bluuebunny/crossref_metadata_2025 huggingface dataset:
Activation requirements for the induction of CD4+CD25+ T cell suppressor function
Authors: Thornton Angela M. , Piccirillo Ciriaco A. , Shevach Ethan M.
Published: February 2004

The in vivo differentiation/survival of CD4+CD25+ T suppressor cells is dependent on IL‐2 and CD28‐mediated costimulatory signals. To determine the cytokine and costimulatory requirements for CD25+ T cells in vitro, we established a two‐stage culture system where CD25+ T cells were activated in a primary culture. In the subsequent culture, activated CD4+CD25+ cells were then mixed with responders in order to assess their suppressor function. Pre‐culture of CD25+ T cells with anti‐CD3 alone resulted in poor survival and minimal induction of suppressor activity. Pre‐culture in the presence of anti‐CD3 and IL‐2 or IL‐4, but not IL‐6, IL‐7, IL‐9, IL‐10 or IL‐15, resulted in proliferation of the CD25+ cells and induction of potent suppressor function. Inhibition of the interaction of CD28 or cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4) with CD80/CD86 in the pre‐culture of CD4+CD25+ cells did not prevent the induction of suppressor function. Furthermore, the inhibition of costimulatory signals did not inhibit the ability of fresh CD25+ T cells to inhibit CD8+ responders under conditions where activation of the responders was independent of CD80/CD86. These studies support the view that activation of CD25+ T cells requires IL‐2/IL‐4 for their survival/differentiation into effector cells, but is independent of CD28/CTLA‐4‐mediated costimulation.
SMUCKLER/TIM4 is a distinct member of TIM family expressed by stromal cells of secondary lymphoid tissues and associated with lymphotoxin signaling
Authors: Shakhov Alexander N. , Rybtsov Stanislav , Tumanov Alexei V. , Shulenin Sergey , Dean Michael , Kuprash Dmitry V. , Nedospasov Sergei A.
Published: February 2004

Lymphotoxin‐α (LTα) was originally linked to delayed‐type hypersensitivity and its production was later attributed to Th1, but not Th2 cells. Studies employing knockout mice demonstrated that LT signaling is essential for the development and functional compartmentalization of lymphoid tissues. Here, using gene expression profiling, we identified a novel gene termed SMUCKLER (spleen, mucin‐containing, knockout of lymphotoxin), that is selectively down‐regulated in spleens of LTα‐ or LTβ‐deficient mice. The encoded transmembrane protein contains immunoglobulin V and mucin domains and is identical to TIM4, a predicted member of recently identified TIM family (T cell immunoglobulin‐ and mucin‐domain‐containing molecule). Unlike TIM1 and TIM3, which were implicatedin T cell‐mediated functions, SMUCKLER lacks tyrosine phosphorylation motif in its intracellular domain and is not expressed by bone marrow‐derived cells. In situ hybridization of spleen sections demonstrated SMUCKLER expression by stromal cells predominantly in the marginal zone and to a lesser extent throughout the white pulp. Similarly to other TIM genes, SMUCKLER maps to a locus associated with predisposition to asthma both in mice and in humans (11.b1 and 5q33, respectively) and shows coding sequence variations between BALB/c and DBA mice. Therefore, SMUCKLER/TIM4 may be considered as a candidate disease‐predisposition gene for asthma.
Identification of pro‐interleukin 16 as a novel target of MAP kinases in activated T lymphocytes
Authors: Laurence Arian , Astoul Emmanuelle , Hanrahan Sarah , Totty Nick , Cantrell Doreen
Published: February 2004

T lymphocyte activation is controlled by a coordinated web of tyrosine and serine kinases. There is a large body of information about tyrosine kinase substrates in T cells but analysis of serine kinase substrates has been more difficult. Recently we described an antiserum that recognizes serine‐phosphorylated peptides corresponding to the substrate sequences for AGC serine kinases. This antiserum, termed PAP‐1 (phospho antibody for proteomics‐1), has proven useful for probing the serine phosphoproteome of antigen receptor‐activated T lymphocytes. The present study shows that PAP‐1 can also be used to explore serine kinases activated by cytokines and chemokines in T cells. Using PAP‐1, together with proteomic analysis, the precursor form of the cytokine IL‐16 (ProIL‐16) was shown to be phosphorylated on Ser144 in antigen receptor‐, SDF1α‐ and IL‐2‐activated T cells. Genetic and pharmacological‐inhibitor experiments showed that the phosphorylation of ProIL‐16 is dependent on activation of the kinases Erk1/2. IL‐16 is secreted by mitogen‐activated T cells, and the biochemical link between ProIL‐16 and Erk1/2, revealed by studies with PAP‐1, prompted analysis of the role of MAP kinases in this response. We show that TCR‐mediated secretion of IL‐16 is dependent on MAP kinases. The present study thus reveals how phosphoproteomic analysis opens previously unrecognized avenues for research, and yields novel insights about targets for MAP kinases in T lymphocytes.
Immunoglobulin gene conversion in chicken DT40 cells largely proceeds through an abasic site intermediate generated by excision of the uracil produced by AID‐mediated deoxycytidine deamination
Authors: Noia Javier M. Di , Neuberger Michael S.
Published: February 2004

