bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterisation of Leucaena condensed tannins by size and protein precipitation capacity
Authors: Osborne Nicholas J T , McNeill David M
Published: September 2002

The ability of differently sized condensed tannins from the genus Leucaena, a fodder tree‐legume, to bind protein at different pH values was evaluated to characterise their potential biological effects. Two factors affecting the ability of condensed tannin to bind protein, its major biological activity, have been purported to be the condensed tannin size and the pH of the reaction environment. To test these hypotheses, the protein‐precipitating capacities of condensed tannin extracted from four Leucaena genotypes, L leucocephala (UHK636), L pallida (CQ3439), L trichandra (CPI46568) and L collinsii (OFI52/88), were assessed. Condensed tannin from L leucocephala had approximately 50% of the ability to precipitate protein on a g g−1 basis than L pallida or L trichandra, while L collinsii gave no measurable ability to precipitate protein (reaction environment pH 5.0). Increasing or decreasing the pH of the reaction solution away from pH 5.0 (approximately the isoelectric point of the protein) reduced the ability of condensed tannin from all the species to precipitate protein, the decrease being higher at pH 2.5 than at pH 7.5. Condensed tannins from each Leucaena species were also separated by size exclusion chromatography, and the fractions examined for protein‐precipitating capacity. In general, it was found that the larger‐sized condensed tannin of the accessions L pallida and L trichandra could precipitate more protein than the smaller‐sized condensed tannin. This pattern was not found for L leucocephala.

© 2001 Society of Chemical Industry.
Catalytic cracking, dehydrogenation, and aromatization of isobutane over Ga/HZSM‐5 and Zn/HZSM‐5 at low pressures
Authors: Sun Yanping , Brown Trevor C.
Published: September 2002

Isobutane cracking, dehydrogenation, and aromatization over Ga/HZSM‐5 and Zn/HZSM‐5 has been investigated in a Knudsen cell reactor and the kinetics of the primary reaction steps for isobutene and propene formation have been accurately determined. Although cracking is the dominant reaction channel, with propene and methane being primary products, methane formation is significantly less than propene formation. This indicates that a proportion of the cracking proceeds via Lewis acid attack at CC bonds, and not just via alkanium ion formation at Bronsted acid sites. This is particularly apparent over Zn/HZSM‐5. Intrinsic rate constants for cracking, calculated from the rate of propene formation, are

equation image

equation image

and for dehydrogenation, calculated from the rate of isobutene formation, are

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Large preexponential factors for cracking and dehydrogenation over Ga/HZSM‐5 indicate that either the coverage of active sites is significantly less than the coverage of exposed sites or the intrinsic reaction step involves a large entropy change between reactant and transition state. For Zn/HZSM‐5 the small preexponential factors suggest either small entropy changes during activation, perhaps initiated by Lewis acid sites, or a steady‐state distribution of active and exposed sites is rapidly reached. Differences in intrinsic activation energies may reflect the ratio of Lewis and Bronsted acid sites on the respective catalyst surfaces. Aromatization is more prolific over Ga/HZSM‐5 than over Zn/HZSM‐5 under the low‐pressure conditions. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 467–480, 2002
Bond dissociation energies and the Hammett correlation, Part 1: Remotely substituted aromatic compounds and vitamin E
Authors: Luo Yu‐Ran
Published: September 2002

Four hundred and seventy nine experimental values of XZ bond dissociation energies (BDEs) of para‐, ortho‐, meta‐, and multisubstituted aromatic compounds were reproduced by the following simple equations:

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Here X represents a wide variety of univalent atoms or groups; Y is one or several various remote substituents; and Z represents an oxygen, nitrogen, carbon, or sulfur atom. DH0(XZC5H6) is a known reference/anchor point for a series of XZ bonds. Esr is the remote conjugation energy between the substituents and the reaction center (broken bond), and can be expressed as a Hammett‐type correlation. σ+(Y) is the Brown–Okamoto constant of a substituent Y or the sum of several substituent constants. The Hammett slope or reaction constant ρ is a linear function of the difference between the covalent potentials Vx(Z) and Vx(X). It has been found that

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and

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The set of equations are very powerful for the prediction of BDEs, chemical reactivity, and reaction center (or active site) in antioxidants, nutrients, pharmaceuticals, toxicants, carcinogens, and explosives. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 453–466, 2002
Kinetics of hydrogen abstraction reaction between trifluoromethyl formate and OH radical: A theoretical investigation
Authors: Chandra Asit K. , Urata Shingo , Uchimaru Tadafumi , Sugie Masaaki , Sekiya Akira
Published: September 2002

Kinetics and mechanism of the hydrogen abstraction reaction between trifluoromethyl formate, CF3OCHO, and OH radical have been investigated by using ab initio molecular orbital theory up to G2(MP2) level. The hydrogen abstraction rate constant has been calculated for the first time over a temperature range of 250–450 K by using standard transition state theory including the tunneling correction. Arrhenius parameters of the reaction have been estimated from the temperature dependence of the calculated rate constant. The calculated value for the rate constant (2.0 × 10−14 cm3 molecule−1 s−1) at 298 K is found to be in very good agreement with the recent experimental results. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 500–507, 2002
Gangliosides in rat femoral injury: Early effect on intimal hyperplasia
Authors: Castro Leonardo C. , Montero Edna F.S. , Pedrosa Marcelo E. , Von Kossel Karen , Simões Manuel J. , Nigro Amaury J.T.
Published: September 2002

