. , Tang Haiying , Yang Edward S. , Kwong Kenneth K. , Wu Ed X.
Published: August 2004

The potential application of gas microbubbles as a unique intravascular susceptibility contrast agent for MRI has not been fully explored. In this study, the MR susceptibility effect of an ultrasound microbubble contrast agent, Optison®, was studied with rat liver imaging at 7 T. Optison® suspension in two different doses (0.15 mL/kg and 0.4 mL/kg) was injected into rats, and induced transverse relaxation rate increases (ΔR2*) of 29.1 ± 1.6 s−1(N= 2) and 61.5 ± 12.9 s−1(N= 6), respectively, in liver tissue. Liver uptake of intact albumin microbubbles was observed 10 min after injection. Eight of the 16 rats studied showed no susceptibility enhancement. This is probably attributable to the intravascular microbubble growth due to transmural CO2supersaturation in the cecum and colon in small animals that causes microbubble aggregation and trapping in the inferior vena cava (IVC). In vitro ΔR2* measurements of Optison® suspension at different concentrations are also reported. Magn Reson Med 52:445–452, 2004. © 2004 Wiley‐Liss, Inc.
Measurement of tumor interstitial volume fraction: Method and implication for drug delivery
Authors: Kim Y.R. , Savellano M.D. , Savellano D.H. , Weissleder R. , Bogdanov A.
Published: August 2004

It is important to evaluate the tumor interstitial volume fraction that is accessible for drug accumulation during the distribution phase in order to determine the potential efficacy of cancer chemotherapy. In this study, we performed simulations of magnetic resonance imaging (MRI) signal intensity using a two‐compartment tissue model for quantitative analyses of absolute interstitial volume measurements while we experimentally characterized a mouse tumor model with a dual MR contrast‐agent method. Previously, consecutive intravenous injections of a strictly intravascular T1 contrast agent followed by an extravasating agent were used as a strategy for the quantification of both relative blood volume (Rel_BV) and relative interstitial volume (Rel_ITST) (Weissleder et al. Eur J Cancer 1998;34:1448–1454; Bogdanov et al. Neoplasia 1991;1:438–435). In the current study, we demonstrate that this approach can be further improved, and that it enables one to accurately evaluate both relative and absolute interstitial volumes. The animal data indicated that a significant difference exists between the absolute interstitial volume fractions of subcutaneously implanted MDA PCa 2b tumor and skeletal muscle tissue (27.5 ± 9.1% and 15.9 ± 0.7%, respectively (P < 0.05)), while only a minor difference was found for the absolute blood volumes (Abs_BV) (Kim et al. Magn Reson Med 2002;47:1110–1120) of these tissues. Magn Reson Med 52:485–494, 2004. © 2004 Wiley‐Liss, Inc.
Highly resolved in vivo 1H NMR spectroscopy of the mouse brain at 9.4 T
Authors: Tkáč Ivan , Henry Pierre‐Gilles , Andersen Peter , Keene C. Dirk , Low Walter C. , Gruetter Rolf
Published: August 2004

An efficient shim system and an optimized localization sequence were used to measure in vivo 1H NMR spectra from cerebral cortex, hippocampus, striatum, and cerebellum of C57BL/6 mice at 9.4 T. The combination of automatic first‐ and second‐order shimming (FASTMAP) with strong custom‐designed second‐order shim coils (shim strength up to 0.04 mT/cm2) was crucial to achieve high spectral resolution (water line width of 11–14 Hz). Requirements for second‐order shim strengths to compensate field inhomogeneities in the mouse brain at 9.4 T were assessed. The achieved spectral quality (resolution, S/N, water suppression, localization performance) allowed reliable quantification of 16 brain metabolites (LCModel analysis) from 5–10‐μL brain volumes. Significant regional differences (up to 2‐fold, P < 0.05) were found for all quantified metabolites but Asp, Glc, and Gln. In contrast, 1H NMR spectra measured from the striatum of C57BL/6, CBA, and CBA/BL6 mice revealed only small (<13%, P < 0.05) interstrain differences in Gln, Glu, Ins, Lac, NAAG, and PE. It is concluded that 1H NMR spectroscopy at 9.4 T can provide precise biochemical information from distinct regions of the mouse brain noninvasively that can be used for monitoring of disease progression and treatment as well as phenotyping in transgenic mice models. Magn Reson Med 52:478–484, 2004. © 2004 Wiley‐Liss, Inc.
In vivo diffusion tensor imaging of the human prostate
Authors: Sinha Shantanu , Sinha Usha
Published: August 2004