Diversification of the primary antibody repertoire in chickens is achieved by a gene conversion process that uses a set of immunoglobulin variable (IgV) pseudogenes as templates. Studies usingthe chicken DT40 B lymphoma cell line have shown that this gene conversion is dependent on activation‐induced deaminase, which deaminates deoxycytidine to deoxyuridine in the IgV gene. The mechanism by which the resultant deoxyuridine/deoxyguanosine (dU/dG) mismatch acts to initiate the gene conversion process is unknown but likely involves either (i) recognition of the dU/dG pair by the mismatch repair complex or (ii) recognition of the dU itself by uracil‐DNA glycosylase. To discriminate these possibilities, we have investigated the effects on IgV gene conversion of inhibiting uracil‐DNA glycosylase. We find that such inhibition diminishes gene conversion, biasing instead towards point mutations. These results demonstrate that IgV gene conversion in DT40 cells is substantially dependent on uracil excision and implies that it proceeds by a pathway involving an abasic site, which could be acted upon by an apyrimidinic endonuclease to generate a DNA strand break facilitating the conversion process.
Phage‐displayed libraries of peptide/major histocompatibility complexes
Authors: Dogan Ismail , Dorgham Karim , Chang Hsiu‐Ching , Parizot Christophe , Lemaître Fabrice , Ferradini Laurent , Reinherz Ellis L. , Debré Patrice , Gorochov Guy
Published: February 2004

Characterizing peptide epitopes targeted by major histocompatibility complex (MHC)‐restricted T cells of unknown specificity would have broad implications. In this article we introduce and validate an original phage‐displayed library of noncovalent complexes of peptide and MHC (P/MHC). We show that soluble MHC molecules associate with peptides presented by a phage, thereby resulting in the formation of multivalent P/MHC phages. Complex formation is stabilized by the interaction of the soluble partner (MHC) with two components, peptide and β2‐microglobulin, both of which are covalently linked to the phage. As proof of concept, we have used this strategy to express peptide libraries in the context of H‐2Kb. Using monoclonal antibody 25D (specific for ovalbumin/H‐2Kb) as a template to screen the library, we were able to select a variant epitope functionally and structurally related to the wild‐type peptide. Interaction studies between monoclonal antibody 25D and cells suggest that the variant peptide has been selected on the basis of a decreased dissociation rate between the peptide/H‐2Kb complex and its ligand. A weak agonist of the N15 TCR (vesicular stomatitis virus/H‐2Kb‐specific) was also isolated from another P/MHC library. This strategy opens up new perspectives for antigen discovery and the manipulation of T cell responses.
Synthesis of Nitrogen‐Containing Spiro Compounds from Lactams by Allylboration and Subsequent Ring‐Closing Metathesis
Authors: Nieczypor Piotr , Mol Johannes C. , Bespalova Natalia B. , Bubnov Yuri N.
Published: February 2004

A series of nitrogen‐containing spiro[4.n]alkenes was prepared with excellent yields starting from lactams in two steps: allylboration on the carbonyl carbon and subsequent ring‐closing metathesis of the 2,2‐diallyl N‐heterocycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
An Efficient Route for the Synthesis of New Analogues of Polyaminocarboxylic Acid Incorporating O, N, and S Atoms
Authors: Gouin Sébastien G. , Benoist Eric , Gestin Jean‐François , Meslin Jean Claude , Deniaud David
Published: February 2004

We have synthesised three rigid polycarboxylated hexadentate ligands that differ only in the nature of their heteroatom, either oxygen (1), nitrogen (2), or sulfur (3). These compounds were obtained in four or five steps from substituted orthoanilines after protection/deprotection sequences. An aromatic backbone was chosen to stiffen the structure of the ligands and, thus, facilitate complexation (preorganization concept). A preliminary chelation test revealed a marked selectivity of the nitrogen‐containing ligand for indium‐111. In accordance with the hard and soft acid and base (HSAB) theory, the choice of ligand should result in notable differences in behaviour during complexation and, thus, augment selectivity with regard to the metal. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Exclusive β‐Substitution in the Reaction of Octafluoronaphthalene with Secondary Amines
Authors: Sorokin Vladimir I. , Ozeryanskii Valery A. , Pozharskii Alexander F.
Published: February 2004

The reaction between octafluoronaphthalene and dimethylamine, pyrrolidine or piperidine in DMF, dimethyl(ethylene)urea (DMEU) or without solvent leads to the exclusive substitution of β‐fluorine atoms giving naphthalene derivatives with four NR2 groups. This was proved by 19F NMR of the products and a crystal structure determination for 1,4,5,8‐tetrafluoro‐2,3,6,7‐tetrakis(piperidin‐1‐yl)naphthalene. The main feature of the reaction in DMF was a transamidation process. The remaining four fluorine atoms in the synthesised tetraamines could be smoothly replaced by reduction with LiAlH4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of Peptide‐PNA‐Peptide Conjugates by Semi‐Solid‐Phase Chemical Ligation Combined with Deactivation/Capture of Excess Reactants
Authors: de Koning Martijn C. , Filippov Dmitri V. , van der Marel Gijsbert A. , van Boom Jacques H. , Overhand Mark
Published: February 2004

An expeditious route to peptide‐PNA‐peptide conjugates following a two‐step native chemical ligation (NCL) strategy is described. A cys‐PNA‐thioester is immobilized on PEGA‐aldehyde resin by thiazolidine formation, followed by capping of excess resin aldehydes. The first NCL reaction is then performed with the immobilized PNA‐thioester, to give, after release from the solid support, the cys‐PNA‐peptide intermediate with relatively high purity. The latter is then converted into the target compound by the second NCL reaction with a thioester peptide, the excess of which is captured using a cysteine‐PEGA resin. The resulting peptide‐PNA‐peptide can then be readily isolated by a simple purification step. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
One‐Pot Ring‐Closing Metathesis‐Alkene Cross Metathesis Reactions of Sulfamide‐Linked Enynes
Authors: Salim Sofia S. , Bellingham Richard K. , Brown Richard C. D.
Published: February 2004