Previous studies demonstrated that some immunosupressive agents inhibit arterial intimal hyperplasia. Our previous studies demonstrated that gangliosides (Gang) have an immunosuppressive effect on as well as an anti‐inflammatory role in the wound‐healing process. Therefore, we decided to examine the effect of Gang on intimal hyperplasia. Twenty Wistar isogenic rats received a transverse division of the anterior wall of the femoral artery, followed by suturing using mononylon 10‐0 under surgical microscopy and were then divided into two groups: Gang group, 3 mg/kg per day of Gang, and control group, vehicle, intramuscularly from surgery to death (1 and 3 weeks, respectively). Concentric intimal hyperplasia was observed in arteries stained by hematoxylin‐eosin in control and Gang groups. However, the media layer did not demonstrate any major alterations. After 3 weeks, the Gang group showed more intimal hyperplasia than the control group. Therefore, because intimal hyperplasia worsened in the presence of Gang after 3 weeks, further studies will be necessary to clarify its role in intimal proliferation. © 2001 Wiley‐Liss, Inc. MICROSURGERY 21:170–172 2001
Antigenic load and peripheral chimeric levels in entire and partial liver allograft recipients
Authors: Sun Junhong , Qin Guang , Wu Lujia , Wang Chuanmin , Ross Sheil A.G.
Published: September 2002

Orthotopic partial liver transplantation (PLT) models were developed in rats to explore the unique role of the liver in transplant tolerance. In PVG rats, syngeneic PLT established that surgical reduction to one‐third of the liver and orthotopic transplantation permitted survival. Allogeneic PLT in the PVG to DA liver‐tolerant model, both 50% and 33%, did not affect the tolerogeneic property of the liver, with all PLT recipients surviving indefinitely. Blood samples taken at various time points for detection of donor cells using flow cytometry showed a steady increase in donor cell chimerism in both PLT and whole liver transplantation (WLT) recipients that persisted throughout the 3‐month observation period. At each time point, the level of donor cell chimerism in PLT was higher than that in WLT. We conclude that transplantation of one‐third of the liver is compatible with survival in rats. Reduction of antigenic load by means of hepatectomy does not affect the tolerogenic effect of the liver in the PVG to DA LT model because of the remarkable regeneration capability of the liver. Peripheral chimeric levels increase progressively after WLT, suggesting that this is an ongoing immunological phenomenon. The earlier and increased chimerism after PLT may be associated with liver regeneration. © 2001 Wiley‐Liss, Inc. MICROSURGERY 21:183–187 2001
A comparison between two hybrid techniques for the scattering from finite frequency‐selective surfaces
Authors: Pochini C. , Toso G. , Pelosi G. , Roederer A.
Published: September 2002

The scattering from finite frequency selective surfaces (FSSs) characterized by planar interfaces is analyzed, resorting to two PO‐based hybrid techniques. The hybrid techniques, validated with a full‐wave numerical technique, are easy to implement, fast, and already quite accurate for medium‐size FSSs. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 248–252, 2001.
Pulse‐wave velocity measured in one heartbeat using MR tagging
Authors: Macgowan Christopher K. , Henkelman R. Mark , Wood Michael L.
Published: September 2002

A noninvasive method for measuring the aortic pulse‐wave velocity (PWV) in a single heartbeat is introduced. The method sinusoidally tags a column of blood within the vessel, and rapidly acquires a series of 1D projections of the tags as they move (in practice, 64 projections at 4‐ms intervals). From these projections, the relative motion of blood at different positions along the vessel is measured. The PWV is obtained by fitting a mathematical model of blood flow to the tag trajectories. Tests of this method in a pulsatile flow phantom are presented using latex and polyurethane tubes. The PWV measured in these tubes was (mean ± standard deviation) 4.4 ± 0.5 m/s and 2.3 ± 0.2 m/s, respectively. The distensibility of each tube was calculated from the PWV (latex = (7 ± 2) 10−3 mm Hg−1, poly. = (25 ± 4) 10−3mmHg−1) and found to agree within error with distensibility measurements based on the change of tube area with pressure (latex = (6.3 ± 0.3) 10−3mmHg−1, poly. = (27 ± 1) 10−3 mmHg−1). To test its feasibility, the PWV measurement was applied to four normal volunteers. The measured PWV values were 3.9 ± 0.8 m/s, 3.6 ± 0.9 m/s, 3.9 ± 0.5 m/s, and 5.3 ± 0.8 m/s. By acquiring an independent PWV measurement each heartbeat, errors introduced by arrhythmia and trigger variability appear to be avoided with this method. Magn Reson Med 48:115–121, 2002. © 2002 Wiley‐Liss, Inc.
Validation of diffusion tensor MRI‐based muscle fiber tracking
Authors: Damon Bruce M. , Ding Zhaohua , Anderson Adam W. , Freyer Andrea S. , Gore John C.
Published: September 2002

Diffusion‐tensor (DT) MRI fiber tracking may potentially be used for in vivo structural analysis. The purpose of this study was to assess quantitatively the ability of a DT‐MRI fiber‐tracking algorithm to measure the fiber orientation (pennation) in skeletal muscle in vivo. In five adult Sprague‐Dawley rats, the pennation angle (θ) was measured in the rat lateral gastrocnemius with DT‐MRI (θDT‐MRI) and by direct anatomical inspection (DAI) (θDAI). The mean θDT‐MRI was not significantly different from the mean θDAI. In addition, the two methods were highly correlated (r = 0.89) and the regression of θDT‐MRI on θDAI resulted in a slope not significantly different from 1 and an intercept not significantly different from zero. These data indicate that DT‐MRI‐based fiber tracking as implemented here is a valid tool for in vivo structural analysis of small‐animal skeletal muscle. Magn Reson Med 48:97–104, 2002. © 2002 Wiley‐Liss, Inc.
Discontinuous analysis of softening solids under impact loading
Authors: Wells G. N. , Sluys L. J.
Published: September 2002

