bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of catalysts on the reaction of an aliphatic isocyanate and water
Authors: Ni Hai , Nash Heather A. , Worden James G. , Soucek Mark D. 
Published: August 2002

AbstractThe kinetics of the reaction of aliphatic isocyanate with water were investigated with hexyl isocyanate as a model compound. The kinetic study was carried out with a titration method to determine the concentration of the isocyanate group as a function of time. Gas chromatography was used to augment the kinetic data obtained from the titration method. The effects of an organic acid [p‐toluene sulfonic acid monohydrate (p‐TSA)], a tertiary amine {diazabicyclo[2.2.2]octane (DABCO)}, and an organotin compound [dibutyltin dilaurate (DBTDL)] on the reaction were investigated for the conversion of isocyanate to a urea. Under the reaction conditions in this study, urea was the only product observed. The rate constants indicated that p‐TSA had low catalytic activity, DABCO had intermediate catalytic activity, and DBTDL had high catalytic activity. A reaction mechanism was proposed for each of the catalysts. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1677–1688, 2002
Crosslinkable maleimide copolymers for stable NLO properties
Authors: Serhatli İ. E. , Yagci Y. , Hattemer E. , Zentel R. , Schmälzlin E. , Hohenadl S. , Bräuchle C. , Meerholz K. 
Published: August 2002

AbstractSecond‐order, nonlinear optical polymers based on epoxy‐substituted methylvinylisocyanates and N‐substituted maleimides were synthesized and characterized with spectral and thermal analysis. The photocrosslinking and thermal‐crosslinking reactions of copolymers with different chromophore contents were studied. Thermally induced crosslinking during the poling process, performed at the glass‐transition temperature (Tg), was prevented by Tg being decreased through the addition of a plasticizer. Electrooptic coefficients (r33), measured for crosslinked and noncrosslinked systems, had similar absolute values and relaxation dynamics. This behavior was explained in terms of the similar rotational mobility of the chromophore units and the paucity of crosslinking sites. © 2001 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 1589–1595, 2001
Annealing‐induced increase of permeability and amorphous‐phase mobility in an ethylene–vinylacetate copolymer
Authors: Gelfer M. Y. , Waddon A. , Schmidt‐Rohr K. , Gale R. , Kleiner L. , Berggren R. 
Published: August 2002

AbstractThe 50% increased permeability after annealing of semicrystalline poly(ethylene/vinylacetate) containing 3 mol % vinylacetate is linked to increased mobility in the amorphous phase, as identified by line‐narrowing of 1H wideline nuclear magnetic resonance (NMR) spectra and by reduced cross‐polarization efficiency in 13C NMR. Other morphological parameters, such as crystallinity, measured as 30 to 35% by differential scanning calorimetry (DSC) and NMR, are hardly changed by annealing. Small‐angle X‐ray scattering and NMR studies, using spin diffusion as well as T1ρ and T1 relaxation, detected only a small increase in crystallite thickness. The annealing‐induced enhancement in segmental mobility in the amorphous regions corresponds to a temperature shift of about 10 K, from which an increase of the motional rate by a factor of 2 is estimated, and which can account for the enhancement in the permeability. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2774–2780, 2001
Analysis of blends of poly(styrene‐co‐acrylonitrile) with an epoxy/aromatic amine resin using scanning thermal microscopy
Authors: Barral L. , Cano J. , Díez F. J. , López J. , Ramírez C. , Abad M. J. , Ares A. 
Published: August 2002

AbstractUsing a microthermal analyzer TA Instruments 2990 μTA, we have analyzed the morphologies developed for the resin tetraglycidyl‐4,4′‐diaminodiphenylmethane cured with an aromatic amine 4,4′‐diaminodiphenylsulphone modified with different amounts of poly(styrene‐co‐acrylonitrile) (SAN) thermoplastic. The phase‐separation phenomenon induced by polymerization was also followed by scanning electron microscopy. Using the modulated local thermal‐analysis mode of μTA, the glass‐transition temperatures of different domains for each sample were evaluated. Dynamic mechanical analyzer experiments were made to evaluate the macroscopic thermal properties of the blends. A morphology was well established for all blends examined with these techniques showing a nodular structure, the epoxy‐rich phase, and a continuous phase, the SAN‐rich phase, that forms the matrix. From both microscopic and macroscopic thermal analyses, it is concluded that a phase separation exists for the blends investigated. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 284–289, 2002
Quantifying phase behavior in partially miscible polystyrene/poly(styrene‐co‐4‐bromostyrene) blends
Authors: Gorga Russell E. , Jablonski Erin L. , Thiyagarajan P. , Seifert Soenke , Narasimhan Balaji 
Published: August 2002