Ring‐closing metathesis (RCM) of sulfamide‐linked enynes 7, 11 and 12 containing disubstituted alkynes afforded a series of novel 7‐membered cyclic sulfamides 13−15 in good yield. Substrates 5, 9 and 10 containing mono‐substituted alkynes gave either simple RCM products 18a−c or those arising from combinations of enyne RCM and olefin cross metathesis 16/17a−c depending on the reaction conditions. Notably, in the presence of two equivalents of styrene or ethyl acrylate, substrates 5, 9 and 10 containing terminal alkynes underwent selective enyne‐RCM‐olefin‐cross metathesis to provide cyclic sulfamides 17a−c and 19b,c in yields of 54−83%. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Regime switching in the yield curve
Authors: Christiansen Charlotte
Published: February 2004

The article investigates the effect of interest‐rate variance on the shape of the yield curve with the
use of a bivariate two‐state Markov switching model for the short‐rate changes and the yield curve
slope. The two states are characterized by the variance of the short‐rate changes: low and high variance.
In the high‐variance regime the yield curve becomes steeper with the interest‐rate variance; in
the low‐variance regime the slope is independent hereof. A nonswitching specification amounts to
averaging across the two states. The economy is in the high‐variance state during unusual economic
periods. © 2004 Wiley Periodicals, Inc. Jrl Fut Mark 24:315–336, 2004
The index futures markets: Is screen trading more efficient?
Authors: Copeland Laurence , Lam Kin , Jones Sally‐Ann
Published: February 2004

This article uses a nonparametric test based on the arc‐sine law (see, e.g., Feller, 1965), which involves comparing the theoretical distribution implied by an intraday
random walk with the empirical frequency distribution of the daily high/low times, in order to address the
question of whether the abandonment of pit trading has been associated with greater market efficiency. If market
inefficiencies result from flaws in the market microstructure of pit trading, they ought to have been eliminated
by the introduction of screen trading. If, on the other hand, the inefficiencies are a reflection of investor
psychology, they are likely to have survived, unaffected by the changeover. We focus here on four cases. Both the
FTSE‐100 and CAC‐40 index futures contracts were originally traded by open outcry and have moved
over to electronic trading in recent years, so that we are able to compare pricing behavior before and after the
changeover. The equivalent contracts in Germany and Korea, on the other hand, have been traded electronically
ever since their inception. Our results overwhelmingly reject the random‐walk hypothesis both for
open‐outcry and electronic‐trading data sets, suggesting there has been no increase in efficiency
as a result of the introduction of screen trading. One possible explanation consistent with our results would be
that the index futures market is characterized by intraday overreaction. © 2004 Wiley Periodicals, Inc. Jrl
Fut Mark 24:337–357, 2004
Metabolism of Deuterated threo‐Dihydroxy Fatty Acids in Saccharomyces cerevisiae: Enantioselective Formation and Characterization of Hydroxylactones and γ‐Lactones
Authors: Garbe Leif‐A. , Tressl Roland
Published: February 2004

Biotransformation of (±)‐threo‐7,8‐dihydroxy(7,8‐2H2)tetradecanoic acids (threo‐(7,8‐2H2)‐3) in Saccharomyces cerevisiae afforded 5,6‐dihydroxy(5,6‐2H2)dodecanoic acids (threo‐(5,6‐2H2)‐4), which were converted to (5S,6S)‐6‐hydroxy(5,6‐2H2)dodecano‐5‐lactone ((5S,6S)‐(5,6‐2H2)‐7) with 80% e.e. and (5S,6S)‐5‐hydroxy(5,6‐2H2)dodecano‐6‐lactone ((5S,6S)‐5,6‐2H2)‐8). Further β‐oxidation of threo‐(5,6‐2H2)‐4 yielded 3,4‐dihydroxy(3,4‐2H2)decanoic acids (threo‐(3,4‐2H2)‐5), which were converted to (3R,4R)‐3‐hydroxy(3,4‐2H2)decano‐4‐lactone ((3R,4R)‐9) with 44% e.e. and converted to 2H‐labeled decano‐4‐lactones ((4R)‐(3‐2H1)‐ and (4R)‐(2,3‐2H2)‐6) with 96% e.e. These results were confirmed by experiments in which (±)‐threo‐3,4‐dihydroxy(3,4‐2H2)decanoic acids (threo‐(3,4‐2H2)‐5) were incubated with yeast. From incubations of methyl (5S,6S)‐ and (5R,6R)‐5,6‐dihydroxy(5,6‐2H2)dodecanoates ((5S,6S)‐ and (5R,6R)‐(5,6‐2H2)‐4a), the (5S,6S)‐enantiomer was identified as the precursor of (4R)‐(3‐2H1)‐ and (2,3‐2H2)‐6). Therefore, (4R)‐6 is synthesized from (3S,4S)‐5 by an oxidation/keto acid reduction pathway involving hydrogen transfer from C(4) to C(2).