Softening solids are analysed under impact loading using a new numerical method which allows displacement discontinuities to propagate arbitrarily through a finite element mesh. The Dirac‐delta distributions that arise in the strain field of classical continuum theory in the presence of strain softening are interpreted as discontinuities in the displacement field. A new finite element procedure with Heaviside jumps added to the underlying displacement interpolation basis is able to capture displacement jumps independent of the spatial discretisation. The amplitudes of displacement jumps are represented by extra degrees of freedom at existing nodes. Numerical results for mode‐I and mode‐II failure due to impact loading are presented. The numerical results highlight the objectivity of the approach with respect to spatial discretisation under dynamic loading conditions. Copyright © 2001 John Wiley & Sons, Ltd.
Evolution of elastic properties in finite poroplasticity and finite element analysis
Authors: Bernaud D. , Deudé V. , Dormieux L. , Maghous S. , Schmitt D.P.
Published: September 2002

The formulation of the poroelastoplastic constitutive equations at large strains of a fully saturated material is performed focusing on the usually ignored influence of large strain plasticity on the poroelastic properties. A micromechanics approach allows to take into account the evolution of the microstructure geometry which in turn induces a coupling between elasticity and plasticity. Such a coupling results in an additional term in the macroscopic Cauchy stress rate equation derived from inclusion‐based estimates that leads to a modified Jaumann derivative. The pressure rate equation is also analysed. The finite element discretization of finite poroplasticity is then presented taking into account the elasticity–plasticity coupling. Application to the consolidation situation shows that the coupling may lead to non‐negligible effects. Copyright © 2002 John Wiley & Sons, Ltd.
Nonconforming Galerkin methods for the Helmholtz equation
Authors: Douglas Jim , Santos Juan E. , Sheen Dongwoo
Published: September 2002

Nonconforming Galerkin methods for a Helmholtz‐like problem arising in seismology are discussed both for standard simplicial linear elements and for several new rectangular elements related to bilinear or trilinear elements. Optimal order error estimates in a broken energy norm are derived for all elements and in L2 for some of the elements when proper quadrature rules are applied to the absorbing boundary condition. Domain decomposition iterative procedures are introduced for the nonconforming methods, and their convergence at a predictable rate is established. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17: 475–494, 2001
Characterisation of new oligoglycosidic compounds in two Chinese medicinal herbs
Authors: Apers Sandra , Huang Ying , Miert Sabine Van , Dommisse Roger , Berghe Dirk Vanden , Pieters Luc , Vlietinck Arnold
Published: September 2002

A series of caffeic acid derivatives (3,5‐dicaffeoyl‐quinic acid, 3,4‐dicaffeoyl‐quinic acid, and 4,5‐dicaffeoyl‐quinic acid), and the new compound β,3,4‐trihydroxyphenethyl‐O‐[β‐apiofuranosyl‐(1→4)‐α‐rhamnopyranosyl‐(1→3)]‐(4‐O‐caffeoyl)‐β‐glucopyranoside (wedelosin), as well as three known flavonoid glycosides (quercetin 3‐O‐β‐glucoside, kaempferol 3‐O‐β‐apiosyl‐(1‐2)‐β‐glucoside, and astragalin or kaempferol 3‐O‐β‐glucoside) were isolated from the Chinese medicinal herb Wedelia chinensis. Wedelosin showed an inhibitory activity on both the classical and the alternative activation pathway of the complement system. Another Chinese medicinal herb, Kyllinga brevifolia, yielded two known flavonoid glycosides [kaempferol 3‐O‐β‐apiosyl‐(1‐2)‐β‐glucoside and isorhamnetin 3‐O‐β‐apiosyl‐(1‐2)‐β‐glucoside], and a new quercetin triglycoside [quercetin 3‐O‐β‐apiofuranosyl‐(1→2)‐β‐glucopyranoside 7‐O‐α‐rhamnopyranoside]. The latter compound showed a moderate anti‐viral activity. Copyright © 2002 John Wiley & Sons, Ltd.
First trimester PAPP‐A in the detection of non‐Down syndrome aneuploidy
Authors: Ochshorn Yifat , Kupferminc Michael J. , Wolman Igal , Orr‐Urtreger Avi , Jaffa Ariel J. , Yaron Yuval
Published: September 2002