This study demonstrates the feasibility of in vivo prostate diffusion tensor imaging (DTI) in human subjects. We implemented an EPI‐based diffusion‐weighted (DW) sequence with seven‐direction diffusion gradient sensitization, and acquired DT images from six subjects using cardiac gating with a phased‐array prostate surface coil operating in a linear mode. We calculated two indices to quantify diffusion anisotropy. The direction of the eigenvector corresponding to the leading eigenvalue was displayed by means of a color‐coding scheme. The average diffusion values of the prostate peripheral zone (PZ) and central gland (CG) were 1.95 ± 0.08 × 10–3 mm2 s and 1.53 ± 0.34 × 10–3 mm2 s, respectively. The average fractional anisotropy (FA) values for the PZ and CG were 0.46 ± 0.04 and 0.40 ± 0.08, respectively. The diffusion ellipsoid in prostate tissue was anisotropic and approximated a prolate model, as shown in the color maps of the anisotropy. Consistent with the tissue architecture, the prostate fiber orientations were predominantly in the superior–inferior (SI) direction for both the PZ and CG. This study shows the feasibility of in vivo DTI and establishes normative DT values for six subjects. Magn Reson Med 52:530–537, 2004. © 2004 Wiley‐Liss, Inc.
View ordering for magnetization prepared steady state free precession acquisition: Application in contrast‐enhanced MR angiography
Authors: Spincemaille Pascal , Nguyen Thanh D. , Wang Yi
Published: August 2004

Magnetization prepared segmented acquisition requires a view order that maximizes signal contrast during the acquisition of the central portion of k‐space. Steady state free precession (SSFP) acquisition further requires a view order that minimizes changes in phase‐encoding gradients from one repetition to the next in order to minimize eddy current artifacts. In this article, optimal view ordering schemes satisfying these two requirements are formulated and applied to inversion prepared 3D SSFP contrast‐enhanced MR angiography (MRA). Experiments on phantoms and pigs demonstrated improved background suppression and reduced image artifacts. Magn Reson Med 52:461–466, 2004. © 2004 Wiley‐Liss, Inc.
Self‐calibrated spiral SENSE
Authors: Qian Yongxian , Zhang Zhenghui , Stenger V. Andrew , Wang Yi
Published: August 2004

Current standard sensitivity‐encoded parallel imaging (SENSE) utilizes a fully sampled low‐resolution reference scan to estimate the coil sensitivities. This reference scan adds scan time and may introduce misregistration artifacts. The purpose of this study was to investigate the feasibility of estimating the coil sensitivities for spiral SENSE directly from an undersampled k‐space center. The limited spatial frequencies of the coil sensitivities, and the undersampling beyond the Nyquist radius cause image artifacts. A point spread function (PSF) analysis and experiments on both phantoms and humans identified an optimal radius for the k‐space center by minimizing these image artifacts. The preliminary data indicate that self‐calibrated SENSE is as accurate as standard SENSE, which uses a fully sampled reference scan. Magn Reson Med 52:688–692, 2004. © 2004 Wiley‐Liss, Inc.
Improvement of the asymptotic behaviour of the Euler–Maclaurin formula for Cauchy principal value and Hadamard finite‐part integrals
Authors: Choi U. Jin , Kim Shin Wook , Yun Beong In
Published: August 2004

In the recent works (Commun. Numer. Meth. Engng 2001; 17: 881; to appear), the superiority of the non‐linear transformations containing a real parameter b ≠ 0 has been demonstrated in numerical evaluation of weakly singular integrals. Based on these transformations, we define a so‐called parametric sigmoidal transformation and employ it to evaluate the Cauchy principal value and Hadamard finite‐part integrals by using the Euler–Maclaurin formula. Better approximation is expected due to the prominent properties of the parametric sigmoidal transformation of whose local behaviour near x = 0 is governed by parameter b.

Through the asymptotic error analysis of the Euler–Maclaurin formula using the parametric sigmoidal transformation, we can observe that it provides a distinct improvement on its predecessors using traditional sigmoidal transformations. Numerical results of some examples show the availability of the present method. Copyright © 2004 John Wiley & Sons, Ltd.
A three‐dimensional model describing stress‐temperature induced solid phase transformations: solution algorithm and boundary value problems
Authors: Auricchio Ferdinando , Petrini Lorenza
Published: August 2004

An always increasing knowledge on material properties as well as a progressively more sophisticated production technology make shape memory alloys (SMA) extremely interesting for the industrial world. At the same time, SMA devices are typically characterized by complex multi‐axial stress states as well as non‐homogeneous and non‐isothermal conditions both in space and time.

This aspect suggests the finite element method as a useful tool to help and improve application design and realization. With this aim, we focus on a three‐dimensional macroscopic thermo‐mechanical model able to reproduce the most significant SMA features (Int. J. Numer. Methods Eng. 2002; 55: 1255–1264), proposing a simple modification of such a model. However, the suggested modification allows the development of a time‐discrete solution algorithm, which is more effective and robust than the one previously discussed in the literature.