In an analogous experiment, methyl (9S,10S)‐9,10‐dihydroxyoctadecanoate ((9S,10S)‐10a) was metabolized to (3S,4S)‐3,4‐dihydroxydodecanoic acid ((3S,4S)‐15) and converted to (4R)‐dodecano‐4‐lactone ((4R)‐18).
Synthesis of (±)‐Kempa‐6,8‐dien‐3‐ol (=(2aRS,3SR,4aSR,7RS,7aSR,10bSR,10cSR)‐2,2a,3,4,4a,5,6,7,7a,8,10b,10c‐Dodecahydro‐2a,7,10,10c‐tetramethylnaphth[2,18‐cde]azulen‐3‐ol)
Authors: Kato Tadahiro , Tanaka Motoyuki , Takagi Shin‐suke , Nakanishi Keita , Hoshikawa Masahiro
Published: February 2004

The synthesis of kempa‐6,8‐dien‐3β‐ol (4a), as a synthetic leading model of the natural product 4b, was carried out starting from intermediate 12, the synthetic route of which has been developed previously (Scheme 1). The conversion of 12 to the model compound 4a involved the elaboration of three structure modifications by three processes, Tasks A, B, and C (see Scheme 2). Task A was achieved by epoxy‐ring opening of 41 with Me3SiCl (Scheme 9), and Task B being performed by oxidation at the 13‐position, followed by hydrogenation, and then epimerization (Schemes 4 and 5). The removal of the 2‐OH group from 12 (Task C) was achieved via 30b according to Scheme 6, whereby 30b was formed exclusively from 30a/31a 1 : 1 (Scheme 7). In addition, some useful reactions from the synthetic viewpoint were developed during the course of the present experiments.
Berberine/γ‐Cyclodextrin Inclusion Structure Studied by 1H‐NMR Spectroscopy and Molecular‐Dynamics Calculations
Authors: Kamigauchi Miyoko , Kanbara Narumi , Sugiura Makiko , Iwasa Kinuko , Ohishi Hirofumi , Ishida Toshimasa
Published: February 2004

To understand the increased solubility and decreased bitter taste of berberine, a clinically important isoquinoline alkaloid, in the presence of cyclodextrins, the interaction with γ‐cyclodextrin (γ‐CD) in aqueous solution was studied by a combination of 1H‐NMR analyses and molecular‐dynamics calculations. The proposed complexation mode of berberine by γ‐CD could explain the increased solubility in water. No difference in germicidal activity between berberine alone and its inclusion complex with γ‐ or β‐CD was observed, which is important to further develop the pharmacological application of berberine.
Palladium‐MOP Chemistry: Pseudo‐cis‐Allyl MOP Complexes and Flexible Olefin Bonding. Preliminary Communication
Authors: Dotta Pascal , Kumar P. G. Anil , Pregosin Paul S. , Albinati Alberto
Published: February 2004

We show that both palladium(0) and palladium(II) metal centers are capable of coordinating two monodentate MOP (=(R)‐2‐(diarylphosphino)‐1,1′‐binaphthalene) ligands in a pseudo‐cis orientation, despite published statements to the contrary. In addition to [Pd(η3‐C3H5)(MeOMOP)2]BF4 (MeOMOP=(R)‐2‐(diphenylphosphino)‐2′‐methoxy‐1,1′‐binaphthalene), the first examples of chiral bis κC1‐prop‐2‐enyl (η1‐CH2CHCH2) complexes [cis‐Pd(κC1‐C3H5)2(MeOMOP or MOP)2], are shown to be relatively stable. Further, coordinated MOP and MeOMOP both show stronger propensity towards novel intramolecular π‐olefin complexation than the CNMOP analogue. The solid‐state structure of [Pd(fumaronitrile)(MOP)2] is reported.
Phosphodiesterase‐Inhibiting Glycosides from Symplocos racemosa
Authors: Ahmad Viqar Uddin , Abbasi Muhammad Athar , Zubair Muhammad , Fatima Naheed , Farooq Umar , Choudhary M. Iqbal
Published: February 2004

Phytochemical investigation of Symplocos racemosa resulted in the isolation of two new glycosides, symploracemoside (1) and symplomoside (2), which are structurally related to the reported benzoylsalireposide (3) and salireposide (4). The structure elucidation of the isolated compounds was based primarily on 1D‐ and 2D‐NMR analysis, including COSY, NOESY, HMQC, and HMBC correlations. These glycosides showed inhibitory activity against snake‐venom phosphodiesterase I.
Construction of a GBS‐GAS DNA subtraction library allows discovery of previously unidentified GBS genes and rapid location of unique regions on the GBS chromosome
Authors: Suvorov Alexander N. , Ferretti Joseph J.
Published: February 2004

A subtraction library of group B streptococcus (GBS) strain O9OR with GAS chromosomal DNA (strain SF370) was constructed and more than 100 plasmid clones sequenced. DNA sequences of the plasmid inserts were analyzed using the BLAST gene search. Most inserts had little or no homology to GAS chromosomal DNA and 26 clones from the library had no gene homologues in the gene bank. The majority of genes discovered represented house keeping GBS genes, but several could be considered as possible virulence factors. Inserts from 21 clones were labeled and used as probes for hybridization with GBS DNA fragments separated by pulsed field electrophoresis. A genetic map of GBS strain O9OR was constructed.
Examination of membrane protein expression in Paracoccus denitrificans by two‐dimensional gel electrophoresis
Authors: Bouchal Pavel , Kučera Igor
Published: February 2004

The well‐known metabolic versatility of the soil bacterium Paracoccus denitrificans poses a challenge for modern proteomic approaches. We describe here improved preparation conditions that allow good separation and quantitative analyses of hundreds of membrane or periplasmic proteins. To illustrate this optimized procedure, the results of a screening for membrane proteins associated predominantly with aerobic or anaerobic (denitrifying) modes of growth are presented.
Isolation and characterization of pathogenic Vibrio alginolyticus from diseased cobia Rachycentron canadum
Authors: Liu Ping‐Chung , Lin Ji‐Yang , Hsiao Pei‐Tze , Lee Kuo‐Kau
Published: February 2004