Combined first trimester screening using pregnancy associated plasma protein‐A (PAPP‐A), free β‐human chorionic gonadotrophin, and nuchal translucency (NT), is currently accepted as probably the best combination for the detection of Down syndrome (DS). Current first trimester algorithms provide computed risks only for DS. However, low PAPP‐A is also associated with other chromosome anomalies such as trisomy 13, 18, and sex chromosome aneuploidy. Thus, using currently available algorithms, some chromosome anomalies may not be detected. The purpose of the present study was to establish a low‐end cut‐off value for PAPP‐A that would increase the detection rates for non‐DS chromosome anomalies. The study included 1408 patients who underwent combined first trimester screening. To determine a low‐end cut‐off value for PAPP‐A, a Receiver–Operator Characteristic (ROC) curve analysis was performed. In the entire study group there were 18 cases of chromosome anomalies (trisomy 21, 13, 18, sex chromosome anomalies), 14 of which were among screen‐positive patients, a detection rate of 77.7% for all chromosome anomalies (95% CI: 55.7–99.7%). ROC curve analysis detected a statistically significant cut‐off for PAPP‐A at 0.25 MoM. If the definition of screen‐positive were to also include patients with PAPP‐A<0.25 MoM, the detection rate would increase to 88.8% for all chromosome anomalies (95% CI: 71.6–106%). This low cut‐off value may be used until specific algorithms are implemented for non‐Down syndrome aneuploidy. Copyright © 2001 John Wiley & Sons, Ltd.
Allele‐specific amplification for preimplantation genetic diagnosis (PGD) of spinal muscular atrophy
Authors: Moutou Céline , Gardes Nathalie , Rongières Catherine , Ohl Jeanine , Bettahar‐Lebugle Karima , Wittemer Christiane , Gerlinger Pierre , Viville Stéphane
Published: September 2002

We have developed a new allele‐specific amplification method for the preimplantation genetic diagnosis (PGD) of spinal muscular atrophy (SMA; Werdnig‐Hoffmann disease) from a single cell. This method is based on the detection of the deletion of exon 7 of the telomeric copy of the survival motor neurone (SMNt) gene. An oligonucleotide was designed to be specific to the SMNt nucleotidic sequence with exonic mismatch G (for SMNt)→A (for SMNc) at its 3′ end. This test produces reliable PCR products in 95% of single lymphoblasts (85/88) tested as well as in 16/16 blastomeres from normal controls. Specificity analysis showed that we were able to detect homozygous deletion of the SMNt gene in 99% of single lymphoblasts (103/104) from a SMA patient. No contamination was detected in 68 blanks tested. Multiple cell and DNA dilution analysis revealed that the test is accurate and specific up to 100 pg DNA and should thus also be suitable for PGD at the blastocyst stage. This rapid procedure requires a single round of fluorescent PCR and no restriction digestion, while previously described single cell methods include nested PCR followed by restriction enzyme digestion. Two PGD cycles for SMA using this procedure were performed in our centre. Copyright © 2001 John Wiley & Sons, Ltd.
Preimplantation genetic diagnosis of the fragile X syndrome by use of linked polymorphic markers
Authors: Apessos A. , Abou‐Sleiman P. M. , Harper J. C. , Delhanty J. D. A.
Published: September 2002

Fragile X syndrome is the most common cause of familial mental retardation. The most common mutation is expansion of a triplet (CGG)n repeat in the 5′ untranslated region of the FMR1 gene on Xq27.3. The expansion is refractory to PCR due to preferential amplification of the smaller allele in heterozygous cells and the high GC content of the repeat and surrounding sequences. Direct detection of the normal parental alleles in preimplantation embryos has been used for preimplantation genetic diagnosis (PGD) of this disorder. However, this approach is only suitable for approximately 63% of couples due to the heterozygosity of the repeat in the normal population. As an alternative we investigated the use of polymorphic markers flanking the mutation to track the normal and premutation carrying maternal chromosomes in preimplantation embryos. Using a panel of 11 polymorphisms, six (CA)n repeats and five single nucleotide polymorphisms, diagnosis was developed for 90% of referred couples. Multiplex amplification of informative markers was tested in 300 single buccal cells from interested couples with efficiency and allele drop out (ADO) rates ranging from 69% to 96% and 6% to 18%, respectively. Use of this approach is accurate and applicable to a larger number of patients at risk of transmitting fragile X to their offspring. Copyright © 2001 John Wiley & Sons, Ltd.
Prenatal ultrasonographic detection of gastrointestinal obstruction: results from 18 European congenital anomaly registries
Authors: Haeusler Martin C. H. , Berghold Andrea , Stoll Claude , Barisic Ingeborg , Clementi Maurizio
Published: September 2002

Objectives

We evaluated the prenatal detection of gastrointestinal obstruction (GIO, including atresia, stenosis, absence or fistula) by routine ultrasonographic examination in an unselected population all over Europe.

Methods

Data from 18 congenital malformation registries in 11 European countries were analysed. These multisource registries used the same methodology. All fetuses/neonates with GIO confirmed within 1 week after birth who had prenatal sonography and were born during the study period (1 July 1996 to 31 December 1998) were included.

Results

There were 670 793 births in the area covered and 349 fetuses/neonates had GIO. The prenatal detection rate of GIO was 34%; of these 40% were detected ≤24 weeks of gestation (WG). A total of 31% (60/192) of the isolated GIO were detected prenatally, as were 38% (59/157) of the associated GIO (p=0.26). The detection rate was 25% for esophageal obstruction (31/122), 52% for duodenal obstruction (33/64), 40% for small intestine obstruction (27/68) and 29% for large intestine obstruction (28/95) (p=0.002). The detection rate was higher in countries with a policy of routine obstetric ultrasound. Fifteen percent of pregnancies were terminated (51/349). Eleven of these had chromosomal anomalies, 31 multiple malformations, eight non‐chromosomal recognized syndromes, and one isolated GIO. The participating registries reflect the various national policies for termination of pregnancy (TOP), but TOPs after 24 WG (11/51) do not appear to be performed more frequently in countries with a liberal TOP policy.