We verify the computational tool ability to simulate realistic mechanical boundary value problems with prescribed temperature dependence, studying three SMA applications: a spring actuator, a self‐expanding stent, a coupling device for vacuum tightness. The effectiveness of the model to solve thermo‐mechanical coupled problems will be discussed in a forthcoming work. Copyright © 2004 John Wiley & Sons, Ltd.
A three‐dimensional model describing stress‐temperature induced solid phase transformations: thermomechanical coupling and hybrid composite applications
Authors: Auricchio Ferdinando , Petrini Lorenza
Published: August 2004

Between composite materials, shape memory alloy (SMA) composites are having a more and more relevant role. Typically, SMA wires are embedded in a metallic or a polymeric matrix to obtain materials with native multi‐functionality and adaptive properties. This work approaches the computational study of the mechanical response of a composite in which SMA wires, previously deformed, are activated by electrical current heating, and accordingly try to recover the original shape inducing a shape change or a prestress in the structure.

In particular, since the SMA behaviour is strongly affected by the thermo‐mechanical coupling, in the first part of this work we present a 3D phenomenological model able to take into account this aspect. The model time‐discrete counterpart is used to develop a 3D solid finite element able to describe the thermo‐electro‐mechanical coupled problem due to shape memory alloy response and to Joule effect. Finally, in the second part of the paper, we employ the developed computational tool to simulate different feasible SMA composite applications. Copyright © 2004 John Wiley & Sons, Ltd.
Numerical comparison of some explicit time integration schemes used in DEM, FEM/DEM and molecular dynamics
Authors: Rougier E. , Munjiza A. , John N. W. M.
Published: August 2004

Discontinua simulations are becoming an important part of Computational Mechanics to the extent that Computational Mechanics of Discontinua is becoming a separate subdiscipline of Computational Mechanics. Among the most widely used methods of Computational Mechanics of Discontinua are Discrete Element Methods, Molecular Dynamics Methods, Combined Finite‐Discrete Element Methods, DDA, Manifold Methods, etc. The common feature of all these methods is time discretization of the governing equations and the resulting mostly explicit time integration schemes. A wide range of time integration schemes is available in the literature. In this paper a comparative study of some of the most commonly used explicit time integration schemes is made in terms of accuracy, stability and CPU efficiency. The study has been performed using numerical experiments based on a one degree of freedom mass‐spring system. The results are presented as charts that can be used when deciding which scheme to use for a particular discontinua problem. Copyright © 2004 John Wiley & Sons, Ltd.
On general isotropic tensor functions of one tensor
Authors: de Souza Neto E. A.
Published: August 2004

This paper discusses general isotropic real symmetric tensor‐valued functions of one real symmetric tensor. By exploiting the eigenprojection‐based spectral representation of such functions, eigenprojection‐based closed formulae for the function derivatives are derived. The derived formulae provide an alternative to the eigenvector‐based derivative expressions proposed by Chadwick and Ogden (Arch. Rat. Mech. Anal. 1971; 44:54–68) for the same class of functions and are an extension of the eigenprojection‐based derivative expressions obtained by Carlson and Hoger (Quart. Appl. Math. 1986; 44(3):409–423) for a subset of the present class of functions. The material presented here is restricted to two‐ and three‐dimensional spaces, which are of particular relevance to continuum mechanics. For completeness, algorithms for closed form computation of the isotropic tensor functions as well as their derivatives, based on the eigenprojection representation, are also presented. These should be of interest to computational mechanics researchers dealing with functions of the present type. Copyright © 2004 John Wiley & Sons, Ltd.
Was sind Phytoestrogene und Phyto‐SERMs?: Pflanzeninhaltsstoffe mit Wirkung auf das Hormonsystem
Authors: Vollmer Günter , Zierau Oliver
Published: August 2004

Phytoestrogene sind Inhaltsstoffe von Pflanzen, die mit estrogenabhängigen Signalkaskaden interagieren und ihre Wirkung bevorzugt über die Rezeptoren ER‐α und ER‐β ausüben. Werden nicht alle Wirkungen hervorgerufen, die auch durch Estradiol auszulösen sind, sondern organspezifische, mehr oder weniger selektive Wirkprofile stimuliert, so spricht man von einem “Selectiven Estrogen Receptor Modulator” (SERM). Dieser SERM‐Begriff, angewandt auf Phytoestrogene, führt zur Klassifizierung einiger Phytoestrogene als Phyto‐SERMs. Pflanzliche Inhaltsstoffe mit estrogener Aktivität weisen mehr oder weniger stark ausgeprägte SERM‐Eigenschaften auf. Prinzipiell handelt es sich bei diesen “Phyto‐SERMS” um pharmakologisch interessante Substanzen, die zwar schon z.T. klinisch genutzt werden, für die aber aus der Sicht Molekularer Endokrinologen durchaus noch ein mehr oder weniger stark ausgeprägter Bedarf zur weiteren Charakterisierung besteht.
Latent photochromism (pseudothermochromism) and photofatigue of crystalline 2‐(2′,4′‐dinitrobenzyl)pyridine
Authors: Naumov Panče , Ohashi Yuji
Published: August 2004