Outbreaks of serious mortality among cultured juvenile cobia Rachycentron canadum L. (weighing 8–10 g) characterized by lethargy, dark skin and ascites in the peritoneal cavity while some fish possessing damaged eyes occurred in July and August of 2001 in Taiwan. Fifteen motile bacterial strains were isolated from head kidney and/or the ascites on tryptic soy agar supplemented with 1% NaCl (TSA1) and/or thiosulphate citrate bile salt (TCBS) sucrose agar plates during the two outbreaks. All the isolates were characterized and identified as Vibrio alginolyticus on the basis of biochemical characteristics, and comparisons with those of the reference strain V. alginolyticus ATCC 17749. The strain C3c01 (a representative of the 15 similar field isolates), was virulent to the cobia with an LD50 value of 3.28 × 104 colony forming units/g fish body weight. All the moribund/dead fish exhibited lethargy, dark skin and ascites in the peritoneal cavity as that observed in natural outbreaks. The same bacteria could be reisolated from kidney and the ascites of fish after bacterial challenge using TSA1 and TCBS plates. The results reveal that V. alginolyticus is an infectious agent of vibriosis in the cobia.
The synergy between deformation and anodic dissolution of an austenitic stainless steel in acidic chloride solution
Authors: Yanliang H.
Published: February 2004

In corrosion medium, metals can deform under tensile stress and form a new active surface with the anodic dissolution of the metals being accelerated. At the same time, the anodic dissolution may accelerate the deformation of the metals. The synergy can lead to crack nucleation and development and shorten the service life of the component. Austenitic stainless steel in acidic chloride solution was in active dissolution condition when stress corrosion cracking (SCC) occurred. It is reasonable to assume that the anodic dissolution play an important role, so it's necessary to study the synergy between anodic dissolution and deformation of austenitic stainless steels. The synergy between deformation and anodic dissolution of AISI 321 austenitic stainless steel in an acidic chloride solution was studied in this paper. The corrosion rate of the steel increased remarkably due to the deformation‐accelerated anodic and cathodic processes. The creep rate was increased while the yield strength was reduced by anodic dissolution. The analysis by thermal activation theory of deformation showed a linear relationship between the logarithm of creep rate and the logarithm of anodic current. Besides, the reciprocal of yield strength was also linearly dependent on the logarithm of anodic current. The theoretical deductions were in good agreement with experimental results.
A solution to identities problem in 2‐element HSI‐algebras
Authors: Asatryan Gurgen R.
Published: February 2004

All arithmetical identities involving 1, addition, multiplication and exponentiation are valid in every 2‐element HSI‐algebra. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Quasi‐complements of the cappable degrees
Authors: Wu Guohua
Published: February 2004

Say that a nonzero c. e. degree b is a quasi‐complement of a c. e. degree a if a ∩ b = 0 and a ∪ b is high. It is well‐known (due to Shore) that each cappable degree has a high quasi‐complement. However, by the existence of the almost deep degrees, there are nonzero cappable degrees having no low quasi‐complements. In this paper, we prove that any nonzero cappable degree has a low2 quasi‐complement. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Low‐temperature route to thermoplastic polyamide elastomers
Authors: Rabani Gouher , Rosair Georgina M. , Kraft Arno
Published: February 2004

Thermoplastic polyamide elastomers were obtained by polymerization of aminobenzoyl‐substituted telechelics derived from poly(tetrahydrofuran)‐diols (number‐average molecular weight: 1400 or 2000 g mol−1) with several diacid dichlorides (terephthaloyl dichloride, 4,4′‐biphenyldicarbonyl dichloride, or 2,6‐naphthalenedicarbonyl dichloride) and chlorotrimethylsilane in N,N‐dimethylacetamide at 0–20 °C. The as‐prepared polymers had melting temperatures above 190 °C and exhibited elastic properties at room temperature, as evidenced by dynamic mechanical analysis and stress–strain measurements. The polymer with 2,6‐naphthalenedicarboxamide hard segments had the widest rubbery plateau within the series, the highest extension at break, and good recovery properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1449–1460, 2004
Effect of the synthetic method and support porosity on the structure and performance of silica‐supported CuBr/pyridylmethanimine atom transfer radical polymerization catalysts. I. Catalyst preparation and characterization
Authors: Nguyen Joseph V. , Jones Christopher W.
Published: February 2004

Silica‐supported CuBr/pyridylmethanimine (PMI) complexes that facilitate the atom transfer radical polymerization of methyl methacrylate have been prepared and characterized. Four different synthetic routes, including multistep‐grafting (M1), two‐step‐grafting (M2), one‐pot (M3), and preassembled‐complex (M4) methods, have been evaluated on three different silica supports (mesoporous SBA15 with 48‐ and 100‐Å pores and nonporous Cab‐O‐Sil EH5). The resulting solids have been characterized by a battery of techniques, including thermogravimetric analysis/differential scanning calorimetry, FT‐Raman spectroscopy, 13C and 29Si magic‐angle‐spinning and cross‐polarity/magic‐angle‐spinning spectroscopy, low‐temperature nitrogen physisorption, and elemental analysis. The combination of elemental analysis and spectroscopic results has indicated that a variety of different surface species likely exist for most catalysts, including copper species that are both monocoordinated and biscoordinated by PMI ligands, and PMI‐free copper bromide species interacting with the silica surface. M4 appears to give a material that has the smallest amount of the uncomplexed ligand (by FT‐Raman spectroscopy) and is, therefore, the most homogeneous. After M4, the metallation efficiency decreases in the order M2 ≥ M3 > M1, with M1 giving a material with a highly heterogeneous surface composition. The ligand loading on all the catalysts has been determined to be approximately 1 mmol/g of SiO2, with Cab‐O‐Sil‐supported materials giving much higher ligand densities because of its lower surface area. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1367–1383, 2004
Effect of the synthetic method and support porosity on the structure and performance of silica‐supported CuBr/pyridylmethanimine atom transfer radical polymerization catalysts. II. Polymerization of methyl methacrylate
Authors: Nguyen Joseph V. , Jones Christopher W.
Published: February 2004