AbstractThe phase behavior of thin‐film blends of polystyrene (PS) and the random copolymer poly(styrene‐co‐4‐bromostyrene) (PBS) was studied with atomic force microscopy (AFM) and small‐angle X‐ray scattering (SAXS). Phase behavior was studied as a function of the PBS and PS degree of polymerization (N), degree of miscibility [controlled via the volume fraction of bromine in the copolymer (f)], and annealing conditions. The Flory–Huggins interaction parameter χ was measured directly from SAXS as a function of temperature and scaled with f as χ = f2χS–BrS [where χS–BrS represents the segmental interaction between PS and the homopolymer poly(4‐bromostyrene)] Simulations based on the Flory–Huggins theory and χ measured from SAXS were used to predict phase diagrams for all the systems studied. The PBS/PS system exhibited upper critical solution temperature behavior. The AFM studies showed that increasing f in PBS led to progressively different morphologies, from flat topography (i.e., one phase) to interconnected structures or islands. In the two‐phase region, the morphology was a strong function of N (due to changes in mobility). A comparison of the estimated PBS volume fractions from the AFM images with the PBS bulk volume fraction in the blend suggested the encapsulation of PBS in PS, supporting the work of previous researchers. Excellent agreement between the phase diagram predictions (based on χ measured by SAXS) and the AFM images was observed. These studies were also consistent with interdiffusion measurements of PBS/PS interfaces (with Rutherford backscattering spectroscopy), which indicated that the interdiffusion coefficient decreased with increasing χ in the one‐phase region and dropped to zero deep inside the two‐phase region. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 255–271, 2002
Anisotropic properties of poly(ethylene terephthalate) by Brillouin spectroscopy: Anisotropic properties of oriented bulk and nanostructured poly(ethylene terephthalate) determined by Brillouin spectroscopy and birefringence experiments
Authors: Anders Stefan H. , Eberle Reinhold , Peetz Ludwig , Krüger Jan‐Kristian , Göschel Ulrich , Pietralla Martin 
Published: August 2002

AbstractUsing Brillouin spectroscopy (BS), the tensor of the elastic constants of oriented poly(ethylene terephthalate) was determined for a variety of morphologies obtained by different uniaxial drawing procedures. The extreme values of the moduli along the drawing direction at frequencies of a few gigahertz were C33 = 40 GPa and C44 = 1.8 GPa. As a result of the invariants of the single‐phase aggregate model, the oriented state is dominated by the Reuss average even at extreme draw ratios and subsequent to a deformation‐induced crystallization. This is documented in both the BS orientation parameter and the BS mode numbers in comparison with birefringence. Additional spectral lines observed at draw ratios larger than 6 are discussed in relation to the formation of nanostructured phases. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1201–1213, 2002
Dynamic mechanical and dielectrical properties of poly(vinyl alcohol) and poly(vinyl alcohol)‐based nanocomposites
Authors: Cendoya Ione , López Daniel , Alegría Angel , Mijangos Carmen 
Published: August 2002

AbstractIn this article we report on the investigation of the dynamics of poly(vinyl alcohol) (PVA) and PVA‐based composite films by means of dielectric spectroscopy and dynamic mechanical thermal analysis. Once the characterization of pure PVA was done, we studied the effect of a nanostructured magnetic filler (nanosized CoFe2O4 particles homogeneously dispersed within a sulfonated polystyrene matrix) on the dynamics of PVA. Our results suggest that the α‐relaxation process, corresponding to the glass transition of PVA, is affected by the filler. The glass‐transition temperature of PVA increases with filler content up to compositions of around 10 wt %, probably as a result of polymer–filler interactions that reduce the polymer chain mobility. For filler contents higher than 10 wt %, the glass‐transition temperature of PVA decreases as a result of the absorption of water that causes a plasticizing effect. The β‐ and γ‐relaxation processes of PVA are not affected by the filler as stated from both dynamic mechanical thermal analysis and dielectric spectroscopy. Nevertheless, both relaxation processes are greatly affected by the moisture content. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 1968–1975, 2001
Effects of socioeconomic status on presentation with acute lower respiratory tract disease in children in Salvador, Northeast Brazil
Authors: Nascimento‐Carvalho Cristiana M. , Rocha Heonir , Benguigui Yehuda 
Published: August 2002