Along with the metastable 2‐(2′,4′‐dinitrophenylmethylidene)‐1,2‐dihydropyridine (NH) and the unstable 6‐aci‐nitro‐2‐nitro‐5‐(2′‐pyridylmethylene)‐1,3‐cyclohexadiene (OH), the stable form of 2‐(2′,4′‐dinitrobenzyl)pyridine (DNBP), CH, is photochemically converted into small amounts of 1,2‐bis(2′,4′‐dinitrophenyl)‐1,2‐bis(2′‐pyridyl)ethane, trans‐bis[5‐nitro‐2‐(pyridine‐2‐carbonyl)phenyl]diazene N‐oxide, 6‐nitro‐3‐(2′‐pyridyl)‐2,1‐benzisoxazole and 3‐nitropyrido[1,2‐b]quinolin‐6‐ium‐11‐olate. The latent photochromism of DNBP, as shown by x‐ray analysis of the structures of the side‐products and ESR/IR measurements, is attributed to open‐shell reactions that are initiated by hydrogen photoabstraction and subsequent creation of two monoradicals, NH. and OH.. Large amounts of the radicals (ca 50% NH. and 70% OH.) confined in the crystalline interior are persistent under ambient conditions. Through quasi‐periodic reactions, the remaining radicals partially recover the ground‐state isomers CH, NH and OH, or decay to the side‐products, which results in crystalline photofatigue. Together with proton tunneling from the excited CH, the radical reactions represent dominant mechanism for the creation of NH and OH in the low‐temperature regimes, but are successfully competed by the closed‐shell reactions at higher temperatures. The precursor state, whose existence was assumed previously from transient absorption spectroscopy, may be identified as the radical OH.. The present work represents the first study of the photofatigue of a 2‐(2′,4′‐dinitrobenzyl)pyridine compound and extends the ‘classical’ mechanism of the photochromic reactions of nitrobenzylpyridines with a set of open‐shell radical reaction routes. Copyright © 2004 John Wiley & Sons, Ltd.
Synthesis and surface properties of fluorinated block copolymers containing sulfonic groups
Authors: Wang Feng , Li Hong , Zhang Zhao Bin , Hu Chun Pu , Wu Shu Sen
Published: August 2004

A series of fluorinated block copolymers with different fluorinated block lengths and compositions were synthesized by atom transfer radical polymerization (ATRP), and then the block copolymers containing sulfonic groups with various sulfonation levels were successfully prepared further via a sulfonation reaction. These well‐defined block copolymers were characterized by means of Fourier transform infrared (FTIR), 1H‐nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). The surface activities of the fluorinated block copolymers containing sulfonic groups in N‐methyl pyrrolidone solution and the surface properties of the films prepared from such a solution were examined, and the experimental results showed that the fluorinated block copolymers exhibited a high surface activity in solution and quite a low solid surface energy of films, even though they contain hydrophilic sulfonic groups. The critical surface tensions of these copolymers were estimated and were comparable to that of polytetrafluoroethylene. Even more interestingly, the surface activities of the block copolymers containing sulfonic groups or sodium sulfonate groups in aqueous solution were also measured. It was found that the surface activity in aqueous solution was weaker than that in N‐methyl pyrrolidone solution and depended on both the length of the fluorinated block and the sulfonation level of the block copolymers. The surface properties of the films prepared from the block copolymers in aqueous solution were tested, and most of these films exhibited a hydrophilic surface property. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4809–4819, 2004
Thermal stability of the fullerene‐chain link in 6‐arm PS stars with a C60 core
Authors: Audouin Fabrice , Nuffer Richard , Mathis Claude
Published: August 2004

The thermal stability of well‐defined hexa‐adducts (PS)6C60 in solution at temperatures around 100 °C has been studied by multi‐detector Size Exclusion Chromatography. The degradation reaction corresponds to a quantitative release of the polystyrene arms from the fullerene core through thermal cleavage of the PS‐C60 link. From the kinetics of formation of cut arms and the progressive decrease of the stars' functionality, we could establish that the reaction follows a stepwise “breaking” mechanism where a 6‐arm star is first converted to a 5‐arm star, then to a 4‐arm star, and so on down to the ungrafted arm. Furthermore, not only does the thermal stability of the PSC60 bond increase if the functionality of the star decreases, but the difference is large enough to allow determination of the kinetics constants for the first three steps. The activation energy for the breaking of an arm‐C60 link is about 65 kJ/mol. The stability of (PS)6C60 slightly decreases with an increase of the arm length. MALDI‐TOF mass spectroscopy has shown that both CC bonds in α and β positions to C60 can be cut, but the breaking of the direct fullerene‐arm bond is favored. We have also found that a polyisopreneC60 bond is about seven times less stable than a PS‐fullerene link upon heating. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4820–4829, 2004
Preparation and characterization of SBA‐15 supported iron(II)‐bisimine pyridine catalyst for ethylene polymerization
Authors: Guo Chao , Jin Guo‐Xin , Wang Fusong
Published: August 2004