A systematic study of the effect of the synthesis method and catalyst structure on the atom transfer radical polymerization (ATRP) performance of copper(I) bromide/pyridylmethanimine complexes supported on silica is described. Four different synthetic routes, including multistep‐grafting (M1), two‐step‐grafting (M2), one‐pot (M3), and preassembled‐complex (M4) methods, have been evaluated on three different silica supports (mesoporous SBA15 with 48‐ and 100‐Å pores and nonporous Cab‐O‐Sil EH5). The resulting solids have been used for ATRP of methyl methacrylate. The catalysts allow for moderate to poor control of the polymerization, with polydispersity indices (PDIs) ranging from 1.46 to greater than 2. The materials made with the preassembled‐complex (M4) and one‐pot (M3) approaches are generally more effective than those prepared with a grafting method (M1 and M2) on porous silica, whereas all the methods provide similarly performing catalysts on the nonporous support. Nonporous Cab‐O‐Sil EH5 is the most effective support because of its small particle size, lack of porosity, and relative compatibility in the reaction media. All the catalysts leach copper into solutions in small amounts. In addition, the catalysts can be effectively recycled, with improved controlled character in recycle runs (PDI ∼ 1.2). Control experiments have shown that this improved performance of the used catalysts is likely due to the presence of a soluble Cu(II) complex in the materials that effectively deactivates the growing polymer chain, leading to narrow PDIs and controlled molecular weights. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1384–1399, 2004
Dendritic aromatic polyamides and polyimides
Authors: Jikei Mitsutoshi , Kakimoto Masa‐aki
Published: February 2004

The syntheses and properties of dendritic and hyperbranched aromatic polyamides and polyimides are reviewed. In addition to conventional stepwise reactions for dendrimer synthesis, an orthogonal/double‐stage convergent approach and dendrimer syntheses with unprotected building blocks are described as new synthetic strategies for dendritic polyamides. Hyperbranched polyamides and polyimides composed of various repeating units are presented. Besides the self‐polycondensation of AB2‐type monomers, new polymerization systems with AB4, AB8, A2 + B3, and A2 + BB′2 monomers have been developed for hyperbranched polyamides and polyimides. The copolymerization of AB2 and AB monomers is discussed separately with respect to the effects of branching units on the properties. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 1293–1309, 2004
Formation of hydrogen bonding in ionized poly(N‐isopropylacrylamide) gels by continuous water exchange
Authors: Hirashima Y. , Tamanishi H. , Sato H. , Saito K. , Naito A. , Suzuki A.
Published: February 2004

The effects of continuous water exchange on the swelling behavior of poly(N‐isopropylacrylamide‐co‐sodium acrylate) gel were studied. The diameter of gels and the Na+ concentration in the solvent were measured at several constant intervals after the solvent (the distilled deionized water) was exchanged. The diameter decreased at room temperature as the solvent was exchanged with water, and it continued to decrease even after more than about 97% of the initial Na+ diffused into the water. Thus, the final swelling ratio of the gel was only slightly larger than that of the neutral poly(N‐isopropylacrylamide) gel. To reveal the structural change in molecular level, solid‐state 13C cross‐polarization/magic‐angle spinning, solid‐state 1H combined rotation and multiple‐pulse spectroscopy, and swollen‐state 13C dipolar decoupled/magic‐angle spinning NMR experiments were carried out for several dried and swollen samples by varying the times of water exchange. As a result, the intensity and position of the carboxyl peak changed, and the relative intensity of the nonionized carboxyl groups of gels increased with an increasing number of water exchanges. These results indicated that hydrogen bonding was formed between the two, nonionized carboxyl groups (COOH) and/or between the COOH and CONH groups. The macroscopic polymer network shrinkage is discussed in terms of the replacement of counterions Na+ by H+ and of the formation of intermolecular hydrogen bonding. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1090–1098, 2004
Thermally stimulated depolarization current in electron‐irradiated poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers
Authors: Guo S. S. , Li W. P. , Zhao X.‐Z. , Peng Z. , Lau S. T. , Chan H. L. W. , Choy C. L.
Published: February 2004

The effect of electron irradiation on poly(vinylidene fluoride‐trifluoroethylene) (56/44 mol %) copolymers was studied with dielectric constant measurements, differential scanning calorimetry (DSC), X‐ray diffraction, thermally stimulated depolarization current (TSDC) spectroscopy, and polarization hysteresis loops. The dielectric relaxation peaks, obeying the Vogel–Fulcher law, indicated that the copolymers were transformed from a normal ferroelectric to a relaxor ferroelectric. The X‐ray and DSC results showed that both the crystalline and polar ordering decreased after irradiation, indicating a partial recovery from trans–gauche bonds to local trans bonds (polar ordering). Moreover, the peak temperature decreased with the irradiation dose in the TSDC spectra; this demonstrated fewer dipoles and crystalline regions in the irradiated copolymer films during the ferroelectric–paraelectric transition and was consistent with polarization hysteresis loop measurements. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1099–1105, 2004
Inhibition of microbial growth in ready‐to‐eat food stored at ambient temperature by modified atmosphere packaging
Authors: Chen S. C. , Lin C.‐A. , Fu A.‐H. , Chuo Y. W.
Published: February 2004