AbstractTwo different socioeconomic groups of children with pneumonia were studied, and their clinical and demographic aspects were evaluated. The diagnosis of pneumonia was based on findings of cough and tachypnea, or on crackles on auscultation or on radiologically confirmed infiltrate. This was a prospective cross‐sectional study conducted at the Professor Hosannah de Oliveira Pediatric Center, which cares for children of lower socioeconomic status (PHOPC), and at one private hospital which cares for children from middle to high socioeconomic status (Aliança Hospital, AH). Demographics and clinical differences were assessed by the Pearson chi‐square test or Fisher's exact test as appropriate; means of continuous variables were compared by Mann‐Whitney U‐test.In a 26‐month period, 3,431 cases were recruited. The 2,476 cases identified at the PHOPC were younger than the 955 identified at AH (2.2 ± 2.3 vs. 4.5 ± 3.1 years, P < 0.0001) and had higher scores for severity (3.5 ± 1.5 vs. 2.7 ± 1.7, P < 0.0001), duration of hospitalization (days) (10.9 ± 12.1 vs. 6.2 ± 7, P < 0.0001), frequency of tobacco smoker in the household (48% vs. 31%, P < 0.0001), cardiopathy (15.3% vs. 5.9%, P = 0.003), fever (44.4% vs. 36.3%, P = 0.0001), tachypnea (67.6% vs. 32.3%, P < 0.0001), crackles (69.5% vs. 64.9%, P = 0.02), somnolence (19.9% vs. 10.4%, P < 0.0001), malnutrition (13.7% vs. 5%, P < 0.0001), hospitalization rate (27.4% vs. 22.5%, P = 0.003), and death (0.9% vs. 0.1%, P = 0.009). However, other features were more frequent among AH cases: parent's university level of education (38.2% vs. 1.0%, P < 0.0001), underlying chronic illness (40.6% vs. 28.5%, P < 0.0001), asthma (62.7% vs. 50.8%, P = 0.01), rhinitis (9.2% vs. 0.4%, P < 0.0001), previous use of antibiotics (34.3% vs. 27.1%, P = 0.001), and wheezing (53.1% vs. 42.2%, P < 0.0001).Children of lower socioeconomic status have more serious lower respiratory tract disease, whereas children with pneumonia of middle to high socioeconomic status have more allergic diseases (rhinitis, asthma) and wheezing. Pediatr Pulmonol. 2002; 33:244–248. © 2002 Wiley‐Liss, Inc.
Efficacy of once‐daily tobramycin monotherapy for acute pulmonary exacerbations of cystic fibrosis: A preliminary study*
Authors: Master Vahid , Roberts G.W. , Coulthard K.P. , Baghurst P.A. , Martin A. , Roberts M.E. , Onishko C.R. , Martin A.J. , Linke R.J. , Holmes M. , Jarvinen A. , Kennedy D. , Colebatch K.A. , Hansman D. , Parsons D.W. 
Published: August 2002

AbstractOur objective was to compare the efficacy, safety, and microbiology of once‐daily intravenous (IV) tobramycin with conventional 8‐hourly tobramycin/ceftazidime IV therapy for acute Pseudomonas aeruginosa (PA) pulmonary exacerbations in cystic fibrosis (CF). CF patients with PA‐induced pulmonary exacerbations were allocated to receive either once‐daily tobramycin (Mono) or conventional therapy with tobramycin/ceftazidime given 8‐hourly (Conv). The two longitudinal groups received therapy in a double‐blind, randomized manner over a period of 2 years. Tobramycin doses were adjusted to achieve a daily area under the time‐concentration curve of 100 mg·hr/L in both groups. Results were assessed for both short‐term changes (efficacy and safety after 10 days of IV antibiotics during acute exacerbations) and long‐term changes (efficacy, safety, and sputum microbiology between study entry and exit).Pulmonary function tests (PFTs) on admission were similar in both groups. After 10 days of IV antibiotics, absolute mean improvements in percent of predicted PFTs were 12.8, 12.1, and 13.7 for forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), and forced expired flow between 25–75% of FVC (FEF25–75%) in the Conv group (n = 51 admissions( compared to 10.6, 9.9, and 10.6 in the Mono group (n = 47((P<0.05 for all). Sixteen percent in the Conv group and 15% of patients in the Mono group did not respond to therapy by day 10. Long‐term PFT patterns were similar for the Conv and Mono groups. The time between admissions did not differ. The Mono group showed a significant increase in tobramycin minimum inhibitory concentrations (MICs) against PA from study entry to study exit (P = 0.02, n = 27 strains); this failed to reach significance in the Conv group (P =  0.08, n = 25). There was no significant increase in the number of isolates, with MIC≥8 mg/L in both groups. No short‐ or long‐term changes in audiology or serum creatinine were found in either group. After 10 days of IV therapy, the urinary enzyme N‐acetyl‐beta‐d‐glucosaminidase/creatinine ratios increased in both groups (P0.05). This increase was greater in the Conv compared to the Mono group (P < 0.05).We conclude that this pilot study indicates once‐daily tobramycin therapy to be as effective and safe as conventional 8‐hourly tobramycin/ceftazidime therapy. Combination antibacterial therapy appears to offer no clinical advantage over once‐daily tobramycin monotherapy. Tobramycin once‐daily monotherapy is a potential alternative to conventional IV antibacterial therapy which deserves further investigation, including the impact on susceptibility of PA to tobramycin. Pediatr Pulmonol. 2001; 31:367–376. © 2001 Wiley‐Liss, Inc.
Histamine H1 receptor activation inhibits the proliferation of human prostatic adenocarcinoma DU‐145 cells
Authors: Valencia Sandra , Hernández‐Angeles Adriana , Soria‐Jasso Luis‐Enrique , Arias‐Montaño José‐Antonio 
Published: August 2002