Conclusion

This European study shows that the detection rate of GIO depends on the screening policy and on the sonographic detectability of GIO subgroups. Copyright © 2002 John Wiley & Sons, Ltd.
Long‐term follow‐up of infants after transcervical chorionic villus sampling and after amniocentesis to compare congenital abnormalities and health status
Authors: Schaap Arty H. P. , van der Pol Hans G. , Boer Kees , Leschot Nico J. , Wolf Hans
Published: September 2002

Objectives

Next to procedure‐related fetal loss, other adverse effects of invasive prenatal diagnosis have been reported: limb defects after chorionic villus sampling (CVS) or early amniocentesis and respiratory distress after amniocentesis (AC). Because minor abnormalities may be overlooked in routine follow‐up, we obtained long‐term follow‐up data after CVS and AC.

Methods

1509 women with a singleton pregnancy who had transcervical CVS were matched by age and season of conception with 1509 women with singleton pregnancies who had AC. All procedures were performed during 1985–1991 for advanced maternal age >35 years. Data regarding congenital malformations (classified according Eurocat), neonatal and paediatric morbidity and complications of motor development, speech, hearing and visual function were obtained by questionnaire in 1993–1995.

Results

Short‐term outcome was known in all but ten infants. Questionnaires with a structured design were mailed to all women with a surviving infant (n=2810); 86.7% responded. No difference was detected between infants after CVS compared with infants after AC regarding congenital malformations (7.2% versus 6.3%), neonatal morbidity (15.1% versus 15.9%), paediatric morbidity with clinical treatment (7.7% versus 6.3%) or outpatient treatment only (43.9% versus 40.3%) and evident function disturbance (2.0% versus 2.0%) or doubtful function disturbance (6.3% versus 6.8%). The number of infants with physical growth <10th centile for Dutch infants was equal (10.1%). Sub‐analysis for limb abnormalities or respiratory complications did not demonstrate differences between infants after CVS and AC. Only 10% of all congenital malformations were already known through routine post‐partum follow‐up.

Conclusion

An extensive long‐term survey could not demonstrate differences of health status between infants after prenatal diagnosis by transcervical CVS and AC. Copyright © 2002 John Wiley & Sons, Ltd.
Postmarketing surveillance of medications and pregnancy outcomes: Clarithromycin and birth malformations*
Authors: Drinkard Carol R. , Shatin Deborah , Clouse Jon
Published: September 2002

Purpose

This retrospective surveillance study used linked administrative claims data and medical records to determine the rate and types of birth malformations in infants born to women exposed to the antibiotic, clarithromycin (Biaxin®), during the first trimester of pregnancy.

Methods

Pharmacy and hospital claims from eight geographically diverse health plans were used to identify women who had a delivery claim within 270 days of a clarithromycin prescription over a 5‐year period (1991–1995). Hospital delivery admission medical records for 143 mothers and their 149 infants were abstracted to identify birth malformations.

Results

Five infants were identified with major malformations, three with minor malformations, and four with undescended testicles likely to resolve with time. The observed rate of 3.4% (95% CI, 0.5, 6.3) for major malformations was not statistically significantly different compared to an expected rate of 2.8% based on earlier national data. There was no consistency across types of major malformations.

Conclusions

These results provide no evidence that clarithromycin is a likely major teratogen in humans. Use of claims data is one way to evaluate quickly and efficiently the safety of prescription medications in humans during pregnancy, especially when both exposure and outcome are rare. Copyright © 2000 John Wiley & Sons, Ltd.
Stannous(II) trifluoromethane sulfonate: a versatile catalyst for the controlled ring‐opening polymerization of lactides: Formation of stereoregular surfaces from polylactide “brushes”
Authors: Möller Michael , Nederberg Fredric , Lim Lisa S. , Kånge Rikard , Hawker Craig J. , Hedrick James L. , Gu Yuedong , Shah Rahul , Abbott Nicholas L.
Published: September 2002

A general method for the controlled synthesis of polylactide in solution and from solid supports is presented. The evaluation of stannous(II) trifluoromethane sulfonate [Sn(OTf)2] and scandium(III) trifluoromethane sulfonate [Sc(OTf)3] as catalysts for the ring‐opening polymerization (ROP) of L‐, D‐, and L,D‐lactide is described as a route to polylactide using mild and highly selective conditions. These triflate catalysts must be used in conjunction with a nucleophilic compound such as an alcohol that is the actual initiating species via the active metal alkoxide species. Consistent with this process, 1H NMR analysis revealed that the α‐chain‐end bears the ester from the initiating alcohol, and upon hydrolysis of the active metal alkoxide chain end, a ω‐hydroxyl chain end was clearly detected. Polymers of predictable molecular weights and narrow polydispersities were obtained in high yields in accordance with a controlled polymerization process. The addition of base either as a solvent or additive significantly enhanced the polymerization rate with minimal loss to the polymerization control. The ROP of lactide isomers from an initiator, HO(CH2CH2O)3(CH2)11SH, self‐assembled onto a gold surface using Sn(OTf)2 produced polylactide brushes under living conditions and provides the opportunity to prepare stereoregular or chiral surfaces by polymerization of enantiomerically pure monomers. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3529–3538, 2001
Modeling molecular weight distribution in emulsion polymerization reactions with transfer to polymer
Authors: Sayer C. , Araújo P. H. H. , Arzamendi G. , Asua J. M. , Lima E. L. , Pinto J. C.
Published: September 2002