This study was undertaken to develop a modified atmosphere package to control microbial growth in ready‐to‐eat (RTE) products stored at ambient temperature. Ethanol and/or limonene associated with modified atmosphere (CO2 : O2 : N2 = 30% : 5% : 65%) was used to inhibit the growth of total air‐borne microorganisms and Escherichia coli in RTE products stored at 25°C. The results indicated that 0.05% ethanol vapour in the headspace was effective to inhibit the growth of air‐borne microorganisms and E. coli at 25°C for 72 h in a model study, and the effectiveness was related to ethanol content. Both 73 ppm limonene and 0.05% ethanol vapour enhanced the bacteriostatic effect of modified atmosphere in RTE sushi roll products, and no off‐flavour was detected using this formulated gas; however, no significant inhibitory effect was observed for RTE cold noodle products. This study concludes that combinations of carbon dioxide, ethanol or limonene vapours are effective to inhibit microbial growth in RTE food at ambient temperature, and the outcome may be due to the hurdle effect. Copyright © 2003 John Wiley & Sons, Ltd.
Simulation of dispersionless injections and drift echoes of energetic electrons associated with substorms
Authors: Li Xinlin , Baker D. N. , Temerin M. , Reeves G. D. , Belian R. D.
Published: February 2004

The term “dispersionless injection” refers to a class of events which show simultaneous enhancement (injection) of electrons and ions with different energies usually seen at or near geosynchronous orbit. We show that dispersionless injections can be understood as a consequence of changes in the electric and magnetic fields by modeling an electron injection event observed early on January 10, 1997 by means of a test‐particle simulation. The model background magnetic field is a basic dipole field made asymmetrical by a compressed dayside and a weakened nightside. The transient fields are modeled with only one component of the electric field which is westward and a consistent magnetic field. These fields are used to model the major features of a dipolarization process during a substorm onset. We follow the electrons using a relativistic guiding center code. Our simulation results, with an initial kappa electron energy flux spectrum, reproduce the observed electron injection and subsequent drift echoes and show that the energization of injected electrons is mainly due to betatron acceleration of the preexisting electron population at larger radial distances in the magnetotail by transient fields.
Heterogeneous chemistry of NO2 on mineral oxide particles: Spectroscopic evidence for oxide‐coordinated and water‐solvated surface nitrate
Authors: Miller T. M. , Grassian V. H.
Published: February 2004

In this study, transmission FT‐IR and diffuse reflectance UV‐vis spectroscopies were used to probe the heterogeneous chemistry of gaseous nitrogen dioxide on mineral oxide particles. In particular, the role of pre‐ and post‐adsorbed water on the heterogeneous chemistry of NO2 on Al2O3 and TiO2 was investigated. At 298 K, NO2 reacts with the surface of these mineral oxides to form surface nitrite and nitrate. The spectroscopic data show that two distinct types of surface nitrate exist, oxide‐coordinated and water‐solvated nitrate. The relative amounts of oxide‐coordinated and water‐solvated nitrate are dependent on the coverage of adsorbed water on the surface of the mineral oxide particle. The importance of this water layer in the heterogeneous atmospheric chemistry of mineral oxide aerosol is discussed.
On the mechanisms controlling the formation and properties of volatile particles in aircraft wakes
Authors: Yu Fangqun , Turco Richard P. , Kärcher Bernd , Schröder Franz P.
Published: February 2004

New observations taken in aircraft wakes, including the DLR ATTAS, provide strong constraints on models of aircraft plume aerosols. Using a comprehensive microphysics code, we have performed sensitivity studies to identify the key microphysical mechanisms acting in such plumes. Analysis of these simulations reveals that the largest volatile plume particles—those most likely to contribute to the background abundance of condensation nuclei—are dominated by ion‐mode particles when chemiions are included. Moreover, such modeling demonstrates that standard treatments of plume microphysics—in the absence of chemiions—fails to explain field measurements. The principal factor controlling the population of ultrafine plume particles is the number of chemiions emitted by the aircraft engines. Since the ions are a byproduct of the combustion itself, and their abundance in the exhaust stream is controlled by ion‐ion recombination, the initial ion concentrations—and so the eventual emission indices for ion‐mode particles—are expected to be relatively invariant. Our results indicate that reductions in fuel sulfur content, while not likely to lower the total number of volatile particles emitted, would decrease the size of the ion‐mode particles in fresh aircraft wakes, reducing their atmospheric lifetimes and potential environmental effects.
Coupled ocean‐atmospheric waves on the equatorial front
Authors: Xie Shang‐Ping , Ishiwatari Masaki , Hashizume Hiroshi , Takeuchi Kensuke
Published: February 2004

Striking 20–30‐day sea surface temperature waves observed along the equatorial front in the later half of the year are generally believed to be of an oceanic origin. Here we report the detection of atmospheric waves that are unambiguously tied to these oceanic waves, using new satellite measurements of surface winds. A general circulation model simulation reveals that these atmospheric waves have a shallow vertical structure trapped in the planetary boundary layer (PBL), unlike El Nino/Southern Oscillation where changes in deep convection are the cause of anomalous winds. Vertical wave motion penetrates well above the PBL and is likely to impact the distribution and transport of climatically important gas species such as ozone and dimethyl sulfide.
Plasma and magnetic flux transport associated with auroral breakups
Authors: Lui A. T. Y. , Liou K. , Newell P. T. , Meng C.‐I. , Ohtani S.‐I. , Ogino T. , Kokubun S. , Brittnacher M. J. , Parks G. K.
Published: February 2004

Auroral breakups are the first visible sign of a substorm expansion onset. Keying the plasma sheet behavior to onset times of auroral breakups may help to identify the substorm onset process. With this goal in mind, we have identified a list of auroral breakups based on global imaging data from the Ultraviolet Imager of the POLAR spacecraft for two favorable viewing periods and have examined the simultaneous plasma measurements in the tail from GEOTAIL. Synoptic patterns of plasma transport and magnetic field changes in the tail surrounding the times of auroral breakups are constructed. The results indicate that the plasma sheet activities associated with auroral breakups are transient and spatially localized. These findings are consistent with the scenario in which expansion phase activities are dominated by localized, transient disturbances as portrayed by the substorm synthesis model.
First observations of type‐1 sporadic E Irregularities in the equatorial anomaly region using the Chung‐Li VHF radar
Authors: Huang Chien‐Ming , Chu Yen‐Hsyang
Published: February 2004