2,6‐Diacetylpyridinebis (2,6‐diisopropylani) iron dichloride, a late‐transition metal catalyst for olefin polymerization, was supported on SBA‐15 successfully and the property of the supported catalyst was carefully studied. Ethylene polymerization was systematically investigated in the presence of MAO under various conditions employing this type of catalyst system. In general, after support, a decrease in the catalytic activity was observed and higher molecular weight and fibrous morphology of polyethylene were obtained. The “extrusion polymerization” phenomenon was observed in ethylene polymerization by using the supported catalyst system. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4830–4837, 2004
Polyampholytes
Authors: Dobrynin Andrey V. , Colby Ralph H. , Rubinstein Michael
Published: August 2004

Polyampholytes are charged polymers with both positively and negatively charged groups. The conformation of these polymers in solutions strongly depends on the distribution of charged monomers along the polymer backbone and their environment. In this review we summarize the current level of understanding of such amphoteric polymers in solutions and their interactions with surfaces and polyelectrolytes. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3513–3538, 2004
Familial susceptibility to severe respiratory infection in early life
Authors: Goetghebuer Tessa , Kwiatkowski Dominic , Thomson Anne , Hull Jeremy
Published: August 2004

Lower respiratory tract infections (LRTI) are common in the first year of life and are mostly caused by viruses. Severity of LRTI in infants is associated with early‐life environmental factors. Genetic association studies also suggest a role of heredity in susceptibility to acute bronchiolitis. We designed a case control study to further investigate relative importance of familial influences in risk of LRTI in early childhood compared to environmental factors. From a hospital database, we selected 1,308 children (436 cases; 872 controls) living in Oxfordshire. Cases were children under age 5 years admitted to hospital with LRTI. Parental history and other exposures were recorded in cases and controls by postal questionnaire. Maternal history of asthma increased the risk of severe LRTI in the first year of life, independent of subsequent asthma in a child. History of maternal bronchiolitis also increased the risk of infant LRTI. These results further suppoprt the possibility that genetic factors play an important role in susceptibility to severe viral respiratory infections in early life, and suggest that this effect may be independent of subsequent childhood asthma. Pediatr Pulmonol. 2004; 38:321–328. © 2004 Wiley‐Liss, Inc.
Effect of inhalation times on exhaled NO
Authors: Zacharasiewicz Angela , Wilson Nicola , Lex Christiane , Li Albert , Bush Andrew
Published: August 2004

Recent work suggests that exhaled nitric oxide (eNO) can be divided into airway and alveolar components, using varying expiratory flow rates. It is known that higher values of eNO are found with lower expiratory flow rates, thought to be due to prolonged contact of the expirate with the bronchial epithelium. However, whether a prolonged inspiratory time could contaminate the alveolar signal with bronchial derived NO, by the same mechanism, is unknown. We aimed to study the effect, including repeatability, of inhalation time on eNO measurements performed at three different flow rates. We measured eNO in 21 children with asthma of different severity (no steroids, n = 2; inhaled corticosteroid (IC) dose up to 200 mcg/day, n = 3; IC up to 500 mcg/day, n = 3; IC >500 mcg/day, n = 6; IC >500 mcg/day and oral steroid, n = 7) and 24 normal adult controls at 50, 100, and 200 ml/s expiratory flow rate. The effect of either a rapid or a slow inhalation on measured eNO was studied at each flow rate. Furthermore, 12 asthmatic children and 12 adults had repeated measurements 1 hr apart. Repeatability within 1 day was assessed by calculating the single‐determination standard deviation (SD) and 95% range. Our results showed that repeatability was equally good for the three expiratory flow rates, and inhalation time had no influence on the results. The inhalation maneuver does not influence eNO measurements using the variable expiratory flow technique. Pediatr Pulmonol. 2004; 38:335–338. © 2004 Wiley‐Liss, Inc.
Fourier Transform Raman Spectroscopy of the Four Crystallographic Phases of α, β, γ and ε 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazatetracyclo[5.5.0.05,9.03,11]dodecane (HNIW, CL‐20)
Authors: Goede Patrick , Latypov Nikolaj V. , Östmark Henric
Published: August 2004

Fourier transform Raman Spectroscopy (Nd : YAG laser at 1064 nm) was used to characterize the four stable phases of 2,4,6,8,10,12‐Hexanitro‐2,4,6,8,10,12‐hexaazatetracyclo[5.5.0.05,9.03,11]dodecane (HNIW, CL‐20). Raman spectra are reported over the region from 0–4000 cm−1, relative to the laser line. A tentative assignment of the most predominant Raman peaks was made with the aid of QM calculations at the B3LYP/6‐31G(d) level. A method for detecting polymorphic impurities in ε‐CL‐20 was also developed. The detection level for polymorphic impurities was determined to be below 2%. A method for producing γ‐CL‐20 is also presented.
Combustion Mechanism of Consolidated Mixtures of 5‐amino‐1H‐tetrazole with Potassium Nitrate or Sodium Nitrate
Authors: Miyata Yasuyoshi , Date Shingo , Hasue Kazuo
Published: August 2004