A mathematical model was developed for the computation of the dynamic evolution of molecular weight distributions (MWDs) during nonlinear emulsion polymerization reactions. To allow the direct computation of the whole MWD, an adaptive orthogonal collocation technique was applied. The model was validated with experimental methyl methacrylate/butylacrylate (BuA) semicontinuous and vinyl acrylate (VA)/Veova10 continuous emulsion polymerization results. Both systems considered introduce significant chain‐transfer reactions to polymer chains as a result of the presence of BuA and VA, respectively. The model developed was able to represent quite properly the kinetics and MWD of polymer samples during emulsion polymerizations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3513–3528, 2001
Atom transfer radical polymerization of acrylates in an ionic liquid: Synthesis of block copolymers
Authors: Biedroń Tadeusz , Kubisa Przemysław
Published: September 2002

Atom transfer radical polymerization (ATRP) of acrylates in ionic liquid, 1‐butyl‐3‐methylimidazolium hexaflurophospate, with the CuBr/CuBr2/amine catalytic system was investigated. Sequential polymerization was performed by synthesizing AB block copolymers. Polymerization of butyl acrylate (monomer that is only partly soluble in an ionic liquid forming a two‐phase system) proceeded to practically quantitative conversion. If the second monomer (methyl acrylate) is added at this stage, polymerization proceeds, and block copolymer formed is essentially free of homopolymer according to size exclusion chromatographic analysis. The number‐average molecular weight of the copolymer is slightly higher than calculated, but the molecular weight distribution is low (Mw/Mn = 1.12). If, however, methyl acrylate (monomer that is soluble in an ionic liquid) is polymerized at the first stage, then butyl acrylate in the second‐stage situation is different. Block copolymer free of homopolymer of the first block (with Mw/Mn = 1.13) may be obtained only if the conversion of methyl acrylate at the stage when second monomer is added is not higher than 70%. Matrix‐assisted laser desorption/ionization time‐of‐flight analysis confirmed that irreversible deactivation of growing macromolecules is significant for methyl acrylate polymerization at a monomer conversion above 70%, whereas it is still not significant for butyl acrylate even at practically quantitative conversion. These results show that ATRP of butyl acrylate in ionic liquid followed by addition of a second acrylate monomer allows the clean synthesis of block copolymers by one‐pot sequential polymerization even if the first stage is carried out to complete conversion of butyl acrylate. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2799–2809, 2002
Maleation of poly(3,4‐epoxy‐1‐butene) for accelerated crosslinking in the presence of a redox catalyst
Authors: Yoo Youngtai , Johnson Larry K. , Falling Stephen N. , Lizotte Jeremy R. , Long Timothy E.
Published: September 2002

Accelerated crosslinking of novel poly(3,4‐epoxy‐1‐butene) (3,4‐PEPB) oligomers in the presence of a cobalt‐based redox catalyst was investigated. Previous studies using model compounds, 3,4‐dimethoxy‐1‐butene and 1,4‐dimethoxy‐2‐butene, suggested that maleation of hydroxyl‐terminated 3,4‐PEPB oligomers would result in more rapid crosslinking in thin films. Novel maleated oligomers offered a unique combination of both electron‐rich and electron‐poor olefinic sites, and quantitative maleation significantly increased the crosslinking rate of 3,4‐PEPB. Efficient copolymerization between terminal maleate groups and olefinic groups in the repeating unit was proposed to account for accelerated crosslinking rates. Furthermore, the addition of novel reactive diluents, such as maleic acid mono‐ethyl ester, also effectively improved the 3,4‐PEPB crosslinking rate. Sol fraction measurements as a function of coating thickness revealed that the crosslinking rate versus oxygen diffusion was less significant for the maleated oligomers because of the presence of reactive electron‐poor olefins. Sol fractions were constant for catalyst concentrations greater than 0.25–0.50 wt % (as compared with oligomer feed). This observation suggested that a redox process was not a dominant factor in determining crosslinking rates at various experimental conditions. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2789–2798, 2002
Cation environment in polyether complexes based on poly(tetramethylene glycol) doped with zinc and cobalt chlorides
Authors: Furtado C. A. , Porto A. O. , Silva G. G. , Silva R. A. , Pimenta M. A. , Martins‐Alves M. C. , Schilling P. J.
Published: September 2002

X‐ray absorption spectroscopy [extended X‐ray absorption fine structure (EXAFS) and X‐ray absorption near‐edge structure (XANES)], differential scanning calorimetry, and Raman spectroscopy measurements were performed for a series of liquid polyether/salt systems prepared with poly(tetramethylene glycol) (PTMG) and the copolymer poly(tetramethylene glycol‐co‐ethylene glycol) as matrices and zinc and cobalt chlorides as dopants in the concentration range of n = 30–90, where n is the molar ratio of oxygen to metal cation. According to EXAFS, XANES, and Raman results, even in diluted solutions, these complexes exist mostly as undissociated ZnCl2 and CoCl2 species, presenting a weak cation–polymer interaction. EXAFS results indicate that for polymer/ZnCl2 systems, the nearest metal neighbors are only chlorine atoms. However, for polymer/CoCl2 samples, oxygen is also observed coordinating the metal. Raman spectra do not support any feature related specifically to the cation–polymer interaction. Nevertheless, for both salts the symmetric stretching vibrations are located in frequencies characteristic of salt in solution, which means that the polymer solvating action is effective. Differential scanning calorimetry data show an increase in the glass‐transition temperature for all polymer/salt systems in relation to the pure polymer samples, a consequence of the increase in the macromolecular chain stiffening produced by the presence of the salt. This result corroborates the existence of polymer–salt interactions. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2572–2580, 2001
Quantitative PCR monitoring of the effect of azoxystrobin treatments on Mycosphaerella graminicola epidemics in the field
Authors: Rohel Eric A , Laurent Paul , Fraaije Bart A , Cavelier Nadine , Hollomon Derek W
Published: September 2002