In this paper we present the characteristics of mid‐latitude irregularities first observed with the 52 MHz Chung‐Li radar. Intense type‐1 echoes with Doppler velocities of about 270 m/s (slightly smaller than the nominal ion‐acoustic wave speed of 360 m/s) in the height range from 103.1 km to 104.5 km lasted for about 2 minutes. The range‐time variations of sequential power spectra indicate that the patch of type‐1 irregularities moved toward the radar at a rate of about 42 m/s. The zonal drift motions of the type‐1 and type‐2 irregularities obtained from an interferometry technique showed that the irregularities drifted eastward with an average speed of 84 m/s.
The effect of the tilt of the HCS on the solar wind speed in the outer heliosphere
Authors: Richardson J. D. , Wang C.
Published: February 2004

The flow of solar wind from the Sun is bimodal. High speed, low density plasma comes from high magnetic latitude regions and low speed, high density flow from near the heliospheric current sheet (HCS). We investigate whether this bimodal flow combined with the HCS tilt controls the solar wind velocities in the outer heliosphere near solar minimum when the Sun's magnetic field is roughly dipolar. We present a simple model of radial solar wind flow with regions of fast and slow flow and a HCS tilt provided by the Wilcox Solar Observatory. This is the first time a model has been used to make quantitative predictions of the solar wind speed in the outer heliosphere based on solar observations. A reasonable fit to the main features of the observed velocity profile at Voyager 2 is obtained if the full‐width of the slow speed region is 30°. We conclude that the main physical parameter determining the solar wind speed observed by Voyager 2 near solar minimum in the outer heliosphere is the tilt of the HCS.
Alongslope current generated by obliquely incident internal gravity waves
Authors: Dunkerton Timothy J. , Delisi Donald P. , Lelong M.‐Pascale
Published: February 2004

A simple laboratory experiment in stratified salt water demonstrates that an obliquely incident internal gravity wave generates a mean horizontal current when approaching a sloping boundary from above. The alongslope current is in the same direction as the transverse component of wave propagation and coexists with a turbulent bore propagating diagonally up and along the slope. Mean‐flow generation is observed for vertical angles of incidence above and below the critical angle as well as for steeper angles in which the viscous dissipation of waves is smaller initially.
Diurnal occurrence of thin metallic ion layers in the high‐latitude ionosphere
Authors: Bedey D. F. , Watkins B. J.
Published: February 2004

Evidence is presented that during the summer months intense (density greater than 105 cm−3), thin metallic ion layers are most likely to occur in the lower E region over Sondrestrom, Greenland, during the period 2200–0100 UT (∼2000–2300 MLT), based on a three‐year series of incoherent‐scatter radar observations. In the high‐latitude ionosphere, theory indicates that a convective electric field with a westward component should be conducive to layer formation. However, we observed that the presence of a favorable electric field does not guarantee the existence of intense thin layers. We suggest that the preferred time of occurrence and the apparent insufficiency of westerly electric fields to produce detectable layers is caused by variation in ion abundance. Our observational results are shown to be consistent with a previously published model of the large‐scale, horizontal transport of metal ions which predicts enhanced metallic ion abundances at the same time that layers are most frequently observed.
Evolution of tropospheric ozone radiative forcing
Authors: Stevenson D. S. , Johnson C. E. , Collins W. J. , Derwent R. G. , Shine K. P. , Edwards J. M.
Published: February 2004

We present the first estimate of the evolution of tropospheric ozone (O3(T)) radiative forcing since 1860 and into the future. The UKMO 3‐D chemistry‐transport model (STOCHEM) was used to simulate the tropospheric composition in 1860, 1950, 1970, 1990 and 2100, by changing trace gas emissions. The future scenario used a doubled CO2 climate. STOCHEM includes extensive non‐methane hydrocarbon (NMHC) chemistry, and produces a reasonable simulation of present‐day O3(T). Radiative forcings caused by the modelled changes in O3(T) since 1860 were calculated using the UKMO radiation code, and included clouds and stratospheric temperature adjustment. Calculated changes in the global annual mean forcing since 1860 were 0.13, 0.22, 0.29 and 0.48 W m−2 for the four years. Up to 1990 this forcing scales linearly with the change in total NOx emissions since 1860; this linearity breaks down in 2100. The 1990 forcing is at the lower end of the range from previous modelling studies (0.28–0.51 W m−2), but is still significant, enhancing the well‐mixed greenhouse gas forcing by over 10%.
Diurnal oscillations in atmospheric pressure at twenty‐five small oceanic islands
Authors: Ray Richard D.
Published: February 2004

The diurnal oscillation in atmospheric surface pressure—the S1(p) tide—is estimated at 25 oceanic stations. The estimated mean amplitudes and phases are compared to two theoretical predictions of the migrating S1 component recently computed by Braswell and Lindzen and to the older wavenumber‐1 decomposition of Haurwitz and Cowley. The new S1 amplitudes are weaker than the Haurwitz‐Cowley amplitudes everywhere, suggesting that their model may have been unduly influenced by nonmigrating components from continental stations. The observations show best agreement with a theoretical model having 25 W m−2 additional atmospheric energy absorption relative to that inferred from general circulation models. Stations polewards of the S1 critical latitude are somewhat anomalous.