Recently, 5‐amino‐1H‐tetrazole is developed for practical use as a substitute for sodium azide, which is conventionally used as a fuel component of gas generating agents for automobile airbags. In this study, the combustion mechanisms of the mixtures 5‐amino‐1H‐tetrazole/potassium nitrate and 5‐amino‐1H‐tetrazole/sodium nitrate have been examined. It has been found that the Granular Diffusion Flame model is applicable to the tested samples even when a molten layer exists at the burning surface. In addition, it is shown that within the pressure range of 1–5 MPa, the greatest factor which affects the burning rate is the diffusion process. It is also demonstrated that the fuel component decomposes first, and the oxidizer decomposes next. Meanwhile, it has also been confirmed that the burning rate increases with an increase in pressure because the flame approaches the burning surface and the amount of heat transfer to the solid phase increases. In spite of a decrease in the amount of heat transfer from the gas phase to the solid phase and an increase in the thickness of the condensed phase reaction zone for a mixture with higher fuel content, there are little differences in the burning rates probably because of an increase in the rate of decomposition of the solid phase.
Dynamic Plate Thickness of ERA Sandwiches against Shaped Charge Jets
Authors: Held Manfred
Published: August 2004

The equation for the dynamic plate thickness is derived as a function of standoff distance Z0, jet tip velocity vj0, cutoff velocity vjc, plate velocities vPI and NATO angle of the ERA sandwich. The dynamic thickness is presented as functions of the different parameters for the front plate – flying against the shaped charge jet – and the rear plate – flying with the shaped charge jet. But the dynamic thickness is only one of the reduction factors of ERA sandwiches.
Theoretical Calculation and Molecular Design for High Explosives: Theoretical Study on Polynitropyrazines and Their N‐oxides
Authors: Li Jinshan , Huang Yigang , Dong Haishan
Published: August 2004

The geometries of polynitropyrazines and their N‐oxides have been fully optimized employing the density functional B3LYP method and the 6‐31++G** basis set. For polynitropyrazines and their N‐oxides we have obtained the enthalpies of formation (at p=1.013×105 Pa and T=298.15 K) by designing isodesmic reactions and the detonation velocities by using the Stine method. Calculated results show that the aromaticity of the pyrazine ring of polynitropyrazine is lower than that of its N‐oxide. From the acquired relationship between the experimental impact sensitivity H50 (12B type) and the least CNO2 bond order the predicted H50 values for compounds 2,5‐diamino‐3,6‐dinitropyrazine and 2,5‐diamino‐3,6‐dinitropyrazine‐1‐oxide are 83 cm and 59 cm, respectively, implying that they are low sensitive explosives. The enthalpy of formation of polynitropyrazine is much less than that of its N‐oxide. The calculated density (1.90 g/cm3) for 2,6‐diamino‐3,5‐dinitropyrazine‐1‐oxide (LLM‐105) is close to the experimental value (1.918 g/cm3), and from both sensitivity and detonation velocity it has been deduced that LLM‐105 is superior to other diaminodinitropyrazines and their N‐oxides. The largest density and detonation velocity obtained in this work are 2.02 g/cm3 (2‐amino‐3,5,6‐trinitropyrazine) and 9.34 km/s (2,3,5,6‐tetranitropyrazine), respectively.
Combustion of Propellants with Ammonium Dinitramide
Authors: Chakravarthy Satyanarayanan R. , Freeman Jeffrey M. , Price Edward W. , Sigman Robert K.
Published: August 2004

This paper reports a series of experiments involving ammonium dinitramide (ADN), a new energetic oxidizer of potential use in composite solid propellants. The experiments include (a) self‐deflagration of pressed pellets of ADN; (b) combustion of sandwiches with ADN laminae on both sides of a binder lamina that is either “pure” or filled with particulate oxidizer and other additives; and, (c) combustion of propellants with a bimodal oxidizer size distribution, wherein, combustion of coarse ADN and fine AP (ammonium perchlorate) and vice versa were used, in addition to mixtures of coarse ADN and AP, fine ADN and AP, and all‐ADN or all‐AP formulations.
A Dde resin based strategy for inverse solid‐phase synthesis of amino terminated peptides, peptide mimetics and protected peptide intermediates
Authors: Rai Aman , Gutheil William G.
Published: August 2004

This report describes a Dde resin based attachment strategy for inverse solid‐phase peptide synthesis (ISPPS). This attachment strategy can be used for the synthesis of amino terminated peptides with side chains and the carboxyl terminus either protected or deprotected. Amino acid t‐butyl esters were attached through their free amino group to the Dde resin. The t‐butyl carboxyl protecting group was removed by 50% TFA, and inverse peptide synthesis cycles performed using an HATU/TMP based coupling method. Protected peptides were cleaved from the resin with dilute hydrazine. Side chain protecting groups could then be removed by treatment with TFMSA/TFA. The potential of this approach was demonstrated by the synthesis of several short protected and unprotected peptides in good yield and with low epimerization. Its potential for peptide mimetic synthesis was demonstrated by the synthesis of two peptide trifluoromethylketones. Copyright © 2004 European Peptide Society and John Wiley & Sons, Ltd.
Electronic properties of Co and Ni silicides: a theoretical approach using extended Huckel method
Authors: Galvan D. H. , Posada Amarillas A. , Samaniego Reyna J. C. , García‐Méndez M. , Farías M. H.
Published: August 2004

Calculations of electronic structure, total and projected density of states (DOS), crystal orbital overlap population (COOP), and average net charge, and also Mulliken population analysis, were performed to study electronic properties of Co and Ni silicides. Analysis of the energy bands depicts metallic behavior for both silicides.