Quantitative PCR and visual monitoring of Mycosphaerella graminicola epidemics were performed to investigate the effect of curative and preventative applications of azoxystrobin in wheat field crops. A non‐systemic protectant and a systemic curative fungicide, chlorothalonil and epoxiconazole, respectively, were used as references. PCR diagnosis detected leaf infection by M graminicola 3 weeks before symptom appearance, thereby allowing a clear distinction between curative and preventative treatments. When applied 1 week after the beginning of infection, azoxystrobin curative activity was intermediate between chlorothalonil (low effect) and epoxiconazole. When applied preventatively, none of the fungicides completely prevented leaf infection. There was some indication that azoxystrobin preventative treatments may delay fungal DNA increase more than epoxiconazole at the beginning of leaf infection. Both curative and preventative treatments increased the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Azoxystrobin only slightly decreased the speed of necrotic area increase compared with epoxiconazole. Hence, azoxystrobin activity toward M graminicola mainly resides in lengthening the time lapse between the earliest PCR detection and the measurement of a 10% necrotic leaf area. Information generated in this way is useful for optimal positioning of azoxystrobin treatments on M graminicola.

© 2002 Society of Chemical Industry
Chemical alternatives to methyl bromide for the control of root‐knot nematodes in greenhouses
Authors: Giannakou Ioannis O , Sidiropoulos Artemios , Prophetou‐Athanasiadou Demetra
Published: September 2002

The complete phase‐out of methyl bromide from use in developed countries by 1 January 2005 will cause many problems in agricultural industries that are now heavily reliant on its use. Three field experiments were established to compare management tactics on tomato and cucumber in commercial greenhouses naturally infested with root‐knot nematodes (Meloidogyne spp). Reduction of nematode juveniles in soil and roots to nil detection levels was observed in all plots following soil fumigation with methyl bromide. A significant reduction of nematode juveniles and root‐galling index was observed in plots treated with metham‐sodium, dazomet and 1,3‐dichloropropene compared with the control and plots treated with non‐fumigant nematicides. Reduction of the nematode population led to an increase in fruit yield. However, data collected from the second cultivation season indicated that single control methods such as fumigant or contact nematicides alone cannot drastically decrease initial nematode population and those nematodes which escape control lead to population increase by the end of the cropping season.

Copyright © 2002 Society of Chemical Industry
Computational chemistry study of the environmentally important acid‐catalyzed hydrolysis of atrazine and related 2‐chloro‐s‐triazines
Authors: Sawunyama Phillip , Bailey George W
Published: September 2002

Many chlorine‐containing pesticides, for example 2‐chloro‐s‐triazines, are of great concern both environmentally and toxicologically. As a result, ascertaining or predicting the fate and transport of these compounds in soils and water is of current interest. Transformation pathways for 2‐chloro‐s‐triazines in the environment include dealkylation, dechlorination (hydrolysis), and ring cleavage. This study explored the feasibility of using computational chemistry, specifically the hybrid density functional theory method, B3LYP, to predict hydrolysis trends of atrazine (2‐chloro‐N4‐ethyl‐N6‐isopropyl‐1,3,5‐triazine‐2,4‐diamine) and related 2‐chloro‐s‐triazines to the corresponding 2‐hydroxy‐s‐triazines. Gas‐phase energetics are described on the basis of calculations performed at the B3LYP/6‐311++G(d,p)//B3LYP/6‐31G* level of theory. Calculated free energies of hydrolysis (ΔhG298) are nearly the same for simazine (2‐chloro‐N4,N6‐diethyl‐1,3,5‐triazine‐2,4‐diamine), atrazine, and propazine (2‐chloro‐N4,N6‐di‐isopropyl‐1,3,5‐triazine‐2,4‐diamine), suggesting that hydrolysis is not significantly affected by the side‐chain amine‐nitrogen alkyl substituents. High‐energy barriers also suggest that the reactions are not likely to be observed in the gas phase. Aqueous solvation effects were examined by means of self‐consistent reaction field methods (SCRF). Molecular structures were optimized at the B3LYP/6‐31G* level using the Onsager model, and solvation energies were calculated at the B3LYP/6‐311++G(d,p) level using the isodensity surface polarizable continuum model (IPCM). Although the extent of solvent stabilization was greater for cationic species than neutral ones, the full extent of solvation is underestimated, especially for the transition state structures. As a consequence, the calculated hydrolysis barrier for protonated atrazine is exaggerated compared with the experimentally determined one. Overall, the hydrolysis reactions follow a concerted nucleophilic aromatic substitution (SNAr) pathway.

Published in 2002 for SCI by John Wiley & Sons, Ltd
Disruption of responses to pheromone by (Z)‐11‐hexadecenyl trifluoromethyl ketone, an analogue of the pheromone, in the cabbage armyworm Mamestra brassicae
Authors: Renou Michel , Berthier Andrée , Guerrero Angel
Published: September 2002

The effects of (Z)‐11‐hexadecenyl trifluoromethyl ketone (Z11‐16:TFMK) a fluorinated pheromone analogue, on the responses to sex pheromone of the male cabbage armyworm, Mamestra brassicae, have been investigated in an actograph and by electroantennography (EAG). In spite of its structural proximity with the natural pheromone, Z11‐16:TFMK was poorly active in EAG, and not active on male behaviour. When permeated in the air, Z11‐16:TFMK reversibly inhibited the electroantennographic responses to (Z)‐11‐hexadecenyl acetate (Z11‐16:Ac), the main component of the sex pheromone. In the actograph, the latency of the activation was increased and the intensity of the behavioural activity of males in response to Z11‐16:Ac was significantly reduced in the presence of Z11‐16:TFMK. These results, along with others previously reported by us, provide new pointers to the possible use of Z11‐16:TFMK in pest‐control strategies.