AbstractBackgroundHistamine stimulates cell proliferation in some tumor cell lines through the activation of H1 receptors coupled to phosphoinositide hydrolysis. We therefore set out to study the presence of H1 receptors in the prostate cancer cell line DU‐145 and the effect of their stimulation on cell growth.MethodsThe presence of histamine receptors was studied by radioligand binding. Phosphoinositide hydrolysis was assessed by measuring [1H]‐inositol phosphate ([1H]‐IPs) accumulation and changes in the intracellular concentration of free Ca2+ ([Ca2+]i). Proliferation was assessed by cell counting and by [1H]‐thymidine incorporation.ResultsDU‐145 cells express H1 receptors (110±14 fmol/mg of protein) whose stimulation results in [1H]‐IPs accumulation (602±23% of basal, EC50 2.2±0.4 μM) and calcium mobilization (resting level 96±5 nM, Δ[Ca2+]i 517±32 nM, EC50 6.2±0.1 μM). Incubation with histamine (100 μM, 24 hr) resulted in a decrease in both cell number and [1H]‐thymidine incorporation, blocked by the H1 antagonist mepyramine (1 μM).ConclusionsHistamine inhibits the proliferation of DU‐145 cells through the activation of H1 receptors coupled to phosphoinositide hydrolysis. Prostate 48:179–187, 2001. © 2001 Wiley‐Liss, Inc.
Structural basis for the appearance of a molten globule state in chimeric molecules derived from lysozyme and α‐lactalbumin
Authors: Joniau Marcel , Haezebrouck Petra , Noyelle Katrien , Van Dael Herman 
Published: August 2002

AbstractThe problem as to why α‐lactalbumin, in the absence of Ca2+, forms a molten globule intermediate, in contrast to its structural homologue lysozyme, has been addressed by the construction of chimeras of human lysozyme in which either the Ca2+‐binding loop or a part of helix C of bovine α‐lactalbumin were transplanted. Previously, we have shown that the introduction of both structural elements together in the lysozyme matrix causes the apo form of the resulting chimera to display molten globule behavior during the course of thermal denaturation. In this article, we demonstrate that this molten globule character is not correlated with the Ca2+‐binding loop. Also, the Del 101 mutant in which Arg101 was deleted to simulate the α‐lactalbumin conformation of the connecting loop between helix C and helix D, does not show a stable equilibrium intermediate. Rather, the molten globule character of the chimeras has to be related with a specific part of helix C. More particularly, attention is drawn to the four hydrophobic side‐chains I93, V96, I99, and L100, the lysozyme counterparts of which are constituted of less bulky valines and alanine. Our observations are discussed in terms of decreased stability of the native form and increased stability of the intermediate molten globule. Proteins 2001;44:1–11. © 2001 Wiley‐Liss, Inc.
Elucidating protein secondary structures using alpha‐carbon recurrence quantifications
Authors: Webber Charles L. , Giuliani Alessandro , Zbilut Joseph P. , Colosimo Alfredo 
Published: August 2002