The projected DOS yields an indication that hybridization occurs for Co and Ni silicides. The hybridized band in CoSi2 is composed of Co d and p orbitals and Si p and s orbitals, while in NiSi2 the hybridized band is formed by Ni d and p orbitals with Si p orbitals. The fact that the Fermi energy crosses a small part of the DOS, as is the case of CoSi2, yields an indication of the different electronic properties of CoSi2 when compared to NiSi2. The hybridization is stronger in CoSi2 than in NiSi2. Mulliken population analysis provides an indication that a smaller charge distribution exists in NiSi2 when compared to CoSi2. This difference in charge distribution accounts for the different electronic behavior, in agreement with the DOS analysis. Moreover, COOP analysis provides an indication of the existence of covalent bonding between M and Si (M = Ni, Co), this being stronger in Co than in Ni silicides. Furthermore, the average net charge in both compounds yields an indication that there is a charge transfer from M towards Si. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
First‐principles elastic constants and electronic structure of BP, BAs, and BSb
Authors: Meradji H. , Drablia S. , Ghemid S. , Belkhir H. , Bouhafs B. , Tadjer A.
Published: August 2004

We have carried out a first‐principles total‐energy calculation of the structural and the elastic properties for the series of boron compounds BP, BAs, and BSb. We have applied the augmented plane‐wave plus local‐orbitals method with both the local‐density approximation (LDA) and the generalized gradient approximation (GGA). Since there have been no previous theoretical or experimental determinations, our calculations provide the first available information on the elastic constants of these materials. The elastic constants have been derived by the stress‐strain relation. We have calculated all of the equilibrium structural parameters for both phases: rock salt and zinc blende structures. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Interstitial substitutions of vanadyl ions doped in single crystals of hexaimidazole cobalt sulphate: An EPR study
Authors: Sougandi I. , Velavan K. , Venkatesan R. , Sambasiva Rao P.
Published: August 2004

Electron paramagnetic resonance studies on single crystals of hexaimidazole cobalt(II) sulphate doped with VO(II) are carried in the temperature range 77–300 K at X‐band frequencies. Single crystal EPR spectra indicate the presence of vanadyl impurity positioned in four sites with intensity ratios of 45:36:6:1. Angular variation studies in all the three orthogonal planes confirm that both the intense vanadyl sites have occupied interstitial positions in the lattice. The spin Hamiltonian parameters, calculated for the two sites, indicate orthorhombic nature for the impurity. However, the analysis of powder spectrum reveals the presence of only one site. The spin‐lattice relaxation parameters have been calculated at various temperatures from line width measurements. The admixture coefficients have also been calculated. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Temperature shift of the Fe2+ absorption band in LiNbO3:Fe crystal
Authors: Yükselici M. H. , Allahverdi Ç. , Tunç A. V.
Published: August 2004

The temperature dependence of the Fe2+ absorption band of a strongly oxidized LiNbO3:Fe crystal is reported over the range from 25 to 350 °C, where the effect of temperature on the band is reversible. The band broadens and shifts to lower energy as temperature is increased. The rate at which the absorption peak energy decreases with increasing temperature is calculated as –6.8 × 10–5 eV/°C from the slope of the straight‐line fit to the temperature against peak position energy graph. We propose that the origin of the temperature shift is due to both a shift of the energetic position of impurities and the decrease of the band gap energy. The consistency between the calculated rate by the help of a simplified model which describes the shift of the band gap energy in the frame of the lattice dilation and the observed rate suggests that the lattice dilation might be responsible for the temperature shift of the band. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Radiative properties of Er(DBM)3(TPPO)2 doped solid poly(methyl methacryate) matrix
Authors: Liang Hao , Chen Biao , Zheng Zhiqiang
Published: August 2004

Er(DBM)3(TPPO)2 doped solid poly(methyl methacryate) (PMMA) matrix was prepared and its optical absorption and fluorescence spectra were presented. The Judd–Ofelt parameters obtained for Er3+ in PMMA are 43.84 × 10–20 cm2, 2.31 × 10–20 cm2 and 1.12 × 10–20 cm2. The radiative properties, such as transition probabilities, fluorescence branching ratios and radiative lifetime have been predicted and evaluated. The calculated radiative lifetime and stimulated emission cross section of 4I13/2 → 4I15/2 transition revealed that it is promising for Er(DBM)3(TPPO)2 doped PMMA to be used in rare earth containing polymer based optical devices. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dielectric and optical studies of phase transitions in [(CH3)2NH2]5Cd2CuCl11 crystal
Authors: Elyashevskyy Yu. , Dacko S. , Kosturek B. , Czapla Z. , Kapustyanik V. B.
Published: August 2004