© 2002 Society of Chemical Industry
Resource sustainability in commodity systems: the sawmill industry in the Northern Forest
Authors: Jones Andrew , Seville Don , Meadows Donella
Published: September 2002

Many natural resource‐based commodity systems exhibit a trio of undesirable behaviors—price instability, resource unsustainability, and inequity among people along the commodity chain. In this article we share findings from a modeling project that focuses primarily on the second problem, unsustainability, in the forest products economy and forest ecosystem of the Northeastern United States. The model shows the structural potential for lumber industry capacity to overshoot the timber resource of the regional forest. Many of the policies commonly advocated in response to resource shortage, such as boosting mill efficiencies and eliminating log exports, appear unlikely to solve the problem. We identify several policies with the potential to help sustain both the industry and resource base. We also share insights on how to design a modeling and intervention process when addressing policy problems for which no single organization has direct responsibility. Finally, we consider ways to navigate through three prevalent “defensive routines”—denial, resignation, and despair—that are often barriers to constructive discussion on how to address potential limits to growth. Copyright © 2002 John Wiley & Sons, Ltd.
Multi‐state models and outcome prediction in bone marrow transplantation
Authors: Keiding Niels , Klein John P. , Horowitz Mary M.
Published: September 2002

Multi‐state models have proved versatile and useful in the statistical analysis of the complicated course of events after bone marrow transplantation. Working from data from the International Bone Marrow Transplant Registry, we show that summary probability calculations may be useful to explore hypothetical scenarios where some transition intensities are set by the researcher. A multi‐state Markov process model is specified with six states: the initial state 0; acute; chronic and both acute and chronic graft‐versus‐host disease A, C and AC; relapse R and death in remission D. Transition rates between the states are estimated using Nelson–Aalen estimators and Cox regression models and combined to transition probability estimators using Aalen–Johansen product integration. Besides the estimated transition probabilities to D and R we explore hypothetical probabilities obtained by artificially changing certain transition intensities, with the general purposes of getting summary views of the development for actual patients ‘in this world’ and of exploring the intrinsic information from real patients about consequences of various changed conditions. Copyright © 2001 John Wiley & Sons, Ltd.
Whose house is it? Exploring user participation in the design process of residences
Authors: Misra Kajri
Published: September 2002

User participation in the design of built environments has been seen as essential from functional, social, psychological and political perspectives, given the intricacy of human–environment relationships. These concerns are most important in residential environments to which people relate continuously and intimately. This paper explores client–user participation in the architectural design process for their houses. The design process in seven projects by five small architectural firms was analysed in detail to map existing patterns of user participation in India. Significant producers of these patterns include, inter alia, the architect's approach to the project and to client–user participation, the client's awareness of design aspects and expectations of professional services, and the arrangements for interactions and communication; how these modulate the variables is discussed. Finally, the institutional frameworks that configure these factors and the obstacles to change have been highlighted. Copyright © 2002 John Wiley & Sons, Ltd.
Age‐related changes of dopamine D1‐like and D2‐like receptor binding in the F344/N rat striatum revealed by positron emission tomography and in vitro receptor autoradiography
Authors: Suzuki Mitsuru , Hatano Kentaro , Sakiyama Yojiro , Kawasumi Yasuhiro , Kato Takashi , Ito Kengo
Published: September 2002

To clarify age‐related changes in dopamine D1‐like and D2‐like receptor binding in the striatum, positron emission tomography (PET) and in vitro receptor autoradiography (in vitro ARG) were performed using F344/N rats of various ages (6, 12, 18, and 24 months). In the PET study, [11C]SCH23390 and [11C]raclopride were used to image dopamine D1‐like receptors and dopamine D2‐like receptors, respectively, while [3H]SCH23390 and [3H]raclopride were used for the in vitro ARG study. With PET, we calculated the binding potential (= k3/k4, Bmax/Kd) of [11C]SCH23390 and [11C]raclopride in the striatum according to the curve fitting (CF) and the Logan plot (LP) methods. The binding potential of [11C]SCH23390 in the striatum demonstrated significant decrease as a function of age (max. decrease −26%) by the LP method, while this was not observed in the data analyzed by the CF method. In contrast, the binding potential of [11C]raclopride in the striatum decreased significantly with age by both the CF (max. decrease −28%) and the LP (max. decrease −36%) methods. However, no significant difference by either method was observed in rats between 6 and 12 months old using either ligand. In the in vitro ARG study, the specific binding (fmol/mg tissue) of [3H]SCH23390 and [3H]raclopride in the striatum were determined. Both [3H]SCH23390 and [3H]raclopride binding declined considerably with age as noted by comparing 12, 18, and 24‐month‐old rats against those 6 months old (max. decrease −29% and −31%, respectively). The substantial difference in binding shown in 12‐month‐olds in comparison with 6‐month‐olds using either ligand with in vitro ARG was in contrast with the PET results. These distinctions between the PET and the in vitro ARG studies may be attributed to the receptor microenvironment created under these experimental conditions. The results indicate that PET with LP analysis is useful in obtaining age‐related changes of D1‐like and D2‐like receptor binding in the striatum of living rats. Synapse 41:285–293, 2001. © 2001 Wiley‐Liss, Inc.