AbstractSecondary structures of proteins were studied by recurrence quantification analysis (RQA). High‐resolution, 3‐dimensional coordinates of alpha‐carbon atoms comprising a set of 68 proteins were downloaded from the Protein Data Bank. By fine‐tuning four recurrence parameters (radius, line, residue, separation), it was possible to establish excellent agreement between percent contribution of alpha‐helix and beta‐sheet structures determined independently by RQA and that of the DSSP algorithm (Define Secondary Structure of Proteins). These results indicate that there is an equivalency between these two techniques, which are based upon totally different pattern recognition strategies. RQA enhances qualitative contact maps by quantifying the arrangements of recurrent points of alpha carbons close in 3‐dimensional space. For example, the radius was systematically increased, moving the analysis beyond local alpha‐carbon neighborhoods in order to capture super‐secondary and tertiary structures. However, differences between proteins could only be detected within distances up to about 6–11 Å, but not higher. This result underscores the complexity of alpha‐carbon spacing when super‐secondary structures appear at larger distances. Finally, RQA‐defined secondary structures were found to be robust against random displacement of alpha carbons upwards of 1 Å. This finding has potential import for the dynamic functions of proteins in motion. Proteins 2001;44:292–303. © 2001 Wiley‐Liss, Inc.
Lactoferrin–melanin interaction and its possible implications in melanin polymerization: Crystal structure of the complex formed between mare lactoferrin and melanin monomers at 2.7‐Å resolution
Authors: Sharma Ashwani K. , Kumar S. , Sharma Vandana , Nagpal Akanksha , Singh Nagendra , Tamboli Irfan , Mani Indu , Raman G. , Singh Tej P. 
Published: August 2002

AbstractThe concentration of melanin determines the intensity of colors of the skin and hair of animals. Melanin pigments are tyrosine‐based polymers formed in melanocytes within specialized organelles called melanosomes. In order to understand the mechanism of melanin polymerization, lactoferrin, a basic protein with a pI value of 9.0, has been used to produce melanin. Lactoferrin is a monomeric iron‐binding protein with a molecular weight of 80 kDa. The crystals of lactoferrin were soaked in a solution containing dihydroxyphenylalanine (DOPA) and tyrosinase enzyme. These crystals were used for X‐ray intensity data collection. The intensity data were collected to 2.7‐Å resolution to an overall completeness of 91% with an Rsym of 0.071. The crystals belong to orthorhombic space group P212121 with cell dimensions: a = 85.0 Å, b = 99.8 Å, c = 103.4 Å. The structure was determined by molecular replacement method, using the model of diferric mare lactoferrin, and refined to an R‐factor 0.215 (Rfree = 0.287) for all the data to 2.7‐Å resolution. The final model comprises 5,281 protein atoms from 689 amino acids, 2Fe3+, 2CO ions, 2 indole‐5,6‐quinone molecules (IQ), and 73 water molecules. Two IQ molecules, one in each lobe, bind to lactoferrin. In the C‐lobe, the IQ binds in the iron‐binding cleft, whereas in the N‐lobe, it is located in the side pocket between two α‐helices, filled with solvent molecules in the native iron‐saturated mare lactoferrin. The IQ molecules interact with protein molecule mainly through glutamic acid in both lobes, without significant perturbation to the protein structure. The orientation of N‐ and C‐lobes in the present structure is similar to that observed in the native iron‐saturated protein. However, as a result of the binding of IQ molecules, the orientations of the domains N1, N2 and C1, C2 in the two cases differ slightly. Proteins 2001;45:229–236. © 2001 Wiley‐Liss, Inc.
Identification of novel inhibitors of calling and in vitro [14C]acetate incorporation by pheromone glands of Plodia interpunctella
Authors: Hirashima Akinori , Eiraku Tomohiko , Watanabe Yasuyuki , Kuwano Eiichi , Taniguchi Eiji , Eto Morifusa 
Published: August 2002

AbstractSome octopamine agonists were found to suppress in vitro biosynthesis of the calling pheromone of the Indian meal moth, Plodia interpunctella. Isolated pheromone‐gland preparations incorporated sodium [14C]acetate at a linear rate for 3 h when incubated with the pheromone biosynthesis activating neuropeptide (PBAN). This incorporation was dependent on the dose of PBAN (up to 0.5 µM). Thin‐layer chromatography of a pheromone‐gland extract revealed quantitative incorporation of radioactivity into a product exhibiting the same mobility as (Z,E)‐9,12‐tetradecadienyl acetate, the main component of the calling pheromone of P interpunctella. Twenty‐seven octopamine agonists were initially screened using a calling behaviour bioassay of female P interpunctella. Four derivatives with activity in the nanomolar range were identified which were, in order of decreasing pheromonostatic activity: 2‐(2,6‐diethylphenylimino)thiazolidine > 2‐(2,6‐diethylphenylimino)oxazolidine > 2‐(2,6‐dimethylphenylimino)thiazolidine > 2‐(2‐ethylphenylimino)oxazolidine. These compounds also showed in vitro inhibitory activity in intracellular de novo pheromone biosynthesis. The results of the present study indicate that these derivatives could provide useful information in the characterization and differentiation of octopaminergic receptor types and subtypes.© 2001 Society of Chemical Industry