Single crystals of [(CH3)2 NH2]5Cd2CuCl11 have been grown and their dielectric and optical properties have been studied. Electric permittivity, losses and linear optic birefringence measurements have shown that the obtained new crystal is isomorphous with the original one – [(CH3)2 NH2]5Cd3Cl11. Phase transitions were observed at 175 K (continuous) and 120 K (first order). It means that partial replacing of cadmium atoms by copper ones does not change the structure and the heavy Cd2CuCl11–2 anions do not influence significantly the interaction of dimethylammonium cations. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Human tumor suppressor p53 and DNA viruses
Authors: Collot‐Teixeira S. , Bass J. , Denis F. , Ranger‐Rogez S.
Published: August 2004

Human tumor suppressor protein p53 plays a major role in the cell cycle, orchestrating a number of important genes involved in cell‐cycle control and apoptosis, and seems to be one of the most important molecules protecting cells from malignant transformation. Mutations in the p53 gene are observed in about 50% of primary tumors, inducing defective p53 protein no longer capable of binding DNA and of activating transcription. Certain DNA viruses are thought to act in a similar way and may also contribute to the progression of invasive cancer in infected tissue. One of the most effective strategies employed by these viruses is the inhibition of p53 protein by interaction with viral oncoproteins, implying a direct but also an indirect role of these viruses in the impairment of p53 structure and function. This article provides a summary of current knowledge concerning p53 tumor suppressor protein and reviews the different mechanisms adopted by different DNA viruses in undermining p53 function. Copyright © 2004 John Wiley & Sons, Ltd.
Therapeutic potential of nucleoside/nucleotide analogues against poxvirus infections
Authors: De Clercq Erik , Neyts Johan
Published: August 2004

Several nucleoside and nucleotide analogues have been identified as potent antiviral agents with convincing activity against poxviruses (including variola, vaccinia, monkeypox, cowpox, molluscum contagiosum, orf). Among the nucleoside analogues, 8‐methyladenosine and 2‐amino‐7‐[(1,3‐dihydroxy‐2‐propoxy)methyl]purine (S2242), have been identified as promising anti‐poxvirus agents. Among the nucleotide analogues, (S)‐1‐(3‐hydroxy‐2‐phosphonylmethoxypropyl)cytosine [(S)‐HPMPC, cidofovir], (S)‐9‐(3‐hydroxy‐2‐phosphonylmethoxypropyl)‐2,6‐diaminopurine [(S)‐HPMPDAP] and (S)‐6‐(3‐hydroxy‐2‐phosphonylmethoxypropyl)oxy‐2,4‐diaminopyrimidine [(S)‐HPMPO‐DAPy] have been identified as promising anti‐poxvirus agents. These nucleoside and nucleotide analogues have proved to be efficacious in various animal models for poxvirus infections. Only one compound, cidofovir, has also proved efficacious against poxvirus infections in humans, i.e. molluscum contagiosum and orf (sheep pox). Cidofovir is formally licensed for clinical use (intravenous administration for the treatment of cytomegalovirus retinitis in AIDS patients); however, it could also be formulated for topical administration, or for oral administration in prodrug form, i.e. as 1‐O‐hexadecyloxypropyl‐cidofovir. Copyright © 2004 John Wiley & Sons, Ltd.
HIV fusion and its inhibition in antiretroviral therapy
Authors: Greenberg Michael , Cammack Nick , Salgo Miklos , Smiley Lynn
Published: August 2004

The end of the twentieth century saw dramatic improvements in the prognosis of HIV infection brought about by the introduction of new agents (the protease inhibitors and the non‐nucleoside reverse transcriptase inhibitors) and their use in highly active combinations. However, the durability of these combination treatments is limited by a number of factors including adverse effects and extensive intra‐class cross‐resistance so that new antiretrovirals acting on alternative targets and having improved systemic tolerability profiles are required. The HIV binding and entry process offers several potential targets for antiviral interaction. These include gp120 binding to CD4 and to chemokine co‐receptor molecules as well as the fusion process itself, which involves interactions between two leucine zipper‐like 4‐3 repeat regions within gp41 known as heptad repeat (HR)1 and HR2. Peptides such as enfuvirtide (formerly DP178 or T‐20), that mimic the HR2 region of gp41, inhibit HIV‐1 by a mechanism that is thought to involve competitive binding to HR1. This review summarises the clinical development of enfuvirtide, providing an overview of the pharmacokinetic, efficacy and safety data in various patient populations, and also considers the evidence for the key role of genotypic changes in the HR1 region (amino acids 36–45) in determining viral susceptibility to inhibition by enfuvirtide. Copyright © 2004 John Wiley & Sons, Ltd.